US2343139A - High speed forging press - Google Patents

Description

Feb. 29, 1944. N T 2,343,139

HIGH SPEED FORGING PRESS Original Filed Jan l5, 1940 4Sheets-Sheet 1 III 7 INVENTOR WALTER ERNST ATTORNEYS Feb. 29, 1944. w; ERNST 2,343,139

I HI GH SPEED FORGING PRESS Original File d Jan; v15, 1940 4 Sheets-Sheet 2 jBT'E.

[NVENTOQ WALTER ERNST- ATfbRNEYa Feb. 29, 1944. w, ERNST 2,343,139

I HIGH SPEED FORGING PRESS Original Filed Jan. 15, 1940 4 Sheets-Sheetfi WORK Rcsn-rmu: I07

INVENTOR WALRR Emm RTTORNEYb Feb. 29, 1944. w, ERNST v 2,343,139 HIGH SPEED FORGING PRESS.

Original Filed Jan. 15, 1940 4 Sheets-Sheet 4 JTEr. 4.

, INVENTOR WALTER 'ERNST Anemia:

Patented Feb. 29, 1944 HIGH SPEED FORGING PRESS Walter Ernst, Mount Gilead, Ohio, assignor to The Hydraulic Development Corp., Ina, Wilmington, Rel a corporation oi Delaware Original application January 15, 1940, Serial No.

1941, Serial No. 402,119

6 Claims.

The primary object of the present invention is to provide a means and method for operating a press where a relatively long working stroke of the press is necessary at relatively high speeds in order to economize time in the cycle of operations and where the final stroke of the press must be at speeds as high as the initial speed and at high pressures.

It is an object of this invention to provide a press, for such purposes as forging of steels, injection molding, die casting and the like. Heretofore where a relatively long working stroke at high pressures has been necessary, particularly in connection with forging presses, it has necessitated the use of a very large operating system of hydraulic accumulators, the first cost of which was prohibitive. Also, due to the relatively short portion the working cycle is of the total cycle of operations the system was highly inemcient.

The object of this invention is to provide a movement to the work at low pressure and high speed, giving a rapid traverse stroke; and to thereafter provide continued high speed at high pressure in order to impart tremendous pressures to the work, preferably without sudden shock, as is required-in the case of forging metal billets, compressing plastics, etc.

Another'object of this invention is to secure the advantages of a closed circuit with a reversible pump so that the direction of movement can be reversed without shock while securing the advantages of sudden high pressure. Thus shock is eliminated at the end of the reverse of the stroke which is. characteristic of the accumulator type of press.

It is a further object to protect the press and the entire system against thelaccide'ntal de-' velopment of undue pressures, by the provision of safety valves at the necessary points in the system.

The press of this invention is especially intended for operations in which it is desirable or Divided and this application July 1 die member to press the heated billet downwardly, forcing it to assume the shape of the lower portion of the cavity. The length of stroke necessary to accomplish this operation might be from several inches to more than a foot, depend ing on the particular workpiece in process. At any rate, the stroke must be executed rapidly, to prevent too great cooling of the part, in. view of furthef pressing strokes yet to be performed.

' The first male die member must then be withdrawn, again at a high rate of speed, and a second die member moved into place. This done, another stroke of the press is efiected, either by manual or automatic control means, for example to form the interior of the shell by displacing some of the previously formed metal upward- 1y into the space between the two die halves. This operation, although requiring high pressures acting through a long stroke, must as before, be performed with great rapidity, to prevent the. cooling of the shell to the point of shrinking upon the punch. Similarly, any subsequent pressing strokes will require rapid press action, the more numerous and the deeper these are, the more imperative becoming the high speed.

It is to meet the requirements of such a pressing operation, and to do this with economy of equipment and space, and with smoothness and efllciency, that this press has been invented.

This case is a division of my prior application Serial No. 313,852 filed January 15, 1940, an

entitled High speed forging press.

Referring to the drawings:

'Figures 1 to 4 are diagrammatic views of the press and its operating system, showing the sig nificant stages of a pressing operation.

Figure 1 illustrates the idling stage of the press -and system, preparatory to a working stroke.

imperative to executea relativelylong high pressure stroke at'hi'gh speed. Examples of such operations are found abundantly in forging, injection molding, or die casting. A specific example taken from the field of power forging, .is the making of long steel shells. In this case a billet, heated to the correct temperature, is placed in the cavity of the lower die member, the

first of two or more pressing movements being immediately thereafter initiated. This first movement might, for example, bring the upper male die member into the cavity of the lower Figure 2 illustrates the'inltial stage of a working stroke, in which the press platen is caused to 1 approach the work at a rapid -rate,'and under no pressure.

Figure} illustrates the reversing stage, the platen having completed its work, and the press controls being operative to initiate its return.

