US Patent #  6,527,525

Hydristor Control Means

( March 4, 2003 )


A variable pump or motor is providing including a housing with inlet and outlet ports and a vaned rotor. Spool ends are provided at either end of the rotor thereby enhancing the effective sealing of the pump and its overall efficiency. Piston actuators are also described. A sealing means is provided in conjunction with the use of a flexible belt wherein volumetric efficiency is substantially improved.

Current U.S. Class:  418/31 ; 418/156; 418/173; 418/268
Current International Class:  F04C 5/00 (20060101); F04C 2/00 (20060101); F04C 2/344 (20060101); F01C 001/344 (); F01C 021/14 ()
Field of Search:  418/24-26,31,82,153,156,173,268
References Cited: U.S. Patent Documents --- 2016315  October 1935  Calzoni // 2564237  August 1951  Segsworth // 2589449  March 1952  Stageberg // 2641195  June 1953  Ferris // 2804016  August 1957  Moore // 3065706  November 1962  Shoosmith // 3130681  April 1964  Fetherston // 3153984  October 1964  Fikse // 3187676  June 1965  Hartmann // 3187677  June 1965  Stieber //  3361076  January 1968  Davis // 3627456  December 1971  Gerlach // 3642387  February 1972  Sundberg // 3672796  June 1972  Mitchell // 3807912  April 1974  Keller // 3808814  May 1974  Macy, II // 3813194  May 1974  Scholz // 4348159  September 1982  Acheson // 5243822  September 1993  Vismara // 5961307  October 1999  Key et al. // 6022201  February 2000  Kasmer

Foreign Patent Documents:  225748  Aug., 1985  DE // 1000591  Aug., 1965  GB //  58-152103  Sep., 1983  JP



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.


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.RTM., 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,,, and 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 rack, or radially disposed screw drives to each piston. Another type of piston control means would be the joining of an analog type electric servo motor drive to a ball screw mechanism with an encoder position feedback; which arrangement would easily lend itself to digital control. Whatever the method of controlling the movement of the piston, the final purpose is to controllably elliptasize the flexible band from an axial perspective so as to cause the controlled and varying degrees of swept volume of fluid flow per revolution of the vane pump or motor. In the basic embodiment of this invention, opposing pairs of pistons move simultaneously towards or away from each other, while the remaining set of opposed pistons behave in simultaneous opposition to the action of the first pair. This behavior results in varying degrees of elliptic reshaping of the flexible band viewed from the axial perspective of the vane rotor. A novel and significant aspect of this device is the freedom of movement of the flexible band, which is impossible in the prior art. This includes a special manipulation of the pistons and band that allow the combination of this invention to simultaneously manipulate two common fluids, but hydraulically separate, outputs of this device as pump or motor. The variable pressure balanced design has two equal and identical pressure fluid outputs which will be merged so as to drive a hydraulic motor to form what is called a hydrostatic transmission. This is a second embodiment of the present invention. In addition, a second variable vane device of the proposed design may act as a motor in a conventional type of hydrostatic transmission with all of the current results, but with much greater efficiency and range. Another embodiment of the invention is a special piston manipulation that causes this invention to act like the early variable non-pressure balanced construction pumps with a single input and output. In the present invention, there is shown two separate hydraulic circuits with separate inputs and outputs where a single pump of the proposed design is separately connected to two fixed displacements hydraulic motors. Motor Number 1 will connect in closed hydrostatic loop with the first and second quadrant ports of the pump, while motor Number 2 will connect in closed hydrostatic loop to the third and forth quadrants with no interconnection. The plumbing of the motor circuits would be such that both motors would have the correct shaft rotation direction for a hypothetical example, say forward. If the 12 o'clock and 6 o'clock pistons were directed inward, the 3 o'clock and 9 o'clock pistons would be forced outward with equal hydraulic flow to both motors occurring, causing the motors to turn at the same controlled speed in the forward direction. Now assume that the original circular flexible band shape is modified such that the 3 o'clock piston is moved inward and the 9 o'clock piston is moved outward, while holding the 12 o'clock and 6 o'clock pistons at neutral, the band remaining circular in shape. A first motor connected to the first and second quadrants will reverse shaft directions, with a speed equal to that of a second motor whose direction is still forward. If the 3 o'clock and 9 o'clock piston were both moved the other way, the second motor would instead reverse rotation in relation to the first motor. Combine this action with the original action of the basic embodiment as described, and one motor can be caused to rotate deliberately and controllably faster than the other motor, such as is the case for an axle set of a vehicle going around a turn. Another embodiment of the invention has two separate piston control methods which can be algebraically mixed to effect differential control means of axle rotation for negotiating a turning radius. Another embodiment comprises a fixed displacement motor of the prior art constructed in the manner of this invention, with the pistons permanently fixed. This arrangement will be much more efficient than conventional hydraulic motors. A still further embodiment is the case of fixed displacement motors and pumps which can greatly improve the efficiency of existing vane pump and motors; namely that one or several flexible bands-of the proposed invention construction can be closely fitted to be movable just inside the fixed elliptic or circular cam ring surface of conventional units, with a small clearance between the flexible ring exterior and the fixed cam ring interior, said clearance supporting an oil film which has minimal friction, while the vane outer edges are now supported by the innermost flexible band's inner surface. This construction provides some of the advantages of the subject invention, such as containment of vane centripetal force, and the replacement of vane-to-fixed cam ring friction with broad oil film friction that is much less, and not speed squared dependent. The primary invention configured as a fixed unit will still be most efficient due to the open chamber between each fixed piston pair. A smaller total oil film in this case will give the least loss. A significant advantage of the just described construction is the ability to fix existing design, or even retrofit field product without any mechanical change required. Existing vane units could compete with fixed piston pumps and motors in terms of efficiency, but would be less efficient than the basic embodiment. This is a fifth embodiment of the invention.


