Description SKATEBOARD

Technical Field

[1] The present invention relates to a skateboard, and more particularly, to a skateboard wherein a structure, in which a directional caster is coupled to elastic restoring means mounted to a lower surface of a board, is adopted, so that people can easily enjoy skateboarding even without sufficient practice and even a beginner can balance easily, turn smoothly, and ride stably. Background Art

[2] Recently, various kinds of stake boards for leisure time activities have been disclosed in the art, and have generated considerable consumer interest.

[3] A typical example of such skateboards is described in Korean Patent No.

10-0394848 entitled "Skateboard having directional caster."

[4] FIG. 1 is a perspective view illustrating the overall construction of a conventional skateboard.

[5] Referring to FIG. 1, at least one of front and rear boards 10 and 20 includes at least one of directional casters 13 and 23 which are attached to the lower surfaces of plates 11 and 21. A connection member between the front and rear boards 10 and 20 has an elastic element which permits elastic restoring of the connection member when the connection member is twisted or bent.

[6] In order to enable both riding and turning using each of the front and rear boards 10 and 20, it is essential that only one of the directional casters 13 and 23 be mounted to each of the front and rear boards 10 and 20.

[7] However, the conventional skateboard has a problem in that, when a plurality of directional casters is mounted to each of the front and rear boards 10 and 20, turning cannot be properly conducted, and the fun of skateboarding is markedly decreased.

[8] Also, it takes a long time to become a skilled rider, and it is difficult for a beginner to balance and ride while placing the feet on the front and rear boards 10 and 20 to thus easily enjoy skateboarding.

[9] Further, in the case of the conventional skateboard, the connection member, which has a torsional pipe 40 and the elastic element (not shown), is likely to break when the connection member collides with a projection on the ground, thus incurring a substantial cost to repair or replace the connection member. Disclosure of Invention Technical Problem

[10] Accordingly, the present invention has been made in an effort to solve the problems

occurring in the related art, and an object of the present invention is to provide a skateboard which allows a beginner to balance easily, turn smoothly, and ride stably even without sufficient practice, and which enables spectacular tricks to be easily practiced.

[11] Another object of the present invention is to provide a skateboard which can efficiently generate propulsive force without the nuisance of having to kick the ground. Technical Solution

[12] In order to achieve the above objects, according to one aspect of the present invention, there is provided a skateboard comprising a board; at least one fixed member mounted to each of front and rear parts on the lower surface of the board to extend in the lengthwise direction of the board; elastic restoring means coupled to each fixed member to be twisted in a horizontal direction with respect to the board by a vertical load applied from the upper part of the board; and a directional caster coupled to the elastic restoring means.

[13] According to another aspect of the present invention, the fixed member comprises a front fixed member having a coupling hole having a circular sectional shape, and a rear fixed member having a tubular configuration which is closed and defined with a fastening groove at one end thereof and is open at the other end thereof so that a guide path is defined in the lengthwise direction of the rear fixed member; and the coupling hole and the fastening groove are aligned with each other.

[14] According to another aspect of the present invention, the elastic restoring means comprises a rotation shaft having a front end which is coupled into the coupling hole of the front fixed member and a rear end which is defined with a locking groove; a torsion bar, one end of which is fitted into the fastening groove and the other end of which is fitted into the locking groove, to be repeatedly twisted and then restored to its original shape corresponding to movement of the rotation shaft; and an adjustor having a shape corresponding to the sectional shape of the guide path and defined with an opening which has a sectional shape corresponding to the shape of the torsion bar and through which the adjustor is movably fitted around the torsion bar to adjust the twisting of the torsion bar.

[15] According to another aspect of the present invention, the adjustor is fastened to the torsion bar by means of a fastener which is threaded through a hole defined in one side wall of the adjustor.

[16] According to another aspect of the present invention, the torsion bar is formed by stacking a plurality of metallic plates.

[17] According to another aspect of the present invention, the directional caster is rotatably coupled to the lower end of a bracket which is provided to the rotation shaft.

