| 摘要 |
36 A pump assembly or for pumping one or more fluids includes a drive piston pump which reciprocates to drive proportion pumps. Fluid to the drive piston pump is controlled through a pair of two-position, three-port valves which communicate pressurized fluid sequentially above and below the drive pump piston to reciprocate the piston. while applying fluid pressure to one face of the piston, the opposite face is vented to tank such that no back pressure exists in the system. A proportion pump is provided for each fluid pumped by the system and is designed to pump upon movement in either direction. A check valve is fitted on the outlet of the proportion pump to maintain constant pressure in the hose attached to the proportion pump and to prevent back flow of fluid from the hose into the system. The hose is of sufficient length so as to modulate any variations in the pumping pressure. |
