US2866048A - Switch contact - Google Patents

Description

Dec. 23, 1958 L. A. HULTEEN ET AL 2,866,048

SWITCH CONTACT Filed June 21, 1956 3 Sheets-Sheet 1 INVENTORS LEONARD A. HULTEEN BY WESLEY J. GORDER ATTORNEY Dec. 23, 1958 A. HULTEEN ETAL I 2,866,048

SWITCH CONTACT Filed June 21, 1956 5 Sheets-Sheet 2 IE.- 5 22 E INVENTORS LEONARD A. TEEN y WESLEY J.- RDER ATT'OR NEY Dec. 23, 1958 L. A. HULTEEN ET AL 2, 48

SWITCH CONTACT Filed June 21, 1956 I s Sheets-Sheet 5 INVENTORS 68 1 LEONARD A. HULTEEN 5' 7o 69 BYWESLEY J. GORDER ATTO RNEY trite swircn CONTACT Leonard A. Huiteen, South Milwaukee, andWesley J. Gorder, Qndahy, Wis.,- assignors to McGraW-Edison Company, a corporation of Delaware Application June 21, 1956, Serial No. 592,968

Claims. (Cl. 200-170) very tightly so that joint resistance manifested by heating is not excessive when the switch is closed and conducting heavy current.

There are a number of conventional means for establishing low resistance connections between the movable parts of a switch. One is to shunt the pivoted joint by a flexible braided jumper. This method is not preferred, however, because jumpers tend to corrode and break after prolonged use and exposure to the elements. Another way is to effect a wiping contact between the components, but this has the disadvantage of causing undue friction, wear and of requiring inspection and cleaning in order that contact resistance be kept low.

An object of this invention is to overcome the problem of transferring current between the relatively movable parts of a switch by using a ball contact adaptedto permit free relative movement between the switch parts through low friction rolling action which is converted to high pressure electrical engagement when the switch closes. 1

Another object is to provide a simple, effective and inexpensive contact which may be readily incorporated in a wide variety of electric switches or mechanical devices;

A general object is the provision of a new and improved electric switch ,and more specific objects will appear periodically throughout the ensuing specification.

Briefly stated, the invention involves transferring current between movable switch parts through a plurality of conductive balls disposed on a circumference concentric with or spiralled about the rotational axis. The parts may be normally biased toward each other by their inherent resilience and further by reinforcement from a compressive backup spring. Each of the balls resides in an individual pair of elongated companion cam grooves disposed opposite to each other in the respective movable members. The cam grooves are preferably of a comet configuration having a-deeply recessed head portion and a shallow tail portion. For certain positions of the movable members, the balls are adapted to roll into the deep pol: tions of the cam grooves to relieve the effect of the compression spring, at the same time reducing contact pressure; and for other positions of the switch, the shallower portions of the grooves coincide, whereupon the members tend to spread, due to the presence of the balls, and cause a high pressure electrical engagement between the parts. The deep and shallow portions of the cam grooves join with each other at an apex caused by their inclination in opposite directions so that when the balls are in either Patent U joint of the switch in Fig. 1;

changing current between switch parts; and, holding theswitch blade in definite openedor closed positions.

Detailed illustrations of the invention will be set forth in the specification in conjunction with the following drawings in which:

Fig. 1 is a plan view of a connect switch incorporating the ball contact forming the subject of this invention; I 1

Fig. 2 is a side elevational view of the switch shown in Fig. 1;

Fig. 3 is an enlarged fragmentary view of the hinge Fig. 4 is a fragmentary side elevational view taken on Fig. 3;

Fig. 5 is a fragmentary view of part of the switch blade showing the location, of the cam grooves;

Fig. 6 is a partial top sectional view taken on a plane" transversely through a pair of co-mpaniongrooves whichf retain one ball, the position of the ball and grooves corresponding with the switch blades of Fig. 4'being rotated to a partially switch open position;

Fig. 7 shows the same parts as Fig. 6 but with the switch in open position;

Fig. 8 is a plan view of a horizontal break switch iu-,

corporating the invention; 1

Fig.. 9 illustrates the position of certain parts of the" bracket 3 by means of the novel ball contact.

