Pipe position indicator for pipe rackers

Claim 1

In well-drilling derrick apparatus of the type having spacedapart sides with rack means for receiving pipe stands and supporting the same in spaced vertical positions, said rack means including a plurality of fingers disposed in parallel spaced relation with respect to a side of said derrick, racker means for moving said pipe stands into and out of said rack means, said racker means including a longitudinally extended racker arm, means for supporting said racker arm for longitudinal movement in a horizontal plane between projected and retracted positions relative to said rack means and for movement laterally with respect to said rack means to place said pipe stands between said fingers, a racker head carried by said racker arm, said racker head including means selectively and releasably engageable with a shoulder on said pipe stands, and means for moving said arm longitudinally and laterally, the improvement comprising in combination therewith: a. indicator means driven by said racker means positionable in response to longitudinal and lateral movement of said racker arm for indicating the relationship of said racker head with respect to said fingers and the vertical center of said derrick; b. receiver means representing longitudinal and lateral movements of said racker arm included in said indicator means; c. said receiver means including synchro motor means for driving said receiver means; and d. transmitter means including synchro generator means adjustably responsive to movements of said racker arm to adjust said synchro motor means.