FR3103420A1 - SOLUTION FOR ADJUSTING THE POSITION OF A SEAT ON THE STRUCTURE OF A KART - Google Patents

Abstract

One-piece seat kart (1) with adjustable position relative to the frame of said kart, said seat (1) having a backrest (11) and a seat (12), said backrest (11) being connected by an articulation (13) to said frame and said seat (12) being carried by a support tube (14) movable relative to said frame between at least two predetermined adjustment positions. According to the proposed technique, said frame carries at least a first rack (2) defining, for each of said adjustment positions, a notch for receiving said support tube (14) and in that said seat (1) carries a lever (3) ) unlocking, having a lever rod (31) provided at one of its ends with a handle (32) and carrying or forming at a second of its ends a rotation shaft extending along an axis offset with respect to said support tube (14), said lever rod (31) cooperating with a lug extending from said support tube (14) to ensure the release of said support tube (14) from one of said notches, when said lever (3) is moved from a rest position to an unlocked position. Figure 1

Description

SOLUTION FOR ADJUSTING THE POSITION OF A SEAT ON THE STRUCTURE OF A KART

The present invention relates to the field of leisure vehicles, and in particular to karts. More specifically, the invention relates to the seats intended to be fitted to such vehicles, and more particularly to the adjustment of the position of these seats.

Such adjustable seats are usually implemented in karts intended to be used by several pilots, in particular karts rented. These adjustable seats can also be implemented in competition karts, for which a precise adjustment of the tub can be desirable, in particular to optimize the distribution of the masses.

Prior art

We know, in the field of karts, the seats permanently fixed to the structure of the kart. When it comes to a competition kart, the position is precisely adapted to the driver's morphology. On the other hand, when the kart is intended to be used by several pilots, the position of the seat is fixed at a chosen intermediate position, to the detriment of the comfort of the pilot, as soon as the latter has a different morphology from that which served as a reference.

To overcome this drawback, consideration has been given to adapting to karts systems with slideways and detents, originally intended for seats for motor vehicles. This technique effectively makes it possible to modify the position of the seat. However, it has several major drawbacks, not allowing easy and effective adaptation to karts.

In particular, these systems are complex, have a large number of parts and therefore require precise assembly which is relatively difficult. These slides are thus poorly suited to karts, both in terms of ergonomics (in particular because the seat of a kart is one-piece) and technically or economically.

Another known technique, described in document FR 2788023 filed by the applicant, consists in mounting the seat of the kart on rails, or slides. Locking means (operating like a jaw, for example), mounted on the seat and actuated by the user, allow the seat to be locked in relation to the rails.

This technique makes it possible to adjust the position of the seat relatively efficiently along the rails and makes it possible to dispense with the implementation of predetermined positions, in depth and/or in inclination, depending on the shape of the rails.

However, a drawback of this technique lies in the fact that the chosen position may not be perfectly stable. Indeed, the different positions obtained by the locking means not being indexed, there is a risk that the seat will move in an undesired manner on the rails, in particular due to the vibrations or shocks that the kart may undergo during of his move. In addition, with wear, the risk of unwanted movement of the seat on the rails is increasingly high.

In this document, a side handle is provided to actuate the locking means. However, this manipulation is often impractical, since access to the handle and/or its movement can be difficult, both for the driver installed in the seat and for a person not installed in the kart.

On certain karts currently distributed, the locking means are actuated, for locking and/or unlocking, via a strap or a handle placed between the driver's legs, and passing through the seat cushion.

The implementation of a strap or a handle located between the pilot's legs is not satisfactory. In fact, its manipulation can be difficult and/or uncomfortable, whether it is performed by the pilot himself, already seated in the seat, or by an outside party, helping the pilot to settle down.

Another disadvantage of implementing such a strap or such a side handle lies in the fact that it is not easy for the user to determine whether the locking means are actuated (unlocked position) or no (locked position) and therefore whether adjustment of the seat position is authorized or not. There is therefore a risk that the locking is not carried out, and that the driver is driving with an unsecured seat.

Whatever the known technique used among those described above, it is observed that in practice the adjustment of the position of the seat of a kart can be unsatisfactory, difficult to use and sometimes dangerous.

