ALTERNATE ACTION SWITCH MECHANISM
United States Patent 3824362
An alternate action switch mechanism is achieved by means of a cam including a cam slot into which a cam follower is inserted to engage a plurality of cam surfaces that are formed as a series of ramps and drop-offs. The cam slot is formed as a closed loop so that the cam follower repeatedly falls into one drop-off after another after it rides up the associated ramp surfaces. The cam follower is thereby prevented from returning to the previous ramp by each drop-off and it, therefore, traverses the cam slot in a single direction. At one position of the cam follower, resulting from a first depression of the plunger, the switch is locked into an actuated position. When the plunger is subsequently depressed, the cam follower returns to its original position, thereby deactuating the switch.
US Patent References:
PUSHBUTTON SWITCHES
Schadow - June 1971 - 3582592
Push-push switch convertible to momentary switch
Piber - November 1966 - 3288973
Alternate action arrangement
Ensign, Jr. et al. - October 1960 - 2956446
PUSHBUTTON SWITCHES
Schadow - June 1971 - 3582592
Push-push switch convertible to momentary switch
Piber - November 1966 - 3288973
Alternate action arrangement
Ensign, Jr. et al. - October 1960 - 2956446
Application Number:
05/363228
Publication Date:
07/16/1974
Filing Date:
05/23/1973
Export Citation:
Assignee:
Illinois Tool Works Inc. (Chicago, IL)
Primary Class:
International Classes:
H01H13/56; H01H13/50; H01H13/56
Field of Search:
200/153J,153R
View Patent Images:
Primary Examiner:
Schaffer, Robert K.
Assistant Examiner:
Smith, William J.
Claims:
What is claimed is
1. An alternate action switch mechanism comprising a switch housing having an outer surface with an aperture therein, a projection extending from said housing parallel to said surface, an actuating member mounted for movement in said aperture between an initial position and a locked position, spring means for biasing said actuating member towards its initial position, said actuating member having a cam associated therewith, an elongated wire cam follower having a portion located under said projection so that said projection limits the movement of said cam follower to prevent said cam follower from being released from said housing during actuation of said switch mechanism, said cam follower also having first and second ends with the major length of said cam follower between said first and second ends being located on the exterior of said housing so as to be readily removable therefrom when momentary switch action is desired, said first end being secured to said switch housing and said second end serving as the cam following portion of said cam follower, which is positioned to interact with said cam, said cam follower rotating under said projection and over said surface of said housing during actuation of said actuating member with said cam and said cam follower being constructed to interact so as to lock said actuating member in its locked position upon a first actuation of said actuating member and so as to release said actuating member to its initial position upon a second actuation of said actuating member when said cam follower is secured to said housing.
2. An alternate action switch mechanism as set forth in claim 1 wherein said actuating member is a depressable plunger and said cam is integrally formed therewith.
3. An alternate action switch mechanism as set forth in claim 2 wherein said cam follower is C-shaped.
4. An alternate action switch mechanism as set forth in claim 3 wherein said cam comprises a cam guide, a cam slot having closed-loop configuration which encircles said cam guide and cam surfaces in said cam slot and wherein said cam following portion of said cam follower is inserted in said cam slot.
5. An alternate action switch mechanism as set forth in claim 4 wherein said cam surfaces comprise a series of flat surfaces, ramp surfaces and drop-offs and said cam following portion rides on said flat surfaces and said ramp surfaces and over said drop-offs said cam following portion thereby undergoing one general direction of travel around said cam slot.
6. An alternate action switch mechanism as set forth in claim 5 wherein said cam following portion engages at least a portion of said cam guide as said cam following portion travels around said cam slot.
7. An alternate action switch mechanism as set forth in claim 3 wherein said cam comprises a cam slot of a closed-loop configuration and cam surfaces in said cam slot and wherein said cam following portion of said cam follower is inserted into said cam slot and moves around said closed loop upon a first and a second actuation of said actuating member while undergoing one general direction of travel.
