Multiple chambered gas powered seismic source

Pneumatic apparatus suitable for producing a shock wave in a liquid, comprising:

• a shuttle movable through a stroke having a central shuttle shaft with an axis;
• first and second outer sealing pistons mounted axially on the shaft proximate to its opposite ends and each of the first and second outer sealing pistons having an inner face;
• and
• first and second inner sealing pistons mounted axially on the shuttle shaft respectively adjacent and interior to the first and second outer sealing pistons and each of the first and second inner sealing pistons having an outer face;
• and
• first and second control pistons mounted axially on the shaft, respectively adjacent and interior to the first and second inner sealing pistons, each of the first and second control pistons having an outer face, being an equal distance from the midpoint of the shuttle shaft, substantially round and of the same diameter, and
• the pistons being spaced on the shuttle shaft such that the distance between the inner face of the first outer sealing piston and the outer face of the first inner sealing piston, the inner face of the second outer sealing piston and the outer face of the second inner sealing piston, and the outer face of the first control piston and the outer face of the second control piston are all essentially the same stroke length, and
• a gas passage running the axial length of the shuttle shaft, and
• a passage located in the shaft between first and second control pistons connecting the outside of the shuttle shaft with the gas passage;
• and
• a first gas storage means mounted about the axis formed by the shuttle shaft at the first end of a control chamber means and disposed about the first outer sealing piston and the first inner sealing piston and having a first gas chamber with walls, an outer end, terminated at an inner end by a first shoulder, and disposed about the first outer sealing piston, and
• a first shoulder having an outer sealing face adapted to substantially seal against the inner face of the first outer sealing piston, an inner sealing face adapted to substantially seal against the outer face of the first inner sealing piston, and an opening about the axis of the shuttle shaft larger than the shuttle shaft, and
• first exhaust port means located between the first shoulder and the first end of a control chamber;
• a second gas storage means mounted about the axis formed by the shuttle shaft at the second end of the control chamber means and disposed about the second outer sealing piston and the second inner sealing piston having
• a second gas chamber with walls, an outer end, terminated at an inner end by a second shoulder, and disposed about the second outer sealing piston, and
• a second shoulder having an outer sealing face adapted to substantially seal against the inner face of the second outer sealing piston, an inner sealing face adapted to substantially seal against the outer face of the second inner sealing piston, and an opening about the axis of the shuttle shaft larger than the shuttle shaft, and
• second exhaust port means located between the second shoulder and the second end of the control chamber;
• a control chamber having
• an interior wall substantially circular, parallel to the axis of the shuttle shaft, adapted to fit the first and second control pistons, and having a gas charge inlet in a mid portion of the wall, and
• a first end having openly terminated therein a first control gas line, a hole adapted for the axial passage of the shuttle shaft between first control piston and first inner sealing piston, gas sealing means in said hole substantially preventing the passage of gas through the hole, and
• a second end having openly terminated therein a second control gas line, a hole adapted for the axial passage of the shuttle shaft between second control piston and second inner sealing piston, gas sealing means in said hold substantially preventing the passage of gas through the hole, and
• control valve means capable of alternately directing a pressurized gas through the first control gas line while simultaneously venting gas from the second control gas line or directing a pressurized gas through the second control gas line which simultaneously venting gas from the first control gas line.