Patent Publication Number: US-9409743-B2

Title: Sheet ejecting device and image forming apparatus

Description:
INCORPORATION BY REFERENCE 
     The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2014-131533, filed Jun. 26, 2014. The contents of this application are incorporated herein by reference in their entirety. 
     BACKGROUND 
     The present disclosure relates to a sheet ejecting device and an image forming apparatus. 
     A sheet ejecting device in an image forming apparatus has an actuator (sheet detection mechanism) at a sheet exit port for detecting a sheet load or the presence or absence of a sheet jam. In an image forming apparatus, a photointerrupter detects a jam or fullness of an exit tray by turning of a filler. 
     SUMMARY 
     A sheet ejecting device according to the present disclosure ejects a sheet conveyed thereto. The sheet ejecting device includes a sheet conveyance path, an exit port, at least one ejection roller pair, and a sheet detection portion. The sheet is conveyed along the sheet conveyance path. The sheet is ejected from the exit port. The ejection roller pair is disposed at the exit port. The ejection roller pair includes a drive roller and a driven roller. The drive roller and the driven roller provide a nip therebetween. The ejection roller pair ejects the sheet. The sheet detection portion is disposed along the sheet conveyance path and located upstream of the at least one ejection roller pair in a sheet conveyance direction. The sheet detection portion detects the sheet being ejected. The sheet detection portion includes an actuator and a sensor. The actuator is disposed along the sheet conveyance path and extends from a location upstream of the at least one ejection roller pair in the sheet conveyance direction to the at least one ejection roller pair. The actuator moves by contact with the sheet passing along the sheet conveyance path. The sensor detects the actuator. The actuator moves between a detectable position where the actuator is detectable by the sensor and an undetectable position where the actuator is not detectable by the sensor. The actuator has a sheet guide portion. The sheet guide portion extends along the sheet conveyance direction. The sheet guide portion moves, in a direction transverse to the sheet conveyance direction such that the actuator moves to the detectable position, by contact with the sheet passing along the sheet conveyance path and guides the sheet in the sheet conveyance direction. 
     An image forming apparatus according to the present disclosure includes the above-described sheet ejecting device and an image forming section. The image forming section forms an image on a sheet. The sheet ejecting device ejects the sheet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of a sheet ejecting device according to an embodiment of the present disclosure. 
         FIG. 1B  is an enlarged view of a central part of  FIG. 1A . 
         FIG. 2  is a perspective view of an actuator in a sheet detection portion of the sheet ejecting device according to the embodiment of the present disclosure. 
         FIGS. 3A and 3B  are perspective views of the sheet detection portion and an urging member. 
         FIGS. 4A and 4B  are perspective views of the sheet ejecting device according to the embodiment of the present disclosure. 
         FIG. 5  is a schematic illustration of the actuator and ejection roller pairs in the sheet ejecting device according to the embodiment of the present disclosure. 
         FIG. 6  is a cross sectional view illustrating general configuration of an image forming apparatus according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that in the drawings, elements that are the same or substantially equivalent are labelled using the same reference signs and explanation thereof is not repeated. 
     A sheet ejecting device  10  according to an embodiment of the present disclosure will be described with reference to  FIGS. 1A and 1B .  FIG. 1A  is a perspective view of the sheet ejecting device  10  according to the embodiment of the present disclosure.  FIG. 1B  is an enlarged view of a central part of  FIG. 1A . An X axis and a Y axis are perpendicular to each other and parallel to a horizontal plane. A Z axis is parallel to a vertical direction. 
     The sheet ejecting device  10  includes a sheet conveyance path  80 , an exit port  90 , two ejection roller pairs  40 , and a sheet detection portion  60 . The sheet ejecting device  10  is for example mounted in an image forming apparatus. The sheet conveyance path  80  extends to the ejection roller pairs  40 . The exit port  90  is elongated in a Y axis direction. 