1. An alternate action switch mechanism comprising a switch housing having an outer surface with an aperture therein, a projection extending from said housing parallel to said surface, an actuating member mounted for movement in said aperture between an initial position and a locked position, spring means for biasing said actuating member towards its initial position, said actuating member having a cam associated therewith, an elongated wire cam follower having a portion located under said projection so that said projection limits the movement of said cam follower to prevent said cam follower from being released from said housing during actuation of said switch mechanism, said cam follower also having first and second ends with the major length of said cam follower between said first and second ends being located on the exterior of said housing so as to be readily removable therefrom when momentary switch action is desired, said first end being secured to said switch housing and said second end serving as the cam following portion of said cam follower, which is positioned to interact with said cam, said cam follower rotating under said projection and over said surface of said housing during actuation of said actuating member with said cam and said cam follower being constructed to interact so as to lock said actuating member in its locked position upon a first actuation of said actuating member and so as to release said actuating member to its initial position upon a second actuation of said actuating member when said cam follower is secured to said housing.
2. An alternate action switch mechanism as set forth in claim 1 wherein said actuating member is a depressable plunger and said cam is integrally formed therewith.
3. An alternate action switch mechanism as set forth in claim 2 wherein said cam follower is C-shaped.
4. An alternate action switch mechanism as set forth in claim 3 wherein said cam comprises a cam guide, a cam slot having closed-loop configuration which encircles said cam guide and cam surfaces in said cam slot and wherein said cam following portion of said cam follower is inserted in said cam slot.
5. An alternate action switch mechanism as set forth in claim 4 wherein said cam surfaces comprise a series of flat surfaces, ramp surfaces and drop-offs and said cam following portion rides on said flat surfaces and said ramp surfaces and over said drop-offs said cam following portion thereby undergoing one general direction of travel around said cam slot.
6. An alternate action switch mechanism as set forth in claim 5 wherein said cam following portion engages at least a portion of said cam guide as said cam following portion travels around said cam slot.
7. An alternate action switch mechanism as set forth in claim 3 wherein said cam comprises a cam slot of a closed-loop configuration and cam surfaces in said cam slot and wherein said cam following portion of said cam follower is inserted into said cam slot and moves around said closed loop upon a first and a second actuation of said actuating member while undergoing one general direction of travel.
Description:
BACKGROUND OF THE INVENTION
One type of electrical switch of great utility is the alternate action switch in which the actuating member for the switch may be depressed once to actuate the switch, so that the switch will remain locked "on" in the actuated state following release of the actuating member and, when the switch is depressed a second time the switch will be deactuated. In the manufacture of alternate action switches, it is desirable that the alternate action mechanism be constructed so that it cannot interfere with the switching mechanism of the switch, thereby avoiding possible switch failure. Moreover, it is also desirable to be able to provide an alternate action switch mechanism which may be used with many different types of switches. Since the manufacture and sale of switches is highly competitive, it is necessary that any alternate action mechanism of wide use must be designed to be constructed in a simple and reliable manner at a minimum of additional cost over and above the cost of the other switch parts. It is also desirable that the alternate action switch be constructed so that it can serve as a single action switch by slight modification that does not require disability of the switch or removal of the switch from a circuit assembly.
It is, therefore, an object of the present invention to provide an alternate action switch in which the alternate action mechanism is obtained by a cam that is integrally formed on the actuator or plunger of the switch and a cam follower, which is removably secured to the external housing of the switch body, wherein the interaction of the cam and the cam follower provides an alternate action mechanism that does not interfere with the switching mechanism of the switch.
It is an additional object of the present invention to provide an alternate switch mechanism in which alternate action is achieved by the interaction of a cam and the cam follower in which the cam comprises a continuous closed slot having camming surfaces therein that are formed with a series of ramps and drop-offs and the cam follower is formed of a spring wire member with a cam following end that rides in the cam slot and is controlled by the camming surfaces so that the cam follower traverses around the cam slot in only a single direction wherein the actuator of the switch is preferably a plunger that is depressed a first time to lock the switch in its actuated state, due to interaction of the cam follower and the cam, and is depressed a second time to return the plunger to its initial position, at which position the switch is deactuated.
It is another object of the present invention to provide a switch which may be converted from an alternate action switch to a single action or a momentary action switch merely by the removal of a cam follower which is secured to the exterior of the switch housing when an alternate action switch is desired.
