Abstract:
A three stage, sixteen-speed, planetary driving wheel, with the pedal drive shaft on the axis of the wheel and vehicle interface fittings on both sides inboard of the pedal crank arms, for mounting in pedal powered vehicles to replace the chain and derailleur system used in conventional multiple speed bicycles. Because the planetary gear arrangement is completely enclosed inside the wheel hub where it is well protected from dirt, and because this driving wheel provides five low range speeds below direct drive, it is well suited for mountain bicycles or for transporting the payload of a bicycle camper up steep grades.

Description:
BACKGROUND OF THE INVENTION 
     1 Field of the Invention 
     This invention relates generally to drive mechanisms for pedal powered vehicles such as bicycles and tricycles and more particularly to bicycle drive mechanisms of the chainless planetary type. 
     2. Description of the Prior Art 
     The most common multiple speed bicycle uses a chain and derailleur system. The chain requires periodic cleaning and oiling to prevent premature chain failure and must be removed from the rear sprocket to change the tire. Chain maintenance is particularly troublesome if the bicycle is ridden extensively on dirt roads and trails. Also, when the rider is bearing down hard on the pedals on a hill, the derailleur usually will not carry the chain to a lower gear. Consequently, with a chain/derailleur system, the cyclist must anticipate the terrain and shift gears before getting on a hill in a gear that is too high, since he may not then be able to shift to a lower gear. Further, all the gears of a conventional ten or twelve speed drive are not efficiently usable because of the angle the chain makes with the sprockets, and shifting is not done in a simple set sequence that is easily mastered. These problems are eliminated with the present invention, as will be seen. 
     The transmission described in U.S. Pat. No. 2,505,464 by Debuit is a chainless type, located on the axis of the front wheel concentric with the pedal drive shaft, but Debuit&#39;s transmission is not planetary, is mounted alongside the wheel hub rather than inside it, is limited in the number of gear ratios it makes available (four plus a direct drive option), and carries the pedal torque through single gear teeth requiring large-tooth gears to prevent early fatigue failure. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide a compact, durable, low maintenance, multiple speed drive suitable for pedal powered vehicles intended for off-road operation, a particular embodiment being adapted for use on a bicycle camper, with gear ratios low enough to permit transporting the camper payload up steep grades, and high enough to permit conventional bicycle speeds on paved roads. 
     The three stage planetary driving wheel in accordance with the present invention includes a pedal drive shaft mounted in bearings on the axis of the wheel; a sun gear carrier, a planet gear carrier, and a ring gear all rotatably mounted inside the wheel hub; five sets of different size planet gears with three planet gears in each set mounted on bearings in the planet gear carrier, with each planet gear in constant mesh with a sun gear freely rotating on the sun gear carrier, and in constant mesh with the ring gear; a drive fitting with its axial position adjustable for selectively driving either the ring gear or the planet gear carrier from the pedal drive shaft; means for locking any selected one of the freely rotating sun gears to the sun gear carrier; means for selectively locking either the ring gear or the sun gear carrier to the vehicle frame; and three free-wheel ratchet mechanisms coupling, respectively, the planet gear carrier, the ring gear, and the sun gear carrier with the wheel hub. Five first stage speeds are obtained by driving the ring gear from the pedal drive shaft with the sun gear locked to the vehicle frame and with the planet gear carrier driving the wheel hub through the first free-wheel ratchet mechanism. A direct drive is obtained by driving the planet gear carrier from the pedal drive shaft with both the ring gear and the sun gear carrier free to rotate. Five second stage speeds are obtained by driving the planet gear carrier from the pedal drive shaft with the sun gear locked to the vehicle frame and with the ring gear driving the wheel hub through the second free-wheel ratchet mechanism; and five third stage speeds are obtained by driving the planet gear carrier from tne pedal drive shaft with the ring gear locked to the vehicle frame and the sun gear carrier driving the wheel hub through the third free-wheel ratchet mechanism. Thus, sixteen speeds are available with this particular embodiment of the present invention. 
     Other aspects and advantages of the present invention will become apparent from the following more detailed description taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a right side elevation view of the planetary driving wheel; 
     FIG. 2 is an enlarged cross sectional view taken along the line 2--2 of FIG. 1; 
     FIG. 3 is an enlarged partial view of the central portion of the wheel hub; 
     FIG 4 is a partial cross sectional view taken along the line 4--4 of FIG. 2; 
     FIG. 5 is a partial cross sectional view taken along the line 5--5 of FIG. 2; and 
     FIG. 6 is a partial cross sectional view taken along the line 6--6 of FIG. 2. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 2, the planetary driving wheel in accordance with the present invention includes a wheel hub 7; a ring gear 8; ring gear locking teeth 9; a sun gear carrier 10; sun gear carrier locking teeth 11; a planet gear carrier 12; a drive fitting 13; a second stage driving plate 14; a first and third stage driving plate 15; a right side vehicle frame interface fitting 16; a left side vehicle frame interface fitting 17; pedal crank arms 18; and pedal drive shaft 19. 