     The ejection roller pairs  40  each include a drive roller (rotatory body)  41  and a driven roller (rotatory body)  42 . The ejection roller pairs  40  are provided at the exit port  90 . The two drive rollers  41  are arranged around a drive roller shaft  43  with a space therebetween. Each drive roller  41  is rotatable integrally with the drive roller shaft  43 . The drive roller shaft  43  is elongated in the Y axis direction. The two driven rollers  42  are arranged around a driven roller shaft  44 . Each of the two driven rollers  42  is located opposite to the corresponding drive roller  41 . Each drive roller  41  and the corresponding driven roller  42  provide a nip therebetween. A peripheral surface of each driven roller  42  is pressed against a peripheral surface of the corresponding drive roller  41 . A sheet passes between the peripheral surfaces of the driven rollers  42  and the peripheral surfaces of the drive rollers  41 . Each drive roller  41  rotates with rotation of the drive roller shaft  43  that is driven by actuation of a drive motor. Each driven roller  42  rotates in response to the rotation of the corresponding drive roller  41 . Using the ejection roller pairs  40 , the sheet ejecting device  10  ejects, in a direction D 1  from the exit port  90  toward an exit tray  160 , a sheet conveyed thereto along the sheet conveyance path  80 . For duplex printing, each drive roller  41  rotates in a reverse direction to convey a sheet in a direction D 2  for switching back once a part of the sheet is ejected. 
     The sheet detection portion  60  has an actuator  20  and a sensor  30 . The sheet detection portion  60  detects a sheet being ejected. The sheet detection portion  60  is provided at the exit port  90 . The sheet detection portion  60  is disposed along the sheet conveyance path  80  and located upstream of the ejection roller pairs  40  in the sheet conveyance direction D 1 . The sheet detection portion  60  is provided near a central part of the sheet ejecting device  10 . The ejection roller pairs  40  are provided at opposite sides of the sheet detection portion  60 . The actuator  20  extends from a location upstream of the ejection roller pairs  40  in the sheet conveyance direction D 1  to the ejection roller pairs  40 . The actuator is disposed between the nips that are adjacent to one another in a direction parallel to the drive roller shaft  43  and the driven roller shaft  44 . 
     The actuator  20  of the sheet ejecting device  10  according to the present disclosure will be described with reference to  FIG. 2 .  FIG. 2  is a perspective view of the actuator  20  of the sheet ejecting device  10 . 
     The actuator  20  has a sheet guide portion  28 , a pressing portion  26 , an engagement portion  23 , an engagement portion  24 , and a rear end portion  27 . The sheet guide portion  28  has a guide surface  21 , a back surface  25 , and a detection plate  22 . The back surface  25  is located at an opposite side of the guide surface  21 . The pressing portion  26  is located downstream of the sheet guide portion  28  in the sheet conveyance direction (ejection direction) D 1 . 
     The sheet guide portion  28  extends at an angle upwardly and downstream in the sheet conveyance direction D 1 . The guide surface  21  has an upward arc shape (an arc shape with a circle center thereunder). The guide surface  21  is in a position that can be in contact with a sheet. The sheet is conveyed while in contact with the guide surface  21 . Thus, the sheet can be guided to the pressing portion  26 . The pressing portion  26  has a downward arc shape (an arc shape with a circle center thereabove). The shape facilitates the sheet to be conveyed smoothly when the sheet is ejected in the ejection direction D 1  or when the sheet is conveyed in the direction D 2  for switching back. The pressing portion  26  has a pressing face  29 . The pressing face  29  presses a top surface of the sheet that is conveyed to the ejection roller pairs  40  and ejected from the ejection roller pairs  40  to curve the sheet. 