FIG. 1 is an isometric view of the invention with a partial frontal cutaway to expose details of construction.

FIG. 2 is an axial view of plane 2--2 of FIG. 1 that shows piston, flexible band, rotor, vanes, and kidney ports.

FIG. 3 shows the front plate with kidney ports, with the first quadrant cutaway as in FIG. 1.

FIG. 4 depicts control pressure being applied to the 12 o'clock and 6 o'clock pistons, causing an elliptical reshaping of the flexible band.

FIG. 5 depicts control pressure being applied to the opposite set of pistons with opposite reshaping behavior.

FIG. 6 shows the differential behavior of the invention caused by moving the 3 o'clock and 9 o'clock pistons in the same direction.

FIG. 7 shows the differential-sum behavior of the invention when more control pressure flow volume is directed to the 3 o'clock control port than is directed to the 9 o'clock port.

FIG. 8 shows a simple schematic connection of the basic embodiment of the invention connected in a closed hydraulic loop together with a conventional hydraulic motor.

FIG. 9 shows a schematic connection of a variable pump connected to two fixed displacement hydraulic motors which drive vehicular wheels.

FIG. 10 shows the addition of a flexible band to a conventional fixed displacement vane unit pump or motor with a fixed internal cam ring.

FIG. 11 is a view showing the multilayer flexible band nests and rack and pinion piston drive.

FIGS. 12a-12c are views showing a crankshaft piston drive utilizing a right angle slot.

FIG. 13 shows a lever control to effect movement of a piston.

FIG. 14 depicts the control forces acting on a piston.

FIG. 15 shows a piston actuator containing a control screw.

FIG. 16 depicts a closed-loop servo system functioning as a piston actuator.

FIG. 17 shows a piston actuator containing an externally controlled cam and a cam roller.

FIG. 18 shows a first control linkage.

FIG. 19 shows a second control linkage.

FIG. 20 shows a third control linkage.

FIG. 21 shows a fourth control linkage.

FIGS. 22a-22c show a variable stroke crankshaft actuator.

FIGS. 23a and 23b show a spool rotor having spool ends.

FIGS. 24a and 24b depict a sealing mechanism including a pair of flaps.

FIGS. 25a-25c depict a sealing mechanism including an insert housed within a groove on an end plate.


The isometric view shown in FIG. 1 has a frontal first quadrant cutaway that exposes some very important features of the invention. The rear end plate 1 is shown with the first quadrant kidney port 16 exposed. The front end plate 2 is partially cutaway with the kidney ports 17, 18, and 19 respectively in the second, third and fourth quadrants showing. The rear end plate 1 has like kidney ports 20, 21, and 22 in axial alignment with ports 17, 18, and 19, but those ports in plate 1 are out of view in this drawing. This view shows like kidney ports front and back. However, it is only necessary to have one port per quadrant chamber to allow for fluid flow into and out of the chamber. Either the front or rear ports can be utilized, or both can be used to increase the flow capacity. Also, referring to FIG. 4, any other means of porting which allows fluids to flow into or out of the volume 33, 34, 35, or 36 when they rotate in alignment with "quadrants one, two, three, or four" may be used. Front kidney port 23 is in the cutaway portion of end plate 2, and is in axial alignment with port 16. Piston 12 is exposed and is itself cut away at an angle to expose the high pressure fluid film 13 which exists between the curved inner surface of the piston, and the outer circumferential area of the flexible band nest 14. The piston interface shape as shown is curved; however, any surface shape that supports the fluid film 13 can be used. Each of the four pistons has a fluid film 13. Several vanes 24 are exposed by the cutaways. The outer casting 25 has four piston guides and four control ports 26. The ports 26 direct the inlet and exhaust of fluid control pressure to the four pistons to effect reshaping of flexible band 14. The invention is totally symmetric in hydraulic function and can function interchangeably as a hydraulic motor. The front end plate 2 has a hole 27 in it to permit the insertion of a drive shaft that will couple to the rotor 15 by means of the internal splines 28. The drive shaft is not shown so as to minimize the complexity of the figure. Seals and bearings of conventional design are also left out for the same reason. The shaft requires both a seal and bearing in plates 1 and 2 to facilitate the rotation of the rotor 15, the vanes 24. The four holes 29 in each of plates 1 and 2 would allow for four bolts which would tightly hold both of the end plates against the outer casting 25; however, any appropriate number of bolts may be used, and any other means of construction which hydraulically contains the rotor 15, vanes 24, band 14, and shape control means such as the pistons 12, 3, 6, and 9 may also be used.

