GB1603289A - Expansion mandrel - Google Patents

Description

(54) EXPANSION MANDREL (71) We, MARCEL HELEN S. A., a French company of 152 Boulevard Haussmann, 75008 Paris, France, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an expansion and/ or positioning tool for enabling a hollow body to be stressed from within and at three or more spaced points of contact.

According to the invention such a tool comprises a central body, at least three oblique milled cavities in the body extending from an end of the body and terminating at the side faces of the body, fingers positioned in the milled cavities, a disc adjacent to the said end of the central body and having a rounded bearing surface for engaging the heads of the fingers, and tightening means for moving the disc relatively towards the central body and against the heads of the fingers so as to cause the fingers to project laterally while permitting the disc a degree of lateral play.

In a preferred embodiment, the central body has at least three other oblique milled cavities starting from the opposite end and terminating at the side faces of the central body, other fingers in the other milled cavities, and a second disc having a rounded bearing surface for engaging the heads of the other fingers and movable relatively towards the central body and against the heads of the other fingers so as to cause the other fingers to project laterally by tightening means which permit the second disc a degree of lateral play.

Preferably the discs are interconnected by a common tightening means which includes a rod passing with clearance through a bore within the central body. The rod may have at one of its ends a head engaging with one of the discs and at the other end a threaded part engaging with a corresponding threaded part of the other disc.

A rod may also be provided to engage with the tightening means and to effect from a distance the clamping of the tool against the piece to be stressed.

The sides of the fingers projecting laterally from the body may be machined to correspond to the internal shape of the piece to be stressed by the tool.

The accompanying drawings show by way of example one embodiment of an expansion tool enabling a hollow body to be stressed from within and at a distance at three or more points of contact.

In the drawings: Figure 1 is a view from above of the expansion mandrel, a circular clamping member being shown partially removed, and Figure 2 is a section along the line 11-11 of Figure 1, showing the complete tool.

The expansion tool (Mandrel) 1 shown in the drawings is a relatively simple piece of apparatus enabling a circular or polygonal member to be stressed from within and along eight directions shown in Figure 1 by the arrows 2, 3, 4, 5, 6,7,8 and 9. As can be seen from Figure 1, the stresses are exerted in the directions 2,4,6 and 8 from the faces 10,11 and 12 and 13, and the stresses along the directions 3,5,7 and 9 from faces 14,15,16 and 17. Consequently, the forces exerted by the surfaces 10 to 13 can be applied at points closer to the centre of the tool than the forces exerted by the faces 14 to 17. It is obvious to those skilled in the art that the arrangement of the tool of Figures I and 2 is not limited to the example described, and that the forces represented by the arrows 2 to 9 may be exerted for example by faces placed around a circumference or faces placed around the centre of the tool in accordance with an irregular configuration.

The expansion tool I comprises a housing 18 having a central bore 19 through which passes with clearance a rod 20 having a threaded end 21 and a tightening head 22 at the other end. A disc 23 whose surface adjacent to the housing 18 has a rounded part 24 is screwed on the threaded end 21 of the rod 20. At the other end of the rod 20 is arranged a second disc 25 of smaller diameter than the disc 23 and having a central bore 26 through which the rod 20 passes, the disc 25 having a shoulder 27 against which the head 22 bears. The surface of the disc 25 adjacent to the casing 18 has, like the corresponding surface of the disc 23, a rounded part 28.

The periphery of the housing 18 has slots defining the faces 10,11,12,13 and 14,15, 16,17 respectively.

A milled cavity 30 is machined along an oblique axis 31 from an end of the housing 18 to each of the faces 10,11,12 and 13 in such a way as to open onto the respective face. The milled cavities shown at 30 are terminated before passing completely through the housing 18 so as to form stop surfaces 32 which will act as a bearing for springs 33 exerting a force on fingers 34 introduced into the cavities 30. The fingers 34 have rounded heads 35 to engage the rounded portion 28 of the disc 25, and lateral bevelled surfaces 36 parallel to the surfaces 10, 11, 12 and 13 of each recess.

In the same way, a milled cavity 37 is machined along an oblique axis 38 from the other end of the housing 18 to each of the faces 14,15,16 and 17 so as to open onto the said faces 14 to 17 and provide stop surfaces 39 which will serve as a bearing for springs 40 exerting a force on fingers 41 introduced into the bores 37. The fingers 41 are identical to the fingers 34 and have rounded heads 42 which engage the rounded portion 24 of the disc 23, and alteral bevelled surfaces 43 parallel to the surfaces 14,15,16 and 17.

