Abstract:
Drums each having an independent drive source is installed on a trolley and each of the drums has a lifting rope which is wound around it and has an unwound end locked on a suspension piece, which will suppress any need to design the lifting rope in longer length and the drums in larger size. 
     Sun gears, carriers and planetary gears disposed in each of the drums as well as internal teeth in each of the drums so as to be integrally rotated with the drum constitute a speed reducing mechanism for transmitting rotation of a drive source to each of the drums, will enable the entire hoist to be compact in size. 
     Unwound length of the lifting rope from each drum is adjusted to control posture of the suspension piece and load in adequate state.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a hoist used in a container crane. 
     FIG. 1 shows a container crane and FIG. 2 illustrates a boom derrick, a head block lifter and a trolley traverser used in the container crane. More specifically, the container crane comprises land- and seaward rails Q 1  and Q 2  on a quay P at harbor S, a traveler  2  with legs  1   a  and  1   b  running on the rails Q 1  and Q 2 , a girder  3  substantially horizontally mounted on a top of the traveler  2 , a boom  4  pivoted to a tip of the girder  3  so as to be swung upward, a main trolley  5  traversing along the girder  3  and boom  4 , a head block  6  suspended from and vertically movable relative to the trolley  5 , a spreader  7  mounted on the block  6  and with which a container C is to be locked, a first catenary trolley  19  positioned closer to a base end of the girder  3  than the main trolley  5  and traversing along the girder  3  and boom  4  and a second catenary trolley  20  positioned closer to the tip of the boom  4  than the main trolley  5  and traversing along the girder  3  and boom  4 . 
     In the container crane as described above, unloading of the container C from a ship V to the quay P and loading of the same from the quay P to the ship V are carried out in combination of operations such as motion of the traveler  2  along the quay P, traverse of the trolley  5  on the girder  3  and boom  4 , vertical motion of the block  6  relative to the trolley  5  and locking of the container C by the spreader  7 . 
     Disposed on the girder  3  is a machine room  8  with a drum  11  for derricking motion of the boom  4 , drums  15   a  and  15   b  for vertical motion of the block  6 , a drum  13  for traverse of the main trolley  5  and drums  9   a  and  9   b  for traverse of the catenary trolleys  19  and  20 . 
     Rotation of the drum  11  in normal and reverse directions causes a boom-derricking rope  12  to be wound and unwound, respectively, resulting in change of angle of the boom  4  to the girder  3 . 
     Rotation of the drums  15   a  and  15   b  in normal and reverse directions causes block-lifting ropes  16   a  and  16   b  to be wound and unwound, respectively, resulting in vertical motion of the block  6  relative to the trolley  5 . 
     Rotation of the drum  13  in normal and reverse directions causes trolley-traversing ropes  14   a  and  14   b  to be wound and unwound, resulting in traverse of the trolley  5  towards the base and tip ends of the boom  4 , respectively, since the rope  14   a  is locked at its opposite ends to the drum  13  and engaged at its intermediate portion with the trolley  5  via the base end of the girder  3  and the rope  14   b  is locked at its opposite ends to the drum  13  and engaged at its intermediate portion with the trolley  5  via the tip of the boom  4 . 
     Rotation of the drums  9   a  and  9   b  in normal.and reverse directions causes trolley-traversing ropes  10   a  and  10   b  to be wound and unwound, resulting in traverse of the trolleys  19  and  20  towards the base and tip ends of the boom  4 , respectively, since the rope  10   a  is locked at its opposite ends to the drums  9   a  and  9   b  and engaged at its intermediate portion with the trolley  19  via the base end of the girder  3  and the rope  10   b  is locked at its opposite ends to the drums  9   a  and  9   b  and engaged at its intermediate portion with the trolley  20  via the tip of the boom  4  and since the trolleys  19  and  20  are interconnected through a rope  17 . 
     The catenary-trolley drums  9   a  and  9   b  are adapted to be rotated in synchronization with rotation of the main-trolley drum  13 . The first catenary trolley  19  follows after the main trolley  5  so as to be positioned intermediately between the base end of the girder  3  and the trolley  5 . The second catenary trolley  20  follows after the main trolley  5  so as to be positioned intermediately between the tip end of the boom  4  and the trolley  5 . 
     The catenary trolleys  19  and  20  have rollers (not shown) pivoted to the trolleys  19  and  20  to support the main-trolley-traversing ropes  14   a  and  14   b  from below, respectively. The roller pivoted to the trolley  19  serves to suppress any excessive loosening of the rope  14   a  between the base end of the girder  3  and the trolley  5 . The roller pivoted to the trolley  20  serves to suppress any excessive loosening of the rope  14   b  between the tip of the boom  4  and the trolley  5 . 
     In recent years, there is a trend of increased traverse distance of the main trolley  5  as well as increased lift of the head block  6  in such container crane in association with a tendency of building larger-sized ships V. 
     In the conventional container crane, however, the block-lifting ropes  16   a  and  16   b  are wound on sheaves  18  pivotally supported at four corners of the block  6  to have eight turns in total so as to suspend the block  6  from the trolley  5 . Therefore, increased traverse distance of the main trolley  5  and/or increased lift of the head block  6  will lead to prolongation of the block-lifting ropes  16   a  and  16   b  and increase in size of the block-lifting drums  15   a  and  15   b . This may disadvantageously result in increase in weight of the system above the traveler  2  and/or difficulties in maintenance and inspection of the ropes  16   a  and  16   b.    
