Patent Publication Number: US-2017368697-A1

Title: Wrist Structure of Industrial Robot

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a wrist structure of an industrial robot provided with wrist elements having three degrees of rotational freedom. 
     2. Description of the Related art 
     Conventionally, in industrial robots, a wrist structure having a first wrist element, a second wrist element rotatably supported by a distal end of the first wrist element, and a third wrist element rotatably supported by a distal end of the second wrist element, wherein the power of a motor for a second wrist and a motor for a third wrist, which are provided in the first wrist element, is transmitted to the second wrist element and the third wrist element via hypoid gear sets each having a pinion gear and a ring gear, has been known (see, for example, Japanese Patent No. 4233578 and Japanese Unexamined Patent Publication (Kokai) No. 2014-213437). 
     SUMMARY OF THE INVENTION 
     In a wrist structure, an operation tool is often situated at an offset position relative to a wrist flange. Further, even when the operation tool is disposed on a rotation axis of the wrist flange, an umbilical member for controlling the operation tool may be disposed outside an arm as described in Japanese Patent No. 4233578 and Japanese Unexamined Patent Publication (Kokai) No. 2014-213437. 
     In such a case, a gravitational load caused by, for example, the umbilical member for controlling the operation tool, acts on each output axis of wrist axes. Thus, at the time of shutdown or emergency shutdown, members associated with wrist axes tend to be accidentally detached. Further, when all of first to third axes of the wrist are situated at offset positions, depending on the orientation of the second and third axes, a gravitational load of the operation tool, which acts on the first axis, increases, and accordingly, the possibility that members associated with the axes may be accidentally detached increases. 
     In order to prevent the members associated with the axes from being accidentally detached, it is preferable that a brake is attached to each of the wrist axes (first to third axes) of the wrist structure. However, attaching the brake to each wrist axis increases the entire weight of the wrist structure, and accordingly, makes it difficult for the wrist structure to quickly move and to be precisely positioned. 
     The present invention was made in light of the circumstances described above and has an object to provide a wrist structure of an industrial robot, which can quickly move and can be precisely positioned without accidental detachment of members associated with axes. 
     A first aspect of the invention provides a wrist structure of an industrial robot. The wrist structure includes a forearm, a first wrist element which is hinge-connected to a distal end of the forearm and which is rotatable about a first axis, a second wrist element which is provided in the first wrist element so as to be rotatable about a second axis perpendicular to the first axis, a third wrist element which is provided in the second wrist element so as to be rotatable about a third axis perpendicular to the second axis, and an umbilical member which connects an operation tool attached to a tool attachment part of the third wrist element to a tool management relay device disposed behind the forearm, to supply at least one of power, a signal, and a material to the operation tool. The wrist structure of the industrial robot also includes a first reduction gear for rotationally driving the first wrist element, a first deceleration unit and a second deceleration unit for rotationally driving the second wrist element; a third deceleration unit for rotationally driving the third wrist element; a motor for a second wrist and a motor for a third wrist, which respectively drive the second wrist element and the third wrist element, and a transmission mechanism for the second wrist and a transmission mechanism for the third wrist, which respectively transmit a rotationally driving force of the motor for the second wrist and a rotationally driving force of the motor for the third wrist to the second wrist element and the third wrist element and which include hypoid gear sets. A first hollow part having a center axis coincident with the first axis is formed in the forearm. A through passage, which communicates with the first hollow part, is formed in the first wrist element. A second hollow part having a center axis coincident with the third axis is formed in the third wrist element. The umbilical member is inserted through the first hollow part, the through passage, and the second hollow part. A brake device is eliminated from at least one of the motor for the second wrist and the motor for the third wrist. 
     These objects, features, and advantages of the present invention and other objects, features, and advantages will become further clearer from the detailed description of typical embodiments illustrated in the appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view illustrating the internal configuration of a wrist structure of an industrial robot according to an embodiment of the present invention. 
         FIG. 2  is a side view illustrating the internal configuration of a wrist structure of the industrial robot according to an embodiment of the present invention. 
         FIG. 3  is a side view illustrating an example of an industrial robot to which a wrist structure according to an embodiment of the present invention is applied. 
         FIG. 4  is a side view illustrating an example of an industrial robot to which a wrist structure according to an embodiment of the present invention is applied. 
