WO1995033575A1

WO1995033575A1 - Device for coloring in embossed plates, in particular motor vehicle license plates

Info

Publication number: WO1995033575A1
Application number: PCT/DE1994/000647
Authority: WO
Inventors: John Dziersk; Katharina Quent
Original assignee: Dziersk, Wilfried
Priority date: 1992-12-04
Filing date: 1994-06-07
Publication date: 1995-12-14
Also published as: DE4480979D2; AU6841194A; DE4240938C2; DE4240938A1

Abstract

The invention pertains to a device for coloring in embossed plates, in particular motor vehicle license plates, using a heated stamping roller. With known hot-stamping devices the temperatures required for the hot stamping are produced in very inefficient ways. The aim of the invention therefore is to provide a hot stamping device that operates with a very energy-efficient and technologically advantageous heating system. This is done by arranging inside the stamping roller (8) a heat source (12) that heats the support body (10) of the stamping roller (8) to a temperature at which this body emits infrared radiation to meet the detachment temperature of the specific stamping foil (5) being used, with the rubber coating (11) around the support body (10) being essentially diathermanous. With the invention the rubber coating (11) heats up only very slightly and most of the heat radiated from the support body (10) passes through the rubber coating (11) and radiates directly onto the stamping foil (5). This yields a very effective transmission of heat onto the foil (5).

Description

Device for coloring embossed signs, in particular motor vehicle license plates

The invention relates to a device for coloring embossed plates, in particular motor vehicle license plates, with a heated embossing roller, consisting of a support body and a rubber layer enveloping it, a counter-pressure roller, and a take-off and a take-up spool for an embossing film , wherein the embossing film is passed between the embossing roller and the counter-pressure roller, and the signs to be embossed, in particular motor vehicle license plates, are drawn in during operation to carry out the embossing process between the embossing roller and the counter-pressure roller.

Hot stamping has been used for many years. After initially being limited to the printing sector, it has now found its way into almost all industries. In addition to the well-known applications in the printing industry, the product range extends, for example, from car radiator grills hot-stamped with chrome embossing foil to hot-stamped wooden surfaces on television front frames and hot-stamped digits on tachometer number rolls. - 2 -

In hot stamping, color layers are released from a carrier film under the action of pressure and heat and transferred to a substrate to be coated. An embossing machine which has a heated embossing member is used to carry out the method. Only at the points at which the embossing element touches the film does the ink detach from its carrier layer and melt onto the material to be embossed or crosslink with it. Depending on the design of the embossing element and / or the material to be embossed, a distinction can be made between positive embossing, negative embossing, surface embossing and continuous embossing.

The advantage of hot stamping, which has also contributed to its rapid spread, is that it is a dry printing process. This eliminates the disadvantages known when processing wet colors, e.g. Odor and pollution, relatively long drying and difficulties in changing colors completely. Other advantages are the special surface effects and the brilliance that are possible through hot stamping. In addition, the range of hot stamps available is constantly being expanded, so that new areas of application keep opening up.

One area of application which has opened up to hot stamping in recent years is the labeling of signs. DE-OS 37 41 232 describes a device for hot stamping signs, in particular motor vehicle license plates. This device has a support table over which a rotating conveyor belt runs. Above the conveyor belt, approximately half the length of the support table, there is a heatable and, to a limited extent, swiveling embossing roller which consists of a roller-shaped support body which absorbs the forces and a rubber layer enveloping it from the outside. An unwinding spool and a winding spool are axially parallel to this embossing roller

^^ sentence ia - 3 - stored for a carrier film coated with heat-releasable paint. To label the signs, they are placed one after the other on the running conveyor belt and are conveyed by the latter under the still-standing embossing foil. A limit switch is triggered, which causes the heated embossing roller to be lowered onto the film strip and, under the pressure and heat of the embossing roller, the ink is detached from its carrier layer and applied to the label to be inscribed. The used film is wound onto the take-up spool driven by a slip drive.

