Abstract:
A cleaning sheet and a cleaning tool which have improved usability. The cleaning sheet is attachable to a cleaning-sheet mounting member. The cleaning sheet has a center section made up of a cleaning surface and at least one end section disposed at one or more sides with respect to the center section in a predetermined direction. The end section has a first portion having a first elongation percentage and a second portion having a second elongation percentage which is higher than that of the first portion. The second portion is disposed in said direction between the first portion and the center section and is constructed so as to be supported by the cleaning-sheet mounting member at the boundary between the first and second portions. The cleaning tool is provided with the cleaning sheet.

Description:
RELATED APPLICATION 
     This application is a 35 U.S.C. §371 national phase filing of International Patent Application No. PCT/JP2010/066694, filed Sep. 27, 2010, through which and to which priority is claimed under 35 U.S.C. §119 to Japanese Patent Application No. 2009-273981, filed Dec. 1, 2009. 
     FIELD OF THE INVENTION 
     The invention relates to cleaning sheets and cleaning tools, and more particularly to a cleaning sheets and cleaning tools which can be suitably used for wiping an object to be cleaned such as floor. 
     DESCRIPTION OF THE RELATED ART 
     Japanese non-examined laid-open Patent Publication No. 2007-20615 discloses a cleaning sheet having an inner layer sheet and outer layer sheets integrally formed with the inner layer sheet on both sides of the inner layer sheet. In use, the cleaning sheet can be attached to a cleaning sheet mounting member of a cleaning tool. Central portion of the cleaning sheet is placed on a cleaning side of the cleaning sheet mounting member. Both ends of the cleaning sheet are pushed in between holding members provided in the cleaning sheet mounting member and held between the holding members. According to the known cleaning sheet, low-hydroentangled part is provided with the central portion and high-hydoroentangled part is provided with ends of he cleaning sheet. 
     STATE OF THE ART 
     Patent Prior Art 
     Japanese non-examined laid-open Patent Publication No. 2007-20615 
     SUMMARY OF THE INVENTION 
     In operation of cleaning floor or other objects having a high frictional resistance, with a cleaning sheet attached to a cleaning sheet mounting member of a cleaning tool, a tensile stress acts upon the cleaning sheet in a direction opposite to the direction of movement of the cleaning sheet mounting member. According to the known cleaning sheet, the end portion of the sheet has substantially the same elongation rate across the entire region of the end portion. In this connection, when a tensile stress acts upon the cleaning sheet during cleaning operation and the elongation rate of the end portion is set as relatively low (namely, the rigidity of the end portion is relatively high), the ends of the cleaning sheet easily become detached from the holding members. On the other hand, when a tensile stress acts upon the cleaning sheet during cleaning operation and the elongation rate of the end portion is set as relatively high (namely, the rigidity of the end portion is relatively low), the ends of the cleaning sheet held by the holding member may be easily broken by the tensile stress. In this regard, the known cleaning sheet is in difficulty both to avoid unwilling detachment of the cleaning sheet and to secure rigidity for avoiding easy break of the cleaning sheet held by the holding member. 
     Accordingly, it is an object of the invention to enhance a usability of cleaning technique. 
     Above described object can be achieved by the claimed invention. According to the invention, a representative cleaning sheet is provided. The cleaning sheet is attachable to a cleaning sheet mounting member for cleaning operation. As a cleaning sheet, non-woven fabric sheet may preferably be utilized. 
     The cleaning sheet has a central portion which defines a cleaning face and at least one end portion formed at least one of both sides of the central portion in a predetermined direction. The end portion may preferably be provided only at one end of the central portion or at both ends of the central portion. The end portion has a first part having a predetermined first elongation rate. The end portion also has a second part having a predetermined elongation rate higher than the first elongation rate. The second part is provided along the predetermined direction between the first part and the central portion. The cleaning sheet is detachably held by the cleaning sheet mounting member at a boundary between the first part and the second part. 
     The elongation rate according to the invention is a measure of stretchiness of the cleaning sheet, and is preferably defined by an equation of “mm/N” in which “mm” represents milimeter and “N” represents Newton. The higher the elongation rate is, the more stretchy the sheet becomes. 
     The elongation rates of the first and second parts may be changed, for example, by changing the number of layers of the sheet elements in the first and second parts. Otherwise, the elongation rates of the first and second parts may be changed by changing the entangled state of fibers in the first and second parts. Further, the elongation rates of the first and second parts may be changed by changing the constitution of raw cotton in the first and second parts can be used. 
     According to the invention, the second part is disposed between the central portion and the first part in the predetermined direction. A boundary is provided between the first part and the second part. The cleaning sheet is detachably held by the cleaning sheet mounting member at a boundary between the first part and the second part. The cleaning sheet may be held by the cleaning sheet mounting member at least at a part of the boundary. By this construction, when a tensile stress during a cleaning operation acts upon the cleaning sheet attached to the cleaning sheet mounting member, the second part at the boundary having a relatively higher elongation rate (more stretchy) elongates and absorbs the tensile stress, while the first part at the boundary having a relatively lower elongation rate (namely being relatively higher rigidity) securely maintains the engagement between the cleaning sheet and the cleaning sheet mounting member. Thus, at a region where the boundary of the cleaning sheet is held by the cleaning sheet mounting member, the second part with relatively high rate of elongation prevents the cleaning sheet from being unwillingly detached from the cleanings sheet mounting member during the cleaning operation and at the same time, the first part with relatively low rate of elongation prevents the cleaning sheet from being broken due to the tensile stress during the cleaning operation. 
     As another aspect of the invention, the elongation rates of the first and second parts are changed according to the number of layers of the sheet elements in the first and second parts. The second part may preferably be formed by a single sheet element or by a plurality of sheet elements stacked in layer and bonded to each other. The first part may preferably be formed by sheet elements stacked in layer and bonded to each other. The number of sheet elements in layer of the first part may be set lager in number than the number of sheet element(s) of the second part such that the second elongation rate is higher than the first elongation rate. Sheet elements in layer may be provided by stacking different sheet elements separately prepared to each other. Otherwise, sheet elements may be provided by folding one sheet element. The stacked sheet elements may preferably be bonded together. With such a construction, predetermined elongation rate can be easily secured. Further, because the first part and the second part is visibly differentiated due to the different number of sheet elements is layer, boundary between the first and second parts can be easily identified by the user for holding by the cleaning sheet holding member. 
     Further, as another aspect of the invention, the stacked sheet elements in the first part are bonded together by embossing. Preferably, the sheet elements containing thermoplastic fibers are stacked in layer and bonded together by hot embossing. 
     Further, as another aspect of the invention, the end portion may preferably have a third part having a lower elongation rate than the second part. The third part may be disposed between the central portion side and the second part in the predetermined direction. The third part may have the same elongation rate as the first part. Otherwise, the third part may have a different elongation rate from the first part. 
     According to this aspect, the strength of the central portion side can be enhanced, while the cleaning sheet can be prevented from becoming detached from the cleaning sheet mounting member. 
     Further, as another aspect of the invention, cleaning tool may be provided to have the cleaning sheet and a cleaning sheet mounting member as described above. 
