GB2279303A - Two-wheel-drive bicycle. - Google Patents

Abstract

The bicycle comprises a toothed pulley F, Fig. 1 fitted to the rear wheel which transmits drive to a gearbox A, Fig. 2 mounted at the bottom of the bicycle head tube B, Fig. 2 by means of a toothed belt. Drive is taken from the gearbox at the head tube by means of a drive shaft B, Fig. 3, K, Fig. 2, to a gearbox A, Fig. 3 mounted on a free wheel hub at the front wheel. The drive belt may be provided with a tensioner, 1, Fig. 2. The gearbox at the head tube A, Fig. 2 may contain an epicyclic gear arrangement that allows steering to be effected whilst maintaining a constant speed of rotation of the output shaft. The drive components to the front wheel may be detachable. <IMAGE>

Description

TWO-WHEEL-DRIVE BICYCLE This invention relates to modifications to a pedal bicycle such that both wheels of the bicycle act in propelling the bicyle along.

A pedal bicycle is propelled by the feet of the rider which push against pedals hich are connected by means of cranks to a toothed chainwheel or chainwheels mounted on the frame which is(are) connectes by a chain to another toothed chainwheel or chainweels attached to the reat wheel of the bicycle which turns the rear wheel of the bicycle ro propelling the bicycle along.

This arrangement is satisfactory for road riding or modest offroad riding using an all-terrain of mountain bike. However, on more taxing off-road routes involving steep hills on muddy or gritty tracs, the rear-wheel drive bicycle begins to suffer from loss of adhesion of the rear wheel, especially when the rider is standing on the pedals, which results in transfer of the riders's weight off the rear driving wheel According to the presetn invention, a standard bycycle is modified by the addition of certain components the subject of this invention such that the action of the rider in turning the pedals of the bicycle causes the front wheel as well as the rear wheel to turn and thus act in propelling the bicycle.

According to the present invention, a toothed pulley is fixed to the rear wheel of the bicycle which drives a toothed drive belt which twists through an angle of ninety degrees as it transmits the driving force to another toothed pulley fixed to the underside of a gearbox mounted on the bottom of the bicycle head- tube from which a drive sat transmits the drive to a gearbox mounted on the splined hub of the front wheel. The design oW the gearbox mounted on the head-tube is such that transmission of the drive from the rear to the front wheels has no adverse effect crn the steering of the bicycle, and conversely that turning the steering has no effect on the rotation of the wheels.

A specific example of the arrangement of pulleys, belt and gearboxes and a specific design of the head-tube gearbox and te front wheel gearbox will now be described. Exact details of numbers of teeth, pitch circle diameter and DP number of the various gears and pulleys are given which produce the desired effect, however cther combinations of sizes could be used.

Figures 1 , 2 and 3 show a general arrangement of the additional components of this invention mounted on the bicycle.

Figure 1 shows the rear wheel of the bicycle viewed from behind and from the left hand side. The Wot lowing are the components of a normal bicycle and are not the subject of this invention. The wheel As is mounted in the frame B with the drive sprockets. C on the right hand side driven by the drive chain n which also runs on the rear derailleur E. The following items are additional components the subject of this invention. A toothed pulley F (54 teeth, 10mm pitxh, 16,, width) is fixed to the hub of the rear wheel by bolts of any other suitable method. A toothed belt G TWO-WHEEL-DRIVE BICYCLE runs. on the pulley and connects. to a FiulleY mounted on the headtube of the bicycle. The pulley F has a single flange on the wheel side to prevent the belt G from falling off.

Figure 2 shows the Front of the frame of the bicycle viewed from behind and from the right hand side. P gearbox h is mounted on the bottom of the head-tube B of the bicycle. A gear C is fixed to the head-tube c- the bicycle which engages. with a gear D on the top of the gearbos A. The gear C is fixed and does not rotate, also it is not a complete circle. The gearbox A is connected to the forks F by a stay E. This causes the gearbox to turn with the steering, which could be through an angle of up to ninety degrees in either direction. As the steering is turned, the gear D on the top of the gearbox A rolls around the fixed gear C on the head-tube B. The rotation of the gear D drives a compensating mechanism which ensures that the gearbox output shaft L (see below) does not turn relative to the forks when the steering is turned.. A toothed pulley G (24 teeth, 10mm pitch, 16mm width) is mounted on the underside of the gearbox A which engages with the toothed drive belt H (G in figure 1). The axis of rotation of the pulley G is at right angles to the axis of rotation of pulley F (figure 1) fixed to the rear wheel and the drive belt H (G in figure 1) twists between the pulleys to allow for this. A tensioner I is fixed to the bicycle down-tube J, which serves the dual purpose of maintaining a suitable tension in the belt, and of guiding the belt around the down-tube so that it aligns correctly with the top of the pulley (F in figure 1) fixed to the rear wheel. P drive shaft K engages with the output shaft L | of the gearbox A and transmits the driving Worce to the gearbox mounted on the splined hub of the front wheel. Items B (head.tube), F (forks) and J (down-tube) are parts of a normal bicycle and are not the subject of this invention.

