Abstract:
An incubator is provided that prevents damage to the arm of an operator when an arm abuts against the upper end segment of a baby guard relatively hard while inserting the arm into an infant accommodation space. The walls of the baby guards around the infant accommodation space have bent segments that are sufficiently strong to serve as a guard structure on the periphery of the infant accommodation space. Each of the bent segments in the upper end segments of the walls includes an inclined segment and a substantially horizontal segment integrally connected to a distal end of the inclined segment. At least some of the walls can pivot between upward and downward positions, thereby closing or revealing cassette trays.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This patent application claims priority to Japan Patent Application No. 2014-244840, filed Dec. 3, 2014, the disclosure of which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to an incubator including baby guards for forming the periphery of an infant accommodation space. 
       BACKGROUND OF THE INVENTION 
       [0003]    A conventional incubator is described in Japanese Patent Laid-Open No. 2012-223320. In the conventional incubator described in Japanese Patent Laid-Open No. 2012-223320, a flat container-shaped bed base is provided on an incubator base. The incubator base is provided with a fixed wall member (or fixed baby guard) which generally forms a wall member on the head side of an infant, a leg-side movable wall member (or movable baby guard) which generally forms a wall member on the leg side of the infant, a left movable wall member (or movable baby guard) which generally forms a wall member on the left side of the infant, and a right movable wall member (or movable baby guard) which generally forms a wall member on the right side of the infant. These wall members are provided in a substantially rectangular shape as a whole when viewed from above. An infant accommodation space having a substantially rectangular parallelepiped shape with an open upper surface is constituted by the bed base (in other words, a mattress on the bed base), the one fixed wall member, and the three movable wall members. Note that each of the one fixed wall member and three movable wall members can take a substantially rectangular shape and can be substantially transparent. In addition, each of the three movable wall members and one fixed wall member can be formed, substantially as a whole, from a substantially transparent plastic plate. Each of the three movable wall members can pivot forward and backward, about pivot support shafts on the left and right sides or the front and rear sides provided in a region including a lower side and its vicinity in the substantially upward position (to be referred to as “the above-described upward position” hereinafter), between the above-described upward position and the substantially downward hanging position (to be referred to as “the above-described hanging position” hereinafter). 
         [0004]    In a conventional incubator, the plate thickness of each of the three movable wall members and one fixed wall member for forming an open type incubator is approximately 5 mm. On the other hand, when an operator lays an infant, for example, a newborn infant down on the mattress of the open type incubator or holds up the infant from the mattress, he/she inserts his/her arm to the infant accommodation space. In this case, the arm of the operator can abut against the upper end portion of at least one of the three movable wall members and one fixed wall member. There is the risk that if the arm of the operator abuts against the upper end portion of the wall member relatively hard, the operator feels a pain or the arm gets hurt. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention effectively solves the above-described problem in the conventional incubator described above. 
         [0006]    The present invention relates to an incubator in which at least part of a baby guard includes a bent segment, the bent segment forms an upper end portion of the baby guard while the baby guard is in a substantially upward position, and the bent segment while the baby guard is in the substantially upward position includes an inclined segment integrally connected to an upper end of a substantially upward segment of the baby guard with the bent segment to extend obliquely upward in a direction substantially perpendicular to the substantially upward segment when viewed from above, and a substantially horizontal segment integrally connected to a substantially distal end of the inclined segment to further extend in the same direction as the direction in which the inclined segment extends when viewed from above. 
         [0007]    According to a first aspect, the present invention can be configured such that a thickness of the bent segment of the baby guard while the baby guard is in the substantially upward position falls within a range of 3 mm to 14 mm (preferably a range of 4 mm to 12 mm, and more preferably a range of 5 mm to 10 mm), a height of the bent segment while the baby guard is in the substantially upward position falls within a range of 21 mm to 39 mm (preferably a range of 23 mm to 37 mm, and more preferably a range of 25 mm to 35 mm), and a length in a direction from an inside to an outside of the bent segment while the baby guard is in the substantially upward position falls within a range of 10 mm to 30 mm (preferably a range of 13 mm to 27 mm, and more preferably a range of 15 mm to 25 mm). According to a second aspect, the present invention can be configured such that the baby guard comprises four baby guards including a front baby guard, a rear baby guard, a left baby guard, and a right baby guard, where at least three movable baby guards of the four baby guards can individually pivot forward and backward between the substantially upward position and a position except for the substantially upward position, and an upper end segment of each of the at least three movable baby guards in the substantially upward position forms the bent segment along a substantially full length of the upper end segment. 
         [0008]    According to a third aspect, the present invention can be configured such that the inclined segment extends toward an outside of an infant accommodation space when viewed from above, and the substantially horizontal segment further extends toward the outside of the infant accommodation space from the distal end of the inclined segment. According to a first mode of the third aspect, the present invention can be configured such that the bent segment while the baby guard is in the substantially upward position includes a second inclined segment integrally connected to the substantially horizontal segment on an opposite side of the inclined segment when viewed from above at a distal end of the substantially horizontal segment on the opposite side of the inclined segment, and the second inclined segment while the baby guard is in the substantially upward position extends obliquely downward toward a substantially outside from the substantially horizontal segment. According to a first case of the first mode of the third aspect, the present invention can be configured such that the bent segment, while the baby guard is in the substantially upward position, includes a hanging segment integrally connected to the second inclined segment on the opposite side of the substantially horizontal segment at a substantially distal end of the second inclined segment on the opposite side of the substantially horizontal segment, and the hanging segment, while the baby guard is in the substantially upward position, extends substantially downward from the second inclined segment. 
