US3288949A

US3288949A - Multiple switch assembly having stator contacts with prestressed jaws and alignment means

Info

Publication number: US3288949A
Application number: US338431A
Authority: US
Inventors: Jr Sidney L Brown
Original assignee: Ledex Inc
Current assignee: Ledex Inc
Priority date: 1964-01-17
Filing date: 1964-01-17
Publication date: 1966-11-29
Anticipated expiration: 1983-11-29

Description

Nov. 29, 1966 s L. BROWN, JR 3,288,949

MULTIPLE SWITCH ASSEMBLY HAVING STATOR CONTACTS WITH PRESTRESSED JAWS AND ALIGNMENT MEANS Filed Jan. 17, 1964 2 Sheets-Sheet l INVENTOR. S/DNE Y L. HKOWNJR Nov. 29, 1966 L BROWN, JR 3,288,949

5.. MULTIPLE SWITCH ASSEMBLY HAVING STATOR CONTACTS WITH PRESTRESSED JAWS AND ALIGNMENT MEANS Filed Jan. 17, 1964 2 Sheets-$heet 2 I NV ENTOR. S/DA/E Y L. BEUM/A/JZ United States Patent Ofiice Patented Nov. 29, 1966 MULTIPLE SWITCH ASSEMBLY HAVING STATQR CGNTACTS WITH PRESTRESSED JAWS AND ALIGNMENT MEANS Sidney L. Brown, J12, Union, Ohio, assignor to Ledex,

Inc, Dayton, Ohio, a corporation of Ohio Filed Jan. 17, 1964, Ser. No. 338,431 29 Claims. (Cl. 200-41) The present invention relates to a new and improved switch construction and more particularly to rotary selector switches for controlling electrical circuits. However, the invention is not necessarily so limited.

Modern rotary selector switches typically comprise a stator assembly including a series of annular insulating wafers mounted in fixed spaced relation and a rotor assembly including an equal number of insulating rotor wafers secured in axially spaced relation on a control shaft mounted for rotation within the stator assembly. Conductive contact elements secured respectively to the rotor and stator wafers are positioned to make electrical contact at selected rotary positions of the control shaft.

In the more popular construction the contacts on the rotor elements are in the form of thin, annular conductive strips having one or more blades projecting radially outwardly therefrom. correspondingly, the contacts on the stator wafers comprise radially inwardly directed fingers or jaws pre-stressed so as to have contacting surfaces at the innermost ends thereof. In operation, the contact blades of the rotor wafers wedge a path between the jaws of the stator contacts as the rotor wafers are rotated into contacting position. The pre-stressed condition in the jaws of the stator contacts is intended to assure a firm contact pressure between the rotor and stator contact elements.

Switch constructions of the foregoing type have been widely accepted in electrical industries and have long served the needs of these industries. However, a continuing demand for switch constructions having greater flexibility of assembly and greater reliability of operaton have exposed certain limitations in the construction techniques currently in use. As one example, the more popular switch constructions in use prior to the present invention involved the use of rivets or equivalent fastening means for fastening the stator contact elements to their supporting wafers. The passage of a rivet through the stator contact and its adjacent stator wafer unavoidably limits the effective length of the jaws of the stator con tact. This limitation in effective length becomes important when it is considered that the jaws of this contact are spread apart by flexure each time the rotor contact blade moves therebetween, and in the course of the operating life of a selector switch millions of such flexures may occur. This repeated flexure of the contact jaws produces metal fatigue. Obviously, with a shorter efi'ective jaw length, the jaw flexure is more intense and metal fatigue and consequent fracture sets in more rapidly.

An object of the present invention is to provide a new and improved selector switch construction which eliminates the need for rivets or equivalent fasteners for the stator contact elements and otherwise permits a maximum effective jaw length in the stator contact elements.

A problem related to that discussed in the preceding remarks resulted from the fact that the stator contact elements are ordinarily riveted or otherwise fastened to either one face or the opposite face of the supporting stator wafer. As a result, one jaw of the stator contact element either abuts or is positioned very closely to one face of the stator wafer, while the other jaw arches away from the face of the stator wafer. For satisfactory operation under these conditions, it has been necessary in the past to have an asymmetric design in the stator contact jaws which compensates for the limitations in movement of that stator jaw, which is adjacent the face of the supporting wafer element. Typically the asymmetric design in the jaws of the stator contact produces a greater contact pressure on one side of the rotor blades than on the other as the rotor blade moves between the jaws with the result thatfrictional wear between the rotor blades and the stator contact jaws is not uniformly distributed and one jaw or the other is premature damaged by excessive frictional wear.

Another object of the present invention is to provide a new and improved selector switch construction wherein a contact blade is caused to move between pre-stressed contact jaws and wherein the contact jaws are formed symmetrically so as to distribute frictional wear equally between the two contact jaws.

The pre-stressed jaws in the stator contacts of the prior art constructions are used to assure adequate contact pressure between the rotor contact blade and the stator contact jaws. However, even when pre-stressed jaws are employed, the contact pressure is limited by the tensile strength characteristics of the material forming the jaws and again is influenced by the effective length of the jaws. Thus, for a given contact material comparatively large contact pressures are obtainable when the jaws are short, but as the length of the jaws is increased to prolong jaw life the contact pressure reduces. Thus, in the prior art constructions there is an unavoidable conflict between the need for adequate contact pressure and a need for a maximum possible effective jaw length, i.e., operating life.

