US 2223975 A
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Dec. 3, 1940. o. c. TRAVER ELECTRIC CIRCUIT BREAKER w/////// n////// .a I. a.
Ifiventor": Olive? C. Tr ver: y I'lis ttorrwey.
Patented Dec. 3, 1940 UNITED STATES PATENT OFFICE ELECTRIC CIRCUIT BREAKER Oliver 0. Traver, Drexel Hill, Pa, assignor to genital Electric Company, a corporation of New Application September 1, 1 939, Serial No. 293,085 6 Claims. (01. 200-149) The present invention relates to electric cirstationary contact I are pressed when the switch cuit breakers, and more particularly to expulsion is assembled. type circuit breakers in which the arc is extin- The movable contact of the switch is in the guished by gas liberated from the walls of an arcform of an elongated hollow rod l1 having an exconfining chamber under the action of the arc tension or pencil it of insulating material secured heat. to the inner end thereof in any suitable manner In breakers of the gas expulsion type the as by the screw-threaded connection illustrated. amount of gas available for extinguishing the The movable contact I! is arranged to engage the arc is dependent upon the arc heat and, as a refixed contact H in the closed circuit position of i0 suit, the amount of gas available when the curthe circuit breaker to complete a circuit from m rent being interrupted is small is sometimes inthe conducting housing which may serve as one sufllcient to successfully interrupt the arc. If terminal of the breaker to the other terminal of the arc passageismade of sufllciently limited area the breaker y a Suitable Sleeve Co t ct ot to create an effective arc-extinguishing gas presshown). The movable contact is reciprocated in sure by the small amount of gas liberated when a the -c fi tube y y Suitable e 1 light current are is drawn, destructive pressures anism (not shown) in a manner well understood will be built up in the restricted arc-confining by those skilled in the art. passage when a heavy current are is drawn. This As the movable contact [1 is withdrawn from characteristic of breakers of this type oft n prethe fixed contact during the circuit-interruptvents their use where a wide range of currents ing Operation of the breaker, the pencil I8 is 20 must be interrupted. It is accordingly an imdrawn into the passage in the arc-confining tube portant object of the inventi n t provide n imlli defined by the liner [3. In accordance with proved construction and arrangement in circuit the present invention the movable contact and breakers of the above type which is effective to the filler pencil l8 are made as nearly the size 5 interrupt currents of widely varying magnitude. of the passage through the liner l3 as possible Further objects and advantages of the present without causing undesirable friction between the invention will become apparent as the following relatively movable parts, so that there is very description proceeds, reference being had to the little space between the inner wall of the liner accompanying drawing in which Fig. 1 is an elei3 and the outer surface of the movable contact.
vational view in section of a circuit breaker em- In order to provide arc-confining passages, the 30 bodying the invention; Fig. 2 is a sectional view filler Pencil s provided with a plurality o taken along the line 2-2 of Fig. 1, and Fig. 3 grooves l9 which extend generally in the direcis an elevational view of a modification thereof. tion of the relative movement between the fixed Referring to Fig. 1, I have shown my invention and movable contacts. The grooves l9 are conembodied in a circuit breaker comprising an arcnec ed o e y a Passage 20 o ed on the 35 confining structure ill in the form of an elongated surface of the pencil l8 and extending sufiiciently tube of insulating material. The tube In is conaround the same to form a headerjor the grooves nected to a supporting insulator H by a two-part S. The passage 20 is preferab y formed adhouslng ll of conducting material. The tube l0 jacent the inner end of the movable contact ll is provided with a lining of gas-emitting matewhere it is in communication with a root of the 40 I rial which, in the present case, is in the form of arc and will be effective to distribute the current a removable liner l3 which is recessed at its upof a heavy C e t arc O g the o es H in per end to receive a fixed contact I. The liner a manner which will be more fully set out at a is secured in the tube III by a threaded member later point in the specification.
