US2577425A

US2577425A - Thermal cutout switches

Info

Publication number: US2577425A
Application number: US165404A
Authority: US
Inventors: Marcoz Jean
Original assignee: Individual
Current assignee: Individual
Priority date: 1949-07-29
Filing date: 1950-06-01
Publication date: 1951-12-04
Anticipated expiration: 1968-12-04
Also published as: BE496580A; GB684868A; DE903481C; FR995685A; NL154197C

Description

Dec. 4, 1951 J, R -z 2,577,425

THERMAL CUTOUT SWITCHES Filed June 1, 1950 EPatesited fies. 4, 395i NITED STATES PATENT OFFICE mama CUTOUT swrrcins Jean Marcos, nun-Mums, France Application June 1, 1950, Serial No. 185,4

France July 29, 1049 2 Claims. (CL 200-118) This invention relates to automatic cut-out switches of the kind used to protect branch circuits against overload and short circuits. Such devices are particularly useful in cases where circuit-breakers having a high breaking capacity would be too expensive or too spaceconsuming to be practical.

In cut-out switches of this class, the switch operates to cut the circuit under the influence of a heat-responsive device, the electro-magnetic means used in the larger circuit-breakers are not practicable because they would be too complicated and expensive. As a result, the breaking power of such small automatic cutout switches is much lower than that of the circuitbreakers, because the breakage period is longer and the resulting arc is not efficiently blown out.

Another drawback of known cut-out switches of the category contemplated by the invention is that if it is desired to prevent the possibility or forcibly maintaining the device in engaged or contact-making condition after it has operated due to an overload, by continued pressure on its push-button, it is generally necessary to provide a comparatively intricate device, sometimes known as an interlock, interposed between the push-button and the movable contacts and acting to make it impossible to prevent the device from disengaging its contact freely as long as an overload condition persists in the rcuit. I

It is an object of this invention to provide an improved automatic cut-out switch of the class described, including a heat-responsive controlmeans, which is free of the above-defined inconveniences, and is particularly simple in construction and efficient in operation.

My improved cut-out switch essentially comprises at least one pair of movable cooperating contacts, possessing a circuit-making position in which said contacts are engaged with each other, means biassing one of said contacts away from and the other contact towards said position, spring-latch means adapted to releasabiy retain said one contact in its said position, currentresponsive means such as a bi-metal strip adapted under an overload to withdraw said latch to release said one contact, and a movable operating member, such as a push-button, adapted when actuated first to positively move said one contact to its said position against its related biassing means and then to positively move said other contact slightly away from its said position against its related bias-sing means,

said operating member when released allowing said other contact to return to its contactmakin position under the action of its related biassing means and being moved itself to a position clear of said one contact.

The movable contacts are preferably carried on parallel-spaced spring arms the inherent resiliency of each of which provides the said respective biassing means, both said arms being biassed so as to be urged in a common direction, and said other arm being positively arrested in said direction at its said contact-making position by a stop.

The operating member is preferably a pushbutton provided with a weak spring, said button being adapted to occupy a different one of two positions in each condition of the switch, thereby clearly showing whether the switch is engaged or disengaged.

According to another feature, the bi-metal strip is U-shaped and the spring-arms of the contacts and the arms of the U-shaped strip are used to form a pair of serially connected parallelly-disposed loop circuits providing an arc blowout circuit.

The device so constructed has a high breaking power because its circuit-breaking action is very fast and because of the provision for blowing the arc, the arc blow-out means being obtained in a very simple manner and without having to provide any additional parts or connections simply by an appropriate relative arrangement between the contacts and the bi-metal strip. Moreover, the switch does not include an interlook while at the same time making it possible, as will more clearly appear hereinafter, to prevent the circuit from being broken in case of an overload.

Furthermore, the device is comparatively very simple, being free of pivots, pawls, levers, sliders and similar mechanical parts found in conventional units of this class, and this makes for increased ruggedness at the same time as a high degree of accuracy and positiveness in operation, since it does not include a single mechanical part liable to acquire play.

The above and further objects, features and advantages of the invention will appear from the ensuing description made with reference to the accompanying drawing, in which:

Fig. 1 shows one embodiment of a circuitbreaker according to the invention, in engaged or circuit-making condition;

Fig. 2 is a cross-section of Fig. 1 on a transverse plane;

Fig. 3 is a view similar to Fig. 1 showing the device in disengaged or circuit-breaking condition;

Fig. 4 diagrammatically illustrates the conmotions and the current path through the movable contacts and a bi-metal strip, providing an arc-blowout loop circuit.

