US3260805A

US3260805A - Rotary switch with detent

Info

Publication number: US3260805A
Application number: US376522A
Authority: US
Inventors: George E Pihl
Original assignee: Miniature Electronic Components Corp
Current assignee: Minelco Inc; Miniature Electronic Components Corp
Priority date: 1964-06-19
Filing date: 1964-06-19
Publication date: 1966-07-12
Anticipated expiration: 1983-07-12

Description

July 12, 1966 ca. E. PIHL 3,260,805

' ROTARY SWITCH WITH DETENT Filed June 19, 1964 FIG. 2

TNVENTOR.

GEORGE E. PiHL ATTORNEY United States Patent 3,260,805 ROTARY SWITCH WITH DETENT George E. Pihl, Abington, Mass., assignor to Miniature Electronic Components Corp., Holbrook, Mass., a corporation of Massachusetts Filed June 19, 1964, Ser. No. 376,522

11 Claims- (Cl. 20011) This invention relates to switches and more particularly to miniature multi-position rotary switches.

The trend to smaller and smaller electronic components has created a need for miniature multi-position rotary switches. Although at first blush it would appear that thisjneedcould be satisfied by simply miniaturizing a conventional, larger-scale design, further consideration reveals, that this approach is not satisfactory because the small volume of space available in a miniature housing will notaccommodate all of the elements required by the conventional design, even though reduced in size, or because certain elements cannot 'be reduced in size without impairing their effectiveness. Particular difiiculty has been incurred in keeping the axial length of the switch housing to one-half inch or less and also in providing satisfactory detent means for restraining the operating shaft so. that its rotational movement from one position to another is characterized by a snap action. Other problems having been difiiculty of assembly, erratic behavior under varying atmospheric conditions, and limited number or" switch positions.

Accordingly, the primary object of the present invention is to provide a new andimproved miniature rotary switch. further object of the present invention is to provide a multi-position rotary switch which can be contained in a housing whose length and breadth are in the order of one-halfinch or less. Another object'of this invention is to provide a new and :improved rotary switch of the type embodying a pluralityof switch segments each positioned to be selectively engaged by a contact member attached to and movable with a rotatable operating shaft, the new switch including a novel detent mechanism for the. shaft which permits the contact member to be stepped from one switch segment to another yet holds the contact member on a selected switch segment in the absence of a turning force applied externally to said shaft.

Other objects and many of the attendant advantages of the present invention will become more readily apparent from thefollowing detailed specification when considered together with the accompanying drawings wherein:

FIG. 1 is a perspective view of a switch unit representing a preferred embodiment of the present invention;

' FIG. 2 is a vertical sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a plan sectional view taken along line 33 of FIG. 2;

' FIG. 4 is a plan sectional view taken along line 4-4 of FIG. 2.; and

FIG. 5 is a bottom view of the same switch unit.

. Referring now to FIGS. 1 and 2, the illustrated embodiment. comprises a cylindrical housing 2 which as. formed is open at one end 4 and has an end wall 6 at the other end. The end wall has an offset portion 8 with a=centrally located opening 10 to accommodate an operating shaft 12. The offset in end wall 6 provides a recess to accommodate a resilient O-ring 14.

. The upper end of shaft 12 projects out from end wall 6- and is provided with a kerf as shown at 16 to accommodate a screwdriver whereby it may be rotated. The shaft has a bottom end portion 20 of substantially reduced diameter, and immediately adjacent thereto -it is provided with a cam in the form of a polygonally shaped 3,260,805 Patented July 12, 1966 flange 22. In the illustrated embodiment of the invention, flange 22 has six flat edge surfaces 24 (seen best in FIG. 3). Attached to the upper side of flange 22 is a stop member 26 in the form of a thin plate having a central aperture so as to fit over shaft 12. Stop member 26 has a circular outer edge 28 (FIG. 3) characterized by a projecting portion 30 which extends over a predetermined angle. Cooperating with stop member 26 is a cylindrical ring 32 which is secured within housing 2 adjacent to end wall '6. Preferably, ring 32 is press-fitted in the housing. Ring 32 has an inwardly propecting portion 34 which may be considered a stationary stop member. The projecting portion 34 terminates short of the circular outer edge 28 of stop member 26 but extends far enough to intercept its projecting portion 30 when the shaft is rotated.

