Circuit breaker

Nov. 17, 1959 r. j. d. Roberts 2,913,552

CIRCUIT BREAKER

Filed May 15, 1958

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INVENTOR.

Ray J. Z? Roberts

BY &amp;ttorr?ey.s

United States Patent Office

2,913,552

Patented Nov. 17, 1959

2,913,552

CIRCUIT BREAKER

Ray J. D. Roberts, Chicago, HI., assignor to Charles D. Hummel, Sr., New York, N.Y.

Application May 15, 1958, Serial No. 735,430

Claims. (Cl. 200—115.5)

My invention relates to an improved circuit breaker and, more particularly, to a trip-free thermostatically operated circuit breaker of compact and rugged structure which is readily insertable into an electric circuit to protect that circuit against overload.

Although the art relating to circuit breakers is extensive, a circuit breaker embodying my invention and constructed in accordance with the principles thereof is singularly effective, sure in operation and yet compact and inexpensive to manufacture. My invention contemplates the use of a switch normally biased to its open position and adapted readily to be connected into an electric circuit, and has a latching mechanism for holding the switch in its closed position until released by heat or excessive current flow.

In the disclosed switch, I have provided a temperature responsive latch in which the latching element is movable along the temperature responsive element in the direction of switch contact movement with one of the switch actuating parts and is movable by the temperature responsive element in a direction lateral to that of switch contact movement to and from a latching position, whereby the latching element moves with the switch actuating element when the contacts are manually operated and is held away from the latching position by action of the temperature responsive element.

A circuit breaker constructed in accordance with my invention is well suited to being built into a compact connector unit quickly connectible into the circuit for the protection of household appliances, either to be furnished with an appliance or as a separate component. The structure and arrangement of parts in my circuit breaker is such that it avoids the necessity of a high degree of precision in either the manufacture of parts or the assembly, and, thus, a circuit breaker incorporating my invention may be inexpensive, durable and well suited to household use.

Other objects and advantages of my invention will be apparent from the following description and the several views of the drawings, wherein:

Fig. 1 is a perspective view of a combination electrical connector plug, circuit breaker and receptacle embodying a preferred form of my invention;

Fig. 2 is a side elevation of the device of Fig. 1 as seen with the near half of the housing removed and the circuit breaker in its circuit closing position;

Fig. 3 is a view similar to Fig. 2, but showing the circuit breaker in its open position;

Fig. 4 is a transverse central section through the device taken substantially on the line 4—4 of Fig. 1 looking in the direction of the arrows and illustrating the parts of the circuit breaker in their normal circuit closing positions;

Fig. 5 is a view similar to Fig. 4 showing the circuit breaker in its open position;

Fig. 6 is an exploded view of the circuit breaker latching and trip mechanism; and

Fig. 7 is a fragmentary longitudinal section through the circuit breaker mechanism and is taken substantially at the position of the line 7—7 of Fig. 4, looking in the direction of the arrows.

The exemplary embodiment of my invention which is 5 disclosed herein for illustrative purposes includes a housing 10 divided longitudinally into two separable parts 11 and 12 and desirably made of an insulating material, such as hard rubber or a strong thermo-setting plastic. The housing is generally rectilinear and has two holes 10 14 in predetermined spaced relationship to one another in one end to provide for the insertion of connecting prongs of another device, and has prongs 16 extending from the other end of the housing, prongs which are for making electrical connections to a source of power 15 such as an electric outlet, an extension cord or the like. A head 18 of a re-set button 20 extends through appropriate facing channels 21 in the housing parts to protrude outwardly of the housing on one side thereof.

Interiorly, the housing parts are formed to provide, 20 when assembled together, adjacent chambers 22 and 24 separated by a partition 26 which has an aperture 28 therein.

A conductor strip 30 has a contact end 32 in the form of a prong extending into one of the holes 14 to make 25 contact with a prong of a plug-in connector inserted into hole 14 from the end of the housing, the conductor strip following an outwardly offset path in appropriate opposed grooves in the housing parts to terminate at its other end in the chamber 22 on one side of the re-set button 20, 30 and has a contact 34 mounted thereon and secured thereto at the end within the chamber. On the other side of the re-set button in the chamber 22, a second contact 36 is secured to the end of the conductor strip which follows a path offset inwardly in appropriate facing, grooves in the 35 housing halves to terminate in one of the plug-in prongs 16.

The other prong 17 and a receptacle contact 42 are parts of a unitary in sub-assembly, as shown at the lower portion of Fig. 6. The prong 17 consists of a conductor 40 strip offset outwardly inside the housing 10 in appropriate grooves and terminates at 44 in the chamber 24. The receptacle contact 42 is likewise a conductor strip offset outwardly inside the housing 10 and terminating in the chamber 24 of the housing 10 in aligned and spaced rela45 tionship to the end 44 of prong 17. A rectangular bimetallic plate 48 has integral ears 50 extending in right angular relationship from the corner portions of one edge thereof. The ears are secured by means such as rivets 52 to the inner end 44 of the prong 17 and the inner 50 end 46 of the receptacle contact 42. The bimetallic plate thus stands upright relative to the prong and contact within the chamber 48 and is offset with respect to the longitudinal center line of the housing 10.

