Patent Grant
7140605
1. Field of the Invention
The present invention relates to a sheet feeding apparatus and an image forming apparatus equipped with this sheet feeding apparatus, and particularly to a configuration for separating sheets that tend to stick to each other and feeding individual sheets.
2. Related Background Art
A conventional image forming apparatus, such as a copier or a printer, includes a sheet feeding apparatus wherein sheets stacked on sheet stacking means are sequentially fed, beginning with the uppermost sheet, by sheet feeding means, which is a pickup roller, and are separated by a sheet separating portion and individually supplied to an image forming portion.
Cut sheets, generally of high-quality paper or of a standard paper designated by a copier maker, are employed for the sequential feeding performed by a thus arranged sheet feeding apparatus. And to steadily separate and feed cut sheets individually, various sheet separating systems have been employed, such as a sheet separating pad system that, to prevent the double feeding of sheets, brings a friction member into contact with a feed roller.
As another separating system, there is a retard separating system wherein a separating portion is constituted by a feed roller, which is rotated in a sheet conveying direction, and a separating roller, which is driven at a predetermined torque in a direction opposite to the sheet conveying direction and which contacts the feed roller under a predetermined pressure, and wherein the separating portion passes only the uppermost sheet of a stack of sheets that is fed by a pickup roller, and returns, toward the sheet mounting means, other sheets that accompany the uppermost sheet, so that double feeding is prevented.
When one of the sheet separating systems, such as a retard separating system, is employed to steadily separate and individually feed sheets, a return torque and a pressurization force for a separation roller are optimized while taking the friction force of a sheet into account.
Recently, as the variety of types of sheets (recording media) has increased, the demand has likewise increased for the forming of images not only on very thick paper, OHP sheets and art films, but also on coated sheets, for which a surface coating process has been performed to obtain white and glossy colors that satisfy market demands for color.
However, when very thick paper is to be fed, it can not be picked up because the weight of the paper resists its conveyance, and a paper jam occurs. Further, when resin sheets, such as OHP sheets and art films, that tend to acquire a charge are to be fed in a low relative humidity environment, the surfaces of the sheets are gradually charged by rubbing against other sheets, and a Coulomb force causes then to attract to each other. As a result, either a sheet cannot be picked up, or the double feeding of sheets occurs.
Furthermore, a property of coated sheets the surfaces of which are covered with a coating material, is that when stacked they attract to each other, especially in a high relative humidity environment. Therefore, the coated sheets cannot be picked up individually, and the double feeding of sheets occurs.
The friction force exerted between the special sheets described above is equal to or smaller than the friction force for standard paper. However, in a low relative humidity environment, the attraction of resin sheets to each other is induced by an attractive force considerably stronger than the force generated by friction, and in a high relative humidity environment, the attraction of coated sheets to each other is induced by another attractive force that is considerably higher than the friction force. Therefore, the conventional separation system cannot perform individual sheet separation.
That is, since for the conventional sheet separation system only the friction force exerted between sheets is considered, this system cannot steadily separate individual sheets when an attractive force other than the friction force acts on sheets.
In order to eliminate the very high attractive force exerted between the sheets, conventionally, the printing industry and some copier manufacturers have adopted a sheet separation and feeding system as disclosed in Japanese Patent Application Laid-Open No. H11-005643. According to this system, individual sheets are raveled out in advance by blowing air against the side of a stack of sheets to remove attractions between sheets. In this state, the individual sheets are picked up, start with the uppermost, and are separated by a sheet separating portion located downstream. In the sheet separation and feeding system that comprises means (hereinafter referred to auxiliary raveling-out means) for blowing air against the side of a stack of sheets, the sheets (recording media) that tend to attract to each other are raveled out before the sheet feeding, and the attractions removed. Therefore, the efficiency of the sheet separation function is increased compared with the previously described system that relies only on the friction force.
