FR2470289A3 - FREE WHEEL GROUP FOR BICYCLE - Google Patents

Abstract

FREEWHEEL GROUP FOR BICYCLES, INCLUDING A CROWN 1 WITH INTERNAL TEETH 2 WITH A PAIR OF TEETH AS WELL AS A PAIR OF RATCHETS 5, 6 WITH SPRINGS 7, 8 MOUNTED IN POSITIONS DIAMETRALLY OPPOSED ON THE INTERNAL BODY 4 OF THE FREE WHEEL SO AS TO BE ABLE TO ATTACK TWO TEETH OF THE SAID CROWN SIMULTANEOUSLY.

Description

The present invention relates to improvements

  brought to freewheel groups for bicycles.

  It is known that a freewheeling group is constituted by two coaxial bodies, namely an inner body mounted integral in rotation with the hub of the rear wheel of the bicycle and an outer body carrying a plurality of toothed sprockets for the chain. of the same bicycle,

as well as by snap-on means intended to make the

said coaxial bodies integral with the rotation only in the direction of rotation which corresponds to the direction of travel. he

  It is also known that said snap-fastening means

  usually take a crown with solid inner teeth

  of the outer body and a pair of spring pawls capable of attacking said teeth of the crown in a given direction of relative rotation between said bodies and on the contrary to slide freely above said teeth in the direction of

opposite relative rotation.

  In the freewheel groups built so far the two pawls are mounted on the inner body in diametrically opposite positions while due to the inner gear crown provides an odd number of teeth, so that the reciprocal attachment between the two coaxial bodies of the group in the direction of travel is only ensured by a pawl at a time which acts on a tooth of the crown. The main reason for this provision derives from the need to limit the idle travel to a minimum. This must be done by the transmission (and therefore the pedal controlled by the cyclist) when changing from the freewheeling condition to

that of walking.

  In normal type freewheels, for which steel toothed rings are adopted, the arrangement which has just been described has no disadvantages from the point of view of efficiency and duration, although it gives rise to imperfectly balanced mating between

  two bodies which constitute the freewheel.

  However, this provision may give rise to

serious safety and timing issues

  that we adopt, to meet the requirements of perfection-

product for cycling competitions,

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light materials for the production of the inner gear ring of the freewheel. Indeed, the resistance of these materials is lower than that of steel, so that

the stress generated on a single point of said cou-

sound by one of the transmission pawls, as is the

  case in the known technique, may prove to be excessive and

  talk about ruptures, which we should naturally avoid

with the utmost care.

  The problem of successfully adopting freewheels fitted with lighter sprockets without sacrificing the advantages of safety and

  duration is solved by this utility model, depending on-

  which the internal gear crown of the freewheel group

  is a crown with an even number of teeth and in the-

  which transmission pawls are mounted in posi-

diametrically opposed, so that two teeth, also diametrically opposed, can be attacked simultaneously

that same crown.

  The invention will be better understood on reading the

  detailed description which follows given here next to the drawing

  attached which shows by way of example a form of realization

sation preferred and whose only figure is a sectional view taken through the freewheel group according to the present

utility model.

  The only figure represents a toothed crown 1 with tooth-

  inner re 2 and a plurality of toothed pinions 3 for the transmission chain (not shown) of the bicycle of the outer body of the freewheeling group according to the present invention, as well as a part of the inner body 4 of this same group equipped with pawls 5 and 6 intended to attack the teeth

2 of the crown under the action of springs 7 and 8.

  The crown gear 1 has an even number of teeth 2, while the pawls 5 and 6 are mounted in positions

  diametrically opposite on the body 4.

  Thanks to this arrangement, the pawls 5 and 6 are pushed by the springs 7 and 8 to simultaneously attack two opposite teeth of the crown 1, so that the stresses applied to it are well balanced and distributed,

  and therefore well absorbed by the structure illustrated.

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  In practice, the unit stresses on the points of

  attack between the pawls and the ring gear are reduced

your are about half of those normally provided in conventional freewheels in which there is only one pawl at a time which attacks the teeth of the crown. Thanks to this fact, the material of the stressed parts can

  be chosen from among those with integrated properties

strong and desired - like lightness - even if they

  have lower resistance than those who are

commonly used for this purpose.

On the other hand, it can be noted that thanks to the arrangement of the present invention, a better distribution is obtained.

  clearances between the balls interposed between the internal body

the outside body of the freewheel, as well as a

better distribution of the burdens on them.

  Furthermore, by reducing the internal diameter of the crown 1, and consequently the toothing 2 thereof, relative to normal, it is possible to limit the increase

of the idle stroke of the transmission at the time of its

  depending on what this device would tend to produce,

so that from this point of view moving from the

  sition with a single ratchet engaging the known technique

  to that of the present invention with two simultaneous pawls

  ment engaged with the crown has no drawbacks.

Claims (1)

CLAIM   Freewheeling group for a bicycle, of the type constituted by two coaxial bodies, including an inner body (4) mounted integral in rotation with the hub of the rear wheel of the bicycle and an outer body carrying a plurality of pi- toothed pins (3) for the transmission chain of said bi- bicycle as well as by snap-fastening means suitable for   dre said coaxial bodies integral with the single rotation- lying in the direction which corresponds to the direction of travel of the   bicycle, characterized in that said means to-   ratchet comprises a crown (1) with internal teeth (2), integral with the external body of the freewheel and provided with an even number of teeth, as well as a pair of pawls (5) and (6) with springs (7) and (8) mounted in diametric positions   trally opposite on the inner body (4) of the li-   bre, so that two teeth can be attacked simultaneously,   also diametrically opposite, of said crown (1).