US3781499A

US3781499A - Selector switch with particular operator means,and detents which are restrained from rotation

Info

Publication number: US3781499A
Application number: US00286531A
Authority: US
Inventors: G Reichert; E Moehrle
Original assignee: Allen Bradley Co LLC
Current assignee: Allen Bradley Co LLC
Priority date: 1972-09-05
Filing date: 1972-09-18
Publication date: 1973-12-25
Anticipated expiration: 1990-12-25
Also published as: CA983076A

Abstract

A selector switch actuator includes an actuator sleeve having a cam surface formed around its interior surface. A rotor is journaled within the actuator sleeve and includes a bias spring located within a transverse opening formed through the rotor. A roller is rotatably attached to each end of the spring by a spring seat and the rollers are forced radially outward with equal, but opposite force against the cam surface to force the rotor into one of a plurality of selectable positions. An easily assembled knob structure is shown which includes a threaded cover that attaches to the actuator sleeve to fasten the switch to a mounting wall.

Description

United States Patent 1 Reichert et a1.

[ Dec. 25, 1973 1 SELECTOR SWITCH WITH PARTICULAR OPERATOR MEANS, AND DETENTS WHICH ARE RESTRAINED FROM ROTATION [75] Inventors: Gilbert A. Reichert, Greendale; Earl R. Moehrle, Milwaukee, both of Wis.

[73] Assignee: Allen-Bradley Company,

Milwaukee, Wis.

[22] Filed: Sept. 18, 1972 [21] Appl. No.: 286,531

[56] References Cited UNITED STATES PATENTS 7/1970 Kaiser 200/166 SD X 11/1969 Klein 4/1961 Nabstedt 200/166 SD UX 2,701,286 2/1955 Slate et a1. 200/172 R X 2,774,852 12/1956 Boardman 200/172 R FOREIGN PATENTS OR APPLICATIONS 721,989 l/1955 Great Britain 200/166 SD 1,018,357 1/1966 Great Britain 200/166 SD Primary E.raminerRobert K. Schaefer Assistant ExaminerRobert A. Vanderhye Attorney-Barry E. Sammons et a1.

[ 5 7 ABSTRACT A selector switch actuator includes an actuator sleeve having a cam surface formed around its interior surface. A rotor is journaled within the actuator sleeve and includes a bias spring located within a transverse opening formed through the rotor. A roller is rotatably attached to each end of the spring by a spring seat and the rollers are forced radially outward with equal, but opposite force against the cam surface to force the rotor into one of a plurality of selectable positions. An easily assembled knob structure is shown which includes a threaded cover that attaches to the actuator sleeve to fasten the switch to a mounting wall.

11 Claims, 4 Drawing Figures 9 I 1 1,57 Ji l/" In ""1.

PATENTEB [H25 5915 SHEET 10? 3 PATENTEDDEEZS 1975 saw an? 3 SELECTOR SWITCH WITH PARTICULAR OPERATOR MEANS, AND DETENTS WHICH ARE RESTRAINED FROM ROTATION BACKGROUND OF THE INVENTION The invention relates to control switches, and more particularly, to the switches of the rotary selector type commonly attached to control panels associated with electrical apparatus.

Selector switches are used in industry where they are employed to control such electrical equipment as motor starters, motor speed control circuits, and numerical control directors. The switches are sealed to prevent the entry of oil and other foreign materials into the equipment enclosure.

Prior selector switches include detent mechanisms which operate to provide a plurality of switch positions. Such detent mechanisms are located within the actuator section of the switch and include a ball which is spring biased against a surface that contains a plurality of detents. Many of these detent mechanism arrangements include one or more springs which bias an associated ball in the direction of the central switch axis against a detent plate. Such an arrangement of elements is disclosed in US. Pat. No. 2,748,208 issued to Koertge on May 29, 1956. On the other hand, to reduce the axial length of the switch, a number of prior detent mechanisms orient the bias spring to force its associated ball in a direction radially outward from the central axis of the switch. Such an arrangement is disclosed in US. Pat. No. 2,947,827 issued to Bondy et al, on Aug. 2, 1960. Not only do such detent mechanisms exert a radial thrust on the shaft of the switch which tends to bind and wear the switch elements, but the ball tends to wear a groove in the detent plate and the mechanism loses its crisp, snap action.