The flow path moving means 157 includes a guide rail (not shown), used to support the air blowing means 71 so it is movable vertically; an electric motor 121; and a cam plate 123, which contacts the lower face of the air blowing means 71 and moves the air blowing means 71 vertically. In the flow path moving means 157, when the electric motor 121 is rotated, the air blowing means 71 is moved vertically by the cam plate 123, and accordingly, an air channel is moved vertically. Since the opening (air blowing port) of the air blowing means 71 has a constant predetermined opening dimension, the side of the sheet S is exposed at the opening as the air blowing means 71 is lowered. Then, the dimension of the opening is reduced, and the direction in which air is blown from the opening is narrowed. As a result, the sheets P are floated beginning with the uppermost sheet S, and the attraction between all the sheets S is removed. Another example sheet separating and feeding system for blowing air against the side of a stack of sheets is disclosed in Japanese Patent Application Laid-Open No. 2001-048366. According to this system, blown air is heated by a heater to remove humidity from the sheets P in order to reduce the attractive force between the sheets (coated sheets), especially in a high relative humidity environment.
However, for a sheet feeding apparatus that employs the sheet separation and feeding system for blowing air against the side of a sheet stack, when air is blown, especially in a low relative humidity environment, only part of the stacked sheets close to the air blowing port is dried.
When the sheets are only partially dried, the surface resistance on the sheet plane is uneven, and as a result, when a sheet is fed to the image forming portion of the image forming apparatus, this dry portion causes a transfer failure, and an image defect occurs. Especially for an electrophotographic system wherein the image forming portion employs an electrostatic charge to transfer a toner image to a sheet, since the transfer function is greatly affected by the surface resistance of the sheet, the uneven surface resistance causes an uneven image transfer, so that considerable image deterioration occurs and the obtained image is very unsatisfactory.
While taking these shortcomings into account, it is one objective of the present invention to provide a sheet feeding apparatus that can steadily separate and feed individual sheets without causing an image detect, such as a transfer failure, and an image forming apparatus employing this sheet feeding apparatus.
According to one aspect of the present invention, a sheet feeding apparatus for feeding sheets, comprises:
sheet feeding means for feeding sheets stacked on elevatable sheet stacking means,
air blowing means for blowing air against an end face of a sheet stack supported by the sheet stacking means;
sheet position detection means for detecting that a top face of the sheet stack has reached a sheet feeding position whereat a sheet feeding operation by the sheet feeding means is enabled,
wherein, after a predetermined waiting time that a sheet is not actually fed by said sheet feeding means has elapsed since the sheet position detection means has detected that the top face of the sheet stack has reached the sheet feeding position, or since the sheet feeding means has finished the sheet feeding operation, the air blowing means starts an air blowing operation during a predetermined air blowing period.
According to another aspect of the invention, a sheet feeding apparatus for feeding sheets comprises:
a elevatable lifter support on which a stack of sheets is mounted;
a pickup roller for conveying the sheets from the lifter support;
an air blow opening located opposite an end face of the sheet stack mounted on the lifter support;
a fan for blowing air from the air blow opening; and
a paper position sensor for detecting that a top face of an uppermost sheet of the sheet stack on said lifter support has reached a sheet feeding position whereat a sheet feeding operation is enabled,
wherein, after a predetermined waiting time that a sheet is not fed by said pickup roller has elapsed since the paper position sensor has detected that the top face of the uppermost sheet on the sheet stack has reached the sheet feeding position, or since the pickup roller has finished the sheet feeding operation, the fan blows air during a predetermined air blowing period.
The preferred embodiment of the present invention will now be described in detail while referring to the accompanying drawings.
In
The scanner 2000 for reading a document includes an optical scanning system light source 201, an original glass 2020, a document pressing plate 203 that is opened and closed, a lens 203, a light-receiving (photo-electric) device 205, an image processing portion 206, and a memory portion 208 used to store image processing signals obtained by the image processing portion 206.
