Abstract:
Provided is a chain block with which a reduction in size can be achieved while inhibiting a reduction in strength. A chain block is provided with: a load-sheave hollow shaft which is provided with a load sheave that rotates to feed a load chain, said load-sheave hollow shaft having a hollow core along the axial direction thereof; a drive shaft which is inserted into the hollow core, and which is provided with a flange portion protruding radially outward from one end side to a base side of a separate gear part; and a reduction gear member provided with a first reduction gear part which meshes with the gear part. An accommodating recess is provided at the one end side of the hollow core, said accommodating recess having a bottom part which is where the flange part is positioned, and which is in contact with the flange part. An inclined portion, which gradually inclines further towards the gear part side as said inclined portion approaches a centre side in the radial direction, is provided to the flange portion. A chamfered portion is provided to a side of the reduction gear member, said side being the side nearest to the flange portion.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a chain block for use in a load hoisting work. 
       BACKGROUND ART  
       [0002]    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 is 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 and Patent Literature 2. 
       CITATION LIST  
     Patent Literature  
       [0003]    [PTL 1]: JP 59-195193 Y 
         [0004]    [PTL 2]: JP 2011-201637 A 
       SUMMARY OF INVENTION  
     Technical Problem 
       [0005]    Meanwhile, to improve portability, easiness of attachment and detachment, and the like of the chain block, it is desirable to promote size reduction of the chain block. However, mere size reduction of the chain block brings about a problem of a decrease in strength of the chain block. 
         [0006]    The present invention is achieved based on the above circumstances, and an object thereof is to provide a chain block enabling achievement of size reduction while inhibiting a decrease in strength. 
       Solution to Problem 
       [0007]    To solve the above problems, according to a first aspect of the present invention, a chain block is provided including a load-sheave hollow shaft around which a load chain is wound, which includes a load sheave feeding the load chain along with rotation, and which includes a hollow hole passing therethrough along an axial direction, a drive shaft which is inserted in the hollow hole, which includes on a first end side a gear portion meshing with a reduction gear member, and which has on a base end side of the gear portion away from the first end side a flange portion projecting to an outer circumferential side, and the reduction gear member including a first reduction gear portion meshing with the gear portion. On a first end side of the hollow hole is provided a housing recess including a bottom portion on which the flange portion is situated and abuts. The flange portion is provided toward a center side in a radial direction with an inclined portion gradually inclined toward a side of the gear portion. On a side of the first reduction gear portion in proximity to the flange portion is provided a chamfered portion. 
         [0008]    Also, according to another aspect of the present invention, in the aforementioned invention, the load-sheave hollow shaft is preferably provided with a load gear meshing with a second reduction gear portion out of the reduction gear member and rotated integrally with the load-sheave hollow shaft, and this load gear preferably abuts in a state in which movement thereof along a second end side in the axial direction is regulated by a fixing step of the load-sheave hollow shaft. On a center side in the radial direction at least on one end surface side of the load gear is preferably provided a recess further dented than on an outer circumferential side. 
         [0009]    Further, according to another aspect of the present invention, in the aforementioned invention, the reduction gear member is preferably provided with the first reduction gear portion having a chamfered portion, the second reduction gear portion meshing with the load gear. The first reduction gear portion is preferably provided with expanding portions projecting from an opposite end surface thereof of the second reduction gear portion, and a pivotally supporting portion preferably projects from the expanding portions toward a direction away from the first reduction gear portion. The expanding portions preferably expand outward in the radial direction so as to have larger diameters than that of the pivotally supporting portion and preferably expand intermittently along a circumferential direction, and between the adjacent expanding portions are preferably provided a plurality of dented portions each having a smaller diameter than that of the expanding portion. On an outer circumferential side of the pivotally supporting portion is preferably provided a groove along the axial direction of the reduction gear member, and this groove preferably communicates with at least one of the dented portions. 
         [0010]    Still further, according to another aspect of the present invention, in the aforementioned invention, a thickness of a tip of a tooth of the gear portion in the drive shaft is preferably set to be larger than a thickness of a tip of a tooth of the first reduction gear portion of the reduction gear member. 
