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] Device and method for coating a cylindrical body with a polymer

[0002] The invention relates to a coating device for coating a cylindrical substrate with a flowable material.

[0003] Such a substrate can be, for example, a printing form that can be coated with a polymeric coating material. The term "substrate" or "printing form" is used below as a generic term for gravure printing forms, relief printing forms, or structural forms for embossing, but also for coating rollers or inking rollers.

[0004] WO 2021 / 052641 A1 discloses a printing form and a polymeric coating material therefor. The coating material is a polymeric nanocomposite that can be built up as a single layer for 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 that has, for example, cells or structures for ink absorption or embossing, as also described in WO 2021 / 052641 A1.

[0005] Applying and curing a still-flowing polymer, such as the nanocomposite mentioned above, is complex. Curing is primarily achieved with UV light. To achieve efficient and low-emission (i.e., ozone-free) curing, UV LEDs are increasingly being used. These LEDs rely on surface inerting due to the predominant oxygen inhibition of the surface during radical polymerization.

[0006] The surface quality requirements of the polymer coating are high, as this can directly impact print quality when the cylindrical substrate is a printing cylinder, such as a gravure cylinder. An uneven polymer surface would result in a poor print image.

[0007] For thin metallic wear-resistant coatings, electroplating and vacuum processes such as PVD or CVD have become established. For thicker hard coatings, flame spraying processes such as HVOF are well-known. Thin plastic coatings can be applied using spraying methods, for example, for low-viscosity paints or powders.

[0008] For web coatings, roller, doctor blade, slot die or printing processes can be used.

[0009] Thicker plastic layers are often applied using an extruder. This results in overlaps that can lead to significant variations in layer thickness.

[0010] However, the processes mentioned either cannot achieve the required surface quality and uniformity of the layer thickness or cannot be operated economically.

[0011] Therefore, the object of the invention is to provide a device and a method which enable a format and circumference-independent, but at the same time efficient, precise and seamless coating of various cylindrical substrates with a flowable material.

[0012] The object is achieved according to the invention 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 specified, comprising a feed nozzle for applying the material to a substrate; a smoothing blade arranged downstream of the feed nozzle and designed to smooth a surface of the material applied to the substrate; and a force generating device for applying a force to the smoothing blade and thus deflecting the smoothing blade from a rest position and moving the smoothing blade towards the surface of the material applied to the substrate; wherein the force that can be applied to the smoothing blade by the force generating device is variable; and wherein the force generating device has 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 forms or cylinders, structural forms or cylinders, embossing forms or cylinders and relief printing 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, as described, for example, 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 that has 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 whose size is in a 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 a range between 1 nm and 99 nm, wherein the sub-microscale filler consists of at least one metal oxide and / or a semimetal oxide selected from metal oxide-coated mica,TiO2 or (Sn, Sb)O2, wherein the nanoscale filler comprises metal and / or semi-metal oxides selected from Al2O3, SiO2, iO2, ZrO2, or organometallic particles, wherein the sub-microscale filler is covalently incorporated into a polymer matrix of the starting material, wherein the nanoscale filler is included to increase wear resistance and is covalently incorporated into the polymer matrix of the starting material, and wherein the sub-microscale filler in the starting material can cause 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 gaps that have arisen between adjacent material layers when the material was applied.

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

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

[0020] The force-generating device is designed to deflect and move the smoothing blade from its rest position. The rest position is, in this respect, a starting position. Using the force-generating device and the associated force control, the force applied to the smoothing blade by the force-generating device can be precisely adjusted so that the smoothing blade, in turn, 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, especially 10 to 250 µm as the target layer thickness. Deviations from the target layer thickness should be minimal, e.g., within a range of up to +5% or up to ±3%.

[0022] A conveying device may be provided for conveying the flowable material from a material reservoir to the feed nozzle. Flowable polymer, in particular, requires sophisticated conveying. This can be achieved, for example, by a syringe pump, an eccentric screw pump, or a dispenser. If necessary, a sieve or filter can be interposed at a suitable location.

