GB2178709A - Chainless bicycle - Google Patents

Abstract

A chainless bicyle has a driving mechanism which is mounted on the frame of the bicycle and which includes a housing (10) attached to the front ends of the rear fork tubes (20). A crank shah (30) is transversely mounted in the housing and has cranks (36) attached to its two ends. Pedals are pivoted to the cranks. First gear transmission means includes a first shaft (50) longitudinally mounted in one of the rear fork tubes, and intermeshed gears (43, 44) mounted on the first shaft and the crank shaft, respectively. A second shaft (80) is mounted transversely between the tips (22) of the rear forks, and a rear wheel hub (70) is rotatably mounted on the second shaft. Second gear transmission means includes a second set of intermeshed gears (61, 62) mounted on the first shaft and the hub to drive the wheel. A free-wheel mechanism may be provided in the housing or in the hub, and change-speed gearing may be provided in the housing. <IMAGE>

Description

SPECIFICATION Chainless bicycle This invention relates to a chainless bicycle, and particularly to the transmission mechanism of a bicycle which does not require a transmission chain.

While there are many kinds of bicycle, in general a bicycle comprises, as shown in Figure 1 of the accompanying drawings, a top tube (crossbar) 1, a down tube 2, a seat tube 3, a seat stay 4, two rear fork tubes 5, a front fork 6, a crank shaft 7, two cranks 71, two pedals 72, a chainwheel 8, a chain 9, handlebars 110, a saddle 111, a front wheel and a rear wheel. The driving and transmission of such a bicycle are accomplished in such a manner that the crank shaft is rotated by operating the pedals and the crank, and the movement of the crank shaft is transmitted to the rear wheel through the chainwheel 8 and the chain 9. This type of the transmission system has been utilized for many years. However, it has a disadvantage in that dusty material easily adheres to the chain, so that in use of the bicycle the material may soil the clothing of the rider.If the chain is covered by a chainguard, the chainguard, which is easily distorted by impact, can cause undesirable noise by making contact with the moving chain.

An object of the invention is to provide a chainless bicycle to alleviate the above-mentioned disadvantages.

According to the invention there is provided a bicycle, comprising a frame which includes a front fork and a rear fork, the rear fork comprising two rear fork tubes and rear fork tip plates at the rear ends of the rear fork tubes respectively; a front wheel attached to the front fork; a drive mechanism which is mounted on the frame and which includes a housing attached to the front ends of the rear fork tubes, a crank shaft transversely mounted in the housing and having the two ends thereof extending out of the housing, a respective crank member attached to each end of the crank shaft, a respective pedal attached to each crank member, first gear transmission means which includes a first shaft longitudinally mounted in one of said rear fork tubes, and a first set of intermeshed gears mounted on the first shaft and the crank shaft; a second shaft having the two ends thereof mounted to the rear fork tip plates; a rear wheel assembly which includes a rear wheel with a hub rotatably mounted on the second shaft; and second gear transmission means which includes a second set of intermeshed gears mounted on the first shaft and the hub.

The first gear transmission means may include a third transmission shaft mounted in the housing parallel to the crank shaft, and a set of speed change gears mounted on the crank shaft and the third transmission shaft.

The rear side of the housing may be provided with two apertures and two tubular mounting seats mounted in the apertures with one of the mounting seats extending into the housing, the front ends of the rear fork tubes being fitted in the mounting seats.

The transmission means may include a freewheel assembly which may be mounted on the crank shaft or on the hub of the rear wheel assembly, and which limits driving of the rear wheel assembly to a single angular direction.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a conventional bicycle, as described above; Figure 2 is an exploded view of a crankoperated part of a drive mechanism of a bicycle according to the present invention; Figure 3 is an exploded view of a wheeldriving part of the drive mechanism, associated with a rear fork tube and a rear fork tip plate; Figure 4 is a partly-broken away sectional view of the crank-operated part of the drive mechanism shown in Figure 2, in combination with the wheel-driving part shown in Figure 3; Figure 5 is a sectional view of a crank-operated part of a drive mechanism which includes a set of speed-change gears; Figure 6 is a sectional view of a crank-operated part of a drive mechanism which includes a crank shaft with a freewheel;; Figure 7 is a sectional view taken along a line 7-7 of Figure 6; and Figure 8 is a sectional view of a wheeldriving part of the drive mechanism to be used in connection with crank-operated part of Figure 6.

Referring to Figure 2 of the drawings, there is shown a bicycle incorporating a driving mechanism which includes a box 10 which is mounted on the frame of the bicycle in such a manner that the rear side thereof is connected to the front ends of a pair of rear fork tubes 20 and the top thereof is connected to the lower ends of a down tube 11 and a seat tube 12. The front ends of the rear fork tubes 20 are inserted into two tubular mounting bosses 13 and 14 which are fixed to the rear side wall of the box 10. Two tubular mounting seats 15 and 16 are provided in two opposite side walls of the box 10 for mounting a crank shaft 30, and two tubular mounting seats 17 and 18 are provided for mounting a rotary shaft 45. The mounting seats 15 and 16 are provided with internal screw threads 151 and 161 respectively.The bottom of the box is provided with a bottom cover 19 which is attached to the box by means of screws 191.

