US2164640A - Press combination having means for avoiding jamming - Google Patents

Description

July 4, 1939. I E. CANNON 2,164,640

PRESS COMBINATION HAVING MEANS FOR AVOIDING JAHMING Filed May 6, 1957 4 Sheets-Sheet 1 INVENT OR. ARL CANNON E. CANNON July 4, 1939.

PRESS COMBINATION HAVING MEANS FOR AVOIDING JAHMING 4 Sheets-Sheet 2 Filed May 6, 1937 //4 MOTOR /0.9

I 7'0 CLUTCH y 1939 I E. CANNON 2,164,640

PRESS COMBINATION HAVING MEANS FOR AVOIDING JAHMING Filed May a, 1937 4 Sheets-Sheet s INVENTOR.

I E/IRL CANNON BY July 4, 1939. CANNON 2,164,640

' PRESS COMBINATION HAVING MEANS FOR AVOIDING JAMMING Filed May 6, 1937 4 Sheets-Sheet 4 v PRESSURE fiEsuL 1-77wvs L /NE Patented. July 4, 1939.

PATENT OFFICE PRESS COMBINATION HAVING MEANS FOR AVOIDING JAIH'MING Earl Cannon, Rockville Centre, N. Y., assignor to E. W. Bliss Company, Brooklyn, N. Y., a corporation of Delaware Application May 6, 1937, Serial No. 141,033

11 Claims.

This invention relates to mechanical presses which include means for preventing jamming or breaking when the resistance encountered by the tool-carrying parts exceeds the rated working force of the press, and provides improvements therein.

Jamming and breaking of presses arise from a number of causes. For example, tools and pieces of metal accidently left between the press tools (dies, or dies and punch) are such causes. In forging presses, the billet or piece to be shaped may have cooled too much before being struck, or have been too large. In extrusion presses, also, the billet may have cooled too much before or during extrusion.

The present invention provides a press combination which avoids jamming or breaking of the press, and which, when the tools of the press encounter a. resistance which in ordinary presses would cause jamming or breaking, allows the press to complete its cycle of operation without stopping, or the press-parts to be backed off after stopping. The stopping or not stopping is a matter of the nature of the obstruction and of the design of the press-combination. The invention further provides a press combination which is self-acting to restore the parts to normal operating position or condition after operating to avoid jamming.

There are many practical limitations to overcoming the problem which has been solved by the present invention, especially in presses designed to apply a large working force. Take, for instance, a press designed to deliver a working force of 1200 tons. There are practical limits to the pressures which can be used in hydraulic and pneumatic means. On the "her hand high pressures must be used to keep the size of hydraulic and pneumatic elements down to a practical relation to the size of the other press parts. The present invention takes into account these limitations and provides a press combination incorporating hydraulic and elastic (mechanical or pneumatic) elements, whichoperates to avoid jamming, is self-acting to restore the parts to normal operating position after operating to avoid jamming, as heretofore stated, and in which the hydraulic and elastic elements are of a size to be readily combined with other parts of a press, without increasing the size of the press-parts over that required for the force to be delivered, and without exceeding practical hydraulic and pneumatic pressures.

The invention also provides advantages not attainable in a purely hydraulic means for the purpose heretofore mentioned. A liquid being substantially incompressible, a hydraulic means could not yield sufiiciently except by venting liquid. At pressures of the order of a 1000 pounds per square inch and over, the so-called wire 5 drawing effect on, or scoring of, the valves and valve seats would be so great as to impair the effectiveness of the means after a few operation-s;

in fact, it is believed that at pressures of the order of 3000 pounds per square inch the valve would be so greatly impaired after one operation as to be useless. As already stated, the present invention avoids the venting of liquid.

Moreover, the present invention maintains the normal rigidity of the operating parts of the press and avoids the disadvantages of a mechanism comprising hydraulic means which is not pre-stressed by a hydraulic force equaling or approximating the rated working force of the press. By pre-stressing hydraulic means as herein described, much of the spring" of the bed or slide is overcome when the working force is applied by the press, the cylinder walls are expanded to a degree beyond that which would occur when a working force within the rated 9 working force of the press is applied, and the oil and the air occluded therein is compressed to a degree beyond that which would occur when a working force within the rated working force of the press is applied. Expansion of the cylinder walls and compression of the oil and of the air occluded therein would act to cushion the force with which the tools are applied, and is undesirable where a positive action throughout the full working stroke of the press is desired.

