Patent Publication Number: US-10781064-B2

Title: Method for applying air to sheets stacked on sheet stacking apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a method for applying air to sheets stacked on a sheet stacking apparatus. 
     Description of the Related Art 
     There are cases where a sheet feeding apparatus is connected to an image forming apparatus to form images on a large amount of sheets. The sheet feeding apparatus feeds sheets one by one to the image forming apparatus from a sheet bundle that is stacked on a tray. To separate a sheet from a sheet bundle, there is a variety of separation methods, such as the retard separation method and the Duplo method. 
     However, compared with plain paper, coated paper and OHP sheets that have good surface properties involve large adsorption force and negative pressure that are generated between sheets, and accordingly, there have been cases where sheets are not sufficiently separated with a conventional separation mechanism. Japanese Patent Laid-Open No. 2005-96994 proposes a method of blowing air toward sheets to cancel close contact between the sheets, and thereafter feeding the sheets. 
     However, in a sheet feeding apparatus described in Japanese Patent Laid-Open No. 2005-96994, separation performance is likely to decrease when the remaining amount of sheets has become small. If the remaining amount of sheets is small, the thickness of a sheet bundle is smaller than the height of an air nozzle. A part of the air collides with a side face of a sheet tray, on which the sheet bundle is stacked, then proceeds upward, and pushes up the bottom face of the sheet bundle. Since gravity and a force that is applied by the air flowing above the sheet bundle and pushes down the sheet bundle are exerted on the sheet bundle, the sheets are further brought into close contact with each other. If the sheets are brought into close contact, it is difficult for air to enter between the sheets, resulting in a decrease in separation performance. 
     SUMMARY OF THE INVENTION 
     The present invention provides a sheet stacking apparatus comprising a stacking unit on which a sheet bundle is to be stacked, a lifting unit configured to lift up and down the stacking unit, and an air blower unit configured to apply air to a side face of the sheet bundle via an air blowing port. The stacking unit further includes a stacking face that comes into contact with and holds a lowermost sheet of the sheet bundle, and a support portion that supports a portion of the stacking face near an end portion thereof, and has a face that is not parallel to the stacking face. The support portion includes a ventilating portion that allows air blown out by the air blower unit from a portion of the air blowing port to pass through the ventilating portion, the portion being below the stacking face. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional diagram of an image forming system. 
         FIGS. 2A and 2B  illustrate a sheet feeding apparatus. 
         FIGS. 3A to 3F  illustrate a tray. 
         FIGS. 4A and 4B  illustrate a flow of air. 
         FIGS. 5A and 5B  illustrate a modification. 
         FIG. 6  illustrates a modification. 
         FIG. 7  is a plan view illustrating a modification. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Sheet Feeding Apparatus 
       FIGS. 1, 2A, and 2B  are schematic cross-sectional diagrams of a feeding apparatus  1 . The feeding apparatus  1  is a sheet feeding apparatus for feeding sheets to an image forming apparatus  10 . As shown in  FIG. 2A , a tray  2  is a stacking unit that can be lifted up and lowered and on which a sheet bundle S is stacked. A motor M 1  is joined to the tray  2  via a wire and a plurality of pulleys. The tray  2  is lifted up when the motor M 1  rotates forward, and the tray  2  is lowered when the motor M 1  rotates backward. As shown in  FIG. 2B , the motor M 1  lifts up the tray  2  every time the amount of sheets stacked on the tray  2  decreases. 
     A rear end restricting plate  3  is a restricting unit for restricting the position of the rear end of the sheet bundle S. The rear end refers to an upstream end in the sheet feeding direction. A pair of side end restricting plates  4  are restricting members for restricting the positions of both side ends of the sheets in the width direction, which is perpendicular to the sheet feeding direction. When feeding the sheets S, a pickup roller  5  is lowered, comes into contact with the uppermost sheet S 1  of the sheet bundle S, and then rotates to feed the sheet S 1 . A feed roller  6  is a conveyance member for conveying sheets conveyed by the pickup roller  5 , further toward the downstream side. A retard roller  7  rotates so as to return the sheet fed by the pickup roller  5  toward the upstream side, and separates the uppermost sheet S 1  from the other fed sheets. 
