FR2846889A1 - Skateboard has at least one wheel axle mounted on leaf spring to allow controlled movement of axle - Google Patents

Abstract

The skateboard has a board (1) with at least two axles (2) each with wheels (21) at their ends. A leaf spring (3) carries one axle (2) at its end, with the other end attached to the board via a support (31). The spring extends mainly horizontally and is deformable in a plane parallel to that of the board.

Description

e- Skateboard with at least one of the axles carried by a

leaf spring.

  The invention relates to the field of sports and leisure. More specifically, the invention relates to a skateboard, of the type comprising a plate under which two sets of casters are mounted. In the field of skateboards, the front and rear roller trains are traditionally mounted on articulations, called "trucks", making it possible to execute turns when the user imposes an inclination

lateral to the plate.

  To start a movement of the board, or to make it take some

  speed, the user generally maintains one foot on the board while with the other foot he pushes successively on the ground. Experienced users also use another technique which consists in lifting the front of the board (the front axle no longer being in contact with the ground) then in imposing a pendulum movement.

  Another type of skateboard is also known, described in document GB - 2 318 519, according to which the wheels are mounted at the ends of articulated arms on the board, the articulations in question being composed - for the rear axle: two ball joints; - for the front axle: five ball joints defining a deformable parallelogram. In this way, the inclination of the board can be achieved around

  several axes, making it possible in particular to raise the front of the board during a turn (the wheels remaining in contact with the ground) and to restore propellant energy when returning to straight travel.

  Also the user can print on the board a pendulum movement during which the front of the board rises and falls successively in order to initiate a movement, then to gain speed, this without being

  necessary to directly push on the ground.

  However, from a practical point of view, the combination of movements that the user must perform is relatively complex, the latter having to impart a pendulum movement both laterally and back and forth, which requires

  a strong sense of balance that is not within the reach of any user.

  On the technical level, this solution also has several drawbacks.

  First, the solution described is of relatively complex design.

  Indeed, the wheelsets are coupled to a large number of articulations which results in: - a significant assembly time; - the manufacture of specific mechanical parts;

  - the need to make adjustments.

  This has a direct consequence on the cost price of such a skateboard. In addition, the numerous joints are subject to contamination and to wear which quickly adversely affects the proper functioning of the assembly. At the very least, regular maintenance is necessary to ensure lubrication

  satisfactory of all joints.

  The invention particularly aims to overcome the drawbacks of the prior art. More specifically, the invention aims to provide a skateboard allowing the user to propel himself by his only physical force on a horizontal ground, that is to say without the need to exercise a thrust on the ground directly by the user, and this by holding the four wheels in

contact with the ground.

  The invention also aims to provide such a skateboard which is more easily manageable in order to transmit propellant energy to it.

  compared to the solutions of the prior art.

  The invention also aims to provide such a skateboard which

  is simple in design, and which can be manufactured and assembled more easily and quickly than known solutions.

  Another object of the invention is to provide such a skateboard whose mechanical parts are simple to maintain and which are not very prone

  to the effects of possible contamination or wear.

  These objectives, as well as others which will appear subsequently, are achieved by virtue of the invention which relates to a skateboard, comprising a platform coupled to at least two axles, one said before, the other said rear, each carrying at least one wheel at each of its ends, characterized in that it comprises at least one leaf spring carrying at one of its ends one of said axles, the other of its ends being mounted fixed on support means 10 integral with said plate, said leaf spring (s) extending substantially horizontally and being deformable essentially in bending in a

  plane substantially parallel to the plane of said plate.

  In this way, the leaf spring makes it possible to transform the thrusts

  printed on the board by the user's feet in propulsive energy.

  Indeed, the user who pushes with his feet in an alternating lateral movement on the platform creates an offset of it relative to the axles (the wheels tend to stay in place because of their resistance to lateral sliding on the ground ). The leaf spring (s) then work in alternating and successive elastic flexions to the right and to the left of the longitudinal axis of the board, these successive flexions inducing alternating deviations of the axles and transforming the lateral thrusts of the user into force of propulsion (the axles having a decomposed movement similar to that of a skater's step).

  According to a preferred solution, the board comprises two leaf springs, one carrying said front axle, the other carrying said rear axle.

  Thus, two different movements of the user can cause the advancement of the board: that indicated above and another consisting of pushing with the feet on the plate to offset it on either side of its longitudinal axis. Such a movement tends to tilt the platform slightly towards the inside of the curve of its trajectory, the respective movements of the user and the board being similar to that of a cyclist in "dancer" and of his bicycle or

  of a surfer and his surf during a succession of turns.

