US2102396A - Circuit breaker - Google Patents

Description

Dec. 14, 1937.

L. S. WALLE CIRCUIT BREAKER Filed May 29, 1936 7% JMJ by HWI/L7 M1 is Attorneg.

Patented Dec. 14, 1937 UNITED STATES CIRCUIT BREAKER Ludwig S. Walle, Lansdowne, Pa., assigner to General Electric Company, a corporation of New York Application May 29,

Claims.

My invention relates to circuit breakers, more vparticularly to circuit interrupting devices of the compression chamber type particularly adaptedior use in connection with combined manual and 5 automatic circuit breakers, and has for an object the provision oi an improved circuit interrupting device of this type.

In my copending application Serial No. 667,856, led .April 25, 1933, entitled Circuit breaker, now Patent No. 2,047,842, issued July 14, 1936, I have described and claimed a circuit interrupting device of the compression chamber type, comprising relatively movable contacts disposed Within a gas-tightly sealed compression chamber and having a volume such that the air entrapped at atmospheric pressures is heated by the arc formed upon separation of the contacts to generate pressures of suiiicient magnitude to interrupt quickly the arc. It is essential in the operation of interrupting devices of this type that high gas pressures be built up very quickly within the compression chamber, and the interrupting device shown in my aforesaid patent is provided With bushings formed of kerosene-free fibre or of some equivalent material capable oi evolving large quantities of gas when exposed to the arc, and of withstanding the high temperatures produced within the compression chamber.

While the device disclosed in my said patent is quite satisfactoryior the purposes intended, I have found that improved interruption of large currents, for example, 5000 amperes at voltages of 200 volts or above, may be obtained in general by properly proportioning the volume of the compression chamber and the amount of gas evolv.

ing material therein, and particularly by locating a portion of the gas evolving material in the region in which the most intense arcing occurs. While the compression chamber may, of course, be formed entirely of gas evolving material, or completely lined with such material, I have found that the large amount of gas evolving material present in such a construction will often effect the generation of such high pressures as to rupture the compression chamber. Accordingly, it is a further object of my invention to provide an improved circuit interrupting device of the compression chamber type, in which the compres- 50v sion chamber is provided with a predetermined amount of gas evolving material located in proximity to the arc so as to build up quickly pressures of sufficient magnitude to extinguish the arc.

55 In carrying out my invention in one form, I

1936, Serial N0. 82,486

(Cl. 24m- 144) provide a circuit interrupting device, comprising a pair of relatively movable contacts disposed within a gas-tightly sealed compression chamber and. a gas evolving member formed of a material capable of evolving substantial quantities 5 oi gas when exposed to an arc, disposed within the chamber closely adjacent the point of sep aration of the contacts. The proportions oi the gas evolving member and the volume oi the compression chamber are so related that upon separation oi the contacts and the consequent formation of an arc in proximity to the gas evolving member, pressures are quickly generated within the chamber oi suoient magnitude to extin guish the arc. More particularly, the gas evolv ing member comprises an annular member which surrounds the contacts, one of which'is reciprocally movable, and this annular member is positioned adjacent the point of separation of the contacts by a pair oi annular spacing members, the spacing members being formed ci a material which is incapable of evolving gas in appreciable quantities when exposed to an arc.

For a more complete understanding of my invention, reference should now be had to the drawing in which Fig. 1 is an elevation view, partly in section, of a circuit breaker provided with an interrupting device embodying my invention, and Fig. 2 is a fragmentary view, partly in section, of the interrupting device, showing the contacts in their open circuit position.

Referring now to the drawing, the circuit breaker comprises a base I0, preferably formed of insulating material, which includes a housing portion II within which my improved interrupting device is contained. As shown, the interrupting device comprises a metallic cylinder I2, preferably formed of steel or other suitable pressure resisting mate iai, in the opposite ends of which are disposed suitable bushings I3, preferably formed of molded insulation, the bushings I3 each having a narrow peripheral portion I4 which cooperates with the cylinder I2 to form a tightly sealed connection. Engaging the inner edge of each of the bushings I3, is an annular insulating member I5, a portion of which extends into a counter-sunk aperture in the adjacent bushing I3, as shown, to support a plurality of sealing washers I6 and I'l. As described in my above referred to patent, the washers I'I are provided with inwardly extending cylindrical portions, as shown, and a similarly shaped guard I8 is provided, preferably formed of soft copper.

Disposed within the cylinder I2 between the annular members I5, I provide a pair of annular g spacing members i9 formed of steel or other suitable heat resisting material which is incapable of kevolving gas in appreciable quantities when exposed to an arc. The outer edge of each of the spacing members l engages the adjacent one of the annular members l5, and a narrow annular member 20 formed of kerosene-free fiber or other suitable gas evolving material is supported between the inner edges of the spacing members i0.

