Patent Publication Number: US-9414981-B2

Title: Bed and separating method of the same

Description:
TECHNICAL FIELD 
     The present invention relates to a bed in which a part thereof can be separated as a wheelchair, and a separating method of the same. 
     BACKGROUND ART 
     In nursing care, there is a case where a care-receiver is moved from a bed into a wheelchair or a case where the care-receiver is moved from the wheelchair onto the bed. The care-receiver indicates for example, a bedridden aged person or an ailing person. Such movement is difficult and there is a possibility that a care worker suffers from lumbar pain at the time of the movement. Thus, a bed device in which a part of the bed is dividable and the part can be changed to a wheel chair is proposed (for example, refer to Japanese Unexamined Utility Model Publication No. 5-51330). 
       FIG. 16  is a perspective view of a conventional bed device  10 . As shown in  FIG. 16 , abed surface of the bed device  10  is composed of three plates of a side bed plate  2 , a center bed plate  3 , and a side bed plate  4 . In order to form the bed surface, there is a need for moving the center bed plate  3  of a wheelchair  5  in a flat posture to a space  3   a  between the side bed plate  2  and the side bed plate  4  as shown in  FIG. 16 . Therefore, with a rotation mechanism  7 , by firstly rotating an arm  8  in the arrow  7   a  direction about a rotation center of the rotation mechanism, the care worker brings the side bed plate  4  fixed to the arm  8  up to the upper side of a bed main body  1 . 
     The care worker moves the wheelchair  5  on which the care-receiver rides to the space  3   a  in a state that the side bed plate  4  is brought up to the upper side of the bed main body  1 . After the wheelchair  5  is moved to the space  3   a , when the side bed plate  4  is returned to the original position, the bed surface is composed of the side bed plates  2 ,  4  and the center bed plate  3 . In such a way, the care-receiver can be easily moved from the wheelchair  5  to the bed device  10 . By performing the procedure reverse to the above description, the care-receiver can be easily moved from the bed device  10  to the wheelchair  5 . 
     It should be noted that at the time of coupling the wheelchair  5  to the bed main body portion  1 , a pair of rails  9  of the wheelchair  5  utilized as armrests are shifted into insertion holes  9   a ,  9   b  of the bed main body portion  1  from the wheelchair  5  and utilized as side rails for the bed device  10 . 
     In such a way, by using the bed device  10  having the wheelchair  5  as a part thereof, labor of the care worker to move the care-receiver between the wheelchair  5  and the bed main body  1  can be reduced. 
     TECHNICAL PROBLEM 
     However, in the conventional bed device  10 , length of the rails  9  on the both sides is short in comparison to length in the longitudinal direction of the bed device  10 . Therefore, when the care-receiver moves his/her body, the care-receiver cannot be supported by the rails  9 , and the care-receiver is sometimes slipped off. 
     Thus, an object of the present invention is to provide a highly safe bed having a low possibility that a care-receiver is slipped off, and a separating method of the bed. 
     SUMMARY OF THE INVENTION 
     In order to achieve the above object, the present invention is formed as below. 
     In order to solve the problem, a bed of the present invention 
     A bed of the present invention, comprises: 
     a first rail; 
     a second rail; 
     a wheelchair having a first armrest mounting unit to and from which the first rail is attachable and detachable in one side part thereof, and a second armrest mounting unit to and from which the second rail is attachable and detachable in an other side part thereof; and 
     a bed main body portion having a first support portion and a second support portion in one side part and a bed rail in an other side part thereof, wherein 
     the first support portion has a first bed mounting unit to and from which the first rail or the second rail is attachable and detachable, and 
     the second support portion has a second bed mounting unit to and from which the first rail or the second rail is attachable and detachable. 
     A bed of the present invention, comprises: 
     a first rail; 
     a second rail; 
     a wheelchair having a first armrest mounting unit to and from which the first rail is attachable and detachable in one side part thereof, a second armrest mounting unit to and from which the second rail is attachable and detachable in an other side part, and a first bed mounting unit and a second bed mounting unit arranged so as to sandwich the first armrest mounting unit in the one side part thereof; and 
     a bed main body portion having a bed rail in a side part thereof, wherein 
     the first rail or the second rail is attachable to and detachable from the first bed mounting unit and the second bed mounting unit. 
     A separating method of a bed of the present invention is a separating method of the bed having a first armrest formation step for removing the second rail from the second bed mounting unit and installing the second rail in the second armrest mounting unit, and a second armrest formation step for removing the first rail from the first bed mounting unit and installing the first rail in the first armrest mounting unit. 
     Advantageous Effects of Invention 
     In the present invention, a highly safe bed having a low possibility that a care-receiver is slipped off, and a separating method of this bed can be provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The features of the present invention will become clear from the following description taken in conjunction with the embodiments thereof with reference to the accompanying drawings, in which: 
         FIG. 1A  is a perspective view of a bed in a separated state for illustrating the bed according to a first embodiment of the present invention; 
         FIG. 1B  is a perspective view of the bed in a coupled state for illustrating the bed according to the first embodiment of the present invention; 
         FIG. 1C  is a perspective view of the bed in a wheelchair state for illustrating the bed according to the first embodiment of the present invention; 
         FIG. 2  is a side view of a first rail of the bed according to the first embodiment; 
         FIG. 3A  is a front view of the first rail in a bed state of the bed according to the first embodiment; 
         FIG. 3B  is a front view of the first rail and a second rail in the wheelchair state of the bed according to the first embodiment; 
         FIG. 4A  is a flowchart of a separating method of a wheelchair from a bed main body portion according to the first embodiment; 
         FIG. 4B  is a flowchart of a separating method of the wheelchair from the bed main body portion according to a modification of the first embodiment; 
         FIG. 5A  is a plan view of the bed at the time of coupling for illustrating separation of the wheelchair from the bed main body portion according to the first embodiment; 
         FIG. 5B  is a first plan view of the bed in a locked state for illustrating the separation of the wheelchair from the bed main body portion according to the first embodiment; 
         FIG. 5C  is a second plan view of the bed in the locked state for illustrating the separation of the wheelchair from the bed main body portion according to the first embodiment; 
         FIG. 5D  is a third plan view of the bed in the locked state for illustrating the separation of the wheelchair from the bed main body portion according to the first embodiment; 
         FIG. 5E  is a plan view of the bed at the time of separation for illustrating the separation of the wheelchair from the bed main body portion according to the first embodiment; 
         FIG. 5F  is a plan view of the bed at the time of coupling for illustrating separation of the wheelchair from the bed main body portion according to the modification of the first and second embodiments; 
         FIG. 5G  is a first plan view of the bed in the locked state for illustrating the separation of the wheelchair from the bed main body portion according to the modification of the first and second embodiments; 
         FIG. 5H  is a second plan view of the bed in the locked state for illustrating the separation of the wheelchair from the bed main body portion according to the modification of the first and second embodiments; 
         FIG. 5I  is a third plan view of the bed in the locked state for illustrating the separation of the wheelchair from the bed main body portion according to the modification of the first and second embodiments; 
         FIG. 5J  is a plan view of the bed at the time of separation for illustrating the separation of the wheelchair from the bed main body portion according to the modification of the first and second embodiments; 
         FIG. 6A  is a partially sectional view of the bed at the time of coupling for illustrating separation of the wheelchair from the bed main body portion according to the second embodiment; 
         FIG. 6B  is a partially sectional view of the bed at the time of lowering the bed main body portion for illustrating the separation of the wheelchair from the bed main body portion according to the second embodiment; 
         FIG. 6C  is a partially sectional view of the bed in the locked state for illustrating the separation of the wheelchair from the bed main body portion according to the second embodiment; 
         FIG. 7  is a plan view of the bed in the locked state according to the second embodiment; 
         FIG. 8  is a partially sectional view of the bed at the time of separation according to the second embodiment; 
         FIG. 9  is a bottom view of the first rail according to a third embodiment of the present invention; 
         FIG. 10  is a plan view of the bed in the locked state according to the third embodiment; 
         FIG. 11A  is a side view of a first rail according to a fourth embodiment of the present invention, with the first rail being in a folded state; 
         FIG. 11B  is a side view of the first rail according to the fourth embodiment of the present invention, with the first rail being in an extended state; 
         FIG. 12  is a side view of major parts of the bed according to the fourth embodiment; 
