US3055226A - Overtravel and snap-back control device for limit switch arms - Google Patents

Description

Sept. 25, 1962 zss mg 3,055,226

OVERTRAVEL AND SNAP-BACK CONTROL DEVICE FOR LIMIT SWITCH ARMS Filed Oct. 8, 1959 IN VENTOR. zQl/aai/ H Aiess/irzg 3,055,226 Patented Sept. 25, 1962 31955326 OVERTRAVEL AND SNAP-EACK IONTROL DE- VICE FOR LIMIT SWITCH ARMS Rudoir H. Kiessling, Miiwankee, Wis, assignor to Square 1) Company, Detroit, Mich, a corporation of Michigan Filed Oct. 8, 1959, Ser. No. 845,246 7 Claims. (Cl. 74-96) The present invention relates to a motion translating device for translating movement in a first direction in a first plane to movement in a second direction in a second plane.

One of the applications of the invention is in the elec tric switch field wherein movement of an object causes the object to bump the operating arm of an electrical switch to actuate the switch. Usually the switch per se is of the type commonly known as a snap switch or as a push button switch in which the button is moved axially in a line of movement for a very short, limited distance to cause operation of the switch. The operating mechanism for moving the button of the switch generally has a rocker arm or a switch actuating arm which is pivotally movable and operates through a shaft and a crank or button abutting arm to effect movement of the push button.

In many instances it is necessary to provide for excessive overtravel or excessive movement of the rocker arm while limiting the movement of the push button. The conditions relating to excessive overtravel and length of movement of the actuating arm relative to the limited length of movement the button abutting arm is permitted to make are never known at the time of manufacturing of the switch. Switch manufacturers have long encountered this problem of devising a device which automatically permits various lengths of movement of the actuating lever while limiting the length of movement of the button abutting arm and especially wherein that device can be constructed with the switch at the time of manufacture and will not have to be adjusted at the time the switch is installed and used. A further problem also encountered by switch manufacturers is that of providing a force transmitting device which transmits forces to move the switch button while it is being moved within the limits of its travel and which absorbs forces tending to move the button beyond the limits of its distance of travel.

One of the objects of the present invention is to provide a motion translating device which overcomes the aforementioned problems and others.

Another object of the present invention is to provide a motion translating device in which the distance of travel on the output side of the device is limited or maintained constant regardless of the distance of movement on the input side of the device beyond a predetermined distance of movement.

A further object of the invention is to provide a motion translating device for translating movement of an uncontrolled length in a first direction in a first plane to movement of a fixed length in a second direction in a second plane.

A still further object of the invention is to provide a limit switch having a push button and a button actuating rocker arm with a resilient interconnection between the arm and the switch button to transmit movement therebetween until a predetermined distance of movement has occurred and to then prevent further transmittal of move ment therebetween beyond that predetermined limit.

Other objects and a fuller understanding of the present invention may be had by referring to the appended claims defining the present new, novel and useful invention or discovery, to the following description of a specific means or method contemplated by the inventor for carrying out his invention, and to the accompanying drawings in which:

FIGURE 1 is a perspective view of a limit switch incorporating the features of the present invention;

FIGURE 2 is a view taken approximately along the line 2-2 of FIGURE 1;

FIGURE 3 is a sectional view taken along the line 3-3 of FIGURE 2;

FIGURE 4 is a perspective view of the force transmitter interposed in the shaft of the switch operating mechanism;

FIGURE 5 is a plan view of the force transmitter of FIGURE 4 to illustrate the construction thereof; and

FIGURE 6 is a sectional view taken along the line 6--6 of FIGURE 5.

The following description of the attached drawings and the accompanying claims jointly set forth one or more modifications incorporating the present invention and the advancement in the art of motion translating devices. As used throughout the present description and claims the specific terms used to identify the parts or components have been arbitrarily chosen to indicate to others commercially available parts or components which may be readily obtained to carry out the specific mode of the invention as described herein, and they are to be interpreted in their broad sense wherein they include electrically or mechanically equivalent components which will provide the same functions as those mentioned herein.

The motion translating device 10 is illustrated in the figures as being applied to an electrical switch '11 mounted within a suitable supporting housing 12. The electrical switch 11 is illustrated in dotted lines in FIGURE 3 and has a push button 13 movable in and out of the switch or in a line of movement represented by the bi-directional arrow 14 superimposed on FIGURES l and 3. The switch 11 may be of any suitable design, including the switch illustrated in Patent Number 2,328,154, issued to G. A. Lennholm on August 31, 1943.

