Patent Publication Number: US-10787348-B2

Title: Chain block and built-in cover

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a U.S. national stage of application No. PCT/JP2016/083343, filed on Nov. 10, 2016. Priority under 35 U.S.C.§ 119(a) and 35 U.S.C.§ 365(b) is claimed from Japanese Patent Applications No. 2015-221983 filed on Nov. 12, 2015, the disclosure of which is also incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a chain block used for work of discharging a cargo and to a built-in cover built in the chain block. 
     BACKGROUND ART 
     An electric chain block that moves up and down a load utilizing the driving force of a motor has a built-in gear unit including a plurality of gears, and the driving force is transmitted via the gear unit to a load sheave. For example, as disclosed in PTL 1, the gear unit is generally housed in a case. PTL 1 discloses a configuration that the gear unit is covered by a cover integrally formed with a gear case to prevent lack of lubricating oil around the gears. 
     CITATION LIST 
     Patent Literature 
     
         
         {PTL 1} Japanese Laid-Open Patent Application Publication No. 07-048093 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     As described above, in the configuration disclosed in PTL 1, the gear unit is covered by the cover integrally formed with the gear case to suppress scattering of liquid lubricating oil in a wide range to thereby achieve prevention of the lack of lubricating oil. However, in the case of employing such a configuration, if the gear ratio or the gear configuration is changed, the gap between the cover and the gear changes. This reduces the effect of preventing the lubricating oil from scattering to the surroundings, easily causing occurrence of lack of lubricating oil. 
     It is also conceivable to produce a gear case in a new configuration every time when the gear ratio or the gear configuration is changed, in order to prevent the lack of lubricating oil. However, in this case, it is necessary to change the facility for forming the gear case, for example, a metal mold for die-casting, unfavorably leading to increased cost. 
     Note that in the gear unit configured by combining a plurality of gears overlapped, it is often difficult to integrally form a cover with the gear case in a manner not to obstruct its assembly performance, the cover being effectively preventing scattering of the lubricating oil. 
     Besides, an example of changing the gear configuration is a case in which a load gear with a larger diameter is arranged to be coaxial with a pinion gear. In this case, the pinion gear is set to be located not at a position closer to an outer wall of the gear case as disclosed in PTL 1, but at a relatively center side of the gear case in order to make the gear case compact. A problem in such a case is that particularly the pinion gear is apt to lack lubricating oil, leading to a decrease in life of the chain block. This tendency becomes conspicuous, in particular, in the gears rotated at high speed including the pinion gear. 
     In particular, for some electric chain blocks, employment of not the liquid lubricating oil but grease is under consideration in order to facilitate maintenance. Also the electric chain block of such type is desirably configured to be able to re-supply the grease to the gears rotated at high speed including the pinion gear. 
     The present invention has been made in consideration of the above circumstances, and its object is to provide, without obstructing assembly performance of a gear unit, a chain block and a built-in cover which are capable of relatively easily preventing lack of lubricating oil even in a case where a gear ratio or a gear configuration is changed and in a case with gears rotated at high speed. 
     Solution to Problem 
     To solve the above problem, according to a first aspect of the present invention, there is a provided a chain block configured to move up and down a load via a chain wound around a load sheave member, by transmitting driving force generated by a motor unit to the load sheave member, the chain block including: a gear unit including a pinion gear configured to transmit the driving force generated by the motor unit, and a load gear coaxially and rotatably attached to the pinion gear and configured to rotate integrally with the load sheave member; a case body configured to house the gear unit and to be supplied with grease being semifluid or semisolid at a working temperature as a lubricant; and a built-in cover provided separately from the case body and arranged inside the case body, wherein: the built-in cover includes a first peripheral wall part configured to cover an outer peripheral side of the pinion gear, and a second peripheral wall part provided to be larger in diameter than the first peripheral wall part by covering a periphery of a first driven gear body, the first driven gear body including a first large-diameter driven gear meshing with the pinion gear and being larger in diameter than the pinion gear; and the built-in cover is provided in a circulation shape without a break by continuation of the first peripheral wall part and the second peripheral wall part. 
     Besides, in another aspect of the present invention, it is preferable in the above invention that the second peripheral wall part is formed with an opposed receiving part configured to be opposed to the first large-diameter driven gear while projecting toward a center side in a radial direction of the second peripheral wall part to hold the grease. 
     Besides, in another aspect of the present invention, it is preferable in the above invention that: the first driven gear body is provided with a first small-diameter driven gear coaxially and integrally with the first large-diameter driven gear; the gear unit is provided with a second driven gear body, and the second driven gear body is provided with a second large-diameter driven gear meshing with the first small-diameter driven gear; the built-in cover is provided with a third peripheral wall part configured to cover an outer peripheral side of the second large-diameter driven gear; and the third peripheral wall part is provided to be continuous with the first peripheral wall part and with the second peripheral wall part to provide the built-in cover in a circulation shape without a break. 
