US2473676A - Control system for hydraulic machinery - Google Patents

Description

June 21, 1949. L. A. CAMEROTA 2,473,676

common SYSTEM FOR HYDRAULIC MACHINERY Filed March 9, 1946 6 Shegts-Sheet 1 El 67 M a; E 3 E El N INVENTOR:

m lax/15A flame/via,

Wgwm BY MW ATTORNEYS.

L. A. CAMEROTA CONTROL SYSTEM FOR HYDRAULIC MACHINERY June 21, 1949.

6 Sheets-Sheet 2 Filed March 9, 1946 mwN R N UQNW W1 'I'NESSES ZMZQZJMJ June 21, 1949.

L. A. CAMERQTA CONTROL SYSTEM FOR HfbRAULIC MACHINERY 6 Sheets-Sheet 3 Filed March 9, 1946 INVENTOR: 10111514. flame/'07:;

ATTORNEYS.

MR NE N gm W0? MEL/$9):

June 21, 1949. A. CAMEROTA CONTROL SYSTEM FOR HYDRAULIC MACHINERY 6 Sheets-Sheet 4 Filed March 9, 1946 W $6 mm.

'June 21, 1949. A. CAMEROTA CONTROL SYSTEM FOR HYDRAULIC MACHINERY 6 Sheets-Sheet 6 Filed March 9, 1946 .INVEINTOR: ZazzzsAfiamemia,

ATTORNEYS.

Patented June 21, 1949 CONTROL SYSTEM FOR HYDRAULIC MACHINERY Louis A. Camerota, Burlington, N. J assignor to Florence Pipe Foundry & Machine Company, Florence, N. J a corporation of New Jersey Application March 9, 1946, Serial No. 853,413

9 Claims.

This invention relates to a control system for hydraulic machinery and more particularly for use with hydraulic presses or the like operated through the medium of a pump having a flow control member which is adapted to be shifted to different positions by means of a servo-motor. Presses operated by such instrumentalities are well known in the art, and my invention is directed to improvements which provide a more versatile control for a hydraulic press or the like, which safeguard against improper operation or excessive loads upon the power transmission lines. and which involve advantages as more fully set forth in this specification.

The use of the rotary piston type pump, combining variable volume and variable pressure, and of the servo-motor for shifting the rotor or flow control member of such a pump to effect volume and directional control, as well as other well known improvements relating to presses or other hydraulic machinery, and to apparatus for controlling their operation, has made possible the design of very large hydraulically operated units which are capable of exerting a great force in a limited space. This has resulted in a tendency favoring high speed and high capacity press units requiring a large pump with consequent increase in the horse-power of the prime mover which drives the pump, especially at peak loads.

It follows that where an electric motor is employed as the main prime mover of the system, in starting a motor of the size required, particularly if it is attempted to start the motor while the pump driven thereby is on stroke or under pressure, a tremendous demand is created upon the power lines. Even under conditions where the pump is in the neutral or no-delivery position the starting of the motor may require more current than the lines normally installed in a factory or mill can safely conduct. On account of its particular characteristics, the use of a synchronous motor has been suggested, it being well known that very little current is required to start a sym chronous motor as compared with other types. But although synchronous motors have a better power factor they cannot be used to advantage except where the starting torque required is small, or the load can be relieved during the starting period. Furthermore, in a plant where a large hydraulic press of the type referred to herein is operated by an electric motor other than a synchronous motor, and adequate transmission lines are installed, for meeting the peak loads, the starting of the motor under load will cause 2 heavy demands which should, if possible, be avoided.

With theseconsiderations in mind it is one of the principal objects of my invention to provide in such a hydraulic system means for preventing the electric motor used as the prime mover from being started when the pump is on stroke or in a position to deliver pressure to the hydraulically operated machine. This is accomplished by control devices which make it a condition precedent to the starting of the motor that the flow control member of the pump be shifted to the neutral or no-delivery position so that the motor is always permitted to start with only its own frictional load and that of the pump to overcome.

A further object of the invention is to provide in such a system a full set of controls, whereby the various functions of a press or the like may be performed automatically in the desired sequence, or at the will of the operator, and preferably including a manually operated control, which, if the electrical appliances fail, or under any emergency or unusual condition, can be relied upon to predominate over other controls and move the press platen as desired.

A further object of the invention is to reduce to a minimum the number of valves and the amount of exterior piping associated with the press by combining the functions of such valves, to a greater extent than has heretofore been accomplished, and by placing them in juxtaposed relation within a unitary structure desirably mounted integrally with the pump, or in close relation thereto.

Further objects of my invention and advantages which result from the use thereof will become more apparent from the description of a preferred embodiment of the invention which follows hereinafter and which has reference to the accompanying drawings wherein:

Fig. 1. shows a diagrammatic layout of the hydraulic elements of the control system with the press idle and its platen at the upper limit of travel, and with none of the pumps operating.

Fig. 2 shows the same layout with the press idle but with the servo-motor pump operating.

Fig. 3 shows the same layout with the press platen closed against the work piece.

Fig. 4 shows the same layout with the press platen moving up.

Fig. 5 shows a diagram of the electrical circuit for operating the main motor which drives the main pump.

