US2072488A - Press system - Google Patents

Description

T. F. STACY PRESS SYSTEM March 2', 1937.

NNY

4 Sheets-Sheet 2 T. F. STACY PRESS SYSTEM March 2,l 1937.

T. F. STACY PRESS SYSTEM vFiled July 28, 1951 March 2, 1937.

4 Sheets-Sheet 5 MPX/77747 JMWXJ T. F. STACY March 2, 1937.

PRESS SYSTEM Filed July 28, 1931 4 Sheets-Sheet 4 Patented Mar. 2, 1937 PATENT OFFICE PRESS SYSTEM Thomas F. Stacy, Piqua, Ohio, assigner to The French Oil Mill Machinery Co., Piqua, Ohio Application July 28, 1931, Serial No. 553,549

27 Claims. (Cl. 60-52) This invention relates to hydraulic press systems, and particularly to the control of the main and pull-back rams.

- the platen will be held in its returned position" underpressure Without heating of the continu- An object of this invention is to improve the construction and operation of such systems.

Another object of the invention is to provide an improved press system with which vibration of the controls will be prevented; with which heating of the pump and operating iluid will be reduced to a minimum; with which the speed of operation ofthe press will .be increased; with which the maximum, desired pressure in the main ram may be maintained automatically for a desited interval of time and the press then opened automatically; and which will be relatively simple, compact and inexpensive.

A `further 4object of the invention is to provide an improved system with which fully or partially automatic and continuous operation of the rams may be obtained selectively; with which the pres- Sure stroke of the platen may be stopped and a return movement started quickly at any point in the pressure stroke of the platen; with which ously operating pump; with which the pressure stroke of. the platen may be initiated under manual control, and after the resistance has reached a desired maximum pressure, the return movement of. the platen automatically initiated a predeterminedinterval thereafter; and with which said platen may be caused to travel alternately in opposite directions continuously.

Various other objects and advantages will be apparent from the following description of an embodiment of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

In the accompanying drawings:

Fig. l is aschematic diagram illustrating one embodiment of. the improved system;

Fig. 2 is a side elevation of the automatic control therefor, with the air chest cap removed;

Fig. 3 is a plan of the same;

Fig. 4 is a sectional elevation of the same, the section being taken approximately along the line 4-4 of Fig. 3.

Fig. 5 is a sectional elevation of the same, with the section taken approximately along the line 5--5 of Fig. 3; and Fig. 6 is a diagram of part of. the system showing the changes necessary when a uni-directional r'pump is substituted for a reversible pump.

hydraulic press of any suitable or usual construe` tion, including a platen IIJ which moves toward and from a xed platen, not shown, under the action of the main ram II and a pull-back ram I2. 'I'he cylinder of the main ram I I is connected by a pipe I3 to one end of the chamber I4 of. a dilerential valve housing I5, and a similar but smaller pipe I 6 connects the cylinder of the pullback ram I2 to the other end of the chamber I4. A pipe Il connects an intermediate or central part of the chamber I4 with a source I8 of iluid under pressure. In this instance this course may comprise a tank having an air chamber inits upper end, in which air is compressed so as to exert a yielding pressure on the liquid in the lower part of the tank. The use of such a tank as a source of fluid under pressure is disclosed in my prior U. S. Patent 1,765,627.

A valve ring or seat I9 is disposed across the chamber I4 between the connection thereto of the pipes I3 and I1, and a similar valve seat or ring 20 is disposed across the chamber I4 between the connections thereto of pipes I6 andA I'I. The opening in the valve seat I9 is larger than that of the seat 20, and is normally closed by the valve element 2I having a stem or tail part 22slidingly mounted in a socket or `cavity in the adjacent end of the chamber I4.

A helical compression spring 23 is disposed in the chamber I4 and acts upon the valve element 2l so as to urge this valve element 2| yieldingly against its seat I9. The guiding tail or part 22 of the valve element 2l may be made tubular or hollow to receivethe spring 23. A valve element 24 is disposed in the other end of the chamber I4 for cooperation with the seat 20, and includes an operating stem 25 which extends through a wall n of the housing I5 into an air cylinder or chamber 26 where it carries an operating piston 21.

'Ihe two valve elements 2| and 24 therefore control communication between the pipe I'I and the pipes I3 and I 6, these valve elements moving away from one another to permit iiuid ilow from the pipe I'I toward both of. said rams, and automatically closing to prevent return ilow into the pipe I'I from the rams. In this respect the valve elements function as two separate free check valves, but one of the valve elements, such as the element 24, is provided with a stem 28 which engages with the element 2l and pushes it into open position when the element 24 is pushed into closed position. By reason of this stem 28, Simultaneous seating of both of those Valve elements is automatically prevented, yet either element may Seat freely when the other element is in open position, and both valves may be open at the same time.

A pump 29, which may be of the reversible and Variable or constant delivery type, is connected at one side by a pipe 39 to the pipe I3 leading to the main ram II, and this connection may conveniently be obtained by connecting the pipe 30 to the end of chamber I4, in the differential valve housing I5, at the side of the seat I9 Where the pipe I3 is connected, so that the pipes 30 and I3 will always be in communication with one another regardless of the position of the Valve element",` 2l. Similarly, the other side of the pump 29 may be connected by the pipe 3I to the pipe I6 leading to the cylinder of the pullback ram, the connection being made through the opposite end of the chamber I4 so that this connection will not be affected by the position of the valve element 24.

A free check valve 32 is included in the pipe 3I in such a manner as to open freely and permit fluid ilow from the pump through the pipe 3| to the pipe I6, and automatically to close and prevent reverse flow. The pump is therefore so arranged as to deliver fluid under pressure to said rams alternately, and the delivery of fluid from the pump to either of these rams is under the control of a regulating member 33.

Reversible, variable delivery pumps of this type are well known in the art and hence it has been shown only diagrammatically, and will not be described in detail.

A branch pipe 34 is connected to the pipe 3| between the pump and the check valve 32, and is connected to a pump bypass valve 35, which also is connected by a pipe 36 to the chamber I4 at a point between the seats I9 and 20. The pipe 36 is in reality directly connected to the pipe I1, leading to the reservoir or source I8 of uid under pressure. The valve 35 includes a valve element 31 engaging with a valve seat 38 disposed between the connections thereto of the pipes 34 and 36, so as to control communication between the pipes 34 and 36. The valve element 31 is provided with a stem 39 which depends outside of the valve housing and is yieldingly urged in a direction to close the valve by a spring 40. The spring 40 normally urges the valve 31 into closed position, and therefore in a sense, the valve is in the nature of a check valve which opens automatically to permit flow from the pipe 36 into the pipe 34, and closes automatically when the ilow is in the opposite direction.

