| 摘要 |
<p>In a blood dialysis system a proportioning pump accurately mixes precise quantities of water and concentrate. A double-acting piston assembly is disposed in a stepped cylinder which has proximity sensing switches at both ends thereof. These are operated as the piston assembly reaches the end of its stroke in each direction. The switches alternate a bistable solenoid valve system which directs pressurized water to opposite sides of a large central piston, thus causing the piston assembly to reciprocate. Small pistons, attached on opposite sides of the large piston, move in small pump chambers, with check valves. The small pistons pump concentrate in a precise ratio to the volume of water driving the large piston.</p> |
