Patent Publication Number: US-9850083-B2

Title: Sheet conveying apparatus and image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a sheet conveying apparatus conveying a sheet and an image forming apparatus including the same. 
     Description of the Related Art 
     Conventionally, an image forming apparatus, in which a sheet tray is detachably mounted on an apparatus body and a sheet that is stacked in the sheet tray is fed by a pickup roller, is disclosed in JP-A-2014-88227. A sheet tray and a sheet-feeding mechanism including the same configuration as the above-described image forming apparatus are illustrated in  FIG. 10 . 
     A sheet-feeding mechanism  332  includes a separating roller  316 , a pickup roller  308 , and an abutting portion  350 . The pickup roller  308  is swingably supported by a holder  347  about a roller shaft  343  of the separating roller  316 . The abutting portion  350  is configured to interlock with the pickup roller  308  via a link  310 . 
     A sheet tray  324  includes cams  324   a ,  324   b ,  324   c , and  324   d  in a left end portion thereof. When the sheet tray  324  is mounted on an apparatus body, the abutting portion  350  engages with the cam  324   d  and the pickup roller  308  is positioned at a first position in which the pickup roller  308  abuts against a sheet that is stacked in the sheet tray  324 . When the sheet tray  324  is removed from the apparatus body, the abutting portion  350  moves away from the cam  324   a  and the pickup roller  308  is positioned at a second position in which the pickup roller  308  moves upward away from the sheet that is stacked in the sheet tray  324  by an urging force of a spring  333 . 
     By the way, in recent years, demand for a compact printer and a copier in the office or at home has been increasing. Thus it is desirable to downsize a sheet conveying apparatus, which is provided in the printer and the copier, in the height direction. 
     However, upon downsizing a product with that sheet-feeding mechanism  332 , there is a concern that the holder  347  and the link  310  interfere with a conveyance guide provided above the pickup roller  308  in a case when the pickup roller  308  is moved from the first position to the second position. Thus, it has been difficult to achieve both downsizing of the product and ensuring a sufficient moving space for the pickup roller  308  to contact with and apart from the sheet. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, a sheet conveying apparatus includes a stacking unit, a feeding member, a conveyance guide, and a movement unit. The stacking unit is drawably mounted on an apparatus body and includes a stacking member on which a sheet is stacked. The feeding member feeds the sheet stacked on the stacking member. The conveyance guide is provided with an opening and disposed above the stacking unit. The conveyance guide configures a conveyance path through which the sheet is conveyed. The movement unit moves the feeding member between a first position on which the feeding member comes into contact with the sheet stacked on the stacking member and a second position disposed above the first position. The movement unit includes an entry portion configured to be located within the opening in a state where the feeding member is positioned at the second position. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating a printer according to the first embodiment. 
         FIG. 2  is a perspective view of a movement unit viewed from below. 
         FIG. 3A  is a perspective view illustrating the movement unit in a state where a pickup roller is positioned at the second position. 
         FIG. 3B  is a perspective view illustrating the movement unit in a state where the pickup roller is positioned at the first position. 
         FIG. 4  is a block diagram illustrating a control unit. 
         FIG. 5A  is a perspective view illustrating a conveyance guide and an entry portion in a state where the pickup roller is positioned at the second position. 
         FIG. 5B  is a perspective view illustrating the conveyance guide and the entry portion in a state where the pickup roller is positioned at the first position. 
         FIG. 6A  is an enlarged perspective view illustrating the conveyance guide and the entry portion in a state where the pickup roller is positioned at the second position. 
         FIG. 6B  is an enlarged perspective view illustrating the conveyance guide and the entry portion in a state where the pickup roller is positioned at the first position. 
         FIG. 7A  is a side section view illustrating the conveyance guide and the entry portion in a state where the pickup roller is positioned at the second position. 
         FIG. 7B  is a side section view illustrating the conveyance guide and the entry portion in a state where the pickup roller is positioned at the first position. 
         FIG. 8A  is an enlarged perspective view illustrating a conveyance guide and an entry portion according to a second embodiment in a state where a pickup roller is positioned at a second position. 
