Patent Publication Number: US-9427754-B2

Title: Rotary atomizer

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/598,589, entitled “Rotary Atomizer,” filed Nov. 2, 2009, which claims priority to and the benefit of PCT Application No. PCT/JP2007/059803 entitled “Rotary Atomizer,” filed on May 2, 2007, all of which are herein incorporated by reference in their entirety for all purposes. 
    
    
     BACKGROUND 
     The present invention relates to a rotary atomizer. 
     A rotary atomizer includes a rotating bell which is coupled to a rotating shaft of an air motor and has a plurality of orifices and a paint passage for supplying paint from a paint source to the orifices of the rotating bell, thus dispensing the paint through the orifices toward an object to be painted. In a painting operation, when the rotating shaft of the air motor and the rotating bell are rotated, the paint discharged through the orifices flows radially outwardly along a distal end face of the rotating bell, due to the centrifugal force, toward the peripheral edge of the rotating bell, then the paint is sprayed when separating from the peripheral edge of the rotating bell. 
     BRIEF DESCRIPTION 
     Recently, water-based paints have often been used instead of solvent-based paints in view of the state and local government regulations concerning environmental issues. A water-based paint, particularly, a quick-drying water-based emulsion paint turns into a gel immediately after the material has come into contact with the air. For example, when thirty minutes have passed after the start of painting operation, paint clots are deposited around the orifices, the distal end face and/or the outer periphery of the rotating bell, which causes a deformed pattern is deformed, which is a problem. 
     Further, when the supply of paint is stopped for a certain time period, the paint turns into a gel at the distal portion of the paint passage so that its paint port would be clogged. 
     In view of the above-mentioned problem of the prior art, an object of the present invention is to provide a rotary atomizer capable of avoiding the deposition of paint clots onto the distal end face of the rotating bell. 
     Further, another object is to provide a rotary atomizer capable of avoiding the clogging of a paint port at the distal portion of a paint passage. 
     According to the present invention, there is provided a rotary atomizer including a rotating bell secured to a rotating shaft of an air motor held in an atomizer body, the rotating bell defining a plurality of orifices for dispensing paint to an object to be painted, the rotation of the rotating bell atomizing the paint so as to spray the paint toward the object to be painted, the rotary atomizer comprising: a paint passage having a paint port, at a distal end thereof, fluidly communicating with the orifices of the rotating bell; a water passage disposed outside of the paint passage and having a water port, at a distal end of the water passage, fluidly communicating with the orifices of the rotating bell, and the paint and the water being simultaneously dispensed through the orifices of the rotating bell. 
     According to another aspect of the present invention, there is provided a rotary atomizer including a rotating bell secured to a rotating shaft of an air motor held in an atomizer body, the rotating bell having a plurality of orifices for dispensing paint to an object to be painted, the rotation of the rotating bell atomizing the paint so as to spray the paint toward the object to be painted, the rotary atomizer comprising: a paint passage having a paint port, at a distal end thereof, fluidly communicating with the orifices of the rotating bell; and a needle for opening and closing the paint port. 
    
    
     
       DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is a cross-sectional view illustrating a rotary atomizer taken along its axis in accordance with a preferable embodiment of the present invention. 
         FIG. 2  is a plan view of the rear end face of the manifold of the rotary atomizer. 
         FIG. 3  is an end view of the rotary atomizer showing a rear end face thereof. 
         FIG. 4  is a partial section of the front part of the rotary atomizer. 
         FIG. 5  is a sectional view of the dual-tube assembly taken along its axis. 
         FIG. 6  is a block diagram of a preferable embodiment of a painting system suitable for incorporating with the rotary atomizer of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to the drawings, an embodiment of the present invention will be described below. 
     Referring to  FIG. 1 , a rotary atomizer  10  is provided with an atomizer body formed by a cylindrical cover  12 , an end plate  16  closing a rear end opening of the cylindrical cover  12 , and a manifold  18  mounted on a distal end opening portion opposite to the end plate  16 , with an axis O of the cylindrical cover  12  defining a longitudinal axis of the atomizer body. Formed on a rear end face of the manifold  18  ( FIG. 2 ) are three screw holes  56  which are equidistantly provided on the periphery direction around the axis O. 
     The end plate  16  defines through holes  16   a  which are axially aligned with the screw holes  56  of the manifold  18 . Further, within an internal space  14  of the atomizer body, three stays  26  extend parallel to the axis O. The stays  26  define, at the distal ends thereof, screw portions  26   a  which engages with the screw holes  56  of the manifold  18 , and at the rear ends thereof, screw holes  26   b  which receive and engage with screw bolts  25 . Thus, the manifold  18 , the stays  26 , the cylindrical cover  12  and the end plate  16  are assembled as illustrated in  FIG. 1 , and then, the screw bolts  25  are engaged and tightened with the screw holes  26  to unify the manifold  18 , the cylindrical cover  12  and the end plate  16 . 