[0023] The material flow should be pulsation-free, constant, and adjustable with sufficient precision to achieve the desired layer thickness and quality. Depending on the requirements, permissible deviations in material flow can be small, for example, up to ±3% or, even better, up to +1%.

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

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

[0026] The taper angle at the material outlet can be, for example, 1 to 7°. The taper angle thus causes an increasing flow velocity, which is beneficial for the creation 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 e.g. 1 S to 4 S, where S is the desired layer thickness.

[0028] The smoothing blade can have a front side that can be brought into contact with the material to be smoothed, as well as a rear side opposite the front side. The rear side 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 squeegee can consist of a plastic sheet and thus be unstable in terms of its shape. A direct effect of the force-generating device, e.g. a pressure piston, on the unstable smoothing squeegee would disrupt the shape of the smoothing squeegee, meaning that the smoothing squeegee could no longer fulfill its task of evenly smoothing the surface of the material to be smoothed. The supporting squeegee behind it, on the other hand, is dimensionally stable and can be made of, for example, a spring plate or spring steel. It is able to absorb the force from the force-generating device and transfer it evenly across the entire back of the smoothing squeegee, or at least part of it. The supporting squeegee thus ensures that the smoothing squeegee retains its flat shape and cannot be deformed when subjected to force from the force-generating device.

[0030] The force generating device can have a pressure piston that acts against the back of the smoothing squeegee or against the back of the supporting squeegee. As already explained above, it is particularly advantageous if the force generating device acts on the back of the supporting squeegee so that the force of the force generating device can be transmitted evenly and across the surface from the supporting squeegee to the smoothing squeegee. The pressure piston can be actuated pneumatically, for example, which allows for good controllability. At least part of the smoothing squeegee can be supported on its front side by a return squeegee. The return squeegee can consist of a sheet metal or spring plate and extend, for example, only half or only one-third of the front surface of the smoothing squeegee. It should be ensured that the return squeegee does not come into contact with the substrate or the flowable material to be smoothed.Contact should only be made via the smoothing squeegee.

[0031] Due to its spring action, the return squeegee generates a counterforce to the force of the force-generating device, which is applied via the support squeegee. The return squeegee can move the smoothing squeegee, together with the support squeegee, back to their initial or rest position, particularly when the force of the force-generating device is reduced or completely switched off.

[0032] In this way, the force-generating device and the return squeegee interact, so that the position of the smoothing squeegee and the support squeegee 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 squeegee is deflected against the action of the return squeegee. If, however, the force from the force-generating device is reduced, the return squeegee pushes the smoothing squeegee back to its original position.

[0033] Furthermore, a coating system for coating a cylindrical substrate with a flowable material is specified, comprising a coating device of the type described above; a substrate holder for supporting the cylindrical substrate; a translation device for moving the coating device in a translation direction; a rotation device for moving the substrate supported by the substrate holder in a rotation direction; and a movement controller 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.

[0034] In this way, the coating device can be moved relative to the rotating substrate. The translation direction can in particular be the longitudinal direction of the substrate, for example its central axis, while the substrate itself is rotated about its main axis or central axis. The desired relative spiral movement can be achieved through the superimposed movement of the rotation of the substrate and the translation of the coating device. This allows the flowable material to be applied evenly to the surface of the substrate, taking up a spiral path. The path elements should be placed next to one another without gaps so that the remaining small gap can be easily closed by the action of the smoothing doctor blade. Ideally, the spiral movement can be adjusted so precisely that practically no gaps arise between the adjacent layers.

[0035] 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.

[0036] The positioning device may comprise a distance control device, wherein the distance control device may comprise a distance measuring device for measuring the distance between the coating device and the substrate, and wherein the distance control device may comprise a distance setting device for adjusting the distance of the coating device to the substrate such that the distance corresponds to a predetermined value.

[0037] The distance measurement can be performed inductively, capacitively, or laser-assisted, allowing the distance to be adjusted variably and with mechanical precision. The distance measuring device thus represents a distance sensor.

