Sheet feeding device

Information

  • Patent Grant
  • 6446960
  • Patent Number
    6,446,960
  • Date Filed
    Monday, March 6, 2000
    24 years ago
  • Date Issued
    Tuesday, September 10, 2002
    22 years ago
Abstract
Roller pairs comprise respective upper rollers and respective lower rollers. The lower rollers are associated with respective displacement members connected thereto. The displacement members have oblong holes defined therein, and eccentric shafts fixed to respective ends of a rotatable shaft connected to a motor are supported in the respective oblong holes. A transversely shifting mechanism has a pair of transversely shifting fingers for transversely pressing a recording sheet toward a center thereof, and a displacing mechanism for displacing the transversely shifting fingers. The displacing mechanism comprises a pair of racks disposed on transverse shifters movable back and forth in the transverse direction of the recording sheet, an a pinion held in mesh with the racks and rotatable by a motor. The transverse shifters have integral transversely shifting fingers, respectively, for pressing the recording sheet.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to a sheet feeding device, and more particularly to a sheet feeding device having a nip mechanism in a roller pair for feeding a sheet and a transversely shifting mechanism for transversely shifting a sheet.




2. Description of the Related Art




Generally, a roller pair of feeding a sheet comprises a fixed roller and a nip roller movable toward and away from the fixed roller.




Some sheet feeding devices comprise two roller pairs that are successively operated into open and closed positions. The nip rollers of the respective roller pairs are individually associated with respective displacing mechanisms for displacing the nip rollers. Because of these displacing mechanisms, the sheet feeding device are poor in durability and high in cost. The individual displacing mechanisms take up a large installation space, resulting in a difficulty in effectively utilizing an available space.




Heretofore, the sheet feeding devices have a positioning mechanism for transversely positioning a sheet. The positioning mechanism comprises a positioning plate extending along the direction in which to feed the sheet and a presser for pressing the sheet against the positioning plate. The positioning plate positions one side edge of the sheet. If the positioning mechanism is used to position a sheet in an apparatus for reading or recording images, then an image can accurately be read from or recorded on the sheet at a desired position thereon.




The positioning mechanism positions the sheet with respect to one of its side edges. Therefore, if sheets of different sizes are used in the image reading or recording apparatus, then a sheet is fed in a different position depending on the size of the sheet. At this time, the pressure applied to the rollers for feeding the sheet is brought out of transverse balance, with the result that the sheet may not be kept in an accurate position in its transverse direction.




SUMMARY OF THE INVENTION




It is therefore an object of the present invention to provide a sheet feeding device which is highly durable, can be manufactured inexpensively, and has a nip mechanism that allows an available space to be utilized effectively.




Another object of the present invention is to provide a sheet feeding device which is simple in structure and has a transversely shifting mechanism capable of positioning a sheet accurately in the transverse direction thereof.




The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a perspective view of an image recording apparatus according to an embodiment of the present invention;





FIG. 2

is a schematic vertical cross-sectional view showing structural details of the image recording apparatus illustrated in

FIG. 1

;





FIG. 3

is a perspective view of a transversely shifting mechanism of the image recording apparatus illustrated in

FIG. 1

;





FIG. 4

is a cross-sectional view of the transversely shifting mechanism shown in

FIG. 3

;





FIG. 5

is an enlarged fragmentary cross-sectional view of the transversely shifting mechanism shown in

FIG. 3

;





FIG. 6

is a side elevational view of the transversely shifting mechanism shown in

FIG. 3

; and





FIGS. 7A through 7D

are side elevational views showing a sequence of operations of the transversely shifting mechanism shown in FIG.


3


.











DESCRIPTION OF THE PREFERRED EMBODIMENT




A preferred embodiment of an image recording apparatus which incorporates a sheet feeding device according to the present invention will be described in detail below with reference to the accompanying drawings.




An image recording apparatus according to the embodiment of the present invention is a dry system in which a latent image on an image recording medium is developed into a visible image on dry development principles, i.e., without using developing liquid solutions, by the application of a laser beam to the image recording medium.




The following dry development principles (1) through (4) may be employed in the image recording apparatus.




(1) A photosensitive medium on which a latent image is formed is superposed on an image receiving medium, and the photosensitive medium and the image receiving medium are heated and, if necessary, simultaneously pressed together to transfer the latent image from the photosensitive medium to the image receiving medium (see, for example, Japanese laid-open patent publications Nos. 5-113629, 8-62803, 9-152705, 9-258404, 9-61978, 10-71740, 11-288070, 10-254111, and 11-84610).




(2) A photosensitive medium on which a latent image is formed is superposed on a processing medium, and the photosensitive medium and the processing medium are heated to develop the latent image into a visible image (see, for example, Japanese laid-open patent publications Nos. 9-274295 and 11-212230).




(3) After a latent image is formed on a photosensitive medium which has a photosensitive layer comprising a silver halide acting as a photocatalyst, a silver salt acting as an image forming substance, and a silver ion reducing agent, etc., all dispersed in a binder, the photosensitive medium is heated to a certain temperature to develop the latent image into a visible image (see, for example, “Thermally Processed Silver Systems”, D. Klosterboer, Imaging Processes and Materials, Neblette, 8th edition, edited by Sturge, V. Walworth, and A. Shepp, Chapter 9, Page 279, 1989, Research Disclosure 17029 (1978), EP803764A1, EP803765A1, and Japanese laid-open patent publication No. 8-211521).




(4) A photosensitive thermosensitive recording medium having a photosensitive thermosensitive recording layer comprising thermally responsive microcapsules which contain an electron-donative colorless dye, a compound having an electron acceptor and a polymerizable vinyl monomer in the same molecule, and a photopolymerization initiator is used (see, for example, Japanese laid-open patent publication No. 4-249251), or a photosensitive thermosensitive recording medium having a photosensitive thermosensitive recording layer comprising thermally responsive microcapsules which contain an electron-donative colorless dye, an electron-acceptive compound, a polymerizable vinyl monomer, and a photopolymerization initiator is used (see, for example, Japanese laid-open patent publication No. 4-211252).




