Drive transmission group to a steer wheel of a vehicle

A drive transmission group to a steer wheel of a vehicle at least a drive chain ring associable to actuating means in rotation able to impart a rotary motion to the chain ring, at least a driven chain ring solidly associated in rotation coaxially to the steer wheel, at least a first intermediate chain ring and a second intermediate chain ring connected respectively to the drive chain ring and to the driven chain ring by means of respective flexible organs, a universal joint comprising a joint spider on a first arm of which the first intermediate chain ring is associated, rotatably with respect to an axis of the first arm, and on a second arm of which the second intermediate chain ring is associated, rotatably with respect to an axis of the second arm, wherein the first intermediate chain ring is concentric to the spider.

TECHNICAL FIELD

The present invention relates to a drive transmission group to a steer wheel of a vehicle.

In greater detail, the invention relates to a drive transmission group to a steer wheel of a three-wheeled vehicle, such as a tricycle (also “recumbent bike” or “trike”), an assisted-pedal bicycle, a motor cycle or the like.

PRIOR ART

Vehicles for transport of persons are known, such as recumbent bicycles or trikes, assisted-pedal bicycles or motorcycles, having three wheels, for example two rear wheels and a steering front wheel.

These vehicle are classified in two main categories, of which a first category known as “rear wheel drive”, in which the drive wheels are the rear wheels, and a second category known as “front-wheel drive”, in which the drive wheel is the front wheel.

In particular, the present invention relates to those vehicle in which the steer wheel is also the drive wheel, and in particular those front-wheel traction vehicles in which the front wheel is the steer wheel.

These vehicles, though known, are rare as they are difficult to construct and exhibit considerable structural limitations, in particular in relation to the maximum steering radius possible with the drive transmission mechanisms to the front wheel.

In particular, U.S. Pat. No. 6,062,581 discloses a drive transmission group going from the pedals (and/or the motor if provided) to a steer wheel of a vehicle comprising:a drive chain ring solidly associated in rotation coaxially to the front steer wheel,a driven chain ring solidly associated in rotation coaxially to the front steer wheel,at least a first intermediate chain ring and a second intermediate chain ring respectively connected to the drive chain ring and the driven chain ring by means of respective chains,a universal joint, which comprises a spider centred on the steering axis of the steer wheel.

The first intermediate chain ring is associated via a first fork to a first arm of the spider, rotatably with respect to the axis of the first arm, and the second intermediate chain ring is associated via a second fork to a second arm of the spider, rotatably with respect to the axis of the second arm.

The arrangement of the first intermediate chain ring is therefore offset with respect to the central longitudinal plane of the vehicle and consequently also the drive chain ring, which must be parallel and aligned as much as possible to the first intermediate chain ring, is necessarily offset with respect to the central longitudinal plane with a consequently greater discomfort in pedalling by the user.

Further, in order to support the first and the second fork bearings are necessary (two in number for each fork), which being very near to one another must support heavy loads and therefore be of large dimensions.

Further, in these known-type vehicles it is not possible to insert a suspension on the front drive wheel, and this makes the vehicle particularly sturdy and not very comfortable.

An aim of the present invention is to obviate the above-mentioned drawbacks in the prior art, with a solution that is simple, rational and relatively inexpensive.

The aims are attained by the characteristics of the invention reported in the independent claim. The dependent claims delineate preferred and/or especially advantageous aspects of the invention.

DISCLOSURE OF THE INVENTION

In particular, the invention provides a drive transmission group to a steer wheel of a vehicle which comprises:at least a drive chain ring associable to actuating means in rotation able to impart a rotary motion to the chain ring,at least a driven chain ring solidly associated in rotation coaxially to the steer wheel,at least a first intermediate chain ring and a second intermediate chain ring connected respectively to the drive chain ring and to the driven chain ring by means of respective flexible organs,a universal joint comprising a joint spider on a first arm of which the first intermediate chain ring is associated, rotatably with respect to an axis of the first arm, and on a second arm of which the second intermediate chain ring is associated, rotatably with respect to an axis of the second arm.

According to the invention, the first intermediate chain ring is concentric to the spider.

With this solution, apart from obviating the problems of the prior art, it is possible to reduce the spatial encumbrance of the transmission group, the stresses on the organs thereof and minimizing the problems of balancing.

