Patent Grant
8146529
1. Field of the Invention
The present invention relates to a liquid application apparatus and a printing apparatus, and more particularly, to a liquid application apparatus and a printing apparatus for applying a liquid to a printing medium for a predetermined purpose of accelerating coagulation of ink and the like.
2. Description of the Related Art
At present, spin coater, roll coater, bar coater, and die coater systems have been known as systems for applying a liquid or material in a liquid state to printing media to be printed by printing apparatuses. These systems assume continuously performing application to a relatively long applied medium. Therefore, when, for example, relatively small sized applying media are intermittently transferred and application is performed for these printing media, a uniform coating film may not be obtained for each applied medium due to disturbance in a coating bead at positions to start and end application thereof or the like.
As a method for solving such a problem, for example, Japanese Patent Laid-Open No. 2001-70858 discloses a method that uses a rotating rod bar in a die coater system. In the method using a rod bar, an application liquid is discharged from a discharging slit onto the rod bar to form a coating film on the rodbar. Then, the formed coating film contacts an applied medium to be transferred as a result of a rotation of the rod bar. In such a method, when the coating film formed on the rod bar is not transferred or applied to an applied medium, the application liquid returns into a head due to a rotation of the rod bar and is recovered via a recovering slit. More specifically, the rod bar continues to rotate even at the non-application time, and the application liquid has formed a coating film on the rod bar. This makes it possible, even when applying media are intermittently supplied and application is intermittently performed for those, to obtain a uniform coating film.
In addition, for example, Japanese Patent Laid-Open No. 2002-517341 discloses a technique which uses a doctor blade being in contact with a roller for accumulating an application liquid between the blade and roller, and imparts the application liquid to the roller as a result of a rotation of the roller. In the present technique, as a result of a rotation of the roller, the application liquid that has been imparted is transferred and applied to a support to be conveyed between the roller and another roller. Further, Japanese Patent Laid-Open No. H08-72227 (1996) discloses a mechanism that applies in advance a processing liquid (application liquid) to insolubilize a dye prior to printing. In the technique, the application liquid in a replenishment tank is drawn out by being adhered to a rotating roller, and the drawn-out application liquid is simultaneously applied to a printing medium.
According to each of the techniques disclosed in the above patent documents, while a rod bar or a roller rotates, an application liquid is imparted and supplied to the surface of the bar or roller. A part opened to the atmospheric air or communicated therewith performs the imparting and supplying. Therefore, the application liquid possibly evaporates. Moreover, when the apparatus is changed in posture, the application liquid may leak accordingly.
To cope therewith, it has been known to seal a part to impart and supply a liquid such as ink to a roller. In, for example, an apparatus disclosed in Japanese Patent Laid-Open No. H08-58069 (1996), an ink chamber having doctor blades is abutted against the peripheral surface of a roller to thereby form a liquid chamber (ink reservoir) with respect to the roller. This allows suppressing evaporation and leakage of the liquid.
Further, an apparatus disclosed in Japanese Patent Laid-Open No. 2005-254229 can, by abutting an annular-shaped member against a roller to form a hermetically-sealed region to hold an application liquid, prevent the liquid from evaporating.
However, in the application mechanisms disclosed in Japanese Patent Laid-Open No. H08-58069 (1996) and Japanese Patent Laid-Open No. 2005-254229, the application liquid is to remain on the doctor blade that scrapes away the application liquid or the seal plate. Although it is possible to reduce the same by utilizing an interval regulating plate or by using a water-repellent material, the application liquid remains in a nip portion between the application member and liquid chamber and the vicinity thereof. When the apparatus is kept stopped in this state for an extended period of time, the application liquid interposed between the application member and liquid chamber and in the vicinity thereof may be increased in viscosity so that the application liquid is fixedly adhered. In the case of an increase in viscosity and fixed adhesion of the application liquid in the nip portion between the application member and liquid chamber, a large amount of application liquid adheres to only a part, on the application member, corresponding to the nip portion with the liquid chamber, and it becomes difficult to form a uniform layer on the surface of the application member. Therefore, the application liquid may partially become nonuniform.
To cope therewith, a technique disclosed in Japanese Patent Laid-Open No. 2002-96452 discloses a unit for performing a roller rotating operation at regular time intervals in a standby state for a printing operation so as to prevent fixed adhesion. In a printing apparatus disclosed in Japanese Patent Laid-Open No. 2002-96452, by performing an idle rotation of a roller at regular time intervals during standby for a printing operation, an application liquid increased in viscosity that has been adhered on to the roller is returned to a normal viscosity. Then, by separating the opposed roller at the elapse of every regular time interval, the application liquid is suppressed from fixedly adhering to the nip portion.
However, according to the technique disclosed in Japanese Patent Laid-Open No. 2002-96452, since the operation is performed at the elapse of every regular time interval during standby, the longer the standby time, the more power consumption increases. Moreover, when the apparatus is left in a power off state, a mechanism such as a built-in power becomes necessary. Further, since the opposed roller is separated at the elapse of every regular time interval, a mechanism to separate the roller becomes necessary besides an ordinary application mechanism, so that the mechanism of an application apparatus is complicated, and it may be inevitable to increase the size of the apparatus.