Referring also to Figure 4, the crank shaft 30 has two retaining rings 31 and 32 and is journalled in two ball retaining nuts 312 and 322 which are threadedly inserted in the mounting members 15 and 16. A locking nut 33 is attached to the ball retaining nut 322 and abuts with the end face of the seat 16.

Steel balls 311 are provided between the retaining ring 31 and the ball retaining nut 312, and steel balls 321 are provided between the retaining ring 32 and the nut 322. A respective crank 36 is attached to each end of the shaft 30 by means of a cotter pin 34 and a nut 35. A respective pedal (not shown) is attached to the end of each crank.

A gear 41 is mounted on the intermediate portion 37 of the shaft 30 by means of a key 411 and a screw 412. A spur gear 42, which is meshed with the gear 41, and a bevel gear 43 are mounted on the shaft 45. The shaft 45 is journalled in two bearing assemblies 451 and 452 which are mounted in the two mounting seats 17 and 18 provided in the walls of the box 10. A nut 453 is attached to the threaded end of the shaft 45, and two cap nuts 454 and 455 are fixed to the mounting seats 17 and 18.

The bevel gear 43 is meshed with another bevel gear 44 which is mounted on a shaft 443 by means of a key 442 and a screw 441. The shaft 443 is rotatably mounted in the tubular mounting member 14 by means of a bearing assembly 444 and a cap nut 445.

At one end of the shaft 443 is provided an axial recess 446 of rectangular cross-section which is used to receive a portion 51 of rectangular cross-section of a shaft 50. The shaft 50 is mounted in one of the rear fork tubes 20 so as to be extended to the rear wheel.

Referring to Figs. 3 and 4, to the end of the rear fork tube 20, which is adjacent to the seat stay 21, is attached a plate or a rear fork tip 22. The plate 22 is provided with apertures 221 and a notch 222 which is used for mounting a shaft 80 of the rear wheel. The rear end of the shaft 50 has a rear end portion 52, of rectangular cross-section, which is extended out of the rear fork tube 20 and inserted into a bore 613 of the shank 611 of a bevel gear 61. Onto the shank 611 are sleeved a bearing seat 618, a bearing retaining nut 616 and a locking nut 617. The nuts 616 and 617 are engaged with the screw thread 612 of the shank 611. Steel balls 614 are provided between the bevel gear 61 and the bearing seat 618, and steel balls 615 are provided between the bearing seat 618 and the retaining nut 616.The bearing seat 618 is connected to the plate 22 with screws 620 which are threaded into the holes 619.

The hub 70 of the rear wheel comprises a tubular body 71 which is sleeved onto the shaft 80 and on which are sleeved two spoke nipple mounting seats 72. Two ball retaining bowls 73 and two dust covers 74 are fitted into the two hollow ends of the tubular body 71 and the bearing steel balls 75 are held in the retaining bowls by attaching retaining nuts 76 and 77, sleeves 81 and 82, washer plates 83 and 84, and locking nuts 85 and 86 to the shaft 80.

Each of the spoke nipple mounting seats 72 is provided with mounting holes 721 for the mounting of the spoke nipples (not shown).

One of the spoke nipple mounting seats 72 is provided with a screw thread 722 through which a freewheel assembly is mounted on the hub 70. The freewheel assembly can regulate the rotation of the rear wheel so that the rear wheel can only rotate in a single direction. It includes a ball retaining seat 90 which is threadedly coupled with the mounting seats 72, and is provided with two annular grooves 901 and 902 for receiving steel balls 95, and two recesses 903 into which are fitted two pawls 93 and two springs 94. The steel balls 95 are held against the grooves 901 and 902 by a ratchet wheel 91 and a cap nut 92, which are threadedly interconnected and are provided around the seat 90. The inner side of the ratchet wheel 91 is provided with inclined teeth 911, which surrounds the retaining seat 90, and an internal screw thread 912.The pawls 93 are biassed by the corresponding springs 94 so that they are in contact with the inclined teeth 911. The pawls 93 will catch the inclined teeth 911 when the ratchet wheel 91 is rotated in a direction that will cause the rear wheel to move backward.

There is further provided a bevel gear 62 which is meshed with the bevel gear 61 and is sleeved onto the retaining nut 77 and the sleeve 82. The ratchet wheel 91 is coupled with the bevel gear 62 by means of its internal screw thread 912. A locking nut 96 is further provided adjacent to the cap nut 92, and is threadedly coupled with the ratchet wheel 91.