     Further, the holding member may preferably have a plurality of elastic holding pieces oppositely provided to each other and the boundary of the cleaning sheet may be held by the holding member such that the boundary is pushed to penetrate the holding member through holding pieces and cramped by holding pieces. 
     According to the claimed invention, usability of cleaning sheets and the cleaning tools are enhanced. Other objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims. Other objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a representative embodiment of a cleaning tool according to the invention. 
         FIG. 2  is a plan view of a head. 
         FIG. 3  shows a schematic structure of a cleaning sheet  200  according to one embodiment. 
         FIG. 4  is a sectional view taken along line IV-IV in  FIG. 3 . 
         FIG. 5  shows the cleaning sheet  200  of the first embodiment in the unfolded state. 
         FIG. 6  is a sectional view taken along line VI-VI in  FIG. 5 . 
         FIG. 7  is a sectional view taken along line VII-VII in  FIG. 5 . 
         FIG. 8  is a sectional view taken along line VIII-VIII in  FIG. 5 . 
         FIG. 9  is a sectional view taken along line IX-IX in  FIG. 5 . 
         FIG. 10  is a sectional view taken along line X-X in  FIG. 2 . 
         FIG. 11  is a view for illustrating operation of this invention. 
         FIG. 12  shows the schematic construction of embodiment 1. 
         FIG. 13  shows the schematic construction of embodiments 2 and 3. 
         FIG. 14  shows the schematic construction of embodiment 4. 
         FIG. 15  shows the schematic construction of comparative example 1. 
         FIG. 16  shows the schematic construction of comparative examples 2 and 3. 
         FIG. 17  shows the schematic construction of comparative examples 4 to 6. 
         FIG. 18  shows the schematic construction of comparative example 7. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Each of the additional features and method steps disclosed above and below may be utilized separately or in conjunction with other features and method steps to provide and manufacture improved cleaning sheets and cleaning elements and method for using such cleaning sheets and cleaning elements and devices utilized therein. Representative examples of the present invention, which examples utilized many of these additional features and method steps in conjunction, will now be described in detail with reference to the drawings. This detailed description is merely intended to teach a person skilled in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Combinations of features and steps disclosed within the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe some representative examples of the invention, which detailed description will now be given with reference to the accompanying drawings. 
       FIG. 1  is a perspective view showing an embodiment of a cleaning tool  100  according to this invention. The cleaning tool  100  of this embodiment has a head  110  to which a cleaning sheet  200  is attached, a pipe  130  and a handle  150 . The pipe  130  is formed by coupling a plurality of pipe elements  133  by coupling mechanisms. Each of the coupling mechanisms includes, for example, a male coupling member provided on one end of one pipe element and a female coupling member provided on the other end of the other pipe element. The connection between the male coupling member and the female coupling member is covered with a cover  132 . The one end of the pipe  130  is connected to the handle  150 . The other end of the pipe  130  is connected to a connecting mechanism  131  provided on the head  110 . In this embodiment, the head  110 , the handle  150  and the pipe  130  are features that correspond to the “cleaning sheet mounting member”, the “holding member” and the “connecting member for connecting the head and the handle”, respectively, according to this invention. The number of the pipe elements  133  forming the pipe  130  can be appropriately selected. Further, the handle  150  may also be directly connected to the connecting mechanism  131  provided on the head  110 . 
     The head  110  is shaped like a plate as shown in  FIG. 2  and has an upper side  112  on which the connecting mechanism  131  is mounted, and a lower side (mounting side or cleaning side)  111  (see  FIG. 10 ) opposite from the upper side  112 . Holding members  120  are provided on the upper side  112 . As shown in  FIG. 2 , each of the holding members  120  has a plurality of elastic holding pieces  121  which are defined by cuts. 
     As shown in  FIGS. 5 and 6 , the cleaning sheet  200  has a central portion  200   b  and end portions  200   a ,  200   c  provided on both sides of the central portion  200   b , which will be described below in detail. The central portion  200   b  provides a cleaning face as a main cleaning area of the cleaning sheet  200  during a cleaning operation. The end portion  200   c  defines a mounting portion to the cleaning sheet mounting member (head  110 ). 
     The central portion  200   b  of the cleaning sheet  200  is placed to face the lower side (mounting side or cleaning side)  111  of the head  110 , and the end portions  200   a ,  200   c  are placed on the upper side  112 . Specifically, the cleaning sheet  200  is attached to the head  110  such that the head  110  is covered with the central portion  200   b  and the end portions  200   a ,  200   c . In the state in which the end portions  200   a ,  200   c  of the cleaning sheet  200  are placed on the upper side  112 , points of the end portions  200   a ,  200   c  which are located right above the holding members  120  (holding pieces  121 ) are pressed down by user&#39;s fingers. Thus, the end portions  200   a ,  200   c  of the cleaning sheet  200  are held partly caught between the adjacent holding pieces  121  provided to oppose to each other. 
     In a cleaning operation using the cleaning tool  100  of this embodiment, generally, the head  110  is moved in a direction transverse to the direction (along a boundary (e.g. folding lines  201 ,  202  which are described below) between the central portion  200   b  and the end portion  200   a  or  200   c . The head  110  can also be moved in the other directions. 
     An embodiment of a cleaning sheet  200  for use with the cleaning tool  100  of this embodiment is now explained. 
     As shown in  FIG. 4 , the cleaning sheet  200  has a three-layer structure having a single inner layer sheet  210  and single outer layer sheets  220 ,  230  disposed on the both sides of the inner layer sheet  210 . The “cleaning sheet having a three-layer structure” here includes not only a cleaning sheet having a three-layer structure across the entire region, but a cleaning sheet having a three-layer structure in its main region (e.g. the central portion  200   b ) and not having a three-layer structure (e.g. having a single or two-layer structure) in the other regions. This is also true for multi-layer structures other than the three-layer structure. 
     A hydrophilic nonwoven fabric sheet is used as the inner layer sheet  210 . It is essential for the hydrophilic nonwoven fabric sheet to be hydrophilic as a whole, and the nonwoven fabric sheet may be formed of hydrophilic fibers and hydrophobic fibers. The hydrophilic fibers include rayon fibers, cotton fibers and pulp fibers. In this embodiment, the nonwoven fabric sheet is formed only of rayon fiber having high water absorbency and high moisture retentivity. The inner layer sheet  210  is a feature that corresponds to the “impregnated element”, the “third nonwoven fabric sheet” or the “third sheet” according to this invention. 
