US2358353A - Hydraulic press - Google Patents

Description

Sept. 19, 1944. T. F. STACY HYDRAULIC PRESS Filed July 20, 1957 5 Sheets-Sheet 1 ATTORN EYS P 1944- T. F. STACY HYDRAULIC PRESS Filed July 20, 1937 5 Sheets-Sheet 2 eoew INVENTOR m fag ATTORNEYS Sept. 19, 1944. F STACY 2,358,353

HYDRAULIC PRES S Filed July 20, 1937 3 Sheets-Sheet 3 Q Q 9 i 2 O D: Z 2 Q X I i #w T i I N s N \1 INVENTOR ATTORNEYS Patented Sept. 19, 1944 UNITED STATES HYDRAULIC PRESS Thomas F. Stacy, Piqua, Ohio, assignor to The French Oil Mill Machinery 00., Piqua, Ohio,

Application July 20, 1987, Serial No. 154,605

, 16 Claim.

This invention relates tohydraulic presses and particularly to the control of the same.

An object of the invention is to generally improve hydraulic presses and their control.

Another object of the invention is to provide an improved hydraulic press and control means therefor, with which piston rings may be employed in the hydraulic ram for advancing the working member, and with which scoring of the cylinder wall by leakage of operating liquid past the piston rings under a high pressure differential will be eifectively prevented or rendered negligible. 7

Another object of the invention is to provide an improved hydraulic press and operating system therefor, with which the working member may be given a rapid,- preliminary advance movement and then at a desired position or point in such advancement, or as soon as predetermined pressure conditions on said working member have been reached, the travel slowed down and increased pressure made available automatically.

Another object of the invention is-to provide an improved hydraulic press and operating system therefor with which the advancement and retraction of the working member may be accomplished under the control of a single master valve in a simple and practical manner, with which the working member may be stopped and held in any position in its advancement or retraction in a simple, practical and inexpensive manner, with which the working member will automatically stop its retraction, and hold it in retracted position, at any predetermined position in its retraction, and. with which rapid retraction of the working member may be obtained.

Another object of the invention is to provide an improved hydraulic press and operating system therefor, with which the rate of travel of the working member may be eflectively and automatically controlled beginning at any selected, intermediate point in its advancing movement.

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

In the accompanying drawings:

Fig. 1 is a diagram of a hydraulic press and an improved operating system for. the same, constructed in accordance with this invention and illustrating one embodiment thereof;

(Chm-16) Fig. 2 is a sectional elevation througha portion of a valve operating mechanism which forms a part of the system according to this embodiment of the invention, and illustrating dlflerent operating positions for-this part;

Fig. 2A is a sectional elevation of that valve in a diiferent operative position from that-shown in Fig. 1;

Fig. 3 is a perspective of a hydraulic press and operating system therefor constructed in ac cordance with this invention and illustrating the self-contained and compact arrangement of the same, the embodiment of the invention'being the same as that shown diagrammatically 1 Fi Fig. 4 is a sectional elevation of amodiflcation of one of the valve mechanisms and operating means therefor illustrated in Fig. 1;

Fig. 5 is a sectional elevation of still another 2o modification of the same'valve mechanism; 1

Fig. 6 ma sectional elevation-through the main v or three-position valve illustrated in Fig. 1 which j controls the direction of travel of the working--v member or platen, the valve element thereof being shown in the operative position it is given 7 1 when advancement of the working memberli's desired;

Fig. 'I is-a similar, sectional elevation of the a;

same valve, but with the. valve elementthereof in another operative position which it is'given. of .the working member is '1 when retraction desired;

Fig. 8' is another perspective similar to- 3 1 but from the opposite face thereof;

Fig. 9 isa front elevation" of a portion-of the press and system shown in Figs. Sand ii -but with a portion of the tank housing broken away J to show the manner of operating the main con trol or three-position valve thereof;

.Fig. 10 is an elevation, partly in section, of a composite valve .arrang'ementthat-may be substituted for the valve of Fig. 1 which connects the primary and secondary hydraulic advancing I means for said working member, and'thus illu'sl trates still. another. embodiment. thereof; and

Fig. 11 is an elevation, partly in section, 'of a modification 0! the three-position or main control valve illustrated in Fig. 1,.and.which may I .be substituted therefor. 1

so Referring first particularly to Figs. 1 to 3, 6,17, 8 and 9, theimproved hydraulic'press includes a tank or reservoir ll of any suitable shape and size, and which is much larger than isnecessa'ry; I I

for storing the .surplusoperating liquid for the '55 presa, m the diagram of Fig. 1,- instead of Sh ing a large tank I0, a plurality of small tanks l are illustrated for different connections, but

it will be understood that all, of'the small tanks I3 has not been disposed within the tank which contains the surplus or reserve operating liquid. A platen-or working member I4 is slidingly mounted on the strain rods |2 for reciprocation therealong toward and from the fixed head I2,

and this member II has a post or piston l6 depending or projecting therefrom througha wall of the tank In and into the cylinder l3, where it forms with the cylinder l3 a hydraulic device by which the working member I4 is advanced toward the head l2 or retracted. The hydraulic device may be single acting or double acting, or separate means may be employed for retracting the platen or working member. The hydraulic device is illustrated as of the double acting type, although it will be understood that this is merely apreferred arrangement and that instead of it, separate and supplementary hydraulic devices may be connected to the working member for advancing the latter first through a rapid, press closing movement, and then with a slower movement but at a much'higher possible pressure on the working member when resistance is encountered.

The cylinder l3, Fig. 1, as illustrated, has an open end through which the piston or post l5 extends, the other end of the cylinder l3 being closed except for connections thereto. The end of the piston l5 which extends within the cylinder I3 is provided with an enlarged head l6 which cooperates with the cylinder wall to form a fairly close slidable fit between them. The periphery of this head |6 is provided with one or more annular grooves l1, and in each groove one or more piston rings l8 may be disposed so asto efiectively close the clearance between the piston head and the cylinder wall in the same manner that the pistonrings of an internal combustion engine or a steam engine provide a reasonably tight, sliding connection with the cylinder wall.

The open end of the cylinder I3 through which riphery of the piston IS. The shell or auxiliary cylinder 20 may be secured to the main cylinder N in any suitable manner such as by cap screws 23.

In the broader aspects of the invention, any source of operating liquid under pressure may be employed, but in order that the pressing system may-be self contained as far as possible, I preferably utilize a variable delivery, pressure holding type of rotary pump 24, Fig. 1. This type of pump is well known and extensively used in the industry for the operation of hydraulic presses, and is shownmerely conventionally in Fig. 1. Pumps of this type are disclosed, for example, in U. S. Patents 1,077,979, 1,656,034, 1,638,653 and 1,250,170. Such a pump utilizes a shiftable yoke 26, which by its lateral shifting movement (in Fig. 1) varies therate of delivery of the pump.

