US3525959A - Circuit breaker with improved latch reset - Google Patents

Description

Aug"; 3% J. P. ELLSWORTH ET L 3525,59

CIRCUIT BREAKER WITH IMPROVED LATCH RESET 4 Sheets-Sheet 1 Filed Dec. 5, .1968

Aug. 25, 1970 P, ELLSWORTH ET AL 3,525,959

CIRCUIT BREAKER WITH IMPROVED LATCH RESET 4 Sheets-Sheet Filed Dec. 5Q 1968 Aug. 25, 1970 Filed Dec. 5, 1968 J. P. ELLSWORTH "ET AL CIRCUIT BREAKER WITH IMPROVED LATCH RESET 4 Shets-Sheet a 'FIG.3.

Aug. 25, 1970 J. P. ELLSWORTH ET AL 3,525,959

CIRCUIT BREAKER WITH IMPROVED LATCH RESET 4 Sheets-Sheet 4 Filed Dea. 5, 1968 H FIG.5.

United States Patent 3,525,959 CIRCUIT BREAKER WITH IMPROVED LATCH RESET James P. Ellsworth, Beaver, and John Majeher, Beaver Falls, Pa., assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Dec. 5, 1968, Ser. No. 781,514

Int. Cl. H01h 77/00 US. Cl. 335-166 Claims ABSTRACT OF THE DISCLOSURE A circuit breaker comprises improved means for resetting the latch and trip means following a tripping operation. The latch and trip means will not reset following release thereof if the contacts are welded closed, and the operating handle cannot be put in a maintained open position when the contacts are welded closed.

CROSS-REFERENCE TO RELATED APPLICATION A circuit breaker of the general type herein disclosed is disclosed in the copending application of Nick Yorgin et al., Ser. No. 621,321, filed Mar. 7, 1967, now Pat. No. 3,460,075.

BACKGROUND OF THE INVENTION Field of the invention Circuit breakers of the type comprising latch and trip means automatically releasable to effect tripping operations and manually resettable following tripping operations.

Description of prior art In prior art circuit breakers of the type disclosed in the above-mentioned Pat. No. 3,460,075 and in the patent to Walker et al., No. 2,892,054, a trip member, which is latched by latch means, is automatically released upon the occurrence of certain overload current conditions to move to a tripped position to effect automatic opening of the breaker. The trip member is reset by movement of the operating handle to a resetting position in proximity to the open or off position thereof during which movement the handle engages the trip member and moves the trip member to a position wherein the trip member engages the latch means to move the latch means to a latch ing position, whereupon the operating handle may be released and the breaker will be in the reset or open position with the handle in the open or ofi? position.

SUMMARY OF THE INVENTION A circuit breaker comprises a stationary contact and a movable contact arm structure carrying a movable contact thereon, which contact arm structure is movable between open and closed positions to open and close the contacts. Latch and trip means comprises a trip member latched in a latched position by a latch member which is in turn latched by a trip bar. An operating mechanism comprises a toggle connected at one end thereof to the movable contact arm structure and at the other end thereof to the trip member, and an operating spring that is connected between the knee pivot of the toggle and a manually operable operating member. With the trip mem ber in the latched position, the operating member is movable from a closed or on position to an open or off position to change the line of action of the operating spring whereupon the operating spring collapses the toggle to move the contact arm structure to the open position. The operating member is movable from the off to the on position to change the line of action of the operating spring whereupon the operating spring operates to erect the toggle to move the contact arm structure to the closed position. A trip device comprises means automatically operable upon the occurrence of overload current conditions above a predetermined value to release the trip bar and latch member to thereby release the trip member whereupon the operating spring operates to move the trip member to a tripped position to cause collapse of the toggle and opening of the contact arm, and to move the operating handle to a position intermediate the on and off positions to provide a visual indication that the breaker has tripped open. Following a tripping operation, the trip bar, latch member and trip member must be reset before the circuit breaker can be operated. The breaker is reset by movement of the operating member to a position slightly past the off position during which movement the operating member engages the trip member to move the trip member toward the latched position and during which movement the toggle engages the latch member to move the latch member to a latching position whereupon the trip bar latches the latch member in the latching position and the latch member latches the trip member in the latched position so that whenthe operating handle is released the circuit breaker will be latched or reset. In the reset position the operating spring maintains the handle in the off position with the circuit breaker contacts in the open position and the toggle in the collapsed condition. Upon the occurrence of a tripping overload when the contacts are welded in the closed position the trip device will operate to unlatch the trip bar and latch member to thereby release the trip member, and the operating spring will move the trip member toward the tripped position; but the weld will prevent movement of the contacts to the open position. The breaker is constructed such that in this condition the op erating spring will maintain the operating member in the on or closed position to provide a visual indication that the circuit breaker contacts are in the closed position. If an attempt is made to reset the trip member, the operating member can be moved to the resetting position moving the trip member to the resetting position; but the toggle, which is connected to the movable contact arm structure, will not move to the resetting position so that the latch member and trip bar will not be reset by this operation of the operating member and the operating member will be returned to the on or closed position upon release thereof. Thus, the operating member will be maintained in the on or closed position to provide an indication that the contacts are welded closed, and an operator will not be able to put the operating member in a maintained open position so long as the contacts are welded closed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side sectional view, through the operatingmechanism pole unit, of a multipole circuit breaker constructed in accordance with principles of this invention;

