US Patent 7101258 Double sided polishing machine

Double-sided polishing machine with an upper and a lower working disc, each comprising a polishing disc and a carrier disc. The working disc are co-axially arranged and rotatable relative to each other, a polishing gap being formed between the polishing discs. Said workpieces are machined in the polishing gap. A temperature control device being at least provided for the upper working disc by which a temperature control fluid can be conveyed through passages in the upper working disc. A spacing measuring device being associated with the working discs which measure the spacing in the polishing gap (gap width μ) at two radial spaced points of the polishing gap.