WO2007057198A1

WO2007057198A1 - Rocker for the rear derailleur of a bicycle

Info

Publication number: WO2007057198A1
Application number: PCT/EP2006/011048
Authority: WO
Inventors: Angelo Pionna
Original assignee: Angelo Pionna
Priority date: 2005-11-18
Filing date: 2006-11-17
Publication date: 2007-05-24
Also published as: ITTO20050164U1

Abstract

Described herein is a rocker for the rear derailleur of a bicycle, said rocker being connected to the rear stays by means of a dropout (2), the rear derailleur being of the type that comprises a pinion pack (6) with a number of gears and is provided with a rocker for shifting the chain from one gear to another, either from a lower gear to a higher gear or vice versa; the rocker (13) has a V- shaped fork-like arm (14), with a toothed freewheel (16, 17, 18) pivoted to each end of said V.

Description

Rocker for the rear derailleur of a bicycle

DESCRIPTION

The present invention relates to a rocker for the rear derailleur of a bicycle, in particular a racing bicycle or else a mountain bike.

Current bicycles of the type referred to above have an increasingly higher number of gears. In particular, the pinion pack can reach a number of gears which up to now was considered unthinkable and can consequently present considerable thicknesses. In fact, currently present on the market are pinion packs with ten gears starting from eleven teeth up to twenty-five teeth or, for mountain bikes, over thirty teeth.

In order to be able to operate with differences in the number of teeth engaged by the gear ratios of this sort, the rear derailleur must necessarily have a rocker of appropriate dimensions, which means that it must have a length such as to be able to compensate for the variations in length of the chain when passing from the highest gear ratio (where with a single revolution of the pedal the greatest distance is covered) to the lowest gear ratio (where the greatest number of revolutions of the pedal is necessary to cover the same distance) .

On racing bicycles, in certain situations a very long rocker of the rear derailleur may prove cumbersome, whilst on mountain bikes it may even bump against obstacles such as rocks, tree trunks, or similar obstacles, with the risk of undesirable failure.

The purpose of the present invention is to provide a rocker such that, whilst managing to keep a large number of gears, the distance between the bottom edge of the chain and the ground will be considerably decreased.

Said purpose is achieved by the present invention, the subject of which is a rocker for the rear derailleur of a bicycle, which presents the characteristics of Claim 1.

Further characteristics and advantages will emerge clearly from the ensuing description, with reference to the attached plate of drawings, which regards a preferred embodiment of the invention, provided by way of non- limiting example, and in which:

- Figure 1 is a view of the rear derailleur for a bicycle provided with a rocker of a classic and known type;

- Figure 2 is a view of the rear derailleur for a bicycle provided with the rocker according to the invention; and

- Figure 3 is an enlargement of another embodiment of a detail of Figure 2.

With reference to Figures 1 and 2, designated by 1 are the rear stays of a bicycle, provided with a dropout 2, inserted in which is the pin 3 of the rear spoked wheel 4.

Fitted on the pin 3 of the wheel is a pinion pack 6, provided with at least six gears 7. Shown in Figure 1 is a rocker 8 of a known type, connected to the ,dropout 2 and made up of a rectilinear arm 9, provided at the end of which are two toothed freewheels 10 and 11, run over which is the chain 12 that transmits the motion from the pedals (not illustrated) to the spoked wheel 4.

Figure 2 illustrates, instead, the rear derailleur for a bicycle provided with the rocker 13 according to the invention.

Said rocker has a V-shaped fork-like arm 14, made up of two shaped metal plates joined by pins 15 at the three ends. Pivoted to said ends, between the two plates and on the pins 15, are three toothed freewheels 16, 17, 18 over which the chain 12 is run. On the first freewheel 16, which is at the base of the V and is the closest to the pinion pack, the chain is wound in the counterclockwise direction; on the second freewheel 17, at one end of the V, the chain is wound in a clockwise direction; instead, on the third freewheel 18, at the pther end of the V, the chain only rests and runs in the clockwise direction, so as to be kept tensioned.

The rocker 13 is articulated in rotation to an L- shaped bracket 19, which, in this embodiment, is connected in rotation to the dropout 2, but which may be supported in any other known way, without thereby departing from the sphere of protection of the present invention.

The bracket is provided with a spring (not visible in Figure 2) , which tends to cause rotation thereon of the rocker in a clockwise direction, so as to maintain the chain 12 always tensioned.

Of the three freewheels set on the rocker 13, the first two 16 and 17, over which the chain is run, have the same diameter, whilst the third 18 has, preferably, a smaller diameter. The three freewheels are surrounded by cages 20 for containment of the chain 12, which are made of a single piece with the plates forming the arm of the rocker and the first two of which are shaped like a semiannulus, whilst the third is shaped like an annulus 22 made up of crescents of different width in order to contain the chain as well as possible (Figure 3) .

It may be readily verified that the rocker 13 according to the invention (Figure 2) is much shorter than a rocker 8 currently in use (Figure 1) given the same type of rear derailleur and use.

Claims

1) A rocker for the rear derailleur of a bicycle, said rocker being connected to the rear stays by means of a dropout (2) , the rear derailleur being of the type that comprises a pinion pack (6) with a number of gears and is provided with a rocker for shifting the chain from one gear to another, either from a lower gear to a higher gear or vice versa, said rocker (13) being characterized in that it has a V-shaped fork-like arm (14) , with a freewheel (16, 17, 18) pivoted to each end of the said V.

2) A rear derailleur for a bicycle according to Claim

1, characterized in that the fork-like arm (14) is articulated in rotation to an L-shaped bracket (19) .

3) The rear derailleur for a bicycle according to Claim 1, characterized -in that one (16) of the freewheels of the fork-like arm rotate in a counterclockwise direction, whilst the remaining two (17, 18) rotate in a clockwise direction.

4) The rear derailleur for bicycle according to Claim

2, characterized in that provided on the fork-like arm (14) are cages (20) for containment of the chain in an area corresponding to the three freewheels (16, 17, 18) and in that for the third freewheel (18) said cage (22) is shaped like an annulus made up of crescents.