Device for fastening a cycle wheel
Skewer for tightening a cycle wheel to the cycle frame, such skewer including a first end having a threaded portion cooperable with a female thread of a first frame portion, and a second end having axial abutment mechanisms for contacting a second frame portion, as well as drive mechanisms to enable a user to alternately exert a tightening torque or a loosening torque. A torque limiting mechanism operational in the tightening direction is positioned between the drive mechanisms and the rod. The skewer further includes a braking device to increase the torque required to initiate the rotation of the drive mechanisms in the loosening direction. The braking device includes two mutually contacting friction surfaces when the axial abutment mechanisms are in contact with the second frame portion. When the torque limiting mechanism is operational, the braking device becomes non-operational because the friction surfaces are no longer in mutual contact.
1. Tightening skewer for fastening a cycle wheel to a cycle frame, said skewer comprising:
a rod extending along a longitudinal axis, said rod comprising:
a first end comprising a threaded portion configured to cooperate with a female thread provided in a first portion of the cycle frame;
a second end provided with axial abutment mechanisms configured to come into contact with a second portion of the frame of the cycle; and
a central portion extending between the first and second ends;
drive mechanisms configured to enable a user to alternately exert a tightening torque or a loosening torque;
a torque limiting mechanism operational in a tightening direction and positioned between the drive mechanisms and the rod; and
a braking device configured to increase a torque required to initiate rotation of the drive mechanisms in a loosening direction.
2. Tightening skewer according to claim 1 , wherein:
the braking device comprises two friction surfaces that are in contact with one another when the axial abutment mechanisms are in contact with the second frame portion.
3. Tightening skewer according to claim 1 , wherein:
the torque limiting mechanism comprises two cam rings juxtaposed and movable in relation to one another in translation along the longitudinal axis and in rotation along to the longitudinal axis; and
each of the cam rings comprises cams for varying a relative axial position of the two rings between a “close together” position and a “spaced apart” position.
4. Tightening skewer according to claim 3 , wherein:
the braking device is positioned between the drive mechanisms and the rod.
5. Tightening skewer according to claim 4 , wherein:
the braking device comprises a cylindrical sleeve, said cylindrical sleeve comprising:
a first axial end constituting said axial abutment mechanisms; and
a second end configured to come into contact with a surface affixed to the drive mechanisms.
6. Tightening skewer according to claim 5 , wherein:
the axial length of the sleeve is such that:
when the two cam rings of the torque limiting mechanism are in the “close together” position, the second end of the sleeve is in contact with the surface affixed to the drive mechanisms; and
when the two cam rings are in the “spaced apart” position, the second end of the sleeve is not in contact with said surface.
7. Tightening skewer according to claim 1 , wherein:
the torque limiting mechanism has a trigger value between 3.0 and 20 Nm.
8. Tightening skewer according to claim 1 , wherein:
the torque limiting mechanism has a trigger value between 6.0 and 12 Nm.
9. Tightening skewer according to claim 7 , wherein:
when the user initiates a loosening phase, the braking device generates a friction torque that is greater than 5% of the value of the trigger torque of the torque limiting mechanism.
10. Tightening skewer according to claim 7 , wherein:
when the user initiates a loosening phase, the braking device generates a friction torque that is greater than 10% of the value of the trigger torque of the torque limiting mechanism.
11. Tightening skewer according to claim 8 , wherein:
when the user initiates a loosening phase, the braking device generates a friction torque that is greater than 5% of the value of the trigger torque of the torque limiting mechanism.
12. Tightening skewer according to claim 8 , wherein:
when the user initiates a loosening phase, the braking device generates a friction torque that is greater than 10% of the value of the trigger torque of the torque limiting mechanism.