The present invention has been made in view of the above problems, and it is an object of the present invention to provide a liquid application apparatus and a printing apparatus capable of performing stable application by efficiently removing an application liquid increased in viscosity and fixedly adhered to an abutting portion between an application member and a liquid supplying member, without providing a new mechanism.
In order to achieve the above-mentioned object, the present invention provides a liquid application apparatus including an application member that applies a liquid supplied to an applied face to a printing medium by rotating an application roller and a liquid holding member that abuts against the applied face to form a liquid holding space for holding the liquid, wherein the amount of liquid that is held in the liquid holding space and makes contact with the application member in unit time is larger before an applying operation for applying the liquid to the printing medium than in the applying operation.
According to the above apparatus, a liquid remaining and fixedly adhered between the application member and liquid holding member and in the vicinity thereof can be redissolved before an applying operation, and non-uniformity of a liquid to be adhered onto the surface of the application member can be suppressed. As a result, an even applying operation can be performed for a printing medium.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1. Liquid Applying Section
The liquid application unit includes a circular cylindrical application roller 1001, a circular cylindrical counter roller (medium support member) 1002 arranged opposed to the application roller 1001, and a roller drive mechanism 1003 that drives the application roller 1001. The roller drive mechanism 1003 is composed of a roller drive motor 1004 and a power transmission mechanism 1005 having a gear train or the like to transmit a driving force of the roller drive motor 1004 to the application roller 1001. The application roller 1001 and the counter roller 1002 are, respectively, freely rotatably attached, at their both ends, to an unillustrated frame, and freely rotatably supported by mutually parallel shafts.
The liquid supplying unit includes a liquid holding member 2001 that holds an application liquid between the same and the application roller 1001, and an unillustrated liquid flow path 3000 to be described later that supplies the liquid holding member 2001 with a liquid. The liquid holding member 2001 extends almost over the entire length of the application roller 1001 in the longitudinal direction. In addition, the liquid holding member 2001 is movably attached to the unillustrated frame via a mechanism that enables an approaching and separating operation with respect to the peripheral surface of the application roller 1001.
The counter roller 1002 is urged toward the peripheral surface of the application roller 1001 by a spring member 2006. Due to such a construction, by rotating the application roller 1001 in the direction of an arrow X, an applied medium P to be applied can be sandwiched between both rollers, and the applied medium P is transferred in the direction of an arrow Y.
Moreover, the liquid holding member 2001, when abutting by being urged against the peripheral surface of the application roller 1001 by an urging force of the spring member 2006, forms a long liquid holding space S that extends across the entire region of liquid application by the application roller 1001. Into the liquid holding space S, an application liquid is supplied from the liquid supply flow path 3000 to be described later via the liquid holding member 2001. The liquid holding member 2001 of the present embodiment can, when the application roller 1001 is in a stopped state, prevent or reduce unexpected outward leakage of the application liquid from the liquid holding space S. Also, the liquid holding member 2001 can simultaneously suppress evaporation of the liquid.
As shown in
As above, the liquid holding member 2001 of the present embodiment abuts, at the abutting member 2009 formed integrally without seams, against the outer peripheral surface of the application roller 1001 in a continuous state without a gap by an urging force of the spring member 2006. As a result, the liquid holding space S becomes a substantially blocked space formed by the abutting member 2009, one face of the space forming base material 2002, and the outer peripheral surface of the application roller 1001, and an application liquid is held in the space. In a state where rotation of the application roller 1001 has stopped, the abutting member 2009 and the outer peripheral surface of the application roller 1001 can maintain a liquid-tight state so as to reliably prevent the liquid from leaking outside. Also, in this case, an abutting state of the abutting member 2009 includes a state of abutting against the outer peripheral surface of the application roller 1001 via a film of the liquid formed by a capillary force, besides a state of direct contact of the abutting member 2009 with the outer peripheral surface of the application roller 1001. On the other hand, when the application roller 1001 rotates, the application liquid slides away between the outer peripheral surface of the application roller 1001 and the abutting member 2009, and adheres to the outer peripheral surface of the application roller 1001 in a layer state.
Moreover, as shown in
For the space forming base material 2002, as shown in
2. Applying Liquid Flow Path and Liquid Circulating Section
Next, each element of an application liquid flow path and a liquid circulating section of the liquid application mechanism, which has been schematically described in the above, will be described in greater detail.
Also, the application liquid to be used in the present embodiment is a liquid used for the purpose of accelerating coagulation of pigment in the case of printing with an ink using the pigment as a coloring material. Examples of components of the liquid to be applied are as follows:
Water remainder, and
the viscosity of the application liquid is 5 cP to 6 cP (centipoise) at 25° C. Also, as a matter of course, the application liquid of the present invention is not limited thereto. For example, it is also possible to use, as the application liquid, a liquid containing a component to insolubilize or aggregate a dye. It is also possible to use, as the application liquid, a liquid containing a component to suppress an applied medium from curling (a phenomenon where the medium has a curved shape).