     Besides, according to a second aspect of the present invention, there is a built-in cover used for a chain block, housed in a case body housing a gear unit including a plurality of gears for transmitting driving force generated by a motor unit to a load sheave member, and provided separately from the case body, the built-in cover including: a first peripheral wall part configured to cover an outer peripheral side of a pinion gear of the gear unit; and a second peripheral wall part provided to be larger in diameter than the first peripheral wall part by covering a periphery of a first driven gear body, the first driven gear body including a first large-diameter driven gear meshing with the pinion gear and being larger in diameter than the pinion gear, wherein the built-in cover is provided in a circulation shape without a break by continuation of the first peripheral wall part and the second peripheral wall part. 
     Besides, in another aspect of the present invention, it is preferable in the above invention that the second peripheral wall part is formed with an opposed receiving part configured to be opposed to the first large-diameter driven gear while projecting toward a center side in a radial direction of the second peripheral wall part to hold the grease. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to relatively easily prevent lack of lubricating oil even in a chain block having gears rotating at high speed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating the whole configuration of a main body of a chain block according to an embodiment of the present invention; 
         FIG. 2  is an exploded perspective view illustrating a configuration around a gear unit and a body of the chain block illustrated in  FIG. 1 ; 
         FIG. 3  is a plan view illustrating a side where a gear case is attached, of the body included in the chain block illustrated in  FIG. 1 ; 
         FIG. 4  is a perspective view illustrating a gear box part side of the body included in the chain block illustrated in  FIG. 1 , and a view illustrating a state where a built-in cover is detached; 
         FIG. 5  is a perspective view illustrating a configuration of the built-in cover according to an embodiment of the present invention; and 
         FIG. 6  is a plan view illustrating a state where the built-in cover illustrated in  FIG. 5  is attached to the gear box part. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a chain block  10  according to a first embodiment of the present invention will be described referring to the drawings. Note that in the following description, an explanation will be given using an XYZ orthogonal coordinate system as needed. An X-direction in the XYZ orthogonal coordinate system is assumed to be an axial direction of a load sheave member  50  in  FIG. 2 , and an X1 side indicates a lower light side in  FIG. 2  and an X2 side indicates an upper left side opposite thereto. Further, a Z-direction indicates a direction in which the chain block  10  is suspended, and a Z1 side indicates a deep side of paper in  FIG. 1  and  FIG. 2  and a Z2 side indicates a near side of paper opposite thereto. Further, a Y-direction indicates a direction orthogonal to the X-direction and to the Z-direction, a Y1 side indicate an upper right side in  FIG. 2  and a Y2 side indicates a lower left side opposite thereto. 
     The chain block  10  in this embodiment can employ one using method, namely a normal suspension, of moving up and down a load in a state where a main body is attached to an upper part, and additionally employ another using method, namely a reverse suspension, of moving up and down a main body together with a load in a state where a hook is hooked on an engaging portion at an upper part. The reverse suspension is preferable for work of lifting up and installing equipment for illumination and sound at a place where attachment of the main body is difficult, such as a stage, concert hall, event hall or the like. 
     &lt;Regarding the Whole Configuration of the Chain Block  10 &gt; 
       FIG. 1  is a perspective view illustrating the whole configuration of a main body  11  of the chain block  10 .  FIG. 2  is an exploded perspective view illustrating a configuration around a gear unit  30  and a body  40  of the chain block  10 . As illustrated in  FIG. 1  and  FIG. 2 , the chain block  10  includes a motor unit  20 , the gear unit  30 , the body  40 , the load sheave member  50 , a control unit  60  and so on. 
     In the chain block  10  illustrated in  FIG. 1  and  FIG. 2 , the driving force from the motor unit  20  is transmitted to the gear unit  30 , reduced in speed at a predetermined reduction gear ratio, and then transmitted to the load sheave member  50  arranged in the body  40  to rotate the load sheave member  50 . 
     Here, around the load sheave member  50 , a not-illustrated load chain is wound, and the load chain is hoisted and lowered to relatively change the distance between a not-illustrated hook and the main body  11 . Under the above mentioned state, a load can be lifted up with respect to the main body  11  located above in the case of the normal suspension. Besides, the load can be lifted up together with the main body  11  in the case of the reverse suspension. 
     &lt;Regarding Configurations of the Gear Unit  30 , the Body  40 , and a Gear Case  70 &gt; 
     Next, the gear unit  30  will be described. As illustrated in  FIG. 2 , the gear unit  30  includes a pinion gear  31 , a first driven gear body  32 , a second driven gear body  33 , and a load gear  34 . The pinion gear  31  is coupled to a motor shaft (not illustrated) of the motor unit  20 . Further, the pinion gear  31  meshes with a first large-diameter driven gear  32   a  of the first driven gear body  32 . The first driven gear body  32  is integrally and coaxially provided with a first small-diameter driven gear  32   b  smaller in number of teeth and in diameter than the first large-diameter driven gear  32   a , in addition to the first large-diameter driven gear  32   a.    
     A second large-diameter driven gear  33   a  of the second driven gear body  33  meshes with the first small-diameter driven gear  32   b  (see later-described  FIG. 4  and  FIG. 6 ). The second driven gear body  33  is integrally and coaxially provided with a second small-diameter driven gear  33   b  smaller in number of teeth and in diameter than the second large-diameter driven gear  33   a , in addition to the second large-diameter driven gear  33   a.    
