NOZZLE APPARATUS IN A SPRAY COATING STATION AND A METHOD FOR CHANGING THE MOUTHPIECE

Abstract: The present invention relates to a nozzle device for use in a spry coating station designed for coating a paper or board web, said device comprising a nozzle device body (1), a replaceable nozzle piece (2) and clamping means (3, 4) suited to lock said nozzle piece (2) to said nozzle device body (1). New nozzle pieces (2) are stored in a nozzle replacement apparatus (5, 6) which facilitates rapid replacement if an in-used nozzle piece (2). In the replacement operation, the clamping means (3, 4) serving to lock said nozzle piece (2) are first actuated in order to release said nozzle piece whereafter the worn nozzle piece (2) is removed with the help of transfer means (6) and a new nozzle piece (2) is moved to the nozzle device, and finally said new nozzle piece (2) is locked by said clamping means (3, 4) to said nozzle device body (1).

Description: Nozzle apparatus in a spray coating station and a method for changing the mouthpiece The present invention relates to a nozzle device according to the preamble of claim 1, said device comprising at least a nozzle device body with a nozzle orifice located therein. Such nozzle devices are used in spray coating stations designed for coating a paper or board web, whereby a single coating station may include up to hundreds of nozzles. The invention also concerns a method according to the preamble of claim 12 for replacing a nozzle piece in the nozzle device of a spray coating station. Coating of paper by means of high-pressure coat jets is described in patent applications PCT/FI96/ 00525 and PCT/FI96/00526. Conventionally, the nozzle used in spray coating is made from a wear-resistant material such as a ceram or ceram-clad steel, for instance. The function of the nozzle is to atomize the ejected coat jet into an aerosol and then to direct this aerosol to the surface of the web being coated. Hence, the nozzle must be capable of spraying the coat in a homogeneous and all-covering manner in order to achieve a high-quality and homogeneous layer of the applied coat. The coat formulation contains a lot of clay or other solids and the pressure levels employed at the nozzle are high. For instance, the solids may be in the range of about 40-60 % and the operating pressure in the order of 100-200 bar (10-20 MPa) . Hence, the wear of the nozzle orifices is rapid and their replacement must be performed at short intervals notwithstanding the fact that they are made from the most wear-resistant materials. In the prior art, it has been necessary to replace the entire nozzle which is a clumsy and time-consuming operation. Moreover, the replacement has typically been necessary for a large number of nozzles simultaneously. For reasons of efficient production, the nozzle parts should be replaceable without stopping the ongoing coating and affecting the coat quality in a noticeable manner. This need requires that the nozzles must be replaceable in small batches, preferably individually. Hence, the replacement of nozzles could be staggered between the nozzles of the coating station, thus assuring smooth and uninterrupted coating despite the nozzle replacements. However, this requirement cannot be fulfilled by conventional techniques or equipment. It is an object of the present invention to provide a novel type of nozzle device and method for the replacement of nozzle pieces in modern nozzle assemblies. In this fashion, the above-described drawbacks of conventional techniques can be overcome. The goal of the invention is achieved by making the nozzle orifice, which is particularly subject to wear, in a separate, replaceable part hereafter called a nozzle piece. After the nozzle orifice has reached an excessive degree of wear, the performance of the nozzle can be restored by replacing merely the nozzle piece instead of dismounting the entire nozzle assembly. Easy replacement of the nozzle pieces is attained by mounting them, e.g., on a band or plate. The nozzle device is provided with elements serving to retain the nozzle piece in place and elements sealing the nozzle piece against the nozzle device body, said elements having a design favouring easy dismounting and remounting. Additionally, the nozzle device is provided with dedicated nozzle piece changeover means. More specifically, the nozzle device according to the invention is characterized by what is stated in the characterizing part of claim 1. Furthermore, the method according to the invention for nozzle piece replacement is characterized by what is stated in the characterizing part of claim 12. The invention offers significant benefits. The