US3691333A - Alternate action mechanism - Google Patents

Abstract

The present invention relates to a new improved alternate action mechanism for control devices, such as switches, which utilizes a pawl mounted for free rotation on an actuator and for operative association with camming surfaces formed in an associated hollow casing. The camming surfaces act to partially rotate the pawl on an initial downward stroke of the actuator to such an extent that the pawl cooperates with the camming surfaces to preclude total return of the actuator without subsequent reciprocal motion of the actuator further rotating the pawl. Contiguous opposite sides of a pawl tooth are engaged by a shoulder portion of said camming surfaces to prevent return.

Description

United States Patent Elliott 51 Sept. 12, 1972 [54] ALTERNATE ACTION MECHANISM 22 Filed: March 19,1971

211 Appl.No.: 126,162

[52] US. Cl. ..200/153 J [51] Int. Cl. ..l-10lh 13/56 [58] Field of Search ..200/153 J, 169 PB [56] References Cited UNITED STATES PATENTS 3,165,612 1/1965 Bailey ..200/153 UX J 3,153,714 10/1964 Bury ..200/153J 3,148,255 9/1964 Myrent et al ..200/153 J FOREIGN PATENTS OR APPLICATIONS 1,171,778 11/1969 Great Britain ..200/153 J Primary Examiner-David Smith, Jr.

Assistant Examiner-Robert A. Vanderhye Att0meyRobert W. Beart, Jack R. l-lalvorsen, Thomas W. Buckman and Edward L. Benno 57 ABSTRACT The present invention relates to a new improved alternate action mechanism for control devices, such as switches, which utilizes a pawl mounted for free rota tion on an actuator and for operative association with camming surfaces formed in an associated hollow casing. The camming surfaces act to partially rotate the pawl on an initial downward stroke of the actuator to such an extent that the pawl cooperates with the camming surfaces to preclude total return of the actuator without subsequent reciprocal motion of the actuator further rotating the pawl. Contiguous opposite sides of a pawl tooth are engaged by a shoulder portion of said camming surfaces to prevent return.

6 Claims, 5 Drawing Figures llllillllllllllllll Illllllllllllllli lllllllllllll ALTERNATE ACTION MECHANISM Many new innovations have been developed in the electrical control field which have advanced the state of the art to a high level. In one area of this field, repetitive actuator and re-ease mechanisms, more commonly known as alternate action mechanisms, have been developed for actuating a control device and maintaining the same in either of two positions when operated. Such mechanisms provide alternate operation of a switch where controlled by successive actuations of an operator, such as a plunger, push button or the like.

The various configurations of the prior art alternate action mechanisms generally require a relatively longreset stroke and quite often do not lend themselves to true and positive resetting without repeated movements of the actuator.

Accordingly, it is an object of this invention to provide an alternate action mechanism which is reliable and provides a positive uninterrupted action.

A further object of this invention is to provide an alternate action mechanism which requires a short reset stroke following the actuating stroke.

Yet another object of the present invention is a provision of an alternate action mechanism which is relatively simple and inexpensive and yet has a strong and rigid construction.

Still a furtherobject of the present invention is the provision of a new and improved alternate action mechanism which can be utilized with avariety of switch mechanisms. I

The above stated and other objects of the invention are accomplished by the provision of an actuator keystem mounted in a hollow casing for reciprocal movement therein. A freely rotatable pawl is mounted on the keystem for association with a plurality of camming surfaces which act to alternately restrict movement of the actuator toward its initial position and allow the actuator to resume its initial position.

Other objects and advantages will become apparent from the following description when taken in connection with the accompanying drawings wherein:

FIG. 1 is an exploded view of a key switch including the new alternate action mechanism.

FIG. 2 is a front view of the switch in its normal or undepressed condition.

FIG. 3 is a sectional side view taken along the line 3-3 of FIG. 2.

FIG. 4 is an enlarged fragmentary view of the pawl and camming surfaces of the alternate action mechanism.

FIG. 5 is a side elevation view of the pawl member.

