Patent GB-932967-A (GB)
Title: Improvements in or relating to the forming of hollow articles
Inventor: PARK ROBERT HIRAM
IPC: B29C48/475
Filed: 1960-12-30
Abstract: 932,967. Blow moulding hollow articles. BROCKWAY GLASS CO. Inc. Dec. 30. 1960. No. 44879/60. Class 87(2). In a method of forming from thermoplastic material a blown hollow article, the material in a softened state is forced through a supply passage and is extruded through an annular orifice about a hollow cylindrical mandrel or blow tube 55 to form a tube of the material, whence a sleeve 43 axially slidable on the blow tube is moved into the orifice to sever the extruded tube from the thermoplastic material in the passage, and fluid under pressure is supplied to the interior of the extruded tube through the blow tube to cause the tube to expand to conform with the wall 40 of a mould cavity formed in mould parts 25, 26. The blow tube is also moved downwardly but with a larger displacement so that the extruded tube is stretched and thinned on the blow tube as shown in Fig. 6 prior to the closing of the mould parts 25, 26. The passageway for the supply of thermoplastic material 46 is formed in the join of two blocks 15, 16 which may be taken apart to aid cleaning and interchange of the extrusion parts. The movement of the blow tube is controlled by a hand operated lever 80, Fig. 2, pivoted at 85 to a lever 84 connected to the frame of the apparatus, the lever 80 being connected to the blow tube holder at 81. The movement of the sleeve 43 is controlled by a hand operated lever 109 which operates a lever 90 through a rack 100 and pinion 107, the lever 90 being pivoted at 91 and connected to the degating sleeve holder at 98. A link 115 having a bifurcated end 117 provides a lost motion connection between the levers 80, 90. Alternatively automatic operation means may be provided. The blow tube 55 is cooled by water circulated through concentric tubes disposed on the inside of the blow tube (not shown), the blowing air being supplied through the innermost tube. These tubes are slidable inside the blow tube to control the rate of cooling, and the mould parts 25, 26, may also be water cooled. The mould parts are actuated by air cylinders and each mould part is fitted with a toothed rack which engages one on either side of a toothed wheel to ensure that the mould opens and closes equally on both sides, Fig. 1 (not shown). Centring plates 138 engage with the extrusion nozzle 42 as the mould closes to ensure the correct orientation of the nozzle. After the mould has closed about the thinned extruded tube portion disposed on the blow tube 55, Fig. 6, the blow tube may be retracted slightly so that the shoulders of the article when blown are not too thin. The filling of the threads in the neck of the formed article may be accomplished by slow withdrawal of the blow tube after blowing accompanied by downward pressure from the end of the sleeve 43, which also finishes the top of the article, or the blow tube may be withdrawn rapidly with the air supply still connected so that the extruded tube is blown into the threads. With wide mouth hollow articles it is preferable to use a false neck portion corresponding to the neck shown in Fig. 6, when the real neck is blown as part of the mould cavity 40.