Fluid pumping apparatus

Details Fluid pumping apparatus Fluid pumping apparatus

2000-06-13

2001-07-03

Yuen, Henry C. (Department: 3747)

Pumps

Three or more cylinders arranged in parallel, radial, or...

C417S539000

Reexamination Certificate

active

06254357

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to an axial piston fluid pumping apparatus, and more particularly to such an apparatus which uses a wobble piston, the stroke for which is provided by a nutating plate.
Two known types of compressors are the wobble piston type and the swashplate type. The wobble piston type is exemplified by U.S. Pat. No. 3,961,868 issued Jun. 8, 1976, to Droege, Sr., et al. for “Air Compressor”. Such a compressor uses a piston whose head has a peripheral seal that seals with a cylinder bore. The piston rod is mounted radially on a crankshaft. The piston includes no joints or swivels. As a result, the piston head is forced to “wobble” in two dimensions within the cylinder bore as it is driven by the crankshaft.
The swashplate type compressor uses a plurality of axial cylinders arranged in a circle about a drive shaft. A swashplate is inclined relative to the shaft axis such that the plate gyrates as the drive shaft is rotated. Pistons are mounted in each of the cylinders. The ends of the piston rods are connected to elements that slide over the surface of the swashplate as the swashplate rotates. The result is that the centerline of the piston head is moved solely in an axial direction as the pistons are stroked within the cylinders. An example of such an axial piston swashplate compressor is found in U.S. Pat. No. 5,362,208 issued Nov. 8, 1994 to Inagaki, et al. for “Swashplate Type Compressor”. Another example is U.S. Pat. No. 4,776,257 issued Oct. 11, 1988, to Hansen for “Axial Pump Engine”. In the Hansen patent, the centerline of the piston heads are inclined relative to the centerline of the cylinder bore, but the piston heads are moved only along the piston head centerline in one direction.
The present invention combines the wobble pistons normally used in radial piston pumps with a nutating plate rather than the swashplate normally used in axial piston pumps. The result is a simple and effective fluid pumping apparatus.
SUMMARY OF THE INVENTION
In accordance with the invention, a fluid pumping apparatus includes a drive shaft and a cylinder having a bore. Fluid inlet and outlet valves communicate with the cylinder bore. A bearing is mounted on the shaft with the centerline of the bearing at an angle to the shaft axis. An arm is mounted on the bearing. A wobble piston is rigidly attached to the arm and is disposed in the cylinder bore. As the drive shaft rotates, the centerline of the bearing will precess about the shaft axis, and the arm will be moved, thereby causing the wobble piston to move in three dimensions within the cylinder bore.
Further in accordance with the invention, the bearing is mounted on a hub that is secured to the shaft with the axis of the hub at an acute angle to the shaft axis.
Preferably, two or more cylinders are arranged symmetrically about the shaft axis with a wobble piston in each cylinder bore.
The centerline of the cylinder bore may be parallel with the shaft axis, or may be parallel with the bearing centerline, or may be formed as an arc of a circle whose center is at the intersection of the bearing centerline and the shaft axis.
In another preferred embodiment, the drive shaft is a through-shaft of an electric motor. Two or more cylinders are spaced about each end of the through-shaft. A nutating plate containing two or more arms is mounted about a bearing on each end of the through-shaft. Wobble pistons are rigidly attached to each arm and disposed in a respective cylinder. Preferably, the cylinder bores on one end of the through-shaft are axially aligned with the cylinder bores on the other end, and the pistons in aligned cylinder bores move opposite to each other.
The inlet and outlet valves may be formed in separate valve plates associated with each cylinder. Alternately, the inlet valve may be formed in the piston which may be provided with a central passage leading to the exterior. A filter may be inserted in the passage to prevent contamination of the cylinder.
In a further embodiment, plural cylinders are formed in a common cylinder sleeve with a single valve plate containing inlet and outlet valves for each of the cylinders. The valve plate and cylinder sleeve stacks with a head member that contains inlet and exhaust chambers that are shared by all cylinders. The stacked cylinder sleeve, valve plate and head may be connected to a motor housing at one end and to a fan housing on the other end, with a motor shaft extending through the stack to mount the hub that supports a carrier for the wobble pistons and which also mounts a fan.
The plurality of cylinder bores may be of identical size or the bores may be of different diameters arranged either at the same distance or different distances from the shaft axis.
The face of the valve plate that confronts the piston head is preferably inclined to be nearly parallel with the surface of the piston head when the piston is at top dead center.
It is a principal object of the invention to provide a simplified axial piston pumping apparatus using wobble pistons.
It is another object of the invention to provide an axial piston pump which does not require the use of sliding elements requiring continuous lubrication.
The foregoing and other objects and advantages of the invention will be apparent from the following detailed description. In the description, reference is made to the drawings which illustrate preferred embodiments of the invention.


REFERENCES:
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patent: 4776257 (1988-10-01), Hansen
patent: 4801249 (1989-01-01), Kakizawa
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patent: 5006047 (1991-04-01), O'Connell
patent: 5070765 (1991-12-01), Parsons
patent: 5147190 (1992-09-01), Hovarter
patent: 5167181 (1992-12-01), Lee
patent: 5362208 (1994-11-01), Inagaki et al.
patent: 5593291 (1997-01-01), Lynn
patent: 4411383A1 (1994-11-01), None

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