GB2109892A

GB2109892A - A chainwheel and a pedal crank for a bicycle

Info

Publication number: GB2109892A
Application number: GB08228043A
Authority: GB
Inventors: Dino Perotti; Mario Perotti
Original assignee: PEROTTI OFMEGA SNC
Current assignee: PEROTTI OFMEGA SNC
Priority date: 1981-10-16
Filing date: 1982-10-01
Publication date: 1983-06-08
Also published as: FR2514717A3; GB2109892B; FR2514717B3; IT8107074V0

Abstract

A chainwheel (1) for a bicycle includes a plurality of spokes (2) converging towards a central portion or boss (3), a pedal crank (4) being affixable to or being capable of being integrally formed with the central portion or boss, each spoke (2) of the chainwheel having a parallelogram shaped cross-section, two opposing sides (20-20) of the parallelogram extending parallel to the plane of rotation of the chainwheel and the other pair of opposed sides (21-21) intersecting the plane of rotation of the chainwheel at an angle other than a right angle. The pedal crank (4) has a polygonal-shaped cross-section having two opposing sides (40-40) extending substantially parallel to the plane of rotation of the crank and a further pair of opposing other sides (41-41) orientated so as to intersect the plane of rotation at an angle other than a right angle, the further pair of opposed sides extending substantially parallel to one another. <IMAGE>

Description

SPECIFICATION A chainwheel and a pedal crank for a bicycle The present invention relates to a chainwheel for a bicycle, a pedal crank for a bicycle and to a combination of a chainwheel and a pedal crank.

Many known chainwheels, pedal cranks or combinations of such chainwheels and cranks for bicycles do not have the aerodynamic or air-flow characteristics which are desirable to contribute to the efficient conversion of the effort of the cyclist to the movement of the bicycle. Thus, known chainwheel and crank arrangements generally suffer from the disadvantage of having a boss or portion of cylindrical or similar shape which projects outwardly at right angles with respect to the plane of the spokes of the chainwheel, the boss being located in the region of the junction between the pedal crank and the chainwheel.

The present invention seeks to provide in one aspect a spoked chainwheel, and in a second aspect, a pedal crank, the spokes of the chainwheel and the crank pedal each having polygonal cross-sections so as to achieve maximum air-flow through and around such components.

A further aspect of the present invention seeks to provide a chainwheel and pedal crank assembly for a bicycle in which the junction zone between the spokes of the chainwheel and the corresponding pedal have a continuous spherical or convex shape so as to eliminate any significant projecting portions so as to confer improved aerodynamic properties on the assembly.

The present invention also seeks to provide, in a further aspect, an assembly in which the pedal, when fixed to the chainwheel, has its end encased in the region in which the spokes of the chainwheel converge.

According to one aspect of the present invention, there is provided a chainwheel for a bicycle having a plurality of spokes converging towards a central portion or boss, a pedal crank being affixable to or being capable of being integrally formed with the central portion or boss, each spoke of the chainwheel having a parallelogram-shaped cross-section, two opposing sides of the parallelogram extending parallel to the plane of rotation of the chainwheel and the other pair of opposed sides being orientated so as to intersect the plane of rotation of the chainwheel at an angle which is not a right angle, one of the other pair of opposed sides extending towards the direction of rotation of the chain wheel and the other in the opposite direction.

According to a second aspect of the present invention, there is provided a pedal crank for a bicycle which is capable of being affixed to the central portion or boss of a chainwheel or is capable of being integrally formed therewith, the crank having an irregular polygonal-shaped crosssection, the polygonal cross-section having two opposing sides extending substantially parallel to the plane of rotation of the crank and a further pair of opposing other sides orientated so as to intersect the plane of rotation at an angle other than a right angle, the further pair of opposed sides extending substantially parallel to one another, one extending substantially in the direction of rotation of the crank and the other in the opposite direction.

According to a third aspect of the present invention, there is provided a chainwheel and pedal crank assembly for a bicycle, the chainwheel comprising a plurality of spokes, each spoke having a substantially parallelogramshaped cross-section, opposing sides of the parallelogram extending substantially parallel to the plane of rotation of the chainwheel and the other two opposing sides intersecting the plane of rotation at an angle other than a right angle, the pedal crank having a polygonal cross-section having two opposed sides extending substantially parallel to the plane of rotation of the crank and a further pair opposing sides which extend substantially parallel to one another and intersect the plane of rotation of the crank at an angle other than a right angle, the spokes and the pedal crank being connected together or being integrally formed with one another to provide a continuous spherical or convex frontal surface.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figs. 1 and 2 show, respectively, front and rear perspective views of a combined chainwheel and pedal crank in accordance with the present invention; Fig. 3 shows a side view of the combination shown in Figs. 1 and 2; Fig. 4 shows a transverse section through a pedal crank in accordance with the present invention, and Fig. 5 shows a transverse section through one of the spokes of a spoked chainwheel in accordance with the present invention.