There is therefore a need to provide a technique for adjusting the position of a seat of a kart which can be implemented throughout the world and which is more reliable and easier to use than those of the prior art. .

The present invention makes it possible to solve at least some of the drawbacks raised by the prior art. The present technique in fact relates to a kart with a one-piece seat with an adjustable position relative to the chassis of said kart. Said seat has a back and a seat, said back being connected by an articulation to said frame and said seat being carried by a support tube movable relative to said frame between at least two predetermined adjustment positions.

According to the invention, said frame carries at least a first rack defining, for each of said adjustment positions, a notch for receiving said support tube and, said seat carries an unlocking lever, having a lever rod provided at a first of its ends a handle and carrying or forming at a second of its ends a rotating shaft extending along an axis offset from said support tube, said lever rod cooperating with a lug extending from said support tube to ensure the release of said support tube from one of said notches, when said lever is moved from a rest position to an unlocking position.

In this way, the adjustment of the position of the seat is obtained by a simple action of the user on an unlocking lever, from the rest position to the unlocking position, in order to move the support tube out of a notch. of the first rack and thus allow movement of the seat relative to the chassis of the kart.

As will appear later more clearly, the mechanism of the invention implements an unlocking handle: it is in fact only used for unlocking, and resumes a rest position as soon as it is released. The return of the support tube in one of the notches of the rack is done automatically, under the effect of the weight of the seat, and if necessary of the driver. It is not necessary for the driver to perform a lock action.

The proposed technique, which is very different from all the techniques of the known prior art, thus provides a solution for adjusting the position of a kart seat which is easy to implement on any type of kart, simple to use and reliable.

In a particular embodiment, said lever rod is capable of moving said lug when passing from said rest position to said unlocking position, when said lever is actuated by a user, and said lever returns to its rest position, when released by said user, regardless of the position of said lug.

Thus, when the support tube is released from the notch of the first rack, the release lever can be released and the seat moved to the next predetermined adjustment position. It is therefore not necessary to keep the release lever raised to allow adjustment of the seat position.

According to a particular aspect, said lug forms a hook, a portion of which extends above said lever rod, so that the latter drives said hook when it is moved from a rest position to an unlocking position .

In this way, moving the unlocking lever towards the unlocking position directly drives the lug into its unlocking position, which causes the support tube to move out of the notch of the first rack. In addition, the lug being placed above the lever rod, the lever can be released in order to return to the rest position without affecting the position of the lug.

According to another particular aspect, said support tube carries at least one movable cam in at least one rail, which can assume two extreme positions:

• a locked position, said support tube resting in one of said notches of the at least one first rack;
• an unlocked position, in which said support tube is moved above said notches, when said lug is brought into said unlocked position.

Thus, the cam is able, when the lug is moved into the unlocking position, to pivot so as to release the support tube from the notches so that it can be moved above the notches of the first rack to allow seat position adjustment. When the lug returns to the locked position, the cam pivots again, in the opposite direction, and the support tube is then housed in one of the notches of the first rack to lock the seat adjustment position.

According to yet another particular aspect, said cam carries at least one first locking finger:

• being housed in a locking slot of at least one second rack, among at least two locking slots corresponding to said predetermined adjustment positions, when said cam is in its locked position; And
• extracted from said locking slot to come into an upper groove of said at least one second rack, allowing a change of adjustment position, when said cam is in its unlocked position.

In this way, additional means ensure the adjustment and the locking of the predetermined adjustment position of the seat. More particularly, the displacement of the cam causes a displacement of the locking finger between the different locking slots. The movement of the locking finger between the locking slots is synchronized/simultaneous with the movement of the support tube between the notches of the first rack.

According to a particular aspect, said locking slots are inclined, so that in the locked position, a portion forming an abutment extends above said first locking finger, between said slot and said groove.

Thus, in the locking position, the locking finger cannot be extracted from the locking slot because it is blocked by the stop portion. The predetermined adjustment position of the seat is therefore secured.

According to another particular aspect, said cam carries a second guide finger remaining permanently in said groove.

