Device for applying a fluid to a roller

Abstract

A fluid distribution device, for applying a fluid onto a transfer roller, includes an elongated chamber, at least one inlet for letting a fluid into the chamber, a longitudinal opening extending in the axial direction and adapted to face a transfer roller to allow fluid to exit the chamber and contact the transfer roller, and at least one wiper blade extending along at least a portion of the longitudinal opening. The chamber includes, at each of the two axial ends of the chamber, a wall separating the chamber from a cavity. The wall has a wall surface arranged to face the transfer roller when the device is in use. The wall is dimensioned so that the wall surface will be distanced from the transfer roller when the device is in use, so as to allow fluid to be present in a gap between the wall surface and the transfer roller.

Claims

1. A machine comprising a transfer roller and a fluid distribution device for applying a fluid onto the transfer roller, the fluid distribution device comprising an elongated chamber extending in an axial direction, at least one inlet for letting a fluid into the chamber, a longitudinal opening extending in the axial direction and adapted to face the transfer roller when the device is in use so as to allow fluid to exit the chamber and contact the transfer roller, and a wiper blade extending along at least a portion of the longitudinal opening, in the axial direction, the chamber having two axial ends; wherein the chamber includes, at each of the two axial ends of the chamber, a wall separating the chamber from a cavity, wherein the wall has a wall surface arranged to face the transfer roller when the device is in use, the wall being dimensioned so that the wall surface will be distanced from the transfer roller when the device is in use, so as to allow fluid to exit the chamber via a gap between the wall surface and the transfer roller, wherein the wall surface is spaced from a surface of the transfer roller by the gap, the gap having a size, at a lowermost portion of the gap, in a radial direction of at least 5 mm, wherein no friction seal elements arranged to contact the transfer roller are provided to close the chamber at the axial ends thereof, and the device comprises only one wiper blade, the wiper blade being arranged at a lower edge of the longitudinal opening, the transfer roller being arranged to rotate in a direction such that a surface of the transfer roller facing the longitudinal opening moves downwards during rotation of the transfer roller and the wiper blade is configured to remove excess fluid received by the transfer roller via the opening during rotation of the transfer roller, wherein the cavity is configured to receive the fluid that exits the chamber through the gap and is configured to lead the fluid towards a drain outlet, and whereby the drain outlet is connected to and extends from the cavity, the drain outlet being configured to receive the fluid entering the cavity from the chamber, such that the fluid is drained through the drain outlet and recirculated.

2. The machine of claim 1, wherein the wall surface has a width of at least 20 mm in the axial direction.

3. The machine of claim 1, wherein the wall surface comprises at least one portion substantially shaped as an arc of a circle, in a plane perpendicular to the axial direction.

4. The machine of claim 3, wherein the portion of the wall surface substantially shaped as an arc of a circle is shaped so as to substantially match the transfer roller when the device is in use, so that, along at least part of the portion substantially shaped as an arc of a circle, the wall surface will be spaced from a surface of the transfer roller by a gap having a size in a radial direction wherein the size of the gap in the radial direction is more than 0.5 mm and less than 20 mm.

5. The machine of claim 1, wherein the chamber is embodied in a beam member, and wherein the walls are integral parts of said beam member.

6. The machine of claim 1, wherein the walls are of the same material as a body in which the chamber is formed.

7. The machine of claim 1, wherein the wall has a thickness in the axial direction that decreases from a root of the wall towards the wall surface.

8. The machine of claim 1, comprising a plurality of inserts wherein each insert is configured to provide a width to the wall surface.

9. The machine of claim 1, wherein the gap has a lowermost point, and wherein the cavity has a bottom portion, said bottom portion being arranged at a level of at least 10 mm below the lowermost point of the gap, at least one drain opening being present in said bottom portion, and wherein the cavity has an end wall defining an axial end of the cavity, said end wall being arranged not to contact the transfer roller when the device is in use.

10. The machine according to claim 1, wherein the gap has a size in the radial direction of the transfer roller, and wherein the device is pivotally arranged so that when the machine is being used, the device will pivot towards the transfer roller due to a reduction of the size of the wiper blade due to wear, so that the size of the gap will decrease during use as a result of the reduction of the size of the wiper blade.

