Patent Application
20110261102
1. Field of the Invention
The present invention relates to a printing apparatus which makes prints with ink.
2. Description of the Related Art
Printing apparatus ink typically is dried at some point in the printing process to avoid streaking or “offsetting,” in which wet ink smears or transfers from one sheet to an adjacent sheet. Japanese Patent Laid-Open No. 2001-71474 discloses an inkjet image forming apparatus provided with a drying unit (i.e., a drying and fixing unit) for drying ink. In the drying unit, heated air is blown onto a sheet surface by an air blowing unit constituted by a heater and a fan. The blown air is collected in an air collecting chamber and is made to recirculate to the air blowing unit.
In the apparatus disclosed in Japanese Patent Laid-Open No. 2001-71474, air is made to circulate through a substantially closed space in the drying unit. When such an apparatus is used for long time continuous printing or high-duty printing with heavy ink consumption, the ink evaporates and generates steam, which stays in a circulation flow path. Thus, humidity in the air in the circulation flow path gradually increases. As humidity increases, dew-point temperature is raised. When sheet temperature is at or below the dew point, condensation occurs on a sheet surface, whereby the sheet becomes harder to dry and moisture content in the sheet increases. Thus, efficiency in drying the sheet decreases.
In addition, when the printing apparatus jams and conveyance of a sheet is stopped in a printing process, an operator should perform an unjamming operation by removing the sheet from the drying unit. However, workability of the operator in such an unjamming operation is not considered in the apparatus disclosed in Japanese Patent Laid-Open No. 2001-71474.
An apparatus according to the present invention includes a printing unit and a drying unit. The printing unit performs printing on a sheet using ink. The drying unit dries the sheet on which the ink is applied at the printing unit as the sheet is conveyed in the drying unit. The drying unit causes hot air heated by a heater to circulate through a housing and blows the hot air to the sheet. The housing includes an opening through which movement of gas between inside and outside the housing can be adjusted. When conveyance of the sheet in the drying unit stops, the apparatus is controlled to reduce an output of the heater and to increase the movement of the gas through the opening.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
One of the aspects of embodiments provides a printing apparatus that includes a drying unit that keeps high drying efficiency even after a long time continuous operation and has high energy utilization efficiency. One of the aspects of embodiments also provides a printing apparatus with excellent maintenance workability. With the printing apparatus, an operator can perform an unjamming operation promptly and properly when conveyance of a sheet is stopped due to, for example, a sheet jam in a drying unit.
According to the printing apparatus of the present embodiment, high drying efficiency can be kept even after a long time continuous operation and energy utilization efficiency is high. The printing apparatus of the present invention has excellent maintenance workability. An operator can perform an unjamming operation promptly and properly when conveyance of a sheet is stopped due to, for example, a sheet jam in a drying unit.
The present invention is widely applicable to printing apparatuses, such as a printer, a printer multi-functional peripheral, a copier, a facsimile machine and apparatuses for manufacturing various devices. Any printing system may be selected, including an inkjet printing system, an electrophotography printing system, a heat transfer printing system, a dot impact printing system and a liquid development printing system. The present invention is also applicable to other sheet processing devices which perform various processes that require drying of a continuous sheet (e.g., recording, processing, application, irradiation, reading and inspection).
The sheet feeding unit 1 supports and feeds a rolled-up continuous sheet. The sheet feeding unit 1 can accommodate rolls R1 and R2, one of which is selectively drawn and supplied. The number of rolls in not limited to two and one or three or more rolls may be accommodated. As long as it is continuous, the sheet is not necessarily rolled up. For example, a continuous sheet with perforations formed for each unit length may be folded at the perforations and stacked in the sheet feeding unit 1.
The decurling unit 2 reduces the curling (i.e., warping) of the sheet fed from the sheet feeding unit 1. In the decurling unit 2, the curling is reduced by applying decurling force to the curled sheet which is made to pass through two pairs of pinch rollers driven by a single driving roller such that the sheet might be curled in an opposite direction.
The skew correcting unit 3 corrects an skew (i.e., an inclination to a direction in which the sheet should travel) of the sheet which has passed through the decurling unit 2. The skew of the sheet is corrected by forcing a reference end of the sheet on a guide member.