SUMMARY OF THE INVENTION The present invention relates to an improved selector switch actuator mechanism which is highly resistant to wear. Specifically, the switch actuator includes an actuator sleeve which defines a central opening concentric about the central switch axis, a cam surface formed on the interior surface of said actuator sleeve and facing radially inward toward the central axis, a rotor journaled to the actuator sleeve for rotary motion about the central switch axis and having a transverse opening formed therethrough, a bias spring disposed in the transverse opening, and a pair of rollers connected to the ends of the bias spring with their axes oriented substantially parallel to the central axis of the switch. Each roller is attached to the bias spring by a spring seat which fits over one end of the bias spring and slides within the transverse opening of the rotor. Each roller is rotatably retained to the end of its associated spring seat and a key on the spring seat mates with a keyway along the transverse opening to align the roller axes with the central axis.

A general object of the invention is to improve the snap action of a selector switch. The bias spring is relatively large, both in diameter and length, but because it is aligned to operate in a direction transverse to the central switch axis, the overall length of the switch is minimized.

Another general object of the invention is to improve the wear characteristics of a selector switch mechanism. By connecting the roller to each end of the bias spring, the radial forces generated by the bias spring are equal and opposite to one another to thus minimize the transverse forces on the rotor. This substantially reduces the wear on the bearing surfaces which journal the rotor to the actuator sleeve.

A more specific object of the invention is to minimize wear of the cam surface. By using rollers, a line of contact is made between each roller and the cam surface. As a result, the force generated by the bias spring is more evenly distributed over the cam surface to pre vent the creation of a groove and to thereby extend the useful life of the switch.

Still another specific object of the invention is to minimize wear on both the spring seat and the cam surface. A spindle is formed at the midpoint of each roller and a trunion mount is formed on each spring seat. A slot formed in each trunion rotatably receives and retains its associated roller spindle. The spring seats are slightly flexible, and they also allow a limited pivotal motion which distributes the spring force equally along the length of the roller bearing surface.

Still another object of the invention is to provide a selector switch knob that is easily assembled and disassembled.

The foregoing and other objects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof and in which there is shown a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention and reference is made to the claims herein for interpreting the breadth of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an exploded prospective view of the invented selector switch,

FIG. 2 is a view in cross section of the selector switch mechanism of FIG. 3 taken on the plane 22,

FIG. 3 is a view in cross section of the selector switch mechanism of FIG. 2 taken on the plane 33, and

FIG. 4 is a plan view of spring seat and roller which forms a part of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, the oil tight selector switch includes a contact block 1 comprised of two

switch cartridges

2 and 3. Each

switch cartridge

2 and 3 includes an associated plunger 4 and 5 respectively which'is mounted for translational motion along a central switch axis 6. The plungers 4 and 5 each communicate through a forward wall in its cartridge and is spring biased in a forward, or unactuated position. The plungers 4 and 5 are either mechanically connected to operate switch contacts, or as disclosed in the copending US. Pat. application Ser. No. 285,720 filed Sept. 1, 1972 and entitled Reed Switch Cartridge, are magnetically coupled to operate a pair of reed switches.

The contact block 1 is fastened to the selector switch actuator by a pair of mounting screws 7 which extend through the contact block 1 and are received in threaded openings formed on the back of an actuator sleeve 8. The actuator sleeve 8 is formed of aluminum and includes a threaded bushing 9 having a central opening 10 concentric about the central switch axis 6. The actuator sleeve 8 also includes a bearing plate 11 formed around the periphery of the bushing 9 at its back end and extending radially outward from its threaded surface. A cam surface 12 is formed on the interior surface of the bushing 9 by a plastic insert 12 which fits snugly within the central opening 10. The cam surface is disposed around the perimeter of the bushing 8 and faces radially inward toward the central switch axis 6. A set of four tabs 13 are integrally formed in quadrature around the back edge of the insert 12 and are received in corresponding slots formed in a back wall 14 on the actuator sleeve 8.

Referring to FIGS. 1 and 2, a rotor 15 formed of molded plastic is journaled for rotation within the actuator sleeve 8. It includes a circular, cylindrical body portion 16; a circular, cylindrical head portion 17 disposed axially forward of the body 16; and a circular, cylindrical neck portion 18 disposed axially rearward of the body 16. The perimeter of the head portion 17 rotatably engages the interior surface of the bushing 9 immediately forward of the cam surface insert 12 and the neck portion 18 is rotatably received by an opening formed in the actuator sleeve back wall 14.A groove is formed around the periphery of the head portion 17 and a nitrile buna N rubber ring seal 19 is disposed therein to provide an oil-tight seal. A groove is also formed around the periphery of the neck portion 18 and a lock ring 22 is snapped into place therein to inhibit foward movement of the rotor 15 within the actuator sleeve 8.

