US2262563A - Hydraulic system - Google Patents

Description

Nv. 1l, 1941. 1'. F. sTAcY '2,262,563

HYDRAULIC SYSTEM A Filed Feb. 15, 1959 2 sheets-sheet 1 z5 I .3 Z4 ,66' ,5

,Z7 I d I I j; A C, IrI.L I L, lf-II I d- Z II I 2/ I I I I l ZZ Il .I v

Il "i, I' Il .Z9 f 43 'Lf-f`- nhl-I-I 4 I I I I J8 J5 A 4Z l @e /Z I /3 /0 vIl. Il 9 Z0 f' 9 f5 44 46 i '5I I /7 A I. INI/ENoR ATTORNEYS Nov. 11, 1941. T. F. smc# l HYDRAULIC SYS TEM Filed Feb. l5, 19:59 2 Sheets-Sheet? @szw/vf@ .INVEN-roR ATTORNEYS Patented Nov. 11, 1941 UNITED STAT HYDRAULIC SYSTEM Thomas F. Stacy, Piqua, Ohio, assignor to The French Oil Mill Machinery Co., Piqua, Ohiol Application February 15, 1939, Serial No. 256,562

(Cl. 10S-38)` 16 Claims.

of the type Where a fluid under pressure is delivered alternately to the main and pull-back rams,

to reciprocate a platen. After a large pressure y has been built up, as for example in the main ram, the reversal'of the delivery from the pump, either by reversing the pump itself or by a reversible valve, suddenly places the pump on full delivery into the pull-back ram, which is usually smaller than the main ram, and as a result the pressure starts to build up rapidly in the pullback ram before the pressure on the main ram has been lowered materially. This produces a substantial shock in the hydraulic system and such shock causes severe Wear in the pump.

An object of this invention is to provide an improved hydraulic system for presses and the like, With which the press may be reversed Without material shock in the hydraulic system, and with a. reduction of Wear in the pump; which will not materially decrease the rapidity of operation of the press; which will not require material alteration of existing hydraulicl circuits; and which will be relatively simple, practical, eilicient and inexpensive.

Other objects and advantages will be apparent from the following description of several embodiments of the invention, and the novel features will be particularly pointed out hereinafter invonnection with the appended claims.

, Inthe accompanying drawings:

Fig. 1 is a plan, partly in section, of part of an ordinary hydraulic system, including a variable delivery, reversible pump modiiied in accordance with this invention;

Fig. 2 is a similar plan of a modification of the arrangement shown in Fig. 1;

Fig. 3 is a schematic diagram illustrating a modication of the invention in which a reversing valve is employed with a unidirectional pump; and

Fig. 4 is a similar schematic diagram, and illustrating still another embodiment of the invention but also using a reversing valve to accomplish reversals of travel of the platen.

In the embodiment of the invention illustrated in Fig.v 1, the liquid for the hydraulic system is supplied by a reversible variable delivery pump I. Some of such pumps are known as the Hele- Shaw type, and some are known as radial piston type pumps, but inasmuch as such pumps are in extensive use and are well known, a detailed description will be omitted. Such pumps commonly employ a shiftable yoke or -flow controlling member 2,..and by shifting this yokev or. control-.- ling member in` opposite directions through a central position, ther direction of delivery of the pump maybe reversed and its rate of delivery also varied. Connected to one side ofv the yoke or controlling member 2 are a pair of control rods 3, which extend outwardlyfrom one end ofthe pumpy and are connected to a yoke or cross bar 4. Extending from the yoke or controlling member 2 of the pump in the opposite direction from the pump housing are two control. rods 5` which extend loosely throughV aperturesA Ii in a yoke or bar, 1:. The rods 5 are provided, intermediate of their ends; with enlargements. 8 againstlwhich the yoke or bar 1 abuts. The ends 9-`of therods 5, which are outwardly beyond the enlargements 8, are ofA smaller diameter than the enlargements 8; The ends 9 of the rods 5 arev threaded and carry nuts I0 threaded thereon. Helical compression springs I I are mounted on the rod ends 9 between the nuts I0 and another'yoke or bar I2,. which is slidably mounted on the rod ends 9 so as to abut against. the opposite ends. of' the enlargements 8. The yoke or bar I2V has apertures I3 through'which the rod ends 9 looselyextend. The springs II thus urge the yoke or bari I2 against. the .enlargements lor heads 8 of the rods 5.

The yoke or` bar I2. is also provided with an' openingv I'4 through which loosely extends abolt or cap screw [Shaving a head lli-bearing against the yokef I2, and havingits other end threadedly connectedto a tubular'projection` from apiston Il which operates in a cylinder housing Ill".l A nut I9' is threaded on thebol'ti I5', and a helical compression spring 20 is disposed betweenthe nutV llandthefaceof the yokeor'bar I2l on the opposite side-from the head' I6 ofthe bolt.. The

spring 2`'l'y-ieldingly urges. the yoke or bar I2f againstfthe head' I6 of the bolt I5.