FIG. 2 is an enlarged view, similar to FIG. 1, with the breaker shown in the off or open position;

FIG. 3 is a view similar to FIG. 2 with the breaker shown in the tripped open position;

FIG. 4 is a view similar to FIG. 3 with the breaker shown in a position momentarily reached during a resetting operation;

FIG. 5 is a view similar to FIG. 3 with the breaker shown in a tripped condition when the contacts are welded in the closed position; and

FIG. 6 is a perspective view of a latch member seen in FIGS. 1-5.

Referring to the drawings, there is shown therein, a multi-pole circuit breaker 3 comprising an insulating housing 5 and a circuit breaker mechanism 7 supported in the housing 5. The housing 5 comprises an insulating base 9 and an insulating cover 11 cooperating with the base 9 to enclose the circuit-breaker mechanism 7 that is mounted on the base 9.

The circuit-breaker mechanism 7 comprises an operating mechanism 14, a latch-and-trip means 13 and a thermal-and-magnetic trip device 17.

A stationary contact 19, a movable contact 21 and an arc'extinguishing unit 23 are provided for each pole unit of the breaker. The stationary contact 19 for each pole is rigidly mounted on the inner end of a conducting strap 25 that is secured to the base 9 and that extends outward to an external cavity where a well-known type of solderless tenninal connector 27 is secured to the outer end of the conductor 25. The movable contact 21 for each of the pole units is mounted on a movable contact arm structure 28. The movable contact arm structure 28 comprises a contact arm 29 that is pivotally mounted, by means of a pin 31, on a switch arm 33 that is fixedly secured to an insulating tie bar 35. The switch arms 33 for all of the pole units are secured to the common tie bar 35 for simultaneous movement with the tie bar that is pivotally mounted for movement about an axis normal to the plane of the paper in FIGS. l-5. A torsion spring 37 in each pole unit biases the associated contact arm 29 in a clockwise (FIG. 1) direction about the switch arm 33 to provide contact pressure in the closed position of the contacts.

The operating mechanism 14 is a single operating mechanism disposed in one pole unit compartment. The operating mechanism 14 is suported on two metallic rigid spaced supporting plates 41 that are fixedly secured to the base 9 in the one pole unit compartment. Only one of the plates is seen in the figures. An inverted U-shaped operating member 43 is pivotally supported on the supporting plates 41 with the inner ends of the legs of the member 43 positioned in U-shaped notches in the plates 41. An insulating operating handle member 45 is fixedly secured to the front portion of the operating member 43. The operating handle member 45 comprises an insulating shield 47 and a handle 49. The handle 49 protrudes out through an opening 51 in the cover 11, and the shield 47 closes the opening 51 in all positions of the handle.

