Hydraulic booster device for linear actuator

Claim 1

A linear actuator comprising: a pressurized fluid supply; a housing having a primary piston chamber and a booster piston chamber; a piston rod disposed within said housing; a primary piston secured to one end of said piston rod and disposed within said primary piston chamber, said primary piston chamber having a first primary compartment and a second primary compartment disposed on opposite sides of said primary piston; a booster piston movably disposed about said piston rod within said booster piston chamber, said booster piston chamber having a first booster compartment and a second booster compartment disposed on opposite sides of said booster piston; a thrust column, affixed to said booster piston and movable relatively axially with respect to the piston rod, for pushing directly against said primary piston, responsive to the pressurized supply of fluid to the first booster compartment, which fluid acts against the bottom of said booster piston, so as to provide an initial thrust component to said piston rod, said thrust column being disposed radially between said booster piston and said piston rod so as to define an annular fluid channel extending axially between said first booster compartment and said first primary compartment for enabling said fluid to move therebetween, thereby to contribute a substantial additional thrust component to move said primary piston; a first port, located below the extreme point of travel of said booster piston, when the piston rod is fully extended, said port extending radially in fluid communication with said first booster compartment, thereby to be capable of supplying or draining said fluid to or from said first primary compartment and said first booster compartment concurrently; a second port capable of supplying and draining fluid to or from said second primarly compartment; and a third port capable of supplying and draining fluid to or from said second booster compartment; and, in which, to enable a precisely directed, copious parallel flow of pressurized fluid, said device includes a first axial passageway which connects the first, radially extending port to a point in said first booster compartment immediately adjacent and aligned with said annular fluid channel when the piston rod is fully extended, and further includes a second axial passageway spaced radially from the first axial passageway which connects the first port to a point in said first booster compartment immediately adjacent said booster piston bottom surface when the piston rod is fully extended.