US3522392A - High current rotary switch for connecting one of a first set of terminals to a selected one of a second set of terminals - Google Patents

Description

3,522,392 F A FIRST OP EN {La y D. F. ROHRER HIGH CURRENT ROTARY SWITCH FOR CONNECTING ONE 0 SET OF TERMINALS TO A SELECTED ONE OF- A SECOND SET OF TERMINALS Flled Sept 19 1967 CLOSED LOAD" LOAD*2 LOAD 1: 3

FIG. I

3,522,392 HIGH CURRENT ROTARY SWITCH FOR CON- NECTIN G ONE OF A FIRST SET OF TERMINALS TO A SELECTED ONE OF A SECOND SET OF TERMINALS Daniel F. Rohrer, Hillsboro, reg., assignor to Varian Associates, Palo Alto, Calif., a corporation of California Filed Sept. 19, 1967, Ser. No. 668,808 Int. Cl. H01h 25/06 U.S. Cl. 200-4 8 Claims ABSTRACT OF THE DISCLOSURE A manually operated panel mounted selector switch for connecting one of a first set of terminals to a selected one of a second set of terminals, is capable of carrying hundreds of amperes of current. The controls are concentrically mounted on a single shaft protruding through the panel. Means are provided for de-energizing the contacts and releasing contact pressure before the contact position is changed, thus avoiding arcing and contact abrasion and reducing the force required to move the contacts between positions.

BACKGROUND OF THE INVENTION The present invention relates generally to switches for high current and in particular to a manually operated panel mounted selector switch suitable for connecting a high current power supply to. any one of a plurality of different loads.

Switches suitable for connecting high current sources of the order of 500 amperes to loads have usually been of the familiar knife type. This type of switch works satisfactorily in single throw or double throw configurations, but when a selector switch function is attempted, several switches together with jumper wires generally have to be used, resulting in a clumsy and complex arrangement.

Another approach has been to extend the current capacity of typical rotary selector switches. A variety of problems have resulted. The large contacts and high contact pressures necessary to handle currents in the hundreds of amperes require inconveniently large forces to move the switch from one position to another and result in rapid contact wear. Furthermore, arcing between contacts frequently occurs when switch position is changed, especially when supplying current to a load having appreciable inductance.

Another problem frequently encountered in prior designs has been excessive heating of the contacts caused by inadequate contact pressure and hence high contact resistance together with inadequateventilation or other means of heat dissipation.

SUMMARY OF THE INVENTION According to the present invention a hand operated selector switch suitable for high currents provides convenient means having a large mechanical advantage for alternately applying and releasing high pressure between the contacts. Thus contact pressure may be released before switch position is changed, completely eliminating contact abrasion.

Furthermore, since contact pressure can be released before the switch position is changed, contact pressure can be made very large in order to reduce contact resistance without fear of making switch operation inconveniently stiff. Means are also provided for automatically de-energizing the switch contacts before the contacts are opened, thus eliminating electrical arcing between ter- "United States Patent O minals and contacts. The switch is designed to have excellent ventilation of the contacts so that heat can be rapidly dissipated. Finally, the switch according to the present invention is unusually compact, rugged and simple to operate.

Accordingly, it is an object of the present invention to provide a high current switch in which contact pressure I can be released to facilitate the changing of switch positions.

It is a still further object to provide a switch having to automatically de-energize the switch contacts before the contacts are opened.

It is a still further object to provide a switch having all the controls conveniently located on a single shaft.

It is yet another object to provide a switch having an open construction which permits adequate ventilation.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side view partially in section of a switch according to the present invention;

FIG. 2 is a bottom view of the switch of the present invention;

FIG. 3 is a schematic diagram of a power supply and load circuit utilizing the switch of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 and FIG. 2 a high current switch 1 according to the present invention includes a metal plate 2 through which seven terminals 3 are mounted with insulating sleeves 5. Metal plate 2 is mounted spaced below a front panel 4 by screws which pass through sleeve bushings and spacers 8 into threaded holes in front panel 4. Flanged insulator sleeves 10 electrically isolate plate 2 from front panel 4. The comparatively large open space between plate 2 and front panel 4 permits free circulation of air on all sides of plate 2 for eflicient cooling. In this connection, plate 2 has a relatively large volume and surface area as shown in the drawing to provide the same with a high thermal capacity and large heat dissipative area. Nuts 7 are threaded onto terminals 3 to secure ring lugs 9 to which electrical lead wires 11 are fastened to connect the switch to the power supply or load.

