GB2097854A - A ball and socket joint - Google Patents

Abstract

A ball and socket joint, for use particularly in forming a mandrel for a pipe bending machine. The joint has a ball 28 seated in a socket 32. A portion of the spherical surface of the socket 32 is provided by a retaining insert 33 forming a segment of the socket wall. <IMAGE>

Description

SPECIFICATION A ball and socket joint The present invention relates to a ball and socket joint. The invention also relates to a mandrel assembly incorporating such ball and socket joint and intended particularly but not exclusively for use in pipe bending.

In the bending of pipes, a mandrel is inserted in the pipe in the region at which the bending operation will be performed. The mandrel serves to prevent collapse of the pipe wall under the bending stress.

The mandrel must obviously possess a degree of flexibility to ensure that it is bent with the pipe.

For this purpose, so-called "ball-and-socket" mandrels have been proposed. Such mandrels comprise a number of separate sections joined by ball and socket joints to give the mandrel the required degree of flexibility.

However such "ball-and-socket" mandrels suffer from the disadvantage that the ball is retained in the socket by means such as clips. The use of such clips is however not altogether satisfactory and can lead to difficulties in assembly of the mandrel.

The object of the present invention is therefore to provide a ball and socket joint which is easy to assemble.

According to a first aspect of the present invention there is provided a ball and socket joint in which the ball is articulated in a socket provided with an insert piece forming a closure for the socket, said insert piece being removable to allow the ball to be removed from the socket.

According to a second aspect of the present invention there is provided a mandrel assembly having at least two sections articulated together by a ball and socket joint as defined in the preceding paragraph.

The invention will now be described by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a view partly in section of a complete mandrel assembly; Fig. 2 is a view of part of a mandrel section looking in the direction of arrow A in Fig. 3; Fig. 3 is a view of the mandrel section shown in Fig. 2 looking in the direction of arrow B in that figure; and Fig. 4 is a perspective view of parts of two mandrel sections, as used in the construction of mandrel assembly in Fig. 1, being assembled to form a ball and socket joint.

The mandrel assembly 21 illustrated in Fig. 1 comprises a support 22, which may be part of a bending head of a pipe bending machine, a mandrel section 23 articulated to the support 22 by a ball and socket joint and a mandrel section 24 articulated to mandrel section 23 also by means of a ball and socket joint. Additional mandrel sections may be provided as illustrated.

The mandrel sections are provided with spring and ball detent arrangement as illustrated.

Mandrel sections 23 and 24 are identical so only the former is described. Mandrel section 23 comprises a body 25 supporting an outer ring 26 locating against a shoulder 27 of the body 25.

Body 25 includes a ball 28, a cylindrical body portion 29 (provided with the shoulder 27) and a frusto-conical body portion 30 intermediate the ball 28 and body portion 29, and connected to the ball via a reduced diameter neck portion (Fig. 2).

Within body portions 29 and 30, and opening out on the back face 31 of body 25 (i.e. that face of portion 29 remote from the ball 28) is a spherical socket 32. The back face 31 is dished inwardly as shown in the drawings.

As will be appreciated from Figs. 3 and 4, the body portions 29 and 30 are formed partly by an insert or plug 33 with an undersurface 33a forming part of the spherical surface of the socket 32. The main part of the body portions 29 and 30 (i.e. those portions not defined by insert 33) are formed with a channel 34 which extends radially inwardly from the outer surface of the body and which has a section in the form of a major segment of a circle with a diameter slightly larger than that of a ball to be located in the socket 31.

This channel 34 is open at the rear surface 31 of the body 25 (as clearly illustrated in Figs. 2 and 3).

The channel 34 is terminated by a part (substantially half) spherical seating surface 34a having a curvature corresponding to that of a ball to be located in socket 31.

Insert 33 is formed with a part-spherical undersurface 33a forming a seating surface of the same curvature of surface 34a. The insert 33 is shaped and dimensioned such that, when in position, the socket 31 is formed by the surfaces 33a and 34a and also such that substantially flush outer surfaces are provided for the body 25.

To assemble mandrel sections 23 and 24, the insert 33 of mandrel section 23 is removed and the ball 24a of mandrel section 24 is slid along channel 34 of section 23 in the manner illustrated in Fig. 4 until it seats on surface 34a in the manner clearly illustrated in Fig. 1. The insert 33 is then located in the top of channel 34, and the ring 26 positioned around the body portion 29. The insert 33 and ring 26 are held in position by a circlip 37, or any other suitable means.

With the mandrel sections 23 and 24 thus articulated together, a large degree of movement of mandrel section 24 relative to section 23 is permitted due to the dished rear surface 31 of mandrel section 23 and the frusto-conical form of body portion 30 of mandrel section 24. This feature is clearly illustrated in Fig.1.

The ball and socket joint between mandrel section 23 and support 22 may be formed in similar manner to that described above. In this case, support 22 has a channel 35 with terminal seating surface 35a. An insert or plug 36 with part spherical seating surface 36a is locatable in the top of channel 35 to retain the ball 28 of mandrel section 23 in position and form the ball and socket joint. It is to be noted that ball 28 is not embraced totally by seating surfaces 35a and 36a: it is sufficient for surface 36a to extend only so far as is required to provide necessary degree of retention and articulation of the ball 28.

The channels 34 and 35 may be formed in the respective components by any suitable means e.g.

a bull nosed milling cutter.

The illustrated ball and socket joint may of course be used in applications other than a mandrel assembly.

In a modification (not shown) of the illustrated embodiment, the socket 32 may be so formed that the insert piece 33 need not have a part spherical undersurface 33a and could, for example, have a

Claims (9)

1. A ball and socket joint having a ball seated in a socket wherein a portion of the spherical surface of the socket is provided by a retaining insert forming a segment of the socket wall.

2. A joint as claimed in claim 1 wherein the socket is formed in a body having extending therein a channel with a part circular cross-section corresponding to a major segment of a circle and terminating in a part spherical seating surface forming a part of said socket, said channel being open along the side thereof which is not part of said major segment, and said insert locates in the mouth of said channel and has a part spherical undersurface forming the other part of said socket.

3. A joint as claimed in claim 2 wherein said terminal surface is substantially hemispherical.

4. A joint as claimed in any one of claims 1 to 3 wherein the socket is formed in a body of generally circular section and said retaining insert provides a minor segment of said circular section body.

5. A mandrel assembly for a pipe bending apparatus, said assembly having at least two of sections articulated together by a ball and socket joint as claimed in any one of the preceding claims.

6. A component of a mandrel assembly for a pipe bending apparatus, said component comprising a socket whereof a portion of the spherical surface is provided by a retaining insert forming a segment of the socket wall and a ball for location in a socket of a like component.

7. A ball and socket joint substantially as hereinbefore described with reference to the accompanying drawings.

8. A mandrel assembly substantially as hereinbefore described with reference to the accompanying drawings.

9. A component of a mandrel assembly substantially as hereinbefore described with reference to the accompanying drawings.