In the processes (1) and (2) mentioned above, a small amount of water may be added to the photosensitive medium for accelerating the visualization of the latent image formed on the photosensitive medium.




In the description of the present embodiment, the photosensitive mediums and photosensitive thermosensitive recording mediums in the processes (1) through (4) will hereinafter be referred to collectively as a “thermal development photosensitive medium”.





FIG. 1

shows in perspective an image recording apparatus


10


according to the embodiment of the present invention.




The image recording apparatus


10


has a touch panel


14


in an upper left portion of a front wall of an apparatus housing


10


. The touch panel


14


serves as a control console operable by the operator for controlling the image recording apparatus


10


and a monitor for displaying information for the operator.




The front wall of the apparatus housing


12


has an openable and closable door


16


disposed below the touch panel


14


. When the door


16


is opened, the operator can access a sheet supply unit


22


, a pre-feeder


24


, an image recorder


26


, a transfer unit


28


, a thermal development unit


30


, and a sheet discharger


34


(described later on) disposed in the apparatus housing


12


, for servicing and maintenance.





FIG. 2

schematically shows structural details of the image recording apparatus


10


. The image recording apparatus


10


serves to record an image on a recording sheet


20


as an image recording medium which comprises a thermal development photosensitive medium. The image recording apparatus


10


has the sheet supply unit


22


, the pre-feeder


24


, the image recorder


26


, the transfer unit


28


, the thermal development unit


30


, and the sheet discharger


34


which are successively arranged along a feed path for the recording sheet


20


. The image recording apparatus


10


also has a controller


36


for controlling operation of the sheet supply unit


22


, the pre-feeder


24


, the image recorder


26


, the transfer unit


28


, the thermal development unit


30


, and the sheet discharger


34


.




The apparatus housing


12


has a chamber


42


defined substantially centrally therein by light-shield plates


40




a


,


40




b


,


40




c


. The sheet supply unit


22


is disposed in the chamber


42


.




The chamber


42


is vertically divided into an upper compartment


42




a


and a lower compartment


42




b


by the light-shield plate


40




b


. The upper compartment


42




a


houses therein an upper sheet loader


44




a


and an upper sheet feeder


46




a


, and the lower compartment


42




b


houses therein a lower sheet loader


44




b


and a lower sheet feeder


46




b.






Magazines


48




a


,


48




b


are removably mounted in the upper sheet loader


44




a


and the lower sheet loader


44




b


, respectively. Each of the magazines


48




a


,


48




b


contains a plurality of recording sheets


20


.




Usually, the magazines


48




a


,


48




b


contain recording sheets


20


of different sizes. For example, the magazine


48




a


contains recording sheets


20


having a size of 35.4 cm×43.0 cm or a size B


4


, and the magazine


48




b


contains recording sheets


20


having a size of 20.3 cm×25.4 cm.




As shown in

FIG. 1

, the door


16


has magazine loading/unloading slots


50




a


,


50




b


defined therein in vertically-spaced relationship. The magazines


48




a


,


48




b


can be inserted into and removed from the upper and lower sheet loaders


44




a


,


44




b


through the magazine loading/unloading slots


50




a


,


50




b


.




The magazines


48




a


,


48




b


have respective shutter insertion slots


52




a


,


52




b


defined in front faces thereof. Light-shield shutters


54




a


,


54




b


shown in

FIG. 2

are hung on the outer surface of a left side wall of the apparatus housing


12


. After the magazines


48




a


,


48




b


have been inserted into the upper and lower sheet loaders


44




a


,


44




b


, the operator manually inserts the light-shield shutters


54




a


,


54




b


respectively through the shutter insertion slots


52




a


,


52




b


and places them over the respective magazines


48




a


,


48




b.






The upper sheet feeder


46




a


and the lower sheet feeder


46




b


, which are located in respective upper right portions (as viewed in

FIG. 2

) of the upper and lower compartments


42




a


,


42




b


, have respective suction cups


60




a


,


60




b


coupled to displacing means (not shown) which displace the suction cups


60




a


,


60




b


, respectively. The suction cups


60




a


,


60




b


can be moved into the respective magazines


48




a


,


48




b


by the displacing means.




A roller pair


90


is disposed in the upper compartment


42




a


downstream of the suction cup


60




a


with respect to the direction in which sheets


20


are fed from the magazine


48




a


. Another roller pair


92


disposed downstream of the roller pair


90


. The light-shield plate


40




b


has a passage hole


94


defined therein at a position downstream of and near the roller pair


92


, the passage hole


94


communicating with the lower compartment


42




b.






The light-shield plate


40




c


has a passage hole


98


defined therein at a position below the passage hole


94


, the passage hole


98


communicating with the exterior of the lower compartment


42




b


. Guide plates


102




a


,


102




b


extend vertically from a position near the right-hand edge of the passage hole


94


in the light-shield plate


40




b


to a position near the right-hand edge of the passage hole


98


in the light-shield plate


40




c


. Similarly, guide plates


104




a


,


104




b


extend vertically from a position near the left-hand edge of the passage hole


94


in the light-shield plate


40




b


to a position near the left-hand edge of the passage hole


98


in the light-shield plate


40




c


. The guide plates


102




a


,


102




b


and the guide plates


104




a


,


104




b


jointly define therebetween a space as a feed path for the recording sheets


20


.