         FIG. 13A  is a side view of a first rail according to a fifth embodiment of the present invention, with the first rail being in an accommodated state; 
         FIG. 13B  is a side view of the first rail according to the fifth embodiment of the present invention, with the first rail being in a pull-out state; 
         FIG. 14  is a side view of major parts of the bed according to the fifth embodiment; 
         FIG. 15A  is a perspective view of a bed in the separated state for illustrating the bed according to a sixth embodiment of the present invention; 
         FIG. 15B  is a perspective view of the bed in the coupled state for illustrating the bed according to the sixth embodiment of the present invention; 
         FIG. 15C  is a perspective view of the bed in the wheelchair state for illustrating the bed according to the sixth embodiment of the present invention; 
         FIG. 16  is a perspective view of a conventional bed; 
         FIG. 17A  is a perspective view of the bed in the separated state for illustrating the bed according to a seventh embodiment of the present invention; 
         FIG. 17B  is a perspective view of the bed in the wheelchair state for illustrating the bed according to the seventh embodiment of the present invention; 
         FIG. 18A  is a partially sectional view of the bed at the time of slightly separating from coupling (first separation step S 01 ) for illustrating separation of the wheelchair from the bed main body portion according to a specific example of the first embodiment; 
         FIG. 18B  is a partially sectional view of the bed at the time of lowering the bed main body portion for illustrating the separation of the wheelchair from the bed main body portion according to the specific example of the first embodiment; 
         FIG. 18C  is a partially sectional view of the bed in the locked state for illustrating the separation of the wheelchair from the bed main body portion according to the specific example of the first embodiment; 
         FIG. 18D  is an enlarged sectional view of a part of  FIG. 18C ; 
         FIG. 18E  is a partially sectional view of the bed during cancellation of lock for illustrating the separation of the wheelchair from the bed main body portion according to the specific example of the first embodiment; 
         FIG. 18F  is an enlarged sectional view of a part of  FIG. 18E ; 
         FIG. 18G  is a partially sectional view of the bed after the cancellation of the lock for illustrating the separation of the wheelchair from the bed main body portion according to the specific example of the first embodiment; 
         FIG. 18H  is a partially sectional view of the bed in the middle of starting coupling for illustrating the separation of the wheelchair from the bed main body portion according to the specific example of the first embodiment; 
         FIG. 18I  is a partially sectional view of the bed in the middle of starting the coupling for illustrating the separation of the wheelchair from the bed main body portion according to the specific example of the first embodiment; 
         FIG. 18J  is a partially sectional view of the bed in the middle of locking for illustrating the separation of the wheelchair from the bed main body portion according to the specific example of the first embodiment; 
         FIG. 18K  is a partially sectional view of the bed in the locked state for illustrating the separation of the wheelchair from the bed main body portion according to the specific example of the first embodiment; and 
         FIG. 18L  is a partially sectional view of the bed in the locked state for illustrating the separation of the wheelchair from the bed main body portion according to the specific example of the first embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the same constituent elements will be given the same reference numerals, and description thereof will sometimes be omitted. For easy understanding, the drawings are schematically focusing on the constituent elements. In order to clarify corresponding relationships between the figures, X, Y, and Z axes are appropriately shown in the figures. 
     In the following description, a person who uses a bed is called a care-receiver (for example, a bedridden aged person or an ailing person), and a person who aids the care-receiver to use the bed is called a care worker. 
     First Embodiment 
     A bed according to a first embodiment of the present invention is a bed in which a wheelchair can be separated, and armrests (a pair of rails) drawn from the wheelchair are installed in line on one side of the bed and used as side rails. That is, the pair of rails of the bed according to the first embodiment is used as the armrests in a chair posture C (posture of a wheelchair  14  shown in  FIG. 1C ), and used as the side rails on one side in a bed state B (state that the wheelchair  14  and a bed main body portion  15  are combined shown in  FIG. 1B ). It should be noted that although a detail will be described later, side rails on the other side of the bed are always placed in line on the bed. The wheelchair can be separated from the bed for easily performing a moving task from the bed to the wheelchair. 
       FIGS. 1A and 1B  are views for illustrating a bed  11  according to the first embodiment of the present invention.  FIG. 1A  is a perspective view of the bed  11  in a separated state.  FIG. 1B  is a perspective view of the bed  11  in a coupled state. 
     As shown in  FIGS. 1A, 1B , the bed  11  is provided with a first rail  12 , a second rail  13 , the wheelchair  14 , and the bed main body portion  15 . Although the description will be given later with  FIG. 2 , as shown in  FIG. 2 , the first rail  12  and the second rail  13  respectively have a structure in which two support rod portions  44  protrude from lower parts of a rectangular plate shape support body  41 . 
     The wheelchair  14  has a pair of first armrest mounting units  21  in a center part of one side part (for example, a side part on the near side in  FIG. 1A ). The first rail  12  is attachable to the pair of first armrest mounting units  21  as an armrest, and the first rail  12  can be detachably attached and detached. As one example, the pair of first armrest mounting units  21  is formed as insertion holes to and from which lower ends of the two support rods of the first rail  12  are attachable and detachable. 
     This wheelchair  14  has a pair of second armrest mounting units  22  (refer to  FIGS. 6A to 6C  and  FIG. 7 , etc.) in a center part of the other side part (for example, a side part on the far side in  FIG. 1A ). The second rail  13  can be attached to and detached from the pair of second armrest mounting units  22  attachably and detachably as an armrest. As one example, the pair of second armrest mounting units  22  is formed as insertion holes to and from which lower ends of the two support rods of the second rail  13  are attachable and detachable. 
     When the wheelchair  14  is used as a part of the bed  11 , the wheelchair  14  is in a flat posture F in which an upper surface is flatly placed as shown in  FIGS. 1A and 1B . However, when the wheelchair  14  is used as a single body, as shown in  FIG. 1C , a backrest  14   a  is brought upward and a point  14   c  for supporting legs is lowered, so that the wheelchair  14  is transformed into the chair posture C and utilized as a wheelchair. 
     When the wheelchair  14  is used as a single body, the first rail  12  is attached to the first armrest mounting units  21 , and the second rail  13  is attached to the second armrest mounting units  22 . The first rail  12  and the second rail  13  attached to the second armrest mounting units  22  are respectively utilized as the armrests (arm rests) of the wheelchair  14 . 
     The bed main body portion  15  has one first support portion  31  and one second support portion  32  protruding sideward in one side part (for example, a side part on the near side in  FIG. 1A ). The first support portion  31  and the second support portion  32  of this bed main body portion  15  are to support the wheelchair  14  in the coupled state. 
     The bed main body portion  15  also has two bed rails  33  in the other side part (for example, a side part on the far side in  FIG. 1A ). When the wheelchair  14  is separated from the bed main body portion  15  and when the wheelchair  14  is coupled to the bed main body portion  15 , the two bed rails  33  are not detached but held to be fixed. 
     The first support portion  31  has a pair of first bed mounting units  34  in a front end (an outer end in the width direction of the bed main body portion  15 ). The pair of first bed mounting units  34  is to attachably and detachably attach and detach the first rail  12  as a bed rail. As one example, the pair of first bed mounting units  34  is formed as insertion holes to and from which the lower ends of the two support rods of the first rail  12  are attachable and detachable. 
     The second support portion  32  has a pair of second bed mounting units  35  in a front end (an outer end in the width direction of the bed main body portion  15 ). The pair of second bed mounting units  35  is to attachably and detachably attach and detach the second rail  13  as a bed rail. As one example, the pair of second bed mounting units  35  is formed as insertion holes to and from which the lower ends of the two support rods of the second rail  13  are attachable and detachable. 
     A space between the first support portion  31  and the second support portion  32  of the bed main body portion  15  is an accommodation space G. 
     When the separated state is brought into the coupled state, the second armrest mounting units  22  of the wheelchair  14  are set to face this accommodation space G, and the wheelchair  14  is brought close in the width direction of the bed main body portion  15  in such a manner that the second armrest mounting units  22  are inserted into the accommodation space G, so that the wheelchair  14  and the bed main body portion  15  are coupled. When coupling is performed in such a way, the first armrest mounting units  21  are arranged in the accommodation space G as well as the second armrest mounting units  22 . Thus, the first bed mounting units  34  and the second bed mounting units  35  protrude toward the side of the first armrest mounting units  21 . At this time, the first armrest mounting units  21  are arranged between the first bed mounting units  34  and the second bed mounting units  35 . 
