Centrifugal pump having means for counterbalancing unbalanced fluid pressure radial forces on rotor

Claim 1

A pump apparatus comprising: a pump means including a pump housing, a shaft and a rotary pumping member rotatably disposed in said pump housing and mounted on said shaft for rotation therewith, said pump housing being formed with circumferential spaced suction and discharge ports; driving means drivingly connected to said shaft to rotate said rotary pumping member for pumping a fluid; bearing means rotatably supporting said shaft adjacent to said rotary pumping member; said rotary pumping member having an outer peripheral section formed with at least one circumferential row of vane grooves, said pump housing cooperating with said section to define therebetween a fluid passage circumferentially extending between and communicating with said suction and discharge ports with a seal between said housing and section circumferentially between the ends of said passage; the rotation of said rotary pumping member producing in said fluid passage a circumferentially unbalanced fluid pressure which increases along said fluid passage from said suction port toward said discharge port, the circumferentially unbalanced fluid pressure forming circumferentially unbalanced radially inward forces the resultant force of which is applied through said rotary pumping member to a first side of the peripheral surface of said shaft; counterbalancing means including a pressure introducing opening formed in said bearing means and having an inner end faced to a second side of the peripheral surface of said shaft substantially diametrically opposite to said first side of said shaft; said counterbalancing means further including means establishing a fluid-flow communication between said discharge port and said pressure introducing opening whereby the discharge pressure of said pump means is applied to said second side of said shaft to form a counterbalancing force.