Abstract:
A cleaning sheet that is attachable to a cleaning sheet-attaching component and is characterized in having a central part configuring a cleaning surface and at least one end provided on at least one side of the central part in a prescribed direction. The at least one end has a first part with a first elongation percentage and a second part with a higher elongation percentage than the first part. The second part is provided between the first part and the central part in the prescribed direction, and the sheet is configured so as to be detachably held on the cleaning sheet-attaching component at the boundary between the first part and the second part. Also configured is a cleaning implement provided with said cleaning sheet.

Description:
RELATED APPLICATIONS 
     This application is a 35 U.S.C. §371 national phase filing of International Patent Application No. PCT/JP2011/071708, filed Sep. 22, 2011, through which and to which priority is claimed under 35 U.S.C. §119 to Japanese Patent Application No. 2010-215369, filed Sep. 27, 2010. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a cleaning sheet and a cleaning tool, and more particularly to a cleaning sheet and a cleaning tool which can be suitably used for wiping an object to be cleaned, such as floor. 
     2. Description of the Related Art 
     Various cleaning sheets for wiping an object to be cleaned are known. For example, 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. 
     In this case, a central portion of the cleaning sheet is placed on a cleaning part of the cleaning sheet mounting member. Both ends of the cleaning sheet are pushed in through holding members of the cleaning sheet mounting member and held between the holding members. The known cleaning sheet has a loosely entangled portion in its central portion and a tightly entangled portion in its both end portions. 
     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. In the known cleaning sheet, the loosely entangled portion is formed in its central portion, but each of the end portions of the sheet has a substantially uniform elongation rate across its entire region. Therefore, when a tensile stress acts upon the cleaning sheet during cleaning operation, if the end portions of the cleaning sheet has a lower elongation rate or higher rigidity, the end portions of the cleaning sheet easily become detached from the holding members. On the other hand, if the end portions of the cleaning sheet are designed to have a higher elongation rate or lower rigidity in order to prevent the cleaning sheet from becoming detached, the end portions of the cleaning sheet held by the holding members are easily damaged by tensile stress. Therefore, it is difficult to secure reliable holding of the cleaning sheet and resistance to damage in a balanced manner. 
     Accordingly, it is an object of the invention to provide a technique for improving usability of the cleaning sheet and the cleaning tool. 
     The above-described problem can be solved by the claimed invention. According to this invention, a cleaning sheet which can be attached to a cleaning sheet mounting member is provided. This cleaning sheet is preferably formed of nonwoven fabric. The cleaning sheet according to this invention has a central portion forming a cleaning side and at least one end portion formed on at least one side of the central portion along one predetermined direction. The end portion may be formed along one direction on only one side of the central portion, or it may be formed on both sides of the central portion. The end portion has a first part having a predetermined first elongation rate and a second part having a predetermined second elongation rate higher than the first part. The second part is formed between the first part and the central portion along the above-described one direction. A boundary between the first and second parts is removably held by the cleaning sheet mounting member. It is essential for the boundary to be held at least in part. 
     The “elongation rate (mm/N) of the cleaning sheet” is a measure of stretchiness of the cleaning sheet. The higher the elongation rate, the stretchier the sheet. 
     Various methods can be used to change the elongation rates of the first and second parts. For example, a method of changing the number of thicknesses of the sheet elements in the first and second parts, a method of changing the entangled state of fibers in the first and second parts, or a method of changing the constitution of raw cotton in the first and second parts can be used. 
     With this construction, in this invention, when a tensile stress acts upon the cleaning sheet attached to the cleaning sheet mounting member during cleaning operation, the first portion having a lower elongation rate (less stretchy) is held caught by the cleaning sheet mounting member due to its own rigidity without being damaged by the tensile stress. On the other hand, the second part having a higher elongation rate (more stretchy) stretches and thus effectively absorbs the tensile stress. As a result, the cleaning sheet can be prevented from becoming detached from the cleaning sheet mounting member during cleaning operation. 
     In another embodiment of the invention, the elongation rates of the first and second parts are changed according to the number of thicknesses of the sheet elements in the first and second parts. In this case, the second part having a higher elongation rate may be formed by a single sheet element, or it may be formed by several thicknesses of sheet elements. The second part formed by a single sheet element can be referred to as the “second part having the sheet element in a single layer”. Further, the first part having a lower elongation rate is formed by a larger number of thicknesses of sheet elements than the sheet elements of the second part. As a method of layering sheet elements, a method of overlaying different sheet elements one on another or a method of folding one sheet element can be used. The layered sheet elements are preferably bonded together. Various methods can be used as the bonding method. 