The invention further provides a press combination of the character referred to above, in

.which the hydraulic element and its adjuncts may all be mounted on a moving part of a press, as on the press slide, so-as to avoid high-pressure lines running to the press. The hydraulic elements and its adjuncts may also be combined with the stationary parts of the press.

The invention further provides a press combination of the character referred to above, in which-means for making uplosses of liquid and gas from the hydraulic and pneumatic elements are readily and practically combined with the other parts of the press combination.

The invention further provides novel and useful combinations of press elements hereinafter set forth and defined in the claims.

Three embodiments of the invention are illustrated in the accompanying drawings, wherein:

Fig. 1 is a front elevation, partly in section,

or one embodiment, the press being of the type employed for extrusion.

Fig. 2 is an enlarged vertical section of parts of the press illustrated in Fig. 1.

Fig. 3 is a front elevation, partly in section, of a second embodiment, the press being of the type used for forging.

Fig. 4 is a diagrammatic view of the press combination according to the invention.

Fig. 5 is a diagrammatic View of a third embodiment.

Referring to said drawings, numerals l and l2 designate the tool-carrying parts of the press, on which are mounted the forming-tools N and I5, shown in Fig. l as an extrusion die and punch, respectively. The extrusion features are more fully disclosed in an application of William Klocke, Serial No. 136,764. In presses, one of the tool-carrying parts is usually a stationary bed located at the lower part of the press, and the other tool-carrying part is a slide which reciprocates toward and from the bed, but the position of the bed and slide are sometimes reversed, the press is sometimes horizontal and sometimes inclined, and sometimes the bed is reciprocated, as well as the slide. The press illustrated is a ver tical press having a stationary bed 52 and a reciprocatory slide l0. The elements which yield so as to avoid jamming may be mounted on the slide or on the bed, and may be combined with the press-parts of any of the types of presses referred to above. For the sake of simplicity, the description which follows will ordinarily refer to a vertical type of press with stationary bed and reciprocatory slide.

The press frame may also have various forms usual in presses; as here shown the frame comprises side-pleces I9, 20 and a crown 2E, tied to the bed l2.

Any of the usual, or suitable, mechanical means for driving or reciprocating the slide may be provided. As shown in Fig. l, the driving means comprises a crank-shaft 28, iournaled in hangers 24, 25, and driven by gears 21. 28. The crank-shaft 23 may have double cranks 30. 3|. which transmit the crank-motion to the slide I0 as reciprocating motion through the long connecting rods 33, 34 and trunn ons 35. 36 on the slide. The slide I0 is guided by suitable means. As shown in Fig. 1 the side-pieces I9. 20 are slotted as indicated by numeral 39. and reduced portions 40 of the slide l0, slide in the slots. As shown in Fig. 3, the mechan cal means for driving the sl de I0 is an overhead crank shaft 42 i urnaled in t e crown 2|, having a single crank ll. connected to the slide III by a connecting rod 45. The crankshaft 42 may be driven by a fly-wheel pulley l1 transmitting motion through a clutch 50 to a back-shaft 52 having pinions 58, 55 thereon meshing with gears 81, 58 on the crank-shaft 4!. Symmetry of motion is aided by a second flywheel 60 on back-shaft 52. The gears 21 and 28. Fig. 1 may be driven by a similar arrangement of fly-wheel pulley, clutch. back-shaft and pinions.

One or the other of the tool-carrying parts l8, l2, has a tool-support 82 mounted thereon, which is movable with relation thereto in a manner hereinafter described. In Fig. 1 the tool-support 82 is mounted on the slide ill; in Fig. 3 on the .bed l2.

by the normal forces (opposite to the hydraulic.

arse-e o force) exerted by the driving means on the toolcarrying parts l0 and i2, and the tools thereon, in performing the normal work of the press. For example, if the press had a rated working force of 1200 tons, the hydraulic means 65 would act with a force of 1200 tons plus a safe overload in opposing motion of the tool-support 02. To conform to dimensions of the slide it] or bed l2 which are normal or usual for a design of press based on the ordinary factors of design, high pressures are required in the hydraulic means to enable it to exert a force on the tool-support S2 approximating the rated working force exerted by the driving mechanism. Such design will often call for pressures of 3000 pounds per square inch or thereabout, which approaches the limit imposed by engineering considerations. As shown, the hydraulic means 65 comprises a cylinder 6'! and a piston $8. The cylinder Sl, in Figs. 2 and 5, is formed as a part of slide it.

