Patent Publication Number: US-8109228-B2

Title: Paint coating system

Description:
TECHNICAL FIELD 
     This invention relates to a paint coating system particularly suitable for use, for example, in coating vehicle bodies, furniture, electric appliances and the like. 
     BACKGROUND ART 
     Generally, paint coating systems in use for painting vehicle bodies and the like are largely constituted by a robot device with an articulated arm, and a coater unit mounted on a distal end of the robot arm of the robot device and provided with an atomizing head for spraying atomized paint particles. 
     Among paint coating systems of this sort, there is a system providing a paint cartridge replenished by a paint which will be supplied to an atomizing head of the coater unit and can be replaceably attached to a common body which is mounted on a distal end of a robot arm of the robot device (see, for example, Patent Literature 1: Japanese Patent Laid-Open No. 2000-176333). 
     More particularly, the paint coating system described in the above-mentioned Patent Literature 1 employs a cartridge changer providing a plural number of paint cartridges of each different colors on a mount deck. This cartridge changer is largely constituted by a mount deck on which a plural number of paint cartridges are set, a paint replenisher provided on the mount deck and replenishing consumed paint cartridges, and a cartridge transfer mechanism adapted to transfer a gripped paint cartridge in longitudinal and transverse directions of the mount deck in addition to upward and downward directions. 
     The cartridge transfer mechanism is composed of a first transfer mechanism having a carriage which is movable on and along a pair of rails extending longitudinally of the mount deck, a second transfer mechanism provided on the carriage of the first transfer mechanism having a carriage which is movable on and along a pair of transversely extending rails, and a third transfer mechanism provided on the carriage of the second transfer mechanism to move a cartridge gripper in upward and downward directions. 
     At the time of replacing a paint cartridge on a common body of a coater unit, the coater unit is placed at a predetermined cartridge changing position by an action of a robot arm of a robot device, and the robot arm is stopped at that position. In this state, a used paint cartridge at the changing position is picked up and moved upward by means of the cartridge transfer mechanism of the cartridge changer, disconnecting and separating the used paint cartridge from the common body. In the next place, while the common body is fixedly retained in the predetermined changing position by the robot device, a replenished paint cartridge full of paint is transferred to the changing position and set on the common body from above by the cartridge transfer mechanism. 
     On the other hand, there is a paint coating system providing a plural number of atomizing heads to be replaceably and interchangeably mounted on a common body of a coater unit by means of an atomizing head changer (see, for example, Patent Literature 2: Japanese Patent Laid-Open No. 2001-79463). 
     In the case of the paint coating system described in the above-mentioned Patent Literature 2, when replacing an atomizing head on a common body of a coater unit, a robot arm of the robot device operates to attach an atomizing head which is mounted on the common body to an atomizing head gripper of an atomizing head changing and washing device. In this state, the common body is lifted up by the robot device to detach the used atomizing head from the common body. On the other hand, after detachment of the used atomizing head, the common body is transferred by a robot device to a head changing position for replacement by another atomizing head which is gripped on the atomizing head gripper. 
     Further, there is another paint coating system which is composed of a robot device for coating, a coater unit which is mounted on a robot arm of the robot device for spraying atomizing paint, a number of paint cartridges filled with paint of different colors to be replaceably and interchangeably mounted on the robot arm of the robot device, and a cartridge changer adapted to mount a paint cartridge of a respective color replaceably on the robot arm of the robot device (see, for example, Patent Literature 3: International Publication WO 97/34707). 
     The cartridge changer described in above-mentioned Patent Literature 3 is composed of a rotary table on which a plural number of cartridges are placed in an arcuate formation, and a cartridge gripper which loads a cartridge provided on the rotary table into an opening socket of a robot arm of a robot device. 
     By the way, in the case of Patent Literature 1 mentioned above, the cartridge transfer mechanism is arranged as an XY table to transfer a paint cartridge in the directions of two orthogonal axes by means of the first transfer mechanism extending in the longitudinal direction and the second transfer mechanism extending in the transverse direction of the first transfer mechanism. This XY table is constructed by mounting heavy rails and carriage of the second transfer mechanism on the first transfer mechanism. Due to heavy weight, the two transfer mechanisms are difficult to start and stop a transfer action speedily. That is to say, the cartridge transfer mechanisms of this type are necessarily required to lower the transfer speed in order to transfer a paint cartridge accurately to a specific position, resulting in a longer changing operation time and a considerable degradation in productivity. 
     On the other hand, in the case of the paint coating system described in Patent Literature 2 mentioned above, an atomizing head is replaced by moving a coater unit in downward and upward directions relative to an atomizing head gripper which is held in a fixed state. On the other hand, in the case of the paint coating system of Patent Literature 2, a robot arm of a robot device is stopped at a predetermined cartridge changing position to locate and set a coater unit in that position while a paint cartridge is replaced by a cartridge changer. 
     However, in the case of a robot device which is in use for paint coating operations, with regard to the repeated positioning accuracy in motion control such as moving, stopping, posture and the like of a coater unit which is mounted on a distal end of a robot arm, there is inevitably an error of several millimeters. Therefore, even if the coater unit is moved to a predetermined position for changing an atomizing head or a paint cartridge in response to the same control command after finishing a certain coating operation by the robot device, actually it is often the case that the coater unit is located in a position which is somewhat deviated from the predetermined changing position. Therefore, if the changing operation is carried out depending upon the accuracy of motion control on the part of the robot device alone, this deviation from the predetermined changing position may result in exertion of a forcible load between a common body and the atomizing head or the paint cartridge, shortening the service life of the coater unit by repeated abrasive and damaging contact. 
     Besides, a robot device is required to be operative with an extremely high degree of accuracy in locating a coater unit in a predetermined specific position at the time of changing a paint cartridge, and, in order to meet this requirement, needs to be installed with high dimensional accuracy despite a considerable increase in cost. 
     Further, in the case of the paint coating system according to Patent Literature 3, a coater unit which is attached on a robot arm is not equipped with a replaceable paint atomizing head. Therefore, in this case, there is a problem of low productivity because it is impossible to carry out a paint washing operation and a coating operation simultaneously. 
     In addition, washer is not provided for washing a head portion of a coater unit. This means that it is necessary to wash a robot arm and a coater unit every time when replacing a paint cartridge on the robot arm by a cartridge of a different color. 
     Furthermore, the paint coating system according to Patent Literature 3, a rotary table on which paint cartridges are placed is rotated by a motor while a cartridge gripper is arranged to move linearly, requiring a large space for installation and a mechanism of complicate construction. 
     DISCLOSURE OF THE INVENTION 
     In view of the above-discussed problems with the prior art, it is an object of the present invention to provide a paint coating system adopting a cartridge changer which is reduced in weight and operative smoothly and efficiently in replacing paint cartridges by the cartridge changer. 
     (1) A paint coating system according to the present invention, is composed of: a robot device operative to take coating actions; a coater unit having a common body fixedly mounted on the robot device and an atomizing head replaceably attached to the common body for spraying atomized paint particles; a paint cartridge replaceably attached to the common body of the coater unit to supply paint to the atomizing head; an atomizing head changing and washing device adapted to replace a used atomizing head on the common body of the coater unit by a washed clean atomizing head and to wash the dismantled used atomizing head clean; and a cartridge changer adapted to pick up a selected paint cartridge among a plural number of replenished paint cartridges arrayed on a mount deck, and to replace a used paint cartridge on the common body of the coater unit in changing position of the atomizing head changing and washing device by the selected paint cartridge. 
     In order to achieve the above-stated objectives, the cartridge changer is provided with a swing arm adapted to replace the paint cartridge while being swung to and fro about a swing arm pivoting point along an arcuate path between a position of the replenished paint cartridge on the mount deck and a changing position of the atomizing head changing and washing device. 
     With the arrangements just described, the swing arm of the cartridge changer is put in a swinging movement along an arcuate path about a swing arm pivoting point at the time of replacing a used paint cartridge on a coater unit at a changing position of an atomizing head changing and washing device by a replenished paint cartridge on a mount deck. In this case, although very simple in construction, the swing arm can transfer a plural number of replenished paint cartridges provided on the mount deck by its swinging movements along arcuate paths. 
     As a consequence, the cartridge changer can be significantly reduced in weight of the swing arm to lessen loads which are imposed on various moving parts, guaranteeing higher working speed and improved braking ability. That is to say, the cartridge changer can complete a cartridge replacing operation in a shorter time period without degradations in control accuracy, achieving improvements in productivity. 
     (2) According to the present invention, replenished paint cartridges on the mount deck are arranged in arcuate rows around the swing arm pivoting point. 
     In this case, a plural number of replenished paint cartridges are arranged in arcuate rows on the mount deck along an arcuate path of transfer of the cartridge changer, so that a paint cartridge can be replaced by the swing arm while swung along the arcuate path to transfer. 
     (3) According to the present invention, preferably the cartridge changer is composed of the mount deck adapted to mount the replenished paint cartridges located in arcuate rows about the swing arm pivoting point, an arcuate moving portion provided on the mount deck and circulated to and fro about the pivoting point, a vertical moving portion provided on the arcuate moving portion for vertical upward and downward movements, and the swing arm which extends in a horizontal plane attached to the vertical moving portion at a base end and provided with cartridge grippers at and on a fore free end thereof. 
