US3388225A

US3388225A - Jaw for ice breaking switch

Info

Publication number: US3388225A
Application number: US582885A
Authority: US
Inventors: Foti Arem
Original assignee: ITE Circuit Breaker Co
Current assignee: ABB Inc USA; ITE Circuit Breaker Co
Priority date: 1966-09-29
Filing date: 1966-09-29
Publication date: 1968-06-11
Anticipated expiration: 1985-06-11

Description

June 11, 1968 A. FOTI 3,388,225

JAW FOR ICE BREAKING SWITCH Filed Sept. 29, 1966 5 Sheets-Sheet l {I J] J? 5% 4\ l I I 2% E5: 5. WENTOR.

arr/e dA'F/YA; 455 Gaze ilk/i! June 11, 1968 Filed Sept. 29, 1966 5 Sheets-Sheet 2 03/ l I I June 11, 1968 Filed Sept. 29, 1966 A. FOTI JAW FOR ICE BREAKING SWITCH 5 Sheets-Sheet 3 INVENTOR. HAEM F577 dire 04.91%, 64553 Gzeajfafiw June 11, 1968 A. FOTI 3,388,225

JAW FOR ICE BREAKING SWITCH Filed Sept. 29, 1966 5 SheetsSheet 4 1 N V ENTOR.

iTfd/P VEVJ June 11, 1968 A. FOTI 3,388,225

JAW FOR ICE BREAKING SWITCH Filed Sept. 29, 1966 5 Sheets-Sheet 5 firmed; EMA, F0556 Gzexilmw United States Patent 3,358,225 JAW FOR HIE BREAKING SWITH Arem Foti, Greensburg, Pan, assignor to ll-T-E Circuit Breaker Company, Philadelphia, Pa, a corporation of Pennsylvania Filed Sept. 29, 1966, Ser. No. 582,885 3 Qlaims. (Cl. Mid-48) AEBSTRACT 0F THE DTSCLGSURE This invention broadly relates to a disconnect switch structure capable of being moved to the fully closed or connected position even under the presence of extreme icing conditions. The disconnect switch blade is provided with a beavertail structure having a substantially oval cross-sectional configuration having perpendicularly aligned major and minor diameters such that the major diameter is of the order of three times greater than the minor diameter. The contact surfaces of the beavertail are provided in the immediate region of the extreme ends of the major diameter. The beavertail structure is designed to cooperate with a jaw structure comprised of confronting contact surfaces. One contact surface is substantially flat over its entire length and is substantially vertically aligned. The other confronting surface is flat only a portion of its length with the remaining upper portion being aligned diagonally upward and away from its associated confronting structure to facilitate entry of the beavertail between the confronting contact surfaces of the jaw structure. The operating mechanism causes the beavertail to have its major diameter diagonally aligned as it enters into the region between the confronting surfaces of the jaw structure. The higher of the two beavertail contact surfaces is aligned to make engagement with the jaw structure contact surface which is substantially straight over its entire length when the beavertail is rotated so that its major diameter is substantially horizontally aligned. The substantially straight structure contact surface cooperates with the associated beavertail contact surface to provide a large shearing force upon the structure which is capable of shearing away ice even under the most severe conditions to provide good contact pressure between the beavertail and jaw structure even under severe icing conditions.

The instant invention relates to disconnect switches, and more particularly to disconnect switches employed in high voltage transmission networks having a novel jaw and blade configuration which cooperate to assure safe, effective closure and good contact engagement in the presence of the most severe environmental conditions.

Disconnect switches are well known to the power distribution network art. One typical prior art structure is described in detail in US. Patent No. 2,673,902, issued March 30, 1954 and No. 2,854,553, issued Sept. 30, 1958, both patents having been assigned to the assignee of the instant application. As is conventional in the disconnect switch art, such apparatus is typically comprised of a movable switch blade which is first rotated from a pivot point substantially at one end thereof so as to move into the region of its cooperating jaw contact and during a part of this rotational movement is simultaneously rotated about its longitudinal axis so as to bring its beavertail contact into rigid engagement with the cooperating contact surfaces of the jaw which then provides good engagement under pressure as between jaw contacts and the beavertail contacts.