     With such a configuration, in a state that the wheelchair  14  and the bed main body portion  15  are coupled (that is, the bed state B shown in  FIG. 1B ), the lower ends of the two support rods of the first rail  12  are installed into the insertion holes of the pair of first bed mounting units  34 , and the lower ends of the two support rods of the second rail  13  are installed into the insertion holes of the pair of second bed mounting units  35 . As a result, in the bed state B, the first rail  12  and the second rail  13  are placed in line on one side of the bed  11 . With this configuration, on a side surface of the bed  11  in which the first rail  12  and the second rail  13  are installed, a space formed between the two rails  12 ,  13  where no rail exists (gap in center on the one side of the bed  11 ) can be narrowed. Therefore, even when the care-receiver lying on the bed  11  moves his/her body toward the first rail  12  and the second rail  13 , the side of upper body or lower body of the care-receiver is supported by at least one of the first rail  12  and the second rail  13 , so that a possibility of slipping off the bed  11  is lowered. That is, with the configuration of the first embodiment, the highly safe bed  11  from which the wheelchair  14  is separable can be provided. 
     It should be noted that in the present embodiment, each rail length L of the first rail  12  and the second rail  13  is length which is one third or more and less than one half of the total length in the longitudinal direction of the bed  11 . When the each rail length L of the first rail  12  and the second rail  13  is one third or more of the total length in the longitudinal direction, the rails can be used as the bed rails for preventing fall of a person in the bed state B. When the each rail length L of the first rail  12  and the second rail  13  is less than one half of the total length in the longitudinal direction, the rails can be mounted as the bed rails in terms of structure. For example, in the present embodiment, the total length in the longitudinal direction of the bed  11  is 190 cm. Thus, the each rail length L of the first rail  12  and the second rail  13  is 70 cm. 
     In the first embodiment, by arranging the first bed mounting units  34  and the second bed mounting units  35  in line on the one side of the bed  11 , the bed  11  is formed in such a manner that the first rail  12  and the second rail  13  are easily shifted. For example, when the care worker shifts the first rail  12  and the second rail  13  from the state of  FIG. 1A  into the state of  FIG. 1B , the care worker is not required to move to both the sides of the bed  11 , so that the care worker can shift the first rail  12  and the second rail  13  from the one side of the bed  11 . Specifically, a mat width W 1  of the wheelchair  14  (refer to  FIG. 1B ) is for example about 50 cm. Thus, by extending his/her arm, the care worker can draw the first rail  12  and the second rail  13  and install the rails into the first bed mounting units  34  and the second bed mounting units  35  without moving from the side of the first armrest mounting units  21  of the wheelchair  14 . 
     Meanwhile, in a case where the first bed mounting units  34  and the second bed mounting units  35  of the first embodiment are not used, it is difficult to install the second rail  13  on the other side  15   b  of the bed main body portion  15 . Specifically, a mat width W 2  of the bed main body portion  15  (refer to  FIG. 1B ) is for example about 50 cm, and a width of the bed  11  becomes for example about 100 cm. Thus, in a case where the first bed mounting units  34  and the second bed mounting units  35  of the first embodiment are not used, the care worker is required to shift the rails to positions 100 cm far from the one side by making his/her body overhung the body of the care-receiver. Therefore, in a case where the first bed mounting units  34  and the second bed mounting units  35  of the first embodiment are not used, the care worker is required to go to the other side  15   b  of the bed main body portion  15  and perform installation. When such an action is required, labor and a working time of the care worker are increased. 
     By placing the first bed mounting units  34  and the second bed mounting units  35  in line on the one side  15   a  of the bed  11  in such a way, the care worker is not required to go around the bed  11  and go back and forth to both the sides of the bed  11 . Therefore, by placing the first bed mounting units  34  and the second bed mounting units  35  in line on the one side  15   a  of the bed  11 , the labor of the care worker can be reduced and the working time can be shortened. 
       FIG. 2  is a side view of the first rail  12  according to the first embodiment.  FIGS. 3A and 3B  are front views of the first rail  12  according to the first embodiment (views in which the first rail  12  is seen from the side when installed in the wheelchair  14 ). 
     As shown in  FIGS. 2, 3A, and 3B , the first rail  12  has the support body  41 , an armrest portion  42 , and a plate portion  43 . The support body  41  is a member having the two support rod portions  44  at a lower end. The support body  41  can be composed of processing an iron pipe for example. The armrest portion  42  is a rectangular parallelepiped member provided in an upper part of the support body  41 , the member protruding sideward only on one surface of the support body  41 . The plate portion  43  is a rectangular plate shape member provided in the support body  41 , the member covering a surface of the support body  41 . Instead of a plate shape member, a cloth-like member can be used as the plate portion  43 . The plate portion  43  is not always required but may desirably be provided according to need. A width d 1  of the armrest portion  42  is larger than a width d 2  of the support body  41 . The width d 1  of the armrest portion  42  is larger than the width d 2  of the support body  41  in order to extend an area where an elbow of the care-receiver is disposed. As one example, the width d 1  is about 18 to 25 mm, and the width d 2  is about 45 to 70 mm. The support body  41  is composed of bending a metal pipe into a bracket (]) shape. 
     A space (gap)  12   a  exists between the metal pipe and the metal pipe of the support body  41 . However, this space  12   a  is closed from the outer side by the plate portion  43  while leaving a gap in an upper part. In a case where the space is not closed by the plate portion  43 , the space  12   a  is so large that an arm can be inserted in between the metal pipe and the metal pipe of the support body  41 . In a state that the arm of the care-receiver is inserted in the space  12   a , and when the care worker performs back lifting without knowing the state, there is a risk that the arm of the care-receiver is caught and bones are broken. However, by closing the space  12   a  by the plate portion  43  while leaving the gap in the upper part, such a situation can be prevented. In the first embodiment, the gap in the upper part of the space  12   a  is a gap of an extent that the arm cannot be inserted (for example, about 25 to 35 mm). With the gap to this extent, at the time of attaching and detaching the first rail  12 , the care worker or the like can grip the armrest portion  42 , so that the moving task is easily performed. By forming the plate portion  43  by a transparent plastic plate, visibility of the care-receiver is not narrowed even when the care-receiver lies on the bed  11 , so that the bed  11  becomes comfortable for the care-receiver. For a purpose of easing impact when the care-receiver makes contact, the plate portion  43  may be formed of cloth or the plate portion  43  may be formed of mesh of metal or plastic. 
     The support rod portions  44  of the first rail  12  are inserted into the insertion holes of the first armrest mounting units  21  or the first bed mounting units  34 . Stoppers  44   a  are fixed to intermediate parts of the support rod portions  44 . The support rod portions  44  on the lower sides of the stoppers  44   a  are inserted into the insertion holes of the first armrest mounting units  21  or the first bed mounting unit  34  and the stoppers  44   a  are brought into contact with peripheries of the insertion holes, so that lower end positions of the support rod portions  44  are determined. 
     It should be noted that although the first rail  12  is described with using  FIGS. 2, 3A, and 3B , the second rail  13  also has the support body  41 , the armrest portion  42 , and the plate portion  43  as well as the first rail  12 . However, the protruding direction of the armrest portion  42  of the second rail  13  is opposite to the first rail  12 , and the direction is outward when the second rail  13  is installed in the wheelchair  14  (refer to  FIG. 3B ). That is, the protruding direction of the armrest portions  42  in the first embodiment is outward (the direction moving away from the bed) in both the bed state B and the wheelchair state (chair posture) C. Since the protruding direction of the armrest portions  42  is outward, at the time of inserting the first rail  12  and the second rail  13  into the first armrest mounting units  21  and the second armrest mounting units  22 , a mat portion  61  and the armrest portions  42  are not brought into contact with each other. Therefore, even with the configuration that the first rail  12  and the second rail  13  are provided with the armrest portions  42  as in the first embodiment, a posture of the wheelchair  14  can be changed. 
     Next, a mechanism for coupling the wheelchair  14  and the bed main body portion  15  will be described. 
     As shown in  FIGS. 1A and 1B , the bed main body portion  15  has a mat portion  51 , a bed portion  52 , a bed base portion  53 , a pair of elevating portions  54 , a guide portion  55 , and a coupling mechanism portion  56 . The bed portion  52  supports the mat portion  51 . The bed base portion  53  supports the bed portion  52 . The pair of elevating portions  54  supports the bed base portion  53  and is arranged on the head side and the leg side. The guide portion  55  is coupled to the bed base portion  53  and guides the wheelchair  14  to a coupling position. The coupling mechanism portion  56  is coupled to the bed base portion  53 . The bed base portion  53  has the first support portion  31 , the second support portion  32 , and a center support portion  53   a.    
