JPH0367767B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a press brake that can correct the amount of deflection in the center of an apron depending on the length of a workpiece material.

(Prior art) Generally, when bending is performed using a press brake of the type in which hydraulic mechanisms for raising and lowering the moving apron are located on both sides of the moving apron, the tensile strength, elastic limit, descending point, elastic modulus, etc. of the workpiece material are Forces that resist bending, such as spring back characteristics based on these characteristics, appear as drag forces, which have a significant impact on the finished product.

In other words, in press brake bending work that uses relatively long upper and lower dies, the force that presses the lower dies is located on both the left and right sides of the movable apron to which the lower dies are attached, and the fixed apron that supports the upper dies is placed on both sides. , the moving apron tends to warp downward and the stationary apron tends to warp upward near the left and right centers of the press brake during bending.
As a result, the moving apron and the fixed apron tend to move away from each other in opposite directions near the center,
The bent product has a so-called boat shape, which means that even if both sides are bent accurately, the center part will be incompletely bent, and the product may have bends in opposite directions near the center part. Causes warping.

(Problem to be Solved by the Invention) Conventionally, as a countermeasure to this type of problem, the central part of the moving apron has been made high to counteract the bending moment concentrated at the center. but,
This method is based on the premise that the upper surface of the moving apron and the lower surface of the stationary apron are both horizontal, and ignores the bending resistance characteristics of the workpiece to be bent. Furthermore, since a completely rigid body is impossible, for example, even if the warpage of the movable apron and fixed apron during the final bending process is corrected in advance, it may be possible to adapt to a certain value of bending resistance, but when the bending resistance is He still couldn't stop his tendency to become boat-shaped when it came to things.

Furthermore, even if it is possible to prevent a product of a certain shape from becoming boat-shaped, when processing another product with a different length of the workpiece material, the amount of deflection of the apron will be different, so the same deflection will occur. It is desirable to be able to prevent the occurrence of boat shapes in the processing of products of all shapes and sizes without being able to apply corrections.

This invention was made in view of such conventional problems, and includes a pressure control device installed in a hydraulic cylinder in the center of the apron to correct the amount of deflection of the apron according to the length of the workpiece material. The purpose of this invention is to provide a press brake.

(Example) Hereinafter, examples will be described in detail using the drawings. First, the overall configuration of the press brake will be described in order to facilitate understanding.

FIG. 1 shows the entire press brake according to the present invention. With this press brake,
The upper apron 1 with the upper mold is fixed at a predetermined height, and the lower apron 3 with the lower mold is raised and lowered by hydraulic cylinders 5 and 7 provided on both sides, approaching and moving away from the upper apron 1. can.
A hydraulic cylinder 9 for deflection correction is provided at the center bottom of the lower apron 3.

A connecting rod 11 is attached to this hydraulic cylinder 9, and the outer end of the connecting rod 11 connects to the lower apron 3.
The upper surface of the lower apron 3 can be curved upward when the hydraulic cylinder 9 is driven.

FIG. 2 shows a system diagram of an embodiment of the invention. Hydraulic cylinders 5 and 7 for the pressurizing mechanism of the lower apron 3 are connected by a pump P from piping L ₁ to piping L ₂ ,
Pressure oil is sent through _L3 , and the hydraulic cylinders 5 and 7 are driven up and down by this pressure oil. Further, pressure oil is sent from the pump P to the hydraulic cylinder 9 for deflection correction through a pipe L ₁ , a variable pressure reducing valve V such as an electromagnetic proportional pressure reducing valve, and a pipe L ₄ .

In this embodiment, in order to bend the central part of the lower apron 3 into a convex shape according to the deflection of the upper apron 1, strain detectors SG1 and SG2 are provided on the upper apron 1 and the lower apron 3, respectively.
1. The central part of the lower apron 3 is bent by a hydraulic cylinder 9 so that SG2 maintains a constant relationship.

The distortion detection signals from the distortion detectors SG1 and SG2 are amplified by amplifiers Amp1 and Amp2 and input to the comparator Cmp. A signal is issued to reduce the amount of decompression, and the amplifier
It is input to the pressure reducing valve V via Amp3. Conversely, if the strain on the upper apron 1 is small, a signal is issued to command a large amount of pressure reduction so that the amount of pressure reduction is increased accordingly and the strain on the lower apron 3 is also reduced.
It is input to the pressure reducing valve V.

In this embodiment, if the bending length of the workpiece material is short, the deflection strain of the upper apron 1 is large;
The longer the bending length, the smaller the deflection distortion, so the amount of deflection of the lower apron 3 can be corrected according to the bending length.

This invention is not limited to the above-mentioned embodiment, and for example, the following modifications are also possible.

(A) A hydraulic cylinder for pressurizing the apron shall be installed on the upper apron.

(B) A hydraulic cylinder shall be installed on the upper apron to compensate for the deflection in the center of the apron.

(C) Hydraulic cylinders for pressurization and compensation shall both be installed on the upper apron side.

As can be understood from the description of the above embodiments, this invention is equipped with a hydraulic cylinder that can adjust the pressure to compensate for the deflection of the apron, so the bending length of the workpiece material changes and the shape of the apron deflects. Even when there is a change, the deflection of the apron can be corrected at will. Therefore, according to the present invention, the product can be bent without becoming boat-shaped.

[Brief explanation of drawings]

FIG. 1 is a front view of a press brake used in an embodiment of the invention, and FIG. 2 is a system diagram of an embodiment of the invention.

Claims (1)

[Claims] 1 A fixed apron 1 fixed to a frame and a movable apron 3 provided so as to be freely raised and lowered, and hydraulic cylinders 5 and 7 for raising and lowering the movable apron 3 are provided near both sides of the movable apron 3. , the hydraulic cylinder 9 for apron deflection correction is installed on the fixed apron 1 or the moving apron 3.
The press brake is installed almost in the center of the apron, and the variable pressure reducing valve V can freely control the pressure _P2 of the pressure oil supplied to the hydraulic cylinder 9 for deflection correction, and the fixed apron 1 can adjust the distortion according to the deflection of the fixed apron 1. a first strain detector SG1 for detecting a strain; a second strain detector SG2 for detecting strain according to the deflection of the moving apron 3;
a comparator Cmp that compares strain detection signals of the first and second strain detectors SG1 and SG2 and outputs a signal for controlling the variable pressure reducing valve V;
The press brake is characterized in that it is configured to control the deflection of the movable apron 3 according to the deflection of the fixed apron 1 by controlling the variable pressure reducing valve V based on a signal from the CMP.