US2501155A - Thermostatic circuit breaker - Google Patents

Description

. Filed May 4, 19 44 March 21, 1950 J. D. BOLESKY 2,501,155

THERMOSTATIC CIRCUIT BREAKER 5 SheetsSheet l FIG .7.

March 21, 1950 J. D. BOLESKY 2,501,155

'I'HERMOSTATIC CIRCUIT BREAKER Filed May 4, 1944 s Sheets-Sheet 2 FIG.4.

March 21, 1950 J. D. BOLESKY THERMOSTATIC CIRCUIT BREAKER 5 Sheets-Sheet 5.

Filed May 4, 1944 March 21, 1950 J. D. BOLESKY 2,501,155

THERMOSTATIC CIRCUIT BREAKER Filed May 4, 1944 5 5 Sheets-Sheet 4 2f 1 28 FIG. l5. FIG. l8? 1 a Patented Mar. 21, 1950 UNITED STATES PATENT OFFICE THERMOSTATIC CIRCUIT BREAKER John D. Bclesky, Attleboro, Mass, assignor to Metals & Controls Corporation, Attleboro, Mass., a corporation of Massachusetts Application May 4, 1944, Serial No. 534,092

13 Claims. 1

This invention relates to circuit breakers and more particularly to thermostatically controlled circuit breakers.

Among the objects of this invention are the provision of improved thermostatically controlled circuit breakers; the provision of circuit breakers which are controlled by a thermostatic member. but do not rely upon the movement of contacts attached to said thermostatic member to interrupt a circuit, the provision'of circuit breakers controlled by thermostats but in which the thermostat need not carry the entire current in the circuit; and the provision of circuit breakers of the type indicated which operate efiiciently and which last for long periods of time. Other objects will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

Referring to the drawings in which are illustrated several of the possible embodiments of the present invention.

Fig. 1 is a side elevation ofone form of the invention, a cover part being in section;

Fig. 2 is a vertical section of the Fig. 1 device, parts being shown in elevation;

Fig. 3 is a right-end elevation, cover parts being broken away;

Fig. 4 is a horizontal section taken along the line 4-4 on Fig. 2;

Fig. 5 is a horizontal section taken along the line 5-5 on Fig. 2;

Fig. 6 is a view similar to Fig. 2 but showing parts in different positions;

Fig. 7 is a vertical section taken along the line ll. in Fig. 1;

Fig. 8 is a top plan of another embodiment of the invention;

Fig. 9 is a side elevation of the Fig. 8 embodi ment;

Fig. 10 is an end elevation of the Fig. 8 embodiment;

Fig. 11 is a vertical section taken along the line H-H on Fig. 8;

Fig. 12 is a vertical section taken along the line 12- on Fig. 8;

Fig. 13 is a view similar to Fig. 12 but with parts in different positions;

Fig. 14 is a section taken along the line ll-ll on Fig. 9;

Fig. 15 is a top plan view of another embodiment of the invention;

Fig. 16 is a front elevation of the Fig. 15 embodiment;

Fig. 17 is a rear elevation of the Fig. 15 embodiment;

Fig. 18 is a right-end elevation of the Fig. 15 embodiment;

Fig. 19 is a left-end elevation of the Fig. 15 embodiment;

Fig. 20 is a vertical section taken along line 2020 on Fig. 15;

Fig. 21 is a view similar to Fig. 20 but with parts in different positions;

Fig. 22 is a fragmentary view similar to Figs. 20 and 21 but with parts in other positions;

Fig. 23 is a horizontal detail section taken along the line 23-23 on Fig. 20; and

Fig. 24 is a perspective view of a cam operating member of the Fig. 15 embodiment.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

