US3834214A - Forging press - Google Patents

Abstract

A forging press comprises two press rams slidably movable against each other in rigid slide tracks by a drive including, for each ram, two eccentric shafts coupled for rotation in opposite senses, an eccentric carried by each shaft, a respective slide block surrounding each eccentric, an elliptic chuck containing the two slide blocks, a rotatable screw and thrust rod member extending centrally through the chuck between the slide blocks and having at one end screw threads in threaded engagement with screw threads on the associated press ram, and being corotationally connected at its other end to an adjusting gearing. The rod member is axially displaceable relative to the gearing.

Description

United States Patent [191 Kralowetz [451 Sept. 10, 1974 1 FORGING PRESS [21] Appl. No.: 354,389

[30] Foreign Application Priority Data June 9, 1972 Austria 4975/72 [52] US. Cl. 72/407, 72/452 [51] Int. Cl B2lj 9/18 [58] Field of Search 72/402, 403, 404, 407, 72/452 [56] References Cited UNITED STATES PATENTS 3,135,139 6/1964 Kralowetz 72/402 3,224,244 12/1965 Kralowetz .1 72/402 FOREIGN PATENTS OR APPLICATIONS 16,043 8/1889 Great Britain 72/402 Primary Examiner-C. W. Lanham Assistant Examiner-Gene P. Crosby Attorney, Agent, or Firm-Kurt Kelman [57] ABSTRACT A forging press comprises two press rams slidably movable against each other in rigid slide tracks by a drive including, for each ram, two eccentric shafts coupled for rotation in opposite senses, an eccentric carried by each shaft, a respective slide block surrounding each eccentric, an elliptic chuck containing the two slide blocks, a rotatable screw and thrust rod member extending centrally through the chuck between the slide blocks and having at one end screw threads in threaded engagement with screw threads on the associated press ram, and being corotationally connected at its other end to an adjusting gearing. The rod member is axially displaceable relative to the gearmg.

2 Claims, 3 Drawing Figures PAIENIEU SEP 1 man FORGING PRESS This invention relates to a high-speed forging press, which comprises two press rams, which are slidable in rigid slide tracks and to act against each other and are adapted to be driven by eccentric shafts, slide blocks surrounding the eccentrics on said shafts, and elliptic chucks.

In the development of forging presses there is a trend toward larger forging forces and a higher number of strokes per minute so as to obtain larger outputs per hour and forgings of higher quality. A large number of strokes per minute and a small reduction per stroke are required for a uniform forging effect throughout the workpiece and oppose the formation of cracks and discontinuities A larger number of strokes per minute enables the use of a higher forging speed so that even relatively large workpieces can be forged down without intermediate heating because a better utilization is enabled of the time within which the temperature of the workpiece is lowered to the lowest temperature at which the workpiece can be forged. The service life of the tools is of essential significance for the economy and profitability of such forging press and depends mainly on the time of contact between the tool and the workpiece. This time of contact includes the time of the actual deformation and the times in which the machine exhibits a resilient expansion and contraction. Mainly in hydraulic presses the resilient expansion and contraction take more time than the deformation. An increase of the time of contact is accompanied by an increase of the heat quantity which is transferred from the workpiece to the forging tools. The tools may thus be heated until they are red hot and such a high temperature rise will obviously greatly increase the wear of the tools. This large heat transfer from the workpiece to the tool has also a highly adverse effect on the quality of the forging because it results in a premature formation of cracks on the surface and in a depressing of the surface.

For this reason, consideration must be given mainly to the overall resiliency behavior in the design of a high-speed forging press. Before the workpiece can be deformed, the spring excursions must be overcome, and this requires considerable work, which in an amount up to percent must be considered as a loss because only part of the work of elastic strain can be recovered. It will be understood that the spring capacity of the machine must be overcome and that this spring capacity is of decisive influence on the time of contact between the workpiece and the tool and consequently for the service life of the tool and the quality of the forging. As soon as the tool has engaged the workpiece, the continued movement of the tool is opposed by the resistance of the workpiece to deformation. This resistance exceeds the spring capacity of the machine so that the spring excursions which are inherent in the design of the machine must be overcome before the workpiece can be deformed. Throughout this time, the tool is in close contact with the workpiece, and the time of contact is virtually directly related to the spring excursion of the machine, which spring excursion is to be overcome.