     Further, the rear end face of the manifold  18  includes a screw hole  18   a  engaging with a screw portion  28   a  at the end of a high voltage cable  28  for supplying a voltage to the rotary atomizer  10  to generate an electric field between the rotary atomizer  10  and the object to be painted. The rear end face further includes a first valve receptacle  18   b  for receiving a trigger valve  30 , described below, a second valve receptacle  18   c  for receiving a gate valve  40 , described below, and a plurality of exhaust ports  54 . Further, a paint coupling  42 , a water coupling  44 , a turbine air coupling  46 , a bearing air coupling  48 , a brake air coupling  50  and a shaping air coupling  52  are attached to the rear end face of the manifold  18  by using a coupling method well-known in the art such as a screw coupling. 
     The end plate  16  defines a paint hole  60  and a water hole  62  through which a paint tube  218  ( FIG. 6 ) for supplying paint to the paint coupling  42  from a paint source, described below, and a water tube  220  ( FIG. 6 ) for supplying water to the water coupling  44  from a water source, described below, are introduced into the internal space  14 . Further, air holes  64  and  66  and an exhaust port  68  are formed in the end plate  16 . Through the air holes, a plurality of air tubes  206 - 216  ( FIG. 6 ), for respectively supplying air from an air source, described below, to the turbine air coupling  46 , the bearing air coupling  48 , the brake air coupling  50  and the shaping air coupling  52 , are introduced into the internal space  14 . Reference numeral  70  designates a bracket for mounting the rotary atomizer  10  on a stand (not shown) or a robot hand (not shown). 
     The first valve receptacle  18   b  is a recess formed along the axis O in which the trigger valve  30  is accommodated. Further, a paint chamber  78  adjacent the first valve receptacle  18   a  opens into the end or bottom of the first valve receptacle  18   b.    
     Further, a needle passage  80  fluidly connected to the paint chamber  78  in the manifold  18 . The end of the needle passage  80  opposite to the paint chamber  78  opens into a pocket  88  which opens into a stopper receptacle  89 . The stopper receptacle  89  opens into a motor receptacle  74  formed at the distal end of the manifold  18 . 
     As stated above, the paint chamber  78  is a recess extending along the axis where one end opens into the first valve receptacle  18   b  and the opposite end opens into the pocket  88 . A passage  82 , fluidly communicating with the paint coupling  42 , opens into the side wall of the recess. In this embodiment, the passage  82 , the paint chamber  78  and the needle passage  80  provide a paint supplying passage. 
     The second valve receptacle  18   c  is an axially extending recess which is offset in the radial direction from the first valve receptacle  18   b . The gate valve  40  is held in the second valve receptacle  18   c . At a distal end portion of  40   a , the outer surface of the gate valve  40  defines a peripheral groove  40   b  which opens into a radial passage  40   c . The radial passage  40   c  is fluidly connected to an axially extending internal passage (not shown) of the end portion  40   a.    
     Further, the gate valve comprises an axially reciprocating valve body  40   d , for opening and closing the internal passage of the end portion  40   a , and a coupling  41  for receiving air to activate the valve body  40   d . Further, a passage  84 , fluidly connected to the water coupling  44 , opens into the side wall of the second valve receptacle  18   c . Furthermore, the second valve receptacle  18   c  is fluidly connected via the passage  86  to the pocket  88 . 
     A substantially cylindrical confluence member  90  is provided in the pocket  88 . 
     The confluence member  90  includes a peripheral groove  90   a  formed in its outer surface, a central through hole  90   b  and a radial passage  90   c  extending between the central through hole  90   b  and the peripheral groove  90   a . The passage  86  extending from the second valve receptacle  18   c  is positioned at the side wall of the pocket  88  so that the passage  86  opens into the peripheral groove  90   a  of the confluence member  90 . In this embodiment, the passage  84 , the peripheral groove  40   b , the radial passage  40   c , the internal passage of the end portion  40   a , the passage  86 , the peripheral groove  90   a , the radial passage  90   c  and the central through hole  90   b  provide a water supplying passage. 
     Accommodated in the air motor receptacle  74  is an air motor  20  having a rotating shaft  20   a  extending along the axis O. A rotating bell  92  is secured to the rotating shaft  20   a  of the air motor  20 . The air motor  20  incorporates a turbine (not shown) coupled to the rotating shaft  20   a  and driven by turbine air, as described below. 
     A dual-tube assembly  100  extends through the body portion and the rotating shaft  20   a  of the air motor  20  along the axis O. Referring to  FIG. 5 , the dual-tube assembly  100  comprises an inner tube  102  defining an inner passage  102   a  which provides a paint passage, an outer tube  104  having an inner diameter larger than the outer diameter of the inner tube  102 , a tip member  112  attached to the distal end of the inner tube  102  and a sleeve  106  attached to the distal end of the outer tube  104 . 
