US Patent 7913828 Clutch with dual area piston and independent pressure control

The present invention provides a clutch having two pistons, a first piston defining a first, smaller area and a second piston, defining a second, larger area. The separate pistons are independently provided with flows of pressurized hydraulic fluid from first and second independent modulatable control valves. Engagement of the clutch may be rapid by providing hydraulic fluid to the smaller area piston, provide greater engagement force by providing hydraulic fluid to the larger area piston or a combination of speed and force by utilizing modulated or unmodulated flows of hydraulic fluid to both pistons.