Patent Publication Number: US-8123219-B2

Title: Medium feeding device and guide member

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of U.S. patent application Ser. No. 10/926,747, filed Aug. 26, 2004, and the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to a medium feeding device for feeding a medium such as a recording paper, and particularly to a medium feeding device having ribs on a feeding path of the medium. This invention also relates to a guide member including the ribs, and a manufacturing method of the guide member. 
     A medium feeding device has ribs for guiding a medium along a medium feeding path, as disclosed in Japanese Kokai Patent Publication No. HEI 10-77149. Conventionally, the ribs are formed by injection molding process as is the case with a general plastic product with ribs. In the injection molding process, a molten resin is injected into a mold having cavities formed by electric discharge machining. 
     However, in order to form high ribs, it is necessary to form deep cavities in the mold. Therefore, the time required for machining the mold becomes long, and the finishing and polishing operation of the mold becomes difficult. Moreover, when the resin is injected in the mold, air (or other gas generated in the mold) may remain in the tips of the cavities. In such a case, the resin may not sufficiently be filled in the cavities, and therefore the defective molding may occur. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to prevent the defective molding of ribs and to simplify the machining operation of a mold. 
     The present invention provides a medium feeding device including a rib disposed on a feeding path along which the medium is fed. In a cross section perpendicular to a direction in which the medium is fed along the feeding path, an end side of the rib includes an end portion that guides the medium, and an inclined portion inclined from the end portion. 
     The present invention also provides a medium feeding device including a rib disposed on a feeding path along which a medium is fed. In a cross section perpendicular to a direction in which the medium is fed along the feeding path, an end side of the rib includes a convex portion whose apex guides the medium, and a step portion adjacent to the convex portion. A level difference is formed between the step portion and the apex. 
     The present invention also provides a method for manufacturing a guide member provided in a medium feeding device. The guide member has a rib on a feeding path along which a medium is fed. The method includes the steps of preparing a mold which can split into a plurality of components at a parting surface aligned with a position in the vicinity of an end side of the rib, and injecting resin into the mold to form the guide member. 
     According to the present invention, in the injection molding process, the air (or other gas generated in the mold) escapes outside through the gap formed at the parting surface of the mold. Thus, the resin can sufficiently be filled in the cavity of the mold. As a result, the defective molding can be prevented, even if the rib is high. Moreover, the machining (finishing, polishing or the like) of the mold can be performed in a state where the mold splits into the components, and therefore the machining operation can be simplified. 
     Further, according to the present invention, the end side of the rib has the end portion and the inclined portion (or, the convex portion and the step portion), and therefore the parting surface can be aligned with the end of the inclined portion (or, the step portion and the like). As a result, even if a burr is formed on the rib, it is possible to prevent the rib from reaching the feeding path, with the result that a de-burring operation can be eliminated. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. 
       In the drawings: 
         FIG. 1  is a side view of an image forming apparatus in which a medium feeding device according to the first embodiment of the present invention is employed; 
         FIGS. 2A ,  2 B and  2 C are perspective views of a second guide member, a first guide member, and an eject tray in the medium feeding device according to the first embodiment; 
         FIG. 3  is a perspective view of a medium feeding path according to the first embodiment of the present invention; 
         FIG. 4  is an enlarged cross sectional view of a rib of a guide member according to the first embodiment of the present invention; 
         FIG. 5  is a cross sectional view of a mold used in a manufacturing process according to the first embodiment; 
         FIG. 6  is an enlarged cross sectional view of the mold filled with a resin in the manufacturing process of the first embodiment; 
         FIGS. 7A and 7B  are respectively a cross sectional view and a side view of a burr formed on the rib in the manufacturing process of the first embodiment; 
         FIG. 8  is a schematic cross sectional view of the mold in a state where mold components are not properly aligned with each other; 
         FIG. 9  is a cross sectional view of the rib with a step portion formed by the misalignment of the mold components as shown in  FIG. 8 ; 
         FIG. 10  is an enlarged cross sectional view of a rib of a medium feeding device according to the second embodiment; 
         FIG. 11  is an enlarged cross sectional view of another example of the rib according to the second embodiment; 
         FIG. 12  is an enlarged cross sectional view of the mold filled with the resin in a manufacturing process of the second embodiment; 
         FIG. 13  is an enlarged cross sectional view of a burr formed on the rib in the manufacturing process of the second embodiment; 
         FIG. 14  is an enlarged cross sectional view of a rib of a medium feeding device according to the third embodiment; 
         FIG. 15  is an enlarged cross sectional view of the mold filled with the resin in a manufacturing process of the third embodiment; 
         FIG. 16  is an enlarged cross sectional view of another example of the mold used in the manufacturing process of the third embodiment; and 
         FIG. 17  is a cross sectional view of a burr formed on the rib in the manufacturing process of the third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First Embodiment 
       FIG. 1  is a side view of an image forming apparatus in which a medium feeding device according to the first embodiment is employed. The image forming apparatus is a printer using an electrophotographic technology. The image forming apparatus includes a cassette  1  accommodating a stack of media (for example, recording papers)  34 , a pickup roller  2  for picking up the medium  34  in the cassette  1 , a feeding roller  3  for feeding the medium  34  from the pickup roller  2 , an image forming unit  5  for transferring a toner image to the medium  34 , and a fixing unit  6  for fixing the toner image on the medium  34 . These components are accommodated in a housing  12 . 
