US3904998A

US3904998A - Circuit breaker

Info

Publication number: US3904998A
Application number: US476701A
Authority: US
Inventors: Harold E Belttary
Original assignee: Caribe Circuit Breaker Co Inc
Current assignee: Commander Electrical Equipment Inc; CHALLENGER CARIBBEAN CORP; Osram Sylvania Inc
Priority date: 1974-06-05
Filing date: 1974-06-05
Publication date: 1975-09-09
Anticipated expiration: 1992-09-09
Also published as: CA1034626A

Abstract

A circuit breaker having a simple overload triggering mechanism of a thermostat element clamped at one end by a threaded rod, a leaf spring, and a recess in the housing. The other end of the thermostat element is notched to receive and engage a trip arm which is released to cause opening of the breaker contacts by bending of the thermostat element under overload current conditions.

Description

United States Patent 11 1 Belttary 1 Sept. 9, 1975 154] CIRC UlT BREAKER 3.1715230 3/1965 Klein et a1. 337 75 3.240903 3/1966 Groves et a1 337/75 X [73] Inventor: Hamld Belttary R10 3.257526 6/1966 Ramsey Ct a1. 337/82 x [73] Assignee: Caribe Circuit Breaker Co., Inc.,

San Juan, P R Primary Examiner-G. Harris Attorney, Agent, or Firm-David M. Keay; Elmer J. [22] Fled: June 1974 Nealon; Norman J. OMalley [21] Appl. No: 476,701

[57] ABSTRACT 52 us. c1 335/43; 335/45 A circuit breaker having a Simple Overload triggering [51] Int. Cl. HOIH 71/16 mechanism of a thermostat element clamped at one [58] Field of Search 335/43, 45; 337/75, 82, end y a threaded rod, 3 leaf Spring, and a recess in 337/94 the housing. The other end of the thermostat element is notched to receive and engage a trip arm which is 5 References Cited released to cause opening of the breaker contacts by UNITED STATES PATENTS bending of the thermostat element under overload current conditions. 2,390,819 12/1945 Wheeler 335/43 X y 2,659,783 11/1953 Casey 335/45 X 7 Claims, 4 Drawing Figures 24 27 o I 5 2 l6 9 l1 l l 93 1 i623 l l8 -69 1 ll 51 I" a 63 "O as 62 so 65 3 53 l PATENIED 9W5 3.904898 SHEET 1 BF 2 FIG. 1

I 5; 'rr sem -am BAcRoRouND or THE INVENTION This invention relates ,tocircuit breakers. .lVlore particularly, it is concerned with low voltage circuit breakers for controllinglowand moderate power electrical circuits. I t

A circuit breaker foruse in controlling electrical circuits typically has .a set of contacts, one fixed and one moving, and a toggle, or overcenter mecha nism,,,whichis manually operated to close and openthe contacts. A circuit breaker also includes an overload mechanism for tripping the circuit breaker and opening, the contacts when the electrical current through the circuit breaker exceeds certain predetermined conditions. The overload mechanism may include a thermally responsive member such as a; thermostat element whichfunctions to trip the breaker when an overload current ex ists. The circuit breaker may also include a magnet and,

armature arrangement for tripping thebreaker rapidly in response to certain predetermined current conditions.

A variety of circuit breakers of the general form de scribed above are well-known and widely used. One partieularlyuseful type of circuit breaker employed in protecting low voltage ,low and moderate power circuits is described and claimed in US. Pat. No.

3,671,908 issued on June 20, 1972 to Harold E, Belttary and John G. Palmer entitled Circuit Breaker.

Circuit breakers as described in theaforementioned patent are completely satisfactory for usein their intended applications. However, for certain applications, it is desirable to provide a circuit breaker in which the number and complexity of parts .are reduced, thereby also reducing the costs of fabricating ,and assembling.

the device SUMMARY OF THE INVENTION dance with the present invention includes a. housing of insulating material. A fixed contact is,mounted in the housing and a manually .rnovable handle is also mounted in the housing. A contact carrier on which a movable contact is mounted pivotally engages the handle at a pivot point. The circuit breaker also includes a trip arm which is pivotally mounted in the hosuing. An overcenter spring is connected between the contact carrier and the trip arrn so as to urge the contact carrier against the handle. The handle, contact carrier and overcenter spring form an overcenter arrangement, or

toggle, which acts to close the contacts when the spring is on one side of the pivot point to open the contacts when the spring is one the other side of the pivot point. A load terminal also .mounted in the housing.

