US3038979A - Control apparatus - Google Patents

Description

June 12, 1962 F. F. YANIKOSKI 3,038,979

CONTROL APPARATUS Filed Aug. 19. 1957 4 sheets-sheet 1 June 12, 1962 F. F. YANIKOSKI 3,038,979

CONTROL APPARATUS Filed Aug. 19. 195? 4 Sheets-Sheet 4 uifips' Z; 8 51 7am 78a 13200282308 fi'iofiiwzlimsfdi,

United States Patent Oflice 3,038,979 Patented June 12, 1962 3,038,979 CONTROL APPARATUS Florian F. Yanikoski, Natick, Mass., assignor to Fenwal Incorporated, Ashland, Mass, a corporation of Massachusetts Filed Aug. 19, 1957, Ser. No. 679,010 12 Claims. (Cl. 200-140) This invention relates generally to control apparatus and more particularly to devices for the automatic control of temperature, pressure, or other independent variable. The apparatus of the invention senses and indicates the condition or position being controlled, and functions responsive to variable change at the control or set point to control or operate the remote device by which the variable is regulated. The invention aims to provide an indicating controller which is of simple, uniform design and compact, economical construction, while also efficient and accurate in operation and versatile and flexible in application. A further object of the invention is to provide an indicating controller which is designed for long life and easy, certain manipulation and adjustment. The invention will be better understood from a consideration of the following specification taken in conjunction with the accompanying drawings in which:

FIG. 1 is an assembly view of the invention controller, shown as fitted for temperature control;

FIG. 2 is a larger scale, partly sectioned elevation of the hydraulic actuator;

FIG. 3 shows the housing from the front and with the cover removed;

FIG. 4 is a left side view along the line 4-4 of FIG. 3;

FIG. 5 is a right side view taken along the line 55 of FIG. 3;

FIG. 6 is a top view of the controller as seen with the cover and switch chamber removed;

FIG. 7 is a detailed View, on a larger scale, of the lever mounting;

FIG. 8 is a perspective view with the housing ,broken away to show the switch control mechanism;

FIGS. 911 are like views of modified forms of the switch control mechanism; and

FIG. 12 shows a modification of the invention as adapted for pressure control.

The controller of this invention may be characterized as a control switch with indication of the condition or position of the variable to be controlled, and with calibrated indication also of the set point. It combines means generating a control or expansion-contraction movement responsive to change of the variable being controlled; a switch for controlling a remote variable regulating device; and a control linkage or lever mechanism positionally relating the variable sensing or actuator means and the switch for desired set point operation of the remote device. The controller indication of temperature, pressure, or position correlated with that of the set point, and dial and pointer means are provided for adjusting the set point to any position in the control range.

Referring now to FIG. 1, the clean, compact design of the invention controller is seen in the enclosure and support of the entire apparatus in and from a single small box or housing 15. The controller housing 15 may be of rigid metal construction and is integral except for the removable front and top covers 16, 17 which latter are sealed by gaskets or the like to make the housing splash and dust proof. Brackets 18 may be provided for attaching the box 15 to a wall or like support, or the apparatus may be otherwise fitted as for flush mounting.

The invention controller is designed also for mounting the switch in a fixed position, and so placed that its terminals may be directly connected to the remote temperature regulating means, thereby saving the space and the labor and material cost of a separate external terminal block and connecting wiring. Accordingly, the controller housing is partitioned to provide a switch chamber 19 located beneath the top of the box 15, and a precision snap switch 20 is supported in this chamber with its terminals 21 underlying and for easy access upon removal of the top cover 17. The switch chamber 19 is seen as completely closed off from the remainder of the box except for a bottom wall opening 19a, FIG. 4, exposing the switch button 22 for engagement by the control mechanism. Thus a protective barrier is provided whereby the opening into the chamber 19 for wiring to the terminals 21 affords no risk of injury to the rest of the controller mechanism.

The switch 20 is provided also and at its ends with mounting brackets 23 clamped, as at the bottom wall of the chamber 19, by nut and bolt or the like fastenings 24, one or more of which, as the spring clamping screw 24a, may be vertically adjusting, as for desired positioning relative to the switch control mechanism.

