JPH0353046B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 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.

In general, when bending is performed using a type of press brake in which hydraulic mechanisms for raising and lowering the moving apron are located on both sides of the moving apron, bending is performed based on the properties of the workpiece material such as its tensile strength, elastic limit, yield point, and elastic modulus. Forces that resist bending, such as springback characteristics, appear in the form of drag, which has 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.

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.

The present invention was made in view of such conventional problems, and in order to correct the amount of deflection of the apron according to the length of the workpiece material, a pressure control device is installed in the hydraulic cylinder in the center of the apron. An object of the present invention is to provide an apron deflection correction device for a press brake installed in a press brake.

This invention will be explained in detail below along with embodiments shown in the drawings. FIG. 1 shows the entire press brake according to the present invention. In this press brake, an upper apron 1 with an upper mold is fixed at a predetermined height, and a lower apron 3 with a lower mold is raised and lowered by hydraulic cylinders 5 and 7 provided on both sides, and the upper apron 1 You can approach and move away from it. 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 present 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 .

Here, when the pressure of the pressure oil supplied to the hydraulic cylinders 5 and 7 is P ₁ and the pressure of the pressure oil supplied to the hydraulic cylinder 9 is P ₂ , the pressure reduction of P ₁ - _{P 2} is caused by the pressure reducing valve V. It will be adjusted accordingly. This adjustment is made as follows.

() When the length does not change The relationship between the amount of pressure required for bending and the deflection of the upper apron 1 is proportional when the bending length does not change. For this purpose, the amount of pressure reduction X is kept constant with respect to the pressurizing force _P1 , and the pressurizing force _P2 is also changed together with the pressurizing force _P1 . In other words, P ₁ − P ₂ = X (constant)
It is changed based on the relationship between

In Fig. 2, pressure P ₁ in pipe L ₂ is detected by pressure detector D, converted into an electrical signal s 1 and inputted to arithmetic circuit C, and at the same time, the pressure P ₁ of pipe L 2 is detected by pressure detector D, and the electrical signal s 1 is input to calculation circuit C. An electric signal _{s 2 set} according to the length _of This is done by supplying pressure oil at a pressure corresponding to the signal V s ₁ −s ₂ to the pipe L ₄ .

() When the length changes When the bending length of the workpiece material changes, the length setting signal _s2 from the length setting device S is changed. The length signal of this length setting device S may be set manually using a digital switch type, for example, or a predetermined signal may be sent to a microcomputer in advance according to the bending length for automatic numerical control. It may also be a method of incorporating it so that it comes out.

In this way, the signal s ₃ (=
s ₁ −s ₂ ), this time s ₂ has been changed, so
The value is different from the previous value, and therefore the amount of pressure reduction by the pressure reducing valve V is also changed, and a deflection correction pressure _P2 corresponding to the bending length is obtained.

Specific examples of the amount of pressure reduction depending on the bending length are as follows.

Bending length Decompression amount 2m or less ……P ₁ =P ₂ 2.5m ……P ₁ −P ₂ =200Kg/cm ² 3m ……P ₁ −P ₂ =40Kg/cm ^{2 2} ~2.5m, 2.5~3m The amount of pressure reduction in between is proportional to the length.

FIG. 3 shows a reference example according to the present invention.
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 installed on upper apron 1, respectively.
and lower apron 3, and both strain detectors SG1,
Lower apron 3 so that SG2 has a certain relationship
The central part of the cylinder is bent by a hydraulic cylinder 9.

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.

Even in this embodiment, if the bending length of the workpiece material is short, the deflection strain of the upper apron 1 will be large, and if the bending length is long, the deflection strain will be small. Therefore, it is possible to correct the amount of deflection of 3.

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

(A) Instead of the pressurizing hydraulic cylinders installed on both sides of the apron, use a booster mechanism using a crank or gears.

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

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

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

As can be understood from the above description of the embodiments, in short, the present invention comprises a fixed apron 1 fixed to a frame and a movable apron 3 that can be raised and lowered. Hydraulic cylinders 5 and 7 for raising and lowering are provided near both sides of the movable apron 3, and a hydraulic cylinder 9 for correcting deflection of the apron is a press brake provided approximately in the center of the fixed apron 1 or the movable apron 3 to compensate for deflection. A variable pressure reducing valve V that can freely control the pressure _P2 of pressure oil supplied to the correction hydraulic cylinder 9 and the pressure of the lifting hydraulic cylinders 5 and 7.
A pressure detector D that detects P ₁ , a length setter S that sets the length of the workpiece, and each electric signal S ₁ , S ₂ input from the pressure detector D and length setter S
a control signal _S3 that controls the variable pressure reducing valve V based on
The variable pressure reducing valve V is controlled based on the control signal _S3 from the computing circuit C to calculate and output the pressure of the pressure oil supplied to the hydraulic cylinder 9 for deflection correction. This configuration controls the pressure to a desired level.

Therefore, according to the present invention, when the bending length of the workpiece changes, the deflection of the apron is corrected again using the signal from the length setting device, thereby improving the bending accuracy of the product. It is possible to further improve the

[Brief explanation of drawings]

FIG. 1 is a front view of a press brake used in an embodiment of the present invention, FIG. 2 is a system diagram of an embodiment of the invention, and FIG. 3 is a system diagram of a reference example according to the invention. 1... Upper apron, 3... Lower apron, 5
...Hydraulic cylinder, 7...Hydraulic cylinder, 9...
Hydraulic cylinder for deflection correction, 11... connecting rod,
L ₁ , L ₂ , L ₃ , L ₄ ... Piping, D ... Pressure detector,
C... Arithmetic circuit, S... Length setting device, V... Pressure reducing valve, SG1, SG2... Strain detector.

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 approximately in the center of the press brake, and includes a variable pressure reducing valve V that can freely control the pressure _P2 of the pressure oil supplied to the hydraulic cylinder 9 for deflection correction, and the pressure P of the hydraulic cylinders 5 and 7 for lifting. ₁ , a length setting device S for setting the length of the workpiece, and the above-mentioned pressure detector D and length setting device S.
and an arithmetic circuit C that calculates and outputs a control signal S ₃ for controlling the variable pressure reducing valve V based on the electric signals S ₁ and S ₂ input from the arithmetic circuit C, and a control signal S from the arithmetic circuit C. _3. A press brake characterized in that the pressure of the pressure oil supplied to the hydraulic cylinder 9 for deflection correction is controlled to a desired pressure by controlling the variable pressure reducing valve V based on the above.