The beavertail portion of the disconnect switch blade has a cross sectional configuration such that a first diameter thereof, which is mutually perpendicular with a sec- 3,388,225 Patented June 11, 1968 ond diameter thereof, is further slightly greater in length than the second diameter. In operation the switch blade is closed with the first diameter being substantially upright as the switch blade approaches the cooperating jaw contacts. As soon as the switch blade beavertail portion enters into the region between the jaw contacts the switch blade rotates along its longitudinal axis so as to rotate the first diameter from a substantially upright position to a substantially horizontal position in order to cause the beavertail portion to make rigid contact engagement with the cooperating jaw contacts.

The stationary jaw structure of conventional disconnect switches is typically comprised of a pair of spaced substantially parallel contact surfaces which are significantly flared at their upper ends to facilitate introduction of the switch blade into the region between the contact surfaces of the jaw.

Such conventional disconnect switches have been found to operate satisfactorily through most environmental conditions, however, it has been found that switches of conventional design have been ineffective in the presence of certain environmental conditions. For example, in cold climates icing of the disconnect switch structure is quite prevalent. It is common, in such climatic conditions, to find a coating of ice forming on the surface of the blade and/ or the contact fingers, as well as the remainder of the supporting structure. Substantial icing of these elements have been found to make normal switch operation quite diflicult and in many cases impossible. One prime cause of the ditliculty encountered is the tendency of the relatively long switch blade to deflect, in cantilever fashion, when the beavertail, or contact end of the switch blade strikes against the ice over surfaces of the jaw contact surfaces. In addition thereto, substantially icing up these elements narrows the entrance area of the jaw so as to make entry of the switch blade beavertail portion into the jaw region either diflicult or impossible.

Numerous attempts toward a solution of this problem have been attempted over the years but, up to the present date, no solution has been found which adequately provides reliable operation of the switch when subjected to icing conditions such that the switch is enabled to provide safe, reliable closing and good contact engagement after just one closing operation.

The instant invention is characterized by providing a novel switch blade and jaw structure which is capable of providing switch closure accompanied with good rigid contact engagement through the performance of a single closing operation. The disconnect switch of the instant invention is provided with a switch blade having a beavertail portion whose cross-sectional con-figuration is such that the major, or first, diameter is substantially greater than the minor, or second, mutually perpendicular diameter, and is preferably three times as great as the minor diameter. The jaw structure is comprised of a first contact surface having a substantially straight vertically aligned lower portion and an outwardly flared upper portion. The other contact surface is substantially straight and vertically aligned over its entire length and is of substantially the same height as the contact surface having the outwardly flared upper portion.

In operation, the switch blade is rotated about its first end until the beavertail portion enters the region between the two contact surfaces of the jaw structure. At this time the switch blade begins rotating about its longitudinal axis causing the contact portions of the switch blade beavertail to be moved from a substantially vertically aligned position toward a substantially horizontally aligned position so as to make good rigid contact engagement with the jaw structure when in the fully closed position.

When severe environmental conditions cause icing over of the disconnect switch and more particularly of the switch blade beavertail portion and jaw structure, it has been found that the conventional structures will fail to clear the beavertail portion and jaw structure contact surfaces of ice so as to provide a good contact path. In the instant invention extremely high shearing forces are imparted upon the jaw structure contact surfaces to assure shearing away of the ice from the engaging contact surfaces. The cross-sectional configuration of the switch blade beavertail portion assures entry of the beavertail portion between the jaw structure opposing contact surfaces even under the most severe icing conditions encountered.

It is therefore one object of the instant invention to provide a disconnect switch having a novel switch blade and jaw structure design so as to assure safe, reliable operation under all environmental conditions.