A means iii is also provided for sustaining the action of the force of said hydraulic means 65 (piston 88) on the tool-support 62 in the normal position of the latter, so that said hydraulic means cannot move said tool-support 62, in its normal position, in the direction of the action of the hydraulic force on the piston 68. In Figs. 1, 2 and the means are strong tie-rods 12 which pass through the tool-support 62 and through the slide it (in which the cylinder 6! is formed) and have nuts or heads M, E5 (or other suitable means) which sustain the force exerted by the hydraulic pressure against the cylinder ill and the piston 88. In Fig. 3, the means it are the tie rods 11 which pass through the bed l2, crown 2i,

and lugs I8 on the cylinder 87,-and have nuts or heads I9, 80 (or other suitablemeans) which sustain the force exerted by the hydraulic pressure against the cylinder 61 and the piston 68 and by piston 68 against a shoulder 82 on the bed l2 (in the absence of stress on tool-support 62) and transferred to the tool-support 62 when the force or resistance on the tool and on the tool support exceeds the force exerted by the hydraulic pressure against the piston 58. The tie-rods permit movement of the piston 88 against the hydraulic pressure in the cylinder 61, when the force or resistance on the tool on the tool-support 82 exceeds the force exerted by the hydraulic pressure within the cylinder against the iston 68.

A yieldable or elastic means 85 is provided for counterbalancing the hydraulic means 65. The counterbalanclng means 85, may, as shown in Figs. 1-4, comprise a pneumatic cylinder 86 and a pneumatic piston 88, or, as shown in Fig. 5, comprise springs 81. The cylinder 86 is held by suitable means. As shown in Figs. 1 and 2 the cylinder 86 is fastened to the slide H! by tiebolts 81, and as shown in Fig. 3 is fastened to (or with relation to) the bed l2 by means of nuts on extensions 89 of the tie-rods l1. Inasmuch as good engineering practice and technical design is against the use of high pneumatic or gas pressures (against pressures which are in excess of 100 lbs/sq. inch), the area of the piston 88 would be comparatively large if the hydraulic pressure in the cylinder 61 was directly counterbalanced by the pneumatic pressure in the cylinder 88 acting on the pneumatic piston 88. In order to reduce the size of the cylinder and piston of the pneumatic device to a size conformable to the size of the other parts of the press combination made according to the ordinary considerations of design, the hydraulic device 85 may advantageously comprise a sec- 1 and 2 of the drawings.

ondary cylinder and piston 00 and SI, of consid erably less cross sectional area than the area of the primary cylinder and piston 81, 88. The secondary cylinder 90 is conveniently formed in, or as a part of the pneumatic piston 88, and a conduit 93 is provided for connecting the cylinder 61 with the cylinder 00, so that the hydraulic pressure within the cylinder 81 and is equalized. The conduit 93 is conveniently formed as a bore in the secondary piston M, with a lateral branch or branches as shown. With a hydraulic pressure of 3000 lbs. to the square inch in the cylinder 61, and a pressure at 100 lbs/sq. inch in the pneumatic cylinder 86, a counterbalancing pressure of 3000 lbs./square inch would be maintained in the cylinder 90, by giving the pneumatic piston 88 thirty times the area of the secondary hydraulic piston 9I. With a pressure of 3000 lbs. to the square inch in the. secondary cylinder 90, the pressure in hydraulic cylinder 81 would likewise be 3000 lbs/sq. inch, because of the communication between the cylinders 61 and 90 through the conduit 93. The function and operation of the pneumatic cylinder and piston 86, 88 is to allow movement of the hydraulic piston 60 (when a resistance; is encountered by a tool on the tool-support 62 in excess of that which the press is designed to overcome), without the necessity of venting liquid from the hydraulic device. The advantage of avoiding venting of liquid from the hydraulic device is manifest, when it is realized that a venting device would be so scored by liquid flowing out at 3000 lbs/sq. inch as to make it useless or greatly impaired after one operation.

Moreover, the capacity of the cylinder 86 does not need to be excessive, inasmuch as the design of the hydraulic and pneumatic means may be such as to allow suificient yielding of the toolsupport 68 to avoid jamming or breaking of the press, by a movement of the pneumatic piston 88 such as will reduce the capacity of the cylinder 86 by about 1%. The cylinder 88, may, as here shown, consist in part of a drum 96.