The yoke 26 is connected by alink 26 to one end of a lever 21,- this lever being pivoted at 28 on a suitable bracket of the pump frame. The lever 21 extends beyond the pivot 28 and is pivotally connected at 23 to a link 30 which extends approximately parallel to the link 26. Link 30 has a flange 3| through which slides a rod 32. The rod 32 passes freely through a boss 33 of the pump frame, and a hand wheel 34 is threaded on the outer end of the rod 32. The portion of rod 32 passing through the flange 3| is non-circular in cross section, and the aperture in flange 3| is similarly shaped so as to prevent rotation of the piston l5 extends is closed by a packing gland l9 o1 any suitable construction, such glands being commonly employed in hydraulic presses and need no particular explanation. The gland I3 is merely illustrated conventionally in Fig. 1. Amp shaped shell 20, Fig. 1, is secured at its bottom or closed end to the closed end of the cylinder |3' within the chamber of the cylinder, and it extends into an annular recess 2| provided in thatend face of the piston l5 which is received in the cylinder l3.

The central portion 22 of the piston l5 which is'encompassed by the annular groove 2| acts as an auxiliary or primary piston for the rapid advancement of the working member ina manner which will be explained hereinafter, and this auxiliary piston or post 22 is slidingly received within the cup shaped shell 20 which in fact functions as 'an auxiliary or primary cylinder. The post-22 may also have an enlarged head at its free 'end' which inv its periphery is provided with one or more annular grooves for mounting piston rings in the same manner that such rings are mounted in the grooves I! in theouter pethe rod 32 without restricting its sliding movement. Thus when the hand wheel 34 is rotated in one direction, it will tend to pull the rod 32 through the bracket 33.

The opposite end of the rod 32 is provided with a head or shoulder 35, and a helical compression spring 36 is disposed on the rod 32 under compression between the shoulder 35 and the flange 3 I, so as to urge the rod 32 in a direction to force the hand wheel 34 against the bracket 33 and rock lever 21 clockwise in Fig. 1. The spring 36 thus acts through the link 26 to 'urge the yoke 25 in a direction to cause maximum rate of delivery of the pump, and the pressure which holds the yoke in that position yieldingly, may be varied by varying the stress on the spring 36, merely through rotation of the hand wheel 34 in one direction or the other, depending upon whether an increase or decrease in the holding pressure is desired. The pump is also provided with a small piston 31, disposed in a position to be engaged by the lever 21, and reciprocating in a small cylinder 38 mounted on the frame of the Pump.

Operating liquid is supplied to the cylinder 38 through a pipe 39, and the pressure in the cylinder 38 on the piston 31 urges the lever 21 in a direction to shift the yoke 25 in a manner to decrease the rate of delivery of the pump in opposition to the spring 36. This explanation of the pump and of the parts 25 to 39 is merely typical of pumps of this type now on the market and extensively used in connection with hydraulic presses, and the pump details illustrated in Fig. 1 are to be understood as being merely typical and no part of the invention except in connection with the remainder of the system.

' nected by a pipe 4| to the reservoir or tank I0.

Thus the pump 24 withdraws operating liquid from the tank |0 through pipe 4 I, and delivers it under pressure through outlet pipe 42. The pipe assasss.

42 preferably contains therein a suitable choke valve 48 which creates a slight back pressure on the pump, so as to make available for other purposes a small portion of the operating liquid, as

will be explained shortly. The choke valve 48 may be of any suitable type, which remains closed until a desired pressure has been built,up and then opens and passes all liquid in excess of that necessary to create the desired initial back pressure. Such a choke valve may be spring closed and pressure opened, as shown in Fig. 1. I

The pipe 42 beyond the choke 48 extends directly to the pull-back chamber 44 which, in the illustrated example, is the chamber between the end of the cylinder II that is closed by the gland i9 and the piston head i8, and which, with the piston i8, functions as a pull-back hydraulic device. The pump 24 thus delivers operating liquid.

under pressure to the chamber 44 of the pullback device, and by its action on the annular, exposed or pressure face or the piston head i8 urges the working member in a retracting direction. A branch pipe "leads from the pipe 42, at a point between the choke 48 and the cylinder i8, to a meter valve 48 which is preferably adjustable to regulate the quantity or liquid passing therethrough, that is, the valve 48 has a valveand port 88 and closed by the head 8i oi the valve element 88 when the latter is in an intermediate position, such as shown in Fig. 1, and also on its chamber wall with an annular groove 81 at a point between and spaced from the end port 84 and the inlet port 48.

The periphery of the head 82 oi the valve element 88 is bevelled on opposite faces, so that when the valve element is positioned in an intermediate position, as shown in Fig. 1, in which the head 82 is aligned with the groove 81, liquid may pass from the inlet port 48 around the bevelled periphery of the head 82 and reach the outlet port 84. The port 88 in-valve 49 is connected by a pipe 88 to the chamber 89 at the bottom or closed end of the auxiliary cylinder formed by the shell- 20. The pipe 89 is also connected through a valve 18 to a pipe 1i which communicates with the secondary or main pressure cylinder or chamber 12 surrounding the shell 28 at the closed end of the cylinder i3. When the valve element 88 oi the valve 49 is in the intermediate position shown in Fig. 1, any pressure opening which may be regulated to increase or decrease the space through which the liquid may flow in passing through this valve. Beyond the valve 48 the pipe 48 contains a one-way freecheck valve 41, and then is connected to abort 48 01a three-position or main control valve 49. checkyalve 41 opens freely to pass liquid through the pipe 48 to the valve 49, and closes automati cally to prevent return flow. The arrow below valve 41 indicates the direction in which the free flow may occur.

The three-position valve 49 includes an elongated chamber in which is disposed a valve element 89 mounted for reciprocation endwise .oi the. chamber of the valve. This valve element 88 is provided with a pair of heads 8i and 82 spaced apart a suitable distance on opposite sides of the portv 48 and which engage with the wall or housing oi the valve. The valve element 89 has a reduced extension or rod 88, Fig. 9, passing through one end of the valve casing and through a wall, of the tank i9 into a position to be engaged and depressed by an arm 84, provided on the working member or platen, as the platenapproximately completes its retraction movement. Within the tank It the rod or extension 89 is provided with a rack 88' which meshes'with a'pinion 88 mounted on a shaft 81.

The shaft 51 extends outwardly through a wall of the tank iilyand there carries an operating handle 88,:Figs. 3 and 8.

Thev

of the operating liquid delivered by the pump 24 is exerted on the [pull-back chamber 44 through pipe 42, and all the liquid delivered passes through meter valve 48, pipe 48 and check valve 41 to the valve 49, where it is free to pass around they bevelled head 82 of the valve "element and reach the exhaust port 84 through I which it may pass back to the tank Ill.

Theport 88 is at this time closed by the head 8|, so that no liquid may escape from either of the chambers 89 or 12 and thus the liquid delivered by pipe 48 will pass back to the tank 10 idly. This-prevents any movement of the working memberor platen. under any pressure exerted on the piston i8 through the pullback cham-ber'44. The working member thus is held in the same position notwithstanding the continuous operation 01' the pump.

The exposed annular faceof piston head i8 in chamber 44 of the platen retracting device is smaller in area than the exposed end area of post 22 in the closed end of the shell or cup 28, and also smaller in area than the remaining area of the inner end of piston i8, so that whenever the same pressure per unit area is applied to both chambers 44 and 89, or to chambers 44, 89 and 12, the platen will-always be advanced by the resulting pressure differential.