While the sheet is being conveyed, the printing unit 4 makes printing on the sheet from above by print heads 14 and forms an image. The printing unit 4 also includes a plurality of conveying rollers which convey the sheet. Each of the print heads 14 is a linear printing head constituted by an array of inkjet nozzles disposed over the maximum width of a sheet expected to be used. A plurality of print heads 14 are arranged in parallel along the conveyance direction. In the present embodiment, seven print heads are provided for seven colors of cyan (C), magenta (M), yellow (Y), light cyan (LY), light magenta (LM), gray (G) and black (K). The numbers of the colors and the print heads are not limited to seven. The inkjet printing system may be, for example, a thermal inkjet printing system, a piezoelectric inkjet printing system, an electrostatic inkjet printing system and a MEMS inkjet printing system. Each of the colored ink is supplied to each print head 14 via an ink tube from an ink tank.
The inspection unit 5 optically reads, with a scanner, an inspection pattern and an image printed on the sheet in the printing unit 4, inspects, for example, a state of the nozzles of the print heads, a state of conveyance of the sheet and image positions and determines whether the image has been printed correctly. The scanner includes a CCD image sensor or a CMOS image sensor.
The cutting unit 6 includes a mechanical auto cutter which cuts the sheet after the printing to predetermined lengths. The cutting unit 6 also includes a plurality of conveying rollers which sends the sheet to subsequent next processes after the cutting.
The information recording unit 7 records print information (inherent information), such as a serial number and a printed date, on a non printed area of the cut sheet. Texts or codes are recorded by inkjet printing or heat transfer printing.
The drying unit 8 heats the sheet with an image formed thereon in the printing unit 4 and dries the applied ink in a short time. As the sheet passes through the drying unit 8, hot air is blown at least from below on the sheet and an ink-applied surface is dried.
The sheet conveyance path from the sheet feeding unit 1 to the drying unit 8 described above will be referred to as a first path. The first path turns around between the printing unit 4 and the drying unit 8. The cutting unit 6 is provided in the middle of the turning around portion.
The reverse unit 9 temporarily takes up the continuous sheet which has completed the printing on the front surface thereof and reverses the sheet for duplex printing. The reverse unit 9 is provided in the middle of a path established from the drying unit 8 to the printing unit 4 via the decurling unit 2 (i.e., a loop path; hereinafter, referred to as a “second path”) such that the sheet which passed through the drying unit 8 might be fed to the printing unit 4 again. The reverse unit 9 includes a winding rotary member (i.e., a drum) which rotates to winding the sheet. The continuous sheet which is still uncut after the printing on the front surface is temporarily taken up on the winding rotary member. After the sheet is taken up, the winding rotary member rotates in an opposite direction and the taken up sheet is fed to the decurling unit 2 and sent to the printing unit 4. Since the sheet has been reversed, printing can be made on a back surface of the sheet in the printing unit 4. Detailed description of the operation of the duplex printing will be given later.
The discharge conveying unit 10 conveys the sheet to the sorting unit 11 after the sheet is cut in the cutting unit 6 and dried in the drying unit 8. The discharge conveying unit 10 is provided in a path different from the second path on which the reverse unit 9 is provided (hereinafter, referred to as a “third path”). A path switching mechanism with a movable flapper is provided in a branching position of the paths for a selective guide of the sheet conveyed on the first path to either one of the second or third path.
The sorting unit 11 and the discharge unit 12 are provided at a side of the sheet feeding unit 1 and at an end of the third path. The sorting unit 11 sorts the printed sheet into groups as necessary. The sorted sheet is discharged to the discharge unit 12 which consists of a plurality of trays. As described above, the sheet is discharged along the third path which is disposed below the sheet feeding unit 1 and at a side of the sheet feeding unit 1 opposite to the printing unit 4 and the drying unit 8.
The decurling unit 2, the skew correcting unit 3, the printing unit 4, the inspection unit 5, the cutting unit 6, the information recording unit 7, the drying unit 8, the reverse unit 9 and the discharge conveying unit 10 are independent process units. In order to simplify the maintenance operation, such as an unjamming operation, the operator can manually draw an arbitrary unit independently from the main body of the printing apparatus.
