Such laminator apparatus are known form the state of the art.

Usually the thermoplastic material and the document or the flat element to be laminated are introduced into the introduction gap, pressed between the rollers, advanced and pulled through the apparatus. The thermoplastic material encompasses the docu- ment in a clamping manner and surrounds it completely within the protecting film. The combination of lamination material and document is pulled preferably through two opposite exit rollers, pressed a second time ensuring the necessary pressure, and leaves subsequently the apparatus.

The heating element according to prior art is a heating spiral mounted on an aluminum body encompassing at least one roller for at least 180 degree to heat the thermoplastic material when it is drawn between the rollers.

Such a laminator apparatus known from prior art shows the disad- vantage that it needs a heating time of 10 minutes to heat up the rollers. The thickness of the three layers, i. e. thermoplas- tic material-document-thermoplastic material, may change due to different documents. Therefore the laminator apparatus is adaptable e. g. the upper roller can be floating and is biased

against the lower roller which is positioned in a fixed axial height. The upper roller may go up against the force of sprir. gs when the goods to be laminated are introduced between the roll- ers. This unit shows the disadvantage that the heat transfer from the heating spiral or the upper aluminum body changes when said vertical movement of the upper roller through the relative movement between roller and aluminum body occurs. This chances the heat transmission, subsequently the temperature of the roller and finally leads to poorer lamination results.

Based on this prior art it is an object of the invention to pro- vide a laminator apparatus which ensures a better lamination re- sult with simple means.

It is another object of the invention to provide a laminator ap- paratus which supports a higher lamination speed, without endan- gering the thermoplastic material to be melted through the input of heat.

A laminator apparatus with the above-mentioned features accord- ing to the invention is characterized in that both rollers are encompassed by heating means, which have at each point of their inner surface a predetermined position in relation to their cor- responding roller.

The position of the heating means in relation to their corre- sponding roller is constant. Therefore the distance between these elements can be kept constantly small for controlling the heat input in an efficient way. Furthermore this predetermined small distance minimizes the isolation effect of the air gap.

Within other preferred embodiments the heating means are pro- vided with two different radii in two angle portions. There is a bigger radius provided in the area of the open ends of the heat- ing means. There is a smaller radius in the areas above and be-

low the rollers whereby the radius of the heating means is cho- sen to be approximately the same as the radius of the roller in the heated state of roller and heating means. Under cold condi- tions this radius of the heating means is larger than the radius of the rollers. This presents the advantage that material accu- mulated within the transition areas, especially dirt, is re- moved, e. g. through pulling a sheet of paper through the appara- tus while pre-heating the apparatus. Preferably the heating means are made of aluminum profiles. It is possible to choose other materials, especially ceramics.

Within other preferred embodiments the inner radius of curvature of the heating means changes his value. Starting with a first greater radius at the end of the heating means it is reduced continually to a second smaller radius, preferably the radius of the roller in the heated condition, whereby this second radius or a similar radius is maintained over a angular portion of e. g.

90 degree and whereby finally the radius is enlarged towards the second end of the heating means to the first greater radius.

Further preferred embodiments use the features described in the dependent claims.

In the following several embodiment of the invention are ex- plained in connection with the description of the accompanying drawings: Fig. 1 a cross-sectional view of a first embodiment of the in- vention, Fig. 2 a cross-sectional view of a laminator according to a second embodiment of the invention, Fig. 3 a cross-sectional view of a laminator according to a third embodiment of the invention, and Fig. 4 a perspective view of the rollers and heating means of a laminator according to the first embodiment.

Fig. 1 shows in a schematic view a lamination apparatus. There are only shown elements which are important to the understanding of the device as the presentation table 1 defining, together with the output table 2, the way of the goods to be laminated through the machine. The lamination apparatus is provided with opposite rollers 3 and 13, between which is provided a slot or introduction gap 4. This slot 4 is of a substantial height to allow to pass two opposite sheets of thermoplastic material and a in-between positioned document to be laminated.