A rod 4I is guided vertically in a depending arm 42 of the housingof the valve 35, and at its lower end is guided for reciprocation in a bearing 43 extending laterally from the platen I6. The endwise movement of the rod 4I is limited by the engagement of a head 44 of the rod on its upper end with the support 42. When the head 44 of the rod 4I rests upon the depending support 42, the spring 40 will close the valve element 31. The rod 4I is provided with a collar 45 which is slidable along and adjustably secured to the rod in any suitable manner so that it may be set to be engaged by the bearing 43 of the platen I0 when the platen rises under the action of the pull-back ram.

When the bearing 43 of the platen engages the collar 45, the continued upward travel of the platen will cause a lifting of the rod 4I, and through it, will force the valve element 31 into its open position. The pump then discharges through the pipes 34 and 36 into the pipe I1 to the source I8, but since the valve element 2I would at that time be open, the ilow would actually be from the pipe 36 through the chamber I4 to the pipe 39 and thence to the pump. The pipe 36 may be, and preferably is, connected directly to the tank I8 so that fresh oil or operating liquid will circulate through the pump. The pump then may continue to operate at full capacity but without material pressure, since the fluid will be circulated idly through the pump. The pressure on the iluid in the pull-back ram will tend to cause the fluid to return through the pipe I6 and the pipe 3|, but this is prevented by the valve 32. The pull-back ram is thus held in its elevated position.

The regulating member 33 is operated to reverse the pump or to change its delivery between the pipes 3U and 3| in any suitable manner, but preferably in accordance with this invention, the member 33 extends into an air cylinder 46 and carries within the cylinder a piston or head 41. Pipes 48 and 49 lead to the interior of said cylinder 46 at opposite sides of the piston 41 so that when a compressed uid such as air is admitted to either pipe 48 or 49, such compresed air will force the piston 41 in one direction or another, and thus operate the regulating member 33. A branch 50 connects the pipe 48 with the air cylinder or chamber 26 of the differential valve, at one side of the piston 21 thereof, and a pipe 5I connects the pipe 49 to the air chamber 26 of the differential valve on the other side of the piston 21 from the opening into the pipe 59. The piston 21 will therefore be operated concomitantly with the piston 41.

The control of the compressed air admitted to the pipes 48 and 49 will next be explained, having particular reference to all of the figures of the drawings. Referring rst particularly to Fig. 5, the control device for the compressed air therein illustrated includes the valve body 52 suitably mounted adjacent the press (Fig.` 1). This valve body is provided with an air chamber or chest 53 (Figs. 2 and 5) which is normally closed by a cap 54 secured across an open window 55 (Fig. 2) in any suitable manner, such as by cap screws 56. The wall of the air chest 53, which is opposite the cap 54, is provided with ports 51, 5B, 59, and 60 arranged in a row in a direction lengthwise of the chamber or chest 53, as shown clearly in Figs. 2 and 5. A slide valve or control element 6I is disposed in said air chest 53 and is pressed continuously against the wall having the ports by a spring 62 carried by the cap 54, as shown clearly in Fig. 5.

A valve rod 63 extends through a removable plug 64 in the bottom of the valve body, and through a packing element 65 into the air chamber or chest 53, and is removably connected within the chamber to the slide valve or element 6I. Thus, by reciprocating the valve rod 63, the valve or element 6I may be reciprocated back and forth in the chamber 53 so as to cover and uncover the ports 58 and 60, alternately. The valve element 6I is provided with a cavity or recess 66 on its face which bears against the ported wall, and this cavity 66 connects the port 59 alternately with the ports 58 and 60, so that Whether the valve element is in one position or another, the port 59 will always be connected through the cavity 66 with one, and only one, of the ports 58 or 60.

A suitable source of compressed fluid such as air is connected through a pipe 61 (Fig. 2) and a passage 68 in the valve body, with the port 51, so that the air chest or chamber 53 will always be lled with compressed air. When the valve element 6| is in its lower position, which is shown in Fig. 5, this compressed air will pass through the port 58 into a passage 69 in the valve body to which is connected the pipe 48. The compressed air would therefore pass through the pipes 48 and 58 and cause an operation of the pump regulating member 33 and the differential valve element 24 in a manner to start operation of the pull-back ram to return the platen to the position shown in Fig. 1.

The port 59 is connected by the passage 18 to aplpe 1| which is an exhaust pipe, into which the compressed air or fluid escapes from the pipes 48 and 49. 'Ihe portv 68 is similarly connected by a passage 12 (Figs. 2 and 5) with the pipes 49 and 5|. When the control valve or element 6| is fshifted upwardly from the position shown by full lines in Fig. 5, it will uncover the port 68, and the cavity 66 will connect the ports 58 and 59. This position of the element 6| is shown by the dotted lines in Fig. 5. The compressed air will then no longer pass through the port 58 to the pipe 48, but instead will pass through the port 68 and passage 12 into pipe 49. The exhaust port 59 will be connected with the port 58, so that any compressed air which previously had been admitted to the pipe 48 could escape to atmosphere. This causes an actuation of the regulating member 33 and of the valve element 24 in the opposite directions, so as to start operation of the main ram and force the platen I8 downwardly.

The valve rod 63, at its lower end, is connected to a yoke 13 and the latter in turn is connected to the lower end of a pair of rods 14 which pass upwardly through bearing passages 15 in the valve body 52, and-above the valve body are connected by a yoke 16. The lower ends of the passages 15 are enlarged to form recesses 11 (Fig. 2) which receive helical compression springs 18 surrounding the rods 14 and bearing upon washers 19 held in position on the rods by nuts 88 on the rods 14. The springs 18 urge the rods 14 downwardly, and through the yoke 13 and valve rod 63 urge the slide valve or .Y element 6I downwardly into its lowermost position, shown in full lines in. Fig. 5. A latch or leverk 8| is pivoted at 82 to the yoke 16. A pair of springs 83 are connected between the lever 8| and suitable studs 84 on the yoke 'I6 so as to urge `the latch lever yieldingly in a counterclockwise direction in Fig. 5.

f The latch or lever 8| has a depending nose 85 which, in the position of the yoke 16 shown in Fig. 5, bears against a side face of an abutment 86 that is provided upon the upper end of the valve body 52. When the yoke 13 is elevated, the springs 18 will be compressed to a greater extent, and the latch or lever 8| .will b e bodily elevated with yoke 16 until a notch 81 in the lower end of the nose 85 snaps over an upper corner edge of the abutment 86 underthe action of the springs 83. If then the yoke 13 is released, the springs 18` would urge the yoke 16 and the latch or lever. 8| downwardly, but this downward movement of the yoke 18 will not take place because of the engagement of the latch or lever 8| with the abutment 86. The

slide valve or element 6| will thus be held releasably in its upper position in which it passes compressed air to the pipe 49 to start operation of the main ram.

