Abstract:
A switch actuator is provided with a rotor in a housing and a third class lever having a cam follower operatively engaged against a cam surface of the rotor. A fulcrum of the lever is provided at a location relative to the rotor, which location is adjustable relative to the rotor in response to continued rotation of the rotor after an operative end of the lever has been stopped against a switch.

Description:
FIELD OF THE INVENTION 
   The present invention pertains generally to actuator mechanisms, and, more specifically, to actuator mechanisms for switches such as found in a throttle control mechanism of a gas powered golf cart. 
   BACKGROUND OF THE INVENTION 
   Remote actuators having cam surfaces for driving one or more levers are known for various purposes. By way of example, in a known design of a throttle control mechanism for a gas powered golf cart, several different switches are actuated when the driver depresses an acceleration pedal. Through appropriate linkage mechanism, depressing the pedal causes rotational movement of a rotor in an actuator. The rotor has a cam surface, the movement of which moves levers having cam followers. Movement of the levers actuates switches. Two such switches are actuated in known gas-powered golf cart designs. Upon depressing the pedal, a kill switch opens, and a solenoid switch closes, thereby starting the gas engine. When the cart is stopped, and the accelerator pedal is released from continued pressure, the kill switch is closed stopping the engine, and the solenoid switch is opened, preventing ignition. 
   It is desirable to keep the circuitry, actuators, levers and linkages compact, to minimize space requirements and reduce overall vehicle size. Thus, it is desirable to control the magnitude of movement required of the levers for complete actuation of the switches. When properly adjusted within specification tolerances, operation is smooth and efficient. However, relatively small adjustment errors can be magnified along the linkage train, resulting in over rotation of the cam rotor. In a vehicle such as a golf cart, which operates over uneven terrain, and may be subject to a degree of misuse or abuse, misadjustment can occur with some regularity. Components can move slightly, as mounting structures loosen over time. The resultant change in switch mechanism location and/or linkage operation can be either an under rotation or an over-rotation of the cam relative to the switch operation in either or both directions. 
   Over rotation of the cam rotor, and excessive movement of the levers relative to the switch position can cause levers to bottom out on the switch casing and be subjected to excessive continued force. The result can be damage to the levers and/or damage to the switches operated by the levers. Problems associated with over-rotation of the cam rotor are particularly troublesome when the over-rotation occurs in the static or at-rest position of the device, which may exist for an extended period of time. The prolonged effect of over-rotation present in the at-rest position can lead to unsuspected damage the next time the device is operated. 
   What is needed is a means for absorbing the excessive force and over rotation, to minimize potential damage of the levers or switches in a cam-operated linkage mechanism. 
   SUMMARY OF THE INVENTION 
   The present invention provides a means for protecting switches and levers from excessive force caused by over rotation of a cam rotor operating the levers, by providing the lever with a moveable fulcrum, thereby limiting the pressure exerted by the lever against the switch mechanism. 
   In one aspect thereof, the present invention provides an actuator unit with a housing, a cam and a lever. The lever has a first end, a second end and a cam follower slidably engaged against the cam. A connection between the lever second end and the housing defines a fulcrum for the lever relative to the housing. The connection is movable relative to the cam. Biasing means urges the lever second end in one direction. 
   In another aspect thereof, the invention provides an actuator with a housing, and a rotor in the housing. The rotor has a cam surface. A third class lever has a cam follower engaged against the cam surface, and has a fulcrum at a location that is movable relative to the rotor. 
   In yet another aspect thereof, the invention provides a throttle control unit for a golf cart with a housing and a rotor rotatably disposed in the housing. The rotor has a cam surface. A drive linkage is connected to the rotor for imparting rotation thereto. A third class lever has a first end, a second end and a cam follower riding on the cam surface. A fulcrum at one of the ends is movable relative to the rotor. A switch is engaged against the lever at the other end of the lever, and a biasing means urges the location of the fulcrum toward the rotor. 
   In a further aspect thereof, the invention provides a method for actuating a switch, with steps of providing a switch and a third class lever for operating the switch, the lever having a first end operatively engaged against the switch and a second end defining a fulcrum; providing a rotor adjacent the lever, a cam surface on the rotor and a cam follower on the lever engaged against the cam surface of the rotor; rotating the rotor for moving the lever; providing a stop for the first end of the lever; stopping the first end of the lever; and moving the second end of the lever in response to continued rotation of the rotor after stopping the first end of the lever. 
   An advantage of the present invention is providing a switch actuator that relieves excess pressure on a switch caused by over rotation of a cam lever actuator. 
   Another advantage of the present invention is providing a switch actuator that is robust and suitable for use on a golf cart. 
   Yet another advantage of the present invention is providing a switch actuator that compensates for over rotation of a cam in the actuator. 
   Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an elevational view, in partial schematic, of an accelerator pedal system for a golf cart or the like, the mechanism having a switch actuator of the present invention; 
       FIG. 2  is an enlarged view of the switch actuator of the present invention, shown in a first position of operation; 
       FIG. 3  is a view of the switch actuator of  FIG. 2 , but showing a second position of operation; and 
       FIG. 4  is a view of the switch actuator of  FIGS. 2 and 3 , but showing another condition of operation. 
   

   Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description, or illustrated in the drawings. The invention is capable of other embodiments, and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use herein of “including”, “comprising”, and variations thereof is meant to encompass the items listed thereafter and equivalents thereof, as well as additional items and equivalents thereof. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now more specifically to the drawings, and to  FIG. 1  in particular, a golf cart accelerator pedal system  10  is shown, which includes a switch actuator  12  in accordance with the present invention. While the present switch actuator  12  is shown with respect to use in a gas powered golf cart, it should be understood that actuator  12  of the present invention can be used for other devices, and for switching apparatuses other than accelerator systems. Use in a gas powered golf cart is merely a suitable, advantageous use of the invention. 