     The inner tube  102 , the outer tube  104 , the tip member  112  and the sleeve  106  are concentrically disposed around the axis O so that an annular outer passage  108  is defined between the inner tube  102  and the outer tube  104  to provide a water passage. At the rear end of the dual-tube assembly  100 , the outer passage  108  is attached to the confluence member  90  so that the outer passage  108  is fluidly connected via the central through hole  90   b  of the confluence member  90  to the radial passage  90   c.    
     The tip member  112  has an annular proximal end portion  112   a  and a tapered portion  112   b  coupled to the proximal end portion  112   a . The tapered portion has a diameter gradually decreased toward the distal end and defines a paint port  112   c  fluidly connected to the inner passage  102 . An inner surface of the tapered portion  112   b , converging toward the distal end, provides a valve seat which sealingly contacts with a valve body  94   a , described below. Further, in order to maintain the radial position of the sleeve  106  with respect to the tip member  112 , a ring member  116  with a plurality of axial orifices (not shown) is arranged between the tip member  112  and the sleeve  106 . Thus, an annular water port  114  is defined between the tip member  112  and the sleeve  106 . 
     The trigger valve  30  comprises a pneumatically reciprocating valve stem  30   a  along the axis O and a coupling  32  which receives air for driving the valve stem  30   a . Coupled to the distal end of the valve stem  30   a  is a needle  94  extending along the axis O and defining a valve body  94   a  at the distal end thereof. Thus, the needle  94  extends along the axis O from the valve stem  30   a  via the paint chamber  78 , the needle passage  80  and the inner tube  102  of the dual-tube assembly  100  to the valve body  94   a.    
     A rotating bell  92   b  is mounted to the rotating shaft  20   a  of the air motor  20 . The rotating bell  92   b  includes, as well known in the art, a bell-shaped or cup-shaped distal end face  92   b  and a plurality of orifices  92   a  opening into the distal end face  92   b.    
     Mounted on the distal end of the manifold  18  are an inner ring  22  enclosing the air motor  20  and an outer ring  24  arranged concentrically with the inner ring  22 . A shaping air passage  23 , fluidly connected to the shaping air coupling  52 , is defined between the inner ring  22  and the outer ring  24 . 
     With reference to  FIG. 6 , a painting system which is suitable for incorporating with the rotary atomizer of the present invention will be described below. A painting system  200  comprises a compressor  204  providing an air source (AS), a header  202  fluidly connected to an outlet port of the compressor  204 , a turbine air tube  206  for supplying turbine air to the turbine air coupling  46  to drive the air motor, a bearing air tube  208  for supplying bearing air to the bearing air coupling  48  to suspend the rotating shaft  20   a , a brake air tube  210  for supplying brake air to the brake air coupling  50  to reversely rotate the rotating shaft  20   a , a shaping air tube  212  for supplying shaping air to the shaping air coupling  52  to control the spray pattern, a first valve driving air tube  214  for supplying air to the coupling  32  of the trigger valve  30  to rearwardly drive the valve stem  30   a  along the axis O, a second valve driving air tube  216  for supplying air to the coupling  41  of the gate valve  40  to drive the valve body  40   d , a paint tube  218  for supplying paint to the paint coupling  42  and a water tube  220  for supplying water to the water coupling  44 . 
     Provided on the turbine air tube  206  is a pneumatically-operating normally-closed ON/OFF valve  224  for controlling the supplying and shutting-off of turbine air. The opening and closing of the ON/OFF valve  224  is controlled by opening and closing a solenoid valve  228  provided on a control air tube  226 . The bearing air tube  208  is continuously opened so that bearing air is continuously supplied to the air motor  20  from the activation to the shutoff of the compressor  204 . 
     Provided on the brake air tube  210  is a pneumatically-operating normally-closed ON/OFF valve  236  for controlling the supplying and shutting-off of brake air. The opening and closing of the ON/OFF valve  236  is controlled by opening and closing a solenoid valve  240  provided on a control air tube  238 . 
     Provided on the shaping air tube  212  is a pneumatically-operating normally-closed ON/OFF valve  242  for controlling the supplying and shutting-off of shaping air. The opening and closing of the ON/OFF valve  242  is controlled by opening and closing a solenoid valve  246  provided on a control air tube  244 . 
     Provided on the first valve driving air tube  214  is a pneumatically-operating normally-closed ON/OFF valve  248  for controlling the supplying and shutting-off of air for driving the valve stem  30   a . The opening and closing of the ON/OFF valve  248  is controlled by opening and closing a solenoid valve  252  provided on a control air tube  250 . 