Preferably, the member 2li is formed from a ber made from cotton cellulose treated with zinc chloride, the Zinc chloride being later washed out to reduce its percentage content to less than I have found that a high percentage of zinc chloride causes excessive carbonization of the viiber when subjected to the heat of an electric arc, and accordingly;ber containing a high percentage of zinc chloride is unsuitable for use in devices embodying my invention. Furthermore, the liber from which the ring 20 is formed must be kerosene-free. As will be understood by those skilled in the art, ber materials are ordinarily machined to size, and the usual machining practice is to employ kerosene as a lubricant during the machining operation. I have found, however, that the presence of kerosene in the ber member 20 causes excessive carbonization of the ber, and accordingly, any machining operations performed on the ber ring 20 must be carried out without using kerosene or equivalent lubricants.

Extending through the upper one of the bushings iS, is a iixed contact member 2l, the outer end of which threadedly engages a supporting conductor 22 and the inner end of which abuttingly engages a cooperating, longitudinally movable contact member 23 which is guided for reciprocal movement in the lower one of the bushings !3 and the adjacent insulating member l5. It will be understood of course that the sealing washers it and il, which engage the movable contact 23, exert a wiping action thereon, as described in my above referred to application, and prevent the escape of gas under high pressures while providing for reciprocal movement of the contact 23 to the open circuit position shown in Fig. 2. rIhe washers i6 and ll which engage the xed contact 2l also serve to seal the chamber against the escape of gas at high pressure, and accordingly, a gas-tightly sealed. compression chamber is provided. Although my invention is not limited t`0 the specific arrangement shown, it will be understood that the two ends of the compression chamber are formed of identical parts to provide for economy in manufacture and for ease of assembly.

In assembling the interrupting device,- the Varlous annular members l5, H9 and 20 are rst inserted into the cylinder i2, the sealing washers I6 and il, the guard I8, and the bushings i9 are then arranged in the opposite ends of the cylinder l2, and the ends of the cylinder are anged inwardly, as shown, to engage tightly the narrow peripheral portions lll on the bushings I3. The compression chamber may then be placed in the housing i l and the xed and movable contacts inserted through the respective bushings i3.

It will be remembered that the bushings i3 are formed of molded insulation material, and I have found that this material, which expands only slightly whenv exposed to high temperatures, is particularly effective in maintaining a tightly sealed compression chamber. This molded insulation, however, must be protected to some extent from the excessively high temperatures generated within the compression chamber, and accordingly, the annular members i5 are formed of suitable heat resisting insulating material and closely engage the fixed and movable contacts 20 and 23 respectively, so as substantially to isolate v 5 the insulating bushings i3 from the heat of the arc. Preferably, the insulating members l5 are formed of the same kerosene-free ber which forms the gas evolving member 2Q. Accordingly, these members evolve some gas when an are is 10 drawn between the contacts and assist in quickly building up pressures of sufficient magnitude to extinguish the arc. c

Suitable operating mechanism to bedescribed hereinafter is provided for operating the movable l5 contact 23 through a predetermined range of movement from the closed circuit position shown in Fig. 1 to the open circuit position shown in Fig. 2, and in order that the necessary high pressure may be quickly built up within the compression 20 chamber, the gas evolving member 20 is located adjacent the point of separation of the contact n within the range of movement of the movable contact. Thus, when the circuit breaker operates under short circuit conditions, this annular mem- 25 ber 20 is subjected to intense arcing as soon as the movable contact 23 is disengaged from the fixed Contact 2l, the arc drawn between the contacts bowing outwardly into proximity with the annular member 20, as is well understood by those skilled in the art.

I have found that by properly proportioning the gas evolving member 20 relative to the volume of the compression chamber, an interrupting device may be provided having very quick circuit 35.

interrupting characteristics. The amount of gas evolving material contained in the annular members l5 must also Abe considered of course, but since these members'are disposed at some distance from the region of the most intense arcing, the proportions of the annular member 20 constitute the primary factor to be considered. Circuit interrupting devices embodying my invention have'quickly interrupted 7500 amperes at 230 volts alternating current under short circuit conditions without detrimental burning of the contacts. Under such conditions the` pressures developed withinthe compression chamber are in the neighborhood of 1500 pounds per square inch. Under less severe current and voltage conditions, it will of course be understood that pressures of such magnitude are not developed. For example, under short-circuit conditions at volts, pressures on the order of 300 or 400 pounds only may be developed, and when the circuit breaker is manually operated to its open circuit position to interrupt the circuit with normal rated currents, for example, 50 to 100 amperes, flowing therein, a relatively small arc will be drawn between thev contacts, and comparatively low pressures will effect a quick interruption of the circuit. Likewise, upon operation of the cir- Vcuit breaker in response to normal overload conopen and closed circuitpositions, I have shown for purposes of illustration an operating mechanism of the type described and claimed in a copending application of David C. Prince, Serial No. 75.