         FIG. 5  is a perspective view, seen from obliquely behind, of a first wrist element constituting a wrist structure according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following figures, similar members are designated with the same reference numerals. These figures are properly modified in scale to assist the understanding thereof. 
       FIGS. 1 and 2  are respectively a front view and a side view illustrating the internal configuration of a wrist structure  100  of an industrial robot according to an embodiment of the present invention.  FIGS. 3 and 4  are side views illustrating an example of industrial robots  1 A and  1 B to which the wrist structure  100  is applied. 
     First, the configuration of the industrial robots  1 A and  1 B will be described. The industrial robots  1 A and  1 B shown in  FIGS. 3 and 4  are robots having six degrees of freedom in orthogonal axes. Specifically,  FIG. 3  shows an arc welding robot  1 A provided with a welding torch  2  as the wrist element of the final shaft, and  FIG. 4  shows a handling robot  1 B provided with a hand tool  3  as the wrist element of the final shaft. As shown in  FIG. 3 , a umbilical member  4  comprised of a bundle of a signal cable, a power supply cable, a welding wire, a gas hose, and a wire conduit, is connected to the welding torch  2 . As shown in  FIG. 4 , a umbilical member  4  comprised of a bundle of a signal cable, a power supply cable, an air supply tube, etc., is connected to the hand tool  3 . 
     In  FIGS. 3 and 4 , a base  6  is rotatable about a vertically extending axis, and an upper arm  7  is rotatably supported by the base  6 . A forearm  8  is rotatably supported by a distal end of the upper arm  7 , and a wrist structure  100  is supported by the forearm  8 . The base  6 , the upper arm  7 , and the forearm  8  are rotatable in three degrees of freedom about three rotational axes. Note that the robots  1 A and  1 B in  FIGS. 3 and 4  are different in the configuration of a third wrist element  12  as an end-effector, in the construction of the umbilical member  4  connected to the third wrist element  12 , and in the structure of a feeding device  5  for feeding the umbilical member  4 , but have the rest of the components in common. In short, both robots have the same base  6 , upper arm  7 , and forearm  8 . The aforementioned operation tool, e.g., the welding torch  2  or the hand tool  3  is attached to a tool attachment part of the third wrist element. 
     The wrist structure  100  is comprised of the forearm  8 , a first wrist element  10 , a second wrist element  11 , and the third wrist element  12 , and has three degrees of freedom about three rotational axes. The first wrist element  10  is supported by the distal end of the forearm  8  so as to be rotatable about a first axis L 1  which longitudinally extends. The second wrist element  11  is supported by the distal end of the first wrist element  10  so as to be rotatable about a second axis L 2  intersecting with the first axis L 1 . The third wrist element  12  is supported by the distal end of the second wrist element  11  so as to be rotatable about a third axis L 3  intersecting with the second axis L 2 . 
     The first axis L 1 , the second axis L 2 , and the third axis L 3  intersect at one point, and the wrist structure  100  is constructed as an in-line wrist. This causes, as shown in  FIG. 2 , the first axis L 1  and the third axis L 3  to be situated on the same axis line, and reduces, at the time of rotation of the first wrist element  10 , the interference radii of other wrist elements  11 ,  12 . Further, the wrist structure  100  having good rotational balance as well as good controllability can be realized. Individual driving elements, which constitute the industrial robots  1 A,  1 B, are adapted to be driven by servomotors corresponding to the individual driving elements so as to take predetermined positions and attitudes in accordance with instructions from a robot controller (not shown). 
     The configuration of the wrist structure  100  will be described. Note that, for the purpose of illustration, the up-down direction, the front-rear direction, and the right-left direction are defined as shown in  FIGS. 1 and 2 , and the configuration of each component will be described in accordance with this definition. As shown in  FIGS. 1 and 2 , the first wrist element  10  extends in the front-rear direction, and its rear end is rotatably supported by the distal end of the forearm  8 . A servomotor (not shown) and a first reduction gear RG 0 , which are adapted to rotate and reduce, at a predetermined reduction ratio, the speed of the first wrist element  10 , are provided in the forearm  8 . The first reduction gear RG 0  is contained in the forearm  8  so that its output unit coaxially rotates with the first axis L 1 , and thus, the first wrist element  10  is driven, via the first reduction gear RG 0 , to rotate about the first axis L 1 . 
