High frequency reaction mass and hydraulic cylinder assembly

Claim 1

A seismic transducer apparatus for operation over an operating frequency range extending into the higher seismic frequency range above 80 cycles per second, comprising: a frame; a vertical double rod-end piston member, including a drive piston with upper and lower rods extending from said drive piston and having axial ends attached to said frame, said lower rod being about twice the length of the upper rod; a reaction mass member reciprocally disposed about said piston member and forming a hydraulic drive cylinder around said drive piston; and a hydraulic biasing cylinder formed between an upward facing shoulder of said lower rod and a downward facing shoulder of said reaction mass member; first port means directed for communication adjacent the lower rod with the biasing cylinder; second and third port means directed axially through the short upper rod for communication above and below the drive piston, respectively, with the drive cylinder; hydraulic valve control means mounted proximate the axial end of the upper rod in control communication with said second and third port means; whereby said biasing cylinder is located below said drive cylinder to minimize the length of fluid port means supplying fluid to said drive cylinder through increasing the natural frequency of the spring-mass system represented by the mass of said frame and the spring constant of the trapped fluid in said drive cylinder and said second and third port means to a value above said operating frequency range.