VEHICLE TRANSMISSION SYSTEM AND A BICYCLE

FIELD OF THE INVENTION

The present invention concerns the technical sector relating to vehicles propelled by a person or by a mixed system, i.e. with assisted human propulsion, for example propelled by a human supported by an electric motor. In greater detail, the present invention concerns a gear shift, a gear shift of a chain or cogged belt transmission system provided with the gear shift and a human- or mixed-powered vehicle provided with the gear shift of the chain or cogged belt transmission system or gear shift, preferably a bicycle.

DESCRIPTION OF THE PRIOR ART

It is known that the use of gear shifts or speed changes enables a good coupling to be found between propulsion and load when the operating conditions vary. For example, widely-used transmission systems for bicycles have been known for a considerable time, for the transmission of torque from the bottom bracket to the rear wheel, which comprise a front gear set set in rotation by the bottom bracket, a rear gear set, a chain connecting the front gear set to the rear gear set and derailleurs for engaging the chain on the various gears of the gear sets. In general the rear gear set is connected to the wheel via a free wheel or an overrunning clutch.

A gear set for a bicycle is described, for example, in EP 3037336 B1 .

The last century saw a progressive increase in the number of gears in the gear sets, especially as regards the rear gear set of bicycles, with a consequent increase in the axial extension of the gear set. It follows that the chain is, in a difficult way, arranged or substantially arranged on a perpendicular plane to the rotation axes of the front gear set and of the rear gear set, thus reducing the efficiency of the transmission of the energy or indeed preventing operation with pairs of front and rear gears, the positions of which would make the chain too oblique with respect to the longitudinal direction to correctly engage the coggings and/or derailleurs.

DE 20 2009 001802 U1 and WO 00/68068 A1 describe solutions developed to improve transmission efficiency, guaranteeing that the gear engaged with the chain is always on a same plane. These solutions have a great impact on the axis of the wheel, have a significant overall size and require the displacement of all the gear set each time the engaged gear changes.

The displacement of the chain between the gears of a gear set takes place with external and distinct mechanisms, being shifts or derailleurs, arranged detached from the gear set and which require adjustments for the specific installation and during the course of the working life of the transmission system.

Document WO 2014054017 A1 describes a transmission system of a bicycle comprising a cogged belt, a derailleur and two pinions sets configured to rotate together with the driven shaft which have gears that are movable between a working position, or extracted, and a rest position, or retracted, with the working positions being interposed between the rest positions. The solution of WO 2014054017 A1 enables arranging the chain almost aligned with respect to the longitudinal direction but requires a derailleur and shifts in order to replace a second gear to a first gear engaged with the chain.

The present invention intends to obviate one or more drawbacks of the solutions of the prior art.

SUMMARY OF THE INVENTION A first aim of the present invention is to provide a gear shift which enables the chain or cogged belt to operated in the best conditions, i.e. enables the chain or cogged belt of a transmission system to operate aligned or substantially aligned.

A second aim of the present invention is to provide a gear shift without external or distinct elements, with the exception of those for command and/or control, so as to reduce or eliminate the adjustments following installation on the vehicle, either at the beginning or during the course of the working life thereof.

A still further object of the present invention is therefore to provide a transmission system without a derailleur.

A further aim of some embodiments is to maximise the efficiency of the energy transmission.

A further aim of some embodiments is to facilitate the control and command of the gear shift.

A further aim of some embodiments is to utilise movement devices of the easily- controllable and/or utilisable parts in contexts with long periods between successive maintenance operations.

These and other aims, which will be obvious to the expert in the sector from a reading of the following text, are attained by means of a gear shift of a chain or cogged belt transmission system of a human- or mixed-powered vehicle to vary the rotation velocity of a driven shaft, of a transmission system of a human- or mixed-powered vehicle and a human- or mixed-powered vehicle, preferably a bicycle, according to the claims.

In accordance with the teachings of the present document, the gear shift comprises a first gear, a second gear, a first part, a second part and means for moving the gears. The first gear is a pinion or a crown, has a first cogging for enmeshing with a chain or cogged belt with a first primitive diameter and is configured to be coupled to a driven shaft so as to rotate together with the driven shaft about a respective rotation axis to transfer the drive from the chain or cogged belt to the driven shaft.

The second gear is a pinion or a crown, has a second cogging for enmeshing with the chain or cogged belt with a second primitive diameter that is different to the first primitive diameter and which is configured to be coupled to the driven shaft so as to rotate together with the driven shaft about the rotation axis in order to transfer the drive from the chain or cogged belt to the driven shaft.

The first part is configured to be coupled to the driven shaft so as to rotate together with the driven shaft about the rotation axis and such as to be radially external of the first gear, i.e. so as to be more distant in the radial direction from the rotation axis with respect to the first gear.

The second part is configured to be coupled to the driven shaft so as to rotate together with the driven shaft about the rotation axis and such as to be radially external to the second gear, i.e. so as to be more distant in the radial direction from the rotation axis with respect to the second gear.

The first gear and the second gear are both configured to be coupled to the driven shaft so as to be able to translate in the direction of the rotation axis between a rest position and a working position, and vice versa, and so that the working positions lie, with respect to the rotation axis, between the rest positions of the first gear and of the second gear.