[18] In order to achieve the above objects, according to still another aspect of the present invention, there is provided a skateboard comprising front and rear boards formed separately from each other; at least one fixed member mounted to the lower surface of each of the front and rear boards; elastic restoring means coupled to each fixed member to be twisted in a horizontal direction with respect to the board by a vertical load applied from an upper part of the board; a directional caster coupled to the elastic restoring means; coupling elements projectedly formed on lower surfaces of the front and rear boards, respectively; and a connection pipe having the shape of a rod both ends of which are rotatably coupled to the coupling elements.

[19] According to a still further aspect of the present invention, in each of the front and rear boards, a coupling groove having a diameter corresponding to that of the connection pipe is defined in the coupling element, and a bearing that is brought into contact with the circumferential outer surface of the connection pipe is fitted into the coupling groove.

Advantageous Effects

[20] Thanks to the above-mentioned features of the present invention, advantages are provided as described below.

[21] First, due to the fact that a structure in which at least one elastic restoring means and at least one directional caster are mounted to each of front and rear parts on the lower surface of a board, is adopted, propulsive force can be generated simply by twisting the body or by moving the center of gravity forward or rearward using the feet placed on the board, without the need to kick the ground in order to ride. As a result, even a beginner can easily enjoy skateboarding without much practice, and it is possible to draw considerable consumer interest.

[22] Further, since a structure, in which elastic restoring means is mounted to each directional caster, is adopted, when the elastic restoring means is broken by an external shock, replacement or repair of the elastic restoring means can be easily performed, and the cost thereby incurred is significantly reduced, so that economic efficiency is ensured. In this regard, in the conventional skateboard, the financial burden is increased because the entire connection member including the elastic element must be replaced, or else it is necessary to purchase a new skateboard.

[23] Also, in the present invention, a structure wherein front and rear boards, to each of which a fixed member and elastic restoring means having coupled thereto a directional caster are mounted, are rotatably connected with each other by means of a connection pipe, is adopted. Therefore, highly angular movements, including sudden changes of direction, riding along a sharply curved course, and making 360° turns without moving, can be performed.

Brief Description of the Drawings

[24] The above objects, and other features and advantages of the present invention will become more apparent after reading the following detailed description in conjunction with the drawings, in which: [25] FIG. 1 is a perspective view illustrating the overall construction of a conventional skateboard; [26] FIG. 2 is a perspective view illustrating a skateboard in accordance with one embodiment of the present invention; [27] FIG. 3 is an exploded perspective view illustrating the structures of a fixed member, elastic restoring means and a directional caster, which are the main parts of the skateboard according to the present invention; [28] FIG. 4 is perspective views each illustrating a torsion bar, which is the main part of the skateboard according to the present invention; [29] FIG. 5 is perspective views each illustrating the use of the torsion bar as the main part of the skateboard according to the present invention; [30] FIG. 6 is perspective views illustrating various examples of arranging the assembly of the fixed member, the elastic restoring means and the directional caster, which are the main parts of the skateboard according to the present invention; [31] FIG. 7 is a perspective view illustrating a skateboard in accordance with another embodiment of the present invention; [32] FIG. 8 is an exploded perspective view illustrating an assembly pattern between front and rear boards and a connection pipe which constitute the skateboard in accordance with another embodiment of the present invention; [33] FIG. 9 is conceptual views illustrating examples of elastic restoring means as the main part of the skateboard in accordance with another embodiment of the present invention; [34] FIG. 10 is conceptual views illustrating exemplary operation of the skateboard in accordance with one embodiment of the present invention; [35] FIG. 11 is conceptual views illustrating more exemplary operation of the skateboard in accordance with one embodiment of the present invention; and [36] FIG. 12 is conceptual views illustrating exemplary operation of the skateboard in accordance with another embodiment of the present invention. [37] <Description of Reference Numerals for Main Parts of Drawings>

[38] 10: board

[39] 100, 100' : front and rear boards

[40] 120, 120': coupling elements

[41 ] 20, 200: fixed members

[42] 22, 220: front fixed members

[43] 24, 240: rear fixed members

[44] 30, 300: elastic restoring means

[45] 32, 320: rotation shafts

[46] 34, 340: torsion bars

[47] 36, 360: adjustors

[48] 40, 400: directional casters

[49] 500: connection pipe

[50] 510, 510': bearings

Best Mode for Carrying Out the Invention

[51] Reference will now be made in greater detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts.

