US3247349A

US3247349A - Operating mechanism for limit switch using ball and cam means

Info

Publication number: US3247349A
Application number: US327970A
Authority: US
Inventors: Eugene F Duncan
Original assignee: Cutler Hammer Inc
Current assignee: Cutler Hammer Inc
Priority date: 1963-12-04
Filing date: 1963-12-04
Publication date: 1966-04-19
Anticipated expiration: 1983-04-19
Also published as: GB1064029A

Description

April 19, 1966 E, F. DUNCAN OPERATING MECHANISM FOR LIMIT SWITCH USING BALL AND CAM MEANS 5 Sheets-Sheet 1 Filed Dec. 4, 1963 April 19, 1966 E. F. DUNCAN OPERATING MECHANISM FOR LIMIT SWITCH USING BALL AND CAM MEANS 5 Sheets-Sheet 2 Filed Dec. 4, 1963 -QNN l NM April 19, 1966 E. F. DUNCAN 3,247,349

OPERATING MECHANISM FOR LIMIT SWITCH USING BALL AND CAM MEANS Filed Dec. 4, 1963 5 Sheets-Sheet 3 April 1966 E. F. DUNCAN 3,247,349

OPERATING MECHANISM FOR LIMIT SWITCH USING BALL AND CAM MEANS Filed Dec. 4, 1965 5 Sheets-Sheet 4 r l5av V A 5/ United States Patent Ofitice 3,247,349 Patented Apr. 19, 1966 OPERATING MECHANISM FOR LIMIT SWITCH USING BALL AND CAM MEANS Eugene F; Duncan, Milwaukee, Wis., assignor to Cutler- I-Iammer, Inc., Milwaukee, Wis, a corporation of Delaware Filed Dec. 4, 1963, Ser. No. 327,970 12 Claims. (Cl. 200153) This invention relates to switch operating mechanisms and more particularly to operating mechanisms for limit switches.

It is an object of this invention to provide a limit switch operator which requires a low operating force and permits high overtravel.

It is another object of the invention to provide a limit switch operating mechanism. which is adjustable to permit adaptation of the switch to a variety of applications.

It is a further object of this invention to provide a limit switch operating mechanism which is small in size and which may be easily assembled from easily manufactured parts.

Various other objects and advantages of this invention will hereinafter appear.

The objects of the invention are accomplished by providing a cam rotatable by movement of the actuator, which actuator is exterior to the switch housing, and cam follower means yieldingly engaging the cam for being displaced by the cam to actuate a reciprocatory switch mechanism when the cam is rotated with respect to the cam follower means. The cam follower means is constructed to be freely rotatable with the cam when the cam is rotated in one direction from its center position whereby the cam follower means is not displaced to actuate the switch when the cam is rotated in said one direction. When the cam is rotated in the other direction from its center position, the cam follower means is restrained against rotation, and, as a consequence, the cam follower means is axially displaced to actuate the switch. The switch can thereby be made to respond to movement of the actuator in one direction while being non-responsive to movement in the opposite direction. The direction resulting in actuation of the switch is easily selectable.

There is further provided additional means engaging said cam follower means for locking the cam follower means with respect to the cam when the cam .and cam follower are rotated in the first direction from their center position and for locking the cam follower against rotation in the first direction when the cam is rotated in the second direction from its center position. These locking means provide positive movement and positioning of the mechanism to insure proper operation of the mechanism.

While the device hereinafter described is adapted to fulfill the objects stated it is to be understood that it is not intended that the invention be confined to the particular preferred embodiment disclosed since it is susceptible of various modifications without departing from the scope of the claims.

In the drawings:

FIGURE 1 is a top view of the exterior of a limit switch having an operating mechanism which incorporates the principles of the present invention;

7 FIG. 2 is an elevation view of the switch shown in FIG. 1;

FIG. 3 is an exploded isometric view of the limit switch operating mechanism;

FIG. 4 is a sectional view of the operating mechanism in its normal position taken on line 44 of FIG. 7;

FIG. 5 is a sectional view similar to FIG. 4 but with the operating mechanism in operated position;

FIG. 6 is a fragmentary sectional view taken on line 6-6 of FIG. 4;

FIG. 7 is a top view of the switch with the exterior operator removed and with the operating shaft in section;

FIG. 8 is a sectional view on line 8-8 of FIG. 4; FIG. 9 is a sectional view on line 9-9 of FIG. 4;

FIG. 10 is a sectional view on line 10--10 of FIG. 5;

FIG. 11 is a sectional view similar to FIG. 10, but with the mechanism rotated in the opposite direction;

FIG. 12 is a sectional view similar to FIG. 8, but illustrating the operation of the mechanism when rotated in the non-operating or bypass direction;

FIG. 13 is a fragmentary isometric sectional view of certain elements of the mechanism in operating position;

FIG. 14 is a partially sectional view taken on line 14-44 of FIG. 2; and

FIG. 15 is a front elevation view of a limit switch with its cover plate removed.

