Patent Publication Number: US-6217652-B1

Title: Coating equipment

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention concerns a coating facility adapted for applying pretreatment and coating to works such as car bodies while conveying them by an overhead conveyor, then transferring them to a floor conveyor, drying and then conveying them to a succeeding step after completion of the drying. 
     BACKGROUND ART 
     FIG.  5  and FIG. 6 show a running state and a storage state of an existent coating facility for conducting electrodeposition coating which comprises, along an overhead conveyor  42  formed in a circulation track  41 , a loading device  43  for loading works W conveyed from the preceding step to hangers H each at a predetermined loading position P 1 , a pretreatment device  44  for applying pretreatment such as cleaning, degreasing and chemical formation to the surface of the works W loaded by the loading device  43 , an electrodeposition coating device  45  for forming an electrodeposition coating film on the surface of the works W completed with the pretreatment by the pretreatment device  44 , and a transfer device  48  for down loading the works W from the hangers H after completion of the electrodeposition coating in the electrodeposition coating device  45  and transferring them to carriers T, at a predetermined transferring position P 2 , to a floor conveyor  47  running in a drying furnace  46  in this order. 
     The floor conveyor  47  constitutes a circulation track  47   a  for conveying the carriers T to which the works W are transferred at a transferring position P 2  into the drying furnace  46 , conveying the works W after completion of drying to the succeeding step while loading them as they are on the carriers T and returning the carriers T emptied in the succeeding stage again to the transferring position P 2 . 
     Further, in the circulation track  47   a  of the floor conveyor  47  that returns from the succeeding step is branched to form a reserved carrier storage track  47   b  for storing the emptied carriers T by the number of the works W being conveyed by the overhead conveyor  42  but not yet conveyed to the drying furnace  46 , and the circulation track  47   a  from the exit of the drying furnace  46  to the succeeding step is branched to form a carrier storage track  47   c  for storing all the works W which are being conveyed by the overhead conveyor  42  and the floor conveyor  47  in a state loaded on the carriers T. 
     Then, the carrier storage track  47   c  is adapted such that, at the instance the conveyance of the works from the preceding step and the conveyance to the succeeding step are stopped, it completes drying for the works W conveying by the floor conveyor  47  and stores them while loading on the carriers T as they are, applies pretreatment and completes electrodeposition coating of the works W conveying by the overhead conveyor  42 , transfers them to the carriers T stored in the reserved carrier storage track  47   b,  conveys them successively to the drying furnace  46 , completes drying and then stores them while loading as they are on the carriers T. 
     The overhead conveyor  42  is branched to form a looped empty hanger storage track  41   a  from the circulation track  41  that returns from the transferring position P 2  to the loading position P 1  for storing hangers H which are emptied after transferring the works to the carriers T of the floor conveyor  47 , when the conveyance of the works W from the preceding step is stopped, so that the empty hangers H may be prevented from corrosion caused when left in the pretreatment device  44  or the electrodeposition coating device  45 , and so that the empty hangers H can be delivered immediately to the loading position P 1  as soon as the conveyance of the works W from the preceding step is started. 
     With such a constitution, during operation of the conveying lines between each of the steps, the hangers are circulately run by the overhead conveyor  42 , pretreatment is applied in the pretreatment device  44  while conveying the works W loaded by the loading device  43 , electrodeposition coating is conducted in the electrodeposition coating device  45 , the works W are re-transferred subsequently by the transfer device  48  to the carriers T of the floor conveyor  47 , and the emptied hangers H are returned again to the loading position P 1  to which succeeding works W are loaded and treated continuously. 
     Then, the floor conveyor  47  is adapted such that empty carriers T returning from the succeeding step along the circulation track  47   a  or the reserved carriers T stored in the reserved carrier storage track  47   b  are conveyed to the transferring position P 2 , the works W transferred by the transfer device  48  to the carriers T are conveyed into the drying furnace  46  and conveyed as they are to the succeeding step after the completion of the drying. 
