Abstract:
The invention concerns an articulated vehicle comprising a rear frame ( 1 ) and a front frame ( 2 ) linked by an articulation ( 3 ) associated with the device ( 30, 6 ) for removably locking controlled by a pendular member ( 4, 62 ) mounted oscillating on the front frame ( 2 ) between a median position for unlocking the articulation and a spaced apart position for locking the articulation, at least when the vehicle is stopped. The vehicle comprises means ( 5 ) for controlling the unlocking of the articulation, at least during start-up, including an auxiliary platform ( 5 ) integral in rotation with the rear frame ( 1 ) and comprising, at least, two footrests ( 51 ) arranged at substantially the same level relative to the ground, on either side of the axis (x′x) of the articulation ( 3 ) and constituting each, on the side towards which the front frame ( 2 ) is inclined, a support for said front frame ( 2 ) to be set upright by the vehicle driver, the pendular member ( 4, 62 ) returning to its median position for unlocking the articulation.

Description:
BACKGROUND OF THE INVENTION 
   The object of this invention is an articulated vehicle, and specially, a three-wheeled one fitted with a stabilization device. 
   DESCRIPTION OF THE RELATED ART 
   It is well known that two standards of terrestrial vehicles exist: the first type is represented by vehicles with stationary stability, such as three-wheeled or four-wheeled vehicles; the other type is represented by two-wheel vehicles, which become stabilized only when driven above a minimal speed, and which the driver is able to lean in curves, so as to keep the center of gravity in the plane of the apparent vertical, due to combined gravitational and centrifugal forces. 
   The usual four-wheel vehicles are wider and less workable in city traffic than the two-wheeled ones; as a set off, two-wheeled vehicles can barely be provided with a protection body against collisions or weather inclemency. Indeed, the driver should always be able to set foot on the ground, to the side where the vehicle leans at standstill, and again so as to raise the vehicle back vertically at starting. 
   For several years, a solution to those problems has been sought, such as an intermediate vehicle fitted with two rear wheels in order to provide stability at standstill, but articulated so as to behave while traveling like a two-wheeled dynamically stabilized vehicle, leaning into curves so as to compensate for the centrifugal force. 
   Typically, such a vehicle rests on three wheels, and is constituted of two chassis, pivoted upon each other through a longitudinal axis: respectively a backward chassis, resting on two spaced wheels, and a frontward chassis, resting upon the steering front wheel, and supporting a protection body fitted with at least one seat for the driver. 
   While traveling, the link is disengaged so the driver is enabled to incline the front chassis with the body, in order to keep the longitudinal mid plane of said body in the alignment of the apparent vertical, thus allowing the vehicle to behave similarly to a motorcycle. On the contrary, when the speed is reduced below a certain value, the link is locked and the vehicle becomes stable due to the rear axle. 
   Such vehicles are the object of former patents by same applicant, upon which French patents FR-A-2600612, FR-A-2639016 and FR-A-2688465. 
   Generally speaking, the link is constituted of two parts assembled upon each other and locked in rotation, respectively, from both chassis, and wherein the locking of the link is provided by a pendulum type device, subjected to combined gravitational and centrifugal forces, making both parts of said link integral when deviated to either side of mid-plane of inclined liable. Particularly, at standstill, the chassis carrying the pendulum device inclines soon as the speed is reduced below a certain value, and this inclination of mid-plane creates a swerving of said pendulum, thus operating the locking of the link and consequently ensuring the stabilization of the vehicle. 
   However, this locking system is removable, since the link should be unlocked so as to allow the vehicle to rise back vertically, while pendulum returns into mid-plane of chassis. 
   Particularly, at standstill, the vehicle is slightly inclined, and should be raised while starting so as to unlock link. 
   Similarly, a bicycle or motorcycle rider raises its vehicle when starting it, so as to find himself immediately in a balanced position and travel straight forwards, and therefore he has one foot set on the ground meanwhile he leans on the steering handlebars. 
