Automatic clutch for four-wheel drive vehicles

Claim 1

A selective drive clutch for automatically connecting a driven element to a drive element for conjoint coaxial rotation and for automatically disconnecting same when said drive element is not being driven, comprising: a first interlocking member mountable upon the driven member for rotational movement therewith; a second interlocking member mountable upon the drive element for rotational movement therewith and for axial movement relative thereto between retracted and extended positions; means carried by opposed end portions of said first and second interlocking members effective upon extension of the latter to interengage and effect a driving connection therebetween; first biasing means operatively associated with said second interlocking member normally biasing same into retracted position; and actuating means responsive to limited relative rotational movement between said drive and driven elements for effecting an axial shift of said second interlocking member between its extended and retracted positions, said means including a pair of tooth-carrying elements mounted in axially-spaced face-to-face relation, said elements each having arcuately-curved rows of teeth arranged in opposed relation, the first of said pair of tooth-carrying elements being movable both axially and rotarially with said second interlocking member on the end thereof remote from said first interlocking member, the second of said pair of tooth-carrying elements being mounted for independent rotation relative to said first tooth-carrying member in coaxial relation thereto, one of said curved rows of teeth defining a track encircling the axis of rotation in perpendicular relation thereto, the other of said curved rows of teeth defining at least one concave cam surface having stops at the remote ends thereof and a pair of oppositely-inclined ramps arranged in end-to-end relation therebetween; said actuating means also including a cam follower subassembly located between said first and second tooth-carrying elements, said subassembly having a toothed roller operatively interconnecting the teeth of each cam surface with the teeth of the track opposite thereto so as to define a driving connection therebetween, and roller support means frictionally associated with at least one of said first and second interlocking members for rotational movement therewith when interlocked; and said actuating means further including braking means having a fixed friction surface engaging said second tooth-carrying element operative to yieldably retard rotation thereof, said actuating means being operative in reponse to relative rotation of said drive element in either direction relative to said driven element to overcome the bias exerted upon the second interlocking element by said first biasing means and cause said toothed roller to ascend one of the ramps thereby extending said second interlocking element into interlocked driving engagement with said first interlocking member while said second tooth-carrying element is being held against rotation by the braking means thereof, said actuating means also being operative upon continued rotation of said interlocked first and second interlocking members in the same direction to drive said toothed roller against the stop at the end of said ascended ramp thus preventing further relative rotational movement between said first and second tooth-carrying elements and causing the latter to overcome the frictional contact between it and the braking means thereby causing it to slip relative thereto, said actuating means being further operative in cooperation with said biasing means in response to reversal of said drive element with the first and second interlocking elements interlocked to cause said toothed roller to descend said ascended ramp and ascend the other thus momentarily retracting said second interlocking member before again extending and reconnecting same to said first interlocking member for continued driving engagement in said reverse direction, and said actuating means being still further operative in cooperation with said biasing means in response to deactivation of said drive element into a free-wheeling condition and rotation of said driven element relative thereto in a direction opposite to that in which said drive element was last driven while said braking means remains effective to prevent rotation of said second tooth-carrying means to rotate said interlocked first and second interlocking elements as a unit relative to said cam follower subassembly so as to cause the toothed roller thereof to descend the ramp it has ascended thereby allowing said biasing means to bias said second interlocking member into retracted position and releasing the driving connection between it and said first interlocking member.