US2324149A - Hydropneumatic press - Google Patents

Description

July 13, 1943.

D. E. GRAY 2,324,149

' HYDROPNEUMATIC PRESS Filed Aug. 27, 1940 4 Sheets-Sheet 1 INVENTOR.

Dawn 5. GRAY E. g; /A

July 13, 1943. D, mm 2,324,149

HYDROPNEUMATIC PRESS Filed Aug. 27, 1940 I 4 Sheets-Sheet 3 INVENTOR.

DA W0 A. GH Y AORNkY 4 Sheets-Sheet 4 D. E. GRAY HYDROPNEUMATIC PRESS Filed Aug. 27, 1940 AIR SUPPLY um: I

PRESSURE mcmR PRESSURE. KICKER VA LVE.

EX v 53 TIMER K'CKER VALVE ROTARY STROKE.

VALVE July 13, 1943.

INVENTOR. Dn v/p E. 612m A DRIVE).

VALVE POSITIONS BY TABLE KICKER N m m M E w A v TIMER KICKER E m R a Y R A T O R MOTION BY PIPE 58 PIPE 57 PIPE 56 TO ATMOSPHERE 'ro TIMER TO HIGH PRESSURE CYL.

1 MOTION BY PRESSURE K\CKER PIPE 55 -PIP 54 PIPE 53 PIPE 52 TO AIR SUPPLY LINE T0 Low PRESSURE CHAMBER TO HIGH PRESSURE on.

To ATMOSPHERE MOTION BY CROSSHEA Patentecl July 13, 1943 HYDROPNEUMATIC PRESS David E. Gray, Corning, N. Y., assignor to Corning Glass Works, Corning, N. Y., a corporation of New York Application August 27, 1940, Serial No. 354,450

7 Claims.

The present invention relates to fluid operated presses and particularly to presses wherein certain operations are performed hydraulically and others pneumatically. Hydraulic presses of conventional designs cannot be conveniently shifted from one operating location in a plant to another as is often desirable owing to the necessity of quite elaborate plant equipment to supply the liquid employed in operating such a press or if they include independent sources of liquid supply the weight is excessive. It is possible to manufacture presses to operate pneumatically in a desired fashion but, owing to the fluidity or lack of viscosity of air, parts manufactured to operate in an exacting manner must be made with great care, as slight variations in size of ports and conduits, as well as the lengths of the conduits, are likely to alter the operating characteristics to an objectionable extent. Also, since air is compressible there results a resiliency in operation which is undesirable in glass pressing. A liquid operated press, on' the other hand, has the advantage that the adjustment of control valves, etc., may be much coarser than in the case of a pneumatic press and therefore, conversely, the

controls may be adjusted to a much greater degree of accuracy and much greater pressures may be utilized. The difierence is of the order of 15 to 1.

A prime object of the present invention is an improved hydropneumatic press mechanism.

Another object is a press mechanism having the operating advantages of hydraulic powerand and portability of pneumatically or mechanically operated press.

A further object is a press in which the movement of a mold plunger into and out of an associated mold can be eifected in the exact manner known to produce best results.

Other objects and features of the invention will become apparent from a study of the embodiment of the invention-herein illustrated and described.

The invention is illlustrated and described as embodied in a glass pressing mechanism associated with a table carrying a plurality of molds which, in any conventional manner (not shown), are successively charged with a gob of molten glass and then brought into register with a forming plunger carried by that part of the press mechanism in which the present invention is embodied.

In the accompanying drawings:

Fig. 1 is a front elevational view of the press mechanism;

Fig. 2 is a sectional side elevation of the same;

Fig. 2a and Figs. 3-6 are sectional views of various operating parts of the mechanism;

Fig. 7 is a diagrammatic view illustrating the air passage arrangement of a rotary stroke valve of the mechanism;

Fig. 8 is a schematic view illustrating the interconnection of pipes between the several operating mechanisms;

Fig. 9 is a fragmentary view of the mechanical linkage between the crosshead and the rotary stroke valve; and

Fig. 10 is a diagram designating the mechanism by means of which the rotary stroke valve is advanced to its several positions.