Another object of the present invention is to provide a new and improved switch construction wherein ample contact pressure is obtained without restriction in the effective jaw length and, accordingly, the operating life of the switch is not significantly affected by the magnitude of the contact pressure required.

A further problem brought about by the use of rivets or other fastener means to secure the stator contact elements to their supporting stator wafers resides in the inflexibility of design that this construction produces. Typically the stator wafer will have 12, 18 or 24 contact positions, but only a small fraction of the available contact positions will be used in any given application. In mass production operations, where a great quantity of identical switches are required, always to perform the same function, substantial economies can be effected by purchasing switch assemblies which have stator contacts only at the positions required for performance of the function needed to be performed. For applications involving a smaller volume, however, it is impractical to specially order switches having stator contacts only at selected positions and, accordingly, it is frequently necessary for small quantity users to buy wafer switches having unneeded and unused contact elements.

A further object of the present invention is to provide a new and improved selector switch having movable and replaceable stator contact elements.

Still a further object of the present invention is to provide a rivetless switch construction of a simplified design enabling assembly of contact elements with equal facility either by the switch manufacturer or by the ultimate consumer.

Still another limitation inherent in the rotary switch construction techniques employed today resides in the need for an assembly of spaced stator wa-fer elements. The stator wafer elements are spaced in prior devices to provide operating room for the stator contact jaws which are riveted to the one face or the other of the wafer. Thus, in the typical prior art assembly the stator wafers are separated by spacer elements which ensure an adequate insulating air gap between the jaws of adjacent stator wafers. This adds both to the weight and bulk of the selector switch assembly.

A further object of the present invention is to provide a new and improved rotary switch construction which permits adjacent stator wafers to be assembled in face contacting relation without sacrifice in the insulating medium between the contact elements in the stator assembly.

Yet another object of the present invention is to provide a new and improved rotary switch construction of optimum compactness.

A still further object of the present invention is to provide a new and improved method for the construction of rotary selector switches.

Other objects and advantages reside in the construction of parts, the combination thereof, the method of manufacture and the mode of operation, as will become more apparent from the following description.

In the drawings:

FIGURE 1 is a section view of a rotary selector switch constructed in accordance with the present invention, the section view having been taken along the line 11 of FIGURE 2.

FIGURE 2 is a side elevation view of the assembly from which FIGURE 1 was taken.

FIGURE 3 is a plan view of a blank employed in the construction of contact elements for use in the assembly of FIGURES 1 and 2.

FIGURE 4 is a perspective view illustrating a contact element fabricated from the blank of FIGURE 3.

FIGURE 5 is a plan view of a modified blank for forming contact elements.

FIGURE 6 is a perspective view illustrating a contact element formed with the blank of FIGURE 5.

FIGURE 7 is an end elevation view of a modified contact element formed from the blank of FIGURE 5.

FIGURE 8 is a sectional view taken substantially along the line 88 of FIGURE 1, the view being restricted to three of the five wafer elements which appear in FIG- URE 2.

FIGURE 9 is a perspective view of a modified contact element for use in switch assemblies constructed in accordance with the present invention.

Referring to the drawings in greater detail, one embodiment of the switch assembly of the present invention comprises an assembly of insulating stator wafers 10 which are stacked one on top of the other in face contacting relation. The stator wafers have an annular configuration so as to have concentric inner and outer peripheries. Positioned within the inner periphery of each stator wafer 10 is an insulating rotor wafer 12 which supports an annular, conductive ring 14. The ring 14 is quite thin, so as not to add appreciably to the thickness of the rotor wafer and is fixedly secured to the rotor wafer by any suitable means, such as integral fastener elements 15 embedded into the adjacent face of the rotor wafer.

In the particular switch construction illustrated, the ring 14 supports an integral tab or blade 18, which projects radially outwardly from the ring. This blade is adapted to selectively engage stator contact clips, such as the clips 16 and illustrated in FIGURE 1. Such clips may be supported at various circumferentially spaced positions by the stator wafers. As illustrated, the contact clip 16 may make continuous contact with the ring 14 and the contact clip 20 may be somewhat short in relation to the contact clip 16, so as to make contact with the blade 18 only when the blade 18 is aligned radially with the clip 20. Thus, with the particular assembly illustrated in FIGURE 1, the rotor ring 14 functions to establish a conductive path between the

clips

16 and 20 only when the blade 18 thereon is engaged by the contact clip 20.

For supporting contact clips, such as the

clips

16 and 20, the several stator wafers comprising the assembly illustrated in FIGURES 1 and 2 have circumferentially spaced radially extending grooves 22 formed therein, the grooves extending the full length between the inner and outer peripheries thereof. Similar grooves are formed in each face of each stator wafer, the grooves in one face being in registry with the grooves of the opposite face and the grooves having a depth which is less than half the thickness of the stator wafer, so that thin, insulating webs 21 separate the grooves 22 in the opposite faces of the wafers.

When two like stator wafers 10 are assembled in face contacting relation as shown in FIGURE 2, radially extending passages 23 are established at the interface between the two wafers by the grooves 22. As will be more fully described in the following, stator clips are received in these passages 23 wherever desired.

For the particular wafer embodiment illustrated, the stator clips are anchored in position by means of prestressed tabs which slide through shallow recesses 24 to deeper wells 26 formed adjacent the passages 23.

