Field of the Invention:

This invention relates to power transfer apparatus, and more particularly, to an infinitely variable hydraulic drive for bicycles and the like.

Prior Art:

Various means have been developed in the prior art for transferring power from one system to another. These prior art systems range from devices which act as transducers to convert one form of power to a different form of power, to devices which merely transfer power directly from one system to another. Included within this broad spectrum of power transfer devices are various drives and transmissions which work through one or a combination of gears, chains and sprockets, belts, pulleys and even hydraulic or fluid operated devices.

The evolution of human-powered wheeled vehicles has resulted in the development of a variety of all of the above power transfer devices. Particularly with reference to bicycles, efforts have been made to increase the efficiency of such devices and/or to reduce the cost, weight and complexity of them. However, the system which is currently most widely used comprises the Derailleur gear system, which has a plurality of toothed sprockets driven by foot-operated pedals and which power a plurality of toothed wheels or gears at the hub of the rear wheel via a chain carried on the toothed sprockets and wheels. A complex and rather fragile lever system serves to shift the-chain from one sprocket and/or gear to another to change the gear ratio. This system is relatively cumbersome and expensive and may be difficult to maintain in proper adjustment. Moreover, it is generally advisable to

cease pedalling while a gear change is being effected.

One effort to overcome the difficulties with the Derailleur gear system has been the use of a hydraulic drive, such as described in U.S. patent 4,546,990. In this patent, a hydraulic pump at the sprocket is driven by foot-operated pedals to pressurize a hydraulic fluid. The pressurized fluid is then con¬ veyed via conduits to a hydraulic motor at the hub of the rear wheel. Gear ratio changes are effected by altering the position of rotors or plates in the pump housing.

Other devices have included belt drives and the like, including Reeves pulleys for effecting gear changes. All such systems either offer limited range in making gear changes, or are relatively complex and expensive, or lack the desired efficiency.

Summary of the Invention:

Accordingly, it is an object of this invention to provide a hydraulic drive system which is simple and economical in construction, and which includes means for effecting changes in the drive ratio.

Another object of the invention is to provide a hydraulic drive system including a pump and a motor, in which the pump and motor are mounted in a common housing to reduce cost and weight.

A further object of the invention is to provide a hydraulic drive system having a pump and motor in a common housing, and in which a shift plate separ- ates the pump from the motor, the shift plate being movable to alter the drive ratio between the pump and motor.

A still further object of the invention is to provide a hydraulic pump and motor system contained in a common housing, in which the pump and motor include

rotors mounted in chambers on opposite sides of a shift plate, and in which the shift plate is selectively movable relative to the rotors to effect equal and opposite changes simultaneously in the hydraulic displacements of the pump and motor.

Yet another object of the invention is to provide a hydraulic drive for bicycles and the like, wherein a pump and motor are both contained in the rear hub of the bicycle, enabling easy retrofit to existing bicycles.

These and other objects and advantages of the invention are achieved by the structure of the present invention, wherein an apertured disc-like shift plate is affixed between two substantially identical but radially offset cylindrical pump and motor housings. A drive shaft extends through a central portion of the shift plate perpendicular to the plane thereof, and a pair of rotors are carried coaxially on the shaft, one on each side of the shift plate. This assembly is received in a cylindrical hub, with the shaft coaxial with the hub, and end plates or side covers are secured to each end of the hub to maintain the parts in assembled relationship and prevent loss- of hydraulic fluid. The pump rotor is connected with the drive sprocket via a one-way roller clutch assembly. The motor rotor is adapted to be drivingly engaged and disengaged relative to one of the end plates, and thus the hub, via a ratchet arrangement. Fluid flow passages communicate between the pump and motor to deliver and return hydraulic fluid there- between.

