FR 3095798 A1 20201113 FR 2004536 A 20200507 Description Title of Invention: SUPPORT MECHANISM FOR HEIGHT- ADJUSTABLY SUPPORTING A WINDSCREEN ON A SADDLE- TYPE VEHICLE AND RELATIVE METHOD Technical Field 100011 The present invention relates to a support mechanism for height adjustably supporting a windscreen on a saddle-type vehicle. 100021 The present invention also relates to a method of adjusting the height of a windscreen of a saddle-type vehicle. Background Art [0003] Sad.clle-type vehicles are known comprising a body, a front wheel and a rear wheel which are operatively connected to the body. [0004] Sad.clle-type vehicles are also known comprising one rear wheel and two front wheels, or one front wheel and two rear wheels, or two front and two rear wheels. [0005] Furthermore, sad.clle-type vehicles are also known with two front or rear wheels, which are mounted in such a way to be leaning with respect to the body. [0006] Sad.clle-type vehicles can be configured in a variety of ways, e.g. as motorcycles or as scooters. [0007] Sad.clle-type vehicles generally comprise a front windscreen. [0008] Front windscreens are generally used to shield the rider from the air llow caused by the motion of the vehicle or against road debris. [0009] The amount of air llow received by the rider depends on the height of the windscreen, which in turn corresponds to a position of the windscreen itself. [0010] In particular, the higher the windscreen, the lower the amount of air flow impingine the rider. [0011] However, the higher the windscreen, the higher the aerodynamic drag, which acts on the vehicle. [0012] Various height-adjustable windscreens have been proposed in accordance with the ride-preferences of the rider, the usage of the vehicle and the like. [0013] For example, EP-A-3192729, in the trame of the same Applicant, discloscs a saddlc- type vehicle comprising a support mechanism, which supports the windscreen at an adjustablc height with respect to the body of the vehicle. [0014] In greater detail, the support mechanism comprises: [0015] - a first fixcdframc, which is fixed to the body of the vehicle; and [0016] - a second fratrie, which is fixcd to the windscreen and is movable with respect to the first fixcd fratrie. in ordcr to adjust the height of the windscreen. 2 100171 lii greater detail, the second frame and, therefore, the windscreen can be positioned at plurality of discrete locking positions and respective discrete heiehts with respect to the first fixed 'Trame. Still more precisely, a given locking position of the windscreen corresponds to a relative height of the windscreen. [0018] To this purposc, the first fixed frame comprises a plurality of first teeth and first recesses alternate to one another. [0019] The second frame comprises a plurality of second teeth and second recesses alternate to one anothcr. [0020] The first teeth engage respective second recesses as won as the second teeth engage respective first recesses. [0021] The first and the second teeth have a complementary triangle longitudinal cross section, in particular a sawtooth-shapcd cross section. [0022] -In this way, in cach locking position, the second teeth of the second frame engage different respective first recesses of the first frame. [0023] The user adjusts the height of the windscreen by causing the sliding of the second frame with respect to the first frame, from one locking position to anothcr locking position. [0024] The smallest adjustment possible of the height of the windscreen is limited by the pitch of the first and the second teeth, i.e. by thcir longitudinal dimensions. [0025] The support mcchanism furthcr comprises two adjustment nuts, which arc inscrted by the user inside respective seats defined by the th-st fixed fratrie, so as to fasten the second frame and, therefore, the windscreen to the th-st fixed fratrie in the desired locking position and at the desired height. [0026] Since at least two nuts are used to fix the windscreen to the first fixed frame, it is necessary for the rider to use both hands to move the windscreen first and to fasten the nuts then. [0027] Furthermore, the known support mechanism allows the rider to adjust the height of the windscreen only in a plurality of discrete positions. Accordingly, the windscreen of EP-A-3192729 may be adjusted at a height which is fit for the rider, but which is suboptimal for the reduction of the aerodynamic drag, or vice versa. [0028] A need is therefore telt within the industry to provide a support mechanism, which can be conveniently adjusted by using only one hand and in a single movement, so as to case the adjustment operation. [0029] Furthermore, a need is felt within the industry to allow a continuous adjustment of the height of the windscreen. Disclosure of Invention [0030] It is an object of the present invention to provide a support mechanism, allowing to 3 mect at least one of the aforementioned needs in a simple and cost-effective manncr. [0031] This object is achieved by a support mcchanism for height adjustably supporting a windscreen on a saddle-type vehicle. The support mcchanism comprises a first stationary frame, which is fixablc to a body of said vehicle; said windscreen; and a second adjustablc frame, which is fixcd to said windscreen and is slidablc with respect to said first stationary frame; characterized by comprising a handlc, which is integrally movable with said second adjustablc frame and comprises engaging means; said handlc bcing selectively movable in: at least one locking position, in which said engaging means lock said second adjustablc frame on said first stationary frame, thus fixing said windscreen at a desired height with respect to said first stationary frame; or in at least one unlocking position, in which said engaging means leave free the movement of said second adjustablc frame with respect to said first stationary frame. [0032] The support mcchanism can be further improvcd according to varions advantagcous c mbod ments. [0033] According to one embodiment, said engaging means can Ir frictionally fittcd against said first stationary frame with a first value of a locking force greater than a thrcshold value and directed parallel to a sliding direction of said second adjustablc frame with respect to said first stationary frame, when said handlc is set, in use, in said at least one locking position; said engaging means exerting, in use, a second value of said locking force lowcr than said threshold value or null, when said handlc k set, in use, in said at least one unlocking position. [0034] According to one embodiment, said engaging means can be spaced from saki first stationary frame, when said handle is set, in use, in said at least one unlocking position. [0035] According to one embodiment, the support mechanism can comprise elastic means, which are interposed between said engaging means and said first stationary trame. [0036] According to one embodiment, said elastic means can elastically load, in