     The present invention was made to solve the above problems and has its major object to provide a hoist which is light in weight and compact in size. 
     BRIEF SUMMARY OF THE INVENTION 
     According to a hoist of the invention drums with independent drive sources are mounted on a trolley and an unwound end of the head-block-lifting rope wound around each of the drums is locked on a suspension piece of a container, which suppress any need of the ropes in longer length and the drums in larger size. 
     According to a hoist of the invention sun gears, carriers and planetary gears in each of the drums as well as internal teeth in each of the drums for integral rotation with the drum provide a speed reducing mechanism for transmitting rotation of the drive source to the drum, which contributes to make the entire hoist compact in size. 
     According to a hoist of the invention provided between two drums is a differential gear mechanism for transmitting rotation of drums to an output shaft. Rotation of a drive shaft of the differential gear mechanism may be suppressed to synchronize rotation of the two drums. 
     According to a hoist of the invention provided between two drums is a differential gear mechanism for transmitting rotation of the two drums to an output shaft. The drive shaft of the differential gear mechanism is rotated to vary rotation of the two drums relatively to each other. 
     According to a hoist of the invention when the trolley is to be accelerated, a link is displaced in position in a predetermined direction by an actuator. The positional displacement of the link is transmitted to two paired drums via torque arms so that the drums positioned,ahead in the moving direction of the trolley are rotated in rope-winding direction and the drums positioned behind in the moving direction of the trolley are rotated in rope-unwinding direction. As a result, tensions on the ropes at positions ahead and behind in the moving direction of the trolley are adjusted to apply a force directed in the moving direction of the trolley on the suspension piece. 
     When the trolley is to be decelerated, the link is displaced in position in a direction opposite to the direction during the acceleration. The positional displacement of the link is transmitted to the two paired drums via the torque arms. The drums positioned ahead in the moving direction of the trolley are rotated in rope-unwinding direction and the drums positioned behind in the moving direction of the trolley are rotated in rope-winding direction. As a result, tensions on the ropes positioned ahead and behind in the moving direction of the trolley are adjusted to apply a force directed in a direction opposite to the moving direction of the trolley on the suspension piece of the container. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a general, side elevation showing a container crane; 
     FIG. 2 is,a perspective view showing a head block lift, a boom derrick and a trolley traverser relating to the container crane shown in FIG. 1; 
     FIG. 3 is a sectional view of a drum in a first embodiment of the invention; 
     FIG. 4 is a view looking in the direction of arrows IV in FIG. 3; 
     FIG. 5 is a view looking in the direction of arrows V in FIG. 3; 
     FIG. 6 is a right side elevation of a trolley with the drums shown in FIG. 3; 
     FIG. 7 is a plan view of the trolley shown in FIG. 6; 
     FIG. 8 is a rear view of the trolley shown in FIG. 6; 
     FIG. 9 is a sectional view of a drum using a variation of the speed reducing mechanism; 
     FIG. 10 is a view looking in the direction of arrows X in FIG. 9; 
     FIG. 11 is a view looking in the direction of arrows XI in FIG. 9; 
     FIG. 12 is a sectional view of a drum and a planetary gear mechanism in a second embodiment of the invention; 
     FIG. 13 is a sectional view of a differential gear mechanism in the second embodiment of the invention; 
     FIG. 14 is a right side elevation of the trolley with the drums of FIG.  12  and the differential gear mechanisms of FIG. 13; 
     FIG. 15 is a plan view of the trolley shown in FIG. 14; 
     FIG. 16 is a diagram on posture of a container; 
     FIG. 17 is a sectional view showing a drum in a third embodiment of the invention; 
     FIG. 18 is a view looking in the direction of arrows XVIII in FIG. 17; 
     FIG. 19 is a view looking in the direction of arrows XIX in FIG. 17; 
     FIG. 20 is a right side elevation of a link-mechanism in a third embodiment of the invention; 
     FIG. 21 is a right side elevation of a trolley with the drums of FIG.  17  and the link mechanisms of FIG. 20; and 
     FIG. 22 is a plan view of the trolley shown in FIG.  21 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the invention will be described in conjunction with the attached drawings. 
     FIGS. 3 to  8  represent a first embodiment of the invention in which the same components as in FIGS. 1 and 2 are referred to by the same reference numerals. 
     The hoist comprises first, second, third and fourth hollow drums R 1 , R 2 , R 3  and R 4  each having opposite openings on opposite sides A and B, a drive shaft  25  extending through one of the openings and a fixed shaft  26  extending through the other opening coaxially of the shaft  25 . Each of the drums further has therein first and second rotation shafts  27  and  28 , first and second sun gears  29  and  30 , first and second internal teeth  31  and  32 , first and second carriers  33  and  34  and first and second planetary gears  35  and  36 . 