Further objects and advantages of the present invention will be apparent from the preceding discussion and from the following description, along with the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially sectionalized side view taken along the lines 1--1 of FIG. 3 which shows the upper portion of the switch housing and the actuator for the switch;
FIG. 2 is a side sectional view taken along the lines 2--2 of FIG. 3 which shows the actuator plunger portion of the switch mechanism;
FIG. 3 is a top view which shows the top of the switch housing and the cam follower;
FIG. 4 is an enlarged view of the cam that is formed on the depressible actuator plunger of FIG. 1;
FIGS. 5--8 are cross sectional views which show the profiles of the various cam surfaces of the cam of FIG. 4 in detail, with the Figure number corresponding to the section of FIG. 4 that is designated by the same number;
FIGS. 9-11 are enlarged views of the cam which show the movement of the cam follower in the cam slot during operation of the switch mechanism.
TECHNICAL DESCRIPTION OF THE INVENTION
The alternate action switch mechanism of the present invention is shown in detail in FIGS. 1, 2 and 3 of the drawings. This mechanism can be utilized by many different types of switches in which a moveable actuating member, such as a depressible plunger, is used.
The compact alternate action mechanism of the present invention is referred to generally by the reference numeral 10 in FIG. 1. Only the upper portion 12 of the switch housing is shown in the figures. The upper portion 12 of the switch housing has an upper surface 14 with an integral boss 16 that projects upwardly from the surface 14. The boss 16 has a central aperture 18 into which the actuating element or plunger 20 is positioned. The switch housing 12 and the plunger 20 of the present invention are preferably formed of plastics, and the plunger 20 is preferably molded as a single part. The lower end of the plunger 20 may be bifurcated, as shown in FIG. 2, and the arms 23, 25 may be used to actuate the type of switch which may be turned "on" and "off" by movement of a depressible plunger. This mechanism may also be used to operate special types of switches such as those shown in U.S. Pat. Nos. 3,638,221 and 3,638,222, which are owned by the assignee of the present application.
In order to provide for free motion of the plunger 20 in the boss 16, the outer periphery of the plunger 20 contacts the boss 16 at only several bearing surfaces 24 in order to reduce friction between the plunger 20 and the boss 16. The upper portion 26 of the plunger 20 is formed of a generally rectangular shape and has two keycap retainers 28 of a generally rectangular shape which extend from opposite sides of the upper portion 26. An identification keycap which is unique to the switch may be secured on the portion 26 and the retainers 28. Below the rectangular section 26 there is a larger section 30 of a generally circular shape. Section 30 has an outwardly extending cam block 32 of a generally rectangular shape. The cam 34 is formed in the cam block 32. The generally cylindrical boss 16 is constructed with a generally rectangular enclosure 36 which conforms to the shape of the cam block 32.
In order to return the switch to its initial position upon release of force on the plunger 20, the internal portion of the plunger 20 is formed with a hollow shape for receiving a bias spring 38. The spring 38 is compressible between a surface 40 of the housing 12 and a surface 42 on the plunger 20. When the plunger 20 is depressed the spring 38 supplies a return force to the plunger 20. The manner in which the biasing force is supplied to return the plunger 20, or other actuating member, to its unactuated position may be achieved in a number of different ways within the scope of the present invention.
The cam 34 includes a cam slot 35 that is formed integrally with the cam block 32. As can be seen by reference to FIGS. 1 and 4, the cam slot 35 has a closed loop configuration. When viewed from the front, the bottom portion 35a of the cam slot 35 resembles a "Y" while the upper portion 35b resembles a "V." The cam follower 44 is formed of a spring wire which is C-shaped. The ends of the cam follower 44 are turned inwardly toward each other with one of the other ends, 44a, being substantially shorter than the other outer end 44b. The end 44a is inserted into a receiving aperture 46 that is formed in the boss 16, so as to secure the cam follower 44 to the switch housing 12. The longer end 44b of the cam follower 44 serves as the actual cam following portion of the mechanism, and this end is positioned in engagement with the cam surfaces 37 of the cam slot 34. (FIGS. 5 - 8). The cam following end 44b of the cam follower 44 passes through a retaining slot 48 in the enclosure 36 so that the end 44b of the cam follower 44 is allowed to move to the left or to the right, as viewed in FIG. 3, in the slot 48 but so that the end 44b is restrained from moving substantially in a vertical direction by the enclosure 36. The rear leg 44c of the cam follower 44 is restrained from moving upwardly, which it otherwise would do when the cam following end 44b is at certain positions in the cam slot 35, by means of the outwardly projecting post 50 which extends from the boss 16.
