Presses – Automatic or material triggered control
Patent
1998-07-17
2000-04-11
Gerrity, Stephen F.
Presses
Automatic or material triggered control
100 48, 100344, 100348, 100349, 192129A, 192131R, 192134, B30B 1514, B30B 1526
Patent
active
060476346
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fail-safe automatic sliding operation control apparatus for a press in which the safety of the operator is ensured during sliding operation of the press, and the automatic operation of the slide is made possible.
2. Description of the Related Art
In a press control system, a serious accident may result, should a malfunction occur in the control system. Therefore, it is desired that such a control circuit, which is related to a sliding operation of a press, have a fail-safe constitution. In the following description, the term "fail-safe constitution" refers to those system constitutions for sensors or for control circuits which will never indicate "safety" under a dangerous situation; and those constitutions, in the case of electric/electronic circuits, in which output signals are never generated when a fault has occurred in the circuits.
As shown in FIG. 1, the conventional press has a slide 2 which is reciprocally moved in the vertical direction by means of a crank mechanism (not shown) within a body 1. The slide 2 is located above a bolster 3, and an operation button 4 is provided at the front side of the body 1. Provided between the bolster 3 and the operation button 4 is an optical beam type safety apparatus 5 (referred to as an "optical curtain" hereinafter) for confirming a safe status in the dangerous zone above the bolster 3. Reference numerals 6 and 7 designate metal molds (upper and lower types) which are set on the slide 2 side and bolster 3 side, respectively.
In the operational control for a safety one cycle in such a conventional press, the safe status of the operator is confirmed by means of the optical curtain 5. The slide 2 is lowered only when the operation button 4 is kept pressed by the operator, and the slide 2 is automatically moved upwardly during its rising interval. The operation button 4 is manipulated at each reciprocating motion of the slide 2. Typically, a brake is actuated at a predetermined position in the slide rising interval for each reciprocating motion of the slide 2 so as to confirm the brake function, i.e., to confirm that the slide can be stopped in the vicinity of a top dead center (within a predetermined crank angle range) (overrun monitoring function).
Shown in FIG. 2 is a positional relationship between the optical curtain 5 and the operation button 4 of the press shown in FIG. 1.
In a normal working state, the zone D within a one-dot chain line is a danger zone (as defined according to EN292-1 or ISO/TR12100-1) which is defined by the optical curtain 5 at the front of body 1 and by both sides of the bolster 3. The bolster is typically enclosed by means of block fences for preventing operators from entering the press. This danger zone D is a region determined on the basis of the speed of the slide and a moving speed of an operator, and represents the minimum region required for ensuring the safe status of operators. This region, represented by a distance between the bolster 3 and the optical curtain 5 when viewed from the front of the press, must remain clear, which means that the slide will be suddenly stopped if a hand of the operator enters within this region during the lowering of the slide. Further, the distance L between the optical curtain 5 and the operation button 4 represents a distance by which the hand of the operator should be spaced or drawn from the danger zone D as a re-confirmation of safe status just before the actuation of the slide after the safe status (absence of hand) in the danger zone D has been signaled. The reference character D.sub.N designates a further danger zone which includes the distance L.
The "safety one cycle operation of the press" means that the operator's hands should normally remain outside the danger zone D.sub.N, i.e., the hands should remain on the operation button (or outside the operation button) during the lowering motion of the slide. Thus, in the safety one cycle operation, the optical curtain 5 detects a slide sudden stop cond
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Futsuhara Koichi
Sakai Masayoshi
Shirai Toshihito
Gerrity Stephen F.
The Nippon Signal Co. Ltd.
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