Patent Description:
Among the various types of motor vehicles available on the market, scooters or motor scooters are in great demand. These motorcycles stand out from others for the presence of a frame which is substantially open in the intermediate part and for a footrest which enables the motorcyclist to maintain a riding position with an erect posture and closed and parallel legs. Scooters can have two wheels or three wheels with two steering front wheels and a driving rear wheel.

Compared to other motorcycles, a scooter also stands out by the fact that the engine block is not installed on the frame, but on the contrary is integral with the structure of the rear suspension swingarm. The swingarm-engine block assembly is hinged to the frame by means of a fulcrum so as to constitute a mass oscillating about said fulcrum as a result of loads acting on the rear suspension. In addition to the swingarm, the rear suspension typically comprises one or more spring-shock absorber assemblies interposed between the frame and the swingarm and/or between the frame and the engine block (see the layouts shown in <FIG>, <FIG> and <FIG> relating to known solutions).

Scooters are normally provided with rubber elements between the components of the rear suspension and the frame. In particular, these elements are normally provided at the ends of the spring-shock absorber assemblies and at the fulcrum about which the mass constituted by the swingarm and the engine block oscillates. In this respect, in order to limit the possible yaw movement of this mass with respect to the frame (i.e., the movement about a vertical axis), in many cases a block-holder frame is provided. This represents a sort of mechanical interface between the motorcycle frame and the oscillating mass so that the movements of the latter remain confined substantially to a horizontal plane. A known type of block-holder frame is schematically shown in the layouts shown in <FIG> and indicated by the reference (T-RB). This comprises two connecting rods hinged together and having axes parallel to the axis of rotation of the rear wheel. A first connecting rod (B1) is hinged to the motorcycle frame, while a second connecting rod (B2) is hinged to the oscillating mass (swingarm-engine) (F-BM) at a point hereinafter referred to as engine fulcrum (FM). To avoid a displacement of the engine fulcrum (FM), at least one point (D) of one of the two connecting rods (B1, B2) is connected to the motorcycle frame by means of an element known as silent-block, consisting of two bushings with a rubber buffer therebetween. The two bushings, one being integral with the connecting rod and the other with the frame, can move relative to one another, temporarily losing their coaxiality in a manner depending on the size and stiffness of the rubber used. In this configuration, the instant centre of rotation of the engine block varies continuously with respect to the frame according to the stresses to which the silent-block is subjected.

As an alternative to or in combination with the aforementioned silent-block, two rubber elements (or rubber buffers) are provided at the pivots of the connecting rods (B1-B2) respectively hinged to the motorcycle frame and to the oscillating mass, or even at the hinge (C) between the two connecting rods (B1-B2).

As known, in addition to the vibrations generated by the engine, while the vehicle is moving the rear suspension is also subjected to other vertical and horizontal forces, generated by the contact between the rear wheel and the ground. The horizontal forces are generated by the traction and braking actions to which the motorcycle is subjected, while the vertical forces are generated by the reaction to the weight of the rear part of the vehicle and/or by the conformation of the road surface (presence of bumps or potholes) with which the rear wheel interacts.

With reference to the horizontal forces, these forces compress the rubber buffers (silent-blocks) of the frame-holder, thereby limiting to a certain extent the absorption by the buffers of the vibrations generated by the engine; however, this condition is accepted given the need to transfer the thrust generated by the engine to the motorcycle frame. In fact, the motorcycle is pushed forward by means of said rubber elements.

It is known that vertical thrusts can be cancelled out by properly configuring the suspension, and more precisely by arranging the spring-shock absorber assembly so that the reaction develops in the same direction as the vertical force. In fact, to achieve this condition the spring-shock absorber assembly (AM) must be installed along the vertical, or substantially vertical, direction passing through the axis of the rear wheel (RP), as schematically shown in <FIG>, in which the reference (T) indicates the motorcycle frame, while the reference (F-BM) indicates the mass oscillating about the fulcrum (F) configured by the block-holder frame (T-RB).

Still referring to <FIG>, in order to cancel out the vertical forces, the spring-shock absorber assembly (AM) shall therefore have a particularly set-back position, which evidently remains visible also on a lateral observation plane of the motor vehicle. <FIG> and <FIG> schematically show two known solutions in which the spring-shock absorber assembly is inclined forward (<FIG>) or connected to the oscillating mass (swingarm-engine block) in a position close to the frame (<FIG>). Also in these solutions, however, the spring-shock absorber assembly remains laterally visible.