The manner in which the cam follower 44 and the cam 34 interact to provide the desired alternate action feature of the present invention is described in more detail by reference to FIGS. 4 through 11. As previously mentioned, the cam 34 includes a cam slot 35 in which the cam surfaces 37 are formed. A cam guide 39, which is surrounded by the cam slot 35, is also part of the cam 34. The cam following end 44b of the cam follower 44 traverses the cam slot 35 in a closed loop path in a generally counter clockwise direction, as viewed in FIGS. 9 - 11, when it is in engagement with the camming surfaces 37 of the cam 34. The camming surfaces 37 are shown in detail in the partial sectional views of FIGS. 5 - 8 which show their profiles with the direction of the ramps 56, 64, 70 and 78 rising away from the plunger 20. The Figure numbers of FIGS. 5 - 8 correspond to the segments of the cam 34 that have the same reference numerals in FIG. 4.
In order to described the operation of the alternate action switch mechanism, it is assumed that the plunger 20 is initially in a raised unactuated position. The cam follower end 44b will then be positioned in the cam slot 35 at its lowermost position 52. The position 52 is physically located at the bottom of the cam surface 54 of the cam section of FIG. 5. The cam surface 54 is slightly angled to the right and is flat. The purpose of having the surface 54 flat is to allow for slight "teasing" or partial operation of the switch which invariably occurs, in some keyboard applications, without beginning actuation of the switch and without running the cam following end 44b up the ramp 56. When the plunger is depressed beyond the point where the cam following end 44b has passed the flat section 54, it begins to run up the ramp 56. The cam following end 44b continues up the ramp 56 until it passes over the short flat section 58 and drops into the drop-off 60. Once the cam following end 44b has dropped into the drop-off 60, release of pressure on the plunger 20 will not cause the cam following end 44b to return along the cam sections 56 and 54 to the initial point 52. Thus, the cam following end 44b is constrained to move in a general counter clockwise direction onto the cam surface 61, which allows for some over travel of the plunger 20, to the point 62 and from there onto the flat cam surface 63 and the ramp surface 64. Once the plunger 20 has been fully depressed release of the force applied to the plunger 20 allows the spring 38 to bias the plunger 20 in the upward direction. This causes the cam following end 44b to travel up the ramp 64 and into the drop-off 66 where it is retained against reverse movement, so that the switch is maintained in its actuated position due to locking of the plunger 20 in its depressed condition.
During the depression of the plunge, as the cam following end 44b is traversing the cam surfaces 54 - 58, the cam following end 44b is normally positioned so as to be in contact with the right side 39a of the cam guide 39. This is made possible by rotation of the cam follower 44 in a counter clockwise direction, as viewed in FIG. 3, due to the interaction of the cam following end 44b and the cam surfaces 37. The projecting post 50 on the boss 16 prevents the cam following end 44a from being disengaged from the aperture 46 in the boss 16 during rotation of the cam follower 44. When the switch is fully depressed, and the cam following end 44b is in the drop-off 60, the cam follower 44 will be rotated to its maximum counter clockwise position. The cam following end 44b will then be at its right most point 48R in the slot 48, as viewed in FIG. 3. When the pressure on the plunger is released by the operator and the cam following end 44b has dropped into the drop-off 66, the cam following end 44b is rotated back to substantially a central point 48c in the slot 48.
Actuation of the switch upon the first depression of the plunger has thus been described. When it is desirable to deactuate the switch, which is maintained actuated by the position of the cam following end 44b in the drop-off 66 of the neck of the V-shape portion 35b of the cam slot 35, the plunger 20 is again depressed. Movement of the plunger 20 is possible at this stage because the cam following end 44b is now allowed to rotate in a clockwise direction, as viewed in FIG. 3. The cam following end 44b is then driven along the flat surface 68, which is provided to allow for slight movement or "jiggling" of the plunger 20 without deactuation of the switch. Since the flat surface 68 is substantially shorter than the flat surface 54, the tolerance for "teasing" of the switch in the actuated position is much smaller than it is in the deactuated position.