A thermally responsive latching member is on7..-

nectcd in circuit between the. load terminal and the movable contact. One end of the thermally responsive latching member engages a portion of the housing. A

Support member is mounted in the housing and engages the thermally responsive. latching. member at a point, adjacent to the one end. spring member urges the thermally responsive latching member against the support member. The portion of the housing, the support.

member, and the spring. member, in.c()mbination,-hold. the portion of the thermally responsive latching member adjacent the oneend in fixed position witl' respcet to thehousing- The thermally responsive latching member has a. latching surface adjacent its opposite end which engages the trip arm when the contacts are closed and maintains the trip arm in a set position with the overcenter spring urging the trip arm toward a tripped position, In response to a predetermined current condition the thermally-responsive latching mem ber bends causing its opposite endto move with respect to its one end, thereby disengaging thelatching surface from .the trip arm and releasing the trip arm for movement tov the tripped position. When the trip arm moves to, the tripped position, the overcenter spring is moved tothe other side of the pivot point causing the contacts toopen. I t

IBRIEFDESCRIPTION oF THE DRAWINGS '.Ad ditional objects, features, and advantages of circuit breakers in accordance with the present invention will be apparent from the following detailed discussion together with the accompanying drawings wherein:

FIG. 1 is a side elevational view of a circuit breaker FIG.. 4 is a detailed view taken generally along the line .4 4 of FIG. 3. 7

DETAILED DESCRIPTION OF THE INvENTIoN A circuit breaker in accordance with the present invention as illustrated in the figures includes a housing comprising a case 10 of a suitable insulating material and a cover 11 of similar material. The case and cover are typically of molded plastic. The various elements of the circuit breaker mechanism are mounted within the case 10 and held in place by the cover 11 which is riveted to the case.

-A fixed contact 13 is mounted on a clip 14 which is designed to engage a line bus when the breaker is inserted into a distribution panel box. A moving contact l5 is mounted on a contact carrier 16. A handle 17 of insulating material is pivotally mounted within the case 10 in a conventional manner for manual operation.

The end of the contact carrier 16 is positioned in slots 18 and 19 in two arms extending from the handle 17 so as to provide a pivot point of connection 20 between the contact carrier 16 and the handle 17. A trip arm 23 ismounted on a boss 24 in the case 10 for pivoting between the set position as shown in FIG. 1 and the tripped position as shown in FIG. 2. An overcenter tension spring 26 has one end connected tothe contact carrier l6 and the other end connected to an arm 27 of-the trip arm'23. The handle l7,.contact carrier l6, andspring 26 form an overcenter arrangement, or toggle, which urges the movable contact toward the fixed contact 13 when the spring 26 is one one side of the pivot point as shown in FIG. 1 and urges the movable contact 15 to the open position, when the spring 26 is on the other side of the pivot point 20.

a screw 52 for clamping a wire against the load bar 53.

A thermally responsive latching member 60 is electrically connected between the movable contact and the load terminal 50 by

flexible conductors

61 and 62 of stranded wire, typically copper wire. The thermally responsive latching member 60 as best seen in FIG. 3 is a unitary structure consisting of a generally flat elongated thermostat element. The thermostat element includes at least two layers of metals having different eoeffieients of thermal expansion, so that the element bends as its temperature is increased. One end of the flexible conductor 61 is attached directly to the thermostat element adjacent to one end, and the other end of the flexible conductor 61 is attached to the contact arm 16 at its point of attachment to the movable contact 15. One end of the flexible conductor 62 is connected directly to the thermostat element 60 closely adjacent to a notch 80 (see FIG. 3) in the opposite'end of the thermostat element. The other end of the flexible conductor 62 is attached to the load bar 53 of the load terminal 50.

The thermostat element 60 is held in position at one end by an arrangement including a recess or V-shaped notch 63 in the wall of the housing which receives the end of the thermostat element. A support member ineludes a threaded rod or screw 65 which is threaded in anut 66 and lies generally normal to the thermostat element. The nut is mounted in the case 10 so as to prevent its rotation. The rod 65 has a reduced diameter portion or dog 67 at the end within the housing and-'a shoulder 68 below the'dog. The'dog 67 passes through an opening 70 (FIGS. 3, 4) in the thermostat element which accommodates the dog but does not accommodate the shoulder 68 (see FIGS. 3 and 4).