Referring now to the Figs. 1-7 embodiment, numeral I is a rectangular case surrounding the principal parts of the structure, being covered by a top 3. The main circuit connections are made to terminals 5 and I. A bus bar 9 connects terminal! with a contact H. Contacts H and 15 may be bridged by bar ll having contacts I! and 2| on its opposite ends. Terminal 5 and a bus bar 13 are not directly connected to one another. Terminal 5 is on a post 23 which extends through but is electrically insulated from a cylinder 25. Extension plate 21 is attached to cylinder 25 and carries a contact or line terminal 29. The end of post 23 acts as another contact or line terminal 3| insulated from 21. A dished snap-acting thermostat disc 33, of the type disclosed in Spencer Patent 1,448,240, is located above plate 21, and carries adjacent its periphery contacts 35 and 31 which freely engage contacts 29 and 3| so that the disc bridges the latter. The path of the current in the main circuit when closed is accordingly from terminal I to bus bar 9, contact H, contact 2|, bar [1, contact I9, contact I5, bar I3, cylinder 25, plate 21. contact 29, contact 35, disc 33, contact 31, contact 3|, post 23 to terminal 5.

Bar I1 is mounted on an insulating cross-bar 39 having a narrow central portion 4| and a wider lower portion 43. Member 39 is mounted upon a post 45. Post 45 carries sliding cylinder 41 which is spaced from member 39 by a collar 49. The bottom of post 45 is enlarged, as shown at 5|, to the approximate size of the upper part of the opening 53 in cylinder 41. Between end 5| of post 45 and the top 55 of cylinder located a coil spring 51.

The opening 53 in cylinder 41 is enlarged at the lower section to receive another coil spring 59 which is seated in another cylinder 6|. The spring 59 supports cylinder 41. Post 45 slides in cylinder 41 and collar 49, and cylinder 41 slides in an outer cylinder 63. Cylinder 41 is made of brass or some similar non-magnetic metal while post 45 is of iron or some other magnetic metal.

Surrounding cylinder 63 is a solenoid coil 51 to which current is conducted by leads 69 and 1|. An outer case 13 covers the assembly. It is attached to bottom 65 of case I by bolts 15. Cylinder 5| is attached to bottom plate 11 of outer case 13 through a headed portion 19. Bus bars 9 and I3 are attached to a supporting insulating base 8| by screws 83.

Disc 33 is loosely mounted at the central portion thereof on a post or stem 05 which has a groove 81 for this purpose. Post 85 has a hollow central portion to accommodate a plug 89 and is slidably mounted in an upper insulating support shelf 9|. Shelf 9| has an opening 93 for this purpose, of which the lower portion 95 is enlarged to make room for a coil spring 91. This coil spring is located between the top of enlarged portion 95 and a shoulder 99 on post 95 and biases the disc bodily toward contacts or line terminals 29 and 3|. Guide pins I| are attached to shelf 9| and project through suitable openings in disc 33, to prevent rotation thereof without interfering with its action.

Mounted above shelf 9| is a strip I03 constituting the movable contact member of a holding switch for the solenoid. This has ears I for mounting on brackets I01 which are attached to shelf 9|. One end of strip I03 carries terminal I09 below which is a coil spring III. Spring III is supported by a cylinder 3 having a headed over-portion H5 and which projects through an opening in shelf 9|. The other end of strip I03 carries contacts H1 and 9 on opposite sides thereof. Bracket |2I is likewise attached to shelf 9| and is bent to form a U over strip I03. A contact I23 is attached to this bracket in position to cooperate with contact II1. A contact I25 is mounted on shelf 9| in position to cooperate with contact II9. A terminal I21 is attached to contact I25. A terminal I29 is attached to terminal I09 by a pigtail conductor I3I.

A terminal I33 is connected to contact I23 through bracket |2| and a conductor I35. Lead 1| to solenoid 61 is connected electrically to terminal I33 through post I31. Lead 59 is attached to a terminal I39.

The bar I1 is made of a number of laminations of beryllium copper soldered on each end for electrical conductivity. The laminations are not soldered over the entire area of the adjacent surfaces. 15 laminations of about .009 of an inch thick are, employed (see Fig. 7). The bar I1 can be made of a solid piece of metal if preferred and if the advantages of lamination are not desired.

