DE102023109398A1 - Method for producing a dimensionally stable protective cover for a marking device and marking device with protective cover - Google Patents

Abstract

The invention relates to a method for producing a dimensionally stable protective cover (20) made of optically transparent material for an optical light emitter arrangement (2) of a marking device (1) for use in an optical measuring system and to a marking device (1) with such a protective cover, wherein the protective cover (2) is provided for covering a light-emitting front side (8) of the light emitter arrangement (2). The method steps comprise method steps: providing a mold (35) with a surface contour (36) which envelops the front side of the light emitter arrangement (2), wherein the surface contour (36) has emitter cover surfaces (37) whose position corresponds to the arrangement of light emitters (3) exposed in the light emitter arrangement (2); fixing a blank (25) by means of a deep-drawing device (30) at a distance from the mold (35); heating the blank (25) by means of a first heating device (33) of the deep-drawing device (30); Heating the mold (35) by means of a second heating device (42) of the deep-drawing device (30); deep-drawing the protective cover (20) in the deep-drawing device (30) while lowering the blank (25) onto the heated mold (35); cooling the deep-drawn protective cover (20); removing the deep-drawn protective cover from the mold

Description

The invention relates to methods for producing a dimensionally stable protective cover for a marking device and to a corresponding marking device with protective cover.

Such marking devices are usually used in optical measuring systems in which a marking device is attached to an object and a camera takes an image of the marking device, whereby the location (orientation) and position in space are determined based on the image. This is evident, for example, from the DE 20 2020 103 679 U1 known. The marking device has optically active light emitters in a known light emitter arrangement, from whose image the location and position of the marking device (and thus also of the object to which the marking device is attached) are determined. In the case of a moving object, a movement pattern (tracking) of the marking device or the object can also be recorded.

Such marking devices are therefore frequently used in the industrial sector, for example in the manufacture of products in a production line, in order to monitor and/or control the individual production steps. It is important that the optically active light emitters, e.g. LEDs, are clearly visible in the optically visible or infrared wavelength range. On the other hand, the light emitters are sensitive, optoelectronic components that must be protected against dirt, mechanical damage and electrical interference, such as electrostatic charges, in industrial environments. It is therefore common to protect the light emitter arrangements used for such applications with mechanical cover plates that accordingly limit the beam angle of the light emitters (usually set back from the mechanical cover plate for protection) and thus limit the visibility of the light emitters. Reliable visibility for such marking devices often only covers a beam angle range of around 120°.

From the EP 1 658 819 B1 A casing for markers for tracking systems, in particular medical tracking systems, is known, which is made entirely from an optically transparent material, in particular from a material that is transparent to infrared radiation and/or visible light. The marker casing can be formed, for example, from a suitable film using a deep-drawing process. However, there is the problem that the protective casing is arranged at a certain distance from the light emitters. This can lead to optical distortions or optical artifacts due to reflections on the surface of the casing, in particular when the camera is looking at the markers at an angle.

Against this background, it is the object of the invention to propose a dimensionally stable optical protective cover for an optical light emitter arrangement of a marking device and a method for its production, wherein optical interference is minimized by the protective cover mounted on the marking device.

This object is achieved by a method for producing a dimensionally stable protective cover made of optically transparent material or a method for producing a marking device with such a dimensionally stable protective cover with the features of claim 1 and a marking device with the features of claim 10. According to the method proposed according to the invention, a dimensionally stable protective cover made of optically transparent material is produced for an optical light emitter arrangement of a marking device for use in an optical measuring system, wherein the protective cover is provided for covering a light-emitting front side of the light emitter arrangement. A light-emitting front side is understood to mean that several optically active light emitters are arranged in the front side of the light emitter arrangement, which are exposed in the direction of the light emission. A light emitter is the optically active surface of a lighting device of the light emitter arrangement. The lighting device can preferably be a light-generating device that generates and emits light. Optically active light emitter therefore preferably means that it can be switched on and off in particular to generate light; In particular, optically active light emitters do not have to be permanently optically active, but must be able to be activated to emit light, for example for use in the optical measuring system. In principle, the optically active lighting device can also have or consist of a surface that reflects the light.

1. (a) Vorsehen einer Form (im Sinne einer Positiv- oder Negativform) mit einer Oberflächenkontur, die die Vorderseite der Lichtemitteranordnung einhüllt, wobei die Oberflächenkontur Emitterabdeckflächen aufweist, deren Position der Anordnung von in der Lichtemitteranordnung freiliegenden Lichtemittern derart entspricht, dass eine der Oberflächenkontur der Form folgende Schutzabdeckung (bzw. eine der Oberflächenkontur der Form folgende Oberflächenkontur der Schutzabdeckung) auf die Lichtemitteranordnung auflegbar ist. Erfindungsgemäß erfolgt das Auflegen unter Ausbildung einer gemeinsamen Kontaktfläche von Emitterabdeckflächen der Schutzabdeckung und freiliegenden Lichtemittern. Da die Schutzabdeckung der Oberflächenkontur der Form folgt, bildet auch die Schutzabdeckung bzw. die Oberflächenkontur der Schutzabdeckung selbst Emitterabdeckflächen aus, die den Emitterabdeckflächen der Form bzw. der Oberflächenkontur der Form entsprechen.

The proposed procedure comprises the following steps:

1. (a) Providing a mold (in the sense of a positive or negative mold) with a surface contour that envelops the front of the light emitter arrangement, the surface contour having emitter cover surfaces whose position corresponds to the arrangement of light emitters exposed in the light emitter arrangement such that a protective cover following the surface contour of the mold (or a surface contour of the protective cover following the surface contour of the mold) can be placed on the light emitter arrangement. Invention According to the invention, the application takes place with the formation of a common contact surface of the emitter cover surfaces of the protective cover and the exposed light emitters. Since the protective cover follows the surface contour of the mold, the protective cover or the surface contour of the protective cover itself also forms emitter cover surfaces that correspond to the emitter cover surfaces of the mold or the surface contour of the mold.

