US3009043A

US3009043A - Disconnecting contact

Info

Publication number: US3009043A
Application number: US836408A
Authority: US
Inventors: Jr Edwin C Goodwin; Ira W Paterson
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1959-08-27
Filing date: 1959-08-27
Publication date: 1961-11-14
Anticipated expiration: 1978-11-14

Description

Nov. 14, 1961 E. c. GOODWIN, JR., ETAL DISCONNECTING CONTACT 2 Sheets-Sheet 1 Filed Aug. 27, 1959 (Momma plww J2. swam/14m.

27M fol/MAM W 5.

@MZQW Nov. 14, 1961 E. c. csoonwm, JR., ETAL 3,009,043

DISCONNECTING CONTACT 2 Sheets-Sheet 2 Filed Aug. 27, 1959 UM/0mm 50140144 Edp dwM4,JA.

31km fake/{00M y WM 5 aw/K442 Jnsl rates This invention relates to electric circuit interrupters and more particularly to a new and improved arrangement for primary disconnect contacts wherein each of a plurality of finger contacts is guided and retained within a housing.

In electrical circuit interrupting devices such as high voltage circuit breakers it is necessary to provide primary disconnect contacts so that the circuit breaker can be selectively connected and disconnected from the electrical circuit it protects. Heretofore primary disconnect contacts have been used employing a plurality of finger contacts designed and constructed so that each finger contact may be individually biased by coil springs arranged within a housing. This housing merely serves as an enclosure. It is not flexible enough to compensate for misalignment of the breaker and its cubicle while providing uniform spacing for the contact fingers and springs. The prior art structures are costly to manufacture and require expensive tools to assemble and disassemble in the field.

In accordance with the invention claimed a new and improved primary disconnect contact is provided which employs an interleaved substantial-1y dustproof enclosure which is flexible enough to compensate for misalignment of the circuit breaker and its cubicle. The disconnect contact structure is completely self-contained having no loose parts and the biasing springs located at each end of the contact fingers serve the dual purpose of providing contact finger pressure and the force which locks the parts of the assembly together. The new and improved contact structure provides uniform spacing for the contact fingers and springs, and improved conduction and radiation surfaces are arranged in intimate contact with the side walls of the current carrying finger contacts.

It is, therefore, an object of this invention to provide a new and improved primary disconnect contact structure.

Another object of this invention is to provide 'a new and improved primary disconnect contact in which a housing serves as a positioning, pivoting and retaining means for a plurality of finger contacts.

A further object of this invention is to provide a new and improved primary disconnect contact in which the housing comprising a plurality of interleaved parts is locked together by the contact biasing means.

A still further object of this invention is to provide a housing for a plurality of finger contacts employing improved conduction and radiation surfaces in intimate contact wtih the side walls of the finger contacts.

Objects and advantages other than those set forth will be apparent from the following description when read in connection with the accompanying drawing, in which:

FIG. 1 is an isometric view with parts broken away of a primary disconnect contact embodying the present invention;

FIG. 2 is a left end view of the structure shown in FIG. 1 with parts broken away;

FIG. 3 is 'a cross sectional view of the structure shown in FIG. 2 taken along the line IlIlII;

FIG. 4 is an elevational view of one of the spacer members forming the interleaved housing structure shown in FIGS. 1-3;

FIG. 5 is a plan view illustrating the manner in which two adjacent spacer members interlock together;

FIG. 6 is a cross sectional view illustrating the invenatent "are acters of reference, FIGS. 1, 2 and 3 illustrate an electric.

switch and more particularly a primary disconnect contact 10 for a circuit breaker structure. Contact 10 is attached to an electric conductor or stud 11 usually forming a part of a circuit breaker. The primary disconnect contact 10 comprises a plurality of finger type contacts 12 which are spacedly mounted around stud 11 for independent limited movement in a housing 15. Housing 15 comprises a first ring shaped member 13 and a second ring shaped member 14 with member 14 being mounted at least partly around stud 11 and in spaced relationship with member 13.

Members

13 and 14 are pivo-tally interconnected by a plurality of interleaved spacer members 16 which are arranged to extend substantially longitudinally of stud 11.

Each of the ring shaped

members

13 and 14 is provided with a first arcuate surface 17 extending around its periphery with surface 17 facing the center of the ring, and a flange 18 extending inwardly of surface 17 providing a second arcuate surface 19 spaced from and facing surface '17.