Moreover, when water is used for the liquid to be applied, slidability at an abutting part of the liquid holding member with respect to the application roller of the present embodiment is made satisfactory by making the liquid contain a component to lower surface tension. Examples of such a component of the liquid to be applied include glycerin and surfactant, which contain components to lower the surface tension of water.
(1) Flow Path Configuration
The tube 3101 and the tube 3102 that form the first flow path are provided with a first T-shaped flow path 3301 that couples three ports. The first T-shaped flow path 3301 is coupled with the buffer tank 3002 by the tube 3101. Further, a shutoff value 3201 that enables switching between communication and shutoff is provided at the side of a coupling port to be coupled with the tube 3101 further than a junction that couples the three ports. Moreover, the first T-shaped flow path 3301 couples another coupling port with a tube 3109. The tube 3109 is coupled to the buffer tank 3002 to communicate with the atmospheric air via the buffer tank 3002 and the atmospheric air communication port 3004.
Moreover, at the tube 3109 side of the first T-shaped flow path 3301, a shutoff value 3202 that enables switching between communication and shutoff is provided. Further, the first T-shaped flow path 3301 couples the other coupling port with the liquid supply port 2004 by the tube 3102. This structure of the first shutoff valve 3201, the second shutoff valve 3202, and the first T-shaped flow path 3301 makes it possible to select, by combination of communication and shutoff of the two shutoff valves, a coupling counterpart of the tube 3102 from the atmospheric air and the application liquid stored in the buffer tank 3002.
Further, in the second flow path, the tubes 3103, 3103a, 3104, and 3105, the liquid detection sensor Y001, and a pump 3007 to make the application liquid and air flow by force in the direction of the buffer tank 3002 within the present liquid flow path 3000 are arranged. Of the pump 3007, at a side where the application liquid flows in (hereinafter, referred to also as an “upstream side of the pump”), the tube 3104 is coupled. On the other hand, at a side of the pump 3007 where the application liquid flows out (hereinafter, referred to also as a “downstream side of the pump”), the tube 3105 is coupled. This tube 3105 couples the buffer tank 3002 and the pump 3007.
Coupling, the buffer tank 3002 and the space forming base material 2002 by these first and second flow paths and driving the pump 3007 allows supplying while circulating the application liquid in the buffer tank 3002 to the space forming base material 2002.
The liquid flow path 3000 further has a third flow path (replenishment flow path) that couples a replaceable replacement tank 3001 for storing the application liquid and the second flow path and a fourth flow path that couples the buffer tank 3002 and the replacement tank 3001. Also, the replacement tank 3001 is a tank having a larger capacity than that of the buffer tank 3002.
A tube 3106 included in the third flow path couples with the replacement tank 3001 via an injection needle-shaped first coupling port 3005 and a mount 3003 that forms a coupling flow path. More specifically, as a result of the injection needle-shaped first coupling port 3005 passing through a rubber 3501 provided at the bottom portion of the replacement tank 3001, the tube 3106 is coupled with the replacement tank 3001. The other port of the tube 3106 couples with a second T-shaped flow path 3302. In the present embodiment, the tube 3106 serves as a replenishment flow path to supply the application liquid from the replacement tank 3001 to the buffer tank 3002.
Moreover, the third flow path and the fourth flow path are formed of a material having not only a high water vapor barrier property but also flexibility, which is, for example, high-density polyethylene. This allows suppressing evaporation of the application liquid in the flow path to the minimum and improving assemblability of a printing apparatus loaded with the present circulating section.
The above-mentioned second T-shaped flow path 3302 includes, at the side of a coupling port to be coupled with the tube 3103a further than a junction that couples three ports, a third shutoff valve 3203 that enables switching between communication and shutoff of the tube 3103a and the second T-shaped flow path 3302. The second T-shaped flow path 3302 also includes, at the side of a coupling port to be coupled with the tube 3106 further than the junction, a fourth shutoff valve 3204 that enables switching between communication and shutoff of the tube 3106 and the second T-shaped flow path 3302.
This structure of the third shutoff valve 3203, the fourth shutoff valve 3204, and the second T-shaped flow path 3302 makes it possible to select, by combination of communication and shutoff of the two shutoff valves, a coupling counterpart of the tube 3104 from the replacement tank 3001 and the space forming base material 2002.
The fourth flow path includes tubes 3107 and 3108. The tube 3108 included in the fourth flow path couples with the replacement tank 3001 via an injection needle-shaped second coupling port 3006 and the mount 3003 that forms a coupling flow path. More specifically, as a result of the injection needle-shaped second coupling port 3006 passing through a rubber 3502 provided at the bottom portion of the replacement tank 3001, the tube 3108 is coupled with the replacement tank 3001. The replacement tank 3001 communicates with the buffer tank 3002 via a fifth shutoff valve 3205 that enables switching between communication and shutoff of the tube 3107 and the tube 3108.
