GB2103974A

GB2103974A - An electric upsetting device

Info

Publication number: GB2103974A
Application number: GB08125589A
Authority: GB
Inventors: Toshio Maki; Tetsuo Nihei; Ko Matsumoto; Kazuyoshi Sakuma
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1981-08-21
Filing date: 1981-08-21
Publication date: 1983-03-02
Also published as: GB2103974B

Abstract

A tubing P is inserted into a shaping die 3 to butt, at its one end face, an anvil electrode 1. Thereafter, an electrode 2 is contacted with the tubing P and electric current is caused to pass across the two electrodes 1 and 2, whereby the portion P' of the tubing P between the electrodes 1 and 2 becomes softened by generation of heat. In this state, when the tubing P is pushed in the arrowed direction, the portion P' swells to contact the inner surface of the die 3. As the inner surface of the die is covered with an insulating layer 5, the electric current always flows in the portion P' alone. Thus, the end part of the tubing P becomes sufficiently softened by the heat generation, and is readily deformed by pressure at the time of pushing to be upset until the end part is completely solid. <IMAGE>

Description

SPECIFICATION An electric upsetting device This invention relates to electric upsetting devices for upsetting work pieces in which one end part of the work piece is softened by heat generated by virtue of the electrical resistance of the piece to enable the diameter or cross-sectional area of the work piece to be increased.

In prior electric upsetting devices a die is provided for shaping the external surface of the softened work piece. The inner surface of the die is subject to high temperatures and pressures and, in order to withstand these temperatures and pressures, the die is provided with a heat resistant metal bush made of anti-corrosive nickel alloy (e.g. HASTELLOY - a trade mark for a nickel based alloy produced and marketed by the Union Carbide Corp., U.S.A. consisting of Ni-Mo-Mn-Fe, Ni-Mo-Cr-W-Fe or Ni-Si-Cu-Al).

A prior electric upsetting device is shown in Figures 1 to 3 of the accompanying drawings, in which: Figure 1 is a cross-sectional view of the upsetting device before upsetting of the work piece has commenced; Figure 2 is a similar view to Figure 1 during upsetting of the work piece; and Figure 3 is a similar view to Figure 1 after upsetting of the work piece has been completed.

In Figure 1, the work piece comprises a tubing 1, one end of which butts an anvil electrode 1. A further electrode 2 is held in contact with the tubing P by a clamp or other suitable means (not shown).

The anvil electrode 1 extends within, and is able to move back and forth through, a shaping die 3 with a heat resistant metal bush 4 secured to its inner surface. The internal diameter of the bush 4 is larger than the external diameter of the unworked tube P.

In operation, the end face of the anvil electrode 1 is brought to the entrance of the die 3, and then the end face of the tubing P, to which the contact electrode 2 is clamped, is butted to the anvil electrode 1. Electric current is then conducted across the electrode 1 and the electrode 2, and the tubing P is forcibly pushed into the heatresistant metal bushing 4, while causing the anvil electrode 1 to gradually move backwards, whereby a portion P' of the tubing P situated between the electrodes 1 and 2 is softened by heat generated from the electric conduction, and swells, as shown in Figure 2. When the end face of the anvil electrode is in the retracted position it constitutes the bottom surfaces of the shaping die.

As soon as the outer diameter of the tube portion P' is increased as mentioned above, and comes into contact with the heat-resistant metal bushing 4, the electric current which has so far been passing through the electrodes 1 and 2 also begins to flow through the bushing 4. The electric current is able to flow through the bushing 4 in the direction of arrow A and, as a consequence of this, a portion of the tubing P at the innermost position in the die 3, where the tube does not contact the bushing 4, can no longer raise its temperature, and a hollow cavity B remains in the tubing without the end part thereof being completely upset, as shown in Figure 3. This effect is more apparent when the electrical resistance of the bushing 4 is lower than the electrical resistance in the tubing P between its point of contact with the bushing 4 and the anvil electrode 1.

When a tubing which has been subjected to such upsetting work is used as a power transmission shaft of an automobile or other vehicle, for example, and a joint member is fitted on its outer peripheral end part, for example by a spline connection, the power transmission shaft cannot withstand a high load imposed upon it because the shaft contains the hollow cavity inside its end part, which may fall short of the mechanical strength required of it.

According to the present invention, an electric upsetting device comprises an anvil electrode positioned within a cavity within a shaping die into which, in use, the member is inserted, and a second electrode adapted to be connected to the metallic member in which at least a part of the surface defining the cavity is of electrically insulating material.

With such a device, current may be prevented from flowing through the shaping die to allow substantially all of the end of the metallic member to be softened. Preferably the electrically insulating material is of ceramic material. The internal cross-sectional area of the cavity may decrease in the direction in which, in use, the member is inserted to allow a variety of shapes to be formed by the upsetting device. For example, a work piece may be formed with a conical end portion.

