US2575707A

US2575707A - High-voltage switch assembly

Info

Publication number: US2575707A
Application number: US137618A
Authority: US
Inventors: William H Gilliland; Fitzhugh H Turnham
Original assignee: Usco Power Equipment Corp
Current assignee: Usco Power Equipment Corp
Priority date: 1950-01-09
Filing date: 1950-01-09
Publication date: 1951-11-20
Anticipated expiration: 1968-11-20

Description

Nov. 20, 1951 W. H. GILLILAND ETAL HIGH-VOLTAGE SWITCH ASSEMBLY Filed Jan. 9, 1950 5 Sheets-Sheet l Aller/lays NOV Z0, 1951 w. H. GILLILAND ETAL 2,575,707

HIGH-VOLTAGE SWITCH ASSEMBLY Filed Jan. 9 1950 5 Sheets-Sheet 2 /NvE/roRs 40 W/LL/AM H G/L/LA/VD F/ TZHUGH H. TURA/HAM 6 WMMSLW Attorneys NOV- 20, 1951 w. H. GILLILAND ETAL 2,575,707

HIGH-VOLTAGE SWITCH ASSEMBLY Filed Jan. 9, 1950 5 SheetsSheet 3 l lll-lum 48 illu WM WMM Nov. 20, 1951 w. H. GILLILAND ETAL 2,5751707 HIGH-VOLTAGE SWITCH ASSEMBLY Filed Jan. 9, 195 5 Sheets-Sheet 4 Nov. 20, 195l w. H. GILLILAND ET AL HIGH-VOLTAGE SWITCH ASSEMBLY 5 Sheets-Sheet 5 Filed Jan. 9 1950 W/LL/AM H. G/L/LAND F/TZHUGH H.

TURNHAM B M @n 9L arneys Afl Patented Nov. 20, 1951 HIGH-VOLTAGE SWITCH ASSEMBLY William H. Gilliland and Fitzhugh H. Turnham, Birmingham. Ala., asslgnors to USCO Power Equipment Corp., Birm ration of Alabama ingham, Ala., a corpo- Application January 9, 1950, Serial No. 137,618

18 Claims. 1

such switches and adapted to better handle high amperage current. 1

It is the general object and purpose of the present invention to provide operating mechanism for switches of the above type which embodies a novel assembly of elements for maximum ease of operation of the switch blade, even under severe icing condition, and in which the several parts are so arranged that, after the switch blade is twisted to frictionally grip the contacts, the maximum pressure of the blade on said contacts will be maintained and release thereof by retroactive pressure forces of the contacts on said blade effectively prevented.

Another object is to provide operating means for a switch blade supported near one end for pivotal swinging movement and for rotational twisting movement about its own axis which comprises a motion transmitting rocker arm and separate blade lifting and twisting links, each pivotally connected at one end to the rocker arm, with the other end of the lifting link mounted on a pivot supported in fixed relation to the blade and the other end of the twisting link operatively connected to the blade to rotationally twist the blade only when positioned between the contacts, while the swinging movement of the switch blade is controlled by the lifting link.

The invention has for another object to provide an adjustable universal linkage connection between the rocker arm and switch blade, whereby the extent or amount of twisting motion transmitted to the blade may be exactly adjusted and controlled in accordance with the setting of the stationary contacts.

An additional object, in one embodiment of the invention, is to provide a pivotally mounted swingable support in which the switch blade is supported near one of its ends-with a rocker arm and twist transmitting linkage connected with said support and the adjacent end of the switch blade respectively at the same side of the pivotal axis of said support, whereby in the swinging movement of the blade from closed position the major portion of the blade swings upwardly about the pivotal axis of the support while the remainingportion of the blade and said linkage swings 2 downwardly about said axis. to thereby partially counter-balance the weight of the blade.

An additional object of the invention resides in the provision of a switch blade of improved construction. with novel means for rigidly connectingan arcing horn to the free end of the blade on the center line thereof, so that, in the twisting movement of the blade, said horn will remain in contact with the spaced parts of stationary jaw members, the connection between the horn and blade providing increased thermal conductivity for the transmission of heat from the point of contact.

With the above and other objects in view the invention resides in the improved operating mechanism for electric switches of the twist blade type, and the construction and relative arrangement of its several parts, as will hereinafterbe more fully described, illustrated in the accompanying drawings and subsequently incorporated in the subjoined claims.

