Patent Publication Number: US-6702109-B1

Title: Wet sheet package and method of producing the same

Description:
FIELD OF THE INVENTION 
     The present invention relates to a wet sheet package and a method of producing the same, and provides a wet sheet package and a method of producing the same, wherein the production can be easily speeded up, the decrease of yield due to positional deviation of a cover unit can be prevented, and low cost, easy and efficient production is made possible. 
     BACKGROUND ART 
     Some of the wet sheet packages in the form of wet sheets received in a packaging bag used to wipe dirt off a baby&#39;s body or the like have heretofore been provided with a cover unit on the takeout opening side of the packaging bag. Such cover unit-equipped wet sheet package comprises a stack of wet sheets impregnated with a cleaning liquid, medicine liquid or the like, a packaging bag made of a hermetic packaging sheet material, such as synthetic resin film, for storing said stack, a cover unit mounted on the opening side of the packaging bag, wherein when wet sheets are to be used, the cover body of the cover unit is opened to allow the wet sheets in the package to be taken out one by one through the takeout port. 
     This cover unit-equipped wet sheet package is produced, as described in Japanese Patent Kokai Hei 8-318977, conventionally by a method comprising the steps of forming an opening of suitable size in a packaging sheet material, integrally joining a cover unit to said packaging sheet material as by heat seal so as to correspond to said opening, feeding a stack to a position corresponding to the cover unit on the packaging sheet material, wrapping said stack in said packaging sheet material while sealing the packaging sheet material at required places as by heat seal, thereby forming a packaging bag for packaging the stack. 
     However, in the prior art, because of the steps, employed in producing wet sheet packages, of joining the unit cover to the opening side of the packaging sheet material, feeding the stack onto the packaging sheet material in alignment with the cover unit, and then wrapping the stack in the packaging sheet material so as to form a packaging bag, it is very difficult to speed up the production or high efficiency can hardly be attained, as compared with the type having no cover unit. 
     Further, the cover unit has to be disposed in a predetermined position, such as the middle of the upper surface of the packaging bag. However, the packaging bag is formed such that while conveying the packaging sheet material having the cover unit mounted thereon, the stack is fed onto the packaging sheet material; therefore, the packaging sheet material tends to be deviated owing to vibrations of the cover unit, or the like. As a result, when the packaging bag is formed such that the stack is wrapped in the packaging sheet material, the cover unit tends to deviate from the central region of the upper surface of the packaging bag, lowering the yield of wet sheet packages. 
     Therefore, since the conventional cover unit-equipped wet sheet package is difficult to produce at high speed and is low in production yield, there is a problem that the production cost drastically increases. 
     With the above in mind, the invention has for its object the provision of a wet sheet package, and a method of producing the same, wherein high speeds for production can be easily attained, the decrease of yield due to positional deviation of the cover unit, etc., can be prevented, and low cost, easy and efficient production is possible. 
     DISCLOSURE OF THE INVENTION 
     A wet sheet package according to the invention comprises a stack  1  of wet sheets  2 , a hermitic packaging bag  3  storing said stack  1 , a wet sheet takeout opening  4  formed in said packaging bag  3 , and a cover unit  8  mounted on the opening  4  side of said packaging bag  3 , wherein said cover unit  8  is mounted on said packaging bag  3  from outside through a pressure sensitive adhesive  10 . Therefore, the cover unit  8  can be mounted after the production of the packaging bag  3 , so that, as compared with the prior art, high speeds for production can be easily attained, the decrease of yield due to positional deviation of the cover unit  8 , etc., can be prevented, and low cost, easy and efficient production is possible. 
