US3217125A - Circuit breaker having a cam means for very rapid opening of the contacts - Google Patents

Description

N 9, 1965 L. w. BRACKETT 3, 17,

CIRCUIT BREAKER HAVING A CAM MEANS FOR VERY RAPID OPENING OF THE CONTACTS Filed June '7, 1961 3 Sheets-Sheet l 93 722 1d! 2 91 J? I?) O O 0 ,L,

o flu J 3? 93 30 m1 INVENTOR. [aura/2a Ill Brad??? BY WWMRIW Nov. 9, 1965 w. BRACKETT CIRCUIT BREAKER HAVING A CAM MEANS FOR VERY RAPID OPENING OF THE CONTACTS Filed June '7. 1961 3 Sheets-Sheet 2 Nov. 9, 1965 w. BRACKETT 3,217,125

CIRCUIT BREAKER HAVING A CAM MEANS FOR VERY RAPID OPENING OF THE CONTACTS Filed June 7, 1961 3 Sheets-Sheet 3 United States Patent 3,217,125 CIRQUTT BREAKER HAVING A CAM MEANS FOR VERY RAIIID @PIENING OF THE CQNTACTS Lawrence W. Brackett, Georgetown, Mass, assignor to Wood Electric Corporation, Lynn, Mass, a corporation of Massachusetts lFiied .l'une 7, 1961, Ser. No. 115,381 12 Claims. (Cl. 2661-116) The field of this invention relates to electric switches and more particularly to circuit breakers which are current responsive for protecting a circuit from overloads.

In many applications the circuit breaker must be what is commonly referred to as trip-free, that is the design of the breaker must be such that the circuit under control cannot be forcibly maintained closed under overload conditions.

In certain applications, as in electronic computing machines, it is desirable not only that trip free overload protection be provided but also some means for indicating, at a remote location, the condition of the protected circuit.

Objects of the present invention are to provide a novel trip-free circuit breaker which includes means for indicating remotely the condition of the protected circuit, or which facilitates the inclusion of a condition indicating component; to provide such a circuit breaker which is quick acting, which is sensitive, which provides for the very rapid opening of its contacts, which is dependable in operation, which includes means for manually tripping the breaker mechanism whereby the contacts are opened with a snap action, and which incorporates a double break interruption of the protected circuit; to provide a circuit breaker which, by suitable modification, can be arranged to open either instantaneously upon the application of an overload current or after a predetermined delay; and to provide a breaker of this type which is of relatively simple and inexpensive manufacture and nevertheless fully reliable under the most severe operating conditions.

The substance of the invention can be briefly summarized as to characteristic aspects thereof as follows.

In a principal aspect, the invention involves a circuit breaker comprising in a suitable housing a fixed contact and a movable contact with a first cam movement adapted to drive the movable contact into engagement with the fixed contact, a latch, current responsive means for moving the latch, a pivotally mounted second cam which includes a pawl for releasably engaging the latch thereby to lock the second cam in position unless the pawl is re leased upon response to excessive current, and wedging means adapted to be driven between the two cams to close the contacts, the second, pivotally mounted, cam being oriented so that as the wedging member moves to close the contacts it also moves away from the cams pivot in preparation for imparting to the movable contact an optimal opening force when the pawl is released.

In a more particular aspect the invention contemplates a circuit breaker with a fixed contact mounted within a housing, a slide mounted in the housing, a movable contact carried by one end of the slide, a cam block carried by the other end of the slide, a latch, current responsive means for moving the latch, a two-armed pivoted trip lever one arm of which includes a cam surface extending substantially radially from the levers pivot and the other arm of which includes a pawl for releasably engaging the latch, the cam surface on the one arm of the trip lever operationally facing the cam surface of the cam block, an operating member which projects through the casing, and wedging member carried by the operating member and adapted to be driven between the opposed cam surfaces to close the contacts, the trip lever being oriented so that as the wedging member moves to close the contacts it also moves away from the levers pivot.

