Apparatus for orienting magnetic flakes
A printing apparatus includes a magnetic rotatable roller with a smooth even outer surface for aligning magnetic flakes in a carrier, such as an ink vehicle or a paint vehicle to create optically variable images in a high-speed, linear printing operation. Images can provide security features on high-value documents, such as bank notes. Magnetic flakes in the ink are aligned using magnetic portions of the roller, that can be formed by permanent magnets embedded in a non-magnetic roller body, or selectively magnetized portions of a flexible magnetic cover of the roller. In some embodiments, the roller is assembled for a plurality of interchangeable sections, which can include spinning magnets. Selected orientation of the magnetic pigment flakes can achieve a variety of illusive optical effects that are useful for decorative or security applications.
1. An apparatus for orienting magnetic flakes in a fluid carrier printed on a substrate in a continuous printing process, the apparatus comprising:
a rotatable roller for positioning with an outer surface proximate to the substrate, said roller comprising a cylindrical body of non-magnetic material having one or more cavities, and one or more permanent magnets positioned in said one or more cavities for creating a magnetic field of a pre-determined configuration emanating from the outer surface of the roller into the substrate to orient the magnetic flakes in a selected pattern, wherein the outer surface of the roller is substantially even for providing a substantially uniform contact with the substrate across the outer surface of the roller during the linear printing process; and,
an axle, wherein the cylindrical body of the roller is formed by a plurality of roller sections, each having a generally cylindrical shape and comprising one or more cavities having permanent magnets inserted therein, the permanent magnets shaped for forming magnetic fields of pre-determined configurations emanating from the outer surface of the roller for orienting the magnetic flakes in selected patterns, said roller sections detachably positioned side by side on the axle, wherein at least some of the roller sections are interchangeable for forming different combinations of the magnetic flake patterns on the substrate.
2. An apparatus according to claim 1 , wherein the roller sections have outer surfaces which together provide the substantially even outer surface of the roller.
3. An apparatus according to claim 1 , further comprising a flexible sheet of non-magnetic material encasing the roller sections for providing the substantially even outer surface of the roller.
4. An apparatus according to claim 3 , wherein the roller sections are rotatably mounted on the axle with a bearing, further comprising a gear wheel for rotating the sections about the axle.
5. An apparatus according to claim 1 , wherein the roller sections have first locking means for mutually locking said sections in a fixed relative orientation for rotating together.
6. An apparatus according to claim 1 , wherein the selected pattern forms an image of an object, indicia, or a logo.
7. An apparatus according to claim 6 , wherein the image provides a dynamic optical effect when viewed at a varying viewing angle or at a varying illumination angle.
8. An apparatus according to claim 7 , wherein the image comprises a rolling object or a flip-flop.
9. An apparatus according to claim 7 , wherein the dynamic optical effect comprises color shifting or color changing.
10. An apparatus according to claim 6 , wherein the image provides an illusive optical effect.
11. An apparatus according to claim 10 , wherein the illusive optical effect is an illusion of depth exceeding the substrate thickness.
12. An apparatus according to claim 1 , wherein the flakes comprise at least one of reflective flakes, diffractive flakes, absorptive flakes, taggent flakes and color-shifting flakes.
13. An apparatus for orienting magnetic flakes in a fluid carrier printed on a substrate in a continuous printing process, the apparatus comprising:
an axle;
a rotatable roller for positioning with an outer surface proximate to the substrate, said roller comprising a cylindrical body formed by a plurality of roller sections, each having a generally cylindrical shape and comprising one or more cavities having permanent magnets inserted therein, the permanent magnets shaped for forming magnetic fields of pre-determined configurations emanating from an outer surface of the roller for orienting the magnetic flakes in selected patterns, said roller sections detachably positioned side by side on the axle, wherein at least some of the roller sections are interchangeable for forming different combinations of the magnetic flake patterns on the substrate, wherein the roller sections are rotatably mounted on the axle with a bearing;
a flexible sheet of non-magnetic material encasing the roller sections for providing a substantially uniform contact with the substrate across the outer surface of the roller during the linear printing process; and,
a gear for rotating the sections about the axle;
wherein:
the plurality of roller sections include a first section wherein one of the plurality of cavities extends radially forming a passage from the axle to the outer surface of the first section,
the apparatus further comprising:
a shaft rotationally positioned within the passage, the shaft having an outer end whereto one of the permanent magnets is attached, and an inner end,
a gear means rotationally coupling the axle with the shaft for spinning the one of the permanent magnets when the section is rotated about the axle.
14. An apparatus according to claim 13 , wherein the gear means comprises a first bevel gear mounted on the axle, and a second bevel gear mounted at the inner end of the shaft.
15. An apparatus according to claim 13 , wherein the gear means is positioned in a recess in the first section.