Patent Publication Number: US-2012045257-A1

Title: Endless belt, intermediate transfer belt unit, image forming apparatus and method for manufacturing the endless belt

Description:
CROSS REFERENCE 
     This Nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2010-182758 filed in Japan on Aug. 18, 2010, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to an endless belt in either side edge of which is provided with a travelling guide, to an intermediate transfer belt unit and an image forming apparatus each equipped with the endless belt, and to a method for manufacturing the endless belt. 
     Conventionally, among the endless belts passed over a plurality of rollers in a tensioned condition, there has been one that employs a configuration in which a travelling guide member is provided in either side edge of the endless belt in order to prevent the endless belt from deviating toward the axial directions of the rollers (lateral deviation) as the rollers rotate. 
     For example, in the prior art, an image forming apparatus is disclosed in which lateral deviation of an intermediate transfer belt is prevented by a thin wire-shaped rib member stuck onto either side edge of an internal perimetric face of the intermediate transfer belt along its circumferential direction (for instance, refer to Japanese Patent Unexamined Publication No. 2007-52417 bulletin). 
     Additionally, in the technique according to the patent literature, a configuration is also employed in which a change in belt conveyance speed of the intermediate transfer belt attributable to a slit at a joint of the rib member is reduced, even at the slit at the joint of the rib member, by a support roller that is provided on either side of a tension roller the intermediate transfer belt is passed over in a tensioned condition and that supports both end portions of the rib member. 
     However, with the technique according to the above mentioned patent literature, as shown in  FIG. 1A  and  FIG. 1B , the rib members  196  and  198  in either side edge of the internal perimetric face of the intermediate transfer belt  194  are provided in such a manner that positions of the joints of the rib members  196  and  198  are the same one another in the circumferential direction of the intermediate transfer belt  194 , so that the joints of the rib members  196  and  198  in either side edge pass through the same roller at the same time. As a result, the technique is liable to the behavioral change of the intermediate transfer belt  194  when the joints of the rib members  196  and  198  pass through a roller region in the course of travel of the intermediate transfer belt  194 , so that it is likely to cause an occurrence of an image defect. 
     Besides, what has been experienced when a downtime in a state in which the joints of the rib members  196  and  198  in either side edge at the same time stay wrapping around the same roller extends to a long period of time is that the intermediate transfer belt  194  is likely to be subjected to a load acting thereon; and that this results in occurrences of bending strain, sharp bending and/or the like at joint portions and therefore causes deterioration of durability of the intermediate transfer belt  194 . 
     The present invention is directed to providing an endless belt capable of achieving satisfactory travelling performance and durability, an intermediate transfer belt unit and an image forming apparatus each provided with the endless belt, and a is method for manufacturing the endless belt. 
     SUMMARY OF THE INVENTION 
     An endless belt according to the present invention includes a belt body and a travelling guide member. The belt body has an endless shape, and is configured so as to be passed over a plurality of rollers in a tensioned condition. 
     The travelling guide member is provided in each of a first edge portion and a second edge portion in width direction in an internal perimetric face of the belt body. The travelling guide member is formed with a long film-like sheet body stuck onto the belt body along a circumferential direction thereof. 
     Further, a joint of the travelling guide member provided in the first edge portion and a joint of the travelling guide member provided in the second edge portion are disposed so as to be apart from each other in the circumferential direction of the belt body at least not less than a distance corresponding to a semicircle of a roller having the largest diameter among the plurality of rollers. 
     With this configuration, the joint of the travelling guide member provided in the first edge portion and the joint of the travelling guide member provided in the second edge portion are prevented from passing through the same roller at the same time. Accordingly, behavioral change of the endless belt when either of the joints of the travelling guide members passes through a roller can be reduced to a small degree; so that smooth travelling performance of the endless belt is secured, and thus an occurrence of a deficiency such as image defect attributable to the behavioral change of the endless belt is restrained adequately. 
