US2760015A - High voltage switch - Google Patents

Description

Aug. 21, 1956 A. HORVATH ET Al- HIGH VOLTAGE SWITCH Filed April 6, 1955 4 Sheets-Sheet l u '11a1111,11111,1111,ll/111111111111111111111,1l"

Aug. 2l, 1956 A. HoRvATH E1- AL HIGH VOLTAGE SWITCH 4 Shets-Sheet 2 Filed April 6, 1955 INVENTORS ALEM/vas@ flo/Q VAT# HARRY VAN Eur/w RAY/volvo H. BRESK ATTORNEY Aug. 21, 1956 A. HoRvATH ET A1. 2,760,015

HIGH VOLTAGE SWITCH Filed April 6, 1955 4 Sheets-Sheet 3 I'NVENToRs A wes @2mm RA YMCA/0 h'. BRSK ATTORNEY Aug. 21, 1956 A. HoRvATH ET AL HIGH VOLTAGE SWITCH 4 Sheets-Sheet 4 Filed April 6, 1955 INVENTORS ALXANER HORVATH HARRY VAN ELKAA/ RAY/10H0 H. @RESK 32W www ATTORNEY United States Patent O M' HIGH VOLTAGE SWITCH Alexander Horvath, Clifton, N. J., Harry Van Elkan, New

York, N. Y., and Raymond H. Bresk, Clifton, N. J., assignors to International Telephone and Telegraph Corporation, Nutley, N. J., a corporation of Maryland Application April 6, 1955, Serial No. 499,603

9 Claims. (Cl. ZOO-6) This invention relates to high voltage switches of the open air type, and particularly to a single-pole doublethrow switch.

Many problems arise in making switches for A. C. voltages of the order of tens of thousands of volts, particularly where substantial currents at high frequencies are involved. These problems relate to the provision of adequate conductors for carrying the load, adequate insulation to prevent breakdown and iinally adequate arrangement, configuration of the elements and design to prevent discharges. The prevention of discharge becomes particularly diflicult in encased air type switches. In attempting to solve these problems there has been a tendency to make such switches large, cumbersome and complex.

An object of the present invention is the provision of an improved high voltage switch of the open air type, which is of relatively simple structure and which is adapted to prevent discharges therewithin.

ln accordance with a feature of the present invention the switch is adapted to connecting either of two voltages, at least one being a high voltage, to a common lead, thus being a form of single-pole, double-throw switch. In order to prevent discharge from sharp edges within the switch, the switch is so arranged that when it is passing these high voltages, the sharp edges are within the shadow of rounded surfaces so that said rounded edges intercept the field to the sharp edges and effectively shield the sharp edges.

In accordance with a further feature of the present invention, the switch arm may consist of a flat spring having sharp edges which are exposed when the switch is in the position connecting a low voltage therethrough, but which edges are shadowed by one or more adjacent metallic elements having rounded edges which are closer to the ground plane, to which ground plane discharging would otherwise tend to occur.

The foregoing and other features and advantages of the present invention will be better understood from the following description of embodiments thereof, reference being had to the drawings, in which:

Fig. l is an end view of a high voltage switch according to the present invention;

Fig. 2 is a longitudinal-sectional view taken substantially along the line 2 2 of Fig. l;

Figs. 3, 4, 4A and 5 are cross-sectional views taken substantially along the corresponding lines of Fig. 2, with Figs. 4 and 4A showing the switch arm in different positions;

Fig. 6 is a fragmentary view of a longitudinal section of a modiiied form of switch, showing particularly the high voltage portion thereof;

Fig. 7 is an end view taken along the line 7-7 of Fig. 6; and

Fig. 8 is an end view taken along the line 8 8 of Fig. 6.

Referring now to the drawings and particularly to Figs. l and 2, the switch there illustrated is housed in a cylindrical housing 10 closed at one end by a closure plate 11 2,760,015 Patented Aug. 21, 1956 of insulating material, and partially closed at the other end by a metallic closure plate 12 having an opening 13 in which is set the lead-through 14. The insulating closure plate 11 is suitably fastened to the rear end of the cylindrical housing 10, for example, by screws 15. The metallic closure plate 12 at the other end of housing 10 may be integral therewith as part of a unitary casting. Lead-through 14 and the method of securing it in the opening 13 will be described hereinafter.

