US3544741A

US3544741A - Electric switch having improved blade construction

Info

Publication number: US3544741A
Application number: US790078A
Authority: US
Inventors: Edmund W Kuhn
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1969-01-09
Filing date: 1969-01-09
Publication date: 1970-12-01
Anticipated expiration: 1987-12-01

Description

United States Patent Inventor Edmund W. Kuhn Pittsburgh, Pennsylvania Appl. No. 790,078

Filed Jan. 9, 1969 Patented Dec. 1, 1970 Assignee Westinghouse Electric Corporation Pittsburgh, Pennsylvania a corporation of Pennsylvania ELECTRIC SWITCH HAVING IMPROVED BLADE CONSTRUCTION l0 Claims, 4 Drawing Figs.

U.S. Cl 200/48, 200/ l 70 lnt.Cl ..H01h3l/00 Field of Search 200/170,

170(A), l66(C),48

References Cited UNITED STATES PATENTS 2,759,076 8/1956 Curtis 200/l70A 3,299,240 H1967 Foti 200/l66C Primary Examiner-R0bert K. Schaefer Assistant lz'xaminerH. J. Hohauser AlmmeysA. T. Stratton and C. L. Mc Hale ABSTRACT: An electric switch comprising a switch blade movable between open and closed positions with respect to a relatively stationary contact means with a portion of said blade being formed from aluminum and a portion ofsaid blade being formed from an electrically conducting material other than aluminum.

PATENTED um 19m SHEET 1 OF 2 fol PATENTED BEN SHEET 2 OF 2 |253B|20C IZOA 53A 43 I200 208 l 53C I D 7 I54 I56 '52 F IG.3.

FIG.4.

WITNESSES INVENTOR Edmund W Kuhn a fi w Win/w ATTORNEY ELECTRIC SWITCH HAVING IMPROVED BLADE CONSTRUCTION CROSS REFERENCES TO RELATED APPLICATIONS Certain inventions disclosed in the present application are related to inventions which are disclosed and claimed in my copending U.S. Pat. application Ser. No. 772,715 filed Nov. 1, 1968, which issued Mar. 10, 1970 as U.S. Pat. 3,500,006, and in copending U.S. Pat. application Ser. No. 790,088 filed concurrently by R. E. Frink which are both assigned to the same assignee as the present application.

BACKGROUND OF THE INVENTION This invention relates to electric switches and more particularly to constructions of the blades which form part of such switches.

In certain types of outdoor high voltage electric switches a problem arises in providing a switch construction in which as many of the electrically conducting parts of the switch is possible are formed from a lightweight, electrically conducting material, such as aluminum, to obtain certain advantages such as a reduction in the weight of the parts of the switch which must be supported by the associated insulator supports. This problem arises because of the high resistance oxide coating which forms on aluminum when it is exposed to atmospheric conditions or air and because of the galvanic corrosion which normally results when aluminum is structurally connected to a different electrically conducting material, such as copper or an alloy including copper. Various constructions have been proposed in the past for switch construction of the type described, such as disclosed in U.S. Pat. Nos. 3,206,568, 3,243,561, 3,299,240 and 3,388,225. These known switch constructions have been found to have certain disadvantages either due to difficulties in manufacture or problems arising when such switch constructions are subjected to long continued use in service.

SUMMARY OF THE INVENTION 1 In accordance with the invention, an electric switch includes an elongated switch blade or contact arm having a free end movable into engagement with or to a close position with respect to an associated relatively stationary contact means. The free end of the switch blade includes an electrically conducting portion which is generally rectangular or oblong in configuration in one embodiment and includes a pair of relatively wider opposite planar surfaces interconnected by a pair of relatively narrower opposite surfaces. In the latter embodiment, a pair of electrically conducting contact members are secured to the free end of the blade for movement therewith to engage the associated stationary contact means in the engaged position of the blade. Each of the contact members includes a relatively longer portion having a planar surface which engages one of the wider planar surfaces of the free end of the blade and a relatively shorter generally arcuate portion which is spaced from the adjacent narrower surface of the free end of the blade with the end of the arcuate portion away from the associated longer portion bearing against the end of the longer portion of the other contact member away from its associated arcuate portion.

In a second embodiment of the invention, the free end of the blade includes at least one planar surface and a pair of side surfaces which project generally away from the associated planar surface. Only one contact member is secured to the free end of the blade. The contact member includes a central portion having a planar surface which bears against or engages the planar surface on the free end of the blade and two arm portions which project generally in the same direction as the side surfaces of the free end of the blade. The arm portions of the contact member are disposed adjacent to and spaced from the respective side surfaces of the free end of the blade.

In each of the above embodiments, the blade including the electrically conducting portion at the free end may be formed from aluminum, while the associated contact member from an electrically conducting material other than aluminum, such as copper or an alloy including copper.

