US3229496A - Forging presses - Google Patents

Description

5 Sheets-Sheet f3 IKVBNTOZ. UBHN Fas-val 9.0mm: Cnnc, IM B'w-vmam *BMM J. FOSTER ETAL FORGING PRESSES Jan. 18, 1966 Filed Nov. 14, 1962 Jan. 18, 1966 .1. FOSTER ETAL FORGING PRESSES 3 Sheets-Sheet 2 Filed NOV. 14. 1962 Jan- 18, 1966 J. FOSTER ETAL 3,229,496

FORGING PRES SES Filed Nov. 14. 1962 3 Sheets-Sheet 5 INVENTORS L/afm/ @sz-5,2

United States Patent O 3,229,496 FORGING PRESSES John Foster and Ronald Grace, Openshaw, Manchester, England, assignors to B. de S. Massey & Sons Ltd., a corporation of Great Britain, Northern Ireland, and Isle of Man Filed Nov. 14, 1962, Ser. No. 237,679 Claims priority, application Great Britain, Nov. 1961, 40,792/61 13 Claims. (Cl. 72-429) This invention concerns forging presses and in particular although not exclusively, forging presses adapted to operate at high speeds.

As is generally known forging presses consist basically of a framework within which is slidably mounted a ram, movement of which is derived from an eccentric shaft mounted in bearings in the upper region of the frame. A bolster is located at the lower end of the frame. The ram and the bolster are arranged to carry dies. The eccentric shaft of the press carries at one end a driving gear wheel, or heavy flywheel and at the other end there may be a brake. The ram is connected to the eccentric shaft by means of a heavy connecting rod having, at the eccentric end a big end bearing and at the ram a little end bearing,

As will be appreciated the bearings in a forging press are subjected to very high stresses during their working life and any slackness in the bearings results in sloppy working.

It will also be appreciated that when the pres-s is in operation the lower region of the big end bearing, and the upper regions of the eccentric bearings, together with `the lower region of the little end bearing of the connecting rod are subjected to very high forces as pressure is applied to a workpiece since the reaction in these parts is all in the upward direction.

`If there is any slackness in the bearings the result of the above reaction is to cause the bearing surfaces to hammer together thereby increasing the wear on the bearings and eventually causing breakdown thereof.

To counteract the above effect it has been the practice to attempt to maintain an oil film on the bearings which will serve as a cushion but when some wear has occurred in the bearings this cushion is inadequate and rapid deterioration occurs.

In order to reduce loading on the bearings it has also been the practice to balance the ram statically by means of an air cylinder and piston which in effect, continuously applies a lifting force on the ram which is equivalent to its weight.

It has been appreciated by the applicants that the greatest load is applied to the bearings when the forging operation has reached its final stage since in this case the flash thickness of the forging may only Lbe one sixteenth of an inch thick and the pressure is applied to the workpiece with the connecting rod almost at bottom dead centre and that at this point the rate of deceleration of the ram assembly is at a maximum and this deceleration in a high speed press may be substantially equal to g thus the upward force necessary to maintain bearing contact, taking into account the weight of the reciprocating parts themselves may be substantially equal to 2g When there is wear in the bearings of known presses the ram strikes the forging, in effect freely, until all clearance in the bearings has been taken up and the full pressure is applied to the workpiece by the eccentric. In terms lof time the interval between the ram striking the blow freely and the full pressure on the work- 3,229,496 Patented Jan. 18, 1966 'ice piece applied by the eccentric is very small but the resultant effect on bearing life, heating of the dies and the chilling effect on the forging is large. This effect is very pronounced where the final forging stage is virtually a coining operation because the forging is now effectively only the thickness of the flash (the remaining thickness being substantially catered for by the dies) and the ternperature of the forging has considerably reduced so that the flow characteristics of the metal have considerably changed from the first time pressure was applied on a hot, thick, relatively easily flowing metal workpiece.