The general character of switch 1 will be outlined briefly and the novel hinge contact forming partthereof will be described in detail later. Switch 1 comprises an elongated tubular movable blade 2 adapted to swing into and out of contact engagement with a fixed contact jaw 4 about a transverse hinge pin 5 located at an end remote from the jaw. When in the closed position as in Fig. 2, the current path commences with a line wire adapter 6 which is conductively related to contact jaw .4. Through high pressure engagement with jaw 4, current is transferred to the blade 2 and continues to hinge bracket 3 from which it flows to outgoing line wire adapter 7. Hinge bracket 3 and jaw contact 4 are mounted on insulators 8 and 9, respectively, supported adapted to pivot to a limited degree on a cross pin 15,

extending through the blade for engagement by the hookshaped latch arm 11. Eyeleted latch lever 18 may be rocked by engagement with a hook stick, whereupon a pair of prying cams 16 react against hooked latch arm hookstick operated air dis- 11, causing the latter to rotate in a counterclockwise direction against spring 12 until cross pin 15 on the switch blade is released so that the blade 2 may be swung to open position on hinge pin 5.

Noy'elyportions of switch 1 are depicted enlarged in Figs. 3-7 for facilitating description of the hinge joint assembly. Note that blade 2 is bifurcated to provide two spaced blade, sides 21 which are somewhat resilient because of their being made of hard drawn metal and they are internally stressed for creating a tendency to spreadsaway from each other. The blade is pivoted on ahinge pin spanning opposite legs 22 of hinge bracket 3. Hinge pin 5 may be secured in bracket legs 22 by any suitable means. A high compression coil spring 23 is interposed between blade sides 21 to supplement the inherent force which tends to spread the sides 21 lateral- 1y outward. Hinge bracket 3 is fastened to insulator 8 by means of screws 24.

Blade sides 21 and bracket legs 22 are provided with a pair of oppositely directed, circumferentially spaced, elongated, companion cam grooves 25 and 26, respectively, which act as a track for confining a highly conductive ball 33 of a metal such as aluminum bronze. Grooves 25, 26 may be formed by any method such a casting, coining, planishing or milling. When switch blade 2 is swung between closed position and open position, ball 33 vis adapted to roll in mating pairs of grooves 25, 26 and alternately apply and relieve pressure between the sides of switch blade 21 and the blade bracket 22 in a manner to be described.

Fig. 6 shows how the companion cam grooves 25 and 26 cooperate with each other, when the switch blade 2 is in a position between open and closed, to increase bearing pressure between blade sides 21 and hinge bracket legs 22 through the medium of a ball 33. When the switch attains closed position as in Fig. 4, ball 33 resides in the shallower portions of the opposite cam grooves 25 and 26, and thereby tends to spread bracket legs 22 and blade sides 21 from each other. Because of the inherent resiliency of blade sides 21 and the compressive force of spring 23, ball 33 is placed in greater pressure when in the position of Fig. 6 as compared with Fig. 7.

Although the cam grooves 25, 26 shown in Fig. 6 appear to be linearly disposed, it will be understood that they are actually curvate as clearly shown in Fig. 5. It will be further understood that cam grooves 25 in the switch blade sides 21 are disposed in an opposite direction from their companion cam grooves 26 in the adjacent hinge bracket 22. Consequently, the central angle intercepted by a cam groove in the blade adds to the central angle subtended by a corresponding cam groove in the hinge bracket to yield a total angle which corresponds with the total angular swing of the blade from its closed position such as in Fig. 2 to a diametrically opposite position approximating a swing angle of 180.

Pressure between blade side 21 and bracket leg 22 through the medium of ball 33 is relaxed when switch blade 2 is swung from intermediate position, corresponding with conditions in Fig. 6, to open position corresponding with the relative positions of ball 33, blade side 21, and bracket leg 22, see Fig. 7. If, for example, in Fig. 6, bracket leg 22 is held and blade side 21 shifted to the right, it is obvious that side 21 will roll the ball 33 into the deeper portions of opposite grooves 25 and 26 and that movement of side 21 toward fixed bracket leg 22 will unload compression spring 23, thereby'removing the force from ball 33 as in Fig. 7.

It will be appreciated that when the switch 1 is closed, ball 33 will be seized in very high pressure between the opposed legs 22 of hinge bracket 3 and opposite sides 21 of the blade 2. Thus, in this example, four parallel paths are created for transferring current from blade 2 to the hinge bracket 3. When the current density in two balls 33 per side exceeds acceptable values, additional parallel paths may be provided by providing the switch blade and hinge bracket with an additional set of companion cam grooves, thereby developing four additional parallel paths between blade and hinge bracket. If it is desired that the angle of blade swing be appreciably less than 180, the arcuate cam grooves 25, 26 may be shortened accordingly. Moreover, any amount of blade swing can be achieved by disposing the cam grooves 25, 26 in a spiral about the axis of rotation instead of arcuately concentrically as shown in Fig. 5. In this event, one set of companion cam grooves will cooperate normally With a confined ball but the other set will be able to pass the one set without interference.