Figure 4 illustrates the stage in which the platen is returning to its idling position, and the auxiliary pressure system is storing working energy for the subsequent pressing cycle.

Referring in detail to Figures 1 to 4 of the drawings, the numeral I designates the pressing plunger of a hydraulic press, having at its upper end the double-acting piston 2. Thispiston r'eciprocates within the cylinder -3.- At the lower end of the plunger I is mounted a platen 4 upon which, in turn, is mounted the upper member.

of any suitable work-engaging means. such as a die or iniection. lunger. Disposed above the cylinder 2 and mounted thereon is a reservoir I adapted to store part of the fluid medium by which the pressis operated. Y,

The movement of the platen 4, and the pressures exerted by it upon the work, are determined by two independent pressure generating systems, and by a third interconnecting hydraulic control system.- .There are thus three distinct, but interrelated, hydraulic systems provided for thecontrol of the press: a primary pressure system, a secondary or auxiliary pressure system,

and an interconnecting control system. For the purpose of making clear-the separate action of these systems, they will first be described under separate headings.

. mm Panssuns Svs'rrn The primary pressuresystem is of the closed type and is operative throughout the entirety of a pressing cycle. It derives its flow of pressure fluid from the pump 2, which is of the reversible, variable delivery type, capable of generating high ring .of this pump consist of a pilot cylinder I and a self-centering spring cylinder 2, the design of which is well known, and does not constitute a part of the present invention. u

' The pump l-delivers fluid to the differential areas of the press piston 2 in accordance withdeliver into line H, withdrawing'from lines 2'- and I0, and .thus effect the reverse or upward stroke of the piston. depen g upon the setting of the shift ring to the ght or left of the centerof the pump.-

When a downward. pressing stroke piston 2 late be eflected, the solenoid I2 is energized (by means to be hereinafter described), its resultant motion (see Figure 2)'being' transmitted to the shift ring of pump 2 through the servomotor as described above, the pump then supplying fluid to line 9, and withdrawing it from line H. When the-pressing stroke thus initiated hasbeen completed, the solenoid is de-energized (see Figure 3) and the pump is shifted to reverse it delivery by means of a spring within the servom0tor,- thus to efl'ect an upward, return motion of the piston 2. As this piston nears thelimit of its upward travel, the controlrod I 2, which is carried by platen 4, acts through an adjustable collar 22 to move lever l4 and ultimately the pump shift ring to their neutral positions, in which both pump 8 and piston 2 are caused to idle. Should any leakage of fluid occur to permit piston 2,

. pressures. Preferably the controls for the shift with plunger l and platen 4, to descend of their own weight, control rod l2 and collar 22 will correspondingly descend, permitting the ,pump to again deliver to the push-back side of piston 2, restoring it to its idling position. This condition of the press is shown in Figure l.

In addition to the press controls thus far described, there are provided certain other conand the fluid in the reservoir at certain stages of a pressing cycle. For example, when piston 2 and platen 4 move downwardly at the beginning of a pressing cycle, they do sounder theinfluence of gravity, and at a rate determined by the suc- The position of the shift ring is primarily determined by the action of the operating solenoid l2 and the platen-actuated control rod l2, which transmit their respective motions through the lever l4 and linkage is to the pilot plunger ii. The reciprocation of thisFpilot plunger is .in turn transmitted to the shift ringof the piunp through the hydraulically actuated piston within cylinder 1, this piston being adapted to move directly, in direction and extent, with the pilot plunger.

'I'hesource of fluid pressure for thisise'rvomotor action is the constant deliverypilot pump l1, which draws fluid from the reservoir I through linesfli2 and l2,-dischar8ing it through'line' 22 f to one ofthe'ports of arelief valve 2|. Since the requirement ofthe servomotor for operating fluid is intermittent, as determined by solenoid and control rod-1'12, ,this relief valve normally bypasses the discharge ofpilot pump l1 into'line "22-. and back to the suction side of the pump through line is. When, however, the control element-s12 and I2 set to cause movement of the pilot plunger It in either direction, fluid .pressure within the servomotor is momentarily loweredyand'the spring within the relief valve 2| 'nioves the valve plunger to close the passage between lines 20 and 22. This result in directing tion of the pump 6 drawing fluid from the lower end of press cylinder 2. As the area in this end of the cylinder is relatively small, being only as large in cross section as the push-back side of piston 2, the piston tends to travel downwardly at a speed considerably greater than that at which the pump 8 delivers fluid through lines 2 and III to the upper, pressing side of the Piston 2.

' 2I downwardly against the spring 22, opening a the-output of the pilotpump into the servomotor through line 22, eifecting the required movementof the pmnp shift ring. The exhaust of fluid from the servomotor is by way of lines 24 and 22, either to pump I! or reservoir 5.

passage'between the fluid in reservoir 5 and the space-above piston 2 by way of ports 22 and 22. The space above the piston is thus fllled as rapidly as the pump 8 can remove fluid from the lower end of cylinder 2, making the advance of the platen towards the work as rapid as possible.

