US2629034A

US2629034A - Electrical apparatus

Info

Publication number: US2629034A
Application number: US229585A
Authority: US
Inventors: Marshall C Harrold
Original assignee: General Motors Corp
Current assignee: Motors Liquidation Co
Priority date: 1951-06-02
Filing date: 1951-06-02
Publication date: 1953-02-17
Anticipated expiration: 1970-02-17

Description

Feb. 17, 1953 M, c, HARROLD 2,629,034

ELECTRICAL APPARATUS Filed June 2 1951 2 SHEETS--SHEET 2 32s 374 V k BIMETAL 388 BIMETAL \INSULATION FIG. 4

Patented Feb. 17, 1953 ELECTRICAL APPARATUS Marshall 0. Harrold, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a

corporation of Delaware Application June 2, 1951, Serial No. 229,585

8 Claims.

This invention relates to electrical apparatus and more particularly to current overload protectors especially intended for large electric motors.

In ordinary current overload protectors, the actuating element used to trip open the protector also is generally used for reclosing. For many applications, such as lighting, heating, and small motor circuits, this is sufficient. However, for larger motors such arrangements are inadequate because a quick tripping protector with a long off or open circuit time is required to cut short the heating of the motor and thereafter cool the large motor to a temperature at which it is safe to reclose the protector to permit a restarting attempt.

It is an object of my invention to provide a simple relatively inexpensive overload protector in which the reset time may be made very long and the tripping time very short.

It is another object of my invention to provide a simple relatively inexpensive overload protector in which the reset time and the tripping time may be selected entirely independent of each other.

It is another object of my invention to provide a simple relatively inexpensive overload protector in which the reset arrangement constitutes a separate independent control which is separate from the tripping control.

Several modifications of the invention are disclosed to illustrate the manner in which these objects are obtained. In one form, there is illustrated a simple current heat actuated snapacting toggle bimetal overload device which is not self-resetting. It is reset by an electromagnet device connected in shunt with the protector contacts so that it is energized as soon as the protector contacts open. The electromagnet device is provided with a pneumatic time delay for prolonging the resetting time. To do this, the armature operates within a cylinder substantially closed at one end and the armature acts as a piston within the cylinder. The movement of the armature is slowed down because the trapped air must pass through a metered orifice in the armature before the armature can move a sufficient distance to move the protector from the open position to the closed position for resetting.

In a second form, a similar bimetal overload protector device is provided which cannot reset itself. The resetting is only accomplished after two separate bimetal devices each are heated in succession and the second is used to reset the main protector elements. In a third form, a

similar bimetal overload protector is used which does not reset itself but the reclosing of this protector is prevented until another bimetal arrangement is heated and then when it cools, it resets the protector contacts. A fourth form is provided for three phase motors and if there is an overload in any of the phase conductors, this will cause one or two of the protector elements to trip open. The opening of one protector element will electrically cause the opening of the secondary protector element through the relationship between the phases in a three phase motor. The reclosing of both protectors is controlled by first the heating and then the recooling of an additional electrically heated bimetal element.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a diagrammatic view and wiring diagram of a thermally tripped magnetically reset overload protector embodying one form of my invention;

Fig. 2 is a diagrammatic view and wiring diagram of a thermal trip thermal reclosing overload protector embodying a second form of my invention;

Fig. 3 is a diagrammatic view and wiring diagram of a thermal trip single element thermal reset overload protector embodying a third form of my invention;

Fig. 4. is a diagrammatic view and wiring diagram of my invention particularly adapted for three phase motors; and

Fig. 5 is a fragmentary view illustrating the open circuit position of the protector shown in Fig. 4.

Referring now to the drawings and more particularly to Fig. 1, there is shown a motor circuit including supply conductors 20 and 22. The conductor 20 is connected by a control switch 24 to a conductor 26 connecting with the terminal 28 upon which is mounted a stationary protector contact 30. The entire protector apparatus may be mounted upon a base 21 of electrical insulating material. The conductor 22 connects directly to one of the terminals of an electric motor 32. While any size and type motors or any electric appliance may be used for the purpose of illustrating the invention, it is preferred to illustrate the invention by a large electric motor such as one taking 10,000 watts when stalled.

