GB943759A - Pneumatic motor of the reciprocating type - Google Patents

Abstract

943,759. Reciprocating pneumatic motors. MARTONAIR Ltd. Aug. 28, 1962 [Sept. 6, 1961], No. 31956/61. Headings F1M and F1S. A pneumatic motor includes a piston biased in the direction to engage the head of a coacting cylinder and to cover a small exhaust port therein the heads of the piston and cylinder when in engagement with each other defining between them an annular chamber which extends up to the periphery of the piston and of which chamber the wall formed by the piston head is of substantially less area than the whole cross-sectional area of the piston head and the cylinder being provided with an inlet to the chamber for a gas under pressure to act on the piston in opposition to the bias. In operation the air pump progressively charges the reservoir and the latter delivers the pressurised air to the annular chamber 21 when the pressure in this chamber, which is acting on only a minor proportion of the piston head (i.e. the annulus 35), reaches a value at which the bias acting on the piston is overcome, the piston commences to move away from the cylinder head as soon as this takes place the annular rib 19 breaks the seal with the ring 20 and the whole area of the piston head is thereby exposed to the air pressure achieved in the reservoir with the result that the outward stroke of the piston is made suddenly and at high speed and with only a small loss of pressure through the exhaust port 34 which is then uncovered. This outward movement of the piston and the uncovering of the exhaust post causes the pressure in the reservoir to drop and the bias acting on the piston returns it to its original position until the recharging of the reservoir by the pump causes the reset outward stroke to be made. The bias acting on the piston can be applied in a variety of ways. Thus it could be a coiled compression spring, or it could be provided by applying a sub-atmospheric pressure to the exhaust port 34 or, by applying a positive gas pressure to the underside of the piston or it could be applied in any combination of these ways. The pneumatic motor can be operated in a variety of ways. One method involves limiting the maximum pressure in the reservoir to a value such that the force due to the pressure acting on the annulus 35 is of itself not quite sufficient to overcome the bias, and then momentarily to overcome the bias by admitting air under pressure through the exhaust port alternatively the motor may be fired by removing a subatmospheric pressure at the exhaust port. Other modifications (e.g. Fig. 2) are described. The motor may make a single reciprocation or operate automatically.