use, said handle towards said at least one locking position, when said handle is set in said at least one locking position; and/or in that said elastic means can elastically load, in use, said handle towards said at least one unlocking position, when said handle is set in said at least one unlocking position. [0037] According to one embodiment, said engaging means and elastic means can be configured in such a way that a graph of a further force acted, in use, by said engaging means on said elastic means, orthogonally to said sliding direction, comprises a first increasing stretch, as said handle moves, in use, from said at least one unlocking position towards an intermediate position, which is ananged between said at least one locking position and said at least one unlocking position. [0038] According to one embodiment, said graph can comprise a second decreasing stretch subsequent to said first increasing stretch, as said handle moves, in use, from said in- termediate position to said at least one locking, position. [0039] According tonne embodiment, said cngaging means can comprise at least one cam; said at least one cam being frictionally fittcd against said first stationary frame with said first value of said locking force greater than said thrcshold value and directed parallel to said sliding direction of said second adjustablc frame with respect to said first stationary frame, when said handle is set, in use, in said at least one locking position; said at least one cam exerting, in use, said second value of said locking force lower than said threshold value or null, when said handle is set, in use, in said at least one unlocking position. [0040] According to one embodiment, said at least one cam can Ir rotatable about an axis, transversal to said direction and parallel to said stationary frame, and can comprise a profile contacting said clastic means; said profile intcracting with said clastic means mostly on a first side of a plane, when said handle is set, in use, in said at least one locking position; said profile interacting with said clastic means mostly on a second side, opposite to said first side, of said plane, when said handle is set, in use, in said at least one unlocking position; said plane being defined by said axis and by a furthcr direction orthogonal to said sliding direction and said axis; said at least one cam being movable from said first side towards said second side, when said handle [noves, in use, from said at least one unlocking position to said at least one locking position. [0041] According to one embodiment, said profile symmetrically can extcnd with respect to said plane when said handle is in said intermediate position. [0042] According to one embodiment, said elastic means can comprise at least one spring; said at least one spring comprising: two first portions contacting said first stationary frame; and a second interaction portion, interposed between said first portions and contacting, in use, said profile. [0043] According to one embodiment, said handle can comprise two cams spaced from one another, and by comprising a pair of said spiings interposed, each, between a relative cam and saki first stationary frame. [0044] According to one embodiment, the support mechanism can be characterized in that when said handle is set, in use, in said at least one unlocking position, said windscreen can be moved among a plurality of continuously consecutive positions with respect to said first stationary frame; said windscreen being locked, in use, in a desired one of said continuously consecutive positions, when said handle is set in a respective said locking position). [0045] According to one embodiment, said first stationary frame can comprise a plurality of Bat guides and said second adjustable frame can comprise a plurality of sliders; said sliders being engaged in respective said Bat guides; said sliders being slidable in respective said flat guides among a plurality of continuously consecutive positions of said flat guides, when, said second adjustablc frame slides, in use, with respect to said first stationary frame. [0046] The present invention also relates to a saddle-type vehicle comprising a body and a support mcchanism as described abovc. [0047] The present invention also relates to a method of adjusting the height of a windscreen of a saddle-type vehicle. The method of adjusting the height of a windscrcen of a saddle-type vehicle with respect to a body of said vehicle, comprises the steps of: i) fitting a first stationary frame of a support mcchanism to said body; and ii) adjusting the position of a second adjustablc trame of said support mcchanistn with respect to said first stationary frame; characterized by comprising the further stops of: iii) selectively moving a handle between at least one locking position in which engaging means defined by said handle lock said second adjustablc frame on said first stationary framc, thus fixing said windscreen at a desired height; and at least one unlocking position in which said engaging means leave free the movement of said second adjustablc frame with respect to said first stationary frame. [0048] The method of adjusting the height of a windscreen of a saddle-type vehicle can be further improved according to various advantagcous embodiments. [0049] According to one embodiment, the method can comprise the steps of: iv) frictionally fitting said engaging means against said first stationary frame with a first value of a locking force greatcr than a thrcshold value and directed parallel to a sliding direction of said second adjustable frame with respect to said first stationary trame, when said handle is set in said at least one locking position; and y) exerting a second value of said locking force lower than said threshold value or null by means of said engaging means on said first stationary [rame, when said handle is set in said at least one unlocking position. [0050] According to one embodiment, the method can comprise a step vi) of spacing said engaging means [rom said th-st stationary frame, when said handle is set in said at least one unlocking position. [0051] According to one embodiment, the method can comprise the steps of vii) elastically loading said handle towards said at least one locking position, when said handle is in said at least one locking position; and/or viii) elastically loading said handle towards said at least one unlocking position, when said handle is in said at least one unlocking position; said steps vii) and/or viii) being carried out by means of elastic means. [0052] According to one embodiment, the method can comprise the step ix) of exerting a further force by means of said engaging means on said elastic orthogonally to said sliding direction; a graph of said further force comprising a first increasing stretch, as said handle moves from said at least one unlocking position towards an intermediate position, which is arranged between said at least one locking position and said