US2236154A

US2236154A - Press combination having means for avoiding jamming

Info

Publication number: US2236154A
Application number: US157666A
Authority: US
Inventors: Patrick Isaac; Klocke William
Original assignee: EW Bliss Co Inc
Current assignee: EW Bliss Co Inc
Priority date: 1937-08-06
Filing date: 1937-08-06
Publication date: 1941-03-25
Anticipated expiration: 1958-03-25

Description

March 25, 1941. P c ETAL 2,236,154

PRESS COMBINATION ruwnie usms FOR AVOIDING JAIIING Filed Aug. 6 1937 4 sheets-s eet 2 INVENTORS ISAAC PATRICK BY ILL A KLOCKE ATI'ORNEY.

March 25,1941; I I; PATRICK ETAL 2,236.1

' Puss" COMBINATION rim/me mums FOR ;Avomme .JAIIING,

qFi-l eqi'Aug. e, 1937 v INVENTORS Z ASRHC PATR/CK WM KLOCKE MTTORNEY.

March 25, 1941. l. PATRICK ETAL PRESS COMBINATION HAVING MEANS FOR AVOIDING JAIIING Filed Aug. 6, 1937 -4 Sheets-Sheet 4 RESERVOIR 7'0 CIT/1 NK lllllllll. I11.

5 m J v N E V m u 7 n la 0 7 e M i mwJ [.1 E5 5 Mm 6 6 C 0 E R U O M Mm 2 v m m m w \M, c H\ E 7 a \M M M: Q

4 WILLIAM KLOCKE T0 CLUTCH BY A2 ATTORN EY Patented Mar. 25, 1941- UNITED STATES PATENT OFFICE PRESS COMBINATION HAVING MEANS FOR AVOIDING JAMltflNG I ration of Delaware Application August 6, 1937, Serial No. 157,666

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 improve-' ments therein.

To make sharply defined and accurate forgings and other shapes it is desirable to use a mechanical press in which the reciprocatory tool-carrying part has a definite stroke, such as in a crank-press. It\is also desirable to maintain a great rigidity in the press upon the impact and application of the forming-tools or dies upon the bar or billet-metal to be shaped under the very large working forces usually employed. However, the greater the rigidity of the press, the greater is the likelihood of the press jamming (or even breaking), with the practical necessity in many instances of destroying the dies or cutting the connecting-rod in order to free the press. In either case production would suffer more or less delay depending on the availability of replacement parts, and the cost would be considerable, especially if expensive dies had to be destroyed. In types of presses other than forging presse the consequences of jamming are equally serious.

The present invention provides a press combination, including a hydraulic element, 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, allow 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 1000 tons. When it is considered that a piston of 36 inches diameter and a hydraulic pressure of 2000 pounds to the square inch is required to sustain a force of 1000 tons, it will be seen that the incorporation of a hydraulic element capable of sustaining such a force presents a problem. While piston-area may be reduced by increasing the hydraulic pressure, there is a practical limit to the increase of pressure; so that from the standpoint of either area or pressure, there is a problem of incorporating a hydraulic element in a press capable of sustaining a force of 1000 tons.

The present invention takes into account these limitations and provides a press combination incorporating a hydraulic element, which operates 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 element is of a size to be readily combined with othe parts of a press, without increasing'the size of the press-parts over that ordinarily required for the force to be delivered, and without exceeding practical hydraulic pressures.

The present invention furthermore makes pro vision for certain subtilties in respect to hydraulic means. Oil (a liquid) is commonly regarded as incompressible. But there is some air occluded in the oil and this is compressible. Moreover, cylinder heads and walls, even though massive, expand appreciably at pressures of 1000 tons to the square inch and upward. Unless provision be made for such subtilties, a hydraulic element would not serve satisfactorily in a press in which it is desired to support the formingtools rigidly during the forming operation, to obtain a positive action of the tools throu hout the full working stroke of the press. The pres ent invention therefore includes means for prestressing the hydraulic element with a force equal to or in excess of the rated working force of the press. By pre-stressing the hydraulic means as herein described, much of the "spring of the slide, or other part acting against the hydraulic element, is overcome when the working force is applied by the press, the cylinder walls are expanded to a degree beyond that which a would occur when a working force within the rated 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.

The invention further provides a press combination incorporating a hydraulic element for avoiding jamming, in which means for maintaining constantly the pre-stressed condition of the hydraulic element and for restoring oil vented or lost from the hydraulic element are readily and practically combined with the press, in which rigid connections between the hydraulic element and pressure-maintaining and make-up means are provided, and in which the hydraulic element may be incorporated in the reciprocatory tool-carrying slide of the press and have such rigid connections with the pressure maintaining and make-up means.