     Note that the second driven gear body  33  may be configured such that the second large-diameter driven gear  33   a  and the second small-diameter driven gear  33   b  are rotated together at all times, but may be configured such that they are separately formed and combined together having a friction clutch incorporated between them. In this case, the second driven gear body  33  is configured to have a clutch friction plate, a disc spring or the like, so that upon occurrence of an overload state, the second large-diameter driven gear  33   a  side is rotated but the rotation thereof is not transmitted to the second small-diameter driven gear  33   b  side, which is made to slip, thereby preventing an overload and the hoisting more than specified. 
     Further, the second driven gear body  33  may be configured to have a function of a mechanical brake. In this case, a ratchet tooth (not illustrated) is coaxially attached in addition to the second large-diameter driven gear  33   a  and the second small-diameter driven gear  33   b , and a claw member (not illustrated) for stopping rotation of the ratchet tooth in one direction while being pressed by a spring member is rotatably attached to a gear box part  41 . This makes it possible to constitute a mechanical brake that permits a rotation in one direction and prevents unintended reverse rotation. 
     Further, the load gear  34  meshes with the second small-diameter driven gear  33   b . The load gear  34  is provided to be coaxial with the pinion gear  31  in this embodiment. However, the rotation of the pinion gear  31  is not directly transmitted to the load gear  34 . More specifically, the load gear  34  is spline-coupled to an end portion side of the load sheave member  50  having a hollow portion, whereby the load gear  34  and the load sheave member  50  integrally rotate. However, the pinion gear  31  is inserted through the hollow portion of the load sheave member  50 , so that the load sheave member  50  and the pinion gear  31  are rotatable with respect to each other. 
     Through the gear unit  30  having the above configuration, the driving force generated at the motor unit  20  can be transmitted to the load sheave member  50 . 
     Next, the body  40  and the gear case  70  will be described. The body  40  is a member formed, for example, by casting metal, and a chain wound part  51 , around which the load chain is wound, of the load sheave member  50  is provided in the body  40 . Further, the gear case  70  is also a member formed, for example, by casting metal similarly to the body  40 . 
       FIG. 3  is a plan view illustrating a side (gear box part  41  side) where the gear case  70  is attached, of the body  40 .  FIG. 4  is a perspective view illustrating the gear box part  41  side of the body  40 , and a view illustrating a state where a later-described built-in cover  100  is detached. As illustrated in  FIG. 3  and  FIG. 4 , the body  40  is provided with the gear box part  41  in a recessed shape. Further, in an accommodating recessed part  42  of the gear box part  41 , the above-described pinion gear  31 , first driven gear body  32 , second driven gear body  33 , and load gear  34  are housed. 
     A bottom part  411  of the above-described gear box part  41  is provided with an insertion hole  412  penetrating the bottom part  411 . Through the insertion hole  412 , the pinion gear  31  and one end side (X1 side; gear case  70  side) of the load sheave member  50  project into the accommodating recessed part  42 . Further, a bearing B 1  is fitted in the insertion hole  412  to rotatably support the load sheave member  50 . Further, an oil seal Si also fits in the insertion hole  412  and thereby prevents leakage of grease through the insertion hole  412 , the grease being semifluid or semisolid at an operating temperature (about −20° to 240° C.) and being supplied into the accommodating recessed part  42 . Note that in the accommodating recessed part  42 , the pinion gear  31  is located closer to the one end side (X1 side) than is the load gear  34 . 
     On the other hand, at a bottom part  71  of the gear case  70 , a recessed fitting part  72  into which a bearing B 2  is fitted is provided, and the one side of the pinion gear  31  is rotatably supported to be rotatable via the bearing B 2 . 
     Besides, the first driven gear body  32  is not directly supported on the gear box part  41 . More specifically, on the motor unit  20  side in the accommodating recessed part  42 , the load gear  34  is arranged so as to be coaxial with the pinion gear  31 . Since the load gear  34  is larger in diameter than the pinion gear  31 , the first driven gear body  32  cannot be rotatably supported on the bottom part  411  side of the gear box part  41  due to the existence of the load gear  34 . Accordingly, on the lower side and on the left side in  FIG. 3  of the end surface on the gear case  70  side of the gear box part  41 , a support plate  80  for supporting the first driven gear body  32  is attached, for example, via screws or the like. Note that the support plate  80  is provided with a recessed fitting part into which a bearing B 3  is fitted, and the other end side (X2 side) of the first driven gear body  32  is rotatably supported via the bearing B 3 . 
     Note that the one end side (X1 side) of the first driven gear body  32  is rotatably supported to be rotatable via a bearing B 4  on the gear case  70  side, and the bearing B 4  is fitted in a recessed fitting part  73  formed in the bottom part  71 . This realizes a configuration that both end sides of the first driven gear body  32  are rotatably supported so as to be rotatable. 
     Besides, the other end side (X2 side) of the second driven gear body  33  is rotatably supported via a bearing B 5  fitted in a recessed fitting part  413  (see  FIG. 3 ) existing at the bottom part  411  of the gear box part  41 . On the other hand, the one end side (X1 side) of the second driven gear body  33  is rotatably supported to be rotatable via a bearing B 6  fitted in a recessed fitting part  74  existing at the bottom part  71  of the gear case  70 . 