Cross-bar 4| is held in position by two guide posts |4| attached to shelf 3| and plate 21. Posts |4| are made larger at portions I43 than at portions I45. Cross-bar 4| rides on posts I only up to portions I43 which act as stops.

The operation of the device is as follows: Figs. 1 and 2 show the position of the device when there is no current passing through the circuit and when thermostatic disc 33 is cold. Assume now that current is passed through the circuit between terminals 5 and 1 and simultaneously through the holding circuit between terminals I29 and I39 (see I29, I3I, I09, I03, II1, I23, I2I, I35, I33, I31, 1|, solenoid 01, 69, I39). The current through the holding circuit energizes solenoid 91 thereby closing the main circuit by pulling down bar I1 until contacts 2| and II, and I9 and I5 respectively contact each other. It has been found that by the use of laminations in the manufacture of bar I1, the tendency for the bar and its contacts to bounce when the plunger seats and spring 59 is compressed, is substantially decreased.

The path of the main current it will be noted passes through disc 3. The disc, when cold, has the normal form illustrated in Fig. 2 with its center bowed upward. When heated by flow of overload current therethrough, it snaps to the oppositely bowed form of Fig. 6. This lowers plug 89 which had previously maintained contacts H1 and I 23 together, permitting strip I03, under the bias of spring III, to bring contacts 9 and I25 together. This breaks the circuit through holding coil 51, and spring 59 thereupon separates contacts I9 and 2| from contacts I5 and II respectively.

The current through the main and the holding circuits may be the same or difl'erent value. Thus terminals 5, 1, I29 and I39 may all be connected to the same source of power, or terminals 5 and 1 may be connected to one source of power and terminals I29 and I39 to another source of power. Although the present circuit breaker will interrupt a heavy current passing between terminals 5 and 1, the holding circuit need carry only a small current.

It will be noted that while the disc 33 snaps from its normal bowed form of Fig. 2 to its oppositely bowed form of Fig. 6 when heated by overload current, it remains in bridging engagement with the terminals 29 and 3| after snapping. This is because the disc is biased bodily toward the terminals by the spring 91, which acts to restrain the periphery of the disc against movement away from 29 and 3|. While the disc contacts 35 and 31 may disengage momentarily from contacts 29 and 3| as the disc snaps, spring 91 quickly drives the disc downward to re-engage the contacts.

Referring now to Figs. 8-14 a different embodiment of the invention is shown. A case I41 is made up of two sections, a top segment I49 and a bottom segment I5I. Mounted in the bottom segment |5I by means of an adjustable center pin I53 is a dished, snap-acting thermostatic disc I55 similar in function to disc 33 of the previous embodiment. This disc carries adjacent its periphery contacts I51 which freely engage contacts or line terminals I59 located in case segment I5I. Disc I55 is elongated at the area of contacts I51. Case segment I5I contains an area |6| of the same shape and only slightly larger than the disc I55. The elongated portions 5 I83 the area I8I enclose the elongated portions or the disc I55 to prevent it from rotating.

In case segment I49 are located U-shaped hollow cylinders I85 in which are coil springs I61.

These act against the disc at points adjacent its periphery to bias the disc bodily toward the terminals I59. Also located in segment I49 is a resilient movable contact member I69 having contacts HI and I13 on opposite sides thereof. Cooperating contacts I15 and I11-are located opposite and cooperate with contacts HI and I13 respectively. Contact member I69 is attached electrically to terminal I19 and is biased away from contact I15 toward contact II1. Contacts I15 and I11 are electrically attached respectively to terminals I8I and I83.

Disc I55 is loosely mounted on center pin I53 through post I85. Post I85 is slidably mounted in center pin I53 and holds the disc between shoulder I81 and headed over-portion I89.

The two parts I49 and II of case I41 are held together by bolts I9I. A pin I93 is attached to member I69 to provide a mechanical link between disc I55 and member I89.

