US2302132A

US2302132A - Balancing press platen

Info

Publication number: US2302132A
Application number: US346946A
Authority: US
Inventors: Howard F Macmillin; Paul E Flowers
Original assignee: Hydraulic Development Corp Inc
Current assignee: Hydraulic Development Corp Inc
Priority date: 1940-07-23
Filing date: 1940-07-23
Publication date: 1942-11-17
Anticipated expiration: 1959-11-17

Description

` Patented Nov. 17, 1942 nALaNciNG ranss marmi Howard F. MacMllin and Paul E. Flowers, Mount Gilead, Ohio, assignors to The HydraulicV De-V velopment Corp., Inc., Wilmington, Del., a cor.-

poration o! Delaware Application July 23, 1940, Serial No. 346,946

19 Claims.

This invention relates to presses, and in particular to presses having a relatively long and narrow platen or be'a'm associated with'means for preventing excessive tilting movement of the DIBtenor-beam. *'1

It is an object of the invention to provide a press, such as aspress brake, bending brake, or shear brake, in which a tilting movement of the platen or beam is prevented by hydraulic bal- I ancing means interconnected by simplified oonduit means. 3

Another object of the invention consists in the provision of a press of the above type in which the balancing means comprises hydraulic cylin-` ders movable in unison with theplaten or beam.

Another object consists in providing a press oi' the character set forth in the preceding paragraph in which the balancing cylinders lare so mounted on the platen as to be able to automatically remedy a slight misalignment between the balancing cylinders and the'balancing pistons cooperating therewith.

It is still another object of the invention to provide a press, such as a press brake, bending brake, or shear brake, witha relatively long platen oi' beam, in which a tilting movement oi the platen or beam is prevented by hydraulic balancing means comprising balancing pistons I supported by the platen or beam and cooperating with stationary cylinders associatedwith the 'l press bed and press head respectively.

A still further object of the invention consists in providing a press of the type referred to in the preceding paragraph in which the balancing cylinders hydraulicallycommunicate with each other through the platen or beam.

Another object of the invention consists in providing a press with a relatively long and narrow platen or beam in which .the tilting movement of the platen or beam is prevented by at least fur cooperating cylinder-piston-assemblies 'communicating with each other by a simpliiied uid. Our invention further consists in exhausting said cylinders at the end of each cylinder order to prevent any accumulated error by reason of a supply of an extra amount of duid to any one cylinder in connection with the balancing operations.`

These and other objects and advantages ofthe invention will appear more clearly from the following specication in connection with the accompanying drawingainwhich-t. y

Figure 1 dlametrically illustrates Ya section through' an embodiment of the invention..

Figure 1adiscloses, on `anenlarged scale, a surge valve'used in the structure voi! `Figure 1.

Figure 2 shows a. section throughs `cylinderpiston-assemblv which may be usedvin connection with the present invention.

Figure 3 is a diagrammaticillustration of a further embodiment of the invention.

Figure 4 shows a detailedgconstruction oi' the balancing cylinder-piston-assembly of Figure3.

Figure 5 shows the simpliiled conduit system according to the present invention in connection with a platen or beam having four balancing cy1. inder-piston-assemblies.

Referring ilrst to Figure 1, the numeral I desisnates the press bed of a hydraulic press which may be connected with the press head 2 by any convenient means. The press head 2 comprises a main or pressv cylinder 3 having reciprocably mounted therein a double-acting piston l connected by means of a ram 5 and screwst to the platen l. I'he upper portion oil-the press cylinder 3 communicates through a conduit 8 and conduit 9 with one side of avariable delivery pump I0, while .the other side of thev variable rdelivery pump rIt communicates through a conduit II and conduit vI2 `with the lowerportion of the press cylinder 3. Branching of! from the conduit 9 is a conduit I 3 leading to a tonnage V control valve I 4 which, in response to a predetermined pressure in the press cylinder 3, opens or closes, as the case may be, an'electric circuit comprising a solenoid I5. The tonnage control valve Il does not form part ofthe present invention and may be oi any desired type, for instance, of the type set forth in U. S. Patent No. 2,224,957, issued December 17, 1940.

