US3747034A - Circuit breaker - Google Patents

Abstract

In a molded case circuit breaker having a pair of stationary contacts and a rotary bridging contact cooperating with the stationary contacts to provide a double break, the bridging contact is free floating, being connected to a rotary carrier through spring toggle mechanisms which operate when the carrier is rotated so as to rotate the bridging contact about its floating axis. The bridging contact carries two pairs of contact members adapted to engage and disengage at different times, one pair of contacts being interconnected by a resistive current path to minimize arcing.

Description

United States Patent 1.191

Howchin July 17, 1973 1 4] CIRCUIT BREAKER [76] Inventor: Ronald M. Howchin, 1055 Bloor St., East, Apt. 1220, Mississauga,

Ontario, Canada 221 Filed: Sept. 28, 1972 [21] Appl. No.: 293,046

3,505,622 4/1970 Strobe] 335/191 Primary Examiner-Harold Broome Attorney-J. A. Legris [5 7] ABSTRACT In a molded case circuit breaker having a pair of stationary contacts and a rotary bridging contact cooperating with the stationary contacts to provide a double break, the bridging contact is free floating, being connected to a rotary carrier through spring toggle mechanisms which operate when the carrier is rotated so as to rotate the bridging contact about its floating axis. The bridging contact carries two pairs of contact members adapted to engage and disengage at different times, one pair of contacts being interconnected by a resistive current path to minimize arcing.

11 Claims, 8 raw ng Figures PAIENTEU JUL 1 H913 SHEET 2 [IF 5 PATENTEDJUL 1 ma SHEET 4 [IF 5 PATENTED JUU 3. 747. 03 4 sum 5 or 5 FIG. 6

17/1 11/ l/l/l/l/l l/// ll away;

switch. The effective operation of such a circuit.

breaker depends upon the avoidance of arcing between the contacts as they are separated; the tendency for arcing to occur depends upon the magnitude of the current to be interrupted and the voltage across the contacts at the time of the break.-lt is an object of the present invention to provide a switching mechanism, suitable for use in a molded case circuit breaker, wherein the tendency for arcing to occur, for a given voltage and current rating, is minimized.

A switching mechanism in accordance with the invention is characterized by a pair of stationary contacts and a bridging contact having a rotary action which causes a double break in the circuit, current being interrupted at two points. With a double break the voltage across each pair of contacts and the resultant ionization when current is interrupted is considerably less than if the entire current were handled. by a single breaking contact. It-is known to provide a double break in acontactor, of course, butin order to provide a double break by means of a bridging contact having a rotary action it is necessary to overcome the difficulty of ensuring high contact pressure at each of the stationary contacts. Applicant achieves this by mounting the bridging contact so taht it is free floating instead of having a fixed axis.

According to a subsidiary feature of the invention, the end portions of the bridging contact each comprise first and secondcontactmembers which are engageable with respective contact members of the stationary contacts and which are mounted on respective articulately connected'parts of said end portions, the contact members beingarranged so that the first contact members engage earlier than, and disengage later than, the second contact members during operative movements of the switch mechanism. The said first contact membersof the bridging contact are preferably interconnected by a resistive current path.

In order that the invention may be readily understood, one embodiment thereof as applied to a molded case circuit breaker for use in a three-phase circuit will now be described, by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a general perspective view of the circuit mechanism, part of the switch housing being broken FIG. 3" is a fragmentary perspective view of the switching mechanism in one housing compartment;

FIG. 4 is a fragmentary perspective view of part of the mechanism-shown in FIG. 3, this Figure showing more clearly the arrangement of the operating shaft;

FIG. 7 shows the detail of FIG; 6 with the contacts 1 closed; and

FIG. 8 is a schematic diagram of a modification.

Referring to FIG. 1, the circuit breaker comprises a housing 10 of molded plastics material, the housing being compartmented to provide four compartments ll, l2, l3 and 14. The compartment 11 houses a breaker operating mechanism shown in FIG. 2. The compartments 12, 13 and 14 each house a switching mechanism, the structure of which is illustrated in FIGS. 3 to 7. These switching mechanisms are associated with the respective phases of the three-phase power circuit. FIG. I also shows a switch handle 15 for resetting the circuit breaker.

