Patent Publication Number: US-6908010-B2

Title: Driven rotary body, sheet material conveying apparatus, and recording apparatus

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a driven rotary body rotating due to pressurized contact with a conveyance rotary body and driven by this conveyance rotary body and, e.g., to a pinch roller in pressurized contact with a conveyance roller as a driven rotary body, a sheet material conveying apparatus having the pinch roller, and a recording apparatus having the sheet material conveying apparatus. 
   2. Description of Related Background Art 
   In apparatuses such as printers, photocopiers, and facsimile machines, sheet materials stacked on a sheet material stacking section are separately fed sheet by sheet to effect recording on the sheet materials or to read original documents, and after the front ends of the sheet materials separated at the sheet material conveying section are aligned, the sheet materials are conveyed to a recording reading area. 
     FIG. 5  is a perspective view showing a conveyance portion of a conventional conveying apparatus;  FIG. 6  is a structural cross-sectional view for illustrating a structure of a sheet material conveyance portion of the conventional conveying apparatus. 
   The sheet material separately conveyed from a feeding apparatus (not shown) is so aligned as to arrange the front end thereof at a conveyance portion  110  with a conveyance roller  111  and a pinch roller  104  in pressure contact with the conveyance roller  111 . 
   The sheet material with the aligned front end is transmitted to a recording portion  130  by the conveyance roller  111 , and a recording head  132  records where the sheet material is supported at a platen  131 . 
   The recorded sheet material is delivered to the exterior of the apparatus through a delivery portion  140  formed of at least one delivery roller  141  and corresponding delivery spur  142 . 
   The conveyance roller  111  is a metal roller having a sheet material conveyance surface on which ground particles are coated, and the pinch roller  104  is formed of a molded resin such as POM (polyoxymethylene). 
   The pinch roller  104  has a hole opened in a longitudinal direction, is supported by a pinch roller holder  102  attached rotatably to a body chassis  101  where a metal shaft  105  is penetrated through the hole, and is in pressure contact with the conveyance roller  111  by a pinch roller spring  103 . 
     FIG. 7  shows a shape of the pinch roller  104  in the conventional apparatus as described above. 
   The pinch roller  104 , in which the hole is opened as to receive the metal shaft as shown in FIG.  7 ( a ), is formed by parting the mold around one end of the roller in the longitudinal direction as shown in FIG.  7 ( b ). That is, as shown in FIG.  7 ( b ), the pinch roller  104  is molded in a shape as shown in FIG.  7 ( a ) with molds  151 ,  152  respectively extending in the longitudinal direction and being parted at a partition line PL around the one end of the roller in the longitudinal direction. 
   A surface of the pinch roller  104  is necessarily to be molded with as few scratches as possible to prevent damage from occurring on the sheet material, and the diameter of the center portion is necessarily larger than each end to prevent scratching the sheet material by opposite ends of the pinch roller in the longitudinal direction. That is, where the pinch roller diameters at positions ( 1 ), ( 2 ), ( 3 ) in FIG.  7 ( a ) are φA±a, φB±b, and φC±c, the relation among those diameters is B−b&gt;A+a, and A=C. As shown in FIG.  7 ( a ), length D of the conventional pinch roller  104  in the longitudinal direction is about 20 mm. 
   To the contrary, in a case where the metal shaft is eliminated for cost reduction, where the pinch roller is molded as an integral body to reduce the unit price, and where the length of each roller is made longer to reduce the number of the pinch rollers, the length of the mold for molding the roller may become longer in a longitudinal direction by an extended portion of the roller with a molding method in which the molds are parted at one side in the longitudinal direction of the roller in substantially the same way as in the conventional method. 
   Therefore, problems arise not only in that the production of the mold becomes difficult, but also in that the molding cycle for the roller becomes longer due to cooling of the mold, that accurate sizes tend not to be obtained during molding, and that defects tend to occur, and consequently, the advantages of the cost reduction may be nullified. 
   If the above problems could be solved by using particular resin materials, the valuable advantages of cost reduction may not be adequately achieved due to costs and availability of the materials or the like. 
   SUMMARY OF THE INVENTION 
   This invention is made in consideration of the problems in the prior art as described above, and it is an object to provide a pinch roller that can be molded without any difficulty with an ordinary molding method and ordinary materials even where the pinch roller is molded as an integral body and formed in an extended shape. 