The pump then delivers fluid, under pressure, through pipes 38 and I3 to the main ram I I, and the platen I8 moved downwardly. As the resistanceoffered to the platen I8 increases, the pressure of the acuating fluid in the main ram will increase, and this increased pressure is utilized to disengage the latch 8| a desired interval of time after the maximum desired pressure in the cylinder of the main ram has been reached, as will now be explained.

The valve body 52 is provided with a cylinder or chamber 88 (Fig. 5) which is closed at its lower end by a removable plug 89. A piston 98 reciprocates vertically in the cylinder 88 and is provided with a stem 9| which extends outwardly through a bearing passage in a removable plug 92 which closes the upper end of the chamber 88, a packing gland 93 being provided for the stern 9| before it passes through the plug 92. The outer end of the stern 9| carries an adjustable trip screw 94 which engages a tail 95 of the latch or lever 8|, rocking the latter in a clockwise direction in Fig. 5 against the tension of the springs 83 until it disengages the notch 81 from the abutment 86. Thereupon, the springs 18 force the rods 14 downwardly, and

'thereby shift the slide valve 6| downwardly into the position shown in full lines in Fig. 5. This shifts the delivery of fluid from the pump to the pull-back ram instead of the main ram, and starts a return travel of the platen I8.

The piston 98 telescopes over and slides upon a stud 96 projecting into the chamber or air cylinder 88 from the plug 89, and the stud 96 is provided with a passage 91 extending from end to end. The lower end of stud 96 is connected by a pipe 98 to the cylinder of the main ram II. The iluid pressure in the main ram iI is thus transmitted through the pipe 98 and the passage 91 to the underside of the piston 98. The effective pressure area on the piston is the area of the opening or cavity which ts over the stud 96 and is considerably smaller than the maximum diameter of the piston 98.

`Secured to the upper and outer end of the piston stern 9| by the trip screw 94 is a yoke 99 (Figs.l 3, 4, and 5, and the ends of this yoke are secured to the upper ends of a pair of rods |88 which pass downwardly through the valve body 52 in which they are slidingly mounted. The passages in the valve body 52 through which the rods |88 pass are enlarged at their lower ends and form cavities |8| (Fig. 4). Helical springs |82 are compressed between the upper or inner ends of the cavities and washers |83 conned on the rods |88 by nuts. |84. The springs |82 thus urge the vrods |88 downwardly and .thus through the yoke 99 resiliently urge the piston 98 into its lowermost position, shown in Fig. 5.

No appreciable upward movement of the piston 9 8 will occur until the pressure thereon transmittedl through the passage 91 from the main ram is sufficient to overcome or compress the springs |82. When the pressure on the piston 98 builds up suiciently to overcome the resistance of the springs |82, the fluid displaced in the cylinder 88 by the piston 98 is controlled in its escape in a manner to regulate variably, the rate of travel of the piston 98, and thus delay the tripping of the latch or lever 8| for a desired interval after any selected pre-determined pressure has been built up in the main ram. i

A pipe |85 (Fig. 5) leading from any suitable reservoiror source of iluid (not shown) is connected to a passage |86 in the valve body 52, which passage leads tothe underside of the enlarged head of the piston 98. A branch passage |81 leads -upwardly from the passage |88` into a transversely extending passage |88; `A free seating check valve |89 is provided at` the junction between the passages |81 and |88 so as. to

fl U

permit free upward flow of fluid from the passage |01 into the passage |08. Another passage l0 (Fig. 4) extends downwardly from the passage |08 and intermediate its ends is provided with a seat |H. The portion of the passage H0, which is below the seat HI, is somewhat larger than the portion of the passage above the seat.

A needle valve stem H2 passes through and is threaded into a plug H3 which closes the lower end of the passage H0, and also passes through a packing gland H4 at the upper end of the plug H3. The tapered tip of the needle valve stem cooperates with the seat |H to restrict or regulate variably, the fluid flow along the passage H0. A further branch passage H5 connects the lower end of the passage H0 with the passage |06. The upper end of the cylinder 88 (Fig. 5) is connected with the passage |08 by a short passage H6. (Figs. 4 and 5).

From the foregoing description it will be observed that any fluid displaced from the upper end of the cylinder 88 by the upwardly moving piston 90 (Fig. 5) will pass through passage H6 into the passage |08, and cannot pass downwardly through the passage |01 because of the automatic seating of the check valve |09. Consequently this displaced uid will pass along passage |08 (Fig. 4) and into and through the passage 0 where its flow is regulated by the needle valve, and thence will pass through passage H5 into the passage |06, from which a part of it may enter the space in the cylinder 88 below the piston head 90 and the remainder may pass through the pipe |05 to the source or reservoir (not shown). By suitably adjusting the needle valve stem H2 through manipulation of its head H6, the escape of the displaced uid from the cylinder 88 is regulated, and hence the travel of the piston 90 may be regulated to occupy any desired interval of time after the pressure in the main ram has equaled or exceeded a desired pressure corresponding to that necessary to overcome the springs |02. 'Ihe control of the pump may be set so that when any desired maximum pressure has been reached, the pump will come toward neutral and will maintain this pressure. Such pumps are articles of commerce and, per se, are not part of this invention. The regulation of the time interval through adjustment of the needle valve stem H2 enables one to regulate the time from zero to any desired period during which the pump is holding this desired pressure. In other words, with this combination it is possible to have a time dwell on the press under pressure and the pressure and the time are both adjustable.

When the latch 8| is tripped at the completion of the upward travel of the piston 90, the operation of the platen I0 is reversed and the pullback ram is made effective. The pressure in the mainl ram thereupon falls very materially and quickly, whereupon the springs |02 will return the piston 90 to its lowermoslt position. During this descent of this piston 90, the fluid displaced by its head from the lower part of the chamber or cylinder 88 will escape through passage |06 and pass either directly to the reservoir through passage |05, or will move upwardly in passage |01, lift the check valve |09, and then move through passages |08 and H6 into the upper end of the cylinder 88, so as to occupy the increasing space in the upper end of the cylinder 68 caused by the descent of the piston head. Since the fiuid displaced beneath the piston head will be less than that displaced above the piston head, the fluid which is displaced from beneath the head will all travel upwardly in the passage |01, and s ome of the fluid which was displaced to the reservoir through pipe |05 when the piston 90 was ascending, will return through pipe |05 and passages |06, |01, |08, and H6 to the upper end of the cylinder 88.