The pipe 1i has a branch pipe 13 leading to the tank-i8, and in this pipe 13 is disposed a Referring again to-Fi'gs. 1, e and '1, animal compression spring 88isinterposed between the end of the casing of the valve 49 and thehead- 8i, so as to urge the valve element 89 in a direction to draw the rod 88 further into the valve] casing. The end 88 of the. valve elementf88, at

,the end'opposite the rod or extension-88, ex-

tends into a cylinder 8i through asuit'able pack ing gland 82. when fluid under pressure is adpilot operated check-valve 14. The valve element 18 of this valve is free to open and pass liquidfl'om the tank l lll through the pipes 13 and 1i to the chamber 12 to fill the increasing space created therein .by the advancing piston 8.

The valve element 18 closes automatically in order to prevent reverse flow from the secondary'. cylinder or chamber 12 back to the tank l8. A pilot piston. 18 reciprocates in a pilot cylinder 11 which is connected by a pipe 18 to the groove 81 o! the valve element 49. The pismitted to the cylinder 8i it will force the piston 88 and valve-element 88 in'opposition to .the spring 89, and carry the rod 88 outwardlyaway. from the arm 84 on the platen, it the platen is in retracted position. The valve 48 is provided with end exhaustv ports 88and 84 which are connected by a pipe 88 to the tank III, also with a port which is betweenthe port 48 andthe ton 18 oi. this pilot operated check valve has a stem 18 which extends into a position beneath the valve element 18 so that when sufllcient pressure. is created in the pilot cylinder 11, the piston 18 will be forced in an outward direction and through its stem 19' will .urge the valve ele- I ment18 into open position. 3 A spring tends to return-the pilot piston 18 into retracted position where it releases the valve element 18 and u allows the latter to close. A pipe 8i extends from the pipe ii to the cylinder 98 of the pump control, and therefore the pressure per unit area in the cylinder 38 of the pump control will be substantially the same as and directly responsive to the pressure per unit area in the pipe 1| and chamber 12 which is acting at any time on the main advancing ram in the cylinder I3.

The valve 18 has a spool shaped valve element 82 which reciprocates endwise in the valve housing, and a head 83 on the element 82 closes the port 84 into which the pipe 1! opens. The pipe 68 opensinto the chamber of the valve 18 opposite the intermediate part of the spool, so that communication will be established between the pipes 68 and 1| whenever the valve element 82 of valve 18 is operated endwise to carry head 83 from over the port 84, that is to operate it upwardly in Fig. 1. The valve element 82 has a reduced stem 85 which extends outwardly of the valve 18, through a suitable gland and into a pilot cylinder 86, where it terminates in a pilot piston head 81. Thus by applying fluid under pressure to opposite ends of the pilot cylinder 86, the valve element 82 may be shifted to and from the position shown in Fig. 1 so as to close the port 84, as shown in Fig. 1, or to uncover it and establish communication between pipes 68 and H. The ends of the housing of the valve 18 are connected by a pipe 88 to the tank I8 so that any leakage: of operating liquid along the valve element 82 may return freely to the tank I8 and there will be no opposition of trapped liquid opposing the reciprocation of the valve element 82.

A pilot control valve 89 is disposed in a position for operation by the working member or platen I4 when the latter reaches a desired position in its advancing movement. For this purpose the valve 89 is shown as having a rotary valve element 98 which is provided externally of the valve housing with a forked operating arm 9|, Figs. 1 and 2. A rod 92 is adjustably mounted on the platen to extend in the direction of travel of the platen and is provided at one end with a head or flange 93 which is engageable with the fingers of the fork of the arm 9| to rock the arm 9| between the full and dotted line positions shown in Fig. 2 as the platen moves back and forth. This valve element 98 is of course frictionally held in adjusted positions, and as the head or flange 93 moves the arm 9|, it clears the fork thereof and is able to continue its movement forwardly and backwardly in either di rection, yet asit moves it picks up the arm M and rocks it into its other position and then continues on, free of the arm 9|.

When the valve element 98 is in full line position, shown in Fig. 1, its passage 94 connects pipes 95 and 96, and when the arm 9| is rocked from the full line to the dotted line position of Fig. 2, the passage 94 of the valve element 98 connects the pipe 95 to a pipe 91 and breaks the connection between the pipes 95 and 96, as shown in Fig. 2A. The valve 89 is provided with an outlet pipe 98 which connects with either the pipe 91 or the pipe 96, depending upon the position of the valve element 98. When the valve element 98 is in the position shown by full lines in Fig. 1, pipe 91 is connected to the pipe 98, and when the arm 9I is rocked to turn the valve element 98 counter-clockwise in Fig. 1 into the position shown in Fig, 2A, the pipe 96 will be connected to the exhaust or drain pipe 98. The pipe 95 is connected to the pipe 42 between the pump 24 and the choke valve 43, and thus liquid under pressure will always be supplied through the pipe 95 to the valve 89. The pipe 96 is connected to a pipe 99 which runs between one end of the pilot cylinder 86 and one end of a pilot cylinder I88 of a bypass valve I8 I.

The other end of the pilot cylinder I88 is connected by a pipe I82 to the pipe 91 and also to the other end of the pilot cylinder 86. Thus when the valve element 98 of the platen pick-up valve 89 is in the position shown by full lines in Fig. 1, an operating liquid delivered by the pump will be conducted through pipe 95 to the valve 89 and thence to-the pipe 96 where it divides, a portion being delivered to the outer end of the pilot cylinder 86 to set the valve element 82 in a position to close communication between the pipes. 68 and 1|, that is, between the primary and secondary cylinders acting on the piston I 5. Another portion of the operating liquid delivered through the pipe 96 passes through the pipe 99 to the inner end of the pilot cylinder I88 of by-pass valve MI, and operates a piston I83 in that cylinder.

A valve element I84 of valve IN is connected to the piston I83, and when the latter is moved by liquid from pipe 99, the valve element I84 will be moved into the position shown in full lines in Fig, 1, where the central part of the spool-like valve connects by-pass pipes I85 to one another, and thus establishes a direct by-pass around the meter valve 46. When the valve element 98 of the platen pick-up valve 89 is rotated counterclockwise in Fig. 1 so that its passage 94 will connect the pipes 95 and 91, as shown in Fig. 2A, the pipe 96 will be connected to drain or exhaust pipe 98, and the operating liquid from the pump delivered through pipe 95 will now be conducted by the pipes 91 and I82 to the inner end of pilot cylinder 86 and to the outer end of the pilot cylinder I88. This will cause movement of the valve element 82 upwardly in Fig. 1 so that the head 83 thereof will uncover the port 84 and thus establish a direct communication between the pipes 68 and 1|.

At the same time, the liquid delivered through pipe I82 to the pilot cylinder I88 will force the valve element I84 downwardly in Fig. 1 until a flange of the spool covers and closes the opening into one of the pipes I85, and thus interrupts the liquid flow through the pipes I85, thus making it necessary for all of the liquid passing through pipe 45 to pass through the meter valve 46. The ends of the valve chamber of valve I8I in which the valve element I84 reciprocates are connected by a pipe I88 to the tank I8 so that there will be no trapped liquid in the ends of the valve chamber which will interfere with the movements of the valve element I84.