     Further, a wet sheet package according to the invention is such that said cover unit  8  comprises an attaching base  11  having a takeout opening  9  corresponding to the opening  4  and stuck to said packaging bag  3  through the pressure sensitive adhesive  10 , and a cover body  13  disposed in said attaching base  11  for opening and closing said takeout port  9 , wherein said pressure sensitive adhesive  10  is positioned to surround the entire periphery of said opening  4 . Therefore, the cover unit  8  is simple in construction and allows the user to open the cover body  13  as required to take out a wet sheet  2  in the inside through the takeout port  9  with ease. Further, the attaching base  11  can be easily and reliably stuck to the outer side of the opening  4  in the packaging bag  3  by the pressure sensitive adhesive  10 . 
     Further, a wet sheet package according to the invention is such that said attaching base  11  has an opening/closing label  24  openably/closably stuck thereto through a pressure sensitive adhesive  26  for sealing said takeout port  9 . Therefore, after a wet sheet  2  in the packaging bag  3  has been taken out, the takeout opening  9  can be easily and reliably sealed by the opening/closing label  24 , preventing drying, etc. of the wet sheets  2 . 
     Furthermore, a the wet sheet package according to the invention is such that said packaging bag  3  is formed with said opening  4  in the upper surface side of a packaging sheet material  6  which packages said stack  1 , the packaging sheet material  6  having a longitudinal seal portion  5  formed on the lower surface side thereof for sealing the lug side of said packaging sheet  6  longitudinally of said stack  1 , and transverse seal portions  7  formed in the opposite ends longitudinally of said stack  1  for sealing the opposite ends of said packaging sheet material  6 . Thus, the packaging bag  3  is simple in construction and adhesion of the cover unit  8  to the packaging bag  3  is also easy. 
     A method of producing such wet sheet package according to the invention comprises a packaging bag producing step  39  for producing a packaging bag  3  for wrapping a stack  1  of wet sheets  2  in a hermetic packaging sheet material  6  so as to package said stack  1  in said packaging sheet material  6 , and a cover unit mounting step  40  for mounting from outside a cover unit  8  on the wet sheet takeout opening  4  side of said packaging bag  3  produced by said packaging bag producing step  39 . Therefore, as compared with the prior art, high speeds for production can be easily attained, the decrease of yield due to positional deviation of the cover unit  8 , etc., can be prevented, and low cost, easy and efficient production is possible. 
     Further, a production method according to the invention is such that in producing a wet sheet package A by producing a packaging bag  3  for wrapping a stack  1  of wet sheets  2  in a hermitic packaging sheet material  6  so as to package said stack  1  in said packaging sheet material  6 , said cover unit  8  is mounted from outside on the side of the wet sheet takeout opening  4  formed in said packaging sheet material  6  after said step  34  of wrapping said stack  1  in said packaging sheet material  6 . Therefore, as in the above, high speeds for production can be easily attained, the decrease of yield due to positional deviation of the cover unit  8 , etc., can be prevented, and low cost, easy and efficient production is possible. 
     Furthermore, a production method according to the invention is such that in the step preceding the step of producing the packaging bag  3  using the packaging sheet material  6 , said cover unit  8  is mounted on the opening  4  side of said packaging sheet material  6 . Therefore, there is no problem arising, such as one of the packaging bag  3  being torn by the urging of the cover unit  8 . 
     Further, a production method according to the invention is such that when said cover unit  8  having an attaching base  11  with a takeout port  9  and a cover body  13  installed on said attaching base  11  for opening/closing said takeout port  9  is mounted on said packaging bag  3 , a pressure sensitive adhesive  10  is applied to the attaching base  11  and said attaching base  11  is stuck to said packaging bag  3  through said pressure sensitive adhesive  10  with said takeout port  9  positioned to correspond to said opening  4 . Therefore, as compared with the operation of applying the pressure sensitive adhesive  10  to the packaging bag  3  side, the present operation is easy to perform, and the oozing of the pressure sensitive adhesive  10  from the attaching base  11 , etc. can be easily prevented. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing the opened state of a wet sheet package according to a first embodiment of the invention; 
     FIG. 2 is an exploded perspective view showing said opened state; 
     FIG. 3 is a cross sectional view showing said opened state; 
     FIG. 4 is a longitudinal sectional view showing said opened state;  6   
     FIG. 5 is a longitudinal sectional view showing said opened state; 
     FIG. 6 is a block diagram showing a wet sheet package producing process; 
     FIG. 7 is en explanatory view of the wet sheet package producing process; 
     FIG. 8 is a perspective view of a wet sheet package; 
     FIG. 9 is a block diagram showing a wet sheet package producing process according to a second embodiment of the invention; 
     FIG. 10 is a block diagram showing a wet sheet package producing process according to a third embodiment of the invention; 
     FIG. 11 is a longitudinal sectional view showing the closed state of a wet sheet package according to a fourth embodiment of the invention; and 
     FIG. 12 is a plan view showing the opened state. 