A latching strip 54 extends across the inside face of 55 the bimetallic plate 48 and end portions 56 thereof are bent around the edges of the bimetallic plate and against the outer face thereof to mount the latching strip on the bimetallic plate for vertical sliding movement. The latching strip includes a tongue 58 on the upper edge thereof 60 extending inwardly at right angles thereto.

The re-set button 20 has, inwardly of the head 18 thereof, an integral flange 60 thereon which projects radially of the head 18, and also includes a shank 62 below the flange 60 and which, in the structure shown, has a diam65 eter less than that of the head 18. The collar 60, among other purposes, serves to hold the re-set button 20 within the housing 10, it being too large to pass through the channels 21 through which the head 18 extends. A bridging contact 64 consists of a strip having contacts 66 70 at its ends spaced to engage contacts 34 and 36 on strips 30 and 38. The strip as shown in Fig. 6, has a central portion 68 which is offset downwardly from the end por2,918,552 tions thereof, and has a central bore 70 therein through which the shank 62 of the re-set button 20 extends. A coil type compression spring 72 encompasses the shank 62 and is contained between the collar 60 and the bridging contact 64 of the re-set button 20.

My device likewise includes a sleeve 74 having an internal diameter, sufficient to receive slidably the shank 62 of the re-set button 20. Between its ends the sleeve has a transverse slot 76 therein which extends into the sleeve appreciably further than the thickness of the sleeve wall.

The. re-set mechanism further includes a metal insert 78 which has a base portion of cylindrical form and has an upper end portion 80 of smaller diameter so as to provide a shoulder 82 between the portions. The diameter of the base portion of the insert is such as to fit closely but slidably within sleeve 72.

A second coil compression spring 84 serves as another part of the re-set mechanism and is contained between the floor 86 of the lower cavity 24 and the bottom end of the insert 78 within the sleeve 74. The floor 86 of the lower chamber is recessed as at 88 and the insert 78 is recessed as at 98 to contain the ends of the spring 84.

As was stated before, the bimetallic plate 48 is offset from the lateral center line of the switch housing. Housing part 11 which contains the bimetallic plate 48 is recessed appreciably away from the plate surface, as at 92 in the lower chamber 24, in order to permit outward flexing of the plate when heated.

The operation of the disclosed switch is as follows. The normal, current conducting or closed position of the switch is illustrated in Figs. 2 and 4. The bridging contact 64 is closed against contacts 34 and 36 so as to establish an electrical circuit between prong 16 and receptacle contact 32. The device will be mounted to a wall outlet, for instance, by prongs 16 and 17 and the prongs of an appliance cord inserted into the holes 14 to make contact with receptacle contacts 32 and 42. As the appliance is used, a circuit is closed through prong 38 and receptacle contact 32 by the bridging contact 64, and through the associated prong of the appliance cord, the appliance.and the other or return circuit is made through receptacle contact 42, the bimetallic plate 48 and prong 44.

Under normal load conditions the bimetallic plate 48 is_ relatively unheated and, therefore, stands vertically without material flexure. By virtue of this vertical position the tongue 58 of the latching strip 54 extends into slot 76 of sleeve 74 and is hooked over the shoulder 82 of the metal insert 78. The insert is maintained in its uppermost position by the coil spring 84. Therefore, the latching strip has been carried near the upper edge of plate 48, and the tongue, in turn, has carried sleeve 74 upwardly against the underside of the bridging contact 64 to hold the contacts 66 thereof against contacts 34 and 36. The bridging contact so seated acts as a stop for movement of the sleeve.

In the event that the circuit is overloaded, excessive current will flow through the switch parts, including the bimetallic plate 48 and will result in the heating of that plate. The bimetallic plate then flexes or bends outwardly and away from the sleeve 74, as depicted in Fig. 5. The tongue 58 of the latching strip 54 is thus with-, drawn from engagement with the shoulder 82 of the metal insert 78, thereby to free insert to be moved upwardly by the spring -34. The sleeve 74 is relieved of the force applied by the spring 84 and subject only to the force of the spring 72 wnich drives that sleeve downwardly carrying with it the tongue 58 of the latching strip, which slides downwardly on the plate 48. As the sleeve is thus withdrawn from supporting relation to the bridging contact 64, spring 72 likewise drives the bridging contact along shank 62 of the re-set button 20 to withdraw it from circuit closing relationship with the contacts 34 and 36. -· The circuit breaker of my invention cannot be re-set as long as the bimetallic plate remains hot since the tongue will be withheld from possible engagement with shoulder 82 of the metal insert.

When the plate cools and thus urges tongue 58 further into the slot 76, the device may be re-set. The head of the re-set button is depressed, whereupon the end of the shank 62 forces the metal insert 78 downwardly against the force of spring 84 until the tongue 58 again engages shoulder 82 of the insert. Upon release of the force applied to the re-set button, spring 84 forces insert 78 upwardly carrying tongue 58 and, therefore, sleeve 74 with it to restore the bridging contact to circuit closing position. The movement of the insert likewise drives the reset button 20 back to its normal position.