A laminating apparatus

Abstract: A laminating apparatus is disclosed which is particularlly suited to mount holograms on plastic cards. The apparatus comprises a planar support (10) supporting the work pieces to be laminated. A press stamp (36) has a shape of a sector of a circular cylinder wall and is driven by means of a special gear to perform a hobbing motion along the to-be-laminated area.

Description: The present invention relates to a laminating apparatus. It is wellknown in the art that lamination means to adhere a film or a film portion unto a substrate by means of heat bonding. The present invention is particularly suited to laminate so-called whitle light holograms unto plastic cards, e.g. credit cards. A white light hologram comprises a piece of film having an embossed groove pattern representing a hologram so that it presents an apparent three-dimensional picture when viewed under certain angles even if illumination is with non-polarized light. When laminating such a hologram unto a card both must be very accurately positioned and the embossed pattern must not be damaged. For this purpose two types of laminating apparatus are in use. In the first type, the plastic cards are supported by a planar support, and the holograms are fed on a carrier tape. A heated stamp presses an individual hologram to be transferred unto a card, the stamp being moved orthogonally with respect to the support. There is a risk that air bubbles are trapped even if the working surface of the stamp is ground to assume a somewhat rounded shape; such rounded shape, in turn, results in a pressure which is higher in the central portion of the hologram than adjacent its edges. Consequently, there is a relatively high rejection rate. The second known apparatus comprises a rotating heated stamp cooperating with a pressure roller which is also rotating. During lamination, the card and the hologram are transported through the gap between stamp and roller. It will be understood that the proper positioning causes difficulties, and in result the rejection rate is high again. It is an object of the present invention to provide a laminating apparatus having a very low risk of entrapped air bubbles and, simultaneously, a very low risk of inadequate positioning. The laminating apparatus of the present invention comprises a planar support which serves as an "anvil" during the lamination. Cards and holograms (or other work pieces to be laminated) are fed in superposed relation to the support whereby they may be accurately aligned. A stamp has a working surface shaped as a sector of a circular cylinder wall. A gear system is provided causing the stamp to advance relative to the support in a hobbing motion across the work pieces thereby following a partial cycloidal path. It is to be emphasized that the hobbing motion is not due to frictional engagement between the stamp and the work pieces but is uniquely caused by the particular design of the gear. Air between the hologram and the card may easily escape while proper relative positions of the laminated items is maintained because of the work pieces resting on the support during lamination. A preferred embodiment of the invention is illustrated in the attached drawings and will be explained hereunder. Fig. 1 through 5 show schematically and in side elevation five successive phases of the operation of an apparatus according to the invention, and Fig. 6 and 7 are respectively section views in accordance with lines 6-6 and 7-7. It is to be noted that Fig. 1 through 5 are substantially simplified and show only those elements which are important for the invention. At first the design will be explained with reference to Fig. 1, 6, and 7. Fig. 1 illustrates the first instant of a laminating process. A base frame (not shown) supports a planar and horizontally arranged suport 10 for plastic cards 12 fed from the right side by means of e.g. a carrier tape 11. Holograms 9 to be laminated unto the cards are supplied by means of a carrier tape 13. The holograms are optically aligned with the cards; these alignment means are not shown as they do not form a part of the present invention. Over support 10, a rocker member 16 is mounted pivotably about a shaft 14 carried by the base frame. Rocker member 16 comprises two congruent and parallel plates 18 each provided with guide tracks 20 (in Fig. 1 through 5 symbolized by a straight line), and these guide tracks are congruent, too. A carriage 21 is guided by the straight tracks 20 so as to reciprocate relative thereto. The carriage has two roller bearings 22 (symbolized by small circles) which engage cam tracks 24, 26 on substantially triangular webs 28 which are rigidly fastened on the inner faces of plates 18. A stamp holder 30 is mounted on carriage 21. Holder 30 is pivotable about the axis of a shaft 32 between two end positions; a first end position is shown in solid lines and the second in phantom lines in Fig. 1. In operation, however, the stamp holder is releasably connected to the carriage in said first end position by means of e.g. a ball locking mechanism (not shown) so that they move together. Only if maintenance of the stamp is required the stamp holder may be brought manually into the second end position, for example, when the working surface 34 of a stamp 36 is to be cleaned. Preferably, the stamp is interchangeably mounted on the stamp holder. The working surface has the shape of a sector of a circular cylinder wall and a size adapted to the size of a hologram to be sealed to a card. The center of curvature of the working surface coincides with the axis of shaft 32. A drive motor (not shown) is mounted on the base frame, and its output shaft 37 drives cam member 38 to rotate in a direction indicated by an arrow. The outer circumference of cam mamber 38 is in engagement with cam followers 40, 42 mounted on plates 18. The cam followers may e.g. be the outer races of ball bearings. A crank 46 is pivotably connected to cam member 38 at 44 and its other end is pivotably connected to the carriage 21. Thus, upon each revolution of shaft 37 carriage 21 will perform one reciprocation. The shape of cam tracks 24, 26 is calculated or graphically designed such that the working surface 34 of the stamp performs during the first half cycle (Fig. 1, 2, 3) a hobbing motion of cycloidal kind along the hologram carrier. During this same half cycle, the working diameter of cam member 38 does not change so that rocking member 16 does not pivot either. In consequence, stamp 36 uniformly presses the hologram carrier against the card. During the second half cycle, however, the operative diameter of cam member 38 changes so that the rocking member 16 is pivoted away from the support by a predetermined angle as seen in Fig. 4 and 5. Stamp 36 is preferably heated by means of a temperature-controlled heating element housed in the stamp and interchangeable together therewith.