In this way, the movement of the seat during its adjustment is reliable and simple. Adjusting the seat position is easy.

According to another particular aspect, said groove is closed by an upper portion preventing said finger(s) from being able to come out of said groove in the event of an impact.

Thus, the predetermined adjustment position of the seat is secure and reliable. There is therefore no risk that the seat will move in an undesired manner during an impact suffered by the kart.

According to yet another particular aspect, said support tube cooperates with two symmetrical adjustment units, placed on either side of said seat, each adjustment unit comprising at least said first rack and said second rack.

In this way, both ends of the support tube act when adjusting the position of the seat on the go-kart frame. In addition, the support tube is held and secured at both ends to prevent unwanted movement. The kart according to the proposed technique is therefore more reliable than the known prior art.

According to a particular aspect, each of said adjustment units is in the form of a single piece secured to said frame, having a bottom on which said cam bears and two walls extending from said bottom, a first wall forming said first rack and a second wall forming said second rack.

In this way, the proposed technique can be implemented on any type of kart, without requiring significant and complex modifications to the chassis of the latter.

tricks

Other characteristics and advantages of the invention will appear more clearly on reading the following description of a preferred embodiment, given by way of a simple illustrative and non-limiting example, and the appended drawings, among which:

illustrates in perspective a kart seat comprising the adjustment solution according to the proposed technique;

illustrates in perspective the adjustment solution of Figure 1 in an initial position in the locked state;

illustrates in perspective the adjustment solution of Figure 1 in an initial position in the unlocked state;

illustrates in perspective the adjustment solution of Figure 1 in an intermediate adjustment position;

illustrates a see-through view of the tuning solution of Figure 3; And

illustrates a perspective view from another angle of the adjustment solution according to the proposed technique in an intermediate adjustment position.

Detailed description of the invention

Structure of seat

Figure 1 illustrates an example of seat 1, or bucket, for kart (not shown in full). The seat 1 is a one-piece element, comprising the backrest 11 and the seat 12.

The seat 1 is connected to the chassis of the kart via a pair of hoops 16a, 16b hinged together (according to the principle described for example in document FR 2788023). More precisely, the first hoop 16a, of substantially inverted U-shape, extends from the front end of the seat 1 (in the direction of travel of the kart) to the upper end of the backrest 11. The base of the U of the first hoop 16a extends substantially over the entire length of the upper end of the backrest 11.

The backrest 11 of the seat 1 is fixed to the base of the first hoop 16a while the seat 12 of the seat 1 is fixed, at its front end, to the ends of the first hoop 16a via a fixing base 17 (visible on the figure 6). More particularly, the fixing base 17 allows the seat 12 to be fixed to the first hoop 16a. The fixing base 17 also allows the seat 1 to be fixed to a movable support tube 14 cooperating with at least one unit 6 for adjusting the position of the seat 1. The adjusting unit 6 is described in more detail below. of the description. The fixing base 17 also has a housing 171 intended to receive the unlocking lever 3 described in more detail below.

The second arch 16b extends to the rear of the seat 1 and also has an inverted U shape. The base of the second hoop 16b extends parallel to and close to the base of the first hoop 16A. More particularly, the base of the first hoop 16a and the base of the second hoop 16b are mounted in an articulated manner with respect to each other. To do this, an articulation (not visible), of the pivot connection type, is implemented between the two hoops 16a, 16b in order to allow rotation of the hoops 16a, 16b with respect to each other along an axis of rotation extending substantially parallel to the bases of the arches 16a, 16b.

The ends of the second arch 16b are directly connected to the chassis of the kart via a joint 13. Preferably, the joint 13 is in the form of a pivot connection whose axis of rotation extends substantially parallel to the bases of the arches 16a, 16b.

The implementation of the arches 16a, 16b and the joints described above makes it possible to adjust the inclination of the seat 1 (forwards or backwards) simultaneously with the adjustment of the distance of the seat 1 from the steering wheel. Indeed, the front part of the seat 12 of the seat 1 is movable relative to the chassis of the kart when adjusting the position of the seat 1. Thus, when the seat 1 is moved in the direction of the steering wheel of the kart (towards front), the distance between the ends of the first arch 16a and the pivot connection 13 of the second arch 16b increases, which generates an increase in the angle between the two arches 16a, 16b and an inclination of the seat 1 towards the rear of the kart.