To read a document, the optical scanning system light source 201 emits light to illuminate a document (not shown) placed on the original glass 202. The obtained document image is processed by the image processing portion 206, and is converted into an electric signal 207, which is an electrical code, and the electric signal 207 is transmitted to a laser scanner 111a that serves as image production means. The image data that are encoded by the image processing portion 206 may be temporarily stored in the memory portion 208, and in accordance with a signal transmitted by a controller 120, which will be described later, the image data may be transmitted to the laser scanner 111a, as needed.
The printer main body 1001 includes: a sheet feeding apparatus 1002, for feeding a sheet S; a sheet conveying apparatus 1004, for conveying, to an image forming portion 1003, the sheet S received from the sheet feeding apparatus 1002; and a controller 120, which serves as control means for the printer 1000.
The sheet feeding apparatus 1002 includes cassettes 100, pickup rollers 101, and separating portions constituted by feed rollers 102 and retard rollers 103. The sheets S in the cassettes 100 are separated individually and fed by the pickup rollers 101, which are elevated/rotated at a predetermined timing, and the separating portions. Further, sheet feeding sensors 104 are located downstream, in the sheet conveying direction, in the vicinities of the feed rollers 102 and the retard rollers 103. The sheet feeding sensors 104 detect the passage of sheets S.
Cassette storage portions 1005, wherein the cassettes 100 are stored, are provided in the lower portion of the printer main body 1001. Partitions 106 and 107 delimit the cassette storage portions 1005, and are closed at a predetermined tightness. Temperature and humidity sensors 108, which are provided for the individual cassettes 1005, are means for detecting the temperature and humidity in the vicinities of the cassettes 100 stored in the cassette storage portions 1005. These sensors 108 can independently detect the temperatures and humidities in the cassette storage portions 1005.
A large capacity paper deck 1010 is detachably mounted as an option. A sheet feeding apparatus 1002 and a lifter support (not shown) are provided for the paper deck 1010, as well as for the printer main body 1001. The paper deck 1010 is closed at a predetermined tightness, and a temperature and humidity sensor 108 is provided to detect the temperature and the humidity in the paper deck 1010.
The sheet conveying apparatus 1004 includes conveying roller pairs 105 and a registration roller portion constituted by a pre-registration roller pair 130 and a registration roller pair 110. A sheet S, fed by the sheet feeding apparatus 1002, is conveyed by the conveying roller pair 105 along a sheet conveying path 1008 formed by a guide plate, and is introduced to the registration roller pair 110. Thereafter, the sheet S is conveyed by the registration roller pair 110 to the image forming portion 1003.
The image forming portion 1003 includes a photosensitive drum 112, the laser scanner 111a, a developing device 114, a transfer charging device 115, and a separating charging device 116. For image forming, a laser beam emitted by the laser scanner 111a is reflected by a mirror 113 and projected onto an exposure position 112a on the photosensitive drum 112, which is rotated clockwise. As a result, a latent image is formed on the photosensitive drum 112 and is thereafter visualized as a toner image by the developing device 114.
The toner image on the photosensitive drum 112 is transferred to the sheet S at the transfer portion 112b by the transfer charging device 115. The sheet S bearing the toner image is then electrostatically separated from the photosensitive drum 112, by the separating charging device 116, and is conveyed along a conveying belt 117 to a fixing apparatus 118 to fix the toner image. Thereafter, the resultant sheet P is discharged by discharging rollers 119. A sheet discharging sensor 119a, which detects the passage of the sheet P that is to be discharged, is located along the conveying path extending between the fixing apparatus 118 and the sheet discharging roller 119.
In this embodiment, the printer main body 1001 and the scanner 2000 are separate members; however, they may be integrally formed. Regardless of whether the printer main body 1001 is separately or integrally formed with the scanner 2000, the printer main body 1001 can either function as a copier when the laser scanner 111a receives a signal from the scanner 2000 or as a facsimile machine when a facsimile signal is received, or can also function as a printer when a signal is received from a personal computer.