As will emerge clearly from the reading of the follow description, in the working position the gear does not necessarily enmesh with the chain or cogged belt, for example because the chain or cogged belt might be enmeshed with a larger gear of the same gear set, as occurs in the embodiment of figure 8.

The first part and the second part are both configured to be coupled to the driven shaft so as to contact the chain or cogged belt in the movement of the respective gear between the working position and the rest position.

The means for moving the gears are advantageously configured to move the first gear into the rest position in the movement of the second gear into the working position and to move the second gear into the rest position in the movement of the first gear into the working position so that the chain or cogged belt contacts the first part or the second part, disengaging the gear which is moved into the rest position and engaging the gear which is moved into the working position.

The transmission system comprises a gear shift according to the invention, a chain or cogged belt and tensioning means of the chain or cogged belt.

The human- or mixed-powered vehicle is preferably, though not exclusively, a bicycle and comprises at least a gear shift or a transmission system according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Specific embodiments of the invention will be described in the following part of the present description, according to what is set down in the claims and with the aid of the appended figures, in which: figure 1 is an axonometric view of a portion of an embodiment of the bicycle according to the invention; figures 2 and 3 are lateral views of the portion of figure 1 , with figure 2 illustrating the cutting plan of figures 4 and 7; figure 4 is a section view from below of the portion of figure 1 along plane IV-IV of figure 2; figure 5 is a view from below of the portion of figure 1 ; figure 6 is a view from behind of the portion of figure 1 ; figure 7 is a section view from behind of the portion of figure 1 along plane VII-VII of figure 2; figure 8 is a frontal view of an embodiment of gear shift according to the invention identical to the one used in the portion of figure 1 with a trace line of the cutting plane of the following figure; figure 9 is a section view of the gear shift of figure 8 along plane IX - IX of figure 8; figures from 10 to 13 schematically show the positions of the discs with respect to the structure in various operating conditions of the gear shift of figure 8; figures 14 and 15 are axonometric views from different points of view of a gear shift according to the invention, entirely alike the view of figure 8 but which comprises a driven shaft; figures from 16 to 19 are axonometric views of the gears of the gear shift of figure 8; figures 20 and 21 are axonometric views of the cages of the gear shift of figure 8; figures 22 and 23 are plan views of the cages of the gear shift of figure 8 from the non-visible side of figures 20 and 21 ; figure 24 is a section view of the following figure; figure 25 is a view of some of the components of the gear shift of figure 8 with the trace of plane XXIV - XXIV; figure 26 is an axonometric view of the gear of figure 18, from a different viewpoint; figure 27 is an axonometric view of a further embodiment of a guide element in figure 25; figures 28 and 29 are axonometric views of further embodiments of gears of a gear shift according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to the appended figures, reference numeral 100 denotes a gear shift of a chain or cogged belt transmission system of a human- or mixed-powered vehicle to vary the rotation velocity of a driven shaft (103).

An embodiment of the gear shift (100) comprises a first gear (1 ), a second gear (2), a first part (3), a second part (4) and means for moving the gears (6, 7), i.e. to move at least the first gear (1 ) and the second gear (2).

The first gear (1 ) is a pinion or a crown and has a first cogging (11 ) for enmeshing with a chain or cogged belt (9) of a chain or cogged belt transmission system of a human- or mixed-powered vehicle.

The first cogging (11 ) has a first primitive diameter.

The first gear (1 ) is configured to be coupled to a driven shaft (103) so as to rotate together with the driven shaft (103) about a respective rotation axis (X) to transfer the drive from the chain or cogged belt (9) to the driven shaft (103).

The second gear (2) is a pinion or a crown, i.e. it is a pinion if the first gear (1 ) is a pinion or is a crown if the first gear (2) is a crown and has a second cogging (21 ) for enmeshing with the above-mentioned chain or cogged belt (9).

The second cogging (21 ) has a second primitive diameter that is different to the first primitive diameter, i.e. is different to the first cogging (11 ) so as to vary the rotation velocity of the driven shaft (103).

The second gear (2) is configured to be coupled to the driven shaft (103) so as to rotate together with the driven shaft (103) about the rotation axis (X) to transfer the drive from the chain or cogged belt (9) to the driven shaft (103).

The first part (3) is configured to be coupled to the driven shaft (103) so as to rotate together with the driven shaft (103) about the rotation axis (X) and such as to be radially external of the first gear (1 ).

The second part (4) is configured to be coupled to the driven shaft (103) so as to rotate together with the driven shaft (103) about the rotation axis (X) and such as to be radially external of the second gear (2).

The first gear (1 ) and the second gear (2) are both configured to be coupled to the driven shaft (103) so as to be able to translate in the direction of the rotation axis (X) between a rest position and a working position, and vice versa, and so that the working positions lie, with respect to the rotation axis (X), between the rest positions of the first gear (1 ) and of the second gear (2).

The expert in the sector will understand that there are numerous possible configurations of known type to enable obtaining the described arrangement between the components of the gear shift (100) and the driven shaft (103; only some of these configurations are described in the present description or represented in the appended figures.

The gear shift (100) can be made and marketed with the first gear (1 ) and the second gear (2) already coupled to the driven shaft (103) with the described arrangement or, in an entirely equivalent way, can be configured to be mountable on the driven shaft (103) so as to obtain the arrangement. For example, the gear shift (100) might be configured so as to be adapted to a driven shaft (103) of a common or standard type.