7,085, i'lled February 18, 1935, entitled "Circuit breaker, now Patent No. 2,053,971, issued September 8, 1936.

For the purposes of the present invention, this operating mechanism may be described as comprising a U-shaped frame 25 which is secured to the base l0 adjacent the housing Il in a position such that it abuts a closure member 26 arranged in the open end of the housing Il and maintains it securely in place. As shown, the operating mechanism comprises a pair of overcenter springs 21, only one of which is shown, the respective lower ends of the springs being connected to the opposite ends of a pin 28 which extends through a vertical slot (not shown) in the extending end of the movable contact 23.

The other ends of the overcenter springs are connected to pin 29,` which is supported by a pair of levers 30, only one of which is shown, the opposite ends of the levers 30 being pivotally mounted on the extending ends of a pin 3l` which is supported by the-U-shaped frame 25. As is more fully described in the above referred to Prince patent, the pin 29 engages an operating member 324 which is pivoted on a pin 33 supported by the frame 25, and in order to provide ior reciprocal, longitudinal movement of the contact 23, a guide arm 34 is arranged with one end pivoted on the pin 33 and its opposite 'end connected to the pin 28. Secured to the operating member 32, is an insulated handle 35 which extends through a suitable aperture 36 in the circuit breaker cover 31, and it will be apparent that when the handle 35 is moved to rotate the operating member 32 about 'its pivot 33, the pin 23 will be moved so as to carry the springs 2l over- .center relative to the pivot 33 so as to operate the guide arm 34 and the movable Contact 23 between open and closed circuit positions with a snap action. y

Intermediate its ends, the guide arm 34 is provided with a cross portion 33 .arranged= in cooperating relation with one arm 39 of a bifurcated tripping member which is pivoted on the pin 33, the other arm 40 of the tripping member carrying a latch portion 4l which is arranged to engage a movable latch 42 carried by the free end or" a bimetallic element 43. While any suitable type oi bimetallic element may be provided, l prefer to utilize a device of the type described and claimed in a co-pending application of Henry V. Erben, Serial No. 713,896, iiled March 3, i934, entitled Thermal release device, now Patent No. 2,050,879, issued August 11, 1936. As is more iully described in the said Erben patent, this thermal element comprises a pair of bimetallic strips, only one of which is shown, the lower ends of which are respectively connected to a pair of terminal members 44 and 45, the opposite :free ends of the bimetallic strips being connected together by a conductor bar 46 to which the latch 42 is secured.

Normally, the tripping member 40 is restrained in the position shown against clockwise movement in accordance with the bias of a tripping spring 41. The circuit through the circuit breaker may thus be traced from the terminal member 44 through the bimetallic thermal element 43, the terminal member 45 by Way of a iiekible conductor 48 to the movable contact 23, and through the xed contact 2l and the conductor 22 to a terminal screw 43.

Thus, it will be apparent that with the circuit breaker in the closed circuit position shown in Fig. 1, a current of short-circuit magnitude owing through the circuit breaker will cause the thermal element 43 to flex so that the latch member 42 moves downwardly, as viewed in the drawing, whereupon `the tripping member 40 is released for movement in accordance with its bias in a clockwise direction, and the right-hand end of the arm 39 engages the cross portion 38 on the guide arm 34 to operate the movable contact 23 to its open circuit position against the force of the overcenter springs 21.

As soon as the movable contact 23 is disengaged from the fixed contact 2l, an arc is drawn in proximity to the gas evolving member 20, and a high pressure builds up quickly within the compression chamber due to the heat of the arc and the evolution oi gas from the gas evolving member 20. With the gas evolving member 20 properly proportioned relative to the volume oi? the compression chamber, this pressure, as heretofore indicated, will quickly build up to a suiiiciently high value to eiect a quick extinguishment of the arc. The operation ofthe circuit breaker in response to normal overload currents issimilar to the operation under short-circuit conditions except that pressures of less magnitude are de- Veloped.

