GB2444488A

GB2444488A - Pedal drive system

Info

Publication number: GB2444488A
Application number: GB0624456A
Authority: GB
Inventors: Jonathan Charles Pitts Crick
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-12-07
Filing date: 2006-12-07
Publication date: 2008-06-11
Also published as: GB0624456D0

Abstract

The system, e.g. for a bicycle, comprises a pedal platform 1 rotatably mounted on a pedal shaft 3, a crank 7 to which the pedal shaft is fixed at an end portion thereof, and an interlocking device, e.g a ratchet 5 arranged to fix the platform to the pedal shaft in response to a rotation of the pedal in relation to the shaft in a single direction. The platform 1 is elongate and asymmetrical to the shaft 3 so that a rider's ankle joint is above the shaft. This enables a rider to point a toe at the end of the downward pedal stroke to continue applying torque through the bottom of the stroke.

Description

Drive system The present invention relates to a pedal system for a

vehicle such as a bicycle, as well as to apparatus and in particular vehicles such as bicycles incorporating this system.

As is well known, in a pedal driven apparatus such as a bicycle, the power needed to operate the apparatus (i.e. move the bicycle) is derived from the rider pushing alternately on the pedals.

During each drive stroke on a pedal, which in most conventional bicycles is a downward leg stroke, energy is transferred to the chain wheel from that pedal by way of the crank to which the pedal is attached. Continued rotation of the pedal causes it to pass through a return stroke ready for a second drive stroke, whilst pressure is applied to the other pedal to continue the drive action.

Generally, each pedal comprises a platform, which is mounted on a pedal shaft and freely rotatable about that shaft. An end of the shaft is attached to the crank. As the rider pedals the bicycle, the ankle joint is free to move as it meets minimum resistance from the rotatable platform. When the ankle joint is rotated so that the toe points, the lower leg or calf muscles contract. The energy expended by the lower leg or calf muscles during this contraction is not used in propelling the bicycle, and so represents wasted energy. In addition however, this action acts against the force being expended by the upper leg and trunk muscles at the same time, and so is detrimental to energy efficiency.

Furthermore, it is also clear that the efficiency of the pedal and crank system used to transfer energy from the muscles to the chain wheel differs depending upon the stage of the pedal stroke.

In particular, towards the "end" of the pedal stroke, when the leg of the user is substantially fully extended, and so in a conventional bicycle, the crank is in the substantially vertical position for example, the torque applied to the crank is reduced because at that point, only a small proportion of the downward force is translated to rotational force. At this point also the other pedal is only just beginning to be engaged and so additional force is required to allow it to acquire momentum.

Japanese Patent Application No. 8048277 describes an intermittently applied ratchet to the pedal shaft which is magnetically engaged when the pedal is in line with the crank (which generally occurs when the crank is in the near horizontal position in a conventional bicycle) with the purpose of increasing the effective crank length by the distance from the pedal shaft to the front of the pedal so as to increase the torque on the chain wheel at specifically this phase of the cycle.

This arrangement is complex and only enhances the torque being applied at this one specific phase of the cycle. However, at the point at which the torque applied is reduced, i.e. at the end of the pedal stroke, the ratchet of Japanese Patent Application no. 8048277 is disengaged and the pedal is freely rotatable.

According to the present invention there is provided a pedal system which comprises a platform rotatably mounted on a pedal shaft, a crank to which the pedal shaft is fixed at an end portion thereof, and an interlocking device arranged to fix the platform to the pedal shaft in response to a rotation of the platform in relation to the shaft in a single direction.

By ensuring that the platform becomes fixed in relation to the pedal shaft when is it rotated in one direction, it is possible to transfer more energy from the user to the drive. Specifically by arranging the interlocking device so that when a rider rotates their foot about the ankle to point their toes, the device is activated and the platform is locked against the shaft, the ( torque applied by the movement of the foot is transmitted directly to the crank.

This is particularly useful at the point in the stroke at which the leg of the user is as fully extended as it is going to be, i.e the foot is the furthest point away from the hip joint allowed by the stroke. In a conventional bicycle this is at the base of the downwards stroke, where the crank is substantially vertical or close to vertical, for example within 300 of vertical.

In other types of apparatus, such as pedal boats, or "recumbent" bicycles in which the rider sits in a chair-like saddle with their legs stretched our in front of them, the point of the stroke at which this occurs may be where the crank is at an significant angle to the vertical or even substantially horizontal.

