Abstract:
A three wheeled vehicle ( 1 ) has a front section ( 10 ) having a front frame ( 105 ), a directionally controllable front wheel ( 101 ) and a steering column ( 104 ) with a handlebar ( 1040 ). A rear section ( 11 ) has a rear frame ( 107 ) and two rear wheels ( 102,103 ). The front section ( 10 ) of the vehicle is pivotable about a pivot axis ( 111 ) located intermediate the two rear wheels ( 102,103 ). The pivot axis ( 111 ) includes a pivot bar ( 401 ) and a pivot bar housing ( 402 ) in communication with a transmission mechanism having a first and second gear pairs ( 2 ) ( 3 ). The transmission mechanism is releasably connected to the steering column ( 104 ) and is capable of pivoting the first section ( 10 ) about the pivot axis ( 111 ) towards the center-of-curvature of a turn in accordance with the angle of the front wheel ( 101 ), thus providing greater stability for the vehicle ( 1 ) during a turn.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority under the Patent Cooperation Treaty of serial number PCT/IE2004/000064 having an International filing date of Apr. 5, 2004 and an official priority date of 2 May 2003. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
   Not applicable. 
   INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
   Not applicable. 
   REFERENCE TO A “MICROFICHE APPENDIX” 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Present Disclosure 
   This disclosure relates generally to three-wheeled vehicles with one front wheel and two rear wheels and more particularly to a three-wheeled vehicle having a tilting mechanism, which allows the three-wheeled vehicle to have an improved driving stability and maneuverability. 
   2. Description of Related Art Including Information Disclosed under 37 CFR 1.97 and 1.98 
   Three-wheeled vehicles or tricycles are known to be safer to drive and easier to operate in comparison with two-wheeled vehicles. However, a three-wheeled vehicle has poor stability on bends. When making a turn, the three-wheeled vehicle is laterally inclined towards the outer side of the turn&#39;s curve by a centrifugal force. This is because the centre of gravity of the vehicle is concentrated in the upper part of the vehicle and centrally between both sides of the vehicle. Thus there is a danger of the three-wheeled vehicle turning over if the turn is attempted at a higher speed. Conversely, a two-wheeled vehicle has far greater stability on bends as the rider of the vehicle is able to incline himself towards the centre of curvature of the turn, thus moving the centre of gravity of the vehicle closer to the centre of curvature, thereby counterpoising the centrifugal force more effectively. 
   There have been a number of attempts to equip a three-wheeled vehicle with tilting means in order to improve its stability on bends especially at higher speeds. Typical prior art is shown in U.S. Pat. No. 4,572,535 (Stewart et al) where tilting motion of the vehicle is achieved through body control of the driver; and U.S. Pat. No. 5,927,424 (Van Der Brink et al) where a sensor and a complex tilting structure are provided for stabilizing a vehicle on bends. The prior art devices, however, have not been successful as they are either too costly to produce or uncomfortable and overly complicated for the rider when in use. 
   BRIEF SUMMARY OF THE INVENTION 
   This disclosure teaches certain benefits in construction and use which give rise to the objectives described below. 
   It is the object of the present invention to seek to alleviate the above mentioned disadvantages associated with the prior art. 
   Accordingly, the present invention provides a vehicle with three wheels, the vehicle comprising a front section and a rear section and the vehicle being suitable for travelling with the front section leading and the front section being suitable to accommodate at least one rider, and wherein the front section comprises a front frame, a directionally controllable front wheel and an operating means for controlling said wheel, and the rear section comprises a rear frame and two rear wheels, the wheels being spaced apart from each other, the front section of the vehicle being pivotable with respect to the second section about a pivot axis, the pivot axis being located intermediate the two rear wheels and the pivot axis extending from the rear section towards the front section at an acute angle to the ground, said pivot axis being provided by a pivot means arranged between the front section and the rear section, the pivot means being in communication with a transmission mechanism, the transmission mechanism being releasably connected to the operating means and the transmission mechanism being capable of pivoting the first section about the pivot axis towards the centre of the curvature of the turn in accordance with the angle of turn of the front wheel, thus providing greater stability for the vehicle during a turn while the second section remains in an unchanged position. 
