Pilot-operated slide valve with position indicator

Claim 1

A SLIDE VALVE COMPRISING, IN COMBINATION: (A) A VALVE SLEEVE HAVING AN AXIS, (1) SAID SLEEVE INCLUDING AN AXIAL WALL AND AN END WALL TRANSVERSE OF SAID AXIS, SAID WALLS DEFINING A CAVITY IN SAID SLEEVE, (2) SAID AXIAL WALL BEING FORMED WITH A PLURALITY OF AXIALLY SPACED OPENINGS, AND SAID END WALL BEING FORMED WITH AN APERTURE THERETHROUGH, SAID OPENING AND SAID APERTURE COMMUNICATING WITH SAID CAVITY; (B) VALVE SLIDE MEANS AXIALLY MOVABLE IN SAID CAVITY BETWEEN TWO POSITIONS IN WHICH SAID VALVE SLIDE MEANS DEFINE RESPECTIVE PATHS IN SAID CAVITY CONNECTING ONE OF SAID OPENINGS RESPECTIVELY WITH TWO OTHER OPENINGS; (C) PRESSURE FLUID OPERATED MEANS IN SAID CAVITY FOR MOVING SAID VALVE SLIDE MEANS BETWEEN SAID POSITIONS THEREOF; (D) AN INDICATOR MEMBER MOUNTED ON SAID VALVE SLIDE MEANS FOR AXIAL MOVEMENT THEREWITH, SAID INDICATOR MEMBER PROJECTING AXIALLY OUTWARD OF SAID CAVITY THROUGH SAID APERTURE OF SAID END WALL IN AT LEAST ONE POSITION OF SAID VALVE SLIDE MEANS; (E) A TUBE OF LIGHT-PERMEABLE MATERIAL INTEGRALLY CLOSED AT ONE END AND FORMED WITH AN ORIFICE AT THE OTHER END, SAID TUBE HAVING AN AXIS PARALLEL TO THE AXIS OF SAID SLEEVE AND BEING FORMED WITH A SPACE EXTENDING AXIALLY INWARD OF SAID ORIFICE;