| 摘要 |
<p>Parison of thermoplastic resin particularly used to be subsequently blow moulded to become a plastic bottle and comprising an upper portion (H), a middle portion (L) and an end portion (N), said middle portio n comprising on its lower side near said terminal portion a lower sub-portion (M) which has a thickness that is variable and smaller with respect to the wall thickness of the parison in said middle portion, particularly with a profile in the shape of a downward narrowing frustum of cone. Preferably the thickness in said lower sub-portion (M) is decreased by at least 12 % with respect to the thickness of the remaining middle portion of the parison, and the angle between the sides of said profile in the shape of a frustum of cone and the axis of symmetry i s comprised between 5.degree. and 10.degree.. Advantages: broader process tolerances, elimination of heat conditioning treatments, reduction in resin usage.</p> |