     In this case, a replenished paint cartridge is gripped in a cartridge gripper which is provided at a fore distal end of the swing arm of the cartridge changer, and then the cartridge gripper is lifted up by the vertical moving portion together with the replenished paint cartridge. The cartridge gripper is then moved along arcuate row on the swing arm pivoting point by the arcuate moving portion. Thus, the cartridge changer is capable of dismantling a used paint cartridge from the common body of the coater unit which is fixedly retained at the changing position of the atomizing head changing and washing device, or mounting a replenished paint cartridge. 
     (4) According to the present invention, preferably the cartridge changer is composed of the mount deck adapted to mount said replenished paint cartridges located in a plural number of radially spaced arcuate rows around the swing arm pivoting point, a linear moving portion for shifting the swing arm pivoting point provided on the mount deck in a longitudinal direction, an arcuate moving portion provided on the linear moving portion circulated to and fro about the pivoting point, a vertical moving portion provided on the arcuate moving portion for vertical upward and downward movements, and the swing arm which extends in a horizontal plane attached to the vertical moving portion at a base end and provided with cartridge grippers at and on a fore free end thereof. 
     In this case, a replenished paint cartridge is gripped in a cartridge gripper, which is provided at a fore distal end of the swing arm of the cartridge changer, and then the cartridge gripper is lifted up by the vertical moving portion together with the replenished paint cartridge. The cartridge gripper is then moved along arcuate row on the swing arm pivoting point by the arcuate moving portion, and the position of the cartridge gripper is shifted by the linear moving portion in a longitudinal direction of the mount deck. 
     Thus, the cartridge changer is capable of dismantling a used paint cartridge from the common body of the coater unit which is fixedly retained at the changing position of the atomizing head changing and washing device or mounting a replenished paint cartridge. In this case, a greater number of paint cartridges can be set on the mount deck simply by increasing the number of the arcuate cartridge rows on the mount deck. 
     (5) According to the present invention, preferably the atomizing head changing and washing device is provided with a common body gripper to grip and locate the common body of the coater unit at the changing position “O”, and the cartridge changer is adapted to replace the paint cartridge while the common body is gripped by the common body gripper. 
     In this case, at the time of replacing an atomizing head and a paint cartridge on a common body of a coater unit, the robot device moves the coater unit to the changing position of the atomizing head changing and washing device, and the common body of the coater unit is gripped on a common body gripper which is provided at that changing position. So that, a positional deviation which may have occur due to an error in repeated positioning accuracy of the robot device or due to an installation error of the robot device may be absorbed. Thus, it is possible to position the common body of the coater unit exactly at the changing position of the atomizing head changing and washing device. 
     As a consequence, an atomizing head and a paint cartridge can be dismantled from or mounted on the common body very smoothly to guarantee an elongated service life for these components. Besides, the installation work for the robot device, the installation and possessing work for the atomizing head changing and washing device or the cartridge changer can be carried out efficiently in a facilitated manner. In addition, the cost of a coating line as a whole can be cut down to a significant degree. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a perspective view of a vehicle body coating line incorporating a paint coating system embodying the present invention; 
         FIG. 2  is a plan view of the vehicle body coating line of  FIG. 1 ; 
         FIG. 3  is an enlarged perspective view of a coater unit which is mounted on a wrist of a robot device; 
         FIG. 4  is a longitudinal sectional view of the coater unit, taken from the direction of arrows IV-IV of  FIG. 3 ; 
         FIG. 5  is a longitudinal sectional view, showing a common body portion of the coater unit of  FIG. 4 ; 
         FIG. 6  is a longitudinal sectional view of an atomizing head shown in  FIG. 4 ; 
         FIG. 7  is a longitudinal sectional view of a paint cartridge shown in  FIG. 4 ; 
         FIG. 8  is a front view of an atomizing head changing and washing device and a paint cartridge changer; 
         FIG. 9  is a right-hand side view of the atomizing head changing and washing device and the paint cartridge changer, taken from the direction of arrows IX-IX of  FIG. 8 ; 
         FIG. 10  is a partly cutaway plan view showing on an enlarged scale the atomizing head changing and washing device and the paint cartridge changer of  FIG. 8 ; 
         FIG. 11  is a front view showing on an enlarged scale the atomizing head changing and washing device of  FIG. 8 ; 
         FIG. 12  is a right-hand side view of the atomizing head changing and washing device shown in  FIG. 11 ; 
         FIG. 13  is a plan view of the atomizing head changing and washing device shown in  FIG. 11 ; 
         FIG. 14  is a sectional view of the atomizing head changing and washing device, taken from the direction of arrows XIV-XIV of  FIG. 11 ; 
         FIG. 15  is a front view of a fixed plate and an elevator; 
         FIG. 16  is a right-hand side view of the fixed plate and elevator shown in  FIG. 15 ; 
         FIG. 17  is a schematic illustration explanatory of an operational action of positioning a common body of a coater unit between pawls of a common body gripper; 
         FIG. 18  is a schematic illustration explanatory in an enlarged view of an operational action of positioning the common body of the coater unit between pawls of the common body gripper, taken from the direction of arrows XVIII-XVIII of  FIG. 17 ; 
         FIG. 19  is a schematic illustration explanatory of an operational action of gripping the common body of the coater unit by pawls of the common body gripper; 
         FIG. 20  is a schematic illustration explanatory in an enlarged view of an operational action of gripping the common body of the coater unit between pawls of the common body gripper, taken from the direction of arrows XX-XX of  FIG. 19 ; 
         FIG. 21  is a plan view showing on an enlarged scale a gripping member of an atomizing head gripper; 
         FIG. 22  is a partly cutaway enlarged front view of an atomizing head which is gripped by a gripping member of the atomizing head gripper; 
         FIG. 23  is a front view of a washer which is located on the left side in  FIG. 11 ; 
         FIG. 24  is a right-hand side view of the washer, taken from the direction of arrows XXIV-XXIV of  FIG. 23 ; 
         FIG. 25  is a sectional view of a cartridge changer, taken from the direction of arrows XXV-XXV of  FIG. 10 ; 
         FIG. 26  is an enlarged sectional view of the cartridge changer, taken from the direction of arrows XXVI-XXVI of  FIG. 25 ; 
         FIG. 27  is an enlarged sectional view of a cartridge transfer mechanism, taken from the direction of arrows XXVII-XXVII of  FIG. 26 ; 
         FIG. 28  is an enlarged sectional view of an arcuate moving portion, a vertical moving portion and a swing arm, taken from the direction of arrows XXVIII-XXVIII of  FIG. 27 ; 
         FIG. 29  is a right-hand side view of cartridge grippers on the swing arm, taken from the direction of arrows XXIX-XXIX of  FIG. 28 ; 
         FIG. 30  is a schematic illustration explanatory of an operational action of transferring a coater unit to a common body gripper; 
         FIG. 31  is a schematic illustration explanatory of an operational action of transferring a replenished paint cartridge toward the atomizing head changing and washing device; 
         FIG. 32  is a schematic illustration explanatory of an operational action of positioning a cartridge gripper on the swing arm above a replenished paint cartridge to be used in a next coating operation in a plane view; 
         FIG. 33  is a schematic illustration explanatory of an operational action of moving a replenished paint cartridge toward a changing position side by swing arm in a plane view; 
         FIG. 34  is a schematic illustration explanatory of operational action of detaching a used atomizing head from a common body, while holding a used paint cartridge in a gripped state; 
         FIG. 35  is a schematic illustration explanatory of an operational action of moving an atomizing head gripper to the left and detaching a used paint cartridge; 
         FIG. 36  is a schematic illustration explanatory of an operational actions of mounting a washed atomizing head on a common body, and placing a replenished paint cartridge in a changing position; 
         FIG. 37  is a schematic illustration explanatory of an operational action of mounting a replenished paint cartridge on a common body; 
         FIG. 38  is a schematic illustration explanatory of an operational action, showing the swing arm which has been moved to an upper position; 
         FIG. 39  is a schematic illustration explanatory of operational actions of moving a coater unit to a standby position for coating operation, and moving a used paint cartridge to a cartridge changer; 
         FIG. 40  is a schematic illustration explanatory of operational actions of detaching a used paint cartridge from a common body and attaching a replenished paint cartridge to the common body as a replacement in a plane view; 
         FIG. 41  is a schematic illustration explanatory of an operational action of returning a used paint cartridge to a paint replenishing unit after detachment from the common body in a plane view; 
         FIG. 42  is a schematic illustration explanatory of an operational action of washing a used atomizing head by a washer; 
         FIG. 43  is a schematic illustration explanatory of an operational action of holding a washed atomizing head in a standby state for a replacing operation; and 
         FIG. 44  is a flow chart showing operational steps for replacement of an atomizing head and a paint cartridge. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereafter, with reference to  FIGS. 1 through 44 , the paint coating system of the present invention is described more particularly by way of its preferred embodiment which is applied as a vehicle body painting system, for example. 
     In  FIGS. 1 and 2 , indicated at  1  is a coating line for coating a vehicle body  2 . Moreover, at the half way of the conveyer  3 , paint coating system  11 , which will be described hereinafter, are located on the opposite side of the conveyer  3 . 
     Indicated at  11  are paint coating systems which are located at the half way and cooperatively on the opposite sides of the conveyer  3 . Each one of the paint coating systems  11  is largely constituted by a robot device  13 , a coater unit  14 , an atomizing head changing and washing device  31 , and a cartridge changer  41 , which will be described hereinafter. 
