GB2219541A

GB2219541A - Expanding a tubular metal body

Info

Publication number: GB2219541A
Application number: GB8910893A
Authority: GB
Inventors: Wilhelm Schulte
Original assignee: Hoesch AG
Current assignee: Fried Krupp AG Hoesch Krupp
Priority date: 1988-05-11
Filing date: 1989-05-11
Publication date: 1989-12-13
Anticipated expiration: 2009-05-11
Also published as: IT8920437A0; GB8910893D0; FR2631262A1; FR2631262B1; DE3816090C2; GB2219541B; DE3816090A1; IT1229253B

Description

A A.- D APPARATUS AND METHOD FOR MANUFACTURING A TUBULAR METAL BODY

DESCRIPTION 5

The present invention relates to an apparatus and method for manufacturing a tubular metal body.

Current known methods of manufacturing a hollow metal body involve the extrusion of a portion of the body. However, only a restricted portion of the body can be extruded and so limits are placed on the dimensions of the hollow section that can be provided in the metal body.

The present invention seeks to provide an apparatus and method which allows for the manufacture of a hollow metal body having a hollow section which would be unobtainable using current known methods.

According to one aspect of the present invention there is provided a method of manufacture of a tubular metal body, comprising extruding the metal in a continuous length of hollow cross-section, dividing the extrudate into shorter lengths, heating the shorter lengths and enlarging at least the internal cross-section of the shorter lengths.

Preferably the method includes applying a compressive force to the body in a direction substantially at right angles to the expanding force.

The application of the heat and the compressive force and the enlargement of the internal cross-section may -2be carried out as discreet steps in the method.

According to another aspect of the present invention there is provided apparatus for the manufacture of a tubular metal body, comprising means for extruding the metal in a continuous length of hollow cross-section, means for dividing the extrudate into shorter lengths, means for heating the shorter lengths and means for enlarging at least the internal cross-section of the shorter lengths.

Preferably the means for enlarging the internal crosssection comprises a substantially elongate member the outer contour of which corresponds to the required contour of the hollow section and the outer dimensions of which increase in a direction along the longitudinal axis. As such, the elongate member is moved into the shorter length and contacts the surface thereof so as to apply an expanding force thereto.

Alternatively. the apparatus may include an expansion member arranged to be received in the shorter length and arranged to receive a substantially elongate member which causes the expansion of the expansion member. As such, the expansion member exerts an expanding force on the surface of the shorter length. Such a device is particulary suitable for enlarging short lengths of hollow bodies with a large hollow section.

Preferably the expansion member comprises a substantially annular member formed of a plurality of segments. In this case, each of the segments is displaced in a radial direction as the substantially elongate member is moved therein.

3- Advantageously, the expansion member has a substantially conical recess for receiving a correspondingly substantially conical portion of an elongate member to initiate the expansion of the 5 expansion member.

The apparatus of the present invention may also include a die having an inner contour corresponding to the outer contour of the required tubular metal body so as to receive the latter therein. As such the outer surface of the metal body is received in the die as the internal cross-section of the metal body is enlarged.

Further, the apparatus may include means for exerting a compressive force in the metal body in a direction substantially perpendicular to the enlarging force exerted by the substantially elongate member. Such means for exerting a compressive force may include a press plate and supporting die.

Within the scope of the invention there is therefore provided apparatu.s for enlarging a hollow section formed in a metal body, the apparatus comprising a die and a mandrel wherein the inner contour of the die corresponds to the required outer contour of the metal body and the outer contour of the mandrel corresponds to the required internal contour of the shorter lengths.

The apparatus may also comprise a die, a mandrel and a plurality of expanding segments wherein the inner contour of the die corresponds to the requir!d outer contour of the heated metal body, the outer contour of the expanding segments in the expanded condition correspond to the required inner contour of the shorter lengths, and the outer contour of the expanding segments in the unexpanded condition correspond to the initial internal contour of the shorter lengths and wherein the expanding segments, when contiguous form a conical recess in which the mandrel engages so as to expand the segments.

Due to the extrusion process, and as noted above, the shape of the body prior to- enlargement preferably corresponds substantially to the desired outer and or inner contour of the required final shape of the body. For example, in the case of a hollow cylindrical body provided with cams or lugs on its outer surface, the contour of the outer surface of the initial shape should correspond to that of the final shape so that the enlargement occurs substantially in the inner circumferencial region of the body. It is also appropriate for the initial shape of the body to comprise a wall, the thickness of which is reduced when the internal cross-section of the shorter lengths is enlarged to the size required.

In applying a compressive force to the metal body, an accurate formation of the metal body in the die is achieved. Thus the required final form of the metal body can adhere to fine tolerances. In this case, the need for finishing machining is at least considerably reduced. Moreover, the yield of the metal is substantially increased, which is particularly beneficial when high quality materials are used.

By virtue of the present invention, the production of an extremely complicated or large hollow profile in a tubular metal body can be facilitated in that the enlargement can be performed in repeated stages.

The invention is described further hereinafter, by way of example only, with reference to the drawings, in which:

Fig 1 is a plan view of a tubular metal body, formed according to the present invention; Fig 2 is a part cross-sectional view of apparatus embodying the present invention; Fig 3 is a section along line III - III in Fig 2:

Fig 4 is a part cross-sectional view of the apparatus of Fig 2:

Fig 5 is a part cross-sectional view of further apparatus embodying the present invention: and Fig 6 is a cross-section along line VI - VI in Fig 5. 15 Fig 1 shows in plan view a cylindrical metal member 1.1, 1.2 having cams 1 formed in the outer circumference thereof. The cylindrical metal member 1.1 is illustrated prior to the enlarging process. The member 1.2 illustrated by the chain dotted line shows the dimension of the cylinder and in particular the hollow section thereof once the cylinder has been enlarged. The cylinder 1.1 is formed by extrusion.