The solenoid I5 has its armature I5 connected Witha lever I1. The arm lI8 of the lever I I is connected by means of a linkage I9 with the nowcontrol member (not shown) ofthe variable delivery Dump IIl so that when the solenoid I5 is energized the now-control member of the variable delivery pump I0 will be shifted to cause delivery in one direction, whereas when the solenoid I5 is de-energized a spring 20, likewise cona double-acting balancing vwith the conduit 30.

nected with the flow-control member of the pump I0, shifts the said flow-control member to cause the pump to deliver fluid in the` opposite direction. The tonnage control valve |4v is furthermore adapted to communicate with the fluid tank by means of a conduit 22. 'Ihe fluid tank 2| has mounted therein a main cylinder relief and pump by-pass valve 23 communicating through

conduits

24, 25 and 3 with one side of the pump I0, and through conduits and 26 with the other side of the pump |0 and with the surge 'valve 21 respectively. The main cylinder relief and pump bypass valve 23 and the surge valve 21, which do not form a part of the present invention, serve to prell the main cylinder 3 during the rst portion of the downward stroke of piston 4 and also relieve the pressure side of the main piston 4 at the end of its working stroke to facilitate the initiation of ithe retraction stroke thereof. The operation of the

valves

23 and 2 1 vwill be set forth later in connection with the operation of the press structure-f The

valves

23 and 21 are constructed substantially along the line of the surge valve and cylinder release and pump by-pass valve respectively disclosed in U. S. Patents 2,193,248and 2,268,205, both to Ernst. For a more detailed description of the

valves

23 and 21, reference may vbe had to Ernst U. S. patent application No. 286,063, filed August 24, 1939, and U. S. Patent No. 2,193,248.

The fluid tank 2| furthermore communicates through a conduit 28 with the suction side of a pilot pump 29, the pressure side of which communicates with a conduit 30. Branching off from the conduit 30 is a conduit 3| comprising a safety or relief valve 32 adapted to communicate` through conduit 33 with the iluid tank 2|. The conduit 30 comprising a check valve 34 has a branch line 35 leading to the upper portion of the cylinder bore 36 of a balancing cylinder 31 which is slidably mounted in the press head 2 and movable in unison with the platen 1. The cylinder 31 is connected with the platen 1 by means of a ball joint comprising a ball shaped portion 38 connected with the cylinder 31 and a socket 39 held ln a correspondingly shaped recess of Athe platen 1 by `means of a holding plate 40 and screws 4|. Reciprocably mounted in the cylinder bore 36 is piston 42 .connected with a piston rod 43 fixed to the press head 2 and extending through the ball shaped portion 38.

The lower portion of the cylinder bore 36 cornmunicates with a conduit 44 which, in its turn. communicates with a conduit 45. The conduit 45 comprises a check valve 46 and communicates on one hand with the conduit 30, while on the other hand leading to the upper portion of a cylinder bore 36a of a balancing cylinder 31a. The balancing cylinder 31a corresponds in its construction to the balancing cylinder 31 and is connected with the platen 1 in a similar manner as the balancing cylinder 31. The parts of the cylinder 31aA are, therefore, designated with the same reference numerals as those of the cylinder l 31 but with the additional letter a. The lower portion of the cylinder bore 36a communicates The cylinder 31a has connected therewith ya J-sh'aped arm 41 adapted at the end of its retraction stroke to engage the arm 46 of the lever l1 so as to shift the now-control member of the pump I6 by means of the linkage I3 into neutral or no delivery position.

While the cylinder-piston-assemblies 31, 42,

31a, 42a, may be constructed in various manners,

the construction v illustrated in Figure 2 has proved itself very satisfactory.

According to Figure connected therewith in any convenient manner, for instance by-means of screws 49, a sleeve 50 through which passes a bushing 5|. The bushing 5| is subdivided by a partition 52 defining together with the bushing 5| two separate bores. Connected with the bore 53 is a pipe connection 55 communicating with the conduit 35, while a pipe connection 56 is provided for conveying the fluid from the pipe 44 to the bore 54. The bore 53 is adapted to supply fluid to the upper portion of the cylinder bore 36 above the piston 42, while the bore 54 is adapted to supply fluid to the lower portion of the cylinder bore 36 below the piston 42. To prevent leakage between the piston 42 and the wall of the cylinder 31 a ring 51 engaging a correspondingly shaped recess in the piston 42 is provided as well as packing material 58 compressed by glands 59. The upper portion of the cylinder 31 is closed by a cylinder head 66 connected with the cylinder 31 in any convenient manner and provided with packing material 6| compressed by a gland 62 to prevent leakage from the upper portion of the cylinder 36 to the outside. The lower portion of the cylinder 31 is, as mentioned in connection with the description of Figure l, provided with a ball shaped portion 38 joined in a correspondingly shaped socket 33 held within the platen 1 by means of the holding plate 46 and screws 6| between the cup shaped portion 63 of the platen 1, which surrounds the socket 33, and the socket 39 has a ring 64. The piston rod 43 connected with the piston 42 passes through the ball shaped portion 38 and is surrounded by packing material 65 compressed by a gland 66 to prevent leakage from the lower portion of the cylinder bore 36 toward the outside.

It will be appreciated that the construction gf Figure 2 allows the arrangement of stationary pipes 35 and 44, thereby materially simplifying' the piping system.

