Abstract:
Provided is a chain block with which wheel cover strength can be improved while inhibiting an increase in cost, without the need for separate reinforcement members. A chain block is provided with a wheel cover which is attached to a frame member, and which covers a hand-chain wheel having a hand chain looped thereover. A plurality of fixation holes for having fixation members inserted therethrough during attachment to the frame member are provided in peripheral edge sections of end-surface sides of the wheel cover, said end-surface sides being disposed facing the frame member. Wrap-around portions are provided to wheel-cover side surfaces which intersect the end surfaces, said wrap-around portions being formed so as to surround, at an angle exceeding 90, the fixation holes in the peripheral direction of the fixation holes.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is the U.S. national stage of application No. PCT/JP2013/070458, filed on Jul. 29, 2013. Priority under 35 U.S.C. §119(a) and 35 U.S.C. §365(b) is claimed from Japanese Application No. 2012-168498, filed Jul. 30, 2012, the disclosure of which is also incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a chain block for use in a load hoisting work. 
     BACKGROUND ART 
     In order to move a load in an up-down direction, a chain block is generally used. The chain block includes a hand wheel, a wheel cover, a main body portion, and the like. The main body portion is provided with a load sheave around which a load chain is wound. Then, when a hand chain wound around the hand wheel is wound up, the hand wheel rotates, and the rotation of the hand wheel is transmitted to the load sheave through a predetermined transmission mechanism including gears and the like. Thereby, the load hung on a lower hook are moved in an upward direction. Conversely, when the hand chain is wound down in a state where the load is positioned in the upper side, the load is moved in a downward direction. Such a chain block is disclosed in, for example, Patent Literature 1. 
     In the chain block described in Patent Literature 1, a wheel cover (refer to  FIG. 19 ) is mounted to a second main frame, but the wheel cover is provided in a shape following the contours of a first main frame and the second main frame. 
     CITATION LIST 
     Patent Literature 
     [PLT 1] Japanese Patent Laid-open Publication No. 2011-201637 
     SUMMARY OF INVENTION 
     Technical Problem 
     Now, in order to resist impact or external force acting on a wheel cover, there is a need to improve the strength of the wheel cover. However, in a case where the thickness of a steel plate is increased, a separate reinforcement member is added, or additional work is required so as to improve the strength of the wheel cover, a cost is increased accordingly. Thus, there is a need to improve the strength of the wheel cover while suppressing an increase in weight or cost with no need for a separate reinforcement member. 
     Solution to Problem 
     The present invention has been made under the above-described circumstances, and an object of the present invention is to provide a chain block with which the strength of a wheel cover can be improved while suppressing an increase in weight or cost with no need to increase the thickness of a steel plate nor need for a separate reinforcement member. 
     Advantageous Effects of Invention 
     In order to solve the above-described problem, according to a first aspect of the present invention, is provided a chain block including a wheel cover that is mounted to a frame member and covers a hand wheel over which a hand chain is wound, wherein a plurality of fixation holes into which fixation members are inserted during mounting to the frame member is provided in a peripheral edge portion on an end surface side arranged facing the frame member of the wheel cover, and a wrap-around portion formed surrounding a fixation hole at an angle exceeding 90 degrees in a peripheral direction of the fixation hole is provided in a side surface of the wheel cover, which intersects the end surface. 
     Furthermore, according to another aspect of the present invention, it is preferable that in the above-described invention the wheel cover be provided with a chain guide portion that prevents the hand chain looped over the hand wheel from coming off, and the chain guide portion be provided adjacent to the wrap-around portion, and integrally provided in a continuous state with the wrap-around portion. 
     Further, according to another aspect of the present invention, it is preferable that in the above-described invention the wheel cover be provided with a chain guide portion that prevents the hand chain looped over the hand wheel from coming off, and the chain guide portion be provided adjacent to the wrap-around portion, and provided separately from the wrap-around portion without being continuous with the wrap-around portion. 
     Furthermore, according to another aspect of the present invention, it is preferable that in the above-described invention an outer peripheral edge portion of the frame member be provided with at least a pair of concave portions passing through a center side thereof with a drooping direction interposed therebetween, the drooping direction be a direction in which the hand chain droops when used, and the pair of concave portions be recessed toward the center side of the frame member more than the outer peripheral edge portion of the frame member adjacent to the concave portions. 
     Further, according to another aspect of the present invention, it is preferable that in the above-described invention a tip side spaced apart from the end surface of the chain guide portion be provided with a protruding tip that is inserted into an insertion hole of the frame member. 
     Furthermore, according to another aspect of the present invention, it is preferable that in the above-described invention an outer edge portion on a side spaced apart from the wrap-around portion of the chain guide portion be provided with a folded-back portion formed by hemming processing. 
     Advantageous Effects of Invention 
     According to the present invention, the strength of a wheel cover can be improved while suppressing an increase in weight or cost with no need to increase the thickness of a steel plate in a chain block nor need for a separate reinforcement member. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a front view illustrating an appearance of a chain block according to an embodiment of the present invention. 
         FIG. 2  is a side view illustrating the appearance of the chain block of  FIG. 1 . 
         FIG. 3  is a rear view illustrating the appearance of the chain block of  FIG. 1 . 
         FIG. 4  is a side cross-sectional view illustrating a state in which the chain block has been cut along the line A-A in  FIG. 1 . 
         FIG. 5  is a side cross-sectional view illustrating a state in which the chain block has been cut along the line B-B in  FIG. 2 . 
         FIG. 6  is a front view illustrating the shapes of a first frame and an auxiliary plate in a state where a reduction gear member and a load gear are removed from the chain block in  FIG. 1 . 
         FIG. 7A  is a perspective view illustrating the shape of the auxiliary plate in the chain block in  FIG. 1 , when seen from the front side. 
         FIG. 7B  is a perspective view illustrating the shape of the auxiliary plate in the chain block in  FIG. 1 , when seen from the rear side. 
         FIG. 8  is a diagram illustrating the positional relation of attaching positions of a fixation member and a guide roller with respect to a first frame in the chain block in  FIG. 1 . 
         FIG. 9  is a diagram illustrating an arrangement of a reduction gear member and a load gear with respect to the first frame in the chain block in  FIG. 1 . 
         FIG. 10A  is a perspective view illustrating the shape of the reduction gear member in the chain block in  FIG. 1 , when seen from the front side. 
         FIG. 10B  is a perspective view illustrating the shape of the reduction gear member in the chain block in  FIG. 1 , when seen from the rear side. 
         FIG. 11A  is a perspective view illustrating the shape of a drive shaft in the chain block in  FIG. 1 , when seen from the front side. 
         FIG. 11B  is a perspective view illustrating the shape of the drive shaft in the chain block in  FIG. 1 , when seen from the rear side. 
         FIG. 11C  is a partial expanded side cross-sectional view of the drive shaft in the chain block in  FIG. 1 , illustrating the shape of the vicinity of a flange portion. 
         FIG. 12A  illustrates an engagement state between a pinion gear and a large-diameter gear according to the present embodiment. 
         FIG. 12B  illustrates an engagement state between a pinion gear and a large-diameter gear according to a configuration of the related art. 
         FIG. 13A  is a diagram illustrating the relation in tooth thickness between the pinion gear and the large-diameter gear according to the present embodiment. 
         FIG. 13B  is a diagram illustrating the relation in tooth thickness between the pinion gear and the large-diameter gear according to the configuration of the related art. 
         FIG. 14  is a diagram illustrating an arrangement of a ratchet wheel and pawl members in the chain block in  FIG. 1 . 
         FIG. 15  is a perspective view illustrating the shape of a wheel cover in the chain block in  FIG. 1 . 
         FIG. 16  is a partial expanded plan view of the shape of the vicinity of a protruding portion of an end surface of the wheel cover in  FIG. 15 . 
