| 摘要 |
PCT No. PCT/CA92/00081 Sec. 371 Date Oct. 27, 1992 Sec. 102(e) Date Oct. 27, 1992 PCT Filed Feb. 26, 1992 PCT Pub. No. WO92/15979 PCT Pub. Date Sep. 17, 1992.A positive displacement pump includes a reservoir for storing fluid, a cylinder for receiving and discharging the fluid and a piston within the cylinder for forcing the fluid into and out of the cylinder. The pump further includes a four-way valve having an inlet port connected to a reservoir, a pair of bidirectional ports connected to the opposite ends of the cylinder and an outlet port. Mechanisms are provided for receiving a user flow waveform expressed in terms of predetermined flow rate as a function of time and in response moving the piston and configuring the four-way valve to provide fluid flow from the reservoir through the valve and into one of the opposite ends of the cylinder, and from the other one of the opposite ends of the cylinder through the valve to the outlet port in accordance with the user flow waveform. |
