US2535842A - Stall relief for forging presses and the like - Google Patents

Description

Dec. 26, 1950 w, w, CRILEY 2,535,842

STALL RELIEF FOR FORGING PRESSES AND THE LIKE Filed Jan. 11, 1945 INVENTOR.

W! LLlAM W.CR LEY mgfw ATTORNEYS Patented Dec. 26, 1950 STALL RELIEF FOR FORGING PRESSES AND THE LIKE William W. Criley, Shaker Heights, Ohio, as-

signor to The Ajax Manufacturing Company, Cleveland, Ohio, a corporation of Ohio Application January 11, 1945, Serial No. 572,307

6 Claims.

The present improvements have regard generally to the driving of a reciprocable ram in forging presses and other like machines wherein a ram is actuated by a crank or eccentric to apply pressure to a work-piece through a suitable die or other tool.

As is well known, one of the serious difiiculties encountered in such a press or like machine is.

the stalling of the ram with the crank or eccentric on dead center, either by excessive stock or too tight setting. In machines of the class described, as at present constructed, in order to resume operation the stalling pressure has to be relieved as by driving back the wedge in the bottom die seat of a press, the ram then backed off and the dies reset.

One principal object of the present invention accordingly is to provide a construction of drive mechanism for use in such machines whereby following stalling of the ram 2. sufficient reverse torque in the driving connections will be built up to automatically cause the ram slightly to withdraw from the work-piece and leave the crank or eccentric off center so that normal operation may be resumed Without any of the difficulties just referred to. A further object is the provision of an improved form of slip connection between the flywheel and the shaft whereon it is mounted, such flywheel and shaft forming a part of such driving connections, so that an accurate torque K setting may be given such friction slip connection.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims, the annexed drawing and the following description setting forth in detail certain means and one mode of carrying out the invention, such disclosed means and mode illustrating, however, but one of various ways in which the principle of the invention may be used.

In said annexed drawing:

Fig. 1 is a diagrammatic representation showing in side elevation a forging press including my present improved driving mechanism therefor;

Fig. 2 is a vertical central section of the principal elements of such driving mechanism, the plane of the section being indicated by the line 2-2 Fig. 1;

Fig. 3 is a similar section on a somewhat larger scale showing one preferred form of slip connection between the flywheel and the shaft whereon it is mounted; and

Fig. 4 is a view similar to Fig. 3 but showing an alternative form of slip connection.

As indicated, a forging press is diagrammatically shown in Fig. l by Way of illustrating the manner of application and mode of use of my improved driving connections. The principal parts of the press appearing in Fig. 1 include a bed or base I and an anvil 2 supported thereon at adjustable height by means of a transversely shiftable wedge 3. Reciprocably mounted above the anvil is a ram 4 which is operated through a pitman 5 by a crank or eccentric 6 on the main shaft 1 of the machine. It has been deemed unnecessary for the purpose in hand to show the framework of the press in which, among other things, suitable guides for the ram t will be provided, or to show the die or dies which will be mounted on anvil 2 and ram 4 in the usual manner.

For convenience the main operating shaft 1 will be hereinafter referred to as a crankshaft, by which term it is intended to connote a shaft provided either with a crank or an eccentric for the purpose of effecting reciprocation of the ram through pitman 5.

Referring now to Fig. 2, said main operating or crank shaft 1, it will be seen, is provided at its one end with a fluid actuated friction clutch 8 that carries a large gear 9, the latter in turn meshing with a pinion ID on the corresponding end of a second, or back shaft II. The particular construction of the clutch 8 forms no part of the present invention, the one illustrated being that shown and described in my Patent No. 2,324,613, dated July 20, 1943. It will be sufficient for the present purpose to state that upon supplying suitable fluid under pressure through conduit I2 centrally connected with the clutch, the large gear 9 will be secured to main shaft 1 so as to cause the latter to rotate under any desired degree of frictional resistance on the part of the clutch. Conversely, by relieving the pressure on the clutch, the main shaft will be immediately disconnected from the drive or back shaft H.

Mounted on the opposite end of said shaft H to that which carries pinion H3 is a flywheel l3 which, as shown in Fig. 1, also constitutes a grooved pulley for the belt l4 whereby such flywheel is adapted to be driven by an electric motor 15. The latter will include, as usual, an overload relay, the construction of which is familiar and need not be described, such relay operating automatically to cut out the motor whenever an excessive load is imposed thereon,

as will be the case should the machine become stalled. However, for the purpose in hand the relay in question will preferably be of the quick acting type so that the motor will be thus thrown out almost instantaneously the moment a severe overload is encountered.