While Figure 1 merely illustrates a platen associated with twol balancing cylinders, the platen may, if desired, also be provided with four balancing cylinders. In this instance the piping connection between the cylinders is as diagrammatically illustrated in Figure 5. As will be seen therefrom, only the diametrically opposed cylinders are connected with each other in such a 2, the press head 2 hasA manner that the upper portion of the balancing cylinder 61 is connected with the lower portion of a balancing cylinder 68, while the upper portion of the balancing cylinder 68 is connected with the lower portion of the balancing cylinder 61. Similarly, the upper portion of the balancing. cylinder 63 communicates with the lower portion of the balancing cylinder 10, while the upper portion of the balancing cylinder 10 communicates with the lower portion of the balancing cylinder 63. In other words, the connection is the same as shown in Figure l.

OperatiOn of first embodiment Assuming that the press is in the position shown in Figure l, which position corresponds to the end of the retraction stroke, and that it is now desired to perform a working stroke. To this end, the circuit comprising the solenoid |5 and the tonnage control valve |4 is closed in any con'- venient manner.

energization of the solenoid I5, thereby actuating l Closure of this circuit causes the armature I6 which, in its turn, by means of l the lever |1 and the linkage I9, shifts the flow- 2,soa,isa

control member. of the variable delivery pump Il into full stroke forward position. Pressure fluid is then supplied by the pump Il through the con'- duits l and I into the upper portion of the cylin der 3.

During the first portion of the downward stroke of the piston l, which moves downwardly by gravity, the fluid supplied by the pump Il is supplemented by iluid from the tank 2i which passes through the surge valve 21. It will be appreciated that the suction eilect created in the upper portion of the press cylinder 3 by the downwardlyv moving piston l causes the surge valve plunger Il! to move downwardly. thereby establishing iluid connection between the tank 2i and the upper portionof the press cylinder 3 through the bores III, |52 and Ill. The duid expelled by the piston I passes through the conduits I2 and II to the suction side of the pump Il. Since the pump Il has to deliver more fluid into the upper portion of the cylinder 2 than is expelled by the piston l, additional iiuid is conveyed from the tank through the check valve 1I and conduit II to the suction side of the pump I0. Since the piston I is connected by the ram l with the platen 1 carrying the cylinders 21. 31a, movement oi `the in the surge valve 21, where it acts upon the plunger III. However, since the upper portion oi' the press cylinder l is still lled with fluid, the phmger lli cannot shift' the plunger Illdownwardly and, consequently, no fluid can escape at this time through the surge valve into the tank 2i. The pressure in line II is also conveyed to the bore Il. in the valve 23 where it causes the valve member I Il to-move toward the left so as to piston l downwardly also causes a downward movement of the cylinders 31, 81a, while the balancing

pistons

42, 42a, remain stationary. During this downward movement oi the cylinders 31, 21a, iiuid expelled from the lupper portion of the cylinder bores 36, 26a. is respectively conveyed through the pipes 3l and Il to the lowerportion of the cylinder bores 38a and 2i. As soon as the platen engages the work piece, pressure builds up in the upper portion of the cylinder 3, thereby causing the plunger In of the s'urge valve 21 to move upwardly so as to close the bores IIS. Pressure fluid supplied by the pump I0 now causes a further downward movement of the piston 4 and the cylinders 31'. 21a, until the drawing operation is finished. The pressure prevailing in the upper portion of the press cylinder l is also conveyed through conduitsy 8 and 25 to the right hand end of the bore IN of the valve 2l, where it causes the valve member |55 to move toward the left so as to establish fluid connection between the passageway |56 and the bore Il1 in the valve 22.

Supposing that the work piece is located closer to the cylinder 21 than it is to the cylinder 31a;

' in this instance the cylinder 431a tends to run ahead of the cylinder 21. Such a movement would cause a compression of the fluid between the top of the cylinder 21a and the top of the piston 42a, and due to the communication of the upper portion of the cylinder 21a with the lower portionV of the cylinder 31, the same pressure establish iiuid connection-between the bore Ill and the bore Il1 through the passageway I and -tion of the press cylinder I can escape through conduits l and Il.'bores III and Il! into t'he tank 2|, since' the leftward movement of the valve member Ill has established fluid connection be-` tween the conduit 2l and the bore |62. Due to the release of pressure from the upper portion of the press cylinder I. the pressure prevailing in the conduits II and 2l, and acting on the plunger III, now enables the latter to move the plunger Ill downwardly, thereby establishing :duid connection between the bores |53 and III, so that iiuid can escape-from the upper portion of the cylinder I through said bores to the tank. When the fluid can escape from the upper portion ci' cylinder 2 through the surge valve into the tank, the pressure in' conduit 2|drops and the spring I returns the valve member Il! to the position shown fin Figure 1, in which position fluid connection between the passageway Ill and bore |51 is interrupted.