Each of the spacer members 16 may have, for example, a tr-oughlike shape 26 having flanges 21 and 22 extending therefrom (as shown in FIGS. 4 and 5) along its longitudinal edges. Flange 21 is provided with arcuate projections 23 which fit into a continuous annular recess 24 extending around the circumference of each of the ring shaped

members

13 and 14. Projections 23 of spacer members 16 are loosely arranged or pivotally mounted in recess 24 in ring shaped

members

13 and 14 for providing limited lateral movement of these ring members relative to each other. When spacer members 16 are arranged around ring shaped

members

13 and 14 to form the unitary housing 15, flange 22 of one spacer member overlaps flange 21 of an adjacent spacer member so that an interleaved structure is created interconnecting ring shaped

members

13 and 14. The troughs 20 of spacer members 16 project inwardly of ring shaped members 13 and 14 (as shown in FIG. 1) to form a plurality of cooling cavities extending longitudinally of housing '15 and stud 11. By interleaving spacer members 16, as shown, a predetermined space is provided between adjacent spacer members which space is partially enclosed by the walls forming troughs 2t 1 Finger contacts 12 are each mounted to extend within flanges 18 of ring shaped

members

13 and 14. A pair of spring biasing means such as coil springs are arranged one at each end of finger contacts 12 within flanges 18 of each ring shaped member and within the space between adjacent troughs 2t). Finger contacts 12 are provided at each end thereof with a flat surface 27, and coil springs 26 are each arranged between a surface 27 and a flange 22. These coil springs bias the finger contacts 12 radially inward toward the center of the assembly against the arcuate surfaces 19 of flange 18. Each of the finger contacts 12 is provided with a pair of spaced contact

engaging surfaces

28 and 29 one of which is arranged to engage stud 11 and the other of which is arranged to engage a movable contact stud 30 shown in FIG. 6. In order to firmly attach the disconnect contact structure 19 to stud 11 finger contacts 12 are each provided with a groove 32 into which the outer periphery 33 of ring shaped yoke 34 is arranged to extend. Yoke 34 is threadedly attached to the terminal end of stud 11 by means 3 of bolts 35 spacedly arranged around the periphery of yoke -34.

Since electrical engagement between finger contacts 12 and stud 11 will move contacts 12 radially outward against the bias of coil springs 26 mounted in ring shaped member 14, the arcuate surface 19 of ring shaped member 13 controls the movement of contacts 12. Finger contacts 12 pivot around their contact surfaces 28 and around the outer edge of yoke 34- arranged in groove 32. Surface 19 of ring shaped member 14 controls the movement of finger contacts 12 when stud 30 is forced between the contact surf-aces 29 of finger contacts 12.

The greater the force of the spring biasing means 26 for each finger contact the greater will be the entering force required for electrical engagement between the primary disconnect contact assembly 16 and stud 30.

As noted from FIG. 2 of the drawing, housing 15 comprises a plurality of interleaved spacer members 16 which provide spring openings therebetween evenly spaced around the inside of the periphery of ring shaped

members

13 and 14. Into these openings are arranged coil springs 26 which not only bias the finger contacts toward the longitudinal axis of the housing but bind the primary disconnect contact structure into a unitary device. The finger contacts 12 comprise substantially fiat conducting members having their contact surfaces '28 and 29 spaced from each other at different ends thereof on difierent sides of groove 32. The periphery of yoke 34 loosely fits into groove 32 and the conducting surfaces 28 are brought into high pressure electrical contact with stud 11 when the primary disconnect contact 16 is assembled on stud 11. When the primary conductor stud 30 is moved into engagement with the primary disconnect contact coil springs 26 in ring shaped member 13 bias the contact surfaces 29 of finger contacts 12 into high pressure electrical engagement with primary conductor stud '30. Finger contacts 12 are individually movable and each are pivotally mounted about either of its

surfaces

28 or 29 depending on the alignment of studs 11 and 313'. Each finger contact is provided with its individual biasing means such as coil springs 26 to bias it into high pressure electrical engagement with the contact studs 11 and 30. Thus, in the event any one of the plurality of coil springs should fail there will be sufiicient force from the remaining coil springs on other finger contacts 12 to maintain high pressure electrical engagement. Since each coil spring 26 maintains its individual finger contact 12 in high pressure contact with studs 11 and 30 loss of any one spring merely causes loss of only one point of high pressure contact.