Moreover, in the replacement tank 3001, an atmospheric air communication pipe 3001a is provided. The atmospheric air communication pipe 3001a is connected at its lower end to the second coupling port 3006, and the upper end is protruded into an air layer A of the replacement tank 3001. Such a construction allows, when the fifth shutoff valve 3205 is opened, to balance the internal pressure of the replacement tank 3001 with the open air without making an application liquid L in the replacement tank 3001 flow out to a circulation route. Providing the fourth flow path makes it unnecessary to provide an atmospheric air communication port in the replacement tank 3001. Moreover, providing the fourth flow path allows performing circulating replenishment when replenishing the buffer tank 3002 with the application liquid from the replacement tank 3001. When the application liquid remains in the buffer tank 3002 at the time of replenishment of the buffer tank 3002 with the application liquid, the remaining application liquid may be increased in viscosity due to evaporation etc. However, according to the present embodiment, the application liquid supplied to the buffer tank 3002 and the remaining application liquid dissolve into each other, and further, the mutually dissolved application liquid is sent to the replacement tank 3001 due to circulating replenishment. Accordingly, influence of evaporation in the buffer tank on the application liquid can be further reduced.
Moreover, in the present embodiment, the coupling ports into the replacement tank 3001 are formed in injection needle shapes, and the bottom portion of the replacement tank 3001 is sealed by the rubber, and thus evaporation of the application liquid in the replacement tank when the replacement tank has not been mounted can be suppressed.
Also, switching of each shutoff valve is performed by a control signal from the control section, whereby filling, supply, recovery, or the like of the application liquid is performed. Details of a concrete operation will be described later.
In the present embodiment, at the upstream side of the pump 3007, the recovery flow path and the replenishment flow path are joined, and performed is switching of coupling of the flow path leading to the pump 3007 with the recovery flow path and replenishment flow path. When the recovery flow path and the pump 3007 are coupled at the switching time, the replenishment flow path and the pump 3007 are not coupled. Accordingly, at this time, circulation of the application liquid and supply and recovery of the application liquid for the liquid holding space S can be performed, by the pump 3007, in the first flow path, the liquid holding space S, and the second flow path. On the other hand, when the replenishment flow path and the pump 3007 are coupled by switching, the recovery circuit and the pump 3007 are not coupled. Accordingly, at this time, via the third flow path, the buffer tank 3002 can be replenished with the application liquid from the replacement tank 3001.
As above, in the present embodiment, at the upstream side of the pump 3007, joining of the recovery flow path and the replenishment flow path and switching of these flow paths are performed, and either flow path not communicated with the pump 3007 is shut off from the pump 3007. Therefore, it becomes possible to perform control of the flow path having the buffer tank 3002 and the replacement tank 3001 by the single pump. More specifically, even when a buffer tank and a replacement tank are simultaneously arranged in an identical apparatus, it is not necessary to increase the number of pumps. Accordingly, since there is no need to add to the flow path and control section with an increase in the number of pumps, an increase in the number of components can be suppressed including the pump, which does not cause an increase in the size of the apparatus, and also leads to a reduction in cost.
Moreover, in the present embodiment, if the buffer tank 3002 and the replacement tank 3001 are provided in an identical apparatus, one pump is sufficient. Accordingly, even when a buffer tank is provided for the purpose of head differential control, members necessary for liquid application can be housed in an identical liquid application apparatus.
Further, in the present embodiment, since the application liquid is circulating through the first flow path, the liquid holding space S, the second flow path, and the buffer tank 3002 during an applying operation, dust clogging in the injection needle-shaped coupling port due to dust and paper powder, etc., mixed at the time of the applying operation can be avoided.
For realizing stabilization in the application amount of an application liquid onto the application roller 1001 from the liquid holding space S, it is desirable, even if an application liquid in a storage tank is consumed, to suppress fluctuation in head differential between the liquid level of the application liquid in the storage tank and the liquid holding space S. For suppressing such fluctuation in head differential resulting from consumption of the application liquid in the storage tank, it suffices to provide the storage tank with a small height. However, when considering the fact that the larger the amount of the application liquid that can be stored in the storage tank, the more preferable, for storing a larger amount of application liquid in the storage tank with a small height, the area of the bottom face thereof must be enlarged. This results in an increase in the size of the apparatus. Therefore, in the present embodiment, the replacement tank 3001 and the buffer tank 3002, which are different in roles, are used. More specifically, the buffer tank 3002 having a smaller capacity than that of the replacement tank 3001 and having a smaller height than that of, at least, the replacement tank 3001 is used to perform circulation, filling, and recovery of the application liquid for the liquid holding space S. Moreover, in the identical apparatus, a large amount of application liquid is stored by the replacement tank 3001 having a larger capacity than that of the buffer tank 3002. Since the capacity of the buffer tank 3002 is smaller than that of the replacement tank 3001, the time until the application liquid is used up is also quicker, however, replenishment of the buffer tank 3002 with the application liquid is performed as needed from the replacement tank 3001. As such, while setting the amount of the application liquid that can be stored in the apparatus large, the height of the storage tank (buffer tank) relating to filling, recovery, and circulation of the application liquid for the liquid holding space S can be reduced. As a result, even when the application liquid in the buffer tank 3002 is consumed, fluctuation in head differential between the liquid level of the application liquid in the buffer tank 3002 and the liquid holding space S can be suppressed. As a result, it becomes possible to stabilize the application amount of the application liquid by the application roller 1001.
