Cleaning device

Abstract

To provide a cleaning device that can perform cleaning operations without soiling the surrounding area. [Solution] The system comprises a porous member 21b that is pressed against a nozzle surface 36a having multiple discharge holes of an ink-discharging nozzle, a moving mechanism 22 that moves the porous member 21b in a direction that separates the nozzle surface 36a from the porous member 21b, and a control unit 50 that controls the moving mechanism 22 to perform a purge, in which ink is discharged from the nozzle surface 36a while the porous member 21b is in contact with the nozzle surface 36a.

Description

Technical Field

[0006] , ,

[0001] The present invention relates to a cleaning device for cleaning a nozzle surface such as an inkjet head.

Background Art

[0002] Conventionally, inkjet printing devices that eject ink from an inkjet head to perform printing on paper, film, building materials, decorative panels, etc. have been proposed.

[0003] In an inkjet printing device, ink may adhere to the ink ejection holes of the nozzles, or dust such as paper powder generated from the printing paper may adhere. When ink adheres or paper powder accumulates in the ink ejection holes of the nozzles, ejection defects such as disturbance in the ink ejection direction from the nozzles or non-ejection may occur.

[0004] In order to reduce such ejection defects, a cleaning operation is known in which a so-called purge is performed to forcibly eject ink from the nozzles of the inkjet head, and then the ink ejection holes of the nozzles are wiped by a wiper blade. By the cleaning operation, dust on the ink ejection holes of the nozzles is removed together with the ink adhering to the ink ejection holes of the nozzles.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] As mentioned above, the cleaning operation typically involves wiping after purging the inkjet head. However, purging a large amount of ink can lead to uncertain removal of the adhering ink, and the flexibility of the wiper blade can cause ink to splatter and contaminate the surrounding area. Furthermore, if the inkjet head has a nozzle guard that protects the nozzle surface where the ink ejection holes are arranged, wiping can cause ink to enter the gap between the nozzle guard and the nozzle surface.

[0007] Therefore, Patent Document 1 proposes a method in which an ink absorbent is brought into contact with the nozzle surface before wiping.

[0008] However, in the case of an inkjet printing device where the nozzle surface of the inkjet head is positioned vertically and ink is ejected horizontally, the ink drips downward after purging, making it impossible to perform the cleaning operation by wiping. Also, if, for example, one inkjet head has two rows of nozzles, there is a problem in that it is impossible to avoid mixing of colors when purging large amounts of ink.

[0009] In view of the above circumstances, the present invention aims to provide a cleaning device that can perform cleaning operations without soiling the surroundings. [Means for solving the problem]

[0010] The cleaning apparatus of the present invention comprises a porous absorbent member that is pressed against a nozzle surface having multiple discharge holes of a nozzle for discharging liquid, a moving unit that moves the absorbent member or the nozzle surface in a direction away from the nozzle surface and the absorbent member, and a control unit that controls the moving unit to perform purging by discharging liquid from the nozzle surface while the absorbent member is in contact with the nozzle surface. [Effects of the Invention]

[0011] According to the cleaning device of the present invention, since purging is performed by discharging liquid from the nozzle surface while the absorbing member is in contact with the nozzle surface, the cleaning operation can be performed without soiling the surroundings. [Brief explanation of the drawing]

[0012] [Figure 1] A perspective view showing a schematic configuration of one embodiment of the inkjet printing apparatus body of the present invention. [Figure 2] A diagram showing an example of a line head configuration. [Figure 3] Perspective view showing the appearance of an inkjet head. [Figure 4] Figure 3 shows a portion of the cross-section of the inkjet head along line AA. [Figure 5] A diagram showing an example of the configuration of an absorbent member unit. [Figure 6] Perspective view showing the specific configuration of the absorption section. [Figure 7] Diagram showing the porous material in contact with the nozzle surface. [Figure 8] Diagram for explaining the aperture member [Figure 9] Figure 1 shows a block diagram illustrating the control system of the inkjet printing apparatus. [Figure 10] A diagram showing an example of an inkjet head with two rows of nozzles. [Figure 11] Figure 10 shows a perspective view illustrating an example of an absorption section when using the inkjet head shown. [Modes for carrying out the invention]

[0013] Hereinafter, an inkjet printing apparatus using an embodiment of the cleaning device of the present invention will be described in detail with reference to the drawings. The inkjet printing apparatus of this embodiment is characterized by the configuration and control of the cleaning unit. First, the overall configuration of the inkjet printing apparatus will be described. FIG. 1 is an external perspective view showing the schematic configuration of the inkjet printing apparatus main body 1. In the description of the embodiment shown below, the up, down, left, right, front, and rear directions indicated by the arrows in FIG. 1 are defined as the up, down, left, right, front, and rear directions of the inkjet printing apparatus main body 1. Also, the up and down directions of the inkjet printing apparatus main body 1 are in the vertical direction.