The pump is driven by any suitable means, such as a chain, belt or shaft, powered by ^* foot-operated pedals, engine or motor. Changes in the drive ratio are effected by shifting the relative positions of the rotors and their housings to vary the displacement thereof, and these changes may be made while power is

being applied to the pump rotor. Moreover, the ratios are infinitely adjustable rather than being incremental over a finite number of ratios as in prior art devices. A unique advantage of the invention, particu- larly as it relates to a drive for bicycles, is in its compact size and low weight. In fact, the entire pump and motor assembly are contained in the hub of the rear wheel and may be easily retrofitted to existing bicycles by simply changing the rear wheel assembly on the frame. Although intended for use in bicycles as specifically described in the form disclosed herein, the invention has numerous other applications, including use in motorcycles, right-angle drives for various appli¬ cations, such as automotive, or any other system in which transfer of power from one place to another is desired. It is also contemplated that in some appli¬ cations the housing could be fixed and the pump and motor shafts made rotatable.

Brief Description of the Drawings: The foregoing and other advantages of the invention will become apparent from the following detailed description and appended claims when taken in conjunction with the drawings, wherein like reference characters designate like parts throughout the several views, and wherein:

Fig. 1 is a fragmentary view in side elevation of a rear wheel and portion of the frame of a bicycle incorporating the hydraulic drive of the invention;

Fig. 2 is a fragmentary view in rear elevation of the bicycle of figure 1;

Fig. 3 is an enlarged fragmentary view in side elevation of the unique hydraulic drive hub of the invention;

Fig. 4 is an enlarged fragmentary view of the drive of figure 3, taken from the right hand side of

figure 3;

Fig. 5 is a longitudinal sectional view of the drive, taken along line 5-5 in figure 3;

Fig. 6 is a transverse sectional view of the drive, taken along line 6-6 in figure 5;

Fig. 7 is a top plan view of the displacement ring of the drive of the invention;

Fig. 8 is a side view in elevation of the displacement ring of figure 7; Fig. 9 is a view in section taken along line

9-9 in figure 7;

Fig. 10 is an edge view of the motor rotor used in the drive of the invention;

Fig. 11 is a side view in elevation of the rotor, looking in the direction of the arrow 11 in figure 10;

Fig. 12 is a front view in elevation of one of the rotor vanes used in the drive of the invention;

Fig. 13 is an end view of the rotor of figure 12;

Fig. 14 is a top view of the rotor of figure 12;

Fig. 15 is an exploded perspective view of the displacement ring, rotors, drive tube, shift tube and shaft used in the drive of the invention;

Fig. 16 is a side view in elevation of the shift tube and shift lever;

Fig. 17 is an end view of the shift tube and lever; Fig. 18 is a side view in elevation of the shaft;

Fig. 19 is an end view of the—shaft of figure 18;

Fig. 20 is an exploded perspective view of the hub or housing, end covers and spoke flanges used in the drive of the invention;

Fig. 21 is a side view of the chain drive used to transmit power from the pedals of a bicycle to the drive or power hub of the invention;

Fig. 22 is a side view of a belt drive which may be used with the power hub of the invention; and

Fig. 23 is an end view of the belt drive of figure 22.

Description of the Preferred Embodiments:

Referring more specifically to the drawings, and figures 1 through 4 in particular, the hydraulic drive or power hub of the invention is indicated generally at 10, and comprises a cylindrical hub or housing 11 having spoke flanges 12 and 13 secured on opposite ends thereof for mounting the spokes 14 of a bicycle wheel 15. A shaft 16 extends coaxially through the hub and has a driven sprocket 17 secured thereon for transmitting power to the hub from a drive sprocket 18 and pedals "P" via chain 19. A shift lever 20 is mounted on the shaft at the end of the hub opposite the driven sprocket 17 for effecting changes in the drive ratio of the power hub. A shift cable 21 is connected with the shift lever and extends to any suitable location on the bicycle for manual operation to move the shift lever and effect the changes in drive ratio. As seen in figure 3, a spring 22 is connected between the shift lever and hub to return the shift lever to an at rest position. If desired, the spring may be elimin¬ ated and suitable cable or linkage means may be used to move the shift lever in both directions. Further, as illustrated in figures 22 and 23, types—of drive other than the chain and sprocket may be used, such as the belt 23 and pulley 24 to transmit power from the pedals to the hub.