In operation, the movement of the crank shaft 30 is transmitted to the shaft 45 through the gears 41 and 42, from which the movement is transmitted to the shaft 443 and the shaft 50 by means of gears 43 and 44.

The movement of the shaft 50 is then transmitted to gear 62 through the gear 61.

Since the gear 62 is in connection with the hub 70 because of the ratchet wheel 91, pawls 93, and the ball retaining seat 90, the hub 70 is finally driven by the crank shaft 30.

The direction of the rotation of the hub 70 or the rear wheel is limited to a single direction by the pawls 93 and the ratchet wheel 91.

Referring to Fig. 5, there is shown another embodiment of the invention, wherein the shafts 30 and 45 are provided with a set of speed change gears a, b, c, d, e and f. Although the number of the gears in Fig. 5 is six, it is simply an illustrative example and can be varied as required.

Referring to Figs. 6, 7 and 8, there is shown a further embodiment in which the size of the box 10 is reduced and the driving mechanism does not include the shaft 45. A crank shaft 30 is mounted in the box 10 in the same way as above described. At the intermediate portion of the crank shaft 30 is a portion of larger diameter from around which protrudes an annular member 301. A ratchet gear 302 is sleeved onto the portion of larger diameter and is provided with inclined teeth (not shown) to be engaged with pawls 303 provided in the annular member 301. Steel balls 304 are provided between the adjacent surfaces of the annular member 301 and the ratchet bevel gear 302, and between the adjacent surfaces of the annular member 301 and a cap nut 305 which is threadedly sleeved onto the ratchet gear 302 to retain the balls 304 in their place.

A bevel gear 308 which is meshed with the ratchet gear 302, is mounted on a shaft 443 which is mounted in the mounting seat 14 as described in the previous embodiment. However, the shaft 443 in this embodiment is prolonged and extended to the opposite wall at which the shaft 443 is journalled in a bearing assembly 447. There is also another difference between this embodiment and the previous embodiments in that the shaft 30 and the shaft 443 lie in two different planes.

Fig. 8 shows the hub 70 of the rear wheel and the shaft 50 mounted in the rear fork tube 20. Since the freewheel assembly, i.e.

the assembly of the ratchet gear 302 and the pawls 303, which is used to restrict the rotation of the rear wheel to a single direction is mounted on the crank shaft 30, the hub 70 is not provided with a freewheel.

In view of the above-mentioned embodiment, it can be seen that the configuration of the bicycle according to the invention is quite different from that of the conventional one.

The gears used in the drive mechanism of the invention should preferably be made of plastics material, rather than metal, in order to reduce the total weight of the bicycle.

Claims (6)

1. A bicycle, comprising a frame which includes a front fork and a rear fork, the rear fork comprising two rear fork tubes and rear fork tip plates at the rear ends of the rear fork tubes respectively; a front wheel attached to the front fork; a drive mechanism which is mounted on the frame and which includes a housing attached to the front ends of the rear fork tubes, a crank shaft transversely mounted in the housing and having the two ends thereof extending out of the housing, a respective crank member attached to each end of the crank shaft, a respective pedal attached to each crank member, first gear transmission means which includes a first shaft longitudinally mounted in one of said rear fork tubes, and a first set of intermeshed gears mounted on the first shaft and the crank shaft; a second shaft having the two ends thereof mounted to the rear fork tip plates; a rear wheel assembly which includes a rear wheel with a hub rotatably mounted on the second shaft; and second gear transmission means which includes a second set of intermeshed gears mounted on the first shaft and the hub.

2. A bicycle as claimed in claim 1, in which the rear side of the housing js provided with two apertures and two tubular mounting seats in the apertures, one of the mounting seats extending into the housing; and wherein the front ends of the rear fork tubes are fitted, respectively, in the mounting seats.

3. A bicycle as claimed in claim 1 or claim 2, in which the first shaft extends into the housing; wherein the first set of gears includes a ratchet bevel gear, which acts as a first freewheel assembly to limit driving of the rear wheel assembly to a single angular direction, mounted on the crank shaft, pawl means for engaging with the ratchet bevel gear disposed on the crank shaft, and a first bevel gear which is meshed with the ratchet bevel gear and is mounted on the front portion of the first shaft.

4. A bicycle as claimed in claim 1 or claim 2, wherein the first gear transmission means further includes a set of speed change gears.

5. A bicycle as claimed in claim 1 or claim 2, in which the second set of gears includes a second bevel gear mounted on the rear portion of the first shaft, and a third bevel gear which is meshed with the second bevel gear and is mounted on the adjacent portion of the second shaft; wherein the second gear transmission means further includes a freewheel assembly, which limits driving of the rear wheel assembly to a single angular direction, the freewheel assembly having a ratchet wheel which is mounted on the hub and is connected to the third bevel gear, and pawl means for engaging the ratchet wheel.

6. A bicycle substantially as hereinbefore described, with reference to Figures 2-8 of the accompanying drawings.