| 摘要 |
A hand bicycle pump of generally cylindrical configuration essentially comprising a pump body adapted to be reciprocated on a pump rod. An air circulation chamber communicates at one end through the compression piston with the compression chamber in the pump body and at the other end via a check valve with a connector adapted to couple temporarily the pump to an inflation valve of an inflatable body, e.g. a tire. The desired inflation pressure is preselected by rotating a sleeve, accessible from outside the pump, having an index, relative graduations along a slot in the pump body. The sleeve varies the spring force exerted against one end of a piston control member, the other end of which is subjected to the pressure inside the inflatable body so that once the desired pressure is reach the control member is displaced axially to bring the compression chamber into communication with the atmosphere. In one embodiment valving is effected by a valve control member which embodies the control member too, and in another embodiment the air circulation tube is axially moveable and a valve disc is provided at the end thereof closest the compression chamber for interrupting communication when the desired pressure is reached. In both embodiments pumping pressure is partially compensated for to prevent untimely communication between the compression chamber and the atmosphere when the pump is reciprocated faster than air can be admitted to the inflatable body.
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