US2602294A - Hydraulic and electrical system for operating presses - Google Patents

Description

J y 1952 R. K. SEDGWICK 2,602,294

HYDRAULIC AND ELECTRICAL SYSTEM FOR OPERATING PRESSES Filed Dec. 21, 1950 IN V EN TOR.

Patented July 8, 1952 HYDRAULIC AN D ELECTRICAL SYSTEM FOR OPERATING PRESSES Robert. 'K. Sedgwick,.Sharonville, Ohio, assignor to American Steel Foundries, Chicago, 111., a corporation of New Jersey 1 Application December 21, 1950, Serial'No. 202,023

I 3 Claims.

This invention relates to a system for actuat ing a reversible hydraulic motor such as is commonly utilized to operate an hydraulic press.

A primary object of the invention is to. eliminatethe necessity for using a conventional operating valve, such'as is commonly used to reverse the flow of hydraulic fluid in the system.

Another object of the invention is to prevent hydraulic shocks which are ordinarily generated in the system when an operating valve is used.

A further object of the invention is to lengthen the life of the system by eliminating solenoids for operating the valve, inasmuch as suchsolenoids are notoriously short lived.

A more specific object of the invention is to reverse the fiow of hydraulic fluid by reversing the main pump and its operating motor.

Still another object of the invention is to utilize the elasticity inherent in the hydraulic fiuid itself, as well as in the piping. of the system, for reversing the rotation of the pump at the end of the advance stroke of the hydraulic motor after the operating motor for the pump has been deenergized.

The foregoing and other objects and advantages of the invention will become apparent from a consideration of the following specification and the accompanying drawing, wherein:

The single figure is a combined flow diagram and electrical wiring diagram of an hydraulic press embodying the invention.

In order to avoid unnecessary repetition, the various parts of the novel system will be described in connection with an operating cycle.

A typical operating cycle is initiated by closing a normally open advance switch 2 which establishes an electrical circuit through a normally closed stop switch 4 and through an advance relay 6.

Energization of the advance relay 6 closes normally open switches 8 and I0 which are responsive to said relay. Closing of switch 8 establishes a holding circuit through the advance relay 5, and closing of switch [0 establishes an electrical circuit through a starter relay l2, thereby clos-' ing a set of normally open advance starter switches 14, which are responsive to the relay 12. Closing of the starter switches 14 establishes an electrical circuit through motor leads l6, l8 and 20 having dlsconnect switches- 22therein. Thus the armature shaft 23 of an electric motor 24 is rotated in one direction to rotate a conventional uni-directional pump 26 on its advance stroke whereat hydraulic fluid such as oil is sucked into the pump 26 from a return or pullback line 28 and is pumped under pressure into anadvance line 29. The pullback line 28 is connected to a pullback chamber 32 of an hydraulic cylinder 30 containing a ram 32 which operates a movable platen 34; and the line 28 is also connected by a check valve 35 and a safety relief valve 38 to a tank or reservoir "of hydraulic fluid. The advance line 29 is similarly connected by a check valve 42 and a safety'relief valve 44 to'the tank 40. I

Upon-actuation of the pump 26 on its advance stroke, as above I described, hydraulic pressure fluid is pumped through the line 29 into a sequence valve 45 having a stem lllspring pressed to closed position whereat fiow of fluid from the line 28 is blocked and is forced through a branch line thereof into a rapid advance tube or hol-' lowram 52 carried by the cylinder 30 and having a fluid tight fit at 54 within a chamber'56 in-the ram 32. Flow of fluid into the rapid advance tube SZ-urges-the ram 32 on its rapid advance stroke until the plate 34 engages the work (not shown) whereupon hydraulic pressure builds up in the line 50 urging the stem 48 to open position whereat'fiuid pressure is directed through a line 58 to a p'refillva'lve chamber 60 urging a prefill valve 62 to closed position against resistance of a spring, whereby the valve 62 is effective to cut off flow of hydraulic fiuid from the tank M) to the main advance chamber 66 of the cylinder 30.

After the stem .62 has been actuated to closed position-hydraulic pressure in the line 5B overcomes the resistance of a check valve 68 and flows into the main advance chamber 66 of the cylinder 30, whereupon pressure is applied from the lines 50 and 58 to the maximum cross sectional area of the ram 32.

At this point in the cycle, pressure in the line 58 :is transmitted from a point downstream of the check valve 68 to an hydraulic pressure device 10 which closes a pressure responsive switch [2 establishing a circuit'through a conventionaltimer [4 whenever, pressure is built up in the main cylinder chamber 66 to a predeterminedvalue atv which theswitch l2 closes. The timer 14' then actuates a switch 5 .to a return position thereof after a predetermined time interval elapses according to the requirements of the particular system.

Actuation of the switch 16 from its normal advanceposition to its return position opens its contacts 16, thereby breaking the holding circuit through the advance relay 6, and conecting contacts and establishing an electrical circuit through a return relay 82. Energization of relay cycle, the advance relay 6 is deenergizedand for this reason the starter relay I2 is deenergized and its switches [4 are open so that the electrical motor 24 is deenergized. Thus after a predetermined time interval dependent upon the particular system, the pump 26 comes to a stop and because of the elasticity of the hydraulic fluid as well as the conventional piping of the line 29 and its connections to the chambers 66 and 56, the pump 26 is rotated in the opposite direction on its return stroke, whereupon the timer 88, which is adjusted for this purpose, closes a switch 90 establishing an electrical circuit through a return relay 92 which, when energized, closes its normally open return switches 94 establishing a reverse electrical circuit through the leads l6, l8 and and the motor 24, continuing the rotation of its armature shaft in the opposite direction, and consequently rotating the pump 26 on its reverse stroke.

