Background Art Generally, skateboards are devices for riding upon, comprising a narrow longitudinal board with four wheels mounted to the front and rear parts of the board.

Conventional skateboards are classified into two types: stiff skateboards and flexible skateboards, as well known to those skilled in the art.

The skateboards have evolved from surfboards. That is, some surfboarders wanted to ride their surfboards on the ground as they sometimes could not enjoy surfing on the calm'sea without big waves, so that the surfboarders remodeled their surfboards into skateboards to enjoy board-

riding on the ground. The skateboards have become widely used due to the development of polyurethane wheels that can move the skateboards more quickly and more smoothly.

The conventional skateboards comprise a deck, trucks and wheels. The deck of the skateboards has been typically manufactured in the form of a resilient durable panel of 76 cm length and 10 cm width by cutting gingko wood of good quality to produce a plurality of gingko wood sheets and compressing the sheets to produce a resilient durable laminated panel. In recent years, the gingko wood decks of the skateboards have been changed to aluminum, glass fiber or plastic decks. The trucks are parts that connect the wheels to the deck, while each wheel of the skateboards has a size of 40 mm or 54 mm diameter. As the diameter of the wheels increases, the skateboard may run at higher speeds while allowing a rider to perform a higher riding technique.

In the conventional skateboards, the trucks and the deck are assembled together into a single structure, with a cushion pad interposed between each truck and the board.

The wheels of the skateboards are small-sized wheels that are called"casters"and constitute wheel assemblies in which the wheels are supported by swiveling brackets to allow the running directions of the wheels to freely change. The above-mentioned wheel assemblies with the wheels and the swiveling brackets are mounted to the deck

so that an axle of the swiveling bracket of the wheel assemblies rotates idly around an axis.

Wheel assemblies having the above-mentioned construction have been widely used as front wheels of baby carriages or carts because the running directions of the wheels can easily change to desired directions as a user steers the baby carriage or the cart even though the wheels are in contact with the ground, and thus, the wheel assemblies allow the users to easily change the moving directions of the baby carriages or the carts. However, the wheel assemblies having the swiveling brackets are problematic in that even a small force may undesirably change the directions of the wheels.

As shown in FIG. 1, in conventional skateboards, a wheel assembly 3 is mounted to a deck 1, with a cushion pad 2 interposed between the swiveling bracket of the wheel assembly 3 and the lower surface of the deck 1.

In the wheel assembly 3, a bearing (not shown) is installed in the swiveling bracket to cause the wheel assembly 3 to rotate idly around an idle rotating axle 4.

Thus, the center of gravity of the wheel assembly 3 is not affected by any torque caused by a normal force applied from the ground, so that the wheel cannot move in any direction if any external force is not applied to the wheel.

In other words, the conventional skateboards include

four wheels which are mounted to one longitudinal board.

Thus, a rider standing on the board tilts the deck from side to side with his/her feet, steering the front wheel pair and the rear wheel pair in opposite directions.

However, when the deck tilts to the left at a predetermined angle, the left wheels of the front and rear wheel pairs come into contact with the deck. In the same manner, when the deck tilts to the right at a predetermined angle, the right wheels of the front and rear wheel pairs come into contact with the deck. Thus, the tilt angle of the deck must be limited, reducing the steering angles of the front and rear wheels.

Therefore, the conventional skateboards with the four wheels must have large turning radiuses. If a rider desires to quickly change the moving direction of the skateboard at a large rotation angle, the rider must quickly forcibly turn the deck to a desired direction while raising the front wheel pair from the ground. Furthermore, when riding the skateboard on a horizontal surface, the rider must propel the skateboard with his/her foot like a conventional kickboard. Of course, some riders may forcibly move the skateboards forwards by exquisitely turning the deck while raising the front part of the deck upwards without propelling the skateboard with his/her foot. However, it is very difficult for skilled riders to perform the above- mentioned technique of moving the skateboard forwards

without propelling it with one foot.

Disclosure of the Invention Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a twist skateboard which generates a driving force to run forwards when a rider standing on the skateboard tilts the front and rear decks from side to side to steer the wheels, mounted to lower surfaces of the decks to the left and right, in place of propelling'the skateboard with a rider's foot or a pole.

