Abstract:
An actuator consists of a pair of compact cam plates with compound straight and semicircular toothed racks that engage a single circular gear turned by a single motor. As the gear turns in one direction, the cam plates are pulled toward one another in a guided straight line until they engage and lock around the gear. Continued turning of the gear rotates the locked cam plates with the gear. The motion is reversed as the gear reverses.

Description:
TECHNICAL FIELD 
     This invention relates to actuators in general and specifically to a combination linear and rotary actuator. 
     BACKGROUND OF THE INVENTION 
     Automotive air conditioning housings typically contain at least two flapper type air flow control doors, each rotated between open and closed limit positions by a crank pivoted to and through a wall of the housing. While each can be rotated and controlled by a dedicated, individual motor, it would be potentially a cost and space saving measure to operate and control both doors with a single motor. Prior proposals to do so have involved very complex and bulky systems of multiple levers or multiple gear reduction systems, which involve numerous degrees of freedom and consequent play and rattle in the system, as well as expense and occupied volume that detract from the advantage of using a single motor. 
     SUMMARY OF THE INVENTION 
     The subject invention provides a simple and compact actuator that runs and controls a pair of doors on an air conditioning housing with a single motor. 
     In the embodiment disclosed, a pair of door cranks with pins near the crank ends are pivoted to and through a wall of an air conditioning housing at widely spaced locations. Each crank moves a door inside the housing between open and closed positions as it is rotated over a predetermined arc. 
     A motor support and guide bracket is bolted to the housing wall spaced therefrom and, overlaying the cranks. A single motor mounted to the outside of the bracket wall turns a single circular gear located inside the bracket. Formed through the bracket are a pair of parallel straight guide slots which open into a diagonally opposed, semi circular clearance slots centered on the gear axis. 
     An interleaved pair of first and second cam plates is stacked between the bracket and the housing wall. The inside of each cam plate, facing the circular gear, has a straight toothed rack engaged with one side of the circular gear and a semi circular toothed rack that matches about one quarter of the circular gear The cam plate racks face in opposed directions, and the cam plates are arranged to slide linearly in opposite direction, each with a guide pin that rides in a respective bracket guide slot. In addition, each cam plate has a flange that rides on a straight guide track on the bracket until that is coextensive with the straight toothed rack portion of each cam plate. 
     As the circular gear rotates in one direction, the cam plates are pulled toward one another in a straight line until their toothed arcs concurrently engage the circular gear. As they do so, interfitting slide locks on the cam plates engage to lock the cam plates to the gear. Further rotation of the gear rotates the locked together cam plates about the gear axis as the guide flanges move off of the guide tracks and the guide pins move out of the bracket&#39;s straight guide slots and into the semi-circular clearance slots. Reverse rotation of the gear reverses the path of the cam plates, rotating in the opposite direction and then sliding linearly apart back to the starting point. 
     In the embodiment disclosed, the pins on the ends of the pivoted cranks ride in cam tracks on the inner surface of the cam plates. Each cam track has active and inactive portions, either straight or curved, that respectively actively pivot the cranks over the desired path, or leave them stationary as the cam plates move. Thereby, all of the motion of the single pair of compact cam plates, linear and rotating, can be used to pivot the levers, and thereby operate the valve doors, from a single motor, and in a compact and closely guided fashion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a an exploded perspective view of view of a preferred embodiment of the invention; 
         FIG. 2  is an enlarged view of the actuator components of Figure 
         FIG. 3  is a view like  FIG. 2 , but sighting in the opposite direction; 
         FIGS. 4A-4C  are views of the device looking through the broken away support bracket as it moves, 
         FIGS. 5A-5C  are views of the device corresponding to  FIGS. 4A-4C , but looking in the opposite direction and showing how the actuator device moves the cranks and flapper doors. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to  FIG. 1 , in the preferred embodiment disclosed, the foundation structure is an HVAC housing, indicated generally at  10 , which has a side wall  12  through and which an upper and lower crank  14  and  16  are pivoted. Cranks  14  and  16 , each with an end pin  15  and  17 , move a pair of flapper doors, not visible in the figure, inside housing  10  between limit positions. The combination linear and rotating actuator of the invention, indicated generally at  18 , is shown in a disassembled view, and consists of only four basic compact elements, operated by a single conventional reversible electric motor  20 . Motor  20  would have a conventional controller, not shown, to rotate it back and forth to a degree sufficient to move actuator  18  sufficiently to in turn move cranks  14  and  16 . 
     Referring next to  FIGS. 2 and 3 , one of the four basic components is a molded plastic support bracket  22 , which supports motor  20  on the outside, and which is bolted to the housing side wall  12  with a relatively thin space therebetween. This space is thick enough to house a large toothed circular gear  24 , which is shafted to motor  20  to turn one to one therewith about central axis A. Bracket  24  also contains a pair of upper and lower, straight guide tracks  26  and  28 , and a pair of upper and lower straight guide slots  30  and  32 , all mutually parallel. Each straight guide slot  30  and  32  opens into one of a pair of semi-circular clearance slots  34  and  36  respectively, which are concentric to axis A and diagonally opposed. Again, bracket  22  and all of its structural features are rigid and fixed relative to the housing side wall  12 . 