By operating the piston I1 in the direction B inFig. 1,l the spring 20will resiliently and yield-v ingly urge the yoke or bar I2 in the same direc-- tion; and by the Apressure on the heads or en44` largement's will urge therods 5fyieldingly-in the same direction. By moving the piston I1 in the opposite-direction, that is, in the direction A-.in Fig.v l,`the head1 off the-bolt|5 will pull the yoke I2 and'compress the springs III, and'thus-exert-ay resilient pull on. the yoke rods 5; Thus by operating the piston ITinfopposite directions, a yielding, resilient pressurey will be exerted on thev control member or yoke 2` tendingy t0: shift: itin oneA direction or the. other and thus reversethe.v

direction off delivery of? the pump. Whenlthe i ner tothe main and4 pull-back rams as usual in press systems. 'i

piston I1 is moved in the direction A in Fig, 1, the yoke or controlling member 2 will be urged or shifted in a direction to cause delivery of the pump in the direction C through pipe 2|, and when the piston I1 is` moved in the direction B the yoke or controlling member 2 will be shifted in a manner to cause delivery of liquid by the pump in the direction D to pipe 22.

Extending from oneside of the pump housing I is a small cylinder 'housing` 23, and ay piston 24 extends into this housing 23 through the open, outer end thereof, so as to reciprocate therein in the manner of a ram. 'I'he outer end of the rod or piston 24 is threaded and'extends through the I yoke 4 an-d nuts 25 which are `Vthreaded on the piston or rod 24 on opposite ,sidefs'offthelyoke 4 adjustably position the piston`or smallram 24 with respect to the yoke 4.- The 'inner end of the piston 24 is reduced in diameter slightly as at 26. A pipe 21 opens into the chamber 28 of the housing 23 vatfapoint.beneath the piston.24, and connects 'thechamber 28 with the pipeY 2'I.'

.A vsimilar'housing 29 .extends 'from lthe opposite sideof the pump housing .I,and has'a jcylinder chamber 30. in which another. piston or small ram 3| is received so as to extend loutwardly therefrom. i The ram 3|A is threaded at its outer end and passes throughithe yoke 1 and nuts 32] threadedfon Athe yoke 6. on .opposite sides of the yoke. adjustably secure the piston to the yoke 1. Byadjustingthenuts 25 and 32 along the pistons or rams 24, and 3I.respectively, the'pistonsf24 and 3| may beindividually adjustedendwise with. respect tothe yokes 4 and The chamber 3|)` is connectedby a pipe 33 to the pipe 22.

r .Inthe .base of fthe small housing. 23 is another chamber' 31|.inI which is mounted a piston 35 of considerably largerdiamete'r than ram 24. and which has ja stem -36 that projects into the chamber28 and also acts as a small ram in the chamber' 28. .Theichamber 34 is connected by a pipe 31-to, the Apipe 22 of thezpump. Similarly lthe holusing- 29 hasat its'inner. end another chamber 38 virrvvhich reciprocatesa.piston39 of considerably-larger diameter than the ram 3| zand which also vhasia stem `orreduced extension` 40I which i extendsinto the chamber 30 and-actsas a ram therein. i 42;;respectively therein at the outerends ofthose Chambers 34 and 38 have vents 4I and chambers. The 'chambers' 34- and v3.8 arei larger Y being understood that suitable and well knownL than the chambers 28 and 30for a purpose which will appear shortly. The chamber 38,is connecti ed by a vpipe 43 to the pipe ,2|. The pipes 2| and 22 ofV the pump are connectedl in the usual manof ,a pressl g VWhen the yokeor controlmembenZ isfshifted trolling mechanismby which the piston. I1 1 may 1 through'- center position in the direction A in Fig. -1, the pump will deliver fluid under pressure vthrough the pipe 2I.- to one ofr the rams, such as the Umain ram,and the-pipe 22 is then the suc- 1 tionl pipe which withdraws liquid from the pullbackgram. When the yoke or control member 2 g isv shifted-through center position in the direction 3 B in '-Fig. 1,. the delivery, of the pump will be through pipe,22 and theI pipe 2| will then act as lthejintake orl suction pipe for. the pump. A'Ihe cylinder vfhousing I8 is divided by the piston I1 intoA endichambers 44and 45.y An operating fluid is deliveredto the chamber ,44 by av pipe 46, and similarly affluid ,under pressure is supplied to the lchamber 45jthrough a pipe 4 1. v g i A.The pipes 46` and .41 lead to any suitable c'onpending upon whether fluid under pressure is admitted through pipe 46 or 41. .When operating fluid is admitted through either of the pipes 46 or 41, the other pipe of that pair would, of course, be vented and the pressure difference on opposite faces of the piston I1 will cause it to reciprocate in the direction A or B in Fig. 1.

Considering now the operation of this system, let it be assumed that the pipes 2| and 22 of the pump are connected into a hydraulic circuit leading to the main and pull-back rams respectively of a hydraulic press, as usual in such systems, it

equalizing mechanism, not shown, is included in the hydraulic circuit so as to compensate for the differences in volumes of operating fluid in the main and pull-back cylinders. If it is desired now to cause a pressing or forward actuation of the platen of the press, a compressed fluid is admitted through pipe 46 to chamber 44 and the pipe 41 is at the same time vented. .The pressurerin chamber44 forces the piston I1 in the direction A in Fig. 1 an-d the head I6 on the bolt vI5 pulls the yoke I2 against the action of the springs II. The springs II then` supply a resilient pressure of the yoke rods 5 ytending to shift the'yoke or control member 2 in the direction A and cause delivery of the liquid from the pump through the pipe 2| to the main ram. simuitaneously the pipe 22 withdraws liquid from the pull-back ram. v 1