[0038] A method for coating a cylindrical substrate with a flowable material is provided, comprising the steps:

[0039] Providing a coating device having a feed nozzle for applying the material to a substrate and having a smoothing blade for smoothing a surface of the material applied to the substrate. Moving the substrate in a direction of rotation;

[0040] Moving the coating device along a surface of the substrate parallel to an axis of the substrate; while moving the substrate and the coating device: applying the material to the substrate through the feed nozzle;

[0041] Smoothing a surface of the material applied to the substrate by the smoothing squeegee; applying a force to the smoothing squeegee during smoothing; regulating the force applied to the smoothing squeegee to a preset value.

[0042] These and other features and advantages of the invention are explained in more detail below using examples with the aid of the accompanying figures. They show:

[0043] Fig. 1 shows a coating system for applying a polymer layer to a cylindrical substrate;

[0044] Fig. 2 shows a coating device as part of the coating system of Fig. 1, for coating a cylindrical substrate with a polymer;

[0045] Fig. 3 is a sectional side view of the device of Fig. 2;

[0046] Fig. 4 is an enlarged detail “C” from Fig. 2;

[0047] Fig. 5 shows a curing system for curing a polymer layer on a cylindrical substrate;

[0048] Fig. 6 shows a curing device as part of the curing system of Fig. 5;

[0049] Fig. 7 is an enlarged detail of the hardening device of Fig. 6; and

[0050] Fig. 8 is a partial sectional side view of the hardening device of Fig. 6.

[0051] Fig. 1 shows a perspective view of a coating system as part of a layer production system for producing a polymer layer on a cylindrical substrate 1.

[0052] In the example shown, substrate 1 is a printing form, namely a gravure cylinder for use in gravure printing. The gravure cylinder is to be coated with a flowable polymer. This can be, for example, the nanocomposite known from WO 2021 / 052641 A1. The polymer coating of the gravure cylinder is suitable for laser treatment, in particular with a near-field infrared (NIR) laser, to create small depressions, so-called cells, which can absorb 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), e.g. 10 μm to 500 μm, in particular 10 μm to 250 μm.

[0053] The substrate 1 or the gravure cylinder is held rotatably in a direction of rotation R in a holder not shown.

[0054] A coating device 2 is provided on the outside of the substrate 1, which can be moved in a translation direction X along the outside of the substrate 1. The coating device 2 serves to apply the still-flowable polymer material to the cylindrical outer surface of the substrate 1.

[0055] When the translational movement of the coating device 2 in the translation direction X and the rotation of the substrate 1 in the rotation direction R are superimposed, the coating device 2 performs a spiral movement relative to the outside of the substrate 1, as shown in Fig. 1 by an arrow S. As a result, flowable polymer material with a width of, for example, a few millimeters, for example 5 mm to 30 mm, can be applied to the outside of the substrate 1 using the coating device 2. Due to the spiral relative movement, one polymer layer can be applied next to the other in a spiral or helical manner, so that ultimately the entire outer surface of the substrate or part of it is uniformly covered with a polymer layer.With the help of smoothing elements, which will be explained later, a gap that arises between the adjacent polymer layers can be closed uniformly, so that a uniform, homogeneous polymer layer is created.

[0056] To apply the polymer material, it is necessary for the coating device 2 to maintain a uniform, very close distance from 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). For this purpose, the coating positioning device can have a distance control device with a distance measuring device 3. Depending on the embodiment, the distance measuring device 3 can operate inductively, capacitively, or laser-assisted as a distance sensor and support the distance control. Figs. 2 to 4 show the coating device 2 in detail, with Fig. 2 representing a main section, Fig. 3 a sectional side view of Fig. 2, and Fig. 4 an enlarged detail C of Fig. 2.

[0057] The coating device 2 comprises 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 a continuous, pulsation-free, and precise material feed, e.g., using syringe pumps or eccentric screw pumps (dispensers).