   Ideally, the pivot means comprise a pivot bar rotatable within a housing wherein the pivot bar is fixedly coupled with the front frame and the housing is fixedly coupled with the rear frame. Preferably, the pivot means are located at an angle to the ground so that the pivot axis extends towards the front wheel and meets a point on the front wheel at which the front wheel touches the ground. 
   Ideally, the transmission mechanism comprises a connecting shaft extending between the operating means and the rear frame, a first gear pair, said first gear pair arranged between the operating means and the front end of the connecting shaft and a second gear pair, said second gear pair arranged between the rear end of connecting shaft and the rear frame. 
   Preferably, the operating means comprise a substantially vertical steering column, the steering column being turnable about its longitudinal axis by a handlebar and the steering column being connected to the front wheel so that turning of the steering column results in the front wheel turning in the same direction by a corresponding angle. 
   Preferably, the connecting shaft is mounted on the front frame by means of at least one support member in which support member the connecting shaft is rotatable about its longitudinal axis. 
   Ideally, the connecting shaft comprises a front portion and a rear portion. 
   Advantageously, the first gear pair comprises a front gear rigidly coupled with the steering column and a front pinion rigidly coupled with the front portion of the connecting shaft; and the second gear pair comprises a rear gear rigidly coupled with the rear frame and a rear pinion rigidly coupled with the rear portion of the connecting shaft. 
   Advantageously, the rear gear comprises an arcuate cogged surface, the arcuate cogged surface having a central axis, the central axis coinciding with the pivot axis of the vehicle. 
   Preferably, a release mechanism is provided in the transmission mechanism, the release mechanism being operable to disconnect the transmission mechanism from the operating means thereby preventing the first section from being pivoted about the pivot axis towards the centre of the curvature of the turn in accordance with the angle of turn of the front wheel, the release mechanism being further operable to re-establish the connection between the transmission means and the operating means. The release mechanism is further capable of locking the first section of the vehicle in an upright position. The release mechanism is further capable of providing an intermediate mode of operation for the vehicle in which the at least one rider can use his body weight for pivoting the first section about the pivot axis. 
   Conveniently, a biasing means is provided between the first section and the second section, the biasing means being operable to assist returning of the front section of the vehicle into an upright position. Preferably, the biasing means is a spring mechanism comprising at least one spring extending between the driver&#39;s seat and the rear frame. 
   Advantageously, the vehicle may be driven by an engine which operates and drives the rear wheels and the vehicle&#39;s braking system can be controllable by flexible control cables or flexible pneumatic cables. 
   The invention will now be described more particularly with reference to the accompanying drawings, which show, by way of example only, two embodiments of a three-wheeled tilting vehicle according to the invention having an engine which operates and drives the rear wheels, although not limited to the use of such type of engine in the present invention. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
     Illustrated in the accompanying drawing(s) is at least one of the best mode embodiments of the present invention In such drawing(s): 
       FIG. 1  is a schematic perspective view of a first embodiment of a three-wheeled vehicle in accordance with the invention; 
       FIG. 2  is a schematic side cross sectional elevation thereof; 
       FIG. 3  is a schematic front elevation thereof; 
       FIG. 4  is an enlarged view  FIG. 2 ; 
       FIG. 5  is an enlarged view of area A of  FIG. 4  showing the front gear arrangement of the vehicle; 
       FIG. 6  is a schematic plan view of the front gear arrangement in accordance with  FIG. 2 ; 
       FIG. 7  is an enlarged view of area B of  FIG. 4  showing the rear gear arrangement according to  FIG. 2 ; 
       FIG. 8  is a schematic rear view of the rear gear arrangement of the first embodiment of the vehicle of the invention showing three positions of a rear pinion and of a front frame; 
       FIG. 9  is an enlarged view of area C of  FIG. 4  showing a locking/unlocking mechanism of the vehicle; 
