Patent Publication Number: US-6655415-B2

Title: Copper tubing

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of Application No. PCT/GB00/03933, filed Oct. 12, 2000, which is incorporated here by reference, and which claims the priority of United Kingdom Application No. 9924161.4, filed Oct. 12, 1999. 
     This application relates to Applicant&#39;s application Ser. No. 10/086,634, filed Mar. 4, 2002 which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to copper tubing produced by continuous extrusion apparatus. 
     BACKGROUND OF THE INVENTION 
     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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a cross-section of a die top according to the invention; and 
     FIG. 2 shows a plan view of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     According to the present invention, there is formed an extrudate product in the form of a continuous, seamless, copper tube having a mass in excess of 500 kilograms. 
     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. 
     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). 
     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. 
     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. 
     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. 
     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.