Abstract:
A seat post for a bicycle includes a tubular element that supports a seat of a bicycle and grasping element of a portion of a frame of the seat. The grasping elements are adapted to be coupled to the tubular element and to be selectively activated/deactivated to prevent/allow a translation movement of the seat with respect to the tubular element along a predetermined direction. The grasping elements include abutment elements and can be coupled with the tubular element in operative coupling configurations in which the abutment elements define translation limit positions of the seat with respect to the tubular element in predetermined directions. Abutment elements may be defined on a jaw in asymmetric positions with respect to each other.

Description:
CROSS REFERENCE TO RELATED APPLICATION(S)  
       [0001]     This application is a continuation of PCT/IT2005/000736, filed Dec. 14, 2005, which is incorporated by reference as if fully set forth. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention relates to a seat post for a bicycle. In particular, the invention relates to an adjustable seat post for a racing bicycle.  
       BACKGROUND  
       [0003]     Throughout the present description and the subsequent claims, the expression “seat post for a bicycle” is used to indicate that component of a bicycle that supports the seat on the bicycle frame. In particular, “adjustable seat post” is used to indicate a seat post that allows the position of the seat to be adjusted with respect to the bicycle pedals.  
         [0004]     In the field of bicycles, above all racing bicycles, the use of adjustable seat posts is widespread. The ideal position of the seat is that which allows the most advanced leg of the cyclist to bend to 90° when the pedals are aligned horizontally.  
         [0005]     Of course, the ideal position of the seat depends upon the physiology of the cyclist, in particular the length of his legs. Such an ideal position can be obtained by moving the seat vertically and with respect to a vertical reference plane passing through the axis of the bottom bracket of the bicycle.  
         [0006]     Most of the known seat posts comprise a tubular element adapted to be telescopically inserted, for at least part of the longitudinal extension thereof, in the appropriate tubular seat provided in the bicycle frame and a pair of jaws adapted to grasp the rectilinear portions of the rods of the seat frame to associate the seat with the tubular element.  
         [0007]     The height adjustment of the seat is obtained by sliding the tubular element up and down in the appropriate tubular seat of the frame; in particular, the stable positioning of the seat at the desired height is obtained by clamping appropriate clamping members provided on the tubular seat of the bicycle frame onto the tubular element.  
         [0008]     The adjustment of the seat with respect to the vertical reference plane passing through the axis of the bottom bracket of the bicycle, on the other hand, is obtained by sliding the rectilinear portion of the rods of the frame of the seat with respect to the jaws; in particular, the stable positioning of the seat at the desired distance from the vertical reference plane passing through the axis of the bottom bracket of the bicycle is obtained by clamping the aforementioned jaws on the rods.  
         [0009]     In conventional seat posts of the type described above, the positioning limits of the seat with respect to the vertical reference plane passing through the axis of the bottom bracket of the bicycle are defined by the edges of the jaws, against which the bending points of the rods that define the rectilinear portions grasped by the jaws abut, respectively, in the two directions of translation.  
         [0010]     Generally, in order to be able to obtain optimal positioning of the seat for cyclists of all sizes, seats and seat posts are sold in different sizes.  
         [0011]     Throughout the present description, the expression “horizontal direction,” when referred to the adjustment of the position of the seat, is used to indicate the adjustment of the position of the seat with respect to the vertical reference plane passing through the axis of the bottom bracket of the bicycle, such adjustment being carried out in a predetermined direction that can be perfectly horizontal (i.e. perfectly perpendicular to the aforementioned reference plane) or, preferably, inclined downwards with respect to the horizontal direction by a certain angle, so that the seat always maintains an angular position inclined downwards.  
       SUMMARY  
       [0012]     The present invention therefore relates to a seat post for a bicycle comprising a tubular element adapted to support a seat of a bicycle, and grasping means of a frame portion of the seat. The grasping means is adapted to be coupled to the tubular element and to be selectively activated/deactivated to prevent/allow a translation movement of the seat with respect to the tubular element along a predetermined direction. The grasping means comprises at least one first abutment element and is adapted to be coupled to the tubular element in a first operative coupling configuration in which the at least one first abutment element defines a first translation limit position of the seat with respect to the tubular element in a first way of the predetermined direction. The grasping means comprises at least one second abutment element that defines at least one second translation limit position of the seat with respect to the tubular element in the first way of the predetermined direction. The at least one second translation limit position is translated with respect to the first translation limit position along the first way of the predetermined direction. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING(S)  
       [0013]     Further characteristics and advantages of the present invention shall become clearer from the following detailed description of some preferred embodiments thereof, made as a non-limiting example with reference to the attached drawings. In such drawings:  
         [0014]      FIG. 1  is a schematic side view of a bicycle that comprises a seat post in accordance with the present invention;  
         [0015]      FIG. 2  is a schematic view of a first embodiment of the seat post of the present invention coupled with a seat;  
         [0016]      FIG. 3  is an exploded view of the seat post of  FIG. 2 ;  
         [0017]      FIG. 4  is a top view of the seat post of  FIG. 2  in an assembled configuration without the seat;  
         [0018]      FIG. 5  is a bottom view of a component of the seat post of  FIG. 2 ;  
         [0019]      FIG. 6   a  is a section in plane II of  FIG. 4  of the seat post of  FIG. 2  in a first operative angular positioning configuration;  
         [0020]      FIG. 6   b  is a section in plane II of  FIG. 4  of the seat post of  FIG. 2  in a second operative angular positioning configuration;  
         [0021]      FIG. 7   a  schematically shows the seat post of  FIG. 2  in a first operative coupling configuration to the seat and in a first end stroke position in a first way of the horizontal direction;  
         [0022]      FIG. 7   b  schematically shows the seat post of  FIG. 2  in a second operative coupling configuration to the seat and in a second end stroke position in the aforementioned first way of the horizontal direction;  
         [0023]      FIG. 8   a  schematically shows the seat post of  FIG. 2  in the first operative coupling configuration and in a first end stroke position in a second way of the horizontal direction opposite the aforementioned first way;  
         [0024]      FIG. 8   b  schematically shows the seat post of  FIG. 2  in the second operative coupling configuration and in a second end stroke position in the aforementioned second way;  
         [0025]      FIG. 9   a  schematically shows the seat post of  FIG. 2  in the operative coupling configuration of  FIG. 8   a  and in the operative angular positioning configuration of  FIG. 6   a;    
         [0026]      FIG. 9   b  schematically shows the seat post of  FIG. 2  in the operative coupling configuration of  FIG. 8   b  and in the operative angular positioning configuration of  FIG. 6   a;    
         [0027]      FIG. 10   a  is a schematic view of a second embodiment of the seat post of the present invention in a first operative coupling configuration to the seat and in a first end stroke position in the aforementioned second way of the horizontal direction;  
         [0028]      FIG. 10   b  is a schematic view of the seat post of  FIG. 10   a  in a second operative coupling configuration to the seat and in a second end stroke position in the aforementioned second way of the horizontal direction;  
         [0029]      FIG. 11   a  is a schematic view of a third embodiment of the seat post of the present invention in a first operative coupling configuration to the seat and in a first end stroke position in the aforementioned second way of the horizontal direction;  
         [0030]      FIG. 11   b  is a schematic view of the seat post of  FIG. 11   a  in a second operative coupling configuration to the seat and in a second end stroke position in the aforementioned second way of the horizontal direction;  