A stop 20 is integrally formed to the rotor head 17 and extends radially outward therefrom over a sector of its circumference. The stop 20 rides along the forward edge of the threaded bushing 9 and engages a pair of limit tabs 21 integrally formed to the actuator sleeve 8. When rotated, the stop 20 engages the limit tabs 21 to limit rotor motion to a preset amount.v

A drive shaft 23 having a square cross section is inte grally formed to the back end of the rotor 15. An annular shaped plastic spacer 24 is positioned around the rotor neck 18 and is disposed against the back surface of the actuator sleeve 8. A cam 25 formed of molded plastic and having a central opening 26 is positioned around the drive shaft 23 and is in bearing engagement with the back surface of the spacer 24. The central opening 26 in the cam 25 includes a plurality of equally spaced keyways which allow the cam 25 to be selectively positioned upon the drive shaft 23 in any one of eight orientations. A cam surface 27 of complex shape is formed on the cam 25 and faces axially rearward towards the contact block 1.

Positioned axially between the contact block 1 and the actuator sleeve 8 is a housing 28 formed of molded plastic. The housing 28 provides an enclosure for the cam 25 and the forward ends of the plungers 4 and 5 on the contact block 1. Also, the housing 29 provides two sets of guideways which slidably retain a pair of

cam follower elements

29 and 30. More specifically, the housing 28 includes a top wall 31 and an opposing bottom wall 32 which are joined by a pair of opposing,

arcuate side walls

33 and 34. A pair of

outer guideways

35 and 36 are formed on the interior surface of the top and

bottom walls

31 and 32 respectively, and they each slidably receive a rectangular shaped

outer guide

37 and 38 integrally formed on the respective

cam follower elements

29 and 30. A back wall 39 joins the back edges of the

walls

31, 32, 33 and 34 and a pair of

inner guideways

40 and 41 are integrally formed therein. The

inner guideways

40 and 41 are positioned radially inward from the respective

outer guideways

35 and 36, and they each slidably receive an elongated inner guide 42 and 43 which are intergrally formed on the respective

cam follower elements

29 and 30. The

cam follower elements

29 and 30 are thus retained at each end, but are free to slide in the direction of the central switch axis 6. They are positioned to communicate with both the cam surface 27 on the cam 25 and the forward ends of the plungers 4 and 5 in the contact block 1. A rounded cam follower surface 44 and 45 is formed on the respective

cam follower elements

29 and 30 intermediate their ends. The cam follower surfaces 44 and 45 bear against the cam surface 27 and in response to rotary motion of the cam 25, operate to translate the

cam follower elements

29 and 30 in the axial direction. Formed on the back side of each

cam follower element

29 and 30 is a respective actuator surface 46 and 47. The actuator surfaces 46 and 47 bear against the respective plungers 4 and 5 to transmit the translational motion of the cam follower elemenets 29 and 30 thereto.

The oil tight selector switch is fastened to a panel by inserting the threaded bushing 9 through an opening therein and attaching a knob 50. A set of four neoprene gaskets 51 are placed around the threaded bushing 9 and are disposed between the back surface of the mounting wall and the forward surface of the bearing plate 11 to provide an oil-tight seal.

Referring to FIGS. 1 and 2, the knob 50 includes four elements: an operator 52, a cover 53 and a locking member 54 which are held together by a retainer 55. The cover 53 is formed from aluminum and has a generally circular cylindrical shape. It includes a threaded portion 56 on its interior surface adjacent its back edge 57. The threaded portion 56 engages the threaded bushing 9 and retains the back edge 57 of the cover 53 tightly against the front surface of the mounting panel to provide a clamping force which slightly compresses the gaskets 51 against the back surface of the panel. The cover 53 also includes an integrally formed, annular shaped front wall 58 which defines a circular, concentric cover opening 59 at the forward end of the cover 53.

