Device and method for coating a cylindrical body with a polymer

Abstract

The invention relates to a coating device (2) for coating a cylindrical substrate (1) with a flowable material, comprising a supply nozzle (6) for applying the material onto the substrate (1); a smoothing wiper (10) which is arranged downstream of the supply nozzle (6) and is designed to smooth the surface of the material applied onto the substrate (1); and a force generating device (14, 15) for applying a force to the smoothing wiper (10) and thus deflecting the smoothing wiper (10) out of a rest position and moving the smoothing wiper (10) in the direction of the surface of the material applied onto the substrate (1), wherein the force which can be applied to the smoothing wiper (10) by the force generating device (14, 15) can be modified, and the force generating device (14, 15) has a force controller for adjusting the force which can be applied to the smoothing wiper (10) by the force generating device.

Description

[0001] The invention relates to a coating device for coating a cylindrical substrate with a flowable material.

[0002] Such a substrate could, for example, be a printing plate that can be coated with a polymeric coating material. The term substrate or printing plate will be used below primarily as a generic term for gravure printing plates, relief printing plates, or structural plates for embossing, but also for coating rollers or inking rollers.

[0003] WO 2021 / 052641 A1 discloses a printing form and a polymeric coating material for it. The coating material is a polymeric nanocomposite that can be applied as a single layer to printing forms. The polymeric nanocomposite is applied in flowable form to the cylindrical outer surface of the printing form and subsequently cured by irradiation with UV light. The resulting polymer layer can be structured, for example, using infrared lasers to create a surface structure with, for example, cells or structures for ink retention or embossing, as also described in WO 2021 / 052641 A1.

[0004] Applying and curing a still-flowable polymer, such as the aforementioned nanocomposite, is a complex process. Curing is primarily achieved using UV light. To achieve efficient and low-emission, i.e., ozone-free, curing, UV LEDs are increasingly being used. Due to the prevailing oxygen inhibition at the surface of the radical polymerization, these LEDs require surface inerting.

[0005] The requirements for the surface quality of the polymer coating are high, as this can directly affect print quality, especially when the cylindrical substrate is a printing cylinder, such as a gravure cylinder. An uneven polymer surface would result in a poor print image.

[0006] For thin metallic wear-resistant coatings, electroplating processes and vacuum processes such as PVD or CVD have become established. For thicker hard coatings, flame spraying processes such as HVOF are among those used. Thin plastic coatings can be applied, for example, by spraying, such as with low-viscosity paints or powders.

[0007] For web coatings, roller, doctor blade, slot nozzle coatings or printing processes can be used.

[0008] Thicker layers of plastic are often applied using an extruder. This process results in overlaps, which can lead to significant variations in layer thickness.

[0009] However, the aforementioned methods either fail to achieve the required surface quality and uniformity of layer thickness or cannot be operated economically.

[0010] From DE 196 12 749 A1, a device for coating the outer circumferential surface of a column-like body with a coating agent is known. In this device, the coating agent is scraped off by a scraper blade after exiting a coating unit. The distance between the scraper blade and the body to be coated is adjusted by a roller spacer.

[0011] Therefore, the invention is based on the objective of providing a device and a method with which a format- and circumference-independent, but at the same time efficient, accurate and seamless coating of various cylindrical substrates with a flowable material is made possible.

[0012] The object of the invention is achieved by a coating device having the features of claim 1. Advantageous embodiments are specified in the dependent claims.

[0013] A coating device for coating a cylindrical substrate with a flowable material is described, comprising a feed nozzle for applying the material to the substrate; a smoothing blade arranged downstream of the feed nozzle and configured to smooth the surface of the material applied to the substrate; a force-generating device for applying a force to the smoothing blade, thereby deflecting the smoothing blade from a rest position and moving it towards the surface of the material applied to the substrate; the force that can be applied to the smoothing blade by the force-generating device is variable; and the force-generating device includes a force control for adjusting the force that can be applied to the smoothing blade by the force-generating device.

[0014] The cylindrical substrate to be coated can be rollers of all kinds, in particular printing forms such as gravure printing forms or cylinders, structural forms or cylinders, embossing forms or cylinders, as well as letterpress forms or cylinders or coating rollers and inking rollers, e.g. for flexographic printing.

[0015] The flowable material can, in particular, be a flowable polymer material.