If the yoke 16 has been elevated and latched in elevated position by the latch 8|, the main ram H is effective to cause the descent of the platen |0. The descent of the platen l0 is not stopped until the latch 8l is released by the upward movement of the piston 90 after a desired minimum pressure has been built up in the main ram and maintained therein for a selected interval of time. It may happen that one may desire to check the descent of the platen before a complete cycle has been completed, as a safety feature, and for this purpose a safety release member H1 is slidably mounted for vertical movement in any suitable manner, such as shown in Fig. 2, on the yoke 16, and is provided with a slot H8 extending vertically and into which extends another tail H9 of the latch or lever 8|.

An operating rod |20 depends from the member H1 and is guided vertically in a suitable bearing |20a (Fig. l) on the base of the press and an arm |2| of the platen. A spring |22 on the rod |20 acts between a collar |23 on the rod and the bearing |20a to elevate the rod |20 and hold it in its upper position shown in Figs. 1 and 5. When the member H1 is in this elevated position, as shown in Figs. 1 and 5, the yoke 16 may move upwardly or downwardly in order to cause the engagement of the latch 8| with the abutment 86 or the descent of the yoke after the latch is disengaged from the abutment, and during such movement the tail H9 of the latch 8| moves idly in the slot H8 of the release member I1.

Assuming that the latch has been elevated with the yoke and engaged with the abutment 86, the tail H9 will then be nearer the upper end of the slot H8. If then the release member H1 is moved downwardly by a downward pull on the rod |20, the upper end of the slot H8 will engage the tail H9 and rock the latch or lever 8| clockwise in Fig. 5 and disengage it from the abutment 86. 'I'his causes a movement of the slide valve or element 6| and through initiated by an upward movement of the slide valve or element 6|, suitable means has been provided for causing this movement of the slide valve. A rod |25 (Fig. 1) is suitably guided in the bearing |2| of the platen and in other bearings |26 on the frame of the press, and this rod 25 at its upper end (Figs. 1 and 2) is disposed just below the yoke 13 which is connected to the lower end of the valve operating rod 63. A spring |21 acts between one of the bearings |26 and a shoulder on the rod |25 so as to yieldingly hold the rod in its lower position which is determined by a stop pin |28 in the path of a lever or foot pedal 29 and which engages and operates the lower end of the rod |25, as shown in Fig. 1. The pedal or lever |29 ls pivoted at |30 so that when the free end of the lever is Fil , pipe |34 connecting the pipes 34 and 36.

displaced, the rod |25 will be elevated into engagement with the yoke '|3 and further movement will cause an upward movement of the yoke and the slide valve 6|. ward movement of the platen I0.

According to this arrangement, a downward movement of the platen is initiated by manual operation of the trip pedal |29', but in some lnstances it may be desirable to have full automatic operation or a continuous up and down movement lof the platen. Accordingly, I provide a collar |3|, (Fig. l) upon the rod |25 in a position to be engaged by the bearing |2| on the platen I0, when the platen reaches approximately its upper limit of movement. The final upward movement of the platen thus elevates the rod |25 automatically and through it shifts the valve 6| to start a new downward movement of the platen. The collar |3| is secured in different adjusted positions along the rod |25 in `any suitab-le manner, such as by a set screw |32,

in its upward travel by its engagement with collar 45 before it can operate the slide valve and initiate a downward movement of the platen. It will be understood that when the collar |3| is adjusted into a position to cause a full automatic operation of the platen IU, the collar 45 may be adjusted into a position into which it is not engaged by the platen since the purpose of the pump by-pass valve 35 is to stop the upward travel of the platen and to hold the platen in that stopped or elevated. position.

The rod 4| (Fig. l) may be connected to the stem 39 of the pump by-pass valve element 3l, or it may merely engage the same endwise, but if directly attached to it, it is preferable to provide a second free check Valve |33 in a branch This check valve |33 opens freely to permit flow from the pipe 36 into the pipe 34 and automatically seats to prevent reverse flow.

The operation of this system should be obvious from the foregoing description of the construction, but will be briey summarized. Assuming first that the platen is at its upper limit of movement as shown in Fig. 1, and that the collar |3| is positioned as shown in Fig. 1, so as not to be elevated by the platen, when the platen reaches its upper position, thus making the press set for semiautornatic operation. To initiate an operation of the press, the operator depresses the pedal |23 which causes an elevation of the rod |25 and through it an elevation of the slide valve 6|. Thereupon the compressed air from the chest 53 (Fig. 5) would pass through the port 6|), passage |2 and pipe 49 to the air cylinder 46, and also pass through the branch pipe 5| to the air cylinder 26 of the differential check valve. This causes an operation of the piston 4`| of the air cylinder 46 to the right in Fig. l, so as to cause the pump 29 to deliver fluid under pressure to the pipe 30 and get its suction from the pipes 3| and 34.

At the same time the differential check valve stem 25 is elevatedby the piston 21, thus lifting valve element 24 and opening communication between the reservoir pipe I1 and the pipe I6 leading to the pull-back ram |2. The

This starts a down.

uid in the pull-back ram is then allowed to escape through the seat 20 into the central part of the chamber I4 where it may pass either into the pipe or through the pipe 36 and either or both of the check valves 35 and |33 into the pipe 34 leading to the intake side of the pump. The iiuid or liquid in tank |8 is stored under pressure, which may be either pneumatic pressure, or an accumulator, or the pressure may be created in any other manner. At this time the pressure in the main ram is very small, because it has previously been connected to the intake side of the pump. Immediately at the beginning of the operation of the main ram, the fluid from the tank |8 which has a pressure higher than that of the main ram will force open th-e check valve or element 2|, move rapidly into the main ram, and force the platen I0 downwardly at a rapid rate until the platen meets considerable resistance.

When this resistance approximately balances the pressure created by the iiuid from the tank I8, the check valve element 2| will close under the action of the spring 23, this closing being permitted -since the other check valve element 24 is open. The fluid delivered by the pump through the pipe 30 and pipe I3 to the main ram then builds up the pressure in the main ram to the maximum desired. The pressure in the main ram is transmitted through pipe 93 to the passage 9| in the stud 96 (Fig. 5) and when the pressure on the piston 9 within the cavity which slides over the stud 96 is suflicient to overcome the resistance of the springs |02, the piston 90 will travel upwardly at a rate controlled by the regulation by the needle valve stem ||2, and after an interval which is pre-determined by the regulation of the needle valve stem, the strip screw 94 will engage and rock the latch 8| into disengaged position, whereupon the springs 'i8 will cause the yoke 'i3 to descend and lower the slide valve 6| into the position shown in full lines in Fig. 5.