         FIG. 17A  is a diagram illustrating an image when a force acts on a side surface of a wheel cover according to the configuration of the related art. 
         FIG. 17B  is a diagram illustrating an image when a force acts on a wrap-around portion. 
         FIG. 18  is a partial cross-sectional view illustrating a configuration in the vicinity of a folded-back portion of a chain guide portion of the wheel cover in  FIG. 15 . 
         FIG. 19  is a side view illustrating the shape of a wheel cover according to a modification of the present invention. 
         FIG. 20  is a plan view illustrating the shape of a wheel cover according to the modification of the present invention. 
         FIG. 21  is a perspective view illustrating the shape of the wheel cover according to the related art. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a chain block  10  according to an embodiment of the present invention will be described with reference to the drawings. 
     &lt;1. Regarding Configuration of Chain Block&gt; 
     As illustrated in  FIGS. 1 to 5  and the like, the chain block  10  includes a first frame  11 , a second frame  12 , a gear case  13 , a wheel cover  14 , a load-sheave hollow shaft  20 , and a speed reducing mechanism  30 , and these are fixed via stud bolts SB (corresponding to a fixation member) and nuts N. Then, between the first and second frames  11  and  12 , between the first frame  11  and the gear case  13 , and between the second frame  12  and the wheel cover  14 , respective members are mounted; however, a part of the members protrude from therebetween. Hereinafter, the respective members will be described. 
     Between the first and second frames  11  and  12 , a part of the load-sheave hollow shaft  20 , an upper hook  40 , a guide roller  42 , a metal fastener  43 , a stripper  44 , and the like are positioned. As illustrated in  FIGS. 4 and 5 , the load-sheave hollow shaft  20  is supported by the first and second frames  11  and  12  through bearings B 1  and B 2  such as ball bearings, which are fitted into insertion holes  11   a  and  12   a  of the first and second frames  11  and  12 , respectively. That is, the bearings B 1  and B 2  are positioned in outer peripheries of bearing fitting portions  21   a  and  21   b  of the load-sheave hollow shaft  20 , and further the bearings B 1  and B 2  are positioned in the insertion holes  11   a  and  12   a . Thereby, the load-sheave hollow shaft  20  is supported by the first and second frames  11  and  12 . 
     As illustrated in  FIGS. 6 and 9 , the first frame  11  has a circular portion  110  having a circular contour and a frame protruding portion  111  protruding from the circular portion  110 . Total three frame protruding portions  111 , two frame protruding portions on the upper side (Z1 side) and one frame protruding portion on the lower side (Z2 side) are provided. Furthermore, each of the frame protruding portions  111  is provided with an insertion hole  112  into which the stud bolt SB is inserted. Then, insertion holes are provided in such a manner that when the total three insertion holes  112  are connected to each other, an isosceles triangle is formed; however, the insertion holes may be provided in such a manner that an equilateral triangle or an approximately equilateral triangle is formed. Furthermore, the insertion holes may be provided in such a manner that when the total three insertion holes  112  are connected to each other, other triangle shapes than the isosceles triangle shape are formed. 
     As illustrated in  FIGS. 6 and 9 , a pair of frame protruding portions  111   a  positioned on the upper side (Z1 side) among the above-described frame protruding portions  111  are arranged along the Y direction. Then, a concave portion  113  is formed by a site on the lower side (Z2 side) of an outer peripheral edge portion of each of the pair of the frame protruding portions  111   a  and an outer peripheral edge portion of the circular portion. The concave portion  113  serves as a portion that reduces the width dimension of the first frame  11  between the circular portion  110  and the side of the lower side (Z2 side) of a frame protruding portion  111   a . Thus, the chain block  10  can be grasped by, for example, positioning different fingers or the like in a pair of concave portions  113 , respectively. That is, the chain block  10  can be grasped or held by the concave portion  113 , in addition to the upper hook  40 . Note that a separate grasping member or holding member can be positioned in each of the pair of concave portions  113  instead of fingers to grasp or hold the chain block  10  for the purpose of carrying and storing or packing. 
     Note that the frame protruding portion  111  existing on the lower side (Z2 side) is referred to as a frame protruding portion  111   b , as necessary. An end surface on the Z2 side of the frame protruding portion  111   b  is a flat portion  111   b   1  parallel to the Y axis. The existence of the flat portion  111   b   1  enables the chain block  10  to stand alone without falling down. Thereby, the chain block  10  is easy to carry and store or pack. 
     Furthermore, as illustrated in  FIG. 8 , the second frame  12  is also provided with a circular portion  120 , a frame protruding portion  121  ( 121   a  and  121   b ), an insertion hole  222 , and a concave portion  123 , which are similar to those of the above-described first frame  11 . Since these have similar configurations to the configurations of the respective sites in the first frame  11 , the description of each site is omitted. Furthermore, the second frame  12  corresponds to a frame member. However, the first frame  11  may correspond to a frame member, and both of the first and second frames  11  and  12  may correspond to frame members. 
     Furthermore, as illustrated in  FIGS. 4 and 5 , a gear fitting portion  22  is provided closer to the gear case  13  side than the bearing fitting portion  21   a  on the first frame  11  side of the load-sheave hollow shaft  20 , and a load gear  31  forming the speed reducing mechanism  30  is held in a spline-coupled state by the gear fitting portion  22 . Note that the gear case  13  side of the gear fitting portion  22  is provided with a groove portion  22   a  to which a snap ring E is mounted. By the snap ring E mounted to the groove portion  22   a , the load gear  31  is restricted from moving toward the X2 side of the load gear  31 . On the other hand, a clearance groove  22   b  for a spline process is formed at a site on the bearing fitting portion  21   a  side of the gear fitting portion  22 , and further a fixation stepped portion  22   c  having a larger diameter than that of the gear fitting portion  22  is provided at a site closer to the bearing fitting portion  21   a  side than the clearance groove  22   b . The fixation stepped portion  22   c  restricts the load gear  31  from moving toward the X1 side. 
     Here, the load gear  31  is provided with a central hole  31   a  into which the above-described gear fitting portion  22  is inserted. In addition, as illustrated in  FIGS. 4 and 5 , concave portions  31   b  are provided around the central hole  31   a  on each end side of the load gear  31 . The concave portions  31   b  are provided in the shape of recessing each end surface of the load gear  31  by a predetermined depth. That is, as illustrated in  FIGS. 4 and 5 , a concave portion  31   b   1  recessed from the end surface on the X1 side of the load gear  31  faces the bearing B 1 . However, the existence of the concave portion  31   b   1  can increase clearance between the load gear  31  and the bearing B 1 . Thereby, when the load gear  31  rotates in a state where machine oil (grease) exists between the load gear  31  and the bearing B 1 , a mechanical loss caused by the viscosity of the machine oil (grease) when the load gear  31  rotates can be reduced, and the fluidity of machine oil (grease) can be improved. Similarly, a concave portion  31   b   2  recessed from the end surface on the X2 side of the load gear  31  faces a large-diameter gear  61  of a reduction gear member  60 . However, the existence of the concave portion  31   b   2  can increase clearance between the load gear  31  and the large-diameter gear  61 . Also in this case, when the load gear  31  rotates, a mechanical loss caused by the viscosity of machine oil (grease) when the load gear  31  rotates can be reduced, and the fluidity of the machine oil (grease) can be improved. 
     Furthermore, the load-sheave hollow shaft  20  has a pair of flange portions  23   a  forming the load sheave  23 , and further has a chain pocket  23   b  (refer to  FIG. 4 ) forming the load sheave  23  between the pair of flange portions  23   a . The chain pocket  23   b  is a portion into which a metal hoop C 1   a  of a load chain C 1  is fitted, and has a horizontal pocket (not illustrated) into which the metal hoop C 1   a  is fitted in a state where the direction in which the metal hoop C 1   a  becomes flat is parallel to the axial direction (X direction), and a vertical pocket (not illustrated) which has a deeper groove shape than the horizontal pocket and into which the metal hoop C 1   a  is fitted in a state where the direction in which the metal hoop C 1   a  becomes flat crosses the axial direction (X direction). 
