| 摘要 |
A device for effecting the tearing of a paper sheet (40), or the like, along a pre-punched straight line or area (46) substantially transversal with respect to the sheet is disclosed. The tearing device comprises two roll pairs (10, 12) having opposed cylinders (14, 16) in which the cylinders are so shaped to have two opposed planar faces (36, 38) for delimitating a free passage for the sheet (40) while the remaining faces (42, 44) are of substantially convex shape, so that, when the rolls (10, 12) rotate, said convex faces (42, 44) get each other in touch, grasping the sheet (40). The angular speed of both roll pairs (10, 12) is the same but, according to the invention, the cross-section of the cylinders (16) of the rolls (12) located downstream of the pre-punched area (46) is larger than that of the cylinders (14) of the rolls (10) located upstream of the area so that the peripheral speed of the first ones is higher than that of the second ones, that causing the development of a tensile action on the sheet (40) during the contact time of the sheet itself with the convex faces (42, 44) of the above mentioned cylinders (14, 16) and the tearing of the pre-punched area (46). <IMAGE>
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