It is known, however, that for scooters on the market, it is desired to locate the spring-shock absorber assembly in a more hidden position inside the motorcycle body. However, in scooters on the market, one possibility for achieving this aim could be to modify the body so that it extends substantially up to the height of the rear wheel hub. This solution clearly appears unfeasible since it would make the aesthetics of the rear part of the motor vehicle and its maintenance more complex. Indeed, this solution would result in having always to disassemble the body in order to work on the engine and/or on the rear wheel.

In the configurations shown in <FIG> and <FIG>, as well as in other known configurations, the real position of the spring-shock absorber assembly (AM) thus differs from the ideal position shown schematically in <FIG>. Therefore, the reaction of the spring-shock absorber assembly (AM) is no longer aligned with the vertical force generated by the contact between wheel and ground. As a result, the rubber elements of the mechanical system are also pre-loaded vertically, thereby also transmitting stresses to the rear suspension.

The spring-shock absorber assembly (AM) is advanced towards the fulcrum of oscillation of the swingarm/engine mainly for reasons of size. In most cases, the spring-shock absorber assembly (AM) is inclined towards the front of the motorcycle so that the rubber elements, further to stresses on the rear suspension, are loaded not only vertically, but also horizontally. This obviously leads to a faster deterioration of the elements.

A known solution which aims to partially solve the aforementioned problems is described in the patent document <CIT>.

The document <CIT> discloses the features of the preamble of claim <NUM>.

The Applicant has perceived the need for a new technical solution which on the one hand makes it possible to place the spring-shock absorber assembly in a hidden position, i.e., relatively advanced towards the fulcrum of oscillation of the swingarm/engine, and at the same time makes it possible to cancel out, or at least greatly limit, the vertical forces on the rubber elements of the mechanical system in order to avoid their pre-loading.

In view of the above considerations, the main task of the present invention is to provide a motorcycle that makes it possible to overcome or at least mitigate the drawbacks described above relating to the transmission of loads acting on the rear suspension to the motorcycle frame. Within this task, a first object is to provide a motorcycle in which the shock absorber is hidden or not much visible. A further object is to provide a motorcycle in which the loads acting on the rear suspension are only partially transferred to the frame. In this respect, another object is to cancel out or at least limit as much as possible the transmission to the frame of vertical loads acting on the rear suspension. Yet another object of the present invention is to provide a motorcycle that is reliable and easily manufactured at competitive costs.

The Applicant has noted that said task and said objects can be achieved by means of a saddle-ride motorcycle of scooter type, comprising a frame and a rear wheel operatively connected to the frame by means of a rear suspension comprising a swingarm which constitutes, fully or partially, a mass oscillating with respect to the frame around a first axis of rotation. According to the invention, the rear suspension comprises a first rod hinged to the frame about a second axis of rotation different from the first axis of rotation defined at an intermediate point between two ends of the first rod. The suspension also comprises a second rod hinged to the first rod about a third axis of rotation; in particular, the second rod is rotatably connected, directly or by means of the swingarm, to the pivot of the rear wheel so as to rotate about a fourth axis of rotation. The rear suspension also comprises a spring-shock absorber assembly connected, at a first end thereof, to an end of the first rod and, at a second end thereof, to the frame. According to the invention, the front end of the first rod is connected to the spring-shock absorber assembly, while the rear end of the first rod is connected to the second rod.

This motorcycle allows the spring-shock absorber assembly to be placed in a very advanced, and therefore particularly hidden, position, which improves the aesthetics of the motorcycle, preserving other advantages obtained in terms of reduced loads transferred from the suspension to the frame and to the oscillating mass.

According to a possible embodiment, in an operating condition of the rear suspension, the third axis of rotation and the fourth axis of rotation lie in a substantially vertical plane containing the axis of rotation of the rear wheel, wherein said substantially vertical plane lies within +/- <NUM>° relative to a vertical to the ground.

According to a possible embodiment, the swingarm is connected to an engine block of the motor vehicle. In this embodiment the swingarm and the engine block are part of said oscillating mass. According to a possible embodiment, the second rod is directly hinged to the pivot of said rear wheel and is disengaged from the swingarm; in this embodiment the fourth axis of rotation coincides with the axis of rotation of the rear wheel.