By the present invention the hydraulic and elastic or pneumatic devices may be so compact as to be readily mounted on a moving part of the press, as the slide I0, as illustrated in Figs. To reduce the height of the frame, a central opening may be provided in the crown 2!, as indicated at 90 in Fig. i.

In the hydraulic means 55, it is expected that there should be some leakage. A limited amount of leakage will not afiect the pressure within the hydraulic device because the designated pressure will be maintained by the action of the pneumatic piston 88 (or equivalent elastic device). The secondary hydraulic cylinder 90 isso designed that there is a clearance I Ill between the end of the cylinder and the end of piston 0i when the parts are in normal position, which allows a limited amount of movement of the piston 88 to compensate for loss of liquid from the hydraulic cylinder 61, before the end of piston 9i abuts against the end of cylinder 90. If the end of cylinder 00 abuts against the end of piston iii, the pneumatic piston 88 would no longer act to maintain the pressure following loss of liquid from the hydraulic cylinder 8?. To avoid the result just referred to, a make-up device I05 may be provided, which, as here shown, may comprise a pump I01 and an electric motor I09 for driving it. When the hydraulic means 65 is mounted on the slide I0, the pump I01 and motor I00 are advantageously also mounted on the slide, so that a rigid pipe line III may be provided between the pump I01 and cylinder 61. The intake to the pump I01 may be connected to a sump H3 through a rigid pipe line I I I. The pump I01 will require to be oper- .erated only at infrequent intervals, and then only for short periods in order to lift the end of cylinder 90 off 01' the end of piston St to provide the normal clearance IOI. For this purpose, a pressure-responsive means H5 connected by a pipe II 6 to the line iii, and operative to close a time-switch II! in the circuit to the motor I09, upon a fall in pressure in the hydraulic cylinder 61, may be provided. The timeswitch II1 breaks the circuit to the motor after the pump I01 has been driven thereby for a time predetermined for making up the volume of liquid in cylinder 61, and 90 to provide the desired clearance at H.

An automatic valve I20 in a conduit I22 con nected with a source of compressed air, may be provided for making up losses of air from the pneumatic means 85. When the hydraulic means 65 and the pneumatic means are mounted on the slide I0, the conduit I22 may be a flexible tube, and in this form of the invention, the only connections between the reciprocatory slide H0 and appliances ofi the press are flexible air-tube I22 and a cable I25 containing the electrical conductors which lead to the motor m9, which present no mechanical difiiculties.

It may be desirable to stop the running of the press following the yielding of the piston 68 heretofore described. For this purpose a means may be provided for disengaging the clutch 50. The

clutch 50 may be a fluid-operated clutch construction disclosed in the patent to Klocke and Carter #2,023,597, and the aforesaid means for disengaging the clutch may comprise a switch I30-in an electric circuit with a solenoid I33 for actuating a valve I35 controlling the flow of fluid to the clutch 50. The switch I30 may be mounted on the same part as that on which the hydraulic means 65 is mounted '(for example, in

Figs. 1 and 2, the slide I0) in such manner as to 13 be operated to close the circuit upon relative movement between the tool-support 62 and the tool carrying part I0 or I2 on which it is mounted. As shown in Fig. 2, the tool-support 62 may have a projection or finger I31 thereon projecting into the path of an arm of switch I30 so as to operate the latter to close the circuit through the switch upon the relative movement between the parts it and 02.

A third embodiment of the invention is dia-= grammatically illustrated in Fig. 5%. Here heavy springs 81 are substituted for the pneumatic means Numeral I50 designates a slide, in which is formed the secondary hydraulic cylinder in which the secondary hydraulic piston 9i works. The slide I50 is acted on by an elastic device (springs 81) equivalent to that of the pneumatic device: that is, the force of springs 81 is such as to create a pressure in the hydraulic cylinder 90 equal to the pressure required in the hydraulic means 65 to develop a force on the tool support '62 equal or somewhat,- greater than the rated working force applied by, he driving means of the press. The springs 8 may be stressed between a face of slide I50 and an abutment plate I55 connected to the slide I0 (or other tool carrying part of the press) by bolts I51 and nuts I58. The structure of the embodiment of Fig. 5 may be otherwise the same as shown in Figs. 1 and 2, and may also be incorporated in the bed of the aieaeec press similar to the arrangement shown in Fig. 3. The operation of the embodiment shown in Fig. 5 is similar to the operation of the embodiments of Figs. 1-4.