By hot stamping, the plates, which can also be laminated with a reflective plastic film over the entire surface, as for example in the case of motor vehicle license plates, are provided with a well-adhering and therefore durable color of very good brilliance. In the case of smooth signs to be embossed, the heated embossing elements can determine the writing or the image by appropriately designing their embossing surfaces, or the writing or image are given in the case of smooth embossing elements by relief-like increases in the base to be inscribed.

In addition to the great advantages, the hot stamping devices known today have the disadvantage that the temperatures required for hot stamping are achieved in a very ineffective manner. As a result, relatively high heating outputs are required.

In the device according to DE-OS 37 41 232 described above, inductive heating of the embossing roller is provided. For this purpose, it is designed as a hollow cylinder open on one side, from the open end of which an induction heating coil projects into the embossing roller. The support body of the embossing roller is heated by induction action and from this heat mainly by conduction to the rubber layer

E ^r transfer. Since rubber is known to have a very large specific heat capacity, large amounts of heat have to be transferred from the support body to the rubber layer in order to maintain the surface temperature of approximately 180 ° C. required for the embossing process. So that the required amount of heat is always available, the support body of the embossing roller must be made relatively thick-walled so that it can act as a heat store. In order to bring it up to temperature, it must be preheated for a long time. This preheating time can take up to 30 minutes. Heating must also be carried out continuously during operation, ie the device cannot be switched off during short breaks, since this would otherwise require preheating. In addition to the preheating time, a long run-on time is also required to cool the roll. Apart from the fact that the inductive heating is in itself ineffective for this application, the way of heat transfer to the stamping foil is also ineffective. Probably for this reason, too, the device according to DE-OS 37 41 232, as far as can be seen, has never been used in practice, at least to a considerable extent.

In practical designs of hot stamping devices, the starting point has been the idea of bringing the heat directly from the outside onto the surface of the rubber layer of the stamping roller. For this purpose, infrared heating rods are arranged on about half the upper circumference of the embossing roller, at a distance from the surface of the rubber layer, which are covered at the top by a protective hood. In operation, the embossing roller rotates through this heating zone and absorbs heat, which it then emits again at the embossing point. On this way from the heating zone to the embossing point, the surface of the rubber layer that is no longer heated there would cool down relatively quickly. In order to counteract this, the support body of the embossing roller must also be made relatively thick-walled in this solution so that it can provide heat from the inside as a heat store.

^erδ afe However, this also has the disadvantages of a longer preheating and run-on time in the practical solution described. The heating power required is also quite high with a sufficient amount of 1000 W with a roller width of approximately 140 mm. The result of this is that - due to the arrangement of the heating elements - part of the heat is radiated to the environment and is not available for heating the roller. This loss must be compensated for by increasing the installed capacity. In addition, the directly heated rubber layer becomes brittle after some operating time, so that it has to be peeled off from time to time or even replaced at larger intervals.

The object of the invention is therefore to provide a device for coloring embossed signs, in particular motor vehicle license plates, which operates with heating which is very economical in terms of energy and technology.

According to the invention, this object is achieved in that a heat source is arranged within the embossing roller, which heats the support body of the embossing roller to a temperature at which it emits infrared radiation which is matched to the release temperature of the embossing film used in each case, the rubber enveloping the support body layer essentially diatherman, that is transparent to this particular infrared radiation.

In the previously used stamping foil, consisting of ^'a one side with a hot-removing color coated plastic carrier film be¬ (usually PE or PVC), a wavelength of the infrared radiation in the range of about 3 - 5 microns required. The infrared radiation then emitted by the support body corresponds to a temperature of approximately 180 ° C. When changing the parameters of the embossing foil, e.g. the foil thickness and / or the color, the intensity is the

^{: r} s Adjust the infrared radiation accordingly to set the required peeling temperature for the hot peeling ink. This adjustment can be done in a few attempts.

The rubber layer heats up only slightly in the solution according to the invention, and the major part of the heat radiated by the support body reaches the embossing film through the rubber layer directly by radiation. A very effective heat transfer to the film is thus achieved.