     The elevating portions  54  function as one example of an elevating machine for the bed main body portion  15  and are provided with for example, a link mechanism extendable and contractible in the vertical direction so as to move the entire bed base portion  53  parallel in the vertical direction, and an elevating motor coupled to a link of the link mechanism so as to extend and contract the link mechanism by forward/backward rotation of a rotation shaft. When a position of the bed base portion  53  is raised, a chair base portion  63  of the wheelchair  14  and the coupling mechanism portion  56  are brought into contact with each other, and the chair base portion  63  is supported by the coupling mechanism portion  56 . Meanwhile, when the position of the bed base portion  53  is lowered, the coupling mechanism portion  56  is separated from the chair base portion  63 , and support of the chair base portion  63  by the coupling mechanism portion  56  is cancelled. 
     The coupling mechanism portion  56  is arranged in a center part of the accommodation space G between the first support portion  31  and the second support portion  32  of the bed main body portion  15 . 
     The guide portion  55  includes a plate shape member having an inclined surface  55   a . When the wheelchair  14  and the bed main body portion  15  are coupled, the guide portion  55  guides the chair base portion  63  brought into contact with the inclined surface  55   a  into the accommodation space G. 
     It should be noted that the bed main body portion  15  is provided with known back lifting and knee lifting linear actuators (not shown), so that a back lifting action and a knee lifting action by the mat portion  51  are independently performed. That is, the bed  11  functions as an electric nursing care bed in the coupled state. 
     The wheelchair  14  has the mat portion  61 , a chair portion  62 , the chair base portion  63 , and four casters  64 . The chair portion  62  supports the mat portion  61  and is changeable to the seating posture (chair posture) C and the flat posture F. The chair base portion  63  supports the chair portion  62 . The four casters  64  freely move the chair base portion  63 . It should be noted that parts of the chair base portion  63  are the first armrest mounting units  21  and the second armrest mounting units  22 . 
     In a case where the wheelchair  14  and the bed main body portion  15  are coupled, firstly, as shown in  FIG. 1B , the wheelchair  14  is moved to the accommodation space G serving as the coupling position of the bed main body portion  15 . When the elevating portions  54  of the bed main body portion  15  are raised in such a state, the wheelchair  14  is coupled to the bed main body portion  15 . At this time, the four casters  64  are floated up from a bed surface on which the bed main body portion  15  is mounted. It should be noted that the bed main body portion  15  may be supported by four casters (not shown) having brake movably on the bed surface or may be fixed and arranged on the bed surface by four simple support rods. 
     Next, a separating method of the wheelchair  14 , that is, a method for separating the wheelchair  14  from the bed main body portion  15  will be described. 
       FIG. 4A  is a flowchart of the separating method of the wheelchair  14  from the bed  11  according to the first embodiment.  FIGS. 5A to 5E  are views for illustrating separation of the wheelchair  14  from the bed  11  according to the first embodiment.  FIG. 5A  is a plan view of the bed at the time of coupling.  FIG. 5B  is a first plan view of the bed in a locked state.  FIG. 5C  is a second plan view of the bed in the locked state.  FIG. 5D  is a third plan view of the bed  11  in the locked state.  FIG. 5E  is a plan view of the bed  11  at the time of separation. With using  FIGS. 4A and 5A to 5E , the separating method of the wheelchair  14  will be described. 
     The first rail  12  and the second rail  13  are arranged in such a manner that the armrest portions  42  protrude outward in the bed state B (refer to  FIG. 3A ). With this arrangement, the mat portions  51 ,  61  are not brought into interference with the armrest portions  42 , and the posture of the bed  11  can be changed. 
     In a state of  FIG. 5A , gaps GA 1  are formed between the first rail  12  and the second rail  13 , and the mat portion  61 . Provided that a care-receiver  70  lies in the vicinity of center of the mat portions  51 ,  61 . In such a bed state B, the first rail  12  and the second rail  13  are installed in the first bed mounting units  34  and the second bed mounting units  35 , and the mat portion  61  of the wheelchair  14  can be brought into contact with the first rail  12  and the second rail  13 . Therefore, the wheelchair  14  cannot be separated from the bed main body portion  15  and is brought into the locked state. 
     In the first embodiment, the method for separating the wheelchair  14  from the bed main body portion  15  will be described. Firstly, a position where the care-receiver  70  lies is changed by an action of the care worker or the care-receiver  70  himself/herself so that the care-receiver  70  lies only on the mat portion  61  on the side of the wheelchair  14 . 
     After that, the care worker operates an operation switch or the like so as to drive the two elevating portions  54  and lower the two elevating portions  54  of the bed main body portion  15 . Thus, a position of the coupling mechanism portion  56  is lowered together with the bed base portion  53 , and the coupling mechanism portion  56  is separated from the chair base portion  63  of the wheelchair  14 . 
     When the wheelchair  14  is moved in the direction in which the wheelchair  14  is separated from the bed main body portion  15  along the width direction of the bed main body portion  15  in this state, the gaps GA 1  between the first rail  12  and the second rail  13 , and the mat portion  61  are eliminated and the mat portion  61  of the wheelchair  14  is brought into contact with the first rail  12  and the second rail  13 . Thus, the wheelchair  14  cannot be separated from the bed main body portion  15  anymore. That is, when the mat portion  61  is separated from the mat portion  51  in the bed state B, as shown in  FIG. 5B , a gap GA 2  is formed between the mat portion  51  and the mat portion  61 . Installment parts (insertion holes  23 ) of the pair of second armrest mounting units  22  hidden by the mat portion  61  are exposed in the gap GA 2 . In such a way, a first separation step S 01  for pulling out the wheelchair  14  from the bed main body portion  15  (refer to  FIG. 4A ) is performed. Thereby, as shown in  FIG. 5B , the insertion holes  23  of the pair of second armrest mounting units  22  appear in the gap GA 2  between the mat portion  51  and the mat portion  61 . 
     It should be noted that when the gaps GA 1  exist between the first rail  12  and the second rail  13 , and the mat portion  61  of the wheelchair  14  in the bed state B, there is a risk that fingers of the care worker or the care-receiver  70  are caught or the like. In order to prevent this, desirably, when using as the bed  11 , the gaps GA 1  are not formed, and when the bed main body portion  15  is lowered for separating the wheelchair  14  from the bed main body portion  15 , the gaps GA 1  are formed between the first rail  12  and the second rail  13 , and the wheelchair  14 . 
     Next, as shown in  FIG. 5C , the care worker removes the second rail  13  from the second bed mounting units  35 , and installs this second rail  13  in the pair of second armrest mounting units  22 . This task is a first armrest formation step S 02  (refer to  FIG. 4A ). At this time, the care worker mounts the second rail  13  in the second armrest mounting units  22  in such a manner that the armrest portion  42  of the second rail  13  protrudes outward (refer to  FIG. 3B ). 
     Next, as shown in  FIG. 5D , the care worker removes the first rail  12  from the first bed mounting units  34 , and installs this first rail  12  in the first armrest mounting units  21 . This task is a second armrest formation step S 03  (refer to  FIG. 4A ). At this time, the care worker mounts the first rail  12  in the first armrest mounting units  21  in such a manner that the armrest portion  42  of the first rail  12  protrudes outward (refer to  FIG. 3B ). 
     When the first rail  12  and the second rail  13  are installed in the first armrest mounting units  21  and the second armrest mounting units  22  by the care worker, lock of the wheelchair  14  to the bed main body portion  15  is cancelled, so that a second separation step S 04  for separating the wheelchair  14  from the bed main body portion  15  can be performed. As shown in  FIG. 5E , the care worker performs the second separation step S 04  so as to separate the wheelchair  14 . 
     By separating the wheelchair  14  from the bed main body portion  15  by the above procedure, a risk of drop-off of the care-receiver  70  is reduced, so that the highly safe bed  11  can be provided. 