In a further aspect of the invention, revolving organs are interposed between the first arm and the first intermediate chain ring.

The revolving organs advantageously comprise at least a pair of bearings respectively associated to opposite ends of the first arm and in diametrically opposite points of the first chain ring.

In this way the mechanical friction between the moving organs can be reduced and at the same time the sturdiness of the transmission group is increased.

In a further aspect of the invention a vehicle is provided (for example a three-wheeled vehicle) comprising a frame supported by at least a rear wheel (for example 2 in number) and at least a front steer wheel (for example a single front wheel) which comprises a transmission group as described above.

The vehicle advantageously comprises actuating means mechanically connected to the drive chain ring for activating said ring in rotation.

For example, the actuating means comprise a pair of pedals rotatably associated to the frame and coaxially solid to the drive chain ring.

Additionally or alternatively, the actuating means comprise at least a motor.

In a still further aspect of the invention, the vehicle comprises a fork able to rotatingly support the front wheel and hinged to the frame with respect to a steering axis, the universal joint being directly supported by the fork.

With this solution, it is possible to reduce the risk of interference between the parts in motion, in particular the second flexible organ, with the frame or other fixed parts during the steering.

In practice, the universal joint is associated to the fork in a zone thereof located inferiorly, along the steering axis, with respect to the hinging point of the fork to the frame.

The second arm of the spider is advantageously hinged, with respect to the axis of the second arm, to a fork organ of the universal joint, which in turn is supported rotatably by the fork of the vehicle.

In a further aspect of the invention, the vehicle comprises limiting means of the rotation of the first intermediate chain ring with respect to the steering axis.

With this solution, the risk of the first flexible organ detaching from the drive chain ring and the first intermediate chain ring can be eliminated.

In a preferred embodiment, the limiting means comprise at least a longitudinal appendage inserted in a sleeve fixed to the frame and provided with a cradle able to embrace the first intermediate chain ring from opposite sides.

Further, the cradle advantageously comprises revolving means able to roll, substantially without dragging, on the lateral walls of the first intermediate chain ring.

In this way, even during steering of the vehicle the frictions in play are small, which results in a fluid and comfortable guide of the vehicle.

The appendage is also slidably associated to the frame with respect to the longitudinal axis of the appendage.

In this way the vehicle forks can be suspended, with a greater comfort for those in the vehicle.

BEST WAY OF CARRYING OUT THE INVENTION

With particular reference to the figures,10denotes in its entirety a vehicle, for example a three-wheeled vehicle, such as for example a recumbent bicycle, servo-assisted and/or pedal-powered, a moped or the like.

The bicycle10comprises a bearing frame21, which comprises a longitudinal upright supported by a pair of rear wheels (not illustrated) and hinged frontally to a fork22supporting a front steer wheel23.

The fork22comprises an upper sleeve24inserted in a bushing25realised in the frame21, in which it is blocked axially and free to rotate with respect to a steering axis X.

The fork22is, in the illustrated example, damped, and in particular comprises two telescopic arms (per side) with variable length in opposition to mechanical means and/or hydraulic means and/or resistant pneumatic means.

The frame21is able to support a seat (not shown) and steering means, such as a handlebar or a pair of handles, able to command rotation of the fork22with respect to the steering axis X.

The frame21comprises a pair of shelves26(or tubular elements or the like) which are fixed rigidly to the upright and branch inferiorly (or superiorly or frontally) thereto.

Advantageously but not limitingly the frame21is of an oscillating type, i.e. the rear wheels can oscillate with respect to a substantially parallel axis to the longitudinal axis of the upright which defines the frame21.

The vehicle10further comprises a drive transmission group30which is described in detail in the following.

The drive transmission group30comprises at least a drive chain ring31which is rotatably supported by the pair of shelves26(not indispensable, as they could be realised by the frame21if appropriately profiled).

The pair of pedals32is fixed, as known to the expert in the sector, solidly in rotation with the drive chain ring31and rotatable with respect to the frame21.

The drive transmission group30further comprises a driven chain ring33, for example exhibiting a number of cogs that is lower than the number of cogs of the drive chain ring31, which is associated, solidly in rotation and coaxially, to the front wheel23.

