US3721790A

US3721790A - Contact-pressure linkage for a circuit interrupter of the torsion-spring type

Info

Publication number: US3721790A
Application number: US00141686A
Authority: US
Inventors: C Bice; F Senchur; R Few
Original assignee: Westinghouse Electric Corp
Current assignee: ABB Inc USA
Priority date: 1971-05-10
Filing date: 1971-05-10
Publication date: 1973-03-20
Anticipated expiration: 1990-03-20
Also published as: JPS5133313Y2; AU474579B2; AU4199972A; JPS4733847U; DE2221632A1

Abstract

A rotatable operating shaft carries a contact-pressure torsion spring thereon, one end of the torsion spring being secured to the rotatable operating shaft itself, and the other end of the torsion spring biasing a contact arm, which loosely slides about the rotatable operating shaft. The free end of the contact arm is mechanically linked to the movable contact of a circuit interrupter to cause the opening and closing motions thereof. The rotatable contact arm is affixed to a sleeve which slidably rotates about the operating shaft, and has an abutment portion, which during the opening operation, makes impact engagement with an impact pin, the latter moving with the operating shaft, and striking the abutment portion of the slidable sleeve during the opening operation for impact opening. The contact-pressure linkage is particularly suitable for multiphase operation in which a number of pairs of separable contacts are simultaneously actuated in gang-operation by a single common rotatable operating shaft actuated by a single mechanism.

Description

United States Patent Bice et al.

[ 1March 20, 1973 [54] CONTACT-PRESSURE LINKAGE FOR A CIRCUIT INTERRUPTER OF THE TORSION-SPRING TYPE Inventors: Charles D. Bice, Pittsburgh; Frank W. Senchur, Delmont, both of Pa.; Robert A. Few, Bloomington, lnd.

Westinghouse Electric Corporation, Pittsburgh, Pa.

Filed: May 10, 1971 Appl. No.: 141,686

[73] Assignee:

[56] References Cited UNITED STATES PATENTS Dotto ..200/67 C Prescott 200/67 C Primary Examinerl-l. 0. Jones Attorney-A. T. Stratton, C. L. Mcl-lale and W. R. Crout A rotatable operating shaft carries a contact-pressure torsion spring thereon, one end of the torsion spring being secured to the rotatable operating shaft itself, and the other end of the torsion spring biasing a con-' tact arm, which loosely slides about the rotatable operating shaft. The free end of the contact arm is mechanically linked to the movable contact of a circuit interrupter to cause the opening and closing motions thereof. The rotatable contact arm is affixed to a sleeve which slidably rotates about the operating shaft, and has an abutment portion, which during the opening operation, makes impact engagement with an impact pin, the latter moving with the operating shaft, and striking the abutment portion 0 the slidable sleeve during the opening operation for impact opening.

The contact-pressure linkage is particularly suitable for multi-phase operation in which a number of pairs of separable contacts are simultaneously actuated in gang'operation by a single common rotatable operating shaft actuated by a single mechanism.

ABSTRACT 7 Claims, 4 Drawing Figures 3 6 I aaa (4m V///|\ \w J OPERATING '5 MECHANISM INSULATION D l g s 1 25 22? (I I E8 0 E INVENTOR Charles D Bice, Frank W. Senchur Robert A. Few

P. M ATTORNEY PATENTEUmzomn $721,790

SHEET 2 BF 2 FIG. 2

P ART CONTACT-PRESSURE LINKAGE FOR A CIRCUIT INTERRUPTER OF THE TORSION-SPRING TYPE BACKGROUND OF THE INVENTION In the operation of electrical contacts, particularly those of the butt-contact type, it is often necessary to drive the contacts through a spring-linkage assembly. When more than one contact is gang-driven by one operating mechanism, a spring-assembly linkage is used with each contact to assure a nearly equal contact-closing force for each contact. When contact erosion might cause a decrease of contact-closing force, the springlinkage assembly can minimize this decrease of closing force.

Previous designs of contact-pressure devices have made use of a linear-action compression spring placed in the straight-line translational movement of the contact-closing mechanism, such as U.S. Pat. 3,403,297, for providing the requisite contact pressure for a pair of separable contacts.