A branch I81 of the pipe 95 is connected to an electrically operated valve I88. This valve is provided with a reciprocating, spool shaped valve element I89 having an operating stem II8 passing outwardly through one end of the housing of the valve I88, and there connected to the core III of a solenoid H2. The solenoid II2 receives an energizing current through line wires L and L from any suitable source of current. The line L is connected to a contact 3 of a normally open switch II4, that is, one spring urged into open position, the other contact II5 of that switch being also in contact with a normally closed switch I 16, that is, one spring urged into closed position. The other contact II1 of the switch H6 is connected by a wire H8 to one side of the solenoid H2. The other side of the solenoid is connected to the line wire IF.

The core III of the solenoid I I2 is arranged to engage and electrically connect a pair of contacts H9 and I20 when the valve element I09 has been moved to the right in Fig. l, a distance corresponding to that desired for the valve element I09. The contacts H9 and I20 are connected by wires I2I and I22 respectively to the line wire L and the contact H5. When the valve element I09 is moved to the right from the position shown in Fig. 1 by the solenoid H2 until the core III engages contacts I I9 and I20, the central portion of reduced diameter of the valve element I09 will then be in position to connect the pipe I01 with a pipe I23 leading to the outer end of the pilot cylinder 5 I.

When the valve element I09 is in the position shown in Fig. 1, the valve element I09 will prevent fiuid flow from pipe I01 to pipe I23, and entirely uncover the opening to pipe I23, and connect the latter through the adjacent end of the casing of the valve I08 with an exhaust pipe I24 leading to the tank I 0. A spring I25 in the casing of valve I acts on the valve element I09 and tends to urge it into the position shown in Fig. 1, and thus automatically urges the core III of solenoid II2 into the position shown in Fig. 1.

In pumps of the variable delivery type, such as pump 24, there may be leakage of operating liquid past the pistons and this slippage oil or liquid is usually relatively hot. Heretofore such slippage oil or liquid has been drained directly into the reservoir or tank, and all the liquid in the tank cooled by cooling coils. According to my invention the slippage oil, or operating liquid is drained from the bottom of the pump and con ducted by a pipe I25 through a heat exchanger I21 back to the tank I0. A cooling liquid, such as cold water, is circulated by the pipes I28 and I29 through a jacket surrounding the pipe I25 in the heat exchanger, so as to cool the slippage oil before it is discharged into the tank I0. The cooling water is preferably circulated through the heat exchanger in a direction counter to the flow of the slippage oil through that exchanger in order to obtain maximum cooling efllciency.

The operation of the pressing system just described will now be explained. With the various parts in the positions shown in Figs. 1, 2, 3, 8 and 9, the platen or working member I4 is in its retracted position, where it is urged downwardly by liquid delivered from the pump 24 through the pipe 42 to the retracting cylinder 44, but the piston I cannot further be retracted or descend because escape of liquid from the chamber 69 is prevented by-the valve head SI of the three-position'valve 49, and from chamber I2 is prevented by the valve head 83 and by the now closed, pilot operated check valve I4. The liquid delivered by the pump 24 will thus pass through the pipe 42, choke 43, pipe 45, meter valve 46 and also its by-pass formed by pipes I05 and the valve IOI, and check valve 41 into the chamber of the valve 49.

The liquid then passes around the bevelled head 52 and out through the port 64 and pipe 85 back to the tank I0. There is thus no substantial back pressure or resistance oilered by the valve 49, and consequently the liquid will circulate idly through the valve 49 back to the tank. I0 and thence through pipe 4| to the intake side of the pump 24. Consequently there will be no substantial pressure on the liquid in the pilot operated check valve I4. Even if the valve 14 was forced open, the piston I5 could not valve 49 such as may tend to force open the descend because the escape of liquid from chamber 59 is still prevented by the valve head M of the three-position valve 49. At the same time, the liquid from the pump is delivered through pipe to the valve 89 and thence through the pipes 99 and 99 to the inner end of the pilot cylinder I00 and the outer end of the pilot cylinder 85, so as to hold the valve elements I 04 and 82 in the positions shown in full lines in Fig. 1. The valve element 50 is held in the intermediate position shown in Fig. 1 because of the engagement of its valve rod 53 by the arm 54 on the platen or working member I4 as the latter descended.

In order to initiate an advancing movement of the working member or platen I4, theoperator turns the handle 59 in a direction to. push the valve element 50 of the three-position or main control valve 49 further than that produced by the working member I4 which. would be downwardly in Fig. l, and into the position shown in Fig. 6. When this happens; the valve head 5i will uncover the port 65, and at the same time the bevelled head 52 will pass out of alignment with the groove 61 and will prevent the flow of liquid from pipe 45 to the port 09 and thence through the port 64 to the tank I0. Since the area of the exposed or free end face of the auxiliary piston or stem 22 of the main piston I5 is greater than that of the exposed annular end area of the piston in the chamber 44. the pressure in chamber 59 will cause an advancing movement of the piston I5 and platen I4. The liquid displaced from the chamber 44 by this advancing movement will pass through the pipe 42 into the pipe 45 and thence to the chamber 69 with the other liquid delivered by the pump 24. The space in chamber I2, which is enlarged by the upward travel of the piston I5, will be filled by liquid sucked into the chamber I2 from the tank I0 by means of the pipe 13, the freely opening check valve I4 and the pipe II.

This advancing movement can be stopped at any time by merely returning the handle 58 to the position shown in Figs. 3, 8 and 9, and spring 59 urges return of valve element 50 to the intermediate position. The handle 58 must be held in this intermediate position at this time, however, because the valve rod 53 has been released by the advancing movement of the platen I4, and the spring 59 would otherwise shift the valve element 50 into the other extreme position shown in Fig. 7. The starting and stopping of this advancing movement of the platen I4 through manipulation of the handle 58 is mainly utilized while dies are being set up on the platen or moving member I4 and the fixed head, and usually not in the normal operation 01' the press, although it will be understood that the operation could be fully controlled by the handle 58 in this manner. Instead of using the handle 58 in the normal operation of the press, switch buttons H4 and H9 serve to start and reverse the travel of the press.

Assuming that the parts are in the position shown in Fig. 1, one may start the advancing movement of the platen l4 by momentarily. closing the normally open switch II4. This completes a circuit from line wire L, contact H3, switch II4, contact 5', switch II5,'contact 1, wire H8 and solenoid I I2 to line wire 1?. The solenoid being now energized will shift its core III to the right (Fig. 1) and will connect the contacts H9 and I20. Thereupon a circuit is established-as follows: line wire L', wire I2I,

tact II5, switch I I5, contact 1, wire II8, solenoid H2, and line wire L. The core III thus closes a stick or holding circuit for the solenoid H8 and this holding circuit includes in series therein the normally closed switch H8. The switch II4, being spring urged into open posi tion, opens automatically as soon as it is released. I

When the solenoid H2 is energized, it shifts the valve element I09 to the right in Fig. 1 and connects the pipe I01 to the pipe I23. Liquid from the pump 24 then passes through the pipe 05, pipe II, valve I08 and pipe I23 to pilot cylinder and forces the valve element 50 endwise into the position shown in Fig. 6. This is the same position into which the valve element 50 was moved by the handle 58 as above described, and the platen I4 will now start or continue its advancing movement.

