BACKGROUND ART These days, snowboarding is popular with many people.

A snowboard slides downhill over only snow, so that the snowboarding is not free from a place and a season.

Nevertheless, the snowboard can be freely turned because the snowboard slides over the snow.

Contrary to the snowboard, a skateboard rolls on a ground such as a pavement. Hence, skateboarding is free from a place and a season in comparison with the snowboarding, so that the skateboarding is recently popular with many people as a substitute for the snowboarding as well as itself.

Generally, the skateboard comprises a board supporting two feet of a rider, and a pair of wheel assemblies mounted on the board at front and rear portions of the board. Each wheel assembly includes a pair of fixed wheels rotating about a rotational axis which is transverse to a longitudinal axis of the board.

Thus, the skateboard can roll only forward and backward,

so that it is difficult to freely turn the skateboard in comparison with the snowboard.

Accordingly, there was proposed a skateboard having a turn mechanism in U. S. Patent No. 4202559. This conventional skateboard comprises a rigid elongated board having front and rear portions, a rear wheel assembly being fixedly mounted on the board rear portion, a front wheel assembly and a steering platform being secured to the board front portion, and a linkage system connecting the platform above the board front portion and the front wheel assembly below the board front portion for pivotable movement as a unit relative to the board.

Preferably the angle through which the platform/front wheel assembly unit is pivotable is limited and the platform/front wheel assembly unit is biased to a given orientation. The steering platform is spaced only slightly above the front portion and adapted to be pivoted by the forwardly disposed foot of the skateboard rider. Accordingly, it is provided a skateboard which is steerable by the food of the rider.

However, because the conventional skateboard is steered by the foot, it is inconvenient for the rider.

Further, because the front wheel assembly is pivotably secured to the board, the front wheel assembly may suddenly pivot when the conventional skateboard is

steered, so that the rider is likely to lose balance.

DISCLOSURE OF INVENTION Accordingly, it is an aspect of the present invention to provide a skateboard which allows a rider to easily turn and easily keep balance.

This and other aspects of the present invention may be accomplished by the providing a skateboard comprising a board supporting two feet of a rider; front and rear wheel assemblies mounted on an underside of the board at front and rear portions of the board, and each having a pair of fixed wheels rotating on a rotational axis transverse to a longitudinal axis of the board; a caster axle provided in the front wheel assembly perpendicularly to the board; and a caster assembly having a caster wheel pivotably combined to the caster axle.

According to an aspect of the invention, the front and rear wheel assemblies each includes a wheel base attached to the underside of the board, and the caster axle is provided in the wheel base perpendicularly to board.

According to an aspect of the invention, the caster assembly includes a pivoting collar being pivotably combined with the caster axle ; and brackets linking the pivoting collar with the caster wheel.

According to an aspect of the invention, the brackets

form a pair.

According to an aspect of the invention, the brackets have a single shank.

According to an aspect of the invention, the caster wheel is positioned lower than the fixed wheels.

According to an aspect of the invention, the position of the caster wheel is adjustable up and down.

BRIEF DESCRIPTION OF DRAWINGS The present invention will be better understood and its various aspects and advantages will be more fully appreciated from the following description taken in conjunction with the accompanying drawings, in which: FIG. 1 is a plan view illustrating an underside of a skateboard according to a first embodiment of the present invention; FIG. 2 is a perspective view of a front wheel assembly and a caster assembly in FIG. 1; FIG. 3 is an exploded perspective view of the front wheel assembly and the caster assembly in FIG. 2; FIG. 4 is a side view of the skateboard of FIG. 1; and FIG. 5 is a plan view of a front wheel assembly and a caster assembly according to a second embodiment of the present invention.

MODES FOR CARRYING OUT THE INVENTION

Hereinafter, a first embodiment of preferred embodiments will be described as a representative of the present invention in more detail with reference to the accompanying drawings, and the other embodiments will be described in only respects different from the first embodiment, wherein like reference numerals refer to like elements throughout.