It should be observed that when switch blade 2 is swung to its full open position as in Fig. 7, it tends to remain definitely locked in that position by virtue of ball 33 riding over crests 25 and 26 which separate the shallow portions of the cam grooves 25 and 26 from the deeper portions thereof. The amount of force tending to hold the switch in a definitely open position depends upon the inherent resiliency of blade sides 21 and the residual force of compression spring 23. When the switch is being manually closed from its position in Fig. 7 to that of Fig. 6, the blade side 21 will yield with respect to the leg of hinge bracket 22, allowing ball 33 to ride over the crests 25 and 26' and in the direction of the shallower portions of the cam grooves 25 and 26. Hence, whether the switch is open or closed, the tendency for the balls is to remain firmly seated in their recesses corresponding with the position to which the switch has been intentionally actuated.

Figs. 8-11 illustrate an application of the novel hinge ball contact in connection with a horizontal break switch designated generally by the reference numeral 39. The principal components of switch 39 are conventional in respect that they include a stationary insulator 40 supporting a contact jaw 41, the latter being adapted to engage a swinging switch blade 42 carried on a rotatable insulator 43. Switch blade 42 is clampingly supported in a blade carriage bracket 44 bolted to the rotatable insulator 43. Blade 42 will execute identical angular movement with that of insulator 4-3 when the insulator is rotated.

An outgoing lead wire, not shown, may be connected to switch 39 by means of a terminal adapter 47 which extends into an annular pad 48 constituting one part of a low friction pivotal connection between adapter 47 and the switch blade 42. Immediately above and on the same axis with annular member 48 there is a cap-like member 49 which extends in the direction of blade 42 and is clamped to the latter by bolts 50 which also engage the blade carriage bracket 44. The details for achieving a low friction swivel connection between switch blade 42 and terminal adapter 47 will not be discussed further since they do not constitute part of the instant invention and there are several well known means for accomplishing the same purpose, for example, by a flexible wire connection between the switch blade 2 and adapter 47.

When viewed in Fig. 8, switch blade 42 has been rotated in a counterclockwise direction to its full closed position where a blade tip 51 engages stationary contact jaw 41. Contact jaw 41 includes a pair of oppositely disposed contact fingers 52 spaced at one end for engaging and receiving blade tip 51 therebetween and the fingers are pivotally mounted on a post 53 by anchoring them through the agency of extension pins 54. Each contact finger 52 has juxtaposed to it a leaf spring group 55 which compresses the fingers 52 toward each other by interaction on a tie-bar 56 which passes through them. Hence, the force of leaf springs 55 tends to collapse contact fingers 52 toward each other and it is readily apparent that when blade tip 51 is between them that a high pressure contact will be developed therewith.

In order to prevent switch blade 42 from swinging in a horizontal position past contact jaw 41, and to prevent tied directly by the balls.

complete collapse of fingers 52 toward each other,

the contact fingers 52 are provided with a pair of oppositely directed integral stops 57 which project into the blade tips plane and arrest its swinging movement, see Fig. 10. The switch is provided with the customary arcing horns in the form of a movable born 58 and a stationary born 59.

Fig. 9 discloses that the blade tip 51 is adapted to swivel and toggle with respect to the principal portion of the blade 42. In this particular design, the angle of swivel orcocking between the tip 51 and main portion 42 is preferably approximately 30. The swivel connection between the last mentioned members is effected through a knee joint 62 having the properties of a toggle and including the features of the invention for transferring current from the blade tip 51 to the main portion of the blade 42. When the blade approaches closed position as in Fig. 9, it will be noted that the blade tip 51 strikes contact jaw 41 and enters between spaced fingers 52. When blade tip 51 enters sufliciently to strike stops 57, the blade tip begins to execute a clockwise rotation through a small angle tending to align it with the principal portion of blade 42. It should be readily apparent that when blade tip 51 and the main portion 42 are in perfect alignment, the blade has the greatest total length. Consequently, in order for the tip to complete its alignment with the main portion of the blade it is necessary for the former to advance axially and develop a wiping action with the stationary contact jaw fingers 52. This gives the blade a selfcleaning effect and aids in achieving a better connection with the contact jaw.