The guide plates


102




a


,


102




b


are joined directly to each other. The guide plates


104




a


,


104




b


are joined to each other by a roller pair


106


which is positioned downstream of the suction cup


60




b


of the lower sheet feeder


46




b


with respect to the direction in which sheets


20


are fed from the magazine


48




b.






The roller pair


92


and the roller pair


106


comprise light-shield roller pairs. The roller pair


92


prevents light from entering the upper compartment


42




a


through the passage hole


94


. The roller pair


106


prevents light that has entered the space between the guide plates


102




a


,


102




b


and the guide plates


104




a


,


104




b


through the passage hole


94


or the passage hole


98


from entering the lower sheet loader


44




b


in the lower compartment


42




b.






The pre-feeder


24


is disposed downstream of the sheet supply unit


22


, i.e., in a lower right portion of the apparatus housing


12


underneath the sheet supply unit


22


. The pre-feeder


24


comprises a roller pair (inlet roller pair)


130


disposed near the passage hole


98


, a roller pair (outlet roller pair)


132


disposed downstream of the roller pair


130


, and a pair of transversely shifting fingers (pressers)


134


disposed between the roller pairs


130


,


132


. A displacing mechanism


136


is connected to the transversely shifting finger


134


for displacing the transversely shifting finger


134


in the transverse direction of a recording sheet


20


in the pre-feeder


24


. The pre-feeder


24


also has a plate (guide member)


138


extending along the feed path of the recording sheet


20


.




As shown in

FIG. 3

, the roller pairs


130


,


132


, the transversely shifting finger


134


, the displacing mechanism


136


, and the plate


138


jointly make up a transversely shifting mechanism


140


for transversely positioning a recording sheet


20


.




The plate


138


is inclined about 20° or more to the horizontal plane such that its inlet side (right-hand side) is higher than its outlet side (left-hand side). As shown in

FIG. 4

, the roller pairs


130


,


132


are disposed along respective holes


141




a


,


141




b


defined in the plate


138


. The roller pairs


130


,


132


are spaced from each other by a distance greater than the length of a recording sheet


20


.




The plate


138


has grooves (not shown) defined therein such that the area of contact between the plate


138


and a recording sheet


20


thereon is about 80% or less of the surface area of the recording sheet


20


. The grooves defined in the plate


138


serve to prevent the recording sheet


20


from sticking to the plate


138


due to electrostatic charges and also to reduce frictional forces produced between the recording sheet


20


and the plate


138


.




As shown in

FIG. 3

, the transversely shifting mechanism


140


has a pair of transversely spaced support plates


142




a


,


142




b


extending vertically parallel to each other. The support plates


142




a


,


142




b


support bearings


144


and bearings


146


thereon. The roller pair


130


has an upper roller (first roller, fixed)


130




a


rotatably supported by the bearings


144


, and the roller pair


132


has an upper roller (second roller)


132




a


rotatably supported by the bearings


146


.




Pulleys


148


,


150


are mounted on ends of the rollers


130




a


,


132




a


, and operatively coupled by a belt


152


trained therearound to a pulley


156


which is attached to the rotatable shaft (not shown) of a motor


154


(see also FIG.


4


).




The roller


130




a


is combined with a one-way clutch (not shown) which prevents the roller


130




a


from being reversed.




As shown in

FIG. 3

, the support plates


142




a


,


142




b


support bearings


158


and bearings


160


thereon. The roller pair


130


has a lower roller (first nip roller, movable)


130




b


rotatably supported by the bearings


158


, and the roller pair


132


has a lower roller (second nip roller)


132




b


rotatably supported by the bearings


160


.




The bearings


158


and the bearings


160


are movable toward and away from the bearings


144


and the bearings


146


, respectively. Therefore, the rollers


130




b


,


132




b


are movable toward and away from the rollers


130




a


,


132




a


, respectively. The bearings


144


and the bearings


158


are operatively coupled to each other by springs


162


, and the bearings


146


and the bearings


160


are operatively coupled to each other by springs


162


.




The roller


130




a


is made of a material having a small coefficient of friction, such as POM (polyacetal) or the like, and the roller


130




b


is made of a material having a large coefficient of friction, such as rubber or the like. The roller


132




a


is made of a material having a large coefficient of friction, such as rubber or the like, and the roller


132




b


is made of a material having a small coefficient of friction, such as POM.




Since the roller


130




a


is made of a material having a small coefficient of friction, frictional forces produced between a recording sheet


20


and the roller


130




a


are reduced when the recording sheet


20


is transversely shifted. Furthermore, because the roller


132




b


is made of a material having a small coefficient of friction, a recording sheet


20


is prevented from being fed back upstream when the roller pair


132


is reversed. Accordingly, a recording sheet


20


can accurately be transversely shifted.




Plate-shaped displacement members (cam members)


164


are coupled to the rollers


130




b


,


132




b


by bearings


163




a


,


163




b


. The displacement members


164


extend parallel to the support plates


142




a


,


142




b.






The displacement members


164


have oblong holes (bearing means)


166


defined therein, and eccentric shafts


168


fixed to respective ends of a rotatable shaft


170


which is rotatably supported by the support plates


142




a


,


142




b


. The rotatable shaft


170


is operatively coupled to the rotatable shaft (not shown) of a motor


176


through pinion gears


172


,


174


.




The oblong holes


166


are positioned more closely to the bearings


163




a


than to the bearings


163




b


. Specifically, if it is assumed that a line interconnecting the bearings


163




a


,


163




b


intersects with a line normal to the center of the oblong hole


166


at a reference point O, then the distance L


1


between the reference point O and the bearing


163




a


is about half the distance L


2


between the reference point O and the bearing


163




b.






The nip pressure applied by the inlet roller pair


130


of the transversely shifting mechanism


140


is smaller than the nip pressure applied by the outlet roller pair


132


. This nip pressure setting can be achieved by changing the coefficients of elasticity of the springs


162


.