     In addition, the endless belt is securely prevented from being left for a long period of time in a state in which the joint of the travelling guide member provided in the first edge portion and the joint of the travelling guide member provided in the second edge portion wrap around the same roller together. Therefore, an occurrence of a deficiency such as bending strain or sharp bending at joint portions is restrained; as a result, deterioration of durability of the intermediate transfer belt is prevented. 
     The present invention makes it possible for an endless belt that is provided with a travelling guide member in either side edge of its internal perimetric face to achieve satisfactory travelling performance and durability. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view showing a configurative outline of a conventional endless belt. 
         FIG. 1B  is a top view showing the configurative outline of the conventional endless belt. 
         FIG. 2  is a drawing showing an outline of an image forming apparatus according to an embodiment of the present invention. 
         FIG. 3A  is a sectional view showing an outline of an intermediate belt unit along a belt travelling direction. 
         FIG. 3B  is a sectional view showing an outline of the intermediate belt unit along a direction perpendicular to the belt travelling direction. 
         FIG. 4A  is a perspective view showing a configurative outline of an endless belt according to an embodiment of the present invention. 
         FIG. 4B  is a top view showing the configurative outline of the endless belt according to the embodiment of the present invention. 
         FIG. 5A  is a drawing explaining a relationship between the number of support rollers over which an intermediate transfer belt is passed in a tensioned condition and an angle (wrap angle) over which the intermediate transfer belt wraps around a certain support roller (when the number of the support rollers is 4). 
         FIG. 5B  is a drawing explaining a relationship between the number of support rollers over which the intermediate transfer belt is passed in a tensioned condition and an angle (wrap angle) over which the intermediate transfer belt wraps around a certain support roller (when the number of the support rollers is 3). 
         FIG. 5C  is a drawing explaining a relationship between the number of support rollers over which the intermediate transfer belt is passed in a tensioned condition and an angle (wrap angle) over which the intermediate transfer belt wraps around a certain support roller (when the number of the support rollers is 2). 
         FIG. 6  is a schematic drawing showing an example of a configurative outline of a travelling guide member pasting apparatus. 
         FIG. 7  is a diagram explaining an example of a travelling guide member pasting process. 
         FIG. 8  is a schematic drawing showing another example of a configurative outline of a travelling guide member pasting apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 2  is a drawing showing an outline of an image forming apparatus  50  according to an embodiment of the present invention. The image forming apparatus  50  is one that forms a multicolored or a monochromatic image onto a predetermined paper sheet (recording medium) depending on image data that have been transmitted from outside, and includes an image forming section  82  and a document reading section  58 . 
     The image forming section  82  includes four image forming stations that form black (K), cyan (C), magenta (M) and yellow (Y) color images respectively. Each of the image forming stations includes a developing device  91 , a photoreceptor drum  90 , a cleaner unit  93  and an electrostatic charger  92 . 
     The image forming section  82  further includes an optical scanner  88 , an intermediate transfer belt unit  95 , a fuser unit  74 , a paper feed cassette  71 , a first copy receiving tray  80 , a second copy receiving tray  100 , a plurality of flappers (not illustrated) for changing conveyance directions of the paper sheet, and so forth. 
     On an upside of the image forming section  82  is provided a document loading table  54  made of a transparent glass on which a document is placed, and above the document loading table  54  is installed an automatic document processing unit  56 . The automatic document processing unit  56  automatically conveys the document onto the document loading table  54 . Also, the automatic document processing unit  56  is configured so as to be swung freely, and thereby enables a user to place the document manually on the document loading table  54  when upside thereof is open. 
     The electrostatic charger  92  is a charging means to charge a surface of the photoreceptor drum  90  uniformly at a predetermined electrostatic potential; and other than a non-contact type electrostatic charger as shown in  FIG. 2 , a contact type electrostatic charger such as roller or brush is occasionally used. 
     The optical scanner  88  is configured so as to form on a surface of each of the photoreceptor drums  90  an electrostatic latent image based on the image data inputted. 
