US3127491A

US3127491A - High voltage air switch

Info

Publication number: US3127491A
Application number: US1576A
Authority: US
Inventors: Edmond B Gorman
Original assignee: McGraw Edison Co
Current assignee: McGraw Edison Co
Priority date: 1960-01-11
Filing date: 1960-01-11
Publication date: 1964-03-31
Anticipated expiration: 1981-03-31

Description

United States Patent C 3,127,491 HIGH VOLTAGE AIR SWITCH Edmond B. Gorman, Campbell, Califi, assignor, by mesne assignments, to McGraw-Edison Company, Elgin, Ill a corporation of Delaware Filed Jan. 11, 1960, Ser. No. 1,576 7 Claims. (Cl. 200-166) The present invention relates to switches having wiping contact between a switch blade and a companion stationary contact, and more particularly the present invention relates to high-voltage air switches of the so-called tail-twister type in which the switch blade swings from an open position into closed position and when in the latter position the switch blade rotates or twists in wiping contact with the stationary contact.

Outdoor high-voltage air switches involve arduous duty requirements which engineers have faced over a long period of years. Such switches have operating mechanisms of the tail-twister type which is designed to be operable even under heavy icing conditions. The contact surfaces of the switches is a matter of long-standing concern, development effort being constantly aimed at meeting corrosive environmental conditions and to provide efiicient low-resistance contact. At the hinge end of the switch-blade, in order to avoid the problems involved in providing a good electrical contact between moving parts,

a flexible wire braid has been used between the switch blade and a switch terminal; but such braid has the disadvantage of being chemically attacked when exposed to certain atmospheres. Silver-to-silver contacts have also been tried involving silver inserts in the switch arm and silver inserts in the companion stationary contacts, both at the hinge end of the switch and at the clip end of the switch. That arrangement proved objectionable because, while silver is a material of recognized low contact-resistance, the mechanical effects encountered in switch operation resulted in galling of the contact surfaces, resulting poor contact and excessive resistance. These conditions led to omitting silver at one of each pair of engaging contact members. Silver-to-copper contacts have been widely adopted. Various complex structures have been used for minimizing hinge contact resistance where flexible braid is not acceptable.

An object of the present invention is to improve wiping contacts, and in particular the invention has as an important object the provision of tail-twister switches having improved contacts. A more specific feature of the invention resides in the provision of low-resistance contacts not only at the swinging or air break end of the blade in a tail-twister switch, but also at the hinge end of the tail-twister switch so as to obviate many of the difiiculties heretofore encountered. The improved contact provided'in accordance with the present invention does away with flexible braid connections and their attendant disadvantages, and it also results in a vastly simplified form of connection of the desired durability and lowresistance characteristics.

Still further features of the invention relate to improved electrical contacts for wiping contact switches and to methods of making such contacts.

The nature of the invention and its various features and further objects will be apparentfrom the following details disclosure of a specific illustrative embodiment shown in the accompanying drawings. As will be seen, in making a contact element in this embodiment, an elongated bar of copper has local laminations of silver joined to it, and the composite silver and copper piece is subjected to relatively severe rolling so as to increase its length substantially, the elongation being in the direction in which wiping contact engagement is subsequently to take place in the completed switch. In this embodiistic. or sterling silver for example.

ment, the silver is in the form of a thin layer which is set into a recess formed in a copper bar, flush with the surrounding surface of the copper and brazed or silversoldered in place. The copper is a relatively long and narrow bar, and it is rolled along its length so severely as to eiiect a substantially reduction in cross section,

this reduction being severe enough to work-harden the silver.

The copper bar, which is annealed when the silver layer is being joined to it, is also hardened by the rolling operation which imparts an important spring character- The silver is preferably alloy silver, coin silver Such silver has greater hardness after rolling than would be the case with pure silver. The copper bar may also contain minor constituents for superior spring properties after the reduction of its cross-section.