As soon as the platen 4, or the workmember carried by it, contacts the work, pressure is developed in the upper end of cylinder 2 above piston 2, closing the surge valve 22 by moving piston 2 is'driven upwardly by fluid pressure bearme against its push-back area, this pressure is communicated by the lines 2|, 22 and 22 to the head of a plunger 24 in the upper part 01' the surge valve 20. The plunger is moved downwardly against the compression of spring 2|, its

lower extremity striking the upper surface of the valv member 21, forcing it open against spring 22. This opening of the surge valve again assists in a rapid motion of piston ,2, in this instance by providing a free passage into the reservoir for fluid above the piston in excess of that 52 stands in the branch line 32, protecting therequired by pump 6 to fill the push-back area of cylinder-3.

At the moment of reversal of platen 4, two other control valves are operative. One of these, the tonnage control valve, is designated generally 36. This valve, in fact, initiates the reversal of the platen by causing the de-energization of the solenoid I2 upon the attainment of the desired pressureupon the work. This pressure is communicated to the valve through lines 37 and 39, which are branches of the main pressgre line lllleading to the area above piston 2. From line 38 the pressure is directed against the end of the plunger 39, lifting it in opposition to the force exerted by a compression spring 40. This movement of plunger 39 is transmitted to a cam 4| carried at its upper end, the cam being adapted to trip a normally closed limit switch 42, in series with the contactor circuit for the solenoid l2. The valve 36 is maintained in this position as long as pressure .in line 38 exceeds the compression of spring 40, the flow of fluid'through the valve being exhausted by the line 43 to the reservoir 5.-

It is to be understood that the tonnage control valve just described may be replaced, for the purpose of reversing the motion of the platen.

by a limit switch responsive to the position of the platen. The other valve which becomes operative at the time of press reversal is located within the reservoir 5, and is generally indicated at 44. Its purpose is to relieve the intense working pressure existing in the space above piston 2. and, while doing this, to by-pass to the reservoir the delivery of pump 6 into line H toward the push-back area of piston 2. This pressure-relieving and pump by-passing action provides a shockless reversal of the press. The valve 44 consists of the balanced plungers 45 and 46. both of which are urged toward the right under spring pressure. Normally, the spring pressure upon plunger 45 positions this plunger so as to block the port 47 opening into the reservoir. as ,well as one end of an internal passage 48. Likewise, the spring pressure upon plunger 46 normally positions it so as to block the port 49 opening into the reservoir.

During the working stage of the press. the

push-back side of the system, while valve 53 stands in the branch line 31, protecting the working side of the system. Both safety valves discharge into the reservoir.

There is also provided a check valve 54, its purpose being to permit fluid stored within the reservoir to be drawn into the line 3| and through it andline H to the pump 6, this passag of fluid taking place at certain times during the actual working stage of apressing operation. Its action will be more fully described later in connection with a summary of the combined actions of all three hydraulic systems of this invention.

As stated above. the primary pressure system is operative at all times during a cycle of the press. From the description of this system it will be evident that this is the case; that the system is operative immediately upon the energization of the solenoid l2 to advance the platen toward the work, that it is operative during the working stage to drive the platen downwardly at high pressure and that it is operative, upon de-energization of the solenoid l2, to return the platen to its idling position and to maintain it in this position'until the initiation of a new cycle. The primary pressure system is, indeed, solely operative to produce the first rapid work-approaching stroke of the press, and the entire return stroke. It is in the second, or working stage of the press that the primary pressure system is augmented by the auxiliary pressure system acting through the controls of the interconnecting system, and these systems will now be considered.

AUXIILIARY PRESSURE SYSTEM -'I'he auxiliary pressure system has its pressure source in a pump 55. This is a variable delivery high pressure pump. and may be of any wellstroke, so that the pump will draw fluid from 31 and 50, overcoming the spring tension urging it to the right. When the working pressure reaches its predetermined limit and the tonnage control valve acts to reverse the delivery of pump 6. pressure within push-back line H is transmitted by lines 3| and 5| to the right end of plunger 45, shifting it to the left against its spring, tension. Plungers' 45 and 46 being thus shifted, port 41, passage 48, and port 49 are all uncovered. whereupon working pressurestanding in line 31 is relieved through port 41 to the reservoir, and the delivery of pump 6 is by-passed through lines I 3| and 5|, passage 43, and port 49 to the reservoir.. Working pressure having been relieved. plunger 46 is spring-returned to its normal right-hand position, blocking port 49 and causing the delivery of pump 6 to be directed against the pushback area of piston 2. Aiso,'since this pressure above the piston 2 is relieved, push-back pressure the reservoir 58 through the line 59 and deliver pressure through line 60. The pressure cylinder 55 is connected by the line iii to a part of the pressure circuit in a manner later to be described. so that when pressure is built up in this part of the circuit to a point determined by the tension of the spring in cylinder 51, the pressure will overcome the spring tension and return the shift ring of the pump. to neutral position, or nearly to neutral position. Under these conditions, the pump will deliver just suflicient volume to maintain pressure in the system asdetermined by the setting of the spring in cylinder 5'|.- Two hand wheels. 62 and 63. are provided, one for adjusting the stroke of the pump. and one for adjusting the tension of the spring. The design and operation of this control is well known by those versed in the art.