A first contact block 13, made of silver plated copper for example, provides a low resistance connection between a selected one of terminals 3 and plate 2. Block 13 is provided with two spherical or rounded crowns 14 which contact a chosen one of the terminals 3 and the plate 2 over a small area and at a high pressure. Block 13 is insulatingly fastened to an arm 15 by a single screw which passes through triangular insulators 17 and block 13. Triangular insulators 17 are thus firmly clamped against the sides of block 13 and arm 15 where they are supported within a dovetail-shaped recess. Insulator pad 19 has a convex surface facing block 13 to permit block 13 to pivot slightly about the screw to equalize contact pressure at the two crowns 14.

Arm 15 is mounted on a center shaft 21 as by welding or brazing. Shaft 21 extends upwardly through the front panel 2. A T-shaped handle 25 is pivotally fixed to the -end of shaft 21 by a pin 27. A pointer 29 has a sleeve portion 31 which surrounds shaft 21. Sleeve portion 31 has a counter-bored recess 33 which receives a tube 35. Tube 35 is keyed to pointer 29 by a ball 37 which is received within an elongated slot 39 and a hole in tube 35.

Thus, tube 35 is locked to pointer 29 for rotation therewith.

A second arm 41 is received on and welded to the end of tube 35. Second arm 41 has a second contact block 43 pivotally mounted thereon with triangular insulators and an insulator pad in exactly the same fashion as block :13 is mounted on arm 15. A bushing 44 surrounds tube 35 and is secured within plate 2 by flanged insulator 45. A washer 47 is positioned surrounding tube 35 and next to insulator 45. Conventional disk-shaped springs 49 are positioned between washer 47 and sleeve portion 31. Similarly a wavy spring washer 51 is positioned surrounding tube 35 between second arm 41 and bushing 44.

As best seen in FIG. 1, T-shaped handle 25 has an open position, shown in dotted outline, and a closed" position, shown solid. A camming surface 53 on handle 25 bears against a flat washer 55. When handle 25 is moved from the open to the closed position, the rotation of camming surface 53 against flat washer 55 moves center shaft 21 in a direction to press contact blocks 13 and 43 against selected ones of terminals 3 at the same time partially compressing wavy spring washer 51. Simultaneously, pointer 29 is moved in a direction to compress springs 49. With handle 25 in the closed position contact blocks 13 and 43 are held in good electrical contact with their respective terminals 3 and with plate 2 by springs 49. The combination of a fairly long handle 25 and' the camming surface 53 provides a high mechanical advantage to make application of contact pressure relatively easy.

When handle 25 is moved to the open position the force on springs 49 is released, and wavy spring washer 51 moves the contact blocks away from terminals 3. Either of the contact blocks can "then be moved to a different terminal 3, since pointer 29 and handle 25 can be freely rotated. A brake 57 consisting of a metal strap 59 and a friction band 61 of plastic prevent unwanted rotation of pointer 29 when handle 25 is being rotated. Band 61 surrounds sleeve portion 31 and is held in firm contact therewith by metal strap 59. The other end of metal strap 59 has a hole therein through which one of sleeve bushings '6 passes to secure strap 59 against rotation. The slight friction produced between brake 57 and sleeve portion 31 is suificient to prevent undesired rotation of pointer 29 without making normal operation difficult.

In the embodiment shown, there are seven terminals arranged into a first group of three, any one of which may be selected by contact block 13 by rotating handle 25 to thereby connect the selected terminal to plate 2. Similarly any one of a second group of four terminals can be selected for connection to plate 2 and hence to the selected terminal in the first group by rotating pointer 29. Thus plate 2 serves not only as a convenient and rugged mounting platform for the other components of the switch 1, but also as a jumper wire having high electrical and thermal capacity. Limit pins 63 which may be force fitted in holes in plate 2 are provided to prevent rotation of either handle 25 or pointer 29 beyond the end points of each of the two groups of terminals.

Since the switch is designed to carry currents in the hundreds of amperes to loads which sometimes have appreciable inductive reactance, a mercury switch 65, mounted in a recess within handle 25, is used to interrupt current to contacts 3 before the electrical connection between the terminals and plate 2. is broken. In the illustrated' embodiment, mercury switch 65 is oriented to perform the above function when plate 2 is mounted in a vertical plane with the first group of terminals 3 facing downwardly.