A direct contact surface should be understood in the sense that one (in particular every) emitter cover surface of the protective cover is arranged directly in front of the optically active surface (i.e. in front of the light emitter) with a minimal distance, in particular preferably at a distance of less than 3 mm, more preferably less than 2 mm and particularly preferably less than 1 mm). The term "contact surface" is therefore not to be understood in such a way that the protective cover must be in direct contact (at all or throughout) with the optically active surface (i.e. the light emitter). Such a solution may be preferred, but is not absolutely necessary according to the invention.

1. (b) Festlegen eines Rohlings aus thermoplastisch verformbarem, optisch transparentem Material mittels einer Tiefziehvorrichtung beabstandet von der Form.
2. (c) Beheizen des Rohlings mittels einer Heizeinrichtung der Tiefziehvorrichtung. Für das Umformen mittels Tiefziehen von geeigneten Kunststoffmaterialien, wie erfindungsgemäß bspw. Acrylglas (PMMA - Polymethylmethacrylat) oder ein anderer transparenter thermoplastischer Kunststoff, wird der Rohling typischer Weise auf Temperaturen etwa zwischen 110 °C bis 250 °C, bevorzugt zwischen 120 °C und 180 °C und besonders bevorzugt zwischen 130 °C und 170 °C erwärmt. Zum Vermeiden von Spannungen und/oder Rissen und für eine gute optische Qualität kann erfindungsgemäß bevorzugt vorgesehen sein, dass der Rohling vorab getempert wird, d.h. über einen längeren Zeitraum auf eine Temperatur unterhalb der Schmelztemperatur erhitzt wird, bspw. zwischen etwa 60 °C bis 80 oder 90 °C, und die Temperatur so lange gehalten wird, bis sich der gesamte Rohling gleichmäßig auf diese Temperatur erhitzt hat. Das Tempern kann typischer Weise 2 bis 3 Stunden dauern. Dies fördert das Ausgleichen von Strukturdefekten, verbessert eine kristalline Struktur und vermeidet einen starken thermischen Schock für den Rohling.
3. (d) Beheizen der Form mittels einer Heizeinrichtung der Tiefziehvorrichtung. Typischer Weise ist die Temperatur der Form niedriger als die Temperatur des Rohlings, etwa 10 °C bis 50 °C oder bevorzugt 20 °C bis 40 °C niedriger. Prozentual kann die Temperatur der Form etwa 5% bis 25%, bevorzugt etwa 10% bis 20% niedriger liegen als die Temperatur des Rohlings, um einen thermischen Schock des Rohlings bei Kontakt mit der Form zu vermeiden.
4. (e) Tiefziehen der Schutzabdeckung in der Tiefziehvorrichtung unter Absenken des Rohlings auf die beheizte Form. In diesem Zusammenhang ist das erfindungsgemäße Beheizen der Form, bspw. auf eine ähnliche Temperatur wie die Temperatur des abgesenkten Rohlings, besonders vorteilhaft, weil ein abruptes Abkühlen des Rohlings von einer Temperatur, in der der Rohling thermoplastisch verformbar ist, auf eine Temperatur, in der der Rohling nicht thermoplastisch verformbar ist, vermieden wird. Ein abruptes Abkühlen mit einem zu großen Temperaturgradient kann zu Änderungen der optischen Struktur des thermoplastisch verformbaren Materials und damit zu optischen Störungen führen. Dies wird durch das Beheizen der Form vor dem Absenken des Rohlings vermieden. Vorzugweise liegt die Temperatur der Form bei dem Absenken des Rohlings in einem Bereich von 75% bis 95% der Temperatur des Rohlings. Bei einer Temperatur unter etwa 75% des Rohlings kann der Temperaturgradient zu groß sein, was zu optischen Störungen aufgrund einer sich ändernden Materialstruktur führen kann. Andererseits ist es sinnvoll, wenn die Temperatur der Form geringfügig niedriger ist als die Temperatur des Rohlings. Dann fließt der thermoplastisch verformbare Rohling gut in die Oberflächenkontur der Form ein und beginnt sofort abzukühlen. Hierdurch nimmt die thermoplastische Verformbarkeit sofort ab, und es wird vermieden, dass sich Material des Rohlings in Senken der Oberflächenkontur sammelt. Letzteres könnte zu Linseneffekten und damit einer Ablenkung des Lichtstrahls in der Schutzabdeckung führen, die erfindungsgemäß auch vermieden werden soll.
5. (f) Abkühlen der tiefgezogenen Schutzabdeckung. Dies kann insbesondere durch ein Ausschalten oder Absenken der Temperatur von erster und zweiter Heizeinrichtung erfolgen. Auch bei einem gleichzeitigen Ausschalten von erster und zweiter Heizeinrichtung kühlt sich die Form (aufgrund der größeren Masse und eines höheren Wärmekoeffizienten) langsamer ab als der Rohling. Da der Rohling auf der Form aufliegt, folgt die Temperatur des Rohlings der sich langsamer abkühlenden Form. Das langsamere Abkühlen des Rohlings vermeidet Spannungen in der tiefgezogenen Schutzabdeckung und führt dazu, dass die Oberflächenkontur der Schutzabdeckung sehr detailgetreu der Oberflächenkontur der Form folgt. Hierdurch lässt sich die Position und Ausrichtung der Emitterabdeckflächen in der Schutzabdeckung sehr genau definieren, so dass erfindungsgemäß zuverlässig gemeinsamen Kontaktflächen von Emittarabdeckflächen der Schutzabdekung und freiliegenden Lichtemittern entstehen. Dies führt zu einer hohen optischen Qualität der formstabilen, optisch transparenten Schutzabdeckung.
6. (e) Ausformen der tiefgezogenen Schutzabdeckung. Dieser Verfahrensschritt umfasst das Herausnehmen des tiefgezogenen Rohlings mit der Schutzabdeckung aus der Tiefziehvorrichtung. Typischer Weise werden auch die Ränder des tiefgezogenen Rohlings bearbeitet, damit die Schutzabdeckung genau die gewünschte Form und Größe aufweist.

Even a minimal distance in the predefined sense minimizes optical distortions and/or scattering in the protective cover, which could lead to errors in the position and location detection of the marking arrangement. This is mainly because the distance between the protective cover (more precisely the emitter cover surface of the protective cover) and the light emitter (active optical surface) is so small that the light beam between the light emitter and the camera is deflected to a negligible extent at best. The position of the light emitter recorded by the camera therefore corresponds to the actual position of the light emitter with a very high degree of accuracy that is sufficient for the location and location determination.

