Metal deforming – By plural tool-couples – With means to feed work between plural tool stations
Patent
1998-04-16
1999-06-22
Crane, Daniel C.
Metal deforming
By plural tool-couples
With means to feed work between plural tool stations
7240501, 72 1, 1986211, B21D 4305
Patent
active
059139323
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a transfer press and more particularly to a transfer press with a transfer system which includes servo motors as drive sources to transfer 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 the alignment of dies 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.
There is the danger in such transfer presses having a transfer system driven by the individual driving method that the servo motor is brought into a free-running condition in the event of power failure during the operation of the feed bars, which would cause an interference, for instance, between the cross bars and the dies. To reduce the danger, such transfer presses are provided with a mechanism for rapidly bringing the servo motors to a stop in case of power failure.
This transfer system stopping mechanism incorporated in prior art transfer presses will be described with reference to FIG. 4. In FIG. 4, servo motors 50, 50' for driving feed bars (not shown) are connected to an a.c. power source 53 through their respective servo amplifiers 51, 51' and a converter 52. Each servo amplifier 51 (51') is provided with a control circuit 55 for outputting a control signal to a power transmission 54 for each servo motor 50 (50') to control the rotation of the servo motor 50 (50'). Each control circuit 55 is actuated in response to a command signal sent from a controller 56 and to a start signal from a relay logic 57. Each control circuit 55 is supplied with control power (400V) from the a.c. power source 53 and a capacitor 58 is connected to a point on the electric supply line of each control circuit 55 in order to back up the power source 53 in the event of power failure. A regenerative resistance 59 is connected to the converter 52, for consuming, as heat, regenerative energy that is generated during braking of the servo motors 50, 50'.
In the above circuit configuration, if the a.c. power source 53 is interrupted because of power failure, the supply of power to the electric supply line and therefore to the controller 56, control circuit 55 and relay logic 57 is interrupted. When the start signal from the relay logic 57 goes down, the servo amplifiers 51, 51' mask a command from the controller 56 and the internal logic is put in operation to stop the motors. Concretely, the regenerative energy that has been generated during braking of the servo motors 50, 50' is released to the regenerative resistance 59 as indicated by arrow E whereby the energy is consumed as heat to forcibly bring the servo motors 50, 50' to a stop. In order to allow the control circuits 55 of the servo amplifiers 51, 51' to perform the control for releasing the regenerative energy, the control circuits 55 are supplied with energy drawn (as indicated
REFERENCES:
patent: 3701414 (1972-10-01), Mayer
patent: 4449083 (1984-05-01), Beall
patent: 4664247 (1987-05-01), Wolf
Crane Daniel C.
Komatsu Ltd.
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