Chain transmission, particularly for bicycles, with continuously variable transmission ratio

A mechanical transmission comprising a chainring rotatable around an axis of rotation (x), at least one sprocket and a chain for transmitting to said at least one sprocket the rotary motion of the chainring around the axis of rotation (x),

• wherein the chainring comprises a disc and a plurality of meshing devices which are mounted in radially movable manner on the disc and are arranged to enable engagement of the disc with the chain for transmitting motion from the chainring to said at least one sprocket by means of the chain,
• wherein the transmission further comprises a shifting device for varying the radial position of the meshing devices in order to change the transmission ratio with which the chainring transmits motion to said at least one sprocket,
• wherein each meshing device comprises a support body and a tilting fork which is tiltably supported on the respective support body around a first tilting axis (x′) parallel to the axis of rotation (x) of the chainring and comprises at least one tooth for engaging a link of the chain,
• wherein each meshing device further comprises a braking device for preventing the respective tilting fork from tilting around said first tilting axis (x′),
• wherein said braking device comprises:
• a tilting member supported in tiltable manner on the tilting fork around a second tilting axis (x″) parallel to said first tilting axis (x′),
• a braking member which is supported on the support body for tilting around a third tilting axis (A) normal to said first and second tilting axes (x′, x″) between a first position, in which the braking member does not engage with the tilting member, and a second position, in which the braking member engages with the tilting member so as to prevent the tilting member from tilting, and
• a control element operatively connected to the braking member to control the movement of the braking member between said first and second positions.

A mechanical transmission comprising a chainring rotatable around an axis of rotation (x), at least one sprocket and a chain for transmitting to said at least one sprocket the rotary motion of the chainring around the axis of rotation (x),

• wherein the chainring comprises a disc and a plurality of meshing devices which are mounted in radially movable manner on the disc and are arranged to enable engagement of the disc with the chain for transmitting motion from the chainring to said at least one sprocket by means of the chain,
• wherein the transmission further comprises a shifting device for varying the radial position of the meshing devices in order to change the transmission ratio with which the chainring transmits motion to said at least one sprocket,
• wherein each meshing device comprises a support body and a tilting fork which is tiltably supported on the respective support body around a first tilting axis (x′) parallel to the axis of rotation (x) of the chainring and comprises at least one tooth for engaging a link of the chain,
• wherein each meshing device further comprises a braking device for preventing the respective tilting fork from tilting around said first tilting axis (x′),
• wherein said braking device comprises, for each meshing device:
• a first pack of plates carried by the tilting fork so as to be drivingly connected therewith for tilting around said first tilting axis (x′) and a second pack of plates mounted on the support body, wherein the plates of at least one of said first and second packs of plates are provided with friction linings,
• a braking member which is supported on the support body for tilting around a third tilting axis (A) normal to said first tilting axis (x′) between a first position, in which the braking member does not press the plates of the first pack of plates and the plates of the second pack of plates against each other, and a second position, in which the braking member presses the plates of the first pack of plates and the plates of the second pack of plates against each other so as to prevent the assembly formed by the first pack of plates and the tilting fork from tilting, and a control element operatively connected to the braking member to control movement of the braking member between said first and second positions.