Upon further depression of the switch the cam following end 44b will ride up the ramp 70 and will drop into the drop-off 72 at the end of the ramp 70 to prevent the cam following end 44b from returning to the ramp 70. This again insures that the cam following end 44b continues to traverse the cam slot 35 only in a generally clockwise direction. Having dropped into the drop-off 72, the cam following end 44b now traverses cam surface 75 along the outer wall 35c of the cam slot 35 to the point 74. Then when the pressure on the plunger 20 is released the cam following end 44b follows the cam surface 76 downwardly along the outer wall 35d of the cam slot 35 to the cam ramp surface 78. The cam follower 44 will now be rotated to its maximum clockwise position and the cam follower end 44b will be at its left-most position 48L in the slot 48. When the cam following end 44b reaches the cam ramp section 78, it will follow the cam section 78 upwardly and then it will travel over the flat section 80 and into the drop-off 82. After falling into the drop-off 82, the cam following end 44b will return to its initial starting position 52 along the flat cam section 84.
The design switch of the present invention is specially advantageous in that the switch may be converted to a momentary or a single action type of switch merely by removal of the cam follower 44 from the housing 12. This may be easily achieved since the cam follower 44 is preferably formed of a spring wire of a small diameter which may easily be sprung into position on the switch.
It will be understood that various modifications and embodiments of the present invention may be made without departing from the spirit and scope of the present invention as defined by the following claims.
One type of electrical switch of great utility is the alternate action switch in which the actuating member for the switch may be depressed once to actuate the switch, so that the switch will remain locked "on" in the actuated state following release of the actuating member and, when the switch is depressed a second time the switch will be deactuated. In the manufacture of alternate action switches, it is desirable that the alternate action mechanism be constructed so that it cannot interfere with the switching mechanism of the switch, thereby avoiding possible switch failure. Moreover, it is also desirable to be able to provide an alternate action switch mechanism which may be used with many different types of switches. Since the manufacture and sale of switches is highly competitive, it is necessary that any alternate action mechanism of wide use must be designed to be constructed in a simple and reliable manner at a minimum of additional cost over and above the cost of the other switch parts. It is also desirable that the alternate action switch be constructed so that it can serve as a single action switch by slight modification that does not require disability of the switch or removal of the switch from a circuit assembly.
It is, therefore, an object of the present invention to provide an alternate action switch in which the alternate action mechanism is obtained by a cam that is integrally formed on the actuator or plunger of the switch and a cam follower, which is removably secured to the external housing of the switch body, wherein the interaction of the cam and the cam follower provides an alternate action mechanism that does not interfere with the switching mechanism of the switch.
It is an additional object of the present invention to provide an alternate switch mechanism in which alternate action is achieved by the interaction of a cam and the cam follower in which the cam comprises a continuous closed slot having camming surfaces therein that are formed with a series of ramps and drop-offs and the cam follower is formed of a spring wire member with a cam following end that rides in the cam slot and is controlled by the camming surfaces so that the cam follower traverses around the cam slot in only a single direction wherein the actuator of the switch is preferably a plunger that is depressed a first time to lock the switch in its actuated state, due to interaction of the cam follower and the cam, and is depressed a second time to return the plunger to its initial position, at which position the switch is deactuated.
It is another object of the present invention to provide a switch which may be converted from an alternate action switch to a single action or a momentary action switch merely by the removal of a cam follower which is secured to the exterior of the switch housing when an alternate action switch is desired.
Further objects and advantages of the present invention will be apparent from the preceding discussion and from the following description, along with the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially sectionalized side view taken along the lines 1--1 of FIG. 3 which shows the upper portion of the switch housing and the actuator for the switch;
FIG. 2 is a side sectional view taken along the lines 2--2 of FIG. 3 which shows the actuator plunger portion of the switch mechanism;
FIG. 3 is a top view which shows the top of the switch housing and the cam follower;
FIG. 4 is an enlarged view of the cam that is formed on the depressible actuator plunger of FIG. 1;
FIGS. 5--8 are cross sectional views which show the profiles of the various cam surfaces of the cam of FIG. 4 in detail, with the Figure number corresponding to the section of FIG. 4 that is designated by the same number;
FIGS. 9-11 are enlarged views of the cam which show the movement of the cam follower in the cam slot during operation of the switch mechanism.
TECHNICAL DESCRIPTION OF THE INVENTION
The alternate action switch mechanism of the present invention is shown in detail in FIGS. 1, 2 and 3 of the drawings. This mechanism can be utilized by many different types of switches in which a moveable actuating member, such as a depressible plunger, is used.