At its upper end, the ring 32 is slotted at four different places along two distinct parallel chords, each spaced from the rings longitudinal axis a distance slightly less than the corresponding distance for each edge surface 24. As shown in FIG. 3, one pair of slots is identified by the numeral 38; the other pair by the numeral 40. Each pair of slots accommodates a flat leaf spring, shown at 42 and 44. Each spring has a thickness substantially less than the corresponding dimension of the slot in which it resides. Additionally, its width, i.e., its vertical dimension as seen in FIG. 1, is substantially less than the depth of the slot. The length of each spring is limited so that only one of its ends at a time can engage housing 2. As a consequence, the springs make a loose fit in the slots and will not bear against stop member 26 or flange 54 (described hereinafter). More importantly, the loose fit allows the springs to pivot at their ends on flexing and thus prevents them from rupturing due to bending against the sharp edges which define the inner ends of

slots

38 and 40. The spacing of the slots is such that the springs are bowed outward by flange 22 and press against opposite ones of the edge surfaces 24 (as shown in FIG. 3), thereby providing a detent action for shaft 12. The extent of bowing is sufficient for the springs to engage the opposite edge surfaces only at the ends thereof. This gives a detent action which can be readily felt. The springs oppose rotation of shaft 12 but will flex to permit the shaft to be advanced either clockwise or counterclockwise on application of suflicient torque. The springs will return to their normal bowed position each time the shaft is rotated 60 degrees. In this connection, it is to be noted that projecting

portions

30 and 34 each are 30 wide and that projecting portion 30 is in line with the junction of two of the edge surfaces 24 of flange 22. Therefore, regardless of whether shaft 12 is rotated clock wise or counterclockwise, when its rotation is terminated by engagement of projecting portion 30 with its stationary counterpart 34, two of the fiat surfaces 24 will be substantially parallel to

springs

42 and 44 in the manner shown in FIG. 3. In other words, the

stop members

26 and 34 are designed to permit shaft 12 to occupy any of the six positions determined by the detent mechanism While at the same time preventing it from rotating through an angle of 360 or greater. Of course, elimination of stop member 26 or removal of its projection 30 will free the shaft for rotation through any desired angle. It is to be appreciated also that increasing the circumferential dimension of projection 30 so that it extends through a greater angle will decrease the size of the angle through which the shaft may be rotated before being stopped by the stationary stop member 34. Thus, enlarging projection 30 so as to cover a span of would permit the shaft to assume only five of the discrete positions determined by the detent mechanism. Similarly, enlarging projection 30 so as to to span angles of 210, and 270 would decrease the number of detent-held switch positions to 4, 3, and 2, respectively. The same result also may be achieved by varying the circumferential dimension of stationary stop member 34 by increments of 60. However, the latter approach is not preferred since it is more expensive and less convenient. In practice, the number of positions which the shaft is permitted to assume is keyed to the number of switching operations desired.

Attached to the bottom end of shaft 12 is an assembly comprising an insulator sleeve 58 and a metal sleeve 52. Sleeve 50 is sized to snugly accept the reduced diameter portion of the shaft and has a flange 54 which engages the underside of flange 22. Sleeve and its flange 54 are cemented to shaft 12. The metal sleeve 52 is fitted over sleeve 50 and has a flange 56 which engages flange 54. Sleeve 52 and its flange 56 are cemented to sleeve 58 and its flange 54. As seen best in FIG. 4, sleeve 52 is split at 90 intervals, as shown at 60, and fits onto a metal stud 62 which forms part of a printed circuit board assembly. The latter comprises upper and lower