The mounting arrangement for the thermostat element 60 also'includes a generally J-shaped leaf spring 71 having a long arm the end of which is confined in a pocket 69 in the case 10. The short arm of the leaf spring 71 has a notch 72 (see FIG. 3) at its end which engages the dog 67 of the threaded rod 65.

The J -shaped spring 71 produces a component 'of force that presses the thermostat element 60 against the shoulder 68 of the threaded rod 65. The spring 71 also producesa component of force acting on the dog 67 which in turn bears against the thermostat element 60 urging the edge of the thermostat element into the V-shaped notch 63. Thus, the end portion of the thermostat element 60 is firmly held in position.

Rotation of the threaded rod 65 to advance or retract the rod with respect to the ease together with the action of the loaded spring 71 causes the thermostat element 60 to pivot aboutits end in the recess 63. This action changes the position of the opposite end of the thermostat element and thus the breaker is adjusted fortripping at a different predetermined current value as will be explained hereinbelow.

The notch 80 in the thermostat element 60 is adja cent its opposite end and provides a latching surface 81 against which a flange 82 of the trip arm 23 bears. The trip arm 23 tends to pivot about the boss 24 by virtue of the urging of the overcenter spring 26. The trip arm is maintained in its set position as shown in FIG; 1 by the flange 82 abutting the latch surface 81 and preventing further movement.

The thermostat element 60 has an extension 83 which is angled downward. Thisextcnsion serves as a ramp to deflect the end of the thermostat element 60 downward thus allowing the flange 82 of the trip arm to slide along the extension 83 and enter the notch and reengage the latching surface 81 when the trip arm 23 is being reset from the tripped to the set position. The effective length of the thermostat element lies between the end which engages the recess 63 and the region of the notch 80. Current flows through the thermostat element between the

flexible conductors

61 and 62 which are directly connected to the thermostat element adjacent to its ends.

An upstanding member in the case provides a wall defining the lower portion of the are chute and also provides a stop to limit movement of the contact carrier 16 when the contacts are opened. The upstanding member 90 also serves as a stop for limiting movement of the trip arm 23 and the contact carrier 16 in the tripped position as illustrated in FIG. 2.

The circuit breaker operates in the customary manner for closing and opening the contacts. The contacts are closed by rotating the handle 17 upward to the fully counterclockwise position as shown in FIG. 1. The contacts are opened manually by rotating the handle 17 in a clockwise direction to the fullest possible downward position. This action moves the pivot point 20 of the contact carrier 16 and the handle 17 in a clockwise direction to the opposite side of the overcenter spring 26. With the pivot point 20 on the opposite side of the overcenter spring 26, the force of the spring 26 moves the contact carrier 16 to the open position with the carrier against the stop member 90. I

The closed contacts are opened automatically by the overload mechanism under conditions of predetermined current flow. With the contacts closed, the electrical current flowing through the thermostat element 60 produces heating and causes the end of the element containing the latching surface 81 to bend away from the flange 82 of the trip arm with the increasing temperature. The amount of heating and therefore the amount of movement of the end of the thermostat element is a function of the magnitude of the current flowing through the element 60. If the current flow is sufficient to produce enough heat, the thermostat element bends sufficiently so that the latch surface 81 clears the flange 82 of the trip arm 23 releasing the trip arm. The overcenter spring 26 acting on the arm 27 causes the trip arm 23 to rotate about the boss 24 in a clockwise direction. The trip arm 23 moves to the tripped position abutting the upstanding member 90 as shown in FIG. 2.

As the trip arm 23 rotates in a clockwise direction, the end of the spring 26 carried by the arm 27 also moves in a clockwise direction and carries the spring 26 to the other side of the pivot point 20. With the center line of the'spring 26 on the opposite side of the pivot point 20,. the spring rapidly forces the contact carrier 16 to the tripped position against the member 90 as shown in FIG. 2 separating the

contacts

13 and 15. The handle 17 assumes an intermediate position as shown in FIG. 2.

The tripped circuit breaker is manually reset by rotating thchandle 17 to the manual open or extreme clockwise position. During this movement an arm 93 on the handle 17 engages an area of the trip arm 23 rotating the trip arm in the counterclockwise direction about the boss 24. During this rotation the flange 82 of the trip .arrn'slides along the ramp portion 83 of the thermos't'a't element 60 deflecting the end of the ele ment downward. When the flange 82 reaches the notch 80, the end of the thermostat element 60 moves into position so that the latch surface 81 intercepts the flange 82 resetting the breaker. During the resetting operation, the contact carrier 16 is also restored to the position it assumes when the contacts are opened manually. The contacts may then be closed by rotating the handle 17 in the counterclockwise direction to restore the circuit breaker to the latched condition shown in FIG. 1.