Referring now to FIG. 2, the breaker operating mechanism includes an operating shaft 16 which .is journalled for rotation in bushings 17 mounted in the compartment walls of the housing. The shaft 16 extends through the housing into each of the compartments 12, l3, 14. Connected to the operating shaft 16 is a radially extending lever 18, formed by a plate which lies in a plane perpendicular to the axis of the shaft. One end of the lever 18 is fonned with a projection 19 connected to a spring biasing assembly, the latter comprising a cup member 20 connected to the projection 19 by a hook 21, and a compression spring 22 engaging in the cup member 20 at one end and abutting against a bracket 23 at the other end, the bracket being welded to the compartment walls so as to bridge the compartment 11. The spring assembly biases the lever 18 into the OFF position shown in FIG. 2. When the lever is set in the ON position, it is held against the action of the spring by a pivoted latch 24 which engages and holds the cup member 20. The latch 24 is actuated to release the cup member, in accordance with an overload condition, by a solenoid 25 having a pivoted armature 26, the latter being pulled upwards by the solenoid to engage the underside of the latch. In order to reset the mechanism the switch handle 15 is turned so as to engage and move the end of a pivoted rod 27..The rod 27 carries a cross member 28 which is normally freely rotatable so that, if an attempt is made to reset the circuit breaker during an overload condition, i.e., when the so lenoid 25 is energized, movement of the rod is ineffective to move the lever 18. However, the solenoid mechanism includes a pivoted member 29 which is responsive to the position of the solenoid armature 26. This member 29 has an abutment 30 which, when the solenoid is de-energized so that the armature is in the downward position, engages one end of the cross member 28 (as shown in FIG. 2). In this condition the cross member 28 is prevented from rotating, and therefore movement of the switch handle to reset the circuit breaker causes the cross member 28 to engage the lever 18 and so move the lever to its ON position. Since the solenoid 25 is de-energized for this to be possible,

the lever 18 is held in the ON position once again by.

the latch 24.

The switching mechanisms of the phase circuits will now be described with particular reference to FIGS. 3 to 7.

As best shown in FIG. 5, each of the switching mechanisms comprises a pair of switch terminals 31, 32 mounted in the housing 10, the terminals providing a pair of stationary contacts and being adapted for connection to the bus members of the respective phase. The stationary contacts are adapted to be bridged by a floating bridging contact 33, the end contact portions of which are engageable under one and over the other of said stationary contacts. Each of the spaced stationary contacts comprises a first contact member 31a, or 32a, and a second contact member 31b, or 32b. These pairs of contact members are adapted to engage respective pairs of contact members of the bridging contact 33; each of the latter pairs comprises a first contact member 340, or 34b, and a second contact member 35a, or 35b. The pairs of contact members 340 and 35a, and 34b and 35b, are mounted on respective articulately connected parts of the end portions of the bridging contact; the arrangement is such that during movements of the switch mechanism the cooperating contact members 31a, 34a, and 32a, 35a, engage earlier than, and disengage later than, the cooperating contact members 31b, 34b and 32b, 35b. The bridging contact 33 provides a highly conductive current path between the contact members 34b, 35b; the articulated ends 33a, 33b of the bridging contact are insulated and the contact members carried by them are interconnected by a resistive current path indicated diagrammatically at 36.

A pair of presser arms or plates 37, 38 are pivotally connected to the bridging contact 33 adjacent to its ends, and compression springs 39a, 39b, and 40a, 4% are disposed and arranged between the end portions of the bridging contact and the respective presser arms for urging 'the latter away from the end portions. The springs 39b and 40b are of such a strength as to urge the articulated ends 330, 33bso as to ensure prior engagement of the pairs of contact members 31a, Z-a and 32a, 35a, and prior disengagement of the pairs of contact members 31b, 34b and 32b, 35b.