1. (b) Fixing a blank made of thermoplastically deformable, optically transparent material by means of a deep-drawing device at a distance from the mold.
2. (c) Heating the blank by means of a heating device of the deep-drawing device. For forming by deep-drawing suitable plastic materials, such as acrylic glass (PMMA - polymethyl methacrylate) or another transparent thermoplastic according to the invention, the blank is typically heated to temperatures of approximately between 110 °C and 250 °C, preferably between 120 °C and 180 °C and particularly preferably between 130 °C and 170 °C. To avoid stresses and/or cracks and for good optical quality, the invention can preferably provide that the blank is tempered beforehand, i.e. heated over a longer period of time to a temperature below the melting temperature, for example between approximately 60 °C and 80 or 90 °C, and the temperature is maintained until the entire blank has heated evenly to this temperature. Tempering can typically take 2 to 3 hours. This promotes the compensation of structural defects, improves a crystalline structure and avoids a strong thermal shock to the blank.
3. (d) Heating the mold by means of a heating device of the deep-drawing device. Typically, the temperature of the mold is lower than the temperature of the blank, about 10 °C to 50 °C or preferably 20 °C to 40 °C lower. In percentage terms, the temperature of the mold can be about 5% to 25%, preferably about 10% to 20% lower than the temperature of the blank, in order to avoid thermal shock of the blank when it comes into contact with the mold.
4. (e) Deep-drawing the protective cover in the deep-drawing device while lowering the blank onto the heated mold. In this context, heating the mold according to the invention, for example to a similar temperature to the temperature of the lowered blank, is particularly advantageous because abrupt cooling of the blank from a temperature at which the blank is thermoplastically deformable to a temperature at which the blank is not thermoplastically deformable is avoided. Abrupt cooling with too large a temperature gradient can lead to changes in the optical structure of the thermoplastically deformable material and thus to optical disturbances. This is avoided by heating the mold before lowering the blank. Preferably, the temperature of the mold when lowering the blank is in a range of 75% to 95% of the temperature of the blank. At a temperature below about 75% of the blank, the temperature gradient can be too large, which can lead to optical disturbances due to a changing material structure. On the other hand, it is sensible if the temperature of the mold is slightly lower than the temperature of the blank. Then the thermoplastically deformable blank flows well into the surface contour of the mold and immediately begins to cool down. This immediately reduces the thermoplastic deformability and prevents material from the blank from collecting in depressions in the surface contour. The latter could lead to lens effects and thus a deflection of the light beam in the protective cover, which is also to be avoided according to the invention.
5. (f) Cooling the deep-drawn protective cover. This can be done in particular by switching off or lowering the temperature of the first and second heating devices. Even if the first and second heating devices are switched off at the same time, the mold cools down more slowly than the blank (due to the greater mass and a higher thermal coefficient). Since the blank rests on the mold, the temperature of the blank follows the mold, which cools more slowly. The slower cooling of the blank avoids stresses in the deep-drawn protective cover and means that the surface contour of the protective cover follows the surface contour of the mold very accurately. This allows the position and alignment of the emitter cover surfaces in the protective cover to be defined very precisely, so that according to the invention, reliable common contact surfaces are created between emitter cover surfaces of the protective cover and exposed light emitters. This leads to a high optical quality of the dimensionally stable, optically transparent protective cover.
6. (e) Forming the deep-drawn protective cover. This step involves removing the deep-drawn blank with the protective cover from the deep-drawing device. Typically, the edges of the deep-drawn blank are also machined so that the protective cover has exactly the desired shape and size.

According to a preferred embodiment of the method proposed according to the invention, the method step of deep drawing the protective cover after lowering the blank can comprise the application of a vacuum between the blank and the mold.

As a result, the blank is pulled firmly onto the mold and the contour of the mold is reproduced in the blank particularly precisely and with great detail. According to one possible embodiment of the method step, it can be provided that through holes and/or through slots are provided in the mold, preferably with a diameter or a slot width of less than 2 mm and particularly preferably less than 1 mm, and that the vacuum is generated on a side of the mold opposite the blank in a seal against the mold. Any air (including other gas) remaining between the blank and the mold, e.g. trapped, is sucked out through the through holes and/or through slots, and the molded part is pulled firmly onto the mold. Due to the small holes or slots, the material of the blank is not drawn into them. This avoids undesirable surface irregularities. Vacuum is understood to mean in particular a negative pressure in a pressure range between 0.1 and 0.9 bar, and particularly preferably in a pressure range between 0.1 and 0.4 bar or another pressure range in which undesirable deformations of the blank in the area of the through holes and/or through slots do not (yet) occur.

Such through holes and/or through slots are particularly preferably located (at least also) in the area of the emitter cover surfaces of the surface contour of the mold. This ensures that the protective cover follows the surface contour of the mold in the area of the emitter cover surfaces particularly precisely and the light emission of the light emitters is influenced as little as possible by the protective cover. Ideally, the through holes and/or through slots are arranged directly adjacent to the emitter cover surfaces, preferably several through holes and/or through slots around the emitter cover surfaces. This leads to a uniform vacuum being applied to the emitter cover surfaces. In this way, transparent and optically as undisturbed as possible areas are achieved on the emitter cover surfaces in the optically relevant area.

It is also possible that the process step of deep-drawing the protective cover after lowering the blank includes the application of excess pressure on the side of the blank facing away from the mold. This can be done as an alternative or in addition to the application of the vacuum. In the same way, through holes and/or through slots can be provided in the mold to allow air located between the blank and the mold, in particular trapped air, to escape. By applying excess pressure, for example by blowing compressed air into a closed cavity of the deep-drawing device, the blank is pressed firmly onto the mold during deep-drawing and thus reproduces its surface contour very precisely.

According to the invention, the process step of cooling the deep-drawn protective cover can comprise switching off the heating devices of the blank and switching off the heating device of the mold. In a simplest embodiment, both heating devices are completely switched off at the same time as the vacuum is applied or shortly thereafter, preferably in a period of 10 to 60 seconds after the vacuum is applied. This ensures a high degree of deformability of the blank, while the blank is pulled firmly to the surface contour of the mold due to the vacuum. However, it is also possible to do this At this point in time, only one of the heating devices should be switched off completely, preferably the first heating device of the blank.