Referring to the drawings, FIGS. 1 and 2 show, respectively, a top and an elevation view of a complete limit switch assembly. A switch housing 2 has a cover plate 3 secured by two screws 4. A gasket 5 is interposed between housing 2 and plate 3 to provide a sealed enclosure. A bearing block 6 which houses the switch operating mechanism is fastened to the top surface of housing 2 by four screws 7. Protruding from the top of bearing block 6 there is a rotatable operating shaft 8. A clamp 9 is fastened to the upper end of shaft 8 and holds a radially extending actuating rod 10. It should be understood that during normal operation of the device a force applied to rod 19 serves to rotate clamp 9 and shaft t; to thereby actuate the limit switch.

FIGS. 14 and 15 illustrate the interior of housing 2 wherein there is mounted a switch assembly 12. The base 12a of switch assembly 12 is made of molded insulating material and is fastened to the interior of housing 2 by two screws 13. A roughly cruciform transparent cover 1212 fits over the open front face of base 12 and is fastened thereto by screw 120. Inside the cavity formed by base 12a and cover 12b, there are mounted a pair of upper stationary contacts 12d and a pair of lower stationary contacts 122, between which the movable bridging contact member 12 travels. Two over-center compression springs 12g transmit actuating force to bridging contact member 12 from actuator plate 12h which recipr'ocates vertically within the two opposed grooves mi in base 12a and cover 1212. A compression spring 121' placed below actuator plate 12h biases the switch mechanism upwardly to the position shown in FIGS. 14 and 15. An insulating button 12k is affixed to the upper end of plate 12h and extends upwardly through an aperture in the upper surface of base 12a. A lever 12m within groove 1211 in the upper surface of base 12a has one end resting on the bottom of groove 1211 and its other end pivotally retained within a cylindrical socket 12 in the upper surface of button 12k.

Switch assembly 12 is operated by force applied to the top surface of lever 12m by a pushrod 14 which slides axially within a bushing 11 and is actuated by the operating mechanism contained within the bearing block 6. FIG. 3 best illustrates the individual elements of the operating mechanism. Bearing block 6 is sectioned in FIG. 3 to show its cup-like cylindrical interior upon which there is formed an axially extending ridge 15 having an upper portion 15a and a lower portion 15b. (See also FIGS. 5 and 6.) Also shown in FIG. 3 is a cylindrical bushing 16 which is press fitted in an aperture in the upper surface of bearing block 6. Bushing 16 serves as a bearing for shaft 8. An elastic gasket 17 accommodated by groove 18 in shaft 8 forms a seal between shaft 8 and bushing 16.

Below bearing block 6 in FIG. 3, there is shown a torsion spring 19 which has radial extensions 20 and which provides a center return force for the mechanism.

When assembled, spring 19 surrounds bushing 16 and is retained in place by thrust washer 21. The lower surface of thrust washer 21 serves as the bearing surface for ball bearing assembly 22 consisting of. a retainer 23 and five ball bearings 24. A cam plate 27, when assembled in the mechanism, has its center circular aperture 28 placed over the lower end of shaft 8 and is securely fastened thereto. A center return pin 29 projects upwardly from the top surface of cam plate 27 to cooperate with projections of torsion spring 19. The radius of cam plate 27 is extended at one side to form

stop surfaces

30 and 31. On the lower face of the cam plate 27 there are formed two large

conical depressions

32 and 33 and one smaller depression 34.. The large conical camming surfaces of

depressions

32 and 33 co operate with two

large balls

35 and 36, and the smaller depression 34 cooperates with a smaller ball 37. Depression 34 is formed elongate to facilitate the entry of ball 37 thereinto in the event that the elements of the mechanism do not become perfectly alined during operation.

