Multi-disk friction device having forced lubrication on demand

A friction device comprising:

• a drive member and a driven member which are rotatable about a common axis and which define a clutch housing therebetween;
• an annular clutch pack having an inner diameter and an outer diameter, said clutch pack being operable to connect and disconnect said drive and driven members for transferring and interrupting torque therebetween;
• a piston assembly supported in said clutch housing and defining an expandable chamber between said piston assembly and said clutch housing, said piston assembly including a main body having outer ring annularly disposed about said main body, said outer ring including a plurality of orifices extending through said outer ring arcuately spaced relative to one another about said common axis, said outer ring being movable between a first position wherein said orifices are closed and said drive and driven members are disconnected and a second position wherein said orifices are open to allow flow of pressurized fluid through said orifices and into contact with said clutch pack thereby cooling same when said drive and driven members are operatively connected through said clutch pack;
• a source of pressurized fluid in communication with said expandable chamber, said piston assembly being responsive to the pressure of fluid in said expandable chamber to move between disengaged and engaged positions thereby actuating said clutch pack to connect and disconnect said drive and driven members;
• said piston assembly also operable to control the flow of coolant under pressure from said outer diameter of said clutch pack between said adjacent plates and disks to said inner diameter of said clutch pack to cool same when said drive and driven members are connected and to stop the flow of pressurized coolant to said clutch pack when said drive and driven members are disconnected.