     The first wrist element  10  has a front case  10 A and a rear case  10 B, which are integrally fastened via an attachment surface SA extending in a direction perpendicular to the first axis L 1 , and storage spaces SP 1  and SP 2  are respectively formed inside the cases  10 A and  10 B. A servomotor  13  for driving the second wrist element  11  and a servomotor  14  for driving the third wrist element  12  are disposed in the storage space SP 2  on the rear side. The servomotor  14  is disposed in front of the servomotor  13 . 
     Output shafts  13   a  and  14   a  of the servomotors  13  and  14  project forward in parallel with the first axis L 1 . The servomotor  13  is positioned higher than the servomotor  14 , and accordingly, the output shaft  13   a  extends above the first axis L 1 , and the output shaft  14   a  extends below the first axis L 1 . In other words, the output shafts  13   a  and  14   a  of the servomotors  13  and  14  are situated at offset positions such that they are generally symmetric with respect to a plane containing the first axis L 1  and the second axis L 2 , and the servomotors  13  and  14  are provided in parallel to each other on two sides of the plane containing the first axis L 1  and the second axis L 2  at positions offset relative to each other in forward-rearward direction and partly overlapping each other. 
     Disposing the servomotor  13  for the second wrist on the proximal end side (rear side) of the first wrist element  10  and the servomotor  14  for the third wrist on the distal end side (front side) of the first wrist element  10  enables the two motors  13  and  14  to be arranged in partly overlapping manner, so that the cross sectional area of the first wrist element  10  can be made small. 
     A hypoid gear set  15  for reducing the rotation speed of the servomotor  13  at a predetermined reduction ratio, and a hypoid gear set  20  for reducing the rotation speed of the servomotor  14  at a predetermined reduction ratio are provided in the storage space SP 1  on the front side. The hypoid gear sets  15  and  20  respectively have pinion gears (driving small gear wheels)  16  and  21  to be driven by the servomotors  13  and  14 , and ring gears (driven large gear wheels)  17  and  22  to respectively mesh with the pinion gears  16  and  21 . 
     The pinion gear  16  is provided at the distal end of a shaft  160  extending in the front-rear direction above the first axis L 1 , and the pinion gear  21  is provided at the distal end of a shaft  210  extending below the first axis L 1 . The pinion gear  16  (the shaft  160 ) is supported by the front case  10 A so as to be rotatable about an axis L 16  parallel with the first axis L 1  via bearings (tapered roller bearings)  18   a  and  18   b  provided at the front and rear ends, and a needle bearing  18   c  provided between the bearings  18   a  and  18   b . Likewise, the pinion gear  21  (the shaft  210 ) is supported by the front case  10 A so as to be rotatable about an axis L 21  parallel with the first axis L 1  via bearings (tapered roller bearings)  23   a  and  23   b  provided at the front and rear ends, and a needle bearing  23   c  provided between the bearings  23   a  and  23   b.    
     Bearing nuts  18   d  and  23   d  respectively apply precompression to the bearings  18   a  and  18   b  and the bearings  23   a  and  23   b  in the axial direction, to cause the rotation accuracy of the pinion gears  16  and  21  to be in best condition, and then the pinion gears  16  and  21  are rotatably supported. Providing the needle bearings  18   c  and  23   c  respectively between the paired bearings  18   a  and  18   b  and the paired bearings  23   a  and  23   b  enables, even when an external force exceeding the precompression causes the support by the bearings  18   a  and  18   b  and  23   a  and  23   b  to be incomplete, the needle bearings  18   c  and  23   c  to satisfactorily support the pinion gears  16  and  21 . Note that sleeves can be used in place of the needle bearings  18   c  and  23   c.    
     The ring gear  17  to mesh with the pinion gear  16  and the ring gear  22  to mesh with the pinion gear  21  are provided at the front end of the front case  10 A, so as to be rotatable about the second axis L 2 . The ring gear  17  has a diameter larger than that of the ring gear  22 , and the ring gear  22  is disposed on the right side of the ring gear  17 . The pinion gear  16  is formed with right-hand teeth, and the pinion gear  21  is formed with teeth curved in a (leftward) direction different from the pinion gear  16 . As seen above, the two pinion gears  16  and  21  are formed with symmetrically-formed teeth, and accordingly, the pinion gears  16  and  21  can be disposed at symmetrically offset positions in the direction perpendicular to the second axis L 2 . 