     Each of the developing devices  91  is one that makes an electrostatic latent image formed on the corresponding each of the photoreceptor drums  90  a manifest image with corresponding each of toners for the four colors. Also, the cleaner unit  93  removes and collects the toner which remains on the surface of the photoreceptor drum  90  after an image transfer has been carried out. 
     The intermediate transfer belt unit  95  disposed above the photoreceptor drum  90  includes an intermediate transfer belt  94 , an intermediate transfer belt drive roller  85 , an intermediate transfer belt idle roller  84 , four intermediate transfer rollers  96  and an intermediate transfer belt cleaning unit  86 . 
     The intermediate transfer belt drive roller  85 , the intermediate transfer belt idle roller  84  and the intermediate transfer rollers  96  are configured so as to pass the intermediate transfer belt  94  over them in a tensioned condition. Also, each of the intermediate transfer rollers  96  is configured so as to transfer the toner image on the corresponding photoreceptor drum  90  onto the intermediate transfer belt  94 . 
     The intermediate transfer belt  94  is installed so as to be in contact with each of the photoreceptor drums  90 , and performs a function to form a color toner image (multicolored toner image) on the intermediate transfer belt  94  through sequential superimposition of transfer of the toner images of respective colors formed on the photoreceptor drums  90  onto the intermediate transfer belt  94 . The intermediate transfer belt  94  is formed into an endless shape, for example, with a film of around 100 μm through 150 μm thick. 
     When transfer of the toner image is performed from the photoreceptor drum  90  onto the intermediate transfer belt  94 , a high-voltage transfer bias (a high voltage of reverse polarity (+) to the electrostatic charge polarity (−) of the toner) is applied to the intermediate transfer roller  96  in order to transfer the toner image. The intermediate transfer roller  96  is a roller that is formed with a shaft made of metal (e.g., stainless steel) having a diameter of 8 through 10 mm as a base material with the surface thereof covered with an electrically-conductive elastomer (e.g., EPDM, urethane foam or the like). The electrically-conductive elastomer makes it possible to apply a high voltage uniformly to the intermediate transfer belt  94 . Although roller geometry is used as a transfer electrode in this embodiment, a brush-shaped transfer electrode or the like may be used otherwise. 
     The electrostatic latent image that has been made a manifest image on each of the photoreceptor drums  90  depending on the respective hues as described above is superimposed on the intermediate transfer belt  94 . The image information that has been superimposed in this manner is transferred onto a paper sheet by a secondary transfer roller  87  that is disposed at a position where the paper sheet comes into contact with the intermediate transfer belt  94  as the intermediate transfer belt  94  rotates. 
     At this time, the intermediate transfer belt  94  and the secondary transfer roller  87  are caused to press and contact each other with a predetermined nip pressure, and a voltage (a high voltage of reverse polarity (+) to the electrostatic charge polarity (−) of the toner) to cause the toner image to be transferred onto the paper sheet is applied to the secondary transfer roller  87 . Further, in order to constantly maintain the above described nip pressure, either the secondary transfer roller  87  or the intermediate transfer belt drive roller  85  is chosen to be made of a rigid material (metal, etc.), then to the other is employed a flexible material such as an elastic roller (elastic rubber roller or foamed resin roller, etc.). 
     Also, the intermediate transfer belt cleaning unit  86  is set up so as to remove and collect the toner which adhered to the intermediate transfer belt  94  through its contact with the photoreceptor drum  90  as described above or which remains on the intermediate transfer belt  94  after the transfer has been carried out onto the paper sheet by the secondary transfer roller  87 ; because, otherwise such toner would cause color mixture of toners to occur in the next step. The intermediate transfer belt cleaning unit  86  is equipped with, for instance, a cleaning blade as a cleaning member that is in contact with the intermediate transfer belt  94 , and the intermediate transfer belt  94  with which the cleaning blade is in contact is supported from its backside by the intermediate transfer belt idle roller  84 . 
