Continuous extrusion apparatus

[0002] This application is a continuation of Application No. PCT/GB00/03959, filed Oct. 12, 2000, which claims the priority of United Kingdom Application No. 9924160.6, filed Oct. 12, 1999, and each of which is incorporated herein by reference.

[0003] This application relates to Applicant's co-pending application filed Mar. 1, 2002 (Ser. No. 10/086,622), which is incorporated herein by reference.

[0004] This invention relates to continuous extrusion apparatus for the forming of metals by a continuous extrusion process in which feedstock is introduced into a plurality of circumferential grooves in a rotating wheel to pass into passageways formed between the grooves and arcuate tooling extending into the grooves.

[0005] WO96/29162 discloses continuous extrusion apparatus for the production of copper tubing having a rotatable wheel formed with a plurality of circumferential grooves provided with exit apertures in a die top and abutments displaced in the direction of rotation from the exit apertures.

[0006] According to the present invention, each of the plurality of circumferential grooves is provided with an exit aperture in the die top having a cross-sectional area in excess of twice the radial cross-sectional area of the associated groove and smoothly leading to a passage of minimum length to connect into an annular extrusion die.

[0007] Preferably, the exit aperture has a cross sectional area of three times the radial cross-sectional area of the associated groove.

[0008] Suitably, the exit aperture has a cross-sectional area of four times the radial cross-sectional area of the associated groove.

[0009] Desirably, the exit aperture has a cross-sectional area of five times the radial cross-sectional area of the associated groove.

[0010] The invention also includes an extrudate product in the form of a continuous, seamless, copper tube having a mass in excess of 500 kilograms.

[0011] It will be understood that the term seamless relates to copper tube formed as a tube by an extrusion process as distinct from a copper tube formed by edge joining a strip or strips along abutting edges.

[0012] In one embodiment of the invention, in which FIG. 1 shows a cross-section of a die top 2 corresponding to the plan view of FIG. 2, a rotatable wheel (not shown) is formed with a pair of circumferential grooves registering with abutments 4 formed on the die top 2. Adjacent each abutment 4, the die top 2 is provided with an exit aperture 6 having a cross-sectional area of approximately five times the radial cross-section of the associated groove. Each aperture leads to a passage 8 smoothly diverging to connect into an extrusion die chamber 10 housing an annular extrusion die (not shown).

[0013] In operation, feedstock in the form of continuous rods of copper is fed to each of the grooves and, as the wheel rotates, extrudes through the exit apertures 6 adjacent the abutments 4 and the passages 8 and is extruded from the annular extrusion die in the die chamber 10 as seamless copper tubing. Since the passages 8 are of minimum length, the two flows of extrudate through the passages combine at the annular die at a pressure only slightly lower than the pressure obtaining in the material in the grooves immediately adjacent the exit apertures 6, with a resultant extrusion temperature at the annular die of approximately 750° C. as compared with a temperature of approximately 650° C. achieved in prior art arrangements.

[0014] The relatively high temperature and pressure at the annular die enables the extrusion of sound, thin-walled, copper tubing without imperfections likely to arise from combining flows of extrudate at lower temperatures and pressures.

[0015] It will be appreciated that there is no limitations on the length of seamless copper tubing that may be produced in this manner, so that reels of 500 kilograms or more of continuous seamless copper tubing may be produced. Hitherto, utilising conventional extrusion techniques, it has not been possible to produce seamless, copper tubing in a continuous length of such a mass, even though there is a commercial demand for reels of continuous seamless copper tubing of a mass of 500 kilograms or more.

[0016] While this invention has been described as having a preferred design, it is understood that it is capable of further modifications, and uses and/or adaptations of the invention and following in general the principle of the invention and including such departures from the present disclosure as come within the known or customary practice in the art to which the invention pertains, and as may be applied to the central features hereinbefore set forth, and fall within the scope of the invention or limits of the claims appended hereto.