US2487422A - Resettable circuit breaker - Google Patents

Description

Nov. 8, 1949 R. CARLE RESETTABLE CIRCUIT BREAKER 2 Sheets-Sheet 1 Filed April 6, 1948 INVENTOR. RENE CARLE Nov. 8, 1949 R. CARLE 87,

RESETTABLE CIRCUIT BREAKER Filed April 6, 1948 2 Sheets-Sheet 2 Patented Nov. 8, 1949 2,487,422 RESETIABLE CIRCUIT BREAKER Ben Carlo, Brooklyn, N. Y., assignor, by mesne assignments, to Thermo Electric Fuse Corp., New York, N. Y., a corporation of New York Application April 6, 1948, Serial No. 19,278

14 Claims.

This invention relates to resettable circuitbreakers or overload safety devices-more particularly, although not exclusively, of the type which is screwed into the ordinary socket receptacle such as is provided in household fuseboxes and other electrical installations.

There are certain of this type of resettable units disclosed in prior art patents which embody two desirable features: one, the provision of separate electrical contact surfaces which are independent of the engaging surfaces associated with the latching mechanism; two, the provision of means to prevent the reset button from manually setting and/or maintaining the device in circuit-making condition during current overloads. However. such prior art devices have not been wholly satisfactory, in that they are generally intricate, delicate in structure. easily upset,

'and inherently not capable of meeting various oflicial safety requirements.

This invention provides a construction satisfactory for a resettable overload socket-receiving unit which avoids the difficulties of, and objections to, prior art devices. More particularly. the

improved construction of this invention provides a device which is compact, rugged, adaptable for mass production to market at a commercially acceptable price, and entirely reliable in operation, both from electrical and mechanical requirements.

From another aspect this invention provides a construction for a resettable overload unit of the socket type which will pass the various rigid safety requirements and tests of olilcial fire underwriters and other regulatory ordinances. To meet these rigid requirements there is provided in the improved device, in addition to the aforementioned resettable mechanism, a fusible link element, one of the features of which is the provision of an egress channel for the metallic vapors resulting from the melting of the fusible link. This passage conducts the metallic vapors outwardly and away from the interior of the device; this prevents the metal parts of the circuit-breaker from being vaporized and adding to the vapor pressure and, at the same time, preserves the mechanism.

In the improved construction the electrical contacts are arranged to be in rolling contact when the circuit is closed, so that there will be present an area of contact, rather than merely a line of contact.

A preferred embodiment of the improved resettable unit of this invention is shown on the accompanying drawings, wherein:

Figure 1 is a. perspective view of the improved unit;

Figure 3 is a top view of the improved device with the top cover removed;

Figure 4 is a front-to-rear sectional elevation taken on the line 4-4 of Fig. 3;

Figure 5 is a left-to-right sectional elevation taken on the line 5-5 of Fig. 3;

Figure 6 is a perspective view of the operative parts of the device, including the main slide;

Figure 7 is a front view of the main slide;

Figure 8 is a perspective view showing the rolling electrical contacts in operation;

Figure 9 is a sectional elevation similar to Fig. 5 but showing the device in circuit-breaking condition, following an overload; and

Figure 10 is a similar sectional elevation showing the device in the first phase of the resetting operation, following the, depressing of the resetting button.

The invention is shown and described herein with reference to circuit-breakers or resettable overload devices adapted to be screwed into the sockets provided in household fuse-boxes and other electrical installations-known in the trade as plug-typ'e. But it will be understood that the invention is equally applicable to the cartridge-type of overload devices, as well as to other types of circuit-breakers or overload devices.

The operative parts of the improved device are contained within a hollow body or plug 30 molded or otherwise formed of suitable electrical insulating material. Plug 30 has a separable end piece 33, for purposes fully explained subsequently. Body 30 presents screw-convolutions 3|, which are covered by a thin shell 32 of brass or other conductive material, providing means for screwing into a socket and establishing electrical contact therewith. Electrical connection is made with the base contact of the socket by a central stud or rivet 31 passing through end piece 33. The other end of plug body 30 is closed by a cover disc 39 which is secured thereto by a suitable cement.