The invention further provides a press having a frame of exceptional rigidity, which may be simply or readily formed of sectional parts, which frame is readily erected, and secure when erected and used.

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

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

Fig. l is a front view, partly in section, of one embodiment;

Fig. 2 is a view in elevation looking at the right-hand side of the press shown in Fig. 1.

Fig. 3 is a top plan view;

Figl. 4 is a cross section on the line IV-IV, Fig.

Fig. 5 is a diagrammatic view of the embodiment of the press combination shown in Figs. 1 to 4.

Fig. 6 is a front elevation of a second embodiment of the invention;

Fig. 7 is an enlarged view, in section of the toolcarrying slide shown in Fig. 6.

Fig. 8 is a diagrammatic view of the embodiment of the press-combination shown in Figs. 6 and '7.

Fig. 9 is a diagrammatic view illustrating a means for operating the gag-connection I90 shown in Fig. 1.

In both of said embodiments, the press shown is of the type used for forging; the invention however, is applicable to other types of presses.

Referring to said drawings, numerals 10 and I2 designate the tool-carrying parts of the press on which are mounted the forming-tools l4, l5.

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 positions 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 embodiments of the presses illustrated are vertical presses having a stationary bed l2 and a reciprocatory slide Ill. The strains produced by the tools during the forming operation, and transmitted to the tool-carrying parts Ill and i2, are sustained by a frame it. The element which yields so as to avoid Jamming may be located between two parts of the movable slide 50 (as illustrated in Fig. 6), or between the press frame l6, and any part of the press combination through which the strains produced by the tools during the forming operation, are transmitted to the frame. In Figs. 1 to 5, the yielding element is located between a block on which the crank shaft which drives the slide is mounted, and the frame of the press. For the saite of simplicity the description which follows will ordinarily refer to a vertical type of press with stationary bed and reciprocatory slide.

The press frame l6 may also have various forms usual in presses; in a forging press designed to shape the metal with great precision, it is advantageous to have a frame which is highly rigid. To this end, in the embodiment illustrated in Figs. 1 to 5, the frame I6 is formed of two caststeel upright sections l8 and I9 and transversesections 20, 2|. The transverse-section 20 is at the top of the press and corresponds to the portion usually designated as the crown of the press. The transverse-section 2| is located at the base of the press and functions as the bed of the press. Suitable interlocking means 23 between the upright or longitudinal sections l8, l9 and the transverse-sections 20, 2| are provided, as the interlocking recesses and projections which are shown in the drawings. The four sections of the frame are securely fastened together by means of tie-rods and nuts 25 running transversely of the frame and through the upright sections l8, is.

In Fig. 6, the press frame [6 is composed of cast

iron side pieces

28, 29, crown 30 and bed 3|, which are securely held together by extra strong tie-rods and nuts 33.

Any of the usual or suitable mechanical means for driving or reciprocating the slide l0 may be provided in both embodiments herein illustrated. The illustrated mechanical means for driving or reciprocating the slide is a gear driven crankshaft.

Referring to the embodiment illustrated in Figs- 1 to 5 inclusive, the slide reciprocating means comprises a crank shaft 40 and connecting rod H, the crank shaft 40 having a gear 42 thereon which meshes with a pinion gear on a back shaft 45, and which back shaft is driven by a fly-wheel pulley 41 directly, or through a clutch 49 as may be desired.

Referring to Figs. 6 to 8, the mechanical means for driving or reciprocating the slide l0 comprises a crank shaft 50 having gears 52, 53 thereon, which latter are driven by

pinions

55, 56, on a back-shaft 59, which back-shaft may be driven by a fly-wheel pulley Bl through a clutch 63. 65 designates an auxiliary fly-wheel, and 56 a connecting rod between shaft 50 and slide l0.

Again referring to Figs. 1 to 5 inclusive, the crank shaft 40 is journaled on a block 10, as indicated at 12. The block Ill is mounted between guides 13 on the sides of the frame and is confined by gibs l4.

