Optics: measuring and testing – Angle measuring or angular axial alignment
Patent
1994-06-29
1996-01-30
Gonzalez, Frank
Optics: measuring and testing
Angle measuring or angular axial alignment
35613903, 3561521, 36447407, 72 37, G01B 1126, G01C 100, G06F 1546, B21C 5100
Patent
active
054884705
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a bending angle detector for use in a bending machine that detects a specified angle at which a sheet-like workpiece is bent by an upper bender and lower bender.
BACKGROUND ART
There are known bending machines such as press-brakes in which a sheet-like workpiece is bent in such a way that information, such as the thickness and material of the workpiece and a target bending angle, is input in an NC device; the amount of lowering an upper bender (punch) is calculated based on the input information; and lowering of the upper bender is controlled according to the calculated value, whereby a desired product is produced.
In spite of controlling the amount of lowering the upper bender by the use of the NC device as described above, the bending machines often fail in bending a workpiece at a desired angle, because of variations in the characteristics of materials themselves such as thickness, Young's modulus and n-value as well as various bending conditions. One attempt that has been made to solve the above problem is that trial is carried out by manual control of the upper bender prior to real bending in order to determine a control amount for lowering the upper bender and the control amount thus determined is input in the NC device. However, such a fine adjustment of the amount of lowering the upper bender has to be carried out each time a material lot is changed, and it is therefore very troublesome.
In order to achieve high-accuracy bending by eliminating bending angle errors caused by the above-mentioned variations in the characteristics of materials etc., the following solutions have been proposed. data" which can be obtained in the course of bending. From these characteristics, an angle at which the material is bent is predicted. course of bending.
The first method, in which a bending angle is predicted from "load-displacement data" obtained during bending, includes approximation in the process of calculation, because most of the calculation is performed based on the theory of simple bending. Therefore, a satisfactorily accurate result cannot be expected and in fact, the above method has not come into practice yet.
In contrast with the first one, the second method in which the bending angle of a workpiece is directly detected in the course of bending is easy to carry out since a workpiece, i.e., the object to be controlled itself is directly measured and therefore has high feasibility.
Conventionally, there are two types of detecting mechanisms for detecting an angle at which a workpiece is bent. One is the contact-type and the other is the non-contact type.
As one example of the contact-type detecting mechanism, a continuous follow-up angle detector is disclosed in Japanese Patent. Publication Laid Open No. 273618 (1989). In this detector, a rectangular link is utilized and the inclination of a probe being in contact with the inclined surface of a metal sheet (workpiece) is read by an encoder provided in the link mechanism, thereby detecting an angle at which the metal sheet is bent.
As the non-contact detecting mechanism, there is generally known a method in which a plurality of distance sensors are employed for measuring the distance from each sensor to the bent part of a workpiece and the difference between the distances measured is obtained, whereby the bending angle of a workpiece is detected. One example of such a detecting mechanism is disclosed in Japanese Patent Publication Laid Open No. 49327 (1988), in which overcurrent sensors are employed as the distance sensors. Another example is disclosed in Japanese Patent Publication Laid Open No. 2723 (1989) in which electrostatic capacity sensors are employed as the distance sensors. Also, Japanese Patent Publication Laid Open No. 271013 (1989) and West German Patent No. 3216053 disclose the non-contact type detectors in which optical sensors are used as the distance sensors.
However, the above conventional bending angle detecting mechanisms present the following problems.
Firstly, the contact-
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patent: 4672562 (1987-06-01), Egli et al.
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patent: 5298977 (1994-03-01), Shintani et al.
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patent: 5367902 (1994-11-01), Kitabayashi et al.
Eisenberg Jason D.
Gonzalez Frank
Kabushiki Kaisha Komatsu Seisakusho
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