The port 6|) is then connected to the exhaust port 59 so as to release the pressure in the pipes 49 and 5| (Fig. 1) and at the same time the compressed air from the chest 53 (Fig. 5) will pass through port 58, passage |59 (Figs. 2 and 5), the pipe 48 (Figs. l and 2) to the opposite side of the air cylinder 46, to cause a reverse travel of the piston 4l and a reversal of the delivery of the pump. At the time time air from the pipe 43 (Fig. 1) moves through the branch 5U to the cylinder on the differential check valve, and forces the valve element 24 promptly into closed. position on the seat 24, and in doing so the stem 28 engages and opens the check valve element 2|.

The pump then delivers fluid under pressure into the pipes 3| and 34, but the check Valves 35 and |33 automatically prevent movement of the fluid through pipe 34, and hence the uid travels entirely through the pipe 3| and check valve 32 into the pipe |6 and thence to the pullback ram |2. The platen then starts its upward travel. At the instant that the pump is reversed, the valve element 2| is opened as explained, and the high pressure in the main ram is at once relieved, allowing return of the piston 96 (Fig. 5) into its lowermost position under the action of the springs |02. The main ram has a greater displacement than the pullback ram, and the fluid from the main ram passes through the differential check valve and the pipe I1 into the storage tank or reservoir I8 where the pressure is again built up to the desired extent.

Some of the iluid displaced by the main ram of course passes through the pipe 30 to the intake side of the pump for delivery to the pullback ram. This operation continues until the platen I0 engages the collar 45 at its upper limit of movement, and elevates the rod 4| thus opening the check valve 35. This short circuits the delivery of the pump away from the pull-back ram and directly back to the source I8 or to the pipe 30, since the valve element 2| remains open because of the engagement of the stem 28 therewith. The pump thus may continue to operate at full capacity, but the iluid is circulated idly through the pipes 34, 36,'and 30, so that there will be no heating of the pump since there is practically no load upon it. 'I'he pressure built up in the pull-back ram I2 is maintained, because the check valve 32 prevents return flow, and thus the platen I0 will remain in this position until a new operation is initiated by operation of the lever |29.

Suppose, that full automatic operation of the press now is desired. The operator will move the collar |3I along the rod |25 and secure it thereto in a position to be engaged by the bearing |2I at the same time that the collar 45 is engaged by the bearing 43 of the platen, or at the desired upper limit of movement of the platen. With that setting of collar I3I, when the platen I 0 reaches its desired upper position it engages the collar I 3| and elevates the rod |25 to start a new downward movement in the same manner that operation of the lever |29 at that instant would have done. 'Ihe platen l0 then starts on a new power stroke, and will continue to move upwardly and downwardly automatically in this cycle until the operator shifts the collar I3I out of the range of operation of the platen I0.

In the embodiment of the invention illustrated in Fig. 6, a uni-directional delivery pump |35 is shown as substituted for the reversible pump 29 of Figs. 1 to 5. Changes in the system arising from the substitution of the uni-directional pump are shown in this ligure, the remainder of this system being the same as in Figs. 1 to 5. The intake side of the pump |35, which always operates continuously in the same direction, is connected by pipe I 36 to the source of fluid under pressure which in this embodiment of the invention may be to the pipe I1. 'I'he output side of the pump |35 is connected by a pipe |31 to a port |38 in a valve housing |39. A valve element I 40 is reciprocated in the housing |39 by regulating member 33 and connects the port I 38 alternately with the pipes 30 and 3| of Fig. 1. The valve element |40 when reciprocated by the regulating member 33 therefore delivers the output of the pump to either the pipe 30 or 3| in accordance with the position of the regulating member 33.

In Figs. 1 to 5, the operating medium for the pistons 41 and 21 was mentioned as compressed air by way of example, and it is a simple and inexpensive medium for the purpose. However, it is possible and sometimes desirable to operate the system without the use of compressed air, and one example of the changes which will accomplish this result is shown also in Fig. 6. For this purpose a choke I4I is placed in the pipe |31 so as to insure that the pump will always operate under a selected minimum pressure, such as one hundred pounds per square inch or over. Such chokes are well known in the art and may be of the sliding type, or may be a check valve spring-pressed toward its seat to resist the flow of fluid through the pine |31 until the pressure equals or exceeds that necessary to lift the valve from its seat against the action of its spring, which is said selected minimum pressure. 'I'he pipe 61, which supplies the compressed fluid to the control device, is then connected to the pipe |31 between the pump |35 and the choke |4I, and hence the liquid or other fluid being handled by the pump will be supplied, under a pressure equal to or exceeding said minimum, to the air chest or chamber 53. While only a small amount of this fluid would actually pass out through the exhaust 59 if the exhaust were open, any loss of such fluid may be prevented by connecting the exhaust pipe 1I to the pipe I 1. With this system otherwise arranged as explained in Figs. 1 to 5, the operation is the same.

The pump and operating iluid will not heat while the pull-back ram is holding the platen in its elevated position because the pump is operating idly. The operation of the press under this system is very rapid, and free from undesirable vibrations. While compressed air or other uid has been described as the actuating medium of the controlling mechanism, it will be understood that other equivalent means may be substituted if desired.

It will be understood that by adjusting the tension of the springs |02, which resist the upward movement of the trip piston 90 and stem 9|, one may vary the pressure which must be reached in the main ram before the timing action starts. Consequently, the pressure in the main ram at which the springs |02 are overcome is the pressure which must be reached in the main ram before the timing device begins to operate, and this pressure may also be nearly the maximum pressure when a pump is used of the type which builds up the pressure in the main ram to a desired extent and then holds the pressure unchanged. Where the ordinary pump is used, the timing device begins to operate after the selected pressure has been reached in the main ram, and While the timing device is operating the pressure in the main ram and on the timing piston 90 is increasing above the selected pressure at which movement of the timing piston was initiated.

