Presses – Automatic or material triggered control – Of actuating means
Patent
1996-08-01
1997-12-30
Gerrity, Stephen F.
Presses
Automatic or material triggered control
Of actuating means
100 53, 100 99, B30B 1528
Patent
active
057018111
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a die protection apparatus for a hydraulic press that acts to prevent a die from being damaged under an excessive load.
BACKGROUND ART
In a hydraulic press for forming a workpiece by the use of a pair of dies which constitute an upper die and a lower die, there has hitherto been encountered a problem that either or both of the dies may be damaged due to an excessive load when locally generated upon the same if a foreign matter, i. e. something other than a workpiece, has been intruded between the upper and lower dies while the workpiece is being formed.
In order to obviate such a problem, there have been proposed a variety of die protection arrangements in the prior art.
For example, in Japanese Examined Patent Publication No. Sho 62-18280 there is disclosed an apparatus for protecting both an upper die and a lower die from an excessive load when it is exerted thereon due to a foreign matter that has been present between these dies of a press in the hydraulic press equipment, which dies are movable in its operating process directions by a booster cylinder piston unit with at least one ram and at least one hydraulic ram drive unit. An apparatus of this class is provided on a press machine frame with a limit switch that is designed to monitor the ram working operation. The apparatus is also provided with a pressure sensor which is arranged on a line of action of the at least one booster cylinder piston unit so that while the ram is being moved in a working direction thereof the pressure sensor may be responsive to an abnormal state in the resistance of such a movement. The apparatus for the hydraulic press equipment for protecting both the upper and lower dies is further provided with a control circuit for effecting a stop of the ram, which circuit is configured to provide an error detection signal when the limit switch is operatively responsive after the pressure sensor has been made operatively responsive.
Also, in Japanese Examined Patent Publication No. Hei 4-45330 there is disclosed a press for forming a thermo setting resinous material, which includes a bed for mounting a lower die thereon, a slide movable up and down for mounting an upper die thereto, a pressure cylinder for moving the said slide downwards, four leveling cylinders mounted, respectively, at the four corners of the above mentioned base and adapted to be detachably into abutting contact with the lower surface of the above mentioned slide, a servo pump for supplying the above mentioned pressure cylinder with an operating fluid, a hydraulic pump for supplying the above mentioned leveling cylinders with an operating fluid, a pressure control valve interposed in a hydraulic circuit between the above mentioned servo pump and the above mentioned pressure cylinder, a servo valve interposed in a hydraulic circuit between the above mentioned hydraulic pump and each of the above mentioned leveling cylinders, a pressure detecting means for detecting a pressure in the above mentioned pressure cylinder and a control means which is designed to control the above mentioned servo valve so as to maintain a balance of the above mentioned slide and which, when the value detected by the above mentioned detecting means reaches a predetermined value, is adapted to switch the control of the above mentioned pressure cylinder from a mode of controlling its velocity by means of the above mentioned servo pump to a mode of controlling its pressure by the above mentioned pressure control valve.
It should be noted, however, that in an apparatus of the former class in which the position of the ram that has been located to a predetermined position is detected by the limit switch and the load that has previously be generated between the upper and lower dies is detected by the pressure sensor to determine a said load to be abnormal when it exceeds a predetermined value. Therefore, an only abnormality in the predetermined location can be detected and if the dies are variously altered there may still develop an inconvenie
REFERENCES:
patent: 4524582 (1985-06-01), Lucas et al.
patent: 4633720 (1987-01-01), Dybel et al.
patent: 5379688 (1995-01-01), Ishii
patent: 5483874 (1996-01-01), Shimizu et al.
patent: 5491647 (1996-02-01), O'Brien et al.
Gerrity Stephen F.
Komatsu Industries Corporation
Komatsu Ltd.
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