Clearance for free rotary movement of rotor contact rings 14 and any radially projecting blades 18 thereon is established by providing annular recesses 28 in the opposite faces of the contacting stator wafers at the inner margins thereof. The recesses 28 are preferably not as deep as the grooves 22 and, accordingly, are rendered discontinuous by the passage of the deeper grooves 22 radially through the recesses 28. As will be discussed more fully in the following, the recesses 28 are tapered in their bases so as to increase in depth from the inner peripheries of the stator Wafers to the radial outermost penetration of the recesses into the wafers.

As illustrated in FIGURE 2, the assembly of face contacting stator wafers 10 is capped at its ends by

plates

32 and 34, the entire assembly being secured by screws 30 which pass axially through the assembly at diametrically opposite positions remote from any grooves 22 in the wafer assembly. The rotor wafers 12 are provided with double D apertures which key to a control shaft 38 passing axially through the assembly. As illustrated in FIG- URE l, the double D aperture in each of the rotor wafers 12 may have a notch 40 at the margin thereof, which receives an axially extending rib 41 located on one of the flat sides of the shaft 38. The interfitting rib 41 and notch 40 limit to one the possible rotary positions of the rotor wafers on the shaft 38.

As previously mentioned, one rotor wafer 12 is positioned within each stator wafer 10. For each of the rotor wafers to be functional however, it is necessary to place appropriate grooves 22 in one of the

end plates

32 or 34, or in the alternative to use an extra stator wafer which would require no corresponding rotor wafer. In the assembly of FIGURES l and 2, the end plate 32 has appropriately located grooves 22 in the inside face thereof and appropriately located recesses 24 and wells 26 for receiving and anchoring stator clips between the end plate 32 and the adjacent stator wafer 10, thereby enabling functional cooperation of the rotor wafer received within said adjacent stator wafer 10. Preferably the

end plates

32 and 34 are fabricated from a durable electrically insulating material, such as phenol formaldehyde plastic, so that the control shaft 38 may be journalled for rotation in circular apertures formed at the centers of these plates. However, it will be understood that either or both of the end plates can be of conductive material in switch assemblies wherein a stator clip is not contacted by the conductive plate or plates, or wherein the circuitry renders a conductive end plate desirable.

As clearly appears in FIGURE 8, the annular rings 14 mounted on the rotor wafers 12 each have a greater outside diameter than the diameter of the supporting rotor wafer with the result that the outer margin of the ring 14,

projects into the annular channel between the recesses 28 formed in the stator wafer which receives the supporting rotor wafer and the contacting stator Wafer thereabove. By this construction each of the rotor wafers 12 is secured at its proper axial position in the assembly of stator wafers and there is no need to anchor the rotor wafers 12 against axial movement on the shaft 38. Rather, it is preferred not to anchor the rotor wafers 12 axially on the shaft 38 so that these wafers may home to their proper axial position. Freedom for this axial homing action is permitted by providing a rotor wafer thickness, which is less than the stator wafer thickness by an amount greater than the thickness of the conductive ring 14.

It is apparent that the recesses 28 at their shallowest points, i.e., the inner peripheries of the stator wafers in which they are formed are slightly greater in depth than one half the thickness of an annular ring 14. Thus, the assembled stator wafers 10, as illustrated in FIGURE 2, may be drawn securely into face contacting relation by the screws 30 without interferring with the rotation of the rotor wafers 12. For this same reason the diameter of each of the rotor wafers 12 is made smaller than the diameter of the inner periphery of each of the stator wafers 10.

A stator clip suitable :for use in the switch assembly of FIGURES l and 2 is illustrated in FIGURES 3 and 4. FIGURE 3 illustrates a blank 50 suitable for forming the clip of FIGURE 4. The blank 50 comprises

parallel fingers

52 and 54 terminating at an end of each with

rounded contact plates

56 and 58, respectively. The two

fingers

52 and 54 are joined at their inner margins by a connecting web 60.

Support wings

62 and 64, respectively, project from the outer margins thereof. The wings 6-2 and 64 include outwardly projecting

tabs

66 and 68, respectively. Trailing rearwardly from the

fingers

52 and 54 are

terminal strips

67 and 69, respectively. Preferably a window 70 is cut out of each of said terminal strips.

In forming the clip of FIGURE 4, the

tabs

66 and 68 in the

wings

62 and 64 are folded upwardly at right angles to the plane of the blank and then the clip wrapped in a rectangular box section to bring the

tabs

66 and 68 into substantial face to face contact, the tabs being so bent as to project outwardly from the box section. However, before the clip is wrapped to form the box section, the

contact plates

56 and 58 are dished downwardly into the plane of the paper and the

fingers

52 and 54, respectively, are developed axially to provide in each an arched portion 74 spaced from the contact plate, an oppositely curved spring portion 76 connecting the arched portion 74 with the box section, and an approximately linear strut 78 connecting the contact plate of such finger with the arched portion 74. As best seen in FIGURE 8, the strut portion 78 is essentially a linear extension to the side of the dished contact plate engaged thereby.

At the same time the

fingers

52 and 54 are developed axially, the

tabs

66 and 68 in the blank 50 are curved transversely so as to produce a divergence therebetween in the finally formed clip of FIGURE 4, the divergence increasing in the direction away from the

contact plates

56 and 58. Also, in the same forming operation the terminal strips 67 and 69 are each offset downwardly so that these strips engage in face contacting relation after the clip blank is wrapped into the box section. The Wrapped clip blank is temporarily retained in the desired clip configuration by folding an elongated end 88 of the terminal strip 67 over the end of the terminal strip 69.