Figure 3; shows the front wheel of the bicycle viewed from the right hand side. The hub of the front wheel is a splined freewheel component commonly fitted to the rear wheel of a normal bicycle. The freewheel hub allows the front wheel to rotate Waster than the rear wheel when the steering is turned. A gearbox A the subject oW tis invention slide over the splines of the hub. . A drive shaft B engages with the input shaft C oW the gearbox A and engages also with the output shaft L. (figure 2) of the gead-tube-mounted gearbox A (figure 2). The right side Work C of the bicycle is shaped as illustrated in order to clear the top oW the gearbox A whilst engaging with the front wheel spindle. A stabiliser arm D is fixed to the fork C which engages with a recess in the casing of the gearbox A to resist the rotational farce which is the reaction to the turning force of the driveshaft B.

Figure 4 shows a side view of the head-tube-mounted gearbox with the side cover plate removed, and figure 5 shows a vertical section through the centre of the gearbox. The gearbox casing comprises a flat rectangular top plate A, a Wlat rectangular bottom plate B, a flat rectangular end plate C at each end, and a WIat rectangular side plate on each side (not shown). The gearbox is held together by a bolt at each corner and a bolt each side in the middle passing vertically through the gearbox (not TWO-WHEEL-DRIVE BICYCLE shown). The top and bottom plates each have two large circular holes into each of which is fitted a circular insert D machined externally to fit into the holes from the inside of the gearbox winthout passing completely through, and machined internally to accept a bearing inserted from the inside of the gearbox. The gearbox casing components A, B, C and D could be made from castings, mouldings or pressings or parts machined from solid blocks and be made as fewer components without affecting the substace of this invention.

The following descroption of the internal components of the headtube-mountd gearbox is not in the order in which the gearbox would be assembled and fitted to the bicycle. All gears are shown on the diagrams without teeth.

A tube E slides upwards into the bottom of the bicycle down-tube (not shown). A small stepped tube F fits into the matching bottom of the tube E, and into this is fitted the standard bicycle steering bottom bearing G. The sstem of the front forks of the bicycle (not shown) passes through items, G, F, E and the bicycle head tube and js secured normally at the handlebar stem with the steering top ball race (not shown). A gear H (20 DP, 50 teeth, 2. 5" FCD) has a large hole in the centre and has a tubular extension I on the bottom which has a step J and a threaded end section 1:: which starts with a step. This gear rests on a bearing L:l inserted in the machined insert D1 in the bottom plate of the gearbox B. A toothed pulley M is threaded internally and is screwed onto the threaded bottom section K of gear H until it meets the step P bearing L2 Wits inside the pulley N and is held in position by the small stepped tube F. The drive from the rear wheel is accepted by the pulley M, which in turn turns the gear H. The top of gear H has a recess in which is inserted a bearing L3. Above bearing L3 is a spacing washer N and a bearing L4 which Wits inside insert D2 in the gearbox top plate P and butts against a shoulder on head-tube extension tube E.

When the gearbox is fitted to the bicycle down-tube and the forks are inserted and tightened, the bicycle down-tube, tube E, tube F and bearing G Worm a rigid assembly. During operation oW the bicycle, pulley M and gear H with its extension form a single rotating mass which rotates around tube E on bearings L2 and L3.

The main gearbox casing rotates with the steering around tube E on bearing L4 at the top , and around the extension to gear H on bearing L1 at the bottom.

Gear H meshes with a gear O (20 DP, 50 teeth, 2.5" PCD). Gear O has a hole in the centre, a tubular extension P on the top, and is recessed underneath with four spindles Q arranged evenly round the centre fixed to the top of the gear racing downwards through the recess. On each spindle is placed a roller bearing P and a gear S (32 DP, 20 teeth, .625" PCD) held in position by a circlip T. The roller bearings P improve efficiency but may be omitted to reduce cost and weight. P bearing L5 slides over the extension P of gear O with the inner race resting on a small shoulder. Bearing L5 Wits inside insert D3 which Wits into the gearbox top plate 4. A shaft gear U (2 DP, 20 teeth, .625" PCD) has a step V at the bottom and a step W towards the top. Shaft gear W fits inside gear 0 and its extension P and meshes. with the four gears S. A bearing L6 Wits inside extension P, and shaft TWO-WHEEL-DDRIVE BICYCLE gear U fits inside bearing L6 located by the soulder W. An internally-toothed gear X (32 DP, 60 teeth, 1.875" PCD) has a tubular wxtension Y and a splined output shaft Z. The splines may be conventional splines or as shown in figure 5a. The open end of the internally-toothed gear X fits over the four gears S in the recess in the underside of gear O. A bearing L7 Wits over the tubular extension Y of internally-toothed gear X with the inner race resting on a small shoulder. Bearing L7 fits inside insert D3 which fits into the gearbox bottom plate B. A bearing L8 fits inside extension Y of internally-toothed gear X, and the step V at the bottom of shaft gear U fits inside bearing L8. A gear AA (16 DP, 16 teeth, 1" PCD) is attached by any suitable method to the top of shaft gear U. Gear AA (gear D in figure 2) meshes with gear C in figure 2.