As shown in FIGs. 1 through 3, a skateboard 100 according to a first embodiment of the present invention comprises a board 60 supporting two feet of a rider, front and rear wheel assemblies 70 and 80 mounted on the board 60 at front and rear portions of the board 60, and a caster assembly 40 being pivotably combined to the front wheel assembly 70.

The board 60 is rigid enough to support the weight of the rider and elongated in a longitudinal axis 61.

The front and rear wheel assemblies 70 and 80 each includes a wheel base 10 attached to an underside of the board 60, a caster axle 20 provided in the wheel base 10 perpendicularly to the board 60, a wheel axle 30 disposed in a rotational axis transverse to the longitudinal axis 61 of the board 60 and combined to the caster axle 20, and a pair of fixed wheels 32 rotatably combined to a pair of rotational axles 31 provided in opposite ends of the wheel axle 30.

The wheel base 10 has a rectangular upper surface attached to the underside of the board 60 with bolts or screws, and a lower surface provided with the caster axle 20 perpendicularly thereto and formed with a supporting projection hole 11 in correspondence to a supporting projection 33 (to be described later) of the wheel axle 30.

In an inner circumference of the supporting hole 11 is provided a first elastic sleeve 51 employed for absorbing a shock when the fixed wheel 32 rolls on a ground.

The caster axle 20 has a cylindrical shape so as to be inserted in a fixed collar 34 of the wheel axle 30. An upper end of the caster axle 20 is combined to the lower surface of the wheel base 10, and a lower end thereof has external threads to match internal threads of a nut 21.

The wheel axle 30 is provided with the pair of rotational axles 31 at the opposite ends thereof so as to be rotatably combined to the pair of fixed wheels 32, the supporting projection 33 in the middle thereof so as to be inserted in the supporting projection hole 11 of the wheel base 10, and the fixed collar 34 combined with the caster axle 20.

The supporting projection 33 prevents the wheel axle 30 from rotation relative to the wheel base 10.

Between an inner circumference of the fixed collar 34 and the caster axle 20 is provided a second elastic sleeve 55 employed for absorbing a shock when the fixed wheel 32 rolls on a ground, like the first elastic sleeve 55.

The caster assembly 40 includes a pivoting collar 41 pivotably combined with the caster axle 20 of the front wheel assembly 70, a pair of brackets 42 extended from the pivoting collar 41, and a caster wheel 43 rotatably attached to free ends of the brackets 42.

The pivoting collar 41 has a circular through hole 41a through which the caster axle 20 of the front wheel assembly 70 pivotably passes. In an inner circumference of the through hole 41a is provided a bearing 44 allowing the caster axle 20 of the front wheel assembly 70 to pivot, and in upper and lower sides of the bearing 44 is disposed a plurality of washers 45.

The brackets 42 form a pair and are combined to the pivoting collar 41. Herein, the brackets 42 may be welded to the pivoting collar 41 or molded with the pivoting collar 41 as a single body.

The caster wheel 43 is rotatably attached to the free ends of the brackets 42, and rolls on a ground. Herein, it is preferable that the caster wheel 43 is, as shown in FIG. 4, positioned in height lower than the fixed wheels

32 of the front and rear wheel assemblies 70 and 80.

Therefore, when the rider rides on the skateboard 100, particularly, when the rider turns the skateboard 100, the weight of the rider is concentrated on the caster wheel 43 without being distributed to the fixed wheels 32 of the front wheel assembly 70. According as the weight of the rider is concentrated on the caster wheel 43, the skateboard 100 is speeded up and easily turned. Herein, it is preferable that the caster wheel 43 forms an equilateral triangle together with the fixed wheels 32 of the front wheel assembly 70.

Further, it is possible to lift and lower the position of the caster wheel 43. This is accomplished by increasing and decreasing the number of the washers 45 disposed between the pivoting collar 41 and the wheel base 10. For example, in the case of a beginner, the beginner can decrease the height difference between the caster wheel 43 and the fixed wheels 32 of the front wheel assembly 70 so as to ride the skateboard 100 safely.