     The image forming unit  5  includes a photosensitive drum  51  for carrying a toner image. A charging device, an exposing device, a developing device (not shown) and a transfer roller  52  are arranged along a circumference of the photosensitive drum  51 . The medium  34  is fed through between the photosensitive drum  51  and the transfer roller  52 . The fixing unit  6  includes a heat roller  61  and a pressure roller  62 . The medium  34  is fed through between the heat roller  61  and the pressure roller  62 . At the upstream side of the feeding roller  3 , a medium detection sensor  4  is provided for detecting the passage of the medium  34 . 
     At the downstream side of the fixing unit  6 , a swingable eject tray  8  is provided. The eject tray  8  is swingable about a support shaft  9  between a face-down position (shown by a dashed line) and a face-up position (shown by a solid line). The eject tray  8  guides the medium  34  from the fixing unit  6  to the exterior of the housing  12  through the left side of the housing  12  in  FIG. 1 , when the eject tray  8  is at the face-up position. Further, a first guide member  10  is provided on the housing  12  so as to form the left side wall of the housing  12  in  FIG. 1 . The first guide member  10  guides the medium  34  from the fixing unit  6  upward. A top cover  7  is provided on the top of the housing  12 . A second guide member  11  is provided on the top cover  7  so that the second guide member  11  is disposed at the upper side of the first guide member  10 . The second guide member  11  guides the medium  34  from the first guide member  10  further upward. 
     In the image forming apparatus, the medium  34  is picked up by the pickup roller  2  and fed by the feeding roller  3  toward the image forming unit  5 . In the image forming unit  5 , the toner image is transferred from the photosensitive drum  51  to the medium  34  by the transfer roller  52 . By the rotation of the transfer roller  52 , the medium  34  is fed to the fixing unit  6 . In the fixing unit  6 , the heat roller  61  and the pressure roller  62  apply heat and pressure to the medium  34 , so that the toner image is fixed to the medium  34 . When the eject tray  8  is at the face-down position, the medium  34  that has passed the fixing unit  6  is guided upward by the first and second guide members  10  and  11 , and ejected through a not shown opening formed on the top cover  7  as indicated by an arrow A. When the eject tray  8  is at the face-up position, the medium  34  that has passed the fixing unit  6  is fed through an opening  10   a  ( FIG. 2B ) of the first guide member  10  and guided by the eject tray  8  to the exterior of the housing  12  as indicated by an arrow B, and laid on the eject tray  8 . 
     In the image forming apparatus shown in  FIG. 1 , the medium feeding device is constituted by the eject tray  8 , the first guide member  10 , the second guide member  11  and the mechanism for feeding the medium  34  such as the pickup roller  2  and the feeding roller  3 . 
       FIGS. 2A ,  2 B and  2 C are perspective views respectively of the second guide member  11 , the first guide member  10  and the eject tray  8 . As shown in  FIG. 2A , the second guide member  11  has a base portion  11   a  elongated in the width direction of the medium  34 . The second guide member  11  has a pair of side plate portions  11   b  and  11   c  on both ends of the base portion  11   a  in the longitudinal direction thereof. The side plate portions  11   b  and  11   c  are supported on both side walls of the top cover  7 . A plurality of ribs  16  are formed on the base portion  11   a . The ribs  16  are arranged in the longitudinal direction of the base portion  11   a , i.e., the width direction of the medium  34 . Further, each rib  16  is elongated in the width direction of the base portion  11   a.    