As shown in

FIGS. 4 and 5

, stoppers


178


are fixed to the support plates


142




a


,


142




b


. The stoppers


178


can contact the bearings


158


which support the roller


130




b


to prevent the roller


130




b


from being spaced from the roller


130




a


beyond a predetermined distance.




As shown in

FIGS. 3 and 6

, when the motor


176


is energized to rotate the shaft


170


clockwise in

FIG. 6

, the eccentric shafts


168


move to the right in

FIG. 6

within the oblong holes


166


, angularly moving the displacement members


164


clockwise in

FIG. 6

about the bearings


163




b


. At this time, the roller


130




b


is displaced away from the roller


130




a


against the resiliency of the springs


162


.




Upon continued rotation of the shaft


170


, the bearings


158


are brought into contact with the stoppers


178


, preventing the roller


130




b


from being further displaced (see FIG.


5


). When the shaft


170


is further rotated, the displacement members


164


are angularly moved counterclockwise in

FIG. 6

about the bearings


163




a


, displacing the roller


132




b


away from the roller


132




a.






Therefore, the transversely shifting mechanism


140


functions as a nip mechanism for successively moving the rollers


130




b


,


132




b


toward/away from the rollers


130




a


,


132




a


, respectively, and successively nipping a recording sheet


20


that is fed by the rollers


130




a


,


132




a.






As shown in

FIGS. 3 and 4

, a motor (actuator)


182


is fixedly mounted on a base


180


extending between and fixed to the support plates


142




a


,


142




b


. The motor


182


has a rotatable shaft


182




a


with a pinion


184


mounted thereon.




Two rails


186




a


,


186




b


are attached to and extend between the support plates


142




a


,


142




b


parallel to the base


180


. Two L-shaped transverse shifters


188




a


,


188




b


are movably supported respectively on the rails


186




a


,


186




b.






The transverse shifters


188




a


,


188




b


have respective racks


190


integrally disposed on their portions extending parallel to the rails


186




a


,


186




b


, the racks


190


being held in mesh with the pinion


184


. The transverse shifters


188




a


,


188




b


have the transversely shifting fingers


134


integrally disposed respectively on their portions extending perpendicularly to the rails


186




a


,


186




b


. The transversely shifting fingers


134


project through respective recesses


141




c


,


141




d


defined in the plate


138


upwardly beyond an upper surface of the plate


138


.




The motor


182


, the pinion


184


, the racks


190


, etc. jointly make up the displacing mechanism


136


for displacing the transversely shifting fingers


134


. The transversely shifting fingers


134


and the displacing mechanism


136


may also be referred to as a pressing means for pressing a sheet.




Each of the transversely shifting fingers


134


has an inner surface (pressing surface) which is recessed in a triangular cross section for reliably transversely shifting a recording sheet


20


.




While the displacing mechanism


136


includes the pinion


184


and the racks


190


in the illustrated embodiment, the displacing mechanism


136


may instead include a timing belt, a solenoid, etc.




As shown in

FIG. 2

, a correction roller


194


for correcting the direction in which to feed a recording sheet


20


is disposed downstream of and closely to the roller pair


132


.




The image recorder


26


for forming a latent image on a recording sheet


20


is disposed downstream of the pre-feeder


24


, i.e., in a lower left portion of the apparatus housing


12


. The image recorder


26


has a first roller pair


200


and a second roller pair


202


which are rotatable in synchronism with each other. The first roller pair


200


and the second roller pair


202


can be opened and closed, i.e., they each have rollers that can move toward and away from each other. The first roller pair


200


and the second roller pair


202


jointly make up an auxiliary scanning mechanism


204


for feeding a recording sheet in an auxiliary scanning direction indicated by the arrow A in FIG.


2


.




Between the first and second roller pairs


200


,


202


, there are disposed a guide plate


206


and a presser roller


208


for pressing a recording sheet


20


against the guide plate


206


. The presser roller


208


is freely vertically displaceable such that it can press a recording sheet


20


under its own weight. The presser roller


208


is effective to prevent a recording sheet


20


from sagging.




An optical system


210


is disposed above the auxiliary scanning mechanism


204


for applying a laser beam L to a recording sheet


20


in a main scanning direction (which is substantially perpendicular to the auxiliary scanning direction) while the recording sheet


20


is being fed in the auxiliary scanning direction. The optical system


210


emits the laser beam L between the second roller pair


202


and the presser roller


208


.




The optical system


210


has a laser beam source comprising two semiconductor lasers each having a wavelength of 660 nm and an output power of 30 mW. Laser beams emitted from the semiconductor lasers are combined into a single laser beam, which is deflected by a rotating polygonal mirror, and then applied as the laser beam L by an fθ lens to scan the recording medium


20


. The laser beam L has a beam diameter of 100 μm, and is shifted a pitch of 25 μm in the auxiliary scanning direction.




The laser beam L scans a recording sheet


20


four times based on the same image information. Specifically, each time the laser beam L is shifted 25 μm in the auxiliary scanning direction, the laser beam L scans the recording sheet


20


four times in the main scanning direction to form an image (latent image) as wide as one pixel on the recording sheet


20


.




A sensor


212


for detecting the leading end of a recording sheet


20


is disposed behind the recording sheet


20


remotely from the optical system


210


. A lens


214


is disposed above the sensor


212


along the path of the laser beam L for correcting a positional displacement of the path of the laser beam L.




The-transfer unit


28


is disposed downstream of the image recorder


26


, i.e., in a left portion of the apparatus housing


12


. The transfer unit


28


has two guide plates


220




a


,


220




b


disposed downstream of and closely to the second roller pair


202


of the image recorder


26


. The outer one of the guide plates


220




a


is angularly movable between open and closed positions about a rotatable shaft


220




c


. Therefore, even when a recording sheet


20


is jammed between the guide plates


220




a


,


220




b


, the recording sheet


20


can easily be removed by moving the outer guide plate


220




a


to the open position.