It is therefore an object of this invention to provide an electric switch having an improved blade construction.

Another object of the invention is to provide an improved electric switch construction including a movable switch blade which is formed partially from aluminum and partially from an electrically conducting material other than aluminum.

BRIEF DESCRIPTION OF THE DRAWING Other objects of the invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a partial view, in side elevation, of a disconnecting switch structure embodying the principal features of the invention;

FIG. 2 is a top plan view of the portion of the switch structure which is shown in FIG. 1;

FIG. 3 is an enlarged view, partly in end elevation and partly in section, of a portion of the switch structure shown in FIGS. 1 and 2; and

FIG. 4 is an enlarged view, partly in end elevation and partly in section, of a second embodiment of the invention in a disconnecting switch structure having a modified blade construction but which is otherwise similar to the switch structure shown in FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings and FIGS. 1 and 2 in particular, there is shown a disconnecting switch assembly 10 which comprises three spaced

insulator stacks

32, 34, and 36 which are normally mounted upon a common base support (not shown) as disclosed in detail in U.S. Pat. No. 3,194,905 which issued July 13, 1965 to F. W. Jewell et al. and which is assigned to the same assignee as the present application. Each of the insulator stacks, 32, 34 and 36 comprises a plurality of insulators which are preferably formed from porcelain or a similar insulating material. The number of insulators required in each of the insulator stacks, 32, 34 and 36 depends upon the voltage of the electrical system in which the disconnecting switch 10 is applied. As illustrated, the insulator stacks 32 and 34 may be mounted upon fixed pedestals or spacers (not shown) which, in turn, may be secured to the top of the associated base which may be a metal channel in configuration. As described in the last-mentioned patent, the insulator stack 36 is mounted upon a shaft (not shown), the lower end of which is rotatably mounted in a bearing (not shown) which is secured to the associated base. As indicated in FIG. 2 an operating lever or crank arm 37 may be secured to the shaft provided at the lower end of the insulator stack 36 to rotate the insulator stack 36 with the crank arm 37 being adapted for connection to any conventional means for operating the crank arm 37 to effect rotation of the associated shaft and the insulator stack 36 about its own longitudinal axis.

In order to positively connect or couple the crank arm 37 and the associated rotatable insulator stack 36 to the balance of the operating mechanism of the disconnecting switch 10, as will be described in greater detail hereinafter, a shaft 112 is secured to a flange member 113 which, in turn, is secured to the top of the insulator stack 36. The shaft 112 extends upwardly from the upper end of the insulator stack 36 to thus form an extension of the shaft which is provided at the lower end of the insulator stack 36. The shaft 112 passes through an opening provided in the terminal end casting or member which is substantially alined with the axis of rotation of the shaft 112 and the associated insulator stack 36 and has mounted at the upper end thereof a crank arm I00 which is rotatable with the shaft 112 and which extends generally at an angle or generally transversely with respect to the axis of rotation of the shaft 112. In order to facilitate the rotation of the shaft 112 inside the opening provided in the terminal end member 110, one or more bearings (not shown) may be disposed inside the opening provided in the terminal end member- 110 where desired. It is to be noted that in a particular application, the crank arm 100 may be formed integrally with the shaft 112.

As'illustrated in' FIGS. 1 and 3, the disconnecting switch includes a generally U-shaped relatively stationary contact assembly or break jaw assembly 40 which is mounted on and secured to the top of the insulator stack 32. The stationary contact assembly 40 includes a plurality of pairs of laterally spaced contact jaws 43 which are mounted on and interconnected by a generally U-shaped base member 41 which is 'forged or cast from an electrically conducting'materialand which is secured to the top of the insulator stack 32 by suitable means, such as bolts. The base member or terminal casting 41 is preferably formed from aluminum and in such a construction the contact jaws or members 43 arepreferably formed from an electrically conducting material other than aluminum, such as copper or an alloy including copper in order to avoid the problems associated with the high resistance oxide coating that would result if the contact jaws were also formed from aluminum and exposed to air. or atmospheric conditionsThe contact strips 162 may be secured to the portions of the contact jaws 43 which are engaged by the associated switch blade 50 by suitable means, such as brazing, and are preferably formed from silver or an alloy including silver. After the con tact jaws 43 are bent or formed to the desired shapes, as best shown in FIG. 3, and the contact strips 162 are brazed to the associated contact jaws 43, the-contact jaws 43 and the associated contact strips 162 are preferably provided with a heavy tin coating by hot clipping the;contac't jaws 43 and the associated contact strips 162 in molten tin.

