Patent Publication Number: US-2016229650-A1

Title: Image forming apparatus

Description:
FIELD 
     Embodiments described herein relate generally to an image forming apparatus capable of feeding an envelope. 
     BACKGROUND 
     Conventionally, in an image forming apparatus, a paper taken out from a paper feed cassette is conveyed to an image forming section to form an image on the paper. Further, a pickup roller for picking up paper is arranged in the paper feed cassette. Further, a paper feed roller is arranged nearby the pickup roller. 
     Incidentally, the image forming apparatus feeds an envelope from the paper feed cassette. In a case in which the envelope is fed from the paper feed cassette in a longitudinal direction, the flap of the envelope may open. Further, the rigidity of the part where there is the flap becomes strong. Thus, if the conveyance path is bent, there is a possibility that the conveyance of envelope stalls and a jam occurs. 
     In the past, there is an apparatus in which a pressing member is arranged in a paper feed tray to press the center part of the envelope. The pressing member rectifies the bulge of the envelope. However, to suppress the opening of the flap of the envelope is limited in the paper feed tray. Thus, the flap may open in the conveyance path after the envelope is fed even if the envelope is pressed just before being fed. Further, if the pressing force of the pressing member is weak, there is a disadvantage that the flap opens at a downstream position of the paper feed roller during the conveying, and the envelope is conveyed while the rigidity thereof is strong. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating the constitution of an image forming apparatus according to an embodiment; 
         FIG. 2  is a diagram illustrating the constitution of a paper pickup section according to the embodiment; 
         FIG. 3  is a perspective view illustrating a paper feed cassette and the paper pickup section according to the embodiment; 
         FIG. 4  is a plan view illustrating the paper pickup section when viewed from above according to the embodiment; and 
         FIG. 5  is a perspective view illustrating a modification of the paper pickup section according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In accordance with an embodiment, an image forming apparatus comprises: 
     a paper feed cassette configured to be capable of stacking and housing an envelope with a flap; 
     a pickup roller configured to pick up the envelope from the paper feed cassette; 
     a paper feed roller pair configured in a direction orthogonal to the conveyance direction of the envelope picked up by the pickup roller to convey the envelope with nipping the center area of the envelope; and 
     a pressing roller pair configured in a direction orthogonal to the conveyance direction of the paper feed roller pair adjacent to the paper feed roller pair to convey the envelope with nipping the flap of the envelope, wherein the conveyance force applied to the envelope by the pressing roller pair is weaker than the conveyance force applied to the envelope by the paper feed roller pair. 
     Hereinafter, the image forming apparatus according to the embodiment is described in detail with reference to the accompanying drawings. Further, same components are applied with the same reference numerals in the drawings, and therefore the description thereof is not provided. 
     (A first Embodiment) 
       FIG. 1  is a diagram illustrating the constitution of an image forming apparatus according to the embodiment. In  FIG. 1 , an image forming apparatus  100  is an electrophotographic type copier. In addition to the copier, a printer, a multi-function peripheral (MFP) and the like may also be used as the image forming apparatus  100 . The copier is exemplified in the following description. 
     The image forming apparatus (copier)  100  is provided with a printer section  10  at the center thereof . The printer section includes a rotatable photoconductive drum  11 . The photoconductive drum  11  serving as an image carrier includes an organic photo conductor (OPC) at the outer peripheral surface thereof. If the photoconductive drum  11  is irradiated with light in a state of being applied with a given potential, the potential of the area of the photoconductive drum  11  irradiated with the light is changed. The photoconductive drum  11  maintains the change of the potential as an electrostatic latent image for a given time. 
     An electrostatic charger  12 , an exposure unit  13 , a developing device  14 , a transfer roller  15 , a drum cleaner  16  and a charge removing LED  17  are arranged around the photoconductive drum  11  along a rotation direction T of the photoconductive drum  11 . 
     The electrostatic charger  12  charges the surface of the photoconductive drum  11  to a given potential. The exposure unit  13  irradiates the photoconductive drum  11  with a laser beam LB to expose the photoconductive drum  11 . Through the exposure processing, the electrostatic latent image is formed on the surface of the photoconductive drum  11 . The light intensity of the laser beam LB varies according to image density and the like . 
     The developing device  14  stores two-component developing agent including toner and carrier. The developing device  14  supplies developing agent to the surface of the photoconductive drum  11  to develop the electrostatic latent image on the photoconductive drum  11 . The electrostatic latent image on the surface of the photoconductive drum  11  is visualized to form a toner image. The transfer roller  15  applies a given potential to a paper S serving as an image receiving medium. The transfer roller  15  transfers the toner image on the photoconductive drum  11  to the paper S. The transfer roller  15  constitutes a transfer device. 