         FIG. 8B  is an enlarged perspective view illustrating the conveyance guide and the entry portion of the second embodiment in a state where the pickup roller is positioned at a first position. 
         FIG. 9  is a side section view illustrating the conveyance guide and the entry portion in a state where the pickup roller according to the second embodiment is positioned at the second position. 
         FIG. 10  is a perspective view illustrating a certain conventional sheet-feeding mechanism and a certain conventional sheet tray. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     A first embodiment of this disclosure will be described. A printer  1 , i.e., an image forming apparatus according to the first embodiment, is an electrophotographic laser beam printer. As illustrated in  FIG. 1 , the printer  1  includes a sheet conveying apparatus  106  configured to convey the sheet, a multi-feeding portion  107 , an image forming portion  101 , and a fixing portion  103 . 
     The image forming portion  101  includes a cartridge  200  that is detachable with respect to an apparatus body  100 A, a transfer roller  28 , and a laser scanner unit  104 . The cartridge  200  includes a photosensitive drum  27 , a charger  29 , and a developer  30 . When an image formation command is output to the printer  1 , an image forming process is started by the image forming portion  101  based on image information input from an external device such as a computer connected to the printer  1 . The laser scanner unit  104  applies laser light L to the photosensitive drum  27  based on the input image information. Then an electrostatic latent image is formed by the applied laser light L on the photosensitive drum.  27 , which has been charged in advance by the charger  29 . Thereafter, the electrostatic latent image is developed by the developer  30  and a toner image is formed on the photosensitive drum  27 . 
     A sheet S stacked in an intermediate plate  21  of the sheet conveying apparatus  106  is fed by a pickup roller  8 , i.e., a feeding member, in parallel to the image forming operation described above. The sheets S are separated one by one by a feed roller  16  and a separating roller  9 , and are conveyed to registration roller pair  26  and  42  by conveyance roller pair  23  and  25 . 
     The registration roller pair  26  and  42  form a loop in the sheet S to correct skewing and conveys the sheet S to a transfer nip N formed between the photosensitive drum  27  and the transfer roller  28  at a predetermined conveying timing. A transfer bias is applied to the toner image on the photosensitive drum  27  from the transfer roller  28 , and the toner image is transferred to the sheet S at the transfer nip N. The sheet S to which the toner image is transferred is conveyed to the fixing portion  103  and the toner image is fixed by a heating roller  32  and a pressing roller  31  of the fixing portion  103 . Then, the sheet S is conveyed by conveyance roller pair  33  and  34 , and discharging roller pair  35  and  36 , and is discharged on a discharge tray  105 . 
     Upon forming images on both sides of the sheet S, the discharging roller pair  35  and  36  are driven in a reverse rotation direction after the rear end of the sheet S with the image formed on its first surface (front surface) passes through a conveyance guide  43 . Thus, the sheet S is guided to a duplex path  53  and is conveyed by first duplex conveyance roller pair  75  and  39 . Furthermore, the sheet S is conveyed by second duplex conveyance roller pair  40  and  41 , and is guided to the registration roller pair  26  and  42  by conveyance guides  51  and  52  configuring a part of the duplex path  53 , i.e., a conveyance path. Similar to the first surface, another image is formed on the second surface of the sheet S at the transfer nip N, and the sheet then discharged on the discharge tray  105 . 
     The multi-feeding portion  107  includes a multi-tray  61  that pivotably supports a multi-intermediate plate  62  on which the sheets are mounted, a multi-feeding roller  63 , and a separating pad  64  disposed to face the multi-feeding roller  63 . When a signal for feeding the sheet from the multi-feeding portion  107  is transmitted from a control unit  80  (see  FIG. 4 ), the multi-feeding roller  63  rotates to feed the sheet mounted on the multi-intermediate plate  62  toward the registration roller pair  26  and  42 . The multi-feeding portion  107  is capable of feeding a sheet that cannot be fed from the sheet conveying apparatus  106  such as an A3-size sheet and a postcard-size sheet. 