Each copper bar is provided with two silver inlay areas; and after rolling the copper bar is bent into U shape, for gripping the contact arm of the tail-twister switch. This contact arm or blade has a pair of projecting silver contacts at the hinge contact and it also has a pair of projecting silver contacts at the air-break contact. The soft-silver contacts on the contact arm at each end thereof wipe against the hardened silver inlay contacts during the final closing operation of the tail-twister mechanism. The U-shaped contacts are backed-up by berrylium-copper leaf springs; but the resilience of the U-shaped contact itself is important in providing firm contact with a minimum of mass and therefore with a minimum of resulting bounce, vibration and chatter when contact is being made. The electrical and metallurgical advantages of silver-to-silver contacts are realized in this improved switch, yet galling and its contact-deteriorating effects are avoided.

In the drawings:

FIGURE 1 is the side elevation of the tail-twister switch embodying features of the present invention;

FIGURE 2 is an end view of the left-end portion of the switch in FIGURE 1, drawn to larger scale and shown partly in section;

FIGURE 3 is the left end elevation, partly in section, of the hinge contact at the center of the embodiment in FIGURE 1;

FIGURE 4 and FIGURE 5 are, respectively, an end view and a side view of a contact element of FIGURE 2; and

FIGURE 6 is a cross-sectional view along the line 6-6 in FIGURE 4.

In FIG. 1, three insulator posts, 10, -12, and 14 are supported on a frame 16, insulator 14 being rotatable while insulators 10 and 12 are fixed. Switch blade 18 engages stationary contact assembly 2t] in the closed condition of the switch as illustrated. A connection best illustrated in FIGURE 3 (to be described) connects the switch-blade 18 to conductor 22.. A conductive path is thus provided from terminal 24, through contact 20, switch-blade 18, and conductor 22,, to the opposite terminal 26. A mechanism .23 of conventional construction operates switch-blade 21-3 so as to rotate it about its axis out of pressure contact with stationary contact 20, mechanism 28 operating further to swing switch blade 18, lifting it through a vertical are so as to assume its vertical open position.

An arcing tip 3% on switch-blade 18 engages arcing horn 32. during the opening sweep of the switch blade for avoiding arcing between switch blade 18 and contact 20 during opening of the switch.

Insulator 14 is rigidly connected to a crank 34 that has a lost-motion connection to a connecting rod 36; and this is pivoted to an element 38 'which is fastened to switch-blade .18. During an initial phase of switch-open Patented Mar. 31, 1964 ing operation, crank 34 sweeps from one side of blade 18 to the other, to rotate or, twist switch-blade 18 about its longitudinal axis; and in its thus rotated configuration, switch-blade =18 is then swung upward into its open-circuit position by further operation of crank 34. In \FIGURE 2 the dotted-line representation of blade .18 illustrates the start of switch opening operation. Reverse operation of crank 34 sweeps blade 18 back to its horizontal position as illustrated and then twists blade 18 about its longitudinal axis and into pressure engagement with the contact portions of stationary contact 20'.

r A spring counter-balance 40 is included, being desirable in the case of relatively long or heavy switch-blades 18.

As seen in FIGURE 2, switch-blade 18 has a pair of projecting contacts 42, small bars of silver that are united as by silver-solder to the rod 18 which may be of heavy-walled copper tubing. U-shaped contact element 44 is suitably secured to a metal base 46 and the two legs of contact element 44 are biased against projecting contacts 42 by beryllium-copper leaf-springs 48. A pin 59 extending through

members

46 and 48 locates the lower ends of the leaf springs and the spring-bias is developed by adjustment screws 52 which bear against the intermediate portions of leaf springs 48. A stop member 54 limits travel of the contact arm 18 in the closing direction. U-shaped member 44 is suitably secured to metal base 46 and terminal 24. The legs of this U-shaped member are also resilient, and are resiliently biased against the oppositely projecting contacts 42 of contact arm 18 by leaf-springs 48.