plastic boards

64 and 66, respectively, which are cemented to each other and to the housing by an insulating cement, such as an epoxy cement. Both boards have a central aperture. Stud 62 is mounted in the aperture of board 66 and is provided with a peripheral flange 68 which overlies the inner surface of board 66. The stud is cemented in place with a suitable insulating cement. Alternatively, it could be soldered to the printed circuit board 66 with the latter being provided with a metal land for solder adherence. The aperture in the upper board 64 is larger than the peripheral flange of stud 62 so as to leave an insulating air gap 78. With the printed circuit board assembly secured to the housing, the stud 62 functions to rotatably retain split sleeve 52 with the bottom end of the latter bearing against flange 68 of the stud. The inside diameter of sleeve 52 is made approximately the same or slightly smaller than the outer diameter of the upper part of stud 62. The four splits in sleeve 52 permit it to expand suificiently to fit onto the stud. The inherent resiliency of sleeve 52 causes it to grip stud 62 tight enough to keep shaft 12 aligned and to make good electrical contact with the stud while simultaneously permitting the shaft to be rotated relative to the housing.

As shown in FIG. 4, the upper circuit board 64 is provided with six evenly spaced conductive switch segments 72 on its upper surface. The segments terminate short of the inner and outer edges of board 64 so as to electrically isolate them from each other and the housing. Details of the lower circuit board 66 are illustrated in FIG. 5. Board 66 is provided with six circular conductive layers 74 on its bottom surface. These conductive layers 74 are located at equal distances from the center of the board but are arranged in two groups of threes. The board 66 also is provided with six holes 76, each of which is common to one of the layers 74. However, holes 76 are offset relative to the centers of layers 74- so that each of the aforesaid groups of three are arranged in a straight line. The four corner holes 76a, 76c, 76d, and 767 accommodate terminal wire leads 78 which extend through four correspondingly located holes formed in the upper board 64. Leads 78 are soldered to the conductive layers 74 as well as to the switch segments 72. Two additional terminal leads 82 are positioned in holes 76b and 76a but do not extend into the upper board 64. Leads 82 are soldered to the conductive layers 74 which surround holes 76b and 766. Leads 82 are electrically coupled to separate switch segments 72 by two short wire leads 84 which are located in matching holes formed in the two

boards

64 and 66. Leads 84 are soldered at their top ends to the switch segments and at their bottom ends to the conductive layers 74 which surround and are soldered to leads 82. In addition to terminals leads 78 and 82, a seventh lead 86 is soldered in place in a hole formed in the bottom end of stud 62. A potting compound 87, which is applied to the opened end 4 of the housing after the printed circuit board assembly has been mounted in place, serves to provide support to the

leads

78, 82, and 86 as well as to seal off the interior of the switch unit.

The switch segments ar selectively contacted by a wiper assembly which is secured to sleeve 52. The wiper assembly comprises a spring washer 88 which is bent so that one portion may be welded to flange 56 of sleeve 52, as shown at 90 in FIG. 1, while a diametrically opposed portion will be spaced from flange 56 in offset relation to the welded portion. A button contact 92 is welded to the offset portion of the washer. The latter is made tangent to flange 56 at the area where it is welded thereto so that the washer is always eccentric to the axis of rotation of shaft 12. This eccentricity makes it possible for the button contact to engage each switch segment 72 at a point well spaced from its inner edge without increasing the size of the washer or requiring that the button contact be mounted on an extension attached to the washer. The washer support for the button contact also offers the advantage of identical contact pressure for both clockwise and counterclockwise rotation. The wiper assembly is oriented so that in each given position of the shaft determined by the detent mechanism the button contact 92 will be evenly centered on a switch segment 72. A marker 94 may be provided on the upper end of shaft 12 to indicate the general position of th button contact.

It is believed to be apparent that the illustrated switch permits six different circuits to be selectively connected to leads 86 by way of leads 78 (or 82 and 84), switch segments 72, contact 92, washer 88, flange 56, sleeve 52,

and stud 62. The detent mechanism operates to maintain contact 92 in engagement with a selected switch segment until shaft 12 is rotated to another position. It also is believed to be apparent that the number of switch segments can be made lesser or greater and that the number of flat surfaces on flange 22 can be varied correspondingly. Thus, for example, only four switch segments need be used, in which case, flange 22 would be given a square rather than a hexagonal shape. At the same time, the projecting

portions

30 and 34 which make up the stop mechanism also could be modified to change the limits of movement of shaft 12 to the extent deemed necessary for the lesser number of switch segments.