   This simple act becomes impossible to perpetuate out of an articulated vehicle fitted with a close body, preventing the driver to set the feet on the ground at starting, unless there is an appropriately built-in aperture. Now if the vehicle does not stand vertically at starting, it will turn sideways towards the side upon which it is leaning, before the speed becomes sufficient to provide dynamical stabilization. 
   SUMMARY OF THE INVENTION 
   The aim of the present invention is to solve this problem by operating the unlocking of the link at starting of the vehicle, even when driving inside a totally enclosed body. 
   The invention generally relates to an articulated vehicle traveling longitudinally on the ground, constituted by two chassis connected to each other by an articulation pivoting around a longitudinal axis running parallel to the traveling direction, each of said chassis having its mid-plane running through the articulation axis, respectively a first chassis resting on the ground through a first rolling device centered on a first mid-plane perpendicular to the ground, and a second chassis resting on the ground through a second rolling device, said second device being allowed to be steered relative to the traveling direction, and centered on a second medium plane, liable to be inclined by the ground by rotation around the articulation axis. 
   This articulation may be locked by a device constituted of two parts which are integral in rotation, respectively from the first and the second chassis, and by a removable locking system constituted of a pendulum type device operating the locking of the rotation of said two parts, assembled oscillating on the second chassis, on both sides of the second mid-plane between a medium unlocking position, in relation to which the second mid-plane is directed according to the direction of the pendulum, as well as a spaced unlocking position, a least at standstill of vehicle, through inclination of second chassis in relation to the direction of pendulum. 
   According to the invention, the vehicle comprises a system controlling the unlocking of the articulation, at least at starting of vehicle, constituted of an auxiliary platform, locked in rotation with the first chassis, the said platform including at least two footboards located substantially at the same level above the ground, on both sides of the articulation axis, each of said footboard providing a step on either side towards which the second chassis is leaning, allowing the driver to rise up the vehicle, with the return of pendulum into median unlocking position. 
   In the first embodiment, the locking device comprises a set of articulated bars assembled in a deformable parallelogram system, comprising two spaced bars substantially parallel to the ground, respectively a first bar locked in rotation to the first chassis, and a second bar hinged around a longitudinal axis located on second chassis, in its mid-plane, and two vertical bars located parallel on each side of said mid-plane. In this embodiment, the controlling pendulum device comprises a stiff beam hinged onto the first chassis, transverse located between the two vertical bars, and linked with means to ensure integral in rotation of at least one of the vertical bars with said beam, by traveling it sideways of second mid-plane. 
   Advantageously, the first bar of the articulated system is constituted with two brackets rigidly tighten to the first articulation, located on each side of longitudinal axis of said articulation, while the second bar is constituted with an equalizer, linked to the central part of second chassis, around a longitudinal axis located in the mid-plane of said second chassis, as a column rigidly tighten to the second part of the articulation, bearing at least one seat for the driver. 
   Preferably, the deformable parallelogram is of the same type as described in Applicant&#39;s former French patent 2688465, where the locking system is constituted with two carriages upon which the pendulum cross beam is assembled, so as to slide parallel to itself, while the carriages freely travel along the vertical bars of the parallelogram as long as the center of gravity of said cross beam remains centered within the mid-plane of the second chassis, and where the cross beam causes the locking of at least one of the two carriages on its corresponding vertical bar, operating the locking in rotation of said vertical bar with cross beam, as soon as said cross beam is deviated on either side of the second mid-plane. 
   Advantageously, the auxiliary platform may be simply constituted with two footboards, respectively assembled on each vertical bar of deformable parallelogram. 
   In a different type of embodiment, the locking device of the articulation is constituted with a first collar-type part integral in rotation with the first chassis, mounted around the articulation axle of both chassis, and with a second bracket-type part integral in rotation with the second chassis, mounted transverse to the articulation axle inside the collar, and with a pendulum type control device constituted with an oscillating crutch hinged on one end of said bracket, around an axis running parallel to the articulation axle, located in the mid-plane of the second chassis. The crutch oscillates inside the collar and rests on its lower end against said collar, in case the mid-plane inclines beyond the apparent vertical, thus locking the inclination by buttressing the crutch against the collar. 