[52]

[53] First Embodiment

[54] FIG. 2 is a perspective view illustrating a skateboard in accordance with one embodiment of the present invention.

[55] Referring to FIG. 2, the skateboard having elastic restoring means in accordance with one embodiment of the present invention largely comprises a board 10, at least one fixed member 20 mounted to each of front and rear parts on the lower surface of the board 10, elastic restoring means (not shown in FIG. 2) coupled to the fixed member 20, and a directional caster 40 coupled to the elastic restoring means.

[56] Here, the directional caster 40 is selected so that it can be coupled to the lower part of the elastic restoring means so that its direction can be freely changed.

[57] Hereafter, the main parts of the skateboard according to the present invention will be described in detail with reference to the attached drawings.

[58] FIG. 3 is an exploded perspective view illustrating the structures of the fixed member, the elastic restoring means and the directional caster, which are the main parts of the skateboard according to the present invention.

[59] Referring to FIG. 3, the skateboard according to the present invention enables various motions, such as riding and turning due to the presence of the elastic restoring means 30 and the directional caster 40 which are coupled to the fixed member 20 on the lower surface of the board 10 (see FIG. 2).

[60] At least one fixed member 20 is mounted to each of front and rear parts on the lower surface of the board 10 to extend in the lengthwise direction of the board 10. The fixed member 20 largely comprises a front fixed member 22 and a rear fixed member

24.

[61] While the front and rear fixed members 22 and 24 are illustrated as being manufactured separately from the board 10 and being fastened to the lower surface of the board 10 by means of fasteners 50, the present invention is not limited to the construction shown in this illustration, and it is to be appreciated that the front and rear fixed members 22 and 24 can be manufactured integrally with the board 10.

[62] The front fixed member 22 is defined with a coupling hole 21 which has a circular sectional shape and into which the rotation shaft 32 of the elastic restoring means 30 is coupled.

[63] The rear fixed member 24 has a tubular configuration which is closed at one end thereof and is open at the other end thereof, and defines therein a guide path 25 which extends in the lengthwise direction of the rear fixed member 24.

[64] A fastening groove 23 is defined in one end of the rear fixed member 24, and a plurality of locking holes 26 is defined at regular intervals through the side wall of the rear fixed member 24 along the guide path 25.

[65] A cylindrical coupler 27 is formed on the other end of the rear fixed member 24 such that the rotation shaft 32 is fitted into the cylindrical coupler 27.

[66] Preferably, the coupling hole 21 of the front fixed member 22 and the coupler 27 of the rear fixed member 24 are linearly arranged so as to allow the elastic restoring means 30 to be properly coupled into the coupling hole 21 and the coupler 27.

[67] The elastic restoring means 30 is disposed in the fixed member 20, more concretely, between the front and rear fixed members 22 and 24. The elastic restoring means 30 largely comprises the rotation shaft 32, a torsion bar 34, and an adjustor 36.

[68] The rotation shaft 32 has a predetermined length and has a circular column-shaped configuration. The front end of the rotation shaft 32 is fitted into the coupling hole 21 of the front fixed member 22 and is brought into surface contact with the front fixed member 22. The rear end of the rotation shaft 32 is defined with a locking groove 31 and is fitted into the coupler 27 of the rear fixed member 24 so as to be brought into surface contact with the rear fixed member 24.

[69] The rotation shaft 32 is arranged in the lengthwise direction of the board 10.

[70] Preferably, surface contact or roller bearings are interposed between the front end of the rotation shaft 32 and the coupling hole 21 of the front fixed member 22 and between the rear end of the rotation shaft 32 and the coupler 27 of the rear fixed member 24 to allow the rotation shaft 32 to be rotated within a predetermined angular range in a horizontal direction upon the application of vertical external force from the upper part of the board 10.

[71] The torsion bar 34 is formed by stacking a plurality of metallic plates each having a predetermined length and width. The torsion bar 34 is arranged such that the

lengthwise direction of the torsion bar 34 is parallel to the lengthwise direction of the board 10 and the main surface of each plate is perpendicular to the plane of the board 10.

