Page 280 - Design for Six Sigma a Roadmap for Product Development
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250   Chapter Eight


                Body
                          #8 Seal
                Ring bore
                Spring                                    pressure
                                                           Control
                Rotor                                     port
                Vane



           #4 Seal






              #6 Seal



                                                          #7 Seal

           Figure 8.8 Pump top view.




           expanding and collapsing. Expansion is needed at the pump inlet to
           draw fluid into the pump, while collapsing will occur at the outlet
           to force fluid into the system under pressure. The variable-vane pump
           is a rotary-type pump with variable capacity. The output will vary
           according to the requirements of the transmission to conserve power.
           The advantages are many. Chief among them are the ability to deliver
           a large capacity when the demand is high, especially at low speeds,
           and the minimal effort needed to drive at high speeds.
             The mechanism of operation is as follows. When the priming spring
           moves the slide to the fully extended position, the slide and rotor are
           eccentric. As the rotor and vanes rotate within the slide, the expand-
           ing and contracting areas form suction (expanding) and pressure
           (collapsing) chambers. The hydraulic medium trapped between the
           vanes at the suction side is moved to the pressure side. A large quan-
           tity of fluid is moved from the pressure side back to the suction side as
           the slide moves toward the center (Fig. 8.6). A neutral condition (with
           no volume change) is created when concentricity is attained between
           the slide and rotor.
             The function of the priming spring is to keep the slide in the fully
           expanded position such that full output can be commanded when the
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