US3707255A

US3707255A - Feed arrangement for strip stack

Info

Publication number: US3707255A
Application number: US106151A
Authority: US
Inventors: Merrill L Ridgway; Willard D Kaiser
Original assignee: Nidec Minster Corp
Current assignee: Nidec Minster Corp
Priority date: 1971-01-13
Filing date: 1971-01-13
Publication date: 1972-12-26
Anticipated expiration: 1989-12-26

Abstract

Feed arrangement for feeding strip stock, or the like, into a press in which the feeding mechanism for the stock comprises a drive roller which drives the stock and which also drives a signal producer, the signal from which is compared with another signal preset on a manually adjustable signal producer with the feed being automatically terminated when the two signals bear a certain relation to each other. The signals may be digital signals or analog signals.

Description

United States Patent [151 3,707,255

Ridgway et al. 4 1 Dec. 26, 1972 [54] FEED ARRANGEMENT FOR STRIP [56] References Cited STACK v UNITED STATES PATENTS [72] Inventors: Merrill L. Ridgway, Minster; Willard Kaiser, Grove City, both of 2,693,235 11/1954 Kenworthy ..83/225 Ohio 3,362,601 1/1968 Ford ..226/141 X 3,392,895 7/1968 Ellner ..226l138 [73] Assignee: The Minster Machine Company, 3,504,586 4/1970 Acquaviva ..83/241 Minster, Ohio Primary Examiner-Richard A. Schacher [22] Flled' 1971 Attorney-Jeffers 8L Rickert [21] Appl. No.: 106,151

ABSTRACT Related U.S. Application Data Feed arrangement for feeding strip stock, or the like, [63] -P 0f Sen 832,202, June into a press in which the feeding mechanism for the 1969, abandoned. stock comprises a drive roller which drives the stock and which also drives a signal producer, the signal [52] U.S. Cl. ..226/136, 83/208, 83/241, from which is compared with another signal preset on 83/261, 226/139, 226/154, 226/156 a manually adjustable signal producer with the feed [51] Int. Cl. ..B65h 17/22 being automatically terminated when the two signals [58] Field of Search......226/136, 137, 138,139, 152,

'bear a certain relation to each other. The signals may be digital signals or analog signals.

21 Claims, 10 Drawing Figures PATENTEDIIEc2s I972 SHEET 1 [IF 7 INVENTORS MERRILL L. RIDGWAY WILLARD D. KAISER BY 9% A TORNEYS PATENTEI] nzc 2 6 I972 SHEET 2 [IF 7 INVENTORS L. RIDGWAY D KA|SER MERRILL WILLARD ATTORNEYS PATENTED nc2s I972 SHEET 3 BF 7 INVENTORS MERRILL L. RIDGWAY WILLARD D. KAISER BY WM ATT ORNEYS PATENTED DE 26 I972 3.7 07 2 55 sum u [1F 7 INVENTORS MERRILL L. RIDGWAY WILLARD D. KAISER BYWMW ATTORNEYS PATENTEI] DEC 26 I972 SHEET 1 S (If 7 INVENTO RS MERRILL L. RIDGWAY WILLARD D. KAISER PATENTED IIEII 2 6 I972 SHEEI 6 OF 7 HIGH SPEED RESOLVER {LOW SPEED RESOLVER Q3= ESIHA REFERENCE +lOv. -|O

DEMODULATOR HIGH SPEED SINE SIGNAL LOGIC CIRCUIT G E I I liN 4453 F I G? 9 SERVO SYSTEM INVENTO R S MERRILL L. RIDGWAY WILLARD D. KAISER WWW W ATTORNEYS PATENTEI] UEBZS I972 3 70'i 255 SHEET 7 [IF 7 S 'L g ia pTsg SWITCH TO CONTROL 5 FEED REFERENCE AND ROLL LII-TING 6|2 VOLTAGES E l 1 FFV TIME s R DELAY and and FFE and /606 Ps-i 7 and J 600 -so2 1 .AR/ l BR/ l A B INVENTORS MERRILL RIDGWAY A TORNEYS RELATED APPLICATIONS This inventionis a continuation-in-part of Ridgway application, Ser. No. 832,202, filed June I l, 1969 fo Feed Arrangement, now abandoned.

I BACKGROUND OF THE INVENTION This invention relates to a method and apparatus for feeding strip material and is particularly concerned with the feeding of strip material to a machine such as a press or the like.

Devices for feeding strip material to a press, such as a mechanical press, are known, and usually take the form of a mechanical feed arrangement driven by a mechanism connected to the crank shaft of the press. Such feed devices sometimes have a minor adjustment at the lower end 'where the feeding actually takes place but any major adjustment of the feed must be made up at the crank shaft end thereof which includes an adjustable throw crank. Thus, the adjustment of the feed is time consuming and difficult and precise accuracy can never be obtained.

SUMMARY oF THE NVENT ON With the foregoing in mind, the primary objective of the present invention is to provide a feed arrangement for feeding strip material, particularly to a press or similar machine, in which it is possible readily to adjust the amount of feed quickly and conveniently.

