Patent Publication Number: US-2023150601-A1

Title: Foldable scooter

Description:
TECHNICAL FIELD 
     The disclosure relates to a scooter, and more specifically to a foldable scooter comprising a frame provided with a footboard and supporting a rear wheel rotating about a transverse axis, and a steering column equipped with a front wheel and pivotally mounted on the frame. 
     The disclosure finds a favorite, yet non-limiting, application for a motorized scooter, and in particular an electric scooter, that is to say a motorized scooter with an electric motor. However, the disclosure could be considered with a scooter that is not motorized. 
     BACKGROUND 
     In a known manner, the frame of a foldable scooter comprises a first portion supporting the rear wheel and a footboard, and a second portion pivotally supporting the steering column, wherein the first portion and the second portion of the frame are linked to one another by a swivel joint about a folding axis enabling a relative movability between:
         an unfolded configuration wherein the steering column projects upwards with respect to the footboard for use during a displacement, the steering column extending in a midplane orthogonal to the transverse axis and which includes a longitudinal axis passing through the front wheel and through the rear wheel and parallel to a direction of advance of the scooter when the latter progresses in a straight line; and   a folded configuration wherein the steering column is folded down along the footboard.       

     In a first embodiment, known in particular from the documents FR3070155, FR3041321 and FR3050170, the folding axis is parallel to the transverse axis for a movability of the steering column from the unfolded configuration into the folded configuration wherein the steering column remains in the midplane and extends over the footboard and the rear wheel. In the folded configuration, the scooter is generally symmetrical with respect to the midplane and has a vertical bulk that results from stacking the steering column and the footboard in the midplane. 
     In a second embodiment, known in particular from the document FR3042467, the folding axis is contained in the midplane and is inclined with respect to the longitudinal axis, for a movability of the steering column from the unfolded configuration into the folded configuration wherein the steering column remains in the midplane and extends beneath the footboard and the rear wheel. In the folded configuration, the scooter is generally symmetrical with respect to the midplane and has a vertical bulk that results from stacking the steering column and the footboard in the midplane. 
     The state of the art may also be illustrated by the teaching of the document DE 20 2018 005767 U1 which discloses a foldable scooter which includes a frame comprising, on the one hand, a first portion supporting the rear wheel and a footboard and, on the other hand, a second portion pivotally supporting the steering column which carries the front wheel. This first portion and this second portion of the frame are linked to one another by a swivel joint about an axis of rotation which is included in the midplane and which is inclined downwards, and this swivel joint links the first portion and the second portion by two oblique (non-horizontal) contact surfaces crossed by this axis of rotation. Thus, starting from the unfolded configuration, the second portion pivots about this pivot axis by 180 degrees, and thus, in the folded configuration, the steering column is brought under the footboard, and lies in the midplane, with the same drawbacks as mentioned before, namely a vertical bulk that results from stacking the steering column and the footboard in the midplane. 
     SUMMARY 
     The present disclosure aims at solving all or part of the aforementioned drawbacks, by providing a foldable scooter which, when in the folded configuration, has a reduced vertical bulk. 
     Another aim of the disclosure is to provide a foldable scooter with a relatively concealed swivel joint so that the foldable scooter preserves an elegant line. 
     Another aim of the disclosure is to provide a foldable scooter that is practical and barely bothering when manually carried. 
     To this end, the disclosure provides a scooter of the foldable scooter type, comprising a frame and a steering column equipped with a front wheel and pivotally mounted on the frame about a steering axis, this frame comprising, on the one hand, a first portion supporting a rear wheel rotating about a transverse axis and a footboard and, on the other hand, a second portion pivotally supporting the steering column, wherein the scooter has a midplane orthogonal to the transverse axis and delimiting a first lateral side and a second lateral side opposite to one another, said midplane including a longitudinal axis passing through the front wheel and through the rear wheel and parallel to a direction of advance of the scooter when the latter progresses in a straight line, and the rear wheel has a first lateral face on said first lateral side and a second lateral face, opposite to the first lateral face, on said second lateral side, 
     and wherein the first portion and the second portion of the frame are linked to one another by a swivel joint about a folding axis enabling relative movability thereof between:
         an unfolded configuration wherein the steering column projects upwards with respect to the footboard for use during a displacement, said steering column extending in the midplane; and   a folded configuration wherein the steering column is folded down along the footboard;       

     such a scooter being remarkable in that the swivel joint is arranged for movability of the steering column from the unfolded configuration into the folded configuration wherein the steering column is folded down on the first lateral side with respect to the midplane an extends at distance from said midplane, at least partially beneath the footboard, along a first lateral flange of the footboard located on said first lateral side and facing the first lateral face of the rear wheel. 
     Thus, the disclosure suggests bringing the steering column, in the folded configuration, on the right side (or conversely on the left side) of the footboard and of the rear wheel, asymmetrically with respect to the midplane, rather than leaving the steering column in the midplane once folded like in the prior art. Thus, in the folded configuration, the vertical bulk is reduced because there is no sacking in the midplane of the steering column and of the footboard. Furthermore, such a configuration allows for an easy manual carrying of the scooter folded this way. 
     According to one feature, the folding axis is offset on the first lateral side with respect to the midplane and it extends in an inclined manner with respect to the longitudinal axis with an angle of inclination comprised between 20 and 60 degrees 
     Such a positioning and such an inclination of the folding axis allows achieving the desired tilting of the steering column on the right side (or conversely on the left side) of the footboard and of the rear wheel. 
     Advantageously, the angle of inclination is comprised between 30 and 50 degrees. 
     In a particular embodiment, the folding axis extends parallel to the midplane. 
     In a particular embodiment:
         in the unfolded configuration, the steering axis is vertical or inclined with respect to the vertical by an angle comprised between 0 and 20 degrees; and   in the folded configuration, the steering axis is horizontal or inclined with respect to the horizontal by an angle comprised between 0 and 20 degrees.       

     In the context of the disclosure, by «vertical», reference is made to a vertical direction with respect to a horizontal ground on which the scooter is bearing or rolling with its front wheel and its rear wheel, and by «horizontal», reference is made to a horizontal plane parallel to the horizontal ground on which the scooter is bearing or rolling with its front wheel and its rear wheel. It should be noted that the longitudinal axis of the scooter is horizontal as it is parallel to this horizontal plane. 
     Advantageously, in the folded configuration, the steering axis is parallel, within 5 degrees, to the longitudinal axis. 
     Thus, in the folded configuration, the steering column and the footboard extend parallel to one another, next to one another, the steering column lying beneath the footboard, which represents a particularly practical configuration for carrying the scooter manually. 
     In an advantageous embodiment, the swivel joint is in the form of a hinge provided with a first hinge knuckle secured to an upper segment of the first portion of the frame and with a second hinge knuckle secured to a lower segment of the second portion of the frame, where the first hinge knuckle and the second hinge knuckle are hinged relative to one another by means of a pivot defining the folding axis, so that this swivel joint is pivotally movable between:
         a closed position corresponding to the unfolded configuration of the scooter, wherein the upper segment of the first portion of the frame and the lower segment of the second portion of the frame are in alignment along a secondary axis contained in the midplane; and   an open position corresponding to the folded configuration of the scooter, wherein the upper segment of the first portion of the frame and the lower segment of the second portion of the frame are misaligned and are disposed side-by-side following pivoting about the folding axis.       