     The paper feed cassette  71  is a tray to store paper sheets to be used for image forming, and is installed on a lower side of the optical scanner  88  of the image forming section  82 . The paper sheet(s) to be used for image forming can also be placed on a manual paper feed cassette  78 . 
     Further, the first copy receiving tray  80  is installed above the image forming section  82 , and is configured so as to collect the paper sheet having undergone printing with its printed face looking downward. On the other hand, the second copy receiving tray  100  is disposed on an outside of a casing of the image forming apparatus  50 , and is configured so as to collect the paper sheet having undergone printing with its printed face looking upward. 
     Also, in the image forming section  82  is installed a paper sheet conveying path  77  for conveying the paper sheet on the paper feed cassette  71  or the manual paper feed cassette  78 , by way of the secondary transfer roller  87  and the fuser unit  74 , to either the first copy receiving tray  80  or the second copy receiving tray  100 . In close proximity to the paper sheet conveying path  77  extending from the paper feed cassette  71  or the manual paper feed cassette  78  to the first copy receiving tray  80  and the second copy receiving tray  100  are disposed pickup rollers  73 ,  75 , a plurality of conveyance rollers  62 ,  64 ,  66 ,  68 , a paper stop roller  79 , a secondary transfer roller  87 , a fuser unit  74  and so forth. 
     The conveyance rollers  62 ,  64 ,  66 ,  68  are small rollers to promote and assist conveyance of the paper sheet, and the plurality of them are installed along the paper sheet conveying path  77 . Also, the pickup roller  73  is installed in close proximity to an edge of the paper feed cassette  71 , picks up the paper sheets from the paper feed cassette  71  piece by piece, and supplies it to the paper sheet conveying path  77 . Similarly, the pickup roller  75  is installed in close proximity to an edge of the manual paper feed cassette  78 , picks up the sheets from the manual paper feed cassette  78  piece by piece, and supplies it to the paper sheet conveying path  77 . 
     Also, the paper stop roller  79  is one that holds for a moment the paper sheet being conveyed on the paper sheet conveying path  77 , and has a function to convey the paper sheet to the secondary transfer roller  87  with a timing that adjusts the head of the paper sheet to the head of the toner image on the intermediate transfer belt  94 . 
     The fuser unit  74  includes a heating roller  72  and a pressure roller  76 ; and the heating roller  72  and the pressure roller  76  are configured so as to rotate holding the paper sheet between them. Also, the heating roller  72  is set to a predetermined fusing temperature by a control section based on the signal from a temperature sensor which is not illustrated. The heating roller  72 , in cooperation with the pressure roller  76 , performs a function of heat fusing on the paper sheet by means of the thermo-compression bonding of the toner to the paper sheet through fusing, mixing and pressure-contacting the multicolored toner image that has been transferred onto the paper sheet. An external heating belt  70  is also provided for heating the heating roller  72  from outside. 
     Next, paths through which the paper sheet is conveyed are explained in detail. As described above, the image forming apparatus is equipped with the paper feed cassette  71  for receiving the paper sheets beforehand and the manual paper feed cassette  78 . In order to feed the paper sheets from these paper feed cassettes  71 ,  78 , and then to lead the paper sheets piece by piece to the paper conveying path  77 , the pickup rollers  73 ,  75  are respectively disposed. 
     The paper sheet conveyed from either of the paper feed cassettes  71 ,  78  is conveyed to the paper stop roller  79  by the conveyance roller  62  of the paper sheet conveying path  77 . Then, the paper sheet is conveyed to the secondary transfer roller  87  with a timing that adjusts the head of the paper sheet to the head of the image information on the intermediate transfer belt  94 , and thereby the image information is written onto the paper sheet. Subsequently, unfixed toner on the paper sheet is melted and stuck thereto by heat while the paper sheet passes through the fuser unit  74 ; and then through the conveyance roller  68  disposed downstream from the fuser unit  74 , the paper sheet is discharged onto the first copy receiving tray  80  or the second copy receiving tray  100 . 
