US1963418A - Arc suppressing air-break switch - Google Patents

Description

June 19, 1934. R. R. PITTMAN Er A1.

AHC SUPPRESSING AIR BREAK SWITCH Filedfeb. 25, 19:53

ATTORNEY Patented June 19, 1934 UNITED STATES PATENT OFFICE Anc sUrraEssmG .am-mman swrrcn mph n., Pimm ma camu n. Walsh, Pine' Bluff, Ark.

This invention relates generally to switching equipment for use in connection with electric circuits, and particularly to high-tension switches of the air-break type.

5 Air-break switches of the commonly used type depend i'or their interrupting ability upon the elongation in air oi' the circuit-interrupting arc, usually between arcing horns provided for this purpose. The lengths of these arcs are necessarily such, especially for high tension switches, that it is very difficult, if not economically impossible, to provide sutlicient phase spacing between the units making up a polyphase switch to prevent the arcs attending the opening of the switch from blowing together under wind conditions, and short-circuiting the connected circuit. In addition,it is now well known that the volt-ampere characteristic of an arc playing in air is negative, that is, with increasing current a decreased voltage is required to sustain the arc. It is also well known that the voltage gradient through an arc in which the current is of the order of 1000 en'ective amperes is very low, only approximately 200 or 300 eiective volts per inch length being required to sustainthe arc. From these considerations it is apparent that circuit-interrupting devices for high tension circuits which depend upon the elongation of the circuit-interrupting arc in air are either inetlective as circuit-interrupting devices, or, assuming that the arc path is made sumciently long to make the device eiiective, are, due to the excessive length of arc required, a hazard to both the operator and the connected equipment.

for increasing the voltage gradient of the circuitinterruptingvarc, as measured in terms of volts per inch through the arc path, to the end that the length of arc path required for the extin- `r guishment of the circuit-interrupting arc is only from one-twentieth to one-thirtieth of the openair length. l

A further object is the provision of means depending upon a circuit-opening movement oi' a switch for actuating an arc-suppressing switch having an exceeding high voltage gradient therethrough.

A further object is the provision oi' means for restoring an arc-suppressing device to the initial circuit-interrupting position upon a circuit-closing movement of the switch.

A further object is to provide means depending upon a circuit-opening movement of the switch for transferring the initial circuit-inter- It is an object of this vinvention to provide means rupting arc to a set of contacts within the arcing contact structure.

A further object isthe provision of means depending upon a circuit-opening movement of the switch for actuating the movable contacts of the arcing contact structure at a rate of speed independent of the rate of speed oi the circuit opening movement.

A yet further object is to provide an arrangement for interrupting an electric circuit which consists in establishing in series relation in the circuit an open-air arc, and an additional arc within a conned space between adjacent faces of blocks of insulating material, resiliently biased one toward the other.

An additional object is the provision of a simple, eil'ective and relatively inexpensive device for the purpose stated.

With the above and vother objects in view which will appear as the description proceeds, our invention resides in the novel features of form, construction, arrangement and combination of parts hereinafter described and pointed out in the claims.

In the accompanying drawing (1 sheet) Figure 1 is a side elevational view of one pole of an air-break switch embodying our invention.

Figure 2 is a sectional view of the arcing contact structure of the device, taken on the plane A-A, and illustrated as in a circuit-closed position of the switch.

Figure 3 is a sectional view of the arcing contact structure of the device, also taken on the plane A-A, but here illustrated as in a circuitopened position of the switch.

Referring now more in detail to the accompanying drawing, and particularly to the embodiment" of our invention illustrated by Figure 1, 13 is a mounting base for the device, oi' any suitable material and shape. The stationary insulators 10 and 12 are mountedadjacent to the ends of the base 13 in any suitable manner, and the bracket 16 supports, in a manner usual with switches oi' the general type illustrated, a bearing in which the square shaft 15 is adapted i'or rotation by means ci' the crank arm 14 and any suitable remote control mechanism adapted for connection thereto. 'I'he insulator 11 is rigidly ilxed to the square shaft 15, and adapted for pivotal movement therewith within the limi-t indicated by the solid lines and the broken lines in Fig. 1. The arrangement comprising the ioldable links 1'7 and 18 and the iiexible shunt 19, is a common means used in switches oi this type for providim a flexible connection of the switch blade 20 to the conductor 23.