Numeral I5 designates a hydraulic element. The construction and operation of the hydraulic element is such as to exert a force sufiiciently great to sustain the normal forces (opposite to the hydraulic force) exerted by the driving means on the tool-carrying parts l0 and I2, and the tools thereon, in performing the normal work of the press. For example in a press having a rated working force of 1000 tons, the hydraulic means 15 constantly and immediately acts with a force of 1000 tons plus a safe overload in opposing motion of the block 10 (or equivalently functioning parts in other embodiments). As heretofore stated, the hydraulic element '15 is pre-stressed, or constantly stressed to a degree greater than the rated working force of the press.

Most of the spring of the cross-piece or of the slide (Figs. 6-8) 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 working force of the press is applied through the tools I4, l5, and the oil and the air occluded therein is constantly compressed to a gree beyond that which would occur when a working force within the rated working force of the press is applied. The rigidity of the press under working stresses is largely increased, which contributes importantly to the formation of precise shapes by the tools,

The hydraulic element comprises a cylinder 11 and a piston I8. The sides of the cylinder 11 are conveniently formed as a part of the crosspiece 20 of the frame, and the pressure-end of the cylinder is tightly closed by a cover 00. The cylinder-cover is rigidly supported by the side pieces I8, I9 of the frame, and securely pressed against the piece 20 in which the cylinder is formed, by means of wedges 03 which are forced into grooves in the side pieces I8, I8 above a flange on the cylinder cover 80.

Numeral 84 (in both embodiments) designates an escape-valve through which the hydraulic system is opened and liquid is vented from the hydraulic element I5, when the resistance to the tools I4, I5 exceeds the rated working force of the press, as described herein.

A mechanical means is provided for sustaining the action of the force of said hydraulic means 15 (piston 18) on the block I8 (or equivalently functioning part in other embodiments) in the normal position of the latter, so that said hydraulic means 15 cannot move said block I8, in its normal position, in the direction of the action of the hydraulic force on piston II. In the embodiment under discussion (Figs. 1-5) expansion movement of the piston 18 under the stress of liquid in the cylinder I1 is limited by a strong flange 85 on the cross-piece 20 and the cylinder is held by the wedges 88 actin against the press-frame. The slidable block 10 and the piston I8 of the hydraulic element are in stresscommunication through a disk or short pillar 80. Normally the slidable block I0 rests upon the bottom of the guides I3. The guides I8 are preferably formed parallel to a line tangential to the pitch-circles of the gear 42 and pinion 43 at their point of meeting. Arranged in this way, the crank shaft 40, when the block I0 yields or moves, as hereinafter more fully explained, moves virtually on a radius having its center in the axis of the pinion shaft 45. Moving thus, the meshing of the teeth of the gear 42 and pinion 48 on the pitch-circles is only very slightly affected, so little so that little if any additional strain be-- tween the gear 42 and pinion 43 during driving, is produced, and the gear and pinion are not forced apart even under the very large driving forces transmitted from the pinion to the gear.

There is an important advantage in locating the hydraulic element 15 in the frame above the crank-shaft 40 and the block on which it is journaled. Considering a forging press having a rated working force of 1000 tons, the hydraulic element I5 must be stressed with a force of at least one thousand tons in order to sustain the reactions from the forming tools within the rated working force of the press, so that the press will not yield during normal operations. It is desirable to keep the hydraulic pressure as low as feasible. It is also desirable to maintain a compact structure of the press. That is, it is desirable to design the press as closely as possible in conformity with the ordinary requirements for delivering the rated working force of the press. In such a case the hydraulic element I5 would require a piston of 36 inches in diameter and a hydraulic pressure of 2000 pounds to the square inch' in order to sustain a force of 1000 tons. By locating the hydraulic element above the shaft, as in the embodiment illustrated in Figs. l-5 inclusive, an advantageous location as regards area is obtained and the location is especially favorable in a forging press, which places the hydraulic element ll remotely from the scale which flies from the metal being shaped under the impact of the dies.

The required pressure in the hydraulic element I5, as hereinbefore explained, is constantly maintained by suitable means above a determined minimum approximating the rated working force of the press. For example, referring to Fig. 5 the cylinder of the hydraulic element I5 may be in communication with the delivery end of an intermittently operated motor-driven pump 85 through pipe 81 and a check valve 88. The intake side of the pump may be in communication with an oil reservoir I00 through pipe IN. The oil reservoir may be a sump located on the frame of the press to which 011 vented from the hydraulic element I5, as hereinafter explained, through the escape valve 84, is received. Numeral I04 designates a pipe leading from the escape valve 84 to the reservoir or sump I00. The motor-driven pump 85, (also the pressure responsive device I08, etc.) is advantageously mounted on the press-frame, as shown best in Figs. 2 and 3. In this way all the piping between the pump and the hydraulic element I5 may be rigid and the greatest safety obtained with the high pressures used.

