US3187145A

US3187145A - Circuit breaker with auxiliary contact means

Info

Publication number: US3187145A
Application number: US103349A
Authority: US
Inventors: Grabinski Joseph
Original assignee: Sightmaster Corp
Current assignee: Sightmaster Corp
Priority date: 1961-04-17
Filing date: 1961-04-17
Publication date: 1965-06-01
Anticipated expiration: 1982-06-01

Description

June 1, 1965 J. GRABINSKI 3,187,145

CIRCUIT BREAKER WITH AUXILIARY CONTACT MEANS Filed April 17, 1961 3 Sheets-Sheet l [72 7/672 to 7, tlbs'q vk razz'nskc',

June 1, 1965 .1. GRABINSKI CIRCUIT BREAKER WITH AUXILIARY CONTACT MEANS 3 Sheets-Sheet 2 Filed April 17, 1961 r 3 mm 5 M 4 m4 tfosgvk June 1, 1965 J. GRABINSKI 3,187,145

CIRCUIT BREAKER WITH AUXILIARY CONTACT MEANS Filed April 17, 1961 3 Sheets-Sheet 3 In ven tar, rfos'q vk G'ra 5a'nS/3't;

United States Patent 0 3,187,145 CIRCUIT BMAKER WlTH AUXILIARY CGNTACT MEANS Joseph Grabinski, Providence, KL, assignor to Sighh master Corp., Providence, 11.1., a corporation of New ork Filed Apr. 17, 1961, Ser. No. 163,349 8 Claims. (Cl. 200-113) The present invention relates to a circuit breaker. More particularly, the present invention relates to a circuit breaker for use in a low current circuit wherein a bimetallic actuating element is utilized to move a contact spring to the circuit breaking position thereof when an overload of current is applied to the circuit.

The circuit breaker embodied in the present invention has particular application in low amperage circuits wherein the maximum current is from four to five amps. Because of the relatively low amperage to be used in connection with the circuit in which the present invention is adapted to be incorporated, a relatively flexible leaf spring is utilized to define the circuit breaking element. The leaf spring is normally located such that it is disposed in a bowed position and in contact with a biemtallic actuating element. When an overload of current is applied to the circuit, the bimetallic actuating element expands, thereby forcing the bowed spring to an overcenter position, whereupon it snaps to an outer bowed position and out of contact with the bimetallic actuating element. Upon movement of the leaf spring to the outer bowed position, the circuit is broken since the leaf spring defines a current conducting contact member together with the bimetallic actuating element. In order to return the circuit to the closed position thereof, the leaf spring contact must be snapped inwardly into the normal bowed position thereof in contact with the bimetallic actuating element. The resetting of the leaf spring contact is accomplished by means of a reset plunger that is manually moved to a position wherein it contacts the leaf spring contact in the outwardly bowed position thereof. Depression of the reset plunger causes the leaf spring contact to be moved inwardly to an over center position, whereupon it snaps inwardly to its normally bowed position in contact with the bimetallic actuating element.

Accordingly, it is an object of the present invention to provide a circuit breaker for low current circuits that includes a current conducting leaf spring contact that is adapted to be moved to a circuit breaking position by a bimetallic actuating element when an overload of current is applied to said element.

Another object of the present invention is to provide a current overload circuit breaker that includes a manually operated reset plunger that is adapted to return a current conducting leaf spring contact to the current conducting position thereof after it has been moved to the circuit breaking position by a bimetallic actuating element.

Still another object is to provide a current conducting bracket assembly for use in a circuit breaker that is adapted to maintain electrical engagement with a current conducting spring, and further carries a resetting plunger thereon that is adapted to return the spring to the normal position thereof after it has been moved to the circuit breaking position by a bimetallic actuating element.

Still another object is to provide a bimetallic element for use in a circuit breaker that is conected to a terminal of the circuit breaker and that is adapted to engage a leaf spring contact in the normal position thereof, the bimetallic element being expandable upon the application of an overload current thereto to force the leaf spring contact to a circuit breaking position.

Still another object is to provide a reset plunger for "ice use in a circuit breaker, the reset plunger including a metallic disc that is adapted to normally complete the circuit'through a bracket on which the reset plunger is mounted, and being movable out of engagement with the bracket upon depression of the reset plunger during the resetting operation to break the circuit through the bracket, whereby the circuit is incomplete until the reset plunger is returned to the normal position thereof.