at least 6 one unlocking position. [0053] According tonne embodiment, the method can be characterized in that said graph comprises a second decreasing strctch subsequent to said first incrcasing strctch, as said handlc moves from said intermediate position te said at least one locking position. [0054] According tonne embodiment, the method can comprise the steps of: x) rotating about an axis at least one cam of said cngaging [matis; said axis bcing transversal te said direction and parallel to said stationary framc; xi) contacting at least one spring of said elastic mcans interposed between said at least one can-land said first stationary framc by mcans of a profile of said at least one cam; said step xi) comprises the steps of: xi i) contacting a portion of said at least one spring by means of said profile mostly on a first side of a plane, when said handlc is in said at least one locking position; xiii) contacting said portion of said at least one spring by mcans of said profile mostly on a second side, opposite to said first side, of said plane, when said handlc is in said at least one unlocking position; said plane bcing defined by said axis and by a further direction orthogonal to said sliding direction and said axis; and xiv) moving said at least one cam from said first side towards said second side, when said handlc myes from said at least one unlocking position te said at least one locking position. [0055] According to one embodiment, the method can comprise the step xv) of arranging said profile symmctrically with respect to said plane when said handl° is in said intermediate position. [0056] According to one embodiment, the method can comprise the steps of xvi) increasing a maximum elastic detlection of said portion of said at least one spring parallel to said further direction, when said handle moves from said at least one unlocking position to said intermediate position and said profile approaches said first stationary trame along said further direction ; and/or xvii) decreasing said maximum elastic detlection of said portion of said at least one spring parallel to said further direction, when said handle moves from said intermediate position to said at least one locking position and said profile moves away from said first stationary frame along said further direction. [0057] According to one embodiment, the method can comprise the steps of xviii) moving said windscreen among a plurality of continuously consecutive positions with respect to said th-st stationary fume, when said handle is in said at least one unlocking position; and xix) locking said windscreen in a desired one of said continuously consecutive positions, when said handle is set in a respective said locking position. BRIEF DESCRIPTION OF THE DRAWINGS [0058] One prefen-ed, non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: [0059] [fig.1] is a lateral view of a saddle-type vehicle with a support mechanism for 7 supporting a front windscreen in a height adjustable way accordine to the present invention; [0060] [fig.2a] is a latcral vicw in an enlarged scalc of the support mcchanism of Figure 1 with the windscreen arranged at respective hcights diffcrent from one another; [0061] [fig.2b] is 'aura vicw in an enlarged scalc of the support mcchanism of Figure 1 with the windscreen arranged at respective hcights diffcrent from one another; [0062] [fig.3] is a perspective vicw in an enlarged scalc of the support mcchanism of Figures 1 and 2 respectively in an unlockcd position and in a locked position; [0063] [fig.4] is a perspective vicw in an enlarged scalc of the support mcchanism of Figures 1 and 2 respectively in an unlockcd position and in a locked position; [0064] [fig.5] is a rcar vicw in an enlarged scalc of the support mcchanism of Figures 1 to 4 with the windscreen arranged at respective hcights diffcrent from one another; [0065] [fig.6] is a rcar vicw in an enlarged scalc of the support mcchanism of Figures 1 to 4 with the windscreen arranged at respective hcights diffcrent from one another; [0066] [fig.7] is a perspective vicw in an enlarged scalc of the support mcchanism of Figures 1 to 6, respectively in an exploded and in an assembled vicw; [0067] [fig.8] is a perspective vicw in an enlarged scalc of the support mcchanism of Figures 1 to 6, respectively in an exploded and in an assembled vicw; [0068] [fig.9] is a cross section in a furthcr enlarged scalc of the support mcchanism of Figures 1 to 8, respectively along une IX-IX of Figure 3 and line X-X of Figure 4, with parts removed for clarity; [0069] [fig.10] is a cross section in a Millier enlarged scale of the support mechanism of Figures 1 to 8, respectively along Une IX-IX of Figure 3 and une X-X of Figure 4, with parts removed for clarity; and [0070] [fig.11] is a plot of the force exerted by the support mechanism of Figures 1 to 10 on the vehicle as a function of the position of the support mechanism. Best Mode for Carrying out the Invention [0071] With reference to Figure 1, numeral 1 indicatcs a saddlc-typc vehicle. [0072] In the embodiment shown, the saddle-typc vchicic is a motorcycle. Alternatively, the saddle-typc vchicic is a scooter. [0073] In the following of the present description, expressions like -front", -rem', -bottom", '`upwardly" and "downwardly" are used with reference to a normal advancing direction and operative position of motorcycle 1 shown in the attached Figures. [0074] Motorcycle 1 substantially commises: [0075] - a body 2; [0076] - a fi-ont wheel 3 and a rem- wheel 4; and [0077] - a support mechanism 35, for supporting a front windscreen 6 at a plurality of ad- 8 justablc positions with respect to body 2. [0078] -In dctail, support mcchanism 35 comprises (Figures 2a, 2b, 3 to 8): [0079] - a stationary frame 5, which is fixed to body 2 through first known and not-shown connecting mcans; [0080] - windscreen 6; and [0081] - an adjustable frame 7, which is fixed to windscreen 6, by the use of second known and not-shown connecting tneans. [0082] -In the embodiment shown, adjustable frame 7 is made of plastic. [0083] Stationary frame 5 comprises a bottorn main body 5a and a pair of arms Sb, which protrude upwardly from body Sa and arc spaccd from one another. [0084] Similarly, adjustable frame 7 comprises a bottom main body 7a and a pair of arms 7b, which protrudc upwardly from body 7a and arc spaccd from one another. [0085] Bodies 5a, 7a arc superimposed on one another. Arms 5b, 7b arc superimposcd on one another. [0086] Furthermore, as shown in Figures 5 to 8. stationary frame 5 comprises guides 8, 9 and 10, extending longitudinally to stationary frame 5. and parallel to a direction X. [0087] Adjustablc frame 7 comprises a plurality of slidcrs 11, 12, 13, three in the cm- bodiment shown, which arc slidably mountcd parallel to direction X insidc relative guides 8,9, 10. [0088] Tt is also possible to define an axis Y. perpendicular to direction X and to framcs 5, 7 and an axis Z, perpendicular to direction X and to axis