WO1998028182A2

WO1998028182A2 - Helical drive bicycle

Info

Publication number: WO1998028182A2
Application number: PCT/IB1997/001655
Authority: WO
Inventors: Mighel Doroftei
Original assignee: Helical Dynamics International Inc.
Priority date: 1996-12-23
Filing date: 1997-12-22
Publication date: 1998-07-02
Also published as: WO1998028182A3; US6199884B1; AU5775598A; US6213487B1

Abstract

A bicycle (11) with a drive mechanism (27) using reciprocal rectilinear pedal motion to propel a pinion gear (25) against a crown gear face (23) associated with a rear bicycle wheel (15), rotating the rear wheel (15). The pinion gear (25) receives motion from a helical member (37) surrounded by a slider (43). Each pedal (33) is united with the slider (43) which moves linearly along a guide or track, forcing rotation of the helical member (37) as the slider (43) is pushed rearwardly by a pedal (33). A freewheel or overrunning clutch (45) permits power transfer only when the pedal (33) moves rearwardly and allows freewheeling when the pedal (33) is reset.

Description

HELICAL DRIVE BICYCLE

TECHNICAL FIELD

The invention relates to bicycles, and more particularly to a bicycle frame and drive construction.

BACKGROUND ART The bicycle is a marvelous invention, supporting loads many times its own weight over all types of surfaces and terrain, yet powered by man, mostly without undue stress to the human body. According to Encyclopaedia Britannica, the earliest bicycle was invented in Scotland, about 1839, by Kirkpatrick MacMillan and improved a few years later by Gavin Dalzell. The modern bicycle, known also as the "safety bicycle", was invented by H. J. Lawson in 1876 and was first marketed in a useful form in 1885. One of the features of the modern bicy- cle is a chain or indirect drive, transferring power from pedals driving a crank below and forward of the saddle to a rear gear and axle associated with the rear wheel. Thus, bicycle design has basically remained the same for over 100 years, with improvements in materials, gearing, brakes and manufacturing methods. On the other hand, earlier bicycles, prior to the modern bicycle, frequently employed direct drive, i.e. direct transfer of power to a wheel without use of a chain or belt.

Both early and modern bicycles have relatively high centers of gravity because a rider is seated generally upright. The invention of the recumbent cycle lowers the center of gravity, but this is an exception. See, for example, U.S. Pat. No. 5,280,936 to D. Schmidlin or U.S. Pat. No. 5,242,181 to H. Fales et al . In U.S. Pat. No. 5,156,412, 0. Meguerditchian teaches a bidirectional rectilinear motion system for pedals of a bicycle whereby linear motion is converted to rotary motion for driving a chain and a rear wheel. The linear motion saves energy which is otherwise lost in providing circular motion to a crank. In U.S. Pat. No. 555,242 to J. Hannenbeck, a cycle is shown having pinions on the rear axle which are driven by reciprocating ped- als, connected to jointed arms having toothed sectors at the rearward ends for traveling around the pinions. U.S. Pat. No. 3,998,469 to F. Ruiz teaches a similar drive mechanism.

Notwithstanding advances of the prior art, there is a need for a more efficient bicycle which maximizes human power, while minimizing energy losses. An object of the invention was to provide such a bicycle.

SUMMARY OF THE INVENTION The above object has been achieved with a bicycle which features a direct drive mechanism realizing power from reciprocating rectilinear motion of the legs. The drive arrangement provides for rearward extension of the legs as the pedals are moved backwards, allowing for maximum pushing force similar to weightlifting, and at the same time matching human ergonomics. Pedals are guided along a track in a power assembly. An elongated bar is twisted along its axis by the pedals and is mounted for axial rotation. One end of the bar carries a pinion gear and is mounted next to the rear wheel hub, where a pair of crown gear faces are mounted in power transfer relation to the pinion gear. The crown gear faces may be either a pair of spaced apart gears on opposite sides of the rear hub or a single double sided gear integral with, or surrounding, the rear hub. The opposite end of the power assembly extends toward the front wheel at an angle for convenient pedal motion parallel to the assembly. Each pedal carries a slider which moves along the track of the power assembly and includes a slot which captures the cross-section of the helical bar. Motion of the pedals forces rotation of the helical bar. A freewheel mechanism at the end of the bar, coaxial with the pinion gear, allows power transfer fro the pinion to the crown gear only during rearward pedal motion, corresponding to rotation of the helical bar in one direction and freewheeling during the pedal reset motion. An arc-like position of the bicycle rider can produce a lower center of gravity compared to conventional bicycles, giving a better balance. Forward and downward curved handlebars, possibly made of a composite material, lower the frontal area and silhouette, and create a lower drag coefficient, as well as provide some shock absorption. In this manner, maximum power transfer from the human body to the driving wheel via the helical drive train is achieved. The increased efficiency of the bicycle of the present invention is realized particularly in sprint racing, where simplicity of design is a particular advantage. Since direct drive is used, the frame consists of a single hollow frame tube, a front fork tube for the front wheel and rear forks extending from the frame tube for the rear wheel. This drastically reduces weight compared to the safety bicycle, which typically features a triangular frame, plus front and rear fork tubes. An appropriate gear is selected by choice of front to rear wheel sizes, as well as gear ratios of the crown and pinion gears. In this application, bicycles are intended to include exercise cycles.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic plan side view of a bicycle in accord with the present invention. Fig. 2 is a top plan view of the bicycle of

