Technical Field

The present invention relates to a method of manufac- turing a brazing pin for use at soldering for example a cable lug to a railway rail. The invention also relates to such a brazing pin.

Technical Background

At the alloying of for example a cable lug to a railway rail it is known to use a so called brazing pin. Such brazing pins can also be used in other connections, where it is desired to alloy a metal object to a surface of any kind. At the soldering of a cable lug to a railway rail or some other metal object the brazing pin is brought into the central opening of the cable lug to contact against the rail, whereupon a strong current is applied through the brazing pin and the rail, so that a luminous arc is created for melting down the silver alloy present at the end of the brazing pin and for filling the opening in the cable lug, at the same time as the cable lug is attached by melting to the rail.

In an earlier known brazing pin a small insert of silver alloy material is moulded to one end of the brazing pin, whereupon a relatively thin cap of silver alloy material is attached to the insert. Flux, which is needed for a proper soldering, is arranged in a smaller space between the insert and the cap.

The main part of the brazing pin is preferably manu¬ factured of brass for good current conduction. This main part is suitably provided with a notch, and the portion of the main part in front of this notch will after the soldering operation be a part of the connection together with the silver alloy and assist in filling the opening in the cable lug. Such a brazing pin is comparatively expensive to manufacture, as the main part of the brazing pin of brass

first has to be turned, pressed or cast, whereupon the insert of silver alloy has to be moulded on the main part and a pickling, turning and degreasing will be performed; the pressed cap with flux therein is finally to be attached. Besides its expensive manufacturing, the prior brazing pin has the serious drawback that the cap with the flux is not hermetically closed, which leads to a possible absorption of moisture by the flux, making the brazing pin unusable. The Invention

A new method of manufacturing such a brazing pin is according to the invention characterized in that the main part of the brazing pin is machined, preferably turned or pressed, a stud being formed at one of its ends, that a hollow cap with thick walls of silver alloy material is machined, preferably by cold pressing or turning, the outer diameter of the cap corresponding to the outer diameter of the main part and the inner diameter of the cap being slightly less than the outer diameter of the stud, that the cap is filled with flux, and that the cap with the flux therein is pressed together with the stud of the main part. A brazing pin manufactured in this way is substan¬ tially simpler and cheaper to manufacture than the conven¬ tional brazing pin described above, and the cap is herme¬ tically closed, as it is manufactured by a thicker material and has a slightly smaller diameter than the stud, so that a press fit is accomplished.

The invention also relates to a brazing pin, which is characterized in that a main part of the brazing pin has a stud at one of its ends, that a hollow cap of silver alloy material having an outer diameter corresponding to the outer diameter of the main part and an inner diameter which

is slightly smaller than the outer diameter of the stud, is pressed onto the stud and in that flux is provided in the cap.

The Drawing The invention will be further described below under reference to the attached drawing, in which FIG 1 partly in section shows an earlier known brazing pin and FIG 2, also partly in section, shows a brazing pin according to the invention. Detailed Description of a Preferred Embodiment

A conventional brazing pin shown in FIG 1 has a main part 1 made of brass, for example by turning or pressing. This cylindrical main part 1 is provided with a notch 2, whose purpose is to serve as a kerf at the use of the brazing pin at soldering and to limit the heat transfer backwards or to the left in the main part .

The main part 1 is provided with an insert 3 of silver alloy material at its forward end to the right in FIG 1. This insert 3, which has a slightly smaller diameter than the main part 1, is moulded to the main part 1. A thin cap 4 is pressed of silver alloy plate. A certain volume of flux 5 is filled into the cap 4, whereupon the latter is attached to the insert 3. Due to the thin and soft material in the cap 4 the latter can relatively easily come off from the insert 3 and is not hermetically closed in relation to the insert.

The main part 1 is at its rear end to the left in the drawing provided with a hollow knob 6, in which a thread 7 is inserted and fixed. The purpose of the thread 7 is to serve as a current connector to the brazing pin and to melt by the development of heat at a certain transmitted energy so as to stop the process.

At the use of the brazing pin at soldering the main part 1 of the brazing pin to the right or in front of the

notch 2 will be alloyed, the insert 3 and the cap 4 becoming filling material.

In a corresponding way a brazing pin according to the invention and shown in FIG 2 has a main part 11, a notch 5 12, a knob 16 and a thread 17. These parts have the same function as corresponding parts in the embodiment according to FIG 1. Brazing pins without threads can also be pro¬ vided.

The main part 11 is provided with a stud 13 at the

,10 manufacture, the stud 13 accordingly being integral with the main part 11 and of the same material as the latter, namely normally brass. A cap 14 is preferrably made by cold pressing of silver alloy material . Alternative methods of manufacture are turning and casting. The material thickness

15 of the cap 14 is substantially greater than the material thickness of the cap 4 in the embodiment according to FIG 1. The outer diameter of the cap 14 corresponds to the outer diameter of the main part, whereas the inner diameter of the cap is slightly smaller than the outer diameter of

20 the stud 13, so that a press fit is obtained between the parts 13 and 14. The dimensioning can for example be such that the diameter difference is 0,05-0,15 mm at an outer diameter of the main part 11 and the cap 14 of 8 mm and a diameter of the stud 13 of 4,5 mm. Brazing pins of other

25 sizes are also manufactured.

Before applying the cap 14 on the stud 13 a certain volume of flux 15 is filled into the cap. Due to the con¬ struction as shown and described a certain overpressure prevails in the flux 15 after the mounting of the cap 14 on

30 the stud 13.

The brazing pin according to the invention functions in the same way as the earlier known brazing pin. The difference is above all that the new brazing pin is sub¬ stantially simpler and cheaper to manufacture and that the

35 cap 14, which is the only source for silver alloy material

in the design, is securely fastened on its stud 13 in a hermetically closed fashion.