CA2101984A1

CA2101984A1 - Monitoring and control of fluid driven tools

Info

Publication number: CA2101984A1
Application number: CA002101984A
Authority: CA
Inventors: John Linehan; Angelo L. Tambini
Original assignee: SPS Technologies LLC
Current assignee: Ingersoll Rand Co
Priority date: 1992-08-10
Filing date: 1993-08-05
Publication date: 1994-02-11
Also published as: US5689434A; US5592396A; EP0586811A1; JPH06179177A

Abstract

ABSTRACT OF THE DISCLOSURE
A system for monitoring and/or controlling the torque applied by a fluid driven tool for driving threaded fasteners, such as tools driven by either air or oil. The system includes a fluid flow meter to measure a parameter which is a function of the rate of fluid flow into the tool during operation of the tool, a transducer for converting the measured parameter into an electrical signal, and a data processing unit for processing that electrical signal into a signal representative of the torque applied by said tool. A system for digitally processing the measured parameter and comparing it to predetermined expected parameters to infer the condition of the fluid driven tool and for reporting that inferred condition is also included. The system is applicable to both nutrunner type fluid tools and impact wrenches.

Description

PATENT

2 1019~ 407010-2101 aA~GRouND OF THE INVENTION

This application i6 a continuation-in-part of application serial number 927,853, filed August lo, 1992.
This invention relates generally uto the field of fluid driven tool~ for driving tbreaded fastener~, and more particularly to monitoring and control systems for ~uch fluid driven tools.
Fluid driven tools are very commonly used for driving threaded fasteners. Such tools may be driven by either air or oil. Two types of such fluid driven tools are the nutrunner tool and the impact wrench.
- An air driven nutrunner tool has a continuous drive air motor, such as a turbine, for driving t~e fastener. An oil driven nutrunner operates in a similar manner, but may use a positive di6placement drive (such ns a gear or vane motor) in lieu of t~e turbine. It is desirable to monitor the torque applied by a nutrunner tool in order to monitor and/or control various conditions of the fastener, tool and ~oint, such as lubrication of the tool and/or fastener, existence of cross-threading, ~oint condition, and final tightened tor~ue. Although ~t is p~ssible to measure torque on a nutrunner directly by means of a strain gauge reaction torque transducer, measurement of the torque of a nutrunner by meanC of a strain gauge has been difficult and can be complicated by movement of the tool during ~:~40~7010~2100~SPSRAN.CIP -2-2 1 0 1 9 S ~l PATENT
~ 07010-2101 tiqhtening. Such ctrain gauge transducers al~o considerably lncrease the cost of the nutrunner. Moreover, cucb etrain gauges ~u~t generally be designed $nto the nutrunner, and cannot be conveniently retrofitted.
An impact wrench operates by releasing a periodic build up of kinetic energy in the form of a series of torsional ~hock impul~es transmitted to a fastener assembly, which may typically include a bolt and/or nut. As a result, considerable impact forces can be produced with little reactive torque.
An air driven impact wrench typically includes a vane type air motor and a hammer/anvil mechanism. When the air motor gain~ ~ufficient speed, a high inertia hammer on the motor shaft engages an anvil on the wrench drive shaft. The energy of the blow is converted into ~everal forms. It is (a~ di~sipated as a re~ult of colli6ion inelasticity and friction; (b) stored as torsional 6train energy in the impact mechanism, the wrench drive ~haft and the coupling to the fastener; nnd (c) transferred to the fa~tener, and converted to the work of tightening. The hammer then disengages from the anvil and the motor accelerates for, typically, a complete revolution before delive~ing the next blow.
An oil pulse impact wrench is similar, except t~e hammer/anvil mechani8m i5 enclosed in ~ chamber filled with hydr~ulic fluid and has the effect of damping the backlash a~d A:\40~7010\2100\SPSRAN.CIP -3-2101~S i PATENT

providing more ~ooth operation resulting in less noise and operator fatigue.
It is desireable to monitor and/or control the performance of ~mpact wrenches for many of the same reasons as for nutrunner wrenches. However, because an impact wrench applies torque to the fastener by means of a series of impacts, it is difficl~lt to measure directly the torque applied by an i~pact wrench. Consequently, it is difficult to control tightening accurately.
Due to the foregoing limitations of convenient torque measurement, it has been difficult to monitor and/or control the performance of air or oil powered nutrunner and impact wrenches.
It is a discovery of the present invention that measurement of the fluid flow through a nutrunner or impact fluid powered tool provides information on the torque applied by ~he tool and process conditions affect~ng the tool and the tightening process. This information can then be used either to control or ~onitor the performance of the tool. Furthermore, measurement of the fluid flow to obtain infor~ation on the torque and process condition6 can be Accompli6hed without h~ving ~o moQify the tool.
OBJECTS OF THE INVENTIO~
It i~ an object of the present invention to provide a ~onitoring ~nd control ~ystem for nutrunner ~nd impact fluid tool~ which overcomes the disadvantages of prior sy~tems.

A:~40~7010~2100~SPSRAN.CIP -4-2101 9 ~ 1 PATENT

It is an ob~ect of the present invention to provide a ~onitoring ~nd control 6ystem for nutrunner and impact fluid tools which provides information on the torque applied by the tool by measuring fluid flow to the tool.
It is an object of the present invention to provide a ~onitoring and control system for nutrunner and impact fluid tools which provides information on changes in the expected conditions of tightenin~ of the joint and/or tool by measuring fluid flow to the tool.
It another object of the present invention to provide a monitoring and control ~ystem for nutrunner and impaot fluid tool~ which i~ inexpensive, simple and rugged.
It i6 ~ yet further object of the present invention to provide a monitoring and control system for nutrunner and impact fluid tools that can be fitted in line with the existing fluid tool supply with no ~sdification of the tool.
It is a further object of the present invention to provide process information regarding the tightening performance basea on an automated analysis of the measured data.
SUMMARY OF THE I~VEN~ION
~ hese ~bjectives ~re ~ccomplished in d ~ystem for monitoring ~ fluid driven tool for driving threaded fasteners compri6in~ mean~ for me~suring the rate of fluid flow into the tool during oper~tion of the tool; means for converting the A:~0~701~2100~SPSRAN.CIP -5-~ea~ured fluid flow rate into an electrical ~ignal representative of the magnitude o~ said fluid flow rate; means for electrically proce~sing 6aid ~ignal to compute at least one parameter which is ~ function of 6aid fluid flow rate; and means for displaying said parameter.
These objectives are also accomplished in a system for ~onitoring a fluid driven impact wrench for driving threaded fa6teners compri~ing means for measuring the rate of fluid flow into the wrench during operation of the tool, means for converting the measured fluid flow rate into an electrical ~ignal; means for electrically processing ~aid ~ignal to compute ~t least one parameter which is a function of said fluid flow rate; and means for displaying said parameter.
These objectives are also accomplished in a system for controllin~ a fluid driven impact wrench for driving threaded f~steners comprising means for measuring the rate of fluid flow into the wrench from a fluid 6upply during operation of the tool;
mean6 for converting the ~easured fluid flow rate into an electrical ~ignal; means for eleotrically processing said signal to count the number of blows delivered by the wrenQh; means to ~hut-off the flui~ ~upply to the tool when a predetermined number of blow6 have been delivered and means for displaying the number o blow~ counted.

A:~40~7010~2100~SPSRAN.CIP -6-21019U ~ P~TENT
40~010-2101 These ob~ectives are also accompli~hed in a 6ystem for ~onitoring a flui~ ~riven tool for driving threaded facteners compricing meAns for measuring fluid flow rate into the tool durinq operation of the tool; means for convertinq ~aid measured fluid flow rate into an electrical ~ignal representative of the magnitude of 6aid fluid flow rate; means for electrically processing said signal to compute at least one parameter which is a function of ~aid fluid flow rate; means for comparing ~aid at least one parameter to predetermined expected parAmeters to infer a process condition relating to said fluid driven tool; and means for reporting said inferred process condition.
BRIEF DESCRIPTION OF~HE DRAWINGS
The~e and other objects and advantages of the present invention will be apparent to those skilled in the art upon review of the ~pecification and drawings herein, where:
Fig. 1 i~ a schematic block diagram of a monitoring and control system for an nutrunner fluid tool in accordance with a pr~ferred embodiment of the present invention.
Fig. 2 i~ a 6ectional view of a fluid flow meter for u~e in A ~onitoring and control ~ystem in accordance witb a preferred embodiment of the present invention.
Fig. 3 is a ~chematic circuit diagram for a preamplifier for the flùid flow ~eter depicted ~n Fig. 2, for use A:~40\7010~2100\SPSRAN.CIP -7-40~010-2101 ~n a monitoring and control sy6tem in accordance with a preferred embodi~ent of the ~resent invention.
Fig. 4 i~ ~ graph of a typical flow signal from the fluid flow ~eter of a m~nitoring and control ~ystem in accordance with a preferred embodiment of t~e present invention, used on a nutrunner fluid tool, depicting regions of the flow curve containing important parameters.
Fig. 4a depicts a typical display in graphical format showing the initial flow r~te (prior to snug point) and the flow rate qradient range graph (minimum and maximum) during tightening for the five most recent tightenings, when all tightenings are within ~pecification.
Fig. 4b depicts a typical display in gr~phical format s~owing the initial flow rate (prior to snug point~ ~nd the flow rate gradient range graph tminimum and maximum) during tightening for the five most recent tightenings, when the fifth tightening is outside of specification.
Fig. 5 is a graph of torque V6. angle for three joints having different hardne ses: joint alone; joint and load cell;
~nd ~oint, load cell and gasket.
Fig. 6 i~ a table of data for a serie~ of tightenings ~or the ~oint and load cell graphed in Fig. 5, at an air pressure ~f 60 p~ howing prel~ad (kN); initial flow signal ~v~lt~);