When the pressure on the main ram,' which will correspond substantially tof the pressure in the pipe 2|, reaches or exceeds a predetermined pressure, this pressure, because .of the connection of the pipe 2| through pipe 21to` the chamberf28, exerts a corresponding pressure per'unit area on the ram 24, thus tending to shiftthe yoke or control member 2 of the pump back towards neutral or no delivery position. This decreases the dei I livery rate of the pump and when thepressure in chamber 28 has increased sulliciently;V it will shift the yoke 2 either into'the neutral or no delivery position or just sufficiently outof that position to cause delivery of just sucient liquid by the pump into pipe 2| to maintain the desired pressure. This movement of the yoke of the y piston V24 is resisted by the Vrods 3 Whichlead to the yoke n2, and also byfthe springs VII. The stress in the springs I I thus determines the pressureat which the piston or ram 24 will operate the yoke`2 Ainto substantial nodelivery position; that is, it

determines the pressure which Awill be maintained inthe pipe 2|..v Y. A l y When theoperator desires to reverse the pump, to cause a retraction ofthe platen, the pipe-46 is vented and fluid under pressure admitted through pipe 41 to chamber 45.` This forcesthe piston I1 in the directionrB in Fig. *1, andthe piston I1` acting through the bolt I5 compresses the spring 20 and urges the yoke I2 in the direction B. The yoke I2 bearing on the enlargements or heads`8`of the` yoke rods 5 urgesthe latter, and thereby the controlling memberor yoke 2,. in the direction B `toshiftthe yoke in a direction to cause delivery Iofthe pump through the. pipe 22 inthe directionD instead of` the pipe 2|, and the pipe 2I then lbecomes thein-` in the pump. The means by which this is accomplished will now be explained.

The pressure in the pipe 2| was also transmitted through the pipe 43 to the chamber 38, and this pressure in chamber 38 was exerted on the large piston 39 so as to force it outwardly until it engaged the outer end of the chamber 38, as shown in full lines in Fig. l. The free end of the reduced piston stem 40 in the chamber 30 is in the path of movement of the piston 3| when the latter is being moved with the yoke or controlling member 2, because the heads 8 of the rods bear directly on the yoke 1 and force the piston 3| inwardly during this reversal. It will be understood that at this time, the pressure in the chamber 30 will be the same as in the pipe 22 which is the suction pipe of the pump, and therefore relatively low, The length of the pistonstem 48 from yoke 1 is such that stem 40 will engage the inner end of the piston 3| just after the yoke 2 has slightly passed the neutral or no delivery position and started a very small delivery rate in the direction to deliver fluid into the pipe 22.

The pressure in chamber 38 which is the same as in pipe 2| leading to the main ram, will oppose further movement of the piston 3| under the urging of the spring 2D until the pressure in the pipe 2| and chamber 38 have fallen to a relatively low pressure, whereupon the pressure of the spring 20 is then suflicient to overcome the pressure on piston 39, and the piston 3| will then continue its movement by forcing the piston 39 toward the pump, that is, inwardly in the housing 25. The pump will then go on full stroke. It will be observed that while a slight reversal occurs immediately following operation of the piston |1 in the direction B in Fig. 1, the movement of the yoke or control member is limited to a position just beyond reversal position, so that the pump delivers only at a very slow rate until the pressure on the main ram, which is the same as in the pipe 2|, has fallen sufficiently, and then the yoke is shifted into full stroke position automatically.

This avoids any objectionable shock -in the hydraulic system caused by reversal of the pump while the pressure on the main ram still remains high. The liquid from the pump will then be delivered in the direction D through pipe 22 to the pull-back ram and removed through the main ram to the pipe 2 This will continue until the pressure in the pull-back ram builds up at the end of the return movement and since this pressure will be the same as in the pipe 22, it will be communicated through the pipe 33 to the chamber 3Q. When the pressure on piston 3| is sufficient, it will force the piston 3| outwardly, and through the yoke 1 bearing on the heads 8 of the rods 5, will urge the main yoke or control member 2 in a direction to curtail the rate of delivery. This movement of the rods 5 and of the piston 3| is opposed by the spring 20, and when the pressure has been built up suiciently to overcome the spring 20, the latter will be compressed to such an extent that the yoke or controlling member 2 of the pump will be positioned to provide just sufficient delivery to maintain the selected pressure in the pipe 22.

When the operator desires to reverse the pump and cause another operation of the main ram, the pipe 41 is vented and operating fluid under pressure delivered through pipe 46 to chamber 44 This forces the piston |1 in the direction A and compresses the springs thereby urging the yoke rods 5 in a direction to shift the pump yoke 2 into reversed position. The pressure on the pull-back ram and pipe 22 was, however, communicated through the pipe 31 to the chamber 34, so that thepiston 35 was held outwardly, as shown in full lines in Fig. 1and the piston stem 36 opposed the movement of the piston 24 beyond a position in which the yoke 2 was at aV low delivery rate in the reverse position.

The pump will thus be held at a low delivery rate in a reverse position in which it delivers to the pipe 2|, until the pressure on the pull-back ram, and thus in pipe 22, has fallen sufficiently that the pressure of the springs can overcome the pressure on the piston 35 and permit automatic continuance of the reversal, which places the pump on full stroke, delivering liquid into the pipe 2|. Thus we have a complete cycle of' movement. The pump is driven continuously by any suitable source of power, such as through a coupling 48 from a motor 49. By shifting the pistons 2| and 34 in their yokes 1 and 4 respectively, the extent to which the pump moves on stroke at each reversal before the pressure falls may thus be varied to some extent.