Each of these units is provided with cutters for cutting the continuous sheet. The cutters are each provided in the upstream and the downstream of the sheet conveyance path near each of the units. The operator can use the cutter to cut the sheet near the upstream or downstream of the unit to be drawn for the unjamming operation, whereby the unit can be drawn easily. The cutters are hand cutters operated manually by the operator. The cutters are operated by hand of the operator or driven by an actuator in accordance with an instruction from the operator. As illustrated in
The control unit 13 manages the control of each component of the entire printing apparatus. The control unit 13 includes a CPU, a storage device, a control unit (i.e., a control unit) provided with various control units, an external interface and a manipulation unit 15 for the user input and output. The operation of the printing apparatus is controlled in accordance with instructions from a host device 16, such as a control unit or a host computer connected to the control unit via an external interface.
A dedicated processing section is provided for units that require high-speed data processing. The image processing unit 207 performs image processing of the print data processed in the printing apparatus. A color space (e.g., YCbCr) of the input image data is converted into a standard RGB color space (e.g., sRGB). Various image processing, such as resolution conversion, image analysis and image correction, is performed as necessary to the image data. The print data obtained through the image processing is stored in the RAM 203 or the HDD 204. The engine control unit 208 controls driving of the print head 14 of the printing unit 4 in accordance with the print data on the basis of the control commands received from, for example, the CPU 201. The engine control unit 208 also controls the conveyance mechanism of each component of the printing apparatus. The individual unit control unit 209 is a sub control unit which individually controls the sheet feeding unit 1, the decurling unit 2, the skew correcting unit 3, the inspection unit 5, the cutting unit 6, information recording unit 7, the drying unit 8, the reverse unit 9, the discharge conveying unit 10, the sorting unit 11 and the discharge unit 12. The individual unit control unit 209 controls the operation of each unit in accordance with the instructions from the CPU 201. The external interface 205 is a local I/F or a network I/F provided for connecting the control unit to the host device 16. The components described above are connected by system bus 210.
The host device 16 is a source of supply of image data to be printed on the printing apparatus. The host device 16 may be a general purpose computer or a dedicated computer, or may be dedicated image equipment, such as, a digital camera, a photograph storage device and an image capturer with an image reader. If the host device 16 is a computer, an OS, application software for generating the image data and a printing device driver for the printing apparatus are installed in a storage device of the computer. It is not necessary to implement all of these processes by software, but a part or all of them may be implemented by hardware.
Next, a basic operation for the printing will be described. The simplex printing mode and the duplex printing mode have different print operations, which will be described separately.
In the simplex printing mode, printing is made in the printing unit 4 on the front surface (i.e., the first surface) of the sheet which is fed from the sheet feeding unit 1 and processed in the decurling unit 2 and the skew correcting unit 3. Images of the predetermined unit length in the conveyance direction (i.e., unit images) are printed sequentially on the elongated continuous sheet and a plurality of images are formed and arranged. The printed sheet is made to pass through the inspection unit 5 and is cut for each unit image in the cutting unit 6. Print information is given on the back surface of the cut sheet as necessary in the information recording unit 7. The cut sheet is then conveyed to the drying unit 8 one at a time and is dried. The sheet is then conveyed via the discharge conveying unit 10 and is sequentially discharged and stacked in the discharge unit 12 of the sorting unit 11. The sheet left in the printing unit 4 after the last unit image is cut is made to return to the sheet feeding unit 1 and is taken up on the roll R1 or R2. In this manner, in the simplex printing mode, the sheet is conveyed along the first path and the third path for the processing and is not conveyed along the second path.