Fig. 6 shows a diagram of the electrical circuit for operating the controlling relays of the hydraulic control system.

Fig. 7 shows a diagram of the electrical circuit for operating the motor which drives the pump of the leakage system.

Fig. 8 shows a diagram of the electrical circuit for operating the motor which drives the pump or the servo-motor system; and

Fig. 9 shows an enlarged cross-sectional view of the combined valves which control the flow of hydraulic fluid between the press and the main pump.

General description In the drawings, with special reference to Figs. 1 to 4, a hydraulic press is comprehensively designated at H. Pressure fluid is supplied to the press H through the medium of a reversible variable delivery pump I controlled by a servo-motor 2. It may be assumed that the pump includes a rotor or flow control member (not shown) which is adapted to occupy different positions including a neutral or no-deiivery position and on-stroke positions in which pressure or suction is applied to the connecting lines depending upon which side of the center line the rotor of the pump is moved. The details of construction of the pump I and servo-motor 2 and means for varying the output or the pump I are not shown in the drawings or this application as they do not form any part of my invention and such devices are well known and have long been used with hydraulic presses.

In addition to the main pump I the system includes a hydraulic gear pump 3 operated at, say. one hundred pounds working pressure and used to supply fluid power to the servo-motor 2 and an additional hydraulic gear pump 4 operated at, say, sixty pounds working pressure and used for the leakage system.

A synchronous motor, shown at I in Fig. 5, serves as the prime mover for driving the main pump I. Additional electric motors employed in the system comprise a small induction motor 6, shown only in Fig. 8, which drives the hydraulic gear pump 3 for the servo-motor 2, and a motor 1, shown only in Fig. 'l, which drives the hydraulic gear pump 4 of the leakage system.

The hydraulic press H conventionally illustrated includes a ram 26 reciprocating in a main cylinder 21 and connected at its lower end to a platen 20. For retracting the platen 20 push back cylinders 29 are used, these cylinders having reciprocating plungers 30 therein which are also connected to the platen 20. A pre-flll tank or reservoir 02 supplies fluid at a pressure of, say, thirty-five to forty pounds per square inch through a pipe II' to the top of the main cylinder 21, there being a gate valve in the pipe II for regulating the flow of the pressure fluid to the press cylinder 21, and an air cock I0 in the pipe II between the gate valve 0 and the cylinder 21. A sight gage 46 on the exterior of the pre-flll tank 92 indicates the level of the liquid therein. Associated with the press cylinder 21 there is a filling check valve 8 which controls admission of the pressure fluid from the pipe II to the top of the cylinder. The spindle I5'of the fllling check valve 8 is normally held closed by means of a spring 03 but when pressure in the line 04 is sufllcient to overcome the force of the spring 03 the valve spindle I5 is moved downwardly to open the valve 8 and permit fluid in the pipe II to enter the top of the cylinder 21. Three valves ll. 32 and 33 in the line 98 govern the operation of the filling check valve 8. More speciflcally,-the check valve 3|, which opens against the pressure to vary from zero to, say. three thousand pounds per square inch is fed to the push back cylinders 20 through a pipe 01 which Joins pipes at and 90. Similarly pressure fluid having the same range of pressure is admitted to the main cylinder 21 of the press H through a pipe 00 leading from the pump I. Joining the pipe 00 in the vicinity of the press is an additional pipe 00 which leads to a pressure governor 00.

The suction and discharge points of the main pump I are illustrated at IM and I02. The pump I being reversible the connection at IOI' is a point of discharge when the press is moving down and the connection at I02 is a point of discharge when the press is moving up. It may further be assumed that the reciprocable element I00 which controls the servo-motor 2, when shifted to the left. as viewed in Figs. 1 and 3 of the drawingsherein causes a shift in the flow control member of the pump such that the pump I is on stroke, discharging at connection IOI through pipe 00 and taking suction at connection I02, and that when the reciprocable element I03 is shifted to the right the flow control member moves to a position such that the pumpl is on stroke in the opposite direction discharging at connection I02 through pipe 01 and taking suction at point II. Moreover, when the reciprocabie element I00 occupies a central position the flow control member of the pump I is in the neutral or no-dellvery position.

Mounted on the main pump I and shown in enlarged detail in Fig. 9 is a combination or manifold valve which includes within the same unitary structure I0 a series of serially arranged juxtaposed valves performing various functions. The valve I3 is a check valve having a spring IIO urging it to closed position and having an upper chamber III' into which pressure fluid may be admitted to supplement the force of the spring in urging the valve I3 to closed position. An annular shoulder H2 at the base of the valve is is so proportioned that when the pressure in the passage 2i! reaches a certain point the valve will open. Between the discharge or suction connection I02 and the check valve ii there is interposed a throttle and check valve II which is urged to seated position by means of a spring IIS and which has orifices I IS in the valve part I H which permit a limited flow through the valve part III when it is seated under spring pressure. For controlling the amount of flow through the oriflces I I6 an adjustable throttle rod I I0 is employed, its position being determined by means of a nut I I4 engaging the threads 250 and by means of a spring 2 which presses against a collar 202 of the throttle rod H8. When the pump I discharges at point I02 fluid flows through a passage H0 to a passage I20 lifting the valve part III against the pressure of spring Iii. When the flow is in the opposite direction the valve part I I1 is seated and the orifices II6 and throttle rod lIIl govern the rate of flow through it.