In the finally formed clip of FIGURE 4, the

contact fingers

52 and 54 are symmetrical about a plane passing centrally therebetween, this plane coinciding with the plane of a line of separation between contacting edges of the

wings

62 and 64. The web 60 and the contacting

wings

62 and 64 cooperate to support the proximal. ends of the

fingers

52 and 54 at a minimum separation.

The axial development of the

contact fingers

52 and 54 is such that the contact plate of each would normally pass through the plane of symmetry therebetween. However, this is prevented by contact between the two

plates

56 and 58 at the plane of symmetry, the result being that the spring portions 76 are stressed as the clip blank is wrapped into its box formation.

It will be noted that the windows 70 in the terminal strips 67 and 69 are aligned in the final clip formation of FIGURE 4. This affords a convenient means for the attaching and soldering of wire conductors.

The contact clip of FIGURE 4 is carefully dimensioned with respect to the passages 23 formed in the stator wafers 18. Specifically, the box section which supports the

contact fingers

52 and 54 in confronting relation has a snug fit between the webs 21 which comprise the upper and lower walls of the passages 23. The opposing webs 21 thereby cooperate to limit the separation between the

wings

62 and 64.

The opposing arched portions 74 of the stator clip normally have a separation of their outer apices, which is slightly less than the separation between the webs 21. This provides clearance for separation of the

contact plates

56 and 58 against the bias of the spring portions 76. However, the clearance between each of the arched portions 74 and its confronting web 21 is preferably less than one half the thickness of the rotor blades 18. Thus, as the rotor blade 18 enters between the

contact plates

56 and 58 and wedges these plates apart by entering between the divergent, curved surfaces thereof, the wedging action is initially opposed only by the tension of the spring 76. However, before the blade 18 is fully between the

contact plates

56 and 58 the arched portions 74 contact the confining webs 21. This severely limits the action of the spring portions 76 and produces a positive contact pressure against the rotor blade 18 as this blade slides between the

contact plates

56 and 58.

The preferred dimensional relationship between the stator clips and the stator wafers is best illustrated in FIG- URE 8. This figure illustrates three face contacting stator wafers designated 10a, 16b and 10c. A first stator clip 28a is shown in its position within a passage formed by confronting grooves 22a and 22b in the wafers 10a and 10b, respectively. Within the stator wafer 10a is a rotor wafer 12a suppo ting an annular ring 14a. The angular orientation of the rotor wafer 12a with respect to its stator wafer 10a is such that no contact blade 18 on the annular contact ring 14a enters the stator clip 20a.

A rotor wafer 12]) is positioned within the inner periphery of the stator wafer 10b and supports a contact ring 14b. The angular position of the rotor wafer 12b with respect to its stator wafer 10b is such that a blade 18b is wedged between the contact plates of a stator clip 20b disposed between confronting grooves 220 and 22d in the stator wafers 10b and 100.

FIGURE 8 clearly illustrates that with no blade 18 between the contact plates of the stator clip 28a the arched portions 74 of such stator clip do not contact the webs 21a and 21b of the stator wafers 10a and 1%, respectively.

However, with the blade 1812 between the opposing contact plates of the stator clip 2.611 the arched portions 74 of such stator clip are in contact with the webs 21b and 21c of the stator wafers 10b and 100, respectively. Thus, the blade 18b in passing between the contact plates of the clip 28b has spread these plates against the spring tension in the contact clip 20b until the arched portions 74 have engaged the webs 21b and 2210. Thereafter further spreading of the contact plates has been resisted by the struts 78. Such further separation of the contact plates is accommodated by flexure in the strut 78 and by flexure in the arched portions 74. However, fiexure at these locations creates a restoring force significantly greater than that developed in the spring portions 76, the result being that the opposite sides of the blade 1817 are engaged with a desirably firm contact pressure.

Due to ordinary manufacturing variations, it will sometimes occur that the plane of symmetry between the

contact fingers

52 and 54 is not precisely aligned with the rotor blade which wipes therebetween. When this occurs the rot-or blade 18 may be flexed either upwardly downwardly, and it is to accommodate such flexure that the recesses 28 taper in depth as they advance outwardly from the inner peripheries of the stator wafers 10.

It is believed apparent that a clip, such as illustrated in FIGURE 4, is readily inserted into any of the passages 23 in the stator assembly of FIGURE 2 by advancing the contact fingers of such clip radially inwardly of a passage 23 from the outer periphery of the assembly. In inserting the clip into any desired passage 23, it is only necessary to align the

tabs

66 and 68 of the contact clip with the opening established by the recesses 24 in the opposing faces of the stator wafers 10. These recesses are each provided with a depth which is only slightly greater than the thickness of the original clip blank. Thus, the contacting

tabs

66 and 68 can slide with relative ease through the opening defined by these recesses. Immediately behind this opening, however, is an enlarged opening defined by the wells 26 in the opposing faces of the stator wafers. As soon as the

tabs

66 and 68 have entered this enlarged opening, the spring tension built into these tabs by the transverse curvature thereof causes the trailing margins of these tabs to spread apart, locking the contact clip into position inside the passage 23 into which it has been inserted.

I It will be apparent to those skilled in the art, of course, that a clip blank of the general type illustrated in FIG- URE 3 can serve for either the feeder clip 16, illustrated in FIGURE 1, or the contact clip 20, also illustrated in FIG- URE 1, the only essential difference being in the length of the

contact fingers

52 and 54.