In a different aspect the invention involves a circuit 3,217,125 Patented Nov. 9, 1965 ice breaker of the type in which a wedging member can be driven between two cam members, movement of the first of which will close the contacts and the second of which is releasably locked in position by a current responsive element, which circuit breaker is characterized in further comprising condition indicating apparatus including a lever engageable by the first of the said cam members when the circuit breaker is open and an auxiliary switch actuable by movement of the lever.

In another aspect the invention contemplates for use in circuit breakers of the present type a current responsive component with a plurality of substantially planar resistance elements at least one of which is of bending bimetal construction and each of which includes a reversing current path such that both ends of the path are at the same end of the element, these elements lying in closely adjacent parallel planes and being connected in series electrically.

These and other objects and aspects of the substance and nature of the invention will appear from the following description of several practical embodiments illustrating its novel characteristics.

The description refers to drawings in which FIG. 1 is a plan view of a circuit breaker with one half of its case removed;

FIG. 2 is a section on the line 2-2 of FIG. 1 with the cover plate removed;

FIG. 3 is a rear view of the circuit breaker;

FIG. 4 is a view similar to FIG. 1 with the operating parts in their open circuit position;

FIG. 5 is an edge view of the bi-metal current responsive element employed in this embodiment of the invention;

FIG. 6 is a plan view of the bi-metal element accord ing to FIG. 5;

FIG. 7 is a plan view, similar to FIG. 6, of a modified bi-metal element;

FIG. 8 is a section on the line 88 of FIG. 7;

FIG. 9 is a section on the line 9-9 of FIG. 7;

FIG. 10 is a diagrammatical representation of the assembly of bi-metal elements according to FIGS. 8 and FIG. 11 is a plan View of a modification of the breaker according to FIGS. 1 to 4; and

FIG. 12 is a plan view of another modification.

Referring to FIGS. 1 to 3, a circuit breaker according to the invention has an insulating housing 10 consisting of two halves 19.1, 19.2, through the front face of which projects an operating plunger 12 and a trip pin 14. The two halves of the housing are held together by bolts 11 passing through appropriately placed apertures 11.1. For mounting the circuit breaker on a panel, flanged nuts 15 are provided which are set into suitable recesses 15.1 of the front face of the housing 10.

Inside the housing at one side thereof are two fixed contacts 16 and 18 (FIGS. 1, 4). The contact 16 is connected directly to a terminal 22 which projects through one side of the housing 10 and includes a threaded open ing 22.1 (FIG. 3) for receiving a terminal screw. The other fixed contact 18 is connected by the bus bar 24 and the flexible braid cable 26 to one leg 30.1 of a U- shaped bi-metal element 30 to be described below with reference to FIG. 6. The other leg 30.2 of the bi-metal element is connected to a second terminal 32 which projects from the side of the casing opposite to the terminal 22. This terminal 32 is secured to the casing 10 by screws 36. The upper end of the bi-metal element 30 carries a latch plate 65.

The circuit can be completed across the two fixed contacts 16, 18 by a resilient bar carrying movable contacts 46, 48. The bar 40 is mounted on a switch support such as slide 44 running in elongate grooves 47 in the opposing walls of the housing lit. The movable contacts are urged away from the fixed contacts by the spring 49. Mounted at the other end of the slide 44 from the bridging bar it? is a first carn means in the form of a block 50 made of insulating material. The cam surface of this block is oblique to the sliding direction of the switch support or slide 44.

On the opposite side of the housing from the cam block St) is a two-armed trip lever 54- constituting a second cam means. This trip lever 54 is pivotally mounted between the opposed halves of the housing 10, by means of the pin 56 and one of its arms includes a cam riding surface 53 substantially radial relative to the pin 56. The cam surface 58 is urged in the direction towards the cam block Si by a latch spring 669 whose center portion bears on an edge of lever 54 and whose opposite ends bear on the pin 62. On each side of its center portion the spring is wound around the pin 56 on which lever 54 rotates. The pin 62 also serves to limit the rotation of the trip lever 54 in the opposite or counterclockwise direction. The other arm of the lever 54 terminates in a tooth or pawl 55 which is adapted to engage the latch plate 65 of the bi-metal element 3d, and thereby to lock the cam surface 58 in operating positron.

