N2 Fitting and Machining Theory|Hands-On! 111


the camshaſt. Te other gear is an idler gear, also called the driven gear. Te gear teeth run very close to the inner walls of the housing. Clearance between the gear faces, the housing and the cover is minimal.


oil is carried around casing


pumping cavities


casing driven


outlet port Figure 9.5 A gear pump Operation of gear pump


• When the shaſt drives the drive gear, it drives the driven gear. Small pockets of oil are trapped between the gear teeth and the pump housing (in the pumping cavities).


• Te rotating spaces between the teeth and the housing carry the oil towards the outlet port. Te meshing teeth in the middle of the pump act as a seal so that oil cannot pass through the middle.


• At the same time a partial vacuum is created over the inlet port and oil is drawn from the sump. Oil cannot return between the gear teeth and pressure built up, forcing the oil out through the outlet port, from where it is fed to the oil channels.


Helical screw-type pumps stuffing box


Screw pumps embody two or more firm screws from rotors secured on parallel axes and intermeshing. One screw may be power driven and the others idle, or all may be driven by timing gears with small positive clearances. Screw pumps are regularly used to transfer oil or liquid from one point to another. Tis type of pump is simple in design, but able to function at high speeds.


delivery port grooves Figure 9.7 A screw pump


central screw inlet port


rotor oil flow driver


oil is forced out of pressure port


casing/ housing


drive gear from exit port Figure 9.6 A gear pump with cover plate removed inlet port


partial vacuum pumping cavities


driven gear


to inlet port drive shaft


side screws


Te side screws are driven by the central screw and the oil or fluid is sucked in through the inlet port where it travels through the grooves to be pumped out through the delivery port.


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