The switch arm 33 for the one pole unit is operatively connected, by means of a toggle comprising toggle links 53 and 55, to a releasable trip member or cradle 57 that is pivotally supported on the supporting plate 41 by means of a pin member 59. The toggle links 53, 55 are pivotally connected together by means of a knee pivot pin 61. The toggle link 53 is pivotally connected to the switch arm 33 by means of a pin 63, and the toggle link 55 is pivotally connected to the releasable trip member 57 by means of a pin 65. An overcenter spring 67 is connected under tension between the knee pivot pin 61 and the bight portion of the operating member 43.

With the releasable member 57 in the latched position seen in FIGS. 1 and 2, the contacts are manually operated by movement of the handle 49. The contacts are opened by movement of the handle 49 in a counterclockwise direction from the closed or on position seen in FIG. 1 to the open or off position seen in FIG. 2. This movement carries the line of action of the operating spring 67 to the left causing collapse of the toggle 53, 55 to thereby rotate the tie bar 35 in a counterclockwise direction to simultaneously move the movable contact arm structures 28 to the open position seen in FIG. 2. The contact arm 27 engages a stop 68 in the open position thereof. The contacts are manually closed by reverse movement of the handle 49 from the ad to the on position, which movement carries the line of action of the operating spring 67 to the right to erect the toggle 53, 55 to thereby ortate the tie bar 35 in a clockwise direction to move the movable contact arm structures 28 from the open position seen in FIG. 2 to the closed position seen in FIG. 1.

In addition to the releasable trip member 57, the latchand-trip means 13 comprises a latch member 71 and a trip bar 73. The latch member 71 comprises a generally U-shaped member 75 (FIG. 6) and a roller member 77 movably supported for limited travel on the member 75. The roller member 77 is provided with pin portions at the opposite ends thereof that fit Within elongated slots 79 in the opposite legs of the member 75. A torsion spring 81 biases the roller member 77 toward one end of the slots 79. The latch member 71 is pivotally supported on the supporting plates 41 by means of a pin member 83. As can be understood with reference to FIGS. 1-6, the releasable member 57 moves between the opposite legs of the latch member 71.

The trip bar 73 is an insulating trip bar that extends across all of the pole unit compartments of the breaker. The trip member 71 is suitably supported on the supporting plates 41 for pivotal movement about the elongated axis thereof which axis is normal to the plane of the paper as seen in FIGS. l-S. The trip member 73 is provided with a latch surface 89 that hooks onto a latch surface 91 of the latch 71. A compression spring 93 is positioned between the latch member 71 and the trip bar 73 to bias the trip bar 73 in a clockwise latching direction. The releasable trip member 57 is provided with a lower hook-shaped end 95 that engages under the roller 77 to latch the releasable trip member 57.

There is a separate thermal-and-magnetic trip device 17 in each pole unit. Each of the trip devices 17 comprises a generally L-shaped bimetal member 103 having an adjusting screw 105 supported at the upper free end thereof. Each of the bimetals 103 is secured to the base 9 by means of a bolt 107, and electrically connected to the associated switch arm 33 by means of a flexible conductor 111. Another flexible conductor 113 is connected at one end to the upper end of the associated bimetal 103 and at the other end to the vertical leg of a conductor 115 that extends through an opening at the one end of the housing. A separate solderless terminal connector 117 is secured to the horizontal leg of each of the conductors 115. Each of the trip devices 17 also comprises a generally U-shaped magnetic member 121 that is fixedly secured to the associated conductor 115 with the opposite legs thereof extending on opposite sides of the current-carrying bimetal 103. A separate armature 123 is supported in 'the associated compartment for pivotal movement about a pair of opposite supporting arms 1'27 that rest on ledge parts of the insulating wall portions of the associated pole unit compartment. In each pole unit a spring biases the associated armature 123 to the unattracted position seen in FIGS. 1 and 2. The insulating trip bar 73 is formed with a depending projecting part 161 in each pole unit, with each part 161 being positioned adjacent the upper! end of the associated armature 123 and adjacent the associated actuating screw 105.

The circuit through each pole unit extends from the terminal connector 117 through the conductor .115, the flexible conductor 113, the bimetal 103, the flexible conductor 111, the contact arm 29, the contact 21, the contact 19, the conductor 25 to the other terminal connector 27.