Still another object is to provide a current conducting leaf spring that is mounted between a current conducting bracket and a bimetallic retaining member, the bimetallic retaining member being spaced from the bracket a distance suiiicient to permit the leaf spring to be bowed in the normal position thereof and being expandable to compensate for possible changes in the position of the bimetallic actuating member, due to ambient temperature changes, wherein the circuit breaker may be controlled to operate at a predetermined overload current without being adversely affected by ambient changes;

Still another object is to provide a centering construction for use with a leaf spring in a circuit breaker, the leaf spring being formed with a pointed end that is adapted to extend into an opening formed in a current conducting bracket, the pointed end serving to constantly center the position of the leaf spring so that the undersurface thereof will positively engage a bimetallic actuating element.

Other objects, features and advantages of the invention will become apparent as the description thereof proceeds when considered in connection with the accompanying drawings.

In the drawings which illustrate the best mode presently contemplated by me for carrying out the present invention:

FIG. 1 is a vertical sectional view of the circuit breaker embodied herein, the spring contact of the circuit breaker being shown in full line that defines the closed position thereof; 7

FIG. 2 is a sectional view taken along lines 22 in FIG. 1 with the cover of the circuit breaker removed;

FIG. 3'is a fragmentary side elevational view showing the interengagement of the pointed end of the spring contact with the bracket assembly;

FIG. 4 is a section view taken along lines 4-4 in FIG. 1;

FIG. 5 is a front elevational view of the circuit breaker with a portion of the front Wall of the cover removed and with parts shown in section, the reset plunger being shown in the resetting position thereof and the leaf spring contact member being shown in the normal position in full lines and in the circuit breaking position in' dotted lines;

FIG. 6 is a fragmentary elevation similar to FIG. 5 showing the distribution of forces on the contact spring and the bimetallic elements associated therewith; and

FIG. 7 is a vertical sectional view similar to FIG. 1 illustrating a modified form of the invention.

Referring now to the drawings, the circuitbreaker embodied herein is generally indicated at 10 and includes abase 12 formed of a non-metallic or insulating material such as plastic or the like. Mounted on the underside of the base 12 are

terminals

14 and 16 that are secured thereto in spaced relation by

rivets

18 and 20, respectively.

Leads

22 and 24 are soldered to the terminals 14- and 16 in the conventional manner and are electrically connected in circuit to any conventional electrical component. Secured to the base 12 on the upper surface thereof by the rivet 18 is a bimetallic actuating element generaly indicated at'26. The bimetallic actuating element 26 is formed of

metallic leaf members

28 and 30 each of which has a different coefficient of expansion as a se we s.) is well known in an element of this type. of illustration, the thickness of the

metallic leaf members

28 and 30 is exaggerated, it being understood that the bimetallic actuating element 26 is formed as a relatively thin piece of spring stock and that it is capable of expansion in response to temperature changes. As illustrated more clearly in FIG. 1, the actuating element 26 is normally flexed so that the lower end thereof is secured to the base 12 by the rivet 18, the rivet 18 extending through an opening formed in the base and the edge of the element 26 being downwardly turned for insertion in a slot 31 formed in the base 12. The upper portion of the bimetallic actuating element 2.6 that is flexed to the upper position has a contact button 32. secured to the outer end thereof that faces upwardly with respect to the base 12 as seen in MG. 1. Although not required, an adjusting screw 34 may be employed to preset the position of the bimetallic actuating element 26, and as shown, the adjusting screw 34 threadably engages the base 12, the upper end thereof contacting the upper flexed portion of the actuating element 26 on the underside thereof. The adjusting screw thus controls the overload setting of the circuit breaker, the relative position of the actuating element determining the amount of overload current that is required to break the circuit.

Mounted on the base 12 is a bracket assembly generally indicated at 36 that is defined by two identical brackets 38 and til, the construction and purpose of which will be described hereinafter. The bracket 32% is secured to the base 12 by a rivet 42 that extends through a foot portion 4 thereof, a downwardly turned tab 46 being formed integral with the foot portion and extending through a slot 48 formed in the base 12. As seen in FIG. 3, an

adapted to receive an end of a leaf spring contactor.

member 54 as will be described more fully hereinafter. An upper or top wall 5oof the bracket 38 is joined to the side wall 5% and extends in substantially parallel relation with respect to the base 12, terminating short of the mid-point of the base 12. The bracket 4t) is constructed similarly to the bracket 38 and includes a top Wall 53 that is spaced from the top wall 56 to define an air space so therebetween. Joined to the top wall 53 is a side wall 62 that is disposed in parallel relation with respect to the side wall 5t} and is joined at the bottom end thereby by a foot portion 64 through which the rivet 20 extends for securing the bracket it) to the base 12. Since the rivet 29 is electrically connected to the terminal 16 the bracket 58 defines a current conducting member as will be described hereinafter. The outer end of the foot portion 64 is downwardly turned similar to the tab 46 and extends through a slot 66 for positively mounting the bracket it) on the base 12.

