GB685799A - Improvements in vacuum-actuated sheet-detecting apparatus for printing machines - Google Patents

Abstract

685,799. Travelling - cylinder printing machines; feeding sheets. MIEHLE PRINTING PRESS & MANUFACTURING CO. Oct. 31, 1950, No. 26514/50. Classes 100 (i) and 100 (ii). A printing press of the kind having a rotary, reciprocating impression cylinder, sheet register guides on said cylinder for registering sheets, vacuum-actuated sheet-detecting elements associated with said guides and operable to detect the faulty lay of a sheet at, or the absence of a sheet from said guides, and a vacuum source remote from said cylinder for actuating said elements, is characterized by the provision of substantially stationary coupling means which effect momentary connection between the vacuum source and said elements each time the cylinder reaches a predetermined position in its cycle of operation. As applied to a vertical printing press which comprises a type bed 17 vertically reciprocable by connecting rods 19 and cranks 21, the impression cylinder 23 is rotatably mounted in arms 24 of a frame 26 reciprocated vertically by racks 27 secured to the frame 26 and engaging gears 12 driven by racks 14 carried by brackets 16 supporting the type bed 17. The cylinder is rotated during its upward. or impression stroke and locked during its return stroke. Faulty sheet-feed control devices.-Sheets to be printed are transferred to the cylinder 23 while it is stationary at the bottom of its stroke, vacuum ports 28 being provided in the cylinder 23 for detecting the presence and correct registration of a sheet, the absence of a sheet causing, for example, the tripping of the cylinder 23. A vacuum shoe 31 connects the parts to a vacuum pump 29 so as to provide a sealed connection between a ground face 36 of the shoe and the end face of the cylinder journal when vacuum is applied to the ports. The shoe 31 is supported on a guard 32 by flat spring 33, one end of the spring being secured to the guard by means of screws 34, thus permitting movement of the shoe away from the end face of the journal 44 of the cylinder. The journal 44 has a bore 43 communicating with a chamber 45 leading to the ports 28, while the movement of the shoe 31 is limited by an adjustable screw 46 passing freely through the guard 32, but screwed into the shoe. The top edge of the shoe is bevelled as at 48 for engagement with end face of the journal which presses the shoe into operative position against the action of the spring 33 as the cylinder moves downward.