GB2243351A

GB2243351A - A pedal and crank drive arrangement

Info

Publication number: GB2243351A
Application number: GB9009347A
Authority: GB
Inventors: Malcolm Geoffrey Lawrence
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-04-26
Filing date: 1990-04-26
Publication date: 1991-10-30
Also published as: GB9009347D0

Abstract

A pedal arrangement comprises cranks (1, 2) and a sprocket (5). Each crank (1, 2) is attached to the sprocket (5) by attachment means (6, 9, 11, 13, 14; 7, 10, 12, 15, 16) which act as an elliptical gearing system which cause the relative position of the cranks (1, 2) to vary through the rotational cycle of the cranks. This results in the time taken for one crank to travel from its lowest point to its highest point, to be less than that taken for other crank to travel from its highest point to its lowest point. <IMAGE>

Description

Pedal Arrangement This invention relates to a pedal arrangement for a bicycle, of the type comprising a first pedal attached to a first end of a first crank and a second pedal attached to a first end of a second crank. Each crank is attached at a respective second end to a sprocket. In use, power applied to the pedals results in the cranks rotating about the axis of the sprocket. This in turn results in the rotation of the sprocket, which results in movement of the bicycle.

In known pedal mechanism's the first and second cranks are rotatable about the central axis of the sprocket. They are attached to the sprocket in such a way that the two pedals are always substantially 180 degrees apart. In other words, when the first pedal is at the highest point of its cycle, the second pedal is at its lowest, and vice versa. The time taken for one pedal to travel from its highest point to its lowest point is exactly the same as that for the other pedal to travel from its lowest point to its highest point.

It is well known in the art, that the power applied to a pedal in order to make the sprocket rotate, is applied from the time when the pedal is at its highest point, to the time when it is at its lowest. Once the pedal is at its lowest point, power is applied to the other pedal which is now at its highest point, in order to make the sprocket rotate. Thus power is applied to only one pedal at a time in order to ,,cause the sprocket to rotate.

The present invention seeks to improve the efficiency of the pedal arrangement by allowing power to be applied to both pedals at certain times during the rotational cycle of the cranks.

Accordingly there is provided a pedal arrangement comprising a first pedal attached to a first end of a first crank and a second pedal attached to a first end of a second crank, a sprocket positioned between the first and second cranks and rotationally attached to each crank at a respective second end of each crank, characterised in that the sprocket is attached to each crank by attachment means attached to the sprocket and to each second end and operable to cause the relative positions of the cranks to vary during the rotational cycle of the cranks.

In use, therefore, the position of the pedals relative to one another will vary and thus for most of the rotational cycle of the cranks they will not be 180 degrees apart. This means that, in use, both pedals will be travelling between their highest points and their lowest point for part of the rotational cycle. Power may therefore be applied to both pedals during this part of the cycle, thus increasing the efficiency of the pedal arrangement.

Preferably, the attachment means causes the relative position of the cranks to vary by causing the time taken for a pedal to be travel from its lowest position to its highest position to be less than that taken for a pedal to travel from its highest position to its lowest position.

The time during which no power is applied to a pedal is therefore reduced relative to the time during which power is applied to a pedal.

Preferably the attachment means comprises a first wheel positioned between the sprocket and the first crank and a second wheel positioned between the sprocket and the second crank, each wheel being rotationally fixed to the sprocket and a respective crank, and rotatable about the axis of rotation of the sprocket, and each crank being fixed to a respective wheel at a point offset from the axis of rotation of the sprocket and rotatable about a crank axis offset from the axis of rotation of the sprocket.

The attachment means thus serves as an elliptical gearing system and result in the variation in the relative position of cranks.

Conveniently, each wheel includes a slot extending from the circumference of the wheel to a central region of the wheel, and an elongate member rotatably fixed at one end to the respective crank axis, and having a peg attached at another end, the peg being engageable in the slot.

Such an arrangement enables the wheel to rotate about a different axis to the crank.

The slot may extend to the centre of the wheel, to a point near to the centre of the wheel or to a point beyond the centre.

The invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a schematic representation of a pedal arrangement according to the invention; and Figure 2 is a plan view of the pedal arrangement.