In the duplex printing mode, after a print sequence for the front surface (i.e., the first surface) is completed, a print sequence for the back surface (i.e., the second surface) is performed. First, in the print sequence for the front surface, the sheet feeding unit 1 to the inspection unit 5 each operate in the same manner as in the above-described simplex printing mode. The sheet is not cut in the cutting unit 6 and is conveyed as the continuous sheet to the drying unit 8. After the ink on the front surface is dried in the drying unit 8, the sheet is guided not to the path at the side of the discharge conveying unit 10 (i.e., the third path) but to the path at the side of the reverse unit 9 (i.e., the second path). The sheet is wound by the winding rotary member of the reverse unit 9 which is rotating in a forward direction (i.e., the counterclockwise direction in the drawing) in the second path. When all the scheduled printing on the front surface is completed in the printing unit 4, a trailing end of the printing area of the continuous sheet is cut in the cutting unit 6. The continuous sheet in the downstream of the conveyance direction (i.e., the printed side) from the cut position is completely taken up to the trailing end (i.e., the cut position) of the sheet in the reverse unit 9 via the drying unit 8. At the same time with the winding operation in the reverse unit 9, the continuous sheet left at the upstream side (i.e., the side of the printing unit 4) from the cut position in the conveyance direction is returned to the sheet feeding unit 1 and wound on the roll R1 or R2 such that the leading end of the sheet (i.e., the cut position) might not be left in the decurling unit 2. Such a back feeding system avoids collision with a sheet which is fed again for the subsequent print sequence for the back surface.
After the above-described print sequence for the front surface is completed, the print sequence for the back surface is started. The winding rotary member of the reverse unit 9 rotates in a reverse direction of the winding direction (i.e., a clockwise direction in the drawing). An end of the wound sheet (the trailing end of the sheet at the time of winding becomes the leading end of the sheet at the time of sending out) is sent to the decurling unit 2 along the path of the dashed line in
Next, the drying unit 8 in the thus-configured printing apparatus will be described in more detail.
The heating unit 42 causes the hot air to circulate through the housing of the drying unit 8 and blows the hot air on the sheet. The heating unit 42 includes a heater 36 and a fan 37. The heater 36 raises the temperature of (i.e., heats) the air and produces the hot air. The fan 37 causes the hot air to circulate and blows the hot air on the sheet. The hot air sent by the fan 37 is moved upward through a plurality of slit-shaped ejection ports 41 provided in positions corresponding to the clearances between the conveying rollers 35 and is blown on the sheet surface. The hot air is then returned to the fan 37 and is made to circulate through the housing. A temperature sensor 45, such as a thermistor, for detecting temperature of the hot air is provided on an inner wall surface of the housing near the ejection ports 41. A hygrometer 46 (i.e., a humidity detector) for detecting humidity of the hot air is provided near the temperature sensor 45. The humidity detector for detecting humidity information is not limited to that which directly detects humidity using a hygrometer. For example, humidity may also be indirectly detected by detecting temperature using a temperature sensor or by estimating humidity with parameters such as ink depth and printing duty.
A heat transfer plate 38 and a surface heating element 39 are provided as an integrated structure inside the conveying belt 34. Heat generated in the surface heating element 39 is transferred to the heat transfer plate 38 which is a thermal conductor. As the conveying belt 34 is rotated, the inner surface of the conveying belt 34 slides in surface contact with a surface of the heat transfer plate 38. Since the conveying belt 34 and the heat transfer plate 38 are in contact with each other, heat is transferred from the heat transfer plate 38 to the conveying belt 34 and the temperature of the entire conveying belt 34 increases. When the sheet is conveyed inside the drying unit 8, the outer surface of the conveying belt 34 is in surface contact with the sheet and the sheet is heated. Thus, the sheet is dried in an accelerated manner. That is, the sheet is dried highly efficiently by being heated from both surfaces. In particular, the heater 42 blows the hot air on the front surface and the conveyer belt 34 heats the sheet on the back surface.
The heating unit 42 and the conveying unit 43 are accommodated in the housing of the drying unit 8 which consists of a first housing segment 52 (i.e., an upper cover) and a second housing segment 53 (i.e., a main part of the housing). The heating unit 42 and the conveying unit 43 (i.e., the conveying roller 35) are partially held by the second housing segment 53. As described later, the first housing segment 52 and the second housing segment 53 are hinged together and can be disengaged as an alligator mouth such that the operator might access the inside the drying unit 8 easily.
