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FIELD OF THE INVENTION 
   The present invention relates to overhead carriages that run along a track provided above a floor surface, and in particular, to construction of a carrying system for preventing collision of the carriage. 
   BACKGROUND OF THE INVENTION 
   An overhead carriage has been known which has a running portion placed inside a rail laid on the ceiling and an article placing portion provided outside the rail (see the Unexamined Japanese Utility Model Application Publication (Jikkai-sho) 60-161664). This carriage is placed so as to run at a height position where it normally does not come into contact with an operator. The carriage also has a safety device that detects an obstacle entering a running route of the carriage and stops the carriage when detecting an obstacle. 
   The term “running route” as used herein refers to the whole space through which the carriage passes. A space through which the running portion passes is covered with the rail, whereas a space through which the article placing portion passes is exposed to the exterior. The safety device is actuated not only when an operator crosses the running route but also when, for example, for replacement of an article processing device, an obstacle such as the processing device is transported across the running route. As such a safety device, an obstacle sensor such as a reflective optical sensor is mounted on the carriage. 
   An obstacle suddenly entering the running route may come into collide with the accidentally passing carriage (article placing portion), or even if the carriage is running at a position located away from the obstacle entry position, such a collision may occur when the carriage approaches the object but the breaks fail to be applied in time. Thus, when any obstacle possibly crosses the running route, the carriage is not operated. However, this may disadvantageously reduce carrying efficiency. That is, a problem to be solved by the present invention is that an exposed portion of the running route of the carriage (space through which the carriage passes) may cause an obstacle to enter the running route. 
   SUMMARY OF THE INVENTION 
   A description has been given of the problem to be solved by the present invention. Now, the description will be given of means for solving the problem. 
   According to a first embodiment, there is provided a carrying system comprising a carriage including a hoist that elevates and lowers an article in a vertical direction and a running portion, and a track which internally houses the running portion and which is suspended from a ceiling, the carrying system having at least one cover placed parallel to the track to prevent entry of an obstacle into the track, the cover being provided below the track so as not to hinder the elevation and lowering of the article executed by the hoist. 
   According to a second embodiment, the carrying system has lateral moving means for horizontally moving the hoist in a lateral direction, and the cover has an opening so as not to hinder the movement executed by the lateral moving means. 
   According to a third embodiment, the covers cover laterally opposite side surfaces of the article and carriage, and an inner side surface of the covers is subjected to diffused reflection-proof finish. 
   The present invention exerts the following effects. 
   According to the first embodiment, the entire running route of the carriage is covered to prevent an obstacle from entering the running route. This eliminates the need to stop the carriage in fear of entry of an obstacle into the running route. A decrease in carrying efficiency is also prevented. 
   According to the second embodiment, even a carriage that transfers articles not only in a vertical direction but also in a lateral direction can successfully transfer the articles. 
   According to the third embodiment, it is unnecessary to provide a polarizing sensor for preventing erroneous detections caused by diffused reflection. This allows the carriage to be also operated at curves. 
   Other features, elements, processes, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front sectional view showing a track and a carriage. 
       FIG. 2  is a side view showing the carriage. 
       FIG. 3  is a planar sectional view showing the carriage. 
       FIG. 4  is a side view showing the track and the carriage. 
       FIG. 5  is a front sectional view showing the carriage with a cover provided on only one of laterally opposite sides thereof. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to  FIGS. 1 to 5 , a description will be given of configuration of a carrying system according to an embodiment of the present invention. 
   The carrying system is composed of a carriage  1 , a track  12 , and covers  13 ,  13  arranged parallel to the track  12  to prevent an obstacle from entering the track  12 . A shown in  FIGS. 1 and 2 , the carriage  1  has a running portion  2  in its upper part and an article supporting device  3  in its lower part. The running portion  2  and the article supporting device  3  are coupled together via a coupler  6 . The carriage  1  runs along the track  12  suspended from a ceiling. A feeder line holder  34  for feeding electricity to the carriage  1  and the covers  13  are fixed to the carriage  1 . The running portion  2  of the carriage  1  is accommodated in the track  12 . The article supporting device  3  is covered with the laterally opposite covers  13 ,  13  on its respective lateral sides. 
   As shown in  FIG. 3 , the running portion  2  is composed of a central main frame  31  and wheel supporting portions  32 ,  32  located in front of and behind the main frame  31 . The wheel supporting portions  32 ,  32  are coupled to the main frame  31  via shafts  33 ,  33  so as to be freely rotatable with respect to the main frame  31 . This enables the carriage  1  to run along curves formed in the track  12 . The article supporting portion  3  in which an article can be loaded is provided below the running portion  2 . The article supporting device  3  is supported by the running portion  2  via the coupler  6 . 