The switch serves to selectively connect the lead-through 14 to one of two voltage sources, a high voltage A. C. source and a low voltage A. C. source. For example, the high voltage source may be 20 kv., the low voltage source 6 kv., at a frequency of from 300 kc. to 30 mc. It is preferred that switching is accomplished under noload conditions, that is, the power is shut oi when switching occurs, and the power is only turned on after the switch is in the desired position. The design is such, however, that occasional switching under power will not damage the final contact surfaces of the switch. The apparatus for turning on and off the power is no part of the present invention and is not described herein.

The switching is accomplished by rotating a shaft 16 in a bearing 17 iixed in the insulating closure plate 11, and in another bearing 18 formed in a central insulating plate 19. The central insulating plate 19 is parallel to the closure plates 11 and 12 and roughly halfway between them so as to divide the housing into two main parts 20 and 21.

The end 22 of shaft 16 is a metallic rod which rides in bearing 17 passing therethrough to the interior part 20 of the housing, wherein it is mechanically attached by a collar to an insulating portion of the shaft 23 which rides in bearing 18 and is locked against longitudinal movement by having enlarged portions 24 and 25 on opposite sides of the central insulating plate 19.

The low voltage lead-in is through the metallic rod 22 of shaft 16 via a bendable flat spring 26 which connects said rod 22 to a conducting rod 27. Rod 27 passes through a sleeve 28 mounted in the central insulating plate 19 by the sleeve 28 being secured in plate 19 by means of set-screw 29. An end portion 30 of rod 27 extends beyond the sleeve 28 and is provided with a diametrical slot 31 in which one end 32 of a at spring 33 is set mechanically and soldered to make a good electrical connection.

At the other end 34 of spring 33 there is provided a contact in the form of a small hollow cap 35 pushed over said end 34 of at spring 33, the cap 35 being cylindrical and the closed top thereof being rounded so as to present no sharp points in the direction of high voltage. ln itself it shields the sharp edges of spring 33 behind.

The high voltage lead-in is via a relatively heavy metallic rod 36 which passes through a large hole 37 in the insulating closure plate 11 and terminates in a contactmaking cap 38. To support the cap 38, a sector 39 of the central insulating plate 19 is cut away except for a projection 40 extending radially of the longitudinal central axis. The cap 38 is pushed over the projection 40 and secured by suitable means, such as fastening pins (not shown). The cap 3S is very much larger than cap 35 in diameter since the former is used for the high-voltage contact. The cross-sectional configuration of cap 38 is roughly cylindrical except for a flattened portion 41 (see Fig. 2) on the side of said member facing towards the front end of the switch, that is, towards lead-through 14. The top 42 of cap 38 is rounded where it meets the side walls so as to leave only rounded edges.

Cap 38 is the high Voltage contact and cap 35 is the low voltage contact of the switch controlled by shaft 16. The switching arrangement, generally designated by the numeral 43, which makes contact with these two caps consists of a hollow metal disk 44 which is mounted on the insulating portion of shaft 16 by any suitable means, such as by pushing the disk 44 over the end of portion 25 and securing it in place by pins or any other suitable means. The disk 44 is rounded where its dat top surface 45, meets its cylindrical perimeter 46. The disk 44 is provided with a slot parallel to the at surface 45 in which a flat spring which serves as the movable switch arm 47 is fastened. The fiat spring switch arm 47 is terminated by a hollow contact button 48 which is slipped over the outer end of arm 47 and fastened thereto, for example, by soldering. Switch arm 47 is of sufficient length so that when shaft 16 is rotated, the top of contact button 48 will ride under the low voltage cap 35 and force cap outward in a radial direction, pressure being maintained by spring 33 to force cap 35 against button 48. It will be noted that in this position the spring switch arm 47 is relatively stiff as the pressure applied thereto by cap 35 against button 48 is in a radial direction. This position is clearly shown in Fig. 4. When the shaft is rotated counterclockwise, as seen in Fig. 4A, the switch arm 47 moves contact button 48 so that it rides over the fiattened surface 41 of the high voltage cap 38. Pressure in this case is the result of the bending of spring 47 since cap 38 is rigidly secured to the projection 40 of central insulating plate 19. As contro-l button 48 rides over cap 38 the switch arm 47 is bent in a direction perpendicular to the plane in which it lies. Thus, by rotating shaft 16 contact can be made to either the high voltage lead or the low voltage lead.

To complete the connection to the common lead, leadthrough 14, use is made of a sliding contact arrangement as described hereinafter (see Fig. 5). A spring contact arm 49 is mounted, for example, by means of screws 50 on a hollow metallic disk 51 whose edge is carefully rounded. The screws 50 pass through the disk 51 into appropriate threads in lead-in conductor 52, the lead-in conductor 52 being surrounded by an insulating member, generally designated by the numeral 53, and terminating in a metal end piece 54 with a metal tip 55 to which contact is made by suitable means not pertinent to the present invention.