In practical operation it is desirable to maintain a force on the piston 18 somewhat in excess of the rated working force of the press. Take for example, a design in which the force acting on the piston I8 is ten percent over the rated working force of the press. The action of the motor driven pump and its accessories would'be to force oil into the cylinder 11 until the pressure therein created a force on the piston I8 ten percent in excess of the rated working force of the press, and then stop. When the pressure within the cylinder 'II .falls to a predetermined amount (through leakage or by venting through the escape valve 84) say to a pressure at which the force on the piston I8 approximates the rated working force of the press, the motor driven pump 85 would be started so as to pump oil into the cylinder I1 until the desired or designed pressure is again established in said cylinder 11, which pressure, in the example under discussion would be that at which the force on the piston 18 is ten percent over the working force of the press. Thereupon the motor driven pump would be stopped.

The starting and stopping of the motor driven pump 95 may be automatically accomplished by any suitable means. As shown in Fig. 5, said means comprises a pressure responsive device I06 and a switch I08. In Fig 5, the pressure responsive device I06 and the switch I08 are shown in a position in which they are just about to operate to stop the operation of the motor driven pump 85. The pressure responsive device I06 is in communication with the cylinder 11 through a pipe IIO branching from the pipe 81. The pressure in the device I08 is approaching the pressure which produces a force within the hydraulic element I5 ten percent over the rated working force of the press, and has forced the piston II! to a corresponding position. A slight increase in pressure in the cylinder 11 and in the pressure responsive device I06 will throw the switch arm H5 to the position H6 where it will be held by the spring H8. The movement of the switch arm II 5 carries with it the plate I20 having the bridging contact I22 thereon, which breaks the circuit I device i06 reaches the dotted line position, the

switch arm I [5 will be shifted to its opposite position indicated by the dotted line I26 and held in this position by the spring I I8. In moving to the position indicated at I26, the switch arm H5 will shift the plate I carrying the bridging contact I22 to close the circuit to the electric motor through the contacts I24, and thereupon start the motor-driven pump 05, and the motor-driven pump 95 will continue to run and force oil into the cylinder 11 of the hydraulic element 15 until the pressure responsive device I06 operates to shift the switch arm I I5 to the position indicated by the dotted line H6, whereupon the operation of the motor driven pump 95 is again stopped.

A suitable means I may be provided for stopping the operation of the press when the reaction to the working force of the press exceeds the rated working force of the press (plus such overload factor as may be incor rated in the design of the hydraulic element 15). As shown in Fig. 5 the means I30 may comprise an electric circuit leading to the clutch 49 having one contact I32 on the slidable block 10, and another I34, on the side piece I8 of the frame. When the block 10 moves, a circuit is completed through the contacts I32, and I 34, and the clutch is disengaged to disconnect the crank shaft from the driving pulley 41. The clutch 49 may be a fluid-operated clutch such as shown and described in U. S. Patent 412,023,597, December 10, 1935, and the valve controlling the clutch may have associated therewith a solenoid (not shown) for operating said clutch controlling valve in the manner described, when the circuit is completed through the contacts I32 and I34.

Referring again to the embodiments illustrated in Figs. 6 to 8 inclusive, the hydraulic element 15 is located in the slide 10. To this end the slide comprises two parts I0", I0. One of the forming dies, as a tool I4, is mounted on the slide part I0", which latter acts as a support for said forming tool I4. The hydraulic element 15 comprises a cylinder I 40, the side walls and head of which are formed in the slide part I 0. Numeral I42 indicates the piston of the hydraulic element, the outer end of which bears against the slide part I0 which supports the tool I4.

Numeral I45 designates the means for sustaining the action of the force of said hydraulicv means 15 (piston I42) on the slide part I0 in the normal position of the latter, so that said hydraulic means 15 cannot move said slide part I0", in its normal position, in the direction of the action of the hydraulic force on piston I42. In the present embodiment, the means I45 may comprise strong bolts or tie-rods I41 which pass through flanges on the slide parts I0, I0 which tie-rods have nuts on their ends and sustain the full force of the hydraulic pressure acting between the cylinder head and piston I42. The tierods however, allow the slide part I0 to move toward the slide part I0 when the resistance offered by the metal being shaped by the tools I4, I5'oifers a resistance in excess of the rated when the resistance offered by the tools I4, I5.

exceeds the force exerted by the compressed liquid in the cylinder 40, venting liquid through a duct I53, which vented liquid is advantageously received in a reservoir III on the slide part I0.

