- Patent JPS50119314

Document Type and Number:

Japanese Patent JPS50119314

Kind Code:

A

Abstract:

1479993 Pressure gauges DAHLTRON CORP 17 Feb 1975 [22 Feb 1974] 6685/75 Heading G1L [Also in Division F1] A double-acting hand pump, especially for inflating tyres, comprises a piston 42 dividing a cylinder 22 into working chambers 44, 46 a hollow piston-rod 48 through which air pumped from the working chambers 44, 46 is delivered, and a permanent restricted passage 106 inter-connecting one of the working chambers to the piston-rod interior whereby, on releasing the cylinder 22 from a position in which the one working chamber is a minimum, air flows through the passage 106 and expands the one working chamber by an amount proportional to the inflation pressure. In the embodiment shown the restricted passage 106 leads to the chamber 46 and is constituted by the clearance between the engaging screw threads 102, 104 on the piston and piston-rod, respectively. As the chamber 46 expands it compresses air trapped in the other chamber 44 until equilibrium is reached. By constructing the cylinder 22 or a portion thereof of clear plastics the equilibrium position of the piston can be read off on a calibrated pressure scale 40 on the cylinder 22. Opposite end of the cylinder 22 are closed by perforated end closures 26, 30 mounting annular valve members 72, 88, the latter comprising lips 78, 94 which flex inwardly to allow the entry of air to the cylinder when the adjacent working chamber is expanding. Air compressed in the contracting working chamber enters the piston-rod through an annular groove 110 and passages 112 in the piston 42, the groove 110 containing a piston ring 114, 118 provided with lips 116a, 116b which co-operate with the sides of the groove 110 to form non-return delivery valves. A hose 58 is stored within the piston rod 48 and is withdrawn to a position in which a frusto-conical end 124 thereof engages a complementary seating 122 in a handle 24 secured to the rod 48. If the tyre is over inflated the hose 58 may be moved away from the seating 122 to allow air to escape from the tyre, Fig. 4 (not shown).

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