Command device for a bicycle gear change

A command device for a bicycle gear change, comprising: a rotating drum (2) provided with a rotation axis (x) and being predisposed to rotate in opposite directions in order to wind at least a portion of a change-activating cable (3) on a lateral surface of the rotating drum (2); means for rotating, predisposed on command to rotate the rotating drum (2) in opposite directions according to predetermined angular steps; means for retaining predisposed to hold the rotating drum (2) in a position in absence of commands made to the means for rotating. The rotation axis (x) of the rotating drum (2) is perpendicular with respect to an advancement direction of the bicycle, that is, parallel to the rotation axis of the front wheel of the bicycle.

TECHNICAL FIELD

The invention relates to a command device for a bicycle gear change.

BACKGROUND ART

Gear commands of known type are generally mounted internally of the support connecting the levers of the brakes to the handlebars of the bicycle and generally comprise a rotating drum, having a rotation axis, which is rotated in opposite directions in order to cause a portion of a gear-activating cable to wind around the lateral surface of the drum. The cable can control the drive wheel gears or the centrally-mounted danger and exerts a force that, through a derailleur mechanism, is directed transversally with respect to the plane containing the transmission chain. This force translates the derailleur of the gear change more or less transversally with respect to the plane containing the transmission chain, so that the chain is moved between adjacent cogwheels mounted on the rotation pivot of the back wheel or the clanger.

Known-type commands further comprise means for rotating the rotating drum, on command and in opposite directions, in predetermined angular steps, and also comprise means for holding the rotating drum in position in the absence of commands on the means for rotation.

The means for rotating are constituted by a series of gears which transmit a couple between a lever, typically associated to a brake lever or constituted by the brake lever itself, and the rotating drum. The run of the lever or the activating lever and the transmission with the rotating drum are determined in such a way that each action on the lever corresponds to a determined rotation of the drum which is converted, through the activating cable, into a translation defined by the derailleur of the gear change mechanism.

The means for retaining generally comprise ratchet gears which, in the absence of commands, maintain the rotating drum in position. These means are necessary because the derailleur of the gear change, whether anterior or posterior, is provided with elastic means which exert an opposite force to the traction exerted by the activation cable.

Known-type commands exhibits some drawbacks. Firstly the rotation axis of the rotating drum is arranged parallel to the advancement direction of the bicycle. This creates a rather complex command architecture, in which both the means for rotating and the means for retaining are constituted by a high number of parts. The activation cable is caused to undergo considerable torsion in the tract thereof which goes from the rotating drum to the command lever, as it is wound in a transversal direction with respect to the rotation axis and exits the drum in a parallel direction to the rotation axis. This leads in particular to a fairly noticeable stiffness of activation of the gear change, and thus requires the use of elastic means and means for retaining which are able to exert considerable forces. Known type gear change mechanisms are in effect rather “hard” and noisy, due to the torsion the cable is subject to and the structural complication which means working with command torque that are unfavourable with respect to the torques of the resistant couples. The resistant couples have an arm that coincides with the radius of the rotating drum as the cable winds externally of the drum, while the activation couples have a smaller arm, as the gears defining the means for rotating are arranged, for reasons connected to their size, internally of the rotating drum.

The main aim of the invention is to provide a command for activation of a bicycle gear change which obviates the drawback in the prior art.

An advantage of the command is that it comprises a number of components which is notably lower with respect to the gear changes in the prior art.

A further advantage of the command mechanism is that it is considerably “softer” and quieter than known-type gear change mechanisms.

A further advantage of the invention is that the command mechanism is decidedly smaller in size than known-type mechanisms.

With reference to the figures of the drawings, number1indicates in its entirety a command mechanism according to the present invention. The command mechanism comprises a cylindrical rotating drum2, provided with a rotation axis x, predisposed to be activated to rotate in opposite direction in order to wind around its lateral surface (and unwind therefrom) a portion of an activation cable3of the gear mechanism. The command mechanism further comprises means for rotating which are predisposed to activate the rotating drum2, on command, in rotation in opposite directions, according to predetermined angular steps. The command mechanism also comprises means for retaining which are predisposed to hold the rotating drum2in position in the absence of a command to the means for rotating. The rotation axis x of the rotating drum2is perpendicular with respect to the advancement direction of the bicycle, i.e. it is parallel to the rotation axis of the front wheel inasmuch as typically the command mechanism is mounted on the handlebars of the bicycle. Thanks to the special arrangement of the rotation axis x of the rotating drum2, the portion of the cable3which winds and unwinds on and from the rotating drum2is always tangential with respect to the rotating drum2, i.e. the cable3, in proximity of the command mechanism, always lies on planes that are perpendicular with respect to the rotation axis x.