The insulating member 53 consists of three major portions. A cylindrical portion S6 within the switch merges into a round disk 57 which fits closely into the opening 13 of metallic closure plate 12, and next to disk 57. There is a roughly cone-shaped portion 58 whose base is of larger diameter than the disk 57 so that it abuts the portion of the metallic closure plate 12 adjacent the opening 13. The insulator 53 is held rigidly in place against the metallic plate 12 by means of an annular collar of insulating material 59 which has a portion 60 overlying the base of the conical portion 58, the collar 59, in turn, being secured to the metallic end plate by means of screws 61.

In order to prevent burn through of the insulation surrounding the lead-through conductor 52, it is essential that no air pockets form between said conductor and the surrounding insulator. For this purpose, conductor 52, as well as the opening in insulator 53 in which it fits, are both slightly tapered, and the conductor 52 is swaged into the opening in the insulator. Further, to prevent the formation of air pockets between conductor 52 and the insulator, oil is applied around the outside of the conductor 52 before it is inserted in the insulator, this oil filling any pockets in the surrounding insulation.

It will be noted that while the sharp or thin edge of switch arm 47 is exposed when the switch arm brings cap 35 and button 48 together, this is the low voltage connecting condition and no problem will raise with respect to accidental discharges. It will furthermore be noted that when the switch arm 47 is in the position in which cap 38 and button 48 contact, the high voltage condition, the entire length of arm 47 is adjacent to disk 51 or cverlies it, as shown in Fig. 4A. Thus, disk 51 serves eiectively to shield the sharp edges of arm 47. In addition, the rounded edge of button 48 prevents discharges from the outer end of the switch arm while the inner end of the switch arm likewise terminates in disk 44 with its rounded perimeter 46. Thus, the arrangement is such that in the high voltage position the sharp edges of the switch arm are effectively shielded from discharge to the outer metallic cylinder 10. As seen in Fig. 4A, the top of the switch arm 47 is also beneath the top of the high voltage Contact cap 38 and the top of this cap 38 serves as additional protection in shielding the switch arm.

While the switch of Figs. 1 5 is designed to handle high voltages, it is preferred where heavy currents are to be carried, to use the form of switch shown in the modification of Figs. 6-8.

Referring now to Figs. 6-8, the high voltage lead-in is modified by replacing cap 38 with a contact disk 62 mounted on the end of the lead-in 36 which passes through a suitable opening in the central partition 19. Directly opposite disk 62 is another disk 63 whose top is aligned with the top of disk 62, with disk 63 being of somewhat greater diameter so the bottom thereof extends below the level of the bottom of disk 62. Disk 63 is mounted by screws 64 on the end of conductor 52. Likewise insulator rods 65 securely attach disk 62 to disk 63 thereby rigidly mounting disk 62. The shaft 16 has a metallic cap 66 at the end thereof in which the switch arm 47 is fixed. A short distance from the cap 66 along arm 47 two contact buttons 67 and 68 are mounted. This may be done, for example, by providing a hole in arm 47 with button 68 being solid and having a small projection 69 passing through said hole and entering into a receiving opening in the bottom of button 67, buttons 67 and 68 being forced together so that the projection 69 is forced into the opening and thereby mechanically securely attached thereto. To insure an adequate electrical connection solder may be placed around the base of both buttons 67 and 68 on arm 47. Buttons 67 and 68 make contacts with spring fingers 78 and 71 fastened to caps 63 and 62, respectively (see Figs. 7 and 8). It is to be noted that when switch arm 47 is rotated in the position in which buttons 67 and 68 make contact with spring fingers 70 and 71, the switch is in its high voltage position. In this position the sharp edges of the spring fingers are within the shadow of the two rounded caps 62 and 63. This is likewise true of the sharp edge of switch arm 47 Thus discharge from these sharp edges is inhibited due to the shielding effect. When the switch arm 47 is moved into the position in which it contacts the low voltage cap 34, as shown in Fig. 4, it is of no importance that the sharp edge is exposed and away from the shielding effect of caps 62 and 63 as the voltages involved are insufficient to cause discharge. It may be also pointed out that the spacing between caps 62 and 63 is such that the low voltage will not jump thereacross. A further detail in which the modification of Figs. 6-8 differs from that of the previous figures is in the brush arrangement to cap 66. In this arrangement the spring 72 is attached at one end to the cap 63 and rides over the flat face of cap 66. When the low voltage contact is made by contact 48, current ows through the switch arm and partially through cap 66 and via spring 72 to cap 63 and the lead-through conductor 52.

