Abstract:
A conveying apparatus comprising a traveling unit which runs; a winding roller which is supported by the traveling unit; a belt which is wound on the winding roller so as to be unwound and wound by the winding roller; a pulley which has a peripheral surface guiding the belt and a diameter smaller than the diameter of the winding roller; and the pulley having no flange on both ends thereof; a belt positioning guide which is provided below the pulley and guides both edges of the belt in the win direction thereof so that the belt is positioned in the width direction; and a support unit which is attached to the belt and supports a conveyed object.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a conveying apparatus in which an unit for supporting a conveyed object is suspended by a belt so as to be lifted and lowered by winding and unwinding the belt extending from a traveling unit for transportation. 
   Priority is claimed on Japanese Patent Application No. 2005-206975 filed Jul. 15, 2005, the content of which is incorporated herein by reference. 
   2. Description of Related Art 
   In a configuration of a conveying apparatus (conveyer) wherein an unit for supporting a conveyed object (load) is suspended by windable belts so as to be lifted and lowered by winding and unwinding the belts fed from a traveling unit for transportation provided with winding rollers for winding and unwinding the belts. A belt fed from the winding roller is guided by a guiding pulley at a fixed position and is suspended to a downward direction. At that state, the support unit is suspended at the end of the belts. Conventionally, in conveying apparatus of this type, for example, as disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 11-11299, a flanged pulley that have flanges holding the belt from both width directional sides of the belt has been utilized as the guiding pulley for downwardly suspending the belt. In this case, in order to reduce size and weight of the conveying apparatus, and reduce costs, it is usual for the flanged pulley to be configured to have smaller diameter than the winding roller 
   In a conventional configuration of the conveying apparatus that utilizes a flanged pulley as a guiding pulley for downwardly suspending the belt, dust is generated by wear of the belt at the position of the flanged pulley. Therefore, the conventional type conveying apparatus cannot be used in working environments requiring dust-free clean atmosphere, for example, in a clean room for semiconductor production. 
   In conveying apparatuses of this type, a flanged pulley having flanges that hold the belt from both width directional sides of the belt is also utilized as a winding roller for winding and unwinding the suspending belt. This winding roller has a large diameter because of requirement for winding a long length of a belt. On the other hand, in order to satisfy a demand for reducing cost, and for downsizing and weight saving the conveying apparatus, a flanged pulley as a guiding pulley for downwardly suspending the belt is usually configured to have as small a diameter provided that an overstress is not caused in the belt to be guided. In such a configuration, the circumferential speed of the guiding pulley is remarkably faster than the circumferential speed of the winding roller. Therefore, regarding a relative sliding rate between the flange and the side edge of the belt departing from the rotating body in the tangential direction, the relative sliding rate at a position of the guiding pulley is extremely higher than that at a position of the winding roller. Therefore, regarding a sliding friction causing generation of wear dust originated from side edges of the belt, sliding friction between the belt and the flanges of the winding roller scarcely or do not cause a wear dust, whereas a sliding friction between the belt and the flanges of the guiding pulley remarkably cause a generation of wear dust. As described-above, dust generation is considered to be an obstruction to the use of conveying apparatus in clean rooms. The present invention has an object of providing a conveying apparatus by which the above-described conventional problems can be solved. 
   SUMMARY OF THE INVENTION 
   In order to solve the above-described problem, a conveying apparatus of the invention comprises: a traveling unit which runs; a winding roller which is supported by the traveling unit; a belt which is wound on the winding roller so as to be unwound and wound by the winding roller; a pulley which has a peripheral surface guiding the belt and a diameter smaller than the diameter of the winding roller; and the pulley having no flange on both ends thereof; a belt positioning guide which is provided below the pulley and guides both edges of the belt in the width direction thereof so that the belt is positioned in the width direction; and a support unit which is attached to the belt and supports a conveyed object. 