The motion translating device 10 is mounted on housing 12 and operates to translate movement from an object abuttable operating arm 15 to the push button 13. Motion translating device :10 translates the movement of the free end 16 of arm 15 along a line of movement indicated by the bi-directional arrow 17 superimposed on end 16, to movement of button 13 along the line of movement indicated by the bi-directional arrow 14.

Motion translating device 10 includes a housing 20 adapted to be fitted to the housing 12 to support the motion translating device 10 in operative relationship with push button 13. Mounted in housing 12 is a rocker shaft 21 having an axis, represented by the dash-dot line 22 in FIGURE 1, which extends parallel with the bi-directional arrow 14 and transverse to a plane containing bi-directional arrow 17. Operating arm 15 extends radially from rocker shaft 21 and is thus movable in the plane containing the line of movement indicated by bi-directional arrow 17.

Also secured to rocker shaft 2-1 is a second rocker arm mechanism 23 which is located internally of housing 20. Rocker arm mechanism 23 rocks about the shaft axis upon movement of operating arm 15. The line of movement of rocker arm mechanism 23 is in a plane generally transverse to bi-directional arrow 14. Therefore a bell crank 24 is pivoted by axle 25 internally in housing 20 and has one end 26 interconnected by a connector 27 to rocker arm mechanism 23. Bell crank 24 also has an opposite end 28 operatively disposed on the opposite side of axle 25 and positioned to be abutta-bly engageable with push button 13 to move push button 13- along the line of movement of bi-directional arrow 14. Thus 28 is also movable along the line of movement indicated by bidirectional arrow 14 and towards and away from the plane containing the line of movement of rocker arm 23.

Rocker arm mechanism 23 is biased against movement inone direction by a biasing spring 30 and sometimes 'also a biasing spring 31. .Biasing spring 30 is interposed between an end wall 32 of housing and a shoulder 33 on rocker arm mechanism 23 so that its direction of biasing force is generally parallel with axle and transverse I in an opposite direction.

When it is used, biasing spring 31 is positioned between free end 34 of rocker arm mechanism 23 and a side wall 35 of housing 20 so that its biasing force is in a direction transverse to the biasing force of spring 30 and in a plane parallel to the plane containing bi-directional arrow 17. The biasing force of spring 31 is either in addition to or in opposition to the biasing force of spring 30, depending on which side of rocker shaft 21, biasing spring 30 has been positioned.

In this instance, rocker arm mechanism 23 has also been constructed from two pieces, each of which is carried by rocker shaft 21. One of these pieces, namely, piece 40, is secured to rocker shaft 21 for movement therewith and provides the shoulders 33 and 33'. The other piece,

'namely piece 41, extends beyond piece 40 to terminate in free end 34. Piece 41 is loosely bearinged about rocker shaft 21. Rotational forces from rocker shaft 21 are transmitted through piece 40 to piece 41 by means of a coil spring 42 which encircles rocker shaft 21. Piece 40 and piece 41 have fingers 43 and 44 respectively extending next adjacent each other and positioned at a distance from rocker shaft 21. The opposite ends of coil spring 4-2 engage both of these fingers 4-3 and 44 to transmit movement therebetween.

Movement of free end 16 is transmitted to rocker shaft 21 by a force transmitter which comprises an inner annulus 51 and an outer annulus 52. These annuli 51 and 52 are spaced apart radially to receive a coil spring 53 tion 55 is arranged to pass between projections 54a and 54b. The spring 53 in this instance is a coil spring having a normal relaxed length at least equal to the circumference of the inner annulus and a diameter less than the distance between the inner and outer annuli.

