A moistening system for paper sheets

Abstract

The present invention relates to a moistening system for paper sheets, specifically applied to machines for making corrugated cardboard. In particular, the invention relates to a moistening system (100) for paper sheets or strips in a cardboard making machine, comprising a frame (8) that supports a plurality of nozzles (9) for spraying water, characterized in that it comprises a microperforated plate (12) comprising holes (19) for distributing atomized water and micro-holes (20) for dispensing a ventilation air flow.

Description

[0001] The present invention relates to a moistening system for paper sheets, specifically applied to machines for making corrugated cardboard.

[0002] Machines for making multi-layer cardboard, such as corrugated cardboard, conventionally comprise systems for unwinding paper from special reels, systems for corrugating the intermediate layer(s) and systems for coupling and gluing the various layers.

[0003] A conventional structure of corrugated cardboard provides two layers of corrugated paper separated by a flat sheet and closed on the two outer sides by flat sheets of paper called covers.

[0004] In order to promote the coupling and gluing of the various corrugated and flat layers of paper to one another by a starch-based glue, it has proven to be suitable to moisten the sheets of paper prior to the coupling. Various moistening systems are known, inter alia rollers over which the water is dosed and over which the paper is passed, or specific moistening bars. Indeed, specific bars were prepared, equipped with nozzles that vaporize water over paper sheets which are unwound from reels. The water is dosed so as to obtain the moistening of the paper which, as mentioned, is advantageous in the gluing process.

[0005] Such bars may be arranged above, below, or in certain cases, also beside the paper strip unwound from the reel, but when the bars in particular are arranged above the paper - which is the most convenient and widespread circumstance-condensation is created on the lower surface thereof which tends to drip onto the underlying paper, thus inducing actual wetting in the contact point. Such a wetting is detrimental for the quality results of the corrugated cardboard production method. Indeed thereby, instead of being homogeneously moistened, the paper has uneven areas in which it may be soaked in water.

[0006] The problem at the basis of the present invention therefore is providing a moistening system for paper in cardboard making machines which overcomes the drawbacks of the prior art.

[0007] Such a problem is overcome by a system as defined in the appended claims, the definitions of which form an integral part of the present description.

[0008] The subject matter in the preamble of claim 1 is known from US 2005 / 082398 A1.

[0009] The object of the present invention is a moistening system for paper sheets or strips in a cardboard making machine, comprising a frame which supports a plurality of nozzles for spraying water, comprising a micro-perforated plate comprising holes for distributing atomized water and micro-holes for dispensing a ventilation air flow, wherein the system comprises a plate which supports a plurality of ventilation nozzles, wherein the plate is sandwiched between the frame and the micro-perforated plate.

[0010] Another object of the invention is a corrugated cardboard making machine comprising one or more moistening systems as defined above.

[0011] Further features and advantages of the present invention will become more apparent from the description of certain embodiments thereof, given hereinbelow only by way of a non-limiting, indicative example, with reference to the following figures: Figure 1 shows an overall diagrammatic side view of a corrugated cardboard making machine; Figure 2 shows a side view of a detail of the machine in Figure 1; Figure 3a shows a perspective view of a paper moistening system according to the present invention; Figure 3b shows an exploded perspective view of the moistening system in Figure 3a; Figure 4 shows a view of the moistening system in Figure 3a according to the cross section III-III.

[0012] With reference to the drawings, the corrugated cardboard making machine, indicated as a whole by numeral 1, comprises, in the order from left to right, that is according to the processing line indicated by the horizontal arrow I, the following working units: i) a first paper unwinding unit 2a comprising a paper reel 3; ii) a first corrugation unit 4a for the paper unwound from unit 2a; iii) a second paper unwinding unit 2b comprising a paper reel 3 configured to couple a flat sheet of paper to the corrugated sheet of paper from the corrugation unit 4a; iv) a third paper unwinding unit 2c comprising a paper reel 3; v) a second corrugation unit 4b for the paper unwound from the unit 2c; vi) a fourth paper unwinding unit 2d comprising a paper reel 3 configured to couple a flat sheet of paper to the corrugated sheet of paper from the corrugation unit 4b; vii) a fifth paper unwinding unit 2e comprising a paper reel 3 for a cover layer; viii) an alignment unit 5 for the sheets of paper A, B, C from the second, fourth and fifth paper unwinding units 2b, 2d, 2e; ix) a set of three preheating rollers 6a, 6b, 6c for preheating the sheets of paper A, B, C from the alignment unit 5; x) a hot gluing unit 7 for gluing the sheets A, B, C with paper starch glue by hot pressing to form a sheet of corrugated cardboard.