         [0009]    According to the first mode of the first aspect, the present invention can be configured such that a length of each of a first baby guard and a second baby guard of the four baby guards, which face each other, is longer than a length of each of a third baby guard and a fourth baby guard of the four baby guards, which face each other, the length of each of the first baby guard and the second baby guard falls within a range of 500 mm to 830 mm (preferably a range of 530 mm to 800 mm, and more preferably a range of 560 mm to 760 mm), the length of each of the third baby guard and the fourth baby guard falls within a range of 340 mm to 560 mm (preferably a range of 360 mm to 545 mm, and more preferably a range of 380 mm to 530 mm), a ratio of the length of each of the first baby guard and the second baby guard to the length of each of the third baby guard and the fourth baby guard falls within a range of 1.2 to 1.8 (preferably a range of 1.25 to 1.7, and more preferably a range of 1.3 to 1.6), a length in a substantially vertical direction of each of the first baby guard, the second baby guard, the third baby guard, and the fourth baby guard in the substantially upward position falls within a range of 175 mm to 340 mm (preferably a range of 190 mm to 320 mm, and more preferably a range of 200 mm to 300 mm), each of the first baby guard, the second baby guard, the third baby guard, and the fourth baby guard is curved to protrude in an arc shape toward an outside when viewed substantially from above in the substantially upward position, a length in a thickness direction of an inside surface of each of the first baby guard and the second baby guard falls within a range of 19 mm to 37 mm (preferably a range of 21 mm to 35 mm, and more preferably a range of 23 mm to 33 mm), a length in a thickness direction of an inside surface of each of the third baby guard and the fourth baby guard falls within a range of 16 mm to 34 mm (preferably a range of 18 mm to 32 mm, and more preferably a range of 20 mm to 30 mm), a ratio of the length in the thickness direction of the inside surface of each of the first baby guard and the second baby guard to the length of each of the first baby guard and the second baby guard falls within a range of 0.025 to 0.06 (preferably a range of 0.03 to 0.055, and more preferably a range of 0.035 to 0.05), and a ratio of the length in the thickness direction of the inside surface of each of the third baby guard and the fourth baby guard to the length of each of the third baby guard and the fourth baby guard falls within a range of 0.035 to 0.08 (preferably a range of 0.04 to 0.075, and more preferably a range of 0.045 to 0.07). 
         [0010]    According to a fourth aspect, the present invention can be configured such that each of the movable baby guards includes a supporting member pivotably attached to an incubator base, and a baby guard main body attached to the supporting member and supported by the supporting member, the baby guard main body includes a thick portion whose longitudinal section in a direction substantially perpendicular to the baby guard main body has a substantially triangular shape, the thick portion swells from a bottom of an inside surface and an outside surface of the baby guard main body, and a lower surface of the thick portion is in contact with a cover member covering a proximal end of the baby guard main body from an opposite side of the supporting member. According to the first mode of the fourth aspect, the present invention can be configured such that a thickness of the baby guard main body gradually increases upward from an upper end of the thick portion to a lower end of the bent segment while each of the movable baby guards is in the substantially upward position, and a thickness of the bent segment increases to be substantially equal to a thickness of the lower end of the bent segment. According to the first mode of the second aspect, the present invention can be configured such that the incubator comprises a cassette tray accommodation space formed between an incubator base and a bed base, the cassette tray accommodation space includes at least three tray loading/unloading ports selected from a front tray loading/unloading port, a rear tray loading/unloading port, a left tray loading/unloading port, and a right tray loading/unloading port, the at least three tray loading/unloading ports are closed by the at least three movable baby guards, respectively, in a backward pivoting state in which each of the at least three movable baby guards is in the substantially upward position, and the at least three tray loading/unloading ports corresponding to the at least three movable baby guards or wall members are opened when each of the at least three movable baby guards pivots forward in a substantially hanging direction (or downward position). 
         [0011]    According to the present invention, it is possible to obtain the first effect where an operator inserts his/her arm to the infant accommodation space to lay an infant, for example, a newborn infant down on the mattress of the incubator or hold up the infant from the mattress, even if the arm of the operator abuts against the upper end segment of the baby guard relatively hard, it is possible to avoid the risk that the operator feels a pain or the arm gets hurt. In addition, according to the present invention, it is possible to obtain the second effect in which the baby guards with the bent segments can have a sufficient strength as the peripheral guards of the infant accommodation space since each bent segment includes the inclined segment and the substantially horizontal segment. 
         [0012]    According to each of the first aspect, the second aspect, and the first mode of the first aspect of the present invention, it is possible to more satisfactorily obtain the first and second effects described above. According to the third aspect of the present invention, it is possible to more satisfactorily obtain the first effect obtained according to the present invention. According to each of the first mode of the third aspect and the first case of the first mode of the third aspect of the present invention, it is possible to more satisfactorily obtain the second effect obtained according to the present invention. According to the fourth aspect of the present invention, with a relatively simple arrangement, it is possible to relatively effectively prevent foreign substances such as dirty water or dust from entering at least a portion between the baby guard main body and the cover member out of a portion between the supporting member and the baby guard main body and the portion between the baby guard main body and the cover member. According to the first mode of the fourth aspect of the present invention, each bent segment has a stable appearance in design and has a higher strength. In addition, it is possible to decrease the weight of each movable baby guard, and reduce raw materials such as a plastic material. 
         [0013]    Furthermore, according to the first mode of the second aspect of the present invention, tray loading/unloading ports are respectively provided on at least three of the front, rear, left, and right sides of the cassette tray accommodation space. Consequently, even if a doctor or nurse performs an operation in a region including one or two of the three tray loading/unloading ports and its vicinity or their vicinities in a region including the cassette tray accommodation space and its vicinity, he/she can readily store or take out a cassette tray in or from the cassette tray accommodation space through the remaining one tray loading/unloading port or one of the remaining two tray loading/unloading ports. Furthermore, even if a bulky article such as a bulky medical apparatus exists in the region including one or two of the three tray loading/unloading ports and its vicinity or their vicinities in the region including the cassette tray accommodation space and its vicinity, it is possible to relatively readily store or take out the cassette tray in or from the cassette tray accommodation space through the remaining one tray loading/unloading port or one of the remaining two tray loading/unloading ports. 
         [0014]    The above, and other, objects, features and advantages of this invention will become readily apparent from the following detailed description thereof which is to be read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0015]      FIG. 1  is a perspective view showing an open type incubator in a normal use state according to an embodiment to which the present invention is applied. 
           [0016]      FIG. 2  is a perspective view showing the open type incubator shown in  FIG. 1  while movable wall members in two directions are open. 
           [0017]      FIG. 3  is a partial cross-sectional view taken along a line A-A in  FIG. 2 . 
           [0018]      FIG. 4  is a partial front view showing the open type incubator shown in  FIG. 1  by partially, longitudinally cutting the movable wall member. 
           [0019]      FIG. 5  is a plan view showing movable wall members in two directions shown in  FIG. 1 . 
           [0020]      FIG. 6  is a partial cross-sectional view taken along a line B-B shown in  FIG. 2 . 
           [0021]      FIG. 7  is a cross-sectional view similar to that of  FIG. 6  while an X-ray tray is mounted from the first direction. 
           [0022]      FIG. 8  is a cross-sectional view similar to that of  FIG. 6  while the X-ray tray is mounted from the second direction. 
           [0023]      FIG. 9A  is a cross-sectional view showing a region including the distal end segment of a right movable wall member shown in  FIG. 3 , and its vicinity. 