A relief valve 64 is provided as a protection to prevent excessive'pressures being built u in line 60 or in other parts of the auxiliary pressure system. in the event the pump control should fall from any cause. This relief valve exhausts throu h line 65 to reservoir 59. The shut-off 55 is delivered consists of a high pressure cylinder 68, having a bore 6! in which is fltted piston II; and of an enlarged cylinder ll having a bore I! in which is fltted piston 13. The two pistons, II and II, are rigidly interconnected by the rod It. In the drawings the cylinder ii is shown broken above piston 13, to indicate that the height of this portion of the cylinder is dependent upon the particular pressure drop to be allowed between the uppermost and lowermost positions of the piston. For instance, if a 20 per cent drop is decided upon, the total height of the cylinder will be flve times the stroke or the piston.

The space abov piston I3 is fllled with an elastic fluid medium; as for example with air, or some inert gas-such as nitrogen, helium or pressure within the bore 9, it is subjected to that pressure through the valve 'I'l only when the positions of pistons IO and 13 indicate that the pump has fully performed its charging funcneon. It will be readily recognized that as fluid pressure is pumped into the bore i! of the accumulator 61, piston Ill, rod I4 and piston 13 will be pushed upwardly tocompress the elastic medium in bore 12 above piston 13.

Attached to piston Ill, asby rod I5, is a cam 16 which is located outside the accumulator 61 and is adapted to actuatethe control valve 'll, this valve being located in the line II and being designed to control the stroke of pump ll. Valve 11 contains a piston "I8 on the right end of tion.- It will be noted that because of this provision, pump will always be delivering at its maximum rate during a downstroke of piston ll, thus supplementing the stored volume of accumulator fluid in producing the high speed stroke of the press at high pressure.

For replenishing any of the gaseous medium that may be lost from the accumulator, there is provided a supply line Ha, in which is placed a shut-oi! valve 'lib. Normally the valve lib is closed, the accumulator requiring no operating connection to its source of gas supply. When the addition of gas to the accumulator is found necessary, valve Ilb is opened to permit a flow from the gas source to the accumulator. The

, pressure of the gas supply will be equal to the which is mounted a ball, or roller, for contacting cam l8. Piston I8 is forced to its extreme righthand position by a, spring 1:, this position of the piston being seen in Figures 3 and 4. While in this position, the piston shuts oil passage of fluid from the line 80 to the line I, the line ll being a branch of line I leading to the fluid pressure bore 8! of the accumulator 81. At the same time, line 6!, which is connected to thepressure cylinder 58, is in communication with lin 82, in turn connected to exhaust line 83,

which leads to the reservoir 58. Under this condition, no pressure can exist in cylinder 56, and pump 55 will be held on iull stroke position by.

the spring in cylinder 51, so that the full delivery of the pump is directed into the accumulato 61, storing pressure fluid in the bore 9;

In Figure 4, the accumulator is shown nearly sued, with the piston n of valve "standing in its extreme right-hand position. A slight additional upward movement or the accumulator piston, which position is illustratedin Figure 1. will bring cam 16 into contact with a roller on the end of piston 18, forcing this piston to the left against the pressure of. spring 10. This action of the piston will close connection between lines minimum gas pressure within the accumulator, that is, thepressure when piston I3 is at the bottom of its stroke.

The cylinder H is also provided, at its lower end, with a breather line He, the purpose oi. this line being to maintain atmospheric pressure on the underside of piston 13'.

There. is provided in'thd upper end of cylinder 68 a port 84 by which thedrain line 83 is connected to'the bore 69 above the piston head III.

This arrangement provides for conducting back to the reservoir 58 any fluid which leaks past the piston head Ill from the lower, high pressure end oithe bore 69.

The reservoir ii is joined with the reservoir I of the primary pressure system by the pipe line II. Pressure fluid transferred from the accumulator to the press is ultimately returned to the reservoir 58 from which it originally was taken,

1 by being expelled into the reservoir I upon the lust sufllcient fluid into the accumulator I! to maintain it fully charged.