     Next, the sheet conveying apparatus  106  will be described. As illustrated in  FIGS. 1 and 2 , the sheet conveying apparatus  106  includes a cassette  24 , i.e., a stacking unit, the pickup roller  8 , the feed roller  16 , the separating roller  9 , the conveyance guide  52 , and a movement unit  70 . The cassette  24  is provided drawably from the apparatus body  100 A and includes the intermediate plate  21 , i.e., stacking unit a stacking member, on which the sheets are stacked. 
     The intermediate plate  21  is provided pivotable about a supporting point  21   a  and a lift plate  22  is provided below the intermediate plate  21 . A gear (not illustrated) is provided in one end of the lift plate  22  and power is transmitted to the gear (not illustrated) from a transmission gear provided in the cassette  24 . The transmission gear is driven by a feeding motor M described below and the intermediate plate  21  pivots in response to the upward and downward movement of the lift plate  22  so as to move upward and downward. 
     The separating roller  9 , which is in pressure contact with the feed roller  16 , forms a separation nip between the separating roller  9  and the feed roller  16  where the sheets are separated one by one. A torque limiter (not illustrated) is provided in the separating roller  9 . The torque of the torque limiter is set such that the separating roller  9  is rotated together with the feed roller  16  when a single sheet is fed by the pickup roller  8 . The torque is also set such that the separating roller  9  does not rotate when multiple sheets are fed by the pickup roller  8 , so that the sheets are separated one by one in the separation nip. 
     Here,  FIG. 4  illustrates a block diagram of the control unit  80  according to the present embodiment. A position detecting sensor  55  is connected to the control unit  80  on an input side and the feeding motor M is connected to the control unit  80  on an output side. 
     As illustrated in  FIGS. 2, 3A, and 3B , the movement unit  70  includes a feed roller shaft  44  that rotatably supports the feed roller  16  and a roller holder  47 , i.e., a support member. The roller holder  47  is pivotably supported on the feed roller shaft  44 . The roller holder  47  supports the pickup roller  8  swingably between a first position (see  FIG. 3B ) and a second position (see  FIG. 3A ) above the first position. 
     In addition, the movement unit  70  includes a detecting mechanism  71  and a cam mechanism  72 . The detecting mechanism  71  includes a sheet position detecting lever  37  pivotably supported on the apparatus body  100 A and the position detecting sensor  55 . In the present embodiment, a photo interrupter is used as the position detecting sensor  55 . An abutting portion  37   b  and a flag portion  37   a  are respectively formed on one and the other end of the sheet position detecting lever  37  across a pivotal shaft  37   c . The abutting portion  37   b  is formed to abut against the sheet S stacked on the intermediate plate  21 . The flag portion  37   a  is formed to be able to cover the position detecting sensor  55 . 
     The sheet position detecting lever  37  is urged by a spring (not illustrated) in such a direction that the abutting portion  37   b  approaches the sheet S. In a state where the cassette  24  has been just mounted on the apparatus body  100 A, the abutting portion  37   b  has been moved downward since the sheet position detecting lever  37  is urged by the spring (not illustrated). Thus, the position detecting sensor  55  covered by the flag portion  37   a  is in a non-detection state. 
     Then, if the position detecting sensor  55  is in the non-detection state, the control unit  80  drives the feeding motor M and moves the intermediate plate  21  upward via the lift plate  22 . The abutting portion  37   b  is pressed upward by the sheet S mounted on the intermediate plate  21  moving upward, and the flag portion  37   a  moves downward. If the position detecting sensor  55  is intercepted by the flag portion  37   a  moving downward to go into a detection state (see  FIG. 3B ), the control unit  80  stops driving of the feeding motor M and the upward movement of the intermediate plate  21  is stopped. In a position of the sheet position detecting lever  37  in which the position detecting sensor  55  is in the detection state, the sheet S abuts against the pickup roller  8  that is positioned at the first position by a predetermined pressure and feeding of the sheet S can be performed by the pickup roller  8 . 