     The above-mentioned conveyance path is the one for single sided printing onto the paper sheet. On the other hand, in the case of duplex printing, the paper sheet that has undergone the single sided printing as described above and has passed through the fuser unit  74  is held at its rear edge by the final conveyance roller  68 . Subsequently reversing the rotational direction of the conveyance roller  68  and switching positions of the flappers (not illustrated) cause the paper sheet to be led to a return conveying path on which the conveyance rollers  66 ,  64  are disposed. Then, the paper sheet from the return conveying path passes through the paper stop roller  79 , and on reaching the position at which it comes into contact with the intermediate transfer belt  94 , undergoes printing on its rear face. After that, the paper sheet is discharged onto the first copy receiving tray  80 . 
     Next, using  FIG. 3A  and  FIG. 3B , configuration of the intermediate belt unit  95  is explained. As shown in the figures above, the intermediate transfer belt  94  of the intermediate belt unit  95  is passed over the intermediate transfer belt idle roller  84 , the intermediate transfer belt drive roller  85 , and a plurality of rollers including the intermediate transfer rollers  96  in a tensioned condition. In this embodiment, design has been made so that the intermediate transfer belt drive roller  85  has the largest diameter among the intermediate transfer belt idle roller  84 , the intermediate transfer belt drive roller  85  and the intermediate transfer rollers  96 . 
     When a rotational drive power is supplied to the intermediate transfer belt drive roller  85 , the intermediate transfer belt drive roller  85  rotates, and travel of the intermediate transfer belt  94  starts; then motions of the intermediate transfer belt idle roller  84  and the intermediate transfer rollers  96  follow this. In this regard, in order to prevent the intermediate transfer belt  94  from deviating in axial directions of the intermediate transfer belt idle roller  84 , the intermediate transfer belt drive roller  85  and the intermediate transfer rollers  96 , a first travelling guide rib  942  and a second travelling guide rib  944  are provided in either edge portion in width direction (direction parallel to the axial directions of the respective rollers) in an internal perimetric face of the intermediate transfer belt  94 . 
     Here, using  FIG. 4A  and  FIG. 4B , configuration of the intermediate transfer belt  94  is explained. As shown in the figures above, the first travelling guide rib  942  is provided in a first edge portion in width direction in the internal perimetric face of the intermediate transfer belt  94 , whereas the second travelling guide rib  944  is provided in a second edge portion in the width direction. The first travelling guide rib  942  and the second travelling guide rib  944  are respectively formed with a long film-like sheet member (for instance, urethane sheet), and are stuck onto the internal perimetric face of the intermediate transfer belt  94  with an adhesive. 
     Since the first travelling guide rib  942  and the second travelling guide rib  944  are stuck along a circumferential direction onto the internal perimetric face of the intermediate transfer belt  94 , a first joint  12  is formed between a pasting start point and a pasting end point of the first travelling guide rib  942 , while a second joint  14  is formed between a pasting start point and a pasting end point of the second travelling guide rib  944 . Here, although an example is illustrated in which both ends in lengthwise direction of each of the first travelling guide rib  942  and the second travelling guide rib  944  are cut obliquely in consideration of stability of travelling of the intermediate transfer belt  94 , it is not always necessary to employ such a configuration. 
     Also, it is preferred that the first joint  12  and the second joint  14  are respectively provided with a predetermined gap. The reason is that providing a suitable gap for the joint position can prevent the first travelling guide rib  942  or the second travelling guide rib  944  from self-overlapping, which would otherwise occur due to a difference in thermal expansion property between the main body (base material) of the intermediate transfer belt  94  and the first travelling guide rib  942  or the second travelling guide rib  944 . 