FIG. 2 shows an axial end view of the invention with the end plates removed, and with dotted outlines of end plate 2 with ports 17, 18, 19, and 23 outlined. The four control pistons numbered 12, 3, 6, and 9 are now shown. Shaded areas 31 are filled or exhausted by the control ports 26 to allow control fluid into and out of the chamber 31 behind the four pistons 12, 3, 6 and 9. As shown in FIG. 11, the flexible band 14 had three concentric members 52, 53, and 54. These bands are preferably of stainless steel, each having a thickness in the order of 0.015 inches. The actual number and thickness of bands to be utilized will be determined by the design requirements. Also, as shown in FIG. 11, each vane 24 has compression springs 32 mounted in rotor 15 that force the vane out from the center of the rotor 15 into contact with the inner surface of the band 14. Three springs and bores are provided for mating with three pins 51 on each vane with the pins being equally spaced along the base of the vane. Such band and spring combinations are found in U.S. Pat. No. 4,325,215 which is incorporated by reference herein. This action assures that the vanes will seal fluid pressure at zero speed. It is a very important feature of this invention that the rotor 15, all the vanes 24, and the flexible band 14 will rotate as a group. At very slow speeds, the band will slip very slightly with regards to the vane speed, much like a squirrel cage a.c. induction motor rotor will slip behind the field rotation speed. This slow drift is the result of fluid shear drag caused by the four fluid films 13, which act so as to slow down the flexible band 14 speed. This drag force is counteracted by the combined line contact friction of, in this example, nine vanes. The vane friction is much greater than the fluid film friction, and the vane friction increases as the speed squared. Thus, as the speed of rotation increases, the flexible band will begin to rotate as substantially the same speed as the rotor. Since the vane and band speed never quite equalize, the wear on the inner surface of the flexible band is evenly distributed over the entire inner band surface, and the maximum wear life is achieved. Since the centrifugal, speed squared forces are totally contained by the flexible band, the wear and failure mechanism of high-speed vane type pumps and motors is eliminated. The added friction of four fluid contact areas 13 is small compared to the combined vane friction, and does not increase significantly with higher speed. The result is a device which is much more efficient than any conventional design and which will operate efficiently at much higher speeds. These factors also allow for quieter operation at higher operating pressure. In FIG. 3, areas of the end plate 2 are marked 30 with identical areas axially in line therewith on end plate 1. A radial wedge shaped chamber 33 is shown directly under piston 3. Referring to FIG. 2, the front and back aligned areas 30 completely cover the axial ends of the chamber 33. Fluid pressure in quadrants one is prevented from directly flowing into quadrants two, and vice versa. If the rotation of the rotor is clockwise, the volume of chamber 33 will move from quadrant one to quadrant two in one ninth of a revolution. Since the chamber 33 is now closed on both ends by the presence of solid area 30, the volume of chamber 33 which was part of the first quadrant chamber volume is now forced into the second quadrant chamber. Simultaneously, 34 rotated from the fourth quadrant chamber into the first quadrant chamber. If the flexible band is formed to a circle, then volume 33 is equal to volume 34, and there is no gain or loss of fluid volume in any of the four quadrant chambers. This is true regardless of speed or direction. If ports 18 and 23 were connected to the inlet port of a separate fixed displacement hydraulic motor, and the motor's return port was connected to device ports 17 and 19, the shape of the flexible band would be called neutral because the pump would not move any fluid into or out of the motor, and the motor shaft would not turn since a fixed displacement of fluid must occur in order for the motor to turn. If ports 23 and 17 were connected to one fixed displacement motor, and ports 18 and 19 were connected to another such motor, the result would be exactly the same. In either case, the input shaft of the variable pump would continue to turn with no motion ever on a motor shaft.