While in the foregoing remarks, a technique has been described for providing an initially low resistance to entry of the rotor blades 18 between the

contact plates

56 and 58 of the stator clip, followed by a markedly increased resistance as the arched portions 74 of the stator clip engage the confining webs 21, it is to be understood that variations are possible. Thus, by providing a greater initial separation between the arched portions 74 and their confining webs 21, the contact pressure between the

contact plates

56 and 58 and the rotor blade 18 may be reduced to that provided only by the tension in the spring portions 76. As another variation, the contact pressure may be increased substantially by designing the arched portions '74 with an initial separation greater than that between the confining webs 21, with the result that the effective spring length in the

contact fingers

52 and 54 is substantially reduced. As a furthe variation, the

contact fingers

52 and 54 may be normally separated slightly (a distance less than the thickness of the blade 18) so as to be fully relaxed before entry of the rotor blade therebetween. This provides a more favorable entry angle for the blade 18 without reducing the final contact pressure once the blade is fully between the

contact plates

56 and 58,

One of the numerous beneficial results of the present construction is that the contact clips may be removed, replaced and changed in position at will. Non-destructive removal is readily accomplished by a loosening of the screws 30 which secure the stator wafers so as to allow a sufficient opening between normally contacting stator wafers for removal of the clip.

For most constructions it is preferred that the stator wafers be fabricated of a material which is substantially stronger than the comparatively thin sheet material used in the formation of the stator clips. This permits the stator clips to be removed destructively without loosening of the screws 30 and without harm to the stator wafers. In such destructive removal, the clip is pulled firmly out of its passage 23, causing the

tabs

66 and 68 of the clip to tear sufficiently from the balance of the clip to permit withdrawal of the clip. To facilitate such removal the

tabs

66 and 68 may be weakened by score lines. Such removal can also be facilitated by tapering the radial outermost walls of the wells 26 so that the

wings

62 and 64 of the clip receive an inward force causing these wings to fold inwardly as a strong radial outward force is applied to the clip.

FIGURE 5 illustrates a modified clip blank and FIGURE 6 illustrates a modified clip formed fro-m the blank of FIGURE 5. The clip blank 100 comprises axially

parallel contact fingers

104 and 106 interconnected by an elongated terminal strip 102.

Wings

112 and 114 flank the contact finger 104 and

wings

116 and 118 flank the contact finger 106.

Tabs

120, 122, 124 and 126 project outwardly from the

wings

112, 114, 116 and 118, respectively.

The clip blank of FIGURE 5 is adapted to be formed into a clip by folding the terminal strip 102 at its midpoint, so as to bring the

contact fingers

104 and 106 into confronting parallel relation. Before the terminal strip is folded, however, forming operations similar to those performed on the clip blank of FIGURE 3 are performed. Thus, contact plates and 107 at the distal ends of the

contact fingers

104 and 106 are dished and the remainder of each finger developed axially to form therein an arched portion 127, a spring portion 128 and a strut 130, as previously described. The

various tabs

120, 122, 124 and 126 are also turned at right angles to their respective wings and twisted transversely for the reasons previously described. The

wings

112, 114, 116 and 118 are also turned at right angles to the initial plane of the clip blank and the terminal strip 102 is offset from the plane of the clip blank.

When the terminal strip 102 is folded along its center line the

wings

112 and 116 engage in edge to edge contact as their

respective tabs

120 and 124 move into confronting relation. Similarly, the

wings

114 and 118 engage in edge to edge contact as their

respective tabs

122 and 126 move into confronting relation. As with the previous embodiment, the

contact fingers

104 and 106 move into positions which are symmetric about a plane passing therebetween. Due to the axial development of the contact fingers, as illustrated in FIGURE 6, the

contact plates

105 and 107 engage one another before the terminal strip 102 has been folded a full Thus, when the terminal strip is ultimately folded a full 180 the spring portions 128 of the contact members are stressed, thus accomplishing substantially the same prestressed condition described in connection with the clip of FIGURE 4.

In its final form the clip of FIGURE 6 has structural features substantially identical to those described in connection with the clip of FIGURE 4, the chief difference being that the clip of FIGURE 6 has two lines of separation in the plane of symmetry. The first line of separation is between the

wings

112 and 116 and the second line of separation is between the

wings

114 and 118. A further structural distinction arises from the fact that the particular clip illustrated in FIGURE 6 is provided with two pairs of oppositely extending tabs, whereas the clip of FIGURE 4 has only a single pair of tabs.

Due to the provision of a second pair of tabs in the clip of FIGURE 6, the stator wafers which receive this clip require a modification (not shown) over those illustrated in FIGURES l and 2. Specifically, the stator wafers are modified by providing adjacent each of the grooves 22 therein a second recess and well on the side opposite the recesses 24 and wells 26, already illustrated in FIGURE l.v

This provides a means for receiving and looking into position both pairs of tabs illustrated in the clip embodiment of FIGURE 6.

It will be recognized by those skilled in the art that the insertion, operation and removal of the clip of FIGURE 6 is accomplished in essentially the same fashion as the in- 9 sertion, operation and removal described with reference to the clip of FIGURE 4.

As previously described with reference to the clip of FIGURE 4, suitable windows 134 may be provided in the terminal strip 102 of the clip of FIGURE 6 to facilitate attachment of wire conductors and the like to the terminal portion of the clip.