For this reason, hydraulic forging presses are highly undesirable because in addition to the mechanical compliance of the various components of the machine, such as rams, press frame, and the likethere is a hydraulic compliance, which is a multiple of the strictly mechanical compliance and is due to the compressibility of the hydraulic fluid used in relatively large amounts, and to the elasticity of the pipelines and containers etc. which are required.

In the previously known, semihydraulic forging presses it has been attempted to solve the problem which is due to the compliance in that the rams are hydraulically driven and mechanical means are used to adjust the stroke position. This enables a saving of large amounts of hydraulic fluid so that the spring excursions can be considerably reduced. These measures do not give satisfactory results, however, in forging presses operating at a particularly high speed and exerting high forging pressures.

As regards work of elastic strain and the spring excursions, the strictly mechanical forging press is most desirable. The forging press is mechanically driven, in most cases by eccentrics, and in its stroke position can be adjusted by mechanical means, so that the spring excursions are within tolerable limits. A comparison of the spring excursions of a mechanical forging press, a semihydraulic forging press and a fully hydraulic forging press shows that the use of a hydraulic fluid adds greatly to the spring capacity. For instance, in a press capable of exerting a force of 1,000 metric tons, the spring excursion is about millimeters in a fully hydraulic plant, about 15 millimeters in a semihydraulic plant, and only 5 millimeters in a strictly mechanical plant. It is apparent from these values that the times of contact vary greatly in the different types of machines.

A great disadvantage of mechanical forging presses, however, is the fact that they permit only of a relatively complicated and closely limited adjustment of the stroke position because separate adjusting housings are required for this purpose and large machine components are needed as the forging forces increase. To enable the use of presently conventional forging forces of up to 3,000 or 5,000 metric tons, the driving eccentric shafts would have to be very large in diameter so that their manufacture would become too difficult and the size of their bearings in the machine and consequently the overall size of the entire machine would become intolerably large. Besides, in such large machines the expenditure involved in the conventional means, such as adjusting housings or the like, required to adjust the stroke position would hardly be justifiable. For this reason, the previously known, strictly mechanical forging presses can be used only to exert small forging forces.

In view of the above it is an object of the invention to avoid the above-described advantages and to provide a high-speed forging press which is of the kind described first hereinbefore and which has a minimum overall compliance, and which is as simple and rugged as possible in structure and in which the stroke position can be adjusted within very wide limits and without accessories involving a large expenditure.

This object is essentially accomplished according to the invention in that each press ram has associated with it at least two eccentric shafts, which are coupled to rotate in opposite senses, and that the associated slide blocks are contained in a common elliptic chuck, which is connected to the press rarn by a rotationally adjustable drive mechanism, which includes a screw, which serves also as a thrust rod and extends between the slide blocks centrally through the elliptic chuck and is rotatable in and axially fixed to said elliptic chuck and is guided at one end in female screw threads of the press ram and at the other end is corotationally connected and axially displaceable relative to an adjusting gearing, preferably a worm gearing. Because this highspeed forging press according to the invention is driven and operated by strictly mechanical means, the spring excursion is minimized and the at least two eccentric shafts provided for each press ram prevent an excessive increase of the dimensions of components of machines designed for exerting large forging forces. The load previously applied to one eccentric shaft is shared by a plurality of such shafts so that machines having components having approximately the same dimensions as before can be used to exert much larger forging forces. The slide blocks which are guided in a common elliptic chuck and which during the reciprocation of the press ram slide toward or apart from each other constrain the screw to move exactly in the axis of the press ram and ensure a steady and reliable operation of the press ram. To enable an adjustment of of the stroke positions, the screw is guided by female screw threads of the press ram so that a rotation of the screw will result in a change of the distance between the elliptic chuck and press ram since the screw is axially fixed and rotatable relative to the elliptic chuck. The adjusting means, i.e., the screw, can be driven because the same carries at its end remote from the press ram a drive wheel, which is part of an adjusting gearing and transmits its rotation to the screw. The drive wheel must be slidable along the axis of the screw so that theadjusting gearing can be mounted in a fixed position and yet the screw can perform its working movement without complications although the adjusting gearing is mounted in a fixed position. In this connection, the term working movement refers to the reciprocating motion which is imparted to the screw by the eccentrics, the slide blocks and the elliptic chuck and which is transmitted by the screw to the press ram. There are virtually no limits to the range in which the press rams can be adjusted because this range depends only on the axial extent of the female screw threads and of the screw-threaded portion of the screw. In spite of the advantages which can be achieved with this machine, the structural expenditure remains within the conventional range and the structure of the machine itself is sufficiently rugged to ensure an operation involving no problems.