Referring now to FIG. 2, for temperature control the invention apparatus incorporates an hydraulic actuator comprising a closed, sealed fluid system consisting of a probe or bulb 25 adapted to be mounted in or for exposure to the space or process to be controlled and connected by a capillary tube 26 to the operating or motor bellows. For strength and corrosion resistance the bulb 25 is of stainless steel, while for economy the tube 26 may be fashioned of nickel plated copper. The motor bellows consists of an annular block 27 apertured to receive the capillary 26 and also the filling tube 28, and having an upstanding tubular stem 29. A bellows 30 is received over and sealed at its lower end to an annular flange 29a at the base of said stem 29. Telescoping within it is a pin or push rod 31 having an upwardly projecting rounded head or contact 31a and beneath it an annular flange 31b overlying the upper end of stem 29 and to which the upper end of bellows 30 is sealed.

Calibration rate adjustment, compensating for unavoidable diiferences in bellows activity, is aiforded the invention controller by mounting the hydraulic actuator for shift entire to the right or left of the controller housing, for varying the efiective length of the lever arm of the control mechanism which is engaged by the actuator push rod. The actuator motor bellows is seen more particularly to be supported in an actuator housing or tube 32 fixed or welded at its upper end to a lateral mounting flange 33 such as adapting it for support as by bolts or the like fastenings 34 at the base of the controller housing 15. An economical and accessible lateral adjustment of the flange 33 is provided by forming in the housing bottom Wall an elongated slot 35 receiving the fastenings 34 and also the actuator push rod. The slot is sealed at its outer face by a rubber gasket 36 clamped under flange 33, and it is interiorly covered by a smooth sliding nut plate 37 to which the fastenings 34 are secured and which in combination with the flange and gasket 33, 36 afford the desired sealing of the housing 15 and accuracy of the calibration rate adjustment. The accurate rate adjustment is seen to flow from the co-action of the nut plate 34 with the housing bottom wall, which plate and wall may be smooth surfaced, and will have a smooth sliding engagement assuring the desired shift of the actuator housing 32 in parallelism with said bottom wall.

Economical and exterior calibration offset adjustment is also provided the invention controller, herein by olfset adjustor nut 38 threaded in the end of housing 32 and having the desired swivelling and supporting fit over the block 27. The adjustor nut 38 is seen to be fixed in any desired vertical or ofi'set position by means of lock nut 38a threaded over the same and turned up to bind against the end of tube 32.

The actuator fluid system 25, 26, will be understood to be filled through the tube 28 with a suitable liquid, as for example normal propyl alcohol, which expands predictably on heating. Expansion of the system is of course expressed as the elongation of bellows 30 and the advance or upward movement of push rod 31. The rod head 31a is seen to engage a bearing plate 3 9. A main spring is compressed between housing flange 33 and the opposite face of the bearing plate and so as to stiffen or bias the motor bellows for reliable return, and more generally for sensitive and accurate two Way response.

Further in accordance with the invention, ambient compensator means are provided which are arranged as an integral part of the hydraulic actuator and for sealing within actuator housing 32, and herein comprising a small or compensator bellows 41 which is inverted, or mounted for expansion oppositely to the motor bellows by support at its upper end from a tube 42 supported on hearing plate 39. The lower end of bellows 41 is seen as connected to the actuator force transmitting assembly, which comprises U strap 43 interfitting, as through the slots 4211, with tube 42 and mounting a sleeve or tube 44 telescoping with said tube 42 and closed at its upper end by a plug or pin 45. A smaller or ambient compensator spring 46 is compressed between actuator pin and the tube 42 for return movement of bellows 41, and a fill tube 47 may be mounted through one of the bellows end supports.

Compensating bellows 41 will be understood to act to offset or cancel the expansion of the motor bellows 3t), and so to prevent false output motion of the actuator pin 45, under conditions of slow heating, or ambient temperature change. It will be appreciated also that variation in the hydraulic actuator activity, such as flowing from modification of the capillary tube 26 length and volume, or from change of the filling liquid, requires a corresponding variation in the activity of the compensator. This may be accomplished by changing either the compensator length or the compensator liquid, or both. However, it is convenient to standardize on the same bellows 41, and there is a limited choice of suitable liquids.