In FIG. 4, control pressure is injected into the control ports 26 for pistons 12 and 6 causing them to move radially inward. Any other mechanical means of control, such as rack 58 and pinion 60 actuable by lever 61 as shown in FIG. 11, would act in a similar manner to the pressure and cause pistons 12 and 6 to move radially inward due to external mechanical force. The spring action of the flexible band causes it to bulge out in equal measure against the pistons 3 and 9, while causing those pistons to move radially outward while exhausting the control fluids volume out through control ports 26. The use of mechanical control here would require that the mechanical controls means would retract to allow for the spring action of the band 14 to push pistons 3 and 9 outward. The arrows at the control ports 26 show the direction of fluid flow. Now for this discussion, a clockwise rotation is chosen. FIG. 4 also shows maximum deflection of the flexible band 14. Rotating vane chambers 34 and 35 are shown as minimized, while the chamber 33 and 36 are maximized. Since chamber 33 is removing a much larger volume of fluid from the first quadrant than the chamber 34 is carrying in, the difference must be provided via either kidney ports 23 or 16. Therefore, ports 23 or 16 are suction ports that can be connected to an external hydraulic circuit, and fluid is drawn into "quadrant one" through those ports. Chamber 33 is very large when it rotates into the second quadrants, and chamber 35 now is very small in exiting. The large difference of the volumes must therefore be forced out kidney ports 17 or 20 into the external hydraulic path. Ports 23 and 16, and 17 and 20 form a hydrostatic loop when connected to an external fixed displacement hydraulic motor. For reference, look at schematic connection in FIG. 9. By varying the radial positions of the pistons 12, 3, 6, and 9, the fluid displaced can be fully controlled from zero to the maximum in any increment. Now, ports 18 and 21, and 19 and 22 will form a second Siamese hydrostatic loop when they are connected to a second external hydraulic motor. For like displacements of the pistons 12 and 6, and opposite and equal motion of pistons 3 and 9, the fluid flow through fluid circuit A which consists of ports 23 and 16, and 17 and 20 will exactly equal the flow through fluid circuit consisting of ports 18 and 21, and 19 and 22. This described the case of straight motion for a set of vehicle axles. The simple case of ports 23 and 16 paired with 18 and 21, and 17 and 30 with 19 and 22, and then connected to a single fixed or variable hydraulic motor is also straight-line motion. For Reference, look at the fluid connection shown in FIG. 8. As the rotor, vane, and flexing band assembly rotate, the action of the elliptasized band will be to force the compression and extension of the vanes 24, with regard to angular position only. The pressure being applied to pistons 12 and 6 through ports 26 causes the pistons to move inward. For the clockwise rotation, output hydraulic pressure will escalate in the second and fourth quadrants chambers. As the chamber pressure increases, an increasing radial outward force develops on the underside of pistons 12 and 6, thereby reducing the respective piston inward force. When the outward force is equal to the inward force, the piston inward motion ceases. As the external hydraulic motor circuit responds to pressure and turns, the developed pressure drops slightly, and allows the pistons 12 and 6 to move slightly more inward, and this in turn increases the volume of fluid passing through the variable pump, in turn causing the motor to turn faster, thus causing a further line drop, causing more piston motion in, and so on. Therefore, the pressure developed in the quadrant chambers is equal to, or in proportion to the control force, and the variable pump automatically changes its displacement to accommodate changing external flow, while holding the out pressure proportional to the control pressure. Thus the hydraulic motor torque is a function of control pressure regardless of variable pump input speed and direction and output motor speed.

FIG. 5 depicts the opposite case of piston operation in that pistons 3 and 9 are pressurized, causing them to move radially inward. Pistons 12 and 6 are forced out and the ellipse flexible band major axis is now vertical. Swept chamber volume 34 now is large, as is volume 35, while volumes 33 and 36 are now small. There is now an excess of fluid entering the first and third quadrant chambers and kidney ports 23 and 16, and 18 and 21 become pressure ports, while a shortage of fluid in the second and fourth quadrants results in kidney ports 17 and 20, and 19 and 22 becoming suction ports and the hydraulic motor would now reverse direction. Note that in the case of FIGS. 4 and 5, if the shaft rotation of the pump input were reversed, the external fluid direction would also reverse and the manipulation of the opposed sets of control pistons, both the volume and direction of the fluid output can be fully controlled. Also note that by pressurizing the opposite sets of pistons to the pair shown in FIGS. 4 and 5, the subject pump can be used as a variable hydraulic motor. This is an ideal component for interface between an energy storage flywheel and road wheels. The device as a pump can also interface to a flywheel or electric motor including a pancake design motor and can act to use or recover flywheel or motor energy directly. During acceleration, the pump will withdraw the prestored kinetic energy from the flywheel and direct it to the road wheels so as to accelerate a vehicle. During braking, the opposite pistons try to force the flexible band back into a circular shape and in so doing, cause the pump to behave like a motor which then will act to re-accelerate the flywheel to near its initial speed. During the braking action, straight-line vehicle energy is recycled back into the flywheel and the vehicle is brought to a standstill. The braking action is the same for either a single output motor or two motors.