         [0031]      FIG. 12   a  is a schematic view of a fourth embodiment of the seat post of the present invention in a first operative coupling configuration to the seat and in a first end stroke position in the aforementioned second way of the horizontal direction;  
         [0032]      FIG. 12   b  is a schematic view of the seat post of  FIG. 12   a  in a second operative coupling configuration to the seat and in a second end stroke position in the aforementioned second way of the horizontal direction;  
         [0033]      FIG. 13  is a longitudinal section of a fifth embodiment of the seat post of the present invention;  
         [0034]      FIG. 14  is a longitudinal section of a sixth embodiment of the seat post of the present invention;  
         [0035]      FIG. 15  is a longitudinal section of an embodiment of a first component of the seat post of  FIG. 2 ; and  
         [0036]      FIG. 16  is a schematic top view of an alternative embodiment of a second component of the seat post of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)  
       [0037]     Introduction  
         [0038]     Advantageously, the seat post described herein allows obtaining extreme positioning limits of the seat in the horizontal direction wider than those that can be obtained with conventional seat posts, without needing to replace any components and at the same time keeping a large grasping zone of the seat so as to ensure high reliability of the grasp. Indeed, with conventional seat posts, once the seat has been selected, the widening of the adjustment stroke in the horizontal direction beyond the translation limits defined by a specific seat post can only be obtained by replacing the seat post with another one having shorter grasping members in the horizontal translation direction of the seat, with a consequent reduction of the grasping zone of the seat. Differently and advantageously, the seat post allows the adjustment stroke to be widened in at least one way of the horizontal direction by simply changing the operative coupling configuration of the grasping means. In other words, the seat post of the present invention makes it possible to pass from a first operative coupling configuration that ensures a first adjustment stroke in at least one first way of the horizontal direction to a different operative coupling configuration that ensures an additional adjustment stroke in the aforementioned way.  
         [0039]     In a first embodiment of the seat post of the present invention, the at least one first abutment element can be removably associated with the at least one second abutment element. For example, the at least one first abutment element can be associated by a joint with the at least one second abutment element.  
         [0040]     Advantageously, in such an embodiment the first abutment element can be removed from the grasping means so that they provide for the abutment a second abutment element positioned at a distance from the tubular element shorter than that of the first abutment element, thus obtaining an additional adjustment stroke. More preferably, the second element can also be removed from the grasping means so that they provide for the abutment a third abutment element positioned at a distance from the tubular element shorter than that of the second abutment element, thus obtaining a further additional adjustment stroke. Obviously, it is possible to foresee further steps of removing abutment elements to obtain further additional adjustment strokes.  
         [0041]     In a preferred embodiment of the seat post, the at least one first abutment element is made integrally with the at least one second abutment element and the at least one second abutment element defines the at least one second translation limit position of the seat in at least one second operative coupling configuration of the grasping means with the tubular element. Advantageously, in such an embodiment the passage from the first operative coupling configuration to a different operative coupling configuration is carried out by simply moving the first abutment element to a different position so as to provide for a different abutment element into the abutment position, the different abutment element ensuring an additional adjustment stroke with respect to that which can be obtained through the first abutment element. Obviously, it is possible to foresee further steps of moving the abutment elements to obtain further additional adjustment strokes.  
         [0042]     In the aforementioned preferred embodiment of the seat post, preferably, when the grasping means are in the first operative coupling configuration, the at least one second abutment element defines a translation limit position of the seat with respect to the tubular element in a second way of the predetermined direction opposite the first way. Advantageously, in this case the translation limits in the two opposite ways of the horizontal direction are defined by the same abutment element. It is therefore possible to obtain additional adjustment strokes both in a first way of the horizontal direction and in the opposite way by simply moving the second abutment element by 180°. More advantageously, the use of the same abutment element to obtain the additional adjustment strokes in the two opposite ways of the horizontal direction allows the grasping zone to be extended at the side opposite where such an abutment element is located, for example, as shall be described more clearly hereafter, by providing an asymmetrical shape with respect to a coupling portion of the grasping means with the tubular element. In this way an excellent compromise is achieved between reduction of the weight of the component (requirement always sought after in the field of racing bicycles) and reliability of the grasp of the seat.  
         [0043]     Preferably, the grasping means comprise a coupling portion with the tubular element, and at least one grasping portion to the seat portion extending cantilevered asymmetrically from, and substantially perpendicular to, the coupling portion, in which the at least one first abutment element is defined by a first end surface of the at least one grasping portion.  
         [0044]     In a first example of an embodiment, the at least one grasping portion extends cantilevered only from one side of the coupling portion and the at least one second abutment element is defined on the coupling portion on the opposite side to that from which the at least one grasping portion extends.  
         [0045]     In a preferred example of an embodiment, the at least one grasping portion extends cantilevered asymmetrically from opposite sides of the coupling portion and the at least one second abutment element is defined by at least one second end surface of the at least one grasping portion arranged on the opposite side to the first end surface with respect to the coupling portion.  
         [0046]     Preferably, the at least one second abutment surface is arranged, with respect to the coupling portion, at a shorter distance away than the distance between the first abutment surface and the coupling portion.  
         [0047]     Advantageously, in both of the examples of embodiments discussed above, the asymmetry of the grasping portion allows the aforementioned additional adjustment stroke to be obtained in both of the ways of the horizontal direction (provided suitable positioning of the second abutment surface at the side at which one wishes to obtain the additional adjustment stroke). More advantageously, in the example embodiment in which the grasping portion extends cantilevered asymmetrically from opposite sides of the coupling portion, it is possible to obtain a widening of the grasping portion at the side opposite the one where the second abutment element is situated and a uniform distribution of the stress due to the weight of the cyclist on the two opposite sides of the coupling portion, thus avoiding the occurrence of a bending stress with respect to the tubular element. This allows the components of the seat post to be made from a lighter material.  
         [0048]     In the preferred embodiment of the seat post, the grasping means comprise a pair of jaws that can be coupled together through clamping means, the at least one first and at least one second abutment element being defined in an upper jaw of the pair of jaws. Advantageously, the clamping means can be activated to clamp the jaws on the rods of the seat frame and simultaneously locking them in the desired position along the horizontal adjustment direction.  
         [0049]     Preferably, the jaws of the pair of jaws can be rotatably associated with the tubular element with respect to an axis perpendicular to a plane of longitudinal symmetry of the frame of the bicycle. Advantageously, the clamping means can also be activated to lock the jaws on the rods of the frame in a plurality of predetermined angular positions with respect to the tubular element.  
         [0050]     Preferably, the grasping means can be positioned in both of the configurations defining the translation limits of the seat in at least two of the predetermined angular positions, more preferably in all of the aforementioned predetermined angular positions. In such a way the angular adjustment of the seat does not influence its adjustment in the horizontal direction.  