Further, when a signal obtained by the image processing portion 206 of the scanner 2000 is to be transmitted to another facsimile machine, the printer main body 1001 can also function as a facsimile machine. In addition, an automatic document feeding apparatus 250, indicated by a dashed double-dotted line, may be mounted instead of the pressing plate 203, so that a document can be automatically read.
In
The cassette 100 can be pulled along rails 19 and 20 in
A detection signal obtained by the cassette attachment and detachment detection sensor 17 is transmitted to the controller 120, which employs the received detection signal to determine whether the cassette 100 is attached to the cassette storage portion 1005 or has been pulled out.
In each of the cassettes 100, as is shown in
For example, when a user stores a cassette 100 in which sheets S are mounted, and when the controller 120 detects this based on a signal received from the cassette attachment and detachment detection sensor 17, the controller 120 drives the lifter motor 18 to elevate the lifter support 16. Then, when the user pulls out the cassette 100 to set sheets S and the controller 120 detects this, based on a signal received from the cassette attachment and detachment detection sensor 17, and the controller 120 drives the lifter motor 18 to lower the lifter support 16 to a lower limit position.
At the upper portion of each of the cassette storage portions 1005, a sheet surface position detection sensor 15 is provided to determine whether the face of the uppermost sheet S1 mounted on the lifter support 16 is appropriately positioned for sheet feeding, i.e., to determine whether the face of the uppermost sheet has reached the sheet feeding position.
When the lifter support 16 is to be elevated, the rotation of the lifter motor 18 is continued until the sheet surface position detection sensor 15 detects the position of the face of the uppermost sheet S1. When the sheet surface position detection sensor 15 detects the uppermost sheet S1, the controller 120, based on a detection signal received from the sheet surface position detection sensor 15, halts the lifter motor 18. Through this processing, an appropriate height can be maintained for the sheet S1.
As the sheet feeding operation is initiated, the sheets S are sequentially fed, from the uppermost location, and as the height of the sheets is gradually reduced and the sheet surface position detection sensor 15 is turned off, the controller 120 drives the lifter motor 18 again to elevate the lifter support 16 Through-this processing, the height of the face of the uppermost sheet can be constantly controlled, within a predetermined range.
As is described above, for coated sheets, an attraction phenomenon occurs in high humidity. The clarification of an attraction mechanism, obtained by the present inventor, will now be explained.
As is apparent from in
Through various experiments conducted by the present inventor, the attraction mechanism for the coated sheets can be explicated as follows.
As is shown in
Since the reverse surface of the uppermost sheet S1 is less elongated than the obverse, as is shown in
When the moisture absorption occurs on the side edge portions of the sheet stack SA for sheets other than the uppermost sheet S1, the center of the sheet stack SA does not swell while the side edge portions do. Thus, the volume is increased in the direction of the thickness of the sheets, and a negative pressure is generated between the sheets that causes the sheets to attract to each other. This phenomenon is hereinafter called attraction through moisture absorption by the side edge portions.
Furthermore, as is shown in
As is described above, for the coated sheet attraction mechanism in high relative humidity are three types of attraction phenomena, the attraction through moisture absorption by the uppermost sheet, the attraction through moisture absorption by the side edge portions, and the attraction through chain deformation. Since these three attraction phenomena are caused by the swelling or the elongation of the coated sheets through moisture absorption, and the generation of a negative pressure, the attraction phenomena can be prevented and negative pressure removed by the flow of air between the coated sheets. Further, since the temperature of the air flow is increased, the coated sheets can be dehumidified and dried, and protected from swelling, and the phenomenon, where coated sheets again attract to each other, can be prevented.
Therefore, according to the embodiment, as is shown in
Between the fans 4 and 5 and the air duct ports 2a and 2b, shutters 10 and 11 are provided that are elevatable by a swing motor 13 and an elevating mechanism (not shown). As air is blown onto the sheets S, the shutters 10 and 11 are gradually swung vertically to direct the air so that it sequentially flows between the sheets S, and the effect produced by raveling-out the sheets is increased.