The operator 52 is formed from zinc and includes a circular flange 60 which extends radially outward around its perimeter. The operator 52 is disposed within the cover 53 and the flange 60 butts against the back surface of the cover front wall 58. A pedestal 61 is integrally formed to the front of the operator 52 and extends axially forward through the cover opening 59 to provide support for a pair of radially outward extending tabs 62 and 63. The tabs 62 and 63 each define a bearing

surface

64 and 65 respectively which face substantially in the axial direction toward the rear of the switch. A coaxialchannel 66 is formed in the pedestal 61 and it receives a guidepost 67 integrally formed to the front surface of the rotor 15. A pair of

pins

68 and 69 are integrally formed to the back surface of the operator 52 and are received by two of four guide holes 70 formed in the front surface of the rotor 15. The guide holes 70 are positioned in quadrature about the guidepost 67 and the operator 52 is, therefore,'coupled to the rotor 15 in one of four selectable orientations.

The locking member 54 is formed from molded plastic and includes a circular base 71 which bears against the front surface of the cover front wall 58. It also includes a pair of spaced side walls 72 and 73 which extend axially forward from the base 71 and are joined together along their edges to define an elongated chamber 74. As shown best in FIG. 2, a first retaining surface 75 is integrally formed on the interior of one wall of the chamber 74 and it faces rearward in a substantially axial direction. A second retaining surface 76, also facing in a substantially axial direction towards the rear of the switch, is formed on the end of an arm 77. The arm 77 is integrally formed to the interior surface of a second chamber wall and includes a short radial portion 77a and a longer axial portion 77b. Also located within the chamber 74 and extending axially forward from the base 71 are a pair of integrally formed pawls 78 and 79. The end of each pawl 78 and 79 defines a locking surface 80 and 81 each of which faces forward substantially in the axial direction. The pawls 78 and 79 and the first and second retaining surfaces 75 and 76 are disposed in the same plane, parallel to the side walls 72 and 73 and passing through the central switch axis 6.

The retainer 55 is formed from molded plastic and includes an elongated base portion 80 which encloses the forward end of the chamber 74 of the locking member 54. An arm 81 is integrally formed to one end of the base portion 80 and extends axially rearward along one edge of each of the side walls 72 and 73. The base portion 80 also provides support for a pairof

bifurcated legs

82 and 83 which extend into the chamber 74 in the plane of the pawls 78 and 79. Each

leg

84 and 85 includes a pair of

tongs

86, 87, 88 and 89 which are joined at their outer ends to form a

hook member

90 and 91. The tongs 8689 curve outward over a section of their length to form a resilient, bulbous wedging member on each

leg

84 and 85.

The pedestal 61 on the operator 52 extends through an opening in the base 71 of the locking member 54 and into the chamber 74. When the retainer 55 is inserted into the chamber 74, the

hooks

90 and 91 on the ends of the

bifurcated legs

84 and 85 flex radially outward in a snap action to bear against the retaining surfaces 75 and 76 formed on the chamber walls. When thus snapped into place the resilient wedging member on the leg 84 is wedged between the arm 77 and the pawl 78 to deflect the pawl 78 radially inward against the pedestal 61. Similarly, the wedging member on the leg 85 is wedged between the lower wall of the chamber 74 and the pawl 79 to deflect the pawl 79 radially inward against the pedestal 61. As a result, the locking surfaces 80 and 81 on the respective pawls 78 and 79 are brought into bearing engagement with the bearing surfaces 64 and 65 on the pedestal 61 to fasten the locking member 54 to the operatr 52. The knob 50 is thus easily assembled and may be easily disassembled by the user if it is necessary to replace any one or more of the elements therein.

The rotor cooperates with the cam surface 12 formed on the interior surface of the actuator sleeve 8 to provide a plurality of selectable positions. A transverse, circular opening is formed through the body portion 16 of the rotor 15 and a bias spring 94 is positioned therein. Referring to FIGS. 1-4, a pair of

spring seats

95 and 96 are disposed around each end of the bias spring 94. The spring seats 95 and 96 are formed of molded plastic and are generally sleevelike in shape having a circular outer surface which mates with and slides within the transverse opening formed in the rotor 15. Each

spring seat

95 and 96 incudes a circular top portion 97 which encloses one end and which provides a surface against which the end of the bias spring 94 bears. A trunion mount 98 is integrally formed to the top 97 of each spring seat and 96 and a slot 99 is formed in the outermost edge of each. The slots 99 are aligned with an operating axis 100 which is coaxial with the center of the transverse opening in the rotor 15 and perpendicular to the central switch axis 6.

