US3234348A

US3234348A - Circuit breaker with ambient temperature compensation

Info

Publication number: US3234348A
Application number: US71994A
Authority: US
Inventors: Frank B Desio
Original assignee: Littelfuse Inc
Current assignee: Littelfuse Inc
Priority date: 1960-11-28
Filing date: 1960-11-28
Publication date: 1966-02-08
Anticipated expiration: 1983-02-08

Description

F. B. DESIO 3, 3

CIRCUIT BREAKER WITH AMBIENT TEMPERATURE COMPENSATION Feb. 8, 1966 Filed Nov. 28, 1960 N V EN TOR.

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United States Patent 3,234,348 CIRCUIT BREAKER WITH; AMBIENT TEMPERATURE COMPENSATION Frank B. Desio, Melrose Park, Ill., assignor. to Littelfuse, Inc, DesPlaines, Ill, a corporation of Illinois NOY- 2' 60; g i- N9. 8 Cla ms (01,-. ZQQ l -Q) This.v invention relates to circuit breakers of the resettable ype w c p d ta ome Pr dstflmimd increase in rated current to open the circuit automatically and which, in addition, include provision for compensation in, accordance with the ambient temperaure. 'ljhus, the value of or range of overload current for which the device is designed will remain substantially unafiected due to variation. in ambient temperature.

The invention device is capable of being initially calibrated to, open the circuit at some predetermined'value of overload current or may be later adjusted, within limits, to. operate at some other. value of overl oad current.

Among the objects of the invention are the. provision of a Circuit b e the e e al. c ass. a a ss l fuh qh.

is Simple in o s s an reliable in q e a a Pro id s good wiping action of the contacts when released and when reset, and may be easily adjusted to obtain circuit opening action within the range of values of overload current which the device is intended to accommodate. Generally arded th nvent de in n aspa comprises n in a p as whia u p rts a p of m na wh r y ha' v s ay e assed in e s in the cui a d u er nd 9W? b m al switch members bearing mutually latching contacts. These latter are provided with faces adapted to abut to complete the circuit for normal current flow and to release when overload current is applied. lfor low, current applications, at least one of the switch members is not adapted to carry the current through the switch whereas the other switch member may carry current. The configuration of the switch members, their lamina,- tions and relative position are so selected that, when influenced by changes in ambient temperature they move in unison to preserve their latched condition but will operate to unlatch in response to the overload current. By providing an electric heater in heat-transferring relation with the switch member not carrying current and passing the current through the heater, the switch may be rendered more sensitive to low overload current without afiecting that function of the switch members providing accommodation to change in the ambient temperature.

In another aspect the invention comprises simple, inexpensive means for rapid initial calibration of the device or for subsequent recalibration thereof.

A reset button is provided for relatching the contacts following abatement of the overload condition, this button desirably being carried in a cover secured to the insulating base and having associated therewith bias means for maintaining the button in a normal position.

Other objects and advantages of the invention will become apparent from the ensuing description which, taken with the accompanying drawing, discloses a preferred form in which the invention may be embodied in practice.

In this drawing:

FIG. 1 is a perspective view of the device its errc i pec FIG. 2 is a longitudinal medial cross section through the device showing the switch open;

FIG. 3 is a cross section, on somewhat reduced scale, taken on the line 3-3 ofFIG. 2; and

FIG. 4 is a view similar to that of FIG. 2 showing the switch closed and the resetbutton partially operated, as in the resetting operation. '7

Turning to the drawing, I have shown a circuit breaker in accordance with the principles of the invention comprising a base 10 of suitable electrically-insulating material having an elongated recess Q and a through aperture 11 adjacent one end "for passage of a rivet 12 or equivalent fastening means. The terminals 15' and 16 each pass through respective apertures 17 and18, in they base 10 and are desirably bent over at their inner ends to provide portions for a purpose to appear. Otherwise the terminals rnay take any of available conventional forms and arrangement. i i

A lower switch member 25 comprises a bimetallic strip as customarily employed for the basic function of the member, namely transverse mechanical fiexure in response to change in temperature and, since such construction is common per se, the laminations are not illustrated in detail. However, at this juncture, it is pointed out that the member is so constructedand positioned that increase in temperature will cause flexure of the principal or horizontal portion 25a thereof, down wardly'as indicated by the arrow 1 and, upon decrease in temperature, in the direction D. At the same time, the vertical portion 25b moves or deflects in the respective directions I and as shown. Portion 21 of terminal 15 is current carrying relation with member 25. The member- 25 is of relatively large cross sectional dimensions so that the passage of current therethrough will have substantially no effect upon the temperature thereof.

