Automatically engaging and disengaging dog clutch

Claim 1

Automatically engaging and disengaging dog clutch between an input shaft and an output shaft, said clutch comprising a first straight-toothed clutch boss, a second helical-tooth clutch boss, an axially slidable clutch spider, a synchronizing sleeve within said clutch spider and rotatable and axially immovable therein, screw-threading means of coarse pitch connecting the synchronizing sleeve to the second clutch boss, straight toothing on the clutch spider engaging the straight toothing on the first clutch boss to retain the clutch spider and the first clutch boss in constant mesh, the clutch spider being adapted for optional engagement with an disengagement from the second clutch boss, a ratchet tooth system on the synchronizing sleeve and cooperating sensing pawls in the clutch spider adapted to sense relative engagement between the clutch spider and the second clutch boss, characterized in that said sensing of said relative engagement produces automatic clutch engatement in two phases, namely a first engagement phase in which said coarse-pitch screw-threaded means causes axial movement of the synchronizing sleeve and clutch spider towards the second clutch boss and produces partial engagement of the clutch spider with the second clutch boss, fuRther characterized in that the pitch of the helical gear tooth system of the second clutch boss is greater than the pitch of the said coarse screw-threaded means and a stop means is disposed between the clutch spider and the second clutch boss, whereby, under the effect of a torque exerted by the input shaft on the output shaft the clutch spider is fully engaged with the second clutch boss up to the said stop means in the second engagement phase during which the sensing pawls are disengaged and do not participate in transmitting power when the clutch is fully engaged.