5 upper chamber I22. The spring in may be adiusted by means oi a nut 253 engaging a threaded pin 254 having an enlarged -lower end 255 which engages the top of the. spring I2I. When the pressure at discharge point III acting against the annular shoulder I23 exceeds the combined force of spring I2I and of the pressure in the chamber I22 the valve I liits permitting flow into internal passages I23 and":l24. interposed between passages I24 and 3I3 there is a check valve 33 urged to closed position by a spring I25. Valve 33 permits only one-way ilow. between passages I24 and 3I3 this flow being from the former to the latter passage when the pressure from beneath is sufllcient to llit valve 30. The force of spring I25 may be varied by manipulation oi a nut 251 engaging a threaded pin 253 which bears against a loose collar 259 engaging the top oi the spring I25. An additional check valve I4 urged to closed position by a spring I2I permits only one-way flow between passages I23 and I II, the flow being from the former to the latter when the pressure diflerential is sumcient to overcome the force of 'the spring I21. It will be observed that Passage I23 leads from valve II to passage III through check valve I4 and by-passes all other valves embodied in structure II.

A pilot valve 25 controls the admission oi pressure fluid to the upper chambers I II and I22 of valves I3 and I9. The pilot valve 23 is actuated by a solenoid 0. Under the influence of a spring I29 the valve stem I30 is urged to the raised position shown in Figs. 1, 2, 4 and 9. but when the solenoid C, is energized the valve stem I30 is drawn downwardly to the position shown in Fig. 3. In the raised position the reduced portion I3I oi the stem I30 uncovers the'ports I32a and l32b and permits communication between pipes I33 and pipe I I 3 admitting pressure from pipe I33 to pipe H3 and thence to the top chamber III of valve I3. In the lowered position oi valve stem I30 ports I32a and I32b are covered and ports I34a and I34b are uncovered by the reduced portion I35 of valve stem I30 permitting communication between pipe I35 and pipe I 31 and hence admitting pressure to the top chamber I22 of valve I 6. When thevalve stem I30 is raised there is also communication from pipe I34a and port I30 to discharge pipe III.

Servo-motor system The reciprocable element I53 which controls the position of the flow control member oi the pump 1 through the medium of the servo-motor 2 moves within a centralizing cylinder 50. When the plunger I39 which is amxed to the reciprocable element I03 occupies the position represented in Fig. 2 which is midway between its limits of movement the flow control member of the pump I is maintained in the neutral or nodelivery position. Two collars I40 float within the centralizing cylinder 50. When pressure is admitted to the centralizing cylinder 50 through branches I4'Ia and I4": 01 pipe I the floating collars I40 are urged towards each other until they each strike the abutment I42 within the cylinder which limits their movement. Such movement of the collars causes them also to enage the plunger I39 and to urge the reciprocable element I03 to its centralized position. Moveinent of the reciprocable element I03 may also be eflected manually or electrically through a bell crank lever 53 connected at I43 to the end of reciprocable element I93 which projects beyond the centralizing cylinder 59. Fluid under a pressure I3'I through port 01, say. eighty to one hundred pounds per square inch is supplied to the servo-motor 2 and the centralizing cylinder 50 by means of the pump 3. In the branch pipe I44 which Joins pipe I and leads to the servo-motor 2 there is interposed a throttle valve II for controlling the flow of the hydraulic fluid to the servo-motor 2. Although no details 01' the servo-motor 2 have been illustrated, such devices being well known and commonly used in hydraulic systems, it will be understood that whenfluid under pressure is admitted through pipe I44 the servo-motor 2 is in readiness to effect a movement oi the flow control pump I in the neutral or no-delivery position.

The servo-motor pump 3 at its suction side is connected to the pre-fill tank 92 through pipe I45 which has a shut-ofl valve I8 therein. It discharges through pipe I which has a check valve 22 therein permitting only one-way flow to the servo-motor 2 and centralizing cylinder 50. Connected to discharge pipe I is a pipe I46 which leads to a-pressure switch 43 which closes the electric circuit to the main electric motor 5 when a predetermined pressure has been reached in the servo-motor system. Also connected to discharge pipe I is a pipe I" leading to an air bottle accumulator 9i employed to build up and maintain pressure in the servo-motor system. Desirably the pipe I4! is provided with a drain valve 23 for draining the accumulator 9|, and air valves 35 and 36 are provided in a pipe I48 leading to the top of the accumulator 9| for respectively admitting or discharging air from the accumulator.

Also connected to discharge pipe I is a pipe I49 leading through a restraining valve 2 I, a heat exchanger 43, a check valve 20 and a shut-off valve I6 to a pipe I49 which is connected to the pre-flll tank 92. Restraining valve 2| is used to permit the building up of a predetermined pressure in the servo-motor system. When the pressure in the system is such that there is no further flow therein it permits flow of the hydraulic medium through the heat exchanger 43, which heats or cools the liquid as desired, and returns it to the pre-fill tank 92. A relief valve 12 is desirably connected to pipe I 49 to prevent excessive pressure from building up in the heat exchanger 43. An additional relief valve [39 connected to pipe I41 prevents pressure in the servomotor system from increasing beyond a predetermined point. Both relief valves 39 and I2 discharge through pipes I50 and I5I to a drainage tank I 52. A throttle valve 90 is inserted in each of branch pipes I4Ia, I4Ib.