The leaf spring contactor member 54 is formed of a relatively thin stock of spring steel or nickel silver and is adapted to be disposed in bowed relation with respect to the bimetallic actuatingspring element 26 so that in the lower or normal position thereof it engages the contact button 32. In order to mount the leaf spring member 54 in the position as shown, the left end thereof as seen in FIGS. 1 and 2 is pointed as indicated at 68 so as to be received within the opening 52 that is formed in the side wall 50 of the bracket 56. The pointed end 68 of the leaf spring member 54 in effect causes the relatively flat spring material from which the spring member is formed to be centered with respect to the opening 52 and thus forces the spring member 54 to assume a position that enables the under surface thereof to positively engage the contact button 32 when the spring member 54 is located in the normally inwardly bowed position. The other or right end of the spring member 54 as seen in FIGS. 1 and 2, is mounted on a retaining member or bar '70 that is formed of a bimetallic For purposes material similar to the construction of the bimetallic actuating element 26, the bimetallic retaining member '7 being secured to the base 12 by a rivet '72 that extends through an integral foot portion 7a joined thereto. A downwardly extending tab 76 joined to the foot portion 74 extends through a slot in the base 12 and cooperates with the rivet '72 to positively mount the post 70 on the base 312. In order to removably mount spring member 54 on the retaining member '7, the extreme end thereof is formed with a notch 7t": that defines cars "59 and As seen in FIG. 4, the ears 8d and 82 extend into V-shaped opposed notches 84 formed in the bimetallic post 769, the notch 78 cooperating with the ears Sit and E52 to positively lock the contact spring member 54 on the bimetallic retaining member "ill. The bimetallic member 7h is positioned on the base 12 and spaced from the wall 5% of the bracket 56 such that when the spring member 54 is secured between the side wall dtland the member Ytl it assumes a bowed configuration as shown in FIG. 1. in the normal position thereof, the spring member will be bowed downwardly toward the bimetallic actuating element 26 so that it engages the contact button and as such makes electrical communication therewith. It is seen that. if the circuit in which the circuit breaker ltl is located is overloaded, the resulting temperature rise in the bimetallic actuating element 26 will cause the members 23 and 3b to expand at different rates, thereby producing an upward surge in the actuating element 26. Upward movement of the actuating element as will produce a corresponding movement of the spring member 54 engaged therewith. As soon as the contact spring member 54 moves past a center position as indiea ed in dotted lines in FIG. 1, it will snap to an upwardly bowed position as further illustrated in dotted lines in FIG. 1, thereby breaking electrical contact with the actuating element 26. As will be described hereinafter, this breaks the electrical communication in the circuit breaker lit and until the spring member 54 is returned into engagement with the actuating element 26, the circuit in which the circuit breaker in is located is broken.

As described hereinabove, the terminals for the circuit breaker is are located at lid and to, the terminal 14 being electrically connected to the bimetallic actuating element 25. The terminal is electrically connected to the bracket 4t) through the rivet 2i and since the air space as separates the brackets 38 and of the bracket assembly a circuit cannot be completed from the bracket tl't'o the spring member and the bimetallic actuating element 233 unless the air space 6% is bridged by an electrical conducting element. This electrical bridging is accomplished by a contact washer or disc 6 mounted on the upper side of a head that is joined integral to a plunger The plunger 9Q. to which the head 88 is joined is provided for resetting the spring member after the circuit has been broken and for this purpose extends through the space 66. ft is seen that in resetting the circuit breaker the plunger hil is depressed to cause the head to engage the upwardly bowed spring mem ber 54 as it appears in the circuit breaking position thereof. in the upper or normal position of the plunger 9%, the contact disc $6 is disposed in engaging relation with the underside of the top walls 5% and 53 of the brackets 33 and dill, and thereby bridges the space therebetween to complete the circuit through the bracket assembly. In order to bias the plunger in the upper or normal position thereof a spring 92 is provided and bears against a phenolic or insulating washer 94 through which the plunger extends and which is disposed on the upper surfaces of the

