US3544742A - Electric switch having improved blade construction - Google Patents

Description

United States Patent Inventor Russell E. Frink Pittsburgh, Pennsylvania Appl. No. 790,088

Filed Jan. 9,1969

Patented Dec. 1, 1970 Assignee Westinghouse Electric Corporation Pittsburgh, Pennsylvania a corporation of Pennsylvania ELECTRIC SWITCH HAVING IMPROVED BLADE CONSTRUCTION 7 Claims, 4 Drawing Figs.

U.S. Cl 200/48, 200/170 Int. Cl "01h 31/00 Field of Search 200/ l 70,

[56] References Cited UNITED STATES PATENTS 2,759,076 8/1956 Curtis ZOO/170A 3,299,240 l/l967 Foti 200/l 66C Primary Examiner Robert K. Schaefer Assistant Examiner-H. J. Hohauser Attorneys-A. T. Stratton and Clement L. McHale 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 of said blade being formed from an electrically conducting material other than aluminum.

E 4? I93 4| W////////V//////// PATENTED DEC! 1970 SHEET 10F 2 PATENTEU um 19m 334474 2 SHEET 2 OF 2 INVENTOR Russell E. Frink ATTORNEY ELECTRIC SWITCH HAVING IMPROVED BLADE CONSTRUCTION CROSS-REFERENCES TO RELATED APPLICATIONS Certain inventions disclosed in the present application are related to inventions disclosed and claimed in copending U.S. Pat. application Ser. No. 772,715 filed Nov. 1, 1968 which issued Mar. 10, 1970 as U.S. Pat. No. 3,500,006 and Ser. No. 790,078 filed concurrently by E. W. Kuhn 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 a construction 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 as possible are formed from 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 a copper alloy. Various constructions have been proposed in the disclosed in U.S. Pat. Nos. 3,206,568; 3,243,561; 3,299,240 and 3,388,225. These known switch structures have been found to have certain disadvantages due to difficulties in manufacturing or when subjected to long continued use in service.

SUMMARY OF THE INVENTION In accordance with the invention, an electric switch includes an elongated switch blade or contact arm having one end movable into and out of engagement with an associated relatively stationary contact means. The end of said switch blade which is movable into engagement with the stationary contact means includes a portion which is substantially rectangular in cross section and which includes a pair of relatively wider opposite planar surfaces interconnected by a pair of relatively narrower opposite planar surfaces. A pair of generally L-shaped electrically conducting contact members is secured to the last-mentioned end of the blade for movement therewith to engage the stationary contact means. Each of the contact members includes a relatively longer planar surface which is disposed to engage one of the wider planar surfaces .of the last-mentioned end of the blade and a relatively shorter planar surface which is disposed to engage one of the adjacent narrower planar surfaces of said one end of the blade. In one preferred embodiment, the blade including the end which engages the stationary contact means is formed from aluminum and the associated contact members on said one end of the blade are formed from copper or a copper alloy.

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 DRAWINGS 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 switch structure shown in FIG. I;

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 side elevation and partly in section, of the portion of the switch structure shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings and FIGS. I 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 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 ofthe associated shaft and the insulator stack 36 about its own longitudinal axis.