   A representative structure of a drive rotary body of the invention for accomplishing the above objects is as follows: a driven rotary body rotating in pressure contact with and driven by a conveyance rotary body, said drive rotary body comprising: a shaft portion molded from a resin in a united body; a recess for parting a mold in the longitudinal direction of the driven rotary body; and a roller portion positioned on each side of the recess. 
   A structure of a representative sheet material conveying apparatus according to the invention to accomplish the above objects includes: a conveyance roller for conveying a sheet material; a pinch roller driven by the conveyance roller to rotate, the pinch roller having a shaft portion molded from a resin in a united body, a recess for parting a mold in the longitudinal direction of the driven rotary body, and a roller portion positioned on each side of the recess, a pinch roller holding means for holding the pinch roller; and a pressing means for contacting the pinch roller to the conveyance roller with pressure. 
   As described above, according to the invention, with the drive rotary body rotating in pressure contact with and driven by a conveyance rotary body, the length of the molds for the driven rotary body can be shortened by providing the recess for parting the molds in the longitudinal direction of the driven rotary body. Therefore, where the bearing is molded with a resin in a united body to extend the length of the driven rotary body in the longitudinal direction, the rotary body does not worsen the molding cycle for cooling the molds and can effect excellent molding without using any particular material, so that the production costs thereof can be reduced. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing the entire structure of a recording apparatus in a first embodiment; 
       FIG. 2  is a top view of the recording apparatus shown in  FIG. 1 ; 
       FIG. 3  is a structural cross-sectional view of the recording apparatus shown in  FIG. 1 ; 
       FIG. 4  is an illustration showing a pinch roller of the recording apparatus shown in  FIG. 1 ; 
       FIG. 5  is a perspective view showing a conveyance unit of a conventional conveying apparatus; 
       FIG. 6  is a structural cross-sectional view illustrating a structure of a sheet material conveying unit of the conventional conveying apparatus; and 
       FIG. 7  is an illustration showing a conventional pinch roller. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Hereinafter, referring to the drawings, preferred embodiments of the invention are described in detail in an exemplifying manner. The sizes, materials, shapes, and correlative positions of structural parts as set forth in the embodiments below can be modified properly according to the apparatus structure to which this invention applies and to various conditions and terms, and if there is no specific description, the scope of this invention is not intended to be limited. 
   First Embodiment 
   Hereinafter, the first embodiment of the invention is described with reference to the drawings.  FIG. 1  is a perspective view showing the entire structure of a recording apparatus in a first embodiment;  FIG. 2  is a top view of the recording apparatus shown in  FIG. 1 ; and  FIG. 3  is a structural cross-sectional view of the recording apparatus shown in FIG.  1 . 
   As shown in  FIGS. 1-3 , a recording apparatus  1  includes a feeding unit  2  for stacking and separately feeding sheet materials as recording media, a conveyance unit  3  for conveying the fed sheet materials, a delivery unit  4  for delivering the sheet materials to the exterior of the recording apparatus, a carriage unit  5  on which a recording head is mounted for recording on the sheet materials, and a cleaning unit  6  for cleaning the recording head. Hereinafter, the structure of the respective units and their operation will be described. 
   The feeding unit  2  is rotatably attached to a base  11  around a rotary shaft as a center. The feeding unit  2  is constituted of a pressure plate  21  stacking the sheet materials serving as recording media, a pair of a feeding roller  22  and a separation roller  23  for separately feeding the stacked sheet materials sheet by sheet, a pressure plate spring  24  urging the pressure plate  21  to the feeding roller  22 , and a movable side guide  25  limiting the stacking position of the sheet materials in the lateral direction. 
   During a waiting state, the pressure plate  21  is pushed down by a cam or the like (not shown) to a prescribed position, and this disengages the contact between the pressure plate  21  and the feeding roller  22 . 
   During the feeding operation, the pressure plate  21  is lifted by the cam or the like (not shown) to contact the feeding roller  22  with the sheet material, and the sheet material is conveyed according to the rotation of the feeding roller  22  to be sent to the conveyance unit  3  after being separated sheet by sheet with the feeding roller  22  and the separation roller  23 . 
