(57) A pattern (11) for forming a sand mould for use in producing a one-piece annular
casting (1) having a radially inner shell (12), a radially outer blade support (13),
and a plurality of angled blades (14) extending in a spaced, annular array (22). The
pattern includes a plurality of similar segments (15), each having an inner end portion
(18) defining a portion of the profile of the shell, and an outer end portion (21)
defining the profile of the blade. The segments are supported in annular array about
a mandrel (25) and are circumscribed by a split ring (26) defining the pattern for
the outer blade support portion of the wheel (10). The inner portions of the segments
are defined by inclined side surfaces (16,17) which, in alternate ones of the segments
in the annular array, converge and diverge toward the centre of the array. Upon completion
of the forming of the sand mould aboutthe pattern, the mandrel and outer ring are
removed, permitting the segments having the inwardly diverging side faces to be withdrawn
inwardly from the array and permit the remaining segments then to be withdrawn inwardly
therefrom.
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