. In FIG. 3 directly below

balls

35, 36 and 37, there is shown a ball cage 38 having a cup-shaped lower surface produced by a circular wall 39 extending therefrom. A flange 40 extends radially from the periphery of ball cage 38 for the greater portion of its circumference. The ends of flange 40 form stop surfaces 41 and 42. A circular aperture 44 is formed in the center of ball cage 38. There are also three

ball retaining apertures

45, 46 and 47 (FIG. 13) formed in ball cage 38. Apertures 45 and 46 as shown in FIG. 13, serve to retain

balls

35 and 36, respectively, while aperture 47 retains the smaller ball 37. Directly below ball cage 38 in FIG. 3, there is shown a circular pressure plate 48 with a conical center portion 49.

A retaining ring 50 has formed in its upper surface a V-shaped radial groove 51 (see FIG. 6) which cooperates with the smaller ball 37 Also formed in retainer ring 50 are two threaded

apertures

52 and 53, either of which will accommodate a set screw 54. The point 55 of set screw 54, serves as a stop point which cooperates with stop surfaces 41 and 42 of ball cage 37. The rotation of retainer ring 50 is prevented by an axial groove 56 formed in the periphery of ring 50 which engages the lower por tion 15b of ridge 15 on the interior of bearing block 6.

As shown in FIGS. 4 and 5, the central conical portion 49 of pressure plate 48 pivots upon the conical upper end of axially movable switch actuating pushrod 14. A flexible gasket 57 has the edge of its center aperture retained in the circumferential groove 58 in pushrod 14. The periphery of gasket 57 is clamped between switch housing 2 and the lower edge of bearing block 6.

The operation of the device will now be explained. The normal unactuated position of the mechanism is illustrated in FIGS. 4, 8, 9, 14 and 15. The pressureof the extensions 20 of center return spring 19 maintains pin 29 in alinement with ridge 15a. When cam plate 27 is in normal position, camming recesses 32 and 33 are alined respectively with

apertures

45 and 46 in ball cage 38 so that

balls

35 and 36 are free to be pressed upwardly into

recesses

32 and 33 by pressure plate 48. The upward biasing force is provided by spring 12 (FIG. 14) through actuator plate 12h, button 12k, lever 12m and pushrod 14. The smaller recess 34 is positioned above aperture 47 while groove 51 in retaining ring 50 is alined oppositely below aperture 47. The smaller ball 37 is therefore free to move within aperture 47 either upwardly toward recess 34 or downwardly into groove 51.

The operating shaft 8 may be rotated in either direction from its normal center position. A choice of types of operation is available by selective placement of one or two set screws 54 in

apertures

52 and 53 of retainer ring 50. If one set screw is used the switch 12 will be actuated by rotation of shaft 8 in one direction from center while rotation in the opposite or bypass direction.

will not cause actuation. The placement of a set screw ate switch 12 while the use of aperture 53 will result in actuation upon counterclockwise rotation of shaft 8. If set screws are placed in both of

apertures

52 and 53, switch 12 will be actuated upon rotation in either direction.

First assume that set screws 54 are placed in both of

aperatures

52 and 53. Stop surfaces 41 and 42 will engage the stop points 55 of set screws '54 and ball cage 38 will be restrained from rotation in either direction and will be held in the position shown in FIG. 8. Rotation of cam plate 27 in either direction will cause

balls

35 and 36 to be forced downwardly against pressure plate 48 by the sloping conical surfaces of depressions 32 and 33 (see FIGS. 5 and 13). The downward movement of pressure plate 48 in'turn causes the pushrod 14 to be depressed to actuate switch 12. As camming plate 27 rotates, the friction therewith causes

balls

35 and 36 to rotate within

apertures

45 and 46, and pressure plate 48 consequently rotates on the pointed end of pushrod 14 to minimize friction and thereby reduce the force required to cause actuation of switch 12.

After switch 12 has been actuated, continued rotation of cam plate 27 will force

balls

35 and 36 out of

depressions

32 and 33 to roll on the flat lower surface of plate 27. Further movement of plate 2! is then limited only by the engagement of either of stop surfaces 30 or 31 with ridge 15b to provide a high degree of angular o-vertravel.

When the actuating force is removed from shaft 8, camrning plate 27 is free to return to itsnormal position as a result of the pressure of spring 19 against center return pin 29. As camming plate assumes its

normal position balls

35 and 36 become alined with

depressions

32 and 33, respectively. Thereupon pressure plate 48, pushrod 14 and the mechanism of switch 12 are returned to their normal positions by the force of spring 12 The aforedescnibed operations will occur when shaft 8 is rotated clockwise (FIG. 11) or counterclockwise (FIG. 10) from its normal center position when ball cage 38 is restrained from rotation in both directions by set screws 54 in both of

apertures

52 and 53.