In the latter case, it is particularly advantageous if the heating device of the mold is switched off in a controlled or regulated manner according to a predetermined temperature profile, in particular in order to slow down the cooling process of the protective cover. In this embodiment of the invention, the second heating device is therefore only switched off completely when the temperature profile specifies complete switching off. Until the complete switching off, the temperature profile can, for example, specify a gradual or continuous reduction in the temperature, which can be controlled or regulated, for example, by the level of the current flowing through an electrical heating device. In principle, the temperature profile can specify any temperature profile that does not require active cooling.

In particular, slower cooling of the mold enables the protective cover to be shaped with great detail and leads to high dimensional stability in accordance with the surface contour of the mold. If the protective cover cools down too quickly, tensions in the material can lead to deformations and thus deviations from the surface contour specified by the mold. This should be avoided in particular in the area of the emitter cover surfaces. According to the invention, the temperature profile can also be suitably specified and thus controlled by specifying a cooling coefficient of the mold (i.e. a material constant of the mold), without an actively controlled or regulated setting, for example by specifying a heating current.

According to a preferred embodiment of the proposed method, it can be provided to use a thermally conductive material for forming the mold, in particular a metal with a comparatively low heat capacity, which is in any case higher than that of plastic, and/or a good thermal conductivity coefficient, the latter in particular with active cooling of the mold. The temperature of the mold thus follows a predetermined temperature profile controlled by the heating and/or cooling device. In this case, an electrically operated heating element attached to the mold in a heat-conducting system can be used as a simple heating device, the temperature of which can be specified or set according to the current flow through the heating element. This enables very simple control. Cooling can be achieved, for example, by a heat exchanger through which liquid flows.

A preferred embodiment provides that the mold is designed as a negative mold. As a result, the surface facing the light emitter arrangement is not damaged by contact with the mold. This avoids optical artifacts when light enters the protective cover and leads to optically improved light passage.

An infrared-permeable thermoplastic film can be used as a blank. Particularly suitable materials can be, for example, amorphous thermoplastics (e.g. PMMA, PVC, PC, SAN, ABS and PS) or semi-crystalline plastics (e.g. PP, PE), for example in film form.

According to the invention, the method step of shaping the deep-drawn protective cover can include cutting away an overhang on the edges of the protective cover. The cutting away can preferably be done using a laser cutter. This minimizes mechanical impact on the rest of the protective cover, which can lead to damage or deformation when using cutting or punching tools, for example. With appropriately suitable cutting or punching tools, the edges can also be cut away according to the invention using cutting or punching tools. An overhang is an area of the protective cover deep-drawn from the blank that protrudes over the light emitter arrangement and is not used as a fastening section of the protective cover for securing the protective cover to the marking device. The fastening section can be designed as an edge that projects beyond the light emitter arrangement and can be secured to a frame of the marking device, for example by gluing, clamping or similar material and/or form-fitting connection, wherein the light emitter arrangement can be accommodated in the frame of the marking device. In other words, according to the invention, the light emitter arrangement can be inserted in particular into the frame of the marking device and fixed there without the frame of the marking device protruding in the axial direction over the light emitters (i.e. the optically active surfaces of lighting devices). The light emitter arrangement lies in the frame with exposed light emitters, wherein the frame preferably leaves at least an area of +/- 90° around the optical axis (main beam direction of the light emitters) free. This enables a high visibility of the light emitters in the measuring system from different viewing angles, i.e. almost a measuring range of 180°.

In the area of the cut-off overhang of the deep-drawn protective cover, the blank can, according to the invention, have at least four holes for clamping the blank in a holding device of the deep-drawing device during the process ing step of securing the blank. Preferably, exactly four of the at least four (or more) holes are provided at the corners of a rectangular, e.g. square, blank. This allows the blank to be clamped under tension in any direction in the deep-drawing device. Additional holes along the sides of the blank (in the overhang) allow the clamping force to be distributed even more evenly during clamping. This further reduces possible material stresses in the deep-drawn protective cover.

By fixing the protective cover produced as described above to a prefabricated frame and/or a light emitter arrangement with the features described in connection with the invention (e.g. by gluing), the marking device can also be produced according to the invention by the proposed method.

Accordingly, the invention also relates to a marking device with the features of claim 10 for use in an optical measuring system with a light emitter arrangement with a plurality of optically active light emitters arranged in the front of the light emitter arrangement in the direction of light emission and exposed. The marking device also has a frame in which the light emitter arrangement is accommodated (in particular inserted and fixed in a specific position), and a protective cover for the light emitter arrangement made of optically transparent material, wherein the protective cover is produced using the described method or parts thereof, in particular according to one of claims 1 to 9.

According to a preferred embodiment of the marking device according to the invention, the protective cover can have a fastening section which projects laterally beyond the light emitter arrangement and with which the protective cover is fixed to the frame, in particular glued or clamped.

According to the invention, the light emitter arrangement can be designed in particular as a circuit board on the front of which several light emitters are arranged. According to the invention, the light emitters can be designed as a lighting device each as an LED (light emitting diode), preferably as an infrared LED that emits light in the infrared wavelength range. The protective cover is accordingly designed as a thermoplastic film that is permeable to infrared light (i.e. permeable to light in the infrared wavelength range). The optically transparent protective cover is preferably made of an electrically insulating material. The protective cover therefore not only provides mechanical protection for the light emitters against direct damage to the optically active surfaces (light emitters) or protection against contamination, such as dust or liquid deposited on the light emitters (such as oil or the like), which impairs the optical properties of the light emitter arrangement, but also protects the light emitters against electrostatic discharges. This means that the protective covers can be easily cleaned, for example by rubbing them with a cloth, without risking damage to the light emitters through electrostatic charging and then discharging. Alternatively or additionally, it is also possible to provide at least one side of the protective cover, in particular the side facing away from the light emitters, with ESD protection (ESD - Electro Static Discharge), for example by vaporizing a high-resistance material, whereby the vaporization does not affect the light transmission (in particular in the visible or infrared wavelength range).