The compact alternate action mechanism of the present invention is referred to generally by the reference numeral 10 in FIG. 1. Only the upper portion 12 of the switch housing is shown in the figures. The upper portion 12 of the switch housing has an upper surface 14 with an integral boss 16 that projects upwardly from the surface 14. The boss 16 has a central aperture 18 into which the actuating element or plunger 20 is positioned. The switch housing 12 and the plunger 20 of the present invention are preferably formed of plastics, and the plunger 20 is preferably molded as a single part. The lower end of the plunger 20 may be bifurcated, as shown in FIG. 2, and the arms 23, 25 may be used to actuate the type of switch which may be turned "on" and "off" by movement of a depressible plunger. This mechanism may also be used to operate special types of switches such as those shown in U.S. Pat. Nos. 3,638,221 and 3,638,222, which are owned by the assignee of the present application.
In order to provide for free motion of the plunger 20 in the boss 16, the outer periphery of the plunger 20 contacts the boss 16 at only several bearing surfaces 24 in order to reduce friction between the plunger 20 and the boss 16. The upper portion 26 of the plunger 20 is formed of a generally rectangular shape and has two keycap retainers 28 of a generally rectangular shape which extend from opposite sides of the upper portion 26. An identification keycap which is unique to the switch may be secured on the portion 26 and the retainers 28. Below the rectangular section 26 there is a larger section 30 of a generally circular shape. Section 30 has an outwardly extending cam block 32 of a generally rectangular shape. The cam 34 is formed in the cam block 32. The generally cylindrical boss 16 is constructed with a generally rectangular enclosure 36 which conforms to the shape of the cam block 32.
In order to return the switch to its initial position upon release of force on the plunger 20, the internal portion of the plunger 20 is formed with a hollow shape for receiving a bias spring 38. The spring 38 is compressible between a surface 40 of the housing 12 and a surface 42 on the plunger 20. When the plunger 20 is depressed the spring 38 supplies a return force to the plunger 20. The manner in which the biasing force is supplied to return the plunger 20, or other actuating member, to its unactuated position may be achieved in a number of different ways within the scope of the present invention.
The cam 34 includes a cam slot 35 that is formed integrally with the cam block 32. As can be seen by reference to FIGS. 1 and 4, the cam slot 35 has a closed loop configuration. When viewed from the front, the bottom portion 35a of the cam slot 35 resembles a "Y" while the upper portion 35b resembles a "V." The cam follower 44 is formed of a spring wire which is C-shaped. The ends of the cam follower 44 are turned inwardly toward each other with one of the other ends, 44a, being substantially shorter than the other outer end 44b. The end 44a is inserted into a receiving aperture 46 that is formed in the boss 16, so as to secure the cam follower 44 to the switch housing 12. The longer end 44b of the cam follower 44 serves as the actual cam following portion of the mechanism, and this end is positioned in engagement with the cam surfaces 37 of the cam slot 34. (FIGS. 5 - 8). The cam following end 44b of the cam follower 44 passes through a retaining slot 48 in the enclosure 36 so that the end 44b of the cam follower 44 is allowed to move to the left or to the right, as viewed in FIG. 3, in the slot 48 but so that the end 44b is restrained from moving substantially in a vertical direction by the enclosure 36. The rear leg 44c of the cam follower 44 is restrained from moving upwardly, which it otherwise would do when the cam following end 44b is at certain positions in the cam slot 35, by means of the outwardly projecting post 50 which extends from the boss 16.
The manner in which the cam follower 44 and the cam 34 interact to provide the desired alternate action feature of the present invention is described in more detail by reference to FIGS. 4 through 11. As previously mentioned, the cam 34 includes a cam slot 35 in which the cam surfaces 37 are formed. A cam guide 39, which is surrounded by the cam slot 35, is also part of the cam 34. The cam following end 44b of the cam follower 44 traverses the cam slot 35 in a closed loop path in a generally counter clockwise direction, as viewed in FIGS. 9 - 11, when it is in engagement with the camming surfaces 37 of the cam 34. The camming surfaces 37 are shown in detail in the partial sectional views of FIGS. 5 - 8 which show their profiles with the direction of the ramps 56, 64, 70 and 78 rising away from the plunger 20. The Figure numbers of FIGS. 5 - 8 correspond to the segments of the cam 34 that have the same reference numerals in FIG. 4.