The drive transmission group30, as can be seen in figures from5to10, comprises an at least first intermediate chain ring34, which is associated to the frame21rotatably with respect to the central axis thereof, but constrained thereto such as to be substantially parallel (and aligned) to the drive chain ring31(in practice being rotatably associated to the fork22with respect to the steering axis X thereof).

The transmission group30comprises a first flexible organ35, for example a chain or a belt or a further flexible organ, loop-closed and wound about a drive chain ring31and to the first intermediate chain ring34, which first flexible organ35is able to transfer the rotation drive imparted by the drive chain ring31to the intermediate chain ring34.

The transmission group30further comprises a second intermediate chain ring36, which is associated to the fork22rotatably with respect to the central axis thereof, but constrained thereto, both in rotation with respect to the steering axis X and in translation, such as to be substantially parallel (and substantially aligned) to the driven chain ring33.

The transmission group30comprises a second flexible organ37, for example a chain or a belt or another flexible organ, loop-closed and wound about the driven chain ring33and the second intermediate chain ring36, which second flexible organ37is able to transfer the rotation motion which is imparted by the second intermediate chain ring36(by the first intermediate chain ring34, as will be described in the following) to the drive chain ring33and then to the front wheel23.

Respective chain-stretchers can be associated to the frame21and/or the fork22, able to respectively tension the first flexible organ35and/or the second flexible organ37.

The drive transmission group30comprises a universal joint50comprising a spider51, on a first arm511of which the first intermediate crown34is associated, rotatably with respect to the axis of the first arm511, and on the second arm512of which the second intermediate crown36is associated, rotatably with respect to the axis of the second arm.

In particular, the first intermediate crown34is concentric to the spider51.

In practice, the first intermediate crown34lies on a plane containing the axis of the first arm511of the spider51.

The first intermediate chain ring34, therefore, also function as a fork for the universal joint50, directly transferring the drive from the first intermediate chain ring to the spider51, without interposing further fork organs and universal shafts.

The first intermediate chain ring34comprises a central cavity340from which two diametrically-opposite radial pins341project, which pins341have first ends thereof facing towards the centre of the first intermediate chain ring34.

Each pin341is, for example, fixed to the first intermediate chain ring34by means of screws (for example 3 in number).

The first arm511of the spider51is substantially hollow (at least at the free ends thereof), such that the ends of the first arm511can house the pins341.

The pins341are then rotatably inserted internally of the cavity of the first arm511by interposing respective bearings342, and the first arm511is blocked in translation between the two pins341.

The first intermediate chain ring34further comprises a pair of annular bodies343, coaxial and fixed at opposite sides of the first intermediate chain ring, able to keep the first flexible organ35enmeshed on the first intermediate chain ring.

The first arm511comprises a through-cavity513with an axis perpendicular to the axis of the first arm and located in a central position (the central axis of which intersects the axis of the first arm511at the centre of the spider51, i.e. at the centre of the first intermediate chain ring34).

In particular, the second arm512(substantially cylindrical) is inserted in the through-cavity513of the first arm511, for example with a transition fit, such that the ends of the second arm512project externally of the first arm.

The universal joint50comprises a fork organ52rotatably coupled to the ends of the second arm512of the spider51.

The fork organ52comprises a central shaft520provided with a central bifurcation521defining a substantially circular eyelet522located in the central portion of the central shaft.

In practice, the fork organ52is conformed as a head joint of two symmetrical forks.

The fork organ52comprises, at the central bifurcation521, a cylindrical through-seating523with an axis perpendicular to the axis of the central shaft520(and the eyelet522) which defines two cylindrical cavities on each branch of the central bifurcation521. Each cylindrical seating523is able to house internally thereof the free ends of the second arm512of the spider51, for example by interposing two respective bearings524blocked axially by suitable blocking organs.

In practice, the fork organ52is rotatably coupled to the second arm512.

The second intermediate chain ring36is coaxially splined on one of the end portions of the central shaft520.

In particular, a cylindrical broadening525is defined on the end portion of the central shaft520, on which the second intermediate chain ring36is inserted and blocked, for example by left-handed threads or another reciprocal blocking systems.

The free ends of the central shaft520are rotatably connected, with respect to the axis of the central shaft, to the fork22, as will be more fully described in the following.

The fork22comprises support means60able to support the universal joint50.

In particular, the support means60comprise two parallel and separate uprights61rising from a crossbar62.