     Still referring to  FIGS. 2 and 3 , the other two basic components of the invention are a pair of actuator members, which are upper and lower cam plates indicated generally at  38  and  40 . Cam plates  38  and  40 , also molded plastic, are nested and stacked in the space between the inside of bracket  22  and outside of housing side wall  12 , so as to be able to slide back and forth without mutual interference. On their outer surfaces, facing the inside of bracket  22 , each cam plate  38  and  40  has a straight toothed rack  42  and  44  respectively, parallel to one another, culminating in a semi-circular toothed rack  46 ,  48 , diagonally opposed to one another, and matching the diameter of the gear  24 . All toothed racks interfit with the circular gear  24  closely. In addition, each cam plate  38  and  40  has a respective guide flange  50 ,  52  that rides freely but closely along a respective guide track  26 ,  28  on bracket  22 . The outer surface of each respective cam plate  38  and  40  also has a projecting guide pin  54 ,  56  that rides closely in an aligned pair of guide slots  30 ,  32  and clearance slots  34 ,  36 . Finally, each cam plate  38 ,  40  has a straight sided hook  58 ,  60  at the end of respective semi-circular toothed rack  48 ,  46 , sized to slidably receive the end of the straight tooted rack  44 ,  42  respectively of the opposite cam plate  40 ,  38 . 
     Referring next to  FIGS. 4A-4C , the basic operation of the actuator  18 , which is to say, its basic motion divorced from components that it operates, is illustrated. As seen in  FIG. 4A , as gear  24  begins to turn in the clockwise direction, the straight toothed racks  42  and  44  are pulled together in a straight line in opposite directions, guided by the engagement of the guide flanges  50  and  52  with the bracket guide tracks  26  and  28 , and also by the guide pins  54  and  56  riding in the straight guide slots  30  and  52 . This initial motion continues until, as seen in  FIG. 4B , the circular toothed racks  46  and  48  engage the gear  24  and the ends of the straight guide tracks  42  and  44  slide into the hooks  60  and  58 . This serves to lock the cam plates  38  and  40  tight to the gear  24  as, concurrently, the guide pins  54  and  56  move into the semicircular clearance slots  34 ,  36 . At that point, the cam plates  38  and  40  are caused to rotate with gear  24 , as seen in  FIG. 3C , and the flanges  50  and  52  rotate away from the guide tracks  26  and  28  until the motor  20  and gear  24  are stopped by the non illustrated control system. The motion reverses itself as motor  20  and gear  24  rotate in the opposite direction, back to the  FIG. 4A  position. Thereby, essentially all of the available motion of gear  24  is turned into potentially useful motion of the cam plates  38  and  40 , linear and rotating, closely guided with very little play, and all within the relatively compact space between bracket  20  and the housing side wall  12  and bracket  24 . 
     Referring next to FIGS.  3  and  5 A- 5 C, the inside surfaces of the cam plates  38  and  40 , those facing the side wall  12 , have additional structure that serves to translate the basic motion just described into motion of the cranks  14  and  16 . Cam plate  38  has a basically linear cam track  62 , sloped upwardly relative the bracket guide tracks  26  and  28 , which receives the crank pin  15 . Linear cam track  62  terminates in a semi-circular clearance track  64 , which is concentric to gear  24 . Cam plate  40  has an arcuate cam track  66 , which is not concentric to gear  24 , and which receives the crank pin  17 . Arcuate cam track  66  terminates in a straight clearance track  68 , which is parallel to the bracket guide tracks  26  and  28 . Finally, each crank  14  and  16  is fixed to a respective flapper door  70  and  72  (a double door in the case of door  72 ) which rotate between limit positions to control various air flows within the housing  10 . 
     Referring now to  FIGS. 5A-5C ,  FIG. 5A  shows the starting position, equivalent to  FIG. 4A . As gear  24  begins to rotate (counterclockwise, but only from the perspective of  FIG. 5A ) and the cam plates  38  and  40  are pulled together, upper crank pin  15  is pulled through cam track  62  as lower crank pin  17  is pulled through straight lower clearance track  68 . As straight cam track  62  is upwardly sloped relative to the guide tracks  26  and  28 , crank pin  18  is pushed up, rotating crank  14  clockwise, and rotating flapper door  70  with it. 
     Concurrently, lower crank pin  17  rides freely in the clearance track  68 , and crank  16  is unaffected, as is flapper door  72 . When the cam plates  38 ,  40  are pulled all the way together, and lock to gear  14 , as shown in  FIG. 5B  (equivalent to the  FIG. 4B  position), upper crank pin  15  moves into the semi-circular clearance track  64 , where, since it is concentric to gear  24 , it creates no more motion in upper crank  14 . 
     Concurrently, lower crank pin  17  moves into arcuate cam track  66 , which, since it is not concentric to gear  24 , rotates lower crank  16  clockwise, also rotating flapper door  72  to the position shown in  FIG. 5C  (which corresponds to  FIG. 4C .) The doors  70  and  72  are thus reversibly rotated between their limit positions by a single motor  20  and gear  24  combination, and only three other compact components, the cam plates  38 ,  40  and guide bracket  22 . No second motor or complex crank or gear mechanisms are needed. The system is compact and well guided, with very limited rattle, and fully reversible. 
     The basic invention could be incorporated in environments other than that disclosed. Fundamentally, the actuator&#39;s reversible combination of linear and rotating motion could be used to operate a number of different actuating members, any that could translate both linear and rotating motion into useful work. In the preferred embodiment disclosed, the semicircular clearance slots  34  and  36  are not necessary for the basic operation of the actuator, but do help to guide the guide pins  54  and  56  back into the straight guide slots  30  and  32 . Likewise, the clearance tracks  64  and  68  are not necessary to the basic operation of the cranks  14  and  16 , but do serve to guide the cam pins  15  and  17  into the active cam tracks  62  and  66 .