This disclosure relates generally to systems for cleaning image receiving surfaces in printers, and more particularly, to systems for cleaning image receiving surfaces in printers that treat the image receiving surface with surface preparation materials.
Some inkjet printing systems or printers that treat the image receiving surface with surface preparation materials include a cleaning device to remove certain materials from an image surface without removing all of the surface preparation material for the next printing cycle. Surface preparation material is any substance applied to the image receiving surface to enable an ink image to be formed on the surface and to facilitate the transfer of the ink image from the surface to media. Examples of a surface preparation material or a blanket coating include, but are not limited to, a skin coating, a fluid coating, a combination thereof, or the like. In some previously known systems, a blade cleaner is used to remove materials from the image surface. The materials removed from an image surface to replenish the ability of the image surface to form quality images include ink, surface preparation substances, media debris, and the like. Blade cleaners are effective because they can provide higher pressures on the imaging surface, but these pressures can result in a shorter life of the image forming surface and the blade cleaner. Additionally, blade cleaners need a higher blade load required to clean the image surface. The blade cleaners also have a poor reliability because they have a single cleaning edge that slides across a high friction elastomer blanket surface.
In some previously known system, a web cleaner is used to remove materials from the image surface. However, web cleaners have a high consumable cost of web materials and cost of disposal of the webs. While the fiber edges on the web can provide a better redundant cleaning with respect to the blade, the thinness of the web provides little volume for storing the detached ink as it is transported out of the cleaning nip. As such, a web cleaner must be translated through the nip at a rate to transport cleaned ink out of the nip faster than the rate at which the ink enters the nip. Additionally, the web cleaners also have a limited cleaning capacity. The limited ink capacity of webs makes them impractical in high ink density situations.
To address the issues related to blade and web cleaners, some previously known aqueous ink printing systems have used a foam roller that rotates against the movement of the image receiving surface to scruff and carry material away from the surface. In aqueous ink printing systems, the image receiving surface that is cleaned by the foam roller is a blanket of material wrapped around an endless support surface, such as a rotating drum or belt. To enhance the surface properties of the blanket so ink adheres to it during image formation and then releases the ink image during transfer to media, the blanket is treated with a surface preparation material that forms a skin on the blanket surface. This surface preparation material is applied to the surface of the blanket after the ink image has been transferred to media and the blanket surface has been cleaned of the skin and residual ink from the previous imaging cycle. Ideally, the pressure of the foam roller should split and remove the ink layer while only hydrating the skin layer so it can be replenished. If the pressure applied to the blanket by the foam roller is too high, however, the thin skin layer under the ink layer also splits. This splitting of the skin layer enables some of the loosened ink to contact the blanket surface, which has an affinity for the ink. Consequently, the ink adheres to the blanket surface and is harder to remove than ink on the skin preparation material. Thus, the cleaning of the blanket is adversely impacted and image quality can be affected in subsequent imaging cycles.
In certain previously known aqueous ink printing systems, the ink is dried to a semi-wet consistency to enable the transfer of the ink image onto media before the imaging surface is cleaned by the cleaning device. In most cases, the semi-wet ink is easier to clean since the density of the ink is small. However in certain cases, the ink is over-dried. Over-dried ink can occur regularly in machine operation due to machine faults. For example, faults such as media handling faults, control faults and other situations can result in the machine shutting down during the printing operation. The processing of these faults can leave the ink image under the dryers longer than desired. The extra drying can make the dried ink harder to clean. Over drying can also reduce efficiency of the ink image transfer to the media causing a larger amount of the harder-to-clean ink to be introduced to the cleaning device in the printer system. To compensate for the occurrence of these situations, a blade cleaner may be employed since the blade cleaner can apply the higher pressures required to remove dried ink with the attendant risks noted previously.