The-provision of the valve I1 in the auxiliary pressure circuit insures that whenever the accumulator is not fully charged, the pump is will supply pressure fluid to the accumulator 01 at its maximum output capacity. As indicated above, valve 11 is not actuated by cam l8, and' the control ll of the pump is not, therefore, sub.- iectcd 'to pressures within the accumulator 81, until cam Ilhasbeen carried by pistons II and 13 almost to the upper limit of its travel, where the elastic medium above piston II has been retraction stroke of the press, and 11 8 into the line I.

'Im'sncomcrmc Comor. Srsrsu The purpose-oi the systemnow to be described then overflowis .to release, during the working stage of they press cycle, the kinetic energy of the gaseous medium compressed above piston it of the ac-,

accumulator.

The e of fluid from the accumulator is 1 through line II and valve 8' into line 81. The.

valve 88 is simply a service 'valve similar to the valve I, and is normally fully open. Line '81 leads to a metering minim-pressure fluid being discharged from this valve through-a choke valve II and thence, through line as, to a pilot operated tw'o-way valve ll. A line .2 leading from this two-way valve joins the main pressure lin ll,

-and it is by opening a passage into-this line at irom line II that the two-way valve ll opens a passage from the accumulator '1 to the press.

The open or closed position of valve ll is de-. terminedbypilotpressureinthelinesfl and It. This pilot pressure istaken from the pressure line ll through branch line ll, choke valve '0, and line I! tothe four-way pilot valve ll. Depending upon the setting oi this pilot valve, fluid is conducted from line I! into either pilot compressed to the desired point, and the bore line I} or. for controlling the position of the two-way valve 9|. The setting of valve 99 is determined by the energization or de-energization of a solenoid 99, and by the compression of aby the pull of the solenoid core; When, however,

the solenoid 99 is de-energized, the spring I actuates the valve piston |0| so as to connect lines 91 and 93, exhausting line 94 to the drain line 93. a a

The solenoid is shown in its de-energized state in Figures 1, 2, 3 and 4. From these views of the drawings and from the foregoing description,

it will be apparent that energization of the solehold 99 results in the opening of the two-way valve 9|, and that de-energization of the solenoid results in the closing of this valve, by directing pressure into pilot lines 94 and 93 respectively. The choke valve 99 standing in the inlet line 91 of the pilot valve 99, regulates the fluid velocity into the pilot lines 93 and 94, and consequently, the speed of opening or closing of the two-way valve 9|.

The purpose of the metering valve 99 and the choke valve 89 is to regulate the transfer of fluid from the accumulator to the press, once that flow has been started by the energization of solenoid 99 and the consequent opening of valve 9|. The

setting of the choke valve 99 is responsible for the general rate at which the transfer of fluid takes place, while the metering valve 99, in cooperation with the choke valve 89, serves to maintain that rate constant against varying resistances ofiered by the work, and also, at the moment of opening of valve 9|, serves to cushion the impact of accumulator pressure upon the press.

- Valves 99 and 99 may be regarded as two chokes in the pressure line between the accumulator and the press. Valve 99, after being manually ad'- justed, is a fixed'choke, while valve 99 is a variable choke, its restriction of the pressure line increasingand decreasing inversely with pressures in line 90.

Briefly, the metering valve consistsof a plunger I02 urged in one direction by a spring I03. The plunger I02 is provided with metering flutes or grooves I04, these flutes permitting more or less passage of fluid from the line 91 to the choke valve 89, as plunger I92 is raised and lowered, respectively. The pressure on the inlet side of the choke valve 99 is communicated to the end of the plunger I02 opposite the spring I93 by the line I05. The pressure on the outlet side of the choke valve 99, that is, the pressure identical with that exerted upon press piston 2, is communicated to the spring loaded end of the plunger I92 by the line I09. 1

During the idling stage of the press, when no how ofpressure fluid is taking place through valves 98 and 99, pressures in the control lines I09 and I08 are identical and spring I03 holds the plunger I02 in its uppermost position, where the flutes I04 present the least possible restriction to fluid now. This position of the metering valve is seen in Figure 1. At the instant that twoway valve 9| is opened to discharge the accumulator, the pressure in line 90 on the outlet side of choke 99 will momentarily drop, and this change will be communicated to the metering valve through line I08. The efiect of this sudden drop of pressure bearing upwardly against the plunger I02 will be to permit this plunger to move downwardly, pressure in line I05 still being, relatively high. Because of this downward motion, the restriction through the flutes I04 is greatly increased, with the result that the tendency of accumulator pressure fluid to rush into the pressing area of cylinder 3 is checked. Gradually, as pressure rises in line 90, the restriction at valve 99 decreases and the rate of flow to the press increases. The metering valve thus releases accumulator pressure without shock upon the press.

During the pressing operation, varying work resistances will be registered upon the metering valve plunger I02 through the line I09.