Preferably, the light emitter arrangement according to the invention can have light emitters in at least two different parallel planes. The parallel planes mean that the direction of radiation of the light emitted by the light emitters points in the same direction. Preferably, the parallel planes are arranged perpendicular to the direction of radiation and form a stepped front side in the direction of radiation. In other words, the parallel planes of the front side of the light emitter arrangement are at different heights.

According to the invention, the protective cover can be fixed to the light emitter arrangement to form a common contact surface of emitter cover surfaces of the protective cover and exposed light emitters.

Preferably, the frame and the protective cover can be connected to one another in a sealing manner, for example by gluing or clamping under contact pressure. The sealing connection reliably protects the light emitter arrangement, in particular against the ingress of dust, splash water or other liquids, and against electrical or electrostatic charging and discharging.

A preferred use of the marking arrangement described above, in particular according to one of claims 10 to 14, can be provided in an optical measuring system in which the marking arrangement is or is attached to an object in space and in which the location and position of the marking arrangement is determined by recording of the light emitted by the light emitters can be determined in an image using an optical recording device.

Further advantages, features and possible applications of the invention also emerge from the following description of embodiments and the drawing. All described and/or illustrated features together or in any combination that makes sense to a person skilled in the art belong to the subject matter of the invention, regardless of their summary in described or illustrated embodiments or in the claims.

• 1 schematisch eine Aufsicht auf eine Markiervorrichtung gemäß einer Ausführungsform der Erfindung ohne Schutzabdeckung;
• 2 schematisch die Markiervorrichtung gemäß 1 in einem Querschnitt entlang der Linie A-A aus 1;
• 3 schematisch eine Aufsicht auf die Schutzabdeckung der Markiervorrichtung aus 1 gemäß einer Ausführungsform der Erfindung;
• 4 schematisch die Schutzabdeckung gemäß 3 in einem Querschnitt entlang der Linie B-B aus 3;
• 5 schematisch einen Querschnitt der Markiervorrichtung aus 2 mit an der Markiervorrichtung festgelegter Schutzabdeckung aus 4;
• 6 schematisch eine Aufsicht auf die Markiervorrichtung aus 1 mit an der Markiervorrichtung festgelegter Schutzabdeckung aus 3;
• 7 einen Rohling zur Herstellung der Schutzabdeckung in einem Verfahren gemäß einer Ausführungsform der Erfindung;
• 8 den Rohling aus 7 in einem Zwischenschritt des erfindungsgemäßen Verfahrens nach dem Tiefziehen gemäß einer Ausführungsform;
• 9 die Schutzabdeckung aus 3 als Produkt des Herstellungsverfahrens gemäß einer Ausführungsform der Erfindung;
• 10a eine Ausführungsform einer Tiefziehvorrichtung mit einer Form zum Tiefziehen der Schutzabdeckung aus 9 in einem Verfahrensschritt des Herstellungsverfahrens gemäß einer Ausführungsform der Erfindung;
• 10b die Tiefziehvorrichtung aus 10a in einem weiteren Verfahrensschritt des Herstellungsverfahrens gemäß einer Ausführungsform der Erfindung;
• 10c die Tiefziehvorrichtung aus 10a in einem weiteren Verfahrensschritt des Herstellungsverfahrens gemäß einer Ausführungsform der Erfindung;
• 10d die Tiefziehvorrichtung aus 10a in einem weiteren Verfahrensschritt des Herstellungsverfahrens gemäß einer Ausführungsform der Erfindung;

They show:

• 1 schematically a plan view of a marking device according to an embodiment of the invention without protective cover;
• 2 schematically the marking device according to 1 in a cross section along the line AA 1 ;
• 3 schematically a top view of the protective cover of the marking device from 1 according to an embodiment of the invention;
• 4 schematically the protective cover according to 3 in a cross section along the line BB 3 ;
• 5 schematically a cross-section of the marking device 2 with protective cover attached to the marking device 4 ;
• 6 schematically a top view of the marking device 1 with protective cover attached to the marking device 3 ;
• 7 a blank for producing the protective cover in a method according to an embodiment of the invention;
• 8 the blank 7 in an intermediate step of the method according to the invention after deep drawing according to one embodiment;
• 9 the protective cover 3 as a product of the manufacturing process according to an embodiment of the invention;
• 10a an embodiment of a deep-drawing device with a mold for deep-drawing the protective cover from 9 in a process step of the manufacturing process according to an embodiment of the invention;
• 10b the deep-drawing device 10a in a further process step of the manufacturing process according to an embodiment of the invention;
• 10c the deep-drawing device 10a in a further process step of the manufacturing process according to an embodiment of the invention;
• 10d the deep-drawing device 10a in a further process step of the manufacturing process according to an embodiment of the invention;

A marking device according to the invention with a protective cover according to the invention and a method for producing the protective cover according to the invention and fixing it on the marking arrangement according to a preferred embodiment are described below. The invention should not be understood as being limited to this embodiment. In particular, the embodiment includes many features of preferred configurations that can be implemented together or individually according to the invention, in accordance with the expert's understanding of the following description and the drawing. The drawing represents a schematic possibility for implementing the invention.

1 shows a marking device 1 that can be used in an optical measuring system (not shown), for example, to determine the location (alignment) and position of the marking device in space. For this purpose, an image of the marking device 1 is recorded with a camera (optical recording device) calibrated in space and the location and position of the marking device 1 are determined from the image of the marking device 1. Methods for this are known to the person skilled in the art from the prior art.

The marking device 1 has a light emitter arrangement 2 with several optically active light emitters 3 arranged on the front side of the light emitter arrangement 2 in the direction of light emission and exposed. Light emitters 3 are optically active surfaces of lighting devices 4, which typically have a housing and electronic components contained therein for generating light. The lighting devices 4 shown here as examples are LEDs (light emitting diodes) that emit light in the optically visible and/or infrared wavelength range. Infrared LEDs are particularly preferred as lighting devices 4.

