Metal deforming – With randomly-actuated stopping
Patent
1998-04-29
1999-10-26
Crane, Daniel C.
Metal deforming
With randomly-actuated stopping
7240501, 7240516, B21D 4305, B21D 5500
Patent
active
059707631
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a transfer press and more particularly to a transfer press comprising a transfer system for transferring workpieces to be pressed.
BACKGROUND OF THE INVENTION
There are known transfer presses which include a transfer system for conveying workpieces to be pressed through a series of work stations in timed relation with performance of a series of pressing operations. Typically, the transfer system comprises a pair of feed bars juxtaposed so as to extend in a workpiece transferring direction and cross bars each spanned between these feed bars. The transfer system conveys workpieces held by vacuum caps by vacuum adsorption, these vacuum caps being attached to the cross bars. Alternatively, the transfer system conveys workpieces gripped at both sides by fingers attached to the feed bars. In this case, the pair of feed bars perform two-dimensional or three-dimensional movement to transfer an individual workpiece from one station where a set of dies are disposed to the next adjacent station where another set of dies are disposed.
The most typical method for driving the feed bars is a mechanical driving method in which the feed bars are driven, being linked to the press system with a cam and link mechanism. This method however reveals the disadvantage that adjustment at the time of die replacement is extremely difficult and therefore the individual driving method becomes prevailing recently according to which the feed bars are driven with motors (servo motors) different from the motor for the press system. Such transfer presses having a transfer system driven by the individual driving method has the advantage that the transfer system can be changed arbitrarily in its movement and has a simple configuration.
In the transfer press of this type, the transfer system is driven synchronously with the movement of the press slide and is designed to move, drawing a motional trajectory in which interference does not occur between the cross bars etc. of the transfer system and the dies. If a failure occurs in the servo driving systems (e.g., servo amplifiers) during operation of the transfer system, the control of the servo motors cannot be continued. The measure usually taken in the even of such a failure is such that the servo driving systems are disconnected from the servo motors by means of hard logic and then the servo motors are D.C. braked thereby stopping the servo motors immediately. Meanwhile, the press slide of the press system is brought to an emergency stop, by being braked upon detection of a failure in the transfer system. In this way, the press system and the transfer system are independently stopped in the event that a failure occurs in the servo driving systems of the transfer system.
As far as the press slide and the transfer system can be stopped simultaneously in the event of a failure in the transfer system, there is no problem. However, in reality, the transfer system is stopped before a stop of the press slide because the inertia force of the press slide is much greater than that of the transfer system. If the transfer system deflects from the set course of feeding motion during stopping or stops at a wrong position in the case of emergency stop, there will be the danger that the press slide crashes to the transfer system because of the inertia of the press slide, thereby damaging the press dies or transfer system which are very expensive.
In cases where the transfer press is installed in the production line for automobiles for example, the pressing line is situated in the upstream of the welding, painting and assembly lines and therefore the emergency stop of the pressing line would involve and cause a trouble to the overall production line.
The present invention is directed to overcoming the foregoing problems and it is therefore one of the objects of the invention to provide a transfer press which can be continuously driven or safely stopped without loosing synchronization of the transfer system with the press system in the event of a failure in
REFERENCES:
patent: 4133199 (1979-01-01), Shirao
patent: 4540087 (1985-09-01), Mizumoto
Crane Daniel C.
Komatsu Ltd.
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