GB2143599A

GB2143599A - Two-speed gear for a bicycle

Info

Publication number: GB2143599A
Application number: GB08318738A
Authority: GB
Inventors: Liu Jo-Kuei
Original assignee: JO KUEI LIU
Current assignee: JO KUEI LIU
Priority date: 1983-07-11
Filing date: 1983-07-11
Publication date: 1985-02-13
Also published as: GB2143599B; GB8318738D0

Abstract

A two-speed gear for a bicycle which the chain (24) extends around two gear wheels (21, 22) of different sizes on the rear wheel axle, each said gear wheel driving the rear wheel when rotated forwards but free-wheeling when rotated backwards, whereby the rear wheel is driven at different speeds by respective forward and rearward rotation of the pedal-driven chain wheel (25). <IMAGE>

Description

SPECIFICATION Gears This invention relates to gears, particularly but not exclusively for bicycles and tricycles. Of course, multi-gear mechanisms for bicycles have been known for very many years, but they are all more or less complicated and prone to failure in operation, as well as being expensive to manufacture.

Furthermore, although the general user feels a need for more than a single gear, he does not find much use for a multi-gear mechanism. It is therefore one object of the present invention to provide a simple, reliable and inexpensive two-gear mechanism for a bicycle or tricycle.

According to the invention there is provided a two-speed gear comprising a driving wheel, two driven wheels of different diameters mounted on an axle parallel to the axis of the driving wheel and each connected to said axle so as to drive the same when rotated in one (and the same) direction and to free-wheel thereon when rotated in the other direction, and an endless transmission element drivingly interconnecting said driving and driven wheels in such a manner that rotation of the driving wheel in either direction causes the driven wheels to rotate in mutually opposite directions, whereby rotation of the driving wheel in one direction causes one of said driven wheels to drive the axle and the other driven wheel to free-wheel, whilst rotation of the driving wheel in the other direction causes the said other driven wheel to drive the axle and the said one driven wheel to freewheel.

Thus the axle is driven in the same direction but at different speeds depending on the direction of rotation of the driving wheel. When the concept is applied to a bicycle to drive the rear wheel, forward rotation of the driving wheel by the pedals drives the rear wheel at one speed, e.g. in low gear, whilst rearward rotation of the driving wheel drives the rear wheel at another speed, e.g. in high gear. Clearly the principles of the invention may be applied not only to a bicycle (or tricycle) but to any apparatus in which a simple and reliable means of driving an axle at two different speeds is required.

In a preferred arrangement the said endless transmission element extends, from the said driving wheel, first around one of the driven wheels in one direction, then around an idler wheel, then around the other driven wheel in the other direction, and then back to the driving wheel. The said idler wheel is preferably spring-biassed away from the said driven wheels to tension the said endless transmission element.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is the side view of a bicycle according to the invention; and Figure 2 is a diagram illustrating an alternative arrangement of a two-speed gear according to the invention.

Figure 1 shows how a two-speed gear of the invention is applied to a bicycle. The apparatus includes two driven gear wheels 21, 22 of different sizes mounted on the rear wheel axle 11, and an idler gear wheel assembly 23. An endless transmission element in the form of a chain 24 extends around a pedal-driven driving wheel 25, the two driven gear wheels 21, 22 and an idler gear wheel 232. Each of the two gear wheels 21, 22 drives the rear wheel axle only when rotating clockwise; they free-wheel when rotating counter clockwise; and the arrangement is such that when one of them ro- tates clockwise the other has to rotate counterclockwise.

The idler gear wheel assembly consists of mounting member 231, idler gear wheel 232, idler gear wheel base 233, spring 236, bolt 234, and nut 235; mounting member 231 is secured to the bicycle frame 12 and supports bolt 234, idler gear wheel 232 is fixed on base 233 which is mounted on one end of bolt 234, bolt 234 passes slidably through a hole 237 in mounting member 231, and spring 236 encircles bolt 234, on which nut 235 is screwed.

Chain 24, if driven counterclockwise by driving wheel 25, goes in order from the top of wheel 25 past the top and bottom of gear wheel 21, the bottom and top of idler gear wheel 232, then past the bottom and top of gear wheel 22, and finally to the bottom and back to the top of wheel 25, the original starting point. On the other hand, if driven clockwise by driving wheel 25, chain 25 goes in order past the top and bottom of gear wheel 22, the top and bottom of idler gear wheel 232, then past the bottom and the top of gear wheel 21, and finally to the top and back to the bottom of driving wheel 25, the original starting point.

When driving wheel 25 is turned clockwise by the pedals to drive the chain 24 in the direction A as shown in Figure 1, gear wheel 21 turns clockwise, while gear wheel 22 turns counterclockwise, whereby gear wheel 21 drives the rear wheel axle whilst gear wheel 22 free-wheels thereon. On the other hand, if the pedals are turned counterclockwise gear wheel 22 drives the rear wheel axle but gear wheel 21 free-wheels. When the pedals are not moved but the bicycle is moving, both gear wheels 21, 22 are effectively turning counterclockwise and therefore free-wheel.

The purpose of idler gear wheel assembly 23 is to keep the slack side of chain 24 in proper tension so that the chain 24 will not come off; a desired tension may be set by turning nut 235 to compress or relax spring 236.

Thus the gear of Figure 1 provides two different speeds, a fast one operated by pedaling forwards (clockwise), and a slow one operated by pedaling backwards (counterclockwise). Figure 2 shows a reversed arrangement as compared with Figure 1, providing a slow speed by pedaling forwards and a fast speed by pedaling backwards.

In general, a two-speed gear according to preferred embodiments of the invention has been found to have several advantages, as follows: 1. Easy operation in changing gear. The operation of changing gear is so simple that the device will not be liable to get out of order, because the user only needs to change the pedaling direction without having to manipulate various parts by hand as in other kinds of multi-gear bicycles.

2. Easy manufacture and low cost. Its simple structure makes manufacturing easy and the cost low.

3. Practical speeds. The slow speed is suitable for starting, going against the winds or going up a slope; the fast one for rapid riding on flat roads.

4. Easy maintenance. As its structure is so simple and every part can be reached from the outside, any fault may be corrected without much trouble, unlike other kinds of mechanism having multiple internal parts.

Claims

1. A two-speed gear comprising a driving wheel, two driven wheels of different diameters mounted on an axle parallel to the axis of the driving wheel and each connected to said axle so as to drive the same when rotated in one (and the same) direction and to free-wheel thereon when rotated in the other direction, and an endless transmission element drivingly interconnecting said driving and driven wheels in such manner that rotation of the driving wheel in either direction causes the driven wheels to rotate in mutually opposite directions, whereby rotation of the driving wheel in one direction causes one of said driven wheels to drive the axle and the other driven wheel to free-wheel, whilst rotation of the driving wheel in the other direction causes the said other driven wheel to drive the axle and the said one driven wheel to freewheel.

2. A two-speed gear as claimed in claim 1 wherein the said endless transmission element extends, from the said driving wheel, first around one of the driven wheels in one direction, then around an idler wheel, then around the other driven wheel in the other direction, and then back to the driving wheel.

3. A two-speed gear as claimed in claim 2, wherein the said idler wheel is spring-biassed away from the said driven wheels to tension the said endless transmission element.

4. A two-speed gear substantially as hereinbefore described with reference to the accompanying drawings.

5. A bicycle or tricycle incorporating a twospeed gear as claimed in any of claims 1 to 4, said driving and driven wheels being toothed wheels and the said endless transmission element being a chain, the said driving wheel being pedal-driven, the said axle being the rear wheel axle.