     The drum cleaner  16  removes and collects the toner left on the surface of the photoconductive drum  11 . The charge removing LED  17  removes the charge left on the photoconductive drum  11 . Further, a fixing device  19  is arranged at the downstream side of the transfer roller  15 . The fixing device  19  conveys the paper S, and meanwhile heats and presses the paper S at a given temperature. The toner image is fixed on the paper S by the fixing device  19 . 
     Further, a developing agent cartridge  18  for housing toner and developing agent is arranged above the developing device  14 . After the toner and the developing agent in the developing device  14  are consumed, the toner and the developing agent are supplied from the developing agent cartridge  18  to the developing device  14 . 
     Further, a scanner section  20  is arranged at the upper portion of the image forming apparatus  100 . The scanner section  20  includes a light source  22 , a reflecting mirror  23  and an image sensor  24 . The light source  22  irradiates the document placed on a document placing table  21  with light. The reflecting mirror  23  reflects the light reflected from the document. The image sensor  24  receives the light reflected from the reflecting mirror  23 . 
     Further, a document cover  25  is arranged at the upper portion of the document placing table  21  in an openable manner. Further, an operation panel  26  is arranged nearby the scanner section  20 . The operation panel  26  includes a touch panel type display section  27  and operation keys  28 . 
     Further, a paper feed cassette  31  is arranged at the lower portion of the image forming apparatus  100 . A plurality of paper feed cassettes  31  may be arranged according to the paper size or paper type. For example, the paper feed cassette  31  may be constituted by two parts, the upper part thereof is used to house normal paper, and the lower part thereof is used to store envelopes. 
     The paper S in the paper feed cassette  31  is picked up by a pickup roller  41 . The picked up paper S is guided to the transfer roller  15  by a conveyance roller  32  and a register roller  33 . The pickup roller  41  picks up the paper S in the paper feed cassette  31  one by one. The conveyance roller  32  rotates at given timing to align the positions of the paper S and the toner image formed on the photoconductive drum  11 . Through the rotation of the conveyance roller  32 , the paper S is conveyed to the transfer roller  15 . The paper S passing through the transfer roller  15  is conveyed to the fixing device  19 . The paper S passing through the fixing device  19  is discharged to a paper discharge tray  36  by a paper discharge roller  35 . 
     In a case of simplex printing, the paper S is conveyed through a conveyance path  37 . The paper S is conveyed from the register roller  33  to the transfer roller  15 . Further, the paper S is conveyed from the transfer roller  15  to the paper discharge roller  35  via the fixing device  19 . 
     Further, a reversal conveyance path  38  is arranged, independent from the conveyance path  37 , to be used in a case of duplex printing. In a case of duplex printing, the paper S is temporarily conveyed from the paper discharge roller  35  towards the paper discharge tray  36 . Then the paper S is switched back and conveyed to the reversal conveyance path  38 . The reversal conveyance path  38 , which is provided with a plurality of conveyance rollers, reverses and guides the paper S to the register roller  33 . 
     When forming an image, the document on the document placing table  21  is irradiated with the light from the light source  22 . The light reflected from the document is reflected by the reflecting mirror  23  to the image sensor  24 , in this way, the document image is read by the image sensor  24 . The laser beam LB is output from the exposure unit  13  based on the information read by the image sensor  24 , or the image information supplied from an external device such as a PC (Personal Computer) and the like. The surface of the photoconductive drum  11  is irradiated with the laser beam LB. The surface of the photoconductive drum  11  is charged to negative polarity by the electrostatic charger  12 . The photoconductive drum  11  is exposed by emitting the laser beam LB from the exposure unit  13 . In this way, the electrostatic latent image is formed on the surface of the photoconductive drum  11 . 
     If the paper S taken out from the paper feed cassette  31  is conveyed to the transfer roller  15 , the toner image on the photoconductive drum  11  is transferred to the paper S by the transfer roller  15 . The paper S to which the toner image is transferred is conveyed to the fixing device  19 . The paper S is heated and pressed by the fixing device  19  to fix the image on the paper S. The paper S on which the image is fixed is discharged to the paper discharge tray  36  through the paper discharge roller  35 . 
       FIG. 2  is a diagram illustrating the constitution of a paper pickup section  40  for picking up a paper from the paper feed cassette  31 . In the following example, a case in which an envelope E is housed in the paper feed cassette  31  is exemplified.  FIG. 3  is a perspective view illustrating the paper feed cassette  31  in which the envelope E is housed and the paper pickup section  40 . 
