GAS IMPINGEMENT DEVICE, RECORDING SUBSTRATE TREATMENT APPARATUS AND PRINTING SYSTEM COMPRISING SUCH GAS IMPINGEMENT DEVICE

Abstract

A gas impingement device includes a first surface including a pattern of a plurality of gas outlets, the pattern including a number of substantially parallel rows of gas outlets, the rows arranged in a direction, which direction is at a skew angle α with a front edge of the first surface of the gas impingement device. A recording substrate treatment apparatus and a printing system including such a gas impingement device and a method of drying a recording substrate by using the gas impingement device are also disclosed.

Claims

1. A gas impingement device comprising: a hollow body; a gas inlet fluidly connected to the hollow body; and a first surface comprising a first axis and a second axis, wherein the second axis is substantially perpendicular to the first axis, wherein the first surface is provided with a plurality of gas outlets, each of the plurality of gas outlets having a diameter d.sub.outlet, the plurality of gas outlets being fluidly connected to the body and being arranged in a pattern, wherein the pattern comprises a number of substantially parallel rows extending in a second direction, each row comprising a fraction of the plurality of gas outlets such that the plurality of gas outlets is substantially equally distributed across the first surface and such that the fraction of the plurality of gas outlets on each row is arranged at an equidistant stitch, d.sub.stitch, wherein the second direction is arranged at an angle α with the first axis of the first surface, wherein α≧arctan(d.sub.outlet/d.sub.stitch), and wherein in operation a sheet of a printing substrate is transported in a first direction such that an edge of the printing substrate is substantially parallel to the first axis of the first surface.

2. The gas impingement device according to claim 1, wherein the pattern of the plurality of gas outlets comprises a first row comprising a first fraction of the plurality of gas outlets and a second row comprising a second fraction of the plurality of gas outlets, the first row extending in the second direction and the second row being substantially parallel to the first row, wherein the first row and the second row are arranged at a distance d.sub.row, and wherein the second fraction of gas outlets comprised in the second row is shifted in the second direction by x*d.sub.stitch, relative to the first fraction of gas outlets comprised in the first row, wherein 0≦x<1 and α≦arctan(d.sub.row/((1+x)*d.sub.stitch)).

3. The gas impingement device according to claim 2, wherein dr.sub.ow=y*d.sub.stitch, wherein 0≦y1 and d.sub.row>d.sub.outlet.

4. The gas impingement device according to claim 4, wherein x=0.5 and y=0.5*√3.

5. The gas impingement device according to claim 4, wherein x=0.5 and y=0.5.

6. The gas impingement device according to claim 4, wherein x=0 and y=1.

7. The gas impingement device according to claim 5, wherein d.sub.outlet is in a range of between 0.5 mm and 6 mm.

8. The gas impingement device according to claim 5, wherein d.sub.stitch is in a range of between 2 mm and 50 mm.

9. The gas impingement device according to claim 1, wherein the surface provided with a plurality of gas outlets comprises a plate comprising a plurality of orifices.

10. A recording substrate treatment apparatus, comprising: the gas impingement device according to claim 1; and a transporting device configured to transport the recording substrate underneath the gas impingement device through a gas impingement region.

11. A printing device comprising the gas impingement device according to claim 1.

12. A printing device comprising the recording substrate treatment device according to claim 10.

13. The printing device according to claim 11, further comprising an imaging device.

14. The printing device according to claim 12, further comprising an imaging device.

15. A method of drying a recording substrate comprising a wet surface, said method comprising the steps of: using a recording substrate treatment apparatus comprising the gas impingement device according to claim 1 and a transporting device configured to transport a sheet of the recording substrate underneath the gas impingement device; transporting a sheet of the recording substrate comprising the wet surface with the transporting device underneath the gas impingement device and through a gas impingement region of the gas impingement device; and impinging gas at the wet surface of the recording substrate at a gas velocity of between 40 m/s and 90 m/s.