According to another embodiment, the second rod is hinged to the swingarm and the fourth axis of rotation is distinct from the axis of rotation of said rear wheel.

According to one embodiment, the length of said first rod is greater than the length of the second rod.

According to one embodiment, said length of the first rod, considered along a theoretical line orthogonal to the second axis of rotation and to the third axis of rotation, substantially corresponds to the length of the oscillating mass, considered along a second theoretical line orthogonal to the first axis of rotation and to the axis of rotation of the rear wheel.

Preferably, theoretical line is substantially parallel to said second theoretical line.

In a possible embodiment, the first rod and the second rod are located above a theoretical line orthogonal to the axis of rotation of the rear wheel and to the first axis of rotation, wherein said position is considered on a lateral observation plane of the motorcycle.

According to a possible embodiment, the spring-shock absorber assembly is arranged within a body so as not to be visible when the motor vehicle is observed on a lateral observation plane. In a possible embodiment, the second rod supports a braking device configured to brake the rear wheel.

According to a possible embodiment, the swingarm comprises a first part and a second part, wherein the first part is folded inwards with respect to the second part; said first part being rigidly connected to the engine block and said second part being rotatably connected to the pivot of the rear wheel.

According to a possible embodiment, for each half-plane identified by a longitudinal plane of symmetry of the rear wheel orthogonal to its axis of rotation, the rear suspension comprises a first rod and a second rod hinged to the corresponding first rod, wherein the first rod located in one half-plane is connected to the first rod located in the other half-plane by means of at least one connecting member so that the two first rods move as a single translating body; said first rods and said second rods being arranged in a mirror-like manner with respect to the longitudinal plane of symmetry.

With reference to the embodiment just mentioned, preferably, but not exclusively, the rear suspension comprises two spring-shock absorber assemblies, each comprising a first end connected to a first rod and a second end connected to said frame, wherein said spring-shock absorber assemblies are arranged in a substantially mirrored position with respect to the longitudinal plane of symmetry.

Further characteristics and advantages of the invention will become more apparent from the following detailed description of some preferred, but not exclusive, embodiments of a vehicle, illustrated herein for indicating and non-limiting purposes, with the aid of the accompanying drawings, wherein:.

With reference to the aforementioned figures, the present invention therefore relates to a saddle-ride vehicle <NUM>, wherein by this expression it is meant any motorbike or motorcycle having at least two wheels, i.e., at least one front wheel and at least one rear wheel. Therefore, this expression also includes three-wheeled motorcycles, having two front steering wheels and a rear driving wheel, or alternatively a front steering wheel and a pair of rear driving wheels. Hereinafter, the saddle-ride vehicle will be indicated more simply by the term motorcycle <NUM>.

The motorcycle <NUM> comprises a frame <NUM> to which a front wheel <NUM> and a rear wheel <NUM> are operatively connected. In particular, the rear wheel <NUM> is connected to the frame <NUM> by means of a rear suspension <NUM> which includes a swingarm <NUM> integral with an engine block <NUM>. By the term "engine block" it is generally meant the structure that incorporates the engine of the motorcycle <NUM> and/or the mechanical transmission through which the torque generated by the engine is transferred to the rear wheel. The frame <NUM> supports a body <NUM>, wherein by this term it is generally meant an assembly of components that together constitute the outer protective covering of the motor vehicle <NUM>.

The swingarm <NUM> is connected to the frame <NUM> by means of connecting means defining a first axis of rotation <NUM>, hereinafter also indicated by the term fulcrum <NUM>. The swingarm <NUM> forms, fully or partially, an oscillating mass M which oscillates about said first axis of rotation <NUM>. In a first embodiment, visible in the figures, the swingarm <NUM> is rigidly connected to the engine block <NUM>. Therefore, in this configuration, the oscillating mass M comprises the swingarm <NUM> and also the engine block <NUM>. In the layout shown in <FIG>, as well as in other layouts shown in the accompanying figures, the oscillating mass M is purposely split into two parts by a dashed line in order to identify, in a purely schematic and indicative way, the swingarm <NUM> and the engine block <NUM>. In an embodiment alternative to that just described above (and not visible in the figures), the swingarm is separated from the engine block, which can, for example, be arranged inside the volume of the rear wheel rim, i.e., directly connected to the wheel hub, according to a configuration known as "wheel hub motor". In this case, the engine block is not part of the mass oscillating about the aforementioned fulcrum.