FIG. 6 shows control pressure being injected into port 26 causing piston 3 to move inward. Control fluid flows from port 26 of piston 9, and the entire flexible band moves toward piston 9 while maintaining a circular shape. Rotating chambers 34 and 33 behave as in FIG. 5 although with lesser amounts of fluid displacement per revolution. However, if a second motor is connected to ports 18 and 19, as shown in FIG. 9, it would experience a reversal of direction because chamber 36 is now larger than chamber 35, while at the same time, chamber 36 is larger than chamber 34. The third quadrant becomes suction while the fourth quadrant becomes the pressure. This is the behavior of some industrial skid-steer loaders that reverse the rotation of the wheels on one side of the vehicle with respect to the other side, causing the vehicle to spin on its vertical axis. If piston 9 were pressurized instead 3, both fluid circuits would reverse, and the two motors would now spin in opposite directions which are both reverse according to the original directions. During all of the above behavior, note that the control ports 26 of pistons 12 and 6 were quiescent with no inward or outward motion of these pistons. Also, during this differential action, a pressure balance within the pump is no longer maintained, and such differential action should be limited in duration and power level so as to minimize shaft bearing load and therefore maximize pump life. FIG. 7 combines the differential control action with the normal displacement control to achieve special unequal flow to the motors for the purpose of driving two wheels unequally, but correctly around a turn, since the outside wheel rotates faster than the inside wheel. Further, the amount of differential action can be directly related to the correct wheel track in response to a steering input. Thus, a very unique control mechanism is obtained for driving both wheels in turns and this will greatly enhance vehicle traction and safety. In this case, differential control pressure 37 is applied to ports 26 of pistons 3 and 9, while normal control pressure 38 now is simultaneously applied to those same ports. The resultant control pressure 39 and volume obtain at piston 9 may be different from the control pressure and volume obtained 31 applied to piston 3. The result is the combination of circular displacement of the flexible band 14 with reshaping of the band at the same time. The result is a different but controlled speed of one more with respect to a second, as shown in FIG. 9 resulting in a differential two-wheel drive. The differential portion of the control can be derived from the steering system, while the go and stop motion can be derived from brake and acceleration pedals. FIG. 8 shows the variable pump connected to either a fixed displacement hydraulic motor or another variable pump that is used as the motor to form a hydrostatic transmission. The conventional hydraulic motor case is limited to the range of one-to-one and one-to-infinity, where the use of a second variable unit extends the range to infinity to one.

FIG. 9 shows the schematic connection of one variable device to two fixed hydraulic motors, utilizing the Siamese ports of the invention to drive two separate outputs. This connection will allow the differential feature of the invention to be in use to differentially drive the two motors so as to effect a differential drive to the motor outputs, which is the case in a vehicular axle set negotiating a turn.

FIG. 10 shows the installation of a flexible band 14 in a conventional vane pump. The vanes 24 and rotor 15 are of conventional construction, like the proposed invention. The outer housing 40 is of conventional manufacture and chamber design, and the oil film 41 separates the band 14 from the outer housing 40 which will reduce operating friction in conventional units. The oil film 41 in this case is the full length of the ground internal chamber of the conventional outer housing. The sliding friction of the set of vanes is eliminated, and replaced by a broad oil film 41 of lesser friction; and, the efficiency of the conventional vane pump or motor is improved. Fixing the piston arrangement shown in FIGS. 4 through 7 will result in a fixed displacement pump or motor, whose efficiency will be the highest of all due to a reduced oil film 41 area.

For referential purposes, all radial orientation described hereinbelow is with respect to the axial center of a rotor in accordance with the present invention, unless otherwise stated. Stated another way, "radial" in this context means to emanate to and from the axial center of the cylindrical rotor, unless otherwise stated.

FIGS. 12a-12c are views showing a crankshaft piston drive 100 utilizing a right angle slot 102 in the piston 104 relative to the length and motion of the piston. As shown in FIGS. 12a-12c, when the crankshaft 106 is rotated counter clockwise relative to the crankshaft rotational center 108 shown, the piston moves from a neutral position to a position radially inward. Thus, the crankshaft exerts a radially inward movement thereby forming a flush communication between a contoured and curved end of the piston and the flexible band 110, depressing the band radially inward. Conversely, when the crankshaft is rotated clockwise of the crankshaft rotational center, the piston retracts radially outward from the flexible band, and the spring action of the band causes it to follow the piston.

Stated another way, in the embodiment shown in FIGS. 12a-12c, a control crankshaft operates in a right angle slot in the piston. The crankshaft throw is typically positioned at a right angle to the direction of piston travel, and is rotated plus or minus 90 degrees to cause a sinusoidal motion of the piston thereby resulting in a radially reciprocal (radially inward and then radially outward) motion of the piston. Thus, the linear and radial reciprocal motion of the piston corresponds to a sine wave responsive to each degree of crankshaft rotation. The spring like nature of the band causes it to remain in intimate contact with the piston surface via a thin oil film, thus forming a hydrodynamic bearing from the oil film.

In FIG. 13, yet another piston actuator is shown wherein a lever is externally controlled to effect respective radially inward and outward motions of the piston. The lever can thus be controlled by any connection that provides a common manipulation of the plurality of pistons (or shape actuators of the flexible band) shown in the Figures, or the lever can be individually controlled. For example, simple manipulation of a foot pedal (an accelerometer for example) can effect manual control of the piston through the use of the lever.

FIG. 14 generally depicts the forces acting on a given piston. A steady state control pressure is radially inwardly applied to a radially outward cross-sectional area of the piston. During operation, as the work pressure increases below the flexible band, it exerts a radially outward force acting upon a radially inward contoured section of the piston. As the work pressure increases and decreases, therefore, the piston is cycled radially outward and radially inward.

Stated another way, FIG. 14 illustrates that relative to direct hydraulic piston control, an area radially outward of the piston is subject to a controlled hydraulic pressure which causes the piston to move radially inward. This action causes the pump to develop a greater work pressure by virtue of the fact that radially inward movement of the piston causes increased displacement output of the pump. This in turn causes the working pressure to rise. When the work pressure has reaches a value which balances the net force created on the piston by the control pressure, the piston inward motion ceases, providing a servo-type of control function wherein the pump working pressure tracks the control pressure. Thus, this type of control system forms a power amplifier where the output pressure of the pump tracks the control pressure with the result that the control pressure controls the power output linearly. This same operating principle is exhibited by the embodiment shown in FIG. 16, as described below.