The two separable, but normally engaging,

. contacts of the device are designated by reference characters I and 2. Electrical contact I is secured to, and carried by, a bimetallic element 3 which is L-shaped, as clearly shown, with its base leg secured to the floor of the plug, this securement being conveniently achieved by the aforesaid contact stud 31. The other electrical contact 2 is mounted at one end of a U-shaped member 4, the other end of which is secured to the plug by a screw 6 which establishes electrical connection with the threaded shell 32 through a wire I the purpose of which will be subsequently explained.-

For some purposes, U-shaped member I may Figure 2 is an exploded, perspective viewwnbe made of spring material to maintain its conthereof;

fer to make member 4 of copper, a superior electrical conductor but devoid of resilient properties and provide an auxiliary spring means such as the spring tempered wire 5 in the form of a U-shaped loop, the ends of which are upturned, as indicated at 5*, 5*, (Fig. 8). Ends 5, 5 of spring wire 5 are received in holes 30*, 30* provided in the end wall of plug body 30. It should be mentioned that the end piece 33 of the plug has an upstanding annular wall 34, which flts within the base of body 30 of the plug. This annular wall 34 has a pair of slots 34 34 wherethrough spring wire 5 clears. The auxiliary spring 5 normally maintains contacts I, 2 closed, thus completing the circuit through the device, as traced above.

The means for interrupting contacts I, 2 upon the occurrence of an overload comprises a main slide generally designated I and an auxiliary slid generally designated 20 and carried by, and

slidable on, main slide Ill. Main slide III is preferably constructed of a channel-sectioned frame I to which is secured a partition I4 of suitable electrical insulating material. Main slide III, that is, its frame I5, is slidable in a pair of diametrically-opposed grooves 35 in the internal surface of plug 30. In the normal or lower position of main slide II), as seen in Fig. 5, its partition I4 is below the contacts I, 2. Upon the occurrence of an overload, main slide I ll-iscaused (as will more clearly hereinafter appear) to move upwardly to interpose its partition I4 between the contacts I and 2 to break the circuit, as shown in Fig. 9. -A spring is provided which urges main slide I0 upwardly to this upper, circuit-breaking position. Conveniently, this is a wire spring formed L-shaped with a vertical leg II and a horizontal leg I2 (see especially Fig. 6). Horizontal leg I2 of the wire has an upturned end I2 which is received in an aperture I6 in a lug I6 projecting laterally from the frame I5 of the main slide. The vertical leg I I of the spring wire is received in a hole 3|] in the wall of plug body 30 (see especially Fig. 4).

The action of spring II-I2 to urge main slide I0 upwardly to circuit-breaking position is normally thwarted by a latch means which holds the slide in its downward circuit-closing position. This latch means comprises a latch head 8 at the distal end of bimetallic strip 3 which hooks over a lug I8 laterally projecting from the frame I5 of the main slide, more particularly, from the side opposite the lug it, (see Figs. 5, 9 or 10). When an overload occurs in the line, the overheating of bimetallic strip 3 causes it to warp away (to the right, Figures 9, 10) from the main slide, causing its latch head 8 to be withdrawn from lug I8, whereupon spring III-I2 drives main slide I0 upwardly. The upper edge of insulation partition I4 is bevelled. as indicated at IN, to facilitate the entry of the part tion between the contacts I, 2 and the separation thereof. The lower edge of partition I4 may also be bevelled, as indicated at I4. This is for production reasons and also to facilitate the assembly of the device by easing the placing of the main slide III and its partition I4 between the contacts I, 2.

The auxliary slide is preferably made integrally of suitable insulating material and presents a partition portion 24, and normal thereto, a finger portion 28, the two portions 24, 28 forming an inverted-T, as best seen in Fig. 7. The ends of the artition portion 24 are slidably received between the channels of the channel frame 4 I5 of main slide II), the auxiliary slide being disposed in overlying relation to the main slide.