The embodiment of figure 14 differs from that of figure 8 in that it comprises the driven shaft (103). With the arrangement, once coupled to the driven shaft (103), the first gear (1 ) and the second gear (2) rotate together with the driven shaft about the rotation axis (X) and can translate so that the first cogging (11 ) and the second cogging (21 ), in the rest position, lie on two distinct points of the driven shaft (103) and, in the working position, lie on a same point interposed and preferably equidistant from the two distinct points. In other embodiments the first cogging (11 ) and the second cogging (21 ), in the working position, can lie on two distinct points of the driven shaft (103), but in any case interposed.

The first part (3) is configured to be coupled to the driven shaft (103) so as to contact the chain or cogged belt (9) in the movement of the respective gear (1 , 2) between the working position and the rest position.

The first part (3) preferably internally houses the first gear (1 ) in the rest position.

The second part (4) is configured to be coupled to the driven shaft (103) so as to contact the chain or cogged belt (9) in the movement of the second gear (2) between the working position and the rest position.

The second part (4) preferably internally houses the second gear (2) in the rest position.

The means for moving the gears (6, 7) are advantageously configured to move the first gear (1 ) into the rest position in the movement of the second gear (2) into the working position so that the chain or cogged belt (9) contacts the first part (3), disengaging the first gear (1 ), i.e. the gear which is moved into the rest position, and engaging the second gear (2), i.e. the gear which is moved into the working position.

Further, the means for moving the gears (6, 7) are configured to move the second gear (2) into the rest position in the movement of the first gear (1 ) into the working position so that the chain or cogged belt (9) contacts the second part (4) or the second gear (2), i.e. the gear which is moved into the rest position, and engaging the first gear (1 ), i.e. the gear which is moved into the working position.

The expert in the sector will understand that there are numerous possible configurations of known type which enable obtaining the arrangement and the movements described in the foregoing of which only some are illustrated in the present description or represented in the appended figures.

The gear shift (100) described in the foregoing obviates a number of drawbacks of the solutions of the prior art. In particular, it enables the chain or cogged belt (9) to operate in the best conditions as the chain or cogged belt (9) is always between the rest positions, i.e. between the first part (3) and the second part (4).

Further, the action of changing gear does not require external or distinct elements, especially a derailleur, and the gear shift (100) of the invention reduces or eliminates the need for adjustments during the working life thereof.

In experimental testing the conformations of the gears in use in the pinion sets of bicycles, together with the corresponding chains or cogged belts (9), guarantee the disengaging of the chain or cogged belt (9) in the contact with the first part (3) or with the second part (4). However, it is possible to include coggings (11 , 21 , 31 , 41 ) that are specially conformed, for example with tapering or bevels (16, 26, 36, 46) as can be observed by way of example in figures from 16 to 19.

The gear shift (100) according to the invention can easily be produced in a single block to be coupled to the driven shaft (103) or to the frame (102) of the human- or mixed-powered vehicle so as to reduce as far as possible the operations necessary for installation and to maximise the benefits obtained by the mounting thereof in the industrial field. Preferably in the working positions of the first gear (1 ) and the second gear (2), the first cogging (11 ) and the second cogging (21 ) lie on a same perpendicular plane (0) to the rotation axis (X), i.e. are configured to lie on a same point of the driven shaft (103).

It is thus possible to optimise the arrangement of the chain or cogged belt (9) so that it operates in the best possible condition. This is so in particular in a case where the drive gear is fixed or in a case where the transmission system comprises a further gear shift (100) according to the invention which moves the chain or cogged belt (9), especially if the other gear shift (100) is made according to the preferred embodiment described above.

There are various factors in operation to determine the engagement of the gear in extraction by the chain or cogged belt (9); among these is the rotation velocity of the chain or cogged belt (9), the possible presence of tensioning means (10), the conformation of the gear and the chain or cogged belt (9) and the entity of the thrust towards the gear. Although the definition of the appropriate arrangements and spaces falls into the area of detail design, it is preferable for the distance (d), calculated along the rotation axis (X), between the first gear (1 ) in the rest position and the second gear (2) in the working position to be less than the width (I) of the chain or cogged belt (9). As can be observed in figure 4, this condition, guaranteed by the width of the spacer (8) in the embodiment shown, ensures the contact of the chain or cogged belt (9) with the gear in extraction after the disengagement. The width of the chain or cogged belt (9) is generally a value or an assembly of common or standard values.

In the simplest form the gear shift (100) can exclusively comprise the first gear (1 ) and the second gear (2), thus being a two-ratio gear shift. The first part (3) and the second part (4) can therefore be preferably fixed or be configured so as to be fixed to the driven shaft (103) and operate as the cages (5, 50) described in the following.

However it is common for the gear shift (100) to have further ratios due to the presence of a plurality of gears, i.e. it comprises at least one gear set. In this case the simplest form includes a first gear set which cooperates with the second gear (2) to offer three ratios, as the chain or cogged belt (9) can engage three different coggings (11 , 21 , 31 ). In general the gear shift (100) comprises a first gear set and a second gear set, with the gears in relation with one another, as will be described in the following.