The fans 4 and 5 and the swing motor 13 are independently driven in accordance with signals transmitted, by the controller 120, via fan driver circuits 4a and 5a and a swing motor driver circuit 13a shown in
Furthermore, as is shown in
A thermistor 7a is attached to the heat sink 7 to detect the temperature of the surface of the heat sink 7, and a detection signal is transmitted by the thermistor 7a to the controller 120, as is shown in
As is shown in
In this case, when the rear ends of sheets S, such as the small sheets S2 shown in
Therefore, a sheet size detection sensor 14, as shown in
Through this process, a negative pressure is eliminated by flowing air between the sheets S, and the temperature of the air is increased to dehumidify and dry the wet, coated sheets, to prevent them from swelling and to prevent the occurrence of attraction.
The present inventor found through an experiment that, as the characteristic of the coated sheets, the attractive force reached its highest level immediately after a package of coated sheets was opened.
As is apparent from the measurement results shown in
Next, the present inventor supplied air at a high temperature to coated sheets that were attracted to each other, raveling-out the sheets, and measured the temporal change in the attractive force.
As is apparent from the measurement results shown in
Furthermore, in order to examine the affect on an image (transfer performance) when a coated sheet is partially dried using air at a high temperature, the present inventor blew warm air at 45° C. onto a coated sheet for one minute at a temperature of 30° C. and a relative humidity of 80%, and at a temperature of 5° C. and a relative humidity of 10%, and measured the water content in part of the coated sheet. As a result, in the environment at a temperature of 30° C. and a humidity of 80%, uneven water content was almost not observed, while in the environment at a temperature of 5° C. and a humidity of 10%, a considerably uneven water content was observed.
Further, when the image forming portion 1003 transferred an image to the coated sheet used in the environment at a temperature of 30° C. and a humidity of 80%, no problems occurred. However, when the image was transferred to the coated sheet used in the environment at a temperature of 5° C. and a humidity of 10%, the transfer performance was deteriorated at the portion having a small water content, and a satisfactory density could not be obtained.
That is, through the experiment performed by the present inventor, in an environment at a high temperature and a high humidity, the coated sheets absorb considerably moisture, and image forming is not affected by raveling-out these sheets using air at a high temperature. However, since the coated sheets do not attract to each other in an environment at a low temperature and a low humidity, the sheets need not be raveled out by air blown at a high temperature, and if air is blown onto the sheets, an image defect occurs.
The present inventor also found that an image detect due to a transfer failure in the low humid environment was correlated not only with the temperature of the air, but also with the period air was blown and the air flow rate.
Based on these obtained results, in this embodiment, the following arrangement is employed.
Since the coated sheets tend to attract to each other immediately after a package is opened, when a cassette 100 is loaded into the cassette storage portion 1005, and when the surface of the uppermost coated sheet is detected by the sheet surface detection sensor 14, i.e., when the stack of coated sheets reaches a position for sheet feeding, air blown to fan the sheets for a predetermined time T1 is enough. This operation is hereinafter called the initial swing operation.
Furthermore, before the sheet feeding is initiated, air is blown for a predetermined time T2 to sufficiently fan the sheets, This operation is hereinafter called a pre-job swing operation.
In addition, as is described above, since the coated sheets strongly attract to each other in a high relative humidity environment, and do not attract in a low relative humidity environment, the temperature of the heater 6 must be designated in accordance with the environment.
When a predetermined period, i.e., a period beginning after a cassette 100 is loaded into the cassette storage portion 1005 and is raised to the position for sheet feeding, and continuing until the sheet feeding operation is started, or a period beginning after that, since the sheet feeding operation initiated and continued until the next sheet feeding operation is started is long, the sheets may not be appropriately raveled out by the pre-job swing operation.