Fig. 1.

Fig. 3 is a top plan view of an alternate embodiment of a drive mechanism used in the bicycle of Fig. 1. Fig. 4 is a front plan view of a pedal and slider mechanism. Fig. 5 is a top plan view of the slider mechanism of Fig. 4.

Fig. 6 is an alternate embodiment of the bicycle shown in Fig. 1. Fig. 7 is a side plan view of a bicycle wheel used in the embodiment shown in Fig. 6.

Fig. 8 is a sectional view of a clutch used to couple power from the drive shaft to drive gears.

Figs. 9-13 are alternate drive shaft construc- tions.

Fig. 14 is a cross-sectional view of a slider for the drive shaft of Fig. 13.

BEST MODE FOR CARRYING OUT THE INVENTION With reference to Figs. 1 and 2, a bicycle 11 is shown having a front wheel 13 and a rear wheel 15. A frame extends between the wheels with a frame bar 17 having rear forks 19 supporting a hub 28 of the rear wheel 15. The rear hub carries a pair of crown gears 23 on opposite sides of the hub facing the forks. A power assembly 27 has a first end 29 mounted near the rear hub and a free end 31 extending toward the front wheel, with each power assembly having a pedal 33 moving with linear motion along the length of the assembly. The power assembly 27 includes a mechanism, described below, for converting the linear reciprocal pedal motion to rotational motion of the crown gear 23, without a chain or belt, i.e. by direct drive. In Fig. 1, handle bar members 12 may be anchored to fork 14 below the tube 16 which contains steering bearings. This provides a rider with a lower center of gravity than found in the usual handle bar position.

In Fig. 3, the rear wheel hub 28 is seen to support a pair of pinion gears 25 and 26 on opposite sides of the rear wheel, not shown. Each of the power assemblies 27 include an elongated bar 37 having a helical twist about a central axis. Each bar is support- ed by bearings 39 and 40 for rotation about the axis in the direction indicated by arrow A. A linear track 41, parallel to the axis of the bar, guides an edge of a slider 43 so that the slider travels parallel to track 41 without twisting. Although not shown, a second track could be opposite and parallel to the first track, within or outside of a cylindrical housing for the power assembly. Slider 43 has a . rectangular slot for allowing the cross-section of bar 37 to pass therethrough, with bear- ings of the slider contacting the bar. The slot in the slider forces rotation of the bar as the pedals push the slider linearly toward pinion gear 25. Bar 37 and support bearings 39 and 40 may reside in the cylindrical housing 35 to keep dirt out of the slider and provide for smoother slider motion over the bar, but the housing is optional. Housing 35 has a lengthwise slot to permit pedal 33 to protrude therethrough. Similarly, housing 36 has a slot to permit pedal 34 to protrude therethrough and reciprocate linearly over the length of bar 37. A freewheel 45 or overrunning clutch connects pinion gear 25 to bar 37 and bearings 39 and 40. The freewheel member has the function of transferring torque from bar 37 to pinion gear 25 when the helical bar moves in one direction upon rearward pedal motion. However, during forward pedal motion, the freewheel member 45 idles, without power transfer. This is explained further below with reference to Fig. 8.

