WO2003080422A1

WO2003080422A1 - Improved pedal unit for bicycles

Info

Publication number: WO2003080422A1
Application number: PCT/IT2002/000192
Authority: WO
Inventors: Enos Polvanesi
Original assignee: Enos Polvanesi
Priority date: 2002-03-26
Filing date: 2002-03-26
Publication date: 2003-10-02
Also published as: AU2002253530A1

Abstract

A pedal unit for bicycles comprising a toothed crown wheel (2) rotatably connected to the frame (1) of the bicycle, a pedal crank (3) that is rigidly attached to the crown wheel and extends radially from the centre thereof and a pedal that is rotatably connected with the free end of the crank pedal, which is made up of a fixed part (3a) rigidly connected to the crown wheel and a mobile part (3b) that can slide along the fixed part and carries the pedal at one of its ends. The other end of the mobile part is constrained to follow a circular trajectory that is eccentric with respect to the centre of the crown wheel, thereby realizing a maximum lengthening of the crank pedal when in the course of its rotation it finds itself in a substantially horizontal position and points forward, i.e. in the direction of motion of the bicycle.

Description

^'IMPROVED PEDAL UNIT FOR BICYCLES

DESCRIPTION

Field of the invention The present invention relates to an improved pedal unit for bicycles .

Description of the prior art

As is well known, a pedal unit for bicycles consists of: a toothed crown wheel pivotally connected to the frame of the bicycle and engaging with the chain that transmits the motion to the pinion of the rear wheel; a pedal crank integral with the toothed crown wheel and extending radially from the centre thereof; and a pedal pivotally connected to the free end of the pedal crank. In particular, the cycle frame comprises a saddle tube that connects the saddle, borne at its upper end, to the pedal unit attached to its opposite end.

It is also known that, all other things (i.e. overall weight, slope of the ground, gear ratio) being equal, the length of the pedal crank determines the magnitude of the effort that has to be made by the cyclist to turn the toothed crown wheel and therefore to cause the bicycle to move forward. Nevertheless, the need for avoiding the pedal touching ground in the bottom dead centre position and an excessive raising of the knee in the top dead centre position sets certain limits beyond which the length of the pedal crank cannot be extended. In practice one has to note that any lengthening of the pedal crank necessarily calls for a lowering of the saddle, since the distance between the saddle and the pedal in the bottom dead centre position must obviously be equal to the length of the cyclist's fully extended leg and has therefore to be kept constant. On the other hand, since the angular excursion of the knee in the course of a revolution corresponds to twice the length of the pedal crank, the lowering of the saddle implies an inclination of the femur above the horizontal in the top dead centre position and this may be found to be excessive and unnatural .

Summary of the invention

The object of the present invention is to provide an improved pedal unit for bicycles that will make it possible to obtain a better ^' output from each push on the pedal .

A particular aim of the present invention is to provide an improved pedal unit of the aforementioned type that comprises a pedal crank of variable length and will not therefore create the difficulties recalled above when the pedal passes the top and bottom dead centre positions in the course of its rotation.

These aims are attained by the improved pedal unit in accordance with the present invention, which has the essential characteristics that the pedal crank is made up of a fixed part, connected to the toothed crown wheel, and a mobile part capable of sliding along the fixed part, carrying the pedal at one end and having its other end constrained to describe an eccentric circular trajectory around the centre of the toothed crown wheel, so that said mobile part will realize a maximum lengthening of the pedal crank, when, in the course of its rotation, it finds itself in a substantially horizontal position and pointing forward with respect to the direction of motion of the bicycle . In one embodiment of the invention the mobile part of the crank pedal is rotatably connected to a hinge pin carried in eccentric rotation around the axis of rotation of the toothed crown wheel, said mobile part being connected to the fixed part by means of two arms that are parallel to each other and spaced therebetween. In a particularly advantageous variation of this embodiment one of the two arms is rotatably connected to said hinge pin in eccentric rotation. In another embodiment of the invention the fixed and the mobile part of the crank pedal are telescopically connected with each other.