The metal blade 20, rigidly xed to the movable insulator 11 by means of the cap screws 31, is adapted to engage the stationary main contact 28 to close a circuit, the latter being rigidly xed to the top of the insulator 12 by means of the cap screws 30. It will be apparent from Figure 1 that the main current carrying path through the switch is from conductor 24 to the main contact 28, thence through the blade 20 and the iiexible conductor 19 to the conductor 23. The switch blade 20 is provided with a forwardly extending portion for engaging the roller 32, and in this manner the circuit-closing movement of the blade is transmitted to the arcing contact structure of the switch.

We will now describe in detail the arcing contact structure, or arc-suppressing switch, illustrated in Figures 2 and 3. The side walls 57 and 58, the end walls 63, and the top and the bottom 59 are all of some suitable insulating material, a material such as horn fiber having desirable physical properties and a comparatively low cost, and are assembled in the form of a box in any suitable manner, as by the cap screws 36 and 2'7. The base member 26 is provided with a longitudinally extending portion at one end for bolting to the cap of the insulator 12, and thus forms a support for the arcing contact structure. In addition, the base member 26 serves to conduct the current through the device from the conductor 24 to the main contact 28, being provided with an extending portion to provide means for this connection by the screws 25.

The stationary contacts 40 and 42 extend through the side walls 57 and 58 near the midpoint thereof, and in a direction normal thereto. IPhe contact 42 is electrically connected by means of the metal member 44 to the base 26 by the bolts 37, and the contact 40 is electrically con.- nected to the hook-shaped arcing horn 29 by the metal member 39. The metal members 44 and 39 are provided with 11p-standing portions having tapped holes extending therethrough, for the purpose of supporting the contacts 40 and 42. The lock nuts 41 and 43 are simply for the purpose of rigidly locking the contacts 40 and 42 in place. The flexible conducting braid 62 provides a low-resistance path for current passing between the arcing horn 29 and the metal member 39.

The bridging member of the arc-suppressing switch comprises a pair of axially spaced disks 64 and 65, also of some suitable insulating material. Adjacent the midpoint of the disks 64 and 65, we provide the moving contacts 50 and 53, extending normal into the disks 64 and 65 for a distance substantially equal to the thickness of the contacts. The bolts 5l and 52 rigidly fix the contacts 50 and 53 to the disks 64 and 65, and in addition provide means for connecting the contact 50 to the contact 53 by means of the flexible conductor 55. The inner adjacent faces of the disks 64 and 65 are provided with circular grooves, into whichv is tted the spring 54. It will be apparent that the spring 54 is adapted to urge the disks 64 and in an axial direction away from one another, and against the insulating walls 57 and 58 respectively.

The operating rod or plunger 45, preferably of some suitable insulating material, is provided at a point adjacent its lower end with the crossmember 49, the latter being adapted to extend e. short distance in openings provided near the the yoke.

upper portions of the disks 64 and 65, this arrangement providing a means for attaching the disks 64 and 65 to the operating rod 45. The upper portion of the operating rod 45 extends through the sleeve 48 in the top 60, and has a threaded end portion for rigidly attaching the roller bracket 33, the hood 34 and the lock nut 61. For urging in an upward direction the operating rod 45, together with the other portions of the arcing contact structure attached thereto, the concentric coil spring 35 is provided between the inner Wall of the hood 34 and the top 60. The opening through the sleeve 48 is somewhat larger than the cross-sectional area of the operating rod, so that the latter is free to reciprocate through the former. The stationary contacts 40 and 42 and the movable contacts 50 and 53 are all arranged in substantially the same vertical plane, and in this manner a reciprocatory movement of the operating rod 45 causes a passing engagement of the stationary and movable contacts to close and open a circuit through the arcing contact structure.

The substantially J shaped metal horn 29 is arranged for pivotal movement in a bearing formed by an upstruck portion of metal member 39, and the latch member 16 is pivotally connected adjacent the upper end of the short arm of the J by means of the yoke 47, which may be screwed on the end of the short arm of the J, and the latch member 16 attached in any suitable manner, as by a pin extending through The flat metal spring 66 is provided for biasing the latch member 16 against the operating rod 45, and the latter is provided with a notched portion adapted for registering with the latch member 16.

We will now explain the operation of our switch, and describe the action of the various cooperating parts as a circuit through the switch is closed and opened.

