Prior art rotary positive displacement motor and pump devices have directed themselves to improving mechanical, hydraulic, and volumetric efficiencies, increasing longevity, making manufacturing easier, improving the size-to-delivery and weight-to-delivery ratios, and to including the ability to run dry without damage. Many conventional positive-displacement rotary pumps are based on a chamber with expanding and contracting volumes that provide a pumping action. Such devices usually depend on a vane, lobe or piston that is mechanically swept by a cam, crank, lever, or gear.
Piston pumps include connecting rods and crankshaft or a swash plate, and are heavy apparatus that require lubrication. This makes the efficiency of the apparatus low, because a heavy weight needs to be repeatedly started and stopped. In addition, the friction of the seals (piston rings, in this case) robs power, and requires lubrication. Vane pumps also have metal parts that are repeatedly started and stopped. These parts have sliding friction as well as momentum, and have a pressure-loaded mechanical or hydraulic seal. In addition, these pumps require complex porting for hydraulic loading of the seals. Gear or lobe pumps are better, as the abutment has a rotary motion. However, precision gearing is required, and there is significant friction as well. Screw type pumps suffer from the same difficulties, and are even harder to manufacture. Nutating and gyrotor pumps require complex gearing or other assemblies to give them the special motion that characterizes them. Finally, flexible impeller pumps, although they are sold in the hundreds of thousands, have serious friction losses, and they cannot be run dry without damaging the impeller.
The closest related art found was C. F. Davis, Jan. 1 1946, U.S. Pat. No. 2,392,029, which discloses a rotor with elliptical groove and a land ring and two disk-like cylindrical abutments. However, his device has a number of differences from the present invention.
First, the ports are small and of the wrong shape, so that the device will not work well as a practical pump. Second, the Davis et al invention provides only a line contact seal between the land ring and the groove in the rotor. Third, although it is asserted that the Davis et al invention will provide non-pulsating flow, it will not do so. This is because the two sides of the pump are in phase, and so their large discharges and small discharges coincide. Fourth, in the Davis patent the ports are described as being rotary valved. Thus, the ports are completely closed during part of the cycle, so the fluid is forced to stop and start, causing large hydraulic losses.
What is needed is a rotary pump that has little or no frictional or other energy losses, has little or no mechanical wear and that can be utilized in many different applications.
An object of the present invention is to provide a rotary pump with at least two chambers and a near frictionless abutment balanced between the chambers that does not present a load that rubs on the walls of the chambers.
A further object of the present invention is to provide a rotary pump with high mechanical and volumetric efficiencies.
Another object of the present invention is to provide a near frictionless rotary pump subject to minimum wear.
A further object of the present invention is to provide a reversible rotary, high-speed, positive displacement pump and motor with very little friction that can deliver relatively high flow rates at moderate to high pressures with good overall efficiency while also being able to run dry without damage.
A still further object of the present invention is to provide rotary motors and pumps that can easily be multiple staged in a single unit and provide non-pulsating efficient liquid flow.
Another object of the present invention is to provide a heat engine using Brayton, or other thermodynamic cycles, that is easy to manufacture, simple, durable, and low-cost.
Briefly, a rotary pump embodiment of the present invention comprises a complementary pair of expansible chambers (or lobes) radially divided by a land ring and longitudinally segmented by an abutment that seals the chambers against reverse leakage. The pair of expansible chambers is formed from a single groove in the end face of a rotor. The land ring divides the pair of chambers into complementary expansible chambers, is concentric on the end face of a stator, and extends fully into the groove. The inner and outer land rings of the groove have a constant radial separation dimension, and the abutment is urged to follow the eccentricity of the groove by positioning of the abutment in a slot in the land ring. The abutment is slightly smaller in radial dimension than the groove and is floated to avoid hard contact with the inner and outer land rings of the groove by a balancing of the Bernoulli effects that develop between the abutment and both the inner and outer land rings of the groove. Preferably, the abutment is approximately spherical and can roll in the slot radially inward and outward.
An advantage of the present invention is that a rotary pump is provided that is nearly frictionless.
Another advantage of the present invention is that a rotary pump is provided that exhibits very high mechanical and volumetric efficiencies.
A further advantage of the present invention is that it provides rotary motors and pumps which can easily be arranged to form multiple phased, parallel and serial stages in a single assembly, to thereby provide smoothed, high volume, and high pressure liquid flow.
Another advantage of the present invention is that a heat engine is provided using Brayton, and other thermodynamic cycles, that is easy to manufacture, simple, durable, and low-cost.
A still further advantage of the present invention is that a tolerance pump or motor is provided with no contacting surfaces. As such, the mechanical efficiency is essentially a function of the viscosity of the pumped liquid or gas.
Another advantage of the present invention is that embodiments can be made with only three main parts: the rotor, the stator, and the abutment. Standard milling techniques can be used to fabricate such components by casting, injection molding, sintering, or other high-volume, low cost manufacturing processes. Still further objects and advantages will become apparent from the following description and accompanying drawings.