The present invention relates to a pivot unit.

Pivot units are widely known in different shapes and for different applications.

The present invention aims to provide a pivot unit which is typically suitable for steering mechanisms of rides such as bicycles, karts, tricycles, ride-on toys and the like, and which returns towards its original condition after

pivoting due to a resetting force which occurs upon pivoting.

For this purpose the pivot unit according to the invention comprises a first pivot part and a second pivot part which are coupled to each other and rotatable with respect to each other about a pivot axis, and at least two elongated springs, which are coupled to the first pivot part at

respective first coupling locations and to the second pivot part at respective second coupling locations and which springs extend along the first and second pivot parts in transverse direction of the pivot axis at opposite sides of the pivot axis, wherein the first coupling locations are provided at a separate first coupling element which is mounted to the first pivot part and the second coupling locations are provided at a separate second coupling element which is mounted to the second pivot part.

An advantage of the pivot unit according to the invention is that the first and second coupling elements can be easily replaced by first and second coupling elements having a different number of first and second coupling

locations. This means that pivot units can be assembled which have a different number of springs for different applications, but the same first and second pivot parts. For that reason, different products can be created with a minimum of different components. For example, if a pivot unit including a relative strong resetting force is desired the pivot unit can be provided with coupling elements having a relative high number of coupling locations for applying a corresponding high number of springs. The possibility of using the same first and second pivot parts is beneficial since existing well-functioning modular basic parts can be used for creating pivot units including different resetting force characteristics.

In an advantageous embodiment the first coupling element and the second coupling element are identical, since this further reduces the number of different components to be assembled and/or to be kept in stock.

The pivot unit may have at least two pairs of elongated springs, each pair extending at each of said

opposite sides of the pivot axis and extending in transverse direction of the pivot axis, wherein the first and second coupling elements each have at least four first and second coupling locations, respectively, at which the respective springs are coupled. In this case the pivot unit has a total of four springs.

Preferably, the first and second coupling elements and the first and second pivot parts are shaped such that the first coupling element fits to the first pivot part and the second coupling element fits to the second pivot part such that they are locked with respect to each other in rotational direction about an axis extending transversely to the pivot axis, since this facilitates the process of assembling the pivot unit.

In a particular embodiment the first pivot part is provided with at least two lateral projections located at opposite sides thereof and directed in transverse direction of the pivot axis, wherein the pivot unit has a rest condition in which the springs extend between the respective first and second coupling locations along the respective projections and a loaded condition in which the first pivot part and the second pivot part are rotated with respect to each other about the pivot axis away from the rest condition, hence stretching one of the springs, and in which loaded condition the

stretched spring contacts the corresponding projection. This embodiment provides the opportunity to manipulate the

resetting force progression as a function of the angle of pivoting in case of springs that have a non-linear elastic modulus. During increasing the angle of rotation between the first pivot part and the second pivot part the contact force between the stretching spring and the corresponding lateral projection will increase. This causes increased friction between the spring and the lateral projection, which may lead to limited or no movement of the spring along the lateral projection. Consequently, the effective spring length is shortened to a distance between the lateral projection and the coupling location at the second coupling element, hence changing the actual elastic modulus. Another advantage of this embodiment is that the lateral projections may form stops for limiting the rotation angle of the first pivot part and the second pivot part with respect to each other.

It is noted that when the pivot unit is in the rest condition the springs may already be biased.

In a particular embodiment each of the projections extends beyond the first and second coupling locations of the corresponding spring in transverse direction of both the pivot axis and the spring when the pivot unit is in its rest

condition. In this case the springs may already be in contact with the lateral projections in the rest condition. The pivot unit may have a rest condition and/or a loaded condition in which the stretched spring only contacts the corresponding projection between the corresponding first and second coupling location . Preferably, end portions of the respective projections are curved, since this avoids excessive stress peaks between the lateral projections and the elastic bands, which could damage the springs. Besides, curved edges also contribute to safety, particularly if the pivot unit is applied in a toy for children.

The springs may be elastic bands, for example made of rubber .