Y. Axes Y and Z define a plane P. [0089] When sliders 11, 12, 13 are engaged with the corresponding guides 8,9 and 10, ad- justable frame 7 can slide with respect to stationary frame 5 along direction X. [0090] Since windscreen 6 is fixed to adjustable frame 7, windscreen 6 moves integrally with adjustable frame 7. [0091] Sliders 11 and 12 protrude from respective arms 7b of adjustable trame 7 towards stationary frame S. Guides 8, 9 are formed within respective arms 5b of stationary frame S. [0092] Slider 13 protrudes from main body 7a and guide 10 is formed within main body 5a. [0093] In particular, sliders 11 and 12 are provided with a through hole 16 each, extending parallel to axis Z (Figure 7). [0094] Guides 8, 9 and 10 are shaped like rectangles, having a certain length, measured parallel to direction X and a certain width, measured parallel to axis Z. Therefore, guides 8, 9 and 10 are flat and toothless. [0095] Furthermore, slider 13 is provided with a stopper 38 at its side facing stationary frame S. As shown in Figures 5 to 8, stopper 38 is integral with slider 13 and it is larger than the width of guide 10. 9 [0096] -In greater detail, when slidcrs 11, 12, 13 arc engaged with the corrcsponding guides 8,9 and 10, stopper 38 protrudcs from guide 10, whilc being in contact with stationary frame 5, as shown in Figures 5, 6 and 8. [0097] Thanks to stopper 38, when adjustable frame 7 is movcd with respect to stationary frame 5 parallel ta direction X, adjustable frame 7 is prevented from being disengaged from stationary frame 5. [0098] The length of guides 8,9, 10 &fines the strokc length of windscreen 6 along direction X. [0099] Advantagcously, support mcchanism 35 comprises a handlc 14 (Figures 3, 4, 9, 10), which is intcgrally movablc with adjustablc frame 7; handlc 14 comprises cngaging means 15 and is selectively movablc in a plurality of locking positions L (one of which shown in Figures 4, 10), in which cngaging means 15 lock adjustablc frame 7 on stationary frame 5 or in a plurality of unlocking positions U (one of which is shown in Figures 3, 9) in which cngaging means 15 leave free thc [nover-rient of adjustable frame 7 with respect to stationary frame 5. [0100] -In particular, for cach position of adjustable framc 7 along direction X. it is possible to identify a locking position L and a relative unlocking position U of handl° 14. [0101] -In dctail, handlc 14 comprises: [0102] - a grip portion 14a, which can be held with a single hand by the rider; and [0103] - a pair of amis 14b protruding from the grip portion 14a and hinged to respective holes 16 with two pins 18 about axis Z. Consequently, handle 14 can be switched from the locking position L to the unlocking position U, by its rotation about axis Z. [0104] In the embodiment shown, engaging means 15 comprise two cams 32, 33, spaced from one another (Figures 3, 4). [0105] In particular, cams 32, 33 are integral with handle 14, therefore they are rotatable about axis Z as well. [0106] In other words, handle 14, cams 32, 33 and adjustable frame 7 form a single assembly. [0107] Support mechanism 35 further comprises elastic means 19 which are interposed between respective cams 32, 33 and stationary frame 5. In the embodiment shown, elastic means 19 comprise a pair of springs 17, associated to respective cams 32, 33 (Figures 3, 4, 9, 10). [0108] Preferably, springs 17 are part of the same single assembly made of handle 14, cams 32, 33 and adjustable frame 7. [0109] As it will be evident from the foregoing of the present description, cams 32, 33 are frictionally fitted against stationary frame 5 with a tangential force T. Value Tl of tangential force T is higher than a threshold value TO and is parallel to direction X, when handle 14 is in the locking position L, so as to keep locked stationary frame 5 and adjustablc frame 7 tonne anothcr (Figure 10). [0110] When handlc 14 is in the unlocking position U, stationary framc S exerts on cams 32, 33 a value T2 of tangential force T, which is lower than the thrcshold value TO, so as ta render adjustablc framc 7 freely movable along direction X with respect to stationary framc 5 (Figures 3 and 9). [0111] In particular, each cam 32, 33 &fines respective end positions of corresponding arms 14b of handlc 14, which arc opposite to grip portion Ma. [0112] In dctail, each cam 32, 33 comprises: [0113] - a profile 34, which contacts the relative spring 17; and [0114] - a profile 37, which rcmains substantially dctached from relative spring 17. [0115] Profiles 34 and 37 of each cam 32, 33 arc sharply jointcd, in the cmbodiment shown, in an cdgc 39, parallel to axis Z. [0116] Profiles 34, 37 eccentrically extend about axis Z of relative cams 32, 33. [0117] In the embodiment shown, each cam 32, 33 furthcr comprises a respective &tent 36. When handlc 14 is in the locking position L, detcnts 36 arc in contact with slidcrs 11, 12. [0118] Detcnts 36 arc uscd to prevent handlc 14, when rotating from the unlocking position U towards the locking, position L, from rotating bcyond the locking position L. [0119] In particular, each spring 17 has a prevalent extension parallel to direction X. [0120] Each spring 17 comprises (Figures 9 and 10): [0121] - a pair of portions 17a, contacting stationary frame 5 at spaced locations parallel to direction X; [0122] - an interaction portion 171,, contacting relative cam 32, 33 and interposed between respective portions 17a along direction X; and [0123] - a pair of curved portions 17c, each interposed between respective poilions 17a and respective interaction portion 17b along direction X. [0124] In an undeformed condition of springs 17, interaction portions 17b are interposed between respective cams 32, 33 and stationary fi-ame 5 along axis Y and substantially extend parallel to direction X. [0125] In the undetbrmed condition, each spring 17 extends symmetrically with respect to plane P. [0126] In the undeformed condition, curved portion 17c of each spring 17 protrude from in- teraction portion 17b towards handle 14. [0127] Furthermore, springs 17 comprise respective openings 17d, through which sliders 11, 12 pass. [0128] In detail, cams 32, 33 exert on relative springs 17 normal forces N, parallel to axis Y. [0129] In particular, when handle 14 is set in the locking position L, nonnal force N is equal to a value Ni (Figures 10 and 11). 