Equipment is disclosed that conveniently provides effective cleaning of envelope-folding, paper-converting or similar machinery containing perforated cylinders having a hollow interior and communicating with a vacuum system, for the manipulation or conveyance of one or more pieces of substantially imperforate sheet-like materials held against the exterior of the cylinders by ordinary atmospheric pressure. Equipment is provided comprising a reservoir chamber, pump means for forcing liquid from the chamber to a manifold, individual means communicating with the manifold for conveying liquid to the interior of the cylinders, and means connected with the vacuum system associated with the cylinders in the vicinity of the main pump, for returning liquid to the reservoir chamber, which is preferably evacuated. This yields effective cleaning of dirt, dust and lint not only from the perforations but also from valve faces, elbows, and other constrictions in the vacuum system.