In FIG. 15, yet another piston actuator is shown containing a control screw 114 threadedly received in an axial bore 116 of the piston 104. The control screw is thus rotatable to advance or retard piston position. The control is linearly related in that the degree of screw rotation is directly related to the cyclic and radial piston motion. Given the screw's inherent design inhibition for radially outward retraction of the piston, this type of piston actuator is particularly useful in preventing feedback (and an applied torque to an associated actuator) due to applied torque or work performance spikes. For example, the standard jarring caused during tractor operation may result in an associated pressure spike within the rotor that is then transmitted through the piston and into the actuator. Therefore, the resultant torque absorbed by other types of actuators, a rack and pinion for example, could potentially fracture the actuator assembly. The retraction inhibition of this embodiment is one solution to this problem. Nevertheless, a ball-screw control means may be used to reduce the friction of the control screw if desired.

In accordance with yet another aspect of the invention, FIG. 16 depicts yet another piston actuator that can be described as a small closed-loop servo system. A piston spool housing 118 is formed as an axial bore within the piston 104. A plurality of radially extending passages, relative to the axial bore of the piston, facilitate injection and exhaust of fluidic pressure within the piston spool housing. A spool 120 having a plurality of turns 122 (two as shown) is slidably received within the piston spool housing.

As shown in FIG. 16, the spool and piston are shown in a balanced position. Stated another way, the control pressure force exerting a radially inward force on the piston and the opposing working pressure exerting a radially outward force on the piston are substantially equivalent wherein the spool exhibits an equilibrium position relative thereto. In operation, assume the spool is forced radially inward into the piston housing. A fixed control pressure is then injected through passage 124 given that the turn blocking the passage has been thrust radially inward thereby opening passage 124. The control pressure then flows radially outward through passage 126 in fluid communication with the pressure chamber 125 behind the piston 104. As a consequence, the control pressure increases the radially inward force applied to the radially outward cross-section of the piston (within the control pressure chamber) thereby biasing the piston radially inward. As this occurs, the working pressure against the piston (pump output) increases, and the relative position of the spool is returned to a neutral balance as the physical position of the piston moves to realign with the new neutral spool position.

If the working pressure overcomes the applied piston control pressure, the spool is retracted radially outward through the piston spool housing by virtue of the physical movement of the piston body relative to the existing spool position, thereby opening passages 128 and 130 and thus enabling exhaust of the control pressure and effectively reducing the associated piston control force. The reduction in the control pressure force results in the working pressure biasing the piston radially outward thereby reducing pump displacement and the localized working pressure. The reduction of working pressure continues until the working pressure is reduced to a point less than the remaining control pressure (and the spring energy exerted by a spring locator (not shown) on the radially outwardmost end of the spool) within the control pressure chamber. The piston thus "tracks" the piston control pressure and again seeks the balanced position of the spool as described above. The valving arrangement results in low requirements of the force applied to the spool compared to the piston reaction force, or, the working force applied against the piston. Thus, the force requirement on the spool for control is minimized by means of the secondary power servo spool system described.

Stated another way, the system described in FIG. 16 is a hydraulic control amplifier spool means useful in applications where the working pressure forces exerted on the piston(s) are relatively very high. A secondary dedicated spool amplifier may be employed thus permitting a greatly reduced control force requirement, and thereby facilitating the control of very large levels of power with a small control force. A transistor analogue would be the Darlington amplifier. Relative thereto, the control means described in FIG. 16 may also be referred to as a "Darlington Power Amplifier".

FIG. 17 shows yet another piston actuator containing an externally controlled cam 132 and a cam roller 134. The cam roller is fixed to a radially outward portion of the piston. The cam profile 132 is slidably engaged with the roller in linear motion thereto, and thus effects a radial reciprocal movement of the piston 104. The cam motion can be linear as shown, or the cam motion can be circular around the pump rotor center. Related thereto, FIG. 21 shows a circular cam ring 135 containing four cam profiles 136 each cam corresponding to a piston within the four-piston model shown. In motion, the cam ring thus facilitates common and simultaneous control of all four pistons wherein the cam profiles may all be the same or different, and may be linear and/or nonlinear.

FIGS. 18-20 each also illustrate a control linkage means for facilitating common and simultaneous operation or control of a plurality of pistons. A "pump center of rotation" is defined for each control linkage and is merely the axial center of the rotor and pump (not shown). Thus, each control linkage surrounds a rotor/pump as shown in FIGS. 1-11 for example.

FIG. 18 shows a plurality of sprockets 138 (four) corresponding to an equal plurality of pistons (not all shown) and associated crankshafts (not all shown). Each sprocket rotatably communicates with a respective crankshaft that upon revolution results in radial reciprocation of the respective piston. An externally driven chain 140 results in simultaneous rotary motion of the sprockets.