In order to secure the contact jaws 43 to the associated base member 41 with a relatively low electrical resistance joint between the assembled parts, the base member 41 includes accurately machined planar or substantially flat surfaces on the outside of each of the sidewall portions of the base member 41 which are adapted to receive the generally U-shaped contact jaws 43, as best shown in FIG. 3. Prior to the assembly of the contact jaws 43 on the base member 41, the machined surfaces on the base member 41 which are adapted to engage the outer portions of the contact jaws 43 are coated with a suitable grease-type, petroleum base joint compoundsuch as that which is sold under the trade name No-Ox-Id, Grade A Special." Next, the surfaces of the base member to which the contactjaws 43 are tobe secured are thoroughly abraded through .the joint compound with a wire'brush. The presence of the joint compound substantially prevents oxidation of the newly exposed aluminumsurfaces' which result fromthe abradingof the contact surfaces on the base member 41. The contact jaws 43 are then bolted firmly to the base member 41 by suitable means such as the bolts or studs 152, as shown in FIG. 3.

minal casting 41. An upwardly extending member 44 may also be formed integrally with or secured to the other side of the base member 41 to act as a stop for the movement of the associated switch blade 50 into engagement with the contact jaws'43. It is to be noted that the stationary contact assembly 40, as just described, is of the reverse loop type which has the I characteristic of magnetically forcing the associated switch blade 50 downwardly between the contact jaws 43. in a In order to bias eachcontact jaw 43 toward the opposite associated contact jaw of each pair in order that said contact jaws grip the free end of the associated switch blade 50 when the disconnecting switch 10 is in a closed circuit condition as shown in FIGS. 1 and 2, a compression spring 154 may be disposed between the inner portion 43A of each contact jaw 43 and the adjacent sidewall portion of the base member 41,

as shown in FIG. 3. More specifically, each of the biasing I springs 154 may be mounted on an extension of one of the bolts 152 with the extended portion of the bolt or stud 152 having a reduced crosssection and withthe shoulder thus formed acting as one spring seat for the associated compression spring 154. An electrically insulating cap- 156 may be disposed to receive the other end of each compression spring 154 and to bear against the inner portion 43A of the associatedcontact jaw 43. The electrically insulating cap 156 substantially prevents or eliminates the flow of electrical current through the associated compression spring 154 during the operation of the disconnecting switch 10.

As best shown in FIGS. I and 2, a terminal pad 42 which is adapted to receive a terminal connecter may be formed integrally with or secured to one side of the base member or terdirection toward the base member 41 and against the blade stop 44 when relatively high momentary currents flow through the disconnecting switch 10. g

In order to provide an electrically conducting path between the stationary contact assembly 40 and the electrically conducting parts of the disconnecting switch 10 which are mounted on top of the insulator stack 34 when the switch 10 is in a closed circuit condition, as shown in FIGS. 1 and 2, a movable switch blade 50 is provided. The blade 50 is elongated in shape and includes a main body portion 56 which, as illustrated, is generally tubular in configuration and which is preferably formed from a lightweight electrically conducting material, such as aluminum. The blade 50 also includes an end portion or beavertail member 53 at its left or free end. The beavertail member 53 is also preferably formed by suitable means, such as casting or forging, from aluminum to avoid any problems of galvanic corrosion due to dissimilar metals at the joint between the beavertail member 53 and the main body portion 56 of the blade 50. The beavertail member 53 of the blade 50 includes a portion which is generally rectangular in cross section, as indicated at 53A in FIG. 3. As shown in FIG. 3, the beavertail portion 53A includes a pair of relatively wider opposite planar surfaces 538 and 53D which are inter connected by a pair of relatively narrower opposite

planar surfaces

53C and 53E. It is to noted that the beavertail member 53 is secured to the main body portion of the blade 50 for movement therewith by suitable means, such as welding, as indicated at 55 in FIGS. 1 and 2.

In order to avoid the problems which would otherwise result if the beavertail member 53 were simply formed from aluminum and contact areas were provided on the beavertail member 53 to directly engage the stationary contact assembly 40 and, consequently, such contact areas were subject to the formation of a high resistance oxide coating when exposed to air or atmospheric conditions, a pair of generally .l-shaped electrically conducting

contact members

120 and 130 are secured to the beavertail member 53 for movement therewith to engage the stationary contact assembly 40 when the disconnecting switch is in a closed circuit'condition, as shown in FIGS. I and 2. The