In order to described the operation of the alternate action switch mechanism, it is assumed that the plunger 20 is initially in a raised unactuated position. The cam follower end 44b will then be positioned in the cam slot 35 at its lowermost position 52. The position 52 is physically located at the bottom of the cam surface 54 of the cam section of FIG. 5. The cam surface 54 is slightly angled to the right and is flat. The purpose of having the surface 54 flat is to allow for slight "teasing" or partial operation of the switch which invariably occurs, in some keyboard applications, without beginning actuation of the switch and without running the cam following end 44b up the ramp 56. When the plunger is depressed beyond the point where the cam following end 44b has passed the flat section 54, it begins to run up the ramp 56. The cam following end 44b continues up the ramp 56 until it passes over the short flat section 58 and drops into the drop-off 60. Once the cam following end 44b has dropped into the drop-off 60, release of pressure on the plunger 20 will not cause the cam following end 44b to return along the cam sections 56 and 54 to the initial point 52. Thus, the cam following end 44b is constrained to move in a general counter clockwise direction onto the cam surface 61, which allows for some over travel of the plunger 20, to the point 62 and from there onto the flat cam surface 63 and the ramp surface 64. Once the plunger 20 has been fully depressed release of the force applied to the plunger 20 allows the spring 38 to bias the plunger 20 in the upward direction. This causes the cam following end 44b to travel up the ramp 64 and into the drop-off 66 where it is retained against reverse movement, so that the switch is maintained in its actuated position due to locking of the plunger 20 in its depressed condition.
During the depression of the plunge, as the cam following end 44b is traversing the cam surfaces 54 - 58, the cam following end 44b is normally positioned so as to be in contact with the right side 39a of the cam guide 39. This is made possible by rotation of the cam follower 44 in a counter clockwise direction, as viewed in FIG. 3, due to the interaction of the cam following end 44b and the cam surfaces 37. The projecting post 50 on the boss 16 prevents the cam following end 44a from being disengaged from the aperture 46 in the boss 16 during rotation of the cam follower 44. When the switch is fully depressed, and the cam following end 44b is in the drop-off 60, the cam follower 44 will be rotated to its maximum counter clockwise position. The cam following end 44b will then be at its right most point 48R in the slot 48, as viewed in FIG. 3. When the pressure on the plunger is released by the operator and the cam following end 44b has dropped into the drop-off 66, the cam following end 44b is rotated back to substantially a central point 48c in the slot 48.
Actuation of the switch upon the first depression of the plunger has thus been described. When it is desirable to deactuate the switch, which is maintained actuated by the position of the cam following end 44b in the drop-off 66 of the neck of the V-shape portion 35b of the cam slot 35, the plunger 20 is again depressed. Movement of the plunger 20 is possible at this stage because the cam following end 44b is now allowed to rotate in a clockwise direction, as viewed in FIG. 3. The cam following end 44b is then driven along the flat surface 68, which is provided to allow for slight movement or "jiggling" of the plunger 20 without deactuation of the switch. Since the flat surface 68 is substantially shorter than the flat surface 54, the tolerance for "teasing" of the switch in the actuated position is much smaller than it is in the deactuated position.
Upon further depression of the switch the cam following end 44b will ride up the ramp 70 and will drop into the drop-off 72 at the end of the ramp 70 to prevent the cam following end 44b from returning to the ramp 70. This again insures that the cam following end 44b continues to traverse the cam slot 35 only in a generally clockwise direction. Having dropped into the drop-off 72, the cam following end 44b now traverses cam surface 75 along the outer wall 35c of the cam slot 35 to the point 74. Then when the pressure on the plunger 20 is released the cam following end 44b follows the cam surface 76 downwardly along the outer wall 35d of the cam slot 35 to the cam ramp surface 78. The cam follower 44 will now be rotated to its maximum clockwise position and the cam follower end 44b will be at its left-most position 48L in the slot 48. When the cam following end 44b reaches the cam ramp section 78, it will follow the cam section 78 upwardly and then it will travel over the flat section 80 and into the drop-off 82. After falling into the drop-off 82, the cam following end 44b will return to its initial starting position 52 along the flat cam section 84.
The design switch of the present invention is specially advantageous in that the switch may be converted to a momentary or a single action type of switch merely by removal of the cam follower 44 from the housing 12. This may be easily achieved since the cam follower 44 is preferably formed of a spring wire of a small diameter which may easily be sprung into position on the switch.
It will be understood that various modifications and embodiments of the present invention may be made without departing from the spirit and scope of the present invention as defined by the following claims.