Another object of the instant invention is to provide a novel disconnect switch having a beavertail portion and jaw structure which is highly effective in removing ice from the contact surfaces thereof during a closing operation which is performed in an environment which subjects the disconnect switch to severe icing conditions.

Still another object of the instant invention is to provide a novel disconnect switch having a dual motion blade and cooperating jaw structure wherein reliable operation is readily achieved even under severe icing conditions and wherein the construction of the switch does not necessitate any additional costly elements.

These and other objects of the instant invention will become apparent when reading the accompanying description and drawings in which:

[FIGURE 1 is a perspective view showing features of a novel switch construction wherein the disconnect switch blade is shown in the partially open position.

FIGURE 2 is a side elevational view of the disconnect switch of FIGURE 1 shown in the closed position.

FIGURE 3 is an end view of the disconnect switch of FIGURES 1 and 2 showing the beavertail and jaw structure in greater detail and with the beavertail being shown in the position as it enters between the opposing contact surfaces of the jaw structure.

FIGURE 3a shows the beavertail and jaw structure of FIGURE 3 wherein one edge of the beavertail is shown abutting a layer of ice formed upon one of the jaw structure contact surfaces.

FIGURE 3b shows the beavertail and jaw structure of FIGURE 3 and 3a with the beavertail shown in the fully closed position.

FIGURE 30 shows the beavertail and jaw structure of a conventional disconnect switch with one contact surface of the beavertail abutting a layer of ice formed upon one surface of the jaw structure.

FIGURE 4 shows a side view of the beavertail structure of FIGURES 3-3b.

FIGURES 5-5b are top, side and end views, respectively, of an alternative beavertail structure.

FIGURE 6 shows a side view of the jaw structure.

Referring now to the drawings, the high voltage disconnect switch, generally designated as 10, chosen to illustrate the features of this invention, is shown in its closed position in FIGURE 2, wherein the switch support is horizontally arranged. Switch 10 is mounted on a base 11 by means of

insulation spacers

12 and 13,

upstanding support posts

14 and 15, and the

insulators

16 and 17 mounted on the upper ends of

posts

14 and 15, respectively.

A shaft 18, disposed below an insulator 19, has a crank 20 secured thereto in any suitable manner such as by bolts 21 connected to the flange or crank blade 22. Bolts 23 secure a stop plate 24 in position, the stop plate being provided at its opposite ends with adjustable stops which engage at either of their ends the stop 25 on the operating crank 20.

A shaft 26 extends above insulator 19 as a continuation of the shaft 18. A crank 27 is secured to the upper end of shaft 26 and is preferably formed integral therewith, so that crank 27 rotates along with shaft 26. Crank 27 extends horizontally, or essentially parallel, to the base 11 and rotates in the horizontal plane.

The outer end of crank 27 is flattened at 28, and is provided with a circular opening 29 through which a pin 39 passes. A clevis member 31 receives the flattened extension 28 and is provided with suitable openings in its legs, in registry with openings 29, to thereby enable clevis member 31 to receive the pin 30.

The clevis 31 is integrally formed with a threaded extension 32 which is received within a suitably threaded bore in a forked link 33. The engagement between extension 32 and forked link 33 is such that when extension 32 rotates with respect to forked link 32, a linear movement is simultaneously imparted thereto.

A pin 34 is passed through suitable openings in link 33 and a crank 35 to pivotally connect forked link 33 to crank 35. A blade support sleeve casing 36 carries a tubular switch blade 37, the blade 37 being secured within sleeve casing 36 and rotatable therewith.

Blade support sleeve casing 36 is mounted for rotation about longitudinal axis on an extension of a hinge 38 which, in turn, is rotatably mounted by a hinge bearing 39 on the frame casting 40.

The free or contact end of the tubular switch blade 37 carries suitable contacts which are engageable with a stationary contact jaw 41 in a manner more fully described below.