The stationary contacts or line terminals I59 are connected by posts I95 to terminals I91. The circuit from one terminal I91 to the other terminal I91 is accordingly from one terminal I91, one post I95, one contact I59, one contact I51, disc I55, other contact I51, other contact I59, other post I95 to the other terminal I91.

The circuit which includes terminals I19, I8I and I83 is controlled by the position of member I69 which in turn is controlled by the position of thermostat I55. Assuming now that thermostat I55 is in the Fig. 11 position, member I69 is forced upward so that contacts HI and I15 are together (see also Fig. 13). When thermostat I55 has snapped to its position of opposite curvature the pressure on member I89 is relieved and this member assumes the Fig. 12 position wherein contacts I13 and I11 are together.

When the contacts HI and I15 are together the circuit closed is as follows: Terminal I8I to contact I 15, contact I1I, member I59, terminal I19. When the device is in the Fig. 12 position the circuit closed is from terminal I83 to contact I11, contact I13, member I59 to terminal I19.

The operation of the device is as follows: The circuit from one terminal I91 to the other terminal I91 passes through disc I55. If this current reaches a dangerously high level disc I55 is heated so that it snaps from the Fig. 13 position to the Fig. 12 position. This snapaction breaks the circuit from terminal I8I to terminal I19 and makes the circuit from terminal I83 to terminal I19. The snapping of disc I55 from one position of curvature to another does not 0perate to break the circuit between terminals I91. The disc center merely moves downward carrying with it post I85 which is slidably mounted, as stated previously, in threaded post I53. Disc contacts I51 remain in engagement with line terminals I59 after the disc has snapped. The

. shoulder I81 on post I85 operates as a stop but is not located so that the circuit through the disc is broken by the snapping of disc I55. Post I85 has an enlarged portion I99 on the end opposite I 89 which operates as a stop when the disc snaps in the opposite direction.

The location of the disc is controlled by the adjustment of threaded post I53. screwin this post in or out changes the location of shoulders I81 and I99, and thereby aflects the snapping temperature of disc I55.

Referring now to Figs. 15-24 another alternative form of the invention is disclosed which is particularly applicable to circuit breakers which are intended for interrupting heavy currents.

A main base 20I of insulating material provides a mount. On this base are mounted contact plates 203 and 205. On these plates are respectively contacts 291 and 209. A bus bar or contact member 2 carries contacts 2I3 and 2I5 which cooperate with contacts 201 and 209 respectively. Bar 2 is mounted on post 2I1 and is loosely held thereon between the cylinder 2I9 and handle 22I by means of spring 223 (see Fig. 21). Handle 22I screws on a threaded extension 225 of post 2I1. The various partsreferred to are kept in alignment by bracket 221 which has a suitable opening to accommodate handle 22I.

A guide post 229 is attached to base 20I and bracket 221 and cooperates with a finger member 23I attached to bar 2. This finger member and post 229 maintain the bar 2 and its contacts 2I3 and 2I5 in position to meet contacts 20'! and 209 when the device is in the position shown in solid lines in Fig. 16. The post 2I1 is bolted to a cam member 233. Member 233 has cam shaped openings 235 on opposite sides thereof which cooperate with a follower or detent 231. Member 233 slides in a channel 239 which is bolted to base 29I as shown at 24I. Follower 231 is held in a slot 243 on each side of the channel 239. Follower 231 can move either up or down said channel in response to the cam action of 235. It will be noted that cam 235 has a notch 245 providing a latch element at the end nearest post 2I1. This holds follower 231 when the device is in the position shown in Fig. 17, for example. Springs 241 attached to a bar 249 at one end thereof, which bar 249 is bolted to the member 233, and to the base 20I by a hook mem- -ber 25I, tend to move the cam to the position shown in Fig. 21. Terminals 253 attached to bus bar 255 are connected to bus bar 251 through heater 259. Bus bar 251 is connected to contact plate 295 by a projecting portion which extends through base 20I and to which plate 205 is bolted, as shown at 26I.