11 [0130] As a consequence of the normal force N and of the consequent clastic deflection of springs 17, springs 17 in turn exert a furthcr force on stationary framc 5 at the contact points between springs 17 and stationary framc 5. [0131] This furthcr force has, duc to the friction, a component parallel to direction X which is opposite and cqual in amplitude with respect to tangential force T. [0132] Differently, when handle 14 is set in the unlocking position U, normal force is cqual to a value N2 (Figures 9 and 11). [0133] in the embodiment shown, when handle 14 k set in the unlocking position U, cams 32, 33 are spaccd from stationary framc 5 and value T2 is substantially null (sec Figures 3 and 9). [0134] in furthcr dotai', the thrcshold value TO is the minimum value of the tangential force T that stationary &mue 5 nceds to mea on springs 17, as an indirect consequence of the normal force N that cams 32, 33 men on relative springs 17, so as to frictionally keep adjustable framc 7 against stationary framc 5. This Encans that value T1 of tangential force T is highcr than or cqual to the rcsultant of external forces which act on support mcchanism 35 having a componcnt directed downwardly parallel to direction X, such as a wcight force. [0135] Cams 32,33 and respective springs 17 arc shapcd in such a way that normal force N exerted by cams 32,33 on relative springs 17 follows the trend of the graph of Figure 11. [0136] In particular, the graph of normal force N comprises an increasing stretch 25, as handle 14 moves from the unlocking position U towards an intermediate position S (not shown in Figures 9 and 10), which is an-anged between the locking position L and the unlocking position U. [0137] Furthermore, the graph of normal force N comprises a decreasing stretch 26, as handle 14 moves from inteimediate position S to the locking position L. [0138] In the embodiment shown, profile 34 of each cam 32, 33 contacts a relative spring 17 on a fu-st and/or on a second side 34a, 34b of plane P (respectively bottom side and top side with reference to Figures 9 and 10), opposite to each other. [0139] When handle 14 is in the unlocking position U (Figures 3 and 9), profile 34 of each cam 32, 33 interacts with interaction portion 17b of relative spring 17 mostly on the first side 34a of plane P. Conversely, when handle 14 is in the locking position L (Figures 4 and 10), profile 34 of each cam 32, 33 interacts with interaction portion 17b of relative spring 17 mostly on the second side 34b of plane P. [0140] As shown in Figures 9 and 10, profile 34 of each cam 32, 33 approaches stationary frame 5 parallel to axis Y when, in use, handle 14 moves from unlocking position U to intermediate position S, so as to increase the elastic detlection of springs 17 parallel to axis Y. 12 [0141] In this condition, as the clastic deflection increases, the distances d of stationary framc 5 from respective interaction portions 17b parallel to axis Y &creuse from a value dl (Figure 9) to a value d2 (not shown). [0142] Similarly, profile 34 of each cam 32,33 movcs away from stationary framc 5 parallel to axis Y when, in use, handle 14 [noves from intermediate position S to locking, position U, so as to &creuse the clastic deflection of springs 17 parallel to axis Y. [0143] Accordingly, as the clastic deflection decreases, distances d increase from value d2 to a value d3 (Figure 10). [0144] In the embodiment shown, value d2 is highcr than values dl, d3 of distances d parallel to axis Y. [0145] Preferably, when handle 14 is in the intermediate position S, profile 34 extends sym- metrically with respect to plane P and normal force N is cqual to a maximum value Nmax (Figure 1 1 ). [0146] As an indirect consequence of the fact that cams 32, 33 mort on springs 17 the maximum value of normal force N, stationary fratrie 5 exerts on springs 17 a carresponding maximum value Tmax of tangential force T, which is highcr than the thrcshold value TO. Nmax corresponds to the maximum value between the increasing strctch 25 and the decreasing strctch 26 of normal force N of the graph of Figure 11. [0147] With reference to Figure 10, consequently to the action of normal forces N having value N1 actcd by relative cams 32, 33 on respective interaction portions 17b when handle 14 is in the locking position L, interaction portions 17b exert on respective cams 32, 33 respective first reaction forces FI at the contact points between respective cams 32, 33 and springs 17 parallel to axis Y and directed towards cams 32, 33. First reaction forces FI have equal amplitude and opposite direction with respect to relative normal forces N having respective values NI. [0148] Axis Z is offset from the lines of action parallel to axis Y of first reaction forces Fi. Therefore, a first moment ami_ bl can be measured between the line of action of each first reaction force Fi and axis Z. As a result, first reaction forces FI generate respective first torques MI (anticlockwise with reference to Figure 10), thus elastically keeping handle 14 in the locking position L. [0149] In a similar manner (Fig. 9), consequently to the action of the normal force N with value N2 acted by cams 32, 33 on relative interaction portions 17b when handle 14 is at the unlocking position U, interaction portions 17b exert on cams 32, 33 relative second reaction forces F2, parallel to axis Y. [0150] Also in this condition, axis Z is offset from the lines of action parallel to axis Y of the second reaction forces F2. Therefore, a second moment arm b2 can be measured between the line of action of each second reaction force F2 and axis Z. As a result, second reaction forces F2 generate respective second torques M2 (clockwise with 13 reference to Figure 9), which clastically keep handl° 14 in the unlocking position U. [0151] -In the embodiment shown, first and second torques Ml, M2 arc opposite to one another. [0152] More gencrally, a gencric moment ami can be ineasured between axis Z and the une of action of a gencric rcaction force that cach spring 17 acts on respective cam 32, 33, parallel to axis Y, when handlc 14 is in one of the continuously consecutive positions between unlocking position U and locking position L, except for the intermediate position S. [0153] Therefore, while handlc 14 is in one of the continuously consecutive positions from locking position L to intermediate position S, two first gcncric torques act on handlc 14, tcnding to clastically bring back handlc 14 in the locking position L. [0154] Sitnilarly, while handlc 14 is in one of the continuously consecutive positions from intermediate position S to unlocked position U. two second gcncric torques act on handlc 14, tending to clastically bring handlc 14 in the unlocking position U. [0155] -In use, the operation of support mcchanism 35 is described as of a condition of Figure 2a, in which windscreen 6 is at a first height with respect to body 2 and handlc 14 is in locking position L. [0156] -In ordcr to adjust the height of windscreen 6 with respect to body 2, the user se- lectively rotatcs handlc 14 about axis Z between the locking position L and the unlocking position U (Figures 3, 4, 9, 10), passing through the intermediate position S. Cams 32, 33 rotate integrally with handle 14. [0157] At this stage, the rider moves handle 14 along direction X with respect to stationary frame 5. In this way, the rider arranges windscreen 6 in one of the continuously consecutive positions which corresponds to a desired height of windscreen 6 (Figure 2b), within the stroke length of windscreen 6. [0158] Once windscreen 6 has been positioned at the