It should be noted, however, that the type of propulsion used to generate the driving torque is not relevant to the invention. The propulsion type can be thermal or electric. Alternatively, the propulsion can be of a hybrid type, i.e., a propulsion comprising a thermal engine and an electric motor that can operate independently or in combination according to known principles. An example of a hybrid propulsion system is shown and described in patent <CIT> to the same Applicant.

The oscillating mass M (whether constituted by the swingarm <NUM> alone or by the assembly comprising the swingarm <NUM> and the engine block <NUM>) is in any case connected to the frame <NUM> by means of connecting means defining the first axis of rotation <NUM>. These connecting means may consist of a single pivot or alternatively of a connecting frame, for example a block-holder frame such as that described above in connection with prior art. In any case, preferably at least one rubber element is provided to limit the transmission of the vibrations generated by the engine to the frame. In the case of a connecting frame, the rubber element can be formed by as a "silent-block" according to a known solution already described above.

The swingarm <NUM> rotatably supports the rear wheel <NUM> in order to allow it to rotate about an axis of rotation <NUM> (hereinafter indicated by the term wheel axis <NUM>) which is located in a distal position relative to the fulcrum <NUM>, substantially at an end of the oscillating mass M opposite the end near which the fulcrum <NUM> is located. At the same time, the mass M oscillates about the axis of rotation <NUM> with respect to the rear wheel <NUM>.

The rear suspension <NUM> comprises a bar <NUM> (or first rod <NUM>) hinged to the frame <NUM> at a second axis of rotation <NUM> different from the abovementioned fulcrum <NUM>. In particular, the term "different" is used to indicate a condition whereby the second axis of rotation <NUM> is located in a position different from the fulcrum <NUM>, wherein said position is considered on a lateral plane of the motorcycle <NUM> (plane of <FIG>).

The rear suspension <NUM> also comprises a connecting rod <NUM>, or second rod <NUM>, which is hinged to the first rod <NUM> at a third axis of rotation <NUM>. The connecting rod <NUM> can be rotatably connected directly to the pivot of the rear wheel <NUM> at a fourth axis of rotation which (in an embodiment not illustrated) coincides with the axis of rotation <NUM> of the rear wheel <NUM>. The connecting rod <NUM> therefore retains one rotational degree of freedom, about the pivot of the rear wheel <NUM>, with respect to the oscillating mass M.

In particular, assuming that the motorcycle <NUM> is resting on a horizontal plane PO, the third axis of rotation <NUM> is coplanar with the axis of rotation <NUM> of the rear wheel <NUM>. More precisely, the axis of rotation <NUM> of the rear wheel <NUM> and the third axis of rotation <NUM> (between the connecting rod <NUM> and the first rod <NUM>) lie on the same vertical or substantially vertical plane PV. By the term 'substantially vertical' it is meant a plane lying within +/- <NUM>° relative to the vertical to the ground.

The rear suspension of the motorcycle <NUM> also comprises a spring-shock absorber assembly <NUM> having the purpose of dampening the oscillation and/or slowing down the movement of the suspension (i.e., of the assembly including the wheel, the oscillating mass M, the first rod <NUM>, the connecting rod <NUM>) with respect to the frame <NUM>. The spring-shock absorber assembly <NUM> may take on a per se known configuration and is operatively placed between the first rod <NUM> and the frame <NUM>. More precisely, a first connecting end 70A is hinged to the first rod <NUM>, while a second connecting end 70B, opposite the first connecting end 70A, is hinged to the frame <NUM> at a position different from that taken by the first axis of rotation <NUM> and by the second axis of rotation <NUM>, wherein this position as well is considered from a lateral observation plane of the motorcycle <NUM>.

As apparent from <FIG>, the suspension of the motorcycle <NUM> is configured as a sort of quadrilateral, wherein the first rod <NUM> and the oscillating mass M constitute two "cranks" hinged on one side to the frame <NUM> and on the other side to the connecting rod <NUM> defined above. As a result of this arrangement, the first rod <NUM>, the spring-shock absorber assembly <NUM> and the frame <NUM> constitute a separate assembly which exchanges direct loads with the oscillating mass M in the same way as the connecting rod <NUM>. As a result of the vertical or substantial vertical arrangement of the connecting rod <NUM> (mutual orientation of axes <NUM> and <NUM>), the vertical component of the loads acting on the suspension is only minimally transferred to the frame <NUM> by means of the rubber element(s) (silent-block). These elements are mainly affected by the possible horizontal component of the loads.