     Furthermore, the load-sheave hollow shaft  20  is provided with a hollow hole  24 . A drive shaft  70  is inserted into the hollow hole  24 , and an end portion on the second frame  12  side of the hollow hole  24  is provided with a bearing stepped portion  26  for receiving a bearing B 3  which shaft-supports the drive shaft  70 . Here, an end portion on the gear fitting portion  22  side of the hollow hole  24  is provided with a receiving concave portion  27  for receiving a flange portion  71  of the drive shaft  70 . By the flange portion  71  of the drive shaft  70  positioned in the receiving concave portion  27 , the length along the axial direction (X direction) of the drive shaft  70  can be reduced, and the dimension along the X direction (the axial direction of the drive shaft  70 ) of the chain block  10  can be reduced. Furthermore, By the reduced length along the axial direction of the drive shaft  70 , the strength of the drive shaft  70  can be improved. 
     As illustrated in  FIGS. 1 to 6 , the upper hook  40  is mounted to the first and second frames  11  and  12  through a connecting shaft  41  (refer to  FIGS. 6 and 8 ), and mounted in a rotatable state with respect to the connecting shaft  41 . A hook latch  40   a  which is biased in a closing direction by a basing unit (not illustrated) is mounted to the upper hook  40 . 
     One end side and the other end side of the guide roller  42  illustrated in  FIGS. 2 and 8  are shaft-supported rotatably with respect to the first frame  11  and the second frame  12 , respectively. For example, a pair of guide rollers  42  are provided at an interval of 180 degrees with the center of the load-sheave hollow shaft  20  interposed therebetween. The guide roller  42  is a member which rotates as the load chain C 1  is wound up or the like, and mounted facing the load sheave  23  and being separated by a distance to prevent the load chain C 1  from coming off the chain pocket  23   b.    
     The metal fastener  43  illustrated in  FIGS. 1 to 4 and 9  is a portion to which a metal fitting pin  43   a  is mounted, and the metal fitting pin is inserted into the metal hoop C 1   a  in an end portion of the load chain C 1 , which is opposite to the side to which the lower hook  45  is mounted. One end side and the other end side of the metal fastener  43  are also shaft-supported rotatably with respect to the first frame  11  and the second frame  12 , respectively. 
     The stripper  44  illustrated in  FIG. 4  is a member that prevents the occurrence of a lock state in which the load chain C 1  looped over the load sheave  23  follows the load sheave  23  more than necessary and the load sheave  23  is stuck. Respective end portions on one end side and the other end side of the stripper  44  are inserted into respective support holes  11   b  and  12   b  existing in the first and second frames  11  and  12 , and thus the stripper  44  is mounted to the first and second frames  11  and  12 . 
     Furthermore, as illustrated in  FIGS. 4 to 6 , an auxiliary plate  50  illustrated in  FIGS. 7A and 7B  is mounted to an end surface on the side facing the gear case  13  of the first frame  11 . The auxiliary plate  50  is provided with a flange portion  51  and a drawing portion  52 . The flange portion  51  is a portion that comes in contact with the end surface of the first frame  11 , and the flange portion  51  is provided with a fixation hole  53 . Then, the auxiliary plate  50  is mounted to the first frame  11  by inserting a fixation member  55  such as a rivet (refer to  FIG. 5 ) into the fixation hole  53  and a mounting hole  11   c  provided in the first frame  11 . Furthermore, the drawing portion  52  is a portion positioned closer to the center side than the flange portion  51 , and is a portion formed by, for example, drawing the center side of the auxiliary plate  50  so as to be spaced by a predetermined distance from the end surface of the first frame  11 . In the present embodiment, the drawing portion  52  has a recessed portion existing on the outer peripheral side thereof due to the existence of the fixation hole  53  in the configuration illustrated in  FIGS. 6, 7A, and 7B ; however, the drawing portion  52  has a corner formed in an R-shaped approximately rhombic shape, except the recessed portion. 
     Here, the mounting positions of the above-described fixation member  55  and the guide roller  42  with respect to the first frame  11  are in a positional relation illustrated in  FIG. 8 . That is, the pair of guide rollers  42  are mounted adjacent to respective fixation members  55 , and arranged at symmetrical positions with the center interposed between the guide rollers  42 . Furthermore, the guide rollers  42  are provided adjacent to the fixation members  55  ( 55   a ) separated from the rotation center of the load sheave  23  or the like, and are also provided at positions spaced apart from the fixation members  55  ( 55   b ) close to the center with the Y direction interposed therebetween. In such an arrangement, when the load chain C 1  is wound up, the entire chain block  10  tends to rotate along a rotation direction M of  FIG. 8  such that a direction F of a force received from the load chain C 1  becomes a direction orthogonal to a line L connecting the fixation members  55  adjacent to each other. In such rotation, when the guide rollers  42  are arranged as illustrated in  FIG. 8 , a line connecting the pair of guide rollers  42  approaches the horizontal state, and a guide property of the load chain can favorably be maintained. 
     Furthermore, as illustrated in  FIGS. 6, 7A, and 7B , a central hole  56  is provided on the center side of the drawing portion  52 . The central hole  56  is provided on the same axis as the above-described insertion hole  11   a , and has the same diameter as that of the insertion hole  11   a . Then, the above-described bearing B 1  is positioned in the central hole  56  to support the load-sheave hollow shaft  20 . Furthermore, the drawing portion  52  is provided with a bearing hole  57  along a diagonal in the longitudinal direction of the approximately rhombic shape thereof. For example, a pair of bearing holes  57  are provided at positions by an equal distance from the center of the central hole  56 , and are each formed in a shape having a rising portion  57   a  by burring processing, for example. A shaft support portion  63  on one end side of the reduction gear member  60  (X1 side in  FIG. 5 ) is inserted into the bearing hole  57 , and the reduction gear member  60  is shaft-supported by the bearing hole. Note that a shaft support portion  64  on the other end side of the reduction gear member  60  (X2 side in  FIG. 5 ) is inserted into a bearing hole  13   a  of the gear case  13  through a bearing B 4  such as a bush, and the reduction gear member  60  is shaft-supported by the bearing hole  13   a.    
     As illustrated in  FIGS. 5, 10A, and 10B , each of a pair of reduction gear members  60  (the arrangement of the pair of reduction gear members  60  is also illustrated in  FIG. 9 ) is provided with the large-diameter gear  61  (corresponding to a first reduction gear member) and a small-diameter gear  62  (corresponding to a second reduction gear member), and is also provided with the shaft support portion  63  inserted into the bearing hole  57  and the shaft support portion  64  inserted into the bearing hole  13   a  as described above. The large-diameter gear  61  engages with a pinion gear  72  of the drive shaft  70 , and a driving force is transferred from the drive shaft  70  to the reduction gear member  60  at a first reduction gear ratio. Furthermore, the large-diameter gear  61  is provided with a chamfered surface portion  61   a . The chamfered surface portion  61   a  is provided at a site on the X1 side of the outer peripheral side of the large-diameter gear  61 , and is provided having a smaller diameter than that of another site of the large-diameter gear  61 . The existence of the chamfered surface portion  61   a  prevents the large-diameter gear  61  from interfering with an inclined portion  73  and a curved surface portion  74  of the drive shaft  70 . 