     As shown in  FIG. 2B , the first guide member  10  has a base portion  10   a  elongated in the width direction of the medium  34 . The base portion  10   a  constitutes a side wall of the housing  12 . An opening  10   b  is formed at the lower part of the base portion  10   a . A plurality of ribs  16  are formed on the base portion  10   a , and are disposed on the upper part of the opening  10   b . The ribs  15  are arranged in the longitudinal direction of the base portion  10   a , i.e., the width direction of the medium  34 . Further, each rib  15  is elongated in the width direction of the base portion  10   a.    
     As shown in  FIG. 2C , the eject tray  8  has a base portion  8   a  elongated in the width direction of the medium  34 . The eject tray  8  has a pair of side plate portions  8   c  and  8   d  on both ends of the base portion  8   a  in the longitudinal direction thereof. Each of the side plate portions  8   c  and  8   d  has an engaging portion  8   b  that engages the support shaft  9  ( FIG. 1 ). A plurality of ribs  14  are formed on the base portion  8   a . The ribs  14  are arranged in the longitudinal direction of the base portion  8   a , i.e., the width direction of the medium  34 . Further, each rib  14  is elongated in the width direction of the base portion  8   a.    
       FIG. 3  is an enlarged perspective view illustrating the structure for guiding the medium  34 . Hereinafter, the eject tray  8  ( FIG. 2C ), the first guide member  10  ( FIG. 2B ) and the second guide member  11  ( FIG. 2A ) are described as “a guide member  18 ” as shown in  FIG. 3 . The respective ribs  14  ( FIG. 2C ),  15  ( FIG. 2B) and 16  ( FIG. 2A ) are described as “ribs  20 ” as shown in  FIG. 3 . The respective base portions  8   a  ( FIG. 2C ),  10   a  ( FIG. 2B) and 11   a  ( FIG. 2A ) are described as “a base portion  25 ” as shown in  FIG. 3 . 
     In  FIG. 3 , the Y-direction is used to mean the direction in which the medium  34  is fed (i.e., length). The X-direction is used to mean the direction of the width of the medium  34  or each rib  20 . The Z-direction is used to mean the direction in which the ribs  20  protrude from the base portion  25  (i.e., height). Each rib  20  extends in a plane parallel to the YZ-plane. The feeding path of the medium  34  is defined by tips of the ribs  20 . 
       FIG. 4  is a cross sectional view in the XZ-plane of the tip (i.e., an end side) of the rib  20 .  FIG. 4  corresponds to the cross section taken along a plane IV in  FIG. 3 . Each rib  20  has a convex portion  20   a  at the tip thereof. The convex portion  20   a  has a curved surface that forms an upward convex curve in the XZ-plane. Two side surfaces  20   b  of each rib  20  in the X-direction (i.e., the width direction) are plane surfaces substantially in parallel to the YZ-plane. The medium  34  ( FIG. 3 ) is fed in the Y-direction in such a manner that the medium  34  contacts the apexes of the convex portions  20   a . In other words, the apexes of the convex portions  20   a  define a feeding surface G for guiding the medium  34 . 
     The manufacturing process of the guide member  18  ( FIG. 3 ) will be described.  FIG. 5  is a cross sectional view of a mold  37  used in the manufacturing process of the guide member  18 . The mold  37  has a cavity  38   a  for forming the base portion  25  ( FIG. 3 ) and cavities  38   b  for forming the ribs  20 . The mold  37  can split into a plurality of mold components  37   a ,  37   b  and  37   c  at parting surfaces  39 . Each parting surface  39  is aligned with the tip (i.e., the convex portion  20   a ) of the rib  20 , and extends in parallel to the YZ-plane. The mold  37  further includes another mold component  36  at the cavity  38   a  side. The mold component  36  can be separated from the mold components  37   a ,  37   b  and  37   c  at a parting surface  35  that extends in parallel to the XY-plane. 
       FIG. 6  is an enlarged cross sectional view of the mold  37  in the vicinity of the parting surface  39 . In a preferred example, the parting surface  39  is aligned with the apex of the convex portion  20   a  (i.e., the center of the convex portion  20   a  in the X-direction). The gap formed at the parting surface  39  is, for example, from 0.01 to 0.02 mm. The mold  37  is made of, for example, an aluminum, a pre-hardened steel, or a quenching and tempering steel. 