     The pedal drive shaft 19 is splined for the transfer of torque from the crank arms 18 to the drive fitting 13. The crank arms 18 and drive shaft 19 are held centered in the vehicle frame interface fittings 16 and 17 by the ball bearings 21. Each of the crank arms 18 is held seated against a splined washer 22 and snap ring 23 by a spanner bolt 20. The inner race of each of the bearings 21 is captive between a shoulder on its respective crank arm 18 and the washer 22, and the outer race is captive between a snap ring and a shoulder on its associated vehicle frame interface fitting 16 or 17. 
     The ring gear 8 is held centered on the right side vehicle frame interface fitting 16 by the ball bearing 34. The inner race of the bearing 34 is captive between a snap ring and a shoulder on the interface fitting 16, and the outer race is captive between a snap ring and a shoulder on the ring gear 8. The right side driving plate 14, which is installed in the wheel hub 7 with right hand threads so that the driving torque is tightening, is held centered on the ring gear 8 by the ball bearing 36. 
     The axial position of the drive fitting 13 is adjustable between an inboard position where it drives the planet gear carrier 12, and an outboard position where it drives the ring gear 8. The drive fitting 13 is held in its inboard position by the compression spring 33 which holds the drive fitting seated against a snap ring on the drive shaft 19. Movement to the outboard position is accomplished with the drive fitting positioner 31, which is fabricated in the form of a ball bearing with its inner race captive in the drive fitting 13, and its outer race keyed to axial tracks in the frame interface fitting 16. Axial location of the positioner 31 is controlled by the positioner actuation cable 32 which passes out through two axial holes in the vehicle frame interface fitting 16, wraps around a 90 degree radius in the outboard end of each of the axial holes, and, as seen in FIG. 1, wraps around the pulley 61 whose position is controlled by a two position lever of the vehicle frame. 
     As best seen in FIG. 6, the ring gear 8 has an internal spline 62 for engaging the drive fitting 13 which matches an identical internal spline in the planet gear carrier 12. As seen in FIGS. 2 and 6, a pair of spring loaded dogs 55 are installed in the ring gear 8 with steel pins 56. The dogs 55 engage machined cogs in the second stage driving plate 14 in a conventional free-wheel ratchet arrangement, and drive the wheel when the ring gear is driven by the selected set of planet gears. When the ring gear is driven by the drive fitting 13, a tooth on the drive fitting 13 engages a radial tab on each of the dogs 55 and holds the dogs out of engagement with the cogs machined in the driving plate 14 so that the wheel can be driven at a rate slower than the ring gear. 
     As seen in FIG. 2, the sun gear carrier 10 is held centered on the left side vehicle frame interface fitting 17 by the ball bearing 35. The inner race of the bearing 35 is captive between a snap ring and a shoulder on the vehicle frame interface fitting 17, and the outer race is captive between a snap ring and a shoulder on the sun gear carrier 10. The first and third stage driving plate 15, which is installed in the left end of the wheel hub with left hand threads so that the driving torque is tightening, is held centered on the sun gear carrier by the ball bearing 37. As seen in FIGS. 2 and 4, a pair of spring loaded dogs 58 are installed in the driving plate 15 with the steel pins 59 and engage cogs machined in the sun gear carrier 10 in a conventional free-wheel ratchet arrangement so that the sun gear carrier drives the wheel. As also seen in FIGS. 2 and 4, the spring loaded dogs 52 are installed in the first stage drive ring 26 with steel pins 53. The drive ring 26 is attached to the planet gear carrier 12 with three screws 51. The dogs 52 engage cogs machined in the driving plate 15 so that the ring 26 drives the wheel when the sun gear is locked against rotation. 
     As seen in FIG. 2, a split ring 27 is installed in each of five circumferential grooves in the sun gear carrier 10. An involute sun gear is installed over each of the five split rings with projections on the split rings 27 keying them to the gears, as seen in FIG. 5. The sun gears slide freely on oil-filled porous bronze bushings 25 which maintain the spacing between the gears. The five sun gears have 60, 66, 78, 96, and 126 teeth, respectively, as noted in FIG. 2. Speed selection is achieved through locking a selected one of the five sun gears to the sun gear carrier 10 by positioning a sun gear selector 28 in the plane of the selected gear with a sun gear selector actuation cable 29. 
     As seen in FIG. 5, four radial projections on the sun gear selector 28 slide in axial slots in the sun gear carrier 10 and key the split ring in the plane of which it is located to the sun gear carrier. The sun gear selector 28 is made up in the form of a ball bearing with the outer race keyed to and rotating with the sun gear carrier, and with the inner race keyed to an integral cylindrical extension of the vehicle frame interface fitting 17. The axial position of the selector 28 is controlled by the sun gear selector return spring 30 and the selector actuation cable 29 which passes out through two diametrically opposed axial holes in the vehicle frame interface fitting 17, wraps around a 90 degree internal radius in the end of each of the axial holes and passes out through two parallel holes orthogonal to the axial holes to wrap 180 degrees around a pulley 61 in an arrangement identical to that shown in FIG. 1 for the drive fitting positioner actuation cable 32. 