In brief, in the present embodiment of the invention, a pressing cycle is initiated through the medium of a pilot valve actuated each time a newly charged mold is brought into register with the forming plunger of the press mechanism. The actuation of this pilot valve causes a kicker, hereinafter referred to as a table kicker, to advance a five position rotary control valve from its position I to its position 2. In position 2 this valve connects a ram cylinder, previously charged with compressed air, with a low pressure liquid supply chamber to force liquid therefrom to a cylinder to lower a crosshead carrying the forming plunger. The crosshead is so mechanically linked to the rotary valve that after approximately five-sevenths of the downward movement of. the crosshead such valve is brought to position 3 and near the end of the downward movement is advanced to position 4. In position 3 the valve connects a head of air directly to the low pressure chamber insuring continuance of the downward movement of the crosshead, and in position 4 supplies air to a high pressure cylinder to operate a ram which increases the downward pressure on the crosshead beyond that exerted by application of air to the low pressure chamber and finally in its lowering movement increases such pressure to a maximum desired value. After a predetermined pressure has been developed, a second kicker, hereinafter referred to as a pressure kicker, is actuated under control of a pressure adjuster and pressure kicker valve to advance the rotary stroke valve to position 5. The rotary stroke valve in position 5 connects all air supply lines extending to the press operating mechanism to atmosphere, so that all downward pressure by the crosshead mechanism is removed excepting such as results from its dead weight and supplies air to a timer which, after the expiration of a predetermined period of dwell of the plunger in the mold, causes a third kicker, hereinafter referred to as a timer kicker, to advance the rotary stroke valve to position I. In this position the rotary stroke valve supplies air to the high pressure cylinder to effect the return of the ram and crosshead to their up-positions in readiness for use in a subsequent pressing cycle, whenever such cycle is initiated by advancement of a newly charged mold into register with the press mechanism.

In detail, the structure illustrated comprises a rotatable table II provided with suitable molds |2 which are brought, in any known manner, successively under a forming plunger 2| carried by a crosshead 22. This crosshead and the associated mechanism for operating it through a pressing cycle are carried by a frame consisting primarily of a base and two upright supports 23 bridged by a table or platform 21.

The crosshead 22 closes the lower end of a crosshead actuating cylinder containing a piston 3| carried by a tubular piston rod 32 the upper end or head portion 34 of which is secured to the lower side of platform 21 and is so formed as to serve as the bottom end of a low pressure fluid chamber 35 in part formed by a hole 33 through platform 21 covered by part 34 of the piston rod. A cylinder 33 whose inner wall is of the same diameter as that of hole 33 is secured to the upper side of platform 21 in register with hole 33 and is of such height as to give chamber 33 the desired capacity. The upper end of this chamber is closed. by a head serving as the lower head for a high pressure cylinder 4|. This latter cylinder is closed at the top by a suitable head 42 and contains a ram 43 having an operating piston 44. This ram passes through head 40, the chamber 35, and on down into the central or main bore 45 of the crosshead rod 32. To lower the crosshead, liquid I3 is pneumatically driven from chamber 35 into cylinder 30 beneath piston 3|.

Passages for the flow of liquid from chamber 35 to cylinder 33 initially include multiple paths from chamber 35 into the bore 45 of rod 32 as well as multiple paths between the bore 43 and the cylinder area under piston 3|. The one former path includes passages 43 and 41 through the lower end of ram 43 .and a check valve 38 and the other comprises a by-pass passage 31 (Fig. 2a) in head portion 34 of rod 32 opening into chamber 35 and into bore 45 at a point just below the lower end of the ram in its uppermost or normal position. One of the paths between bore 43 and the lower side of piston 3| includes a row'of graduated apertures 48 in rod 32 in communication with a passage 43 therein passing through piston 3|. The other pathis directly through an aperture 34 in the piston. That portion of cylinder 30 above it piston 3| and surrounding rod 32 is full of liquid N supplied to it from cylinder 4| via a path which includes a pipe 33, a regulating valve 33, a needle valve 31, a pipe 33, and a passage 39. The needle valve is normally held wide open by a spring 10, but is aidapted to be almost closed through the medium of a bell crank 33 having a roller 32 engaged by an adjustable cam 3| on the crosshead as it approaches its lowermost position.