In the illustrated light emitter arrangement 2, the lighting devices 4 are arranged in three parallel lines (vertical in the illustration according to 1 ), whereby lighting devices 4 and thus also the light emitters 3 of one (e.g. the middle) of the three lines are arranged opposite the lighting devices 4 and light emitters 3 of the other two lines are arranged raised on a dome 6. The lighting devices 4 and light emitters 3 of the other two (e.g. lateral) lines are arranged directly on a carrier plate 5 of the light emitter arrangement 2. Both the carrier plate 5 and the dome 6 can be designed as a circuit board with further electronic components and conductor tracks, which are not shown in the drawing for the sake of clarity. The electronic components can also have a computing unit for controlling the lighting devices 4 or light emitters 3 and an accumulator for energy supply. For the sake of clarity, 1 Only one of the lighting devices 4 with the light emitters 3 is provided with a reference symbol per line.

As the sectional view of 2 As can be seen, the light emitter 3 in the housing of the lighting device 4 can be arranged slightly set back from the front side, preferably not more than 3 mm, particularly preferably not more than 1 mm. This determines the light emission angle, which is approximately 180°, depending on the arrangement of the light emitters 3 in the lighting devices 4, preferably in an angle range between 200° and 150°.

The light emitter arrangement 2 is accommodated in a frame 7 of the marking device 1, in particular by the carrier plate 5 being placed in a frame opening 9 and fixed there (with holders not shown). The lighting devices 4 fixed on the front of the light emitter arrangement 2 are positioned such that the optically active light emitters 3 are arranged exposed in the direction of the light emission. This means that the frame 7 does not interfere with the light propagation from the light emitters 3 and thus does not interfere with the visibility of the light emitters 3 by an optical recording device (camera). This is referred to as exposing the light-emitting front side 8 of the light emitter arrangement 2. On the back of the carrier plate 5 (circuit board) opposite the light-emitting front side 8, further electronic components (not shown) can be arranged, which are also accommodated in the frame opening 9 of the frame 7.

This arrangement according to the invention of the light-emitting front side 8 of the light emitters 3 or the light emitter arrangement 2 achieves optimum visibility of the light emitters 3 and optical distortions of the emitted light do not occur. However, the optically active light emitters 3 are located in the 1 and 2 The arrangement shown is completely unprotected, not only against mechanical influences, but also against contamination by deposits of substances such as dust, oil drops, paint particles or the like. In order to avoid this and to influence the light emission by the light emitters as little as possible, the invention proposes a protective cover 20 made of optically transparent material, which is intended to cover the light-emitting front side 8 of the light emitter arrangement 2 and is designed to be dimensionally stable.

This protective cover 20 is described below with reference to the 3 to 6 described. 3 shows a plan view of the protective cover 20 with a surface contour 21 which envelops the front side 8 of the light emitter arrangement 2. In particular, the surface contour 21, the shape of which follows the sectional view in 4 can be seen particularly clearly, the lighting devices 4 arranged on the front side 8 of the light emitter arrangement 2 with the light emitters 3. The protective cover 20 forms emitter cover surfaces 22, the position of which corresponds to the arrangement of light emitters 3 exposed in the light emitter arrangement 2 such that the protective cover 20 can be placed on the light emitter arrangement 2 to form a common contact surface 23 of emitter cover surfaces 22 of the protective cover 20 and exposed light emitters 3 of the light emitter arrangement 2.

4 is a sectional view of the protective cover 20 along the line BB from 3 . 5 shows the arrangement of the protective cover 20 on the light emitter arrangement 2 to form an embodiment of a marking device 1 according to the invention. In this embodiment, the protective cover 20 is fixed to the frame 7 of the marking device 1 by gluing. In this way, the light emitter arrangement 2 is sealed against environmental influences and accommodated in the marking device 1.

When the protective cover 20 is placed or fixed, the common or direct contact surface 23 is formed according to the invention between the emitter cover surface 22 of the protective cover 20 and the light emitter 3. This means that one (in particular each) emitter cover surface 22 of the protective cover 20 is arranged directly in front of the optically active surface (ie in front of the light emitter 3) with a minimal distance, in particular preferably at a distance of less than 3 mm, preferably less than 2 mm and particularly preferably less than 1 mm. The term "contact surface 23" is not to be understood in such a way that the protective cover 20 must be in direct contact with the optically active surface in the area of the emitter cover surface 22 (at all or throughout). Such a solution may be preferred, but is not absolutely necessary. Even a minimal distance in the predefined sense minimizes optical distortions and/or scattering. of the emitted light in the protective cover 20, which could lead to errors in the position and location detection of the marking device 1.

6 shows the marking arrangement 1 with light emitter arrangement 2, frame 7 and protective cover 20 in a top view, with the light emitter arrangement 2 and the frame 7 shown in dashed lines for the sake of clarity. A fastening section 24 is provided on the edge of the protective cover, which extends to the edge 7 of the marking device. In the fastening section 24, the protective cover 20 is glued to the edge 7 in a sealing manner.

The following is based on the 7 to 9 as well as 10a to 10d a preferred embodiment of a method according to the invention for producing the dimensionally stable protective cover 20 is described.

The starting point for the production of the protective cover 20 is a blank 25 ( 7 ) made of a flat, optically transparent and thermoplastically deformable film. Examples of suitable materials have already been mentioned at the beginning. Holes 26 are provided in the corners of the preferably rectangular or square blank 25 for clamping the blank 25 in a holding device 31 of a deep-drawing device 30, for example by laser cutting or punching processes. Such a device is shown schematically in the 10a to 10d shown.

The deep-drawing device 30 comprises a holding device 31 to which the blank 25 can be fixed. In the embodiment shown, this is done by clamping the blank 25 with the holes 26 in the holding device 31, as in all 10a to 10d schematically represented by clamping elements 32. The holding device 30 further comprises a first heating device 33, which can be electrically operated and serves to heat the blank 25 for thermoplastic deformation.

The deep-drawing device 30 also has a mold 35 with a surface contour 36. In the process for producing the protective cover 20, the mold 35 transfers the surface contour 36 of the mold 35 to the surface contour 21 of the blank 25. The blank 25 from which the protective cover is formed therefore takes on the surface contour 36 of the mold 35.

The manufacturing process is also referred to as deep drawing. After deep drawing, the surface contour 36 of the mold 35 and the surface contour 21 of the protective cover 20 correspond to one another.