[0014] As shown in FIG. 1, the inkjet printing apparatus main body 1 includes a head unit 10, a conveyance unit 2, and a cleaning unit 20.

[0015] The conveyance unit 2 conveys the printing medium P in the direction of the arrow shown in FIG. 1. As the printing medium P, for example, a three-dimensional object (such as a cardboard box) having a printing surface Ps standing perpendicular to the conveyance surface as shown in FIG. 1 can be used, but it is not limited to this. In this embodiment, the conveyance surface is parallel to the horizontal plane.

[0016] The conveyance unit 2 includes a support base 3 and a conveyance belt unit 4. The support base 3 is a base that supports the conveyance belt unit 4.

[0017] The conveyance belt unit 4 includes a plurality of rollers extending in a direction perpendicular to the conveyance direction of the printing medium P and a conveyance belt. The plurality of rollers are spaced apart and arranged in parallel in the conveyance direction of the printing medium P. An annular conveyance belt is stretched between the plurality of rollers arranged in parallel. When the rollers rotate, the conveyance belt moves, and thereby the printing medium P is conveyed.

[0018] The head unit 10 performs printing by ejecting ink perpendicular to the printing surface Ps of the printing medium P conveyed by the conveyance unit 2.

[0019] As shown in Figure 1, the head unit 10 has four line heads 11, 12, 13, and 14. The four line heads 11 to 14 extend vertically and are arranged parallel to the transport direction of the printing medium P.

[0020] The four line heads 11-14 eject inks of K (black), C (cyan), M (magenta), and Y (yellow), respectively.

[0021] As shown in Figure 2, line heads 11 to 14 of this embodiment each have six inkjet heads 16a to 16f. The six inkjet heads 16a to 16f are arranged so that the direction of ink ejection is perpendicular to the printing surface Ps. In other words, in this embodiment, they are arranged so that the direction of ink ejection is horizontal. Hereinafter, any of the six inkjet heads 16a to 16f may simply be referred to as inkjet head 16.

[0022] Each inkjet head 16a to 16f has a plurality of nozzles 17 arranged in a predetermined direction. The nozzles 17 eject the ink supplied to each inkjet head 16a to 16f toward the printing surface Ps.

[0023] As shown in Figure 2, the six inkjet heads 16a to 16f are arranged so that the nozzles 17 are aligned vertically, and are further arranged in a staggered pattern in the transport direction. In this embodiment, some of the nozzles 17 of vertically adjacent inkjet heads are arranged to overlap vertically.

[0024] As described above, ink is ejected from the six inkjet heads 16a to 16f at pre-set timings, thereby printing a straight line extending vertically.

[0025] Figure 3 is a perspective view showing the external appearance of the inkjet head 16a, and Figure 4 is a diagram showing a part of the cross-section of the inkjet head 16a along line AA shown in Figure 3. Although the configuration of the inkjet head 16a is described here, the inkjet heads 16b to 16f have a similar configuration.

[0026] As shown in Figure 3, the inkjet head 16a includes a nozzle plate 36 and a nozzle guard 32. The nozzle plate 36 has a nozzle row (discharge hole row) in which multiple discharge holes 37 of the nozzles 17 that eject ink are arranged. In this embodiment, as shown in Figure 2, the nozzle row of the inkjet head 16a is arranged to face vertically.

[0027] As shown in Figures 3 and 4, the nozzle guard 32 has an opening 46 in the portion of the nozzle plate 36 corresponding to the nozzle row, and is provided with a gap 40 between it and the nozzle surface 36a on which the nozzle row is arranged. In this embodiment, the nozzle surface 36a is the surface on which the nozzle discharge holes 37 are arranged, and is the same surface as the surface of the nozzle plate 36.