The means for rotating predisposed to rotate the rotating drum2on command in opposite directions at predetermined angular steps comprise a cylindrical cover4which is coaxial of the rotating drum2and rotating with respect to the rotation axis x. The cylindrical cover4is predisposed at least partially to close internally thereof the rotating drum2, and is provided on a lateral surface thereof with a through-passage4aand a maneuvering appendage4bwhich projects about radially towards the outside of the cylindrical cover4. The through passage4aenables passage of the cable3which extends between the rotating drum2and the gear change, while the maneuvering appendage4b, as will be better described herein below, has the function of a trigger, enabling a user to rotate the cylindrical cover4using a finger.

Also provided are means for realising a solid coupling in rotation between the cylindrical cover4and the rotating drum2.

The means comprise a circular-developing frontal cogging5, arranged internally of a first end surface4cof the cylindrical cover4, coaxially to the rotation axis x. The frontal cogging is solid in rotation with the cylindrical cover4.

The means further comprise an internal radial cogging6which is solidly constrained to the lateral surface of the cylindrical cover4in proximity of a second end surface4dof the cylindrical cover4, and which is coaxial to the rotation axis x.

The means also comprise a second circular-developing frontal cogging7, coutershaped to the first frontal cogging5and predisposed to enmesh therewith solidly in rotation in a single direction. The second frontal cogging7is arranged on an end surface of the rotating drum2coaxially to the rotation axis x, and is solid in rotation to the rotating drum2.

The first frontal cogging5and the second frontal cogging7, in a preferred embodiment, exhibit a “saw-tooth” shape. Each cog exhibits a flat front surface perpendicular to the drum rotation direction, and a surface portion, opposite the front surface, which is inclined with respect to the front surface. When the cogs enmesh, in one rotation direction the frontal surfaces of opposite cogs enter into reciprocal contact, solidly constraining the two coggings in rotation. In the opposite rotation direction, the front surfaces of the opposite cogs detach, while the inclined portions of surface run freely on one another without there being any rotation constraint between the two sets of cogs.

The means for enabling a solid rotation coupling between the cylindrical cover4and the rotating drum2also comprise a cogwheel8, which is coaxial to the rotation axis x, solid in rotation with the rotating drum2and arranged on the opposite side of the rotating drum2with respect to the second frontal cogging7. At least an idler wheel9, associated to a support element9afixed in rotation with respect to the rotation axis x, is arranged in such a way as constantly to enmesh with the cogwheel8. The idler wheel9is predisposed to enmesh on command also with the internal cogging6. In a preferred embodiment, illustrated in the attached figures, two idler wheels9are included, arranged at diametrically opposite positions with respect to the cogwheel8. In a non-illustrated preferred embodiment, the two idler wheels9are solidly constrained to the cylindrical cover4and constantly enmesh with the internal cogging6, and can on command enmesh with the cogwheel8.

The cylindrical cover4is slidable on command along the rotation axis x between a first position (FIG. 4), in which the first frontal cogging5enmeshes with the second frontal cogging7and the internal cogging6does not enmesh with the idler wheel9, and a second position (FIG. 5) in which the first frontal cogging5does not enmesh with the second frontal cogging7, being distanced therefrom, and the internal cogging6enmeshes with the idler wheel9which is as above-mentioned enmeshed at the same time with the cogwheel8. This is made possible by the size and arrangement of the various elements described: the distance that separates the first frontal cogging5from the internal cogging6, measured along the rotation axis x, is greater than the distance that separates the second frontal cogging7from the idler wheel9.

Also included are elastic means which, in the absence of a command, maintain the cylindrical cover4in one of the first and second positions.

In order fully to illustrate the functioning of the command mechanism of the present invention, the means for retaining the rotating drum in position2in the absence of a command on the rotation means will now be described.