The second terminal of the motor 32 is connected by the conductor 34 to a terminal 36. The terminal 35 connects to a ribbon type heater 353, the other end of Which is connected along with the cantilever type main operating bimetal 4% to a wide U-shaped frame 42. The main operating bimetal 40 carries the movable primary contact 44 shown in Fig. l as being in engagement with the stationary contact 30. The free end of the operating bimetal 40 is connected by a C-shaped toggle spring 46 with the free end of a cantilever type compensating bimetal 48 anchored by an electrical insulating mounting to the opposite end of the U-shaped frame 42 from that which the main operating bimetal 40 is anchored.

When there is an excessive current flow,

flected in accordance with changes in environment temperatures to compensate for the effect of the changes in environment temperatures upon the main operating bimetal 40. The main operating bimetal 40 has suflicient travel that in the open circuit position it is carried beyond the adjacent end of the compensating bimetal 48 a suflicient distance that the angularity of the toggle spring 46 is sufficiently great that the mere cooling of the main operating bimetal 40 is not sufficient for it to overcome the opposing toggle force applied by the toggle spring 46.

The resetting of the main operating bimetal 40 is only accomplished by the electromagnet device 50. This device 50 includes an electromagnet coil 52 having one of its terminals connected by the conductor 54 to the conductor 34 on one side of the

protector contacts

30 and 44, while the second terminal of the coil 52 is connected by the conductor 56 to the conductor on the opposite side of the protector contacts and 44. Thus, as soon as the

contacts

30 and 44 are opened, the electromagnet coil 52 is energized. Because of the low Wattage required by the coil 52 no extensive wiring is required, but

a simple shunt connection is adequate since the i current is so low that it can be carried through the motor circuit Without any damage.

The electromagnet coil 52 is provided with an armature 58 slidably mounted within a cylinder 60 having its upper end closed by the yoke of the frame 42. Operating through a concentrically located aperture in the frame 42 is an operating pin 52. This operating pin 62 keeps the aperture in the frame 42 substantially closed. The armature 58 fits the cylinder 6!) Well enough that air is trapped between the top of the armature 53 and the top of the cylinder 60 which is formed by the adjacent portion of the frame 42.

The armature 58 is provided with a number of air passages 64 which extend through it from top to bottom. All except the central passage are closed by a normally closed check valve 66 provided on top of the armature. The central passage 68 also passes completely through the armature 50 from top to bottom but it also continues through the peg 12 on which the check valve 66 is mounted so that it is never closed by the check valve 66. The bottom of the cylinder 60 is provided with an adjustable threaded member I0 which is threaded into the bottom of the cylinder 60 so as to support the lower end of the armature 58 in any selected position when the electromagnet coil 52 is deenergized to adjust the reset time to various selected values. The threaded member I0 is provided with a large aperture to permit the movement of air into and out of the cylinder 60.

When the electromagnet coil 52 is energized by the opening of the

protector contacts

30 and 44, the armature 58 will be immediately attracted and a lifting force will immediately be present. The rapid lifting of the armature 58 is prevented, however, by the trapping of the air in the top of the cylinder 50. This air can only escape by leakage around and through the armature 58 as well as the pin 62. This rate is relatively slow and serves as a dash pot time delay for slowing up the movement of the armature 58. The central passage 68 and the leakage around the armature 58 and the pin 62 are sufiiciently slow that it takes several minutes before the armature 58 reaches its uppermost position. In this uppermost position, the peg 12 upon the top of the armature engages the pin 62 and moves the pin upwardly to engage and move the main operating bimetal from its open position to its closed position when the protector contact 44 is again in engagement with the stationary contact 30.