[0013] The machine briefly illustrated above is of the conventional type and therefore will not be described in greater detail.

[0014] The moistening system 100 according to the invention, shown in Figures 3a, 3b and 4, may be placed at one or more of the down arrows shown in Figure 1 according to the requirements of the system, the will of the user and the moistening level required in the various production steps. For example, the moistening system 100 may be placed: between the first paper unwinding unit 2a and the first corrugation unit 4a, and / or between the third paper unwinding unit 2c and the second corrugation unit 4b, and / or at the alignment unit 5 for the sheets of paper, and / or immediately downstream of the set of three preheating rollers 6a, 6b, 6c, and / or immediately upstream of the hot gluing unit 7.

[0015] The moistening system 100 comprises a frame 8 that supports a plurality of spray nozzles 9 configured to dispense a mixture of water and air, a plate 10 that supports a plurality of ventilation nozzles 11 configured to dispense air, and a micro-perforated plate 12 comprising holes 19 for distributing atomized water over a paper sheet or strip (which is, for example positioned at a predefined distance below system 100) and micro-holes 20 for dispensing a ventilation air flow, in which plate 10 is sandwiched between frame 8 and the micro-perforated plate 12.

[0016] Frame 8 comprises a nozzle-holder bar 13 and two lateral closing sides 14a, 14b.

[0017] A first and a second series of spray nozzles 9 are arranged on opposite sides of the nozzle-holder bar 13. In the preferred embodiment of the drawings, the nozzles 9 of the two series are placed in staggered positions so as to optimize the distribution of the atomized water over the surface of the paper sheet or strip.

[0018] Plate 10 comprises a plurality of openings 10a for housing the spray nozzles 9 and a plurality of holes 10b for housing the ventilation nozzles 11.

[0019] Plate 10 further comprises peripheral sides 22 on which the micro-perforated plate 12 is fastened so that a chamber 23 for the circulation of air is formed between the surface of plate 10 and the micro-perforated plate 12.

[0020] As shown in Figures 3b and 4, the ventilation nozzles 11 are arranged in two substantially parallel series between frame 8 and plate 10 and are inserted into the holes 10b of plate 10 so as to face chamber 23.

[0021] The ventilation nozzles 11 in a series are connected to one another by a pipe 18 in which ventilation air flows.

[0022] As shown in Figure 4, the spray nozzles 9 comprise a hollow body 15 which has a first transverse hole 16 and a second transverse hole 17, said transverse holes 16, 17 facing each other, wherein the first transverse hole 16 is connected to an atomized water delivery pipe (not shown) and the second transverse hole 17 is connected to an atomizing air delivery pipe (not shown). The nozzles 9 end with a tip 21 for dispensing the atomized water which is introduced into the openings 10a of plate 10 and into the holes 19 of the micro-perforated plate 12 so as to emerge outside and thus spray water towards the paper sheet or strip.

[0023] On one of the lateral closing sides 14a, 14b of frame 8, there are arranged: openings 24a, 24b which connect the water pipes connected to the respective transverse holes 16 of the spray nozzles 9 inside frame 8 to an external source of pressurized water, preferably pressurized hot water; an opening 25 which connects the air pipes connected to the respective transverse holes 17 of the spray nozzles 9 to an external source of pressurized air; ventilation air delivery openings 26 which connect the pipes 18 connected to the ventilation nozzles 11 to a source of ventilation air.

[0024] In certain embodiments, the moistening system 100 according to the invention comprises a command and control unit configured to control the adjustment of the individual spray nozzles 9 by dosing the flow rate both of the water to be atomized and the atomizing air. Thereby, a better adjustment of the amount of water to be atomized may be obtained with respect to the known solutions which provide exclusively adjusting the flow rate of water. By virtue of the adjustment of the individual nozzles 9, various portions of the paper sheet or strip may be moistened in a different manner, for example the outer flaps more than the inner portion.

[0025] Therefore, the moistening system 100 of the invention allows avoiding the condensation on the outer face of the plate that comprises the dispensing openings of the atomized water. Indeed, the circulation of ventilation air in chamber 23 and through the micro-holes 20 of the micro-perforated plate 12 forms a barrier which prevents the rising of the water aerosol, thus preventing the condensation of water droplets and the successive dripping onto the paper sheet or strip.

[0026] It is apparent that only certain particular embodiments of the present invention have been described, to which those skilled in the art can make those modifications required for adapting it to particular applications, without moreover departing from the scope of protection of the present invention.