     As shown in  FIG. 2 , the positional relationship between the pinion gears  16  and  21  and the ring gears  17  and  22  is adjusted by a SIMM. In other words, a SIMM SM 1  disposed in front of the bearings  18   a  and  23   a  adjusts the position of the pinion gears  16  and  21  in the front-rear direction, a SIMM SM 2  disposed on the right side of a bearing  19  and a bearing  32   a  adjusts the position of the ring gears  17  and  22  in the right-left direction. This enables adjustment of backlash and tooth contact between the pinion gears  16  and  21  and the ring gears  17  and  22 . 
     The ring gear  17  is integrally coupled to the second wrist element  11 . The ring gear  17  is rotatably supported in the first wrist element  10  via the bearing  19 , and the rotation of the ring gear  17  causes the second wrist element  11  to rotate about the second axis L 2 . 
     A bevel gear  31 , the rotation center of which is the second axis L 2 , is provided in the second wrist element  11 . The shaft of the bevel gear  31  extends along the second axis L 2  in the right-left direction, and the inner peripheral surface of the ring gear  22  is splined to the shaft. The shaft of the bevel gear  31  is rotatably supported in the ring gear  17  via the paired bearings  32   a  and  32   b , and the bevel gear  31  rotates about the second axis L 2  together with the ring gear  22 . 
     A bevel gear  33 , the rotation center of which is the third axis L 3 , is provided in the third wrist element  12 . The bevel gear  33  meshes with the bevel gear  31 , and the rotation of the ring gear  22  causes the bevel gear  33  to rotate via the bevel gear  31 . This causes the third wrist element  12  to rotate about the third axis L 3 . The outer diameter of the bevel gear  31  is larger than that of the bevel gear  33 , and accordingly, when the power is transmitted from the bevel gear  31  to the bevel gear  33 , the rotation speed of the bevel gear  33  increases. 
     An attachment surface  12   a  is formed at the front end of the third wrist element  12 , and an attachment AT (the welding torch  2  of  FIG. 3 , the hand tool  3  of  FIG. 4 , etc.) adapted to the contents of work is detachably attached to the attachment surface  12   a . The wrist structure  100  of this embodiment has three degrees of freedom about three rotational axes, and accordingly, can freely change the position and orientation of the attachment AT. In this instance, the distance between the second axis L 2  and the center of the attachment AT is longer than the distance between the third axis L 3  and the center of the attachment AT, and accordingly, driving torque larger than that necessary to drive the third wrist element  12  is needed to drive the second wrist element  11 . In short, it is necessary to increase the reduction ratio of the servomotor  13  for the second wrist. When an attempt to obtain this reduction ratio from only the hypoid gear set  15  is made, the reduction ratio of the hypoid gear set  15  increases, and the power transmission efficiency reduces. Taking this point into consideration, in this embodiment, the wrist structure  100  is constructed as follows. 
     As shown in  FIGS. 1 and 2 , the wrist structure  100  has a power transmission unit  50  for the second wrist, which transmits the power of the servomotor  13  for the second wrist to the second wrist element  11 , and a power transmission unit  55  for the third wrist, which transmits the power of the servomotor  14  for the third wrist to the third wrist element  12 . 
     The power transmission unit  50  for the second wrist has the hypoid gear set  15 , and a first deceleration unit RG 1  and a second deceleration unit RG 2 , which are provided between the servomotor  13  and the hypoid gear set  15 . A drive shaft  51  extends in the front-rear direction above the servomotor  14 , and spur gears  52  and  53  are attached to the front and rear ends of the drive shaft  51 . The drive shaft  51  is supported by the rear case  10 B via a pair of bearings  51   a  and  51   b , so as to be rotatable about an axis parallel with the first axis L 1 . Note that oil seals  51   c  and  51   d  are respectively provided behind the bearing  51   a  and in front of the bearing  51   b , to prevent lubrication oil for the bearings  51   a  and  51   b  from entering toward the servomotor  14 . 