     Designated at  12  are tracking rails which are located in predetermined transversely spaced positions on the opposite side of the conveyer  3  in parallel relation with the latter. Each one of these tracking rails  12  constitutes a tracking mechanism to let each robot device  13 , which will be described hereinafter, follow movements of a vehicle body  2  which is transferred by the conveyer  3 . 
     Indicated at  13  are robot devices which are mounted on the tracking rails  12  for coating actions. The robot devices  13  are operative for painting the vehicle body  2  complying with the teaching instruction while letting coater units  14  provided on the distal ends of the robot device  13 , which will be described hereinafter, follow the vehicle body  2 . 
     Further, the robot devices  13  are mounted on the tracking rails  12  and moved substantially in parallel relation with the conveyer  3 , while each one of coater units  14  is put in coating actions along the vehicle body  2  to paint the latter from front to rear side. Moreover, the robot devices  13  are able to move a coater unit  14  as far as an atomizing head changing and washing device  31  to locate the coater unit  14  in a predetermined changing position “O” for replacement. 
     Each robot device  13  which is mounted on the tracking rails  12  is provided with a multiarticular arm, and constructed of a carriage  13 A which is movable in the transfer direction of the conveyer  3 , a vertical arm  13 B which is rotatably and swingably mounted on the carriage  13 A, a horizontal arm  13 C which is swingably connected to a fore distal end of the vertical arm  13 B, and a wrist  13 D which is rotatably and pivotally provided at a fore distal end of the horizontal arm  13 C. 
     In this instance, when a common body  15  of a coater unit  14  is gripped by a common body gripper  33 , which will be described hereinafter, robot devices  13  are controlled in a reduced power mode, lowering levels of driving forces (driving torques) which are generated in rotating motors, reciprocating actuators and the like (none of which is shown in the drawings) to put the arms  13 B and  13 C and the wrist  13 D in predetermined motions. In this reduced power mode, the arms  13 B and  13 C as well as the wrist  13 D and the like of the robot device  13  is freely movable state when an external force is applied. Thus, the common body  15  of the coater unit  14  becomes freely movable in any direction, permitting the common body gripper  33  to move the coater unit  14  in an arbitrary direction to set the common body  15  accurately in a predetermined changing position “O”. 
     Indicated at  14  is a coater unit which is mounted on the wrist  13 D at the fore distal end of the horizontal arm  13 C which constructs the robot device  13 . This coater unit  14  is operative for painting the vehicle body  2  and built as a rotary atomizing head type coating apparatus with a rotary atomizing head  22 , which will be described hereinafter. As shown in  FIG. 3 , the coater unit  14  is largely constituted by a common body  15  and an atomizing head  19  and the like, which will be described hereinafter. 
     Indicated at  15  is a common body which is fixedly mounted on the robot device  13 , and on which a washed atomizing head  19  and a replenished paint cartridge  24  are to be mounted as replacements for a used atomizing head  19 ′ and a used paint cartridge  24 ′, respectively. As shown in  FIGS. 3 and 4 , the common body  15  is composed of a neck portion  15 A which is attached to the wrist  13 D at the fore distal end of the horizontal arm  13 C and a cylindrical mount portion  15 B which is integrally formed at the fore distal end of the neck portion  15 A. 
     Further, as shown in  FIG. 5 , provided on the front side of the mount portion  15 B is an atomizing head coupler  15 C to which an atomizing head  19  is replaceably connected as described hereinafter. On the other hand, provided on the rear side of the mount portion  15 B is a cartridge holder socket  15 D which replaceably hold a paint cartridge  24 . Further, a feed tube receptacle hole  15 E is formed axially at the center of the mount portion  15 B to receive a feed tube  27  of a paint cartridge  24  therein. 
     In this instance, as shown in  FIGS. 3 ,  17  and  18  and the like, the mount portion  15 B of the common body  15  is formed with a pair of grip surfaces  15 F. These grip surfaces  15 F serve as positioning portions for bringing the mount portion  15 B to position in a rotational direction and also in a vertical direction at the time when the mount portion  15 B is gripped on a common body gripper  33 , which will be described hereinafter. More particularly, the grip surfaces  15 F are in the form of indented surfaces which are formed in radially opposite positions on the circumference of the mount portion  15 B. And, the grip surfaces  15 F are defined by flat surfaces  15 F 1  which are parallel with each other in a radial direction, and one and the other inclined surfaces  15 F 2  and  15 F 3  rising from rear and front ends of the flat surfaces  15 F 1 , respectively. In this instance, one and the other inclined surfaces  15 F 2  and  15 F 3  are inclined in axially forward and rearward directions of the mount portion  15 B in a diverging fashion. 
     As shown in  FIG. 19 , each grip surfaces  15 F is gripped by a radial positioners  33 D of a common body gripper  33 , which will be described hereinafter, with the flat surfaces  15 F 1  in abutting engagement with flat surfaces  33 D 1 , to bring the common body  15  to position in the rotational direction relative to a vertical center axis O 1 -O 1  of a changing position “O”. Further, when the grip surfaces  15 F are gripped in the radial positioner  33 D of the common body gripper  33 , one and the other inclined surfaces  15 F 2  and  15 F 3  are respectively abutted against inclined surfaces  33 D 2  and  33 D 3  on the part of the radial positioner  33 D as shown in  FIG. 20  to locate the common body  15  in position in the vertical direction. 
     Denoted at  16  is a high voltage generator which is provided on the neck portion  15 A of the common body  15 . For example, this high voltage generator  16  is constituted by a Cockcroft circuit, and adapted to apply a high voltage, e.g., a high voltage elevated to −60 to −120 kV, to a rotary atomizing head  22  through a rotational shaft  21 B of an air motor  21 , which will be described hereinafter. 
     Designated at  17  is an extruder liquid passage which is provided on the side of the common body  15  to circulate a liquid for extruding paint out of a paint cartridge  24  which is loaded on the common body side. Indicated at  18  is an extruder liquid valve which is provided in the course of the extruder liquid passage  17  in the common body  15 . The supply of an extruder liquid to the paint cartridge  24  is controlled by opening and closing the extruder liquid passage  17  by this extruder liquid valve  18 . 
     Indicated at  19  is an atomizing head which is removably connected to the atomizing head coupler  15 C of the common body  15  (see  FIG. 4 ). By this atomizing head  19 , paint which is supplied from a paint cartridge  24 , which will be described hereinafter, is sprayed toward the vehicle body  2 . For example, two atomizing heads  19  are provided and interchangeably used properly. As shown in  FIG. 6 , each atomizing head  19  is constructed as a rotary atomizing head which is constituted by a body  20 , an air motor  21 , a rotary atomizing head  22  and a shaping air ring  23 , which will be described hereinafter. 
     In this instance, in the description of operational actions which will be described hereinafter, a clean atomizing head from which paint has been washed off is referred to as “a washed atomizing head  19 ”, and an atomizing head which is smudged with paint as a result of a coating operation is referred to as “a used atomizing head  19 ′”. 
     Indicated at  20  is a body of the atomizing head  19 , which forms an outer shell of the atomizing head  19 . The body  20  is formed in a tapered cylindrical shape having a diameter which is gradually reduced in a forward direction. A motor receptacle cavity  20 A is provided internally of the body  20 . On the outer peripheral side of the body  20  is provided with, for example, three grip holes  20 B (only two of which are shown in the drawings) to be engaged with protrusive  35 E which are provided on a gripping member  35 C of an atomizing head gripper  35  as shown in  FIGS. 21 and 22 . Further, a positioning pin  20 C is projected from the rear end of the body  20  to be engaged with a positioning hole (not shown) on the part of the common body  15  for setting position in the rotational direction. 
     Denoted at  21  is an air motor which is accommodated in the motor receptacle cavity  20 A within the body  20 . By an air turbine  21 C of this air motor  21 , a hollow rotational shaft  21 B which is rotatably supported in a motor case  21 A is driven to rotate at a high speed, for example, at a speed in the range of from 3000 r.p.m. to 150,000 r.p.m. 
     Indicated at  22  is a rotary atomizing head which is mounted on a fore end portion of the rotational shaft  21 B of the air motor  21 . This rotary atomizing head  22  is put in high speed rotation by the air motor  21 , so that paint which is discharged from a feed tube  27  of a paint cartridge  24  is sprayed in the form of finely divided particles under the influence of centrifugal force. 
     Indicated at  23  is a shaping air ring which is provided at the fore end of the body  20 , on the outer peripheral side of the rotary atomizing head  22 . From this shaping air ring  23 , shaping air is spurted forward to control a spray pattern of paint particles which are sprayed from the rotary atomizing head  22 . 
     Indicated at  24  is a paint cartridge which is detachably fitted in the cartridge holder socket  15 D of the common body  15 . A plural number of paint cartridges  24  of each different colors are mounted on a mount deck  42  of a cartridge changer  41  which will be described hereinafter. As shown in  FIGS. 4 and 7 , each paint cartridge  24  is largely constituted by a tank  25 , a piston  26  and a feed tube  27 . 
     In the description of operational actions which will be given hereinafter, a paint cartridge  24  which has been replenished with paint of a next color within the tank  25  is referred to as “a replenished paint cartridge  24 ”, while an empty paint cartridge which has been consumed paint of a previous color within the tank  25  is referred to as “a used paint cartridge  24 ′”. 
