US3146322A

US3146322A - Rotary electric switch having a plurality of contacts

Info

Publication number: US3146322A
Application number: US52983A
Authority: US
Inventors: Terence M P Farrell
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-08-30
Filing date: 1960-08-30
Publication date: 1964-08-25
Anticipated expiration: 1981-08-25

Description

Aug. 25, 1964 -r. M. P. FARRELL 3,146,322

ROTARY ELECTRIC SWITCH HAVING A PLURALITY OF CONTACTS Filed Aug. 30, 1960 2 Sheets-Sheet 1 INVENTOR. Te/ehpe /"drre// rN/M 41g, 01 W ATTORNEYS 25, 1964 'r. M. P. FARRELL 3,146,322

ROTARY ELECTRIC SWITCH HAVING A PLURALITY 0F CONTACTS Filed Aug. 30, 1960 2 Sheets-Sheet 2 FIG. IO

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3,146,322 ROTARY ELECTRIC SWlTtIH HAVING A PLURALETY F CONTACTS Terence M. P. Farreli, 15 Idlewell St., Weymouth, Mass. Filed Aug. 30, 1960, Ser. No. 52,983 3 Claims. (Cl. 200-23) This invention relates to switching devices and more particularly comprises a new and improved rotary switch suitable for many and diverse applications.

The primary object of this invention is to provide a rotary switch having a minimum number of parts, a long life, which is easily assemblable and which is relatively inexpensive to manufacture.

To accomplish this general objective, my rotary switch includes an annular stator which may be molded of any suitable non-conducting material, and a bar-shaped rotor substantially square in cross section and supported at its center for rotation about an axis coincident with the axis of the stator. Embedded in the stator about its inner edge are one or more pins which form contacts on that inner surface. The rotor carries a pair of contacts, one extending radially outward from an end of the bar and biased to run about the inner surface of the stator when the rotor turns. The second contact carried by the rotor runs about a ring contact disposed adjacent to the rotor. This second contact is also biased to engage the ring contact. The two contacts carried by the rotor are mounted in sleeves, and these sleeves made of electrically conducting material physically engage the contacts and are in turn electrically connected to one another. Thus, the ring contact continuously engaged by one of the contacts of the rotor is successively electrically connected to the contacts in the stator over which the other contacts on the rotor passes.

The rotary switch of my invention is suitable for programming or for use in any type of electrical system where intermittent cylical switching is required. The contact carried by the rotor successively engages each of the contacts carried by the stator to complete the same or different circuits which include on one side of the switch the ring contact and on the other side one or all of the contacts carried by the stator.

The manner in which the stator is made contributes to the relatively long life of the rotary switch. The stator may be made of a moldable material formed in a die previously provided with the one or more pins which later serve as contacts in the stator. These pins extend parallel to and are each spaced a fixed distance from the stator axis. The pins are also spaced from the inner surface of the annular rotor as defined by the die cavity so that when the rotor is molded the pins are not exposed at its inner surface. After the stator is removed from the mold, its inner surface is machined so as to gradually increase the inner diameter of the stator. Continued machining of the moldable material which forms the stator frame gradually exposes the pins embedded in the material, and ideally the machining is continued until the pin diameters lie at the inner surface of the stator. Formed in this manner, the inner surface of the stator about which the contact of the rotor runs has maximum smoothness to reduce wear of the contacts on the rotor and stator.

To provide the stator with additional strength and ruggedness, the stator may be made with an annular aluminum frame within which are embedded contact pins ex tending parallel to the axis of the annulus. These pins may be insulated from the aluminum frame of the stator by a non-conducting material of the same character as employed in the stator fabricated in the manner described This material serves not only to insulate the pins from the aluminum frame, but also provides a coating about the entire inner surface of the stator between the exposed pins spaced about that surface.

