Method for producing a light guide

Abstract

The present invention relates to a method for producing a light guide, the method comprising the following steps: extrusion of a light guide, contacting the extruded light guide with an embossing roller which has an embossing profile on its outer side, by means of which an output geometry for light is embossed into the extruded light guide, the embossing roller rotating while the light guide is moved past it.

Description

The present invention relates to a method for producing a light guide.It is known from the prior art to produce light guides with a geometric coupling out of light in an injection molding process. Furthermore, it is known to produce the decoupling geometry of a light guide by means of lasers, i.e. by introducing a laser structure or by means of screen printing.A light guide with a geometric decoupling structure for the light (e.g. in the form of decoupling prisms) usually has a structure in which the decoupling geometry changes over the length of the light guide. In order to obtain homogeneous coupling-out of light along a light guide with geometric coupling-out of light, the coupling-out geometry along the light guide must change in such a way that "little" is coupled out from the "many" light at the beginning of the light guide, i.e. at the location of the coupling-in of light, and "much coupled out" from the "few" light at the end of the light guide.This is achieved, for example, by decoupling geometries, for example in the form of prisms or wedges, which are slightly pronounced at the beginning of the light guide, i.e. in the vicinity of the light coupling in and are somewhat more (deeper) pronounced at the end.The object of the present invention is to provide a method with which a light guide with a high-quality output coupling geometry can be produced cost-effectively.This object is achieved by a method having the features of claim 1.According to this, it is provided that the method has the following steps: a) extrusion of a light guide, b) contacting the extruded light guide with an embossing roller which has an embossing profile on its surface, by means of which an output geometry for light is embossed into the extruded light guide, c) wherein the embossing roller rotates while the light guide is moved past the latter.The light guide is thus produced by an extrusion process.The quality of extruded profiles has improved considerably in recent years, so that the provision of a high-quality light guide is possible. The advantage of extruded light guides with embossed coupling-out of light to light guides with a laser structure or screen printing is that the basic profile is more variable. When introducing a laser structure and in a screen printing method, the light guide should be as flat as possible; no such restriction exists in the case of an extruded light guide.According to the invention, the extruded light guide is brought into contact with an embossing roller which has an embossing profile on its surface with which it contacts the light guide, which embossing profile projects outwards from the surface. By the embossing roller rotating while the extruded light guide is moved past the latter, an output geometry for the light is embossed into the light guide over its length, which geometry is complementary to the embossing profile of the embossing roller.The embossing roll is preferably motor-driven, so that the rotational speed can be adapted to the extrusion speed.Alternatively, it is provided that the embossing roller is not driven by motor, but is set into a rotational movement by the extrusion strand which exits from the extruder.By selecting and arranging the embossing profile of the embossing roller, it is possible to determine exactly at which position (in the longitudinal direction) of the light guide which decoupling geometry is to be applied.In a preferred embodiment of the invention, it is provided that the embossing roller is provided with different embossing profiles over its outer periphery, so that different decoupling geometries are produced over the length of the extruded light guide. Thus, it is possible, for example, to meet the above-described requirement for the most homogeneous possible light output by virtue of the embossing profile having comparatively small or slightly deep profiles in a starting position or starting position of the embossing roller, the size and / or shape of which increase or change in the direction of rotation of the embossing roller.In one conceivable embodiment, the embossing roller rotates about an axis which runs perpendicular to the longitudinal extent of the light guide.In order to ensure as reliably as possible that the embossing profile of the embossing roller is reproduced as exactly and completely as possible in the light guide, it can be provided that a contact pressure is exerted by a preferably rotating contact pressure roller on the surface of the extruded light guide opposite the surface connected to the embossing roller. In this case, the extruded light guide is thus guided through a gap between the embossing roller and the pressing roller.If the desired length of the light guide is reached, it can be provided that the light guide is cut off by means of a cutting device when its desired length is reached.Depending on how qualitative the cutting-to-length is (e.g. laser cut instead of sawing), possibly no further reworking is necessary. In principle, any desired method of lengthening is possible.In one embodiment of the method, it is provided that the embossing process is ended by means of the embossing roller, once the embossing roller has carried out a complete rotation or a partial angle of a complete rotation.In this case, the circumference of the embossing roller corresponds