   In the above-described conveying apparatus, the support unit may be suspended by a single belt, utilizing a winding roller, a guiding pulley and a belt positioning guide. Alternatively, the support unit may be suspended by a plurality of belts, utilizing a plurality of winding rollers, guiding pulleys, and belt positioning guides. 
   In a conveying apparatus of the above-described configuration, the belt positioning guide may comprise a bilateral pair of positioning rollers (left roller and right roller) which hold the belt from left side and right side of the belt. 
   The above-described bilateral pair of positioning rollers of the belt positioning guide may be provided with recessed grooves which engage with the side edges of the belt from left side and right side of the belt. 
   The recessed grooves of the bilateral pair of positioning rollers may be configured such that each groove is in contact with both thick-directional corners in a side edge of the belt, and a section of the groove has arc-like or V-like shape. 
   In any one of above-described configurations of the conveying apparatus, it is preferable that a surface portion of the belt positioning guide being in contact with the belt is composed of a synthetic resin. 
   In the above-described configuration of the conveying apparatus, the guiding pulley for downwardly suspending the belt is configured to be a pulley without flanges on both axial ends thereof. Therefore, even when the diameter of the pulley is reduced to a minimum value barely satisfying a necessity, there are no contact at which the rotor is mutually rubbing with the belt. Therefore, wear of the belt is substantially negligible. In conventional case, width directional movement (with directional drifting) of the suspending belt caused by misalignment of horizontal shaft of the guiding pulley or uneven surface smoothness of the both faces (front face and back face) of the belt cannot be controlled at a position of a guiding pulley. However, in the configuration of the invention, since a belt positioning guide for controlling a position of a belt is provided in a vicinity of the guiding pulley, the width directional movement of the belt at the position of the guiding pulley can be controlled to essentially the same degree as the conventional configuration in which a flanged pulley was used as the guiding pulley. 
   As is clear from the explanation above, by employing the configuration of the invention, down sizing of the conveying apparatus and cost reduction can be achieved without making the guiding pulley for downwardly suspending the belt to have a large diameter, in other words, while restricting the guiding pulley to have a diameter of a necessary minimum. At the same time, it is possible to solve the conventional problem of wear dust of the belt being generated at the position of the guiding pulley. In addition, width directional drifting of the belt can be controlled to the same degree as the conventional case in which a flanged pulley was used as the guiding pulley. Therefore, the conveying apparatus of the invention can be advantageously used as a conveying apparatus used in a clean room. 
   The belt positioning guide is provided independently from the guiding pulley. If the belt positioning guide is configured by a bilateral pair of positioning rollers which hold the belt from the left side and right side of the belt, it is also possible to effectively suppress the generation of wear dust associated with the mutual rubbing between the belt and the belt positioning guide. 
   In this case, by providing the bilateral pair of positioning rollers as constituents of the belt positioning guide with recessed grooves which engage with the side edges of the belt from left and right sides of the belt, it is also possible to control the position of the belt in the direction of thickness, and inhibit the drifting of the belt in the direction of thickness, 
   At that case, if the recessed grooves of the bilateral pair of positioning rollers are configured such that each groove being in contact with corners at the both ends in a thickness direction of the side edge of the belt, and the section of the groove has arc-like or V-like shape, the contact between the belt and the recessed grooves of the bilateral pair of positioning rollers can be made a point contact, or a state close to it. Consequently, the generation of wear dust from the belt caused by mutual rubbing between the belt and the recessed grooves of the rotor can be effectively inhibited. 
   In any case, by employing a configuration wherein the contact face between the belt positioning guide and the belt is made of a synthetic resin, the frictional coefficient of the surface of the belt positioning guide being in contact with the belt is reduced, thus suppressing wear of the belt, and even more effectively suppressing the generation of wear dust. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of the overall conveying apparatus. 
       FIG. 2  is a front view of the vertical-drive suspending unit. 
       FIG. 3  is a plan view of the vertical-drive suspending unit. 
