| | Rotating eccentric weight seismic sources and a seismic exploration method - Patent 4143737 |
 | | Accordingly, for vertical exploration of earth strata underlying a horizontal surface, it is preferred that the axis of rotation is substantially horizontal, i.e., parallel to the surface of the earth. |
 | | Consequently, rotatable elements 111 and 112 are counter-rotated about a first axis of rotation, rotatable elements 111a and 112a are counter-rotated about a second axis of rotation, with rotatable elements 111 and 111a being rotated about their respective axes in opposite directions, as are elements 112 and 112a. |
 | | The rotation of weights 18 and 18a is always twice that of rods 28 and 28a due to (1) the angle of rotation of the rods and (2) the rotation of conversion gears 27 and 27a due to movement past stationary gears 26 and 26a. |
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