US2064998A - Switch contact - Google Patents

Description

R. A. WAITE SWITCH CONTACT Dec. 22, 1936.

Filed Aug. 27. 1935 F: G. 5 7 WW WWW INVENTOR/ v ATTORNEY Gil Patented Dec. 22, 1936 NlTED STATES PATENT OFFICE 2.964.998 swrrcn comuc'r Application August 27, 1935, Serial No. 38,011

1 Claim.

This invention relates to electric contacts and to the method of manufacture of such contacts.

Contacts in electric circuits are subject to wear due in part to burning caused by the arcing which occurs as a circuitis made and broken. Worn contacts require replacement at intervals according to the rate of wear, which depends upon the particular service required of such contacts. Such replacements involve considerable expense in time and materials. It has been found that by using a copper contact having a cadmium insert as one of a pair ofcontacts the wear thereon caused by arcing has been minimized, especially when used in cooperation with a cadmium impregnated carbon contact. For example, with a certain switch having a copper contact cooperating with a carbon contact, the life of the carbon contact was about three months and that of the copper contact about six months in commercial operation. Upon replacing the carbon contact with a cadmium impregnated carbon contact, the life of the copper contact was less than when used with the carbon contact without cadmium impregnation. Upon, using a copper contact having cadmium inserted in its face in place of the copper contact for cooperating with the cadmium impregnated carbon contact, the switch has continued in commercial operation for over a year without appreciable wear on the contacts.

A feature of the invention is the use of cadmium as an insert in a metallic contact.

A second feature of the invention is a simple and economical method of manufacturing the contact involved in this invention.

A third feature of the invention is the -provision of a pair of contacts, one contact/having a cadmium insert and the other contact being of carbon impregnated with cadmium.

Other features and advantages will be apparent.

from the following description and appended claim.

The invention will be described by way of iilustration in connection with a switch adapted to open and close an electric circuit.

In the drawing: I

Figure 1 is a side view of a switch having contacts embodying the invention:

Figure 2 is an enlarged view of the face of the movable contact shown in Figure 1;

Figure 3 is a section taken along the line 2-4 of Figure 2;

Figure 4 is a view of the face of another style of contact in accordance with the invention: and

Figure 5 is a section taken along the line 5-8 of Figure 4.

Referring to the drawing, a switch I I embodyingthe present invention. is mounted on an insulating panel l2. Switch ll upon energization and deenergization of a magnet coil I2, is arranged to attract and release an armature I4 and a switch arm i5 secured thereto. A movable contact i8, carried by arm and insulated therefrom by a bushing i1, is adapted upon movement of the arm to cooperate with a fixed contact It in the making and breaking of an electric circuit. A spring between arm l5 and bushing ll acts to cushion the closing movement of the contacts. Fixed contact 18, clamped in a holder 2i secured to panel 12, is made of carbon impregnated with cadmium.

.Movable contact l8, shown enlarged in Figures 2 and 3, consists mainly of an integral head 22 and stem 23 made of copper. Stem 28 is suitably machined for accommodating various necessary electrical connections. Head 22 is provided with an undercut recess 24 of dovetail section, in which a cadmium insert 25 is fixedly secured.

Insert 25 covers the greater part and is flush with a contacting surface 26. Insert 25 is formed in head 22 of contact it by pouring molten cadmium into recess 24, with the contact cold, the copper walls of the recess being at the time relatively clean and free of oxide. The contact is then heated to the melting point of cadmium. This heating process causes the cadmium to adhere or bind to the copper in much the same manner as solder to a cleaned and tinned surface. Upon cooling the cadmium insert is finished flush with surface 28.

As previously stated. contact It consists of carbon impregnatedwith cadmium. When both contacts are of metal there is a possibility that they might fuse or freeze together due to arcing. i

It has been found that by using a contact of carbon against one of metal the possibility of freezing together is eliminated. The use of a carbon contact impregnated with cadmium. such as contact l8, combines the non-freezing feature of carbon with the long wearing feature of cadmium.

Head 22 may contain more than one cadmium insert and these inserts may be of different anchoring shape. One such variation is shown in Figures 4 and 5, where head 22 has a plurality of cadmium inserts 2! embedded therein in apertures 28 of screw thread section. Inserts 21 are formed and secured in head 22 in a manner as previously described for insert 25.

What is claimed is:

In an electric switch, a copper contact with a cadmium insert embedded therein, said insert covering a portion of the contacting face of said contact and being flush with said face, and a carbon contact impregnated with cadmium for cooperating with said copper contact.

RAYMOND ALONZO WAITE.

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