A carrier member 41 is connected to the operating shaft 16 for pivotal movement about the axis of the shaft when the latter is rotated. Rotation of the shaft between first and second operative positions corresponding to the ON and OFF positions of the lever 18 (FIG. 2). A pair of support housings 42, 43, connected to'the respectiveends of the carrier 41. The support housings in the present example are not symmetrically arranged, since their spatial relationship is determined by the position of the carrier 41 in the switch housing compartment, but this is purely a design feature. A pair of spring toggle mechanisms 44, 45 are connected betweenthe support housings and the respective presser arms 37, 38, and first and second toggle actuating means 46, 47 are mounted in the respective support housings. The toggle mechanisms and actuating means will now be described with particular reference to FIGS. 6 and 7, which show the toggle mechanism 45 and actuating means 47 in the OFF and ON positions, respectively.

The toggle mechanism 45 comprises a first toggle member 48 pivotally connected to a projection 49 on the presser arm 38, a second toggle member 50 pivotally connected to the wall of the support housing 43, and a tension spring 51. The toggle is movable across a dead centre position (shown in chain-dot in FIG. 7) between its operative positions shown respectively in FIGS. 6 and 7. An abutment am 52 extends radially from the toggle member 50. The toggle actuating means 47 comprises a first lever 53 which is pivotally mounted on a pin 54 extending from the wall of the support housing. The lever 53 is biassed by a tension spring 55 into abutting engagement with an abutment member 56, the latter being a stationary member which is mounted on the wall of the main housing compart- In operation of the circuit breaker, with the circuit breaker set to its ON position with the bridging contacts engaging the pairs of stationary contacts, substantially the whole of the bus current in each phase is carried by the respective bridging contact. Overload current in any phase causes the respective solenoid 25 (FIG. 2) to be energized, the armature 26 being raised thereby disengaging the latch 24 from the cup-member 20; the lever 18 is thus urged to its OFF position by the spring 22, thereby rotating the operating shaft to its second operative position. At the same time the pivoted member 29 is raised to disengage the abutment 30 from the cross member 28; in this condition it is not possible to reset the circuit breaker by moving the switch handle 15.

Now rotation of the shaft 16 to its second operative position rotates the carrier 41, the support housing 42 being lowered and the support housing 43 being raised. When this happens the levers 53 are initially disengaged from the stationary abutments 56, the springs 55 pivoting the radial arms 57, 58 and the arms 58 moving the abutment arms 52 sufficiently to move the toggle mechanisms past their dead centre positions. The bridging contact is thereby disengaged from the stationary contacts, the pairs of contact members 31b, 34b, and 32b, 35b, disengaging before the pairs of contact members 31a, 34a and 32a, 35a. For a moment during operation of the breaker, therefore, the current in each phase is carried by the respective resistive current path 36, thus reducing the likelihood of arcing.

When the circuit fault has been removed, the solenoid 25 being de-energized, the arm 29 falls to its lower position. Therefore, operation of the switch handle 15 is effective to reset the circuit breaker, the cross member 28 being'prevented from rotating by the stop 30 and so engaging the radial lever 18 to move the latter to the ON position. The shaft 16 is thus rotated, causing the carrier 41 with support housings 42, 43 to move to the engagement position; during such movement the levers 53 pivot about the pins 54, causing the radial arms 57 to displace the abutment arms 52, thereby tripping the toggle mechanisms 44, 45 across their dead centre positions.

In the modification illustrated diagrammatically in FIG. 8, the arcing contact members 340 and 35b are each located in an air gap of a magnetic circuit, the magnetic circuits being formed by soft iron cores A, B carried by the bridging contact 33 (not shown in FIG. 8). The contact members 340, 35a are interconnected by a conductor 60 which is wound upon the cores A, B After separation of the arcing contact membersany arcing current magnetises the cores A, B, the resultant field in each of the air gaps serving to deflect and lengthen the are, which can be broken up against a series of de-ionising plates.