FIGS. 1 through 3 illustrate a preferred embodiment of the invention comprising a housing or guide support means 10, a magnetic core 12, first and second permanent magnets 14 and 16, a keystem l8 and a keystem return spring 20. A keycap 22 is attached to the top of the keystem. The core 12 and permanent magnets 14 and 16 comprise the switching mechanism particularly shown and claimed in co-pending, commonly assigned application, Ser. No. 879,220 filed Nov. 24, 1969 which on Aug. 16, 1971, issued as US. Pat. No. 3,638,221. The particular details of the switches are not important to the invention and it should be understood that a variety of mechanical switching mechanisms can be utilized in lieu of the magnetic switching mechanism, without departing from the invention.

The housing is an elongated body which may be square and need be no wider than the dimensions of the keycap. The housing may be formed with an overhanging ledge portion 100 extending partially around this top, A portion of two opposing sides of the housing are formed at an angle to the length of the housing so as to provide two cars 1011. The cars 10b have a certain degree of resiliency so that the switch housing may be inserted downwardly through a hole in a support plate 24 as shown in FIG. 2. After the ears pass through the hole, they expand outwardly to prevent upward movement of the housing. The ledge 10a prevents downward movement. Thus the housing may be firmly locked in position in the support plate. If necessary, the housing may be removed from the plate by pressing the ears inwardly and lifting the housing. The housing has a longitudinal opening 11 for receiving the keystem 18 which, as shown in FIG. 1, is a generally box like structure having two legs 18a and 18b. A central portion 10c of the housing extends from one side of the housing to the other, thus bisecting the lower portion of the opening 11. A post 10d extends upwardly from the central portion 100 to retain a compression spring 20 which is compressed between portion 100 of the housing and the underside of the tip portion of the keystem 18.

The lower portion of the housing 10 is formed so as to have a recess l0e extending across it between opposite sides. A further recess is formed perpendicular to recess 10c and extending through the central portion 10c of the housing. A ferrite toroidal core 12 is positioned in the further recess so that its center opening is aligned with recess 102. As shown in FIG. 3, this arrangement locates the core 12 so that it may be readily threaded by one or more windings 26. The core may be force fit into the recess or held in place by a suitable adhesive material. The legs 18a and 18b of the keystem are punched to form tangs 18e which hold permanent magnets 14 and 16. When the switch is in the depressed statethe permanent magnets are moved away from the core 12 and the core desaturates. The particular switching mechanism thus described can readily be exchanged with snap action switching mechanisms as described in US. Pat. No. 3,300,611 or other switching mechanisms without departing from the scope of this invention.

As shown in FIG. 1, the keystem actuator 18 carries a pawl 29 which may be snapped in an aperture in leg 18a for free rotation therewith. The pawl is in registry with an aperture 28 formed in one side of the casing 10.

The aperture 28 in combination with the pawl 29 provides a reliable alternate action switching mechanism as will be set forth below. The aperture is of an irregular shape and includes a plurality of camming surfaces 30, 32, 34, 35, 36, 37, 38, 40, 42, 44, and 46 as shown in FIG. 4.

The pawl 29 is formed in a generally trapezoidal shape having a pair of short sides 48 and a pair of long sides 50. The trapezoidal shaped pawl includes a pair of acute angles A forming relatively sharp teeth 52 at junctures of sides 48 and 50. The remaining junctures of sides 48 and 50 are formed in a generally obtuse included angle and are relatively smooth surfaces.

FIG. 2 shows the cam and actuator in an initial position biased outwardly as a result of spring 20. In the initial position of the pawl, as seen in FIG. 2, the long side 50 of the pawl, and surface 30 of the aperture extend in planes generally parallel to a longitudinal axis of the keystem 18, which longitudinal axis may also be used to describe the orientation of the aperture with the casing and the keystem. The aperture 28 is arranged relative to the pivot point of the pawl so as to position a long side 50 closely adjacent to a side support surface 30 which tends to orient the pawl along the above mentioned longitudinal axis of the actuator. It should also be noted that the angle formed by the intersection of surfaces 30 and 46 is preferably equal to angle A thus additionally serving to orient the pawl 29 within the aperture 28. j

The aperture 28 includes a pocket-like portion formed from the surfaces 38 and 40. Likewise a first shoulder-like portion is formed from surfaces 32 and 34. FIG. 4 further shows a second shoulder-like portion formed from surfaces 40 and 42. The importance of these portions in conjunction with the particular configuration of the pawl will be apparent in the following detailed description of the operation of the device.

A description of the consecutive positioning of the pawl will be clarified by the use of suffixes a through d when referring to four basic positions of the mechanism.