on the one hand to the desired length of the light guide and on the other hand the embossing geometry for the light decoupling can change over the circumference of the roller. After each revolution of the roller, a light guide is stamped and can then be cut to length.In principle, several or only a partial revolution of the embossing roller is also conceivable for producing a light guide.The invention also includes the case in principle that the embossing geometry is constant over the circumference of the embossing roller.It is also conceivable that the embossing roller is lifted off the extruded light guide after the embossing process, the extrusion process is then continued and the light guide is only then cut to length, so that a length section of the light guide without decoupling geometry is formed. It is thus also possible for the light guide to be longer, i.e. to have one or more regions without decoupling geometry and only the length of the decoupling geometry to correspond to the circumference of the roller. In this case, the embossing roller must then be raised after each revolution until a new light guide is to be embossed.Preferably, it is provided that the extrusion is carried out such that the side of the extruded light guide into which a decoupling structure is impressed is planar or also curved. However, any embossing roller which follows the profile of the light guide is also to be considered.The present invention furthermore relates to an extruded light guide having an output coupling geometry for light, wherein the production of the light guide and the embossing of the output coupling structure were carried out by means of a method according to the invention.The present invention further relates to a refrigeration and / or freezer with a refrigerated interior as well as with lighting means in the refrigerated interior and / or with lighting means on the outside of the appliance, wherein the lighting means comprise a light source and a light guide and wherein the light guide is a light guide according to the invention.The light source can be, for example, an LED. The light fed into the light guide by means of the LED is emitted at the decoupling geometries.The present invention further relates to an apparatus for producing a light guide by a method according to the invention.The device has an extruder with an embossing roller arranged downstream of the extrusion opening, which is arranged relative to the extrusion opening in such a way that the embossing roller stands with the extruded light guide emerging from the extrusion opening, wherein the embossing roller is provided with an embossing profile for producing the decoupling geometry into the extruded light guide.There may be a cutting device which is preferably arranged downstream of the embossing roll and which is designed to separate the extruded light guide. The term "downstream" is to be understood as meaning that the cutting device is located behind the embossing roll in the extrusion direction.The device can furthermore have a pressure roller which is arranged in such a way that the light guide emerging from the extrusion profile is arranged between the pressure roller and the embossing roller.The embossing roller preferably has an axis of rotation which runs perpendicular to the longitudinal axis of the light guide which is in contact with the embossing roller. The same can also apply to the pressure roller.The embossing roller and / or the pressing roller can either have rigidly arranged axes of rotation or axes of rotation which are arranged radially displaceably and are preferably spring-loaded in order to deviate accordingly in the case of a desired thickening of the light guide and to follow the narrowing in the case of a desired tapering of the light guide.It is pointed out at this point that the terms "a" and "an" do not necessarily refer to exactly one of the elements, although this represents a possible embodiment, but rather can also denote a plurality of the elements. Likewise, the use of the plural also includes the presence of the element in question in the singular, and conversely the singular also includes a plurality of the elements in question.Furthermore, all features of the invention described herein can be claimed as being combined with one another or isolated from one another as desired.Further details and advantages of the invention are explained in more detail with reference to an exemplary embodiment shown in the drawing.The following are shown: FIG. 1 : shows a schematic illustration of an extruded light guide of length x with indicated light decoupling geometries, and FIG. 2 : shows a schematic illustration of an apparatus for producing a light guide according to the present invention.FIG. 1 shows a light guide with the reference numeral 10.The light guide is characterized in that it has a coupling point 12 into which light from a light source 14 is radiated, which is, for example, one or more LEDs.The light guide 10 has a number of decoupling geometries A over its length, which are to be understood as regions of the light guide from which a portion of the coupled-in light emerges in each case, for example in order to illuminate or illuminate the interior of a cooling and / or freezing appliance.The light guide 10 is made of an extruded material.FIG. 2 shows an apparatus for producing such a light guide 10.In an extruder 100, a mass of suitable light pipe starting material is formed into a strand which exits the extrusion orifice 110.The strand has a cross-sectional shape defined by the shape of the extrusion orifice.The strand is identified in FIG. 2 by the reference sign 120.The strand 120 does not yet have any decoupling geometry.Downstream of the extrusion die 110 in the extrusion direction is the