In an advantageous embodiment the springs are

releasably mounted to the first coupling element and the second coupling element, since this provides the opportunity to easily replace springs in case of wear. Besides, it is possible to apply springs which have different spring rates in order to apply the same first and second pivot parts for different applications requiring different resetting force characteristics .

In practice each end portion of the springs may comprise an eye which fits about lateral ears at the first and second coupling locations at the first and second coupling elements, respectively.

The pivot unit may have identical end portions remote from the pivot axis. This provides the opportunity to mount the pivot unit to a standardized frame. For example, the end portions may comprise threaded ends which are directed in opposite directions in the rest condition of the pivot unit, which allows to insert the threaded ends into cooperating nuts in slots of respective sections, which have standardized dimensions .

The springs may be adapted such that when the first and second pivot parts are rotated with respect to each other about the pivot axis, one spring is stretched whereas the other spring at opposite side of the pivot axis is compressed. Compression of the springs may be achieved by guiding the springs along guides during pivoting, hence preventing buckling of the springs. This creates a compression force upon pivoting in addition to the stretching spring.

The invention is also related to a coupling element to be used as the first or second coupling element of a pivot unit as described hereinbefore, which coupling element

comprises T-shaped ears at opposite sides thereof and which coupling element is made of one piece, for example by means of injection moulding. In a particular embodiment each of the opposite sides comprises a row of T-shaped ears.

The invention is also related to a vehicle which is provided with a pivot unit as described hereinbefore.

The vehicle may comprise a front frame including a front wheel and a rear frame including a rear wheel, wherein the front frame and the rear frame are interconnected through the pivot unit. The vehicle may be a bicycle, a kart, a tricycle, a ride-on toy, etc. The pivot unit may form a steering mechanism in this case, providing a steering

stabilizer due to generating a resetting force upon turning the first pivot part and the second pivot part of the pivot unit with respect to each other.

The invention will hereafter be elucidated with reference to the schematic drawings showing an embodiment of the invention by way of example.

Fig. 1 is a perspective view of an embodiment of a pivot unit according to the invention.

Fig. 2 is a perspective exploded view of the pivot unit of Fig. 1.

Fig. 3 is a top view of the pivot unit of Fig. 1, showing the pivot unit in a rest condition.

Fig. 4 is a similar view as Fig. 3, but showing the pivot unit in a loaded condition and without springs.

Figs. 1-4 show an embodiment of a pivot unit 1 according to the invention. In this case the pivot unit 1 forms a steering mechanism of a kart for children (only shown in part) , but the pivot unit 1 is suitable for numerous alternative applications. The kart has a modular frame which is composed of similar sections 2. In the figures one of the sections 2 is part of a front frame including front wheels and the other one of the sections 2 is part of a rear frame including rear wheels. The front frame and the rear frame are interconnected through the pivot unit 1, hence forming the steering mechanism. Each of the sections 2 is provided with four longitudinal slots 3.

The pivot unit 1 comprises a first pivot part 5 and a second pivot part 6. The first and second pivot parts 5, 6 are coupled to each other through a pivot shaft 7 and rotatable with respect to each other about a pivot axis A. The first pivot part 5 is provided with two lateral projections 8 which are located at opposite sides of the first pivot part 5, see Fig. 3. The first pivot part 5 and the second pivot part 6 are each provided with a bolt 15, see Fig. 2, which can be turned by a tool when the first and second pivot parts 5, 6 are temporarily dismantled with respect to each other. Each of the first and second pivot parts 5, 6 is fixed to the

corresponding section 2 by screwing the bolt 15 into a nut 4 which is slid in the slot 3.

Furthermore, the pivot unit 1 comprises four elongated springs in the form of elastic bands 9, two at each side of the first and second pivot parts 5, 6. The elastic bands 9 are made of rubber or an alternative flexible

material. The elastic bands 9 extend in transverse direction of the pivot axis A and at a distance thereof and they are provided with eyes 10 at their end portions. The eyes 10 fit about T-shaped lateral first ears 11 which provide first coupling locations and T-shaped lateral second ears 12 which provide second coupling locations. The lateral first and second ears 11, 12 have fixed positions with respect to the first and second parts 5, 6, respectively. Due to the flexibility of the elastic bands 9, the shapes and dimensions of the eyes and of the first and second lateral ears 11, 12 the elastic bands 9 are releasably mounted to the first and second lateral ears 11, 12.