As the pump 26 is actuated on its reverse stroke it sucks hydraulic fluid from the line 29 and delivers hydraulic fluid under pressure into the return line 28. Thus, when pressure has been relieved in line 29, the prefill valve stem 6-2 opens accommodating flow of fluid from the main advance'chamber 66 into the tank 40, and the sequence valve stem 48 opens accommodating flow of fluid from the line 58 through a line 96 into the tank 40 to release fluid from the prefill valve chamber 68 thereby accommodating opening of the stem 62. Under these conditions, the pump 26 is supplied with hydraulic fluid from the tank 40 through the check valve 42 and from the branch line 50, and the pump 26 delivers pressure fluid through the line 28 into the pullback chamber 32 actuating the ram 32 on-its return or pullback stroke.

As the ram 32 nears the end of itspullback stroke, an actuator 98 carried by the platen 34 opens a normally closed switch I80 thereby breaking the holding circuit through the relay 82 and deenergizing the same. Deenergization of the return relay 82 opens its switches 84 and 88 and consequently deenergizes the starter relay 92 opening its switches 94 and deenergizing the motor 24.

Under these conditions, the Weight of the ram 32 urges it to the end of its return position. As the ram 32 reaches the bottom of the cylinder 30, before the motor 24 and pump 26 have stopped rotating, the relief valve 38 opens momentarily to relieve pressure in the line 28 until the motor 24 has been stopped by the torque reaction from the pump 26.

It maybe noted that, if desired, the pullback stroke of the ram 32 may be eifected when the relay 6 is deenergized by closing a normally open push button switch I02, which, when closed, cstablishes a circuit through the relay 82 and normally closed switch I88. utilized in preadjustment of press parts or to accomplish the pullback stroke if the device 10 becomes intentionally or accidentally inoperative.

It will also be understood that the rapid advance feature may be eliminated, if desired, and that the rapid advance chamber 56, main advance chamber 66, and pullback chamber 32 may be in separate cylinders containing separate rams This feature may be connected to the platen 34, as is conventional in the art.

I claim:

1. Ina system for operating an hydraulic motor having advance and pullback chambers and ram means reciprocal therein; the combination of pump meanshaving opposite sides thereof connected to respective chambers, an electric motor having an armature shaft connected to the pump means, said pump means being adapted .upon rotation of the shaft in one direction to suck fluid from one side of said pump means and to urge fluid from the other side thereof, and said pump means being adapted upon rotation of the shaft in the opposite direction to suck fluid from said other side of said pump means and to urge fluid from said one side thereof, said pump means having sufficient capacity to compress said fluid on advance stroke of said ram means after said ram means has encountered resistance of associated work, and an electrical system operatively associated with said electric motor, said electrical system comprising switch means adapted when closedto establish an electrical circuit through said electric motor to rotate said shaft in said one direction thereby effecting advance stroke of the ram means, said switch 'means being adapted when open to break said circuit thereby deenergizing said electric motor during a predetermined period of time until said advance stroke of said ram means has terminated and until expansion of said fluid has initiated rotation of said shaft in said opposite direction thereby initiating pullback stroke of said ram means, and said switch means comprising time delay means adapted upon termination of said predetermined period of time to automatically close another circuit through said electric motor to rotate said shaft in said opposite direction and thereby complete said pullback stroke of said ram means.

2. In a system for operating an hydraulic mo-' tor having a rapid advance chamber, a main advance chamber, a return chamber, and ram prefilled means for closing the same, said branch.

also being connected to the main'advance chamber, valve means in said branch for yieldingly resisting fllow of fluid to the prefill valve means to delay closingthereof until the ram means has reached the end of a rapid advance stroke, a pullback line connected to the pullback chamber, each of said lines havingrelief valve means accommodating flow of fluid at a predetermined maximum pressure value to said reservoir and having one-way check valve means accommodating flow of fluidfrom the reservoir, a pump having opposite sides thereof connected to respective lines upstream of the check and relief valve means, said pump being adapted when rotated in one direction to deliver pressure fluid from one side of the pump while sucking fluid from the other side of the pump, said pump being adapted when rotated in the opposite direction to deliver pressure fluid from said other side of the pump while sucking said. fluid from said one side of the pump, a reversible electric motor having an armature shaft connected to said pump for rotating the same, and an electrical system operatively associated with the electric motor for rotating its armature shaft first in one direction and then in the opposite direction.

3. A system, according to claim 2, wherein the electrical system comprises means for automatically deenerg'izing the electric motor after a predetermined pressure has been developed in the advance chamber, and said electrical system comprises means for automatically reversing rotation of the armature shaft after a predetermined time interval subsequent to said deenergization of the electric motor to accommodate initial reversal of the rotation of the pump by elasticity of the hydraulic fluid and lines.

ROBERT K. SEDGWICK.

REFERENCES CETED The following references are of record in the file of this patent:

UNITED STATES PATENTS

Images