Rotatably attached to each

spring seat

95 and 96 is a

roller

101 and 102 respectively. The

rollers

101 and 102 are formed from carbon steel drill rod and include a medial spindle portion 103 which is received in the slot 99 formed in the trunion 98. The spindles 103 are circular in cross section and the slots 99 are slightly enlarged at their bottom to have a circular shape. The

rollers

101 and 102 are pressed into the slots 99 where they snap into position and are rotatably retained by the trunions 98. Also, the trunions 98 are constructed of crystalline acetal copolymer based on trioxane and therefore have a limited amount of flexibility which allows a slight pivotal action of the

rollers

101 and 102 about the operating axis 100. The

rollers

101 and 102 are each aligned with its axis of rotation oriented parallel to the central switch axis 6 and each is forced radially outward against the cam surface 12 by the bias spring 94. This alignment is retained by a pair of keys 104 integrally formed to the top portion 97 of each

spring seat

95 and 96. The keys 104 extend radially outward from the operating axis 100 and slide within a pair of opposing keyways 105 which are formed along the transverse opening in the rotor 15.

By rotating the knob 50 and coupled rotor 15, the operating axis 100 is revolved in a plane perpendicular to the central switch axis 6. The bias spring 94 operates in the direction of the axis 100 to force the rollers 10] and 102 radially outward in opposite directions from the central switch axis 6. The resulting equal but opposite radial forces generated by the bias spring 94 are translated into a torque by the action of the

rollers

101 and 102 against the sloped portions of the cam surface 12. Referring specifically to FIG. 3, the torque thus generated revolves the rotor 15 into one of three stable, selectable positions in which the roller 101 rests in one of three nodes 106 formed in the cam surface 12 and the roller 102 rests in one of three nodes 107. Referring particularly to FIG. 2, the

rollers

101 and 102 make continuous contact with the cam surface 12 along a line parallel to the central switch axis 6. The slight pivotal action of the

rollers

101 and 102 around the operating axis 100 allows them to self-adjust with wear and to thereby evenly distribute the bias spring force equally along the line of contact. The formation of a groove in the cam surface 12 is thus eliminated and the useful life of the switch is substantially increased.

It should be apparent to those skilled in the art that a variety of cam surfaces 12 can be used to provide different switch functions. That illustrated herein is a three position switch, however by replacing the plastic insert on which the cam surface 12 is formed, other functions can be obtained. Also, the plastic insert used herein is made of a type 6 unfilled nylon sold commercially under the trademark Fosta Nylon X887, however, other materials might also be used.

We claim:

1. A switch actuator, the combination comprising:

an actuator sleeve having a circular cylindrical shape that defines a central opening concentric about a central switch axis;

a cam surface formed on the interior surface on said actuator sleeve and facing radially inward towards said central switch axis;

a rotor journaled in said actuator sleeve for rotation about said central switch axis and including a transverse opening which defines an operating axis which is perpendicular to said central switch axis and which intersects said central switch axis;

a bias spring disposed in said transverse opening and confined within said rotor concentric about said operating axis;

a pair of rollers, one disposed radially outward from each end of said bias spring and each being forced radially outward in opposite directions from said central switch axis along said operating axis into bearing engagement with said cam surface; and

a pair of spring seats, each slidably disposed within the transverse opening of said rotor, and each including means for preventing its rotation therein, each spring seat being associated with a roller and being disposed between one end of the bias spring and its associated roller, wherein each roller is rotatably attached to a spring seat to rotate about an axis parallel to the central switch axis.

2. The switch actuator as recited in claim 1 in which each spring seat is retained to slidably operate in said transverse opening along said operating axis and each spring seat includes a key which mates with a keyway formed along said transverse opening to prevent rotation of said spring seats about said operating axis.

3. The switch actuator as recited in claim 1 in which each roller includes a medial spindle and each spring seat includes a trunion having a slot which receives and rotatably retains the spindle of its associated roller.

4. The switch actuator as recited in claim 3 in which said spring seats are formed from a copolymer and each has sufficient flexibility to allow a pivotal adjustment motion of its associated roller about said operating axis.

5. The switch actuator as recited in claim 3 in which each spring seat is disposed within said transverse opening and includes a key which extends radially outward from said operting axis to mate with a keyway formed in said rotor along said transverse opening.

6. The switch actuator as recited in claim 1 in which said cam surface is formed on an insert molded from a nylon material.

7. The switch actuator as recited in claim 6 which includes a cam connected to said rotor for rotation thereby about said central switch axis, and a cam follower element connected to said actuator sleeve for slidable motion along said central switch axis and positioned in bearing engagement with said cam.