Still another object of this invention is the provision of an apparatus for effecting the feeding of strip material into a press which can be incorporated not only in new manufacture but also in existing presses and the like.

Still another object of this invention is the provision of a method and apparatus'for feeding strip material to a press or the like in which the feeding can be accomplished exceedingly rapidly and during that portion of the main machine cycle best adapted for the feeding of the material.

The objects referred to above as well as still other objects and advantages of the present invention will become more apparent upon reference to the following detailed specification, taken in connection with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS:

FIG. 1 is-an elevational view showing a press and a feeding arrangement according to the present invention associated therewith;

FIG. 2 is a somewhat schematic perspective view showing some of the essential elements of the feeding mechanism; 7

FIG. 3 is a plan view looking on top of the apparatus according to the present invention;

FIG. 4 is a view lookinginto the right side of the feeding apparatus;

FIG. 5 is a fragmentary sectional view showing how the feed rollers are formed so as to be light in weight;

FIG. 6 is a perspective view showing a counter arrangement;

FIG. 7 is a schematic representation of a hydraulic and electrical control circuit for the apparatus;

FIG. 8 is a block diagram showing a modified control arrangement;

FIG. 9 shows part of the circuitof FIG. 8 in more detail; and

FIG. 10 shows a logic circuit.

DESCRIPTION OF THE PREFERRED.

1 EMBODIMENT Referring to the drawings somewhat more in detail, FIG. 1 is a schematic illustration of a press generally indicated at 10 and having positioned adjacent thereto a feed mechanism according to the present invention schematically indicated at 12. The press has a bed 14, a head 16, uprights 18, and a press platen or slide 20 guided on the uprights and driven in reciprocation in a conventional manner by a crank shaftand connecting rod mechanism, not shown.

- Resting on bed 14 is a bolster plate 22 and secured to the bolster plate 22 is the lower part 24 of a die set, the upper part 26 of which is secured to slide 20.

As slide 20 reciprocates, strip -material fed from the supply 28 thereof through the feed mechanism 12 is fed into the space'between the parts of the die set and the material fed into the press is operated in the die. The die may consist of a single station in which piercing or blanking and forming is done, or it may be a progressive or multiple station die in which several operations are performed one after the other in order to arrive at a relatively complex workpiece or workpieces. Such die arrangements and the like are well known in the trade 4 and the die arrangement per se forms present invention. I

schematically shown in FIG. 1 is a limit switch LSI mounted on the press frame and actuating cam therefor indicated at 30 and mounted on the press slide. The arrangement is such that the cam 30 actuates the limit switch LSI only during retracting or upward movement of slide 20 and limit switch LSI, when actuated, initiates a feed cycle of the feed mechanism 12. In this manner the feeding of material into the press is coordinated with the operation of the press and a feed cycle occurs each time the press slide retracts.

Turning now to the feed mechanism itself, this is somewhat schematically illustrated in FIG. 2 where it will be seen that the feed mechanism is made up of a pair of

rollers

40 and 42 in a frame 43 and arranged in superimposed relation so that the strip 44 to be fed into the machine can be gripped therebetween and will be advanced thereby when the rollers are driven in rotano part of the tion. Lower roller 40 is connected via a coupling 46- with a reversible hydraulic motor 48. Hydraulic motor 48 is under the control of a valve mechanism 50 by means of which the motor can be caused to run in one direction or the other or by means of which the rotation of the motor can be interrupted.

The upper roller 42 is rotatably mounted on the outer ends of a pair of arms 52 which are stationarily pivoted by pivot means 54 at their'other ends in frame 43. Spring means 56 continuously urge arms 52 in a direction to separate roller 42 from roller 40 to release strip 44 from therebetween. Roller 42 is pressed toward roller 40 to grip strip 44 between the rollers by hydraulic actuator means indicated schematically at 58.

The

rollers

40 and 42 are preferably made as shown in FIG. 5 with an outer shell 60 having end members 62 secured thereto and centrally located shaft means 64' projecting from the ends of the rollers. Anti-friction bearings 66 rotatably support the shaft means of roller 40 in frame 43. With the rollers hollow as illustrated in FIG. 5, the moment of inertia of the rollers is kept to a minimum andthey can be accelerated quickly in either direction of rotation or can quickly be brought to a halt. Further, swinging movement effected with less power.

FIG. 2 also illustrates a clamping arrangernent for clamping the strip against movement when roller 42 is lifted away from roller 40; This clamping arrangement is schematically illustrated as a reciproc able clamping member 70 adapted to be pressed downwardly on top of the sheet by operation of a fluid actuator.72. The strip, in the region thereof beneath clamp member 70 is supported so that when the strip is engaged by the clamp member the strip is held against movement. The clamp member 7Q,-similarly to the roller 42 is spring biased in the retracting direction and is moved into clamping engagement by the application of fluid pressure to actuator 72. V

In operation, to bring about feeding of strip 44, roller 42 is pressed downwardly toward roller 40 and strip 44 is gripped therebetween. Energization of motor 48 by shifting of valve S'to rotate roller 40 in the counterclockwise direction, as it is viewed from the left end, will bring about advancing of strip 44 into the working space in the press. After a predetermined rotating movement of motor 48, the feed is stopped. Then roller 42 is lifted away from roller 40 to permit final alignment of the strip 44 by guide pins (not shown) contained in the operating die set. it is understood that with the interruption of the feeding of strip 44, clamping member 70 is operated by its actuator 72 to engage the strip and clamp it against further movement.

