Testing of surface straightness

Claim 1

APPARATUS FOR MEASURING LACK OF STRAIGHTNESS ALONG A SURFACE, COMPRISING A FEELER, A CARRIAGE ON WHICH THE FEELER IS MOUNTED, MEANS FOR URGING THE FEELER INTO ENENGAGEMENT WITH THE TEST SURFACE, AN APPROXIMATELY STRAIGHT ELONGATED DATUM ELEMENT GENERALLY SYMMETRICAL ABOUT ITS LONGITUDINAL AXIS, MEANS FOR MOUNTING THE DATUM ELEMENT GENERALLY PARALLEL TO THE TEST SURFACE, MEANS FOR ROTATING THE APPROXIMATELY STRAIGHT DATUM ELEMENT GENERALLY ABOUT ITS AXIS SO THAT THE MEAN POSITION OF SUCH AXIS CONSTITUTES AN ACCURATELY STRAIGHT DATUM LINE FOR MEASUREMENT OF THE LACK OF STRAIGHTNESS OF THE SURFACE , MEANS FOR MOVING THE FEELER CARRIAGE LENGTH WISE OF THE DATUM ELEMENT,A CAUSE THE FEELER TO TRANSVERSE A NOMINALLY STRAIGHT PATH ACROSS THE TEST SURFACE, WHEREBY THE FEELER EXECUTES A WORKING MOVEMENT GENERALLY NORMAL TO THE TEST SURFACE DURING TRAVERSING IN ACCORDANCE WITH THE LACK OF STRAIGHTNESS OF SUCH SURFACE, THE ARRANGEMENT BEING SUCH THAT THIS WORKING MOVEMENT OF THE FEELER IS EFFECTIVELY CONTAINED, THROUGHOUT TRAVERSING, SUBSTANTIALLY IN THE PLANE NORMAL TO THE TEST SURFACE THROUGH THE DATUM LINE, DETECTING MEANS RESPONSIVE TO THE WORKING MOVEMENT DURING TRAVERSING, AND ELECTRICAL MEANS OPERATED UNDER THE CONTROL OF THE DETECTING MEANS FOR CAUSING TO BE FED TO A MEASURING INSTRUMENT AN ELECTRICAL SIGNAL REPRESENTING THE WORKING MOVEMENT OF THE FEELER DURING TRAVERSING RELATIVE TO THE DATUM LINE AFFORDED BY THE ROTATING DATUM ELEMENT.