Patent ID: 9079738
Filing Date: 2015-07-14
Classification: B65H,Y10S,Y10T

Abstract:
1. An apparatus for causing paper webs to tear off within rewinding machines, the web being provided at regular intervals with transverse perforation lines which subdivide the web into sheets joined to each other but able to be separated in correspondence of the perforation lines, the apparatus comprising: a web-feeding and winding roller comprising a plurality of circumferential grooves, said web-feeding and winding roller winding the web onto at least one log, said web-feeding and winding roller moving the web along at least a portion of a path of the web, said web-feeding and winding roller rotating at a first speed such that said web is in a non-stretched state, said web-feeding and winding roller rotating at a second speed such that a portion of said web in an area of a selected perforation line of said web is in a stretched state against said web-feeding and winding roller, said first speed being less than said second speed; a pneumatic means for tearing the web upon passage of the selected perforation line which separates a last sheet of a log being formed from a first sheet of a next log to be formed, said pneumatic means comprising a reservoir of compressed air and a plurality of nozzles associated with a plurality of solenoid valves, said pneumatic means producing a jet of compressed air in a direction of said selected perforation line via said reservoir of compressed air, one or more of said solenoid valves and one or more of said plurality of nozzles, said plurality of nozzles, said solenoid valves and said reservoir of compressed air being located at a position external to said web-feeding and winding roller, wherein at least a portion of one or more of said circumferential grooves receives an extended and curved body portion of one of said nozzles, said one or more of said circumferential grooves having a curved groove orientation, said curved body portion having a curved body orientation, said curved body orientation substantially corresponding to said curved groove orientation, said web-feeding and winding roller rotating at said second speed such that said portion of said web in said area of said selected perforation line is in said stretched state when said selected perforation line is separated via said jet of compressed air, said one or more of said circumferential grooves having a minimal depth such that the outer surface of the curved body portion of one of said nozzles is substantially aligned with an outer surface of said web-feeding and winding roller and immediately adjacent to the web to tear the web when in its stretched state.