Terminals 263 are attached to bus bar 265, a projecting portion of which passes through base 20I and to which plate 203 is bolted, as shown at 264.

It will be seen that the current passes through terminals 253, bus bar 255, heater 259, bus bar 251, plate 205, contact 209, contact 2I5, bar 2, contact 2I3, contact 201, plate 203, bus bar 265 to terminals 263.

Follower 231 has attached thereto a central post 261 on which is mounted a thermostatic disc 269. This disc is similar to disc I55 shown in the previous embodiment. To opposite points on the disc are attached contacts 2' and 213 which cooperate with contacts or line terminals 215 and 211 attached respectively to bus bars 251 and 255. The disc 269 therefore shunts the heater 259, but because of the relative current capacities thereof the disc 269 carries only a relatively small proportion of the current.

Insulating shields 219 and 28I are preferably provided to surround the contacts 21I, 213, 215 and 211. These shields are held on respectively by bolts 280 and 282. They restrain the periphery of disc 269 against movement away from line terminals 215 and 211.

A manual release button 283 is located close to the handle 22I and is mounted on an extension 235 of bracket 221. Button 233 is attached to post 231 which passes through an opening in extension 235, the foot of bracket 221, and base 20I, to project to the other side of base 20L Channel 239 carries a supporting bracket 299 which is rectangular in shape with an opening 29! therein. This bracket 289 likewise supports a cross pin 293 which has an extending tongue 295, the end of which lies against the end of post 291. Pin 293 extends through both sides of bracket 209 and on each end is mounted a crossbar 291. These cross-bars carry at their ends, opposite to that at which they are attached to pin 293, pins 299 to which are attached links 30!, the other ends of which are attached to follower 231. Pushing button 283 in will, through the linkage described, push follower 231 out of notch 245, whereupon springs 241 can pull the cam assembly to the Fig. 21 position.

The operation of the device is as follows: Contacts 201 and H3, and 209 and 2|5 are closed by pushing handle 22! down. This closes the circuit through bar 2, tensions springs 241 and seats follower 231 in notch 245. The passage of current through heater 259 heats thermostatic disc 269. When the current passing reaches an undesirable high, disc 269 snaps thereby raising follower 231, which is attached to the center of disc 269, out of notch 245. The springs 241 thereupon return the device to the Fig. 21 position. This opens contacts 201 and 213, and 209 and H5. If the device is in the Fig. 20 position, the circuit can be opened by pressing on knob 283.. As explained previously, this raises follower 231-out of notch 245 thereby permitting springs 241 to return the device to the Fig. 21 position.

Since disc 269 is in shunt with heater 259 the disc carries only a small proportion of the current, yet receives the heating effect of the entire current. It will be noted that when thedisc snaps from its Fig. 20 to its Fig. 22 position, disc contacts 2H and 213 remain in engagement with line terminals 215 and 211.

Cross-reference under Rule 43 is made to applicants divisional application, Serial No. 633,239, filed December 6, 1945.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above construct-ions without departing from the scope of the invention, it is intended that all matt r contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a thermostatic circuit breaker, a support, line terminals on the support, a dished, snapacting thermostatic disc having contacts on one face thereof adjacent its periphery freely engaging said terminals, said disc having a normal form bowed in one direction and adapted to snap to an oppositely bowed form upon heating in response to flow of overload current therethrough, means independent of the line terminals holding said disc in place on the support with its periphery restrained against movement away from the terminals but free of the support and terminals and with its center free to snap so that its contacts remain in engagement with the terminals in either of its oppositely bowed forms, a switch mounted on the support, and means operable by the center of the disc for operating the switch.

2. In a thermostatic circuit breaker, a support, line terminals on the support, a dished, snapacting thermostatic disc bridging said terminals, said disc having a normal form bowed in one direction and adapted to snap to an oppositely bowed form upon heating in response to flow of overload current therethrough, said disc being mounted on the support for axial movement toward and away from the terminals, means biasing the disc bodily toward the terminals so that the disc bridges the terminals in either of its oppositely bowed positions, the center of the disc being free to snap and its periphery being free of the support and terminals, a switch mounted on the support,.and means operable by the center oi the disc for operating the switch.