         [0051]     Preferably, the coupling portion of the grasping means is defined in a central body portion of both of the jaws of the pair of jaws.  
         [0052]     More preferably, the central body portion comprises a cylindrical surface portion extending along a respective longitudinal axis.  
         [0053]     Even more preferably, the at least one grasping portion comprises a first pair of grasping surfaces of the seat portion, the grasping surfaces of the first pair of grasping surfaces extending parallel to each other at opposite free ends of the central body portion of a first jaw of the pair of jaws, and a second pair of grasping surfaces of the seat portion, the grasping surfaces of the second pair of grasping surfaces extending parallel to each other at opposite free ends of the central body portion of a second jaw of the pair of jaws.  
         [0054]     Advantageously, in the jaws of the seat post, the coupling zone with the tubular element and the grasping zone to the rods of the seat frame are functionally distinct from each other, and can thus be shaped and sized independently of each other so that each one carries out its function optimally.  
         [0055]     Preferably, the first and at least one second abutment surface are defined in an upper jaw of the pair of jaws (in particular, in the jaw that in use acts as an upper jaw), at opposite front end surfaces of the grasping surfaces.  
         [0056]     In an embodiment of the seat post, the jaws of the pair of jaws are specular, or mirror images. This allows the two jaws to be freely exchanged or be rotated in a mirror-like manner with respect to the planes of symmetry of the respective coupling portions.  
         [0057]     However, Applicant has observed that the lower jaw and the upper jaw actually carry out at least in part different functions. The upper jaw, indeed, cooperating with the lower jaw , ensures that the rods of the seat frame are gripped and defines the translation limit positions in the horizontal direction. The lower jaw, on the other hand, as well as contributing to the grasping of the rods of the seat frame, directly receives the weight of the cyclist and transmits it to the tubular element. Applicant has therefore discovered that the jaws of the pair of jaws of the seat post can be of a different shape and be positioned independently from each other, so that each one carries out its intended function optimally.  
         [0058]     In the seat post of the present invention, therefore, the first and at least one second abutment surface are preferably defined in the first jaw of the pair of jaws and the grasping surfaces of the first pair of grasping surfaces extend asymmetrically with respect to the longitudinal axis for a first predetermined length portion. Advantageously, the asymmetry of such a jaw ensures, as well as obtaining the additional adjustment strokes discussed above, a good extension and distribution of the grasping surface of the rods of the seat frame.  
         [0059]     More preferably, in the seat post of the present invention, a jaw (adapted to act in operation as an upper jaw) has a grasping zone that is asymmetric with respect to the plane of symmetry of the respective coupling portion and the other jaw (adapted to act in operation as a lower jaw) has a grasping zone to the rods of the seat frame larger than that of the upper jaw. As a matter of fact, it is advantageous to make the lower jaw stronger and with a contact zone with the rods of the seat frame larger than the upper jaw; the lower jaw must, indeed, bear the weight of the cyclist and transmit it to the frame of the bicycle.  
         [0060]     In a first preferred embodiment of the seat post, the grasping surfaces of the second pair of grasping surfaces extend on the second jaw symmetrically with respect to the longitudinal axis for a second portion of length greater than the first portion of predetermined length.  
         [0061]     In a second preferred embodiment of the seat post, the grasping surfaces of the second pair of grasping surfaces extend on the second jaw asymmetrically with respect to the longitudinal axis for a second portion of length greater than the first portion of predetermined length.  
         [0062]     In all of the embodiments discussed above, the jaws can be configured so that the first and at least one second abutment element are defined by curved surfaces having a concavity facing outwards. Such a provision allows a further additional adjustment stroke to be obtained, in addition to the one obtained with the asymmetry of the upper jaw.  
         [0063]     In all of the embodiments discussed above, the tubular element preferably comprises a first rectilinear body portion adapted to be, at least in part, telescopically inserted in a tubular housing seat formed in the frame of the bicycle and a second body portion that is inclined with respect to the first body portion, the second body portion comprising a coupling free end to the grasping means.  
         [0064]     Preferably, the second body portion of the tubular element comprises, at the free coupling end, a first flange made integrally with the second body portion and comprising a housing seat of the coupling portion of the grasping means.  
         [0065]     More preferably, the first flange comprises, at opposite sides to the housing seat, a pair of tabs extending cantilevered from the housing seat and defining angular limit positions of the grasping means.  
         [0066]     Even more preferably, the tabs of the pair of tabs are arranged at different heights.  
         [0067]     In particular, in operation the inclined portion of the tubular element is advantageously intended to face the back of the bicycle, so as to keep the seat away from the handlebars. In such a position, the most advanced tab is advantageously arranged at a lower height than the other. In this way it is ensured that the seat can always maintain an angular position sloping forwards, a position that is particularly preferred by cyclists.  
         [0068]     Preferably, the clamping means comprise a pair of screws and respective nuts, the screws being adapted to pass in respective through holes formed on the first flange at the tabs and in respective slots formed on the grasping means on opposite sides to the coupling portion to fix in position the grasping means with respect to the tubular element. Advantageously, in the adjustment step the holes keep the screws in position fixed with respect to the tubular element along the horizontal direction, whereas the slots allow the displacement in rotation of the grasping means. Therefore, there is no risk that the operator, when adjusting the angular position of the seat, involuntarily modifies its position in the horizontal direction.  
         [0069]     In any case, embodiments of the seat post are foreseen in which, instead of the aforementioned through holes, slots are formed on the first flange.  
         [0070]     Preferably, the grasping means comprise a second flange adapted to be coupled to the first flange through the clamping means, in which the slots are formed in the second flange.  
         [0071]     In a preferred embodiment of the seat post, the second flange is made in a distinct piece from the jaws of the pair of jaws.  
         [0072]     In this embodiment, preferably, at least one jaw of the pair of jaws comprises means for pulling the second flange into rotation. Such means can be defined by knurled surfaces at the outer surface of the coupling portion of the upper jaw and at the inner surface of the second flange, or, preferably, by a small tooth made on the inner surface of the second flange and a respective coupling hole made on the coupling portion of the upper jaw (or of both jaws).  
         [0073]     In a variant embodiment, the second flange is made in a single piece with a jaw of the pair of jaws.  
         [0074]     Preferably, the tubular element of the seat post has, for at least part of the longitudinal extension thereof, an asymmetric cross section, with a portion of the section having increased thickness. In particular, at the part of the tubular element with asymmetrical cross sections, the greater thickness is provided on the side intended to face towards the back of the bicycle.  
         [0075]     More preferably, the asymmetric cross section entirely involves the second body portion and partially the first body portion for a first part adjacent to the second body portion. Indeed, these are the zones of maximum stress of the tubular element; these zones are thus strengthened, whereas the other zones of the tubular element that are unloaded are lightened to keep the overall weight of the component as low as possible.  
         [0076]     Alternatively, the tubular element has a symmetrical cross section along its entire longitudinal extension. Preferably, a first portion of the first body portion of the tubular element adjacent to the second body portion has increased thickness.  