As further shown in Fig. 2, and on a larger scale in Fig. 3, the flywheel It has a friction slip connection with the shaft H on which it is mounted. This connection, in the form illustrated in the figures just referred to, comprises a fixed flange IT on the hub E8 of the wheel and a second flange i9 that is axially movable on such hub. The main body of the wheel includes a web portion 26 which is held between flanges I! and i9 and is frictionally engaged thereby. A series of circumferentially spaced bolts 2! extend through flange l9 and are threaded or otherwise secured in the base of flange l'l. Between a nut 22 on the outer projecting end of each such bolt and the adjacent face of flange [9 are inserted a plurality of Belleville disc type springs 23. The latter are simply discs which have been cupped and are capable of developing very high pressures with limited travel. Preferably, as shown, they will be empioyed in pairs with their cupped faces opposed to each other. The number employed will depend upon the size and other characteristics.

The calibration of the spring under load provides for the accurate torque adjustment of the friction slip hub and for maintaining this adjustment despite slight wear. As a result of the construction just described, it will be seen that by adjusting the nuts 22 on the flywheel clamp bolts 25 the flanges or clamp plates El and i9 may be drawn together so as to exert a definite pressure on the web 253 and thus preload the friction slip connection of the flywheel with drive shaft H so as to give an accurate torque setting on the friction slip.

The friction slip connection must be capable of accurate adjustment as to its frictional engagement so that it correlates several operating characteristics. The resultant correlation is such that, upon jamming of the ram and resultant stalling of the machine, the flywheel imposes a heavy torsional strain on, wind; up, the driven shaft H in the driving direction and yet slips suificiently to maintain this imposed torsional strain, after the machine has stalled and until after the overload relays operate to cut off the motor. At the same time, it is such that the flywheel can be brought to rest abruptly after the overload relays operate instead of continuing at a gradually decrescent value in opposition to the reversed rotation of shaft If during recovery of the shaft from its original torsional stress. These conjoint effects produce in the shaft l I a torsional stress capable of providing a powerful reverse or restoring torque when the opposition of the forwardly driving flywheel and energized driving motor are removed. Since the opposition of the motor and flywheel is removed in sequence, first by cutting out the motor by the relays while the torsional stress is being maintained at a high value by the flywheel, and then secondly by abruptly stopping the flywheel promptly thereafter so that its forward rotating force does not continue in opposition to the restoring torque and reverse rotation to the shaft H, the stored energy of the shaft H is not dissipated in frictional heat. Instead, it is converted fully into counter-torque or counter-rotation "which, under the effect of the flywheel,

which is reversely driven thereby, rotates the gear 9 sufliciently to operate the press in the reversed direction and back up the ram and movable die to relieve the jam. This movement is suflicient so that the jammed metal can readily be removed from between the dies without disassembly of the dies and machine.

Thus, as in the present structure, by properly correlating the frictional engagement of the slip connection and an inertia member, such as the flywheel, with an overload releasing device, such as the overload relays, a stress heretofore considered useless, and in fact undesirable, is utilized to reduce greatly the work heretofore necessitated by jamming of a work-piece in the dies.

In order to appreciate more fully the work necessitated by the jamming of a workpiece in the dies, it is pointed out that in such an instance the usual manner of removing the workpiece is flrst to bump or jar the adjusting wedge beneath the bolster back of the press for relief, If this fails, the next attempt to relieve the jam is to jack the crank shaft off dead center. If the jam is such that it cannot be re li vcd in either manner described, it is sometimes necessary to cut out the dies with a torch, which of course destroys the dies. These methods of relieving the jam are time consuming not only in effecting the relief but in readjusting the dies after the jam has been relieved. It will be understood that the momentum of the flywheel must be sufficiently great to cause it to continue to rotate, its forward direction after the machine has stalled, long enough for the overload relay of the motor to throw out before the flywheel comes to rest so that its reversal will not be opposed by the motor.

In the alternative construction illustrated in Fig. l, coil springs 25 are utilized in place of the Belleville disc type springs 23. Since such coil springs have less pressure capacity and take up considerably more space, I prefer, as previously indicated, to employ the Belleville springs for the purpose of providing such adjustable slip connection between the flywheel and the drive shaft.

Whatever adjustment is made in respect to such flywheel slip connection with its shaft, the torque friction of clutch 8 when in operation should be greater; in other words, the slip connection of the flywheel should yield before that of the clutch.