contact members

120 and 130 are preferably formed from an electrically conducting material other than aluminum, such as extruded copper. The contact member 120 includes a relatively longer, generally straight portion 120A having a planar surface 120C which engages or bears against the wider planar surface 538 of the beavertail member 53 and a relatively shorter generally arcuate or curved portion 1208 which is disposed adjacent to but spaced bears against the other wider planar surface 53D of the beavertail member 53 and a relatively shorter generally arcuate or curved portion 1308 which isdisposed adjacent to but spaced from the narrower surface 53C which, as illustrated, is also generally arcuate or curved similarly to the opposite narrower surface 5350f the beavertail member 53. The spacing between the shorter portions 1208 and 1308 of the contact member and 130, respectively, and the adjacent surfaces 53C and 5315, respectively, is important in order to avoid or minimize possible galvanic corrosion between the different electrically conducting materials from which the beavertail portion 53A and the contact members 120 and are formed. It is also important to note that the end of the shorter portion 1208 of the contact member 120 away from the associated longer portion 120A bears against the end of the longer portion 130A of the contact member 130 away from the shorter portion 1308. Similarly, the end of the shorter portion 130B away from the longer portion 130A bears against the end of the longer portion 120A of the contact member 120 away from the associated shorter portion 120B for reasons which will be explained hereinafter.

Prior to the assembly of the

contact members

120 and 130 with the beavertail member 53 of the blade 50, the

contact members

120 and 130 are preferably provided with a heavy coating of tin by hot dipping the

contact members

120 and 130 in molten tin. In addition, the

planar surfaces

53B and 53D which engage or make contact with the

contact members

120 and 130 respectively are coated with a grease-type, petroleum base joint compound such as that previously mentioned and then abraded through the compound with a wire brush to expose unoxidized portions on the planar surfaces of the aluminum beavertail member 53. The

contact members

120 and 130 are then firmly secured to the beavertail member 53 by suitable means, such as a plurality of axially spaced bolts 172, which pass through substantially alined openings in the

contact members

120 and 130 and the beavertail member 53. In order to insure that the

contact members

120 and 130 are retained in assembled relation with the beavertail member 53 over long periods of use in service. the internal surface of the opening in the contact member 130 and the external surface of the lower portion of the bolt 172 may include substantially alined helical grooves which when the parts are assembled form a generally helical passageway in which a helical wire 174 is disposed, as shown in FIG. 3. It is to be noted that the

contact members

120 and 130 may be shaped or formed to include the shoulder portions 120D and 130D, respectively, which will assist in breaking ice formations on the beavertail member 53 or on the associated contact jaws 43 during the opening or closing of the disconnecting switch 10.

When the disconnecting switch is to be applied at high transmission voltages, a corona shielding member 46 may be mounted at the left end of the beavertail member 53 of the blade 50. More specifically, the corona shielding member 46 may be generally hollow spherical in configuration and include a threaded portion which is adapted to screw into an internally threaded opening which may be provided at the left end of the beavertail member 53 of the blade 50 with the corona shielding member 46 being formed from an electrically conducting material, such as aluminum.

In order to support the blade 50 for rotation about its own axis and for arcuate movement about an axis which extends generally perpendicular to the axis of the blade 50, the right end of the main body portion 56 of the blade 50 may be secured to the left end of a generally tubular crank member 60 for movement therewith, as described in detail in my copending U.S. Pat. application Ser. No. 772,7 l5 filed Nov. I, 1968, which is assigned to the same assignee as the present application. Where the main body portion 56 of the blade 50 is formed from aluminum, the crank member 60 is also preferably formed from aluminum to avoid the problems associated with galvanic corrosion at the joint between the respective parts which would otherwise result if the parts were made from different electrically conducting materials.

In order to support the crank member 60 and, in turn, the blade 50 for rotation about a common axis which extends longitudinally of the blade 50, the disconnecting switch 10 includes a hinge member 70 having a generally tubular portion 79 on which the crank member 60 is rotatably supported, as described in detail in the last-mentioned copending application. In order to limit axial movement of the blade 50 and the associated crank member 60 with respect to the hinge member 70, an electrically conducting shaft (not shown) may be secured to the inside of the crank member 60 and include a threaded portion which engages an internally threaded portion of the hinge member 70, as disclosed in detail in the lastmentioned copending application. An electrically conducting path may be provided between the crank member 60 and the hinge member 70 by one or more resilient electrically conducting members (not shown) disposed between the crank member 60 and the tubular portion 79 of the hinge member 70, as disclosed in the above-mentioned copending application. It is to be noted that the electrically conducting shaft which is disposed inside the crank member 60 and the hinge member 70 are both preferably formed from an electrically conducting material other than aluminum such as copper or an alloy including copper in order to avoid the problems associated with the use of aluminum when it is required to conduct electrical current between relatively movable parts, such as the hinge member 70 and the shaft disposed inside the crank member 60.