These and other objects and features of my invention will be better understood and appreciated from the following detailed description of two embodiments thereof, selected for purposes of illustration, and shown in the accompanying drawing, in which:

FIG. 1 is a cross sectional elevation view of a rotary switch constructed in accordance with my invention;

FIG. 2 is a plan view of the rotary switch shown in FIG. 1;

FIGS. 3 and 4 are plan views suggesting the successive steps employed in the manufacture of the stator shown in the rotary switch of FIGS. 1 and 2;

FIGS. 5, 7, 9 and 11 are plan views, in some instances fragmentary suggesting an alternative method of making a stator for use in the rotary switch of FIGURES 1 and 2; and

FIGS. 6, 8 and 10 are fragmentary cross sectional views taken along the corresponding section lines in FIGURES 5, 7 and 9, respectively.

The rotary switch shown in FIGS. 1 and 2 includes in its general organization a rotor 10 supported on shaft 12 and a stator 14 extending about the rotor.

The rotor 10 is shown to be substantially square in cross section and may be made of a non-conducting material such as a square mica bar. A sleeve 16 extends through the rotor at its center and receives the end of shaft 112 which supports the rotor for rotation about the shaft axis. A set screw 18 or other convenient means may be employed to hold the rotor firmly on the shaft.

The rotor 10 carries adjacent each of its

ends contact assemblies

20 and 22 which form the extremes of a circuit defined by the rotor itself. The contact assembly 20 includes a metallic electrically conductive cap 24 embedded in the bar and open at its bottom. A contact 26 made of graphite or other electrically conductive material is disposed in part within the cap 24 and is biased out of the cap by means of a rubber insert 28 which serves as a spring bearing against the closed end of the cap 24 and the inner end of the contact. The contact 26 engages the inner surface of the cap 24, and, therefore, the two are electrically connected.

Disposed beneath the rotor 10 is a ring contact 30 coaxial with the shaft 12 and spaced from the shaft axis the same distance as the contact 26. The rubber insert 28 which urges the contact 26 out of the cap 24, serves to maintain engagement of the contact 26 with the ring contact 30 as the shaft turns the rotor assembly. The ring contact 30 may in turn be supported by braces 32 or other convenient means connected to the stator 14 or some other part of the switch assembly such as its housing (not shown).

The contact assembly 22 is substantially identical to the assembly 29. It includes a metallic electrically conductive cap 34, a contact 36, made of graphite or other conducting material, and a rubber insert 38 which biases the contact 36 out of the sleeve 34. Unlike the contact 26 which extends downwardlygenerally parallel to the shaft 12, the contact 36 extends radially from the shaft 12 and engages the inner surface 40 of the stator. As the rotor 10 rotates about anaxis coincident with the axis of the stator 14, the contact 36 maintains continued engagement with the inner surface 40 of the stator. The rubber insert 38 exerts adequate pressure on the contact .36 to insure this firm engagement.

A pair of machine screws 42 and 44 are screwed into the rotor bar 10 and engage the caps 24 and 34, respectively. The machine screws are electrically interconnected by means of a conductor 46 having its ends connected to the screws. The conductor 46 may be a wire lead or any equivalent form. The conductor 46 serves to complete a continuous circuit from the contact 26 through the cap 24, machine screw 42, conductor 46 itself, machine screw 44, and cap 34 to the contact 36.

The stator 14 made of an epoxy resin or other nonconducting material carries a plurality of pins 56 made of a highly conductive material such as coin silver. The pins 50, which as described below may originally be cylindrical in shape, have their diameters coincident with the inner surface 40 of the stator 14-. It is highly desirable that the exposed portion of each pin 56 form an extremely smooth surface with the epoxy material 48 which forms the main frame of the stator. The smoother the surface defined by the frame material 4% and the pins 56, the less wear will occur as the contact 36 rides about the inner surface 40 of the stator in response to rotation of the shaft 12. It will, of course, be appreciated that although eight pins are shown in FIG. 2 spaced equidistant about the surface 40, a greater or lesser number of pins may be carried by the stator 14, and they may be spaced varying distances from one another.