  Also, the plate being inclined relative to the ground while the wheels remain in contact with the ground, the leaf springs work in elastic torsion combined with alternating flexions and impart to the axles movements similar to skaters' steps, the axles having substantially parallel movements. The user can therefore choose between two techniques for advancing the board: one according to which he performs a movement of the body and feet which can be compared to the dance of the "twist", the other according to which he performs a

  body and feet movement close to that of a surfer during a turn.

  Furthermore, the leaf springs which constitute the basis of the invention prove to be a technical solution responding to a completely new approach compared to conventional solutions of "trucks" or articulations put in place.

  work in the skateboard described in GB - 2 318 519.

  The advantages of the invention are numerous.

  First of all, the invention proposes a technical solution making it possible to offer new perspectives for the use of skateboards, as mentioned previously. Then, on the technical level, the proposed solution is simple to manufacture and

  mount, without the need for complex adjustments.

  In addition, the leaf springs are not sensitive to the effects of possible fouling, are not subject to wear phenomena and do not involve any risk of jamming requiring special maintenance such as regular lubrication.

(unlike the joints).

  According to a first embodiment, said two leaf springs extend

  substantially in the extension of one another, in a plane orthogonal to that of said plate and passing through the longitudinal axis of said plate.

  One obtains with such an arrangement, a board substantially symmetrical with respect to its longitudinal axis, and on which the user finds a position of equilibrium essentially by placing his feet in alignment with the axis

longitudinal of the board.

  According to a second embodiment, said two leaf springs extend parallel to the longitudinal axis of said plate, substantially equal

  distance on either side of said longitudinal axis of said plate.

  According to this arrangement, the user is encouraged to place his feet on the board along a line slightly across the longitudinal axis of the board. This embodiment is therefore more particularly intended for a mode of use according to which the user produces movements similar to those

  a surfer during the turns, as mentioned above.

  According to either of these embodiments, the skateboard

  preferably comprises means for maintaining said axle (s) at a substantially constant distance from said plate.

  This avoids subjecting the leaf springs to overhang, these forces being able to be all the more substantial as the length of the

leaf springs increases.

  In this case, said holding means advantageously comprise at least one roller carried by said axle (s), said roller (s) being intended to move in contact with said tray or with a track secured to said tray. In this way, the rollers remain permanently in contact with the plate or

  the track secured to the plate, constantly ensuring that the leaf springs 25 are kept in a horizontal position.

  It is noted that, according to another possible embodiment, the track could

  be carried by the axle and the rollers mounted on the platform.

  According to yet another possible embodiment, the track and the one or more

  corresponding rollers could be positioned along the length of the leaf springs.

  Preferably, said track extends in an arc of a circle over approximately 1700.

  Such a track keeps the leaf springs in their plane

  horizontal, including when these have significant bending.

  However, this track angle may vary as much as necessary, in particular as a function of the length of the leaf springs (this length having a direct effect on the degree of bending, for the same thickness).

  It should be noted that the track can be an insert on the plate but can also form a one-piece assembly with the plate, the latter then having

  growths corresponding to the ends of the runway.

  According to an advantageous solution, the skateboard comprises means

  shock absorbers inserted between said track and said plate.

  This ensures permanent contact between the rollers and the track, including

  understood when the platform is inclined relative to the ground.

  According to another characteristic, the skateboard comprises at least two stops on either side of said leaf spring or springs, against which

  said leaf spring or springs are liable to come into bracing.

  In this way, from a predetermined deflection in bending of the leaf spring, it comes to bear against the corresponding stop and can continue its

  bending with respect to this stop but with greater rigidity.

  The return force of the leaf spring will therefore be increased as well as, correspondingly, the propulsive energy which it transmits to the wheels of the corresponding axle. Preferably, said leaf spring or springs are made of a material having the flexural characteristics of having a deflection of approximately 70 mm under a load of approximately 16 kg applied approximately 255 mm from a fixed point.

said spring.

  A satisfactory compromise is thus obtained between the effort which the user must produce against the return effort of the leaf spring and the energy

  propellant transmitted by the leaf spring to the wheels of the board.

  According to an advantageous solution, said plate carries means for wedging the

  feet of the user of said board.

  Thus, it is easier for the user to print a movement on the platform.

  The good adhesion of the feet to the platform can also be ensured in a complementary manner by any suitable non-slip coating attached to the platform.

  According to an advantageous variant, said plate carries a handlebar.

  In this case, said handlebar is advantageously integral in rotation with said support means of said leaf spring carrying said front axle, the board with 10 rollers comprising locking / unlocking means in rotation of said

handlebar relative to said plate.

