In printing processes, marking material is applied onto substrates to form images. The images can be subjected to a combination of heating and applied pressure to fix the marking material to the substrates.
It would be desirable to provide fixing devices, printing apparatuses and methods for fixing marking material to a web that can provide adjustable contact pre-heating of the marking material for different web types.
Fixing devices for fixing marking material to a web, printing apparatuses and methods of fixing marking material to a web are provided. An exemplary embodiment of the fixing devices comprises a first roll including a heated outer surface; a second roll forming a fixing nip with the outer surface of the first roll at which a continuous web on which marking material is disposed is received; a third roll positioned to contact the web prior to entering the fixing nip; and an adjustment mechanism connected to the third roll, the adjustment mechanism being operable to move the third roll to vary a wrap length of the web contacting the outer surface of the first roll upstream from the fixing nip to control pre-heating of the web and marking material by contact with the outer surface prior to entering the fixing nip. The first roll and second roll are operable to apply heat and pressure to the pre-heated web and marking material at the fixing nip to fix the marking material to the web.
The disclosed embodiments include fixing devices for fixing marking material to a web. An exemplary embodiment of the fixing devices comprises a first roll including a heated outer surface; a second roll forming a fixing nip with the outer surface of the first roll at which a continuous web on which marking material is disposed is received; a third roll positioned to contact the web prior to entering the fixing nip; and an adjustment mechanism connected to the third roll. The adjustment mechanism is operable to move the third roll to vary a wrap length of the web contacting the outer surface of the first roll upstream from the fixing nip to control pre-heating of the web and marking material by contact with the outer surface prior to entering the fixing nip. The first roll and second roll are operable to apply heat and pressure to the pre-heated web and marking material at the fixing nip to fix the marking material to the web.
The disclosed embodiments further include printing apparatuses. An exemplary embodiment of the printing apparatuses comprises a marking device for applying marking material to a continuous web; and a fixing device downstream from the marking device for fixing the marking material to the web. The fixing device comprises a first roll including a heated outer surface; a second roll forming a fixing nip with the outer surface of the first roll at which the web is received; a third roll positioned to contact the web prior to entering the fixing nip; and an adjustment mechanism connected to the third roll. The adjustment mechanism is operable to move the third roll to vary a wrap length of the web contacting the outer surface of the first roll upstream from the fixing nip to control pre-heating of the web and marking material by contact with the outer surface prior to entering the fixing nip. The first roll and second roll are operable to apply heat and pressure to the pre-heated web and marking material at the fixing nip to fix the marking material to the web.
The disclosed embodiments further include methods of fixing marking material to a web. An exemplary embodiment of the methods comprises applying a marking material to a continuous web; feeding the web to a fixing nip formed by a heated outer surface of a first roll and a second roll; positioning a third roll on which the web is entrained upstream from the fixing nip with an adjustment mechanism connected to the third roll, the adjustment mechanism moving the third roll to vary a wrap length of the web contacting the outer surface of the first roll upstream from the fixing nip to control pre-heating of the web and marking material by contact with the outer surface of the first roll prior to entering the fixing nip; and applying heat and pressure to the pre-heated web and marking material at the fixing nip with the first roll and second roll to fix the marking material to the pre-heated web.
Printing processes can utilize dry toner materials to form images on substrates, such as paper. In such printing processes, the toner images can be fixed to the substrates by applying thermal energy and pressure to the images at a fixing nip. Substrates can be heated prior to entering a fixing nip using a non-contact heating device including a radiant heating device, such as flash lamps and radiant heaters, or a convective heating device, such as a forced hot air device. It has been noted that flash heating systems may need frequent replacement and costly filtration systems, and radiant heating may cause defects for coated substrates and exposed lamps may pose fire risks. Convective heating systems may have the disadvantage of lower heat transfer efficiency to substrates.
In light of these and other considerations, fixing devices for fixing marking material to a web are provided. The fixing devices utilize contact pre-heating of the web and marking material prior to final fixing of the marking material to the web at a nip by the use of applied thermal energy and pressure. By increasing the marking material/substrate temperature by pre-heating prior to entering the fixing nip, the fixing nip can then be operated at lower process conditions including lower temperature, lower pressure and/or shorter dwell time.
The web feeding device 120 comprises back tension rolls 122, 124, which produce controlled back tension in the web 102, i.e., braking action. Aligning rolls 126 (only one roll is shown) axially bias the web 102 to one side. A drive roll 130 is used to maintain a desired amount of tension in the web 102 and a desired speed of the web 102 through the printing apparatus 100. Idler rolls 128 support the web 102.
The illustrated marking device 140 includes marking stations 142, 144, 146 and 148 arranged in series along the process direction of the web 102. The marking stations 142, 144, 146 and 148 can, e.g., include a supply of a black, cyan, magenta and yellow marking material, respectively. The marking materials can be applied to the surface 104 of the web 102 to form a color image 150. The marking device 140 can also produce monochromatic images. The marking materials comprise toner, and can also comprise carriers and one or more additives to provide the desired properties to the marking material.