Lowered pressures in this line will permit the valve plunger to movedownwardly under the influence of the pressure in line I95, this movement resulting in a greater restriction of the fluid passage along the flutes I04, thereby reducing the flow from line 91 to the choke 99. Increased pressures, on the contrary, cause the valve plunger to move upwardly, so that 'larger areas of the flutes'IM-are exposed to the fluid passage,

and the 'flow to valve 99 is increased. The press movement is thus maintained at a constant rate, namely, the rate predetermined by the manual adjustment of choke 99.

Energization of the solenoid 99, to initiate the transfer of pressure fluid from the accumulator to the press, takes place just before the platen 4 engages the work. To provide for this accurately timed energization, there is attached to the platen a control rod IIlI having the cam face I99, this cam face being adapted to engage and close a normally open limit switch I99. The position of this limit switch is adjusted to meet the requirements of difierent pressing operations.

OPERATION or COMBINED SYSTEMS Idling in its idling, state, the platen 4 being fully withdrawnfrom the work, and dwelling in this condition, although in readiness for a. pressing stroke. No appreciable flow of pressure fluid is taking place in the primary system, the pump 9 being held in its neutral, no-delivery position by the upward force of the collar 25 of the control rod I3 acting upon one end of the lever I4. Such flow as does occur is toward the push-back area of piston 2, and is due 'to leakage of pressure fluid from this area, with the consequent lowering of the platen and actuation of the pump through collar 25, to delivery into line II an amount of fluid suflicient to compensate for the leakage.

As to the auxiliary pressure system, the pump 59 has moved the pistons I0 and I3 of accumulator 9! to their fully charged positions, and has itself been shifted to neutral position in response to pressure within bore 99. It is, at this time, operative only to restore the accumulator to its maximum pressure state as fluid within the bore 99 is lost through leakage.

The accumulator is maintained in its -passive condition by the blocking of its pressure fluid in the interconnecting system, specifically at the valve 9|, which is closed. This valve is forcibly maintained in its closed position by the action of static fluid "pressure from the accumulator,

traoerse toward work When it is desired to start a pressing operationcrease. In this event, pressure would be built up on-the push-backside of the press. This presthe operator closes the energizing circuit for the pump solenoid H. The pump 9 is immediately actuated to deliver at its maximum rate into lines Its entire fluid supply is taken fom the pushback side of this piston through line II. This piston, with plungeri and platen 4, drop of their own combined weights as rapidly as withdrawal 9 and Illtoward the pressing side of piston 2,

of push-back fluid takes place. Since the-volume [into the pressing space.

Figure 2 of the drawings illustrates'the condition just described, solenoid n being shown collapsed, arrows indicating the'direction of flow of fluid, the platen shown descending, and surge valve shown atically in its opened position. No change in the condition of the auxiliary and interconnecting systems has occurred,

.the solenoid 99 not yet having been energized.

Only the primary system is operative at this stage. 1

- Working stroke The distance from its idling' position to the work piece having been traversed, the platen 4, through the rod I91 and cam I98, actuates the limit switch I89, which controls the energizing circuit for the solenoid 99, and closes this switch, thereby energizing the solenoid. 99. By this ac- 7 tion, the platen of the press causes the interconnecting control system to release the stored energy of the auxiliary pressuresystem, directing it to the pressing side of piston 2. Figure 3 of the Y drawings shows the press and the system controls in the positions they assume immediately after.

this release of accumulated energy takes place. The flow of pressure fluid, is indicated by bold arrows, while the flow of pilot fluid is indicated by light arrows.

In the primary system, no significant change has occurred except that the surge valve has been closed bythe development of pressure in the space above piston 2. The pump, however, continues to withdraw from the push-back side of the piston 2, and to supply fluid, now under high'pressure, to the main working area of the piston.

Upon energization of solenoid 99, plunger l8| of pilot valve 98 is moved so as to expel the fluid from line 93 into line '83, while pilot pressure is conveyed into line 94 The two-way valve 8| is thus moved to its upper or open position and the flow oi. pressure fluid from line '99 to lines 92 and I8 immediatelyensues. The rate at which this flow takes place is governed by the Openin of the choke valve 89, and when this valve is appropriately adjusted by the operator, this rate will b such'a's to cause the pressing piston 2 to move into the work without a reduction of its previous rapid traverse speed. -That is, the large volume of pressure fluid supplied by the accumulator, added to the smaller volume supplied by I pump 8 will equal the previous sum of the make- -:up volume from the reservoir 5 and the output of pump i.

It the operator has opened choke valve 99 too. much so that toogreat a volume of pressure gfluidis delivered from the accumulator into the 7 press cylinder, the press speed may tend to inpressure 9|.

sure will act through line H and branch lines 31 and il into the valve 44, which valve will thus be opened to relieve excess pressure fluid in the press cylinder, just as at the time of press reversal. The action of valve 44 in this connection determines the maximum speed of pressing.