They comprise at least a shaped element10, which in a preferred embodiment is a spherical bearing, contained in a housing11amade in a cage11solid in rotation with respect to the rotating drum2and the cylindrical cover4. The shaped element10is predisposed to engage, by means of the action of an elastic means arranged in the housing11a, in one of a plurality of chambers12made externally of at least a portion of the lateral surface of the rotating drum2and arranged at determined angular steps. In the preferred embodiment two shaped elements10are included, contained in respective housings11aarranged parallel to one another and aligned with respect to the rotation axis x, and two series of chambers12, defined by cylindrical sectors impressed transversally on two annular surface portions2athat project radially from the lateral surface of the rotating drum2and are coaxial to the rotating drum2. The housings11aare constituted by cylindrical channels arranged radially with respect to the rotating drum2and open towards the rotating drum. The two shaped elements10, or spheres, are pushed by the elastic means towards the outside of the housings in such a way that if the rotating drum2is in a suitable angular position the spheres penetrate at least partially internally of a respective chamber12. The force with which the spheres are pressed in the direction of the chambers12, which is radially directed with respect to the rotating drum2, is sufficient to maintain the rotary drum2in the corresponding angular position.

The cylindrical cover4rotates on command about the rotation axis x between two extreme positions separated by an angular step so that, by rotating from a first to a second of the extreme positions, the cylindrical cover4induces on the rotary drum2a rotation which is sufficient at least to bring the shaped element10from a chamber12to an adjacent chamber12. Elastic means are provided which maintain the cylindrical cover4in one of the extreme positions in the absence of a command.

In a further embodiment (not illustrated) the means for retaining predisposed to hold the rotating drum2in position in the absence of a command on the rotating means can be constituted by a friction device, i.e. a device which does not include engagement between various elements, but which exploits a friction determined between at least two surfaces. It is possible, for example, to include a friction surface arranged blow the cage11which interacts with the annular surface portions2aof the rotating drum2. In this case, obviously, the cage11does not internally contain the housings11a.

Now we move on to illustrating the functioning of the command in relation to the preferred embodiment.

Let us consider that the rotation axis x is fixed with respect to the handlebars of the bicycle (the constructional details will be clarified hereinafter). The cylindrical cover4is maintained by the elastic means therefor in the first position (FIG. 4), in which position the first frontal cogging5enmeshes with the second frontal cogging7and the internal cogging6does not enmesh with the idler wheel9. Pulling with a finger on the manoeuvring appendage4btowards the handlebars, a rotation is induced by one determined angular step of the cylindrical cover4between the described extreme rotation positions. In the figures, this rotation is in the direction of the rotation axis x, indicated to simplify the present description The frontal coggings5,7, in this rotation direction, are solidly reciprocally constrained, so that the rotating drum2is drawn in rotation with the cylindrical cover4, for example winding the cable3. In performing this rotation, the chambers12translate with respect to the shaped elements or spheres10. Supposing that at the start of rotation the spheres10are engaged in respective chambers12, at the end of the rotation they will be engaged in chambers12one step along from before the rotation of the rotating drum12. By releasing the manoeuvring appendage4b, the cylindrical cover4returns to the initial position, after having made an oppositely-direction rotation with respect to the previous one, i.e. not in the direction of the rotation axis x. In this rotation direction, the frontal coggings5,7, freely run one on another, thus the rotating drum2is maintained in the position reached.

To unwind the cable3a rotation in the direction of the rotation axis x must be induced on the rotating drum2. To obtain this result it is sufficient to translate the cylindrical cover4along the rotation axis x from the first position to the second position (FIG. 5), i.e. the position in which the first frontal cogging5does not enmesh with the second frontal cogging7, being distanced therefrom, and the internal cogging6enmeshes with the idler wheel9, which at the same time enmeshes with the cogwheel8. The translation of the cylindrical cover4along the rotation axis x can be induced very simply by acting on the manoeuvring appendage4b. In these conditions, a rotation of the cylindrical cover4in the direction of the rotation axis x induces a rotation in the other direction of the rotating drum2, which will cause the cable3to unwind.

The interaction between the spheres10and the chambers12is the same as described herein above, obviously developing in the opposite direction. By releasing the manoeuvring appendage4b, the cylindrical cover4is brought back into the first position with respect to the translation along the rotation axis x and at the same time it rotates in an opposite direction with respect to the direction of the rotation axis x, without interfering with the rotating drum2. The unwinding of the cable3is thus obtained by pulling the manoeuvring appendage firstly slightly diagonally, then in a perpendicular direction with respect to the rotation axis x.

