Injection moulding process for plastics hollows, esp. for IC engines - has hollow metal or plastics core permanently moulded in for complex shapes, improved corrosion resistance and low cost

摘要

Injection moulding process for hollow objects into which a hollow core is permanently incorporated and bonded by moulding a continuous layer of plastic round the core. The core may be of metal or plastic, pref. of two separate sections, esp. axi-symmetric halves, which are then joined to form the hollow core. USE/ADVANTAGE - Hollow plastic mouldings, e.g. pipes, pump housings, valves and pipe fittings, esp. of complex curvature for the motor vehicle and chemical industries. A moulded pipeline with flanges integral with a continuous outer plastic layer and tubular inner core of different material, plastic or metal, e.g. resistant to hydrocarbons, for a motor vehicle engine is specifically claimed. Compared with metal castings, this process avoids: a) core removal and risk of residual contamination b) rough internal (flow) surface from sand cores c) coat of material and mfr. of solid cast metal cores d) removal of metal sprues and runners and machining of fixing flanges etc. e) rough external surfaces f) poor dimensional accuracy g) cost and time of above finishing processes. Compared with blow moulding, this invention gives greater choice of plastic materials and greater freedom of design, e.g. for complex shapes or inclusion of fixing and connecting flanges. Compared with hollows moulded in sections and then joined, the seamless outer moulding avoids failure at seams under high internal pressure. Compared with above methods, this invention avoids machining and assembly for delicate electronic sensors; these may be precisely positioned and moulded in, esp. in inaccessible positions, also permitting (with transparent materials) flow visualisation. By use of plastics with differing physical properties for core and outer moulding, the former may be resistant, e.g. to corrosion, from internal fluids whereas the latter may have heat- and deflection-resistance suitable to the environment, esp. 'under the bonnet' applications. Also the cost of expensive material for the whole moulding is reduced when this is used only for the core (lining).