With this type of control, the tripping characteristics are governed entirely by the heating of the bimetal 40 and the elements which cooperate with it. The reclosing of the protector contacts and the main operating bimetal 40 is governed entirely by the characteristics of the electromagnet device which can be adjusted to vary the reset time by adjusting the threaded member 10. The tripping of the protector can be adjusted by bending either of the bimetals or by bending the ribbon heater 38 to provide varying tripping characteristics.

In the form shown in Fig. 2, no electromagnet device is used. The device may be mounted upon a base I27 of electrical insulation indicated diagrammatically by dot and dash lines. The device includes similar protector contacts I33 and I44. The contact I30 is mounted upon a terminal I28 connected by the conductor I26 and the switch I24 to the supply conductor l2i'l. The contact I44 is mounted upon the free end portion of the cantilever bimetal I40 which is anchored to the U-shaped frame I42. Similarly anchored to the frame I42 is a ribbon heater I38 extending parallel to and adjacent the bimetal I40. The ribbon heater I38 is connected to the terminal I3S which in turn is connected by the conductor I34 to one terminal of the motor I22, the other terminal of which is connected to the supply conductor I22. The C-shaped toggle spring I46 extends between the free end of the main operating bimetal I40 and the compensating bimetal I48. The position and characteristics of the compensating bimetal I48 and the toggle spring I46 are such that the main operating bimetal I40 will trip quickly to the open circuit position when a safe current flow is exceeded. However, these factors are also arranged so that when the main operating bimetal I40 does move to the open position, the bimetal I40 does not have sufficient power to move itself out of that position even though cooled.

To reset the main operating bimetal I40 after a long definite period of time, there is provided a resetting pin I 62 which is slidably supported by the frame I42 as well as the frames I and I80 which are likewise U-shaped. The frame IBI'I has mounted thereon a cantilever operating bimetal I52. Its free end is connected by the G-shaped toggle spring I54 to a cantilever type compensating bimetal I55 which is anchored to the lower end of the frame I60. The operating bimetal I52 carries a movable contact I58 adapted to cooperate and make engagement with a stationary contact I63. This contact IE3 is connected by a conductor to a ceramic type resistance heater I54 which is also connected to the frame I42. The U-shaped frame I69 is connected by the conductor I65 to the terminal I28.

By virtue of this arrangement, there is set up a shunt circuit across the contacts I30 and HM which includes the conductor I 56, the bimetal I52, the contacts I53 and IE3, the heater I64, the frame I42 and the operating bimetal I49. This shunt circuit is deenergized or shunted out whenever the contacts I38 and Hi l are closed. However, when the contacts I36 and 1M are open, full voltage is applied to this shunt circuit. This shunt circuit carries only a relatively small amount of current due to the presence of the ceramic heater Hi l. This heater I65 heats very slowly. In about three minutes of time after a sufficient quantity of electric current has passed through the heater IE4 it will heat the operating bimetal I52 suiiiciently to cause it to open. The opening of this operating bimetal I52 will cause its back contact I68 to engage the back contact IlI.

The back contact III is connected by a conductor I12 shown for the purpose of clarity in dotted lines to a contact I14. This contact I'M is normally engaged by a contact I16 provided upon the free end of an operating bimetal I78. This operating bimetal H8 is of the cantilever type and has one end anchored to the U-shaped metal frame I39. The free end. of the operating bimeta-l I18 is connected by the C-shaped toggle spring I82 to the free end of a compensating bimetal I34 anchored to the opposite end of the U-shaped frame I89. This last named operating bimetal I18 is of the self-resetting type. That is, it is capable of moving by the power of its bimetal to its original position after it has tripped to the open position. The operating bimetal I18 is connected electrically by a conductor to the ceramic resistor I88 which in turn is connected by the conductor I88 to the frame I42.