Conversely, when the seat 1 is moved away from the steering wheel of the kart (movement of the seat backwards), the distance between the ends of the first hoop 16a and the pivot connection 13 of the second hoop 16b decreases, which generates a reduction in angle between the two arches 16a, 16b and an inclination of the seat 1 towards the front of the kart.

The implementation of the hoops to carry the seat 1 therefore allows simultaneous adjustment of the inclination of the seat 1 with the position of the seat 1 on the chassis of the kart.

Of course, the proposed technique also applies to a seat whose inclination is not adjustable.

Structure of 'a a nity of adjustment of the position of the seat

The go-kart frame has at least one adjustment unit 6. This adjustment unit 6 is in the form of a single piece intended to be secured/fixed to the go-kart frame by fastening means, for example a screw and its nut (as shown in figure 6). Alternatively, the adjustment unit 6 can be integrated into the chassis of the kart, that is to say that the adjustment unit 6 is an integral part of the chassis of the kart.

As illustrated in Figure 1 , the kart comprises in this embodiment two adjustment units 6, arranged on either side of the seat 1, and more particularly of the support tube 14. One could consider implementing only 'a single adjustment unit 6, at one end of the support tube 14. In this case, the other end of the support tube 14 would be provided with a conventional slide, for example.

The adjustment unit 6 comprises a first rack 2, which extends substantially parallel to the longitudinal axis of the kart.

As illustrated in Figure 6 , the first rack 2 has a wall 62 vertical. In other words, the wall 62 extends substantially perpendicular to the ground on which the kart rests.

The wall 62 of the first rack 2 has a plurality of notches 20a, 20b, 20c, 20d which each define a predetermined adjustment position of the seat 1 on the kart. In this example, the first rack 2 comprises four notches, corresponding to four predetermined adjustment positions. It is obviously understood that a greater number of notches could be implemented in order to obtain a more precise adjustment of the position of the seat. In other words, the number of notches is defined according to the number of desired predetermined adjustment positions.

The notches 20a, 20b, 20c, 20d are of substantially semi-circular shape and are more generally configured/dimensioned to receive the support tube 14, taking into account its section and to ensure effective maintenance. The notches 20a, 20b, 20c, 20d are arranged at regular intervals. In a variant (not shown), the intervals between two notches 20a, 20b, 20c, 20d could be irregular.

The adjustment unit 6 comprises a second rack 4 extending substantially parallel to the first rack 2. The second rack 4 also has a vertical wall 63, which extends parallel to the wall 62 of the first rack 2.

The wall 63 of the second rack 4 has a guide groove, or slideway, 42 which extends substantially over the entire length of the wall 63, in the vicinity of its upper edge.

A plurality of locking slots 41a, 41b, 41c, 41d is also formed in the wall 63 of the second rack 4. More precisely, the number of locking slots 41a, 41b, 41c, 41d is equal to the number of notches 20a , 20b, 20c, 20d of the first rack 2.

In this example, the second rack 4 therefore comprises four locking slots 41a, 41b, 41c, 41d, located opposite the notches 20a, 20b, 20c, 20d of the first rack 2. These slots 41a, 41b, 41c, 41d each correspond to a predetermined adjustment position of the seat 1 of the kart.

Lock slots 41a, 41b, 41c, 41d extend from guide groove 42 and slope toward the rear of the kart. In other words, the upper end of each locking slot 41a, 41b, 41c, 41d opens into the guide groove 42. The other end of each locking slot 41a, 41b, 41c, 41d has a portion forming stopper.

The locking slots 41a, 41b, 41c, 41d are arranged in the second rack 4 so as to correspond to the arrangement of the notches 20a, 20b, 20c, 20d in the first rack 2. In other words, the locking slots locking respect substantially the same spacing/interval as the notches 20a, 20b, 20c, 20d.