As the actuator begins a downward stroke, the pawl 29 remains in alignment with the longitudinal axis of the actuator as a result of the support surface 30. At the lowermost portion of the downward stroke the teeth 52a contact rotation inducing surface 38 in the pocket which forces the pawl out of axial alignment with the longitudinal axis. Rotation limiting surface 40 of the pocket restricts this rotation to that of a predetermined extent. It should be noted that the particular angular relationship of the rotation inducing ramp 38 with a horizontal axis, in conjunction with acute angle A of the pawl insures that this rotation takes place. The complement of the angle A is shown to be greater than the angle B defined by a horizontal plane and ramp surface 38. An example of values of these respective angles which has been found to be adequate in actual operation are approximately 54 for angle A and 30 for angle B.

After the pawl and actuator reach the bottommost portion of the aperture 28, the biasing means acts to force the actuator to return to its initial position. However, as a result of the partial rotation of the pawl, tooth 52b is now aligned with a shoulder portion formed from surfaces 32 and 34. This shoulder portion retains the pawl from further rotation and further upward movement of the actuator. Thus the actuator is held from releasing the switch mechanism. The switch mechanism is released by subsequent movement of the keystem actuator against the bias of the return spring 20. This further reciprocation of the keystem results in tooth 52c abutting a second shoulder means formed from surface 42 and 40. This shoulder means further rotates the pawl as a result of the camming action of side 48 on surface 42. The further rotation places tooth 52d out of alignment with the first shoulder portion 32, 34 and brings tooth 52d into alignment for subsequent contact with a surface 35. As a result of the bias of the return spring and the camming action of tooth 52d on surface 35, the pawl is rotated further in the upward stroke of the actuator and eventually assumes a position 180 from the initial position. The initial orientation is achieved as a result of the aforementioned surfaces 30 and 46.

The axial distance between the surfaces 32 and 42 is slightly larger than the length of the longer side 50. It will be apparent that this relationship results in an extremely short reset stroke. The sharp corners of the teeth 52 aid in properly seating and locking the pawl in the shoulder 32 and 34, which are similarly joined in a sharp angular relationship.

A further embodiment of the invention includes a sharp projection 54 on surface 32 of the first shoulder means which presents a slight interference in the seating of the pawl and presents a snap-like feel to the actuator.

From the forgoing, it will now be apparent that the present invention contemplates a novel and unique alternate action mechanism capable of being moved quickly from an at rest to a latched position and back again utilizing a relatively short reset stroke. The positive lock and the capability of use for many switching mechanisms makes the instant alternate action mechanism desirable for many commercial applications. While the preferred embodiment of the present invention has been shown and described herein, it is obvious that many structural details may be changed without departing from the spirit and scope of the appended claims.

lclaim:

1. An alternate action mechanism comprising, in combination a hollow casing, a switch actuator mounted in the casing for straight line reciprocating movement therein, means biasing the actuator in a first direction, switch means operatively associated with the actuator, pawl means carried for free rotation on the actuator, an aperture in the hollow casing forming camming surfaces and arranged for operative association with the pawl means, said pawl means comprising a pawl member having a pair of teeth on the opposite ends thereof, the camming surfaces comprising pocket and shoulder portions, the pocket portion positioned to engage one of said teeth when said pawl member is in an initial position and partially rotate said pawl member responsive to movement of the actuator in a direction opposite to the bias, the shoulder portion formed and positioned to lockingly engage contiguous opposite sides of the second tooth of said pawl member to preclude the return of the actuator to its initial position responsive to said partial rotation of said pawl member, a second shoulder portion positioned to engage said one of said teeth and further rotate said pawl responsive to a second movement of the actuator in a direction opposite to the bias, and said camming surfaces including a further surface engaging and rotating said pawl member to an initial position responsive to further movement of the actuator in the direction of said bias.

2. An alternate action mechanism in accordance with claim 1 wherein the camming surface is in the form of an aperture in one wall of the hollow casing and said further surface comprises a side support surface extending from the uppermost portion of the aperture in a plane generally parallel to the plane including the longitudinal axis of the actuator, the pocket portion forming the lowermost extremity of the aperture and including a rotation inducting ramp surface and a rotation limiting abutment surface wherein the side support surface axially aligns the pawl member within the aperture while the rotation inducing and limiting surfaces force the pawl member into a predetermined angular relationship with the longitudinal axis of the actuator.