In accordance with the teachings of the invention, the gear shift (100) comprises a first gear (1 ) or a first gear set, at least in the retracted position/s, and on a first side of the chain or cogged belt (9) and a second gearing (2) or a second gear set which, at least in the retracted position/s, and on a second side of the chain or cogged belt (9), opposite the first side. For example, observing figure 1 , the first gear set is on the left, in proximity of the wheel, and the second gear set is on the right of the chain or cogged belt (9) with respect to the advancement direction of the bicycle (101 ).

In the case of further gears beyond the first gear (1 ), the second gear (2), the first part (3) and the second part (4), the further gears are configured so as to contact the chain or cogged belt (9) in the movement of the immediately smaller gear of the respective gear set between the working position and the rest position.

In the case of a plurality of gears, the means for moving the gears (6, 7) are configured to move each gear (1 , 2, 3, 4) into the rest position and into the working position. By way of example, in the appended figures the first gear set comprises the first gear (1 ) and the first part (3) while the second gear set comprises the second gear (2) and the second part (4). Obviously the gear shift (100) can, on the basis of the teachings of the present document, be modified so as to have available the same number of ratios as the present transmission systems on the market, or, indeed, a greater number of ratios.

The gear shift (100) preferably comprises a cage (5) and a first gear set which comprises gears (1 , 3) which comprises gears (1 , 3) that are pinions or crowns, i.e. all pinions or all crowns. Each of these gears has a cogging (11 , 31 ) for enmeshing with the chain or cogged belt (9) and has a primitive diameter that is different to the primitive diameter of the other gears.

The first gear (1 ) is the smallest gear of the first gear set and the first part (3) is a gear of the first gear set, i.e. the immediately-larger gear of the first gear (1 ).

The cage (5) accommodates the gears (1 , 3) of the first gear set arranged in radial succession and each translatable with respect to the cage (5) between a rest position, or retracted, and a working position, or extracted, and vice versa. For example in figure 7 the first gear (1 ) and the first part (3) in the rest positions are collected internally of the cage (5).

By way of example, figure 7 illustrates the openings (51 ) which enable the sliding of the first gear (1 ) and the first part (3) with the cage (5); the figure also illustrates the coupling part (52) to the driven shaft (103) provided with grooves for transmitting thereto the drive received, by via the gears (1 , 3) from the chain or cogged belt (9). The cage (5) is configured to be fixed to the driven shaft (103) so as to rotate together with the driven shaft (103) about the rotation axis (X); the expert in the sector will understand how the example of the coupling part (52) of figure 22 is only an example as the cage (5) might be welded or fixed in another known way.

It is further specified that in the embodiment of figure 1 the first gear (1 ) and the second gear (2) are also directly coupled to the driven shaft (103) via the grooves which engage respective grooves of the driven shaft (103) which extend in the direction of the rotation axis (X). The grooves are visible in figures 16 and 17, while in figure 7 they are visible after the coupling thereof with the driven shaft (103).

Figure 7 also shows numerous couplings described in the present description. In particular, the seats on the cage (5) and on the second cage (50) are visible for the first part (3) and for the second part (4); in the example the seats are conformed so as to follow the third cogging (31 ) and the fourth cogging (41 ), as can be observed by way of example in figures 22 and 23.

The cage (5) is advantageously configured to contact the chain or cogged belt (9) in the movement of the most external gear of the first gear set between the working position and the rest position, thus performing the same function as the first part (3) for the first gear (1 ).

The cage (5) and/or the second cage (50) preferably accommodates the gears (1 , 2, 3, 4) of the first gear set, or of the second gear set in the rest positions thereof, as already illustrated with reference to figure 7.

Further, the primitive diameter of the second gear (2) is intermediate between the primitive diameter of the first part (3) and the primitive diameter of the first gear (1 ). More generally the primitive diameters of the gears (1 , 2, 3, 4) of the first gear set, or of the second gear set increase from the smallest to the largest alternated between the first gear set and the second gear set. For example, with reference to the gear shift (100) of figure 1 , the first gear (1 ) has a diameter of 14 millimeters, the second gear (2) has a diameter of 20 millimeters, the first part (3) has a diameter of 26 millimeters and the second part (4) has a diameter of 32 millimeters.

The cage (5) guarantees a compact gear shift (100), with movements as certain as possible and limits undesired displacements in the direction of the rotation axis (X) of the chain or cogged belt (9).

The gear shift (100) preferably further comprises a second cage (50), for example illustrated in figures 21 and 23, with the same functioning and advantages. The second cage (50) houses the gears (2, 4) of a second gear set arranged in radial succession and each translatable with respect to the second cage (50) between a rest position and a working position and vice versa.

The second gear set comprises gears (2, 4) which are pinions or crowns, i.e. all pinions or all crowns on the basis of the first gear set. Each of these gears has a cogging for enmeshing with the chain or cogged belt (9) and has a primitive diameter that is different to the primitive diameter of the other gears.

The second gear (2) is the smallest gear of the second gear set and the second part (4) is a gear of the second gear set, i.e. the immediately-larger gear of the second gear (2).

The second cage (50) comprises openings (51 ) which enable sliding of the second gear (2) and of the second part (4) with the second cage (50).

