US 3592996 A
Description (OCR text may contain errors)
United States Patent METHOD OF SECURING AN ELECTRICAL CONTACT TO A SUPPORT 2 Claims, l Drawing Fig.
U.S.Cl 2l9/l2l, 200/166 Int. Cl 523k 15/00 Field of Search 29/630;
 References Cited UNITED STATES PATENTS 2,057,604 10/1936 Zickrick 200/166 2.987.610 6/ I961 Steigerwald 0. 219/117 3,075,281 1/1963 Spooner 29/l55.55 3,240,908 3/1966 Marcoux H 200/138 Primary Examiner-J. V. Truhe Assistant Examiner-R. E. O'Neill Attorney-Holman and Stern ABSTRACT: in manufacturing a movable contact for use in electrical apparatus, for example a contact breaker in a distributor, the contact is maintained in facial engagement with a support which has a lower melting point than the contact. An electron beam is then caused to traverse the contact in support in such a way that the part of the support traversed by the beam melts and an area of the contact close to the melted portion of the support is heated to a temperature between the melting points of the contact and support so that the support flows to form a joint.
METHOD OF SECURING AN ELECTRICAL CONTACT TO A SUPPORT in the manufacture of a movable contact for use in electrical apparatus, for example a contact breaker in a distributor for a road vehicle, it is necessary to secure the actual contact, which may be made from tungsten, to a spring support, which typically will be made from steel. The usual way of effecting such a connection is to braze the contact to a support pin, then to insert the support pin through a hole in the spring support and rivet the pin in position. Clearly, it would be much more convenient to secure the contact directly to the spring support, but this operation leads to difficulty. The spring support has to be subjected to a heat treatment to give it the required properties, and if the contact is brazed to the support before this heat treatment, the brazing joint is ruined by the heat treatment. The alternative is to braze the contact to the spring support after the heat treatment, but then the brazing operation ruins the spring properties.
The present invention seeks to overcome this problem, but although it provides primarily a method of securing a contact to a spring support, it can also be used advantageously to secure a contact to a support which does not have to have resilient properties. in the latter case, straightforward brazing can of course b employed, but the method in accordance with the invention is more convenient.
The method according to the invention comprises maintaining a contact in facial engagement with a support, the contact having a higher melting point than the support, and causing an electron beam to traverse the contact and support in such a way that the part of the support traversed by the beam melts and an area of the contact close to the melted portion of the support is heated to a temperature between the melting points of the contact and support so that the support flows to form a joint.
Preferably the support is formed with a hole through which the contact is exposed, and the portion of the support around the hole is melted.
The accompanying drawing illustrates diagrammatically one example of the invention.
Referring to the drawing, it is desired to secure a contact 11 formed from tungsten to a spring steel support 12. The support 12 is formed with a circular hole 13, and the contact I] is supported in facial contact with the support 12 so that the contact H is exposed through the hole 13. The joining is effected by means of an electron beam having a focus indicated at 14. with the focal axis indicated at 15. The axis impinges on the contact 1! adjacent the edge of the hole 13, and because the focus 14 is above the support 12, the beam diverges as indicated and impinges on the support 12. The focus is moved in a circular path indicated at 16 so that the axis 15 moves in a circular path parallel to the edge of the hole 13. and the arrangement is such that the support 12 melts and the contact is heated to a temperature above the melting point of the support, so that the melted support flows to the hotter region and effects the required joint. The differential heating could of course be achieved in other ways, for example by controlling the beam density and/or path of traverse. For example the focus could be on or below the contact and the beam moved in a circular path but with a sinusoidal component. Alternatively, the voltage which accelerates the electrons from their source could be suitably controlled.
The invention is of particular use with movable contacts for distributor contactsets, and has been found to increase contact life and substantially increase the permissible operating speed of the contacts.
Having thus described my invention what I claim as new and desire to secure by Letters Patent is:
l. A method of securing an electrical contact to a support, comprising the steps of maintaining the contact in facial engagement with the support, the contact having a higher melting point than the support, and the support being formed with a ole through whic the contact is exposed, and causing an electron beam to traverse the contact and the region of the support directly adjacent the hole in such a way that the region ofthe support traversed by the beam melts and an area of the contact close to the melted region of the support is heated to a temperature between the melting points of the contact and support so that the melted region of the support flows into said hole to form a joint between the contact and the support.
2. A method as claimed in claim 1 in which the support is a spring support.