   The conveyance unit  3  includes a conveyance roller  31  as a conveyance rotary body for conveying the sheet materials, a pinch roller  32  formed in contact with the conveyance roller  31  for serving as a driven rotary body driven by the conveyance roller  31 , a pinch roller holder  33  attached rotatably to a chassis serving as a holding means, a pinch roller spring  34  as a pushing means for urging the pinch roller  32  in pressing contact with the conveyance roller  31 , and a PE sensor lever  35  attached rotatably to the pinch roller holder  33  for detecting the front and rear ends of the sheet materials. 
   The conveyance roller  31  rotates upon receipt of the drive of a conveyance motor  13  via a motor gear  14  as well as via a conveyance gear  36  secured to the conveyance roller  31 . An output gear  37  is secured on the opposite side of the secured portion of the conveyance gear  36  of the conveyance roller  31  for transmitting drive of the conveyance motor  13  to the conveyance unit  2 . 
   The sheet material sent to the conveyance unit  3  is guided on a guide surface  16  of the base  11  and a lower surface of the pinch roller holder  33 , sent to a roller pair of the conveyance roller  31  and the pinch roller  32 , and conveyed to a downstream side of the conveyance roller  31  after the front end of the sheet material is aligned. 
   The PE sensor lever  35  is moved pivotally by the front end of the sheet material midway of the above operation, and the front end of the sheet material is detected upon operation of a PE sensor  91  formed on an electric substrate  9  secured to the chassis  9 . From the detected result, the conveyed amount of the sheet material can be determined up to the position for beginning the recording. 
   The sheet material conveyed to the downstream side of the conveyance roller  31  is subject to image formation with a recording head  7  mounted on the carriage  50  while the sheet material is guided on a platen surface  12  formed on the base  11 . 
   The delivery unit  4  is constituted of a delivery roller  41  for conveying the sheet materials sent from the conveyance unit  3 , a delivery spur driven rotatably by the delivery roller  41 , and a delivery idling gear  44  for transmitting the drive from the conveyance motor  13  to a delivery gear  43  formed at the delivery roller  41 . 
   The sheet material formed with images is conveyed by being sandwiched between the delivery roller  41  and the delivery spur  42  and delivered onto a delivery tray  15 . 
   Next, the pinch roller as the driven rotary body according to the embodiment is described.  FIG. 4  is an illustration showing the pinch roller according to this embodiment. 
   The pinch roller  32  as the driven rotary body driven to rotate by pressure contact with the conveyance roller  31  as the conveyance rotary body is molded of a resin with pinch roller bearings  32   a ,  32   b  to form a united body. 
   The pinch roller  32  is supported on a pinch roller holder  33  (see  FIG. 3 ) as a holding means with the pinch roller bearings  32   a ,  32   b , pressed with the pinch roller spring  34  (see  FIG. 3 ) as a pushing means and urged to the conveyance roller  31 . 
   In this embodiment, as shown in  FIG. 3 , four of the pinch rollers  32  are arranged to be extending in a width direction substantially perpendicular to the sheet material conveyance direction, and each pinch roller spring  34  urges the pinch roller  32  at five locations around the bearings of the pinch roller holders  33 . The urging forces from the respective pinch roller springs  34  is designed such that the relation among those urging forces becomes β=2α where the force is denoted as α at two locations of the opposite ends of the four pinch rollers thus arranged and as β at three other locations. 
   A recess  32   c  is formed at a center in the longitudinal direction of the pinch roller  32 , and when molded, the molds are parted horizontally in the longitudinal direction at a portion of the recess  32   c . More specifically, as shown in FIG.  4 ( b ), in this embodiment, regarding the pinch roller  32 , two molds  38 T,  38 U parting vertically with respect to the longitudinal direction form the recess  32   c , and two molds  39 L,  39 R parting horizontally in the longitudinal direction at a parting line PL with respect to the molds  38 T,  38 U form roller portions  32   d ,  32   e  located on the respective sides of the recess. Those molds form the recess  32   c  and mold the pinch roller  32  as shown in FIG.  4 ( a ) extending in the axial direction with which the bearings  32   a ,  32   b  are molded in a united body. 
   Thus, the recess  32   c  is formed at the center in the longitudinal direction of the pinch roller  32 , and the molds  39 L,  39 R are divided horizontally at a portion (parting line PL) of the recess  32   c , thereby rendering short the length of the mold for the roller in the longitudinal direction even where a roller elongated in the longitudinal direction is molded. Therefore, even where the length of the pinch roller  32  in the axial direction is extended where the bearings  32   a ,  32   b  are molded in the united or integral body to the roller, the molding cycle for cooling the molds is not worsened, and the molding can be performed in a good shape with a resin such as POM (polyoxymethylene) used conventionally without using any particular material, so that cost reduction can be achieved. 