     If the sheets S mounted on the intermediate plate  21  are sequentially fed, a height of an upper surface of the sheet S is decreased. Thus, the pickup roller  8  moves downward by an urging force of a tension spring  38  described below, and continuously abuts against the sheet S. On the other hand, the sheet position detecting lever  37  is rotated along with the height of the upper surface of the sheet S being decreased and if the abutting portion  37   b  moves downward by a predetermined amount, the position detecting sensor  55  is in the non-detection state in which the light is not intercepted by the flag portion  37   a.    
     When the position detecting sensor  55  comes into the non-detection state, the control unit  80  drives the feeding motor M to move the intermediate plate  21  upward using the lift plate  22 . Thus, the abutting portion  37   b  moves upward and the flag portion  37   a  moves simultaneously downward, while the position detecting sensor  55  covered by the flag portion  37   a  comes into the detection state. When the position detecting sensor  55  comes into the detection state, the control unit  80  stops driving of the feeding motor M. Controlling the feeding motor M to move the intermediate plate  21  upward and downward as described above, the apparatus is able to maintain the upper surface level of the sheet as long as a sheet S to be fed remains so that the pickup roller  8  reliably feed the sheet S. 
     The cam mechanism  72  includes a pressing lever  46 , i.e., a swing member, and a releasing lever  50 , i.e., a release member. The pressing lever  46  and the releasing lever  50  are respectively supported on a pivotal shaft  48  provided in the apparatus body  100 A and are respectively rotatable with respect to the pivotal shaft  48 . In addition, the cam mechanism  72  includes the tension spring  38 , i.e., a second urging member, a compression spring  54 , i.e., a first urging member, and a cam surface  74  formed on the upper surface of the cassette  24 . It is noted that the resilient members, the tension spring  38  and the compression spring  54 , may be replaced by, for example, magnets. 
     On one end of the pressing lever  46  is formed an entry portion  46   a  with an opening  46   b , i.e., a cavity portion. The opening  46   b  is engaged with a protrusion portion  47   a , i.e., an engagement portion, provided at the end portion of the roller holder  47 . Here, the roller holder  47  and the entry portion  46   a  are connected so that a backlash to absorb posture change of the pressing lever  46  in swinging is formed between the protrusion portion  47   a  and the opening  46   b . The tension spring  38  is stretched between the apparatus body  100 A and an end portion opposite to the entry portion  46   a  of the pressing lever  46 . The tension spring  38  urges the pressing lever  46  counterclockwise in  FIG. 3B . Since the pressing lever  46  is urged counterclockwise, the entry portion  46   a  comes to press downward the protrusion portion  47   a  of the roller holder  47 . Thus, the pickup roller  8  is supported on the roller holder  47  is positioned at the first position on which the pickup roller  8  comes into contact with the sheet S. That is, the tension spring  38  defines an abutting pressure of the pickup roller  8  with respect to the sheet S by pressing the pickup roller  8  to the first position. 
     The releasing lever  50  includes a releasing portion  50   a  and a cam follower  50   b , i.e., a movable portion, on the end portion opposite to the pivotal shaft  48 . The compression spring  54  is stretched between the cam follower  50   b  and the apparatus body  100 A. The compression spring  54  urges the releasing lever  50  clockwise in  FIGS. 3A and 3B , while the releasing portion  50   a  is formed so as to abut against the upper surface of the pressing lever  46 . The cam follower  50   b  is provided on a side portion in a width direction orthogonal to a feeding direction, i.e., a sheet conveyance direction, while the entry portion  46   a  is provided on a middle portion in the width direction. The pressing lever  46  and the releasing lever  50  configure a connection portion  73  that connects the entry portion  46   a  and the cam follower  50   b.    
     The cam surface  74  formed on the upper surface of the cassette  24  includes a first horizontal surface  74   a , a second horizontal surface  74   c , and an inclined surface  74   b . The second horizontal surface  74   c , i.e., a contact portion, is formed above the first horizontal surface  74   a . The inclined surface  74   b  connects the first horizontal surface  74   a  and the second horizontal surface  74   c . The cam follower  50   b  of the releasing lever  50  moves upward and downward along the cam surface  74  under the urging force of the compression spring  54 . 
