Patent ID: 7137730

Claim:
A blender for mixing electrographic developer, comprising: an elongate shaft having two ends and an intermediate location between said two ends; an inner helical ribbon mounted concentrically to said elongate shaft for rotation therewith and having a pitch; an outer helical ribbon mounted concentrically to said elongate shaft for rotation therewith and having an opposite pitch relative to said pitch, said inner helical ribbon being disposed within said outer helical ribbon; another inner helical ribbon mounted to said elongate shaft for rotation therewith adjacent to said inner helical ribbon and having another pitch; another outer helical ribbon mounted to said elongate shaft for rotation therewith adjacent to said outer helical ribbon and having another opposite pitch relative to said another pitch, said another inner helical ribbon being disposed within said another outer helical ribbon; said outer helical ribbon and said another outer helical ribbon being terminated to provide an opening spanning said intermediate location through which developer is drawn into said inner helical ribbon and said another inner helical ribbon upon rotation of said longitudinal shaft.