A:\40~701Q~2100\SPS~AN.CIP -8-2101~S 1 PATEN~

bre~kforward torgue (Nm); and flow gradient (mAximum and minimum).
Fig. 7 i~ ~ table of data for ~ 6eries of tightenings for the joint with load cell grap~ed in Fig. 5, at an air pres~ure of 70 psi, chowing preload (kN); initial flow ~ignal (volts); breakforward torque (Nm); and flow gr~dient (maximum and minimum) .
Fig. 8 is ~ table of data f~r a 6eries of tightenings for t~e joint with load cell graphed in Fig. ~, at an air pressure of B0 psi, ~howing preload (kN); initial flow ~ignal (volt~); breakforward torque (Nm); and flow gradient (maximum and minimum).
Fig. 9 is a table of data for a series of tightenings ~or the joint load cell ~nd gasket graphed in Fig. 5, ~t ~n air pressure of 70 psi, ~howing preload (kN); initial flow signal (volts); breakforward torque (Nm); and flow gradient (maximum and minimum).
Fig. 10 is a table of data for a ~eries of tightenings ~or the joint only graphed in Fig. 5, at an air pressure of 70 psi, ~howing preload (kN); initial flow ignal (volts);
~reakforward torque (Nm); and flow gradient (~aximum and ~ini~um).
Fig. 11 is a graph of bot~ air flow v time ~nd torque v~. ti~e for t~e tightenings summarized in Fig. 6.

A:~40~70~Q~210Q\SPSRAN.CIP -9-21019S-~
PATENT

Fig. 12 is a graph of both air flow V5 . time and torgue v~. time for the t-i~hteni~gs ~ummarized in Fig. 7.
Fig. 13 is ~ graph of both air flow vs. ti~e and torque . time for the tig~teninqs summarized in Fig. 8.
Fig. 14 is a schematic block diagram of a monitoring ~nd control cy6tem for an impact fluid tool in accordance wit~ a preferred embodiment of the present invention.
Fig. 15 is a graph of the output 6ignal from the flow meter of the monitoring and control system of the present invention vs. time, during tightening by an impact air w.rench.
Fig. 16 is a graph of the output ~ignal from the flow meter of the monitoring and control system of the present invention vs. time, during untightening by an impact air wrench.
Fig. 17 is a graph of the output ~ignal from the flow meter of the monitorinq and control ~ystem of the present invention vs. time, during tightening of a pretightened screw by an impact ~ir wrench.
Fig. 18 depicts i5 a ~ectional view of an alternative -embodiment of a fluid flow meter for use in a monitoring and control 8y5tem in ~ocordance with a preferred embodiment of the pre~ent invention.
Fig. 19 i~ a ~chematic block diagram of an alternative ~rrangement of the monitoring and control system for a fluid A:~40~7010~2100\SPSRAN.CIP -10-2101~ 1 PATENT

driven tool ln accordance with a preferred embodiment of t~e present invention., ' Fig. 20 is a chart depicting typical computed parameters, ~nferred process conditions corresponding to particular values of the parameters, and probable causes of those conditions for ~ fluid driven RAN tool as reported by a system in accordance with a preferred embodiment of the present invention.
Fig. 21 is a chart depicting typical computed parameters, inferred process conditions corresponding to phrticular values of the parameters, and probable c~uses of those conditions for ~ fluid driven impact wrench as reported by a sy~tem in accordance with a preferred embodiment of the present invention.
Fig. 22 is a representation of a typical displsy of the ~tatus of the inferred process condition as reported by ~ system in ~ccordance with a preferred embodiment of the present invention, where the inferred proc~ss condition i5 normal.
'' Fig. 23a is a representation of a typical display of the st~tu~ of the inferred process condition as reported by a sy~tem ln accordance with a preferred embodiment of the present invention, where the inferred process condition is abnormal.
F~g. 23b is ~ representation of a typical display of the probable c~uses of ~he ~bnormal inferred process condition depict~d in Fig 23a.

A:~40\7010\2100\SPSRAN.CIP

21~19S 1 PATEN~

~ ig. 24 is ~ graph of an idealized flow/time curve, chowing typical lo~tions on the curve where flow ~easurements ~re taken and from which certain parameters are computed.
a~SCRIPTION OF THE PREFERRED EMBODIMENT
Referring first to Fig. 1, a torque monitoring system 20 for 8 fluid driven nutrunner tool 30 i6 depicted. Nutrunner tool 30 includes a fluid motor (not shown in Fig. 1), which is typically of t~e vane, or turbine, type. Although a nutrunner type fluid tool is depicted, it is to be understood that the invention is also applicable to an impact type air or oil pulse tool, which also includes an air or ~il drive~ mot~r.
Since there ~s typically only a small amount of expansion of the pressurized fluid within either an air or oil fluid motor, the fluid motor has the characteristics of ~
constant volume metering pump. It has been discovered that the fluid flow through the tool is substantially proportional to the rot~tional speed W. Furthermore, it has been discovered that the fluid flow may be determined by measuring the differential pressure across ~ venturi and that this pressure measurement may ~e performed using an ine~pensive and rugged solid State differential pressure transducer.
At ~ fixed fluid pressure the output torque To i6 rela~ed to the rotational speed W by the following formula:
To ' T" - 1~

~:~43~7010~2100~SPSRAN.CIP -12-210 1 3 S i PATEN~

vbere T~ i6 the stall torque ~nd X is ~ constant, the value of which i~ unigue for ~ particular nutrunner tool and fluid pressure.
Torgue monitoring system 20 includes a fluid flow meter 36 ~ounted in the fluid line to the tool, preferably within about 10 feet from the tool. Fluid flow meter 36 is shown schematically in ~ig. 1 ~nd in cross secti~n in Fig. 2. In the preferred embodiment depicted, flow meter 36 i6 a standard venturi-type differenti~l pressure flow meter, ~aving a venturi 38 with ~ hig~ pressure take-off 40 on the fluid inlet side 42 ~nd a low pressure take-off 44 at the neck of the venturi. Low pressure take-off 43 leads to a pressure chamber 46. There, a tr~nsducer 48 is situated between the high pressure take-off 40 ~nd pressure chamber 46, to measure the differential pressure c~used ~y flow through the venturi.
Transducer 48 i5 preferably a low cost semiconductor pressure sensor, and fluid flow meter 36 can be made not much bigger than a standard air fitting. The transducer 48 preferably ~nE ~ 0 to 5 psi r~nge but the overall pressure losses through the venturi would normally not be more than about 1 psi.
Although the preferred embodiment of fluid flow meter 36 is depicted ~s employing ~ venturi and differential pressure sensor, it ~s to be understood that other flow measure~ent means, ~uch 25 ~ turbine or vortex ~hedding meter, could be employed.

A:\40~7010~2100~5PSRAN.CIP -13-2101 9 ~ I PATENT

A venturi type flow meter i6 non linear and the fluid flow i8 proportional to t~e ~quare root of the differential pres6ure signal. Accordingly, the theoretical relationship for the output torque is:
T~ ~ T~ - xl ~Ip where xl i~ a constant and P i5 the differential pressure measured at the venturi.
This rel~tionship, which applies to any continuously rotatinq fluid tool, shows that the fluid flow can be used as a measurement and control parameter as it is directly correlated with the torque. Of course, flow may al60 be affected by many ot~er factors, ~uch as lubrication of the tool, pressure and ~oint conditions. These other factors complicate calibration of the monitoring 6ystem for measuring torque zpplied to the fastener per se. However, measurement of fluid flow is very useful in a monitoring system for a nutrunner tool to indicate when conditions change.
Of course, in an impact wrench, the fluid motor is only ~ontinuously rotating during the rundown phase. However, for practical purposes, the foregoin~ formula iE al60 generally ~pplicable to impact wrenches. In addition, in an i~pact wrench, the pulsed nature of the flow siqnal during the tiyhtening (hammerin~) ~llows the~blows (impacts~ to be easily ~unted for ~onitoring or ~ontrol purposes.

