GB575323A - Improvements in injection moulding machines for thermosetting materials - Google Patents

Abstract

575,323. Injection-moulding machines. WINDSOR, R. H., and GASPAR, E. Dec. 8, 1943, Nos. 20514/43 and 852/44. [Class 87 (ii)] A machine of the type having two relatively movable platens is convertible from a condition suitable for end sprue moulding to a condition suitable for split centre sprue moulding. The injection plunger 17 is fixed to a cross-head 18 slidable on vertical columns 19, and is reciprocated by means of toggle links 21, 22 and a manually-operated lever 24. The injection cylinder bore 16 is formed in a block 15 secured to the platen 13, and is electrically heated. Reciprocable within the bore are the plunger 17, and a plunger 39 which has two functions, viz. : (1) to hold a pellet of (thermosetting) moulding powder in a cavity (44, Fig. 6, not shown) at its upper end, and (2) to break off the residual cured material 45 in the cylinder bore from the sprue 47. The plunger 39 is slidable in a cross-bar 38 attached to the crosshead 18 by bolts 37, and is urged downwardly by a compression spring 43 acting on abutments 143 and 41. Operation : (1) The cross-head 18 is raised, thus raising the plungers 17, 39 (the cross-bar 18 works between abutments 41 and 42). (2) A pellet of powder is placed in cavity 44 and the moulds 26, 28 are closed. (3) The cross-head 18 is lowered and the powder, rendered plastic by the heated cylinder, is forced by the plunger 17 through an aperture 35 into the moulds, the plunger 39 coming to rest on a shoulder 140 in the cylinder bore, as shown. (4) After a time sufficient for curing, the cross-head 18 is raised and the moulds are opened, the moulded article 34 being ejected from mould 28. In order to ensure that the article will cleave to mould 28, a recess 46 is formed in that mould. If the sprue breaks off and sticks in the passages 35, 36, it is dislodged by pushing in a plunger 51. The cylinder bore 16 may be-formed integrally with the platen 18 or with the mould 26 fixed thereto. To convert the machine to split centre sprue moulding, the rods 37 and plunger 39 are detached from cross-head 18, platen 13 is moved to the right (Fig. 8) on its four horizontal tie bars 11 by adjusting nuts (not shown) on the bars, the moulds 26, 28 are replaced by moulds 126, 128, and movable platen 12 is adjusted to ensure proper closing of the moulds. The platens may move vertically and.the plunger 17 horizontally. A pair of moulds may be mounted on each platen, each pair having its own injection plunger, as in Specification 571,071. The platens may each be split in two, each part carrying a mould and having an independent operating mechanism, so that different curing times may be used for the two moulds.