   The recess  32   c  of the pinch roller  32  is made wider in a direction from the rotary center to the roller outer periphery. This is not only for parting the molds  39   a ,  39   b  horizontally in the longitudinal direction as shown in FIG.  4 ( b ) at the boundary of a portion (parting line PL) of the recess  32   c , but also for preventing the molds  38 T,  38 U at a portion of the recess  32   c  from not releasing in the vertical direction with respect to the longitudinal direction. 
   Regarding the pinch roller  32 , the outer diameter of the recess  32   c  is smaller than the outer diameter of the roller portion. More specifically, the outer diameters of the opposite ends of the recess  32   c  are smaller than the outer diameters around the center of the roller portions  32   d ,  32   e  located on both sides of the recess. That is, as shown in FIG.  4 ( a ), in one pinch roller  32 , the right and left roller portions  32   d ,  32   e  astride the recess  32   c  satisfy the diameter relations of B−b&gt;A+a and A=C, where the roller diameters at positions ( 1 ), ( 2 ), ( 3 ) are φA±a, φB±b, and φC±c. 
   It is to be noted that in this embodiment as shown in FIG.  4 ( a ), diameter H 1  of the roller portions  32   d ,  32   e  of the pinch roller  32  is about 5 mm; diameter H 2  of the recess  32   c  is about 4 mm; depth H 3  of the recess  32   c  is about 0.5 mm; width H 4  in the axial direction of the recess  32   c  on a side of the roller outer peripheral surface is about 2 mm; and length H 5  in the longitudinal direction of the entire pinch roller molded as an integral body is about 48 to 50 mm. 
   Other Embodiments 
   Although in the embodiment described above the pinch roller driven to rotate in pressure contact with the conveyance roller for conveying the sheet materials is exemplified as a driven rotary body driven to rotate in pressure contact with a conveyance rotary body, the invention is not limited to this, and is properly applicable according to demands. 
   Although in the embodiment described above the kind and number of the recording heads are not exemplified specifically, the invention is applicable, notwithstanding the kind and number of the recording heads, to any apparatus such as an inkjet recording apparatus using a single recording head, a multicolor inkjet recording apparatus using multiple recording heads in which inks of different colors effect recording, and a grayscale-type inkjet recording apparatus using plural recording heads in which inks of the same color but different densities effect recording, so that the advantages described above can be achieved. 
   As a recording means (recording head), any structure of the recording means and the ink tank, such as a structure of a cartridge type in which a recording head and an ink tank are united, or a structure in which a recording head and an ink tank are separated and connected via an ink supplying tube, is applicable in substantially the same way, and substantially the same advantages can be obtained. 
   Where this invention is applied to an inkjet recording apparatus, this invention is applicable to a structure using a recording means using, e.g., an electro-mechanical converter such as a piezo device or the like, and, inter alia, an excellent advantage can be achieved by an inkjet recording apparatus using recording means of an ink discharging method utilizing thermal energy. With this method, recording is achieved with high density and high definition. 
   Furthermore, this invention is effectively applicable to a recording head of a full line type having a length corresponding to the maximum width of the recording medium on which the recording apparatus can record. As such a recording head, either of a structure satisfying the length in combination of plural recording heads or a structure of a sole recording head formed as a united body can be used. In addition, even in the serial type described above, this invention is advantageous when using a recording head secured to the apparatus body, a recording head of a replaceable chip type in which ink can be supplied from the apparatus body and in which electrical connection is made when attached to the apparatus body, or a recording head of a cartridge type in which an ink tank is formed in a united body with the recording head itself. 
   As a system of the inkjet recording apparatus described above, this invention is applicable not only to an apparatus used as an image output terminal apparatus of an information processing apparatus such as a computer, but also to such as an inkjet input/output apparatus capable of attaching a scanner or the like rather than the recording head on the carriage, a photocopier in combination with a reader and the like, and a facsimile machine having a transmitting and receiving function. 
   In the embodiment described above, the inkjet recording method is exemplified as the recording method, but this invention is not limited to this. This invention is applicable to a thermal transfer method, a thermosensitive recording method, an impacting recording method such as a wire dot recording method, and other recording methods such as electrophotographic methods.