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 printing process, the apparatus comprising:
a rotatable roller for positioning with an outer surface proximate to the substrate, said roller comprising:
a cylindrical body comprising a cavity, and
a magnet rotatably positioned within the cavity for creating a magnetic field emanating from the outer surface of the roller into the substrate, so as to orient the magnetic flakes in a pattern forming an image providing an illusion of depth when the magnet is rotated within the cavity during the printing process.
2. The apparatus of claim 1 , further comprising a means for spinning the magnet within the cavity during the printing process.
3. The apparatus of claim 1 ,
comprising an axle upon which the rotatable roller is mounted.
4. The apparatus of claim 3 wherein the magnet is positioned for spinning about an axis normal to the outer surface of the roller.
5. The apparatus according to claim 3 , comprising: a rotatable shaft extending radially within the cavity and having an inner end towards the axel and an outer end whereto the magnet is attached.
6. The apparatus according to claim 5 , wherein the cylindrical body is rotatably mounted on the axle.
7. The apparatus according to claim 6 , comprising a first gear for rotating the cylindrical body of the roller about the axle.
8. The apparatus according to claim 7 , wherein the first gear comprises a gear wheel fixedly attached to the cylindrical body of the roller for rotating thereof about the axel.
9. The apparatus according to claim 6 , comprising a gear for coupling the magnet with the axle for spinning the magnet within the cavity when the rotatable roller is rotated about the axle.
10. The apparatus according to claim 6 comprising a first bevel gear mounted on the axle, and a second bevel gear mounted at the inner end of the shaft for engaging the first bevel gear, for spinning the magnet within the cavity when the rotatable roller is rotated about the axle.
11. The apparatus according to claim 1 , wherein the cylindrical body is of non-magnetic material.
12. The apparatus according to claim 1 , wherein the magnet is recessed relative to an outer surface of the cylindrical body of the rotatable roller.
13. The apparatus according to claim 12 , further comprising a flexible sheet of non-magnetic material encasing the rotatable roller for providing the outer surface of the roller.