Referring now to the embodiment of the invention shown in F'ig. 2, the construction and arrangement is the same as in Fig. 1, except that the chambers 34 and 38 and pistons 35 and 39 are omitted, and certain other changes made which will now be explained. It will be understood that the parts in Fig, 2 which are the same as corresponding parts in Fig. l will be given the same reference characters, and will not be described in detail. In this embodiment of the in- Vention, the piston |1 is provided with another rod 5|) which extends outwardly of the cylinder housing I8, and the outer end of this rod 50 is connected by a pin 5| to one arm of a lever 52. The connection of the pin 5| to the lever 52 is by a slot, not shown, in lever 52 and running in a direction lengthwise thereof so as to provide for lost motion.

The lever 52 is pivoted at 53 and carries another arm 54. arranged on opposite sides ofthe arm54. In the chamber 55 is arranged the piston 51 having a stem '58 extending outwardly therefrom into a positi-on adjacent one face of the arm 54. A piston 59 operates in the cylinder 56 andhas a stem 60 extending outwardly thereof into a position adjacent the other face of the arm. 54. When the pistons 51 and 59 are both forced outwardly as shown in Fig. 2, there will be suflicient clearance between the outer ends of the stems 58 and 60 and the arm 54 to allow limited movement of the arm 54 which is suflicient, through its connection to the pump yoke, to shift the pump yoke through no delivery position a short distance to opposite sides thereof, and place the pump on very short stroke when delivering in either direction.

The stems 58 and 60 prevent movement of the pump yoke or control member into full stroke positions in both directions. Thus when the piston |1 is moved in the direction B in Fig. 2, the arm 54 will engage the stem 60 and be limited thereby to such an extent that the pump yoke only goes on stroke slightly to deliver liquid into pipe 2| at a relatively small'rate. Similarly when the pump is reversed, the stem 58 will limit movement of arm 54 and consequently of the piston yoke to allow the pump to go 'only on a short stroke in the opposite direction. The cyl-- inder chamber 55 is connected by a pipe 6|to Similar chambers 55 and 56 are thelpipe 22, and chamber '56 is connected by pipe 62; to the'pipe 2|,.Thus the pistons'51 and 59 function in the same manner as the pistons 35 and39 'respectively of Fig. 1, and the operation will otherwise be the same as described for Fig. 1. Referring now to the embodiment of the inventionshown in Fig. 3, the pump 63, as illustrated, is of the uni-directional but variable delivery type, which has a yoke 64 which varies the rateof delivery of the pump as it is shifted. A spring 65 acting on the Ayoke 64 tends to shift it into the full stroke position in which the pump delivers liquid at its maximum rate into the pipe 66, and liquid is supplied to the pump from the reservoir 61 by a pipe 68. The pipe 66 is connected to a port 69 of a reversing valve 18. A valve element 1| reciprocates in the valve housing 18 and is provided with lands 12 and13 which are spaced apart along the valve element. A pipe 14 connects a port 15 of the valve 10 withthe pull-back ram chamber 16, and similarly a pipe 11 connects `the main ram cylinder 18 to a port 19 in the valve housing 10. The pipe.' 68 is also connected by a branch 8|] to the opposite endsof the valve to serve as exhaust connections thereto. When the valve element 1| is in an intermediate position, such as shown in full lines in Fig. 3, the lands 12 and 13 will be -in alignment with the ports and 19 respectively. The land 12 completely closes the port 15, and the land 13 is bevelled so that its eiective peripheral surface does not completely close or bridge the port 19. Liquid delivered to the valve housing through pipe 66 may thus circulate around the land 13 at port 19 and pass through the adjacent end of the valve housing back to pipe 86, thence to the reservoir 61 or through the pipe 68 to the intake side of the pump.

When'thevalve element 1| is shifted upwardly in Fig. 3 to place the land 13 between the port 19 and the opening to pipe 80, the land 12 will uncover port 15 and be disposed between ports 15 and 69. The land 13 will thus prevent escape of the liquid delivered by the pump through the pipe 80' and consequently it will pass through pipe 11 to the main ram cylinder 18 and cause an advancement of the ram 8|. At the same time, land 12 uncovers port 15 and connects pipe 14 to pipe 80 allowing escape of liquid ,from the pull-back cylinder 16. When the valve element 1| is'moved downwardly in Fig. 3 from the position shown in full lines, it similarly moves the land 13 between the ports 69 and 19 and positions the land 12 between the port 15 and the lower exhaust to pipe 80.

Then the delivery from the pipe 66 will pass through the pipe 14 i to the pull-back cylinder 16, and liquid from the l cylinder 18 will pass through the pipe 11, and the upper end of the valve housing in Fig. 3

to the branch pipe 80, and thence back to the pipe 68 or the reservoir.

Such reversing valves are well known in the 3 art, and any suitable type may be employed. In the simple illustration given, the outer end ofthe valve stem 1| carries a pin 82 which runs i in a slot 83 in a handle or operating lever 84, whichv is pivoted at 85, and this handle 84 may g be secured in different adjusted positions in any suitable manner. Y It will be understood that this reversing valve may, if desired, be controlled or operated in the manner shown in my copending .application Serial No. 204,375, led April 26,v

1938, but any other type of reversing valve control may also be employed. i Y ,In order to prevent shock in the system when the type which opens to pass liquid from the pipev 66 to the pipe 92 when the pressure in pipe 66 exceeds a predetermined pressure for which the valve 93 isset. Such pressure relief valves Vare common in the art, and a detailed description is therefore believed unnecessary. The valve 93 thus passes liquid in the direction of the arrow a when the pressure in pipe 66` is sufliciently high, and the free check valve opens freely to pass liquid in the direction of the arrow b but closes automatically to prevent reverse ow.