In addition, the inner annulus has means, for example; bore 56, for receiving the end of shaft 21 and set screw STthreaded therein and tightenable against rocker shaft '21 to secure rocker shaft 21 and inner annulus 51 to- Outer annulus 52 and inner annulus 51 have gether. axially extended concentric portions 62 and 61 respectively which are spaced apart and receive friction rings 63 therebetween. Outer annulus 52 and inner annulus 51 are held against relative axial movement by a screw 64 which is located internally of concentric portion 62 and is threaded into concentric portion 61. It is noted that concentric portion 62 has an internal flange through which concentric portion 61 extends and that one or more friction rings 63 are disposed between this flange 65 and the head 66 of screw 64. In this instance, friction rings 63 were constructed of several O-rings or washers constructed of a material having relatively high friction characteristics and a material, for example, rubber, which normally radially expands when compressed axially. Tightening of screw 64 moves head 66 towards flange 65 to increase the friction drive between concentric portions 61 and 62 and through friction rings 63. In the preferred form of the invention the screw 64 is of the well known self-locking type and a slip ring 63a of low friction material is positioned between the remaining friction ring 63 and the head 66 to prevent loosening of the screw due to movement of the friction rings 63 Operating arm 15 is secured with concentric portion 62 to prevent relative movement therebetween by providing operating arm 15 with a split collar 70 which encircles concentric portion 62 with a clamp screw 71 to clamp split collar 70 on to concentric portion 62.

Movement of operating arm 15 along the line of movement indicated by bi-directional arrow 17 will cause movement of end 23 and thus push movement of button 13 along the line of movement of bi-directional arrow 14. This movement is transmitted from concentric portion 62 and the integrally, interconnected outer annulus 52 through coil spring 53 to inner annulus 51 and rocker shaft 21 upon being moved, causes movement of bell crank 24- about axle 25 and thereby movement of end 28. The motion translating device, because of the characteristics of force transmitter 50, thus provides excessive overtravel or movement of operating arm 15 along the line indicated by bi-directional arrow 17 without causing movement of push button 13 beyond a desired or preselected amount of limited movement.

Normally, projections 54a and b are aligned on a common radius extending from dot-dash line 22. If operating arm 15 is moved through an overtravel distance, projection 55 is moved angularly away from projections 54a and b to a position wherein projections 54a and b and projection 55 are displaced radially from each other. Upon release of force against operating arm 15, coil spring 53 tends to snap the projections 54a and b and 55 back into the position illustrated wherein they are aligned on a common radius from dot-dash line 22. As illustrated in FIGURE 5, the individual turns in the coil spring 53 engage the inner surface of the outer annulus 52 because the spring tends to straighten itself out and also because the spring is usually at least partially compressed when it is in the position of FIGURE 5. There is a slight static and sliding friction between each individual turn in the coil spring 53 and the outer annulus 52.

Assuming arm 15 has been angularly moved about dot-dash line 22, and projection 54 has been moved out of axial alignment with projection 55, coil spring 53 is compressed to a length shorter than its relaxed length, or its length when projections 54 and 55 are radially aligned as illustrated in FIGURE 5. Coil spring 53 now exerts force on projections 54 and 55 to urge them back into the radial alignment illustrated. To return the projections to radial alignment, the spring must exert force suiucient to overcome the static friction between the individual turns of coil spring 53 and the inner surface of outer annulus 52 and thereafter overcome the sliding friction. It is also recognized that if all of the turns release from the inner surface of outer annulus 52 simultaneously so that there is an elimination of static friction therebetween, and if there is no introduction of sliding friction, the force in the spring will snap projections 54 and 55 into radial alignment at an undesirable rate of speed.

projections 54 and 55 slowly return to their illustrated I position without any jolting or unnecessary snapping of the parts. Tightening or loosening of the screw 64 controls the total frictional resistances and provides for adjustment of the rate of returning of the projections 54 and 55 to their original position as illustrated in FIGURE 5.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

l. A torque transmitting device for use between a rotatable shaft and a movable actuating arm comprising; an outer member having a pair of axially spaced internal annular surfaces and an external portion conuectible to the actuating arm, an inner member conuectible to the shaft and having a pair of axially spaced external cylindrical surfaces respectively of smaller diameter than the annular surfaces of the outer member said members being nested together in coaxial alignment so a pair of spaced annular spaces are provided between the annular and cylindrical surfaces of the outer and inner members, a coil spring positioned in one of said annular spaces, means on the outer and inner members alignable when the members are in a predetermined neutral relative angular position and engageable with the spring for compressing the spring when the members are displaced in either direction from the neutral angular position whereby the spring constantly opposes relative angular rotation between said members, and an adjustable friction means in the other annular space for frictionally opposing any angular rotation between the members and thereby opposing the opposition exerted by the spring to the angular displacement of the members from neutral position.