Ha which engages the lower end of the tube. In some applications it is desirable to provide 45 The contact II is annular in shape and formed an arc passage of increasing cross-sectional area of a plurality of spring-biased segments. The as the contacts are separated, in order to procontact is connected to the housing I2 in any vide a larger space for the heated gases and to suitable manner as by the conducting strips I5 preven o rea an i cr in pr ur This 'which are clamped between the upper part of desirable feature may be incorporated readily in 50 the housing and an annular washer l6 of insuthe present construction by simply increasing lating material. The washer is received between the cross-section of the grooves I! as they ap the two parts of the housing at its outer edge and proach the end of the pencil. This is a simple extends inwardly to form a header against which operation from a manufacturing standpoint and the arc-confining tube ll, the liner l3 and the permits the construction of a switch having an 55 arc-confining passage of progressively varying cross-section without appreciably increasing the expense of manufacture. -In other applications it may be desirable to decrease the cross-sectional 5 area of the arc-confining passage as the separation of the relatively movable contacts increases in order to provide a snufling action on the arc. For such installations the grooves I 9 may be formed with gradually decreasing cross-section 0 as the distance from the movable contact increases. Such a construction is particularly adapted for use in breakers handling relatively small currents where the quantity of arc-extinguishing gas liberated is small and the snufllng action of the tapered arc-confining passage aids in increasing the pressure of the gas available for extinguishing the arc.
In the arrangement shown the arc-confining tube l0 and the liner I3 are provided with intermediate passages 2| which communicate with the interior of an expansion chamber 22 secured to the exterior of the arc-confining tube 10 in any suitable manner as by the screw-threaded connection illustrated in the drawing. The ex- 'pansion chamber which permits the highly heated and ionized gases exhausted from the arc-confining chamber to expand and cool before they are exhausted into the surrounding atmosphere is, as illustrated in the drawing, divided into upper and lower expansion chambers 23 and 24 by a transversely extending partition 25 having openings 26 formed therein. Suitable mufliers 21 in the form of wire mesh are provided in each of the expansion chambers to deaden the sound of the arc and to aid in cooling and removing the metal vapor or particles from the hot gases before they are exhausted to the atmosphere through openings 28 formed in the outer wall of the chamber 22. The advantages of the structure described above will be better understood from a consideration of the circuit-interrupting operation of a breaker in which it is embodied. With the contacts of the breaker in their closed circuit position, as illustrated, a circuit is completed from the housing l2, through the strip I5, the fixed contact 14, the movable contact II, to the other terminal of the breaker (not shown). When the movable contact is moved downwardly to separate it from the contact I the pencil I8 is drawn into the interior of the arc-confining tube l0 and an arc is drawn between the relatively movable contacts. As previously pointed out, the interior of the lining of the arc-confining tube conforms closely in size with the outer surface of the movable contact I! and the filler pencil l8 attached thereto so that the arc, when drawn, is confined within one of the grooves N. If the current is small, the gas liberated from the walls 50 of the groove and the liner I3 is small and the resulting pressure, while not great, is suflicient to extinguish the arc confined in the single groove. As the contact I! is withdrawn from the arc-confining tube the gases liberated by the 5 are are exhausted through the passages 2| into the expansion chambers 23 and 24 and into the atmosphere through the passages 28. When the movable contact is'completely withdrawn from the arc-confining tube the gases may also exhaust directly from the lower end of the tube.
If a large current is being interrupted the arc drawn in one of the passages l9 liberates larger amounts of arc-extinguishing gas because of the greater are heat. The provision of the passage 20 for connecting the grooves I 9 together provides means for transferring the gases from one groove to the other and for dividing the are into a plurality of parallel branches. Placing the passage 20 adjacent the end of the movable contact at which the arc is drawn renders it very eifective to cause a division of the are when the current is large. The splitting of the heavy current arcs by the structure described above may be understood from a consideration of the voltage current characteristics of a closely confined electric arc. When an arc is unconfined the arc voltage decreases with an increase in current and, under such circumstances, a division of the arc would not occur. However, when an arc is closely confined, as with the present construction, the voltage drop across the arc increases with the current flow after a certain current level is reached and, under these circumstances, the arc will seek a parallel path and .a divided arc will be maintained whenever it can be established with a lesser voltage gradient than that required to maintain the total arc current in a single groove.