     Then, when the operations for one day are completed, the conveying lines between each of the steps are stopped and conveyance from the preceding step and conveyance to the succeeding step of the works W are stopped, the works W in the drying furnace  46  are stored being loaded as they are on the carriers T in the carrier storage track  47   c,  while the works W in the pretreatment device  44  and the electrodeposition coating device  45  are completed with the pretreatment and the electrodeposition coating, transferred by the transfer device  48  to the reserved carriers T on the floor conveyor  47 , dried in the drying furnace  46  and then stored while being loaded as they are on the reserved carriers T in the carrier storage track  47   c,  while the hangers H emptied after transferring the works to the carriers T are stored in the empty hanger storage track  41   a.    
     Then, when the conveyance from the preceding step and conveyance to the succeeding step of the works W are started in the next morning, the empty hangers H stored in the empty hanger storage track  41   a  are delivered to the circulation track  41  of the overhead conveyor  42  and caused to stand-by at the loading position P 1  and the coating operation is started by successively loading the works W conveyed form the preceding step and at the same time, the works W stored in the carrier storage track  47   c  are successively conveyed together with the carriers T to the succeeding step, and the empty carriers T returned from the succeeding step are delivered to and stored in the reversed carrier storage track  47   b  successively till the leading work W conveyed by the overhead conveyor  42  reaches the transferring position P 2 . 
     In accordance with the coating facility described above, even when conveyance from the preceding step and the conveyance to the next step of the works W are stopped, since all the works W that are being conveyed in the overhead conveyor  42  and the floor conveyor  47  can be stored in a state completed with the coating and the drying for the coated film, there is no worry that the works are left during or at the completion of the pretreatment, during or at the completion of the electrodeposition coating and, further, left undried during the drying operation, so that the coating quality can be maintained constant. 
     However, there are problems in this case for the requirement of additionally providing, in a restricted site of a factory site, a space for storing empty carriers T not used during the running state of applying pretreatment, electrodeposition coating and drying to the works W while conveying them, a space for storing all the works W that are being conveyed by the overhead conveyor  42  and the floor conveyor  47  while loading them on the carriers T at the instance the conveyance from the preceding step and the conveyance to the succeeding step of the works W are stopped, and a space for storing empty hangers. 
     For instance, assuming that 49 sets of works W are conveyed into the pretreatment device  44  and the electrodeposition coating device  45 , while 24 sets of works W are conveyed in the drying furnace  46 , and that the storage pitch for the hangers H and the carriers T is about 7 m, the entire length of the empty hanger storage track  41   a  is: 49×7≈350 m, the entire length of the reserved carrier storing track is: 49×7≈350 m and the entire length of the carrier storage track  47   c  is: (49+24)×7≈520 m, so that the total extension of all the storage tracks  41   a,    47   b  and  47   c  reaches 1200 to 1300 m. 
     Further, since it is adapted to store all the works W being conveyed in the overhead conveyor  42  and the floor conveyor  47  while loading them to the carriers T, carriers T are required at least by as much as 49+24=73 as the total for the carriers T for conveying the works W in the drying furnace  46  and reserved carriers T for loading the works by the number of them conveyed in the pretreatment device  44  and the electrodeposition device  45 . 
     As described above, since it requires a great amount of carriers T for storing all the works W and a wide storage space, there is a problem of increasing the installation cost. 
     Further, upon conveying the works W to the succeeding step, the carriers T bring heat in the drying furnace  46  to the outside and are returned being cooled to a room temperature after handing the works W to the succeeding step and they are heated again when entered into the drying furnace  46 , so that a great amount of heat in the furnace is lost to result in a problem that a large amount of heat in the drying furnace  46  is consumed to increase the running cost. 
     In view of the above, it is a technical subject of the present invention to reduce the storing space and the scale of the facility upon storing an identical number of works, thereby improving the space utilization efficiency and decreasing the installation cost, as well as economize the amount of heat consumed in the drying furnace, thereby decreasing the running cost. 