It will be appreciated that by means of the above described mechanism, which is more fully described in the said 'Patent No. 2,673,902, that by suitable operation of the crank 20, the switch blade 37 may be rotated in the vertical plane into and out of engagement with the stationary jaw 41, while being simultaneously rotated about its longitudinal axis.

It will be further appreciated that the movement of switch blade 37 may be effected either manually or by a control motor (not shown) operating in conjunction with crank 20.

Clamping portion 42 is firmly secured by any suitable means, to the contact end of switch blade 37 and has integrally formed therewith a flattened or beavertail section 43. As seen best in FIGURES 55b, the flattened holder section 43 combines with the beavertail 49 to form an oval shaped or ellipsoidal cross-section 47, wherein the length of the diameter along the major axis A of the ellipse is substantially greater than the diameter along the minor axis A A transverse slot 44 is formed through holder section 43 and two parallel rows of equally spaced openings 45, each of which is countersunk as at 46, pass through holder section 43.

The conducting beavertail 49, preferably formed of an integral casting, is snugly inserted into slot 44 and has openings 47a arranged coaxially with the openings 45 in holder section 43. Bolts 48, threaded at their lower ends, are passed through

openings

45 and 47a and are tightened to firmly retain beavertail 49 within holder section 43, so that beavertail 49 rotates along with holder section 43 and thereby with switch blade 37.

Beavertail 49 comprises an elongated central portion 47b and opposed arcuate contacting sections 49a extending from each end of section 47b, beyond the confines of the holder section 43 (FIGURE 5). It will also be noted that the transverse dimension of beavertail 49 is substantially greater than the height of the holder section 43 and that it also exceeds the diameter of the main portion of the switch blade 37. For extra high voltage switches, to prevent corona discharge, a hollow conducting sphere 50 (see FIGS. 1 and 2) is attached by suitable means to the free end 42a of clamp 42. The arcuate surface 42b (see FIG. 5a) abuts and seats one portion of the sphere 50.

The stationary jaw 41 is supported on a casting base 51 which is rigidly secured to insulator 17 by any suitable means. Base 51 extends upwards to define spaced apart

upstanding walls

52 and 53 and a tongue portion 54, extending from base 51, contains openings 55 adapted to receive an external power line (not shown).

A set of straight contact fingers 57 is secured to wall 52 by means of bolts 58, and a set of flared contact fingers 59 is secured to wall 53 by similar means. As seen in FIGURE 6, contact fingers 59 are conventionally formed and have a fastening arm 60, an outwardly flared loop portion 61, and a resilient contact arm 62 extending into the interior of jaw 41. A compression spring 63 surrounds bolts 58 and is terminated by a spring cap 64 which rests against the contact arm 62 of contact finger 59.

In contrast to the configuration of the flared contact fingers 59, the contact fingers 57 each comprise a fastening arm 65, an intermediate loop portion 66, and a straight contact arm 67 extending into the interior of the jaw 41. Once again bolts 58 are each surrounded by a compression spring 63 and a spring cap 64, the end of the spring cap 64 resting against the contact arm 67.

During the closing operation of the switch 10, the switch blade 37 is rotated downwards towards the jaw 41. During this downward movement, the orientation of the beavertail 47 is as shown in FIGURES l and 3 so that when switch blade 37 enters into jaw 41, the upper and lower surfaces of the holder section 43 are substantially parallel to the

contact arms

67 and 62 of the

contact fingers

57 and 59, respectively. As a result, there is a generous clearance between the entering beavertail 49 and the jaw 41, so that in the event a coating of ice has formed on the surfaces of the

contact fingers

57 and 59, there will still be sutficient clearance to permit the unimpeded entry of the beavertail 49 into the jaw 41.