SUMMARY OF THE INVENTION The proposed torsion-spring electrical contact operator of the present invention makes use of a torsion spring placed in a rotational portion of the contact-closing mechanism. The contact-closing force, provided by this design, is determined by the torque of the torsion spring, and the effective moment arm a of the contact-operating arm. This design allows gangoperation of more than one pair of contacts by a single shaft, and limits the decrease of contact-closing force, due to contact erosion, by the use of an individual spring with an acceptably low spring constant for each pair of separable contacts. Unlike previous designs, which limit the decrease contact closing force due to contact erosion, the proposed design of the present invention relates to a torsion spring of proper spring rate, which can keep the contact-closing force constant, or increase it with contact erosion.

Accordingly, it is a primary object of the present in vention to provide an improved contact-pressure linkage-for a circuit interrupter of the torsion-spring type.

Another object of the present invention is the provision of an improved simplified type of contact-pressure linkage for a multi-phase type of circuit interrupter.

Still a further object of the present invention is the provision of an improved contact-pressure linkage for a circuit interrupter of the torsion-spring type, in which a rotatable operating shaft, constituting a part of the operating mechanism, is utilized to effect an encircling mounting arrangement for the torsion spring for each individual pair of separable contacts of the interrupter.

In accordance with a preferred embodiment of the presentinvention, there is provided a rotatable operating shaft, which carries one end of a torsion spring encircling the same shaft. The other end of the torsion spring biases a portion of a rotatable contact-operating arm, the latter being slidably rotatably mounted about the aforesaid operating shaft. Preferably, an abutment member, such as a shaft pin moving with the shaft, strikes an abutment portion of the slidable sleeve, which carries the contact-operating arm, so that an impact opening force may be exerted during the opening operation to thereby break any welds which possibly are formed at the separable contacts.

Further objects and advantages will readily become apparent upon reading the following specification taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevational view, partially in vertical section, of the improved contact-pressure linkage of the present invention, as adapted for a multi-phase circuit interrupter having two or more pairs of separable contacts, the contacts being illustrated in the closedcircuit position;

FIG. 2 is an end elevational view of the circuit interrupter of FIG. 1 taken substantially along the line 11-11 of FIG. 1;

FIG. 3 is a view similar to that of FIG. 2, but showing the impact force which occurs during the opening separating movement of the separable contacts; and,

FIG. 4 illustrates a prior-art type of contact-pressure linkage as applied specifically to a vacuum-type circuit interrupter.

DESCRIPTION OF THE PREFERRED EMBODIMENT As well known by those skilled in the art, in the operation of circuit interrupters, particularly those of the multi-phase type, in which a plurality of separable contacts are provided for the several phases, it is desirable to achieve a uniform contact pressure in the closed-circuit position of the device. As the contacts erode, perhaps in an uneven fashion, between the different phases, it is desirable to provide a resilient contact pressure device to insure a proper contact pressure between the several separable contacts. As well known by those skilled in the art, unless a proper contact pressure is achieved, there occurs a high resistance between the contacts, which leads to heating and to excessive contact erosion. It is, therefore, desirable to provide a contact'pressure device, which is reliable, of low cost, and highly effective in providing the proper contact pressure regardless of contact erosion.

In addition to the foregoing requirement of proper contact pressure, it is additionally desirable to effect a device, which will assure a proper breaking of any welds which occur between the contacts. Particularly in the case of vacuum bottles, or vacuum-type circuit interrupters, such as shown in FIG. 4, welding may occur during the closing of the vacuum-type circuit interrupter due to the oxygen-free condition within the vacuum envelope. Consequently, a weld may occur during the closing of such a vacuum-type circuit interrupter, which must be broken during the opening operation if the contacts are to separate.

Accordingly, it is desirable to provide a contact-impact device, which will break any ensuing welds, which have occurred during the previous closing of the contacts of the interrupter.

Referring to FIGS. 1 and 2, it will be noted that there is provided a rotatable operating shaft, designated by the reference numeral 1, and carrying therewith a spacing sleeve 2, about which is disposed an encircling torsion spring 3. The torsion spring 3 has one end 3a thereof secured about a shaft pin 4, which may extend into the shaft 1 as shown. Encircling the operating shaft 1 and slidable thereon is a contact-operating sleeve 6, carrying a rotatable contact-operating arm 7 therewith.

The free end 711 of the contact-operating arm 7 is pivotally connected, as by a pivot pin 9, to a movable contact 11, the latter making separable engagement with a stationary contact 12.

