Abstract: A method and an apparatus for mass retrieval for an acoustic pulse generator are disclosed herein. In an impulse type seismic generating apparatus an air spring, mechanical spring, controlled pressurization of an air spring or other energy storage medium is employed to use potential energy to raise the impact mass to a resting position above an earth contacting baseplate as quickly as possible after the impact mass strikes the baseplate.

Abstract: A retractable dust control hood for a rotary table saw includes a generally hollow box member which is supported for movement between a working position directly over the saw blade and a retracted position substantially above the saw blade to permit ease of handling workpieces with respect to the saw and a saw support table surface. The hood is supported from a member disposed above the table surface by parallelogram linkage and a counterbalance mechanism including a rod extending between one set of parallelogram link members and a second set of parallelogram link members. A coil spring is disposed around the rod and acts to move the parallelogram link members relative to each other to counterbalance the weight of the hood. The hood includes a transparent window and a lamp for illuminating the interior space of the hood for ease of viewing the workpiece during operation of the saw.

Abstract: Multiple vehicle-transported impact-type surface seismic sources designed to shoot along slant paths to create combined compressional and shear wave pulses in the earth are provided with radio controlled actuators. The azimuth of each shooting path is automatically referenced to magnetic north so that signals of equivalent wave form contents are produced despite vehicle misalignments and without reliance upon individual vehicle operators.