Fluid is supplied to the top of cylinder 4| to drive the piston 44 downward to-lower the ram. As soon as the ram has been lowered a short distance, the by-pass 31 around check valve 33 is closed by the ram. However, liquid continues to b forced from chamber 33 .through passages 43 and 41 and check valve 33 until such time as the velocity of the ram equals the velocity of the flow of liquid. When this occurs check valve 33 closes and all further supply of liquid to the under side of piston 3| results from the movement of ram 43. As the ram continues downward it successively closes the ports 48 thus diminishing the speed at which the liquid is introduced to the under side of the piston 3| until finally it passes solely through aperture 34. As the crosshead approaches its lowermost position cam 3| engages roller 32 on bell crank 33 and partially closes needle valve 61 against the pressure of spring 10, thus the flow of liquid from the upper side of piston 3| is choked for the further control of the speed of liquid to the under side of the piston. The ram is raised by fluid supplied to a portion of cylinder 4| at a point below the downmost position of piston 44. When the ram has been fully raised the by-pass 31 around check valve 38 is again open. This enables the free return of the liquid in cylinder 30, in the area below piston 3|, to chamber 35 by pressure developed in cylinder 4|. Such pressure forces liquid l4 therefrom to the area of the cylinder 30 above piston 3| via the previously traced path to raise the crosshead. The raising movement is initially very slow as a result of needle valve 61 restricting the flow of liquid to cylinder 30 and is done to guard against deformation of freshly pressed ware such as might result if the initial upward movement of the plunger were too rapid. Subsequently the cam 5| clears roller 62 enabling valve'31 to open wide so that liquid I4 is rapidly supplied therethrough to raise the crosshead.

The operations of the crosshead and ram assemblies are under control of a rotary stroke valve 50 which comprises a cylindrical housing 3| (Figs. 4 and 9) with outlets having connected pipes 52-58, as designated in Fig. 7, and contains a drum suitably grooved to selectively establish communication between the housing outlets. This drum designated with the numeral 59 is diagrammatically illustrated in Fig. 'I wherein its five different positions relative to the housing outlets are illustrated. A shaft 30 (Figs. 4 and 9) connected with the drum 59 of the rotary valve 33 projects out through the end of its housing and affords a means by which the drum can be rotated through its various operating positions. Movement of the drum from position I (its normal position) to position 2 is effected by a mechanism hereinafter referred to as the table kicker 1| (Figs. 1 and 4) This mechanism comprises a single notch disc 15 fixed to haft 30 and a pawl 13 so associated therewith that it can be lowered into the notch of disc 15 when the drum is in position I and can then be raised to advance the drum to position 2. The pawl 15 is carried by an arm 11 having one end freely supported by shaft 30 and having its other end connected to a link 32 suspended from the lower end of a pneumatically operable connecting rod An intermediate portion of thi rod is provided with a piston 85 operative in a cylinder 33 and with the upper end of rod 83 projecting into a relatively small diameter cylinder 81.

I The top of the upper cylinder 81 is connected with a branch pipe H of a high pressure air supply line I03 (Fig. 1), so that a head of air is permanently maintained in cylinder 31 and tends to drive the rod 33 down to a position to register with the notch in disc 15. The lower and larger diameter cylinder 33 at its bottom end is connected with a pipe I03 to which air can be supplied to drive the rod upward to advance the rotary stroke valve drum to position 2.

To move the drum from position 2 'to position 4, shaft 60 is provided with a single notch disc 9| (Fig, 9) adapted to be driven by a pawl 92. This pawl is mounted on an arm 93 fixed to a pinion 95 rotatable about shaft 60. The pinion 95 is in mesh with a rack 96 fixed to and movable vertically with the crosshead 22, as

clearly illustrated in Fig. 2. The notch in disc 9I is so located and the rotary movement imparted to the associated pawl 92 by means of the rack and pinion is such that the pawl advances the rotary valve drum from position 2 to to position 4 in the course of the downward movement of the crosshead. Specifically, the drum reaches position 3 when the crosshead is approximately flve-sevenths of the way down and. position 4 slightly before the downward movement of the crosshead has been completed.

The movement of valve drum 59 from position 4 to position 5 is by a pressure kicker 12 (Fig. 1) and from position 5 to position I by a timer kicker 13. These kickers are similar to kicker 1| except for the difference in radial orientation of the notches in their discs.

The table kicker 1i is under control of a pilot valve I04 (Fig. 2) which normally supplies a head of air from a branch I02 of supply line I to pipe I03 extending between the valve and the lower cylinder 06 of the table kicker 1i, so that normally its rod 83 is in the up-position, as i1 lustrated in Fig. 4.- One of a number of cams I on the under side of table I'I moves the valve to an alternative position when the table is rotated to advance a newly charged mold into register with the press plunger, and another such cam restores the valve to its initial position as the table is brought to a stop. With valve I04 in its alternative position it blocks pipe I02 and exhausts pipe I03 to the atmosphere, thereby permitting the pressure applied to the upper cylinder of table kicker H to drive the kicker rod and its pawl down. When the table comes to rest, the normal connection of pressure to the lower cylinder is re-established and the kicker rod is raised and advances the rotary valve drum to position 2.