A pair of links 66, 67 (FIG. 2) of insulating material are connected to the inside end of the operating plunger 12 by a pin 68 which rides in slots 76) in the opposed walls of the housing 19 thereby restraining the plunger to straight motion. At the free end of the links 66 are mounted three coaxial metal wedging rolls '72, 73 and 74 by means of a headed pin 76. These rolls are adapted to be driven between the cam block 50 and the opposing, actuating cam riding surface 58 of the trip lever 54, the two larger, outer, rolls 72, 74 bearing against the cam block 50 and the smaller, inner roll '73 bearing against the cam surface 58. The shapes of the respective cam surfaces are such that, when the trip lever 54 is locked in place, the depression of the plunger 12 will drive the slide 44 laterally, as shown in FIG. 1, so that the circuit across the two fixed contacts 16, 18 is closed by the bridging bar 48. Further, the shape of the cams, particularly the cam surface 58, are such that, once the contacts are closed, the plunger 12 will be retained in depressed position. It should be noted that the arrangement of the trip lever 54 is such that, as the breaker is closed, the rolls move away from the pivot of the trip lever in preparation for the tripping action to be explained below.

For the convenient and snap-action opening of the contacts when the circuit is in use but not subject to overload conditions there is provided a trip pin lid having a wedging surface ltd-.1 normally adjacent to the latch plate 65. The trip pin is normally urged upwards, out of the path of the free end of the bi-metal 39, by the spring 13 which is at its fixed end Wound around a pin 13.1.

For auxiliary purposes such as for providing a remote indication of the condition of the main circuit as will be described below, the circuit breaker according to the invention incorporates a separate auxiliary switch 8%. The switch shown is of a type available commercially and known generally as microswitches, but it will be understood that any switch properly functioning for the auxiliary purpose in question and structurally compatible with the principle circuit breaker configuration, can be used instead. The microswitch selected for the present embodiment has an upper and a lower fixed contact, 82 and 84 respectively, (FIG. 2) which correspond respectively to the normally closed and normally open wiring configurations available through terminals 83 and 85 respectively. A movable contact 86 is carried by a snap yoke 88 and is connected, through the yoke, to the common terminal 90. Each of the terminals has associated with it a connector block 92 (FIG. 3) each having for example three receptacles )4 for receiving taper-pin connector plugs. The blocks 92 have pin projections 93 which engage corresponding openings 95 in the microswitch terminals. The other ends or" the block 92 have cars 91 (FIGS. 1, 3) by which they are held in position in apertures of an insulating cover plate 96 secured to the housing 10 by a screw 97. The microswitch 86 itself is held in place in fitted recesses 79.1, 79.2 in the two halves 10.1, 10.2 respectively, of the casing 10.

The main switch 224t 24 is linked to the auxiliary switch Ed by a bell crank lever 93 of insulating material which pivots on a cantilever pin 99 fixed to the housing half 10.2 as shown in FIG. 2. One arm, 98.1 operates the microswitch whereas the other arm 98.2 reaches towards the cam block 56. The microswitch spring 83 retains the arm 98.2 in contact with slide cam 5%).

The operation of the circuit breaker as described above is as follows.