   Switch actuator  12  is shown disproportionately large in  FIG. 1 , in comparison to other components of system  10 . Actuator  12  is connected to a linkage train  14  including shafts  16 ,  18  and  20 , and interconnecting gears and/or linkages depicted schematically by boxes  22  and  24 . A foot pedal  26  is provided connected to shaft  16 , for actuation of system  10 , by depressing or releasing foot pedal  26 . It should be understood that the components in accelerator pedal system  10 , such as shafts  16 ,  18 ,  20  and gears represented by boxes  22  and  24  and foot pedal  26  depict a suitable environment for use of the invention, and other linkage trains also can be used. 
   Switch actuator  12  includes a rotor  30  attached to shaft  20 , for rotation of rotor  30  by shaft  20  upon a user depressing pedal  26 , or releasing pedal  26  from a depressed position. Rotor  30  is contained within a housing  32 , and is suitably mounted in housing  32  for rotation therein. Rotor  30  rotates upon depressing pedal  26 , or upon releasing pedal  26  from a depressed position, and may rotate through only a relatively small arc less than a complete revolution of rotor  30 . Rotor  30  is shaped to include one or more lobes or cams  34 ,  36 , and as depicted in the drawings ( FIGS. 2-4 ) includes two cams  34 ,  36 . One or more switches  40  having electrical leads  42 ,  44 ,  46  attached thereto are operated upon rotation of rotor  30 , via a switch button  48  housed in a switch casing  50 . One such switch  40  is shown in  FIGS. 2-4 . A lever  60  operates switch button  48 , with switch button  48  being depressed or released by movement of lever  60 . Lever  60  is caused to move against or away from switch button  48  upon rotation of rotor  30 , as will be described more fully hereinafter. 
   Lever  60  is a third class lever, having a first end  62  operatively positioned in association with switch  40  for depressing button  48 , and a second end  64  forming and defining with housing  12  a fulcrum  66  for lever  60 . A cam follower  68  is provided between first end  62  and second end  64 . Cam follower  68  is operatively associated with cams  34 ,  36  of rotor  30 . 
   Fulcrum  66  is created by a knob  70  of housing  32  disposed in an oblong opening  72  formed in lever  60  at second end  64 . Knob  70  and opening  72  are operatively associated such that lever  60  can rotate about knob  70  in opening  72 . The shape of opening  72  is oriented with respect to rotor  30  such that opening  72 , and thus second end  64  of lever  60 , can slide slightly away from rotor  30  under conditions to be described subsequently herein. 
   A biasing means in the nature of a spring  74  is provided to urge second end  64  of lever  60  toward rotor  30 . Spring  74  is operatively connected between a boss  76  on lever  60  and a spring retainer  78  in housing  32 . 
   A desirable “at rest” position for switch actuator  12  is shown in FIG.  2 . Lever  60  is moved by cam  36  to depress button  48 . To activate system  10  from the “at rest” position, foot pedal  26  is depressed, causing rotor  30  to rotate in a clockwise direction as depicted in FIG.  3 . First end  62  of lever  60  falls away from button  48  as cam follower  68  slides past cam  36 .  FIGS. 2 and 3  thus illustrate the desired positions when system  10  and actuator  12  thereof are operating within designed conditions. Spring  74  urges second end  64  toward rotor  30 , such that knob  72  is engaged against a surface of opening  72  that is furthest from rotor  30 . 
   Under desired “at rest” conditions, first end  62  of lever  60  gently touches casing  50  of switch  40 , with switch button  48  being fully depressed. However, as illustrated in  FIG. 4 , through various mispositionings or tolerance stack up, it is possible for casing  50  to be slightly mispositioned relative to first end  62  of lever  60 . The potential relative mispositioning of casing  50 , for example, is illustrated by the dashed line shown in  FIG. 4 , indicated by numeral  80 . Under this condition, as first end  62  of lever  60  bottoms out prematurely against casing  50 , rotor  30  continues to rotate, and the action of cam  36  would, absent the present invention, urge first end  62  of lever  60  more firmly against casing  50 . This condition could result in damage. However, as a result of the present invention, lever  60  adjusts such that opening  72  moves along knob  70 , to effectively absorb the over-force applied against cam follower  68 . Lever  60  is allowed to pivot at the contact of end  62  against casing  50 . Essentially, a fulcrum  90  is formed at first end  62 , as end  62  bottoms out against casing  50  and the biasing force of spring  74  is overcome. Second end  64  moves laterally, as opening  72  is allowed to slide along knob  70 , until knob  70  contacts the area of opening  72  nearest rotor  30 , as shown in FIG.  4 . 
   The present invention compensates for tolerance stack-up or potential component mispositioning by allowing flexibility in the relative position of a lever fulcrum with respect to the force applied to the lever. In the present invention, a third class lever has force applied thereto intermediate first and second ends of the lever. The first end of the lever moves as a spring biased fulcrum is created at the second end. Upon the lever first end encountering resistance to continued movement, continued application of force on the lever overcomes the spring biasing force, causing the fulcrum of the lever to occur at the first end, and allowing the second end of the lever to move. 
   Variations and modifications of the foregoing are within the scope of the present invention. It is understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned, or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art. 
   Various features of the invention are set forth in the following claims.