     In this embodiment, the first and second parts are different in the number of thicknesses of the sheet elements, so that it can be easy to visually check the boundary between the first and second parts. Thus, the operation of holding the boundary by the holding member is easily performed. Further, the cleaning sheet in which the end portion has the first and second parts having different elongation rates can be manufactured at lower cost. 
     In a further embodiment of the invention, the layered sheet elements in the first part of the end portion are bonded together by embossing. Preferably, the sheet elements containing thermoplastic fibers are overlaid one on another and bonded together by hot embossing. Various kinds of sheet elements can be used as the sheet elements containing thermoplastic fibers. 
     In this embodiment, the elongation rates of the first and second parts can be more easily changed. 
     In a further embodiment of the invention, the end portion has a third part having a lower elongation rate than the second part. The third part is formed between the second part and the central portion along the one direction. The third part may have the same elongation rate as the first part, or it may have a different elongation rate from the first part. 
     In this embodiment, with the construction in which the third part having a lower elongation rate than the second part is disposed on the central portion side of the second part, the strength of the central portion side can be maintained, while the cleaning sheet can be prevented from becoming detached from the cleaning sheet mounting member. 
     In a further embodiment of the invention, a cleaning tool having the cleaning sheet and the cleaning sheet mounting member as described above can be provided. 
     Further, in a further embodiment of the invention, the holding member has a plurality of elastic holding pieces which are opposed to each other, and the boundary of the cleaning sheet is pushed in through the holding member between the holding pieces and caught by the holding pieces. In this manner, the boundary is held by the holding member. 
     According to this invention, a cleaning sheet or a cleaning tool is provided which is improved in usability. Other objects, features and advantages of this 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 an embodiment of a cleaning tool. 
         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 one 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 improved cleaning sheets or cleaning tools and components utilized therein. Representative examples of the 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. Only the claims define the scope of the claimed invention. Therefore, 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  100  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  via coupling mechanisms. Each of the coupling mechanisms includes, for example, a male coupling element provided on one end of one pipe element and a female coupling element provided on the other end of the other pipe element. The connection between the male coupling element and the female coupling element 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 part)  111  (see  FIG. 10 ) opposite to 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  forms a main cleaning side of the cleaning sheet  200 . Further, the end portion  200   c  forms a mounting portion which is mounted to the cleaning sheet mounting member (the head  110 ). 
     The central portion  200   b  of the cleaning sheet  200  is placed to face the lower side (mounting side or cleaning part)  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  (the holding pieces  121 ) are pushed in by user&#39;s fingers. Thus, the end portions  200   a ,  200   c  of the cleaning sheet  200  are caught in part and removably held between the adjacent holding pieces  121 . 
     In a cleaning operation using the cleaning tool  100  of this embodiment, generally, the head  110  is moved in a direction (the vertical direction as viewed in  FIG. 2 ) transverse to a 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 its 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 intertlaced 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 direction of feed 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 include nonwoven fabric sheets manufactured by other methods, such as through-air bonding, spun bonding, 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 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 hydrophobic as a whole, 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 layers  221 ,  231  consist, for example, of thermoplastic fibers of polyethylene terephthalate (PET) in major proportions and the rest are 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) having a fineness of 2.2 dtex 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, the known cleaning sheet has a loosely entangled portion in its central portion, but each of its end portions has a substantially uniform elongation rate across its entire region. Therefore, during cleaning operation which is performed with the end portions 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 a position such that it can be 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 ) has a base  220   c  ( 230   c ) and a folded part  220   a  ( 230   a ) having a predetermined fold length from its one edge in the width direction. The folded part  220   a  ( 230   a ) is folded over to the inner layer  222  ( 232 ) side along a folding line  220   b  ( 230   b ) and overlaid on 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 . At this time, the inner layer  222  of the outer layer sheet  220  and the inner layer  232  of the outer layer sheet  230  are arranged on the inner layer sheet  210  side (so as to be opposed to each other). Further, the inner layer sheet  210  is centrally located in the direction of the width M (the vertical direction as viewed in  FIG. 3  and the horizontal direction as viewed in  FIG. 4 ). 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, from one end (the other end) in the width direction, a first part  200   a   1  ( 200   c   1 ) of a two-layer structure having the folded part  220   a  ( 230   a ) and part of the base  220   c  ( 230   c ) of the outer layer sheet  220  ( 230 ), 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 the base  230   c  of the outer layer sheet  230 . 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 . 