~:\40\7010\2100\SPSRAN.CIP -14-2lnls~ l PATENT
~07010-2~01 As depicted in Figs. 1 and 3, the electrical ~ignal from transducer 48 is fed to a data collection computer 52, which ~ncludes a suitably programmed microprocessor, through a data acquisition board 8D. Data ~cquisition board 80 is preferably a ~CL 818 16 channel data acquisition board. It should be noted, however, that a single fluid tool only requires one data channel.
~hus, a single 16 channel data acquisition board can accommodate up to 16 separate tools.
A pre-amplifier 54, as depicted in Fig. 1 And 3, is also preferably included on the output from flow transducer 4B to amplify the signal from transducer 48 prior to feeding it through data acquisition board 80 to data collection computer 52. The distAnce between the 6ensor and the preamplifier should preferably be limited to 70 feet. The distance between the preamplifier 54 and the data acquisition computer i6 not important.
In addition, preamplifier 54 could incorporate circuits to conYert the analogue si~nal to serial data format for tran~mission to the data acquisition computer.
An output 50 from computer 52 to pre-amplifier 54 may optionally enable or disable the pre-amplifier.
A~ 6chematically depicted in Fig. 19, the need for an Qxternal preampli~ier, 54 may be ~liminated by the use of a n~m~rt~ BenSOr 48', ~uch AS the 180PC from Honeywell Microswitch, A:~40j7010\2100\SPSRAN.CIP -15-~n place of the conventi~nal transducer 48. T~e circuit of a ~cmart~ ensor 48' includes an on board amplifier 54'. This . . .
el~minates the need for careful wiring cf low level signals and outputs a voltage which may be directly connected to the analog to digital input on the PC card. In addition, other circuits may be added ~n board the "smart" 6ensor 4~' to perform temperature compensation and signal linearization.
As depicted in Fig. 1, data collection co~puter 52 is in two-way communication with operator display and input computer 56. The Gperator display and input computer 56 includes a suitably programmed microprocessor to perform mathematical operations on the data ~upplied it by data collection computer 52, to compute certain parameters as required, 6uch as the snug point, which is computed as a percentage of the initial fluid flow rate to the tool during rundown. This enables the ~icroprocessor to identify a portion of the ~ignal representative of the fluid flcw rate during tightçning of the fastener beyond the 6nu~ point.
Operator display and input computer 56 outputs to a di play 57, ~uch as a CRT or a printing device, for displaying desired data. Preferably, the pertinent data is displayed in a graphical format, ~uch as depicted in ~igs. 4~ and 4~, but may alE~ be di~played numerically or in any ~ther intelligible ~anner. Preferably, display 57 is capable of ~imultaneously A:~40~7010\21~0\SPSRAN.CIP -16-~1~) 1 ('.`` 1 PA~EN~

di~pl~ying pertinent data for at least two, up to about 15 or ~ore, of the most recent tightenings. Operator display and input computer 56 ~lso preferably includes input means 55, such as a keyboard, for the operator to input certain required parameters and ~pecifications into the system.
The purpose of the computer 52 is to acquire the 6ignal, process it and derive critical parameters according to predetermined algorithms, to compare this derived data with predetermined limit~ and to format the data for transfer to other computing devices S6 for ~torage, ~nd to do further stati6tical proces6ing of the derived parameters. It may also control interface device 51 to alert the operator as to tightening gtatus. The ~ystem may be operated independent of computer 56.
Computer 56 may be part cf the installed ~ystem or part of the u~er'~ QWn production Etatistical process control system, ~s ~epicted in the alternative sy~em c~nfiguration depicted in Fig. 19. Its purpose is to accept the formatted data from computer 52 and to perform statistical process monitoring rules on the incoming data. It may also, while the system i6 in a "Learn" ~ode, that is, gathering data about a new fa~te~er/~oint/tool system and perf~rming statistical analy~i~ on thi6 d~ta (to ~e described below), sugge~t the control limits to ~e applied to the derived parameters in the d~ta acgu~siti~n co~puter 52. ~t ~ay al o record on hard disk or ot~er long term A~4Q~731~ 0~SP~RA~ P ~17-PATENT
2 101~S l 407010-2101 media ~ll acquired and derived data for later retrieval or for archiving purpo~es.
The data will be processed within computer S2 and checked against upper and lower limit6 that have been previously et and for~atted for transmission to operator display and input computer 56. The data transmitted to operator display and input csmputer 56 will include, at least, (l) average free run flow rate (i.e., average initial flow rate); ~2) change of flow rate durinq tightenin~; (3) tool identification; (4) time at which tightening takes place (i.e., snug point); and (S) rundown time.
Not ~ll of this data need be displayed on display 57 at any one time. However, it is preferable to simultaneously display at least the initial fluid flow rate (prior to snug point) ~nd the ~inimum and maximum range of fluid flow rate gradient, i.e., rate of ch~nge, during tightening, for each tightening displayed.
- Of course, data collection computer 52 and operator di~play and input computer 56 may be physically separate or may employ the s~me ~uita~ly programmed microprocess~r. The present sy6tem can be used for a single tool or, expand~d for use in larger installations for the collection of data over a complete plant.
~ ata collection computer 52 also optlonally outputs to ~ ~top valve 58 (sh~wn in Fig. 1), which is used to control the t~rque ~pplied by the tool by shutting o~f t~e fluid ~t the Ao~40~7010~210Q~SPSRAN~CIP

~10 1')~ ~
PATENT

de~ired point. To use fluid flow as a control parameter in a nutrunner tool, i . ë;, to control the torque applied by the tool a~ well ~s measure it, reguires that shut-2ff valve 58 be of the f~t acting type.
The data collection computer includes a buffer 6torage for the last 30 tightenings. Permanent storage of all tightelling5 i6 ~ccomplished in the input and display computer 56 ~uch as, for example, stora~e on a magnetic disk.
The data stored includes the data transmitted plus the raw data ~amples that are used to measure the ~lope of the fluid f le~w curve. The data itself is clocked at a fixed clock rate independent of the computer.
An operator interface unit 51 is preferably included for e~ch tool and operatively connected to, and in two-w~y communicat.on wit~, the data c~llection computer 52 and the operator display and input computer,56. Interface unit 51 i~
preferably located near the tool, preferably within 12 feet or 60, to permit the operat~r of the nutrunner tool to monitor the pexformance of the tool. Interface unit 51 includes an "Operate"
~witch 81, an ~Acknowledge" butteOn 82 ~ an "OX" light 83, a "NOT
OKI' light 84, ~nd a "Ready" light 85.
"Readys' light 8~ i6 lit by a signal from datB
6011ection computer 52 whe~ the data colle~tion oomputer 52 is re~dy t~ collect data~ "Okay" lig~t 83 is lit when the data A~40~7010\2100~SPSRAN.CIP -19-2101.,.,i 407010-2101 collection computer 6ignals that the data collected i6 in acccrdance with speclfication, that is, when the data collected i6 within predetermined mi~imum and maximum values. ~Okay" lig~t 83 ~tays on for preferably two ~econds to give the operator time to take ~ction. "Not okay" light 84 is lit when the data collected i~ not in spec~fic2tion, and ~tays on permanently until the "Acknowledge" button 82 i6 pressed by the operator. The posStion of "Acknowledge bu'ton 82" is preferably communicated to both data collection computer 52 and operator display and input computer 56. I~ lieu of lights, other visual displays for the "Okay" and "Not Okay" conditions may be employed.
Placing the "~perate" switch 81 in the "off" positi~n inctructs the data collection computer 52 that data should not be collected, cuch as by a ~ignal thr~ugh ena~le/disable connection 50 to preamplifier 54. Placing the "Operatel' switch 81 in the "On" position enables data collection. The p~sition of "Operate"
~witch 81 is preferably communicated to both data collection computer 52 and operator di~play and input computer 56.
In the y~tem depicted in Fig. 1, the sampled data fr~m ~ixteen tools is ~tar wired to a da~a collection computer 52.
The data collection computer 52 processes the data and derives the par~meter ~rom the ~mpled data. The parameter data ~ay then be forwarded th,oughout the plant over a network to wherever ~t i6 required.