[0016] For example, it can be a polymeric coating material, such as that described in WO 2021 / 052641 A1. In particular, the polymer can be a coating material for coating a printing form, comprising a liquid starting material that is polymerizable by UV light to form a polymer matrix, a filler having a sub-microscale size, wherein the coating material contains, in addition to the sub-microscale filler, a further filler, wherein the sub-microscale filler is in particle form and its size is in the range between 100 nm and 999 nm, wherein the further filler is a nanoscale filler such that the further filler has filler particles with a nanoscale size in the range between 1 nm and 99 nm, wherein the sub-microscale filler consists of at least one metal oxide and / or a semi-metal oxide selected from metal oxide-coated mica.TiO₂ or (Sn, Sb)O₂, wherein the nanoscale filler is metal and / or semimetal oxides selected from Al₂O₃, SiO₂, TiO₂, ZrO₂ or organometallic particles, wherein the sub-microscale filler is covalently embeddable in a polymer matrix of the starting material, wherein the nanoscale filler is included to increase wear resistance and is covalently embeddable in the polymer matrix of the starting material, and wherein the sub-microscale filler in the starting material can effect an absorption of IR radiation that is higher than an absorption without filler.

[0017] The smoothing blade is arranged downstream of the feed nozzle and is suitable for smoothing the layer of material applied to the substrate and, in particular, for closing gaps and crevices that have formed between adjacent layers of material during application.

[0018] For this purpose, the smoothing blade is pressed onto the material layer using the force generation device, with the contact pressure ideally being regulated. Excessive contact pressure leads to a significant change in the layer thickness distribution, while insufficient contact pressure prevents the transition gap between adjacent layers from closing. It has been shown that, due to varying viscosities, surface tensions, and other material variables, different surface pressures should be achievable with the smoothing blade.

[0019] The smoothing squeegee can consist of a thin plastic sheet that can be deformed in a suitable way so that it adapts to the surface of the material to be smoothed.

[0020] The force generation device is designed to deflect and move the smoothing blade from its rest position. The rest position is, in this sense, a starting position. With the aid of the force generation device and the coupled force control, the force applied to the smoothing blade by the force generation device can be precisely adjusted so that the smoothing blade is pressed onto the material to be smoothed with the appropriate force.

[0021] The material layer thickness can be, for example, 10 to 500 µm, particularly 10 to 250 µm as the target layer thickness. The deviation from the target layer thickness should be minimal, for example, within a range of up to ±5% or up to ±3%.

[0022] A conveying system may be provided to transfer the free-flowing material from a material reservoir to the feed nozzle. Free-flowing polymers, in particular, require sophisticated conveying. This can be achieved, for example, by a syringe pump, a progressive cavity pump, or a dispenser. A sieve or filter may be installed at a suitable point along the system.

[0023] The material flow should be pulsation-free, constant, and sufficiently precise to achieve the desired layer thickness and quality. Permissible deviations in material conveyance can be small, depending on the requirements, for example, up to ±3% or, ideally, up to ±1%.

[0024] The feed nozzle can have a cylindrical inlet and a material outlet that follows it in the flow direction. The material outlet then ends at the nozzle opening of the feed nozzle.

[0025] The material outlet or nozzle opening can have a slot-shaped cross-section that tapers at a specific angle. This slot-shaped cross-section can be essentially square or rectangular. To create a thin coating on the substrate, the width of the slot-shaped cross-section should be significantly greater than its depth. For example, the width can be 5 to 30 mm, while the depth can be 1 to 3 mm. This allows for the production of a thin but sufficiently wide material strand. Sufficient width is necessary to coat the substrate quickly and economically.

[0026] The tapering angle at the material outlet can be, for example, 1 to 7°. This tapering angle results in an increasing flow velocity, which is advantageous for the formation of the material layer.

[0027] The distance between the feed nozzle or the material outlet of the feed nozzle and the substrate can be in the range of, for example, 1 S to 4 S, where S is the desired layer thickness.

[0028] The smoothing blade can have a front surface that can be brought into contact with the material to be smoothed, as well as a back surface opposite the front surface. The back surface of the smoothing blade can be supported by a support blade, with the force-generating device acting on the support blade.

[0029] As explained above, the smoothing blade can be made of a plastic sheet and is therefore unstable in shape. Direct force from the power source, such as a piston, on the unstable smoothing blade would disrupt its shape, preventing it from fulfilling its function of uniformly smoothing the surface of the material being smoothed. The supporting blade behind it, however, is dimensionally stable and can be made of, for example, spring steel. It is able to absorb the force from the power source and distribute it evenly across the entire back surface, or at least a portion of it, of the smoothing blade. The supporting blade thus ensures that the smoothing blade retains its flat shape and cannot be deformed by the force applied by the power source.