But the heating itself is also effective. The fact that the support body envelops the heat source to a certain extent means that heat losses do not occur, as in the prior art described above. Infrared emitters are particularly suitable as heat sources because of the favorable service life.

On the basis of the solution according to the invention, an installed heating power of approximately 180 W based on a roll length of 140 mm and the stamping film previously used for this purpose are sufficient to achieve the temperature required for the stamping process. With longer roll lengths, the heating power must be increased accordingly, as with the known solutions. Another advantage of the invention can be seen in the fact that the support body can be made relatively thin-walled in comparison with the prior art, since due to the heat transfer mechanism, its heat storage capacity is no longer critical. However, this also eliminates the long preheating and run-on times, which are reduced by the invention to a fraction of what has hitherto been the case.

In order to avoid an undesired outflow of heat from the support body of the embossing roller, in a further embodiment of the invention it is in blocks of one material

SPARE BLADE stored with low thermal conductivity.

In consistent pursuit of the inventive concept of transferring the heat required for the embossing process to the embossing film with as little loss as possible, the problem set out at the outset can also be achieved by arranging a heat source within the embossing roller, which is adjusted to the detachment temperature of the particular one ¬ set embossing foil emits coordinated infrared radiation, both the support body of the embossing roller and the rubber layer covering this for the infrared radiation being essentially diatherman

In this solution, the support body of the first solution, which acts as a wavelength converter, and thus also a source of loss, is eliminated. The heat transfer is thereby even more effective because the infrared radiator radiates through the roller body to a certain extent, i.e. the heat is transferred to the embossing foil essentially by direct radiation without "detours". The required heating power can be reduced further to about 100 W. In addition, this solution does not require a preheating or a run-on time, since the required embossing temperature is immediately available when the heater is switched on.

Although some materials are transparent to infrared radiation, they are out of the question for the invention, since in addition to this property the support body must also have sufficient heat resistance. For example, hard glass as used in the production of H4 lamps could be used as the material for the support body in the sense of the invention.

In a further embodiment of the two solutions according to the invention, the embossing roller is surrounded by an insulation which is spewed on the inside and which is broken through only in the area in which the embossing process takes place. Thereby

^he heat losses due to radiation in undesired directions are reduced.

The invention is explained in more detail below on the basis of an exemplary embodiment. The associated drawing shows a highly schematized hot stamping device, such as is used in particular for the stamping of motor vehicle license plates.

The device has a housing 1 which at the same time forms the base 2 of the device. An unwinding spool 3 and a winding spool 4 for the stamping film 5 are rotatably mounted in the housing 1. The stamping foil 5 is guided over the usual tensioner 6. A commercially available film with a thickness of 19 μm and a plastic carrier layer is used.

In the front and the rear wall of the housing 1, a block 7 made of a glass-epoxy resin fabric is inserted, in which an embossing roller 8 and a counter-pressure roller 9 are rotatably but fixedly mounted. The length of the embossing roller is 140 mm.

The embossing roller 8 consists of a cylindrical, hollow support body 10 and a layer 11 of silicone rubber, which envelops it from the outside. The silicone rubber is selected so that it is essentially transparent to infrared radiation in the wave range of approximately 2-3 μm. Its absorption rate is approximately 5%. The stated wave range corresponds approximately to an operating temperature of 180 ° C, which is required for the stamping process.

The carrier body 10 is thin-walled compared to the prior art, which results in very short heating times. Steel with the steel material number 1.48 / 41 is used as the material in order to ensure sufficient strength of the supporting body at the operating temperatures that occur

^εr® at 10 to guarantee. The ends of the support body 10 which protrude beyond the silicone rubber coating 11 are mounted in sintered plain bearings, not shown, which are embedded in the blocks 7. This storage ensures that no heat sinks occur in the edge zones of the embossing roller 8 and that the storage functions even at temperatures of 180 ° C. Instead of the sintered plain bearings, carbon graphite bearings can also be used, only then the ends of the supporting bodies 10 would have to be polished, since these bearings would otherwise wear out very quickly. The supporting body 10 is blackened from the inside for better radiation absorption.