     The gear unit  30  having the above configuration is housed in the accommodating recessed part  42  of the gear box part  41 . Further, the gear box part  41  and the gear case  70  are attached, for example, via bolts or the like in a state where a not-illustrated packing arranged between them. Thus, between the gear box part  41  and the gear case  70 , a gear accommodating space GS including the accommodating recessed part  42  is formed. Note that the gear box part  41  and the gear case  70  correspond to a case body, but any one of them may be made to correspond to the case body. 
     &lt;Regarding the Built-In Cover  100 &gt; 
     In the above-described gear accommodating space GS, the built-in cover  100  is arranged. Hereinafter, the built-in cover  100  will be described.  FIG. 5  is a perspective view illustrating a configuration of the built-in cover  100 .  FIG. 6  is a plan view illustrating a state where the built-in cover  100  is attached to the gear box part  41 . 
     As illustrated in  FIG. 6 , the built-in cover  100  is a member that covers the periphery of the gear unit  30  excluding the load gear  34 . The built-in cover  100  is formed of a rubber material, for example, nitrile rubber having oil resistance and slight elasticity. Note that the material of the built-in cover  100  is not limited to nitrile rubber, but another rubber-based material such as styrene butadiene rubber (SBR), fluorine rubber, chloroprene rubber (CR), silicone rubber, epichlorohydrin rubber, acrylic rubber, or urethane rubber, or a synthetic resin may be used. Note that use of the rubber material having elasticity at a certain degree facilitates assembly and holding of the rubber material in the box and can also contribute to prevention of sound generated from the gear and the like. 
     As illustrated in  FIG. 5  and  FIG. 6 , the built-in cover  100  is provided in a state where three peripheral wall parts in total are continued. Mores specifically, the built-in cover  100  is provided with a first peripheral wall part  110 , a second peripheral wall part  120 , and a third peripheral wall part  130 . In the built-in cover  100 , an opposed receiving part  140  also exists in addition to the three peripheral wall parts  110 ,  120 ,  130 . 
     The first peripheral wall part  110  is a portion covering the outer peripheral side of the pinion gear  31 , and is provided to have a smallest diameter among the three peripheral wall parts  110 ,  120 ,  130 . Further, as illustrated in  FIG. 2 , the pinion gear  31  is provided to have a relatively large length in the X-direction. Accordingly, the first peripheral wall part  110  covering the outer peripheral side of the pinion gear  31  is provided to have a relatively large dimension in a depth direction in  FIG. 5  and  FIG. 6  (X-direction in  FIG. 2 ). However, the height of the first peripheral wall part  110  is provided to be smaller than the height of the third peripheral wall part  130 . 
     In this embodiment, the first peripheral wall part  110  is opposed to the outer periphery of the pinion gear  31  with a gap of, for example, about 2 mm intervening therebetween. Accordingly, even if the pinion gear  31  is rotated and the grease is scattered to the outer peripheral side due to the centrifugal force thereof, the first peripheral wall part  110  can catch the scattered grease. Therefore, it is possible to reduce occurrence of lack of grease. 
     Note that the gap between the pinion gear  31  and the first peripheral wall part  110  is not limited to about 2 mm, but can be variously set within a range capable of effectively preventing lack of grease, such as within a range of, for example, 1 mm to 5 mm. 
     Besides, the second peripheral wall part  120  is a portion covering the outer peripheral side of the first driven gear body  32 . The second peripheral wall part  120  is provided to continue to the first peripheral wall part  110 . More specifically, since a peripheral wall part, if existing at a portion where the first peripheral wall part  110  and the second peripheral wall part  120  intersect with each other, is an obstacle to mesh between the pinion gear  31  and the first large-diameter driven gear  32   a , no peripheral wall part exists at the intersection portion. Therefore, in a plan view of the first peripheral wall part  110  and the second peripheral wall part  120 , their appearance is provided in an almost gourd shape in which a large-diameter circle and a small-diameter circle continue. 
     Further, the second peripheral wall part  120  is opposed to the outer periphery of the first driven gear body  32  (first large-diameter driven gear  32   a ) with a gap of, for example, about 2 mm intervening therebetween. Accordingly, even if the grease is scattered to the outer peripheral side due to the rotation of the first driven gear body  32  (first large-diameter driven gear  32   a ), the second peripheral wall part  120  can catch the grease. Therefore, it is possible to reduce occurrence of lack of grease also on the outer peripheral side of the first driven gear body  32  (first large-diameter driven gear  32   a ). 
     Note that also the gap between the first large-diameter driven gear  32   a  and the second peripheral wall part  120  is not limited to about 2 mm. The gap can be variously set within a range capable of effectively preventing lack of grease, such as within a range of, for example, 1 mm to 5 mm. 
     Here, the second peripheral wall part  120  is provided with an outer peripheral wall part  121  existing on a side not adjacent to the third peripheral wall part  130 , and with an inner peripheral wall part  122  existing at a portion adjacent to the third peripheral wall part  130 . The outer peripheral wall part  121  is provided at the same level as the height (depth) of the above-described first peripheral wall part  110 . The outer peripheral wall part  121  is supported on the above-described support plate  80  at the deep side (X2 side). 
