Patent ID: 7685929

Claim:
A hydraulic bore seal telescopic hoist, comprising: a cylindrical housing; a series of fluid pressure actuatable tubular sections telescopically received in said housing, each successive tubular section being of a smaller diameter and nested within each prior successive tubular section such that each tubular section has telescopically sliding surfaces; each said tubular section being open to allow ambient air to freely enter on a first end thereof and each tubular section, other than the tubular section having the smallest diameter, closed by a piston head with an inlet port for passage of a pressure fluid therethrough; and a bore seal mounted in each of said piston heads, for confining said fluid on the second end; said tubular sections being formed of a nitrided steel such that a film of the fluid forms on and in connection with asperities on the telescopically sliding surfaces of the tubular sections on the second end as they are telescopically displaced under action of the fluid under pressure, such that the tubular sections have semi-lubricated contact between each other.