[0028] The nozzle guard 32 protects the nozzle surface 36a of the nozzle plate 36. Specifically, the nozzle guard 32 has a bottom plate 41 formed to cover the periphery of the nozzle row and side walls 42 erected on the periphery of the bottom plate 41. The bottom plate 41 has the aforementioned opening 46, and a gap 40 is formed between the bottom plate 41 and the nozzle surface 36a. The opening 46 is formed in an elongated rectangular shape in the front-to-back direction, so as to expose the discharge holes 37 of all nozzles. The gap 40 is formed by the space sandwiched between the bottom plate 41 of the nozzle guard 32 and the periphery of the nozzle surface 36a facing the bottom plate 41 when the nozzle guard 32 is attached to the nozzle plate 36.

[0029] The cleaning unit 20 absorbs and removes ink adhering to the nozzle surfaces 36a and nozzle guards 32 of the inkjet heads 16a to 16f during the cleaning operation.

[0030] The cleaning unit 20 comprises four absorbent member units 20a to 20d, each provided for each line head 11 to 14 of the head unit 10. Figure 5 shows the configuration of absorbent member unit 20a. The absorbent member units 20b to 20d have the same configuration as absorbent member unit 20a shown in Figure 5.

[0031] Figure 5 is a view of the absorbent member unit 20a from the right side. As shown in Figure 5, the absorbent member unit 20a has six absorbent parts 21. The six absorbent parts 21 are positioned opposite the six inkjet heads 16a to 16f.

[0032] Figure 6 is a perspective view showing the specific configuration of the absorption section 21. As shown in Figure 6, the absorption section 21 comprises a base 21a and a porous member 21b (absorbent member). The base 21a is a flat plate-shaped member, and the porous member 21b is provided on the base 21a. The porous member 21b is formed from, for example, a sponge, and absorbs ink adhering to the nozzle surface 36a of the inkjet head 16a and the surface of the nozzle guard 32. In this embodiment, the porous member 21b is formed from a sponge, but it is not limited to this, and any porous material that can absorb ink, such as paper, may be used.

[0033] As shown in Figure 6, the porous member 21b is formed in the shape of a rectangular parallelepiped, and the surface that contacts the inkjet head 16a has an area sufficient to adequately cover the nozzle surface 36a of the inkjet head 16a and the surface of the nozzle guard 32. Furthermore, the height (thickness) of the porous member 21b from the base 21a is such that it can adequately absorb ink, and is preferably 5 mm or more.

[0034] The cleaning unit 20 then moves in a direction in which the nozzle surface 36a of each inkjet head 16a to 16f and the absorption section 21, which is located opposite each inkjet head 16a to 16f, move toward and away from each other. In other words, the cleaning unit 20 is equipped with a moving mechanism 22 (see Figure 9) that moves in the direction of arrow A (left and right direction) as shown in Figure 1. The moving mechanism 22 is composed of predetermined actuators.

[0035] The moving mechanism 22 is operated by control of the control unit 50, which will be described later. Specifically, when printing is to be performed on the printing medium P, the control unit 50 positions the cleaning unit 20 in a location where the printing medium P can pass between the cleaning unit 20 and the head unit 10.

[0036] Then, when performing a cleaning operation, the control unit 50 controls the moving mechanism 22 to move the cleaning unit 20 to the right as shown in Figure 1, and moves the cleaning unit 20 to a position (cleaning position) where the porous members 21b of each absorption part 21 of the cleaning unit 20 are pressed against each inkjet head 16a to 16f with a predetermined pressing pressure, as shown in Figure 7.

[0037] Then, a purging cleaning operation is performed, and the ink adhering to each inkjet head 16a to 16f is absorbed by the porous material 21b. The cleaning operation will be described in detail later.

[0038] Next, after the cleaning operation is completed, the control unit 50 controls the moving mechanism 22 to move the cleaning unit 20 to the standby position shown in Figure 1, making it ready for printing.