top walls

56 and 58 of thebrackets 38 and iii also bridging the air space 6%). The upper end of the spring 92 is engaged by a cup member 95, the cup member as being prevented from upward movement by a pin 98 that extends through the plunger 9% and acting to limit downward movement of the plunger 94 The spring 92 is thus biased between the cup member )6 and the insulating washer 9t) and acts to normally retain the plunger 96 in the upper position thereof. It is seen that in the normal position of the reset plunger 90, the spring 92 biases the head 83 of the plunger 90 upwardly to cause the contact washer 86 to bridge the space 69 between the top walls and 58 of the brackets. This completes the circuit between the brackets, and assuming that the spring member 54 is inwardly bowed into engagement with the bimetallic actuating element 26, a circuit Will be completed from the terminal 22 to the terminal 24.

In order to complete the assembly of the circuit breaker It a cover member 163% is provided and includes a top wall 1'92; and side walls 1% that surround the bracket assembly 36. An opening 1% is formed in the top wall H32 of the cover member tee and provides access for the plunger 9% so that it may be depressed with the cover member in position on the base 12. The cover member is secured to the base 12 by means of spaced tabs 1% that extend through corresponding tab slots lit) formed in the base.

In operation, the circuit breaker 1t) completes a circuit between the

terminals

22 and 24, the electrical circuit being defined by the bimetallic actuating element 26, the contact spring member 54, the bracket 3%, disc 86 and the bracket 40. If an overload in the circuit occurs, the bimetallic actuating element 26 will be flexed upwardly as shown in dotted lines in FIG. 1, thereby causing the spring member 54 to be moved past an overcenter position. Since the contact spring member 54 is originally disposed in an inwardly bowed condition, movement past the overcenter position thereof will cause it to snap to the outwardly bowed position as shown in dotted lines in FIG. 1. This will break the circuit between the spring member 54 and the bimetallic actuating element 2 6, and will thereby interrupt the circuit in which the

terminals

22 and 24 are located. Since the retaining member 79 that cooperates with the side wall 50 to retain the spring member 54 in the bowed position is formed of a bimetallic material, it will also flex in response to increase of temperature applied thereto. This flexing of the bimetallic retaining member compensates for the movement of the bimetallic actuating element 26 due to changes in the ambient temperature. The retaining member thereby acts to maintain the relative position of the actuating element 26 with respect to the spring member 54 so that the spring member will always be responsive to movement of the actuating element at a preselected overload current as determined by the setting of the adjusting screw 34.

When it is desired to reset the spring member 54 in engagement with the bimetallic actuating element 26 to complete the circuit between the terminals 22' and 24, the plunger is depressed, thereby causing the head 83 to engage the upper surface of the spring member 54. As the spring member 54 is moved to an overcenter position thereof upon depression of the plunger 9%, it will snap downwardly to the lower bowed position and will once again engage the contact button 32 of the bimetallic actuating element 26. It is understood that the plunger 9t) is moved downwardly against the action of the spring Q2, and upon release of the plunger 90, will be automatically returned to the upper position thereof as illustrated in FIG. 1.

In order to assure the intended operation of the circuit breaker, the circuit therethrough is complete only when the plunger 90 is retracted. Thus any attempt to nullify the operation of the circuit breaker by continuously depressing the plunger 90 will be defeated. Hence, the contact disc 86 is carried downwardly with the head 88 to which it is secured, so that the circuit between the

top walls

56 and 58 of the bracket assembly 36 is broken when the plunger is depressed. When the plunger is returned to the upper position thereof by the spring 92, the contact disc 86 once again bridges the air space 6th to establish electrical communication between the top walls 65 56 and 58 of the bracket assembly and the circuit is then once again complete between the

terminals

22 and 24. It is thus seen that unless the plunger is in the normal or upper position the circuit through the bracket assembly is incomplete.

If it is necessary to adjust the position of the bimetallic spring element 26 in order to vary the overload current required to break the circuit, the adjusting screw is pro vided and may be rotated as desired to bring about the required adjustment.