8. A switch actuator, the combination comprising:

a cam surface formed on the interior surface of said actuator sleeve and facing radially inward toward said central switch axis;

a rotor journaled in said actuator sleeve for rotation about said central switch axis and including a transverse opening which defines an operating axis perpendicular to said central switch axis;

a bias spring disposed in said transverse opening;

a pair of rollers, one connected to each end of said bias spring and each being forced rapidly outward in opposite directions from said central switch axis along said operating axis into bearing engagement with said cam surface; and a knob fastened to said actuator sleeve and including:

a cover having an annular shaped front wall which defines a cover opening;

an operator disposed in said cover and in bearing engagement with the backside of said front wall, said operator being coupled to said rotor and having a pedestal which extends axially forward through said cover opening to define a bearing surface;

a locking member connected to said operator and in bearing engagement with the front surface of said cover front wall, said locking member having a plurality of walls which define a chamber;

a retaining surface formed on the interior surface of one of said chamber walls.

9. The switch actuator as recited in claim 8 in which said bearing surface faces substantially axially towards the back of said switch actuator and said retaining surface faces substantially axially towards the back of said switch actuator.

10. The switch actuator as recited in claim 9 in which a second retaining surface is formed on one of said chamber walls, a second pawl is integrally formed to said operator, and a second leg is formed on said retainer, wherein said second leg is disposed between said second retaining surface and said second pawl.

11. The switch actuator as recited in claim 10 in which said legs are each bifurcated to provide a relatively flexible wedging portion.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Ne. 3,781,499 Dated December 25, 1973 Inventor(s) Gilbert A. Reichert and Earl R. Moehrle It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 28 change foward to forward Column 3, line 55 change housing 29 to housing 28 Column 4, line change intergrally to integrally Column 4, line 21 change elemenets to elements Column 5, line 52 change operatr to operator Column 5, line 67 change incudes to includes Column 6,

lines

3 and 14 change trunion to trunnion Column 6, line 1 9 change ti-unions to trunnions Claim 3, line 36 change trunion to trunnion e I Claim 5, line 45 2 change operting to operating Claim 8, line 18 C I change rapidly to radially igned and sealed this 23rd day of April 197b,.

(SEAL) Attest:

EDWARD l'LFLETC'HERJR. C. MARSHALL DANN Attesting Officer Commissionerof Patents L- g J

Claims

1. A switch actuator, the combination comprising: an actuator sleeve having a circular cylindrical shape that defines a central opening concentric about a central switch axis; a cam surface formed on the interior surface on said actuator sleeve and facing radially inward towards said central switch axis; a rotor journaled in said actuator sleeve for rotation about said central switch axis and including a transverse opening which defines an operating axis which is perpendicular to said central switch axis and which intersects said central switch axis; a bias spring disposed in said transverse opening and confined within said rotor concentric about said operating axis; a pair of rollers, one disposed radially outward from each end of said bias spring and each being forced radially outward in opposite directions from said central switch axis along said operating axis into bearing engagement with said cam surface; and a pair of spring seats, each slidably disposed within the transverse opening of said rotor, and each including means for preventing its rotation therein, each spring seat being associated with a roller and being disposed between one end of the bias spring and its associated roller, wherein each roller is rotatably attached to a spring seat to rotate about an axis parallel to the central switch axis.

8. A switch actuator, the combination comprising: an actuator sleeve having a circular cylindrical shape that defines a central opening concentric about a central switch axis; a cam surface formed on the interior surface of said actuator sleeve and facing radially inward toward said central switch axis; a rotor journaled in said actuator sleeve for rotation about said central switch axis and including a transverse opening which defines an operating axis perpendicular to said central switch axis; a bias spring disposed in said transverse opening; a pair of rollers, one connected to each end of said bias spring and each being forced rapidly outward in opposite directions from said central switch axis along said operating axis into bearing engagement with said cam surface; and a knob fastened to said actuator sleeve and including: a cover having an annular shaped front wall which defines a cover opening; an operator disposed in said cover and in bearing engagement with the backside of said front wall, said operator being coupled to said rotor and having a pedestal which extends axially forward through said cover opening to define a bearing surface; a locking member connected to said operator and in bearing engagement with the front surface of said cover front wall, said locking member having a plurality of walls which define a chamber; a retaining surface formed on the interior surface of one of said chamber walls.