It is further noted that when stud 31 is removed from the primary disconnect contact 14 the coil springs 26 arranged within ring shaped member 13 combine with the arcuate surface 19 of flange 18 to maintain finger contacts 12 in their given circular configuration. The inner rim of the ring shaped members 13- and 14 and particularly their arcuate surfaces 19 act as stops to limit the positions of the finger contacts 12 in the stud disengaged positions. Thus limited, the force required to initiate contact engagement is held to a minimum. This condition also provides the required electrical clearance in the test position of the circuit breaker using this disconnect contact structure with a minimum of breaker withdrawal motion.

In view of the fact that

rings

13 and 14 are flexibly supported by the interleaved spacer members 16 in alateral plane independently of each other, they provide outer support for the finger contacts and thereby maintain continuous equalized pressure of each individual finger contact within the prescribed limits of misalignment of the circuit breaker and its associated contact studs. These limits are defined by the engagement clearances between the mounting plate or yoke 34 and the slots or grooves 32 in the finger contacts 16 with which yoke 34 mates. The leading edge 37 of flange 18 of ring shaped member 13 may also be contoured to readily engage cubicle stud 30 and flexibly align the primary disconnect contact 11) therewith to assure substantially concentric engagement of the stud with the finger contact assembly.

As readily noted from the drawing the primary disconnect contact when completely assembled provides relatively large surface areas for dissipation of heat. In order to further increase the heat dissipation of the contact, assembly flanges 18 of ring shaped

members

13 and 14 are each provided with a plurality of apertures or slots 38 which in combination with the spaces between the finger contacts 12 provides venting passageways through the primary disconnect contact longitudinally thereof.

These passageways provide additional heat dissipation by convection.

FIGS. 7 and 8 illustrate a modification of the structure shown in FIGS. 1-6 wherein the annular ring shaped

members

13 and 14 are provided with a plurality of indentations 39 spaced around their circumferences in place of the continuous annular recess 24 shown in FIGS. 1, 2 and 3. indentations 39 form pockets for loosely receiving projections 23 of spacer members 16 thereby providing pivotal connections of spacer members 16 to ring shaped

members

13 and 14. indentations 39 also form a given position for the mounting of spacer members 16 around ring shaped

members

13 and 14 and assures a given space between each of the spacer members.

Although but two embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of invention or from the scope of the appended claims.

What is claimed is:

1. A contact structure for a circuit breaker stud comprising a plurality of contacts, means for mounting said contacts around said stud for independent limited movement, said means comprising a pair of spaced members one at least partly surrounding said stud and spacer members for pivotally interconnecting said spaced members for limited lateral movement of said spaced members, each of said spaced members having a first surface extending substantially longitudinally of said stud and a flange extending inwardly of said first surface, said flange providing a second surface spaced from and facing said first surface, said contacts each being mounted to extend with-in said flange of each of said spaced members, and a plurality of spring biasing means one arranged at each end of said contacts within said flange of each of said spaced members and between said first surfaces and said contacts, said biasing means biasing the ends of said contacts toward said second surface of said spaced members, at least a part of said contacts engaging said stud when said stud is inserted within one of said spaced members.

2. A contact structure for a circuit breaker stud comprising a plurality of finger contacts, means for mounting said finger contacts around said stud for independent limited movement, said means comprising a pair of arcuate spaced members one at least partly surrounding said stud and spacer members for pivotall-y interconnecting said spaced members, each of said spaced members having a first surface extending substantially longitudinally of said stud and a flange extending inwardly of said first surface, said flange providing a second surface spaced from and facing said first surface, said finger contacts each being mounted to extend within said flange of each of said spaced members, and a plurality of spring biasing means one arranged at each end of said finger contacts within said flange of each of said spaced members and between said first surfaces and said finger contacts, said biasing means biasing the ends of said finger contacts toward said second surface of said spaced members, said finger contacts each being provided with a pair of spaced contact engaging surfaces, one of said surfaces of each of said finger contacts engaging said stud when said stud is inserted within one of said spaced members.