A printer cleaning device has been configured to enable the removal of material from an image receiving surface of a printer system. The printer cleaning device is included in the printing system that treats the image receiving surface with a surface preparation material. The printer cleaning device includes a roller having a cylindrical wall about an interior volume configured to hold a fluid. The cylindrical wall has a plurality of apertures to enable the fluid within the interior volume to pass through the cylindrical wall. The roller has an opening to enable the interior volume to be fluidly coupled to a source of fluid. The roller is configured to rotate about a longitudinal axis of the cylindrical wall. A foam material is configured to fit about the cylindrical wall and receive the fluid passing through the cylindrical wall. An actuator is operatively connected to the roller to move the roller into and out of engagement with the image receiving surface and a controller is operatively connected to the actuator, the controller being configured to operate the actuator to move the roller into and out of engagement with the image receiving surface to remove material from the surface selectively.
A new method for cleaning an image receiving surface treated with a surface preparation that enables removal of material from the image receiving surface of a printer system. The method includes providing a pump with a fluid to an interior volume within a cylindrical wall of a roller having apertures in the wall to enable the fluid to pass through the cylindrical wall, applying the fluid to the image receiving surface with a foam material mounted about the cylindrical wall, and operating the actuator with a controller to move the roller towards and away from the image receiving surface to enable the foam material to engage and disengage the image receiving surface and selectively remove material from the surface.
The foregoing aspects and other features of a printer cleaning device that enables the removal of a material are explained in the following description, taken in connection with the accompanying drawings.
For a general understanding of the present embodiments, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements.
The surface of the foam 112 of the roller 104 contacts with the image receiving surface of the blanket 124 to apply a portion of the fluid 148 onto the blanket 124 and hydrate materials 160 on the blanket 124. The foam 112 also selectively releases certain materials 160 from the surface of the blanket 124. The surface of the foam 112 contains open cells that function as tiny cleaning blades to release and wipe materials 160 from the surface of the blanket 124. These blades also provide a redundant scrubbing action on the surface of the blanket 124. The redundant scrubbing action by the foam 112 can provide a better reliability and cleaning of the surface of the blanket 124 at lower pressures than other cleaning systems such as a blade cleaner. The open cells in the foam 112 adjacent to the cells in contact with the surface of the blanket 124 also provide capacity to store the released materials 160 from the surface of the blanket 124. The foam 112 has the ability to store a greater amount of materials 160 compared to other cleaning systems such as a web cleaner. The retained materials 160 are flushed from the cells of the foam 112 using the fluid 148. A combination 128 of the materials 160 and fluid 148 flushed from the roller flow off or drip into a housing 152 surrounding the roller 104.
As the blanket 124 continues past the roller 104, a portion of the fluid 148 remains on the blanket 124. After interfacing with the roller 104, the blanket 124 reaches a wiper 120 that applies a blade with sufficient pressure to wipe excess fluid 148 from the surface of the blanket 124. As the wiper 120 wipes the fluid 148 from the surface of the blanket 124, it leaves a relatively dry surface on the blanket 124 before another skin layer is applied to the blanket 124 prior to another imaging cycle. The removed excess fluid flows off onto the roller 104 or into the housing 152.
The housing 152 channels the fluid combination 128 or the removed excess fluid 148 into a collection drain 160 at the bottom of the housing 152. The combination 128 and excess fluid 148 flows through the drain 160 and is transported through a filter 136 to separate the materials 160 from the fluid 148. A pump 144 pumps the filtered fluid 148 back into interior volume 108 of the roller 104. An additional fluid 148 from another source (not shown) can be provided to the interior volume 108 of the roller 104. The separated materials 160 from the filter 136 can be collected for disposal within, for example, the filter 136, a filter media inside the filter 124, a separate container 140, or the like.
