US2351426A - Electric switch - Google Patents

Description

June 13, -1944. G. A. HEALIS 2,351,426

ELECTRIC SWITCH v Filed Au 22, 1942 Inventor:

George AHealis,

b W 4 112221 y His Attorney.

Patented June 13, 1944 2,351,426 snso'rarc swrron George General New York A. Healis, Lansdowne, Pa., assignor to Electric Company, a corporation of Application August 22, 1942, Serial No. 455,771

. viewed in Fig. 2, the main blade 3 comprises a Claims.

My invention relates to electric switches, more particularly to those of the load-break switch type wherein means are provided for interrupting load power currents as well as for carrying the normal load current and disconnecting the' circuit.

The problem of both interrupting and disconnecting a high voltage power circuit at points where conventional power circuit breakers, such as oil circuit breakers, are impractical or uneconomical involves a number of difficulties including those associated with the usual requirements for simplicity and ruggedness in structure, compactness, economical construction and operation, and electrical eiiiciency in both interrupting the load power are and disconnecting the circuit. Although a great deal of design work has been devoted to this type switch, the devices in general have been somewhat complicated and expensive, particularly for moderate interrupting duty such as for example interrupting the magnetizing current of a 15,000 volt power transformer.

A principal object is the provision of an improved load-break switch that is simple, rugged and inexpensive in construction, and that is capable of efliciently interrupting moderate load currents in high voltage power circuits and disconnecting the power circuits.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referringto the drawing, Fig. l is an elevational view, partly in section, of a load-break switch embodying the present invention in the closed circuit position thereof, Fig. 2 is an elevational end view, partly in section, of the switch shown by Fig. 1, Fig. 3 is a detail view of the switch contact structure illustrating the switch in the partly open position thereof, and Fig. 4 is a similar view showing the contact structure in the open circuit disconnecting position.

fTh'e load-break switch shown by Fig. 1 comprises a pair of stationary terminals l and 2 to which the fixed and movable contact structures, respectively, are connected. The terminals to which the power circuit is connected at l and 2', respectively, are adapted to be bridged and electrically connected by a main current-carrying contact blade 3 pivotally mounted at l on a pair of spaced conducting members I provided at opposite ends oi the blade with spring washers 5 for biasing the blade into clamping engagement with the associated terminal members. At the terminal I, the blade is adapted to engage a conducting extension i", the contact engagement between the blade and the co-acting fixed contact I" being made at ridges I on the blade. The ridges are biased by the spring washers 5 into high pressure line contact with the fixed contact. An electrical contact is similarly made at the lower terminal contact 2" so that the blade 3 in the closed circuit position shown is capable of carrying large power currents across the switch terminals without overheating.

For the purpose of interrupting load power currents when the switch is to be opened, there is mounted on a bracket i'a on the upper terminal an arc extinguishing structure 1, such as an arc chute of the narrow slot type. There is also provided an arcing contact 8 that is pivotally of my invention, therefore,

mounted at 9 on the main blade and operable within the arc chute for extinguishing arcing at the terminal I. As best shown by Fig. 2, the arcing contact 0 and its cooperating arc chute I are materially oilset with respect to the blade 3 so that the blade operates free oi the arc chute so as not to be subject to the effects -of arcing. The arcing contact 0 is provided with contact portion 8 arranged to engage a combined arcing contact and runner it within the are chute.

The contact i0 is connected to the terminal I through a magnetic blowout coil H, one terminal of which at II" is connected to the contact ill and the other termia'nl at H to the switch terminal I. Accordingly it will be seen that the blowout coil is energized when are current flows conducting extension 2" of the terminal I. As

between the arcing contacts II and l. The blowout coil II is provided, in accordance with well known practice, with iron pole pieces I! placed gt opposite sides of the are chute as shown in The are chute that I have shown merely by way of example, comprises a pair of spaced insulating plates i3 clamped together at it and having on the inner sides facing each other insulating liner plates ll composed of a suitable arc resisting material such as asbestos. The asbestos plates are quite closely spaced so as to form a narrow slot for the arcing contact 8 and are so shaped that the resulting slot-like arc chamber is is tapered so that the exhaust opening it at the top of the chute is but a slit.

An important feature ormy invention is the contact arrangement whereby the main blade 3 is first opened, thereby shunting the power current through the blowout coil and the arcing contacts i and 8, and after the blade contact has moved a safe distance from the fixed contact the arcing contact 8 is opened to draw the interrupting are within the chute at a rate that is determined solely by and in accordance with the opening movement of the blade 3. To this end the contact 8 is provided with a tail-like extension it below the pivot 9 arranged to be directly in they path of a fixed ofiset pin I 1 carried by a bracket l3 that is mounted on the 'lower terminal 2. The contact 8 is also provided with a biasing spring l3 mounted on the pivot pin 9 and secured at and 2i, respectively, to the blade 3 and contact 3 for biasing the arcing contact counter-clockwise about its pivot 9 toward contact making'engagement with the fixed contact l0.