In practice the last stroke may only reduce the flash thickness by a few thousandths of an inch and thus accurate control of the stroke is essential. This cannot be achieved if the bearings are Worn and the action of the ram is sloppy.

It has been suggested that the ram could be in effect statically overbalanced by the air cylinder arrangement so that, `assuming the ram has a weight of six tons, it could be statically overbalanced by an additional six tons but such a press would not be a practical proposition because of the extra power that would be required to drive the ram downwards and as a result, presses are not constructed in this way.

A `further reason for not overbalancing the ram in the manner just suggested lies in the fact that, in such an arrangement, should inching be required under certain circumstances, the rarn would rise and thus inching would be impossible.

The object of the present invention is to provide .a forging press in which the disadvantages above referred to are overcome, or at least substantially overcome so that the stroke control can be accurately controlled and wear in the bearings considerably reduced.

According to the present invention there is provided a forging press in which in addition to static balancing of the ram there i-s provided dynamic balancing of the ram and pre-loading of the eccentric bearings, the dynamic balancing being arranged to become operative just prior to the application of pressure to the workpiece and to remain operative until the pressure is relieved by the commencement of upward movement of the ram.

Preferably there is provided a dynamic balancing arrangement including a connecting-rod connected to the ram and to a piston contained, for example, in a pneumatic cylinder, the arrangement being such that the ram is subjected to an upward force equivalent to its weight during the major part of its downward travel, there being, adjacent to the lower end of the cylinder a plurality of balancing fluid escape port-s arranged to allow for very free escape of balancing fluid during the major portion of the downstroke of the ram, the ports being arranged to be closed by the piston to prevent escape of balancing fluid during the latter part of the downstroke of the ram whereby compression of the fluid, and consequent dynamic balancing of the ram is achieved.

Preferably the eccentric shaft is pre-loaded at each end by means of a fluid cylinder, for example, a multi-piston cylinder, the piston or pistons thereof being attached by means of a single connecting rod to a bearing cage for anti-friction race or races mounted upon the eccentric shaft.

In an alternative construction the eccentric shaft bearings are pre-loaded at each end by resilient means consisting of a pack of spring discs, or a coil spring or the like, the resilient means being connected to a bearing cage for anti-friction race or races mounted upon an eccentric shaft.

The invention will be described further, by Way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a part sectional View of part of a forging press made in accordance with the invention,

FIG. 2 is a detail of part of the press shown in FIG. 1 and FIG. 3 is av detail view of another part of the press shown in FIG. 1.

In the following description only those parts of a forging press which relate to the invention will be referred to.

Referring to FIG. l it will be seen that across the upper end of the side frames of a forging press is mounted an eccentric shaft 10, the shaft being mounted in Phosphor bronze bearings 11. In the central region of the eccentric shaft is formed an eccentric 12 upon which is mounted the end of a connecting rod 13 in which is provided a Phosphor bronze big-end bearing 14. The other end of the connecting rod 13 is provided with a little end bearing 15 and carries the ram 16.

The eccentric shaft 10 is pre-loaded so that, at all times, it tends to run on the upper region of the Phosphor bronze bearings 11. There is in practice, an oil lm between the bearings 11 and the eccentric shaft 10.

At the end of the eccentric shaft 10 upon which is mounted the combined clutch and flywheel 17 and as shown in FIG. 2, there is provided around the shaft 10 a pair ofl ball races 18. The ball races 1S are mounted in an annular carrier 19 to which are secured two connectors 20. The connectors 20 are spaced apart by a spacer ring 21. Between the connectors 20 and above the eccentric shaft 10 is a link member 22. The connectors 20 and the link member 22 are bored to receive the connector pin, generally indicated at 23, which is substantially cylindrical in shape but whose diameter has three barrel shaped sections 24 along its length so that at the centre of the bore in the two connectors 20 and the link member 22 the diameter of the connector pin is greater than at the edges of the connectors 2i) and the link member 22 and is in fact substantially the same diameter as the bore of the connectors 20 and link member 22. The connector pin is held in position by the provision of end plates 23a, secured to the outer faces of the connectors 20 to blank off the bores therein.