         [0011]    Still further, according to another aspect of the present invention, in the aforementioned invention, to the frame member is preferably rotatably supported a pair of guide rollers guiding feeding of the load chain together with the load sheave. The guide rollers as the pair are preferably arranged at symmetric positions with a rotation center of the drive shaft interposed therebetween. The guide rollers as the pair are preferably arranged so that, as a result of entire turning in load hoisting with use of the load chain, a line connecting the guide rollers as the pair may be further nearly horizontal than in an unloaded case in the load hoisting. 
         [0012]    Still further, according to another aspect of the present invention, in the aforementioned invention, the load-sheave hollow shaft is preferably pivotally supported in an insertion hole of the frame member. To the frame member is preferably attached via fixing tools a plate member having a center hole provided coaxially with the insertion hole. The plate member is preferably provided with a flange portion abutting on the frame member and a draw portion situated further on a center side than the flange portion and raised from the flange portion so as to be spaced apart from the frame member. The plate member is preferably attached to the frame member at the flange portion via the fixing tools. A pair of fixing tools is preferably provided on each side with the rotation center of the drive shaft interposed therebetween. The fixing tools as each pair are preferably provided at positions at which, as a result of entire turning in load hoisting with use of the load chain, a line connecting the fixing tools as each pair further approaches to a direction perpendicular to an acting line of a force at the time of load hoisting than in an unloaded case. 
       Advantageous Effects of Invention 
       [0013]    According to the present invention, a chain block enables achievement of size reduction while inhibiting a decrease in strength. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  is a front view illustrating an appearance of a chain block according to an embodiment of the present invention. 
           [0015]      FIG. 2  is a side view illustrating the appearance of the chain block in  FIG. 1 . 
           [0016]      FIG. 3  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 . 
           [0017]      FIG. 4  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 . 
           [0018]      FIG. 5  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 . 
           [0019]      FIG. 6A  is a perspective view illustrating the shape of the auxiliary plate in the chain block in  FIG. 1 , when seen from the front side. 
           [0020]      FIG. 6B  is a perspective view illustrating the shape of the auxiliary plate in the chain block in  FIG. 1 , when seen from the rear side. 
           [0021]      FIG. 7  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 . 
           [0022]      FIG. 8  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 . 
           [0023]      FIG. 9A  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. 
           [0024]      FIG. 9B  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. 
           [0025]      FIG. 10A  is a perspective view illustrating the shape of a drive shaft in the chain block in  FIG. 1 , when seen from the front side. 
           [0026]      FIG. 10B  is a perspective view illustrating the shape of the drive shaft in the chain block in  FIG. 1 , when seen from the rear side. 
           [0027]      FIG. 10C  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. 
           [0028]      FIG. 11A  illustrates an engagement state between a pinion gear and a large-diameter gear according to the present embodiment. 
           [0029]      FIG. 11B  illustrates an engagement state between a pinion gear and a large-diameter gear according to a configuration of the related art. 
           [0030]      FIG. 12A  is a diagram illustrating the relation in tooth thickness between the pinion gear and the large-diameter gear according to the present embodiment. 
           [0031]      FIG. 12B  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. 
           [0032]      FIG. 13  is a diagram illustrating an arrangement of a ratchet wheel and pawl members in the chain block in  FIG. 1 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS  
       [0033]    Hereinbelow, a chain block according to an embodiment of the present invention will be described with reference to the drawings. 
       &lt;1. Regarding Configuration of Chain Block&gt; 
       [0034]    As illustrated in  FIGS. 1 to 4  and the like, a 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 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. 
         [0035]    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. 3 and 4 , 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 . 
         [0036]    Also, 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. 
         [0037]    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. 3 and 4 , 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. 3 and 4 , 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. 
         [0038]    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). 
         [0039]    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. 
         [0040]    As illustrated in  FIGS. 1 to 5 , the upper hook  40  is mounted to the first and second frames  11  and  12  through a connecting shaft  41  (refer to  FIGS. 5 and 7 ), 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 . 
         [0041]    One end side and the other end side of the guide roller  42  illustrated in  FIGS. 2 and 7  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.    
         [0042]    The metal fastener  43  illustrated in  FIGS. 1 to 3  and  8  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. 
         [0043]    The stripper  44  illustrated in  FIG. 3  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 . 
         [0044]    Furthermore, as illustrated in  FIGS. 3 to 5 , an auxiliary plate  50  illustrated in  FIGS. 6A and 6B  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. 4 ) 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. 5 ,  6 A, and  6 B; however, the drawing portion  52  has a corner formed in an R-shaped approximately rhombic shape, except the recessed portion. 