Accordingly when the blade 3' is opened by conventional means, such as a pole hook (not shown), the arcing contact 8 will at first remain in engagement with the arcing contact ll so as to provide for arc-free opening of the blade 3. After predetermined opening movement of the blade 3, the pivot 3 or the arcing contact has moved clockwise suiliciently to cause the tail ii to strike'the fixed pin l'l. Continued opening movement of the blade 3 thereupon causes clockwise rotation oithe arcing contact 3 at a rate dependent on the rate of opening movement of the blade 3. Since the contact 3 in addition to rotating clockwise about its pivot 9 is also rotat 'ing clockwise about the blade pivot 4, it will be apparent that the opening speed of the arcing contact is greater than that of the blade 3 so that at some point in the opening movement the two will have reached the same position. This position is shown by Fig. 4 which represents the open and disconnected position of the switch. In this position it will be noted that the blade and arcing contact are compactly arranged with their longitudinal axes substantially in alinement with each other and thereby provide the maximum disconnecting gap between the movable contact structure and the terminal l with the minimum space requirement.

In closing the switch, the blade and arcing contact move as a unit from substantially the 90 open position until the blade 3 has completed an angular movement of approximately 60 degrees. At this point the arcing contact 3 hasmoved sufiiciently in advance of the .blade in the inanner above described to make contact at Ill with the fixed terminal structure. Since the circuit is now complete through the arcing contacts the blade 3 can be moved into engagement with its fixed contact I" as shown in Fig. 1, without arcing.

By reason of the controlled movement of the arcing contact, it is possible to extinguishvhigh voltage arcsentirely within the chute I. If the arcing contact were not so controlled and were operated for example by snap-action the arc might in some cases be drawn too quickly through the chute so as to be drawn exteriorly oi the chute before it is extinguished. Such operation is very undesirable as arcing exteriorly of the chute is objectionable to operatives.

It should be understood that my invention is not limited to specific details or construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric switch comprising relatively movable contact structures, one of said contact structures including a pivoted current-carrying member and an arcing member, said arcing member being pivotally mounted on and carried by said current-carrying member, a member fixed with respect to both said members, said arcing member having means arranged to engage said fixed member after predetermined opening movement of said current-carrying member for causing positive opening movement of said arcing member at a rate controlled by and in accordance with the opening movement of said currentcarrying member, said arcing member being therebymoved to the open circuit disconnecting position with said current-carrying member, and means for causing said pivoted current carrying member and said arcing member to have their longitudinal axes substantially in alinement when said switch is in the open circuit disconnecting position.

2. A load-break switch comprising fixed contact structure and a relatively movable blade member having a fixed pivotal mounting, an arcing contact pivotally mounted on and carried by said blade member, means for resiliently biasing-said arcing contact toward said fixed contact structure so that said blade member can separate from the fixed contact prior to separation of said arcing contact, a fixed member coacting with said arcing contact after predetermined opening movement of said blade member for causing positive separation of said arcing contact from the fixed contact against said bias, the rate of separating movement of said arcing contact being solely and directly controlled by the movement of said blade member, and means for causing said blade member and said arcing contact to have their longitudinal axes substantially in alinement when said load'break switch isin the open circuit position.

3. A load-break switch comprising a fixed conmounting, an arcing contact pivotally mounted on and carried by said blade at a point interme diate the fixed contact and said blade pivotal mounting, means for resiliently biasing said arcing contact toward said fixed contact structure so that opening movement of said blade precedes that of said arcing contact, said arcing contact having an extension beyond its pivot in a direction away from the fixed contact, and a fixed member coacting with said extension for causing after predetermined opening movement of said blade positive separation ofsaid arcing contact at'an' angular rate greater than the angular rate of separation of said blade, said arcing contact being thereby moved to the open circuit disconnecting position into substantial juxtapo-. sition with said blade. 4. A load-break switch comprising fixed contact structure having arc-extinguishing means and a coacting pivoted, blade member, an arcing contact pivotally-mounted on and carried by said blade member for coacting with saidarc-extin; guishing means, means for resiliently biasingsaid arcing contact toward said fixed contact StlllCr; ture so thatopening movement of said blade-pres cedes that of said arcing contact, and meansac' a; actingv with said blade and arcing contact :for

causing in response to opening movement of said blade positive separation of said arcing contact at an angular rate greater than the angular rate of separation of said blade, said blade and arcing contact being movable simultaneously to an open circuit disconnecting position at which position said arcing contact is in substantial alinement with said blade.

5. A load-break switch comprising fixed contact structure having arc-extinguishing means and a pivoted blade member, an arcing contact pivotally mounted on and carried by said blade member for coacting with said arc-extinguishing means, means for resiliently biasing said arcing contact toward said fixed contact structure so that opening movement of said blade member precedes that of said arcing contact, a fixed stop member arranged in the path of a portion of said arcing contact for engaging said portion at a predetermined point in the opening movement of said blade thereby causing positive opening movement of said arcing contact at an angular rate controlled solely by the movement of said blade member, said biasing means during the circuit closing operation causing said arcin contact to precede said blade and make the circuit substantially at said predetermined point, and means including said portion of said arcing contact and said fixed stop member for causing said pivoted blade member and said arcing contact to have their longitudinal axes in substantial alinement when said load break switch is in its open circuit position.

GEORGE A. HEALIS.

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