In the illustrated embodiment, an actuator 110 is operatively connected to the roller 104 and a controller 114 is operatively connected to the actuator 110 to operate the actuator 110 and rotate the roller 104 in a direction opposite to the motion of the blanket 124. Alternatively, the roller 104 can freely rotate with the blanket so the roller 104 rotates in the direction of movement of the blanket. Another actuator 111 is operatively connected to the wiper 120 and the controller 114 is operatively connected to the actuator 111 to operate the actuator 111 and move the wiper 120 into and out of engagement with the blanket 124.
Materials can be any substance that is carried by the surface of the blanket 112 after the blanket 112 passes through the nip that transfers an image to media. Examples of materials 160 on the surface of the blanket 124 include, but are not limited to, aqueous ink, semi-dried aqueous ink, surface preparation material layers or skin layers, debris, combinations thereof, or the like. Ink can be any substance applied to the image receiving surface to produce an image that is transferred to media. Fluid 116 can be any substance that hydrates a material such as ink or a surface preparation material. Examples of the fluid 148 include, but are not limited to, water, a solvent, a dilate solution of a solvent with water, a dilate solution of a solvent with chemicals such as surfactants, or the like.
In one embodiment, the fluid 148 that is applied to the surface of the blanket 124 reduces the adhesion force of the ink on the surface of the blanket 124. Additionally, the open cell wall edges of the foam 112 apply a tangential force on the surface of the blanket 124 by providing a scrubbing action as the foam 112 slides across the surface of the blanket 124. This force detaches ink from the surface of the blanket 124 and transports the detached ink to the foam 112 and into the volume of the open cell structure of the foam 112. The fluid 148 then flushes the ink from the foam 112.
This force that detaches the ink from the surface of the blanket 124 can be increased by certain techniques that include, but are not limited to, increasing the roller 104 interference with the surface of the blanket 124, increasing the density of the pores in the foam 112, increasing the stiffness of the foam 112, increasing the rotational speed of the roller 104, or the like. The capacity of the foam 112 to absorb the detached ink from the surface of the blanket 124 can be modified by certain techniques that include, but are not limited to, changing the density of pores in the foam 112, changing the interference between the foam 112 and the surface of the blanket 124, the thickness of the open cell wall of the foam 112, and the rotational speed of the roller 104. The rotational speed of the roller 104 can also determine the effective cleaning nip against the surface of the blanket 124. Certain chemicals such as surfactants added to the fluid 148 can also reduce the adhesion of ink or other materials 160 with the surface of the blanket 124. These chemicals that reduce the adhesion of ink may also improve the ability to flush the ink from the foam 112. Other factors that influence the ability to flush ink from the foam 112 include, but are not limited to, the chemistry of the fluid 148 used, the flow rate of the fluid 148 through the foam 112, the adhesion of the ink to the foam 112. The adhesion of ink to the foam 112 depends on factors such as the chemistry of the ink and the foam 112. In one example, foam 112 is a hydrophobic foam because aqueous ink has a higher adhesion to hydrophilic foam than it does to hydrophobic foam. Consequently, aqueous ink is more easily removed from hydrophobic foam than from hydrophilic foam. Example 1 below and
Additionally, in one embodiment, the material of the foam 112 should be able to sufficiently retain the fluid 148. For example, if fluid 148 flows out of the foam 112 too easily, then the fluid 148 may run out of the bottom of the roller 104 and not provide adequate hydration to the surface of the blanket 124. If the fluid 148 is poorly retained in the foam 112, an excessive spray of the fluid 148 may occur at high rotational speeds of the roller 104. Certain foam materials can be used for the roller 104 that appropriately retain the fluid 148. For example, a foam with a high pore density may retain the fluid 148 better than a foam with a lower pore density.