The tool that has just been described is used to press eight pieces of rectangular shap (not shown in the drawing) into corresponding recesses within a positioning plate of circular configuration, four recesses situated at right angles with respect to one another being more distant relative to a common centre than the other four recesses situated at 45 with respect to the first recesses. In order to press these eight rectangularly shaped pieces (not shown), it is sufficient to turn the head 22 and the rod 20 in an anti-clockwise direction to cause the be velled surfaces 36 and 43 to enter the casing so that these surfaces are in the same plane as the faces 10, 11, 12,13 and 14,15,16,17 respectively. The tool 1 is then placed in position, if necessary by means of a rod, against the eight rectangularly shaped pieces and the head 22 is turned clockwise by means of a key, not shown.

The discs 23 and 25 are brought closer to the housing 18 and press the fingers 34 and 41 against the action of the springs 33 adn 40, causing the lateral advance of the bevelled surfaces 36 and 43 which, in its turn, stresses the eight rectangular pieces by pressing them into the recesses in the positioning plate.

The tool 1 that has just been described permits the fingers to slide to a certain extent on the rounded surfaces 24 and 28 of the discs 23 and 25, which is allowed by the degree of play of the whole arrangement. This sliding enables side differences between two bearing surfaces at 90 to be compensated.

Furthermore, the too ! described %'ith regard to Figures 1 and 2 may be simplified and may, for example, comprise only four or even three lateral wedge surfaces integral with four, three fingers dispose in the milled cavities made in the same end of the casing. The lateral thrust surfaces may also be arranged in an asymmetric manner with respect to the centre of the tool.

Also, the thrust surfaces may have a specific geometrical shape and be adapted to the pieces that are to be stressed, for example they may have a rounded shape if the tool is used to stress circular pieces.

The tool described is used in particular in the nuclear industry in order to stress rods defining lowering channels for neutron absorber rods within circular plates before the said rods are welded to the plates. This very special use is, however, not limitative and the tool may be used in engineering in general, especially where parts or components must be stressed from within against a polygonal or circular member, for example to compensate for contraction after a welding operation.

The principal feature of the tool that has just been described is the fact that it is an expansion tool enabling a hollow body to be stressed from within at several points of contact and from a distance using a key, wherein the hollow body may be one having curved surfaces or may be of regular or irregular polygonal shape.

The tool may also be used as a positioning tool to position a member within a hollow body In this case it will have a rod or positioning tube (not shown) which will preferably be secur to a central body 18. This tube or rod may be provided with angular and/or depth reference or adjusting marks to enable exact positioning.

In order to hold the member and release it after the positioning, a tightening rod engaging with the head 22 is used. Those skilled in the art will understand that the positioning that has just been described may be an axial and longitudinal positioning (in depth), and it will be sufficient to choose appropriate reference marks.

Claims (12)

WHAT WE CLAIM IS:

1. An expansion and/or positioning tool for enabling a hollow body to be stressed from within and at three or more spaced points of contact, comprising a central body, at least three oblique milled cavities in the body extend ing from an end of the body and terminating at the side faces of the body, fingers positioned in the milled cavities, a disc adjacent to the said end of the central body and having a rounded bearing surface for engaging the heads of the fingers, and tightening means for moving the disc relatively towards the central body and against the heads of the fingers so as to cause the fingers to project laterally while permitting the disc a degree of lateral play.

2. A tool according to Claim 1, wherein the central body has at least three other oblique milled cavities starting from the opposite end and terminating at the side faces of the central body, other fingers in the other milled avit : : s, and a second disc having a rounded bearing surface for engaging the heads of the other fingers and movable relatively towards the central body and against the heads of the other fingers so as to cause the other fingers to project laterally by tightening means which permit the second disc a degree of lateral play.

3. A tool according to Claim 2, wherein the discs are interconnected by a common tightening means which inclues a rod passing with clearance through a bore within the central body

4. A tool according to any one of Claims 1 to 3, wherein the sides of the fingers which project laterally from the body are machined to correspond to the internal shape of the piece to be stressed by the tool.

5. A tool according to any one of Claims 1 to 4, wherein the sides of the fingers which project laterally from the body have a flat bevelled surface corresponding to a polygonal configuration having planes parallel to the axis of the tool.

6. A tool according to any one of Claims 1 to 4, wherein the sides of the fingers which project laterally from the body have a rounded surface corresponding to a cylindrical configuration.

7. A tool according to Claim 3, wherein the rod which passes through one of the discs has a head engaged with said one disc at one of its ends and a threaded portion at its other end that engages with a corresponding thread on the other disc.

8. A tool according to Claim 7, further comprising a tightening rod engageable with the head for expanding the tool in the hollow body that is to be stressed.

9. A tool according to any one of the preceding Claims, wherein the fingers have rounded heads.

10. A tool according to Claim 1, further comprising a positioning rod or tube designed to be secured to the central body.

11. A tool according to Claim 10, wherein the rod or tube comprises reference marks intended for an angular positioning and/or depth positioning.

12. An expansion and/or positioning tool for enabling a hollow body to be stressed from within and at three or more spaced points of contact substantially as hereinbefore described with reference to the accompanying drawings.