US2799752A - Quick break oil switch - Google Patents

Description

July 16, 1957 J. H. NICHOLAS QUICK BREAK OIL SWITCH Filed April 18, 1955' JAMEs H. NICHOLAS Unite States QUICK BREAK GIL SWITCH Application April 18, 1955, Serial No. 501,827

'7 Claims. (Cl. Mil-146) This invention relates generally to electric circuit interrupting devices, and more particularly to load break switches which are capable of interrupting appreciable load currents with a minimum of arcing.

To minimize arcing during the opening of a load break switch it has been heretofore proposed to provide a switch construction having a pair of relatively movable main current carrying contact members and a pair of auxiliary contact members which shunt the contact-making portions of the main contact members and maintain contact following the separation of the main contact. The auxiliary or shunt contacts are separated quickly once the main contacts reach a predetermined spaced apart position which prevents arcing between the main contacts. In this way, the switch cannot be accidentally left in an open position where an are between the main contacts could be maintained, damaging the switch.

It is one of the objects of this invention to provide a quick break shunt-type load break switch design which requires only few changes or additions to presently used load break switches which do not have quick-breaking shunt contacts to convert the same to a switch having this feature.

It is another object of this invention to provide a load break switch of the aforementioned type utilizing only a single auxiliary quick break contact element which cooperates with one of the main switch contact elements to provide the quick break shunting current path.

in accordance with a preferred form of the invention, the main movable contact of the load switch is a pivotally supported contact member having resilient, bifurcated contact-making portions adapted to engage the main stationary contact of the switch. A single auxiliary quick break contact is provided which is pivotally secured to and is spring-urged toward the main stationary contact about a pivot axis which is spaced from and parallel to the pivot axis of the main movable contact. The main movable contact and the auxiliary contact are constructed and arranged so that the bifurcated contact-making portions of the main movable contact pass over the auxiliary contact in its movement toward the main stationary contact. A portion of the auxiliary contact is made thicker than the main stationary contact so that upon reverse movement of the main movable contact to open the switch, the bifurcated portions of the movable contact will abut against saidv thicker portion of the auxiliary contact and pull the distal end thereof away from the main stationary contact against the return force of the spring biasing means.

The portion of the main movable contact which first engages with the auxiliary contact upon said reverse movement thereof is. suitably shaped to provide a hearing or abutment shoulder which prevents the spring means of the auxiliary, contact from pulling the same between and away from the bifurcatedportions of the main movable contact. before. the main contacts have reached a predetermined spacing which. will inhibit any arcing therebetween. Because these two contacts are mounted for pivotal movement about spaced axes, they will eventually separate when the auxiliary contact rides over the top of the main movable contact. Their pivot axes are spaced apart so that this separation will occur when the main contacts are spaced far enough apart to prevent arcing therebetween. Upon separation of these contacts the aforementioned spring means associated with the auxiliary contact will snap the auxiliary contact back into its position adjacent to the main stationary contact. At no time, therefore, will a condition exist where the main movable switch contact will be left in a position where arcing will occur, since the latter contact can assume only positions in contact with the main stationary contact or the auxiliary contact, or spaced therefrom an amount which will prevent any arcing therebetween.

These and other objects, advantages and features of the invention will become apparent upon making reference to the accompanying specification, taken in conjunction with the drawings showing an exemplary form of the invention.

In the drawings:

Fig. 1 is a diagrammatic view of a single pole double throw switch which incorporates features of the present invention;

Fig. 2 is an enlarged side view of the switch of Fig. 1 with the movable contact element thereof in engagement with one of the stationary contact elements;

Fig. 3 is a generally top view of the switch apparatus of Fig. 2 as seen along reference line 3-3 in the direction of the arrows;

Fig. 4 is an enlarged section through the switch apparatus taken along section line 4-4 in Fig. 3;

Fig. 5 is a partly broken away side view of the position of the switch elements shown in Fig. 1 when the main switch elements have been separated; and

Fig. 6 is a view of the inner face of the movable switch contact body.

Refer now to the drawings where like reference numerals indicate like elements throughout.

The embodiment of the invention illustrated in the drawings shows a high voltage switch assembly, generally indicated by the reference numeral 1, which includes an outer casing 3 filled with insulating oil to the level shown in dotted lines. Immersed within the insulating oil is a single pole double throw. switch assembly including a movable bifurcated switch member 5 adapted to make selective engagement with stationary switch blades 77. The bifurcated switch member 5 is mounted for pivotal movement about an axis 9. Electrical connections with the contact members 5 and 77- are made by conductors 11, 13, and 15, respectively, passing through respective insulator bushings 17 supported on the outside of the casing 3.