   In both embodiments, the pendulum device controls the locking of the articulation by moving away from the mid-plane of second chassis, and this may happen while traveling, in case the driver does not incline the body of the vehicle correctly, by holding the mid-plane of second chassis coincident with the direction of the pendulum, that is the result of combined gravitational and centrifugal forces. 
   As described in former patents of same Applicant, this system prevents driving errors such as a lack of inclination given to the vehicle by an inexperienced driver from inside the body. This applies also to slow speed traveling in busy road traffic situations. 
   By contrast, while the vehicle travels at a speed that is sufficient to ensure dynamical stabilization naturally, it may be preferable to avoid any risk of abnormal locking, due for instance to a wrong gesture of driver, or to a major unevenness of the road. 
   In a preferred embodiment, the vehicle comprises a removable bolting system of the pendulum device in its median unlocked position for road traveling, with a control of the bolting device above a certain speed value. 
   Thus, above a certain speed value which may be chosen either by the manufacturer or possibly by the driver, the locking system is not effective any further, the body of the vehicle is uninhibited, and its driving becomes absolutely similar to usual two-wheeled vehicle driving. 
   Such a bolting system may be constituted with a bolt that is displaceable between a spaced position allowing the release of the pendulum device so as to lock the said pendulum in its median position, with a speed detector, and with a control device for the displacement of the bolt from released to engaged position, operated by the speed detector when the speed exceeds a certain value. 
   Advantageously, the control device for the displacement of the bolt from released to engaged position may be operated electrically with the means of impulses transmitted by the speed detector pitched in t 1  time intervals inversely proportional to the speed of the vehicle, through a temporized relay fitted with an impulse reception circuit, a supply circuit for the control device during a t 2  time from the impulse, a primary closing circuit for the supply circuit with a given T delay time after each impulse, and a secondary closing circuit for the supply circuit during a given To time after the impulse, thus closing the supply circuit continuously when T 1  time between two impulses is shorter than T delay time of primary closing circuit, and continuously opening in the opposite circumstance. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     However, the invention will be substantially understood with the following descriptions of specific embodiments, as non-restrictive examples illustrated on appended drawings. 
       FIG. 1  depicts a partial perspective view of a first embodiment of the vehicle, articulated according to the invention. 
       FIG. 2  shows in perspective view a second embodiment of articulated vehicle. 
       FIG. 3  is a diagrammatic longitudinal view of a pendulum type locking device such as used in embodiment shown in  FIG. 2 . 
       FIG. 4  is a front view of pendulum bolting device. 
       FIG. 5  schematically shows the functioning of the pendulum and a bolting device. 
       FIG. 6  is an electrical supply scheme for the bolting device. 
       FIGS. 7   a ,  7   b ,  7   c  are diagrams depicting the functioning of the electrical bolting device. 
       FIG. 8  schematically shows a hydraulic bolting control system. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  depicts a partial perspective view of the vehicle, articulated according to the invention, comprising two chassis, respectively a rear chassis  1  and a front chassis  2 , hinged on top of each other around a longitudinal axis x′x, by means of articulation  3  constituted of a central tube  11  and a tubular sheath  21 , assembled in rotation by the means of non-depicted bearings. 
   Central tube  11  is integral with rear chassis  1 , and bears on its rear end two brackets  12   a  and  12   b , both resting on non-depicted rear axle which rests on the ground by the means of two spaced wheels, which rotates around a transverse axis located orthogonal to longitudinal axis x′x of central tube  11 . Tubular sheath  21  is integral with front chassis  2 , which rests on a front steering wheel  22 , mounted on steering column  23  and directed by the means of handlebars or steering wheel  26 . Furthermore, front chassis  2  bears at least one seat for the driver. The whole unit is enclosed in a non-depicted protection body. 