     Indicated at  25  is a tank of the paint cartridge  24 , which is in the form of a tubular container closed at opposite axial ends. Further, projected on the rear side of the tank  25  is a grip portion  25 A to be clasped by cartridge grippers  48 B and  48 C on a swing arm  48  which will be described hereinafter. A piston  26  is fitted in the tank  25  displaceably in the axial direction, defining a paint chamber  25 B and an extruder liquid chamber  25 C on the front and rear sides thereof. A paint passage  25 D is provided in a front side portion of the tank  25 , communicating a paint supply passage  27 A of a feed tube  27  with the paint chamber  25 B. 
     Denoted at  27  is a feed tube which is provided at the front end of the tank  25 . At a base end, the feed tube  27  is securely fixed to a front portion of the tank  25 . On the other hand, as shown in  FIG. 4 , in a fore end portion, the feed tube  27  is extended through the feed tube receptacle holes  15 E of the common body  15  and opened toward the rotary atomizing head  22 . Further, as shown in  FIG. 7 , a paint supply passage  27 A is formed internally of the feed tube  27  in communication with the paint chamber  25 B of the tank  25 . Furthermore, the paint supply passage  27 A is reduced stepwise in diameter in a fore end portion of the feed tube  27  to provide a valve seat  27 B. 
     Indicated at  28  is an extruder liquid passage on the side of the paint cartridge, which is formed in the tank  25  in communication with the extruder liquid chamber  25 C. As shown in  FIG. 4 , this extruder liquid passage  28  is communicated with the extruder liquid passage  17  on the side of the common body when the paint cartridge  24  is fittingly set in the cartridge holder socket  15 D on the common body  15 . 
     Designated at  29  is a paint valve which is provided in a front end portion of the tank  25  for the purpose of on-off control of paint supply to the atomizing head  19  from the feed tube  27 . This paint valve  29  is constituted by an axially displaceable piston  29 A, and a valve body  29 B which is extended through the paint supply passage  27 A of the feed tube  27  from the piston  29 A and seated on and off the valve seat  27 B at its fore end. 
     Now, with reference to  FIGS. 2 ,  8  to  39 , the description is directed to the construction of an atomizing head changing and washing device  31  which plays the roles of interchangeably mounting a couple of atomizing heads  19  and  19 ′ on the common body  15  of the coater unit  14  located on the robot device  13  and washing a dismantled used atomizing head  19 ′. 
     Namely, indicated at  31  is an atomizing head changing and washing device adopted in the present embodiment. As shown in  FIG. 2 , the atomizing head changing and washing device  31  is located within an operating range of the robot device  13  and in a position free of possibilities of interference with coating operations, for example, in a narrow space between the tracking rail  12  and a wall of a coating booth (not shown). By this atomizing head changing and washing device  31 , a used atomizing head  19 ′ on the common body  15  of the coater unit  14  is replaced with a washed atomizing head  19 , and the dismantled used atomizing head  19 ′ is washed clean. To serve for these purposes, as shown in  FIGS. 11 to 13 , the atomizing head changing and washing device  31  is constituted by a fixed plate  32 , a common body gripper  33 , an elevator  34 , an atomizing head gripper  35 , and washers  36  and  37  and the like which will be described hereinafter. 
     Denoted at  32  is a fixed plate serving as a fixing member, which is a base of the atomizing head changing and washing device  31 . This fixed plate  32  is in the form of a plate-like structure which is extended in a vertical direction. As shown in  FIGS. 8 and 12 , for example, the fixed plate  32  has its rear side securely fixed to the front side of a mount deck  42  of a cartridge changer  41 , which will be described hereinafter, and has its lower side abutted on a floor surface and the like. 
     Indicated at  33  is a common body gripper which is fixedly mounted in a position where it can grip the common body  15  of the coater unit  14  on the robot device  13 , that is, in an upper portion of the fixed plate  32  as shown in  FIG. 14  and the like. By this common body gripper  33 , the common body  15  is fixedly positioned in the changing position “O” of the atomizing head changing and washing device  31  at the time of replacing an atomizing head  19  and a paint cartridge  24  on the common body  15  of the coater unit  14 . 
     In this instance, as shown in chained line in  FIGS. 11 ,  13 ,  17  and  18 , the changing position “O” of the atomizing head changing and washing device  31  means a position at which the grip surfaces  15 F of the common body  15  are fixedly gripped by radial positioners  33 D of the respective gripping pawls  33 C of a common body gripper  33 , which will be described hereinafter. Since the common body gripper  33  is fixedly mounted on the fixed plate  32 , the changing position “O” can be determined as an immovable specific position (a specific space) which is surrounded by a pair of pawls  33 C. Therefore, when gripped by the common body gripper  33 , the common body  15  is fixedly retained in a specific position on a vertical center line O 1 -O 1  passing through the center of the changing position “O”. 
     As shown in  FIG. 13 , the common body gripper  33  is largely constituted by a mount frame  33 A which is mounted on and forwardly projected from an upper portion of the fixed plate  32 , an actuator  33 B which is transversely attached to a fore distal end of the mount frame  33 A, a pair of gripping pawls  33 C which are mounted in transversely confronting positions to each other on the actuator  33 B for movement toward and away from each other, and radial positioners  33 D which are attached in confronting positions on the gripping pawls  33 C. In this instance, the actuator  33 B, for example, provides drive members which are moved toward and away from each other by an air cylinder or a motor (none of which are shown in the drawings) or the like and the gripping pawls  33 C are attached to drive members to put the gripping pawls  33 C in gripping and releasing motions. 
     Further, as shown in  FIGS. 19 and 20 , after transfer to the changing position “O” of the atomizing head changing and washing device  31  by the robot device  13 , the mount portion  15 B of the common body  15  of the coater unit  14  is fixedly gripped between the gripping pawls  33 C. Each one of the gripping pawls  33 C is provided with inclined surfaces  33 C 1  in base and fore end portions in parallel relation with the vertical center line O 1 -O 1  passing through the changing position “O”. Under guidance of these inclined surfaces  33 C 1 , the mount portion  15 B of the common body  15  is brought into alignment with the changing position “O” of the atomizing head changing and washing device  31  when gripped by the gripping pawls  33 C. 
     The radial positioners  33 D are each provided with flat surfaces  33 D 1  which are disposed parallel with the center line O 1 -O 1  and faced toward each other across the center line O 1 -O 1 , and one and the other inclined surfaces  33 D 2  and  33 D 3  which are provided at the opposite ends of each one of the flat surfaces  33 D 1 . In this instance, one inclined surface  33 D 2  is inclined substantially at the same angle as one inclined surface  15 F 2  of the grip surface  15 F on the common body  15 , while the other inclined surface  33 D 3  is inclined substantially at the same angle as the other inclined surface  15 F 3  of the grip surface  15 F. 
     Thus, as the mount portion  15 B of the common body  15  is gripped between the gripping pawls  33 C, the radial positioners  33 D are abutted against the grip surfaces  15 F on the mount portion  15 B, and as a result the common body  15  is automatically set in the changing position “O”. Namely, as shown in  FIG. 19 , the flat surfaces  33 D 1  of the radial positioners  33 D are brought into abutting engagement with the flat surfaces  15 F 1  of the grip surfaces  15 F provided on the common body  15  thereby bringing the common body  15  automatically into position in the rotational direction. In addition, as shown in  FIG. 20 , by abutting engagement of the inclined surfaces  33 D 2  and  33 D 3  with the inclined surfaces  15 F 2  and  15 F 3  of the grip surfaces  15 F, the common body  15  is at the same time automatically set in position in a vertical direction. 
     In this instance, at the time of gripping the mount portion  15 B of the common body  15  by the respective gripping pawls  33 C and radial positioners  33 D of the common body gripper  33 , a control mode is switched to a reduced power mode as shown in Step  4  in the flow chart of  FIG. 44 . Namely, the robot device  13  is switched to a reduced power mode, lowering the level of a driving force, such as a rotational torque which is applied to the arms  13 B and  13 C and the wrist  13 D of the robot device  13  from a rotational motor or a reciprocating actuator (none of which is shown in the drawings), permitting to move the arms  13 B and  13 C and the wrist  13 D freely by an external force. As a result, the common body  15  of the coater unit  14  is put, so to say, in a free state and can be turned to an arbitrary direction by application of an external force. 
     Therefore, by gripping the mount portion  15 B of the common body  15  which was delivered by the robot device  13  by use of each gripping pawls  33 C, the common body gripper  33  which is mounted on the fixed plate  32  can easily correct a positional deviation against the robot device  13  by each inclined surface  33 C 1  and set the position of the mount portion  15 B of the common body  15  to the changing position “O” of the atomizing head changing and washing device  31 . 
     Besides, even if the common body  15  is located in a deviated position in a rotational direction as shown in  FIG. 17 , such a positional deviation in a rotational direction of the common body  15  can be corrected by the common body gripper  33  as shown in FIG.  19  by abutting engagement of the flat surfaces  33 D 1  of the radial positioners  33 D of the common body gripper  33  with the flat surfaces  15 F 1  in the grip surfaces  15 F on the mount portion  15 B. 
     Further, when the grip surfaces  15 F of the common body  15  are gripped between the radial positioners  33 D, the inclined surfaces  33 D 2  and  33 D 3  of the radial positioners  33 D are brought into abutting engagement with the inclined surfaces  15 F 2  and  15 F 3  on the part of the grip surfaces  15 F. As a consequence, even if the common body  15  is in a vertically deviated position as shown in  FIG. 18 , such a vertical positional deviation of the common body  15  can be corrected by the common body gripper  33  as shown in  FIG. 20 . 