     Each of the drums R 1 , R 2 , R 3  and R 4  comprises a cylindrical drum body  38  which extends substantially horizontally and which has a rope groove  37  formed on an outer surface of the drum body  38 , a flange  39  coaxially bolted to an end surface of the drum body  38  facing to the side A, a cylindrical journal  40  contiguous with the flange  39  and coaxially extending outwardly of the drum body  38 , a flange  41  coaxially bolted to the other end surface of the drum body  38  facing to the other side B and a cylindrical hub  42  contiguous with the flange  41  and coaxially extending inwardly of the drum body  38 . 
     The drum body  38  is peripherally rotatably supported by a bearing  43  which circumscribes the journal  40 , a bracket  44  on which the bearing  43  is mounted, a bearing  45  which inscribes the hub  42  and circumscribes the fixed shaft  26  and a bracket  46  to which the shaft  26  is fixed. 
     The journal  40  is inscribed via a bearing  47  by the drive shaft  25 . 
     The drive shaft  25  is connected at its one end facing to the side A with an output shaft of a drive source  57  such as a motor. 
     The drive shaft  25  is formed at its other end facing to the other side B with a recess  48  into which the first rotation shaft  27  is coaxially fitted at its end facing to the side A. The rotation shaft  27  is coaxially fitted at its other end facing to the other side B, via a bearing  50 , into a recess  49  on an end of the rotation shaft  28  facing to the side A. Thus, the drive shaft  25  and rotation shaft  27  can be peripherally rotated relative to the drum body and to the rotation shaft  28 . 
     The rotation shaft  28  is fitted at its other end facing to the side B, via a bearing  52 , into a recess  51  on an end of the fixed shaft  26  facing to the side A. Thus, the rotation shaft  28  can be peripherally rotated relative to the rotation and fixed shafts  27  and  26 . 
     The sun gears  29  and  30  are fitted over intermediate portions of the rotation shafts  27  and  28 , respectively. 
     The internal teeth  31  and  32  are formed on an inner surface of the drum body  38  to peripherally surround the sun gears  29  and  30 , respectively. 
     The first carrier  33  is disposed on the side B with respect to the first sun gear  29  and is fitted into an end of the second rotation shaft  28  facing to the side A so that the carrier  33  can be rotated together with the rotation shaft  28  relative to the drum body. 
     The second carrier  34  is disposed on the side B with respect to the second sun gear  30  and is fitted into an end of the fixed shaft  26  facing to the side A. 
     The first carrier  33  pivotally supports, as shown in FIG. 4, via bearings  53  three first planetary gears  35  which in turn are meshed with the first sun gear  29  and first internal teeth  31 . The second carrier  34  pivotally supports, as shown in FIG. 5, via bearings  54  three second planetary gears  36  which in turn are meshed with the second sun gear  30  and the second internal teeth  32 . 
     In the hoist shown in FIGS. 3 to  8 , the drive source  57  is actuated so as to transmit its rotation power to the fixed shaft  26  via the drive shaft  25 , the rotation shaft  27 , the sun gear  29 , the planetary gear  35 , the carrier  33 , the rotation shaft  28 , the sun gear  30 , the planetary gear  36  and the carrier  34 . 
     In this case, however, since the drum body of each of the drums R 1 , R 2 , R 3  and R 4  is pivotally supported on the brackets  44  and  46  via the bearings  43  and  45  and the carrier  34  is constrained from peripheral displacement by the bracket  46  via the fixed shaft  26 , the rotating power of the sun gear  30  is transmitted via the planetary gear  36  to the internal teeth  32  so that at the number of rotations corresponding to gear ratio of the internal teeth  32  to the sun gear  30 , the drum body is rotated in the direction opposite to that of the sun gear  30 . 
     The carrier  33  is relatively rotated in opposite direction to that of the drum body so that, at the number of rotations corresponding to gear ratio of the internal teeth  31  to the sun gear  29 , the carrier  33  is rotated in the same direction as that of the sun gear  29 . 
     As a result, with respect to the drive sources  57 , the drums R 1 , R 2 , R 3  and R 4  are driven with reduced speed at the number of rotations corresponding to gear ratio of a first half of the speed reducing mechanism (which comprises the sun gear  29 , the carrier  33 , the planetary gear  35  and the internal teeth  31 ) and a second half of the speed reducing mechanism (which comprises the sun gear  30 , the carrier  34 , the planetary gear  36  and the internal teeth  32 ). 
     The drums R 1 , R 2 , R 3  and R 4  are installed at right land- and seaward positions and left land and seaward positions, respectively, on the trolley  55  which traverses along the girder  3  and boom  4  of the container crane (long beam of the loading and unloading facility). 
     Wound around each of the drums R 1 , R 2 , R 3  and R 4  is a head-block lifting rope  56 . An unwound end of the rope  56  is locked on the head block  6  on which in turn the spreader  7  engageable with the container C (See FIG. 1) is mounted. 
     Therefore, concurrent actuation of the drive sources  57  of the drums R 1 , R 2 , R 3  and R 4  causes the drums R 1 , R 2 , R 3  and R 4  to be rotated in normal or reverse direction so that the ropes  56  are wound or unwound in association with the rotation of the drums R 1 , R 2 , R 3  and R 4 . As a result, the head block  6  is lifted up or down relative to the trolley  55 . 