           [0024]      FIG. 9B  is a cross-sectional view showing a region including a distal end segment and its vicinity according to the first modification of the right movable wall member shown in  FIG. 9A . 
           [0025]      FIG. 9C  is a cross-sectional view showing a region including a distal end segment and its vicinity according to the second modification of the right movable wall member shown in  FIG. 9A . 
           [0026]      FIG. 9D  is a cross-sectional view showing a region including a distal end segment and its vicinity according to the third modification of the right movable wall member shown in  FIG. 9A . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    A specific preferred embodiment and first to third modified embodiments in which the present invention are applied to an open type incubator (or infant warmer) will be described in “1. Overall Schematic Arrangement of Incubator”, “2. Arrangements of Movable Wall Member Structure and Fixed Wall Member Structure”, “3. Arrangement of Cassette Tray Mounting Structure”, “4. Operations of Movable Wall Member Structure and Fixed Wall Member Structure”, and “5. Operation of Cassette Tray Mounting Structure”, respectively, with reference to the accompanying drawings. 
       1. Overall Schematic Arrangement of Incubator 
       [0028]    As shown in  FIGS. 1 and 2 , an open type incubator  11  includes a carriage  14  to which wheels  12  and a main strut  13  are attached. More specifically, the wheels  12  are attached below the four corners of the carriage  14 . The main strut  13  is attached on the carriage  14 . An incubator base  21  is provided on the main strut  13 . A flat container-shaped bed base (in other words, mattress tray)  22  is provided on the incubator base  21 . Note that a mattress  15  on which an infant, for example, a newborn infant, can be laid down can be placed on the bed base  22 . The incubator base  21  is provided with a fixed wall member (so-called fixed baby guard)  23  which is adjacent to an accessory support strut  33  provided on the main strut  13  and generally forms a wall member on the head side of the infant, a leg-side movable wall member (or movable baby guard)  24  which generally forms a wall member on the leg side of the infant, a left movable wall member (so-called movable baby guard)  25  which generally forms a wall member on the left side of the infant, and a right movable wall member (so-called movable baby guard)  26  which generally forms a wall member on the right side of the infant. These wall members are provided in a substantially rectangular shape as a whole when viewed from above. 
         [0029]    As shown in  FIGS. 1 and 2 , an infant accommodation space  27  having a substantially rectangular parallelepiped shape with an open upper surface is constituted by the bed base  22  (in other words, mattress  15 ), and the fixed wall member  23  and movable wall members  24  to  26 , each of which can take a substantially rectangular shape and can be substantially transparent. Therefore, the left movable wall member  25  and the right movable wall member  26  can have substantially the same dimensions. The fixed wall member  23  and the leg-side movable wall member  24  whose lengths are slightly shorter than those of the movable wall members  25  and  26 , can have substantially the same dimensions except for three, for example, notch-shaped concave segments  28  provided in the upper side portion of the fixed wall member  23 . The movable wall members  24  to  26  each can pivot forward and backward, about pivot support shafts  18 ,  19 , or  20  (see  FIG. 4 ) on the left and right sides or the front and rear sides provided in a region including a lower side and its vicinity in the substantially upward position (to be referred to as “the above-described upward position” hereinafter) shown in  FIG. 1 , between the above-described upward position shown in  FIG. 1  and the substantially downward hanging position (to be referred to as “the above-described hanging position” hereinafter) shown in  FIG. 2  (note that  FIG. 2  shows the movable wall member  26  in the above-described upward position). Note that each of the fixed wall member  23  and the movable wall members  24  to  26  can be formed, substantially as a whole, from a substantially transparent plastic plate which can be formed by plastics molding using plastic such as acrylic resin as a material. 
         [0030]    As shown in  FIG. 1 , a proper number (three in the embodiment shown in  FIG. 1 ) of grommet members  32  each having cuts  31  for holding a cable can be attached to the notch-shaped concave segments  28  of the fixed wall member  23 . A longitudinal member (not shown) such as an oxygen supply tube can be held in the cuts  31  while extending through the grommet member  32 . An infrared heater  34  is provided on the upper end portion of the accessory support strut  33 . Various kinds of measurement/control means  35  for body temperature, SpO 2 , etc. are provided on the accessory support strut  33  so as to be substantially located between the infrared heater  34  and the infant accommodation space  27  when viewed from the front. More specifically, a body temperature control means of the measurement/control means  35  is configured to display a body temperature by receiving a signal from a body temperature probe which measures the body temperature of an infant, and control, for example, the heating temperature of the infrared heater  34 . Note that SpO 2  indicates a measurement value obtained by measuring the oxygen (that is, O 2 ) saturation of blood (in other words, blood carried from the heart to the whole body) in the artery of the infant or the like using a pulse oximeter. 
       2. Arrangements of Movable Wall Member Structure and Fixed Wall Member Structure 
       [0031]    As shown in  FIGS. 1 to 3 , each of the movable wall members  24  to  26  and the fixed wall member  23  includes a wall member main body  41 , and a supporting member  43  to which a substantially lower end segment  48  of the wall member main body  41  is screwed and fixed by screws  42 . The substantially entire inside surface of the substantially lower end segment  48  of each wall member main body  41  is covered by a cover member  44 . As shown in  FIGS. 1 and 6  and the like, each of the movable wall members  24  to  26  is pivotably attached to attachment members  45  by the pair of pivot support shafts  18 ,  19 , or  20  in regions including the left and right sides or front and rear sides of the lower end portion of the supporting member  43  of the movable wall member  24 ,  25 , or  26 , and their vicinities. Note that the attachment members  45  are attached and fixed to the substantially four corners of the incubator base  21 . 
         [0032]    As shown in  FIGS. 2 and 6  and the like, the fixed wall member  23  is attached and fixed to the attachment members  45  on the left and right sides of the fixed wall member  23  by a pair of left and right coupling members (these coupling members are not shown but correspond to the pivot support shafts  18 ,  19 , or  20 ) in regions including the left and right sides of the lower end portion of the supporting member  43 , and their vicinities. The pair of left and right coupling members are detachably engaged with the engaged portions (not shown) of the attachment members  45  provided on the left and right sides of the fixed wall member  23 . As shown in  FIGS. 1 and 3  and the like, a segment, adjacent to the upper surface of the supporting member  43  from substantially above, of the wall member main body  41  of each of the movable wall members  24  to  26  and fixed wall member  23  is formed as a thick segment  74  ( FIG. 3 ) whose longitudinal section has a substantially triangular shape. Furthermore, the thick segment  74  is provided along the substantially full length in the substantially horizontal direction (in other words, the longitudinal direction) of each of the wall members  23  to  26 . Therefore, to prevent dirty water, dust, or the like from entering between the lower end segment  48  and the supporting member  43  or between the lower end segment  48  and the cover member  44 , one side portion of the lower end surface on each of the two sides of the thick segment  74  in the thickness direction abuts against the substantially upper surface of the supporting member  43  and the other side portion of the lower end surface abuts against the substantially upper surface of the cover member  44 . 