       FIG. 10  is an exploded view of a part of  FIG. 2  showing a horizontal part of the frame of the vehicle, the front and rear gear arrangements and the locking/unlocking mechanism in an unlocked mode; 
       FIG. 11  is an enlarged view of part of  FIG. 2  showing a spring mechanism of the vehicle; 
       FIG. 12  is a schematic rear view of the first embodiment of the vehicle showing the spring mechanism when the vehicle is turning left; 
       FIG. 13  is a schematic rear view of the vehicle of  FIG. 12  showing the spring mechanism in an upright position; 
       FIG. 14  is a schematic rear view of the vehicle of  FIG. 12  showing the spring mechanism when the vehicle is turning right; 
       FIG. 15  is a schematic side cross sectional elevation of a second embodiment of the vehicle in accordance with the invention; 
       FIG. 16  is an enlarged portion of  FIG. 15  showing the locking/unlocking mechanism in an unlocked mode; 
       FIG. 17  is a cross section of the locking/unlocking mechanism of  FIG. 16  taken along line B-B; 
       FIG. 18  shows the locking/unlocking mechanism of  FIG. 16  in an intermediate mode; 
       FIG. 19  shows the locking/unlocking mechanism of  FIG. 16  in a locked mode; and 
       FIG. 20  is a cross section of the locking/unlocking mechanism of  FIG. 19  as taken along line C-C. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The above described drawing figures illustrate the described apparatus and its method of use in at least one of its preferred, best mode embodiment, which is further defined in detail in the following description. Those having ordinary skill in the art may be able to make alterations and modifications what is described herein without departing from its spirit and scope. Therefore, it must be understood that what is illustrated is set forth only for the purposes of example and that it should not be taken as a limitation in the scope of the present apparatus and method of use. 
   Referring initially to  FIGS. 1 to 4  of the drawings, a first embodiment of the three-wheeled tilting vehicle of the invention is indicated generally by reference numeral  1 . The three wheeled tilting vehicle  1  comprises two main sections, a front section  10  and a rear section  11 . The front section  10  is tiltable towards the centre of curvature of a turn or bend in the road or surface on which the vehicle is being driven and the rear section  11 , which is not tiltable and which remains in an upright position whether the vehicle is performing a turn or moving in a straight direction. 
   The front section  10  comprises a front frame, generally indicated by reference numeral  105  and a front wheel  101 , connected to each other by connection means  106 . In this preferred embodiment the connection means  106  is in the form of a connecting fork. The fork  106  has a rigid connection to a steering column  104 . The steering column has a handlebar  1040  and is in communication with a front gear arrangement  2 . A connecting shaft, generally indicated by reference numeral  120 , extends between the steering column  104  and the rear section  11 . The connecting shaft  120  comprises a front portion  209  and a rear portion  309 . The vehicle  1  also includes a driver&#39;s seat  115 , a footrest  117  and a spring mechanism, generally indicated by reference numeral  5 . 
   The front frame  105  includes a generally vertical tubular portion  1051  within which the steering column  104  is rotatably mounted and a generally horizontal tubular portion  1050  within which the connecting shaft  120  is rotatably mounted. The steering column  104  is rotatable about its longitudinal axis  1043  and is supported in the vertical portion  1051  by a lower bearing  1042  and an upper bearing  1041 . The connecting shaft  120  is supported in the horizontal part  1050  by a bearing  1021  at its front portion  209  and by a bearing  1022  at its rear portion  309  (shown in  FIG. 7 ). The bearing  1021  is retained in position by a bearing holder  1023  and the bearing  1022  is retained in position by a bearing holder  1024 . 
   The rear section  11  comprises a rear frame  107 , two rear wheels  102  and  103  set apart from each other and connected by a shaft  109  which is perpendicular to the median plane A-A of the vehicle  1  (shown in  FIG. 3 ), an engine (not shown in the drawings), a rear gear arrangement, indicated generally by reference numeral  3 , a pivot bar  401  attached rigidly to a rear vertical portion  1052  of the front frame  105  by means of an extension  405  and a collar  406 ; and a pivot bar housing  402  rigidly attached to the rear frame  107  by means of fixing members  409 . 