In one embodiment, as in Fig. 3, each bar 37 should be a steel or titanium member having a thickness of about 1/4 inch and a width of slightly less than 1 inch. The number of twists depends upon the desired ultimate velocity and the load being propelled. The length of each bar is between 12 and 18 inches, with a maximum of about 36 inches. It should be noted that when a pedal is pushed fully rearwardly, the pedal extends behind the rear hub because of a rearward offset 38 which allows the pedal to extend rearward of the rear hub 28, for maximum leg extension. Once the pedal 34 reaches its maximum rearward travel, a rider begins pushing the opposite pedal 35 so that pedal 33 may be disengaged from power transfer by the freewheel, depending on whether optional synchronizing gears 52 and timing gear 54 are used. If used to set the desired synchronism of the pedals, a pair of synchronizing gears 52 mesh with timing gear 54. A cable 56 will pull a flange 58, compressing spring 57 allowing the pedals to be positioned wherever desired by allowing freewheel turning of bars 37. Once set in a desired position, opposing pedals can be locked in place by allowing timing gear 54 to mesh with synchronizing gears 52. Note that crown wheels 23 and 24 rotate in the same direction, indicated by arrow B. This means that pinions 25 and 26 rotate oppositely. This can only occur when one pedal travels rearwardly and essentially drives both pinion gears, although the second pinion gear is idling where the optional synchronizing gears are not used. The rearwardmost pedal must be reset to a forward position, and this is done by allowing the corresponding helical bar to idle by means of a freewheel while the pedal is reset by a rider pulling the pedal back with a shoe cleat or the like fastened to the pedal.

In Figs. 4 and 5, the slider 43 has a central cutout region 61 which accommodates the helical bar. On either side of the helical bar are rollers, including a fixed roller 63 and an adjustable roller 65. The adjustable roller is biased by springs 67 and 69 to press the roller against the bar 61 for tight rolling contact. By providing springs, any dirt or debris which lands on the surface of the bar will still allow propulsion without jamming. Pedal 33 is a unitary metal or polymer member of strength such that the pedal does not bend significantly during maximum power strokes. The inward end of the pedal may be threaded for screwing into the slider, which is a metal block which may be made of sections to accommodate the bar opening 61 and the fixed and adjustable rollers 63 and 65.

Fig. 6 resembles Fig. 2, except that the spaced apart crown gears 23 and 34 of Fig. 2 have been joined together to form a single double-sided gear 100 having opposed gear faces 103 and 104. The opposed gear faces mesh with pinions 105 and 106 at the end of a respective power assembly 27. IJy collapsing the two crown gears together, the two gear faces may reside in a plane which is coplanar with the wheel itself. The single two-faced gear has a central aperture .for a hub to pass there through. However, unlike conventional hubs, the hub does not contain spoke flanges. The spoke flanges may be at the outer periphery of the gear, as shown in Fig. 7. In Fig. 7, wheel 110 includes a gear face 111 having a central aperture 113 for a wheel hub 114 to be connected thereto. At the radial outer periphery 115 of the gear face, holes exist for anchoring spokes 117, providing support for rim 119. The appearance of the opposite side of the wheel is substantially identical. Rim 119 is supported by spokes anchored at the outward radial periphery of opposing gear faces.

In Fig. 8, the rear end of bar 91 is fit as a spline within a rotary vane member 81 of overrunning clutch 80. The rotary vane is locked to the bar so that when the bar turns, the rotary vane also turns. Rotary vane 81 is fit within a tubular sleeve 83 which is connected to pinion gear 92. Rotary vane 81 has sloped shoulders 87 which serve to wedge cylindrical rollers 85 when the vane turns in the direction of arrow A, but allows free rolling of the rollers when the vane turns in the direction indicated by arrow B. Such overrunning clutches or free wheels are well known in conventional hub construction. The rear cycle hub may be equipped with conventional internal gears. A small chain extending into a metal sleeve coaxial with the hub is used to shift gears inside of the hub. Figs. 9-12 show helical drive bars with varying amounts of twist in each bar within a power assembly. In Fig. 9, the helical bar 91 has two full twists uniformly extending over the length of the shaft from the free end to the pinion gear 92. In the helical bar of Fig. 10, the bar 93 has a first portion 95, toward the free end of the helical bar which is identical to the bar of Fig. 9. However, toward the end 97 of the bar nearest the pinion gear 92, the bar twists more rapidly so that at the pinion gear, two-and-a-half twists have been made by increasing the rate of twist at end 97.

