Presses – Automatic or material triggered control
Patent
1997-07-29
1998-09-29
Gerrity, Stephen F.
Presses
Automatic or material triggered control
72 211, 72446, 100 48, 100 99, 100231, 100257, B30B 1514, B30B 1526
Patent
active
058133224
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a die height correcting apparatus for a press which enables a high precision press process.
BACKGROUND
The conventional press machine has a slide (or a ram) mounted on a press body and vertically movable on the press body. The machine also includes a bolster (or head) fixed to the press body. The bolster is constructed to place a work between an upper die mounted on the slide and a lower die set on the bolster to perform press work by using the slide to lower the upper die toward the lower die.
In the press machine as set forth above, a distance (die height) from an upper surface of the bolster to a lower surface of the slide must be set to define a predetermined distance between the upper and lower dies each time that a die is changed. The die height must be adjusted with high precision when performing high precision press work.
However, even when the die height is adjusted with high precision before press work, the die height still may vary if so-called mouth opening, which results when the opening formed between the upper and lower jaws of the frame opens, is caused by deformation of a C-shape frame by press load during the press process. When mouth opening occurs and, for example, a coining process is performed, the coining amount may become insufficient, so as to produce a defective product, or the coining amount may become excessive, which damages the die or causes quick wearing.
Therefore, the prior art has proposed various ways to avoid influence on working accuracy when mouth opening is caused in the C-shape frame.
For example, in Japanese Examined Patent Publication (Kokoku) No. Showa 57-44415, there is proposed a stroke adjusting apparatus for a press brake, in which a portal guarder is fixed between frames at a position not influenced by an expansion during the working process. A pair of lower limit stroke control valves are arranged on the portal guarder. Right above these control valves, an actuation mechanism is provided to push valve rods of the control valves to stop an up/down cylinder when the ram is lowered.
Alternatively, in Japanese Examined Utility Model Publication No. Heisei 3-41916, there is proposed a ram guide adjusting apparatus for a press machine, in which sensors for detecting deformation of ram guide in the back-and-forth direction are provided on left and right support frames provided in the vicinity of both C-shaped side frames. By adjusting the ram guide in the back-and-forth direction on the basis of a value detected by the sensors, more precise press work can be performed.
In addition, variation of the die height in the press is caused not only by the occurrence of deformation of the frame due to press load but also by thermal expansion or contraction influenced by temperature variation during press work.
Therefore, there have been proposed various ways to avoid influence of temperature variation on the die height.
For example, Japanese Unexamined Utility Model Publication (Kokai) No. Heisei 2-1599 discloses a temperature sensor that detects a temperature of a press machine. A bottom dead center position correcting apparatus preliminarily stores variation amount of the bottom dead center of the slide corresponding to the temperature of the press machine. The apparatus performs calculation of a correction amount of the bottom dead center position corresponding to a temperature signal from the temperature sensor to control driving of the driving motor on the basis of the result of calculation.
Japanese Unexamined Patent Publication No. Heisei 4-190921 discloses an edge distance correcting apparatus which detects thermal displacements of the frame, upper and lower tables, and upper and lower dies caused by respective temperature variation thereof to perform a correction process for correcting the edge distance between the upper die and the lower die to a preliminarily set value on the basis of respective detection values.
However, the foregoing stroke adjusting apparatus or the foregoing ram guide adjusting apparatus, w
REFERENCES:
patent: 4621517 (1986-11-01), Hatanaka et al.
Gerrity Stephen F.
Komatsu Industries Corporation
Komatsu Ltd.
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