     The spur gear  53  meshes with the output shaft  13   a  of the servomotor  13 , and the rotation of the servomotor  13  is transmitted to the drive shaft  51  via the spur gear  53 . The outer diameter of the spur gear  53  is larger than that of the output shaft  13   a , and the output shaft  13  and the spur gear  53  constitute the first deceleration unit RG 1 . The rotation of the servomotor  13  is reduced by the first deceleration unit RG 1  at a predetermined reduction ratio, and the drive shaft  51  rotates at a speed lower than that of the servomotor  13 . 
     The front end of the drive shaft  51  projects into the front case  10 A, and the spur gear  52  is disposed within the front case  10 A. A spur gear  54 , which is rotatable about the axis L 16 , is attached to the rear end of the shaft  160  of the pinion gear  16 . The spur gear  52  meshes with the spur gear  54 , and the rotation of the drive shaft  51  is transmitted to the pinion gear  16  via the spur gears  52  and  54 . The outer diameter of the spur gear  54  is larger than that of the spur gear  52 , and the spur gears  52  and  54  constitute the second deceleration unit RG 2 . The rotation of the drive shaft  51  is reduced by the second deceleration unit RG 2  at a predetermined reduction ratio, and the pinion gear  16  rotates at a speed lower than that of the drive shaft  51 . 
     As seen above, the rotation of the servomotor  13  for the second wrist is transmitted to the pinion gear  16  via the two deceleration units RG 1  and RG 2 . This enables the second wrist element  11  to rotate at a predetermined driving torque without mush increase of the reduction ratio of the hypoid gear set  15 . For example, the reduction ratio of the first deceleration unit RG 1  and the reduction ratio of the second deceleration unit RG 2  can be set at 1:1.5 to 4, and the reduction ratio of the hypoid gear set  15  can be set at 1:8 to 20. Regarding the distribution in the reduction ratio of the first deceleration unit RG 1  and the second deceleration unit RG 2 , an optimal value should be selected taking the structure of a portion, to which each deceleration unit is mounted, into consideration. For example, 1:1.5 can be selected in the first deceleration unit RG 1 , and 1:4 can be selected in the second deceleration unit RG 2 . Consequently, the reduction ratio of the hypoid gear set  15  can be reduced to 20 or below. Thus, the reduction ratio of the hypoid gear set  15  can be prevented from being excessive, and the transmission efficiency can be prevented from reducing. 
     The power transmission unit  55  for the third wrist has the hypoid gear set  20 , the paired bevel gears  31  and  33 , and a third deceleration unit RG 3  provided between the servomotor  14  and the hypoid gear set. A spur gear  56 , which is rotatable about the axis L 21 , is attached to the rear end of the shaft  210  of the pinion gear  21 . The spur gear  56  meshes with the output shaft  14   a  of the servomotor  14 , and the rotation of the servomotor  14  is transmitted to the pinion gear  21  via the spur gear  56 . The outer diameter of the spur gear  56  is larger than that of the output shaft  14   a , and the output shaft  14   a  and the spur gear  56  constitute the third deceleration unit RG 3 . The rotation of the servomotor  14  is reduced by the third deceleration unit RG 3  at a predetermined reduction ratio, and the pinion gear  21  rotates at a rotation speed lower than that of the servomotor  14 . 
     The rotation of the servomotor  14  for the third wrist is transmitted to the pinion gear  21  via the deceleration unit RG 3 . The distance between the third axis L 3  and the center axis of the attachment AT is small, and accordingly, large driving torque necessary for the second wrist element  11  is not needed for the third wrist element  12 . This enables only one deceleration unit RG 3  to rotate the third wrist element  12  at a predetermined driving torque without much increase of the reduction ratio of the hypoid gear set  20 . For example, the reduction ratio of the third deceleration unit RG 3  can be set to be 1:3 to 5, and the reduction ratio of the hypoid gear set  20  can be set to be 1:10 to 20. Consequently, the reduction ratio of the hypoid gear set  20  can be reduced to 20 or below. Thus, the reduction ratio of the hypoid gear set  20  can be prevented from being excessive, and the transmission efficiency can be prevented from reducing. 
