GB547007A - Improvements in or relating to optical projection apparatus for checking the dimensions of articles - Google Patents

Abstract

547,007. Linear-dimension gauges. HOOVER, Ltd., and THOMAS, A. H. Feb. 7, 1941, No. 1660. [Class 106 (ii)] [Also in Group XX] Apparatus for checking dimensions of objects by optical projection comprises a table supporting the object and a rod movable across the projection axis towards and from the table, so that when one end of the rod engages the object the image of the other end of the rod is visible on a screen. As shown, a lamp C and condenser C<SP>1</SP> illuminate the pointed end D<SP>1</SP> of an axially movable rod D, and a lens C<SP>2</SP>, prism C3, and mirror C4 produce an image of the end D<SP>1</SP> on a translucent screen B bearing a datum line and upper and lower limit lines. The rod D may be raised against the action of a spring D4 by a lever D<SP>21</SP> so that a standard object may be supported on a table A<SP>1</SP>; the distance of the table from the rod, or the effective length of the rod, may then be adjusted so that when the rod engages the object, the image of the point of the rod coincides with the datum line. The object to be checked may be substituted for the standard object and its accuracy determined with the aid of the datum and limit lines. The table A<SP>1</SP> may carry two or more supporting surfaces at different levels and be rotatable or slidable so that two or more dimensions of the object may be successively checked. A construction is described for checking one dimension of small objects, wherein the rod carries a head which is pressed into engagement with the object against the action of a spring, and the translucent screen is carried in a hinged hood arranged at the top of the casing of the apparatus.