Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS3858130 A
Publication typeGrant
Publication dateDec 31, 1974
Filing dateDec 4, 1973
Priority dateDec 4, 1973
Also published asCA1013846A1
Publication numberUS 3858130 A, US 3858130A, US-A-3858130, US3858130 A, US3858130A
InventorsMisencik J
Original AssigneeWestinghouse Electric Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Ground fault circuit breaker with cold temperature bimetal constriction
US 3858130 A
Abstract
A ground fault circuit interrupter characterized by a circuit breaker and a ground fault detector contained within an insulating housing. The circuit breaker comprises an elongated current-carrying bimetal element for tripping a pair of cooperable contacts from the closed to the open position, one end portion of the bimetal element being fixedly mounted and the other end being free to move in one direction in response to an increase in temperature. A bi-metal stop projection within the housing to prevent movement of the bimetal element from its latched position to the other direction in response to extremely cold ambient temperatures.
Images(1)
Previous page
Next page
Description  (OCR text may contain errors)

United States Patent [1 1 Misencik GROUND FAULT CIRCUIT BREAKER WITH COLD TEMPERATURE BIMETAL CONSTRICTION [75] Inventor: John J. Misencik, Shelton, Conn. [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Dec. 4, 1973 211 Appl. No.: 421,573

[52] US. Cl. 335/18, 337/55 [51] Int. Cl. H01h 83/02 [58] Field of Search 335/18, 37; 337/55, 57

[56] References Cited UNITED STATES PATENTS 2,691,708 10/1954 Drobney et a]. 335/37 2,786,917 3/1957 Casey 335/37 3,636,482 1/1972 Edmunds 335/18 Dec. 31, 1974 Primary Examiner-Harold Broome Attorney, Agent, or Firm-l... P. Johns [5 7] ABSTRACT A ground fault circuit interrupter characterized by a circuit breaker and a ground fault detector contained within an insulating housing. The circuit breaker comprises an elongated current-carrying bimetal element for tripping a pair of cooperable contacts from the closed to the open position, one end portion of the bimetal element being fixedly mounted and the other end being free to move in one direction in response to an increase in temperature. A bi-metal stop projection within the housing to prevent movement of the bimetal element from its latched position to the other direction in response to extremely cold ambient temperatures.

5 Claims, 3 Drawing Figures GROUND FAULT CIRCUIT BREAKER WITH COLD TEMPERATURE BIMETAL CONSTRICTION BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a circuit breaker and more particularly it pertains to a ground fault circuit interrupter having restriction means for preventing movement of a bimetal element when subjected to inordinately cold temperatures.

2. Description of the Prior Art A standard circuit breaker includes elements for sensing current overloads and consist primarily of a straight bimetal element and a latch assembly. When thermal overloads occur the bimetal element deflects in one direction by a distance which is a function of the amount of current overload and thereby releases the spring loaded latch to trip the circuit breaker to the open position. This uncompensated bimetal arrangement is an economical method for general circuit breaker usage.

In a ground fault circuit breaker a standard circuit beaker is utilized but it can be inadequate because only temperature ranges above C are important. Building code restrictions govern the circuit breaker usage in cold ambient environments. The specific temperature range for ground fault circuit breakers is 35C to about 66C which offers maximum protection. It is important to aid the bimetal element for the following reasons: (a) severe cold temperature causes opposite movement of the normal bimetal element thereby causing excessive deflection in the wrong direction; (b) resultant movement in the wrong direction (toward the latch assembly) causes undue and inconsistent latch spring release pressures; and (c) ability to repeat the normal circuit breaker action and maintenance of accurate calibration are impaired.

SUMMARY OF THE INVENTION Generally, in accordance with this invention, it has been found that the foregoing difficulties may be overcome by providing a ground fault circuit interrupter comprising a circuit breaker and a ground fault detector within an insulation housing, the circuit breaker comprising a pair of cooperable contacts operable between open and closed positions, a releasable member in an initial position and movable when released to a tripped position to effect automatic opening of the contacts, an elongated current-carrying bimetal element for tripping the releasable member when a predetermined current overload effects a deflection of said bimetal element in one direction from a latched position, a bimetal stop means such as a projection integral with the insulating housing for preventing the bimetal element from moving in the other direction from the latched position when subjected to excessively low ambient temperatures, the ground fault detector comprising a current-monitoring core and a plurality of primary windings on the core, each being one of a line and a neutral conductor of an A.c. electrical distribution system, a secondary winding sensing current imbalance between the primary windings, means responsive to a predetermined sensing signal to open said line conduc tors, the means responsive to the predetermined sensing signal including a pivotally movable member movable against the bimetal element to unlatch the releasable member, and the pivotally movable member being adjacent to the bimetal element on the side of the stop means.