     DISCLOSURE OF THE INVENTION 
     In order to solve the subject, the present invention provides a coating facility comprising, along an overhead conveyor formed in a circulation track, a loading device for loading works conveyed from a preceding step at a predetermined loading position to hangers of the overhead conveyor, a pretreatment device for applying pretreatment to the surface of the works loaded by the loading device, a coating device for dipping the works completed with the pretreatment in the pretreatment device into a coating material to deposit the coating material on the surface thereof, and a lifting device for down loading the works from the hangers deposited with the coating material in the coating device and transferring them at a predetermined transferring position to carriers of a floor conveyor that runs in a drying furnace that are arranged in this order, and in which the pretreatment and the coating are applied while the works are conveyed on the overhead conveyor, then the works are transferred to the carries of the floor conveyor, dried during conveyance and then conveyed to a succeeding step after the completion of drying, wherein the floor conveyor is formed in a circulation track that runs in the drying furnace, passes from the exit of the drying furnace through the transferring position and returns to the entrance of the drying furnace, the lifting device is disposed successively along the circulation track of the floor conveyor from the exit of the drying furnace to the transferring position for re-transferring works completed with drying in the drying furnace at a predetermined re-transferring position from the carriers of the floor conveyor to the hangers of the overhead conveyor again, and an unloading device is disposed successively along the circulation track of the overhead conveyor returning from the re-transferring position to the loading position for down loading the works re-transferred to the hangers at a predetermined unloading position from the overhead conveyor and conveying them to a succeeding step, a looped first storage track is disposed for storing works corresponding to a predetermined number of the hangers conveyed on the circulation track of the overhead conveyor in a state suspended from the hangers such that a pull-in side and a delivery side thereof are branched from and joined with the circulation track between the re-transferring position and the unloading position of the overhead conveyor, a second storage track is branched from the circulation track between the exit of the drying furnace of the floor conveyor and the re-transferring position for storing the works in a state loaded to the carriers running on the circulation track of the floor conveyor, and in which pretreatment, coating and drying are completed for all the works during conveyance in the overhead conveyor and the floor conveyor at the instance conveyance from the preceding step and conveyance to the succeeding step of the works are stopped, a predetermined number of leading works are re-transferred to the hangers at the re-transferring position and then stored in the first storage track in a state suspended from the hangers, while the remaining works are delivered out of the drying furnace and then stored in the second storage track in a state loaded on the carriers. 
     According to the present invention, the works conveyed from the preceding step are loaded to the hangers of the overhead conveyor at a loading position, the works are pretreated at the surface by the pretreatment device and formed with a coating film on the surface thereof by the coating device while being conveyed by the overhead conveyor, transferred to the carriers of the floor conveyor at a transferring position, entered into the drying furnace and dried, re-transferred again at a re-transferring position to the hangers of the overhead conveyor, unloaded each at an unloading position from the hangers and conveyed to the succeeding step. 
     In this case, the floor conveyor is formed as the circulation track that runs in the drying furnace, passes from the exit of the drying furnace through the re-transferring position and the transferring position and returns to the entrance of the dry furnace, in which the carriers, upon getting out of the drying furnace, pass through the re-transferring position and the transferring position and directly enters into the drying furnace without running to the succeeding step, so that they are caused to run circulately in the drying furnace again before being cooled to a room temperature. Accordingly, the amount of heat in the drying furnace is less deprived by the carriers to decrease the running cost and, since the entire length of the floor conveyor is shortened and number of the carriers is also reduced, the installation cost can be decreased. 
     Further, when the operation for one day is completed and conveying lines between each of the steps are stopped, after the completion of pretreatment, coating and drying for all the works during conveyance by each of the conveyors, a predetermined number of preceding works are re-transferred to the handers that are conveyed on the circulate track of the overhead conveyor and stored in the first storage track in a state being suspended from the hangers, and the succeeding works are conveyed out of the drying furnace stored in the second storage track while they are loaded as they are on the carriers that runs on the circulation track of the floor conveyor. 
     In this case, it may suffice that the first and the second storage tracks have such a length as capable of storing all of the works during conveyance in each of the conveyors when the conveying lines between each of the steps are stopped, and it may suffice that there are provided hangers by a predetermined number for pretreatment and coating of the works and carriers by a predetermined number for running in the drying furnace, so that no additional hangers or carriers for storage are required at all, a space for storing empty carriers is saved at all and a space for storing work-loaded carriers is also reduced and the number of the carriers is also reduced remarkably and, accordingly, the space utilization efficiency can be improved remarkably and, at the same time, facilities required for storage can be reduced to decrease the installation cost. 