In this embodiment, therefore, a waiting operation interval T3, which is an operating interval time (waiting time) for the swing operation in the waiting state, is determined in accordance with the detection results obtained by the temperature and humidity sensor 108. When the waiting operation interval T3 has elapsed, air is blown during a waiting swing operation time T4. This operation is hereinafter called a swing operation on waiting. When the swing operation on waiting is repeated until the sheet feeding operation is started, the re-attraction as time elapses, which occurs while the sheet feeding apparatus 1002 is in the waiting state, can be eliminated.
The air blowing period control table for the initial swing operation and the pre-job swing operation, the heating temperature control table and the swing operation control table, which is a time control table shown in
When a sheet type input portion 21 included in an operating portion in
For resin sheets, such as OHP or art films, since attraction immediately after a package is opened or re-attraction as time elapses does not occur in a high relative humidity environment, the initial swing operation, the pre-job swing operation and the swing operation in the waiting state need not be performed. Further, since the attraction mechanism for these sheets is attraction due to charging, the air need not be heated by the heater 6. Therefore, a period required for temperature adjustment to be completed by the heater 6 can be removed.
Further, since standard sheets do not originally attract to each other, raveling-out of these sheets using air is not required during the sheet feeding operation. As is described above, since the initial swing operation, the pre-job swing operation, the swing operation in the waiting state, and the temperature control operation by the heater 6 are not performed if not necessary, the FCOT is quickly ready, and for a user, the usability of a printer can be increased.
The initial swing operation will now be described while referring to a flowchart in
When the cassette 100 is loaded into the cassette storage portion 1005, and when the cassette attachment and detachment detection sensor 17 detects this and is in the ON state (Y at step 1), the controller 120 rotates the lift motor 18 to raise the lifter support 16 (step 2). Then, the level of the sheet stack is gradually raised, together with the lifter support 16, until the sheet surface position detection sensor 15 detects the surface of the uppermost sheet and is set in the ON state (Y at step 3) Thereafter, the lift motor 18 is halted (step 4)
Next, the temperature and humidity sensor 108 detects the temperature and the humidity in the cassette storage portion 1005 (or the cassette 100) (step 5), and based on the temperature and humidity reading thus obtained, data for the temperature of the heater 6 and the initial swing time T1 are read from the control tables shown in
When the temperature control operation performed by the heater 6 is completed (Y step 7), the fans 4 and 5 and the swing motor 13 are turned on (step 8). Following which, when the initial swing time T1 obtained from the control table has elapsed (Y at step 9), the fans 4 and 5 and the swing motor 6 are turned off (halted) (step 10).
Through this processing, immediately after a package of coated sheets is opened, warm air can be blown onto the coated sheets to remove attractions, so that the coated sheets can be appropriately raveled out. As a result, a reliable sheet feeding apparatus can be provided that prevents the occurrence of a paper jam or double feeding. In addition, since the initial swing time T1 and the adjusted temperature are designated based on the optimal tables that have been determined, through experiment, to establish both the coated sheet raveling-out capability and the image quality, image deterioration, such as a transfer failure, does not occur.
When there is a possibility that the coated sheets are not appropriately raveled out during the initial swing operation, the job start instruction may be rejected until the initial swing operation has been completed, or a job may be started after the job start instruction has been accepted and the initial swing operation has been completed.
While referring to a flowchart in
When a user depresses a job start button, first, the temperature and humidity sensor 108 detects the temperature and the humidity in the cassette storage portion 1005 (the cassette 100) (step 21), and based on the obtained temperature and humidity, data for the pre-job swing time T2 and the adjusted temperature for the heater 6 are read from the control tables in
Thereafter, the controller 120 renders the heater 6 conductive to adjust the temperature of the heater 6, and when the temperature control operation for the heater 6 has been completed (Y at step 23), the fans 4 and 5 and the swing motor 13 are turned on to perform the pre-job swing operation (step 24). When the pre-job swing time T2 obtained from the control table has elapsed (Y at step 25), the sheet feeding operation is initiated (step 26). And when a predetermined job is terminated, i.e., when the final sheet for the job has been fed (Y at step 27), the fans 4 and 5 and the swing motor 13 are turned off (halted) (step 28).