The advantage of the device of this invention is that the stop means for constriction insures reliable operation of the ground fault circuit breaker when subjected to excessively cold temperatures, and when the bimetal element is restricted. The force required by an intermittent duty solenoid in the ground fault detector is minimized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a ground fault circuit breaker structure of this invention;

FIG. 2 is a vertical sectional view taken on the line II-II of FIG. 1 and showing the circuit breaker side of the invention in the closed position; and

FIG. 3 is a sectional view taken along the line III-III of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 a ground fault circuit breaker structure is generally indicated at 3 and it comprises a housing 5 which is composed of electrically insulating material such as a thermosetting resin. The housing 5 includes a pair of box-like containers or tray portions 7 and 9 and a side cover 11, which are secured in place by suitable means such as rivets 12 (FIG. 2) in a conventional manner.

Inasmuch as a detailed description of both the ground fault detector portion and the circuit breaker portion is set forth in the application of Kenneth R. Coley and John J. Misencik, Ser. No. 287,921, filed Sept. 1 l, 1972, the description of those portions is limited to the parts that are essential to the operation of the invention disclosed herein.

As shown in FIG. 3 the tray portion 7 comprises a back wall 8 and the tray portion 7 comprises a back wall 13 that serves as a single partition wall between compartments 15 and 17 formed between the back walls 8 and 13 and the side cover 11. A circuit breaker mechanism is disposed within the compartment 15 and a ground fault circuit interrupter is disposed within the compartment 17.

Briefly, the circuit breaker structure comprises a stationary contact 21, a movable contact 23, a supporting metal frame 25, an operating mechanism 27, and a trip device 29. Among other things the operating mechanism 27 comprises a contact arm 31 and a releasable member 33 which is pivotally supported at one end thereof on a pivot 35 when the circuit breaker is opened manually a handle 37 is rotated from the on to the off position, whereby the contact arm 33 moves the movable contact 23 away from the stationary contact 21 in a conventional manner.

The contact arm 31 is electrically connected to the lower end of an elongated bimetal element or bimetal 39 by a flexible conductor 41. The bimetal 39 is part of the trip device 29 and is secured at its upper end to a flange 43 of the frame 25.

A flexible conductor 45 connects the upper end of the bimetal 39 with a terminal strap 45 having a terminal connector 47. Thus, the closed circuit through the circuit breaker extends from a terminal 51 through the stationary contact 21, the movable contact 23, the contact arm 31, the flexible conductor 41, the bimetal 39, the flexible conductor 45, the terminal strap 47 to the terminal connector 49.

The trip device 29 comprises the bimetal 39, an elongated rigid magnetic armature or latch member 53, an end portion 55 of the releasable member 33, and a projection 57 of a lever 59 (FIG. 3). The latch member 53 ing 63 which includes a latch surface 65 at the base of the opening in the reset position of the circuit breaker as shown in the drawings. The end portion 55 of the releasable member 33 is latched in the opening 63 of the latch member 53, and more particularly is lodged upon the latch surface 65. Upon the occurrence of a sustained overload current above a first predetermined value the bimetal 39 which is heated by the current flowing therethrough, deflects from the position shown in FIG. 2 to a thermally tripped position to the right of that shown in FIG. 2, whereupon the end portion 55 drops from its position on the latch surface 65.

In accordance with this invention bimetal stop means or construction or a projection 67 is provided to prevent the bimetal 39 from moving to the left of the latched position (FIG. 2) such as when the bimetal is exposed to severely cold ambient temperature conditions such as of the order of 35C. The projection 67 is preferably a molded part of the tray portion 9 and extends outwardly from the back wall 13 as well as a bottom wall 69. However, the projection 67 would function satisfactorily if it were part of the cover 11. In the position shown in FIG. 3 the upper end of the projection 67 extends slightly above the lower end of the bimetal 39 so as to prevent the bimetal from moving to the left in response to severely cold ambient temperatures. The projection 67 however may be located at another position along the length of the bimetal so long as it is suitably disposed to prevent the bimetal from moving unduly to the left beyond the latched position of FIG. 2. In effect a thermal restriction is produced within the compartment 15 so that upon a limited movement of the bimetal 39 when subjected to cold temperature, a motion takes place where the lower free end of the bimetal engages the projection 67 to restrict further deflection. As a result a binding effect between the spring loaded end portion 55 of the releasable member 33 and the latch surface 65 is avoided and the bimetal 39 is free to operate in a conventional manner.