As soon as the surge valve 21 has opened in the manner just described, the pressure iluid conveyed through 'conduits II and I2 to the lower portion of the press cylinder 2 causes the plunger l to move upwardly. The platen 1 and the cylinders 21l and 31a will then move upwardly so that fluid expelled from the lower portion of the cylinder bore It will be conveyed to the upper portion of thecylinder bore 28a, while fiuid'expelled from the lower portion of the cylinder bore 26a will be conveyed through the conduit into the upper portion -of the cylinder bore "L -It will be noted that, during the retraction stroke of piston l, the

would prevail in the lowerportion of the cylinder y bore 20, thereby either causing the cylinder 21 to speed up or, if the cylinder 21 cannot speed up. slowing down the movement ofthe cylinder 31a. At any rate, the result will be a synchronous movement of the cylinders 31 and 21a, thereby preventing tilting of the platen 1.

As soon as the pressure acting upon the piston l, during the working stroke, has reached a predetermined value, the tonnage control valve Il opens the circuit comprising the solenoid IB. thereby de-energizing the latter. then shifts the flow-control member of the pump I0 to full stroke retraction position for initiation of the retraction stroke of the press. When this shifting movement has been effected, the conduit I I becomes the pressure line, and pressure in line The spring 20 check valves M and are closed, due to the pressure in the conduits 2l and Il respectively. Since no pressure is exerted upon the platen during the retraction stroke. the cylinders 31 and 31a will, in general, move upwardly in' synchronismfv When the piston 4 approaches the end of its retraction stroke, the Jeshaped arm I1 will engage the lever arm Il 'and shii'tthe latter so that the now-control member of the pump Il will move toneutral position'. The press will then come to afstand-1 still vand is ready" for a new cycle.

4It .will be noted that at the end of the retraction stroke ofthe piston #the initial hydraulic conditions are restored and that whatever leakage vmay have occurred in the cylinder bores 36,' 26a, will have been made up by the pilot pump 29. In case any excess pressure should occur in the conduits Il and 2|, this excessive pressure will be relieved through the safety valve 22.

I-f, instead of two balancing cylinders, four balancing cylinders are provided, as indicated in Figure 5, the balancing operation will be exactly the same as that disclosed in connection with Figure l. In other words, cylinder 61 will be held in synchronism-by cylinder 68 and vice versa, and t'lae same conditions apply to the cylinders 69 and Second embodiment Referring now to Figure 3, the press disclosed therein comprises a-press bed 12l and a press head 13 connected with each other by any convenient means. The'press4 head 13 has connected therewith a main cylinder 14 in which a doubleacting piston 15 is reciprocably mounted. The piston 15 is connected with a platen 16 by means of a ram 11. The piston 15 and the ram 11 comprise a cylinder bore 18 in which-is stationaril-y mounted boosterplunger 19 with a bore V8l) therethrough. The bore 60 communicates through a conduit 8| with a reversible variable delivery pump 82 and is adapted. to communicate through a conduit 8 3 andv check valve 84 with the fluid tank 85.,

Branching oil from the conduit 8| is a conduitl 86 leading to lan admission valve, generally designated 81. The admission valve 81 comprises a casing 89 having reciprocably mounted therein a piston 89 continuously urged by a springA 99 tow-ard the left so as to close communication between the conduit 86 and a conduit 9| leading to the upper portion of the main cylinder bore 92. The upper portion of the cylinder bore 92 is adapted to communicate through surge valves 93 and conduits 94 with a conduit 95 connected on one hand with a conduit 86 leading tothe pump 82 and the lower portion ofthe cylinder bore 92, and on the other vhand with. a check valve 91 adapted to admit fluid from the tank 85 into the conduit 95. r A

Branching off from the conduit 94 is a conduit 98 leading to a main cylinder relief and pump by-pass valve 99 which lattenthrough conduits and |0|', communicates with the conduit 9i. The surge valves 83 and the main and pump by-pass valve 99 correspond in their construction and purpose to that ci the surge valve 21 and the main cylinder relier and pump by-pass valve 23 of Figure 1. Y.

The fluid -tank 86 further communicates `through a conduit |02 with a control valve, gen erally designated |03, and comprises a cylinder bore |04 havingfreciprocablypmounted therein Ya valve member |66. operatively connected with the valve is a valve rod |06 passing through an arm |01 of the platen 18 and having adjustably mounted thereon a collar |08 ladapted to be engaged by the arm |01. The valve member |05 is adapted to control communicationbetween the conduit |02 and aconduitl09 comprising a check valve l l0 and leading to a conduit il l. The coner I8 is provided with a bore |23 communicating through a passagewayv|24 in the platen 16 with the bore |25 in the plunger |22 so as to continuously eiect communication between the cylinder bore |26 of the balancing cylinder ||4 and the cylinder bore |21 of the balancing cylinder H1. Similarly, the cylinder bore |28 of the balancing cylinder ||5 continuously communicates with the cylinder bore |29 of the cylinder H6 through the bore |30 in the plunger I9, the passageway |3| in the platen 16 and the bore |32 in the plunger |2I.