[72] It is to be understood that the torsion bar 34 can be formed of other conventional materials well known in the art, such as synthetic resin, synthetic rubber, and the like, as long as the torsion bar 34 can be twisted upon the application of vertical external force from the upper part of the board 10.

[73] While the main surface of each plate constituting the torsion bar 34 according to the present invention is illustrated as being perpendicular to the plane of the board 10, the present invention is not limited to the construction shown in this illustration, and the torsion bar 34 can be arranged in a manner such that the main surface of each plate is parallel to the plane of the board 10, so long as the structure can allow the twisting of the torsion bar 34.

[74] One end of the torsion bar 34 is fitted into the fastening groove 23 of the rear fixed member 24, and the other end of the torsion bar 34 is fitted into the locking groove 31 of the rotation shaft 32. To this end, each of the fastening groove 23 and the locking groove 31 has a sectional shape which corresponds to that of the torsion bar 34 and is defined to be perpendicular to the plane of the board 10.

[75] As in the case of the torsion bar 34, while each of the fastening groove 23 and the locking groove 31 is illustrated as being defined to be perpendicular to the plane of the board 10, the present invention is not limited to the construction shown in this illustration, and each of the fastening groove 23 and the locking groove 31 can be defined to be parallel to the plane of the board 10.

[76] The fastening groove 23 of the rear fixed member 24 and the locking groove 31 of the rotation shaft 32 are linearly arranged.

[77] The torsion bar 34 is twisted upon the application of vertical external force from the upper part of the board 10, that is, by the weight of a rider.

[78] This is permissible because one end of the torsion bar 34 is securely coupled into the fastening groove 23 of the rear fixed member 24 and serves as one fixed end, and the other end of the torsion bar 34 is coupled into the locking groove 31 of the rotation shaft 32 having the front end fitted into the coupling hole 21 to be brought into surface contact with the front fixed member 22 and to be rotated within the predetermined angular range, and serves as the other fixed end.

[79] The adjustor 36 is mounted to adjust the twisting degree of the torsion bar 34.

[80] The adjustor 36 has the configuration of a quadrangular tube which has a shape corresponding to the sectional shape of the guide path 25 of the rear fixed member 24, and defines an opening 35 which has a sectional shape corresponding to the shape of the torsion bar 34. The adjustor 36 can adjust the twisting degree of the torsion bar 34

while being moved on the torsion bar 34.

[81] The adjustor 36 is fastened to the torsion bar 34 by means of a fastener 38 which is threaded through a through-hole 37 defined in a side wall of the adjustor 36.

[82] The fastening of the adjustor 36 is not limited to threaded fastening, and as an alternative, various fastening schemes, such as engagement between a projection and a groove, can be adopted.

[83] By aligning one of the locking holes 26 defined in the side wall of the rear fixed member 24 with the through-hole 37 of the adjustor 36 and then threading the fastener 38 through the locking hole 26 and the through-hole 37, the adjustor 36 can be securely fastened around the torsion bar 34.

[84] A slit which has a width roughly corresponding to the diameter of the threaded portion of the fastener 38, is defined in the side wall of the rear fixed member 24 so as to extend parallel to the guide path 25. Therefore, by grasping the head portion of the fastener 38 and moving the adjustor 36 in the lengthwise direction of the torsion bar 34, the twisting degree of the torsion bar 34 can be easily adjusted.

[85] The directional caster 40 is rotatably coupled to the lower end of a bracket 41 which is provided to the rotation shaft 32. The lower end of the bracket 41 is inclined with respect to the plane of the board 10 so as to define an acute angle therebetween.

[86] The bracket 41 is rotated within the predetermined angular range in the horizontal direction parallel to the plane of the board 10, following the movement of the rotation shaft 32.

[87] In the skateboard according to the present invention, constructed as mentioned above, the torsion bar 34 can be modified and applied in a variety of ways as shown in FIGs. 4 and 5.

[88] FIG. 4 is perspective views each illustrating the torsion bar as the main part of the skateboard according to the present invention, and FIG. 5 is perspective views each illustrating the use of the torsion bar as the main part of the skateboard according to the present invention.