[0058] The feed nozzle 6 has a cylindrical material feed 8 that tapers conically toward 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.

[0059] In addition, the feed nozzle 6 can taper toward the outlet opening 9 (material outlet) at a taper angle. A taper angle a of, for example, 1° to 7° ensures laminar flow and an increasing fluid velocity of the coating material 7 shortly before the material exits.

[0060] It has been found that at distances between the feed nozzle 6, or 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 created at the nozzle outlet, ensuring complete wetting across the entire nozzle width. A constant distance thus also results in a constant layer thickness.

[0061] Downstream of the feed nozzle 6, as seen 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 be, for example, a plastic sheet. The plastic surface of the smoothing blade 10 is well suited to achieving the desired surface quality on the smoothed polymer.

[0062] A support squeegee 11 is arranged on the back of the smoothing squeegee 10, extending over the entire back surface of the smoothing squeegee 10. The support squeegee 11 can be made of spring steel. The support squeegee 11 thus supports the shape of the smoothing squeegee 10 and ensures a sufficiently large pressure force of the smoothing squeegee 10 on the polymer to be smoothed or spread.

[0063] Fig. 4 shows the smoothing squeegee 10 and the supporting squeegee 11 in an enlarged view.

[0064] At the front of the smoothing blade 10, a return blade 12, also made of steel or spring steel, is provided, which extends over a partial surface of the smoothing blade 10 (Fig. 4). For example, the return blade 12 can extend over half or one-third of the surface of the smoothing blade 10.

[0065] The doctor blades 10, 11, 12 are jointly attached laterally to a doctor blade attachment 13 on the carrier body 5.

[0066] Located at the rear of the smoothing squeegee 10 is a pressure piston 14, which is actuated and moved by a pneumatic cylinder 15, which in turn is controlled by compressed air via a pneumatic supply 16. The compressed air in the pneumatic cylinder 15 can press the pressure piston 14 downward against the support squeegee 11 and thus the smoothing squeegee 10, thus pressing the support squeegee 11 with the smoothing squeegee 10 against the return squeegee 12. The return squeegee 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 squeegee 10 against the polymer material to be smoothed to be precisely adjusted.

[0067] The contact pressure of the smoothing blade 10 on the applied polymer layer can be adjusted using a control system. Excessive contact pressure leads to a significant change 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 different viscosities, surface tensions, and other material variables, a range of surface pressures of the smoothing blade 10 on the polymer material must be feasible.

[0068] The width of the smoothing blade 10 can be two to three times, up to five times, or up to ten times the width of a spiral layer in order to ensure a large contact surface and uniform layer homogenization.

[0069] 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 components shown in Fig. 5 can, in particular, represent a supplement to the components shown in Fig. 1, so that the entire layer production system combines the components of Figs. 1 and 5, i.e., first applying a layer of a flowable polymer to the substrate 1 and then curing the polymer layer on the substrate 1.

[0070] Accordingly, in the curing system of Fig. 5, it is assumed that the substrate 1 is already covered with a flowable polymer layer, which now has to be cured in order to become dimensionally stable and to be able to serve its actual purpose, e.g. as a gravure printing roller.

[0071] The substrate 1, e.g. the gravure roller, is - as in the system of Fig. 1 - still held in the holder not shown and rotated in the direction of rotation R.

[0072] A curing device 20 is arranged on the circumference of the substrate 1, which cures the polymer layer using UV light.

[0073] The entire layer generation system formed with components from Figs. 1 and 5 can thus comprise the coating device 2 shown in Fig. 1 and the curing device 20. This allows a polymer layer to be first applied to the outer surface of the substrate 1 by the coating device 2 and subsequently cured by the curing device 20 using UV light irradiation. In 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 the outer surface.

[0074] When UV curing polymers using LEDs, there is a risk that the free radicals of the photoinitiator released by the UVA radiation from the LED will be bound by atmospheric oxygen, thus preventing complete surface curing. Therefore, UV irradiation must be carried out in an inert gas atmosphere. To achieve this, the curing device 20 comprises not only a UV light device 21 but also an inert gas supply device 22.