Comparing the embodiment of Figure 3 with that of Figures 1 and 2, it will be noted that aside from the fact that the balancing cylinders are stationary and the plungers are movably mounted, each balancing cylinder is split up into two balancing cylinders and the conduit system connecting the balancing cylinders of Figure 1 is replaced by passageways through the platen.

`The embodiment of Figure 3 furthermore cornprises a conduit |33 with a check valve |34 which 'is adapted to eect communication between the cylinder bore |26 and the conduit |09. A conduit |35 likewise branching off from the conduit comprises a pilot pump |36 which is connected with the fluid tank 85. Branching ofi from the conduit |35 is a conduit |31 having arrangedV therein a relief valve |38 and leading likewise to the uid tank 85.

While the plungers H8, H9, |21 and |22 may be constructed in any convenient manner, a preferable construction of the said plungers isA illustrated in Figure 4. As will be seen therefrom, the press head 13 comprises the stationary cylinder i it, while the press bed 12 comprises the stationary cylinder |56. In contradistinction to the embodiment of Figure 3 however,

-the plungers H8 and ii are replaced by -a single plunger |39 having its upper portion reciprocably mounted in the cylinder l I4, whereas the Y lower portion 16| is reciprocably mounted in the cylinder relief duit Ii comprises two check valves H2 and H3 and leads on one hand to the upper portion of a balancing cylinder |4 and on the other hand to a balancing cylinder H5. These balancing cylinders are in contradistinction to the embodiment in Figure 1, arranged stationarily and cooperate with balancing cylinders ||6 and ||1stationarily arranged in the vpress 4loecl 12. Ylteciprocably mounted in the cylinder bores |14 and H5 are plungers H3 and ||9 connected in any convenient maur-er, for instance, by screws |20, with the upper portion of the platen 16. Similarly, plungers ii and-l22 adapted to the lower portion of the platen 16 respectively, cooperatewith the balancing cylinders I6 and H1. The plungcylinder l i6. The central portion of the plunger 139 is connected with the platen 16 in any convenient manner. The plunger portion |40 has aV longitudinal bore |42 which communicates with the passageway |24 of the platen 16, and the plunger portion i2! has a longitudinal bore |43 communicating with the passageway |3| in the platen v16. To prevent leakage irom lthe cylinders H4 and H6, the plunger portions |42 and |43 are respectively surrounded with packing materil |43 and 145,'compressed by glands |46 and |41 respectively. i

Operation of second embodiment Assuming that the press is in its retracted position, that is, that the main pressing piston 15 is somewhat higher than the position shown in Figure 3, and that it is now desired to perform a working stroke.- To this end the reversible variable deliveryy pump 82 is shifted to full stroke forward position by any convenient means, for instance, by means of the solenoid |5, illustrated in Figure l. While the piston 15, during the first portion of its Working stroke, moves downwardly by gravity, pressure fluid is supplied by the pump 82 through the conduit 8| and bore 80 into the booster cylinder bore 16, thereby speeding up the downward movementI of the piston. Simul- .taneously therewith, the upper portion of the main cylinder bore 92 is filled by fluid from the tank-` passing through check valve 91, the conduit 94 4and the surge valves 93. Fluid expelled fromi the lower portion of the cylinder bore 92 passes through the conduit 96 to the suction side of the pump 82. Simultaneously with the downward movement of the ram 11 and the platen 16 connected therewith, also the balancing plungers ing this operation fluid expelled by the plunger |2| passes through the bore |32, the passageway |8| and the bore |38 into the balancing cylinder bore |28. Similarly, the uid expelled bythe plunger |22 from the balancing cylinder bore |21 .passes through the bore |25, the passageway |28 and the plunger bore |28 into the inder bore |26.