     A nonwoven fabric sheet (spun lace nonwoven fabric sheet) manufactured by a water jet method (hydroentangling method) is used as the inner layer sheet  210 . In the water jet method, spun lace nonwoven fabric of interlaced fibers is manufactured by jetting high-pressure water, for example, onto a web of randomly arranged fibers from a plurality of nozzles disposed in an orientation transverse to the feeding direction of the web. In this embodiment, each of the nozzles for jetting high-pressure water has orifices having a diameter of 92 μm and continuously arranged over the width of 2.0 mm and such nozzles are arranged at intervals (orifice pitches) of 3.0 mm. By using such nozzles, air-through portions are formed in the spun lace nonwoven fabric, and a striped pattern appears on a finished spun lace nonwoven fabric. Thus, the specific volume ratio of the inner layer sheet  210  increases, so that the amount of impregnation (the amount of water retention) of the inner layer sheet  210  increases. The striped pattern is a feature that corresponds to the pattern of the “patterned indented surface of the inner layer sheet” according to this invention. The orifice pitch (interval of indentations) is set within the range of 2.0 to 10.0 mm, or more suitably, within the range of 2.0 to 3.0 mm. If the orifice pitch exceeds 10.0 mm, fibers are more loosely entangled with each other, so that fluff loss of fibers increases. Further, the strength decreases, so that it becomes difficult to form the nonwoven fabric sheet only of hydrophilic fibers. The inner layer sheet  210  may also be manufactured by other methods, such as through-air bonding, spunbonding, thermal bonding, point bonding, melt blowing, chemical bonding and air-laid methods. 
     The basis weight of the inner layer sheet  210  is preferably set within the range of 40 to 70 gsm (grams per square meter) from the viewpoint of the amount of release of the cleaning solution, but it may exceed 70 gsm. 
     A hydrophobic nonwoven fabric sheet is used as the outer layer sheets  220 ,  230 . It is essential for the hydrophobic nonwoven fabric sheet to be predominately hydrophobic, and the nonwoven fabric sheet may be formed of hydrophilic fibers and hydrophobic fibers. The hydrophobic fibers include polyethylene terephthalate (PET) fibers, polypropylene (PP) fibers, polyethylene (PE) fibers and nylon fibers. One of the outer layer sheets  220 ,  230  and the other are features that correspond to the “first nonwoven fabric sheet” or the “first sheet” and the “second nonwoven fabric sheet” or the “second sheet”, respectively, according to this invention. 
     Further, in this embodiment, a spun lace nonwoven fabric sheet manufactured by a water jet method (hydroentangling method) is used as the outer layer sheets  220 ,  230 . Nonwoven fabric sheets manufactured by various other methods may also be used as the outer layer sheets  220 ,  230 . 
     In the cleaning sheet  200  of this embodiment, as shown in  FIG. 4 , the outer layer sheet  220  ( 230 ) has a two-layer structure having a layer (inner layer)  222  ( 232 ) facing the inner layer sheet  210 , and a layer (outer layer)  221  ( 231 ) on the opposite side from the side facing the inner layer sheet  210 . 
     In this embodiment, the outer layer sheets  220 ,  230  are formed of fibers mainly consisting of thermoplastic fibers. Thermoplastic fibers forming the inner layers  222 ,  232  have a lower melting point than thermoplastic fibers forming the outer layers  221 ,  231 . 
     The outer layer sheets  220 ,  230  consist, for example, of polyethylene terephthalate (PET) fibers which are thermoplastic fibers, in major proportions and of rayon fibers. For example, the compounding ratio of polyethylene terephthalate (PET) fibers and rayon fibers is 80% by weight: 20% by weight. Further, the polyethylene terephthalate (PET) fibers consist of those having a fineness of 1.1 dtex and those having a fineness of 3.3 at the ratio of 30% by weight:50% by weight. 
     As the thermoplastic fibers forming the inner layers  222 ,  232 , polyethylene (PE) fibers/polyethylene terephthalate (PET) fibers (core-in-sheath structure) are used. For example, the compounding ratio of polyethylene (PE) fibers/polyethylene terephthalate (PET) fibers and rayon fibers is 70% by weight: 30% by weight. 
     The basis weight of the outer layer sheets  220 ,  230  is preferably set within the range of 35 to 40 gsm from the viewpoints of the functionality, productivity, costs, etc., though, if it exceeds 30 gsm, there is no particular problem from the viewpoints of the amount of release of the cleaning solution. 
     By thus forming the inner layers  222 ,  232  of the outer layer sheets  220 ,  230  by using thermoplastic fibers having a lower melting point than thermoplastic fibers of the outer layers  221 ,  231 , even if the inner layer sheet  210  contains no thermoplastic fibers, the inner layer sheet  210  and the outer layer sheets  220 ,  230  can be bonded together by the thermoplastic fibers having a lower melting point which are contained in the inner layer  222  of the outer layer sheet  220  and the inner layer  232  of the outer layer sheet  230 . 
     When the outer layer sheet  220  ( 230 ) having the inner layer  222  ( 232 ) and the outer layer  221  ( 231 ) is heated at a temperature which is higher than the melting point of the thermoplastic fibers of the inner layer  222  ( 232 ) and lower than the melting point of the thermoplastic fibers of the outer layer  221  ( 231 ), a fusion bonded layer is formed in the inner layer  222  ( 232 ). As a result, most of the fibers in the inner layer  222  ( 232 ) of the outer layer sheet  220  ( 230 ) are joined together by fusion bonding, so that the amount of the cleaning solution which is released from the inner layer sheet  210  to the outer layer sheet  220  ( 230 ) is controlled. 
     As described above, in the prior art, each of the ends of the sheet has substantially the same elongation rate across its entire region, while low-hydroentangled part is provided with the central portion. Therefore, during cleaning operation which is performed with the ends of the cleaning sheet held by the holding members of the head of the cleaning tool, the cleaning sheet easily becomes detached from the holding members. 
     Therefore, in this invention, each of the ends of the cleaning sheet has a first part having a first elongation rate and a second part having an elongation rate higher than the first elongation rate. The second part is disposed on the central portion side of the first part, and a boundary between the first and second parts is formed at the point which is held by the holding members  120  of the head  110  of the cleaning tool. 
     The inner layer sheet  210  and the outer layer sheets  220 ,  230  are arranged as shown in  FIGS. 3 and 4 .  FIG. 4  is a sectional view taken along line IV-IV in  FIG. 3 . 
     As shown in  FIG. 3 , the cleaning sheet  200  has a rectangular shape having a width M (e.g. 205 mm) and a length S (e.g. 275 mm). The inner layer sheet  210  has a rectangular shape having a width N (e.g. 90 mm) and the length S. The outer layer sheets  220 ,  230  have a rectangular shape having a width (e.g. 190 mm) shorter than the width M and the length S. 
     The outer layer sheet  220  ( 230 ) includes a base  220   c  ( 230   c ). One end of the outer layer sheet  220  ( 230 ) in the width direction is folded over to the inner layer  222  ( 232 ) side along a folding line  220   b  ( 230   b ) at a predetermined distance from the one end, so that a folded part  220   a  ( 230   a ) is formed. The folded part  220   a  is stacked with a part of the base  220   c  ( 230   c ). As shown in  FIG. 4 , the outer layer sheets  220 ,  230  having the respective folded parts  220   a ,  230   a  are arranged on the both sides of the inner layer sheet  210  so as to oppose to each other. At this time, inner layer  222  of the outer layer sheet  220  and inner layer  232  of the outer layer sheet  230  are located to the inner sheet  210  so as to oppose to each other. The inner layer sheet  210  is centrally located in the direction of the width M. The folded parts  220   a ,  230   a  of the outer layer sheets  220 ,  230  are arranged on the opposite sides of the inner layer sheet  210  in the width direction. Further, the folding lines  201 ,  202  are provided in the cleaning sheet  200  toward the center in the width direction and spaced a distance R apart from each other which is equal to or longer than the width N of the inner layer sheet  210  (R≧N). 
