Rotary expansible chamber devices – With changeable working chamber magnitude – Intermeshing rotary members
Patent
1995-09-29
1997-04-15
Freay, Charles G.
Rotary expansible chamber devices
With changeable working chamber magnitude
Intermeshing rotary members
F01C 2116
Patent
active
056203152
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a gear pump for feeding of fluids, in which the pump includes gears arranged axially parallel to each other and meshing in pairs within a housing having a peripheral wall. One gear is axially fixed to the housing while the other is movable in the axial direction.
Gear pumps of this type are employed for stationary as well as for mobil applications. The known advantages mainly consist in the fact that high and super high pressures may be achieved, thereby allowing for relatively exact volumetric metering.
It has become known in the relevant art to shift gears which are meshing with each other, in an axial direction relative to each other, in order to change the amount of pumped fluid during operation. This concept is disclosed in U.S. Pat. No. 5,184,947 wherein a gear which is axially non-shiftable is journalled in a housing. A second gear which meshes with the first gear, is supported by a slide block, which is shiftable relative to the axis of the first gear.
German Patent No. OS-41 21 074 A1 describes an external gear pump for a continuously variable flow of fluid. This patent discloses two gears which are shiftable relative to each other. The driven gear is journalled in a housing, whereas the idle gear may be shifted depending on the pressure differential of the fluid at the pump.
It is the disadvantage of all these known devices that the sealing of the pumping chamber is not satisfactory. The sealing devices are subject to very substantial pressures and therefore to a high wear which limits the lifetime of the gear pump.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a gear pump according to the above description which meets the main requirement of an easy and rapid change of the volume of pumped fluid during operation, while at the same time, subjecting the sealing devices to much less wear compared to known gear pumps, and thereby keeping the costs of manufacture relatively low.
The present invention, in one form, is a fluid gear pump or motor. The fluid gear pump or motor comprises a casing having a peripheral wall with the peripheral wall having an inner surface. A pair of gears, a fixed gear and a movable gear, are mounted inside of the casing. The fixed gear has two ends, a fixed end and a free end, with the fixed end being rotatably mounted in the casing. The movable gear, which has a first and second end, is axially parallel to, and meshes with the fixed gear.
Also within the casing are first and second end walls which rotatably receive the first and second ends of the movable gear. These two end walls are in slidable sealing contact with the interior surface of the peripheral wall of the casing. Aside from the movable gear, the two end walls are also bridged by a wall, which has an interior wall surface. The first and second walls and the bridging wall together form a carriage which is slidable within the casing. The interior wall surface together with the axially fixed gear and the axially movable gear form a first delivery gap and a second delivery gap which extend across part of the circumference of the axially fixed gear and the axially movable gear. Each delivery gap has an entry area provided with a low-pressure space having an inlet and an outlet area provided with a high pressure space having an outlet.
A third end wall, also within the casing rotatably receives the free end of the fixed gear. This third end wall bears under seal on the interior wall surface of the bridging wall.
BRIEF DESCRIPTION OF THE DRAWINGS
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:
FIG. 1 depicts a longitudinal sectional view of a gear pump comprising two gears;
FIGS. 2-5 are cross-sectional views in the planes A--A, B--B, C--C and in the offset plane D--D;
FIG.
REFERENCES:
patent: 2633806 (1953-04-01), Perkins
patent: 3588295 (1971-06-01), Burk
patent: 5184947 (1993-02-01), Coombe
Freay Charles G.
Hutter Sandra
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