Cover disc 39 is provided with a centrally located slot 38 through which finger portion 28 of the auxiliary slide clears. The upper branch of channel frame I5 is provided with a slot I! through which finger portion 28 clears. The width of partition portion 24 of the auxiliary slide 20, i. e., its verticaldlmension as viewed in the figures, is considerably less than the distance between the top edge of partition I4 of main slide III and the upper branch of channel frame I5, so that auxiliary slide 20 has an extent of vertical movement relative to the main slide l0. Spring means are provided for maintaining the auxiliary slide in its upper position abutting the top branch of frame I5, and presenting a wide opening between the lower edges of the auxiliary slide partition 24 and the upper edge of the main slide partition I4. Conveniently, this is a wire spring formed of a pair of legs 28, 21

with a-loop between both legs which tends to urge them apart. Upper leg 21 of spring 28-21 has an upturned end 2'I which is received in an aperture 28 in finger portion 28 of the auxiliary slide. Lower leg 28 of spring 28-21 has an upturned end 26 which is received in an aperture I8 in lateral lug I8 of channel frame II of the main slide.

Wire spring 25-21 is thus effective to normally separate the main and auxiliary slides, maintaining the auxiliary slide in its upper position and providing a wide opening between the facing edges of the main partition I4 and the auxiliary partition 24. As previously stated, the main slide I0 itself is normally in its lowermost position,

being latched in that position against the upward urging of the main slide spring III2. In the normal, lowermost (latched) position of main slide I0 and in the normal, uppermost position of auxiliary'slide 20, the said wide opening between their two insulated partitions I 4, 24 is disposed in a position, as seen best in Fig. 5, permitting the contacts I, 2 to come into mutual engagement. As previously explained, when an overload or short circuit occurs and latch head 8 is retracted, main slide II) is urged upwardly by its spring II-I2, carrying the auxiliary slide 20 with it. The parts are shown best in Fig. 9 in circuit-breaking position.

To reset the device to its normal circuit-closing condition, the finger 28 of the auxiliary slide is pushed downwardly (or inwardly). During the first phase of this downward movement of the auxiliary slide, it moves relatively to the main slide II), its partition portion 24 sliding in the channels of frame I5, until the facing edges of the two partitions are in abutment. Further downward force on reset finger 28 then causes the main slide II) to move downwardly until it reaches its lowermost position. Normally, in this lowermost position of main slide II) the two contacts I, 2 would be engaged (since main partition I 4 is below the contacts); but engagement of contacts I, 2 is prevented by the interposition of partiton 24 of the auxiliary slide 20 (see Fig. 10), the aux liary slide being held in this lowermost position by manual pressure on finger 28.

It is thus seen that the resettable overload socket-receiving unit of this invention can not be held in circrit-closing condition either purposely by manually holding finger 28 downward or accidentally by some member falling or pressing against the reset finger. In either case, downward movement of the finger would immediately interpose insulating partition 24 of the auxiliary slide between the contacts, as in Fig. 10. It is only when the hand is withdrawn from reset flnger 28, that the two contacts I, 2 become engaged to complete the circuit. This occurs when the auxiliary springs 26--21 moves the auxiliary slide 20 upwardly to withdraw its partition 24 from between contacts I, 2, the main slide, however, remaining in lowermost position by reason of the re-latching of its lug ill-provided, of course, that the overloading condition no longer exists so that latch head -8 has returned to normal, latching position.

To facilitate the entry of insulating partition 24 of the auxiliary slide, its lower edge is bevelled, as indicated at 24?. Inasmuch as there are thus provided two facing bevelled edges 24 of the auxiliary partition 24 and I4 of the main partition I4, this might present the danger of one thin partition edge slipping behind or in front of the other edge. To avoid this possibility, the end portions of the facing edge of the auxiliary partition 24 are not bevelled, as indicated at 24", but are flat surfaces as compared with the edges of the opposing bevelled edge l4 of the main partition H.

To visually indicate that the device is in circuit-breaking condition, in which case its reset finger 28 extends a greater distance beyond cover disc 39which can be read ly s en by comparing the position of reset finger 28 in Fig. 9 (circuitbreaking condition) and in Fig- 5 (normal, circuit-closing condition)a red band 28a is painted on reset finger 28 in such position that, when the device is in normal, circuit-closing condition, the red band 28a will be below the cover disc 39 (see Fig. 4) but, when an overload or short circuit had occurred, red band 28a will appear above the top of the cover disc, as in Fig. 9.