When the circuit breaker is in the latched position seen in FIG. 1, the tension spring 67 operates through the toggle link 55 and pivot 65 to force the trip member 57 in a clockwise direction about the pivot 59. Clockwise movement of the releasable trip member 57 is restrained by the engagement of the free end 95 thereof under the roller member 77 of the roller latch 71 with the releasable trip member 57 pulling the latch member 71 in a clockwise direction about the pivot 83. Clockwise movement of the latch member 71 about the pivot 83 is restrained by the engagement of the latch surface 91 of the latch member 71 with the latch surface 89 of the insulating trip bar 73. The force of the roller latch member 71 against the trip bar 73 operates through the axis of the pivot of the trip bar so that clockwise movement of the latch member 71 is restrained by the trip bar 73 without tending to move the trip bar about the axis thereof.

Thus, the trip bar 73 is in a latching position latching the latch member 71 and releasable member 57 in the latched position seen in FIGS. 1 and 2.

The circuit breaker is shown in the closed position in FIG. 1. Upon the occurrence of a sustained overload current above a first predetermined value and below a second predetermined value in any of the pole units, the bimetal 103 in the overloaded pole unit becomes heated and flexes to the right with a time delay whereupon the screw 105 engages the associated part 161 of the trip bar 73 to rotate the trip bar 73 in a counterclockwise unlatching direction. During this movement, the latch surface 89 of the trip bar 73 clears the latch surface 91 of the latch member 71 to release the latch member 71 whereupon the latch member 71 releases the released trip member 57. Upon release of the latch member 7.1-, the spring 67 operates to rotate the releasable trip member 57 in a clockwise direction to the tripped position seen in FIG. 3. The releasable trip member 57 is stopped in the tripped position when it engages the stop 68. Upon movement of the releasable trip member 57 to the tripped position seen in FIG. 3, the line of action of the spring 67 is moved to the left and the spring 67 causes collapse of the toggle 51, 53to rotate the tie bar 35 in a counterclockwise direction to move the movable contact arm structures 28 to the open position seen in FIG. 3. As can be seen in FIG.

3, the latch member 71, which is biased to the tripped position by the spring 93, engages a pin 164 that limits movement of the latch member 71 in the tripped position. As can be seen in FIG. 3, the operating spring '67 biases the trip member 57 to the tripped position, and the spring 67 biases the operating member 43 counterclockwise where an extension 165 on the operating member 43 engages a shoulder 167 on the releasable trip member 57 to maintain the operating member '43 and handle 49 in a tripped position intermediate the on and off positions to provide a visual indication that the circuit breaker has tripped open.

Before the breaker can be manually operated following an automatic tripping operation, the breaker mechanism must be reset and relatched. Resetting is eifected by movement of the handle 49 from the intermediate position seen in FIG. 3 to a position slightly past the full off position. The parts are shown in FIG. 4 in a position momentarily reached during a resetting operation.

During the resetting movement of the handle 49, the

extension 165 on the operating member 43 operates against the shoulder 167 of the releasable trip member '57 to rotate the trip member 57 in a counterclockwise direction about the pivot 59. During resetting movement of the handle 49, the trip member 57 moves counterclockwise moving the toggle '55, 53 to the left whereupon a radius 171 at the knee of the toggle 53, 55 engages a surface 173 on the latch member 71 (FIG. 4) to move the latch member 71 in a counterclockwise direction about the pivot '83. During this movement, the end 95 of the releasable trip member 57 Wipes past the roller 77, and the latch member 71 moves against the spring 93 to move the trip bar 73 in a clockwise direction to the latching position wherein the latch surface 89 on the trip bar 73 engages the latch surface 91 on the latch member 71. Thereafter, upon release of the handle 49 by the operator, the spring 67 will again bias the toggle link 55 to bias the releasable trip member 57 in a clockwise direction to move the releasable trip member 57 up to engage the roller 77 in the latched position seen in FIG. 2, in which position the latch member 71 is latched by the trip bar 73 in the same manner as was hereinbefore described. Thereafter, the handle 49 can .be manually moved be tween the OE and on positions to operate the contacts in the same manner as was hereinbefore described.