     Note that the outer peripheral wall part  121  is provided with a positioning recessed part  121   a  for positioning. The positioning recessed part  121   a  is a portion recessed by a predetermined amount to be directed from the deep side (X2 side) to an open side (X1 side) of the outer peripheral wall part  121 . The support plate  80  is located in the positioning recessed part  121   a  so as to position the built-in cover  100  with respect to the support plate  80 . Further, at a portion where the support plate  80  is not located in the circumferential direction of the outer peripheral wall part  121 , the outer peripheral wall part  121  can be located at a deeper side (X2 side) than is the support plate  80 , and can effectively prevent lack of grease. 
     On the other hand, the inner peripheral wall part  122  is provided to have a dimension in the depth direction significantly smaller than that of the outer peripheral wall part  121 . This is because the second large-diameter driven gear  33   a  of the second driven gear body  33  is located on the lower side of the inner peripheral wall part  122 . Accordingly, the inner peripheral wall part  122  is provided in an arc shape having a small dimension in the depth direction so as to connect (bridge) the first peripheral wall part  110  and the outer peripheral wall part  121 . 
     Note that the inner peripheral wall part  122  exists not only in the second peripheral wall part  120  but also in the first peripheral wall part  110  (hereinafter, the inner peripheral wall part in the first peripheral wall part  110  is an inner peripheral wall part  112 ). 
     Besides, the third peripheral wall part  130  is a portion covering the outer peripheral side of the second driven gear body  33 . The second driven gear body  33  is provided with the second large-diameter driven gear  33   a  having a diameter larger than those of the pinion gear  31  and the first large-diameter driven gear  32   a . Accordingly, the third peripheral wall part  130  is provided to have a diameter larger than those of the first peripheral wall part  110  and the second peripheral wall part  120 . 
     The third peripheral wall part  130  is provided with a gear recessed part  131  for preventing interference with the load gear  34 . However, the load gear  34  is provided to be located at a deeper side (X2 side; bottom part  411  side) of the accommodating recessed part  42  than is the second large-diameter driven gear  33   a  of the second driven gear body  33 . Therefore, the dimension in the depth direction (X-direction) of the third peripheral wall part  130  is provided to be larger than the dimensions in the depth direction of the first peripheral wall part  110  and the second peripheral wall part  120 , also at a portion where the gear recessed part  131  exists. 
     Further, the third peripheral wall part  130  is opposed to the outer periphery of the second driven gear body  33  (second large-diameter driven gear  33   a ) with a predetermined gap intervening therebetween. This gap can be set to be larger than the gap between the first driven gear body  32  (first large-diameter driven gear  32   a ) and the second peripheral wall part  120  such as about 5 mm in consideration that the first large-diameter driven gear  32   a  has a diameter larger than that of the second large-diameter driven gear  33   a . However, the gap between the second driven gear body  33  (second large-diameter driven gear  33   a ) and the third peripheral wall part  130  may be set to the same amount as the gap between the first driven gear body  32  (first large-diameter driven gear  32   a ) and the second peripheral wall part  120 . 
     Note that the gap between the second driven gear body  33  (second large-diameter driven gear  33   a ) and the third peripheral wall part  130  is not limited to about 5 mm. The gap can be variously set within a range capable of effectively preventing lack of grease, such as within a range of, for example, 1 mm to 10 mm. 
     Further, the third peripheral wall part  130  is also provided with an outer peripheral recessed part  132  for escaping from a rib, a boss or the like of the gear box part  41 . Further, the third peripheral wall part  130  is provided with fitting recessed parts  133 . The fitting recessed part  133  is a portion for fitting with the boss or the like of the gear box part  41  to position the built-in cover  100 , and is provided to be long in the depth direction (X-direction). As illustrated in  FIG. 5  and  FIG. 6 , the built-in cover  100  in this embodiment is provided with two fitting recessed parts  133  in total. However, the number of the fitting recessed parts  133  to be provided may be arbitrarily set according to the boss and the like of the gear box part  41 . 
     Note that bump parts  134 , the fitting recessed parts  133 , the positioning recessed part  121   a , and the gear case  70  press down the built-in cover  100  inside the gear accommodating space GS. Accordingly, the built-in cover  100  can be fixed in the gear accommodating space GS without a screw or the like. 
     Further, the third peripheral wall part  130  is provided with the bump parts  134 . The bump part  134  is a portion that abuts against the bottom part  411  of the gear box part  41  and thereby decides the position in the height direction of the built-in cover  100  in the recessed fitting part  42 . In this embodiment, the bump parts  134  are provided at two locations in the circumferential direction of the third peripheral wall part  130 , but the number of the bump parts  134  may be arbitrarily set. 
     Further, the built-in cover  100  is also provided with the opposed receiving part  140 . As illustrated in  FIG. 5  and  FIG. 6 , the opposed receiving part  140  projects from the inner wall of the second peripheral wall part  120  toward the center in the radial direction, and has an appearance in an arc shape. The opposed receiving part  140  is provided to be opposed to the lower surface (surface on the deep side) of the first large-diameter driven gear  32   a . Accordingly, the opposed receiving part  140  is also opposed almost parallel to the bottom part  411 , but does have to be almost parallel to the bottom part  411 . The opposed receiving part  140  is preferably provided as long as possible, and is therefore provided to reach the boundary of the inner peripheral wall part  122  from the boundary of the first peripheral wall part  110 , of the inner wall of the outer peripheral wall part  121  of the second peripheral wall part  120 . 