   Rear chassis  1  is centered on a longitudinal mid plane P 1  crossing articulation axis x′x and orthogonal to the ground, while front chassis  2  is centered on a longitudinal mid plane P 2  which may incline on either side in relation to first mid plane P 1 , by rotating around articulation axis x′x. However, the inclination of front chassis  2  in relation to rear chassis  1  may be prevented by locking device  30  of articulation  3 , operated by pendulum device  4 . 
   In the embodiment shown on  FIG. 1 , the locking device is of the type of a deformable parallelogram, the design of which has been described in details in former French patent 2688465 of same Applicant. 
   Generally speaking, such a system comprises a set of articulated bars constituting a deformable parallelogram assembly, fitted with two spaced bars located substantially parallel to the ground, respectively a lower bar  31  and an upper bar  32 , both articulated around respectively lower axles  35  and upper axles  35 ′, on two vertical bars  33   a  and  33   b  located on either sides and parallel to mid plane P 2  of the front chassis  2 . 
   In the embodiment according to the present invention, as depicted on  FIG. 1 , the lower bar is constituted with two brackets  31   a  and  31   b , assembled on central axle  11  of rear chassis  1 , and located on either side of said chassis  1 , while upper bar  32  is hinged around an axle  34 , the said axle  34  running parallel to articulation axis x′x, on a central column  24  tighten by its lower end to tubular sheath  21 , and consequently integral in rotation with front chassis  2 . For instance, the central column  24  may advantageously bear at least one seat for the driver. 
   It is now obvious that an inclination of mid plane P 2  of front chassis  2  in relation to the ground causes a deformation of parallelogram  30 , with an inclination of both vertical bars  33   a  and  33   b , which are parallel to mid plane P 2 , while upper bar  32  remains parallel to lower bar  31 , the said lower bar being kept parallel to the ground by the two wheels  13 . 
   Generally speaking, the articulation locking system comprises two parts, respectively integral to each of the two articulated chassis, that is to say a first part constituted with two bars  31  and  32 , integral in rotation with rear chassis  1 , and a second part, constituted with the two vertical bars  33   a  and  33   b , integral in rotation with front chassis  2 . The articulation may be locked by the means of integrating the two parts, in order to prevent the deformation of parallelogram  30 . 
   For this purpose, a pendulum type device will be used, constituted with a transverse beam  4  assembled to two self locking carriages  41   a ,  41   b , which detailed description is the object of formerly quoted French patent 2688465 of same Applicant. 
   When the vehicle stands in a position where both mid planes are coincident, the transverse beam  4  provides a parallel beam to bars  31  and  32 , the said bars being parallel to the ground, and consequently substantially horizontal. 
   As mentioned in French patent 2688465, transverse beam  4  is hung with front chassis  2  by the means of two rods  42   a  and  42   b , the said rods being hinged respectively by their lower end  43  with said transversal beam  4 , and by their upper end  43 ′ with central column  24  of front chassis  2 . 
   However, in the embodiment of French patent 2688465, the two suspension rods of pendulum beam converge to a point located substantially higher above the upper longitudinal articulation axis, constituting an instantaneous rotation center of pendulum, while in the present embodiment, the two suspension rods  42   a  and  42   b  are mounted crosswise, with their lower articulation axis  43  and upper articulation axis  43 ′ respectively located on either side of mid plane P 2  of second chassis  2 . It actually appears that such a device fitted with crosswise mounted rods operates in a rather sensitive and fast way, especially when rods  42  are inclined at a 45° angle from the vertical while vehicle stands in balanced position. 
   As substantially described in French patent 2688465, hung beam  4  behaves as a pendulum, detecting any variations of inclination of the body of vehicle, carried by front chassis  2 , in relation to the direction of the apparent vertical. In case of deviation towards either side, this pendulum type beam locks the bars of parallelogram  30  integral, thus preventing its deformation, and consequently locking articulation  3 . 