     As shown in FIG. 2, the planet gear carrier 12 is held centered inside an inboard cylindrical extension of the ring gear 8 by a ball bearing 38. The inner race of the bearing 38 is captive between a snap ring and a shoulder on the planet gear carrier 12, and the outer race is captive between a snap ring and a shoulder on the ring gear 8. Five sets of planet gears, with three planet gears in each set, are installed on bearings in the planet gear carrier 12, with each set of planet gears in constant mesh with the 174 tooth ring gear 8 and with one of the five sun gears freely rotating on the sun gear carrier 10. As shown in FIGS. 2 and 5, three 57 tooth planet gears, in mesh with the 60 tooth sun gear, are each mounted on a ball bearing 40 with the inner race of the bearing clamped in the planet gear carrier 12 by a screw 41. Three 54 tooth planet gears, in constant mesh with the 66 tooth sun gear, are mounted on the ball bearing 42 with the inner race of the bearing 42 clamped in the planet gear carrier 12 with a screw 43. Three 48 tooth planet gears, in constant mesh with the 78 tooth sun gear, are each mounted on a ball bearing 44 with a pin 45 in the planet gear carrier 12. Three 39 tooth planet gears, in constant mesh with the 96 tooth sun gear, are each mounted on a ball bearing 46 with the inner race of the bearing clamped in the planet gear carrier 12 with a screw 47. Three 24 tooth planet gears, in constant mesh with the 126 tooth sun gear, are each mounted on an oil-filled porous bronze bushing 50, with the bushing 50 rotating on a polished steel sleeve 49, with the sleeve 49 clamped in the planet gear carrier 12 by the screw 51. The three planet gears in each set are located 120 degrees apart, as shown in FIG. 5, and the planet gears in adjacent sets are located 60 degrees apart. 32 pitch gears are used in the 16-speed example design selected to illustrate the planetary driving wheel in accordance with the present invention. 
     The exposed outboard end of an integral cylindrical extension on the ring gear 8 has an external tooth form 9, and the exposed outboard end of an integral cylindrical extension on the sun gear carrier 10 has an identical external tooth form 11, which are used for locking the ring gear or the sun gear carrier against rotation through engagement with actuated blocks with mating tooth forms sliding in tracks on the vehicle frame. When the sun gear carrier 10 is locked against rotation and the ring gear 8 is driven from the pedal drive shaft 19 by the drive fitting 13, with the wheel hub driven by the planet gear carrier 12, the first stage gear ratio is given by (0.5N+n)/(N+n) where N is the number of teeth on the selected sun gear and n is the number of teeth on each of the three mating planet gears. 
     When the sun gear carrier 10 is locked against rotation and the planet gear carrier 12 is driven from the pedal drive shaft 19 by the drive fitting 13 with the ring gear 8 driving the wheel hub, the second stage gear ratio is given by (N+n)/(0.5N+n) where, as before, N is the number of teeth on the selected sun gear, and n is the number of teeth on each of the three mating planet gears. 
     When the ring gear 8 is locked against rotation and the planet gear carrier 12 is driven from the pedal drive shaft 19 by the drive fitting 13 with the sun gear carrier 10 driving the wheel hub, the third stage gear ratio is given by (N+n)/0.5N. In the table below the number of teeth on the selected sun gear and on each of its mating planet gears is given with the resulting gear ratios for each stage together with the vehicle speed for a pedal speed of 80 rpm and a 27 inch diameter driving wheel. In the example design selected to illustrate the planetary driving wheel in accordance with the present invention, 32 pitch gears are used with 174 teeth and a resultant pitch diameter of 5.4375 inches for the ring gear 8. 
     
         ______________________________________   SPEED   N      n       RATIO  MPH______________________________________first stage     one       126    24     .580  3.727     two       96     39     .644  4.138     three     78     48     .690  4.433     four      66     54     .725  4.659     five      60     57     .744  4.781   six     direct drive                      1.00     6.426second stage     seven     60     57    1.345  8.643     eight     66     54    1.379  8.861     nine      78     48    1.448  9.305     ten       96     39    1.552  9.973     eleven    126    24    1.724  11.078third stage     twelve    126    24    2.381  15.300     thirteen  96     39    2.813  18.076     fourteen  78     48    3.231  20.762     fifteen   66     54    3.636  23.365     sixteen   60     57    3.900  25.061______________________________________ 
    
     The gears and resulting gear ratios listed above are presented for illustrative purposes and the present invention should not be considered as limited to them. 
     While this invention has been described in terms of a preferred embodiment, it is anticipated that persons reading the preceding descriptions and studying the drawings will realize many possible modifications thereof. For example, two or four planet gears could be used in each set instead of three, and they could be rotatably mounted on the planet gear carrier with roller bearings or plain bearings instead of ball bearings. Likewise, the addition of a sun gear and mating set of planet gears would result in a nineteen speed planetary driving wheel, while the deletion of a sun gear and mating set of planet gears would result in a thirteen speed driving wheel. 
     It is therefore intended that the following appended claims be interpreted as including all such modifications and alterations as fall within the true scope and spirit of the present invention.