Plate clamping device for intaglio printing presses

Claim 1

A system for clamping and tightening printing plates on a form cylinder of an intaglio printing press, comprising a form cylinder, printing plates on the cylinder, said cylinder having circumferentially spaced apart cylinder grooves in which extends for securement the leading end of one and the trailing end of another of the printing plates and a convex transition curve portion adjacent the sides of the cylinder groove having one end portion adjacent the cylinder groove sloping into the cylinder groove and over which the ends of the plates are led, the other end of said convex transition curve portion lies in a common tangent to a radius of the form cylinder and joins with the cylinder surface, said transition curve having a curvature which curves the plate such that the elastic limit of the plate is not exceeded, and the plate fits snugly around the cylinder surface, slidably mounted clamping bars in the cylinder grooves having means thereon for securing respectively thereto said leading and trailing ends of the plates, each clamping bar having a convexly curved surface portion in its upper portion joining at its upper end with a flat surface portion thereon lying in a plane extending tangentially to the radius of curvature of said convexly curved surface portion of said clamping bar and adjacent said convex transition curve portion on the cylinder, said one end portion of the transition curve portion adjacent the cylinder groove lying in said plane extending tangentially to said radius of curvature of said clamping bar each said clamping bar receiving and directing the end of the printing plate into the cylinder groove, said printing plates being very rigid and of high stability and having a portion of their ends prebent to conform to said convexly curved surface portion of the clamping bars, said printing plate ends extending over said upper flat surface portion of the clamping bar as a straight-line plate portion and lying in said plane that is tangent to the radius of the clamping bar and thence on to where they lie in said convex transition curve portion of the cylinder, each clamping bar being slidably mounted in the cylinder groove on a mounting that is parallel to said flat surface portion in its upper portion whereby said plate as it leaves said curved portion of the cylinder lies in said plane and extends in a straight-line portion as said clamping bar is moved for clamping purposes, said convex curved surface portion of the clamp bar moves parallel to the straight-line portion of the printing plate, the clamp bar for the trailing plate edge being subdivided into a plurality of sections, and each section having a spring bias means between it and said cylinder groove, a pressure screw means mounted on said clamping bar for the leading end of a printing plate and acting against a wall of its mounting groove in the cylinder, and a pressure screw means mounted on said clamp bar for the trailing plate and acting on said spring means for generating a tension in said printing plate, whereby the spring bias means for each clamping bar section for the trailing plate edge maintains the printing plate in its tightened position in spite of the fulling effects and avoids an overtensioning due to wrong handling.

Claim 2

A system for clamping and tightening printing plates on a form cylinder of an intaglio printing press, comprising a form cylinder, printing plates on the cylinder, said cylinder having circumferentially spaced apart cylinder grooves in which extends for securement the leading end of one and the trailing end of another of the printing plates and a convex transition curve portion adjacent the sides of the cylinder groove having one end portion adjacent the cylinder groove sloping into the cylinder groove and over which the ends of the plates are led, the other end of said convex transition curve portion lies in a common tangent to a radius of the form cylinder and joins with the cylinder surface, said transition curve having a curvature which curves the plate such that the elastic limit of the plate is not exceeded, and the plate fits snugly around the cylinder surface, slidably mounted clamping bars in the cylinder grooves having means thereon for securing respectively thereto said leading and trailing ends of the plates, each clamping bar having a convexly curved surface portion in its upper portion joining at its upper end with a flat surface portion thereon lying in a plane extending tangentially to the radius of curvature of said convexly curved surface portion of said clamping bar and adjacent said convex transition curve portion on the cylinder, said one end portion of the transition curve portion adjacent the cylinder groove lying in said plane extending tangentially to said radius of curvature of said clamping bar each said clamping bar receiving and directing the end of the printing plate into the cylinder groove, said printing plates being very rigid and of high stability and having a portion of their ends prebent to conform to said convexly curved surface portion of the clamping bars, said printing plate ends extending over said upper flat surface portion of the clamping bar as a straight-line plate portion and lying in said plane that is tangent to the radius of the clamping bar and thence on to where they lie in said convex transition curve portion of the cylinder, each clamping bar being slidably mounted in the cylinder groove on a mounting that is parallel to said flat surface portion in its upper portion whereby said plate as it leaves said curved portion of the cylinder lies in said plane and extends in a straight-line portion as said clamping bar is moved for clamping purposes, said convex curved surface portion of the clamp bar moves parallel to the straight-line portion of the printing plate, the clamp bar for the trailing plate edge being subdivided into a plurality of sections, and each section having a spring bias means between it and said cylinder groove, a pressure screw means mounted on said clamping bar for the leading end of a printing plate and acting against a wall of its mounting groove in the cylinder, and a pressure screw means mounted on said clamp bar for the trailing plate and acting on said spring means for generating a tension in said printing plate, whereby the spring bias means for each clamping bar section for the trailing plate edge maintains the printing plate in its tightened position in spite of the fulling effects and avoids an overtensioning due to wrong handling.