From a constructional point of view, the command mechanism comprises a support pivot13which is coaxial to the rotation axis x, on which the rotating drum2, the cylindrical cover4and the support element9aof the idler wheel9are mounted. The support pivot13is solidly constrained to a part of the bicycle, typically to the handlebars in proximity of a brake lever. The rotating drum2is solidly constrained to the pin13for displacements parallel to the longitudinal axis x, while it is free in rotation. The cylindrical cover4, apart from being free in rotation between its extreme positions, is longitudinally slidable with respect to the pin13between the first and second positions. The support9ato which the idler wheel9is associated in solidly constrained to the pin13.

The cylindrical cover4, in the preferred embodiment, it made of two parts a first portion41, cylindrical and open at an end, and a second portion42, provided with a central opening which enables passage of the support pivot13and is predisposed to be located at the open end of the first portion41, closing it.

The cage11, which in the preferred embodiment of the command mechanism, comprises two housings11a, is maintained in position at a correct radial distance with respect to the rotating drum2by means of two shaped rings43which are arranged about the rotating drum2by a side and externally of the annular surface portions2a. The cage11and a portion of the shaped rings43project externally of the cylindrical cover4through the passage4aand are held in position with respect to the bicycle at one of these projecting parts. On one side the projecting parts strike against a surface which is solidly constrained to the handlebars, and on the other side, in the rotation direction of the rotating drum2, the projecting parts are pressed towards the surface which is solidly constrained to the handlebars thanks to the elastic means. In this way the cage11can rotate, small rotations with respect to the rotations of the rotating drum2and the cylindrical cover4, about the rotation axis x in order to compensate for any play in the cable3.

The cable3in wound on the rotating drum2on the surface portion thereof comprised between the annular surface portions2a. Means of known type are provided to enable hooking an end of the cable to the rotating drum2.

The elastic means mentioned in the description are constituted by: a first helix spring100, arranged between the cylindrical cover4and a part of the handlebars of the bicycle, which exerts a force directed along the rotation axis x that pushes the cylindrical cover4towards the first position; a second helix spring101, also arranged between the cylindrical cover4and a part of the bicycle's handlebars, which exerts a torque about the rotation axis x which pushes the cylindrical cover4towards the first extreme rotation position; two helix springs102, arranged internally of the housings11a, arranged to exert a radial force with respect to the rotating drum2which pushes the spheres10towards the rotating drum2.

With reference toFIGS. 6,7,8,9,10a,10b,10c, a description will follow of a further preferred embodiment of the command mechanism of the present invention.

In the second preferred embodiment, the means for rotating, predisposed to rotate the rotating drum2in opposite directions according to determined angular steps, comprise a ratchet gear for rotating the rotating drum2in the winding direction of the cable3. With reference toFIG. 7, the rotation direction of the rotating drum2, which leads to a winding-on of the cable3onto the rotating drum, is an anticlockwise rotation, while inFIG. 8the rotation is clockwise.

The ratchet gear comprises a first cogging21, saw-tooth shaped and arranged peripherally of the rotating drum2, and a pawl22, an end of which is predisposed to engage with the first cogging21.

A shaped element23, constrained to the pawl22, is predisposed to activate is the pawl22in translation along a direction which is tangential to the rotating drum2. The shaped element23comprises two annular portions23a, parallel to one another, which are connected by a connection portion23band which comprise the rotating drum2between them. Also in this second preferred embodiment of the command mechanism, the rotating drum2is mounted coaxially to a support pivot13which is coaxial to the rotation axis x of the rotating drum2itself. The annular portions23aof the shaped element23are also arranged coaxially to the support pin13so that the shaped element23is rotatable about the rotation axis x.

The pawl22is rotatably constrained to the shaped element23, in particular to the connection portion23bthereof, at an opposite end to the end predisposed to engage to the first cogging21. Elastic means, preferably a helix spring interpositioned between the connection portion23band the pawl22, are predisposed to maintain the pawl22in contact with the first cogging21. By rotating the shaped element23the pawl22is translated along a direction which is tangential to the rotating drum2. The first cogging21and the pawl22are shaped and arranged so that with reference toFIG. 8a rotation in a clockwise direction of the shaped element23translates the pawl tangentially to the rotating drum2in a direction in which the pawl22blocks in the first cogging21. Thus the shaped element23and the rotating drum2are solid in rotation in a direction that causes the cable3to wind onto the rotating drum2.