With the plunger T2 depressed as shown in FIG. 1, the insulating carn block 5% is forced outwardly by the roller 7'3 against the force of spring 49 and a circuit is thus established between the terminals 22 and 32 through the contacts 16, 46, the bridging bar it the contacts 46, 48, the bus bar 24, the braid 26, and the U-shaped bi-metal element 30, so that a current can pass through the device. If this current reaches overload proportions the bi-metal element 30, heated by its resistance dissipation, will deflect to the position shown in FIG. 4. This deflection will cause the latch plate 65 to unlock the two armed cam trip lever 54 at 55. At this point the force of the spring 49 will drive the bridging bar 40, the slide 4-4, the links 66.1, 66.2 and the Wedging rolls 72, '73, 74 against the torque of latch spring 60 to the right as shown in FIG. 4 thereby causing the cam lever 54 to rotate on pin 56 in a counterclockwise direction, and permitting the wedging rollers and the cam to move towards the right and thus the contacts to open. Since the wedging rolls are, at the moment of opening, at the end of the cam riding surface 58 furthest from the trip levers pivot, this action occurs very rapidly because the torque available from the contact spring 49 to overcome the force of the latch spring is then a maximum. This feature is believed to be one of the principal advantages of the arrangement according to the present invention. The corresponding movement of the bridging bar 40 will open the circuit as clearly shown in FIG. 4, thereby preventing the application of dangerous overload current to the apparatus to be protected.

The positions of the various parts as shown in FIG. 4 exist only immediately following the tripping of the circuit breaker for, in this position is inherent an upwards force exerted on the plunger 12 by the cam lever spring 60. This force will immediately return the operating parts to their normal open circuit position with the plunger in the dotted line position so that, once the bi-metal element 30 has again cooled, the circuit can again be closed merely by depressing the plunger 12. It should be noted, however, that the operation of this circuit breaker is trip free, that is, so long as the bi-rnetal element is conditioned by a current overload, the circuit cannot be kept closed by forcefully maintaining the plunger T2 in its depressed position. Any attempt to do so will only result in the parts of the breaker assuming the position shown in FIG. 4- with the contacts being open.

When it is desired to trip the circuit breaker manually the plunger 12, is pulled outwardly, or the trip pin 14 is depressed thereby deflecting the bi-metal element 30 in a manner similar to that produced by a current overload and causing the snap-action opening of the contacts.

The operation of the auxiliary switch 8th depend on the condition of the main circuit. The arm 98.1 of the lever 98 will operate the microswitch by depressing the contact 83 when the other arm 98.2 is engaged by the cam block Stl as that block moves to its open circuit position. It is an advantage of this arrangement that the operation of the microswitch is dependent only upon the condition of the main circuit proper and is not dependent upon the position of the operating plunger 12. Thus, just as the main circuit cannot be maintained closed in the presence of an overload current, neither can the auxiliary, such as indicating, circuit be closed depending on a condition of the main contacts other than that to which it is supposed to be tied.

FIGS. 5 to illustrate embodiments of the bi-metal and terminal assembly advantageously incorporated into the circuit breaker shown in FIGS. 1-4 but having other appropriate uses.

In the assembly according to FIGS. 5 and 6, the one leg 30.1 of the U-shaped bi-metal element 30 is welded directly to the terminal 32. To the other leg 30.2 of the bi-metal element are welded the braid cable 26 and a suport plate 35. The terminal 32 (compare FIGS. 1 and 4) has a hole 32.1 for a screw 32.2 securing it to the housing half 10.2. The support 35 has, similarly, a hole 35.1 for a screw 35.2 to secure it .to the casing half 10.1. The latch plate 65 which cooperates with the trip lever 54 has been described above with reference to FIGS. 1 and 4, the pawl or tooth 55 being indicated also in FIG. 5.

While the bi-metal element shown in FIGS. 5 and 6 is suitable for use in applications Where a comparatively heavy current i to be passed, difficulty is experienced in constructing a single layer bi-metal element which will heat sufiiciently to trip the circuit breaker at lower current levels. The modified bi-metal assembly shown in FIGS. 7-10 overcomes this problem.

