GB1071071A - Improvements in or relating to forming shell moulds - Google Patents

Abstract

1,071,071. Apparatus for making shell moulds. ROLLS ROYCE Ltd. May 10, 1965 [May 13, 1964], No. 20021/64. Heading B5A. Apparatus for forming shell moulds on an expendable pattern 20, e.g. of wax or synthetic resin, comprises a support 15 for the pattern mounted for rotation about a primary axis 25, there being a plurality of stations along the circular path described by the support, each station comprising dipping or showering means for applying a hardenable slurry to the pattern, means for applying a refractory material to the pattern and liquid or gaseous means for hardening the slurry so that during each rotation of the support about the axis the pattern is provided with a plurality of coats of refractory material. A plurality of supports 15, equal to the number of stations, are mounted on arms 14 extending radially from a hub 13 rotatably mounted on a shaft 12. Each support comprises a shaft 16 at right angles to the arm and a shaft 17 at right angles to the shaft 16. A multi-limb member 18, fixed to the shaft 17 supports four expendable patterns 20. Electric motors 21 and 23 are provided to cause rotation of shafts 16 and 17, whereby the patterns can be rotated about three axes, namely the primary axis 25, and secondary axes 22 and 24. Each station comprises three containers 30, 31 and 32. Container 30 contains hardenable slurry and is provided with a stirrer 33; container 31 contains refractory powder kept fluid by a fluidized bed arrangement; container 32 has supply tubes, 36 for ammonia and 37 for air, covers 40 and 41 being provided to close the container. The patterns 20 are rotated about axis 25 until they are vertically above container 30 when they are lowered into the slurry by a ratchet device 45. Whilst in the slurry the patterns are rotated about secondary axis 24. They are then lifted out by the ratchet device and rotated about axis 22 to remove excess slurry whilst moving on to the next container by rotation about axis 25. The patterns are lowered into container 31, rotated about axis 24 and become coated with sand. The patterns are then moved on into container 32, the doors 40 and 41 closed and ammonia gas pumped in to harden the slurry, after which air is pumped in and the patterns removed. The cycle is repeated until the patterns have made a complete revolution and thus received six coatings of sand and slurry. The patterns are melted out and the shells baked. Machine details are given in Figs. 3-7 (not shown).