When suflicient current flows through the heater I38 and the operating bimetal Iii), the operating bimetal I43 will be heated sufiiciently to open the contacts I38 and I44 and move into I engagement with the adjacent end of the pin I62. The tripping of the operating bimetal I49 may be done by an overload in from two to four seconds. This energizes the ceramic resistance heater I64 which, after about three minutes, will have supplied sufficient heat to the operating bimetal I52 to cause it to open the contacts I58 and I52 and close the contacts Hi3 and ITI. This will energize the ceramic heater I86 and after about three additional minutes, the ceramic heater IBE will supply sufficient heat to the bimetal I78 that the bimetal Iiii will move to the open circuit position against the adjustable stop I96. At the same time the operating bimetal will engage the adjacent end of the pin I62 and cause the collar I92 which fixed to the pin I=I52 to move the operating bimetal 552 back to its original position and also cause the head of the pin I62 to move the main operating bimetal I40 to its original closed position thereby ac.-

complishing the resetting of the protector contacts after about six minutes. It will be seen that the tripping and the resetting of this protector are accomplished by separate mechanisms and they may be separately selected and the trip and reset time for each may be selected independently of each other.

In Fig. 3, there is shown a similar tripping and resetting unit which may be mounted on a base 221 of electrical insulation indicated by dot and dash lines. The unit includes a U-shaped frame 242 which, at the one end carries the ribbon heater 238 and the main operating biinetal 246. The other end of the frame 242 carries the canti lever type compensating bimetal 255. The C- shaped toggle spring 246 is connected between the free ends of the bimetals 24B and 256. The main operatin bimetal 249 carries the movable contact 244 whil the stationary contact 230 with which it makes engagement is mounted upon the terminal 228. This terminal 223 is connected by the conductor 226 to the switch 224 in turn connected to the supply conductor 226. 'The ribbon heater 238 is connected to the terminal 235 connected by the conductor 234 with the motor 232 connected to supply conductor 222. The main operating bimetal 24!! is provided with operating characteristics similar to the operating bimetals 4i? and MG so that it will trip upon an overload in from two to four seconds but it is not capable of resetting itself. Slidably mounted in the frame 252 and the frame 260 is a resetting bar 262. This resetting bar 2552 is guided by projections 243 on the frame 242 and the projections 25% on the frame 255 The resetting bar 262 is provided with a shoulder 263 engaged upon the opening movement by the free end of the main operating bimetal 242 to carry it to the right. This movement is limited by the notch 265 provided in the bar 262 which cooperates with the projection 259 for limiting the movement of the bar 262 in either direction.

The terminal 228 is connected by the conductor 2% to the stationary contact 25?. This stationary contact 257 is normally contacted by the contact 258 carried upon the movable end portion of a cantilever type operating bimetal One end of the main. operating bimetal 252 is anchored to the lower end of the frame while the other end is connected by a C-shaped toggle spring 255 to the cantilever type compensating bimetal 235. The anchored end or the operating bimetal 252 is connected by an electric conductor to the ceramic resistance heater 264 in turn connected to the frame 222.

This arrangement connects the conductor 2% to contacts 251 and 253, the bimetal 252 and the ceramic resistance heater 264 as well as the frame 242 and the bimetal 259 in shunt circuit arrangement across the main protector contacts 244 so that whenever these circuits are closed the shunt circuit will. be deenergized; whereas when opened, the shunt circuit is fully energized. Because of the ceramic high resistance heater in the circuit only a small amount of electric energy flows when the protector contacts and 244 are open. This slowly heats the operating bimetal 252 so that it takes about three minutes for this operating bimetal 252 to move to the open position against the reset stop screw following the tripping of the main operating bimetal 2%. Prior to the time that the operating bimetal 252 moves to itsopen circuit position, its free upper end supports the end of a trigger lever 292 pivoted by a pin 25 to the bar 252 directly beneath the free end of the main oper ,7 ating'bimetal 240. The trigger lever 292 has an arm 233 extending upon the opposite side of the free end of the-main operating bimetal 249 from the shoulder 253. There is provided about a thirty-second. of an inch gap between the arm 293 and the shoulder 263.