3. In a thermostatic circuit breaker, a support, line terminals on the support, a dished, snap-acting thermostatic disc bridging said terminals having a normal form bowed in one direction and adapted to snap to an oppositely bowed form upon heating in response to flow of overload current therethrough, said disc being. mounted on the support for axial movement toward and away from the terminals with its periphery free of the support and terminals, at least one spring biasing the disc bodily against the terminals so as to hold it in engagement with the terminals in either of its oppositely bowed forms while permitting its center to snap, a switch mounted on the support and means operable by the center of the disc for operating the switch.

4. In a thermostatic circuit breaker, a support, line terminals on the support, a dished, snapacting thermostatic disc having contacts adjacent its periphery freely engaging said terminals, said disc having a normal form bowed in one direction and adapted to snap to an oppositely bowed form upon heating in response to flow of overload current therethrough, the disc being mounted for bodily movement toward and away from the terminals by means of a stem fixed to the center oi the disc extending axially therefrom and slidable in the support, a spring biasing the disc toward the terminals to hold the disc contacts in engagement with the terminals when the disc is in either its normal form or oppositely bowed form, the center of the disc being free to snap, and a switch mounted on the support having a movable contact member biased away irom a normal non-overload position, said stem engaging said contact member when the disc is in its normal form to hold the contact member against its bias in non-overload position.

5. A circuit breaker comprising a support, line terminals on the support, a dished, snap-acting thermostatic disc freely bridging said terminals, said disc having a normal form bowed in one direction and adapted to snap to an oppositely bowed form upon heating in response to flow of overload current therethrough, said disc being mounted on the support with its periphery free 0! the support and terminals to remain in position freely bridging the terminals in either of its oppositely bowed forms and with its center free to snap, a solenoid switch mounted on the support and connected in series through the terminals with the disc, and a holding switch for the solenoid mounted on thesupport and connected in a holding circuit for the solenoid, said holding switch being operable by the center of the disc to open to deenergize the solenoid upon snapping of the disc in response to flow of overload current therethrough.

6. In a thermostatic circuit breaker, a support,

line terminals on the support, a dished, snapacting thermostatic disc having contacts adjacent its periphery freely engaging said terminals, said disc having a normal form bowed in one direction and adapted to snap to an oppositely bowed form upon heating in response to fiow oi overload current therethrough, a stem fixed to the center of the disc extending axially therefrom and being slidable in the support to carry the disc for movement toward and away from'the terminals, a spring biasing the disc toward the terminals to hold the disc contacts in engagement with the terminals when the disc is in either its normal form or oppositely bowed form, the center of the disc being free to snap, a solenoid switch mounted on the support and connected through the terminals in series with the disc, and a holding switch for the solenoid mounted on the support and connected in a holding circuit for the solenoid, said holding switch .having a movable contact member biased away from a normal holding-circuit-closing position, said stem engaging said contact member when the disc is in its normal form to hold the contact member against its bias in holding-circuit-closing position.

'7. A circuit breaker comprising a support, line terminals on the support, a dished, snap-acting thermostatic disc having contacts adjacent its periphery freely engaging said terminals, a stem fixed to the center of the disc extending slidably through an aperture in the support and carrying the disc for movement toward and away from the terminals, springs acting against the disc at points adjacent its periphery to bias the disc bodily toward the terminals, a switch mounted on the support having a resilient contact member biased toward the disc and held in a non-overload position againts its bias by the center of the disc when the latter is in a first bowed position, said disc being adapted to snap to an oppositely bowed position upon heating in response to flow of overload current therethrough to release said contact member for movement away from its said non-overload position, the springs holding the disc in postion for engagement of its contacts with the terminals in either of the bowed positions of the disc.

