Hydristor control means

Details Hydristor control means Hydristor control means

2001-02-08

2003-03-04

Vrablik, John J. (Department: 3748)

Rotary expansible chamber devices

With changeable working chamber magnitude

Cylinder or cylinder portion moved linearly and radially

C418S156000, C418S173000, C418S268000

Reexamination Certificate

active

06527525

ABSTRACT:

BACKGROUND OF INVENTION
This application incorporates by reference related patents U.S. Pat. Nos. 6,022,201; 3,153,984; and 2,589,449, and, GB Patent No. 1,000,591 each in their entirety.
Early devices to vary the displacement of vane pumps involved the deliberate offset of the rotational center of the vane rotor with respect to the geometrical center of the circular outer case. The amount of offset would then control the swept volume of the pump and thereby provide a desired volumetric output for each rotation of the rotor. Several problems with this design limited its use.
First, the pressure unbalance caused by the hydraulic-based force on the radial cross-section of the rotor and vanes at the axis viewed from the radial perspective severely limited the power capability and power density of these pumps and resulted in very heavy, inefficient, and cumbersome devices. Second, the centrifugal force of each vane during high-speed rotation caused severe wear of the vane outer edge and the inner surface of the outer containment housing.
Later fixed displacement design were conceived around the concept of pressure balance in which two geometrically opposed high pressure chambers would cause a cancellation of radial load due to equal and opposed cross-section pressure areas and opposite vector direction which resulted in a zero net force radially on the shaft bearing. The design is referred to as the pressure balanced vane pump or motor. Typical efficiency of these devices is 70 to 85% under rated loading and speed. Still later improvements include changing the chamber shape of pressure balanced vane style devices and involved the use of several types of adjustable inner surfaces of the outer housing for guiding and radially adjusting the vanes as they rotate. One improvement is a continuous band, which is flexible and subject to radial deformation so as to cause displacement control of the vanes. However, these flexible bands did not rotate.
SUMMARY OF INVENTION
The basic embodiment of this invention is a rotor with spring-biased, radially extensible vanes that are constrained in their outward radial movement, away from the rotor center of rotation, by the inner circumferential area of a continuous flexible band that has the same axial width as the rotor and vanes. It is especially important to notice in the basic embodiment that the flexible band is designed to rotate with the vanes and rotor. The spring loading of the vanes is by conventional means as is the practice with existing vane pumps and motors; namely that the spring is compressed between the rotor itself and the radially inward edge of the vane so as to drive every vane radially out from the rotor body against the inner area of the flexible band. The spring preload causes the vanes to contact the flexible band inside surface at slow speeds that include zero. This is especially important if this embodiment is to be used as a variable or fixed displacement hydraulic motor because hydraulic sealing of the vane's outer edge is assured at zero speed. Since the flexible band is totally free to rotate with the vanes and rotor, a very big source of friction, wear, and inefficiency is eliminated due to the teaching of this invention. The well known limitation of the prior art; namely the sliding edge friction associated with the combined outward radial force of the vanes is totally eliminated since there is substantially no relative motion between outside edges of the vanes and the interior constraining surface of the flexible containment band. Further, as the rotor's speed increases, the speed-squared radially outward combined force of the set of vanes is fully contained by the continuity of the flexible band simulating a pressure-vessel type of containment, as if the flexible band were a cross section of a pressure containment cylinder, and the individual radial outward force of the vanes were the pictorial radially outward arrows that are used in drawings to depict the action of the force which is contained. Since the action of the flexible band is to fully contain these combined radial forces of the vanes, there is absolutely no increase of frictional forces due to increasing radial vane force, and this invention solves a very severe limitation of the prior art in that the rotating speed of the fixed devices built according to the prior art is limited to about 4,000 revolutions per minute, while the upper speed limit of the subject invention is substantially higher, say to the range of 30,000 revolutions per minute, governed largely by the design strength and durability of the flexible band. In fact, testing showed that the efficiency of this invention utilizing the rotating components of a commercially available pump having an advertised efficiency of 88% resulted in efficiency measurements of 93.5 to 94.1% when used in combination with the rotating flexible band. The greater efficiency of the instant invention over the prior art will result in much smaller variable pumps and motors in severe applications such as spacecraft. The flexible band design and construction can cover a wide range of variables, from a single circumferentially continuous flexible band to concentric nesting of any practical number of individual circumferentially continuous flexible bands. The smallest circumference band is concentrically nested within a slightly larger second band and the second band is concentrically nested within a still larger inside circumference of a third and yet larger band, and so on, up to the largest outside band whose exterior surface is the exterior surface of the nest and the smallest inner band has its interior surface in contact with the exterior edge of each of the vanes. The construction is similar to the case of a stranded cable of a specific diameter having a much greater strength than a solid rod of the same diameter. Also, the stranded cable is more flexible without failure than the solid rod. The individual clearances between each of the bands in such a collective nest is chosen to allow slippage and lubrication from one band to the next. This nested band-to-band clearance results in a greater efficiency at very high operating speed by allowing a nested concentric set of bands to slip in speed from one concentric member to the next, with the inner band rotating at substantially the same speed as the rotor and the outer bands rotating increasingly slower. The material used to make the endless flexible band can be any appropriate metal, but other appropriate materials, such as plastic, fiberglass, carbon fiber, or KEVLAR®, can be used. This construction material range applies whether a single thickness endless band is constructed, or a concentric nesting of two or more bands is used to make a concentric nesting of a number of bands. The description thus far is of a flexible circular and continuous containment band with the band confining all the radial centrifugal forces of vanes and eliminating contemporary problems such as sliding vane friction, the speed-squared frictional dependence, and the rotor speed limitation. The flexible band construction will also allow for the shape manipulation of the circumference of the band so as to permit varying the swept chamber volume as the rotor turns.
Reshaping of the flexible band is necessary to control the swept chamber volume of the pump as the rotor is turning and comprises an array of radially moveable pistons which are at 0°, 90°, 180°, and 270° around a full circle, i.e., at 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock of a clock face. Each of the pistons has an appropriate curvature to contact the flexible band external surface in the positions cited. If the 12 o'clock and 6 o'clock pistons are caused to move inward, the fixed circumference of the flexible band causes the 3 o'clock and 9 o'clock pistons to move outward by an equal amount. The inward or outward movement of the pistons may be driven by individual controlled hydraulic pressure, or the movement can be caused by mechanical means such as a gear and ra

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