Hydraulic gear pump with hydrostatic shaft bearing and isolated case drain and method of operating a hydraulic gear pump

A gear pump comprising:

• a pump ring gear;
• a pump shaft;
• a pump pinion mounted to the pump shaft and disposed within the pump ring gear, such that external teeth of the pump pinion engage with internal teeth of the pump ring gear, wherein the pump shaft is configured to rotate the pump pinion, thereby rotating the pump ring gear engaged therewith to displace fluid from an inlet chamber to an outlet chamber of the gear pump;
• a pump cover comprising one or more cross-holes and a pocket;
• a thrust plate interposed axially between the pump cover and the pump ring gear, wherein the thrust plate comprises a through-hole fluidly-coupled to the outlet chamber, and wherein the pump cover comprises a blind hole receiving fluid from the through-hole of the thrust plate, and wherein a cross-hole of the one or more cross-holes of the pump cover is fluidly-coupled to the blind hole, wherein the one or more cross-holes comprise:
• a first cross-hole fluidly-coupled to the blind hole,
• a second cross-hole fluidly-coupled to the first cross-hole, and
• a third cross-hole fluidly coupling the second cross-hole to the pocket;
• and
• a bushing disposed about the pump shaft, wherein an exterior surface of the bushing interfaces with an interior surface of the pump cover, wherein the pocket is formed about a portion of the bushing, wherein the one or more cross-holes of the pump cover fluidly couple the outlet chamber to the pocket, thereby causing fluid in the pocket to apply a supporting force to the pump shaft.

A method comprising:

• rotating a pump shaft of a gear pump, wherein a pump pinion is mounted to the pump shaft and disposed within a pump ring gear of the gear pump, such that external teeth of the pump pinion engage with internal teeth of the pump ring gear, and wherein rotating the pump shaft rotates the pump pinion, thereby rotating the pump ring gear engaged therewith to displace fluid from an inlet chamber to an outlet chamber of the gear pump, wherein the gear pump further comprises an end cover having a drain chamber formed therein;
• providing fluid from the outlet chamber to a pocket formed about a portion of a bushing disposed about the pump shaft, wherein the bushing has a cross-hole fluidly-coupled to the pocket;
• communicating fluid from the pocket via the cross-hole of the bushing to within the bushing at an interface between an exterior surface of the pump shaft and an interior surface of the bushing;
• applying a supporting force to the pump shaft by fluid communicated from the pocket via the cross-hole;
• communicating fluid that has applied the supporting force to the drain chamber formed in the end cover;
• and
• draining fluid from the drain chamber of the end cover to a drain port in the end cover, wherein the drain port is isolated from the inlet chamber.