     Air blower mechanisms  8   a  and  8   b  for separating sheets by means of air are provided on at least one of the two side end restricting plates  4 . The air blower mechanisms  8   a  and  8   b  have a fan and air blowing ports  9   a  and  9   b . As a result of air blown out from the air blowing ports  9   a  and  9   b  being blown between sheets, a plurality of sheets are loosened up so as to be separated into individual sheets. 
     Tray 
       FIG. 3A  is a plan view of the tray  2 . Two cutouts  13   a  and  13   b  are provided near a right end portion of a stacking face  30  of a stacking plate that constitutes the tray  2 . The cutouts  13   a  and  13   b  are provided at positions opposing the air blowing ports  9   a  and  9   b . The cutouts  13   a  and  13   b  function as ventilating portions for letting a part of the air blown out from the air blowing ports  9   a  and  9   b  escape toward the bottom face of the sheet bundle S when the amount of stacked sheets has become small. 
       FIG. 3B  shows a support member  31  located on a right side face of the tray  2 . The support member  31  supports the stacking plate that has the stacking face  30 , and restrains deformation of the stacking face  30  due to the load of the sheet bundle S. Note that the two cutouts  13   a  and  13   b  extend from the stacking face  30  to the support member  31 . Note that the width W of the two cutouts  13   a  and  13   b  may be equal to the width of the air blowing ports  9   a  and  9   b , but specifically, the loosening effect will increase if the width W is made wider than the width of the air blowing ports  9   a  and  9   b . Meanwhile, if the width W is made extremely wide, the bottom face of the lowermost sheet may be rubbed against end portions of the cutouts  13   a  and  13   b . Accordingly, the width W is determined so that sheets will not be soiled or damaged. 
       FIG. 3C  shows a support member  32  that is located on a left side face of the tray  2 . The support member  32  supports the stacking plate that has the stacking face  30 , and restrains deformation of the stacking face  30  due to the load of the sheet bundle S. 
       FIG. 3D  is a side view showing a rear end of the tray  2 .  FIG. 3E  is a cross-sectional view obtained by cutting off the tray  2  along a cut-off line V-V′ shown in  FIG. 3A . Specifically,  FIG. 3E  clearly shows that the cutout  13   a  is provided near a connecting portion at which the stacking plate  33  that has the stacking face  30  is connected to the support member  31 . 
       FIG. 3F  is an enlarged view of the cutout  13   a . The height h and depth d of the cutout  13   a  are determined so that the sheet-loosening effect can be readily achieved. The depth d refers to the depth of the cutout  13   a  when viewed from a side end portion of the support member. Each of the height h and the depth d need only be 5 mm or greater, for example. Meanwhile, the height h and the depth d are determined as values that do not allow a finger of an average adult to be inserted into the cutout  13   a . In this embodiment, each of the height h, the depth d, and the length x of an imaginary inclined plane (imaginary hypotenuse) obtained by compositing the height h and the depth d is less than 14.9 mm (mechanical tolerance is ±5% or less). More preferably, it will be difficult for an index finger to be inserted into the cutout  13   a  if each of the height h, the depth d, and the length x is less than 11.9 mm. 
     Although the cutout  13   a  has been described here, the cutout  13   b  may also have equal dimensions. The number of cutouts  13  need only be one or more. However, the number of cutouts  13  is the same as the number of air blower mechanisms  8 . Characters a and b that follow the reference numerals are used when distinguishing between a plurality of items, but are omitted when not distinguishing therebetween. 
     Effects of Ventilating Portions 
     As mentioned above, each air blower mechanism  8  blows out air from the air blowing port  9  before sheets start to be fed, and thus executes sheet separation (loosening of sheets). As shown in  FIG. 2A , if the height (thickness in the vertical direction) of the sheet bundle S is greater than the height (length in the vertical direction) of the air blowing port  9 , air enters between sheets in a sheet group to which air is applied in the sheet bundle S, and the sheets float up in the air. Thus, the sheet bundle S is loosened up, and the sheets therein are separated. 
