Rotary vane pump with pressure biased flow directing end plate

Claim 1

In a rotary vane pump including a housing (1) enclosing a suction chamber (15, 15A) and an outlet chamber (20) from which fluid is discharged under a pump pressure, a cam ring (7) mounted in the housing and having an outer peripheral portion, a rotor (6) mounted within the housing and formed with slots extending radially outward from inner ends relative to a rotor axis, a plurality of vanes (8) slidable within said slots and engageable with the cam ring to form variable volume vane chambers, and flow control surface means (4, 10) fixed to the housing on opposite axial sides of the rotor for conducting fluid from the suction chamber to the vane chambers and from the vane chambers to the outlet chamber, including a flow directing plate (10) having an upstream side confronting the rotor, a downstream side confronting the outlet chamber, circumferentially spaced suction passages (12, 12A) in fluid communication with the suction chamber, and outlet passages (11, 11A) in fluid communication with the outlet chamber, the improvement comprising seal means (21) on the flow directing plate limiting exposure of the downstream side thereof to the pump pressure within a predetermined pressure area (22) thereon having a radially outer chordal portion bordering the peripheral portion of the cam ring in spaced relation to the suction passages, and a radially inner constricted portion spaced radially inwardly of said suction passages and the inner ends of those of the vane slots aligned with the suction passages during rotation of the rotor about the rotor axis for exerting pressure forces on the downstream side of the flow directing plate unbalanced on the upstream side within a radially inner zone through which the rotor axis extends, whereby clearances between the plate and the rotor are reduced by bending of the plate with maximum flexure within said radially inner zone.