US3619534A

US3619534A - Snap action circuit breaker

Info

Publication number: US3619534A
Application number: US281A
Authority: US
Inventors: Richard E Perkins
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1970-01-02
Filing date: 1970-01-02
Publication date: 1971-11-09
Anticipated expiration: 1988-11-09

Abstract

A snap action circuit breaker having encapsulating means such as a casing and a support secured within the encapsulating means. The support is designed to accommodate the components of circuit breakers such as the lead-in wires, snap blade and contact in predetermined fixed positions within the encapsulating means.

Description

United States Patent Richard E. Perkins South Windham, Maine Appl. No. 28l

Filed Jan. 2, 1970 Patented Nov. 9, 1971 Assignee Sylvania Electric Products Inc.

Inventor SNAP ACTION CIRCUIT BREAKER 1 Claim, 6 Drawing Figs.

U.S. Cl 200/168 G, 337/112,335/151 Int. Cl. H0lh 9/04 Field of Search 200/168 6,

[56] References Cited UNITED STATES PATENTS 2,516,584 7/1950 Parr 200/168 G X 2,870,287 1/1959 Corbitt, Jr. 200/168 G X 3,171,918 3/1965 Killion 335/153 X 3,307,126 2/1967 Shaw et a1... 335/154 3,434,079 3/1969 Ege,Jr 335/151 Primary Examiner-H. 0. Jones Attorneys-Norman J. OMalley and Owen J. Meegan ABSTRACT: A snap action circuit breaker having encapsulating means such as a casing and a support secured within the encapsulating means. The support is designed to accommodate the components of circuit breakers such as the lead-in wires, snap blade and contact in predetermined fixed positions within the encapsulating means.

PATENTEDunv 9 l97l 3,619,534

24 FIG.4

RICHARD E. PERKINS mv NTOR 8Y6 2 ATT RNEY SNAP ACTION CIRCUIT BREAKER BACKGROUND OF THE INVENTION 1. Field Of The Invention This invention relates to circuit breakers. More precisely, the invention disclosed herein relates to an improved snap action circuit breaker which is temperature and/or current sensitive and which can beemployed in known manners to control or provide protection for electrical circuits.

2. Description Of The Prior Art Circuit breakers, especially snap action type circuit breakers, are known products of commerce. The types best known essentially comprise a bimetallic, thermostatic strip or blade arranged in combination with suitable contact means so that contact can be made or broken in response to predetermined conditions such as specific current loads or temperatures. The blade and contact means are arranged within a conductive or nonconductive hermeticallysealed casing and the components are connected to lead-in wires which carry current from some source external to the casing. In general, the strip or blade is usually connected directly to one of the leadin wires. This lead-in wire blade assembly is normally suspended within the casing and arranged overanother contact connected to a second lead-in wire. The contact and the second lead-in wire assembly may be-maintained in a fixed or suspended position. Details relating .to snap action circuit breakers similar to the type to which the present invention pertains can be found-in U.S. Pat. Nos. 3,312,967 3,066,205, 2,978,556, 2,925,483 and 2,424,909, all of which are incorporated herein byv reference.

Those skilled in the art-know that there are many outstanding problems in the production of snap action circuit breakers. These problems chiefly arise by reason of the miniature size of the components involved and the requirementthat such components be assembled and hermetically sealed within a suitable encapsulating casing. For example, in many existing circuit breakers, the lead-in wires are especially fragile and easily bent since they are oftentimes of an CD. of about 0.030inch. The assembly of suchlead-in wires with the other components causes special complications in view of .the fact that the straightness of the lead-in wires, the thickness of the welds involved in connecting the lead-in wires to the other components, e.g. the blade or the contact and the spacing of the lead-in wires, are all factors that can adversely affect the precision and accuracy of the overall performance of the circuit breaker. The effects of the above-mentioned factors are particularly difficult to control when the encapsulating means involves a glass casing or envelope.

SUMMARY OF THE INVENTION The present invention provides an improved snap action circuit breaker of a unique structure which pennits simple assembly and at the same time minimizes and permits effective control over variations in such factors as lead-in wire bending, lead-in wire spacing and weld thickness, all of which can adversely afi'ect the performance characteristics of the circuit breaker. Essentially, the snap action circuit breaker of the present invention comprises a support assembled in a fixed position withinencapsulating means such as a glass casing or envelope. The support can be cast, formed, shaped or otherwise assembled or a nonconductive material such as a ceramic and is designed to provide a capability for securing the lead-in wires in a fixed spaced apart position within the casing. For example, the support can provide channels which can closely accommodate the lead-in wires when inserted therein or secured thereto by manners known to the art. When so secured in their respective fixed positions, one of the lead-in wires is operationally connected to the snap blade such as by welding or the like. The other lead-in wire is operationally connected to a contact which is also secured in a fixed position by the support in a predetermined relationship with the contact of the snap blade to provide the desired make or break response. In the preferred embodiment of the present invention, the lead-in DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiments of the present invention will be better understood by reference to the following drawings wherein:

FIG. 1 is a top view of a support of the present invention shown accommodating lead wires, snap blade and a contact.

FIG. 2 is an elevational side view of the support of FIG. 1.

FIG. 3 is viewalong line 3-3.

FIG. 4 is a view along line 4-4.

FIG. 5 is a sectional top view of a snap action circuit breaker having the support of FIGS. 1-4 secured within a glass envelope.

FIG. 6 is a cross-sectional view along the line 6-6 of FIG. 5.