In order to support the hinge member 70 for rotation about an axis which is generally transverse or perpendicular with respect to the axis of the blade 50 and to support the blade 50 which is assembled on the hinge member 70 for arcuate movementor travel about said axis, the spacedarms 82 of the hinge support member 80 are disposed on opposite sides of the hinge member 70, as best shown in FIG. 2. The hinge member 70 includes a pair of hinge portions which project generally perpendicularly with respect to the axis of the tubular portion 79 of the hinge member 70 with the hinge member 70 being pivotally supported between the arms 82 of the hinge support frame 80 by electrically conducting hinge pins or studs (not shown), as described in the last-mentioned copending application. The hinge pins which support the hinge member 70 are preferably formed from copper or an alloy including copper and an electrically conducting path may be provided between said hinge pins and the hinge member 70 by one or more resilient electrically conducting members (not shown) which may be disposed inside the generally tubular hinge portions of the hinge member 70 to engage both the hinge member 70 and the hinge pins which are secured to the arm 82 of the hinge support frame 80.

In order to provide an electrically conducting path between the hinge support member 80 which is preferably formed from aluminum in order to reduce the weight of the electrically conducting parts of the disconnecting switch 10 and the terminal end casting or member 110, a generally tubular electrically conducting member 86 structurally and electrically connects the hinge support member 80 and the terminal end member 110. The electrically conducting member 86 is also preferably formed from aluminum. The hinge support member 80 includes a flange portion 84 having an opening therein which is adapted to receive the left end of the electrically conducting member 86. The left end of the conducting member 86 may be secured to the flange portion 84 by any suitable means, such as welding. Similarly, the terminal end member also includes a flange portion 114 having an opening therein which is adapted to receive the other end of the conducting member 86. The right end of the conducting member 86 may be secured to the flange portion 114 by any suitable means, such as welding. The electrically conducting member 86 may also serve as a housing for a counterbalancing mechanism or means which is described in detail in U.S. Pat. No. 3,074,474 which issued Feb. 26, I963 to E. F. Beach et al. and which is assigned to the same assignee as the present application. The terminal end member 110 is also preferably formed from aluminum in order to avoid the problems of galvanic corrosion at the joint between the conducting member 86 and the flange portion 114 of the terminal end member I10 which would result if said parts were formed from different electrically conducting materials.

When the disconnecting switch 10 is in the closed circuit condition shown in FIGS. 1 and 2, an electrically conducting path extends from the terminal pad 42 at the left end of switch 10 to the terminal pad 116 at the right end of the switch 10 through the base member 41 and the contact jaws 43 of the stationary contact assembly 40, the contact members 120 and on the beavertail member 53 of the blade 50, the beavertail member 53, the main body portion 56 of the blade 50, the crank member 60, the shaft inside the crank member 60, the electrically conducting members inside the crank member 60,

the hinge member 70, the electrically conducting members in side the hinge member 70, the'electrically conducting hinge v border to operatively connect ormechanically couple the.

crank arm 100 which is mounted on or formed integrally with the shaft 112 which is secured to the top of the rotatable insulator stack 36 and the crank member 60 in order to permit the movement of. the blade 50 during opening and closing operations of the switch, 10, the switch 10 includes the operating link 90 which is pivotally connected to the crank member 60,

eliminate any longitudinal pull on the operating link 90 but to transmit a force from the crank arm 100 to the operating link 90 through the clevis member 93 which provides a lateral force on the crank member 60 to rotate the blade 50 about its own axis to efiect a disengagement of the blade 50 from the contact jaws 43 of the stationary contact assembly 40. Continued counterclockwise movement of the crank arm I prothe slip joint 92 and the universal joint 180 which operatively connects the slip joint 92 to the crank arm 100.

More specifically, the crank arm 100 includes a clevis portion which comprises the spaced arms 101 at the upper end thereof, asbest shown in P16. 1. The crank arm 100, as just mentioned, is operatively connected to the operating link 90 by the universal joint structure 180 and the slip joint structure 92. The universal joint structure 180 comprises a trunnion member 102 which is pivotally supported in substantially alined openings provided in the spaced arms 101 of the crank arm 100 by a pair of pivot pins 103 which are secured to the trunnion member 102 for movement therewith. The universal joint'structure' 180 additionally includes a clevis member 93 which is pivotally connected to'the trunnion member 102 by the pivot pin 104 for rotation about an axis which is generally perpendicular to the other axis of rotation of the trunnion member 102. The clevis member 93 includes a partially threaded extension which passes into a bore provided in the right end of the operating link.90 and has disposed thereon an adjusting nut 99 which forms part of the slip joint structure 92, as described in detail in U.S. Pat. No. 3,194,905 previously mentioned. Asdisclosed in the last-mentioned patent, the slip joint 92 permits limited. relative movement between the vides a longitudinal pull on the operating link 90 since the I lengthening of the operating link 90 is limited by the slip joint structure 92 and a force is therefore transmitted to the crank member 60 to actuate arcuate movement of the blade 50 along with the hinge member. 70 in a counterclockwise direction about the axis defined by the hinge pins which supportthe hinge member 70 until the blade 50 is in a substantially. vertical position, as viewed in FIG. 1.