         [0033]    As shown in  FIGS. 1 and 2  and the like, the fixed wall member  23  can have substantially the same shape as that of the leg-side movable wall member  24  except that the fixed wall member  23  includes the notch-shaped concave segments  28  and grommet members  32 . The left movable wall member  25  can have substantially the same shape as that of the movable wall member  26 . Note that to form recess segments for the four attachment members  45 , notched segments  46  are formed in segments corresponding to the attachment members  45  in the two end segments of each of the supporting members  43  of the wall members  23  to  26 . Therefore, the length of each supporting member  43  in the substantially horizontal direction is slightly shorter than that of a corresponding one of the wall members  23  to  26  in the substantially horizontal direction. A notched segment  47  connecting to each notched segment  46  is formed in a region including the lower end segment on each of the left and right sides or front and rear sides and its vicinity while the wall member main bodies  41  of the wall members  23  to  26  are in the above-described upward position. Furthermore, each of the movable wall members  24  to  26  and the fixed wall member  23  is curved to protrude to some extent in an arc shape from the inside to the outside when viewed substantially from above in the above-described upward position, as shown in  FIGS. 5 and 6  and the like. In this case, when viewing, substantially from above, each of the wall members  23  to  26  in the above-described upward position, the center segment of each of the wall members  23  to  26  in the length direction has a substantially arc shape with a relatively large diameter (in other words, a substantially arc shape with a relatively small degree of curvature), and each of the two end segments of each of the wall members  23  to  26  in the length direction has a substantially arc shape with a relatively small diameter (in other words, a substantially arc shape with a relatively large degree of curvature). Each of the wall members  23  to  26  has a continuous curved surface substantially without any corners from one of the two end segments to the other through the center segment. 
         [0034]    More specifically (in other words, in this embodiment), a length L 1  between the substantially left and right ends (in other words, in the substantially length direction) of each of the leg-side movable wall member  24  and fixed wall member  23  is approximately 455 mm, when viewed substantially from above. A length L 2  in the substantially back-and-forth direction (in other words, in the substantially thickness direction) of the inside surface of each of the leg-side movable wall member  24  and fixed wall member  23  is approximately 25 mm, when viewed substantially from above. A length L 3  between the substantially front and rear ends (in other words, in the substantially length direction) of each of the movable wall members  25  and  26  on the left and right sides is approximately 660 mm. A length L 4  in the substantially right-and-left direction (in other words, in the substantially thickness direction) of the inside surface of each of the movable wall members  25  and  26  on the left and right sides is approximately 28 mm, when viewed substantially from above. A length L 5  in the substantially vertical direction of a segment, protruding substantially upward from the supporting member  43 , of the wall member main body  41  of each of the wall members  23  to  26  in the above-described upward position is approximately 190 mm, as shown in  FIG. 4 . Note that the lower end of the length L 5  can be at a height substantially coinciding with the lower or upper surface of the bed base  22  or with a substantially middle segment between the lower surface and the upper surface. A length L 6  in the substantially vertical direction of each of the movable wall members  24  to  26  and fixed wall member  23  in the above-described upward position is approximately 250 mm, as shown in  FIGS. 3 and 4  and the like. A length L 7  in the substantially vertical direction of the wall member main body  41  of each of the movable wall members  24  to  26  and fixed wall member  23  in the above-described upward position is approximately 280 mm. A length L 8  in the substantially vertical direction of a bent segment  51  of each of the movable wall members  24  to  26  and fixed wall member  23  in the above-described upward position is approximately 30 mm, as shown in  FIG. 9A  and the like. An interval L 9  between the distal end of the bent segment  51  and the inside surface of a substantially upward segment (to be referred to as an “upward segment” hereinafter)  52  of the bent segment  51  in the above-described upward position is approximately 20 mm, when viewed substantially from above. A thickness L 10  of a segment (except for the bent segment  51 ) of the wall member main body  41  above the thick segment  74  is approximately 6 mm at the lower end and approximately 8 mm at the upper end. The thickness substantially continuously and gradually increases from the lower end (in other words, approximately 6 mm) to the upper end (in other words, approximately 8 mm). The thickness of the bent segment  51  can be substantially equal to that of the upper end, and is approximately 8 mm. By increasing the thickness of the bent segment  51  to be equal to that of the upper end while gradually increasing the thickness L 10  from the lower end to the upper end, the bent segment  51  has the stable appearance in design, and the strength of the bent segment  51  also increases. Furthermore, by increasing the thickness of a segment on the lower end side of the segment of the wall member main body  41  above the thick segment  74  to be larger than that of a segment on the upper end side of the segment above the thick segment  74 , it is possible to decrease the weight of each of the movable wall members  24  to  26  and fixed wall member  23 , and reduce raw materials (more specifically, a plastic material such as acrylic resin) for manufacturing the wall members  23  to  26 . 
         [0035]    In terms of practical use, the length L 1  between the substantially left and right ends (in other words, in a width direction) of each of the leg-side movable wall member  24  and fixed wall member  23  generally preferably falls within a range of 340 mm to 560 mm, more preferably a range of 360 mm to 545 mm, and most preferably a range of 380 mm to 530 mm, as shown in  FIGS. 5 and 6  and the like. In terms of practical use, the length L 2  in the substantially back-and-forth direction (in other words, a concave depth) of the inside surface of each of the leg-side movable wall member  24  and fixed wall member  23  generally preferably falls within a range of 16 mm to 34 mm, more preferably a range of 18 mm to 32 mm, and most preferably a range of 20 mm to 30 mm. In terms of practical use, the length L 3  between the substantially front and rear ends (in other words, in the longitudinal direction) of each of the movable wall members  25  and  26  on the left and right sides generally preferably falls within a range of 500 mm to 830 mm, more preferably a range of 530 mm to 800 mm, and most preferably a range of 560 mm to 760 mm. In terms of practical use, the length L 4  in the substantially right-and-left direction (in other words, a concave depth) of the inside surface of each of the movable wall members  25  and  26  on the left and right sides generally preferably falls within a range of 19 mm to 37 mm, more preferably a range of 21 mm to 35 mm, and most preferably a range of 23 mm to 33 mm. 