         [0077]     In this case, preferably, the tubular element has a zone of increased thickness at a first part of the first body portion adjacent to the second body portion. In this case the most stressed portion of the tubular element is strengthened, whereas the weight of the other unloaded portions inside and outside the frame of the bicycle is kept low.  
         [0078]     Preferably, the tubular element is made from a light metal alloy. Alternatively, the tubular element can be made from composite material. In any case, an optimal compromise between structural strength and lightness is obtained.  
         [0079]     Preferably, the jaws are made from the same material from which the tubular element is made.  
         [0080]     In the embodiment in which the jaws are made in distinct pieces from the second flange, the jaws can, for example, be made from composite material and the second flange from metal alloy. Preferably, the tubular element is made from carbon fibre and the second flange and the jaws from light metal alloy. It is, however, possible to foresee further combinations of different materials for tubular element, jaws and possibly second flange.  
       DETAILED DESCRIPTION  
       [0081]     In  FIG. 1 , a bicycle, in particular a racing bicycle, is indicated with 1. Such a bicycle  1  comprises a seat  2  associated with a frame  3  of the bicycle  1  through a seat post  10 . The bicycle  1  also comprises a bottom bracket  4  and handlebars  5 , both of the conventional type.  
         [0082]      FIG. 2  shows the seat post  10  comprises a tubular element  11  adapted to be inserted telescopically, for at least part of the longitudinal extension thereof, in an appropriate tubular seat  12  provided in the frame  3  of the bicycle  1  ( FIG. 1 ) and a pair of jaws  13  intended to be integral with the tubular element  11  and adapted to grasp the seat  2  to associate it with the tubular element  11 . In particular, the jaws  13  grasp rectilinear portions  14  of the rods  15  of the frame of the seat  2 . Typically, the frame of the seat  2  comprises two rods  15  disposed side-by-side and the rectilinear portion  14  of each rod  15  is delimited by a front bending point CF and a back bending point CB.  
         [0083]     The seat post  10  is an adjustable seat post. It thus allows the adjustment of the position of the seat  2  in height (in the two ways of the direction z in  FIG. 1 ) and in a horizontal direction (in the two ways of the direction x in  FIG. 1 ) substantially perpendicular to a vertical reference plane π passing through the axis of the bottom bracket  4  of the bicycle  1 .  
         [0084]     The adjustment of the position of the seat  2  in height takes place in a totally conventional manner. It is obtained, in particular, by sliding the tubular element  11  up and down in the suitable tubular seat  12  of the frame  3 . Once the seat  2  has been positioned at the desired height, the tubular element  11  is locked with respect to the frame  3  by clamping onto the tubular element  11  suitable jaws  110  ( FIG. 1 ) appropriately provided on the tubular seat  12  of the frame  3 .  
         [0085]     The adjustment of the seat  2  in a horizontal direction with respect to the plane π is, on the other hand, obtained by sliding the rectilinear portion  14  of the rods  15  of the seat  2  with respect to the jaws  13 . Once the seat  2  has been positioned at the desired distance x, the seat  2  is locked in position clamping the jaws  13  on the rods  15 .  
         [0086]     As already stated previously, in this description, when we speak of the adjustment of the position of the seat with respect to the plane π, we shall always refer to the adjustment along the horizontal direction x shown in  FIG. 1 , meaning by the expression “horizontal direction” not only a perfectly horizontal direction, but also a direction inclined with respect to the direction x by a predetermined angle so that the seat  2  always maintains an angular position inclined downwards.  
         [0087]     In  FIG. 1 , the seat  2  is arranged so that its front end is at a distance x0 from the plane π. The extreme positioning limits of the seat  2  in its translation stroke along the direction x are indicated with x1 and x2: x1 is the distance from the plane π at which the seat  2  is situated in its extreme horizontal advanced position, whereas x2 is the distance from the plane π at which the seat  2  is situated in its extreme horizontal withdrawn position. The seat  2  can thus be positioned with respect to the plane π at any distance x within the range between x1 and x2.  
         [0088]     With reference to the embodiment of the seat post  10  of the present invention illustrated in  FIGS. 2-5 ,  6   a ,  6   b ,  7   a ,  7   b ,  8   a ,  8   b ,  9   a ,  9   b , the pair of jaws  13  comprises, in particular, an upper jaw  130  and a lower jaw  230 . The upper jaw  130  is adapted to cooperate with the lower jaw to clamp the seat  2  on the tubular element  11 . The clamping takes place through a pair of screws  20 ,  21  and respective cylindrical nuts  22 ,  23 .  
         [0089]     As illustrated in particular in  FIG. 3 , the upper jaw  130  comprises a substantially semicylindrical central body portion  131 , a first pair of grasping portions  132 ′,  132 ″ of a rod  15  of the seat  2  and a second pair of grasping portions  133 ′,  133 ″ of the other rod  15  of the seat  2 . The central body portion  131  extends along a respective longitudinal axis S-S (shown in  FIG. 4 ). The grasping portions  132 ′,  132 ″ extend cantilevered at a first free end of the central body portion  131  at opposite sides to the longitudinal axis S-S of the central body portion  131  and in a direction substantially perpendicular to such an axis. Similarly, the grasping portions  133 ′,  133 ″ extend cantilevered at a second free end, opposite the first free end, of the central body portion  131  at opposite sides to the longitudinal axis S-S of the central body portion  131  and in a direction substantially perpendicular to such an axis. Grooves  134 ′,  134 ″,  135 ′,  135 ″ for housing the rectilinear portions  14  of the rods  15  of the frame of the seat  2  are formed on the grasping portions  132 ′,  132 ″,  133 ′,  133 ″ (in  FIG. 3  just the grooves  134 ″ and  135 ″ can be seen, in  FIGS. 4 and 5  the longitudinal axis of such grooves is shown).  
         [0090]     Similarly, the lower jaw  230  comprises a substantially semicylindrical central body portion  231 , a first pair of grasping portions  232 ′,  232 ″ of a rod  15  of the seat  2  and a second pair of grasping portions  233 ′,  233 ″ of the other rod  15  of the seat  2 . The central body portion  231  extends along a respective longitudinal axis S′-S′ (represented in  FIG. 5 ). The grasping portions  232 ′,  232 ″ extend cantilevered at a first free end of the central body portion  231  at opposite sides to the longitudinal axis S′-S′ of the central body portion  231  and in a direction substantially perpendicular to such an axis. Similarly, the grasping portions  233 ′,  233 ″ extend cantilevered at a second free end, opposite the first free end, of the central body portion  231  at opposite sides to the longitudinal axis S′-S′ of the central body portion  231  and in a direction substantially perpendicular to such an axis. Grooves  234 ′,  234 ″,  235 ′,  235 ″ for housing the rectilinear portion  14  of the rods  15  of the frame of the seat  2  are formed on the grasping portions  232 ′,  232 ″,  233 ′,  233 ″.  