During a closing operation of the disconnecting switch 10, the crank arm 100 is actuated or moved in a clockwise direction from the undertoggle position which corresponds to the open position of the switch 10. During a closing operation of the switch 10, when the crank arrn 100 is moved in a clockwise direction from the undertoggle position, the blade 50 is rotated in a counterclockwise direction from the open position untilthe blade 50 and, more specifically, the left or free end of the blade 50 is actuated to a position between the contact jaws 43 and the beavertail member 53 of the blade 50 rests upon the blade stop 44. Further rotation of the crank arm 100 effects movement of the toggle linkage which includes the operating link 90 and the crank arm 100 through the dead center position to the overtoggle position to thereby extend the slip joint structure 92 and to rotate the free end of the blade 50 into full engagement with the contact jaws 43 of the stationary contact assembly 40, while the blade itself rests on the blade stop 44. In summary. the operating mechanism of operating link 90and the clevis member 93 and includes a spring (not shown) which prevents bouncing of the blade 50 during closing operations. The operating link 90 which is of the forked type is pivotally connected to the crank portion 66 of the 'crank member 60 by the pivot pin 67 which passes through anopening provided in the crank portion 66 of the crank member 60. t

In the operation of the disconnecting switch 10, as described in greater detail in the last-mentioned patent, it is assumed initially that the blade 50 is in the-closed or engaged position as shown in FIGS. land 2 with the

movable contact members

120 and 130 in engagement with the contactjaws 43, of the stationary contact assembly and the beavertail member53 of the blade in engagement with the blade stop 44. Under these conditions, the operating mechanism of the disconnecting switch 10 which includes the operating link 90,

the slip joint structure 92, the universal, joint structure 180 and the crank arm 100 considered as an overall toggle mechanism is in an overtoggle position, as best shown in F IG. 2.

During an opening operation of the disconnecting switch 10 when the crank arm 100 is rotated in the counterclockwise direction as viewed in FIG. 2, the toggle mechanism of the disconnecting switch as just described moves through a dead center position to an undertoggle position to effect opening of the switch 10 to thereby actuate the blade 50 from the closed position shown in FIG. 1 to an open position in which the blade 50 is angularly displaced from the closed position by approximately 90 in a clockwise direction about the axis defined by the hinge pins which support the hinge member 70.

the switch10 separates the rotary movement of the blade 50 about its own axis which is necessary to either cause the left or free end of the blade 50 to fully engage the stationary contact assembly 40 or to disengage the free end of the blade 50 from the stationary contact assembly 40 and the generally arcuate movements of the blade 50 between the open and closed positions just described.

I During the operation of the disconnecting switch 10, when the switch 10 is in the closed circuit condition as shown in FIGS. 1 and 2 and the switch 10is called upon to carry relatively high momentary currents such as 50,000 amperes or more, the construction of the stationary contact assembly 40 which is of the reverse loop type will result in greatly increased 'forced being applied 'to the opposite sides of the beavertail member 43 and the associated

contact members

120 and 130 by the contact jaws 43. The construction of the beavertail member 53 and the associated

contact members

120 and 130 is uniquely adapted to withstand the increased forces which result during such an operating condition since the forces acting on each of the

contact members

120 and 130 is substantially balanced with the forces acting on each of the contact members by one of the contact jaws 43. of each pair being substantially balanced by the forces exerted on the same contact member by the opposite contact jaw 43 which is transmitted exerted on the beavertail member 53 and the associated con- 7

tact members

120 and 130 are withstood by the disclosed construction while any mechanical stress exerted on the bolted contact surfaces of the contact members and and the adjacent contact surfacesof the beavertail portion 53A are substantially eliminated to thereby maintain a relatively low electrical resistance joint between the

contact members

120 and 130 and the associated blade 50 during such operating conditions. As previously mentioned, the spacing between the portions of the

contact members

120 and 130 which are not part of the bolted electrical joint between the relatively longer portions of said contact members and the adjacent surfaces of the beavertail portion 53A substantially eliminates any problems due to galvanic corrosion between those parts of 7 said contact members and the aluminum beavertail portion main body portion (not shown) which is generally tubular in configuration and which is preferably formed from a lightweight electrically conducting material such as aluminum. The blade 250 also includes an end portion or beavertail member 253 at its free end. The beavertail member 253 is also preferably formed by suitable means, such as casting or forging, from aluminum and may be secured to the associated main body portion by suitable means, such as welding. The beavertail member 253 of the blade 250 includes a portion which is generally trapezoidal in configuration, as shown in FIG. 4. The beavertail member 253 includes a planar contact surface 253A and a pair of

side surfaces

2538 and 253C which project away from the planar upper surface 253A and interconnect the planar surface 253A with the bottom surface of the beavertail member 253. It is to be noted that the width of the beavertail member 253 tapers from a maximum width at the bottom surface of the beavertail member to a minimum width at the upper planar contact surface 253A.