For supplying fluid under pressure to valve.50 for energizing fluid motor 48, there is provided a pump 80 driven by electric motor82. Pump 80 draws fluid from a reservoir 84 and discharges it under pressure into a conduit 86 leading to valve50. An exhaust conduit 88 leads from valve 50 through a cooler 90 back into reservoir 84. I

The control of the amount of feed movement of the strip 44 by the feeding mechanism on each cycle is controlled in a novel manner according to the present invention. As will be seen in FIG. 2, fluid motor 48 drives a transducer or pulse generator 92 which provides pulses for every certain amount of angular movement of motor 48. Such transducer devices take different forms and are known by different names and can be driven directly, as shown in FIG. 2, or can be driven through no back-lash gearing or precision belting or the like in order to increase the transducer speed relative to the speed of the driving motor.

The transducer 92 can be arranged to provide a pulse or a count, for example, for each thousand of an inch of movement of strip 44. The angular movement required by motor 48 to produce linear movement of one thousand of an inch of strip 44 will depend, of course, on the size of roller 40 and this roller is, therefore, advantageously make relatively small in diameter.

The pulses or counts produced by transducer 92 are delivered to a comparator and are compared in a known manner by a system to be generally described hereinafter with a count previously established by an adjustable device so that the amount of feed of the strip 44 is predetermined in thousands of an inch. FIG. 6 diaof rollerv42 can be 4 grammatically illustrates one arrangement whereby the count-to be matched by the count produced by transducer 92 can be preset. In FIG. 6 a counterdevice 94, such as a Veeder Root counter is illustrated with numeric indicating wheels 96 can be set by rotation of the crank 98 to indicate an amount from zero to themaximum for which the counter is designed in steps of one.

The number of rotations of crank 98 are'transferred via worm gearing 100 to pulse generators or transducers 102 which supply the signal to the comparator to run up a count therein which is to bematched by the count run up by transducer 92 during the feeding of strip 44. It will be evident that the manual counter 94 can easily be adjusted and if unity on counter 94 equals one thousandths of an inch of feed of strip 44, the feeding of strip 44 can be controlled extremely closely.

An alternate arrangement for the introduction of feed length commands into the systemwouldemploy a punched card, punched or magnetic tape, or a computer-type magnetic or electronic memory as the storage medium for command data. A card or tape reader or other appropriate interface element would receive the stored command data from the storage medium and introduce this data into the logic system 250 of the feed system indicated in block form in F IG. 7

' Turning now to FIG. 3 and 4, the physical nature of the feeding mechanism 12 is more fully disclosed. In these Figures it will be noted that the feed mechanism comprises a base 120, made up of interconnected channel members, for example, and including'a top plate 122. A frame 124 at each side of the feed mechanism includes a pneumatic cushion arrangement 126 which forms the actual support for the feed mechanism. The cushions 126 not only support the feed mechanism and serve to isolate it from shocks'which might interfere or lowering of the feed mechanism bodily to adjust the height at which the strip is fed therethrough tothat of the particular die'set mounted in the press.

Upstanding from top plate 122 of the base at opposite sides thereof are bracket members 128 and pivotally connected to the bracket members 128, as by vibration cushioning mountings 130, are links 132 extending toward press 10.

Press 10, on the other hand, has a structure 134 secured to the sides thereof that comprises a pair of spaced vertically extending plates 136. The plates 136 have upper pivot mountings 138 and lower pivot mountings 140 thereon.

Lower pivot mounting 'of the plate 136, which is shown in FIG 4, is pivotally connected to the forward end of link 132 and the upper pivot mounting'138 of this plate is pivotally connected to the front end of an upper link 142. The rear end of upper link 142 is pivotally connected by a vibration absorbing pivot mounting. 144 to a bracket member 146 which is fixed to a vertical plate 148 projecting upwardly from base plate 122.

The upper and lower pivot mountings of the plate 136 which is toward the tope in H6. 3 have connected thereto relatively short upper and lower link segments 150 which are parallel to and coplanar with

links

132 and 142 and which are joined thereto by the laterally extending plates 15-2 at the top, and 154 at the bottom.

l060l2 c200 Plates

152 and 154 extend on past the link segments 150 to the other side of the feed mechanism and, at their other ends, are connected to other link segments 156 which extend backwardly along the feed mechanism frame and are connected to respective pivot axes which are coaxial with

pivot axes

144 and 130 previously described; Each of

links

132 and 142, and 150 have tumbuckl means 158 therein for precise positioning of the feed device relative to the press frame.