embossing roll 200 which is rotatable about an axis perpendicular to the plane of the paper.The axis of rotation of the embossing roll 200 is thus perpendicular to the longitudinal extension and to the extrusion direction, which extends to the right according to FIG. 2.The embossing roller 200 has a circumferential surface which is not planar but is provided with a relief-like embossing structure. The embossing structure thus protrudes with respect to the other circumferential surface of the embossing roller 200.As can be seen from FIG. 2, after leaving the extrusion die 110, the strand 120 comes into contact with the surface of the embossing roll 200 in such a way that the embossing profile of the embossing roll 200 is embossed into the surface of the preferably planar side of the light guide which is in contact with the embossing roll 200.During the embossing operation, the embossing roller 200 rotates clockwise.To prevent deflection of the strand 120 away from the embossing roller and to ensure contact and sufficient embossing force between the embossing roller 200 and the strand 120, a nip roller 300 is provided which is on the opposite side of the optical fiber strand 120 than the embossing roller 200.During the embossing operation, the nip roller 300 rotates counterclockwise.After passing the rollers 200, 300, the light guide 10 has an output geometry which is introduced by the embossed structure of the surface of the embossing roller 200. This section of the strand extends to the right of the rollers 200, 300 according to FIG. 2 and is marked 130.Once the desired length of the strand 130, i.e. of the light guide finished with regard to the decoupling geometries, such as e.g. the length x according to FIG. 1, is reached, the cutting device 400 is activated, which cuts off the light guide 130.The embossing roller 200 can have over its circumference the same embossing structures and / or embossing structures which have the same distance from one another in the circumferential direction of the embossing roller.However, a preferred embodiment of the invention consists in that a) the distance between the embossing structures in the circumferential direction of the embossing roll changes, in particular decreases in the rotational direction starting from a starting point, such as e.g. the marking M in FIG. 2, and / or b) the size, such as e.g. the width, length or depth, of the embossing structures changes in the circumferential direction of the embossing roll, in particular increases in the rotational direction starting from a starting point, such as e.g. the marking M in FIG. 2.If the spacing of the embossed structures decreases in the circumferential direction of the embossing roller starting from a starting point and / or if the size of the embossed structures increases in the circumferential direction of the embossing roller starting from a starting point, this leads to the light guide having comparatively few and / or small decoupling points in the vicinity of the coupling-in point for the light and having more and / or larger decoupling points with increasing distance from the coupling-in point for the light.The starting point is a specific angle of rotation of the embossing roller 200, which can be characterized, for example, by a marking M.Both result in the "many" light in the vicinity of the coupling-in point exiting through relatively few and / or small coupling-out points and in the light decreasing with the length of the light guide exiting through relatively many and / or larger coupling-out points.Both measures make it possible-if desired-to emit light uniformly over the length of the light guide.This can be seen in FIG. 2 in that few decoupling geometries A are present in the end of the light guide shown on the right, which end forms the coupling-in point 12 for the light, and that their density, i.e. number per unit length, increases toward the left, i.e. with increasing distance from the coupling-in point 12.In principle, other arrangements of the decoupling geometry figures are of course also conceivable.The embossing roller 200 can be designed such that the circumference of the roller 200 corresponds on the one hand to the desired length X of the light guide and on the other hand over the circumference of the roller the embossing geometry for the light decoupling changes.For example, after each rotation of the roller, a light guide is stamped and can then be cut to length.That is to say, if the marking M, i.e. the starting point, is for example again at the top (cf. FIG. 2 ) or has reached another angle of rotation, then the roller 200 has stamped one revolution and thus an extruded light guide profile with the decoupling geometry and can be cut to length.Depending on how qualitative the cutting-to-length is (e.g. laser cut instead of sawing), possibly no further reworking is necessary.It is also conceivable for the light guide to be longer and only the length of the decoupling geometry to correspond to the circumference of the roller 200. In this case, after each revolution, the embossing roller must then be lifted from the light guide until a new light guide is to be embossed.In principle, it is conceivable for the embossing roller 200 and / or the pressing roller 300 to be set into a rotational movement by the movement of the extruded profile 120.However, it is also conceivable for the embossing roller 200 and / or the pressing roller 300 to be driven by motor either individually, i.e. separately from one another, or to be driven via two synchronized drives, or for a drive unit and a drive belt etc. to be provided, which drive unit operate the two rollers 200, 300 at exactly the same rotational speed in order to avoid shear stresses in the longitudinal direction of the light guide 10.