The elastic bands 9 extend in longitudinal direction of the first and second pivot parts 5, 6 when the pivot unit is in a rest condition as illustrated in Figs. 1 and 3. In this condition the first pivot part 5 and the second pivot part 6 are aligned and each of the elastic bands 9 extends between the corresponding first and second lateral ears 11, 12 and along the corresponding projection 8. The lateral

projections 8 are directed in transverse direction of both the pivot axis A and the corresponding elastic band 9. In the rest condition of the pivot unit 1 as shown in Fig. 3 the lateral projections 8 contact the corresponding elastic bands 9, since each of the lateral projections 8 extends beyond the first and second coupling locations at the first and second lateral ears 11, 12 in transverse direction of both the pivot axis A and the elastic bands 9 when the pivot unit 1 is in its rest condition. In an alternative embodiment the elastic bands 9 may be free from the corresponding lateral projections 8 in the rest condition.

When the first pivot part 5 and the second pivot part 6 are rotated with respect to each other from the rest

condition the pivot unit 1 will change from the rest condition into a loaded condition in which the elastic bands 9 at one side of the pivot unit 1 are stretched whereas the stretched elastic bands 9 also contact the lateral projection 8 at that side. In order to minimize local stress peaks onto the elastic bands 9 in the loaded condition end portions of the lateral projections 8 which contact the elastic bands 9 are curved.

Figs. 3 and 4 show that the pivot unit 1 has identical opposite end portions in the form of the threaded ends of the bolts 15 located remote from the pivot axis A. This provides great flexibility in applying the pivot unit 1 in a modular frame, which is built up of similar bars like the sections 2 as shown in Figs. 1-4.

Fig. 2 shows that the lateral first ears 11 are provided at a separate first coupling element 13 which is mountable to the first pivot part 5 and the second ears 12 are provided at a separate second coupling element 14 which is mounted to the second pivot part 6. The first and second coupling elements 13, 14 are identical. The first and second coupling elements 13, 14 and the first and second pivot parts 5, 6 are provided with cooperating protrusions and recesses which fit to each other such that upon placing the first and second coupling elements 13, 14 to the first and second pivot parts 5, 6 they are locked to each other in rotational direction about an axis extending transversely to the pivot axis A.

Since the first and second coupling elements 13, 14 are separate parts they can be easily replaced by first and second coupling elements having a different number of lateral ears 11, 12 whereas a corresponding number of elastic bands 9 can be applied in order to adapt the spring characteristics for creating different resetting force characteristics. This provides the opportunity to use the same basic first and second pivot parts and elastic bands 9, hence reducing the number of parts which should be kept in stock.

The invention is not limited to the embodiment shown in the drawings and described hereinbefore, which may be varied in different manners within the scope of the claims and their technical equivalents.

For example, in another aspect of the invention the pivot unit may be provided with the lateral projections, wherein the lateral first and second ears form part of the first and second pivot parts. More in general terms, the pivot unit comprises a first pivot part and a second pivot part which are coupled to each other and rotatable with respect to each other about a pivot axis, and at least two elongated springs, which are mounted to the first pivot part at

respective first coupling locations and to the second pivot part at respective second coupling locations and which springs extend at opposite sides of the first and second pivot parts in transverse direction of the pivot axis, wherein the first pivot part is provided with at least two lateral projections located at opposite sides thereof and directed in transverse direction of the pivot axis, wherein the pivot unit has a rest condition in which the springs extend between the respective first and second coupling locations along the respective projections and a loaded condition in which the first pivot part and the second pivot part are rotated with respect to each other about the pivot axis away from the rest condition, hence stretching one of the springs, and in which condition the stretched spring contacts the corresponding projection.