US3670280A - Circuit breaker - Google Patents

Abstract

A circuit breaker has a support on which a one-piece bimetallic strip is mounted. The strip has two arms which together define a substantially U-shaped configuration, and a portion narrower than one of the arms and fast with the same as well as with the support. A first electrical contact is provided on the support and a cooperating second electrical contact on the other of the arms and heating of the bimetallic strip due to occurrence of an overload in a circuit in which it is interposed, causes temporary bending deformation of the other arm and of the narrower portion in mutually opposite directions, thereby resulting in interruption of the circuit due to disengagement of the electrical contacts.

Description

United States Patent Nagele June 13, 1972 CIRCUIT BREAKER 3,386,066 5/1968 Audette ..337/373 X 2,255,169 9/1941 Ireland ...73/363.5 X [72] Invent Nagele Gemmy 1,658,669 2/1928 Cohn et a1 ..73/363.5 x [73] Assignee: Robert Bosch Gmbl-l, Stuttgart, Germany Primary ExaminerBemard A. Gilheany [22] Flled 1970 Assistant ExaminerDewitt M. Morgan [21] Appl. No.: 98,288 Attorney-Michael S. Striker 57 ABSTRACT [30] Foreign Application Priority Data J A circuit breaker has a support on which a one-piece bimetal- Dec. 19, 1969 Germany ..P 19 63 666.9 6 Strip is mumed The Strip has two arms which together define a substantially U-shaped configuration, and a portion [52] i narrower than one of the arms and fast with the same as well 5; 200/126 337/1/l1 as with the support. A first electrical contact is provided on 1 le 0 are 337/373 the support and a cooperating second electrical contact on the other of the arms and heating .of the bimetallic strip due to occurrence of an overload in a circuit in which it is interposed, [56] Rekrences Cited causes temporary bending deformation of the other arm and UNITED STATES PATENTS of the narrower portion in mutually opposite directions, thereby resulting in interruption of the circuit due to disen- 2,585,068 2/1952 Wood ..337/1 1 l X gagement fh electrical contacts 2,267,386 12/1941 Wmbome.... .....337/373 X 2,015,545 9/1935 Bletz et al. ..337/373 X 4 Claims, 2 Drawing Figures PATENTED 13 1973 3.670 280 INVENTOR Erwin NAGELE his ATTORNEY CIRCUIT BREAKER BACKGROUND OF THE INVENTION The present invention relates generally to a protective switch, and more particularly to a circuit breaker.

Switches or circuit breakers of this type are used invarious applications, particularly but not exclusively for the protection of electric motors against the occurrence of overloads, for instance in tools and the like. Such circuit breakers, which are known in a variety of different constructions are interposed in the motor circuit with the result that, if an overload arises, the bimetallic strip becomes heated due to the excessively high current and temporarily undergoes a bending deformation, thereby interrupting a circuit ordinarily closed between two contacts one of which is carried by a portion of the bimetallic strip which upon heating undergoes the bending deformation. When the strip cools again it returns to its normal position and closes the circuit.

As already pointed out, circuit breakers of this type are known in a variety of different constructions. It has been found objectionable, however, that certain ones of these known circuit breakers do not always function reliably while on the other hand others, which do in fact function reliably, are quite complicated and therefore relatively expensive to manufacture, to assemble and to sell.

SUMMARY OF THE INVENTION It is, accordingly, an object of the present invention to provide an improved circuit breaker of the type under discussion which is not possessed of these disadvantages.

More particularly it is an object of the present invention to provide such an improved circuit breaker which is highly reliable in its operation under all circumstances.

A concomitant object of the invention is to provide such an improved circuit breaker which is very simple in its construction, therefore can be readily assembled and is concomitantly inexpensive.