Referring now more particularly to Figs. 2 through 6, the pivotally mounted bifurcated switch member 5 has a conductive shank 29 from which extends spaced arms 22-22 which carry respective floating contact assemblies 23. The shank fits into an insulator 24. Each assembly 23 includes a metal contact shoe 25 which has a channel 27 formed in its outer faces which partially receives the associated arm 22. The contact shoes 2525 have parallel, flat inner contact making surfaces 2828 joining rounded side surfaces 3030. Each contact assembly 23 also includes a pair of flexible braided wire straps 29-29 which carry most of the current flowing between the contact shoe 2S and the contact arm 22. The straps extend the width of the assembly and pass outside of the associated switch arm 22. The ends of the flexible straps 29 are folded around respective clamping plates Sit-31 which in turn are anchored to the associated switch contact shoe 25 by screws 33 within recesses 35 formed in the rounded surfaces 30-30 of the contact shoe 25. Each of the straps 29 is anchored to the switch arm 22 by a clamping plate 38 and a clamping screw 40 which is threaded into the switch arm 22 to press against a lock washer 41 which forces the plate 38 against the flexible strap 29. Each assembly has a metal wire clasp 44 passing around the outside of the arm 22 and through holes in the clamping plates 31-31. The ends of the wire clasp are bent outwardly and lie within holes 46-46 formed in the inner face of the contact shoe. The fiat inner faces 28-28 of opposed contact shoes are urged toward each other and into parallel relation by leaf springs 42-42 interposed between the arms 22-22 and the shoes 25-25.

In accordance with the invention, at each corner of the end of each contact shoe 25 which is farthest from the pivot axis 9 of the bifurcated contact member 5, a fiat wall surface 48 is ground in the rounded side surface 30 to form two pairs of opposed co-planar abutment shoulders 50-50 on the opposed contact shoes 25-25. The shoulders 50-50 extend at right angles to the flat inner contact shoe faces 28-28. The abutment shoulders 50-50 on each contact body merge with the end of the contact body via rounded wall portions 52-52.

The bifurcated assembly is pivoted midway between the stationary contact members 7-7 and is symmetrically formed about a line passing longitudinally of the shank 20.

Each stationary contact member 7 includes a generally disk-shaped head portion 57 from which extends a doumwardly inclined switch blade portion 60 which has a contact-making end portion 61 having rounded corners 63-63 along its inclined upper edge. The blade portion 61 is thicker than the normal spacing between the contact shoes 25-25.

In accordance with the invention, an auxiliary quick break contact bar 59 is pivotally mounted to the top of the switch blade 60 by a pivot pin 62 extending through spaced pivot support ears 64-64 on the blade 60. The top of the distal end of the quick break switch bar 59 is beveled at 70-70 to provide cam surfaces for separating the contact shoes 25-25 of the bifurcated movable switch member 5. A flexible braided strip of metal 65 forms a good permanent electrical connection between the quick break switch bar 59 and the disk-like portions 57 of the stationary contact assembly 7. Coil springs 68-68 are anchored at one end to one of the side faces of the switch blade 60 and at the other to one of the sides of the quick break bar 59 to normally urge the quick break switch bar 59 into a position where it rests on the top inclined edge of the switch blade 60. The width or thickness of the quick break contact bar 59 is made greater than the thickness of the switch blade portion 61 and is centered with respect thereto so that when the quick break bar 59 is in its position resting on top of the switch blade it overhangs the parallel sides of the switch blade portion 61 a small but significant amount.

The axis of rotation of the movable switch element 5 is positioned so that the inner end of the leading face of the bifurcated portion thereof initially makes contact with the beveled edges 70-70 of the quick break switch bar 59. The beveled edges 70-70 of the quick break switch bar 59 and the leading rounded edge 30 of the switch contact shoes 25 cooperate to cam the switch contact shoes apart so that the bifurcated switch contact may pass around the quick break bar 59 into full engagement with the contact blade portion 61, as shown in Fig. 1. In this position, the top of the bifurcated contact member 5 is below the quick break switch bar 59 resting on the top of the switch blade 60. When the bifurcated contact element is rotated in a direction to open the switch, the top transverse shoulders 50-50 of the contact shoes 25-25 make engagement with the oven hanging portions of the quick break switch bar 59 to prevent the bar from knifing through the bifurcated member 5. Upon further movement of the bifurcated switch member 5, the quick break bar 59 is lifted and carried with the same into a position shown in Fig. 5. As the movable contact member 5 is moved further away from the stationary contact member 7, the end of the quick break bar 59 rides over the rounded abutment shoulder por tions 52-52 of the contact shoes 25-25 and then finally snaps back into a position contiguous to the top edge of the switch blade when the movable contact member 5 is moved completely out of the way of a quick break bar 59. The location of the pivot axis of the movable contact member 5 is such that the aforementioned separation of the contact member 5 and the quick break bar 59 occurs when the stationary switch blade and the movable contact member 5 are separated an amount which is suificient to interrupt the ensuing are at the operating voltage involved. Thus, if the movable contact member 5 is accidentally left in a partially opened position, continued arcing between the contacts will not occur.