[0030] The force-generating device can include a pressure piston that acts against the back of the finishing blade or against the back of the support blade. As explained above, it is particularly advantageous if the force-generating device acts against the back of the support blade so that the force of the force-generating device can be transferred evenly and over a wide area from the support blade to the finishing blade. The pressure piston can be pneumatically actuated, for example, which allows for good controllability.

[0031] At least part of the smoothing blade can be supported at its front by a return blade. The return blade can be made of sheet metal or spring steel and may extend, for example, only halfway or one-third of the front surface of the smoothing blade. It should be ensured that the return blade does not come into contact with the substrate or the flowable material being smoothed. Contact should occur exclusively via the smoothing blade.

[0032] The return blade, due to its spring action, generates a counterforce to the force applied by the force-generating device via the support blade. In particular, when the force of the force-generating device is reduced or completely switched off, the return blade can move the smoothing blade and the support blade back to their initial or rest position.

[0033] In this way, the force-generating device and the return blade interact, ensuring that the position of the smoothing blade and the support blade are always defined and can be determined by the force-generating device. The greater the force from the force-generating device, the more the smoothing blade is deflected against the force of the return blade. Conversely, if the force from the force-generating device is reduced, the return blade pushes the smoothing blade back into its starting position.

[0034] A coating system for coating a cylindrical substrate with a flowable material is further specified, comprising a coating device of the type described above; a substrate receptacle for supporting the cylindrical substrate; a translation device for moving the coating device in a translational direction; a rotation device for moving the substrate supported by the substrate receptacle in a rotational direction; and a motion control configured to coordinate the movement by the translation device with the movement of the rotation device such that the coating device performs a spiral movement relative to the substrate.

[0035] In this way, the coating device can be moved relative to the rotating substrate. The direction of translation can be, in particular, the longitudinal direction of the substrate, i.e., its central axis, while the substrate itself is rotated around its main or central axis. The desired relative spiral motion can be achieved through the superimposed movement of the substrate's rotation and the translation of the coating device. This allows the flowable material to be applied evenly to the substrate's surface, following a spiral path. The path elements should be positioned next to each other without gaps, so that any remaining small gap can be easily closed by the smoothing action of the squeegee. Ideally, the spiral motion can be adjusted so precisely that virtually no gaps remain between the adjacent layers.

[0036] A positioning device may be provided for positioning the coating device relative to the substrate in the radial direction of the substrate. In this way, the feed nozzle and the smoothing blade, in particular, can be positioned, i.e., held and / or moved, relative to the substrate.

[0037] The positioning device can include a distance control device, wherein the distance control device can include a distance measuring device for measuring the distance between the coating device and the substrate, and wherein the distance control device can include a distance adjusting device for adjusting the distance of the coating device to the substrate such that the distance corresponds to a predetermined value.

[0038] Distance measurement can be performed inductively, capacitively, or using a laser, allowing for variable and mechanically precise adjustment of the distance. The distance measuring device thus constitutes a distance sensor.

[0039] A method for coating a cylindrical substrate with a flowable material is described, comprising the following steps: Providing a coating device, with a feed nozzle for applying the material to a substrate and with a smoothing squeegee for smoothing a surface of the material applied to the substrate; moving the substrate in a rotational direction; moving the coating device along a surface of the substrate parallel to an axis of the substrate; during the movement of the substrate and the coating device: Applying the material to the substrate through the feed nozzle; smoothing the surface of the material applied to the substrate using the smoothing blade; applying force to the smoothing blade during smoothing; regulating the force applied to the smoothing blade to a preset value.

[0040] These and other features and advantages of the invention are explained in more detail below with the aid of examples and the accompanying figures. These show: Fig. 1a coating system for applying a polymer layer to a cylindrical substrate; Fig. 2a coating device as part of the coating system of Fig. 1 , for coating a cylindrical substrate with a polymer; Fig. 3. A cutaway side view of the device of Fig. 2 ; Fig. 4a close-up "C" from Fig. 2 ; Fig. 5. A hardening system for hardening a polymer layer on a cylindrical substrate; Fig. 6. A hardening device as part of the hardening system of Fig. 5 ; Fig. 7. A close-up of the hardening device from Fig. 6 ; and Fig. 8 A cutaway side view of the hardening device of Fig. 6 .