What I claim as my invention is:

I. An electric switch mechanism comprising:

a pair of spaced stationary contacts,

'a bridging contact having end portions engageable respectively with said stationary contacts,

first and second presser arms connected respectively adjacent the end portions of the bridging contact,

compression springs disposed and arranged between the end portions of the bridging contact and the respective presser arms for urging the latter away from said end portions,

an operating member movable between first and second operative positions,

first and second stationary abutment members,

first and second spring toggle mechanisms connected between the operating member and the respective presser arms,

each spring toggle mechanism having a dead centre position, and being operable upon movement from one side to the other of the dead centre position to urge the presser arm towards the respective end portion of the bridging contact so as to urge the latter into engagement with the respective stationary contact, and

I first and second toggle actuating means mounted on the operating member,

each said toggle actuating means being engageable with a respective one of said abutmentmembers upon movement of the operating member from its first-to its second operative position, whereby to actuatethe respective toggle mechanism and set it on said other side of the dead centre position.

2. An electric switch mechanism according to claim 1, wherein each of the presser arms is pivotally connected at one end to the bridging contact.

3. An electric switch mechanism according to claim I, wherein each of the spaced stationary contacts comprises first and second contact members, and each of said bridging contact end portions comprises first and second contact members engageable respectively with the contact members of the stationary contacts, and

mounted on respective articulately connected parts of said end portions, the contact members being arranged so that the pairs of first contact members engage earlier than, and disengage later than, the pairs of second contact members during movements of the switch mechanism. X

f 4. An electric switch mechanism according to claim 3, wherein the first contact members of the bridging contact are interconnected by a resistive current path.

5. An electric switch mechanism comprising:

' a switch housing, v

a pair of spaced stationary contacts mounted in the housing, i a bridging contact having end contact portions engageable under one and over the other of said stationary contacts for bridging same,

' first and second presser arms pivotally connected to the bridging contact adjacent the respective end portions thereof,

compression springs disposed and arranged between the end portions of the bridging contact and the respective presser arms for urging the latteraway from said end portions,

a carrier pivotally mounted in the housing for pivotal movement about a transverse axis,

an operating shaft connected to the carrier for pivotally moving the carrier between first and second operative positions,

first and second stationary abutment members mounted in the housing,

first and second support means mounted on the carrier one on either side of said axis,

first and second spring toggle mechanisms connected respectively between said support means and said presser arms,

each spring toggle mechanism having a dead centre position and being movable from one side to the other of the dead centre position to urge the presser arm towards the respective end portion of the bridging contact so as to urge the latter into engagement with the respective stationary contact, and

first and second toggle actuating means mounted respectively on said support means,

each said toggle actuating means being engageable with a respective one of said abutment members upon movement of the carrier from its first to its second operative position, whereby to actuate the respective toggle mechanism and set it on said other side of the dead centre position.

6. An electric switch mechanism according to claim 5, wherein each of said toggle actuating means comprises a first lever pivotally mounted on a respective one of said support means, spring means biasing the lever into abutting engagement with the respective abutment member, and a second lever connected to said first lever for pivotal movement about a common pivotal axis, said second lever being engageable, during pivotal movement against the spring means, with an abutment arm carried by the respective toggle mechanism for tripping said mechanism.

7. An electric switch mechanism according to claim 6, wherein the second lever carries an abutment stop adapted to engage said abutment arm when the toggle mechanism is on said other side of the dead centre position.

8. An electric switch mechanism according to claim 7, wherein each of the spaced stationary contacts comprises first and second contact members, and each of said bridging contact end portions comprises first and second contact members engageable respectively with the contact members of the stationary contacts, and mounted on respective articulately connected parts of said end portions, the contact members being arranged so that the pairs of first contact members engage earlier than, and disengage later than, the pairs of second contact members during movements of the switch mechanism.

9. An electric switch mechanism according to claim 8, wherein the first contact members of the bridging contact are interconnected by a resistive current path.