Accordingly, additional compensator activity adjusting means are employed by the invention controller and comprise one or more, herein three, steel or the like balls 48 having a low coeflicient of expansion and deposited in the bellows 41. The balls 48 will be understood to desensitize the compensator fluid, so that by the use of a selected number of the balls, and for the same compensator bellows length and liquid fill, a certain desired adjustment of the compensator activity may be had.

The switch controlling and actuating mechanism of the invention comprises a unique differential device providing a flexible linkage which allows the switch to remain in a fixed position, and which is conditioned also for prompt and accurate control movement. The differential has a first input or lower lever or plate 49 welded or otherwise fixed near its one, herein right hand, end by a lateral pivot rod or shaft 50 engaging a bracket 51 mounted at the base of the housing 15 and having upstanding arms 52 receiving the shaft ends. The plate 49 is seen to extend laterally from said bracket 51 to overlie housing bottom opening 35 for engagement of its longer, herein left hand, lever arm by actuator pin 45.

Above and aligned with lever 49 is the output or upper lever 54, which is conveniently formed as a vertical bar, as shown. The bar 54 is pivoted on a rod or shaft 55 passed through its right hand end and supported by a bracket 56 paralleling bracket 51. The bracket 56 is mounted at the bottom wall of switch chamber 19 and for receiving the shaft 55 ends through its downwardly extending arms 57. The upper lever 54 is seen to extend beneath switch chamber 19 in the similar generally horizontal attitude as lower lever 49 projects over the housing bottom, and so as to underlie the opening through which the switch button 22 is exposed.

One disadvantage of the usual annular shaft bearing finished to the usual manufacturing tolerance is that the shaft tends to climb or roll around the bearing before starting to slip in position. The lever shaft bearings of this invention are made independent of manufacturing tolerances and are assured desired centering and repeatability by forming in the bracket arms 52, 57 the upwardly and downwardly inclined notches or slots 53, 58 of a width slidably to receive the shafts 50, 55 and defined at their ends by formations 53a, 58a characterized by straight sides intersecting at an angle to provide the desired two-point contact with the same. The lever shafts 5t), 55 are clamped against the non-round bearing formations 53a, 58a by a spring 59 stretched between the short or right hand lever arms and having the further functions as hereinafter mentioned. The levers 49, 54 pivots will be understood by this spring clamping and two-point bearing support to be accurately positioned regardless of the wide tolerance which may be given the slots 53, 58, and to be positively held against shift of the shafts 50, 55 in the bearing formations 53a, 58a.

The second input of the differential switch control device of the invention is seen as an adjusting shaft 60 mounted intermediate the lower and upper levers 49, 54 and for projection through front cover 16, there to mount externally accessible manipulating knob 61. The adjusting shaft 60 has rotary bearings which are free of undesired backlash effects, and which comprise at the front bearing a lateral block 62 apertured to receive the shaft and fixed to a block 63 extending rearwardly to the back wall of housing 15 and supported there as by screw fastenings 63a. Tolerances in the front bearing are taken up by a nylon plug 64 and set screw 65 received in a block 62 bore passage intersecting the shaft 60 opening therein. It will be appreciated that when set screw 65 is turned down on plug 64 sufiiciently to hold shaft 60 securely in position, it serves additionally to subject the shaft to desired looking or braking action.

Desired dust proof sealing of housing 15 is preserved at front projecting shaft 60 by sealing the same with one or more soft rubber doughnuts 66 snugly embracing the shaft, and which are ordered for even closer fit by their compression between the front cover 16 and the lateral block 62.

At the rear end of adjusting shaft 60 is a needle hearing which is pretensioned automatically, requiring no adjustment for the purpose, and which comprises a flat spring 67 clamped at its one end between the block 63 and the housing rear wall. The spring strap 67 is bent outwardly at its free end, FIG. 6, and is there apertured for reception over the adjusting shaft, and more particularly for engagement against a tapered or conical seat 60a formed on said shaft 60. The rear bearing of the adjusting shaft is thus positively held in and uniformly centered to the desired operating position.