     The opposed receiving part  140  is opposed to the lower surface (surface on the deep side) of the first large-diameter driven gear  32   a  with a gap of about 2 mm intervening therebetween. However, the gap between the lower surface of the first large-diameter driven gear  32   a  and the opposed receiving part  140  is not limited to about 2 mm, but can be variously set within a range capable of effectively preventing lack of grease, such as within a range of, for example, 1 mm to 10 mm. 
     Further, the inner peripheral wall part of the opposed receiving part  140  is opposed to the first small-diameter driven gear  32   b  of the first driven gear body  32 . Further, the end portions in the circumferential direction of the opposed receiving part  140  are opposed to the pinion gear  31  and the second large-diameter driven gear  33   a  respectively. The gap between them is about 2 mm as described above in some cases, but is not limited to about 2 mm and can be variously set within a range capable of effectively preventing lack of grease, such as within a range of, for example, 1 mm to 10 mm. 
     The above-described built-in cover  100  is attached to the accommodating recessed part  42 . 
     Note that the gear unit  30  is being supplied with grease. The grease is high in viscosity than oil being liquid and is inferior in flowability. Therefore, the grease is semisolid or semifluid at an operating temperature. Note that to prevent the grease from flowing to the outside in a state where the grease is supplied to the gear unit  30 , the packing intervenes between the gear case  70  and the body  40  (gear box part  41 ). In other words, the body  40  (gear box part  41 ) and the gear case  70  are fixed to each other with screws or the like with the packing intervening between them. 
     &lt;Regarding Behavior of the Gear Unit  30  When the Built-In Cover  100  is Attached&gt; 
     Next, the behavior of the gear unit  30  in the case where the built-in cover  100  is attached in the gear accommodating space GS will be described. In the case where the main body  11  is attached in a reverse suspension state, when the motor unit  20  drives, the driving force is transmitted via the gear unit  30  to the load sheave member  50  and thereby winds up the load chain to move up and down the main body  11  together with the load. 
     The pinion gear  31  is coupled to the motor shaft here, so that when the motor unit  20  drives, the pinion gear  31  is rotated at the same number of rotations as that of the motor shaft. Accordingly, the pinion gear  31  is brought into a state of rotating at high speed. Therefore, even if grease adheres to the pinion gear  31 , the grease is apt to be scattered to the outer peripheral side by the centrifugal force at the time when the pinion gear  31  is rotated. 
     However, in this embodiment, the first peripheral wall part  110  is provided around the outer peripheral side of the pinion gear  31 . Accordingly, the first peripheral wall part  110  can catch the grease scattered by the centrifugal force at the time of rotation, and can bounce the grease back toward the pinion gear  31 . Therefore, the grease is held in the vicinity on the outer peripheral side of the pinion gear  31  and the grease is supplied again to the pinion gear  31 . 
     Note that in the reverse suspension state, the first peripheral wall part  110  is preferably located on the lower side in the vertical direction than is the second peripheral wall part  120 . In this case, the grease moves by gravity from the second peripheral wall part  120  side to the first peripheral wall part  110  side. This is because when the pinion gear  31  is rotated at high speed in a state where the grease is stored at the first peripheral wall part  110 , meshing of the pinion gear  31  with the first large-diameter driven gear  32   a  or the like makes it possible to relatively easily supply the grease to the gears including the first large-diameter driven gear  32   a.    
     Further, the pinion gear  31  meshes with the first large-diameter driven gear  32   a , and around the outer peripheral side of the first large-diameter driven gear  32   a , the second peripheral wall part  120  is arranged. The first large-diameter driven gear  32   a  meshes with the pinion gear  31  and is larger in diameter than the pinion gear  31 . Accordingly, the centrifugal force by the rotation of the first large-diameter driven gear  32   a  is relatively large. Therefore, the grease is apt to be scattered to the outer peripheral side by the centrifugal force at the time when the first large-diameter driven gear  32   a  is rotated. 
     However, around the outer peripheral side of the first large-diameter driven gear  32   a , the second peripheral wall part  120  is provided. Accordingly, the second peripheral wall part  120  can catch the grease scattering by the centrifugal force at the time of rotation, and can bounce the grease back toward the first large-diameter driven gear  32   a . Therefore, the grease is held in the vicinity on the outer peripheral side of the first large-diameter driven gear  32   a  and the grease is supplied again to the first large-diameter driven gear  32   a . Note that when grease adheres to the first large-diameter driven gear  32   a , the grease is supplied also to the first small-diameter driven gear  32   b  along the outer peripheral surface or the like of the first large-diameter driven gear  32   a  and the grease is supplied also to the pinion gear  31 . 