An insulating spacer or block 31 is received in and held against rotation by the recess 9 in the base 10. A projection 32 on the base 10 and a corresponding recess in the block 31 prevents longitudinal movement of the block 21 with respect to the base 10. Assuming that the stack assembly is complete and under the tension of the rivet 12 the block 31 maintains the member 25 in operative position and abutting portion 21 of the terminal 15.

Means are provided for shifting the member 25 longitudinally to alter the degree of latching engagement of the contacts to be subsequently detailed and hence, the response of the switch. For example, the anchored end of the member is illustrated as provided with a lengthwise slot 36 slidable on the sides of the projection 32, and a more or less centrally positioned aperture 37 confronting an access opening 38 in the base 16 for engagement by a tool passed through the aperture is provided tov shift the member 25 lengthwise for calibration purposes. The pressure applied to the secured end of the member 25 is, as will appear, of a character permitting such adjustment and its reliable retention notwithstanding repeated operation of the device.

The other switch member 41, cooperative with the member 25, is also bimetallic and of the same general character as the member 25 except that it is arranged to flex in such manner that the generally horizontal portion 41;: thereof moves upwardly upon increase in tempertaure, as indicated by the arrow 1, and in the direction of the arrow D upon decrease in temperature; while the substantially vertical portion 41b of the member 41 deflects in the respective directions I and D Each of the

members

25 and 41 is provided at its free or distal end with

respective contacts

43 and 44 having mutually camming faces 43a and 44m and latching faces 43b and 44b. FIG. 2 shows the members unlatehed, i.e., the circuit is broken and FIG. 4 shows the same latched, i.e., the circuit is closed.

It will be noted that member 41 is provided with an anchoring end 51 apertured to pass the rivet 12 and bent Patented Feb, 8, 1966 separated therefrom by an insulator 67, is the bent portion 22 of the terminal 16 which extends to a position whereat connection thereto of a heater winding 53 may be made, as by welding or soldering at 54. Terminal 16 is suitably located on the block 31 by a projection 55 thereof receiving a mating opening 56 in the portion 2 2.

Lateral positioning of the switch member 41 and the reset mutton spring 61 (to be alluded to later) is achieved by flanking, upstanding posts 57 (FIG. 3) preferably formed integrally with the block 31. Theleaf spring 61 is desirably dished in the region 63 overlapped by the head of the rivet 12 in order that, when the latter is suitably upset the region 63 serves as a compression spring maintaining, in a simple, inexpensive manner, the

parts

15, 16, 25, 31, 41, 61 and 67 in proper operating relationship.

Heating element 53 is preferably in the form of ahelical winding positioned over the member 41 over the greater part of its length and embracing the portions 41a and 41b thereof. To obtain optimum heat transfer the several coils are flattened into intimate contact with the switch members, or the element may be initially wound in coils of flat oval configuration. 7 Such element is of any well-known type, e.g., Nichrome suitably insulated to avoid short-circuiting or miniaturized version of the wellknown Calrod elements available from General Electric Co., and has its ends bared and connected respectively to the portion 41b at 65 and the bent-over leg 22 of the terminal 16 at 54. end connection may be availed of so long as the current through the switch member 25 and contacts 43 and 4.4 also traverses the heater winding. It will also be clear that the heating element must be sufficiently flexible over its length as not to inhibit flexure of the member 41 in response to variation in temperature. The insulator 67 interposed between the member 41 and leg 22 insures that line current does not pass through the member 41.