[0041] Fig. 1 Figure 1 shows a perspective view of a coating system as part of a layer generation system for producing a polymer layer on a cylindrical substrate.

[0042] In the example shown, substrate 1 is a printing form, specifically a gravure cylinder for use in gravure printing. The gravure cylinder is to be coated with a flowable polymer. This could, for example, be the nanocomposite known from WO 2021 / 052641 A1. The polymer coating of the gravure cylinder is suitable for creating small depressions, so-called cells, by laser treatment, particularly with a near-field infrared (NIR) laser. These cells can then hold the printing ink and transfer it to the object to be printed. For this purpose, the polymer layer must have a relatively small thickness (layer thickness), for example, 10 µm to 500 µm, and in particular 10 µm to 250 µm.

[0043] The substrate 1 or the gravure cylinder is held rotatably in a rotational direction R in a photograph not shown.

[0044] A coating device 2 is provided on the outer surface of the substrate 1 and can be moved in a translational direction X along the outer surface of the substrate 1. The coating device 2 serves to apply the still-flowable polymer material to the cylindrical surface of the substrate 1.

[0045] When the translational movement of the coating device 2 in translational direction X and the rotation of the substrate 1 in rotational direction R are superimposed, the coating device 2 performs a helical movement relative to the outside of the substrate 1, as shown in Fig. 1 This is indicated by an arrow S. Using the coating device 2, flowable polymer material with a width of, for example, a few millimeters, e.g., 5 mm to 30 mm, can be applied to the outside of the substrate 1. The spiral relative movement allows one polymer layer to be applied next to another in a spiral or helical pattern, so that ultimately the entire surface of the substrate or a portion thereof is uniformly covered with a polymer layer. With the aid of smoothing elements, which will be explained later, any gap that arises between the adjacent polymer layers can be uniformly closed, resulting in a smooth, homogeneous polymer layer.

[0046] For the application of the polymer material, it is necessary that the coating device 2 maintains a uniform, very close distance to the substrate surface. For this purpose, the coating device 2 can be moved in the radial direction Z of the substrate 1 by a coating positioning device (not shown). The coating positioning device can include a distance control device with a distance measuring device 3 for this purpose. Depending on the embodiment, the distance measuring device 3 can operate inductively, capacitively, or using a laser as a distance sensor and support the distance control.

[0047] The Fig. 2 bis 4 show the coating device 2 in detail, wherein Fig. 2 represents a main section Fig. 3 a cutaway side view of Fig. 2 and Fig. 4 a section enlargement C of Fig. 2 .

[0048] The coating device 2 has a carrier body 5. A feed nozzle 6 is held in the carrier body 5, to which coating material 7 in the form of a flowable polymer material is fed. The coating material 7 can be fed by continuous, pulsation-free and precise material delivery, e.g. by means of syringe pumps or progressive cavity pumps (dispensers).

[0049] The feed nozzle 6 has a cylindrical material feed 8 that tapers conically towards an outlet opening 9. The outlet opening 9 can have a depth T of, for example, 1 to 3 mm and a width B of 5 to 30 mm, although other dimensions are also possible.

[0050] Furthermore, the feed nozzle 6 can taper towards the outlet opening 9 (material outlet) with a tapering angle. A tapering angle α of, for example, 1° to 7° ensures laminar flow and an increasing fluid velocity of the coating material 7 shortly before the material exits.

[0051] It has been found that at distances between the feed nozzle 6, and in particular the outlet opening 9 of the feed nozzle 6, and the substrate 1 in the range of 1xS to 4xS, where S is the desired layer thickness on the substrate 1, a sufficiently large meniscus or heel is generated at the nozzle outlet, thus ensuring complete wetting across the entire nozzle width. A constant distance therefore also results in a constant layer thickness.

[0052] Viewed downstream of the feed nozzle 6 in the direction of rotation, a smoothing blade 10 is attached to the carrier body 5 to smooth the surface of the polymer material applied to the substrate 1. The smoothing blade 10 can, for example, be a plastic sheet. The plastic surface of the smoothing blade 10 is well suited to achieving the desired surface quality on the smoothed polymer.

