A
power take off coupling for connecting an engine (20, 21) to
a site accessory (16, 14, 17), comprises a resilient
power transmission component (3) within the
coupling; a latching device (8, 46, 9) to mechanically latch the accessory to the engine (20, 21), with a manually operable release
handle (13) to effect unlatching. A
power output shaft of the engine (20, 21) carries one half (5) of a
dog clutch with the other half (7) carried by the accessory (16, 14, 17).; An alignment arrangement comprises a first annulus ring (18) attached coaxiaily to an output shaft
assembly of the engine (20, 21 ), and a second annulus ring (19) attached coaxiaily to an input shaft
assembly of the accessory, with the two rings (18, 19) being of different diameters, such that one ring is adapted to be engaged coaxiaily within the other ring with close tolerances, such that the external periphery of the smaller ring (18) engages at least parts of the internal periphery of the larger ring (19) to provide for accurate coaxial alignment of the
power output shaft of the engine (20, 21) and the power input shaft of the accessory.; The invention also includes a
dog clutch coupling, with one
dog clutch half (5) biased by springs (4), such that should the dog
clutch teeth initially foul one another, rather than mesh, the dog
clutch half (5) retracts to permit meshing, and then advances.