   The running portion  2  has a motor  16  as means for driving the carriage  1  as shown in  FIG. 1 . The motor  16  is attached to the main frame  31 . A driving wheel  25  is connected to a motor shaft of the motor  16 . The driving wheel  25  is drivingly rotated by the motor  16 . 
   The wheel supporting portion  32  has cross section shaped like the letter U that is open at the top as viewed from a running direction. Running wheels  23 ,  23  having lateral axles are arranged on the laterally opposite sides in a lower portion of the wheel supporting portion  32 . The running wheels  23 ,  23  are fixed to the wheel supporting portion  32 . The running wheels  23  are placed on the laterally opposite sides of each of the front and rear wheel supporting portions  32 . The running portion  2  as a whole has four running wheels  23  located in its front and rear and on its laterally opposite sides. The running wheels  23 ,  23 , . . . are in contact with running surfaces  40 ,  40  (described later) formed in the track  12  to support the carriage  1  on the track  12 . 
   As shown in  FIG. 1 , paired pickup units  9 ,  9  are provided on the laterally opposite sides of the coupler  6  as means for feeding electricity to the carriage  1 . Each pickup unit  9  comprises an E-shaped core  15  having an opening through which a feeder lines  5  provided below the track  12  can be inserted. By utilizing electromagnetic induction caused by magnetic fields generated by an alternating current flowing through each of the feeder lines  5 ,  5 , a pickup coil  17  provided in the core  15  receives electricity. Each of the feeder lines  5 ,  5  is supported by a feeder line holder  34  provided below the track  12 . The means for feeding electricity to the carriage  1  is not limited to the non-contact feeding scheme using the cores and feeder lines. 
   As shown in  FIG. 4 , the carriage  1  has a reflective optical sensor  19  for detecting the preceding carriage  1 . The sensor  19  is attached to the front surface of the carriage  1  to detect the distance to the preceding carriage  1 . The principle of detection is that light is flooded by a light emitting portion and reflected light is received so that the distance can be determined from the intensity of the received light. When the sensor  19  detects that the preceding carriage  1  is running at a short distance from the succeeding carriage  1 , the succeeding carriage  1  stops. Each carriage  1  has a reflector on its rear surface to efficiently reflect light flooded by a respective succeeding carriage  1 . In the present embodiment, the carriage  1  is configured to run only forward along the running route and not to run backward. Accordingly, the sensor  19  is provided only on the front surface of the carriage  1  so as to be able to detect the preceding carriage  1 . When the carriage  1  is configured to run both forward and backward, the sensor  19  is also provided on the rear surface of the carriage  1 . 
   The track  12  is provided above the floor surface, and the carriage  1  runs while being suspended from the track  12 . The track  12  is composed of a base  42  having a cross section shaped like the letter U that is open at its bottom as viewed from the track direction and extending in a horizontal direction, and side walls  41 ,  41  extending downward from the opposite ends of the base  42 . A horizontal portion is also extended inward from the lower ends of the side walls  41 ,  41  and has a top surface formed into a running surface  40  contacted by the running wheels  23 . The bottom surface of a lateral center portion of the base  42  is formed into a running surface  42   a  contacted by the driving wheel  25 . 
   Paired guide wheels  24 ,  24  having vertical axles are provided on the laterally opposite sides of top of each wheel supporting portion  32 . The right and left guide wheels  24 ,  24 , . . . are almost in contact with the side walls  41 ,  41  formed on the track  12 . This allows the carriage  1  to run along the track  12  without shifting in the lateral direction. 
   Next, the configuration of the article supporting device  3  will be described. The article supporting device  3  has a hoist  7  that suspends an article  4 , and lateral moving means  8  for enabling the hoist  7  to be moved in the lateral direction with respect to the track direction. The hoist  7  is placed below the lateral moving means  8 . The covers  13  cover laterally opposite sides of the article supporting device  3 . 
   The lateral moving means  8  is composed of lateral moving rails and a lateral feeding mechanism. The hoist  7  is supported by its upper part being sandwiched between the lateral moving rails. The lateral moving mechanism operates to move the hoist  7  along the lateral moving rails. 
   The hoist  7  is composed of a chuck mechanism  10  and a winch  11  that is means for elevating and lowering the chuck mechanism  10 . The chuck mechanism  10  is placed below the winch  11 . The tip of a wire (not shown in the drawings) is attached to the chuck mechanism  10 . Winding or winding back the wire enables the chuck mechanism  10  to be elevated or lowered. 
   The article  4  has a handle  4   a  at its upper end which is gripped by the chuck mechanism  10  to support the article  4 . The handle  4   a  is T-shaped as viewed from the horizontal direction. 