16. The method according to claim 15, wherein the recording substrate treatment apparatus further comprises a heating device; and wherein method further comprises the step of heating the recording substrate prior to the gas impingement step.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

[0058] FIG. 1 is a schematic representation of a recording substrate treatment apparatus according to an embodiment of the present invention;

[0059] FIG. 2A and FIG. 2B are schematic representations of a pattern of gas outlets comprised in a first surface of a gas impingement device, wherein FIG. 2A is according to the background art and FIG. 2B is according to an embodiment of the present invention;

[0060] FIG. 3 is a schematic representation of the determination of the lower boundary of the skew angle α of a skewed pattern of gas outlets comprised in a first surface of a gas impingement device according to the present invention;

[0061] FIG. 4A and FIG. 4B are schematic representations of the determination of the upper boundary of the skew angle α of a skewed pattern of gas outlets comprised in a first surface of a gas impingement device according to the present invention, wherein FIG. 2A is an equilateral triangular pattern and FIG. 2B is a nested square pattern; and

[0062] FIG. 5 is a schematic representation of a pattern of gas outlets comprised in a first surface of a gas impingement device according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0063] The present invention will now be described with reference to the accompanying drawings, wherein the same or similar elements are identified with the same reference numeral.

[0064] FIG. 1 is a schematic representation of a substrate treatment apparatus 1 comprising a transporting device 2, in this particular example being a drum, and a gas impingement device 3 comprising a hollow body 4, a gas inlet, indicated with arrow 5 and a plurality of gas outlets arranged in a pattern in a first surface of the hollow body 4 (not shown here). The first surface is arranged opposite a transporting surface 6 of the transporting device and at a distance 7 from the transporting surface 6, in this particular example substantially 8*d.sub.outlet. In operation, the transporting device 2 carries one or more printed sheets of recording substrate 8, and 8′ on transporting surface 6, which sheets are transported in a direction as indicated with arrow 9. In operation, a gas flow, usually air, is fed to the hollow body 4 of the gas impingement device 3 as is indicated with arrow 5. Said gas flow enters the hollow body 4 and is distributed among the plurality of gas outlets into a plurality of high velocity impinging gas flows (indicated with multiple arrows 10) towards the sheet of recording substrate 8 that is transported underneath the gas impingement device 3 at that instant. The gas velocity is preferably between 50 m/s and 80 m/s.

[0065] The sheets of recording substrate can be held down onto the transporting surface 6 of the transporting device 2 in several ways, such as electrostatically, by vacuum force, by grippers, etc.

[0066] FIG. 2A and FIG. 2B are a schematic representation of a pattern of gas outlets comprised in a first surface 21 of a gas impingement device 3 shown in FIG. 1 and described above. FIG. 2A shows a pattern of gas outlets according to the background art. Arrow 9 indicates the transportation direction of a sheet of recording substrate (see also FIG. 1). A front edge of the sheet of recording substrate (not shown) will be substantially in parallel with the front edge 22 of the gas impingement device when the sheet enters the air impingement region. The first row of gas outlets 23, in this particular example comprising 10 gas outlets, impinge the front edge of the sheet of recording medium at once and simultaneously. The impinging air flow of the first row of gas outlets 23 may cause floating and/or curling of the sheet of recording medium and even blowing away said sheet. In an embodiment according to the present invention and shown in FIG. 2B, the pattern of gas outlets is skewed at an angle α with reference to the front edge 22 of the gas impingement device 3. In this arrangement, only 2 gas outlets (23a and 23b) impinge the front edge of the sheet of recording medium at once and simultaneously. Therefore, the total impinging gas flow acting on the front edge of a recording substrate is much lower compared to the pattern of gas outlets of the background art (FIG. 2A), in this particular example only 20%, assuming that in both cases (FIG. 2A and FIG. 2B) the gas flow per gas outlet is substantially the same. Therefore, the risk of causing floating and/or curling of, or even blowing away a sheet of recording substrate upon transportation underneath a gas impingement device is significantly reduced. Upon further transportation of the recording substrate, more of the plurality of impinging gas flows may act on the front edge of the recording substrate, however, by then a significant part of the surface of the recording substrate is impinged, such that the blowing force acting on said surface is large enough to hold the recording substrate down.

[0067] For an effective design of a gas impingement device, two adjacent gas outlets in the same row (e.g. 23 in FIG. 2A) may impinge a front (or trailing) edge of a sheet of recording substrate simultaneously.