     Thus, by the common body gripper  33 , the coater unit  14  can be automatically set in the proper changing position “O” of the atomizing head changing and washing device  31  in a correctly oriented state, permitting to mount and dismantle the atomizing head  19  and paint cartridge  24  against the common body  15  free of interferences which would result in exertion of unduly large loads. 
     Indicated at  34  is an elevator which is provided on the front side of the fixed plate  32  to move up and down an atomizing head gripper  35  as well as washers  36  and  37 , which will be described hereinafter. Further, as shown in  FIGS. 11 to 16 , the elevator  34  is largely constituted by a mount plate  34 A which is disposed face to face with the fixed plate  32 , a guide rail  34 B which is located between the mount plate  34 A and the fixed plate  32  to guide upward and downward movements of the mount plate  34 A, a feed screw  34 C for moving the mount plate  34 A up and down, and a motor  34 D which is mounted above the fixed plate  32  to drive the feed screw  34 C. 
     As the feed screw  34 C is rotationally driven by the motor  34 D of the elevator  34 , the atomizing head gripper  35 , and washers  36  and  37  are moved up and down along with the mount plate  34 A to and from three vertically shifted positions (i.e., position A, position B and position C) which will be described hereinafter. 
     Indicated at  35  is an atomizing head gripper which is mounted on the mount plate  34 A of the elevator  34 . This atomizing head gripper  35  is largely constituted by a cylinder  35 A which is mounted transversely on a lower portion of the mount plate  34 A, a movable plate  35 B of substantially T-shape which is attached to the cylinder  35 A for movements in rightward and leftward directions, a U-shaped gripping member  35 C which is projected forward from a left side of the movable plate  35 B, and other U-shaped gripping member  35 D which is projected forward from right side of the movable plate  35 B. In this instance, the cylinder  35 A, for example, employs a rodless cylinder type actuator operated by pneumatic pressure or magnetic force. 
     As shown in  FIG. 21 , each one of the left and right gripping members  35 C and  35 D is provided with protrusive prongs  35 E in three positions, i.e., in right, left and inner side positions. As shown in  FIG. 22 , as soon as an atomizing head  19  is located in the gripping member  35 C or  35 D, each protrusive prong  35 E is driven to protrude toward the atomizing head  19  by supply of driving air. At this time, the respective protrusive prongs  35 E are urged to fit in grip holes  20 B which are formed on the body  20  of the atomizing head  19  and to fix the atomizing head  19  in place. 
     Further, as shown in  FIG. 13 , the atomizing head gripper  35  is so arranged that a center line P 1 -P 1  of the gripping member  35 C on the left side is at a distance W 1  from a center line P 2 -P 2  of the gripping member  35 D on the right side. This interval W 1  between the paired gripping members  35 C and  35 D is ½ of an interval W 2  between washers  36  and  37  which will be described hereinafter (W 1 =W 2 /2). 
     As shown in  FIG. 30 , when the common body  15  of the coater unit  14  is gripped by the common body gripper  33 , the atomizing head gripper  35  is located in the uppermost position A by the elevator  34 . In this position A, as shown in  FIG. 31 , the atomizing head gripper  35  can grip a used atomizing head  19 ′ by the gripping member  35 C( 35 D) simultaneously with the gripping operation by the common body gripper  33 . 
     Further, when the atomizing head gripper  35  is lowered to position B as shown in  FIG. 34 , the atomizing head  19 ′ can be dismantled from the common body  15 . In position B, by means of the cylinder  35 A, the atomizing head  19  on the gripping member  35 C( 35 D) can be moved in a leftward direction along with the movable plate  35 B as shown in  FIG. 35 . 
     In this instance, when the movable plate  35 B is shifted in a rightward direction by the cylinder  35 A, as shown in  FIG. 34 , the center line P 1 -P 1  of the gripping member  35 C on the left side is located on the center line O 1 -O 1  passing through the changing position “O” of the common body gripper  33 , while the center line P 2 -P 2  of the gripping member  35 D on the right side is located on a center line Q 2 -Q 2  of a washer  37  on the right side. On the other hand, as shown in  FIG. 35 , when the movable plate  35 B of the atomizing head gripper  35  is shifted in a leftward direction by the cylinder  35 A, the center line P 1 -P 1  of the gripping member  35 C on the left side is located on a center line Q 1 -Q 1  of a washer  36  on the left side, which will be described hereinafter, while the center line P 2 -P 2  of the gripping member  35 D on the right side is located on the center line O 1 -O 1  passing through the changing position “P” of the common body gripper  33 . 
     Further, as shown in  FIG. 42 , by lowering the atomizing head gripper  35  largely to position C, a used atomizing head  19 ′ which is embraced in the gripping member  35 C( 35 D) can be put in a waste liquid collecting container  38 , which will be described hereinafter. 
     Indicated at  36  is a left washer which is mounted on a left position on the mount plate  34 A of the elevator  34 . The washer  36  is movable between upper and lower positions (between position D and position E) which will be described hereinafter. As shown in  FIGS. 23 and 24 , the washer  36  is largely constituted by a cylinder  36 A vertically mounted on a left side portion of the mount plate  34 A, a movable plate  36 B substantially in the shape of a rectangular strip attached to the cylinder  36 A for vertical movements, and a washing tool  36 C located in a projected position on the front side of the movable plate  36 B. In this instance, as the cylinder  36 A, the washer  36  employs a rodless cylinder type actuator operated by pneumatic pressure or magnetic force. 
     Further, the washing tool  36 C is provided with a wash liquid feed tube  36 D for spurting a wash liquid toward the rotary atomizing head  22 . In addition to a wash valve which opens and closes a passage in the wash liquid feed tube  36 D, the washing tool  36 C is further provided with a driving air passage for supply of compressed air or to drive the air motor  21 , and a shaping air passage for supply of shaping air (both not shown in the drawings). The washing tool  36 C as well as the wash liquid feed tube  36 D is located on the center line Q 1 -Q 1 . 
     On the other hand, indicated at  37  is a right side washer which is located in a right side position on the mount plate  34 A of the elevator  34 . This washer  37  is also movable between upper and lower positions (between position D and position E). In the same way as the washer  36  on the left side, the washer  37  on the right side is largely constituted by a cylinder  37 A, a movable plate  37 B, a washing tool  37 C and a wash liquid feed tube  37 D. The washing tool  37 C as well as the wash liquid feed tube  37 D is located on the center line Q 2 -Q 2 . Therefore, as shown in  FIG. 13 , the left washer  36  is at a distance W 2  from the right washer  37 . 
     As described above, the washing tools  36 C and  37 C of the washers  36  and  37  are movable to and from an upper lifted position D on the mount plate  34 A (e.g., the position shown in  FIG. 31 ) and a lowered position E in the proximity of the waste liquid collecting container  38  (e.g., the position shown in  FIG. 42  by the cylinders  36 A and  37 A). 
     The washing tools  36 C and  37 C are in a standby state when in the upper lifted position D. When in the lowered position E, the wash liquid feed tube  36 D or  37 D of the washing tool  36 C or  37 C is inserted into a used atomizing head  19 ′ to take a washing position. In this washing position, a wash liquid is spurted out from the washing liquid feed tube  36 D or  37 D to wash off paint which has deposited on the used atomizing head  19 ′. 
     Indicated at  38  are left and right waste liquid collecting containers which are located underneath the left and right washers  36  and  37 , respectively. Each one of these waste liquid collecting container  38  is constituted by a bottomed cylindrical container which is located in a vertically aligned position relative to the washing tool  36 C or  37 C. Further, each one of the waste liquid collecting containers  38  serves to collect a waste wash liquid which is scattered around while an atomizing head  19  is washed by the washer  36  or  37 . Each waste liquid collecting container  38  is internally provided with nozzles (not shown in the drawings) to spurt a wash liquid toward outer peripheral surface of the rotary atomizing head  22  and shaping air ring  23  and the like to wash off paint which has deposited on outer peripheral surfaces of the rotary atomizing head  22  and shaping air ring  23 . 
     Now, following is a description of the construction of a cartridge changer  41  which is capable of interchangeably mounting a selected paint cartridge  24  on the common body  15  of the coater unit  14  which is provided on the robot device  13 , with reference to  FIGS. 8 to 10  and  25  to  29 . 
     Namely, indicated at  41  is a cartridge changer which is located behind the atomizing head changing and washing device  31 . This cartridge changer  41  serves to replace a used paint cartridge  24 ′ on the common body  15  of the coater unit  14  by a fresh paint cartridge  24  which has been replenished with paint. As shown in  FIGS. 25 and 26 , the cartridge changer  41  is largely constituted by a mount deck  42 , a paint replenishing unit  43  and a cartridge transfer mechanism  44 , as described below. 
     Denoted at  42  is a mount deck which constitutes a main body structure of the cartridge changer  41 . This mount deck  42  is adapted to hold a plural number of paint cartridges side by side, and located within an operating range of a swing arm  48  which will be described hereinafter. In this instance, the mount deck  42  is constituted by a frame structure  42 A built in a rectangular shape which is elongated in a transverse direction (in the transfer direction of the vehicle body  2 ), a rectangular shaped lower deck plate  42 B which is supported substantially horizontally on the intermediate position closer to the bottom of the frame structure  42 A, and a rectangular shaped upper deck plate  42 C which is supported substantially horizontally on the intermediate position closer to the top of the frame structure  42 A. 