When the platen I4 reaches a desired position in its advancing movement, such as when the dies interposed between the platen I4 and fixed head I2 are about to engage, the rod 92 which has been previously set by adjustment on the platen I4 will by means of the head 83 engage with the forked arm 8| and rock it from the position shown in full lines in Fig. 2 to the dotted line position in that figure, which shifts the valve element 90 from the position shown in full lines in Fig. 1 to that shown in Fig. 2A. When this happens, liquid from the Pump 24 is delivered through pipes 42' and 95, and valve 89 to pipes 91 and I02 which conduct the liquid from valve 88 to the inner end of the pilot cylinder 85 and to the outer end of the pilot cylinder I00. Since the opposite ends of those pilot cylinders are then exhausted through valve 88, the valve elements 82 and I04 will be shifted to their other positions in which the pipe 08 is connected to pipe II and the by-pass around the meter valve 45 is closed.

All of the liquid delivered by the pump to the chambers 89 and I2 will then be obliged to pass through the meter valve 48, and by suitable regulation of the latter the rate of travel of the platen can be regulated. After the valve element 82 has been moved, as just explained, to connect the pipes 58 and II, the liquid delivered by the pump through pipe 45 will then pass to both of the cylinder chambers 88 and I2 and force the platen I4 further in an advancingdirection but at a slower speed. When this happens the pressure in pipe I3 will cause the valve element I5 to seat, so that the liquid delivered to the chamber 12 cannot escape through the valve I4 back to the tank I0. This advancing movement of the platen I4 will continue, and as the material between the dies is compressed, the pressure in the chambers 59 and I2 will build up through continued operation of the pump 24,

The increasing pressure in the chamber I2 will be communicated through the pipes II and 8| to the small cylinder 38 of the pump 24 and act through the piston 31 on the lever 21 in a direction tending to set the yoke 25 for zero delivery of the pump. This movement of the lever 21 by the piston 31 is opposed by the spring sure is reached the-piston 31 of the pump will automatically set the yoke 25 to zero delivery position, but the pump 24 will continue to opcontact I20, core II I, contact II8, wire I22, concrete, yet deliver only suflicient liquid'to the chambers 69 and I2 tomaintain the desired pres- After this pressure has been maintained for the desired duration, the attendant pushes the button llli which opens the holding circuit for the solenoid H2, whereupon the valveielement I09 will be shifted back into the positionlshown in Fig. 1 by the spring I25, withtheresultthat liquid no longer can pass through from pipe 10'! into pipe I23, and the latter willthenbe vented f through pipe I24. The. pressure inpilot cylinder 5| of the valve 49 is then relieved, andthe spring 59 shifts the valve element .50 to the other extreme position shown in Fig. 7., Whenthis happens the valve head 5I will movebetween the ports 48 and and stop the delivery of liquid through pipe 45 to pipe 58, and-the latter pipe will then be connected through the lower end (Fig. l) of the valve T48 1 to the port 83 which allows escape of liquid from the chamber 69 through pipes 88 and 65 back to the tank I0. At the same time,' the"bevelled valve head 52 is disposed beyond the. groove 81 and prevents the flow of liquid from theinlet port 48 to the port 64 and consequently thelliquid entering the valve through the port 48 will pass-through the groove 51 and pipe" to the pilot cylinder 11 and there, by its action on the piston I5, will force open the check valve I5. This, allows liquid topass from the cylinder chamber I2 vback to the tank I0 directly. I

The valve element 82 has remained in the same position and consequently as soon as the pipe 58 was connected to the port 53, the pressure was relieved in not only the chamber 59 but also in the chamber I2, since the liquid would escape from the chamber I2 through the pipe II and valve I0 back to the pipe 58. As soon as the tank I 0. At the same time, the pump 24 is de-' livering liquid through the pipe .42 .to the pull back chamber '44 and since' there is now no opposing or back pressure in the chambers 59 and I2, the pressure in the chamber .44 will force the piston I5 downwardly or inwardly in the cylinder I3 and retractthe working member I4.

As the platen or working member I4 approachesthe desired limit of its retraction, the arm 54 thereon, Figs. 8 and'9, will engage the valve rod 53 and force it inwardly into the tank I0 and thus shift the valve element 50 into the intermediate position shown in full lines in Fig. l,

where further escape of liquid from the pipe 88 is prevented so as to stop'the further retraction of the piston I5, and liquid delivered by the pump circulates idly through the port 64 and pipe 05 back to the tank I0. This position of the valve element 50 also releases the pressure in the pipe I8 and pilot cylinder 11, and the valve I4 is then free to close.

It will benoted, however, that as soon as the platen I4 started its retraction, the head' 03 moved backwardly and soon engaged the forked arm SI and rocked the valve element back into the position "shown in Fig. l, whereupon the valve elements I04 and 82 were returned to the positionshown in Fig. 1. The platen I4 will thus come to rest at the end of its return travel and remain there until the operator either closes the switch I I4 to start a regular normal advancement of the member I4, or operates the handle.

58 to initiate an advance movement of the member I4. Any slippage of the operating liquid in. the pump will drain through pipe I26 and heat exchanger I21 into the tank I0, and be cooled thereby before it is mixed with the liquid in the tank I0.

Instead of employing the valve 89 for controlling the valve 82, the platen or working member I4 may directly control the valve element 82 of valve 10, as shown in Fig. 4. In this embodiment of the invention the valve element 32 is provided with an operating stem I30, Fig. 4, which extends outside of the casing of the valve and is connected to a rod I3I which passes.

loosely through an aperturein the platen I4. An adjustable abutment I32 is provided on the upper or outer end of the rod I3I, so that when platen I4 reaches the desired position, such as where the dies are engaging or are about to engage the work, the platen I4 will engage the abutment I32 and shift it and rod I3I endwise, thereby moving the valve element 82 sufliciently to uncover the opening into pipe H and establish communication between pipes 68 and H. This communication will continue, even though the valve element 82 may continue its movement for a further distance sufliciently to complete the pressing operation. A spring I33 tends to return the valve element 82 to its position shown in Fig. 4, as soon as the rod I3I is released during the retraction of the platen I4.

Still another means for operating the valve element 82 is shown in Fig. 5 in which the platen I4 is directly coupled to a rod I34 which is suitably guided at its free end in a bearing I35. This rod I34 has a bevelled cam surface I33 atone end of an enlargement I31. The valve element 82 has an operating rod I38 extending outwardly on the casing of the valve 10, where it is connected by a pin and slot connection to one arm of a bell crank lever I39, which is pivoted at I40 on a bearing arm I extending from the casing of the valve 10. The other arm of the bell crank I39 mounts a roller or cam follower I42 which is normally disposed in the path of travel of the enlargement I31. Hence, as the platen I4 advances, the cam I36 will engage the roller I42 and cam it in a direction to move the valve element 82 endwise and uncover the pipe 1|. This required movement of the valve element 02 is obtained by the time the roller I42 reaches the cylindrical part of the enlargement I31, after which the travel of platen I4 and rod I34 in the advancing direction may continue without further operation of the valve 82. During retraction of the platen I4, as soon as the .roller I42 is again opposite the cam I35, it will ride down the same under the action of a spring I43, and the valve element 82 will be returned by spring I43 to the normal position shown in Figs. 1

. and 5.