[0053] A support blade 11 is arranged across the entire back surface of the smoothing blade 10 on its rear side. The support blade 11 can be made of spring steel. The support blade 11 thus supports the shape of the smoothing blade 10 and ensures a sufficiently high contact force of the smoothing blade 10 with the polymer to be smoothed or spread.

[0054] Fig. 4 shows the smoothing squeegee 10 and the support squeegee 11 in enlarged view.

[0055] A reset blade 12, also made of steel or spring steel, is provided on the front of the smoothing blade 10 and extends over a partial surface of the smoothing blade 10 ( Fig. 4 ). For example, the reset squeegee 12 can extend over half or a third of the area of ​​the smoothing squeegee 10.

[0056] The squeegees 10, 11, 12 are attached together laterally to a squeegee attachment 13 on the carrier body 5.

[0057] On the rear side of the smoothing blade 10 is a pressure piston 14, which is actuated and moved by a pneumatic cylinder 15. The pneumatic cylinder 15 is in turn controlled by compressed air via a pneumatic supply 16. The compressed air in the pneumatic cylinder 15 allows the pressure piston 14 to be pressed downwards against the support blade 11 and thus against the smoothing blade 10, thereby pressing the support blade 11 and the smoothing blade 10 against the return blade 12. The return blade 12 exerts a counterforce against the action of the pressure piston 14, so that a force equilibrium is established depending on the applied air pressure. This allows the contact force of the smoothing blade 10 against the polymer material to be smoothed to be precisely adjusted.

[0058] The contact pressure of the smoothing tool 10 on the applied polymer layer can be adjusted by means of a control system. Excessive contact pressure leads to significant changes in the layer distribution, while insufficient contact pressure prevents the transition gap between the individual spiral coatings from closing. It has been shown that, due to varying viscosities, surface tensions, and other material variables, a range of surface pressures of the smoothing tool 10 on the polymer material must be achievable.

[0059] The width of the smoothing squeegee 10 can be two to three times, or up to five times, or up to ten times the width of a spiral layer to ensure a large contact area and uniform layer homogenization.

[0060] Fig. 5 shows a curing system as a further part of the layer production system for producing a polymer layer on a cylindrical substrate. The in Fig. 5 The components shown can in particular complement those in Fig. 1 The components shown represent the entire layer generation system, such that the components of the Fig. 1 and 5 In summary, this involves first applying a layer of a flowable polymer to substrate 1 and then curing the polymer layer on substrate 1.

[0061] In the hardening system of Fig. 5 It is therefore assumed that the substrate 1 is already covered with a flowable polymer layer, which now needs to be hardened to become dimensionally stable and to be able to serve its actual purpose, e.g. as a gravure printing roller.

[0062] The substrate 1, e.g. the gravure printing roller, is – as in the system of Fig. 1 - continued to be held in the unseen position and rotated in the direction of rotation R.

[0063] A curing device 20 is arranged around the circumference of the substrate 1, which cures the polymer layer using UV light.

[0064] The entire, with components of the Fig. 1 and 5 The formed layer generation system can thus be used in Fig. 1 The illustrated coating device 2 and the curing device 20 comprise this system. This allows a polymer layer to first be applied to the surface of the substrate 1 by the coating device 2 and subsequently cured by the curing device 20 using UV light irradiation. During both process steps, the substrate 1 can be rotated about its main or longitudinal axis while the coating device 2 and the curing device 2 are moved along its surface.

[0065] When UV curing polymers using LEDs, there is a risk that the free radicals of the photoinitiator released by the LED's UVA radiation will be bound by atmospheric oxygen, thus preventing complete surface curing. Therefore, UV irradiation must take place under an inert gas atmosphere. To achieve this, the curing device 20 includes not only a UV light unit 21 but also an inert gas supply unit 22.

[0066] Analogous to the coating device 2 in Fig. 1 The curing device 20 also includes a curing translation device (not shown) with which the curing device 20 can be moved in a translational direction X along the longitudinal axis of the substrate 1. Parallel to this, the substrate rotates in the rotational direction R, resulting in the spiral movement S.

[0067] In this way, the curing device 20 with the UV light device 21 can coat the entire surface of the polymer layer applied to the outer surface of the substrate 1 and thus cure the polymer.

[0068] Analogous to the coating device 2 described above, the curing device 20 also has a curing positioning device (not shown) with a distance control device to adjust the distance of the curing device 20 in the Z direction, i.e., in the direction of the surface of the substrate 1 (radial direction of the substrate 1). A distance measuring device 23 is provided for this purpose. Precise maintenance of the distance is important to achieve a satisfactory curing result.