[89] The torsion bar 34 according to the present invention is formed by stacking the plurality of metallic plates. In this regard, by stacking more metallic plates as shown in FIG. 4(b), compared to FIG. 4(a), the twisting degree of the torsion bar 34 can be decreased.

[90] That is to say, in consideration of the weight of a rider, the number of plates which constitute the torsion bar 34 can be appropriately increased or decreased. For example, in the case where the skateboard according to the present invention is used by a child, a smaller number of plates constituting the torsion bar 34 can be stacked to allow the torsion bar 34 to be more easily twisted.

[91] Meanwhile, the twisting of the torsion bar 34 can be adjusted depending upon a

position of the adjustor 36 which is moved on the torsion bar 34. [92] For reference, in FIG. 5, illustrating the torsion bar 34 and the adjustor 36, it is assumed that the left sides of FIGs. 5 (a) and 5(b) represent the front, in which the front fixed member 22 is mounted, and the right sides of FIGs. 5 (a) and 5(b) represent the rear, in which the rear fixed member 24 is mounted. [93] As shown in FIG. 5(b), if the adjustor 36 is moved forward when compared to the adjustor 36 shown in FIG. 5(a), because the adjustor 36 of FIG. 5(b) hinders the twisting of the torsion bar 34 to an increased extent, it is more difficult to twist the torsion bar 34 of FIG. 5(b) compared to the torsion bar 34 of FIG. 5 (a). [94] Therefore, in the case where the skateboard according to the present invention is used by an adult, by moving the position of the adjustor 36 forward, it becomes more difficult to twist the torsion bar 34. [95] Also, by adequately changing the locations of the directional casters 40 on the lower surface of the board 10, the skateboard according to the present invention, constructed as mentioned above, can be modified in a variety of ways, as shown in

FIG. 6. [96] First, as shown in FIG. 6(a), a construction, in which two directional casters 40 are located on each of the front and rear parts of the lower surface of the board 10, can be considered, and as shown in FIG. 6(b), one directional caster 40 can be located on each of the front and rear parts of the lower surface of the board 10. [97] Besides, as shown in FIG. 6(c), one directional caster 40 can be located on the front part and two directional casters 40 can be located on the rear part, and in contrast, as shown in FIG. 6(d), two directional casters 40 can be located on the front part and one directional caster 40 can be located on the rear part. [98] Thus, by locating directional casters 40 on the lower surface of the board 10 in a variety of ways, as shown in FIG. 6, it is possible to best match a skateboard to the various abilities of a beginner, an expert and an intermediate rider. [99] For example, an expert who can easily balance, can use the skateboard shown in

FIG. 6(b), a beginner can use the skateboard shown in FIG. 6(a), and an intermediate rider, situated between the expert and the beginner, can use the skateboard shown in

FIG. 6(c) or 6(d). [100] When a rider rides on the skateboard according to the present invention and moves straight ahead, the torsion bar 34 (see FIG. 3) arranged on the lower surface of the board 10 leans outward with respect to the board 10 under the action of vertical external force applied by the weight of the rider. [101] In other words, as the torsion bar 34 leans outward with respect to the board 10, the distance between the ground and the board 10 is shortened, as a result of which the rider can more stably ride on the ground.

[102] The skateboard according to the present invention, constructed as mentioned above, can be applied to another embodiment, as shown in FIG. 7.

[103]

[ 104] Second Embodiment

[105] Referring to FIG. 7, the skateboard in accordance with another embodiment of the present invention includes front and rear boards 100 and 100' which are separately formed and arranged in front and rear positions. Each of the front and rear boards 100 and 100' comprises at least one fixed member 200 mounted to the lower surface of the board, elastic restoring means (not shown in FIG. 7) coupled to the fixed member 200, and a directional caster 400 coupled to the elastic restoring means. Coupling elements 120 and 120' are projectedly formed on the lower surfaces of the front and rear boards 100 and 100', respectively, and a connection pipe 500 is coupled to the coupling elements 120 and 120'.