   The longitudinal axis  111  of the pivot bar  401  is located within the median plane A-A of the vehicle  1  at an angle to the ground so that an imaginary extension  112  of the longitudinal axis  111  meets the point  113  where the front wheel  101  touches the ground. The pivot bar  401  and the pivot bar housing  402  have to be strong enough to avoid flexing in any direction, as they bear most of the weight of the front section  10  of the vehicle  1 . Also, the pivot bar  401  and the pivot bar housing  402  have to have a sufficient ground clearance  114 , which may vary for light weight vehicles and heavy weight vehicles. The pivot bar  401  is rotatable within the pivot bar housing  402 . Since the front frame  105  and the pivot bar  401  are connected rigidly to each other, the front frame  105  rotates together with the pivot bar  401 . The pivot bar  401  is prevented from axial movement within the pivot bar housing  402  by means of a retaining nut  410 . 
   The rear section  11  of the vehicle  1  remains in an upright position regardless of whether the vehicle  1  is moving in a straight ahead, linear direction or turning, whereas the front section  10  together with the driver is tiltable laterally about the longitudinal axis  111  of the pivot bar  401  when the vehicle  1  is performing a turn. 
   Tilting of the front section  10  is achieved by transferring rotary motion of the steering column  104  through the front gear arrangement  2  and through the connecting shaft  120  to the rear gear arrangement  3  and to the pivot bar  401 . The handlebar  1040  of the steering column  104  enables the driver to control the steering column  104 . When the steering column  104  is rotated, the fork  106  rotates together with the steering column  104 , thereby turning the front wheel  101  coupled with the fork  106 . 
   Referring now to  FIG. 5  and  FIG. 6  of the drawings, the front gear arrangement  2  comprises a gear  201  rigidly attached to the steering column  104 . The gear  201  has a shape of a disk or a part of a disc with cogs  2010  on a part of a circumference of one of its faces  2011 . Preferably, the gear  201  is located between the steering column  104  and the fork  106 . The gear  201  is engaged with a front pinion  202 , preferably of a conical shape, attached to the front portion  209  of the connecting shaft  120 . 
   The functioning of the vehicle in use for performing a turn will now be described. When the vehicle  1  is performing a turn, the gear  201  rotates together with the steering column  104 . Since the gear  201  is engaged with the front pinion  202 , the gear  201  transfers the rotary motion of the steering column  104  to the front pinion  202 . The front pinion  202  rotates the connecting shaft  120  thereby transferring the rotary motion to the rear gear arrangement  3 . Referring now to  FIG. 7  and  FIG. 8  of the drawings, the rear gear arrangement  3  comprises a rear pinion  302 , preferably of a conical shape, attached to the rear portion  309  of the connecting shaft  120  and engaged with a gear  301 , attached rigidly to the rear frame  107  of the vehicle and having a shape of a part of a disc, preferably a segment of a disc, the longitudinal axis (not shown) of which coincides with the longitudinal axis  111  of the pivot bar  401 . The gear  301  has cogs  3010  on its circular surface  3011 . The amount of cogs for different types of vehicles may vary and depends on the degree of tilt required in accordance with the weight of the vehicle. Smaller tilting angle is required for heavy weight vehicles. The rear pinion  302  rotates together with the connecting shaft  120  and, being engaged with the gear  301  travels around the circular surface  3011  of the rear gear  301  in one direction or in the opposite direction, in accordance with the direction of rotation of the steering column  104 , thereby enabling the front section  10  to tilt around the longitudinal axis  111  of the pivot bar  401 , while the rear section  11  of the vehicle  1  remains in an upright position. 
   In  FIG. 8  of the drawings, a schematic rear elevation view of the rear gear arrangement  3  illustrates three positions of the rear pinion  302  together with the rear vertical portion  1053  of the frame  105 . Position  20  is the middle position of the second rear pinion  302  on the rear gear  301  when the front section  10  vehicle is in an upright position. Position  21  is the end position of the rear pinion  302  on the gear  301  when the vehicle is turning right. Position  22  is the end position of the rear pinion  302  on the gear  301  when the vehicle is turning left. 