     As shown in  FIG. 10 , the upper deck plate  42 C is formed with a transversely extending slot  42 D at a position closer to its front side. This slot  42 D is provided to permit linear leftward and rightward movements of a cylindrical swiveling column  46 B of an arcuate moving portion  46 , which will be described hereinafter. Further, the mount deck  42  is enclosed in a sheet-like decorative cover  42 E composed by a thin plate (see  FIGS. 1 and 2 ). 
     Indicated at  43  are a plural number of paint replenishing units (see  FIGS. 25 and 26 ) which are mounted on the lower deck plate  42 B of the mount deck  42 . By one of these paint replenishing units  43 , a used paint cartridge  24 ′ is replenished with paint of a color same as a previous one. A suitable number of paint replenishing units  43  are provided depending upon the number of paint colors or types to be replenished. Furthermore, each one of the paint replenishing units  43  is connected to a paint source (which is not shown). A used paint cartridge  24 ′ is set at the paint replenishing units  43  to insert a feed tube  27  from the upper side. In such a case, the paint chamber  25 B of the tank  25  will be replenished through the paint supply passage  27 A of the feed tube  27 . 
     In this instance, as indicated by broken lines in  FIG. 26 , the plural number of paint replenishing units  43 , for example, four units are located on the loci of arcuate line S drown by radius R about a pivoting point Sp of a swing arm  48  moved by arcuate moving portion  46 . Furthermore, the paint replenishing units  43  are arranged in six arcuate rows S 1  to S 6  from left side to the right, for example, at uniform intervals in the longitudinal direction of the mount deck  42 , each row having four replenishing units  43  located along an arcuate lines across the width (between the front and rear sides) of the mount deck  42 . 
     In such a case, the paint cartridges  24  which is provided at the paint replenishing unit  43  to supply paint are arrayed in six arcuate rows at uniform intervals as four paint cartridges in each row which are located on the arcuate line S, similar to the respective paint replenishing unit  43 . 
     Further, as shown in  FIG. 26 , of the six arcuate rows S 1  to S 6  of which the paint replenishers  43  (the paint cartridge  24 ), for example, the arcuate row S 3  which is in the third position from left is located in an intersecting position relative to the vertical center line O 1 -O 1  passing through the head changing position “O” of the atomizing head changing and washing device  31 . Namely, the arcuate row S 3  is located on a locus of a movement taken at the time of transferring a replenished paint cartridge  24  on the mount deck  42  to replace a used paint cartridge  24 ′ on the common body  15  which is fixedly gripped at the changing position “O” of the atomizing head changing and washing device  31 . 
     Indicated at  44  is a cartridge transfer mechanism which is provided on the mount deck  42 . This cartridge transfer mechanism  44  is a mechanism for transferring a used paint cartridge  24 ′ or a replenished paint cartridge  24  along an arcuate transfer line to or from a paint replenishing unit  43  on the mount deck  42  and the common body  15  of the coater unit  14  located in the changing position “O”. The cartridge transfer mechanism  44  is constituted by a linear moving portion  45 , an arcuate moving portion  46 , a vertical moving portion  47  and a swing arm  48 , which are described below. 
     Indicated at  45  is a linear moving portion which is provided on the upper deck plate  42 C of the mount deck  42 . This linear moving portion  45  is operative to shift positions of an arcuate moving portion  46 , a vertical moving portion  47  and a swing arm  48 , which will be described hereinafter, linearly in the longitudinal direction of the mount deck  42 . In this instance, as shown in  FIGS. 10 and 25 , the linear moving portion  45  is largely constituted by a pair of guide rails  45 A which are located longitudinally on the opposite sides of the slot  42 D in the upper deck plate  42 C, a carriage  45 B which is movably mounted on the guide rails  45 A, a screw feeder  45 C which is located between the guide rail  45 A and the slot  42 D, and a motor  45 D which is mounted on a right end portion of the upper deck plate  42 C to drive the screw feeder  45 C. As shown in  FIG. 27 , the screw feeder  45 C is constituted by a screw rod  45 C 1 , and a block  45 C 2  which is attached to the lower side of the carriage  45 B, in threaded engagement with the screw rod  45 C 1 . 
     Indicated at  46  is an arcuate moving portion which is mounted on the carriage  45 B of the linear moving portion  45 , the arcuate moving portion  46  turn (swing) a cartridge gripper  48 B provided at the fore end along an arcuate path, by oscillating (revolving) a swing arm  48  which will be described hereinafter, in horizontal plane upon pivoting point Sp. Further, as shown in  FIG. 27 , the arcuate moving portion  46  is largely constituted by a stationary cylindrical outer shell  46 A which is fixedly provided substantially at the center of the carriage  45 B, a swiveling column  46 B rotatably fitted in the outer shell  46 A for swiveling movements about a vertical axis, and a rotational drive motor  46 C for turning the swiveling column  46 B which is mounted on the carriage  45 B. 
     In this instance, the swiveling column  46 B is rotatably supported in the outer shell  46 A through a bearing  46 B 1 . A gear  46 B 2  is provided on the outer periphery of an upper end portion of the swiveling column  46 B, in meshing engagement with a gear  46 C 1  on the part of the rotational drive motor  46 C. As the rotational drive motor  46 C is rotatably actuated, the swiveling column  46 B is turned through the gears  46 C 1  and  46 B 2 . Thus, the swing arm  48  can be turned (can be put in a swinging motion) by the arcuate moving portion  46  which is very simple in construction. 
     Designated at  47  is a vertical moving portion which is attached to the swiveling column  46 B of the arcuate moving portion  46 . This vertical moving portion  47  is provided for lifting a swing arm  48  up and down (upward or downward shifts of arm position), which will be described hereinafter. Namely, as shown in  FIGS. 27  and  28 , the vertical moving portion  47  is largely constituted by a guide member  47 A which is securely fixed to the inner periphery of the swiveling column  46 B of the arcuate moving portion  46  and extended downward of the swiveling column  46 B, a lifter block  47 B which is vertically and movably mounted on the guide member  47 A, a rod screw  47 C which is extended vertically and rotatably within the guide member  47 A and meshed with a threaded meshing member  47 B 1  of the lifter block  47 B, and a motor  47 D which is mounted on the carriage  45 B of the linear moving portion  45  for rotationally driving the rod screw  47 C. Further, an arm body proper  48 A of a swing arm  48  is securely attached to the lifter block  47 B. 
     Indicated at  48  is a swing arm which is attached to the lifter block  47 B of the vertical moving portion  47 . This swing arm  48  is operative to pick up paint cartridges  24  which are arrayed on the upper deck plate  42 C of the mount deck  42 . As shown in  FIGS. 28 and 29 , the swing arm  48  is largely constituted by an arm body proper  48 A which is horizontally extended from the lifter block  47 B, and left and right cartridge grippers  48 B and  48 C which are provided side by side at a fore distal end of the arm body proper  48 A. 
     The cartridge gripper  48 B on the left side is provided with a pair of gripping pawls  48 B 1  which are turned toward and away from each other by means of an actuator (not shown). These gripping pawls  48 B 1  are turned toward each other at the time of catching a grip knob  25 A which is provided on the tank  25  of a paint cartridge  24 . Similarly, the cartridge gripper  48 C on the right side is provided with paired gripping pawls  48 C 1  which can be likewise turned toward and away from each other by means of an actuator (not shown). In this instance, each one of the cartridge grippers  48 B and  48 C is located on an arc of radius R around the pivoting point Sp of the arcuate moving portion  46 . 
     In this instance, the swing arm  48  of the cartridge transfer mechanism  44  is linearly moved in a longitudinal direction (in a leftward or rightward direction of the mount deck  42 ) by the linear moving portion  45 , and put in a swing motion (an arcuate movement) by the arcuate moving portion  46  simultaneously with a lift up or a lift down movement (an upward or downward movement) by the vertical moving portion  47 . Thus, the cartridge transfer mechanism  44  can pick up a replenished paint cartridge  24  from a replenishing unit  43  and transfer the same to a position on the vertical center line O 1 -O 1  passing through the changing position “O” of the atomizing head changing and washing device  31 . Also, the cartridge transfer mechanism  44  can return a used paint cartridge  24 ′ to the paint replenishing unit  43 . 
     At this time, the cartridge gripper  48 B of the swing arm  48  is lifted up to position F (shown in  FIGS. 31 and 39 ), and lowered from position F to position G (shown in  FIGS. 34 and 37 ), at the time of replacing a used paint cartridge  24 ′ with a replenished paint cartridge  24  by an arcuate moving portion  46 . On the other hand, for replacing a used paint cartridge  24 ′ by a replenished paint cartridge  24 , the cartridge gripper  48 B can be stopped at the level of position H (shown in  FIGS. 35 and 36 ) which is lower than position F, because there is no paint cartridge  24 ′ which is in the way as an obstacle. 
     The above-described paint coating system  11  of the present embodiment is put in operation in the manner as follows. 
     In the first place, in order to paint a vehicle body  2  which is being transferred by the conveyer  3 , the robot device  13  is moved on and along the tracking rail  12  while coating operation is put in action by the robot device  13 . At this time, a washed clean atomizing head  19  is connected to the head coupler portion  15 C of a common body  15 , and a replenished paint cartridge  24  which is filled with a desired paint color is set in the cartridge holder portion  15 D. Thus, a cartridge type rotary atomizing head type coater unit  14  is set up by the common body  15 , atomizing head  19  and the paint cartridge  24 . 