     Furthermore, the small-diameter gear  62  engages with the load gear  31 , and the driving force transferred to the reduction gear members  60  is transferred to the load gear  31  at a second reduction gear ratio. Note that the small-diameter gear  62  and the above-described large-diameter gear  61  are integrally formed by cold forging, for example. However, the small-diameter gear  62  and the large-diameter gear  61  may be integrally formed by a combination of other processing such as precise forging and cutting, and may be separately formed by a combination of the above-described processing and thereafter coupled to each other. 
     As illustrated in  FIG. 10A , a swelling portion  65  is provided closer to the large-diameter gear  61  side (X1 side) than the shaft support portion  64  of the reduction gear member  60 . The swelling portion  65  is provided in a concave portion  60   a  provided in a central portion of an end surface of the reduction gear member  60 , but the swelling portion  65  is a portion swelling toward the outside in the radial direction so as to have a larger diameter than that of the shaft support portion  64 , and is intermittently swelling along the peripheral direction (in  FIG. 10A , three swelling portions  65  are provided). Then, a recessed portion  66  having a relatively smaller diameter than that of the swelling portion  65  exists between the adjacent swelling portions  65 . Furthermore, the outer peripheral side of the shaft support portion  64  is provided with an oil groove  64   a  along the axial direction (X direction) of the reduction gear member  60 , and the oil groove  64   a  is in communication with any one of recessed portions  66 . Thereby, machine oil (grease) can be supplied to the bearing B 4  such as a bush through the concave portion  60   a  and the oil groove  64   a . Furthermore, the existence of the above-described swelling portion  65  can make the large-diameter gear  61  spaced apart from the bearing B 4 , and the existence of the concave portion  60   a  and the oil groove  64   a  can reduce a mechanical loss caused by the viscosity of the machine oil (grease) between the large-diameter gear  61  and bearings B 4  and B 5 , and improve the fluidity of the machine oil (grease). 
     As illustrated in  FIGS. 4 and 5 , the drive shaft  70  (refer to  FIGS. 11A to 11C ) is a member extending from the gear case  13  side to the hand wheel  80  side along the X direction. The drive shaft  70  is inserted into the hollow hole  24  of the load-sheave hollow shaft  20  as described above, and provided rotatably with respect to the load sheave  23  through the bearing B 3  at the bearing stepped portion  26 . Furthermore, the drive shaft  70  is provided with the flange portion  71 , and the flange portion  71  is positioned in the receiving concave portion  27 . Then, by the flange portion  71  received in a bottom portion  27   a  of the receiving concave portion  27 , the drive shaft  70  is restricted from moving toward the hand wheel  80  side, and the dimension in the axial direction of the drive shaft  70  can be reduced. 
     A portion protruding from the hollow hole  24  toward the gear case  13  side (X2 side) of the drive shaft  70  is provided with the pinion gear  72  (corresponding to a first gear) engaging with the above-described large-diameter gear  61 . In  FIG. 12A , the pinion gear  72  has five teeth  721 . A thickness Da of each tooth  721  of the pinion gear  72  is set to be different from a thickness Db of a tooth  721 H of a pinion gear  72 H according to the related art as illustrated in  FIG. 13B . That is, in the pinion gear  72  according to the present embodiment, the thickness Da of a tooth tip  722  of each tooth  721  (hereinafter, the thickness Da of the tooth tip  722  is referred to as a thickness Da2 as illustrated in  FIG. 13A ) is provided to be larger than the thickness Db of a tooth tip  722 H of each tooth  721 H according to the related art (hereinafter, the thickness Db of the tooth tip  722 H is referred to as a thickness Db2 as illustrated in  FIG. 13B ). 
     Note that, as described above, when the thickness Da2 of the tooth tip  722  is made larger than the thickness Db2 of the tooth tip  722 H according to the related art, the thickness Da of each tooth  721  can be made as follows. That is, in the pinion gear  72  according to the present embodiment, a dimension Ba (not illustrated) of a tooth bottom  723  existing between the neighboring teeth  721  is provided to be smaller than a dimension Bb (not illustrated) of a tooth bottom  723 H of the pinion gear  72 H according to the related art. Thus, on the tooth bottom  723  side, the thickness Da of the tooth  721  (hereinafter, the thickness Da on the tooth bottom  723  side is referred to as a thickness Da1 as illustrated in  FIG. 13A ) is provided to be larger than the thickness Db of the tooth  721  according to the related art (hereinafter, the thickness Db on the tooth bottom  723 H side is referred to as a thickness Db1 as illustrated in  FIG. 13B ). 
     In addition, the thicknesses Da and Db at each site of the teeth  721  and  712 H are considered as illustrated in  FIGS. 13A and 13B . In this case, in the configuration illustrated in  FIG. 13A , the ratio of a thickened portion  724  in the tooth thickness Da of the tooth  721  in the present embodiment is set to increase from the side of the tooth bottom  723  to a side of the tooth tip  722 , as compared with the tooth thickness Db of the tooth  721 H in the related art. Accordingly, since the ratio of the thickened portion  724  is larger on the side of the tooth tip  723 , strength of the tooth  721  on the side of the tooth tip  723  can be improved significantly. 
     Note that the thickness Da of each tooth  721  may be set as follows. That is, the thickness Da1 on the tooth bottom  723  side may be set to be equal to the thickness Db1 on the tooth bottom  723 H side of the tooth  721 H according to the related art. In this case, however, it is necessary to prevent an undercut from occurring on the tooth bottom  723  side. Note that, when the thickness Da1 on the tooth bottom  723  side is provided as described above to be equal to the thickness Db1 on the tooth bottom  723 H side of the tooth  721 H according to the related art, the dimension of the thickened portion  724  may be set to become large from the tooth bottom  723  toward the tooth tip  722 . 
     Furthermore, each tooth  611  of the large-diameter gear  61  engaging with the pinion gear  72  as described above is thinned by an amount corresponding to thickening of the thickened portion  724  of the tooth  721 . That is, in the large-diameter gear  61 , a tooth thickness Dc (refer to  FIG. 13A ) of the tooth  611  is smaller than a tooth thickness Dd (refer to  FIG. 13D ) of the tooth  611 H according to the related art as much as the increasing amount from the tooth thickness Db of the tooth  721 H of the pinion gear  72 H according to the related art to the tooth thickness Da of the tooth  721  of the pinion gear  72 . At this time, the thickness Da2 of the tooth tip  722  of the pinion gear  72  is provided to be larger than the thickness Dc1 of the tooth tip  612  of the large-diameter gear  61 . Here, in a portion where the tooth  721  and the tooth  611  come in contact with each other, the change in the thickness Da of the tooth  721  from the tooth bottom  723  side to the tooth tip  722  side in the pinion gear  72  (the thickened portion  724 ) corresponds to the change in the thickness Dc of the tooth  611  from the tooth tip  612  side to the tooth bottom  613  side in the large-diameter gear  61 . Thereby, the favorable engagement between the pinion gear  72  and the large-diameter gear  61  is realized. 
     Note that, in the configurations illustrated in  FIGS. 12A ,  12 B,  13 A, and  13 B, the pinion gear  72  is provided with the five teeth  721 , and the large-diameter gear  61  is provided with  35  teeth  611 . Moreover, a pair of large-diameter gears  61  (reduction gear member  60 ) are arranged at symmetrical positions with the pinion gear  72  interposed therebetween, and the pinion gear  72  is engaged with both of the pair of large-diameter gears  61 . Thus, when the tooth  611  of the large-diameter gear  61  rotates once, the tooth  611  of the large-diameter gear  61  comes in contact with the tooth  721  of the pinion gear  72  only once; however, during one rotation of the large-diameter gear  61 , the tooth  721  of the pinion gear  72  comes in contact with the tooth  611  of the large-diameter gear  61  fourteen times. 