In Fig. 11 a slight modification in' the threeposition valve 49 of Fig. 1 is shown. Instead of utilizing the pilot cylinder 5| to secure the valve element 50 in the Fig. 6 position, the valve 50 is provided with a valve rod 53a which extends beyond the casing of the valve and carries a head I44. A latch lever I45, pivoted at I45, is engageable behind the head I44 when the valve element 50 is shifted endwise against the action of the spring 59 into the Fig. 6 position. A spring I41 acting on the latch lever I45 urges it into latching position behind the head I44. Thus,

when the valve element 50 is shifted from the neutral or intermediate position, shown in Figs. 1 and 11, into the position shown in Fig. 6, it will be latched by the lever I45 in that position.

While a manual release may be provided for the lever I45, the release may be accomplished in a simple manner by the use of a solenoid I40 which acts on the lever I45 in a direction to unlatch it from behind the head I44. The solenoid I48 is supplied with current from a circiiit which includes line wires L and 1., and a normally open switch I49, the latter being in series with the solenoid. Thus, when one desires to release the latch I45 and start a retraction of the platen or working member I4, one merely closes the switch I40 momentarily so as to energize the solenoid I48 and unlatch the head I44. The spring 59 then returns the valve element 50 to the Fig. 7 position, and starts a retraction of the platen. as explained above in connection with F18. 1.

The valve 10 of Figs. 1, 4, and 5 may also be replaced by a spring closed and pressure opened valve and a check valve, connected in parallel to one another, as shown in Fig. 10. Referring now particularly to Fig. 10, the valve 10 may be replaced by a valve I50 which is of the spring closed and pressure opened type, with the direction of flow indicated by the arrow beneath the same, and with the connections to the pipes 83 and H as indicated in Fig. 10. The valve element I5I of the valve I50 will remain closed until the pressure builds up in the pipe 68 willciently to unseat it, and then it will automatically pass a liquid to the main pressure chamber 12 of the cylinder I3. W1th such an arrangement, the platen I4 will be given its rapid movement, with only the chamber 69 furnishing the advancing pressure,-unti1 a desired resistance is encountered by the platen, such as after the dies have engaged the work. Then the valve element I5I will be forced open by the increasing pressure in pipe- 68, and the pressure will be built up in chamber 12 as well as 69.

As soon as the pressure in pipe68 falls, however, which occurs when the'three-position or main controlling valve element 50 is set in the Fig. 7 position to initiate the retraction of the platen, the valve element I5I will closeand further escape of liquid from the chamber 12 would then be prevented. The escape of liquid from chamber 12 is essential at this time, however, and therefore I connect a free check valve I52 by pipes I53 and I54 to the pipes-B8 and II, in parallel to the valve I5I, but the-check valve I52 operatesto open automatically in the direction of the arrow shown below it, and pass liquid only in the opposite direction from that passed by valve I50, so that the liquid from the chamber "can then pass through pipe 1I, pipe I54, free check valve I52, and pipe I53back to pipe- 83.

- From, pipe 68 it continues to tank I0 with the liquid from chamber $9.1m this manner, the

pressure in chamber 12 is reduced sufllciently to allow the pilot operated check valve 14 to open.

In the foregoing description, it willbe under- .stood that the meter valve I46 is illustrated merely conventionally, and that any suitable 'type of meter valve, many of which are available in the open market, may be used for that purpose. It will be noted that one may stop the travel of the platen I4 at any intermediate position in its advancement or retraction, and hold it in that position, and cause any increments of movement in either direction therefrom, merely by manipulation of valve 49. It will also be noted that the speed of travel of the platen is relatively rapid until a desired position is reached, or until desired resistance is encountered. and then the rate of travel of the platen will be slowed down materially or to any desired extent. The advancement of the platen will cont nue until a desired pressure has been built up, whereupon the pump 24 will set itself to short stroke and maintain that pressure as long as desired. When a retraction of the platen is initiated, it will continue unless stopped by a manual operation of the valve 49, until the platen reaches the desired retracted position in whcih it automatically sets valve 49 to intermediate position.

By using the pressure controlled, variable delivery type of pump, the travel of the platen is slowed down as the final or maximum desired pressure is approached, which is advantageous when molding certain products under pressure, such as phenylaldehyde condensation resins, commonly known as Bakelite." This slowing down in the pressing operation, just before the maximum pressure is reached, is important with such materials as Bakelite because the material in the molds which is becoming plastic at this time, is allowed more time to flow out into the various parts of the die. This slowing down in the pressing operation is by this invention automatically controlled. This slowing down as the dies are closing, such as by having the platen automatically slow down the rate of its advancement at a desired position, is important when the press is used to close and hold closed the dies or molds utilized in die casting, because if the dies are moving too rapidly as they close, they may hit with too much impact or force with resulting breakage, battering or other injury thereto. High clamping or holding pressures on the dies are, however, available for die casting purposes.

During a, retraction of the working member or platen l4, and after the pilot operated check valve 14 has been opened, the operating liquid may escape from the secondary or high pressure chamber 12 directly back to the tank I, and the liquid in the primary chamber 69 is free to escape directly back to the tank l through the three-position valve. The resistance to retraction of the platen is therefore rather small, and if the piston I is upright so that gravity aids in the retraction of the platen, the platen may tend to descend more rapidly than liquid is supplied by the pump 24 to th chamber 44, with the result that the piston l5 would tend to create a suction in the pipe 42 and also in the pipe 45 which is connected thereto.

If such a suction is created, the pressure in the pipe I8 would fall and the valve element I5 controlling the escape of liquid from the secondary or high pressure chamber would close, and thereupon the descent of the platen would be stopped. This would be only momentary however, because the pressure in pipes 42 and 45 would soon build up again and force open the valve element 15. Hence the platen would tend to settle or be retracted by jerky or intermittent increments of movement, but the insertion of valve 41 in the pipe 45 will effectively prevent this and allow for asmooth, continuous and rapid retraction of the platen. The valve 41 opens to pass operating liquid through the pipe 45 to the pipe 48 and pilot cylinder 11, and force open the valve element 15 early in the downward travel or retraction of the platen, and if a suction or fall of pressure should be momentarily created in the pipes 42 and 45, the check valve 41 would immediately clos and prevent any back travel in the pipe 18 which would allow premature closure of the valve element 15.

While I have illustrated the pump 24 as being of the pressure holding, variable delivery type as the preferred embodiment of the invention, it will be understood that other means for supply ing the liquid under pressure may be employed. For example, an ordinary pump with a by-pass through a spring loaded, release valve could be utilized for this purpose and is to be considered as the mechanical equivalent of the pump 24 in the broader interpretation of the invention.