In order to accomplish the above object, the present invention provides a twist skateboard, comprising front and rear decks each having a wheel assembly and coupled to each other into a single structure so that the decks tilt relative to each other, wherein front and rear wheel assemblies are mounted to the front and rear decks so that a wheel axle of each of the wheel assemblies is offset from a vertical axis at an inclination angle relative to the vertical axis by means of an inclined support plate; pipe holders are mounted to lower surfaces of the front and rear decks, with a connection pipe coupled to the pipe holders at both ends thereof by engagement of guide

protrusions of the pipe holders with longitudinal guide holes provided on both ends of the connection pipe, so that the decks tilt to the left and right within a range determined by the guide holes without being removed from each other; a torsion spring serving as a horizontality restoring means is placed in the connection pipe, with bent arms provided on both ends of the torsion spring being locked to locking holes provided on the pipe holders, thus generating a restoring force during a tilting motion of the decks ; and elastic bands couple the front and rear decks to each other so that front and rear decks tilt to the left and right within the range determined by the longitudinal guide holes without allowing the connection pipe from being removed from the pipe holders.

Brief Description of the Drawings FIG. 1 is an enlarged view illustrating the construction of a wheel assembly mounted to a conventional skateboard ; FIG. 2 is a perspective view illustrating the construction of a twist skateboard according to a first embodiment of the present invention; FIG. 3 is a bottom perspective view illustrating the construction of wheel assemblies of the skateboard according to the first embodiment of the present invention ;

FIG. 4 is a side view illustrating the construction of the skateboard according to the first embodiment of the present invention; FIG. 5 is a sectional view illustrating in detail the construction of a connection pipe of the skateboard according to the first embodiment of the present invention; FIG. 6 is a partially broken perspective view illustrating in detail the construction of the connection pipe of the skateboard according to the first embodiment of the present invention; FIG. 7 is a side view illustrating the construction of a twist skateboard with inclined support plates according to a second embodiment of the present invention ; FIG. 8 is a side view illustrating the construction of a twist skateboard with auxiliary wheels according to a third embodiment of the present invention; FIG. 9 is an enlarged sectional view illustrating the construction of a twist skateboard with an equalizing spring as a horizontality restoring means according to a fourth embodiment of the present invention; FIG. 10 is a bottom perspective view illustrating the construction of a twist skateboard according to a fifth embodiment of the present invention; FIG. 11 is a side sectional view illustrating the construction of the skateboard according to the fifth embodiment of the present invention; and

FIG. 12 is an exploded perspective view illustrating the construction of a connection pipe provided in the skateboard according to the fifth embodiment of the present invention.

Best Mode for Carrying Out the Invention The present invention will be described in detail herein below with reference to the accompanying drawings.

FIGS. 2 through 6 illustrate the construction of a twist skateboard according to a first embodiment of the present invention.

The skateboard comprises a front deck 11 and a rear deck 31 which are coupled together into a single structure so that the front and rear decks 11 and 31 tilt and turn relative to each other, with one wheel assembly 21,41 mounted to a lower surface of each of the front and rear decks 11 and 31, as shown in the drawings.

The wheel assemblies 21 and 41 are mounted to the front and rear decks 11 and 31 so that the wheel axle 23,43 of each wheel assembly 21,41 is offset from a vertical axis of the wheel assembly 21,41 by means of an inclined support plate 22,42.

The steering angle of each of the wheel assemblies 21 and 41 mounted to the inclined support plates 22 and 42 is limited by stoppers 27,47 which are provided at opposite

sides of each wheel assembly.

A pipe holder 12,32 is mounted to the lower surface of each of the front and rear decks 11 and 31 by means of a locking member 13,33. A longitudinal connection pipe 51 is coupled to the pipe holders 12 and 32 at both ends thereof.

In that case, a guide protrusion 53,55 which is provided on each of the pipe holders 12 and 32 engages with a longitudinal guide hole 52,54 which is formed in a circumferential direction on each end of the connection pipe 51. Thus, the connection pipe 51 is able to rotate within a range determined by the guide holes 52 and 54, without being undesirably removed from the pipe holders 12 and 32.