A roller pair


221


is disposed downstream of the guide plates


220




a


,


220




b


, and two guide plates


222




a


,


222




b


are disposed downstream of the roller pair


221


. The outer one of the guide plates


222




a


is angularly movable between open and closed positions about a rotatable shaft


222




c


. Therefore, even when a recording sheet


20


is jammed between the guide plates


222




a


,


222




b


, the recording sheet


20


can easily be removed by moving the outer guide plate


222




a


to the open position.




Two roller pairs


223


,


224


are disposed downstream of the guide plates


222




a


,


222




b


. The roller pairs


223


,


224


have rotatable shafts (not shown) combined with one-way clutches (not shown) for limiting rotation of the roller pairs


223


,


224


. A cleaning roller


225


is disposed downstream of the roller pair


224


.




The thermal development unit


30


for visualizing (thermally developing) a latent image formed on a recording sheet


20


is disposed downstream of the transfer unit


28


, i.e., in an upper left portion of the apparatus housing


12


. The thermal development unit


30


has four plate heaters


230




a


through


230




d


disposed in one circular pattern. The plate heaters


230




a


through


230




d


have respective inner surfaces


232




a


through


232




d


each having a substantially arcuate cross section. The inner surfaces


232




a


through


232




d


jointly make up a circular feed path for a recording sheet


20


.




Three presser rollers


234


are held in rolling contact with each of the inner surfaces


232




a


through


232




d


of the plate heaters


230




a


through


230




d


. A roller pair


236


is disposed upstream of and closely to the plate heater


230




a


, and a roller pair


238


is disposed downstream of and closely to the plate heater


230




d


. A roller pair


240


is disposed downstream of the roller pair


238


.




A sensor unit


242


for measuring the density of an image recorded on a recording sheet


20


is disposed downstream of and spaced a predetermined distance from the roller pair


240


. The sensor unit


242


comprises a light-emitting element


242




a


and a light-detecting element


242




b


. The sensor unit


242


is coupled to a displacing mechanism (not shown), which can displace the sensor unit


242


along the feed path of a recording sheet


20


. By adjusting the position of the sensor unit


242


with the displacing mechanism, it is possible for the sensor unit


242


to measure the density of an image recorded on a recording sheet


20


after the recording sheet


20


is sufficiently cooled.




The thermal development unit


30


has a fan


243


for discharging air out of the apparatus housing


12


. However, no fan is disposed in the sheet supply unit


22


, the pre-feeder


24


, the image recorder


26


, and the transfer unit


28


. Therefore, no dust particles are produced in the sheet supply unit


22


, the pre-feeder


24


, the image recorder


26


, and the transfer unit


28


.


24


, the image recorder


26


, and the transfer unit


28


. Therefore, no dust particles are produced in the sheet supply unit


22


, the pre-heater


24


, the image recorder


26


, and the transfer unit


28


.




A heat insulating pad


244


is attached to an inner wall surface of the apparatus housing


12


in surrounding relation to the thermal development unit


30


. The heat insulating pad


244


serves to prevent heat from the plate heaters


230




a


through


230




d


from being transmitted to recording sheets


20


that have been discharged onto a second discharge tray


292


(described later on).




The sheet discharger


34


is disposed downstream of the thermal development unit


30


, i.e., in an upper right portion of the apparatus housing


12


.




The sheet discharger


34


has a roller pair


250


and a movable guide plate


252


disposed downstream of the roller pair


250


for switching between different feed paths. The movable guide plate


252


is coupled to an actuator (not shown) such as a solenoid or the like, and is angularly movable about a rotatable shaft


253


within a certain angular range by the actuator.




Downstream of the movable guide plate


252


, there are disposed a first guide plate


254


which defines a feed path (lower feed path), and a second guide plate


256


which defines another feed path (upper feed path).




The apparatus housing


12


has a right side wall having a first discharge slot


258


defined therein downstream of the first guide plate


254


. A roller pair


260


is disposed near the first discharge slot


258


immediately upstream thereof. A direction in which a recording sheet


20


is discharged from the roller pair


260


via the first discharge slot


258


to a first discharge tray


290


(described later on) will hereinafter be referred to as a first discharge direction “a”.




The second guide plate


256


is of a curved shape and has a downstream end positioned in an upward bulge


262


in an upper right corner of the apparatus housing


12


. The upward bulge


262


has a second discharge slot


266


defined in a left side wall thereof downstream of the second guide plate


256


. A roller pair


268


is disposed near the second discharge slot


266


. A direction in which a recording sheet


20


is discharged from the roller pair


268


via the second discharge slot


266


to the second discharge tray


292


will hereinafter be referred to as a second discharge direction “b”.




As shown in

FIGS. 1 and 2

, the first discharge tray


290


is mounted on the right side wall of the apparatus housing


12


below the first discharge slot


258


. The first discharge tray


290


serves to receive recording sheets


20


discharged from the first discharge slot


258


. As shown in

FIG. 2

, the second discharge tray


292


is integrally formed with the apparatus housing


12


on its upper surface downstream of the second discharge slot


266


.




The controller


36


is disposed in the apparatus housing


12


on the bottom panel thereof. The controller


36


comprises a control unit


310


and a power supply


312


. The controller


36


also has a cooling fan


314


for applying cooling air to the power supply


312


.




The image recording apparatus


10


according to the present invention is basically constructed as described above. Operation and advantages of the image recording apparatus


10


will be described below.




The magazines


48




a


,


48




b


each containing a stack of recording sheets


20


are placed respectively in the upper sheet loader


44




a


and the lower sheet loader


44




b


(see FIG.