The strength of the foam 112 may assist the roller 104 to avoid tearing and extend the life of the roller 104. Examples of foam materials that can be used include, but are not limited to, polyurethanes, which can have a good strength and wear resistance, or the like. The friction coefficient between the foam 112 and the material 160 or the surface of the blanket 124 may also affect the life of the roller 104. For example, a foam with a lower friction coefficient encounters less stress so the life of the roller 104 is extended. The amount of torque required to drive the roller 104 and the steering forces on the surface of the blanket 124 are also lower for foam having a lower friction coefficient. A lower torque reduces the strength requirements for the adhesive used to bind the foam 112 to the perforated cylindrical wall 116. Materials such as silicone foams can provide a lower friction coefficient than materials such as urethane foams, however, the silicone foams are usually made with closed cells.
The compression stiffness of the foam 112 can also influence the effectiveness of the roller 104. The cleaning load is generated by compressing the foam 112 on the roller 104 against the surface of the blanket 124 to form a cleaning nip. Stiffer foam generates the load required to clean the blanket with a narrower nip width than a softer foam. Factors that affect the compression stiffness of the foam 112 include, but are not limited to, the modulus of the foam material, the density of the pores in the foam, the thickness of the cell walls of the foam, or the like. When the foam 112 is saturated with the fluid 148, any compression of the foam 112 expels the fluid 148 from the foam 112. In one example, as the roller 104 enters the cleaning nip, the fluid 148 is expelled as the foam 112 is being compressed. As the roller 104 leaves the cleaning nip, the foam 112 expands and attempts to draw in fluid to fill the voids with the cells of the foam 112. The fluid 148 is pumped from within the interior volume 108 through the foam 112 to prevent the materials 160 from being drawn into the roller 104. A larger cleaning nip compresses a larger volume of the foam 112 and requires more flow of the fluid 148 through the roller 104. As such, to minimize the volume of wasted fluid 148 that is filtered, the width of the cleaning nip may be minimized while still maintaining a good cleaning. A stiffer foam 112 assists in minimizing the filtration needs of the system.
The resistance of the flow of the fluid 148 through the perforated cylindrical wall 116 and into the foam 112 can also influence the effectiveness of the roller 104. Factors that can influence the flow resistance of the fluid 148 through the roller 104 include, but are not limited to, thickness of the foam 112, the size of the perforation holes in the cylindrical wall 116, the spacing of the perforation holes in the cylindrical wall 116, the density of the pores in the foam 112, the internal structure of pores in the foam 112 (for example the thickness and surface area of the pores), or the like. In one example, a uniform distribution of the fluid 148 flowing from the perforations in the cylindrical wall 116 can provide an efficient roller 104. For example, if the spacing of the perforation holes in the cylindrical wall 116 is too small, then the cylindrical wall 116 may have insufficient area to reliably bond the foam 112 to the cylindrical wall 116. Too many perforation holes in the cylindrical wall 116 can enable the cylindrical wall 116 to become weaker and the cylindrical wall 116 may fracture if it bends as the roller 104 loads against the surface of the blanket 124. However, if the flow resistance of the foam 112 is too low, then a uniform flow of the fluid 148 through the perforations in the cylindrical wall 116 may be difficult to achieve because the fluid 148 can easily flow out of the perforations holes without much spreading. If the flow resistance of the foam 112 is too high, then excessive pressure may be required to achieve the desired rate of flow of the fluid 148 through the roller 104. A higher flow resistance of the foam 112 can also place additional stress across the thickness of the foam 112 that could lead to a failure of the foam 112 bonding with the cylindrical wall 116 or a tearing of the foam. In another example, the flow of the fluid 148 in the roller 104 is relatively high at very low pressures. The reader should understand that other techniques can be used to design the system 100 in order to provide the desired fluid 148 and the flow to the roller 104.
The dimensional stability of the foam 112 in the roller 104 can also influence the effectiveness of the roller 104. For example, certain foams 112 swell to different extents with different fluids 148. Foams, such as Capu-Cell, can significantly swell when saturated with water. When such a foam dries, it returns to its original size. As such, in one example, the roller 104 is designed by taking the amount of swelling into account. The reader should understand that the amount of swelling may change over time. For example, as the foam 112 in the roller 104 accumulates materials 160, such as ink and skin, the swelling characteristic of the foam 112 may change. With enough accumulated materials 160, the foam 112 in the roller 104 may not return to its original shape when the foam 112 dries. Accumulation of the materials 160 in the foam may also increase the stiffness of the foam 112.