FIGURE 7 illustrates a modified development of the blank of FIGURE 5. In this modification the

wings

112, 114, 116 and 118 of the FIGURE 5, blank, instead of being turned at right angles to the plane of the clip blank as previously described, are developed into the circuit configuration illustrated in FIGURE 7. The axial development of the contact fingers 1M and 106 is the same as that previously described.

The clip of FIGURE 7 is suitable for use in the basic stator assembly illustrated in FIGURES 1 and 2, the only modification required being the provision of additional recesses and wells to receive the extra set of locking tabs provided in the clip of FIGURE 7. Of course, the modification of FIGURE 7 makes possible a further modification in the stator wafer assembly in that the grooves 22 formed therein may be formed in the shape of semi-circular troughs, so as to provide circular passages extending radially between the stator wafers rather than the rectangular passages 23 illustrated in FIGURE 2.

FIGURE 9 illustrates a further modification in the clip design. The clip of FIGURE 9 is fabricated from a clip blank similar to that illustrated in FIGURE 3, the essential difference being that the

tabs

66 and 68 are eliminated from the blank and a tongue 86 is struck upwardly from the web 60, so as to project rearwardly of the contact fingers '52 and 54. The structural features of the clip of FIGURE 9 are otherwise substantially identical to the structural features of the clip of FIGURE 4.

The clip of FIGURE 9 offers the advantage that the recesses 24 and adjacent wells 26 in the stator wafers 10 of the preferred embodiment may be eliminated and the clip of FIGURE 9 secured in position solely by friction arising from pressure of the upwardly struck tongue 86 against the side Walls of the radial passages 23. Alternatively suitable notches, not illustrated, may be provided in the side walls of the grooves 22 to receive the upwardly struck tongue 86 of the clip of FIGURE 9 and thereby positively lock the clip in position.

In the preferred construction of switch devices embodying the present invention, the stator wafers 10 comprise a molded plastic material of suitable insulating qualities which may or may not incorporate a filler such as natural or synthetic fibers. The stator contact clips and the rotor contact rings are preferably formed from a mild steel which is easily cut to the desired clip blank shape and developed to the final clip shape.

In producing the clips it is found convenient to commence with a continuous strip which is pierced to form a continuing series of clip blanks interconnected at the wings or tabs which flank the contact plates. If desired, the contact plates may be electroplated at this point with suitable metal to improve the contact qualities thereof. The clip blanks of the interconnected series are then fed successively into a forming die which forms the final clip and at the same time separates the blank being formed from the continuing series of clip blanks which follow it.

From the foregoing description it Will be apparent that the present invention provides a selector switch construction which is readily produced with conventional fabricating equipment and which offers the advantages of prolonged contact life, greatly enhanced design flexibility, and simplified assembly and repair.

Although the preferred embodiments of the invention have been described, it will be understood that within the purview of this invention various changes may be made in the form, details, proportion and arrangement of parts, the combination thereof and mode of opera- 10 tion, which generally stated consist in a device capable of carrying out the objects set forth, as disclosed and defined in the appended claims.

What is claimed is:

1. A conductive contact element comprising a single sheet of conductive material shaped to have an annular body portion surrounding a central axis, a pair of elongated contact fingers supported by diametrically opposite wall portions of said annular body and extending axially therefrom in generally parallel coextensive and confronting relation, each said contact finger including a contact plate at the end thereof distant from said annular body and arched means intermediate said contact plate and said annular body, said contact fingers being substantially symmetric about a plane passing through said central axis and said contact plates being in confronting relation.

2. A conductive contact element according to claim 1 wherein said annular body has a seam of separation between normally contacting margins of said sheet material, said seam being parallel to said plane of sym metry and including an integral tab of said sheet material projecting radially outwardly from said annular body from each said margin, said tabs having confronting but oppositely inclined faces.

3. A conductive contact element comprising a pair of resilient elongated contact fingers and support means engaging proximal ends of said contact fingers to support same in generally parallel coextensive and confronting relation, each said contact finger including a contact plate at the distal end thereof, a resilient spring portion adjacent the proximal end thereof, and an arched portion interconnecting said contact plate and said spring portion, said contact fingers being substantially symmetric about a plane passing centrally therebetween, said spring portions being longitudinally arcuate with the convex surface of the spring portion of one contact finger confronting the convex surface of the spring portion of the other contact finger, the arched portions in said contact fingers confronting one another and arching oppositely away from one another.

4. An conductive contact element according to claim 3 wherein said support means supports the proximal ends of said contact fingers at an inclination to and separation from said plane of symmetry which normally would require that each contact finger cross said plane of symmetry, the construction being such that said contact plates contact one another in said plane of symmetry and said spring portions of said contact fingers bias said contact plates together.

5. A conductive contact element according to claim 4 wherein the apices of said confronting arched portions have a separation therebetween which is less than the separation between the proximal ends of said contact fingers.

6. A contact element according to claim 3 wherein said contact plates each have a transversely extending convexly curved surface confronting the other contact plate.

7. In a device of the class described, an electrically insulating mounting having spaced confronting wall portions, a conductive contact element, said contact element comprising a supporting body supported by said mounting and generally parallel elongated and coextensive finger portions supported at proximal ends thereof by said supporting body, said finger portions projecting lat erally between said wall portions, said finger portions having confronting contact plates at the distal ends thereof and having confronting arched portions intermediate the proximal and distal ends thereof, said confronting arched portions arching oppositely away from one another toward said opposing wall portions, a contact blade, and means supporting said contact blade for movement relative to said mounting along a path passing between said contact plates, the thickness of said blade exceeding any difference between the distance between said wall portions 1 l and the distance between said arched portions at their outer apices.