    
    
     BEST MODE FOR EMBODYING THE INVENTION 
     Embodiments of the invention will now be described in detail with reference to the drawings. FIGS. 1 through 8 illustrate a first embodiment of the invention. This wet sheet package A, as shown in FIGS. 1 through 5, comprises a stack  1  of wet sheets  2 , such as wet towels, a packaging bag  3  for packaging the stack  1  in its stored state, and a cover unit  8  mounted on the packaging bag  3  from outside. 
     The stack  1  is obtained in that a plurality of wet sheets  2  folded in zigzag or in other form are stacked substantially in a cubic form as a whole. The wet sheets  2  are staked in such a manner that the ends of upper and lower wet sheets  2  are placed on each other over a predetermined range so that when a wet sheet  2  is taken out, the ends of the upper and lower wet sheets  2  coordinate with each other. 
     The packaging bag  3  is formed with an opening  4  above the upper surface side of the stack  1  for taking out wet sheets  2  and a cover unit  8  is stuck from outside to the upper surface so as to correspond to the opening  4 . For the packaging bag  3 , use is made of a hermetic packaging sheet material  6 , for example, a single film, such as a synthetic resin film of polyethylene, polypropylene, polyester, polyamide, polyvinyl chloride, polyvinylidene chloride, cellophane, or acetate, a composite film of two or more of these materials, or a superposed film in the form of an aluminum foil superposed on such single or composite film. 
     The packaging bag  3  is sealed, with the stack  1  of the wet sheets  2  wrapped therein, such that the lower surface side opposite to the opening  4  is longitudinally sealed at a longitudinal seal portion  5  in the widthwise middle of the stack  1  and such that the longitudinal opposite ends of the stack  1  are sealed at transverse seal portions  7  through gussets  6   a . In addition, the seal portions  5  and  7  are each joined by heat seal or any other joining method. The opening  4  is formed oval substantially in the middle of the upper surface side above and longitudinally of the stack  1 . 
     The cover unit  8  comprises an attaching base  11  having a takeout port  9  formed therein and stuck to the upper surface side of the packaging bag  3  through a pressure sensitive adhesive  10 , a cover body  13  openably/closably pivoted to the attaching base  11  by hinges  12 , and an elastic body  14  interposed between the attaching base  11  and the cover body  13  on the hinge  12  side and urging the cover body  13  in the opening direction. 
     And, the cover unit  8  is provided on the attaching base  11  side with an fitting support portion  15   a  and on the cover body  13  side with an engaging portion  16  adapted to releasably engage the engaging support portion  15   a  when the cover body  13  is closed, and with an operating portion  17  for operating the engaging support portion  15   a  in the direction to release it from the engaging portion  16  when the cover body  13  is opened. 
     In addition, the attaching base  11  and cover body  13  of the cover unit  8  are each integrally formed of a synthetic resin material having a suitable degree of rigidity and elasticity. 
     The attaching base  11 , which is long lengthwise of the stack  1 , flat and substantially rectangular, is formed substantially in the middle with the oval takeout port  9  corresponding to the opening  4  in the packaging bag  3  and, besides this, it is integrally formed with an outer peripheral projecting edge  18  in the outer periphery, a fitting support portion  19 , projecting upward, in the inner side thereof, and a notch  20  on the side opposite to the hinges  12 . 