Resume of operation If and when the tools i l, 55 on the tool-carrying parts l0 and i2 meet a resistance exceeding the rated working force of the press, applied by the driving mechanism (as for example when a billet between an extrusion punch and die has cooled to such an extent that the resistance ofiered by the billet to the advance of the punch near the end of the extrusion operation becomes so great, that in a press without means for preventing jamming, the driving mechanism would eXert such a force on the stalled tools as to either jam the press, or to break the bed or crown), the tool-support 52 acting through the piston 68 increases the pressure of the liquid in the cylinder 6'1, which increase of pressure in the cylinder cl is transmitted through the conduit 93 to the cylinder 96. The increased hydraulic pressure acting on the pneumatic piston 88 (or equivalent elastic device such as springs 871') causes the piston 88 to move and compress the air in the cylinder (and drum 96). In this way the driven tool-carrying part Hi can continue to move under the force of the driving mechanism against the hydraulic and pneumatic pressures in the hydraulic and pneumatic devices 65 and 85, even though the tools M and i5 are stalled. The movement of the slide ill) with relation to the tool-support 62, in the manner aforesaid, may be sufficient to enable the cranks 3b, 3!, Fig. 1 and 45, Fig. 3, to pass through the dead center, thereby avoiding jamming or breaking of the press. However, the design of the hydraulic means 65 and of the elastic or pneumatic means 85 or 81 may be such as to only allow such a limited amount of movement between the tool carrying slide l0 and the tool support 62 as to make it desirable to stop the press before the dead center position of the cranks 30, 3| and 45 is reached. Accordingly, after the driven slide H! has moved a predetermined amount with relation to the tool-support 62, the finger or projection I31 operates the electric switch at 530 to energize the solenoid I33 to turn the valve I35 to position to vent fluid from the clutch 50, and thereby bring about the disengaging of the clutch through which the crank shaft 23, (Fig. 1, or 42, Fig. 3, is driven. Thereafter the direction of the rotation of the crank shaft may be reversed, the tools l4, l5 backed off from the obstruction, and the obstruction removed.

After the cranks 30,31, Fig. 1, or 45, Fig. 3, have either passed through their dead center position, or have'been backed off from their dead center position, following an obstruction to the movement of the tools I4, and i5, as heretofore explained, the hydraulic means 65 and the pneumatic means 85 (or springs 81) act to restore the parts to normal operating position. That is, the pressure of the air in the cylinder 86 (or of springs 81) which has been increased when the obstruction to the tools M, l5 was encountered, acts on the pneumatic piston 88 (or slide I50) which latter acts on the liquid in the cylinders 90 and 61 and moves the hydraulic piston 68 until further movement thereof is stopped by the abutment of the tool-support 62 against the nuts on the tie-pieces 12, Figs. 1 and 2, or against shoulder 82, Fig. 3.

Incidental loss of air in the pneumatic cylinder 36 is made up from the source of compressed air through the tube iii and automatic valve l2il.

incidental loss of liquid in the hydraulic cylinders l and Gil is made up by means of a motor driven pump Hill. The pump i0! is connected to a pump (1 l3 on its intake side, and to the cylinder on its output side. The make up of loss of liquid is ordinarily at infrequent intervals, and the electric motor N39 for driving the pump id! is automatically started and stopped through a time switch ill. The time switch may be actuated to close the circuit by a pressure responsive device Hi5 which is in communication with the hydraulic cylinder 61 through the pipes lit and Hi. When the end of the cylinder 98 comes to rest on the end'of the secondary hydraulic piston 91, further loss of liquid will bring about a drop of pressure in the hydraulic cylinder 5'5, and this drop of pressure in the cylinder 87 will cause the pressure responsive device H5 to close the circuit to motor 609 through switch iii and start the time mechanism to run. After the time mechanism of switch l H has run for a predetermined time, which may be about five secends, the time switch in breaks the circuit to motor 669, stops the motor, and ends for the time being the make-up of liquid to the cylinder 61.

The invention may receive other embodiments than those herein specifically illustrated and described.