A cover 71 is secured to the base 10, as by cars 72 extending through notches in the base and bent under the base, to enclose the parts of the assembly, other than the

terminals

15 and 16 and the reset button 75. This latter is of insulating material and is guided in a sleeve 76 formed in the top of the cover 71 for free sliding movement. A head 79 limits outward displacement, and retention of the button in its normal, i.e., upper, position is the result of upward bias applied by the leaf spring 61. The button is so positioned that, when actuated it will abut the switch member 41 at approximately the highest point thereof, namely the junction of the portions 41a and 41b thereof, although other forms of reset means may be availedof.

Assuming that the device is connected in circuit and has been operated to closed condition (FIG. 4) by thrusting the reset button 75 inwardly against the bias of the restoring spring 61 and that of the members 41, the

contacts

43 and 44 will be interengaged. Such action occurs as a result of the

camming surfaces

43a and 44a sliding one on the other and deforming the

respective members

25 and 41 momentarily until latching occurs, whereafter the contact surfaces 43b and 44b remain latched, during normal or rated current flow, to complete the circuit. Following closure of the contacts the button 75 is released and is restored outwardly by the spring 61.

In the absence of overload current any change in ambient temperature is ineffective to unlatch the contacts. As stated hereinbefore the bimetallic character oft-he

members

25 and 41 is such that increase in ambient temperature will flex member portion 25a downwardly (I) and portion 25b'outwardly (I) while member portion 41a will flex upwardly (I and portion 41b also outwardly (I Accordingly, the compensating function just described maintains the

contacts

43 and 44. latched It will be apparent that other forms of V the circuit (FIG. 3).

in a substantially constant degree of overlap. Upon decrease in ambient temperature the situation is reversed (arrows D and D and compensation prevails.

However, upon flow of overload current the heater Winding 53 is instrumental in causing a rapid rise in temperature of the switch member 41. Heating of the portion 41a operates to increase the contact pressure between the contact latch surfaces 43b, 44b, and when the portion,

41b is heated sufficiently to disengage the contact latch surfaces 43b, 44b, the

contacts

43 and 44 are released with a snap action for rapid and non-arcing interruption of Reset, following relief of overload, is believed to be obvious from the preceding description in reference to FIG. 4. If the reset button 75 is pushed in all the way, the

contacts

43 and 44 will be separated and the circuit opened. Thus, it is impossible to hold the circuit closed by pressing on the reset button, and trip-free resetting is thereby provided. The

contacts

43 and 44 cannot be relatched until the bimetallic member 41 is cooled sufliciently to allow relatching thereof. It the overload condition still persists upon resetting, the

contacts

43 and 44 will immediately release to again open the circuit.

From the foregoing it will have become apparent that the invention device is characterized by reliable compensation in accordance with variation in ambient temperature and rapid, non-arcing opening of the circuit. Moreover it will be seen that as long as overload subsists the device may not be latched in closed position or held in closed position by improper, sustained application of pressure on the reset button for, in such case, the

contacts

43 and 44 continue to remain separated and cannot be re-latched until the overload current is reduced to normal. Thereupon, cooling of the switch member 41' and the heater winding 53 will allow the contacts to resume a relative position permitting relatching.

For higher current applications, the heater 53 may be eliminated, and the load current passed directly through the bimetallic member 41 for directly heating the same. In this connection the insulator 67 is omitted so that electrical contact is made between the member 41 and the portion 22 of the contact 16. The cross sectional dimensions of the member 41 are relatively small, so that the resistance to current flow therethrough directly heats the member 41 to separate the

contacts

43 and 44 upon the occurrence of an oveload condition. Outside of directly heating the member 41, the operation of this arrangement is the same as descibed above and accordingly a further description of the operation is not considered necessary.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

I claim:

1. An ambient temperature compensated circuit breaker comprising: a base, first and second resilient switch members cantilever-mounted at a common end to said base and electrically insulated thereat, both members comprising laminated material differentially expansible to flex the member transversely when subjected to change in temperature, each member having its free end bent substantially perpendicularly to the remainder thereof, said bent portions being substantially confronting and each being provided with a contact at the free end thereof, said contacts each having a face adapted for mutual overlapping latching engagement when the circuit is closed and a camming face adapted for mutual sliding abutment to dis the laminated material comprising each member being such that,-up on variation in ambient temperature, the