Leakage system The leakage system comprehends the drainage tank I52 and associated piping and instrumentherein a filter 42 and a shut-oi! valve 15, to

the re-fill tank it. A pressure relief valve ll connected to pipe Ill is employed to prevent the building up of excessive pressure between pump 4 and shut oil valve II and safeguards against the contingency that the operator might accidentally start the pump l with the valve ll closed. An air cleaner ll is preferably associated with the drainage tank to filter the air therein. Connected to pipe Ill is a drain valve Il employed to drain the pre-fill tank l2. Drain valve Il may also be used as a suction connection between drainage tank in and the source of liquid supply for filling the pre-flll tank II.

A combined throttle and stop valve I2 located on the operating panel I" permits a bleeding down of the pull-back cylinders ll of the press H. When the valve I2 is opened liquid in pipe l'l may be controllably bled through pipe Ill and thence through pipe Ill directly to the drainage tank Ill. and hence the press platen may be lowered. whenever it may be desirable to do so, without starting the main motor 5. Liquid discharged from either of relief valves ll and 12 drains to the tank I52 through pipes Ill and Ill. Similarly, when the pilot valve ll is in the raised position indicated in Fig. 2 of the drawing liquid may be discharged from the top chamber I22 of the quick-discharge valve Il through pipe Ill and port Ill of pilot valve ll to pipe Ill and thence to the drainage tank Ill.

Manual control For manually controlling the operation of the press 11 a hand lever 54 is used. This lever I4 is fulcrumed at Ill and has an arm Ill pivotally joined to the lower end of a control rod Ill. At its upper end the control rod Ill is plvotally joined to the arm Ill of a threearmed bell crank lever 53 which swings about a fulcrum point Ill. When the lever I4 is in the position represented in Fig. 2, the arm I of bell crank lever ll occupies a horizontal position and the reciprocable element I ll of centralizing cylinder 50 is in its midway position within the cylinder 50. In an obvious manner a downward movement of the hand lever ll produces an outward movement of the reciprocable element Ill within the cylinder ll whereas an upward movement of the hand lever ll produces an inward movement of the reciprocable element Ill. Thus there is at all times and under all conditions a direct mechanical control over the functions of the servo-motor 2. Pivotally connected to the arms Ill and Ill respectively of bell crank lever ll are the plungers Ill and I ll of solenoids B and A which effect the normal automatic control of the reciprocable element Ill through electrical circuits hereinafter described. The lower arm I'll of bell crank lever 53 engages a limit switch ll and serves to close the switch 80 when the arm I'll is in the perpendicular position and otherwise to permit the switch to remain open. Aifixed to the control rod I63 is a collar lI adapted to be engaged by a bracket Ill projecting from the press platen 28 so that as the ram ll travels upwardly and before reaching the top limit of its stroke the bracket I ll will come in contact with the collar 8i and force the con: trol rod I63 upwardly in the event that the rod I63 has not already been moved to its fully raised position. A limit switch l2 is adapted to be mechanically engaged by the hand lever 54 and to occupy two positions dependent upon the position of the hand lever. when the hand 8 leverllisinits depressedpositionasrepresentedinPiaaiandlthelimitswitch-llisin "down" position. when the handlever ll horisontalorisraisedthelimit switchllis up" position. Depending from the press llisastrokerodllwhichhaa-acam II its lower end which is adapted to engageanc ditional limit switch ll. when the rain and the press H is fully open the limit switch ll engages the cam Ill and is held open. Under other conditions the limit switch ll is not engaged and remains closed.

Electrical system On the instrument panel Ill. as shown in Ilgs 1 to 4. there are three push button type switch ll, l'l and ll. Switch ll has start and buttons for operation of the main motor I. Switch l'l has start and stop buttons for motor I which drives the pump 3 of the servomotor system. Switch ll has start and stop buttons for the operation of the motor I which drives the pump 4 of the leakage system. Additional switches shown in the vicinity of the instrument panel are a cycle start button ll. an emergency stop button ll, and a foot actuated cycle start switch ll the functions of which are more specifically described hereinafter.

with special reference to Fig. 5 the main electric motor 5 which drives the main pump I is represented as a synchronous motor energized by lines U, U and 1. when the switch blades I'll. Ill and I'll of relay Rl are closed. Connected to line L is a wire I" leading through solenoid I'll of relay Rl, pressure switch ll, the stop element I'll of main motor switch ll, the starting element Ill of that switch and thence to wire Ill, which leads through limit switch ll to wire Ill which Joins line L. A wire Ill leads from line L through solenoid Ill of relay Rl to wire I". An additional wire Ill connected between the starting element Ill and stop element Ill leads through switch blade Ill to wire Ill and thence to line L.