     Thus, as shown in  FIG. 3 , the cleaning sheet  200  is divided into the centrally located central portion  200   b  and the end portions  200   a ,  200   c  provided on the both sides of the central portion  200   b  in the width direction by the folding lines  201 ,  202 . The end portion  200   a  ( 200   c ) has a first part  200   a   1  ( 200   c   1 ) of a two-layer structure having the folded part  220   a  ( 230   a ) and a base  220   c  ( 230   c ) of the outer layer sheet  220  ( 230 ) stacked in layer, a second part  200   a   2  ( 200   c   2 ) of a single-layer structure having the base  220   c  ( 230   c ) of the outer layer sheet  220  ( 230 ), and a third part  200   a   3  ( 200   c   3 ) of a two-layer structure having the base  220   c  of the outer layer sheet  220  and a base  230   c  of the outer layer sheet  230  stacked in layer. The central portion  200   b  has a three-layer structure having the base  220   c  of the outer layer sheet  220 , the base  230   c  of the outer layer sheet  230  and the inner layer sheet  210  stacked in layer. 
     The folding lines  201 ,  202  serve as guides for positioning the central portion  200   b  of the cleaning sheet  200  such that it faces the lower side (cleaning side)  111  of the head  110  when the cleaning sheet  200  is attached to the head  110  of the cleaning tool  100 . A width R of the central portion  200   b  of the cleaning sheet  200  (distance between the folding lines  201 ,  202 ) is preferably equal to or longer than a width W of the lower side (mounting side)  111  of the head  110  of the cleaning tool  100  (R≧W). Further, the width N of the inner layer sheet  210  is preferably equal to or shorter than the width W of the lower side (mounting side)  111  of the head  110  of the cleaning tool  100  (N≦W). The relationship between the distance R, the width N and the width W is not limited to this. 
     In this embodiment, a direction (the horizontal direction as viewed in  FIG. 3 ) along the folding lines  201 ,  202 ,  220   a ,  230   a  is referred to as the “length direction”, and a direction transverse (perpendicular) to the folding lines  201 ,  202 ,  220   a ,  230   b  is referred to as the “width direction”. In the case of the cleaning sheet  200  having no folding lines  201 ,  202 ,  220   b ,  230   b , the predetermined direction of the cleaning sheet  200  in which end portions  200   a  and  200   c  extend is referred to as the “length direction”, and a direction transverse (perpendicular) to the predetermined direction is referred to as the “width direction”. The “width direction” in this embodiment corresponds to the “the predetermined direction” according to this invention. 
     The inner layer sheet  210  and the outer layer sheets  220 ,  230  are bonded together as shown in  FIGS. 5 and 6  in order to fix the inner layer sheet  210  to the outer layer sheets  220 ,  230  in the state in which the inner layer sheet  210  and the outer layer sheets  220 ,  230  are arranged as shown in  FIGS. 3 and 4 .  FIG. 6  is a sectional view taken along line VI-VI in  FIG. 5 . 
     When the inner layer sheet  210  is bonded to the outer layer sheets  220 ,  230 , the cleaning solution impregnated in the inner layer sheet  210  is released from the inner layer sheet  210  to the outer layer sheets  220 ,  230  via bonded portions between the inner layer sheet  210  and the outer layer sheets  220 ,  230 . Therefore, a bonding area of bonding the inner layer sheet  210  and the outer layer sheets  220 ,  230  is preferably located away from the center of an area (main cleaning area) of the cleaning sheet which is used for normal cleaning operation. In other words, the bonding area is preferably located at a position in which the cleaning operation is less affected by the cleaning solution via the bonded portions. In this embodiment, the central portion  200   b  in which the inner layer sheet  210  is disposed is located to face the lower side (mounting side)  111  of the head  110  of the cleaning tool  100 , and therefore, cleaning is performed with the central portion  200   b . Thus, the central portion  200   b  of the cleaning sheet  200  forms a “main cleaning area”. 
     Therefore, in this embodiment, as shown in  FIG. 5 , the inner layer sheet  210  is bonded to the outer layer sheets  220 ,  230  on edges (ends) of the outer layer sheets  220 ,  230  on the both ends in the length direction (horizontal direction as viewed in  FIG. 5 ). Specifically, the bonding area of bonding the inner layer sheet  210  and the outer layer sheets  220 ,  230  is located away from the center of an area (main cleaning area) of the cleaning sheet which is used for normal cleaning operation. 
     In this embodiment, a hot embossing method is used for the bonding. In  FIG. 5 , hot embossed portions  203  are formed on the edges of the outer layer sheets  220 ,  230  on the both ends in the length direction. As shown in  FIG. 7 , the hot embossed portions  203  and bonded portions  203   a  in which the inner layer sheet  210  is bonded to the outer layer sheets  220 ,  230  are formed by hot embossing the outer layer sheets  220 ,  230 . In this embodiment, the outer layer sheets  220 ,  230  are formed of fibers containing thermoplastic fibers. Therefore, the inner layer sheet  210  is bonded to the outer layer sheets  220 ,  230  via the thermoplastic fibers forming the outer layer sheets  220 ,  230  (particularly, the thermoplastic fibers which have a lower melting point and are contained in the inner layer  222  of the outer layer sheet  220  and the inner layer  232  of the outer layer sheet  230 ) by hot embossing the outer layer sheets  220 ,  230 . 
     In this specification, hot embossing for bonding the inner layer sheet  210  and the outer layer sheets  220 ,  230  is referred to as the “first hot embossing”. 
     In this embodiment, it is necessary to prevent the cleaning solution impregnated in the inner layer sheet  210  from leaking out from its ends in the width direction. 
     In this embodiment, as shown in  FIG. 6 , in the third parts  200   a   3 ,  200   c   3  located on the both sides of the inner layer sheet  210  in the width direction, the outer layer sheets  220 ,  230  are bonded together. Various bonding methods can be used for bonding the outer layer sheets  220 ,  230 . In this embodiment, the outer layer sheets are bonded together by hot embossing using a roller having depressions and projections. As shown in  FIG. 8 , hot embossed portions  204  and bonded portions  204   a  in which the inner layer sheet  210  is bonded to the outer layer sheets  220 ,  230  are formed by hot embossing the outer layer sheets  220 ,  230 . 
     In this embodiment, thermoplastic fibers having a lower melting point are disposed in the outer layer sheets  220 ,  230 . Further, the inner layer sheet  210  is not disposed in the third parts  200   a   3 ,  200   c   3 . Therefore, in the third parts  200   a   3 ,  200   c   3 , the outer layer sheets  220 ,  230  can be easily bonded together by hot embossing. 
     The strength of the outer layer sheets  220 ,  230  is increased by bonding the outer layer sheets  220 ,  230  by hot embossing. 
     In this embodiment, hot embossing for bonding the outer layer sheets  220 ,  230  is referred to as the “second hot embossing”. 
     In this embodiment, only the edges of the inner layer sheet  210  on the both ends in the length direction are subjected to first hot embossing, but the edges of the third parts  200   a   3 ,  200   c   3  on the both ends in the length direction may also be subjected to first hot embossing. 