         [0091]     The size of the grooves  134 ′,  134 ″,  135 ′,  135 ″ of the grasping portions  132 ′,  132 ″,  133 ′,  133 ″ of the upper jaw  130  and the size of the grooves  234 ′,  234 ″,  235 ′,  235 ″ of the grasping portions  232 ′,  232 ″,  233 ′,  233 ″ of the lower jaw  230  are such that each of such grooves partially houses a portion of a rod  15  of the frame of the seat  2 . When the jaws  130 ,  230  face one another and are clamped against each other, the rods  15  of the frame of the seat  2  are arranged between the grooves  134 ′,  134 ″,  135 ′,  135 ″ of the upper jaw  130  and the grooves  234 ′,  234 ″,  235 ′,  235 ″ of the lower jaw  230 .  
         [0092]     As shown for example in  FIG. 2 , the tubular element  11  comprises a first rectilinear body portion  11   a  adapted to be, at least in part, inserted in the tubular housing seat  12  formed in the frame  3  of the bicycle  1  and a second body portion  11   b  inclined with respect to the first body portion  11   a , the second body portion  11   b  being intended to remain outside the tubular seat  12 .  
         [0093]     In operation, the second portion  11   b  of the tubular element  11  is intended to face towards the back of the bicycle  1 , so as to keep the seat  2  away from the handlebars  5  (see  FIG. 1 ).  
         [0094]     With reference once again to  FIG. 3 , the second body portion  11   b  of the tubular element  11  comprises a coupling free end to the seat  2  on which a flange  16  is integrally formed. As better illustrated in  FIG. 15 , such a flange  16  in turn comprises a housing seat  17  for the central body portion  231  of the lower jaw  230  and, at opposite sides to the housing seat  17 , a pair of tabs  18  extending cantilevered from the housing seat  17  and adapted to act as stop surfaces of the angular rotation of the jaws  130 ,  230  about an axis parallel to the longitudinal axes S-S and S′-S′ of the respective central body portions  131 ,  231 , as shall be described more clearly below.  
         [0095]     The housing seat  17  of the lower jaw  230  is defined by a cylindrical surface portion having a shape matching that of the central body portion  131 ,  231  of the jaws  130 ,  230 . In particular, the housing seat  17  and the central body portion  131 ,  231  of the jaws  130 ,  230  have the same diameter. The seat  17  and the central body portion  231  of the lower jaw  230  are adapted to be coupled together in abutment.  
         [0096]     Also, the tabs  18  are defined by a cylindrical surface portion and are arranged at different heights with respect to the end portion of the tubular element  11  on which the flange  16  is formed. In particular, when the tubular element  11  is mounted on the frame  3  of the bicycle, the tab  18  closest to the handlebars  5  is at a lower height than the other tab  18 ; this ensures that the seat  2  takes up a position sloping forwards, such a position being particularly preferred by cyclists.  
         [0097]     On each tab  18  a cylindrical through hole  19  (or a slot) is formed in which a respective clamping screw  20 ,  21  is inserted. In the clamping step, the heads of the clamping screws  20 ,  21  stop by abutment on the lower surfaces of the tabs  18  through interposition of suitable washers  20   a ,  21   a.    
         [0098]     The seat post  10  also comprises a second flange  30  adapted to cooperate with the flange  16  of the tubular element  11  to clamp the jaws  130  and  230 . For such a purpose, the flange  30  is coupled on the top thereof with the upper jaw  130  and comprises, on the lower surface thereof, a central housing seat  31  for the central body portion  131  of the upper jaw  130  and, on the upper surface thereof, a pair of side seats  32 ,  33  extending from opposite sides to the seat  31  and adapted to house the nuts  22 ,  23  in the clamping step.  
         [0099]     The housing seat  31  of the upper jaw  130  is defined by a cylindrical surface portion having a shape matching that of the central body portion  131 ,  231  of the jaws  130 ,  230 . The housing seats  32 ,  33  of the nuts are also defined by cylindrical surface portions. The surfaces of the seats  32 ,  33  for the nuts  22 ,  23  are oriented with concavity opposite the surface of the housing seat  31  for the upper jaw  130 . In the assembled configuration of the seat post  10 , the seat  31  of the flange  30  couples in abutment to the central body portion of the upper jaw  130 , the seat  32  is arranged between the coupling portions  132 ′ and  133 ′ of the same upper jaw  130  and the seat  33  is arranged between the coupling portions  132 ″ and  133 ″ of the same jaw.  
         [0100]     On each seat  32 ,  33  for the nuts  22 ,  23  a slot  34  is formed through which passes the respective clamping screw  20 ,  21  to screw into the respective nut  22 ,  23 .  
         [0101]     In the clamping step, by acting on the screws  20 ,  21 , the flange  30  is pulled towards the tubular element  11  and the jaws  130  and  230  are clamped against each other locking the seat  2  in position with respect to the tubular element  11 .  
         [0102]     With particular reference to  FIG. 3  and to  FIGS. 6   a ,  6   b ,  9   a ,  9   b , the central body portion  131  of the upper jaw  131  has a central hole  138  in which a small tooth  35  formed centrally in the seat  31  of the flange  30  can be inserted. The coupling of the small tooth  35  in the hole  138  allows the flange  30  to be pulled into rotation by the upper jaw  130 , as shall be described more clearly hereafter.  
         [0103]     In the embodiment of the seat post  10  illustrated in  FIGS. 2-5 ,  6   a ,  6   b ,  7   a ,  7   b ,  8   a ,  8   b ,  9   a ,  9   b , the interface surfaces between the jaws  130 ,  230  and the seats  17  and  31  all have the same diameter, so that the upper jaw  130  and the lower jaw  230  can be exchanged and/or rotated in a mirror-like way about an axis perpendicular to the axes of longitudinal symmetry S-S and S′-S′ of the respective central body portions  131 ,  231 . In order to promote such an exchange and/or rotation, the jaws  130 ,  230  are made identical to each other.  
         [0104]     The central body portion  231  of the lower jaw  230  is adapted to rotate in the seat  17  of the flange  16  of the tubular element  11  about the axis S′-S′. When the rods  15  are inserted in the grooves  134 ′,  134 ″,  235 ′,  235 ″, the lower jaw  230 , rotating, pulls the upper jaw  130  into rotation with it which in turn, by means of the small tooth  35 , pulls in rotation the flange  30 . The flange  30  and the jaws  130 ,  230  are thus integral in rotation and can be locked in a predetermined angular position through the screws  20 ,  21 .  
         [0105]     In particular, by screwing one screw and unscrewing the other it is possible to rotate the jaws  130 ,  230  with respect to the tubular element  11  up to a desired angular position.  FIGS. 6   a ,  6   b  show two extreme angular positions of the jaws  130 ,  230 , in which the outer surfaces of the seats  32 ,  34  of the flange  30  are in abutment in a first case on one of the tabs  18  of the flange  16  of the tubular element  11  (the tab on the left in  FIG. 6   a ) and in the other case on the other tab  18  (the tab on the right in  FIG. 6   b ).  
         [0106]     In an alternative embodiment that has not been illustrated, the pulling into rotation of the flange  30  by the upper jaw  130  is not achieved through the coupling between small tooth  35  and hole  138 , but rather by providing appropriate knurlings on the outer surface of the central body portion  131  of the upper jaw  130  and on the inner surface of the seat  31  of the flange  30 .  