Preferably, the anvil electrode is movable with respect to the shaping die. One advantage of this is that the anvil electrode may be used as a knockout member for taking out the member after the upsetting work has been completed.

According to another aspect of the present invention, a method of electrically upsetting a metallic member comprises inserting one end of the member into a cavity in a shaping die to butt and press against an anvil electrode, in which the inner surface of the cavity is of electrically insulating material, passing an electric current through the member between the anvil electrode and a second electrode electrically connected to the member so as to soften the end of the work member. When a member is electrically upset by such a method, the current may always flow through the member between the electrodes without any current flowing through the shaping die, thus allowing substantially all of the end of the member to be softened. This has the advantage that a satisfactory end to the member is formed by the upsetting.

It will be appreciated that the member can be of any suitable shape, for example it may be a rod or a piece of tubing. Where tubing is to be electrically upset, the present invention allows the end of the member to be made completely solid.

When such an upset member is used as a power transmission shaft, for example, it is able to withstand higher loads than a member which has been upset by a device according to the prior art.

The invention may be carried into practice in various ways, but two embodiments will now be described by way of example and with reference to the accompanying drawings, in which: Figure 4 is a cross-sectional view of the electric upsetting device before upsetting of a work piece has begun; Figure 5 is a similar view to Figure 4 after upsetting of the work piece has begun; Figure 6 is a similar view to Figure 4 showing completion of the upsetting or shaping work; and Figure 7 is a similar view to Figure 6 showing a modified shaping die.

Referring first to Figure 4, the tubing P to be worked or upset is inserted into the shaping die 3 to butt, at its one end face, the anvil electrode 1.

Thereafter, the electrode 2 is contacted with the tubing P and electric current is caused to pass across the two electrodes 1 and 2, whereby the portion P' of the tubing P between the electrodes 1 and 2, whereby the portion P' of the tubing P between the electrodes 1 and 2 becomes softened by generation of heat. In this state, when the tubing P is pushed in the arrowed direction, the portion P' swells as shown in Figure 5 to contact the inner surface of the die 3. Since the inner surface of the die is covered with an insulating layer 5, the electric current always flows in the portion P' alone. A suitable material for the insulating layer may be ceramics.Thus, the end part of the tubing P becomes sufficiently softened by the heat generation, and is readily deformed by pressure at the time of pushing to be upset as shown in Figure 6, where it has become completely solid at its end.

When the anvil electrode 1 is made movable both in the forward and backward directions, the anvil electrode 1 can be utilized as a knock-out member for taking out the shaped article after completion of the upsetting work. Further, when the inner peripheral surface of the shaping die 3 is tapered as shown in Figure 7, the end part of the tubing material can be made solid in the tapered shape P".

When the tubing material with its end part having been made completely solid in the manner as mentioned above is used as a power transmission shaft, it works very satisfactorily because of its light weight and high mechanical strength.

Thus the provision of a heat resistant insulating layer of ceramics on the inner surface of the shaping die allows the electrical upsetting device to heat up the entire part of the raw material to be worked to make it sufficiently soft to facilitate the shaping of an article. Such an upsetting device is of simple construction and may be readily made.

Claims

1. An electric upsetting device for upsetting a metallic member comprising an anvil electrode positioned within a cavity within a shaping die into which, in use, the member is inserted, and a second electrode adapted to be connected to the metallic member in which at least a part of the surface defining the cavity is of electrically insulating material.

2. A device as claimed in Claim 1 in which the electrically insulating material is of ceramic material.

3. A device as claimed in Claim 1 or 2 in which the internal cross-sectional area of the cavity of the die decreases in the direction in which, in use, the member is inserted.

4. A device as claimed in any preceding claim in which the anvil electrode is movable with respect to the shaping die.

5. A device as claimed in any preceding claim in which the cavity is of circular cross-section.

6. An electric upsetting device substantially as herein specifically described with reference to Figures 4 to 6 or Figure 7 of the accompanying drawings.

7. A method of electrically upsetting a metallic member comprising inserting one end of the member into a cavity in a shaping die to butt and press against an anvil electrode, in which the inner surface of the shaping die is of electrically insulating material, passing an electric current through the member between the anvil electrode and a second electrode electrically connected to the member so as to soften the end of the member.

8. A method as claimed in Claim 7 in which the anvil electrode moves with the metallic member into the cavity.

9. A power transmission shaft in which one end has been electrically upset by the method of Claim 7 or 8.

10. A method of electrically upsetting a metallic member substantially as herein specifically described with reference to Figures 4 to 6 or Figure 7 of the accompanying drawings.