[106] The front and rear boards 100 and 100' are connected with each other so that each of the front and rear boards 100 and 100' can be rotated through 360° around the axis of the connection pipe 500.

[107] Regarding the detailed structures of and the coupling relationships among the fixed member 200, the elastic restoring means 300 and the directional caster 400, refer to FIG. 3. As can be seen, the detailed structures of and the coupling relationships between the fixed member 200, the elastic restoring means 300 and the directional caster 400 are the same as those of the aforementioned embodiment, thus detailed descriptions thereof will be omitted herein.

[108] In the skateboard according to this embodiment of the present invention, constructed as mentioned above, as shown in FIG. 8, the front and rear boards 100 and 100' are connected with each other by the connection pipe 500. Both ends of the connection pipe 500 are rotatably coupled into the coupling grooves 110 and 110' defined in the coupling elements 120 and 120', which are projectedly formed on the lower surfaces of the front and rear boards 100 and 100'.

[109] The coupling grooves 110 and 110' of the coupling elements 120 and 120' have a diameter which substantially corresponds to the diameter of the connection pipe 500. Preferably, bearings 510 and 510' are interposed between the coupling elements 120 and 120' and the circumferential outer surfaces of both ends of the connection pipe 500.

[110] The bearings 510 and 510' may comprise rolling contact or surface contact bearings or bush bearings. Meanwhile, it can be envisaged that the connection pipe 500 is made of a material having a low frictional coefficient, and can be rotatably coupled directly to the coupling elements 120 and 120'.

[I l l] In the skateboard according to the present invention, as shown in FIG. 9, the

component of the elastic restoring means 300 which is equivalent to the torsion bar 340 can be embodied as one of various parts.

[112] Regarding the reference numerals which are not described in FIG. 9, FIGs. 3, 7 and

8 can be referred to, and this also applies to FIG. 12, which will be described later.

[113] In the present invention, as shown in FIG. 9(a), the torsion bar 340 can be provided as the component of the elastic restoring means 300 which is disposed in the fixed member 200. Also, as shown in FIGs. 9(b) and 9(c), wing plates W are formed on both sides of the rotation shaft 320, and a coil spring S or a leaf spring P is disposed between the wing plates W and each of the boards 100 and 100'.

[114] Hereinbelow, various operation of the skateboards according to the first and second embodiments of the present invention will be described.

[115] FIG. 10 is conceptual views illustrating exemplary operation of the skateboard in accordance with one embodiment of the present invention.

[116] It is assumed that, between the two feet (not shown) placed on the board 10, the foot adjacent to the arrow shown in the drawing represents the left foot, and the other foot represents the right foot. Also, it is assumed that the direction indicated by the arrow represents a forward direction, and that the direction opposite to that indicated by the arrow represents a rearward direction.

[117] The states of the board 10 and the torsion bars 34, which are illustrated in front of the board 10, are obtained through viewing the skateboard according to the present invention from the front with respect to the movement direction indicated by the arrow.

[118] The states of the board 10 and the torsion bars 34 which are illustrated at the back of the board 10 are obtained through viewing the skateboard according to the present invention from the rear with respect to the movement direction indicated by the arrow.

[119] This also applies to FIG. 11.

[120] First, with both feet positioned on the board 10, if a rider applies force F to the rear portion of the left foot by twisting the body leftward as shown in FIG. 10(a), that is, to the left part of the board 10 in the position of the left foot when viewed from the movement direction indicated by the arrow, the directional casters 40 provided to the front part of the board 10 are rotated rightward about their rotation shafts 32, and the skateboard moves forward.

[121] At this time, the torsion bars 34 provided to the front part of the board 10 are twisted leftward when viewed in the movement direction indicated by the arrow, in conformity with the rotation of the rotation shafts 32.

[122] Then, as the rider applies opposite force F to the front portion of the left foot by twisting the body rightward, the skateboard can move in the direction indicated by the arrow in FIG. 10(a).

[123] As the rider applies opposite force F, the torsion bars 34 provided to the front part

of the board 10 are untwisted to be perpendicular to the ground and then twisted rightward when viewed in the movement direction indicated by the arrow.

