Abstract: A toothed clutch is arranged between a first rotary clutch part and an intermediate part connected by straight splines to a second rotary clutch part. If engagement of the toothed clutch is attempted while the rotary clutch parts are in relative rotation in one direction, blocking members frictionally engaged with the intermediate member slide along surfaces, inclined to the axis of rotation, of baulking members carried by the first rotary clutch part and engage baulking abutments, whereby engagement of the toothed clutch is baulked. When the first and second rotary clutch parts are brought to rotational synchronism, e.g. by engagement of a friction clutch, movement of the intermediate part to engage the toothed clutch is accompanied by movement of the blocking members away from the inclined surfaces of the baulking members and clear of the baulking abutments.

Abstract: A pawl and ratchet mechanism has a baulking member which may be set in a ratcheting condition, a pawl free condition, and a baulking condition. A thrust member, engageable with the baulking member, is movable in first and second directions in which the baulking member is respectively moved towards and away from the ratcheting condition. A solenoid valve is settable in first and second conditions in which thrust is imparted to the thrust member to cause the latter to move respectively in the said first and second directions and detector means detects when the baulking member has moved into or out of the baulking condition, and into the pawl free condition, the detector means controlling the setting of the solenoid valve to that when the baulking member is in the baulking condition, the solenoid valve is so set that the thrust moves the baulking member towards the pawl free condition, the solenoid valve is so set that the thrust moves the baulking member towards the ratcheting condition.

Abstract: A power transmission system comprises a synchronous main toothed clutch 20 and a subsidiary toothed clutch 21 arranged in parallel in main and subsidiary power paths 6, 7 respectively between an input shaft 1 and an output shaft 2. When the main clutch 20 is engaged this causes engagement of the subsidiary clutch 21. The main power path 6 has a torsional stiffness which is substantially less than that of the subsidiary power path 7 over at least an initial part of the range of torque loading between zero and full power, such that at full power or at a pre-determined proportion of full power the main power path 6 and the subsidiary power path 7 transmit substantially the same load.