Contact arm 18 is seen to have an additional pair of oppositely projecting silver contacts 55 (like contacts 42) which are engaged by U-shaped contact member 58 (like contact member 44). The legs of member 58 are resiliently pressed against contacts 56 by leaf springs 60 (like springs 48). U-shaped contact member 58 and springs "60 are carried by a metal base 62, and conductor 22 is also carried by, and suitably secured to this base 62. Member 64 is pivoted on trunnions 65 to member 22, and a pivoted anchor 66 is provided for spring counter-balance element 40. A portion of member 64 (not shown) forms a rotary bearing for switch arm :18, generally as shown in U.S. Patent 2,328,171 to Schw-ager et al.

Members

44 and 58 are made by the same process and they are sufficiently similar so that only contact member 44 need be described. As seen in FIGURES 4 to 6, contact member 44 is in the form of an elongated bus bar of copper, which may be resilient alloy copper, having silver contacts 68 in the legs 70 of the U-shaped member. These silver contacts 6-8 (best seen in FIGURE 6) are in portions of the legs 70 that are convex and face each other so as to grip contacts 42 on switch-blade 18 between them.

In an example, by way of providing an indication of proportions involved in high-voltage air-break switches, member 44 may be formed of a copper bar 15 inches long, 1% inch wide, and 4 inch thick, in its finished form. The silver inserts 68 in finished form in this example are approximately 2 inches long by 4 inch wide by 0.02 to 0.03 inch in thickness.

Member 44 is made in the following manner: A copper bar of suitable length and thickness and of about the same width as is desired in the finished part, has a pair of recesses formed therein as by machining or coining to receive complementary silver inserts. The inserts should be flush with the surrounding surface of the copper bar; and they are silver-soldered in place with silver solder flowing throughout the opposed faces of each silver insert and of the recess, and the silver solder extending all around the edges of the recess and the insert. The copper bar with its silver inserts thus united in place as by silver soldering, is then subjected to a longitudinal rolling operation in a manner to retain initial width but to reduce the thickness approximately 30 percent, this operation inherently "producing corresponding elongation of the cop- 4 per bar. The silver inserts of course are elongated correspondingly. The rolling operation of that severity effects hardening of the copper and of the silver inserts.

It will be understood that the silver-soldering operation for fixing the insert to the bar leaves the silver and the copper quite soft in the region of the silver-soldering operations. In order that the entire copper bar may be of equal softness, preparatory to the rolling operation, the copper bar with its silver inserts is annealed so as to be uniformly soft before the rolling operation.

After the rolling has sufficiently elongated the copper bar with its silver contact inserts to attain the desired hardening, (30 percent reduction in cross section being recommended) the rolled blank has its ends suitably rounded and the copper bar that is flat during the rolling operation is formed so as to give it a convex curvature (see FIGURE 6) in the regions of the two silver insert contact areas. The rolled blank is also bent into the required U-shaped configuration in FIGURES 4 and 5 as well as in FIGURE 2.

The switch is shown in its closed configuration in FIG- URE 1, in solid lines in FIGURE 2, and in FIGURE 3. When unit 14 is twisted about its vertical axis, crank 34 sweeps from one side of member 22 to the other, and connecting

links

36 and 38 enforce corresponding twist of switch-blade 18 about its longitudinal axis. Switch-blade 18 twists, and contacts 42 wipe across the faces of the silver-insert contacts; and similarly silver contacts 56 wipe across companion hard-silver contacts in U-shaped contact member 58. Thereafter, as switch blade 18 is swung through a vertical angle, arcing tip 30 wipes across arcing horn 34, the circuit breaks, and switch blade 18 reaches its vertical or nearly vertical open position. Closing of the switch follows the same mechanical operations in reverse, including the contact-wiping action as previously described, both at the hinge contacts and the air-break contact end of switch arm.

Twisting of the switch blade 18 causes any ice covering the contacts to crumble and shatter, freeing the switch blade for opening travel. Further, the wiping contact resulting from the twisting of switch-blade 18 enhances the electrical character of the closed contacts. The hardened silver inserts in

U-shaped contact members

44 and 58, eliminates the troublesome galling experienced in the past when soft silver was used for both opposing contacts. Further, U-shaped switch member 44 is a relatively lowmass copper bar made resilient by rolling and tends to grip the contact arm 18 firmly when the switch is swung closed. Where soft silver contacts were brazed in place in the past, the brazing operation no doubt impaired any resilience that the copper might have had. The possibility of bouncing of the contacts away from the switch blade is virtually of no concern in the present switch because of the relatively low mass of the contact member 44 and the pressure resulting from the resilience of member 44 and the resilience of leaf-springs 48.