   The vehicle of the invention can also be provided with a locking/unlocking mechanism  6 , one embodiment of which is illustrated in  FIG. 9  and  FIG. 10  of the drawings. The locking/unlocking mechanism  6  allows the front section  10  to be locked in an upright position by disengaging the front portion  209  of the connecting shaft  120  from the rear portion  309  of the connecting shaft  120  and by securing the front section  10  to the rear section  11  and thereby preventing the rear pinion  302  from moving around the gear  301 . This mode of operation of the vehicle is a “locked” mode. The locking/unlocking mechanism  6  is also operable so that it can be released to permit the rear pinion  302  to move around the gear  301 , thereby permitting tilting of the front section  10 , in accordance with user&#39;s requirements. This mode of operation of the vehicle is a “controllably tilting” (“unlocked”) mode. 
   A way of transition between the “controllably tilting” and “locked” modes of operation of the vehicle will now be described below. 
   A locking bar  601  is located within the horizontal part  1050  of the front frame  105  and is slideable inside an aperture  1025  of the bearing holder  1023  and inside an aperture  1026  of the bearing holder  1024 . The locking bar  601  has a number of cogs  6010 . A sliding tube  602  is mounted on the outer surface of the connecting shaft  120  so that a part of the front portion  209  and a part of the rear portion  309  of the connecting shaft are surrounded by the tube  602 . The sliding tube  602  has a number of cogs  6020  on its outer surface, each cog  6020  being in the form of a circular ledge on the circular surface  6022  of the sliding tube  602 . A slot  6021  in the wall of the sliding tube  602  is engagable with a centring pin  606  of the rear portion  309  of the connecting shaft  120 . The slot  6021  is engaged with the centring pin  606  when the tilting mechanism is unlocked and rigidly links the front portion  209  and the rear portion  309  of the connecting shaft  120 . A cog wheel  603  is located within the horizontal part  1051  of the front frame  105  between the locking bar  601  and the sliding tube  602 . The cog wheel  603  has cogs  6030  engaged with the cogs  6010  of the locking bar  601  and with the cogs  6020  of the sliding tube  602 . The cogwheel  603  has a lever  604  located outside the front frame  105 . When the cog wheel  603  is rotated by rotating the lever  604  in direction I ( FIG. 9 ) the cog wheel  603  pushes the sliding tube  602  forward, away from the rear portion  309  of the connecting shaft  120  disengaging the slot  6021  from the centring pin  606 , thereby disconnecting the front portion  209  from the rear portion  309  of the connecting shaft  120 , leaving the front portion  209  rotatable by the front pinion  202 ; and at same time the cog wheel  603  pushes the locking bar  601  towards the rear frame  107  until the locking bar  601  enters a locking aperture  1071  in a protruding part  1070  of the rear frame  107 , thereby preventing the rear pinion  302  from moving around the gear  301 . 
   When the cog wheel  603  is rotated by rotating the lever  604  in direction II ( FIG. 10 ) the cog wheel  603  pushes the sliding tube  602  back towards the rear portion  309  of the connecting shaft  120  so that the slot  6021  engages the centring pin  606 , thereby connecting the front portion  209  with the rear portion  309  of the connecting shaft  120 . The front wheel  101  has to be oriented straight forward to ensure that the slot  6021  engages the centring pin  606 ; and at same time the cog wheel  603  pushes the locking bar  601  away from the rear frame  107  until locking bar  601  comes out from the locking aperture  1071 , thereby permitting the rear pinion  302  to travel around the rear gear  301 . 
   For additional driving safety and comfort, a spring mechanism  5 , illustrated in  FIG. 11  of the drawings, is provided in the vehicle of the invention. The spring  502  provides a quicker return of the front section  10  of the vehicle  1  together with driver into upright position on completion of a turn. The spring  502  also keeps the front section  10  in the upright position when the vehicle  1  is not occupied and resists tilting caused by vibrations. 
   Preferably, one end  5020  of the spring  502  is fixed by means of a connecting member  5022  to a seat support bar  504  and another end  5021  of the spring  502  is fixed by means of a connecting member  5023  the rear frame  107  of the vehicle. The seat support bar  504  is attached to the front frame  105  at its one end and to the driver seat  115  at its other end and has to be strong enough and rigid to avoid flexing in any direction. 