Air for raising the connecting rod of the pressure kicker 12 to advance the rotary valve from position 4 to position 5 is supplied from supply pipe I00 through a branch pipe I06 (Figs. 1 and 5), a pressure kicker valve I20 (Fig. 5), and a pipe I32 extendin to the lower cylinder of valve 12. The pressure valvecomprises a housing having connected upper and lower cylinders HI and I22 with the upper cylinder of small cross sectioncompared to that of the lower cylinder, A slide I25 operates in these cylinders and has an upper portion lapped to fit the upper cylinder. That portion ofthe slide member within cylinder I22 is in the form of a spool hav ing heads I26 and I21. The cylinder I22 has an exhaust passage I26 through. its wall, a second passage in communication with branch pipe I05, and a third passage in communication with pipe I32. These passages are so located that, with the slide member I25 in its rip-position. heed I21 blocks the passage to pipe I06 and. head I26 uncovers the exhaust passage I28 thereby exhausting air from pipe I32 so-that the rod of the pressure kicker 12 is down. When, however, the slide member I25 is in its down-position, head I26 blocks the. exhaust passage I28 and the other passages are in the space between heads cylinder.

I26 and I21, enabling the passage 066th from pipe I06 to I32 to effect raising of the pressurekicker plunger to advance the valve 50. The slide member is normally held in its upper position by air supplied to the lower .end of cylinder I22 from pipe I06 via a passage I29 in the valvecylinder wall extending into the top of cylinder I2I and through a vertical bore. I30 through the slide member to the lower end of cylinder I22. The lower end of bore I30 is constructed so that it is unable to supply air pressure to the lower side of slide member I25 except at a very slow rate. To lower the slide member, the bottom of the cylinder I22 is provided with a poppet valve I33 normally held closed by air pressure in the lower end of the This valve, when unseated, rapidly exhausts air from the lower end of cylinder I22 through an exhaust aperture I34, thus enabling air supplied to the upper end of cylinder I2I to force the slide member down, thereby enabling air to be supplied from pipe I06 through cylinder I22 and pipe I32 to raise the pressure kicker to advance the rotary valve drum. The raising of the poppet valve off its seat is arranged to occur when a predetermined. pressure has been built 1 up in the crosshead cylinder 30 under piston 39 and is accomplished by a piston I 30 within a cylinder ME in the low pressure chamber 35 adapted to be raised by liquid supplied to the cylinder I4I via a passage I 42 in the wall of the rod 32 in communication with the lower end of the crosshead cylinder 30. The piston I40, when raised, transmits this movement to the poppet valve stem via a pressure adjusting mechanism I45 which includes a. lever I46 connected to one end of a rod I41. This rod extends outside the low pressure chamber 35 and there carries an arm I48 supporting a shaft I43 having a hand wheel I49 and having threaded thereon a fulcrum block I50 on which the free end of a lever I5I, pivoted at I52, rests and whose upper free end is arranged to lift the poppet valve I33. By actuation of the hand wheel I49, the position of block I50 can be readily shifted to modify the leverage between the piston I40 and the poppet valve as required to lift the poppet valve against the pressure in cylinder I 22 at any crosshead cylinder pressure at which it is desired to advance the rotary stroke valve to position 5.

The supply of air to the lower cylinder of the timer kicker 13 (Fig. 1) to advance the valve 50 from position -5 to position. I is from the main air supply line I00 through branch pipe leading to the valve 50, through this valve in position 5 and pipe 51, which extends to the upper end of cylinder I59 of a timer valve I60 (Fig. 3), and thence to a pipe I6I' extending to the lower cylinder of the timer kicker 13. The timer valve, however, contains a spool piston I62 which in position 2 and position 3 of the rotary stroke valve is moved to its up-position by liquid I3 driven from the low pressure chamber 35 through a pipe I63 past a check'valve I64 and passages I65 and I66 and viaa parallelpath through a needle valve I61 into the-lower end of the timer in valve I60 but these are closed at this time by the lower head of the piston, so'that all liquid is forced to pass through the associated needle valve I61 until just before the piston completes its downward travel, at which time the piston affords a passage between the by-pass channels I10 and II I' allowing the piston to suddenly complete its downward movement to connect pipe I6I extending to the lower cylinder of the timer kicker I3, with air from pipe 51 enabling such kicker to advance the rotary stroke valve to position I. With the valve in this position, air is supplied to pipe 56 once more to force the ram piston to return to its up-position and to effect raising of the crosshead in the manner already made clear.