[124] Conversely, when the rider applies force F to the rear portion of the right foot by twisting the body rightward as shown in FIG. 10(b), that is, to the left part of the board 10 in the position of the right foot when viewed from the movement direction indicated by the arrow, the directional casters 40 provided to the rear part of the board 10 are rotated rightward about their rotation shafts 32, and the skateboard moves forward.

[125] At this time, the torsion bars 34 provided to the rear part of the board 10 are twisted leftward when viewed in the movement direction indicated by the arrow, in conformity with the rotation of the rotation shafts 32.

[126] Then, as the rider applies opposite force F to the front portion of the right foot by twisting the body leftward, the skateboard can move in the direction indicated by the arrow in FIG. 10(b).

[127] As the rider applies opposite force F, the torsion bars 34 provided to the rear part of the board 10 are untwisted to be perpendicular to the ground and then twisted rightward when viewed in the movement direction indicated by the arrow.

[128] Also, the rider can simultaneously apply force F to the rear portion of the left foot and the front portion of the right foot by twisting the body to ride in the direction indicated by the arrow in FIG. 10(c).

[129] Namely, if the rider applies force to the left part of the board 10 in the position of the left foot and to the right part of the board 10 in the position of the right foot when viewed from the movement direction indicated by the arrow, the directional casters 40 provided to the front part of the board 10 are rotated rightward about their rotation shafts 32, and the directional casters 40 provided to the rear part of the board 10 are rotated leftward about their rotation shafts 32, and thus the skateboard starts to move forward.

[130] At this time, the torsion bars 34 provided to the front part of the board 10 are twisted leftward when viewed in the movement direction indicated by the arrow, in conformity with the rotation of the rotation shafts 32. Further, the torsion bars 34 provided to the rear part of the board 10 are twisted rightward when viewed in the movement direction indicated by the arrow, in conformity with the rotation of the rotation shafts 32.

[131] Then, as the rider applies opposite force F to the front portion of the left foot and to the rear portion of the right foot, the skateboard can move in the direction indicated by the arrow in FIG. 10(c).

[132] As the rider applies opposite force F, the torsion bars 34 provided to the front part of the board 10 are untwisted to be perpendicular to the ground and then twisted rightward, and the torsion bars 34 provided to the rear part of the board 10 are

untwisted to be perpendicular to the ground and then twisted leftward, when viewed in the movement direction indicated by the arrow. [133] Meanwhile, the skateboard according to the present invention can move while a rider alternately applies force F to the front and rear portions of both feet as shown in

FIG. 11.

[134] In FIG. 11, reference character f designates a foot.

[135] First, with both feet f positioned on the board 10, if a rider applies force F to the front portions of the left and right feet as shown in FIG. 1 l(a), the directional casters

40 provided to the front part of the board 10 are rotated leftward about their rotation shafts 32, and the directional casters 40 provided to the rear part of the board 10 are rotated rightward about their rotation shafts 32, when viewed in the direction indicated by the arrow, by which the skateboard starts to move forward. [136] At this time, the torsion bars 34 provided to both front and rear parts of the board 10 are twisted rightward when viewed in the movement direction indicated by the arrow, in conformity with the rotation of the rotation shafts 32. [137] In succession, if the rider applies force F to the rear portions of the left and right feet, as shown in FIG. 1 l(b), in accordance with the opposite principle to that of FIG.

1 l(a), the directional casters 40 provided to the front and rear parts of the board 10 are rotated, and the skateboard continues to move. [138] At this time, the torsion bars 34 provided to the front and rear parts of the board 10 are untwisted to be perpendicular to the ground and then twisted leftward when viewed in the movement direction indicated by the arrow. [139] Hereinbelow, exemplary operation of the skateboard in accordance with the second embodiment of the present invention, which is shown in FIG. 7, will be described with reference to FIG. 12. [140] It is assumed that, of the two feet f and f placed on the front and rear boards 100 and 100' in FIGs. 12(a) and 12(b), the foot f represents the left foot, and the other foot f represents the right foot. Also, it is assumed that the direction indicated by the arrow represents a forward direction, and the direction opposite to that indicated by the arrow represents a rearward direction. [141] The states of the front board 100 and the torsion bars 340 which are illustrated in front of the front board 100 are observed by viewing the skateboard according to the present invention from the front in the movement direction indicated by the arrow. [142] The states of the rear board 100' and the torsion bars 340 which are illustrated at the back of the rear board 100' are observed by viewing the skateboard according to the present invention from the rear in the movement direction indicated by the arrow. [143] FIG. 12(a) illustrates states in which force F is applied to both front portions of both feet f and f and to both rear portions of both feet f and f , and FIG. 12(b) illustrates