The mechanical means for maintaining the required pressure in the hydraulic element 15, in the embodiment under discussion, may comprise a variable delivery motor-driven pump I60, in which the volume oi liquid delivered is governed by the pressure. There are a number of these variable delivery pumps on th market. The pump illustrated is a Racine" pump manufactured by Racine Tool 8: Machine Co. of Racine, Wisconsin. The pump is in communication, on its compression side, with the cylinder I40 of the hydraulic element 15 through a pipe or duct I62, and on its intake side communicates with the reservoir I through a pipe or duct I64. I66 designates a pressure responsive device which is in communication with the cylinder I40 of the hydraulic element 15 through a pipe or conduit I which branches from the pipe or conduit I62. The pressure responsive device I66 comprises a piston I10 against one side of which a spring I12 acts. When the pressure in the cylinder I 40 of the hydraulic element 15,- and in the ducts from the compression side of the pump I60, increases, the piston I10 of the pressure responsive device I66 rises aganist the pressure of the spring I12. As the piston I10 rises, the axis of the barrel I15 of the pump approaches the axis of the rotor-drum I 11. The pressure of the spring I12 may be set so as to control the movement of the piston I10 that the axis oi the barrel I15 of the pump will coincide with the axis of the rotordrum I11 when the pressurewithin the cylinder I40 of the pressure responsive device I15 reaches, or remains at, such a pressure as to produce a force within the hydraulic element 15 equal to the rated working force of the press, plus such excess as is determined or desired to maintain in the hydraulic element 15, The motor driven pump I60 therefore may be run constantly; when the pressure within the hydraulic element 15 is such as to produce the desired force, the pump ceases to deliver oil to the hydraulic element; and when the pressure of the liquid within the hydraulic element 15 falls, (by reason of leakage or by reason of opening of the escape valve 04 to vent liquid) the pump is immediately operative to deliver oil to the cylinder of the hydraulic device 15, which delivery continues until pressure within the hydraulic element 15 is such as to provide the desired or determined force. During the normal operation of the press, the hydraulic element 15 is always stressed with a force equal to the rated working force of the press plus such overload as that at which the hydraulic element 15 is designed to yield against the reactions on the tools I4 and I5.

A suitable means I30 may be provided for stopping the operation of the press when the hydraulic element 15 yields, as previously described. The means may be similar to that shown and described with reference to'the embodiment illustrated in Figs. 1 to 5 inclusive and include an electrical circuit having a contact I00 on the slide part I0 and another contact I8I on the slide part I0, which contacts are open in the normal position of the parts, and are closed when the hydraulic element 15 yields, whereupon the clutch 63 is operated to disengage the slide I0 from the driving means, as previously described inreference to Figs. l to 5 inclusive.

The motor driven pump I60 is advantageously mounted on the part Il of the slide I0, and

thereby the pipes connecting the pump and hydraulic element be rigid.

In the embodiment illustrated in Figs. 1-5 inclusive, the slide I0 may comprise two parts, I0, l0, having between them a gag connection I90. The gag connection I90 comprises two castellated blocks I9I, I92. One of the castellated 1 blocks, as the castellated block I92 is rotatable with relation to the other, and the two slide parts I0 and I0 are connected by a bolt I93 long enough to allow the castellated blocks I9I, I92 to abut end to end, as shown in Fig. 1. A means I95 is provided for turning the castellated part I92 a. sufiicient amount to bring the notches of the part I 92 opposite the projections I91, of the part I9I, so that the projections I91 may enter the said recesses, and the part I0 of the slide reciprocate without moving the part I 0 of the slide, when it is desired to have the press skip one or morestrokes without stopping the driving mechanism. The weight of the slide part I0 may be counter-balanced in the upper position of the slide by suitable means I99, which as shown in Fig. 1, may comprise a spring I in position between a nut 203 on a rod 205 fastened to a bracket-arm 206 on the slide part 1', and a bracket 208 fixed on the press frame I8. At the back of the ess there is a duplication (not shown) of t e parts 20I to 208. The turning of the part I92 of the gag connection I90 is effected by suitable means, which may be as follows: The part I92 has an arm 2I0 thereon (Fig. 9) which is engaged by a fork 2I2 on a shift-bar 2. One end of the bar 2 I4 may be pivoted to an eccentric pin 2I6 on a pinion 2I8 which engages a rackbar 220. The rack-bar 220 is connected at one end to a pivoted lever 225, which latter lever has a roller 226 on the opposite end which engages a cam 228 on the crank shaft 40. The roller 226 is held against the cam 228 by a spring 230 acting between a bracket 282 on the press frame I6 and a. shoulder 234 on the rack bar 220. A dog 240, connected to a treadle 244 is provided for engaging the shoulder 234 when the rack bar 220 is raised :by the action of cam 228 on lever 225.