Knee joint 62 is made up of a casting which includes a cup-like portion 63 having an integral socketed portion 64 extending therefrom. Socket 64 is split, as is clearly evident in Fig. 8, and clamped by means of bolts 65 to the round tubular portion 42 of the switch blade. Projecting from the bottom of annular cuplike portion 63 is a rectangular pad 66 provided with silver inserts 67 near its bottom for the purpose of interchanging current through a low resistance wiping connection with the bottom of an annular cavity 68 located in the blade tip 51. A stud shaft 69 is fixedly pinned at 70 to blade tip 51 and extends into cup 63 by passing through rectangular pad 66 relatively freely. Rotation of blade tip 51 is limited with respect to the longitudinal axis of main blade 42 by a stop 71 located in the lower current interchange current cavity 68. Stop 71 is nothing more, when viewed from the top, than a sector of a circle extending from the peripheral walls of cavity 68 and presenting radial surfaces which may strike the margins of rectangular pad 66 when the blade tip is rotated in either direction. Current interchange cavity 68 may be completely filled with a non-oxidant lubricant such as silicone base grease and sealed by an elastic O-ring 72.

Stud shaft 69 has loosely surrounding it a floating plate 75 which is prevented from rotating about shaft 69 by a pin 76 extending radially through floating plate 75 and into a longitudinal key-way 77 in the periphery of shaft 69.

The principle of effecting high pressure contact relationship between two relatively movable members at a predetermined time is employed in the knee joint 62 similarly to the manner in which it was in the first embodiment of the invention except that now current is not car- The balls 78 are interposed between grooved floating plate 75 and the bottom of a grooved cup-like portion 63. Here, however, it is deemed preferable to use at least three balls 78 because cam grooves 79, see Fig. 12, may be shorter than those in Fig. 5 because of the reduced angular swing in this instance. Of course, floating plate 78 and the bottom of cup 73 are impressed with oppositely directed companion cam grooves defining tracks as in the preceding example.

Stud shaft 69 projects upwardly where it terminates pression spring 82 is interposed between the bearing ring and floating plate in such manner that there is always a yielding axial force exerted downwardly on the floating plate and upon stud 69. A cap member 83 is threaded for engagement with a corresponding thread 84 on cup member 63 so that the components of the knee joint may be positively sealed against entry of contaminants and also for the purpose of containing lubricant.

It will be evident that when the switch is in the position of Fig. 11, corresponding with closed position in Fig. 8,

balls 78 will reside in the shallower portions of cam grooves 79 thereby tending to spread the floating plate 75 axially away from the bottom of cup-shaped member 63. The force so developed is transmitted from the floating plate 75 through the spring 82 to the stud shaft 69 upon which it exerts an upward or axial force. This axial force tends to increase the contact pressure between the lower end of rectangular pad 66, containing the silver inserts 67, and the bottom of cavity 68 in blade tip 51. Since the angle of swing and the angle intercepted by cam grooves 79 is relatively small in this instance, it will be apparent that blade tip 51 is free to swivel with respect to the principal portion of the blade 4-2 when the switch approaches closed position as in Fig. 9. However, after the blade tip 51 enters the space between contact fingers 52 and begins advancing in an axial direction toward alignment with blade 42, the balls 78 will be rolled to the position where they cause a strong axial force to be exerted along stud shaft 69, thereby causing high pressure engagement between rectangular pad 66 and the bottom of cavity 68 only when the switch is in its fully closed position.

it is important to note that when main switch blade 42 is closed, blade tip 51 swings past true alignment with the blade to a toggle position slightly beyond their common longitudinal center. This corresponds with balls '78 coming to rest in the shallower portion of groove 79 so that to open t1 e switch would require having the balls pass over crest 85 in the grooves. The purpose of this is to make the switch blade close tighter in the event that the switch itself is subjected to heavy fault current which would develop a magnetic field having a tendency to open the switch. When the blade tip 51 is in toggle open position as in Fig. 9, the same effect is achieved through i the balls coming to rest in the deeper portions of the grooves 79 on an opposite side of crest 85. Consequently, whenever the switch is swung open, blade tip 51 will deflect to a predetermined fixed angle with respect to the principal portion 4-2 of the blade and stop in lock-ed position. The blade tip 51 and portion 42 will deflect to a cocked position as in Fig. 9 whenever the switch is open, due to the tendency for the balls to move to a position which unloads compression spring 82. The assembly just described also has particular use in the blade joints of a tilting insulator type air disconnect switch.

From the aforegoing specification it will be seen that a novel contact pressure ball and cam groove arrangement has been described which is applicable to any hinge joint wherein it is desired to swing relatively movable members freely through a certain angle and to terminate their movement in a definite position whereupon the members are locked tightly with respect to each other. It has been further shown how the balls may be used to directly transfer current through them as in Fig. 3, or, as a means for merely effecting high pressure relation between another set of contacts as is more clearly evident in Fig. 11. Accordingly, although only illustrative examples of the invention have been set forth, it will be appreciated that the invention may be variously embodied and is to be interpreted according to the scope of the claims which follow.