Where a ground fault occurs and is detected in the ground fault detector 71 in the compartment 17 as set forth in the above mentioned application the lever 59 is actuated to cause the projection 67 at the lower end thereof to move the latch member 53 to the right and thereby disengage the end portion 55 of the releasable member 33 from the latch surface 65. In ground fault circuit breakers where the unit has been subjected to a temperature of as low as -35C for a period of hours ordays the circuit breaker must nevertheless be able to trip free in 0.25 milliseconds or less when subjected to 260 milliampere ground fault circuits which are unable to heat the bimetals to cause deflection. A ground fault circuit breaker mechanism is activated on a ground fault by the use of a toroid sensor, electronic amplifier and power device, and a solenoid, as disclosed in the above indicated patent application. The solenoid is the action member which depresses the spring latch to effect disconnection. If the bimetal 39 is deflected in the direction to cause latch interference, the solenoid is unable to depress the latch sufficiently to overcome the excessive deflection caused by cold temperature on the bimetal and thereby causing an inoperative device.

According the device of this invention satisfies problems existing in prior art devices and results in an improved ground fault circuit breaker.

What is claimed is:

l. A circuit breaker comprising an electrically insulating housing and including a box-like container and a cover therefor, a circuit breaker structure within the housing and comprising a pair of separable contacts operable between open and closed positions, a releasable member in an initial position and movable when released to a tripped position to effect automatic opening of the contacts and comprising an elongated currentcarrying bimetal for tripping the releasable member when a predetermined current overload effect deflection of said bimetal in one direction from a latched po sition, the bimetal being mounted at one end portion and disposed in an unbiased position, bimetal stop means for preventing said bimetal from moving in the other direction from said latched position when the bimetal is subjected to extremely cold ambien temperature, and the container and the cover being molded members one of which comprises an integral molded projection at the other end of the bimetal.

2. A ground fault circuit interrupter for use in a load center and comprising a circuit breaker, a ground fault detector, and an insulation housing therefor; the circuit breaker comprising a pair of cooperable contacts operable between open and closed positions, a releasable member in an initial position and movable when released to a tripped position to effect automatic opening of the contacts, an elongated current-carrying bimetal element for tripping the releasable member when a predetermined current overload effects deflection of said bimetal element in one direction from a latched position, the bimetal being mounted at one end portion and disposed in an unbiased position, bimetal stop means for preventing said bimetal element from moving in the other direction from said latched position when the bimetal is subjected to extremely cold ambient temperature; the ground fault detector comprising a current monitoring core, a plurality of primary windings on the core, each being one of a line and a neutral conductor of an AC, electrical distribution system, a secondary winding sensing current imbalance between the primary windings, means responsive to a predetermined sensing signal to open said line conductors, the means responsive to a predetermined sensing signal including a pivotally movable member movable against said bimetal element to unlatch the releasable member, and the pivotally movablemember being adjacent to the bimetal element on the side of the bimetal stop means.

3. The ground fault circuit breaker of claim 2 in which the bimetal stop means comprises a projection extending into a position on the side of the bimetal element opposite the direction of deflection thereof.

4. The ground fault circuit breaker of claim 3 in which the projection is an integral portion of one of the container and cover.