The invention herein described and illustrated has certain notable advantages. For one thing, the switch can be made very small; six position switches have been made with an overall housing height of about .240 inch and a diameter of less than .35 inch. Another advantage is that the detent mechanism is simple yet dependable and has a long life. A third advantage is that the illustrated embodiment is easy to assemble since it comprises discrete subassemblies which can all be inserted from the bottom end of the housing. terminal leads 78, 82, and 86 are arranged in three straightline groupings which facilitate printed circuit board or panel mounting. A fifth advantage is that excellent insulation of parts is achieved where necessary but not at the expense of introducing cumbersome structural components. In this connection, it is to be observed that both housing 2 and shaft 12 may be made of conductive or nonconductive materials without affecting operation of the invention since they are both insulated with respect to the switch segments and the wiper assembly.

It is to be understood that the invention is not limited in its application to the details of construction and arrange- .ment of parts specifically described or illustrated, and that within the scope of the appended claims, it may be practiced otherwise than as specifically described or illustrated.

I claim:

1. A rotary switch comprising a housing; a printed circuit board assembly secured in one end of said housing; said assembly comprising a plurality of conductive switch segments and terminal leads connected to said segments and accessible for circuit connections outside of said housing; a shaft rotatably mounted in and protruding from the Still another advantage is that the other end of said housing; a sleeve extension on the inner end of said shaft; bearing means supported -by said circuit board assembly and coacting with said sleeve to limit movement of said shaft toward said circuit board and also to maintain said shaft in alignment within said housing, said bearing means comprising a stud having a first portion that fits within said sleeve and a second portion adapted to engage the end of said sleeve; a wiper assembly connected'to said shaft, said wiper assembly including a contact member for engaging each switch segment in turn as said shaft is rotated; and another terminal lead electrically coupled to said wiper assembly through said bearing means, saidanother terminal lead secured directly to said stud.

2. A rotary switch as defined by claim 1 further including detent means for imparting a snap action to said shaft, said detent means located between said wiper assem bly and said one end of said housing.

3. A rotary switch as defined by claim 2 wherein said detent means comprises a plurality of flat surfaces on said shaft and a pair of flat springs supported within said housing on opposite sides of said shaft and positioned to engage only the ends of different ones of said surfaces, said spring only the ends of different ones of said surfaces, said springs yielding on rotation of said shaft but pressing against said surfaces to hold said shaft stationary in the absence of an externally applied turning force.

4. A rotary switch as defined in claim 3 further including a ring with slots secured in said housing, said springs having their ends disposed in said slots and supported by said ring.

5. A rotary switch as defined by claim 4 further including stop means for limiting rotation of said shaft, said stop means comprising a first projecting portion rotatable with said shaft and a second projecting portion formed integral with said ring, said second projecting portion positioned to intercept said first projecting portion :as it rotates, whereby to stop further movement of said shaft in the same direction.

6. A rotary switch as defined by claim 1 wherein said sleeve is electrically conductive and said wiper assembly is connected thereto.

7. A rotary switch as defined by claim 1 wherein said sleeve is split so as to be expanded by said stud when applied thereto.

8. A rotary switch comprising a casing, a stationary switch disc within said casing provided with a plurality of spaced conductive switch segments, a plurality of terminal leads each connected to one of said switch segments, a shaft rotata bly disposed in said casing, a contact member, means connecting said contact member to said shaft for movement in a circular path as said shaft rot-ates, said contact member disposed to engage each switch segment in turn as said shaft is rotated, a flange on said shaft providing a polygon array of flat surfaces, said polygon array being concentric with said shaft and the planes of said flat surfaces being parallel to the axis of said shaft, a pair of fiat springs disposed on opposite ides of said shaft and extending at right angles thereto in coplanar relation to said flange, and means attached to said casing supporting the opposite ends of both springs so that intermediate said ends they are bowed outwardly away from each other by said flange and can engage different ones of said flat surfaces only at the ends of said flat surfaces, said flat surfaces and springs coacting to establish a plurality of predetermined shaft positions equal in number to said flat surfaces and restrain said shaft against movement from one to the other of said predetermined shaft positions, said contact member disposed so as to engage a different switch seg' ment at each of said predetermined shaft positions.