In the drawings wherein we have disclosed sev eral simple and practical embodiments of the invention and `in which similar reference characters designate corresponding parts throughout the several views:

Figure 1 is a side elevation of an electric switch of the twist blade type provided with one embodi` ment of our improved operating mechanism:

Figure 2 is a fragmentary side elevation on an enlarged scale, the switch blade being in its closed position, and the operating links illustrated by dotted lines in their relative positions after the switch blade has been twisted;

Figure 3 is a vertical sectional view taken substantially on the line 3-3 of Figure 2 showing the operating linkage in end elevation;

Figure 4 is a detail elevation showing a modification of the adjustable twist transmitting linkage;

Figure 5 is a side elevation showing the switch blade in open position;

Figure 6 is a top plan View of the socket bearing structure for the switch blade:

Figure 7 is an enlarged` detail plan view of the arcing horn assembly on the free end of the switch blade;

Figure 8 is a side elevation thereof;

Figure 9 is a transverse sectional view taken on the line 9 9 of Figure 8;

Figure 10 is a side elevation of a modied embodiment of the invention, designed for ultra-high voltages;

Figure 11 isa perspective view of the switch blade operating mechanism'shown in Figure 10: Figure 12 is an end elevation thereof partly in section;

Figure 13 is a detail vertical section taken substantially o n the line i3-I3 of Figure 10; 'and Figure 14 is an end elevation illustrating the spring adjustment.

Referring in further detail to the drawings,

and for the present, more particularly to Figures 1 to 6 thereof, upon a base structure I0 spaced stationary insulators I2 and I4 respectively are rigidly mounted. In laterally spaced relation from the insulator I2 a rotary insulator I6 has a downwardly extending spindle rotatably supported in a suitable bearing |8 mounted on the base structure |0. Suitable operating means (not shown) is connected with the crank 20 which is rigidly fixed to the insulator I6.

p The supporting casting 22 of electrically conductive metal, for the switch operating mechanism, is rigidly secured to the top of the stationary insulator I2 and is formed with a horizontally disposed arm 24 extending over the rotary insulator I6 and in which the top spindle 26 on said insulator is journalled. To this spindle one end of the crank arm 28 is securely fixed. The end of arm 24 projects laterally beyond the spindle 26 and to the same a conductor terminal 30 is connected in the. usual manner.

Upon the other stationary insulator I4 an electrically conductive casting 32 is rigidly secured. Upon this casting a pair of vertically disposed opposed resiliently yieldable contact members, indicated at 34, are mounted. In rearwardly spaced relation from the contact members a pair of vertically disposed arcing horn jaw members 36 are also rigidly fixed to the casting 32 at their lower ends and beyond said jaw members the conductor terminal 38 is connected to the casting 32.

To the extent above described, the mounting and arrangement of the several parts is substantially in accordance with conventional practice. Our improved switch blade operating mechanism is operatively supported upon the casting 22. This casting is formed with upwardly projecting spaced side portions 40 which receive the pivot pins 42 swingably supporting the switch blade bearing structure 44 shown in Figure 6 of the drawings. As shown therein, this bearing structure comprises a one piece casting having parallel side portions 46 which are provided with openings at one end to receive the pivot pins 42 and are integrally connected by longitudinally spaced bearing portions 48 in which the switch blade 50 at one of its ends is rotatively supported. This switch blade is preferably formed from heavy gage cylindrical copper tubing and between the bearing portions 48 of the swingable structure 44 a collar 52 is rigidly fixed to the blade and is provided with a bifurcated lug 54 radially projecting outwardly and downwardly at one side of the collar. This rotatively supported end of the switch blade is connected by a flexible shunt 56 to the casting 22.

The other or free end of the switch blade 50 carries an arcing horn 58 for engagement between and with the jaw members 36. Preferably, as shown in Figures 1, 8 and 9 of the drawings in order to obtain maximum thermal conductivity and transmission of heat from the point of contact between horn 58 and jaw members 36, we provide an elongated rectangular plate 60 upon which the end portion of the tubular switch blade is flattened or swaged, as indicated at 62. The plate 6D has a narrow end flange 64 abutting the end edge of the flattened tube section. upon which a tubular boss 66 is centrally formed to receive one end of the arcing horn '58 which is rigidly secured against axial or rotative movement on the center line of the blade by a set screw 68.