While l have shown a particular embodiment ci my invention, it will be understood, of course, that I do not wish to be limited thereto, since many modifications may be made and I, therefore, contemplate by the appended claims to cover any such modiiications as iall 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:

l. A circuit interrupting device comprising a pair or relatively movable contacts having a predetermined range oi movement between open and closed circuit positions, walls ci pressure resistant material surrounding said contacts to form a substantially gas-tightly sealed compres= sion chamber, and a gas evolving member disposed within said chamber adjacent the point oi separation or said contacts and entirely within said range of movement, said member being formed or" a cellulose material contamng no substantial amount ci" kerosene whereby substantial quantities of gas are evolved when said member is heated by the arc between said contacts, the proportions of said gas evolving member and the volume oi said chamber being so related that upon operation of said contacts to an open oircuit position and the consequent formation or an arc in proximity to said gas evolving member, pressures are quickly generated within said chamber oi sumcient magnitude to extinguish the arc.

2. A circuit interrupting device comprising walls of pressure resistant material arranged to form a gas-tightly sealed compression chamber, a stationary contact within said chamber, a cooperating reciprocal contact within said chamber having a predetermined range of movement between open and closed circuit positions, an annular, gas evolving member surrounding said contacts in spaced relation thereto entirely within said range of movement, said gas evolving member being formed of a cellulose material containing not substantially over .02% zinc chloride and 'no substantial amount of kerosene whereby substantial quantities of gas are evolved when said member is heated by the arc between said contacts, the proportions of said gas evolving member and the volume of said chamber being so related that upon separation of said contacts and the consequent formation of an arc within said annular gas evolving member, pressures oi' sucient magnitude to extinguish the arc are quickly generated Within said chamber.

3. A circuit interrupting device comprising a pair of relatively movable contacts, walls oi pres= sure resistant material surrounding said contacts to form a gas-tightly sealed compression cham= ber and a plurality of annular members disposed in side-by-side relation within said chamber surrounding said contacts, at least one of said annular members being formed of a cotton cellulose material containing not substantially over .02% zinc chloride and no substantial amount of kero--` sene whereby substantial quantities of gas are evolved when said member is heated by the arc between said contacts, the annular members im mediately adjacent and on each side of said gas evolving member constituting spacers formed of a material incapable of evolving gas in appreciable quantities when exposed to an arc, and the outermost ones of said annular members en gaging said walls to position said gas evolving member adjacent the point of separation oi said contacts, the proportions of said gas evolving member and the volume of said chamber being so related that upon separation of saidvcontacts and the consequent formation of an arc in pron-s irnity to said gas evolving member pressures are quickly generated in said chamber oi suiicient magnitude to extinguish the arc.

li. A circuit interrupting device comprising a metallic cylinder, a pair of insulating bushings respectively secured to the ends of said cylinder and forming therewith a gas-tight circuit interrupting chamber, a stationary contact member extending through one of said bushings into said chamber, a cofacting movable contact guided for reciprocal longitudinal movement Within the other of said bushings into and out of contact with said stationary contact member, packing means co-operating with each of said contacts and its associated bushing to seal said chamber against the escape of gas at high pressures, a plu= rality o annular members disposed in side-byside relation within said cylinder between said bushings, at least one of said annular members being formed of a material capable of evolving gas in substantial quantities when exposed to an arc, the remainder of said annular members serving to position said gas evolving member adjacent the point of separation of said contacts, the annular members immediately adjacent said gas evolving member and on each side thereof being formed of a material incapable of evolving gas in appreciable quantities when exposed to an arc, the proportions of said gas evolving member and the volume o f said chamber being so related that upon separation of said contacts and the consequent formation of an arc in proximity to said gas evolving member pressures of suiicient magnitude quickly to extinguish the arc are generated within said chamber.

5. A circuit interrupting device comprising a metallic cylinder, an insulating bushing mounted at each end of said cylinder and forming therewith an interrupting chamber, a stationary contact member supported by one of said bushings, a co-acting movable Contact member mounted in the other of said bushings and guided thereby for reciprocal movement into and out of engagement with said stationary contact said reciprocal Contact having a predetermined range of movement to provide an interrupting gap between said contacts when in an open circuit position, sealing means between said movable contact member and its guiding bushing for substantially gas-tightly sealing said chamber, an annular member disposed Within said metallic cylinder surrounding said contacts and formed of a materiai capable of evolving gas in large quantities when exposed to an arc, means including a pair of metallic rings respectively disposed on each side oi said gas evolving member for locating said gas evolving member in spaced relation to said bushings and Within said range of movement of said reciprocal contact, whereby said gas evolving member is directly exposed to the arc drawn between said contacts, the proportions of said gas evolving member and the volume of said chamber being so related that upon operation of said movable conta/ct to its open circuit position pressures are generated quickly within said chamber of sumcient magnitude to extinguish the arc.

LUDWIG S. WALLE.

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