The electrical contacts I and 2 are maintained in close area engagement at all times up to the instant that the circuit is broken by withdrawal of latch head 8 upon occurrence of an overload or short circuit. The bimetallic strip 3, functioning as it does by reason of the difierences in the coeilicients of thermal expansion of its two constituent materials, naturally will begin to warp (or bend to the right, Figures 9, 10) at currents much lower than that at which its latch head 8 is completely withdrawn from lug l8. This bending of bimetallic strip 3 below circuit-breaking currents is indicated in Fig. 8, between the solid line and dot-and-dash position of the parts. The contact 2 maintains itself in en a ement with the contact I carried by the bimetallic strip 3 by reason of the resilient action of its auxiliary spring 5. It is desirable that this enga ement be along an area, rather than a line. throughout this angular movement of the two enga ed contacts (between the solid and dot-and-riash positions of Fig. 8). The improved device of this invention achieves this by providing one of the contacts, the following contact 2. as a half cvlinder, as shown in Fig. 8, secured at the distal end of the U-shaped connector 4, and making the other contact I in the form of a cylinder normally disposed relatively to the half-cylinder contact 2 with one end secured to the b metallic strip 3 and with its distal end en aged with halfcylinder contact 2. The rounded surfaces of contacts I and 2 provide an area contact there between throughout the various angular positions of the supporting leg of contact 2 and the bimetal ic strip 3 which supports the contact i.

As mentioned earlier, the improved resettable overload device is provided with a fusable link element I, in the form of a wire having a calibration nick 1* and is passed through a drilled passage 36 provided in the wall of plug body 30. Drilled passage 38 extends from the upper annular ledge oi plug body 30 adjacent to screw 6 which, besides serving to anchor the upper end of wire I, also serves to secure one leg of U-shaped conductor 5 to the plug body. The other, lower end of drilled passage 33 opens into the lowermost of the screw convolutions 3| of the plug body, as clearly seen in Fig. 2. The end of wire 1 extends out of the passage 36 and is bent upwardly, as indicated at 9. This portion of the wire is sufficiently long to underlie the entire extent of the brass shell 32 (thus making full contact therewith) and extends beyond the upper edge of shell 32 so that it may be soldered thereto, as indicated at 9, Fig. 10.

A recessed chamber 2| (Fig, 2) is provided where the drilled passage 36 opens into screw convolutions 3|. When the end piece 33 is in abutting position closin the lower opening or plug body 30, its annular shoulder 33* closes the lower opening of chamber 2| (see also Fig. 10). The purpose of the chamber 2! and the annular shoulder 33 is to constrain the vapors of the fused wire to follow a path of least resistance through the screw convolutions and to escape at the top edges of screw shell 32. It should be noted in this connection that the threads 3! of the plug body 30 and the threads of the brass shell 32 are shaped so that a small area of clearance 3| (see Figs. 5, 9, 10) is provided for egress oi the metallic vapors. It should also be noted that the upstanding annular wall or flange 34 of end piece 33 is disposed behind or interiorly at the chamber 2! (see Fig. 2) and thus additionally serves to block escape of the metal vapors towards the interior of the device.

In the above description, the invention has been disclosed merely by way of example and in preferred manner; but obviously many variations and modifications may be made therein wh ch will still be comprised within its spirit.

It is to be understood, therefore, that the invention is not limited to any specific form or manner of practicing same, except insofar as such limitations are specified in the appended claims.

Ielaim:

1. In a device of the class described, a body member provided with a pair of contacts springurged into en agement; a main slide having an insulating partition and being slidably mounted within said body portion and movable between two predetermined limiting positions along a plane between said contacts, said insulating partition in one of said positions being disposed between the contacts whereby the device is in a c rcuit-opening condition, the partition in the other of said positions being withdrawn from said contacts whereby the device is in a circuitclosing condition; a main spring urging said main slide to said circuit opening position; a retractable latch including a thermal-responsive strip, said latch being normally in latching engagement with the main slide against the action of the main spring to hold the slide in said circuit closing position; an auxiliary slide having an insulating partition and slidably mounted on said main slide between two limiting positions, said auxiliary partition in one of said positions being disposed between the contacts whereby the device is in a circuit-opening condition, the

- 7 auxiliary partition in the other of said positions being withdrawn from said contacts whereby the device is in a circuit-closing condition; an auxiliary spring urging said auxiliary slide to said circuit-closing position; and a manually manipulatable resetting finger extending from said auxiliary slide, whereby upon an operative actuation of said finger there will be a concomitant movement of the auxiliary slide to circuit-opening position and said main slide to normal circuitclosing position, said auxiliary spring returning the auxiliary slide to circuit-closing position upon an operative release of said resetting finger.