Further in accordance with the invention, the differential inputs, namely lever 49 and adjusting shaft 60, are coupled to the output, namely lever 54 by a deformable linkage capable of deflecting or releasing on overtravel of the variable sensing or actuator means, and herein comprising a flexible non-extensible metal band 68 which is wound and welded at its one end around a stiff wire 69 supported as by clamps 70 at the end of the lower lever 49. For engagement with the band 68 and also with the switch 20, the upper lever 54 mounts a fixed plastic or other substantially frictionless pulley 71 to which is conveniently applied the upwardly projecting cam 72 by which the movement of the upper lever is transmitted to the switch 20, and which has an arm 72a hooked over the pulley 71 and for engaging switch button 22, FIGS. 4, 5 and 8. The metal band 68 is seen to be passed over the fixed pulley 71 and arranged for winding on adjusting shaft 60 by reception at its other end on a stud 73a projecting radially of a pulley 73 keyed to, said shaft 60.

For calibrated set point indication there is provided a pointer 74 supported from a pulley 75 keyed to the adjusting shaft, which pointer extends to the rear of and has a conical tip 74a turned down over the face of a temperature scale 76 supported in box and for viewing through a transparent panel 16a in the front cover 16. For temperature, pressure, or position indication there is provided a pointer 77 having a tip 77a extending upwardly over the face of scale 76 in opposition to tip 74a. The pointer 77 is supported on a pulley 78 loose on shaft 60 and driven or made to follow the switch actuator movement by a metal band 79 having its one end fixed to wire 69 and its other end received on a pulley stud 78a. A spring 80 stretched between the base of the box 15 and a stud 78b at the opposite side of pulley 78 from said stud 78a tensions the pulley and said band 79 for desired accurate positioning of the indicating pointer 77.

Referring still to the differential switch control mechanism, the same will be understood to incorporate also the aforementioned lever setting spring 59, which is seen to form a closed loop with the flexible linkage 67. In addition to taking up slack in the lever pivot bearings the spring 59 is thus seen to subject the band 68 to a tension which, while it allows overtravel beyond the control setting without subjecting the snap switch to excessive forces, still maintains the linkage sufliciently taut to provide accuracy of control action and eliminate back-lash effects. It will be appreciated also that the floating support or loop closing arrangement of the spring 59 provides a tension ing which is constant throughout the range of control action.

The invention is characterized also by the mounting of the same spring 59 for accomplishing still another function, namely, biasing the control linkage downwardly against and for following or return movement in contact always with actuator pin 45. To this end the spring 59 is fastened to the lower lever 49 at a greater distance from the lever pivot or fulcrum than on the upper lever 54. This will be seen to unbalance the loop, and permit the spring 59 to drive the linkage to the position of shortest spacing of the right hand lever arms. With the described spring arrangement the right hand lever arms move upwardly to close, so that the action of spring 59 is to drive the left hand lever arms as deisred to their lowermost or actuator pin engaging position.

The simplicity of design and versatility of application of the invention controller is further shown in the modified forms of FIGS. 91 1. It may be desired for example to control a process at one temperature and also to actuate a remote alarm or safety device when the process is heated to a higher or overheat temperature. For this twoswitch control with fixed temperature differential it is necessary only to mount an overheat alarm switch 81 in the chamber 19 along side process control switch to pivot a lever 82 on shaft 55 beside lever 54; to tension the lever by a spring 83 stretched between it and the lever 49; and to adapt said lever 82 for difierential actuation of said switch 81 by a bent strap 84 secured to the lever end and having an arm 84a engaging the switch contact button and an arm 84b engaging at its underface fixed pulley 71. A set screw 85 threaded through strap 84 and bearing against the pulley may also be provided for fine adjustment of the temperature differential.

Referring now to FIG. 10, if it is desired to provide visual indication of the differential temperature at which the controller is set to actuate overheat switch 81, there may be employed in lieu of lever 82 a lever 86 duplicating lever 54 and positioned similarly by a band 8 7, which band is fastened to Wire 69, passed over fixed pulley 88, and secured to adjusting shaft pulley 89 mounting overheat indicating pointer 90.