Next assume only one set screw 54 is used and is inserted in threaded aperture 53. When shaft 8 is rotated in a direction counterclockwise with reference to FIG. 5, surface 42 of ball cage 38 engages the point 55 of set screw 54 in aperture 53 to restrain ball cage 38 from counterclockwise rotation.

Balls

35 and 36 will thereupon be depressed and switch 12 actuated as previously described.

As'cam plate 27 rotates with respect to ball cage 38, depression 34 moves out of alignment with ball 37, and the lower surface of cam plate 27 holds ball 37 in engagement with groove 51 in retainer ring 50 (-see FIGS. 5 and 13). Ball 37 thereupon becomes effective in locking ball cage 38 against rotation with respect to retainer ring 50 when calm plate 27 snaps back to its original center position. This locking of ball cage 38 insures correct real-inemen-t of cam plate 27 with ball cage 38 upon release of actuator rod 10 and thereby insures the proper release of switch 12.

When shaft 8 is rotated from its normal position in the bypass direction, which in this assumed situation is clockwise, ball cage 38 is freeto'rotate as shown in FIG. 12,

As cam plate 27 and ball cage 38 are rotated in unison in the bypass direction, the smaller ball 37 within aperture 47 is moved out of lalinernent with groove 51 in retaining ring 50. Ball 37 therefore is forced into engagement with the recess 34 by the upper surface of retainer ring 50.

The engagement of ball- 37 with depression 34' and aperture 47 causes ball cage 38'andcantplate27 robe locked together when rotated in the bypass dir'ctiori- This locking together insures that: ca'm plate 27 and ball cage 38 will rotate in unison until the mechanism returns to its normal center position.

When cam plate 27 returns toits normal position; ball 37 is againalined with grodve SI andisfreet'odisengage depression 34. Cam plate 27 and ball: cage 38' are thereupon unlocked and the mechanism is again free to operate as previously described.

If the single set screw 54 is inserted in threaded aperture 52, ball cage 38 is blocked from clockwise movement causing switch 12 to be actuated by a clockwise rotation of shaft 8. The mechanism then functions ina manner similar to that previously described except that the actuating and bypass directions of rotation" are reversed.

I claim: 1. An electric switch operating mechanism comprising: a rotatable cam having a normal center position and being rotatable in either of two directions from said center position;

cam follower means yieldingly engaging said cam for being displaced by said cam to actuate a switch when said cam is rotated with respect to said cam follower means; said cam follower means being freely rotatable in place with said cam when said cam is rotated in one direction from said center position to allow said cam follower means to remain undisplaced and therefore not actuate the switch when said cam is rotated in said one direction; and means for restraining said cam follower means against rotation in the other direction when said cam is rotated in said other direction from said center position to causesaid cam follower means to be displaced to actuate the switch by rotation of said cam in said other direction. 2. The invention as defined in claim 1 together with means for locking said cam follower means to said cam for rotation with said cam which becomes operable when said cam and cam follower are rotated in said one direction from their center positions.

3. The invention as defined in claim 1 together with stationary member and means for locking said cam follower means to said stationary member against rotation in either direction when said cam is rotated in said other direction.

4. The invention as defined in claim 1 together with means engaging said cam follower means for locking said cam follower means with respect to said cam when said cam and cam follower means are rotated in said one direction from said center position and for locking said cam follower means against rotation in either direction when said cam is rota-ted in said other direction from said center position.

5. An electric switch operating mechanism comprising: a plurality of cam follower balls; rotatable cam rollingly engaged by said balls having a center position and being rotatable in either direction from said center position for displacing said balls in a direction parallel to the rotational axis of said cam when rotated with respect to said balls;

means rotatable about the rotational axis of said cam for being rollingly engaged by said balls and for being displaced to actuate a switch in a direction parallel to the rotational axis of said cam by said balls; and

means for restraining said balls from movement with said cam about the rotational axis of said cam in one direction from a center position but not the other whereby rotation of said cam in said one direction from its center position is effective to actuate the switch and rotation of said cam in the other direc- 6 tion fromits center position is ineffective to actuate the switch. 6. The invention as defined in claim 5 together with: ar'eciprocatory pushrod for actuating said electric switch and wherein said means rotatable about the rotational ends-of said cam comprises a plate pivotally mounted on the end of said pushrod 7.- An electric switch operating mechanism comprismg:

a plurality of cam following balls; rotatable came means' r 'ollingly engaged by said balls havinga center position and being rotatable in either direction from said center position for displacing saidballs in a direction parallel to the rotational axis of said am means when said cam means is rotated with respect to said balls; means rotatable about the rotational axis of said cam means for being rollingly engaged by said balls and for being displaced thereby in a direction parallel to the rotational axis of said cam means to actuate a switch;

means for controlling the movement of said balls about the rotational axis of said cam means comprising a ball retainer rotatable about the rotational axis of-said cam means and having a normal position;

and means for stopping said ball retainer from rotation with said cam means in a first direct-ion from said normal position but not a second direction to cause said balls to be axially displaced to actuate said switch when said cam means is rotated in said first direction and to allow said balls to remain undisplaced axially when said cam means is rotated in said second direction.

8. The invention as defined in claim 7 together with means for locking said ball retainer to said cam means for rotation with said cam means which becomes operable when rotated in said second direction from said normal position.

'9. The invention as defined in claim 7 together with means for locking said ball retainer against rotation in either direction from said normal position when said cam means is rotated in said first direction from said center position.

10. The invention as defined in claim 7 together with means engaging said ball retainer for locking said ball retainer with respect to said cam means when said cam means and ball retainer are rotated in said second direc- U011. from said normal position and for locking said ball retamer against rotation in either direction when said cam means is rotated in said first drection from said center position.

11. An electric switch operating mechanism comprising:

a plurality of cam following balls; rotatable cam means rollingly engaged by said balls having a center position and being rotatable in either direction from said center position for displacing said balls in a direction parallel to the rotational axis of said cam means when said cam means is rotated with respect to said balls; means rotatable about the rotational axis of said cam means for being rollingly engaged by said balls and and for being displaced thereby in a direction paral lel to the rotational axis of said cam means to actuate a switch;

means for controlling the movement of said balls about the rotational axis of said cam means comprising a ball retainer rotatable about the rotational axis of said cam means and having a normal position;

means for stopping said ball retainer from rotation with said cam means in a first direction from said normal position but not a second direction to cause said balls to be axially displaced to actuate said switch when said cam means is rotated in said first direction and to allow said balls to remain undisplaced 7 axially when said cam means is rotated in'said second direction; v and means engaging said ball retainer for lockingsaid ball retainer with respect tov said cam means when said cam means and balls retainer are rotated in 'said second direction from said-normal position and for locking said ball retainer against rotation in-- said second direction when said cam means is rotated in said first direction from said center position comprising:

an additional ball which is displaceable in a direction parallel to the rotational axis of said cam means within an aperture in said 'ball retainer; a depression in said cam means for being engaged by said additional ball to lock said ball retainer to said cam means; and a stationary member on the side of said ball retainer oppositesaid cam means having a de pression for beingtengaged by said additional .ball to locksaid ball retainer against'rotation. 12.The invention definedt'int claim 7 wherein said means for stopping said 'ballretainer from rotation comprises means for selectively stopping rotation of said ball retainer in either one or the other direction to provide a choice as to which direction of rotation of said cam means will cause actuation of said switch. 9

References Cited by the Examiner UNITED STATES PATENTS 2,603,731 7/1952 Weiss et a. 200-153 KATHLEEN H. CLAFFY, Primary Examiner. ROBERT K. SCHAEFER, xam ner,

Claims

1. AN ELECTRIC SWITCH OPERATING MECHANISM COMPRISING: A ROTATABLE CAM HAVING A NORMAL CENTER POSITION AND BEING ROTATABLE IN EITHER OF TWO DIRECTIONS FROM SAID CENTER POSITION; CAM FOLLOWER MEANS YIELDABLY ENGAGING SAID CAM FOR BEING DISPLACED BY SAID CAM TO ACTUATE A SWITCH WHEN SAID CAM IS ROTATED WITH RESPECT TO SAID CAM FOLLOWER MEANS; SAID CAM FOLLOWER MEANS BEING FREELY ROTATABLE IN PLACE WITH SAID CAM WHEN SAID CAM IS ROTATED IN ONE DIRECTION FROM SAID CENTER POSITION TO ALLOW SAID CAM FOLLOWER MEANS TO REMAIN UNDISPLACED AND THERE-