Even further twisting can be accomplished, as seen in Fig. 11, where once again the free end of the bar 96 has the same twist ratio as in Figs. 8 and 9, but the end of the bar, 99, closest the pinion gear 92, twists at a greater rate, achieving three full twists over the length of the bar. The rate of twist is varied to accommodate application of power to the power assembly. At the first portion of a power stroke, twisting is gradual to facilitate the initial application of energy to the bar. As the stroke progresses, rotational velocity of the bar would tend to increase if resistance were not provided. Additional resistance comes from increased twists, which allows greater amounts of power to be transferred to the pinion gear, while maintaining the slider at approximately a uniform velocity through the length of a stroke. Uniform velocity of the pedal allows maximum power transfer to the cycle and prevents leg muscles from becoming overly tired due to variations of effort.

A similar effect to varying the twist ratio may be achieved by tapering the bar. Fig. 12 shows a gradual taper along the length of bar 101. At the free end of the bar 103, where a stroke begins, full leverage across the width of the bar facilitates turning of the bar. As the slider progresses toward the center of the bar, less of the slider is in contact with the bar, and because the bar has narrower width, less of a mechanical advantage is obtained in turning the bar. Finally, at the end 105, the slider provides the minimal mechanical advantage to rotation of the bar, since the effective lever arm for twisting is shortest, thereby requiring greater effort from a rider. Thus, there is less resistance to turning the bar at the free end 103 and greater resistance at end 105, closest the pinion gear. This tapering effect tends to provide for uniform velocity of the slider across the length of the bar as power is initiated from the free end of the bar toward the pinion gear, as in the variable twist ratio designs shown in Figs. 10 and 11.

Fig. 13 shows a cylindrical member 111 in place of a bar. The cylindrical member has symmetric double helical grooves 113 and 115 over the length of the cylinder. Fig. 11 shows an annular slider 121 having splines 123 and 125 which follow helical grooves 113 and 115. Bearings 127 about the inner periphery of the slider provide for smooth contact with the cylinder 111. Slider 121 carries a pedal, not shown, and is a component of one of two power assemblies for each bicycle in the manner shown in Fig. 2. The helical grooves may be uniform over a length of a cylinder or may be varied in a manner of the helical bars, as shown in Figs. 10 and 11. In operation, the new bicycle drive system of the present invention produces a more efficient bicycle configuration. The drive system of the present invention is more closely linked to direct drive designs of the original bicycle than to the indirect drive mechanisms of modern bicycles. Additionally, the design of the bicycle of the present invention allows for a low center of gravity, small rider and cycle cross-sections in the direction of travel and an efficient power transfer mechanism. Although a bicycle with a face forward rider has been described, the drive mechanism of the present invention is also applicable to recumbent cycles where the rider is mounted with the head toward the rear of the cycle.

Claims

1. A bicycle comprising, spaced apart front and rear wheels supported by a frame extending between the wheels, the frame having rear forks supporting a rear wheel hub having a pair of opposed crown gear faces associated with opposite sides of the hub, a pair of pinion gears transferring rotary energy to the crown gear faces, the pinion gears mounted at ends of linear power assemblies having one end mounted near one of the wheel hubs and a free end extending toward the other wheel, each power assembly having a pedal moving linearly along the length of the assembly, the assembly having means for directly converting linear reciprocating pedal motion to rotational motion of the pinion gear without a chain or belt.

2. The bicycle of claim 1 wherein said opposed crown gear faces are formed on opposite sides of a unitary member coaxial with the rear wheel hub.

3. The bicycle of claim 1 wherein said opposed crown gear faces are formed on first and second members spaced apart on opposite sides of the rear wheel hub.

4. The bicycle of claim 1 wherein each power assembly comprises an elongated bar, supported by bearings with the assembly, helically twisted about an axis for axial rotation, with a housing associated with the assembly mounted parallel to each bar having a guide path for a pedal in linear movable relation along the assembly and having a slider in capture relation with the bar, the end of the bar near a pinion gear carrying a freewheel member supporting the pinidn gear for turning in one direction only corresponding to rotation of an associated helical bar in one direction as a pedal forces turning of the bar at the slider, but freewheeling during rotation of the associated helical bar in the opposite direction during pedal reset.