8. A circuit breaker comprising a support, line terminals on the support, a dished, snap-acting thermostatic disc having contacts on one face thereof adjacent its periphery freely engaging said terminals, said disc having a normal form bowed in one direction and adapted to snap to an oppositely bowed form upon heating in response to flow of overload current therethrough, means on the support independent of the line terminals extending over the periphery of the disc on the side thereof opposite the contacts holding said disc in place on the support with its periphery restrained against movement away from the terminals and with its center free to snap so that its contacts remain in engagement with the terminal in either of its oppositely bowed forms, a switch mounted on the support having a movable contact member biased to open-circuit position, a latch element on said contact member, and a detent operable by the disc and engageable with the latch element to latch the contact member in closed-circuit position against its bias as long as the disc is in its normal form.

9. A circuit breaker as set forth in claim 8, further including a manual control member for releasing the detent manually to open the switch.

10. In a thermostatic circuit breaker, a support, line terminals on the support, a snap-acting thermostatic element having contacts on one face thereof on opposite sides of its center freely engaging said line terminals, said element having a normal form bowed in one direction and adapted to snap to an oppositely bowed form upon heating in response to flow of overload current therethrough, means independent of the line terminals holding said thermostatic element in place on the support in such manner that the contacts thereon are restrained against movement away from the terminals but free of the support and terminals and with the center of the thermostatic element free to snap so that its contacts remain in engagement with ,the terminals in either of its oppositely bowed forms, a switch mounted on the support, and means operable by the center of the thermostatic element for operating the switch.

11. In a thermostatic circuit breaker, a support, line terminals on the support, a snap-acting thermostatic element bridging said terminals, said thermostatic element having a normal form bowed in one direction and. adapted to snap to an oppositely bowed form upon heating in response to flow of overload current therethrough, said thermostatic element being mounted on the support for movement in opposite directions normal to the general plane of the element toward and away from the terminals, means biasing the thermostatic element bodily toward the terminals so that the thermostatic element bridges the terminals in either of its opnositelv bowed positions, the center of the thermostatic element being free to snap and the portions thereof engaging the terminals being free of the support and terminals, a switch mounted on the support, and means operable by the center of the thermostatic element for operating the switch.

12. A circuit breaker comprising a support, line terminals on the support, a snap-acting thermostatic element freely bridging said terminals, said thermostatic element having a normal form bowed in one direction and adapted to snap to an oppositely bowed form upon heating in response to flow of overload current therethrough, said thermostatic element being mounted on the support with the portions thereof which engage the terminals free of the support and terminals to remain in position freely bridging the terminals in either of its oppositely bowed forms and with its center free to snap, a solenoid switch mounted on the support and connected in series through the terminals with the thermostatic element, and a holding switch for the solenoid mounted on the support and connected in a holding circuit for the solenoid, said holding switch being operable by the center of the thermostatic, element to open to de-energize the solenoid upon snapping of the thermostatic element in response to flow of overload current therethrough.

13. A circuit breaker comprising a support, line terminals on the support, a snap-acting thermostatic element having contacts on one face thereof on opposite sides of its center freely engaging said terminals, 'said thermostatic element having a normal form bowed in one direction and adapted to snap to an oppositely bowed form upon heating in response to flow of overload current therethrough, means on the support independent of the line terminals extending over the edge of the thermostatic element on the side thereof opposite the contacts holding the thermostatic element in place on the support with its contactcarrying portions restrained against movement away from the terminals and with its center free to snap so that its contacts remain in en- 11 mement with the terminals in either or its oppositely bowed forms, a, switch mounted on the support having a movable contact member biased to open-circuit position, a, latch element on said contact member, and a detent operable by the thermostatic element and engageable with the latch element to latch the contact member in closed-circuit position against its bias as long as the thermostatic element is in its normal form. JOHN D. BOLESKY.

REFERENCES crr'En The following references are of record in the tile oi this patent:

UNITED STATES PATENTS Number Name Date 1,652,527 Hodgkiml Dec. 13, 192':

Number

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