| 摘要 |
<p>A liquid additive injection pump has a hydraulic motor comprising a differential piston assembly reciprocable in a housing under the urging of a primary liquid into which an additive is to be injected. The piston assembly (30, 224) includes snap action valves (76, 88, 232, 238) to effect transfer of a primary fluid charge from the pump motor to a discharge passage (310) and to effect reciprocation of the piston assembly. The motor piston (31, 225) is connected to a piston rod (57, 262) which extends into a pump cylinder (48, 280, 284). In one embodiment a floating pump piston (166) has a stack of displacement control washers (162, 164) engaged therewith and disposed on the piston rod (57). In another embodiment the pump piston (330) passes through a seal member (419) between a pump chamber (412) and a bypass chamber (408). An elongated spiral groove (354) is formed on the periphery of the pump piston. An external adjustment mechanism is provided for variably presetting the effective displacement of the pump.</p> |