As above brought out, the application of air to cylinder 4| to raise the ram and the crosshead into the positions shown is through the rotary valve when in its position I to which it is advanced by the timer kicker at the conclusion of a pressing cycle. With the valve in this positon, air is supplied from the pressure pipe I and its branch 55 through the valve 50, as indicated in Figy'l, to pipe 56 conne'cted with the lower end of cylinder 4|. The air introduced into this cylinder, in addition to acting on piston 44 to raise its ram 43 to the position shown, also forces liquid in this cylinder to flow through pipe 65, regulating valve 6.6, the needle valve 61, pipe 68, and passage 69 into'cylinder 30, thereby hydraulically raising it and its crosshead to the position shown. With the valve in position I, it will be observed from Fig. '7 that pipe 53, extending to the upper end of cylinder 4|, and pipe 54, extending to thelow pressure chamber, are connected to atmosphere via the rotary valve and pipe 52, so that there is no back pressure in cylinder M or chamber 35 to prevent or retard the return of the cross-head or ram. Also, pipe 51, which extends to the timer valve I60 and, at this time, in communication with the lower cylinder of the timer kicker 63, is placed in communication with the exhaust pipe 58 and, accordingly, the timer kicker moves its pawl to the downposition.

As has already been made clear, a pressing cycle is initiated by movement of the rotary stroke valve to position 2 following the registration of a freshly charged mold under the pressing plunger.

In position 2, the branch 55 of supply line I00 is blocked and the pipe 56, extending between the high pressure cylinder 4| and the rotary valve, is brought into communication with pipe 54 leading to the low pressure chamber 35, so that pressure is built up in this chamber until it equalizes that in the charged cylinder 4|. This pressure in chamber 35 forces a flow of liquid through by-pass passage 31 and the ram passages 46 and 41, apertures 48, and passage 40 to the under side of piston 3|, thus initiating the downward movement of the crosshead 22. By the time the crosshead has been lowered approximately five-sevenths its distance of travel, it has, through the medium of its rack 96, advanced the rotary stroke valve 50 to position 3. In this position of the valve, the upper end of cylinder 4| and the timer valve I 60 are still exhausted to atmosphere through valve 50 and, also, the pipe 56 is exhausted to atmosphere via pipe 58. The branch 55 of air pressure supply line I00 is also in communication with pipe 54 extending to the low pressure chamber 35 and, accordingly, the flow of fluid from chamber 35 to cylinder 30 is continued under an increased pressure.

By the time the crosshead has almost completed its downward travel, it has advanced the rotary stroke valve 50 to position 4. In this position, air from the branch pressure pipe 55, in addition to remaining in communication with pipe 54 leading to the low pressure chamber, is also brought into communication with pipe 53 extending to the upper .end of cylinder 4| thereby causing the piston 44 to lower the ram 43. When a desired pressure has been developed in the crosshead cylinder, as determined by the setting of the hand wheel I49 of pressure adjusting mechanism I45 (Fig. 6), the piston I40 in the low pressure chamber 35 will rise and through the mechanism already described raise poppet valve I33 of the pressure kicker valve I off its 7 seat, thereby causing such valve to operate and supply air to the lower cylinder of the pressure kicker I2 causing it to advance the rotary stroke valve to position 5.

In position 5 of the rotary stroke valve, the branch pressure pipe 55 is brought into communication with pipe 51 extend ng to the timer valve I60 to effect the operation of the timer kicker I3 to advance the rotary stroke valve to position I. The remaining pipes 53, 56 and 51 are connected to atmosphere via the pipes 52 and 58. With pipe 53 connected to atmosphere, all downward pressure on the crosshead is removed except that exerted by the weight of the assembly. The time period or dwell of the plunger in the mold before its withdrawal therefrom, of course, depends upon the period of delay of advanc of the rotary stroke valve from position 5 to position I by the timer kicker, as determined by the setting of the needle valve I6I of the timer valve assembly I60.