[0039] The cleaning unit 20 also includes a squeezing member 23 for squeezing out the ink absorbed by the porous member 21b of the absorption section 21. The squeezing member 23 is composed of, for example, a roller member extending in the front-rear direction (a direction perpendicular to the longitudinal direction of the porous member 21b). When not squeezing, the squeezing member 23 is positioned above the porous member 21b, as shown in Figure 8A. When squeezing is performed, the squeezing member 23 is moved downward by a roller moving mechanism 24 (see Figure 9), crushing the porous member 21b with a predetermined pressure, as shown in Figure 8B. This pushes the ink absorbed by the porous member 21b out of the porous member 21b.

[0040] Then, when the constricting member 23 passes the porous member 21b, the roller moving mechanism 24 moves the constricting member 23 upward again to the standby position shown in Figure 8A. The roller moving mechanism 24 is controlled by the control unit 50 and is equipped with predetermined actuators and the like.

[0041] In this embodiment, a throttling member 23 is provided for each absorption section 21, but the configuration is not limited to this. For example, a throttling member 23 may be provided for each of the six absorption sections 21 corresponding to each of the line heads 11 to 14, and one throttling member 23 may be used to throttle the porous members 21b of the six absorption sections 21, or one throttling member 23 may be used to throttle the porous members 21b of all absorption sections 21.

[0042] Furthermore, as described above, the ink squeezed out from the porous member 21b by the squeezing member 23 will fall downward due to its own weight, and a receiving tray (not shown) is provided inside the cleaning unit 20 to receive the fallen ink. The receiving tray may be provided for each absorption section 21, or for each of the six absorption sections 21 corresponding to each line head 11 to 14, or one receiving tray may be provided for all absorption sections 21.

[0043] Figure 9 is a block diagram showing the configuration of the control system of the inkjet printing apparatus according to this embodiment. The control unit 50 includes a CPU (Central Processing Unit) and storage media such as semiconductor memory and a hard disk, and controls the entire inkjet printing apparatus. The control unit 50 controls the operation of each part of the inkjet printing apparatus by executing a control program pre-stored in the storage media such as the semiconductor memory or hard disk, and by operating electrical circuits.

[0044] In particular, the control unit 50 controls the transport unit 2 to transport the printing medium P, and controls the inkjet heads 16a to 16f of each line head 11 to 14 based on the image data to be printed, and performs printing by ejecting ink from each inkjet head 16a to 16f at a predetermined ejection timing.

[0045] Then, the control unit 50 performs the cleaning operation described above at a predetermined time other than the printing process. Specifically, the control unit 50 moves the cleaning unit 20 to the cleaning position described above. Next, the control unit 50 presses the porous member 21b against the nozzle surface 36a of each inkjet head 16a and performs purging by controlling each inkjet head 16a to 16f to eject a preset amount of ink.

[0046] The ink ejected from each inkjet head 16a to 16f by purging is absorbed by the porous material 21b pressed against each inkjet head 16a to 16f, thereby removing the ink from the nozzle surface 36a and the surface of the nozzle guard 32 of each inkjet head 16a to 16f.

[0047] Next, after purging, the control unit 50 controls the moving mechanism 22 to move the cleaning unit 20 to the standby position. Then, the control unit 50 controls the roller moving mechanism 24 to move the squeezing member 23 downward as shown in Figure 7B, thereby squeezing out the ink absorbed by the porous member 21b during purging. Finally, the control unit 50 controls the roller moving mechanism 24 to return the squeezing member 23 to the standby position.

[0048] The above describes the cleaning operation of this embodiment. The timing of the cleaning operation may be, for example, when the user gives an instruction using an input device (not shown), when the printing process has been performed on the printing medium P a predetermined number of times, or when the inkjet printer is powered on.

[0049] According to the inkjet printing apparatus of the above embodiment, since purging is performed with the porous member 21b in contact with the nozzle surface 36a, the cleaning operation can be performed without soiling the surroundings.

[0050] Furthermore, in the inkjet printing apparatus of the above embodiment, a squeezing member 23 is provided to squeeze the porous member 21b after purging, so that the porous member 21b can be used repeatedly.

[0051] Furthermore, in the above embodiment, ink is removed from the inkjet heads 16a to 16f by pressing the porous member 21b against the inkjet heads 16a to 16f during the cleaning operation. However, the surface of the inkjet heads 16a to 16f may also be wiped using the absorbent part 21.

