CS244982B1 - The method of bending pipes, mainly circular cross-section and the equipment for carrying this method - Google Patents

Abstract

The invention relates to a method and a device for bending pipes, mainly of circular cross-section, in which special emphasis is placed on the minimum percentage of deformation of the cross-section and the change in wall thickness at the bending point. Its essence lies in the fact that in the first supports the pipe is pre-bent into an unfolded shape and in the second supports the pre-bent shape is bent by the action of a pair of forming forces while simultaneously twisting the cross-section into the desired shape. The device for implementing the method consists of two parts, one of which contains a bender equipped with a guide and a first forming surface and the second part contains a bender with a cavity, the walls of which form a guide and support for the pre-bent blank from the outside and pass into the hollow forming surface. The production bends show high geometric and dimensional accuracy with a minimum percentage of change in wall thickness. The bend itself can be made at any point on the pipe with the smallest possible bend radius and with a different bend angle.

Description

BACKGROUND OF THE INVENTION The present invention relates to a method and apparatus for bending pipes, in particular of circular cross-section, in which a special stop is placed on at least a percentage of cross-sectional deformation and variation in wall depth at the bend.

It is based on the fact that in the first abutments the tube is bent into a deployed shape and in the second abutments by a pair of forming forces the bent shape is bent while twisting the cross-section to the desired shape.

The apparatus for carrying out the method comprises two parts, one of which comprises a bend provided with a guide and a first forming surface and the other part comprises a bend with a cavity, the wall of which forms a guide and support for the preformed blank from the outside and passes into the hollow forming surface.

The production bends show high geometric and dimensional accuracy with a minimum percentage of wall rake change. The bend itself can be made at any point of the pipe with at least a possible bend radius and a different bend angle.

Fig. 1

BACKGROUND OF THE INVENTION The present invention relates to a method of bending pipes, in particular of circular cross-section, in which a special stop is applied to at least a percentage of the cross-section deformation and wall tube change at the bend and apparatus for carrying this.

It is necessary to bend tubes of mainly circular cross-section with small bending radii for at least a possible percentage of deformation of the cross-section and change of wall depth at the bending point for various technological devices, from the point of construction and technological.

Pipe bending methods developed hitherto can be used for bending, compression or combination bending and for bending where, in addition to the aforementioned methods, simultaneous torsion of the cross-section at the bending point is involved.

During bending, the tube is pulled and bent over the movable part of the tool. The stress of the material approaches the tensile strength, which ultimately affects the risk of cracks and fracture at the bending point. The elongation of the tube wall material on the outer radius is relatively large, resulting in a thinning of the wall thickness.

A partial minimization of the wall thickness thinning occurs during pressure bending where the tube is pushed by the movable part of the tool onto the fixed part of the tool.

The combination of tensile and compression bending exploits and combines the advantages of the prior art.

From the viewpoint of minimizing wall thickness thinning, bending associated with torsion is most preferred. The prior art methods using twist bending are very demanding in terms of process kinematics and hence the complexity of the tools. In addition to the bending device, there is a need for an additional step-by-step twisting device.

The above-mentioned drawbacks are eliminated by a method for bending tubes, mainly a circular cross-section, and a device for transferring this method, which consists in the fact that in the first operation the tube is bent to its unfolded shape and in the second operation by one pair of forming forces tubes along the entire length of the bend, to the desired shape, wherein the bend is provided with a guide surface that passes into a face that forms a mirror image to the face flat in the bend.

The method and apparatus for bending pipes according to the invention are characterized by the simplicity of the bending kinematics and the construction of the tool itself. One pair of forces causes bending and at the same time torsion of the pipe cross-section along the entire length of the required bending. The individual longitudinal fibers of the tube are bent into a helix by bending and twisting the cross-section, which has a major effect on reducing the difference in length between them during the entire bending process to the desired shape. The mutual minimum difference between the longitudinal fibers ultimately affects at least a reduction in the wall depth at the outer part of the bend and at least an increase in the wall depth at the inside of the bend.

Production bends show high geometric and dimensional accuracy with a minimum percentage of wall thickness change.

An example of manufacturing circular tube bending by the method and apparatus of the invention is shown schematically in the accompanying drawing.

In FIG. 1 is a front view of a tool for a second operation, and FIG. 2, the bottom part of the tool is shown in plan view.

The method of manufacturing circular cross-section tubes consists of two operations.

In the first operation, the pipe is routed to the developed helix shape by conventional means. In the second operation, the pre-bent blank 1 is inserted into the cavity of the bend, where it is guided from the outside and at the same time supported from below by the forming surface. From above, the blank 1 is bent while being deformed by the forming force through the guide and forming surface of the bending machine, and at the same time twisted into the desired shape. The molding surfaces on the bend and bend are mirrored. The folder consists of an anchoring plate 2, on which a replaceable bending mandrel 5 is fastened by means of a sleeve 3 and screws 4. The folding bar is made up of a bandage 6 into which the insert of the folding bar 9 is fastened by means of clips 7 and screws

8. The bandage 6 together with the insert of the bend 9 are fixed by bolts 10 to the bottom washer 11, which has a removable insert 12 in the middle part. In the exchangeable insert 12 there are ejectors 13 with bad springs 14.

In addition to the advantages and advantages of the invention mentioned above, the advantages of the invention are that no special equipment is required to bend the tubes.

A further advantage is that the bend can be made with any length of straight arms, at any point in the pipe with at least a possible bend radius and a different bend angle.

SUBJECT

Claims (4)

Method of bending tubes, mainly of circular cross-section, associated with torsion, characterized in that in the first operation the tube is bent to the developed shape and in the second operation by applying a pair of forming forces the bent shape is bent while twisting into the desired shape. 2. The method of claim 1, wherein the deployed shape is a helix. 3. The method of claim 1, wherein the deployed shape is part of an ellipse. 4. Equipment for carrying out the process according to points 1 to 3, comprising two BACKGROUND OF THE INVENTION separate bending mandrel and bending parts, characterized in that the bending mandrel (5) is provided with a guide surface for guiding and supporting the bent preform (11) from the inside extending into the first forming surface and the second part comprising a bending part (9) ) with a cavity, the wall of which forms a guide and support for the preformed workpiece (1) from the outside and passes into a second molding surface, the first and second molding surfaces being mirrored. 2 sheets of drawings