The aforementioned base plate 122 and the upstanding plate 148 previously referred to, form a part of a frame work that makes up the aforementioned reservoir 84.. The top of the frame work includes a rigid top plate 160 on which is mounted the frame 43 within which the

aforementioned feed rollers

40 and 42 are mounted.

Secured to frame 43 and extending toward the press and between the uprights 18 thereof, or through an opening-in one side of the uprights, is a pair of spaced vertical plates 164 between which is suspended a plate 166 over which the feed material 44 slides toward the space between the parts of the die set which is to operate the material.

On the other side of frame 43 is another frame arrangement comprising a pair of spaced plates 168 between which is rotatably journalled a plurality of support rollers 170 over which the strip 44 moves in approaching the feed rollers. The strip is advantageously held down on rollers 170 by other rollers 172 carried on arms 174 pivotally mounted at 176 between plates 168.

Referring further to the cushions 126, each has a conduit 127 leading therefrom to a valve 131 which has connected thereto an air pressure line 129 and which also has an exhaust port. Each valve 131 has a lever 133 which, upon upward movement, admits pressure from conduit 129 to conduit 127 whereas, upon downward movement, conduit 127 is connected to exhaust. Each lever 133 is connected by link 135 with one end of a slide 137 that extends laterally completely across the front of the feed mechanism.

Slide 137 is vertically slidable on structure 134 that is attached to the press. Slide 137'is connected to the plate 139-which, at its upper end, is rotatably connected to an adjusting screw 141 which is threaded through threaded block 143 fixed to the upper end of structure 134. A knob 145 is provided on screw 141 and a lock means 147 is provided for locking the screw in any desired position of adjustment.

Slide 137 is held against tilting movement so that only one adjusting screw on one side of the feed mechanism is required for raising and lowering the feed mechanism.

Cooperating elements of a pointer and slide at 149 are provided on one of plates 136 fixed to the press and slide 137 so that the exact height at which the feed mechanism will supply stock can be readily indicated thereby.

HYDRAULIC AND ELECTRICAL CIRCUIT Schematically illustrated in FIG. 7 is a representative hydraulic and electrical control circuit for the operation of the feed system according to the present invention.

In FIG. 7, reference numeral 250 represents in block form the logic circuit by means of which the count developed by the motor driven transducer 92 is compared with the count preset on the hand driven counter 94. A voltage source at 252 has one side connected to ground and the other side supplying energy to the system. Switch LSI is coupled to logic circuit 250 through wire 312 to provide a signal regarding the position of press slide 20 so that the operation of the feed system maybe properly synchronized with the operation of the press. Limit switch LSI is closed during upward movement of press slide 20.by cam 30 carried thereby. Cam 30 is made effective only on the upward movement of the press slide by inserting a pivoted lever 258between cam 30 and limit switch LSI. An alternate limit switch arrangement could employ a rotary switch driven by the press crank shaft.

The circuitry indicated at 250 is adapted for supplying energy to a pair of wiresv 256 to operate control solenoids S2 and S3 of servo valve 50 shown schematically in FIG. 7, which in turn, controls the flow of fluid to motor 48 to drive feed roll 40. Circuitry 250 is also I release of clamp 70, logic circuit 250 will energize control solenoids S2 and S3 of servo valve 50 with a signal of such a polarity as to move valve member 298 upward, causing hydraulic motor 48 to turn feed roll 40 in a clockwise direction.

When motor 48 has rotated transducer 92 suftiv ciently to produce a count indicating that the commanded feed length is being approached, logic circuit 250 will change the level of signals carried by wires 256 to control solenoids S2 and S3 so as to change the position of valve member 298 to reduce the speed of motor 48. Logic circuit 250 will contain suitable compensating networks .to smoothly bring motor 48 to a stop at the desired feed length position.

When feed roll 40 is stopped at the correct position of rotation, having accomplished the proper advance of strip 44, logic circuit 250 will remove the excitation from control solenoid S1 of valve 266 so as to apply clamp to hold stock 44 and to lift roll 42 out of contact with stock 44. The holding power of clamp 70 will be limited to the extent that the stock 44 may be moved slightly if required by the action of guide pins (not shown) in the die set passing through guide holes (not shown) punched in the stock on the previous press 7 stroke.

Turning now to the hydraulic circuit which is controlled by the electrical circuit briefly'described above,

conduit 86 previously referred to as supplying valve 50 a shiftable valve member 268. When valve member 262 of valve 260 is moved downwardly, conduit 264 is connected to exhaust conduit 270.