Brief description of the drawings

Further characteristics and/or advantages of the improved pedal unit for bicycles in accordance with the present invention will be brought out more clearly by the following description of a particular embodiment thereof, which is to be considered as an example and not limitative

- in any way, said description making reference to the attached drawings of which:

Figure 1 shows a side elevation of a bicycle frame on which there is mounted the improved pedal unit in accordance with the invention;

Figure 2 shows an enlarged plan view of the central part of the frame on which there is mounted the pedal unit in accordance with the invention;

Figure 3 shows the four details a) , b) , c) and d) that illustrate, respectively, the configurations assumed by the pedal crank in four successive phases of its rotation;

Figure -4 shows a variation of the pedal unit illustrated by the preceding figures, the details a) and b) illustrating, respectively, the positions in which the crank pedal assumes its maximum and minimum extension;

Figure 5 shows a second embodiment of the pedal unit in accordance with the invention, the details a) and b) illustrating, respectively, the positions in which the crank pedal assumes its maximum and minimum extension. Description of the preferred embodiment Referring to Figures 1, 2 and 3, the reference number 1 indicates a generic bicycle frame comprising a saddle tube la that extends between a saddle (not shown) and a pedal unit generically indicated by the reference number 10; the reference number 2 indicates a toothed crown wheel that engages with the motion transmission chain (not shown) , while the reference number 3 generically indicates a pedal crank that at its free end carries a rotatably connected pedal (not shown) . Toothed crown wheel 2 is keyed to a hub 4 of the pedals, which is rotatably mounted on frame 1 and constitutes the axis of rotation of pedal unit 10. According to the invention, crank pedal 3 is made up of a fixed part 3a and a mobile part 3b. Fixed part 3a has one of its ends keyed to hub 4, while mobile part 3b, which at its free end carries the pedal (not shown) , can slide along fixed part 3a, since it is connected to said fixed part 3a by means of two arms 5a, 5b that are parallel to each other and spaced therebetween, these arms being pivotally connected at their respective ends to both fixed part 3a and mobile part 3b. The other end of mobile part 3b is rotatably connected to a hinge pin 6 that extends at right angles from a ring 7 capable of rotating on a circular support 8 rigidly connected to frame 1 and eccentric with respect to the toothed crown wheel 2. More precisely, the centres of rotation of toothed crown wheel 2 and ring 7 are both situated on a substantially horizontal axis, but the centre of rotation of ring 7 is in a more forward position, where forward is to be understood as in the direction of motion of bicycle, i.e. closer to the front end of frame 1.

As can be seen also from Figure 3, given the eccentric arrangement of ring 7 with respect to toothed crown wheel 2, the mobile part 3b of pedal crank 3 will perform a reciprocating movement with respect to the fixed part 3b, reaching its maximum excursion when the pedal crank points about horizontally forward (see Figure 3a) and its minimum excursion when the pedal crank -points about horizontally backward (see Figure 3c) with respect to its axis of rotation X-X; on the other hand, the pedal crank will assume its average length more or less when it reaches the top and bottom dead centre positions (see Figures 3b and 3d) . The length of the pedal crank will therefore be greater than average throughout the useful part of the rotation, so that any given force applied to the pedal will always produce a greater moment about the axis of rotation.

Figure 4 shows a variation of this embodiment in which hinge pin 6 of eccentric ring 7 is connected to the innermost arm 5a rather than to the mobile part 3a of the pedal crank. In this way, given the smaller distance that separates pin 6 and the axis of rotation of arm 5a from the fixed part 3a of pedal crank 3, mobile part 3b will evidently perform a greater excursion at any given eccentricity.