FIG. 19 shows an alternative control linkage means that again contains a plurality of gears 142, a corresponding plurality of crankshafts, and a corresponding plurality of pistons. In concert therewith, an externally driven ring gear 144, radially external or internal of the plurality of gears, facilitates a common and simultaneous control of the pistons. The ring gear is formed with a plurality of sets of teeth symmetrically spaced about the circumference of the ring, each set of teeth corresponding to a piston. In the embodiment shown, the teeth are formed at the 12, 3, 6, and 9 o'clock positions. In operation, the sets of teeth of the ring gear engage the teeth of a respective sprocket or gear thereby throwing the crankshaft and facilitating radial movement of the associated piston.

The embodiment of FIG. 20 operates very similarly to FIGS. 18 and 19. However, FIG. 20 employs a plurality of crowned flat pulleys 146 or gears (again corresponding to an equal number of pistons and crankshafts) driven by a belt 148 for simultaneous control of the plurality of pistons.

Relative to FIG. 22, a differential gear set with independent control inputs can be added to pistons at the 3 and 9 O'clock positions in the embodiment shown in FIG. 7, for example, thereby facilitating differential behavior of a vehicle per operation of a rotor as shown in FIG. 7. In certain cases relative to vehicle operation, for example, it is undesirable to allow the differential input to cause opposite wheel rotation. For example, if the differential gear control were connected to a tractor steering wheel without any relation to the forward or reverse speed setting, the tractor would stand still and turning the steering wheel would cause one wheel to back up, while the other would drive forward with the result that the wheels would chew up the surface and dig two holes for the drive wheels. This is of course unacceptable. A solution has been discovered whereby a third axial control system for the 3 O'clock and 9 O'Clock crankshafts is introduced. In neutral position (stopped), the crankshafts are at 90 degrees to the piston direction (See FIG. 12a). The solution is to vary the actual stroke of the crankshaft by means of an axial ramp system which is able to vary the stroke in response to an axial (with respect to the crankshaft) control input motion. As shown in FIGS. 22a-22c, the stroke can be changed when the piston is in the neutral position without causing any change in the piston position. If the crank were at perhaps 30 degrees of control rotation, increasing or decreasing the stroke would as shown affect the piston position. If the 3 O'Clock stroke was increased while the 9 O'Clock stroke was decreased by the same amount, the effect would be to create a shift in the flexible belt position, causing a differential behavior, while allowing the speed control portion of the control to ellipticize the belt, causing perhaps forward motion. The result is a mathematical addition of flows on one side of the rotor, and a mathematical subtraction of flows on the other side of the rotor, and a true differential drive system results.

If the speed were increased, the crankshaft control angle would increase, but the variable crankshaft strokes would have same mathematical effect on the combined differential/speed behavior, and the drive wheels would again be mathematically corrected to turn at the correct, yet faster rate for the turn. The same principles apply for the reverse direction. A separate control input can be accomplished to only cause differential behavior. This is only applicable for a four-wheel drive unit. This can be accomplished by connecting a properly sized hydraulic wheel motor for, perhaps the left front wheel tire (sized to reflect the smaller tire diameter of that front tire) in hydraulic series with the left rear wheel (larger) motor with the result that the hydraulic pressure forced through the left hydraulic circuit is shared by the two motors, and their speeds are locked in synchronicity; a series non-slip system. The same system can be used for the right side with similar results. In normal four-wheel drive, the four wheels are driven at the correct rate in terms of the tire patches on the ground, and the effect is as if all axles were locked for straight-line travel, with maximum traction, even though the vehicle is turning. This system results in giving the maximum traction under all ground conditions, and is thought to be a form of analog hydraulic computer which calculates, using the laws of geometry, the correct hydraulic behavior in response to control inputs.

In accordance with yet another aspect of the present invention, FIGS. 23a and 23b describe a spool rotor having spool ends that are then mated respectively to wear plates known in the art. See U.S. Pat. No. 6,022,201 for example. Slots 107 facilitate fluid flow in and out of the chambers defined between the vanes. The spool ends eliminate the wear pattern normally caused by the flexible belt as the edges of the belt abrade the inner surfaces of the wear plates adjacent each respective spool end. The use of the spool thus eliminates the effective motion between the edges of the vanes:extending from the axis to the flexible belt and the stationary wear plates. The spool ends are instead in rotary communication with the stationary wear plates. As a result, the vanes can be individually sealed along their individual radial lengths and along the interface between an inner surface of the spool end and the radial lengths of the vanes. Additionally, a flexible o-ring or seal may be place between belt and the radial outer edges of the vanes in communication with the flexible belt that is then flexibly adjusted during rotation to retain a seal between the radial outer edges of the vanes and the inner surface of the rotational flexible belt. Accordingly, employment of the spool ends substantially improves the volumetric and overall efficiency of the pump. For example, in certain cases the volumetric efficiency is improved from 85% to 97% or greater.