The combined chainwheel and pedal crank shown in Figs. 1 to 3 comprises a chainwheel 1 having a plurality of spokes 2, all of the spokes converging towards a central portion or boss 3 from which a pedal crank 4 extends. The chainwheel 1 may be a single or double chainwheel and the rim thereof may be affixed to the spokes 2, as shown in the drawing, or may form an integral unit therewith.

Similarly, the pedal crank 4 may be inserted into the central portion or boss 3 as shown in the drawing and be affixed therein or form an integral unit with the boss 3, spokes 2 and chainwheel 1.

When the pedal crank 4 is inserted and fixed in position, the end 4' thereof associated with the chainwheel 1 is enclosed in the central portion or boss 3. Accordingly the frontal surface of the central portion or boss 3, that is say, the portion extending to the right of the chainwheel 1 in Fig.

3 forms, desirably, a part of a continuous spherical surface or at least presents a substantially convex shape.

Each spoke 2 of the chainwheel has a substantially parallelogram-shaped cross-section, as shown in Fig. 5. Such parallelogram has two opposing sides 20 which extend substantially parallel to the plane in which the chainwheel rotates and the other pair of opposing sides 21 intersect the plane at an appropriate angle which is not a right angle.

Similarly, the pedal crank 4 has an irregular polygonal-shaped cross-section as can be seen in Fig. 4. The pedal crank has two sides 40 which extend substantially parallel to the plane of rotation of the pedal crank and another two further opposing sides 41 extending substantially parallel to one another, one of the sides 41 extending towards the direction of rotation of the crank and the other opposite thereto. The two sides 41 intersect the plane of rotation of the crank at an appropriate angle which is not a right angle.

These specific cross-sections for the spokes 2 of the chainwheel, for the pedal crank and the spherical or convex surface of the boss when the crank and chainwheel form an assembly, taken separately or in combination provide an improved air-flow which provides a more efficient utilisation of the effort exerted by the cyclist.

Claims

1. A chainwheel for a bicycle having a plurality of spokes converging towards a central portion or boss, a pedal crank being affixable to or being capable of being integrally formed with the central portion or boss, each spoke of the chainwheel having a parallelogram-shaped crosssection, two opposing sides of the parallelogram extending parallel to the plane of rotation of the chainwheel and the other pair of opposed sides being orientated so as to intersect the plane of rotation of the chainwheel at an angle which is not a right angle, one of the other pair of opposed sides extending towards the direction of rotation of the chainwheel and the other in the opposite direction.

2. A chainwheel as claimed in claim 1 constructed substantially as herein before described with reference to and as illustrated in Figs. 1 to 3 and 5 of the accompanying drawings.

3. A pedal crank for a bicycle which is capable of being affixed to the central portion or boss of a chainwheel or is capable of being integrally formed therewith, the crank having an irregular polygonal-shaped cross-section, the polygonal cross-section having two opposing sides extending substantially parallel to the plane of rotation of the crank and a further pair of opposing other sides orientated so as to intersect the plane of rotation at an angle other than a right angle, the further pair of opposed sides extending substantially parallel to one another, one extending substantially in the direction of rotation of the crank and the other in the opposite direction.

4. A pedal crank as claimed in claim 3 constructed substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 4 of the accompanying drawings.

5. A chainwheel and pedal crank assembly for a bicycle, the chainwheel comprising a plurality of spokes, each spoke having a substantially parallogram-shaped cross-section, opposing sides of the parallelogram extending substantially parallel to the plane of rotation of the chainwheel and the other two opposing sides intersecting the plane of rotation at an angle other than a right angle, the pedal crank having a polygonal crosssection having two opposed sides extending substantially parallel to the plane of rotation of the crank and a further pair opposing sides which extend substantially parallel to one another and intersect the plane of rotation of the crank at an angle other than a right angle, the spokes and the pedal crank being connected together or being integrally formed with one another to provide a continuous spherical or convex frontal surface.

6. An assembly as claimed in claim 5 constructed substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.