The fixing device 160 includes idler rolls 162 supporting the web 102. A fixing roll 164 and a pressure roll 166 form a fixing nip 169 through which the web 102 is advanced during printing. Typically, the fixing roll 164 is the drive roll. The fixing roll 164 and pressure roll 166 apply sufficient thermal energy and pressure to the web 102 at the nip to fix or fuse the image 150 to the web 102.
A pre-nip tension roll 168 is disposed directly upstream of the fixing roll 164 and pressure roll 166. The pre-nip tension roll 168 typically has a cylindrical configuration and can be a hard roll. An adjustment mechanism 170 is connected to the pre-nip tension roll 168. The adjustment mechanism 170 is operable to adjustably move the pre-nip tension roll 168 relative to the fixing nip 169. For example, the pre-nip tension roll 168 can be mounted to an arm, or the like, and the adjustment mechanism 170 can include a mechanism connected to the arm. The adjustment mechanism 170 can be connected to a controller (not shown) to control its operation.
The fixing device 160 further includes a post-nip tension roll 172. As shown, the post-nip tension roll 172 is adjustably movable to vary the amount of tension in the web 102 as depicted at 172′. A sub-drive roll 174 is further provided in the fixing device 160. The rotation speed of the sub-drive roll 174 is dependent on the position of the pre-nip tension roll 168.
By configuring the rolls in the fixing device 160 so that the roll immediately prior to the location of the web 102 wrap (i.e., the pre-nip tensioning roll 168) functions as the tensioning roll, space and the number of rolls effective to provide the desired fixing of marking material onto the continuous web 102 can be minimized in the fixing device 160.
As shown in
As shown in
When the wrap length of the web 102 is set, the pre-nip tension roll 168 can be positioned to adjust tension in the web 102 to the desired level. Adjusting the tension in the web 102 by moving the pre-nip tension roll 168 substantially does not affect the total energy transfer from the fixing roll 164 to the web 102 and marking material 160 in either the low-pressure nip formed by the web 102 wrap or the relatively high-pressure fixing nip 169 formed by the fixing roll 164 and pressure roll 166.
The fixing roll 164 can be internally and/or externally heated. For example, the fixing roll 164 can include at least one internal heating element 167, such as at least one axially-extending lamp, to heat the outer surface 165 to the desired temperature. In embodiments, the outer surface 165 can be comprised of a relatively-hard material, such as a metallic or ceramic material. For example, the fixing roll 164 can comprise an aluminum core and the outer surface 165 can be comprised of anodized aluminum. Although the web 102 is simultaneously present in the low-pressure nip defined by the wrap length L1 of the web 102 and the higher pressure fixing nip 169 formed by the fixing roll 164 and the pressure roll 166, the hard outer surface 165 is effective to minimize relative motion of the web 102 between these two nips and substantially eliminate stresses between these nips. Consequently, web defects including stretching, wrinkle and/or image smearing caused by relative motion of a web present in two nips can be minimized. In addition, stripping of the web 102 from the outer surface 165 is enhanced by the web 102 being actively pulled from the exit end of the fixing nip 169 by tension in the web 102.
The pressure roll 166 can comprise, e.g., a non-deformable core and at least one layer of a deformable polymeric material overlying the core and forming the outer surface 173. For example, the deformable material can be an elastomeric material, such as silicone rubber, or the like. In other embodiments, the pressure roll 166 can comprise a harder, less deformable polymeric material, such as polyurethane, or the like, overlying the core. The harder polymeric material can have a total thickness of about 1 mm to about 7 mm, for example. The harder polymeric material can be applied as a single layer, or as two or more layers. Different layers of multi-layer constructions can have a different composition and properties from each other, e.g., a different elastic modulus.
In the printing apparatus 100 with continuous feeding of the web 102, the type of web 102 that is run normally is not changed abruptly during printing. It is desirable to run the fixing roll 164 at about the same speed for different types of the web 102 that can be used in the printing apparatus 100. High printing speeds can be used in the printing apparatus 100 for all types of the web 102. The wrap length of the web 102 on the fixing roll 164 can be adjusted for each different type of the web 102 by positioning the pre-nip tension roll 168 at a selected position that provides a selected wrap length of the web 102. For example, for a heavy-weight web 102, the wrap length can be increased to the wrap length L3 (
Increasing the wrap length of the web 102 on the fixing roll 164 increases the amount of time (dwell) that the web 102 contacts the outer surface 165 of the fixing roll 164 before advancing to the fixing nip 169. Increasing the dwell increases the amount of thermal energy conducted from the heated outer surface 165 of the fixing roll 164 to the web 102 and marking material 150 before the web 102 advances to the fixing nip 169. Pre-heating the web 102 and marking material prior to entering the fixing nip 169 allows the fixing nip 169 to be operated at a lower temperature, pressure and/or dwell time (i.e., higher process speed), as compared to not using pre-heating. Some amount of fixing or fusing of the marking material 150 to the web 102 may occur during pre-heating, depending on the temperature reached. Final fixing or permanence of the marking material is achieved after the web 102 passes through the fixing nip 169.
