Pressure signalling apparatus for tires

Claim 1

Apparatus for signalling a pressure drop in a pneumatic tire comprising a housing body, a bolt slidably mounted in the body for movement between a cocKed position and a released position, spring means for urging the bolt towards the released position whereby to cause the operation of a signalling means, a latch pin having a shoulder and being mounted in the body to engage and retain the bolt in cocked position, trigger means operatively engaging the latch pin and including a disc rotatably mounted in the body, said disc having a radial finger adjacent the shoulder when the latch pin is in latching engagement with the bolt, air pressure gauging means in the body and including a through bore and a cylinder at one end thereof, valve means mounted on the body and being connectable to a valve stem of the tire to permit inflation of said tire to a selected pressure, said valve means including a fitting forming a head for the cylinder, said air pressure gauging means having a piston mounted in the cylinder, a sleeve member slidably mounted in the through bore, a plug threadedly secured within an end of the through bore opposite the cylinder, a compression spring interposed between the plug and the sleeve member to bias said piston outwardly of the cylinder, said piston being forced inwardly by air pressure common to both the valve means and the tire to compress the compression spring, a connector pin operatively connecting the sleeve member to the disc, said compression spring moving the sleeve member outwardly when the force applied to the piston by the tire pressure drops below a predetermined level, said outward movement of the sleeve member withdrawing the latch pin thereby allowing the bolt to move from cocked position to released position.