Rollers 3 and 13 are connected with a motor unit (not shown in the figures) which moves and advances the thermoplastic material in the direction of the arrow 5. The motor unit comprises at least one motor driving the rollers 3 and 13 in counterrotation with the same speed. Exit rollers 6 and 16 are positioned in the direction of the arrow 5 behind the rollers 3 and 13. The exit rollers rotate to guide the laminated material through the exit funnel 7 to the output table 2. Preferably the diameter of the exit rollers 6 and 16 is larger, e. g. by some tenth of a milli- meter for a diameter of the roller of two centimeter, than the diameter of the rollers 3 and 13. This achieves a greater angu- lar speed of the exit rollers to pull the laminated material be- tween the exit rollers and to stretch it.

Preferably the motor unit directly drives the rollers 3 and 13.

A set of gears is provided to drive the exit rollers 6 and 16.

According to another embodiment the exit rollers 6 and 16 may be dragged although a direct connection is preferred.

As can be seen in Fig. 1, the lower rollers 3 and 6 are mounted on a fix axis. Rollers 13 and 16 are mounted on a movable axis, whereby the axis can be displaced in the direction of the arrow 8 when pushed upwards by the thermoplastic material introduced in the apparatus. Rollers 13 and 16 are biased with springs against the lower rollers 3 and 6 when in the resting condition

as shown in Fig. 1. It is also possible to provide fixed rollers 13 and 16 and rollers 3 and 6 displaceable in the direction of the arrow 8.

Said rollers 3 and 13 are equipped with heating means 9 and 19. These heating means 9 and 19 are preferably aluminum elements in tubular form encompassing rollers 3 and 13 as much as possible. They cover an angular portion of at least 270 degree and have a constant predefined distance 11 of some tenth of millimeters (e. g. 1/10-5/10 millimeters) in respect to the rollers 3 and 13. The heating means 9 and 19 are flattened on the side towards the presentation table 1 and connected with electrical heating elements 10 and 20, e. g. ceramic heating elements. A temperature sensor 12 is provided on the upper heating element to control the temperature of element 19.

The temperature sensor 12 is connected with an integrated cir- cuit which comprises a control circuit. The control circuit may include a detection circuit to detect the thickness of the ele- ments to be laminated to control the amount of heat which has to be transferred into the said elements to ensure a good lamina- tion quality. Preferably there is provided a switch for the user to communicate the kind of lamination material he uses (in terms of thickness) to the circuit. Said quality depends mainly on the amount of heat which is accumulated by the document and lamina- tion materials and less on the temperature detected with the heating elements.

Heating means 9 is mounted and fixed to the roller 3. Heating means 19 is mounted in a fixed manner in relation to the rota- tional axis of the roller 13 to ensure a constant distance 11 when roller 13 is moved in direction of the double pointed arrow 8. Heating means 9 and 19 are tapered towards their free ends 14, whereby on the input side is provided a solid portion 15.

Slot 4 is provided with two opposite plates 17 and 27 in direc-

tion of the presentation table 1. These plates ensure a preheat- ing effect. These plates 17 and 27 are connected in one piece with heating means 9 and 19, respectively, whereby preferably a transversal groove 18 is provided for diminishing the heat transfer out of area 15 to the plates 17 and 27 and so the heat is mainly guided to rollers 3 and 13. All rollers 3,13 and 6, 16 consist out of a silicon cover mounted on thin tubular steel elements. More explanation on this can be found in the descrip- tion relating to Fig. 4.

The amount of heat can be controlled through providing a con- trolled distance and especially overheating of the thermoplastic material can be avoided. This provides a higher laminating speed.

The laminated material is further pressed by exit rollers 6 and 16, guided to the funnel of the output slot 7 and evacuated.

In the case that thicker thermoplastic material is used the slowly rotating rollers conduct all the heat provided by the heating means through the polyester material towards the glue.

If a thinner thermoplastic materials is used, the preheating plates 17 and 27 allow for a higher working speed of the appara- tus. Through the preheating effect of these plates 17 and 27 the thinner polyester layers are preheated and the faster rotating rollers can add the necessary heat for heating the glue layer sufficiently. A higher amount of heat in the same period of time applied to the rollers 3 and 13 would result to overheating and deterioration of the laminated document when used with thinner thermoplastic materials. If rollers of about 12 millimeters ra- dius are used, preheating of thinner thermoplastic materials al- low to double the speed of the lamination process in relation- ship to the prior art, i. e. up to eight rotations per minute.