11. The machine according to claim 10, wherein the device is pivotally arranged so that pivotation towards the transfer roller due to reduction of the size of the wiper blade is caused by biasing means.

12. A method of operating a machine according to claim 10, including the following steps: placing the device in relation to the transfer roller so that the longitudinal opening faces the transfer roller; circulating a fluid by pumping the fluid into the chamber and causing part of the fluid to enter the gaps between the wall surfaces and the transfer roller, so that the walls act as partial axial end closures of the chamber, and so that fluid exits the chamber through the gaps; and pivoting the device towards the transfer roller compensating for a reduction of the size of the wiper blade due to wear, rotating the transfer roller in a direction such that a surface of the transfer roller facing the longitudinal opening moves downwards during rotation of the transfer roller and the wiper blade removes excess fluid received by the transfer roller via the opening while rotating the transfer roller, receiving the fluid that exits the chamber through each gap in the respective cavity, and each respective cavity leads the fluid towards a drain outlet that is connected to and extends from the cavity, and draining the fluid through the drain outlet and recirculating the fluid.

13. A method of operating a machine according to claim 1, including the following steps: placing the device in relation to the transfer roller so that the longitudinal opening faces the transfer roller; and circulating a fluid by pumping the fluid into the chamber and causing part of the fluid to enter the gaps between the wall surfaces and the transfer roller, so that the walls act as partial axial end closures of the chamber, and so that fluid exits the chamber through the gaps, rotating the transfer roller in a direction such that a surface of the transfer roller facing the longitudinal opening moves downwards during rotation of the transfer roller and the wiper blade removes excess fluid received by the transfer roller via the opening while rotating the transfer roller, receiving the fluid that exits the chamber through each gap in the respective cavity, and each respective cavity leads the fluid towards a drain outlet that is connected to and extends from the cavity, and draining the fluid through the drain outlet and recirculating the fluid.

14. The machine of claim 1, wherein the wall surface has a width of at least 10 mm in the axial direction.

15. The machine of claim 1, wherein the wall surface has a width of at least 5 mm in the axial direction.

16. A machine comprising a transfer roller and a fluid distribution device for applying a fluid onto the transfer roller, the fluid distribution device comprising an elongated chamber extending in an axial direction, at least one inlet for letting a fluid into the chamber, a longitudinal opening extending in the axial direction and adapted to face the transfer roller when the device is in use so as to allow fluid to exit the chamber and contact the transfer roller, and only one wiper blade extending along at least a portion of the longitudinal opening, in the axial direction, the chamber having two axial ends; wherein the chamber includes, at each of the two axial ends of the chamber, a wall separating the chamber from a cavity, wherein the wall has a wall surface arranged to face the transfer roller when the device is in use, the wall being dimensioned so that the wall surface will be distanced from the transfer roller when the device is in use, so as to allow fluid to exit the chamber via a gap between the wall surface and the transfer roller, wherein the wall surface is spaced from a surface of the transfer roller by the gap, the gap having a size, at a lowermost portion of the gap, in a radial direction of at least 5 mm, wherein the cavity is configured to receive the fluid that exits the chamber through the gap and is configured to lead the fluid towards a drain outlet, whereby the drain outlet is connected to and extends from the cavity, the drain outlet being configured to receive the fluid entering the cavity from the chamber, such that the fluid is drained through the drain outlet and recirculated, and wherein the only one wiper blade is arranged at a lower edge of the longitudinal opening, the transfer roller being arranged to rotate in a direction such that a surface of the transfer roller facing the longitudinal opening moves downwards during rotation of the transfer roller and the only one wiper blade is configured to remove excess fluid received by the transfer roller via the opening during rotation of the transfer roller.

17. The machine of claim 16, wherein the gap is configured to be at least partially filled with fluid, such that the walls disposed at each of the two axial ends partially close the ends of the chamber, providing a controlled and substantially laminar flow of fluid exiting the chamber.