     As shown in  FIG. 2B , there are cases where the height of the sheet bundle S is smaller than the height of the air blowing port  9 .  FIG. 4A  is a schematic cross-sectional diagram of the tray  2  and the air blower mechanism  8  in a comparative example in which no cutout  13  is provided. The arrows indicate the direction and flow of air. When the remaining amount of sheets has become small, the support member  31  provided at an end portion of the tray  2  blocks the lower portion of the air blowing port  9 . Air blown out from the lower portion of the air blowing port  9  collides with the support member  31 . A part of the air proceeds upward along the support member  31 , and the other part of the air proceeds downward along the support member  31 . In particular, the air that proceeds upward collides with the bottom face of the lowermost sheet of the sheet bundle S and pushes up the sheet bundle S. As a result, sheets come into close contact with each other, then it is difficult for the air to enter between the sheets, and separation performance deteriorates. 
     In this embodiment, as shown in  FIG. 4B , the cutout  13  provided near the connecting portion at which the stacking face  30  is connected to the support member  31  guides the air blown out from the lower portion of the air blowing port  9 , downward of the sheet bundle S. That is to say, air is restricted so as not to proceed upward. Sheets in the sheet bundle S that are on the lower side are pulled downward by the gravity and a force according to the Bernoulli theorem. Sheets in the sheet bundle S that are on the upper side are pulled upward by the force according to the Bernoulli theorem. Thus, gaps between the sheets expand, making it easy for air to enter between the sheets, and separation performance increases. In addition, by thus providing the cutout  13  near the connecting portion at which the stacking face  30  is connected to the support member  31 , sheets can be stacked without damaging end faces of the stacked sheets even if a burr or the like has been made during processing. 
     Summary 
     The tray  2  is an example of a stacking unit on which the sheet bundle S is stacked. The motor M 1  is an example of a lifting unit for lifting up and down the stacking unit. The air blower mechanism  8  is an example of an air blower unit for applying air to a side face of the sheet bundle S to separate a plurality of sheets that constitute the sheet bundle S from each other. The pickup roller  5  is an example of a feeding unit for feeding the uppermost sheet S 1  of the sheet bundle S. Note that a conveyance belt that suctions the uppermost sheet S 1  to convey this sheet may be employed in place of the pickup roller  5 . The tray  2  has the stacking face  30  that comes into contact with and holds the lowermost sheet of the sheet bundle S. The cutout  13  is an example of a ventilating portion for guiding air that is blown out from a portion of the air blowing port  9  of the air blower unit, the portion being below the stacking face  30 , so that the air passes below the stacking face  30 . Since the ventilating portion thus allows the air blown out from a portion of the air blowing port  9 , the portion being below the stacking face  30 , to escape so that the air passes below the stacking face  30 , sheet separation performance is maintained even when the remaining amount of sheets has become small. Although, in  FIG. 2B , air is blown out toward the right side face of the sheets, the air blower mechanism  8  may be provided so that air is blown out toward at least one of the left side face of the sheets, a side face thereof on the leading end side, and a side face thereof at the rear end. In this case as well, the cutout  13  is provided at a position opposing the air blowing port  9 . 
     As shown in  FIGS. 3A to 3E , the tray  2  may have the stacking plate  33  that has the stacking face  30 , and the support member  31  that supports a portion of the stacking plate  33  near an end portion thereof, and has a face that is not parallel to the stacking face  30  of the stacking plate  33 . The cutouts  13   a  and  13   b  shown in  FIG. 3A  function as ventilating portions for allowing air to escape so that the air blown out from the air blower unit is not deflected by the support member  31  to push up the bottom face of the sheet bundle S. Here, the ventilating portion may be an opening that is only provided in the support member  31 , and is not provided in the stacking face  30  of the stacking plate  33 . Note that the opening may be a plurality of holes that are opened by machining equipment such as a drill. The loosening effect is particularly maintained when the width W of the cutout  13  is greater than the width of the air blowing port  9  of the air blower unit. However, the dimensions of the cutout preferably are those that do not allow a finger of an average adult to be inserted into the cutout. A comparatively high loosening effect is achieved if the height h of the cutout provided in the support member  31  is 5 mm or greater. Similarly, a comparatively high loosening effect is achieved if the depth d of the cutout  13  provided in the stacking face  30  of the stacking plate  33  is 5 mm or greater. Note that the stacking plate  33  and the support member  31  that form the tray  2  may be a common member that is formed by bending a metal plate. In the case of thus performing a bending process, an effect of readily absorbing an error that occurs during the process can also be achieved by providing the cutout  13  near the connecting portion (continuous portion) at which the stacking face  30  is connected to the support member  31 . As shown in  FIG. 3D , the stacking face  30  and the face of the support member  31  may be perpendicular to each other. This is effective from the viewpoint of maintaining the stacking face  30  flatly. 