Still another adaptation of the invention controller is shown in FIG. 11 to comprise an adjusting shaft 91 mounted at the opposite side of block 63 from pulley 89, and supported front and rear by a block 92 and spring 93 duplicating, herein integrally, block 62 and spring 67. The overheat setting or adjusting shaft 91 is seen to be coupled by a metal band 94 to a pulley 95 integral with or secured to and for controlling the orientation of pulley 75. This described arrangement will be understood to provide independent external setting as well as indication of the process and overheat control temperatures.

The operation of the invention apparatus will be readily appreciated by those skilled in the art to be one in which the actual temperature cycles about the set point temperature. That is, upon temperature increase above the set point the motor bellows 30 expands and drives the control linkage 49, 68, 54 so as to engage by the cam 72 the switch button 22. The shifting of the switch 20 between the normally open or closed positions makes or breaks the circuit by which the remote process control means, which may be a heater or refrigerator, or more particularly a gas or steam valve, is governed. Lowering of the process temperature to below the set point is reflected at the controller by contraction of the bellows 30, with following movement of the control linkage, and thereby release of the switch 20 for return to its normal position.

It will be understood that the invention apparatus may be adapted for the control of variables other than temperature merely by change or substitution of the variable sensing or actuator means. In FIG. 12 the controller is shown as fitted for pressure control, and to have a housing or chamber 96 supported beneath box 15 in the similar fashion as housing 32. Chamber 96 is fitted with a tube 97 for communication with the apparatus or system whose pressure is to be controlled and indicated. A bellows 98 is sealed in chamber 96, and more pa ticularly clamped at its outer end between the housing and the bottom wall of control box 15 and for vertical shifting of its free lower end responsive to pres sure changes. The bellows movement is transmitted by an actuator or push rod 99 having a stem 99a projecting through the bottom wall opening to engage lever 49, and having a flange 99b to which the bellows lower end is sealed. For return movement of the bellows a calibrated spring 100 is mounted between the control box 15 and said actuator flange 9912.

From the foregoing it will be appreciated that the controller may without departing from the invention be fitted for control of still other variables, as for example position. For controlling position, as for example the position of a valve stem of an air, steam, or water-flow control apparatus there need be provided only a simple actuator linkage to the lower lever 49 from and for movement of the lever directly by the valve stem.

From the foregoing it will be appreciated also that the present invention provides a controller characterized by a unique combination of advantageous features, and by a design which is as simple as the several functions of the apparatus will allow. More particularly, it is distinguished by the arrangement of the switch in a fixed position and with its terminals accessible for connection directly to the external control device, and without risk of injury to the controller mechanism. The invention controller is improved further by a flexible linkage providing overtravel release, and also coupled and tensioned for positive positioning and repeatability, and freedom from backlash effects,

The invention apparatus has been shown still further to be distinguished by convenient and economical calibration and offset rate adjusting means, by unique compensator activity adjusting means, and by single spring means providing the control mechanism tensioning and centering and overtravel release.

The simplicity and versatility of the invention controller is shown finally by its modification from oneto two-point control and indication with maximum use of standard and minimum number of added parts.

It will he understood that my invention is not limited to the particular embodiments thereof illustrated and de scribed herein, and I set forth its scope in my following claims.

I claim:

1. In a controller of the class having an independent variable sensing actuator and a remote device regulating switch, a differential switch control comprising a first input means engaged and shittable by said actuator, a second input means including a control point adjusting element, an output member engaging and to shift said switch, flexible non-extensible linkage interconnecting said first and second input means and said output member such that the shift switching movement of said output member is the sum of the input movements and resilient means engaged btwn two of said input and output means and member and to tension said linkage whereby the movement of said input means is transmitted through said linkage to said output member.