As described previously, when the main oper ating bimetal 240 trips to the open circuit position it engages the shoulder 263 and carries the reset bar 262 to the left until the shoulder at the one end of the notch 265 engages the projection 259. There ensues a heating period of about three minutes after which the operating hinietal 252 trips to its open circuit position into contact with its resetting stop screw 2%. At this time the extreme upper end of the operating bimetal has moved beyond the end of the trigger lever 29?. so that this. end of the trigger lever then drops down into the position vacated 11- 1 the free end of the operating biinetal The operating bimetal 252 and the ceramic resistance heater 2554 then. slowly cool. Alter aoout three minutes, the operating bimetal ha" ac quired sufficient force due to cooling that it powerful enough to overcome the resistance or" the toggle spring 254i as well as the toggle coin.-

pcnents oi the main operating bimetal P to move the main. operating bimetal 2% to it -scrl position. to complete the resetting cperati soon the resistance to the closing mov it ceases, the operating bimetal wi ctrio energy from the supply conductors 3 and The supply conductor connect-s o ectly to the motor 3%. The supply conductor 224, however, connects with a terminal connecting to one end of a ribbon heater The opposite end of the ribbon heater is connected to the U-shaped frame 332 which also supports the anchored end of an operating bimetal 334. The free end of this operating bimetal 33% carries a dual contact which is normally in engagement with the stationary contact 333 connected to the terminal 34%. The terminal will is connected by the conductor to the central terminal of the three phase motor The free end of the main operating bimctal 334 is connected .by a C-shaped toggle spring 3 14 through the compensating loimetal anchored to the opposite end of the U-shaped frame The supply conductor 326 is connected to a terininal fiat connecting to one end of a ribbon type heater The other end of the ribbon type heater 3553 is connected to the U-shaped frame This frame also carries a cantilever type main operating bimetal 354 carrying near its free end a dual contact 355 which is normally in engagement with the stationary contact 3 53 connected to the third terminal of the three phase motor 320. The free end of the operating bimetal 354 is connected by a C-shapcd toggle spring 364 with the free end of a cantilever type compensating bimetal 3B6 anchored to the lower end of the U-shaped. frame 352.

Both of these overload protecting devices are the type which rapidly trip to the open circuit position upon-an overload within two to four seconds. Their toggle arrangement is such that they will not reset themselves. If there is an overload in one of the conductors, for example, either the

conductor

342 or 362, its protector will quickly trip to the open circuit position in from two to four seconds. This :will then efiectively provide the motor 328 with a current supply which is the equivalent of only a single phase supply which will throw an additional load upon the

supply conductors

322 and 362 which will rapidly cause the operating bimetal 354 to move to its open circuit position.

When the operating bimetal 334, because of an overload in the conductor 342, trips to the open circuit position, the contact 336 will engage the back contact 338. This back contact 368 is connected by a conductor strip 376 to a terminal 312 connected by the conductor 3H with a terminal 316. When an overload in the conductor 352 causes the operating bimetal 354 to trip to the open circuit position, the dual contact will engage the back contact 31S connected by a conductor strip 330 with a terminal 382. This terminal 382 is connected by the conductor with a terminal 386. The terminal 335 is connected by a conductor strip with the frame 333 of the reset operating mechanism. The upper end of this U-shaped frame 388 carries the anchored end of a cantilever operating bimetal sen carrying the movable contact 392. This contact 39?. is adapted to be normally in engagement with a contact provided upon the adjacent end of the terminal This terminal 394 is connectedto another terminal 396. Connected between the terminals and 395 is a ceramic electric high resistance heater 3% located adjacent the reset operatin bimetal 390 in heat transfer relationship therewith. The reset operating bimetal 39?] is connected by a C-shaped toggle spring 42% with the free end of a cantilever type compensating bimetal 422, anchored by an insulating mounting to the lower end of the frame 388.

Each of the frames 332, 35?? and are provided with similar bearing members 524, 526 and 428 which slidably support the reset operating bar 430 made of a suitable electrical insulation material. This bar 430 is provided with a stop pin 432 for limiting its movement to the left. It is also provided with a notch 434 which receives the free end of the main operating biinetal 334. The reset bar 430 has a single notch 436 for receiving the free end of the main operating bimetal 354. The opposite side of the bar 438 also has an additional notch 438.