states in which force F is diagonally applied to the front portion of the left foot f and the rear portion of the right foot f ' and to the rear portion of the left foot f and the front portion of the right foot f ' .

[144] First, if a rider applies force F to the front portions of both feet f and f positioned on the front and rear boards 100 and 100' as shown in the upper drawing of FIG. 12(a), the directional casters 400 provided to the front board 100 are rotated leftward about their rotation shafts 320, and the directional casters 400 provided to the rear board 100' are rotated rightward about their rotation shafts 320, which causes the skateboard starts to move forward.

[145] At this time, the torsion bars 340 provided to the front and rear boards 100 and 100' are twisted rightward when viewed in the movement direction indicated by the arrow, in conformity with the rotation of the rotation shafts 320.

[146] Thereafter, as the rider applies force F to the rear portions of both feet f and f ' , as shown in the lower drawing of FIG. 12(a), in accordance with the opposite principle to that of the upper drawing of FIG. 12(a), the directional casters 400 provided to the front and rear boards 100 and 100' are rotated, and the skateboard continues to move.

[147] The torsion bars 340 provided to the front and rear boards 100 and 100' are untwisted to be temporarily perpendicular to the ground, and then twisted leftward when viewed in the movement direction indicated by the arrow.

[148] At this time, the front and rear boards 100 and 100' lean toward the side to which the force F is applied, when viewed from the position of the connection pipe 500.

[149] Therefore, after the rider starts the operation shown in any one of the upper and lower drawings of FIG. 12(a), by repeating the operations shown in the upper and lower drawings of FIG. 12(a), the skateboard can continue to move in the direction indicated by the arrow.

[150] Meanwhile, the rider can apply force F to the front portion of the left foot f and the rear portion of the right foot f ' , or to the rear portion of the left foot f and the front portion of the right foot f ' to rotate rightward or leftward in the direction indicated by the arrow as shown in the upper and lower drawings of FIG. 12(b).

[151] Thus, as the rider repeats the operations shown in the upper and lower drawings of

FIG. 12(b), wavelike motion can be realized, in which the skateboard moves forward in the direction indicated by the arrow while tracing an 'S '-shaped curve.

[152] Depending upon the acting direction of the force F diagonally applied to the front and rear portions of the feet f and f by the rider, by increasing the angle α defined between the front and rear boards 100 and 100' connected by the connection pipe 500 and the ground, an action such as a sudden directional change or 360° rotation in a standing position can be implemented.

[153] As a result, it is to be readily understood that the basic technical concept of the

present invention, constructed as mentioned above, is directed to providing a skateboard which allows a beginner to balance easily, turn smoothly and ride stably even without much practice, enables splendid tricks to be easily performed, and efficiently generates propulsive force without the nuisance of having to kick the ground.

[154] Further, in the present invention, it is to be appreciated that, no matter whether the board is integrally formed as in the first embodiment or is divided into the front and rear boards, as in the second embodiment, the elastic restoring means coupled to the fixed member on the lower surface of the board is twisted in a horizontal direction by a load applied from the upper part of the board so as to ensure stable riding of the skateboard. Industrial Applicability

[155] As is apparent from the above description, in conformity with the increase in the number of people wanting to enjoy skateboarding, it is possible to provide a skateboard having a new concept for a driving pattern, which is distinguished over the conventional skateboard, in which propulsive force is generated merely by simply kicking the ground.

[156] In the drawings and specification, typical preferred embodiments of the invention have been disclosed, and although specific terms are employed, they are used in a generic and descriptive sense only and not for the purposes of limitation, the scope of the invention being set forth in the following claims.