The link member 22 is connected to the piston rod 25 of an air cylinder 26 having a number of spaced apart pistons 27 in tandem.

The arrangement above described with slight modifications as shown in FIG. 3 is also provided at the end of the eccentric shaft 10 which carries the usual brake 28 but since the load on this end of the shaft 10 is substantially less than that at the clutch and flywheel end only one ball race 29 is provided. In this case the air cylinder 30 requires fewer pistons 31. Since only one bearingA 29 is provided there is only one connector 32 and the connector pin 33 has only one barrel shaped section 34. A link member 35 connects the connector 32 to the piston rod 36 of the air cylinder 30.

The` reason for the connector pin 23 having the shape above described lies in the fact that the loading on the bearings 18 at the flywheel end of the shaft 10 is to be evenly distributed and therefore by virtue of the rocking motion which can occur between the connectors 20 andthe link member 22 the total loading on the ball races 18 is automatically evenly distributed on the ball races 18.

The construction above described is used in view of the high cost and difficulty experienced in producing matched bearings which of course, could be used as an alternative to the ball races used if it were a commercial proposition.

In use, air is supplied to the air cylinders 26 and 30v at sufficient pressure to maintain the eccentric shaft 10 hard up against the upper region of its Phosphor bronze bearings 11 during operation of the press.

The air cylinders 26 and 30 above referred to may be replaced by resilient means such as a coil spring or pack of spring washers or the like and in this case mechanical loading of the spring or washers would be provided.

In a further alternative hydraulic cylinders operated with oil could be used in place of the air cylinders 26 and 30.

The ram is balanced statically and dynamically by means of an air cylinder 37 having provided therein a connecting piston 38 which is connected to a piston rod 39, the latter being itself connected to the ram 16. Air at the required pressure is supplied to the air cylinder 37 from an air chamber 41 by means of a conduit not shown.

In the lower region of the cylinder 37 is provided a ring of ports 40 which communicate with the air charnber 41. The base of the cylinder 37 is provided with a bypass valve 42 which also communicates with the air chamber 41. The by-pass valve 42 is normally closed but becomes operative when inching of the ram is necessary, as will herein be referred to.

In normal use of the press the air pressure in the air cylinder 37 is such as statically to balance the ram 16 and for the major portion of the downward stroke of the ram 16 this pressure remains constant since air can escape through the ring of ports 40 to the air chamber 41 as the piston 38 descends.

Towards the end of the stroke the piston 38 overruns the ring of ports 40 and traps air in the cylinder 37. Continued downward movement of the ram 16 and piston 38 compre-sses the air and effectively overbalances the ram 16 thereby causing any slackness in the big and small end bearings 14 and 15 of the connecting rod 13 to be taken up.

When the pressure is applied to the workpiece therefore there is no sloppiness in the bearings 11, 14 and 15 and a controlled blow is achieved. This is most important when final forging is taking place, since the full pressure on the workpiece is in effect taken for the purpose, in many cases, of reducing the thickness of the forging by only a few thousandths of an inch.

If, as is often the case in known arrangements, there is clearance in the bearings, an initial blow is struck with the ram in effect falling freely, the full pressure on the workpiece only being effective when all the clearance has been taken up.

It has in fact, been known for there to be suicient clearance in the bearings for the ram to be able to effect a heavy blow on the dies when no forging was located therebetween.

In the press according to the above description, the tendency for wear to occur in the bearings is reduced because of the provision of the pre-loading arrangement and the ability dynamically to balance the ram just before pressure is applied to the workpiece. Obviously wear will occur but this is reduced substantially and in any event sloppiness in the bearings is prevented by virtue of the pre-loading and balancing of the ram.