nozzle device according to the invention facilitates rapid and remote-controlled replacement of nozzle orifice. By virtue of equipping a spray coating station with nozzle devices according to the invention, it will be possible to produce a high-quality coat in a continuous run also when using spray coating techniques. By virtue of utilizing the novel nozzle devices as disclosed in the method according to the invention, the nozzles of a spray coating station can be replaced in a staggered manner, whereby the replacement of one nozzle or a few nozzles at a time does not affect coat quality in coating stations having a plurality of nozzle rows adapted to operate downstream in parallel, whereby the jets of the individual nozzles will partially overlap each other also in the cross-machine direction. In the following, the invention will be examined in greater detail by making reference to exemplifying embodiments and appended drawings in which Figure 1 shows in a partially sectional view a first embodiment of the nozzle device according to the invention for use in the coating of a paper or board web in a spray coating station; Figure 2 shows a side view of the nozzle device of Fig. l; Figure 3 shows a second embodiment of the nozzle device according to the invention for its nozzle piece related parts and in a partially sectional view; and Figure 4 shows schematically a third embodiment of the nozzle device according to the invention. Referring to Figs. 1 and 2, the nozzle device shown therein comprises a device body 1, nozzle pieces 2 mounted on a nozzle piece carrier band 5, a clamp member 3 , a clamp actuator 4 and transfer means 6 of the carrier band 5. The nozzle device is mounted on the spray coating station structures via its body 1, however, with the exception of the band transfer means 6 which may be mounted on their dedicated transfer means support in the coating station. Reference in the description is made to a nozzle device mounted as in Figs. 1 and 2 to directions in such a design. Obviously, the nozzle device can be used mounted at any angle with regard to the horizontal plane, for instance, so that the jet is directed straight upright. The nozzle device body 1 is made hollow with a channel and nozzle 7 therein for passing the coating into the interior of the nozzle device body and therefrom further to the nozzle piece 2. The lower part of the body 1 includes a sealing seat surface 8, which may be bevelled as shown in Figs. 1 and 2. To the nozzle device body 1, e.g. , to its upper part, is connected the clamp actuator 4 which at its one end is also connected to the clamp member 3. The clamp member 3 is shaped so that it has second sealing seat surfaces 9 with a shape compatible of those of the sealing seat surfaces 8 of the nozzle device body 1 and further is aligned in regard to the nozzle device body 1 so that said sealing seat surfaces 8 and 9 will be disposed at a small distance from each other and at least essentially aligned with respect to each other. The clamp actuator 4 is arranged to move the clamp member 3 with regard to the nozzle device body 1 so that the distance between the sealing seat surfaces 8 and 9 is adjustable and that a relatively high compressive force can be exerted thereinbetween. The nozzle device is provided with transfer means 6 and 6* of the nozzle carrier band 5 that via the carrier band 5 are connected to each other. The band transfer means 6 and 6 1 are mounted so that the nozzle carrier band 5 can pass from the first transfer means 6 into the gap between the sealing seat surfaces 8 and 9 of the nozzle device body 1 and the clamp member 3 and therefrom further to the second transfer means 6 1 . Additionally, the edge of the nozzle carrier band 5 may have a particular perforation helping to control the location of the nozzle pieces and the movement of the nozzle carrier band 5 by means of the transfer means 6 and 6 ' . The nozzle pieces 2 comprise a body part with a nozzle orifice 10 made thereto. At least the rim of the nozzle orifice 10 is made from an extremely wear-resistant material such as a ceram. In the embodiment illustrated in Figs. 1 and 2, the nozzle pieces 2 are mounted on the nozzle carrier band 5. The nozzle pieces 2 are mounted at a constant spacing from each other and in identical positions with regard to the crossband direction of the band 5 in order to facilitate accurate positioning of the nozzle pieces 2 by virtue of the transfer means 6 and 6'. The body part of the nozzle pieces 2 is shaped so that, when the nozzle piece is pushed with the help of the clamp member 3 against the seat surface 8 of the nozzle device body 1, the nozzle piece remains