     Furthermore, each of the reduction gear member  60  and the drive shaft  70  is made of a metal and is preferably made of an iron-based metal from a viewpoint of abrasion resistance. Furthermore, the reduction gear member  60  and the drive shaft  70  are preferably made of similar materials. However, at least the pinion gear  72  of the drive shaft  70  may be made of a material having wear resistance more excellent than that of the large-diameter gear  61  of the reduction gear member  60 . 
     A portion protruding from the hollow hole  24  toward the gear case  13  side (X2 side) of the drive shaft  70  is provided with the pinion gear  72  (corresponding to a gear portion) engaging with the above-described large-diameter gear  61 . As illustrated in  FIGS. 11A and 11C , a base portion of the pinion gear  72  with respect to the flange portion  71  is provided with the inclined portion  73 . Further, the predetermined curved surface portion  74  is provided between each tooth of the pinion gear  72  and the inclined portion  73 . The curved surface portion  74  is formed in a round shape, for example. Then, the existence of the inclined portion  73  and the curved surface portion  74  can prevent concentration of stress from occurring in a boundary portion between the pinion gear  72  and the flange portion  71 . It is to be noted that the curved surface portion  74  has only to be 1/10 or larger of the inclined portion  73 , and by setting the ratio thereof in the inclined portion  73  to 1/10 or larger, the stress concentration can be prevented favorably. 
     Here, the thickness on the tip side of the tooth of the pinion gear  72  is provided to be larger than the thickness on the tip side of the large-diameter gear  61  engaging with the pinion gear  72 . Thus, the lifetime of the pinion gear  72  can be prolonged. That is, since the number of teeth of the pinion gear  72  is smaller than the number of teeth of the large-diameter gear  61 , each tooth of the pinion gear  72  slides more times than each tooth of the large-diameter gear  61 . Thereby, each tooth of the pinion gear  72  wears earlier than each tooth of the large-diameter gear  61 . However, by setting the tooth thickness on the tip end side of the tooth of the pinion gear  72  to be larger than the tooth thickness on the tip end side of the large-diameter gear  61  and setting the tooth width to be larger, lifetime of the pinion gear  72  can be prolonged. 
     Furthermore, the drive shaft  70  is provided with a shaft support portion  75  closer to the gear case  13  side (X2 side) than the pinion gear  72 . The shaft support portion  75  is a portion to which the bearing B 5  is mounted on the outer peripheral side thereof, and the bearing B 5  is mounted to a bearing mounting portion  13   b  provided in the gear case  13 . Thereby, an end portion on the X2 side of the drive shaft  70  is rotatably supported by the gear case  13  through the bearing B 5 . Further, a male screw portion  76  is provided on the hand wheel  80  side of the drive shaft  70 . The male screw portion  76  is a portion to which a female screw portion  81  of the hand wheel  80  or a female screw portion  91   a  of a brake receiver  91 , which will be described below, are screwed. Note that an end portion on the X2 side of the male screw portion  76  is provided with a stepped portion  77 , and the brake receiver  91  to be described below is locked by the stepped portion  77 . Furthermore, a stopper receiving portion  78  having a pin hole  78   a  is provided closer to the X1 side than the male screw portion  76 , and a wheel stopper  84  to be described below is arranged in the stopper receiving portion  78  and retained by a stopper pin  79 . 
     Note that the gear case  13  is a member that covers the speed reducing mechanism  30  such as the reduction gear member  60  and the load gear  31 , and the gear case  13  is fixed to the first frame  11  via the stud bolt SB and the nut N. 
     As illustrated in  FIGS. 4 and 5 , an end surface of the second frame  12  on the side not facing the first frame  11  is provided with the hand wheel  80  and a brake mechanism  90 . The hand wheel  80  has the female screw portion  81  on the center side thereof, and the female screw portion  81  is screwed to the male screw portion  76  of the drive shaft  70 . Furthermore, a chain pocket  82  similar to the above-described load sheave  23  is provided between sites of the outer peripheral side of the hand wheel  80 , facing a pair of flange portions  80   a . The chain pocket  82  is a portion into which a metal hoop C 2   a  of a hand chain C 2  is fitted, and has a horizontal pocket (not illustrated) into which the metal hoop C 2   a  is fitted in a state where the direction in which the metal hoop C 2   a  becomes flat is parallel to the axial direction, and a vertical pocket (not illustrated) which has a deeper groove shape than the horizontal pocket and into which the metal hoop C 2   a  is fitted in a state where the direction in which the metal hoop C 2   a  becomes flat crosses the axial direction. Note that the wheel stopper  84  is provided closer to the tip side of the male screw portion  76  (X1 side) than the hand wheel  80  via a collar  83  or the like. The wheel stopper  84  is a ring-shaped member and has a through-hole  84   a  along the radial direction. Then, by inserting a stopper pin  85  into the through-hole  84   a  and the pin hole  78   a  of the stopper receiving portion  78 , the wheel stopper  84  is restricted from moving in the X direction of the drive shaft  70 . The existence of the wheel stopper  84  restricts the hand wheel  80  from moving to the X1 side. 
     Furthermore, the brake mechanism  90  includes the brake receiver  91 , a brake plate  92 , a ratchet wheel  94 , a pawl member  95 , and like as main components. As illustrated in  FIGS. 4 and 5 , the brake receiver  91  is arranged on the second frame  12  side of the male screw portion  76  of the drive shaft  70 . The brake receiver  91  has the female screw portion  91   a  on the center side thereof, and further has a flange portion  91   b  and a hollow boss portion  91   c . The female screw portion  91   a  is a portion that is screwed to the male screw portion  76  of the drive shaft  70 , and the flange portion  91   b  of the brake receiver  91  is locked by the stepped portion  77  by the screwing of the female screw portion. The flange portion  91   b  is provided to have a larger diameter than that of the hollow boss portion  91   c , and can receive the brake plate  92  to be described below. The hollow boss portion  91   c  is positioned closer to the hand wheel  80  side (X1 side) than the flange portion  91   b , and supports the ratchet wheel  94  via a bush  93  to be described below. 
     The brake plate  92  ( 92   a ) is positioned between the flange portion  91   b  and the ratchet wheel  94  to be described below. When pressurized from the hand wheel  80  side, the brake plate applies a large frictional force between the flange portion  91   b  and the ratchet wheel  94  to be described below, and the brake receiver  91  integrally rotates with the ratchet wheel  94  by the large frictional force. Note that the brake plate  92  ( 92   b ) is also arranged between the ratchet wheel  94  and the hand wheel  80  and applies a large frictional force between the ratchet wheel  94  and the hand wheel  80  by being pressurized from the hand wheel  80 , and the hand wheel  80  integrally rotates with the ratchet wheel  94  by the large frictional force. 
     As illustrated in  FIGS. 4 and 5 , the bush  93  is mounted to the hollow boss portion  91   c  of the brake receiver  91 , and the ratchet wheel  94  is provided on the outer peripheral side of the bush  93 . Thereby, the ratchet wheel  94  is provided rotatably with respect to the brake receiver  91 . As illustrated in  FIG. 14 , a tip end of each pawl member  95  engages with a tooth portion  94   a  of the ratchet wheel  94 , and the engagement thereof forms a ratchet wheel mechanism which prevents the ratchet wheel  94  from rotating in the opposite direction (rotating in the winding-up direction). Note that the pawl member  95  is rotatably provided through a pawl shaft  95   a , and one end of a biasing spring  95   b  is attached to the pawl member  95 , so that a basing force is applied such that the tip of the pawl member  95  always engages with the tooth portion  94   a  of the ratchet wheel  94 . 