As well known by those skilled in the art, the connection between the operating shaft 1, which is usually at ground potential, and the movable contact 11, which is generally at high potential, is effected by the use of an insulating operating rod 14 having one end linked, as previously described, to the pivot pin 9, whereas the lower actuating end of the insulating operating rod 14 is connected to the movable contact 11 of the interrupter, and effects the opening and closing motions thereof.

As shown in FIG. 1, the right-hand end of the torsion spring 3 has a hook portion 3b, which engages a recess 15 provided in an intermediate portion of the contactoperating arm 7, and thereby biases the arm 7 in a closing direction, as viewed more clearly in FIG. 2 of the drawings.

An impact pin, or a shaft pin, 17 driven into the operating shaft 1, separates from an offset, or shoulder portion 19 of the slidable operating sleeve 6 during the closed position, as viewed in FIG. 2, leaving a gap separation distance .r" therebetween. During the opening operation, however, the impact pin 17 rotates in a clockwise direction, and strikes with an impact force the shoulder portion 19 of the operating sleeve 6, and effects forcibly a clockwise opening rotative movement of the contact-operating arm 7, as shown more clearly in FIG. 3 of the drawings. This impact force is desirable to break any welds, which have occurred at the contacts 11 and 12 during the previous closing operation. Such a problem is particularly acute in vacuum-type circuit interrupters, such, for example, as set forth in U.S. Pat. Nos. 3,403,297 and 3,048,681.

An additional advantage occurs by the use of the torsion-spring type of contact-pressure linkage of the present invention, in that the total insulation distance A (FIG. 1) between the mechanism operating parts of the interrupter, which are normally at ground potential, and the high-voltage part of the separable contacts is not decreased by the use of the torsion spring 3, whereas if a compression spring were used, as utilized in the prior art, such as U.S. Pat. No. 3,403,297, shown in FIG. 4, this insulation distance would be considerably necessarily increased. FIG. 4 represents a vacuum-type circuit interrupter 21 comprising an evacuated envelope 22, interiorly of which is disposed a pair of separable contacts 11, 12 respectively connected to line connections L L For effecting the operation of the movable contact 11, and also for providing the desired contact pressure, there is provided an insulating operating rod 23 biased, in the opening direction, by an opening accelerating spring 24. It will be observed that the opening accelerating spring 24 is interposed between a spring-seat 25, affixed to, and movable with the upper extremity 23a of the operating rod 23.

The lower end of the opening accelerating spring 24 is seated against a fixed spring seat 27. In the closedcircuit position of the interrupter 21, the operating rod 23 is latched by a trip rod 28, electrically actuated by a solenoid 30, and mechanically engaging a nose 31, constituting an integral part of the movable operating rod 23. Suitable means, not shown, effects downward closing motion of the operating rod 23. A contact-compression spring 34 is disposed within a spring holder 35 affixed to the upper end of the contact stern 110. Thus, there is provided a lost-motion connection 40 between the operating rod 23 and the spring-holder, or actuating member 35, for the movable contact 11. In the prior-art construction 21, it will be noted that the disposition and use of the contact-biasing means 45, comprising the wiping" spring 34 and the spring-cage 35, necessarily takes considerable longitudinal space along the operating rod 23, and requires a considerable distance A"' between the movable contact stem 11a and the grounded parts of the linkage. Thus, by a use of the torsion-spring device of the present invention, which closely encircles the operating shaft 1, a greater distance A of insulation along the insulating operating rod 14 may be used, or a cheaper form of insulation may be utilized. This insulation distance is generally i1- lustrated by the distance A in FIGS. 1 and 3.

By way of recapitulation, during the closing operation, as shown in FIG. 2, the operating shaft 1 rotates in a counterclockwise direction carrying therewith the end of the torsion spring 3, which biases the contactoperating arm 7 to straightened position, as shown in FIG. 2. This effects closure of the contacts, as shown in FIG. 2, and provides an in toggle relationship, as shown in FIG. 2. The circuit is consequently closed through the separable contacts 11 and 12 which may include a vacuum bottle of the type described hereinbefore and shown in FIG. 4.