The second cage (50) is also configured to be fixed to the driven shaft (103) so as to rotate together with the driven shaft (103) about the rotation axis (X); the expert in the sector will understand how the example of the coupling part (52) of figure 20 is only an example as the second cage (50) might be welded or fixed in another known way.

The second cage (50) is configured so as to contact the chain or cogged belt (9) in the movement of the most external gear of the second gear set between the working position and the rest position, thus performing the same function as for the second gear (2) and the second part (4).

The gears preferably comprise means for preventing (12, 22) the return of the gear (32, 42) from the working position to the rest position, so as to maintain the gear in the working position regardless of the action of the means for moving (6, 7).

The means for preventing (12, 22, 32, 42) can be in a single piece with the cogging, for example a part made of a flexible material, or can comprise elements distinct from the cogging and coupled thereto, such as, for example, spheres and springs. In a preferred embodiment the means for preventing (12, 22, 32, 42) comprises a spring presser, for example with a ball point, as schematically shown by way of example in the appended figures. Spring pressers with a butterfly tip which engage the adjacent body might guarantee the stability of the position in both directions of movement. Typically the means for preventing (12, 22, 32, 42) cooperate with the cage (5) or with the second cage (50).

In an equivalent way the cage (5) or the second cage (50) might comprise spring pressers which cooperate with special workings made on the gears (1 , 2, 3, 4).

In line with the above illustration, the gears (1 , 3) of the first gear set preferably comprise means for preventing (12, 32) the return of the gear (1 , 3) from the working position to the rest position.

Likewise it is preferable that the gears (2, 4) of the second gear set comprise means for preventing (22, 42) the return of the gear (2, 4) from the working position to the rest position. The means for moving the gears (6, 7) can comprise actuators that move the gears having a part that is solidly constrained to the driven shaft (103) or to the frame (102) of the vehicle propelled by a human- or mixed-powered vehicle. For example, it is possible to use magnetic devices which push the gears (1 , 2, 3, 4) into the working position, or vice versa, preferably remotely commandable.

It is generally preferable that the means for moving the gears (6, 7) require a limited energy, which function after long periods of non-activity and/or in particularly difficult conditions, for example subjected to great stresses and/or damp.

WO 2014054017 A1 illustrates an example of movement of gears of a mechanical type.

The means for moving the gears (6, 7) preferably comprise a first pushing device

(6) for pushing the first gear (1 ) into the working position, a second pushing device

(7) for pushing the second gear (2) into the working position and a spacer (8) placed between the first gear (1 ) and the second gear (2) so as to bring the first gear (1 ) into the rest position in the movement of the second gear (2) into the working position and to bring the second gear (2) into the rest position in the movement of the first gear (1 ) into the working position.

By using devices which move in only one direction, the means for moving the gears (6, 7) are simpler, less subject to breakage and guarantee the simultaneousness of the displacements on the basis of structure of the gear shift (100) and the relative arrangement between the first gear (1 ), the second gear (2) and the spacer (8). With the special version of the gear shift (100) according to the invention the extraction of a gear (1 , 2, 3, 4) of a gear set determines the retrocession of another gear (1 , 2, 3, 4) of the other gear set. The spacer (8) also guarantees the reciprocal distance between the first gear (1 ) and the second gear (2), at least at an instant of the movement.

More preferably, the gears (1 , 3) of the first gear set are configured to lie on same planes perpendicular to the rotation axis (X) respectively in the working positions and in the rest positions and are configured to push the smallest gear in the movement between the rest position and the working position so that the first gear (1 ) pushes the spacer bringing the second gear (2) into the rest position and to push the immediately-larger gear in the movement thereof between the working position and the rest position so that the first gear (1 ) pushed by the spacer (8) brings the gears, for example the first part (3), into the rest position.

The presence of a spacer (8) between the first gear (1 ) and the second gear (2) can be advantageously exploited to move the gear extracted from the second gear set into the rest position or the gears of the first gear set further to the first gear (1 ) into the rest position.

This results in a fluid and simple movement of the gears (1 , 2, 3, 4).

In a case where the second gear set comprises further gears beyond the second gear (2) it is necessary for the above teachings to be replicated to obtain the same movement modality for the further gears. Consequently it is also preferable for the gears (2, 4) of the second gear set to be configured to lie on same planes perpendicular to the rotation axis (X) respectively in the working positions and in the rest positions and be configured to push the immediately smaller gear in the movement thereof between the rest position and the working position so that the second gear (2) pushes the spacer bringing the first gear (1 ) into the rest position and the gears (2, 4) of the second gear set be configured to push the immediately- larger gear in the movement thereof between the working position and the rest position so that the second gear (2) pushed by the spacer (8) brings the gears, for example the second part (4), into the rest position.

In a preferred embodiment the largest gears of the first gear set, or of the second gear set, comprise a pushing part (35, 45) configured to contact the cogging of the immediately smaller gear in reciprocal movement between the rest position and the working position of the gears from the working positions to the rest positions. For example, with reference to figure 18, the pushing part (35) pushes the first cogging (11 ) in the passage from the rest position to the working position of the first part (3) the first cogging (11 ) pushes the pushing part (35) in the passage from the working position to the rest position of the first gear (1 ).