Claims

1. A moistening system (100) for paper sheets or strips in a cardboard making machine, comprising a frame (8) which supports a plurality of nozzles (9) for spraying water, comprising a micro-perforated plate (12) comprising holes (19) for distributing atomized water and micro-holes (20) for dispensing a ventilation air flow, characterized in that the system (1) comprises a plate (10) which supports a plurality of ventilation nozzles (11), wherein the plate (10) is sandwiched between the frame (8) and the micro-perforated plate (12).

2. The system (100) according to claim 1, wherein the frame (8) comprises a nozzle-holder bar (13) and two lateral closing sides (14a, 14b), a first and a second series of said spray nozzles (9) being arranged on opposite sides of the nozzle-holder bar (13), wherein the nozzles (9) of the two series are preferably placed in staggered positions.

3. The system (100) according to claim 1 or 2, wherein the plate (10) comprises a plurality of openings (10a) for housing the spray nozzles (9) and a plurality of holes (10b) for housing the ventilation nozzles (11).

4. The system (100) according to any one of claims 1 to 3, wherein the plate (10) comprises peripheral sides (22) on which the micro-perforated plate (12) is fastened so that a chamber (23) for the circulation of air is formed between the surface of the plate (10) and the micro-perforated plate (12) .

5. The system (100) according to claim 4, wherein the ventilation nozzles (11) are arranged in two substantially parallel series between the frame (8) and the plate (10) and are inserted into the holes (10b) of the plate (10) so as to face the chamber (23), and wherein the ventilation nozzles (11) in each series are connected to one another by a pipe (18) in which ventilation air flows.

6. The system (100) according to any one of claims 1 to 5, wherein the spray nozzles (9) comprise a hollow body (15) which has a first transverse hole (16) and a second transverse hole (17), said transverse holes (16, 17) facing each other, wherein the first transverse hole (16) is connected to a water-to-be-atomized delivery pipe and the second transverse hole (17) is connected to an atomizing air delivery pipe, and wherein the nozzles (9) end with a tip (21) for dispensing the atomized water which is introduced into the openings (10a) of the plate (10) and into the holes (19) of the micro-perforated plate (12) so as to emerge outside and thus spray water towards the paper sheet or strip.

7. The system (100) according to claim 6, wherein on one of the lateral closing sides (14a, 14b) of the frame (8), there are arranged: - openings (24a, 24b) which connect the water pipes connected to the respective transverse holes (16) of the spray nozzles (9) inside the frame (8) to an external source of pressurized water, preferably pressurized hot water; - an opening (25) which connects the air pipes connected to the respective transverse holes (17) of the spray nozzles (9) to an external source of pressurized air; - ventilation air delivery openings (26) which connect the pipes (18) connected to the ventilation nozzles 11 to a source of ventilation air.

8. The moistening system (100) according to any one of claims 1 to 7, comprising a command and control unit configured to control the adjustment of the individual spray nozzles (9) by dosing the flow rate both of the water to be atomized and the atomizing air.

9. A corrugated cardboard making machine (1), comprising the following working units in sequence: i) a first paper unwinding unit (2a) comprising a paper reel (3); ii) a first corrugation unit (4a) for the paper unwound from the unit (2a); iii) a second paper unwinding unit (2b) comprising a paper reel (3) configured to couple a flat sheet of paper to the corrugated sheet of paper from the corrugation unit (4a); iv) a third paper unwinding unit (2c) comprising a paper reel (3); v) a second corrugation unit (4b) for the paper unwound from the unit (2c); vi) a fourth paper unwinding unit (2d) comprising a paper reel (3) configured to couple a flat sheet of paper to the corrugated sheet of paper from the corrugation unit (4b); vii) a fifth paper unwinding unit (2e) comprising a paper reel (3) for a cover layer; viii) an alignment unit (5) for the sheets of paper (A, B, C) from the second, fourth and fifth paper unwinding units (2b, 2d, 2e); ix) a set of three preheating rollers (6a, 6b, 6c) for preheating the sheets of paper (A, B, C) from the alignment unit (5); x) a hot gluing unit (7) for gluing the sheets (A, B, C) with paper starch glue by hot pressing to form a sheet of corrugated cardboard, characterized in that it comprises one or more paper moistening systems (100) according to any one of claims 1 to 8.

10. The machine (1) according to claim 9, wherein the moistening system (100) is placed: - between the first paper unwinding unit (2a) and the first corrugation unit (4a), and / or - between the third paper unwinding unit (2c) and the second corrugation unit (4b), and / or - at the alignment unit (5) for the sheets of paper, and / or - immediately downstream of the set of three preheating rollers (6a, 6b, 6c), and / or - immediately upstream of the hot gluing unit (7) .

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