   For this purpose, beam  4  is assembled to side bars  33  by the means of two carriages  41   a  and  41   b , mounted sliding on beam  4 , by the means of two pairs of bearings, respectively external bearings  44  and internal bearings  45 , while each side bar  33   a  and  33   b  of deformable parallelogram  30  is guided with a slight clearance between the corresponding bearings of carriages  41   a  and  41   b.    
   Consequently, both carriages  41   a  and  41   b  may move freely along side bars  33   a  and  33   b , as long as said side bars remain perpendicular to pendulum beam  4 . 
   By contrast, if a side bar  33  inclines in relation to beam  4 , it bears against two opposite bearings, respectively external bearings  44  and internal bearings  45 , being driven by friction if the inclination continues. 
   However, external upper bearings  44   a  and  44   b , as well as internal lower bearings  45   a  and  45   b  are fitted with free rollers mounted so as to roll only in the corresponding direction aiming to decrease the angle included between upper end of side bar  33  and central part of transversal beam  4 , so as to lift mid plane P 2 , and tending to bring gravitational center of beam  4  back into said mid plane. 
   Consequently, when traveling on the road, the driver may incline the vehicle into the curves, while maintaining mid plane P 2  of front chassis  2  within the plane of the apparent vertical, due to combined gravitational and centrifugal forces. The gravitational center of transversal beam  4 , which is suspended like a pendulum to central column  24 , remains in mid plane P 2  of front chassis P 2 . Transversal beam  4  rotates with central column  24  and remains orthogonal to mid plane P 2  and to both side bars  33   a  and  33   b  of deformable parallelogram  30 , while carriages  41   a  and  41   b  slide in free motion along said side bars, carried by transversal beam  4 . 
   Consequently, the vehicle behaves on the road similarly to a two-wheel dynamically stabilized vehicle. 
   By contrast, when the vehicle stops, its speed decreases beyond a value allowing dynamical stabilization. Front chassis  2  tends to incline in relation to the ground, causing its mid plane P 2  to swerve either side of mid plane P 1  of rear chassis  1 , which remains perpendicular to the ground. 
   The two side bars  33   a  and  33   b  of parallelogram  30 , which are parallel to second mid plane P 2 , tend to incline in relation to transversal beam  4 , which is subjected exclusively to gravitational force, thus remaining substantially horizontal. For example, if the body carried by front chassis  2  inclines towards the right side when looking forwards, the angle generated by side bar  33   b  of parallelogram  30  with the central part of transversal beam  4  tends to open above 90°, and side bar  33   b  than relies upon upper external bearing  44   b  and upon lower internal bearing  45   b  of carriage  3 ,  41   b , strictly sliding against the sides of bar  33   b , but prevented to roll by the means of the free wheels allowing the motion of the carriage exclusively towards the lower direction in relation to the corresponding side bar. Consequently, carriage  41   b  is locked in relation to side bar  33   b , while said side bar is locked in relation to transversal beam  4 . The parallelogram  30  becomes non-deformable while side bars  33   a  and  33   b , parallel to second mid-plane P 2 , become integral in rotation with brackets  31   a  and  31   b  assembled with rear chassis  1 , the said brackets remaining parallel to the ground. Thus the articulation  3  is locked and front chassis  2  remains slightly inclined in relation to the ground. 
   At standstill, this stability allows the vehicle to be equipped with a protection body for the driver, carried by front chassis  2 . 
   However, as mentioned above, front chassis  2  remains slightly inclined in relation to the ground at standstill, so as to ensure the locking of articulation  3 . Consequently, if vehicle starts in this position, it will slightly turn towards the side it is leant on before allowing the driver to find sufficient dynamical stability so as to raise the second mid plane P 2  coincident with first mid plane P 1  of rear chassis. 
   This disadvantage does not exist with a conventional two-wheeled vehicle, since the rider, by stepping foot on the ground, raises it in order to start straight forwards, but it is impossible to do so from inside an enclosed body. 
   The present invention solves this problem, by the means of an auxiliary platform  5  constituting a virtual ground, on which the driver applies so as to raise up the front chassis of the vehicle at starting, by unlocking the articulation. 