In the connection pipe 51, a torsion spring 56 serving as a horizontality restoring means is locked, at bent arms 57 and 58 provided on both ends thereof, to locking holes 14 and 34 formed on the pipe holders 12 and 32. Thus, a restoring force is generated in the torsion spring 56 during a tilting motion of the front and rear decks 11 and 31.

The coupling of the front and rear decks 11 and 31 is reinforced by elastic bands 15 and 16, so that the front and rear decks 11 and 31 can tilt at a predetermined tilt angle determined by the connection pipe 51 which is able to rotate within a range determined by the longitudinal guide holes 52 and 54, without being undesirably removed from the pipe holders 12 and 32.

The twist skateboard according to the first embodiment

of the present invention having the above-mentioned construction is assembled as follows: The pipe holders 12 and 32 are mounted to the lower surfaces of the front and rear decks 11 and 31. Thereafter, the connection pipe 51 is coupled to the pipe holders 12 and 32 at both ends thereof, with the longitudinal guide holes 52,54 of the connection pipe 51 movably engaging with the guide protrusions 53 and 55 of the pipe holders 12 and 32. Thus, the connection pipe 51 is able to rotate within a range determined by the guide holes 52 and 54, without being undesirably removed from the pipe holders 12 and 32.

The front and rear wheel assemblies 21 and 41 are mounted to the front and rear decks 11 and 31, respectively, so that the wheel axles 23 and 43 of the wheel assemblies 21 and 41 are offset from vertical axes of the wheel assemblies 21 and 41 at predetermined inclination angles relative to the vertical axes by means of the inclined support plates 22 and 42. To ride the twist skateboard, the rider places his/her left foot on the front deck 11 at a position just above the front wheel assembly 21, and thereafter, places his/her right foot on the rear deck 31 at a position just above the rear wheel assembly 41.

When the rider in the above state tilts his/her right foot to the left, the wheel axle 43 of the rear wheel assembly 41 mounted to the rear deck 31 tilts in the same direction relative to the vertical axis at a predetermined

angle.

In that case, the wheel axle 43 of the rear wheel assembly 41 intends to restore its original position. Thus, when the rider restores the original position of the rear deck 31 and, thereafter, tilts the rear deck 31 to the right with his/her right foot, a restoring force to restore the wheel axle 43 of the rear wheel, assembly 41 to its original position is generated. Thus, the twist skateboard generates a driving force to run forwards.

The restoring force to restore the original position of the wheel axle increases by the torsion spring 56 which serves as a horizontality restoring means. The spring 56 is locked, at bent arms 57 and 58 provided on both ends thereof, to the locking holes 14 and 34 of the pipe holders 12 and 32.

The torsion spring 56 thus increases the driving force to cause the skateboard to run forwards and maintains horizontality of the front and rear decks 11 and 31 even though the skateboard is used over a long period.

Each of the wheel assemblies 21 and 41 is limited in its steering angle by the stoppers 27,47 which are provided on each of the inclined support plates 22 and 42 at opposite sides of an associated wheel assembly. Thus, the rider enjoys board-riding stably and safely using the skateboard which reliably runs in a desired direction.

When the rider alternately tilts the rear deck 31 to the left and right as described above, the restoring force to

restore the wheel axle 43 of the rear wheel assembly 41 from a tilted position relative to the vertical axis to an original position is generated, and thus, the driving force to run the skateboard forwards is generated in the rear deck 31.

While the rear deck 31 moves forwards by the driving force generated by the rear wheel assembly 41, the rear deck 31 stably tilts to the left or right relative to the front deck 11 without being separated from the front deck 11 due to the elastic bands 15 and 16 and the connection pipe 51 which is supported at both ends thereof by the pipe holders 12 and 32 of the front and rear decks 11 and 31.

In that case, the rear deck 31 tilts within the range determined by the longitudinal guide holes 52 and 54 of the connection pipe 51, which engage with the guide protrusions 53 and 55 of the pipe holders 12 and 32.