Claims

A method for producing a light guide, wherein the method comprises the following steps: a) extruding a light guide, b) contacting the extruded light guide with an embossing roller which has an embossing profile on its outer side, by means of which an output geometry for light is embossed into the extruded light guide, c) wherein the embossing roller rotates while the light guide is moved past the latter.Cooling and / or freezing appliance according to claim 1, characterised in that the embossing roller is provided over its outer periphery with different and / or differently spaced embossing profiles, so that different and / or differently spaced decoupling geometries are produced over the length of the extruded light guide.Method according to one of the preceding claims, characterized in that the embossing roller rotates about an axis which runs perpendicular to the longitudinal extent of the light guide.Method according to one of the preceding claims, characterized in that a contact pressure is exerted on the contact point between the embossing roller and the light guide by a preferably rotating contact pressure roller on the surface of the extruded light guide opposite the surface connected to the embossing roller.Method according to one of the preceding claims, characterized in that the light guide is cut off by means of a cutting device when its desired length is reached.Method according to one of the preceding claims, characterized in that the embossing process is ended by means of the embossing roller, when the embossing roller has carried out a complete rotation, a plurality of rotations or a partial angle of a complete rotation once.Method according to one of the preceding claims, characterized in that the light guide is cut to length once the embossing roller has carried out a complete rotation, a plurality of rotations or a partial angle of a complete rotation.Method according to one of Claims 1 to 7, characterized in that the embossing roller is lifted off the extruded light guide after the embossing process, the extrusion process is then continued and the light guide is only then cut to length, so that a length section of the light guide without decoupling geometry is formed.Method according to one of the preceding claims, characterized in that the extrusion is carried out in such a way that the side of the extruded light guide into which a decoupling structure is impressed is planar or curved.Extruded light guide having an output coupling geometry for light, wherein the production of the light guide and the embossing of the output coupling structure have been carried out by means of a method according to one of Claims 1 to 9.A refrigeration and / or freezer appliance having a refrigerated interior and lighting means in the refrigerated interior and / or lighting means on the outside of the appliance, characterized in that the lighting means comprise a light source and a light guide, wherein the light guide is a light guide according to claim 10.Device for producing a light guide according to a method according to one of Claims 1 to 9, wherein the device has an extruder with an embossing roller arranged downstream of an extrusion opening, which embossing roller is arranged relative to the extrusion opening in such a way that the embossing roller stands with the extruded light guide emerging from the extrusion opening, wherein the embossing roller is provided with an embossing profile for producing the decoupling geometry into the extruded light guide.Device according to claim 12, characterised in that a cutting device is provided, which is preferably arranged downstream of the embossing roller and which is designed to separate the extruded light guide.Device according to claim 12 or 13, characterised in that a pressure roller is provided, which is arranged in such a way that the light guide emerging from the extrusion profile is arranged between the pressure roller and the embossing roller.

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