A first sheet sensor 62 for detecting existence of the sheet is provided near an inlet of the sheet in the drying unit 8 (i.e., the upstream side when seen from the drying unit 8). A second sheet sensor 63 for detecting existence of the sheet is provided near an outlet of the sheet in the drying unit 8 (i.e., the downstream side when seen from the drying unit 8). These sheet sensors function as a part of a jam detector which detects occurrence of a jam during the conveyance of the sheet in the drying unit 8. A sensor (i.e., a drawing detector) which detects that the drying unit 8 has been drawn from the main body of the printing apparatus is provided in the main body of the printing apparatus. The seventh cutter 23 and the eighth cutter 24 each include a sensor (i.e., a sheet cutting detector) which detects operations of cutting the sheet S by each of the cutters. With the sensor, the control unit can recognize that the operator has operated the cutter.
Here, circulation of the hot air inside the drying unit 8 will be described.
As a variant example, the openings 50 and 51 may each include a fan which rotates at varying rotational state (i.e., with varying blowing capacity). The amount of movement of the gas can be adjusted by the rotational state of the fan. With active supply and exhaust ventilation using the fans provided in the openings, the air is ventilated in a shorter time. Although a functional separation is made between the introducing opening 50 and the exhausting opening 51 in this example, such a functional separation is not necessary: a single opening may alternatively be provided for both the introduction and exhaustion. Further alternatively, three or more openings may be provided.
When an air current is created by the fan 37, an upstream side of the fan 37 is slightly negatively pressurized and a downstream side of the fan 37 is slightly positively pressurized along the direction of the air current. In
If the temperature of the introduced ambient air is below the temperature of the air inside the drying unit 8, the temperature of the air inside the drying unit 8 will also decrease. Usually, since a relative temperature difference between the room temperature in which the printing apparatus is installed and the heated air in the drying unit 8 is large, the temperature of the air inside the drying unit 8 can be reduced rapidly. If the humidity of the introduced ambient air is below the humidity of the air inside the drying unit 8, the humidity of the air inside the drying unit 8 will also decrease. Usually, since a relative humidity difference between the humidity in the room in which the printing apparatus is installed and the inside the drying unit 8 is large, the humidity of the air inside the drying unit 8 can be reduced rapidly.
As illustrated in
When the drying unit 8 is drawn, the first housing segment 52 pivots about a distal hinge 54 as a rotation axis and the side of the operator opens as an alligator mouth. The opened first housing segment 52 keeps its open state by an urging mechanism (e.g., a gas spring, a hinge spring and a torsion spring). The first housing segment 52 holds an upper part of the conveyance mechanism of the drying unit 8 (i.e., the conveying belt 34, the heat transfer plate 38 and the surface heating element 39). The second housing segment 53 holds a lower part of the conveyance mechanism (i.e., the conveying roller 35). Thus, when the first housing segment 52 is opened, the conveyance mechanism is separated to expose the sheet S inserted between the conveying belt 34 and the conveying roller 35 whereby the operator can remove the sheet S easily.
Next, occurrence of a jam in the thus-configured printing apparatus and an accompanying unjamming operation will be described with reference to
Upon detection of occurrence of a jam by the jam detector, the control unit stops the driving motors of all the conveying rollers related to the conveyance of the sheet in the sheet conveyance path. This is for the purpose of limiting the influence of the jam within the place in which the jam occurred and avoiding the influence from extending to the rest of the components. The control unit displays the jammed place and instructions on a display device of the manipulation unit 15 or the host device 16 to encourage the operator to manually perform the unjamming operation. In response to the instructions, the operator performs a manual unjamming operation by manually removing the jammed sheet left in a troubled place.
In the following description, an example will be described in which a jam occurs in a region including the drying unit 8 in the printing sequence for the first surface in the duplex printing mode. In the printing sequence for the first surface in the duplex printing mode, the continuous sheet passes through the drying unit 8 (see
In the simplex printing mode or in the printing sequence for the second surface in the duplex printing mode, a sheet cut for each unit image in the cutting unit 6 is made to pass through the drying unit 8. If a jam occurs and the conveyance is stopped, the leading and trailing ends of the sheet left in the drying unit 8 are already cut. Thus, the operator can draw the drying unit 8 without the need of cutting the sheet using the hand cutter. That is, the sheet cutting operation illustrated in
A method of controlling the thus-configured drying unit 8 will be described. Occurrence of a jam of a sheet being conveyed in the drying unit 8 is detected by the above-described jam detector. Upon occurrence of a jam, the control unit decreases the output of the heater 36 of the heating unit 42 (i.e., turns the heater 36 off). At the same time, the control unit increases the amount of movement of the gas through the opening by increasing the opening (at least one of the openings 50 and 51). Due to a synergistic effect of stopping the heating by the heater 36 and the ventilation with ambient air through the opening, the air temperature inside the drying unit 8 decreases quickly. Accordingly, when the conveyance of the sheet is stopped in the drying unit, the operator can start the unjamming operation quickly. Thus, maintenance workability is improved. When the conveyance of the sheet is stopped by reasons other than the jam, similar operations can be performed.