In the meantime, when the rider tilts the front deck 11 to the left or right with his/her left foot placed on the front deck 11, a driving force to run the front deck 11 forwards is generated in the same manner as that described for the operation of the rear deck 31. Furthermore, when the rider tilts the front and rear decks 11 and 31 to the left or right at the same time, a higher driving force is generated.

In addition, the rider selects a moving direction of the skateboard by actuating the front deck 11. In that case, the twist skateboard smoothly turns to the left or right at

the junction between the front and rear decks 11 and 31 which are coupled to each other by means of both the connection pipe 51 and the elastic bands 15 and 16. Thus, the rider easily steers the skateboard to a desired direction.

FIG. 7 illustrates the construction of a twist skateboard with inclined support plates according to a second embodiment of the present invention.

Wheel assemblies 21 and 41 of this embodiment are mounted to front and rear decks 11 and 31 by means of inclined support plates 24 and 44 which are mounted to fixing bosses 25 and 45 of the decks 11 and 31 using locking bolts 25a and 45a, with springs 26 and 46 fitted over the locking bolts 25a and 45a to support the inclined support plates 24 and 44. Thus, the heights of the inclined support plates 24 and 44 from the lower surfaces of the decks 11 and 31 can be controlled by tightening or loosening the locking bolts 25a and 45a. Therefore, the rider adjusts the offset distances and the inclination angles of the wheel axles 23 and 43 of the wheel assemblies 21 and 41 relative to the vertical axes of the wheel assemblies 21 and 41 as desired. The restoring force of the wheel axles 23 and 43 increases in proportion to the offset distances and the inclination angles of the wheel axles 23 and 43 relative to the vertical axes of the front and rear wheel assemblies 21 and 41, in which the offset distances and the inclination angles of the wheel axles relative to

the vertical axes can be adjusted by controlling the heights of the inclined support plates 24 and 44. The skateboard having a higher restoring force runs fast, causing danger, so that the function of controlling the restoring force by adjusting the offset distances and the inclination angles of the wheel axles relative to the vertical axes must be limitedly used by highly skilled riders.

FIG. 8 illustrates the construction of a twist skateboard with auxiliary wheels mounted to the rear deck according to a third embodiment of the present invention.

Two auxiliary wheels 35 of this embodiment are mounted side by side to the rear portion of the rear deck 31 having a reverse turn. This skateboard allows the rider to quickly turn the skateboard to a desired direction or smoothly pass over or by an obstacle while raising the front wheel assembly 21 of the front deck 11 upwards from the ground and maintaining both the rear wheel assembly 41 and the two auxiliary wheels 35 which are in contact with the ground.

FIG. 9 illustrates the construction of a twist skateboard with an equalizing spring used as a horizontality restoring means according to a fourth embodiment of the present invention.

Pipe holders 12 and 32 of this embodiment are mounted to the lower surfaces of front and rear decks 11 and 31 by

means of locking members 13 and 33. A longitudinal connection pipe 51 is coupled to the pipe holders 12 and 32 at both ends thereof, with guide protrusions 53 and 55 of the pipe holders 12 and 32 engaging with longitudinal guide holes 52 and 54 of the connection pipe 51.

Furthermore, equalizing springs 17 and 36 are mounted to the lower surfaces of the front and rear decks 11 and 31 to elastically support the connection pipe 51.

The middle portions of the equalizing springs 17 and 36 are in contact with the upper portion of the connection pipe 51, while opposite parts 18, 37 of each of the equalizing springs 17 and 36, which are bent upwards to provide elasticity, are in contact with the lower surface of an associated deck 11,31. The equalizing springs 17 and 36 thus elastically bias the connection pipe 51.

When the front deck 11 and the rear deck 31 tilt to the left or right, the equalizing springs 17 and 36 increase the restoring force of the front and rear wheel assemblies 21 and 31, thus providing a higher restoring force. The equalizing springs 17 and 36 thus increase the driving force to cause the skateboard to run forwards and maintain horizontality of the front and rear decks 11 and 31 even though the skateboard is used over a long period.

FIGS. 10 through 12 illustrates the construction of a twist skateboard according to a fifth embodiment of the present invention.