         [0036]    In this embodiment, the ratio of the length L 3  to the length L 1  (that is, L 3 /L 1 ) is approximately 1.45. In terms of practical use, L 3 /L 1  generally preferably falls within a range of 1.2 to 1.8, more preferably a range of 1.25 to 1.7, and most preferably a range of 1.3 to 1.6. In this embodiment, the ratio of the length L 4  to the length L 2  (that is, L 4 /L 2 ) is approximately 1.12. In terms of practical use, L 4 /L 2  generally preferably falls within a range of 0.9 to 1.6, more preferably a range of 1 to 1.5, and most preferably a range of 1.1 to 1.4. In this embodiment, the ratio of the length L 2  to the length L 1  (that is, L 2 /L 1 ) is approximately 0.055. In terms of practical use, L 2 /L 1  generally preferably falls within a range of 0.035 to 0.08, more preferably a range of 0.04 to 0.075, and most preferably a range of 0.045 to 0.07. In this embodiment, the ratio of the length L 4  to the length L 3  (that is, L 4 /L 3 ) is approximately 0.04. In terms of practical use, L 4 /L 3  generally preferably falls within a range of 0.025 to 0.06, more preferably a range of 0.03 to 0.055, and most preferably a range of 0.035 to 0.05. Furthermore, in terms of practical use, the length L 5  generally preferably falls within a range of 140 mm to 240 mm, more preferably a range of 150 mm to 230 mm, and most preferably a range of 160 mm to 220 mm. 
         [0037]    In terms of practical use, the length L 6  in the substantially vertical direction of each of the movable wall members  24  to  26  and fixed wall member  23  in the above-described upward position generally preferably falls within a range of 175 mm to 340 mm, more preferably a range of 190 mm to 320 mm, and most preferably a range of 200 mm to 300 mm, as shown in  FIGS. 3 and 4  and the like. In terms of practical use, the length L 7  in the substantially vertical direction of the wall member main body  41  in the above-described upward position generally preferably falls within a range of 220 mm to 360 mm, more preferably a range of 230 mm to 340 mm, and most preferably a range of 240 mm to 320 mm. In this embodiment, the ratio of the length L 5  to the length L 6  (that is, L 5 /L 6 ) is approximately 0.75. In terms of practical use, L 5 /L 6  generally preferably falls within a range of 0.5 to 1, more preferably a range of 0.55 to 0.9, and most preferably a range of 0.6 to 0.85. In this embodiment, the ratio of the length L 7  to the length L 6  (that is, L 7 /L 6 ) is approximately 1.1. In terms of practical use, L 7 /L 6  generally preferably falls within a range of 0.9 to 1.4, more preferably a range of 0.95 to 1.3, and most preferably a range of 1 to 1.25. In this embodiment, the ratio of the length L 5  to the length L 7  (that is, L 5 /L 7 ) is approximately 0.68. In terms of practical use, L 5 /L 7  generally preferably falls within a range of 0.5 to 0.9, more preferably a range of 0.55 to 0.85, and most preferably a range of 0.6 to 0.8. 
         [0038]    In terms of practical use, the length (that is, the height) L 8  in the substantially vertical direction of the bent segment  51  of each of the movable wall members  24  to  26  and fixed wall member  23  in the above-described upward position generally preferably falls within a range of 21 mm to 39 mm, more preferably a range of 23 mm to 37 mm, and most preferably a range of 25 mm to 35 mm, as shown in  FIGS. 3 and 9A  and the like. In terms of practical use, the interval L 9  generally preferably falls within a range of 10 mm to 30 mm, more preferably a range of 13 mm to 27 mm, and most preferably a range of 15 mm to 25 mm. In this embodiment, the thickness L 10  of a segment (including an inclined segment  53  and a horizontal segment  54 ) of the wall member main body  41  of each of the wall members  23  to  26  substantially above the thick segment  74  in the above-described upward position changes within a range of approximately 6 mm to approximately 8 mm. In terms of practical use, the thickness L 10  generally preferably falls within a range of 3 mm to 14 mm even if the thickness changes or is substantially constant, more preferably falls within a range of 4 mm to 12 mm even if the thickness changes or is substantially constant, and most preferably changes within a range of 5 mm to 10 mm or is substantially constant. 
         [0039]    In a region including the upper end segment of the wall member main body  41  of each of the movable wall members  24  to  26  and fixed wall member  23  (except for the notch-shaped concave segment  28 ) in the above-described upward position and its vicinity, the bent segment  51  is integrally formed in the wall member main body  41  as part of the wall member main body  41 , as shown in  FIGS. 3, 5, and 9A  and the like. Each bent segment  51  includes the inclined segment  53  integrally formed at the upper end of the upward segment  52  of the wall member main body  41  in the above-described upward position, and the substantially horizontal segment (to be referred to as the “horizontal segment” hereinafter)  54  integrally formed on the upper end side of the inclined segment  53  to be substantially horizontal in the above-described upward position. Note that in the above-described upward position, the inclined segment  53  can be inclined at, for example, an angle of approximately 45° from the substantially lower side to the substantially upper side from the inside surface to the outside surface of the upward segment  52 . Furthermore, the horizontal segment  54  can substantially horizontally extend from the upper end of the inclined segment  53  to the outside in the above-described upward position. Referring to  FIGS. 3 and 9A , a boundary between the inside surface of the upward segment  52  and that of the inclined segment  53  is rounded to have a radius R 1  of approximately 14 mm. A boundary between the inside surface of the inclined segment  53  and the upper surface of the horizontal segment  54  is rounded to have a radius R 2  of approximately 2 mm. In addition, the upper and lower ends of the distal end segment of the horizontal segment  54  are each rounded to have a radius R 3  of approximately 2 mm. Therefore, a portion from the inside surface in a region including the upper end portion of the upward portion  52  and its vicinity to the lower surface of the horizontal segment  54  through the inclined surface on the upper side (that is, inside) of the inclined segment  53  and the upper surface of the horizontal segment  54  is a continuous curved surface substantially without any corners. 