  However, we understand that a simple handlebar allowing the user to

  hold to keep balance can be expected.

  Other characteristics and advantages of the invention will appear more clearly on reading the following description of an embodiment.

  preferred of the invention, given by way of illustrative and nonlimiting example, and of the appended drawings among which: - Figure 1 is a bottom view of a skateboard according to the invention; - Figure 2 is a side view of a skateboard according to the invention, according to the broken section BB indicated in Figure 1; FIGS. 3 to 8 illustrate the breakdown of the relative movements of the plate, of the leaf springs and of the axles of a skateboard according to the invention, according to a first technique of use;

  - Figures 9 to 14 illustrate the decomposition of the relative movements of the plate, leaf springs and axles of a skateboard according to the invention, according to a second technique of use.

  Referring to Figures 1 and 2, a skateboard includes a tray

  1 carrying two axles 2 on each of which are mounted wheels 21.

  As an indication, the plate 1 has a length of between 700 mm and 1000 mm and a width of around 200 mm, these dimensions possibly depending on the morphology of the user. According to the present embodiment of the invention, each of the axles 2 is carried by one of the ends of a leaf spring 3, the other end of the spring to

  blade being fixed to the plate using the brackets 31.

  As an indication, the leaf springs have the following dimensions: 10 - length: 280 mm to 400 mm;

  - width: 20mm to 40mm; - thickness: 3 mm to 10 mm.

  Again, these dimensions may vary within the ranges indicated above or be adapted as a function of the morphology of the user, and also as a function of the material from which the leaf spring is made.

  According to the present embodiment, the leaf springs are made of a composite material comprising an epoxy resin and glass fibers (and / or

  carbon fibers according to another possible embodiment).

  It is noted, however, that the leaf springs can be made of any other material having a satisfactory modulus of elasticity and high elastic limits. Preferably, the material chosen has characteristics such that, under the effect of a load of 16 kg applied at a distance of 255 mm from the

  brackets 31, the leaf springs flex with an arrow of about 70 mm.

  As illustrated in FIGS. 1 and 2, the two leaf springs 3 extend in line with one another, in a plane orthogonal to that of the plate and

  passing through the longitudinal axis of the plate 1.

  It is however conceivable, according to another conceivable embodiment, that the two leaf springs extend parallel to the longitudinal axis of the plate 1, being substantially at equal distance on either side of the axis

longitudinal of the plate.

  Furthermore, to avoid any overhang phenomenon which could be exerted on the leaf springs 3, each axle 2 carries two rollers 22 provided to be kept in contact with a track 11 secured to the plate 1. Thus, during the bending of the leaf springs 3 in a plane parallel to the plane of the plate 1, the rollers 22 roll against the track 11 and ensure the maintenance of the

  springs in a horizontal position, without overhang.

  According to this embodiment, the track 1 1 is a piece in the form of an arc 10 of a circle extending over approximately 1700, attached under the plate 1, a plate in

  elastomeric foam 12 being interposed between each of the tracks 11 and the plate 1.

  According to a possible variant, it can be provided to bring under the plate 1 stops 13 (shown in dotted lines in Figure 1) on either side of each of the leaf springs and halfway therebetween. Such stops 15 make it possible to stiffen the corresponding leaf spring, while the latter comes

  lean against a stop while continuing to flex.

  According to another characteristic of the invention, the plate 1 carries means

  of wedging 14 of the feet of the user as well as a non-slip coating 15.

  According to another conceivable variant, a handlebar (not shown) is attached to the plate 1. An improvement of this variant consists in rendering

  integral in rotation with such a handlebar to the bracket 31 mounted at the front of the skateboard and to provide means for locking / unlocking the rotation of the handlebar relative to the plate. Thus, the user could choose to make the front axle directional or, alternatively, to keep the front end of the leaf spring fixed in order to use it for its ability to flex.

  Two techniques for using a skateboard according to the invention will now be explained in more detail using FIGS. 3 to 8, then

Figures 9 to 14.

  Beforehand, it should be noted that FIGS. 3 to 14 illustrate the decomposed and successive movements essentially of the plate, of the leaf springs and of the axles, this in order to better understand the description which will follow. The successive positions of the board with respect to a trajectory considered are therefore

  fictitious and do not necessarily correspond to reality.

  According to a starting position, illustrated by FIG. 3, in which the 5 leaf springs 3 extend in the extension of one another along the longitudinal axis of the plate 1, a first technique called "twist" consists , on the part of the user to print on the plate a movement as indicated by the arrow F1 with the aid of his front foot and a movement as indicated by the arrow F2 to

using his back foot.