     Then, when the conveying lines between each of the steps are operated in the next morning, hangers stored in the first storage track are successively delivered on the circulation track of the overhead conveyor and conveyed to the unloading position, the works are down loaded from the hangers of the overhead conveyor by the unloading device, handed to a conveyor for conveying them to the succeeding step, the emptied hangers are conveyed to the loading position, at least one leading hanger is passed at the loading position, while being emptied as it is, and the works conveyed from the preceding step are successively loaded to the succeeding hangers, and the pretreatment and coating operations are started. 
     Then, when the empty hanger at the top arrives at the re-transferring position, the carrier T stored in the second storage track is delivered from the delivery side to the circulation track of the floor conveyor, the work loaded on the carrier is re-transferred to the hanger at the re-transferring position, the emptied carrier is sent to the transferring position, the work suspended from the succeeding hanger is transferred to the carrier and entered to the drying furnace, while the emptied hanger is conveyed to the re-transferring position. 
     In this way, the hanger emptied at the transferring position is sent to the re-transferring position, and the work stored in the second storage track is re-transferred to the hanger at the re-transferring position and subsequently, the works delivered out of the drying furnace are re-transferred to the hangers and conveyed to the unloading position, the emptied hangers are conveyed again to the loading position, and the works conveyed from the preceding step are loaded, and then the coating operation is continued. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view showing a running state of a coating facility according to the present invention, 
     FIG. 2 is a plan view showing a storage state thereof, 
     FIG. 3 is a plan view showing a running state of another embodiment according to the present invention, 
     FIG. 4 is a plan view showing a storage state thereof, 
     FIG. 5 is a plan view showing a running state of an prior art apparatus and 
     FIG. 6 is a plan view showing a storage state of the prior art. 
    
    
     BEST MODE FOR PRACTICING THE INVENTION 
     The mode for practicing the present invention will be explained next specifically based on the drawings. 
     A coating facility  1  shown in FIG.  1  and FIG. 2 has an overhead conveyor  2  formed in a circulation track  3  for conveying works W while suspending them upstairs by hangers H, in which are arranged, along the overhead conveyor  2 , a loading device  4  for loading the works W conveyed from a preceding step to hangers H each at a loading position P 1 , a pretreatment device  5  for applying pretreatment such as cleaning, degreasing and chemical formation to the surface of the works W loaded by the loading device  4 , an electrodeposition coating device  6  for forming an electrodeposition coating film on the surface of the works W downstairs after completion of the pretreatment in the pretreatment device  5  and a lifting device  7  for descending the works W after completion of electrodeposition coating by the electrodeposition coating device  6  each at a transferring position P 2 . 
     In the downstairs, a floor conveyor  9  for running carriers T for loading works W at a predetermined interval is formed in a circulation track  10  that runs in the drying furnace  8 , goes from the exit  8 out of the drying furnace, around the periphery of the lifting device  7  and returns to the entrance  8 in of the drying furnace. The lifting device  7  has a transferring position P 2  at the front and is adapted to down load the works W after completion of the electrodeposition coating by the electrodeposition coating device  6  from the hangers H of the overhead conveyor  2  in the upstairs and re-transfer them to the carriers T in the floor conveyor  9  laid in the downstairs, lift up the works W after completion of the drying in the drying furnace  8  from the carriers T on the floor conveyor  9  in the downstairs and re-transfer them on the hangers H of the overhead conveyor  2  in the upstairs each at a re-transferring position P 3  at the back thereof. 
     The circulation track  3  for the overhead conveyor  2  is formed so as to pass the transferring position P 2  and the re-transferring position P 3 , while going around the periphery of the lifting device  7  and return to the loading position P 1 , and an unloading device  12  is disposed between the re-transferring position P 3  and the loading position P 1  for descending the works W re-transferred to the hangers H each at the re-transferring position P 3  from the overhead conveyor  2  at a predetermined unloading position P 4  and handing them to a conveyor  11  for conveying them to the succeeding step. 
     A looped first storage track  13  formed to such a length as capable of storing the works W, each in a state being suspended from the hangers H, by a predetermined number (for example 49) of the hangers H to be conveyed on the circulation track  3  for the overhead conveyor  2  is laid such that a pull-in side  13   a  and a delivery side  13   b  thereof are branched from and joined with the circulation track  3  between the re-transferring position P 3  and the unloading position P 4  of the overhead conveyor  2 . 