     According to one possibility, the secondary axis is inclined with respect to the longitudinal axis by a secondary angle comprised between 45 and 90 degrees, and in particular between 50 and 80 degrees. 
     According to another possibility, the folding axis is inclined with respect to the secondary axis by an intermediate angle which is comprised between 90 and 120 degrees. 
     Advantageously, the folding axis is inclined with respect to the secondary axis by an intermediate angle equal to 90 degrees, which enable the upper segment of the first portion of the frame and the lower segment of the second portion of the frame to be parallel in the unfolded configuration. 
     In a particular embodiment, the first portion has two successive tubular sections:
         a central section on which the footboard is fastened and which extends along the longitudinal axis; and   an inclined section which projects from the central section and which extends along the secondary axis.       

     In a first embodiment, the central section has a front end which extends in an elbow, this elbow being, in turn, extended by the inclined section. 
     In a second embodiment, the first portion further comprises:
         a front section fastened on a front end of the central section, at the front and at distance from a junction between the inclined section and the central section, and   a reinforcing section extending between the front section and the upper segment of the first portion, this reinforcing section extending between the secondary axis and the longitudinal axis to form a reinforcing structure with an inverted triangular geometry.       

     In this second embodiment, the frame has a reinforced structure at the front, with the reinforcing section which will form an inverted triangular geometry that is very suited for the distribution of forces. 
     In a particular embodiment, the swivel joint integrates a locking mechanism adapted to lock the swivel joint in the unlocked configuration. 
     According to one possibility, the locking mechanism comprises:
         a movable locking element attached to one amongst the first hinge knuckle and the second hinge knuckle;   a complementary locking element attached to the other one amongst the first hinge knuckle and the second hinge knuckle, this movable locking element and this complementary locking element being adapted to cooperate together in a locking position to lock the swivel joint in the closed position, from an unlocking position wherein said movable locking element and said static locking element do not cooperate together so as to enable movability towards the open position; and   a manual actuator shaped so as to act on said movable locking element to bring and block said movable locking element in the locking position.       

     Advantageously, the locking mechanism comprises an elastic biasing member urging the movable locking element towards the unlocking position. 
     According to another possibility, the movable locking element comprises a hook and the complementary locking element is formed by a complementary element adapted to be hooked by this hook in the locking position. 
     According to another possibility, the manual actuator comprises a tapped rod provided with a gripping head and with a free end adapted to abut against the movable locking element, this manual actuator being displaceable by screwing so as to act on the movable locking element. 
     According to another possibility, the first hinge knuckle comprises a first clamping jaw clasping the upper segment of the first portion of the frame, and the second hinge knuckle comprises a second clamping jaw clasping the lower segment of the second portion of the frame. 
     According to one variant, the movable locking element is mounted on one amongst the first clamping jaw and the second clamping jaw, and the static locking element is mounted on the other one amongst the first clamping jaw and the second clamping jaw, and the manual actuator is mounted like the static locking element on the other one amongst the first clamping jaw and the second clamping jaw. 
     According to one variant, the movable locking element is mounted inside one amongst the first clamping jaw and the second clamping jaw, and the static locking element is mounted inside the other one amongst the first clamping jaw and the second clamping jaw. 
     In a particular embodiment, the movable locking element is mounted on a rod fastened inside one amongst the first clamping jaw and the second clamping jaw, and the static locking element is formed by a rod fastened inside the other one amongst the first clamping jaw and the second clamping jaw. 
     Advantageously, the rods cross the first clamping jaw and the second clamping jaw and also cross the upper segment of the first portion of the frame and the lower segment of the second portion of the frame. 
     Thus, these rods contribute to the rigidity of the set, by adding to the clamping of the jaws around the upper segment of the first portion of the frame and the lower segment of the second portion of the frame. 
     In one variant, the first hinge knuckle comprises a first sleeve intended to be fastened inside the upper segment of the first portion of the frame, and the second hinge knuckle comprises a second sleeve intended to be fastened inside the lower segment of the second portion. 
     In another variant, the first hinge knuckle has an upper face wherein at least two centering holes are formed, and the second element has a lower face from which at least two centering pads, advantageously conical-shaped, project where in the closed position of the swivel joint, the centering pads fit inside the respective centering holes, which have shapes complementary to those of the centering pads. 
     In another variant, the first hinge knuckle has a first locking lip, for example beveled-shaped, diametrically opposite to the pivot, and the second hinge knuckle has a second locking lip, for example beveled-shaped, and where in the closed position, these two locking lips are pressed against one another. 
     In another variant, the locking mechanism comprises the movable locking element which has a groove which has a shape complementary to the two locking lips when pressed against one another in the closed position, and thus, in the closed position and in the locking position, the movable locking element sets the two locking lips within its groove and thus locks the swivel joint in the closed position. 
     In another variant, the manual actuator comprises a tapped rod screwed into a threaded sheath integrated to the first hinge knuckle, and the second hinge knuckle has a groove in order to receive the threaded sheath in the closed position. 
     Advantageously, the steering column has an upper end secured to a handlebar extending transversely and provided with two grips respectively to the right and to the left and, in the folded configuration, the rear wheel and the two grips gave respectively three bearing points extending in the same plane enabling an upright bearing of the scooter on these three bearing points resting on a horizontal plane. 
     Thanks to folding of the steering column on a lateral side, it is thus possible to provide for three bearing points (a bearing point on the rear wheel and two bearing points to the right and to the left on the respective grips) to make the scooter hold upright on a horizontal ground, with the steering column and the footboard which lie substantially vertically and with the front wheel at the top. This shape is particularly advantageous for a barely bulky storage of the scooter on the ground. 
     Moreover, in an advantageous embodiment, in the folded configuration, the handlebar is inclined in a direction with respect to a base plane that is orthogonal to the transverse axis, and the front wheel is inclined in an opposite direction with respect to this same base plane. 
     These opposite inclinations of the handlebar and of the front wheel with respect to this base plane contribute to a reduced lateral bulk, advantageous when manually carried at the level of the steering column, with the base plane lying substantially horizontally. 
     The disclosure also concerns the feature according to which the rear wheel is carried by a rear transverse shaft extending along the transverse axis, and this rear transverse shaft is supported by a rear structure fastened to the frame and extending laterally on the second lateral side with respect to the midplane, and thus facing the second lateral face of the rear wheel, opposite to the first lateral face, so that the rear transverse shaft protrudes from the rear structure to support the rear wheel in a cantilevered manner, and that the first lateral face of the rear wheel is cleared. 
     Thus, the first lateral face of the rear wheel is cleared, which allows bringing the steering column, upon folding, the closest to this first lateral face of the rear wheel, for a reduced lateral bulk. Moreover, this feature allows clearing the first lateral side of the rear wheel (in this instance the lateral side opposite to the rear structure) which allows for a free access to the rear wheel, in particular to extract it easily and quickly in order to facilitate maintenance and repair tasks in an everyday environment. 
     In a particular embodiment, the scooter is motorized by comprising a motor equipped with a motor shaft driven in rotation about a motor axis and coupled to the rear wheel to drive it in rotation via a transmission system. 
     In an advantageous embodiment, the transmission system comprises:
         the rear transverse shaft having two opposite end portions, respectively a first end portion and a second end portion, the rear wheel being rotatably coupled on the second end portion of the rear transverse shaft;   a gear system comprising a gear ring meshing with a gear pinion, this gear ring being rotatably coupled on the first end portion of the rear transverse shaft, and this gear pinion being rotatably coupled to the motor shaft, so that a rotation of the motor shaft is convertible by this gear system into a rotation of the rear transverse shaft and of the rear wheel about the transverse axis;   the rear structure fastened to the frame and supporting at least the gear pinion and the first end portion of the rear transverse shaft, this rear structure extending laterally only on the second lateral side with respect to the midplane so that the second end portion of the rear transverse shaft protrudes from the rear structure to support the rear wheel in a cantilevered manner.       