If the operator has opened valve 89 only partially, the working stroke of piston 2 will pro- -ceed at a rate slower'than the work-approachingrate, and some fluid will be drawn from the res-' ervoir 5 through check valve 54 by the pump 8. The amount of fluid so drawn from the reservoir will be that required by pump 8 in excess Initiation of reversal The working stroke of the press continues at highppeed and high pressure until the pressure setting of the tonnage control valve 38 is reached.

The actuation or this valve is the first event in x the initiation of the return of the press platen, its opening, and the actuation of other controls immediately thereafter ure 3.

In this figure the press platen has progressed downwardly to its limit for the particular work piece in the press, as likewise the moving element of the accumulator. Back pressure in line 38 to tonnage control valve 36 has collapsed the spring within this valve, moving cam 4| into position to open limit switch 42. As explained above, opening of this switch breaks the circuit to all electrical controls, and, consequently, solenoids l2 and 99 are now in their extended positions. I

Solenold l2, upon de-energization, has per-" mitted the spring within the control 'I of pump 8 to shift the pump to its full delivery position in the direction of the push-back area of piston 2. This piston is, at the moment, locked against movement by the extreme pressure on its upper surface, and the discharge of pump 6 is conducted through branches 9i and SI to the by-pass and relief valve 44. The plunger 45 of this valve yields to the left under the pressure in line Si, and the output of pump 8 is then by-passed through passage 48 and port 49 to the reservoir, the port." already being opened by the movement of plunger 46 to the left under the influence of working back-pressure in line 59. As soon as the movement of plunger 45 uncovers port 41, this back pressure is relieved, passage of fluid being from lines In to 31, and through port 41- to the reservoir. This action of valve -from the accumulator to the press, this action proceeding from the upward shifting of plunger I" of pilot valve 98, and the reversal of pilot in the lines 83 and 94 to close the valve being illustrated by Fig- The pump 55 is, of course, delivering at its full rate into the line 60, having been put on stroke shortly after the engagement of the work by the press, and the opening of control line 6| through valve 11 to the reservoir by the downward motion of cam I6; As this cam has moved to a still lower position tha in Figure 3, the line BI is still connected to the reservoir through valve Return stroke Figure 4 shows the return stroke of the press, I

and the simultaneous re-charging stroke of the accumulator. This view is representative of the entire press return movement, no change in the setting of the controls taking place until the idling position is reached.

The platen is returned solely by the delivery of pump 6 toward the push-backside of piston 2. Part of the fluid above this piston is drawn upon by the pump through lines 9 and ill, the remainder being exhausted through the surge valve 28 to the reservoir 5, from which the proper proportion is carried by the pipe line 85 to the reservoir 58. The surge valve is forcibly held open by the push-back pressure communicated *to it through branches 3| and 33 of line H. The action of the surge valve in this stage of the press cycle aids in producing a rapid motion of the platen, just as in the work-approaching,

stage. In both stages, it serves to make up the diflerence in the volumetric requirements of the cylinder 3 above and below the piston 2, the speed of the piston being determined by the full capacity of pump 6 in delivering to, or drawing from the relatively small push-back area.

The valve ill of the interconnecting controls having closed at the point of press reversal, it remains closed even though limit switch IDS is contacted by cam )8 during the press return movement.

In the stage illustrated by Figure 4, the accumulator is being charged at the full delivery rate of pump 55, the valve 11 preventing fluid pressure within bore 59 from being communicated to the pump control 56, until the cam 16 shifts the valve; indicating complete charging of the accumulator.

Representative pressures The press as described lends itself to a wide range of pressures, of which -the following are to be considered merely representative.

Pressure upon the piston 2 may be at about 1250 pounds per square inch during the working r pounds per square inch.

This is the pressure that would be exerted by the gaseous medium on the pressure fluid of the accumulator at the limit of the downward stroke of the accumulator pistons, or, in other words,

when the gas had reached its maximum allow- When the accumulator is fully charged and standing in its uppermost position, this pressure will, of course, be higher. a typical increase being about 20 per cent. In the present able expansion.

working stroke of high press movement.

instance, this would give a maximum accumula-' P tor pressure or 1620 pounds per square inch.

Again allowing for frictional losses in the accumulator and the circuit, the pump 55 would be designed for pressures greater than this maximum. A loss of pounds or pressure, for ex- 'ample, would require that this pump have a peak Summary of main features The press platen of this invention is moved to andfrom the work at high speed by'the pump of a .primary pressure system, this pump also being operative to assist in effecting the high pressure stroke.