Assume the switch to be in the position illustrated by the broken lines in Figure 1, and that the crank 14 is rotated in any suitable manner in a direction to close a circuit through the switch. As the blade 20 approaches its cooperating main contact 28, the forwardly extending portion of the blade 20 first engages and passes in sliding engagement the upwardly and laterally extending portion of the arcing horn 29. With a continued rotary movement, theforwardly extending portion of the blade 20 next engages the roller 32, in this manner urging in a downward direction the'movable portions of the arcing contact structure until the latch 16, under the bias of the spring 66, engages the notch in the operating rod 45. Simultaneously with the downward movement of the roller 32, the blade 20 engages its cooperating main contact 28 to close the circuit through the main current carrying switch. The condition just described is illustrated by the solid lines in Figure 1, and the position of the various members of the arcing contact structure is illustrated in Figure 2.

Assume now that the switch is in the closed circuit position described above, and that a circuit is to be opened by the switch. The crank 14 is now rotated in a clockwise direction, and the blade 20 iirst moves away from the roller 32 and the main contact 28. Since the movable contacts 50 and 53 are latched out of engagement with the stationary contacts 40 and 42, no arc is drawn from the roller 32 to the blade 20 The circuit-interrupting arc is therefore first drawn from the main contact 28 to the blade 20. As the circuit-opening movement of the blade 20 continues, it slidingly engages the downwardly and laterally sloping portion of the arcing horn 29, and urges this portion of the horn in a lateral direction. This movement of the horn 29 causes the latch 16 to disengage the operating rod 45, so that the latter, along with the other movable portions of the arcing contact structure, s moved rapidly in an upward direction under the bias of the spring 35.

It will be seen that the stationary contact is at the same potential as the blade 20 at the time the latter engages the arcing horn 29, and further, that the stationary contact 42, being electrically connected to the base member 26, is at the same potential as the main contact 28. Under these conditions, it is obvious that a movement resulting in a low resistance metallic connection, or short-circuiting, of the stationary contacts 40 and 42 will reduce the potential to substantially zero and thus extinguish any arc existing between the blade 20 and the main contact 28. Such an action occurs as the movable contacts and 53 pass in sliding engagement over the stationary contacts 40 and 42, and in this manner the circuit-interrupting arc is transferred from the main contacts of the switch to" the arcing contact structure.

Upon the continued upward movement o1' the movable contacts 50 and 53, the circuit interrupting arc is drawn between the stationary contact 42 and the movable contact 53, and the stationary contact 40 and the movable contact 50, and in the confined space between the adjacent faces of the insulating members 57 and 64, and 58 and 65, respectively. It is now well known that the voltage gradient through an arc path of the character here described is exceedingly high in comparison with an arc playing in the open air, and we employ this principle to increase the eiectiveness of our switch as a circuit-interrupting device.l In adapting the length of the arc-path to the particular circuit voltage, the voltage required to sustain the arc is adjusted to a value in excess of the circuit voltage, with the result that the arc is always extinguished in a very short time, about 1/ cycle being required on a sixty cycle alternating current system. Figure 3 illustrates the position of the various parts of the arcing contact structure following a circuitopening movement.

It will be apparent from the description here recited that the rate of movement of the movable portions of the arcing contact structure is independent of the rate of the movement of the switch blade 20, and that, in addition the continued circuit-opening movement of the blade 20 results in a seriesv arrangement in the circuit of the open air arc between the horn 29 and the blade 20 and the confined arc within the arcing contact structure.

The vent pipe 56extends through the bottom member 59 of thearcing contact structure, and is provided for the purpose Ao1' venting to the air any gases generated due to the action of the arc upon the insulating materials used to conilne the arc, and the spring 54 provides the necessary resilience in order to prevent the device being damaged by gas pressure.

Referring further to the arcing contact structure, we will now point out our reasons for latching the movable contacts 50 and 53 in a position out of engagement with the stationary contacts 40 and 42. While our invention will operate if this arrangement is not provided, we have found that the time for interrupting the arc is less, and the burning of the electrodes and insulating material correspondingly reduced, if the movable contacts are arranged, as here shown, for'rapidly passing engagement over the stationary contacts for closing the circuit for a very short interval of time.

While we have here described one embodiment of our invention, we are aware that the particular embodiment may be variously modiiied without departing from the spirit of our invention.

Weclaim as our invention:

1. An air break switch comprising, in combination,movable means for actuating a blade to close and open a circuit, an arcing contact structure having a movable member adapted to extinguish the circuit interrupting arc, means biasing said movable member, a latch mechanism restraining the movement of said movable member, said latch mechanism including a swingably mounted arcing .horn disposed for lateral movelment in the path of movement of said blade, means biasing said arcing horn laterally in one direction, and lmeans responsive to a lateral movement of said arcing hornI in the opposite direction for releasing said movable member.