A.~40~7010~2100~5PSk~N.CIP -20-2101 3 ~ 1 PATENT
~07010-2101 In the alternative ~cheme depicted in Fig. 19, ~he ~en~or 4~ and ampiifier 54 are replaced with a ~smart" censor ~8', ~nd a dedicated processing unit 62 is provided, packaged together or clocely. The processing unit 62 has an integral multidrop network connection. A separate local interface unit 51 on or ~n in close proximity to tool itself, may also be part of thi~ assembly. In this case, the local interface unit 51 may be controlled either by the dedicated processing unit 62 or by the computex 56 across the networ~. The use of a dedicated micr~processor for each tool is advantage~us because it limits the ~mount of data traffic networked across the plant and introduces robust digital data transmissisn as early as possible in the data acguisition 6ystem. It also reduces or eliminates, depending on the 60phistication of the dedicated microprocessors, t~e need for 6eparate data collection computers.
The monitoring sy~tem of the present inventi~n operates ~s follows. To initially set up the system, the system is first ~witched on by a power switch (not shown). After switch on, a ~pecial "~et up" program is ~ut~matically called up ~y operat~r di play ~nd input computer 52 to enable the operator to make t~e following 6ettings on operator input and display computer 52 for e~ch channel of data collect~onO

- G~in - Initial trigger level - Delay before measure~ent - Measuring period for flow r~te A:\4U~7Q10~21QO~SPSRAN.CIP ~21 21~ PATENT

- Trigger point for-flow gr~dient measurement - Chord length f~r--flow gradient - Sample r~te - Delay t~me before next measurement ~n channel - Maximun and ~inimum values for flow, flow gradient ~nd run down t~e Preferably, the program 6hould prompt and advise the operator on which values to use, e.g. that the chord length setting could be based upon a hard, normal or 60ft joint c~ar~cteristics.
After set up is complete, data collec~ion may begin when the operator actuates the "Operate" switch 81 cn interface unit 51. At the start of data collection, the "Ready" light 85 come~ on. Next, the operation of the ~luid to~l causes the siqnal representative of flow to increase until it reaches the "trigger" value (approximately 1.8 volts), which automatically c~uses the ~ystem to begin to collect and process data. The signal i~ then checked by t~e 6ystem to determine if the values of flow, flow gradient and rundown times are within predetermined minimum and m~ximum limit~ ~et by the operator.
When all values ~re accep~able, the nOXay'1 signal is given, lighting the "3kay" liqht 83. This light then switches off ~fter tw~ ~2conds an~ the ~Ready" light 85 comes bac~ on.
The ~N~t O~ay" liqht 84 is lit given when one or more of the pAr21meter~ et in compùter 52 are QUt 0~ fipecification. "Not Ok~y" l ight 84 remains l it until the ~perator presses the ~Ac~nowledge" butt~n 82.

A:i40\70~0~21QO~SPSRAN.CIP 22-0~ PATENT
40~010-2101 In addition, when the system i5 not in t~e "Operate"
~ode it ~ay be in "Learn" mode. This i6 used when the limit values to be u~ed are ~nknown. A ~eries of "normal" tightenings, preferably at least 25, may be performed and the results recorded ~anually or transferred automatically to the computer 56 ~or computer 52). By statistically evaluating these results in computer 56 ~or computer 52), useful limits may then be 6et in computer 52. These limits may then be used for trapping (i~entifying~ trends or deviati~ns from learned normal conditions.
T~ accomplish this, preferably, the ~ystem includes means for recording at least one parameter f~r a series of tightenings during normal conditions, means for statistically processinq the parameter to compute appropriate limits for the normal conditions for this parameter, and means for storing these limit6. During ~ubsequent tightenings, the parameter computed during subsequent tightenings will,~e ~tatistically processed by eit~er c~mputer 52 or 56 to identify trends or deviations from the normal conditions. Means for notifying hn cperator cf ~uch trends or deviati~ns are also included. This may include an ~larm, or ~imply a di~play reflecting the existence of such trends ~r deviations.
During data collection, data is held temp~rarily in a bu~fer ~toraqe ~not s~own3 in ~ata collection computer 52, and A:~40~7Q10~21GO\SPSRAN.CIP -23~

~10 1'~
PATENT

then formatted and transmitted to operator input and display computer 56. Data from the last 30 tig~tenings only will be held ln the buffer. This data will ~lso include the sample6 used for flow meaeurement. When this data is being viewed, the data collection will ~top ~nd the "Ready" light ~5 goes off.
During data collection, the operator input and display computer 56 preferably displays the status of each channel, updated every one half second. That is, the ~tatus of each data channel is indicated with the c~annel number, whether it is ~oxayn, "Not Okay", and "Ready" or not. When "Not Okay" is di~played, the reason for the failure is also displayed on the operator input ~nd display computer 56 display 57 or computer 52.
Thi~ i~ held until the "Acknowledge" button 82 is pressed. It 6hould also be noted that in the context of the present invention, the Okay" or "Not Okay" conditions ~re themselves parameters which are functions of the fluid flow r~te to the tool, Rince they depend up~n the magnitude of the ~luid flow rate (h6 well ~s ti~e, and other variables).
During operation, the computer displ~ys the information on t~e initi 1 flow and the rate of decrease of t~is flow for the pr~vious 15 ~ightenlngs or ~o in a chart recorder, or other type o~ displny, ~ ~hown in Figs. 4a and 4b. This enables ~ny devi~tion~ from normal oper~t.ons to be e~sily detec~ed. For exa~plc, in ~ig 4a, all displayed values for the ive tightenings A:~40~7010~2100~SPSRAN.CIP -24-~ 1 9 '~ ~ PATENT

~re within ~pecification. In ~ig. 4b, the last tightening is out~ide of ~pecification, which i5 immediately ~pparent from the di~plny.
ln addition, a suitable menu is preferably displayed cn display 57 of operator display and input computer 56 to facilitate operator interaction with the fiystem.
The monitoring and control system of the present invention could be powered either by available AC power or by battery, and would only require a very simple low cost electronic circuit. The ~ystem can be configured as a stand al~ne device or can be part of a plant wide information colle~t~on system.
Furthermore, all the elements could be incorporated into one unit which can then be mounted remotely from the wrenoh.
The siqnal obtained during a typical tightening is shown in Fig. 4. Particular regions of interest on this curve are denoted ~s ~-e, where a represents tool "~witch on" (i.e., fluid begin to flow to tool 30); b represents the initial fluid surge to the tool, c represents the initial flow, prior to r~ac~ing the snug point, d represents the tightening phase, and e represents the fl~w rate ~fter the tool has stalled. The dotted line e' represent~ another possible flow rate at ~tall for the ~ame c~nditions.
Al~ no~ed on this graph are the meaning o various pÆr~eter~ required to 6et Up the ~ystem tc enable pr~per data A:~40\7010\2100~SPSRhN.CIP =25-2 1 ~1 1 3 S i PATENT

collection, and typical values for those parameters. These include:
~ymbol a~scription Iypical Values TH - Trigger threshold for 1.8 ~ign~l, Volts WA - Delay to ~liminate initial ~urge, 6.0 milli~econds AV - Time over which flow measurement are averaged, millisec~nds 50 SN - DrGp in flow used to trigger slope measurements, volts 0.8 ~A - Transducer energisation, voltage 7 ~F - Slope measurements either side of maximum used to determine minimum, number 3 LD - Approximate delay ~etween ~amples, microseconds 600 It should be noted that "AV" in t~e foregoing table, ~nd on FigO 4, has the ~ame meaning as ~TaV~ sn Fig. 24. "SN" in the foregoin~ tahle, and on Fi~. 4, has the meaning as "Tl %" on Fig. 24.
The actual values, of course, depend upon the nature of t~e joint, tool, fastener etc., ~nd are set by the operator during ~et-up.
The active part of a tightening perf~rmed by an air driven power tool may be completed as quickly as 10 msecs. To der~ve a usable gradie~t p~rameter, a ~ample ra~e o~ ~ least 2~Hz 16 xequired~

A:~40\7010\2100~SPSRAN.CIP -26-1 a ~ PATENT

With respect to the fluid flow r~te curve itself, that i6, the fluid flow signal outp~t from the transducer during operation of the tool, two of the most import~nt pieces of infor~ation in this signal are the initial flow rate c, and the rate of decrease of this 6ignal as the tool ~lows down during the tightening prDcess d. The time elapsed during the rundown pha~e (i.e., region ~ also an important parameter.
Measurement of fluid flow after the tool has stalled (in region e and e') has been found to be less useful. This is because the vanes in the fluid motor can come to rest in different positions which will ~ive different resistances to the fluid flow, resulting in guite a lar~e variation in the signal f~r otherwise ~imilar oonditions.
It has been discovered that the peak, b, ~hown on the curve of Fig. 4 is caused by the volume of air enclosed in the ch~mber, 46. Thi~ ~urge may be eliminated in ~nother flow ~ensor configuaticn as depicted in Fig. 18. In this design, a tra8sducer 4R i6 contained within the ~ealed chamber 46~
Transducer 4' has respective connections to an upstream pressure connection 40' and a throat pressure connection 43'. ~ ~eparate up~tream pressure connec~i~n 47 is used to ~pply a ~ommon mode pres~lre t~ the int~rior of ~ealed chamber 46, and thus t~ the out~ide ~f ~ensor 48. However, upstream pressure ~onnection 40' ~ separ~te fr~m the YOlUme of chamber 46 and the pressure in the A:~40~7010~2100\SP5RAN~CIP -27-~tn~
PATENT