The uprights61and/or the crossbar62are rigidly constrained to the fork22, for example inferiorly of the bifurcated portion of the lower arms thereof which support the front wheel23.

A respective cylindrical seating610is defined on each upright61, in which a respective end of the central shaft520is inserted, for example by interposing suitable bearings63, such that the uprights61support the central shaft520is rotation with respect to the axis thereof.

The support means60further comprise limiting means of the rotation of the first intermediate chain rings34with respect to the steering axis X.

In practice, the limiting means are able to maintain the first intermediate chain ring34substantially parallel to the drive chain ring31also during steering of the front wheel23.

In a first embodiment, illustrated inFIGS. 1-10, the limiting means comprise a longitudinal appendage64(for example having a circular section) inserted in a sleeve27fixed to the frame21, such that it can slide with respect to the frame, and provided with a cradle65which defines at least two lateral walls able to embrace the first intermediate chain ring34on opposite sides.

The cradle65is constrained in translation and hinged to the crossbar62, by means of a hinge pine660coaxial (and/or parallel) to the steering axis X of the front wheel23(i.e. the fork22with respect to the frame21).

In this way, the cradle65maintains the first intermediate chain ring34aligned with the frame21also during the steering of the front wheel23.

The cradle65comprises revolving means, such as further bearings66(for example four in number, i.e. two per side) able to roll, substantially without dragging, on the lateral walls of the first intermediate chain ring34, in particular on the annular bodies343thereof.

In a second embodiment shown inFIGS. 11-12, the limiting means comprise an articulated appendage67comprising a first portion671, hinged to the frame21with respect to a first axis, that is substantially parallel to the rotation axis of the drive chain ring31, and a second portion672, hinged to the first portion671with respect to a second axis, parallel to the first axis.

A circular chain ring673is constrained to the free end of the second portion672, which can be splined with play on the central shaft520and be rested on a flank of the first intermediate chain ring34(in particular of one of the annular bodies343) in order to maintain it aligned with the frame21also during the steering of the front wheel23.

Thus, apart from the function of the limitation of the rotation of the first intermediate chain ring34, the sliding of the appendage64or the articulation of the articulated appendage67enable displacement of the fork22along the steering axis X with respect to the frame21, enabling use in the vehicle10of damped forks.

The vehicle10can further comprise abutting means, such as ratchets, guides or other types, for example fixed to the frame21, able to define a lateral abutting element for the first flexible organ35, such as to keep the flexible organ35on the first intermediate chain ring34and the drive chain ring31.

In the embodiment of figures from1to10, the abutting means are defined by the cradle65which comprises a through-opening for the passage of the first flexible organ35, the lateral walls of the cradle functioning as a guide and abutting element for the first flexible organ.

Further, the vehicle10can comprise at least a motor, for example an electric motor, which can assist the pedal motion, for example by activating the drive chain ring31in rotation, as known to the technical expert in the sector.

Alternatively the vehicle10might not comprise pedals, but could be a motor cycle, with the drive chain ring31directly activated by a motor, for example electric and/or internal combustion.

Further, the use of a plurality of driven chain rings33could be used, with a gear reducer, for varying the transmission ratio between the drive chain ring31and the driven chain ring33, as known to the expert in the sector.

In the light of the foregoing, the functioning of the drive transmission group30of the vehicle10is as follows.

By activating the drive chain ring31in rotation, for example by means of the pedals32, the first intermediate chain ring34is rotated by means of the first flexible organ35.

The rotation of the first intermediate chain ring34with respect to the axis thereof transfers the rotary motion to the central shaft520and from this to the intermediate chain ring36.

The rotation of the second intermediate chain ring36is transferred to the driven chain ring33by means of the second flexible organ37and from there to the front wheel23, i.e. the drive wheel of the vehicle10.

When the vehicle proceeds along a straight trajectory the first and the second intermediate wheel34and36are flanked to one another, coaxial and parallel; should a steering action be imparted on the front wheel23the second intermediate wheel36rotates, identically to the front wheel23with respect to the first intermediate wheel34.

The invention as it is conceived is susceptible to numerous modifications and variants, all falling within the scope of the inventive concept.

Further, all the details can be replaced by other, technically equivalent elements.

In practice the materials used, as well as the contingent forms and dimensions, can be any according to requirements without forsaking the protective scope of the following claims.