The plate 80 is rigidly secured against movement axially of the blade by means of the spaced bolts 'I0 having nuts 12 threaded thereon.

It will be seen from the above that the attened end 62 of the switch blade is strongly reinforced by the plate 60 and the opposite side edges thereof maintained in the required predetermined spaced relation relative to the spacing between the contact members 34 so that the side edges of the switch blade, when in closed position, will have heavy frictional bearing contact with the members 34. The flattening or swaging of the end of the switch blade on the arcing horn plate 60 eliminates an extra joint in the path of the circuit and by reason of the large area of surface contact between the copper switch blade tubing and the plate 60 maximum thermal conductivity for the transmission of heat from the point of contact of arcing horn 58 with jaw members 36 is obtained. As the horn is accurately centered with respect to the blade it will remain in constant contact with jaw members 36 as the blade is twisted.

Upon one side portion of the casting 22 and below the pivot axis 42 of the bearing structure 44, a rocker arm 14 is supported at its lower end for pivotal rocking movement about the pivot pin 16. This rocker arm extends upwardly from pivot pin 16 between the side portions 46 of the bearing structure 44 and then rearwardly over said bearing structure, terminating in an upward extension l1. This rearwardly and upwardly extending portion of the rocker arm is integrally connected by a transverse web or top wall I8 with an opposite side portion 80 of similar shape or form. The free end of crank 28 is operatively connected with the upper end of the space side portions of rocker arm I4 by the universal joint units 82 and 84 and connecting rod 86.

The forward bearing portion 48 of the swingable bearing structure 44 is provided with an upwardly projecting apertured ear 88 in which one end of a pivot pin 90 is supported, the other end of said pin being supported in one side portion 46 of said bearing structure. On this pin the lower forward end of a lifting link 92 is pivotally supported. This link extends upwardly and rearwardly between the side portions of rocker arm 14 with which the rear end of said link is pivotally connected by the pin 94 mounted at its ends in the side portions of the rocker arm.

The linkage for transmitting rotational or twisting movement to the switch blade 50 includes a bifurcated clevls member 96 pivotally connected with one end of the pin 94 and straddling one side portion of the rocker arm 14. This member 96 is connected by a threaded rod 98 with a similar threaded member |00, said members being adjusted and retained in spaced apart relation by a nut |02 on rod 98. Threaded member |00 is pivotally connected by pin |04 with the upper end of a link element |06 the lower end of which is pivotally connected with the bifurcated lug 54 on collar 52 by pin |08, it being noted that the axes of pins |04 and |08 are disposed at right angles to each other, thus providing a universal linkage connection with collar 52. A slight modification of the twist transmitting link is shown in Figure 4 of the drawings in which the clevls member 96 is replaced by a knuckle sleeve IIIl mounted on the end of pin 94 between link 92 and side portion 80 ofl the rocker arm 14 and with this sleeve member I I2 threaded on rod 98 is pivotally connected by pin II4 having its axis disposed at right angles to pin 94 and the pin |04 connecttween said contact members.

ing member to the link element |06. Thus a universal connection is also provided between the lrod 98 and the rocker arm 14. It will of course be evident that a similar member 2 may be pivotally connected with member 96 in the arrangement shown in Figure 3 of the drawings.

`By proper adjustment of this twist transmitting linkage the required amount of twist may be imparted to the switch blade in the movement of rocker arm 'I4 so that in the closed position of the switch blade the flattened end portion 62 thereof will be disposed in a plane substantially at right angles to the contact members 34 to exert the maximum frictional bearing pressure against said contact members.

Referring now to Figures 1 and 2 of the drawings, it will be noted that the linkage pivots 90 and 94 are so located relative to the pivots 42 and 16 of the structure 44 and the rocker arm 14 respectively, that in the initial portion of the upward swinging movement of the rocker arm the ends of the link elements connected with pivot 94 move upwardly along substantially the same arcuate path and, while the bearing structure 44 remains stationary, the twist transmitting linkage is pulled upwardly, thereby rotatively twisting the switch blade 50 through substantially 90 degrees to disrupt the frictional bearing pressure of the blade against contacts 34 and position the fiattened end 62 of the blade in substantially a vertical plane between said contacts. The relative angular positions of the lifting and twist transmitting links at this time is illustrated in dotted lines in Figure 2. In the further upward swinging movement of the rocker arm, this angular relationship of the links is maintained and the bearing structure 44 and the switch blade z50 are swung upwardly by link 92 about the pivotal axis of the bearing structure 44 to dispose the switch blade in open position, as shown Figure of the drawings.