With reference to valves 266, valve member 268 thereof is normally held by spring 272 in the upper position illustrated wherein pressure conduit 264 is connected to conduit 274 while a second conduit 276 is connected to the aforementioned exhaust conduit 270. Upon energization of a solenoid S1, however, valve member 268 will be shifted downwardly so that pressure conduit 264 is connected to conduit 276 while conduit 274 is connected to exhaust conduit 270. Conduit 274 leads through a pressure reducing valve 278 to the inlet of a flow restrictor 280 and to the inlet of a piston device 282 having a spring 281 and to the inlet side of a check valve 284. The other side of restrictor 280 and piston device 282 and the outlet side of check valve 284 are interconnected and lead via a conduit 286 to the fluid actuator 72 that operates the clamp member 70. The arrangement is such that when conduit 274 is exhausted, spring 288 biases clamp member 70 and its piston upwardly and actuator 72 exhausts via piston device 282 and restrictor 28l).

However, when conduit 274 is supplied with pressure fluid, the piston of actuator 72 is driven downwardly first by fluid displaced by the piston in piston device 282 and then by fluid passing through check valve 284 if further fluid is required.

Conduit 276 is connected with one side of another restrictor 290 and with one side of another piston device 292 and with one side of a pressure relief valve 294. The other sides of

components

290, 292, and 294} are connected together and by a conduit 296 with actuator 58 'for operating roll 42 in its downward direction.

When conduit 276 is exhausted, the piston in actuator 58 is urged upwardly by the spring 56, whereas, when conduit 176 is subjected to pressure, the piston in actuator 58 is displaced downwardly initially by the fluid displaced from the piston device 292, and thereafter by fluid passing through restrictor 290 if further fluid is required.

Upon the energization of solenoids S2 and S3 with one polarity pertaining to valve member 298, valve member 298 shifts upwardly and connects pressure conduit 86 with forward conduit 304 to produce clockwise rotation of motor 48 (as viewed in FIG. 7) which will bring about feeding of strip 44 when roll 42 is pressed downwardly on roll 40.

Energization of solenoids S2 and S3 with reversed polarity, however, will move valve member 298 downwardly and pressure conduit 86 will be connected with reverse conduit 366 while forward conduit 384 will be connected to the exhaust line 88 and this will produce a reverse torque to stop the motor. A relief valve 308 can be connected between

conduits

304 and 306 to relieve pressure in either direction.

OPERATION In operation, counter 94 is preset by a crank 98 to shown the amount of stock to be fed on each cycle. Valve member 262 is then shifted to its uppermost position. With the apparatus at rest, all parts of the system will occupy the position in which they are illustrated in FIG. 7 with the strip 44 clamped, and with

rolls

40 and 42 separated. if now, the switch LSI is closed, as by cam 30 moving upwardly past the end of lever 258, logic circuit 250 will receive a command to initiate feeding operations as previously described.

In order to insure that roll 42 is firmly pressed against roller 40 prior to motor 48 commencing to rotate, logic circuit 250 may include a time delay circuit to provide that the signal to advance motor 48 is not applied to solenoids S2 and S3 of servo valve 50 until after the signal to clamp roll 42 against strip 44 has been applied to solenoid S1 of valve 266, and actuator 58 has had time enough to clamp roll 42 in good gripping engagement with strip 44.

It will be evident that other means of controlling the amountof feed on each feed cycle can he arrived at using substantially the same components.

The control system previously described in detail is, essentially, a digital system in that the presettable mechanism 94 registers a count while the transducer 92 develops pulses which count down the registered count. It is also possible, however, to effect control by an analog system and such a system has certain advantages in that it is not subject to the same disturbances and sources of error that can effect a digital system. I

A variation of the control system for the stock feed which is substantially analog in nature is disclosed in FIGS. 8 to 12 and is described below.

In FIG. 8, reference numeral 500 is a shaft which rotates with the feed rolls during the time the feed rolls are feeding stock. if the hydraulic motor is directly connected with one of the feed rolls, shaft 500 maybe the hydraulic motor shaft. Mounted on shaft 500 is a two speed resolver 582, a tachometer 504, and an accelerometer or pressure transducer 506. The two speed resolver is a known item of commerce and supplies to wire 508 a cosine signal which is a function of the angular rotation of shaft 500 and to wire 5E0 supplies a sine signal which is a function of the rotation of shaft 500.

To

lines

512 and 514 the resolver supplies cosine and sine signals, respectively, at a multiple of the frequency of the signals supplied to

lines

508 and 510. By supplying the signals at two different frequencies, the lower frequency signal can be employed for roughly determining the rotation of shaft 500 and, therefore, the length of feed while the higher frequency signal can be employed for measuring the rotation of shaft 500 within small limits and thereby control the length of feed with a high degree of accuracy.

The setting of the length of thefeed is accomplished by a two-geared resolver arrangement at 516 which is manually adjustable to determine exactly the desired amount of feed; A fixed reference voltage source at 518 is provided to determine the stopping position of shaft 509 when it reverses at the end of a feed cycle and resets preparatory to the next following feed cycle.

The outputs from

components

516 and 518 are connected to a forward-reverse switching network 520 which is also connected to logic circuit 522 and also back to the two speed resolver 502.

The component 516 is connected to a switching component 524 which develops 'a reference voltage pertaining to velocity feedback switching and which reference voltage is conveyed by a line 526 to a switch component 528 which also receives .signals from tachometer 504 via line 536.

