Servo-actuator mechanism

Claim 2

In a pressurized fluid servo-actuator mechanism having a cylinder with a piston rod extending from an exit end of the cylinder with first sealing means for the piston rod at the exit end, in combination with a housing surrounding the piston rod and extending from the exit end of the cylinder, an annular space between said piston rod and said housing to prevent any contact therebetween, second sealing means for the piston rod disposed within the housing at a distance greater than one stroke length from the first sealing means, the portion of the piston rod passing through said first and second sealing means having a generally constant cross-section, whereby the portion of the piston rod passing through the first sealing means is always enclosed within the housing or within the cylinder to prevent that portion of the piston rod from being contaminated by foreign material, which may cause damage to the piston rod and the first sealing means and thereby prevent said first sealing means from leaking.

Claim 3

In a pressurized fluid servo-actuator mechanism as set forth in claim 1 and further comprising in combination drain means associated with the first sealing means and the housing being adapted to be filled with an unpressurized lubricating fluid, whereby the sealing means are lubricated and pressurized fluid leaking through the first seal means flows through the drain means without pressurizing the fluid in the housing, thereby minimizing leakage through the second sealing means.

Claim 4

In a pressurized fluid servo-actuator mechanism as set forth in claim 2 and further comprising in combination means for retarding the movement of the piston as the piston rod approaches that end of its stroke wherein the piston rod approaches its fully extended position.

Claim 5

In a pressurized fluid servo-actuator mechanism as set forth in claim 2 and further comprising in combination scraping means encompassing the piston rod and disposed outboard of the second sealing means.

Claim 6

In a pressurized fluid servo-actuator mechanism as set forth in claim 2 and further comprising in combination bearing means disposed adjacent the second sealing means to provide additional stability to the piston rod.

Claim 7

In a pressurized fluid servo-actuator mechanism as set forth in claim 5 and further comprising in combination bias means encompassing said housing, said biasing means being disposed to move said piston rod to its fully extended position, said housing being disposed to act as an internal guide for said bias means.

Claim 8

In a pressurized fluid servo-actuator mechanism having a cylinder with a piston rod extending from an exit end of the cylinder with first high pressure sealing means fOr the piston rod at the exit end, in combination with a housing surrounding the piston rod and extending from the exit end of the cylinder, second sealing means for the piston rod disposed within the housing at a distance greater than one stroke length from the first sealing means, said housing being adapted to be filled with an unpressurized lubricating fluid, drain means associated with the first sealing means so that pressurized fluid flowing therethrough will flow into said drain means and not pressurize said housing, scraping means encompassing the piston rod and disposed outboard of the second sealing means, the portion of the piston rod passing through said first and second sealing means having a generally constant cross-sectional area, whereby that portion of the piston rod which passes through the first sealing means is always lubricated and continuously enclosed within the housing or the cylinder to protect that portion of the piston rod and the first sealing means from foreign material which could damage them.

Claim 9

In a pressurized fluid servo-actuator mechanism having a cylinder with a piston rod extending from an exit end of the cylinder with first high pressure sealing means fOr the piston rod at the exit end, in combination with a housing surrounding the piston rod and extending from the exit end of the cylinder, second sealing means for the piston rod disposed within the housing at a distance greater than one stroke length from the first sealing means, said housing being adapted to be filled with an unpressurized lubricating fluid, drain means associated with the first sealing means so that pressurized fluid flowing therethrough will flow into said drain means and not pressurize said housing, scraping means encompassing the piston rod and disposed outboard of the second sealing means, the portion of the piston rod passing through said first and second sealing means having a generally constant cross-sectional area, whereby that portion of the piston rod which passes through the first sealing means is always lubricated and continuously enclosed within the housing or the cylinder to protect that portion of the piston rod and the first sealing means from foreign material which could damage them.