volume of fluid in chamber 46 only serYes to equalize pressure on the out6ide of 6ensor 48. Thus, t~e surge represented by point b on Fig. 4 ~ay be ~inimized or eliminhted. Of course, a ~smart"
ensor 48' ~ay al50 be employed.
The initial flow rate indicates any changes in fluid pressure and Yariations during the rundown phase. Changes in the initial fluid flow and/or length of rundown time, between otherwise ~imilar tig~tenings indicate changes in fluid pressure, lubrication of the fastener, rundown torque of the fastener, and tool conditions. The slope of the curve in the tightening region d indicates joint conditions, including ~ardness of the joint, ~nd improper operation, i.e. free running or pretightened fnstener, and any variations t~at occur during the tightening phase. Changes in the rate of decrease sf the flow between ot~erwise similar tighteninss indicate that the joint conditions have changed, i.e. threads cros6~d,-hole not properly tapped, gasket material omitted, etc.
The system will need to be set-up initially ~r each tool and joint but will then qive a very ~e~sitive lndication of ~ny changes t~at take place during operation between otherwise nominAlly identical fasteners.
To infer prccess condition~ relating to t~e tightening proce~s, during ~ tighteninq cycle, the derived parameter, for *x~mple, ~pe~d duri~g rundown, i~ determined accor ing to the A:\40\7010\2100\SPSR~.CIP -2~-~l~l"S ~
PATENT
4~7010-2101 ~easured data ~nd preprogrammed formulae and compared to predetermined expected limits or ranges (i.e., high speed, low rpeed, outside low speed limit, normal).
The prepr~grammed formulae may include, for exa~ple, formulae relating flow rate to t~ol ~peed (listed above), formulae for calcul~ting of flow rate gradient during tightening, ~nd ~tatistical process control formulae used for deriving the desired parameters.
In the preferred embodiment a number of parameters ~re derived to help select the appropriate portion of the flow time curve over which to measure t~e average peed. These include a threshold (trigger) value TH, a time delay WA and an averaging time taV. The speed is then computed as the arithmetic mean of the samples taken in the time period t~v.
~ n the preferred embodiment a number of paramet~rs are derived to help ~elect the appropri~te portion of the flow time curve over which to measure the flow gradient during the active pha~e of the tightening process. These levels ~re expres6ed ~s a percentAge of the previously de~cribed mean ~peed level. The mean gradient is ~easured betwe~n the two points T1 % and T2%
~ccording to the following f~rmula. For each ~ample, i, of i ~ 1 to n ~amples: ~

Tfi G T~ + ~TEi ~ 4 [ Tfo ~) ]
Tfl ~ Tf$-cl ~ Tf~ c 0, f~r i ~ c13 ~:~40~7010~21~SP~AN.C~P ~29-V~ PATENT

w~ere T~ ~re--the sample values Tfi are filtered sample values Gi ~re the gradient values cl i~ the chord length The mean gradient i6 taken as the arithmetic mean of Gi, for i ~ 1 to n.
~ ime may be measured from any significant point on the curve to ~ny other significant point on the curve. In the preferred embodiment time is measured form the threshold point TH
on the curve to the point T2~ on the curve.
Fig. 24 diagrammatically represents an idealized curve of flow versus time ~or the purpose of illustrating the mean.ing of ~ome of the foreg~ing settings as the affect data collection ~nd computation of pertinent parameters. In Fig. 24, the initial trigger level i~ represented as "TH", which is conveniently appr~ximately one half of the magnitude of the expected rise in the ~easured flow rate. The purpose sf the trigger setting "TH"
i~ permit the cyfitem ts relinbly ~utomatically deteo~ that a new tightening cycle i~ being ~t~rted, while ignoring 13w level n~ise and fal~e fitarts.
The delay before the initial measureme;lt periGd begins i~ repr~ent~d ~ ti~e period '~WA" on Fig. 2~. ~uring time per~d ~WAff ~ flow ~eaureme~ts ~re ignored by the ~y~tem, at least A:~4Q~7Q10~2100~SPSR~.CIP -30-~ 1 0 1 J ~ 1 PATENT

for purpo6es of deter~ining the flow r~te during the rundown phase. Time period "WA" is set for a sufficiently long period of time to cn~ure that measurements are not taken until past the fir6t "knee" on the flow~time curve, and for a short enough period BO that ~de~uate time remains during the rundown phase the plate~u on the curve) to obtain several flow measurements.
The measuring period for flow rate is represented on t~e curve of ~ig. 24 as time period "t~ve". Time period ~t~ve" is ~et ~ufficiently long so that several flow measurements can be taken and averaged together, but sufficiently short 50 that the ~econd "knee" of the flow/time curve is avoided. The ~verage of the flow measl~rement taken during "tave" gives a parameter representative of the average speed of the tool during the rundown phase.
Flow rate measurements continue following the termination of "tave". ~veral measurements are preferrably averaged together to minimize the effect of noise. The measured flow rate during this period is compared to the predetermined trigger point for determination ~f the gradient of the flow during t~e tightening phase. The triqger point is represented as ~Tl %" on ~iy. 24, and corresponds to an assumed "snug point".
~T1 %" i~ prefera~ly such ~s to be past the ~econd "knee" on the curv~, while leaving u~ficient time for several measureme~ts of flow r~te during the tightening phase, prior to ~2 ~", which Ae\40\7010\2100~SPSRAN~CIP -31-21~ P~TENT
407010-21Gl rspresents the ~nd of flow mea6urements used to determine the average gradient (i_e., the rate of decrease of flow rate over time). ~ typicAl value of nTl S" is 70% of the aver~ge fl~w measured during "tave". "T2 ~" may be any value sufficent to permit enough measurements of flow/time to minimize the effects of noise prior to the point at which the fastener i5 fully t$ghtened.
The time period between flow measurements used to determine the gradient i5 referred to as the "chord lenqth", and is represented ~n Fig. 24 as "cl". As noted on Fig. 24, the time periods (i.e., chord lengths) of successive "Ti" gradient mea~urement time periods may, and preferably d~, overlap. This allows more measurements during a shorter period, thus helping to minimize the effect of noise. The chord length "cl" ~hould be 6ufficiently long to minimize the effect of noise, but ~ort enough to permit several measurements of flow/time between ~Ti %"
~nd "T2 %"-Fig. 20 is ~ prese~tation of the logic ~nd methodologyused to derive (i.e., in~er) the process inf~rmation regarding the tightening performance (i.e., the process conditions) and to ~etermine and/or report probable causes of the inferred process condition) of a RA~ tool~ The leftmost column çon~ains ~he deri~d ~i.e., computed~ parameter, e.g., speed, ioint ~lope (gr~dient). ~he next column states the valu~ of the measured A:~40~7Q10~2100~SPSR~N.CIP -32-~ 1 0 1 ~ U i PATENT

data with respect to predetermined limits or ranges to which the ~easured dat~ ~a6 been compared, the rightmost column names the ~nferred process condition and Yarious probable causes of the prosess conditions that would generate ~uch measured data. The probable causes of t~e particular inferred process condition are listed in ~eguence top to bottom in order of most probable first.

Predetermined expected limits or ranges for the ~e~ured data, ~nd various inferred proces~ conditions for the particular predetermined expected limits or ranges, and the probable causes for those inferred pr~cess conditions, are ~tored in either computer 52 or 56. These predetermined limit values or ranges of the derived parameters are those either entered during Lyctem setup or 'learned' through a run of at least about twenty five '~ood' tightenings and generated autGmatically.
If all derived parameter~ are in the normal range, this ~s reported to either or both ~f computers 52 and 56 and prefera~ly displayed to the operator, preferably by mean~ of an slpha numeric di~play such a~ is depicted in Fig. 22. Thi~
di~pl~y indirat~s the tightening number (i.e., "~") and the proces~ condition statu~ (i.e., "Tool ~nd Joint OX"). This qu~ckly a~sure6 the operator that the performance of the tool and ~he ~oint components ~re all AS they were on system ~etup ~nd calibration.