Wheel assemblies 71 and 91 of this embodiment are mounted to front and rear decks 61 and 81 by means of inclined support plates 72 and 92 which are mounted to locking bosses 73 and 93 of the decks 61 and 81 by means of locking bolts 73a and 93a. Springs 74 and 94 are fitted over the locking bolts 73a and 93a to support the inclined support plates 72 and 92. Thus, the heights of the inclined support plates 72 and 92 from the lower surfaces of the front and rear decks 61 and 81 can be controlled by tightening or loosening the locking bolts 73a and 93a.

Therefore, the offset distances and the inclination angles of wheel axles 75 and 95 of the wheel assemblies 71 and 91 relative to vertical axes of the wheel assemblies 71 and 91 can be adjusted as desired.

Furthermore, pipe holders 62 and 82 are mounted to the lower surfaces of the front and rear decks 61 and 81.

Each of two connection pipes 63 and 83, which : are coupled to the pipe holders 62 and 82 at first ends thereof, are provided with two slits 64 and 65,84 and 85 at diametrically opposite sides of a second end thereof, with two longitudinal guide holes 66,86 formed on upper and lower parts of the second end of each connection pipe.

A coupling pipe 101 having a protrusion 102,103 at each end thereof is coupled by hinges to the second ends of the two connection pipes 63 and 83 by engagement of the protrusions 102 and 103 with the slits 64 and 65,84 and 85

of the connection pipes 63 and 83. The connection pipes 63 and 83 thus turn to the left and right due to the slits 64 and 65,84 and 85. Furthermore, the longitudinal guide holes 66 and 86 of the connection pipes 63 and 83 are coupled to bolt holes 104 and 105 formed on both ends of the coupling pipe 101 by means of bolts 106 and nuts 107. Thus, the connection pipes 63 and 83 are able to tilt to the left or right within a range determined by the guide holes 66 and 86 without being undesirably removed from each other.

In the skateboard having the above-mentioned construction, the wheel assemblies 71 and 91, which are mounted to the front and rear decks 61 and 81, are constructed so that the offset distances and the inclination angles of the wheel axles 75 and 95 relative to the vertical axes of the wheel assemblies can be adjusted as desired by means of the inclined support plates 72 and 92 of which the heights from the lower surfaces of the front and rear decks can be controlled by tightening or loosening the locking bolts 74 screwed to the locking bosses 73.

Furthermore, the pipe holders 62 and 82 are mounted to the lower surfaces of the front and rear decks 61 and 81.

Thereafter, the two connection pipes 63 and 83 are coupled to the pipe holders 62 and 82 at first ends thereof, while the coupling pipe 51 is coupled by hinges to the second ends of the connection pipes 63 and 83 by engagement of the

protrusions 52 and 53 of the coupling pipe with the slits 64 and 65, 84 and 85 of the connection pipes 63 and 83. Thus, the connection pipes 63 and 83 turn to the left and right within a predetermined range.

In addition, the longitudinal guide holes 66 and 86 of the connection pipes 63 and 83 are coupled to the bolt holes 54 and 55 formed on both ends of the coupling pipe 51 by means of bolts 56 and nuts 57. Thus, the connection pipes 63 and 83 are able to tilt to the left or right within a range, determined by the longitudinal guide holes 66 and 86, without being undesirably removed from each other.

The wheel assemblies 71 and 91 of this embodiment, which are mounted to the front and rear decks 61 and 81, are designed so that the offset distances and the inclination angles of the wheel axles 75 and 95 relative to the vertical axes of the wheel assemblies 71 and 91 can be controlled as desired by means of the inclined support plates 72 and 92 of which the heights from the lower surfaces of the decks can be controlled by tightening or loosening the locking bolts 74 that are screwed to the fixing bosses 73. The rider thus increases or reduces the offset distances and the inclination angles of the wheel axles relative to the vertical axes of the wheel assemblies by controlling the heights of the inclined support plates 72 and 92 according to his/her board-riding technique.

To ride the skateboard after the heights of the

inclined support plates 72 and 92 are appropriately controlled, the rider places his/her left foot on the front deck 61 at a position just above the front wheel assembly 71, and thereafter, places his/her right foot on the rear deck 81 at a position just above the rear wheel assembly 91.

