Patent ID: 6868949

Claim:
A start-up clutch assembly ( 10 ) for translating torque between a prime mover and a transmission, said clutch assembly comprising: a drive member ( 16 ), a driven member ( 24 ), said drive and driven members ( 16 , 24 ) rotatable about a common axis and defining a housing ( 28 ) therebetween; a clutch pack ( 30 ) supported in said clutch housing ( 28 ), interposed between said drive and driven members ( 16 , 24 ) and operable to move between a closed pack mode wherein torque is translated across said clutch pack ( 30 ) and an open pack mode wherein torque is interrupted across said clutch pack ( 30 ) to connect and disconnect said drive and driven members ( 16 , 24 ) to selectively transfer and interrupt torque translation therebetween; a torque apply piston assembly ( 54 ) supported in said clutch housing ( 28 ), said torque apply piston assembly ( 54 ) including a piston ( 56 ) that is rotatably supported by said drive member ( 16 ) about said common axis of rotation and includes an annular flange ( 60 ) extending in the direction of said common axis of rotation, a piston head ( 62 ) operable to engage said annular clutch pack ( 30 ) and an annular seat ( 64 ) formed between said piston head ( 62 ) and said axially extending flange ( 60 ) and a torque piston biasing member ( 58 ) that acts on said seat ( 64 ) to bias said piston head ( 62 ) toward said clutch pack ( 30 ), said torque apply piston assembly ( 54 ) operable to move between a disengaged position wherein said clutch pack ( 30 ) operates in open pack mode and an engaged position wherein said torque apply piston assembly ( 54 ) moves said clutch pack ( 30 ) to said closed pack mode to connect and disconnect said drive and driven members ( 16 , 24 ), said torque apply piston assembly ( 54 ) operable to provide a constant biasing force so that said clutch pack ( 30 ) normally operates in said closed pack mode to translate torque between said drive and driven members ( 16 , 24 ); a torque interrupt actuator assembly ( 68 ) operatively connected to said torque apply piston assembly ( 54 ), said torque interrupt actuator assembly ( 68 ) operable to selectively move said torque apply piston assembly ( 54 ) from said engaged position to said disengaged position thereby interrupting torque translation between said drive and driven members ( 16 , 24 ) through said clutch pack ( 30 ); and a return piston assembly ( 84 ) supported by said clutch housing ( 28 ) and connected to said clutch pack ( 30 ), said return piston assembly ( 84 ) operable to provide a constant biasing force in a direction opposite to the constant biasing force generated by said torque apply piston assembly ( 54 ) to move said clutch pack ( 30 ) from said closed pack mode to said open pack mode when said torque interrupt actuator assembly ( 68 ) moves said torque apply piston assembly ( 54 ) from said engaged position to said disengaged position.