The locking slots 41a, 41b, 41c, 41d are configured/dimensioned to receive a finger, or a pin, or a pad, for locking 143. The guide groove 42 is configured/dimensioned to receive the locking finger 143 as well as a finger, or pin or pad, guide 144. The locking fingers 143 and guide 144 are described in more detail in the following description.

The walls 62 and 63 of the first 2 and second 4 racks are connected at their lower ends by a bottom wall 61. The space provided between the walls 62, 63 of the racks 2, 4 and the bottom wall 61 defines a rail 21 for receiving and guiding a cam 142 connected to the support tube 14. This cam 142 is described in more detail below.

The support tube 14 is rotatably mounted in the fixing base 17 of the seat 1. To do this, the fixing base 17 comprises slots for receiving the support tube 14 configured to allow rotation of the support tube 14.

The support tube 14 comprises, at each of its ends, a cam 142 which carries a locking pin 143 and a guide pin 144. Note that in the variant implementing only one adjustment unit 6, the corresponding end of the support tube 14 would not have such a cam 142, but a shoe intended to cooperate with a conventional slide, for example.

The cam 142 has a general shape substantially in the form of a right-angled triangle, the hypotenuse of which would be rounded. It can also be considered that the cam 142 has a substantially rectangular shape in which one of the corners is trimmed according to a rounded cutout. This rounded portion of the cam 142 is intended to come into contact with the bottom wall 61 of the rail 21.

The outer face of the cam 142, i.e. the face opposite the support tube 14, carries the locking 143 and guide 144 fingers.

The locking finger 143 is configured and placed to move between two positions, namely an unlocked position in which it is free to move in the groove 42 and a locked position in which the locking finger 143 is lodged in one locking slots 41a, 41b, 41c, 41d.

The guide finger 144 is itself configured and placed to move only within the groove 42 of the second rack 4. Indeed, the shape of the cam 12 as well as the arrangement of the locking finger 143 prevents the finger from lock 144 to fit into lock slots 41a, 41b, 41c, 41d.

The groove 42 is closed by an upper portion 43 of the wall 63 in order to prevent the fingers 143, 144 from being able to extract themselves from the groove 42, in particular in the event of an impact suffered by the kart.

The support tube 14 comprises, close to the cam 142 and at the level of the front of the seat 1, a hook, or lug, 141. More precisely, the hook 141 protrudes with respect to the support tube 14. The hook 141 comprises a first portion 141a extending substantially perpendicular to the support tube 141 and a portion 141b, perpendicular to the first portion 141a, extending substantially parallel to the support tube 14.

The hook 141 is configured to cooperate with an unlocking lever 3 intended to be actuated by a user when adjusting the position of the seat 1 in order to cause the support tube 14 to pivot. on the second portion 141b of the hook 141 so as to lift the latter and cause the support tube 14 to pivot.

The unlocking lever 3 has a lever rod 31 extending substantially perpendicular to the support tube 14. It is provided at one of its ends with a handle 32. The lever rod 31 and the handle 32 are arranged so as to allow easy gripping by the pilot and/or by a user located next to the kart, for example a monitor.

The other end of the lever rod 31 carries, or forms, a rotation shaft 33 extending parallel to the axis of the support tube 14. More precisely, the rotation shaft 33 is rotatably mounted within of the housing 171 provided in the fixing base 17 of the seat 1. The rotation shaft 33 is therefore slightly offset with respect to the axis of the support tube 14. The unlocking lever 3 is nevertheless located close to the adjustment unit 6, opposite the hook 141 of the support tube 14.

In this example, the unlocking lever 3 is implemented only on the left side of the seat 1 of the kart, as shown in Figure 1. In a variant (not shown), an unlocking lever 3 is implemented each side of the seat 1 in order to allow adjustment of the position of the seat 1 by action on one or the other of the levers 3. Thus, the monitor located next to the kart can easily adjust the position of the seat 1, regardless where the monitor is in relation to the kart.

Adjusting the seat position

The adjustment unit 6 and the support tube 14 according to the proposed technique are intended to allow easy adjustment of the position of the seat 1 on the chassis of the kart.

Figures 2 to 4 show different positions of the lever and of the support tube 14 allowing a better understanding of the way in which the position of the seat 1 is adjusted.