18. The machine of claim 16, wherein the gap has a lowermost point, and wherein the cavity has a bottom portion, said bottom portion being arranged at a level of at least 10 mm below the lowermost point of the gap, at least one drain opening being present in said bottom portion, and wherein the cavity has an end wall defining an axial end of the cavity, said end wall being arranged not to contact the transfer roller when the device is in use.

19. A method of operating a machine according to claim 16, including the following steps: placing the device in relation to the transfer roller so that the longitudinal opening faces the transfer roller; and circulating a fluid by pumping the fluid into the chamber and causing part of the fluid to enter the gaps between the wall surfaces and the transfer roller, so that the walls act as partial axial end closures of the chamber, and so that fluid exits the chamber through the gaps, rotating the transfer roller in a direction such that a surface of the transfer roller facing the longitudinal opening moves downwards during rotation of the transfer roller and the wiper blade removes excess fluid received by the transfer roller via the opening while rotating the transfer roller, receiving the fluid that exits the chamber through each gap in the respective cavity, and each respective cavity leads the fluid towards a drain outlet that is connected to and extends from the cavity, and draining the fluid through the drain outlet and recirculating the fluid.

20. A machine comprising a transfer roller and a fluid distribution device for applying a fluid onto the transfer roller, the fluid distribution device comprising an elongated chamber extending in an axial direction, at least one inlet for letting a fluid into the chamber, a longitudinal opening extending in the axial direction and adapted to face the transfer roller when the device is in use so as to allow fluid to exit the chamber and contact the transfer roller, and a wiper blade extending along at least a portion of the longitudinal opening, in the axial direction, the chamber having two axial ends; wherein the chamber includes, at each of the two axial ends of the chamber, a wall separating the chamber from a cavity, wherein the wall has a wall surface arranged to face the transfer roller when the device is in use, the wall being dimensioned so that the wall surface will be distanced from the transfer roller when the device is in use, so as to allow fluid to exit the chamber via a gap between the wall surface and the transfer roller, wherein the wall surface is spaced from a surface of the transfer roller by the gap, the gap having a size, at a lowermost portion of the gap, in a radial direction of at least 5 mm, wherein the wiper blade is arranged at a lower edge of the longitudinal opening, the transfer roller being arranged to rotate in a direction such that a surface of the transfer roller facing the longitudinal opening moves downwards during rotation of the transfer roller and the wiper blade is configured to remove excess fluid received by the transfer roller via the opening during rotation of the transfer roller, and wherein the cavity is configured to receive the fluid that exits the chamber through the gap and is configured to lead the fluid towards a drain outlet, whereby the drain outlet is connected to and extends from the cavity, the drain outlet being configured to receive the fluid entering the cavity from the chamber, such that the fluid is drained through the drain outlet and recirculated.

21. The machine of claim 20, wherein no wiper blade is arranged at an upper edge of the longitudinal opening such that the chamber is open in correspondence with the upper edge.

22. The machine of claim 20, wherein the gap is configured to be at least partially filled with fluid, such that the walls disposed at each of the two axial ends partially close the ends of the chamber, providing a controlled and substantially laminar flow of fluid exiting the chamber.

23. The machine of claim 20, wherein the gap has a lowermost point, and wherein the cavity has a bottom portion, said bottom portion being arranged at a level of at least 10 mm below the lowermost point of the gap, at least one drain opening being present in said bottom portion, and wherein the cavity has an end wall defining an axial end of the cavity, said end wall being arranged not to contact the transfer roller when the device is in use.