   On the other hand, the chuck mechanism  10  is capable of supporting a horizontal portion of the T-shaped handle  4   a . The chuck mechanism  10  supports the handle  4   a  provided on the top of the article  4 . Then, the winch  11  and the horizontal moving means  8  drivingly lift the article  4  to a maximum extent to house the article  4  between the covers  13 . When the winch  11  raises the chuck mechanism  10  supporting the article  4  to its highest position, the article  4  is housed in the article supporting device  3 . 
   The hoist  7  can also be drivingly moved perpendicular to the track  12  by the lateral moving means  8 . This allows the hoist  7  to transfer to a position other than the one immediately below the track  12 . 
   Next, a detailed description will be given of the covers  13 ,  13  surrounding the article supporting device  3 . The covers  13 ,  13  are arranged below and parallel to the track  12  to cover the carriage  1  and the article  4  suspended by the hoist  7 , at the laterally opposite side surfaces of the carriage  1 . The covers  13 ,  13  extend downward from the lower end of the side walls  41 ,  41  of the track  12  so as to be flush with the side walls  41 ,  41 . The covers  13 ,  13  do not hinder the article  4  from being elevated or lowered. The covers  13 ,  13  provided on the track  12  eliminate a member for suspending the covers  13 ,  13  from the ceiling. This allows the covers  13 ,  13  to be easily provided along the track  12 . Since the covers  13 ,  13  are provided flush with the side walls  41 ,  41 , steps are prevented from being created at joints between the covers  13 ,  13  and the side walls  41 ,  41 . Thus, when the carrying system is installed in a clean room, down flows from the ceiling can be prevented from being disturbed. 
   As shown in  FIG. 1 , the covers  13  have an openings  21  that are open toward the lateral moving route so as not to hinder the hoist  7  from being moved by the lateral moving means  8 . That is, since the openings  21 ,  21 , . . . are appropriately formed at positions where transfer operations are performed, a route is established along which the article supporting device  3  is moved by the horizontal moving means  8 . This enables the article  4  to be smoothly moved. 
   An inner side surface of each of the covers  13  is subjected to diffused reflection-proof finish. Specifically, the inner side surface of the covers  13  is subjected to matte black coating to prevent light flooded by the sensor  19  from being diffusely reflected. Various devices such as processing devices for processing the article  4  are arranged by the side of the track  12 . Accordingly, light flooded by the sensor  19  is reflected by the outer surfaces of these devices, and the reflected light may be erroneously detected by the sensor  19  of the carriage  1 . Thus, by providing the covers  13 , it is possible to prevent detection errors in the sensor  19  caused by flood light diffusely reflected by peripheral objects. 
   The detection by the reflective sensor  19  is effective in detecting the preceding carriage  1  in a straight part of the running route. However, it is difficult to detect the preceding carriage  1  in a curved part of the running route. However, by providing a mirror or the like inside the covers  13  to refract flooded and reflected light, it is possible for the sensor  19  to detect the preceding carriage  1  even in a curved part. 
   The covers  13  are not required to cover all of the laterally opposite side surfaces of the carriage  1  and the article  4  lifted by the hoist  7 . For example, when one of the laterally opposite sides faces a wall of a building, the cover  13  may be provided on only one of the laterally opposite sides through which an obstacle may enter the running route. As shown in  FIG. 5 , the carriage  1  can also be kept safe by providing the cover  13  on only one of the laterally opposite sides of the carriage  1 , that is, the side located opposite the wall and on which the carriage  1  may come into collide with an operator (side on which high-place work may be performed). The covers  13  may be formed of a mesh instead of a plate. In short, it is only necessary to protect the whole space through which the carriage  1  and the article  4  supported by the carriage  1  entirely pass, that is, the running route of the carriage  1 , from the entry of an obstacle. That is, the covers  13  make the space inside the covers  13  independent of the other spaces. Further, the covers  13  in the present embodiment are placed below the track  12 . However, the covers  13  may be suspended from the ceiling. The position to which the covers  13  are mounted is not limited. 
   While the present invention has been described with respect to preferred embodiments thereof, it will be apparent to those skilled in the art that the disclosed invention may be modified in numerous ways and may assume many embodiments other than those specifically set out and described above. Accordingly, it is intended by the appended claims to cover all modifications of the present invention that fall within the true spirit and scope of the invention.

Summary:
The present invention prevents an obstacle from entering a running route of an overhead carriage to allow the carriage to run smoothly, increasing carrying efficiency. The present invention provides a carrying system including a carriage  1  having a hoist  7  that elevates and lowers an article in a vertical direction and a running portion  2 , and a track  12  which internally houses the running portion  2  and which is suspended from a ceiling. The carrying system has a cover  13  placed parallel to the track  12  to prevent entry of an obstacle into the track; the cover  13  is provided below the track  12  so as not to hinder the elevation and lowering of the article executed by the hoist  7.