In FIG. 1, I have suggested a circuit composed of two

leads

52 and 54 which may be closed and broken by the rotary switch. Obviously, each of the pins 50 carried by the stator may be electrically connected to one another or separately connected into different circuits. In the first engagement, rotation of the rotor 10 Will cause the single circuit intermittently to close and open each time the contact 36 passes over a pin 50. In the second arrangement, the rotary switch will cause the several circuits which include the separate pins 56 to sequentially close and open as each of these pins is engaged by the contact 36 carried by the rotor.

In FIGS. 3 and 4, one manner of fabricating the stator 14 is suggested. In FIG. 3, I suggest that the epoxy resin or other material 48 used as the main composition of the stator is initially formed as an annulus with the pins 50 embedded in it and spaced from the inner surface 40 as well as the outer surface 56 of the stator. After the stator is molded as shown in FIG. 3, its inner surface 40 is machined so as to enlarge its inner diameter. Continued machining of the inner surface 46 ultimately results in the exposure of the pins 50. In FIG. 4, I suggest that the machining is continued until substantially the diameter of the pins 50 is exposed. While one half of the pins are machined away as suggested in FIG. 4, obviously machining may be discontinued after some lesser amount of the pins is exposed.

In FIGS. -11, an alternative method is suggested for fabricating a stator suitable for use in the rotary switch shown in FIGS. 1 and 2. A stator made in accordance with the following method will be somewhat more durable than that described above and is better able to withstand physical abuse to which the rotary switch may be subjected upon occasion. In FIGS. 5 and 6, I show an annular stator element 60 supported on a micarta backing plate 62 secured together by any convenient means. Preferably, the stator element 60 is made of aluminum and is provided with holes 64 concentric with smaller holes 66 formed in the plate 62. The concentric pairs of

holes

64 and 66 may be spaced at regular or irregular distances about the element 60 and their number and positions are determined by the end use of the rotary switch assembly. To fabricate the stator, the inner surface 68 of the element 60 is machined or ground to enlarge the inner diameter. This machining or grinding is continued until the holes 64 are opened on the inner surface of the stator element 66, as suggested in FIG. 7. Thereafter, the contact pins 70 of a diameter very slightly larger than the diameter of the holes 66 in the micarta plate 62 are force fitted into the holes 66 as suggested in FIG. 8. While the pins 70 have a forced fit in the holes 66, their cylindrical surfaces are spaced from the walls of the holes 64 as is particularly evident in FIG. 8.

After the pins are mounted in the holes, a dam in the form of a ring 72 is seated on the plate 62 concentric with the stator element 69. The diameter of the ring 72 is just small enough so that the ring clears the pins 70. After the ring is seated on the plate 62, the cavity defined by the inner surface 63 of the stator element 60 and the ring 72 is filled with an insulating material such as epoxy resin 74. The resin also fills the space between the pins and the surfaces of the holes 64 so that the pins '76 are completely insulated from the frame element 66. After the plastic material 74 sets, the dam or ring 72 is removed and the inner surface 76 of the stator assembly is machined. Initial machining of the surface 76 serves to remove only the epoxy resin 74, and continued machining ultimately exposes the pins 7% The machining should be continued until a substantial width of the pins '70 are exposed but should be discontinued before the resin is removed from the surface 68 of the stator element 66. In this manner, the stator ultimately takes the form shown in FIG. 11 wherein the pins 70 are exposed and the epoxy resin 74 serves to coat the inner surface of the element 66 and insulate the pins 76 from the stator element.

A stator manufactured in accordance with either of the two suggested methods includes an inner surface which is extremely smooth so as to reduce wear on the contact bar 36 of the rotor to a minimum. While the inner surface in each of the stator constructions is made up of alternate sections of insulating and conducting material, nevertheless, the surface is continuous and smooth to assure a surface of maximum uniformity for the contact bar 36 of the rotor.

From the foregoing description, it will be recognized that the rotary switch accomplishes the general objectives recited in the introduction. The rotary switch is of extremely simple design and is constructed to result in minimum wear of the parts. The rotor parts are effectively balanced about the axis of the shaft 12 to prevent oscillation of the assembly regardless of the speed at which the rotor turns.