2. A torque transmitting device for use between a rotatable shaft and a lever which is oscillatable in a plane normal to the shaft about a point on the axis of the shaft, comprising; a pair of nested members in coaxial alignment with each other and each having annular surfaces disposed and sized to provide a pair of axially spaced annular spaces between the members, one of said members being connectible with the shaft and the other member being conuectible to the lever, means including a coil spring disposed in one of the annular spaces for resiliently opposing any rotative movement between said members from a neutral position, and adjustable friction means in the other annular space for opposing any relative rotation between said members, said friction means being adjustable for varying the rate of relative rotation between said members caused by the spring toward the neutral position subsequent to the displacement of the members from the neutral position.

3. The torque transmitting device as recited in claim 2 wherein the inner of said nested members is conuectible to the shaft and the outer member is conuectible to the lever.

4. The torque transmitting device as recited in claim 2 wherein the means for resiliently opposing relative rotation between the members includes a single lug on one of the members and a pair of spaced lugs on the other member with the lugs extending into the space between the members so as to engage the ends of the spring and wherein the single lug is disposed to pass between the spaced pair of lugs.

5. The structure as defined in claim 2 wherein the spring means is a coil spring having a coil diameter less than the distance between said inner and outer annular surfaces of the members providing the annular space wherein the spring is positioned and a relaxed coil length at least equal to the outer circumference of the annular surface of the inner member. I

6. A motion translating device adapted to translate movement of a first element in a first line of movement in a first plane to movement of a second element in a second straight line of movement in a second plane which intersects the first plane, said device comprising, a rocker shaft angularly movable about a first axis extending parallel to the second line of movement and transverse to the 5 first plane, a first lever arm secured to said rocker shaft and extendng radially therefrom and terminating in a free end movable in a plane parallel to said first plane about said first axis, a second lever arm extending radially from said shaft and terminating in an operating end, 10 a bell crank pivotal about an axis transverse to said first axis and to said second line of movement, said bell crank having one end thereof operatively interconnected with said operating end of said second lever and having the other end thereof engageable with the second element and operatively movable along said second line of movement, support means supporting said rocker shaft and said bell crank for movement about their respective axes and for limiting the movement of the bell crank and the first lever, resilient means reacting through the second lever arm for biasing said bell crank for movement of said operating end in one direction along said second line of movement, a first force transmitting means including a coil spring surrounding said rocker shaft to transmit movement from said first lever arm to said second lever arm while the operating end of the bell crank is within the limit of its distance of travel and to absorb forces from said first lever arm tending to move said bell crank beyond the limits of said distance of travel and a second force transmitting means consisting of inner annulus connected to the rocker shaft and an outer annulus connected to the first element for transmitting movement of the first element to the rocker shaft, said annuli being radial- -ly spaced from each other and each of said annuli having a projection positioned in the space between the annuli for alignment next adjacent each other and for displacement from each other upon angular movement of one annulus relative to the other annulus, and spring means in said space between the inner and outer annuli and having opposite ends abuttable against both of said projections for normally maintaining the projections in alignment, and friction means resisting movement of either annulus relative to the other annulus by said spring means.

7. In combination with a switch having a rotatable 5 actuating shaft which is rotatable between predetermined limits from an at rest position, a lever for rotating the shaft from the at rest position, said lever being oscillatable from an at rest position in a plane normal to the shaft about a point on the axis of the shaft, means connected between the shaft and lever for transmitting movement of the lever to the shaft in response to an external force on the lever and for absorbing the movement of the lever when the lever is moved beyond those positions determining the rotatable limits of the shaft, said means including lever returning means for returning said lever to the at rest position when the external force on the lever is removed, and means associated with the lever and shaft and acting in opposition to said lever returning means for maintaining the return movement of the lever at an adjustable controlled rate.

References Cited in the file of this patent UNITED STATES PATENTS 1,814,608 Schuh et al. July-14, 1931 2,460,695 Hennessy Feb. 1, 1949 2,474,945 Johnson July 5, 1949' 2,673,468 Immel et a1. Mar. 30, 1954 2,729,485 Schlage Ian. 3, 1956 2,760,736 Mihalko et al. Aug. 28, 1956 2,788,402 Iglehart et a1 Apr. 9, 1957 2,833,347 Terry May 6, 1958 FOREIGN PATENTS 350,328 Germany Mar. 17, 1922

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