Fish & Richardson P.C.
Tire pressure gage
 A tire pressure gauge includes a tubular housing, an elongated plunger extending longitudinally in the tubular housing, and a pen element inserted in an axial bore of the plunger. The tubular housing has a first end portion and a second end portion formed with an axially extending elongated guide slot that extends from a distal end face thereof. The plunger has a driven end portion to be driven by a piston in the tubular housing, and a guided end portion provided with a radial pin which is extendible outwardly of the tubular housing via the guide slot. The pen element has a writing end which extends outwardly of the bore of the plunger. The writing end is retracted into the tubular housing when the radial pin is moved in the guide slot toward the first end portion of the tubular housing, and is exposed from the tubular housing when the radial pin is moved to extend out of the guide slot. The plunger is rotatable axially relative to the tubular housing to engage the radial pin with the distal end face of the tubular housing when the radial pin is extended out of the guide slot to maintain the writing end in an exposed position. 
G
G01L
inventional
Tien-Tsai
Huang