Similarly to the construction of the blade 50, in order to avoid the problems which would otherwise result, if the beavertail member 253 were simply formed from aluminum and contact areas were provided on the beavertail member 253 to directly engage the contact jaws 43 of the stationary contact assembly, the blade 250 includes a generally U-shaped electrically conducting contact member 240 which is secured to the beavertail member 253 for movement therewith to engage the stationary contact assembly 40 when the disconnecting switch 200 is in the closed circuit position shown in F IG. 4. The contact member 240 is formed from an electrically conducting material other than aluminum, such as extruded copper, and includes a central or bight portion 240A having planar contact surface 240D which is disposed to engage or bear against the planar surface 253A of the beavertail member 253. The contact member 240 also includes a pair of laterally spaced

arm portions

240B and 240C which project generally away from the associated planar surface 240D in the same direction as the adjacent pair of respective side surfaces 253C and 2533 of the beavertail member 253. It is important to note that the arm portions 2408 and 240C are disposed adjacent to the side surfaces 253C and 2538, respectively, of the beavertail member 253 and are spaced from the adjacent side surfaces in order to avoid the problems associated with galvanic corrosion between the parts of the contact member 240 and the adjacent side surfaces 253C and 2538 of the beavertail member 253. The contact member 240 also includes the

shoulder portions

240E and 240F which are provided on the arm portions 2403 and 240C, respectively, in order to assist in breaking up ice formations which may occur during certain weather conditions and otherwise interfere with opening and closing operations of the disconnecting switch 200.

Prior to the assembly of the contact member 240 with the beavertail member 253 of the blade 250, the contact member 240 is preferably provided with a heavy coating of tin by hotdipping the contact member 240 in molten tin. In addition, the planar surface 253A is coated with a greasetype, petroleumbase joint compound such as that previously mentioned and then abraded through the compound with the wire brush to expose unoxidized portions on the planar surface 253A of the beavertail member 253. The contact member 240 is then firmly secured to the beavertail member 253 by suitable means, such as a plurality of axially spaced bolts 272, which pass through substantially alined openings in the contact member 240 and the beavertail member 253 to engage an internally portion of the opening in the beavertail member 253.

The operation of the disconnecting switch 200 as just described is the same as the operations of the disconnecting switch 10 previously described in detail. It is important to note that when the disconnecting switch 200 is in the closed condition as shown in FIG. 4, and when the disconnecting switch 200 is called upon to carry relatively high momentary currents, greatly increased forces will be exerted on the switch blade 250 and more specifically on the beavertail member 253 and the associated contact member 240 due to the construction of the stationary contact assembly 40 which is of the reverse loop type. The construction of the contact member 240 is arranged to withstand such greatly increased forces and to permit the deflection of the arm portions 2408 and 240C without placing any mechanical stress on the bolted connection between the central or bight portion 240A of the contact member 240 and the beavertail member 253 to maintain the relatively low resistance electrical joint between the contact member 240 and the beavertail member 253 during such operating conditions. In addition, as just mentioned, the spacing between the arm portions 2408 and 240C and the adjacent surfaces of the beavertail member 253 substantially prevents the problems associated with galvanic corrosion between said arm portions and the adjacent side surfaces 253C and 2538, respectively, of the beavertail member 253. In other words, the construction of the blade 250 is such as to permit deflection of the arm portions 2408 and 240C without causing relative separation of the

planar surfaces

240D and 253A. It is to be noted that the contact member 240 may be formed from a material which combines relatively high electrical conductivity with resilient properties to permit the deflection of the arm portions 2408 and 240C without disturbing the bolted connection between the central or bight portion 240A of the contact member 240 and the adjacent planar surface 253A of the beavertail member 253.

It is to be understood that the teachings of the invention may be applied to a disconnecting switch construction in which only the main body portion 56 of the blade 50. the beavertail member 53, and the crank member 60 of the disconnecting switch 10 or the corresponding parts of the disconnecting switch 200 are formed from aluminum, while the balance of the electrically conducting parts of the disconnecting switch are formed from an electrically conducting material other than aluminum, such as copper or any alloy including copper. In such a construction, is to be understood that the stationary contact assembly 40 may alternatively be formed with the contact jaws and the associated base member combined in a unitary member which is formed from a suitable electrically conducting material which combines relatively high electrical conductivity with excellent spring or resilient characteristics, such as zirconium-copper or phosphorusbronze, as described in detail in US. Pat. No. 3,079,474 previously mentioned.