     In this embodiment, in order that the first part  200   a   1  ( 200   c   1 ) has a lower elongation rate than the second part  200   a   2  ( 200   c   2 ), the folded part  220   a  and the base  220   c  of the outer layer sheet  220  (the folded part  230   a  and the base  230   c  of the outer layer sheet  230 ) are bonded together in the first part  200   a   1  ( 200   c   1 ). Various bonding methods can be used for bonding the folded part  220   a  and the base  220   c  of the outer layer sheet  220  (the folded part  230   a  and the base  230   c  of the outer layer sheet  230 ). In this embodiment, they are bonded together by hot embossing using a roller having depressions and projections. 
     In this embodiment, thermoplastic fibers having a lower melting point are contained in the outer layer sheet  220  ( 230 ). Further, the inner layer sheet  210  is not disposed between the folded part  220   a  and the base  220   c  of the outer layer sheet  220  (the folded part  230   a  and the base  230   c  of the outer layer sheet  230 ). Therefore, in the first part  200   a   1  ( 200   c   1 ), the folded part  220   a  and the base  220   c  of the outer layer sheet  220  (the folded part  230   a  and the base  230   c  of the outer layer sheet  230 ) can be easily bonded together by hot embossing. 
     By this hot embossing, the first part  200   a   1  formed by the folded part  220   a  and the base  220   c  of the outer layer sheet  220  and the first part  200   c   1  formed by the folded part  230   a  and the base  230   c  of the outer layer sheet  230  have a lower elongation rate than the second parts  200   a   2 ,  200   c   2 . Specifically, the first parts  200   a   1 ,  200   c   1  are harder to stretch than the second parts  200   a   2 . 
     The elongation rate (mm/N) of the sheet is a measure of stretchiness. The higher the elongation rate, the more stretchy the sheet. 
     In this specification, hot embossing for bonding the outer layer sheets  220 ,  230  in the first parts  200   a   1 ,  200   c   1  is referred to as the “third hot embossing”. 
     Further, the inner layer sheet  210  is impregnated with cleaning solution. An appropriate cleaning solution by which dirt or contamination of the object to be cleaned can be removed can be used as the cleaning solution. For example, water-based cleaning solution containing alcohol, a surfactant, a solvent, an antiseptic, etc. can be used. Further, a floor protective agent, an abrasive, a freshener, perfume, etc. may be added to the cleaning solution. The amount of cleaning solution to be impregnated into the inner layer sheet  210  can be appropriately determined. For example, cleaning solution of two to five times the weight of the yet-to-be impregnated cleaning sheet  200  (the inner layer sheet  210  and the outer layer sheets  220 ,  230 ) is impregnated into the inner layer sheet  210 . Various methods can be used for impregnating the cleaning solution into the inner layer sheet  210 . For example, the cleaning sheet  200  may be formed by using the inner layer sheet  210  which is impregnated with the cleaning solution in advance. Alternatively, after the cleaning sheet  200  is formed, the cleaning solution may be applied to the central portion  200   b  of the outer layer sheets  220 ,  230  so that the inner layer sheet  210  is impregnated with the cleaning solution via the outer layer sheets  220 ,  230 . 
       FIG. 10  shows the cleaning sheet  200  in this embodiment which is attached to the head  110 .  FIG. 10  is a sectional view taken along line X-X (in the width direction) in  FIG. 2 . 
     As shown in  FIG. 10 , the central portion  200   b  of the cleaning sheet  200  is located to face the lower side (mounting side)  111  of the head  110 . The end portions  200   a ,  200   c  of the cleaning sheet  200  are folded over along the folding lines  201 ,  202  and placed on the upper side  112  of the head  110 . In this embodiment, the length of the first parts  200   a   1 ,  200   c   1  (the length of the folded parts  220   a ,  230   a ) is set e.g. to 20 mm. Therefore, when the central portion  200   b  of the cleaning sheet  200  is placed to face the lower side (mounting side)  111  of the head  110 , and the end portions  200   a ,  200   c  are placed on the upper side  112  of the head  110 , part of a boundary  200 P 1  between the first part  200   a   1  and the second part  200   a   2  and part of a boundary  200 Q 1  between the first part  200   c   1  and the second part  200   c   2  are placed to face the holding members  120  (holding pieces  121 ). 
     In this state, when the portions facing the holding pieces  121  are pushed in between the holding pieces  121  by the fingers and then released, part of the boundary  200 P 1  between the first part  200   a   1  and the second part  200   a   2  and part of the boundary  200 Q 1  between the first part  200   c   1  and the second part  200   c   2  are caught and held between the holding pieces  121 . As shown in  FIG. 11 , the intermediate parts of the boundary  200 P 1  and  200 Q 1  cramped and held by the holding pieces  121  are pushed to penetrate the holding pieces  121 . At this time, as shown in  FIG. 10 , the first parts  200   a   1 ,  200   c   1  are located nearer to the center than the second parts  200   a   2 ,  200   c   2  (on the opposite side from the central portion  200   b ) and held by the holding pieces  121 . 
     According to this embodiment, boundary  200 P 1  ( 200 Q 1 ) between the first part  200   a   1  with relatively low elongation rate and the second part  200   a   2  with relatively high elongation rate is partly held by the holding pieces  121  opposing to each other. In other words, inflecting region of the elongation rate is held by the holding pieces  121 . 
     Therefore, even if a tensile force acts upon the cleaning sheet  200  in a direction opposite to the direction of movement of the head  110  by a frictional force of the area to be cleaned during cleaning operation which is performed with the ends  200   a ,  200   c  of the cleaning sheet  200  held by the holding pieces  112 , such tensile force is buffered by the second part  200   a   2  and/or  200   c   2  with high elongation rate. As a result, the ends  200   a ,  200   c  of the cleaning sheet  200  can be prevented from becoming detached from the holding pieces  121 . Further, when user of the cleaning tool tries to detach the cleaning sheet  200  from the head  110 , the sheet  200  can be easily detached from the head  110  such that the first part  200   a   1  ( 200   c   1 ) is pulled out and the boundary  200 P 1  ( 200 Q 1 ) is pulled out from the gap between the adjacent holding pieces  121 . 
     Further, according this embodiment, the second part  200   a   2  ( 200   c   2 ) with relatively high elongation rate is formed by a single layer, while the first part  200   a   1  ( 200   c   1 ) with relatively low elongation rate is formed by two layers by folding and stacking the sheet element. As a result, the cleaning sheet  200  can be manufactured at low cost. 
     Further, according to this embodiment, the first part  200   a   1  ( 200   c   1 ) is provided with 2 layers, while the second part  200   a   2  ( 200   c   2 ) is provided with a single layer, the boundary  200 P 1  ( 200 Q 1 ) can be visibly clearly identified. Thus, usability of the cleaning sheet  200  is enhanced. 