     Here, the surface on the deep side of the first large-diameter driven gear  32   a  is opposed to the opposed receiving part  140 . Accordingly, the grease trying to move from the surface on the deep side of the first large-diameter driven gear  32   a  can be caught by the opposed receiving part  140  and held at the opposed receiving part  140 . Note that a part of the load gear  34  extends to or a part of the pinion gear  31  extends to a portion where the opposed receiving part  140  does not exist on the inner peripheral side of the second peripheral wall part  120 . Therefore, at the portion where the opposed receiving part  140  does not exist, the grease adheres to the load gear  34  and the pinion gear  31 , whereby recirculation of the grease is achieved. 
     Further, the first small-diameter driven gear  32   b  of the first driven gear body  32  meshes with the second large-diameter driven gear  33   a  of the second driven gear body  33 . Further, around the outer peripheral side of the second large-diameter driven gear  33   a , the third peripheral wall part  130  is arranged. Generally, the rotation speed of the second large-diameter driven gear  33   a  is significantly lower than that of the pinion gear  31 . Therefore, the centrifugal force at the second large-diameter driven gear  33   a  is decreased, but the grease adhering to the second large-diameter driven gear  33   a  is apt to move to the outer peripheral side more than at the time of no rotation. Further, the second large-diameter driven gear  33   a  is rotated at a rotation speed to scatter the grease by the centrifugal force in some cases depending on the gear ratio. 
     Accordingly, the third peripheral wall part  130  can catch the grease scattered and moved to the outer peripheral side by the centrifugal force at the time of rotation of the second large-diameter driven gear  33   a , and can bounce the grease (though a smaller amount of grease as compared with those by the first peripheral wall part  110  and the second peripheral wall part  120 ) back toward the second large-diameter driven gear  33   a . Therefore, the grease can be held in the vicinity on the outer peripheral side of the second large-diameter driven gear  33   a  and the grease can be supplied again to the second large-diameter driven gear  33   a.    
     Note that when grease adheres to the second large-diameter driven gear  33   a , the grease is brought into a state of being supplied also to the second small-diameter driven gear  33   b  along the outer peripheral surface or the like of the second large-diameter driven gear  33   a . Further, the grease is supplied also to the load gear  34  via the second small-diameter driven gear  33   b  or the like, and the grease is supplied also to the first small-diameter driven gear  32   b.    
     Here, it has been confirmed in an experiment that the difference in life due to lack of grease between the chain block  10  in this embodiment and the conventional chain block in which the built-in cover  100  is not arranged in the accommodating recessed part  42 , is at least twice or more. Note that the above-described difference in life of twice or more includes a case of five times or more, and also includes 10 times or more. 
     &lt;Regarding Effects&gt; 
     According to the chain block  10  and built-in cover  100  with the above configurations, the built-in cover  100 , provided separately from the gear box part  41  which accommodates the gear unit  30  and is supplied with the grease being semifluid or semisolid at the temperature (operating temperature) during operation of the chain block  10  as a lubricant, is arranged inside the accommodating recessed part  42  of the gear box part  41 . The built-in cover  100  includes the first peripheral wall part  110  that covers the outer peripheral side of the pinion gear  31 , and the second peripheral wall part  120  that is provided to be larger in diameter than the first peripheral wall part  110  by covering the periphery of the first driven gear body  32  including the first large-diameter driven gear  32   a  which meshes with the pinion gear  31  and is larger in diameter than the pinion gear  31 . In addition, the built-in cover  100  is provided in a circulation shape without a break, by continuation of the first peripheral wall part  110  and the second peripheral wall part  120 . 
     Here, since the pinion gear  31  and the load gear  34  are arranged to be coaxial as in this embodiment, the pinion gear  31  is located not at a portion closer to the outer wall portion of the gear box part  41  but at a portion relatively closer to the center of the gear box part  41 . Therefore, at the pinion gear  31  rotated at high speed, the grease is likely to be scattered toward the outer peripheral wall, causing a state where lack of grease is likely to occur. 
     However, in this embodiment, since the first peripheral wall part  110  covers the periphery of the pinion gear  31 , the first peripheral wall part  110  can catch the grease scattered from the pinion gear  31  toward the outer peripheral side, and can bounce the grease back toward the pinion gear  31 . Therefore, it is possible to suppress occurrence of lack of grease at the pinion gear  31 , thereby increasing the life of the chain block  10  and decreasing the frequency of maintenance. 
     Note that there is a secondary effect capable of decreasing the used amount of grease relatively expensive by providing the built-in cover  100  to suppress the scattered amount of grease. 
     Further, also at the first large-diameter driven gear  32   a , the grease adhering to the first large-diameter driven gear  32   a  is scattered to the outer peripheral side by the centrifugal force at the time when the first large-diameter driven gear  32   a  is rotated, and the second peripheral wall part  120  can catch the scattered grease and bounce the grease back toward the first large-diameter driven gear  32   a.    
     Further, the first peripheral wall part  110  and the second peripheral wall part  120  are formed in a circulation shape without a break. Here, in the case where the circulation shape has a break, the grease possibly flows out through the break portion to a further outer peripheral side, but the above circulation shape enables circulation of the grease adhering to the first peripheral wall part  110  and the second peripheral wall part  120 . Accordingly, it is possible to effectively prevent lack of grease at the pinion gear  31  and at the first large-diameter driven gear  32   a  (first driven gear body  32 ), thereby increasing the life of the chain block  10 . 