2


). Based on a command entered via the touch panel


14


by the operator, a recording sheet


20


is taken from either one of the magazines


48




a


,


48




b.






A recording sheet


20


is taken from the magazine


48




a


as follows: The displacing means (not shown) coupled to the suction cup


60




a


is actuated to move the suction cup


60




a


into the magazine


48




a


and attract a recording sheet


20


therein. The displacing means is further actuated to supply the recording sheet


20


attracted by the suction cup


60




a


to the roller pair


90


. The roller pair


90


feeds the recording sheet


20


to the roller pair


92


, which feeds the recording sheet


20


downwardly via the passage hole


94


to a position between the guide plates


102




a


,


102




b


and the guide plates


104




a


,


104




b


in the lower compartment


42




b.






A recording sheet


20


is taken from the magazine


48




b


as follows: The displacing means (not shown) coupled to the suction cup


60




b


is actuated to move the suction cup


60




b


into the magazine


48




b


and attract a recording sheet


20


therein. The displacing means is further actuated to supply the recording sheet


20


attracted by the suction cup


60




b


to the roller pair


106


. The roller pair


106


feeds the recording sheet


20


downwardly between the guide plates


102




a


,


102




b


and the guide plates


104




a


,


104




b.






The recording sheet


20


, from either the magazine


48




a


or the magazine


48




b


, is fed between the guide plates


102




a


,


102




b


and the guide plates


104




a


,


104




b


, and supplied via the passage hole


98


to the roller pair


130


of the pre-feeder


24


.




As shown in

FIG. 7A

, at the time the recording sheet


20


is supplied to the roller pair


130


, the roller pair


130


and the roller pair


132


are in a closed position. At this time, the roller pair


130


and the roller pair


132


are rotated in a normal direction to feed the recording sheet


20


downstream by the motor


154


(see FIG.


3


). The rotation of the roller pair


130


feeds the recording sheet


20


along the plate


138


to the roller pair


132


.




As shown in

FIG. 7B

, when the recording sheet


20


is supplied to the roller pair


132


, the displacement members


164


are angularly moved clockwise in

FIG. 6

about the bearings


163




b


, thus opening the roller pair


130


(see FIGS.


3


and


6


). Specifically, the roller


130




b


supported on an end of the displacement members


164


is displaced away from the roller


130




a


. The motor


154


is operated to reverse the roller pair


132


in a direction to feed the recording sheet


20


upstream.




At this time, the motor


182


is energized to rotate the pinion


184


counterclockwise in

FIG. 3

, causing the racks


190


meshing with the pinion


184


to displace the transverse shifters


188




a


,


188




b


toward each other along the rails


186




a


,


186




b


. The transversely shifting fingers


134


of the transverse shifters


188




a


,


188




b


transversely shift the recording sheet


20


on the plate


138


to the center of the sheet


20


. The inner surfaces of the transversely shifting fingers


134


are positioned transversely within a range of ±1 mm from a desired position of the side edges of the recording sheet


20


.




After the recording sheet


20


is transversely shifted, the motor


182


rotates the pinion


184


clockwise in

FIG. 3

to displace the transverse shifters


188




a


,


188




b


away from each other.




Then, as shown in

FIG. 7C

, the motor


176


is operated to turn the displacement members


164


counterclockwise in

FIG. 6

about the bearings


163




b


for thereby closing the roller pair


130


(see FIGS.


3


and


6


). Specifically, the roller


130




b


supported on the end of the displacement members


164


is displaced into contact with the roller


130




a


. The motor


154


is operated to rotate the roller pair


132


in the normal direction to feed the recording sheet


20


downstream.




As shown in

FIG. 7D

, the recording sheet


20


is supplied via the correction roller


194


to the first roller pair


200


of the auxiliary scanning mechanism


204


. At this time, the displacement members


164


are angularly moved clockwise in

FIG. 6

about the bearings


163




b


, thus opening the roller pair


130


(see FIGS.


3


and


6


). Specifically, the roller


130




b


supported on the end of the displacement members


164


is displaced away from the roller


130




a.






When the bearings


158


are brought into contact with the stoppers


178


, the displacement members


164


are angularly moved counterclockwise in

FIG. 6

about the bearings


163




a


, opening the roller pair


132


. That is, the roller


132




b


supported on an opposite end of the displacement members


164


is displaced away from the roller


132




a.






When the recording sheet


20


passes across the correction roller


194


disposed downstream of the roller pair


132


, the recording sheet


20


is corrected to be fed in a certain direction depending on the angle of tilt of the correction roller


194


.




As shown in

FIG. 2

, the recording sheet


20


supplied to the first roller pair


200


is further supplied to the roller pair


202


. The recording sheet


20


is fed in the auxiliary scanning direction indicated by the arrow A in

FIG. 2

by the first and second roller pairs


200


,


202


that are rotated in synchronism with each other. At this time, the recording sheet


20


is pressed against the guide plate


206


by the presser roller


208


.




While the recording sheet


20


is being fed in the auxiliary scanning direction by the first and second roller pairs


200


,


202


, the laser beam L emitted from the optical system


210


is applied to the recording sheet


20


in the main scanning direction, forming a latent image on the recording medium


20


. At this time, the leading end of the recording sheet


20


is confirmed by the sensor


212


which detects the laser beam L from the optical system


210


through the lens


214


.




The recording sheet


20


on which the latent image has been formed by the image recorder


26


is fed by the second roller pair


202


. The recording sheet


20


is then fed through the guide plates


220




a


,


220




b


of the transfer unit


28


to the roller pair


221


. The recording sheet


20


is further fed by the roller pair


221


, and supplied through the guide plates


222




a


,


222




b


to the two roller pairs


223


,


224


.




The rotation of the roller pairs


223


,


224


is limited by the one-way clutches (not shown) combined with the rotatable shafts thereof.