when and only when the pressure switch ll is closed by reason of the existence of a predetcrmined pressure in the servo-motor system the main motor 6 may be started by closing the starting element Ill which allows current to fiow from line L through wire I", solenoid Ill. the presure switch ll. the stop element I'll and starting element Ill of main motor switch ll. the limit switch ll, which is closed when the bell crank lever ll is in its intermediate position shown in Fig. 2, and wire Ill to wire I This energizes solenoid Ill and closes switch blades Ill, ill, I" and Ill causing current to be subplied through lines U. L? and U to the main electric motor l. Under this condition current also flows from line L through wire Ill and solenoid Ill of relay RI to wire I'I'l. energizing relay Rl whereby the control circuits shown in Fig. 6 are rendered operative. When switch blade Ill has closed. solenoid I'll will remain energized through the holding circuit involving pressure switch ll. stop element I'll, wire "I, switch blade Ill and wire Ill, and the motor 5 will continue to run until the opening of either the pressure switch ll or the stop element Ill.

Ii desired, a speed control mechanism may be connected to the synchronous motor l in order to open the circuit by which the motor is energired in the event that a load is applied to the motor I before it has reached its maximum speed,

but such a mechanism has not been illustrated since. it constitutes an adaptation which is not essential to the present invention.

The control circuit for operation of the press H is shown in Fig. 6. It comprehends two relays RI and R2 and the switch blade I88 of relay R5, the solenoid I83 of which is shown in Fig. 5. All of the electrical instrumentalities are represented in the condition which they assume when the press is idle and in the position represented in Fig. 1. The operation of this circuit is described in connection with the description hereinafter of the operation of the press.

The electrical system for the leakage pump is shown in Fig. 7. Lines L L and L energize the motor I which drives the leakage pump 4 when the switch blades I90, I9I and I92 of relay R4 are closed. From line L a wire I93 leads through the leakage motor starting switch 68 and through mercoid liquid level switch 41 to the solenoid I95 of relay R4 and thence to line L If the level of the liquid in the drainage tank I52 is below a predetermined point the mercoid liquid level switch 41 will be closed. The solenoid I95 may then be energized by closing the starting switch 68, or it may be de-energized by opening switch The electrical system for the servo-motor systern is shown in Fig.8: Lines L L and L energize the motor 6, which drives the servo-motor pump 3, when the switch blades I96, I91 and I98 of relay R3 are closed. From line L a wire I99 leads through the solenoid 200 of relay R3 and thence through the stop element 20I of the start and stop switch 81 of the servo-motor system and through the starting element 202 of the same switch to wire 203 which joins line L When switch elements 20I and 202 are closed the solenoid 200 will be energized and the motor 6 will start. Moreover, through a holding circuit which includes switch blades 204 and wire 205 the solenoid will remain energized until the stop element MI is actuated to break the circuit through wire I99 and solenoid 200.

Operation The operation of the press H and the control system therefor is as follows.

In Fig. l the ram 26 and pull back plungers 30 of the press H are shown in their raised position at the upper limit of travel. All motors and pumps may be assumed to be idle and the various electrical switches and relays are as represented in Figs. 5, 6, '7 and 8. It may be assumed that the gate valve 9 is open admitting pressure at, say, thirty-five to forty pounds per square inch from the pre-flll tank 92 to the top of the press cylinder 21 and that high pressure fluid is trapped in the pull back cylinders 29, the valve I2 on the instrument panel I51 being closed.

Under these conditions the operator presses the start button of switch 68 of the leakage system so that the motor I which drives the leakage pump 4 may be energized whenever the liquid level in the drainage tank I52 is such as to cause the mercoid switch 41 to close. He also presses the start button of the servo-motor switch 61 closing the starting element 202 of that switch.

It will be particularly observed that if prior to attempting to start the main electric motor the reciprocal element I03 is in any position other than a central position within the centralizing cylinder 50, such as represented in Fig. 1 of the drawings, the admission of pressure fluid to cylinder 50 through pipe MI and branch pipes Ia and II: will urge the floating collars I40 hence insure that the flow control member of the main pump I is in the neutral or no-delivery position. Centralizing the reciprocal element I03 moves the bell crank lever 63 to a position where the arm H0 is perpendicular and engages limit switch to close the same. Starting of the servo-motor pump 3 causes fluid under pressure to flow through pipe I and its branches I36,'

I44, Ia and I4Ib to the centralizing cylinder 50 and servo-motor 2. When the required predetermined pressure is reached in pipe I46 leading to pressure switch 48 of the servo-motor system, that switch will close. With the closing of the start element I85, of limit switch 80 and pressure switch 48 the circuit leading through wire I" and solenoid I18 of relay R6 will be closed, starting main motor 5 which drives main pump I.

The control circuit is now ready to function, and as soon as the pump I has reached its maximum speed the press operation can be started. All elements of the control system are now in the position represented in Fig. 2 of the drawings.