     In this embodiment, the first joint  12  and the second joint  14  are disposed so as to be apart from each other in the circumferential direction of the intermediate transfer belt  94  at least not less than a distance (refer to the arrow  16  in  FIG. 4B ) corresponding to one-half of a perimeter of the intermediate transfer belt drive roller  85 . The reason is to prevent the first joint  12  and the second joint  14  from wrapping around the same roller at the same time. Here, the distance corresponding to one-half of the perimeter of the intermediate transfer belt drive roller  85  is employed as a reference, because design has been made so that the intermediate transfer belt drive roller  85  has the largest diameter among the intermediate transfer belt idle roller  84 , the intermediate transfer belt drive roller  85  and the intermediate transfer rollers  96 ; however, in a case where another roller has the largest diameter, a distance corresponding to one-half of a perimeter of the roller should be employed as a reference. 
     Next, using  FIG. 5A  through  FIG. 5C , technical significance of disposing the first joint  12  and the second joint  14  apart from each other in the circumferential direction of the intermediate transfer belt  94  not less than the distance corresponding to one-half of the perimeter of the intermediaLe transfer belt drive roller  85  is explained. As shown in  FIG. 5A  and  FIG. 5B , as the number of the support rollers over which the intermediate transfer belt  94  is passed in a tensioned condition decreases, an angle (wrap angle) alpha over which the intermediate transfer belt  94  wraps around the intermediate transfer belt drive roller  85  becomes bigger. Then, as shown in  FIG. 5C , the angle (wrap angle) alpha reaches 180 degrees (straight angle) when the intermediate transfer belt  94  is supported by two support rollers; however, the angle (wrap angle) alpha never exceeds 180 degrees (straight angle) except for a special case where diameters of two support rollers are extremely different. 
     For this reason, as in the configuration according to this embodiment, disposing the first joint  12  and the second joint  14  apart from each other in the circumferential direction of the intermediate transfer belt  94  not less than the distance corresponding to one-half of the perimeter of the intermediate transfer belt drive roller  85  having the largest diameter can securely prevent the first joint  12  and the second joint  14  from wrapping around the same roller at the same time. As a result, behavioral change of the intermediate transfer belt  94  when the first and the second joints  12 ,  14  of the first and the second travelling guide ribs  942 ,  944  pass through each of the rollers can be reduced to a small degree. Accordingly, smooth travelling performance of the intermediate transfer belt  94  is secured, and thus an occurrence of a deficiency such as an image defect attributable to the behavioral change of the intermediate transfer belt  94  is restrained adequately. 
     Moreover, the intermediate transfer belt  94  is securely prevented from remaining stationary for a long period of time in a state in which the first and the second joints  12 ,  14  together wrap around the same roller. Therefore, an occurrence of a deficiency such as bending strain or sharp bending at the first or the second joint  12 ,  14  in the intermediate transfer belt  194  is restrained; and as a result, deterioration of durability of the intermediate transfer belt  94  is prevented. 
     Next, using  FIG. 6 , a method for manufacturing the intermediate transfer belt  94  is explained. When the first and the second travelling guide ribs  942 ,  944  are stuck onto the intermediate transfer belt  94 , a guide rib pasting apparatus  30  as shown in  FIG. 6  is used. 
     The guide rib pasting apparatus  30  includes an idle roller  22 , a drive roller  24 , a guide roller  20  and a tension roller  26  each to support the intermediate transfer belt  94 . The tension roller  26  is supported movably upward and downward, and a tensile force can be applied to the intermediate transfer belt  94  by the tension roller  26  lowered to a position. Additionally, at a position corresponding to the guide roller  20  is installed a pressure roller  18  movably supported so as to be apart from and get close to (or in touch with) the guide roller  20 . 
     The first and the second travelling guide ribs  942 ,  944  before they are stuck onto the intermediate transfer belt  94  are respectively covered by a sheet of releasable paper on their adhesive surfaces. When the first and the second travelling guide ribs  942 ,  944  are adhered, each sheet of releasable paper thereof is removed at its head end portion to a matter of 10 cm, and then, with each exposed adhesive surface being opposed to the internal perimetric face of the intermediate transfer belt  94 , the head end portions of the first and the second travelling guide ribs  942 ,  944  are led to a pressure-bonding section of the guide roller  20  and the pressure roller  18 . 