         [0040]    In this embodiment, a width (in other words, a length in a direction from the substantially inside surface to the substantially outside surface of each of the wall members  23  to  26 ) L 11  on the upper surface side of the horizontal segment  54  of the bent segment  51  in the above-described upward position is approximately 4 mm by excluding the rounded portion of the inner and outer ends of the upper surface of the horizontal segment  54 . In terms of practical use, the length L 11  generally preferably falls within a range of 2 mm to 10 mm, more preferably a range of 2.5 mm to 9 mm, and most preferably a range of 3 mm to 8 mm. In this embodiment, a width (in other words, a length in a direction from the substantially inside surface of each of the wall members  23  to  26  to the substantially upper surface of the horizontal segment  54 ) L 12  on the upper side of the inclined segment  53  of the bent segment  51  in the above-described upward position is approximately 21 mm by excluding the rounded portion of the upper and lower ends of the inside surface of the inclined segment  53 . In terms of practical use, the length L 12  generally preferably falls within a range of 10 mm to 34 mm, more preferably a range of 13 mm to 30 mm, and most preferably a range of 16 mm to 26 mm. In terms of practical use, the radius R 1  of the boundary between the inside surface of the upward segment  52  and that of the inclined segment  53  generally preferably falls within a range of 10 mm to 18 mm, more preferably a range of 11 mm to 17 mm, and most preferably a range of 12 mm to 16 mm. In terms of practical use, each of the radius R 2  of the boundary between the inside surface of the inclined segment  53  and the upper surface of the horizontal segment  54 , and the radius R 3  of the upper and lower ends of the distal end segment of the horizontal segment  54  generally preferably falls within a range of 1.4 mm to 2.6 mm, more preferably a range of 1.5 mm to 2.5 mm, and most preferably a range of 1.6 mm to 2.4 mm. 
         [0041]    The shape of the bent segment  51  of each of the movable wall members  24  to  26  and fixed wall member  23  need not be limited to the shape shown in  FIGS. 3, 5, and 9A  and the like, and can be changed to various shapes, as shown in, for example,  FIGS. 9B to 9D . Note that in the first modification shown in  FIG. 9B , the bent segment  51  is different from that in the embodiment shown in  FIG. 9A  and the like in that an inclined segment  75  on the distal end side as the second inclined segment is integrally formed at the end of the horizontal segment  54 . A boundary between the upper surface on the proximal end side of the second inclined segment  75  and the upper surface of the distal end of the horizontal segment  54  can be rounded to have a radius substantially equal to the radius R 2  (that is, for example, approximately 2 mm). The upper and lower ends of the distal end segment of the second inclined segment  75  can each be rounded to have a radius substantially equal to the radius R 3  (that is, for example, approximately 2 mm). Therefore, a segment from the inside surface in a region including the upper segment of the upward segment  52  and its vicinity to the inclined surface on the upper side of the inclined segment  75  on the distal end side through the inclined surface on the upper side of the inclined segment  53  and the upper surface of the horizontal segment  54  is a continuous curved surface substantially without any corners. In the second modification shown in  FIG. 9C , the bent segment  51  is different from that in the first modification shown in  FIG. 9B  in that a hanging segment  76  is integrally formed at the distal end of the inclined segment  75  on the distal end side. A boundary between the upper end of the outside surface of the hanging segment  76  and the upper surface on the distal end side of the second inclined segment  75  can be rounded to have a radius substantially equal to the radius R 1  (that is, for example, approximately 14 mm). The outer and inner ends of the distal end segment of the hanging segment  76  can each be rounded to have a radius substantially equal to the radius R 3 . Furthermore, in the third modification shown in  FIG. 9D , the bent segment  51  is different from that in the second modification shown in  FIG. 9C  in that an inclined segment  77  on the distal end side as the third inclined segment is integrally formed at the distal end of the hanging segment  76 . A boundary between the upper end of the outside surface of the inclined segment  77  on the distal end side and the lower end of the outside surface of the hanging segment  76  can be rounded to have a radius substantially equal to the radius R 1  (that is, for example, approximately 14 mm). The outer and inner ends of the distal end segment of the inclined segment  77  can each be rounded to have a radius substantially equal to the radius R 3 . 
       3. Arrangement of Cassette Tray Mounting Structure 
       [0042]    As shown in  FIGS. 2, 3, and 6  and the like, the incubator base  21  includes an upper-side support plate member  55  as a tray support means. On upper surfaces at the substantially four corners of the upper-side support plate member  55 , four strut members  56   a  to  56   d  for attaching and fixing the bed base  22  are provided integrally or individually with the upper-side support plate member  55 . The four attachment members  45  are attached and fixed to the substantially four corners of the incubator base  21 , respectively. Furthermore, the bed base  22  is attached and fixed on the four strut members  56   a  to  56   d . Consequently, a tray accommodation space  62  capable of accommodating a cassette tray  61  is formed between the bed base  22  and the upper-side support plate member  55 . The tray accommodation space  62  includes a leg-side tray loading/unloading port (in other words, a front tray loading/unloading port)  63   a , a left tray loading/unloading port  63   b , and a right tray loading/unloading port  63   c . Note that the leg-side tray loading/unloading port  63   a  is formed by a space existing between the strut members  56   a  and  56   b . The left tray loading/unloading port  63   b  is formed by a space existing between the strut members  56   a  and  56   c . The right tray loading/unloading port  63   c  is formed by a space existing between the strut members  56   b  and  56   d . Note that as shown in  FIG. 6  and the like, on the upper-side support plate member  55 , three grooves  59  extending along the full length in the substantially back-and-forth direction and three grooves  60  extending along the full length in the substantially right-and-left direction are formed to improve the moldability of the upper-side support plate member  55  formed by plastics molding using plastic such as polypropylene resin or ABS resin as a material, and to prevent deformation of the upper-side support plate member  55 . 
         [0043]    As shown in  FIGS. 2, 7, and 8  and the like, the cassette tray  61  can have a substantially rectangular tray shape when viewed from above. On the side surfaces of the two end segments of the cassette tray  61  in the longitudinal direction, a pair of grip segments  64   a  and  64   b  each having a substantially concave shape are provided. A cassette  65  that can accommodate imaging materials such as an imaging film and CCD image sensor (that is, an image sensor using a charge coupled device) which can be used for X-ray imaging or the like is arranged on the cassette tray  61 . The width of the cassette tray  61  can be substantially equal to the interval between the strut members  56   a  and  56   c  (in other words, the interval between the strut members  56   b  and  56   d ) or slightly smaller than the interval. Alternatively, the width of the cassette tray  61  can be substantially equal to the interval between the strut members  56   a  and  56   b  or slightly smaller than the interval. The interval between the strut members  56   a  and  56   c , that between the strut members  56   b  and  56   d , and that between the strut members  56   a  and  56   b  can be substantially equal to each other. 