     Next, the action of the pickup roller  8  in mounting operation and drawing operation of the cassette  24  will be described. When the cassette  24  is mounted on the apparatus body  100 A, as illustrated in  FIG. 3B , the cam follower  50   b  abuts against the second horizontal surface  74   c . In this state, the releasing portion  50   a  of the releasing lever  50  is away from the pressing lever  46 . Since the pressing lever  46  has been released from regulation, the pressing lever  46  is urged counterclockwise by the tension spring  38 . Thus, the pickup roller  8  is positioned at the first position and comes into contact with the sheet S, as described above. 
     When the cassette  24  is drawn from the apparatus body  100 A, the cam follower  50   b  moves downward, under the urging force of the compression spring  54 , by sequentially sliding on the second horizontal surface  74   c , the inclined surface  74   b , and the first horizontal surface  74   a . The cam follower  50   b  moving downward, the releasing portion  50   a  of the releasing lever  50  comes to press the pressing lever  46  to rotate the pressing lever  46  clockwise as illustrated in  FIG. 3A . That is, the pressing lever  46  is restricted moving along the urging direction of the tension spring  38  by the releasing lever  50  and is moved along the urging direction of the compression spring  54 . Thus, the entry portion  46   a  which moves upward makes the roller holder  47  pivot, and the pickup roller  8  is positioned at the second position on which the pickup roller  8  is away from the sheet S. It is noted that the urging force of the compression spring  54 , in a state where the cassette  24  is removed from the apparatus body  100 A as illustrated in  FIG. 3A , is set to be greater than the urging force of the tension spring  38 . 
     In other words, in drawing operation of the cassette  24  from the apparatus body  100 A, the second horizontal surface  74   c  is separated from the cam follower  50   b  by the urging force of the compression spring  54  so that the pickup roller  8  moves from the first position to the second position. 
     Upon mounting the cassette  24  on the apparatus body  100 A, the cam follower  50   b  moves upward sequentially sliding the first horizontal surface  74   a , the inclined surface  74   b , and the second horizontal surface  74   c  against the urging force of the compression spring  54 . The cam follower  50   b  moving upward, the releasing portion  50   a  of the releasing lever  50  moves upward and the pressing lever  46  is rotated counterclockwise as illustrated in  FIG. 3B  under the urging force of the tension spring  38 . Thus, the entry portion  46   a  which moves downward makes the roller holder  47  pivot, and the roller holder  47  stops at a position on which the pressing lever  46  abuts against a stopper (not illustrated). Now, the pickup roller  8  is positioned at the first position, on which the pickup roller  8  comes into contact with the sheet S, and a feeding operation of the sheet is performed with the pickup roller  8 . 
     In other words, in mounting operation of the cassette  24  on the apparatus body  100 A, the second horizontal surface  74   c  presses the cam follower  50   b  against the urging force of the compression spring  54  so that the pickup roller  8  is moved from the second position to the first position by the tension spring  38 . 
     Meanwhile, the conveyance guide  51  is provided above the cassette  24  mounted on the apparatus body  100 A. As illustrated in  FIGS. 5 and 6 , an opening  51   a  into which the entry portion  46   a  is moved is formed in a middle portion, in a direction orthogonal to the feeding direction, of the conveyance guide  51 . As described above, drawing the cassette  24  from the apparatus body  100 A, the pickup roller  8  moves upward from the first position to the second position. In this case, the entry portion  46   a  provided in the pressing lever  46  also moves upward. The opening  51   a  is provided such that the entry portion  46   a  moved upward does not interfere with the conveyance guide  51 . In recent years, the demand for such a product has been met that has a low height, i.e., a printer downsized in the height direction. In such a printer, distances between the entry portion  46   a , the roller holder  47 , and the conveyance guide  51  become shorter. 