   When the front section  10  of the vehicle together with the driver is tilted by the tilting mechanism during a turn in a manner described above, the spring  502  stretches accordingly between the connecting members  5022  and  5023  towards the side of the tilt as illustrated on  FIG. 12  to  FIG. 14 . Thus, the spring  502  does not allow the front section  10  of the vehicle  1  together with the driver tilt too low. On completion of the turn, the driver turns the steering column  104  by turning the steering handle  1040  back into its initial position as before the turn, thereby bringing the front wheel  101  in line with the road. At the same time, the centrifugal influence on the vehicle terminates and the front section  10  together with the driver is brought back into upright position as the tilting mechanism works astern. The spring  502  then compresses, thereby helping the front section  10  together with the driver overcome the gravity and facilitating the return of the front section  10  together with the driver into upright position on completion of the turn. Several parallel springs can be employed in the mechanism. 
   The ratio between the front gear arrangement  2  and the rear gear arrangement  3  determines the angle of tilt in relation to the angle of turn of the front wheel  101 . For a lightweight vehicle the preferred ratio between the front gear arrangement  2  and the rear gear arrangement  3  is such that two degrees of turn of the front wheel  101  provide one degree of tilt. A heavy weight vehicle can have a smaller tilting angle than that of a lightweight vehicle at the same speed and at the same angle of turn of the front wheel. 
   The vehicle&#39;s braking system is controllable by flexible control cables. Flexible pneumatic cables may also be used to control the vehicle&#39;s braking system. 
   The vehicle can be driven by various types of engines, e.g. a battery engine or a petrol engine, or by foot pedals. 
   Shown in  FIGS. 15 to 20 , is a second embodiment of the tilting vehicle of the invention which is indicated generally by reference numeral  7 . The vehicle  7  differs from the vehicle  1  in that a locking/unlocking mechanism  8  is provided instead of the locking mechanism  6 . Functions of the locking/unlocking mechanism  8  are generally similar to the functions of the locking mechanism  6  of the vehicle  1 , except that the locking/unlocking mechanism  8  is further operable to provide an intermediate free tilting (“bicycle”) mode of operation for the vehicle  7 . 
   In the intermediate mode of operation, the front portion  708  of the connecting shaft  70  is disengaged from the rear portion  709  of the connecting shaft  70 , whereas the rear pinion  732  is movable about the rear gear  731 . This mode of operation of the vehicle  7  enables the rider to tilt the front section  710  of the vehicle  7  using his body weight. This means that in this mode the driver can incline his body, and, accordingly, the front section  710  of the vehicle  7 , during a turn towards the centre of the turn curve in a manner similar to that of a driver of a bicycle. This mode of operation can be useful for travelling at low speeds, when it is not necessary for the front section  710  of the vehicle  7  to use the maximum possible tilting angle during a turn, as it would be the case for travelling at higher speeds. 
   The locking/unlocking mechanism  8  comprises a sliding tube  802  which encompasses the front portion  708  of the connecting shaft  70  with its front end  802   a , and the rear portion  709  of the connecting shaft  70  with its rear end  802   b . The sliding tube  802  is slidably movable along the exterior surfaces of the front portion  708  and the rear portion  709  of the connecting shaft  70 . 
   The sliding tube  802  is engageable with the front portion  708  by means of a first spline joint, which comprises grooves  812  in the interior surface of the sliding tube  802  and corresponding keys  712  on the exterior surface of the front portion  708  of the connecting shaft  70 . The sliding tube  802  is engageable with the rear portion  709  by means of a second spline joint, which comprises grooves  813  in the interior surface of the sliding tube  802  and corresponding keys  713  on the exterior surface of the rear portion  709  of the connecting shaft  70 . 
   The locking/unlocking mechanism  8  further comprises a rack tube  803  having a rack  807  projecting radially along the outer surface of the rack tube. The rack tube  803  is mounted intermediate the first spline joint and the second spline joint on the outer surface of the sliding tube  802 . Axial movement of the rack tube  803  on the sliding tube  802  is prevented by stop rings  805 . A rack guide  809  (best shown in  FIG. 17 ) projects from an upper face  705   a  of the front frame  705 . The rack guide  809  is provided for the rack  807  to prevent rotation of the rack tube  803  on the sliding tube  802  and to maintain correct orientation of the rack on the sliding tube  802 . 