Moreover, by suppressing fluctuation in head differential, wear of the application roller 1001 and the abutting member 2009 can be reduced. In the present embodiment, the pump 3007 is provided at a recovery side to the buffer tank 3002, and thus, when circulating the application liquid, the pressure at the liquid recovery port 2005 becomes relatively lower than that at the liquid supply port 2004, so that circulation by a decompression system is achieved. Accordingly, a negative pressure is generated in the liquid holding space S, and the negative pressure is increased as the head differential is increased. In the present embodiment, although the abutting member 2009 is pressed against the application roller 1001 by spring urging of the spring member 2006, because of an increase in negative pressure due to an increase in head differential, the pressing force is also increased. Due to the increase in pressing force, wear of an abutting portion between the application roller 1001 and the abutting member 2009 is also increased. However, in the present embodiment, since fluctuation in head differential can be suppressed, wear can be reduced, so that it becomes possible to improve durability of the application roller 1001 and the abutting member 2009.
(2) Control System
The control section 4000 is connected with an input operating section 4004 including a keyboard to input a predetermined command or data or the like or various types of switches and a display section 4005 that performs various displays including an input/setting state of the liquid application apparatus. Also, the control section 4000 is connected with a detecting section 4006 including a sensor for detecting a position of the applied medium and an operation state of each section. The aforementioned liquid detection sensor Y001 is a part of the detecting section 4006. Further, the control section 4000 is connected with the roller drive motor 1004, a pump drive motor 4009, and first to fifth switching valves 3201 to 3205 via drive circuits 4007, 4008, and 4011, respectively.
(3) Liquid Applying Operation Sequence
The combinations of opening and closing of the respective shutoff valves are provided as four combinations of “standing,” “replenishment,” “circulation,” and “recovery.” The control section 4000 selects a combination appropriate for the state of the apparatus, and sends a control signal to each shutoff valve so as to operate according to the selected combination.
Here, the “standing” means a state of the respective shutoff valves, during a non-operation time, where the application liquid has been recovered from the liquid holding space S. The “replenishment” means a state of the respective shutoff valves when replenishing the buffer tank 3002 with the application liquid from the replacement tank 3001. The “circulation” means a state of the respective shutoff valves when circulating the application liquid in the buffer tank 3002, the first flow path, the liquid holding space S, and the second flowpath. The “recovery” means a state of the respective shutoff valves when recovering the application liquid from the liquid holding space S into the buffer tank 3002.
Moreover, as the state of the “standing,” it is also possible to switch the second shutoff valve into a “close” state. In this case, since the liquid holding space S and the buffer tank 3002 are completely shut off, in any situation of the non-operation time, the application liquid in the buffer tank 3002 no longer intrudes into the liquid holding space S.
(3-1) Filling Process
Thereafter, while whether the liquid exists is monitored by the liquid detection sensor Y001, the pump 3007 is driven at a normal speed (step S12). By driving the pump 3007, the application liquid is supplied to the first flow path, the liquid holding space S, the tube 3103, and the liquid detection sensor Y001, in order. Then, when the flow path Y001a of the liquid detection sensor Y001 is filled with the application liquid, it is judged whether a state where the liquid is present has been detected by the liquid detection sensor Y001 (step S13). If the liquid is detected by the liquid detection sensor Y001, driving of the pump 3007 is stopped. In this case, since the application liquid has been supplied to the application roller 1001, application onto an applied medium becomes possible (step S16), and an applying operation is performed (step S17).
On the other hand, if a state where the liquid is present has not been detected by the liquid detection sensor Y001, the application roller is driven (step S14). More specifically, even when the pump 3007 is driven by a sufficient amount for filling the liquid detection sensor Y001 with the liquid, the liquid detection sensor Y001 may not be able to detect the presence of the liquid. The reason is, for example, a defect in the pump or circulation route. As another reason, the application liquid is increased in viscosity in the pump to reach a high viscous resistance, so that the pump does not normally function at a normal pump speed. As still another reason, the application liquid has been increased in viscosity in the circulation route, and the flow rate has been decreased. As a further reason, even when there is the application liquid in the flow path Y001a of the liquid detection sensor Y001, it is not detected that the liquid is present.
As above, when a state where the liquid is present has not been detected by the liquid detection sensor Y001 even when the pump 3007 is driven by a sufficient amount (step S13), the roller drive motor 1004 is driven to rotate the application roller 1001 (step S14). A drive load at this time is detected from a drive current of the roller drive motor 1004 or a PWM duty, etc. (step S15). If the load is less than a threshold value, it is judged that the application liquid exists in the liquid holding space S (step S16), and a subsequent applying operation is performed (step S17).
If the load is equal to or more than the threshold value (step S15), it is judged that the application liquid does not exist in the liquid holding space S, and the pump 3007 is again driven at a low speed so as to fill the application liquid (step S19). As a result, if the liquid detection sensor Y001 detects the presence of the application liquid, it is judged that the application liquid exists in the liquid holding space S (step S13, S16), and the process proceeds to a subsequent applying operation (step S17).