' In the normal operation of the press, the part I92 of the gag connection I90 is turned at the upper portion of each stroke, to bring the recess of the castellated part I92 opposite the projections of the castellated part I9l. Unless the treadle 244 is actuated, as soon as the roller 226 runs off of the high point of the cam 228 (which takes place in the upper part of the working stroke) the castellated part is turned back again to bring the projections of the two castellated portions I9I, I92 into end to endabutment. When the tool on the slide part I0. strikes the work, the force of the driving mechanism transmitted to the slide part I0 is transmitted through the gag connection I to the slide part I0=, and the said slide part I0 is rigidly forced downward against the resistance offered against the tools l4 and I 5 by the metal being shaped.

If, however, it is desired to have the slide skip one or more strokes, without stopping the running of the driving mechanism, the operator presses the treadle 244. When the high point of the cam 228 turns the lever 225 and lifts the rack-bar 220, the dog 240 turns to a. position where it engages the underside of the shoulder 234. As the crank shaft 40 continues to turn, the rack bar 220 is held by the dog 240 in the position to which it was raisedby the high point of the cam 228. In this position the castellated which engage threads 261 on the side pieces I,

part I92 is held in a position where the recesses thereof are opposite the projections of the cus tellated part I6I, and as the slide part II moves downward under the action of the crank 48 and connecting rod 4|, the die part II is held in its I raised position by the counter-balancing means I99, the die part I0 moving through a reciprocation without imparting corresponding movement to the slide part I0 because the projections of the castellated part I9I slide idly in the recesses in the castellated part I92. Movement of the slide part I0 with immobility of the die part I0 continues until the treadle 244 is allowed to rise, as by removal of the operator's foot therefrom.

By the use of the gag-clutch, as previously described, in a forging press of the size and rated working force described (or on that order) important advantages are obtained. The inertia of the upper slide-part I0 and of the driving parts and connections does not have to be overcome in stopping and starting the forging operation. These parts can run continuously. A forgingoperation can be skipped merely by shifting the castellated part I92 to bring the projections thereon into line with the recesses in the part I9I, as previously described. The mass of the counterbalanced slide part I0 is the only addition to the masses already in motion, when the forging operation is resumed. By said means, the strain on the driving parts is much less than in the case where the starting and stopping is done through a clutch on the pulley shaft, the horsepower to drive the press may be reduced. and fast forging operations obtained. Fast operation is a prime factor in forging and is often necessary in order to strike a piece of metal before too much cooling has occurred.

To obtain exceptional accuracy of shape or size of a metal part shaped or formed between 40 the tools of the press, means 250 are provided for guiding the slide I0 (or as in Fig. 1, the part I0 of the slide) with extreme accuracy. The guiding means 250 are shown in Fig. 4. The guiding means 250 comprises blocks 252 which 45 are fitted accurately into grooves 254 on each of the side frames I8, I8 and the press. Each of the blocks 252 is provided with a rib 258 having tapered sides which fitsagainst the tapered sides of two pairs-of

ribs

258, 259 on the slide part II. The outside faces of the

ribs

258, 259 contact with the correspondingly tapered sides of two pairs of gibs 26I, 262 fastened on the frame portions I8, I9. Threaded pins 265 are provided 55 I9 of the frame and pass through the said side pieces in the frame to abut against the backs of the blocks 252 which are provided with the ribs 256. By screwing the pins 265 inward the blocks 252 are pressed inward, and the pins 265 provide a means for obtaining an extremely close fit of the ribs 256 against the adjacent sides of the

ribs

258, 259. Other pins 269, threaded into the blocks 252, with nuts at the outer ends, serve to hold the blocks 252 firmly against the ends of the pins 265. Adjustment of gibs 26I, 262 provides a means of obtaining an extremely close fit between the gibs and the outer sides of the

ribs

258, 259.