The

several lines

508, 510, 512 and 514 are connected to a switching network component 532 which supplies signals via line 534 to the switch component 528 and also to a summing amplifier component 536. The summing amplifier component 536 also receives signals from component 528 via line 538 and from component 506 via a line 540 and has an output line 542 leading to a current amplifier 544, the output from which is supplied via line 546 to the servo valve control for the hydraulic motor driving shaft 500.

To alleviate static friction and the like thereby to maintain moving components live and thus as nearly friction free as possible, a source of dither signals at 548 may be connected by line 550 to the summing amplifier component 536.

The circuit of FIG. 8 shows the components of the feedback system in block form and each component, per se, is a substantially conventional component but interconnected in a specific manner to achieve the desired result. I

The two-speed resolver 502 and tachometer 504 can be mounted directly on the hydraulic motor shaft. If desired, motors canbe purchased with the transducers installed. Either an oil pressure transducer or a torsional accelerometer can be used as component 506 to generate the acceleration feedback required for stability. The accelerometer 506 can be mounted on the motor shaft or a differential pressure transducer installed to measure differential motor pressure. It is also possible to differentiate the tachometer signal to obtain an acceleration feedback signal but this signal is preferably produced directly with a pressure oracceleration transducer. g

Reference resolver 516 is panel mounted and has a readout dial so that the total error at the motor shaft of the components is less than about one-half of the allowable. system error. For 4.2-inch diameter rolls, the

of i 0.002 inch. In calculating the system error at the motor, the dial and front panel resolver errors are divided by the resolver speed.

For example, if the combined error of the dial and resolver on the front panel is 30 minutes and a speed resolver is used, the error at the motor shaft will be 1.5 minutes plus the error in the two-speed resolver on the motor shaft. The two sets of reference voltages shown in FIG. 8 at 518 and 524 are the reference voltages for the forward and reverse positions. The adjustable reference voltages are obtained with two resolvers which can be mounted remotely from the main press feed element. The two resolversare geared together with a gear ratio which is the same as the speed of the two-speed resolver 502 on shaft 500. A dial is attached to the high-speed resolver on the remote front panel and is calibrated to read the feed length in inches.

The forward-reverse switching network is used to control which null position the system seeks. This switch is controlled by the logic system. The outputs of the two-speed resolver 502 on the hydraulic motor shaft 500 are sine and cosine voltages. The switch network 532 is used to switch these voltages so that the output of the switching network is constant when the error is greater than 90, and is proportional to the sine of the error when the error is less than 90. A schematic circuit for performing these switching operations is shown in FIG. 9.

' angular error is i 3.28 minutes with a feed length error FIG. 9 shows a simple circuit which can be used to control stock feed up to slightly less than 270. This system works as follows. The voltage, el, is proportional to the sine of the error, A, and the amplifier, A2, with its diode feedback network acts ,as an on-off switch so that when the cosine of the error is negative, e4 is equal to a fixed voltage E.

When the error is between and 270, e4 will actuate the relay R, and supply a constant voltage error signal to the servo system. When the error drops to 90, relay R will release and the servo system will then take its error signal from amplifier A1, for the final 90 of travel. Using this circuit, the feed can be up to 270 or, up to about 1 1 inches with a 5-inch diameter roller.

For longer feed lengths, larger rollers can be used or multi-speed resolver systems can be used. With the multi-speed resolver systems second or third resolvers can be geared to the main resolver to run at a slower speed. The coarse resolver controls the servo system until the error drops low enough so that the high-speed resolver can control the system. The high-speed resolver is then switched into the servo system.

The switching network 532 must also switch from the low speed resolver signal to the high speed resolver signal so that the output will have approximately the same shape as the low speed sine wave. This can be done by attenuating the high speed resolver signal.

FIG. 9 shows a circuit for switching from the low speed to the high speed signal and the type of signals obtained. Type IN 4453 diodes, having a high forward resistance with applied voltages less than about 0.7 volts, provide automatic interruption of the low speed resolver signal, applying the high speed resolver signal to A-3 when the difference between the high speed and low speed resolver signals falls below 0.7 volts. There are other methods of accomplishing this function, only one being shown.

The dither signal source 548 shown in FIG. 8 is a sinusoidal voltage added to the error signal to eliminate friction effects in the valve and the rest of the system by producing a fairly high frequency, low amplitude vibration in the system.

The summing amplifier 536 and current amplifier 544 are conventional operational amplifiers with standard feedback networks to provide the desired summing and current amplification functions, or complete servocontrol units can be purchased which have these components built into them.

The functions which the logic system must perform are as follows:

1. Start the feed cycle upon a command indicating the correct punch press crankshaft position.

2. Determine when the stock has been fed to within the specified accuracy and when the drive motor has essentially stopped.