The circuit breaker is adjusted to cause tripping at a specific value of current by rotating the threaded rod 65 so as to advance it or retract it. As the rod is advanced it forces the region of the opening 70 in the thermostat element 60 upwards further compressing the leaf spring 71 and pivoting the thermostat element 60 clockwise about the edge at the end which is con fined in the V-shaped notch 63. The latching surface 81 of the thermostat element 60 is thus moved with respect to the flange 82 of the trip arm 23 so that a greater amount of current is required to trip the circuit breaker. Retraction of the threaded rod 65 lowers the latching surface 81 so that a lesser amount of current is sufficient to cause bending of the thermostat element to the point of releasing the trip arm 25.

Circuit breakers in accordance with the foregoing description employ very few parts and are extremely simple in construction. Much of the supporting structure is built into the housing which is fabricated of two molded plastic parts, the case and cover 11. The overload triggering mechanism is extremely simple ineluding only the unitary structure of the thermostat element 60 itself, together with the leaf spring 71 and the threaded rod 65 in cooperation with recess 63 in the case. An advantage of this construction, in addition to its simplicity and ease of fabrication and assembly, is that heat dissipation from the thermostat element 60 is at a minimum. No large heat conducting elements contact the thermostat element, nor is its position affected by virtue of having mounting members attached thereto.

Flexible conductors

61 and 62 are employed rather than relatively massive rigid members. Thus, the effective length of the thermostat element 60 which is subject to bending is not greatly reduced. Furthermore, a separate calibration or adjusting mechanism is not required. The threaded rod 65 together with the nut 66 mounted in the case serves both as a support member for the thermostat element 60 and as the overload current adjusting screw.

While there has been shown and described what is considered a preferred embodiment of the present invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention as defined in the appended claims.

What is claimed is:

l. A circuit breaker including in combination a housing of insulating material;

a fixed contact mounted in said housing;

a manually movable handle mounted in said housing;

a contact carrier with a movable contact thereon and pivotally engaging said handle at a pivot point;

a trip arm pivotally mounted in said housing;

an overcenter spring connected between said contact carrier and said trip arm urging said Contact carrier against said handle;

said handle, contact carrier and overcenter spring forming an overcenter arrangement for closing said contacts when the spring is on one side of said pivot point and for opening said contacts when the spring is on the other side of said pivot point;

a load terminal mounted in said housing;

a'therr nally responsive latching member connected in circuit between said load terminal and said movable contact;

one end of said thermally responsive latching member engaging a portion of the housing;

a support member mounted in said housing and engaging said thermally responsive latching member at a point adjacent to said one end; 1

a spring member urging the thermally responsive latching member against said support member whereby said portion of the housing, said support member, and said spring member in combination hold the portion of the thermally responsive latching member adjacent to said one end fixed with respect to the housing;

said thermally responsive latching member having a latching surface adjacent the opposite end thereof engaging said trip arm and maintaining said trip arm in a set position when said contacts are closed, with said overcenter spring urging said trip arm toward a tripped position;

said thermally responsive latching member bending in response to a predetermined current condition to move said opposite end of the thermally responsive latching member and disengage said latching surface from said trip arm releasing said trip arm for movement to the tripped position;

movement of the trip arm to the tripped position moving the overcenter spring to the other side of said pivot point causing said contacts to open.

2. A circuit breaker in accordance with claim 1 wherein said thermally responsive latching member is a unitary structure consisting of a generally flat elongated thermostat element; and

one end of the thermostat element abuts said housing at a recess in said housing.

3. A circuit breaker in accordance with claim 2 wherein:

said thermostat element has an opening therethrough adjacent to said one end;

said support member has a dog extending into said opening and a shoulder larger than said opening; and

said spring member is a curved leaf spring having one arm bearing against said housing and another arm bearing against the thermostat element adjacent said opening whereby the spring member urges the thermostat element against the shoulder of the support member.

4. A circuit breaker in accordance with claim 3 wherein said support member is a threaded rod threadably mounted in said housing for movement generally normal to the thermostat element; and

movement of the threaded rod causes the thermostat element to pivot about said one end in said recess in the housing and adjust the position of the latching surface at the opposite end of the thermostat element with respect to the trip arm.