         [0107]     In an embodiment alternative to the one described above, illustrated in  FIG. 13 , the flange  30 , instead of being made in a single piece distinct from the upper jaw  130 , is made in a single piece with the latter. The upper jaw  130  is thus shaped so as to comprise side portions that define the seats  32 ,  33  for the nuts  22 ,  23 . On such side portions the slots  34  for the passage of the screws  20 ,  21  are formed.  
         [0108]     With particular reference to  FIGS. 2, 3 ,  4 ,  5 , the opposite front end surfaces of the grasping portions  132 ′,  132 ″ of the upper jaw  130  define abutment surfaces  136 ′,  136 ″ against which the front bending points CF and rear bending points CB of one of the rods  15  of the frame of the seat  2  abut, during the adjustment of the position of the seat  2  in the horizontal direction. The grasping portions  133 ′,  133 ″ of the upper jaw  130  have similar abutment surfaces  137 ′ and  137 ″ ( FIG. 2 ).  
         [0109]     As shown in  FIGS. 4 and 5 , the abutment surfaces  136 ′ and  137 ′ have the same distance d from the plane of symmetry of the central body portion  131  of the upper jaw  130  passing through the longitudinal axis S-S. Similarly, the abutment surfaces  136 ″ and  137 ″ have the same distance D, the distance D being greater than the distance d of the abutment surface  136 ′,  137 ′.  
         [0110]     The upper jaw  130  is therefore asymmetric with respect to the plane of symmetry of the respective central body portion  131  passing through the axis S-S, with the coupling portions  132 ′,  133 ′ extending from the central body portion  131  asymmetrically with respect to the coupling portions  132 ″,  133 ″.  
         [0111]     In the embodiment of the seat post  10  illustrated in  FIGS. 2-5 ,  6   a ,  6   b ,  7   a ,  7   b ,  8   a ,  8   b ,  9   a ,  9   b , the jaws  130 ,  230  are specular with respect to each other. Therefore, similarly to the upper jaw  130 , also the lower jaw  230  comprises opposite abutment surfaces  236 ′,  236 ″ on the grasping portions  232 ′,  232 ″ and opposite abutment surfaces  237 ′,  237 ″ on the grasping portions  233 ′,  233 ″. The lower jaw  230  also comprises, similarly to the upper jaw  130 , a hole  238  formed centrally on the central body portion  231  and adapted to receive the small tooth  35  of the flange  30  when the position of the lower and upper jaws  230  and  130  is inverted.  
         [0112]     The use of the seat post  10  to adjust the position of the seat  2  along the horizontal direction is described with reference to  FIGS. 7   a ,  7   b  and  8   a ,  8   b.    
         [0113]     Starting from an operative coupling configuration of the jaws  130 ,  230  to the seat  2  like that illustrated in  FIG. 7   a , assume that one wishes to proceed to adjust the position of the seat  2  with respect to the vertical plane π passing through the axis of the bottom bracket of the bicycle so as to bring the seat  2  even closer to such a plane.  
         [0114]     As illustrated in  FIG. 7   a , the jaws  130 ,  230  are initially positioned with the abutment surfaces  136 ″,  137 ″,  236 ″,  237 ″ oriented in the direction of the back of the bicycle (on the right of  FIG. 7   a , where only the surfaces  136 ″ and  236 ″ can be seen). Such abutment surfaces are at a distance D from the planes of symmetry of the respective central body portions  131 ,  132  of the jaws  130 ,  230  passing through the longitudinal axes S-S and S′-S′.  
         [0115]     In particular, in  FIG. 7   a  the seat  2  is in a position in which the abutment surfaces  136 ″,  137 ″ of the upper jaw  130  are in abutment against the rear bending point CB of the seat rods  15 . The distance of the seat  2  from the plane π is indicated with X1′ and, in a conventional seat post, this would be the maximum advanced position of the seat  2 .  
         [0116]     Let us now presume that one wishes to position the seat  2  even further towards the plane π. This is possible, according to the invention, by dismounting the flange  30  and rotating the jaws  130 ,  230  by 180° about an axis perpendicular to the axes of symmetry S-S and S′-S′ and lying on the plane of symmetry of the central body portions  131 ,  231  of the jaws  130 ,  230 . One then passes from the operative coupling configuration of  FIG. 7   a  to the operative coupling configuration of  FIG. 7   b . In this operative coupling configuration, the abutment surfaces  136 ′,  137 ′,  236 ′,  237 ′ are oriented in the direction of the back of the bicycle (in  FIG. 7   b  only the surfaces  137 ′ and  237 ′ can be seen). As an alternative to the mirroring rotation of the jaws  130 ,  230 , it is possible to pass from the first operative coupling configuration of  FIG. 7   a  to the second operative coupling configuration of  FIG. 7   b  by rotating the assembly of the jaws  130 ,  230  by 180° about an axis parallel to the longitudinal axes of the central body portions  131 ,  231  of the jaws  130 ,  230 , i.e. exchanging the position of the two jaws.  
         [0117]     Due to the fact that the abutment surfaces  136 ′,  137 ′,  236 ′,  237 ′ are at a distance d from the planes of symmetry of the respective central body portions  131 ,  132  of the jaws  130 ,  230  passing through the longitudinal axes S-S and S′-S′ smaller than the distance D at which the abutment surfaces  136 ″,  137 ″,  236 ″,  237 ″ are located, the seat  2  can be brought closer to the plane π and positioned at a distance X1 from such a plane π smaller than the distance X1′. Compared to a conventional seat post, the seat post of the present invention thus allows an additional adjustment stroke towards the plane π equal to D-d to be carried out. The distance X1 shall thus be: 
 
 X 1= X 1′−( D−d ). 
 
         [0118]      FIGS. 8   a ,  8   b  illustrate the process for adjusting the position of the seat  2  through the seat post  10  of the present invention in the case in which the seat  2  is in the maximum withdrawn position from the vertical plane π passing through the axis of the bottom bracket of the bicycle.  
         [0119]     Starting from an operative coupling configuration of the jaws  130 ,  230  to the seat  2  like the one illustrated in  FIG. 8   a  and assume that one proceeds to adjust the position of the seat  2  with respect to the plane π so as to take the seat  2  further away from such a plane without varying its angular position (i.e. keeping the jaws  130 ,  230  in the illustrated angular position).  
         [0120]     As illustrated in  FIG. 8   a , the jaws  130 ,  230  are initially positioned with the abutment surfaces  136 ″,  137 ″,  236 ″,  237 ″ oriented towards the handlebars of the bicycle (to the left of  FIG. 8   a , where only the surfaces  136 ″ and  236 ″ can be seen).  
         [0121]     In particular, in  FIG. 8   a  the seat  2  is in a position in which the abutment surfaces  136 ″,  137 ″ of the upper jaw  130  abut against the front bending point CF of the rods  15  of the seat  2 . The distance of the seat  2  from the plane π is indicated with X2′ and, in a conventional seat post, this would be the maximum withdrawn position of the seat  2 .  