     Thus, in this advantageous embodiment, it is provided to use a gear system allowing adapting the speed and torque conditions that are output by the motor in one single multiplication step, and therefore also allowing getting rid from component the servicing of which is considerable such as chains and belts, while allowing clearing the first lateral face of the rear wheel completely, which enables free access to the rear wheel on the first lateral (right or left) side, and which also allows bringing the steering column, during folding, the closest to this first lateral face, which allows for a reduced lateral bulk. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present disclosure will appear upon reading the detailed description hereinafter, of two non-limiting examples of implementation, made with reference to the appended figures wherein: 
         FIG.  1    is a schematic perspective front view of a first scooter, according to a first embodiment of the disclosure, in the unfolded configuration; 
         FIG.  2    is a schematic side vie, in this instance the right side, of the first scooter of  FIG.  1    (not represented in its entirety); 
         FIG.  3    is a schematic perspective rear view of the first scooter of  FIGS.  1  and  2    (not represented in its entirety); 
         FIG.  4    is a schematic front view of the first scooter of  FIGS.  1  to  3    (not represented in its entirety); 
         FIG.  5    is a schematic perspective front view of the first scooter of  FIGS.  1  to  4   , in the folded configuration; 
         FIG.  6    is a schematic bottom view of the first scooter of  FIGS.  1  to  5   , in the folded configuration; 
         FIG.  7    is a schematic perspective view of the swivel joint of the first scooter, in the open position; 
         FIG.  8    is a schematic perspective view of the swivel joint of the first scooter, in the closed position; 
         FIG.  9    is a schematic side view of the swivel joint of the first scooter, in the closed position; 
         FIG.  10    is a schematic view of the swivel joint of the first scooter, in the closed position in the sectional plane X-X of  FIG.  9   ; 
         FIG.  11    is a schematic top view of the swivel joint of the first scooter, in the closed position; 
         FIG.  12    is a schematic perspective view of the first scooter of  FIGS.  1  to  6   , in the folded configuration and in an upright situation bearing on three bearing points; 
         FIG.  13    is a schematic top view of the first scooter of  FIGS.  1  to  6   , in the folded configuration; 
         FIG.  14    is a schematic rear view of the first scooter of  FIGS.  1  to  6   , in the folded configuration and in a carry situation; 
         FIG.  15    is a schematic perspective front view of a second scooter, according to a second embodiment of the disclosure, in the unfolded configuration; 
         FIG.  16    is a schematic side view, in this instance the right side, of the second scooter of  FIG.  15   ; 
         FIG.  17    is a schematic perspective front view of the second scooter of the  FIGS.  15  and  16   , in the folded configuration, with zooming on the swivel joint; 
         FIG.  18    is a schematic top view of the second scooter of  FIGS.  15  to  17   , in the folded configuration; 
         FIG.  19    is a schematic front view of the second scooter of  FIGS.  15  to  18   , in the folded configuration and in a carry situation, with zooming on the swivel joint; 
         FIG.  20    is a schematic side view, in this instance the right side, of the second scooter of  FIGS.  15  to  19   , in the folded configuration; 
         FIG.  21    is a schematic perspective view of the swivel joint of the second scooter, in the open position; and 
         FIG.  22    is a schematic side view of the swivel joint of the second scooter, in the open position. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The following description relates to a first scooter  1  and to a second scooter  1 ′, which are respectively in accordance with a first embodiment of the disclosure and with a second embodiment of the disclosure.  FIGS.  1  to  14    relate to the first scooter  1  and  FIGS.  15  to  22    relate to the second scooter  1 ′. The first scooter  1  and the second scooter  1 ′ may also be referred to respectively as the scooter  1  and the scooter  1 ′. 
     For the following description, the same reference numerals will be used to refer to parts and structural elements that are identical or similar for the first scooter  1  and the second scooter  1 ′. On the contrary, distinct reference numerals will be used to refer to parts and structural elements that are structurally (yet not necessarily functionally) distinct for the first scooter  1  and the second scooter  1 ′. In this instance, the first scooter  1  and the second scooter  1 ′ differ by their frame  2 , respectively  2 ′, and their swivel joints  7 , respectively  7 ′, described hereinafter. 
     Referring to  FIGS.  1  to  6  and  15  to  20   , each of the first scooter  1  and second scooter  1 ′ forms a foldable scooter. 
     The scooter  1  (respectively  1 ′) is a two-wheel scooter, comprising:
         a frame  2  (respectively  2 ′) provided with a footboard  20  (respectively  20 ′) and supporting a rear wheel  3  rotating about a transverse axis AT,   a steering column  4  equipped with a front wheel  5 , this steering column  4  being pivotally mounted on the frame  2  (respectively  2 ′).       

     The scooter  1  (respectively  1 ′) has a midplane PM orthogonal to the transverse axis AT and delimiting two right and left lateral sides opposite to one another, namely a first lateral side (in the following description it will include the left side) and a second lateral side (in the following description it will include the right side). This midplane PM also includes a longitudinal axis AL of the scooter  1 , such a longitudinal axis AL passing through the front wheel  5  and by the rear wheel  3  while being parallel to a direction of advance of the scooter  1  (respectively  1 ′) when the latter progresses in a straight line. Thus, this longitudinal axis AL is orthogonal to the transverse axis AT. The midplane PM forms a plane of symmetry for the footboard  20  (respectively  20 ′) and the two wheels  3 ,  5 . 
     The frame  2  (respectively  20 ′) comprises a tubular structure which, without this being restrictive, could be made of a metallic material, and this frame  2  (respectively  2 ′) has two portions  21 ,  22  (respectively  21 ′,  22 ′), respectively:
         a first portion  21  (respectively  21 ′) which supports a rear wheel  3  and the footboard  20  (respectively  20 ′); and   a second portion  22  (respectively  22 ′), extending the first portion  21  (respectively  21 ′), and which pivotally supports the steering column  4 .       

     The following description relates to folding of the scooter  1  (respectively  1 ′). 
     For the scooter  1  (respectively  1 ′) to be foldable, the first portion  21  (respectively  21 ′) and the second portion  22  (respectively  22 ′) of the frame are linked to one another by a swivel joint  7  (respectively  7 ′) about a folding axis AP (respectively AP′) which enables folding and unfolding of the scooter  1  (respectively  1 ′) about this folding axis AP (respectively AP′), this scooter  1  (respectively  1 ′) then forming a foldable scooter. 
     Thus, pivoting of the second portion  22  (respectively  22 ′) relative to the first portion  21  (respectively  21 ′) translates into a tilting (or a pivoting) of the steering column  4  for folding/unfolding of the scooter  1  (respectively  1 ′). 
     Hence, the swivel joint  7  (respectively  7 ′) enables a relative movability between the two portions  21 ,  22  (respectively  21 ′,  22 ′) of the frame  2  (respectively  2 ′) between:
         an unfolded configuration, shown in  FIGS.  1  to  4    for the scooter  1  and in  FIGS.  15  and  16    for the scooter  1 ′, wherein the steering column  4  projects upwards with respect to the footboard  20  for use during a displacement, the steering column  4  then extending in the midplane PM; and   a folded configuration, shown in  FIGS.  5  and  6    for the scooter  1  and in  FIGS.  17  to  20    for the scooter  1 ′, wherein the steering column  4  is folded down on the left side, along the footboard  20  (respectively  20 ′).       

     The following description concerns the shape of the frame  2  of the scooter  1 . 
     The first portion  21  has two successive tubular sections:
         a central section  210  on which the footboard  20  is fastened; and   an inclined section  211  which extends the central section  210  (projecting from the central section  210  upwards) and which forms an elbow directed upwards, with an elbow angle IC (shown in  FIG.  2   ) comprised between 90 and 120 degrees, and in particular between 100 and 110 degrees.       