       FIG. 4  is a right side view of the vertical-drive suspending unit. 
       FIG. 5  is a left side view of the vertical-drive suspending unit. 
       FIG. 6  is a perspective view showing the belt, the winding roller, the guiding pulley, and the belt positioning guide. 
       FIG. 7  is a partial cross-sectional plan view showing a specific configuration of the belt positioning guide. 
       FIG. 8  is a schematic cross-sectional view showing a state of point contact between the positioning roller of belt positioning guide and the belt. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereunder, specific embodiments of the present invention are explained based on the attached drawings. In  FIG. 1 , reference symbol  1  denotes a train type traveling unit for transportation of a conveyed object. The traveling unit  1  is suspended from guide rails  2  by a power trolley unit  3 , and a flee trolley unit  4  such that the traveling unit  1  can runs along the rails  2 . The trolley units  3  and  4  are furnished with horizontal axis wheels  5  and  6  for traveling, and perpendicular as rollers  7  and  8  as steady rests. The horizontal axis wheel  5  of the power trolley unit  3  is rotated by a motor  9  mounted on the power trolley unit  3 . 
   On the traveling unit  1  is provided therebelow, a vertical dive suspending unit (elevating unit)  11  which suspends the support unit  10  such that it is able to be lifted and lowered. Although a support unit exemplified in  FIG. 1  is provided with a gripping device  12  which can be opened and closed for gripping an upper portion of a conveyed object W, the support unit  10  may have various configurations in accordance with the shape of the conveyed object W, or the like. 
   As shown in  FIG. 2  to  FIG. 6 , a vertical-drive suspending unit  11  suspends four positions at front, back, left, and right, of the support unit  10  by four belts  13   a ,  13   b ,  14   a , and  14   b . Width directions of the four belts  13   a ,  13   b ,  14   a , and  14   b  are oriented parallel to the travel direction of the traveling unit  1 . The vertical-drive suspending unit is furnished with winding rollers  15   a ,  15   b ,  16   a , and  16   b  for winding and unwinding the belts  13   a ,  13   b ,  14   a , and  14   b . These four winding rollers  15   a ,  15   b ,  16   a , and  16   b , are coaxially arranged such that they are lined up in the running direction of the traveling unit  1 . At that state, the winding rollers  15   a  and  15   b  for winding and unwinding a front-back pair of belts  13   a  and  13   b  on one side (right side or left side) are positioned on the outer side of the winding rollers  16   a  and  16   b  for winding and unwinding the front-back pair of belts  14   a  and  14   b  on the other side. Specifically, the winding millers  15   a ,  15   b ,  16   a  and  16   b  are attached on a drive shaft  19  of a motor  17  fitted with a speed reducer. The drive shaft  19  protrudes in the front and back directions from the speed reducer  18 , and winding rollers  16   a  and  15   a , and the winding rollers  16   b  and  15   b  are arranged on both the front and back sides of a speed reducer  18 . The winding rollers  15   a  to  16   b  comprise flanged pulleys. Four respectively individual pulleys may be individually installed on the drive shaft  19 . However, in this embodiment, winding rollers  16   a  and  15   a , and  16   b  and  15   b , on both the front and back sides of the speed reducer  18  are configured to have an integral construction in which the intermediate flange is shared by two adjacent winding rollers. 