     In order to start a coating operation by the use of the coater unit  14 , the robot device  13  is put in action to face the rotary atomizing head  22  of the atomizing head  19  toward the vehicle body  2 . The rotary atomizing head  22  is put in high speed rotation by the air motor  21 , while shaping air is spurted out from the shaping air ring  23 . Further, a high voltage is applied to the rotary atomizing head  22  from the high voltage generator  16  through the air motor  21 . In this state, the extruder liquid valve  18  and the paint valve  29  are opened, whereupon the paint in the tank  25  of the paint cartridge  24  is pushed out toward the rotary atomizing head  22  from the feed tube  27  by the action of the extruder liquid. As a consequence, paint particles which are charged with a high voltage are sprayed toward the vehicle body  2  by the rotary atomizing head  22 . 
     Upon finishing a paint coating operation on the vehicle body  2 , a used atomizing head  19 ′ and a used paint cartridge  24 ′ are replaced by a washed atomizing head  19  and a replenished paint cartridge  24 . 
     Given below is a more detailed description of operations for replacement of the atomizing head  19  and the paint cartridge  24 , with reference to the flow chart of  FIG. 44  and to the schematic illustration explanatory of  FIGS. 30 to 43 . 
     As described above, upon finishing a coating operation on a vehicle body  2  by the coater unit  14  (Step  1 ), the robot device  13  is put in an action to bring the coater unit  14  to the changing position “O” of the atomizing head changing and washing device  31  as indicated in two dot line in  FIG. 30  (Step  2 ). At this changing position “O”, the common body  15  of the coater unit  14  is located between each gripping pawls  33 C at the common body gripper  33  of the atomizing head changing and washing device  31  as shown in two dot line in the figure. On the other hand, a used atomizing head  19 ′ is located in a position within a reach of the left side of the gripping member  35 C of the gripping members  35 C,  35 D of the atomizing head gripper  35  which is shown in  FIG. 30 . 
     In Step  3 , a judgment is made as to whether or not the coater unit  14  has already reached the changing position “O” of the atomizing head changing and washing device  31 . The control proceeds to Step  4  in case the coater unit  14  is found to have already been located in the changing position “O” of the atomizing head changing and washing device  31  as shown in two dot line in  FIG. 30 . 
     In Step  4 , the robot device  13  is switched to a reduced power mode. In this case of the paint coating system  11 , the coater unit  14  which should be located correctly at the changing position “O” might have been located in a deviated position for some reason. Therefore, in Step  4 , the robot device  13  is put in a reduced power mode, lowering the levels of driving forces of rotating motors and reciprocating actuators (both not shown) which arcuate the arms  13 B and  13 C and the wrist  13 D of the robot device  13 . That is, in Step  4 , the robot device  13  is controlled to make the common body  15  freely movable by application of an external force to the coating unit  14 . Thus, the coater unit  14  is put in a freely movable state. 
     In Step  5 , as shown in  FIG. 31 , as soon as the coater unit  14  is delivered to the changing position “O” of the atomizing head changing and washing device  31  by the robot device  13 , the mount portion  15 B on the common body  15  of the coater unit  14  is gripped between the right and left gripping pawls  33 C of the common body gripper  33 . The coater unit  14  is put in a free state in Step  4  before gripping the common body  15  of the coater unit  14  by the right and left gripping pawls  33 C of the common body gripper  33 . Therefore, as the mount portion  15 B of the common body  15  is gripped between the gripping pawls  33 C, a positional deviation between the robot device  13  can be corrected automatically by the inclined surfaces  33 C 1  to set the mount portion  15 B of the common body  15  exactly at the predetermined specific changing position “O” of the atomizing head changing and washing device  31 . 
     In case the common body  15  is deviated in a rotational direction, such positional deviation in a rotational direction can also be automatically corrected as the flat surfaces  15 F 1  of the grip surfaces  15 F provided at the mount portion  15 B are gripped between the flat surfaces  33 D 1  of the radial positioners  33 D. Accordingly, as shown in  FIG. 31 , by the common body gripper  33 , the common body  15  can be fixed in a predetermined specific changing position “O” on the center line O 1 -O 1  in between the gripping paws  33 C, in a correctly oriented state in a radial direction and exactly at a predetermined height. 
     In this instance, Step  4  for switching the coater unit  14  provided at the robot device  13  to a freely movable state and Step  5  for gripping the common body  15  of the coater unit  14  are executed substantially at the same time. If necessary, the order of Step  4  and Step  5  may be reversed, putting the common body  15  on the robot device  13  in a free state after the common body  15  of the coater unit  14  is gripped. 
     While Step  4  and Step  5  are being executed, the cartridge changer  41  is put in operation. Namely, before the common body  15  is gripped by the common body gripper  33  in Step  5 , the cartridge changer  41  is put in operation for preparing a replenished paint cartridge  24  to be used in a next coating operation. As shown in  FIG. 32 , for example, this cartridge changer  41  catches a left rear positioned replenished paint cartridge  24  on the arcuate row S 1  of plural number of replenished paint cartridges by the right cartridge gripper  48 C of the swing arm  48 . In this state, the vertical moving portion  47  disconnect the replenished paint cartridge  24  from a paint replenishing unit  43  by lifting up the swing arm  48  along with the replenished paint cartridge  24 . 
     In the next place, by the linear moving portion  45  of the cartridge changer  41 , the position of the swing arm  48  is shifted in a rightward direction from the position of  FIG. 32  to the position of  FIG. 33 , locating its cartridge gripper  48 B on the arcuate row S 3  coinciding with a locus of a transfer movement. In this state, by the arcuate moving portion  46 , the swing arm  48  is swung forward, locating the left cartridge gripper  48 B without the paint cartridge  24 , on the center line O 1 -O 1  and above the changing position  101  as shown in  FIGS. 31 and 33 . At this time, the vertical moving portion  47  lift the feed tube  27  of the replenished paint cartridge  24  to the higher position F, preventing not to contact with other obstacles. Although a linear movement of the swing arm  48  by the linear moving portion  45  is described separately from an arcuate swinging movement of the swing arm  48  by the arcuate moving portion  46  of course, the swing arm  48  may be simultaneously put in linear and arcuate swinging movements. 
     Now, as shown in  FIG. 31 , as soon as the left cartridge gripper  48 B without the paint cartridge  24  is located on the center axis O 1 -O 1  and above the changing position “O”, the operation proceeds to Step  6 . In Step  6 , as shown in  FIG. 34 , the atomizing head gripper  35  is put in an action of gripping a used atomizing head  19 ′ by the gripping member  35 C, followed by an action of lowering the atomizing head gripper  35  to the position B to dismantle the used atomizing head  19 ′ from the common body  15 . Further, in Step  7 , the swing arm  48  is lowered to the position G to grip a used paint cartridge  24 ′ by the left cartridge gripper  48 B. Then, as shown in  FIG. 35 , the swing arm  48  is lifted up to the position H by the vertical moving portion  47  to draw the used paint cartridge  24 ′ out of the common body  15 . 
     In this instance, Step  6  for dismantling a used atomizing head  19 ′ from the common body  15  and Step  7  for unloading a used paint cartridge  24 ′ from the common body  15  may be reversed in order, or may be executed simultaneously. 
     Now, as soon as the feed tube  27  of the paint cartridge  24 ′ is extracted out of the atomizing head  19 ′, the used atomizing head  19 ′ which is gripped on the gripping member  35 C on the left side is moved by the cylinder  35 A as far as a position on the center line Q 1 -Q 1  of the washer  36  on the left side, while the washed clean atomizing head  19  which is gripped on the gripping member  35 D on the right side is shifted to a position on the center line O 1 -O 1  and below the changing position “O”, as shown in  FIG. 35 . 
     Now, in Step  8 , as shown in  FIG. 36 , the gripping member  35 D of the atomizing head gripper  35  is lifted up to position A to mount the washed clean atomizing head  19  which is gripped by the gripping member  35 D on the common body  15 . On the other hand, the cartridge grippers  48 B and  48 C of the swing arm  48  are moved to the left side to relocate the replenished paint cartridge  24  gripped by the right cartridge gripper  48 C in a position on the center line O 1 -O 1  and above the changing position “O”. At this time, by the vertical moving portion  47 , the cartridge grippers  48 B and  48 C are lifted up to position H which is at a lower level than position F, shortening time which is required for shifting the position. 
     Now, the control goes to Step  9  as soon as the replenished paint cartridge  24  is located in a position over the changing position “O”. In Step  9 , as shown in  FIG. 37 , the cartridge gripper  48 C is lowered to position G to load the replenished paint cartridge  24  into the common body  15 . Thereafter, as shown in  FIG. 38 , the paint cartridge  24  is released from the cartridge gripper  48 C as the latter is lifted up to position F. 
     Similarly to above-described Step  6  and Step  7 , if desired, Step  8  for mounting a washed clean atomizing head  19  on the common body  15  and Step  9  for loading a replenished paint cartridge  24  on the common body  15  may be reversed in order or executed simultaneously. 
     As soon as the coater unit  14  becomes ready for a next coating operation by replacing a washed clean atomizing head  19  and a replenished paint cartridge  24  on the common body  15 , the control goes to Step  10  to cancel the reduced power mode of the device force for the robot device  13 . In Step  10 , in addition to cancellation of the reduced power mode, the gripping force of the common body gripper  33  as well as that of the atomizing head gripper  35  is canceled to release the atomizing head  19 . In this state, as shown in  FIG. 39 , the swing arm  48  which carries the used paint cartridge  24 ′ is moved toward the mount deck  42  of the cartridge changer  41 . At the same time, the robot device  13  which is now controlled in a normal drive mode is moved to put the coater unit  14  in a coating standby position on the side of a vehicle body  2 . 