It will be obvious that various changes in the details, 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:

1. In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said platen for operating it alternately in opposite directions, a source of operating fluid, means including a pump connected to said rams for delivering fluid from said source to each of said rams and from each ram to the other alternately in accordance with the desired direction of operation of said platen, a freely opening check valve in the connection from said pump to said pull-back ram separate from the connection from the pump to the main ram permitting free 110W of fluid from the pump to the pull-back ram and automatically preventing reverse Ilow, by-pass valve means connecting said source to the connection between said pump and said check valve.

and operable to by-pass to said source the fluid delivered by `said pump and intended for said pull-back ram, and a free check valve shuntingA said by-pass valve means and opening freely to pass fluid toward said pump, whereby the action of the pull-back ram may be stopped and the platen held in any desired position during the return movement of said platen.

2. In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said platen for operating it alternately in opposite directions, a source of operating fluid, means including a pump connected to said rams for delivering fluid from said source toeach of said rams and from each ram to the other alternately lin accordance with the desired direction of operation of said platen, a check valve in the connection from said pump to said pull-back-rarn separate from the connection from the pump to the main ram, permitting free flow of fluid from the pump to the pull-back ram and automatically preventing reverse flow, a by-pass valve connecting said source to the connection between said pump and said check valve, and operable by said platen when said platen reaches a desired point in its return movement for stopping the delivery of fluid from the pump to the pull-back ram, whereby the action of said pull-back ram will be stopped and said platen held in the position in which it stops, automatically, and a free check valve shuntlng said by-pass'valve and yielding to flow solely in a direction toward said pump and opposltely from the flow through said by-pass valve when the latter is opened by said platen.

3. In a press system, a platen, a pull-back ram and a main ram connected to said platen and operating it in alternate directions, a source of fluid, a variable delivery, reversible pump, pipes to said rams from said pump'for delivering fluid from said source to said rains alternately, a branch pipe from said pump, at ,the side connected to the pull back ram, `to said source, a valve solely in the pipe from said pump to said source and operable automatically when the platen reaches a desired point in its return movement for diverting fluid from said pump to said source, a free check valve by-passing said automatically operable valve in the pipe from said pump to said source, and openingautomatically to pass fluid from said source to said pump and opposing reverse flow, and means for changing the delivery of said pump from the pull-back ram to the main ram to start a new power stroke With said main ram.

4. In a press system, a platen, a pull-back ram and a main ram connected to said platen `and operating it in alternate directions, a source of fluid, a single, high pressure pump for delivering fluid from said source to said rams alternately, a valve operable automatically when the platen reaches a desired point in its return movement for diverting uid from said pump to said source, means for changing the delivery of said pump from the pull-back ram to the main ram to start a new power stroke with said main ram, and

predetermined pressure for changing the deliveryv of fluid by the pump to the pull-back ram instead of the main ram to start the return movement of the platen.

5. In a press system, a platen, a pull-sack ram 75 and a main ram connected to said platen for operating it in alternate directions, a source of fluid, a vpump for delivering fluid from said source to said rams alternately'means for changing the delivery of fluid from said pump to said rams so as to operate either ram selectively, a relatively low pressure, fluid actuated, control device for controlling said last named means and having a controlling valve device operated by the relatively high fluid pressure'in said main ram to change delivery of fluid from said pump to said pullback ram instead of the main ram automatically a predetermined and selected length of timeafter the pressure in the main ram has reached a desired pressure.

6. In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said platen for operating it in alternate directions, a source of fluid, a pump connected to said source and to each of said rams for delivering fluidunder pressure to each of said rams alternately,r means for causingsaid pump to deliver fluid selectively to either of said rams, and a relatively low pressure regulatable dash pot timing device operable on said last named means and controlled by th'e relatively high pressure in the main raml to cause the pump to deliver its fluid to the pull-back ram automatically after the pressure in said main ram reaches a desired pressure.

7. In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said platen for operating it in alternate directions, a source of fluid, a pump connected to said source and to each of said rams for delivering fluid under pressure to each of said rams alternately, means for causing said pump to deliver fluid selectively to either of said rams, and an adjustable timing device operable on said last named means and normally inactive but set into operation automatically Where the pressure in the main ram exceeds a predetermined desired pressure to cause the pump to deliver its fluid to the pull-back ram automatically a pre-determined selected and adjustable interval after the pressure in said main ram reaches said desired pressure.

8. In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said platen for operating it in alternate directions, a source of iluid under pressure, means for transferring fluid between said rams alternately, a `source ci operating fluid, pipe means leading from said source to each ram, said pipe means, said transferring means, said source and said rams together forming a hydraulic system, a valve in the pipe means to each ram, each valve having an individual, movable valve element, said elements being so formed and interacting that when either element is closed, it automatically prevents closing of theother element and each element can open independently of the other, and means separate from said transferring means extending exteriorly of the hydraulic system and operable upon one of said valve elements for shifting it into and out of closed position.

9. In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said platen for operating it in alternate directions, a source of fluid, a valve housing having a chamber, a connection from said chamber to said source, a connection from each ram to different parts of said chamber, a separate valve controlling each connection from a ram to said chamber, said valves being disposed and constructed to engage one another and prevent the simultaneous seating of both, and moving away from one another in an opening direction so that both may be open at the same time, a pump for transferring fluid between said rams alternately, means separate from said pump for causing said pump to deliver to either ram selectively and having a member positively operable directly upon the valve controlling the connection from the pull back ram to said chamber, whereby the valve in the connection to the pull-back ram will be forcibly opened irnmediately when the pump delivers fluid to said main ram and will be forcibly closed to open the other valve in the connection to the main ram, whenever said pump is caused to deliver fluid to the pull-back ram.

10, In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said platen and operating it in alternate directions, means for delivering uid under pressure to said rams alternately, means for controlling the delivery of fluid to each of said rams including a control element yieldingly urged into one position in which the pull-back ram ismade effective and operable against such urging into a position in which the main rarn is made effective, a latch for holding said element releasably in said last named position, a cylinder having a connection to said main ram, a piston in said cylinder operable by pressure in said main ram, a valve controlling escape of fluid displaced by said piston so as to regulate the rate of movement of said piston under the pressure of said main ram, and means yieldingly urging said piston against the pressure of said main ram, whereby said piston will be operated only when the pressure in said main ram exceeds a pre-determined pressure, said piston having a part operable upon said latch to release said element a pre-determined interval after the pressure in said main ram has reached said pre-determined pressure.

11. In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said platen for operating it alternately in opposite directions, a source of fluid connected to both of said rams, a valve in the connection to each ram, a reversible pump connected to both of said rams for transferring uid between them alternately,

means by which simultaneous closing of said valves is prevented, a check valve in the connection from said pump to said pull-back ram, opening freely for the ow from said pump to said pull-back ram and automatically closing to prevent return flow toward said pump, and a connection from said pump at its output side, when delivering to said pull-back ram, to said source and having a check valve therein seating automatically under the pressure from said pump when said pump is delivering toward said pullback ram, and opening automatically when said pump is delivering to said main ram.

