GB2229492A

GB2229492A - Ball joint for pipe-bending mandrel

Info

Publication number: GB2229492A
Application number: GB9004771A
Authority: GB
Inventors: James Churchman
Original assignee: PRESSBEND Ltd
Current assignee: PRESSBEND Ltd
Priority date: 1989-03-02
Filing date: 1990-03-02
Publication date: 1990-09-26
Also published as: GB8904811D0; GB9004771D0

Abstract

In a ball 5 and socket 4 joint the ball 5 is inserted into the part-spherical socket 4 through an entry section thereof and is retained against withdrawal from the socket 4 by at least one pin 9 having a free end locating in the entry section behind the ball. A plurality of such pins 9 may be provided and their inner ends may be formed to define a part seating surface for the ball. A mandrel assembly for use in pipe bending may be formed by a plurality of mandrel elements 1, 2 articulated together by the ball and socket joint. <IMAGE>

Description

BALL & SOCKET JOINT The present invention relates to a ball and socket joint and to a mandrel assembly for use in pipe bending.

It is common practice in the bending of pipes using pipe bending machines to insert a flexible mandrel within the pipe to prevent collapse thereof where the bend is being formed.

Generally such a mandrel assembly comprises a plurality of mandrel elements each articulated to an adjacent element by a ball and socket joint. One such mandrel assembly is shown in GB-A-2097854.

However the ball and socket joints in the assembly shown in 2 097 854 are comparatively difficult to produce and it is an object of the present invention to obviate or mitigate this disadvantage.

According to a first aspect of the present invention there is provided a ball and socket joint wherein the ball may be inserted into the part-spherical socket through an entry section, and the ball is retained against withdrawal from the socket by a least one pin with its free end locating in the entry section behind the ball.

Preferably a plurality of such retaining pins are provided, most preferably equi-angularly spaced from each other.

Preferably each pin is provided in and inserted through a respective passageway formed in the wall of the entry section and preferably also the ends of the pins are shaped such that they provide part of a seating surface for the ball.

The invention also provides and elongate mandrel assembly comprising of mandrel elements each articulated to an adjacent element by a ball and socket joint in accordance with the first aspect of the invention.

Preferably each such mandrel element comprises a mandrel segment with a ball and socket for receiving the ball of an adjacent segment, and a ring which is mounted on the segment and which is of a diameter corresponding to the inner diameter of the pipe to be bent.

Preferably this ring serves to prevent withdrawal of the pin or pins.

The invention further provides a pipe bending machine provided with a mandrel assembly in accordance with the invention.

The invention will be further described by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a cross-sectional view of a part of a mandrel assembly incorporating ball and socket joints in accordance with the invention; Fig.2 is a section on the line II-II of Fig. 1; and Fig. 3 is a section on the line III-III of Fig. 1.

As shown in Fig. 1, a mandrel assembly for location in a pipe to be bent comprises a plurality of mandrel segments (each carrying an outer ring 2) articulated together by ball and socket joints as described in more detail below. For convenience Fig. 1 illustrates three mandrel segments 1 but it will be appreciated that a greater number will generally be present in the complete assembly.

Each mandrel segment 1 comprises a body 3 (in which is formed a socket 4) and a ball 5 which is mounted on the body 3 by a neck 6.

As shown; the body 3 has a frusto-conical surface 7 flaring outwardly from the end of the neck 6.

Socket 4 has a generally cylindrical portion 4a which at one end opens onto the face of body 3 remote from the ball 5 and at the other end opens onto a generally hemi-spherical portion 4b. Both of portions 4a and 4b have a radius just slightly greater than that of the ball to be received by the socket.

Six equi-angularly spaced passageways 8 penetrate the body 3 and open at their radially inner ends into the cylindrical portion 4b of the socket 4. In the assembled joint, these passageways received pins 9 which retain the ball in the socket. Each pin 9 has a chamfered inner end 10 so that these ends of the six pins together form a discontinuous seating surface for the ball.

The pins 9 are retained in position by the ring 2 which is itself held on the segment 1 by a circlip 11.

It will be appreciated that assembly of the joint is effected simply by inserting the ball 5 of one mandrel segment 1 through the open end of the socket 4 of another segment 1 until the ball has been received as far as possible in the hemi-spherical portion 4b. The pins 9 are then inserted in the passageways 8 and the ring 2 located on the body 3.

The outer diameter of the rings 2 corresponds to the inner diameter of a pipe 9 (as shown in chain-dot line) to be bent. The assembly may thus be inserted in such a pipe which may then be bent using standard techniques. The frusto-conical surface 7 of the body portion allows a high degree of articulation between the mandrel segments during such a bending operation.

It will be appreciated that the mandrel assembly may be adapted for the bending of pipes of different diameter simply by using rings 2 of the appropriate size.

Although the invention has been specifically described with reference to six pins 8, it should be appreciated that a greater or lesser number may be used.

Claims

1. A ball and socket joint wherein the ball may be inserted into the part-spherical socket through an entry section, and the ball is retained against withdrawal from the socket by at least one pin with its free end locating in the entry section behind the ball.

2. A ball and socket joint as claimed in claim 1 wherein a plurality of said retaining pins are provided to retain the ball against withdrawal from the socket.

3. A ball and socket joint as claimed in claim 2 or 3 wherein the ends of the pins are shaped such that they provide part of a seating surface for the ball.

5. A ball and socket joint as claimed in any one of claims 1-4 wherein the or each pin is provided in and inserted through a respective passageway formed in the wall of the entry section.

6. An elongate mandrel assembly comprising a plurality of mandrel elements each articulated to an adjacent element by a ball and socket joint as claimed in any one of claims 1-5.

7. A mandrel assembly as claimed in claim 6 wherein each mandrel element comprises a mandrel segment with a ball and with a socket for receiving the ball of an adjacent segment, and a ring which is mounted on the segment.

8. A mandrel assembly as claimed in claim 7 wherein the ring serves to prevent withdrawal of the or each pin.

9. A mandrel assembly as claimed in claim 6 or 7 wherein the mandrel segment comprises said ball, a body in which the socket is formed, and a neck connecting the ball to the body, said body having a frusto-conical portion tapering towards said neck.

10 A mandrel segment comprising a ball connected by a neck to a body portion in which a socket is formed, said body portion having a frusto-conical tapering outwardly away from the neck and a generally cylindrical section wherein the wall of said body portion is formed with at least one passageway for receiving a pin for retaining a ball in said socket.

11. A ball and socket joint substantially as herein before described with reference to the accompanying drawings.

12 A mandrel assembly substantially as herein before described with reference to the accompanying drawings.

13. A mandrel segment substantially as herein before described with reference to the accompanying drawings.