2. In an air break switch, movable means for actuating a blade to engage and disengage a stationary contact to respectively close and open a circuit, insulating means supporting said stationary contact and an arcing contact structure having, a movable member' including an operating md and a helical spring coaxial with said rod for biasing said movable member, contacts carried by' said movable member and adapted to separate from stationary contacts to extinguish the circuit-interrupting arc, and means including a swingably mounted spring-biased arcing horn positioned in the path of said movable blade, and a latch member pivotally mounted on said arcing horn and arranged to engage a stop on said operating rod whereby said movable arcing contact member is released and actuated through the bias of said helical spring upon the occurrence of a circuit-opening movement of said switch.

3. An air break switch comprising, in combination, movable means for actuating a blade arranged to engage and disengage a stationary con- .tact to respectively close and open a circuit, in-

sulating means supporting said stationary contact, an arcing contact structure having a springpressed movable member mounted adjacent to said stationary contact and supported'by said insulating means, a swingably disposed springbiased arcing horn supported by said arcing contact structure and having a latch member pivotally mounted adjacent to the lower end thereof for engaging a stop on said movable member'to restrain the movement of said movable member,

the upper end oi' said arcinghorn extending upwardly iirst into and then out of the plane of movement of said blade, and an extended portion of said blade for cooperating with said arcing horn whereby a circuit-opening movement of said movable means causes the blade to pass in sliding engagement with the upper portion of said arcing horn thereby releasing the said springpressed movable member of the arcing contact structure.

4. An air break switch comprising, in combination.' movable means for actuating a blade arranged to engage and disengage a stationary contact to respectively close and open a circuit, insulating means supporting said stationary contact, an arcing contact structure supported by said insulating means, a movable member in said arcing contact structure arranged to cooperate with a forwardly extending portion of said blade, means biasing said movable member, a swingably disposed arcing horn supported by said arcing contact structure, a latch member pivotally mounted adjacent to the lower end of said arcng horn for engaging a stop on said movable member, means biasing said latch member toward said movable member to restrain the movement thereof, a bent portion adjacent to the upper end of said arcing horn, the said bent portion extending first into and then away from the path of movement of said forwardly extending blade in thel same lateral direction, whereby upon the occurrence of a circuit-closing movement of said movable means the said forwardly extending blade portion passes said horn in sliding engagement to close a circuit through said switch.

5. The combination with a main current carrying switch of a supplementary arc-suppressing switch, said arc-suppressing switch including a housing comprising a hollow body portion of insulating material having contact members extending through a wall thereof, a bridging member having contact members arranged for cooperation with said first-named contact members to close a circuit through said arc-suppressing switch and to open a circuit through said arc-suppressing switch in response to a movement of said bridging member, said bridging member being arranged for movement relative to and entirely within said hollow body portion, elements of insulating material associated with said bridging member arranged for slidable movement over the inner surface of said hollow body portion, the arrangement being such that an opening movement of said bridging member elongates the circuit-interrupting arc between the relatively moving surfaces of said hollow body portion and said elements of insulating material, a passageway extending through a wall of said hollow body portion in communication with the atmosphere whereby the arc products may be vented, means biasing said bridging member towardan open circuit position, latch means restraining the motion of said bridging member, movable means for actuating said main current carrying switch, and means responsive to a movement of said movable means in a direction to open said main current carrying switch for unlatching said bridging member.

6. The combination with an air-break switch having insulating means supporting the live parts thereof and movable means for opening said switch, of an arc-suppressing switch supported by said insulating means, said arc-suppressing switch including a housing comprising a hollow body portion of insulating material having contact members extending through a wall thereof, a bridging member arranged for movement entirely within said hollow body portion, said bridging member having contact members for cooperating with said first-named contact members to close a circuit through said arc-suppressing switch and to open a circuit through said arc-suppressing switch in response to a movement of said bridging member, 100 elements of insulating material associated with said bridging member arranged for movement in close proximity to the inner surface of said hollow body portion, the arrangement being such that an opening movement of said bridging member elon- 105 gates the circuit-interrupting arc between the adjacent surfaces of said hollow body portion and said elements of insulating material, means for venting said hollow body portion to the atmosphere, and means responsive to a movement of 110 said movable means for inserting said arc-suppressing switch in series relation with a circuit and imparting motion to said bridging member.

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