GB2176728A

GB2176728A - Extrusion apparatus

Info

Publication number: GB2176728A
Application number: GB08520716A
Authority: GB
Inventors: John Alan Pardoe
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1985-06-13
Filing date: 1985-08-19
Publication date: 1987-01-07
Also published as: GB2176728B; GB8520716D0

Abstract

Extrusion apparatus for the continuous forming of hollow section material has a die orifice 16 for the extrusion therethrough of the material, and a mandrel 29 located in the orifice 16. The mandrel 29 has at least one relatively small hole 40 therethrough from end to end, so that the material is initially extruded through the hole 40 and heats the mandrel 29, thereby heating the adjacent material which consequently flows more readily through the die orifice 16. <IMAGE>

Description

SPECIFICATION Extrusion Apparatus This invention relates to apparatus for the continuous forming of hollow section material by extrusion.

Examples of apparatus for the continuous forming of material by extrusion are described in British Patent Specifications Nos. 1370894 (United States Patent No.3765216), 1434201,1566152, 1590776, 2028207A, and 21 03527A.

According to the present invention, in apparatus for the continuous forming of hollow section material by extrusion, including a body defining an orifice for the extrusion therethrough of material, and a mandrel means locatable in the orifice so that said material extrudes between the body and the mandrel means, the mandrel means defines at least one relatively small hole therethrough from end to end of the mandrel means, so that said material is initially extruded through the hole(s) and heats the mandrel means and thereby heats the adjacent said material.

The invention will now be further described by way of example only with reference to the accompanying drawings, in which: Figure la shows a side view in part section of an apparatus for continuous forming of hollow section material by extrusion; Figure 1 b shows a modification of the apparatus of Figure 1a; Figure 2 shows a perspective view of a mandrel for use in the apparatus of Figure 1a; Figure 3 shows a perspective view in part section of part of the apparatus of Figure la; Figure 4 shows a plan view of one end of an assembly of the mandrel of Figure 2 and the part of the apparatus shown in Figure 3; Figure 5 shows a fragmentary sectional view of the end of the assembly of Figure 4; Figure 6 shows a fragmentary sectional view in the direction of arrow A of Figure 2; Figure 7 shows a modification of the plan view of Figure 4;; Figure 8 shows an alternative modification of the plan view of Figure 4; and Figures 9 and 10 show alternative extruded hollow sections.

In the above Figures, like parts have like numerals.

Referring now to Figure la an extrusion apparatus 10 for the continuous forming of material by extrusion is shown of the kind described in the aforementioned Patent Specifications, and comprises a wheel 11 rotatably mounted on a shaft 12. The wheel 11 has an endless circumferential groove 13 around its outer edge. A shoe member 14 overlies part of the length of the groove 13, and an abutment portion 15 associated with the shoe member 14 is shaped so as to project into and substantially block the groove 13. The abutment portion 15 has an extrusion orifice 16 through which material 18 in the groove 13 is extruded as the wheel 11 rotates.

As shown in more detaii in Figures 2,3 and 4, the orifice 16 is generally of frusto-conical form, and has an inlet 21 forthe material 18 (not shown) and converges towards an outlet 22 defined by a circular lip 23 with a chamfered inlet 24. Three equi-spaced blind-ended flutes 25 extend from the inlet 21 and terminate near the lip 23. A mandrel 29 locates (see Figure 4) in the orifice 16, and has a frusto-conical body 30 with a cylindrical end portion 35 joined by a slight circular recess 36 to the body 30. Three wing portions 31a, 31b, 31c of the mandrel 29 have outer surfaces 23a, 32b, 32cthat are complementary to that of the inside surface of the orifice 16 so as to mate well with the orifice 16 and distribute the high loading experienced by the mandrel 29 during extrusion.The wing portions 31a,31b,31c define three apertures 26a, 26b, 26c in the orifice 16. Each wing portion 31a, a,31 31c has side tapers 33 coverging towards the end portion 35 and terminates near the recess 36, the end portion 35 extending through the lip 23 (see Figure 5) and defining an annular space 37 therebetween.

As shown in Figure 2, a central hole 40 extends through the mandrel 29 from a domed portion 42 of the mandre 29. The hole 40 has a short cylindrical land portion 44 (see Figure 6) extending from a chamfered inlet 46 to a clearance cylindrical portion 48, for the extrusion of wire (not shown) therethrough.

In operation, with the mandrel 29 assembled in the orifice 16, as the wheel 11 rotates, material 18 from the groove 13 is forced against the abutment portion 15. Because of the greater pressure required to force material 18 through the apertures 26a, 26b, 26c, material 18 is initially extruded as wire through the hole 40. As this extrusion of wire occurs, the mandrel 29 and adjacent abutment portion 15 become heated by the frictional force during extrusion and heat the adjacent material 18. The heated material 18, consequently flows more readily and extrudes through the apertures 26a, 26b, 26c whereupon the extrusion of wire through the hole 40 gradually ceases. Because of the shape of the mandrel 29 at the end portion 35 and of the lip 23, the material 18 extrudes as tubing through the annular space 37.It is found in practice that only a short length of wire is extruded through the hole 40 on start-up. When sufficient tubing has been extruded and rotation of the wheel 11 has stopped, the material 18 ceases to flow in the orifice 16 about the mandrel 29. The mandrel 29 can be removed from the orifice 16 by tapping the mandrel 29 in a direction towards the inlet 21 of the orifice 16 so that the complementary outer surfaces 32a, 32b, 32c of the mandrel 29 disengage from the conical surface of the orifice 16, and the mandrel 29 can be removed.