     As shown in  FIG. 2  and  FIG. 3 , the paper pickup section  40  includes the pickup roller  41  for picking up a paper from the paper feed cassette  31 . The pickup roller  41  is mounted on a rotary shaft  42 . Further, the paper pickup section  40  includes a pair of paper feed rollers  43  and  44 . The paper feed rollers  43  and  44  convey the paper taken out by the pickup roller  41 . The paper feed roller  43  is mounted on a rotary shaft  47 . The paper feed roller  44  is mounted on a rotary shaft  48 . The rotary shafts  47  and  48  are arranged to be parallel to each other in a direction orthogonal to the conveyance direction of the envelope E. 
     The pickup roller  41  rotates in a state of being contacted with the center area of the envelope E in the paper feed cassette  31 . The envelope E in the paper feed cassette  31  is picked up by the pickup roller  41  one by one. The envelope E picked up by the pickup roller  41  is sent to the paper feed rollers  43  and  44 . When a plurality of envelopes E is picked up by the pickup roller  41 , the paper feed roller  44  separates only one envelope E to feed it to the subsequent stage. The paper feed roller  44  is also referred to as a separation roller. 
     The pair of the paper feed rollers  43  and  44  is arranged opposite to each other. The envelope E picked up by the pickup roller  41  is nipped by the paper feed rollers  43  and  44  and then conveyed to the conveyance roller  32  through the rotation of the paper feed rollers  43  and  44 . 
     Further, a pair of pressing rollers  45  and  46  at the rear side in figures is respectively arranged on the rotary shafts  47  and  48  adjacent to the paper feed rollers  43  and  44 . The pressing rollers  45  and  46  are used to press the flap F of the envelope E. The pressing rollers  45  and  46  are mounted on the rotary shafts  47  and  48  at positions corresponding to the flap F. 
     The rotary shaft  42  is rotated by a motor  51 , and the rotary shaft  48  is rotated by a motor  52 . If the paper feed roller  44  rotates along with the rotation of the rotary shaft  48 , the paper feed roller  43  rotates and the rotary shaft  47  also rotates. That is, if the rotary shaft  48  rotates, the rotary shaft  47  is driven to rotate. 
     The rotary shaft  42  rotates by the motor  51  in a direction in which the envelope E is conveyed. Similarly, the rotary shafts  47  and  48  rotate by the motor  52  in directions in which the envelope E is conveyed. Further, the rotary shaft  47  may be rotated by the motor  52 , and the rotary shaft  48  is driven to rotate. Further, as shown in  FIG. 2 , guides  49  are arranged at the downstream side of the paper feed rollers  43  and  44  and the pressing rollers  45  and  46  to support the conveyance of paper. 
     On the other hand, the paper feed cassette  31  includes an L-shaped cassette main body  61 , a tray  62 , side plates  631  and  632 , and a rear plate  64 . A plurality of envelopes E is stacked in the tray  62 . The side plates  631  and  632  regulate and align the two sides of the envelope E. The rear plate  64  regulates the rear end of the envelope E. 
     Further, a spring  65  for lifting and lowering a sheet is arranged between the cassette main body  61  and the tray  62 . The tray  62  is energized upward by the spring  65 . Thus, the envelope E stacked at the top of the tray  62  is contacted with the pickup roller  41 . 
       FIG. 4  is a plan view illustrating the paper pickup section  40  when viewed from above. The pickup roller  41  is positioned near the center of the front end in the feed direction (indicated by an arrow X) of the envelope E. When the pickup roller  41  rotates, the envelope E is picked up from the paper feed cassette  31 . The envelope E picked up by the pickup roller  41  is sent to the paper feed rollers  43  and  44  and the pressing rollers  45  and  46 . 
     As shown in  FIG. 4 , the diameter of the paper feed rollers  43  and  44  is D 1 . Further, the diameter of the pressing rollers  45  and  46  is D 2 . The diameter D 2  of the pressing rollers  45  and  46  is slightly smaller than the diameter D 1  of the paper feed rollers  43  and  44 , that is, D 1 &gt;D 2 . 
     In the embodiment, the pressing roller  45  is mounted on the same rotary shaft  47  as the paper feed roller  43 . The paper feed roller  43  and the pressing roller  45  are rotated and stopped synchronously. Further, the pressing roller  46  is mounted on the same rotary shaft  48  as the paper feed roller  44 . The paper feed roller  44  and the pressing roller  46  are rotated and stopped by the motor  52  synchronously. That is, in order to convey the envelope E, the rotary shafts  47  and  48  are rotated in opposite directions, and rotated and stopped synchronously. Further, a one-way clutch is equipped on the pressing roller  46  (driving-side roller) of the pressing rollers  45  and  46  to carry out the feeding and conveying operations in synchronization with the paper feed roller  44 . Thus, the motor  52  serves as a driving source for synchronously rotating the paper feed rollers  43  and  44  and the pressing rollers  45  and  46  respectively. 