3. An alternate action mechanism in accordance with claim 2 wherein the pawl member is of a generally trapezoidal configuration having opposed pairs of adjacent sides with each pair of adjacent sides forming an acute angle A and defining one of said pair of teeth, the uppermost portion of the aperture formed by a pair of camming surfaces intersecting to form an angle substantially equal to acute angle A, wherein the cooperation of the pawl member with the uppermost portion of the aperture axially aligns the pawl member in the aperture.

wherein a tooth of the pawl member contacts the ramp surface which imparts a slight angular rotation to the pawl member and allows the other tooth to abut the first shoulder portion as the actuator is forced in said first direction and necessitates further movement in the opposite direction to free the pawl. v

5. An alternate action mechanism in accordance with claim 2 wherein the pawl member is shaped as a trapezoid having a pair of short sides and a pair of long sides forming a pair of acute included angles and a pair of obtuse included angles, wherein the acute corners of the pawl define said pair of teeth to operatively engage the pocket and shoulder portions in the aperture.

6. An alternate action mechanism in accordance with claim 5 wherein a long side of the pawl member cooperates with a side support camming surface in the aperture to position the pawl member in axial alignment with the actuator when the actuator returns to its initial position under the influence of the biasing means.

Claims (6)

1. An alternate action mechanism comprising, in combination a hollow casing, a switch actuator mounted in the casing for straight line reciprocating movement therein, means biasing the actuator in a first direction, switch means operatively associated with the actuator, pawl means carried for free rotation on the actuator, an aperture in the hollow casing forming camming surfaces and arranged for operative association with the pawl means, said pawl means comprising a pawl member having a pair of teeth on the opposite ends thereof, the camming surfaces comprising pocket and shoulder portions, the pocket portion positioned to engage one of said teeth when said pawl member is in an initial position and partially rotate said pawl member responsive to movement of the actuator in a direction opposite to the bias, the shoulder portion formed and positioned to lockingly engage contiguous opposite sides of the second tooth of said pawl member to preclude the return of the actuator to its initial position responsive to said partial rotation of said pawl member, a second shoulder portion positioned to engage said one of said teeth and further rotate said pawl responsive to a second movement of the actuator in a direction opposite to the bias, and said camming surfaces including a further surface engaging and rotating said pawl member to an initial position responsive to further movement of the actuator in the direction of said bias.

2. An alternate action mechanism in accordance with claim 1 wherein the camming surface is in the form of an aperture in one wall of the hollow casing and said further surface comprises a side support surface extending from the uppermost portion of the aperture in a plane generally parallel to the plane including the longitudinal axis of the actuator, the pocket portion forming the lowermost extremity of the aperture and including a rotation inducting ramp surface and a rotation limiting abutment surface wherein the side support surface axially aligns the pawl member within the aperture while the rotation inducing and limiting surfaces force the pawl member into a predetermined angular relationship with the longitudinal axis of the actuator.

3. An alternate action mechanism in accordance with claim 2 wherein the pawl member is of a generally trapezoidal configuration having opposed pairs of adjacent sides with each pair of adjacent sides forming an acute angle A and defining one of said pair of teeth, the uppermost portion of the aperture formed by a pair of camming surfaces intersecting to form an angle substantially equal to acute angle A, wherein the cooperation of the pawl member with the uppermost portion of the aperture axially aligns the pawl member in the aperture.

4. An alternate action mechanism in accordance with claim 3 wherein the rotation inducing ramp surface extends at an acute angle B to a plane normal to the axis of movement of the actuator, said acute angle B being less than the complement of acute angle A wherein a tooth of the pawl member contacts the ramp surface which imparts a slight angular rotation to the pawl member and allows the other tooth to abut the firSt shoulder portion as the actuator is forced in said first direction and necessitates further movement in the opposite direction to free the pawl.

5. An alternate action mechanism in accordance with claim 2 wherein the pawl member is shaped as a trapezoid having a pair of short sides and a pair of long sides forming a pair of acute included angles and a pair of obtuse included angles, wherein the acute corners of the pawl define said pair of teeth to operatively engage the pocket and shoulder portions in the aperture.

6. An alternate action mechanism in accordance with claim 5 wherein a long side of the pawl member cooperates with a side support camming surface in the aperture to position the pawl member in axial alignment with the actuator when the actuator returns to its initial position under the influence of the biasing means.

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