In embodiments, the wrap length of the web 102 on the outer surface 165 of the fixing roll 164 can be varied to control image gloss by controlling the temperature reached by the marking material. Generally, increasing the wrap length increases gloss.
The web 102 may or may not be actively heated before it is advanced to the fixing roll 164. When the web 102 is not actively heated in such manner, the web 102 and marking material 150 are typically at about the ambient cavity temperature of the printing apparatus 100 when arriving at the fixing roll 164. The outer surface 165 of the fixing roll 164 typically can be heated to a temperature of about 50° C. to about 200° C. for fixing marking material on different types of the web 102. The pressure applied at the fixing nip 169 can typically be from about 50 psi to about 750 psi. At these temperatures of the outer surface 165, the temperature to which the web 102 and marking material 150 are pre-heated by contact with the outer surface 165 can be kept below about 125° C., such as less than about 100° C., i.e., the boiling point of water at standard conditions, by controlling the temperature of the fixing roll 164 and the wrap length of the web 102. When the marking material 150 is not heated to above 100° C., problems caused by the vaporization of water contained in print media, which include damage to the media (blistering) and/or damage to the images (e.g., blow-off or icicles), can be avoided in the fixing device 160.
As shown in
As shown in
In the fixing device 160, the use of contact pre-heating of the web 102 combined with use of a relatively lower temperature/higher pressure applied at the fixing nip 169 can facilitate the use of low-melting and ultra-low-melting toner materials characterized as having a melting temperature that is altered (lowered) by heating the toner to a temperature above a threshold temperature and then re-heating the toner having a lowered melting temperature. Exemplary ultra-low-melting toners having these characteristics comprise a crystalline polymer material, such as crystalline polyester material, and an amorphous polymer material, such as amorphous polyester material, with the amorphous material having a glass transition temperature (Tg) separate from the melting temperature (Tm) of the crystalline material. In these toners, the crystalline polymer material imparts a low melting temperature to the toner. Heating of the toner causes the crystalline material to plasticize the amorphous material, suppresses Tg of the amorphous material, and essentially eliminates Tm of the crystalline material. Exemplary toners having alterable melting temperature characteristics that may be used in the fixing device are disclosed in U.S. Pat. Nos. 7,402,371; 7,494,757 and 7,547,499, each of which is incorporated herein by reference in its entirety.
Toners having such temperature-alterable melting characteristics can be used in the fixing device 160 to further enhance the effectiveness of the conductive pre-heating of the web 102 and marking material in the fixing process. These toners can undergo a reduction in their melting temperature prior to fixing of the toner at the fixing nip 169. The amorphous polymer material can be plasticized by heating the toner to a temperature above a threshold temperature by pre-heating the web 102 and marking material at the web contact zone with the fixing roll 164, which lowers the melting temperature of the toner. As the web 102 is advanced to the fixing nip 169, additional thermal energy is applied to the web 102 and toner with the heated fixing roll 164. By lowering the toner melting temperature by this pre-heating, the process conditions of temperature, pressure and/or dwell can be lowered in the fixing nip 169.
It will be appreciated that various ones of the above-disclosed, as well as other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also, 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.
This application is related to the applications entitled “MULTI-STAGE FIXING SYSTEMS, PRINTING APPARATUSES AND METHODS OF FIXING MARKING MATERIAL TO SUBSTRATES” (Attorney Docket No. 056-0236); “FIXING DEVICES INCLUDING LOW-VISCOSITY RELEASE AGENT APPLICATOR SYSTEM AND METHODS OF FIXING MARKING MATERIAL TO SUBSTRATES” (Attorney Docket No. 056-0242); “FIXING DEVICES INCLUDING CONTACT PRE-HEATER AND METHODS OF FIXING MARKING MATERIAL TO SUBSTRATES” (Attorney Docket No. 056-0252); “FIXING SYSTEMS INCLUDING IMAGE CONDITIONER AND IMAGE PRE-HEATER AND METHODS OF FIXING MARKING MATERIAL TO SUBSTRATES” (Attorney Docket No. 056-0255); “FIXING DEVICES INCLUDING EXTENDED-LIFE COMPONENTS AND METHODS OF FIXING MARKING MATERIAL TO SUBSTRATES” (Attorney Docket No. 056-0271); and “LOW ADHESION COATINGS FOR IMAGE FIXING” (Attorney Docket No. 0010.0219), each of which is filed on the same date as the present application, commonly assigned to the assignee of the present application, and incorporated herein by reference in its entirety.