Rapid actuating device of hydraulic actuator

A hydraulic actuator for use in extending a ram relative to its associated ram cylinder comprising in combination:

• a first cylinder supported in a base,
• a first piston operatively disposed therein connected to means for translating said first piston within said first cylinder,
• a bore within said first piston defining a second cylinder,
• a second piston operatively disposed within said second cylinder whereby translation of said first piston causes volumetric change in said second cylinder,
• and valved hydraulic fluid conduit means extending between said pistons and said ram whereby translation of said first piston moves said ram,
• wherein said conduit means includes an hydraulic pressure sensitive bypass means whereby a portion of hydraulic fluid pumped by said pistons can be diverted back to a reservoir and said ram will move more slowly,
• wherein said bypass means comprises a relief valve disposed on a passageway which forms a portion of said conduit means, said passageway extends from said first cylinder to said ram,
• wherein said relief valve comprises an elastic piece disposed in a groove on a lower portion of said second piston, said passageway extending through said second piston and communicating with said groove through a hole in said second piston, a ball covering said hole and biased thereagainst by a free end of said elastic piece, a fixed end of which is constrained in said groove on said second piston whereby hydraulic pressure in excess of the elastic piece's resiliencey displaces said ball and causes the hydraulic fluid to bleed therethrough to said reservoir.