The press can be operated either manually by moving the hand lever 54, or electrically by pressing the start button 62 or the foot switch 69. By pressing either the cycle start button 62 or the foot switch 69 the press will be caused to move downwardly through the following operations. At this point the solenoid I83 of relay R5 is energized through the holding circuit shown in Fig. 5 which comprehends wire I88, switch blade I80, stop element I19, solenoid I83 and wire I82. The relay R5 being energized, switch blade I88 shown in Fig. 6 is closed. Current may flow from line L through switch blade I88 of relay R5 to wire 208, thence through emergency stop switch 63 to wires 209 and 2I0 and through either the cycle start switch 62 or the foot switch 69, which ever may be closed, to wire 2I2 through solenoid 2I3 of relay RI and thence to line L When relay RI is energized its switch blades 2I4, 2I5 and 2I6 will close. The closure of switch blade 2 of relay RI will establish a holding circuit for that relay through switch 221 of pressure governor 59, wire 235, switch blade 2| 4, wire 228, solenoid 2I3 and wire 2| 2. The closure of switch blade 2| 5 will establish a circuit leading from wire 2I0 through wire 2H and switch blade 2I5 to line L through solenoid B. When solenoid B is thus energized its plunger I68 will be raised to the position shown in Fig. 3 and the bell crank lever 53 will cause the reciprocal element I03 to move outwardly, or to the left as shown in Fig. 3, which operates the servo-motor 2 and shifts the flow control member of the pump I to a position where that pump will discharge at connection IOI. At the same time the resulting upward movement of the control rod I63 will cause a downward movement of the hand lever 54 and move limit switch 82 to down position. This completes a circuit through the switch 221 of pressure governor 59, wires 235 and 229 to switch 82 and thence through solenoid C of pilot valve 26 to line L energizing solenoid C.

Solenoid C being thus energized the valve stem I30 of pilot valve 26 will be drawn downwardly against the force of spring I29 to the position represented in Fig. 3 allowing fluid trapped in the top chamber III of check valve I3 to be released through pipe H3 and ports I32b and I38 of pilot valve 26 to discharge pipe I5I which leads to drainage tank I52. Draining the trapped fluid iavasre from chamber III allows check valve I2 to open under the influence of pressure in pipe 21 and permits fluid from pipe 21 to flow into passage I20 and thence through the ports I II of throttle valve II, which controls the closing speed of platen 20 by throttling the fluid passing through ports I It, to pump connection I42 which is now the suction side of the pump I. If there is an insufllcientflow of fluid passing by throttle valve II to the suction side of pump I to balance the flow at the discharge side, the check valve I4 will open and make up the discrepancy. Under the influence of pressure from pre-flll tank 22 through pipe II and filling check valve land pressure from pump connection IIII which is now a discharge point, and pipe 22 the ram 22 will be urged downwardly.

When the press platen 22 moves downwardly the cam ill on the stroke rod I disengages limit switch 14 which has heretofore been held open by engagement with cam I'll. This allows limit switch It to close and permits current to flow from wire 2Il through wire 2Il, switch blade 2I8 of relay RI, wire 2", limit switch and wire 220 through solenoid 22I of relay R2 and thence to line L. Relay R2 being energized its switch blades 222 and 222 will be closed and its switch blade 224 will open. Moreover relay R2 will remain energized through a holding circuit from wire 2|. through switch blade 222 of relay R2, wire 2I2, limit switch II, wire 220 and solenoid 22I.

When the press platen 22 has moved downwardly to the point where it is stalled or has come in contact with the work piece W, as shown in Fig. 3, the movement of fluid in the pipes 81 and 92 ceases momentarily. When flow ceases from pre-flll tank 22 through fllling check valve 8 this valve will close and permit high pressure fluid from pump connection Ill andpipe 92 to be trapped in press cylinder 21. The press platen 28 continues to be urged downwardly upon the work piece W under the intensified pressure until that pressure has reached the predeterminedpoint for which the pressure governor 59 is set. At this point pressure in the pipe 92 causes pressure governor S2 to operate opening switch 221 and hence opening the holding circuit which leads through wire 22!, switch blade 2 and wire 228 to solenoid 2I2 of relay RI, de-energizing relay RI opening switch blade III and de-energizing solenoid 3. Similarly the circuit leading from the switch 221 of pressure governor 59 through wires 235 and 229 and through limit switch 82 to solenoid C will be opened de-energizing solenoid C, and causing the valve stem I20 to pilot valve 26 to be raised under the influence of spring I29.

At this point solenoids A and B being de-energized, bell crank lever 62 will he moved under the influence of pressure in the centralizing cylinder 50 first to a central position in which the limit switch is disengaged by the hand lever 54 and hence moved to the "up" position closing the circuit from wire 2I2 and switch blade 222 through wire 22!, limit switch 22 and solenoid A. Thisenergizes solenoid A and causes a further movement of bell crank lever 52 to the position represented in Fig. 4..

Energizing solenoid A moves the reciprocable element I02 inwardly causing the flow control member of the pump I to be shifted so that pump connection IIiI becomes the suction side and pump connection I82 becomes the discharge side, and the flow of fluid is as represented in Fig. 4. Solenoid 0 being de-energized, the valve stem I 01 pilot valve 28 is raised causing fluid trapped in the upper chamber I22 or valve I2 to be discharged through pipe I" and ports I24a andv III of pilot valve 20 to pipe III and thence to drainage tank I42.