Upon the occurrence of an overload above the second predetermined value in any of the pole units, the current flowing through the bimetal 103 energizes the associated magnetic members 121, 123 sufliciently to attract the armature 123 whereupon the armature 123 pivots about the arm portions and the upper end of the armature engages the projection 161 on the trip bar 73 to rotate the trip bar 73 in a counterclockwise direction to effect a tripping operation in the same manner as were hereinbefore described. The circuit breaker is reset following a magnetic instantaneous tripping operation in the same manner as was hereinbefore described following a thermal time-delay tripping operation.

The circuit breaker is shown in FIG. 5 in a position that is reached when the latch-and-trip means 13 is released with the contacts 21, 19 welded in the closed position. As can be seen in FIG. 5, the releasable trip member 57 has been released; but the weld of the contacts has prevented movement of the contact arm structure 28 to the open position. The lower toggle link 53, which is connected to the contact arm structure 28 is held from moving to the tripped position so that the toggle 53, 55 cannot collapse to the tripped position seen in FIG. 3 and the operating spring 67 is maintained in a position wherein the spring biases the operating lever 43 to the on position so that when the latch-and-trip means 13 is released with the contacts welded in the closed position, the external handle 49 will remain in the on position to indicate that the contacts of the circuit breaker are closed. If an attempt is made to reset the circuit breaker by moving the handle 49 to the reset position slightly past the full off position, the toggle 53, 55, which is restrained by the welded contacts 21, 19, will not move to a position wherein the toggle will engage and actuate the latch 71 to the latching position so that upon release of the handle 49 the spring 67 will automatically move the handle 49 back to the on position to provide: an indication that the breaker has not reset and the contacts are closed. Thus, the circuit breaker cannot be reset and the handle 49 cannot be moved to a maintained open position when the latch-and-trip means 13 is released with the contacts 21, 19 welded in the closed position.

We claim:

1. A circuit breaker comprising a stationary contact, a movable contact arm structure carrying a movable contact thereon and movable between open and closed positions to open and close said contacts, latch-and-trip means in a latched position, an operating mechanism comprising an operating handle member and a spring structure, when said latch-and-trip means is latched said operating handle member being operable between open and closed positions to operate said spring structure whereupon said spring structure operates to open and close said contacts, a trip device operable automatically upon the occurrence of overload current conditions above a predetermined value to elfect release of said latch-and-trip means, upon release of said latch-and-trip means said spring structure operating to move said movable contact arm structure to the open position, following release of said latch-and-trip means said operating mechanism being operable to close said contacts only after said latch-and-trip means is relatched in said latched position, following release of said latch-and-trip means said operating handle member being operable toward the open position thereof to operate said latch-and-trip means to said latched position whereupon said operating handle member will remain in the open position upon release thereof, upon release of said latchand-trip means with said contacts welded in the closed position said latch-and-trip means moving out of said latched position and said operating mechanism maintaining said operating handle member in the closed position to provide an indication of the closed condition of said contacts, and safety means rendering said operating mechanism ineffective to relatch said latch-and-trip means upon movement of said operating handle member toward the open position thereof when said contacts are welded in the closed position.

2. A circuit breaker according to claim 1, and upon release of said latch-and-trip means when said contacts are not welded closed said spring structure operating to 7 move said movable contact arm structure to the open position and to move said operating handle member to an intermediate position intermediate the open and closed positions thereof to provide an external visual indication that said contacts are in the tripped open position.

3. A circuit breaker according to claim 1, said latchand-trip means comprising a trip member and a latch member latching said trip member, a trip bar latching said latch member, a toggle comprising a first toggle link connected to said movable contact arm structure and a second toggle link connected to said trip member, a knee pivot connecting said first and second toggle links, said spring structure being connected at one end thereof to said knee pivot and at the other end thereof to said operating handle member, said operating handle member being movable from the open position to the closed position to operate said spring structure to erect said toggle to thereby move said movable contact arm structure to the closed position, said operating handle member being movable from the closed position to the open position to operate said spring structure to collapse said toggle to thereby move said movable contact arm structure to the open position, upon the occurrence of an overload current above said first predetermined value said trip device operating said trip bar to a releasing position to release said latch member to thereby release said releasable member whereupon said releasable member moves to a tripped position to change the line of action of said operating spring structure whereupon said operating spring structure collapses said toggle to move said movable contact arm structure to the open position, said operating handle member being movable to move said trip member and toggle to a resetting position during which movement said toggle engages said latch member to move said latch member and said trip bar to the latching position so that upon release of said operating member following said resetting operation said trip bar will again latch said latch member which will again latch said trip member in the latched position, upon movement of said operating handle member to the resetting position when said contacts are welded closed and said trip member is released the weld of said contacts preventing movement of said toggle to a resetting position to thereby prevent a resetting operation of said cir cuit breaker, and with said contacts welded closed and said trip member released said operating spring structure maintaining said operating handle member in the closed position to provide an external visual indication that said contacts are closed.