Claims: A laminating apparatus, in particular for laminating white light holograms onto a plastic card, comprising: a planar support (10), means (11, 13) for feeding work pieces (9, 12) to be laminated along said planar surface towards a laminating position, a stamp (36) having a working surface (34), said working surface having a shape of a sector of a circular cylinder wall, the centre of curvature of the working surface coinciding with the axis of a shaft (32) to which the stamp is pivotably connected, gear means (20, 22, 24, 26, 38, 40, 46) for causing said stamp working surface to hob along said work pieces thereby following a partial cycloidal path. The apparatus of claim 1 comprising further a stamp-carrying reciprocating carriage (21), means (20) for guiding said carriage along a straight path substantially parallel to said planar support, and means (22, 24, 26) for pivoting said carriage about the axis of shaft (32) which is a center of curvature of said stamp working surface. The apparatus of claim 2 wherein said pivoting means include at least one cam track (24, 26). The apparatus of claim 2 further comprising crank drive means (37, 44, 46) for reciprocating said carriage. The apparatus of claim 1 further comprising means (14, 16, 38, 40) for displacing said stamp working surface away from said planar support (10) after a lamination operation and for returning said stamp into its initial position. The apparatus of claim 2 further including a rocking member (16) having said guiding means (20) and supporting said carriage, said rocking member being pivotable towards and away from said planar support (10), and said rocking member (16) being pivoted in response to positions assumed by said carriage relative to said guide means. The apparatus of claim 6 further including a power driven shaft (37) and a crank (46) coupling said shaft (37) to said carriage (21), and including a cam (38) mounted on said shaft (37) and cooperating with cam followers (40, 42) mounted on said rocking member (16) whereby rotation of said shaft causes a rocking motion of said rocking member. The apparatus of claim 2 further comprising a stamp holder (30), said stamp (36) being mounted on said stamp holder, and said stamp holder being releasably coupled to said carriage. The apparatus of claim 8 wherein said stamp holder is pivotable about said axis through a predetermined angle relative to said carriage. The apparatus of claim 9 further comprising a ball locking mechanism coupling said stamp holder to said carriage.

Inventors: BAIST BERNHARD, BAIST, BERNHARD
Applicants: MELZER MASCHINENBAU GMBH
Application year: 1993
Main classification: B32B31
IPC codes: B29C65, G06K19, B29C63, B32B27, B44F1, B32B37, B29L9