Presses – Automatic or material triggered control – Of actuating means
Patent
1996-10-30
1998-10-20
Gerrity, Stephen F.
Presses
Automatic or material triggered control
Of actuating means
72 199, 72 215, 72427, 7245307, 100218, 10026909, 10026914, 10026917, B30B 1516, B30B 1504, B30B 132
Patent
active
058231048
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a press for cold working of metal workpieces, said workpieces being intended to be given a shape with close tolerances by embossing, deep-drawing, extruding, calibrating, hobbing, or precision-cutting machining, especially a coin or medal embossing press for embossing coins or medals with high surface quality.
2. Description of the Prior Art
Presses having a hydraulic-powered drive and a double-acting linear hydraulic cylinder for example, that can develop shaping forces between 10.sup.6 and 10.sup.8 N, are generally known and described in detail for example in the scientific and technical textbook "Staten und Pressen" Munich 1973, second edition, pages 352 et seq.
In the usual design of such presses, with the working area mounted at the approximate height of an operator's chest for both design and ergonomic reasons, the drive cylinder with whose piston the upper tool of the press, an embossing punch for example, is firmly and releasably connected by its tool holder, is located above the working area, while the lower tool that acts as a counterbearing for the workpiece to be machined is mounted on a tool holder that defines the working area at its underside, said holder forming the counterbearing for the workpiece to be cold worked.
The press frame, which must accept the reactive forces that develop during the shaping operation of the press with a degree of intrinsic deformation that is as small as possible, is usually designed as a frame that is self-contained and whose basic shape is rectangular, said frame comprising a yoke on the drive side, a yoke on the counterbearing side, and lateral cheeks connecting said yokes, with the drive cylinder being mounted inside the frame on the underside of the yoke on the drive side, and the tool holder for the lower tool being supported axially on the lower yoke of the press frame on the counterbearing side.
One disadvantage of the known design of hydraulically driven presses as explained above is the relatively large lateral extent of the press frame, measured at right angles to the central lengthwise axis of the driving hydraulic cylinder, with the cheeks of said frame, projecting laterally on the driving hydraulic cylinder housing, having to be located a relatively long distance from one another, so that significant bending moments develop in the areas of both the drive-side yoke and the counterbearing-side yoke of the press frame as well as in the cheeks that connect the two yokes, said moments being resisted only by appropriate increases in the cross sections of the yokes. The cheeks also undergo considerable elastic elongation under the influence of the press forces, said elongation resulting in additional energy consumption because a considerable portion of the installed power is required to pretension the press frame so that the press forces can be transmitted to the workpiece.
When presses of the known design are used to emboss coins, said coins being intended to have a constant thickness, this goal is accomplished by limiting the impact with the aid of fixed stops, which must be adjusted precisely, located on both sides of the embossing area but with additional lateral space being required as a result of such stops being provided, requiring a corresponding widening and reinforcement of said press frame.
For adjusting the stops to a preset thickness of coins whose embossing also requires a specified minimum force, time-consuming adjustment and embossing tests are required before continuous embossing operation can begin.
SUMMARY OF THE INVENTION
Hence, the goal of the invention is to improve a press of the species recited at the outset in such fashion that, assuming that the press is designed for a specific maximum press force, the press frame is subjected to smaller axial and lateral deformations during press operation with a design that is nevertheless lighter and less bulky, and that it also permits, in addition to pressure-controlled operation without requiring fixed stops,
REFERENCES:
patent: 3138976 (1964-06-01), Robra
patent: 3196647 (1965-07-01), Schneider
patent: 3205790 (1965-09-01), Bollar
patent: 4098105 (1978-07-01), Fullers et al.
patent: 4127019 (1978-11-01), Vasilkovsky et al.
patent: 4831861 (1989-05-01), Hofmann et al.
Beisel Winfried
Budenbender Dieter
Groos Heinz
Kutscher Hans-Werner
Schulze Eckehart
Gerrity Stephen F.
Grabener Pressensysteme GmbH & Co. KG
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