     Hence, the central section  210  has a front end which is extended by an elbow, having the elbow angle IC, this elbow being, in turn, extended by the inclined section  211 . The central section  210  extends along the longitudinal axis AL of the scooter  1 . Moreover, the inclined section  211  has an upper segment (which forms the upper segment of the first portion  21 ) on which the swivel joint  7  is mounted. This upper segment is rectilinear and extends linearly along a secondary axis AS which is inclined with respect to the longitudinal axis AL by a secondary angle IS (shown in  FIG.  2   ), with the following relationship: 15=180-1C. Thus, this secondary angle IS is comprised between 60 and 90 degrees, and in particular between 70 and 80 degrees. 
     In turn, the second portion  22  has:
         a front section  220 , tubular and with a curved shape, which extends the upper segment of the inclined section  211  of the first portion  21 ; and   a steering tube  221 , secured to an upper end of the front section  220 , and inside which the steering column  4  is pivotally mounted.       

     In the unfolded configuration, the steering tube  221  extends about a steering axis AD which is vertical or inclined rearwards with respect to the vertical by a steering angle ID (shown in  FIG.  2   ) comprised between 0 and 20 degrees, and thus the steering column  4  pivots about this steering axis AD. Thus, the steering column  4  is in pivot connection in the steering tube  221 . 
     Whether for the scooter  1  or for the scooter  1 ′, the steering column  4  has a lower end  40 , below the steering tube  221 , which is secured to an arm  41  (or alternatively to a fork); such and arm  41  (or alternatively such a fork) carrying a front transverse shaft  42  on which the front wheel  5  is pivotally mounted. 
     Whether for the scooter  1  or for the scooter  1 ′, the steering column  4  has an upper end  43  secured to a handlebar  44  extending transversely with respect to the steering column  4 , and where this handlebar  44  is provided with two grips  45  respectively right and left grips. There may also be provided a telescopic system  46  on the steering column  4 , above the steering tube  221 , enabling setting of the height of the steering column  4 , and more specifically of the handlebar  44 . 
     It should be noted that the front section  220  of the second portion  22  of the frame  2  has a lower segment (which forms the lower segment of the second portion  22  and which is opposite to the steering tube  221 ) on which the swivel joint  7  is mounted. This lower segment is rectilinear and extends linearly along the secondary axis AS in the unfolded configuration. In other words, in the unfolded configuration, the upper segment of the first portion  21  of the frame  2  and the lower segment of the second portion  22  of the frame  2  are in alignment along this secondary axis AS. 
     Moreover, and as shown in  FIG.  2   , the folding axis AP is inclined with respect to the secondary axis AS by an intermediate angle IT which is larger than 90 degrees, in particular comprised between 100 and 120 degrees, and in particular in the range of 110 degrees. Thus, in the folded configuration, the upper segment of the first portion  21  of the frame  2  and the lower segment of the second portion  22  of the frame  2  are disposed side-by-side but are not parallel, as shown in  FIGS.  5 ,  12  and  13   . 
     The following description concerns the shape of the frame  2 ′ of the scooter  1 ′. 
     The first portion  21 ′ has two successive tubular sections:
         a central section  210 ′ on which the footboard  20 ′ is fastened; and   an inclined section  211 ′ which projects from the central section  210 ′ upwards, thereby defining some kind of an elbow with an elbow angle IC′ (shown in  FIG.  16   ) comprised between 100 and 130 degrees, and in particular between 110 and 120 degrees.       

     The central section  210 ′ extends along the longitudinal axis AL of the scooter  1 ′. Moreover, the inclined section  211 ′ is rectilinear and extends linearly along a secondary axis AS&#39; which is inclined with respect to the longitudinal axis AL by a secondary angle IS&#39; (shown in  FIG.  16   ), with the following relationship: IS′=180-IC′. Thus, this secondary angle IS&#39; is comprised between 50 and 80 degrees, and in particular between 60 and 70 degrees. Thus, this linear section  211 ′ has an upper segment (which forms the upper segment of the first portion  21 ′) on which the swivel joint  7 ′ is mounted, wherein this upper segment is rectilinear and extends along this secondary axis AS′. 
     The central section  210 ′ has a front end on which is fastened, for example by welding, a front section  213 ′ which is in the form of a tube extending parallel to the transverse axis AT. The front section  213 ′ is disposed at the front and at a distance from the junction between the inclined section  211 ′ and the central section  210 ′, and there is provided a reinforcing section  214 ′ extending between the front section  213 ′ and the upper section of the inclined section  211 ′. This reinforcing section  214 ′ is in the form of a tube. This reinforcing section  214 ′ is rectilinear and extends along a reinforcing axis AR′ which is vertical, and possibly inclined, with respect to the vertical by substantially 5 degrees. 
     Also, the frame  2 ′ of the scooter  1 ′ has a reinforced structure at the front, with a vertical (or substantially vertical) reinforcing section  214 ′ which extends between the secondary axis AS&#39; and the longitudinal axis AL, thereby forming an inverted triangular geometry that is very suited for the distribution of forces for the scooter  1 ′. 
     To improve the manufacturing and welding process, the reinforcing section  214 ′ is linked to the front section  213 ′ which is in the form of a horizontal tube, which allows distributing possible stresses over a larger contact surface between the reinforcing section  214 ′ and the front section  213 ′. 
     In turn, the second portion  22 ′ has:
         a front section  220 ′, tubular and with a rectilinear shape, which extends the upper segment of the inclined section  211 ′ of the first portion  21 ′; and   a steering tube  221 ′, secured to an upper end of the front section  220 ′, and inside which the steering column  4  is pivotally mounted.       

     In the unfolded configuration, the steering tube  221 ′ extends about a steering axis AD which is vertical or inclined rearwards with respect to the vertical by a steering angle ID (shown in  FIG.  16   ) comprised between 0 and 20 degrees, and thus the steering column  4  pivots about this steering axis AD. Thus, the steering column  4  is in pivot connection in the steering tube  221 ′. 
     Like with the scooter  1 , the steering column  4  has a lower end  40 , below the steering tube  221 ′, which is secured to an arm  41  forming a one-arm fork (or alternatively, a two-arm fork); such an arm  41  (or alternatively, such a two-arm fork) carrying a front transverse shaft  42  on which the front wheel  5  is pivotally mounted. 
     It should be noted that, in the context of the two scooters  1 ,  1 ′, the front fork therefore comprises a one-arm form, with the arm  41  having to carry alone the front wheel  5 , and this arm  41  is advantageously disposed on the first lateral side, therefore opposite to the motor  6  and to the transmission system  8  described later on in the context of a motor drive of the scooter  1  or  1 ′. Hence, this configuration enables the lower end  40  of the steering column  4  to be closer to the frame  2  or  2 ′, upon folding of the scooter  1  or  1 ′, thereby allowing for more compactness in the folded configuration. 
     It should be note that the front section  220 ′ of the second portion  22 ′ of the frame  2 ′ has a lower segment (which forms the lower segment of the second portion  22 ′ and which is opposite to the steering tube  221 ′) on which the swivel joint  7 ′ is mounted. This lower segment is rectilinear and extends linearly along the secondary axis AS&#39; in the unfolded configuration. In other words, in the unfolded configuration, the upper segment of the first portion  21 ′ of the frame  2 ′ and the lower segment of the second portion  22 ′ of the frame  2 ′ are in alignment along this secondary axis AS′. 
     Moreover, and as shown in  FIG.  16   , the folding axis AP′ is inclined with respect to the secondary axis AS&#39; by an intermediate angle IT which is equal to 90 degrees. Thus, in the folded configuration, the upper segment of the first portion  21  of the frame  2  and the lower segment of the second portion  22  of the frame  2  are disposed side-by-side and are parallel, and even the inclined section  211 ′ and the front section  220 ′ (both of them being rectilinear) are parallel, as shown in  FIGS.  17 ,  18  and  20   . 
     This configuration with the inclined section  211 ′ and the front section  220 ′ parallel in the folded configuration, because of the orthogonal orientation between the folding axis AP′ and the secondary axis AS′, is particularly advantageous for mechanical and compactness reasons. 
     More accurately, the scooter  1  (respectively  1 ′) is therefore configurable between:
         the unfolded configuration wherein the steering tube  221  (respectively  221 ′) and the steering column  4  extending about the steering axis AD which is substantially vertical, or at least which is vertical or inclined with respect to the vertical by an angle comprised between 0 and 20 degrees;   the folded configuration wherein the steering tube  221  (respectively  221 ′) and the steering column  4  extend about the steering axis AD which has tilted so as to be substantially horizontal, or at least which is horizontal or inclined with respect to the horizontal by an angle comprised between 0 and 20 degrees.       