     The fitting support portion  19 , which is in oval form surrounding the takeout port  9 , is spaced a predetermined distance related to a label sticking portion  21  and formed in an oval shape in the outer peripheral side of the takeout port  9  and intermediate between the takeout port  9  and the outer peripheral projecting edge  18 , integrally projecting in rib form from the attaching base  11 . And, the fitting support portion  19  is integrally formed with an engaging support portion  15   a  in the inner side of the straight portion on the side opposite to the hinges  12  and with an operating portion  17  in the outer side thereof. 
     The operating portion  17  is in the form of a plate projecting outward from the fitting support portion  19  in substantially parallel with the attaching base  11 . The notch  20  is formed on the side opposite to the hinges  12 , extending from the outer side and in the vicinity of the fitting support portion  19  to stride across the outer peripheral projecting edge  18 , the operating portion  17  being disposed in said notch  20 . 
     The cover body  13  is in the form of a substantially rectangular plate of such size as to fit in the outer peripheral projecting edge  18  when it is closed. The cover body  13  is formed with a fitting projection  22  in the substantially middle lower side and a notch  23  corresponding to the operating portion  17 , in the end edge on the side opposite to the hinges  12 . The fitting projection  22  is adapted to fit in the fitting support portion  19  when the cover body  13  is closed. And it is formed in an oval shape as in the case of the fitting support portion  19 , projecting downward in rib form from the cover body  13 . And, an engaging portion  16  corresponding to the engaging support portion  15   a  is formed in the inner side of the straight portion of the fitting projection  22 . In addition, the operating portion  17  has such a length as not to project into the outside from the outer peripheral projecting edge  18 . An opening/closing label  24  to cover the takeout port  9  is openably/closably stuck to the label sticking portion  21  of the attaching base  11  through a pressure sensitive adhesive  26 . The opening/closing label  24  is made of the same sheet material as the packaging sheet material  6  or other material and has an opening/closing knob  25  on one lengthwise end side and is peelably stuck to the label sticking portion  21  through the pressure sensitive adhesive  26 . 
     The hinges  12 , two in number, for example, are longitudinally arranged along the end edge on the side opposite to the operating portion  17  of the cover unit  8 . Each hinge  12  comprises a projection  27  integral with the attaching base  11  on the inner side and in the vicinity of the outer peripheral projecting edge  18 , and a pin  28  integral with the end edge side of the cover body  13 , said pin  28  being rotatably inserted in a pin hole in the projection  27 . In addition, instead of using the hinges  12 , the cover body  13  may be pivotally connected at the bend to the attaching base  11 . 
     For the elastic body  14 , a rubber strip or the like is used, disposed substantially in the middle between the two hinges  12 . The elastic body  14  is applied along the attaching base  11  and cover body  13 , with its lengthwise opposite ends abutting against the fitting support portion  19  on the attaching base  11  side and a stop  29  on the cover body  13  side. On the attaching base  11  side, the elastic body  14  is held in position by holding ribs  30  on the opposite sides thereof. 
     This wet sheet package A is produced, as shown in FIGS. 6 and 7, through a punching step  31 , a stacking step  32 , a stack feeding step  33 , a wrapping step  34 , a longitudinal sealing step  35 , a transverse sealing step  36 , a cover unit feeding step  37 , and a cover unit sticking step  38 . In addition, the wrapping step  34 , longitudinal sealing step  35  and transverse sealing step  36  constitute a packaging bag producing step  39 , while the cover unit feeding step  37  and cover unit sticking step  38  constitute a cover unit mounting step  40 . 
     First of all, in the punching step  31 , the packaging sheet material  6  for packaging bags  3  is fed in the longitudinal direction while a punching means, not shown, successively forms openings  4  in the packaging sheet material  6  at a predetermined spacing. On the other hand, in the discrete stacking step  32 , a plurality of wet sheets  2  are stacked to provide a stack  1 . 