Examples of the wiper 120 include, but are not limited to, an elastomer squeegee blade, a polyurethane blade such as Synztec 238707 70 Shore A durometer, xerographic blade, a urethane blade, a higher durometer polyurethane blade, a urethane blade, other elastomers or polymers that have a lower friction against the blanket 124, or the like. In one example, the wiper 120 can be mounted to a housing that operates the wiper 120 with interference loading or the wiper 120 can be mounted on a pivoting holder with a force loading against the blanket 124. Since the wiper 120 is wiping excess fluid 148 from the blanket 124, the load of the wiper 120 against the blanket 124 can be lower relative to a load required to clean materials 160 such as ink.
In one embodiment, the filter 136 can provide micro-filtration, ultra-filtration, nano-filtration, reverse osmosis, combinations thereof, or the like to separate the materials from the combination 128 of fluid 148 and materials 160. The filter 136 can include a porous filter media having very small pore sizes to separate the materials from the combination 128. In one example, different filter medias of varying pore sizes can be used to filter different materials from the combination 128. For example, the filter 136 includes very small pore sizes such as a pore size of about less than 0.01 μm. The filter 136 also includes a skin filter having a pore size of about less than 10 μm. For example, a 1 μm filter allows some smaller skin components to pass through and clogs relatively quickly with the larger components that are filtered. A larger pore size may be required to filter the skin because the components of the skin are larger and can clog the pores required to filter ink. In another example, a series of progressively smaller pore size filters are positioned inside the filter 136 to efficiently separate different materials from the combination 128. The reader should understand that these parameters are exemplary and other pore sizes or filter materials can be used to separate the materials from the combination 128. In one example, the pump 144 can be operated in reverse to pull filtered fluid from the interior volume 108 of the roller 104 and through the filter 136 to back-flush the filter and remove filtered materials from the filter media to enable reuse of the filter media. Alternatively, the filter can be back-flushed with other techniques that include, but are not limited to, using a machine, an external reclamation process, or removing and washing the filter media.
While a roller 104 is described herein, the reader should understand that other components can be used. Examples of these components include, but are not limited to, a foam pad, a sprayer, or the like to enable the fluid 148 to be dripped, sprayed, or dipped onto the surface of the blanket 124. While the foam 112 is described herein, the reader should understand that other materials 112 can be used to scrub the surface of the blanket 124 and store the removed materials 160 from the surface of the blanket 124. While a wiper 120 is described, the reader should understand that other components can be used to wipe or dry excess fluid 148 from the surface of the blanket 124.
The following example of the printer cleaning device 100 is to be considered illustrative in nature, and is not limiting in any way.
It will be appreciated that variations of the above-disclosed apparatus and other features, and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art, which are also intended to be encompassed by the following claims.
Number | Name | Date | Kind |
---|---|---|---|
3468248 | Giori | Sep 1969 | A |
20030156868 | Shin et al. | Aug 2003 | A1 |
20050034621 | McNeil | Feb 2005 | A1 |
20070212128 | Asakura | Sep 2007 | A1 |
20090317555 | Hori | Dec 2009 | A1 |
20100251916 | Peles et al. | Oct 2010 | A1 |
20120256979 | Gordon | Oct 2012 | A1 |
Number | Date | Country |
---|---|---|
2 075 648 | Jul 2009 | EP |
2 281 691 | Feb 2011 | EP |
1244901 | Sep 1971 | GB |
S58-82277 | May 1983 | JP |
2004-271833 | Sep 2004 | JP |
Number | Date | Country | |
---|---|---|---|
20160257147 A1 | Sep 2016 | US |