In this assembly the Working parts include a plurality of edged, substantially planar resistance elements 100 at least one of which, marked 101, is of bi-metal construction. In the version shown the other resistance elements 102 and 103 are merely essentially non-bending heating elements and do not contribute to the actuating force but rather conduct along a tortuous path so as to provide maximum heating effect, it being understood that a higher temperature produces a greater displacement of the latch plate 114 than a lower temperature. By using various combinations 'of bending and non-bending heating elements according to the invention, it is possible to preset circuit breakers for given current ratings.

The various elements 101, 102, 103 are separated from one another by sheets of 105, 106 insulating material as for example mica, except at certain predetermined points at their secured ends. The points at which the insulation is omitted and the adjacent resistance elements are permitted to touch are selected, as shown at a and b in FIGS. 8 and 9, such that the various elements are connected electrically in series as diagrammatically illustrated in FIG. 10. In this way the maximum heating effect for a given current can be achieved. The various insulating and resistor elements are secured together at their ends by rivets 110, 111, the corresponding apertures in the conducting layers being somewhat larger than the shafts of the rivets so as to prevent shorting between layers, and the rivet heads separated from the adjacent bi-rnetal element by insulating washers 110.1, 111.1. The assembled group of elements is secured to the terminal 132 and to the support plate 135 by screws 116, 117, which correspond to similar components 32, 35 of FIGS. 1 and 4. A latch plate 114 is secured to the free end of the bi-metal element 101, similar to the plate 65 of FIGS. 5 and 6.

In some instances it is desirable to arrange a similar assembly in which each of the layers is of bi-metal construction so that a greater actuating force as well as a greater displacement are provided. In such an arrange ment each of the bi-metal layers is arranged as in the example of FIGS. 7-9, preferably of U-shaped configuration so that all portions of the element extending away from the latch plate can be easily secured to the housing. The various bi-metal layers are insulated from one another as in the example of FIGS. 79 and they are thus again electrically in series though mechanically in parallel.

In each of the above-defined multilayer current-responsive elements, the current passes in opposite directions in similar adjacent layers. Accordingly the magnetic fields produced by adjacent layers tend to cancel and the inductance of the current responsive element is kept quite low in spite of its increased sensitivity. This is a distinct advantage if the device is to be operated on alternating currents of relatively high frequency such as, for example, 1000 cycles per second and since electrical power at such relatively high frequencies is being increasingly used in aircraft construction this advantage is felt to be of significance. Obviously if an even number of layers are used, making a corresponding slight modification in the terminal arrangement, the cancellation of magnetic fields is substantially complete. Typically, however, the cancellation of the fields of all but one layer is entirely satisfactory.

When an overload current is applied to a circuit breaker having a current responsive element of the bi-metal type there is a definite delay before the circuit breaker opens during which time the bi-metal element rises in temperature according to a predictable pattern. In many applications this delay is highly desirable so that circuits, such as those used in starting electric motors, are not annoyingly opened by momentary overloads of such short duration as would cause no harm. In other applications however, it is preferable that the circuit breaker open as soon as possible after an overload current is applied. FIGS. 11 and 12 depict modified cicuit breakers according to the invention which are adapted, by means of the inclusion of solenoid coils, to open without appreciable delay upon the application of an overload current.

In the embodiment of FIG. 11 the place of the bi-metal element of FIGS. 1 to 10 is taken by a balanced armature 200 having at one end a latch plate 2 12 constructed similar to the latch plate 65 shown in FIG. 1. The armature is pivotally connected to a frame 2-04 by a pin 206, the frame in turn being rigidly secured to the housing 298 by screws 20%. A spring 212 urges the armature 290 in a counterclockwise direction, as shown, so that the latch plate 2% normally engages a trip lever 214. The trip lever 214 and the rest of the mechanical linkage are arranged similarly to the lever 54 and appertaining components of FIGS. 14.

