Abstract: A pressure gauge for indicating the fluid pressure at a source of pressure such as a tire, for example, has a chamber formed within a body. When the body is disposed on a tire valve stem, for example, a portion of the body depresses a valve core plunger of the valve stem to enable the pressurized fluid in the tire to flow through a longitudinal passage in the body and past a flap valve, which is an O-ring, into the chamber. This pressurized fluid in the chamber acts on a piston head of a piston, which is slidably disposed in a passage in the body communicating with the chamber, to move the piston against the force of a spring within the body passage. An O-ring is mounted in the piston head to seal the body passage. The O-ring acts as an indicator through cooperation with a scale on the body to indicate the pressure of the fluid in the chamber in the body; this is the same pressure as that in the tire since the tire is communicating with the chamber.

Abstract: A combined gauge and inflator for a tire includes a support member threaded on the tire stem with a body slidably disposed within the support member and locked in a first position. The body has a passage extending therethrough with a spring-biased piston slidably disposed therein. With the body in the first position, the piston rests against a spring-biased plunger, which opens the valve in the tire stem when the plunger spring is overcome. The plunger spring is overcome either by an air chuck acting on the piston to move the piston against the plunger or when the body is moved from its first position to a second position in which the body engages the plunger. When the body is moved against the plunger, sealing means on the piston seal the body passage so that air pressure in the tire moves the piston relative to the body. A scale on the piston cooperates with a marker on the body to indicate the pressure of the tire.