Automatic sequential dual action sealing system

Claim 1

In a shock absorbing subassembly including a body, a mandrel slidably and non-rotatively received in the body, means for providing limited relative longitudinal movement therebetween, dampening means between the mandrel and body for absorbing and dampening vibrations and impact loads applied to the body, upper seal means for providing a fluid tight seal between the body and the mandrel above the dampening means, and floating seal means for providing a fluid tight seal between the body and the mandrel below the dampening means, the improvement comprising said body having a radial fluid outlet slightly below the floating seal means; primary annular seal means for providing a fluid tight seal between the body and mandrel below the floating seal means; and secondary annular seal means positioned between the body and mandrel and the floating seal means and said primary seal means, said secondary seal means comprising an annular piston slidably positioned between the body and the mandrel and said radial fluid outlet and said primary seal means, said annular piston being slidable between first and second positions proximate and remote from said primary annular seal means, inner and outer annular seals positioned between said annular piston and the mandrel and the body, respectively, said annular piston being provided with an orifice to facilitate low fluid flow rates through said piston and said radial fluid outlet without causing said piston to move from said first position to said second position, and orifice seal means for sealing said orifice when said piston is in said second position.