[0075] Analogous to the coating device 2 in Fig. 1, the curing device 20 also has a curing translation device (not shown) with which the curing device 20 can be moved in a translation direction X along the longitudinal axis of the substrate 1. Parallel to this, the substrate rotates in the rotation direction R, resulting in the spiral movement S. In this way, the curing device 20 can cover the entire surface of the polymer layer applied to the outer surface of the substrate 1 with the UV light device 21 and thus cure the polymer.

[0076] Similar to the coating device 2 described above, the curing device 20 also has a curing positioning device (not shown) with a distance control device for adjusting 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 for achieving a satisfactory curing result.

[0077] Fig. 6 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.

[0078] Approximately in the middle, the curing device 20 has the UV light device 21, which is arranged vertically in the example shown and at the bottom of which the UV light can emerge via a light opening 21a (Fig. 7), as will be explained later.

[0079] The inert gas supply device 22, located to the right of the UV light device 21 in Fig. 6, has a gas supply line 24 through which inert gas is supplied from a storage device, e.g., a gas cylinder or a gas tank. Nitrogen is particularly suitable as an inert gas. The flow of the inert gas to the light opening 21a of the UV light device 21 is controlled by a mass flow controller 25. This will be explained in more detail later.

[0080] Fig. 7 shows the area below the UV light device 21 in an enlarged view compared to Fig. 6. The light opening 21a, which serves as the exit opening 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.

[0081] 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, spaced therefrom, on the other hand. Upstream of the quartz glass cover 26 and the curing gap 27, the inert gas supply device 22 has a dispensing nozzle 28, through which the inert gas can be introduced into the curing gap 27 via a gas inlet 29. The dispensing nozzle 28 is arranged at the end of a dispensing funnel 30, which is followed by a dispensing channel 31, as shown in Fig. 8.

[0082] Fig. 8 shows a section through the induction channel 31 of Fig. 7. It can be clearly seen that the inert gas supplied via a gas line 32 from the mass flow controller 25 is fanned out in the induction funnel 30 and subsequently calmed in the narrow induction channel 31. In the induction channel 31, which also serves as a calming section, a substantially laminar flow of the inert gas can be achieved, so that the inert gas can be discharged over the entire width of the induction nozzle 28 and can cover polymer material on the substrates 1a, 1b before this region of the polymer material, then protected by inert gas, reaches the light opening 21a on the quartz glass cover 26 in the curing gap 27, where the UV irradiation takes place.

[0083] After leaving the injection nozzle 28, it is to be expected that the inert gas will partially mix with atmospheric oxygen, since the area of ​​the gas inlet 29 into the curing gap 27 cannot be completely sealed from the environment. Thus, the curing gap 27 is not flowed through by pure inert gas, but rather by a gas mixture that, in addition to inert gas, will also contain residual oxygen components. The sealing measures provided to reduce the ingress of ambient air, as well as the measures to achieve a specified proportion of inert gas in the gas mixture, will be explained later.

[0084] 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 create 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 or to the measuring chamber 35, while another portion of the inert gas, not captured by the gas discharge device 34, can escape to the environment.

[0085] To reduce inert gas leaks or losses into the environment, the curing gap 27 is sealed on all sides, i.e., on all four sides, by non-contact seals, which are designed, in particular, as doctor blade seals 36. The doctor blade seals 36 comprise one or more sheet metal elements arranged in staggered rows and representing flow obstructions, so that the inert gas cannot flow out unhindered. This, and in conjunction with a gas conveying device (explained later), ensures that only a relatively small portion of the inert gas escapes into the environment, while the remaining portion is extracted via the measuring chamber.