     As described above, in the hoist shown in FIGS. 3 to  8 , the rope  56  is wound on each of the drums R 1 , R 2 , R 3  and R 4 , and the unwound end of the rope  56  is locked on the head block  6 . Therefore, any increase in length of the ropes  56  and any increase in size of the drums R 1 , R 2 , R 3  and R 4  can be suppressed even when traversing distance of the trolley  55  is prolonged and/or the lift of the head block  6  is increased. 
     As a result, the head-block lifting ropes  56  can be made short in length and have no turns due to rope sheaves so that the ropes have improved durability, can undergo maintenance and inspection much easier and can be replaced with reduced cost, resulting in reduction of the running cost. 
     The entire hoist can be made light in weight and compact in size since each of the drums R 1 , R 2 , R 3  and R 4  has two sets of speed reducing mechanisms comprising the sun gears  29  and  30 , the carriers  33  and  34 , the planetary gears  35  and  36  and the internal teeth  31  and  32 , respectively. 
     Each of the drums R 1 , R 2 , R 3  and R 4  is rotated by the independent drive source  57 . As a result, the container C suspended via the head block  6  and the spreader  7  as shown in FIG. 1 can be maintained in proper posture by adjusting wound or unwound amount of each of the ropes  56 . Moreover, the head block  6 , the spreader  7  and the container C engaged with the spreader  7  can be refrained from being vibrated. 
     FIGS. 9 to  11  represent a variation of speed reducing mechanism associated with the drums R 1 , R 2 , R 3  and R 4 . In these figures, the same components as in FIGS. 3 to  8  are referred to by the same reference numerals. 
     This speed reducing mechanism for each of the drums R 1 , R 2 , R 3  and R 4  comprises a drive shaft  25  extending through one of openings of the drum and a fixed shaft  26  extending through the other opening coaxially of the shaft  25  as well as a rotation shaft  58 , first and second sun gears  29  and  30 , first and second internal teeth  31  and  32 , first and second carriers  59  and  60  and first and second planetary gears  35  and  36  all of which are installed in the drum. 
     The drive shaft  25  is formed at its end facing to the side B with a recess  48  into which the rotation shaft  58  is coaxially fitted at its end facing to the side A. The rotation shaft  58  is coaxially fitted at its end facing to the side B, via a bearing  52 , into a recess  51  formed on an end of the fixed shaft  26  facing to the side A so that the drive shaft  25  and the rotation shaft  58  can be peripherally rotated relative to the drum and to the fixed shaft  26 . 
     The first sun gear  29  is fitted over a longitudinally intermediate portion of the rotation shaft  58  and the second sun gear  30  is loosely fitted over an end of the fixed shaft  26  facing to the side A. 
     The first carrier  59  is loosely fitted over an engaged portion of the drive shaft  25  with the fixed shaft  26  on the side B with respect to the first sun gear  29 . The second sun gear  30  is fitted into the carrier  59  so as to be rotated integrally with the latter. 
     The second carrier  60  is loosely fitted over an intermediate portion of the fixed shaft  26  on the side B with respect to the second sun gear  30 . 
     The first carrier  59  pivotally supports, as shown in FIG. 10, via bearings  53  three first planetary gears  35  which in turn are meshed with the first sun gear  29  and the first internal teeth  31 . The second carrier  60  pivotally supports, as shown in FIG. 11, via bearings  54  three second planetary gears  36  which in turn are meshed with the second sun gear  30  and the second internal teeth  32 . 
     In any of the drums R 1 , R 2 , R 3  and R 4  each using the speed reducing mechanism shown in FIGS. 9 to  11 , the drive source is actuated so as to transmit its rotation power to the fixed shaft  26  via the shafts  25  and  58 , the gears  29  and  35 , the carrier  59 , the gears  30  and  36  and the carrier  60 . 
     In this case, however, since the drum body of each of the drums R 1 , R 2 , R 3  and R 4  is pivotally supported on the brackets  44  and  46  via bearings  43  and  45  and the carrier  34  is constrained from peripheral displacement by the bracket  46  via the fixed shaft  26 , rotating power of the second sun gear  30  is transmitted via the planetary gear  36  to the internal teeth  32  so that at the number of rotations corresponding to the gear ratio of the internal teeth  32  to the sun gear  30 , the drum body is rotated in the direction opposite to that of the sun gear  30 . 
     The carrier  59  is relatively rotated in opposite direction to that of the drum body so that, at the number of rotations corresponding to gear ratio of the internal teeth  31  to the sun gear  29 , the carrier  59  is rotated in the same direction as that of the sun gear  29 . 
     As a result, with respect to the drive sources, the drums R 1 , R 2 , R 3  and R 4  are driven with reduced speed at the number of rotations corresponding to gear ratio of a first half of the speed reducing mechanism (which comprises the sun gear  29 , the carrier  59 , the planetary gear  35 , the internal teeth  31 ) to a second half of the speed reducing mechanism (which comprises the sun gear  30 , the carrier  60 , the planetary gear  36  and the internal teeth  32 ). 
     FIGS. 12 to  16  represent a second embodiment of the invention in which the same components as in FIGS. 3 to  11  are referred to by the same reference numerals. 