2. In a controller of the class having an independent variable sensing actuator and a remote device regulating switch, a difierential switch control comprising a first input means engaged and shiftable by said actuator, an output member engaging and to shift said switch, a second input means intermediate said first input means and said output member, said second input means including a control point adjusting element, a strap fastened at its ends to said first and second input means and passed intermediately around said output member and resilient means engaged between two of said input means and output member and to tension said linkage whereby the movement of said input means is transmitted through said linkage to said output member.

3. In a temperature controller, an actuator, a switch, a differential device engaged by said actuator and con trolling said switch and including a lever member engaging at an arm with one of said actuator and switch members, and means for pivotally mounting said lever member comprising a pivot pin on said member, rotary bearings for said pin, and two-point contact recesses on said bearings.

4. In a temperature controller, an actuator, a switch, a differential device engaged by said actuator and controlling said switch and including a lever member engaging at an arm with one of said actuator and switch members, and means for pivotally mounting said lever member comprising a pivot pin on said member, rotary bearings for said pin, two-point contact recesses on said bearings, and spring means clamping said pin in said bearings and biasing said lever for return movement with said actuator.

5. In a controller having an actuator and a switch, a lever engaged at an arm and driven by said actuator, a lever controlling said switch, parallel pivots for said levers, a flexible strap linking said levers at one side of said pivots, and spring means stretched between said levers at the other side of said pivots and biasing the levers for return movement with said actuator.

6. In a controller, a pivotal lever providing by its arm a first shiftable input means, a rotary shaft arranged as a second shiftable input means, a shiftable output member, flexible non-extensible means differentially linking said input means with said output member, and resilient means engaging said input means and output member to tension said flexible non-extensible means.

7. A controller according to claim-6 wherein said flexible non-extensible means is a tape having reverse passing engagement with one and being secured to the others of said input means and output member.

8. In a controller, a lever having an arm arranged as a pivoted input means, a shaft constituting a rotary input means, a shiftable output member, a flexible tape passed reversely over the output member and secured to said lever arm and shaft input means, and resilient means engaging said input means and output member to tension said flexible tape.

9. The apparatus of claim 1 wherein said contrnl point adjusting element is manipulable to change the effective length of said flexible non-extensible linkage.

10. In a controller having an independent variable sensing actuator and a remote device regulating switch, a lever engaged at an arm and driven by said actuator, a lever engaging at an arm and for controlling said switch, flexible non-extensible linkage connected between said arms of said levers, and means engaged at arms of and biasing the levers so as to tension said linkage.

11. The apparatus of claim 10 wherein said flexible non-extensible linkage is a metal strap.

12. The apparatus of claim 10 wherein said linkage tensioning means is arranged to bias said levers also to follow return movement of said actuator.

References Cited in the file of this patent UNITED STATES PATENTS 436,604 James Sept. 16, 1890 974,991 Radigan Nov. 8, 1910 1,092,971 Burlog Apr. 14, 1914 1,556,862 McKissick Oct. 13, 1925 1,651,629 Phelan Dec. 6, 1927 1,829,117 Stover Oct. 27, 1931 1,848,749 Reichold Mar. 8, 1932 2,025,670 Pettee Dec. 24, 1935 2,053,974 Smith Sept. 8, 1936 2,064,644 Woodworth Dec. 15, 1936 2,065,702 Hubbard Dec. 29, 1936 2,069,727 Spencer Feb. 2, 1937 2,314,211 Hausler Mar. 16,. 1943 2,393,841 Titcomb Jan. 29, 1946 2,460,695 Hennessy Feb. 1, 1949 2,466,820 Oberschmidt Apr. 12, 1949 2,487,213 Bender Nov. 8, 1949 2,517,392 Ettinger Aug. 1, 1950 2,536,831 Allan Jan. 2, 1 951 2,553,291 Barr May 15, 1951- 2,611,061 Richardson et a1 Sept. 16, 1952 2,636,091 Carter Apr. 21, 1953 2,637,794 Grotenhouse May 5, 1953 2,695,939 Filliette Nov. 30, 1954 2,717,938 Laing Sept. 13, 1955 2,768,263 Calliham Oct. 23, 1956 2,791,662 Mertler May 7, 1957 2,797,272 Leupold June 25, 1957 2,863,968 Trautman Dec. 9, 1958

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