   The winding direction of the belts  13   a ,  13   b ,  14   a  and  14   b  with respect to the winding rollers  15   a ,  15   b ,  16   a  and  16   b  is the same. Flangeless guiding pulleys  22   a  and  22   b  are supported by support shafts (support shafts)  20   a  and  20   b , which are parallel with the drive shaft  19 , such that they are adjacent to the belt extending side of the two winding rollers  15   a  and  15   b . The belts  13   a  and  13   b , extending from the upper side of the outer winding rollers  15   a  and  15   b  are suspended spanning the flangeless guiding pulleys  22   a  and  22   b . Flangeless guiding pulleys  23   a  and  23   b  are supported by support shafts  21   a  and  21   b , which are parallel with the drive shaft  19 , such that they are adjacent to the belt extending side of the two winding rollers  16   a  and  16   b . The belts  14   a  and  14   b  extending from the bottom side of the inside winding rollers  16   a  and  16   b  are suspended spanning the flangeless guiding pulleys  23   a  and  23   b . These guiding pulleys  22   a ,  22   a ,  23   a  and  23   b  may have the same width as the width of the belts  13   a ,  13   b ,  14   a , and  14   b . Preferably, the guiding pulleys  22   a ,  22   a ,  23   a  and  23   b  may have a width properly wider than the width of the belts  13   a ,  13   b ,  14   a , and  14   b.    
   In the above-described configuration, the guiding pulleys  22   a  to  23   b  are smaller in diameter than the winding rollers  15   a ,  15   a ,  16   a  and  16   b . The minimum diameter of the guiding pulleys  22   a ,  22   b ,  23   a  and  23   b  is determined based on the range in which an undesirable bending stress does not act on the belts  13   a ,  13   b ,  14   a , and  14   b  when the guiding pulleys  22   a ,  22   b ,  23   a  and  23   b  change the directions of the belts  13   a ,  13   b ,  14   a , and  14   b . In the embodiment of the present invention shown in the figures, the guiding pulleys  23   a  and  23   b , which bend the belts  14   a  and  14   b  in a S-like shape, are made to be larger in diameter than the other guiding pulleys  22   a  and  22   b . By such a configuration, without providing additional guiding pulleys on the guiding pulley  22   a  and  22   b  side, it is possible to control the difference between the length of the belts  15   a  and  15   b  wound by the winding rollers  15   a  and  15   b  and the length of the belts unwound by the winding rollers  16   a  and  16   b  to a value within a range in which a substantial adverse effect does not arise. In other words, the diameters of guiding pulleys  23   a  and  23   b  are larger than the diameters of the guiding pulleys  22   a  and  22   b  such that, when the whole lengths of the belts  13   a  to  14   b  are completely unwound from the winding rollers  15   a  to  16   b , all of which having same diameters of circumference surface for winding, the belts  13   a  and  13   b  extending from the winding rollers  15   a  and  15   b , and the belts  14   a  and  14   b  extending from the winding rollers  16   a  and  16   b , nearly show a point symmetry about the drive shaft  19 . 
   Belt positioning guides  24   a ,  24   b ,  25   a  and  25   b  are installed in the vicinity of the guiding pulleys  22   a ,  22   b ,  23   a  and  23   b . At positions below the guiding pulleys  22   a ,  22   b ,  23   a  and  23   b , the belts  13   a ,  13   b ,  14   a  and  14   b  suspended from the guiding pulleys are positioned in relation to the belt width direction by the belt positioning guides  24   a ,  24   b ,  25   a  and  25   b . The belt positioning guides  24   a ,  24   b ,  25   a  and  25   b  of this embodiment are configured by bilateral (left and right) pairs of positioning rollers  26   a  and  26   b , which hold the respective belts  13   a ,  13   b ,  14   a  and  14   b  from left and right width directional sides of the belts. To explain in further detail, as shown in  FIG. 7 , the left and right pain of rollers  26   a  and  26   b  comprise grooved rollers of a synthetic resin which are furnished with arc-shaped recessed grooves  27  in their circumferences. The recessed grooves  27  are respectively in contact with thick-directional corners in the side edge of the belts  13   a ,  13   b ,  14   a  and  14   b . In each one of the belt positioning guides  24   a ,  24   b ,  25   a  and  25   b , support shafts  28  of the bilateral pairs of rollers  26   a  and  26   b  are supported on a bearing plate  31  in cantilever state by a fastening nut  30 , and an screw shaft  29 . The screw shaft  29  is integrated with the inner end of the support shaft  28  and is biased by an eccentricity α with respect to the support shaft  28 . Reference symbols  28   a  denote a holding nut portion that is integrally formed on the support shafts  28 . While the positioning rollers  26   a  and  26   b  were explained to be grooved rollers made of a synthetic resin in the above-described embodiment, it should be noted that the rotors  26   a  and  26   b  may be made of other materials, provided that the peripheral annular portions which form the recessed grooves being in contact with the belts  13   a ,  13   b ,  14   a  and  14   b  are made of a synthetic resin. 