A: ~40~7010~2100~SP5RANoCIP ~33 ~

w10~9~ 1 PATENT

In the event that one or more of the derived parameters ~re outside the normal range when compared to the predetermined ~xpected v~lues, a particular abncrmal process condition i6 lnferred. For example, the tool rundown speed parameter may be determined to be ~igh, low, or outside the low speed limit, as depicted in middle column in the upper half of Fig. 20. In this case, the corresponding inferred abnormal process condition is reported to either ~r both of computers 52 and 56. It i6 also preferably displayed to the operator, preferably by means of an ~lpha numeric display. A typical example of such a display, generat~d when the measured joint slope (i.e. gradient, or rate of decrea~e of flow over time) fell into the ~'soft" (less steep than normal) range, is depicted in ~ig. 23a. This display indicates the tightening number ~i.e., "1") ~nd t~e inferred process condition ~tatus (i.e., ~NOK" and "Slow shutoff") from a ~oft" ~less steep than normal) gradient during the tiqhtenin~
phase. The operator may then press a key ~for example, "Fl"~ on input device 55 of computer 56 for more informatio~. Doing 50 brings up a new alpha numeric display, as depicted in Fig. 23b, indicating the inferred process condition "slow ~utoff - soft ~oint" and ~ list ~f probable causes of that inferred process condition.
Further derived parameters, ~uch as ~i~e ~from ~ny ~ignifiGant point ~n the flow/time curve), plateau ~ime ~length A:~40~010~21CO~SP5~AN.CIP -34-~ 1 9 ~ ~ 407010-2101 of time during rundown), falloff time (length of time during the tightening phase), total time (from the trigger point to ~hut off~, dead time (the time between separate tightenings), and/or ~ean, ~tand~rd deviation, or trend (of any of the derived parameter~ may be detemined. These additional derived parAmeters could then be included in a table such as Fig. 20, and predetermined expecte~ lim~ts or ranges of t~ese parameters ~tored in either or both of computers 52 or 56. The actual derived parameters would then be compared in t~e computer with the predetermined expe~ted limits or ranges of these parameters in n similar manner to that explained above, to further break down the list of probable causes which w~uld generate a particul~r derived parame~er set.
The analycis ~pproach outlined above for inferring process conditions lends itself to the application of Artificial Intelligence and Fuzzy Logic rules. Preferably, a simple forward chaining rule based expert y~tem ~s used, but this would be further e~hanced by the implementation cf fuzzy logic. For example, instead of a speed having the ~ttribute normal or high, there would be several level~ of speed '~ighness' as in, fairly high, quite hig~, high, very high and extremely high. h~en this analogue or 'fuzzy' approach i6 ~aken to test a parameter value for ~ember6hip of an inference rule, the result need not be expre6sed ~s a certainty, but ~s A pro~ability. This ~ore A:~40~7010~2100\SPSRAN.CIP -35-2101~S l PATENT

clo6ely follows that ~appens in the real world. The software would then list probable process conditions, pr~bable causes, and their respective probabilities, in descending order.
~ presentation of the logic and ~ethodology used to derive (i.e., infer) the process information regarding the tightening performance ~i.e., the process condition) and to determine and/or report probable causes of the inferred process condition) for an impact wrench is depicted in ~ig. 21. In the leftmost column of Fig. 21 are the derived parameters for impact wrenches, the next column the value of the measured data with respect to predetermined limits or ranges to which the measured data has ~een compared, and the rightmost column, the inferred process condition and various probable causes of the inferred process condition or conditions/ in a ~imilar manner to that di~play~d in Fig. 20 for ~ RAN tool. Time is al~o an impor~ant parameter in helping to infer process ronditions for impact wrenches.
Example 1 Measurements were made using a fully instrumented St~nley Right Angle Nutrunner (~AN), Seri~l No. A40 LA 2XNC~ -8/SPI. T~e tosl was operated in the ~tall torque m~de and the torqu~ ~nd air flow monitored for different conditions. Typical r~ult& ~re ~hown in Figs. 11-~4. Ten t~ghtenings of a h~rd ~o~nt (i.e., with no ga~keti were ~ade ~t different ~r pressures A:~40~7010~2100\SPSR~N.CIP 36-~101.,.~i PATENT

~nd they ~ll show a good correlation between the torque and the ~r flow.
Other measurements were ~ade after changing the joint c~nditions. These showed si~ilar ~tart and stop conditions but with a different slope.
Tests were carried out using a joint whose hardness could be varied by including a load cell and gasket material.
Curves showing the hardness characteristics of the joints used are ~hown in ~ig. 5.
The tables o Figs. 6-10 give the results obtained on the joint with load cell (i~e., medium hardness), with preload and breakforward torque with different air pressure. ~he tool is op~rating in stall torque m~de and there is quite a large variation in the results obtained at each pressure level.
However, changing the pressure pr~duces ~ significant change in the initial flow together with a smaller change in the ~l~pe.
The slope changes as ~t i~ measure~ ~ith respect to time rather than angl~, Fig. 9 ~hows the effect of makiny the j~int softer ~i.e., by including a gasket). ~he preload is ~ignificantly changed as i~ the maximum flow gradient. When the joint ifi made hard ~i.e., ~oint only, with no l~ad cell and no gasket~, it was n~ lo~er p~ssible ~o measure the preload. HoweYzr the gradient i6 lncre~ed RS is the torque level.

A:~40~7010~210~\5PSRAN CIP -37-21~19~ ~

PATENT

The monit-Qring and control system of the present invention ~ay al60 ~e used with an impact wrench. Such a configuration is depicted in Fiq. 14 as system 21'. System 21' ~mploy~ an impact wrench 60, ~ flow meter 36~ ~which is conveniently of the same type employed depicted in Fig. 2 for a nutrunner tool), a shut off valv~ 58', and a control computer S2'. Control computer 52' functions in substantially the same manner as the data collection computer 52 used with a nutrunner tool. Preferably, the system also includes an operator interface unit; an operator input and display computer, an input device and a display, in the ~ame manner as for a nutrunner tool. However, for ~i~plicity, these are omitted from Fig. 14.
When the monitoring system of the present invention is used with an impact wrench, additional information, such as detection of impacts, is available This is shown graphically in Figs. 15-17. The individual impacts during tightening ~nd/or untightening ~re clearly shown on theEe graphs ~s peaks on t~e curve of ~ir f low meter output vs~ time. This ~dditlonal lnfoFmation on individual impacts provides a measure of the en~rgy i~parted to the fastener, thus 6implifying ~ control ~y~tem in comparison with a nutrunner tool.
For ex~mple~ à control ~y~tem based on oounting impacts ~mploying ~ control ~-omputer 52' ~ncluding a fiuitably progra~med ~croprooe6~0r could be used which could easily b~ fit~ed to any A:~40~7ClC~2100~SPSR~N~CIP ~3e-~? ~ PATENT
~- ~ ''-"' 407010-2101 i~pact wrench without alteration of the wrench. The wrench would be operated in the normal way, but the control computer 52' would . . .
qenerate a signal after a predetermined number of impacts during t~ghtening had been reached. Thi~ signal would then ~ctivate a ctop valve 58' after t~e predetermined number of impacts had been detected. The unit could have a timed reset or have a separate re~et button for use by the operator. Furthermore, stop valve 58' need not necessarily be of the fast acting type when used with an impact wrench.
An impact wrench has a very different air flow characteristic from a ~AN wrench. See, for example, Fig. 15 (impact wrench) and Fig. 4 (RAN wrench). Different parameterE
and inference rules are used as outlined in Fig. ~1, but the ~ame ~pproach may be taken t~ infer information about the tightening process .
~ The speed of the impact wrench is determined by the impact pul~e height ~nd this deter~ines the amount of energy i~parted to the joint at each impact. The number of pulses are counted and this gives the total energy imparted t~ the j~int during tightening. The presencP ~f a ~low increase of the pulse hei~ht to ~ plateau region indicates a rundown phase, as depicted in ~ig. 15. Its absence indicates a pretightened joint.

A:~4Q\7010~2100~SPSRAN.CIP -39-S ~
PA~ENT

The monitoring ~y6tem of t~e pre6ent invention was applied to a low cost impact wrench manuf~ctured in Japan that did not hnve any man~lfacturer's name or seri~l number. T~e wrench was capable of tightening to torque levels of about lOONm.
Graphs of various tests of the monitoring system applied to this wrench ~re shown in Figs. 15-17. The signals clearly ~how t~e rundown period and also give ~ very clear indication of when t~e unit 6tarts to produce impacts.
There are numerous configurations possible by rearranging the ~ystem level at w~ich the required cystem functions are performed. In the preferred embodiment, the required function6 re ~ense, amplify, digitize, process (generate parameters), compare (apply expert ~ystem rules) and report (to operator, line controller PLC, plant work in process database, statistics processor, tool maintenance database, etc.).
Preferably, the ~ignal i~ also cond~tioned by, for ex~mple, linearization and temperature compensation.
T~e ~tructure and Dperati~n of the monitoring and control 6y~tem of the present invention i~ believed to be fully apparent from the above detailed description. It will be further apparent that changes may be made by person~ ~killed in the art withQut departing from jthe ~pirit of the inYention defîned in the ~ppended cl~i~s.

A:~40~701C~2100~SPSR~N.CIP -40-

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A system for monitoring a fluid driven tool for driving threaded fasteners comprising:
means for measuring fluid flow rate into the tool during operation of the tool;
means for converting said measured fluid flow rate into an electrical signal representative of the magnitude of said fluid flow rate;
means for electrically processing said signal to compute at least one parameter which is a function of said fluid flow rate; and means for displaying said parameter.