Also extending into the chamber 81 is a small ram or stem 95 which is carried by a relatively large piston 96 that operates in a cylinder chamber 91. The end of the chamber 91 adjacent the stem 95 is vented as at 98. The chamber 91, at the opposite side of the piston 91 from the stem 95, is connected by a pipe 99 and a free check valve |00 to the pipe 92, and also through a free check valve ||l| and Aa pipe |02 to. the pipe 11 leading to the main ram cylinder 18. The free check valve 09 opens freely to pass liquid in the direction of the arrow, but closes automatically to prevent reverse flow, and the free check valve |6| also opens freely to pass liquid in the direc- `tion of the arrow but closes automatically to prevent reverse ilo-w.

. In the operation of this embodiment of the invention, let it be assumed that the reversing valve 1| is at the intermediate or neutral position shown in Fig. 3, and then the liquid from the pump will be circulated idly through the reversing valve, and the pipe from the pull-back ram 16 will be closed by the land 12, thereby preventing any movement of the ram 8|. Any liquidA trapped in the chamber 81 may escape through pipes 88, 89, valve 90 and pipe 9| to the pipe 66, and the spring 65 thus shifts the yoke 64 of the pump into full stroke or maximum delivery position. If now the operator moves the valve element 1| in an upward direction, in Fig. 3, to cause an advance or working stroke of the ram 8l, the pipe 66 will be connected to pipe 11 and the pipe 14 from pullback ram will be connected to the branch return pipe 80 during the advance or working stroke of the platen.

When the ram 8| encounters resistance, the pressure in chamber 18 will build up, and consequently the back pressure on the pipe 66 will build up. The valve 98 then automatically closes and when the pressure inthe pipe 66 exceeds the pressure for which the valve 93 is set, liquid will also pass from the pipe 66 through pipe 94, pressure relief valve 93, pipes 92 and 88 to the cylinder chamber 81, and this pressure will force the piston 86 of the yoke in a direction to compress' the spring 65 and move the yoke 64 in a direction to curtail'the rate of delivery. When the pressure in chamber 81 has built upsufliciently toi overcome fully the spring 65, the yoke 64 of the pump will have been shifted intoy a position such that there is just sufficient delivery to maintain that predetermined pressure on the pipe 66. At the same time, the liquid from the pipe 92 will also pass through free check valve |119 and pipe 99 to chamber 91, and would also pass through check valve except for the fact that the pressure in pipe |02 at the opposite side of the valve |0| will be substantially the same as in pipe 66. The pressure in chamber 91 Will force the piston 96 to the right in Fig. 3, but it does not quite engage the yoke piston 86.

When the operator desires to reverse the press, he moves the valve element 1| -downwardly in Fig. 3 to place the land 12 below the port 15 and shift the land 13 into a position between the ports 69 and 19. The pipe 66 will then be connected to the pipe 14, so as to deliver uid to the pull-back cylinder 16, and pipe 11 to the main ram cylinder 18 will now be connected through the pipe 80 to the reservoir 61 and to the intake side of the pump. The pressure at this time in the pull-back cylinder is relatively low, and consequently the pressure in pipe 66 would be relatively low, so that the spring 65 then tends to shift the yoke 64 of the pump into full or maximum stroke position which would cause objectionable shock in the hydr'aulic system. The yspring 65 will shift the yoke 64 until the piston 86 of the yoke engages the stem 95 of the piston 96, which will be at a point such that the yoke will be in a position to set the pump for a relatively low rate of delivery. The piston 96 prevents further movement of the yoke into. full delivery position.

The liquid will escape from the main ram cylinder 18 through pipe 11, and as soon as the pres.. sure in the main cylinder 18 falls sufiiciently, which requires a short interval of time, the valve |0| will open and pass liquid from the chamber 91, thus releasing the pressure on piston 96, whereupon it is moved by the action of spring 65, which forces the yoke into full stroke position. The valve |00 closes. however, automatically to compel release of the pressure on piston 96 through the pipe 11, valve |0| and pipes |02 and 11. Thus the pump will be prevented automatically from going on full stroke until the pressure in the main ram cylinder has fallen to` a reasonably low pressure.

The embodiment yof the invention shown in Fig. 4 is similar to that shown in Fig. 3, except that the cylinder 9'! is connected into the hydraulic circuit in a slightly different manner. Parts which are identical in Figs. 3 and 4 are given the same reference characters. The reversing valve is the same as in Fig. 3, except that an addition is made thereto, either through a separate housing or as a part of the same housing. To the valve a which corresponds generally to the valve 10 of Fig. 3 is added a chamber |03, and the valve element 1|a has an extension |04 passing through a wall |05 into the chamber |03 where it carries a land |96. The pipe 11 has a branch |01 leading to port |08 in the chamber |03, and another port |09 in the chamber |03 is connected by a pipe ||0 to the chamber 91. The pipes 99, |02 and valvesnlll and I0| in Fig. 3 are of course omitted. The chamber |03 is provided with a vent at its lower end in Fig. 4.