5. A circuit breaker in accordance with claim 4 wherein said thermostat element has a notch therein forming the latching surface adjacent .to theopposite end of the thermostat element; and i.

said trip arm abutsthe thermostat'element at the latching surface when in said set position and is urged in thedirection generally along the length of the thermostat element toward the tripped position by said oyercenter spring. ,g i g 6. A circuit breaker in accordance with claim 5 wherein I t said spring member is a generally .l-shaped leaf spring having the end portion of its long arm confined in a pocket in saidhousing, the end surface of its short arm having a notch for engaging the dog of the sup- 'port member extendingthrough the opening in the thermostat element thereby holding the spring member in position as it bears against the thermostat element with the spring member bearing against said dog and urging the one end of the thermostat element into said recess in the housing.

7. A circuit breaker in accordance with claim 6 including a first flexible conductor connected between the thermostat element and the movable contact, said first flexible conductor being directly connected to the thermostat element adjacent to an end thereof; and g l I a second flexible conductor connected between the thermostat element and the load terminal, said second flexible conductor being directly connected to f the thermostat element adjacent to the other end thereof. v

Claims

1. A circuit breaker including in combination a housing of insulating material; a fixed contact mounted in said housing; a manually movable handle mounted in said housing; a contact carrier with a movable contact thereon and pivotally engaging said handle at a pivot point; a trip arm pivotally mounted in said housing; an overcenter spring connected between said contact carrier and said trip arm urging said contact carrier against said handle; said handle, contact carrier and overcenter spring forming an overcenter arrangement for closing said contacts when the spring is on one side of said pivot point and for opening said contacts when the spring is on the other side of said pivot point; a load terminal mounted in said housing; a thermally responsive latching member connected in circuit between said load terminal and said movable contact; one end of said thermally responsive latching member engaging a portion of the housing; a support member mounted in said housing and engaging said thermally responsive latching member at a point adjacent to said one end; a spring member urging the thermally responsive latching member against said support member whereby said portion of the housing, said support member, and said spring member in combination hold the portion of the thermally responsive latching member adjacent to said one end fixed with respect to the housing; said thermally responsive latching member having a latching surface adjacent the opposite end thereof engaging said trip arm and maintaining said trip arm in a set position when said contacts are closed, with said overcenter spring urging said trip arm toward a tripped position; said thermally responsive latching member bending in response to a predetermined current condition to move said opposite end of the thermally responsive latching member and disengage said latching surface from said trip arm releasing said trip arm for movement to the tripped position; movement of the trip arm to the tripped position moving the overcenter spring to the other side of said pivot point causing said contacts to open.

2. A circuit breaker in accordance with claim 1 wherein said thermally responsive latching member is a unitary structure consisting of a generally flat elongated thermostat element; and one end of the thermostat element abuts said housing at a recess in said housing.

3. A circuit breaker in accordance with claim 2 wherein: said thermostat element has an opening therethrough adjacent to said one end; said support member has a dog extending into said opening and a shoulder larger than said opening; anD said spring member is a curved leaf spring having one arm bearing against said housing and another arm bearing against the thermostat element adjacent said opening whereby the spring member urges the thermostat element against the shoulder of the support member.

4. A circuit breaker in accordance with claim 3 wherein said support member is a threaded rod threadably mounted in said housing for movement generally normal to the thermostat element; and movement of the threaded rod causes the thermostat element to pivot about said one end in said recess in the housing and adjust the position of the latching surface at the opposite end of the thermostat element with respect to the trip arm.

5. A circuit breaker in accordance with claim 4 wherein said thermostat element has a notch therein forming the latching surface adjacent to the opposite end of the thermostat element; and said trip arm abuts the thermostat element at the latching surface when in said set position and is urged in the direction generally along the length of the thermostat element toward the tripped position by said overcenter spring.

6. A circuit breaker in accordance with claim 5 wherein said spring member is a generally J-shaped leaf spring having the end portion of its long arm confined in a pocket in said housing, the end surface of its short arm having a notch for engaging the dog of the support member extending through the opening in the thermostat element thereby holding the spring member in position as it bears against the thermostat element with the spring member bearing against said dog and urging the one end of the thermostat element into said recess in the housing.

7. A circuit breaker in accordance with claim 6 including a first flexible conductor connected between the thermostat element and the movable contact, said first flexible conductor being directly connected to the thermostat element adjacent to an end thereof; and a second flexible conductor connected between the thermostat element and the load terminal, said second flexible conductor being directly connected to the thermostat element adjacent to the other end thereof.