     The detection plate  22  is a flat plate. The detection plate  22  projects upward from the back surface  25 . The engagement portion  23  is provided on the pressing portion  26 . The engagement portion  24  is provided on the rear end portion  27 . The engagement portion  23  and the engagement portion  24  extend upward and have a hooked shape. The actuator  20  is attached to a housing thereof provided in the sheet ejecting device  10  with the engagement portion  23  and the engagement portion  24  engaged with the housing. The housing in the sheet ejecting device  10  has a guide groove (not shown) extending in a vertical direction. The actuator  20  is movable along a direction transverse to the sheet conveyance direction. More specifically, the actuator  20  can move in a direction D 4  and in a direction D 5 . In the present embodiment, the direction D 4  is a downward direction, and the direction D 5  is an upward direction. In the present embodiment, the actuator  20  is movable in the upward and downward directions along the guide groove. 
     Sheet detection that is performed in the sheet ejecting device  10  according to the present disclosure will be described with reference to  FIGS. 3A and 3B .  FIGS. 3A and 3B  are perspective views of the sheet detection portion  60  and an urging member  45 . 
     The sensor  30  is for example a photointerrupter sensor. The sensor  30  has a light emitter  31  and a light receiver  32 . The light emitter  31  emits light toward the light receiver  32 . The light receiver  32  receives the light emitted from the light emitter  31 . The sensor  30  detects the actuator  20 . The sensor  30  determines the absence of a sheet based on the light receiver  32  receiving light emitted from the light emitter  31 . 
     The sheet ejecting device  10  further includes the urging member  45 . The urging member  45  is for example a spring. One end of the urging member  45  is connected with the actuator  20 , and the other end is connected with the housing in the sheet ejecting device  10 . The urging member  45  urges the sheet guide portion  28  of the actuator  20  to project toward the sheet conveyance path  80  into a projection position. In the present embodiment, the urging member  45  urges the sheet guide portion  28  of the actuator  20  downward. 
     The sheet is conveyed with a leading edge thereof in contact with the actuator  20 . Once the sheet reaches the actuator  20 , the actuator  20  is pushed up by the sheet to move upward (that is, in the direction D 5 ) (hereinafter, referred to as a sheet present state). Once a trailing edge of the sheet finishes passing the actuator  20 , the actuator  20  moves downward (that is, in the direction D 4 ) because of the downward urging by the urging member  45  (hereinafter, referred to as a sheet absent state). The actuator  20  moves upward and downward depending on the presence and absence of a sheet. 
     During the sheet absent state, that is, while no sheet is being conveyed in the sheet ejecting device  10 , the actuator  20  is in a lower position as illustrated in  FIG. 3A  because of the downward urging by the urging member  45 . In the present specification, a position the actuator  20  is at when the actuator  20  is in a state illustrated in  FIG. 3A  may be referred to as an undetectable position P 1 . The undetectable position P 1  refers to a position of the actuator  20  where the actuator  20  is undetectable by the sensor  30 . When the actuator  20  is at the undetectable position P 1 , light emitted from the light emitter  31  is not blocked by the detection plate  22 , and therefore the light receiver  32  receives the light. As a result, the sensor  30  can determine the absence of a sheet under the actuator  20 . 
     On the other hand, during the sheet present state, that is, while a sheet is being conveyed in the sheet ejecting device  10 , the actuator  20  is pushed up by the sheet, and therefore the actuator  20  is in an upper position as illustrated in  FIG. 3B . In the present specification, a position the actuator  20  is at when the actuator  20  is in a state illustrated in  FIG. 3B  may be referred to as a detectable position P 2 . The detectable position P 2  refers to a position of the actuator  20  where the actuator  20  is detectable by the sensor  30 . When the actuator  20  is at the detectable position P 2 , the light receiver  32  does not receive light since the light emitted from the light emitter  31  is blocked by the detection plate  22 . As a result, the sensor  30  can determine the presence of the sheet under the actuator  20 . 