[0069] Fig. 6 Figure 1 shows the curing device 20 in an enlarged sectional view. The curing device 20 is shown in relation to two substrates 1a, 1b of different sizes to illustrate that the curing device 20 can be used for substrates 1 with significantly different diameters.

[0070] Approximately in the middle of the curing device 20 is the UV light device 21, which in the example shown is arranged vertically and at the underside of which the UV light passes through a light aperture 21a ( Fig. 7 ) can exit, as will be explained later.

[0071] The in Fig. 6 The inert gas supply device 22, located to the right of the UV light device 21, has a gas supply line 24 through which inert gas is supplied from a storage source, e.g., a gas cylinder or a gas tank. Nitrogen is particularly well suited as an inert gas. The flow of the inert gas to the light aperture 21a of the UV light device 21 is regulated by a mass flow controller 25. This will be explained in more detail later.

[0072] Fig. 7 shows the area below the UV light device 21 in a view opposite the Fig. 6 enlarged view. The light aperture 21a, which serves as the exit aperture of the UV light device 21 and through which the UV light exits to irradiate the polymer material, is covered by a quartz glass cover 26.

[0073] A curing gap 27 is formed between the UV light device 21 or the quartz glass cover 26 on the one hand and the surface of the substrate 1 covered with the polymer layer, which is spaced apart from it, on the other hand. Upstream of the quartz glass cover 26 and the curing gap 27, the inert gas supply device 22 has an injection nozzle 28 through which the inert gas can be introduced into the curing gap 27 via a gas inlet 29. The injection nozzle 28 is arranged at the end of an injection hopper 30, to which an injection channel 31 is connected, as shown. Fig. 8 shows.

[0074] Fig. 8 shows a cross-section through the inlet channel 31 of Fig. 7It is clearly visible that the inert gas supplied via a gas line 32 from the mass flow controller 25 is fanned out in the injection hopper 30 and subsequently calmed in the narrow injection channel 31. In the injection channel 31, which also serves as a calming section, a substantially laminar flow of the inert gas can be achieved, allowing the inert gas to be discharged across the entire width of the injection nozzle 28 and thereby cover polymer material on the substrates 1a, 1b before this area of ​​the polymer material, now protected by inert gas, reaches the light aperture 21a on the quartz glass cover 26 in the curing gap 27, where UV irradiation takes place.

[0075] After exiting the injector nozzle 28, the inert gas is expected to partially mix with atmospheric oxygen, as the gas inlet area 29 into the curing gap 27 cannot be completely sealed from the environment. The curing gap 27 will therefore not be filled with pure inert gas, but with a gas mixture containing residual oxygen in addition to inert gas. The sealing measures intended to reduce the ingress of ambient air, as well as the measures for achieving a predetermined proportion of inert gas in the gas mixture, will be explained later.

[0076] Downstream of the quartz glass cover 26 or the curing gap 27, i.e., after UV irradiation, the curing gap 27 ends at a gas outlet 33. A gas discharge device 34 with a downstream measuring chamber 35 is provided there. The gas discharge device 34 can, in particular, be designed as a gap and provide a connecting channel from the end of the curing gap 27 (gas outlet 33) to the measuring chamber 35. A portion of the inert gas is thus discharged via the gas discharge device 34 to the measuring chamber 35, while another portion of the inert gas, not captured by the gas discharge device 34, can escape into the environment.

[0077] To reduce inert gas leakage or losses into the environment, the curing gap 27 is sealed on all four sides by non-contact seals, which are primarily designed as doctor blade seals 36. The doctor blade seals 36 have one or more sheet metal elements arranged in a staggered pattern, creating flow obstructions so that the inert gas cannot escape freely. This, in conjunction with a gas conveying device described later, ensures that only a relatively small portion of the inert gas escapes into the environment, while the remainder is extracted via the measuring chamber.

[0078] A lambda probe (λ probe) 37 is provided in measuring chamber 35 as part of an oxygen measuring device. Using this oxygen measuring device, the (residual) oxygen content in the inert gas downstream of the UV irradiation point at the light aperture 21a can be measured. This allows the inert gas flow rate and the ratio of inert gas to oxygen to be controlled by the mass flow controller 25. This ensures that the residual oxygen content, and consequently the inert gas content, remains within a predetermined range, thus guaranteeing effective protection of the polymer surface from oxidation during UV irradiation. A residual oxygen content of 0.1% to 10%, and in particular 0.5% to 5%, has proven suitable, depending on the curing behavior of the polymer mixture.