       FIG. 5  is a perspective view, seen from obliquely behind, of the first wrist element  10 . As shown in  FIG. 5 , a through-hole  41  is made, along the first axis L 1 , in the rear end of the first wrist element  10  (rear cover  10 B), and a reduction gear mechanism (not shown) for reducing the rotation speed of the first wrist element  10  is disposed behind the through-hole  41 . A hollow hole is formed in an output unit of the reduction gear mechanism, and a control cable to be connected to a connection between the servomotors  13  and  14  is inserted to the hollow hole. This absorbs torsion of the cable produced at the time of rotation of the first wrist element  10  about the first axis L 1 , and prevents damage such as breakage of the cable. A cover  42  is detachably attached to the first wrist element  10 . The removal of the cover  42  enables the control cable to be easily attached to and detached from the connector between the servomotors  13  and  14 . 
     As described above with reference to  FIG. 2 , the first reduction gear RG 0  is contained in the forearm  8 . A first hollow part  91  having a center axis coincident with the first axis L 1  is formed in the first reduction gear RG 0 . Note that the first wrist element  10  is attached to the output unit of the first reduction gear RG 0 . Further, a through-passage  92  is formed in the first wrist element  10 . Likewise, a second hollow part  93  having a center axis coincident with the third axis L 3  is formed in the third wrist element  12 . 
     As can be seen from, for example,  FIG. 2 , the umbilical member  4  fed from the feeding device  5  (tool management relay device) extends, through the first hollow part  91 , the through-passage  92 , and the second hollow part  93 , to the hand tool  3  (or the welding torch  2 ). In short, in the present invention, the umbilical member  4  is positioned inside the wrist structure  100 . This minimizes a gravitational load applied from the umbilical member  4  to two axes of the wrist. 
     In this respect, the welding torch  2  or the hand tool  3  having a light weight is attached to the third wrist element  12 . Then the reduction ratio of the hypoid gear set  15  is reduced to, for example, 1:8 to 10. As necessary, the SIMM causes the pinion gear  16  to approach the second axis L 2 . The hypoid gear set  20  and the pinion gear  21  may be set in a similar manner. 
     As described above, when the reverse efficiency etc. of the hypoid gear set is adjusted, at least one of the servomotors  13  and  14  can support the weight load of the welding torch  2  or the hand tool  3  without having a built-in brake. Thus, in the present invention, regardless of the attitude of the robot, there is no possibility that members associated with axes for positioning the welding torch  2  or the hand tool  3 , i.e., the first to third wrist elements may be accidentally detached. 
     In  FIGS. 1 and 2 , positions B 1  and B 2  are respectively designated by dashed lines in the servomotors  13  and  14 . The positions B 1  and B 2  represent portions to which connectors for brakes for the servomotors  13  and  14  are attached. In the present invention, a brake is not needed for at least one of the servomotors  13  and  14 , and accordingly, a connector for the brake can be omitted. 
     In the present invention, a brake and a connector for the brake of at least one of the servomotors can be eliminated, and accordingly, the entire weight of the wrist structure  100  can be reduced. This enables quick movement and precise positioning without accidental detachment of members associated with the axes. 
     Note that, when the welding torch  2  or the hand tool  3  has a relatively large weight, it is preferable that a brake for at least one of the servomotors  13  and  14  is attached. Thus, a connector for a brake may be attached to the positions B 1  and B 2 . This enables a brake to be connected to a connector for the brake as necessary. Further, in order to accomplish this object, in the vicinity of the positions B 1  and B 2 , it is preferable that a space, which is large enough to contain the brake, is prepared within the cover  42 . 
     Effect of the Invention 
     In the first aspect of the invention, gravitational loads based on the operation tool, which act on two axes of the wrist, can be minimized. Thus, when the operation tool has a relatively light weight, appropriately adjusting the reverse efficiency of the hypoid gears enables at least one motor to support the gravitational loads in the operation tool without containing a brake. Thus, members associated with axes, e.g., the first to third wrist elements can be prevented from being accidentally detached. As seen above, a brake of at least one motor can be eliminated, and accordingly, the entire weight of the wrist structure can be reduced. Thus, a wrist structure of an industrial robot, which can quickly move and can be precisely positioned without accidental detachment of members associated with axes, can be provided. 
     The above description is merely an example, and does not limit the present invention, by the aforementioned embodiments and modifications, as far as the features of the present invention are not impaired. Some of the components in the aforementioned embodiments and modifications can be obviously replaced as far as the identicalness of the invention is maintained. In other words, other embodiments derived from the technical idea of the present invention are included in the scope of the present invention. Further, a combination of the aforementioned embodiments and one or a plurality of modifications can be made.