According to a preferred embodiment, not shown, the connecting rod <NUM> of the rear suspension also supports a brake calliper <NUM> which acts on the rear wheel <NUM> to brake it. By the term "brake calliper" <NUM> it is generally meant the component assembly acting on a "disc brake" integral with the rear wheel <NUM> according to a widely known principle. It has been noted that this solution is particularly advantageous since the instant centre of rotation of the suspension moves towards the fulcrum <NUM> thereby making the behaviour of the motorcycle <NUM> when braking particularly stable.

The length of the first rod <NUM> is preferably greater than the length of the second rod <NUM>.

In particular, identifying a first theoretical line L1 orthogonal to the second axis of rotation <NUM> and to the third axis of rotation <NUM> and substantially parallel to a second theoretical line L2 orthogonal to the fulcrum <NUM> and to the wheel axis <NUM>, the length of the first rod <NUM>, considered along the first theoretical line L1, is equal to or smaller than the distance between the fulcrum <NUM> and the wheel axis <NUM>. The length of the oscillating mass M, considered along the second theoretical line L2, instead, substantially corresponds to the distance between the wheel axis <NUM> and the fulcrum <NUM>. In the suspension shown in <FIG>, the connecting rod <NUM> is disengaged from the oscillating mass M and can freely oscillate about the pivot of the rear wheel. The two "cranks" (first rod <NUM> and mass M) of the quadrilateral are, at least partially, substantially parallel to one another. As a result of this arrangement, the load acting on the suspension is not transmitted to the fulcrum <NUM> and thus to the frame <NUM>.

<FIG> shows a variant in which the connecting rod <NUM> is indirectly connected to the wheel body through the oscillating mass M. More precisely, the connecting rod <NUM> is hinged to the oscillating mass M at the fourth axis of rotation <NUM> which, in this case, is not coaxial to the wheel axis <NUM>. Preferably, at least in one operating condition of the suspension, the fourth axis of rotation <NUM> and the third axis of rotation <NUM> may be coplanar with the wheel axis <NUM>, even more preferably may lie in a vertical or substantially vertical plane PV passing through the wheel axis <NUM>.

As shown in <FIG>, the fourth axis of rotation <NUM> oscillates integrally with the oscillating mass M and more precisely moves along a circumference concentric to the wheel axis <NUM>. Therefore, while on the one hand the vertical loads are cancelled out, on the other hand the horizontal component of these loads is transmitted to the rubber elements (e.g., silent block) intended to absorb the vibrations between the oscillating mass M and the frame <NUM> of the motorcycle <NUM>.

In <FIG>, the rear suspension comprises a first rod <NUM> hinged to the connecting rod <NUM> at the third axis of rotation <NUM> defined substantially at a first end <NUM> of said first rod <NUM>. The first rod <NUM> is also hinged to the frame <NUM> through the second axis of rotation <NUM> defined at an intermediate point between the two ends <NUM>, <NUM> of the first rod <NUM>. According to the invention, the spring-shock absorber assembly <NUM> is operatively interposed between the first rod <NUM> and the frame <NUM>. More precisely, in the case shown herein, a first end 70A of the spring-shock absorber assembly <NUM> is connected to the first rod <NUM> at the second end <NUM> thereof, while the second end 70B of the spring-shock absorber assembly <NUM> is hinged to the frame <NUM>. Basically, the front end <NUM> of the first rod <NUM> is connected to the spring-shock absorber assembly <NUM>, while the rear end <NUM> of the first rod <NUM> is connected to the second rod <NUM> (connecting rod <NUM>), and the first rod <NUM> is hinged to the frame <NUM> at an intermediate point between the two ends <NUM>,<NUM>. In this way, the jerking movement of the swingarm <NUM> is transmitted by the second rod <NUM> to the first rod <NUM> and from there to the spring-shock absorber assembly <NUM>, which becomes compressed and expanded with respect to the frame <NUM>.

In this embodiment, the spring-shock absorber assembly <NUM> takes up a very advanced, and therefore particularly hidden, position, other advantages in terms of reduced loads transferred to the suspension and provided by the suspension to the body in terms of stress transmission remaining the same. With this configuration, the spring-shock absorber assembly <NUM> is hidden inside the body <NUM>, thereby improving its level of protection and giving the vehicle an original and distinctive aesthetic impact. Moreover, the spring-shock absorber assembly <NUM> discharges the forces at a point of the frame which is less subject to bending as compared to the conventional rear end thereof, as illustrated in <FIG>.