As shown in the drawings my improved circult-breaker comprises a pair of contacts i and 2 respectively carried by spring-

arms

3 and 4. To the end 5 of the spring-arm 3 there is secured another and weaker spring-arm 6. The pushhutton i is formed with a shank or extension ll which bears on the spring-arm 4. A coil spring 8 urges the push-button I to its depressed position. A spring-plate l0 formed with a proiecting nose 9 near its top releasably engages over the spring-arm 9 and holds it down under tension in the position shown in Fig. 1. The device includes a current-responsive means herein shown as a U-shaped bi-metal strip I2 adapted to be distorted in the event of an overload. The strips or spring-

arms

3 and 4 are connected in a circuit with the arms oi. the U-strip in the manner shown in Fig. 4, forming as shown a pair of parallel paths for the electric current through both of which the current flows in the same direction. A set screw it or the like bearing upon an insulating element I4 is interposed between the strip l0 and the bi-metal strip l2. The part l4 issupported on the strip 10.

The device operates as follows:

In the current-breaking or disengaged position of the device (Fig. 3) the spring-

arms

3 and 8 press the push-button 1 outwardly against the spring-force of the coil spring 9. To coc or engage the device, the button I is depressed, which first applies the arm 6 against the arm I, then, as pressure continues to be applied to the button, causes both said arms to be moved down bodily until the strip or arm 6 engages under the nose 9 of the strip 10. Towards the end of this downward movement, the end of the shank ll extending the push-button engages the top surface of the lower spring-arm 4 and depresses it by a small amount, so that the contact between i and 2 only becomes effective after the button 1 has been released and allowed to move up again slightly under the influence of the resiliency of the spring arm 4. If an overload occurs in the circuit, the bi-metal strip i2 is distorted sufilciently to deflect the strip 10 through the medium of screw l3 and cause the projection 9 to release the spring-arm, so that the spring assembl of

arms

3 and 6 flies upwards under their inherent resiliency more powerful than the force of coil spring 8, thus restoring the device to the circuit-breaking condition of Fig. 3. The screw 13 serves as a set screw and enables adjustment of the operating point of the switch. A stop l6 restricts the upward movement of the spring arm 4 and holds it at its circuit-making position.

The circuit connections between the contacts and the bi-metal strip are so efiected, see Fig. 4, that the current will flow therethrough in the direction indicated by the arrows in that figure; that is the current enters at a into the strip I2, flows out from the strip at b, enters the spring-arm 4 at c, passes through the contacts 4 3-1 and flows out of the arm 8 at d. It will be seen that the arrangement in efleet constitutes a pair of blow-out loops in a common direction adapted to blow the are violently outwardly of the device.

when the switch is in its engaged condition and pressure is maintained on the button E, the disengagement can be normally accomplished in case of an overload, since. as clearly shown in Fig. 1, the base flange it of the push-button does not engage the surface 0! arm 9, and leaves ample clearance for the upward disengaging movement of this spring arm when such movement is allowed by the withdrawal of the latching nose it away from it by distortion oi the bi-metal strip.

It will be understood that many variations may be made in the details of embodiment illustrated and described in connection with the single illustrative embodiment shown, without exceeding the scope of the invention.

What I claim is:

1. Circuit-breaker which comprises in combination a pair of spring-arms each carrying one of a pair of cooperating contacts, one of said arms being biassed away from, and the other towards, a contact-making position, a springstrip resiliently movable in a plane perpendicular to the plane of movement of said arms, a nose projecting from said spring-strip and adapted to retain said one arm in its said position, a bi-metal strip adapted to be distorted under an overload, an adjustable screw carried by said bi-metal strip and engaging said spring-strip, distortion of said bi-metal strip being adapted to axially move said screw to deflect said springstrip to withdraw said nose and release said one contact, and a push-button having a base hearing on said one spring arm and an extension bearing on said other spring arm, the dimensioning being such that depression of said button first moves said one arm to its latched contactmaking position. and then moves said other arm slightly away from its said position, said button when released allowing said other arm to return under its inherent bias to its said position.

2. Circuit-breaker as in claim 1 wherein the spring-arm carrying said one contact has secured to the free end thereof one end of a further spring-strip biassed in the same direction as said spring-arm and the base of said push-button engages said further spring-strip.

JEAN MARCOZ.

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

UNITED STATES PATENTS Number Name Date 2,057,093 Geisslinger Oct. 13. 1936 2,198,358 Vaughan Apr. 23, 1940 2,261,366 Grout Nov. 4, 1941 2,293,382 Case et al. Aug. 18, 1942 2,458,807 Tucker Jan. 11, 1949 FOREIGN PATENTS Number Country Date 334,891 Germany Mar. 23. 1921 370,035 Germany Feb. 26, 1923 794,535 France Dec. 12, 1935