[0052] Specifically, for example, with the porous member 21b pressed against the inkjet heads 16a to 16f as described above, the cleaning unit 20 may be moved vertically by the moving mechanism 22, thereby wiping the surface of the inkjet heads 16a to 16f with the porous member 21b. In this example, wiping is performed by moving the cleaning unit 20 vertically, but the head unit 10 may also be moved vertically.

[0053] As described above, after purging, the reliability of cleaning can be improved by moving the porous member 21b while it is in contact with the nozzle surface 36a and performing wiping.

[0054] Furthermore, when wiping using the porous member 21b as described above, the control unit 50 may control the amount of movement of the cleaning unit 20 to the right by the moving mechanism 22 so that the pressure of the porous member 21b against the nozzle surface 36a during wiping is greater than the pressure of the porous member 21b against the nozzle surface 36a during purging.

[0055] By controlling the pressure applied during wiping in this way, it is possible to prevent ink from being left behind.

[0056] Furthermore, although the above description describes purging with the porous member 21b pressed against the nozzle surface 36a and then moving the cleaning unit 20 in that state to perform wiping, the method is not limited to this. For example, after purging, the porous member 21b may be separated from the nozzle surface 36a of the inkjet head 16, the porous member 21b may be squeezed by the condensation member 23, and then the porous member 21b may be pressed against the nozzle surface 36a again, and the cleaning unit 20 may be moved to perform wiping.

[0057] Furthermore, regarding wiping, instead of using the porous member 21b of the absorbent section 21 as described above, a separate wiping mechanism having a wiper blade may be provided, and wiping may be performed by the wiper blade.

[0058] Furthermore, as the inkjet head 16, for example, as shown in Figure 10, one can be used that has two nozzle rows 38 and 39, and is capable of ejecting ink of different colors (for example, red and black) from each nozzle row 38 and 39. When using such an inkjet head 16, it is preferable that the porous member 21b of the absorption section 21 be provided separately for each nozzle row 38 and 39, as shown in Figure 11.

[0059] By separating the porous member 21b in this way, it is possible to prevent the inks from mixing.

[0060] Furthermore, in the cleaning operation of the above embodiment, purging is performed with the porous member 21b of the absorption unit 21 pressed against the inkjet head 16. However, if the amount of ink ejected from the inkjet head 16 is changed during purging, the pressure at which the porous member 21b is pressed against the inkjet head 16 may be changed according to the amount of ink. Specifically, for example, the amount of ink that the porous member 21b can absorb may be increased by reducing the pressing pressure as the amount of ink increases.

[0061] Furthermore, the stronger the pressing pressure, the more the porous material 21b is compressed, reducing the amount of ink it can absorb. Conversely, the weaker the pressing pressure, the less the porous material 21b is compressed, allowing it to absorb more ink.

[0062] Furthermore, the amount of ink used during purging can be changed, for example, to increase the amount of ink used during purging in cases where the normal amount of ink used during purging is insufficient to remove dirt from the nozzle surface 36a. This change is made in response to a setting input by the user using an input device (not shown).

[0063] As described above, if the pressure applied to the porous member 21b is changed according to the amount of ink during purging, the ink discharged during purging can be absorbed more reliably by the porous member 21b.

[0064] Furthermore, in the cleaning operation of the above embodiment, the porous member 21b may be impregnated with cleaning solution before it comes into contact with the nozzle surface 36a during purging. This can improve the dirt removal ability of the inkjet head 16.

[0065] As a mechanism for impregnating the porous member 21b with cleaning solution, for example, a cleaning tank containing cleaning solution may be provided and the porous member 21b may be immersed in the cleaning tank, or a mechanism may be provided to supply cleaning solution to the porous member 21b.

[0066] Furthermore, in the above embodiment, a squeezing member 23 is provided as a means to remove ink from the porous member 21b of the absorption section 21, but the invention is not limited to this, and a suction mechanism for sucking up the ink absorbed by the porous member 21b may also be provided.

[0067] It should be noted that the present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the embodiments described above. For example, all the components shown in the embodiments may be combined as appropriate. It goes without saying that various modifications and applications are possible without departing from the spirit of the invention.

[0068] The following additional information is disclosed regarding the cleaning apparatus of the present invention.