     Further, a second storage track  14  formed to such a length as capable of storing carriers T running on the circulation track  10  for the floor conveyor  9  in a state of loading the works W by a predetermined number (for example, 24) is formed while being branched from the circulation track  10  at a predetermined position between the exit  8 out of the drying furnace and the re-transferring position P 3 . 
     An embodiment of the constitution of the present invention is as described above, and the function will be explained next. 
     Explanations will be made, for example, to a case where the number of the hangers H conveyed on the circulation track  3  for the overhead conveyor  2  is 49, the number of the carriers T running on the circulation track  10  for the floor conveyor  9  is 24 and the storage pitch is about 7 m. 
     At first, FIG. 1 shows a running state where the conveying lines between each of the steps in a factory are in operation, in which the surface of the works W is pretreated in the pretreatment device  5  and an electrodeposition film is formed on the surface of the works W in the electrodeposition device  6  while the works W loaded to the hangers H of the overhead conveyor  2  each at the loading position P 1  are conveyed in the upstairs during the conveyance of the works W from a preceding step and to the succeeding step. 
     Then, upon reaching the transferring position P 2 , the works W are down loaded from the hangers H of the overhead conveyor  2  by the lifting device  7 , transferred to the carriers T of the floor conveyor  9  in the upstairs, entered into and dried in the dry furnace  8 , then conveyed out of the drying furnace and lifted up by the lifting device  7  at the re-transferring position P 3 , and re-transferred again to the hangers H of the overhead conveyor  2 , then conveyed to the unloading position P 4 , unloaded from the overhead conveyor  2  by the unloading device  12  and handed to the conveyor  11  for conveying them to the succeeding step. 
     In this case, the floor conveyor  9  is formed as the circulation track  10  that runs in the drying furnace  8 , goes from the exit  8 out of the drying furnace around the lifting device  7  and immediately returns to the entrance  8 in of the drying furnace, and the carriers T run almost in the drying furnace  8  and conveyed out of the drying furnace only for transferring/re-transferring the works W relative to the overhead conveyor  2 , and the carriers T are not run to the succeeding step and the circulation track  10  laid outside the drying furnace  8  can be shortened, so that the carriers T run inside the drying furnace  8  again before being cooled to a room temperature. Accordingly, since the amount of heat in the drying furnace to be deprived by the carriers T can be reduced, the running cost can be saved, and since the number of the carriers T may be suffice by the number for running a short circulation track  10  of the floor conveyor  9 , the installation cost can also be decreased. 
     Then, FIG. 2 shows a storage state when the operation for one day is completed and the conveying lines between each of the steps are stopped. When the conveyance from the preceding step and conveyance to the succeeding step are stopped, all the works W conveyed by each of the conveyors  2  and  9  are stored on the first and the second storage tracks  13  and  14 , after completion of drying for those under drying in the drying furnace  8 , after transfer to the carriers T of the floor conveyor  9  each at the transferring position P 2  and completion of drying in the drying furnace  8  for those during electrodeposition coating in the electrodeposition coating device  6 , and after completion of the electrodeposition coating by the electrodeposition coating device  6 , transfer to the carriers T of the floor conveyor  9  each at the transferring position P 2  and completion of drying in the drying furnace  8  for those during pretreatment in the pretreatment device  5 . 
     In this case, among the total 73 works conveyed by the floor conveyor  9  and the overhead conveyor  2 , preceding 49 works W after completion of drying are successively re-transferred to the hangers H of the overhead conveyor each at the re-transferring position P 3  and entered from the pull-in side  13   a  in a state being suspended from the hangers H and stored therein. 
     Then, 24 works W succeeding to the works W stored in the first storage track  13  are conveyed from the drying furnace  8  in a state being placed on the carriers T, sent as they are to the second storage track  14  and stored therein. 
     In this case, assuming the length of the storage pitch as about 7 m, the first storage track  13  requires the distance of 49×7 m≈350 m for storing the 49 works W, and the second storage track requires the distance of 24×7 m≈170 m for storing 24 works W. Accordingly, it may suffice to ensure about 520 m for the total extension, and the space for storing empty carriers required for storage when the entire works W are loaded on the carriers is not necessary at all, and since the space for storing the carriers in a state of loading the works is reduced, the total extension of the storage track is about ½ of that in the existent coating facility, thereby enabling to remarkably improve the space utilization efficiency. 
