Metal deforming – With indication of condition or position of work – product,... – Including deformation by simple bending
Reexamination Certificate
2000-10-06
2003-06-03
Jones, David (Department: 3725)
Metal deforming
With indication of condition or position of work, product,...
Including deformation by simple bending
C072S031100, C072S389300, C072S389600, C072S319000
Reexamination Certificate
active
06571589
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a bending machine such as a press brake and its operation method, and in particular, to a bending machine that can detect an angle during bending.
BACKGROUND OF THE INVENTION
Conventional bending machines such as press brakes measure a bend angle in line to control it during processing or determine whether or not the bend angle of processed work is appropriate. In these bending machines, an angle measuring instrument for measuring the bend angle in line is generally installed near an upper die and installed in and removed from a bent portion of the work using a measuring instrument inserting and removing mechanism. Some angle measuring instruments have been proposed which have an angle measuring instrument integrated into the upper die.
Some bending machines using the above described measuring instrument inserting and removing mechanism insert a corner contacting member shaped like a parallel link into the bent portion of a work such as a metal sheet and detect a bend angle by using a rotary encoder to measure displacement of a linear position of a linkage section occurring when the corner contacting member comes in contact with a corner forming surface of the work (Japanese Patent Publication Number 2630720). According to this patent, the measurement can be made substantially irrespective of the position of the work and regardless of the effect of variations in the thickness of the work or dimensions of opposite surface of a recessed corner of the work.
Since, however, the displacement of the linear position of the corner contacting member is converted into rotation of the encoder, a possible minor error in a motion converting section of the encoder limits measuring accuracy. Accordingly, it is difficult to further improve measuring accuracy. In addition, the needs for the measuring instrument inserting and removing mechanism in turn require the size of the entire measuring apparatus to be increased, so that it is difficult to install a plurality of angle measuring instruments in order to measure the angle at a plurality of locations spaced in a bending line direction of the work. Such measurements at a plurality of locations are desirable for obtaining through accuracy for bending.
Integrating the above described angle measuring instrument into the upper die facilities installation of angle measuring instruments at a plurality of locations, but due to its three-dimensional shape having certain length, breadth and depth dimensions, the rotary encoder cannot be integrated into a flat part such as the upper die of the press brake. The upper die of the press brake has a thickness of, for example, several millimeters and few angle measuring instruments that can be integrated into such a flat press die without affecting its strength have been used for practical applications.
Examples of proposed angle measuring instruments integrated into the upper die of the press brake insert two scanning elements of different widths into a recessed corner of work to bring opposite ends of each of the elements into contact with corresponding surfaces of the recessed corner and convert a difference in recessed corner advancing depth between the scanning elements, into a bend angle. Each of the scanning elements is shaped like a disc or a rod. The difference in advancing depth is detected by an optical sensor such as a PSD (Position Sensing Detector).
The optical sensor, however, is easily affected by heat and has its measuring accuracy reduced by heat generated during bending. In addition, since the upper die must have a split structure only to integrate the angle measuring instrument thereinto, the upper die has a complicated structure and has its strength reduced, thereby requiring the size of the upper die to be increased to compensate for the complicated structure and the reduced strength.
In addition, the bending of work involves a phenomenon called “spring back” where the bend angle is diminished, though slightly, due to the elasticity of the work, thereby precluding accurate detections or requiring a long period of time for detections. For example, to detect the bend angle after spring back, a bending load must be released. In this case, the position of the work may change and such a change in position must be flexibly dealt with. Consequently, the bending machine with an angle measuring instrument integrated thereinto must be improved and a method for effectively operating such a bending machine must be developed.
Other angle measuring instruments installed in the bending machine are applications of image processing, and irradiate a measured target with a slit light from a semiconductor laser and use a CCD camera to pick up an image of a bent portion to determine its bend angle. These measuring instruments, however, have their measuring accuracy significantly affected by variations in ambient brightness and require a complicated and expensive structure.
It is an object of the present invention to provide a bending machine that can build an angle measuring instrument into a mold to accurately measure an angle during bending.
It is another object of the present invention to enable the angle to be accurately measured without attenuating signals attenuation while eliminating the effects of variations in temperature using a simple structure.
It is yet another object of the present invention to allow an angle measuring instrument to be easily built into a mold by splitting the mold.
It is still another object of the present invention to provide a method for operating a bending machine wherein an angle measuring instrument built into an upper die is used to achieve accurate bending taking spring back into consideration.
SUMMARY OF THE INVENTION
The present invention provides a bending machine for carrying out bending by using a linearly extending male and female dies to sandwich a work therebetween, the bending machine being characterized in that the male die has an angle measuring instrument integrated thereinto for measuring a bend angle of the work bent by the male and female dies and the angle measuring instrument has an inductive linear position detector.
With this configuration, the angle measuring instrument is integrated into the male die to enable angle detections during bending. In addition, the angle measuring instrument advances into a bent portion of the work as the male die is elevated or lowered for bending or the like, thereby eliminating the needs for a mechanism exclusively used to drive the angle measuring instrument forward and backward. The angle measuring instrument has the inductive linear position detector, small accurate inductive linear position detectors have been used for practical applications and enable accurate angle detections when used in the angle measuring instrument. Such a linear position detector can also be easily integrated into a male die comprising a flat press die as in a press brake. Various inductive linear position detectors are available including differential transformers and phase shift detectors.
Specifically, the angle measuring instrument comprises a corner contacting member that comes in contact with opposite sides of a recessed corner resulting from the bending of the work to have its linear position displaced depending on an opening angle between corner forming surfaces and an inductive linear position detector for measuring displacement of the linear position of the corner contacting member.
The linear position detector preferably detects a change in linear position based on a change in phase angle and has a function for using an output from a plurality of coils or impedance means to compensate for a temperature characteristics of a coil for detecting the linear position.
When the position detection is based on a change in phase angle, the position can be accurately detected without being affected by signal attenuation. In addition when the linear position detector has a function for using an output from a plurality of coils or impedance means to compensate for a temperature character
Goto Atsutoshi
Ito Shunitsu
Armstrong Westerman & Hattori, LLP
Jones David
Murata Kikai Kabushiki Kaisha
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