It follows that the rest position at least a gear (3) of the first gear set preferably comprises a pushing part (35) configured to contact the cogging (11 ) of the smallest gear in the movement between the rest position and the working position.

In a further embodiment, in figures 28 and 29 by way of example it can be observed that each gear (1 , 2, 3, 4) comprises a ring which has a pushing part (15, 35) so as to obtain the movement illustrated above. The pushing parts (15, 35) can be in a single piece with the respective cogging, (11 , 21 , 31 , 41 ), as shown by way of example in the appended figures, or distinct and connected pieces.

With reference to figures 28 and 29, if the first gear set, in a like way to the second gear set, were to comprise at least a further gear, the first part (3) would have a second pushing part (15, 35) in a radially external position, alike to what is observed for the first gear (1 ) in figure 28. The thrust hierarchy is obtained with a part having a circular crown profile which is, in this case, in a single piece with the respective cogging, (11 , 21 , 31 , 41 ). The diameters of two proximal circular crowns, respectively the internal diameter and the external diameter, are configured so that the circular crown parts interfere in the movement of one of the two gears in the direction of the rotation axis (X).

Regardless of the thrust hierarchy between the gears of the first gear set and, possibly, of the second gear set, it is preferable for each of the gears (1 , 3) of the first gear set to comprise projections (13, 33) on the opposite side to the side facing the second gear (2).

Each projection (13, 33) has an inclined part (14, 34) configured to extend according to a circumferential direction with respect to the rotation axis (X); as illustrated by way of example in figure 8 for the first gear (1 ), the projections on a perpendicular plane to the rotation axis (X) of the inclined parts (14, 34) of a gear (1 , 3) of the first gear set lie on a circumference.

Further, the first pushing device (6) is configured to push each of the gears (1 , 3) of the first gear set with respect to the cage (5) and comprises:

- a structure (61 ) configured to be fixed to the frame (102) of the human- or mixed-powered vehicle;

- a disc (62) which is rotatable with respect to the structure (61 ) about a first axis (X1 ) and which has first openings (63) and second openings (64) which extend in radial directions (R) with respect to the first axis (X1 );

- pusher wheels (65) for engaging the projections (13, 33) of the first gear set, each of which engages a respective first opening (63) and is movable with respect to the structure (61 ) according to a radial direction (R) with respect to the first axis (X1 );

- guide elements (66) each of which has a guide part (67) which engages a respective second opening (64) and an arm (68) which is rotationally coupled to a respective pusher wheel (65). The second openings (64) are configured so that in the rotation between the disc (62) and the structure (61 ) the guide parts (67) move radially away or towards the first axis (X1 ) so as to bring the pusher wheels (65) to the position of the projections (13, 23) of a different gear (1 , 3) of the first gear set or also in intermediate or free positions between gears (1 , 3).

In a preferred embodiment, the second openings (64) are slots appropriately profiled to guide the respective guide part (67) so as to act as the mover of a cam system with the tappet moving translatingly.

The first openings (63) are configured so as to enable the pusher wheels (65) to engage the projections (13, 33) of each gear (1 , 3) of the first gear set and the inclined parts (14, 34) are configured to move the gear towards the working position when the inclined parts (14, 34) enter into contact with the pusher wheels (65).

In other words, the inclination of the inclined parts (14, 34) is such that the projection (13, 33) decreases towards the portion that first contacts the pusher wheels (65), i.e. decreases in the sense of the rotation with respect to the driven shaft (103) for which the respective gear (1 , 3) is configured.

A first pushing device (6) thus realised guarantees effective and safe control of the gear shift (100) and enables activating the change in a simple way, especially in the case the also the second pushing device (7) is realised according to the teachings of the present text. The inclined parts (14, 34) guarantee a progressive and fluent movement of the gear (1 , 3).

In this sense it is preferable that the inclined parts (14, 24, 34, 44) extend circumferentially for at least half, preferably at least two-thirds, of the circumference, as can be observed by way of example in the embodiments of figures from 16 to 19.

With reference to figure 4, the pusher wheels (65) of the first pushing device (6) have been illustrated at the position of the projections (13) of the first gear (1 ) so as to exemplify the instant of gear shift in which the first pushing device (6) begins pushing the first gear (1 ).

More preferably, each of the gears (2, 4) of the second gear set comprises projections (23, 43) on the opposite side to the side facing the first gear (1 ).

Each projection (23, 43) has an inclined part (24, 44) configured to extend according to a circumferential direction with respect to the rotation axis (X); as illustrated by way of example in figure 8 for the first gear (1 ), the projections on a perpendicular plane to the rotation axis (X) of the projections (23, 43) of a gear (2, 4) of the second gear set lie on a circumference.

Further, the second pushing device (7) is configured to push each of the gears (2, 4) of the second gear set with respect to the second cage (50) and comprises:

- a structure (71 ) configured to be fixed to the frame (102) of the human- or mixed-powered vehicle;

- a disc (72) which is rotatable with respect to the structure (71 ) about a second axis (X2) and which has first openings (73) and second openings (74) which extend in radial directions (R) with respect to the second axis (X2);

- pusher wheels (75) for engaging the projections (23, 43), each of which engages a respective first opening (73) and is movable with respect to the structure (71 ) according to a radial direction (R) with respect to the second axis (X2);

- guide elements (76) each of which has a guide part (77) which engages a respective second opening (74) and an arm (78) which is rotationally coupled to a respective pusher wheel (75).