     Further, in this embodiment, even if the gear ratio or the gear configuration is changed, it is unnecessary to change the body  40  and the gear case  70 . Therefore, it is unnecessary to produce relatively large-size metal molds for casting the body  40  and the gear case  70 . Therefore, an increase in cost can be prevented accordingly. 
     Further, in this embodiment, on the inner peripheral side of the second peripheral wall part  120 , the opposed receiving part  140  is provided which projects toward the center side in the radial direction of the second peripheral wall part  120 . Further, the opposed receiving part  140  is opposed to the first large-diameter driven gear  32   a  so that the grease can be held at the opposed receiving part  140 . Therefore, when the grease moves from the deep side (X2 side) of the first large-diameter driven gear  32   a  to a deeper side (X2 side), the opposed receiving part  140  can catch and hold the grease. Accordingly, it is possible to further effectively prevent occurrence of lack of grease at the first large-diameter driven gear  32   a . Further, since the gap between the first large-diameter driven gear  32   a  and the load gear  34  is narrowed, thereby making it possible to prevent occurrence of lack of grease without grease being supplied to the first large-diameter driven gear  32   a  and the load gear  34  due to storage of the grease at an excessive gap. This enables further increase the life of the chain block  10 . 
     Further, the built-in cover  100  is provided separately from the body  40  and the gear case  70 . Accordingly, the built-in cover  100  does not obstruct the assembly performance of the gear unit  30  made by incorporating the gears. More specifically, the gear unit  30  is made by assembling the load gear  34 , then assembling the second driven gear body  33 , thereafter attaching the built-in cover  100  as a separate body to the accommodating recessed part  42 , and finally assembling the first driven gear body  32 . Therefore, the built-in cover  100  never obstructs the assembly performance of the gear unit  30 . 
     Further, in this embodiment, the first driven gear body  32  is provided with the first small-diameter driven gear  32   b  coaxially and integrally with the first large-diameter driven gear  32   a . Further, the gear unit  30  also includes the second driven gear body  33 , and the second driven gear body  33  is provided with the second large-diameter driven gear  33   a  meshing with the first small-diameter driven gear  32   b . Further, the built-in cover  100  is provided with the third peripheral wall part  130  that covers the outer peripheral side of the second large-diameter driven gear  33   a , and the third peripheral wall part  130  is provided to be continuous with the first peripheral wall part  110  and with the second peripheral wall part  120  so as to provide the built-in cover  100  in a circulation shape without a break. 
     Therefore, even if the grease adhering to the second large-diameter driven gear  33   a  is scattered and moved to the outer peripheral side due to the rotation of the second large-diameter driven gear  33   a , the third peripheral wall part  130  can catch the grease and can bounce the grease back toward the second large-diameter driven gear  33   a . In addition, the third peripheral wall part  130  is continuous with the first peripheral wall part  110  and the second peripheral wall part  120 , so that the built-in cover  100  is provided in a circulation shape without a break as a whole. Therefore, the grease adhering to the third peripheral wall part  130  can be made to circulate toward the first peripheral wall part  110  and the second peripheral wall part  120 . Accordingly, the life of the chain block  10  can be further increased. 
     Further, in this embodiment, the built-in cover  100  is formed of a rubber material. In this case, the noise generated by the gear unit  30  can be reduced to improve the quietness of the chain block  10 . Further, since the built-in cover  100  is formed of a rubber material and can be attached while being elastically deformed, rattling of the built-in cover  100  in the gear housing space GS can be reduced. In addition, since the built-in cover  100  is formed of a rubber material having elasticity (flexibility), the built-in cover  100  is easily assembled. 
     MODIFICATION EXAMPLES 
     The embodiments of the present invention have been described above, and the present invention can be variously modified in addition to them. Hereinafter, they will be described. 
     In the above-described embodiment, the built-in cover  100  includes the third peripheral wall part  130  and the opposed receiving part  140  in addition to the first peripheral wall part  110  and the second peripheral wall part  120 . However, the built-in cover  100  only needs to include at least the first peripheral wall part  110  and the second peripheral wall part  120  and may employ a configuration not including at least one of the third peripheral wall part  130  and the opposed receiving part  140 . 
     Further, in the built-in cover  100  in the above embodiment may be additionally provided with a part similar to the opposed receiving part  140  as necessary in order to decrease gaps between gears, at the bottom part  411  of the gear box part  41 , at the bottom part  71  of the gear case  70  and the like. In the case of this configuration, excessive gaps at respective portions can be reduced, and the scattered grease can be held and stored. Accordingly, it becomes possible to further prevent lack of grease in the chain block  10  to further increase the life of the chain block  10 . 
     Further, in the above embodiment, the chain block  10  provided with the motor unit  20  is described. However, the built-in cover  100  of the present invention may be applied to a manual type chain block. 
     Further, in the above embodiment, the gear unit  30  is configured to include the pinion gear  31 , the first driven gear body  32 , the second driven gear body  33 , and the load gear  34 . However, the gear unit  30  is not limited to the configuration. For example, a configuration in which the second driven gear body  33  and the first driven gear body  32  are omitted may be employed. Further, a configuration in which another gear is additionally provided may be employed.