     As described with reference to  FIGS. 3A and 3B , the sensor  30  detects the presence or absence of a sheet by sensing whether or not the detection plate  22  is blocking light emitted from the light emitter  31  toward the light receiver  32 , that is, by sensing the upward or downward movement of the actuator  20 . The state transitions from the sheet absent state to the sheet present state, and then back to the sheet absent state every time a sheet passes the actuator  20 . More specifically, the position of the actuator  20  changes from the undetectable position P 1  to the detectable position P 2  as the actuator  20  moves in the direction D 5 . The position of the actuator  20  changes from the detectable position P 2  to the undetectable position P 1  as the actuator  20  moves in the direction D 4 . On the other hand, in case of a jam in the sheet ejecting device  10 , the sheet present state, that is, the state in which the actuator  20  is at the detectable position P 2  lasts for a long time. The sensor  30  can therefore detect the presence or absence of a jam in the sheet ejecting device  10 . 
     Sheet detection in the sheet ejecting device  10  according to the present disclosure will be described with reference to  FIGS. 4A and 4B .  FIGS. 4A and 4B  are perspective views of the sheet ejecting device  10  according to the embodiment of the present disclosure. The ejection roller pairs  40 , the drive roller shaft  43 , the driven roller shaft  44 , and the urging member  45  are not shown in  FIGS. 4A and 4B . During the sheet absent state, the actuator  20  is urged downward by the urging member  45  and is in a state illustrated in  FIG. 4A . On the other hand, during the sheet present state, the actuator  20  is pushed up by a sheet and is in a state illustrated in  FIG. 4B . 
     As described with reference to  FIGS. 1A to 4B , the actuator  20  in the sheet ejecting device  10  has the guide surface  21  having an arc shape, and the sensor  30  detects the presence or absence of a sheet according to the upward or downward movement of the actuator  20 . According to the configuration, the load of the conveyance that is caused during the sheet detection can be reduced, preventing occurrence of skew. 
     The sensor  30  detects the presence or absence of a sheet by detecting the upward or downward movement of the actuator  20 . According to the configuration, the load of the sheet conveyance can be reduced more compared to a configuration of an actuator that detects the presence or absence of a sheet by its turning. Furthermore, the presence or absence of a sheet can be detected with a small amount of movement of the actuator  20 , reducing the possibility of misdetection of the presence or absence of a sheet. Besides, the presence or absence of a sheet can be detected with simple configuration. 
     Since the sheet ejecting device  10  further includes the urging member  45  that urges the actuator  20  downward, the actuator  20  can be kept in the lower position in a stable manner in the absence of a sheet. The sensor  30  can thus detect the presence or absence of a sheet. 
     The actuator  20  is disposed such that the guide surface  21  extends at an angle upwardly and downstream in the sheet ejection direction D 1 . According to such a configuration, the load of the conveyance that is caused during the sheet detection can be reduced. 
     The arrangement of the actuator  20  in the sheet ejecting device  10  according to the present disclosure will be described with reference to  FIG. 5 .  FIG. 5  is a schematic illustration showing the actuator  20  and the ejection roller pairs  40  in the sheet ejecting device  10  according to the embodiment of the present disclosure. A dashed and double dotted line represents imaginary lines M each defined by an extension of a nip N. 
     When the actuator  20  is at the undetectable position P 1 , the pressing face  29  as viewed in the direction parallel to the drive roller shaft  43  and the driven roller shaft  44  is located close to the rollers of the ejection roller pairs  40  at a side of the undetectable position P 1  based on the nips N (close to the drive rollers  41  in the present embodiment) rather than close to the other rollers. In other words, the actuator  20  is disposed such that the pressing face  29  is at a location lower than the nips N between the respective ejection roller pairs  40  (at a location nearer the position of the sheet conveyance path  80 ). That is, the actuator  20  is disposed such that the pressing face  29  is at a location nearer the position of the sheet conveyance path  80  than the imaginary lines M as viewed in the direction parallel to the drive roller shaft  43  and the driven roller shaft  44 . Since the actuator  20  is disposed such that the pressing face  29  is located close to the rollers of the ejection roller pairs  40  at a side of the undetectable position P 1  based on the nips N rather than close to the other rollers when at the undetectable position P 1 , the actuator  20  presses a top surface of a sheet in a direction (direction D 3 ) perpendicular to the sheet conveyance direction to curve the sheet while the sheet is being conveyed, that is, while the sheet is present under the actuator  20 . That is, the actuator  20  is capable of tensioning (corrugating) the sheet. Thus, the sheet is prevented from being conveyed while in a curled state. Preferably, the level of the pressing face  29  is substantially the same as the level of the nips N when the actuator  20  moves upward by contact with a sheet. Such a configuration further ensures that the sheet is corrugated. 