When the platen 16 engages the work piece, pressure builds up in the upper portion of the main cylinder bore 92 causing the surge valves 88 to close, while the pressure in the conduits 8i and 86 acts upon the piston 89 so as to move the latter against the spring 90, thereby establishing communication between the conduits 86 and 8|. The pump 82 now supplies pressure fluid through the conduits 8|, 86 and 9| into the upper portion of the main cylinder bore 82. Y

If, during the downward or working stroke of the platen 16, the right end of the platen tends to run ahead of the left platen due to the fact that the work piece is located closer to the last mentioned platen, the fluid in the balancing cylinder bore |21 is somewhatfeompressed, while'the pressure of the iluid in the balancing cylinder bore |28 is somewhat relieved. lDue to the communication of the balancing cylinder bore |21 with the balancing cylinder bore 26, the pressure in the balancing cylinder'bore |26 will be the same as that in the balancing cylinder bore |21. Similarly, equal pressure will prevail in the cylinder bore |28 and the cylinder bore |28 of the balancing cylinders ||6 and ||6 respectively. qonsequently, the increased pressure prevailing in the cylinder bore |28will either c ause an additional downward movement of the left platen or the pressure fluid in the cylinder bore |21 will slow down the movement of the right platen. thereby, in each case, re-establishing synchronous movement of the platen ends. l

. When the pressure acting upon theupper portion of the main piston 1l has reached a predetermined value or the platen has reached a predetermined position, the pump 82 is shifted to full stroke retraction position in any convenient manner, for instance, by de-energizing-the balancing cylsolenoid I8 and allowing the spring to act upon the now-control member of the pump, as described in connection with Figure 1. The main cylinder relief and pump by-pass valve 89 then relieves the pressure in the upper portionof the main cylinder 82 while the surge valves 88 open, and the platen 16 starts its retraction stroke.

. ofthe fluid in the right-hand upper cylinder H6 and the lower left-hand cylinder H6, whereas a reduction in pressure would occur inthe upper left cylinder Ill. This reduction in pressure would allow uidto iiow from the pilot pump |88 through the conduits |85 and into the cylinder bore |26 so that at the completion of the operating stroke, the combined volume in the entire system is slightly in excess of 'what it was at the beginning of the stroke. If no provision were made to allow this excess fluid to escape and this` Aoperation were repeated, pressurewould gradually accumulate in the system until an excessive pressure, accumulated in" the system, might the position shown in Figure-3,1111 which com- When the platen 18 approaches the end ot its retraction stroke the pump 82 is shifted by any convenient means, for instance, in a manner 'described in connection. with Figure 1, to neutral position so as to place the press into readiness for a new cycle.

While approaching the end of its retraction stroke, the platen 16 also engages, by means or its arm |81, the collar |88 on the valve rod |88,

therebylifting the valve I 06 so as to establish Y communication between the conduits |88 and |82.

The arrangement of the control valve |88 is'" the following one:

Assuming that a heavy load is thrown on the right-hand cylinder assembly due to an eccentric loading which would cause a slight compression cause serious disturbances. The" purpose ofthe l control valve |08 is to correct this condition byV opening the system to the iiuid tank 85 Aat the beginning of each return stroke. lIt will befohvious that in the example referred to above, excessive uid from thecylinder bore |26 could escape through the conduits IH, |88, the check valve |88, the conduit I0, the safety valve |48 v and the conduit |82 to the tank.

The valve member |85 remains in its lifted its downward movement the valve member |05 follows downwardly by gravity until it reaches Similarly, as described in connection with the I embodiment of Figure 1. the pilot pump |36 makes up for any leakage in the balancing cylinders which may have occurred therein.

If, instead of the two balancing cylinders respectively arranged above and below the .platen 1.6, 'four balancing cylinders would be mounted` on top of the platen and four balancing cylin-` ders below the same, the connection of the balancing cylinders would be 'so that thediametric oppositely arranged balancing cylinders would communicate with each other in the same manner as the balancing cylindersshown in Figure 3. In other words. in` this instance Figure 3 should be considered a section through two diametrivcally arranged balancing cylinder systems.

While theinvention has been described with a press having the pressing'plunger centrally arranged with respect to the platen, it is understood that also a plurality of pressing plungers may be connected with the platen, for-instance.

at the ends thereof without aecting the operation of thebalancing systems described above. It will beunderstood that we desire to comprehend within our invention such modifications as come within the scope of the claims and the invention.

Having'thus fully described our invention, what desire to secure by Letters munciation between'cylinder chambers of two separate Abalancing cylinders.

2. In a press, the combination of motor means, a platen operatively connected with said motor means and adapted to be reciprocated thereby,

` tionary cylinders, and

a plurality of balancing cylinders arranged adjacent the ends of saidf platen, and a plurality of fluid operable balancing plungers associated with said balancing cylinders and operatively connected with said platen to maintain substantially synchronous movement of the ends of said platen, said plungers being provided with passageways therethrough adapted to effect communication between the cylinder chamber above one balancing plunger with the cylinder chamber below another balancing plunger.

3. In apress, the combination of hydraulic motor means, a platen connected with said motor means and adapted to be reciprocated thereby, a plurality of balancing cylinders arranged adjacent the ends` of said platen, and a plurality ci iiuid operable double-acting balancing pistons associated with said balancing cylinders and operatively connected with said platen for preventing tilting movement thereof, each of said balancing pistons comprising a longitudinal bore therethrough for effecting communication between cylinder chambers of separate balancing cylinders.