     In the manufacturing process of the guide member  18  ( FIG. 3 ), the mold components  36 ,  37   a ,  37   b  and  37   c  are assembled into the mold  37  as shown in  FIG. 5 . Then, molten resin is injected into the cavities  38   a  and  38   b  via a not-shown nozzle. The resin is made of engineering plastic such as xylon (R) (modified polyphenylene ether), ABS (acrylonitrile-butadien-styrene), or ABS/PS (the mixture of ABS and PS). The injected resin flows toward the tips of the cavities  38   b . In the tips of the cavities  38   b , the air (or other gas that generates in the mold  37 ) escapes outside through the gap formed at the parting surface  39 , and therefore the resin can be sufficiently filled in the cavities  38   b . Then, the mold  37  is cooled. Further, the mold component  36  is separated from the mold components  37   a ,  37   b  and  37   c  at the parting surface  35  in the direction denoted by C in  FIG. 5 , and a molded piece is taken out of the mold  37 . 
       FIGS. 7A and 7B  are respectively a cross sectional view in the XZ-plane and a side view of the tip of the rib  20  of the molded piece taken out of the mold  37 . As shown in  FIGS. 7A and 7B , a burr  40  may be formed on the convex portion  20   a  of the rib  20 . The burr  40  is formed by the resin entering into the gap formed at the parting surface  39  ( FIG. 6 ). Further, if there is a difference in height between the adjacent mold components  37   a  and  37   b  as shown in  FIG. 8 , an edge portion  41  may be formed on the convex portion  20   a  of the rib  20  as schematically shown in  FIG. 9 . Therefore, a deburring operation is performed after the above described injection molding process, for removing the burr  40  ( FIG. 7A ) or the edge portion  41  ( FIG. 9 ) so that the burr  40  or the edge portion  41  does not interfere with the feeding of the medium  34 . 
     As described above, according to the first embodiment, as the mold  37  has the parting surface  39  aligned with the convex portion  20   a  of the rib  20 , the air (or other gas generated in the mold  37 ) escapes outside through the gap formed at the parting surface  39  of the mold  37 . Thus, the resin can sufficiently be filled in the cavity of the mold  37 . As a result, even when the ribs  20  are high, the defective molding can be prevented. 
     Moreover, the machining (finishing, polishing or the like) of the mold  37  can be performed in a state where the mold  37  splits, and therefore the machining operation can be simplified. 
     Second Embodiment 
       FIG. 10  is an enlarged cross sectional view in the XZ-plane of a rib  20 A of a guide member according to the second embodiment.  FIG. 10  corresponds to the cross section taken along a plane IV in  FIG. 3 . The guide member of the second embodiment is different from the guide member  18  of the first embodiment ( FIG. 4 ) in the shape of the tip of the rib  20 A. 
     In this embodiment, the tip (i.e., an end side) of the rib  20 A includes an end portion  17  that defines the feeding surface G for guiding the medium  34 , and an inclined portion  19  that inclines downward from the end portion  17 . The end portion  17  has a horizontal flat surface. The inclined portion  19  has an inclined flat surface. There is a predetermined difference H in height between the end portion  17  and the lower end (i.e., the farthest end from the end portion  17 ) of the inclined portion  19 . As shown in  FIG. 10 , the inclined portion  19  is preferably provided on only one side of the end portion  17  in a widthwise direction of the rib. The width of the rib  20 A (i.e., the dimension in the X-direction) is, for example, 1.2 mm. The width of the end portion  17  is, for example, 0.5 mm. The height (i.e., the dimension in the Z-direction) of the rib  20 A from the base portion  25  is, for example, 36 mm. The inclination angle R of the inclined portion  19  with respect to the feeding surface G is preferably less than or equal to 45 degrees. 
       FIG. 11  shows an alternative structure of the rib (referred to as a rib  20 B). Although the end portion  17  of the rib  20 A ( FIG. 10 ) has a flat surface, an end portion  17   a  of the rib  20 B ( FIG. 11 ) has a curved surface that forms an upward convex curve in the XZ-plane. This rib  20 B also includes an inclined portion  19   a  that inclines downward from the end portion  17   a.    