Adjacent the end of the armature 2051 which carries the latch plate 202 there is provided a solenoid 220 having a core 221 and a winding 222. The Winding 222 is wound on a bobbin 223 and is connected between the lower fixed contact 224 corresponding to 18 of FIG. 1 and an exteriorly projecting terminal 25 by means of leads 225.1 and 225.2 so as to be in the breaker circuit similarly to the bimetal element 30 of the embodiment of FIGS. 1 to 4. The solenoid is oriented so as to draw the latch plate 202 out of engagement with the trip lever 214 when an overload current is passed through the winding 222. The solenoid is secured to the frame 204 by the machine screw 229 but is held in spaced relation to the frame by the dished or cup-shaped circular spring 2311. By varying the tension placed on the spring 230 by the screw 229 the air gap between the end of the solenoid core 221 and the armature 200 can also be varied. Since the value of current at which the circuit breaker opens is dependent to a certain extent upon the size of this air gap, this adjustment provides a convenient means for adjusting the overall sensitivity of the breaker.

FIG. 12 shows still another modification somewhat similar to FIG. 11, in which the armature 3110 is L-shaped and the solenoid 330 is arranged so as to draw on that arm of the armature which does not carry the latch plate 302. In this example the armature 3th) is pivotally mounted directly on the housing 310 by means of the pin 306 and the solenoid 330 is rigidly secured to the housing by means of the bracket 310 and the screws 312 and 314, there being no means for adjusting the position of the solenoid. However, an adjustment of the value of current at which the breaker opens can be made by adjusting the tension on the spring 320 by means of the set screw 322. This spring 329 urges the armature 3% in a counterclockwise direction so that the latch plate 1W2 is normally engaged with the trip lever arm 303. Since the spring 320 provides the main force against which the solenoid 33kt? must pull, adjustment of its tension is determinative of the value of current at which the breaker will open.

It should be understood that the present disclosure is for the purpose of illustration only and that the present invention includes all modifications and equivalents falling within the scope of the appended claims.

I claim:

1. A circuit breaker comprising:

a housing;

first contact means fixed to said housing;

second contact means movably supported on said housing for circuit making and breaking connection with said first contact means;

first spring means biased to break said connection of said first contact means;

first cam means movably supported on said housing in position to move said second contact means into connection with said first contact means against said first spring means; second cam means pivotally mounted on said housing, including a riding surface facing the first cam means and extending to one end of the second cam means, second spring means tending to oppose connection breaking movement of said first spring means, and pawl means adjacent the other end of said cam means with the pivot of said second cam means located between said riding surface and said pawl means;

current responsive means including a movable member with latch means adapted to engage said pawl means during normal condition of the release means; and

wedging means adapted to be driven between said first and said second cam means for making said connection between said first and second contact;

means mounting said cam means and said wedging means on said housing for positioning said wedging means at outermost position on said riding surface when the first and second contact means, respectively, are in circuit making connection, and including said pivot, such that, upon release of said pawl means, connection between said contact means is rapidly broken by said first spring means then exerting a maximal torque against the break opposing force of said second spring means.

2. Circuit breaker according to claim 1, wherein said current responsive release means includes a bimetal element fastened at one end to the housing, and the other end extending towards said pawl means and carrying said latch means adjacent said other end.

3. Circuit breaker according to claim It wherein said current responsive means includes a plurality of substantially planar resistance means at least one of which is of bending bimetal construction, the remaining resistance means being of non-bending but heating construction, and each of which resistance means includes a U-shaped section and a reversing current path such that both terminals of the current paths are at the same end of the resistance means, said current resistance means lying in closely adjacent parallel planes and being connected electrically in series; and which includes means for connecting said resistance means in electrical series connection; and

insulating means separating said resistance elements with the omission of regions where electrical series connection of the elements is made by directly contacting them.

4. Circuit breaker according to claim 1 wherein said current responsive release means includes a solenoid mounted on said housing, having an armature movably fastened to said housing and a portion of said armature extending essentially towards said pawl means, and carrying said latch means adjacent its end.

5. A circuit breaker according to claim 1 including a tripping means extending through the housing adjacent said latch means and having an oblique surface for driving the latch means out of engagement with said pawl means independently of circuit making movement of said wedging means.