Through this processing, before the sheet feeding operation is initiated for coated sheets that have been exposed from a package for a while; warm air can be blown onto the coated sheets to eliminate re-attraction, and the coated sheets can be appropriately raveled out.
Next, while referring to the flowchart in
When the above described initial swing operation in
Following this, a time 109 (see
For a case wherein there is a long waiting time since a sheet feeding operation was performed before the next sheet feeding operation is started, at step 27 in
Furthermore, the pre-job swing operation and the sheet feeding operation shown in the flowchart in
In the flowchart in
Since the fans 4 and 5 and the swing motor 13 are halted after the job swing operation halt time T5 has elapsed, the coated sheets can be appropriately and smoothly raveled out in the next pre-job swing operation.
As is described above, when a predetermined waiting time that a sheet is not fed has elapsed since it was detected that the sheets had reached the sheet feeding enabled position, or since the sheet feeding operation was finished, the air blowing operation need only be performed during a predetermined period to eliminate the attraction between the sheets that occurs while waiting for the sheet feeding operation. Thus, an image defect, such as an image failure, does not occur, and various types of sheets, such as coated sheets, OHP sheets, art films and very thick paper sheets, can be individually separated and fed. Further, the next sheet feeding operation can be performed smoothly. For each swing operation, only the air blowing operation may be performed while the vertical movements of the shutters 10 and 13 are halted.
In addition, since the temperature for the heater 6 is set in accordance with a signal received from the temperature and humidity sensor 108 located near the cassette 100, a satisfactory sheet feeding function and a high-quality image, without a defect such as an image failure, can be provided.
In this embodiment, the operation for the coated sheets has been explained in detail. However, the present invention is not limited to the coated sheets, and control tables may be prepared for OHP films, art films, very thick paper and other standard paper, in addition to the coated sheets for which the characteristic differs depending on the environment.
For example, as is described above, for an OHP file or an art film, since attraction in a low relative humidity environment occurs as a result of charging, air must be blown at a high flow rate in a low relative humidity environment, while since in a high relative humidity environment attraction by charging almost does not occur, air can be blown at a low flow rate. Further, since resin sheets do not absorb water, warm air is not required, and therefore, the heater can be turned off. In addition, since re-attraction as time elapses does not occur for these types of sheets, the swing operation in the waiting state need not be performed.
For very thick paper, the conveying resistance is increased by its own weight, and a pickup failure occurs. Thus, environmental dependency is not present, and the blowing of air is required in all environments. Further, since the attraction by moisture absorption does not occur for very thick paper, as well as the OHP, warm air is not required, and the heater can be turned off. Furthermore, since re-attraction as time elapses does not occur, the swing operation in the waiting state is not required.
As is described above, the optimal control tables for the heater temperature, the air flow rate and the air blowing period may be prepared for each type of sheet material, the sheet type input portion 21 shown in
Furthermore, a data input portion 22 in
In this embodiment, the fans 4 and 5 and the air duct ports 2a and 2b are located on the side (at one end in the direction of the width of a sheet) of a sheet stack that is mounted on the lifter support 16, and the air is blown onto the side end of the sheet stack. However, the present invention is not limited to this arrangement, and can be applied for a configuration wherein air duct ports are provided to the front, in the direction in which the mounted sheets are fed, and air is blown onto the front end of the sheet stack.
Furthermore, since the initial swing operation, the pre-job swing operation and the swing operation in the waiting state are performed for the sheet deck, a image defect such as an image failure does not occur, and the individual sheets can be appropriately separated and fed.
Further, although in this embodiment the retard system has been employed as sheet separating means, a Duplo system or an air feeding system may be employed.
This application claims priority from Japanese Patent Application No. 2003-301028 filed on Aug. 26, 2003, which is hereby incorporated by reference herein.
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| 2003-301028 | Aug 2003 | JP | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20050046104 A1 | Mar 2005 | US |