         [0122]     Assume that one wishes to position the seat  2  even further back, i.e. even further from the plane π. Similarly to what was described with reference to  FIGS. 7   a ,  7   b , this is possible by dismounting the flange  30  and rotating mirror-like the jaws  130 ,  230  by 180° about an axis perpendicular to the axes of symmetry S-S and S′-S′ and lying on the plane of symmetry of the central body portions  131 ,  231  of the jaws  130 ,  230 . One thus passes from the operative coupling configuration of  FIG. 8   a  to the operative coupling configuration of  FIG. 8   b . In this operative coupling configuration, the abutment surfaces  136 ′,  137 ′,  236 ′,  237 ′ are oriented towards the handlebars of the bicycle (in  FIG. 8   b  only the surfaces  137 ′ and  237 ′ can be seen). Also in this case, as an alternative to the mirror-like rotation of the jaws  130 ,  230 , it is possible to pass from the first operative coupling configuration of  FIG. 8   a  to the second operative coupling configuration of  FIG. 8   b  by rotating the assembly of the jaws  130 , 230  by 180° about an axis parallel to the longitudinal axes of the central body portions  131 ,  231  of the jaws  130 ,  230 , i.e. exchanging the position of the two jaws.  
         [0123]     The seat  2  can thus be taken away from the plane π and positioned at a distance X2 from the plane n greater than the distance X2′. Compared to a conventional seat post, the seat post of the present invention thus allows an additional adjustment stroke away from the plane π equal to D-d to be carried out. The distance X2 shall thus be: 
 
 X 2= X 2′+( D−d ). 
 
         [0124]      FIGS. 9   a ,  9   b  illustrate the same process for adjusting the position of the seat  2  described with reference to  FIGS. 8   a ,  8   b ; in  FIGS. 9   a ,  9   b , however, the seat  2  is in a different angular position (see also the different angular position of the jaws  130 ,  230 ). Moreover, as an alternative to the mirror-like rotation described above with respect to  FIGS. 8   a ,  8   b , in the adjustment process illustrated in  FIGS. 9   a ,  9   b  the jaws  130 ,  230  are exchanged, in the sense that the upper jaw  130  is positioned in the place of the lower jaw  230  and vice-versa. The exchange of the jaws can be carried out by rotating the assembly formed by the two jaws by 180° about an axis parallel to the longitudinal axes S-S and S′-S′ of the central bodies  131 ,  231  of the jaws  130 ,  230 , as indicated by the arrow R in  FIG. 9   b.    
         [0125]     In the embodiment of the seat post  10  illustrated in  FIGS. 2-5 ,  6   a ,  6   b ,  7   a ,  7   b ,  8   a ,  8   b ,  9   a ,  9   b , the upper and lower jaws  130  and  230  are asymmetric and specular. The upper jaw  130  is, in other words, asymmetric with respect to the plane of symmetry of the respective central body portion  131  passing through the axis S-S, with the coupling portions  132 ′,  133 ′ extending from the central body portion  131  asymmetrically with respect to the coupling portions  132 ″,  133 ″. Similarly, the lower jaw  230  is asymmetric with respect to the plane of symmetry of the respective central body portion  231  passing through the axis S′-S′, with the coupling portions  232 ′,  233 ′ extending from the central body portion  231  asymmetrically with respect to the coupling portions  232 ″,  233 ″.  
         [0126]     Nevertheless, embodiments (not illustrated) are foreseen in which the grasping portions extend cantilevered from just one side of the central body portions of the jaws. In particular, in these embodiments, in the jaws  130 ,  230  the coupling portions  132 ′,  133 ′ and  232 ′,  233 ′ are not present and the abutment surfaces  136 ′,  137 ′ and  236 ′,  237 ′ shall be formed directly on the central body portions  131 ,  231  of the jaws  130 ,  230 , on the opposite side to that from which the grasping portions  132 ″,  133 ″ and  232 ″,  233 ″ extend.  
         [0127]      FIGS. 10   a  and  10   b  illustrate the same process for adjusting the position of the seat  2  described with reference to  FIGS. 8   a ,  8   b  for an embodiment of the seat post  10  that differs from the one illustrated and described previously only for the fact that it comprises a symmetric lower jaw  230 . The upper and lower jaw  130  and  230  are thus different; in particular the upper jaw  130  is asymmetric and identical to the one described previously, whereas the lower jaw  230  is symmetrical and longer than the upper jaw  130 .  
         [0128]     More specifically, the distance D of the abutment surfaces  236 ′ and  237 ′ from the plane of symmetry of the central body portion  231  of the lower jaw  230  passing through the longitudinal axis S′-S′ is equal to that of the abutment surfaces  136 ″ and  137 ″ of the upper jaw  130  from the plane of symmetry of the central body portion  131  of the upper jaw  130  passing through the longitudinal axis S-S. The abutment surfaces  236 ″ and  237 ″ of the lower jaw  230  have a distance from the plane passing through the axis S′-S′ equal to the distance of the abutment surfaces  236 ′,  237 ′ from the same plane.  
         [0129]      FIGS. 10   a  and  10   b  show a possible sequence of use in which both of the jaws  130 ,  230  are rotated by 180° about an axis perpendicular to the axes of symmetry S-S and S′-S′ and lying on the plane of symmetry of the central body portions  131 ,  231  of the jaws  130 ,  230 . The upper jaw  130  provides the seat  2  with a reference abutment in the horizontal direction, whereas the lower jaw  230  provides a support for the zone of the seat  2  in which the weight of the cyclist is discharged greater than in the case described with reference to  FIGS. 2-5 ,  6   a ,  6   b ,  7   a ,  7   b ,  8   a ,  8   b ,  9   a ,  9   b.    
         [0130]      FIGS. 11   a  and  11   b  illustrate the same process for adjusting the position of the seat  2  described with reference to  FIGS. 8   a ,  8   b  for a seat post  10  that differs from the one illustrated and described previously for the only reason that it comprises a lower jaw  230  that is asymmetric and of greater length than the upper jaw  130 . The upper and lower jaw  130  and  230  are thus different; in particular the upper jaw  130  is asymmetric and identical to the one described previously, whereas the lower jaw  230  is asymmetric and longer than the upper jaw  130 .  
         [0131]     More specifically, the distance d of the abutment surfaces  236 ′ and  237 ′ from the plane of symmetry of the central body portion  231  of the lower jaw  230  passing through the longitudinal axis S′-S′ is equal to that of the abutment surfaces  136 ′ and  137 ′ of the upper jaw  130  from the plane of symmetry of the central body portion  131  of the upper jaw  130  passing through the longitudinal axis S-S. The abutment surfaces  236 ″ and  237 ″ of the lower jaw  230 , on the other hand, are at a distance D′ from the plane passing through the axis S′-S′ greater than the distance d of the abutment surface  236 ′,  237 ′ from the same plane and than the distance D of the abutment surfaces  136 ″,  137 ″ of the upper jaw  130  from the plane passing through the axis S-S.  