desired height, the rider rotates handle 14 from the unlocking position U towards the locking position L. [0159] In greater detail, while handle 14 is in the unlocking position U, profiles 34 of each cam 32, 33 interact with respective springs 17 mostly on the first sicle 34a of plane P, and stationary frame 5 exerts on springs 17 respective tangential forces T having values T2 (Figure 9). [0160] While handle 14 is in the unlocking position U, distances d of stationary frame 5 from respective interaction portions 17b are equal to first value dl. [0161] Since values T2 are lower than the threshold value TO, cams 32, 33 are not fric- tionally fitted against stationary trame 5. Therefore, as long as handle 14 is in unlocking position U, adjustable trame 7 can be still slid along direction X. [0162] In addition, while the rider moves handle 14 along direction X with respect to stationary frame 5, torques M2 generated by respective springs 17 contribute to 14 elastically keep handle 14 in the unlocking position U. [0163] Furthermore, thanks to stopper 38, when the rider movcs handle 14 with respect to stationary fratrie 5 along direction X, adjustable framc 7 can be prevented from bcing disengaged from stationary frame 5. [0164] When handle 14 is rotated from the unlocking position U towards the intermediate position S, the normal forces N actcd by cams 32, 33 on relative springs 17 increasc from the value N2 up to die maximum value Nmax (along the incrcasing stretch 25 of the graph of Figure 11). [0165] When handle 14 is in the intermediate position S, distances d reach the value d2 and profile 34 preferably cxtends symmetrically with respect to plane P. [0166] When handle 14 is rotated from the intermediate position S to the locking position L, the normal forces N exertcd by cams 32, 33 on relative springs 17 decrease from the maximum value Nmax to the values N1 (along the dccreasing strctch 26 of the graph of Figure 11). Accordingly, distances d of stationary framc 5 from respective interaction portions 17b increase to third value d3. [0167] When handle 14 is in the locking position L. the values of the normal forces N acted by cams 32, 33 on relative springs 17 arc cqual to NI. The corresponding values Tl of tangential forces T. which stationary framc S exerts on springs 17 exceed the thrcshold value TO. [0168] Stationary framc 5 and adjustable fratrie 7 are therefore frictionally fitted. Thus, windscreen 6 is prevented from moving from the desired height. [0169] Furthermore, profiles 34 interact with relative springs 17 mostly on second side 34b of plane P. [0170] Thus, first torques MI generated by relative springs 17, elastically tend to keep handle 14 in the locking position L. Thanks to first torques MI, handle 14 is prevented from rotating undesirably from the locking position L. [0171] In addition, when handle 14 is in one of the continuously consecutive positions from locking position L to intermediate position S, the first generic torques generated by relative springs 17 act on handle 14, tending to elastically bring back handle 14 in the locking position L. [0172] Furthermore, when handle 14 is in the locking position L, detents 36 abut on re- spective sliders 11, 12, thus preventing handle 14 to rotate beyond locking position L. [0173] The advantages of support mechanism 35 and of the method of adjusting the height of windscreen 6 will be clear from the above description. [0174] In particular, adjustable trame 7 can be moved and locked with respect to stationary frame S by respectively moving handle 14 with respect to stationary ti-ame 5 and by rotating handle 14 about axis Z. [0175] Therefore, it is possible to adjust the height of windscreen 6 with respect to stationary frame 7 by casily acting on handle 14. [0176] These operations on handle 14 can be carricd out by the rider in one movement. [0177] ln this way, differently from the known solution described in the introductory part of the description, it is possible to conveniently to adjust the height of windscreen 6 by using only one hand. [0178] The fixing of adjustablc frame 7 to stationary frame 5 is thus made significantly more comfortable, because the rider is no longer required to fastcn or to unfastcn any adjustment nuts. [0179] Furthermore, sincc the movemcnt of adjustment frame 7 with respect to stationary frame 5 is obtaincd by sitnply sliding sliders 11, 12, 13 in respective guides 8,9, 10, which arc flat and toothlcss, windscreen 6 can be adjustcd at any one of the continuous hcights within its strokc lcngth. [0180] ln othcr words, handlc 14 is configured to perform the saine engaging function of teeth and rccesses disclosed in EP-A-3192729, when set in the locking position, for cach of the infinitc hcights at which windscreen 6 may be positioncd within its strokc length. [0181] The adjustment of the height of windscreen 6 with respect to stationary frame 5 is thus made significantly more appropriatc and accuratc, because the rider bas no longer the restriction to position windscreen 6 in fcw discretc positions only. [0182] ln this way, differently from the known solution described in the introductory part of the description, it is possible to conveniently adjust the height of windscreen 6 in the optimal position, which best suits the necessities of the rider and the intention to limit the aerodynamic drag. [0183] Furthermore, it is possible to take advantage of the tact that springs 17 are interposed between relative cams 32, 33 and stationary frame 5. [0184] In particular, the elastic action of springs 17 is effective in recovering the inevitable production tolerances which affect the sizes of profile 34, of stationary frame 5 and of adjustable frame 7 parallel to direction Y. [0185] Furthermore, springs 17 prevent the damaging of profile 34 and of stationary frame when handle 14 is in intermediate position S, in which cams 32, 33 exert the maximum normal force Nmax on relative springs 17, by compensating the rigidity of the parts in contact (34, 5). [0186] Springs 17 are used as well in order to avoid a direct contact between handle 14 and stationary frame 5, thereby lirniting wear of these two parts. [0187] Furthermore, springs 17 elastically load engaging means 15 towards locking position L, when handle 14 is set in locking position L and elastically load engaging means 15 towards unlocking position U, when handle 14 is set in unlocking position U. [0188] As a result, the locking position Lis a stable equilibrium position, because when 16 handlc 14 is slightly displaccd from locking position L, it clastically tends to rcturn to locking position L. [0189] This is highly advantagcous, because handlc 14 could be accidcntally slightly displaccd from the locking position L, for instance duc to vibrations or irregularities of the road surface. [0190] Finally, it is apparent that modifications and variants not dcparting from the invention tnay be made to support rnechanism 35 and method discloscd herein. [0191] In