     It is necessary for the hangers H by the number of 49 and the carriers T by the number of 24, but since they are the minimum number that has to be used for pretreatment, electrodeposition coating and drying of the works W, it is not necessary to provide additional hangers and carriers for storing the works, thereby enabling to decrease the installation cost. 
     In the next morning, when the conveying lines between each of the steps are operated, the hangers H stored in the first storage track  13  are successively delivered to the circulation track  3  of the overhead conveyor  2  and conveyed to the unloading position P 4 , and the works W are unloaded from the hangers H of the overhead conveyor  2  each at the unloading device P 4  and handed to the conveyor  11  for conveying them to the succeeding step, while the emptied hangers H are conveyed to the loading position P 1 . 
     At the loading position P 1 , at least only one empty hanger H at the top is passed as it is and the works W conveyed from the preceding step are successively loaded to the succeeding hangers H, and the pretreatment and coating operations are started. 
     Subsequently, when the empty hanger at the top arrives at the re-transferring position P 3 , the carrier T stored in the second storage track  14  is delivered to the circulating track  10  for the floor conveyor  9 , the work W loaded on the carrier T is re-transferred to the hanger H at the re-transferring position P 3  then the emptied carrier T is sent to the transferring position P 2  then the work W suspended on the succeeding hanger H is transferred successively to the carrier T and entered into the drying furnace  8 , while the emptied hanger H is conveyed to the re-transferring position P 3 . 
     In this way, the hangers. H emptied at the transferring position P 2  are sent to the re-transferring position P 3 , the works W stored in the second storage track  14  are re-transferred to the hangers H each at the re-transferring position P 3 , the works W conveyed out of the drying furnace  8  are subsequently re-transferred to the hangers H and sent to the unloading position P 4 , while the emptied hangers H are conveyed again to the loading position P 1 , and the works W conveyed from the preceding step are loaded and then the coating operation is continued. 
     According to this embodiment, as decreased above, since the works W are stored in a state being suspended from the hangers H sent in the circulation track  3  for the overhead conveyor  2  and being placed on the carriers T running on the circulation track  10  for the floor conveyor  9 , since not only the space can be saved by so much and the space for storing empty carriers is not necessary at all, but also the space for storing the carriers T loading the works W is also reduced and since the number of required carriers can be reduced remarkably, the space utilizing efficiently can be improved outstandingly and, at the same time, equipments required for the storage can also be reduced to decrease the installation cost. 
     In addition, since the carriers T of the floor conveyor  9 , after getting out of the drying furnace  8 , enter immediately into the drying furnace  8  passing around the lifting device  7  without running to the succeeding step, the carriers T run into the drying furnace  8  again before being cooled to a room temperature. Accordingly, the amount of heat in the drying furnace  8  to be deprived by the carriers T is reduced to decrease the running cost and, at the same time, since it may suffice to provide the carriers T by the number for running on the floor conveyor  9 , the installation cost can be decreased. 
     Explanations have been made to the coating facility of using the electrodeposition coating device as the coating device, but the present invention is not limited thereto and, for example, a coating device for conducting dip coating can also be used. 
     In addition, in this embodiment, explanations have been made to the case of using one lifting device  7  in which the works W are transferred from the hangers H of the overhead conveyor  2  to the carriers T on the floor conveyor  9  each at the transferring position P 2  at the front thereof, and re-transferred from the carriers T, to the hangers H at the re-transferring position P 3  at the back, but the present invention is not limited thereto, and separate lifting devices can also be used at respective positions. 
     Another Mode for Practicing the Present Invention 
     FIG. 3 is a plan view showing a running state of another embodiment according to the present invention, and FIG. 4 is a plan view showing a storage state. Identical portions with those in FIGS. 1 and 2 carry same references, with detailed explanations being omitted. 
     According to this embodiment, a second storage track  15  is formed in a looped-shape, in which a pull-in side  15   a  is branched from a circulation track  3  between a re-transferring position P 3  and an unloading position P 4  of an overhead conveyor  2  and a delivery side  15   b  is joined with the circulation track  3  before the re-transferring position P 3  of the overhead conveyor  2 . 
     The second storage track  15  has reserved hangers Hs by the number (for example 24) of the carriers T of the floor conveyor  9  and is determined to such a length as capable of storing the works W in a state they are suspended from the reserved hangers Hs. 