Rsum of operation 70 If and when the tools I4, I5, on the tool-carry ing parts I0 and I2 meet a resistance exceeding the rated working force of the press applied by the driving mechanism (as for example when, a (s press, or to break the bed or crown), the slidable block 10, Figs. 1 to 5 inclusive, acting through the disk 90 and piston 18, or, the slide part I Figs. 6 to 8 inclusive acting through the piston I42, increases the pressure of the liquid in the cylinder of the hydraulic element 15, which increase of pressure within the hydraulic element 15 opens the escape valve 84, thereby opening the hydraulic system to vent liquid through the escape valve, and allows the block 10, or the slide part I0 to yield. In this way the driving mechanism may continue to run even though the tools I4 and I5 are stalled. The movement of the slidable block Figs. 1 to 5, or of the slide part I0, Figs. 6 to 8, in the manner aforesaid, may be suflicient to enable the crank 40 Figs. 1 to 5, or the crank 50, Figs. 6 to 8, to pass through the dead center, thereby avoiding jamming or breaking of the press. The design of the hydraulic element may be such as to only allow such a limited amount of movement of the block 10 or slide part II] as to make it desirable to stop the press before the dead center position of the crank 40 or crank 50 is reached. Accordingly, after the block 10 has risen a predetermined amount, or the slide part I 0 has moved a predetermined amount with relation to the slide part I0 the clutch 49, Figs. 1 to 5 or clutch 63, Figs. 6 to 8 may be operated to disengage the slide reciprocating parts from the driving means through contacts I32, I34, Figs. 1-5, or I80, I8I Figs, 6 to 8, in the manner previously described. Thereafter the direction of the rotation of the crank shaft may be reversed, the tools I4, I5 backed off from the obstruction, and the obstruction removed.

After the crank 40, Figs. 1 to 5, or crank, 50, Figs. 6 to 8 has either passed through its deadcenter position, or been backed-oil from its dead center position, following an obstruction to the movement of the tools I4, I5 as heretofore explained, the hydraulic element 15 is automatically restored to a stressed condition wherein the force exerted or immediately exertable thereby equals the rated working force of the press plus such excess as may be determined. In the embodiment Figs. 1 to 5 this is accomplished through the motor driven pump 95, pressure-responsive device I06 and switch I08 in the manner previously described. That is, with the pressure in the hydraulic element 15 developing a force equal to the rated working force of the press plus say a ten percent overload, the piston I I2 of the pressure responsive device I06 has shifted the switch arm I I5 of the plate I to the position shown by the dotted lines II6, in which position the circuit to the motor driven pump 95 is open through the contacts I22, I24. When the pressure in the hydraulic device 15 falls a predetermined amount, either through venting of liquid through the escape valve 84, or through leakage, the piston II2 of the pressure responsive device will move a predetermined amount (see dotted line position, Fig. 5), and when it has moved this predetermined amount the switch arm II5 will be moved against the action of the spring II8 to the position shown by the dotted line I26, the switch arm H5 moving the plate I20, and the bridging contact I22 thereon with it so as to complete the circuit to the motor driven pump 95 through the contacts I22, I24. The motor driven pump will continue to operate until a pressure is restored in the hydraulic element 15 which produces a predetermined force in the said bydraulic element 15 as heretofore stated, at which time the pressure responsive device I05 operates to break the circuit to the motor driven pump 95 in the manner already described.

In the embodiment, Figs. 6 to 8 inclusive the parts are restored to normal operating position, following the venting of liquid through the escape valve 84, by the following means. As heretofore stated, the motor driven pump I80 runs continuously. When liquid is vented through the escape valve 04 (or when liquid is lost from the hydraulic element 15 through leakage) the pressure drops, and this drop of pressure also occurs in the pressure responsive device I58. The spring I12 thereupon moves the piston I10, and the movement of the piston I10 moves the barrel I15 of the pump so that its axis is eccentric to the axis of the rotor-drum I11 to a greater or less degree depending on the drop of pressure in the hydraulic element 15. When the axis of the barrel I15 becomes eccentric to the axis of the rotor drum i11, .the pump begins to force liquid into the cylinder of the hydraulic element 15, and continues to force liquid into the cylinder of the hydraulic element 15 until a pressure is built up therein which produces a force equal to the rated working force of the press, plus a determined overload, at which time the increased pressure operating on the pressure responsive device I85 moves the piston I10 against the spring I12 to a position where the axis of the barrel I15 of pump I60 becomes concentric with the axis or the rotordrum I11, at which time delivery of liquid to the hydraulic element 15 by the pump I 60 ceases. The pump then continues to run without delivering liquid to the hydraulic element 15, being ready at anytime upon a fall of pressure in the hydraulic element 15 to resume delivery of fluid thereto.

