US2836688A

US2836688A - Electric device

Info

Publication number: US2836688A
Application number: US564732A
Authority: US
Inventors: Fritz E Florschutz
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1956-02-10
Filing date: 1956-02-10
Publication date: 1958-05-27
Anticipated expiration: 1975-05-27

Description

May 27, 1958 F. E. FLORSCHUTZ ELECTRIC DEVICE Filed Feb. 10, 1956 tlill Fig. 2.

Fig.3.

INVENTOR Fritz E. Florschufz.

, y/j/ I ATTORNEY WITNESSES E %W ilnite ELECTRIC DEVICE Appiication February 10, 1956, Serial No. 564,732

7 Claims. (Cl. 209-170) This invention relates, generally, to electric devices and, more particularly, to hinge contacts for electric switches and circuit breakers.

Contact rings, which are usually composed of silver or a silver alloy, are utilized in the hinge contacts of electric switches, particularly those having a high current carrying capacity. The contact rings are often utilized between silver-plated copper switch members to insure low milivolt drops and, because of their controlled hardness, to prevent galling during mechanical operation of the switches.

Heretofore, in order to give the switchblade sufiicient mechanical stability sidewise while it is not engaged with the break jaw, the contact ring in a switch has had a relatively large outside diameter. The inside diameter has been determined by the required contact area and contact pressure. It has been necessary to groove an adjacent member or braze the ring to an adjacent member to center the ring around the hinge bolt because the inside diameter of the ring was greater than the diameter of the bolt. Also, since the rings were usually stamped from sheet metal, a great deal of the metal in each sheet had to be scrapped when making the rings, thereby increasing their cost.

An object of my invention, generally stated, is to provide a contact washer which shall be much less expensive than prior contact rings and which shall be just as satisfactory in service.

A more specific object of my invention is to provide a contact washer which shall be self-centering around the hinge pin or bolt of an electric switch.

Another object of my invention is to provide a contact washer which shall have a greater contact area than prior contact rings in proportion to the amount of material re uired for the rings.

A further object of my invention is to provide a contact .vasher which does not require grooving of either switch member of the switch or bonding of the washer to one of the members.

Still another object of my invention is to provide for utilizing a contact washer much thinner than prior contact rings because no grooving or brazing is required.

Other objects of my invention will be explained fully hereinafter or will be apparent to those skilled in the art.

in accordance with one embodiment of my invention, a square contact washer composed of a metal having a high conductivity is disposed between a switch blade and its supporting member. The washer has a central hole therein of substantially the same diameter as the diameter of the hinge pin or bolt, thereby centering the washer around the bolt. The dimensions or the washer are such that the contact area of the washer is the same as that of a contact ring having a greater outside diameter than the length of one side of the square. Therefore, the contact washer requires less material than a contact ring having the same contact area as the washer.

For a better understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawing, in which:

States atent C Figure l is a view, in perspective, of a disconnecting switch embodying the principal features of the invention;

Fig. 2 is an enlarged view, in section, taken through the hinge contact of the switch; and

Fig. 3 is an enlarged view, in side elevation, of the contact washer with a section through the hinge bolt of the switch.

Referring to the drawing, and particularly to Fig. 1, the switch structure shown therein comprises a base 10, a break contact assembly 11, a hinge contact assembly 12 and a blade assembly 13. The base it? may be composed of steel or a similar material and it is suitable for mounting on a supporting structure (not shown). The break contact assembly comprises a break tongue 14 which is mounted on an insulator 15 which, in turn, is mounted on the base It). The break tongue 14 is connected to a bolt 16 which extends through the insulator i5 and is available for connecting conductors or bus bars at the rear of the base 10.

The break contact assembly 11 also includes a hook member 17 which is engaged by a latch mechanism in a manner well known in the art to retain the switch blades in the closed position. The latch mechanism is disengaged by means of a hook eye 18 which may be engaged by a hook stick to open the switch. The book eye 18 is mounted on a bolt 19 which extends through the switch blades.

The hinge contact assembly 12 comprises a hinge tongue 21 which is mounted on another insulator 15 in a manner similar to the break tongue 14. Two spaced switch blades 22 are mounted on opposite sides of the hinge tongue 21. The blades 22 are supported by a pivot bolt 23 which extends through the blades and the hinge tongue 21. Spring washers 24 are provided at the outer sides of the blades 22 to maintain contact pressure with the hinge tongue. A through bolt 25 extends through the blades where they engage the break tongue 14, and spring washers 24 are provided on this bolt to maintain contact pressure with the break tongue. The switch blades 22, the hinge tongue 21 and the break tongue 14 are preferably composed ofv copper or a copper alloy having a relatively high current conductivity.

As explained hereinbefore, contact rings, preferably composed of silver or a silver alloy, have been provided between the switch blades 22 and the hinge tongue 21 to insure a continually low millivolt drop between the blades and the hinge tongue. Silver has a higher current conductivity than copper and is not adversely aii'ected by oxidation. Another purpose of these rings is to prevent gelling of the switch members during opening and closing of the switch. The contact areas of the switch members are usually silver plated, thereby providing a silver-tosilver contact which may result in galling. The galling can be prevented by utilizing contact rings composed of a silver alloy which is harder than pure silver. The harder rings rub against the softer silver plating, thereby preenting galling. However, silver is expensive, therefore it is desirable to reduce the amount of silver required for the Contact rings.