The silver inserts which are silver-soldered or suitably brazed to the copper bar as previously described, to form the U-shaped contact members 44 and 56 is preferably of sterling silver or coin silver, such alloys gaining substantially greater hardness when subjected to the rolling operation than would be true of pure silver. Such alloy silver actually gets hard faster than the copper, so that by the time the copper bar has been worked sufiiciently to develop its desirable spring characteristics, the silver inserts are adequately hard.

The silver inserts are surrounded by copper; yet silverto-silver contact is assured by virtue of the convex contact surfaces (FIGURE 6) that the arranged to engage respective projecting silver contacts on switch-blade 18. The latter contact elements have straight contact surfaces parallel to the axis of the switch blade.

The foregoing description of the preferred embodiment of the invention is illustrative and is naturally susceptible to a latitude of varied application and modification; and

therefore the appended claims should be broadly construed in accordance with the full spirit and scope of the invention.

What is claimed is:

1. A tail twister switch including, a long switch blade having oppositely disposed lateral contact portions at one end thereof, a pair of oppositely disposed contact fingers at said one end of said switch blade and having a pair of opposed contact portions for resiliently embracing and gripping the respective oppositely disposed contact portions on said switch blade in the closed position of said switch, a tail twister mechanism of the type that swings the switch blade between open and closed positions and including means for twisting the blade along its longitudinal axis for driving the contact portions on said switch blade into pressure engagement with the contact portions on said contact fingers, the contact portions on one of said switch blade and contact fingers being composed of soft silver and projecting from the surface thereof, the contact portions on the other of said switch blade and contact fingers being a work hardened silver lamination united thereto, said laminations being disposed for wiping engagement by the respective oppositely projecting contacts.

2. A tail twister switch having a long switch blade, a pair of oppositely projecting lateral contacts of soft silver at each end of the blade, a pair of U-shaped contact members each embracing and resiliently gripping a respective pair of said projecting contacts, a tail-twister mechanism adapted to swing the switch blade between open and closed positions and including means for twisting the blade about its longitudinal axis and thereby driving said projecting contacts in wiping engagement with the respective Uehaped contact members, each U-shaped memher being an oriented directionally hard rolled copper bar having an oriented directionally hard rolled silver lamination united thereto and flush with a surrounding copper surface, each silver lamination being disposed opposite a respective one of said projecting contacts in the closed condition of the switch, said copper bar and said silver lamination being oriented along the direction of wiping contact and the copper bar with its silver laminations having a convex curvature in the region of engage ment by a respective one of said projecting silver contacts.

3. A tail-twister switch including a long switch blade having an air-break end and :a hinge end, a taiLtwister mechanism of the type that swings the switch blade between open and closed positions and including means for twisting the blade about its longitudinal axis when in closed position, a contact assembly at one end of said blade, a pair of soft silver contacts projecting oppositely from said switch blade at said one end, said contact assembly including a pair of oriented directionally hard rolled contact elements having oriented directionally hard rolled silver laminations disposed for wiping engagement by the respective oppositely projecting contacts, said contact elements and the silver laminations thereon being oriented in the direction of the wiping contact.

4. A tail-twister switch having a long switch blade, a pair of oppositely projecting lateral contacts of soft silver at each end of the blade, companion contact assemblies at each end of said switch blade embracing and resiliently gripping a respective pair of said projecting contacts, a tail-twister mechanism adapted to swing the switch blade between open and closed positions and including means for twisting the blade about its longitudinal axis and thereby driving said projecting contacts in Wiping engagement with the respective U-shaped contact members, each of said contact assemblies including a metal bar having a hard-coin silver lamination united thereto opposite a respective one of said projecting contacts in the closed condition of the switch, said metal bar with its silver lamination having a convex curvature in the region of engagement by a respective one of said projecting soft silver contacts.