Figures 5a and 5b illustrate another embodiment of the invention in which the fixed part 3a is contained telescopically within the mobile part 3b, which is connected to hinge pin 6 of eccentric ring 7. This solution is more compact than the previous one, but has fewer adjustment possibilities. The maximum excursion of pedal crank 3 can either be made to coincide with the horizontal axis, as shown in the figures, or be slightly anticipated and made to occur when the pedal crank becomes perpendicular to saddle tube la, the position in which the component of the force the cyclist applies to the pedal attains its theoretical maximum value. In actual practice, however, this maximum value may be reached when the pedal crank reaches some angular position intermediate between the horizontal and the perpendicular to the saddle tube, the precise position depending on the way the cyclist seats himself on the saddle, so that the angular position of hinge pin 6 with respect to the horizontal has to be adjusted by the cyclist according to his particular needs.

It clearly follows from what has been said above that the pedal crank in accordance with the invention realizes all the objectives the invention set out to attain. In particular, thanks to the lengthening of the crank during the useful part of the rotation, the efficiency of the pedal unit can be considerably improved without having to modify the circular arrangement. For example, bearing in mind that the length of a pedal crank is usually comprised between 170 and 175 mm, rarely reaching 177.5 mm, with the improved pedal unit in accordance with the invention the pedal crank lengthens up to 198 mm during the useful part of the rotation. A pedal crank of this length would be altogether unthinkable in a prior art bicycle, because it would imply an excursion of the knee of the order of 400 mm, with consequent need to lower the saddle and the risk of making it extremely difficult to push the pedal on account of an excessive inclination of the femur above the horizontal whenever -the top dead centre position is reached.

Variations and/or modifications could be brought to the improved pedal unit for bicycles in accordance with the present invention without departing from the scope of the invention as defined by the claims hereinbelow.

Claims

1. A pedal unit for bicycles comprising a toothed crown wheel (2) rotatably connected to the frame (1) of the bicycle, a pedal crank (3) that is rigidly attached to said crown wheel and extends radially from the centre thereof and a pedal that is rotatably connected with the free end of said crank pedal, characterized in that said pedal crank is made up of a fixed part (3a) connected to said crown wheel and a mobile part (3b) that can slide along said fixed part and carries said pedal at one end and has its other end constrained to follow a circular trajectory that is eccentric with respect to the centre of said crown wheel, thereby realizing a maximum lengthening of said crank pedal when in the course of its rotation it finds itself in a substantially horizontal position and points forward, with respect to the direction of motion of the bicycle.

2. A pedal unit in accordance with claim 1, wherein the centres of said crown wheel (2) and said eccentric circular trajectory are situated on a substantially horizontal axis, the centre of said circular trajectory being arranged forwardly with respect to the centre of said crown wheel in the advancing direction of the bicycle .

3. A pedal unit in accordance with claim 2, wherein said frame comprises a saddle tube (la) and the axis on which there are situated the centres of said toothed crown wheel

(2) and said eccentric circular trajectory extends in a position intermediate between the horizontal and a direction perpendicular to said saddle tube.

4. A pedal unit in accordance with any one of the preceding claims, wherein the mobile part (3b) of said pedal crank is connected to an annular element (7) that can rotate around a circular support (8) rigidly attached to the frame (1) and is mounted in an eccentric position with respect to said toothed crown wheel (2) .

5. A pedal unit in accordance with any one of the preceding claims, wherein the mobile part (3b) of said pedal crank is connected to said fixed part (3a) by means of two parallel arms (5a, 5b) that are rotatably connected to said fixed part.

6. A pedal unit in accordance with any one of the preceding claims, wherein a hinge pin (6) extends from said annular element (7) in a direction perpendicular to the plane of said element and has said mobile part (3a) rotatably attached to it .

7. A pedal unit in accordance with any one of the claims 1 to 5, wherein a hinge pin (6) extends from said annular element (7) in a direction perpendicular to the plane of said element and has the arm (5a) closer to the centre of said toothed crown wheel (2) rotatably connected to it at some point between the two ends of said arm.

8. A pedal unit in accordance with any one of the claims 1 to 4, wherein said mobile part is mounted telescopically on said fixed part.