The apparatus embodying the teachings of this invention has several advantages. For example, a switch construction is disclosed including an improved blade construction which is uniquely adapted to the use of aluminum in the main body portion and in the beavertail member while providing reliable electrical and mechanical joints between the contact members at the free end of the blade and the associated beavertail member. In addition, the movable contact members disposed on the associated blade in the switch constructions disclosed are easily replaceable, as required in long continued service, and the blade construction is relatively easy to manufacture. Another important advantage is that the surfaces of the beavertail member which must be accurately machined to receive the associated contact members is held to a minimum of one surface for each associated contact member and the problems of galvanic corrosion between the bolted electrically conducting parts of the beavertail member and the associated contact member or contact members are substantially eliminated or reduced to a minimum. The latter advantage is accomplished by spacing those portions of the respective contact members which do not participate in the bolted electrical joints between the parts away from the adjacent surfaces of the beavertail member, as previously described. Finally, the switch constructions disclosed have the advantage that the electrical joints between the contact members and the associated beavertail member of the blade constructions are substantially free from mechanical stresses when the switch which includes such blade constructions is called upon to carry relatively high momentary currents which results in greatly increased mechanical stresses on the other blade parts.

Since numerous changes may be made in the above described apparatus, different embodiments of the. invention may be made without departing from the' spirit and scope thereof, itis intended that 'all .the matter contained in the foregoing descriptionor shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

lclaim:

l. A disconnecting switch comprisinga relatively stationary contact means, an elongatedswitch blade having oneend movable between engaged and disengaged positions with respect to said stationary contact'means, said one end of said blade including an electrically conducting portion whichis generally rectangular and includes a pair of relativelywider opposite planar surfaces interconnected by a pair of relatively narrower opposite surfaces, a pair of electrically conducting contact members securedto said one end of said blade for movement therewith to engage said stationary contact means in the engaged position of said blade, each of said contact members including a relatively longer portion having a planar surface which engages one of the wider planar surfaces of said one end of said blade and a relatively shorter generally arcuate portion which is spaced from the adjacent narrower surface of said one end of said; blade, the end of the arcuate portion of each contact member away from the associated longer portion bearing against the end of the longer portion of the other contact member away from its associated arcuate portion, the arcuate portions only of said pair of contact members being disposed to engage said stationary contact means when said blade is in the engaged position with respect to said stationary contact means.

2. The combination as claimed in claim 1 wherein said switch blade including said one end is formed from aluminum and said pair of contact members is formed from copper.

3. The combination as claimed in claim 1 wherein said switch blade including said one end is formed from aluminum and said pair of contact members is formed from' an electrically conducting material other than aluminum.

4. The combination as claimed in claim 1 wherein said contact members are secured to said one end of said blade by a plurality of spaced bolts which are disposed generally perpendicular to the wider surfaces of said portion of said one end of said blade and to the longer planar surfaces of said contact members. 7

5. The combination as claimed in claim I wherein said stationary contact means includes a plurality of pairs of spaced contact jaws formed from an electrically conducting material, the respective pairs of said contact jaws being engaged by the arcuate portions of said contact members when said blade is in the engaged position.

6. A disconnecting switch comprising a relatively stationary contact means, an elongated switch blade having one end movable between engaged and disengaged positions with respect to said stationary contact means, said one end including an electrically conducting portion having a planar surface and a pair of side surfacesprojecting away from said planar surface, and a generally U-shaped, electrically conducting contact member secured to said one end of said blade for movement therewith to engage said stationary contact means in the engaged position of said blade, said contact member including an intermediate planar surface which is disposed to engage the planar surface of said one end of said blade and a pair of spaced arm portions which'project away from the associated planar surface generally in the same direction as the pair of side surfaces of said one end of said blade, said arm portions being disposed adjacent to and spaced from the respective side surfaces of said one end of said blade, said arm portions only being disposed to engage said stationary contact means when said blade is in the engaged position with respect to said stationary contact means.

7. The combination as claimed in claim 6 wherein said blade tact member is formed from copper.

8. The combination as claimed in claim 6 wherein said blade including said one end is formed from aluminum and said contact member is formed from an alloy including copper.

9. The combination as claimed in claim 6 wherein said stationary contact includes a plurality of pairs of spaced contact jaws formed from an electrically conducting material, the jaws of the respective pairs being engaged by said pair of arm portions when said blade is in the engaged position.

.10. The combination as claimed in claim 6 wherein said contact members is secured to said one end of said blade by a plurality of spaced' bolts which pass through substantially alined openings in said contact members and said one end of said blade and are disposed generally perpendicular to the planar surfaces of said contact member and said one end of said blade.