In pursuance of the above objects, and others which will become apparent hereafter, one feature of the invention resides in a circuit breaker which comprises, briefly stated, a support and a one-piece bimetallic strip mounted in the support. This strip comprises a first portion of substantially U- shaped configuration and having two superposed arms, and a second portion narrower than one of the arms and fastwith the same as well as with the support. A first electrical contact is provided on the support and a cooperating second electrical contact is provided on the other of the arms, and heating of the bimetallic strip due to occurrence of an overload in a circuit which includes the circuit breaker, results in temporary bending deformation of the other arm and of the second portion of the strip in mutually opposite directions with concomitant interruption of the circuit.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partially sectioned side view of a circuit breaker according to the present invention; and FIG. 2 is a top-plan view of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing now the drawing in detail it will be seen that the exemplary embodiment of the novel circuit breaker as illus trated in FIGS. 1 and 2, comprises a support 11 consisting usually of-electrically conductive material, such as sheet metal. It comprises a first wall section portion 13 formed with an aperture 12 by means of which it can be secured in requisite position, for instance on a motor housing or the like, and a second wall section composed of two additional wall portions 14 and 15 both of which extend at substantially right angles to the wall portion 13 and are spaced from one another. The portions 14 and 15 are located in a common plane as shown in the drawing.

One free end 16 of a one-piece bimetallic element or strip 17 is fast with the wall portion 14, and the opposite free end 18 of the strip 17 carries a second contact 19 which cooperates with a stationary first contact 20 mounted on the wall portion or leg 15 and is electrically insulated with reference to the latter.

As already pointed out, and as also evident from the drawing, the bimetallic strip 17 is of one piece. It comprises a first portion part which has in cross-section a substantially U- shaped configuration whereby two arms 21 and 22 are provided which are superimposed with reference to one another as shown. It is the first arm 21 which carries at its free end the contact 19 and whose other end is connected via the bight of the U with an end of the second arm 22 which extends in partial parallelism with the first arm 21. The strip 17 includes a second part 37 which constitutes an integral extension of the second arm 22, and projects normal to the elongation of the second arm 22. The second part 37 furthermore merges with the portion 23 which latter is a third part of the strip 17. The free end 16 of the third part 23 is connected in suitable manner with the leg of the U-shaped support 1 1, for instance by spot welding (not shown) or in another manner. In the embodiment illustrated, the third part 23 is of smaller transverse cross-section than arms 21 and 22.

The third part 23 constitutes an integral extension of the second part 37 and extends substantially parallel to the second arm 22. As already stated, the second contact 19 is mounted on free end 18 of first arm 21 of the first part of bimetallic element 17. Furthermore, means is provided for mounting the free end 16 of the third part 23 on the support 1 1, so that the second contact 19 is located opposite the first contact 20.

Preferably, but not necessarily, the third part 23 as well as the arm 22 will be located in a common plane as is the case in the drawing (compare FIGS. 1 and 2) and will be elongated in the same direction as shown in the drawing, that is that their free ends (in the case of the arm 22 the end which is connected via the bight with the arm 21) are both remote from the point where the arm 22 and the portion 23 are joined. However, according to a further embodiment of the invention it is also possible for the portion 23 to have a general plane which is inclined at any desired angle with reference to the general plane of the arm 22, for instance an angle on the order of However, in this case it would be necessary to extend the wall portion or leg 14 in the direction in which the portion 23 is inclined, so that if the portion 23 were for instance inclined upwardly in FIG. 1 analogous to the wall portion 13 but at a lesser angle, at least a part of the wall portion 14 would have to be similarly inclined to have the end 16 of the portion 23 connected thereto.

As most clearly evident from FIG. 1, the contact 20 stationary with the support 11 has a contact plate 24 which is fast with the head 25 of a bolt 26 whose diameter is smaller than that of the contact plate 24. A bore 27 is provided in an insulating-material member 29 supported on the wall portion 15 and fixed thereon by impressed projections 28. The bolt 26 extends through the bore 27 and through a similar bore or aperture 30 provided in the wall portion or leg 15 as well as through a bore or aperture 31 of a similar insulating-material member 32 provided at the opposite side of the portion 15 from the member 29. Finally, at this opposite side the bolt 26 also extends through a bore or'aperture 33 of a terminal 35 and is upset at 36 to prevent undesired disconnection of the terminal 35. A mounting hole 34 is provided in the terminal 35 for permitting connection of a currentconductor. Another current conductor is connected in suitable manner to the support 1 1 directly.