The pressure against the annular shoulder I22 at the lower end of valve I! will then be suflicient to raise valve I4 against the pressure of spring I2I releasing pressure from pipe 22 and pump connection III and allowing fluid to pass through valve I 6 and to flow through pipe 222 and passage I22 in the valve structure II. Pressure in the main press cylinder 21 is thereby gradually relieved. A decompression of the fluid is caused. and this prevents the shock which would otherwise be attendant upon the sudden release of pressure.

Fluid discharged at pump connection I02 raises valve II from its seat and flows from passage us to passage I22 in the valve structure It. The pressure is sufllcient to raise valve I2 from its seat so that the fluid flows through pipe 21 into the pull back cylinders 22. The same pressure is applied through pipe 24 to the fllling check valve 2 causing it to open. In an obvious manner pressure applied to the plungers 22 of the pull back cylinders 29 lifts the platen 22 together with the ram 26 forcing fluid out of the main cylinder 21 of the press H into the pre-flll tank 92 through pipe I As soon as the platen 24 in its upward movement has reached the point where the cam Ill on stroke control rod l5 engages the limit switch I0 this switch will open. Opening of the limit switch III breaks the circuit. shown in Fig. 6, leading through wire 220 to solenoid 22I of relay R2. When relay R2 thus becomes de-energized, switch blade 222 will open, breaking the circuit through wire 22! and limit switch 22 and deenergizing solenoid A. Pressure in the servomotor system applied to both ends of the centralizing cylinder III will immediately shift the reciprocable element I02 to its central position and shift the flow control member of the pump I'to the neutral position. Accordingly the press H will come to rest and remain in the open position. The cycle is now ready to be repeated.

Should the limit switch 10 fall to function for any accidental or unforeseen reason, the platen 28 would continue to move upwardly and the solenoid A would remain energized. To prevent this from occurring the bracket I64 attached to the platen 28 comes in contact with the collar 8i on the control rod I62 forcing this rod upwardly overcoming the force of the solenoid A and moving the hand lever 54 downwardly until it comes in contact with the limit switch 42 moving that switch to its "down position breaking the circuit through wire 22! and switch 82 and deenergizing solenoid A.

At any point in the operation the press may be stopped by actuating the emergency stop button 62. When the emergency stop button 62 is pressed all circuits leading to the switch blades of relays RI and R2 are opened except that the circuit leading to switch blade 224 of relay R2 is closed. With the switch 22 pressed downwardly the latter circuit is closed through wire 22I, switch blade 224 of relay R2 and solenoid A.

When the press H is idle and the main motor 1 has been shut down if it is desired to move the platen 28 to closed position this may be done by opening the valve I2 on the instrument panel I51. Opening the valve I2 permits pressure fluid to be discharged from the pull back cylinders asvaevs I3 29 through pipe u to pipes Ill and III and thence to drainage tank I82.

When the press is electrically operated the condition or the solenoids A, B and C is as represented in the following table: M

When the press is moving up, solenoid A is energized; solenoid Bis de-energized; solenoid C is de-energized (limit switch 82 being in-the "up" position).

When the press is moving down, solenoid A is de-energized; solenoid B is energized;-solenoid C is energized (limit switch 82 being in the "down" position).

When the press is stationary, solenoid A is deenergized; solenoid B is lie-energized; solenoid C is de-energized (limit switch 82 being in the up position).

Manual operation of the press through manipulation of hand lever 54 may be eiiected at any time while the main motor 5 is running. Any

movement of the hand lever 54 will predominate over the forces exerted on the bell crank lever 53 by solenoids A and B. When hand lever it is raised or depressed manually the reciprocable element I03 is moved inwardly or outwardly by direct mechanical leverage. Incident to such movements the limit switch 82 is moved to its up" or "down" positions, opening or closing the circuit leading through solenoid C and operating pilot valve 26 in the desired manner.

When the press H is manually operated the condition of solenoids A, B and C is as represented in the following table:

When the press is moving up, solenoid A is deenergized; solenoid B is de-energized; solenoid C is de-energized (limit switch 82 being in the up position).

When the press is moving down, solenoid A is de-energized; solenoid B is de-energized; solenoid C is energized (limit switch 82 being in the down position).

When the press is stationary, solenoid A is deenergized; solenoid B is de-energized; solenoid C is de-energized (limit switch 82 being in the up position).

While I have described in some detail a preferred embodiment of my invention it will be apparent that various modifications may be made in the system herein described and illustrated without departing from the spirit of the invention, and that certain features of the invention may be used to advantage without use of other features, and that the invention may be applied to various types of hydraulic machinery other than the particular type 01 press illustrated in the drawings.

Having thus described my invention, I claim: 1. In a control system for a hydraulically operated machine including an electric motor and a 'reversible pump driven thereby for supplying pressure fluid to said-machine, said pump having a flow control member and means for shifting the same from neutral to on-stroke position; a pressure-urged reciprocable element connected to said shifting means and governing through it the direction and delivery of said pump, an electric circuit for supplying current to said motor, and means interposed in said circuit for preventing starting of the motor unless as a condition precedent the reciprocable element has been urged to a position which maintains the flow control member of the pump in neutral position.