12. In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said platen for operating it alternately in opposite directions, a source of uid conected to both of said rams, a valve in the connection to each ram, a reversible pump connected to both of said rams for transferring fluid between them alternately, means by which simultaneous closing of said valves is prevented, a check valve in the connection from said pump to said pull-back ram, opening freely for the flow from said pump to said pull-back ram and automatically closing to prevent return flow toward said pump` a connection from said pump at its output side, when delivering to said pull-back ram, to said source and having a check valve therein seating automatically under the pressure from said pump when said pump is delivering toward said pull-back ram, and opening automatically when said pump is delivering to said main ram, and means operable by said platen when said platen reaches a desired point in its return movement under the action of the pullback ram for opening forcibly said second check valve to permit delivery of fluid from said pump directly to said source.

13. In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said platen for operating it alternately in opposite directions, a source of fluid connected to both of said rams, a valve in the connection to each ram, a reversible pump connected to both of said rams for transferring fluid between them alternately, means by which simultaneous closing of said valves is prevented, a check valve in the connection from said pump to said pull-back ram, opening freely for the flow from said pump to said pull-back ram and automatically closing to prevent return flow toward said pump, a connection from said pump at its output side, when delivering to said pull-back ram, to said source, a valve in said connection from said pump to said source and operable by said platen into open position when said platen reaches a desired point in its return movement under the action of the pull-back ram, whereby the by-passing of the fluid from said pump to said source instead of the pull-back ram, stops the operation of said pull-back ram, and a free check valve connected in parallel to said platen operated valve and opening freely under now of uid from said source to said pump, and automatically seating to prevent return flow.

14. In a press system, a platen, a pull-back ram and a main ram connected to said platen for operating it in alternate directions, a source of fluid, a pump, connections from said pump to said rams for delivering fluid from said source to said rams alternately, means for changing the delivery of fluid from said pump to said rams so as to operate either ram selectively, a pressure opened choke in the connections from the output side of said pump to said rams to cause said pump to operate at all times under a pressure above a selected minimum, and opening to pass fluid freely whenever the pressure of fluid delivered by said pump exceeds said minimum, and means connected to the output side of said pump between said pump and said choke and controlled by the platen at a desired point in its return movement for changing the delivery of said pump from the pull-back ram to the main ram to start a new power stroke of the main ram.

15. In a press system, a platen, a pull-back ram and a main ram connected to said platen for operating it in alternate directions, a source of fluid, a pump, connections from said pump to said rams for delivering fluid from said source to said rams alternately, means for changing the delivery of fluid from said pump to said rams so as to operate either ram selectively, a pressure opened choke in the connection from the output side of said pump to said rams to cause said pump to operate at all times under a pressure above a selected minimum, and opening to pass fluid freely whenever the pressure of fluid delivered by said pump exceeds said minimum, and means connected to the Aoutput side of said pump between said pump and said choke and controlled by the pressure in said main ram for changing the delivery of said pump to said pull-back ram after a desired pressure has been created in the main ram.

16. In a press system, a platen, a pull-back ram and a main ram connected to said platen for operating itin alternate directions, a source of fluid, a pump, connections from said pump to said rams for delivering fluid from said source to said rams alternately, means for changing the delivery of fluid from said pump to said rams so as to operate either ram selectively, a pressure opened choke in the connections from the output side of said pump to said rams to lcause said pump to operate at all times under a pressure above a selected minimum, and opening to pass iiuid freely whenever the pressure of fluid delivered by said pump exceeds said minimum, means connected to the output side of said pump between said pump and said choke and controlled by the platen at a desired point in its return movement, and by the pressure in the main ram after a desired pressure has been created in the main ram, for changing the delivery of fluid from one ram to the other and thereby maintain continuous reciprocatory movement of said platen.

17. In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said platen for operating it in alternate directions, a source of uid under pressure, means including a pump and selectively operable for transferring fluid between said rams alternately, a valve device having a chamber connected to said source and to each of said rams, said valve having separate valve elements, one controlling flow in the connection from said source to one ram and the other controlling flow in the connection to the other ram, said valve elements having interengaging parts by which simultaneous closing by both valves is prevented, means for reversing the delivery of said transferring means from one ram to the other, and means operable by said reversing means from the exterior of the valve chamber for forcibly opening one of the valve elements when the pump delivers fluid to said main ram, andforcibly closing said one of said valve elements when said pump delivers uid to said pull-back ram.

18. In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said platen for operating it in alternate directions, a source of fluid under pressure, a connection from said source to each of said rams, a valve in the connection to each ram and having a movable -valve element controlling fluid ow in that connection, said valve elements having parts interengaging one another by which simultaneous closing of both valve elements is prevented, a piston connected to the valve element of that valve which is in the connection to the pull-back ram for forcibly operating that valve element in both directions, uid pressure actuated means for operating said piston selectively in either direction, a pump for transferring liquid from one ram to the other in either direction selectively, fluid actuated means for changing the delivery of said pump from one ram to another, and a common controlling means for both of said fluid actuated means.

19. In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said platen for operating it in alternate directions, a source -of uid under pressure, a connection from said source to each of said rams, a separate check valve in the connection to each ram and having a movable valve element opening f or flow from said source to the ram. and automatically closing to prevent reverse flow, the valve elements of said check valves having interengaging parts by which simultaneous closing of both valve elements is prevented, a piston connected to the valve element of that check valve which is in the connection to the pull-back ram for forcibly operating that check valve in both directions, fluid pressure actuated means for operating said piston selectively in either direction, a pump for transferring liquid from one ram to the other in either direction selectively, fluid actuated means for changing the delivery of said pump from one ram. to another, a controlling device for regulating the movement of actuating fluid to said piston and to said pump delivery changing means, manual means for controlling said controlling device, and means operated au;-V

tomatically bythe platen for also controlling said controlling device in accordance with `the movements of the platen.