In the downward movement of rocker arm 14 from the position of Figure 5 to close the switch, the reverse of the above described operations occurs and, without change in the angular relation of the lifting and twist transmitting linkage, bearing structure 44 and switch blade 50 are first swung downwardly about pivot 42 with the fiattened end 62 of the blade disposed in a, vertical plane until said end of the blade is positioned beward bearing pressure against the resilient contact members 34 until said end of the blade is disposed in substantially a, horizontal plane be- The lifting and twist transmitting linkage will then be again disposed in the relative angular positions shown in full lines in Figure 2, and it will be seen that in view of the relative positions of the linkage pivots 90, 94 and |04, maximum bearing pressure contact between the blade and the contacts will be maintained notwithstanding reactionary pressure forces by the contacts against the side edges of the end 62 of the blade tending to rotate the blade and release or diminish said 4bearing pressure.

Referring again to Figure 5 of the drawings, it will be noted that in the movement of the switch blade to closed position, the bladetwisting linkage is disposed entirely outside of the lines of force transmitted by the operating connections with crank 28 through the rocker arm 14 and that this force is applied in a direct line substantially parallel with the path of movement of pivot 94 to the pivot of the lifting link 92. Thus, there is no tendency to twist the switch blade until it reaches its closed position between the spaced contacts 34. This feature is of particular importance in the case of severe icing conditions.

The above described embodiment of our invention is designed primarily for use in connection with electrical circuits having a current carrying capacity of approximately 600 amperes. In Figures 10 to 13 of the drawings we have disclosed another embodiment of the invention intended for use more particularly in circuits having even higher current carrying capacities in the order of 2000 amperes, which will now be described in further detail.

In Figure 10 of the drawings the mounting and arrangement of stationary insulators I I6 and I8 and the rotary insulator |20 is the same as that previously described. Upon the top of insulator ||6 casting |22 is rigidly secured and provided at its opposite side edges and at one end thereof with upstanding portions |24 to which a pair of parallel copper bars |26 are securely bolted as at |28 at one of their ends. These bars extend forwardly at opposite sides of the rotary insulator |20 and are also rigidly bolted as at |30 to theA l bearing for the top spindle of said insulator, to

the upper end of which a curved forwardly extending arm |32 is securely fixed.

To the inner face of each of the bars |26 above the insulator ||6 a series of resilient contact members |34 are secured as at |36, the corresponding members in each of said series being arranged in opposed relation and extending above the bars |26.

Similar copper bars |38 are also secured to opposite side portions of the casting |40 rigidly fixed upon the top of insulator ||0 and to the inner faces of said bars, opposed series of resilient contact members |42 are also secured in similar manner to the contacts |34. We have shown four contact members in each series, though it will be understood that a greater or less number may be used. While the contact members |34 and |45! may be of any approved construction, in Figure 13 l of the drawings we have shown a preferred U- shaped form of contact having one vertical leg |44 thereof secured to the bar |30 with the other resiliently yieldable leg |46 of the contact member extending upwardly in spaced relation to the fixed leg |44 and terminating at its upper end in an outwardly angled portion |48. It will be understood that normally the resiliently yieldable legs |46 of the opposed contacts extend upwardly in convergent relation to each other between the spaced bars |38. Optionally the U-shaped spring contact members |42 of Figure 13 may be reversed so that their rounded ends face upwardly and A projecting outwardly above bars |28.

The springs |62 resiliently resist rocking of shaft |54. When it is desired to vary the torsional resistance of rocking of the springs, the adjustment plate |66 is pushed in far enough axially to clear lugs |69, rotated by applying a wrench to boss |61 to wind or unwind the spring and then Areleased to reengage with lugs |69.

Between the arms |50, a part of a switch blade bearing structure |10 is secured on shaft |54 as by pin |1I. In this case. the switch blade is in the form of a rectangular copper tube |12 one end of which is closed by a member formed with a stud shaft |14 extending in coaxial relation with the switch blade. The other end of the tubular blade is closed by a plate |16 carrying the arcing horn |18 for engagement between the stationary jaw members (not shown), in the manner above described.