As also previously explained, the contact rings have been made with a relatively large outside diameter to provide a mechanical support for the switch blades to prevent sidewise movement of the blades during closing of the blades. The inside diameter of the rings has been determined by the contact area required to provide the desired current carrying capacity and the desired contact pressure. Thus, the inside diameter and hence the opening in each ring has been considerably-larger than the diameter of the hinge or pivot bolt which supports the switch blades. 7 V

In order to keep the contact rings centered around the pivot bolt, it has been in the switch blades, or the hinge tongue, in which the rings are placed, or to braze the rings to the switch blades or the hinge tongue; Either one of these operations increases the .cost of the switch. Furthermore, it was necessary for the" contactrings to he thicker'than otherwise would have been required. a The increased thickness increased the amount of silver required for the contact rings. 1

In order to overcome the foregoing disadvantages of the round contact ring, I have devised a square contact washer 26. As shown in Fig.3, the washer 26 has a central opening 27 which is only slightly larger 'than'the diameter of the pivotbolt 23. Therefore, the washer 26 is self-centering'around the pivot bolt 23 and it is not necessary to provide groovesto retain the washer in place. or to braze the washer to the switch members. Accordingly, the thickness of the washer, can be reduced. A relativelysthick ring was required to extend above the groove or to'withstandfthe brazing operation.

a By way of comparison with a typical contact ring having an outside diameter of 1% inches and an inside diameter of 1 inches, a 11 4 inch square washer having a necessary to provide grooves I claim as my invention:

1. In an electric switch, in combination, a hinge tongue,

' current conducting member, another current conducting inch hole for the pivot bolt has practically the'same 3 contact area. The area of acircle of 1% inch diameter is 2.4 square inches. Thearea of a circle of 1 91 inch diameter is 1.1 square inches. The ditference between these .two is 1.3 square inches which is the contact area of the circular contact ring. The area of a 1% inch.

square washer is 1.5 square inches. The area of the.% inch hole is .2 square inch. The difference between these two is 1.3 square inches which is the contact area of the square washer. The square washer can be made from a 1% inch square sheet thereby requiring 1.5 square inches of sheet silver. The round ling requires a sheet 1% inches square. or approximately 3 square inches of material. As previously explained, the waste material fro punching the round rings must be scrapped.

Furthermore, as previously explained, the thickness I of the square washer can be reduced from approximately inch for the round ring to inch for the. square washer. Thus, the raw material volume of the square washer is ll 4 1% which equals .024 cubic inch of silver. The raw material volume of a 1% x square sheet required to make the round contact ring is .144

cubic inch. Therefore, .themetalratio of the square.

washer to the round washeris 1 to 6.

The distance across the corners or the diagonal diwasher in position, the cost of using the. square washer is considerably less than .thatof a .round'contact ring.

' Since the square washer has the. same contact area and hence the same contact pressure as the round ring, the

current conductivity'is the same. Also, the square washer provides the same mechanical support to prevent sidewise movement of the switch blade.

member movably attached to the stationary member, and a flat rectangular washer disposed between and. indirect contact with said members, said washer being composed of a metal which has a ditferent ,degree of hardness and has a higher current conductivity than said members.

3. In an electrical device, in combination, a supporting member, a conducting member disposed on said supporting member, pivot means attaching the co'nductingmember to the supporting member, and a flat washer of silver disposed between the conducting member-and the sup: porting member, said washer being in direct contactwith the conducting member and the supporting member, said washer having a central'hole therein only slightly larger than the diameter of said pivot means and being held in place with respect to said supporting member and said conducting member only by said pivot means passing through the central hole therein.

4. In an electric switch, in combination, a supporting member, a pair of switch bladesdisposed on opposite sides of said member, pivot means attaching the blades to the supporting member, a fiat square washer disposedbetween each blade and the supporting member, said washer being in direct contact with'the blade and the supporting member, each washer having 'acentral hole therein slightly larger than the diameter of said pivot means, and each'washer being composed of a metal which hasadiffere'nt degree of hardness and has a higher current conductivity than said blades and the supporting member.

5. In an electric switch, in combination, a supporting member, a pair-of switch blades disposed on opposite sides of said member, pivot means attaching the blades to the supportingmember, a fiat silver washer disposed between each blade and the supporting member and unattached thereto, each washer having a central hole therein slightly larger than the diameter of.said" pivot means which passes'through the hole to support the.

to the supporting member, a flat washer disposed be tween each blade andthe supporting member and unattached thereto, each {washer having a central hole therein slightly larger than the diameter of said pivot means, said blades and said supporting'member having fiat surfaces directly engaged by said washers, said washers being composed of a metal which is harder than Therefore, I have provided a hinge contact member which is an improvement over the members previously utilized in electric switches and other electrical devices.

. The saving effected by utilizing the present contact member is important in an industry which utilizes large numbers of contact members of'the present type.

Since numerous changes may be made in the abovedescribed construction, and, different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter containedin the foregoing description or shown in the ac companying drawing shall be interpreted as illustrative and not in alimiting sense; p I 1 the metal on thesurfa ces of said blades and said support- 7 ing member, each washer having a plurality of straight sides, and a diagonal dimension of each washer being greater than the distance between any two sides.

' 7. In an electric switch, in combination, a supporting member, a pair of switch blades pivotally disposed on opposite sides of: said member, a fiat washer disposed between and indirect contact with each blade and the supporting member, said washer'having a plurality of straight sides, and, adiagonal dimension of said washer being greater than the distance between any 'two'sides.

References Citedin thefile of this patent UNITED STATES PATENTS 1,826,225 Schuster Oct. 6, 1931