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.

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'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.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first toFIG. 1, in the preferred embodiment disclosed, the foundation structure is an HVAC housing, indicated generally at10, which has a side wall12through and which an upper and lower crank14and16are pivoted. Cranks14and16, each with an end pin15and17, move a pair of flapper doors, not visible in the figure, inside housing10between limit positions. The combination linear and rotating actuator of the invention, indicated generally at18, is shown in a disassembled view, and consists of only four basic compact elements, operated by a single conventional reversible electric motor20. Motor20would have a conventional controller, not shown, to rotate it back and forth to a degree sufficient to move actuator18sufficiently to in turn move cranks14and16.

Referring next toFIGS. 2 and 3, one of the four basic components is a molded plastic support bracket22, which supports motor20on the outside, and which is bolted to the housing side wall12with a relatively thin space therebetween. This space is thick enough to house a large toothed circular gear24, which is shafted to motor20to turn one to one therewith about central axis A. Bracket24also contains a pair of upper and lower, straight guide tracks26and28, and a pair of upper and lower straight guide slots30and32, all mutually parallel. Each straight guide slot30and32opens into one of a pair of semi-circular clearance slots34and36respectively, which are concentric to axis A and diagonally opposed. Again, bracket22and all of its structural features are rigid and fixed relative to the housing side wall12.

Still referring toFIGS. 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 at38and40. Cam plates38and40, also molded plastic, are nested and stacked in the space between the inside of bracket22and outside of housing side wall12, so as to be able to slide back and forth without mutual interference. On their outer surfaces, facing the inside of bracket22, each cam plate38and40has a straight toothed rack42and44respectively, parallel to one another, culminating in a semi-circular toothed rack46,48, diagonally opposed to one another, and matching the diameter of the gear24. All toothed racks interfit with the circular gear24closely. In addition, each cam plate38and40has a respective guide flange50,52that rides freely but closely along a respective guide track26,28on bracket22. The outer surface of each respective cam plate38and40also has a projecting guide pin54,56that rides closely in an aligned pair of guide slots30,32and clearance slots34,36. Finally, each cam plate38,40has a straight sided hook58,60at the end of respective semi-circular toothed rack48,46, sized to slidably receive the end of the straight tooted rack44,42respectively of the opposite cam plate40,38.

Referring next toFIGS. 4A-4C, the basic operation of the actuator18, which is to say, its basic motion divorced from components that it operates, is illustrated. As seen inFIG. 4A, as gear24begins to turn in the clockwise direction, the straight toothed racks42and44are pulled together in a straight line in opposite directions, guided by the engagement of the guide flanges50and52with the bracket guide tracks26and28, and also by the guide pins54and56riding in the straight guide slots30and52. This initial motion continues until, as seen inFIG. 4B, the circular toothed racks46and48engage the gear24and the ends of the straight guide tracks42and44slide into the hooks60and58. This serves to lock the cam plates38and40tight to the gear24as, concurrently, the guide pins54and56move into the semicircular clearance slots34,36. At that point, the cam plates38and40are caused to rotate with gear24, as seen inFIG. 3C, and the flanges50and52rotate away from the guide tracks26and28until the motor20and gear24are stopped by the non illustrated control system. The motion reverses itself as motor20and gear24rotate in the opposite direction, back to theFIG. 4Aposition. Thereby, essentially all of the available motion of gear24is turned into potentially useful motion of the cam plates38and40, linear and rotating, closely guided with very little play, and all within the relatively compact space between bracket20and the housing side wall12and bracket24.

Referring next to FIGS.3and5A-5C, the inside surfaces of the cam plates38and40, those facing the side wall12, have additional structure that serves to translate the basic motion just described into motion of the cranks14and16. Cam plate38has a basically linear cam track62, sloped upwardly relative the bracket guide tracks26and28, which receives the crank pin15. Linear cam track62terminates in a semi-circular clearance track64, which is concentric to gear24. Cam plate40has an arcuate cam track66, which is not concentric to gear24, and which receives the crank pin17. Arcuate cam track66terminates in a straight clearance track68, which is parallel to the bracket guide tracks26and28. Finally, each crank14and16is fixed to a respective flapper door70and72(a double door in the case of door72) which rotate between limit positions to control various air flows within the housing10.

Referring now toFIGS. 5A-5C,FIG. 5Ashows the starting position, equivalent toFIG. 4A. As gear24begins to rotate (counterclockwise, but only from the perspective ofFIG. 5A) and the cam plates38and40are pulled together, upper crank pin15is pulled through cam track62as lower crank pin17is pulled through straight lower clearance track68. As straight cam track62is upwardly sloped relative to the guide tracks26and28, crank pin18is pushed up, rotating crank14clockwise, and rotating flapper door70with it.

Concurrently, lower crank pin17rides freely in the clearance track68, and crank16is unaffected, as is flapper door72. When the cam plates38,40are pulled all the way together, and lock to gear14, as shown inFIG. 5B(equivalent to theFIG. 4Bposition), upper crank pin15moves into the semi-circular clearance track64, where, since it is concentric to gear24, it creates no more motion in upper crank14.

Concurrently, lower crank pin17moves into arcuate cam track66, which, since it is not concentric to gear24, rotates lower crank16clockwise, also rotating flapper door72to the position shown inFIG. 5C(which corresponds toFIG. 4C.) The doors70and72are thus reversibly rotated between their limit positions by a single motor20and gear24combination, and only three other compact components, the cam plates38,40and guide bracket22. 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'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 slots34and36are not necessary for the basic operation of the actuator, but do help to guide the guide pins54and56back into the straight guide slots30and32. Likewise, the clearance tracks64and68are not necessary to the basic operation of the cranks14and16, but do serve to guide the cam pins15and17into the active cam tracks62and66.