     Furthermore, a pair of pawl member  95  are provided. In the configuration illustrated in  FIG. 14 , one pawl member  95  is arranged at a position where the pawl member is inclined at a predetermined angle such as 30 degrees to the vertical direction. Furthermore, the other pawl member  95  is provided at a position adjacent to the one pawl member  95 . However, the arrangement mode thereof is an arrangement where the pair of pawl member  95  are both fitted into the same quadrant such as the first quadrant of the orthogonal coordinate system. Thereby, a space S is formed at a position corresponding to the third quadrant with respect to the first quadrant of the orthogonal coordinate system (a position on the Z2 side and the Y2 side in  FIG. 14 ), and when the load chain C 1   a  is wound up, the lower hook  45  can be positioned in the space S. However, other arrangements may be employed as the arrangement of the pair of pawl member  95 , and for example, a configuration of arranging each of the pair of pawl members in a diagonal direction with the rotation center of the ratchet wheel  94  interposed therebetween may be employed. 
     The wheel cover  14  is a member that covers the upper side of the hand wheel  80  and the upper side of the brake mechanism  90  (refer to  FIGS. 1 to 3  and the like), and the wheel cover  14  is fixed to the second frame  12  through the stud bolt SB and the nut N. The wheel cover  14  is formed by plastic working such as press working, and includes, as illustrated in  FIG. 15 , a flange portion  141 , a side surface  142 , and an end surface  143 , which are formed by the plastic working. The flange portion  141  is a portion that abuts against the second frame  12 . The flange portion  141  is surface-bonded to the second frame  12 , and thereby provided in a state of favorably resisting a tightening force between the stud bolt SB and the nut B. In order to realize such surface-bonding, the flange portion  141  is formed to expand outward with respect to the side surface  142  in parallel to the second frame  12  toward the tip side (X2 side) spaced apart from the end surface  143 . 
     Note that the flange portion  141  is bent at an angle nearly perpendicular to the side surface  142 ; however, in a state where the wheel cover  14  is mounted, the side surface  142  is not necessarily perpendicular to the second frame  12 . Thus, the flange portion  141  may be bent at an angle perpendicular to the side surface  142 , but not necessarily bent perpendicularly. 
     Furthermore, the wheel cover  14  illustrated in  FIG. 15  and the like may be formed by deep-drawing a steel plate or the like. 
     The side surface  142  is a portion that connects between the flange portion  141  and an outer periphery edge portion of the end surface  143 , and is formed as illustrated in  FIG. 1  so as to have a large dimension in the approaching and separating direction (X direction) relative to the second frame  12 . Furthermore, the side surface  142  is not provided over the entire outer peripheral edge portion of the end surface  143 . That is, the side surface  142  has a portion positioned on the upper side (hereinafter, referred to as an upper side surface  142   a  as necessary) and a portion positioned on the lower side (hereinafter, referred to as a lower side surface  142   b  as necessary). Note that a pair of sets of stud bolts SB and nuts N are provided on the upper side of the wheel cover  14  (Z1 side) along the Y direction. On the other hand, only one set of the stud bolt SB and the nut B exists on the lower side (Z2 side) of the wheel cover  14 . Thus, the upper side surface  142   a  is provided to have a larger dimension in the Y direction than the lower side surface  142   b , and a pair of wrap-around portions  148  (described below) also exist in the upper side surface  142   a.    
     Note that the hand chain C 2  can extends from a notched portion  144  between the upper side surface  142   a  and the lower side surface  142   b . Furthermore, a left-right side surface  145  is provided at a site closer to the end surface  143  side than the notched portion  144 . The left-right side surface  145  is a portion extending toward the second frame  12  more than the end surface  143  in a similar manner to the upper side surface  142   a  and the lower side surface  142   b ; however, the left-right side surface  145  is provided to have the length toward the second frame  12  significantly smaller than those of the upper side surface  142   a  and the lower side surface  142   b , due to the existence of the notched portion  144 . 
     Furthermore, the end surface  143  is a portion facing to the hand wheel  80  of the wheel cover  14 . The end surface  143  is provided so as to be continuous with the upper side surface  142   a , the lower side surface  142   b , and the left-right side surface  145  in the outer peripheral edge portion thereof. Furthermore, the end surface  143  has large dimensions in the Y direction and the Z direction (corresponding to the drooping direction) in  FIG. 15 . The end surface  143  may be provided in a planar shape; however, as illustrated in  FIG. 15 , a configuration where unevenness exists may be employed in order to improve the designability and improve the strength of the wheel cover  14 . 
     Furthermore, as illustrated in  FIGS. 3 and 15 , in the present embodiment, the end surface  143  is provided with a circular portion T1 having a circular shape where the radius from the center to the edge portion is R1 (in  FIGS. 3 and 15 , the circular shaped portion has a partially circular shape of which a portion on the upper side is cut; however, such a partially circular shape is described hereinafter being included in the circular shape) overlapping a triangular portion T2 having a triangle shape where the distance from the same center to the edge portion is R2. Here, the radius R1 and the distance R2 has the relation of R2&gt;R1. Thereby, the corner sides of the triangular portion T2 are provided to protrude from the circular portion T1. Hereinafter, the portion protruding from the circular portion T1 is referred to as a protruding portion  146 . 
     Furthermore, in the present embodiment, the triangular portion T2 is provided in an isosceles triangle shape of which the base is positioned on the upper side and of which the vertex is positioned on the lower side; however, the triangular portion may be provided in an equilateral triangle shape or an approximately equilateral triangle shape. Furthermore, the triangular shaped portion may be provided in other triangle shapes than the isosceles triangle shape. 
     As illustrated in  FIGS. 3 and 15 , the protruding portion  146  is provided with a bolt hole  147  (corresponding to the fixation hole). Since the bolt hole  147  is provided in the protruding portion  146 , three bolt holes  147  are provided on the outer peripheral edge portion side of the wheel cover  14 , and two of the bolt holes are provided along the Y direction on the upper side (Z1 side). 
     As illustrated in  FIGS. 3, 15, and 16 , the upper side surface  142   a  is provided with a wrap-around portion  148 . The wrap-around portion  148  is provided in such a manner that the upper edge side thereof (an edge portion on the Z1 side) is continuous with the protruding portion  146 . Furthermore, in the wrap-around portion  148 , an angle θ formed by a tangential line A 1  (may be set to a planar tangential surface A 1 ) and a tangential line A 2  (may be set to a planar tangential surface A 2 ) in  FIG. 16  is provided to become an acute angle. 
     In the configuration illustrated in  FIG. 16 , the angle formed by the tangential line A 1  (tangential surface A 1 ) and the tangential line A 2  (tangential surface A 2 ) is provided to be approximately 60 degrees. Furthermore, a line connecting the intersection between the tangential line A 1  (tangential surface A 1 ) and the tangential line A 2  (tangential surface A 2 ) to the center is a bisector A 3  or approximates the bisector A 3  of the angle formed by the tangential line A 1  (tangential surface A 1 ) and the tangential line A 2  (tangential surface A 2 ). 
     Here, in the wheel cover  14 H according to the related art, an angle α formed by the tangential line A 1  (tangential surface A 1 ) and the tangential line A 2  (tangential surface A 2 ) in the upper side surface  142 H is provided to become an obtuse angle, as illustrated in  FIGS. 17A, 17B, and 21 . Thus, when the wrap-around portion  148  of the wheel cover  14  according to the present embodiment is compared to the vicinity of the mounting site of the stud bolt SB of the wheel cover  14 H according to the related art (a portion corresponding to the wrap-around portion  148 ; hereinafter referred to as a corner portion  148 H), the wheel cover  14  according to the present embodiment has characteristics of larger strength. 