If a state where the liquid is present has not been detected by the liquid detection sensor Y001 even when driving of the pump 3007 is retried, the application roller 1001 is again driven (step S14), and a drive load of the roller drive motor 1004 is detected (step S15). If the drive load is less than the threshold value, it is judged that the application liquid exists in the liquid holding space S (step S16), and a subsequent applying operation is performed (step S17). On the other hand, if the drive load is again equal to or more than the threshold value, it is judged that some abnormality has occurred in the pump 3007 or the liquid flow path 3000, and a circulation system error is output through step S18 (step S20).
Also, in the present embodiment, when retrying driving of the pump 3007 in step S19, driving speed of the pump is changed. However, driving of the pump of the present invention may be retried at the same speed as that of driving of the pump 3007 in step S12. For example, when the driving speed is accelerated, a larger negative pressure can be generated by the pump, so that the flow velocity that has been decreased due to an increase in viscosity of the liquid can be increased. When the driving speed is decelerated, the pump can be almost normally functioned even when the application liquid has been increased in viscosity in the pump.
Alternatively, for driving of the roller drive motor 1004 in step S14, a preliminary operation for performing a conveying operation of a printing sheet can be used. The preliminary operation is, for example, an operation for removing a fixedly adhered liquid to be described later. This makes it unnecessary to add a new operation for detecting whether the application liquid exists in the liquid holding space S, which leads to a reduction in operating time.
(3-2) Replenishing Process
In step S1 of
In
The opening portion 3404 is not restricted in position in the vertical direction. The position in the vertical direction of the opening portion 3404 of the present embodiment is provided as a position shown in
As shown in
Also, as another construction, a sensor for detecting a water level lower in the direction of gravity than the position of the atmospheric air communication port 3401 may be installed in the buffer tank 3002. In this case, the fourth flow path becomes unnecessary. However, in consideration of the case where the sensor for detecting a water level breaks down, both of the fourth flow path and the above-mentioned sensor may be provided.
Also, another water level sensor may be installed at a side closer to the bottom face of the buffer tank than that of the sensor for detecting a water level lower in the direction of gravity than the position of the atmospheric air communication port 3401. In this case, since a state where the amount of liquid in the buffer tank has become small can be detected, it becomes possible to perform a replenishing process using the detection as a trigger.
Moreover, in the present embodiment, the end portion 3402 of the first flow path located in the buffer tank 3002 is located in the vicinity of the bottom portion of the buffer tank 3002. This allows suppressing the mixing of bubbles into the first flow path.
As above, the buffer tank 3002 according to the present embodiment has functions of not only management of the head differential, storage of the liquid, and management of the water level in the tank, but also deaeration.
(3-3) Applying Process
Referring again to
Then, an applied medium P is conveyed to a portion between the application roller 1001 and the counter roller 1002 by an applied medium feed mechanism 1006, and the applied medium P is inserted between these rollers. Concurrently therewith, the applied medium P is conveyed toward a paper discharge section of the application roller 1001 with a rotation of the application roller 1001 and the counter roller 1002 (step S5). In the course of the conveyance, the application liquid L applied to the outer peripheral surface of the application roller 1001 is, as shown in
In
The application liquid L remaining on the application roller 1001, against the pressing force of the abutting member 2009 of the liquid holding member 2001 toward the application roller 1001, slides away between the application roller 1001 and the upper edge portion 2010 of the abutting member 2009 and returns into the liquid holding space S. The application liquid L that has returned into the liquid holding space S is mixed with the application liquid L filled in the same space S.
The returning operation of the application liquid L is similarly performed also when the application roller 1001 is rotated in a state where the applied medium P does not exist as shown in
(3-4) Fixedly Adhered Liquid Removing Operation
In the following, the fixedly adhered liquid removing operation of the present embodiment will be described in detail.
In the present embodiment, in the returning operation of the application liquid described above, most of the application liquid slides away between the upper edge portion 2010 of the abutting member 2009 and the application roller 1001. However, some of the application liquid is scraped away by the upper edge portion 2010 of the abutting member 2009, and there is also an application liquid remaining in the nip portion between the application roller 1001 and the abutting member 2009 and the vicinity thereof. Moreover, the application liquid may be shaped into drops depending on the surface tension of the liquid. When the application liquid is left standing in this state for a long time, moisture in the application liquid evaporates, so that the application liquid increased in viscosity is interposed on the surface of the application roller 1001. Further, when the application liquid is kept standing, only a nonvolatile content in the application liquid remains, and a phenomenon that the application liquid is fixedly adhered to the nip portion between the application roller 1001 and the abutting member 2009 occurs. When an applying operation is executed in a state where the application liquid has been increased in viscosity or fixedly adhered, a large amount of application liquid adheres to only a part, on the application roller 1001, corresponding to the nip portion with the abutting member 2009. As a result, a uniform application liquid layer cannot be formed on the application roller 1001, and application onto the applied medium P becomes nonuniform.
To cope therewith, making, before an applying operation, the volume of the liquid being held in the liquid holding space S with which the application roller 1001 makes contact in unit time larger than that in the applying operation makes it possible to promote redissolution of the fixedly adhered application liquid.