4. In a press,the combination ofhydraulic motor means, a platen operatively cdnnectadwith said motor means and adapted to be reciprocated thereby, a plurality of fiuid operable balancing plungers arranged on opposite sides of said platen and respectively reciprocable in stameans connecting said balancing plungers with said platen, each of said plungers being provided with passageways therethrough for effecting hydraulic communication between two separate balancing cylinders.

.5. In a hydraulic press, the combination of motor means, a platen connected with said motor means and adapted to be reciprocated thereby, spaced balancing cylinders connected with said platen and adapted to be reciprocated thereby, a plurality of stationary double-acting balancing plungers associated with said balancing cylinders for substantially maintaining synchronous movement of the platen ends, and conduit means adapted to eiect communication between a cylinder portion above one balancing plunger with a cylinder portion below another balancing plunger.

I surface of one balancing piston and the pressure acting upon the lower surface of another balancing piston for preventing tilting movement of said platen.

'1.v In a press, the combination of hydraulic motor means, a variable delivery pump for supplying iluid to said motor means to actuate the same, a platen connected with said motor means and adapted to be reciprocated thereby, a plurality oi balancing cylinders for maintaining said platen level, a pilot pump independent of said variable delivery pump for filling and maintaining said cylinders filled with fluid, a plurality of balancing plungers reciprocable in said balancing cylinders and operatively connected with said platen, each o said plungers being provided with passageways therethrough for effecting fluid communication between two of said balancing cylinders.

8. In a hydraulic press, the combination of a mainV cylinder-piston-assembly, a iiuid source adapted to supply pressure fluid to said main cylinder-piston-assembly for operating the same, a platen operatively connected with said main cylinder-piston-assembly, a plurality of stationary double-acting balancing pistons, aplurality of reciprocable balancing cylinders cooperating with said balancing pistons and jointly connected with said platen for facilitating adjustment of said balancing cylinders, a pilot pump hydraulically connected with each of said balancing cylinders for maintaining said balancing cylinders lled with fluid, and conduit means associated with said balancing cylinders and adapted to effect communication between the upper surface of one balancing piston with the lower surl face of another balancing piston.

9. In a press, the combination of a hydraulically operable main cylinder-piston-assembly, a fluid source, pressure creating means to cause the ow of pressure fluid to said main cylinderpiston-assembly for actuating the same, a relatively long and narrow platen connected with said main cylinder-piston-assembly and adapted to be reciprocated thereby, a plurality of spaced uid operable balancing assemblies operatively connected with two opposite ends of said platen for preventing tilting movement of said platen, each of said balancing assemblies comprising a cylinder i and a piston therein, and means independent of said pressure creating means for maintaining said balancing cylinders lled with iiuid, each of said balancing pistons having a bore therethrough and being connected with a conduit system sogas to effect communication between two separate balancing cylinders.

Y 10. In a press, the combination oi motor means, a platen connected with said motor means and adapted to be reciprocated thereby, a plurality of balancing cylinders, each havinga hydraulically operable plunger movable relative thereto and being operatively connected with one of four corners of said platen, means for continuously maintaining said balancing cylinders filled with fluid, and conduit means communicating with bores through said balancing plungers so as to effect hydraulic communication between the respective balancing cylinders at diagonally opposed corners oi said platen.

l1. A press comprising in combination a press head and a press bed, hydraulic motor means, a fluid source adapted to supply fluid to said motor means for actuating the same, a. platen connected with said motor means and adapted to be reciprocated thereby, a plurality of balancing cylinders, half the number of said balancing cylinders being supported by said press head and the other half being supported by said press bed, a plurality-of hydraulically operable balancing plungers associated with said balancing cylinders, and means for supplying iuid to said balancing cylinders, said balancing plungers and said platen being provided with passageways therethrough and adapted to effect communication of one balancing cylinder supported by said press head with a balancing cylinder supported by said press bed remote from the plunger cooperating with said rst mentioned balancing cylinder.

l2. In a press, the combination of hydraulic motor means, a platen connected with said moto means and adapted to be reciprocated thereby,

plurality of stationary balancing cylinders, means to supply iluid to said balancing cylinders, and a plurality of fluid operable balancing plungers associated with said balancing cylinders and connected with said platen for preventing tilting movement of said platen, said balancing plungers and said platen being provided with passageways therethrough, adapted to connect cylinder por-` tions of separate balancing cylinders with each other.