As regards the unwinding-direction rotation of the cable3from the rotating drum2, the means for rotating predisposed to rotate the rotating drum2comprise elastic means24, in particular a spiral spring associated to the rotating drum2and predisposed to rotate the drum itself in the direction of unwinding of the cable3. An arresting mechanism25is activatable between a is stop configuration, in which rotation of the drum is prevented in the unwinding direction of the cable3, and a release configuration in which the rotation by one determined angular step of the rotating drum is permitted, by effect of the action of the elastic means24.

The arrest mechanism25comprises a second cogging26, solid in rotation with the rotating drum2. A stop cog27is mobile between a first position, in which it is engaged to the second cogging26and prevents a rotation of the rotating drum2in the unwinding direction of the cable (FIG. 10a), and a second position, in which does not engage with the second cogging (FIGS. 10band10c).

The arrest mechanism also comprises an oscillating cog28, rotatingly constrained to the stop cog27about an oscillation axis, and free to rotate by a predetermined angle. The oscillating cog28is positioned, with respect to the stop tooth27, in such a way that in the first position the stop cog27(FIG. 10a) does not engage with the second cogging26, while in the second position of the stop cog27(FIGS. 10band10c), the oscillating cog28engages with the second cogging26.

The oscillating cog28engages in the second cogging26at a first end of the rotation angle (FIG. 10b). The cog28is rotated by the rotating drum2up to a second of the rotation angle, at which it stops and also arrests the rotation of the rotating drum (FIG. 10c). Elastic means are predisposed to push the oscillating cog28to rotate from the second end towards the first end of the rotation angle.

As can be seen inFIGS. 9,10a,10b,10c, the stop cog27is solidly constrained to a trigger29oscillating on command about an axis b. The oscillating cog29is rotatingly constrained to the trigger29so that, by rotating the trigger29bout its oscillation axis b, the stop cog27is displaced between its first and second position with respect to the second cogging26, drawing the oscillating cog28with it. InFIG. 10athe stop cog27is shown in the first position.

By rotating the trigger about its oscillation axis b, the stop cog can be brought into the second position, illustrated inFIGS. 10band10c, in which it is not in contact with the second cogging26. For a tract of the run of the stop cog27between the first and second positions, both the stop cog27and the oscillating cog28are in contact and engaged to the second cogging26. InFIG. 10bthe oscillating cog28is represented at a start stage of engagement of the oscillating cog28to the second cogging26, in which it is at the first end of the rotation angle. InFIG. 10cthe oscillating cog28is shown at an end stage of the engagement of the oscillating cog28to the second cogging26, in which it is at the second end of the rotation angle. In the configuration ofFIG. 10cthe rotating drum2has made a rotation by an angle corresponding to the rotation angle made by the oscillating cog28. The rotation angle of the oscillating cog28is such that, when the oscillating cog28is at the second end of the rotation angle, the second cogging26is in a position in which the stop cog27, passing from the second to the first position, engages with the cog of the consecutive second cogging26with respect to the cog with which it was engaged at the start stage, illustrated inFIG. 10a, previously to the described sequence.

The activation of the means for rotating the rotating drum2, both in the winding and in the unwinding directions of the cable3, can be very simply performed using a shaped lever30. The shaped lever30is rotatingly constrained to the shaped element23about the oscillation axis b of the trigger29. The shaped lever30is solidly constrained to the shaped element23with respect to rotation about the rotation axis x and is also associated to the trigger29in such a way as to activate the trigger in rotation about its own oscillation axis b. Preferably the shaped lever30is solidly constrained to the trigger29with respect to rotation about the oscillation axis b of the trigger itself.

With reference toFIG. 8, to rotate the rotating drum2in the cable3winding direction, it is sufficient to exert a force on the shaped lever30which exhibits at least one component which is parallel and directed equally to the force indicated by vector T. As the shaped lever30is solid in rotation with the shaped element23with respect to the rotation axis x of the rotating drum2, the action of the force T induces a rotation in a clockwise direction of the shaped element23about axis x. The rotation of the shaped element23, by means of the pawl22and the first cogging21, is transmitted to the rotating drum2, which is drawn in rotation about the axis x in a clockwise direction, i.e. in the cable3winding direction. Elastic means31, preferably a spiral spring, are interpositioned between the shaped element23and the support pivot13and exert on the shaped element23an action which contrasts the rotation of the shaped element23in a clockwise direction. In the absence of force T, the spiral spring31rotates the shaped element23in anticlockwise direction up until it reaches a start position. The anticlockwise rotation of the shaped element23does not induce a corresponding rotation of the rotating drum2as the pawl22, in this rotation direction, does not engage on the first cogging21. The elastic means31can be substituted by any means able to exert on the shaped element23an action which is equivalent to an action exerted by the elastic means31.