5. The bicycle of claim 1 wherein each power assembly comprises a cylinder, supported by bearings with the assembly, having helical grooves spiraling about an axis, with a means associated with the assembly mounted parallel to each cylinder for guiding a pedal in movable relation along the assembly and having a slider in capture relation with the cylinder, the rearward end of the cylinder carrying a freewheel member supporting the pinion gear for turning in one direction only corresponding to rotation of an associated cylinder in one direction as a pedal forces turning of the cylinder at the slider, but freewheeling during rotation of the associated cylinder in the opposite direction during pedal reset.

6. The bicycle of claim 4 wherein said bar is uniformly helically twisted from one end to the other.

7. The bicycle of claim 4 wherein said bar is non-uniformly helically twisted from one end to the other.

8. The bicycle of claim 4 wherein said bar is tapered from one end to the other.

9. The bicycle of claim ^"4 wherein said slider has bearings in contact with the bar.

10. The bicycle of claim 9 wherein said bearings extend uniformly across the bar.

11. The bicycle of claim 9 wherein said bearings are symmetrically spaced apart from the axis of the bar.

12. The bicycle of claim 1 wherein the power assemblies have pedal synchronizing gears mounted at the free ends.

13. A bicycle comprising, spaced apart front and rear wheels, each having a hub, supporting a frame, including a steering member, and a drive mechanism having a pair of helical members supported on opposite sides of the frame near the rear wheel and extending toward the front wheel, each helical member having twists about an axis for rotation about the axis, with a rigid track mounted parallel to each helical member, guiding a pedal in movable relation along the track, and having a slider in capture relation with the helical member, the rearward end of the helical member carrying a freewheel member supporting a pinion gear for turning in one direction only corresponding to rotation of an associated helical member in one direction, but freewheeling during rotation of the associated helical member in the opposite direction, and a pair of crown gear faces mounted in drive relation to the rear wheel, in gear communication with a respective pinion gear, such that reciprocal motion of the pedals along the helical members cause rotation of the helical members, thereby turning the pinion gears and the crown gear faces, with linearly reciprocal pedal motion communicating drive power through the pinion gears to associated gear faces and the rear wheel of the bicycle.

14. The bicycle of claim 13 wherein the helical member is a bar.

15. The bicycle of claim 13 wherein the helical member is a cylinder.

16. The bicycle of claim 13 wherein the frame comprises a single framebar extending from a position above the rear wheel hub horizontally toward the front wheel, a front forks tube extending from the front wheel hub upwardly to meet the framebar at a first junction and a steering tube extending above the front forks tube above the first junction.

17. The bicycle of claim 16 wherein said single framebar is arcuate.

18. The bicycle of claim 13 wnerein said opposed crown gear faces are formed on opposite sides of a unitary member coaxial with the rear wheel hub.

19. The bicycle of claim 13 wherein said opposed crown gear faces are formed on first and second members spaced apart on opposite sides of the rear wheel hub.

20. A drive mechanism for a bicycle of the type having spaced apart wheels supporting a frame comprising, a pair of helical members supported on opposite sides of the frame rtear a driven wheel and extending toward the opposite wheel, each helical member symmetric about an axis for rotation about a respective axis, with a rigid track mounted parallel to each helical member and guiding a pedal in movable relation along the track and having a slider in capture relation with the helical member, the end of the helical member near the driven wheel carrying a freewheel member supporting a pinion gear for turning in one direction only corresponding to rotation of an associated helical member in one direction, but freewheeling during rotation of the associated helical member in the opposite direction, and a pair of crown gear faces mounted in drive relation to the rear wheel, in gear communication with a respective pinion gear, such that reciprocal motion of the pedals along the helical members cause rotation of the helical members, thereby turning the pinion gear faces, communicating drive power to associated crown gear faces and the driven wheel of the bicycle.

21. The drive mechanism of claim 20 wherein said helical member is an axially twisted elongated bar.

22. The drive mechanism of claim 20 wherein said helical member is a cylinder.

23. A wheel for a bicycle comprising, a hub having an axis of rotation, a pair of crown gear faces facing in opposite directions and coaxially surrounding the hub, the radially outward periphery of each crown gear face having a flange portion adapted to receive first spoke ends, a wheel rim adapted to receive a bicycle tire, the rim also adapted to receive second spoke ends, and a plurality of spokes with first and second ends connecting the wheel rim to the flange portions of the crown gears.