In order to positively connect 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 hereinafter, a shaft 112 secured'to and extends upwardly from 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 110 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 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 sleeve bearings (not shown) may be disposed inside the opening provided in the terminal end member 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. 3 and 4, the disconnecting switch 10 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 spaced contactjaws 43 which are mounted on and interconnected by a generally U-shaped base member 41 which is forged or cast from an electrically conducting material and which is secured to the top of the insulator stack 32 by suitable means, such as the bolts 193. The base member or terminal casting 41 is preferably formed from aluminum and in such a construction, the contact jaws or members 43 are preferably formed from copper or an alloy of copper in order toavoid the problems associated with the high resistance oxide coating that would result if the contactjaws 43 were also formed from aluminum and exposed to air or atmospheric conditions. In order to substantially eliminate the need for additional or separate spring or biasing means to bias the contact jaws 43 toward one another for gripping the free end of the associated switch blade 50 when the disconnecting switch is in a closed circuit condition, as shown n in FIGS. 1 and 2, the contact jaws 43 may be-formed froma suitable electrically conducting material which combines relatively high electrical conductivity with excellent spring or resilient characteristics, such as beryllium-copper; cadmium-chrome-copper, zirconiumcopper, phosphorus-bronze or the like. Where desired, separate resilient means, such as springs (not shown) may be provided to additionally bias the contact jaws 43 toward one another. The contact strips 172 maybe secured to the portions of thecontact jaws 43 which are engagedby. the associated switch blade 50 by suitable means, such as brazing, and are preferably formed from silver or a silver alloy. After the contact jaws 43 are bentto the desired shapes, as best shown in H6. 3, and the contact strips 172 are brazed to the associated contact jaws 43, the contact jaws 43 and the associated contact strips 172 are'preferably provided with a heavy tin coating by hot dipping the contact jaws 43 and the associated contact strips 172 in molten tin.

In order to secure the contact jaws43 to the associated base member 41 with arelatively low electrical resistance joint between the assembled parts, the base member 41 includes accurately machined surfaces on the outside of each of the sidewall portions of the base member 4l 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 the surfaces of 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 compound such as that which is sold under the trade name No-Ox-ld, Grade A Special. Next,-the surfaces of the base member 41 to which the contact jaws 43 are to be secured are thoroughly abraded through the joint compound with a wire brush. The presence of the joint compound substantially preventsoxidationof the newly exposed aluminum which results from the abrading of the contact surfaces on the base member 41. The contact jaws 43 are then bolted firmly to the base member by suitable means, such as the bolts 152 as shown in FIG. 3. t

As best shown in H05. 1 and.2, a terminal pad 42 which is adapted to receive a terminal connecter may be formed integrally with or secured to one side ofthe base member or terminal 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 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; at the joint between the beavertail member 53 and the, main body portion 56of the blade 50. The beavertail member 53 of the blade 50 includes a portion which is substantially rectangular in cross section, as indicated at 53A in FIG. 3. The beavertail portion 53A includes a pair of relatively wider opposite planar surfaces 53C and 53E which are interconnected by a pair of relatively narrower opposite planar surfaces 53B and 531), as best shown in FIG. 3. It is to be noted that the beavertail member 53 is secured to the main body portion 56 of the blade 50 for movement therewith by suitable means, such as welding, as indicated at 55 in H6. 4.

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 engage the stationary contact assembly 40 and 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'l82 and 184 are secured to the beavertail member 53 for movement therewith to engage the stationary contact assembly 40 when the disconnecting switch 10 is -in the closed circuit condition shown in FlGS. l and 2. The contact members 182 and 184 are formed froman electrically conducting material other than aluminum such as extruded copper and may have secured thereto by suitable means, such as brazing, contact inserts 18 6 and 188, respectively, which are preferably formed from silver or a silver alloy. The contact member 182 includes a relatively longer planar surface 182A which engages the wider planar surface 53C of the beavertail member 53 and a relatively shorter planar surface 1828 which engages the adjacent narrower planar surface 53D of said beavertail member. Similarly, the contact member 184 includes a relatively longer planar surface 184A which engages the other of the wider planar surfaces 53E of the beavertail member 53 and a relatively shorterplanar surface 1848 which engages the other of the adjacent narrower planar surfaces 53B of said beavertail member. it is also to be noted that the contact members 182 and 184 include the recesses indicated at 182C and 184C, respectively, in order to prevent the contact members 182 and 184 from bearing against one another when assembled on the beavertail member 53 and to permit the full force of each of the bolts 162 to be applied between the contact members 182 and 184 and the beavertail member Prior to the assembly of the contact members 182 and 184 with the beavertail member 53 of the blade 50, the contact members 182 and 184 are preferably provided with a heavy coating of tin by hot dipping the contact members 182 and 184 and the associated contact inserts 186 and 188, respectively, in molten tin. ln addition, the planar surfaces 53B, 53C, 53D and 53B of the beavertail member 53 which engage or make contact with the contact members 182 and 184 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 ofthe aluminum beavertail member 53. The contact members 182 and 184 are then firmly secured to the beavertail member 53 by suitable means,