If the rider deliberately points their toes downwards in this region of the stroke, the additional torque created will assist in taking the pedal through the end point and will provide additional power to the crank at a time when it would naturally be low.

If, once this region of the stroke has been passed, the rider then lifts the foot back so that the angle between the leg and foot is reduced, for example during the upstroke of the pedal in a conventional bicycle, the interlocking device is released and the platform becomes freely rotatable again. The platform can then reassume a "relaxed" position, for example a substantially horizontal orientation in a conventional bicycle, and the procedure repeated during the subsequent pedal stroke.

Thus by modifying the pedalling action, a more efficient use of energy may be achieved, and greater levels of torque can be maintained throughout the stroke.

Suitable interlocking devices for fixing the pedal to the pedal shaft in response to a rotation of the pedal relative to the shaft in a particular direction include ratchet mechanisms, which are well known in the art. In general, these utilise a pawl mechanism which engages with sloping teeth provided in a wheel or bar, so as to allow movement in one direction only. Ratchet mechanisms which are substantially silent in operation, are also now available. However, other devices involving levers, stops, pawis etc. for may be envisaged by the skilled person.

The interlocking device may be arranged at any convenient position on the pedal shaft and platform. Conveniently however, it may be mounted on the pedal shaft for example directly adjacent the crank so as to ensure that it does not interfere with the users foot.

Such pedal systems are particularly useful for pedal driven vehicles such as bicycles, tricycles, pedal boats such as pedallos and so on as well as in pedal driven apparatus or machinery, such as pedal driven power generators which may be used in areas where conventional power sources are unavailable.

However, they find particular application in bicycles.

In such cases, the pedal systems are applied so that the rotation of the platform is limited by the interlocking device to the direction opposite to that of the chain wheel (i.e. anticlockwise for the right side pedal and clockwise for the left).

In a particular embodiment, the platform of the pedal system is elongated so as to increase the lever effect achievable. For example, the platform may acconmodate substantially the entire foot of the user.

In particular in this case, the platform is suitably asymmetrically arranged with respect to the pedal shaft, so that in use, the pedal shaft is generally positioned in line with the ankle joint, so that the pedal shaft is directly below an ankle joint when the platform is in a substantially horizontal position. This means that the shaft, acting as the fulcrum is optimally placed to transfer as much torque as possible from the action of rotating the ankle to point the toes.

If required, the platform is provided with restraining means, such as toe stops or straps, to hold a foot in a position in which the ankle joint is generally above the pedal shaft.

As described above, the pedal system of the invention may be generally incorporated into any a pedal-driven apparatus and such apparatus forms a further aspect of the invention. Particular apparatus of the invention will be a bicycle, which includes two pedal systems as described above. These will be arranged so that rotation of the pedal platform will be restricted in the interlocking device in the direction which is opposite that of the chain wheel of the bicycle.

Generally the pedal system described above will be supplied as a complete unit including the crank. However, pedals (comprising the platform, the pedal shaft and the interlocking device) ready for attachment to cranks may also be provided and such pedals form a further aspect of the invention.

In a further aspect, the invention provides a method of operating a pedal driven apparatus incorporating a pedal system as described above, said method comprising pedalling the apparatus whilst maintaining a substantially perpendicular foot position during an early portion of a drive stroke, rotating the foot about the ankle joint to point the toes so as to engage the interlocking device during an end portion of a drive stroke, and returning the foot to the substantially perpendicular foot position as the pedal goes through a return phase of the stroke.

As used herein, a reference to "substantially perpendicular foot position" means that the foot is held such that the interlocking device is not engaged. Generally this will mean that the ankle joint is arranged so that the foot and the leg inclined at from 45 to 1200 to each other, and are preferably substantially perpendicular to each other. In a conventional bicycle, this means that the foot is held in a substantially horizontal orientation with respect to the ground but this may vary depending upon the nature and parameters of the interlocking device, as well as the nature of the apparatus.

In addition, the "end portion of a drive stroke" refers to the portion of the stroke at which the leg is substantially fully extended, so that the foot is further from the hip joint than in other regions of the stroke. In a conventional bicycle, this will occur when foot has moved in the downwards direction, and the crank approaches and passes through a vertical orientation.

However, as described above, other crank orientations are possible at this stage, depending upon the nature and arrangement of the apparatus into which the pedal is incorporated.

Similarly the "early portion of a drive stroke" refers to the stage at which pressure begins to be applied to a particular pedal.