What is claimed is:

1. A press comprising tool-carrying parts, one a reciprocatory slide, mechanical means for reciprocating said slide with a definite stroke, and

means for preventing the jamming or breaking of the press when the resistance encountered by the tool-carrying parts exceeds the rated working force of the press, said means comprising a tool support on one of said tool-carrying parts and movable relative thereto, hydraulic means between said tool-support and tool-carrying part for exerting hydraulic force on said tool support sufficiently great to prevent movement of said tool support by opposite forces exerted in performing the normal work of the press approximating the rated working force of the press, means for sustaining the action of the force of said hydraulic means on said tool-support in its normal position, and means for counter-balancing the hydraulic force acting upon the said hydraulic means, said counterbalancing means comprising an elastic means and a slide or piston acted on in opposite directions by said elastic means and by hydraulic pressure within said hydraulic means, said elastic means, upon an increase of hydraulic pressure, yielding until the increased pressure thereof, counterbalances the increased hydraulic pressure, said slide or piston which is oppositely acted on by said elastic means and hydraulic pressure moving when said elastic means yields so that liquid within said hydraulic means is displaced without venting or loss thereof, and said tool support may yield when it encounters a resistance approximately the rated working force of the press. said elastic means expanding after the abnormal resistance exerted on the tool-support has passed, to re-establish the parts in normal counterbalanced position.

2. A press according to claim 1, wherein said hydraulic means and said elastic means are mounted on and move with the slide.

3. A press according to claim 1, wherein said hydraulic means and said elastic means are mounted on and move with the slide, and further comprising a motor-driven pump for makcluding a clutch in said mechanical means for reciprocating the slide, and means operable upon relative movement betweensaid tool-support and the tool-carrying part on which it is mounted, to disengage said clutch.

5. A press according to claim 1-, wherein said slide or piston has a hydraulic cylinder therein, and wherein said hydraulic means comprises a primary cylinder and piston and a secondary piston of smaller diameter than the primary, said secondary hydraulic piston working in said hydraulic cylinder in said slide or piston of said elastic means, and a conduit connecting said primary hydraulic cylinder and the hydraulic cylinder in said slide or piston of said elastic means, so as to equalize the hydraulic pressure in said cylinders.

6. A press comprising tool-carrying parts, one a reciprocatory slide, mechanical means for reciprocating said slide with a definite stroke, and means for preventing the jamming or breaking of the press when the resistance encountered by the tool-carrying parts exceeds the rated working force of the press, said means comprising a tool support on one of said -toolecarrying parts and movable relative thereto, hydraulic means between said tool-support and tool-carrying part for exerting hydraulic force onsaid tool support sufilciently great to prevent movement of said tool support by opposite-forces exerted in performing the normal work of the press approximating the rated working force of the press, means for sustaining the action or the force of said hydraulic means on said tool-support in its normal-position, and means for counterbalancing the hydraulic force acting upon the said hydrualic means, said counterbalancing means comprising pneumatic means, and a slide or piston actedon in opposite directions by said pneumatic means and by hydraulic pressure within said hydraulic means, said pneumatic means, upon an increase of hydraulic pressure, yielding until the increased pressure thereof, counterbalances the increased hydraulic pressure, said slide or piston which is oppositely acted on by said pneumatic means and hydraulic pressure moving when said pneumatic means yields so that liquid within said hydraulic means is displaced without venting or loss thereof, and said tool support may yield when it encounters a resistance aproximating the rated working force of the press, said pneumatic means expanding after the abnormal resistance exerted on the tool support has passed, to re=-establish.

the parts in normal counterbalanced position.

7. A press according to claim 6, wherein said hydraulic means and said pneumatic means are mounted on and move with the slide.

8. A press according to claim 6, wherein said hydraulic means and said pneumatic means are mounted on and move with the slide, and further comprising a motor-driven pump for making up loss of liquid in said hydraulic means, also mounted on said slide.

9. A press according to claim 6, further including means for making up loss of liquid in said hydraulic means, and means for making up loss of gas in said pneumatic means.

10. A press according to claim 6, wherein said pneumatic means comprises a piston having a hydraulic cylinder therein, and said hydraulic means comprises a primary cylinder and piston and a secondary piston of smaller diameter than the primary, said secondary hydraulic piston working in said hydraulic cylinder in said pneumatic piston, and a conduit connecting said primary hydrauiic cylinder and the hydraulic cylinder in said pneumatic piston, so as to equalize the hydraulic pressure in said cylinders.

11. A press according to claim 1, wherein said elastic means comprises a spring or the like.

EARL CANNON.

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