     Specifically, the corner portion  148 H in the configuration illustrated in  FIG. 21  is provided so as to be separated from the stud bolt SB and the bolt hole  147 , compared to the wrap-around portion  148  according to the present embodiment as illustrated in  FIGS. 15 and 16 . Thus, when a load acts, the end surface  143  around the bolt hole  147  is easier to deform than the case where the wrap-around portion  148  according to the present embodiment exists. In contrast, in the present embodiment, the wrap-around portion  148  is positioned inside the end surface  143  and provided adjacent to the stud bolt SB and the bolt hole  147 , compared to the configuration of the related art as illustrated in  FIG. 21 . Thus, even when a load acts on the end surface  143  around the bolt hole  147 , the end surface  143  and the wrap-around portion  148  become difficult to deform. 
     Here,  FIGS. 17A and 17B  illustrate images when an external force acts on the wrap-around portion  148  and the end surface  143 . A case where as illustrated in  FIG. 17A , ‘F’ going toward the rotation center acts on a portion corresponding to the wrap-around portion  148  according to the configuration of the related art, and similarly, as illustrated in  FIG. 17B , ‘F’ going toward the rotation center also acts on the wrap-around portion  148  according to the present embodiment is considered. As apparent from  FIGS. 17A and 17B , a component of a force along the upper side surface  142   a  becomes larger in the configuration of the related art. Thereby, when the wrap-around portion  148  according to the present embodiment exists, the strength becomes larger than in the configuration of the related art as illustrated in  FIGS. 17A and 21 . 
     Furthermore, as illustrated in  FIGS. 2 and 15 , the wrap-around portion  148  is provided with a chain guide portion  149  in a continuous state. The chain guide portion  149  is a portion provided adjacent to the hand chain C 2 , and is a portion for preventing the hand chain C 2  from coming off the chain pocket  82  even when the hand chain C 2  significantly moves (even when the hand chain C 2  “rages”). The chain guide portion  149  is provided so as to be positioned on the lower side (Z2 side) of the wrap-around portion  148 , and the chain guide portion  149  has a guide bent portion  149   a , a leg portion  149   b , and a protruding tip  149   c . The guide bent portion  149   a  is a portion facing the chain pocket  82  of the hand wheel  80 . An end portion along the X direction of the guide bent portion  149   a  is provided facing each flange portion  80   a.    
     Note that clearance between the end portion of the guide bent portion  149   a  and the flange portion  80   a  is preferably smaller than the diameter of the metal hoop C 2   a  of the hand chain C 2 . In such a configuration, even when the hand chain C 2  significantly moves (even when the hand chain C 2  rages), the hand chain C 2  is prevented from coming off the chain pocket  82 . 
     Furthermore, an end portion on the X2 side of the leg portion  149   b  is provided at the same position as the flange portion  141 , and an end surface of the leg portion  149   b  can abut against the second frame  12 . Furthermore, the end surface of the leg portion  149   b  is provided with the protruding tip  149   c . The protruding tip  149   c  is a portion inserted into an insertion hole  124  (refer to  FIG. 14 ) provided in the second frame  12 . By the protruding tip  149   c  inserted into the insertion hole  124 , the strength of the chain guide portion  149  can be improved. 
     Here, as illustrated in  FIG. 18 , a folded-back portion  150  formed by hemming processing exists in an outer edge portion on the lower side of the chain guide portion  149 . The folded-back portion  150  is provided over the entire part of the guide bent portion  149   a  and the leg portion  149   b . Then, the existence of the folded-back portion  150  can improve the strength of the chain guide portion  149 . Furthermore, the existence of the folded-back portion  150  can increase safety when a site such as hands comes in contact with the folded-back portion  150 . However, the folded-back portion  150  is not necessarily provided over the entire part of the guide bent portion  149   a  and the leg portion  149   b , and a configuration where the folded-back portion  150  does not exist in a site of at least a part of the guide bent portion and the leg portion may be employed. 
     &lt;2. Regarding Action of Chain Block&gt; 
     In the chain block  10  of the above-described configuration, when the hand chain C 2  is operated in the winding-up direction in a state where load is hung on the lower hook  45 , the hand wheel  80  rotates; however, at this time, due to the engagement of the female screw portion  81  with the male screw portion  76  of the drive shaft  70 , the hand wheel  80  travels in the direction to pressurize the brake plate  92  ( 92   b ) (direction toward X2 in  FIGS. 3 and 4 ) and strongly pressurizes the brake plate  92  ( 92   b ). Subsequently, the hand wheel  80  and the drive shaft  70  integrally rotate, and a driving force caused by the rotation is transferred to the load gear  31  through the pinion gear  72 , the large-diameter gear  61 , and the small-diameter gear  62  to rotate the load-sheave hollow shaft  20 . Thereby, the load chain C 1  is wound up and the load is lifted. 
     Conversely, when the lifted load is lowered, the hand chain C 2  is driven in the opposite direction to when the load is lifted. Then, the hand wheel  80  releases the pressurization on the brake plate  92   b . The drive shaft  70  rotates in the opposite direction to the winding-up direction of the load by an amount of the releasing. Thereby, the load is gradually lowered. 
     Note that, in a stopped state of the ratchet wheel  94 , the tip of the pawl member  95  engages with the tooth portion  94   a  of the ratchet wheel  94 . Moreover, even when the hands are released from the hand chain C 2  at the time of winding-up to rotate the drive shaft  70  in the opposite direction by the action of gravity from the load, the brake plate  92   b  is pressed against the ratchet wheel  94  by the hand wheel  80  in a state where the hand wheel  80  does not rotate, and further the brake plate  92   a  is pressed against the flange portion  91   a  of the brake receiver  91  by the ratchet wheel  94 . Thereby, a brake force resisting the gravity of the load is applied to prevent the load from being lowered. 
     &lt;3. Regarding Effect&gt; 
     According to the chain block  10  of the above-described configuration, the side surface  142  of the wheel cover  14  is provided with the wrap-around portion  148  illustrated in  FIGS. 3, 15 , and the like. Thus, due to the existence of the wrap-around portion  148 , the end surface  143  around the bolt hole  147  is difficult to deform, compared to the configuration of the related art as illustrated in  FIG. 21 . Thereby, the strength of the wheel cover  14  can be improved. 
     Furthermore, when the wrap-around portion  148  exists in the wheel cover  14  as illustrated in  FIG. 17B , a force acting on the upper side surface  142   a  (wrap-around portion  148 ) can be made small, compared to the configuration of the related art as illustrated in  FIG. 17A . In addition, in the present embodiment, when an external force acts as illustrated in  FIG. 17A , the existence of the wrap-around portion  148  decreases a component of the force involving flexural deformation of the upper side surface  142   a  (wrap-around portion  148 ), and increases a component of the force involving shear deformation of the upper side surface  142   a  (wrap-around portion  148 ), compared to the configuration of the related art in which the wrap-around portion  148  does not exist. Thereby, in the present embodiment, the strength of the wheel cover  14  can also be improved. 
     Furthermore, in the present embodiment, the chain guide portion  149  is provided adjacent to the wrap-around portion  148 . Here, due to the existence of the wrap-around portion  148 , a portion toward the rotation center is formed in the side surface  142  of the wheel cover  14 , and thereby, the chain guide portion  149  can be integrally formed in a continuous state with the wrap-around portion  148 . 
     Furthermore, by integrally forming the chain guide portion  149  in a continuous state with the wrap-around portion  148  in the above-described manner, a site on the wrap-around portion  148  side (a site on the upper side) of the chain guide portion  149  is supported by the wrap-around portion  148 . Thereby, the strength of the chain guide portion  149  can be improved. Furthermore, when the chain guide portion  149  is integrally provided in a continuous state with the wrap-around portion  148 , the number of processes when the wheel cover  14  is formed can be reduced. That is, in the configuration of the related art, as illustrated in  FIG. 21 , the chain guide portion  149 H is separately provided, and the separate chain guide portion  149 H is mounted to the wheel cover by welding. In the present embodiment, however, the wheel cover  14  and the chain guide portion  149  can be integrally formed by plastic working such as press working or deep-drawing working. Thereby, work such as welding becomes unnecessary, and the number of processes required for the welding and the like can be reduced. 