The second openings (74) are configured so that in the rotation between the disc (72) and the structure (71 ) the guide parts (77) move radially away or towards the second axis (X2) so as to bring the pusher wheels (75) to the position of the projections (23, 43) of a different gear (2, 4) of the second gear set or also in intermediate or free positions between gears (2, 4).

In a preferred embodiment, the second openings (74) are slots appropriately profiled to guide the respective guide part (77) so as to act as the mover of a cam system with the tappet moving translatingly.

The first openings (73) are configured so as to enable the pusher wheels (75) to engage the projections (23, 43) of each gear (2, 4) of the second gear set and the inclined parts (24, 44) are configured to move the gear towards the working position when the inclined parts enter into contact with the pusher wheels (75).

In other words, the inclination of the inclined parts (24, 44) is such that the projection (23, 43) decreases towards the portion that first contacts the pusher wheels (75), i.e. decreases in the sense of the rotation with respect to the driven shaft (103) for which the respective gear (2, 4) is configured.

The conformation of the first openings (63, 73) and second openings (64, 74) can be defined during the detail design by the expert in the sector and the conformations shown in figure 10 are presented merely by way of example.

A first device (6) and a second device (7) made in this way can be moved together with a single rotation, thus enabling changing gear (1 , 2, 3, 4) with a single action. This is clearly illustrated, again by way of example, by the cogged wheels visible in figures 8 and 11 associated to a remotely movable shaft. The discs (62, 72) comprise teeth (62a, 72a) which enmesh with the cogged wheels so as to rotate with respect to the structure (61 , 71 ).

In the case where the discs (62, 72) are opposite and commanded by a same rotation, it is necessary for the first openings (63, 73) and the second openings (64, 74) to extend appropriately in the radial directions (R) so that both bring the pusher wheels (65, 75) towards the first axis (X1 ) or the second axis (X2) or in a moving away direction from the first axis (X1 ) or the second axis (X2).

Preferably, the discs (62, 72) of the first gear set, or of the second gear set, as well as the second openings (64, 74), are configured so that the distance covered in the respective radial direction by the pusher wheels (65, 75) of the first gear set and of the second gear set is the same, as shown by way of example in figures from 10 to 13. This proves to be particularly easy by virtue of the hierarchy of the gears (1 , 2, 3, 4) of the first gear set and the second gear set.

The circumference of figure 8 also schematises the pathway that the pusher wheels (65) follow in the position determined by the second openings (64), on the basis of the position of the disk (62) with respect to the structure (61).

The embodiments of the first pushing device (6) and of the second pushing device (7) have been described in the case of a first gear set and, possibly, a second gear set, as they facilitate the management of many gears (1 , 2, 3, 4). However one or both the pushing devices (6, 7) might move one gear (1 , 2) only, when the second part (4) and, possibly, the first part (3) perform the same function as the second cage (50) or as the cage (5).

In the instant when the pusher wheels (65, 75) are moved to engage the projections (13, 23, 33, 43) they can laterally touch the projections and might present some de-alignments with the projections (13, 23, 33, 43) that they should be engaging.

With the aim of limiting the friction and/or improving the pusher wheels (65, 75) - projections (13, 23, 33, 43) contact, the first pushing device (6), like the second pushing device (7), preferably comprises elastic means (60a, 60b) and the arm (68) comprises a protrusion (68a) configured to remain internally of a respective pusher wheel (65) which is internally hollow. The elastic means (60a, 60b) are interposed between the pusher wheel (65) and the protrusion (68a). The elastic means (60a, 60b) preferably comprise a first spring (60a) and a second spring (60b) respectively interposed between the pusher wheel (65) and a first side of the protrusion (68a) and between the pusher wheel (65) and a second side of the protrusion (68a), opposite the first side.

From an observation of figure 24 it can be understood how the first spring (60a) and the second spring (60b) allow the alignment of the pusher wheel (65) to the projections (13, 23, 33, 43) also starting from a lateral friction position with the projections (13, 23, 33, 43), thus reducing the effects of an imperfect initial alignment between the pusher wheels (65, 75) and the projections (13, 23, 33, 43). By way of example, figures from 10 to 13 illustrate the following succession: the pusher wheels (65) of the first pushing device (6) engage the projections (13) of the first gear (1 ) and the pusher wheels (75) of the second pushing device (7) are in a free position with respect to the projections (23, 43) of the gears (2, 4) of the second gear set; the pusher wheels (75) of the second pushing device (7) engage the projections (23) of the second gear (2) and the pusher wheels (65) of the first pushing device (6) are in a free position with respect to the projections (13, 33) of the gears (1 , 3) of the first gear set; the pusher wheels (65) of the first pushing device (6) engage the projections (23) of the first part (3) and the pusher wheels (75) of the second pushing device (7) are in a free position with respect to the projections (23, 43) of the gears (2, 4) of the second gear set; the pusher wheels (75) of the second pushing device (7) engage the projections (43) of the second part (4) and the pusher wheels (65) of the first pushing device (6) are in a free position with respect to the projections (13, 33) of the gears (1 , 3) of the first gear set.