     It should be noted that in the first embodiment, at the time of separating the wheelchair  14  from the bed main body portion  15 , the wheelchair  14  cannot be separated in a state that the first rail  12  and the second rail  13  are attached to the first bed mounting units  34  and the second bed mounting units  35 . By installing the first rail  12  and the second rail  13  in the respective installment parts of the first armrest mounting units  21  and the second armrest mounting units  22 , rails for preventing the fall can be formed on both sides of the wheelchair  14 . In such a way, the bed  11  of the first embodiment is a bed with a less risk that the care-receiver  70  is slipped off. 
     By providing the first armrest mounting units  21  and the second armrest mounting units  22  near the first bed mounting units  34  and the second bed mounting units  35 , the care worker can perform the task without leaving the bed  11  even in a state that the care worker changes installment positions of the first rail  12  and the second rail  13 . Therefore, the bed  11  of the first embodiment is a bed with which the care worker can perform the task while visually recognizing a state of the care-receiver  70 , the bed being capable of reducing the risk of the drop-off of the care-receiver  70 . 
     It should be noted that although the second armrest formation step S 03  is performed after the first armrest formation step S 02  in the above description, the first armrest formation step S 02  may be performed after the second armrest formation step S 03 . In a case where the first armrest formation step S 02  is performed after the second armrest formation step S 03  in such a way, at least one of the first rail  12  and the second rail  13  always exists on the side of the first armrest mounting units  21 . Therefore, in a case where the first armrest formation step S 02  is performed after the second armrest formation step S 03  in such a way, the risk of the drop-off of the care-receiver  70  can also be reduced. 
     It should be noted that any of installment positions of the first rail  12  and the second rail  13  may be changed firstly. That is, in the above description, the first rail  12  and the second rail  13  may be switched with each other. 
     It should be noted that in a case where the second armrest formation step S 03  is performed after the first armrest formation step S 02 , the care worker can stand in the vicinity of the first armrest mounting units  21  so as to install the second rail  13  in the second armrest mounting units  22 . Therefore, when the second armrest formation step S 03  is performed after the first armrest formation step S 02 , the method becomes excellent in care-worker-friendliness. 
     It should be noted that in a case where the first rail  12  or the second rail  13  can be installed in the second armrest mounting units  22  in the bed state B, the first separation step S 01  can be omitted. 
     It should be noted that when the wheelchair  14  is coupled to the bed main body portion  15 , reverse actions to the separating procedure may be performed. 
     Specific Example of the First Embodiment 
       FIGS. 18A, 18B, 18C, 18E, 18G  are partially sectional views of the bed for illustrating separation of the wheelchair from the bed main body portion according to a specific example of the first embodiment (sectional views of a part corresponding to a part of the line A-A of  FIG. 1B ).  FIGS. 18D and 18F  are enlarged sectional views of parts of  FIGS. 18C and 18E , respectively.  FIGS. 18H to 18L  are partially sectional views of the bed for illustrating coupling of the wheelchair to the bed main body portion according to the specific example of the first embodiment (sectional views of the part corresponding to the part of the line A-A of  FIG. 1B ). 
     In the specific example of the first embodiment, a locking mechanism and support rod portions of the first and second rails have more specific structures than the above first embodiment. Specifically, instead of lowering a locking projection  57  by the support rod portion  44  as in the above first embodiment, the locking projection  57  is lowered by a support rod portion  44 U with a rounded front end in the specific example of the first embodiment. The locking projection  57  and a convex portion  65  are brought into contact with and locked to each other in the above first embodiment, whereas the locking projection  57  is locked to a U shape engagement member  65 U arranged in the horizontal direction to the locking projection  57  in the specific example of the first embodiment. Hereinafter, parts in the specific example of the first embodiment, which is different from the above first embodiment will be described. 
     When the wheelchair  14  is separated from the bed main body portion  15 , actions are performed in order of  FIGS. 18A, 18B, 18C, 18E, 18G . 
     Firstly, as shown in  FIG. 18A , in a state that the wheelchair  14  is coupled to the bed main body portion  15  (bed state B), a height of the mat portion  61  of the wheelchair  14  is the same as a height of the mat portion  51  of the bed main body portion  15 . When the coupling mechanism portion  56  is lowered by the elevating portion  54  in order to separate the wheelchair  14  and the bed main body portion  15 , the state becomes a state shown in  FIG. 18B . When the care worker grips the first rail  12  or the like so as to move the first rail  12  in the direction in which the wheelchair  14  is separated from the bed main body portion  15  in this state, as shown in  FIGS. 18C and 18D , the locking projection  57  and the U shape engagement member  65 U are locked to each other, so that the wheelchair  14  cannot be separated from the bed main body portion  15  anymore. This state is the first separation step S 01  of  FIG. 4A . 
     Next, as shown in  FIG. 18E , the care worker installs the second rail  13  in the second armrest mounting units  22 . This task is the first armrest formation step S 02  of  FIG. 4A . As shown in  FIGS. 18E and 18F , when the support rod portion  44 U of the second rail  13  is brought into an insertion groove  23 U of the second armrest mounting unit  22 , the second rail  13  is fixed to the second armrest mounting unit  22 , and a lower end of the support rod portion  44 U passes through the insertion groove  23 U of the second armrest mounting unit  22 , protrudes from the lower side of the insertion groove  23 U, and presses the locking portion  57  downward. The locking portion  57  is pressed by the lower end of the support rod portion  44 U so as to press a spring  56   b  placed between the locking portion  57  and a locking portion accommodating recess portion  58 , and thus, accommodated in the locking portion accommodating recess portion  58 . When the locking portion  57  is accommodated in the locking portion accommodating recess portion  58 , the locking portion  57  does not exist in the horizontal direction to the U shape engagement member  65 U (in other words, lock of the U shape engagement member  65 U and the locking portion  57  is cancelled). As a result, the care worker can largely separate the wheelchair  14  from the bed main body portion  15  in the separating direction (the right direction of  FIG. 18G ). That is, the lock of the locking projection  57  and the U shape engagement member  65 U is cancelled. 
     Successively, after the second armrest formation step S 03  of  FIG. 4A  is performed, the second separation step S 04  of  FIG. 4A  is performed in order to separate the wheelchair  14  from the bed main body portion  15 . 
     Conversely, when the wheelchair  14  is coupled to the bed main body portion  15 , actions are performed in order of  FIGS. 18H to 18L . 
     Firstly, as shown in  FIGS. 18H and 18I , when the wheelchair  14  is brought close to the bed main body portion  15 , the second armrest mounting unit  22  and the U shape engagement member  65 U are brought into contact with an inclined surface  57   a  of the locking projection  57 , so as to press the locking projection  57  downward against a bias force of the spring  56   b . After that, by further moving the wheelchair  14  to the far side in the bed main body portion  15 , as shown in  FIG. 18J , the lower end of the U shape support rod portion  44 U is brought into contact with the inclined surface  57   a  of the locking projection  57 , so as to further press the locking projection  57  downward against the bias force of the spring  56   b.    
     Next, the second rail  13  is drawn from the second armrest mounting unit  22  and installed in the second bed mounting unit  35 . At this time, by drawing the second rail  13  from the second armrest mounting unit  22 , the U shape support rod portion  44 U pressing down the locking projection  57  is eliminated. Thus, by the bias force of the spring  56   b , the locking projection  57  is raised. As a result, as shown in  FIG. 18K , an upper end of the locking projection  57  is brought into contact with a lower surface of the second armrest mounting unit  22  around the insertion groove  23 U. 
     Next, when the coupling mechanism portion  56  is raised by the elevating portion  54 , the chair base portion  63  of the wheelchair  14  is raised together with the bed base portion  53 , the four casters  64  are separated from the bed surface, the chair base portion  63  of the wheelchair  14  is supported by the coupling mechanism portion  56 , the height of the mat portion  61  of the wheelchair  14  becomes the same as the height of the mat portion  51  of the bed main body portion  15 , and as shown in  FIG. 18L , the state becomes the state that the wheelchair is coupled to the bed main body portion  15  (bed state B). 
     Finally, when the wheelchair  14  is further pressed and moved to the side of the bed main body portion  15  in order to eliminate the gap GA 2  between the mat portion  51  and the mat portion  61 , the coupling is completed. 