Mercury switch 65 comprises a glass envelope 66 partially filled with mercury and sealed. Two contact wires 68 extend into the envelope and terminate therein. A protective sleeve 70 of plastic, for example, cushions the exposed end of the envelope. When switch 65 is oriented so that the mercury flows away from the end covered by sleeve 70, the exposed ends of contact wires 68 are covered by the mercury, closing the switch.

Turning now to FIG. 3, there is shown a power supply and load circuit in which the switch 1 of the present invention is useful. A source of alternating current is connected to input terminals 67. Current flows through a manually operated switch 69 when switch 69 is closed and to the contacts of a relay-operated switch 71. Switch 71 is operated by mercury switch 65 in handle 25. When handle 25 is in the closed position mercury switch 65 is closed, relay-operated switch 71 is closed and current flows to the primary Winding 73 of a transformer 75. The secondary winding 77 is provided with four taps which supply dilferent voltages to each of the second group of four terminals 3 of the switch of the present invention. The first group of three terminals is shown connected to three loads with a ground return line connected to the secondary of the transformer.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A switch for selectively connecting one of a first plurality of terminals to one of a second plurality of terminals comprising a metal plate, said first and second pluralities of terminals being insulatingly supported in said metal plate, a first contact means movable between the terminals of said first plurality of terminals for electrically connecting any selected one of said first plurality of terminals to said metal plate, and a second contact means movable between the terminals of said second plurality of terminals for electrically connecting any selected one of said second plurality of terminals to said metal plate, said metal plate having a large thermal capacity and heat dissipative surface and acting as a jumper wire between said selected ones of said terminals, and clamp ing means operatively connected between said contact means and said plate and having a closed position in which said first contact means is biased against said selected one of said first plurality of terminals and against said plate and said second contact means is biased against said selected one of said second terminals and against said plate, said clamping means also having an open position in which said first contact means is biased away from said selected one of said first plurality of terminals and away fromsaid plate and said second contact means is biased away from said selected one of said second plurality of terminals and away from said plate.

2. The switch according to claim 1 wherein said clamping means comprises a handle, pin means operatively connected between said first contact means and said handle to permit said handle to be pivoted between said open and closed positions, first spring means operatively connected between said plate and said first contact means to cause said first contact means to be biased against said any one of said first plurality of terminals and against said plate when said first spring means is compressed, camming means on said handle to cause said first spring means to be compressed only when said handle is in the closed position, and second spring means operatively connected between said plate and said first contact means to cause said first contact means to be biased away from said plate when said handle is in the open position.

3. The switch according to claim 1 further including switching means operatively connected to said clamping means to apply a selected potential to at least one of said selected terminals only when said clamping means is in the closed position.

4. The switch according to claim 3 wherein said clamping means includes a handle operatively connected to said first contact means, said handle being movable between said open and closed positions and said switching means comprises a mercury switch connected to said handle, said mercury switch being open in said open position and closed in said closed position.

5. The switch according to claim 1 further including means to move said first contact means to engage a selected one of said first plurality of terminals and means to move said second contact means to engage a selected one of said second plurality of terminals.

6. The switch according to claim 5 wherein said means to move said first contact means comprises a rotatable shaft extending through said plate and an arm connecting said shaft to said contact means.

7. The switch according to claim 6 wherein said first contact means comprises a metal block pivotally and insulatingly mounted to said arm.

8. The switch according to claim 1 wherein said first movable contact means comprises a metal block, one surface thereof having a first crowned portion for contacting said one of said first plurality of terminals over a References Cited UNITED STATES PATENTS 2,163,069 6/1939 Stringer 2004 2,512,880 6/1950 Russell 200-4 X 2,594,181 4/1952 Kliegl et a1. 200--4 X 3,214,531 10/1965 Dux 2'00 14 X 2,553,238 5/1951 Caswell. 2,671,149 3/1954 Hubbell et al. 200- FOREIGN PATENTS 824,367 10/ 1936 France.

557,191 2/1957 Italy.

ROBERT K. SCHAEFER, Primary Examiner R. A. VANDERHYE, Assistant Examiner US. Cl. X.R. 200155, 172

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