   When the belt positioning guides  24   a ,  24   b ,  25   a  and  25   b  have the above-described configuration, by relaxing the fastening nut  30  and by rotating the support shaft  28  about the central axis of the eccentric screw shaft  29  via the holding nut portion  28   a , the position of the rollers  26   a  and  26   b  can be moved within a range of twice the eccentricity α in the width direction of the belts  13   a ,  13   b ,  14   a  and  14   b  which are respectively held between two rollers  26   a  and  26   b . Accordingly, by adjusting the position of the rollers  26   a  and  26   b  as mentioned above, the position of the belts  13   a ,  13   b ,  14   a  and  14   b , which are respectively held between two rollers  26   a  and  26   b , can be fine tuned in the width direction thereof, and the spacing D between respective pairs of two rollers  26   a  and  26   b  can be fine tuned. Following this fine tuning, by tightening the fastening nut  30  in a state where the support shaft  28  is fixed through the holding nut portion  28   a , the support shaft  28  (the rollers  26   a ,  26   b ) can be fixed to the bearing plate  31 . 
   As shown in  FIG. 3 , an electromagnetic brake  32  is installed on one end of the drive shaft  19 . Moreover, on the other end of the drive shaft  19  is installed a slip ring device  33 . Metallic wires may be embedded in the belts  13   a ,  13   b ,  14   a  and  14   b  along the length direction of the belts as reinforcements. The reinforcement metallic wire of at least one belt may be utilized as an electrical supply wire to, for example, a motor that drives the holding device  12  of the support unit  10 , and the like. In such a case, the slip ring device  33  may be used as a current collector. Accordingly, the support shafts  20   a  and  21   a  of the guiding pulleys  22   a  and  23   a  for guiding the belts  13   a  and  14   a  can be installed between a side plate  34   a  which is positioned on one side of the speed reducer  18 , and a support plate  35  which supports the slip ring device  33  for current collection. The support shafts  20   b  and  21   b  of the guiding pulleys  22   b  and  23   b  for guiding the belts  13   b  and  14   b  can be installed between a side plate  34   b  which is positioned on the other side of the speed reducer  18 , and a support plate  36  which supports the electromagnetic brake  32 . Furthermore, a mounting plate  39  is connected to the bearing plate  31  of the belt positioning guides  24   a  and  24   b  towards the upper inside direction. By utilizing this mounting plate  39 , the belt positioning guides  24   a  and  24   b  can be installed on the side plates  34   a  and  34   b . The belt positioning guides  25   a  and  25   b  can be installed by bolting the bearing plate  31  thereof to a mounting plate portion  38  which is installed on the bottom side of a base plate  37  that supports the speed reducer  18 . 
   In accordance with the above-described configuration of the vertical-drive suspending unit  11 , lifting and lowering process of the support unit can be explained as follows. When the belts  13   a ,  13   b ,  14   a  and  14   b  are completely wound up by the winding rollers  15   a ,  15   b ,  16   a , and  16   b , the support unit  10  is positioned at a ceiling position represented by the imaginary line (two-dot chain line) in  FIG. 1 . By releasing the electromagnetic brake  32 , forward-driving the drive shaft  19  by operating the motor  17  fitted with a speed reducer, and by turning the four winding rollers  15   a ,  15   b ,  16   a  and  16   b  in the belt unwinding direction, the belts  13   a ,  13   b ,  14   a  and  14   b  are fed by a gravitational force acting on the support unit  10  suspended by the belts, and the support unit  10  is lowered. At a point of time at which the support unit  10  has been lowered to a predetermined level, the motor  17  fitted with a speed reducer is stopped, the electromagnetic brake  32  is operated, and the winding rollers  15   a ,  15   b ,  16   a  and  16   b  are stopped. After that, the loading or unloading of the conveyed object (load) may be performed with respect to the support unit  10 . 