Still in reference toFIG. 8, to activate the rotating drum2in the cable3unwinding direction, i.e. in an anticlockwise direction, it is sufficient to exert on the shaped lever30a force which has at least one component which is parallel and same-directed as the force indicated by vector S. The action of force S induces a rotation of the shaped lever30and the trigger29about the oscillation axis b of the trigger itself which leads to the displacement of the stop cog27from the first to the second position. As mentioned above, in the second position the stop cog27is not engaged to the second cogging26which is engaged by the oscillating cog28. The oscillating cog28, which is free to rotate by a determined angle, is drawn in rotation by the rotating drum2by the push of the elastic means24up to a second end of the rotation angle at which it stops and also stops the rotation of the rotating drum2. Elastic means32, preferably a helix spring, are associated to the trigger29and are predisposed to exert an action which is opposed to the force S. In the absence of the force S the elastic means32bring the trigger29and the shaped lever into a start position in which the stop cog27engages with the second cogging26, blocking the rotating drum2in position. The elastic means32can be substituted by any means able to exert on the trigger29and action which is equivalent to that exerted by the elastic means32.

Advantageously the shaped lever30comprises two portions30a,30b, which are hinged to one another about an intermediate hinge axis s. Elastic means are predisposed to push the two portions30a,30binto a determined relative position, suitable for activation of the shaped lever30. A blocking device is actionable between a configuration in which it prevents relative rotation between the two portions30a,30b, and a configuration in which it enables a relative rotation between the two portions30a,30bof the shaped lever30.

The blocking device comprises a rod33which, at one end, is rotatingly constrained to one portion30aof the shaped lever30, the other end30bbeing predisposed to engage in a seating33bwhich is solidly constrained to the other portion30bof the shaped lever30a,30b. The rod33is rotatable between a position in which it engages in the seating33band prevents relative rotation between the two portions30a,30b, and a position in which it does not engage in the seating33band enables relative rotation between the two portions30a,30bof the shaped lever30. In the position in which it prevents the relative rotation between the two portions30a,30b, shown inFIGS. 8 and 9, the rod33functions as a strut between the two portions30a,30b. Elastic means are included for pushing the rod33into the blocking positioning which it prevents the relative rotation between the two portions30a,30b.

Advantageously the blocking device is activatable by means of an activating brake lever50. Preferably the shaped lever30is arranged in such a way that when the brake lever50is rotated, the blocking device is brought by the activating lever50into the configuration in which it does not prevent relative rotation between the portions30a,30bof the shaped lever. In these conditions the lower portion30bcan be drawn in rotation with respect to the upper portion30aof the shaped lever30by the brake lever50.

In more detail, the brake lever50is predisposed to interfere with an appendage33aof the rod33. The activation of the brake lever50leads to a rotation of the rod33into the position in which it does not engage in the seating33band permits relative rotation between the portions30a,30bof the shaped lever30.

The preferred arrangement of the shaped lever30, and in general of the command of the invention, is illustrated inFIG. 6. The shaped lever30is brought adjacent to the external side of the brake lever50. All the elements of the command which are activated by the shaped lever30are contained internally of the body51connecting the lever50to the handlebars of the bicycle. As can easily be deduced fromFIG. 6, the shaped lever30can be activated by the cyclist's fingers when the hand grips the handlebars or the body51. Traction of the brake lever50is not influenced by the presence of the shaped lever30which, thanks to the presence of the blocking device, is free to follow the rotation of the brake lever50.

The gear change made of the present invention offers important advantages.

Firstly, the arrangement of the rotation axis of the rotating drum considerably limits the overall size of the command mechanism. The cable is not subject to twisting and deviations, apart from being wound about the rotating drum.

Thanks to this arrangement, the number of components required for the command to function is very much lower than in known-type command mechanisms. A further advantage connected to the special arrangement of the rotation axis of the rotating drum is that the command mechanism proposed is considerably “softer” and quieter than in known-type mechanisms.

The absence of high torque on the cable and the fact that the arm of the couple and resistance are about the same lead to a reduction of the forces required for activating the command mechanism.