Referring now to FIG. 6 the balance of forces that are exerted on the bimetallic elements and the normal spring pressure exerted by the spring member 54 are illustrated when :an increase of ambient temperature results. When the ambient or room temperature varies, in order to prevent the position of the bimetallic actuating element 26 from moving to sufficiently change its position so that the current required to break the circuit is varied from a predetermined setting, the bimetallic retaining member '74 is provided and as shown exerts a force in the direction of the arrow to maintain the spring member 54 in the bowed position thereof. Thus, the combination of the spring pressure of the spring member 54 and the bias exerted by the retaining member 79 due to any increase in ambient temperature counteracts any surge experienced by the bimetallic actuating element 26 resulting from an increase in the ambient or room temperature. By providing the bimetallic retaining member 7%, the circuit can only be broken due to an increase in current over the value as preselected.

Referring now to FIG. 7, a modified form of the inven tion is illustrated that defines a simplified version of the construction illustrated and described above. The modified form of circuit breaker is generally indicated at 112 and includes a base 114- formed of an insulating material. Secured to the underside of the base 114 by spaced rivets 116 and M8 are terminals 126 and 122 respectively. Suitable leads may be soldered to the terminals and are adapted to be electrically interconnected to an electrical component. Secured to the upper surface of the base 114 by the rivet 1-16 is a bimetallic actuating element 124 on the free end of which a contact button 126 is secured.

As described above the fixed end of the actuating elernent 124 extends through a convenient slot that is formed in the base 114. Although an adjusting screw is not provlded in the modified form of the invention for adjusting the position of the bimetallic element 124, it is understood that such an arrangement is contemplated and is within the spirit of the invention illustrated in FIG. 7.

Mounted on the base 114 is a bracket assembly generally indicated at 123 that includes a fixed bracket 139 and a spring bracket 132 that is movable with respect to the bracket 13%). The bracket is formed in substantiall the same manner as bracket 38 described above and is secured to the base 114 by a rivet 134 that extends through the foot portion thereof. The spring bracket 132 is formed of spring stock and includes a support leg 136 that has a foot portion joined thereto through which the rivet 118 extends for securing the spring bracket to the base 114. .Integrally joined to the support leg 136 and inwardly turned with respect thereto is an inclined port1on 138 that terminates in an outer extension that projects underneath a portion of the free end of the bracket 13% and is located in parallel face-to-face relation with respect thereto. The engaging brackets 139 and 132 are thus disposed in electrical contact and normally establish a circuit through the circuit breaker as will be described. Struck out from the extension 140 and extend- ,ing inwardly with respect thereto are a series of tabs or tongues that define a self-locking push nut 142. Projectmg through an opening 144 that is formed in the free end of the bracket 13% and that is aligned with the push nut :142 is an elongated plunger 146, the innermost end of which projects through the push nut M2 and is locked therein by the tongues thereof. The extension 149 is energies 7 normally retained in engagement with the free end of the bracket 136 by the spring action of the material from which it is formed but is adapted to be urged inwardly by theplunger it! to break the circuit between the brackets 1130 and 132 during the resetting operation of the circuit breaker.

In order to establish electrical communication between the bimetallic actuating element 124 and the bracket assembly 1918 a contact spring member generally indicated at 14% is provided. The contact spring member 148 includes a main portion 15% that is normally bowed inwardly to engage the contact button are of the actuating element 124. An inclined portion 152 is integrally joined to the main portion 15b and is bent at an angle with respect thereto. A foot portion is joined to the inclined portion 152 and extends beneath the foot portion of the bracket 1%, the foot portion 154 being held in electrical communication against the foot portion of the bracket 13% by the rivet 134. The free end of the bowed main portion 15b is formed in a pointed construction that projects through an opening 155 formed in a bimetallic ambient compensating bar 153. The bar 158 is similar to the retaining member 7% described above and is fixed on the base lit by a rivet 16% that extends through an inturned foot thereof.