3. A contact structure for a circuit breaker stud comprising a plurality of finger contacts, means for mounting said finger contacts on said stud for indepedent limited movement, said means comprising a first ring shaped member, a second ring shaped member and spacer members for pivotally interconnecting said first and second ring shaped members for limited lateral movement, each of said ring shaped members having a first surface extending substantially longitudinally of said stud and a flange extending inwardly of said first surface, said flange providing a second surface spaced from and facing said first surface, said finger contacts each being mounted to extend within said flange of each of said ring shaped members, and a plurality of spring biasing means one arranged at each end of said finger contacts within said flange of each of said ring shaped members and between said first surfaces and said finger contacts, said biasing means biasing the ends of said finger contacts toward said second surface of said ring shaped members, said finger contacts each being provided with a pair of spaced co-ntact engaging surfaces, one of said surfaces of each of said finger contacts engaging said stud when said stud is inserted within one of said ring shaped members.

4. A contact structure for a circuit breaker stud comprising a plurality of finger contacts, means for mounting said finger contacts on said stud for independent limited movement, said means comprising a first ring shaped member, a second ring shaped member and spacer members for pivotally interconnecting said first and second ring shaped members for limited lateral movement of said ring shaped members, each of said ring shaped members having a first surface extending substantially iongitudinally of said stud and a flange extending inwardly of said first surface, said flange providing a second surface spaced from and facing said first surface, said finger contacts each being mounted to extend Within said flange of each of said ring shaped members, and a plurality of spring biasing means one arranged at each end of said finger contacts within said flange of each of said ring shaped members and between said spacer members and said finger contacts, said biasing means biasing the ends of said finger contacts toward said second surface of said ring shaped members, said finger contacts each being provided with a pair of spaced contact engaging surfaces, one of said surfaces of each of said finger contacts engaging said stuid when said stud is inserted within one of said ring shaped members.

5. A contact structure for a circuit breaker stud comprising a plurality of finger contacts, means for mounting said finger contacts on said stud for independent limited movement, said means comprising a first ring shaped member, a second ring shaped member and spacer members for interconnecting said first and second ring shaped members, each of said ring shaped members having a first surface extending substantially longitudinally of said stud and a flange extending inwardly of said first surface, said flange providing a second surface spaced from and facing said first surface, each of said spacer members being pivotally connected at different ends thereof to said first surface of different ones of said ring shaped members for providing limited lateral movement of said ring shaped members, said finger contacts each being mounted to extend within said flange of each of said ring shaped members, a plurality of spring biasing means one arranged at each end of said finger contacts within said flange of each of said ring shaped members and between said spacer members and said finger contacts, said means biasing the ends of said finger contacts toward said second surface of said ring shaped members, said finger contacts each being provided with a pair of spaced contact engaging surfaces, one of said surfaces of each of said finger contacts engaging said stud when said stud is inserted within one of said ring shaped members.

6. A contact structure for a circuit breaker stud comprising a plurality of finger contacts, means for mounting surface extending substantially longitudinally of said stud and a flange extending inwardly of said first surface, said flange providing a second surface spaced from and facing said first surface, each of said spacer members being pivotally connected at different ends thereof to said first surface of different ones of said ring shaped members for providing limited lateral movement of said ring shaped members, said finger contacts each being mounted to extend Within said flange of each of said ring shaped members, a plurality of spring biasing means'one arranged at each end of said finger contacts within said flange of each of said ring shaped members and between said spacer members and said finger contacts, said biasing means biasing the ends of said finger contacts toward said second surface of said ring shaped members, said finger contacts each being provided with a pair of spaced contact engaging surfaces, a groove arranged within each of said finger contacts between said contact engaging surfaces, and a ring shaped yoke arranged to extend within said grooves of each of said finger contacts for mounting said structure to an end of said stud.

7. A contact structure for a circuit breaker stud comprising a plurality of finger contacts, means for mounting said finger contacts on said stud for independent limited movement, said means comprising a first ring shaped member, a second rin-g shaped member and spacer members for interconnecting said first and second ring shaped members, each of said ring shaped members having a first arcuate surface extending around its periphery with said first surface facing the center of said ring shaped member and a flange extending inwardly of saidfirst surface, said flange providing a second arcuate surface spaced from and facing said first surface, each of said first surfaces being provided with a plurality of spaced indentations extending around its circumference, each of said spacer members being provided with a protrusion at each end thereof for connecting with said indentations of said first surface of different ones of said ring shaped members for providing limited lateral movement of said ring shaped members, said finger contacts each being mounted to extend within said flange of each of said ring shaped members, a plurality of spring biasing means one arranged at each end of said finger contacts within said flange of each of said ring shaped members and between said spacer members and said finger contacts, said means biasing the ends of said finger contacts to- Ward said second surface of said ring shaped members and said protrusions into said indentations, said finger contacts each being provided with a pair of spaced contact engaging surfaces, one of said surfaces of each of said finger contacts engaging said stud when said stud is inserted within one of said ring shaped members.

