| 摘要 |
An adjustable vol. of air is delivered (13) whenever the bellows (7) is expanded and compressed by the fall and rise of a horizontal bar (15) coupled to its baseplate (14). The ends of the bar are fixed to respective vertical endless toothed belts (16) driven reversibly by a stepping motor (5). The vol. is determined by the position of e.g. a Hall effect transducer (10) co-operating with a magnet on the bar to terminate the compression stroke. The motor shaft (18) carries a coil spring (20) which stores energy during the expansion stroke for release if the motor should stall. <IMAGE> |