4. A circuit breaker according to claim 3, and said operating spring structure comprising a tension spring structure supported under tension between said knee pivot and said operating handle member.'

5. A circuit breaker according to claim 4, and upon release of said trip member when said contacts are not in the welded position, said trip member moving to change the line of action of said tension spring structure and said tension spring structure operating to collapse said toggle to move said movable contact arm structure to the open position during which movement said tension spring structure operates to move said operating member to an intermediate position intermediate the open and closed positions to provide an external visual indication that said contacts have tripped open.

6. A circuit breaker comprising a stationary contact, a movable contact arm structure carrying a movable contact thereon and being movable between open and closed position to open and close said contacts, latch-and-trip means comprising a trip member and a latch member in a latched position latching said trip member in a latched position, a trip bar in a latching position latching said latch member in the latched position, a toggle comprising a first toggle link pivotally connected to said movable contact arm structure and a second toggle link pivotally connected-to said trip member, a knee pivot pivotally connecting said first and second toggle links, an operating handle member, a spring structure connected between said knee pivot of said toggle and said operating handle member, with said trip member in the latched position said operating handle member being movable from an open position wherein said toggle is collapsed to a closed position to operate said spring structure whereupon said spring structure operates said toggle to an erected condition to move said movable contact arm structure to the closed position, with said trip member in the latched position said operating member being movable from said open position to a closed position to operate said spring structure whereupon said spring structure operates said toggle to a collapsed condition to move said movable contact arm structure to the open position, a trip device operable automatically upon the occurrence of overload current conditions above a predetermined value to move said trip bar to a tripped position to release said latch member whereupon said latch member moves to a tripped position to release said trip member and said trip member moves to a tripped position to change the line of action of said spring structure whereupon said spring struc ture operates to collapse said toggle to move said movable contact arm structure to the open position, following release of said trip member said operating handle member being movable to a resetting position in proximity to the open position thereof to move said trip member and toggle to the reset position during which movement said toggle engages said latch member to move said latch member to the latched position and said trip bar to the latching position so that upon release of said operating member said trip bar again latches said latch member in the latched position and said latch member latches said trip member in the latched position.

7. A circuit breaker according to claim 6, upon release of said trip member with said contacts welded closed said spring structure maintaining said operating handle member in the closed position to provide a visual indication that said contacts are'closed and upon movement of said operating handle member toward the resetting position said movable contact arm structure and toggle being prevented by the weld from moving to a position wherein said toggle engages said latch member to move said latch member to the latched position whereby upon release of said operating handle member said operating spring structure will move said operating handle member back to the closed position to indicate that said latch and trip means has not been reset and to indicate that said contacts are in the closed position.

-8. A circuit breaker according to claim 7, said operating spring structure comprising a tension spring structure connected under tension between the knee of said toggle and said operating handle member.

9. A circuit breaker according to claim 8, said movable contact arm structure being supported for movement about a first axis, said trip member being supported for movement about a second axis parallel to said first axis, said latch member being supported for movement about a third axis parallel to said first and second axes, and said trip bar being supported for movement about a fourth axis parallel to said first second and third axes.

10. A circuit breaker according to claim 9, and spring means between said trip bar and latch member biasing said trip bar toward the latching position and biasing said latch member toward the unlatching position.

References Cited UNITED STATES PATENTS 2,306,235 12/1942 Walle 337-52 2,426,880 9/1947 Jackson 337-48 3,460,075 8/1969 Yorgin 335-9 BERNARD A. GILH-EANY, Primary Examiner H. BROOME, Assistant Examiner US. Cl. X.R. 33524

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