     And, in the stack feeding step  33 , stacks  1  are fed to positions corresponding to individual openings  4  in this packaging sheet material  6  synchronously with the feed rate of the punched, packaging sheet material  6 , and then in the wrapping step  34 , the packaging sheet material  6  is wrapped around the outer periphery of the stack  1  while being guided by the guide means  41 , whereby the stack  1  is wrapped therein. 
     Subsequently, in the longitudinal sealing step  35 , with the opposite edges of the packaging sheet material  6  superposed on each other on the lower side of the stack  1 , the edges are sealed along the feed direction to form a longitudinal seal  5 , and the excessive edges of the packaging sheet material  6  are cut off by melting. And, in the transverse sealing step  36 , the back side of the preceding stack  1  and the front side of the following stack  1  are each formed with a gusset  6   a , and the front end of each gusset  6   a  is transversely sealed to form a transverse seal  7 , whereupon the packaging sheet material  6  is severed between the two seals  7  to complete the production of the packaging bag  3  for the preceding stack  1 . 
     And, when the production of the packaging bag  3  is completed, in the next cover unit feeding step  37 , a cover unit  8  is fed to the opening  4  side of each packaging bag  3  and temporarily fixed in position by a pressure sensitive adhesive  10 . In the cover unit sticking step  38 , the cover unit  8  is urged against the packaging bag  3  side and the attaching base  11  is stuck from outside to the upper surface side of the packaging bag  3  through the pressure sensitive adhesive  10 . In addition, the cover unit  8  has the pressure sensitive adhesive  10  applied in advance to substantially the entire surface of the attaching base  11  so as to surround the takeout port  9 , and in this state, the cover unit  8  is fed. Of course, it is fed in the state in which the cover body  13  is closed, and attaching base  11  stuck to the packaging bag  3  through the pressure sensitive adhesive  10 . Thereby, as shown in FIG. 8, the wet sheet package A can be produced with the stack  1  stored in the packaging bag  3 , with the cover unit  8  provided on the opening  4  side of the packaging bag  3 . 
     Employing the method in which after the stack  1  has been wrapped in the packaging sheet material  6  to produce the packaging bag  3  in this manner, the cover unit  8  is stuck to the opening  4  side through the pressure sensitive adhesive  10 , provides the merits that high speeds for production of wet sheet packages A can be easily attained, that the decrease of yield due to positional deviation of the cover unit  8 , etc., can be prevented, and that low cost, easy and efficient production is possible. 
     That is, until the packaging bag  3  is produced by wrapping the stack  1  in the packaging sheet material  6 , it can be produced in substantially the same step as in the ordinary case having no cover unit  8 . Further, in mounting the cover unit  8  on the packaging bag  3 , the cover unit  8  has only to be stuck to the packaging bag  3  through the pressure sensitive adhesive  10 ; therefore, as compared with the conventional production method for producing the packaging bag  3  by wrapping the stack  1  in a packaging sheet material  6  equipped with a cover unit  8 , high efficiency of production of wet sheet packages A can be easily attained. 
     Furthermore, since the cover unit  8  is stuck to the opening  4  side after the production of the packaging bag  3 , there are merits that the position where the cover unit  8  is stuck to the packaging bag  3  is stabilized, that positional deviation of the cover unit  8 , etc., can be easily prevented, and that the yield of wet sheet packages A improves. Further, since the attaching base  11  can be temporarily fixed on the opening  4  side of the packaging bag  3  by the pressure sensitive adhesive  10 , positional deviation of the cover unit  8 , etc., after it has been fed can be prevented. This, coupled with the attainment of high speeds for production described above, enables wet sheet packages A to be produced at low cost and easily and efficiently. 
     Further, the cover unit  8  is pressed against the packaging bag  3  side during the sticking of the cover unit  8 ; however, the presence of the opening  4  in the packaging bag  3  allows the air in the packaging bag  3  to be extracted outside through the opening  4 , so that there is no problem such as one of the packaging bag  3  bursting due to the pressure produced during pressing. 