When the valve element 1|a is in the intermediate position shown in Fig. 4, which corresponds to the intermediate position shown in Fig. 3, the pump of course circulates liquid idly through the reversing valve, and the ram 8| is held in stationary position. When the reversing valve element 1|-a is moved upwardly in Fig. 4 to cause lan yadvance or working stroke of the platen, the land |06 will move upwardly in the chamber |03 and keep the` port |08 closed, and thus'` keep the pipe H0 closed in the port |09. When the pressure in the pipe 66 builds up, due to resistance encountered by the ram 8|, the pressure relief valve 93 will open andpass liquid to the, chamber 81 and cause a resetting of the pump yoketo no delivery position orjust suiciently `on'stroke to maintain thedesired pressure, as explained in connection with Fig.l 3.

When the reversing valve is operated to reverse the system, and cause a retraction of the ram 8|, the land |06 will be carried downwardly in Fig. 4so as to uncover the port |08 just prior to or at about the same time that the pump is connected by pipe 66, the reversing valve and pipe 14 to the pull-back ram cylinder 16. This connects thepipe 11 to pipe ||0 and the chamber 91, so that the chamber 91 is immediately placed under the same pressure as the main ram chamber 18. This forces the piston 96 to the right in Fig. 4 and forcibly moves the yoke piston 86 to aposition inwhich it places the pump only slightly on stroke. As soon as the pressure in the main ram chamber 18 falls, the pressure in chamber 91 will fall and the spring can then displace the piston 96 to the left in Fig. 4 and shift the yoke of the pump back into full stroke position. Thus, upon actuation of the reversing valve to retract the ram, the pump will` be prevented from going on stroke until the pressure in the main ram has fallen to a desired extent. When the reversing valve is moved into either the intermediate or upper position in Fig. 4, the port |08 will be closed, which removes the chamber 91 from responsiveness to the pressure in the pipe 11.

It will be understood that various changes in the details and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art, within the principle and' scope of the invention, as expressed in the appended claims.

I claim as my invention:

1. In a hydraulic motor system of -the type employing a reversible, variable delivery pump with a controlling member shiftable to reverse the direction of delivery ofthe pump, and to vary the rate of delivery thereof, the improvement in the control of said member which comprises means yieldingly urging said member in opposite directions to reverse the pump selectively, and means responsive to the hydraulic pressure of the iiuid deliveredby the pump for preventing movement of saidmember beyond a selected minor extent past reversing position until the pressure of the fluid delivered by the pump prior to the attempted reversal falls below-a predetermined selected pressure.

2. An improved control for a variable delivery, reversible pump having a pair of pipes, each of which serves as a rdelivery pipe when the other serves as an intake pipe, depending upon the direction of delivery of said pump, said Dump having a controlling member shiftable to vary the rate and direction of delivery of the pump, and a hydraulic device responsive to pressure in one of said pipes for preventing movement of said controlling member into full stroke position for delivery to the other of said pipes but allowing movement through reversing position into a partial delivery position to said other pipe while the pressure in said' one pipe exceeds a predetermined pressure, and releasing said member for continued movement into full stroke position when the pressure in said one pipe falls to a selected low pressure. v

3. In a lhydraulic press system, a reversible, variable delivery pump having a controlling member shiftable to vary the direction and rate ofdelivery of the pump, means connected to said member for operating it in opposite directions to reverse the pump and `having resilient connections to said member, and means responsive to the pressure vin the pipe connections to the pump for restricting the movement ofA said member beyond a position causing a partial rate of delivery during a reversal and after reversal, until the uid pressure in the delivery pipe of the pump Ybefore reversal has fallen to a predetermined extent, said pressure responsive means including hydraulically actuated abutments shiftable by hydraulic pressure into positions conning movement of said member to a restricted partial delivery zone having limits on opposite sides o f the neutral delivery position.

4. An improved control for a reversible, variable delivery pump having a controlling member shiftable in opposite directions to reverse the pump and operable when in intermediate positions to control the rate of delivery of said pump, which comprises yieldable means connected to said member for urging said member in opposite directions to reverse the pump, abutments operable into and out of positions to oppose movement of said member into full delivery positions, hydraulic means for shifting said abutmentsv into obstructing positions in which they limit the movement of said member to partial delivery positions in both directions, the hydraulic means for one of said. abutments being controlled by the delivery from on'e delivery pipe of the pump, and for the other abutment being controlled from the other delivery'pipe of the pump, the delivery pipeof the pump to which each said hydraulic means is connected being that which is the delivery pipe before reversal of delivery of the pump and when the controlling member was on the opposite side of no-delivery position from that occupied when that particular abutment is effective to limit movement of said member,

whereby pressure in the pipe of the pump before reversal will limit movement of the controlling member beyond reversal to a specified low rate delivery position until the pressure in the previous delivery side of said pump has fallen to a predetermined extent.

5. In a hydraulic motor system of the type employing a variable delivery, reversible pump with a pair of pipes, each of which serves as an intake pipe when the other serves as a delivery pipe, depending upon the direction of delivery of the pump, and with acontrolling member shiftable to varyrthe rate and direction of delivery f the pump,v that improvement in the control of said pump which comprises means for resiliently urging said member in either direction to set the pump for full delivery in one direction or -the other,.depending upon the direction of delivery desired, means responsive to the pressure ofr the fluid delivered by the pump through one of said pipes for limiting the movement of said controlling member to a selected portion only of` its possible movement through delivery reversal position 'when discontinuing delivery through said one pipe and starting removal of fluid therethrough, until the pressure of the fluid in said one `Vpipe has fallen to a predetermined low pressure.