In the present embodiment, by executing, before an applying operation, a rotating operation of the application roller 1001 at a low speed, in a state where the application liquid has been filled in the liquid holding space S, without passing the applied medium P (hereinafter, referred to also as a “fixedly adhered liquid removing operation”), nonuniform application is avoided. As shown in
Moreover, at the time of rotation of the application roller in the fixedly adhered liquid removing operation, the rotating operation amount of the application roller 1001 may be increased so as to increase the time for which the fixedly adhered liquid T contacts the application liquid L interposed in the liquid holding space S. In the case of the present embodiment, by increasing the rotating operation amount of the application roller 1001, a force to scrape away the fixedly adhered liquid T by the upper edge portion 2010 of the abutting member 2009 is secondarily added, and the rotating operation becomes more effective.
Data from which application uniformity has been confirmed, using the present embodiment, by varying the rotating operation speed and rotating operation amount of the application roller 1001 at the time of the fixedly adhered liquid removing operation is shown in Table 2. In the present table, shown are data when the peripheral speed and the number of rotations of the application roller 1001 were varied under conditions corresponding to when it was left standing for 60 hours and when left standing for 120 hours. “o” indicates that there is no problem in application uniformity, “Δ” indicates that there is a slight application non-uniformity, and “x” indicates that there is application non-uniformity. It can be understood from the results that, for the problem of application non-uniformity due to the fixedly adhered liquid T, the rotating operation of the application roller 1001 is effective when at a low speed and a large amount of rotation.
Moreover, when a standby time is provided in a state where the fixedly adhered liquid T on the application roller 1001 is in contact with the application liquid being held in the liquid holding space S (state shown in
Moreover, it is also effective to generate, in a state where the fixedly adhered liquid T is in contact with the application liquid being held in the liquid holding space S on the application roller 1001 (state shown in
In the present embodiment, during a fixedly adhered liquid removing operation, by using such a liquid supply unit to make the application liquid in the liquid holding member 2001 flow continuously or intermittently, redissolution of the fixedly adhered liquid T is accelerated. Since the liquid supply unit is a negative pressure circulating system, by increasing the speed of the pump 3007, the flow velocity in the liquid flow path 3000 and in the liquid holding space S is increased, and apparently, an abutting pressure of the liquid holding member 2001 against the application roller 1001 is increased. Therefore, secondarily, an effect to scrape away the fixedly adhered liquid T is enhanced.
The degree of increase in viscosity and fixed adhesion of the fixedly adhered liquid T varies depending on the standing time of the mechanism, as this is caused by evaporation of moisture of the application liquid L. The longer the standing time, the greater the degree of increase in viscosity and fixed adhesion is promoted. On the other hand, as described above, in the fixedly adhered liquid removing operation, although the lower the speed of rotation of the application roller 1001 or the longer the standby time, the greater the effect on removal of the fixedly adhered liquid is, there is also a disadvantage that the time to begin an applying operation is delayed. Therefore, when the standing time is short, the degree of fixed adhesion is also slight, and thus appropriately selecting the rotating speed or the amount of rotation of the application roller 1001 and the standby time makes it possible to shorten the fixedly adhered liquid removing operation in time.
More specifically, having an acquisition unit for acquiring information concerning the time of last driving, and calculating, by use of the acquisition unit, an elapsed time from that time at the time of a fixedly adhered liquid removing operation and selecting operation conditions according to a value thereof allows performing an effective fixedly adhered liquid removing operation.
In Table 3, shown are examples of a fixedly adhered liquid removing sequence in the present embodiment. In the present embodiment, an unillustrated electrical printing section is provided at a part of the control section 4000, the time where the applying operation has ended is stored in the printing section, and this is updated to the latest applying operation end time as needed. At the time of a fixedly adhered liquid removing operation, time of the last paper passing operation is acquired, an elapsed time from that time is calculated, and the rotating speed and the amount of rotation of the application roller 1001 are selected according to an output result thereof. Table 3 shows examples of the elapsed time and driving conditions of the application roller 1001. In the present embodiment, efficiency of the start-up time is improved while application uniformity is secured. In addition, the rotation speed of the pump 3007 is increased at the time of a fixedly adhered liquid removing operation to promote redissolution of the fixedly adhered liquid T.
Further, in the present embodiment, an operation to reduce the amount of the application liquid that will remain on the surface of the application roller 1001 (hereinafter, referred to also as a “remaining liquid reducing operation”) is performed after end of the applying operation for reducing the amount of the application liquid that will remain in the abutting portion between the application roller 1001 and the abutting member 2009. The slower the rotation speed of the application roller 1001, the less the application liquid adheres onto the application roller 1001 according to Newton's law of viscosity. Moreover, as described above, since the negative pressure value in the liquid holding space S is increased when the rotation speed of the pump 3007 is increased, the apparent abutting pressure of the abutting member 2009 against the application roller 1001 is increased, and the amount of the application liquid to flow out of the liquid holding member 2001 is reduced. Combining these operations allows greatly reducing the amount of the application liquid that will remain on the application roller 1001. As a result, the amount of the application liquid that remains between the application roller 1001 and the abutting member 2009 and in the vicinity thereof is reduced, so that the amount of the fixedly adhered liquid T can be reduced.