     This wet sheet package A has the attaching base  11  of the cover unit  8  stuck to the opening  4  side of the packaging bag  3  through the pressure sensitive adhesive  10  and the opening/closing label  24  stuck to the label sticking portion  21  of the attaching base  11 , said opening/closing label  24  sealing the takeout port  9 ; therefore, the interior of the packaging bag  3  can be kept substantially hermetic, preventing the drying of the wet sheets  2 . 
     When a wet sheet  2  inside the packaging bag  3  is to taken out for use, the operating portion  17  is pressed. Thereupon, the fitting support portion  19  side is elastically outwardly deformed by the pressing on the operating portion  17 , so that the engaging portion  16  on the cover body  13  side is released from the engaging support portion  15   a  on the attaching base  11  side and the cover body  13  is turned open around the pins  28  of the hinges  12  by the urging force of the elastic body  14 . In addition, the cover body  13  will stop in its elected state. 
     After the cover body  13  has been opened, the user pinches the knob  25  to peel the opening/closing label  24 , opening the takeout port  9 . In addition, the side of the opening/closing label  24  opposite to the knob  25  is fixed to the attaching base  11  at a position remote from the opening  4  or is made harder to peel than the other portion; in order to peel this opening/closing label  24 , only the portion which closes the opening  4  may be peeled. This makes it possible to take out a wet sheet  2  inside the packaging bag  3  from the uppermost side of the stack  1  successively through the opening  4  and takeout port  9 . 
     When the top wet sheet  2  is drawn out, part of the underlying wet sheet  2  is drawn out together with the overlying wet sheet  2  into the takeout port  9 ; thereafter, the following wet sheets  2  can be successively easily taken out through the takeout port  9  by pinching the portion projecting out of the takeout port  9 . 
     After use, the opening/closing label  24  is stuck to the label sticking portion  21  to seal the takeout port  9 , and then the cover body  13  is closed against the force of the elastic body  14 , whereupon the engaging portion  16  engages the engaging support portion  15   a . Therefore, the engagement between the engaging portion  16  and the engaging support portion  15   a  can easily lock and hold the cover body  13  in the closed state. 
     FIG. 9 illustrates a second embodiment of the invention, wherein interposed between the longitudinal sealing step  35  and the transverse seal  36  are the cover unit feeding step  37  and the cover unit sticking step  38 , so that the cover unit  8  is fed in the course of the packaging bag producing step  39  and stuck to the packaging sheet material  6 . 
     That is, in producing wet sheet packages A, the stack  1  is wrapped in the packaging sheet material  6  in the wrapping step  34 , and opposite edges of the packaging sheet material  6  are longitudinally sealed to form a longitudinal seal portion  5  in the longitudinal sealing step  35 , and then the cover unit  8  is fed to the opening  4  side of the packaging sheet material  6  in the cover unit feeding step  37 . And, the cover unit  8  is stuck to the opening  4  side of the packaging sheet material  6  in the cover unit sticking step  38 , and then in the transverse sealing step  36  the transverse seal portions  7  are sealed to complete the production of the packaging bag  3 . 
     Even in this manner, as compared with the case of using a packaging sheet material  6  having the cover unit  8  to wrap the stack  1  therein, high speeds for production can be easily attained, the decrease of yield due to positional deviation of the cover unit  8 , etc., can be prevented, and low cost, easy and efficient production is possible. Further, even if the cover unit  8  is pressed against the stack  1  side in sticking the cover unit  8 , since this is prior to sealing the transverse seal portions  7 , there are no problems such as one of the packaging bag  3  bursting due to the pressure produced during pressing, so that the cover unit  8  can be firmly stuck to the packaging sheet material  6  by the pressure sensitive adhesive  10 . 
     FIG. 10 illustrates a third embodiment of the invention, wherein the wrapping step  34  is followed by the cover unit feeding step  37  and the cover unit sticking step  38 , and the feeding and sticking of the cover unit  8  are performed substantially concurrently with the longitudinal sealing step  35 . 