When both of the operating bimetals 334 and 354 trip to the open circuit position, the bar 438 will be moved to the left with a stop pin 432 against the bearing member 424 as shown in Fig. 5. At the same time, the contact 336 wil1 engage the contact 338 and the contact 355 will engage the contact 378. This will close the circuit which includes the conductor 324, the ribbon heater the bime-tal 334, the contacts 335 and 383, the conductor strip 3'10, the conductor 314, the ceramic heater 338, the contact 3il2, the bimetal 35 i}, the conductor 334, the conductor strip 380, the contact 3T8, the bimetal 354, the ribbon heater are and the conductor 326. The circuit will energize the ceramic heater 398 while the motor 326 will be deenergized. After a period of time, such as three minutes, for example, the ceramic heater 398 and the reset operating bimetal 399 will be heated sufiiciently to move the contact 392 away from the contacton the terminal 394. This will cause the bimetal 390 to move with a snap action into contact with the adjustable stop screw 440.

It will also cause the bimetal 390 to move substantially into engagement with the adjacent end of the reset bar 430.

The extreme end portion of the reset bimetal 499 is provided with a hook-shaped extension 3! which is a sufficient distance in the direction perpendicular to the blade 490 and has a sumcient hook at its end to engage the notch 438 in the bar 430 as shown in Fig. 5 when it is at its tripping temperature. There now ensues a cooling period during which the bimetal 39c and the ceramic heater 398 slowly cool. This takes a constant period of time such as three minutes before the bimetal 390 acquires sufiicient power to overcome the toggle spring 420 and the toggle force connected with the

bimetals

334 and 356 to move the bar 36 to the right to the original position shown in Fig. 4 to reset the bimetals 334 and 35d. At the same time, the bimetal 390 will have sumcient power to overcome its own-toggle spring 320 and return to its closed circuit position shown in Fig. 4. The bimetal 390 and its heater 398 and its toggle arrangement is sufficient as to provide slow tripping and slow return while the

bimetals

334 and 354 and the toggle mechanisms are of such characteristics as to provide quick tripping without being capable of resetting themselves. This arrangement provides excellent protectors for three phase motors which are usually made in very large sizes and therefore require a protector with a very quick trip and a very long resetting time.

It should be noted that all forms are compensated for variations in the environment temperature. In each of the forms, the current required for the resetting device is so low that it can be carried through the motor circuit Without any damage thereby making possible the use of a simple shunt connection and therefore no extensive wiring is required.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. A current overload protector for an electric circuit having an independent quick tripping mechanism and an independent slow resetting mechanism timed entirely independent of the tripping mechanism including a snap acting toggle switch means having a toggle means for biasing it into either the open or closed position, said switch means including current responsive means responsive to an overload in said circuit for causing movement from the closed to the open position upon a quantitative current flow, and a current operated timing means normally disconnected from said switch means and said current responsive means and connected only for moving said switch means from the open position to the closed position, said timing means having a timing arrangement energized in response to the opening of said switch means for timing the movement of said switch means from the open to the closed position entirely independently of the tripping time.

2. A current overload protector for an electric circuit having an independent quick tripping mechanism and an independent slow resetting mechanism timed entirely independent of the tripping mechanism including a snap acting toggle switch means having a toggle means for biasing it into either the open or closed position, said switch means including current responsive means responsive to an overload in said circuit for causing movement from the closed to the open position upon a quantitative current flow, a snap acting bimetal means normally disconnected from said switch means and said current responsive means, means for heating said bimetal means in response to the opening of said switch means, and means operated by said bimetal means for moving said switch means from the open position to the closed position.

