US2476886A

US2476886A - Contact construction

Info

Publication number: US2476886A
Application number: US488980A
Authority: US
Inventors: Miller Stephan; Peter A Pontius
Original assignee: Westinghouse Electric Corp
Current assignee: Westinghouse Electric Corp
Priority date: 1943-05-29
Filing date: 1943-05-29
Publication date: 1949-07-19
Anticipated expiration: 1966-07-19

Description

July 19, 1949. s. MILLER Erm.

CONTACT CONSTRUCTION Filed May 29, 1943 Fly a.

INVENTORS Szepbafn Mller Pele rA. Ponft'us. B21/ ATrORN Patented July 19, 19,49L y I ww tins, East Pittsburgh, Pa.,

rs to Weltinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 29, 1943, Serial No. 488.980

1 Claim. (Cl. 173-324) This invention relates, in general, to electrical contact structures, and more specifically to resilient contact structures. There are many applications where electrical contact structures having resilient characteristics are required. In many of these applications, the contacts are subjected to alternate heating and cooling, and it is necessary that the resilient characteristics of the contact remain unimpaired under such conditions in order that adequate contact pressure be assured at all times. l

In the past, the problem has been solved by adding spring reinforcing members to brace contacts of a non-resilient material, such as copper. Such reinforcing members comprise extra parts added to conventional contacts and materially increased the complexity and cost of the contacts. Another approach to this problem has been the use of copper alloys as contact materials. This, however, involves the use of relatively rare metals, and also increases the cost.

One object of this invention is to provide a novel resilient contact construction which is etilcient in operation yet economical of manufacture.

A more specic object of the invention is to provide a novel contact structure comprising a core of resilient material at least the major por- 'tion of which is clad with a good electrical conducting material.

Another object of this invention is to provide a novel contact construction embodying a core of a material capable of heat treatment to obtain resilient properties, with at least the major portion of the core clad with a good electrical conducting material.

Another object of this invention `is to provide a novel contact structure comprising a core of resilient material clad with a good electrical conducting material, and having on at least the contacting portion thereof a layer of a noble metal.

Another object of this invention is to provide a novel contact structure bent to shape from composite strip material which is capable of heat treatment after bending to obtain resilient properties.

These and other objects of this invention will become more apparent upon consideration of the following detailed description of preferred embodiments thereof when taken in connection with the atta/cned drawing, in which:

Figure 1 is a side elevation view of a fuse mounting having contact clips constructed in accordance with this invention;

2 tact clips constructed in accordance with this invention;

Fig. 3 is a section through one contact clip shown in Fig. 1, and taken substantially along the line III-III thereof;

Fig. 4 is a section through a contact clip taken substantially on the line IV-IV oi Fig. 2;

Fig. 5 is an enlarged transverse section taken through one leg of the clip shown in Fig. 4 substantially on the line V-V thereof;

Fig. 6 is an enlarged transverse section taken through one leg of the clip shown in Fig. 3 substantially on the line VI-VI thereof;

Fig. '1 is an enlarged transverse section through one leg of the clip of Fig. 3 taken substantially on the line VII-VII of Fig. 3;

Fig. 8 is a section of a clip similar to Fig. 4, but illustrating a modified form; and Fig. 9 is an enlarged transverse section taken through one leg of the clip shown in Fig. 8.

The contact constructions constituting this invention may be embodied in various types of electrical apparatus wherein resilient contacts are required. The invention is illustrated in the drawing as embodied in contact clips which must Fig. 2 is a side elevation view of a combined n fuse and disconnect switch mounting having conhave resilient characteristics in order to provide an adequate contact pressure when a cooperating contact is inserted in the clip.

In Fig. 1, there is illustrated contact clips constructed in accordance with this invention for cooperation with a fuse. The fuse is preferably mounted on a base 2 of insulating material, such as porcelain or a molded insulating material. Generally U-shaped contact clips l and t are supported on the base and secured thereto by bolts 6 extending through apertures provided in the bight portions of the clips, respectively, and through apertures in base 2.

In accordance with this invention, the contact clips 4 and 5 are preferably made by cutting strips of suitable length from composite strips, straps, flat rectangular wires or the like. These composite strips or the like comprise a central layer or lamination I of a resilient material, preferably a material such as carbon steel which is responsive to heat treatment to acquire increased spring characteristics. The central layer l is clad with a relatively good electrical conducting matcrlal I0, such as copper, brass, silver, or the like. Any desired method may be employed for securing the layers 8 and Il together. One method which may be employed comprises supporting a steel billet in a mold and pouring the molten copper or other good electrical conducting material around the steel billet to completely enclose the 'mcnbasell Another method for making the strips from which fuse clips may be cut, is to apply the strips oi copper or other good conducting material to opposite sides of a steel billet, sheet or the like. and roll the resulting sandwich-like structure at a predetermined high temperature to cause the outer and inner layers to become intimately bonded together. Such a structure may then be rolled to the desired thickness, and the strip of material produced will be substantially as shown in Fig. 5, that is, the central steel layer will be provided with good conducting material Il only on opposite sid thereof, with the edg of the steel layer exposed. This method of making strips from which fuse clips may be cutl will be hereinafter referred to as the rolling method.