24. A method of operating a machine according to claim 20, including the following steps: placing the device in relation to the transfer roller so that the longitudinal opening faces the transfer roller; and circulating a fluid by pumping the fluid into the chamber and causing part of the fluid to enter the gaps between the wall surfaces and the transfer roller, so that the walls act as partial axial end closures of the chamber, and so that fluid exits the chamber through the gaps, rotating the transfer roller in a direction such that a surface of the transfer roller facing the longitudinal opening moves downwards during rotation of the transfer roller and the wiper blade removes excess fluid received by the transfer roller via the opening while rotating the transfer roller, receiving the fluid that exits the chamber through each gap in the respective cavity, and each respective cavity leads the fluid towards a drain outlet that is connected to and extends from the cavity, and draining the fluid through the drain outlet and recirculating the fluid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) To complete the description and in order to provide for a better understanding of the disclosure, a set of drawings is provided. Said drawings form an integral part of the description and illustrate embodiments of the disclosure, which should not be interpreted as restricting the scope of the disclosure, but just as examples of how the disclosure can be carried out. The drawings comprise the following figures:

(2) FIG. 1 is a schematic cross sectional view of a printing machine in accordance with an embodiment of the disclosure;

(3) FIG. 2 is an enlarged view of a portion of the machine illustrated in FIG. 1;

(4) FIG. 3 is a cross-sectional top view of the fluid distribution device in accordance with this embodiment of the disclosure, arranged facing a transfer roller;

(5) FIGS. 4-7 are lateral cross sectional views of the fluid distribution device facing a transfer roller, at different axial positions;

(6) FIG. 8 is a partial top view of a machine in accordance with an embodiment of the disclosure, with the fluid distribution device pivoted away from the roller;

(7) FIG. 9 is a partial perspective view of the machine according to this embodiment, with the fluid distribution device pivoted away from the roller;

(8) FIG. 10 is a schematic cross-sectional top view illustrating a modular wall arrangement;

(9) FIGS. 11A and 11B are schematic cross sectional side views of an embodiment of a machine with a pivotally arranged fluid transfer device; and

(10) FIG. 12 is schematic perspective view of the device in accordance with an alternative embodiment of the disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

(11) FIG. 1 schematically illustrates a printing machine in accordance with one possible embodiment of the disclosure, including typical components of a flexographic printing machine. The machine is adapted to print web-like objects 100 such as cardboard objects, fed between a plate roller 3 and another roller 4, as known in the art. Ink is transferred to the plate roller 3 using a transfer roller 2. The rollers have cylindrical shapes and circular cross sections, as known in the art. The transfer roller 2 can be an anilox roller with a surface featuring cells, as known in the art.

(12) The transfer roller 2 is arranged to receive a fluid, such as for example ink, from a fluid distribution device 1 of the so-called doctor chamber type, which comprises a beam-like member 13 with a longitudinal recess or chamber 10 extending in an axial direction (parallel with the axis of the transfer roller 2) and with an opening arranged to face the transfer roller, as shown in FIG. 1. A first axially extending doctor blade 11 is arranged at a lower edge of the opening, and in FIG. 1 a second axially extending doctor blade 12 is arranged at an upper edge of the opening. In the invention, only the first doctor blade 11 is present, as in the embodiment schematically illustrated in FIGS. 4-7.

(13) The first 11 and second 12 doctor blades can also be observed in FIG. 2, which is an enlarged view of a portion of the machine shown in FIG. 1. In FIG. 2, a wall 15 is shown. This wall 15 is arranged to partially close off the chamber 10 at one axial end thereof. The wall has a surface 15A facing the transfer roller 2, and this surface is shaped as an arc of a circle, in the plane perpendicular to the axis of the transfer roller. Thus, a curved arc-like gap 20 is established between the surface 15A of the wall 15 and the transfer roller 2. This gap 20 typically has a width (when referring to this gap, the term “width” refers to the size of the gap in the radial direction) in the order of 0.5-20 mm, such as in the order of 1-15, 1-10, 1-5 or 1-3 mm. A suitable gap size can be chosen by the person skilled in the art depending on the other characteristics of the system, such as the size of the transfer roller, the desired flow rate and viscosity of the fluid, etc. In this embodiment, the width of the gap is substantially constant, but in other embodiments of the disclosure, the width of the gap can vary along the gap, in the circumferential direction.