   The rack  807  is meshable with a cog wheel  830 . The cog wheel  830  is rotatably mounted on the frame  705  and is located beneath the rack  807 . The cog wheel  830  is provided with lever  840 . 
   The locking/unlocking mechanism  8  further comprises a disk  806  fixed on the outer surface of the sliding tube  802  at the rear end  802   b  of the sliding tube  802 . The disk  806  is provided with a radial slot  806   a  (best shown in  FIG. 20 ) formed transversely through the body of the disk. The slot  806   a  is engageable with a stop  706 , which projects upwardly from the upper face  705   a  of the front frame  705 . The disk  806  is fixed on the sliding tube  802  so that the slot  806   a  and the stop  706  are in register when the front frame  705  is in an upright position. 
   In the “controllably tiltable” mode of operation (see  FIG. 16 ), the grooves  812  and keys  712  are engaged in the first spline joint. The grooves  813  and the keys  813  are partially engaged in the second spline joint, so that a sufficient part of the length of each groove  813  remains unoccupied. The slot  806   a  and the stop  706  are disengaged. In this mode, the front section  710  is controllably tiltable around the longitudinal axis  711  of the pivot bar  741  by means of transition of a rotary motion from a steering column  74  through a front gear arrangement  72  to a rear gear arrangement  73  as described in detail with reference to the first embodiment of the vehicle. 
   A way of transition between the “controllably tiltable”, “free tilting” and “locked” modes of operation of the vehicle  7  will now be described. Referring initially to  FIG. 16 , when the cog wheel  830  is rotated by rotating the lever  840  in the direction of arrow III, the rack  807  together with the sliding tube  802  are pushed towards the rear of the vehicle  7 , and the grooves  812  disengage from the keys  712 . This mode is the “free tilting” (“bicycle”) mode of operation and is best illustrated in  FIG. 18 . In this mode, a rotary motion transferred from the steering column  104  via the front gear arrangement  72  causes the front portion  708  of the connecting shaft  70  to rotate freely within the sliding tube  802  without transferring the rotary motion to the rear gear arrangement  74 . The rear pinion  732  however is movable about the gear  731 , and the driver can tilt the front section  710  of the vehicle  7  using his body weight as described earlier. Upright position of the front section  710  is maintained by a spring mechanism as described with reference to the first embodiment of the vehicle. 
   By rotating the lever  840  in the direction of arrow IV of  FIG. 18 , the rack  807  together with the sliding tube  802  are pushed further towards the rear section  711  of the vehicle, and the slot  806   a  of the disk  806  engages with the stop  706 . This mode is the “locked” mode of operation of the vehicle in which the front section  710  remains in an upright position regardless whether the vehicle is turning or moving straight. This mode is best illustrated in  FIG. 19 . 
   The enablements described in detail above are considered novel over the prior art of record and are considered critical to the operation of at least one aspect of the apparatus and its method of use and to the achievement of the above described objectives. The words used in this specification to describe the instant embodiments are to be understood not only in the sense of their commonly defined meanings, but to include by special definition in this specification: structure, material or acts beyond the scope of the commonly defined meanings. Thus if an element can be understood in the context of this specification as including more than one meaning, then its use must be understood as being generic to all possible meanings supported by the specification and by the word or words describing the element. 
   The definitions of the words or drawing elements described herein are meant to include not only the combination of elements which are literally set forth, but all equivalent structure, material or acts for performing substantially the same function in substantially the same way to obtain substantially the same result. In this sense it is therefore contemplated that an equivalent substitution of two or more elements may be made for any one of the elements described and its various embodiments or that a single element may be substituted for two or more elements in a claim. 
   Changes from the claimed subject matter as viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalents within the scope intended and its various embodiments. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements. This disclosure is thus meant to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, what can be obviously substituted, and also what incorporates the essential ideas. 
   The scope of this description is to be interpreted only in conjunction with the appended claims and it is made clear, here, that each named inventor believes that the claimed subject matter is what is intended to be patented.