It will be understood 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 as my invention:

1. In a hydraulic press, a main cylinder, a ram extending into said cylinder and having within the cylinder a piston head cooperating with the wall of the cylinder, said cylinder at its open end through which said ram extends having a packing gland slidingly engaging said piston, the exposed'area of one face of said piston head being substantially greater than on its opposite face, said piston head mounting piston rings in its periphery which engage said cylinder wall, a source of fluid under pressure connected separately to said cylinder at opposite sides of said piston head, and always exerting the same pressure per unit area upon both sides of said head when applied to both sides of the head, means for controlling the passage of said fluid under pressure to said cylinder through said separate connection to the cylinder at the side of the piston head of greater exposed area, and for exhausting said fluid from that side of the piston head, whereby the ram will travel in one direction or the other selectively in accordance with whether said means is causing admission of said fluid to or exhaust from said cylinder, and scoring of said cylinder wall by liquid passing said rings under high pressure will be prevented, 2. In a hydraulic press, a main cylinder, a ram in said cylinder and having within the cylinder a piston head cooperating with the interior wall of said cylinder, the exposed face pressure area of said head at one side of said head being materially less than on the other side, said head having an annular groove in its periphery, a piston ring in said groove and engaging the cylinder wall for closing the space between said head and cylinder, means for applying a fluid under high pressure to that face of said head having the greater exposed face pressure area for forcing said ram in one direction, and means for supplying to the cyl inder at the face of said head having the lesser exposed face pressure area, a fluid under a pressure per unit area approximately equal to that on the opposite face of said head whereby the pressure diflerential per unit area on opposite faces of said piston will be sufli-ciently small so that leakage along the cylinder wall past said piston under a high pressure differential and tending to score said cylinder walls will be substantially avoided.

3. In a hydraulic press, a cylinder, a ram operating in said cylinder and having a piston head cooperating with the cylinder wall and with difof, said head an annular groove in its p r p ry. a piston ring loose in said groove and ensuing the cylinder wall to close the space between said head and the cylinder wall, means for supplying a high pressure fluid to said cylinder at that side of said head having the sreater pressure iace area for forcing the ram in one direction in said cylinder, and means for concomitant; ly supplying to said cylinder at the opposite side of said head, a fluid pressure per unit area approximately equal to that onthe other side of said head, whereby the pressurediflerential per unit area on opposite faces of said piston will be so small that leakage of actuating fluid under a high pressure differential past said ring and tending to score the cylinder wall will be substantially avoided.

, within the cylinder an external peripheral flange forming a piston head cooperating with the wall of the cylinder, said cylinder at its open end through which said ram extends having a packing gland slidingly engaging said ram, a tubelike wall projecting from the closed end of said cylinder within the cylinder and spaced from the wall thereof, said ram having in its inner end a deep, annular recess to loosely telescopewith said tube-like wall, theportion oi the inner end oi! said ram encircled by said recess having an outside peripheral flange forming an auxiliary and smaller piston head cooperating with the inner surface otsaid tube-like wall, the outside peripheral surfaces oi! said piston heads having annular grooves, piston rings confined in said grooves and making tight sliding seals between the piston head and their said cooperating walls,

a source of fluid under pressure connected to said cylinder between the flrst mentioned piston head and said gland, means connecting said source to the closed end of said cylinder within the space encircled by said tube-like wall, means'for-coma variable delivery pump, a connection between.

said pump and said reservoir by which the pump withdraws an operating fluid from the reservoir and delivering it under pressure, said pump having an outlet for slippage operating fluid, a'conduit connecting said outlet to said reservoir for conducting the slippage fluid back to said reservoir, and means associated with said conduit for cooling said slippage fluid before its discharge into said reservoir. I

6. In a hydraulic press, a platen, hydraulic pull-back means acting on said platen for retracting it, primary hydraulic means acting on said platen; to advance it into pressing position, secondary hydraulic means for, supplementing eraole selectively into three diiierent positions to connect said source to said primary means. to

close the pipe to said primary means, or to conduct liquid away from said primary means depending upon the'position of said valve element, a connection between said primary and secondary hydraulic means, a valve in said connection for closing and opening communication between said primary and secondary hydraulic means, a reservoir, and a check valve connected between said reservoir and said secondary hydraulic means and opening freely to conduct liquid from said reservoir to said secondary hydraulic means and automatically closing to prevent reverse flow, and means controlled by said valve element and operable when pressure on said primary hydraulic means has been released for forcibly opening said check valve to pass liquid from said secondary means directly to said reservoir during. retraction of said platen.

"I. In a hydraulic press, a' vertically moving platen, hydraulic pull-back means acting on said platen for retracting it downwardly, primary hydraulic means acting on said platen to advance it upwardly into pressing position, secondary hydraulic means for supplementing the pressing action of said primary means, a source of operating liquid under pressure, a valve, a pipe connectin said source to said valve, and said valve to said primary hydraulic means and operable selectively to connect said source to said primary means, to close the pipe to said primary means, or to conduct liquid away from said primary means depending upon the position of said valve, 9. check valve in the connection from said source to said first valveand opening to pass fluid solely towards said valve from said source, a connection between said primary and secondary hydraulic means, a valve in said connection for closing and opening communication between said primary.

and secondary hydraulic-means, a reservoir, and another check valve connected between said reservoir and said secondary hydraulic means and openingv freely to conduct liquid from said reser- I voir to said secondary hydraulic means and automatically closing to prevent reverse flow, means operable when pressure on said primary hydraulic means has been released for forcibly opening said check valve to pass liquid from said secondary means directly to said reservoir during retraction of said platen, and a separate connection from the pressing action of said primary means, a-

source of operating liquid under pressure, a valve, a pipe connecting said source to said valve, and

said valve to said primary hydraulicmeans and said valvehaving a movable. valve element opsaid source to said pull-back means for supplying liquid under pressure to said pull-back means continuously.

8. In a hydraulic press, a working member, bydraulic pull-back means acting on said member for retracting it, primary hydraulic means for advancing said working member, secondary hydraulic means also acting on said working member to advance it and supplement the pressure of said primary means on said member, a conduit including a valve connected between said primary and secondary means, a continuously operating pump forming a source of operating liquid under pressure connected to said pull-back means, a three-position valve, a pipe connecting said three-position valve to said source, a pipe connecting said three-position valve to said primary means, an exhaust'pipe also connected to said three-position valve, said three-position valve having therein a valve element movable into one position in which it connects said source directly to said primary means and closes said exhaust connection, into an intermediat position in which it closes the pipe to said, primary means and connects the pipe from said source to said exhaust pipe, and into-a third position in which it connects the pipe to said primary means with said exhaust pip and closes communication between said pipe leading from said source and said exhaust pipe, means yieldingly urging said valve element into said third position, means operated by said working member while travelling in a retraction direction for operating said valve element against the action of said urging means into said intermediate position, means for operating said valve element also against the, action of said urging means from said third position selectively into the intermediate or flrst positions, and means for also operating said valve element into said first position against the action of said ursing means and holding it in that position.

9. In a hydraulic press, a working member, hydraulic pull-back means acting on said member for retracting it, primary hydraulic means for advancing said working member, secondary hydraulic mean also acting on said working member to advance it and supplement the pressure of said primary means on said member, a conduit including a valve connected between said primary and secondary means, a continuously operating pump forming a source of operating liquid under pressure connected to said pull-back means, a three-position valve, a pipe connecting said three-position valve to said source, a pipe connecting said three-position valve to said primary means, an exhaust pipe also connected to said three-position valve, said three-position valve having therein a valve element movable into one position in which it connects said source directly to saidprimary means and closes said exhaust connection, into an intermediate position in which it closes the pipe to saidprimary means and connects the pipe from said source to saidexhaust pipe, and into a third position in which it connects the pipe to said primary means with said exhaust pipe and closescommunication between said pipe leading from said source and assasss rate oi delivery oi liquid from said source to said hydraulic means, a bypass around said meter valve, and means operable for closing said bysaid exhaust pipe, means yieldingly urging said valve element into said third position, means operated by said working member while travelling in a retraction direction for operating said valve element against the action of said urging means into said intermediate position, means for operating said valve element also 'against'the action of said urging means fromsaid third position selectively into the intermediate or first positions, meansfor also operating said valve element into said first position against the action of said urging means and holding it in that position, means including a check valve for connecting said secondary means to said reservoir, and opening treely to'pass liquid from said reservoir to said secondary means when said working member is advancing and when said first valve is closed, a pilot device for forcibly opening said check .valve, and a connection from said pilot device to said threeposition valve at a point therein to receive actuating liquid from said source whenever said valve element is in said third position.

