Blow moulding of long hollow plastic products and blow moulding plant

摘要

A process for prodn. of long hollow plastic products by inflating a parison in a horizontal, split mould involves : a) extruding a tubular parison from above into a preforming tool(30) whose cavity profile is similar to that of an upper half(13) of a subsequent blowing tool(12,13) and holding under vacuum; b) rotating the preforming tool (30) through 180 deg around a horizontal axis and moving to a position above the cavity of the lower blowing tool half(12); c) transferring the preform to the lower tool(12) cavity. In a process variation the parison is extruded into a vertically divided preforming tool, which then moves to a position above the lower blowing tool cavity and opens to transfer the parison to the latter. A claimed blowing machine for the process comprises an extruder(21) above a frame(11) carrying the lower half(12) of a horizontally split blowing tool(12,13) and a tool closure unit(14,15,16,17) for lowering the upper tool half(13). A preforming tool(30) on the frame(11) has a cavity profile similar to that of the upper blowing tool half(13). The extruder(21) and/or preforming tool(30) move along a horizontal axis relative to each other, while the preforming tool(30) can rotate through 180 deg on a horizontal axis and move relative to the lower blowing tool half(12) between a first position to the side of and a second position immediately above the latter(12). In a machine variation the preforming tool is split vertically into two halves which open to release the preform into the lower blowing tool(12) cavity.