2. The system defined in claim 1, wherein said means for measuring said fluid flow rate includes a venturi.

3. The system defined in claim 2, wherein said means for converting said measured fluid flow rate into an electrical signal further includes a transducer arranged so as to detect the differential pressure caused by flow through said venturi.

4. The system defined in claim 3, wherein said means for electrically processing aid signal includes a suitably programmed microprocessor.

5. The system defined in claim 4, wherein said suitably programmed microprocessor is configured to identify a portion of the signal representative of fluid flow rate corresponding to the initial fluid flow rate during rundown of the fastener, prior to commencement of tightening of said fastener.

6. The system defined in claim 5, further including display means for displaying said initial fluid flow rate of at least the most recent tightening.

7. The system defined in claim 6, wherein said display means displays said initial fluid flow rate in n graphical format.

8. The system defined in claim 5, wherein said display means is adapted to simultaneously display the initial fluid flow rate of at least the two most recent tightenings.

9. The system defined in claim 8, wherein said display means displays said initial fluid flow rates in a graphical format.

10. The system defined in claim 5, wherein said suitably programmed microprocessor is configured to calculate the snug point of said fastener as a percentage of said initial fluid flow rate.

11. The system defined in claim 5, wherein said suitably programmed microprocessor is further configured to identify a portion of the signal representative of the fluid flow rate during tightening of the fastener beyond said snug point.

12. The system defined in claim 11, further including display means for displaying said fluid flow rate of at least the most recent tightening.

13. The system defined in claim 12, wherein said display means is adapted to display said fluid flow rate in a graphical format.

14. The system defined in claim 11, wherein said display means is adapted to simultaneously display fluid flow rates for at least the two most recent tightenings.

15. The system defined in claim 14, wherein said display means displays said fluid flow rates in a graphical format.

16. The system defined in claim 11, wherein said suitably programmed microprocessor is further configured to calculate a rate of change of the fluid flow rate during tightening of the fastener beyond said snug point, and to determine maximum and minimum rates of change during said tightening.

17. The system defined in claim 16, further including display means for displaying said minimum and maximum rates of change of the fluid flow rates for at least the most recent tightening.

18. The system defined in claim 17, wherein said display is adapted to display said minimum and maximum rates of change an a graphical format.

19. The system defined in claim 17, wherein said display means is adapted to simultaneously display said minimum and maximum rates of change of the fluid flow rates for at least the two most recent tightenings.

20. The system defined in claim 19, wherein said display is adapted to display said minimum and maximum rates of change in a graphical format.

21. The system defined in claim 17, wherein said display is adapted to simultaneously display said minimum and maximum rates of change and said initial fluid flow rate for at least the most recent tightening.

22. The system defined in claim 21, wherein said display is adapted to simultaneously display said minimum and maximum rates of change and said initial fluid flow rate for at least the most recent two tightenings.

23. The system defined in claim 22, wherein said display is adapted to simultaneously display said minimum and maximum rates of change and said initial fluid flow rates in a graphical format.

24. The system defined in claim 5, wherein said suitably programmed microprocessor is configured to determine whether said initial fluid flow rate is within predetermined values.

25. The system defined in claim 24, further including indicating means for indicating whether said initial fluid flow rate is within predetermined values.

26. The system defined in claim 11, wherein said suitably programmed microprocessor is configured to determine whether said fluid flow rate during tightening is within predetermined values.

27. The system defined in claim 26, further including indicating means for indicating whether said fluid flow rate during tightening is within predetermined values.

28. The system defined in claim 16, wherein said suitably programmed microprocessor is configured to determine whether said rate of change of said fluid flow rate during tightening is within predetermined values.

25. The system defined in claim 28, further including indicating means for indicating whether said rate of change of said fluid flow rate during tightening is within predetermined values.

30. The system defined in claim 28, further including indicating means for indicating whether rundown time during initial tightening is within predetermined values.

31. The system defined in claim 5, further including indicating means for indicating whether a plurality of parameters which are functions of time and rate of fluid flow during rundown and/or tightening Are within predetermined values.

32. A system for monitoring a fluid driven impact wrench for driving threaded fasteners comprising:
means for measuring the fluid flow rate into the wrench during operation of the tool;
means for converting the measured fluid flow rate into n electrical signal;
means for electrically processing said signal to compute at least one parameter which is a function of said fluid flow rate; and means for displaying said parameter.

33. The system defined in claim 32, wherein said means for processing said electrical signal further comprises means for counting fluid flow peaks corresponding to individual impacts of said wrench.

34. The system defined in claim 33, wherein said means for processing said electrical signal further comprises means for calculating the torque applied by the wrench during tightening by counting fluid flow peaks corresponding to individual impacts of said wrench.

35. The system defined in claim 34, wherein said means for processing said electrical signal further comprises means for generating a signal after a predetermined number of impacts during tightening has been reached.

36. The system defined in claim 35, further comprising means for shutting off fluid to said wrench in response to said signal.

37. A method for monitoring a fluid driven tool for driving threaded fasteners comprising the steps of:
measuring the fluid flow rate into the tool during operation of the tool;
converting the measured fluid flow rate into an electrical signal representative of the magnitude of said fluid flow rate;
electrically processing said signal to compute at least one parameter which is a function of said fluid flow rate; and displaying said parameter.

38. The method defined in claim 37, wherein said processing includes mathematical processing by a suitably programmed microprocessor.

39. The method defined in claim 38, further including the step of identifying a portion of the signal representative of fluid flow rate corresponding to the initial fluid flow rate during rundown of the fastener, prior to commencement of tightening of said fastener.

40. The method defined in claim 39, further including the step of displaying said initial fluid flow rate of at least the most recent tightening.

41. The method defined in claim 40, wherein said initial fluid flow rate is displayed in a graphical format.

42. The method defined in claim 40, wherein said displaying includes simultaneous display of the initial fluid flow rate of at least the two most recent tightenings.

43. The method defined in claim 42, wherein said initial fluid flow rates are displayed in a graphical format.

44. The method defined in claim 39, further including calculation on a suitably programmed microprocessor of the snug point of said fastener as a percentage of said initial fluid flow rate.

45. The method defined in claim 39, further comprising the step of identifying a portion of the signal representative of the fluid flow rate during tightening of the fastener beyond said snug point.

46. The method defined in claim 45, further including the step of displaying said fluid flow rate of at least the most recent tightening.

47. The method defined in claim 46, wherein said fluid flow rate is displayed in a graphical format.

48. The method defined in claim 45, wherein said displaying includes simultaneous display of fluid flow rates for at least the two most recent tightenings.

49. The method defined in claim 48, wherein said flow rates are displayed in a graphical format.

50. The method defined in claim 45, further including the step of calculation of a rate of change of the fluid flow rate during tightening of the fastener beyond said snug point, and the step of determining the minimum and maximum rates of change during said tightening.

51. The method defined in claim 50, further including the step of displaying said minimum and maximum rates of change of the fluid flow rates for at least the most recent tightening.

52. The method defined in claim 51, wherein said minimum and maximum rates of change are displayed in a graphical format.

53. The method defined in claim 51, wherein said di playing includes simultaneous display of the minimum and maximum rates of change of the fluid flow rates for at least the two most recent tightenings.

54. The method defined in claim 53, wherein said minimum and maximum rates of change are displayed in a graphical format.

55. The method defined in claim 51, wherein said displaying includes simultaneous display of said minimum and maximum rates of change and said initial fluid flow rate for at least the most recent tightening.

56. The method defined in claim 55, wherein said displaying includes simultaneous display of said minimum and maximum rates of change and said initial fluid flow rate for at least the most recent two tightenings.

57. The method defined in claim 56, wherein said displaying includes simultaneous display of said minimum and maximum rates of change and said initial fluid flow rates in a graphical format.

58. The method defined in claim 39, further including the step of determining whether said initial fluid flow rate is within predetermined values.

59. The method defined in claim 58, further including the step of indicating whether said initial fluid flow rate is within predetermined values.

60. The method defined in claim 45, further including the step of determining whether said fluid flow rate during tightening is within predetermined values.

61. The method defined in claim 60, further including the step of indicating whether said fluid flow rate during tightening is within predetermined values.

62. The method defined in claim 50, further including the step of determining whether said minimum and maximum rates of change of said fluid flow rate during tightening are within predetermined values.

63. The method defined in claim 62, further including the step of indicating whether said minimum and maximum rates of change of said fluid flow rates during tightening are within predetermined values.

64. The method defined in claim 62, further including the step of indicating whether rundown time during initial tightening is within predetermined values.

65. The method defined in claim 39, further including the step of indicating whether a plurality of parameters which are functions of time and rate of fluid flow during rundown and tightening are within predetermined values.