3. A current overload protector for an electric circuit having an independent quick tripping mechanism and an independent slow resetting mechanism timed entirely independent of the tripping mechanism including a snap acting toggle switch means having-a toggle means for biasing it into either the open or closed position, said switch means including current responsive means responsive to an overload in said circuit for causing movement from the closed to the open position upon a quantitative current flow, a snap acting thermally operable switch means normally disconnected from said toggle switch means and said current responsive means, an electric heating circuit portion arranged in heat transfer relationship to said thermally operable switch means and connected in shunt circuit relationship to said toggle switch means for opening said thermally operable switch means in response to the opening of said toggle switch means, and means controlled by said thermally operable switch means for closing said toggle switch means.

4. A current overload protector for an electric circuit having an independent quick tripping mechanism and an independent slow resetting mechanism timed entirely independent of the tripping mechanism including a snap acting to gle switch means having a toggle means for biasing it into either the open or closed position, said switch means including current responsive means responsive to an overload in said circuit for causing movement from the closed to the open position upon a quantitative current flow, a snap acting thermally operable switch means normally disconnected from said toggle switch means and said current responsive means, an electric heating circuit portion arranged in heat transfer relationship to said thermally operable switch means and connected in shunt circuit relationship to said toggle switch means for opening said thermally operable switch means in response to the opening of said toggle switch means, a second snap acting thermally operable switch means having means effective upon its opening movement for reclosing said toggle switch means, and a second electric heating circuit portion arranged in heat transfer relationship to said second thermally operable switch means and connected in shunt circuit arrangement to said first mentioned thermally operable switch means for opening said second thermally operable switch means.

5. A current overload protector for an electric circuit having an independent quick tripping mechanism and an independent slow resetting mechanism timed entirely independent of the tripping mechanism including a snap acting switch means having current responsive means responsive to an overload in said circuit for causing its movement from the closed position to the open position upon a quantitative current flow, means normally disconnected from said switch means and said current responsive means, for

delaying the reclosing of said switch means including a thermally operable means and an electrically energized heating means, means for energizing said heating means when said switch means moves to the open position, means for deenergizing said heating means when said thermally operable means is heated, and means operated in response to the cooling of said thermally operable means for assisting in the reclosing of said switch means.

6. A self-resetting current overload protector for an electric circuit having an independent quick tripping mechanism and an independent slow resetting mechanism timed entirely independent of the tripping mechanism including a current responsive tripping mechanism responsive to an overload in said circuit for opening the protector upon a quantitative current flow and a separate independent timing resetting mechanism operable in response to the tripping of said tripping mechanism for resetting said protector after a measured period of time.

'7. A current overload protector for an electric circuit having an independent quick tripping mechanism and an independent slow resetting mechanism timed entirely independent of the tripping mechanism including a snap acting toggle switch means having a toggle means for biasing itinto either the open or closed position constituting the sole restraining means in the operation of the switch means, said switch means including current responsive operating means responsive to an overload in said electric circuit for causing movement without restraint except for the toggle means from the closed to the open position upon a quantitative current flow, and a timing resetting means normally disconnected from said toggle switch means and said operating means, said timing resetting means including an electrically powered reset- 12 ting means connected in electrical shunt circuit arrangement with said switch means and having means effective only when the switch means is 'in the open position for engaging and moving.

said toggle switch means from the open position to the closed position.

8. A current overload protector for an electric circuit having an independent quick tripping mechanism and an independent slow resetting mechanism timed entirely independent of the tripping mechanism including a snap acting toggle switch means having a toggle means for biasing it into either the open or closed position constituting the sole restraining means in the operation of the switch means, said switch means including current responsive operating means responsive to an overload in said electric circuit for causing movement without restraint except for the toggle means from the closed to the open position upon a quantitative current flow, and a timing resetting means normally disconnected from said toggle switch means and said operating means, said resetting means including a snap acting bimetal means and a resetting actuator engageable with said switch means only when said switch means is in the open position, said resetting means also including an electric heating circuit for said bimetal means connected in shunt circuit arrangement with said switch means.

MARSHALL C. HARROLD.

REFERENCES CITED The following references are or" record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,684,709 Lowenstein Sept. 18, 1928 2,446,474 Harrold Aug. 3, 1948 2,490,103 Stilwell Dec. 6, 1949