There is provided an accumulator for adding pressure fluid to that supplied by the pump of the primary system, so as to produce a press speed-as well as high pressure. This accumulator is part of an auxiliary pressure system, having a separate pump and being charged by this pump at full delivery in all except its fully charged position. The

pump stores hydraulic fluid in the accumulator,

and at the same time compresses a gas therein. At the appropriate time in a pressing cycle, the pressure. of this gas, reacting upon the body of hydraulic fluid, forces this fluid through an interconnecting system to the press. 1

The release of accumulator pressure fluid is timed by the. position of the press platen acting through electrical control meansto open a valve in the interconnecting system. This occurs just prior to the closing of the press upon the work. The tendency of accumulator pressure to be released with shocking force upon the press is checked by a metering valve, responsive to pressures at the inlet and outlet of a choke valve,

' the latter being the manual control of the transations in thi rate.

positioned, the choke valve in the fluid transfer line makes possible a pressing speed as high as the initial approaching speed of the press. This high speed is effective throughout as longa working stroke as the fluid storage capacity of the accumulator is designedto produce. 1 An electrical circuit is provided, in which originates the control impulses for starting-the press, releasing accumulator energy, and reversing the The second of these steps is made dependent upon the first, so that it can not occur during the return stroke.

Reversal of the press is accomplished either in response to the pressure or position attained by the press. Shock due to reversal is eliminated by a valve which momentarily opens to relieve the high working pressure above the press piston, and to by-pass thepump which at that moment has been'actuatedto deliver toward the push-back side oi! the piston. 1 j

When properly An important advantage of the invention is of the pumps produces all other motions of the press. while the output of the other pump simultaneously charges the accumulator.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims and vention.

Having thus fully described my invention, what the in- I claim as new and'desire to secure by Letters Pat nt is:

1. In combination in a hydraulic system, a pump: fluid operable means for moving said pump from full stroke to neutral position, an accumulator adapted to be charged with fluid from said pump, valve means normally preventing fluid connection between said fluid operable means and said accumulator, and means responsive to the connection between saidfluid operable means and said accumulator thereby causing said pump to move to neutral position 2. The combination in a hydraulic system of a pump. fluid operable means including a pressure chamber for movingsaid pump from full stroke to neutral position, an accumulator adapted-to becharged with fluid from said pump, valve means including a valve member normally preventing fluid-communication between said pressure chamber and said. accumulator, and means movably connected with said accumulator, and

'. adapted in response to a predetermined position of the latter to establish said fluid communication to thereby cause said pump to move to said neutral position.

'3, The combination in a hydraulic system of a variable delivery-pump, fluid operable means operable to move said pump from full stroke to substantially neutral or no-delivery position, an accumulator adapted to be charged with fluid from said pump, valve means interposed between completion of the charging oi said accumulator for causing said valve means to establish fluid cause said pump to stop charging said accumu lator.

4. In combination in a hydraulic system, a variable delivery pump, fluid operable means operable to move said pump from full stroke to substafltially neutral or no-delivery' position, an

accumulator adapted to be charged with fluid from said pump, said accumulator including a cylinder with a fluid operable plunger reciprocably mounted therein, control valve means including a valve member normally preventing fluid connection between said fluid operable means and 5 Q said cylinder, and means operable by-said plunger and adapted in response to a predetermined position of the latter to move said valve member into positionfor establishing said fluid connection, to thereby bring about a return of said pump to neutral position. l

5. In combination in a hydraulic system, a pump, means including a pressure chamber for moving said pump-from full stroke to neutral, an

accumulator containing a piston which is actu-- ated by pressure fluid derived-from said pump. said fluid being admitted to said' accumulator only on one side of the piston, a flxed gas in said accumulator on the other side oi the piston, a control valve interposed between the accumulator and the pump for controlling the flow of pressure fluid to the accumulator, and means including a cam secured to said piston for closing and opening said valve whereby when the valve is opened fluid pressure is admitted to one end I or said accumulator to compress the gas at the other end of the accumulator.

'6. In combination in a hydraulic system, a

fluid pressure pump, means including a pressure chamber for moving said pump from full stroke to neutral, and -an accumulator of fluid energy,

said accumulator comprising a closed cylinder containing a double-headed piston, the space betweenone side of said piston and the adjacent end of said cylinder being in communication with the pump for the purpose of actuating said piston, the space between the other side of said piston and the adjacent end of said cylinder be ing filled with a compressible gas so that as pressure fluid is admitted into the cylinder from said pump said gas is compressed and the energy oi the compressed gas is available to force the pressure fluid at the opposite side or the piston into the hydraulic system, the end of the cylinder said fluid .operable means and said accumulator for controlling fluid communication therebetween, said valve means including a reciprocable member and yielding means normally holding said member'in position for preventing said fluid communication, and meanson said accumulator and adapted inresponse to a predetermined position thereof to move said member against the thrust of said yielding means into position for establishing said fluid communication, to thereby to which the pump is connected being in communlcation with said pressure chamber or the pump through a control valve, said valve being controlled by the movement of the piston in said accumulator during the compressing action of the compressible gas to efl'ect a. return of the pump to neutral when the compressing operation oi the gas hs been completed. and the is full of fluid energy derived from the pump.

' WALTER mms'r.

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