Fig. 2 shows a cross-sectional view of a laminator according to a second embodiment of the invention. Same reference numerals refer to identical features. Rollers 3 and 13 have identical bearings in comparison to Fig. 1. Heating means 19 are now lying with their weight on roller 13. According to another embodiment a spring can be used to raise or to lower the pressure of the heating means 19 on the roller 13. Between the axes of the roller 3 and heating means 9 is a springy relationship. The spring (not shown in the Fig.) pushes the heating means 9 with a force against the roller 3 which is the double of the roller's weight.

Heating means 9 and 19 are mainly identical to those shown in Fig. 1 relating to the areas 14 and 15 and the heating device 10,20. Rollers 3,13 comprise a radius 30 in the heated state.

Within this embodiment the tubular heating means 9 and 19 com- prise in the area directly above and below their axis an inner radius 32 which is identical to radius 30 of the rollers 3,13.

The inner radius 32 widens in both directions towards the free ends 14 and 15, respectively, as shown with reference 31 and as can be seen with the gap 34. There is provided an angular por- tion 33, within which the heating means 9 and 19 are lying on the rollers 3 and 13, respectively. This portion encompasses at least 45 preferably 90 degree. This achieves a predefined excel- lent heat contact between rollers 3 and 13 and heating means 9 and 19, which is active immediately after switching-on the heat- ing elements 10,20 and which remains active during the lamina- tion process.

Fig. 3 shows a cross-sectional view of a laminator according to a third embodiment of the invention. Rollers 3 and 13 have bear- ings as shown in Fig. 2 and heating means 9 and 19 are lying with their weight on the rollers and/or are pressed through the action of a spring against the rollers. Heating means 9 and 19 are constructed in a different way. Rollers 3,13 have a radius

30 when heated. The tubular heating means 9 and 19 according to this embodiment have an inner radius 32 which is identical to the radius 30 of the rollers 3,13 in the areas above and below their axis. A step in direction of a larger inner radius 41 is provided in both directions towards the free ends 14 and 15, re- spectively. Therefore it is provided an angular portion 43, within which the heating means 9 and 19 are lying on the rollers 3 and 13, respectively. This portion extends over at least 45 preferably 90 degrees. This achieves a predefined excellent heat contact between rollers 3 and 13 and heating means 9 and 19, which is active immediately after switching-on the heating ele- ments 10,20 and which remains active during the lamination pro- cess.

Dirt will accumulate in the area 35 of the upper roller 13 and in the area 36 of the lower roller 3. In the cold condition upon switching-on of the apparatus these materials are staying on the rollers, since the diameter of the rollers is smaller than the radius 30 shown in Fig. 3, and they can be carried away with a special cleaning element or e. g. a first sheet of paper drawn between the rollers.

Fig. 3 shows another alternative for two further angular por- tions 53 and 63. The angular portion 43 provided by elements 9 and 19 is asymmetrical and has a larger part on the side in di- rection of the material to be laminated. The angular portion with the reference 53 is essentially symmetrical in relation to the vertical axis and the angular portion 63 is only provided on the side in direction of the material to be laminated.

Fig. 4 shows a perspective view of the rollers and heating ele- ments of a laminator according to the first embodiment, whereby in the drawings the upper roller 13 is axial displaced for bet- ter understanding. Rollers 3 and 13 are made out of silicone and are mounted on thin steel tubes 45. Spigots 46 are pressed into

the tubes, supporting shafts 47 and 48, respectively. The con- nections between the bearing of the rollers 3,6,13 and 16 and the respective surrounding heating element 9,19 must be pre- cisely machined with very small tolerances and these connections should undergo least possible thermal expansion or this expan- sion must be taken into consideration when positioning said rollers in said heating elements.

Additionally it is possible to provide a heat cover above the heating means 9 and 19, e. g. in a distance of a centimeter, hin- dering heated air to dissipate, protecting the casing against the heat and avoiding heat losses.

In another embodiment (not shown in the drawings) similar to the embodiment shown in Fig. 2 every heating means 9 and 19, respec- tively, have an inner radius which is, in the heated condition of the corresponding rollers 3 and 13 and of the heating means 9 and 19, slightly larger than the outer radius of the roller 3 and 13, respectively.