     Operation of this invention is conceptually explained with reference to  FIG. 11 . In  FIG. 11 , for the sake of simplicity of explanation, the end  200   a  ( 200   c ) of the cleaning sheet  200  has a first member X having a first elongation rate and a second member Y having a second elongation rate higher than the first elongation rate and located between the central portion  200   b  and the first member X. The first member X corresponds to the first part  200   a   1  ( 200   c   1 ) and the second member Y corresponds to the second part  200   a   2  ( 200   c   2 ), respectively. Further, the head  110  is moved in a direction shown by the hollow arrow G (rightward) in  FIG. 11  with a boundary Z between the first member X and the second member Y partly held by the holding members  120  (the holding pieces  121 ) of the head  110 . The boundary Z corresponds to the boundary  200 P 1  ( 200 Q 1 ). 
     When the head  110  is moved in the direction of the hollow arrow G, as shown in  FIG. 11  ( 1 ), a tensile stress acts in the direction of the solid arrow F upon the second member Y of the end which is located in the direction of the hollow arrow G. 
     In the prior art, each of the ends of the sheet has substantially the same elongation rate across its entire region, so that the member held by the holding members  120  (the holding pieces  121 ) uniformly stretches. Therefore, the end  200   a  ( 200   c ) of the cleaning sheet  200  easily becomes detached from the holding members  120  (the holding pieces  121 ). 
     On the contrary, according to this embodiment, as shown in  FIG. 11  ( 2 ), the second member Y having a higher elongation rate tends to stretch and tensile force is absorbed by the second member Y. In this case, the boundary Z between the first member X and the second member Y is held by the holding pieces  121  and kept in this state, so that the end  200   a  ( 200   c ) of the cleaning sheet  200  is prevented from becoming detached from the holding pieces  121 . 
     When the tensile stress acting upon the end of the cleaning sheet  200  increases, as shown in  FIG. 11  ( 3 ), the boundary Z between the first member X and the second member Y is pulled and detached from the holding pieces  121 . In this case, the end  200   a  ( 200   c ) of the cleaning sheet  200  becomes detached from the holding pieces  121 . 
     Energy required for removing the cleaning sheet held by the holding pieces is measured in embodiments 1 to 4 and comparative examples 1 to 7 of the cleaning sheets of this invention.  FIGS. 12 to 18  show the constructions of the cleaning sheets of embodiments 1 to 4 and comparative examples 1 to 7. 
     In embodiments 1 to 4 and comparative examples 1 to 7, the width M is 205 mm. Further, if the boundary Z between the first member X and the second member Y is located within the range of 20 to 40 mm from the ends (edges) in the width direction, the boundary Z between the first member X and the second member Y is placed to face the holding pieces of the head when the cleaning sheet is attached to the head. 
     In the following description, the “MD direction” represents the direction of the machine during manufacturing, and the “CD direction” represents a direction perpendicular to the MD direction. 
     Embodiment 1 
     Embodiment 1 has the construction shown in  FIG. 12 . Each of outer layer sheets  220 ,  230  has a width of 190 mm and has one end in the width direction which is folded so that folded part  220   a  or  230   a  is formed. The folded parts  220   a ,  230   a  have a length T 1  of 20 mm. The outer layer sheets  220 ,  230  are arranged on both sides of an inner layer sheet  210 . In each embodiment, hot embossing is performed on a needed area, which is not particularly specified. 
     In embodiment 1, a first part  200   a   1  ( 200   c   1 ) or the first member X having a lower elongation rate has a two-layer structure having the outer layer sheets  220 ,  230 . A second part  200   a   2  ( 200   c   2 ) or the second member Y having a higher elongation rate has a single-layer structure having the outer layer sheet  220  ( 230 ). Further, the CD direction of the outer layer sheets  220 ,  230  coincides with the width direction of the sheet (the horizontal direction in  FIG. 12 ). 
     According to the embodiment 1, the first member X has the elongation rate of 1.00 mm/N, and the second member Y has the elongation rate of 3.30 mm/N. 
     Embodiment 2 
     Embodiment 2 has the construction shown in  FIG. 13 . Each of outer layer sheets  320 ,  330  has a width T of 170 mm. The outer layer sheets  320 ,  330  are arranged on both sides of an inner layer sheet  310 , and outer layer sheets  340 ,  350  having a width K of 20 mm are arranged on the both ends (edges) of the sheet in the width direction. 
     In embodiment 2, a first part  300   a   1  ( 300   c   1 ) or the first member X having a lower elongation rate has a two-layer structure having the outer layer sheets  320  ( 330 ),  340  ( 350 ). A second part  300   a   2  ( 300   c   2 ) or the second member Y having a higher elongation rate has a single-layer structure having the outer layer sheet  320  ( 330 ). Further, the CD direction of the outer layer sheets  320 ,  330  coincides with the width direction of the sheet (the horizontal direction in  FIG. 13 ), and the MD direction of the outer layer sheets  340 ,  350  coincides with the width direction of the sheet. 
     According to the embodiment 2, the first member X has the elongation rate of 0.08 mm/N, and the second member Y has the elongation rate of 3.30 mm/N. 
     Embodiment 3 
     Embodiment 3 has the construction shown in  FIG. 13 . Each of the outer layer sheets  320 ,  330  has a width T of 170 mm. The outer layer sheets  320 ,  330  are arranged on the both sides (edges) of the inner layer sheet  310 , and 70 g/m 2  spunbond nonwoven fabrics (SB)  340 ,  350  having a width K of 20 mm are arranged on the both ends (edges) of the sheet in the width direction. 
     In embodiment 3, the first part  300   a   1  ( 300   c   1 ) or the first member X having a lower elongation rate has a two-layer structure having the outer layer sheet  320  ( 330 ) and the 70 g/m 2  spunbond nonwoven fabric  340  ( 350 ). A second part  300   a   2  ( 300   c   2 ) or the second member Y having a higher elongation rate has a single-layer structure having the outer layer sheet  320  ( 330 ). Further, the CD direction of the outer layer sheets  320 ,  330  coincides with the width direction of the sheet (the horizontal direction in  FIG. 13 ). 
     According to the embodiment 3, the first member X has the elongation rate of 0.06 mm/N, and the second member Y has the elongation rate of 3.30 mm/N. 
     Embodiment 4 
     Embodiment 4 has the construction shown in  FIG. 14 . Each of outer layer sheets  420 ,  430 ,  440 ,  450  has a width T of 170 mm. The outer layer sheets  420 ,  430  and  440 ,  450  are arranged on the both sides of the inner layer sheet  310 , and 70 g/m 2  spunbond nonwoven fabrics  340 ,  350  having a width K of 20 mm are arranged on the both ends (edges) of the sheet in the width direction. 
     In embodiment 4, a first part  400   a   1  ( 400   c   1 ) or the first member X having a lower elongation rate has a three-layer structure having the outer layer sheet  420 ,  430  ( 440 ,  450 ) and the 70 g/m 2  spunbond nonwoven fabric  460  ( 470 ). A second part  400   a   2  ( 400   c   2 ) or the second member Y having a higher elongation rate has a two-layer structure having the outer layer sheets  420 ,  430  ( 440 ,  450 ). Further, the CD direction of the outer layer sheets  420 ,  430 ,  440 ,  450  coincides with the width direction of the sheet (the horizontal direction in  FIG. 14 ). 
     According to the embodiment 4, the first member X has the elongation rate of 0.06 mm/N, and the second member Y has the elongation rate of 1.00 mm/N. 