With this configuration, the process of assembling the skateboard 100 according to the first embodiment of the present invention will be described hereinbelow.

In the process of assembling the skateboard 100, the process of mounting the front wheel assembly 70 and the caster assembly 40 on the board 60 is as follows. First,

the upper surface of the wheel base 10 of the front wheel assembly 70 is attached to the underside of the board 60.

Thereafter, the caster axle 20 provided in the lower surface of the wheel base 10 of the front wheel assembly 70 is inserted in the bearing 44 provided in the pivoting collar 41 of the caster assembly 40. At this time, it is preferable that the plurality of washers 45 is disposed in the upper and lower sides of the pivoting collar 41.

Thereafter, the caster axle 20 inserted in the pivoting collar 41 of the caster assembly 40 is inserted in the second elastic sleeve 55 provided in the fixed collar 34 of the wheel axle 30, and simultaneously, the supporting projection 33 of the wheel axle 30 is inserted in the first elastic sleeve 51 provided in the supporting projection hole 11 of the wheel base 10. Thereafter, the nut 21 is fitted on the screw threads formed in the lower end of the caster axle 20. Herein, the supporting projection 33 prevents the wheel axle 30 of the front wheel assembly 70 from rotation relative to the wheel base 10, so that the front wheel assembly 70 does not rotate against the board 60. Oppositely, the pivoting collar 41 of the caster assembly 40 is pivotably combined to the caster axle 20 provided in the wheel base 10, so that the caster assembly 40 is pivotable against the board 60. The angle through which the caster assembly 40

is pivotable is limited by the fixed wheels 32 attached to the rotational axles 31. The caster assembly 40 is pivotable within an angle of about 120° because the caster wheel 43 and the fixed wheels 32 of the front wheel assembly 70 form an equilateral triangle.

Further, the process of mounting the rear wheel assembly 80 on the board 60 is equal to the foregoing process of mounting the front wheel assembly 70 and the caster wheel assembly 40 on the board 60 except that the caster assembly 40 is combined to the caster axle 20, and therefore repetitive descriptions will be avoided. Like the front wheel assembly 70, the rear wheel assembly 80 does not rotate against the board 60. With the above processes, the skateboard 100 according to the first embodiment of the present invention is completed.

FIG. 5 is a plan view of a front wheel assembly and a caster assembly according to a second embodiment of the present invention. According to the second embodiment of the present invention, a caster assembly 40a includes a single shank 42a unlike the pair of brackets 42 according to the first embodiment. Because of the single shank 42a, the caster assembly 40a according to the second embodiment is pivoted better than the caster assembly 40 according to the first embodiment, so that the skateboard 100 can be more easily turned. The more easily the

skateboard 100 can be turned, the more difficult the rider rides standing balanced on the skateboard 100.

With this configuration, the skateboard according to the present invention comprises the caster assembly having the caster wheel and being pivotably attached to the front wheel assembly. Accordingly, when the rider goes straight by the skateboard, the weight of the rider acting on the front portion of the skateboard is concentrated on the caster wheel, so that the skateboard can be speeded up.

When the rider turns the skateboard right by leaning to the right, the caster assembly is pivoted to the left, and the caster wheel and the right fixed wheel of the front wheel assembly come in contact with the ground.

Oppositely, when the rider turns the skateboard left by leaning to the left, the caster assembly is pivoted to the right, and the caster wheel and the left fixed wheel of the front wheel assembly come in contact with the ground. Thus, the rider turns the skateboard left and right, keeping balance safely and easily.

Further, the caster assembly is pivotable within an angle of about 120°, that is, the caster assembly can be pivoted to the left and the right at an angle of about 60°, respectively. Thus, when the skateboard is turned left and right, the caster assembly is not excessively pivoted,

so that the rider can safely enjoy skateboarding.

As described above, a rider can speed up a skateboard, and safely and easily keep balance while turning the skateboard.

Although the preferred embodiments of the present invention have been disclosed for illustrative purpose, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.