     On the other hand, concurrently with Step  10  or after Step  10 , the cartridge changer  41  is put in an operation of returning the used paint cartridge  24 ′, which has been dismantled from the common body  15 , to a specific position on the mount deck  42 . Namely, as shown in  FIG. 40 , the cartridge gripper  48 B which holds the used paint cartridge  24 ′ is moved to the rear side by the arcuate moving portion  46  along an arcuate row S 3 . Thus, as shown in  FIG. 4 , by the action of the arcuate moving portion  46 , the used paint cartridge  24 ′ is relocated in a specified position at the upper side of the paint replenishing unit  43  on the arcuate row S 3 . In this state, by the vertical moving portion  47 , the used paint cartridge  24 ′ is lowered together with the cartridge gripper  48 B and connected to a paint replenishing unit  43 . Consequently, the paint is replenished at this point. 
     In a next step, in Step  11 , as shown in  FIG. 42 , the atomizing head gripper  35  is lowered to position C by the elevator  34  to put a fore end portion of the used atomizing head  19 ′ in the waste liquid collecting container  38 . Further, the washing tool  36 C of the left washer  36  is lowered to position E to insert the wash liquid tube  36 D in the used atomizing head  19 ′. In this state, a wash liquid is spurted out from the wash liquid tube  36 D of the washer  36  to wash the rotary atomizing head  22  without scattering around splashes of the wash liquid. 
     Upon finishing a washing operation on the atomizing head  19 , as shown in  FIG. 43 , the atomizing head gripper  35  is elevated to position A, and the washer  36  is elevated to position D. Accordingly, it is possible to stand by for the next operation, exchanging the atomizing head  19 ,  19 ′ and the paint cartridge  24 ,  24 ′. 
     As described above, according to the present embodiment, the cartridge changer  41  is constituted by the linear moving portion  45  which is adapted to shift the position of the swing arm  48  linearly in a longitudinal direction (rightward or leftward) of the mount deck  42 , the arcuate moving portion  46  which put the swing arm  48  in a swinging motion (an arcuate movement) in a horizontal plane, the vertical moving portion  47  which moves the swing arm  48  attached to the arcuate moving portion  46  upward and downward (the heave) and the swing arm  48  which hold the paint cartridge  24  attached to the vertical moving portion  47 . 
     Thus, by putting the swing arm  48  in an arcuate swinging motions, the arcuate moving portion  46  can move the cartridge grippers  48 B and  48 C in a longitudinal direction (in a leftward or rightward direction) and in a transverse direction (in a forward or rearward direction) of the mount deck  42 . Therefore, the cartridge changer  41  can be built in a more compact form as compared with a handling robot with a multiarticular arm or a cartridge changer incorporating a double layered complicate XY table. That is to say, the paint coating system  11  can be installed even in a space which has thus far been considered too narrow for installation. 
     In case it becomes necessary to increase the number of paint cartridges  24  on the mount deck  42 , this can be coped with simply by elongating the guide rail  45 A of the linear moving portion  45 . 
     On the other hand, the cartridge changer  41  has a plural number of paint cartridges  24  and the paint replenishing unit  43  arrayed in six arcuate rows S 1  to S 6  in longitudinal direction of the mount deck  42  of radius R around a swing arm pivoting point Sp of the arcuate moving portion  46 , four of them in each row. Of the six arcuate rows S, the third row S 3  is located on passing through the changing position “O” of the atomizing head changing and washing device  31 . 
     Thus, simply by putting the swing arm  48  in a swinging motion across the width of the mount deck  42 , the cartridge changer  41  can relocate a paint cartridge  24  on the cartridge gripper  48 C at the changing position “O”. This means that the cartridge changer  41  can operate very efficiently in relocating paint cartridges  24 . 
     Further, according to the present embodiment, the common body gripper  33  is mounted on the fixed plate  32  of the atomizing head changing and washing device  31 , thereby fixedly gripping a common body  15  of a coater unit  14  in a predetermined position at the time of replacing an atomizing head  19  and a paint cartridge  24 . Therefore, a common body  15  can be fixedly retained in position by the common body gripper  33  while replacing an atomizing head  19  and a paint cartridge  24  on the common body  15  of the coater unit  14 . Thus, the common body gripper  33  is so arranged to locate a common body  15  in a predetermined changing position “O” of the atomizing head changing and washing device  31 . 
     That is, according to the present embodiment, the common body gripper  33  is adapted to absorb positional deviations which might occur depending upon repeated positioning accuracy of the arms  13 B and  13 C of the robot device  13 , as well as positional deviations which might have occurred in the course of installation of the robot device  13 , the atomizing head changing and washing device  31  and the cartridge changer  41 . It follows that the coater unit  14  can be located exactly in the predetermined immovable changing position “O” each time when replacing the atomizing head  19  and the paint cartridge  24 . 
     Since a common body  15  is accurately located at a predetermined changing position “O” of the atomizing head changing and washing device  31 , an atomizing head  19  and a paint cartridge  24  can be attached to or detached very smoothly without necessitating forcible actions. Thus, it contributes to suppress abrasion and bruises of the common body  15 , atomizing head  19  and paint cartridge  24  to guarantee higher durability and reliability, while permitting a reduction in maintenance cost of the coating line  1 . 
     Further, the accuracy in locating a common body  15  of a coater unit  14  exactly at a predetermined changing position “O” of the atomizing head changing and washing device  31  permits to carry out an installation work for the robot device  13  in a more efficient and facilitated manner, and to fabricate and install the atomizing head changing and washing device  31  and the cartridge changer  41 . Furthermore, it is possible to allow a significant reduction in cost of the coating line  1  as a whole. 
     Further, since the common body gripper  33  is mounted in a fixed state on the fixed plate  32 , the common body  15  can be gripped in the same position every time. That is to say, the atomizing head changing and washing device  31  as well as the paint cartridge changer  41  can smoothly mount or dismantle an atomizing head  19  or a paint cartridge  24  on or from the common body  15  which is located exactly in a predetermined position. 
     On the other hand, according to the present embodiment, when the common body  15  is gripped by the common body gripper  33 , the robot device  13  is controlled in a reduced power mode in which driving forces (driving torques) of the robot arms  13 B and  13 C and wrist  13 D are cut down to a low level, permitting to move the common body  15  freely by application of an external force. Thus, the coater unit  14  which is mounted on the wrist  13 D is now, so to say, in a free state and can be moved in an arbitrary direction by an external force. Accordingly, in case there is a positional deviation between the coater unit  14  and the common body gripper  33 , the coater unit  14  can be located accurately at the changing position “O” without being affected or obstructed by the driving force of the robot device  13 . 
     Besides, the grip surfaces  15 F are provided on the common body  15 . On the other hand, paired gripping pawls  33 C are provided on the part of the common body gripper  33  for gripping and locating the common body  15  at the changing position “O”, in combination with the radial positioners  33 D which are provided on the gripping pawls  33 C and brought into abutting engagement with the grip surfaces  15 F of the common body  15  to grip the common body  15  in position in a radial direction and in a vertical direction as well. 
     Thus, by the common body gripper  33 , the common body  15  of the coater unit  14  can be automatically located in a predetermined specific changing position “O” accurately in both vertical and radial directions. As a result, an atomizing head  19  and a paint cartridge  24  can be smoothly mounted on or dismantled from the common body  15  without applying forcible connecting and disconnecting actions, to guarantee higher reliability and elongated service life. 
     In the above-described embodiment, by way of example, the fixed plate  32  of the atomizing head changing and washing device  31  is securely fixed to the mount deck  42  of the cartridge changer  41 . However, needless to say, the present invention is not limited to this particular example shown. For example, the fixed plate  32  may be provided independently and separately of the mount deck  42  of the cartridge changer  41  as long as it is located within a reach of the cartridge grippers  48 B and  48 C on the swing arm  48 . 
     Further, in the above-described preferred embodiment, the mount deck  42  of the cartridge changer  41  is arranged to hold paint cartridges  24  (paint replenishing units  43 ) in six arcuate rows S 1  to S 6  of radius R about a shifting swing arm pivoting point Sp in the longitudinal direction along the mount deck  42 , with four paint cartridges in each one of the arcuate rows S 1  to S 6 . However, the present invention is not limited to the particular example shown. The mount deck  42  may be arranged to hold two, three or more than five paint cartridges  24  in each one of less than five or more than seven arcuate rows S which are provided at intervals in the longitudinal direction. 
     Furthermore, in the above-described preferred embodiment, the mount deck  42  is by way of example arranged such that the changing point “O” of the atomizing head changing and washing device  31  is located on an extension of an arc of the third arcuate row S 3  of paint cartridges  24  (paint replenishing units  43 ). However, the present invention is not limited to the particular example shown. If desired, the changing position “O” may be located on an extension of an arc of any one of other arcuate rows S 1 , S 2  and S 4  to S 6  or on an arc which is drawn separately from the arcs of the arcuate rows S 1  to S 6 . 
     Furthermore, in the above-described embodiment, the atomizing head  19  is shown as an atomizing head of the rotary atomizing head type which provides a rotary atomizing head  22 . However, the present invention is not limited to this particular type and can be applied to atomizing heads of other types, for example, to an atomizing head with pneumatic or hydraulic atomization nozzles.