     Advantageously, in the folded configuration, the steering axis AD is parallel (within five degrees) to the longitudinal axis AL, so that the steering column  4  extends parallel to this longitudinal axis AL. 
     Although not illustrated, it is advantageous to provide for a means for blocking the scooter  1  (respectively  1 ′) in the folded configuration, in order to avoid it being inadvertently unfolded in particular when it is manually transported or when it is set on the ground. 
     As regards the swivel joint  7  (respectively  7 ′), the latter is in the form of a hinge provided with a first hinge knuckle  71  (respectively  71 ′) secured to the upper segment of the first portion  21  (respectively  21 ′) and with a second hinge knuckle  72  (respectively  72 ′) secured to the lower segment of the second portion  22  (respectively  22 ′), where the first hinge knuckle  71  (respectively  71 ′) and the second hinge knuckle  72  (respectively  72 ′) are hinged relative to one another by means of a pivot  73  (respectively  73 ′) (that is to say a physical axis) defining the folding axis AP (respectively AP′). 
     Thus, this swivel joint  7  (respectively  7 ′) is pivotally movable between:
         a closed position corresponding to the unfolded configuration of the scooter  1  (respectively  1 ′), wherein the upper segment of the first portion  21  (respectively  21 ′) and the lower segment of the second portion  22  (respectively  22 ′) are in alignment along the secondary axis AS (respectively AS′); and   an open position corresponding to the folded configuration of the scooter  1  (respectively  1 ′), wherein the upper segment of the first portion  21  (respectively  21 ′) and the lower segment of the second portion  22  (respectively  22 ′) are misaligned and are disposed side-by-side following pivoting about the folding axis AP (respectively AP′).       

     As shown in  FIGS.  5  and  6    and in  FIGS.  17  and  18   , the swivel joint  7  (respectively  7 ′) is arranged for movability of the steering column  4  of the unfolded configuration towards the folded configuration wherein the steering column  4  is folded down on the first lateral side (for reminder, the left side in the figures) with respect to the midplane PM and extends at a distance from this midplane PM (in other words off the midplane PM), at least partially below the footboard  20  (respectively  20 ′), along a first lateral flange  201  (respectively  201 ′) of the footboard  20  (respectively  20 ′) located on the first lateral side and facing the first lateral face  31  of the rear wheel  3 . This footboard  20  (respectively  20 ′) also has a second lateral flange  202  (respectively  202 ′) located on the second lateral side, and therefore opposite to the first lateral flange  201  (respectively  201 ′) with respect to the midplane PM, this second lateral flange  202  (respectively  202 ′) being cleared and free in the folded configuration. 
     To this end, the folding axis AP (respectively AP′) is offset on the first lateral side with respect to the midplane PM, and it extends, on the one hand, parallel to the midplane PM and, on the other hand, in an inclined manner with respect to the longitudinal axis AL with an angle of inclination IP (respectively IP′) (shown in  FIG.  2    and in  FIG.  16   ), comprised between 20 and 60 degrees, and in particular comprised between 30 and 50 degrees. 
     Thus, this swivel joint  7  (respectively  7 ′) allows folding the scooter  1  (respectively  1 ′), by switching from the unfolded configuration into the folded configuration, in one single movement, namely a rotational movement of the steering column  4  about the folding axis AP (respectively AP′) defined by the swivel joint  7  (respectively  7 ′). 
     Moreover, as shown in  FIGS.  12  and  13    for the scooter  1  (and which also applies to the scooter  1 ′), in the folded configuration, the rear wheel  3  has a bearing point  35  (the farthest point of the rear wheel opposite to the front wheel  5 ) and the two grips  45  have two bearing points  47 ,  48  respectively to the right and to the left, and these three bearing points  35 ,  47 ,  48  extend in the same bearing plane PA, possibly provided that the steering column  4  is stowed in the case where a telescopic system  46  is present. In other words, these three bearing points  35 ,  47 ,  48  are coplanar, and this bearing plane PA is substantially orthogonal to the longitudinal axis AL. As shown in  FIG.  12   , this coplanarity of these bearing points  35 ,  47 ,  48  enables an upright bearing of the scooter  1  on these three bearing points  35 ,  47  resting on a horizontal ground (in the same manner as a tripod), with the longitudinal axis AL and the steering axis AD substantially vertical (a vertical axis Z being illustrated in this  FIG.  12   ), and therefore with the steering column  4  and the footboard  20  (or  20 ′) which are substantially vertical and with the front wheel  5  at the top. 
     Moreover, in the folded configuration, it is possible to carry the scooter  1  (respectively  1 ′) with the hand by placing the hand on the steering column  4 , at the level of a central portion  48  shown in  FIGS.  12  and  13    and in  FIG.  18   , and with the scooter  1  (respectively  1 ′) which is laid down, that is to say with the longitudinal axis AL and the steering axis AD substantially horizontal (a horizontal axis X being illustrated in  FIGS.  13  and  14   , as well as in  FIG.  18   ), and therefore with the steering column  4  and the footboard  20  (respectively  20 ′) which are substantially horizontal and with the front wheel  5  which is at the rear (conversely at the front) of the carrier and the rear wheel  3  at the front (conversely at the rear) of the carrier. 
     As shown in  FIG.  14    for the scooter  1  and in  FIG.  19    for the scooter  1 ′, in the folded configuration, the handlebar  44  is inclined in one direction with respect to the base plane PB which is orthogonal to the transverse axis AT (for reminder, the axis of rotation of the rear wheel  3 ) and which passes through the center of gravity G of the folded scooter  1 . Similarly, the front wheel  5  is inclined in an opposite direction with respect to this base plane PB so that, viewed from the rear (like in  FIG.  12   ) or from the front (like in  FIG.  19   ), the handlebar  44  and the front wheel  5  form together a «X»-like shape. When carried as described in the paragraph hereinabove, the central portion  48  is located vertically above the center of gravity G, and the scooter  1  (respectively  1 ′) is balanced naturally with the base plane PB horizontally and therefore with the transverse axis AT vertically (a vertical axis Z being illustrated in this  FIG.  14    and in this  FIG.  19   ). 
     Thanks to the opposite inclinations of the handlebar  44  and of the front wheel  5  in the folded configuration, during such carrying, the scooter  1  (respectively  1 ′) has a lateral balance between the right and the left, as well as a lateral bulk EL that is reduced, and thus the handlebar  44  and the front wheel  5  do not bother the carrier. Moreover, the space between the front wheel  5  and the rear wheel  3  is free for the passage of the legs of the carrier along the steering column  4 . 
     The following description relates to the structure of the swivel joint  7  of the scooter  1 . 
     Referring to  FIGS.  7  to  11   , it should be noted that the first hinge knuckle  71  comprises a first clamping jaw  710  intended to clasp the upper segment of the first portion  21 , and the second hinge knuckle  72  comprises a second clamping jaw  720  intended to clasp the lower segment of the second portion  22 . 
     The first clamping jaw  710  comprises a slit clamping collar, that is to say delimiting a rectilinear slot  711  over the height thereof, and equipped with one or several clamping screw(s)  712  which cross the slot  711  in order to enable clamping/unclamping of the slot  711  and thus enable clamping/unclamping around the upper segment of the first portion  21 ; such an upper segment being tubular and having a circular section. 
     Similarly, the second clamping jaw  720  comprises a slit clamping collar, that is to say delimiting a rectilinear slot  721  over the height thereof, and equipped with one or several clamping screw(s)  722  which cross the slot  721  in order to enable clamping/unclamping of the slot  721  and thus enable clamping/unclamping around the lower segment of the second portion  22 ; such a lower segment being tubular and having a circular section. 
     The first clamping jaw  710  and the second clamping jaw  720  are provided respectively with a first housing  713  and with a second housing  723  projecting outwardly from the respective collars, and receiving the physical axis forming the pivot  73  at the bottom. These two housings  713 ,  723  are disposed diametrically opposite to the respective slots  711 ,  721  with respect to the secondary axis AS. Advantageously, the two clamping jaws  710 ,  720  are identical, and they are mounted head-to-tail or symmetrically so as to receive the pivot  73  together. 
     In the closed position, the two clamping jaws  710 ,  720  are centered on the secondary axis AS, with the slots  711 ,  721  which extend parallel to the secondary axis AS, and furthermore the first clamping jaw  710  has a circumferential upper face  714  which bears on a circumferential lower face  724  of the second clamping jaw  720  in a bearing plane PA orthogonal to the secondary axis AS. 
     The pivot  73  extends about the folding axis AP which extends in an inclined manner with respect to the bearing plane PA with an angle of inclination IA (shown in  FIG.  9   ), comprised between 10 and 40 degrees, and in particular comprised between 20 and 30 degrees. 
     The swivel joint  7  is also intended to integrate a locking mechanism  74  adapted to lock the swivel joint  7  in the closed position, where this locking mechanism  74  could be manually handled so as to be able to open and close the swivel joint  7  during the folding and unfolding operations. 
     Referring to  FIGS.  7  to  11   , the locking mechanism  74  comprises:
         a movable locking element formed by a hook  75  hanging on an upper rod  750  fastened inside the second clamping jaw  720 ;   a static locking element formed by a lower rod  76  fastened inside the first clamping jaw  710 , the hook  75  and the lower rod  76  being adapted to cooperate together in a locking position (as shown in  FIG.  10   ) to lock the swivel joint  7  in the closed position;   an elastic biasing member formed by a spring  77  mounted inside the second clamping jaw  720  and urging the hook  75  towards an unlocking position (as shown in  FIG.  7   ) wherein the hook  75  and the lower rod  76  do not cooperate together to enable movability of the swivel joint  7  towards the open position; and   a manual actuator  78  mounted on the first clamping jaw  710  and shaped so as to act on the hook  75  against the spring  77  to bring and block the hook  75  in the locking position.       