Figure 2 illustrates an initial position, in which the position of the seat 1 corresponds to the most forward position of the seat 1 towards the front of the kart. Figure 2 illustrates a state where the position of the seat 1 locked. Thus, the support tube 14 rests in the first notch 20a of the first rack 2 and the locking finger 143 is housed/received in the first locking slot 41a of the second rack 4. In the locked state, the lever 3 lock is lowered (rest position, taken by default), just like the hook 141 of the support tube 14. The cam 142 is itself in a locked position and the locking finger 143 is lodged in abutment in the slot of lock 41a. Whatever the state, the guide finger 144 is always located in the groove 42.

Figure 3 illustrates the initial position of Figure 2 in an unlocked state. To do this, the pilot or a user has actuated the unlocking lever 3 to move it to the unlocking position (raised position). In the unlocked position, the lever 3 is raised/raised and causes the hook 141 of the support tube 14 in its travel. Thus, the support tube 14 pivots and the cam 142 causes a movement of the support tube 14 above/ out of the notch 20a of the first rack 2. This rotation of the cam 142 also causes a displacement of the locking finger 143 out of the locking slot 41a of the second rack 4. In other words, the locking finger 142 is extracted from the locking slot 41a.

Thus, the seat 1 can be moved to another predetermined adjustment position. When moving the seat between two predetermined adjustment positions, the support tube 14 is located above the notches 20a, 20b, 20c, 20d, as illustrated in Figure 6. The notches 20a, 20b, 20c, 20d do not therefore not prevent the movement of the support tube 14. In addition, in the unlocked state, the locking 143 and guide 144 fingers are both in the groove 42 of the second rack 4 in order to allow movement of the cam 42 in the track.

Figure 4 illustrates an intermediate adjustment position in which the seat is located between two predetermined adjustment positions. It is observed that the locking 143 and guide 144 fingers are both in the groove 42 of the second rack 4 and that the support tube 14 is located above the notches 20a, 20b, 20c, 20d of the first rack 2.

In this intermediate position, lever 3 can be released so that it returns to the rest position (as illustrated in Figures 2 and 4). The movement of the seat 1 is however always authorized since the locking finger 143 is located in the groove 42. The movement of the seat 1 is free until the locking finger 143 falls into the locking slot 41a, 41b, 41c , 41d which follows. In other words, the movement of the seat 1 causes a movement of the locking fingers 143 and guide 144 in the groove 42 until the locking finger 143 is located vis-à-vis a slot of locking 41a, 41b, 41c, 41d.

Locking in one of the predetermined adjustment positions takes place automatically. Indeed, the pilot's weight on the seat 1, and therefore on the support tube 14, forces the locking finger 143 to lodge in the locking slot 41a, 41b, 41c, 41d that it encounters during its movement. in the throat 42.

As a reminder, the guide finger 144 is prevented from being lodged in the locking slots 41a, 41b, 41c, 41d because the locking finger 143 constitutes a rotation stop for the cam 142. The guide finger 144 therefore always remains in the throat 42 (whether in the locked state or the unlocked state).

If we refer to Figure 4, we see that if the seat 1 moves towards the rear of the kart, the locking pin 143 will be housed in the second locking slot 41b of the second rack 4. The cam 142 will then pivot until the support tube 14 rests in the second notch 20b of the first rack 2 and the locking finger 143 abuts against the bottom of the locking slot 41b.

In the locked state, the predetermined adjustment position is secured on the one hand by the support tube 14 which rests in a notch 20a, 20b, 20c, 20d of the first rack 2, and on the other hand by the locking finger 143 which is housed in a locking slot 41a, 41b, 41c, 41d of the second rack 4. Thus, the risks of the position of the seat 1 being modified unintentionally are eliminated.

If it is desired to move the seat 1 from a first predetermined adjustment position to another predetermined adjustment position not adjacent to the first predetermined adjustment position, it is necessary to maintain the lever 3 in the unlocked position in order to prevent the locking finger 143 does not become lodged in the locking slot 41 corresponding to the predetermined adjustment position adjacent to the first predetermined adjustment position.