[0069] (Note 1) The cleaning apparatus of the present invention comprises a porous absorbent member that is pressed against a nozzle surface having multiple discharge holes of a nozzle for discharging liquid, a moving unit that moves the absorbent member or the nozzle surface in a direction away from the nozzle surface and the absorbent member, and a control unit that controls the moving unit to perform purging by discharging liquid from the nozzle surface while the absorbent member is in contact with the nozzle surface.

[0070] (Note 2) The cleaning apparatus described in Appendix 1 may be equipped with a squeezing member for squeezing the absorbent member after purging has been performed.

[0071] (Note 3) In the cleaning apparatus described in Appendix 1 or 2, the moving part can wipe by moving the absorbent member or nozzle surface while the absorbent member and nozzle surface are in contact after purging.

[0072] (Note 4) In the cleaning apparatus described in Appendix 3, the control unit can control the moving part so that the pressure of the absorbing member against the nozzle surface during wiping is greater than the pressure of the absorbing member against the nozzle surface during purging.

[0073] (Note 5) In the cleaning apparatus described in any of Appendix 1 to 4, the control unit can change the pressure of the absorbing member by controlling the moving part according to the amount of liquid discharged from the nozzle surface during purging.

[0074] (Note 6) In the cleaning apparatus described in any of Appendix 1 to 5, the nozzle surface can discharge liquid in a horizontal direction, and the moving part can move the absorbing member or nozzle surface in a horizontal direction during purging.

[0075] (Note 7) In the cleaning apparatus described in any of the appendices 1 to 6, the nozzle surface has a plurality of rows of discharge holes arranged therein, and different colored inks can be discharged as liquid from each of the plurality of rows of discharge holes, and an absorbent member can be provided separately for each row of discharge holes.

[0076] (Note 8) In the cleaning apparatus described in any of Appendix 1 to 7, the absorbing member can be impregnated with the cleaning solution before it comes into contact with the nozzle surface during purging. [Explanation of Symbols]

[0077] 1. Inkjet printing device main unit 2 Conveyor Units 3 Support stand 4. Conveyor belt section 10 Head Units 11-14 Line Head 16a~16f Inkjet Head 17 nozzles 20 Cleaning Units 20a~20d Absorbing material unit 21 Absorbent part 21a Base 21b Porous material 22 Moving mechanism 23. Restriction member 24 Roller moving mechanism 32 Nozzle Guard 36 Nozzle Plate 36a Nozzle surface 37 Discharge hole 38,39 Nozzle rows 40 gaps 41 Bottom plate 42 Side wall 46 Aperture 50 Control Unit P Print media Ps printing side

Claims

1. A porous absorbent member is pressed against the nozzle surface, which has multiple discharge holes arranged in a nozzle that discharges liquid, A moving part that moves the absorbent member or the nozzle surface in a direction that causes the nozzle surface and the absorbent member to move away from each other, A cleaning device comprising a control unit that controls the moving part to bring the absorbing member into contact with the nozzle surface and performs purging by discharging liquid from the nozzle surface.

2. The cleaning apparatus according to claim 1, further comprising a squeezing member for squeezing the absorbing member after the purging has been performed.

3. The cleaning apparatus according to claim 1, wherein the moving part moves the absorbing member or the nozzle surface while the absorbing member and the nozzle surface are in contact after the purging has been performed to wipe.

4. The cleaning apparatus according to claim 3, wherein the control unit controls the moving part such that the pressure of the absorbing member against the nozzle surface during wiping is greater than the pressure of the absorbing member against the nozzle surface during purging.

5. The cleaning apparatus according to claim 1, wherein the control unit controls the moving part according to the amount of liquid discharged from the nozzle surface during purging, thereby changing the pressure of the absorbing member against it.

6. The nozzle surface discharges the liquid in a horizontal direction. The cleaning apparatus according to claim 1, wherein the moving part moves the absorbing member or the nozzle surface horizontally during the purging.

7. The nozzle surface has a plurality of rows of discharge holes in which the discharge holes are arranged, and different colored inks are discharged as liquid from each of the plurality of rows of discharge holes. The cleaning apparatus according to claim 1, wherein the absorbing member is provided separately for each row of discharge holes.

8. The cleaning apparatus according to claim 1, wherein the absorbing member is impregnated with a cleaning solution before contacting the nozzle surface during the purging process.

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