Referring now to FIG. 1-4, the support, molded of ceramic material is shown as 10 and has

shoulders

30 and 40 respectively at opposite ends. A'first lead-in wire 12 extends axially through channel 1'22 (FIG. 3) and is secured in a fixed position as shown, such as by a holder bar 16. First lead-in wire 12 is operationally connected to snap blade 18 by welding, brazing or the like. A second lead-in wire 14 extends axially through shoulder 40 by way of channel 24 (FIG. 4) and is secured as shown in channel 24 bythe fixed contact 20. Fixed contact 20 is supported, on its edges, by the sides of the channel 24 and lead-in wire 14. Second lead-in wire 14'is operationally connected (preferably by resistance welding) to contact 20which is secured in a fixed-position on support 10. Therelativeposition of contact 20 with respect to contact 19 of blade 18 is determined inaccordance with theparticular-make or break response desired between

contacts

19 and 20.

Referring now to FIG. 5, the support and components of FIG. 1-4 are shown secured within. glass envelope 50 which is hermetically sealed about the support. In one embodiment, the support can be secured within the envelope by bonding a surface of the-support, such as the bottom thereof, to a portion of the inner surface of the envelope by bonding materials and methods known to the art. Alternatively, as shown in FIG. 6, the support 30 can be sufficiently large to abut against the walls of the envelope so thereby holding it firmly in place. The hermetic sealing of the envelope about the support and the lead-in wires can be accomplished by manner known to the art.

The encapsulated snap action circuit breaker of FIG. 5 provides special advantages over those presently employed in the art, especially when the circuit breakers of the present invention are employed as protectors on circuits such as motor windings. Because of the high inductive voltages induced in motor windings, arc tracking can occur at the interface between the snap blade, contact arm and lead-in wires of many of the snap action circuit breakers known to the art. This arc tracking can destroy a circuit breaker in a short time. In the circuit breaker of FIG. 5, however, arc tracking is effectively eliminated by reason of the fact that lead-in

wires

12 and 14, snap blade 18 and contact 20 are arranged and maintained in fixed positions on support 10. Accordingly, as blade 18 opens, the

spacing contacts

19 and 20 and therefore the spacing between lead-in wires 12-14 becomes progressively wider, thereby extinguishing the arc. This advantage is most effectively assured by the arrangement of the lead-in

wires

12 and 14 shown in FIG [-5 wherein each lead-in wire extends axially through opposite ends of the casing and this arrangement of lead-in wires is definitely preferred. However, it is to be understood that the circuit breakers of the present invention include other arrangements wherein, for example, the lead-in wires are secured by the support in a fixed, spacedapart relationship but extend into the casing from the same end.

By way of illustration only, the actual dimensions of a ceramic support similar to that of HG. 1-4 are as follows:

overall length-1.06 inches; spaced-apart overall width-0.100 inch;

overall height at shoulders-0.240 inch;

height of shoulders0.060 inch;

ID. of channels 22 and 24-0062 inch;

length of channels 22-14/32 inches and 24 1 3/32 inches The lead-in wires inserted into

channels

22 and 24 are Kovar (or No. 4 Alloy) and have an CD. of 0.050 inch. The snap blade 18 is Chace No. l05 lnvar-steel Alloy, contact 19 is coin silver-steel backed, welded to the blade which is welded to lead-in wire 12 by resistance weld. Contact 20 was coin silver-steel backed 3/16 inches diameter X3/64 inches thick, and was operationally connected to lead-in wire 14 by resistance welding. A circuit breaker of the type described above can operate in the 35-50 ampere range.

As can be appreciated from FIGS. 1-4, the design of support provides a capability for maintaining the components of the snap action circuit breaker in fixed relationships and also provides a convenient manner for integrating or assembling the components. Bending of the lead-in wires, for example, is minimized and easily controlled. Also, the support maintains the lead-in wire, snap blade assembly in a fixed position and permits only the blade to move. As mentioned, in prior art devices, the lead-in wires, blade assembly is usually suspended within the encapsulating means and the whole assembly moves in making or breaking contact. This feature provides undesirable stain characteristics which can adversely affect the fragile assembly as well as the seal about the lead-in wire and casing. The feature also permits undesirable variations between lead-in wire spacing to occur during operation.

Since certain changes may be made in the above product without departing from the spirit and scope of the invention involved, all matter contained in the above description or shown in the accompanying drawings should be construed as illustrative and not in a limiting sense.

Having described the invention together with preferred embodiments thereof, as well as manners of practicing same, what I declare as new and desire to secure by U.S. Letters Patent is as follows:

As my invention, I claim:

1. A snap action circuit breaker comprising: a tubular hermetically sealed glass envelope; an elongated unitary insulative support disposed within said envelope, said support including a first longitudinal groove at one end thereof and a second longitudinal groove at the other end thereof; a first leadin wire hermetically sealed through one end of said envelope and extending into said first groove; a second lead-in wire hermetically sealed through the other end of said envelope and extending into said second groove; a bimetallic snap-acting thermostatic element longitudinally disposed on said support, one end of said element being welded to the end of said first lead-in wire that is in said first groove; a first electrical contact disposed on the other end of said element; and a second electrical contact welded to the end of said second lead-in wire that is in said second groove, said first and second contacts being normally closed, said first and second contacts opening upon actuation of said snap-acting element.

Claims

1. A snap action circuit breaker comprising: a tubular hermetically sealed glass envelope; an elongated unitary insulative support disposed within said envelope, said support including a first longitudinal groove at one end thereof and a second longitudinal groove at the other end thereof; a first lead-in wire hermetically sealed through one end of said envelope and extending into said first groove; a second lead-in wire hermetically sealed through the other end of said envelope and extending into said second groove; a bimetallic snap-acting thermostatic element longitudinally disposed on said support, one end of said element being welded to the end of said first lead-in wire that is in said first groove; a first electrical contact disposed on the other end of said element; and a second electrical contact welded to the end of said second lead-in wire that is in said second groove, said first and second contacts being normally closed, said first and second contacts opening upon actuation of said snap-acting element.