20. In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said' platen for operating it in alternate directions, a source of uid under pressure, a connection from said source to each of said rams, a separate check valve in the connection to each ram and having a movable valve element opening for flow from said source to the ram and automatically closing to prevent reverse ow, the valve elements of said check valves having interengaging parts by which simultaneous closing of both valve elements is prevented, a pilot cylinder having a 'piston reciprocating therein and' connected to the valve element of that check valve which is in the connection to said pull-back ram, connections for admitting a uid under pressure selectively to opposite sides of said piston for causing movement of said piston in a desired direction, a pump connected to said rams for transferring fluid from one ram to another in either direction selectively, a device for regulating the delivery of said pump in order to change the delivery from one ram to the other, an operating cylinder having a reciprocating piston therein connected to said regulating device for operating the latter, connections to said operating cylinder on opposite sides of its piston for causing selected actuation of that piston, a controlling device to which the connections from said operating cylinder and said pilot cylinder lead, whereby the pistons in both of these cylinders will be operated concomitantly in a direction determined by said control device, and manually operated means for operating said control device to admit fluid to said pilot and operating cylinders in a manner to cause a downward movement to said platen.

21. In a hydraulic press system, a platen, a main ram and a pull-back ram connected to said platen for operating it in alternate directions, a source of fluid under pressure, a connection from said source to each of said rams, a separate checkyalve in the connection to each ram and having a movable valve element opening for flow from said source to the ram and automatically closing to prevent reversev flow, the valve elements of said check valves having interengaging parts by which simultaneous closing of both valve elements is prevented, a pilot cylinder having a piston reciprocating therein and connected to the valve element of that check valve which is in the connection to said pull-back ram,

therein connected to said regulating device for operating the latter, connections to said operating cylinder on opposite sides of its piston for causing selected actuation of that piston, a controlling device to which the connections from said operating cylinder and said pilot cylinder lead, whereby the pistons in both of these cylinders will be operated concomitantly in a direction determined by said control device, manually operated means for operating said control device to admit fluid to said pilot and operating cylinders in a manner to cause a downward movement to said platen, and means responsive to the pressure in said main ram for operating said control device in a manner to cause a return movement of said platen after the pressure in said main ram has reached a selected pressure.

`from said source to each of said rams, a separate check valve in the connection to each ram and having a movable valve element opening for flow from said source to the ram and automatically closing to prevent reverse flow, the valve elements of said check valves having interengaging parts by which simultaneous closing of both valve elements is prevented, a pilot cylinder having a piston reciprocating therein and connected to the valve element of that check valve which is in the connection to said pull-back ram, y

5 erating cylinder on opposite sides of its piston for causing selected actuation of that piston, a controlling device to which the connections from said operating cylinder and said pilot cylinder lead, whereby the pistons in both of these cylinders will be operated concomitantly in a direction determined by said control device, manually operated means for operating said control device to admit fluid to said pilot and operating cylinders in a manner to cause a downward movement to said platen, and means responsive to the pressure in said main ram and operable on said control device to cause a return movement of said platen, a pre-determined and ad` directions, additional fluid actuated means operable for changing said delivering means and causing a change in the ram to which fluid is delivered, and thus cause operation of said rams selectively in either direction, a master valve controlling admission of fluid to said fluid actuated 'means, means yieldingly urging said master valve into one operative position in which it causes operation of said pull back ram, manually controlled means for operating said master valve against said urging means into a different position in which it causes actuation of said main ram, a latch for releasably securing said master valve in said last named position, and means responsive to the pressure in said main ram and operable upon said latch to release said master valve element when the pressure in said main ram reaches a pre-determined pressure.

24. In a hydraulic press system, a platen, a main ram and a pull back ram connected to said platen for operating it in alternate directions, means for delivering a fluid under pressure to said rams selectively to operate them in alternate directions, fluid actuated means for determining the operation of said fluid delivery means to cause selected operation of said rams, a master valve controlling admission of fluid to said uid actuated means, means yieldingly urging said master valve into one operative position in which it causes operation of said pull back ram, manually controlled means for operating said master valve against said urging means into a different position in which it causes actuation of said main ram, a latch for releasably securing said master valve in said last named position, means responsive to the pressure in said main ram and operable upon said latch to release said master valve element when the pressure in said main ram reaches a pre-determined pressure, and means for retarding the operation of said last named means upon said latch for a selected interval of time after said pre-determined pressure has been reached.

25. In a hydraulic motor, an operated member, a main ram and a pull-back ram connected to said member for operating it in alternate directions, a source of fluid under pressure, means including a pump and selectively operable for transferring fluid between said rams alternately, a passage connecting said source and each ram, a valve in each passage, means cooperating with said valves to prevent simultaneous closing of both valves, the valve in the passage to the main ram being a free check valve and normally closing to prev-ent fluid flow from said main ram toward said source, means for reversing the delivery of said transferring means from one ram to the other, fluid pressure operated means outside of said passages and connected to and operating the valve in the passage to the pull-back ram in both directions selectively, fluid pressure operated means connected to and operating said reversing means, and m-eans for controllingV the flow of operating iiuid under pressure to both of said pressure operated means.

26. In a hydraulic motor, an operated member, a main ram and a pull-back ram connected to said member for operating it in alternate directions, a source of fluid under pressure, means including a pump connected to said rams and selectively operable for transferring fluid between said rams alternately and cause operations of said member, valve means in the connection from said transferring means to said pull-back ram operable for preventing flow therethrough in a direction from said pull-back ram towards said transferring means, a conduit connecting said source to said connection having the valve means, at a point between said transferring means and said valve means, a valve in said conduit operable to prevent flow therethrough in a direction from the pump toward said source, and to pass fluid in the opposite direction, and means operable by said member during an operation of said member by said pull-back ram, for passing :duid from said transferring means, at the conduit connected side, to said source, to stop said member and hold it in stopped position While said transferring means continues to deliver fluid towards said pull-back ram. f

27. In a hydraulic motor, an operated member,

a main ram and a pull-back ram connected to said member for operating it in alternate directions, a source of fluid under pressure, means including a pump connected to said rams and selectively operable for transferring fluid between said rams alternately and cause operations of said member, valve means in the connection from said transferring means to said pull-back ram operable for preventing flow therethrough in a direction from said pull-back ram toward said transferring means, a conduit connecting said source to said connection having the valve means,

at a point between said transferring means and said valve means, a valve in said conduit operable to prevent flow therethrough in a direction from the pump toward said source, and to pass fluid in the opposite direction, means operable by said member during an operation of said member by said pull-back ram, for passing fluid from 'said transferring means, at the conduit connected side, to said source, to stop said member and hold it in stopped position while said transferring means continues to deliver fluid toward said pull-back ram, pipe means connecting said source to each of said rams, a valve in the pipe means leading to the main ram, a valve inthe pipe means leading to the pull-back ram, and means for preventing simultaneous closing of both valves in said pipe means.

THOMAS F. STACY.

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