Figures from 10 to 13 enable an observation of the fluidity of the passage of the pusher wheels (65, 75) between the gears (1 , 2, 3, 4) of the first gear set and of the second gear set, so as to enable the gear shift.

Figure 9 shows the second gear (2) in the working position so as to contact the chain or cogged belt (9), a working condition corresponding to the one illustrated in figure 11 .

As can be observed in the accompanying figures, the structure (61 , 71 ) preferably comprises guides (69, 79) arranged in radial directions (R) which guide the pusher wheels (65, 75) and/or the guide elements (66, 76) so as to make the movements safer and so as to require a particularly simple coupling between the guide elements (66, 76) and the second openings (64, 74). The guides (69, 79) can be, for example, cylindrical rods.

The guides (69, 79) preferably enable the guide elements (66, 76) to move along a line which crosses the centre of rotation of the cam system.

As can be observed for example in figures from 16 to 19, the projections (13, 23, 33, 43) of each gear (1 , 2, 3, 4) are preferably circumferentially distanced from one another so as to enable the pusher wheels (65, 75) to move in the radial directions (R), passing between an inclined part (14, 24, 34, 44) and the successive projection (13, 23, 33, 43).

Generally, and preferably the gear shift (100) is configured so that the first axis (X1 ) and the rotation axis (X) coincide, as shown by way of example by the embodiment of figure 8. In general and more preferably the second axis (X2) also coincides with the rotation axis (X).

As already mentioned in the foregoing, it can be preferable that the first cogging (11 ) and the second cogging (21 ) comprise cogs bevelled on the side, or tapered towards the free end of the side, of the cogging configured to face respectively the first part (3) in the working position of the first gear (1 ) or the second part (4) in the working position of the first gear (1 ) or of the second gear (2) so as to facilitate the extraction of the chain or cogged belt (9).

Likewise it can be preferable that the cogging (11 , 21 , 31 , 33) of each gear (1 , 2, 3, 4) of the first gear set or the second gear set comprises cogs bevelled on the opposite side, or tapered towards the free end of the opposite side, to the gear set so as to facilitate extraction of the chain or cogged belt (9).

Figure 1 enables observing a part of an embodiment of the activation means of a gear shift (100) according to the invention. In particular three cogged wheels fixed on a shaft with the cogged wheel not engaging the discs (62, 72) can be observed which can be appropriately moved with devices of known type and can be remotely controlled, for example from the handlebar (not illustrated) of a bicycle (101 ). Merely by way of example, the shaft can be moved by an electrical servomotor controlled at the handlebar or by cables of a lever change. Like controls and commands are known to the expert in the sector who can apply them appropriately to the present invention according to specific needs. Figure 1 shows only a portion of bicycle (101 ) as the elements not represented can be of known type.

The invention also relates to a vehicle transmission system of a human- or mixed- powered vehicle comprising a gear shift (100) according to the invention.

An embodiment of the transmission system comprises a chain or cogged belt (9) and tensioning means (10) of the chain or cogged belt (9), as can be observed for example in figure 1 .

The tensioning means (10), as well as guaranteeing the transmission of the drive, facilitate the displacement of the chain or cogged belt (9) between the gears (1 , 2, 3, 4).

The transmission system preferably comprises a driven shaft (103) configured to rotate with respect to the frame (102) of a human- or mixed-powered vehicle about the rotation axis (X).

The driven shaft (103) bears the first gear (1 ) and the second gear (2) so as to rotate together and so as to translate in the direction of the rotation axis (X), and bears the first part (3) and the second part (4) so as to rotate together.

The driven shaft (103) is configured to be coupled to a wheel (104) so as to transmit the drive of the chain or cogged belt (9) to the wheel (104).

There has already been a discussion in the foregoing of how the gear shift (100) can comprise, or not, a driven shaft (103) and it is clear to the expert in the sector how there can be various connection modalities between the gears (1 , 2, 3, 4) of the gear shift (100) and the wheel, some of which use free wheels or an overrunning clutch, so as to transmit the energy only when it is useful for traction.

Although figure 1 illustrates a crown set of known type connected to pedals (105) via a central mechanism, the working position of the chain or cogged belt (9) would give a higher performance in a transmission system comprising a second gear shift according to the invention. The expert in the sector will understand how the second gear shift replaces the crown set in the example of figure 1 .

The transmission system preferably comprises a second gear shift (not illustrated) according to the invention the gears of which are crowns wherein the gears of the gear shift (100) are pinions. The gear shift (100) and the second gear shift are advantageously configured and arranged with respect to the frame (102) of the human- or mixed-powered vehicle in such a way that the coggings of the crowns and the coggings (11 , 21 , 31 , 41 ) of the pinions lie or substantially lie on a same plane (P) in the working positions. In this way the coggings engaged with the chain or cogged belt (9) are advantageously aligned.

The invention relates to a human- or mixed-powered vehicle comprising a gear shift (100) according to the invention.

An embodiment of the vehicle comprises a transmission system according to the invention.

The human- or mixed-powered vehicle is preferably a bicycle (101 ).

The invention can operate with both a chain and with a cogged belt; in the appended figures a chain (9) is illustrated.

It is understood that the above has been described by way of non-limiting example and that any constructional variants are considered to fall within the protective scope of the present technical solution, as claimed in the following.