6. A circuit breaker comprising:

a housing;

fixed contact means mounted within said housing;

a block slidably mounted on said housing having on one side movable contact means for connection with said fixed contact, and a cam surface on the other side;

first spring means for biasing said block to separate said fixed and movable contact means, respectively;

current responsive means having a latch moving according to current conditions;

a two armed trip lever having pivot means mounted on said housing, one arm of the trip lever including a riding surface extending substantially radially from said pivot means and facing said cam surface of the block, the other arm of the trip lever extending substantially radially from said pivot means substantially opposite of the first arm and including a pawl for releasably engaging said latch, and including second spring means biasing the riding surface towards the cam surface of the block;

operating means mounted on the housing; and

wedging means connected to said operating means for forcing the wedging means between said cam sur faces of the block and said riding surface of the trip lever for making connection between said contacts when the wedging means is in outermost position on said riding surface of the trip lever and said latch is engaged by said pawl, such that, upon release of said pawl by said latch the contact connection is rapidly broken by said spring means then exerting a maximal torque against the bias of said second spring means.

7. A circuit breaker of the type having a housing and mounted thereon a pair of contacts, first movable cam means for closing said contacts, second movable cam means which is releasably locked in position by a current responsive element, and wedging means that can be forced between the two cam means for closing the contacts when the second cam means is locked in position, in combination with auxiliary signaling means comprising:

a switch mounted on the housing, and

a rigid two armed lever pivotally mounted on the housing with one arm engaging said first cam means and with the other arm engaging said switch for actuating the switch in response to movement of said first cam means.

8. A circuit breaker according to claim 7 in which said switch is of the snap-action type having movable spring means engaged with said other arm of the twoarmed lever, retaining the first arm of the lever in contact with the first cam means.

9. Circuit breaker according to claim 1 further comprising:

an auxiliary switch mounted on said housing adjacent said first cam means; and

an auxiliary lever pivotally mounted on said housing, engageable by said first cam means, and oriented to actuate said auxiliary switch when the contact means are separated.

10. A circuit breaker comprising:

a housing;

a fixed contact mounted within the housing;

a contact support slidably mounted on the housing;

a movable contact carried by one end of said support;

a cam block carried by the other end of said support and including a cam surface which is oblique to the sliding direction of the contact support;

operating means projecting through a wall portion of said housing;

a current-responsive element one end of which is secured to said housing and the other end of which is free, carries a latch, and projects towards said wall portion, said current-responsive element having a plurality of resistance means at least one of which is of bimetal construction and each of which includes a loop shaped section and a current reversing path such that both terminals of the current path are at the same end of the resistance means, and said resistance means lying in closely adjacent substantially parallel planes, said current-responsive element having insulating means separating adjacent resistance means with each of said insulating means being cut away adjacent one terminal of each of the respective current paths with alternate insulating means being cut away at opposing path ends, and said current-responsive element having means for connecting said resistance means electrically in series;

a two-armed trip lever having pivot means mounted on said housing one arm of the trip lever have a pawl for releasably engaging said latch of the currentresponsive element and the other arm having a riding surface extending substantially radially from said pivot means in a direction away from said wall portion, and said riding surface facing said cam surface of the cam block;

wedging means carried by the operating means and adapted to be driven between the opposed cam and riding surfaces so as to close the contacts;

an auxiliary switch; and

an auxiliary lever engageable by said cam block and oriented to actuate said auxiliary switch when the contacts are open,

11. A current-responsive element comprising:

two groups of edged resistance elements, one group of at least one element being of bending birnetal construction and the other group being of non-bending but heating construction, and each bending and non-bending element including a loop shaped section 1.0 and a current reversing path such that both terminals of the current path are at the same edge of the respective resistance element, said resistance elements lying in closely adjacent substantially parallel planes;

insulating means between each pair of adjacent resistance elements, each of said insulating means being cut away adjacent one terminal of each of the respective current paths with alternate insulating means being cut away at opposing path ends; and

conductors connecting said resistance elements in series at said terminals where the adjacent insulating means are cut away.