  Because of the resistance to lateral sliding of the wheels on the ground, the user thus creates an offset of the plate 1 relative to the axles 2 causing the bending of the leaf springs 3 (FIG. 4), this offset and these bending going amplifying

(figure 5).

  According to this technique, the leaf springs flex inversely from one another, on either side of the longitudinal axis of the board.

  Due to the elasticity of the leaf springs 3, they tend to return gradually in the extension of one another, as illustrated by the

Figures 6 and 7.

  This return movement of the leaf springs in the extension of one another imposes a displacement in an arc of a circle of the axles 2, favoring a forward thrust (according to arrow F3) of the wheels on the ground and creating a propelling force. The user then prints on the tray movements as indicated

  by arrows F4 and F5, respectively opposite to those indicated by arrows 25 FI and F2.

  The renewal of the successive stages which have just been indicated

  allow the user to quickly gain speed.

  From the position illustrated in FIG. 9, a second technique called "offset" consists, on the part of the user in printing on the plate a movement as indicated by the arrows F6 and F7 using his two feet, this displacement being accompanied by an inclination of the plate (its straight edge on the

  Figure 10 being lower than the left edge).

  Due to the resistance to lateral sliding of the wheels on the ground, the user thus creates an offset of the plate 1 relative to the axles 2 causing the bending 5 of the leaf springs 3 (FIG. 10), this offset and these bending going s 'amplifying

(figure 11).

  According to this technique, the leaf springs flex significantly

  identical, on the same side of the longitudinal axis of the board.

  Due to the elasticity of the leaf springs 3, they tend to return gradually in the extension of one another, as illustrated by the

Figures 12 and 13.

  According to the same phenomenon as that described in the previous technique, the

  return movement of the leaf springs in the extension of one another requires a displacement in an arc of a circle of the axles 2, favoring a forward thrust (according to arrow F3) of the wheels on the ground and creating a propulsive force.

  The user then prints on the tray movements as indicated

  by arrows F8 and F9, opposite to those indicated by arrows F6 and F7.

  The renewal of the successive stages which have just been indicated

  allow the user to quickly gain speed.

Claims (11)

  1- Skateboard, comprising a plate (1) coupled to at least two axles (2), one said to be front, the other said to be rear, each carrying at least one wheel (21) at each of its ends, characterized in that it comprises at least one leaf spring (3) carrying at one of its ends one of said axles (2), the other of its ends being mounted fixed on support means (31) integral with said plate (1), said leaf spring (s) (3) extending substantially horizontally and being deformable essentially in bending in a plane substantially parallel to the plan of said plate (1).   2 - Skateboard according to claim 1, characterized in that it comprises two leaf springs (3), one carrying said front axle, the other carrying said rear axle.   3 - Skateboard according to claim 2, characterized in that said two leaf springs (3) extend substantially in the extension of one another, in a plane orthogonal to that of said plate (1) and passing by the axis longitudinal of said plate (1).   4 - Skateboard according to claim 2, characterized in that said two leaf springs (3) extend parallel to the longitudinal axis of said plate (1), substantially equidistant from either side of said axis longitudinal of said plate (1).   - Skateboard according to any one of claims 1 to 4, characterized in that it comprises means for maintaining said axle (s) (2) at a substantially constant distance from said platform (1).   6 - Skateboard according to claim 5, characterized in that said holding means comprise at least one roller (22) carried by said axle (s) (2), said roller (s) (22) being intended to move in contact said   plate (1) or a track (1 1) integral with said plate (1).   7 - Skateboard according to claim 6, characterized in that said   track (11) extends in an arc of a circle for approximately 170.   8 - Skateboard according to one of claims 6 and 7, characterized in that it comprises damping means (12) interposed between said track (11) and said tray (1).   9 - Skateboard according to any one of claims 1 to 8, characterized in that it comprises at least two stops (13) on either side of said one or more leaf springs (3), against which said or said springs to   blades (3) are likely to brace themselves.   - Skateboard according to any one of claims 1 to 9, 10 characterized in that said one or more leaf springs (3) are made in one   material having the flexural characteristics of having a deflection of approximately 70 mm under a load of approximately 16 kg applied to approximately 255 mm from a point fixed of said spring.   11 - Skateboard according to any one of claims 1 to 10, 15 characterized in that said plate carries wedging means (14) of the feet the user of said board.   12 - Skateboard according to any one of claims 1 to 11,   characterized in that said plate (1) carries a handlebar.   13 - Skateboard according to claim 12, characterized in that said handlebar is integral in rotation with said support means (31) of said leaf spring (3) carrying said front axle (2) and in that it comprises means of   locking / unlocking in rotation of said handlebar relative to said plate (1).