         [0045]    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. 7 . 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. 7  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. 7 , 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. 
         [0046]    Furthermore, as illustrated in  FIGS. 5 ,  6 A, and  6 B, 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. 4 ) 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. 4 ) 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.    
         [0047]    As illustrated in  FIGS. 4 ,  9 A, and  9 B, each of a pair of reduction gear members  60  (the arrangement of the pair of reduction gear members  60  is also illustrated in  FIG. 8 ) 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 . 
         [0048]    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. 
         [0049]    As illustrated in  FIG. 9A , 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. 9A , 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). 
         [0050]    As illustrated in  FIGS. 3 and 4 , the drive shaft  70  (refer to  FIGS. 10A to 10C )           the gear case  13  side to the hand           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. 
         [0051]    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. 11A , 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. 12B . 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 Da 2  as illustrated in  FIG. 12A ) 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 Db 2  as illustrated in  FIG. 12B ). 
         [0052]    Note that, as described above, when the thickness Da 2  of the tooth tip  722  is made larger than the thickness Db 2  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 Da 1  as illustrated in  FIG. 12A ) 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 Db 1  as illustrated in  FIG. 12B ). 
         [0053]    In addition, the thicknesses Da and Db at each site of the teeth  721  and  712 H are considered as illustrated in  FIGS. 12A and 12B . In this case, in the configuration illustrated in  FIG. 12A , 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. 
         [0054]    Note that the thickness Da of each tooth  721  may be set as follows. That is, the thickness Da 1  on the tooth bottom  723  side may be set to be equal to the thickness Db 1  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 Da 1  on the tooth bottom  723  side is provided as described above to be equal to the thickness Db 1  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 . 
         [0055]    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. 12A ) of the tooth  611  is smaller than a tooth thickness Dd (refer to  FIG. 12D ) 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 Da 2  of the tooth tip  722  of the pinion gear  72  is provided to be larger than the thickness Dc 1  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. 
         [0056]    Meanwhile, in the configuration illustrated in  FIGS. 11A ,  11 B,  12 A, and  12 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. 
         [0057]    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 . 
         [0058]    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. 10A and 10C , 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. 
         [0059]    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. 
         [0060]    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 receiving portion  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 . 
         [0061]    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. 
         [0062]    As illustrated in  FIGS. 3 and 4 , 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 a center side thereof, and this 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 on an outer peripheral side of the hand wheel  80 . 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. 
         [0063]    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. 3 and 4 , 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. 
         [0064]    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. 
         [0065]    As illustrated in  FIGS. 3 and 4 , 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. 13 , 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 . 
         [0066]    Furthermore, a pair of pawl member  95  are provided. In the configuration illustrated in  FIG. 13 , 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. 13 ), 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. 
         [0067]    Meanwhile, the wheel cover  14  is a member covering an upper side of the hand wheel  80  and an upper side of the brake mechanism  90  and is fixed on the second frame  12  via the stud bolts SB and the nuts N. 
       &lt;2. Regarding Action of Chain Block&gt; 
       [0068]    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 a 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. 
         [0069]    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. 
         [0070]    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; 
       [0071]    According to the chain block  10  configured as above, on one end side of the hollow hole  24  of the load-sheave hollow shaft  20  is provided the receiving concave portion  27  including the bottom portion  27   a  on which the flange portion  71  of the drive shaft  70  abuts. Accordingly, movement of the drive shaft  70  to the side of the hand wheel  80  is regulated, and the dimension of the drive shaft  70  in the axial direction (X direction) can be reduced. Since the dimension of the drive shaft  70  in the X direction is reduced, size reduction of the chain block  10  can be achieved as much, and weight reduction of the chain block  10  can be achieved. Also, since the dimension of the drive shaft  70  in the axial direction (X direction) is reduced, strength of the drive shaft  70  against torsion, shear, and the like can be improved as much as the reduced amount of the dimension. 