       FIGS. 5A and 5B  show a modification in which a support member  31  is provided in place of the above-described ventilating portion, the support member  31  serving as a guiding portion for guiding a part of the air blown out from the air blowing ports  9   a  and  9   b  toward the bottom face of the sheet bundle S when the amount of stacked sheets has decreased. The guiding portion is a portion of the support member  31 , and this portion, which opposes the air blowing ports  9   a  and  9   b  of the air blower unit, may be formed by the stacking face  30  and a face of the support member  31  that opposes the air blowing ports  9   a  and  9   b  forming an angle θ that is greater than 270 degrees or more, with the stacking face  30  serving as a reference. By thus inclining the support member  31 , the support member  31  functions as a guiding portion for guiding the air blown out from a portion of the air blowing port  9 , the portion being below the stacking face  30 , so that the air passes below the stacking face  30 . 
       FIG. 6  shows a modification of the guiding portion. The guiding portion may be an eaves member  35  that protrudes toward the air blower mechanism  8 , further than the connecting portion at which the stacking member that has the stacking face  30  is connected to the support member  31 . The air blown out from a portion of the air blowing port  9 , the portion being below the stacking face  30 , collides with the support member  31 , and a part of the air is deflected upward. This part of the air collides with the eaves member  35  and is deflected again, and proceeds downward. That is to say, the air blown out from a portion of the air blowing port  9 , the portion being below the stacking face  30 , is guided by the eaves member  35  so that the air passes below the stacking face  30 . Note that the eaves member  35  may be a portion of the stacking plate  33 . 
       FIG. 7  shows a modification of the stacking plate  33 . Opening holes  601   a  and  601   b  are provided in the stacking face  30  of the stacking plate  33 . The opening holes  601   a  and  601   b  are formed in the stacking face  30  so that the side restricting members  80  and  83  can move. Also, a rear end restricting member  87  is arranged so as to restrict a rear end portion of sheets stacked on the stacking face  30 . The rear end restricting member  87  is supported so as to be able to move in a direction parallel to the sheet feeding direction. This rear end restricting member  87  can move along an elongated positioning hole portion  61   c  that is formed in a center portion of the stacking face  30 . The air blower mechanism  8   a  is provided in the side restricting member  80 , and the air blower mechanism  8   b  is provided in the side restricting member  83 . When the side restricting members  80  and  83  move, the air blower mechanisms  8   a  and  8   b  move together with the side restricting members  80  and  83 . In the stacking plate  33  that has the above-described configuration as well, the cutouts  13   a  and  13   b  are provided at positions through which the air blown out from the air blowing ports  9   a  and  9   b  of the air blower mechanisms  8   a  and  8   b  passes, respectively. For example, the cutout  13   a  may be provided so as to oppose the air blowing port  9   a , and the cutout  13   b  may be provided so as to oppose the air blowing port  9   b . Thus, the cutouts  13   a  and  13   b  function as ventilating portions that guide the air blown out from portions of the air blowing ports  9   a  and  9   b , the portions being below the stacking face  30 , so that the air passes below the stacking face  30 . Also, there is a possibility that the air that passes below the sheets enters the elongated hole portion  61   c , causing a force that pushes up the sheets. An increase in separation efficiency at a sheet end portion allows air to enter between sheets from a sheet end portion, and separation performance for a bundle of sheets will further improve. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2017-154673, filed Aug. 9, 2017, and Japanese Patent Application No. 2018-130861, filed Jul. 10, 2018, which are hereby incorporated by reference herein in their entirety.