     Second Embodiment 
       FIGS. 6A, 6B, and 6C  are views for illustrating separation of the wheelchair  14  from the bed main body portion  15  according to a second embodiment.  FIG. 6A  is a partially sectional view of the coupling mechanism portion  56  of the bed  11  at the time of coupling the bed main body portion  15  and the wheelchair  14  (sectional view of the part corresponding to the part of the line A-A of  FIG. 1B ).  FIG. 6B  is a partially sectional view of the bed  11  at the time of lowering the bed main body portion  15  (sectional view of the part corresponding to the part of the line A-A of  FIG. 1B ).  FIG. 6C  is a partially sectional view of the bed  11  in the locked state (sectional view of the part corresponding to the part of the line A-A of  FIG. 1B ).  FIG. 7  is a plan view of the bed  11  in the locked state according to the second embodiment.  FIG. 8  is a partially sectional view of the bed  11  at the time of separation according to the second embodiment (sectional view of the part corresponding to the part of the line A-A of  FIG. 1B ). 
     Hereinafter, points in which the second embodiment is different from the above first embodiment will be described with reference to the figures. 
     As shown in  FIGS. 6A to 6C, 7, and 8 , the bed  11  according to the second embodiment is characterized in that a locking cancellation mechanism  60  for canceling the lock of the wheelchair  14  to the bed  11  is provided in the coupling mechanism portion  56  and the chair base portion  63 . In this locking cancellation mechanism  60 , by installing the second rail  13  in the second armrest mounting unit  22 , the lock of the wheelchair  14  is cancelled. 
     This locking cancellation mechanism  60  includes the spring  56   b  and the locking projection  57  in the locking portion accommodating recess portion  58 , and the convex portion  65  serving as one example of a locking end (locking member) of the second armrest mounting unit  22  of the chair base portion  63 . 
     The locking projection  57  is arranged in the locking portion accommodating recess portion  58  of a second mounting unit engagement portion  56   c  of the coupling mechanism portion  56 . This locking projection  57  is biased in the upward-protruding direction by the spring  56   b  functioning as one example of an elastic portion, and retained and arranged. The second mounting unit engagement portion  56   c  is a part of the coupling mechanism portion  56  positioned on the lower side of the pair of second armrest mounting units  22  of the chair base portion  63  when the wheelchair  14  is coupled to the bed main body portion  15 . The inclined surface  57   a  inclined obliquely upward in the coupling direction (opposite to the separating direction) of the wheelchair  14  is formed in the upper end of the locking projection  57 . The upper end of the locking projection  57  is capable of sliding on a lower surface of the chair base portion  63  serving as a bottom surface of the second armrest mounting unit  22  of the wheelchair  14 , and also of being locked to the convex portion  65 . 
     The convex portion  65  is arranged in an outer peripheral part of the insertion hole  23  of the second armrest mounting unit  22 , and protrudes downward from the lower surface of the chair base portion  63 . This convex portion  65  is to lock the locking projection  57  and the convex portion  65 . 
     The convex portion  65  is formed in such a manner that the locking projection  57  is positioned on the lower side of the insertion hole  23  at the time of coupling the wheelchair  14 . At the time of separating the wheelchair  14 , the support rod portion  44  of the second rail  13  inserted into the insertion hole  23  passes through the insertion hole  23 , and the support rod portion  44  further presses down the locking projection  57  against the bias force of the spring  56   b , so that lock of the locking projection  57  and the convex portion  65  can be cancelled. 
     Motion of the locking cancellation mechanism  60  when the wheelchair  14  is coupled to the bed main body portion  15  will be described with using  FIGS. 6A to 6C . 
     Firstly, the wheelchair  14  is moved toward the bed main body portion  15 . When the convex portion  65  passes over the locking projection  57 , the locking projection  57  once pushed into the locking portion accommodating recess portion  58  by the convex portion  65  protrudes upward from the locking portion accommodating recess portion  58  by the bias force of the spring  56   b  (refer to  FIG. 6C ). Since the inclined surface  57   a  is formed in the locking projection  57 , the convex portion  65  can pass over the locking projection  57  without any resistance at the time of coupling the wheelchair  14 . When the wheelchair  14  is moved toward the bed main body portion  15  by a distance of the gap GA 2  in this state, the upper end of the locking projection  57  slides on the lower surface of the chair base portion  63  of the wheelchair  14 , so that the gap GA 2  between the wheelchair  14  and the bed main body portion  15  is eliminated (refer to  FIG. 6B ). After that, when the bed base portion  53  is raised by the elevating portion  54 , the mat portion  51  and the mat portion  61  are flattened, so that the wheelchair  14  and the bed main body portion  15  are coupled (refer to  FIG. 6A ). 
     Successively, motion of the locking cancellation mechanism  60  when the wheelchair  14  is separated from the bed main body portion  15  will be described with using  FIGS. 6A to 6C . 
     As shown in  FIG. 6A , in a state that the wheelchair  14  is coupled to the bed main body portion  15  (bed state B), the height of the mat portion  61  of the wheelchair  14  is the same as the height of the mat portion  51  of the bed main body portion  15 . That is, the mat portion  61  and the mat portion  51  are closely attached to each other. 
     When the bed base portion  53  is lowered by the elevating portion  54  in order to separate the wheelchair  14  and the bed main body portion  15 , the chair base portion  63  of the wheelchair  14  is lowered together with the bed base portion  53 , the four casters  64  are brought into contact with the bed surface, and the chair base portion  63  of the wheelchair  14  is separated from the coupling mechanism portion  56 . As shown in  FIG. 6B , a level difference is generated between the mat portion  61  supported by the four casters  64  via the chair base portion  63  and the mat portion  51  supported by the bed base portion  53 . Since the chair base portion  63  is away from the coupling mechanism portion  56  and the four casters  64  are grounded to the bed surface, the care worker can separate the wheelchair  14  from the bed main body portion  15  by the gap GA 1  in the separating direction. At this time, in the second embodiment, by bringing and locking the convex portion  65  protruding to the lower side of the second armrest mounting unit  22  into contact with and to the locking portion  57  of the coupling mechanism portion  56 , the wheelchair  14  cannot be separated from the bed main body portion  15  by a predetermined distance (that is, by the gap GA 1 ) or more.  FIG. 6C  shows a state that the convex portion  65  is brought into contact with and locked to the locking portion  57  (that is, the locked state). When the care worker separates the wheelchair  14  from the bed main body portion  15  until the convex portion  65  is brought into contact with and locked to the locking portion  57 , as shown in  FIG. 6C , the insertion holes  23  of the pair of second armrest mounting units  22  emerge from the gap GA 2  between the mat portion  61  and the mat portion  51 . 
       FIG. 7  is a plan view of the bed  11  in the locked state according to the second embodiment. As shown in  FIG. 7 , in the locked state, the insertion holes  23  of the pair of second armrest mounting units  22  emerge from the gap GA 2  between the mat portion  61  and the mat portion  51 . In the second embodiment, in such a locked state, the care worker shifts the second rail  13  from the second bed mounting units  35  into the second armrest mounting units  22 . 
       FIG. 8  is a partially sectional view of the bed  11  at the time of the separation according to the second embodiment (sectional view of the part corresponding to the part of the line A-A of  FIG. 1B ). As shown in  FIG. 8 , when the support rod portions  44  of the second rail  13  are respectively brought into the insertion holes  23  of the pair of second armrest mounting units  22 , the second rail  13  is fixed to the second armrest mounting units  22 . At the same time, the lower ends of the support rod portions  44  pass through the insertion holes  23  of the second armrest mounting units  22 , protrude from the lower side of the insertion holes  23 , and press the locking portion  57  downward. The locking portion  57  is pressed by the lower ends of the support rod portions  44  so as to press the spring  56   b  placed between the locking portion  57  and the locking portion accommodating recess portion  58 , and accommodated in the locking portion accommodating recess portion  58 . When the locking portion  57  is accommodated in the locking portion accommodating recess portion  58 , the locking portion  57  does not exist in the horizontal direction to the convex portion  65  (in other words, the lock of the convex portion  65  and the locking portion  57  is cancelled). As a result, the care worker can largely separate the wheelchair  14  from the bed main body portion  15  in the separating direction (the left direction of  FIG. 8 ). 
     In such a way, the bed main body portion  15  of the second embodiment has the coupling mechanism portion  56  capable of bringing the wheelchair  14  into the locked state. When the second rail  13  is installed in the second armrest mounting units  22 , the coupling mechanism portion  56  for bringing the wheelchair  14  into the locked state cancels the lock of the wheelchair  14 . 