3. Clamp the stock, disengage the drive motor by lifting the rolls or releasing a clutch, and reverse the drive motor.

4. Determine when the drive motor has returned to the back position within specified error limits.

5. Engage the feed rolls and release the stock clamp.

FIG. 10 is a block diagram showing one combination of components which might be used to perform the desired logic functions. The circuit works as follows:

l. The absolute value'of the angular error A and the absolute value of the angular velocity B are compared by

comparators

600 and 602 with reference values AR and BR to determine when they are within specified limits. When the error and velocity are within limits, and circuit 604 produces a

signal C. Ands

606, 608, 610 are used into both flip flops FFE and FFV so that no switching operations can be performed until the feed has stoppedand is with specified error limits.

2 A starting pulse, PS, and signal C combine to set the flip flop circuit FFE so that there is a voltage at E in component 612 and the forward feed reference voltages are switched on. The feed then runs in the forward direction. I

3. The unit runs forward until there is no error. At that time the flip flop circuit FFV is reset to the reverse position by E6 and signal C and FFE is reset by signal C. The valve controlling roll lifting and stock clamping is switched for reverse operation at the same time FEE switches to reset, but a time delay delays the switching of the reference voltages until the clamping operations have been performed The unit then reverses to the starting position.

4. When the motor has backed up to the starting position, signal C and E7 sets FFV, and clamping control valve switches to forward, and theunit is ready for the next cycle.

What is claimed is: 1. A feed arrangement for feeding strip stock into a machine, such as a press or the like and comprising: a

' frame, a pair of feed rolls in said frame between which supplying a first signal in conformity with the setting of said adjustable means, a signal developing means operable during the feeding of stock by said rolls to develop a second signal in conformity with the amount of rotation of said feed rolls, comparing means connected to receive and compare said first and second signals and adapted to supply a third signal as the feed rolls rotate an amount such that the peripheral movement thereof is substantially equal to said predetermined feed length, first control means operable when actuated to cause said drive means to drive and stop said feed rolls, said first control means when actuated energizing said actuating means and also energizing said drive means for forward rotation, and second control means to actuate said first control means thereby to initiate the feed cycle.

2. A feed arrangement according to claim 1 which includes actuator means operatively connected to said second control means and under the control of the machine into which the stock is fed for actuating said second control means when said machine is at a predetermined point in its cycle of operation.

3. A feed arrangement according to claim 2 in which said machine is a press and said actuator means including a limit switch adapted for actuation by a movable part of said press.

4. A feed arrangement according to claim 1 in which said drive means is a rotary motor.

5. A feed arrangement according to claim 4 in which said rollers are movable relatively toward each other. to grip the stock and away from each. other to release the stock, actuator means energizeable for moving said rollers toward each other to grip said stock prior to energization of said drive motor fora feed cycle, means for moving said rollers away from eachother upon 'deenerg'ization of said actuator means, said drive means comprising a reversible motor, said first control means when actuated energizing said actuator means and also energizing said drive-motor for forward rotation, said signal developing means being driven by said drive motor, and said first control means being operable to energize said drive motor for reverse rotation upon separation of said rolls thereby to return said signal developing means to the condition thereof at the beginning of said feed cycle.

6. A feed arrangement according to claim 5 which includes actuating means operatively connected to said second control means and under the control of the machine into which the stock is fed for actuating said second control means when said machine is at a predetermined point in its cycle of operation.

7. A feed arrangement according to claim 6 which includes stock clamping meansactuata'ble for engaging and clamping said stock against movement in the feed direction, and third control means being operable when actuated for actuating said clamping means so as to prevent movement of said stock after termination ofa feed cycle.

8. A feed arrangement according to claim 7 in which said machine is a press, and support means supporting said frame adjacent said press for adjustment relative to the press in the direction of movement of the press slide so as to accommodate the feed arrangement to the heights of various die sets placed in the press.

,9. A feed arrangement according to claim 8 in which said support means includes a support member fixed to the press, spaced links pivoted at their one ends to said member and at their other ends to said frame, expansible fluid cushion means at the bottom of the frame to support the frame on a-supporting surface such as a floor, valve means on the frame connected to said fluid cushion means and having movable valve member means to control the supply of fluid to and from said fluid cushion means, lever means pivoted to the frame and to said valve member means, a slide adjustable on said support member, and link means connected at one end to the slide and at the other end to said lever means.

10. A feed arrangement according to claim 9 in which said links are parallel and the points of connection thereof with the press and with the frame are coaxial.

l l. A feed arrangement according to claim 10 which includes screw threaded means connecting said slide to said support member and operable for adjusting said slide on said support member in the direction of movement of said valve member means in said valve means, cooperating elements of a scale and pointer on said support member and slide to show the position of the slide on the support member, and means for locking the slide to the support member in' adjusted positions thereon.

12. A feed arrangement according to claim 11 which includes a said expansible fluid cushion, said valve mans comprising a valve for the cushion, said lever means including a lever connected to the valve member.

13. A feed arrangement according to claim 11 in which said frame includes a platform extending therefrom toward the working space in the press and at a level with the stock passing between the rollers.

