Patent ID: 7665431

Claim:
A drive piston assembly operable to selectively open a poppet valve, the drive piston assembly comprising: a cartridge defining a generally stepped bore; a drive piston movable within said generally stepped bore; a boost sleeve coaxially disposed with respect to said drive piston; wherein the drive piston includes a shoulder portion operable to engage said boost sleeve to enable unitary movement between said drive piston and said boost sleeve; a main fluid chamber at least partially defined by at least one of said generally stepped bore, drive piston, and boost sleeve; first and second feedback chambers at least partially defined by said drive piston and each disposed at opposite ends of said drive piston; and wherein at least one of said drive piston and said boost sleeve is sufficiently configured to move within said generally stepped bore in response to fluid pressure within said main fluid chamber to selectively open the poppet valve.