The recording sheet


20


that has passed through the roller pairs


223


,


224


is fed to the cleaning roller


225


, which removes dust particles from the recording sheet


20


. The recording sheet


20


is then fed to the thermal development unit


30


.




In the thermal development unit


30


, the recording sheet


20


is fed successively to the plate heaters


230




a


through


230




d


by the roller pair


236


. At this time, the recording sheet


20


is pressed against the plate heaters


230




a


through


230




d


by the presser rollers


234


, and the latent image on the recording sheet


20


is developed into a visible image by the heat from the plate heaters


230




a


through


230




d


. After the latent image has been developed into the visible image, the recording sheet


20


is fed downstream by the roller pairs


238


,


240


.




The speed at which the recording sheet


20


is fed by the presser rollers


234


is adjusted so as to be lower than the speed at which the recording sheet


20


is fed by the roller pairs


223


,


224


. This speed difference is effective to prevent the recording sheet


20


from being pushed in between the plate heaters


230




a


through


230




d


and the presser roller


234


. The one-way clutches associated with the roller pairs


223


,


224


allow the recording sheet


20


to be transferred smoothly from the roller pairs


223


,


224


to the thermal development unit


30


.




The light-emitting element


242




a


and the light-detecting element


242




b


of the sensor unit


242


disposed downstream of the roller pair


240


measure the density of the image recorded on the recording sheet


20


. The recording sheet


20


that has left the sensor unit


242


is fed to the sheet discharger


34


.




The recording sheet


20


are supplied to the roller pair


250


of the sheet discharger


34


, and then fed thereby. One of the feed paths for the recording sheet


20


is selected by the movable guide plate


252


disposed downstream of the roller pair


250


. When the movable guide plate


252


is shifted downwardly, the recording sheet


20


is fed to the lower feed path along the first guide plate


254


. When the movable guide plate


252


is shifted upwardly, the recording sheet


20


is fed to the upper feed path along the second guide plate


256


.




The recording sheet


20


as fed to the lower feed path is supplied along the first guide plate


254


to the roller pair


260


, and then fed by the roller pair


260


to the first discharge slot


258


. The recording sheet


20


is then discharged from the first discharge slot


258


along the first discharge direction “a”, and placed in the first discharge tray


290


disposed below the first discharge slot


258


.




The recording sheet


20


as fed to the upper feed path is supplied along the second guide plate


256


to the roller pair


268


, and then fed by the roller pair


268


to the second discharge slot


266


. The recording sheet


20


is then discharged from the second discharge slot


266


along the second discharge direction “b”, and placed on the second discharge tray


292


.




In the illustrated embodiment, as described above, the transversely shifting mechanism


140


has both a function to open and close the roller pair


130


and a function to open and close the roller pair


132


. Specifically, the roller pairs


130


,


132


are successively opened and closed when the eccentric shafts


168


supported in the respective oblong holes


166


are rotated to rotate the displacement members


164


.




Since the transversely shifting mechanism


140


is structurally simpler than if the roller pairs


130


,


132


were associated with respective opening and closing mechanisms, the; transversely shifting mechanism


140


has increased durability, can be manufactured inexpensively, and allows an available space to be utilized effectively.




In this embodiment, the transversely shifting mechanism


140


is mainly constructed of the roller pairs


130


,


132


arranged along the plate


138


, the transverse shifters


188




a


,


188




b


disposed between the roller pairs


130


,


132


, and the motor


182


for displacing the transverse shifters


188




a


,


188




b


. Consequently, the transversely shifting mechanism


140


is relatively simple in structure.




Since the transversely shifting mechanism


140


is capable of transversely positioning a recording sheet


20


with respect to its transversely central area, the recording sheet


20


can accurately be transversely positioned downstream of the transversely shifting mechanism


140


.




Because the rollers


130




a


,


130




b


are made of a material (POM, etc.) having a small coefficient of friction, frictional forces produced between the rollers


130




a


,


130




b


and the recording sheet


20


are reduced, allowing the recording sheet


20


to be positioned accurately.




As described above, the sheet feeding device according to the present invention has a nip mechanism which is relatively simple in structure, high in durability, can be manufactured at a reduced cost, and allows an available space to be utilized effectively.




Furthermore, the sheet feeding device according to the present invention has a transversely shifting mechanism which is relatively simple in structure, can reliably transversely shift a recording sheet, and can accurately position a recording sheet in the transverse direction.




Although a certain preferred embodiment of the present invention has been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.