During deep drawing, a mold 35 is provided with a surface contour 36 related to the specific application. In the present case, the mold 35 has a surface contour 36 that must meet the later intended use of the protective cover 20. In other words, the later intended use, here to form a protective cover 20 "for a light emitter arrangement 2 of a marking device 1", has an impact on the specific surface contour 36 of the mold 35 in such a way that the protective cover 20 must fit a specific marking device 1 with a light emitter arrangement 2. The mold 35 is designed as a positive mold or a negative mold, with the application-specific design of its surface contour 36 necessarily being defined by the object to be covered by the protective cover 20, i.e. specifically by the light-emitting front side 8 of the light emitter arrangement 2, which is to be covered by the protective cover 20. This is clear to the person skilled in the art. The latter understands the explanation to mean that the surface contour 36 of the form 35 is designed such that it envelops the front side 8 of the light emitter arrangement 2. The surface contour 36 has emitter cover surfaces 37, the position of which corresponds to the arrangement of light emitters 3 exposed in the light emitter arrangement 2 such that a surface contour 21 of the protective cover 20 following the surface contour 36 of the form 35 can be placed on the light emitter arrangement 2 (i.e. does not collide with the elements arranged on the front side 8 of the light emitter arrangement 2 or the carrier plate 5, such as the illuminant directions 4 and the dome 6). When the protective cover 20 is placed on the light emitter arrangement 2, a common contact surface 23 is formed between the emitter cover surfaces 22 of the protective cover 20 and the exposed light emitters 3.

For deep drawing, the heated blank 25 is lowered by means of a mechanism 34, which is usually provided in deep drawing devices and is known to the person skilled in the art, in order to bring the blank 25 into contact with the mold 35. For the sake of simplicity, the mechanism 34 is simply shown as an arrow in 10a shown.

The deep-drawing device 30 further comprises a vacuum device 38 with a vacuum generator 39 designed as a vacuum pump and a vacuum chamber 40 connected thereto, which is connected in a sealing manner to the mold 35. Through openings 41 opening into the vacuum chamber 40 are formed in the mold 35, which can also be designed as through slots 41 and extend into the surface contour 36 of the mold 35. This makes it possible to generate a vacuum between the surface contour 36 of the mold 35 and a blank 25 resting on the mold 35, which vacuum ling 25 is drawn particularly into depressions of the surface contour 36 of the mold 35 and results in the surface contour 21 of the protective cover 20 following the surface contour 36 of the mold 35 as closely as possible and corresponding to it after deep drawing. In the 10a to 10d A total of eight through openings 41 are shown, although for the sake of clarity not all of them are marked with the reference number 41.

On the side of the mold 35 opposite the surface contour 36, a second heating device 42 is arranged, which is shown in four parts in the drawing in order to show a connection of the through openings 41 to the vacuum chamber 40. According to the invention, the second heating device 42 preferably lies on the mold 35 over as large an area as possible in order to heat it as evenly as possible. The second heating device 42 can be designed in one or more parts and/or can also be arranged laterally on the mold 35. In one embodiment, the through openings 41 (different from the one shown) can also open into a vacuum chamber 40 that runs laterally around the mold 35. The illustration in the 10a to 10d is to be understood schematically and is not intended to limit the possible construction of the deep-drawing device 30.

The first heating device 33 and/or second heating device 42 can also have a temperature control or temperature regulation and/or a temperature sensor, such as a PTC sensor (Positive Temperature Coefficient), which are not shown in the drawing, however. The purpose and functioning of a temperature control or temperature regulation, in particular with the second heating device 42, have already been explained at the beginning.

10a shows a method step of an embodiment of the method proposed according to the invention, in which a mold 35 with a suitable surface contour 36 (as described above) was provided, i.e. produced and inserted into the deep-drawing device 30. The blank 25 was prepared accordingly from thermoplastically deformable, optically transparent material and fixed in the deep-drawing device 30 at a distance from the mold 35, preferably by clamping in the holding device 31. The blank 25 can be made by cutting a thermoplastically deformable film and making at least four holes 26, for example by means of a 2-dimensional plotter or a laser cutter, which enables the blank 25 to be prepared flexibly and in a way that is gentle on the material. The mold 35 consists of a heat-conducting material, such as a metal, and in the example shown here is designed as a negative. This means that the surface contour 36 of the mold 35 corresponds to the outer surface contour 21 of the protective cover 20 to be produced. In the case of a mold 35 designed as a positive, the surface contour 36 of the mold 35 would correspond to the inner surface contour 21 of the protective cover 20 to be produced. Such an embodiment is also covered by the subject matter of the invention.

In the 10a In the process step shown, the blank 25 is already heated by means of the first heating device 33 and the mold 35 is already heated by means of the second heating device. This means that the blank 25 is in a state in which the blank 25 is thermoplastically deformable.

In the next step, as described in 10b As shown, the lowering of the blank 25 onto the heated mold 35 is carried out by means of the mechanism 34 of the deep-drawing device 30 in the direction of the 10a After lowering the blank 25, it begins to deform, particularly due to gravity, and flows into depressions in the surface contour 36. This is shown in 10c shown.

In this in 10c In the state shown, in a next process step, a vacuum is created between the blank 25 and the mold 35. This is done by activating the vacuum device 38 and the vacuum pump 39, which generates a negative pressure in the vacuum chamber 40 and sucks out remaining air from the gaps 43 between the mold 35 and the blank 25 via the through holes 41. This also creates a negative pressure in the gaps 43 between the mold 35 and the blank 25, which further deforms the blank 25 and draws it into the mold 35, so that the surface contour 21 of the blank 25 or of the protective cover 20 formed from the blank 25 follows and corresponds to the surface contour 36 of the mold 35.

This condition is in 10d shown. In this state, the first heating device 33 and the second heating device 42 are switched off, whereby the mold 35 cools more slowly than the molding 25 with the deep-drawn protective cover 20 due to the greater mass and heat capacity. This slowed cooling process means that the formation of the protective cover 20 is particularly detailed and follows the surface contour 36 of the mold 35 in a dimensionally stable manner. Optionally, the switching off of the second heating device 42 can be controlled or regulated in order to further slow down the cooling process and to specify it in a controlled manner so that the cooling of the mold 35 follows a predetermined temperature profile. This enables a process design under optimized conditions and leads to a controlled reproducibility of the protective covers produced 20.