compressed between the seat surfaces 8 and 9 of the nozzle device body 1 and the clamp member 3, respectively, whereby it is sealed pressure-tightly against at least one of these seat surfaces. Thus, the nozzle piece will remain tightly sealed seating, e.g., against the seat surface 8 of the nozzle body 1 over the entire rim length of said surface 8 on the nozzle device body 1. The corresponding seat surfaces of the nozzle pieces 2 mating with the seat sur- faces 8 and 9 are denoted in the diagrams as seat surfaces 18 and 19, respectively. Advantageously, the seat surfaces 8, 9, 18 and 19 are made conical. In an embodiment of the method according to the inven- tion, the replacement of the nozzle piece 2 is carried out stepwise in the following sequence: - Coating mix infeed to the nozzle device body 1 is closed by means of a device-specific check valve (not shown) . - Operating the clamp actuator 4, compression at the nozzle piece 2 is released and the clamp member 3 is moved in regard to the nozzle device body 1 so that the seal surfaces 8 and 9 of the clamp member 3 and the nozzle device body 1, respectively, are moved sufficiently far apart from each other, thus facilitating unobstructed transfer of the nozzle piece 2 off from between said seal surfaces 8 and 9. - The nozzle carrier band 5 is moved by the transfer means 6 and 6 ' for a distance equal to that of mutual distance of the nozzle pieces 2 on the carrier band 5, whereby the worn nozzle piece 2 is moved away from between the seat surfaces 8 and 9 and a new nozzle piece 2 is moved into the gap between said seat surfaces. - With the help of the clamp actuator 4 , the clamp member 3 is moved in regard to the nozzle device body 1 in such a direction and with such a force that the distance between the seal surfaces 8 and 9 of the clamp member 3 and the nozzle device body 1, respectively, are moved Φ H N N 0 β εr> β -H J rd rH ft Φ SH Φ XJ 4-J . X! TJ Φ XJ CO 3 ft Φ TJ •H CO rd TJ Φ o rd rH ft to •H J φ A H H -H £ In Fig. 4 is shown an embodiment, in which the nozzle pieces 2 are unconnected and the unused nozzle pieces 2 are stacked in a tubular container 12. Between the tubular container 12 and the nozzle device 17 is adapted a rotatory disc 14 having six holes suited to support the nozzle pieces 2. In this embodiment, the replacement of the nozzle pieces 2 is carried out so that, as soon as the nozzle device 17 has released the worn nozzle piece 2, the disc 14 is rotated 60°, whereby the next nozzle piece 2 will be aligned with the sealing seat surfaces of the nozzle device body. Simultaneously, a new nozzle piece 2 will be lowered into the empty hole introduced by the rotating disc 14 under the exit end of the tubular container 12 and the worn nozzle piece is removed by means of a nozzle piece collection mechanism (not shown) . The locked sealing of the nozzle piece 2 against the nozzle device body 1 and unlocking thereof, respectively, are arranged in a similar manner as described above. Also an embodiment adapted to use the disc 14 as the clamp member 3 (cf. Figs. 1 and 2) is feasible. In addition to those described above, alternative embodiments of the present invention may be contemplated. An embodiment having the nozzle pieces arranged on a carried band is shown in Fig. 1. Differently from this, the nozzle carrier band 5 with the separate nozzle pieces 2 being carried on the band may be replaced by a single rigid carrier body with the nozzle pieces 2 integrated thereon. Also along the length of such a rigid carrier body 5, the nozzle orifices are most advantageously located at a constant spacing from each other. The nozzle piece carrier body 5 may also have its edges provided with perforation or holes helping to control the location of the nozzle orifices and the movement of the nozzle carrier body 5 by means of gears, for instance. An embodiment having the nozzle pieces 2 handled as separate pieces and the new nozzle pieces 2 arranged into a stack is shown in Fig. 3. The transfer of these nozzle pieces 2 in Fig. 3 is shown implemented using a pusher rod 11. Differently from this, the transfer of the nozzle pieces may be arranged to occur by means of, e.g., a band adapted to run under the tubular container 12 and the nozzle device body 1 and, simultaneously, above the mating surface of the clamp member 3. Now referring to the embodiment shown in Fig. 4, an alternative possibility is to manufacture the nozzle pieces 2 as integral elements of the discs 14. In this type of embodiment, the entire disc 14 may be replaced by a new disc 14 after all the nozzle pieces 2 of the first disc 14 are worn out. Thence, the tubular container 12 would be redundant.