2. In a control system for a hydraulically operated machine including an electric motor and a reversible pump driven thereby for supplying pressure fluid to said machine, said pump having a flow control member and means for shifting the same "from neutral to on-strcke position, a centralizing cylinder having therein a reciprocable element connected to said'shiiting .means and governing through it the direction and delivery of said pump, an electric circuit for supplying current to said motor, and, means interposed in said circuit for preventing starting-oi the motor unless as a condition precedent pressure has been admitted to said centralizing cylinder to maintain the flow control member of the pump in neutral position.

3. In a control system for a hydraulically-operated machine including an electric motor and a reversible pump driven thereby for supplying pressure fluid to said machine, said pump having a flow control member and servo-motor for shiit-" ing the same from neutral to on-stroke position, a centralizing cylinder having therein a reciprocable element connected to said servo-motor and governing through it the direction and delivery of said pump, means for supplying pressure fluid simultaneously to said servo-motor and centralizing cylinder, an electric circuit for supplying current to said electric motor, and means interposed in said circuit for preventing starting of the motor unless as a condition precedent pressure has been admitted to'said centralizing cylinder to maintain the flow control member of the pump in neutral position. I

4. In a control system for a hydraulically operated machine including an electric motor and a reversible pump driven therebyfor supplying pressure fluid to said machine, said pump having a flow control member and means for shifting the same from neutral to. on-stroke position, a

centralizing cylinder having therein a reciprocable element connected to said shifting means and governing through it the direction and delivery of said pump, means mechanically connected to said reciprocable element for governing the desired sequence of operations of the pump, an electhe same from neutral to on-stroke position, a,

centralizing cylinder having therein a reciprocable element connected to said shifting means and governing through it the direction and delivery of said pump, electro-mechanical means connected to said reciprocable element for automatically effecting the desired sequence of operations of the pump, manually operated means also connected to said reciprocable element for operating the pump according to the will 0! the operator, an electric circuit for supplying current to said electric motor, and means interposed in said circuit for preventing starting of the motor unless as a condition precedent pressure has been admitted to said centralizing cylinder to maintain the flow control member of the pump in neutral position.

6. In a control system for a hydraulically operated machine includin a reversible pump for supplying pressure fluid to said machine, said pump having a flow control member and pressure operated means for shifting the same from neushifting the same to neutral or either on-stroke position whereby the pump may at all times be controlled manually at the will of the operator.

'7. In a control system for a hydraulic press or the like having a reciprocating platen and cylinder means for moving said platen in opposite directions, means including a reversible pump for supplying fluid, varying in pressure and direction. to the cylinder means of said press, two spaced connections on said pump, each serving either as a suction or discharge point and having communication with said cylinder means through pipe lines leading thereto, a set of valves arranged in juxtaposed relation between said spaced connections, means for operating said valves in predetermined sequence to control the direction of flow in the pipe lines to and from the press, said -valves including a throttle valve for controlling the quantity of fluid flow in one of said lines, and said valves being embodied in a unitary structure mounted on said reversible pump and having internal passages by which the valves are serially connected, and an additional internal passage in said structure leading from one pump connection to the other and by-passing the throttle valve aforesaid.

8. In a control system for a hydraulic press or the like having a reciprocating platen and cylinder means for moving said platen in opposite directions, means including a reversible pump for supplyin fluid, varying in pressure and direction, to the cylinder means of said press, two spaced connections on said pump, each serving as a suction or discharge point and having communication with said cylinder means through pipe lines leading thereto; a set of valves arranged in juxtaposed relation between said spaced connections with inter-communicating passages between said valves, said valves and passages being embodied in a unitary structure, mounted on said reversible pump and including a quick discharge valve serving to prevent shock when pressure is released in said cylinder means, and means for operating said valves in predetermined sequence-to control the direction and pressure of fluid flow in the pipe lines to and from the press.

9. In a control system for a hydraulically operated machine including a reversible pump for supplying pressure fluid to said machine for its operation, said pump having a flow control member and pressure operated means for shifting the same from neutral to on-stroke position, a multiposition reciprocable element connected to said shifting means and governing through it the direction and delivery of the pump, fluid pressure means for urging said reciprocable element towards its neutral position whenever pressure is admitted to said shifting means, electro-mechanical means connected to said reciprocable element and having a force sumcient to overcome the force of said fluid pressure means and thereby efl'ect the desired sequence of operations of the pump, and a manually operated predominantly controlling device, having a direct mechanical connection with said reciprocable element for shifting the same to neutral or either on-stroke position whereby the pump may at all times be controlled manually at the will of the operator.

LOUIS A. CAMEROTA.

REFERENCES CITED The following referenlces are ofrecord in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,927,583 Ernst Sept. 19, 1933 2,080,810 Douglas May 18, 1937 2,210,144 Day Aug. 6, 1940 2,213,968 Rose Sept. 10, 1940 2,258,886 Ernst Oct. 14, 1941 2,298,359 Ernst et a1 Oct. 13, 1942 2,298,393 Lindner Oct. 13, 1942 2,302,922 Tucker Nov. 24, 1942 2,392,644 Camerota Jan. 8, 1946 2,417,858 Becker Mar. 25, 1947

Images