The bearing structure |10 is also provided 'with integrally formed spaced arms |88 projecting upwardly above the shaft |54 to which the side flanges |92 of the rocker arm |90 are pivotally connected by the pin |94 supported at its oppor site ends in the arms |88. One side flange of the rocker arm at its forward end is formed with an apertured ear |96 carrying the pivotV pin |88 to which the upper end of the twist transmitting linkage 200 for the switch blade is connected.

.I This linkage is substantially the same as that previously described and is connected at its lower end by pivot. pin 202 to the bifurcated lug |86 of the collar |82.

The rocker arm |90 extends rearwardly ,from pivot pin |94 over the rod |52 and to the rea:` end of each side flange of the rocker arm, one end of a lifting link 204 is pivotally connected as at 208. The other or forward end of each oi' these links is pivotally mounted on rod |52. y

A universal joint unit 288 is connected with upwardly projecting spaced lugs 2|0 on the rear end of rocker arm |90, said unit being connected by the rod 2|2 with a similar universal joint unit 2|4 connected with the rear end of the curved arm |32 xed to the upper end of the spindle of the rotary insulator |20.

when the switch blade m is in its closed position between the opposed contacts |84 and |42,

one of the greater diameters of the rectangular blade is disposed in a plane at right angles to the contact members and the opposite corner edges of the blade have heavy frictional bearing pressure against the resilient legs |46 of the opposed contact members, as most clearly seen in Figure 13 of the drawings. Upon rotation of the rotary insulator |28 to move the switch blade to open position rocker arm |90 is swung upwardly about pivot pin |94 in counterclockwlse' direction, link 204 swinging upwardly with the rocker arm about the stationary pivot |52. In the initial part of this movement of the rocker arm, a downward thrust is applied by the linkage 200 to collar |82', thereby rotating or twisting the switch blade |12 through substantially 90 degrees to disrupt the frictional bearing contact of the switch blade against the stationary contact members and position opposite flat side faces of the blade between and substantially' out of bearing contact with said members. Thus, in the further counter-clock# wise movement of rocker arm |90 and link 204 about the fixed pivot rod |52 a downward thrust force is applied by the rocker arm upon pivot pin |94 forwardly of the supporting shaft |54 for the bearing structure |10 so that said bearing structure and the switch blade as well as linkage 200 are rocked about the axis of said shaft. The greater portion of the bearing structure |10 to# gether with the twist transmitting linkage 200 and a part of the switch blade is thus swung downwardly about the axis of shaft |54 while the remaining part of the switch blade swings upwardly and forwardly between the opposed contacts |34 and |42 to an open position, thus tending to partially counter-balance the weight of the switch blade.

In the movement of the switch blade |12 to its closed position, rocker arm |90 and links 204 first rock in clockwise direction about the axis of pivot rod |52 as a unit so that an upward force is applied by the rocker arm |90 to pivot pin |94, thereby swinging the switch blade |12 downwardly around shaft |54 without change in the angular relationship between the rocker arm and linkage 200 until the switch blade is disposed in substantially horizontal position between opposed contacts |34 and |42, when opposite flat surfaces ofthe blade will be opposed to the contacts and out of bearing engagement therewith. In the final portion of the clockwise movement of rocker arm an angular movement of said rocker member relative to link 204 about the axis of the pivot rod |52 occurs and the rocker arm then pivots about the pin |94, thus applying a lifting force to the linkage 200 so that the switch blade |12 is rotated or twisted to the position shown in Figure 13 of the drawings to engage opposite corner edges of the blade on one of its longer diam.- eters with high frictional bearing pressure against the opposed resilient contact elements.

From the above description and the accompanying drawings, it is thought that the construction, manner of operation and several advantages of the disclosed embodiments of the invention will be fully understood. In each of the operating mechanisms, it will be seen that we provide a novel arrangement of the linkage connections with the rocker arm so that the operating forces are most advantageously transmitted to the switch blade to obtain maximum ease of operation and the application of maximum pressure force by the switch blade to separate the opposed resilient contacts. In the assembly of the blade operating mechanism, by proper adjustment of the twist transmitting linkage. every 9 blade will have exactly the required amount o twist. in accordance with the spacing of the opposed contact elements, to insure the application of maximum pressure force by said elements against the switch blade. Also in each case, the twist transmitting linkage is so arranged relative to the switch blade and the pivotal axis of the rocker arm as to eiectively resist any tendency event of serious damage, can be readily replaced l at nominal expense.