As seen' best in figures 5 through 20, the

unique hydraulic drive of the invention for transmitting power from the shaft to the hub comprises a cylindrical drive tube 25 (figures 5 and 15) mounted coaxially on a reduced diameter portion 26 of the shaft 16 through a plurality of roller bearings 27, whereby the drive tube turns freely on the shaft. An o-ring seal 28 is also disposed between the drive tube and shaft for a purpose described later herein. The driven sprocket 17 is fixedly mounted to the drive tube via a sprocket nut 29 press-fitted on the tube and threaded or otherwise suitably engaged with the sprocket.

A pump rotor 30 is coaxially mounted on the drive tube via one-way roller bearings or clutch 31, so that rotation of the shaft in a forward direction (clockwise as viewed in figure 6) effects rotation of the pump rotor. By reversing the direction of rotation of the driven sprocket, or by holding it stationary during forward movement of the bicycle, the one-way clutch disengages, enabling free-wheeling movement of the pump rotor on the shaft.

The pump rotor 30 is rotatable in a displace¬ ment ring 32, consisting of a central, disc-like shift plate 33 having a cylindrical pump ring 34 fixed on one side thereof and a cylindrical motor ring 35 fixed on the other side. The pump ring and motor ring define a pump chamber 36 and motor chamber 37, respectively. As seen in figures 6 through 9 and 15, the pump ring 34 and motor ring 35 are slightly smaller in diameter than the shift ring and are laterally or radially offset from one another on opposite sides of the shift plate. In other words, as viewed in figures 7 and 8, the pump ring 34 is flush on its left side with the left side of the shift plate but terminates short of the right side of the shift plate, while the motor ring 35 is flush at its right side with the right side of the shift plate and terminates short of the left side of the shift plate.

A first arcuately slotted, circumferentially extending port 38 extends through the shift plate 33 in the top portion thereof for conducting pressurized hydraulic fluid from the pump chamber 36 to the motor chamber 37 and is open to both the pump chamber and the motor chamber from leading end 40 to trailing end 41. The arcuately slotted port 38 is on an ever increasing radius such that the leading end 40 is closer to the center of the chamber than is the trailing end 41. A relieved or cutaway portion 42 in the side of plate 33 in the pump chamber extends beyond trailing end 41 to relieve the high pressure encountered as the pump vanes approach the area of narrowest constriction in the pump chamber, i.e., approaching the horizontal centerline of the pump.

A second elongate, arcuately slotted port 43 is formed through the plate 33 in the bottom portion thereof for conducting spent hydraulic fluid from the motor chamber back to the pump chamber, and has a leading end 44 and trailing end 45. The slot is formed on an ever decreasing radius such that the leading end 44 is farther from the center of the pump than the trailing end. A relieved area or cut-away extension 46 of the slotted port is formed in the surface of the plate 33 in the pump chamber.

Similar but opposite relieved areas or extensions of the slots are formed in the motor chamber side of the plate 33, as shown at 47 and 48.

The relationship of these ports to the pump and motor chambers is thus such that as the pump displacement is decreasing, the increasingly more highly pressurized fluid is forced through part 38 into the motor chamber, and as the pump chamber displacement is increasing (at the bottom of the device, as viewed in figure 6, for example), the reduction in pressure in the pump chamber draws the fluid froitf the motor chamber and

back into the pump chamber through port 43 to be pressurized and forced back into the motor chamber.