     Comparative Example 1 
     Comparative example 1 has the construction shown in  FIG. 15 . Each of outer layer sheets  520 ,  530  has a width of 150 mm. The outer layer sheets  520 ,  530  are arranged on both sides of an inner layer sheet  510 . 
     In comparative example 1, a first part  500   a   1  ( 500   c   1 ) having a width of 55 mm from the end of the sheet in the width direction has a single-layer structure having the outer layer sheet  520  ( 530 ). Further, the CD direction of the outer layer sheets  520 ,  530  coincides with the width direction of the sheet (the horizontal direction in  FIG. 15 ). 
     According to the comparative example 1, the first member X has the elongation rate of 3.30 mm/N, and the second member Y has the elongation rate of 3.30 mm/N. 
     Comparative Example 2 
     Comparative example 2 has the construction shown in  FIG. 16 . Each of outer layer sheets  620 ,  630  has a width of 205 mm. The outer layer sheets  620 ,  630  are arranged on both sides of an inner layer sheet  610 . 
     In comparative example 2, a first part  600   a  ( 600   c ) having a width of 55 mm from the end of the sheet in the width direction has a two-layer structure having the outer layer sheets  620 ,  630 . Further, the CD direction of the outer layer sheets  620 ,  630  coincides with the width direction of the sheet (the horizontal direction in  FIG. 16 ). 
     According to the comparative example 2, the first member X has the elongation rate of 1.00 mm/N, and the second member Y has the elongation rate of 1.00 mm/N. 
     Comparative Example 3 
     Comparative example 3 has the construction shown in  FIG. 16 . Each of outer layer sheets  620 ,  630  has a width of 205 mm. The outer layer sheets  620 ,  630  are arranged on both sides of an inner layer sheet  610 . 
     In comparative example 3, a first part  600   a  ( 600   c ) having a width of 55 mm from the end of the sheet in the width direction has a two-layer structure having the outer layer sheets  620 ,  630 . Further, the CD direction of the outer layer sheet  620  and the MD direction of the outer layer sheet  630  coincide with the width direction of the sheet (the horizontal direction in  FIG. 16 ). 
     According to the comparative example 3, the first member X has the elongation rate of 0.08 mm/N, and the second member Y has the elongation rate of 0.08 mm/N. 
     Comparative Example 4 
     Comparative example 4 has the construction shown in  FIG. 17 . Each of outer layer sheets  720 ,  730  has a width T of 150 mm. The outer layer sheets  720 ,  730  are arranged on both sides of an inner layer sheet  710 . Further, outer layer sheets  740 ,  750  having a width K of 20 mm are arranged 20 to 40 mm away from the end of the sheet in the width direction. 
     In comparative example 4, a first part  700   a   1  ( 700   c   1 ) having a width of 20 mm from the end of the sheet in the width direction has a single-layer structure having the outer layer sheet  720  ( 730 ). A second part  700   a   2  ( 700   c   2 ) extending in the range of 20 to 40 mm from the end of the sheet in the width direction has a two-layer structure having the outer layer sheet  720 ,  740  ( 730 ,  750 ). Further, the CD direction of the outer layer sheets  720 ,  730 ,  740 ,  750  coincides with the width direction of the sheet (the horizontal direction in  FIG. 17 ). 
     According to the comparative example 4, the first member X has the elongation rate of 3.30 mm/N, and the second member Y has the elongation rate of 1.00 mm/N. 
     Comparative Example 5 
     Comparative example 5 has the construction shown in  FIG. 17 . Each of outer layer sheets  720 ,  730  has a width T of 150 mm. The outer layer sheets  720 ,  730  are arranged on both sides of an inner layer sheet  710 . Further, outer layer sheets  740 ,  750  having a width K of 20 mm are arranged 20 to 40 mm away from the end of the sheet in the width direction. 
     In comparative example 5, a first part  700   a   1  ( 700   c   1 ) having a width of 20 mm from the end of the sheet in the width direction has a single-layer structure having the outer layer sheet  720  ( 730 ). A second part  700   a   2  ( 700   c   2 ) extending in the range of 20 to 40 mm from the end of the sheet in the width direction has a two-layer structure having the outer layer sheet  720 ,  740  ( 730 ,  750 ). Further, the CD direction of the outer layer sheets  720 ,  730  and the MD direction of the outer layer sheets  740 ,  750  coincide with the width direction of the sheet (the horizontal direction in  FIG. 17 ). 
     According to the comparative example 5, the first member X has the elongation rate of 3.30 mm/N, and the second member Y has the elongation rate of 0.08 mm/N. 
     Comparative Example 6 
     Comparative example 6 has the construction shown in  FIG. 17 . Each of outer layer sheets  720 ,  730  has a width T of 150 mm. The outer layer sheets  720 ,  730  are arranged on both sides of an inner layer sheet  710 . Further, 70 g/m 2  spunbond nonwoven fabrics  740 ,  750  having a width K of 20 mm are arranged 20 to 40 mm away from the end of the sheet in the width direction. 
     In comparative example 6, a first part  700   a   1  ( 700   c   1 ) having a width of 20 mm from the end of the sheet in the width direction has a single-layer structure having the outer layer sheet  720  ( 730 ). A second part  700   a   2  ( 700   c   2 ) extending in the range of 20 to 40 mm from the end of the sheet in the width direction has a two-layer structure having the outer layer sheet  720  ( 730 ) and the 70 g/m 2  spunbond nonwoven fabric  740  ( 750 ). Further, the CD direction of the outer layer sheets  720 ,  730  coincide with the width direction of the sheet (the horizontal direction in  FIG. 17 ). 
     According to the comparative example 6, the first member X has the elongation rate of 3.30 mm/N, and the second member Y has the elongation rate of 0.06 mm/N. 
     Comparative Example 7 
     Comparative example 7 has the construction shown in  FIG. 18 . Each of outer layer sheets  820 ,  830 ,  840 ,  850  has a width T of 150 mm. The outer layer sheets  820 ,  830  and  840 ,  850  are arranged on both sides of an inner layer sheet  810 . Further, 70 g/m 2  spunbond nonwoven fabrics  860 ,  870  having a width K of 20 mm are arranged 20 to 40 mm away from the end of the sheet in the width direction. 
     In comparative example 7, a first part  800   a   1  ( 800   c   1 ) having a width of 20 mm from the end of the sheet in the width direction has a two-layer structure having the outer layer sheets  820 ,  830  ( 840 ,  850 ). A second part  800   a   2  ( 800   c   2 ) extending in the range of 20 to 40 mm from the end of the sheet in the width direction has a three-layer structure having the outer layer sheets  820 ,  830  ( 840 ,  850 ) and the 70 g/m 2  spunbond nonwoven fabric  860  ( 870 ). Further, the CD direction of the outer layer sheets  820 ,  830 ,  840 ,  850  coincide with the width direction of the sheet (the horizontal direction in  FIG. 18 ). 
     According to the comparative example 7, the first member X has the elongation rate of 1.00 mm/N, and the second member Y has the elongation rate of 0.06 mm/N. 
     Energy (J) required to remove the sheets according to embodiments 1 to 4 and comparative examples 1 to 7 from the holding pieces  121  of the head  110  was measured under the following conditions. 
