| 摘要 |
<p>A hollow moulded article such as a ball of the kind used in play areas where children jump on and swim through a volume of the balls. During moulding, date coding is impressed on the ball is in a way which enables the older balls to be identified and replaced when necessary. The date coding is provided in two ways, one is to provide an adjustable pin within a part of the mould cavity, and the other is to provide indicia whose positions can be changed by rotation of the air venting plug within the mould.</p> |