particular, support tnechanism 35 could not comprise springs 17. In this case, cams 32, 33 and stationary framc S would be in direct contact when handlc 14 is in the locking position L. whilc thcy would be preferably spaccd apart when handlc 14 is in the unlocking position U. [0192] Furthermore. whilc handlc 14 is in unlocking position U and/or in intermediate position S, springs 17 could be elastically dcflected, so that respective portions 17b could bc in direct contact with stationary framc 5 and value d3 would be null. [0193] Furthermore. cams 32,33 could be configurcd in such a way that profiles 34,37 do not converge in respective edges 39, but towards furthcr profiles, extended parallel to direction X. [0194] Finally, when handlc 14 is in intermediate position S, REVENDICATIONS1. A support mechanism (35) for height adjustably supporting a windscreen (6) on a saddlc-typc vehicle (1), comprising: - a first stationary frame (5), which is fixablc to a body (2) of said vehicle (1); - said windscreen (6); and - a second adjustable frame (7), which is fixcd to said windscrcen (6) and is slidable with respect to said first stationary framc (5); characterized by comprising a handle (14), which is integrally movable with said second adjustable frame (7) and comprises engaging means (15); said handle (14) being selectively movable in: - at least one locking position (L), in which said engaging means (15) lock said second adjustable frame (7) on said first stationary frame (5), thus fixing said windscreen (6) at a desired height with respect to said first stationary frame (5); or in - at least one unlocking position (U), in which said engaging means (15) leave free the movement of said second adjustable fraine (7) with respect to said first stationary fratrie (5). 2. The support mechanism of claim 1, characterized in that said engaging means (15) are frictionally fitted against said first stationary fnune (5) with a first value (Ti) of a locking force (T) greater than a threshold value (TO) and directed parallel to a sliding direction (X) of said second adjustable fnune (7) with respect to said first stationary frame (5), when said handle (14) is set, in use, in said at least one locking position (L); said engaging means (15) exerting, in use, a second value (T2) of said locking force (T) lower than said threshold value (TO) or null, when said handle (14) is set, in use, in said at least one unlocking position (U). 3. The support mechanism of claim 1 or 2, characterized in that said engaging means (15) are spaced from said first stationary frame (5), when said handle(14) is set., in use, in said at least one unlocking position (U). 4. The support mechanism of any one of the foregoing claims, characterized by comprising elastic means (19), which are interposed between said engaging means (15) and said first stationary frame (5). 5. The support mechanism of claim 4, characterized in that said elastic 18 [Imans (19) clastically load, in use, said handle (14) towards said at least one locking position (L), when said handle (14) is set in said at least one locking position (L); and/or in that said clastic means (19) clastically load, in use, said handlc (14) towards said at least one unlocking position (U), when said handlc (14) is set in said at least one unlocking position (U). 6. The support mcchanism of claim 4 or 5, characterized in that said cngaging mcans (15) and clastic mcans (19) arc configurcd in such a way that a graph of a furthcr force (N) actcd, in use, hy said cngaging [Imans (15) on said clastic means (19), orthogonally to said sliding direction (X), comprises a first incrcasing strctch (25), as said handlc (14) movcs, in use, from said at least one unlocking position (U) towards an intermediate position (S), which is arrangcd hetween said at least one locking position (L) and said at least one unlocking position (U). 7. The support niechanism of claim 6, characterized in that said graph comprises a second decreasing strctch (26) suhsequent to said first incrcasing strctch (25), as said handle (14) movcs, in use, from said intermediate position (S) to said at least one locking position (L). 8. The support niechanism of claims 2 to 7, characterized in that said engaging means (15) comprise at least one cam (32, 33); said at least one cam (32, 33) being frictionally fitted against said first stationary frame (5) with said first value (Ti) of said locking force (T) greater than said tlu-eshold value (TO) and directed parallel to said sliding direction (X) of said second adjustable frame (7) with respect to said first stationary frame (5), when said handle (14) is set, in use, in said at least one locking position (L); said at least one cam (32, 33) exerting, in use, said second value (T2) of said locking force (T) lower than said threshold value (TO) or null, when said handle (14) is set, in use, in said at least one unlocking position (U). 9. The support mechanism of claim 8, when depending on any one of claims 4 to 7, characterized in that said at least one cam (32, 33) is rotatable about an axis (Z), transversal to said direction (X) and parallel to said stationary frame (5), and comprises a profile (34) contacting said elastic means (19); said profile (34) interacting with said elastic means (19) mostly on a first sicle (34a) of a plane (P), when said handle (14) is set, in use, in 19 said at least one locking position (L); said profile (34) interacting with said clastic Enclins (19) mostly on a second side (34b), opposite to said first side (34a), of said plane (P), when said handle (14) is set, in use, in said at least one unlocking position (U); said plane (P) being defined by said axis (Z) and by a further direction (Y) orthogonal to said sliding direction (X) and said axis (Z); said at least one cam (32, 33) being movablc from said first sidc (34a) towards said second side (34b), when said handle (14) moves, in use, from said at least one unlocking position (U) to said at least one locking position (L). 10. The support tnechanisrn of claim 9, when depending on claims 6 to charactcrized in that said profile (34) symmetrically extcnds with respect to said plane (P) whcn said handl° (14) is in said intermediate position (S). 11. The support tnechanisrn of claim 9 or 10, characterized in that said clastic mcans (19) comprise at least one spring (17); said at least one spring (17) comprising: - two first portions (17a) contacting said first stationary trame (5); and - a second interaction portion (17b), interposcd between said first portions (17a) and contacting, in use, said profile (34). 12. The support mechanism of any one of claims 8 to 11, characterized in that said handle (14) comprises two cams (32, 33) spaced from one another, and by comprising a pair of said springs (17) interposed, each, between a relative cam (32, 33) and said first stationary trame (5). 