     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 part)  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 (cleaning part)  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 (cleaning part)  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   b ,  230   b  is referred to as the “length direction”, and a direction transverse (perpendicular) to the folding lines  201 ,  202 ,  220   b ,  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 , an extending direction of the end portions  200   a ,  200   c  (the horizontal direction as viewed in  FIG. 3 ) is referred to as the “length direction”, and a direction (the vertical direction as viewed in  FIG. 3 ) transverse (perpendicular) to the extending direction of the end portions  200   a ,  200   c  is referred to as the “width direction”. The “width direction” in this embodiment corresponds to the “one direction” according to this invention. 
     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 , the inner layer sheet  210  and the outer layer sheets  220 ,  230  are bonded together as shown in  FIGS. 5 and 6 .  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 such that 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 (cleaning part)  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  in the length direction (the 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. 
     Various methods can be used for such bonding. 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 third parts  200   a   3 ,  200   c   3  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  in the third parts  200   a   3 ,  200   c   3  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 part of the base  220   c  of the outer layer sheet  220  (the folded part  230   a  and part of 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 part of the base  220   c  of the outer layer sheet  220  (the folded part  230   a  and part of 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 part of the base  220   c  of the outer layer sheet  220  (the folded part  230   a  and part of 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 part of 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 part of 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 not as stretchy as the second parts  200   a   2 ,  200   c   2 . 
     The elongation rate (mm/N) of the sheet is a measure of stretchiness. The higher the elongation rate, the stretchier 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, with respect to the weight of the yet-to-be impregnated cleaning sheet  200  (the inner layer sheet  210  and the outer layer sheets  220 ,  230 ), two to five times its volume of the cleaning solution 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 (cleaning part)  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 to 20 mm. Therefore, when the central portion  200   b  of the cleaning sheet  200  is placed to face the lower side (cleaning part)  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  (the holding pieces  121 ). In this state, when the portions of the sheet facing the holding pieces  121  are pushed in through 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 . Further, the parts of the boundary  200 P 1  and the boundary  200 Q 1  caught between the holding pieces  121  are pushed in through the holding pieces facing each other by the user&#39;s fingers (see  FIG. 11 ). At this time, as shown in  FIG. 10 , the first parts  200   a   1 ,  200   c   1  are located inward of the second parts  200   a   2 ,  200   c   2  or toward the center in the width direction (on the opposite side from the central portion  200   b ) and held by the holding pieces  121 . 
     In this embodiment, part of the boundary  200 P 1  ( 200 Q 1 ) between the first part  200   a   1  ( 200   c   1 ) having a lower elongation rate and the second part  200   a   2  ( 200   c   2 ) having a higher elongation rate is caught by the holding pieces  121  facing each other. Specifically, a point of change in the elongation rate of the sheet 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  (for example, the horizontal direction as viewed in  FIG. 10 ) by a frictional force of an area to be cleaned during cleaning operation, the second part  200   a   2  or  200   c   2  having a higher elongation rate can effectively absorb the tensile stress, so that the end portions  200   a ,  200   c  of the cleaning sheet  200  can be prevented from becoming detached from the holding pieces  121 . 
     Further, in order to detach the cleaning sheet  200  from the head  110 , the first part  200   a   1  ( 200   c   1 ) having a lower elongation rate is pulled so that the boundary  200 P 1  ( 200 Q 1 ) can be easily pulled out through the holding pieces  121 . Thus, the cleaning sheet  200  can be easily detached from the head  110 . 
     In this embodiment, the second part  200   a   2  ( 200   c   2 ) having a higher elongation rate is designed as a single-layer structure and the first part  200   a   1  ( 200   c   1 ) having a lower elongation rate as a two-layer structure. With such a construction, the cleaning tool having the first part  200   a   1  ( 200   c   1 ) and the second part  200   a   2  ( 200   c   2 ) which are different in elongation rate can be easily manufactured at lower costs. 
     In this embodiment, with the construction in which the first part  200   a   1  ( 200   c   1 ) has a two-layer structure and the second part  200   a   2  ( 200   c   2 ) has a single-layer structure, the boundary  200 P 1  ( 200 Q 1 ) between the first part  200   a   1  ( 200   c   1 ) and the second part  200   a   2  ( 200   c   2 ) can be readily recognized by outward appearance, so that ease of mounting the cleaning sheet can be enhanced. 