         [0132]      FIGS. 11   a  and  11   b  show a possible sequence of use in which both of the jaws  130 ,  230  are rotated by 180° about an axis perpendicular to the axes of symmetry S-S and S′-S′ and lying on the plane of symmetry of the central body portions  131 ,  231  of the jaws  130 ,  230 . The upper jaw  130  provides the seat  2  with a reference abutment in the horizontal direction, whereas the lower jaw  230  provides a support for the zone of the seat  2  in which the weight of the cyclist is discharged greater than in the case described with reference to  FIGS. 2-5 ,  6   a ,  6   b ,  7   a ,  7   b ,  8   a ,  8   b ,  9   a ,  9   b ,  10   a ,  10   b.    
         [0133]      FIGS. 12   a  and  12   b  illustrate a seat post  10  that differs from the one illustrated in  FIGS. 11   a ,  11   b  for the only reason that in the lower jaw  230  the distance D of the abutment surfaces  236 ′ and  237 ′ from the plane of symmetry of the central body portion  231  of the lower jaw  230  passing through the longitudinal axis S′-S′ is equal to that of the abutment surfaces  136 ″ and  137 ″ of the upper jaw  130  from the plane of symmetry of the central body portion  131  of the upper jaw  130  passing through the longitudinal axis S-S. The abutment surfaces  236 ″ and  237 ″ of the lower jaw  230 , on the other hand, are at a distance D′ from the plane passing through the axis S′-S′ greater than the distance D of the abutment surface  236 ′,  237 ′ from the same plane.  
         [0134]      FIGS. 12   a  and  12   b  show a possible sequence of use in which only the upper jaw  130  is rotated by 180° about an axis perpendicular to the axis of symmetry S-S and lying on the plane of symmetry of the central body portion  131  of the jaw  130 . The upper jaw  130  provides the seat  2  with a reference abutment in the horizontal direction, whereas the lower jaw  230 , already being located in the position in which it provides the maximum support to the zone of the seat  2  in which the weight of the cyclist is discharged, is not moved.  
         [0135]     In all of the embodiments discussed above, the jaws can be shaped so that the aforementioned abutment surfaces  136 ′,  136 ″,  137 ′,  137 ″,  236 ′,  236 ″,  237 ′,  237 ″ are curved, with a concavity facing towards the outside of the seat post  10 . Such a provision allows a further additional adjustment stroke to be obtained, in addition to the one obtained with the asymmetry of the upper jaw  130  (and possibly the lower jaw  230 ).  
         [0136]      FIG. 6   a  shows an embodiment of the seat post of the present invention in which the portion  11   b  of the tubular element  11  of the seat post  10  has an asymmetric section along its entire longitudinal extension with an increased thickness S′ at the side intended to face towards the back of the bicycle. The side of the portion  11   b  of the tubular element  11  intended to face towards the handlebars of the bicycle has a thickness S smaller than the thickness S′. A first part of the portion  11   a  of the tubular element  11  adjacent to the portion  11   b  has an asymmetric section with increased thickness S′. Such a first part is adapted to remain outside the tubular seat  12  provided in the frame  3  of the bicycle. The lower part of the portion  11   a , on the other hand, has a symmetric section with a thickness S equal to that of the side of the portion  11   b  of the tubular element  11  intended to face towards the handlebars of the bicycle. Such a lower part is intended to be telescopically inserted into the tubular seat  12  provided in the frame  3  of the bicycle.  
         [0137]      FIG. 6   b  shows an alternative embodiment of the seat post of the present invention in which the portion  11   b  of the tubular element  11  has a symmetric cross section of thickness S along the entire longitudinal extension thereof.  
         [0138]      FIG. 14  shows an embodiment of the seat post of the present invention in which the portion  11   b  of the tubular element  11  has a symmetric cross section with a thickness S, like in  FIG. 6   b , and in which a first part of the portion  11   a  of the tubular element  11  adjacent to the portion  11   b  has a symmetric section with increased thickness S′, whereas the lower part of the portion  11   a  has a symmetric section with a thickness S. Also in this case, the increased thickness is provided in the part of the tubular element  11  that remains outside the tubular seat  12  provided in the frame  3  of the bicycle.  
         [0139]      FIG. 15  shows a further embodiment of the tubular element  11  of the seat post  10  of the present invention. In such an embodiment, the portion  11   b  and a first part of the portion  11   a  of the tubular element  11  have an asymmetric cross section with increased thickness S′ at the side intended to face towards the back of the bicycle. The lower part of such a first part of the portion  11   a  is intended to be telescopically inserted into the tubular seat  12  provided in the frame  3  of the bicycle. The part further lower of the portion  11   a , instead has a symmetric section with constant thickness S which is the same as that of the side of the portion  11   b  of the tubular element  11  intended to face towards the handlebars of the bicycle.  
         [0140]      FIG. 16  shows an alternative embodiment of the upper jaw  130  (and possibly the lower jaw  230 ) of the seat post  10  of the present invention. Such an embodiment differs from the one described previously for the only reason that it comprises a removable abutment element  330  associated, for example by a joint, for example a dovetailing joint, with the upper jaw  130  at the abutment surfaces  136 ′,  137 ′. The abutment element  330  comprises coupling surfaces  336 ′,  337 ′ to the jaw  130  and an opposite abutment surface  331 . When coupled with the jaw  130 , the abutment surface  331  is at a distance D′ from the axis S-S greater than the distance d of the abutment surfaces  136 ′,  137 ′.  
         [0141]     In such an embodiment, the abutment element  330  can be removed from the jaw  130  so that the latter provides the abutment surfaces  136 ′,  137 ′ for the abutment, obtaining an additional adjustment stroke, as described above. Of course, it is possible to foresee a plurality of abutment elements  330  that can be removably coupled together and removed individually to obtain different additional adjustment strokes.  
         [0142]     The seat post  10  of the present invention can be made from light metal alloys or also from composite material. The composite material can comprise structural fibers incorporated in a polymeric material.  
         [0143]     Typically, the structural fibers are chosen from the group comprising carbon fibers, glass fibers, aramidic fibers, ceramic fibers, boron fibers and combinations thereof. Carbon fibers are particularly preferred.  
         [0144]     The arrangement of the structural fibers in the polymeric material can be a random arrangement of pieces or small sheets of structural fibers, an ordered substantially unidirectional arrangement of fibers, an ordered substantially two-dimensional arrangement of fibers, or a combination of the above.  
         [0145]     Preferably, the polymeric material is thermosetting. However it is possible to use a thermoplastic material.  
         [0146]     More preferably, the polymeric material comprises an epoxy resin.  
         [0147]     The tubular element  11 , the jaws  130 ,  230  and the flange  30  can be made from the same material.  
         [0148]     In the embodiments in which the flange  30  is made in a different piece to the upper jaw  130 , the jaws can, for example, be made from composite material and the flange  30  can be made from light metal alloy.  
         [0149]     In a preferred embodiment of the seat post  10  of the present invention, the tubular element  11  is made from carbon fiber whereas the flange  30  and the jaws  130 ,  230  are made from light metal alloy.