     The manufacturing process of the guide member of the second embodiment will be described.  FIG. 12  is a cross sectional view of a mold  27  used in the manufacturing process of the guide member of the second embodiment. The mold  27  has cavities  42  for forming the ribs  20 A and a cavity  38   a  ( FIG. 5 ) for forming the base portion  25  ( FIG. 3 ). The mold  27  can split into a plurality of mold components  21  and  22  at parting surfaces  23  (only one parting surface  23  is shown in  FIG. 12 ). The parting surface  23  is aligned with the lower end (i.e., the farthest end from the end portion  17 ) of the inclined portion  19 , and extends in parallel to the YZ-plane. The material of the mold  37  and the gap formed at the parting surface are the same as those described in the first embodiment. Other structures of the mold  27  is the same as those of the mold  37  described in the first embodiment. 
     In the manufacturing process of the guide member, the mold components are assembled into the mold  27  as shown in  FIG. 12 . Then, molten resin is injected into the mold  27 . The resin is made of the engineering plastic described in the first embodiment. The injected resin flows toward the tips of the cavities  42 . In the tips of the cavities  42 , the air (or other gas that generates in the mold  27 ) escapes outside through the gap formed at the parting surface  23 , and therefore the resin can be sufficiently filled in the cavities  42 . Then, the mold  27  is cooled, and the mold  27  splits as described in the first embodiment, so that a molded piece is taken out of the mold  27 . 
       FIG. 13  is a cross sectional view in the XZ-plane of the tip of the rib  20 A of the molded piece taken out of the mold  27 . As shown in  FIG. 13 , a burr  24  may be formed on the lower end of the inclined portion  19 . However, if the burr  24  does not reach the feeding surface G, it is not necessary to remove the burr  24 , because the burr  24  does not interfere with the feeding of the medium  34 . In a preferred example, the deburring operation is performed when the height of the burr  24  exceeds a predetermined height (for example, 0.2 mm). Alternatively, because the height of the burr  24  depends on the viscosity of the resin injected into the mold  27 , it is also possible to adjust the viscosity of the resin so that the height of the burr  24  is less than the predetermined height. In the case where the rib  20 B ( FIG. 11 ) is formed instead of the rib  20 A, the manufacturing process can be performed in a similar manner. 
     In the above described manufacturing process, since the inclination angle R of the inclined portion  19  with respect to the feeding surface G (i.e., the end portion  17 ) is less than or equal to 45 degrees, the angle of an acute-angle portion  22   a  of the mold component  22  between the inclined portion  19  and the parting surface  23  is relatively large. Thus, the damage of the acute-angle portion  22   a  can be restricted. 
     As described above, according to the second embodiment, as was described in the first embodiment, the air (or other gas generated in the mold  27 ) escapes outside through the gap formed at the parting surface  23  of the mold  27 , and therefore the resin can sufficiently be filled in the cavity  42  of the mold  27 . Therefore, the defective molding can be prevented, even when the ribs  20 A are high. Additionally, the machining of the mold  37  can be performed in a state where the mold  37  splits, and therefore the machining operation can be simplified. 
     Moreover, according to the second embodiment, the parting surface  23  is aligned with the lower end of the inclined portion  19  of the rib  20 A. Thus, if the height of the burr  40  is less than the predetermined height, the deburring operation can be eliminated, and therefore the manufacturing process can be simplified. 
     Third Embodiment 
       FIG. 14  is an enlarged cross sectional view in the XZ-plane of a rib  20 C of a guide member according to the third embodiment.  FIG. 14  corresponds to the cross section taken along a plane IV in  FIG. 3 . The guide member of the third embodiment is different from the guide member  18  of the first embodiment ( FIG. 4 ) in the shape of the tip of the rib  20 C. 
     In this embodiment, the tip (i.e., an end side) of the rib  20 C includes a convex portion  26  that defines the feeding surface G for guiding the medium  34 , and a step portion  28  adjacent to the convex portion  26 . The convex portion  26  has a curved surface that forms an upward convex curve in the XZ-plane. The apex of the convex portion  26  defines the feeding surface G for guiding the medium  34 . The step portion  18  has a flat surface substantially in parallel to the feeding surface G. There is a predetermined difference D in height (i.e., level difference) between the apex of the convex portion  26  and the step portion  18 . In other words, the step portion  18  is distant from the feeding surface G. The width (i.e., the dimension in X-direction) of the rib  20 C is, for example, 1.2 mm. The width of the step portion  28  is, for example, 0.4 mm. The convex portion  26  has a cross section of a semi-circle whose radius is 0.4 mm. The difference D in height between the convex portion  26  and the step portion  28  is, for example, 0.4 mm. 