The bracket assembly 128, base lid and contact spring member assembly are enclosed by a cover member 162 that is similar to the cover member ltltl, an opening 164- being punched in thet-op wall or. the cover member to accom-odate the plunger i146 that projects outwardly therefrom. Tabs 166 are shown struck out of the top wall of the cover member and may be utilized for mounting purposes. Openings 168 may also be formed in the side Walls of the cover member to provide for air circulation or heat transfer.

in use, a circuit is normally established through the circuit breaker M2 and is defined by the terminal 1.20, bimetallic actuating element 124, contact spring member 14%, bracket 1%, spring bracket 132 and terminal 1.22. If an overload in the circuit occurs, the actuating element 124 will be flexed upwardly to the dottedline position shown in FIG. 7, thereby causing the main portion 15d of the spring member 143 to be moved through an overcent-er position. This will cause the spring member 148 to snap to the outer position as seen in FIG. 7 and out of contact with the actuating element Electrical communication is then broken to interrupt the circuit between the terminals 129 and 122. in order to reset the circuit breaker, the plunger i l-6 is pushed inwardly a distance suiiicient to cause the innermost end thereof to force the spring mem e r 148 to return to the original position thereof. During the resetting operation the plunger 146 disengages the brackets 13d and 132 which prevents the circuit from being established until the plunger is released. The operation of the ambient compensating bar 158 is similar to the retaining member itl described above, the only distinction being that the opening 156 is formed therein for receiving the pointed free end of the spring member 143 and therefore ditlers from the notched construction illustrated in FIG. 2. The pointed end of the spring member 143 is thus centered in the ambient compensating bar 158 and acts to maintain the spring member in proper position for movement by the actuating element 124.

It is seen that the circuit breaker embodied in the present invention defines a current overload protector in which the contact resistance between the circuit breaking elements decreases as the device approaches the breaking point. Positive contact in the circuit is further insintained until the moment of break, since the actuating element and spring member are forced together under a progressively increasingly increasing pressure until the overcenter position of the spring member is reached. At this point the spring member snaps away and the circuit is opened.

ating element during an overload of the circuit, wherein While there is shown and described herein certain specific structure embodying the invention, it will be manitest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insotar as indicated by the scope of the appended claims.

What is claimed is:

l. in a circuit breaker for low current circuits, a nonmetallic base having terminals secured thereto in spaced relation, a bimetallic actuating element mounted on said base and secured to one of said terminals, a current conducting bracket assembly mounted on said base and secured to the other of said terminals, said bracket including at least one ieg, a retaining member mounted on said base and spaced from said leg, a space formed in said bracket assembly defining an air gap, a spring member mounted between said leg of said bracket assembly and said retaining member and being norm-ally bowed inwardly with respect to said base into contact with said actuating element, said spring member being movable to a circuit breaking position out of engagement with said actuating element upon the expansion of said actuating element in response to an overload of current applied thereto, said spring member being bowed outwardly in the circuit breaking position, and a reset plunger extending through the space in said bracket assembly and including a metallic disc that norm-ally bridges said space to complete the circuit from said first terminal to said second terminal when said spring member is located in the normal position thereof, said reset plunger being movable into engagement with said spring member in the outwardly bowed position thereof tor forcing said spring member inwardly to its inwardly bowed position and into contact with said actuating element, said metallic disc being moved out of the bridging position during the resetting of said spring member.

2. In a circuit breaker as set forth in claim it said bracket leg being formed with an opening and the end of said spring member adjacent said leg being formed with a reduced portion that is received within said opening, wherein said spring member is constantly centered with respect to said bracket assembly and bimetallic actuating element.

13. In a circuit breaker for low current circuits, at base of non-conducting material having electrical terminals secured thereto in spaced relation, a bimetalic actuating element mounted on said base, one end of said actuating element being secured to one said terminals and the other end being spaced from said base and being movable outwardly with respect thereto in response to an overload of current applied thereto, a bracket assembly mounted on said base and being secured to the other of said terminais, said bracket assembly having an air space formed therein, a metallic disc secured to a reset plunger and normally bridging said air space, and a spring member mounted on said bracket assembly and being normally bowed inward-1y into contact with said actuating element and being movable to an overcenter position by said actusaid spring member is snapped to an outwardly bowed position to break contact with said actuating element, said plunger being movable into engagement with said spring member in the outwardly bowed position and being adapted to reset said spring member by forcing it inwardly to an overcenter position, wherein said spring member is snapped to the inwardly bowed position in contact with said actuating element.

4. In a circuit breaker as set forth in claim 3, means extending through said base and engaging said actuating element for presetting the position of said actuating element with respect to said base and thereby adjusting the normal position of said spring member.