6. In a hydraulic motor system of the type;

employing `a reversible, variable delivery pump having a controlling member shiftable in op-` posite directions to `vary the directionand rate of delivery of the pump, and a pair of pipes, each of which serves as an intake pipe rwhen the other serves as a delivery pipe, the improved control for said controlling member which comprises means resiliently connected to said member for operating it in opposite directions to reverse the direction of delivery of the pump, and means responsive to the pressure in the pump pipes for restricting the movement of said member beyond a position causing a partial rate of delivery during a reversal and after reversal until the uid pressure in the delivery pipe of said pump before in each of said pipes for restricting the movement of said member beyond a position causing a partial rate of delivery during a reversal and after reversal, until the fluid pressure in the delivery pipe of the pump before reversal has fallen to a predetermined extent, said pressure responsive means including hydraulically actuated abutments shiftable by hydraulic pressure into positions for conning movement of said member to a restricted, partial delivery zone having limits on opposite sides of the neutral delivery position of said member.

8. In a hydraulic motor system of the type employing a reversible, variable delivery pump having a controlling member shiftable in opposite directions to vary the direction and rate of delivery of the pump, and a pair of pipes, each of which serves as an intake pipe when the other serves as a delivery pipe, the improved control for said controlling member which comprises an operating member, an arm having an aperture through which said operating member slidingly extends, an abutment on said operating member engageable with one face of said arm, a spring acting between said operating member and said arm for yieldingly urging said abutment against said arm, said arm also having another aperture through which said control member slidingly extends, said control member also having a shoulder engageable against that face of said arm which is engaged by said abutment, a spring acting between said control member and said arm for resiliently urging said arm against said shoulder, and means responsive to the pressure in each of said pipes for restricting movement of said control member in a reversing direction, which would discontinue delivery of fluid under pressure to one of said pipes and draw fluid therefrom, to a part only of the possible movement of said control member beyond neutral position during such reversing movement until the fluid pressure in said pipe serving as a delivery pipe prior to such reversal hasv fallen to a desired extent.

9. In a hydraulic motor system of the type I employing a reversible, variable delivery pump having a controlling member shiftable in opposite directions to vary the direction and rate of delivery of the pump, and a pair of pipes, each of which serves as an intake pipe when the other serves as a delivery pipe, the improved control for said controlling member which comprises an operating member, an arm having an aperture through which said operating member slidingly extends, an abutment on said operating member engageable with one face of said arm, a spring acting between said operating member and said arm for yieldingly urging said abutment against said arm, said arm also having another aperture through which said control member slidingly extends, said control member also having a shoulder engageable against that face of said arm which is engaged by said abutment, a spring acting between said control member and said arm for resiliently urging said arm against said shoulder, a pair of pistons, a chamber for each piston, a pair of plungers, one operable on said controlling member to urge it in one direction and the other operable on said controlling member to urge it in the opposite direction, one of said pistons being operable to oppose movement of one of said members in one reversing direction beyond a part only of its possible movement past neutral, no-delivery position, the other of said pistons being similarly operable to oppose movement of said one of said members in the opposite reversing direction beyond a part only of its possible movement past said no-delivery position, means for operating each of said pistons into opposing position and responsive to fluid pressure in the pump pipe which is the delivery pipe before the reversal movement which is opposed by that piston, and individual means for operating each of said plungers, each of which individual means being responsive to the fluid pressure in that pump pipe which will cause the control member to be shifted into said no-delivery position when a predetermined pressure in said last-mentioned pipe is reached.

10. In a hydraulic motor system of the type employing a reversible, variable delivery pump having a controlling member shiftable in opposite directions to vary the direction and rate of delivery of the pump, and a pair of pipes, each of which serves as an intake pipe when the other serves as a delivery pipe, the improved control for said controlling member which comprises an operating member, an arm having an aperture through which said operating member slidingly extends, an abutment on said operating member engageable with one face of said arm, a spring acting between said operating member and said arm for yieldingly urging said abutment against said arm, said arm also having another aperture through which said control member slidingly extends, said control member also having a shoulder engageable against that face of said arm which is engaged by said abutment, a spring acting between said control member and said arm for resiliently urging said arm against said shoulder, a pair of cylinders, each having a, relatively large chamber closed at one end and opening outwardly at the other end through a relatively small bore, a piston in each chamber, a plunger in each bore and movable therein into and out of engagement with the piston in the connected chamber, one of said plungers being operable on said control member to urge it in one direction and the other of said plungers being operable on said control member to urge it in the opposite direction, a conduit connecting the closed end of each chamber to one of said pump pipes, another conduit connecting the inner end of the bore opening outwardly from that same each chamber to the other of said pump pipes, each of said another conduits being connected to that pump pipe which serves as the intake pipe for said pump before the control member is shifted through neutral position in a direction opposed by the piston of the same cylinder.

11; In a hydraulic motor system of the type employing a reversible, variable delivery pump having a controlling member shiftable in opposite directions to vary the direction and rate of delivery of the pump, and a pair of pipes, each of which serves as an intake pipe when the other serves as a delivery pipe, the improved control for said controlling member which comprises an operating member, resilient connecting means between said members, a pair of cylinders, each having a relatively large chamber closed at one end and opening outwardly at the other end through a relatively small bore, a piston in each chamber, a plunger in each bore and movable therein into and out of engagement with the piston in the connected chamber, one of said plungers being operable on said control member to urge it in one direction and the other of said plungers being operable on said member to urge it in the opposite direction, a conduit connecting the closed end of each chamber to one of said pump pipes, another conduit connecting the inner end of the bore opening outwardly from that same each chamber to the other of said pump pipes, each of said another conduits being connected to that pump pipe which serves as the intake pipe for said pump before the control member is shifted through neutral position in a direction opposed by the pistonl of the same cylinder.