     In this embodiment also, when the stack  1  is wrapped in the packaging sheet material  6 , a predetermined tension exists on the packaging sheet material  6  and there is no wrinkle or the like in the opening  4 , so that it is possible, substantially concurrently with the sealing of the longitudinal seal portion  5 , to temporarily fix and stick the cover unit  8  on the opening  4  side of the packaging sheet material  6 . The same merits as those in the second embodiment are also attained in this embodiment. 
     FIGS. 11 and 12 illustrate a fourth embodiment of the invention, wherein the attaching base  11  is stuck to the upper surface of the packaging bag  3  at hot melt portion  43 , the cover body  13  is openably/closably and bendably connected to the attaching base  11  by a bend  44 , and the operating portion  17  is removably attached to the holding portion  45  of the attaching base  11  on the side opposite to the bend  44  with respect to the cover body  13 . 
     The attaching base  11  is circumferentially integrally formed with a upwardly projecting, outer peripheral projecting edge  18  and a fitting support portion  19 , and a holding portion  45  having a recess  46  is integrally formed on the side opposite to the bend  44  and between the outer peripheral projecting edge  18  and the fitting support portion  19 . The hot melt portion  43  is so formed as to surround the opening  4  in the packaging bag  3 . The cover body  13  has a size such that it fits in the outer peripheral projecting edge  18 , and is formed with a notch  47  on the side opposite to the bend  44 . 
     In addition, the bend  44  is made by integrally molding or welding the outer peripheral projecting edge  18  of the attaching base  11  and the cover body  13 , and through this bend  44  is the cover body  13  openably/closably connected to the attaching base  11 . Therefore, the cover body  13  has only to be openably/closably connected to the attaching base  11 , not always requiring the use of pin type hinges  12 . 
     The fitting projection  22  of the cover body  13  is adapted to fit on the outer side of the fitting support portion  19  on the attaching base  11  side when the cover body  13  is closed, and an engaging portion  16  and an engaging support portion  15   a  are provided between the fitting projection  22  and the fitting support portion  19  and on the side opposite to the bend  44 . The engaging portion  16  and the engaging support portion  15   a  are constituted by a projection and a recess. In addition, either the engaging portion  16  or the engaging support portion  15   a  may be a projection or a recess. 
     The operating portion  17  is disposed between the cover body  13  in its closed state and the outer peripheral projecting edge  18  so that when the cover body  13  is closed, the operating portion  17  corresponds to the interior of the notch  47 , with the upper surface being substantially flush with the upper surface of the coverbody  13  in its closed state. The operating portion  17  has a pair of projections  48  on its lower side, said projections  48  being adapted to removably engage the recess  46  of the holding portion  45 , whereby the operating portion  17  is mounted on the attaching base  11  side. And, this operating portion  17  has the engaging edge  49  on one end side thereof adapted to engage the lower side of the attaching base  11  and when it is pressed at the other end side thereof, the engaging edge  49  pushes up the cover body  13  in the opening direction with the projection  48  side serving as a fulcrum. In addition, the elastic body  14  is fixed at least at one end side thereof to the attaching base  11  side as by pressure sensitive adhesion and is abutted at the other end side against the fitting projection  22 . 
     In this embodiment, after the stack  1  has been wrapped, it is only necessary to stick the attaching base  11  of the cover unit  8  to the upper side of the packaging bag  3  at the hot melt portion  43  in such a manner as to surround the opening  4 . Therefore, the attaching base  11  of the cover unit  8  can be easily and firmly stuck to the packaging bag  3  even in the hot melt system without using the pressure sensitive adhesive  10  used in the first embodiment. 
     When the cover body  13  of the cover unit  8  is to be opened, the outer end side of the operating portion  17  is pressed, whereupon the angle of the operating portion  17  changes, with the intermediate projection  48  side serving as a fulcrum, and the engaging edge  49  pushed the end of the cover body  13  upward. This causes the engaging portion  16  to disengage the engaging support portion  15   a , thereby allowing the cover body  13  to be turned open around the bend  44 . 