     Further, the conveyance force applied to the envelope E by the pressing rollers  45  and  46  is smaller than the conveyance force applied by the paper feed rollers  43  and  44 . That is, as stated above, by setting the diameter D 1  of the paper feed rollers  43  and  44  and the diameter D 2  of the pressing rollers  45  and  46  to meet the following relation: D 1 &gt;D 2 , the conveyance force applied to the envelope E by the pressing rollers  45  and  46  is reduced. 
     Since the envelope E has the flap F, the thickness thereof at the side of the flap F is increased. Thus, the conveyance force is reduced by weakening the force used to nip the envelope E by the pressing rollers  45  and  46 . Even if the conveyance force is reduced, the force used to nip the center area of the envelope E is almost equivalent to the force used to nip the flap F because the side where there is the flap F is thick. In this way, the envelope E is conveyed with equal conveyance force in the center area and the part of the flap F. The envelope E is conveyed with equal conveyance force in the center area and the part of the flap F of the envelope E, thereby preventing the skew of the envelope E. 
     If the flap F of the envelope E opens, the rigidity of the envelope E becomes strong. When the rigidity of the envelope E becomes strong, the conveyance resistance is increased at the curved part of the guides  49 . If the conveyance resistance is increased, the envelope E cannot be conveyed smoothly and a jam may occur. 
     In the embodiment, the bulge or the opening of the flap F of the envelope E can be prevented through the pair of the pressing rollers  45  and  46 . After passing through the paper feed rollers  43  and  44 , the envelope E is conveyed along the curved guides  49 . By preventing the bulge or the opening of the flap F, the rigidity of the envelope E is weakened and the envelope E can be conveyed smoothly when it is passed through the curved part of the guides  49 . As a result, it is possible to reduce the occurrence of a jam. 
     Further, in the example described above, since the conveyance force applied by the pressing rollers  45  and  46  is smaller than the conveyance force applied by the paper feed rollers  43  and  44 , the diameter of rollers is set to meet the following relation: (D 1 &gt;D 2 ). However, in addition to selecting the diameter of rollers, the friction coefficient of the pressing rollers  45  and  46  may be smaller than the friction coefficient of the paper feed rollers  43  and  44 . That is, the pressing rollers  45  and  46  and the paper feed rollers  43  and  44  may use materials having different friction coefficient. 
       FIG. 5  is a perspective view illustrating a modification of the paper pickup section  40  according to the embodiment. 
     The orientation of the envelope E housed in the paper feed cassette  31  is different from that in  FIG. 3 . The flap F of the envelope E is positioned at the side of the side plate  631  in  FIG. 3 , while the flap F of the envelope E is positioned at the side of the side plate  632  in  FIG. 5 . 
     Thus, the pair of the pressing rollers  45  and  46  is arranged at positions corresponding to the flap F of the envelope E. That is, the pair of the pressing rollers  45  and  46  arranged at the nearer side on the rotary shafts  47  and  48  is adjacent to the pair of the paper feed rollers  43  and  44 . 
     In  FIG. 5 , the bulge or the opening of the flap F of the envelope E can be prevented through the pressing rollers  45  and  46 . The rigidity of the envelope E is weakened by the pressing rollers  45  and  46  and the envelope E can be conveyed smoothly. As a result, it is possible to reduce the occurrence of a jam. 
     Further, it is exemplified in  FIG. 3  and  FIG. 5  that the envelope E is housed in the paper feed cassette  31 , and the normal paper may also be housed. In a case in which the normal paper is housed, the center area of the normal paper is conveyed by the paper feed rollers  43  and  44 . Since the conveyance force of the pressing rollers  45  and  46  is weaker than the conveyance force of the paper feed rollers  43  and  44 , the normal paper is mainly conveyed by the paper feed rollers  43  and  44 . Thus, it is possible to convey the normal paper, and meanwhile reduce the occurrence of a jam. 
     In accordance with the image forming apparatus according to the embodiment described above, in a case in which the envelope E is housed in the paper feed cassette  31 , the bulge or the opening of the flap F of the envelope E can be prevented by the pressing rollers  45  and  46  when the envelope E is being conveyed, thereby reducing the occurrence of a jam. 
     Further, the present invention is not limited to the embodiment described above, and various applications are possible. For example, the present invention may be applied to a quadruple tandem image forming apparatus provided with a plurality of developing units for different colors. Further, a scanning head including LED elements may be used instead of the exposure unit  13  including the laser light source. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.