Preferably after waiting for a cooling time specified according to the invention, which can also be defined, for example, by reaching a temperature threshold measured on the mold 35, the deep-drawn protective cover 20 is formed. This includes in particular the removal of the blank 25 with the deep-drawn protective cover 20 from the holding device 21 of the deep-drawing device 30. The removed blank 25 is in 8 This shows (within the dashed demarcation line 27 between the deep-formed protective cover 20 and an overhang 28 of the blank 25 after deep-forming beyond the protective cover 20) the protective cover 20 which is still surrounded by the overhang 28.

In a further process step for forming the protective cover 20, the overhang 28 is removed, for example by cutting off the overhang 28 or cutting out the protective cover 20 along the 8 dashed demarcation line 27 (which does not necessarily have to be visible on the blank 25, but can also be created in the blank 25 by the mold 35 if necessary). For this purpose, the blank 25 with the deep-formed protective cover 20 can be clamped into a laser cutter, for example, and the overhang 28 can be cut off. In principle, other cutting processes such as punching or the like are also conceivable. The finished protective cover is in 9 and corresponds to the representation according to 3 .

Subsequently, an automated optical inspection and fit check of the protective cover 20 can optionally be carried out.

To produce a marking device 1 with a protective cover, which is also covered by the subject matter of the invention, a prefabricated frame 7 and a prefabricated light emitter arrangement 2 are assembled and the protective cover 20 is inserted into the fastening section 24 (cf. 6 ) is glued to the frame 7 of the marking device in a sealing manner. This also allows the light emitter arrangement 2 to be fixed in the frame 7 according to the invention. The light emitter arrangement 2 shown and described represents a preferred embodiment for a marking device 1 according to the invention.

List of reference symbols:

1

marking device

2

light emitter arrangement

3

light emitter (optically active surface of a lighting device LED)

4

lighting device

5

carrier plate (circuit board)

6

dome (board)

7

Frame

8

light-emitting front

9

frame opening

20

protective cover

21

surface contour

22

emitter cover area

23

common or direct contact surface

24

fastening section

25

blank

26

hole for clamping the blank

27

demarcation line

28

overhang

30

deep-drawing device

31

holding device

32

clamping element

33

first heating device

34

mechanism for lowering the holding device

35

form

36

surface contour

37

emitter cover surface

38

vacuum device

39

vacuum generator (vacuum pump)

40

vacuum chamber

41

through holes / through slots

42

second heating device

43

space between

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 202020103679 U1 [0002]
• EP 1658819 B1 [0004]

Claims (15)

Method for producing a dimensionally stable protective cover (20) made of optically transparent material for an optical light emitter arrangement (2) of a marking device (1) for use in an optical measuring system, wherein the protective cover (2) is provided for covering a light-emitting front side (8) of the light emitter arrangement (2), comprising the following method steps: Providing a mold (35) with a surface contour (36) that envelops the front side of the light emitter arrangement (2), wherein the surface contour (36) has emitter cover surfaces (37) whose position corresponds to the arrangement of light emitters (3) exposed in the light emitter arrangement (2) such that a protective cover (20) following the surface contour (36) of the mold (35) can be placed on the light emitter arrangement (2) to form a common contact surface (23) of emitter cover surfaces (22) of the protective cover (20) and exposed light emitters (3); Fixing a blank (25) made of thermoplastically deformable, optically transparent material by means of a deep-drawing device (30) at a distance from the mold (35); Heating the blank (25) by means of a first heating device (33) of the deep-drawing device (30); Heating the mold (35) by means of a second heating device (42) of the deep-drawing device (30); Deep-drawing the protective cover (20) in the deep-drawing device (30) while lowering the blank (25) onto the heated mold (35); Cooling the deep-drawn protective cover (20); Shaping the deep-drawn protective cover (20). procedure according to claim 1 , characterized in that the method step of deep drawing the protective cover (20) after lowering the blank (25) comprises applying a vacuum between the blank (25) and the mold (35). procedure according to claim 1 or 2 , characterized in that the method step of deep-drawing the protective cover (20) after lowering the blank (25) comprises the application of an overpressure on the side of the blank (25) facing away from the mold (35). Method according to one of the Claims 1 until 3 , characterized in that the method step of cooling the deep-drawn protective cover (20) comprises switching off the first heating device (33) of the blank (25) and switching off the second heating device (42) of the mold (35). Method according to one of the Claims 1 until 4 , characterized in that the switching off of the second heating device (42) of the mold (35) is controlled or regulated according to a predetermined temperature profile. Method according to one of the preceding claims, characterized in that a thermally conductive material is used for forming the mold (35). Method according to one of the preceding claims, characterized in that the mold (35) is designed as a negative mold. Method according to one of the preceding claims, characterized in that an infrared-transparent thermoplastic film is used as the blank (25). Method according to one of the preceding claims, characterized in that the method step of forming the deep-drawn protective cover (20) comprises cutting away an overhang (28) at edges of the protective cover (20). Marking device for use in an optical measuring system with a light emitter arrangement (2) with a plurality of optically active light emitters (3) arranged on the front side (8) of the light emitter arrangement (2) in the direction of light emission, with a frame (7) in which the light emitter arrangement (2) is accommodated and with a protective cover (20) for the light emitter arrangement (2) made of optically transparent material, characterized in that the protective cover (20) is produced using a method for producing the protective cover (20) according to one of the Claims 1 until 9 is manufactured. marking device according to claim 10 , characterized in that the protective cover (20) has a fastening section (24) which projects laterally beyond the light emitter arrangement (2) and with which the protective cover (20) is fixed to the frame (7). marking device according to claim 10 or 11 , characterized in that the light emitter arrangement (2) has light emitters (3) in at least two different parallel planes. Marking device according to one of the Claims 10 until 12 , characterized in that the protective cover (20) is arranged on the light emitter arrangement (2) to form a common contact surface (23) of emitter cover surfaces (22) of the protective cover (20) and exposed light emitters (3). Marking device according to one of the Claims 10 until 13 , characterized in that the frame (7) and the protective cover (20) are sealingly connected to one another. Use of a marking device (1) according to one of the Claims 10 until 14 in an optical measuring system in which the marking device (1) is attached to an object in space and the location and position of the marking device (1) are determined in an image by recording the light emitted by the light emitters (3) with an optical recording device.