In operating a press or like machine equipped with the driving mechanism just described, I have found that when the press is stalled, as by excessive stock or too tight setting, the ram will rebound rather than stick on the bottom dead center from which it can be relieved only by driving back the wedge in the bottom of the die seat or otherwise relieving the pressure between the tool carriedby the ram and the work-piece. This result is due to the fact that the flywheel, when connected with the back shaft through a properly adjusted slip connection, has enough energy or forward momentum to continue for at least a partial rotation in the forward direction after the press is stalled and until after the overload relay on the motor has cut the latter out. Enough torque or Wind-up is produced in the back shaft ill by this action of the flywheel so that when the flywheel stops it will be kicked into rotation in the opposite or reverse direction. Since the overload relays have operated to disconnect the motor during the flnal forward, rotation of the flywheel and before it stops, due to .75 the accurate adjustment of the friction slip joint for torque obtained with the structure described, the motor does not apply any torque on the crankshaft when the flywheel is kicked in said reversed direction and the flywheel, being unopposed by the motor, is operative in turn to rotate the crankshaft reversely sufficiently to back up the ram from its stalled position. Accordingly, operation may be resumed without the labor of backing the press off of dead center, resetting the dies, and the like.

While I have described my improved drive mechanism as applied to a forging press, this it will be understood is merely by way of illustration, since such drive mechanism may be equally advantageously employed in other similar types of machines wherein a crank actuated reciprocable ram is employed to apply pressure to a work-piece.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the means and the steps herein disclosed, provided those stated by any of the following claims or their equivalent be employed.

I therefore particularly point out and distinctly claim as my invention:

1. The combination with a mechanism of the character described, including a reciprocable ram adapted to apply pressure to a Work-piece and a rotatable shaft having a crank connected with said ram for reciprocating the same, a second shaft intergeared with said crank shaft, an electric motor having an overload relay for driv ing said second shaft, and a flywheel on said second shaft, of a slip connection between the flywheel and second shaft, such connection being accurately adjusted for torque so that following stalling of said ram the flywheel continues rotation relative to the second shaft until after said overload relay has operated to deenergize the motor and is stopped suddenly thereafter, whereby said flywheel will be kicked into reverse rotation by the torque induced in said second shaft.

2. In mechanism of the character described, the combination with a reciprocable ram adapted to apply pressure to a work-piece, a rotatable shaft having a crank connected with said ram for reciprocating the same, a second shaft intergeared with said crank shaft, a friction clutch included in the gearing connection said shafts, an electric motor having an overload relay for driving said second shaft, a flywheel on said second shaft having a slip connection therewith, of calibrated springs adapted accurately to adjust the torque of such connection and also to maintain, the friction of said slip connection being less than that of such clutch, whereby when said flywheel stops, following stalling of said ram, said flywheel will be kicked into reverse rotation by the torque induced in said second shaft.

3. In mechanism of the character described, including a reciprocable ram adapted to apply pressure to a work-piece and a rotatable shaft having crank connected with said ram for reciprocating the same, the combination of a second shaft intergeared with said crank shaft, an electric motor having an overload relay for driving said second shaft, 9. flywheel on said second shaft, and an accurately adjustable springloaded friction slip connection between the latter and said flywheel, whereby said flywheel may be allowed sufficient forward rotation following stalling of said ram to build up and maintain a reverse torque in said second shaft until after the relay of said motor throws out.

4. In a press including a reciprocable ram, a prime mover, driving means operatively connecting the ram and prime mover, an overload device operative to cause a cessation of the drive of said driving means by the prime mover upon jamming of the ram, an inertia member, a friction slip connection between the inertia member and driving means and having frictional engagement on the inertia member correlated with the overload device to impose the force of the inertia member on the driving means in the driving direction upon jamming of the ram and to maintain said force until after the overload device has operated.

5. In a press including a reciprocable ram, a prime mover, driving means operatively connecting the ram and prime mover, an overload device operative to cause a cessation of the drive of said driving means by the prime mover upon jamming of the ram, an inertia member, a friction slip connection between the inertia member and driving means and having frictional engagement on the inertia member correlated with the overload releasing device to impose the force of the inertia member on the driving means in the driving direction upon jamming of the ram and to maintain said force until after the overload device has operated, and being further operative to stop the movement of the inertia member in the driving direction abruptly after operation of the overload device.

6. A mechanism including a reciprocable ram adapted to apply pressure to a work-piece, a rotatable shaft drivingly connected to the ram for reciprocating the ram, a flywheel on said shaft, a friction slip connection between the shaft and flywheel, and a prime mover drivingly connected to the shaft, and overload means operative to cause a cessation of the drive of said shaft by the prime mover upon jamming of the ram, characterized in that an adjustable resilient means is operatively connected to the flywheel and friction slip connection and causes the friction applied by the connection to be within a range such that the forward torque of the flywheel, upon jamming of the ram, is maintained until after the operation of the overload means.

WILLIAM W. CRlLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS- Number Name Date 424,383 Walker Mar. 25, 1890 1,981,167 Frost Nov. 20, 1934 2,169,747 Treer Aug. 15, 1939 2,288,849 Schmitzer July '7, 1942 Certificate of Correction Patent 2,535,842 December 26, 1950 WILLIAM W. CRILEY It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 5, line 51, for the word connection read connecting;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office. Signed and sealed this 13th day of February, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

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