66. A method for monitoring a fluid driven impact wrench for driving threaded fasteners comprising:
measuring the rate of fluid flow into the wrench during operation of the tool;
converting the measured fluid flow rate into an electrical signal;

electrically processing said signal to compute at least one parameter which is a function of said fluid flow rate; and displaying said parameter.

67. The method defined in claim 66, further including the step of counting fluid flow peaks corresponding to individual impacts of said wrench.

68. The method defined in claim 67, further comprising the step of calculating the torque applied by the wrench during tightening by counting fluid flow peaks corresponding to individual impacts of said wrench.

69. The method defined in claim 67, further comprising the step of generating a signal after a predetermined number of impacts during tightening has been reached.

70. The method defined in claim 69, further comprising the step of shutting off fluid to said wrench in response to said signal.

71. A system for controlling a fluid driven impact wrench for driving threaded fasteners comprising:
means for measuring the rate of fluid flow into the wrench from a fluid supply during operation of the tool;
means for converting the measured fluid flow rate into an electrical signal;
means for electrically processing said signal to count the number of blows delivered by the wrench;

means for shutting off the fluid supply to the tool when a predetermined number of blows have been delivered and means for displaying the number of blows counted.

72. A system for monitoring a fluid driven tool for driving threaded fasteners comprising:
means for measuring fluid flow rate into the tool during operation of the tool;
means for converting said measured fluid flow rate into an electrical signal representative of the magnitude of said fluid flow rate;
means for electrically processing said signal to compute at least one parameter which is a function of said fluid flow rate;
means for displaying said parameter;
means for recording said at least one parameter for a series of tightenings during normal conditions, means for statistically processing said at least one parameter to compute appropriate limits for said normal conditions for said at least one parameter;
means for storing said limits;
means for statistically processing said parameter computed during subsequent tightenings to identify trends or deviations from said normal conditions and means for notifying an operator of such trends or deviations.

73. The method defined in 37, further comprising recording said at least one parameter for a series of tightenings during normal conditions;
statistically processing said at least one parameter to compute appropriate limits for said normal conditions for said at least one parameter;
storing said limits into storage means;
statistically processing said parameter computed during subsequent tightenings to identify trends or deviations from said normal conditions and notifying an operator of such trends or deviations.

74. A system for monitoring a fluid driven tool for driving threaded fasteners comprising:
means for measuring fluid flow rate into the tool during operation of the tool;
means for converting said measured fluid flow rate into an electrical signal representative of the magnitude of said fluid flow rate;
means for electrically processing said signal to compute at least one parameter which is a function of said fluid flow rate;

means for comparing said at least one parameter to predetermined expected parameters to infer a process condition relating to said fluid driven tool; and means for reporting said inferred process condition.

75. The system defined in claim 74 wherein said at least one parameter includes the rundown speed of the tool.

76. The system defined in claim 75 wherein said means for comparing is configured to detect at least high speed, low speed, outside low speed limit, and normal rundown speed conditions.

77. The system defined in claim 74 wherein said at least one parameter further includes the rate of decrease of tool speed during tightening.

78. The system defined in claim 77 wherein said means for comparing is configured to detect at least hard rate of decrease, soft rate of decrease, outside rate of decrease limit, and normal rate of decrease conditions.

79. The system defined in claim 74 wherein said means for reporting further includes means for reporting at least one probable cause of said inferred process condition.

80. The system defined in claim 74 wherein said means for comparing employs a forward chaining rule based expert system.

81. The system defined in claim 74 wherein said means for comparing employs a fuzzy logic based expert system.

82. The system defined in claim 74 wherein said means for reporting is an alpha numeric display.

83. A system for monitoring a fluid driven impact wrench for driving threaded fasteners comprising:
means for measuring the fluid flow rate into the wrench during operation of the tool;
means for converting the measured fluid flow rate into an electrical signal;
means for electrically processing said signal to compute at least one parameter which is a function of said fluid flow rate;
means for displaying said parameter;
means for comparing said at least one parameter to predetermined expected parameters to infer a process condition relating to said fluid driven tool; and means for reporting said inferred process condition.

84. The system defined in claim 83 wherein said at least the parameter includes the rundown speed of the tool.

85. The system defined in claim 84 wherein said means for comparing is configured to detect at least high speed, low speed, outside low speed limit, and normal rundown speed conditions.

86. The system defined in claim 83 wherein said means for processing said electrical signal further comprises means for counting fluid flow peaks corresponding to individual impact pulses of said wrench and said at least one parameter further includes the number of impact pulses during tightening.

87. The system defined in claim 86 wherein said means for comparing is configured to detect at least high number of impact pulses, low number of impact pulses, no impact pulses, and normal number of impact pulses during tightening.

88. The system defined in claim 83 wherein said means for reporting further includes means for reporting at least one probable cause of said inferred process condition.

89. The system defined in claim 83 wherein said means for comparing employs a forward chaining rule based expert system .

90. The system defined in claim 83 wherein said means for comparing employs a fuzzy logic based expert system.

91. The system defined in claim 83 wherein said means for reporting is an alpha numeric display.

92. A system for monitoring a fluid driven tool for driving threaded fasteners comprising:
venturi means for measuring fluid flow rate into the tool during operation of the tool based, said venturi means including and a first and second upstream pressure connection and a throat pressure connection;
a sealed housing, said sealed housing having means connecting to said first upstream pressure connection so that the interior of said housing is maintained at substantially said upstream pressure;
transducer means for converting said measured fluid flow rate into an electrical signal representative of the magnitude of said fluid flow rate, said transducer means including respective means connecting to said second upsteam pressure connection and said throat pressure connection, said transducer means being disposed within said sealed housing;
means for electrically processing said electrical signal to compute at least one parameter which is a function of said fluid flow rate; and means for displaying said parameter.

93. A system for monitoring a fluid driven tool for driving threaded fasteners comprising:
means for measuring fluid flow rate into the tool during operation of the tool;
means for converting said measured fluid flow rate into an amplified electrical signal representative of the magnitude of said fluid flow rate;

means for electrically processing said amplified signal to compute at least one parameter which is a function of said fluid flow rate; and means for displaying said parameter.

94. The method defined in claim 93 wherein said amplified electrical signal is also conditioned.

95. The method defined in claim 94 further including digitizing said amplified and conditioned electrical signal.

96. A method for monitoring a fluid driven tool for driving threaded fasteners comprising the steps of:
measuring fluid flow rate into the tool during operation of the tool;
converting said measured fluid flow rate into an electrical signal representative of the magnitude of said fluid flow rate;
electrically processing said signal to compute at least one parameter which is a function of said fluid flow rate;
comparing said at least one parameter to predetermined expected parameters to infer a process condition relating to said fluid driven tool and;
reporting said inferred process condition.

97. The method defined in claim 96 wherein said at least one parameter includes the rundown speed of the tool.

98. The method defined in claim 97 wherein said comparing detects at least high speed, low speed, outside low speed limit, and normal rundown speed conditions.

99. The method defined in claim 96 wherein said at least the parameter further includes the rate of decrease of tool speed during tightening.

100. The method defined in claim 96 wherein said comparing detects at least hard rate of decrease, soft rate of decrease, outside rate of decrease limit, and normal rate of decrease conditions.

101. The method defined in claim 96 wherein said reporting further includes reporting at least one probable cause of said inferred process condition.

102. The method defined in claim 96 wherein said comparing employs a forward chaining rule based expert method.

103. The method defined in claim 96 wherein said comparing employs a fuzzy logic based expert method.

104. The method defined in claim 96 wherein said reporting includes alpha numeric displaying.

105. A method for monitoring a fluid driven impact wrench for driving threaded fasteners comprising the steps of:
measuring the fluid flow rate into the wrench during operation of the tool;

converting the measured fluid flow rate into an electrical signal;
electrically processing said signal to compute at least one parameter which is a function of said fluid flow rate;
displaying said parameter;
comparing said at least one parameter to predetermined expected parameters to infer a process condition relating to said fluid driven tool; and reporting said inferred process condition.

106. The method defined in claim 105 wherein said at least one parameter includes the rundown speed of the tool.

107. The method defined in claim 106 wherein said comparing detects at least high speed, low speed, outside low speed limit, and normal rundown speed conditions.

108. The method defined in claim 105 wherein said processing of said electrical signal further comprises counting fluid flow peaks corresponding to individual impact pulses of said wrench and said at least one parameter further includes the number of impact pulses during tightening.

109. The method defined in claim 107 wherein said comparing detects at least high number of impact pulses, low number of impact pulses, no impact pulses, and normal number of impact pulses during tightening.

110. The method defined in claim 105 wherein said reporting further includes reporting at least one probable cause of said inferred process condition.

111. The method defined in claim 105 wherein said comparing employs a forward chaining rule based expert method.

112. The method defined in claim 105 wherein said comparing employs a fuzzy logic based expert method.

113. The method defined in claim 105 wherein said reporting includes alpha numeric displaying.