     Embodiments of the present invention have been described so far, but the invention is not limited thereto. For example, in producing wet sheet packages A, substantially concurrently with the longitudinal sealing step  35  for sealing the longitudinal seal portion  5 , the cover unit  8  may be fed and temporarily fixed and pressed against the stack  1  side to be stuck to the opening  4  side of the packaging sheet material  6 . 
     Further, concurrently with the wrapping of the stack  1  in the wrapping step  34 , the cover unit  8  may be fed and stuck. In other words, in the packaging bag producing step  39 , the cover unit  8  can be mounted on the packaging sheet material  6  at a suitable point of time. 
     At the time of taking out a wet sheet  2 , if it is desired to apply resistance to the following wet sheet  2  at the takeout port  9 , this may be attained by making the size of the takeout port  9  smaller than that of the opening  4  on the packaging bag  3  side. Further, if it is desired to apply resistance on the opening  4  side of the packaging bag  3 , reversely, the size of the opening  4  may be made smaller than that of the takeout port  9 . In this case, the opening  4  may be oval as illustrated in the embodiments or it may be provided in the packaging bag  3  in slit form. 
     The cover unit  8  in the embodiments is also shown by way of example, and various changes are possible. Concerning the cover unit  8 , the end edge of the cover body  13  may be bendably welded to part of the outer peripheral projecting edge  18  of the attaching base  11 , or the attaching base  11  and the cover body  13  may be openably/closably connected together without using hinges  12  provided with pins  28 , or the like, as by bendably integrally molding the outer peripheral projecting edge  18  and the cover body  13 . 
     Besides, in the case where the opening  4  in the packaging bag  3  is smaller than the takeout port  9  of the attaching base  11 , the opening/closing label  24  may be stuck to the packaging bag  3  side within the takeout port  9 . In the case where the arrangement in which the opening/closing label  24  is stuck to the packaging bag  3  side is employed, the cover unit  8  may be of a construction having no sealing function. 
     Further, in the case where the opening/closing label  24  is to be provided on the packaging bag  3  side, a method may be employed in which a wet sheet package A having the opening  4  sealed by the opening/closing label  24 , and a cover unit  8  having a releasing sheet stuck to the pressure sensitive adhesive  10  side, may be sold separately or as a set, so that before use the user removes the releasing sheet of the cover unit  8  and sticks the cover unit  8  to the packaging bag  3  through the pressure sensitive adhesive  10  in such a manner that the opening/closing label  24  may be received in the takeout port  9 . 
     In this case, if the attaching base  11  has been stuck to the packaging bag  3  by the pressure sensitive adhesive  10 , then when no wet sheet  2  is left inside, the cover unit  8  may be removed from the packaging bag  3  and stuck to a new one. 
     In addition, the attaching base  11  of the cover unit  8  may be bonded to the packaging bag  3  by other adhesive agent than the pressure sensitive adhesive  10  illustrated in the first embodiment, or it may be mounted by some other bonding method. Further, the hot melt system illustrated in the second embodiment or some other mounting system may be employed. In brief, the cover unit  8  has only to be mounted on the opening  4  side of the packaging bag  3 , and means therefor is of no concern. 
     It is only necessary for the operating portion  17  of the cover unit  8  to be of such construction that when pressed, it is capable of canceling the engagement between the engaging portion  16  and the engaging support portion  15   a , it would be possible to install it on the cover body  13  side, depending on the engagement construction. Further, the cover unit  8  may not be provided with an operating portion  17  and instead it may be so designed that the cover body  13  is opened by putting the user&#39;s finger or the like to the cover body  13  side. 
     INDUSTRIAL APPLICABILITY 
     As described above, the wet sheet package according to the invention is useful in that it contains wet sheets used either in wiping dirt off the body for babies, etc., or in wiping dirt off OA equipment or other precision instruments, and the method of producing wet sheet packages according to the invention is very useful as such.