         [0072]    Also, the flange portion  71  is provided with the inclined portion  73 . Thus, existence of the inclined portion  73  can prevent stress concentration from being generated on the base end part of the pinion gear  72  on the side of the flange  71  and can prevent the teeth of the pinion gear  72  from cracking. Also, since the large-diameter gear  61  of the reduction gear member  60  is provided with the chamfered surface portion  61   a,  the large-diameter gear  61  can be prevented from interfering with the inclined portion  73  and the like of the drive shaft  70 . Also, existence of the chamfered surface portion  61   a  enables the reduction gear member  60  to be arranged in proximity to the side of the flange portion  71 . That is, existence of the chamfered surface portion  61   a  enables the dimension of the chain block  10  in the X direction to be reduced, and size reduction of the chain block  10  can be achieved. 
         [0073]    Also, in the present embodiment, the load gear  31  is provided with the concave portions  31   b  ( 31   b   1  and  31   b   2 ) formed by denting both the end surfaces of the load gear  31  to a certain extent. Since the concave portion  31   b   1  is opposed to the bearing B 1 , the space between the load gear  31  and the bearing B 1  can be enlarged. Thus, in a case in which the load gear  31  is rotated in a state in which machine oil (grease) exists between the load gear  31  and the bearing B 1 , a mechanical loss generated by viscosity of the machine oil (grease) can be reduced, and fluidity of the machine oil (grease) can be improved at the time of rotation of the load gear  31 . Similarly, since the concave portion  31   b   2  is opposed to the large-diameter gear  61 , the space between the load gear  31  and the large-diameter gear  61  can be enlarged. Thus, in a case in which the load gear  31  is rotated, a mechanical loss generated by viscosity of the machine oil (grease) can be reduced, and fluidity of the machine oil (grease) can be improved at the time of rotation of the load gear  31 . In other words, existence of the concave portions  31  ( 31   b   1  and  31   b   2 ) enables resistance (mechanical loss) in driving (upward and downward winding) of the chain block  10  to be decreased and enables operability to be improved. 
         [0074]    Further, in the present embodiment, the large-diameter gear  61  is provided with the swelling portions  65 . Existence of the swelling portions  65  enables the large-diameter gear  61  to be away from the bearing B 4 . Also, at parts between the adjacent swelling portions  65  are provided the plurality of recessed portions  66 , on the outer circumferential side of the shaft support portion  64  is provided the oil groove  64   a,  and this oil groove  64   a  communicates with any of the recessed portions  66 . This enables the machine oil to be supplied to the bearing B 4  such as a bush via the oil groove  64   a.  Also, existence of the oil groove  64   a  enables fluidity of the machine oil (grease) to be improved. Accordingly, a mechanical loss generated by viscosity of the machine oil (grease) can be reduced at the time of rotation of the large-diameter gear  61 , and operability can be improved. 
         [0075]    Also, in the present embodiment, the tooth thickness Da 2  of the tooth tip  722  of the pinion gear  72  is set to be larger than the tooth thickness Dc 1  of the tooth tip  612  of the large-diameter gear  61 . This enables strength of the teeth  721  of the pinion gear  72  to be improved and enables durability of the pinion gear  72  to 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 abraded easily. Thus, in the conventional pinion gear  72 H, the tooth tips  722  of the teeth  721 H are cracked easily due to abrasion of the teeth  721 H. 
         [0076]    However, as described above, in the case in which the tooth thickness Da 2  of the tooth tip  722  of the pinion gear  72  is set to be larger than the tooth thickness Db 2  of the tooth tip  722 H of the conventional pinion gear  72 H, and in which the tooth thickness Da 2  of the tooth tip  722  of the pinion gear  72  is set to be larger than the tooth thickness Dc 1  of the tooth tip  612  of the large-diameter gear  61 , durability of the teeth  721  against abrasion can be improved. Accordingly, lifetime of the chain block  10  can be extended, and reliability of the chain block  10  can be improved. 
         [0077]    Also, in the present embodiment, the tooth thickness Da of the tooth  721  of the pinion gear  72  is set to be larger than the conventional tooth thickness Db, and the tooth thickness Dc of the tooth  611  of the large-diameter gear  61  is set to be smaller than the conventional tooth thickness Dd. Accordingly, the tooth tips  722  of the teeth  721  of the pinion gear  72  can be prevented from cracking effectively. 
         [0078]    Further, in the present embodiment, the flange portion  71  is provided on the base end side (X1 side) of the pinion gear  72  and is provided to be continuous with the teeth  721 . Thus, strength of each tooth  721  of the pinion gear  72  can be increased. 