Apart from assisting disassembly of the mandrel 29 from the orifice 16, the conical form of the orifice 16 and the conical and tapered form of the mandrel 29 encourage flow together of the material 18 through the apertures 26a, 26b, 26c, with the recess 36 assisting merging together of the separate streams of material 18 through the apertures 26a, 26b, 26c.

The apparatus 10 of Figure 1a has the orifice 16 located in the abutment portion 15 such that the material 18 is extruded tangentially with respect to the wheel 11. However, as shown in Figure ib, an orifice 16 may be located in a shoe member 14a associated with an abutment portion 15a in an apparatus 10a, so that the material 18 extrudes radially through the orifice 16 with respect to the wheel 11. In other respects the apparatus 1 0a of Figure la is the same as the apparatus 10 of Figure 1.

Although the mandrel 29 has been shown with three wing portions, an alternative number of wing portions may be used. In some appiications of the invention (see Figure 7), the wing portions might be dispensed with altogether, apertures 65 for extrusion being defined between a frusto-conical mandrel 60 and enlarged flutes 67 or similar in the surface of the orifice 16. Alternatively (see Figure 8), the flutes in the surface of the orifice 16 might be dispensed with, and apertures 70 for extrusion defined solely between wing portions 71a, 716, 71e of a mandrel 73 and the surface of an orifice 16. The recess 36 although desirable may also be omitted.

The apertures 26a, 26b, 26c have been shown by way of example as of equal cross-section area but they need not all have the same cross-section area.

As the pressure of the material 18 in the vicinity of the abutment portion 15 or 15a might not be uniform, it might be necessary to have dissimilar apertures 26a, 26b, 26c to compensate for differential pressure ofthe material 18 near the abutment portion 15 or 1 5a so as to arrange for substantially uniform flow through the apertures 26a, 26b, 26c. The domed portion 42 may be omitted and that end of the mandrel 29 be either flat, dished, or of some alternative shape if necessary, to assist in balancing the forces between the apertures 26a, 26b, 26c.

The apparatus of the aforementioned invention has an application in the extrusion of copper tubing from solid bar or particulate material, but may be used for the extrusion of alternative materials.

Alternative shapes of tubing such as square or polygonal, and other hollow sections such as externally and/or internally finned tubing as shown in Figures 9 and 10 may be produced by suitable shaping of the outlet end or lip of the extrusion orifice and of the adjacent end portion of the mandrel.

Claims

1. Apparatus for forming hollow section material by extrusion, the apparatus including a body defining an orificeforthe extrusion therethrough of material, and a mandrel means locatable in the orifice so that said material extrudes between the body and the mandrel means, wherein the mandrel means defines at least one relatively small hole therethrough from end to end of the mandrel means, so that said material initially extrudes through the hole(s) and heats the mandrel means and thereby heats the adjacent said material.

2. Apparatus as claimed in Claim 1, wherein the orifice converges towards the outlet thereof, and the mandrel means has portions thereof adapted to abut the adjacent converging surface of the orifice, so as to locate the mandrel means in the orifice.

3. Apparatus as claimed in Claim 1 or Claim 2, wherein the orifice is generally of frusto-conical or of polygonal form.

4. Apparatus as claimed in any one of the preceding Claims, wherein the orifice at the outlet end thereof has a lip portion with an inner surface that is shaped so as to define the outer surface of the hollow section material extruded.

Amendments to the claims have been filed, and have the following effect: Claim one above has been deleted or textually amended.

New or textually amended claims have been filed as follows:- 1. Apparatus forthe continuous forming of hollow section material by extrusion, which apparatus comprises rotatable wheel means constituting a movable member and defining an endless groove around the wheel means for containing material to be extruded, a stationary shoe member adapted to overlie part of the length of the groove, an abutment member associated with the shoe member and adapted to project into the groove so as to substantially block a portion of the groove, at least one die orifice having an inlet and an outlet and associated with the shoe member or the abutment member, said orifice being for the extrusion therethrough of the material in the groove as the wheel means rotates, and a removable mandrel means locatable in the orifice for the extrusion of the material about the mandrel means, wherein the mandrel means defines at least one relatively small hole therethrough from end to end of the mandrel means, so that said material initially extrudes through the hole(s) and heats the mandrel means and thereby heats the adjacent said material.

5. Apparatus as claimed in any one of the preceding claims, wherein the mandrel means comprises a main body thereof and an end portion locatable at the outlet end of the orifice, the end portion being shaped so as to define the inner surface of the hollow section material extruded.

6. Apparatus as claimed in Claim 5, wherein a peripheral recess of curved form is defined at the junction between the end portion and the main body.

7. Apparatus as claimed in Claim 5 or Claim 6, wherein the main body of the mandrel means defines a plurality of wing members, which wing members constitute portions adapted to abut the surface of the orifice so as to locate the mandrel means in the orifice.

8. Apparatus as claimed in Claim 5 or Claim 6, wherein the main body of the mandrel means is of frusto-conical form.

9. Apparatus as claimed in any one of the preceding Claims, wherein the mandrel means at the inlet end of the orifice is of flat, or domed, or of dished form.

10. Apparatus for the continuous forming of hollow section material by extrusion, substantially as hereinbefore described with reference to Figure la or 1L; and Figures 2 to 6, or Figure 7, or Figure 8 of the drawings.

11. Apparatus as claimed in Claim 10, arranged to extrude hollow section material as hereinbefore described with reference to Figure 9, or Figure 10( the drawings.