'I'he invention may be embodied in other specic forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive. the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What 'is claimed and desired to be secured by United States Letters Patent is:

1. In an electric switch having a blade adapted to be twisted about its longitudinal axis and mounted on 'a pivoted support for movement therewith into and out of circuit closing position between a pair of opposed contacts spaced from said support; a motion transmitting arm mounted for rocking movement about a pivot axis in spaced parallel relation to the pivotal axis of said blade support, a rst link mounted at one of its ends for swinging movement about a pivot supported in fixed relation to said blade and having a pivotal connection at its other end with said arm, a second link pivotally connected at one end with said arm, and means connecting said second link at its other end, in spaced relation from the fixed pivot of said rst link, to said blade to impart an axial twisting movement to said blade in relative angular movement of said arm and links during initial rocking movement of said arm, when the blade is in closed position, to free said blade from frictional engagement with the contacts, and said first link thereafter controlling the swinging movement of the switch blade in the continued movement of said rocker arm.

2. Switch mechanism comprising a supporting member, opposed stationary contacts mounted in spaced relation to said supporting member to provide an open-ended blade receiving recess, a bearing structure pivotally mounted on said supporting member, a switch blade journalled in said bearing structure for rotational movement about its longitudinal axis and having portions of unequal cross sectional dimensions along different diameters, said blade, when in open position, being disposed with its smaller cross sectional dimension positioned in a plane for entry between said contacts, an actuating arm rockably mounted to swing bodily around ay pivotal axis spaced from and parallel to the pivotal axis of said bearing structure, and at least one pair of links each having one end pivotally connected to said actuating arm and their other ends'being respectively pivotally connected to said bearing structure and to said switch blade, all of said link pivots having axes parallel to and spaced from thepivotal axes of said arm and bearing structure, whereby upon rocking movement of said actuating arm in one direction, said switch blade will first be bodily swung about the pivotal axis of said bearing structure and positioned between said contacts and then rotated about its longitudinal axis to dispose opposite edges of a blade portion of major cross sectional dimension in frictional bearing engagement with said opposed contacts.

3. In an electric switch of the twist blade type having its blade mounted on a support for pivotal swinging movement into and out of engagement with a pair of opposed contacts; actuating mechanism comprising a first pivot having its axis disposed in spaced` parallel relation to the pivotal axis of the switch blade, a motion transmitting arm supported for rocking movement about said rst pivot, a second pivot having its axis disposed in spaced parallel relation to said first pivot and the pivotal axis of said switch blade, said i'lrst and second pivots being relatively movable, a rst link having one end pivotally mounted on said arm and its other end connected to said second pivot, a second link having one end pivotally mounted on said arm, means pivotally connecting the other end of said second link to the switch blade to angularly twist said blade, said links and first and second pivots being so arranged that, uponrocking movement of said motion transmitting arm in one direction said twist blade is first moved to a closed position between said opposed contacts and is then bodily twisted around its longitudinal axis to establish high pressure circuit closing engagement of said blade with the opposed contacts. and upon rocking movement of said arm in the opposite direction, said blade is first twisted around its longitudinal axis to free the blade from circuit closing engagement with said contacts and is then swung about its pivotal axis to open position.

4. In an electric switch, an insulated contact, an insulated support spaced from said contact,

-a pivot mounted on said support, switch blade bearing structure swingable about said pivot, a switch blade rotatably journalled near one end in said structure and engageable near its other end with said contact, a second pivot spaced from and parallel to said rst pivot in fixed relation to the switch blade, an actuating arm connected at one end for rocking movement about said second pivot, a third pivot mounted in fixed relation to the bearing structure and in spaced parallel relation to said rst and second pivots, said second and third pivots being relatively movable about the axis of said rst pivot, a lifting link pivotally connected at one end to said arm and at its other end to said third pivot and operable in the rocking movement of said arm to swing said bearing structure and switch blade about the axis of said first pivot to and from circuit closing position with respect to said contact, and additional linkage operatively connecting said arm with said switch blade, angularly movable relative to said lifting link during a portion of the rocking movement of said arm in each direction to rotate the blade about its longitudinal axis and establish or release circuit closing pressure engagement between the switch blade and contact. l

5. An electric switch as defined in claim 4 wherein said lifting'link and additional linkage are swingable with the bearing structure relative to said first pivot. l

6. An electric switch as defined in claim 4 wherein said third pivot is carried by said bearing structure for movement therewith relative to said iirst and second pivots.

