Filter gauge

Claim 1

A gauge for registering a predetermined degree of suction pressure within the air intake manifold of an internal combustion engine, as a measure of the clogging of an air intake filter supPlying combustion air to said intake manifold, comprising: a. an open faced annular hollow body portion having a closed bottom wall and an apertured depending bottom extension for connection with said air intake manifold; b. an annular recess extending inwardly from the open face of said body portion in spaced relation to said bottom wall thereof; c. an apertured flexible annular diaphragm mounted within said annular recess and extending across said body portion so as to overlie said bottom wall in spaced relation thereto; d. a spring biasing the central portion of said diaphragm towards said open end; e. headed rigid means mounted in the aperture in said flexible diaphragm and depending therefrom within said apertured bottom extension for movement relative thereto and exposed to suction pressure within the intake manifold; f. closure means mounted in fixed relation within said open face of the hollow body portion in spaced relation to said flexible diaphragm and comprising a transparent disclike body portion having a peripheral depending flange abutting the periphery of said flexible annular diaphragm and the underlying gauge body portion and an upstanding hollow head portion; and g. a torsion-spring-loaded horizontally rotatable and vertically moveable target member underlying the transparent face of closure member in abutting relation to said flexible diaphragm headed rigid means and having an upstanding central portion extending through said closure means, whereby suction within the air intake manifold acting through the flexible diaphragm retracts the headed member therein permitting said torsion spring to rotate the target member to display a change filter signal.