     The upper rod  750  extends orthogonally to the secondary axis AS and therefore parallel to the bearing plane PA, and it also extends parallel to the clamping screw(s)  722 . The hook  75  is pivotally mounted on the upper rod  750  and protrudes from the circumferential lower face  724  of the second clamping jaw  720 . 
     The hook  75  terminates in a notch adapted to cooperate with the lower rod  76 ; this lower rod  76  forming a complementary element adapted to be hooked by the notch of said hook  75  in the locking position. The lower rod  76  extends parallel to the upper rod  750 , and it also extends parallel to the clamping screw(s)  712 . 
     The manual actuator  78  comprises a tapped rod  780  screwed into a threaded hole provided on the first clamping jaw  710  along a direction parallel to the bearing plane PA and orthogonal to the lower rod  76 . This tapped rod  780  is provided with a gripping head  781  disposed outside the first clamping jaw  710  in order to allow grasping thereof to screw/unscrew the tapped rod  780 . This tapped rod  780  is also provided with a free end  782  disposed outside the first clamping jaw  710 , opposite the lower rod  76 , and adapted to abut against the hook  75  to hold it blocked against the lower rod  76  (as shown in  FIG.  10   ). Thus, the locking mechanism  74  is locked and the swivel joint  7  is blocked in the closed position. 
     The direction of advance of the tapped rod  780  is perpendicular to the lower rod  76 , which implies that when the swivel joint  7  is closed and therefore in the unfolded configuration, the rotation of the tapped rod  780  closes the hook  75  against the lower rod  76  while ensuring closure of the set and while making opening thereof impossible thanks to the remaining force that is exerted, similar to a screwed attachment. The two rods  750 ,  76  are disposed so that the hook  75  joins them by using the separating forces of the structure in the same application line. 
     To unlock the locking mechanism  74 , and thus open the swivel joint  7 , all it needs is to unscrew the manual actuator  78  and the spring  77  acts on the hook  75  to make it move backwards and to separate from the lower rod  76 , thereby enabling folding of the scooter  1 . 
     Advantageously, the rods  750 ,  76  cross the two clamping jaws  710 ,  720  (as described hereinabove) and also cross the upper segment of the first portion  21  and the lower segment of the second portion  22 . 
     In other words, when mounting the first hinge knuckle  71 :
         the first clamping jaw  710  is clamped around the upper segment of the first portion  21  so as to align lower orifices formed in both the first clamping jaw  710  and the upper segment of the first portion  21 ; and afterwards   the lower rod  76  is fitted through these lower orifices so as to be secured to both the first clamping jaw  710  and the upper segment of the first portion  21 ;   the lower rod  76  is finally blocked in position for example by means of a nut or a cotter pin.       

     Similarly, when mounting the second hinge knuckle  72 :
         the second clamping jaw  720  is clamped around the lower segment of the second portion  22  so as to align upper orifices formed in both the second clamping jaw  720  and the lower segment of the second portion  22 ; and afterwards   the upper rod  750  is fitted through these upper orifices so as to be secured to both the second clamping jaw  720  and the lower segment of the second portion  22 ;   the upper rod  750  is finally blocked in position for example by means of a nut or a cotter pin.       

