Tool for moulding the top part of a plastics container

DETAILED DESCRIPTION An object of the invention, therefore, is to provide a moulding tool for manufacturing top parts, the tool being free from radially moving parts.
The object of the invention is obtained by providing a tool having an outer part into which an axially movable inner part extends.
The outer part has a peripheral non-divided casing and the one-piece inner part comprises a pin having a first portion which penetrates without clearance into the casing bore.
The inner part also has longitudinal grooves and a second portion having a smaller diameter than the first portion and the sleeve bore.
Since the access passages into the neck channel originate where the first portion of the pin co-operates with the casing bore without clearance, i.
e.
in the peripheral regions of the first portion between the slots, and since these peripheral regions form ribs extending along the entire depth of penetration of the first portion, there is no need for outer or inner undercuts.
The tool can thus be opened and closed simply by axial relative motion of the sleeve and pin, the top part also being releasable from the mould in the axial direction.
The tool according to the invention can be used to produce neck parts by injection or compression moulding.
According to a preferred embodiment of the invention, the end of the second portion of the pin rests in a guide formed by the sleeve bore.
As a result the ribs formed between the slots in the first portion are relieved of pressure, more particularly when the tool is opened or closed, and are less worn by friction.
According to another advantageous feature, the first portion of the pin is conical and engages in a part of the casing boring having the same conicity.
This ensures that the access passages are completely moulded even if the first portion has become worn at the ribs.
Depending on the wear, the pin can penetrate more deeply into the casing until the clearance between the first portion and the corresponding part of the casing bore has come to an end