       4. Operations of Movable Wall Member Structure and Fixed Wall Member Structure 
       [0044]    As shown in  FIGS. 2 and 6  and the like, the fixed wall member  23  is stationarily held in the above-described upward position when it is detachably attached and fixed to the pair of left and right attachment members  45  fixed to the incubator base  21  on the left and right sides of the fixed wall member  23 . To the contrary, when each of the leg-side movable wall member  24  and the left and right movable wall members  25  and  26  pivots forward from the above-described upward position shown in  FIG. 1  to the above-described hanging position exemplified in  FIG. 2  with respect to the movable wall members  24  and  25 , the lock by a lock means (not shown) which locks the forward pivoting movement of each of the movable wall members  24  to  26  is released. The operator can then make each of the movable wall members  24  to  26  pivot forward from the above-described upward position to the above-described hanging position by making each of the movable wall members  24  to  26  pivot forward about the corresponding pair of pivot support shafts  18 ,  19 , or  20 , as needed. Note that the forward pivoting movement of each of the movable wall members  24  to  26  can be performed at low speed by the damper function of a damper (not shown) capable of suppressing the pivoting speed of the forward pivoting movement. To make each of the movable wall members  24  to  26  pivot backward from the above-described hanging position to the above-described upward position, the operator need only manually make each of the movable wall members  24  to  26  pivot backward about the corresponding pair of pivot support shafts  18 ,  19 , or  20  of the movable wall member  24 ,  25 , or  26 . 
         [0045]    When the operator lays an infant, for example, a newborn infant down on the mattress  15  of the open type incubator  11  or holds up the infant from the mattress  15 , he/she inserts his/her arm  66  to the infant accommodation space  27 , as shown in  FIG. 4 . In this case, the arm  66  of the operator can abut against the upper end segments of the movable wall members  24  to  26  and fixed wall member  23 , as shown in  FIG. 4 . However, the upper end segment of each of the movable wall members  24  to  26  forms the bent segment  51  while the upper end segment of the fixed wall member  23  except for the notch-shaped concave segments  28  forms the bent segment  51 . The inclined segment  53  and the horizontal segment  54  are sequentially, continuously formed at the upper end of the upward segment  52  in the bent segment  51 , as shown in  FIG. 3 ,  FIG. 9A  (this matter is substantially same in  FIGS. 9B-9D ), and so on. In addition, joints between the inside surface of the upward segment  52 , the upper surface of the inclined segment  53 , and the upper surface of the horizontal segment  54 , and the distal end segment of the upper surface of the horizontal segment  54  are rounded. Therefore, even if the arm  66  of the operator abuts against the upper end segment (especially, the horizontal segment thereof) of the wall member main body  41  relatively hard, there is no risk that the operator feels a pain or the arm  66  gets hurt. In addition, each of the movable wall members  24  to  26  and fixed wall member  23  slightly swells in an arc shape from the inside to the outside when viewed substantially from above, as shown in  FIGS. 5 and 6  and the like. Therefore, each of the movable wall members  24  to  26  and fixed wall member  23  can have a sufficient strength as the external wall member of the infant accommodation space  27  of the open type incubator  11  in combination with the wall member main body  41  including the bent segment  51 . Furthermore, these two kinds of effects can be obtained not only in the case of the bent segment  51  shown in  FIG. 9A  but also in the case of the bent segments  51  shown in  FIGS. 9B, 9C, and 9D . The bent segment  51  shown in each of  FIGS. 9B, 9C, and 9D  has an equally fine appearance or finer appearance, as compared with that shown in  FIG. 9A . As shown in  FIGS. 5 and 6  and the like, each of the movable wall members  24  to  26  and fixed wall member  23  is curved to protrude to some extent in an arc shape from the inside to the outside when viewed substantially from above in the above-described upward position. Especially, the degree of curvature is larger in the two end segments in the length direction of each of the wall members  23  to  26  than in the center segment in the length direction. Therefore, as the infant accommodation space  27  becomes wider to some extent, a region including the infant accommodation space  27  and its vicinity looks nicer, and the strength of the wall members  23  to  26  improves. 
       5. Operation of Cassette Tray Mounting Structure 
       [0046]    To store the cassette tray  61  in the cassette tray accommodation space  62  of the open type incubator  11 , it is only necessary to insert the cassette tray  61  toward the cassette tray accommodation space  62  from one of the three tray loading/unloading ports  63   a  to  63   c . In this case, when the operator inserts the cassette tray  61  from the tray loading/unloading port  63   b  to the cassette tray accommodation space  62 , he/she makes the left movable wall member  25  pivot forward from the above-described upward position to the above-described hanging position, as shown in  FIGS. 2 and 6  and the like. Subsequently, the operator grips the grip segment  64   a  and the like by the hands and the like, and makes the cassette tray  61  slide on the upper-side support plate member  55  of the incubator base  21 , thereby inserting the cassette tray  61  to the cassette tray accommodation space  62 . In this case, the operator inserts the cassette tray  61  to the cassette tray accommodation space  62  along the substantially longitudinal direction of the cassette tray  61  from a side of the cassette tray  61  on which one of the pair of front and rear grip segments  64   a  and  64   b  is provided. At this time, each of a set of rear surfaces  68  of the strut members  56   a  and  56   b  and a set of front surfaces  69  of the strut members  56   c  and  56   d  serves as a position holding portion serving also as a guide portion, and abuts against a corresponding one of the side wall members  71  and  72  on the long wall sides of the cassette tray  61 . As a result, the cassette tray  61  is arranged symmetrically in the right-and-left direction in the cassette tray accommodation space  62  in  FIG. 7 , as shown in  FIGS. 2 and 7  and the like. 
         [0047]    When the operator takes out the cassette tray  61 , which is accommodated in the cassette tray accommodation space  62  as shown in  FIG. 7 , from the cassette tray accommodation space  62 , he/she grips the grip segment  64   a  or  64   b  by the hand or the like, and makes the cassette tray  61  slide on the upper-side support plate member  55 , thereby pulling out the cassette tray  61  to the right or left side in  FIG. 7  along the substantially longitudinal direction of the cassette tray  61 . In this case as well, each of the set of rear surfaces  68  of the strut members  56   a  and  56   b  and the set of front surfaces  69  of the strut members  56   c  and  56   d  serves as a guide portion to guide a corresponding one of the side wall members  71  and  72  on the long wall sides of the cassette tray  61 . Note that a rectangle  67  indicated by chain lines indicates an estimated cassette mounting position in  FIG. 6 . Referring to  FIGS. 7 and 8 , the cassette  65  is arranged at substantially the same position as that of the rectangle  67  when viewed from above. 