When inching of the ram is required by the by-pass valve 42 in the base of the air cylinder 37 is opened, preferably automatically by operation of the inching control, and thus even when the ring of ports 40 has been closed, air can escape from the volume of the cylinder 37 below the piston 38 through the valve 42. The result of the opening of the valve 42 and the consequent escape of air from the cylinder 37 is that insuicient pressure is built up in the cylinder to hold the ram or cause it to rise ,as referred to herein, thus inching (i.e., slow, short movements of the ram) can be achieved.

Throughout the specification references have been made to the ring of ports being in the lower region of the air cylinder. It should be appreciated however, that the dynamic balancing is required when the ram is about to apply pressure to the workpiece so that if the forging is one which, when finished is relatively thick it is possible to arrange for the ports to be located anywhere along the cylinder. However, since the cylinder length will be comparable with the length of stroke of the ram 13 the ports 4G should always be in the lower half of the cylinder and thus the term lower region of the cylinder should be construed in the light of this possibility.

We claim:

1. A forging press including a framework, a ram slidably mounted in the framework, an eccentric shaft mounted in the framework and attached to the ram by means of a connecting rod, end bearings on the connecting rod for said eccentric shaft and said ram, static and dynamic balancing means for said ram, said static and dynamic balancing means including a cylinder, a piston in said cylinder, a connection between said cylinder and said ram, an operating fluid chamber, a connection between said chamber and said cylinder whereby free escape of an operating iiuid is allowed over a proportion of movement of said piston and is thereafter prevented to achieve dynamic balancing, said dynamic balancing to become operative just prior to the impingement of said ram on a workpiece and to remain operative until the commencement of an upward stroke of said ram.

2. A forging press including a framework, a ram slidably mounted in said framework, an eccentric shaft mounted in the framework and attached to said ram by means of a connecting rod, end bearings on the connecting rod respectively for said eccentric shaft and said ram, a connecting-rod connected to said ram, a cylinder, a chamber in open communication with said cylinder, a piston in said cylinder connected to said last-mentioned connecting-rod, a plurality of ports in said cylinder in the lower region thereof arranged to allow free escape of uid from said cylinder into said chamber during downward movement of said piston until said piston overrides said ring of ports, the arrangement being such as to statically balance said ram until said ring of ports is overrun by said piston and thereafter dynamically balance said ram due to compression of said fluid, cornpression of said iluid occurring during the latter stages of downward movement of said piston and being edective until said ports become uncovered by upward movement of said piston.

3. A forging press as set forth in claim 2 in which said cylinder is supplied with air as the balancing fluid.

4. A forging press as set forth in claim 2 in which said cylinder is supplied with hydraulic oil as the balancing fluid.

5. A forging press including a framework, a ram slidably mounted in said framework, an eccentric shaft mounted in the framework and attached to said ram by means of a connecting rod, end bearings on the connecting rod respectively for said eccentric shaft and said ram, a connecting rod connected to said ram, a cylinder, a chamber in open communication with the cylinder, a piston in said cylinder connected to said last-mentioned connecting-rod, a plurality of ports in said cylinder in the lower region thereof arranged to allow free escape of tluid from said cylinder into said chamber during downward movement of said piston until said piston overrides said ring of ports, the arrangement being such as to statically balance said ram until said ring of ports is overrun by said piston and thereafter dynamically balance said ram due to compression of said fluid, compression of said uid occurring during the latter stages of downward movement of said piston and being effective until said ports become uncovered by upward movement of said piston, said eccentric shaft being preloaded at each end.

6. A forging press including a framework, a ram slidably mounted in said framework, an eccentric shaft mounted in the framework and attached to said ram by means of a connecting rod, end bearings on the connecting rod respectively for said eccentric shaft and said ram, a connecting rod connected to said ram, a cylinder, a piston in said cylinder connected to said last-mentioned connecting rod, a plurality of ports in said cylinder in the lower region thereof arranged to allow free escape of fluid from said cylinder during downward movement of said piston until said piston overrides said ring of ports, the arrangement being such as to statically balance said ram until said ring of ports is overrun by said piston and thereafter dynamically balance said ram due to compression of said fluid, compression of said iiuid occurring during the latter stages of downward movement of said piston and being effective until said ports become uncovered by upward movement of said piston, one end of said eccentric shaft being pre-loaded by means of a multi-piston cylinder, said pistons having a piston rod connected to a pair of connecting rods, a pair of anti-friction bearings on said eccentric shaft, an annular cage for said anti-friction bearings, a link member connecting said last-mentioned connecting rods and said piston rod, a connector pin through said connecting rods and said link member and means for supplying pre-loading fluid to said cylinder.