8. In a device of the class described, the combination according to claim 7 wherein said insulating morunting comprises an insulating body having a passage extending therethrough and receiving said contact element, said opposing wall portions comprising opposite interior walls of said passage.

9. In a device of the class described, the combination according to claim 8 wherein said insulating body is an annular body having an outer periphery and an inner periphery and wherein said passage extends between said inner and outer peripheries.

10. In a device of the class described, the combination according to claim 9 wherein said insulating body comprises two insulating wafers each having inner and outer peripheries and joined in face to face contact, said passage extending between said inner and router peripheries and being located at the interface between said wafers, said opposing wall portions being located one on each wafer.

11. In a device of the class described, the combination according to claim 10 wherein each wafer has a groove traversing the contacting face thereof between said inner and outer peripheries, said grooves being aligned to establish said passage and said "opposed wall portions comprising the bottom surfaces of said grooves respectively.

12. In a device of the class described, an electrically insulating mounting having spaced confronting wall portions, an electrically conducting contact element comprising elongated and substantially coextensive finger portions and means engaging proximal ends of said finger portions to suppolt said finger portions in generally parallel confronting relation, said finger portions having confronting contact plates at the distal ends thereof and having confronting oppositely arched portions intermediate the proximal and distal ends thereof, and interfitting means of said contact element and said mounting securing said contact element to said mounting at a :position wherein said finger portions project laterally between said wall portions and said arched portions arch oppositely toward said wall portions, a contact blade, and means supporting said contact blade for movement relative to said mounting along a path passing between said contact plates, the thickness of said blade exceeding any difference between the distance between said wall portions and the distance between said arched portions at their outer apices.

13. In a device of the class described, the combination according to claim 12 wherein said insulating mounting comprises a pair of annular wafer elements each having concentric inner and outer peripheries, said wafer elements each having a radially disposed groove in one face thereof extending between said inner and outer peripher ies and said wafers being joined in face-contacting relation with the grooves thereof in confronting relation whereby said grooves define a radially disposed passage rat the interface Ibetween said wafers, said finger portions of said contact elements projecting substantially radially in said passage and said opposed wall portions of said mounting comprising opposing bottom surfaces of said grooves.

14. In a device of the class described the, combination according to claim 13 wherein one of said wafers has a recess in a wall thereof confronting the groove therein, and said interfitting means of said contact element and said mounting comprises a tab projecting from said contact element into said recess to interfit the wall thereof.

15. In a device of the class described, the combination according to claim 13 wherein said interfitting means comprises a shoulder on a Wall of one of said wafers confronting the groove therein and a tab projecting from said contact element to engage said shoulder.

16. In a device of the class described, an insulating stator mounting which is a substantially solid annular body having inner and outer peripheries concentric to a common axis, said mounting having a radially extending passage therein communicating between said inner and outer peripheries and having an annular channel at the inner periphery thereof surrounding said common axis and projecting radially outwardly from said inner periphery a limited distance toward said outer periphery, said channel communicating with said passage, a rotor element, means supporting said rotor element within said inner periphery for rotation about said common axis, a first contact member disposed in said radially disposed passage and having a portion thereof in said channel, and a second contact member carried by said rotor element and projecting radially outwardly therefrom into said channel for selective engagement with said first contact member upon rotation of said rotor element relative to said stator mounting to align said second contact member with said first contact member.

17. The combination according to claim 16 wherein said second contact member is a radially disposed blade occuping a plane normal to said common axis and Wherein said annular channel diverges to accommodate flexure of said blade out of the plane thereof.

18. The combination according to claim 16 wherein said first contact member includes a pair of elongated resilient fingers disposed radially in said passage, and means supporting said fingers in confronting coextensive relation, said fingers projecting from said support means toward the inner periphery of said stator mounting and terminating at the ends thereof which are distal with respect to said support means with confronting contact plates, and wherein said second contact member comprises a radially disposed blade occupying a plane normal to said common axis and adapted to wipe between said contact plates.

19. The combination according to claim 18 wherein said fingers each have an arched portion intermediate the contact plate thereof and said support means, said arched portions arching oppositely toward confining Walls of said passage.

20. The combination according to claim 19 wherein said arched portions arch to a maximum separation less than the separation between said confining walls and wherein said blade has a thickness greater than the difference between the separation of said confining walls and said maximum separation of said arched portions.

21. A contact support assembly for use in a rotary selector switch comprising a series of three annular insulating wafers each having inner and outer peripheries encircling a common axis, and means supporting said wafers in face contacting relation with one wafer interposed between the other two, said one wafer having a radially disposed first groove extending between its inner and outer peripheries in each face thereof, said first grooves having a combined depth which is less than the thickness of said one wafer and being in registry whereby a Web of said Wafer separates said grooves, each of said other wafers having a second groove extending between its inner and outer peripheries in the contacting face thereof, the second groove in each other wafer being registered with and confronting the first groove in the face of said one wafer contacted by such other wafer, said confronting grooves in the contacting faces of said wafers establishing a radially disposed passage at each interface between said wafers, said passages each being adapted to receive a conductive contact element for said selector switch and said web in said one Wafer being adapted to insulate said contact elements one from the other.