         [0048]    When the operator inserts the cassette tray  61  to the cassette tray accommodation space  62  from the tray loading/unloading port  63   c , he/she need only perform substantially the same operation except that the cassette tray  61  is inserted from the tray loading/unloading port  63   b  to be symmetrical in the right-and-left direction, as described above, and a detailed description thereof will be omitted. Furthermore, when the operator takes out, from the cassette tray accommodation space  62 , the cassette tray  61  accommodated in the cassette tray accommodation space  62 , he/she grips the grip segment  64   a  or  64   b  by the hand, and makes the cassette tray  61  slide on the upper-side support plate member  55 , thereby relatively correctly and relatively readily pulling out the cassette tray  61  to the right or left side (in other words, the side convenient for the operator at this time) in  FIG. 7 . With respect to this point, it is possible to relatively readily insert the cassette tray  61  to the cassette tray accommodation space  62  by performing the inverse operation of the operation performed when pulling out the cassette tray  61 . 
         [0049]    When the operator inserts the cassette tray  61  from the tray loading/unloading port  63   a  to the cassette tray accommodation space  62  or takes out the cassette tray  61  in the cassette tray accommodation space  62  from the tray loading/unloading port  63   a , it is only necessary to perform the following operation, as compared with a case in which the cassette tray  61  is inserted or taken out from the tray loading/unloading port  63   b . That is, the operator first moves in advance the cassette  65  toward an insertion end  61   a  of the cassette tray  61 , as shown in  FIG. 8 . To do this, on the upper surface or the like of the cassette tray  61 , an instruction line, an instruction groove, an instruction concave segment, or the like for arranging the cassette  65  at the substantially center position on the upper surface of the cassette tray  61 , as shown in  FIG. 7 , can be formed in advance. Furthermore, on the upper surface or the like of the cassette tray  61 , an instruction line, an instruction groove, an instruction concave segment, or the like for arranging the cassette  65  at a position near one end of the upper surface of the cassette tray  61  in the length direction, as shown in  FIG. 8 , can be formed in advance. Subsequently, as shown in  FIGS. 2 and 8  and the like, the operator makes the leg-side movable wall member  24  pivot forward from the above-described upward position to the above-described hanging position. The operator inserts the cassette tray  61  to the cassette tray accommodation space  62  from the tray loading/unloading port  63   a  along the substantially longitudinal direction of the cassette tray  61 , similarly to the above-described case in which the operator inserts the cassette tray  61  to the cassette tray accommodation space  62  from the tray loading/unloading port  63   b . At this time, the inside surface  73  of each of the strut members  56   a  and  56   b  serves as a position holding portion serving also as a guide portion, and abuts against a corresponding one of the side wall members  72  and  71  on the long wall sides of the cassette tray  61 . 
         [0050]    When the operator takes out the cassette tray  61 , which is accommodated in the cassette tray accommodation space  62  as shown in  FIG. 8 , from the cassette tray accommodation space  62 , he/she grips the grip segment  64   a  by the hand or the like, and makes the cassette tray  61  slide on the upper-side support plate member  55 , thereby pulling out the cassette tray  61  along the substantially longitudinal direction of the cassette tray  61  downward in  FIG. 8 . In this case as well, the inside surface  73  of the strut members  56   a  and  56   b  serve as guide portions to guide the side wall members  72  and  71  on the long wall sides of the cassette tray  61 , respectively. 
         [0051]    Having described a specific preferred embodiment and first to third modified embodiments of the present invention with reference to the accompanying drawings, it is to be understood that the present invention is not limited to the embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims. 
         [0052]    For example, in the above-described preferred embodiment and modified embodiments, the present invention is applied to the open type incubator. However, the present invention is applicable to not only the open type incubator but also an open type incubator serving also as a closed type incubator. In this case, it is possible to provide a top hood which can selectively cover the infant accommodation space  27  from above, is movable in the substantially vertical direction and has a substantially box-cover shape. The top hood can be formed from a top member which can be substantially transparent, and an upper wall member which protrudes substantially downward from a region including the periphery of the top member and its vicinity, can be substantially transparent, and has a substantially rectangular shape when viewed from above. When the top hood moves up, the upper surface of the infant accommodation space  27  is opened and the incubator thus serves as an open type incubator, and when the top hood moves down, the upper surface of the infant accommodation space  27  is closed and the incubator thus serves as a closed type incubator. 
         [0053]    In the above-described embodiment and the above-described modifications, among the four baby guards  23  to  26  (in other words, the three movable wall members  24  to  26  and one fixed wall member  23 ), the three baby guards  24  to  26  are movable and the remaining one baby guard  23  is fixed. However, all the four baby guards  23  to  26  can be movable or fixed. Alternatively, two baby guards can be movable and the remaining two baby guards can be fixed. Furthermore, one baby guard can be movable and the remaining three baby guards can be fixed. 
         [0054]    In the above-described embodiment and the above-described modifications, the thick segment  74  of the wall member main body  41  is formed to have a longitudinal section in a substantially isosceles triangular shape. The longitudinal section of the thick segment  74  may have other various shapes which preferably have a smaller width on the upper side, such as a substantially pentagonal shape, a substantially trapezoidal shape, a substantially semi-elliptical shape, a substantially semi-oval shape, or substantially semi-circular shape. Furthermore, in the above-described embodiment and the above-described modifications, the lower end segment at each of the two sides in the thickness direction of the thick segment  74  is formed in the thick segment. However, in terms of preventing entry of the body fluid of an infant, for example, a newborn infant, only the lower end portion of the inside portion in the thickness direction of the thick segment  74  may be formed in the thick segment. In this case, the longitudinal section of the thick segment can have a substantially right-angled triangular shape, a substantially semi-pentagonal shape, a substantially semi-trapezoidal shape, a substantially ¼-elliptical shape (in other words, the shape of one of pieces obtained by cutting an elliptical shape crosswise; the same applies to the following description), a substantially ¼-oval shape, a substantially ¼-circular shape, or the like. Even if the lower end segment at each of the two sides in the thickness direction of the thick segment  74  is formed to have a large thickness, the thick segment of the lower portion of the inside portion in the thickness direction of the thick segment  74  need not always have substantially the same shape as that of the thick segment of the lower portion of the outside portion. For example, one of these thick segments can be formed in a substantially right-angled triangular shape, and the other can be formed in a substantially ¼-oval shape.