     This hoist comprises first, second, third and fourth drums R 1 , R 2 , R 3  and R 4 . Each of the drums comprises a drive shaft  25  extending through one of openings of the drum and a fixed shaft extending through the other opening of the drum coaxially of the drive shaft  25  as well as first and second rotation shafts  27  and  28 , first and second sun gears  29  and  30 , first and second internal teeth  31  and  32 , first and second carriers  33  and  34 , first and second planetary gears  35  and  36  all of which are installed in the drum. The drums R 1 , R 2 , R 3  and R 4  further comprise planetary gear mechanisms G 1 , G 2 , G 3  and G 4 , respectively. Furthermore, a right-side differential gear mechanism GR is arranged for the drums R 1  and R 2  and a left-side differential gear mechanism GL, for the drums R 3  and R 4 . 
     The drums R 1 , R 2 , R 3  and R 4  are installed at right land- and seaward positions and left land- and seaward positions, respectively, on a trolley  55  which traverses along a girder  3  and boom  4  of the container crane (long beam of the loading and unloading facility). 
     Wound around each of the drums R 1 , R 2 , R 3  and R 4  is a head-block lifting rope  56 . An unwound end of the rope  56  is locked on a head block  6  on which in turn a spreader  7  engageable with the container C is mounted. 
     The planetary gear mechanisms G 1 , G 2 , G 3  and G 4  are disposed on the side A with respect to the brackets  44  which support the drums R 1 , R 2 , R 3  and G 4 , respectively. 
     Each of the planetary gear mechanisms G 1 , G 2 , G 3  and G 4  comprises a cylindrical casing  85  with a bolted cover member  88  on the side A and with a flange  83  formed on the other side B, a drive shaft  74  extending through a hub  87  of the cover member  88 , a bearing  90  inscribing the hub  87  and pivotally supporting the drive shaft  74 , a tubular support seat  86  fitted in an opening  84  on an intermediate portion of the casing  85  and bolted to the casing  85 , an input/output shaft  82  extending through the seat  86 , a bearing  89  inscribing the seat  86  and pivotally supporting the shaft  82  as well as a rotation shaft  75 , a sun gear  76 , internal teeth  77 , a carrier  78 , a planetary gear  79  and large and small bevel gears  80  and  81  all of which are installed in the casing  85 . 
     The flange  83  on the casing  85  is bolted to the bracket  44  so that the drive shaft  74  is positioned coaxially of the drive shaft  25  of the drum. 
     The rotation shaft  75  is coaxially fitted at its end facing to the side A into an end of the drive shaft  74  facing to the side B. The other end of the rotation shaft  75  facing to the side B is pivotally supported on the drive shaft  25  of the drum so as to be peripherally rotated. The sun gear  76  is fitted over an intermediate portion of the rotation shaft  75 . 
     The internal teeth  77  are integrally formed on an inner surface of the casing  85  so as to surround the sun gear  76 . 
     The carrier  78  is fitted over one end of the drive shaft  25  of the drum facing to the side A. 
     The planetary gear  79  is pivotally supported on one end of the carrier  78  facing to the side A so as to be meshed with the sun gear  76  and the internal teeth  77 . 
     The large bevel gear  80  is integrally formed on a periphery of the carrier  78  facing to the side B. 
     The small bevel gear  81  is fitted over the input/output shaft  82  so as to be meshed with the large bevel gear  80 . 
     Further, output shaft of a drive source  57  such as a motor having braking performance is connected to an end of the drive shaft  74  facing to the side A. 
     In any of the planetary gear mechanisms G 1 , G 2 , G 3  and G 4  as described above, rotating power of the drive source  57  is transmitted to the carrier  78  via the drive shaft  74 , the rotation shaft  75 , the sun gear  76  and the planetary gear  79  and the drive shaft  25  of the drum is rotated together with the carrier  78  at the number of rotations corresponding to gear ratio of the internal teeth  77  to the sun gear  76 . 
     Moreover, the input/output shaft  82  is rotated at the number of rotations corresponding to gear ratio of the small bevel gear  81  to the large bevel gear  80 . 
     Each of the right and left differential gear mechanisms GR and GL comprises a substantially cylindrical casing  103  with flanges  101  each formed on one and the other sides D and E and having a hub  102  at an intermediate portion of the casing, bearing housings  105  each having a conical flange  104  coaxially bolted to the flange  101  of the casing  103 , a drive shaft  94  extending through the hub  102  of the casing  103 , a bearing  106  inscribing the hub  102  and pivotally supporting the drive shaft  94 , a small bevel gear  95  positioned in the casing  103  and fitted over a tip of the drive shaft  94 , output shafts  100  extending through the bearing housings  105  in a direction perpendicular to the drive shaft  94 , bearings  107  each inscribing the bearing housing  105  and pivotally supporting the output shaft  100 , a large bevel gear  96  with a boss  96   a  fitted over the shaft  100  on the side D via a bearing  115  and meshed with the small bevel gear  95 , a cover member  112  having a boss  113  fitted over the output shaft  100  on the other side E via a bearing  115 , a gear box  111  positioned between and bolted to the bevel gear  96  and the cover member  112 , a support shaft  99  extending in a direction perpendicular to the output shafts  100  and fitted at their opposite ends into openings  110  formed on the gear box  111 , bevel gears  98   a  and  98   b  pivotally supported on the support shaft  99  via bearings  114  and bevel gears  98   c  and  98   d  each fitted over a tip of the output shaft  100  and meshed with the bevel gears  98   a  and  98   b.    