The press embodiment shown in Figs, 15 and 9, may be operated to skip one or more strokes, without stopping the driving mechanism, through the means and by the operation hereinbefore described, which means include the treadle 244 and gag connection I90.

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

What is claimed is:

1. A press comprising a frame, tool-carrying parts, one a reciprocatory slide, mechanical means for reciprocating said slide, and means for preventing the jamming or breaking of the press when the resistance encountered by the tool-carrying parts approximates the rated working force of the press, said means comprising a hydraulic element arranged to sustain the working force applied by said reciprocating means, means for normally maintaining said hydraulic element under a minimum stress approximating the rated working force of the press so that the press normally operates with the rigidity of its frame, including mechanical means for connecting and holding the parts of said hydraulic element so that they cannot be moved apart by hydraulic force therein, and means opening said hydraulic system to vent at reduced pressure liquid from said hydraulic element when the resistance encountered by the tool-carrying parts and transmitted to said hydraulic element approximates the rated working force of the press and the force under which said hydraulic element is stressed.

2. A press comprising a frame, tool-carrying parts, one a reciprocatory slide, mechanical means for reciprocating said slide, and means for preventing the jamming or breaking of the press when the resistance encountered by the tool-carrying parts approximates the rated working force of the press, said means comprising a hydraulic element arranged to sustain the working force applied by said reciprocating means, means for normally maintaining said hydraulic, element under a minimum stress approximating the rated working force of the press so that the press normally operates with the rigidity of its frame, including mechanical means for connecting and holding the parts of said hydraulic element so that they cannot be moved apart by hydraulic force therein, and means opening said hydraulic system to vent at reduced pressure liquid from said hydraulic element when the resistance encountered by the tool-carrying parts and transmitted to said hydraulic element approximates the rated working force of the press and the force under which said hydraulic element is stressed, and a motor-driven make-up pump for replenishingliquid incidently lost or vented from said hydraulic element.

3. A press according to claim 1, wherein said hydraulic element is positioned between parts of said slide.

4. A press according to claim 2, wherein said hydraulic element is positioned between parts of said slide, and said make-up pump is mounted block carrying said crankshaft, said hydraulic,

element being positioned between said slidableblock and the press-frame.

6. A press according to claim 1, wherein said reciprocating means further comprises a crankshaft, 9. driving gear thereon and a driving pinion, and further comprising a slidable block carrying said crank-shaft and driving gear, said hydraulic element being positioned between said slidable-block and the press-frame, and said pinion being mounted on said frame and meshing with said driving-pinion in a line Joining the centers of the gear and pinion which is perpendicular to the direction in which said block slides when said hydraulic element yields.

7. A press according to claim 2, further comprising a hydrostat responsive to pressure within said hydraulic element and means operated by said hydrostat for starting and stopping said motor at differences of pressure corresponding to the rated working force of the press and a predetermined surplus.

8. A press according to claim 2, wherein said make-up pump is of the variable-delivery type, with zero delivery at a pressure within said hydraulic element which stresses the latter with a force approximating the rated working force of the press.

9. A press according to claim 1, wherein said frame comprises side-pieces and transversepieces adjacent the ends of said side-pieces, interlocking joints between said side pieces and transverse pieces, and tie-rods passing through said side-pieces and holding said transversepieces and side-pieces interlocked, said hydraulic element having its cylinder formed in one of said transverse-pieces.

10. A press according to claim 1, wherein said slide reciprocating means further comprises a crank-shaft, and further comprising a slidable block carrying said crankshaft, and wherein said frame comprises side pieces and transversepieces adjacent the ends of said side pieces, inter-locking joints between said side pieces and transverse pieces, and tie-rods passing through said side pieces and holding said transversepieces and side pieces interlocked, said hydraulic element being positioned between said slidable block and one of said transverse-pieces of the frame.

85 11. A press comprising a. frame, tool-carrying parts, one a reciprocatory slide, means for reciprocating said slide, and a hydraulic element situated in the line of strain between one of the tool-carrying parts and the press frame, mechanical means for connecting and holding the parts of the hydraulic element so that they cannot be moved apart by hydraulic force therein, and means for prestressing said hydraulic element at a pressure which imparts to said hydraulic element a force on the order of the rated working force of the press, and means for opening said hydraulic system to vent at reduced pressure liquid from said hydraulic element when the resistance encountedby the tool-c ryin Parts exceeds the rated working force of the press.

ISAAC PATRICK. WILLIAM m.