When strips are cut from a strip or the like formed in accordance with the casting method, they may be further cut along one edge to provide integral tabs l2 which may then be bent inwardly towards each other to form stops. During the cutting operation, the contact clip blanks may also be cut to iorm an integral terminal Il which extends laterally from the bight portion of the clip. The contact clip I shown in Figs. 1, 3, 6 and 7 is bent to shape from material formed by the casting method. It will be noted that this clip has conducting material Hi covering the maior portion of central layer 8, but has the central layer or core 8 exposed at the outer end edges of the leg portions of the clip, and at one side edge, except for the space occupied by stops i2. This clip has the leg portions thereof formed with outwardly curved intermediate portions for receiving terminal ierrules I8 ons fuse Il. Stops I! formed on clips 4 and l are for the purpose of preventing longitudinal movement ci the fuse relative to the clips.

After the contact clip has been bent to shape, such for example as the shape illustrated in Fig. 3, the clip may then be subjected to heat treatment to harden the steel core l and increase the resiliency thereof. Sucha treatment, while hardening the steel and increasing its resilient characteristic. may or may not have this eiiect on the outer layers I 0 depending upon the material used. Thus, relatively pure copper does not have any resilient properties imparted to it by heat treatment but the conductivity thereof is increased by such treatment. 'Certain copper ailoys, however, such as beryllium copper, do have theix milient properti increased by heat treatmen Pour contact clips Il, 22. u and Il are illustratedinl'lg.2asbeingsupportcdonabase2l ofinsulatingmaterial, inthesamemanneras contactclipslandlarelupportedonthebase I of Pig. l. The two intermediate contact clips u and Il are shown as having an integral com- The clips supported on base Ii are formed with leg portions having ilat parallel intermediate portions terminating in flared outer ends for cooperation with the knife blade terminals 2l oi' atuse 3l, and for receiving a disconnecting switch blade 32. The disconnectim twitch blade 32 may be pivotcd on clip 24, al by apivotu, formovementoitheotherendtherso( into and out of engagement with-contact clip Il.

an added layer It applied thereto of a noble metal such as silver. gold. platinum or the like. Figs. B and 9 illustrate a contact clip like that shown in Pig. 4 having an added coating II. Where silver is utilised for the material for coating it, it is preferably electrolytically applied so as to completely enclose central layer I to protect it from corrosion. Layer also serv the purpose of improving the contact surface, and providing a complete jacket for layers l and il of good conducting material. thereby increasing the conductivity oi the clip and decreasing the electrical contact resistance of the'clip.

Contact constructions such as those described above have a relatively high electrical conductivity, and also have very good resilient characteristics. and these results are obtained by the economical use oi relatively common materials. Thus, steel which is a relatively cheap and abundant material constitutes the main portion of the contact, and only a relatively small amount of copper or other good electrical conducting material need be employed, as compared to contacts constructed entirely of copper, or similar material, or alloys thereof. Moreover, by covering substantially the entire surface o! central layer 8, the steel is protected from corrosion, and by using a protective laver of relatively good electrical conducting material, low contact resistance is obtained and the conductivity of the clip is materially increased. As pointed out above, the outer layer Il of good electrical conducting material may cover the entire surface of central layer 8. in which case even better protection oi the central layer is obtained. together with increased conductivity. By providing a covering of good electrical conducting material. at least on opposite sides of the central layer l, a terminal may be formed integral with the contact. or may be secured to either side thereof in engagent with either layer Il oi good electrical conducting material. It is believed apparent that with a contact clip constructed in accordance with this invention, no supplemental reinforcing meam is necessaryaswith solidcopperclips,becauseot the high resiliency oi central layer l. Obviously. leucopperisrequiredthanwithsolidcopper clipsorclipsoi'aoopperallcy. Furthermore. contacts constructed in accordance with this invention maybetirstbenttolbapaafterwhich they may be heat-treated to impart additional resiliency to the central layer I.

Having described preferred embodiments of the invention in accordance with `the patent statutes. it is desired that the invention be not limited to these particular embodiments inasmuchasitwillbeobvioustopenonsskilledin theartthatmanymodiiicationsandcbangesmay be made in these particular embodiment witboutdepartingtromthebroadspiritandscopeot this invention.

We claim as our invention:

An elongated resilient contact member constructsd to engage a cooperating contact member at one point and to have an electric oduct secured thereto at a remote point, comprising, Number an elongated carbon steel lea! spring having rela- 537,538 tively high electrical resistance, said spring' be- 1,001,669 ing clad with a resilient beryllium copper alloy 1,025,246 in a continuous layer connecting said pointe. 5 1,603,682 STEPHAN MILLER. 1,873,931 PETER A. PONTIUS. 1,881,997 1,925,856 REFERENCES CITED 2,181,083 The following references are of record in the 10 23061662 le of this patent: UNITED STATES PATENTS 212711111 Number Name Date 2,281,446

471,271 Metzger Mar. 22, 1892 8 Name Date Metzger Apr. 16,' 1895 Monnot .Aug. 29, 1911 Cole May '1, 1912 Gagnon Oct. 19. 1929 Matsen Aug. 23, 1932 Browne Oct. 11, 1932 Vaughan Sept. 5. 1933 Payette Nov. 21, 1939 Conradi et al July 2, 1940 Staples July 9, 1940 Pierce Jan. 6, 1942l Wul' Jan. 27, 1942 Laise Apr. 28, 1942