US 2898427 A
Description (OCR text may contain errors)
4, 1 5 H. A. NADEAU 2,898,427
ARC EXTINGUISHING MEANS Filed Oct. 10, 1957 INVENTOR. HERMAN A. NADEAU kw i ATTORNEY Unite States Pate Patented Aug. 4, 1959 ARC EXTINGUISHING MEANS Herman A. Nadeau, Forestville, Conn., assignor to General Electric Company, a corporation of New York Application October 10, 1957, Serial No. 689,423 2 Claims. (Cl. 200-144) My invention relates to electric control devices such as switches and circuit breakers, and particularly to are extinguishing means for such devices.
Electric switches and circuit breakers in the past, have ordinarily utilized arc extinguishing means of one of three types, (1) metallic plates spaced one above the other and arranged close to the arc area, (2) chambers having walls of refractory material such as porcelain, (3) chambers constructed of gas-evolving insulating materials, or combinations of these three types. All of these methods have disadvantages, however. None of these methods or combinations thereof, for example, is fully satisfactory for application in extremely small circuit breakers, such for instance as the type disclosed here in, which are required to interrupt relatively high shortcircuit currents. In such applications, the space available for an arc extinguishing chamber is so small that it is not practicable to support a plurality of spaced metallic plates therein, nor to utilize a chamber constructed of refractory material. The use of gas-evolving or noncarbonizing materials alone is also inadequate since they provide no directional effect on the arc, which, because of the space limitations, is needed to keep the arc from damaging the closely adjacent operating mechanism.
The refractory type and gas-evolving material type of arc chambers do not afford either the high heat-absorbing action or the magnetic attraction effect of metallic materials, which effects are very desirable in both switches and circuit breakers. The spaced metallic plate assembly construction, however, is relatively expensive to manufacture and assemble, and introduces problems of supporting such assemblies with respect to the contacts when a chamber or recess is not available to receive the parts.
It is an object of my invention to provide an arc extinguishing construction for circuit breakers where the available space is extremely small such, for example, as where the total width of the circuit breaker is less than one-half inch, and the short-circuit current required to be interrupted is in the neighborhood of 5000 amperes.
It is also an object of my invention to provide an arc extinguishing means which may be readily fabricated by conventional high production manufacturing techniques, and which may be readily and easily assembled.
In accordance with my invention, I provide an electric circuit control device including a one-piece arc extinguishing means comprising a generally U-shaped member of magnetic metallic material having side portions disposed on either side of the path of a movable contact, and extending completely between the contact closed and the contact open positions of the movable contact, the bight portion thereof extending parallel to the path of movement of the movable contact and being provided with a plurality of parallel slots extending generally perpendicular to the path of movement of the movable contact, the slots also being extended into the opposite side portions.
In accordance with another aspect of my invention, I provide an electric circuit breaker including an insulating casing having an arc chamber containing a stationary and a movable contact. The contacts are supported by conductors which extend parallel to each other and in the same direction immediately adjacent the contacts to create a magnetic blowout effect tending to move the arc in the opposite direction. A venting passage is also provided leading from the arc chamber to the exterior of the casing, and the conductor supporting the stationary contact includes an arc-runner portion extending into the venting passage to lead the arc toward and into the venting passage. This action is further assisted in accordance with the invention, by a somewhat similar are runner extension on the other conductor, extending beyond the movable contact toward the venting passage.
In accordance with another aspect of my invention, I provide such a circuit breaker having an arc extinguishing member as set forth and comprising a coating of refractory material to increase its thermal resistance.
My invention will be more fully understood from the following detailed description, taken in conjunction with the accompanying drawing, and its scope will be pointed out in the appended claims.
In the drawings,
Figure 1 is a side elevation view of a circuit breaker embodying my invention, a portion of the side wall being broken away;
Figure 2 is a perspective view of a portion of the arc extinguishing structure of Figure 1;
Figure 3 is a plan view of an arc extinguishing member utilized in another embodiment of the invention, and
Figure 4 is a fragmentary view in perspective showing a portion of an electric switch embodying the invention.