5. A tail-twister switch including a long switch blade having oppositely projecting lateral contacts of soft silver at least one end thereof, a U-shaped contact member at said one end embracing and resiliently gripping the respective oppositely projecting contacts of said switch blade in the closed position of the switch, a tail-twister mechanism of the type that swings the switch blade between open and closed positions and including means for (twisting the blade about its longitudinal axis for driving said projecting contacts into pressure engagement with said U- shaped contact member, said U-shaped member being a hard resilient copper clip having hard alloy' silver laminations united thereto and disposed for Wiping engagement by the respective oppositely projecting contacts.

6-. Switching apparatus including a long switch blade having opposite lateral contacts of soft silver at one end thereof, a U-shaped contact member embracing and resiliently gripping said silver contacts of said blade in the closed condition of the switching apparatus, a mechanism for operating the switch blade between open and closed positions for driving said projecting soft-silver contacts into pressure engagement with said U-shaped contact member, said U-shaped contact member being a hard and resilient copper clip having hard coin-silver laminations united thereto and disposed for wiping engagement by the respective opposite contacts of said switch blade.

7. A switching device including an electrical contact, a tail-twister switch blade having soft-silver contacts, a roughly parallel pair of work hardened copper bars each having a relatively shallow area of reduced thickness adjacent an end thereof and in a broad face thereof, said areas confronting each other, each of said copper bars having surfaces about each such area constituting a frame, and a lamination of work hardened silver united to each copper bar within said frame and flush with said surfaces.

References Cited in the file of this patent UNITED STATES PATENTS 2,261,412 Reeve Nov. 4, 1941 2,303,497 Reeve Dec. 1, 1942 2,419,469 Spiro Apr. 22, 1947 2,646,613 Enzler July 28, 1953 2,703,997 Sowter Mar. 15, 1953 2,818,474 Gussow Dec. 3=l, 1957 2,830,144 Fjellstedt Apr. 8, 1958 2,925,647 Jones et a1. Feb. 23, 1960 2,932,880 Gellatly et a1, Apr. 19, 1960

Claims

1. A TAIL TWISTER SWITCH INCLUDING, A LONG SWITCH BLADE HAVING OPPOSITELY DISPOSED LATERAL CONTACT PORTIONS AT ONE END THEREOF, A PAIR OF OPPOSITELY DISPOSED CONTACT FINGERS AT SAID ONE OF SAID SWITCH BLADE AND HAVING A PAIR OF OPPOSED CONTACT PORTIONS FOR RESILIENTLY EMBRACING AND GRIPPING THE RESPECTIVE OPPOSITELY DISPOSED CONTACT PORTIONS ON SAID SWITCH BLADE IN THE CLOSED POSITION OF SAID SWITCH, A TAIL TWISTER MECHANISM OF THE TYPE THAT SWINGS THE SWITCH BLADE BETWEEN OPEN AND CLOSED POSITIONS AND INCLUDING MEANS FOR TWISTING THE BLADE ALONG ITS LONGITUDINAL AXIS FOR DRIVING THE CONTACT PORTIONS ON SAID SWITCH BLADE INTO PRESSURE ENGAGEMENT WITH THE CONTACT PORTIONS ON SAID CONTACT FINGERS, THE CONTACT PORTIONS ON ONE OF SAID SWITCH BLADE AND CONTACT FINGERS BEING COMPOSED OF SOFT SILVER AND PROJECTING FROM THE SURFACE THEREOF, THE CONTACT PORTIONS ON THE OTHER OF SAID SWITCH BLADE AND CONTACT FINGERS BEING A WORK HARDENED SILVER LAMINATION UNITED THERETO, SAID LAMINATIONS BEING DISPOSED FOR WIPING ENGAGEMENT BY THE RESPECTIVE OPPOSITELY PROJECTING CONTACTS.