5. The ground fault circuit breaker of claim 4 in which the bimetal element is fixedly mounted at one end portion and the other end portion is unattached, and in which the projection is a portion of the container and located at said other end portion thereof.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2691708 *Oct 10, 1951Oct 12, 1954Westinghouse Electric CorpCircuit breaker
US2786917 *Jun 4, 1954Mar 26, 1957Gen ElectricCircuit breaker trip device
US3636482 *May 25, 1970Jan 18, 1972Federal Pacific Electric CoModular circuit breakers and panelboards with ground-fault protection
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3999103 *Mar 14, 1975Dec 21, 1976Westinghouse Electric CorporationMulti-pole ground fault circuit breaker
US5012382 *Jun 14, 1990Apr 30, 1991Teal Electronics CorporationLow impedance power conditioner apparatus and method
US5224006 *Sep 26, 1991Jun 29, 1993Westinghouse Electric Corp.Electronic circuit breaker with protection against sputtering arc faults and ground faults
US5307230 *Aug 26, 1993Apr 26, 1994Westinghouse Electric Corp.Circuit breaker with protection against sputtering arc faults
US5420740 *Sep 15, 1993May 30, 1995Eaton CorporationGround fault circuit interrupter with immunity to wide band noise
US5432455 *Sep 6, 1994Jul 11, 1995Blades; Frederick K.Method and apparatus for detecting arcing in alternating current power systems by monitoring high-frequency noise
US5434509 *Sep 6, 1994Jul 18, 1995Blades; Frederick K.Method and apparatus for detecting arcing in alternating-current power systems by monitoring high-frequency noise
US5682101 *Feb 13, 1996Oct 28, 1997Square D CompanyArcing fault detection system
US5825598 *Feb 11, 1997Oct 20, 1998Square D CompanyArcing fault detection system installed in a panelboard
US5834940 *Sep 24, 1996Nov 10, 1998Brooks; Stanley J.Arcing fault detector testing and demonstration system
US5839092 *Mar 26, 1997Nov 17, 1998Square D CompanyArcing fault detection system using fluctuations in current peaks and waveforms
US5847913 *Feb 21, 1997Dec 8, 1998Square D CompanyTrip indicators for circuit protection devices
US5940256 *Nov 9, 1994Aug 17, 1999Eaton CorporationCircuit breaker responsive to repeated in-rush currents produced by a sputtering arc fault
US5946179 *Mar 25, 1997Aug 31, 1999Square D CompanyElectronically controlled circuit breaker with integrated latch tripping
US5969921 *Jan 29, 1998Oct 19, 1999Eaton CorporationGround fault electrical switching apparatus for coordinating tripping with a downstream ground fault switch
US5986860 *Feb 19, 1998Nov 16, 1999Square D CompanyZone arc fault detection
US6034611 *Feb 4, 1997Mar 7, 2000Square D CompanyElectrical isolation device
US6195241Mar 7, 1997Feb 27, 2001Squares D CompanyArcing fault detection system
US6242993Feb 6, 1997Jun 5, 2001Square D CompanyApparatus for use in arcing fault detection systems
US6246556Feb 19, 1998Jun 12, 2001Square D CompanyElectrical fault detection system
US6259996Aug 5, 1998Jul 10, 2001Square D CompanyArc fault detection system
US6313641Jul 1, 1999Nov 6, 2001Square D CompanyMethod and system for detecting arcing faults and testing such system
US6313642Jan 24, 1997Nov 6, 2001Square D CompanyApparatus and method for testing an arcing fault detection system
US6377427Dec 17, 1999Apr 23, 2002Square D CompanyArc fault protected electrical receptacle
US6452767Jan 27, 1997Sep 17, 2002Square D CompanyArcing fault detection system for a secondary line of a current transformer
US6477021Dec 21, 1999Nov 5, 2002Square D CompanyBlocking/inhibiting operation in an arc fault detection system
US6532424Apr 11, 2000Mar 11, 2003Square D CompanyElectrical fault detection circuit with dual-mode power supply
US6567250Dec 22, 1999May 20, 2003Square D CompanyArc fault protected device
US6591482Nov 17, 2000Jul 15, 2003Square D CompanyAssembly methods for miniature circuit breakers with electronics
US6621669Dec 17, 1999Sep 16, 2003Square D CompanyArc fault receptacle with a feed-through connection
US6625550Oct 26, 1999Sep 23, 2003Square D CompanyArc fault detection for aircraft
US6782329Jan 17, 2001Aug 24, 2004Square D CompanyDetection of arcing faults using bifurcated wiring system
US6822543Sep 24, 2003Nov 23, 2004General Electric CompanySystem and method for controlling trip unit mechanical stress
US7041921Apr 19, 2004May 9, 2006Moeller Gebäudeautomation KGSwitching device
US7068480Mar 27, 2002Jun 27, 2006Square D CompanyArc detection using load recognition, harmonic content and broadband noise
US7136265May 13, 2003Nov 14, 2006Square D CompanyLoad recognition and series arc detection using bandpass filter signatures
US7151656Oct 17, 2001Dec 19, 2006Square D CompanyArc fault circuit interrupter system
US7253637Sep 13, 2005Aug 7, 2007Square D CompanyArc fault circuit interrupter system
CN1957432BApr 15, 2005May 5, 2010穆勒建筑物自动化有限公司Switchgear
CN101145478BOct 12, 2007Jul 28, 2010温州市新蓝天电器有限公司Circuit breaker with leakage, overloading and short circuit protector
EP0320928A2 *Dec 15, 1988Jun 21, 1989ABB Elettrocondutture S.p.A.Device for detecting differential currents in electric systems
WO1991020116A1 *May 23, 1991Dec 26, 1991Teal Electronics CorpLow impedance power conditioner apparatus and method
WO2005101443A2 *Apr 15, 2005Oct 27, 2005Kadan PaulSwitchgear
Classifications
U.S. Classification335/18, 337/55
International ClassificationH01H83/22, H01H71/16, H01H71/12, H01H83/00
Cooperative ClassificationH01H83/226, H01H71/16
European ClassificationH01H71/16