VACUUM DOCUMENT FEEDER

In a document feeder with a vacuum belt platen transport system for transporting document sheets over the platen of a copier under a vacuum plenum backing surface closely overlying the platen and into a registration position for imaging the document sheet, with a registration system for stopping the document sheet at the registration position, the platen transport system including a vacuum source for applying a partial vacuum to a document sheet being transported sufficient to provide transport of the document sheet with movement of the belt transport into the registration system, and a system for automatically reducing the level of the partial vacuum in the vacuum plenum sufficiently to allow slippage of a document sheet relative to the belt transport at the registration system, and wherein the registration system comprises document engaging registration fingers movable into and out of the path of a document sheet being transported by the vacuum belt platen transport system, the improvement wherein the system for automatically reducing the level of the partial vacuum in the vacuum plenum comprises a valve system directly actuated by the registration system by mechanical connection to the movable registration fingers to automatically reduce the vacuum level in the vacuum plenum in direct response to the movement of the registration fingers into the path of a document sheet. This is preferably in a vacuum belt platen transport system having plural unapertured spaced apart moving belts between which the partial vacuum is applied, and wherein the partial vacuum level is automatically so reduced to less than approximately 8 millimeters of water by the valve system after the transporting of the document sheet over the platen of the copier but prior to the transporting of a document sheet into the registration system, and wherein the belts continue to move after the document sheet is stopped at the registration position by the registration system with slippage between the belts and the document sheet. Preferably the valve system comprises a vent aperture in the vacuum plenum to vent it to the atmosphere and a vent door connected to the registration fingers for movement therewith and adapted to close the vent aperture whenever the registration fingers are moved out of the document path and to open the vent aperture whenever the registration fingers are moved into the document path.