13. The support mechanism of any one of the foregoing claims, char- acterized in that when said handle (14) is set, in use, in said at least one unlocking position (U), said windscreen (6) can be moved among a plurality of continuously consecutive positions with respect to said first stationary frame (5); said windscreen (6) being locked, in use, in a desired one of said continuously consecutive positions, when said handle (14) is set in a respective said locking position (L). 14. The support mechanism of any one of the foregoing claims, char- acterized in that said first stationary frame (5) comprises a plurality of flat guides (8, 9, 10) and said second adjustable frame (7) comprises a plurality of sliders (11, 12, 13); said sliders (11, 12, 13) being engaged in respective said flat guides (8, 20 9, 10); said slidcrs (11, 12, 13) bcing slidable in respective said flat guides (8, 9, 10) among a plurality of continuously consecutive positions of said flat guides (8,9, 10), when, said second adjustable frame (7) slides, in use, with respect to said first stationary frame (5). 15. A saddle-type vehicle (1) comprising a body (2) and a support mcchanism (35) according to any one of the forcgoing claims. 16. A method of adjusting the height of a windscreen (6) of a saddle-type vehicle (1) with respect to a body (2) of said vehicle (1), comprising the stcps of: i) fitting a first stationary frame (5) of a support mcchanism (35) to said body (2); and ii) adjusting the position of a second adjustablc frame (7) of said support mcchanism (35) with respect to said first stationary frame (5); characterized by comprising the furthcr stcps of: iii) selectively moving a handle (14) between: - at least one locking position (L) in which engaging means (15) defined by said handle (14) lock said second adjustable framc (7) on said first stationary frame (5), thus fixing said windscreen (6) at a desired height; and - at least one unlocking position (U) in which said engaging means (15) leave free the movement of said second adjustable frame (7) with respect to said first stationary frame (5). 17. The method of claim 16, characterized by comprising the steps of: iv) ti-ictionally fitting said engaging means (15) against said first stationary frame (5) with a first value (T1) of a locking force (T) greater than a threshold value (TO) and directed parallel to a sliding direction (X) of said second adjustable frame (7) with respect to said first stationary frame (5), when said handle (14) is set in said at least one locking position (L); and y) exerting a second value (T2) of said locking force (T) lower than said tlu-eshold value (TO) or null by means of said engaging means (15) on said first stationary frame (5), when said handle (14) is set in said at least one unlocking position (U). 18. The method of claim 16 or 17, characterized by comprising a step vi) of spacing said engaging means (15) from said first stationary fine (5), when said handle (14) is set in said at least one unlocking position (U). 19. The method of any one of claims 16 to 18, characterized by comprising 21 the stops of: vii) clastically loading said handlc (14) towards said at least one locking position (L), when said handlc (14) is in said at least one locking position (L); and/or viii) clastically loading said handlc (14) towards said at least one unlocking position (U), when said handlc (14) is in said at least one unlocking position (U); said stops vii) and/or viii) [ming carried out by means of clastic means (19). 20. The method of claim 19, characterized by comprising the step ix) of cxerting a furthcr force (N) by nicans of said cngaging means (15) on said clastic means (19) orthogonally to said sliding direction (X); a graph of said furthcr force (N) comprising a first incrcasing strctch (25), as said handlc (14) [noves from said at least one unlocking position (U) towards an intermediate position (S), which is arrangcd betwcen said at least one locking position (L) and said at least one unlocking position (U). 21. The method of claim 20, characterized in that said graph comprises a second decrcasing strctch (26) subsequent to said first incrcasing strctch (25), as said handlc (14) movcs from said intermediate position (S) to said at least one locking position (L). 22. The method of any one of claims 19 to 21, characterized by comprising the steps of: x) rotating about an axis (Z) at least one cam (32, 33) of said engaging means (15); saki axis (Z) being transversal to said direction (X) and parallel to said stationary frame (5); xi) contacting at least one spring (17) of said elastic means (19) interposed between said at least one cam (32, 33) and said first stationary frame (5) by means of a profile (34) of said at least one cam (32, 33); said step xi) comprises the steps of: xii) contacting a portion (17b) of said at least one spring (17) by means of said profile (34) mostly on a first side (34a) of a plane (P), when said handle (14) is in said at least one locking position (L); xiii) contacting said portion (17b) of said at least one spring (17) by means of said profile (34) mostly on a second side (34b), opposite to said first sicle (34a), of said plane (P), when said handle (14) is in said at least one unlocking position (U); said plane (P) being defined by said axis (Z) and by a further direction (Y) orthogonal to said sliding direction (X) and said axis (Z); and xiv) moving said at least one cam (32, 33) from said first sidc (34a) towards said second sidc (34b), when said handlc (14) myes from said at least one unlocking position (U) to said at least one locking position (L). 23. The method of claim 22, characterized by comprising the step xv) of arranging said profile (34) symmetrically with respect to said plane (P) when said handlc (14) is in said intermediate position (S). 24. The method of claim 22 or 23, when depending on claim 20 or 21, characterized by comprising the stcps of: xvi) increasing a maximum clastic dcflection of said portion (17b) of said at least one spring (17) parallel to said further direction (Y), when said handlc (14) movcs from said at least one unlocking position (U) to said intermediate position (S) and said profile (34) approachcs said first stationary framc (5) along said further direction (Y); and/or xvii) decreasing said maximum clastic deflection of said portion (17b) of said at least one spring (17) parallel to said further direction (Y), when said handlc (14) [noves from said intermediate position (S) to said at least one locking position (L) and said profile (34) [noves away from said first stationary frame (5) along said further direction (Y). 25. The method of any one of claims 16 to 24, characterized by comprising the steps of: xviii) moving said windscreen (6) among a plurality of continuously consecutive positions with respect to saki first stationary frame (5), when said handle (14) is in said at least one unlocking position (U); and xix) locking said windscreen (6) in a desired one of said continuously consecutive positions, when said handle (14) is set in a respective said locking position (L).