     (1) Part of a specimen is pushed in between the holding pieces  121  of the fixed head. At this time, an artificial finger is used in order to make the amount of pushing in the specimen constant. 
     (2) Then a predetermined point of the specimen held by the holding pieces  121  of the head is pulled. Upon removal of the specimen from the holding pieces  121 , the tensile stress is measured. 
     (3) This measurement is made on several pieces of the same specimen. 
     As a result, energy of 0.09 to 0.20 J is required to remove the sheets of embodiments 1 to 4 from the holding pieces  121 , while energy of 0.01 to 0.05 J is required to remove the sheets of comparative examples 1 to 7 from the holding pieces  121 . In embodiments 1 to 4, it is set such that the elongation rate of the first member X&lt;the elongation rate of the second member Y. In comparative examples 1 to 3, it is set such that the elongation rate of the first member X=the elongation rate of the second member Y. In comparative examples 4 to 7, it is set such that the elongation rate of the first member X&gt;the elongation rate of the second member Y. 
     From the measurements, it has been found that, by making the elongation rate of the first member X lower than the elongation rate of the second member Y, the cleaning sheet  200  can be effectively prevented from becoming detached from the holding pieces  121  of the head  110  during cleaning operation. 
     As described above, in the outer layer sheet arranged on the both sides of the inner layer sheet (impregnated element) in the cleaning sheet of this embodiment, a fusion bonded layer is formed on the side (inner side) of the outer layer sheet which faces the inner layer sheet. With this construction, the amount of the cleaning solution which is released from the impregnated element to the outer layer sheet is controlled. Therefore, during cleaning operation (when a load is put on the surface of the cleaning sheet), an appropriate amount of the cleaning solution can be released from the surface of the cleaning sheet. 
     Further, the inner layer sheet and the outer layer sheets are bonded at the edges of the inner layer sheet, and a space is formed between the inner layer sheet and the outer layer sheets. With this construction, the amount of the cleaning solution which is released from the inner layer sheet to the outer layer sheets via the bonded portions can be controlled. 
     Further, each of the ends of the cleaning sheet has a first part having a lower elongation rate and a second part having a higher elongation rate, and the boundary between the first part and the second part is held by the holding pieces. With this construction, the ends of the cleaning sheet  200  can be effectively prevented from becoming detached from the holding members  120  (holding pieces  121 ) of the head  110  during cleaning operation. 
     In order to form a region having a higher elongation rate, in this embodiment, sheet elements stacked in layer are bonded together by hot embossing. A method of changing the elongation rate is not limited to this. For example, the sheet elements stacked in layer can be bonded together by using methods other than hot embossing. Further, when manufacturing a nonwoven fabric sheet (spun lace nonwoven fabric sheet) by a water jet method (hydroentangling method), the elongation rate of a region of the sheet may be increased by closing the nozzle in such a manner as to render the region out of reach of the water jet, or the elongation rate may be changed by changing the constitution of raw cotton. 
     The constructions that have been described in the above embodiment can be used singly or in combination of appropriately selected ones of them. 
     Further, in this embodiment, the cleaning sheet is described as a wet sheet which is impregnated with cleaning solution so as to be used for cleaning in a wetted state, but it may be designed as a dry sheet which is not impregnated with cleaning solution so as to be used for cleaning in a dry state. 
     The constructions of the cleaning sheet is not limited to those described in the above-described embodiment, but rather, may be added to, changed, replaced with alternatives or otherwise modified. 
     Further, the following aspects can be provided: 
     “The outer layer sheet is formed of fibers containing thermoplastic fibers, and thermoplastic fibers provided on a side of the outer layer sheet facing the inner layer sheet have a lower melting point than thermoplastic fibers provided on the side opposite from the side facing the inner layer sheet.” 
     “The inner layer sheet and the outer layer sheets are bonded at the edges of the outer layer sheet, and a space is formed in a central portion of the inner sheet between the inner layer sheet and the outer layer sheets.” 
     “The inner layer sheet is centrally located in the cleaning sheet which is placed on the cleaning side (mounting side) of the cleaning sheet mounting member,” 
     Each cleaning sheet which is described below may also be used singly (without being mounted to the cleaning sheet mounting member of the cleaning tool). Further, the cleaning sheet or the cleaning tool of this invention can be used to clean objects having planar, curved, uneven or stepped shape. 
     The cleaning sheet which is described below may also be designed to be used in a dry state to clean a cleaning object. 
     As a cleaning sheet to be used in a wetted state to clean an object, for example, a cleaning sheet having an impregnated element (e.g. inner layer sheet) impregnated with cleaning solution, and outer layer sheets disposed on both sides of the impregnated element is used. In this case, the cleaning region (cleaning area) of an object to be cleaned which can be cleaned by such a cleaning sheet in an appropriate wetted state is determined by the property of releasing the cleaning solution from the outer surfaces of the outer layer sheets. Further, the property of releasing the cleaning solution from the outer surfaces of the outer layer sheets may be determined by the property of releasing the cleaning solution from the impregnated element to the outer layer sheets. Further, the property of releasing the cleaning solution from the impregnated element to the outer layer sheets may be determined by the amount of cleaning solution which can be impregnated into the impregnated element, or the amount of cleaning solution which is released from the impregnated element to the outer layer sheets. In order to control the amount of cleaning solution which is released from the impregnated element to the outer layer sheets, as described above, a space (clearance) may be provided between the impregnated element and the outer layer sheets, or a fusion bonded layer may be formed on the inner sides of the outer layer sheets (facing the impregnated element). An embodiment using a method for controlling the property of releasing cleaning solution from the impregnated element to the outer layer sheets is described above. 
     DESCRIPTION OF NUMERALS 
     
         
           100  cleaning tool 
           110  head (cleaning sheet mounting member) 
           120  holding member 
           121  holding piece 
           130  pipe 
           131  connecting mechanism 
           150  handle 
           200 ,  300 ,  400 ,  500 ,  600 ,  700 ,  800  cleaning sheet 
           200   a ,  200   c ,  300   a ,  300   c ,  400   a ,  400   c ,  500   a ,  500   c ,  600   a ,  600   c ,  700   a ,  700   c ,  800   a ,  800   c  end portion 
           200   a   1 ,  200   c   1  first part 
           200   a   2 ,  200   c   2  second part 
           200   a   3 ,  200   c   3  third part 
           200 P 1 ,  200 Q 1  first boundary 
           200 P 2 ,  200 Q 2  second boundary 
           200   b ,  300   b ,  400   b ,  500   b ,  600   b ,  700   b ,  800   b  central portion (cleaning portion) 
           201 ,  202 ,  220   b ,  230   b  folding line 
           220   a ,  230   a  folded part 
           210 ,  310 ,  410 ,  510 ,  610 ,  710 ,  810  inner layer sheet 
           220 ,  230 ,  320 ,  330 ,  420 ,  430 ,  520 ,  530 ,  620 ,  630 ,  720 ,  730 ,  820 ,  830  outer layer sheet 
           221 ,  231  outer layer
         222 ,  232  inner layer (fusion bonded layer)   
     
           203 ,  204  hot embossed portion