22. The contact support assembly according to claim 21 wherein said one wafer has an annular recess adjacent the inner periphery thereof in each face thereof, said recesses providing annular channels projecting radially outwardly from the inner periphery of said assembly at each interface between said wafers, said channels each being adapted to receive a movable contact blade.

23. The contact support assembly according to claim 22 wherein the depth of each said recess progressively increases from the inner periphery of said one wafer to the radial outermost extent of said recess in said one wafer, said channels thereby diverging in depth in progressing outwardly from said inner periphery to provide clearance for flexure of said contact blades.

24. A contact support assembly for use in a rotary selector switch comprising a pair of annular insulating wafer members each having inner and outer peripheries encircling a common axis, each of said wafer members having a radially disposed groove extending between its inner and outer peripheries in a first face thereof, and means supporting said wafers in coaxial relation with the first faces thereof in Contact and with the grooves in said first faces in registry, whereby said grooves define a radially disposed passage at the interface between said wafers, said passage being adapted to receive a conductiv'e contact element for said selector switch.

25. The contact support assembly according to claim 24 wherein each said wafer member has an annular recess in its first face located adjacent its inner periphery, each recess having limited radial outward extent and communicating with the radially disposed groove in the same first face, said recess'es cooperating to provide an annular channel at the interface between said wafers extending radially outwardly from the inner periphery of said assembly for receipt of a movable contact blade for engaging said contact element.

26. The contact support assembly according to claim 25 wherein each said recess has a depth which increases progressively in the radially outward direction from said inner periphery whereby the channel defined thereby diverges in the radial outward direction from said inner periphery to provide clearance for fiexure of said contact blade.

27. In a rotary selector switch the combination comprising, a pair of annular wafers each having inner and outer peripheries encircling a common axis, one of said wafers having a radially disposed groove in one face thereof extending between said inner and outer peripheries, means supporting said wafers in face contacting coaxial relation with the grooved face of said one wafer confronting a face of the other wafer, whereby said groove establishes a radially disposed passage at the interface between said wafers, one of said wafers having an annular recess in the contacting face thereof adjacent the inner periphery thereof, said recess providing an annular channel between said Wafers extending radially outwardly from the inner peripheries thereof and communicating with said passage, a first contact member disposed within said inner peripheries and having a contact portion projecting into said channel, means supporting said first contact member for rotation about said common axis whereby said contact portion has orbital movement through said annular channel, and a second contact member disposed in said passage and engaged by one of said Wafers, said second contact member having a part thereof projecting into said annular channel for engagement with said contact portion.

28. In a rotary selector switch the combination according to claim 27 wherein said first contact member com- .prises a third wafer having an outer periphery fitting within the inner peripheries of said face contacting wafers, and an annular conductive ring supported by said third wafer in concentric relation to said common axis, said conductive ring having a peripheral flange disposed in said annular channel, and said contact portion comprising a blade element supported by said conductive ring projecting outwardly from said peripheral flange in said annular channel, the confronting surfaces of said wafers which comprise the opposite walls of said annular channel confining said peripheral flange within said annular channel.

29. In a rotary selector switch, the combination according to claim 28 including a third contact member supported by one of said face contacting wafers in peripherally spaced relation to said second contact member, said third contact member slidably engaging said peripheral flange whereby said third contact member engages said first contact member at all rotary positions thereof.

References Cited by the Examiner UNITED STATES PATENTS 2,736,875 2/1956 Protz 339-198 2,750,572 6/1956 Fox 339210X 2,828,393 3/1958 Wingard 20011 X 2,924,808 2/1960 Hewes et al 339-210 X 3,104,925 9/1963 MacNamara 339-376 X 3,171,906 3/1965 Allison 200166 X ROBERT K. SCHAEFER, Primary Examiner.

KATHLEEN H. CLAFFY, Examiner.

I. R. SCOTT, Assistant Examiner.

Claims

7. IN A DEVICE OF THE CLASS DESCRIBED, AN ELECTRICALLY INSULATING MOUNTING HAVING SPACED CONFRONTING WALL PORTIONS, A CONDUCTIVE CONTACT ELEMENT, SAID CONTACT ELEMENT COMPRISING A SUPPORTING BODY SUPPORTED BY SAID MOUNTING AND GENERALLY PARALLEL ELONGATED AND COEXTENSIVE FINGER PORTIONS SUPPORTED AT PROXIMAL ENDS THEREOF BY SAID SUPPORTING BODY, SAID FINGER PORTIONS PROJECTING LATERALLY BETWEEN SAID WALL PORTIONS, SAID FINGER PORTIONS HAVING CONFRONTING CONTACT PLATES AT THE DISTAL ENDS THEREOF AND HAVING CONFRONTING ARCHED PORTIONS INTERMEDIATE THE PROXIMAL AND DISTAL ENDS THEREOF, SAID CONFRONTING ARCHED PORTIONS ARCHING OPPOSITELY AWAY FROM ONE ANOTHER TOWARD SAID OPPOSING WALL PORTIONS, A CONTACT BLADE, AND MEANS SUPPORTING SAID CONTACT BLADE FOR MOVEMENT RELATIVE TO SAID MOUNTING ALONG A PATH PASSING BETWEEN SAID CONTACT PLATES, THE THICKNESS OF SAID BLADE EXCEEDING ANY DIFFERENCE BETWEEN THE DISTANCE BETWEEN SAID WALL PORTIONS AND THE DISTANCE BETWEEN SAID ARCHED PORTIONS AT THEIR OUTER APICES.