WASHER 9B6526 - Caterpillar

Illustration 1 g01062104
The gear pump consists of the following items that are shown in illustration 1: (1) seal retainers (2) seals (3) seal backups (4) isolation plates (5) spacers (6) drive gear (7) idler gear (8) housing (9) mounting flange (10) flange sealBearings are mounted in the housing and the mounting flange on the sides of the gears in order to support the gear shafts during rotation.Gear pumps are positive displacement pumps. They deliver the same amount of oil for each revolution of the input shaft. The pump output is controlled by changing the speed of rotation. The maximum operating pressure for gear pumps is limited to 27600 kPa (4003 psi). This pressure limitation is due to the hydraulic imbalance that is inherent in the gear pump design. The hydraulic imbalance produces a side load on the shafts that is resisted by the bearings and the gear teeth to housing contact. The gear pump maintains a volumetric efficiency above 90% when pressure is kept within the designed operating pressure range.Gear Pump Flow
Illustration 2 g01062106
The output flow of the gear pump is determined by the tooth depth and the gear width. Most manufacturer gear pumps standardized on a tooth depth and profile that is determined by the centerline distance (1.6", 2.0", 2.5", 3.0", etc.) between gear shafts. With standardized tooth depths and profiles, the flow differences within each centerline classification of pump is determined by the tooth width.As the pump rotates, the oil is carried between the gear teeth and the housing from the inlet side to the outlet side of the pump. The direction of rotation of the drive gear shaft is determined by the location of the inlet and outlet ports. The direction of rotation of the drive gear will be to move the oil around the outside of the gears from the inlet port to the outlet port. This is true on both gear pumps and gear motors. On most gear pumps, the inlet port is larger in diameter than the outlet port. On bidirectional pumps and motors, the inlet port and the outlet port will be the same size.Gear Pump Forces
Illustration 3 g01080795
The outlet flow from a gear pump is created by pushing the oil out of the gear teeth as they come into mesh on the outlet side. The resistance to oil flow creates the outlet pressure. The imbalance of the gear pump is due to outlet port pressure being higher than inlet port pressure. The higher pressure oil will push the gears toward the inlet port side of the housing. The shaft bearings carry the majority of the side load in order to prevent excessive wear between the tooth tips and the housing. On the higher pressure pumps, the gear shafts are slightly tapered from the outboard end of the bearings to the gear. This design feature allows full contact between the shaft and bearing as the shaft bends slightly under the pressure.The pressurized oil is also directed between the sealed area of