     Furthermore, in the present embodiment, the outer peripheral edge portion of the first frame  11  is provided with the pair of concave portions  113  passing through the center side thereof with the vertical direction (Z direction) interposed therebetween. The concave portions  113  are recessed toward the center side of the first frame  11  more than the outer peripheral edge portion of the first frame  11  adjacent to the concave portions  113 . Similarly, the outer peripheral edge portion of the second frame  12  is also provided with the pair of concave portions  123  passing through the center side thereof with the vertical direction (Z direction) interposed therebetween. The concave portions  123  are recessed toward the center side of the second frame  12  more than the outer peripheral edge portion of the second frame  12  adjacent to the concave portions  123 . Thus, for example, by positioning different fingers in the pair of concave portions  113  and/or the pair of concave portions  123 , respectively, the chain block  10  can be grasped. That is, the chain block  10  can be grasped or held by fingers or a grasping member or holding member, using the concave portions  113 , in addition to the upper hook  40 , and the convenience such as carrying and storing or packing can be improved. 
     Further, in the present embodiment, the tip side (X2 side) spaced apart from the end surface  143  of the chain guide portion  149  is provided with the protruding tip  149   c  which is inserted into the insertion hole  124  of the second frame  12 . Thus, the strength of the chain guide portion  149  can be improved. That is, when the protruding tip  149   c  is inserted into the insertion hole  124 , the chain guide portion  149  is supported on the second frame  12  side. Thereby, the strength of the chain guide portion  149  can be improved. 
     Furthermore, in the present embodiment, the outer peripheral portion on the side spaced apart from the wrap-around portion  148  of the chain guide portion  149  (lower side; Z2 side) is provided with the folded-back portion  150  formed by hemming processing. Thus, the thickness on the lower side (Z2 side) of the chain guide portion  149  can be increased by the existence of the folded-back portion  150 . In addition, the folded-back portion  150  is provided with the bent portion. Thus, when the other portions than the folded-back portion  150  of the chain guide portion  149  flexibly deform, the bent portion is shear-deformed. Thus, when the folded-back portion  150  exists, a large force becomes necessary. Thereby, the strength of the chain guide portion  149  can be improved. 
     Furthermore, in the present embodiment, the thickness Da2 of the tooth tip  722  of the pinion gear  72  is provided to be larger than the thickness Dc1 of the tooth tip  612  of the large-diameter gear  61 . Thereby, the strength of the tooth  721  of the pinion gear  72  can be improved, and the durability of the pinion gear  72  can also be improved. That is, since the number of the teeth  721  of the pinion gear  72  is smaller than the number of the teeth  611  of the large-diameter gear  61 , the teeth  721  of the pinion gear  72  are easy to wear. Thus, in the pinion gear  72 H according to related art, the tooth tip  722  side of the tooth  721 H is easy to break due to the wear of the tooth  721 H. 
     However, when the thickness Da2 of the tooth tip  722  of the pinion gear  72  is made larger than the thickness Db2 of the tooth tip  722 H of the pinion gear  72 H according to the related art and further the thickness Da2 of the tooth tip  722  of the pinion gear  72  is made larger than the thickness Dc1 of the tooth tip  612  of the large-diameter gear  61 , the durability of the tooth  721  against wear can be improved. Thereby, the lifetime of the chain block  10  can be prolonged. Furthermore, the reliability of the chain block  10  can be improved. 
     Furthermore, in the present embodiment, the thickness Da of the tooth  721  of the pinion gear  72  is made larger than the thickness Db according to the related art, and the thickness Dc of the tooth  611  of the large-diameter gear  61  is made smaller than the thickness Dd according to the related art. Thereby, the tooth tip  722  of the tooth  721  of the pinion gear  72  can be effectively prevented from breaking and the like. 
     Further, in the present embodiment, the base side (X1 side) of the pinion gear  72  is provided with the flange portion  71 , and the flange portion  71  and the teeth  721  are provided in a continuous manner. Thus, the strength of each tooth  721  of the pinion gear  72  can be increased. 
     Further, in the present embodiment, the pair of reduction gear members  60  are provided, and the pinion gear  72  is engaged with both the pair of reduction gear members  60 . Then, the pair of reduction gear members  60  are arranged at symmetrical positions with the pinion gear  72  interposed therebetween. In such a case, the teeth  721  of the pinion gear  72  wear earlier; however, even in such a case, by making the thickness Da of the tooth tip  722  large as described above, the tooth tips  722  of the teeth  721  of the pinion gear  72  can be effectively prevented from breaking and the like. 
     &lt;4. Modification&gt; 
     Hereinabove, the embodiment of the present invention has been described, but the present invention can be modified in various manners other than the above-described embodiment. Hereinafter, the modifications will be described. 
     In the above-described embodiment, the chain guide portion  149  is integrally provided in a continuous state with the wrap-around portion  148 . As illustrated in  FIGS. 19 and 20 , however, a configuration of separately providing chain guide portion  149  without being continuous with wrap-around portion  148  may be employed. That is, a configuration of providing the chain guide portion  149  separately from the wrap-around portion  148  by mounting the chain guide portion  149  to an end surface  143  by a technique such as welding may be employed. 
     In such a configuration, the degree of freedom in an arrangement position of the chain guide portion  149  with respect to the end surface  143  can be improved. Furthermore, even in such a configuration, since the wrap-around portion  148  exists in a side surface  142 , the existence of the wrap-around portion  148  can improve the strength of a wheel cover  14 . 
     Furthermore, the above-described embodiment describes the configuration of fixing the auxiliary plate  50  to the first frame  11  through the fixation hole  53  and the fixation member  55 . However, for example, at least one combination of a boss hole and a boss may be used in place of the combination of the fixation hole  53  and the fixation member  55 . In addition, an auxiliary plate  53  may be fixed to a first frame  11  by welding or the like. 
     REFERENCE SIGNS LIST 
       10  chain block 
       11  first frame 
       12  second frame (corresponding to frame member) 
       13  gear case 
       14  wheel cover 
       20  load-sheave hollow axis 
       23  load sheave 
       30  reduction member mechanism 
       31  load gear 
       31   b ,  31   b   1 ,  31   b   2  concave portion 
       40  upper hook 
       42  guide roller 
       45  lower hook 
       50  auxiliary plate 
       52  drawing portion 
       53  fixation hole 
       57  bearing hole 
       60  reduction gear member 
       61  large-diameter gear 
       61   a  chamfered surface portion 
       62  small-diameter gear 
       64   a  oil groove 
       65  swelling portion 
       66  recessed portion 
       70  diving shaft 
       72  pinion gear 
       73  inclined portion 
       74  curved surface portion 
       80  hand wheel 
       90  brake mechanism 
       91  brake receiver 
       92  brake plate 
       94  ratchet wheel 
       95  pawl member 
       110 ,  120  circular portion 
       111 ,  121  frame protruding portion 
       112 ,  122  insertion hole 
       113 ,  123  concave portion 
       124  insertion hole 
       141  flange portion 
       142  side surface 
       142   a  upper side surface 
       142   b  lower side surface 
       143  end surface 
       144  notched portion 
       145  left-right side surface 
       146  protruding portion 
       147  bolt hole (corresponding to fixation hole) 
       148  wrap-around portion 
       149  chain guide portion 
       149   a  guide bent portion 
       149   b  leg portion 
       149   c  protruding tip 
       150  folded-back portion 
     A 1 , A 2  tangential line (tangential surface) 
     A 3  bisector 
     B 1  to B 5  bearing 
     C 1 , C 2  load chain 
     N nut 
     S space 
     SB stud bolt (corresponding to fixation member)