Also, even in a mechanism where no hermetically sealed space is formed, since the phenomenon of increase in viscosity occurs if there is a contact between the liquid level and application member, the above-mentioned unit is effective.
(3-5) Ending Process
Returning again to
Also, the pump 3007 may be stopped in synchronization with driving of the application roller 1001 in the fixedly adhered liquid removing operation, not stopping the pump 3007 in step S8.
Moreover, for the recovery operation, the respective shutoff valves are set to an opening and closing combination of “recovery,” and the pump 3007 is driven for a certain period of time. This opening and closing combinational lows the buffer tank 3002 to communicate with the liquid holding space S through the second flow path and the first flow path to communicate with a communication port 3004 being an atmospheric air communication port for the liquid holding space S. Thereby, the atmospheric air is supplied to the tube 3102, the liquid holding space S, the tube 3103, the tube 3104, the pump 3007, and the tube 3105, and the application liquid L that has been filled is recovered into the buffer tank 3002. By performing this recovery operation, evaporation of the application liquid from the liquid holding space S can be completely prevented or reduced.
Also, after the recovery operation, the respective shutoff valves are set to an opening and closing combination of “standing.” By this opening and closing combination, the replacement tank 3001, the buffer tank 3002, and the liquid holding space S are shut off from each other. Accordingly, a movement of the application liquid L between the tanks or outflow to the outside can be completely prevented or reduced even if the posture of the apparatus is tilted during movement, transportation, and the like.
Although, in the present embodiment, replenishment of the buffer tank 3002 with the application liquid from the replacement tank 3001 and circulation of the application liquid for the liquid holding space S are separately performed, these may be simultaneously performed. In this case, it suffices to close the second shutoff valve 3202 and open the first shutoff valve 3201 and the third shutoff valve 3203 to the fifth shutoff valve 3205.
Although, in the first embodiment, a description has been given of the liquid application apparatus, the present invention can also be applied to an inkjet printing apparatus including the liquid application apparatus described above.
Also, the printing apparatus of the present invention is not limited to a serial-type inkjet printing apparatus, but may be, for example, a so-called full line-type inkjet printing apparatus, which performs a printing operation using a long printing head with nozzles for ejecting ink disposed over the maximum width of a printing medium.
Moreover, the application liquid L to be used in the present embodiment is a processing liquid to accelerate coagulation of pigment in the case of printing with an ink using the pigment as a coloring material. Using a processing liquid as the application liquid allows making the processing liquid react with pigment that is the coloring material of an ink to be ejected to a printing medium P applied with the processing liquid so as to accelerate coagulation of the pigment. This insolubilization can improve the printing density. Further, it becomes possible to reduce or prevent bleeding. As a matter of course, the application liquid to be used in the inkjet printing apparatus is not limited to the example described above.
In the same figure, the processing in steps S101 and S103 to S105 and the processing in steps S108 to S110 are the same as the processing in step S1, S3 to S5, and S8 to S9 shown in
As shown in
After this applying process, a printing operation is performed for the printing medium applied with the application liquid at a part that needs application (step S106). More specifically, the printing head 7 is made to scan the printing medium P that is conveyed in predetermined amounts by the conveying roller 4, and ink is ejected from the nozzles according to the printing data in the course of the scanning and the ink thereby adhered to the printing medium to form dots thereon. Since the adhered ink reacts with the application liquid, it becomes possible to improve the density and prevent bleeding. By repeating the above conveyance of the printing medium and scanning with the printing head, printing is carried out for the printing medium P, and the printing medium for which printing has been completed is discharged onto the paper discharge tray 10. When it is judged in step S107 that printing has been completed, the processing in step S108 onward is performed, and the present process is completed.
In the present embodiment, with liquid application onto the printing medium, printing is sequentially performed onto parts thereof where the application has been completed. More specifically, this is an embodiment where the length of the conveyance path from the application roller to the printing head is shorter than the length of the printing medium, and when a part of the printing medium applied with the liquid reaches the scanning area by the printing head, application is performed by the application mechanism to another part of the printing medium. Owing to this embodiment, liquid application and printing are subsequently performed, for every predetermined amount of conveyance of the printing medium, at different parts of the printing medium. However, the present invention is not limited to such an embodiment, printing may be performed after application onto one printing medium is completed.
Also, in the printing apparatus of the present embodiment, the whiteness degree of the medium can be improved by applying a liquid containing a fluorescent whitening agent by the liquid application mechanism. In this case, the printing unit after liquid application is not limited to the inkjet printing method, but the effect can be obtained also by a printing method such as a thermal transfer method and an electrophotographic method. Also, when the present invention is applied to a printing apparatus by a silver-salt photographic method, a photosensitizing agent may be applied before printing.
That is, the present invention is by no means limited to being applied to an inkjet printing apparatus, but can be applied to any printing apparatus having a mechanism for applying a liquid such as a processing liquid to a printing medium.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2008-013066, filed Jan. 23, 2008 which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-013066 | Jan 2008 | JP | national |
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