| 摘要 |
<p>A positive displacement pump for dispensing metered quantities of fluid. A piston (19') is located for reciprocating movement in a piston chamber (15) with movement in at least one direction being under the action of an applied fluid pressure controlled by a solenoid valve (52). A fluid receiving chamber (14'), is connected to a source of fluid (60). Fluid is drawn into the fluid receiving chamber (14') when the piston (19') moves in a first direction. A valve (56) is operable to permit fluid drawn into the fluid receiving chamber (14') to pass from the chamber to an outlet (55) upon the piston moving in a second direction opposite to said first direction. By controlling valve (56) the volume of fluid drawn into the fluid receiving chamber (14') can be adjusted so as to alter the ratio of mix of fluid from the receiving chamber (14') with fluid being exhausted to outlet (55) from the piston chamber (15).</p> |