(14) This gap 20 is intended to be partially filled with fluid. Another wall and gap closes the other axial end of the chamber. Thus, the walls 15 in combination with the gaps 20 partially filled with fluid close both ends of the chamber 10, thereby avoiding the need for elastomeric seals such as those known in the art. The walls 15 partially close the ends of the chamber 10, allowing a controlled and substantially laminar flow of fluid out of the chamber at the axial ends thereof, between the wall surfaces 15A and the transfer roller 2, that is, through the gap 20, and into the cavity 16.

(15) FIG. 3 is a cross-sectional top view of the device, with the chamber 10 facing the transfer roller. It is shown how the walls 15 extend towards the transfer roller, leaving a gap 20 between the walls 15 and the transfer roller, a gap arranged to be at least partly filled with fluid when the machine is operating. This thin fluid layer thus completes the end closure of the chamber 10, without any need for direct contact between the walls 15 and the transfer roller 2. This fluid lock or fluid bearing thus provides for a low-friction closure of the axial ends of the chamber 10, without any need for parts such as the elastomeric seal elements conventionally used in the art. Fluid will flow in a substantially controlled manner through the gaps into the cavities 16, which are provided with outlet openings 33 so that the fluid entering the cavities 16 from the chamber 10 can be drained and recirculated if this is desired. Further drains 32 of the overflow type are provided in the chamber 10; one such drain 32 is schematically illustrated in FIG. 3.

(16) FIG. 4 is a cross-sectional view of the fluid distribution device facing a transfer roller 2, at an axial position within the chamber 10, in correspondence with one of a plurality of inlets 31 through which the fluid 30, such as ink, can be pumped into the chamber through openings arranged at a bottom portion of the chamber, as schematically illustrated in FIG. 4. The wall 15 with its circular arc shaped surface can be observed at the end of the chamber, and the circular arc shaped gap 20 between the wall 15 and the transfer roller can likewise be observed. FIG. 4 schematically illustrates how the fluid 30 is retained within the chamber, in a space delimited by the wall of the chamber (which is part of the beam 13), the doctor blade 11, and the transfer roller 2.

(17) FIG. 5 is likewise a cross-sectional view at an axial position within the chamber, but here in correspondence with an overflow outlet 32, arranged so that when the fluid 30 reaches a certain level in the chamber, it will start to drain out through the outlet 32.

(18) FIG. 6 is a cross-sectional view at an axial position corresponding to the surface 15A of the wall 15. Here, it can be seen how a portion of the gap 20 is filled with fluid, so that this thin fluid layer, together with the wall 15, constitutes a low-friction lock or closure of the chamber 10, whereby the wall 15 partially closes the chamber, with a controlled flow of fluid through the gap 20 into a cavity 16 arranged axially beyond the wall 15.

(19) FIG. 7 is a cross-sectional view at an axial position beyond the wall 15, through the end cavity 16. This cavity receives fluid 30 that has penetrated through the gap 20, and a drain outlet 33 is provided through which this fluid can be removed and recirculated if desired. It is shown how the cavity 16 has a bottom portion 16A arranged at a distance h below the bottom portion of the gap 20, so that the fluid exiting the gap 20 will flow downwards from the gap 20, towards the bottom of the cavity 16, instead of continuing flowing in the axial direction. An axial end wall 16B that closes off the cavity 16 at its axial end is schematically illustrated in FIG. 8. It is clear that with this arrangement, the axial flow of the fluid out of the chamber 10 can be controlled so that the fluid ends in the chamber 16 and is drained through the outlet 33, without continuing in the axial direction. Thus, contrary to what is conventional in the art, no axial end seals are needed that close off the chamber against the transfer roller by making contact with the transfer roller. That is, there is no frictional contact between any axial end seals and the transfer roller.

(20) In addition, in some embodiments such as the one shown in FIGS. 4-7, there is only one doctor blade 11. This further reduces the number of components subjected to wear due to contact with the transfer roller 2.