13. In a press, the combination of a hydraulic main cylinder-piston-assembly, a fluid source adapted to supply pressure fluid to said main cylinder-piston-assembly, a plurality of stationary balancing cylinders, half the number of said balancing cylinders being arranged on one side of said platen and the other half being arranged on the other side of said platen, a plurality of balancing plungers connected with said platen and being arranged so that each balancing plunger cooperates with two balancing cylinders on different sides of said platen, said balancing plungers and saidplaten having bores therethrough for eiiecting communication of a cylinder arranged on one side of said platen with a cylinder arranged on the other side of said platen but not pertaining to the plunger cooperating with said rst mentioned cylinder.

14. In a hydraulic press, the combination of hydraulic motor means, a fluid source adapted to supply pressure duid to said hydraulic motor means for actuating the same, a platen connected with said motor means and adapted to be reciprocated thereby, a plurality of stationary balancing cylinder pairs, the cylinders of each cylinder pair being mounted in alignment with each other so that one cylinder of each balancing cylinder pair is arranged above said platen and the other cylinder of each balancing cylinder pair is arranged below said, platen, a plurality of balancing plungers adapted to be reciprocated by said platen and arranged so that one balancing plunger cooperates with one balancing cylinder pair,

reciprocated thereby, a plurality of upper balancing cylinders, a plurality of lower balancing cylinders corresponding in number to said upper balancing cylinders, a plurality of double-acting balancing plungers, each plunger being supported by said platen and cooperating with an upper and a lower balancing cylinder, a pilot pump connected with said balancing cylinders and adapted to continuously maintain said balancing cylinders illled with Iiuid, said balancing: plungers and said platen being provided with passageways therethrough adapted to convey' duid from an upper balancing cylinder associated with one balancing plunger to a lower balancing plunger or vice versa, and means automatically relieving any excess duid in said balancing cylinders at the end of the retraction stroke of said platen.

1'7. In a press, the combination of hydraulic motor means, a fluid source adapted to supply pressure iluid to said motor means for actuating the same, a rectangularly shaped platen connected with said motor means and adapted to -be reciprocated thereby, four upper balancing cylinders, four lower balancing cylinders, said cyl,- inders being arranged at the corners of said rectangularly shaped platen, and a fluid source adapted to supply fluid to said balancing cylinders and maintain the same illled with duid, said plungers and said platen being provided with passageways therethrough adapted to eiect communication between an upper balancing cylinder with a lower balancing cylinder arranged diametrically thereto.

18. In a hydraulic press, a main cylinder-piston-assembly, a Pfluid source adapted to supply pressure duid `to said main cylinderpiston-as sembly, a platen connected with said cylinderpiston-assembly and adapted to be reciprocated and means for supplying uid to said balancing cylinders, said balancing plungers and said platen being provided with passageways therethrough adapted to effect communication between the upper cylinder of one' cylinder pair with the lower cylinder of another cylinder pair.

15. In a press, the combination of motor means, a platen connected with said motor means and 'adapted to be reciprocated thereby, a plurality of duid operable balancing plungers operatively connected with said platen and supported thereby, each of said plungers having a portion below said platen and another portion above said platen, a plurality of balancing cylinders cooperating with said balancing plungers, and means for supplying fluid to said balancing cylinders and adapted to maintain said cylinders filled with iluid, said plungers and said platen being4 prothereby, a plurality of balancing cylinder pairs, the cylinders of each cylinder pair being in alignmentwith each other, a plurality of balancing plungers supported by said platen, one plunger being associated with one balancing cylinder pair,

a pilot pump adapted to supply pressure fluid to said balancing cylinders and to maintain said balancing cylinders'tllled with fluid, and means for relieving excessive pressure in said balancing cylinders, said balancing plungers and said platen being provided with passageways therethrough vided with passageways therethrough, adapted i to effect communication between a balancing cylinder cooperating with the upper portion of one balancing plunger and .a balancing cylinder cooperating with a lower portion of another balancing plunger.

16. In a hydraulic press, hydraulic motor means, a duid source adapted to supply pressure fluid to said motor means for actuating the same, a platen connected with said motor means and for effecting communication o! one cylinder pertaining to one cylinder pair with a cylinder pertaining to another cylinder pair to prevent tilting movement of said platen.

19. In a press, a platen, a main actuating ram therefor, a fluid source, pressure creating means to cause the ow of fluid to said ram for actuating the same, a plurality, of balancing cylinders arranged on the corners, of said platen and each having reciprocably mounted thereina plunger with a passageway therethrough for hydraulically interconnecting two diagonally disposed cylinders to maintain said platen constantly in a substantially level condition, means independent of said pressure creating means for filling said balancing cylinders with illuid and maintaining them filled, and means for evacuating said cylinders at the end o1' each cycle to prevent any accumulation of fluid in said cylinders beyond that desired.

HOWARD F. MACMILLIN. PAUL E. FLOWERS.