14. A feed arrangement according to claim 7 in which said drive motor is hydraulically operable, control valve means connected in circuit with said drive motor, at least said first control means including means for shifting said control valve means.

15. A feed arrangement according to claim 1 in which one of said rolls is rotatable on a stationary axis in said frame, a pair of arms pivotally supported at their one ends in said frame and rotatably supporting the other of said rolls at their other ends, biasing means biasing said arms in a direction to move said other roll away from said one roll, and third control means including a fluid actuator means connected to said arms and operable to move the arms against the bias of said biasing means to move said other roll into stock gripping relation with said one roll.

which said adjustable means comprises a digital element presettable to a predetermined count and said signal developing means comprises a pulse generator.

17. A feed arrangement according to claim 1 in which said adjustable means comprises a source of voltage presettable to a predetermined value and said signal developing means comprises resolver means adapted to supply a voltage which varies in conformity with the rotated position of said rolls during feeding of stock thereby.

18. A feed arrangement according to claim 17 in which said resolver means is a multiple speed resolver.

19; A feed arrangement according to claim 1 wherein the drive means is a hydraulic motor.

20. A feed arrangement according to claim 19 wherein said signal developing means is a resolver.

21. A feed arrangement according to claim 1 wherein the driven feed roll is brought to a common reference location for the starting of each feeding cycle. 1

; UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,707,255 Dated December 26, 1972 Inventor(s) Merrill L. Ridgway and Willard D. Kaiser It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title Page, "STACK" should be STOCK Col. 1, line 1, "STACK" should be STOCK Col. 3, line 61, "make" should be made Col. 4, line 28, "FIG." should be "FIGS." Col. 4, line 63, "tope" should be top Col. 6, line 63, "leaks" should be leads Col. .,7, line .39, "176" should be i275 Col. 7, line 62 (second line after heading OPERATION) "shown" should be show Col. 11, line 23, period omitted between "performed" and "The" Column 13, line 3 (Claim 12) mans should be means Signed and sealed this 22nd day of May 1973.

(SEAL) Attest:

EDWARD M. FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents

Claims

1. A feed arrangement for feeding strip stock into a machine, such as a press or the like and comprising: a frame, a pair of feed rolls in said frame between which said stock passes and adapted for feeding said stock, drive means adapted for driving at least one of said rolls in rotation in feed direction, means for actuating the other one of said feed rolls to frictionally engage said stock, a command input device including adjustable means presettable to a predetermined feed length and supplying a first signal in conformity with the setting of said adjustable means, a signal developing means operable during the feeding of stocK by said rolls to develop a second signal in conformity with the amount of rotation of said feed rolls, comparing means connected to receive and compare said first and second signals and adapted to supply a third signal as the feed rolls rotate an amount such that the peripheral movement thereof is substantially equal to said predetermined feed length, first control means operable when actuated to cause said drive means to drive and stop said feed rolls, said first control means when actuated energizing said actuating means and also energizing said drive means for forward rotation, and second control means to actuate said first control means thereby to initiate the feed cycle.

5. A feed arrangement according to claim 4 in which said rollers are movable relatively toward each other to grip the stock and away from each other to release the stock, actuator means energizeable for moving said rollers toward each other to grip said stock prior to energization of said drive motor for a feed cycle, means for moving said rollers away from each other upon deenergization of said actuator means, said drive means comprising a reversible motor, said first control means when actuated energizing said actuator means and also energizing said drive motor for forward rotation, said signal developing means being driven by said drive motor, and said first control means being operable to energize said drive motor for reverse rotation upon separation of said rolls thereby to return said signal developing means to the condition thereof at the beginning of said feed cycle.

7. A feed arrangement according to claim 6 which includes stock clamping means actuatable for engaging and clamping said stock against movement in the feed direction, and third control means being operable when actuated for actuating said clamping means so as to prevent movement of said stock after termination of a feed cycle.

9. A feed arrangement according to claim 8 in which said support means includes a support member fixed to the press, spaced links pivoted at their one ends to said member and at their other ends to said frame, expansible fluid cushion means at the bottom of the frame to support the frame on a supporting surface such as a floor, valve means on the frame connected to said fluid cushion means and having movable valve member means to control the supply of fluid to and from said fluid cushion means, lever means pivoted to the frame and to said valve member means, a slide adjustable on said support member, and link means connected at one end to the slide and at the other end to said lever means.

11. A feed arrangement according to claim 10 whIch includes screw threaded means connecting said slide to said support member and operable for adjusting said slide on said support member in the direction of movement of said valve member means in said valve means, cooperating elements of a scale and pointer on said support member and slide to show the position of the slide on the support member, and means for locking the slide to the support member in adjusted positions thereon.

16. A feed arrangement according to claim 1 in which said adjustable means comprises a digital element presettable to a predetermined count and said signal developing means comprises a pulse generator.

19. A feed arrangement according to claim 1 wherein the drive means is a hydraulic motor.

21. A feed arrangement according to claim 1 wherein the driven feed roll is brought to a common reference location for the starting of each feeding cycle.