[0086] A lambda probe (Z-probe) 37 is provided in the measuring chamber 35 as part of an oxygen measuring device. With the aid of the oxygen measuring device, the (residual) oxygen content in the inert gas downstream of the location of the UV irradiation at the light opening 21a can be measured. This allows the inflow of inert gas or the ratio of inert gas to oxygen to be regulated using the mass flow controller 25 in order to, on the one hand, keep the residual oxygen content within a predetermined range and, on the other hand, also keep the inert gas content within a predetermined range in order to ensure effective protection of the polymer surface from oxidation during UV irradiation. A residual oxygen content of 0.1% to 10%, in particular of 0.5% to 5%, depending on the curing behavior of the polymer mixture, has proven suitable.

[0087] The inert gas flow is achieved by means of a gas conveying device 38, which has an exhaust fan 39. The exhaust fan 39 creates a negative pressure, with which the gas mixture is extracted from the inert gas supply device 22 via the curing gap 27. The gas flow thus occurs via the gas supply line 24, the mass flow regulator 25, the gas line 32, the induction funnel 30, the induction nozzle 28, the curing gap 27, the gas discharge device 34, the measuring chamber 35, and the exhaust fan 39.

Claims

Patent claims 1. A coating device (2) for coating a cylindrical substrate (1) with a flowable material, comprising a feed nozzle (6) for applying the material to the substrate (1); a smoothing squeegee (10) arranged downstream of the feed nozzle (6) and designed to smooth a surface of the material applied to the substrate (1); and a force generating device (14, 15) for applying a force to the smoothing squeegee (10) and thus deflecting the smoothing squeegee (10) from a rest position and moving the smoothing squeegee (10) towards the surface of the material applied to the substrate (1); wherein the force that can be applied to the smoothing squeegee (10) by the force generating device (14, 15) is variable; and wherein the force generating device (14, 15) has a force control for adjusting the force that can be applied to the smoothing blade (10) by the force generating device.

2. Coating device (2) according to claim 1, with a conveying device for conveying the flowable material from a material supply to the feed nozzle (6).

3. Coating device (2) according to claim 1 or 2, wherein the feed nozzle (6) has a cylindrical feed (8) and a material outlet adjoining it in the flow direction.

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

5. Coating device (2) according to one of the preceding claims, wherein the smoothing squeegee (10) has a front side that 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 squeegee (10) is supported by a supporting squeegee (11); and wherein the force generating device (14, 15) acts on the supporting squeegee (11). . Coating device (2) according to one of the preceding claims, wherein the force-generating device comprises a pressure piston (14) acting against the rear side of the smoothing squeegee (10) or against a rear side of the supporting squeegee (11). . Coating device (2) according to one of the preceding claims, wherein at least a portion of the smoothing squeegee (10) is supported at its front side by a return squeegee (12). .Coating system for coating a cylindrical substrate (1) with a flowable material, comprising a coating device (2) according to one of the preceding claims; a substrate holder for supporting the cylindrical substrate (1); a translation device for moving the coating device (2) in a translation direction (X); a rotation device for moving the substrate (1) supported by the substrate holder in a rotation direction (R); and a movement controller designed to coordinate the movement by the translation device with the movement of the rotation device such that the coating device (2) executes a spiral movement (S) relative to the substrate. 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).Coating system according to claim 8 or 9, wherein the positioning device comprises a distance control device; the distance control device comprises a distance measuring device (3) for measuring the distance between the coating device and the substrate; and wherein the distance control device comprises a distance setting device for adjusting the distance of the coating device from the substrate such that the distance corresponds to a predetermined value.

1. A method for coating a cylindrical substrate (1) with a flowable material, comprising the steps:. Providing a coating device (2) with a feed nozzle (6) for applying the material to the substrate (1) and with a smoothing blade (10) for smoothing a surface of the material applied to the substrate (1); - moving the substrate (1) in a direction of rotation; Moving the coating device (2) along a surface of the substrate (1) parallel to an axis of the substrate (1); while moving the substrate (1) and the coating device (2): applying the material to the substrate (1) through the feed nozzle (6); - smoothing a surface of the material applied to the substrate (1) by the smoothing blade (10); during smoothing, applying a force to the smoothing blade (10); Regulating the force applied to the smoothing blade (10) to a preset value.

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