In the embodiments of the rear suspension shown in <FIG>, the connecting rod <NUM>, the first rod <NUM> and the spring-shock absorber assembly <NUM> are located in a position above the theoretical line L2 orthogonal to the fulcrum <NUM> and to the wheel axis <NUM>.

In the embodiment of the rear suspension <NUM> shown in <FIG>, the rear suspension has a substantially asymmetrical configuration relative to the longitudinal plane PL described above. Indeed, one or more of the suspension components are arranged on a same half-plane with respect to said longitudinal plane PL. <FIG>, on the other hand, refer to a further embodiment in which the rear suspension <NUM> has a substantially symmetrical configuration relative to the longitudinal plane PL. In this case, for each half-plane, the rear suspension <NUM> comprises a first rod 51A rigidly connected to the other first rod 51B arranged on the other half-plane. In this respect, connecting elements <NUM> are provided which rigidly connect the two first rods 51A, 51B so that they behave as a single translating body. In the case illustrated in <FIG>, <FIG>, and <FIG>, the connecting elements <NUM> extend in a transverse direction.

Still referring to <FIG>, for each half-plane identified by the longitudinal plane PL, the rear suspension <NUM> comprises a connecting rod 52A, 52B hinged to the corresponding first rod 51A, 51B. In this respect, each connecting rod 52A, 52B is hinged to the oscillating mass M according to the same principle described above in connection with <FIG>. In general, for each half-plane, the suspension shown in <FIG> has a configuration substantially similar to that described above with reference to <FIG>.

In the embodiment shown in <FIG>, a first spring-shock absorber assembly <NUM> and a second spring-shock absorber assembly <NUM>' are provided, each operatively located between the frame <NUM> and a corresponding first rod 51A, 51B of the rear suspension <NUM>. In particular, in the case illustrated, a first end of each spring-shock absorber assembly <NUM>, <NUM>' is connected to the free end of a corresponding first rod 51A, 51B, while the second end is connected to the frame <NUM>, according to the same principle of the layout shown in <FIG>. Indeed, each first rod 51A, 51B is hinged to the frame <NUM> at an intermediate point thereof, according to the same principle shown in the layout of <FIG>.

As apparent from the layouts shown in <FIG>, <FIG>, <FIG>, <FIG>, and <FIG>, in many of the embodiments described above the spring-shock absorber assembly <NUM> is located in a position inside the body <NUM> of the motor vehicle <NUM>, wherein said position is considered on a lateral observation plane (coinciding with the observation plane of the abovementioned figures). Advantageously, the advanced position of the spring-shock absorber assembly <NUM>, enabled by the quadrilateral suspension, allows the assembly to remain hidden inside the body <NUM>, contrary to what happens in a traditional scooter, where the suspension is always visible from the side.

Claim 1:
A saddle-ride motorcycle (<NUM>) of scooter type, comprising a frame (<NUM>) and a rear wheel (<NUM>) operatively connected to said frame (<NUM>) by means of a rear suspension (<NUM>) that comprises a swingarm (<NUM>) which is part of a mass (M) oscillating about a first axis of rotation (<NUM>) wherein said rear suspension (<NUM>) comprises:
- a first rod (<NUM>) hinged to said frame (<NUM>) about a second axis of rotation (<NUM>) different from said first axis of rotation (<NUM>) and defined at an intermediate point between the ends (<NUM>, <NUM>) of the first rod (<NUM>);
- a second rod (<NUM>) hinged to said first rod (<NUM>) about a third axis of rotation (<NUM>), wherein said second rod (<NUM>) is rotatably connected, directly or through said swingarm (<NUM>), to the pivot of said rear wheel (<NUM>), so as to rotate about a fourth axis of rotation (<NUM>);
- at least one spring-shock absorber assembly (<NUM>) connected, at a first end thereof (70A), to an end (<NUM>) of said first rod (<NUM>) and, at a second end thereof (70B), to said frame (<NUM>);
characterised in that the front end (<NUM>) of the first rod (<NUM>) is connected to the spring-shock absorber assembly (<NUM>), while the rear end (<NUM>) of the first rod (<NUM>) is connected to the second rod (<NUM>).