   In the example depicted on  FIG. 1 , this platform is constituted of two footboards  51  assembled horizontally on the lower ends of the two side bars  33   a  and  33   b  of parallelogram  30 . 
   When the driver sits inside the vehicle at standstill, he may shut the body and set a foot on footboard  51  located to the side the body is leant on, so as to raise it by applying towards the opposite direction, for instance upon the steering handlebar  26 . Thus, the mid plane P 2  of front chassis  2  moves back to the vertical of center of gravity of horizontal beam  4 , which becomes free, the articulation is then unlocked, allowing the vehicle to travel straight forwards. As soon as the speed becomes sufficient, the driver may provide dynamical stabilization in a similar way to two-wheeled vehicles. In order to avoid any interference on the deformable parallelogram, it is preferable, on the road, for the driver to let his/her feet rest on another set of footboards  25 , mounted on tubular sheath  21  of front chassis  2 , and rotating with said front chassis around longitudinal articulation axis x′x. 
   The articulation locking device may operate differently, as shown in embodiment depicted on  FIG. 2 . 
   As mentioned above, the vehicle is constituted with a rear chassis  1  and a front chassis  2 , hinged with an articulation  3  fitted with a removable locking device. 
   By the means of a suspension spring  14 , the rear chassis  1  rests on a rear axle  13  fitted with two spaced wheels, the spacing of which allowing sufficient stability at standstill, being however kept narrow enough so as to avoid an oversized caliber of the vehicle. 
   The whole unit of front chassis  2 , bearing steering front wheel  22  and at least one seat  24  for the driver, is enclosed by an close body which has not been depicted on the figure, so as to preserve the legibility of drawing. 
   In this embodiment, the articulation  3 , shown in a detailed description on  FIG. 3 , comprises a central axle  21 ′, integral with front chassis  2 , engaged in the tubular sheath  11 ′ integral with rear chassis  1 , and may be locked by the means of removable device  6 . 
   This locking device  6 , shown in a detailed description on  FIGS. 3 and 4 , is mainly constituted with a casing  61  assembled with tubular sheath  11  of rear chassis  1 , and bounded by a cylindrical collar providing the location of pendulum  62 , suspended around longitudinal axle  63  and bracket  64 , said bracket being integral in rotation with central axle  21  of front chassis  2 , and perpendicular to said chassis. 
   Central axle  21 ′ crosses pendulum  62  through an aperture with a large clearance, allowing an oscillating motion of said pendulum towards either side of median plane P 2  of front chassis  2 , wherein suspension axle  63  of said pendulum  62  is located. The lower of said pendulum is constituted of a weight or bob  65 , fitted with two swellings  66   a  and  66   b , slightly spaced from internal side of collar of casing  61  by narrow clearance j. 
   Consequently, when median plane P 2  of front chassis  2  inclines in relation to the direction of apparent vertical specified by pendulum  62 , the swelling  66  located on the inclined side applies against collar  61 , since the shape of swellings  66  is designed so as to ensure the best contact possible between both parts. 
     FIG. 5  shows the operating forces when the body of the vehicle, integral with front chassis  2 , tends to incline for instance towards the right side, and suspension axle  63  of pendulum carried by bracket  64  integral in rotation with central axle  21 ′ tends to rotate around axis x′ x in the direction of arrow F. 
   The center of gravity of pendulum  62  moves then towards the right in relation to mid-plane P 2 , and corresponding swelling  66   a  of bob  65  applies against casing collar  61  in point A. 
   A force F now appears between point A and center B of articulation axle  63  of pendulum  62 , compensated by the reaction R of casing, and running through center O of collar  61 . 
   If admitted that f&lt;φ.F, φ being the friction coefficient of swelling  66  upon internal surface of casing collar  61 , the crutch created by pendulum  62  will buttress and consequently lock the rotation, since the two parts  11 ′ and  21 ′ become integral in rotation. 
   As mentioned above, the vehicle is fitted with an auxiliary platform  5  allowing the vehicle to be raised up at starting, by unlocking the articulation so as to travel straight forwards. 