such as a plurality of bolts 162, which pass through substantially alined openings in the contact members 182 and 184 and the beavertail member 53. [t is to be noted that when two electrically conducting parts such as the contact members 182 and 184 and the associated beavertail member 53 are bolted together, most of the electrical current which passes between the parts transfers in the areas immediately under the heads of the bolts. A plurality of such current transfer areas have been provided (two per bolt) in the disclosed construction and where additional current carrying capacity is required between the parts, additional bolts may be provided.

When the disconnecting switch 10 isto 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 inmaterial, 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 copending U.S. Pat. application Ser. No. 772,715 filed Nov, 1, 1968 by Edmund W. Kuhn which is assigned to the same assignee as the present application. Where the main body portion 56 of the blade 50 is formed of 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.

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 includes a hinge member 70 having a generally tubular portion 79 on which the crank member 60 is rotatably supported as described 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 last- .mentioned 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 (not shown) 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 a copper alloy, in order to avoid the problems of galvanic corrosion between the relatively movable shaft and the hinge member 70.

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, asjust indicated, for arcuate movement or travel about said axis, the spaced arms 82 of the hinge support member 80 are disposed on opposite sides of the hinge member 70, as best shown in FIG. 2. As shown in FIG. 2, the hinge member 70 includes a pair of hinge portions which project generally perpendicular 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 a copper alloy and an electrically conducting path may be provided between the 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 arms 82 ofthe 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, the generally tubular electrically conducting member 86 structurally connects the hinge support member 80 and the terminal end member 110. The electrically conducting member 86 is 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 with the left end of the conducting member 86 being secured to the flange portion 84 by suitable means, such as welding.

Similarly, the terminal end member 110 also includes a flange portion 114 having an opening therein which is adapted to receive the other end of the conducting member 86 with the right end of the conducting member86 being secured to the flange portion 114 by suitable means, such as welding. The electrically conducting member 86 may also serve as a housing for a counter balancing mechanism or means which is described in detail in U.S. Pat. No. 3,074,474 which issued Feb. 26, 1963 to E. F. Beach et al. and which is assigned to the 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 portion 114 of the terminal end member 110.

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 path 42 at the left end of the disconnecting switch to the terminal pad 116 at the right end of the disconnecting switch 10 through the base member 41 and the contactjaws 43 ofthe stationary contact assembly 40, the contact members 182 and 184 on the beavertail member 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 inside the hinge member 70, the electrically conducting hinge pins associated with the hinge member 70, the hinge support member 80, the electrically conducting member 86, and the terminal end member 110 to the terminal pad 116.

In order to operatively connect or mechanically 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 ofthe disconnecting switch 10, the disconnecting switch 10 includes the operating link 90 which is pivotally connected to the crank member 60, the slip joint 92 and the universal joint 120 which operatively connects the slip joint 92 to the crank arm 100.

More specifically, the crank arm includes a clevis portion which comprises the spaced arms 101 at the upper end thereof, as best shown in FIG. 1. As just mentioned, the crank arm 100 is operatively connected to the operating link 90 by the universaljoint structure and the slip joint structure 92. The universal joint structure 120 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 120 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 slipjoint structure 92, as described in detail in U.S. Pat. No. 3,194,905 previously mentioned. As disclosed in detail in the U.S. Pat. just mentioned, the slip joint 92 permits limited relative movement between the operating link 90 and 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 an opening provided by the crank portion 66 of the crank member 60.