When the rider in the above state tilts his/her right foot to the left, the wheel axle 95 of the rear wheel assembly 91 mounted to the rear deck 81 tilts in the same direction relative to the vertical axis at a predetermined angle.

In that case, the wheel axle 95 of the rear wheel assembly 91 intends to restore its original position. Thus, when the rider restores the original position of the rear deck 91 and, thereafter, tilts the rear deck 91 to the right with his/her right foot, a restoring force to restore the wheel axle 95 of the rear wheel assembly 91 to its original position is generated. Thus, the twist skateboard generates a driving force to run forwards.

When the rear deck 81 alternately tilts to the left and right as described above, the restoring force to restore the wheel axle 75,95 of the wheel assembly 91 from its tilted position relative to the vertical axis to its original position is generated. Thus, a driving force to cause the wheel assembly 91 to run forwards is generated.

In that case, the restoring force to restore the wheel axles 75 and 95 increases in proportion to the offset

distances and the inclination angles of the wheel axles of the wheel assemblies 71 and 91 relative to the vertical axes, which are determined by the inclined support plates 72. The skateboard having a higher restoring force runs fast, causing danger, so that the function of controlling the restoring force must be limitedly used by highly skilled riders.

While the rear deck 81 moves forwards by the driving force generated by the rear wheel assembly 91, the rear deck 81 stably tilts to the left or right relative to the front deck 61 without being separated from the front deck 61 due to the coupling structure in that the longitudinal guide hole 86 of the rear connection pipe 83 which is supported at the first end thereof by the pipe holder 82 of the rear deck 81 is coupled to the bolt hole 105 of the coupling pipe 101 using the bolt 106 and nut 107.

In that case, the rear deck 81 tilts within the range determined by the longitudinal guide holes 66 and 86.

In the meantime, when the rider tilts the front deck 61 to the left or right with his/her left foot placed on the front deck 61, a driving force to run the front deck 61 forwards is generated in the same manner as that described for the operation of the rear deck 81. Furthermore, when the rider tilts the front and rear decks 61 and 81 to the left or right at the same time, a higher driving force is generated.

In addition, the rider selects a moving direction of

the skateboard by actuating the front deck 81. In that case, the twist skateboard smoothly turns to the left or right by the coupling structure in that the front protrusion 102 of the coupling pipe 101 is coupled to the slits 64 and 65 of the front connection pipe 63 of which the first end is supported by the pipe folder 62 of the front deck 61. That is, the protrusion 102 of the coupling pipe 101 turns relative to the slits 64 and 65 of the front connection pipe 63 so that the skateboard moves in a desired direction as the rider steers.

As the front deck 61 moves in the desired direction, the rear deck 81 coupled to the front deck 61 through the coupling pipe 101, of which the rear protrusion 103 is coupled to the slits 84 and 35 of the rear connection pipe 83, stably turns within a predetermined range allowed by, the slits.

In that case, the longitudinal guide holes 66 and 86 of the connection pipes 63 and 83 are coupled to the bolt holes 104 and 105 formed on both ends of the coupling pipe 101 by means of the bolts 106 and nuts 107. Thus, the turning motion of the skateboard is more stably executed, allowing the rider to enjoy dynamic board-riding.

Industrial Applicability As described above, the present invention provides a

twist skateboard, in which wheel assemblies mounted to front and rear decks are constructed so that the offset distances and the inclination angles of the wheel axles of the wheel assemblies relative to vertical axes of the wheel assemblies can be adjusted as desired by means of inclined support plates of which the heights are controlled by tightening or loosening associated locking bolts.

A coupling pipe is coupled between pipe holders mounted to the lower surfaces of the front and rear decks so that the coupling pipe turns to the left and right due to protrusions of the coupling pipe coupled to slits of connection pipes and tilts to the left and right due to bolt holes of the coupling pipe coupled to longitudinal guide holes of the connection pipes. Thus, the skateboard moves forwards as a rider tilts the skateboard to the left and right without imposing another external force on the skateboard. Furthermore, the skateboard is smoothly steered by a tilting motion and a turning motion.