In other words, if it is desired to shift/move the seat 1 from a predetermined adjustment position to an adjacent predetermined adjustment position (for example from the notch 20a to the notch 20b), it suffices to lift the lever 3 in the unlocked position and to release it when the movement of the seat 1 is engaged. Thus, the next predetermined setting position (corresponding to notch 20b) will be locked automatically.

If it is desired to shift/move the seat 1 from a predetermined adjustment position to a non-adjacent predetermined adjustment position (for example from the notch 20a to the notch 20c), it is preferable to hold the lever 3 unlocked position (raised) up to the desired predetermined adjustment position (corresponding to the notch 20c), in order to avoid having to release the lever 3 then raise it again at each predetermined adjustment position (in this case at level of the notch 20b).

Claims (10)

Kart with one-piece seat (1) with an adjustable position relative to the chassis of said kart, said seat (1) having a backrest (11) and a seat (12), said backrest (11) being connected by a joint (13) to said chassis and said seat (12) being carried by a support tube (14) movable relative to said frame between at least two predetermined adjustment positions,
characterized in that said frame carries at least a first rack (2) defining, for each of said adjustment positions, a notch (20a, 20b, 20c, 20d) for receiving said support tube (14) and in that said seat (1) carries an unlocking lever (3), having a lever rod (31) provided at one of its ends with a handle (32) and carrying or forming at a second of its ends a rotation shaft (33 ) extending along an axis offset from said support tube (14),
said lever rod (31) cooperating with a lug (141) extending from said support tube (14) to ensure the release of said support tube (14) from one of said notches (20a, 20b, 20c, 20d ), when said lever (3) is moved from a rest position to an unlocking position. Kart according to claim 1, characterized in that said lever rod (31) is capable of moving said lug (141) when passing from said rest position to said unlocking position, when said lever (3) is actuated by a user, and in that said lever (3) returns to its rest position, when it is released by said user, independently of the position of said lug (141). Kart according to Claim 2, characterized in that the said lug (141) forms a hook, a portion of which (141b) extends above the said lever rod (31), so that the latter drives the said hook (141 ) when moved from a rest position to an unlocked position. Kart according to claim 1, characterized in that said support tube (14) carries at least one movable cam (142) in at least one rail (21), which can assume two extreme positions:

• a locked position, said support tube (14) resting in one of said notches (20a, 20b, 20c, 20d) of the at least one first rack (2);
• an unlocked position, in which said support tube (14) is moved above said notches (20a, 20b, 20c, 20d), when said lug (141) is brought into said unlocked position.

Kart according to claim 4, characterized in that said cam (142) carries at least a first locking finger (143):

• being housed in a locking slot (41a, 41b, 41c, 41d) of at least one second rack (4), among at least two locking slots (41a, 41b, 41c, 41d) corresponding to said predetermined adjustment positions , when said cam (142) is in its locked position; And
• extracted from said locking slot (41a, 41b, 41c, 41d) to come into an upper groove (42) of said at least one second rack (4), allowing a change of adjustment position, when said cam (142) is in its unlocked position.

Kart according to claim 5, characterized in that said locking slots (41a, 41b, 41c, 41d) are inclined, so that in the locked position, a portion forming a stop extends above said first finger (143) locking, between said slot (41a, 41b, 41c, 41d) and said groove (42). Kart according to claim 5, characterized in that said cam (142) carries a second guide finger (144) remaining permanently in said groove (42). Kart according to claim 5, characterized in that said groove (42) is closed by an upper portion (43) preventing said at least one first finger (143) from being able to come out of said groove (42) in the event of an impact. Kart according to Claim 5, characterized in that the said support tube (14) cooperates with two symmetrical adjustment units (6), placed on either side of the said seat (1), each adjustment unit (6) comprising at least said first rack (2) and said second rack (4). Kart according to Claim 9, characterized in that each of the said adjustment units (6) is in the form of a single piece secured to the said chassis, having a bottom (61) on which the said cam (142) bears and two walls (62, 63) extending from said bottom, a first wall (62) forming said first rack (2) and a second wall (63) forming said second rack (4).