Abstract A blowhead for making tubular plastics film in which a housing including an outer part and an inner part having a large central opening for accommodating equipment that is to project into the tubular film is fitted with a nozzle at one end at which the film is blown. Convoluted distributing passages leading to the nozzle are defined between the outer and inner parts of the housing. A lateral supply passage leads molten plastics material to the convoluted distributing passages and includes a cleavage dividing the supply passage into branch passages. The convoluted distributing passages in the direction of the nozzle gradually decrease in depth. Gaps connect adjacent convolutions of the convoluted distributing passages and these gaps in the direction of the nozzle increase in width so that the plastics material as it flows towards the nozzle is gradually led from a convoluted flow path to an axial flow path. Upon introduction the plastics material is distributed as part-streams into the branch passages substantially in a plane which is radial of the blowhead axis and one of the branch passages merges with the associated convoluted distributing passage over a substantially U-shaped bend.
A blowhead for making tubular plastics film, comprising a housing including an outer part and an inner part having a large central opening for accommodating equipment that is to project into the tubular film, a nozzle at which the film is blown, convoluted distributing passages leading to the nozzle and being defined between the outer and inner parts of the housing, a lateral supply passage in the housing for leading molten plastics material to the convoluted distributing passages including a cleavage dividing the supply passage into branch passages, which branch passages lead to respective convoluted distributing passages, said convoluted distributing passages in the direction of the nozzle gradually decreasing in depth, gaps defined in the housing between adjacent convolutions of the convoluted distributing passages said gaps in the direction of the nozzle increasing in width so that the plastics material as it flows towards the nozzle is gradually led from a convoluted flow path to an axial flow path, and wherein the plastics material is distributed as part-streams into the branch passages substantially in a plane which is radial of the blowhead axis, one of the branch passages merging with the associated convoluted distributing passage over a substantially U-shaped bend.
Claim 2
Dependent Claim
200 words
A blowhead for making tubular plastics film, comprising a housing including an outer part and an inner part having a large central opening for accommodating equipment that is to project into the tubular film, a nozzle at which the film is blown, convoluted distributing passages leading to the nozzle and being defined between the outer and inner parts of the housing, a lateral supply passage in the housing for leading molten plastics material to the convoluted distributing passages including a cleavage dividing the supply passage into branch passages, which branch passages lead to respective convoluted distributing passages, said convoluted distributing passages in the direction of the nozzle gradually decreasing in depth, gaps defined in the housing between adjacent convolutions of the convoluted distributing passages said gaps in the direction of the nozzle increasing in width so that the plastics material as it flows towards the nozzle is gradually led from a convoluted flow path to an axial flow path, and wherein the plastics material is distributed as part-streams into the branch passages substantially in a plane which is radial of the blowhead axis, one of the branch passages merging with the associated convoluted distributing passage over a substantially U-shaped bend.
Claim 3
Dependent Claim
52 words
A blowhead according to claim 1, wherein the supply passage and branch passages are defined by channels of substantially semicircular cross-section in the confronting faces of two superposed plates forming part of the housing, the channels being led to the branch passages in opposite directions at the cleavage without a dividing wall.
Claim 4
Dependent Claim
37 words
A blowhead according to claim 1, wherein the convoluted distributing passages are of substantially 270* sector cross-section at their closed portions up to the start of the gaps and the branch passages are of substantially circular cross-section.