     Afterwards, once the two hinge knuckles  71 ,  72  are mounted, the pivot  73  is set in place to rotatably couple the two hinge knuckles  71 ,  72 . Furthermore, the hook  75  is set in place on the upper rod  750 , the spring  77  is also set in place inside the second clamping jaw  720  as well as the manual actuator  78  which crosses both the first clamping jaw  710  and the upper segment of the first portion  21 . 
     Thus, this locking mechanism  74  ensures the rigidity of the connection between the first portion  21  and the second portion  22  of the frame  2  in the unfolded position, for an enhanced safety in use. The rods  750 ,  76  cross the two clamping jaws  710 ,  720  as well as the first portion  21  and the second portion  22  of the frame  2  contribute to the rigidity of the set by a redundant system (as it adds to the clamping of the jaws  710 ,  720  around the portions  21 ,  22  of the frame) thereby ensuring an additional safety at the same time. 
     In a non-illustrated variant, the locking mechanism  74  may be mounted outside the structure while preserving the joining concept thanks to a hook and with blocking by means of a manual actuator movable in screwing/unscrewing. 
     The following description relates to the structure of the swivel joint  7 ′ of the scooter  1 ′. 
     Referring to  FIGS.  21  and  22   , the first hinge knuckle  71 ′ comprises a cylindrical shaped first sleeve  710 ′ intended to be fastened, in particular by welding, inside the upper segment of the first portion  21 ′, and the second hinge knuckle  72 ′ comprises a cylindrical-shaped second sleeve  720 ′ intended to be fastened, in particular by welding, inside the lower segment of the second portion  22 . 
     These two sleeves  710 ′,  720 ′ allow positioning the hinge knuckles  71 ′,  72 ′ in portions  21 ′,  22 ′ with tubular structures, while promoting a suppression of backlashes or movements. These two sleeves  710 ′,  720 ′ also increase the thickness between the contact areas of the portions  21 ′,  22 ′, which optimizes the distribution of the mass in the most loaded area. Thus, it is possible to keep for the frame  2 ′, at the level of the swivel joint  7 ′, a very light tubular structure with the addition of material in the most stressed area where welds would also be located 
     The first hinge knuckle  71 ′ comprises, secured to the first pad  710 ′, a first element  711 ′ forming a hinge knuckle body, and the second hinge knuckle  72 ′ comprises, secured to the second pad  720 ′, a second element  721 ′ forming a hinge knuckle body, where this first element  711 ′ and this second element  721 ′ are provided with respective housings receiving thereinside the physical axis forming the pivot  73 ′. 
     The first element  711 ′ has an upper face wherein two centering holes  712 ′ are formed, and the second element  721 ′ has a lower face from which two centering pads  722 ′, advantageously conical-shaped, project. In the closed position of the swivel joint  7 ′, the upper face of the first element  711 ′ and the lower face of the second element  721 ′ bear against one another in a bearing plane orthogonal to the secondary axis AS′. 
     The pivot  73 ′ extends about the folding axis AP′ which extends parallel to the bearing plane mentioned in the paragraph hereinabove. 
     Moreover, in the closed position of the swivel joint  7 ′, the centering pads  722 ′ fit inside the respective centering holes  712 ′, which have shapes complementary to those of the centering pads  722 ′. The presence of the two centering pads  722 ′ allows enlarging the contact surface between the two hinge knuckles  71 ′,  72 ′ in the closed position. In this manner, the deformation due to bending and to any shear stress present at the contact of the two hinge knuckles  71 ′,  72 ′ is blocked more effectively by these two centering pads  722 ′. 
     The first element  711 ′ also has a beveled-shaped first locking lip  761 ′ which is diametrically opposite to the pivot with respect to the secondary axis AS′. The second element  721 ′ also has a beveled-shaped second locking lip  762 ′ which is diametrically opposite to the pivot with respect to the secondary axis AS&#39; in the closed position. Also, in the closed position, these two locking lips  761 ′,  762 ′ are pressed against one another in the bearing plane. 
     The swivel joint  7 ′ is also intended to integrate a locking mechanism  74 ′ adapted to lock the swivel joint  7 ′ in the closed position, where this locking mechanism  74 ′ could be manually handled so as to be able to open and close the swivel joint  7 ′ during the folding and unfolding operations. 
     Referring to  FIGS.  21  and  22   , the locking mechanism  74 ′ comprises:
         a movable locking element  75 ′ attached to the first hinge knuckle  71 ′;   a complementary locking element formed by the second locking lip  762 ′ and which is therefore attached to the second hinge knuckle  72 ′; and   a manual actuator  78 ′ shaped so as to act on this movable locking element  75 ′.       

     The movable locking element  75 ′ and the second locking lip  762 ′ are adapted to cooperate together in a locking position to lock the swivel joint  7 ′ in the closed position, from an unlocking position (shown in  FIGS.  21  and  22   ) wherein this movable locking element  75 ′ and this second locking lip  762 ′ do not cooperate together to enable movability towards the open position. 
     More specifically, the movable locking element  75 ′ has a groove  77 ′ which has a shape complementary to the two locking lips  761 ′,  762 ′ when pressed against one another in the closed position, and thus, in the closed position and in the locking position, the movable locking element  75 ′ sets the two locking lips  761 ′,  762 ′ within its groove  77 ′ and thus locks the swivel joint  7 ′ in the closed position. 
     The manual actuator  78 ′ is intended to displace the movable locking element  75 ′ and thus bring and block this movable locking element  75 ′ in the locking position by bringing it close to the two locking lips  761 ′,  762 ′, and conversely bring the movable locking element  75 ′ away from the two locking lips  761 ′,  76  so as to lie in the unlocked position and enable opening of the swivel joint  7 ′. 
     The manual actuator  78 ′ comprises a tapped rod  780 ′ screwed into a threaded sheath  79 ′ integrated to the first hinge knuckle  71 ′, and more specifically integrated to the first element  711 ′, projecting from its upper face. This threaded sheath  79 ′ extends between the two centering holes  712 ′. A groove  790 ′ is provided in the lower face of the second element  721 ′ in order to receive the threaded sheath  79 ′ in the closed position, and therefore not disturb bearing in the bearing plane. 
     The tapped rod extends along a direction parallel to the plane PA and orthogonal to the folding axis AP′. This tapped rod  780 ′ crosses the movable locking element  75 ′ and is provided with a gripping head  781 ′ disposed outside in order to allow grasping thereof to screw/unscrew the tapped rod  780 ′, and thus displace the movable locking element  75 ′. Thus, the locking mechanism  74 ′ is adapted to lock and block the swivel joint  7 ′ in the closed position. 
     As shown in  FIG.  22   , the two locking lips  761 ′,  762 ′ are radially set back with respect to the respective sleeves  710 ′,  720 ′, as highlighted in  FIG.  22    by the radial spacing ER′ associated to the second locking lip  762 ′. Thus, in the open position, the movable locking element  75 ′ could remain bearing on top the first sleeve  710 ′, as shown in  FIG.  22   , which enables this movable locking element  75 ′ not to turn about the tapped rod  780 ′ and therefore remain in alignment with the first locking lip  761 ′. Also, it is not necessary to align this movable locking element  75 ′ again during the opening/closing and locking/unlocking operations. 
     The following description relates to the motor drive of the scooter  1  (respectively  1 ′). 
     Indeed, in the example illustrated in the Figures, the scooter  1  (respectively  1 ′) is a motorized scooter and more specifically an electric scooter or a scooter with an electric drive. To this end, the scooter  1  (respectively  1 ′) comprises a motor  6  coupled to the rear wheel  3  via a transmission system  8  to drive it in rotation about the transverse axis AT, the rear wheel  3  thereby forming the drive wheel adapted to propel the scooter  1 . 
     The motor  6  is fixedly mounted, for example by bolting, on a plate  26  (respectively  26 ′) secured to the frame  2  (respectively  2 ′), and more specifically a plate  26  (respectively  26 ′) which is secured to a rear end of the first portion  21  (respectively  21 ′) of the frame  2  (respectively  2 ′). 
     This plate  26  (respectively  26 ′) extends in a vertical plane, orthogonal to the longitudinal axis AL of the scooter  1  (respectively  1 ′). This plate  26  (respectively  26 ′) has two opposite faces, namely:
         a front face directed forwards (front wheel  5  side) and from which the motor  6  projects; and   a rear face directed rearwards (rear wheel  3  side).       