     The right differential gear mechanism GR is installed between the drums R 1  and R 2  on the trolley  55  and its output shafts  100  are connected to the input/output shaft  82   s  of the planetary gear mechanisms G 1  and G 2 . 
     The left differential gear mechanism GL is installed between the drums R 3  and R 4  on the trolley  55  and its output shafts  100  are connected to the input/output shafts  82  of the planetary gear mechanisms G 3  and G 4 . 
     Further, the drive shaft  94  of each of the differential gear mechanisms GR and GL is connected at its base end with an output shaft of a differential-gear drive source  97  such as a motor having braking performance. 
     In each of the differential gear mechanisms GR and GL as disclosed above, rotating power of the drive source  97  is transmitted to each of the output shafts  100  via the drive shaft  94 , the bevel gears  95  and  96 , the gear box  111  and the bevel gears  98   a ,  98   b ,  98   c  and  98   d , so that the input/output shafts  82  of the planetary gear mechanisms is rotated together with the output shafts  100 . 
     When rotation of the output shaft of the drive source  97  is braked, the output shafts  100  are interlocked with each other so that the input/output shafts  82  of the planetary gear mechanisms are rotated in synchronization. 
     In the hoist shown in FIGS. 12 to  16 , actuation of the drive sources  57  for rotation of the drums R 1 , R 2 , R 3  and R 4  in normal or reverse direction causes the ropes  56  to be wound or unwound so that the head block  6  is lifted up or down relative to the trolley  55 . 
     In this case, if the rotation of the output shaft of the drive source  97  for the right differential gear mechanism GR is braked, the output shafts  100  of the gear mechanism GR with which the input/output shafts  82  of the planetary gear mechanisms G 1  and G 2  are connected are interlocked with each other, which causes the drums R 1  and R 2  to be rotated at equal speed so that wound or unwound amounts of the ropes  56  of the drums R 1  and R 2  agree with each other. 
     If the rotation of the output shaft of the drive source  97  for the left differential gear mechanism GL is braked, the output shafts  100  of the gear mechanism GL with which the input/output shafts  82  of the planetary gear mechanisms G 3  and G 4  are connected are interlocked with each other, which causes the drums R 3  and R 4  to be rotated at equal speed so that wound or unwound amounts of the ropes  56  of the drums R 3  and R 4  agree with each other. 
     If the braking of the output of the drive source  97  for the right differential gear mechanism GR is released, the drums R 1  and R 2  are driven at different numbers of rotations by the independent drive sources  57 , respectively. Similarly, if the braking of the output shaft of the drive source  97  for the left differential gear mechanism GL is released, the drums R 3  and R 4  are driven at different numbers of rotations by the independent drive sources  57 , respectively. As a result, wound or unwound amounts of the ropes  56  for the drums R 1 , R 2 , R 3  and R 4  may be adjusted independently with each other to maintain the container C suspended via the head block  6  and the spreader  7  in proper posture. 
     Further, when the respective drive sources  97  are properly operated while the braking of the output shafts of the drive sources  97  is released, relative number of rotations of the drums R 1  and R 2  installed on the right side of the trolley  55  and relative number of rotations of the drums R 3  and R 4  installed on the left side of the trolley  55  can be changed with fine adjustment. As a result, fine adjustment for the posture of the container C can be made which is suspended via the head block  6  and the spreader  7 . 
     More specifically, when the container C is to be lifted up or down without controlling the posture of the container C, the drive sources  97  of the differential gear mechanisms GR and GL are braked to constrain the rotation of the drive sources  97  while the brakes of the drums R 1 , R 2 , R 3  and R 4  are released, Under such conditions, the drive sources  57  for the drums are rotated in the same direction. 
     As a result, the drums R 1  and R 2  are rotated in synchronization and a wound/unwound amount of the headblock-lifting rope  56  for the drum R 1  agrees with that of the rope  56  for the drum R 2  while the drums R 3  and R 4  are rotated in synchronization and a wound/unwound amount of the head-block-lifting rope  56  for the drum R 3  agrees with that of the rope  56  for the drum R 4 . Thus, the container C is lifter up or down. 
     When list (tilt about horizontal axis X in FIG. 16) of the container C is to be controlled, for example the brakes of the drive sources  97  of the differential gear mechanisms GR and GL are released to allow the rotation of the drive sources  97  and the drive sources  57  for the drums R 2  and R 4  are braked to constrain the rotation of the drive sources  57  for the drums R 2  and R 4  while the brakes of the drive sources  57  for the drums R 1  and R 3  are released. In such conditions, the drive sources  57  for the drums R 1  and R 3  are rotated in the same direction. 
     As a result, the drums R 1  and R 3  are rotated to wind or unwind the head-block-lifting ropes  56  for the drums R 1  and R 3  so that the posture of the container C is controlled. 