10. A circuit breaker, adapted for use with a polyphase circuit, comprising in combination:

a molded switch housing providing a plurality of compartments,

said compartments including a first compartment housing a breaker operating mechanism and a plurality of compartments housing respective phase switches,

said breaker operating mechanism comprising:

a. an operating shaft extending into each of the compartments,

b. a radially extending lever connected to the operating shaft,

0. spring means biasing the lever into an OFF position,

d. latching means engageable with said spring means for latching the lever in the ON position,

-e. solenoid means cooperating with the latching means for releasing the latching means whereby to permit the lever to move to the OFF position,

f. resetting means for resetting the lever to the ON position,

g. abutment means connected to the resetting means operable to prevent resetting of the lever to the ON position when said solenoid means is energized, and each phase switch comprising:

a. a pair of stationary contacts mounted in the respective compartment,

b. a bridging contact having end contact portions engageable under one and over the other of said stationary contacts for bridging same,

c. first and second presser arms pivotally connected to the bridging contact adjacent the respective end portions thereof,

d. compression springs disposed and arranged between the end portions of the bridging contact and the respective presser arms for urging the latter away from said end portions e. a carrier pivotally mounted in the compartment for pivotal movement about a transverse axis,

f. said operating shaft-"being connected to the carrier for pivotally moving the carrier between first and second operative positions,

g. first and second stationary abutment members mounted in the compartment, 1

h. first and second support means mounted on the carrier one on either side of said axis,

i. first and second spring toggle mechanisms connected respectively between said support means and said presser arms,

j. each spring toggle mechanism having a dead cen tre position and being movable from one side to the other of the dead centre position to urge the presser arm towards the respective end portion of the bridging contact so as to urge the latter into engagement with the respective stationary contact, and

. first and second toggle actuating means mounted respectively on said support means,

. each said toggle actuating means being engageable with a respective one of said abutment members upon movement of the carrier from its first to its second operative position, whereby to actuate the respective toggle mechanism and set it on said other side of the dead centre position.

11. A circuit breaker according to claim 10 wherein the end contact portions of the bridging contact each provide an arcing contact member, the arcing contact members being interconnected by a conductor which is linked with a pair of magnetic flux paths each providing an air gap wherein a respective arcing contact member is located, arcing current magnetising the paths so as to deflect and lengthen the arcs.

* i t t

Claims (11)

1. An electric switch mechanism comprising: a pair of spaced stationary contacts, a bridging contact having end portions engageable respectively with said stationary contacts, first and second presser arms connected respectively adjacent the end portions of the bridging contact, compression springs disposed and arranged between the end portions of the bridging contact and the respective presser arms for urging the latter away from said end portions, an operating member movable between first and second operative positions, first and second stationary abutment members, first and second spring toggle mechanisms connected between the operating member and the respective presser arms, each spring toggle mechanism having a dead centre position, and being operable upon movement from one side to the other of the dead centre position to urge the presser arm towards the respective end portion of the bridging contact so as to urge the latter into engagement with the respective stationary contact, and first and second toggle actuating means mounted on the operating member, each said toggle actuating means bEing engageable with a respective one of said abutment members upon movement of the operating member from its first to its second operative position, whereby to actuate the respective toggle mechanism and set it on said other side of the dead centre position.

2. An electric switch mechanism according to claim 1, wherein each of the presser arms is pivotally connected at one end to the bridging contact.

3. An electric switch mechanism according to claim 1, wherein each of the spaced stationary contacts comprises first and second contact members, and each of said bridging contact end portions comprises first and second contact members engageable respectively with the contact members of the stationary contacts, and mounted on respective articulately connected parts of said end portions, the contact members being arranged so that the pairs of first contact members engage earlier than, and disengage later than, the pairs of second contact members during movements of the switch mechanism.

4. An electric switch mechanism according to claim 3, wherein the first contact members of the bridging contact are interconnected by a resistive current path.

