| 摘要 |
A tire cap pressure gauge for mounting upon a tire valve stem and measuring tire pressure has a housing, a manually operated plunger extending axially through the housing, a spring extending about the plunger, a piston biased by the spring and having indicia, and a transparent insert member containing said spring, piston and plunger within the housing and having an internally threaded bore for mounting about the periphery of a threaded valve stem. The housing has multiple windows with indicia proximate thereto for viewing the translational position of the piston through the transparent insert member. Two embodiments show a lightweight, compact and easily assembled pressure measuring cap having sealless construction which utilizes close clearances and sharp corners to minimize leakage airflow. A small but insignificant amount of air leaks past the piston, providing an audible signal that the plunger is sufficiently depressed to provide an adequate pressure reading. One embodiment is adaptable to two ranges of use, automobile tire pressures and truck tire pressures, by merely changing the orientation of the plunger thereby changing the effective pressure biasing area of the piston.
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