Field of the Invention
The present invention relates to plastic balls used often for advertisement, education and toys, and is composed of three identical pieces of material wherein a middle layer is provided with an air passage to keep air pressure of two chambers in balance and either one of the other layers is provided with a valve to allow air on. The three pieces can be connected by high frequency waves to form an enclosed body, so that, the preparation of the plastic ball can be simplified and the cost of manufacture can be further reduced.
The conventional air-filled ball is shown in FIG. 1, which utilizes multi-pieces of plastic material to form the same. If said ball is to be made by using six pieces, the ball will be far away from roundness; while if nine pieces are used, better roundness can be expected. Nevertheless, either the six or nine piece method wastes a lot of time in preparing the materials, and the connection will need extra attention for a multi-pieces method; therefore, the efficiency is poor and the cost is high in this respect.