When the switch is in its high voltage position, current will be conducted from cap 62 via spring fingers 70, 71 and buttons 67 and 68 to cap 63. It will be obvious that in this position a much heavier current can be carried due to the diameter of the buttons than would be feasible if the current were being carried through switch arm 47 and spring 72.

The insulating materials used in the switch are obviously those which are suitable for use at relatively high frequencies and `which present high heat resistance and good machinability. Certain polystyrene plastics are particularly suitable for this, such as those known by the trade-names of Textolite and Rexolite. The conductors employed may be of copper, silver, or brass and the contacts may preferably be of hard silver.

While we have described our invention above with reference to specific embodiments, it is to be understood that the invention is to be interpreted by the state of the prior art and the appended claims.

We claim:

1. A high voltage switch for connecting a selected one of two lead-ins to a single common lead comprising a metal housing, a pair of lead-ins at least one being a high voltage lead-in, a first contact element connected to the other lead-in, a second contact element connected to said high Voltage lead-in, a switch arm mounted for movement in a given path between two positions, said first contact element being disposed in said path for engagement by said switch arm at one of said positions, said second contact element being disposed in said path for engagement by said switch arm in its second position, a metallic element adjacent said switch arm in its second position, said metallic element having a smooth portion lying closer to the housing than any point of the switch arm when said switch arm is in its second position to thereby effectively shield the switch arm against discharge when connected to the high voltage lead-in, and means connecting said metallic element to said common lead.

2. A high voltage switch according to claim 1, in which said other lead-in is a relatively low Voltage leadin, said switch arm, in its first position in Contact with said first contact element and thereby connected to the low voltage lead-in, being separated from said metallic element and not shielded thereby.

3. A high voltage switch according to claim l, in which said switch arm is in the form of a metallic flat spring, a metallic button mounted at one end of the spring and being rounded towards the outside thereof, a metallic disk member having a slot therein in which the other end of said spring is fitted, a rotatable shaft on which said disk member is mounted for rotation therewith, and a resilient member between said metallic element and said disk member making resilient contact with one of these and attached to the other.

4. A high voltage switch according to claim 1, further comprising a shaft, means for mounting one end of said switch arm on said shaft for rotation thereby, said switch arm being in the form of a substantially flat spring, a metallic button at the outer end o-f said spring, resilient means for mounting said first contact element in the path of said button so as to be engaged by the outer end of said button, and non-resilient means for mounting said second contact element in the path of said button so as to engage the side thereof, the spring of said switch arm extending in a plane substantially parallel to the surface of said second contact element and exerting pressure against said second non-resilient contact element.

5. A high voltage switch according to claim l, further including a rotatable shaft, means for mounting said switch arm on said shaft, a contact button at one end of said switch arm, said contact button engaging said first contact element in one of said positions, said metallic element and said second contact element being mounted with opposed faces, said switch arm being between said second contact element and said metallic element in its second position and means associated with said switch arm for connecting said second contact element with said metallic element in said second position.

6. A high voltage switch according to claim 5, in which said means for connecting said metallic element and said second contact element comprises a pair of buttons mounted on opposite sides of the switch Iarm intermediate the ends thereof and spring means mounted on each of said metallic elements and said second contact element and making contact with said pair of buttons.

7. A high voltage switch for connecting a selected one of two lead-ins to a single common lead comprising a cylindrically-shaped metal housing, a common lead extending out one end of said housing, an insulating partition and support member extending diametrically within Said housing, a rotatable shaft journaled in said support member, a switch arm mounted on said shaft, a pair of lead-ins extending inwardly from the other end of said housing, one of said lead-ins passing through said partition and being mounted thereon, at least a part of the other lead-in passing through said support member, and a pair of contact elements, each one being supported from the inner end of its corresponding lead-in on the side of the support member adjacent said switch arm.

8. A high voltage switch according to claim 7, wherein said switch arm is in the form of a flat spring having a contact button at the outer end thereof, and the means for mounting said spring on said shaft comprises a disk mounted at the end of the shaft and having a slot therein within which the other end of the Spring is fastened.

9. A high voltage switch according to claim 7, in which said common lead comprises a metallic conductor, an end plate at said first-mentioned end of the metallic housing, said end plate having an opening therein of substantially greater diameter than said conductor, an insulating member surrounding said conductor so closely as to leave substantially no air spaces therebetween, said insulator having a portion thereof of greater diameter than said opening, and means mounting said insulator on said end plate so that the conductor passes through substantially the center of said opening.

No references cited.

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