Figs 2 and 3 illustrate apparatus for forming the cylindrical member 1.1 into the member 1.2. The cylindrical member 1.1 is received in a cylindrical die 3, the inner contour of which corresponds to the contour of the outer surface of the member 1.1. Thus, as shown in Fig 3, the cams 1 are received in recesses in the die 3.

The cylindrical member 1.1 and die 3 are located on an annular base die 2 such that the hollow section of the die 3, cylindrical member 1.1 and base die 2 are -6aligned.

An elongate member or mandrel 4 is positioned above the hollow section of the cylindrical member 1.1. A press plate 5 extends around the shaft of the mandrel 4 and is located at the end of a compression ram 6. The end of the mandrel 4 which extends from the press plate 5 comprises a tapering head 4.1 which allows for ready entry of the mandrel into the-cylindrical member 1.1.

As shown in Fig 2, the diameter of the widest section of the shaft of the mandrel is greater than the diameter of the internal cross-section of the cylindrical member 1.1. Thus, as the cylindrical member 1-1 is heated and as the mandrel moves through the hollow section of the member to the position shown in Fig 4, a force is applied to the cylindrical member 1.1 which tends to enlarge the internal cross-section of the member 1.1. This widening causes the cams 1 to move into the recesses in the die 3.

As shown in Fig 4, the press plate 5 moves into contact with the upper surface of the cylindrical member 1.1. A compressive force is then applied to this upper surface by means of the ram 6. The cylindrical member 1.1 is therefore compressed between the base die 2 and the press plate 5 and this ensures that the outer region of the cylindrical member 1.1 is accurately received in the die 3. Once the cylindrical member 1.1 is cooled and the mandrel 4 removed, a cylindrical member 1.2 (as shown in Fig 1) is provided, the internal cross-section of which is larger than would be obtainable by way of known methods.

Figs 5 and 6 illustrate alternative apparatus embodying the present invention. The apparatus comprises a mandrel 8 having a tapered head 8.1 and four expanding segments 7 which combine to form an annular expanding member. The expanding segments combine to provide a conical recess 7.1 for receiving the mandrel 8. As shown in Fig 5, the expanding segments 7 are received in the cylindrical member 1.1. Again, the cylindrical member 1.1 is located within a die 3 having an inner contour corresponding to the contour of the outer surface of the cylindrical member 1.1.

As the mandrel 8 moves in the direction of arrow B into the expanding member formed by the segments 7, the segments are moved in a direction indicated by arrows A, i.e. in a direction substantially perpendicular to the direction of movement A of the mandrel 8. Thus, the expanding segments 7 act as an to expand the hollow section of the heated cylindrical member 1.1.

The invention is not restricted to the details of the foregoing embodiment. For example, the mandrel and/or expanding segments can be provided in any required form corresponding to the contour of the hollow section.

Claims

1 A method of manufacture of a tubular metal body, comprising extruding the metal in a continuous length of hollow cross-section, dividing the extrudate into shorter lengths, heating the shorter lengths and enlarging at least the internal cross- section of the shorter lengths.

2. A method as claimed in claim 1, further comprising 10 applying a compressive force to the body in a direction substantially at right angles to the expanding force.

3. A method as claimed in claim 2, wherein the heating of the body and the application of the expansive force are carried out prior to the application of the compressive force.

4. A method as claimed in any preceding claim, wherein the heating of the body and the application of the expansive force are carried out as discreet steps in the method.

5. Apparatus for the manufacture of a tubular metal body, comprising means for extruding the metal in a continuous length of hollow cross- section, means for dividing the extrudate into shorter lengths, means for heating the shorter lengths and means for enlarging at least the internal cross-section of the shorter lengths.

6. Apparatus as claimed in claim 5, wherein the means for applying the expansive force comprises a substantially elongate member the outer dimension of which increases in a direction along the longitudinal axis thereof so that as the elongate member moves into the hollow section it begins to exert an expansive force on the surface of the hollow section.

7. Apparatus as claimed in claim 5 or 6, wherein the 35 outer contour of the elongate member corresponds to the required contour of the hollow section of the body.

8. Apparatus as claimed in claim 5, further comprising an expansion member arranged to be received in the shorter lengths and itself arranged to receive a substantially elongate expanding member.

9. Apparatus as claimed in claim 8, wherein the expansion member comprises a substantially annular member formed of a plurality of segments.

10. Apparatus as claimed in claim 8 or 9, wherein the 10 expansion member includes a substantially conical recess for receiving the expanding member.,

11. Apparatus as claimed in any one of claims 5 to 10, further comprising a die having an inner contour corresponding to the required contour of the outer surface of the body so that the die receives the outer surface of the body as the internal cross-section of the body enlarged.

12. Apparatus for the manufacture of a tubular metal body, substantially as hereinbefore described with 20 reference to and as illustrated in Figs 1,2,3 and 4, and Figs 5 and 6 of the drawings.

13. A method of manufacture of a tubular metal body, substantially as hereinbefore described with reference to Figs 1,2,3 and 4, and Figs 5 and 6 of the drawings.

Published 1989 at The Patent Office, State House, 66"71 High Holborn, LondonWC1R 4TP. Further copies maybe obtained from The Patent OfEice. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed bY Multiplex techniques ltd, St Mary Cray, Kent, Cozi. 1187