[0068] FIG. 3 shows a schematic representation of the determination of the lower boundary of the skew angle α of a skewed pattern of gas outlets comprised in a first surface of a gas impingement device according to the present invention. Gas outlets 23′ and 23″ are adjacent gas outlets in row 23 (FIG. 2A), said gas outlets are arranged at a distance d.sub.stitch from one another. Dotted line 30 indicates the position of a front (or trailing) edge of a sheet of recording substrate. In the shown position of said front (or trailing) edge, only one of gas outlets 23′ and 23″ impinges said edge. Therefore, the lower boundary of the skew edge α can be calculated with the following equation: α=arctan(d.sub.outlet/d.sub.stitch). For example, in a pattern of gas outlets having a diameter of 1 mm, and wherein the distance between two adjacent gas outlets in a row is 15 mm, the lower boundary of the skew angle α=3.8.

[0069] It is further preferred that all gas outlets are evenly distributed across the first surface (21 FIG. 2A and FIG. 2B) of the hollow body (4 FIG. 1). Even distribution may be obtained by a regular pattern of gas outlets as is shown in FIG. 4A and FIG. 4B.

[0070] FIG. 4A shows a schematic representation of an equilateral triangular pattern of gas outlets. FIG. 4A shows a first row 40 of gas outlets and a second row 41 of gas outlets. The gas outlets of the second row 41 are shifted relative to the gas outlets in the first row 40 by half the distance between two adjacent gas outlets in a row (i.e. 0.5*d.sub.stitch). The upper limit of the skew angle can be determined by calculating the angle between a front (or trailing) edge of a sheet of a recording substrate as indicated by dotted line 42. This front (or trailing) edge is covered by gas outlet 43 of the first row and gas outlet 44 of the second row. Further increasing the skew angle has no effect on the distance between two gas outlets impinging on the front (or trailing) edge of a sheet of recording substrate. The projection of gas outlet 44 onto the first row 40 shows that the distance in the x-direction equals 1.5 d.sub.stitch, and because each triangle of gas outlets constitutes an equilateral triangle, the distance between two adjacent rows d.sub.row (y-direction), here shown for the first row 40 and the second row 41, equals 0.5*√3*d.sub.stitch. Then, the upper limit of the skew angle α can be calculated as follows: α=arctan(d.sub.row/(1.5*d.sub.stitch))=arctan(⅓*√3)=30.

[0071] FIG. 4B is a schematic representation of a nested square pattern of gas outlets. For this arrangement, a similar calculation as described above can be made. The projection of gas outlet 44′ onto the first row 40′ shows that the distance in the x-direction again equals 1.5 d.sub.stitch, and because each gas outlet on the second row is located in the center of a square formed by the adjacent gas outlets in the first and the third row, the distance between two adjacent rows d.sub.row, here shown for the first row 40′ and the second row 41′ equals 0.5*d.sub.stitch. Then, the upper limit of the skew angle α can be calculated as follows: α=arctan(d.sub.row/(1.5*d.sub.stitch))=arctan(⅓)=18.4.

[0072] Alternatively for a squared pattern (not shown), the upper limit of the skew angle is defined by the angle of the diagonal of a square formed by 4 gas outlets with a base rib of said square, which angle is by definition 45.

[0073] FIG. 5 is a schematic representation of a pattern of gas outlets comprised in a first surface 21 of a gas impingement device. The first surface 21 comprises a first zone 21′ a second zone 21″ and a third zone 21′″. The first zone 21′ is arranged adjacent to the front edge 22 of the first surface 21 and comprises a first plurality of gas outlets having a first diameter, d.sub.outlet1. The second zone 21″ is arranged in between the first zone 21′ and the third zone 21′″ and comprises a second plurality of gas outlets having a second diameter, d.sub.outlet2. The third zone 21′″ is arranged adjacent to the trailing edge 50 of the first surface 21 and comprises a third plurality of gas outlets having a third diameter, d.sub.outlet3. The diameters of the gas outlets in both the first and the third zones are smaller than the diameters of the gas outlets in the second zone. d.sub.outlet1 and d.sub.outlet3 may be the same or different. The transportation direction of a sheet of recording medium is again indicated with arrow 9.

[0074] With this arrangement, the impact of gas impingement on front and trailing edges of cut-sheet recording substrates, when entering the gas impingement region can be further reduced.

[0075] Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually and appropriately detailed structure. In particular, features presented and described in separate dependent claims may be applied in combination and any combination of such claims is herewith disclosed.

[0076] Further, the terms and phrases used herein are not intended to be limiting; but rather, to provide an understandable description of the invention. The terms “a” or “an”, as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language). The term “in fluid connection” or “operatively connected”, as used herein, are defined as connected, although not necessarily directly.

[0077] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.