bers cantilever mounted at a common end to said base and electrically insulated thereat, both members comprising laminated material differentially expansible to flex the member transversely when subjected to change in temperature, each member having its free end bent substantially perpendicularly to the remainder thereof, said bent portions being substantially confronting and each being provided with a contact at the free end together adapted to engage overlappingly latchingly to maintain closed condition of the breaker when the free ends of the members are brought together, the respective arrangement of the laminated material comprising each member being such that, upon variation in ambient temperature, the members flex in respective opposite directions and the bent end portions of the members flex in respective same directions and degrees to preserve a substantially constant degree of overlapping latching engagement of the contacts and, upon passage of overload current through the members, the members and their bent end portions will flex in a direction to release the overlapping latched condition of said contacts, and means for connecting said members in the circuit.

3. A circuit breaker in accordance with claim 1 wherein means are provided for longitudinally adjusting said resilient switch members with respect to each other to adjust the degree of overlapping latching engagement of the contacts for calibration purposes.

4. A circuit breaker in accordance with claim 2 wherein means are provided for longitudinally adjusting said resilient switch members with respect to each other to adjust the degree of overlapping latching engagement of the contacts for calibration purposes.

5. An ambient temperature compensated circuit breaker for a circuit to be protected comprising: a base, a first resilient bimetallic member cantilever mounted at one end on said base and having its free end bent substantially perpendicularly to the remainder thereof to form a substantially perpendicular leg at its free end, a contact having a latch surface carried by the outside of said leg, 21 second resilient bimetallic member cantilever mounted at one end on said base adjacent the mounting of the first bimetallic member and having its free end bent substantially perpendicularly to the remainder thereof to form a substantially perpendicular leg at its free end, a contact having a latch surface carried by the inside of the leg of said second bimetallic member, the latching surfaces of said contacts normally overlapping and engaging each other against the resiliency of the bimetallic members for completing the circuit being protected, said second bimetallic member operating upon an increase in temperature to tend to move away from the first bimetallic member and to move the inside contact thereof outwardly with respect to the outside contact of the first bimetallic member, said first bimetallic member operating upon an increase in temperature to tend to move away from the second bimetallic member and to move the outside contact thereof outwardly with respect to the inside contact of the second bimetallic member to maintain the overlap of said contacts substantially constant regardless of ambient temperature conditions atfecting said first and second bimetallic members, said second bimetallic member being heated by the current flow in the circuit to be protected and being operative upon an excessive current flow to move the latching surface of its contact out of engage- 6, ment with the latching surface of the contact of the first bimetallic member to allow the bimetallic elements to spread apart and break the circuit.

6, A circuit breaker in accordance with claim 5 including means for longitudinally adjusting said bimetallic members with respect to each other to adjust the amount of overlap of the latch surfaces of the contacts for calibration purposes.

7. An ambient temperature compensated circuit breaker for a circuit to be protected comprising, a base having a plurality of openings therein, a first terminal extending through one of the base openings and engaging the interior of the base, a first resilient bimetallic member overlying at one end the first terminal and having its free end bent substantially perpendicularly to the remainder thereof to form a substantially perpendicular leg at its free end, an insulating block overlying said one end of said first resilient bimetallic member, a second terminal extending through another of the base openings and overlying the block, a second resilient bimetallic member overlying at one end the second terminal and having its free end bent substantially perpendicularly to the remainder thereof to form a substantially perpendicular leg at its free end, a dished resilient member overlying said one end of said second resilient bimetallic member, a rivet extending through another of the base openings, said first terminal, said first end of said first resilient bimetallic member, said insulating block, said second terminal, said first end of said second resilient bimetallic member, and said dished resilient member for resiliently clamping the same together, a contact having a latch surface carried by the outside of the perpendicular leg on said free end of said first resilient bimetallic member, a contact having a latch surface carried by the inside of the perpendicular leg on said free end of said second resilient bimetallic member, said latch surfaces of said contacts normally overlapping and engaging each other against the resiliency of the bimetallic members for completing the circuit being protected, said second bimetallic member operating upon an increase in temperature to tend to move away from the first bimetallic member and to move the inside contact thereof outwardly with respect to the outside contact of the first bimetallic member, said first bimetallic member operating upon an increase in temperature to tend to move away from the second bimetallic member and to move the outside contact thereof outwardly with respect to the inside contact of the second bimetallic member to maintain the overlap of said contacts substantially constant regardless of ambient temperature conditions affecting said first and second bimetallic members, said second bimetallic member being heated by the current flow in the circuit to be protected and being operative upon an excessive current flow to move the latching surface of its contact out of engagement with the latching surface of the contact of the first bimetallic member to allow the bimetallic elements to spread apart and break the circuit.

