US3683140A - Electric circuit breaker with arc current shunting blade stacked on contact blade - Google Patents

Abstract

A movable contact blade of an electric circuit breaker is connected in series with a bimetallic strip forming a part of a tripping device. An arc current shunting blade is stacked on the contact blade, insulated therefrom, and connected to a load terminal strap in shunting relationship to the bimetallic strip. An arc which occurs during interruption of a severe overload current is transferred from the contact blade to the arc current shunting blade, causing the high current to bypass the bimetallic strip.

Description

8 United States Patent Peck 1 Aug. 8, 1972 [54] ELECTRHC CIRCUIT BREAKER WITH 2,1 17,047 5/1938 Wheelock ..200/146 R ARC CURRENT SHUNTING BLADE 2,175,827 10/1939 Conklin ..337/41 R STACKED CQNTACT BL DE 2,798,919 7/1957 lngwersen ..337/83 R 2,833,888 /1958 Bessiere ..200/146 R X [721 Invent: Peck west, 0mm", 3,005,066 10/1961 Powell ..337/83 R x Canada [73] Assignee: Square D. Company Canada Primary Examiner Macon Limited, Toronto Ontario, Canada Attorney-Harold J. Rathbun and Paul J. Rose [22] Filed: May 21, 1971 57 ABSTRACT PP Nod 145,817 A movable contact blade of an electric circuit breaker is connected in series with a bimetallic strip forming a s2 u.s.c| ..200/146R 337/41 337/83 P a triWilli; devicearc current shunting 3 6 blade is stacked on the contact blade, insulated [51] Int Cl H01! 33/12 therefrom, and connected to a load terminal strap in [58] Field 83 shunting relationship to the bimetallic strip. An arc which occurs during interruption of a severe overload current is transferred from the contact blade to the [5-6] References cued arc current shunting blade, causing the high current to UNITED STATES PATENTS yp the bimetallic p- 2,( )55,183 9/1936 Sperry ..337/110 R 9 Claims, 6 Drawing Figures PATENTEDAUG 81972 3.683.140

SHEET 1 0F 2 FIG. 2 FIG. 5

INVENTOR. RONALD G. PECK PATENTEDMIB 1972 3.683.140 SHEET 2 BF 2 v INVENTOR.

RONALD G. PECK ELECTRIC CIRCUIT BREAKER WITH ARC CURRENT SHUNTING. BLADE STACKED N CONTACT BLADE This invention is an improvement of the circuit breaker disclosed in U. S. Pat. No. 3,341,791, issued Sept. 12, 1967, to which reference may be had for a complete description of the circuit breaker parts unrelated to the present improvement.

A problem arises in circuit breakers of low rating, because a bimetallic strip of sufficiently. smallcross section for good response to low overload currents is likely to be damaged by severe overload currents. This problem has been solved in thepast by relatively complicated structures including a'second set of contacts which close upon incidence of severe overload current to bypass the current around the bimetallic strip. The present invention relates to a simple arrangementfor bypassing severe overload or'fault currents'around a bimetallic strip without the provision of a second set of contacts and separate operating structure therefor.

An object of the invention is to provide a simple, inexpensive structure for'shunting a bimetallic strip of a circuit breaker upon incidence of severeoverload or fault currents.

Other objects and advantages will become apparent upon consideration of the following specificationalong with the accompanying drawings in which:

F IG. 1 is a fragmentary longitudinal-sectional view of a circuit breaker constructed in accordance withtthe invention, certain portions being omitted for clarity;

FIG. 2 is an enlarged perspective view of an insulator between a contact pressure spring and an arc current shunting blade of this invention;

FIG. 3 is an enlarged perspective view of one of'two insulating retainers between amovablecontact blade and the arc current shunting blade of this invention;

FIG. 4 is an enlarged perspective view of the contact pressure spring;

FIG. 5 is an enlarged perspective view of the arc current shunting blade; and

FIG. 6 is an enlarged perspective view of the-movable contact blade.

With reference to the drawings, FIG. 1 discloses a circuit breaker 10 including a load terminal strap 12 having one end of a bimetallic strip 14 secured to an inner end thereof. The other end of the bimetallic strip 14 is connected by a braided wire 16 to a pivotally mounted end of a movable contact blade l8.having a movable contact 20 secured to the other end thereof for cooperation with a stationary contact 22 secured to a line terminal strap 24 along with an arc runner. 26.

In accordance with the invention, the movable contact blade 18 is shaped as best shown in FIG. 6 and has an arc current shunting blade 28, best shown in FIG. 5, mounted thereon. The arccurrent shunting blade 28 has an arcing contact 30 secured to one endthereof. The other end of the arc current shunting blade 28 is connected by a braided wire 32 to theload terminal strap 12 in shunting relationship to the bimetallic strip 14. A tubular insulating sheath 34 is provided on-the wire 32. The blade 28 is mounted on the blade 18 by means of a pair of spool-shaped insulating retainers 36, one of which is best shown in FIG. 3. Arcuate recesses 18a and 28a (FIGS. 5 and 6) are provided respectively on the blades 18 and 28 for reception of one of the retainers 36, and arcuate recesses 18b and 28b are proendportion of the bimetallic other and forming an outside comer portion of the blade 18. The recesses 28a and 28b are provided respectively on apair of edge surfaces 28c and 28d exten g substantially at right angles to each other and forming aninsidecorner portion of the blade 28 complementary to the outside corner portion of the blade 18.

