Fluid sprinkling – spraying – and diffusing – Processes
Reexamination Certificate
2000-03-06
2001-07-17
Scherbel, David A. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Processes
C239S390000, C239S391000, C239S600000, C029S402080
Reexamination Certificate
active
06260767
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a nozzle 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 for replacing a nozzle piece in the nozzle device of a spray coating station.
BACKGROUND OF THE INVENTION
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.
SUMMARY OF THE INVENTION
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, the 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 comprises a nozzle device body, replaceable nozzle pieces having nozzle orifices, a clamping means for locking the nozzle pieces to the nozzle device body, and a nozzle piece replacement apparatus having a plurality of nozzle pieces, the apparatus being suitable for facilitating rapid replacement of nozzle pieces. The nozzle device body has a surface which is adapted to mate under a compressive force with a surface of the nozzle piece. The clamping means has a clamp member adapted to compress the nozzle piece tightly against the nozzle device body. The clamp member has a surface configured to mate with a surface of the nozzle piece. The clamping means also has an actuator means adapted to produce a force capable of pushing the clamp member toward the nozzle device body and also of separating the clamp member and the nozzle device body so that the nozzle piece may be replaced.
Furthermore, the method according to the invention for nozzle piece replacement is characterized by what comprises removing the nozzle piece from the nozzle device body by releasing the compressive force exerted by the clamp member so that the mating surfaces of the clamp member and the nozzle piece move apart, the released nozzle piece is transferred away from the nozzle device body, a replacement nozzle piece is moved into position, and the replacement nozzle piece is locked to the nozzle device body by compressing the nozzle piece against the nozzle device body with the clamp member.
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.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are intended solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.
REFERENCES:
patent: WO97/13035 (1997-04-01), None
Abstract of JP 5154428 Toshiba KK Jun. 22, 1993.
Abstract of JP 6112638 Sanyo Electric Co. Ltd. Apr. 22, 1994.
Abstract of JP 7185426 Mattsushita Denki Sangyo KK Jul. 25, 1995.
Linnonmaa Jukka
Nissinen Vilho
Vähäkuopus Mika
Cohen & Pontani, Lieberman & Pavane
Ganey Steven J.
Scherbel David A.
Valmet Corporation
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