   For lifting the support unit  10  which has been lowered to the ceiling position represented by the imaginary line (two-dot chain line) in  FIG. 1 , the electromagnetic brake  32  is released, the drive shaft  19  is reverse-driven by operating the motor  17  fitted with a speed reducer, the four winding rollers  15   a ,  15   b ,  16   a  and  16   b  are turned in the belt winding direction, thereby winding the belts  13   a ,  13   b ,  14   a  and  14   b  by the winding rollers  15   a ,  15   b ,  16   a  and  16   b , and the support unit  10  which is suspended by the belts  13   a ,  13   b ,  14   a  and  14   b  can be lifted to the ceiling position. 
   In the above-described manner, by the winding and unwinding operations of the belt  13   a ,  13   b ,  14   a  and  14   b , the support unit  10  can be lifted and lowered with respect to the traveling unit  1 . 
   At that time, the width directional positions of the belts  13   a ,  13   b ,  14   a , and  14   b  are respectively restricted by the recessed grooves  27  of the left and right pair of positioning rollers  26   a  and  26   b  of the belt positioning guides  24   a ,  24   b ,  25   a  and  25   b . Therefore, the belts  13   a ,  13   b ,  14   a , and  14   b  do not move in the width direction on the surfaces of the guiding pulleys  22   a ,  22   b ,  23   a  and  23   b , irrespective of the guiding pulleys  22   a ,  22   b ,  23   a  and  23   b  not having flanges for restricting the width directional positions of the belts. Furthermore, as shown in  FIG. 7  and  FIG. 8 , the belts  13   a ,  13   b ,  14   a  and  14   b  are in contact with the recessed grooves  27  of the left and right pair of positioning rollers  26   a  and  26   b , in an approximate point contact condition in which both thick-directional corners in the side edge of the belts  13   a ,  13   b ,  14   a  and  14   b  are in contact with the recessed grooves  27 . Therefore, along with making the rotors  26   a  and  26   b  of a synthetic resin, the wear of the belts  13   a ,  13   b ,  14   a  and  14   b  can be suppressed, and also the belts  13   a ,  13   b ,  14   a  and  14   b  can be positioned with respect to the thickness direction. Because the guiding pulleys  22   a ,  22   b ,  23   a  and  23   b  do not have flanges for restricting the width directional positions of the belts, wearing of the belts  13   a ,  13   b ,  14   a , and  14   b  while rotating about the circumference of the guiding pulleys  22   a ,  22   b ,  23   a  and  23   b  do not occur, irrespective of the peripheral velocity of the guiding pulleys  22   a ,  22   a ,  23   a  and  23   b  being high in comparison to the peripheral velocities of the winding rollers  15   a ,  15   b ,  16   a  and  16   b.    
   In the above-described embodiment, the support unit  10  is suspended by utilizing four belts  13   a ,  13   b ,  14   a  and  14   b . However the number thereof is not restricted. For example, if a wide belt is utilized, it is possible to suspend the support unit  10  with two belts. Moreover, if the support unit can be suspended by one point directly above the position of the center of gravity, it is also possible to suspend the support unit using one belt. Furthermore, in a case where a plurality of belts are utilized, it is not necessary for the width directions of all of the belts thereof to be mutually parallel. Moreover, the width direction of the belts may be a horizontal direction which is perpendicular to the running direction of the traveling unit  1 . 
   While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.