[0079] The inert gas flow is generated by a gas conveying device 38, which includes an exhaust fan 39. The exhaust fan 39 creates a negative pressure, which draws the gas mixture from the inert gas supply device 22 through the curing gap 27. The gas flow thus proceeds via the gas supply line 24, the mass flow controller 25, the gas line 32, the injector hopper 30, the injector nozzle 28, the curing gap 27, the gas discharge device 34, the measuring chamber 35, and the exhaust fan 39.

Claims

1. A coating device (2) for coating a cylindrical substrate (1) with a flowable material, comprising: - a supply nozzle (6) for applying the material to the substrate (1); - a smoothing blade (10) which is arranged downstream of the supply nozzle (6) and is designed to smooth a surface of the material applied to the substrate (1); characterized in that the coating device (2) further comprises a force generating device (14, 15) for applying a force to the smoothing blade (10) and thus deflecting the smoothing blade (10) out of a rest position and moving the smoothing blade (10) in the direction of the surface of the material applied to the substrate (1); wherein - the force that can be applied to the smoothing blade (10) by the force generating device (14, 15) can be modified, and wherein - the force generating device (14, 15) includes a force control unit for setting the force that can be applied to the smoothing blade (10) by the force generating device.

2. The coating device (2) according to claim 1, comprising a conveying device for conveying the flowable material from a reserve of material to the supply nozzle (6).

3. The coating device (2) according to claim 1 or 2, wherein the supply nozzle (6) has a cylindrical supply (8) and a material outlet connected to it in the direction of flow.

4. The coating device (2) according to any one of the preceding claims, wherein the material outlet has a slot-shaped cross section which tapers over a certain path.

5. The coating device (2) according to any one of the preceding claims, wherein - the smoothing blade (10) has a front side, which can be brought into contact with the material to be smoothed, and a rear side opposite the front side; - the rear side of the smoothing blade (10) is supported by a support blade (11); and wherein - the force generating device (14, 15) acts on the support blade (11).

6. The coating device (2) according to any one of the preceding claims, wherein the force generating device includes a pressure piston (14) which acts against the rear side of the smoothing blade (10) or against a rear side of the support blade (11).

7. The coating device (2) according to any one of the preceding claims, wherein at least part of the smoothing blade (10) is supported at its front side by a reset blade (12).

8. A coating system for coating a cylindrical substrate (1) with a flowable material, comprising: - a coating device (2) according to any one of the preceding claims; - a substrate receptacle for bearing the cylindrical substrate (1); - a translation device for moving the coating device (2) in a translational direction (X); - a rotation device for moving the substrate (1) borne by the substrate receptacle in a rotational direction (R); and comprising: - a motion control unit which is designed to coordinate the movement carried out by the translation device with the movement of the rotation device such that the coating device (2) performs a spiral movement (S) relative to the substrate.

9. The coating system according to claim 8, wherein a positioning device is provided for positioning the coating device (2) relative to the substrate (1) in the radial direction (Z) of the substrate (1).

10. The coating system according to claim 8 or 9, wherein - the positioning device includes a distance adjusting device; - the distance adjusting device includes a distance measuring device (3) for measuring the distance between the coating device and the substrate; and wherein - the distance adjusting device includes a distance setting device for setting the distance of the coating device to the substrate such that the distance corresponds to a predetermined value.

11. A method for coating a cylindrical substrate (1) with a flowable material, comprising the steps of: - providing a coating device (2), comprising a supply nozzle (6) for applying the material to the substrate (1) and comprising a smoothing blade (10) for smoothing a surface of the material applied to the substrate (1); - moving the substrate (1) in a rotational direction; - moving the coating device (2) along a surface of the substrate (1) parallel to an axis of the substrate (1); during the movement of the substrate (1) and the coating device (2): - applying the material to the substrate (1) through the supply nozzle (6); - smoothing a surface of the material applied to the substrate (1) by the smoothing blade (10); characterized in that the method further comprises the following steps: - during smoothing, applying a force to the smoothing blade (10) and thus deflecting the smoothing blade (10) out of a rest position and moving the smoothing blade (10) in the direction of the surface of the material applied to the substrate (1); - adjusting the force applied to the smoothing blade (10) to a preset value.

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