If the temperature detected by the temperature detector becomes lower than the predetermined value at the time of such a rapid decrease in temperature, the control unit controls the amount of movement of the gas through the opening to be decreased by switching the opening (at least one of the openings 50 and 51) from the opened state to the closed state. Such a configuration prevents an unnecessary decrease in the temperature in the drying unit 8 and thereby shortens the standup time after the unjamming operation is completed and the printing is resumed. From another point of view, energy consumption in the drying unit 8 is reduced.
As described above, when a printing apparatus is used for long time continuous printing or high-duty printing with heavy ink consumption, humidity in the air inside the drying unit 8 increases while efficiency in drying the sheet decreases. Even if the air temperature is kept constant, as the humidity increases, the ink becomes harder to evaporate when the hot air is blown on the sheet. As a result, the humidity as well as the temperature should be managed. When the humidity detected by the humidity detector (e.g., the hygrometer 46) exceeds a first predetermined value during the printing process (i.e., during the operation of the drying unit 8), the control unit controls the opening (at least one of the openings 50 and 51) to be switched to the opened state. The ventilation of the air through the opening prevents an excessive increase in the humidity in the air inside the drying unit 8. However, as the humidity decreases, the temperature also decreases and it is possible that an excessive decrease in the temperature might impair the sheet drying performance in the drying unit 8. To address this problem, when the detected humidity is below a second predetermined value (which is smaller than the first predetermined value), the control unit controls the opening (at least one of the openings 50 and 51) to be switched to the closed state. With these operations, the humidity and the temperature of the air inside the drying unit 8 can be kept in suitable ranges after a long time continuous printing.
The main body of the printing apparatus includes a locking mechanism for operator safety. In a locked state, the locking mechanism prevents drawing of the drying unit 8. Since the temperature inside the drying unit 8 becomes high during the printing operation, the drying unit 8 is locked such that the operator cannot draw the same at least during the printing operation (i.e., during operation of the drying unit 8.). Upon detection of a jam, the lock is released under predetermined conditions to allow the operator to draw the drying unit 8. In order to satisfy the predetermined conditions, all of the following conditions should be satisfied.
(1) The jam detector detects a jam during the printing operation on the first surface in the duplex printing mode.
(2) The internal temperature of the drying unit 8 detected by the temperature detector is lower than a predetermined temperature.
In addition to the above conditions (1) and (2), the following conditions may be added such that the lock is released only after it is confirmed that the continuous sheet has been cut at two places. In this manner, the operator safety is enhanced.
(3) Both the first sheet sensor 62 and the second sheet sensor 63 detect the sheet.
(4) The sheet cutting detector detects that the seventh cutter 23 and the eighth cutter 24 have been operated.
The locking mechanism may alternatively lock the first housing segment 52 and the second housing segment 53 from opening. In this case, in addition to the above conditions (1) and (2), an additional condition will be given that the drawing detector detects that the drying unit 8 has been drawn.
According to the embodiment described above, high drying efficiency can be kept even after a long time continuous operation and energy utilization efficiency is high. The printing apparatus of the present invention has an excellent maintenance workability. An operator can perform an unjamming operation promptly and properly when conveyance of a sheet is stopped due to, for example, a sheet jam in a drying unit. Even if the continuous sheet is stopped over a unit upon occurrence of a jam during the printing process, the continuous sheet can be cut with a cutter and the unit can be drawn reliably. With this configuration, the operator can perform the unjamming operation with less time and effort. Thus, maintenance workability is improved.
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. 2010-099148 filed Apr. 22, 2010, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-099148 | Apr 2010 | JP | national |