Claims
  • 1. A sheet feeding device comprising:a first roller and a second roller for feeding a sheet; and a nip mechanism mounted on said first roller and said second roller; said nip mechanism comprising: a first nip roller paired with said first roller; a second nip roller paired with said second roller; a cam member, said first nip roller and said second nip roller being rotatably supported on said cam member; bearing means mounted on said cam member; an eccentric shaft rotatably supported by said bearing means; a stopper for preventing said first nip roller from being spaced from said first roller beyond a predetermined distance; said first nip roller and said second nip roller being movable successively toward or away from said first roller and said second roller, respectively, in response to rotation of said eccentric shaft.
  • 2. A sheet feeding device according to claim 1, wherein said bearing means has an oblong hole defined in said cam member.
  • 3. A sheet feeding device according to claim 2, wherein said oblong hole defined in said cam member is closer to said first nip roller than to said second nip roller.
  • 4. A sheet feeding device according to claim 3, wherein said first roller and said first nip roller are disposed upstream of said second roller and said second nip roller with respect to a direction in which said sheet is fed.
  • 5. A sheet feeding device according to claim 4, wherein a nip pressure applied to said second roller by said second nip roller is greater than a nip pressure applied to said first roller by said first nip roller.
  • 6. A sheet feeding device according to claim 3, wherein a nip pressure applied to said second roller by said second nip roller is greater than a nip pressure applied to said first roller by said first nip roller.
  • 7. A sheet feeding device comprising:a transversely shifting mechanism for transversely positioning a sheet; said transversely shifting mechanism comprising: an inlet roller pair disposed at an inlet of the transversely shifting mechanism, said inlet roller pair being openable and closable; an outlet roller pair disposed at an outlet of the transversely shifting mechanism, said outlet roller pair being openable and closable, and disposed in a position lower than said inlet roller pair; a guide member defining a feed path for the sheet from said inlet roller pair to said outlet roller pair; and pressing means disposed between said inlet roller pair and said outlet roller pair, for pressing said sheet from opposite side edges thereof to a center thereof.
  • 8. A sheet feeding device according to claim 7, wherein said pressing means comprises:a pair of pressers for pressing said sheet; racks disposed respectively on said pressers; a pinion held in mesh with said racks; and an actuator for rotating said pinion.
  • 9. A sheet feeding device according to claim 8, wherein each of said pressers has a pressing surface for pressing said sheet, said pressing surface being recessed in a triangular cross section.
  • 10. A sheet feeding device comprising:a transversely shifting mechanism for transversely positioning a sheet; said transversely shifting mechanism comprising: an inlet roller disposed at an inlet of the transversely shifting mechanism; an outlet roller disposed at an outlet of the transversely shifting mechanism, said outlet roller being disposed in a position lower than said inlet roller; a guide member defining a feed path for the sheet from said inlet roller to said outlet roller; and pressing means disposed between said inlet roller and said outlet roller, for pressing said sheet from opposite side edges thereof to a center thereof; and a nip mechanism for nipping the sheet which is fed from said inlet roller and said outlet roller; said nip mechanism comprising: an inlet nip roller paired with said inlet roller; an outlet nip roller paired with said outlet roller; a cam member, said inlet nip roller and said outlet nip roller being rotatably supported on said cam member; bearing means mounted on said cam member; an eccentric shaft rotatably supported by said bearing means; a stopper for preventing said inlet nip roller from being spaced from said inlet roller beyond a predetermined distance; said inlet nip roller and said outlet nip roller being movable successively toward or away from said inlet roller and said outlet roller, respectively, in response to rotation of said eccentric shaft.
  • 11. A sheet feeding device according to claim 10, wherein said bearing means has an oblong hole defined in said cam member.
  • 12. A sheet feeding device according to claim 11, wherein said oblong hole defined in said cam member is closer to said inlet nip roller than to said outlet nip roller.
  • 13. A sheet feeding device according to claim 12, wherein a nip pressure applied to said outlet roller by said outlet nip roller is greater than a nip pressure applied to said inlet roller by said inlet nip roller.
  • 14. A sheet feeding device according to claim 11, wherein a nip pressure applied to said outlet roller by said outlet nip roller is greater than a nip pressure applied to said inlet roller by said inlet nip roller.
  • 15. A sheet feeding device according to claim 10, wherein a nip pressure applied to said outlet roller by said outlet nip roller is greater than a nip pressure applied to said inlet roller by said inlet nip roller.
  • 16. A sheet feeding device according to claim 10, wherein said pressing means comprises:a pair of pressers for pressing said sheet; racks disposed respectively on said pressers; a pinion held in mesh with said racks; and an actuator for rotating said pinion.
  • 17. A sheet feeding device comprising:a transversely shifting mechanism for transversely positioning a sheet; said transversely shifting mechanism comprising: an inlet roller pair disposed at an inlet of the transversely shifting mechanism, said inlet roller pair being openable and closable; an outlet roller pair disposed at an outlet of the transversely shifting mechanism, said outlet roller pair being openable and closable, and disposed in a position lower than said inlet roller pair; a guide member defining a feed path for the sheet from said inlet roller pair to said outlet roller pair; and pressing means disposed between said inlet roller pair and said outlet roller pair, for pressing said sheet from opposite side edges thereof to a center thereof, wherein said inlet roller pair includes a fixed roller, said outlet roller pair includes a lower roller, and at least one of said fixed roller and said lower roller has a coefficient of friction smaller than rubber.
  • 18. A sheet feeding device according to claim 17, wherein said pressing means comprises:a pair of pressers for pressing said sheet; racks disposed respectively on said pressers; a pinion held in mesh with said racks; and an actuator for rotating said pinion.
  • 19. A sheet feeding device comprising:a transversely shifting mechanism for transversely positioning a sheet; said transversely shifting mechanism comprising: an inlet roller pair disposed at an inlet of the transversely shifting mechanism, said inlet roller pair being openable and closable; an outlet roller pair disposed at an outlet of the transversely shifting mechanism, said outlet roller pair being openable and closable, and disposed in a position lower than said inlet roller pair; a guide member defining a feed path for the sheet from said inlet roller pair to said outlet roller pair; and pressing means disposed between said inlet roller pair and said outlet roller pair, for pressing said sheet from opposite side edges thereof to a center thereof, wherein said inlet roller pair includes a fixed roller, said outer roller pair includes a lower roller, and at least one of said fixed roller and said lower roller is made of polyacetal.
  • 20. A sheet feeding device according to claim 19, wherein said pressing means comprises:a pair of pressers for pressing said sheet; racks disposed respectively on said pressers; a pinion held in mesh with said racks; and an actuator for rotating said pinion.
Priority Claims (2)
Number Date Country Kind
11-057465 Mar 1999 JP
11-057542 Mar 1999 JP
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5996989 Cahill et al. Dec 1999 A
6149150 Onipchenko Nov 2000 A
6164642 Onipchenko et al. Dec 2000 A
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Entry
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Research Disclosure Jun. 1978, 17029 (pp. 9-15).