An infrared radiator 12 is arranged in the longitudinal axis of the embossing roller 8 over its entire working width. It is a halothermal heater with a continuous output dimmed down to 180 W.

The embossing roller 8 is almost completely surrounded by an internally mirrored insulation 14, which is only open towards the top against the counter-pressure roller, that is to say in the embossing area.

Left and right next to the embossing roller 8, spring-loaded guide pins 13 ensure that the embossing film 5 is lifted off the heated embossing roller 8 when there is no sign to be embossed between the embossing roller 8 and the counter-pressure roller 9.

The device works briefly as follows: Simultaneously with the drive, the infrared radiator 12 is switched on. After about 10 seconds, the operating temperature of about 180 ° C. is reached and embossing can be started. For this purpose, the sign is placed on the support surface 15 and pushed between the embossing roller 8 and the counter-pressure roller 9 in the direction of the arrow. The guide pins 13 are pressed down one after the other, as a result of which the preform 5 rests on the heated embossing roller 8. Through the

He Elasticity of the silicone rubber layer 11 ensures the necessary contact pressure of the film 5 on the shield to be embossed, not shown. After the embossing process has taken place under the influence of heat and pressure, the relevant plate on the other side of the device can be removed by the operating personnel.

In addition to the low heating power and the short heating-up time, the invention has a further, essential advantage which has not yet been mentioned and which is also not apparent from the drawing. Because of the invention, not only can the support body 10 of the embossing roller 8 be made thinner, but the embossing roller 8 can have a significantly smaller diameter than has been possible up to now in the prior art. The smaller diameter in turn brings advantages in terms of the weight of the device and the freedom of construction and design.

If, as suggested in the introduction to the description, instead of the supporting body 10 made of steel, a supporting body 10 made of a diathermic, heat-resistant material, for example hard glass, is used, the storage described above in blocks 7 can be omitted, since the Support body only slightly warmed. As already mentioned, the heating power to be installed can be further reduced to approx. 100 W with this solution.

Replacement b

Claims

Patent claims

1. Device for coloring embossed plates, in particular motor vehicle license plates, with a heated embossing roller, consisting of a support body and a rubber layer enveloping it, a counter-pressure roller, and an unwind and a take-up reel for an embossing film, the Embossing foil is passed between the embossing roller and the counter-pressure roller, and the plates to be embossed, in particular motor vehicle license plates, are drawn in during operation to carry out the embossing process between the embossing roller and the counter-pressure roller, characterized in that a heat source is located within the embossing roller (8) (12) is arranged, which heats the support body (10) of the embossing roller (8) to a temperature at which it emits infrared radiation which is matched to the release temperature of the embossing film (5) used, the enveloping body (10) enveloping the support body (10) Rubber layer (11) for the infrared radiation essentially is diatherman.

2. Device according to claim 1, characterized ge indicates that the support body (10) in blocks (7) made of a material with low thermal conductivity is mounted.

3. Device for coloring embossed plates, in particular motor vehicle license plates, with a heated embossing roller, consisting of a supporting body and a rubber layer enveloping it, a counter-pressure roller, and an unwind and a take-up reel for an embossing film, the Embossing foil is passed between the embossing roller and the counter-pressure roller, and the signs to be embossed, in particular motor vehicle identification to embossed signs, in particular motor vehicle license plates, are drawn in during operation to carry out the embossing process between the embossing roller and the counter-pressure roller, characterized in that a heat source (12) is arranged within the embossing roller (8), which one the release temperature of the embossing foil (5) used emits coordinated infrared radiation, both the support body (10) of the embossing roller (8) and the rubber layer (11) enveloping it are essentially diathermanic for the infrared radiation.

4. Apparatus according to claim 1 or 3, characterized in that the embossing roller (8) is surrounded by an internally mirrored insulation (14), which is only in the area in which the embossing process takes place to the working width of the embossing roller (8). is broken.

REPLACEMENT LEAF