     In the above first embodiment, the first rail  12  and the second rail  13  are used as locking portions at the time of separating the wheelchair  14  from the bed main body portion  15 . However, according to a situation, it may be thought that the care worker tries to separate the wheelchair  14  from the bed main body portion  15  in a state that the first rail  12  and the second rail  13  are not inserted into the first bed mounting units  34  and the second bed mounting units  35 . With the configuration of the second embodiment, at the time of separating the wheelchair  14  from the bed main body portion  15 , the wheelchair  14  cannot be separated unless the second rail  13  is placed in the wheelchair  14  on the side of the bed main body portion  15 . Therefore, with the configuration of the second embodiment, at the time of separating the wheelchair  14 , the rail for preventing the fall always exists in the wheelchair  14  on the side of the bed main body portion  15 . Thus, with the configuration of the second embodiment, at the time of separating the wheelchair  14 , even when the body of the care-receiver  70  is slipped in the direction of the bed main body portion  15  by inertia force, the body of the care-receiver  70  can be supported by the second rail  13 . In such a way, with the configuration of the second embodiment, the care-receiver  70  is not slipped off on the side of the wheelchair  14  and on the side of the bed main body portion  15 , so that the further highly safe bed  11  can be provided. 
     As described above, the upper end of the locking portion  57  on the side of the wheelchair  14  serves as the inclined surface  57   a . Thus, when the convex portion  65  and the inclined surface  57   a  of the locking portion  57  are brought into contact with each other at the time of coupling the wheelchair  14  and the bed main body portion  15 , the locking portion  57  is pressed against the bias force of the spring  56   b , and the locking portion  57  is accommodated in the locking portion accommodating recess portion  58 . Therefore, at the time of coupling the wheelchair  14 , the wheelchair  14  can be coupled without being disturbed by the locking portion  57 . 
     Modification of the First and Second Embodiments 
     The separating method of the wheelchair  14  from the bed main body portion  15  is not limited to the methods of the first and second embodiments but may be the following method. 
       FIG. 4B  is a flowchart of a separating method of the wheelchair  14  from the bed  11  according to a modification of the first and second embodiments. This modification shows the method of separating the wheelchair  14  from the bed main body portion  15  without firstly forming the gap GA 2 .  FIGS. 5F to 5J  are views for illustrating separation of the wheelchair  14  from the bed  11  according to the modification of the first and second embodiments.  FIG. 5F  is a plan view of the bed at the time of coupling.  FIG. 5G  is a first plan view of the bed in the locked state.  FIG. 5H  is a second plan view of the bed in the locked state.  FIG. 5I  is a third plan view of the bed  11  in the locked state.  FIG. 5J  is a plan view of the bed  11  at the time of separation. With using  FIGS. 4B and 5F to 5J , the separating method of the wheelchair  14  from the bed  11  will be described. 
     The first rail  12  and the second rail  13  are arranged in such a manner that the armrest portions  42  protrude outward in the bed state B (refer to  FIG. 5F ). This state is the same state as  FIG. 5A  in which the wheelchair  14  is locked to the bed main body portion  15 . 
     Next, as shown in  FIG. 5G , the care worker respectively detaches the first rail  12  and the second rail  13  from the first bed mounting units  34  and the second bed mounting units  35 , and installs only the first rail  12  in the first armrest mounting units  21 . This task is the first armrest formation step S 02  of  FIG. 4B . At this time, the care worker mounts the first rail  12  in such a manner that the armrest portion  42  of the first rail  12  protrudes outward. Since the care worker performs a detachment task of the first rail  12  and the second rail  13  and an installment task of the first rail  12  while standing on the one side of the bed  11 , the care worker can prevent the care-receiver  70  from falling from the one side of the bed  11 . 
     Next, as in  FIG. 5H , the position where the care-receiver  70  lies is changed by the care worker or by the action of the care-receiver  70  himself/herself so that the care-receiver  70  lies only on the mat portion  61  on the side of the wheelchair. After that, when the care worker lowers the bed base portion  53  by the elevating portions  54 , the coupling mechanism portion  56  is separated from the chair base portion  63  of the wheelchair  14 . When the care worker gripping the first rail  12  moves the wheelchair  14  in the direction in which the wheelchair  14  is separated from the bed main body portion  15  along the width direction of the bed main body portion  15  in this state, the locking projection  57  and the convex portion  65  are locked, so that the gap GA 2  is formed between the mat portion  51  and the mat portion  61  (refer to  FIG. 5H ). The installment parts (insertion holes  23 ) of the pair of second armrest mounting units  22  hidden by the mat portion  61  are exposed in the gap GA 2 . This task is the first separation step S 01  shown in  FIG. 4B . 
     Next, as shown in  FIG. 5I , the care worker installs the second rail  13  in the pair of second armrest mounting units  22 . This task is the second armrest formation step S 03  of  FIG. 4B . At this time, the care worker mounts the second rail  13  in the second armrest mounting units  22  in such a manner that the armrest portion  42  of the second rail  13  protrudes outward. Thereby, the lock of the locking projection  57  and the convex portion  65  is cancelled, and the second separation step S 04  for separating the wheelchair  14  from the bed main body portion  15  is enabled. Thus, the second separation step S 04  is performed (refer to  FIG. 5J ). 
     It should be noted that when the wheelchair  14  is coupled to the bed main body portion  15 , reverse actions to the separating procedure may be performed. 
     With this modification of the first and second embodiments, the wheelchair  14  can be separated or combined by pulling the first rail  12  or the second rail  13  in a state that the care worker holds the first rail  12  or the second rail  13  by hand. In such a way, with the modification of the first and second embodiments, the care worker can easily separate or combine the wheelchair  14 . 
     Third Embodiment 
       FIG. 9  is a bottom view of the first rail  12  according to a third embodiment of the present invention.  FIG. 10  is a plan view of the bed  11  in the locked state according to the third embodiment. 
     Hereinafter, points in which the third embodiment is different from the above first embodiment will be described with reference to the figures. 
     As shown in  FIGS. 9 and 10 , the bed  11  according to the third embodiment is characterized in that both a shape of the insertion holes  23  and a sectional shape of support rod portions  75  provided instead of the support rod portions  44  of the first rail  12  and the second rail  13  have directionality. By making both the shape of the insertion holes  23  and the sectional shape of the support rod portions  75  have the directionality, the respective armrest portions  42  of the first rail  12  and the second rail  13  can always protrude to the outer side of the bed  11 . 
     Insertion holes  72  are respectively formed in the first armrest mounting units  21 , the second armrest mounting units  22 , the first bed mounting units  34 , and the second bed mounting units  35 . The insertion holes  72  each have a non-point symmetrical shape with respect to center thereof, and the sectional shape of the support rod portions  75  of the first rail  12  and the second rail  13  have the same shape as the shape of the insertion holes  72 . 
     For example, the insertion holes  72  are formed in a D shape (shape in which one side of a square on the outer side is formed in an arc shape) as shown in  FIG. 10 . Similarly, the sectional shape of the support rod portions  75  is formed in a D shape as shown in  FIG. 9 . In the first rail  12 , the side where a width of the support rod portions  75  is narrow (side of the arc shape side) is the protruding direction of the armrest portion  42 . In the first bed mounting units  34 , the second bed mounting units  35 , and the first armrest mounting units  21 , the side where a width of the insertion holes  72  is narrow (side of the arc shape side) is respectively the direction opposite to the bed main body portion  15 . Similarly, in the second armrest mounting units  22 , the side where width of the insertion holes  72  is narrow (side of the arc shape side) is the direction opposite to the wheelchair  14 . 
     With this configuration, the first rail  12  of the third embodiment can be inserted into the insertion holes  72  only in a case where a protruding point of the armrest portion  42  to the first armrest mounting units  21  is set in the predetermined direction. In such a way, by forming the shape of the insertion holes  72  in such a manner that the protruding direction of the armrest portion  42  of the first rail  12  is set toward the outer side of the wheelchair  14 , the care worker can install the first rail  12  in the first armrest mounting units  21  without making a mistake in the protruding direction of the armrest portion  42 . 
     It should be noted that although a case of the first rail  12  is described above, the care worker does not make a mistake in the protruding direction of the armrest portion  42  regarding the second rail  13  as well. 
     Fourth Embodiment 
       FIGS. 11A and 11B  are views showing a first rail  82  according to a fourth embodiment of the present invention.  FIG. 11A  is a side view of the first rail  82  when an auxiliary rail portion  43  is folded in a support body  84 .  FIG. 11B  is a side view of the first rail  82  when the auxiliary rail portion  43  is opened outward from the support body  84  to a maximum extent. 