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 position as shown in FIGS. 1 and 2 with the movable contact members 182 and 184 in engagement with the contact jaws 43 of the stationary contact assembly and'the beavertail member 53 of the blade 50 in engagement with the blade stop 44. Under these conditions, the operating mechanism of the disconnecting switch 10which includes the operating link90, the slip joint structure 92, the universal jointstructure 120 and the ing of the disconnecting switch 10 to thereby actuate the blade 50 from the closed position shown in FIG. 1 toan open position in which the blade 50 is angular ly 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. During an opening operation of the disconnecting switch 10, the slip joint structure 92 effectively shortens the, length of the operating link 90 as thecrank arm 100 starts to rotate in a counterclockwise direction about its own I axis of rotation to permit the toggle-mechanism which in- ;cludes the operating link 90 and thecrank arm 100 to pass -through the dead center position. As the crank arm 100 rotates further toward the undertoggle position from the dead center position, the slip joint 92 effectively lengthens the operating link 90 to thereby 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. effect a disengagementof theblade 50 from the contact jaws of the stationary contact assembly 40; Continued counterclockwise movement of the crankarm 100 provides a longitudinal pull on the operating link 90since the 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 support the hinge member 70 until the blade gle position, the blade 50 is rotated in a counterclockwise direction from the open position until the blade 50 and, more specifically, the left 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 crankarm 100 through the dead center position to the overtoggle position to thereby extend the slip joint structure 92 and to rotate the left 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 the'disconnecting switch 10 separates the rotary movement of the blade 50 about its own axis which is necessary to either disengage or cause the left end of the blade, 50 ,to fully engage the stationary contact assembly 40 and the generally arcuate movement of the blade 50 between the open and closed positions just described. i

It is to be understood that the teachings of the invention may be applied to a disconnecting switch strut structure in which only the main body portion 56,.the beavertail member 53 and the crank member 60 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 a copper alby. In such a construction it is to be understood that the stationary contact assembly may be formed with the contact jaws and the associated base member combined in a unitary member which is formed from a suitable electrically conductt ing material which combines relatively high electrical conductivity with excellent spring or resilient characteristics such as 'zirconium-copper or phosphorus-bronze, as described in detail in US. Pat. No. 3,079,474 previously mentioned.

The apparatus embodying the teachings of this invention have several advantages. For example, a switch construction is disclosed including an improved blade structure which is uniquely adapted to the use of aluminum in the main body portion and in the beavertail member while providing reliable 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 construction disclosed are easily replaceable, as required, in long continued service and the blade construction is relatively easy to manufacture. A further advantage of the disclosed switch construction is that current transfer is accomplished between the movable blade and the associated contact jaws between relatively movable parts which are formed from an electrically conducting material other than aluminum, such as copper or a copper alloy, with joints between copper and aluminum parts where required being accomplished through the relatively reliable bolted joints describedwhich have been proved dependable in long continued service by past experience. Finally, the disclosed switch construction has the advantage that it does not depend upon the plating of aluminum parts which may separate from the aluminum when exposed to the weather or atmospheric conditions during long continued use in service.

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

Iclaim:

l. 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 which is substantially rectangular in cross section and includes a pair of relatively wider opposite planar surfaces interconnected by a pair of relatively narrower opposite planar surfaces, a pair of generally L-shaped electrically conducting contact members secured to 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 first portion having a relatively longer planar surface which engages one of the wider planarsurfaces of said one end of said blade and a second portion having a relatively shorter planar surface which engages one of the adjacent narrow I planar surfaces of said one end of said blade, said second pertions only of said contact members being disposed to engage said stationary contact means in the engaged position of said blade.

2. The combination as claimed in claim 1 wherein said blade including said one end is formed from aluminum and said pair of generally L-shaped electrically conducting contact members is formed from-copper.

3. The combination as claimed in claim 1 wherein said blade including said one end is formed from aluminunuand said pair of generally L-shaped electrically conducting contact members is formed from an alloy including copper, said first por tions of said contact members each including a recess adjacent to'the second portion of the other contact member to prevent said contact members from bearing against one another when said contact members are secured to said blade.

4. The combination as claimed in claim 1 wherein said stationary contact means includes a plurality of pairs of spaced 6. The combination as claimed in claim 4 wherein said pairs of spaced contact jaws are mounted on a generally U-shaped base member formed from an electrically conducting material.

7. The combination as claimed in claim 5 wherein said pairs of contact jaws are mounted on a generally U-shaped base member formed from aluminum.

Images