12. An improved control for a reversible, variable delivery pump having two pipes and a controlling member shiftable back and forth to vary the direction and rate of delivery of the pump as between said pipes, which comprises means operable on said member, for yieldingly urging it through neutral, no delivery position selectively in either direction to place the pump on full delivery in either direction, and means responsive to the hydraulic pressure in one of said pipes for automatically limiting the mov-ement of said member by said urging means to a selected, partial and incomplete movement beyond neutral, no delivery position in a direction to set the pump for delivery to the other of said pipes, until the pressure in said one pipe drops below a selected, predetermined pressure, but operable automatically to release said member for free and continued movement in the same direction into full delivery position when the pressure in said one pipe drops below said predetermined pressure and said pump is delivering to said other pipe.

13. An improved control for a reversible, variable delivery pump having two pipes and a controlling member shiftable back and forth to vary the direction and rate of delivery of the pump as between said pipes, which comprises means operable on said member, for yieldingly urging it through neutral, no delivery position selectively in either direction to place the pump on full delivery in either direction, means responsive to the hydraulic pressure in one of said pipes for automatically limiting the movement of said member by said urging means to a selected, partial and incomplete movement beyond neutral, no delivery position in a direction to set the pump for delivery to the other of said pipes, until the pressure in said one pipe drops below a selected, predetermined pressure, but operable automatically to release said member for free and continued movement in the same direction into full delivery position when the pressure in said one pipe drops below said predetermined pressure and said pump is delivering to said other pipe, and means responsive to the pressure in said one pipe for also shifting said member into nodelivery position against the action of said urging means upon the attainment of a predetermined pressure in said one pipe while said pump is delivering into said one pipe.

14. An improved control for a reversible, variable delivery pump having two pipes and a controlling member shiftable back and forth to vary the direction and rate of delivery of the pump as between said pipes, which comprises an operating element, resilient means interposed between said member and element for urging said member solely in one direction to cause delivery at a desired rate into one pipe and yieldingly holding it vso urged when said element is operated into and remains in one position, additional resilient means also interposed between said member and element for urging said member solely in the 'other direction to cause delivery at a desired :rate into the other of said pipes and yieldingly holding it so urged when said element is operated into and remains in another position, and means responsive to the hydraulic pressure in said one pipe for temporarily limiting movement vof said member by said additional resilient means to a position beyond no delivery position, but 'only sufficient to cause delivery at a part of its possible rate, when setting said pump for delivery to said other pipe, until the pressure in said one pipe drops below a selected, predetermined pressure, but operable automatically to release said member for free and continued movement in the same direction into full delivery position by said additional means,'after the pressure in said one pipe has dropped below said predetermined pressure and said pump is delivering to said other pipe. l

15. An improved control for a reversible, variable delivery pump having two pipes and a controlling member shiftable back and forth to vary the direction and rate of delivery of the pump as between said pipes, which comprises an operating element, resilient means interposed between .said member and element for urging said member lsolely in one direction to cause delivery at a desired rate into one pipe and yieldingly holding it so urged when said element is operated into and remains in one position, additional resilient 'means also interposed between said member and element for urging said member solely in the other direction to cause delivery at a desired rate into the other of said pipes and yieldingly holding it so urged when said element is operated into for temporarily limiting movement of said memand remalns 1n another pos1t1on, means respon- -sive to the hydraulic pressure in said one pipe 'ber by saidadditional resilient means to a position beyond no delivery position, but only suiiicient'to cause delivery at a part of its possible rate,v when setting said pump for delivery to said other pipe, untilthe pressure in said one pipe drops below a selected, predetermined pressure, but operable automatically to release said member for free and continued movement in the same direction into full delivery position by said addi.- tional means, after the pressure in said one pipe has dropped below said predetermined pressure and said pump is delivering to said other pipe,

iable delivery pump having two pipes and a con- 2oA trolling member shiftable back and forth to vary the direction and rate of delivery of the pump as between said pipes, which comprises an operating element, resilient means interposed between said member and element for urging said member solely in one direction to cause delivery at a desired rate into one pipe and yieldingly holding it so urgedl when said element is operated into and remains in one position, additional resilient means also interposed between said member and element for urging said member solely in the other direction to cause delivery at a desired rate into the otherof said pipes and yieldingly holding it so urged, when said element is operated into and remains in another position, means responsive to the hydraulic pressure in said one pipe for temporarily limiting movement of said `member by said additional resilient means to a position beyond `no delivery position, but only suii'lcient to cause delivery at a part of its possible rate, wheny setting said pump for delivery to said other pipe, until the pressure in said one pipe drops below a selected, predetermined pressure, but operable automatically to release said member for free and continued movement in the same direction into full delivery position by said additional means, after the pressure in said one pipe has dropped below vsaid predetermined pressure `and said pumpis delivering to said other pipe, and meansresponsive to the pressure in either of said pipes for also automatically shifting said member, against the action of whichever of said resilient means has been yieldingly urging it into a delivery position, into no delivery position upon the attainment of a predeterminedpressure in that pipe which causes said automatic shifting and into which said pump is discharging.

THOMAS F. sTAcY.

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