     This plate  26  (respectively  26 ′) is asymmetric with respect to the midplane PM of the scooter  1  by having a lateral portion that protrudes laterally on the second lateral side (for reminder, the right side in the Figures) with respect to the midplane PM. Hence, this lateral portion protrudes on the second lateral side, beyond the frame  2  (respectively  2 ′) and even beyond the footboard  20  (respectively  20 ′), while being located at least partially beneath this same footboard  20  (respectively  20 ′). 
     Also, the motor  6  is fastened on this lateral portion and thus this motor  6  extends on the second lateral side, next to the rear end of the first portion  21  (respectively  21 ′) of the frame  2  (respectively  2 ′). Hence, the motor  6  extends at the rear of the footboard  20  (respectively  20 ′), and partially beneath the footboard  20  (respectively  20 ′), while protruding partially laterally to the right of the footboard  20  (respectively  20 ′). 
     In the case of the scooter  1 , and as shown in  FIGS.  1 ,  2 ,  3  and  5   , the footboard  20  features a rear step  27 , in protrusion, to enable an arrangement of the motor  6  partially beneath this rear step  27 . 
     In the case of the scooter  1 ′, and as shown in  FIGS.  15  and  16   , the footboard  20 ′ is flat, with no raised portion, at the level of its rear end, so that the motor  6  extends partially below the footboard  20 ′ and partially above the footboard  20 ′. 
     The motor  6  is equipped with a motor shaft (not illustrated) driven in rotation about a motor axis AM parallel to the longitudinal axis AL, where this motor shaft crosses the plate  26  (respectively  26 ′) to project beyond the rear face of the plate  26  (respectively  26 ′). 
     As regards the transmission between the motor shaft and the rear wheel  3 , the transmission system  8  comprises a gear system (not illustrated as it is hidden in the Figures by the casing  94 ) forming a bevel gear with a helical or spur toothing provided with a gear ring meshing with a gear pinion. 
     The gear pinion is secured to a pinion shaft extending coaxially with and in the continuation of the motor shaft, and this pinion shaft is rotatably coupled to the motor shaft via an elastomeric coupling  93  (shown in  FIGS.  5  and  6   ). Thus, the rotation of the motor shaft causes the rotation of the pinion shaft and therefore of the gear pinion about the motor axis AM parallel to the longitudinal axis AL. 
     Instead of the elastomeric coupling  93 , it could be considered to provide for other transmission means between the pinion shaft and the motor shaft, such as for example a constant-velocity joint, a transmission joint, a universal joint, or a preliminary gear system (in addition to the aforementioned gear system). 
     The transmission system  8  further comprises a rear transverse shaft extending along the transverse axis AT orthogonal to the motor axis AM. This rear transverse shaft has two opposite end portions, namely:
         a first end portion rotatably coupled to the gear ring, this gear ring being therefore carried by this first end portion;   a second end portion rotatably coupled to the rear wheel  3 , this rear wheel  3  being therefore carried by this second end portion.       

     Thus, a rotation of the motor shaft about the motor axis AM is convertible by this gear system into a rotation of the rear transverse shaft and of the rear wheel  3  about the transverse axis AT. Moreover, this gear system has a transmission ratio between the motor shaft at the input and the rear transverse shaft at the output which is fixed and comprised between 1:2 and 1:5. 
     The transmission system  8  further comprises a rear structure  10  fastened to the frame  2  and supporting the gear system, the rear transverse shaft and the rear wheel  3 . 
     It should also be noted that the rear wheel  3  has two opposite lateral faces  31 ,  32 , namely:
         a first lateral face  31  on the first lateral side (for reminder, the left side in the Figures) with respect to the midplane PM, and   a second lateral face  32  on the second lateral side (for reminder, the right side in the Figures) with respect to the midplane PM.       

     These lateral faces  31 ,  32  form sidewalls to the right and to the left of the rear wheel  31 , which border a circumferential tread  33 . 
     This rear structure  10  extends laterally only on the second lateral side with respect to the midplane PM, the same applying to the motor  6  and the lateral portion of the plate  26  (respectively  26 ′) which also extend on this second lateral side. This rear structure  10  extends partially facing the second lateral face  32  of the rear wheel  3 . 
     This rear structure  10  is fastened on the plate  26  (respectively  26 ′), and more specifically on the lateral portion, and projects from its rear face. Thus, the motor  6  and the rear structure  10  extend on either side of this plate  26  (respectively  26 ′). For example, this rear structure  10  is fastened by bolting, screwing or welding on the plate  26  (respectively  26 ′), this rear structure  10  could also be integral with the plate  26  (respectively  26 ′). 
     This rear structure  10  comprises two covers  11 ,  12 , respectively an inner cover  11  and an outer cover  12 , extending opposite one another and spaced apart from one another. The inner cover  11  extends inside along the rear wheel  3  and facing the second lateral face  32  of the rear wheel  3 , whereas the outer cover  12  extends outside, at a longer distance from the second lateral face  32  of the rear wheel  3  in comparison with the inner cover  11 . 
     These two covers  11 ,  12  extend parallel to the motor axis AM and are orthogonal to the transverse axis AT. These two covers  11 ,  12  extend from the rear face of the plate  26  (respectively  26 ′), on which they are fastened. 
     This rear structure  10  also comprises a tray extending between the two covers  11 ,  12 . This tray extends orthogonally to the motor axis AM and is located at a distance from the plate  26  (respectively  26 ′). Thus, this rear structure  10  has a «H»-like structure with the two covers  11 ,  12  parallel to one another and the tray joining the two covers  11 ,  12  together. This tray is fastened on the two covers  11 ,  12 , for example by screwing, bolting or welding, this tray could also be integral with the two covers  11 ,  12 . 
     This tray is provided with an orifice, called front orifice, crossed by the pinion shaft secured to the gear pinion. This front orifice supports at least one rolling bearing wherein the pinion shaft is rotatably mounted. Thus, the pinion shaft is carried by this tray and is guided in rotation in its front orifice. 
     The elastomeric coupling  93  is located between the tray and the plate  26  (respectively  26 ′), and extends between the two covers  11 ,  12 . 
     The two covers  11 ,  12  have respective orifices, called rear orifices, which are formed facing each other and both of which are crossed by the first end portion of the rear transverse shaft. These two rear orifices support respective rolling bearings wherein the first end portion of the rear transverse shaft is rotatably mounted. Thus, the rear transverse shaft is carried by these two covers  11 ,  12  and is guided in rotation in their rear orifices. 
     The two covers  11 ,  12  surround the gear pinion and the gear ring, and the first end portion of the rear transverse shaft extends mainly between the two covers  11 ,  12  of the rear structure  10 , whereas the second end portion of the rear transverse shaft protrudes from the rear structure  10 , and more specifically protrudes from the inner cover  11  to support the rear wheel  3  in a cantilevered manner. 
     The gear ring is rotatably secured to the rear transverse shaft by means of a key coupling the gear ring to the first end portion of the rear transverse shaft. 
     The rear wheel  3  extends at a fixed distance with respect to the inner cover  11  of the rear structure  10 , and this rear wheel  3  is carried in a cantilevered manner by the second end portion of the rear transverse shaft. It should be noted that the second lateral face  32  of the rear wheel  3  is covered by the rear structure  10  and by the gear system, whereas the first lateral face  31  of the rear wheel  3  is completely cleared and access-free, thanks to this cantilevered mounting. 
     The rear wheel  3  has a hub which is crossed by the second end portion and which is rotatably secured to this second end portion of the rear transverse shaft by means of a key coupling the hub to the second end portion of the rear transverse shaft. 
     Instead of the key coupling between the rear transverse shaft and the hub of the rear wheel, it could be considered to provide for other rotational coupling means, such as for example a flange coupling, a shear pin coupling, a jaw coupling, a collar coupling, . . . . 
     There is provided a casing  94  fastened on the rear structure  10  and comprising:
         a circular-shaped rear portion which wraps the gear ring over the entire circumference thereof, and   a front portion which extends the rear portion and which wraps the gear pinion up to the tray  13 .