Once the beavertail 49 is positioned in the area between the

contact fingers

57 and 59, it undergoes a clockwise rotation as viewed in FIGURE 3, about its longitudinal axis. The beavertail 49 rotates from the nearly vertical entry position shown in FIGURE 3 toward the diagonal position shown in FIGURE 3a, wherein the beavertail surface portion 49a engages the surface of the layer of ice '70 formed upon the portions 6567 of the contact finger.

The force vector is represented by the arrow 71. This vector can be broken into two

rectangular components

72 and 73, respectively. The substantially horizontally aligned vector component 72 acts as a compressional force upon the layer of ice 70. The remaining vector component 73, which is aligned in the downward vertical direction, and which can be seen to be of greater magnitude than the compressional vector 72, acts as a shearing force upon the ice layer 70, thereby causing the ice layer 70 to be sheared from the surface 67 of each of the contact fingers so as to cause the right-hand beavertail contact surface 49 to make good contact engagement with each surface 67 of the contact fingers. It should be noted that like force vectors exists even in the case where the beavertail portion becomes coated with a substantially thick layer of ice. Also, it should be noted that the left-hand conductive surface 49 of the beavertail structure will act in a substantially identical manner in cooperation with the surface 62 of the left-hand contact fingers so as to exert an upward shearing force which will operate with the same effectiveness as the right-hand shearing force represented by vector 73 in FIGURE 3b. Once the ice has been sheared from either the contact finger surfaces 62 and 67, or both the contact finger surfaces and the beavertail surface 49, the beavertail moves to the fully closed position shown in FIGURE 317 wherein the contact sections 49 are in firm conductive contact with the

contact arms

62 and 67. It is to be noted that the spacing between the

contact fingers

57 and 59 prior to the engagement therewith by beavertail 47, is slightly less than the overall distance between the ends of contact sections 49. Consequently, when the beavertail is rotated about its longitudinal axis, left and righthand surfaces 49 rigidly engage the straight contact arm 67 and flared contact arm surfaces. With the beavertail in the fully closed position an electrical circuit is thereby established between terminal and the terminal at tongue 54.

A further distinct advantage of the beavertail and jaw structure configurations is such that the dimensional relationship between the diameters of the beavertail lying along the major and minor axes A and A respectively, allows for generous clearance between the beavertail and the opposing contact surfaces of the jaw structure even in the case where severe icing of these elements occurs.

In tests performed on disconnect switches of the type described herein which were conducted for both single pole and three-pole switches having ratings of 500 kilovolts and 2500 amperes, it was found that all of the ice was sheared from the engaging contact surfaces, that the beavertail came to rest in its proper fully closed position and that good contact engagement was achieved through the performance of only a single closing operation and in environmental conditions wherein layers of ice having a thickness of as much as 1 /2 were formed on surfaces of the beavertail and jaw structures. Conventional switch structures were tested under identical environmental conditions and were found to require as many as eight successive closing operations before all of the ice was removed from the contact surfaces of the beavertail and jaw structures.

FIGURE 30 shows a beavertail 49 and jaw structure 67 of conventional design wherein ice layers 74 and 75, respectively, are formed thereon and with the two layers of ice making abutting engagement. The force vector 76 representing the force supplied to ice layer by the beavertail 49 is substantially entirely a compressional force and exerts no shearing stress whatsoever upon the ice layer thereby making it extremely diflicult, if not impossible, to remove the ice from the contact structure 67 In addition thereto, the compressional force 7 6 causes the contact point 77 between the two

ice layers

74 and 75 to act as a fulcrum point causing the left-hand end of the beavertail to be rotated upwardly in the direction shown by arrow thereby severely restraining the normal closing operation. In addition thereto, the minor diameter 78 of the beavertail 4-9 is only slightly shorter than the major diameter 79 so as to provide insufficient clearance for the beavertail as it enters between the opposing surfaces of the jaw structure in cases where severe icing of the beavertail and jaw structures occur. The effective fulcrum point between the engaging layers of ice cause relatively long switch blades to deflect in cantilever fashion when their contact ends encounter ice blocks in the cooperating jaw members thereby causing either damage' to the switch blade or making the closing operation either difficult or impossible to perform.