Claims: Claims : 1. A nozzle device for use in a spray coating station designed for coating a paper or board web, said device comprising at least a nozzle device body (1) and a nozzle orifice (10) , c h a r a c t e r i z e d by - replaceable nozzle pieces (2) with nozzle orifices (10) , - a nozzle piece replacement apparatus having a plurality of said nozzle pieces (2) adapted therein in a manner facilitating rapid replacement of nozzle devices, and - clamping means (3,4) for locking at least one nozzle piece (2) to said nozzle device body (1) . 2. A nozzle device as defined in claim 1, c h a r a c - t e r i z e d in that said replacement apparatus comprises a nozzle piece carrier band (5) by means of which said nozzle pieces (2) are connected to each other and transfer means (6,6') for moving said nozzle piece carrier band (5) . 3. A nozzle device as defined in claim 1, c h a r a c t e r i z e d in that said replacement apparatus comprises a tubular container (12) into which separate nozzle pieces (2) are stacked and actuator means for transferring the nozzle pieces (2) from the tubular container (12) to said clamping means. 4. A nozzle device as defined in claim 1 or 3 , c h a r a c t e r i z e d in that said nozzle pieces (2) are arranged transferrable to said clamping means by virtue of a disc (14) . 5. A nozzle device as defined in claim 1 or 3 , c h a r a c t e r i z e d in that said nozzle pieces (2) are arranged transferrable to said clamping means by virtue of a band. 6. A nozzle device as defined in claim 1 or 3 , c h a r a c t e r i z e d in that said nozzle pieces (2) are arranged transferrable to said clamping means by virtue of a pusher rod (11) . 7. A nozzle device as defined in claim 1, c h a r a c t e r i z e d in that said nozzle replacement apparatus therein comprises - a nozzle piece disc serving to connect said nozzle pieces (2) to each other, and - means for rotating said nozzle piece disc. 8. A nozzle device as defined in claim 1, c h a r a c t e r i z e d in that said nozzle device body (1) includes a sealing seat surface (8) and said nozzle piece (2) includes another sealing seat surface (18) adapted to mate pressure-tightly with said sealing seat surface (8) of said nozzle device body (1) . 9. A nozzle device as defined in claim 1, c h a r a c t e r i z e d in that said clamping member (3) includes a sealing seat surface (9) and said nozzle piece includes another sealing seat surface (19) adapted to mate pressure-tightly with said sealing seat surface (9) of said clamping member (3) . 10. A nozzle device as defined in claim 8 or 9, c h a r a c t e r i z e d in that at least one of said sealing seat surfaces (8,9,18,19) is shaped essentially into the form of a truncated cone. 11. A nozzle device as defined in claim 1, c h a r a c t e r i z e d in that said nozzle device body (1) includes a surface (8) adapted to mate under a compres- sive force with a surface of said nozzle piece (2) and that said clamping means (3,4) is comprised of a clamp member (3) adapted to compress said nozzle piece (2) pressure-tightly against said nozzle device body (1) , said clamp member having a surface (9) suited to mate with a surface of said nozzle piece (2) , and of an actuator means (4) adapted to produce a force capable of pushing said clamp member (3) toward said nozzle device body (1) on one hand and on the other hand also of separating said clamp member (3) and nozzle device body (1) at their respective surfaces (8,9) tightly mating with those of said nozzle piece (2) in order to release said nozzle piece (2) and to facilitate the replacement of said nozzle piece (2) . 12. A method of replacing a nozzle piece (2) of a nozzle device used in a spray coating station designed for coating a paper or board web, said method comprising the steps of removing said nozzle piece (2) from a nozzle device body (1) and of lockingly replacing the removed nozzle piece (2) with a new nozzle piece, c h a r a c - t e r i z e d in that - compression at the nozzle piece (2) which is being pushed against the nozzle device body (1) by the clamp member (3) is released by virtue of moving apart from each other the surfaces (8,9) of said members that are adapted to compressively mate with those of said nozzle piece (2) , - said nozzle piece (2) is transferred away from the gap between said device body (1) and said clamp member (3) and a second nozzle piece (2) is transferred to said gap by virtue of transfer means (6, 6 • , 11, 14) , and - said second nozzle piece (2) is locked to said nozzle device body (1) by compressing said nozzle piece (2) against said nozzle device body (1) by means of said clamp member (3) .

Inventors: LINNONMAA JUKKA, NISSINEN VILHO, VAEHAEKUOPUS MIKA, LINNONMAA, JUKKA, NISSINEN, VILHO, VAEHAEKUOPUS, MIKA
Applicants: LINNONMAA JUKKA, NISSINEN VILHO, VAEHAEKUOPUS MIKA, VALMET CORP, LINNONMAA, JUKKA, NISSINEN, VILHO, VAEHAEKUOPUS, MIKA, VALMET CORPORATION
Application year: 1998
Main classification: B05B15
IPC codes: B05B1, D21H23