   In the embodiment depicted in  FIG. 2 , auxiliary platform  5  is mounted on its rear end upon tubular sheath  11 ′ and comprises two footboards  52 , located on either side of central axle  21 ′ of front chassis  2 , and resting on said chassis, the said footboards resting at the front end on a bearing  53 , around which axle  21 ′ rotates in case of inclination of front chassis  2 . 
   As mentioned above, the driver may, after having shut the body, apply on either footboard  52  of the side the front chassis  2  is leant on, so as to raise it up in order to unlock the link, the center of gravity of bob  65  thus moving back to mid-plane P 2  of front chassis  2 . When vehicle is traveling on the road, the driver may set both feet upon footboard  25 ′, integral with front chassis  2 . 
   However, as mentioned above, the locking of the inclination of the body is only necessary at a very low speed or at zero speed. If the driver is skilled enough to ensure dynamical stability by inclining the body according to the plane of apparent vertical detected by the direction of pendulum, it is preferable to avoid all risk of inopportune locking caused by an erroneous handling of driver, or by a major unevenness of the road. 
   This explains the presence, in the locking system, of a control command operating the bolting of pendulum above a certain speed value. Above this speed value, equivalent to the value wherefrom dynamical stabilization can be ensured, the articulation locking command is bolted, the body may incline since freed, and the driving of the vehicle becomes similar to usual two-wheeled vehicle driving. 
   Such a bolting device  7  is shown schematically in  FIG. 5 , which depicts a bolt  71  mounted on the end of a bracket  72 , said bracket rotating around axle  70 , assembled so as to slide into slot  67  located in median plane of bob  65 . 
   A return spring  73  operates on bracket  72 , maintaining bolt  71  in a spaced position allowing the functioning of pendulum and the locking of the link, if necessary. 
   However, an electromagnet  74  operated by control device  8 , fitted with a speed-indicator, allows, above a certain speed-value, to slide bolt  71  into slot  67 , and consequently to bolt pendulum  62  in its balanced position, so as to free the link. Below this speed value, electromagnet  74  does not operate, and bolt  71 , being recalled by spring  73 , frees pendulum  62 . 
     FIG. 6  shows, as an example, the scheme of an electric control device for bolt  71 . 
   The speedometer comprises a wheel  75 , linked for instance to either wheel of vehicle or pinion whose rotating speed is proportional with the speed of vehicle. 
   The wheel  75  is fitted with a metal outlined guide mark  76 , whose round passing near a sensor  77  provides an impulse into incoming circuit U of temporized relay  8  comprising functions usually called B or C. 
   Generally speaking, this temporized relay  8  is fitted with incoming circuit U, receives the impulses from sensor  77 , and comprises two connected circuits C 1  and C 2 , constituting the operating circuit, and a supply circuit Z supplying electromagnet  74 , or at least a relay for this electromagnet. 
   As depicted in  FIGS. 7   a ,  7   b ,  7   c , supply circuit Z is not supplied as long as time interval t 1  between two impulses u 1 , u 2  exceeds temporization t, and is supplied continuously as soon as t 1  is below t. One impulse U 1  causes a short closing of circuit C 1 , but only after delay t and immediate closing of circuit C 2  during a t 0  time, slightly inferior to t. 
   At starting, the speed is low, and t 1  interval between two impulses is substantially greater than t. The impulse is ineffective, as the continuity C 1 +C 2  is not ensured, ( FIG. 7   a ), thus link  3  is locked. While speed increases, the impulses draw closer. As soon as time t 1  between two successive impulses equals delay t ( FIG. 7   b ), circuits C 1  and C 2  are closed simultaneously, causing the supplying of supply circuit Z during a time t 2  superior to t, and consequently causing the continuous closing of this circuit, as long as t 1  remains inferior to t ( FIG. 7   c ). 