The symmetrical design of the movable contact member 5 along a longitudinal line passing the center of the contact shank 20 provides identical quick-break operation of the switch when the movable contact is moved into and out of engagement with the right hand and the left hand stationary contact members 7-7.

In compliance with the requirements of the patent statutes I have here shown and described a preferred embodiment of my invention. It is, however, to be understood that the invention is not limited to the precise construction here shown, the same being merely illustrative of the principles of the invention. What I consider new and desire to secure by Letters Patent is:

1. In a switch having a pair of relatively movable main contact means, one of the main contact means having a pair of resilient, contact-making, bifurcated portions adapted to straddle snugly the other main contact means, the improvement comprising an auxiliary quick-break contact means mounted for relative movement between andwith respect to said pair of main contact means and electrically connected with said other main contact means, said bifurcated contact-making portions straddling said auxiliary quick-break contact means during the relative movement of said pair of contact means toward one another, spring means resiliently urging said auxiliary contact means toward said other main contact means, and means for keeping said auxiliary contact means and said bifurcated contact-making portions of one of said contact means together upon separation of said pair of main contact means until said pair of main contact means are spaced apart a distance which will not support an arc therebetween, said spring means arranged to then snap the auxiliary contact means away from said bifurcated contact means and into a position which will extinguish any are therebetween at the operating voltage involved.

2. In a load break switch having a main pivotally mounted, resilient, bifurcated contact element, and a main relatively stationary contact adapted to be snugly straddled by the resilient bifurcated portion of said pivotally mounted contact, the improvement comprising a quick-break auxiliary contact pivotally mounted to the face of said stationary contact which faces said pivotally mounted contact when the latter is in its circuit breaking position, said auxiliary contact being in the path of movement of the bifurcated portion of said pivotally mounted main contact, the portion of the latter contact which first makes engagement with said auxiliary contact when moved toward said stationary contact being shaped to enable the bifurcated portions thereof to readily pass around and move beyond the auxiliary contact into engagement with the stationary contact, the portion of said bifurcated contact which first makes contact with said auxiliary contact when the bifurcated contact is moved away from 7 said stationary contact being shaped to provide an abutment shoulder making a substantial angle, with respect to the direction of movement of the pivotal contact, so that the bifurcated portions of said pivotal contact will not pass around the auxiliary contact, whereby the auxiliary contact will be pivoted away from the stationary contact, spring means resiliently urging said auxiliary contact toward said stationary contact, the pivot axes of said hifurcated contact and said auxiliary contact being spaced apart an amount which insures separation of the bifurcated contact and the auxiliary contact when the main contacts are spaced apart a distance insufiicient to support an are at the operating voltage involved, and said spring means arranged to then snap the auxiliary contact means away from said bifurcated contact means and into a position which will extinguish the are formed therebetween.

3. In a load break switch having a main pivotally mounted contact element and a main relatively stationary contact element, one of said contact elements being bifurcated and adapted to straddle the other contact element, the improvement comprising a quick-break auxiliary contact element pivotally supported on the face of the other contact element which faces toward said bifurcated contact element when the contacts are in their farthest spaced apart position, spring means resiliently urging said auxiliary contact element toward said stationary contact element, the bifurcated contact element contacting said auxiliary contact element during the relative movement of said main contacts toward and away from each other, the portions of said bifurcated and auxiliary contacts which engage when said main contacts are brought together being shaped to enable the ready passage of said auxiliary contact between and past the bifurcated portions of said other contact element, the portions of said bifurcated and auxiliary contacts which engage upon separation of said main contact elements being shaped to prevent initial passage of the auxiliary contact element between the bifurcations of said latter main contact element by the restoring force of said spring means, whereby the auxiliary contact will be pivoted away from the stationary contact upon separation of said main contacts, the pivot axes of said bifurcated contact element and said auxiliary contact element being spaced apart an amount which insures separation of the bifurcated contact and the auxiliary contact when the main contacts are spaced apart an amount which is insufficient to support an arc therebetween at the operating voltage involved, and said spring means then snapping the auxiliary contact means away from said bifurcated contact means into a position that will extinguish any arc therebetween.

