GB2428412A

GB2428412A - Crank system

Info

Publication number: GB2428412A
Application number: GB0514863A
Authority: GB
Inventors: Edward David Reynolds
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-07-19
Filing date: 2005-07-19
Publication date: 2007-01-31
Also published as: GB0514863D0

Abstract

The system 1, which may be mounted on the frame of a bicycle, includes a crank throw control 10. The throw of the crank 4 is caused to extend and retract sequentially during rotation of the crank about its axis 6. The crank 4 may include a box-like structure 13 of elongate form with a telescopically located block 15 slidably disposed within. A cam follower 16 is mounted on the block so as to be located by a continuous groove cam track 17 formed on a cam 18. The crank may be rotated by a pedal.

Description

CRANK SYSTEMS

This invention relates to crank systems and is particularly, but not exclusively, concerned with pedal powered crank systems such as used to propel bicycles.

The invention provides a novel crank system whereby input to the crank is enhanced.

As used herein, the term "bicycle" includes "tricycle" and other pedalpropelled vehicles, such as float supported craft for operating over water.

According to the invention, a crank system is provided with crank throw control means operable so that the throw of the crank is caused to extend and retract sequentially during rotation of the crank about its axis of rotation.

The crank may be of two-part construction whereby one part can extend or retract relative to the other part.

Thus, the crank may be considered as of substantially telescopic form.

The throw control means preferably comprise a cain and cain follower arrangement.

An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, wherein: - Figure 1 is a side view of the novel crank system applied to a bicycle, Figure 2 is a plan view of one of the pedals of the bicycle, Figure 3 is another plan view of the pedal, with added detail, Figure 4 is a view similar to that illustrated by Figure 1, but seen from the opposite side of the bicycle, Figure 5 is a plan view illustrating various parts of the crank system, Figure 6 is a side view of the cam used by the crank system, and Figures 7, 8, and 9 and 10 are side views of the crank system and illustrate various positions of the crank during one revolution.

With reference first to Figure 1, 2, 3 and 5, a crank system 1 mounted on a bicycle frame 20, (Figure 5), is provided with throw crank control means 10 comprising a cam and cam follower arrangement operable so that the throw of the crank 4 is caused to extend (Figure 7) and retract (Figure 9) sequentially during rotation of the crank 4 about its axis of rotation 6.

Two identical crank system, 1, 1 are provided, one on each side of the bicycle frame 5.

Arrow 7 of Figure 1 indicates the front of the bicycle and the direction of travel.

The crank system 1 is disposed on the right hand side of the bicycle. Arrow 8 of Figure 4 indicates the front of the bicycle and the direction of travel, the crank system l being disposed on the left hand side of the bicycle.

As shown in Figures, 2 and 3, the crank 4 comprises a bush 11 disposed at one end of the crank and is mounted on the crank spindle 12 which rotates within the bush about the axis 6.

The rest of the crank 4 comprises a box-like structure 13 of elongate form with open sides and inwardly-turned flange portions 14. It also has closed ends.

A block 15 is slidably disposed within the structure 13 and a cam follower 16 is mounted on the block so as to be located by a track 17 defined by a continuous groove formed on the cam 18.

Thus the crank 4 is of two-part substantially telescopic, construction, whereby one part, i.e. the block 15, can extend or retract relative to the other part, namely structure 13, in a telescopic manner.

The side of the cam track 17 nearest to the frame 20 of the bicycle is closed by a plate 19.

The block 15 is mounted on the crank spindle 12, which also supports a pedal 25 by which the bicycle is propelled.

Figure 5 shows the bicycle frame 20, the cam arrangements, 1, 1, the crank spindle 12 and the chain wheel drive 21 whereby propulsive effort applied to the pedals 25 is imparted to the rear wheel (not shown) of the bicycle.

In the figures, parts shown in Figures 4 and 5 which are identical to those shown in Figurel, have been given the suffix "i".

With reference to Figure 6, a cam 1 (or l) is perforated by holes 26 to provide lightness.

Figures 7, 8, 9 and 10, show how the invention enhances effort applied to the bicycle pedals. Rotation of the crank 4 is indicated by arrows 30.

Figure 7 shows the crank 4 in the fully extended forward position, whereby maximum effort is applied to the pedals.

Figure 8 shows the crank 4 retracted after 90 rotation. Figure 9 shows the crank 4 remaining retracted after a further 90 rotation and Figure 10 shows the crank 4 still retracted after a further 90 rotation.

It will be appreciated therefore that as the crank 4 is rotated through a full 360 about axis 6, the throw of the crank is caused to extend and retract sequentially, maximum effort being applied when the crank is extended, and extra leverage obtained.

Claims

1. A crank system provided with throw control means operable so that the throw of the crank is caused to extend and retract sequentially during rotation of the crank about its axis.

2. A crank system as claimed in Claim!, wherein the crank is of two-part construction whereby one part can extend or retract relative to the other part.

3. A crank system as claimed in Claim 2 wherein the crank is of telescopic form.

4. A crank system as claimed in Claim 1, 2 or 3 wherein the throw control means comprise a cam track and cam follower arrangement.

5. A crank system as claimed in Claim 4, wherein the cam track is defined by a continuous groove.

6. A crank system as claimed in any one of Claim 1 or 5, wherein the crank comprises a box-like structure of elongate form with a block slidably located within the structure and the cam follower is mounted on the block so as to be located by said cam track.

7. A crank system as claimed in any one of Claims 1 to 6, provided with pedals whereby the crank may be rotated about its axis.

8. A crank system as claimed in any one of Claims 1 to 7, mounted on the frame of a bicycle (as herein defined).

9. A crank system substantially as herein before described, with reference to the accompanying drawings.

10. A bicycle (as herein defined), provided with a crank system substantially or hereinbefore described, with reference to the accompanying drawings.