While in the foregoing there has been shown and described the preferred embodiment; of my invention, it is to be understood that minor changes in the details of construction, combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as claimed.

What is claimed is:

1. In a pressing apparatus, a crosshead, a crosshead operating cylinder containing a piston, means having passages for conducting fluid to either side of said piston, a ram to force fluid into said cylinder cooperative with said means to successively block certain of said passages to the flow of fluid into said cylinder, a cylinder containing a piston for operating said ram, and. Y

valve means operable sequentially to direct a flow of fluid into said first cylinder to actuate it through an initial stage of movement, to direct a flow of fluid to said second cylinder to continue the movement of fluid to the first cylinder andlto direct a flow of fluid to said second cylinder to actuate the ram.

2. In a glass working press assembly, a crosshead cylinder containing a piston having an aperture therethrough, a support for the piston having a bore therethrough in communication with said piston aperture and having a passage paralleling such bore and passing through said piston into communication with said cylinder, said support also having a vertical row of horizontal passages extending between its bore and passage, a ram projected into the upper end of the bore of said support and having a one way passage the lower end of which is in communication with said bore, and a fluid chamber in communicative relation with the other end of the ram passage.

3'. In a press mechanism, a plunger, fluid op-- erated means for lowering and raising said plung er, other means for supplying fluid under pressure to said. fluid operated means to lower said plunger, means responsive to pressure developed in lowering said plunger for removing pressure from the fluid operated means, means for there after operating said other means to eiiectraising; of the plunger, and a timing device: for delaying the raisingv operation of the plunger; for a predetermined time period after pressure has been removed from the flu d.

a. In a press mechanism, a crosshead assembly having a hydraulic power unit for lowering and raising the same, a multi-position valve for controlling the operation of said power unit, a first. mechanism for advancing said valve to a position in which it effectsthe operation of said, power unit to lower the crosshead assembly, a mechanlcal linkage between the crosshead assembly and valve for moving the valve into other positions to further control thedownward progress of said crosshead, a second mechanism for advancing said. valve to a position for discontinuing the application of. power to lower the assembly, a pressure valve for delaying the operation of said latter mechanism until the lowering pressure applied has reached a predetermined value, a third mechanism for advancing said valve to its initial position in. which it efiects the restoration of said crosshead to its initial position, and a timer valve rendered operative by th multiposition valve in its position for disconnecting power employed inlowering the assembly for delaying the operation of said latter mechanism until after the expiration of a predetermined time.

5. In a press mechanism, a liquid operated crosshead cylinder, a liquid reservoir, 3, multi-posltion valve for supplying air under pressure to said reservoir to drive liquid to said crosshead cylinder to move it from one position to another, externally controlled mechanism for moving said valve to one of its positions, a mechanical linkage between said valve and crosshead tor moving said valve to other of its positions, mechanism responsive to a predetermined pressure of liquid in said crosshead cylinder to effect movement of thevalve to another position, a timing device whose operation is initiated by fluid fed to it by said valve in the latter position, and means operated through said t ming device to advance said multiposition valve to its initial position after the expiration of a predetermined time; period.

6. Ina press mechanism, a plunger, fluid operated means for lowering and raising said plunger, other means for supplying fluid. under pressure; to said fluid operated means to lower said plunger, pressure responsive. means operated by pressure developed in the lowering of said plunger for removing pressure from the fluid operated means, means for thereafter operating said. other means to effect raising of the plunger, a timing device for delaying the raising of the plunger for a predetermined time period after pressure has been removed fromv the fluid, and means for supplying liquid to said, timing device: while the plunger is being lowered to prepare the timing, device m operation subsequent to the removal of pressure from the fluid operated means.

i. In a glass working machine a crosshead actuating assembly including a piston and cooperative cylinder, a reservoir in communication with said cylinder containing a, liquid, a reservoir charged. with compressed air, a compressed air supply line, a multiposition valve, means for operating said valve to bring said charged reservoir into communication with said first reservoir whereby the compressed. air supplied by the charged reservoir will force liquid from said first reservoir into said cylinder and thus effect an actuation of the crosshead and means responsive to the actuation of the crosshead for operating said valve to establish direct communication between said air supply line and said second reservoir whereby more of the liquid in said first reservoir is forced into said cylinder to efi'ect a furtheractuation of the crosshead.

DAVID E. GRAY.

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