   Electromagnet  74  is then supplied, causing level  72  to swing around axle  70 , integral, so as pendulum suspension axle  63 , with plate  64 , integral in rotation with front chassis  2 . Bolt  71  then slides into slot  67 , so pendulum  62  thus bolt in its median position is unable to cause any locking of front chassis  2  with rear chassis  1 . The vehicle may then be driven in the same way as a two-wheeled engine. 
   Conversely, if the speed decreases, pendulum  62  is unbolted when t 1  exceeds t, and consequently the link is locked, so as to ensure the stabilization of vehicle. 
     FIG. 8  schematically shows another example of a bolting and unbolting control system for pendulum  62 . 
   As mentioned above, pendulum  62  may be locked in its median position, by the means of a bolt  71 , constituted for instance with a roller sliding into slot  67  of pendulum  62 . This bolt  71  is mounted on end of level  72 , rotating around axle  70 , and held in spaced position by the means of return spring  73 . 
   Conversely, a pusher  78 , operating against the action of return spring  73 , allows level  72  to rotate so as to slide bolt  71  into slot  67 . 
   This pusher  78  is mounted on piston  81  of jack  80  fitted with a pressure chamber, supplied by a lift and force pump  82 , constituted by a cylindrical body, wherein a piston  83  is sliding, and operated by the means of wheel  75 , whose rotating speed is in relation to the traveling speed of vehicle. 
   The back-and forth motion of piston  83  is therefore operated by a pair of permanent magnets mounted in opposition, that is to say with the similar poles facing each other, pole  84  located on wheel  75  and pole  85  located at the end of a rod connected to piston  83 . A spring  86  brings piston  83  at rest. 
   Piston  83  receives an impulse each time magnet  84  draws near to magnet  85 , and propels, towards jack  80  and through check valve  86 , a certain amount of fluid so as to move plunger  81  of jack  80  from position V 1  to a position V 2 , and consequently, to move bolt  71  from position T 1  to a position T 2 . Similar successive actions tend to cause the sliding of bolt  71  into slot  47 . However, the jack is fitted with a leakage control aperture  87 , the damping action of which, together with recall of spring  73 , makes the motion of bolt  71  dependent on the frequency of motion of pump  82 , that is to say subordinate to the speed of vehicle. A valve  88  restrains the pressure in the circuits, and brings the fluid back into an out-of-pressure reservoir  89 , when the speed increases. 
   This device operates as follows:
         At standstill, spring  73  forces fluid back from jack  80  to reservoir  89  through leakage control aperture  87 , and bolt  71  slides out of slot  67 . Bob  65  is freed so the locking operates in case of inclination of vehicle;   At start, when first coincidence occurs between the positions of magnets  84  and  85 , piston  83  is pushed and sends a certain amount of fluid to jack  80 ; the fluid removes piston  81  from position V 1  to position V 2 , and removes bolt  71  from position T 1  to position T 2 . Yet this position does not provide the bolting of the weight. The bolting occurs after one or several similar happenings, in relation to the frequency of the repetition of this happening, and in relation to the value of controlled leakage as well as to the specificity of the springs which determine from which impulse frequency on, that is actually from which traveling speed on, the leakage will be compensated by the supply of jack  80 , so as to restrain bolt  71  inside slot  67 . Pendulum  62  becomes then inhibited and chassis  2  may incline freely so as to ensure dynamical stability.       

   Of course, such a bolting system, electrically or hydraulically operated, may be fitted to a deformable parallelogram locking device such as depicted on  FIG. 1 , with bolt  71  sliding into a slot located in the center of transverse beam  4 . 
   As a matter of fact, the invention is not limited to the details of the above mentioned embodiments, since other variations may as well be sought, within the scope of the claims. For instance, it is suitable to design a three-wheeled vehicle with a rear stabilization axle and a front directing wheel, although the said directing wheel might as well be replaced by two spaced wheels carried by the two bars of the deformable parallelogram, said parallelogram being located in the front of vehicle, as mentioned in above quoted French patent 2688465 of same Applicant. 
   The reference numerals inserted after the technical features in the claims are used to allow a better understanding of the claims and not to restrict the scope thereof.