8. A contact structure for a circuit breaker stud comprising a plurality of finger contacts, means for mounting said finger contacts on said stud for independent limited movement, said means comprising a first ring shaped member, a second ring shaped member and spacer members for interconnecting said first and second ring shaped members, each of said ring shaped members having a first arcuate surface extending around its periphery with said first surface facing the center of said ring shaped member and a flange extending inwardly of said first surface, said flange providing a second arcuate surface spaced from and facing said first surface, each of said first surfaces being provided with a plurality of spaced indentations extending around its circumference, each of escapes said spacer members being provided with a protrusion at each end thereof for pivotally connecting with said indentation of said first surface of different ones of said ring shaped members for providing limited lateral movement of said ring shaped members, said finger contacts each being mounted to extend within said flange of each of said ring shaped members, a plurality of spring biasing means one arranged at each end of said finger contacts within said flange of each of said ring shaped members and between said spacer members and said finger contacts, said means biasing the ends of said finger contacts toward said second surface of said ring shaped members and said protrusions into said indentations, said finger contacts being provided with a pair of spaced contact engaging surfaces, a groove arranged within each of said finger contacts between said contact engaging surfaces, and a ring shaped yoke arranged to extend within said grooves of each of said finger contacts for mountnig said structure to an end of said stud.

9. A contact structure for a circuit breaker stud comprising a plurality of finger contacts, means for mounting said finger contacts on said stud for independent limited movement, said means comprising a first ring shaped member, a second ring shaped member and parallelly arranged spacer members for interconnecting said first and second ring shaped members, each of said ring shaped members having a first arcuate surface extending around its periphery with said first surface facing the center of said ring shaped member and a flange providing a second arcuate surface spaced from and facing said first surface, each of said first surfaces being provided with a plurality of indentations equally spaced around its circumference, each of said spacer members being provided with a protrusion at each end thereof pivotally connected with said indentation of said first surface of different ones of said ring shaped members for providing limited lateral movement of said ring shaped members, said finger contacts each being mounted to extend Within said flange of each of said ring shaped members, a plurality of spring biasing means one arranged at each end of said finger contacts within said flange of each of said ring shaped members and between said spacer members and said finger contacts, said means biasing the ends of said finger contacts toward said second surface of said ring shaped members and said protrusions into said indentations, said finger contacts each being provided with a pair of spaced contact engaging surfaces, a groove arranged within each of said finger contacts between said contact engaging surfaces, and a ring shaped yoke arranged to extend within said grooves of each of said finger contacts for mounting said structure to an end of said stud.

10. A contact structure for a circuit breaker stud comprising a plurality of finger contacts, means for mounting said finger contacts on said stud for independent limited movement, said means comprising a first ring shaped member, a second ring shaped member and interleaved spacer members for interconnecting said first and second ring shaped members, each of said ring shaped members having a first arcuate surface extending around its periphery with said first surface facing the center of said ring shaped member and a flange extending inwardly of said first surface, said flange providing a second arcuate surface spaced from and facing said first surface, each of said spacer members being pivotally connected at different ends thereof to said first surface of different ones of said ring shaped members for providing limited lateral movement of said ring shaped members, each of said spacer members being formed to provide a trough extending longitudinally of said spacer member inwardly of said ring shaped members and a pair of flanges one on each side of and extending along said trough, said flanges of said spacer members overlapping to provide a space between adjacent troughs, said finger contacts each being mounted to extend wit-bin said flange of each of said ring shaped members, a plurality of spring biasing means one arranged at each end of said finger contacts between adjacent troughs and within said flange of each of said ring shaped members and between said flanges of said spacer members and said finger contacts, said finger contacts each being provided with a pair of spaced contact engaging surfaces, a groove arranged within each of said finger contacts between said contact engaging surfaces, and a ring shaped yoke arranged to extend Within said grooves of each of said finger contacts for mounting said structure to an end of said stud.