Referring to the figures, a pedal arrangement according to the invention comprises a first crank 1 and a second crank 2 onto which first and second pedals (not shown) may be attached at rods 3 and 4. The cranks 1, 2 are attached to a sprocket 5 via first wheel 6 and second wheel 7. The sprocket is rotatable about an axis of rotation 8. When the pedal arrangement is incorporated into a bycycle, rotation of the sprocket will cause movement of the bicycle. The wheels 6, 7 are also rotatable about the axis of rotation 8. The crank 1 is attached to the wheel 6 at peg 9, and is rotatable about the peg 9. Crank 2 is similarly attached to wheel 7 at peg 10. Although in this embodiment the cranks 1, 2 rotate about different axes, they could also rotate about the same axis as each other. An elongate member 11 is positioned between crank 1 and wheel 6.The member 11 is fixed to the wheel 6 by means of peg 9 and is rotatable about the peg 9.

A peg 13 attached to the member 11 is engageable in a slot 14 in wheel 6. As the crank 1 rotates the wheel 6 rotates and the peg 13 moves along the slot 14 to compensate for the different axes of rotation of the wheel 6 and the crank 1. Crank 2 is si'milarly attached to wheel 7 by means of an elongate member 12 having a peg 15 engageable in a slot 6 in wheel 7.

By means of the pedal arrangement of the invention as shown, the position of the cranks 1, 2 relative to one another varies through the rotational cycle of the cranks.

As can be seen from figure 1, the cranks are arranged to rotate in an anticlockwise manner, and when in the position shown, both pedals (not shown) are between the highest point and the lowest point of the rotational cycle, and thus pressure may be applied to both pedals at this point in the cycle. This helps to improve the efficiency of the arrangement.

Claims

1. A pedal arrangement comprising a first pedal attached to a first end of a first crank (1) and a second pedal attached to a first end of a second crank (2), a sprocket (5) positioned between the first and second cranks and rotationally attached to each crank at a respective second end of each crank, characterised in that the sprocket is attached to each crank by attachment means (6, 9, 11, 13, 14; 7, 10, 12, 15, 16), operable to vary the relative positions of the pedals during the rotational cycle of the cranks.

2. A pedal arrangement according to claim 1 wherein the attachment means (6, 9, 11, 13, 14, 7, 10, 12, 15, 16) is operable to cause the time taken for a pedal to travel from its lowest position to its highest position to be less than that taken for a pedal to travel from its highest position to its lowest position.

3. A pedal arrangement according to claim 1 or claim 2 wherein the attachment means comprises a first wheel (6) positioned between the sprocket and the first crank and a second wheel (7) positioned between the sprocket and the second crank, each wheel being rotationally fixed to the sprocket and a respective crank, and rotatable about the axis of rotation of the sprocket, and each crank being fixed to a respective wheel at a point offset from the axis of rotation of the sprocket (8) and rotatable about a crank axis (9; 10) offset from the axis of rotation of the sprocket.

4. A pedal arrangement according to claim 3 wherein each wheel (6; 7) comprises a slot (14; 16) extending from the circumference of the wheel to a central region of the wheel and an elongate member (11,12) rotatably fixed at one end to the respective crank axis (9; 10), and having a peg (13, 15) attached at another end, the peg being engageable in the slot.

5. An arrangement means as claimed in any one of the preceding claims.

6. A pedal arrangement substantially as hereinbefore described with reference to the accompanying drawings.

6. A pedal arrangement substantially as herein before described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows 1. A pedal arrangment comprising a first pedal attached to a first end of a first crank and a second pedal attached to a first end of a second crank, a sprocket positioned between the first and second crank and rotationally attached to each crank at a respective second end of each crank, characterised in that the sprocket is attached to each crank by attachment means attached to the sprocket and to each second end, and operable to cause the relative position of the cranks to vary during the rotational cycle of the cranks.

2. An arrangement as claimed in claim 1 wherein the attachment means causes the relative position of the cranks to vary by causing the time taken for a pedal to travel from its lowest position to its highest position to be less than that taken for a pedal to travel from its highest position to its lowest position.

3. An arrangement as claimed in claim 1 or claim 2 wherein the attachment means comprises a first wheel positioned between the sprocket and the first crank, and a second wheel positioned betwen the sprocket and the second crank, each wheel being rotationally fixed to the sprocket and the respective crank, and rotatable about the crank axis offset from the axis of rotation of the sprocket.

4. An arrangement as claimed in claim 3 wherein each wheel includes a slot extending from the circumference of the wheel to a central region of the wheel, and an elongate member rotatably fixed at one end to the respective crank axis and having a peg attached at another end, the peg being engageable in the slot.

5. An arrangement as claimed in claim 4 wherein the slot extends to the centre of the wheel.