COPPER-ALUMINIUM COUPLINGS

Abstract: The copper pipe or tube stub (1) has an even thickness, smaller than that of the aluminium pipe stub (4) thereto it is to be welded, and an outer diameter substantially equal to that of the aluminium pipe stub, an increased thickness zone (2) being provided inside the end portion of the copper pipe stub (1), which is formed by butt upsetting and creeping of the metal material, the stub portion adjoining the increased thickness zone being work-hardened in such a way as to allow for the pipe stub to resist against the mechanical stresses occurring during the welding operations.

Description: The present invention relates to a pretreated copper pipe,Xhich has been so shaped as to be particular ly effective to be coupled, the Bo lea flash welding mfthod,to aluminium pipes, of like thickness and diameter, to provide such a copper-aluminium coupling which is suitable for application to the evaporators made by the so-called Roll-bonct method. As it is well knows, the evaporators made by the "Roil-bond" method are hydraulically coupled to the refrigerating circuit by means of aluminium small pipes or tubes, butt welded to copper pipe stubs and coupled to the evaporators. Also known is the fact that1 in order to make the mentioned copper-aluminium couplings, there are required pipes,especiallg copper pipes,havikg particular and well defined constructional and size characteristics. Yore specifically, the butt welding of those pipes has to be carried out by a specifically designed method. Presently the most used method is known to those skilled in the art as the "Schlatter" method, that is a flash welding method. Tilis method,in particular, requires that the pipes which are to be butt welded-one of copper and the other of aluminium-be provided with like outer diameter and thickness. moreover the minimum thickness of said pipes is to be included within 1.25 and 1.53 znm,whereas the purity of the metal material is to be a very high one(99.!-9.) and the aluminium pipe is to be an annealed one, while the copper pipe is to be a crude one. Thus,all the mentioned requirements make the welding process a highly cumbersome one, mainly as it is required that the copper pipe has such a thickness which is excessive tor the conventional use or the pipe itself. Moreover a near crude copper pipe, as required, makes difficult the downstream working operation on the pipe itself, since it is frequently necessary to vary the diameter thereof in order to provide,for exainple, narrower or tapering zones and other modifica- tions. Accordingly, the task of the present invention is to provide such a pretreated and shaped copper pipe which is effective to be coupled to an aluminium pipe, by the conventional welding methods, while having a comparatively smaller thickness thai that presently required, thereby providing great economical advantages. Within that task, it is an object of the present invention to provide such a copper pipe stub which is so treated as to present an increased thickness at the welding zone and, contemporaneously, a workhardened region at the enlarged ana adjoining portion of the pipe, effective to allow for the pipe to resist against the mechanical stresses occurring in the welding end step. According to one aspect of the present invention the above task and object, as well as yet other objects which will become more apparent thereinarter, are achieved by a copper pipe or tube stub, effective to be coupled to an aluminium pipe for making evaporators and the like, characterized in that it has an even thickness, smaller than that of the aluminium pipe thereto it is to be welded, and an outer diameter substantially equal to that of said aluminium pipe, an increased tiches zone being provided inside the end portion of said copper pipe stub to be welded, said increased thickness zone being restrained to the zone which is normally covered by the amorphous aluminium during the welding operations, and being formed by butt upsetting and creeping of the metal material or by like methods, the stub portion adjoining said increased thickness region being work-hardened in such a way as to allow for said pipe stub to resist against the mechanical stresses occurring during the welding operations. hiore specifically the annealed copper pipe stub has, initially, an even thickness of about 0.75 mm and it is enlarged successively at a zone thereof in such a way as to bring the thickness of said zone, at the portion to be welded, to about 1. 25mm, as it is required by the thereinabove mentioned flash welding method. further characteristics of the copper pipe or tube fs according to the present invention, will become more apparent thereinafter from the following detailed description of an embodiment thereof, with reference to the accompanying drawing, where: fig.l is a diametrical longitudinal crosssection view illustrating a copper pipe or tube stub according to the present invention arranged in an aligned position with respect to an aluminium pipe thereto it is to be butt welded; Fig. 2 is a longitudinal cross-section view illustrating a. copper pipe stub according to the present invention, being butt welded to the related aluminium pipe. As thereinabove stated, in order to provide a satisfactory coupling between copper and aluminium pipes, by means of the flash welding method, it is required that said pipes be provided with well defined thickness and outer diameter characteristics, and more specifically: the aluminium pipe is to be a very high purity annealed pipe,whereas the copper pipe is to be a thalf-crude" copper pipe, also of very high purity; moreover, with respect to the thicknesses of said pipes,the required value is to be included within 1.5 and 1.25 mm. The present invention affords the possibility of using copper pipes of comparatively smaller thicknesses, that is of 0.75 mm with great economical and workabili- ty advantages. According to the present invention,the copper pipe stub has an even thickness of about 0.75 mm and it is pre-annealed according to the known methods. In order to bring the thickness of the welding zone A, obtained by adding an outer collar 3 of amorphous aliminium, to the minimum required value of al least 1.25 mm, the ena portion of the copper pipe stub 1 to be welded, is enlarged in the inside thereof by means or butt upsetting, carriect out by known me thods, which causes the metal material to suitably creep in such a way as to provide, inside the zone A, an annular enlarged region or zone,having the desired even thickness. The several mechanical operations, which are necessary tor making the enlarges zone 2,simultaneously provide the remaining portion or the copper pipe or tube stub 1 with an artificial work-hardened structure effective to allow tor the pipe to resist against the compression load occurring during the end welding step, without undergbing any deformations. After having arranged as thereinabove stated the copper pipe stub, the butt welding to an aluminium pipe stub 4 (fig.2) is carries out, easily,by the known slash welding method; the two welded pipes are shown in rig. 2, therein one may see the outer amorphous aluminium collar 3 covering the zone A or the copper pipe stub 1. In practicing the invention, the outer collar 3 may oe replaced by a separate collar to be welded at the required zone by means of known methods.

Claims: CIA IMS 1- A copper pipe or tube stub, effective to be coupl ed to an aluminium pipe tor making evaporators and the like, characterized in that it has an even thickness, smaller than that ot. the aluminium pipe thereto it is to be welcted, and an outer diameter substantially equal to that or said aluminium pipe, an increased thickness zone being provided inside the end portion of said copper pipe stub to be welded, said increased thickness zone being restrained to the zone which is normally covered by the amorphous aluminium during the welding operations, and being formed by butt upsetting and creeping or the metal material or by like methods, the stub portion adjoining said increased thickness region being work-haraened in such a way as to allow ror said pipe stub to resist against the mechanical stresses occurring during the welding operations. S- A copper pipe stub(l)accord:Leg to claim 1, characterized in that said enlarged zone @ 2) has such a thickness as to bring the end thickness at the welaing zone (A) to a value substantially equal to that or the aluminium pipe (4) and at least to the minimum value required Dy the riash welding method. 3- A copper pipe stub, according to claims 1 and 2, characterized in that, before worming said enlarged thickness zone (2), said pipe stu@ is subjected to an annealing treatment. 4- A copper pipe stub, according to the preceding claims, characterized in that the starting thickness there or, after the annealing treatment, is of about O.75nirn.

Inventors: FERRARA, ARTURO
Applicants: O.L.S. S.R.L.
Application year: 1983
Main classification: F16L13
IPC codes: F16L13, B23K11