5. An electric switch mechanism comprising: a switch housing, a pair of spaced stationary contacts mounted in the housing, a bridging contact having end contact portions engageable under one and over the other of said stationary contacts for bridging same, first and second presser arms pivotally connected to the bridging contact adjacent the respective end portions thereof, compression springs disposed and arranged between the end portions of the bridging contact and the respective presser arms for urging the latter away from said end portions, a carrier pivotally mounted in the housing for pivotal movement about a transverse axis, an operating shaft connected to the carrier for pivotally moving the carrier between first and second operative positions, first and second stationary abutment members mounted in the housing, first and second support means mounted on the carrier one on either side of said axis, first and second spring toggle mechanisms connected respectively between said support means and said presser arms, each spring toggle mechanism having a dead centre position and being movable from one side to the other of the dead centre position to urge the presser arm towards the respective end portion of the bridging contact so as to urge the latter into engagement with the respective stationary contact, and first and second toggle actuating means mounted respectively on said support means, each said toggle actuating means being engageable with a respective one of said abutment members upon movement of the carrier from its first to its second operative position, whereby to actuate the respective toggle mechanism and set it on said other side of the dead centre position.

6. An electric switch mechanism according to claim 5, wherein each of said toggle actuating means comprises a first lever pivotally mounted on a respective one of said support means, spring means biasing the lever into abutting engagement with the respective abutment member, and a second lever connected to said first lever for pivotal movement about a common pivotal axis, said second lever being engageable, during pivotal movement against the spring means, with an abutment arm carried by the respective toggle mechanism for tripping said mechanism.

7. An electric switch mechanism according to claim 6, wherein the second lever carries an abutment stop adapted to engage said abutment arm when the toggle mechanism is on said other side of the dead centre position.

8. An electric switch mechanism according to claim 7, wherein each of the spaced stationary contacts comprises first and second contact members, and each of said bridging contact end portions comprises first and second contact members engageable respectively with the contact members of the stationary contacts, and mounted On respective articulately connected parts of said end portions, the contact members being arranged so that the pairs of first contact members engage earlier than, and disengage later than, the pairs of second contact members during movements of the switch mechanism.

9. An electric switch mechanism according to claim 8, wherein the first contact members of the bridging contact are interconnected by a resistive current path.

10. A circuit breaker, adapted for use with a polyphase circuit, comprising in combination: a molded switch housing providing a plurality of compartments, said compartments including a first compartment housing a breaker operating mechanism and a plurality of compartments housing respective phase switches, said breaker operating mechanism comprising: a. an operating shaft extending into each of the compartments, b. a radially extending lever connected to the operating shaft, c. spring means biasing the lever into an OFF position, d. latching means engageable with said spring means for latching the lever in the ON position, e. solenoid means cooperating with the latching means for releasing the latching means whereby to permit the lever to move to the OFF position, f. resetting means for resetting the lever to the ON position, g. abutment means connected to the resetting means operable to prevent resetting of the lever to the ON position when said solenoid means is energized, and each phase switch comprising: a. a pair of stationary contacts mounted in the respective compartment, b. a bridging contact having end contact portions engageable under one and over the other of said stationary contacts for bridging same, c. first and second presser arms pivotally connected to the bridging contact adjacent the respective end portions thereof, d. compression springs disposed and arranged between the end portions of the bridging contact and the respective presser arms for urging the latter away from said end portions e. a carrier pivotally mounted in the compartment for pivotal movement about a transverse axis, f. said operating shaft being connected to the carrier for pivotally moving the carrier between first and second operative positions, g. first and second stationary abutment members mounted in the compartment, h. first and second support means mounted on the carrier one on either side of said axis, i. first and second spring toggle mechanisms connected respectively between said support means and said presser arms, j. each spring toggle mechanism having a dead centre position and being movable from one side to the other of the dead centre position to urge the presser arm towards the respective end portion of the bridging contact so as to urge the latter into engagement with the respective stationary contact, and k. first and second toggle actuating means mounted respectively on said support means, l. each said toggle actuating means being engageable with a respective one of said abutment members upon movement of the carrier from its first to its second operative position, whereby to actuate the respective toggle mechanism and set it on said other side of the dead centre position.

11. A circuit breaker according to claim 10 wherein the end contact portions of the bridging contact each provide an arcing contact member, the arcing contact members being interconnected by a conductor which is linked with a pair of magnetic flux paths each providing an air gap wherein a respective arcing contact member is located, arcing current magnetising the paths so as to deflect and lengthen the arcs.

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