Although the action needed to operate the pedal systems of the invention to achieve maximum efficiency is slightly different to a conventional pedalling action in that the pointing of the toes needs to be co-ordinated to a particular region of the stroke, it is believed that riders would soon become used to this. If, while training, a rider attempted to point the toes in the upper portion of the stroke, they would meet with resistance resulting from engagement of the interlocking device, which would discourage this action.

The invention will now be particularly described by way of example with reference to the accompanying diagrammatic drawing which illustrates a pedal and crank arrangement embodying the invention at various stages of a pedal stroke.

The arrangement illustrated comprises a pedal comprising a platform (1), rotatably mounted on a shaft (3), which is fixed at one end region thereof to an end region of a crank (7). The opposing end region of the crank (7) is linked to the chain wheel (6) so that rotation of the pedal rotates the chain wheel (6) to drive the bicycle in a conventional manner.

In the illustrated embodiment, the platform (1) extends the full length of the foot of the user. The platform is arranged so that in use, the pedal shaft (3), which acts as the fulcrum, is arranged directly below the ankle joint (4) when the platform (1) is in a substantially horizontal position (Figs A, B and E). An adjustable toe stop (2) is optionally provided to ensure that the foot is retained in this relationship to the platform (1).

A ratchet (5) is interposed between the platform (1) and the shaft (3) to that the rotation of the platform (1) relative to the shaft (3) and thus to the crank is limited by a ratchet (5) to the direction (anticlockwise for the right side pedal, clockwise for the left) opposite that of the chain wheel (6).

As the pedal is pushed down (figs. A & B) with the crank (7) pointing forwards, the rider maintains the ankle joint in a position at which the pedal is substantially horizontal. Very little effort is required from the lower leg muscles to maintain this position as there is little torque on the ankle joint (4) at this stage.

As the crank nears the vertical position, the leg is nearly straight at the knee joint so little effort is required to keep it in this position. At this point (figs. C & D) the lower leg muscles can be used to straighten the ankle joint (4) so that the end of the foot points with the toes downwards. This rotates the pedal against the ratchet (5) which locks and fixes the angle (8) between the pedal and the crank. This transmits the rotation to the crank (7) maintaining the torque to the chain wheel (6) through the vertical position of the crank (7) until the other leg can efficiently apply torque via the other pedal.

As the pedal rises with the crank pointing backwards (fig. E) the ankle joint (4) is bent again, which released the ratchet (5) allows it to be brought back to the horizontal and kept so through the rest of the cycle.

The system provides torque during the phase when the cranks are near vertical and allows energy from the lower leg muscles to be applied Out of phase with the mainly downward force on the pedal provided by the upper leg and trunk muscles so that they are not

Claims

Claims 1. A pedal system which comprises a platform rotatably mounted

on a pedal shaft, a crank to which the pedal shaft is fixed at an end portion thereof, and an interlocking device arranged to fix the platform to the pedal shaft in response to a rotation of the pedal in relation to the shaft in a single direction.
2. A pedal system according to claim 1 wherein the interlocking device is a ratchet system.
3. A pedal system according to claim 1 or claim 2 wherein the platform is an elongate platform.
4. A pedal system according to claim 3 wherein the platform is asymmetrically arranged with respect to the pedal shaft, so that in use, the pedal shaft is generally positioned directly below an ankle joint when the platform is in a substantially horizontal position.
5. A pedal system according to claim 4 wherein the platform is provided with restraining means to hold a foot in a position in which the ankle joint is generally above the pedal shaft.
6. A pedal for use in a pedal system according to any one of claims 1 to 5, which pedal comprises a platform, a pedal shaft and an interlocking device.
7. A pedal-driven apparatus incorporating a pedal system according to any one of the preceding claims.
8. A pedal-driven apparatus according to claim 7 which is a bicycle.
9. A bicycle incorporating two pedal systems according to any one of claims 1 to 5, the pedal systems being arranged so that the rotation of the platform of the pedal system is limited by the interlocking device to the direction opposite to that of a chain wheel of the bicycle.
10. A method of operating a pedal driven apparatus incorporating a pedal system according to any one of claims 1 to 5, said method comprising pedalling the apparatus whilst maintaining a substantially perpendicular foot position during an early portion of a drive stroke, rotating the foot about the ankle joint to point the toes so as to engage the interlocking device during an end portion of a drive stroke, and returning the foot to the substantially perpendicular foot position as the pedal goes through a return phase of the stroke.