     When the operation for one day is completed, preceding 49 sets of works W after completion of drying are successively re-transferred to the hangers H of the overhead conveyors  2  at the re-transferring position P 3  and entered from the pull-in side  13   a  in a state being suspended from the hangers H and stored in a first storage track  13 . 
     In addition, succeeding 24 sets of works W after completion of drying are re-transferred to the reserved hangers Hs delivered from the delivery side  15   b  thereof to the re-transferring position P 3  of the circulation track  3  and entered from the pull-in side  15   a  in a state being suspended from the reserved hangers Hs and stored in the second storage track  15 . 
     Then, when the conveying lines between each of the steps are operated in the next morning, the works W stored in the first storage track  13  are handed to the conveyor  11  at the unloading position P 4  and conveyed to the succeeding step, and then the hangers H stored in the second storage track  15  are successively delivered from the delivery side  15   b  to the circulation track  3  for the overhead conveyor  2  and the hangers H are sent to the unloading position P 4  directly or by way of the first storage track  13  to unload the works W, and then sent to the loading position P 1 . 
     When the hanger H at the top arrives at the loading position P 1 , the work W conveyed from the preceding step is successively loaded at the loading position P 1 , and pretreatment and coating operations are started. 
     Then, after transfer to the carriers T of the floor conveyor  9  at the transferring position P 2 , the emptied handers H are successively sent to the second storage track  15 , and the empty hangers H by the number for the reserved hangers Hs are stored as reserved hangers Hs and succeeding hangers H, after transfer to the carriers T of the floor conveyor  9  at the transferring position P 2 , are re-transferred with the works W conveyed from the drying furnace  8  each at the re-transferring position P 3 , and then conveyed to the unloading position P 4 , and further conveyed to the loading position P 1  to load the works conveyed from the preceding step, and the coating operation is continued. 
     Also in this embodiment, since the works W are stored in a state where they are suspended from the hangers H, not only the space can be saved by so much, but also the space for storing the empty carriers and the space for storing the work-loaded carriers are not necessary at all, and since the number of the carries is greatly reduced, the space utilization efficiency can be improved outstandingly and, at the same time, equipments required for the storage can be reduced to decrease the installation cost. 
     In accordance with the same conditions as those for the coating facility shown in FIG.  1  and FIG. 1 in this case, it may suffice to keep a total extension of 520 m for the first and the second storage tracks  13  and  15 . 
     Further, while this requires the hangers H by the number of 49 and the reserved hangers Hs by the number of 24, since the hangers H by the number of 49 are used for the pretreatment and electrodeposition coating of the works W, the number of the hangers increased for the storage is only 24 for the reserved hangers Hs. Further, it may suffice to provide the carriers T by the number of 24 required for drying the works W and, although the number of the hangers is increased by 24 compared with a coating facility of storing all the works W being placed on the carriers, since the number of the carriers is decreased by 49, the installation cost is decreased as a whole. 
     Further, the storage tracks  13  and  15  are not restricted to a case of forming them to separate loops but it may be applicable also to a case, for example, of making the pull-in side  13   a  and  15   a  in common, branching the track at the midway and joining the delivery side  13   a  and  15   b  separately to the circulation track  3  for the overhead conveyor respectively thereby making a portion thereof to be in common. 
     Industrial Field of Application 
     As has been described above, according to the present invention, since the space for storing the empty carriers is saved upon storing an identical number of works, to reduce the space for storing the work-loaded carriers and the number of required carries is greatly decreased, the space utilizing efficiency can be improved outstandingly and, at the same time, equipments required for storage can be reduced to decrease the installation cost, as well as since the floor conveyor is formed such that carriers running in the drying furnace are returned immediately into the drying furnace without conveying the works as far as the succeeding step, it provides an excellent effect capable of economizing the amount of heat consumption in the drying furnace to decrease the running cost. 
     Accordingly, it is suitable to be used for a coating facility, such as a coating facility for car bodies adapted to conduct pretreatment, coating and drying while conveying works and send them to the succeeding step after the completion of drying, in which works during pretreatment, coating, drying are processed as far as drying when the conveying lines between each of the steps are stopped after the completion for one day&#39;s operation, and stored in a state completed with drying.