It is claimed:

1. In an electric switch having a movable conductive member adapted to pivot between'ang'ular" positions about an" axistransverse to the path of the movablemember, a relatively stationary member on which said movable member pivots, resilient means biasing said movable member and relatively stationary member toward each other, each of said members being provided with similar arcuate converse companion carn grooves defining a ball track thereb'etween, each groove having deep and shallow portions superposed in opposite endwise relation with respect to its companion groove and being movable past each other about said-axis for alternately placing the deep and. shallow portions in coincidence with each other, a ball confined by said companion cam grooves and adapted to be rolled by rotational movement of said members between limits established by angular coincidence of said deep and shallow portions of said grooves, crest means in at least one said groove separating said deep and shallow portions so that the ball positively positions in one or the other portion when the movable conductive member is in a correspondingangular position, said ball increasing the pressure onsaid members when in said shallow portion corresponding to an angular position of said movable member and decreasing the pressure when in said deep portions corresponding to another angular position of said movable member.

2. In an electric switcn having blade means adapted to pivot angularly on a transverse axis between opened and closed circuit positions, bracket means supporting said blade means for relative pivotal movement, resilient means biasing said blade and bracket means toward each other along said transverse axis, said bracket means and blade means each being provided with similar arcuate companion cam grooves defining a ball track therebetween, each groove having a deep and a shallow portion in opposite endwise relation with respect to its companion groove and being movable past each other about said transverse axis for alternately placing the deep and shallow portions in coincidence with each other, a ball confined in each companion pair of cam grooves and adapted to be rolled by rotational friction between said blade means and bracket means respectively between limits established by angular coincidence of the deep and shallow portions of said grooves, crest means in at least one said groove separating said deep and shallow portions so that the ball positively positions in one or the other member when the blade means is in a corresponding angular position, said balls tending to spread said blade and bracket means away from each other when simultaneously in said shallow portions and thereby effecting high pressure engagement between said blade means and bracket means under the infiuence of said resilient means, and to relieve said pressure when said blade means is rotated toward open position whereupon said balls move to said deeper portions.

3. The invention set forth in claim 2 wherein said bracket means has legs spaced from each other and supporting said transverse axis thereacross, said blade means having sides at least a portion of which are flat and disposed between said legs, and said resilient means comprising a compression spring interposed between said sides and urging the latter oppositely outwardly toward said legs. 7

4. In an electric switch having conductive members conmember' and having a-free end projecting into the other member for. rotation, spring retaining means adjacent the free end'of said shaft, a floating plate mounted for axially sliding on said shaft, said floating plate and other member each being provided with similar arcuate companion cam grooves jointly defining a ball track therebetween, each groove having a deep and shallow portion in opposite end wise relation to similar portions in its companion groove, the bottom of at least one cam groove having a crest separating said deep and shallow portions, said grooves being movable in substantial parallelism past each other about said transverse axis for alternately'placing the deep and shallow portions in coincidence with each other, a ball confined in each pair of companion cam grooves and adapted to be rolled by rotation of said members for being positively positioned on opposite sides of said crest and.

between limits established by angular coincidence of said deep and shallow portions, said floating plate tending to move axially of said shaft in accordance with the position of said balls in said grooves, and spring means interposed between said retaining means and floating plate and responding to the floating plate by increasing and decreasing the force on said contact means between members.

5. An electric switch comprising a fixed insulator and an axially rotatable insulator spaced therefrom, a contact jaw mounted on the fixed-insulator and a switch blade mounted on the rotatable insulator for swinging into engagement with the jaw, a blade tip pivotally connected to the blade for limited angular movement in the direction of the jaw when the switch is open and adapted to toggle into substantial alignment with the blade when the switch is closed, a cup portion on said blade, a shaft affixed to said tip and projecting into the cup portion, a floating plate slidably keyed on the shaft Within said cup portion, a compression spring biasing said floating plate axially of the shaft, the aforesaid floating plate and cup portion each being provided with companion cam grooves having deep and shallow portions disposed endwise oppositely of each other defining a ball track, the bottom of at least one com groove having a crest separating said deep and shallow portions, a ball disposed in each pair of companion grooves and residing in opposite deep portions when said switch is open and adapted to roll to opposite shallow po'rtions on alternate sides of said crest when said switch is closed and said tip and blade are past alignment with each other whereupon said spring becomes compressed, and current interchange contact means between said cup and tip adapted to be placed in high pressure relation when said spring is compressed.

References Cited in the file of this patent UNITED STATES PATENTS 2,156,024 OBrien Apr. 25, 1939 2,646,487 Johnson July 21, 1953 FOREIGN PATENTS I 589,085 Great Britain lune ll, 1947

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