     The manufacturing process of the guide member of the third embodiment will be described.  FIG. 15  is a cross sectional view of a mold  47  used in the manufacturing process of the guide member of the third embodiment. The mold  47  has cavities  48  for forming the ribs  20 C and the cavity  38   a  ( FIG. 5 ) for forming the base portion  25  ( FIG. 3 ). The mold  47  can splits into a plurality of mold components  29  and  30  at parting surfaces  31  (only one parting surface  31  is shown in  FIG. 15 ). The parting surface  31  is aligned with the step portion  28 . The material of the mold  47  and the gap formed at the parting surface  31  are the same as those described in the first embodiment. Other structures of the mold  47  is the same as those of the mold  37  described in the first embodiment. 
     Due to the above described structure of the mold  47 , opposing parts  29   a  and  30   a  of the mold components  29  and  30  on both sides of the parting surface  31  have shapes with rectangular corners, and therefore the strength of the opposing parts  29   a  and  30   a  can be increased. 
       FIG. 16  shows an alternative structure of the mold  47 . As shown in  FIG. 16 , the parting surface  31  is aligned with the farthest end of the step portion  28  from the convex portion  26 . With such a structure, the mold component  29  has no step portion at the parting surface  31  side thereof, and the width of the above described part  30   a  can be widened, with the result that the strength of the mold components  29  and  30  can be increased. 
     In the manufacturing process of the guide member, the mold components are assembled into the mold  47  as shown in  FIG. 15 . Then, molten resin is injected into the mold  47 . The resin is made of the engineering plastic described in the first embodiment. The injected resin flows toward the tips of the cavities  48 . In the tips of the cavities  48 , the air (or other gas that generates in the mold  47 ) escapes outside through the gap formed at the parting surface  31 , and therefore the resin can be sufficiently filled in the cavities  48 . Then, the mold  47  is cooled, and the mold  47  splits as described in the first embodiment, so that a molded piece is taken out of the mold  47 . 
       FIG. 17  is a cross sectional view in the XZ-plane of the tip of the rib  20 C of the molded piece taken out of the mold  47 . As shown in  FIG. 17 , a burr  32  may be formed on the step portion  28 . However, if the burr  32  does not reach the feeding surface G, it is not necessary to remove the burr  32  because the burr  32  does not interfere with the feeding of the medium  34 . In a preferred example, the deburring operation is performed when the height of the burr  32  exceeds a predetermined height. Further, because the height of the burr  32  depends on the viscosity of the resin injected into the mold  47 , it is also possible to adjust the viscosity of the resin so that the height of the burr  32  is less than the predetermined height. In the case where the mold of  FIG. 16  is used instead of mold  47 , the manufacturing process can be performed in a similar manner. 
     As described above, according to the third embodiment, as was described in the first embodiment, the air (or other gas generated in the mold) escapes through the gap formed at the parting surface  31  of the mold  47 , and therefore the resin can sufficiently be filled in the cavity of the mold  47 , with the result that the defective molding can be prevented even when the ribs  20 C are high. Additionally, the machining of the mold  37  can be performed in a state where the mold  37  splits, and therefore the machining operation can be simplified. 
     Further, according to the third embodiment, because the parting surface  31  is aligned with the step portion  28  (or the farthest end of the step portion  28  from the end portion  17 ), the deburring operation can be eliminated if the height of the burr  41  is less than the predetermined height, and therefore the manufacturing process can be simplified. 
     Moreover, according to the third embodiment, because the opposing parts  29   a  and  39   a  of the mold components  29  and  30  have shapes with rectangular corners, the parts  29   a  and  30   a  can be strengthen, and therefore the lifetime of the mold  47  can be enhanced. 
     Additionally, the ribs  20 C contact the medium  34  at the apexes of the convex portions  26 , and therefore the friction between the medium  34  and the ribs  20   a  decreases. 
     The guide member and the medium feeding device described in the first through third embodiments can be employed in an apparatus (for example, a scanner, a facsimile, a photocopier) in which a medium is fed, and is not limited to the image forming apparatus shown in  FIG. 1 . 
     Further, the medium feeding device of the present invention is not limited to a device that feeds the medium by the feeding roller  3  or the like as shown in  FIG. 1 , but can be any device that has at least one rib disposed on a medium feeding path. 
     In the example shown in  FIG. 3 , the guide member  18  has a plurality of ribs  20  formed on the base portion  25 . However, the present invention is not limited to such a structure. For example, it is possible that the guide member  18  has no base portion  25 . Further, it is possible to provide a single rib  20  for guiding the medium  34 . 
     It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.