Stated another way, in conventional designs, the vanes and the rotor are axially coextensive and fit within wear plates at both ends with a small clearance. This small clearance causes substantial volumetric inefficiency, or bypass of pumped fluid. Also, the radially outer edges of the vanes have a leakage contribution in conventional designs where the vanes slide at speed against the inner surface of the chamber to create the pumping action. U.S. Pat. No. 6,022,201 substantially solved the problem of radial leakage by providing vanes having intimate contact within the inner surface of the belt. Conventionally, the axial ends of the vanes slide at rotor speed against the wear plates making effective sealing impossible. The spool design of the present invention therefore solves several problems. It eliminates the high speed wear at the ends by containing the vanes wholly within the spool ends, so that the only wear on the vanes is relative to the cyclical radial motion of the vanes during operation. This arrangement thus permits a seal system at the vane ends in addition to the vane outer edge abutting the inside surface of the flexible band. By adding a seal between the vane surfaces which are sliding within the rotor guide slots formed within the spool ends, the whole vane/spool ends/belt surface/rotor outer circumference between two adjacent vanes can now be effectively sealed thereby improving the hydristor or pump efficiency to unparalleled levels at 97-98%. The spool ends simply mate with the end or wear plates shown in FIG. 1, for example.

In yet another aspect of the invention, FIGS. 24a and 24b illustrate a sealing mechanism wherein a pair of flaps 150 are counterbored into the wear plates if the rotor has open kidney ports adjacent thereto, and are spaced to flap against the piston edges as it moves flush with a flexible belt. Each piston thus has corresponding flaps that are operable upon the flush communication of the piston's contoured surface and the flexible belt. Volumetric efficiency is thereby enhanced.

In still yet another aspect of the invention, an improvement in the sealing of the invention described in U.S. Pat. No. 6,022,201 and in conventional designs includes an insert 152 slidably engaged within an arcuate groove 154 formed within the wear plate (not shown).

In conventional fixed displacement vane pumps and motors, there is a problem associated with equalizing the pressure at the radially inner and outer vane edges. Chamber pressure must be routed under the vane (at its radially innermost point) to equalize the radially inward force created by the chamber pressure existing between the radial outer edge of the vane and the inner surface of the flexible belt (or the chamber confining contour). Accordingly, it is well known to provide undercuts within the endwalls to facilitate fluid flow and pressure to the radially innermost ends of the vanes (e.g. the source of the fluid pressure in grooves 154). This is true both for conventional fixed designs, and the hydristor variable belt design rotors described in U.S. Pat. No. 6,022,201. In conventional practice, satisfactory sealing has not yet been achieved in bidirectional designs. Either the routing grooves at the axial ends of two opposite chambers where pressure sealing is desired are extended to allow for sealing the vane for the full rotation across the sealing surface (see reference number 30 in FIG. 1, for example), or a compromise is made for all four sealing areas (reference number 30) i.e. the chamber groove to route oil only extends halfway. The first case works well for uni-directional operation and the second case works moderately acceptable for bidirectional operation. During bidirectional operation of the rotor, the inserts 152 are alternatively forced against either "tab" 109 on either side of the groove 154, depending on the rotational direction of the rotor. Tabs 109, basically the interface of the grooves 154 with an adjoining groove, function to stop the movement of the insert 152 within the groove 154 and also function to seal groove 154 and one end of groove 158 in insert 152. Because insert 152 is recessed within groove 154, once insert 152 is seated against tab 109, channel 158 is sealed thereby forcing fluid upward through the slot 152 and out ports 156, rather than into an adjacent groove 154. The underside of the vanes is therefore pressurized without sacrificing operational efficiency due to leakage through the undercut when a bidirectional application is desired.

In accordance with the present invention, a plurality of arcuate grooves are formed within the inner surface of the wear plate, each groove corresponding to an operable quadrant within the rotor. The grooves are symmetrically placed at the beginning of each quadrant and are formed in a sausage-link shape or in a shape that precludes slippage of the insert from within the channel or groove beyond a limited range. Therefore, each end of the groove comprises a narrower.opening thereby precluding slippage of the insert once placed therein. Additionally, each groove is thus formed at the 12, 3, 6, and 9 O'Clock positions in an embodiment containing four pistons placed symmetrically about the rotor periphery.

The valve insert shown in FIG. 25 is slidably engaged within a corresponding groove having an arcuate length approximately equal to the radially inner arcuate length existing between two juxtaposed vanes. As shown in FIGS. 25b and 25c, the insert has a pair of annuli 156 extending through the top of the insert for fluid flow therethrough. Thus fluid initially flowing beneath the insert is channeled through a right hole and then provides pressure over the top surface of the insert. A groove 158 is cut on the underside to facilitate the flow of fluid through the bottom and then out through the top of the insert. The valve insert thus responds to chamber pressure which drives the insert angularly over a small range within the groove so as to extend the vane underpressure for proper vane operation for a given pressure case. This is true for both rotational directions of the rotor. If any other chamber sees pressure, the inserts "switch" to extend the sealing as required for the particular case. This is even true for adjacent chambers as well as opposite chambers. Thus bidirectional volumetric efficiency is improved during single/dual pump operation, or any motor operation.

While the foregoing examples illustrate and describe the use of the present invention, they are not intended to limit the invention as disclosed in certain preferred embodiments herein. Therefore, variations and modifications commensurate with the above teachings and the skill and/or knowledge of the relevant art, are within the scope of the present invention.

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