Thus, it is seen that the present construction provides a circuit breaker having a plurality of arc-confining passages electrically in parallel and adapted to be brought into use automatically by the conditions created in the arc-confining structure by the arc itself. As a result, the conditions existing in any one of the arc-confining grooves l9 vary over a relatively small range as compared with the range of currents being interrupted since any increase in current value beyond a certain point will cause a division of the are among two or more of the grooves. This action results in more uniform interrupting characteristics and, at the same time, increases the range of currents which may be interrupted by the breaker.
In Fig. 3 I have shown a filler pencil 30 which may be substituted for the pencil l8 shown in Fig. 1. In accordance with the modification illustrated in this figure a plurality of spiral grooves 3| are provided in the surface of the pencil 30 and are connected together at their lower ends by a connecting passage 32. The use 1. An electric circuit breaker of the expulsion type comprising means defining an arc passage, a fixed contact, a movable contact engaging said fixed contact in the closed circuit position of said breaker and separable therefrom to draw an arc in said passage and a member of insulating material movable into said passage upon circuit-interrupting operation of said breaker, the walls of said arc-confining passage and said insulating member being closely fitting and gas emitting under the action of the arc and shaped to provide a plurality of interconnected grooves extending generally in the direction of separating movement of said contacts and providing a plurality of arcconfining passages.
2. An electric circuit breaker comprising means defining an elongated passage, a stationary contact, a movable contact extending into said passage and engaging said fixed contact in the closed circuit position of said breaker, a member of insulating material connected to said movable contact and movable therewith into said passage when said movable contact is moved toward circuit-interrupting position, the cooperating surfaces of said member and the walls of said passage having a plurality of interconnected grooves formed thereon to provide a plurality of arcconfining passages.
3. An electric circuit breaker of the gas expulsion type, comprising means defining an elongated arc-confining chamber, a fixed contact, a movable contact movable in and closely fitting said arc-confining passage, an extension of gasemitting material on said movable contact arranged to be drawn into said arc-confining passage upon separating movement of said fixed and movable contacts, said extension being provided with a plurality of grooves extending generally in the direction of separating movement of said contacts and a passage communicating with said grooves adjacent the end of said movable contact and providing for the free transfer of arc gases from one groove to another and a division 01' the arc among the grooves in accordance with the magnitude of the arc current.
4. An electric circuit breaker of the expulsion type comprising means defining an elongated passage, a stationary contact, a movable contact extending into said passage and engaging said fixed contact in the closed circuit position of said breaker, a member of insulating material connected to said movable contact and movable therewith into said passage when said movable contact is moved toward circuit-interrupting position, the cooperating surfaces of said member and the walls of said passage having a plurality of interconnected spiral grooves formed thereon to provide a plurality of arc-confining passages.
5. An electric circuit breaker of the expulsion type, comprising means defining an elongated arc-confining chamber, a fixed contact, a movable contact movable in and closely fitting the walls said arc-confining chamber, an extension of insulating material on said movable contact arranged to be drawn into said arc-confining chamber upon separating movement of said fixed and movable contacts, said extension being provided with a plurality of spiral grooves extending generally in the direction of separating movement of said contacts and a passage communicating with said grooves adjacent the end of said movable contact and providing for the free transfer of gas from one groove to another.
6. An electric circuit breaker of the gas expulsion type comprising means defining an elongated passage, a stationary contact, a movable contact extending into said passage and engaging said fixed contact in the closed circuit position of said breaker, a member of insulating material connected to said movable contact and movable therewith into said passage when said movable contact is moved toward circuit-interrupting position, the cooperating surfaces of said member and the walls 01' said passage being shaped to provide a plurality of interconnected arc-confining passages having a cross-sectional area varying progressively with the separation of said fixed and movable contacts.
OLIVER C. TRAVER.