11. Avcontact structure for a circuit breaker stud comprising a plurality of finger contacts, means for mounting said finger contacts on said stud for independent limited movement, said means comprising a first ring shaped member, a second ring shaped member and spacer members for interconnecting said first and second ring shaped members, each of said ring shaped members having a first arcuate surface extending around its periphery with said first surface facing the center of said ring shaped member and a flange extending inwardly of said first surface, said flange providing a second arcuate surface spaced from and facing said first surface, each of said first surfaces being provided with an annular recess extending around its circumference, each of said spacer members being provided with a protrusion at each end thereof for connecting with said recess of said first surface of different ones of said ring shaped members for providing limited lateral movement of said ring shaped members, said finger contacts each being mounted to extend within said flange of each of said ring shaped members, a plurality of spring biasing means one arranged at each end of said finger contacts within said flange of each of said ring shaped members and between said spacer members and said finger contacts, said means biasing the ends of said finger contacts toward said second surface of said ring shaped members and said protrusions into said recesses, said finger contacts each being provided with a pair of spaced contact engaging surfaces, one of said surfaces of each of said finger contacts engaging said stud when said stud is inserted within one of said ring shaped members.

12. A contact structure for a circuit breaker stud comprising a plurality of finger contacts, means for mounting said finger contacts on said stud for independent limited movement, said means comprising a first ring shaped member, a second ring shaped member and spacer members for interconnecting said first and second ring shaped members, each of said ring shaped members having a first arcuate surface extending around its periphery with said first surface facing the center of said ring shaped member and a flange extending inwardly of said first surface, said flange providing a second arcuate surface spaced from and facing said first surface, each of said first surfaces being provided with an annular recess extending around its circumference, each of said spacer members being provided with a protrusion at each end thereof for pivotally connecting with said recess of said first surface of different ones of said ring shaped members for providing limited lateral movement of said ring shaped members, said finger contacts each being mounted to extend within said flange of each of said ring shaped members, a plurality of spring biasing means one arranged at each end of said finger contacts within said flange of each of said ring shaped members and between said spacer members and said finger contacts, said means biasing the ends of said finger contacts toward said second surface of said ring shaped members and said protrusions into said recesses, said finger contacts being provided with a pair of spaced contact engaging surfaces, a groove arranged within each of said finger contacts between said contact engaging surfaces, and a ring shaped yoke arranged to extend within said grooves of each of said finger contacts for mounting said structure to an end of said stud.

13. A contact structure for a circuit breaker stud comprising a plurality of finger contacts, means for mounting said finger contacts on said stud for independent limited movement, said means comprising a first ring shaped member, a second ring shaped member and parallelly arranged spacer members for interconnecting said first and second ring shaped members, each of said ring shaped members having a first arcua-te surface extending around its periphery with said first surface facing the center of said ring shaped member and a flange providing a second arcuate surface spaced from and facing said first surface, each of said first surfaces being provided with an annular recess spaced around its circumference, each of said spacer members being provided with a protrusion at each end thereof pivotally connected with said recess of said first surface of different ones of said ring shaped members for providing limited lateral movement of said ring shaped members, said finger contacts each being mounted to extend within said flange of each of said ring shaped members, a plurality of spring biasing means one arranged at each end of said finger contacts within said flange of each of said ring shaped members and between said spacer members and said finger contacts, said biasing means biasing the ends of said finger contacts toward said second surface of said ring shaped members and said protrusions into said recesses, said finger contacts each being provided with a pair of spaced contact engage surfaces, a groove arranged Within each of said finger contacts between said contact engaging surfaces, and a ring shaped yoke arranged to extend Within said grooves of each of said finger contacts for mounting said structure to an end of said stud.

14. A contact structure for a circuit breaker stud employing a plurality of movable finger contacts mounted for independent limited movement around said stud and a resilient housing for surrounding said contacts, said housing comprising a pair of spaced ringlike members interconnected by -a plurality of pivotally mounted spaced members, said housing retaining said finger contacts in a given geometrical configuration and forming cooling surfaces for dissipating the heat of current conduction.

References Cited in the file of this patent UNITED STATES PATENTS 2,300,893 Hayford Nov. 3, 1942 FOREIGN PATENTS 273,721 Italy Apr. 30, 1930 392,880 Great Britain May 25, 1933 678,811 Germany July 22, 1939