It can thereby be seen from the foregoing description that the instant invention provides a novel beavertail and jaw structure which assures good contact engagement between these elements even under the most severe climatic conditions and wherein a single uninterrupted closing operation is capable of shearing all ice which may be formed on the engaging surfaces of the contact members. Numerous alternative approaches were attempted toward a solution to this problem but none of these approaches were found to be as successful as that described herein. During the applicants investigative test program other methods were tried and abandoned in favor of the present invention. One method involved the use of Teflon coated parts in which a large portion of the jaw contact fingers and beavertail were coated or covered with shrink-type Teflon, with the exception of the actual electrical contact surfaces. Two associated disadvantages were high costs of the additional exotic material required and the relatively high additional cost for applying the material to the switch parts.

Another method considered was the use of a sleet shield or a protective hinged cover over the jaw parts. This approach necessitates significantly higher costs and provides a potential added source of trouble. Also ice locking of the hinge covers themselves have been found to block travel of the blades.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.

What is claimed is:

1. In a disconnect switch having a switch blade, a cooperating jaw structure and means for rotating said switch blade to move the free end of said switch blade toward and away from said jaw structure and to rotate about its longitudinal axis when entering the immediate region of said jaw structure;

a beavertail portion secured to the free end of said switch blade;

said beavertail portion being formed of a conductive material having a substantially oval shaped crosssectional configuration such as the first diameter lying along the major axis is substantially greater than a second diameter lying along the minor axis which is perpendicular to said major axis;

the improvement comprising:

said jaw structure being comprised of first and second spaced contact members confronting one another and being substantially the same height, said first contact member having a substantially straight contact surface running its entire length;

said second contact member being comprised of first and second straight surface portions integrally joined to one another;

said first straight surface portion of said second contact member being substantially parallel to said first contact member; said second straight surface portion of said second contact member being diagonally aligned relative to said first straight surface portion and extending in a direction away from said first contact member to facilitate entrance of said beavertail portion between said contact members during a closing operation;

said beavertail portion having first and second contact surfaces arranged at the edges of said beavertaii which lie at opposite ends of said first diameter which is perpendicular to the second diameter of the beavertail portion, said first diameter being at least twice as great as said second diameter;

said first diameter being diagonally aligned relative to said first contact member and having its first contact surface positioned so as to enter the region between the jaw structure prior to said second contact surface as the beavertail portion enters the region between the first and second contact members;

means for rotating the beavertail portion after entry between said first and second contact members to align said first diameter substantially perpendicular to said first contact member;

said first contact member being positioned to engage the second contact surface of said beavertail portion when said disconnect switch is in a fully closed position;

the first straight portion of said second contact member being positioned to engage said first contact surface of said beavertail portion when said disconnect switch is in the fully closed position;

the parallel surfaces of the first and second contact members being spaced by a distance providing a generous clearance between the first and second contact surfaces and their associated contact members as the beavertail portion enters into the region between the parallel surfaces of said contact members and before axial rotation thereof;

the distance between the ends of said first and second contact members at which the beavertail portion enters the jaw structure being substantially greater than said first diameter.

2. The switch of claim 1 wherein said first diameter is approximately three times as great as said second diameter.

3. The switch of claim 1 wherein the spacing between the straight parallel surface portions of said contact members are spaced apart by a distance slightly less than said first diameter.

References Cited UNITED STATES PATENTS 2,688,666 9/1954 Gilliland et a1 200-70 2,753,407 7/1956 Hollander 200-43 2,767,264 10/1956 Scott 200-166 3,127,491 3/1964 Gorrnan 20048 3,198,662 8/1965 Seibert 200166 3,243,561 3/1966 Foti.

ROBERT K. SCHAEFER, Primary Examiner.

H. J. HOHAUSER, Assistant Examiner.