     Hereinafter, points in which the fourth embodiment is different from the above first embodiment will be described with reference to the figures. As shown in  FIGS. 11A and 11B , the first rail  82  in the bed  11  has the support body  84 , a rotation hinge portion  85  provided in the support body  84 , and the auxiliary rail portion  83  rotated about the rotation hinge portion  85 . The first rail  82  is composed of rotatably attaching the auxiliary rail portion  83  serving as a plate portion formed in a rectangular plate shape to one side support rod of the support body  84  formed in a quadrilateral frame via the rotation hinge portion  85 . It should be noted that a plate portion  84   a  is arranged in the support body  84 . 
     After the wheelchair  14  is coupled to the bed main body portion  15  in a state that the auxiliary rail portion  83  is folded in the support body  84  via the rotation hinge portion  85 , the auxiliary rail portion  83  is rotated about the rotation hinge portion  85 , so that the auxiliary rail portion  83  is opened from the support body  84 . In such a way, the auxiliary rail portion  83  and the support body  84  can be placed in line substantially in a straight form, so that a gap between the first rail  82  and the second rail  13  can be shortened. 
     In such a way, a space between the first rail  82  and the second rail  13  can be reduced, so that the further highly safe bed can be provided. 
       FIG. 12  is a side view of the bed  11  according to a modification of the fourth embodiment. As shown in  FIG. 12 , in a case where the wheelchair  14  is coupled to the bed main body portion  15 , the first rail  82  and the second rail  13  may be coupled by the auxiliary rail portion  83  by rotating the auxiliary rail portion  83  about the rotation hinge portion  85  and coupling a free end of the auxiliary rail portion  83  to a coupling portion  88  of a support rod in a side part of the second rail  13 . With this configuration, the auxiliary rail portion  83  is supported from both sides by the support body  84  and the second rail  13 . Thus, the auxiliary rail portion  83  can be firmly supported, so that the further highly safe bed can be provided. 
     It should be noted that although the first rail  82  is used instead of the first rail  12 , a second rail in which a position of the rotation hinge portion  85  is arranged on the second rail side may be used instead of the second rail  13 . 
     Fifth Embodiment 
       FIGS. 13A and 13B  are views showing a first rail  92  according to a fifth embodiment of the present invention.  FIG. 13A  is a side view of the first rail  92  in an accommodated state.  FIG. 13B  is a side view of the first rail  92  in a pull-out state. 
     Hereinafter, points in which the fifth embodiment is different from the above first embodiment will be described with reference to the figures. As shown in  FIGS. 13A and 13B , the first rail  92  in the bed  11  has a support body  94  formed in a quadrilateral frame, a slide portion  95  provided in the support body  94 , and an auxiliary rail portion  93 . The auxiliary rail portion  93  is engaged with the slide portion  95  so as to move the slide portion  95  sideways. In the first rail  92 , the auxiliary rail portion  93  can be moved rightward in  FIG. 13A  from the slide portion  95  via a gap in the thickness direction of the support body  94  and extended as in  FIG. 13B , and the auxiliary rail portion  93  can be moved leftward in  FIG. 13B  from the slide portion  95  via the gap in the thickness direction of the support body  94 , so that the auxiliary rail portion  93  can be accommodated in the slide portion  95  of the support body  94  as in  FIG. 13A . 
     After the wheelchair  14  is coupled to the bed main body portion  15 , by pulling out the auxiliary rail portion  93  rightward in  FIG. 13A  from the slide portion  95 , a gap between the first rail  92  and the second rail can be shortened. 
     In such a way, a space between the first rail  92  and the second rail is reduced. Thus, the further highly safe bed  11  can be provided. 
       FIG. 14  is a side view of the bed  11  according to the fifth embodiment. As shown in  FIG. 14 , after the wheelchair  14  is coupled to the bed main body portion  15 , the auxiliary rail portion  93  may be pulled out from the slide portion  95 , so that the first rail  92  and the second rail  13  are coupled. With this configuration, the auxiliary rail portion  93  is supported from both sides by the support body  84  of the first rail  92  and the second rail  13 . Thus, the auxiliary rail portion  93  can be firmly supported, so that the further highly safe bed can be provided. 
     It should be noted that although the first rail  92  is used instead of the first rail  12 , a second rail in which the sliding direction of the slide portion  95  is reversed may be used instead of the second rail  13 . 
     Sixth Embodiment 
       FIGS. 15A to 15C  are perspective views of a bed  11 A according to a sixth embodiment of the present invention. 
     The bed  11 A is characterized in that first bed mounting units  34 A and second bed mounting units  35 A are provided in a wheelchair  14 A. 
     Hereinafter, points in which the sixth embodiment is different from the above first embodiment will be described with reference to the figures. 
     As shown in  FIGS. 15A to 15C , the bed  11 A has the first rail  12 , the second rail  13 , the wheelchair  14 A, and a bed main body portion  15 A. The bed main body portion  15 A has the pair of bed rails  33  on one side. 
     The wheelchair  14 A has the first armrest mounting units  21  to and from which the first rail  12  is attached and detached in a center part of one side part, and has the second armrest mounting units  22  to and from which the second rail  13  is attached and detached in a center part of the other side part. Further, the wheelchair has the first bed mounting units  34 A to and from which the first rail  12  is attached and detached on the head side of the side part where the first armrest mounting units  21  exist, and also has the second bed mounting units  35 A to and from which the second rail  13  is attached and detached on the leg side of the side part where the first armrest mounting units  21  exist. 
     At the time of coupling the wheelchair  14 A to the bed main body portion  15 A, the wheelchair  14 A and the bed main body portion  15 A are coupled by making the second armrest mounting units  22  and the bed main body portion  15 A face each other. 
     In the sixth embodiment, when the first rail  12  is installed in the first bed mounting units  34 A and the second rail  13  is installed in the second bed mounting units  35 A, the first rail  12  and the second rail  13  are placed in line on one side of the bed  11 A. The one side of the bed  11 A is surrounded by the first rail  12  and the second rail  13 . Therefore, a space in front and back of the first rail  12  and the second rail  13  is narrowed. Thus, even when the care-receiver moves the body toward the side of the first rail  12  and the second rail  13 , the body of the care-receiver can be supported by the first rail  12  and the second rail  13 , so that the highly safe bed can be provided. When the first rail  12  and the second rail  13  are respectively detached and then installed, the rails can be immediately installed without placing the first rail  12  and the second rail  13  on the floor. Thus, the task can be efficiently performed. 
     Seventh Embodiment 
       FIGS. 17A to 17B  are a perspective view of the bed in the separated state and a perspective view of the bed in the wheelchair state for illustrating the bed according to a seventh embodiment of the present invention. 
     In this seventh embodiment, arrangement positions of the first bed mounting units  34  and the second bed mounting units  35  of the bed main body portion  15  are arranged at positions respectively displaced to the head side and the leg side with respect to the arrangement positions of the first bed mounting units  34  and the second bed mounting units  35  of the above first embodiment. At the same time, arrangement positions of the first armrest mounting units  21  and the second armrest mounting units  22  of the wheelchair  14  in this seventh embodiment are arranged at positions displaced to the leg side of the wheelchair  14 . Since the bed mounting units  34 ,  35  and the armrest mounting units  21 ,  22  are arranged at the displaced positions in such a way, a space for coupling to the wheelchair  14 , that is, the coupling mechanism portion  56  and the accommodation space G can be enlarged. Therefore, in the seventh embodiment, coupling and separation actions of the wheelchair  14  and the bed main body portion  15  can be stably performed. The arrangement positions of the pair of first armrest mounting units  21  are also arranged at the positions displaced to the leg side of the wheelchair  14 . Thus, when the rail is attached to the wheelchair  14 , the rail protrudes toward the leg side of the wheelchair  14 , so that the rail is stabilized as an armrest of the wheelchair  14 . 
     It should be noted that by appropriately combining arbitrary embodiment(s) or modification(s) among the above various embodiments or modifications, effects provided in the embodiment(s) and the modification(s) can be obtained. 
     INDUSTRIAL APPLICABILITY 
     The bed and the separating method of the same according to the present invention are useful as a bed in which a part thereof can be separated as a wheelchair, the wheelchair and the bed for providing nursing care to a bedridden aged person or an ailing person, and a separating method of the same. 
     Although the present invention has been fully described in connection with the embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.