The pump rotor 30 has a plurality of radial notches 49 in its outer surface and the outer marginal edge closest to the shift plate is chamfered as at 50 to provide clearance for the passages 38 and 43. A plural¬ ity of rectangular, plate-like vanes 51 are radially slidably received in the notches and are biased radially outwardly by springs 52 engaged between the vanes and the bottoms of the notches. As shown in figures 12 through 14, the springs 52 may be seated in pockets 53 drilled or otherwise formed in the inner edge portions of the vanes. As seen in figure 6, the rotor is smaller in diameter than the chamber 36 and the springs 52 serve to bias the vanes 51 outwardly into sliding engagement with the inner surface of the pump ring. Further, as seen in figure 13, the outer edges of the vanes 51 are tapered so that the trailing edge thereof is longer than the leading edge. This prevents the vane from being pushed away from the inner surface of the pump ring as the vane passes the terminal end of the relieved extension of the port 38.

As seen in figures 10 and 11, oil balance grooves 54 are formed in the rear walls of notches 49 to conduct the high pressure fluid to the rear edge of the vanes.

The shift plate 33 also has a generally rect¬ angularly shaped opening 55 through the center thereof, with a notch 56 in the upper edge. The shaft 16 extends through the opening 55 and has a notch 57 in its bottom side with a pin 58 received in the notch and engaged against the bottom edge and sides of the- opening 55 to prevent relative movement between the shaft 16 and plate 33. A shift tube 59 is fixed to the shift lever 20 and extends coaxially over the shaft 16 into the motor

chamber 37 and against one side of the shift plate. An axially extending pin 60 is formed on the inner end of the shift tube and this pin is engaged in the notch 56. Consequently, fore and aft movement of the shift lever 20 causes the shift tube to rotate in a corresponding direction, rocking the pin 60 and thus moving the dis¬ placement ring 32 fore or aft, depending upon the direction of movement of the lever 20. Since the rotor is coaxially fixed relative to the shaft 16 and the shaft is fixed to the frame of the bicycle, movement of the displacement ring effects a change in the radial position of the rotor relative to the pump ring, altering the displacement of the pump. In figure 6, the pump ring is displaced completely to the left relative to the position of the rotor, resulting in a maximum displacement for the pump.

A motor rotor 61 is mounted coaxially on the shift tube and shaft in the motor chamber 37 and is constructed substantially identically to the pump rotor, in that it has radial notches 49, vanes 51, springs 52 and chamfered edge 50. The motor rotor 61 is rotatably mounted on the shift tube via roller bearings 62.

Because of the radially offset relationship of the motor and pump rings, and the coaxial positioning of the rotors on the shaft, movement of the displacement or shift ring as described above to effect a change in the displacement of the- pump causes an equal and opposite displacement of the motor, effectively doubling the displacement change brought about by operation of the shift lever.

As seen best in figures 5 and 20, the spoke flanges 12 and 13 are threaded onto externally threaded end portions 63 and 64 of the hub 11, and side covers or end plates 65 and 66 are threadably engaged inside the spoke flanges and against the opposite ends of the hub 11 to retain the displacement ring and rotors, as well

as hydraulic fluid, inside the hub. The side covers 65 and 66 have suitable recesses 67 in their outer faces for engagement with a spanner wrench or other suitable tool to disengage the side covers from the spoke flanges.

Drive is transmitted from the motor rotor 61 to the hub 11 via a plurality of pawls or ratchet pins 68 carried by the motor rotor and having shaped ends 69 for driving engagement in notches 70 formed in the inner face of side cover 65. The pins are yieldably biased in an outward direction against the side cover by springs 71, and are prevented from rotating about their longi¬ tudinal axis by fins 72 received in slots 73 in the rotor 61 (see figures 5 and 11). Thus, the shaped ends 69 are kept properly oriented so that forward or clock¬ wise rotation of the motor rotor 61 causes the ratchet pins or pawls 68 to slide along the face of the side cover 65 until the shaped ends 69 drop into a respect¬ ive notch 70, whereupon the side cover and thus the hub are caused to rotate with the motor rotor. Reverse motion or cessation of motion of the motor rotor relative to the side cover and hub results in the shaped ends riding up out of the notches 70 so that the side cover and hub can rotate relative to the motor rotor. As seen in the left hand side of figure 5, a thrust bearing 74 is engaged between the shift lever 20 and outer surface of the side cover 65, and a retaining nut 75 is threaded onto the threaded end of the shaft 16 and against the shift lever and outer end of the shift tube. The frame "F" of the bicycle is received on the end of the shaft outboard of the retaining nut 75 and a nut 76 is threaded against the frame to-securely clamp it between the two nuts 75 and 76.