12. A current-responsive element comprising:

a plurality of substantially planar resistance means at least one of which is of bending bimetal construction, the remaining resistance means being of nonbending but heating construction, and each of which resistance means includes a U-shaped section and a current reversing path such that both terminals of the current paths are at the same end of the resistance means, all of said resistance means lying in closely adjacent parallel planes and being connected electrically in series; and

insulating means separating adjacent elements with the omission of regions where electrical series connection of the elements is made by directly contacting them.

References Cited by the Examiner UNITED STATES PATENTS 1,031,849 7/12 Harley 200106 1,612,375 12/26 Hineline 200-413 2,190,299 2/40 Van Valkenberg 200--16 2,528,545 11/50 Pond ZOO-38 2,645,691 7/53 Ingwersen 2001 16 2,952,757 9/60 Ellenberger 2001 16 2,960,587 11/60 Wood 200116 2,981,812 4/61 Piteo et al 200-416 FOREIGN PATENTS 921,210 12/54 Germany.

BERNARD A. GILHEANY, Primary Examiner. 0

ROBERT K. SCHAEFER, Examiner.

Claims (1)

1. A CIRCUIT BREAKER COMPRISING: A HOUSING; FIRST CONTACT MEANS FIXED TO SAID HOUSING; SECOND CONTACT MEANS MOVABLY SUPPORTED ON SAID HOUSING FOR CIRCUIT MAKING AND BREAKING CONNECTION WITH SAID FIRST CONTACT MEANS; FIRST SPRING MEANS BIASED TO BREAK SAID CONNECTION OF SAID FIRST CONTACT MEANS; FIRST CAM MEANS MOVABLY SUPPORTED ON SAID HOUSING IN POSITION TO MOVE SAID SECOND CONTACT MEANS INTO CONNECTION WITH SAID FIRST CONTACT MEANS AGAINST SAID FIRST SPRING MEANS; SECOND CAM MEANS PIVOTALLY MOUNTED ON SAID HOUSING, INCLUDING A RIDING SURFACE FACING THE FIRST CAM MEANS AND EXTENDING TO ONE END OF THE SECOND CAM MEANS, SECOND SPRING MEANS TENDING TO OPPOSE CONNECTION BREAKING MOVEMENT OF SAID FIRST SPRING MEANS, AND PAWL MEANS ADJACENT THE OTHER END OF SAID CAM MEANS WITH THE PIVOT OF SAID SECOND CAM MEANS LOCATED BETWEEN SAID RIDING SURFACE AND SAID PAWL MEANS; CURRENT RESPONSIVE MEANS INCLUDING A MOVABLE MEMBER WITH LATCH MEANS ADAPTED TO ENGAGE SAID PAWL MEANS DURING NORMAL CONDITION OF THE RELEASE MEANS; AND WEDGGING MEANS ADAPTED TO BE DRIVEN BETWEEN SAID FIRST AND SAID SECOND CAM MEANS FOR MAKING SAID CONNECTION BETWEEN SAID FIRST AND SECOND CONTACT; MEANS MOUNTING SAID CAM MEANS AND SAID WEDGING MEANS ON SAID HOUSING FOR POSITIONING SAID WEDGING MEANS AT OUTERMOST POSITION ON SAID RIDING SURFACE WHEN THE FIRST AND SECOND CONTACT MEANS, RESPECTIVELY, ARE IN CIRCUIT MAKING CONNECTION, AND INCLUDING SAID PIVOT, SUCH THAT, UPON RELEASE OF SAID PAWL MEANS, CONNECTION BETWEEN SAID CONTACT MEANS IS RAPIDLY BROKEN BY SAID FIRST SPRING MEANS WHEN EXERTING A MAXIMAL TORQUE AGAINST THE BREAK OPPOSING FORCE OF AID SECOND SPRING MEANS.

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