10. In a hydraulic, press, a working member, primary hydraulic means for advancing said working member, secondary hydraulic means also operable on-said working member to advance it in the same direction and supplement th pressure of said primary means, a source of liquid underpressure, means connecting said source to said primary and secondary means for controlling the activity thereof, a meter valve in said connection from said source for controlling the pass around said meter valve while liquid from said source is being delivered directly to said secondary means, whereby the rate of advancing travel of said working member under pressure from both primary and secondary means may be controlled by said meter valve, and said advancing travel under pressure only from said primary means may be free of control by said meter valve.

11. In a hydraulic press, a platen, ram means connected to said platen ior operating it upwardly in a working stroke and downwardly in a retraction movement-and having a pull-back chamber and two separate advancing chambers, a continuously operating pump, a pipe connecting said pump directly to said pull-back chamber, pipe means for delivering fluid from said pump to one of said advancing chambers and having valve means for controlling the delivery of fluid under pressure to said one advancing chamber and for connecting said chamber to exhaust selectively, a pipe also connecting said valve means to the other or said advancing chambers and having a valve therein, an exhaust pipe connected to said second advancing chamber and having a pilot operated check valve therein, said pilot operated valve normally closing to prevent escape of fluid from said second advancing cham-- ber, a connection from the operating chamber of said pilot valve to said valve means, and said valve means being operable to deliver fluid under pressure to said pilot cylinder whenever said first advancing chamber is connected to exhaust, and a free check valve in said pipe means between said'valve means and said pump, opening to permit flow from said pump to said valve means and automatically closing to prevent reverse flow.

12. In a hydraulic press of the type in which a ram is elevated vertically in a working stroke, hydraulic pull-back means acting on said ram for retracting it, primary hydraulic means acting ing therein a tree check valve opening towards said valve and automatically closing to prevent reverse flow, means connecting said primary and secondary means and having therein a valve controlled by the travel oi the ram and opened at a selected point in the travel oi! the ram and continuing open during the remainder of the elevation of the ram, a pilot operated, preflll valve connected to said secondary means, the pilot chamber of said preflll valve being connected to said first valve, said valve element operable when in intermediate position to close the connection therefrom to said primary advancing means, connect said pipe from the pump to exhaust, and said pilot operated chamber to exhaust, also operable when in One end position to connect the pipe from said pump to said primary means exhaust and said pipe from said pump to said pilot operated chamber, means for yieldingly urging said valve element into said last named end position, and ram controlled means for operating said valve element against said urging lected point in the retraction of said ram.

13. In a hydraulic press, a platen, a ram connected to said piston for operating the same, a

continuously operating pump, a valve having therein a valve element movable between three positions, one of which is an intermediate position and the other two or which are end-positions on opposite sides of said intermediate position, a connection from said pump to said valve, 8. connection from said valve to said ram and closed by said valve element when the latter is in said intermediate position, an exhaust pipe leading from said valve and connected to said pmnp connection through said valve when said valve is in said intermediate position, a pilot operated, preflllvalve connected to said ram and having its pilot operating chamber connected to said valvefor connection to said pipe from the pump when said valve element is in one end position, for connection to said exhaust-and disconnection rrom said pipe from the pump when in said other end position and for connection to exhaust and said pipe from said pump when in said-intermediate position, means yieldingly urging said valve element into said end position in which the pilot valve chamber is connected to said pipe from the pump, platen controlled means tor rorcing said valve element against the action or said urging means into said intermediate position as said platen approaches retracted position, and additional means for selectively forcing said valve element i'urther against said urging means into the end position in which it connects the pipe from said pump to said ram and connects said pilot chamber to exhaust.

14. In a hydraulic press, a-platen, a ram connected to said platen for operating the same, a continuously operating pump, a valve having therein a valve element movable between three means into said intermediate position as said platen approaches retracted position, and additional means operated by the back pressure on said pump for selectively forcing said valve element further'against said urging means into the. end position in which it connects the pipe from said pump to said ram and connects said pilot chambertoexhaust.

15. In a hydraulicmotor, a working member, fluid actuated means for operating said member toward and from work, a control element for said means operable into one position in which it causes a working operation of said member, means for yieldingly urging said element in a direction out of said one position and fully into another position in which it causes a return of said member, a continuous'lyrunning pump, a connection from said pump to said fluid actuated means and having a choke therein to create a minimum predetermined back pressure on the pump, hydraulic means for forcing said element into said one position and holding it in that position, another connection between said pump, before its connection to said choke and said hydraulic means to furnish continuously available fluid under pressure for operating said hydraulic means, a valve in said another connection, and means by which saidvalve may be operated to connect said pump to said hydraulic means or disconnect it therefrom;

16. In a hydraulicv press, a platen mounted for movement upwardly and downwardly, hydraulic positions, one of which is an intermediate position and the other two or which are end positions on opposite sides of said intermediate position, a connection from said pump to said'valve, and having a choke therein to create a selected minimum back pressure on said pump, a connection irom said valve tosaid ram and closed by said valve, element when the latter is in said intermediate position, an exhaust pipe leading from said valve and connected to said pump connection through said valve when said valve is in said intermediate position, a pilot operated, preflll valve connected to said ram and having its pilot operating chamber connected to said valve [or connection to said pipe from the pumpwhen said valve element is in one end position, for connection to said exhaust and disconnection from said pipe from the pump when in said-other end position, and for connection to exhaust and said pipe from said pump when in said intermediate position, means yieldingly urging said valve element into said end position-in which the pilot valve chamber is connected to said pipe from the pump. platen controlled means for iorcing said valve element against the action or said urging means for operating said platen upwardly in a working stroke, and downwardly in a retraction movement, said means including two separate platen elevating chambersand a platen retraction chamber, a continuously operating pump, areservoir connected to the intake side of said pump, a pipe connecting the output side'oi said pump to said retraction chamber, a valve device connected to said pump and to one of said elevating chambers and operable to cause the delivery or fluid under pressure to said one elevating chamber and to connect that chamber to said reservoir selectively, a conduit connecting said elevating chambers to one another and having a valve therein, an exhaust pipe connecting the other or said elevating chambers to said reservoir and having therein a pilot operated check valve that normally closes to prevent escape of fluid irom said other elevating chamber but opens treely t pass fluid from said reservoir to said other elevating chamberga connection from the operating chamber or said pilot valve to said valve device and connected by the latter to said pump when said one elevating chamber is connected bysaid valve device to said reservoir, but disconnected from said pump when said one elevating chamber is connected by said valve device to said pump, and a free check valve in the connection from said valve device to said pump and opening to pass fluid from said pump to said valve device and closing automatically to prevent fluid flow in the opposite direction.

, mousse. STACY.

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