The blades 18 and 28 are provided respectively with contact mounting surface 18a and 282 on which the contacts 20 and 30 are'respectively mounted. The edge surfaces l8eand 28c form equal acute angles respectively with the edge surfaces 18d and 28d, and when the blade 28 is in mounted position on the blade 18, the edge surfacesl-8e and28e are substantially coplanar. The contacts are shaped and mounted in a manner such that the contact30 forms a continuation or extension of the contact20, except for a small air gap between them.

The blade. 28 is'held in positionalso by contact pressure spring 38 best shown inFIG. by a and having end portions. 38a.and 38b anchored in a crossbar 40 and a transverse. portion 380 bearing on a channel shaped insulator 42 best shown in'FIG. 2 and mounted in a notch 28fof the blade 28.

An are occurring between the contacts 20 and 22 upon opening of the circuit breaker under severe overload or'fault conditions tends to travel outwardly, to the left as viewed in FIG. 1, whereupon it establishes itself between the contacts22and 30. The are current at that time flows through the blade 28 and wire 32, rather than through the blade 18, wire 16, and the bimetallic. strip 14. The bimetallic strip 14 is thus protected againstsexcessive. arcing currents.

Other parts of the circuit breaker 10 may be as disclosed in the aforementioned patent. Briefly, upon the occurrence of asustained moderate overload, the free strip 14 will move upwardly, as viewed in FIG. 1, to rotate a common trip bar 44 clockwise and release an intermediate latch member 46.for clockwise movement, whereupon a trip member 48'pivots clockwiseto collapse pairs of toggle .Iink members 49 and50. one of which is shown in The link members 50, only FIG. 1, are connected to a ;driving.bracket52 for the crossbar 40, and collapse of the toggle link members causes the crossbar 40 to move the blades 18 and 28 and open the contacts 20 and 22.

Upon the occurrence of severe overload or fault currents, the common trip bar 44 is rotated clockwise instead by an actuating member 54 secured to an annature rod 56 carrying anarmature member 58 attracted towardamagnetic core member 60 upon flow of the excessive current through the load terminal strap 12.

Various modifications may be made in the structure shown and described without departing from the spirit and scope of the invention.

1 claim:

l. Anelectn'c circuit breaker comprising a movable contact blade .connected in series with a bimetallic strip and a terminal strap, and an arc current shunting blade stacked on the movable contact blade, insulated therefrom, and connected to the terminal strap in shunting relationship to the bimetallic strip.

2. An electric circuit breaker as claimed in claim 1 including a pair of movable contacts mounted respectively on the blades.

3. An electric circuit breaker as claimed in claim 2 including a pair of spool-shaped insulating retainers insulating the blades from each other.

4. An electric circuit breaker as claimed in claim 3 wherein each blade has a pair of arcuate recesses and each spool-shaped insulating retainer is received in one recess on one blade and one recess on the other blade.

5. An electric circuit breaker as claimed in claim 4 wherein the movable contact blade has a pair of edge surfaces extending substantially at right angles to each other, forming an outside corner portion, and each having one of the arcuate recesses therein, and the are current shunting blade has a pair of edge surfaces extending substantially at tight angles to each other, forming an inside corner portion complementary to the outside corner portion of the movable contact blade, and each having one of the arcuate recesses therein.

6. An electric circuit breaker as claimed in claim 5 wherein each blade has a contact-mounting edge surface on which its contact is mounted and the contact-- mounting edge surfaces are substantially coplanar.

7. An electric circuit breaker as claimed in claim 6 wherein the contact-mounting edge surface of one blade fomis an acute angle with an edge surface thereof mounting edge surfaces are substantially coplanar.

9. An electric circuit breaker as claimed in claim 8 wherein the contact-mounting edge surface of one blade forms an acute angle with another edge surface of the respective blade, and the contact-mounting edge surface of the other blade forms on equal acute angle with another edge surface of the respective blade.

Claims (9)

1. An electric circuit breaker comprising a movable contact blade connected in series with a bimetallic strip and a terminal strap, and an arc current shunting blade stacked on the movable contact blade, insulated therefrom, and connected to the terminal strap in shunting relationship to the bimetallic strip.

2. An electric circuit breaker as claimed in claim 1 including a pair of movable contacts mounted respectively on the blades.

3. An electric circuit breaker as claimed in claim 2 including a pair of spool-shaped insulating retainers insulating the blades from each other.

4. An electric circuit breaker as claimed in claim 3 wherein each blade has a pair of arcuate recesses and each spool-shaped insulating retainer is received in one recess on one blade and one recess on the other blade.

5. An electric circuit breaker as claimed in claim 4 wherein the movable contact blade has a pair of edge surfaces extending substantially at right angles to each other, forming an outside corner portion, and each having one of the arcuate recesses therein, and the arc current shunting blade has a pair of edge surfaces extending substantially at tight angles to each other, forming an inside corner portion complementary to the outside corner portion of the movable contact blade, and each having one of the arcuate recesses therein.

6. An electric circuit breaker as claimed in claim 5 wherein each blade has a contact-mounting edge surface on which its contact is mounted and the contact-mounting edge surfaces are substantially coplanar.

7. An electric circuit breaker as claimed in claim 6 wherein the contact-mounting edge surface of one blade forms an acute angle with an edge surface thereof having one of the arcuate recesses therein, and the contact-mounting edge surface of the other blade forms an equal acute angle with an edge surface thereof having one of the arcuate recesses therein.

8. An electric circuit breaker as claimed in claim 2 wherein each blade has a contact-mounting edge surface on which its contact is mounted and the contact-mounting edge surfaces are substantially coplanar.

9. An electric circuit breaker as claimed in claim 8 wherein the contact-mounting edge surface of one blade forms an acute angle with another edge surface of the respective blade, and the contact-mounting edge surface of the other blade forms on equal acute angle with another edge surface of the respective blade.

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