The drive from the rear wheel by means of the drive belt is received by pulley M which turns gear H. Gear H turns gear O on which are fixed the four gears 8. If shaft gear U is stationary, internally-toothed gear C (and consequently output shaft Z) rotates with a speed increase of ; to 4 relative to gear 0. If the steering is turned, shaft gear U is turned by gear AA as it rolls round gear C fixed to the head tube in figure 2. At the same time, gear 0 rolls rotund gear H. The combined effect of these movemetns is that the internally-toothed gear X does not move relative to the gearbox and therefore the output shaft Z does not turn relative to the fors. The result is that power passes through the gearbox whatever the position of the steering, and turning the steering does not turn the output shaft.

Figures 6 to 9 show the gearbox which is mounted on the splined front wheel hub (A in figure 3). Figure 6 shows a side view of the gearbox, figure 7 shows a section through the centre of the gearbox, figure 8 shows a top view of the gearbox and figure 9 shows an end view.

The gearbox casing consists of a bottom plate P, a top plate b, a housing C and end spacers D. These components could be made as castings, pressigs or mouldings or could he machined from solid blocks and be made as fewer components and as a fully enclosed unit without aFfecting the substance of the invention. The bottom plate P has a machined insert E and the top plate B has a machined insert F in which run ball bearing G. A bevel gear H (60 teeth,16 DP, 95.25.. PCD) has a splined centre hole to match the bicycle front hub splines, and grooves in the top and bottom surfaces in which run ball bearings and which align with the inserts E and F in the bottom and top plates A and B. Instead of inserts and separate ball bearings, manufactured bearings could be used. The housing C is bolted to the bottom plate A. The housing C contains a bevel gear I (20 teeth, 16 DP, 31.75 PCD) which has an input shaft J with a shoulder X, a threaded section L and a splined end M. The bevel gear I runs in two bearings N, and is held in position by a nut and locknut O. The top plate B is bolted to the housing C by bolts P, and to the bottom plate A with bolts Q through spacers D. The splines M on the input shaft J of gear I may be conventional splines or mat be as shown in figure 9. . The housing C has a recess R cut in the top.

Stabiliser arm D in figure 3 engages with this recess to prevent the gearbox from twisting as an opposite reaction to the turning force of the gear I.

TWO-WHEEL-DRIVE BICYCLE Figure 10 shows the tensioner (I in figure 2) which is mounted on the bicycle down-tube to guide the slack side of the drive belt round the bicycle down-tube and maintain a suitable tension. A square casing A has a threaded end section B of a smaller diameter than the distance between the faces of the main casing.

A threaded adjuster C fits into the threaded end section. A square shaft D with an integral housing E slides inside the casing A its position determined by the position of the adjuster C. A bolt F passes through the housing E, and a roller bearing G rotates around the bolt F. The drive belt (H in figure 2) runs over the roller bearing, and the adjuster C is turned to provide the required tension, being looser for normal riding and tighter for steep hill climbing.

Claims (6)

1. TWO-WHEEL-DRIVE BICYCLE CLAIMS What I claim is: 1) A mechanism for the transmission of the driving force of the rear wheel of a bicycle to the front wheel of the bicycle comprising a toothed pulley attached to the rear wheel of the bicycle, a toothed drive belt which runs round that pulley, a gearbox mounted on the bottom oW the bicycle head tube with a toothed pulley which accepts the driving force from the belt driven by the rear wheel pulley, a gearbox mounted on the hub nF the front wheel oW the bicycle, a drive shaft to connect the head-tube gearbox to the front wheel hub mounted gearbox and a tensioner mounted on the bicycle down-tube to tension and guide the drive belt.
2. 2) A mechanism as in claim 1 in which the gearbox mounted on the bicycle head-tube rotates with the steering through an angle cat up to ninety degrees in either direction.
3. 3) A mechanism as in claim 1 in which the gearbox mounted on the bicycle head-tube contains a compensating mechanism which comprises an epicyclic arrangement of gears within the gearbox, a gear fixed to the bicycle head-tube and a gear attached to a shat within the epicycle gear arrangement which rolls around the gear fixed to the bicycle head--tube which allows power to pass through the gearbox whatever the position of the steering whilst preventing any change in the speed of rotation of the output shaft due to the turning of the steering.
4. 4) A mechanism as in claim 1 in which the gearbox mounted on the Front wheel hub is detachable by sliding the gearbox off the splines oW the hub when the wheel is removed fro the bicycle.
5. 5) A mechanism as in claim 1 in which the front driveshaft ii detachable by sliding the driveshaft off the splines of the head-tube mounted gearbox and the f front wheel hub mounted gearbox when the front wheel is removed from the bicycle.
6. 6) P mechanism as in claim 1 in which the front forks mounted gearbox may be removed from the bicycle ty sliding it out of the bottom of the bicycle head-tube and detaching it from the forks stay, after which the bottom steering bearing and Works can be replaced in the bicycle head-tube as a normal bicycle.