In the drawing, my invention is shown as embodied in a circuit breaker comprising an enclosing casing 10 of insulating material such, for example, as urea-formaldehyde molding compound. A relatively stationary contact 11 is provided, mounted on a generally U-shaped load terminal member 12 which is provided at its outer end with an inverted U-shaped clamping member 13. The clamping member 13 includes a clamping screw 14 and has aligned openings in the opposed side wall portions thereof adapted to receive the end of a wire, not shown, inserted through the opening 15, and to clamp it against the terminal member 12. The terminal member 12 and the clamping member .13 are both retained in place in the insulating casing 10 by means of the conforming recesses and bosses carried by the two opposed halves of the casing 10.
A relatively movable contact 16 is provided, which is mounted on the edge portion adjacent the end of the elongated contact-carrying member 17 which is supported on the frame member 18 by means including an insulating spacer 18' and rivet 17'. The frame member 18 is mounted on a pivot 18a in the casing 10, and both the frame member 18 and the contact member 17 are adapted to he rotated about the pivot 18a between open and closed circuit positions by means of the operating handle 19. One type of operating mechanism suitable for use herewith is shown in application Serial Number 689,422, filed concurrently herewith, by H. J. Hammerly et al., and assigned to the same assignee as the present invention.
The circuit breaker casing 10 is provided with an arc extinguishing chamber 20, provided with a venting aperture 2.1.
For the purpose of leading the arc toward and into the venting passage 21, the terminal conductor 12 is provided with an integral arc runner extension 12a, extending beyond the stationary contact and part way into the venting passage 21. This action is further assisted by a similar extension 17a on the contact arm 17.
For the purpose of assisting the cooling and extinction of the are drawn in the arcing chamber 20 between the contacts 11 and 16, a generally U-shaped arc extinguish ing member is provided, indicated generally at 22 in Figure 2. The are extinguishing member 22 includes two opposed side portions 23 which extend the full distance between the stationary contact 11 and the fully open position of the movable contact 16, shown in dotted lines in Figure l. The spacing between the opposed side walls 23 of the arc member 22 is only slightly greater than the width of the terminal member 12 at the point adjacent the arc extinguishing member 22. The bight portion of the arc extinguishing member 22 is cut away at 24, and the remaining portion thereof is provided with slots 25 cut therein at an angle to the main portion of the member 22, generally perpendicular to the path of movement of the movable contact 16.
The member 22 is preferably formed of a ferromagnetic metallic member such for instance as steel, and is preferably provided with a finish comprising a plated coating of nickel having a high gloss finish.
In operation, when the contact member 17 moves toward open position, and draws an are between the movable contact 16 and the stationary contact 11, magnetic forces are set up which tend to draw the arc toward the bight of the arc extinguishing member 22, a portion of the are being vented directly out through the vent opening 21 and a portion expanding into the lower portion of the arc extinguishing chamber 20. The magnetic forces referred to represent the combined effect of several factors. One of these factors is the effect of the magnetic fields associated with current being carried through the contact arm 17 approaching the movable contact, and the current carried through the terminal strap 12 leaving the stationary contact. These currents are closely adjacent and opposite in direction, and create magnetic fields which repel each other, the efiect at the contacts being such as to force the arc to the right in a manner well understood in the art.
The major factor affecting the movement of the arc, however, is the attraction created to the right and below the point of incidence of the arc by the ferromagnetic arc extinguishing member 22. The provision of the slots 25 assists in cooling the arc gases. In addition, the slots 25 cause each of the intermediate portions of the member 22 to act is a manner similar to individual U-shaped members to draw the arc toward the closed part of the U and to assist in cooling it as it passes over them.