The operation of the circuit breaker according to the present invention will be obvious. Assuming that the circuit breaker is located in the electrical circuit to be protected, for instance the electrical circuit of an electromotor and an overload occurs resulting in drawing of excessive current into the circuit, heating of the bimetallic strip 17 will follow. Because of the reduced width of the portion 23 with reference to the arm 22 and therefore with reference to the arm 21 which has the same width as the arm 22 the portion 23 'on heating will bend quite rapidly in direction away from the plane of the contact surface of the contact plate 24, which plate is shown in broken lines in FIG. 1 and identified with reference character E. Conversely, the arm 21 will bend relatively slowly upon such heating, but will also bend away from the plane E, except in the direction opposite the portion 23. As a result of the rapid bending of the portion 23, the contact 19 will remain in engagement with the contact 20 until such time as the bending of the arm 21 reaches the point where it lifts the contact 19 off the contact 20, with a concomitant interruption of the circuitwhich permits the bimetallic strip 17 to cool. v

Again, because of its lesser width, the portion 23 will cool more rapidly than the arm 21 and will therefore more quickly resume its normal plane or position shown in the drawing, in which it again approaches the plane E. This initially causes the arm 21 to recede even further from the plane E at the other side therof. However, once the portion 23 has returned to its normal position, the arm 21 during continued cooling thereof will also return towards its normal position until finally the contact 19 again abuts against the contact 20, closing the circuit. lf the overload-causing condition has been rectified, the circuit will remain closed; if the condition still prevails, the circuit breaker will again respond in the same manner just described. Such repeated response will continue until the overload condition is rectified.

The opening and closing times of the circuit breaker can be further influenced in making the arm 21 correspondingly longer with reference to the portion 23, according to a further embodiment of the invention. This is shown in the drawing, but it is pointed out that the arm 21 and the portion 23 could also be of substantially identical length.

it will be appreciated that by making the bimetallic strip 17 of one piece and configurating it in the manner illustrated, its construction and its assembly of the circuit breaker itself is particularly simple and quick, thereby reducing the expenses involved and producing and selling the device. Furthermore, the configuration of the bimetallic strip 17 in accordance with the present invention makes it possible to obtain, quite unexpectedly, relatively long opening and closing times for the circuit via disengagement or engagement of the contacts 19 and It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a circuit breaker, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and rangeof equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A circuit breaker comprising, in combination, a support; a first contact mounted on said support; a one-piece bimetallic element composed of a first part having in cross-section a U- sha ed configuration and including a first arm having a free en and a second arm, a second part constituting an integral extension of said second arm and projecting nonnal to the elongation thereof, and a third part constituting an integral extension of said second part and extending substantially parallel to said second arm and having a free end; a second contact mounted on said free end of said first am of said first part; and means mounting said free end of said third part on said support so that said second contact is located opposite said first contact.

2. A circuit breaker as defined in claim 1 wherein said third part is of smaller cross-section than said arms.

3. A circuit breaker as defined in claim 1, said first contact comprising a contact plate, a bolt of smaller diameter than said contact plate and having a head supporting said contact plate, and a pair of insulating-material members located at opposite sides of said support and provided with openings registering with an opening in said support, said bolt extending through said openings from one to the other of said opposite sides and having a free portion located at said other side; and further comprising a tenninal affixed to said free portion at said other side.

4. A circuit breaker as defined in claim 3, wherein said terminal has an aperture and said free portion extends through and in part beyond the same, and wherein said bolt is upset for preventing separation of said terminal therefrom.

Claims (4)

1. A circuit breaker comprising, in combination, a support; a first contact mounted on said support; a one-piece bimetallic element composed of a first part having in cross-section a Ushaped configuration and including a first arm having a free end and a second arm, a second part constituting an integral extension of said second arm and projecting normal to the elongation thereof, and a third part constituting an integral extension of said second part and extending substantially parallel to said second arm and having a free end; a second contact mounted on said free end of said first arm of said first part; and means mounting said free end of said third part on said support so that said second contact is located opposite said first contact.

2. A circuit breaker as defined in claim 1, wherein said third part is of smaller cross-section than said arms.

3. A circuit breaker as defined in claim 1, said first contact comprising a contact plate, a bolt of smaller diameter than said contact plate and having a head supporting said contact plate, and a pair of insulating-material members located at opposite sides of said support and provided with openings registering with an opening in said support, said bolt extending through said openings from one to the other of said opposite sides and having a free portion located at said other side; and further comprising a terminal affixed to said free portion at said other side.

4. A circuit breaker as defined in claim 3, wherein said terminal has an aperture and said free portion extends through and in part beyond the same, and wherein said bolt is upset for preventing separation of said terminal therefrom.

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