4. In a switch having a pair of main, relatively movable contact elements, one of the elements having a bladelike contact-making portion with flat sides, and the other contact element being bifurcated with spaced apart, resilient, contact-making parts adapted to straddle snugly said fiat sides of said one contact element, the improvement comprising an auxiliary quick-break contact member pivotally mounted upon the edge of the blade-like portion of said one contact element which faces toward said bifurcated contact element when the main contacts are in their furthest spaced apart positions, said auxiliary contact member having a portion which is adapted to pass through said spaced apart contact-making parts of said bifurcated main contact element when said main contact elements are brought together, said latter auxiliary contact portion tapering in thickness from a minimum thickness at its outer edge, which permits the easy passage of said spaced contact-making parts thereover, to a thicker portion which is thicker than the blade-like portion of said one main contact element, the inner face of said auxiliary contact portion opposite said one main contact element providing a flat abutment shoulder making a substantial angle in the direction of relative movement between said main contacts, whereby said spaced apart resilient contact-making parts of said other main contact, element abut said shoulder which prevents the passage of said spaced apart resilient parts around the auxiliary contact member upon initial separation of the main contacts, so that the auxiliary contact member will be pivoted away from said one main contact element during the separation of the main contact elements, and spring means resiliently urging said auxiliary contact member toward said one contact element, the auxiliary contact member snapping back into its position adjacent to said one main contact element when said main contact elements are spaced apart a sufficient distance to prevent arcing therebetween at the operating voltage involved.

5. In a switch having a pair of main, relatively movable contact elements, one of the elements having a bladelike contact-making portion with flat sides, and the other contact element being bifurcated with spaced apart, resilient, contact-making parts adapted to straddle snugly said flat sides of said one contact element, the improvement comprising an auxiliary quick-break contact member pivotally mounted upon the edge of the blade-like portion of said one contact element which faces toward said bifurcated contact element when the main contacts are in their furthest. spaced apart positions, said auxiliary contact member having a portion which is adapted to pass through said spaced apart contact-making parts of said bifurcated main contact element when said main contact elements are brought together, said latter auxiliary portion tapering in thickness from a minimum thickness at its outer edge, which permits the easy passage of said spaced contact-making parts thereover, to a thicker portion which is thicker than the blade-like portion of said one main contact element, the spaced apart resilient parts of said bifurcated main contact element and said thick portion of said auxiliary contact element being shaped to prevent passage of the auxiliary contact element through said resilient parts upon initial separation of said main contact element, whereby said spaced apart resilient contact-making parts of said other main contact element abuts said shoulder and prevent the passage of said spaced apart resilient parts around the auxiliary contact member upon separation of the main contacts, so that the auxiliary contact member will be pivoted away from said one main contact element during the separation of the main contact elements, and spring means resiliently urging said auxiliary contact member toward said one contact element, the auxiliary contact member snapping back into its position adjacent to said one main contact element when said main contact elements are spaced apart a sufficient distance to prevent arcing therebetween at the operating voltage involved.

6. In combination with a switch having a pair of main contact members having mutually engageable contactmaking portions, one of said contact members being mounted for movement relative to the other to open and close the switch, auxiliary shunt circuit-forming contact means for preventing arcing between said main contact members, said auxiliary contact means comprising a single, auxiliary contact member mounted for relative movement with respect to both of said main contact members and electrically connected to a first one of said main contact members, spring means resiliently urging said auxiliary contact member toward said first main contact member, said auxiliary contact member being located between and in the path of relative movement of said contact making portions of said main contact members when the latter are in their separated or circuit breaking position, the contact-making portion of the second main contact member being adapted to engage with said auxiliary contact member as the movable main contact member is moved into contact-making position with the other main contact member, means for holding said auxiliary contact member and said second main contact member together during movement of the movable main contact member away from the other main contact member whereby the auxiliary contact member and said one contact member are separated, until said pair of main contact members are spaced apart a distance which will not support an arc therebetween, said spring means being designed to then overcome the holding force of said holding means to snap the auxiliary contact'member away from said second main contact member into a position which will extinguish any are therebetween at the operating voltage involved.

7. In combination with a switch having a pair of main contact members having mutually engageable contactmaking portions, one of said contact members being mounted for movement relative to the other to open and close the switch, auxiliary shunt circuit-forming contact means for preventing arcing between said main contact members, said auxiliary contact means comprising a single, auxiliary contact member mounted for relative movement with respect to both of said main contact members and electrically connected to a first one of said main contact members, spring means resiliently urging said auxiliary contact member toward said first main contact member, said auxiliary contact member being located between said contact making portions of said main contact members when the latter are in their separated or circuit breaking position, means for holding said auxiliary contact member and the second main contact member together during movement of the movable main contact member away from the other main contact member until said pair of main contact members are spaced apart .a distance which will notsupport an arc therebetween, the two latter contact members being held together by engagement of said contact making portion of the second main contact member with the, auxiliary contact member, said spring means designed to then overcome the holding force of said holding means to snap the auxiliary contact member away from said second main contact member into a position which will extinguish any are therebetween at the operating voltage involved.

References Cited in the file of this patent UNITED STATES PATENTS

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