     When trim (tilt about horizontal axis Y in FIG. 16) of the container C is to be controlled, for example the brakes of the drive sources  97  of the differential gear mechanisms GR and GL are released to allow the rotation of the drive sources  97  and, with the brakes of the drive sources  57  for the drums R 1 , R 2 , R 3  and R 4  being released, the drive sources  57  for the drums R 1  and R 2  are rotated in the same direction while the drive sources  57  for the drums R 3  and R 4  are rotated in a direction reverse to the rotation direction of the drive sources  57  for the drums R 1  and R 2 . 
     As a result, the drums R 1  and R 2  are rotated to wind or unwind the head-block-lifting ropes  56  for the drums R 1  and R 2  while the drums R 3  and R 4  are rotated in a direction reverse to that of the drums R 1  and R 2  to unwind or wind the ropes  56  for the drums R 3  and R 4  so that the posture of the container C is controlled. 
     When skew (rotation about vertical axis Z in FIG. 16) of the container C is to be controlled, for example the brakes of the drive sources  97  of the differential gear mechanisms GR and GL are released to allow the rotation of the drive sources  97  and the drive sources  57  for the drums R 2  and R 3  are braked to constrain the rotation of the drive sources  57  for the drums R 2  and R 3  while the brakes of the drive sources  57  for the drums R 1  and R 4  are released. In such conditions, the drive sources  57  for the drums R 1  and R 4  are rotated in the same direction. 
     As a result, the drums R 1  and R 4  are rotated to wind or unwind the head-block-lifting ropes  56  for the drums R 1  and R 4  so that the posture of the container C is controlled. 
     When any swinging of the container C in the traverse direction (i.e., the direction of the axis X in FIG. 16) is to be suppressed, for example, just like the case of the above-mentioned list control of the container C, the ropes  56  for the drums R 1  and R 3  are wound or unwound while, to the contrary, the ropes  56  for the drums R 2  and R 4  are unwound or wound, so that horizontal center of gravity of the container C is controlled. 
     When any swinging of the container C in the skew direction is to be suppressed, for example, just like the case of the above-mentioned skew control of the container C, the ropes  56  for the drums R 1  and R 4  are wound or unwound to control rotary moment of the container C. 
     FIGS. 17 to  22  represent a third embodiment of the present invention. In the figures, the same components as in FIGS. 3 to  16  are referred to by the same reference numerals. 
     This hoist comprises first, second, third and fourth drum R 1 , R 2 , R 3  and R 4 . Each of the drums comprises a drive shaft  25  extending through one of openings of the drum and a torque arm shaft  63  extending through the other opening of the drum coaxially of the drive shaft  25  as well as first and second rotation shafts  27  and  28 , first and second sun gears  29  and  30 , first and second internal tooth ring  61  and  62 , first and second carrier  33  and  34 , first and second planetary gears  35  and  36  all of which are installed in the drum. The hoist further comprises torque arms  64  and  65 , link mechanisms L and cylinders  73 . 
     Each of the drums R 1 , R 2 , R 3  and R 4  is pivotally supported for peripheral rotation by a bearing  43  which circumscribes a journal  40 , a bracket  44  in which the bearing  43  is fitted, a bearing  45  which inscribes a hub  42  and circumscribes the torque arm shaft  63  and a bracket  67  in which a bearing  66  is fitted to circumscribe an end portion of the torque arm shaft  63  closer to outer end of the drum. 
     Separate head-block-lifting ropes  56  are wound around the drums R 1  and R 3  and around the drums R 2  and R 4  in mutually opposite directions with respect to axes of the drums. 
     Unwound ends of the ropes  56  suspended from the drums R 1  and R 3  are locked on a landward end of the head block  6  while unwound ends of the ropes  56  suspended from the drums R 2  and R 4  are locked on a seaward end of the head block  6 . 
     The drive shaft  25  is connected at its end facing to the side A to an output shaft of the drive source  57 , It is set such that rotation of the drive sources  57  for the drums R 1  and R 3  in normal or reverse direction is opposite that for the drums R 2  and R 4 . 
     The second rotation shaft  28  extends at its end facing to the side B into a recess  6 , formed on an end of the torque arm shaft  63  facing to the side A via a bearing  69  so that the second rotation shaft  28  can be peripherally rotated with respect to the first rotation shaft  27  and the torque arm,shaft  63 . 
     The first internal tooth ring  61  is arranged to peripherally enclose the first sun gear  29  and is bolted to a disk  71  which is pivotally supported on the second rotation shaft  28  via a bearing  70 . 
     The second internal tooth ring  62  is arranged to peripherally enclose the second sun gear  30  and is bolted to the disk  71  and to a flange  72  continuous with a hub  42 . 
     The first carrier  33  pivotally supports, as shown in FIG. 18, via bearings  53  three first planetary gears  35  which are meshed with the first sun gear  29  and with the first internal tooth ring  61 . 
     The second carrier  34  is fitted to an end of the torque arm shaft  63  facing to the side A. The second carrier  34  pivotally supports, as shown in FIG. 19, via bearings  54  three second planetary gears  36  which are meshed with the second sun gear  30  and with the second internal tooth ring  62 . 
     The torque arm  64  is mounted on an end of the torque arm shaft  63  of each of the drums R 1  and R 3  facing to the side B such that its tip end is directed downward. 