2. The combination according to claim 1 wherein said main slide has a channel-section frame, the said main insulating partition being held between facing channels of the frame with its upper edge spaced from the top of the frame, the ends of said auxiliary partition being received between said facing channels for an extent of movement between said upper edge of the main partition and said top of the frame.

3. The combination according to claim 2 wherein said resetting finger extends parallel to the plane of said insulating partition of the auxiliary slide, said top of the main frame having a central slot for said resetting finger, whereby the auxiliary slide is guided in its said movement relative to the main frame.

4. The combination according to claim 1 wherein said body is provided with a recessed hole and wherein said main spring has two legs, one leg of which is received in said recessed body hole, the other leg being secured to the main slide.

5. The combination according to claim 4 wherein said main slide has a lateral lug provided with an aperture, the latter leg of said spring being received in said aperture for securement to the main slide.

6. The combination according to claim 1 wherein said auxiliary spring is a wire looped to present two legs, one of said legs being secured to the auxiliary slide and the other being secured to the main slide.

'7. The combination according to claim 6 wherein said resetting finger of the auxiliary slide is provided with an aperture, the distal end of the first of said auxiliary spring legs being received in said aperture for securement to the auxiliary slide.

8. The combination according to claim 7 wherein said main slide has a lateral lug provided with an aperture, the distal end of the latter of said auxiliary spring legs being received in said aperture for securement to the main slide.

9. The combination according to claim 1 wherein the upper edge of said insulating partition of the main slide is in underlying relation to said pair of contacts when the main slide is in said circuit-closing position, said upper partition edge being bevelled to facilitate entry of the partition to opcratively separate the contacts.

10. The combination according to claim 9 wherein the lower edge of said insulating partition of the auxiliary slide is in overlying relation to said pair of contacts when the auxiliary slide is in said circuit-closing position, said lower partition edge being bevelled to facilitate entry of the partition to operatively separate the contacts during resetting of the device.

11. The combination according to claim wherein only the central portion of the lower edge of the auxiliary partition is bevelled, the lateral portions of said edge being flat, whereby said fiat edge portions are presented to the bevto indicate said open condition.

13. In a device of the class described, a pair of contacts spring-urged into engagement, a main member having an insulating partition and mounted for an extent of movement from a circuit-closing position with its partition withdrawn from said contacts to a circuit-opening position with its partition interposed between said contacts, spring means urging said main member to said circuit-opening position, means including a bimetallic strip for latching said main member in circuit-closing position against said spring urging, an auxiliary member having an insulating partition and mounted on said main member for an extent of movement from a circuit-closing position with its partition withdrawn from said contacts to a circuit-opening position with its partition interposed between said contacts, spring means urging said auxiliary member to said circuit-closing position, and a resetting finger integral with said auxiliary member and accessible for manual operation to concomitantly move said auxiliary member to circuit-opening position and said main member to circuit-closing position, said auxiliary spring moving the auxiliary member to circuit-closing position upon release of the resetting finger.

14. In a device of the class described, a pair of contacts spring-urged into engagement, a main member mounted for an extent of movement from a circuit-closing position to a circuit-opening position, spring means urging said main member to said circuit-opening position, means including a bimetallic strip for latching said main member in circuit-closing position against said spring urging, an auxiliary member mounted on said main member for an extent of movement from a circuit-closing position to a circuit-opening position, spring means urging said auxiliary member to said circuit-closing position, and a resetting finger integral with said auxiliary member and accessible for manual operation to concomitantly move said auxiliary member to circuit-opening position and said main member to circuit-closing position, said auxiliary spring moving the auxiliary member to circuit-closing posi tion upon release of the resetting finger.

RENE: CARLE.

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

UNITED STATES PATENTS Number Name Date 815,764 Tournier Mar. 20, 1906 1,560,597 Meierjohan Nov. 10, 1925 1,621,349 Brown Mar. 15,1927 1,653,823 Pudelko Dec. 27, 1927 1,732,295 Aichele Oct. 22,1929 1,843,804 Christie Feb. 2, 1932 FOREIGN PATENTS Number Country Date 275.038 Great Britain Aug. 4, 1927

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