Automatic on-off valve for use with a pneumatic micrometer

摘要

An automatic on-off valve for use with a pneumatic micrometer connected between the main body of a pneumatic micrometer and its measuring head for economizing the consumption of pressurized air includes a valve body having, between an inlet and an exit thereof, a main flow passage to be opened and closed by a valve member and a sub-flow passage always open with a slight gap. The valve member is automatically turned on or off by the back pressure difference at the measuring head between a measuring state and a not-measuring state. The total open cross sectional area for both of the flow passages are set to be 6 to 9 times as large as the cross sectional area for a flow passage which is formed between a nozzle of the measuring head and an object to be measured upon the object being placed to measure the maximum gap, whereby a measuring error resulting from the disposition of the automatic on-off valve can be minimized within an allowable range to thereby maintain the measuring accuracy a desired high level.