As previously mentioned, the arc cooling member 22 extends the full distance between the stationary contact 11 and the position of the movable contact 16 when in the open circuit position. The arc cooling member 22 does not include, in the preferred embodiment, any insulating material on its inner surfaces between it and the movable contact member. This construction would not normally be considered feasible since it is readily apparent that the arc cooling member 22 substantially reduces the total length of the air path between the movable contact 16 when in its open circuit position and the stationary contact 11, and, in fact, nearly short-circuits the two contacts when in the open circuit position. Nevertheless, it has been found by many tests that the construction described provides a better arc extinguishing action in such circuit breakers than can be achieved by any other known method. Circuit breakers constructed in accordance with the invention have successfully passed all tests required by authorized approving authorities, including the Underwriters Laboratories, whereas circuit breakers otherwise identical but including conventional are extinguishing structures have failed to pass such tests.
In Figure 3 there is shown another embodiment of the invention, in which the thermal resistance of the member 4 26 is greatly increased by the provision of a thin surface coating 27 of refractory material such, for instance, as porcelain or alumina on the inner surfaces thereof.
In Figure 4 there is shown another embodiment of the invention incorporated in an electric switch including an insulating base 28. A terminal member 29 is supported on the base 28 and includes an integral stationary contact portion 30 adapted to be contacted in sliding side-toside engagement by a movable contact 31. An insulating terminal shield or cover 32 is mounted on the base 28 by suitable means, such as by screw 33.
For the purpose of cooling and extinguishing arcs drawn between the movable and stationary contacts, an arc extinguishing member 34 of suitable magnetic material such as steel is provided, which is mounted on the shield 32 by suitable means such as rivet 35 passing through lug 36 integral with the member 34.
The member 34 has a plurality of slots 37 cut in the bight portion thereof and in the opposite side portions. The member 3-1- is disposed at an angle with respect to the base 28 so as to place the bight portion thereof generally parallel to the path of movement of the movable contact member 31. In operation, an are drawn between the stationary and movable contacts is drawn into the member 34 and toward the bight portion thereof by the aifinity of the magnetic field associated with the are for the magnetic material of the member 34. At the same time, a relatively large surface of metal is exposed to the arc and acts upon it to absorb heat therefrom to reduce the temperature thereof below the ionization temperature and to extinguish the arc. It will be observed, nevertheless, that the member 34 does not confine the are or are gases, but permits them to be dissipated into the surrounding air. The member 34 furthermore provides, in effect, a self-supporting assembly of U-shaped arc-cooling members which can be readily and inexpensively fabricated from a single piece of metal and mounted by a single fastening means.
While I have disclosed only three embodiments of my invention, it will be appreciated that many modifications thereof may readily be made, and I therefore intend by the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. An electric circuit breaker comprising an insulating casing having an arc chamber therein, a relatively stationary contact mounted in said are chamber, a relatively movable contact supported for movement in said are chamber into and out of engagement with said stationary contact along a predetermined path, an electrical conductor connected to each of said stationary and movable contacts respectively and extending generally parallel to each other in a first direction immediately adjacent said contact when in closed position, a venting passage extending from said are chamber to the exterior of said casing in a direction generally opposite to said first direction, are cooling and extinguishing means in said are chamber comprising a one-piece generally U-shaped metallic member having its bight portion extending generally parallel to said path of movement of said movable contact and its side portions disposed on opposite sides of said path of movement and extending at least the entire length of said path of movement, a plurality of elongated generally parallel slots in said bight portion of said U- shaped member extending generally perpendicular to said path of movement, said slots each extending at least partially into both of said side portions to provide a plurality of generally U-shaped parallel portions spaced away from each other throughout their intermediate portions but joined together at the ends thereof opposite said bight portions, said U-shaped member having a portion of the bight thereof cut away adjacent said stationary contact and adjacent said venting passage to permit substantially unobstructed flow of arc gases into said venting passage from the portion of said are chamber adjacent said stationary contact.
2. An electric circuit breaker as set forth in claim 1 wherein said conductors connected to said stationary and movable contacts each include an integral extension projecting beyond said contacts respectively in the direction of said venting passage as are runners to lead the are into said venting passage.
References Cited in the file of this patent UNITED STATES PATENTS Jennings June 1, 1943 Walle Sept. 30, 1947 Bennett Jan. 25, 1949 Ellis Oct. 3, 1950 Rypinski Mar. 24, 1953 Cole Sept. 14, 1954