8. A circuit breaker in accordance with claim 7 wherein said first resilient bimetallic member has a hole overlying another opening in the base for receiving a tool projected through said base opening for longitudinally shifting said first resilient bimetallic member with respect to said second resilient bimetallic member for calibration purposes.

References Cited by the Examiner UNITED STATES PATENTS 1,431,220 10/ 1922 Donle 200--116 1,948,938 2/1934 Lawton 200-116 2,023,517 12/1935 Creager 200166 2,148,600 2/1939 Beckler 200-116 2,261,366 11/1941 Grout 200138 2,277,443 3/ 1942 Livingston 200--166 2,293,671 8/1942 Alexander 2001l6 (Other references on following page) 7 UNITED STATES PATENTS Dafiorn 200--138 Howard 200138 Baker 200166 Tucker 2001 16 Marcoz 200-116 Elliott 200-116 Chase et a1 200166 8 2,831,090 4/1958 Kueser 200138 3,038,047 6/1962 Marquis 200116 FOREIGN PATENTS 597,603 9/1925 France. 7 513,143 10/1939 Great Britain.

BERNARD A. GILHEANY, Primary Examiner.

RICHARD M. WOOD, Examiner.

Claims

1. AN AMBIENT TEMPERATURE COMPENSATED CIRCUIT BREAKER COMPRISING: A BASE, FIRST AND SECOND RESILIENT SWITCH MEMBERS CANTILEVER-MOUNTED AT A COMMON END TO SAID BASE AND ELECTRICALLY INSULATED THEREAT, BOTH MEMBERS COMPRISING LAMINATED MATERIAL DIFFERENTIALLY EXPANSIBLE TO FLEX THE MEMBER TRANSVERSELY WHEN SUBJECTED TO CHANGE IN TEMPERATURE, EACH MEMBER HAVING ITS FREE END BENT SUBSTANTIALLY PERPENDICULARLY TO THE REMAINDER THEREOF, SAID BENT PORTIONS BEING SUBSTANTIALLY CONFRONTING AND EACH BEING PROVIDED WITH A CONTACT AT THE FREE END THEREOF, SAID CONTACTS EACH HAVING A FACE ADAPTED FOR MUTUAL OVERLAPPING LATCHING ENGAGEMENT WHEN THE CIRCUIT IS CLOSED AND A CAMMING FACE ADAPTED FOR MUTUAL SLIDING ABUTMENT TO DISPLACE EACH OTHER MUTUALLY AS AT LEAST ONE OF THE MEMBERS IS MOVED TO CIRCUIT-CLOSING POSITION, WHEREAFTER SAID LATCHING FACES MUTUALLY OVERLAPPINGLY ENGAGE BY VIRTUE OF THE RESILIENCY OF SAID MEMBERS, THE RESPECTIVE ARRANGEMENT OF THE LAMINATED MATERIAL COMPRISING EACH MEMBER BEING SUCH THAT, UPON VARIATION IN AMBIENT TEMPERATURE, THE MEMBERS FLEX IN RESPECTIVE OPPOSITE DIRECTION AND THE BENT END PORTIONS OF THE MEMBERS FLEX IN RESPECTIVE SAME DIRECTIONS AND DEGREES TO PRESERVE A SUBSTANTIALLY CONSTANT DEGREE OF OVERLAPPING LATCHING ENGAGEMENT OF THE CONTACTS AND, UPON PASSAGE OF OVERLOAD CURRENT THROUGH THE MEMBERS, THE MEMBERS AND THEIR BENT END PORTIONS WILL FLEX IN A DIRECTION TO RELEASE THE OVERLAPPING LATCHED CONDITION OF SAID CONTACTS FOR SEPARATION THEREOF, AND MEANS FOR CONTACTING SAID MEMBERS IN THE CIRCUIT.