Patent application title: Self-propelled skateboard
Kazumine Kumada (Yokohama-Shi, Kanagawa, JP)
Kazumine Kumada (Kanagawa-Pref, JP)
IPC8 Class: AA63C1712FI
Class name: Coasters occupant-pushed yieldable
Publication date: 2016-01-07
Patent application number: 20160001166
A skateboard has a front wheel, a rear wheel and a board, propelled
without the rider's foot touching the ground, by shifting the rider's
weight up and down. The driving force of the skateboard is generated by
the continuous motion of the rider shifting his/her weight up and down,
causes the board repeatedly being pushed down and bounced back,
synchronized to the rocking motion of the eccentrically mounted rear
1. A skateboard comprising a board, a front wheel and a rear wheel
wherein an axle of the rear wheel is eccentrically mounted.
CROSS-REFERENCE TO RELATED APPLICATIONS
 This application claims the benefit of International Application No. PCT/JP2013/057856, filed Mar. 19, 2013, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
 The present invention is in the technical field of skateboards. More particularly, the present invention is in the technical field of self-propelled skateboards. More particularly, the present invention is in the technical field of self-propelled skateboards which advances by a rider's own driving force without the necessity of the rider's foot touching the ground.
 In conventional skateboard in the said technical field, such as a skateboard with direction-caster, which is disclosed in U.S. Pat. No. 7,195,259, constructed with two boards joined by a bar and a wheel with a caster mounted on each board, a rider requires a motion that the skateboard be twisted back and forth. However, there is a problem with such a construction that it is difficult for the rider to make the skateboard propelled with a continuous strong driving force.
BRIEF SUMMARY OF THE INVENTION
 The present invention is a skateboard propelled by converting, rather than a rider's twisting motion, but a rider's shifting motion of his/her weight up and down to a driving force, which is more spontaneous, continuous and stronger, synchronized to the up and down motion of a board created by mounting an axle of the rear wheel eccentrically.
BRIEF DESCRIPTION OF THE SEVERAL VIEW OF THE DRAWING
 FIG. 1 is a side view of a skateboard's ascending position of the present invention;
 FIG. 2 is a side view of the skateboard's descending position;
 FIG. 3 is a vertical section on an enlarged scale, through the rear wheel 2 of the skateboard taken on the line 3-3 of FIG. 1; and
 FIG. 4 is a perspective view of the skateboard.
DETAILED DESCRIPTION OF THE INVENTION
 The present invention relates to a skateboard propelled without the necessity of the rider's foot touching the ground. While a rider keeps his balance on a board 4 of FIG. 1, showing a side view of the ascending position of the skateboard in the attached drawing, the rider's continuous shifting motion of his/her weight up and down causes the board repeatedly being pushed down and bounced back. The rider synchronizes his/her up and down motion to the rocking motion of the eccentrically mounted rear wheel 2 of FIG. 2, showing a side view of the descending position of the skateboard in the attached drawing.
 FIG. 3 in the attached drawing is a vertical section on an enlarged scale, through the rear wheel 2 of the skateboard taken on the line 3-3 of FIG. 1. An axle 1 of the rear wheel 2 is mounted eccentrically.
 In order to properly start the skateboard, the motion should be initiated from where the axle 1 of the rear wheel 2 sets its position at the farthest from the ground as shown in FIG. 1, while the rider keeps his/her center of gravity slightly forward, the rider strongly shifts his/her weight downward, so the axle 1 moves forward, accompanying a wheel to turn, subsequently, the axle 1 sets its position at the nearest from the ground as shown in FIG. 2. Contiguously rebounding by its inertia force, a rider strongly shifts his/her weight upward, while the rider synchronizes his/her move to the turn of the wheel, setting the skateboard back to the position of FIG. 1. In this manner, the skateboard acquires its driving force, as the rider performs this exercise in succession.
 A preferred embodiment of a skateboard according to this invention comprises in combination of a board 4, a front wheel 6 and a rear wheel 2 as shown in FIG. 4, showing a perspective view of the skateboard in the attached drawing. A front wheel 6 is a normal wheel that an axle 7 runs through the center of the wheel, while the rear wheel 2 has an axle 1 runs through, offset from the center as shown in FIG. 3. The diameter of the rear wheel 2 should be larger than the diameter of the front wheel 6, so that the board 4 becomes parallel to the ground when the axle 1 sets in the nearest position from the ground as shown in FIG. 2.
 In addition, the larger the diameter of the rear wheel 2 is, the more momentum of the rider increases. By using a resilient material such as an elastic carbon for the board 4, not only it can accommodate the rugged ground surface, but also the rider can run the skateboard more effectively by using its repulsive force. To protect the skateboard and the encountering objects, a bumper 5 is installed. Each wheel rim of the front wheel 6 and the rear wheel 2 is covered with a tire 8 and a tire 3. Each of the axle 7 of the front wheel 6 and the axle 1 of the rear wheel 2 is attached to the board 4.
 As a result of the rider running this skateboard spontaneously obtains a large momentum in a short time, stimulating the whole body system, without complicating the structure, puts the invented skateboard not only for the purpose of amusement, but also the practical purpose of the use for an exercise equipment.