     Provided on the second valve driving air tube  216  is a pneumatically-operating normally-closed ON/OFF valve  254  for controlling the supplying and shutting-off of air for driving the valve stem  40   d . The opening and closing of the ON/OFF valve  254  is controlled by opening and closing a solenoid valve  258  provided on a control air tube  256 . 
     Paint is supplied by a paint pump  266  from a paint reservoir  268  via a paint tube  218  to the rotary atomizer  10 . Provided on the paint tube  218  are a pneumatically-operating normally-closed ON/OFF valve  260  for controlling the supplying and shutting-off of paint and a circulation tube  268  for returning paint discharged from the paint pump  266  to the paint reservoir  268  when the ON/OFF valve  260  is closed. The opening and closing of the ON/OFF valve  260  is controlled by opening and closing a solenoid valve  264  provided on a control air tube  262 . A power supply unit  272  supplies electrical power to the paint pump  266 . 
     Water is supplied by a water pump  274  from a water tank  276  via a water tube  220  to the rotary atomizer  10 . Provided on the water tube  220  are a pneumatically-operating normally-closed ON/OFF valve  230  for controlling the supplying and shutting-off of water and a circulation tube  278  for returning water discharged from the water pump  274  to the water tank  276  when the ON/OFF valve  230  is closed. The opening and closing of the ON/OFF valve  230  is controlled by opening and closing a solenoid valve  234  provided on a control air tube  232 . A power supply unit  280  supplies electrical power to the water pump  274 . 
     Herein after, the operation of the present embodiment will be described below. 
     In advance of starting a painting operation, the compressor  204 , the paint pump  266  and the water pump  274  are activated. When the compressor  204  is activated, bearing air is supplied from header  202  via the bearing air tube  208  and the bearing air coupling  218  to the air motor  20  so that the rotating shaft  20   a  of the air motor  20  is suspended. 
     Next, when the ON/OFF valve  224  is opened, turbine air is supplied from the header  202  via the turbine air tube  206  and the turbine air coupling  46  to the air motor  20 , to thereby rotate the rotating shaft  20   a  and the rotating bell  92  secured to the rotating shaft  20   a . Next, when the ON/OFF valve  242  is opened, shaping air is supplied from the header  202  via the shaping air tube  206  and the shaping air coupling  32  to the shaping air passage  23  so that shaping air is discharged through the shaping air port  23   a  between the distal ends of the inner ring  22  and the out ring  24 . In this connection, the supply of shaping air can be started at the same time as the supply of turbine air. 
     Water is supplied from the water tank  274  via the water tube  220  to the water coupling  44 . Simultaneously, when the ON/OFF valve  254  of the second valve driving air tube  216  is opened, air is supplied from the header  202  via the second valve driving air tube  216  and the coupling  41  of the gate valve  40  to the gate valve  40 , so that the valve body  40   d  thereof is forwardly driven, i.e., moved in the left direction in  FIGS. 1 and 4 . Thus, together with paint, water is discharged from the orifices  92   a  of the rotating bell  92  via the water coupling  44 , the passage  84 , the peripheral groove  90   a , the radial passage  90   c  and the central through hole  90   b  of the confluence member  90 , the outer passage  108  of the dual-tube assembly  100  and the water port  114 . In particular, the water discharged through the orifices  92   a  flows outwardly in the radial direction of the rotating bell  92  between the paint discharged through the orifices  92   a  and the distal end faces  92   b  of the rotating bell  92 . 
     When the ON/OFF valve  260  is opened, paint is supplied from the paint reservoir  268  via the paint tube  218  to the paint coupling  42 . Further, when the ON/OFF valve  248  of the first valve driving air is opened, air is supplied from the header  202  via the first valve driving air tube  214  and the trigger valve  30  to the trigger valve  30  so that the valve stem  30   a  thereof is backwardly driven, i.e., moved in the right direction in  FIGS. 1 and 4 . Thus, the valve body  94   a  is disengaged from the inner surface of the tapered portion  112   b  of the tip member  112  providing a valve seat so that the paint port  112   c  is opened. Thus, paint is discharged through the orifices  92   a  via the paint coupling  42 , the passage  82 , the paint chamber  78 , the needle passage  80  the inner passage  102   a  of the dual-tube assembly  100  and the paint port  112   c  of the tip member  112 . 
     Note that the air motor  20  can be of a two speed type where the speed is increased when paint is supplied. 
     In the above-described embodiment, a water film is formed between the paint discharged through the orifices  92   a  and the distal end face  92   b  of the rotating bell  92 , which would prevent paint clots from depositing on the distal end face  92   b  of the rotating bell  92 . 
     Further, in a non-painting operation, since the paint port  112   c  is closed by the valve body  94   a  of the needle  94 , the clogging of the paint port  112   c  in the prior art can be avoided. 
     While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.