7. An electric switch as defined in claim 6, wherein said lifting link and additional linkage have a common pivotal connection with said actuating arm.

8. An electric switch as deiined in claim 4, wherein said additional linkage connects the actuating arm adjacent to said second pivot to the end of the switch blade projecting beyond said bearing structure.

9. In an electric switch, a pair ofxopposed insu-i lated contacts, an insulated support spaced from said contacts, a switch ,blade bearing structure mounted for swinging movement about a fixed pivot on said support, a switch blade rotatably journalled near one end in said structure and having a rectangular portion at its other end for movement to and from circuit closing position between said opposed contacts, an actuating arm mounted for rocking movement on said support about an axis in spaced parallel relation to the pivotal axis of said bearing structure, a lifting link pivotally connected at opposite ends to said actuating arm and bearing structure respectively to swing said bearing structure and switch blade to and from circuit closing position, a second link connected at one end to said actuating arm for angular movement relative to said rst link, and means operatively connecting said second link withl said switch blade, operative to rotate said blade when in circuit closing position to establish or release circuit closing/pressure engagement between said rectangular portion of the blade and said opposed contacts.

10. An electric switch as dened in claim 9. wherein said last named means comprises relatively adjustable parts for determining the angular relation of said rectangular blade portion to the contacts when in circuit closing position.

11. An electric switch as dened in claim 9. wherein said rst and second named links have a common pivotal connection with said actuating arm.

12. In an electric switch of the twist blade type, a tubular electrically conductive switch blade, actuating mechanism operatively connected with one end of said switch blade to swing the same about a xed pivot axis and to rotate said blade about its longitudinal axis to establish and disestablish circuit closing engagement of said blade at its other end with opposed contact members, a rectangular arcing horn plate enclosed within the latter end of said tubular switch blade, said end portion of the blade being swaged or iiattened upon said plate in intimate heat transmitting contact therewith and having a major cross sectional dimension exceeding the diameter of the remaining portion of the blade, an arcing horn, and means rigidly connecting said horn to said plate in coaxially centered relation with the switch blade.

13. In an electric switch, spaced pairs of opposed insulated contacts, a support, a switch blade bearing structure mounted forv pivotal swinging movement on said support, a switch Y 12 blade rotatably journalled near one end in said support and having rectangular portions for movement to and from circuit closing position between said opposed contacts, an actuating arm pivotally mounted at one end for rocking movement on said bearing structure, a fixed pivot on said support, a lifting link mounted at one end on said pivot and pivotally connected with the other end of said actuating arm, and means operatively connecting said actuating arm adjacent to its pivoted end to said switch bladeat the opposite side of the pivotal axis of said bearing structure with respect to the pivotal connection between said lifting link and actuating arm, to rotate the switch blade when in circuit closing position between the opposed contacts and establish or release circuit closing pressure engagement between the rectangular portion of the blade and said contacts.

14. An electric switch as defined in claim 13, wherein said last named means comprises an adjustable linkage connection between said actuating arm and the end of the switch blade projecting beyond said bearing structure.

15. An electric switch as deiined in claim 13, wherein the axis of said fixed pivot and the pivotal axis of said bearing structure are located in a common plane perpendicular to said support.

16. In an electric switch having a 'blade adapted to be twisted about its longitudinal axis and mounted on a pivoted support for movement therewith into and out of circuit closing position between a pair of opposed contacts; a motion transmitting arm mounted for rocking movement about a pivot axis in spaced parallel relation to the pivotal axis of said blade support, a pair of links having a common pivotal connection at one of their ends with said arm, means pivotally connecting the other end of one of said links with said pivoted support, and means pivotally connecting the other end of the other of said links with said blade, whereby in the rocking movement of said arm in one direction said links are independently actuated to rst twist the blade and free the same from frictional engagement with said contacts and thereafter bodily swing said blade about the axis of said support to open-circuit position.

17. An electric switch as dened in claim 16, wherein said motion transmitting arm has a portionpof channel form partially receiving and shielding the link connected with said support when the arm is in circuit closing position.

18. An electric switch as defined in claim 16 wherein the connecting means between said other link and said blade includes relatively adjustable parts operable to predetermine the degree of twist and the angular position of the blade relative to the contacts when the blade is in circuit closing position.

WILLIAM H. GILLILAND. FITZHUGH H. TURNHAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Caldwell Apr. 5. 1949