     As illustrated in  FIGS. 5B, 6B, and 7B , in a state where the pickup roller  8  is positioned at the first position, the entry portion  46   a  is below the conveyance guide  51 . Then, as illustrated in  FIGS. 5A, 6A, and 7A , in a state where the pickup roller  8  is positioned at the second position above the first position, the entry portion  46   a  is located within the opening  51   a  of the conveyance guide  51 . 
     It is noted that, when performing duplex printing in a state where the cassette  24  is mounted on the apparatus body  100 A, the pickup roller  8  is positioned at the first position. In this case, as illustrated in  FIG. 7A , the entry portion  46   a  does not protrude above the opening  51   a . Thus, the sheet S can be smoothly conveyed through the duplex path  53  without interfering with the entry portion  46   a  that is positioned within the opening  51   a.    
     As described above, according to the embodiment, since the opening  51   a  is formed in the conveyance guide  51 , the entry portion  46   a  and the conveyance guide  51  do not interfere with each other in a case when the cassette  24  is drawn and the pickup roller  8  is positioned at the second position, 
     The conveyance guide  51  and the entry portion  46   a  are thereby positioned close to each other in the height direction, enabling reduction (downsizing) of the height of the printer  1 . In addition, while achieving downsizing of the printer  1 , the pickup roller  8  is moved upward sufficiently away from the sheet S, preventing the sheet S from being damaged by the pickup roller  8  in a case when the cassette  24  is drawn. 
     It is noted that, in the present embodiment, the opening  51   a  is formed so that the entry portion  46   a  is positioned within. However, such an alternative configuration is considerable that an opening is formed larger than the opening  51   a  so as to be entered by the roller holder  47 . With such a configuration, the degree of design flexibility of the conveyance guide  51  will be improved while achieving further downsizing of the apparatus. 
     It is noted that the present disclosure is not limited to the printer and can also be applied to another image forming apparatus such as a copier, a facsimile, and a multifunction printer. 
     Second Embodiment 
     Next, a second embodiment will be described. The second embodiment is provided by changing the configuration of the entry portion of the first embodiment. For the same configurations as those of the first embodiment, illustrations will be omitted and description will be provided by giving the same reference numerals. 
     A sheet conveying apparatus  206  according to the second embodiment includes the pressing lever  46 . As illustrated in FIGS.  8  and  9 , an entry portion  146   a  with an opening  146   b  is formed in an end of the pressing lever  46 . A plurality of ribs  146   c , i.e., guide ribs, are formed upward on the upper surface of the entry portion  146   a  and extend along the sheet conveyance direction. 
     As illustrated in  FIG. 8B , in a state where the pickup roller  8  is positioned at a first position, the entry portion  146   a  is positioned below the conveyance guide  51 . On the other hand, as illustrated in  FIGS. 8A and 9 , in a state where the pickup roller  8  is positioned at a second position above the first position, the entry portion  146   a  is positioned within the opening  51   a  of the conveyance guide  51 . 
     Here, in a state in which the cassette  24  is drawn from the apparatus body  100 A and the pickup roller  8  is positioned at the second position, there is a case when the printer  1  performs duplex printing by feeding the sheet from the multi-feeding portion  107 . In the first embodiment described above, however, there is a concern that the sheet S is caught by the entry portion  46   a  and a paper jam occurs, since the entry portion  46   a  protrudes within the opening  51   a , as illustrated in  FIG. 7A , 
     Thus, in the embodiment, the ribs  146   c  are provided on the upper surface of the entry portion  146   a  so as to guide the sheet S passing through the duplex path  53  in a state where the pickup roller  8  is positioned at the second position. 
     Thus, it is prevented that jamming due to interference in the sheet S and the entry portion  146   a . Thus, even in a state where the cassette  24  is drawn from the apparatus body  100 A and the pickup roller  8  is positioned at the second position, the printer  1  is able to perform duplex printing by feeding the sheet from the multi-feeding portion  107 . 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No.2015-043473, filed on Mar. 5, 2015, which is hereby incorporated by reference herein in its entirety.