An embodiment of the invention is shown by way of example on the accompanying drawing, in which FIG. 1 is a side elevation showing partly in section a high-speed forging press according to the invention.

FIG. 2 is a sectional view taken on line lIII in FIG. 1, and

FIG. 3 is a sectional view taken on line Ill-III in FIG. 1.

The high-speed forging press generally designated 1 has two horizontally guided press rams 2, which act against each other and are slidable in rigid slide tracks 4 in a forging box 3. Two eccentric shafts 5 are associated with each press ram 2 and are coupled for joint rotation by a spur gearing 6. Each of the eccentric shafts 5 comprises an eccentric 7, which is surrounded by a slide block 8. The corresponding slide blocks 8 move with mirror symmetry in a common elliptic chuck 9. The elliptic chuck 9 is connected to the press ram 2 by a mechanism which comprises a screw 10, which is axially fixed in and rotatable relative to the elliptic chuck 9 and which transmits the movement of the elliptic chuck to the press ram. The screw 10 extends centrally through the elliptic chuck and between the slide blocks 8. It is guided at one end in female screw threads 11 of the press ram 2 and at the other end is corotationally coupled to and axially displaceable relative to the adjusting gearing 12, which in most cases consists of a worm gearing.

The high-speed forging press 1 is driven by two synchronized motors 13. Each motor 13 rotates by means of clutches 14, 15 and intermediate gear trains 16 the eccentric shafts associated with a press ram 2 so that the working motion is imparted to the press ram 2. To adjust the stroke position of the press rams 2, the screw 10 serving as a thrust rod is rotated by the adjusting gearings 12, which are also synchronized. This results in a change of the distance between the elliptic chuck 9 and the press ram 2 and consequently in a change of the stroke position. Because the forging press according to the invention is driven by strictly mechanical means, it has only a small overall compliance so that only a small spring excursion must be overcome in each working stroke of the press rams. This affords the advantage that only a small loss is involved as this spring capacity is overcome and that the time of contact between the tool and workpiece is short. This is essential for a high quality of the forgings and for the profitability of the machine.

What is claimed is:

l. A forging press, which comprises a frame,

rigid slide track means carried by said frame,

two press rams, which are slidably movable against each other in said slide track means, each of said press rams having female screw threads,

drive means for driving said press rams, said drive means including for each of said'press rams at least two eccentric shafts, means coupling said eccentric shafts for rotation in opposite senses, two eccentrics, each carried by a respective one of said eccentric shafts, two slide blocks, each surrounding a respective one of said eccentrics, an elliptic chuck containing said two slide blocks, a rotatable screw and thrust rod member extending between said slide blocks centrally through said elliptic chuck and being rotatable in and axially fixed to said elliptic chuck and having at one end screw threads in threaded engagement with said female screw threads of the associated press ram, and

an adjusting gearing,

said screw and thrust rod member at its other end being corotationally connected and axially disadjusting gearing is a worm gearing.

Claims (2)

1. A forging press, which comprises a frame, rigid slide track means carried by said frame, two press rams, which are slidably movable against each other in said slide track means, each of said press rams having female screw threads, drive means for driving said press rams, said drive means including for each of said press rams at least two eccentric shafts, means coupling said eccentric shafts for rotation in opposite senses, two eccentrics, each carried by a respective one of said eccentric shafts, two slide blocks, each surrounding a respective one of said eccentrics, an elliptic chuck containing said two slide blocks, a rotatable screw and thrust rod member extending between said slide blocks centrally through said elliptic chuck and being rotatable in and axially fixed to said elliptic chuck and having at one end screw threads in threaded engagement with said female screw threads of the associated press ram, and an adjusting gearing, said screw and thrust rod member at its other end being corotationally connected and axially displaceable relative to said adjusting gearing.

2. A forging press as set forth in claim 1, in which said adjusting gearing is a worm gearing.

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