(21) FIGS. 8 and 9 schematically illustrate the machine in accordance with this embodiment, with the fluid distribution device or doctor chamber pivoted away from the roller 2, and with traces of the fluid left on the roller and along parts of the inner wall and end wall 15 of the chamber. FIG. 9 schematically illustrates a fluid inlet 31 and an overflow drain outlet 32; it can be seen how the level of the fluid within the chamber reached the lower portion of the drain 32. In FIG. 9, the curved surface 15A of the wall 15 can be observed. In FIG. 8, it can be seen how the wall 15 separates the chamber from the end cavity 16, to which the fluid 30 can flow through the gap between wall and roller, as explained above, and exit through the drain 33.

(22) In the illustrated embodiment, the width W of the surface 15A of the wall in the axial direction is relatively substantial, as explained above, facilitating a sufficient pressure drop in the axial direction, from one end of the surface 15A to the other, in the axial direction. The width of the wall at the surface can be selected depending on the estimated viscosity of the fluid to be used. If other parameters are unchanged, in principle, the lower the viscosity, the wider the surface of the wall, that is, the thicker the wall at its surface facing the roller. Thus, in some embodiments of the disclosure, it can be preferred to provide for the possibility of modifying the width of the wall. FIG. 10 schematically illustrates one possible embodiment, in which the wall 15 is established by placing a number of inserts 15a-15d into a recess between the chamber 10 and the cavity 16. By combining higher and lower inserts, the desired width of the surface in the axial direction can be determined. For example, in the case of FIG. 10, the effective width of the surface 15A corresponds to the sum of the widths of the two elements 15a and 15b.

(23) In FIGS. 3 and 9 it can be seen how in the illustrated embodiment, the inner surface of the wall, that is, the surface facing the interior of the chamber 10, has a curved shape, corresponding to a narrowing of the wall in the direction from the root of the wall towards the surface 15A. This can be preferred in order to facilitate that fluid flows towards the gap also from the rear portion of the chamber, that is, the portion of the chamber that is furthest away from the transfer roller when the device is in use. This can be preferred in order to minimize the maximum time that any portion of the fluid will remain within the chamber. That is, this feature can serve the enhance recirculation of the fluid.

(24) FIGS. 11A and 11B illustrate how the device can be arranged to pivot in relation to an axis 17, so that it can pivot towards the transfer roller 2 as a result of wear of the wiper blade 11. Thus, comparing the gap 20 in FIG. 11A with the gap 20 in FIG. 11B, it is clear that the gap will decrease in size—that is, in what regards its size in the radial direction-during use of the machine, especially at the lowermost end of the gap. For example, in one embodiment, the gap can have a size A in the radial direction at a top portion of the gap between transfer roller 2 and the wall 15, and a size B in the radial direction at a bottom portion of the gap. It can be preferred that the size A be in the order of 1-2 mm both when a new wiper blade is applied (FIG. 11A) and after wear (FIG. 11B), whereas size B can be in the order of 6-15 mm when a new wiper blade is applied (FIG. 11A), and reduced to 1-2 mm when the wiper blade is to be replaced (FIG. 11B). It is clear from FIGS. 11A and 11B that in the illustrated embodiment, this kind of pivotation can be produced by suitable biasing means, for example one or more springs biasing the device towards the roller, and/or pneumatic and/or hydraulic biasing means. A further axis 18 is schematically illustrated: the device can be pivoted around this axis 18 so as to pivot away from the transfer roller, for example, when the wiper blade 11 is to be replaced or when access to the chamber 10 is desired, for example, for cleaning. The dimension C schematically illustrates the level of fluid within the chamber 10 during use of the machine, a level that can typically be in the order of 30-60 mm above the level of the free edge of the wiper blade.

(25) In some embodiments, the wiper blade does not extend all the way to the outermost axial ends of the cavities 16. In other embodiments, such as the one shown in FIG. 12, the wiper blade 12 extends at least to the outermost axial end of the cavity 16, for example, all along the beam 13.

(26) In this text, the term “comprises” and its derivations (such as “comprising”, etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc.

(27) Unless otherwise indicated, any ranges referred to in this document include the indicated end points.

(28) The disclosure is not limited to the specific embodiment(s) described herein, but also encompasses any variations that may be considered by any person skilled in the art (for example, as regards the choice of materials, dimensions, components, configuration, etc.), within the general scope of the disclosure.