     Operation of this invention is conceptually explained with reference to  FIG. 11 . In  FIG. 11 , for the sake of simplicity of explanation, it is assumed that the end portion  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 disposed on the central portion  200   b  side of the first member X. The first member X and the second member Y substantially correspond to the above-described first part  200   a   1  ( 200   c   1 ) and the above-described second part  200   a   2  ( 200   c   2 ), respectively. Further, it is assumed that part of a boundary Z between the first member X and the second member Y is held by the holding members  120  (the holding pieces  121 ) of the head  110  and the head  110  is moved in a direction shown by the hollow arrow G (rightward) in  FIG. 11 . The boundary Z substantially corresponds to the above-described 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 ), by frictional force of an area to be cleaned, a tensile stress acts in the direction of the solid arrow F upon the second member Y disposed on the end in the direction of the hollow arrow G. 
     In the prior art, the cleaning sheet has a loosely entangled portion in its central portion and tightly entangled portions on the both ends, but each of the end portions of the sheet has a substantially uniform elongation rate across its entire region. Therefore, the loosely entangled portion is ineffective in absorbing a tensile stress F. Thus, the sheet element held by the holding members  120  (the holding pieces  121 ) uniformly stretches, so that the end portion  200   a  ( 200   c ) of the cleaning sheet  200  easily becomes detached from the holding members  120  (the holding pieces  121 ). 
     In this embodiment, as shown in FIG.  11 ( 2 ), part of the boundary Z between the first member X having a lower elongation rate and the second member Y having a higher elongation rate is held by the holding pieces  121 , so that the second member Y having the higher elongation rate becomes stretchy and can effectively absorb the tensile stress. In this case, part of the boundary Z between the first member X and the second member Y is kept held by the holding pieces  121 . 
     When the tensile stress acting upon the end portion 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 out through the holding pieces  121 . In this case, the end portion  200   a  ( 200   c ) of the cleaning sheet  200  is detached from the holding pieces  121 . 
     Further, by pulling the first member X having a lower elongation rate, the end portion  200   a  ( 200   c ) of the cleaning sheet  200  can be easily 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. 
     Further, in embodiments 1 to 4 and comparative examples 1 to 7, the width M is 205 mm. 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. 
     Further, the “elongation rate (mm/N)” is represented as the inverse of an initial slope of a curve of [tensile stress (N)/amount of elongation (mm)] when the sheet having the width of 25 mm is pulled in a direction perpendicular to the direction of the width. 
     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 a folded part  240  or  250  is formed. The folded parts  240 ,  250  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 given to where it is needed, 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 ). 
     In 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. 
     In 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 of the inner layer sheet  310 , and 70 g/m 2  spun bond 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  spun bond 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 ). 
     In 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 an inner layer sheet  410 , and 70 g/m 2  spun bond nonwoven fabrics  460 ,  470  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  spun bond 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 ). 
     In 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 ). 
     In 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 ). 
     In 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 ). 
     In 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 sheets  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 ). 
     In 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 sheets  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 ). 
     In 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  spun bond 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  spun bond 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 ). 
     In 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  spun bond 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  spun bond 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 ). 
     In 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 of embodiments 1 to 4 and comparative examples 1 to 7 from the holding pieces  121  of the head  110  was measured. The measurements of energy were made as follows: 
     (1) Part of a specimen is pushed in through the holding pieces  121  of the fixed head. At this time, the amount of the specimen to be pushed in is adjusted to be constant by using an artificial finger. 
     (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 is lower than 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 is equal to 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 is larger than 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 second part is disposed on the central portion side of the first part. 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 can be effectively prevented from becoming detached from the holding members  120  (the holding pieces  121 ) during cleaning operation. 
     In order to form a region having a higher elongation rate, in this embodiment, the layered sheet elements are bonded together by hot embossing, but a method of changing the elongation rate is not limited to this. For example, the layered sheet elements 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 the particular 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 in which the cleaning solution is impregnated in the inner layer sheet so as to be used for cleaning in a wetted state, but it may be designed as a dry sheet in which the cleaning solution is not impregnated in the inner layer sheet 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 features can be included in claims of the invention: 
     “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 of the outer layer sheet opposite to 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 part (mounting side) of the cleaning sheet mounting member.” 
     As the 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 the cleaning solution, and outer layer sheets disposed on both sides of the impregnated element is used. In this case, a cleaning region (cleaning part) of the cleaning sheet which can be used to clean an object to be cleaned 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 is 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 is 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, 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). In the above-described embodiment, a method for controlling the property of releasing cleaning solution from the impregnated element to the outer layer sheets is used. 
     The above-described cleaning sheet may also be used singly (without being mounted to the cleaning sheet mounting member of the cleaning tool) to clean an object to be cleaned. Further, the cleaning sheet or the cleaning tool of this invention can be used to clean objects having various shapes, such as planar, curved, uneven or stepped shape. 
     Further, the cleaning sheet may also be designed to be used in a dry state to clean an object to be cleaned. 
     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 part) 
           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