     An image forming apparatus  100  according to an embodiment of the present disclosure will be described with reference to  FIG. 6 .  FIG. 6  is a cross sectional view illustrating general configuration of the image forming apparatus  100  according to the embodiment of the present disclosure. 
     The image forming apparatus  100  includes the sheet ejecting device  10  and an image forming section  50 . The image forming section  50  has a fixing device  110 , a sheet feed cassette  120 , an imaging section  130 , a toner replenishment device  70 , and a sheet conveyance section  170 . The image forming apparatus  100  is for example a printer. The image forming section  50  forms an image on a sheet. The sheet ejecting device  10  ejects a sheet on which an image has been formed. 
     The sheet feed cassette  120  stores therein printing sheets. For printing, a sheet from the sheet feed cassette  120  is conveyed by the sheet conveyance section  170  along the sheet conveyance path  80  of the sheet ejecting device  10  so as to be ejected from the exit port  90  after passing through the imaging section  130  and the fixing device  110 . 
     The imaging section  130  forms a toner image on a sheet. The imaging section  130  includes photosensitive members  52 , developing devices  53 , and transfer devices  54 . 
     An electrostatic latent image is formed on each photosensitive member  52  for example with laser based on an electronic signal representing an image of an original document. Each developing device  53  has a developing roller. Each developing roller supplies a toner to the corresponding photosensitive member  52  for development of the electrostatic latent image to form a toner image on the photosensitive member  52 . The toner replenishment device  70  replenishes each developing device  53  with a toner. 
     Each transfer device  54  transfers the toner image formed on the corresponding photosensitive member  52  onto the sheet. 
     The fixing device  110  applies heat and pressure to the sheet using a fixing member and a pressure member to melt and fix, on the sheet, unfixed toner images formed in the imaging section  130 . 
     Lastly, the sheet on which an image has been formed by the image forming section  50  is ejected in the direction D 1  by the sheet ejecting device  10  toward the exit tray  160 . For duplex printing, the sheet is conveyed in the direction D 2  for switching back once a part of the sheet is ejected. 
     So far, the embodiments of the present disclosure have been described with reference to the accompanying drawings ( FIGS. 1A-6 ). However, the present disclosure is not limited to the above-described embodiments and can be practiced in various ways within the scope not departing from the essence of the present disclosure (e.g., as described below in sections (1) and (2)). The drawings are intended to emphasize the components in a schematic manner to assist with understanding. The thickness, the length, the number, and so on of the components illustrated are not true to scale for diagrammatic purposes. The material, the shape, the dimensions, and so on of each component shown in the above-described embodiments are only exemplary and do not represent any particular limitations. Various alternations can be made thereto within the scope not substantially departing from the effect of the present disclosure. 
     (1) The sheet ejecting device  10  according to the present embodiment includes the urging member  45 . Alternatively, the sheet ejecting device  10  may not include the urging member  45 . For example, the actuator  20  may be pushed up by a sheet passing thereunder and then returned downward only by the weight of the actuator  20  itself. 
     (2) In the present embodiment, description is provided using a printer as an example of the present disclosure. However, the present disclosure may be applied to a different type of image forming apparatus other than the printer (e.g., a multifunction peripheral).