         [0079]    Further, in the present embodiment, the pair of reduction gear members  60  is provided, and both the reduction gear members  60  as a pair mesh with the pinion gear  72 . The reduction gear members  60  as a pair are arranged at symmetric positions with the pinion gear  72  interposed therebetween. In this case, the teeth  721  of the pinion gear  72  are in a state of being abraded earlier. However, even in this case, by setting the tooth thickness Da of the tooth tip  722  to be large as described above, the tooth tips  722  of the teeth  721  of the pinion gear  72  can be prevented from cracking effectively. 
         [0080]    Further, in the present embodiment, the guide rollers  42  as a pair are arranged at symmetric positions with a rotation center of the drive shaft  70  interposed therebetween and are arranged so that, as a result of entire turning in load hoisting with use of the load chain C 1 , the line connecting the guide rollers  42  as a pair may be further nearly horizontal than in an unloaded case in the load hoisting. Accordingly, the load chain C 1  can be fed favorably by the guide rollers  42  even in a loaded state, and it is possible to prevent a problem in which the load chain C 1  comes off of the load sheave  23  from occurring. 
         [0081]    Also, in the present embodiment, as illustrated in  FIG. 7 , as a result of entire turning of the chain block  10  in load hoisting with use of the load chain C 1 , the line L connecting the fixation members  55  as a pair is arranged at a position of further approaching to a direction perpendicular to the acting line F of a force at the time of load hoisting than in the unloaded case. Accordingly, forces applied to the respective fixation members  55  can be distributed favorably, and it is possible to prevent a case in which a significant load is applied to a specific fixation members  55  from occurring. 
       &lt;4. Modification&gt; 
       [0082]    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. 
         [0083]    In the above embodiment, 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 
       [0084]      10  . . . Chain block 
         [0085]      11  . . . First frame 
         [0086]      12  . . . Second frame 
         [0087]      13  . . . Gear case 
         [0088]      14  . . . Wheel cover 
         [0089]      20  . . . Load-sheave hollow shaft 
         [0090]      23  . . . Load sheave 
         [0091]      24  . . . Hollow hole 
         [0092]      25  . . . Bearing step 
         [0093]      27  . . . Receiving concave portion 
         [0094]      27   a  . . . Bottom portion 
         [0095]      30  . . . Speed reducing mechanism 
         [0096]      31  . . . Load gear 
         [0097]      31   b,    31   b   1 ,  31   b   2  . . . Concave portion 
         [0098]      40  . . . Upper hook 
         [0099]      42  . . . Guide roller 
         [0100]      43  . . . Metal fastener 
         [0101]      44  . . . Stripper 
         [0102]      45  . . . Lower hook 
         [0103]      50  . . . Auxiliary plate 
         [0104]      51  . . . Flange portion 
         [0105]      52  . . . Draw forming portion 
         [0106]      53  . . . Fixation hole 
         [0107]      55  . . . Fixation members 
         [0108]      57  . . . Bearing hole 
         [0109]      60  . . . Reduction gear member 
         [0110]      61  . . . Large-diameter gear (corresponding to first reduction gear) 
         [0111]      61   a  . . . Chamfered surface portion 
         [0112]      62  . . . Small-diameter gear (corresponding to second reduction gear) 
         [0113]      64   a  . . . Oil groove 
         [0114]      65  . . . Swelling portions 
         [0115]      66  . . . Recessed portion 
         [0116]      70  . . . Drive shaft 
         [0117]      71  . . . Flange portion 
         [0118]      72  . . . Pinion gear (corresponding to gear portion) 
         [0119]      73  . . . Inclined portion 
         [0120]      74  . . . Curved surface portion 
         [0121]      76  . . . Male screw portion 
         [0122]      77  . . . Stepped portion 
         [0123]      80  . . . Hand wheel 
         [0124]      90  . . . Brake mechanism 
         [0125]      91  . . . Brake receiver 
         [0126]      92  . . . Brake plate 
         [0127]      94  . . . Ratchet wheel 
         [0128]      95  . . . Pawl member 
         [0129]    B 1  to B 5  . . . Bearing 
         [0130]    C 1 , C 2  . . . Load chain 
         [0131]    N . . . Nut 
         [0132]    S . . . Space 
         [0133]    SB . . . Stud bolt