7. A forging press as set forth in claim 6 in which said connecting pin is substantially cylindrical, there being three barrel shaped sections thereon, the diameter at the centre of each of said barrel shaped sections being substantially the same as the diameter of the bore in said connecting rods and said link member through which said pin extends.

8. A forging press including a framework, a ram slidably mounted in said framework, an eccentric shaft mounted in said framework and attached to said ram by means of a connecting rod, end bearings on the connecting rod respectively for said eccentric shaft and said ram, a connecting rod connected to said ram, a cylinder, a piston in said cylinder connected to said last-mentioned connecting rod, a plurality of ports in said cylinder in the lower region thereof arranged to allow free escape of iluid from said cylinder during downward movement of said piston until said piston overrides said ring of ports, the arrangement being such as to statically balance said ram until said ring of ports is overrun by said piston and thereafter dynamically balance said ram due to compression of said uid, compression of said uid occurring during the latter stages of downward movement of said piston, and being effective until said ports become uncovered by upward movement of said piston, one end of said eccentric shaft being pre-loaded by means of a multi-piston cylinder, said pistons having a piston rod connected to a pair of connecting rods, a pair of anti-friction bearings on said eccentric shaft, an annular cage for said anti-friction bearings, a link member connecting said connecting rods and said piston rod, a connector pin through said connecting rods and said link member and means for supplying pre-loading iiuid to said cylinder, the other end of said eccentric shaft being preloaded by means of a cylinder, a piston in said cylinder having a piston rod connected to a connecting rod, an anti-friction bearing on said eccentric shaft, an annular cage for said anti-friction bearing, a link member connecting said connecting rod to said piston rod, a connector pin through said connecting rod and said link member and means for supplying pre-loading fluid to said cylinder.

9. A forging press as set forth in claim 8 in which said connecting pin passing through said single connecting rod and said link member is substantially cylindrical there being one barrel shaped section on said connecting pin the diameter of which at the centre of the barrel is substantially equal to the diameter of a bore in said connecting rod.

10. A forging press as set forth in claim 8 in which said pre-loading fluid is air.

References Cited by the Examiner UNITED STATES PATENTS Bassett 308-184 Criley 10-15 Reed 78-42 Friedman 10-15 CHARLES W. LANHAM, Primary Examiner.

10 WILLIAM J. STEPHENSON, Examiner.

Claims (1)

1. A FORGING PRESS INCLUDING A FRAMEWORK, A RAM SLIDABLY MOUNTED IN THE FRAMEWORK, AN ECCENTRIC SHAFT MOUNTED IN THE FRAMEWORK AND ATTACHED TO THE RAM BY MEANS OF A CONNECTING ROD, END BEARINGS ON THE CONNECTING ROD FOR SAID ECCENTRIC SHAFT AND SAID RAM, STATIC AND DYNAMIC BALANCING MEANS FOR SAID RAM, SAID STATIC AND DYNAMIC BALANCING MEANS INCLUDING A CYLINDER, A PISTON IN SAID CYLINDER, A CONNECTION BETWEEN SAID CYLINDER AND SAID RAM, AN OPERATING FLUID CHAMBER, A CONNECTION BETWEEN SAID CHAMBER AND SAID CYLINDER WHEREBY FREE ESCAPE OF AN OPERATING FLUID IS ALLOWED OVER A PROPORTION OF MOVEMENT OF SAID PISTON AND IS THEREAFTER PREVENTED

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