Because numerous modifications may be made of the described embodiments without departing from the spirit of my invention, I do not intend to limit its breadth to the embodiments described and shown. Rather, I intend that the breadth of my invention be determined by the appended claims and their equivalents.

What is claimed is:

1. A rotary switch comprising a rotor and surrounding annular stator, means for rotating the rotor about the axis of the stator, said stator having a heat conducting outer frame and a heat conducting and electrically insulating inner ring within the frame, spaced contacts embedded in the ring and exposed on the inner surface of the stator, said stator having a smooth continuous inner surface made up of alternate contacts and sections of the electrically insulating rings, a sleeve made of conducting material embedded in the rotor and open in the direction of the inner surface of the stator, a contact bar disposed in and extending out of said sleeve, biasing means disposed in the sleeve behind the contact bar urging that bar into engagement with the inner surface of the stator, a second sleeve embedded in the rotor and made of metallic material, a second contact bar disposed in the second sleeve and extending out of said second sleeve, a ring contact mounted adjacent the rotor and coarcuate with the path defined by the second contact bar when the rotor rotates, biasing means disposed in the second sleeve and urging said second bar into engagement with the ring contact, said contact bars being in electrical contact with their respective sleeves, and means electrically connecting the two sleeves.

2. A rotary switch comprising a rotor and surrounding annular stator, means for rotating the rotor about the axis of the stator, said stator having an aluminum heat conducting outer frame and a heat conducting and electrically insulating inner ring made of an epoxy resin within the frame, spaced contacts embedded in the ring and exposed on the inner surface of the stator, said stator having a smooth continuous inner surface made up of alternate contacts and sections of the epoxy resin, a sleeve made of conducting material embedded in the rotor and open in the direction of the inner surface of the stator, a contact bar disposed in and extending out of said sleeve, biasing means disposed in the sleeve behind the contact bar urging that bar into engagement With the inner surface of the stator, a second sleeve embedded in the rotor and made of metallic material, a second contact bar disposed in the second sleeve and extending out of said second sleeve, a ring contact mounted adjacent the rotor and coarcuate with the path defined by the second contact bar When the rotor rotates, biasing means disposed in the second sleeve and urging said second bar into engagement with the ring contact, said contact bars being in electrical contact with their respective sleeves, and means electrically connecting the two sleeves.

3. A rotary switch comprising a rotor and surrounding annular stator, means for rotating the rotor about the axis of the stator, said stator having an aluminum heat conducting outer frame and a heat conducting and electrically insulating inner ring made of an epoxy resin within the frame, spaced contacts embedded in the ring and exposed on the inner surface of the stator, said stator having a smooth continuous inner surface made up of alternate contacts and sections of the epoxy resin, a

sleeve made of electrically conducting material embedded in the rotor and open in the direction of the inner surface of the stator, a contact bar disposed in and extending out of said sleeve, biasing means disposed in the sleeve behind the contact bar urging that bar into engagement with the inner surface of the stator, a second contact bar carried by the rotor, a ring contact mounted adjacent the rotor and coarcuate with the path defined by the second contact bar when the rotor rotates, biasing means carried by the rotor and engaging the second contact bar and urging the second contact bar into engagement With the ring contact, and means electrically connecting the second contact bar to the sleeves.

References Cited in the file of this patent UNITED STATES PATENTS 1,258,098 De Lorme Mar. 5, 1918 1,357,455 Holway Nov. 2, 1920 1,361,314 De Lorme Dec. 7, 1920 1,400,561 Mason et a1 Dec. 20, 1921 1,411.073 Werner Mar. 28, 1922 1,731,513 Wagner Oct. 15, 1929 2,274,816 Winther Mar. 3, 1942 2,649,515 De Lorme Aug. 18, 1953 2,887,764 Knoll et a1 May 26, 1959 2.934,815 Stumbock May 3, 1960