     From this state, as the intermediate transfer belt  94  is run by the drive roller  24  that is made to rotate while the sheets of releasable paper of the first and the second travelling guide ribs  942 ,  944  are being removed, the first and the second travelling guide ribs  942 ,  944  keep on sticking along the circumferential direction onto the internal perimetric face of the intermediate transfer belt  94 . 
     Here, using  FIG. 7 , a process for sticking the first and the second travelling guide ribs  942 ,  944  onto the internal perimetric face of the intermediate transfer belt  94  is explained. As shown by the upper diagram of  FIG. 7 , first, the first travelling guide rib  942  is stuck to the first edge portion along the circumferential direction in the internal perimetric face of the intermediate transfer belt  94 . 
     Next, as shown by the middle diagram of  FIG. 7 , by the drive roller  24  made to rotate, the intermediate transfer belt  94  is caused to idly travel not less than the distance corresponding to one-half of the perimeter of the intermediate transfer belt drive roller  85 . 
     Subsequently, as shown by the lower diagram of  FIG. 7 , the second travelling guide rib  944  is stuck to the second edge portion along the circumferential direction in the internal perimetric face of the intermediate transfer belt  94 . By following such a procedure, it is easily and securely made possible to have the first joint  12  and the second joint  14  being apart from each other in the circumferential direction of the intermediate transfer belt  94  not less than the distance corresponding to one-half of the perimeter of the intermediate transfer belt drive roller  85 . 
     Although what was explained in  FIG. 7  was an example in which the first and the second travelling guide ribs  942 ,  944  are sequentially stuck onto the internal perimetric face of the intermediate transfer belt  94 , it is also possible to stick the first and the second travelling guide ribs  942 ,  944  simultaneously to either side edge portion of the internal perimetric face of the intermediate transfer belt  94 . 
     Next, using  FIG. 8 , another guide rib pasting apparatus  32  is explained as a variation of the guide rib pasting apparatus  30 . Basic structures of the guide rib pasting apparatus  30  and the guide rib pasting apparatus  32  are the same. But the guide rib pasting apparatus  32  includes a guide roller  202  and a pressure roller  182  for pasting the first travelling guide rib  942 , and a guide roller  204  and a pressure roller  184  for pasting the second travelling guide rib  944 , provided separately from each other. A pressure-bonding section of the guide roller  202  and the pressure roller  182  and a pressure-bonding section of the guide roller  204  and The pressure roller  184  are disposed so as to be apart from each other in the circumferential direction of the intermediate transfer belt  94  not less than the distance corresponding to one-half of the perimeter of the intermediate transfer belt drive roller  85 . Besides, in consideration of workability in pasting of the first travelling guide rib  942 , the guide roller  204  and the pressure roller  184  are disposed in a recessed manner as compared with the guide roller  202  and the pressure roller  182 . 
     When such a guide rib pasting apparatus  32  is used, the head end portion of the first travelling guide rail rib  942  is, with the adhesive surface thereof being opposed to the internal perimetric face of the intermediate transfer belt  94 , set to the pressure-bonding section of the guide roller  202  and the pressure roller  182 ; then the head end portion of the second travelling guide rail rib  944  is, with the adhesive surface thereof being opposed to the internal perimetric face of the intermediate transfer belt  94 , set to the pressure-bonding section of the guide roller  204  and the pressure roller  184 ; and thereby the first and the second travelling guide ribs  942 ,  944  are stuck to either side edge portion of the internal perimetric face of the intermediate transfer belt  94  at the same time. Then, the first joint  12  and the second joint  14  automatically come to be apart from each other in the circumferential direction of the intermediate transfer belt  94  not less than the distance corresponding to one-half of the perimeter of the intermediate transfer belt drive roller  85 . 
     The above explanation of the embodiments is nothing more than illustrative in any respect, nor should be thought of as restrictive. Scope of the present invention is indicated by claims rather than the above embodiments. Further, it is intended that all changes that are equivalent to a claim in the sense and realm of the doctrine of equivalence be included within the scope of the present invention.