During the opening operation, the operating shaft 1 is caused to rotate in a clockwise direction, as viewed in FIG. 3. It will be observed that during the opening rotative motion of the operating shaft 1, the impact-shaft pin 17 strikes the shoulder portion 19 of the slidable sleeve 6, and effects contact opening with an impact force. This is desirable in breaking any welds, which have previously occurred at the contacts 11 and 12. FIG. 3 more clearly illustrates the abutting engagement between the impact pin 17 and the shoulder portion 19 of the slidable contact arm sleeve 6.

From the foregoing description, it will be apparent that there has been provided an improved contact-pressure linkage of the torsion-spring type, which is particularly adaptable for multi-phase circuit interrupters. An accurate contact pressure force is achieved, even through the contact erosion rates may differ between the several pairs of separable contacts. Additionally, the distance A" between the grounded portions of the operating mechanism, as exemplified by the operating shaft and the metal contact arm, and the high-voltage movable contact may be considerably increased by the torsion-spring arrangement, which closely surrounds the operating shaft 1, and requires very little lateral space.

Although there have been illustrated and described a specific structure, it is to be clearly understood that the same was merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art without departing from the spirit and scope of the invention.

We claim as our invention:

1. A circuit interrupter including at least one pair of separable contacts one of which is movable, an operating mechanism having a rotatable operating shaft for effecting the opening and closing motions of said pair of separable contacts, the rotation of said operating shaft in one direction effecting the closing of the pair of separable contacts and the rotation of said operating shaft in the opposite direction effecting the opening of the pair of separable contacts, a rotatable contact operating arm mounted on the operating shaft and mechanically connected to said one movable contact to effect the opening and closing movements thereof, a torsion spring encircling the operating shaft for providing the requisite contact pressure in the closed-circuit position of the interrupter, and one end of the torsion spring being affixed to the operating shaft whereas the other end of the torsion spring biases said rotatable contact arm in the closing direction thereof.

2. The circuit interrupter combination of claim 1, wherein said rotatable contact arm is mounted on a sleeve slidable upon the operating shaft.

3. The combination of claim 2, wherein means affixed to the operating shaft strikes a portion of said slidable sleeve with an impact force during the opening operation.

4. The combination of claim 3, wherein the slidable sleeve has an offset shoulder portion and said means affixed to the operating shaft comprises a shaft pin.

5. A multi-phase circuit interrupter including a plurality of pairs of separable contacts adapted for gang operation, an operating mechanism having a common rotatable operating shaft for operating all of said pairs of separable contacts simultaneously, said operating mechanism effecting the rotation of the common rotatable operating shaft inone direction to thereby effect the closing motion of all the pairs of separable contacts, the operating mechanism effecting the rotation of the common rotatable operating shaft in the opposite direction to effect the simultaneous opening operation of all the pairs of separable contacts, a rotatable contact operating arm for each pair of separable contacts, all of said rotatable contact arms being mounted on said common rotatable operating shaft, each rotatable contact arm being mechanically connected to its respective pair of separable contacts, a torsion spring encircling the common rotatable operating shaft for each pair of separable contacts, for providing the proper contact pressure, one end of each torsion spring being secured to the common rotatable operating shaft so as to rotate therewith, and the other end of each torsion spring biasing its respective rotatable contact arm in a closing direction.

6. The combination of claim 5, wherein the rotatable contact arm of each pair of separable contacts is secured to a sleeve slidably rotatable upon the common rotatable operating shaft.

7. The combination of claim 6, wherein means movable with the common rotatable operating shaft strikes the respective sleeves during the opening operation.

Claims

5. A multi-phase circuit interrupter including a plurality of pairs of separable contacts adapted for gang operation, an operating mechanism having a common rotatable operating shaft for operating all of said pairs of separable contacts simultaneously, said operating mechanism effecting the rotation of the common rotatable operating shaft in one direction to thereby effect the closing motion of all the pairs of separable contacts, the operating mechanism effecting the rotation of the common rotatable operating shaft in the opposite direction to effect the simultaneous opening operation of all the pairs of separable contacts, a rotatable contact operating arm for each pair of separable contacts, all of said rotatable contact arms being mounted on said common rotatable operating shaft, each rotatable contact arm being mechanically connected to its respective pair of separable contacts, a torsion spring encircling the common rotatable operating shaft for each pair of separable contacts, for providing the proper contact pressure, one end of each torsion spring being secured to the common rotatable operating shaft so as to rotate therewith, and the other end of each torsion spring biasing its respective rotatable contact arm in a closing direction.