5. In a circuit breaker, a non-metallic base having opposed terminals secured thereto, a temperature responsive bimetallic actuating element secured to said base and electrically connected to one of said terminals, a bracket assembly formed of electrical conducting material mounted on said base and electrically connected to the other of said terminals, .a circuit breaking member normally engaging said bimetallic actuating element and having one end electrically connected to said bracket assembly for completing a circuit between said terminals, means for retaining the other end of said circuit breaking member in engagement therewith, said circuit breaking member being movable out of engagement with said bimetallic actuating element in response to movement of said actuating element when an overload of current is applied thereto, and means adapted to engage said circuit breaking member in the circuit breaking position thereof for resetting said member into contact with said bimetallic actuating element, said bracket assembly being formed with an air space therein, said resetting means including a plunger formed with a metallic disc that normally bridges said air space for completing the circuit through said bracket assembly, said plunger being movable into engagement with said circuit breaking member in the circuit breaking position thereof for returning said member into contact with said bimetallic actuating element, said metallic disc being moved out of engagement With said bracket assembly during the resetting operation.

6. In a circuit breaker for low current circuits, a nonmetallic base having terminals secured thereto in spaced relation, a current conducting bracket assembly secured to said base, said bracket assembly being formed in two sections, both of which are secured to said base and are normally located in engagement with each other, one of said sections being formed of a spring material for movement and being connected to one of said terminals, the other of said sections being fixed, a bimetallic actuating element mounted on said base and engaging the other of said terminals, a leaf spring secured to said base and electrically engaging the other of said bracket assembly sections, said leaf spring being normally biased into contact with said bimetallic element in current conducting relation for completing a circuit through said circuit breaker, and a reset plunger secured to said one section of said bracket assembly projecting through the other of said sections, said plunger being movable to a reset position for engagement with said leaf spring after said leaf spring has been moved to the circuit breaking position by said bimetallic actuating element in response to an overload of current being conducted thereto, whereby said leaf spring is snapped from the non-conducting position by said reset plunger to the normal conducting position in engagement with said bimetallic actuating contact element and said one contact section is momentarily disengaged from the other contact section for breaking the circuit in said bracket assembly during the resetting operation.

7. In a circuit breaker for low current circuits, a nonmetallic base having terminals secured thereto in spaced relation, a temperature responsive actuating element mounted on said base and having one end electrically connected to one of said terminals, a bracket mounted on said base and electrically connected to the other of said terminals, a retaining member secured to said base within the confines of said bracket, a spring contact member having one end engaging said bracket and the other end mounted in said retaining member for normally locating said spring member in engagement with said actuating element for establishing an electrical circuit therewith, said spring member being movable to a circuit breaking position out of contact therewith in response to movement of said actuating element when an overload of current is applied thereto, means mounted on said bracket for resetting said spring member to the normal position thereof, and spring means for normally retaining said resetting means in a circuit holding position, wherein an electrical circuit is established through said bracket.

8. In a circuit breaker as set forth in claim 7, said retaining member being formed of a bimetallic material and compensating for changes in the ambient temperature of the surrounding atmosphere.

References Cited by the Examiner UNITED STATES PATENTS 1,803,982 5/31 Thomas 200-67 1,958,696 5/34 Digby 200-113 2,191,588 2/40 Sattler 200-116 2,281,021 4/42 Butler et al. 200-139 2,404,874 7/46 Wohi 200-67 2,429,8 13 10/47 Hausler 200-67 2,441,979 5/48 Schm-idinger et al 200-122 2,519,334 8/50 Arbogast 200-67 2,563,175 8/51 Kitman 200-1 16 2,824,932 2/58 Ellenberger 200-116 2,993,102 7/ 61 Anderson et al 200-67 BERNARD A. GILHEANY, Primary Examiner.

Claims

7. IN A CIRCUIT BREAKER FOR LOW CURRENT CIRCUITS, A NONMETALLIC BASE HAVING TERMINALS SECURED THERETO IN SPACED RELATION, A TEMPERATURE RESPONSIVE ACTUATING ELEMENT MOUNTED ON SAID BASE AND HAVING ONE END ELECTRICALLY CONNECTED TO ONE OF SAID TERMINALS, A BRACKET MOUNTED ON SAID BASE AND ELECTRICALLY CONNECTED TO THE OTHER OF SAID TERMINALS, A RETAINING MEMBER SECURED TO SAID BASE WITHIN THE CONFINES OF SAID BRACKET, A SPRING CONTACT MEMBER HAVING ONE END ENGAGING SAID BRACKET AND THE OTHER END MOUNTED IN SAID RETAINING MEMBER FOR NORMALLY LOCATING SAID SPRING MEMBER IN ENGAGEMENT WITH SAID ACTUATING