     The torque arm  65  is mounted on an end of the torque arm shaft  63  of each of the drums R 2  and R 4  facing to the side B such that it is in parallel with the torque arm  64  and its tip end is directed downward. 
     The link mechanism L comprises a lever  22  positioned between the drums R 1  and R 2  or the drums R 3  and R 4  and having its upper end pivoted to a beam  21  on the trolley  55 , a pair of first links  23  pivoted to an intermediate portion of the lever  22  with their base ends overlapped, and a pair of second links  24  each connected at its one end via load cell  91  to a tip end of the corresponding first link  23  and pivoted at its other end to the tip end of the torque arm  64  or  65 . 
     The cylinder  73  has its piston rod pivoted to a lower end of the lever  22  and is pivotally supported on the trolley  55  such that its housing is approximately in parallel with the first links  23 . Expansion and contraction of the cylinder  73  causes the first links  23  to be displaced in landward or seaward direction. 
     In the hoist shown in FIGS. 17 to  22 , the drive source  57  is actuated so as to transmit its rotation power to the torque arm shaft  63  via the drive shaft  25 , the first rotation shaft  27 , the first sun gear  29 , the first planetary gear  35 , the first carrier  33 , the second rotation shaft  28 , the second sun gear  30 , the second planetary gear  36  and the second carrier  34 . 
     In this case, however, the drum body of each of the drums R 1 , R 2 , R 3  and R 4  is pivotally supported on the brackets  44  and  67  via the bearings  43  and  66  and the second carrier  34  is constrained from peripheral displacement by the cylinder  73  via the torque arm shaft  63  and the torque arms  64  and  65 . As a result, rotation power of the second sun gear  30  is transmitted via the planetary gear  36  to the second internal tooth ring  62  so that the drum body is rotated in a direction opposite to that of the second sun gear  30  at the number of rotations corresponding to gear ratio of the second internal tooth ring  62  to the second sun gear  30 . 
     Also, since the first carrier  33  is rotated relatively in reverse direction to that of the drum, the first carrier  33  is rotated in the same direction as that of the first sun gear  29  at the number of rotations corresponding to gear ratio of the first internal tooth ring  61  to the first sun gear  29 . 
     As a result, with respect to the drive source  57 , the drums R 1 , R 2 , R 3  and R 4  are driven with reduced speed at the number of rotations corresponding to gear ratio of a first half of the speed reducing mechanism (which comprises the sun gear  29 , the carrier  33 , the planetary gear  35  and the internal tooth ring  61 ) and a second half of the speed reducing mechanism (which comprises the sun gear  30 , the carrier  34 , the planetary gear  36  and the internal tooth ring  62 ). 
     Further, since rotation of the drive sources  57  for the drums R 1  and R 3  in normal or reverse direction is set opposite to that for the drums  12  and R 4  in normal or reverse direction, the drums R 1  and R 3  and the drums R 2  and R 4  are differently rotated from one another in axes of the drums. 
     As a result, the ropes  56  are wound around or unwound from the drums R 1 , R 2 , R 3  and R 4  and the head block  6  is moved up or down. 
     When the trolley  55  not in operation is to be traversed in a seaward direction or when the trolley traversing in a landward direction is to be stopped, fluid pressure is applied to a head-side fluid chamber of the cylinder  73  so that the cylinder  73  is expanded. As shown in FIG. 20, the expansion of the cylinder  73  is transmitted from the first and second links  23  and  24  to the torque arms  64  and  65  so that the torque arms  64  and  65  are rotated clockwise in FIG. 20 via the links  23  and  24 . As a result, a rotating power is transmitted to the drums R 1 , R 2 , R 3 , and R 4  via the torque arm  63 , the carrier  34 , the planetary gear  36  and the internal tooth ring  62 , and the head-block lifting ropes  56  locked on the seaward end of the head block  6  are wound up on the drums R 2  and R 4  while the ropes  56  locked on the landward end of the head block  6  are unwound from the drums R 1  and R 3 . 
     As a result, tensions on these ropes  56  are adjusted to apply a force directed in seaward direction on the head block  6 , which can suppress any swinging of the head block  6  caused by traversing or stopping of the trolley  55 . 
     When the trolley  55  not in operation is accelerated to be traversed in the landward direction or when the trolley  55  traversing in the seaward direction is decelerated to be stopped, fluid pressure is applied to a rod-side fluid chamber of the cylinder  73  so that the cylinder  73  is contracted. As shown in FIG. 20, the contraction of the cylinder  73  is transmitted from the first and second links  23  and  24  to the torque arms  64  and  65  so that the torque arms  64  and  65  are rotated counterclockwise in FIG. 20 via the links  23  and  24 . As a result, a rotating power is transmitted to the drums R 1 , R 2 , R 3 , and R 4  via the torque arm shaft  63 , the carrier  34 , the planetary gear  36 , and the internal tooth ring  62 . The head-block lifting ropes  56  locked on the seaward end of the head block  6  are unwound from the drums R 2  and R 4 , and the ropes  56  locked on the landward end of the head block  6  are wound up on the drums R 1  and R 3 . 
     As a result, tensions of the these ropes  56  are adjusted to apply a force directed in the landward direction on the head block  6 , which can suppress any swinging of the head block  6  caused by traversing or stopping of the trolley  55 .