Unilinear displacement measuring apparatus

Claim 1

A MEASURING DEVICE COMPRISING THREE THREADED MEMBERS, ONE OF THE MEMBERS BEING FIXED AGAINST AXIS MOVEMEANS AND ROTATION, ANOTHER OF THE MEMBERS BEING KEYED TO THE FIRST SO AS TO BE PREVENTED FROM ROTATING WHILE BEING PERMITTED AXIAL MOVEMENT, THE THIRD MEMBER HAVING TWO THREADED PORTIONS IN SEPARATE ENGAGEMENT WITH THE SAID ONE AND OTHER MEMBERS SO AS TO BE CAPABLE OF ROTATION AND AXIAL MOVEMENT IN RESPONSE THERETO, A RECIPROCATING PART KEYED TO THE THIRD THREADED MEMBER AND HAVING TWO SETS OF PERIPHERALLY SPACED PROJECTIONS, ONE SET OF PROJECTIONS BEING AT ONE END OF THE PART, THE OTHER SET BEING AT THE OTHER END, THE PROJECTIONS OF ONE SET BEING STAGGERED WITH RESPECT TO THE PROJECTIONS OF THE OTHER SET, MEANS PROVIDING TWO CAMMING SURFACES, ONE ENGAGEABLE WITH THE PROJECTIONS OF ONE SET INDIVIDUALLY ON MOVEMENT OF THE RECIPROCATING PART IN ONE DIRECTION ALONG THE THIRD THREADED MEMBER TO SHIFT THE LATTER AND THE RECIPROCATING PART ANGULARLY IN A GIVEN DIRECTION OF ROTATION, THE OTHER CAMMING SURFACE BEING ENGAGEABLE WITH THE PROJECTIONS OF THE OTHER SET INDIVIDUALLY ON MOVEMENT OF THE RECIPROCATING PART IN THE OPPOSITE DIRECTION ALONG THE THIRD THREADED MEMBER TO SHIFT THE LATTER AND THE RECIPROCATING PART ANGULARLY IN THE SAID GIVEN DIRECTION OF ROTATION, MEANS FOR RECIPROCATING THE RECIPROCATING PART, AND MEANS FOR COUNTING THE RECIPROCATIONS OF THE RECIPROCATING PART.