9. A rotary switch comprising a casing, a stationary switch disc secured within said casing at one end thereof, said switch disc having a plurality of spaced conductive switch segments on one surface thereof, a plurality of terminal leads protruding from said one end of said casing, each one of said plurality of terminal leads connec-ted toone of said switch segments, a shaft rotatably disposed in the opposite end of said casing, a contact member attached to and rotatable with said shaft, said contact member disposed to engage each switch segment in turn as said shaft is rota-ted, and detent means located between said contact member and said one end of said casing for holding said shaft in any one of a plurality of predetermined positions with said contact member engaging a different switch segment at each of said predetermined shaft positions, said detent means comprising a polygonal cam on said shaft and a pair of flat springs, said cam comprising a series of flat surfaces with the plane of each surface being parallel to said shaft, said springs disposed on opposite sides of said cam in position to engage different ones of said flat surfaces and thereby resist relative rotation of said shaft, each of said springs mounted and said cam sized so that at all times said cam bows said springs outwardly away from each other.

10. A rotary switch as defined by claim 9 wherein said springs are mounted in a ring secured in said housing, said ring having two pairs of slots with each spring having its opposite ends mounted in a different pair of slot, said springs making a loose fit in said slots so that said springs can pivot at their ends on flexing by said cam during rotation of said shaft.

11. In a rotary switch comprising a casing, a switch disc having a circular array of conductive switch segments, and means securing said disc within said casing, improved means for contact-ing each switch segment in turn, said improved means comprising a shaft, means rotatably supporting said shaft in coaxial relation with said circular array, a flange on said shaft, a circular spring Washer bent so that a first portion thereof is in offset relation to a second portion thereof, said washer surrounding said shaft in eccentric relation thereto with said first portion secured to said flange, and a contact element attached to said second portion, said contact element biased by said washer into engagement with said disc so that it will engage each switch segment in turn as said shaft rotates.

References Cited by the Examiner UNITED STATES PATENTS 1,973,630 9/1934 Johnson 200l1 X 3,030,460 4/1962 Huetten et al. 200-11 FOREIGN PATENTS 1,061,868 7/1959 Germany.

307,920 5/1933 Italy.

ROBERT K. SCHAEFER, Primary Examiner. KATHLEEN H. CLAFFY, Examiner.

J. R. SCOTT, Assistant Examiner.

Claims

1. A ROTARY SWITCH COMPRISING A HOUSING; A PRINTED CIRCUIT BOARD ASSEMBLY SECURED IN ONE END OF SSAID HOUSING; SAID ASSEMBLY COMPRISING A PLURALITY OF CONDUCTIVE SWITCH SEGMENTS AND TERMINAL LEADS CONNECTED TO SAID SEGMENTS AND ACCESSIBLE FOR CIRCUIT CONNECTIONS OUTSIDE OF SAID HOUSING; A SHAFT ROTATABLY MOUNTED IN AND PROTRUDING FROM THE OTHER END OF SAID HOUSING; A SLEEVE EXTENSION ON THE INNER END OF SAID SHAFT; BEARING MEANS SUPPORTED BY SAID CIRCUIT BOARD ASSEMBLY AND COACTING WITH SAID SLEEVE TO LIMIT MOVEMENT OF SAID SHAFT TOWARD SAID CIRCUIT BOARD AND ALSO TO MAINTAIN SAID SHAFT IN ALIGNMENT WITHIN SAID HOUSING, SAID BEARING MEANS COMPRISING A STUD HAVING A FIRST PORTION THAT FITS WITHIN SAID SLEEVE AND A SECOND PORTION ADAPTED TO ENGAGE THE END OF SAID SLEEVE; A WIPER ASSEMBLY CONNECTED TO SAID SHAFT, SAID WIPER ASSEMBLY INCLUDING A CONTACT MEMBER FOR ENGAGING EACH SWITCH SEGMENT IN TURN AS SAID SHAFT IS ROTATED; AND ANOTHER TERMINAL LEAD ELECTRICALLY COUPLED TO SAID WIPER ASSEMBLY THROUGH SAID BEARING MEANS, SAID ANOTHER TERMINAL LEAD SECURED DIRECTLY TO SAID STUD.