The right hand side of figure 5 shows the arrangement, at the other end of the shaft and hub. A first thrust bearing 77 is engaged between the outer

surface of side cover 66 and the inner side surface of sprocket nut 29, and a second thrust bearing 78 is positioned between the outer side of the sprocket nut 29 and a retaining nut 79 threaded onto the shaft 16 and against the outer end of drive tube 25 and the thrust bearing 78. The frame "F" at this side of the bicycle is engaged over the end of the shaft and is secured between the retaining nut 79 and nut 80.

O-ring seals 81 and 82 are engaged between the drive tube and shift tube and their respective side covers to prevent loss of hydraulic fluid from the pump and motor chambers, and an o-ring seal 83 ^' is engaged between the shaft and shift tube to enable the hydraulic fluid to lubricate the shaft in the shift tube but prevent loss of the fluid from the device. The o-ring 28 previously described similarly seals the shaft relative to the drive tube at the other end of the shaft.

An oil return opening 84 is formed in the bottom of the pump ring 34, on the low pressure side thereof, whereby any fluid leaking from the pump or motor chambers is collected in the bottom of the housing 11 and returned to the pump chamber through opening 84. Further, flats 85 and 86 are formed on the top and bottom of the displacement ring, defining clearance spaces for flow from one side of the displacement ring to the other of any fluid which has leaked from the pump or motor chambers, and subsequent return to the pump and motor through opening 84. In a specific embodiment of the invention described herein, using nine vanes, the port 38 has its leading end 40 displaced 15° after -the horizontal centerline, as measured in a clockwise direction, and continues on an arc to be open to the pump and motor chambers until 37° after the vertical centerline. The relieved area or extension 43 continues to a point about

15° above the horizontal centerline. The port 43, on the other hand, has its leading end 44 spaced 28° prior to the vertical centerline (measured in a clockwise direction) and continues on an arc to be open to the motor chamber until 28° after the vertical centerline. The relieved extension 46 of the port 43 then continues to a point 35° before the horizontal centerline.

In the specific example described above, the displacement ring has a width of about 2.3 inches and the pump ring and motor ring each have an inside radius of about 1.375 inches and a width of 1.0 inch.

Operation In operation, a desired drive ratio is selected by moving the shift lever 20 to shift the displacement ring 32 and either increase or decrease the displacement of the pump while at the same time effect¬ ing an opposite change in the motor displacement. The pedals are then driven to rotate the drive sprocket 18 and thus the driven sprocket 17 via chain 19. Since the driven sprocket is fixed on the sprocket nut 29, and since the sprocket nut is fixed on the drive tube 25, rotation of the driven sprocket causes rotation of the drive tube. The one-way clutch 31 engages upon forward or clockwise rotation of the drive tube to cause rotation of the pump rotor 30, pressurizing the hydraulic fluid in the pump chamber and forcing it through the port 38 and into the motor chamber, where it acts on the vanes 51 of the motor rotor 61 to cause the motor rotor to rotate in a forward direction. Rotation of the motor rotor causes the pawls 68 to ride along the inner surface of the side cover 65 until—they drop into the notches 70, thus causing rotation of the side cover and the hub 11, and thence the wheel of the bicycle. The spent hydraulic fluid is returned from the motor chamber to the pump chamber via port 43. A change in the drive

ratio can be effected at any time simply by reposition¬ ing the shift lever 20 to alter the displacement of the pump and motor.

Although the invention has been described with reference to particular embodiments, it is to be under¬ stood that these embodiments are merely illustrative of the application of the principles of the invention. Numerous modifications may be made therein and other arrangements may be devised without departing from the spirit and scope of the invention.