Patent Publication Number: US-7721976-B2

Title: High speed rotating atomizer assembly

Description:
RELATED APPLICATION 
     This application is a continuation in part application of a co-pending patent application Ser. No. 10/895,446 filed on Dec. 17, 2003 and an allowed application Ser. No. 10/624,586 filed on Jul. 22, 2002, all of which are incorporated herewith by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a bearing unit of a rotating atomizer for driving a bell cup coupled to the turbine device for coating a part. 
     BACKGROUND OF THE INVENTION 
     A production paint application process where paint is applied to a substrate, such as, for example a vehicle body moving through a paint booth, requires paint to be transferred from a paint reservoir to a paint applicator robot disposed in the paint booth, where paint is applied by a rotary atomizer as an integral part of the paint applicator robot. Typically, the rotary atomizer includes a turbine device disposed in a housing, a rotating bell unit having a shaft connected to a bell cup and disposed in and rotatable relative to the turbine device and the housing. The bell cup has a generally conical overflow surface between a radially inward central axial opening and a radially outward atomizing edge. At or near the radially outward atomizing edge, the angle of the overflow surface relative to the axis of the bell cup decreases sharply to form a lip adjacent the atomizing edge. The purpose of this lip is to generally direct the atomized paint more axially forward and reduce radial scatter. Typically, an air shaping ring is attached to the turbine device to improve distribution of the paint onto the vehicle body being painted. 
     The art is replete with prior art designs of an air shaping rings for a rotary atomizer. The U.S. Pat. No. 5,775,598 to Takayama et al.; U.S. Pat. No. 5,727,735 to Baumann et al.; U.S. Pat. No. 6,189,804 and U.S. Pat. No. 6,623,561 both to Vetter et al.; and the United States Patent Publication Nos. 2005/0001077 and 2003/0010840 both to Kon et al. The United States Patent Publication No. 2005/0001077 to Kon et al., for example, teaches a rotary atomizer having a housing, a turbine device disposed in the housing, a bell unit disposed in and rotatable relative the turbine device. An air shaping ring is disposed about the turbine device and is connected to the housing by a partially threaded fastener extending to a hook to interconnect the air shaping ring with the housing. This design is complex and requires additional component, such as the aforementioned fastener to interconnect the housing with the air shaping ring. 
     The U.S. Pat. No. 6,623,561 to Vetter et al., on the other hand, teaches a rotary atomizer having a housing, a turbine device disposed in the housing, a bell unit disposed in and rotatable relative the turbine device. An air shaping ring is disposed about the turbine device and between the turbine device and the housing. The air shaping ring of the U.S. Pat. No. 6,623,561 to Vetter et al. does not require additional components, such as, for example, partially threaded fastener extending to a hook, taught by the United States Patent Publication No. 2005/0001077 to Kon et al. to interconnect the air shaping ring with the housing. Hence, the air shaping ring and the turbine device taught by the U.S. Pat. No. 6,623,561 to Vetter et al. do not provide for constant surface to surface contact between the air shaping ring and the turbine device. In addition, none of the prior art patents teaches an improved design of the atomizer having improved rigidly stabilized connection between the turbine device and the housing for maintaining a fixed air gap between the shaft and a paint pipe or line extending through the shaft for keeping the shaft at a fixed distance relative to the paint line as the shaft rotates around the axis. 
     The goal of the invention is therefore to provide an improved design of the turbine device to eliminate at least one of the aforementioned problems associated with prior art atomizers. 
     SUMMARY OF THE INVENTION 
     An atomizer assembly of the present invention fluidly communicates with a fluid source to coat a part, such as, for example, a body of an automotive vehicle. The atomizer assembly includes a housing having at least one fluid line, i.e. paint line connected to the housing and extending therethrough, a turbine device having terminal ends and surrounding an axis and disposed in the housing. An atomizing bell unit has a shaft and an atomizing bell connected to the shaft and is fluidly communicated with the paint line for applying the paint to the body of the automotive vehicle. The atomizing bell unit is disposed in the turbine device surrounding the axis and rotatable around the axis and relative the turbine device. The atomizer bell unit presents terminal ends with one terminal end exposed to the fluid source and the other terminal exposed to the body of the automotive vehicle being coated. 
     The turbine device includes an annular wall extending outwardly from one of the terminal ends of the turbine device. The annular wall circumscribes the atomizing bell unit. The annular wall and the terminal end of the bearing define a seat for engaging the housing to provide a rigidly stabilized connection between the turbine device and the housing thereby maintaining a fixed annular gap between the shaft and the paint line extending through the shaft of the atomizing bell unit at a fixed distance relative to the paint line as the shaft rotates around the axis. A potential member is disposed around the bearing at the atomizing bell for concentrating the paint particles as the paint is applied to the body of the automotive vehicle. A biasing device is disposed in the turbine device for interconnecting the turbine device and the potential member for improved path of continuity and for providing constant surface to surface contact between the turbine device and the potential member as the fluid is applied to the part. 
     An advantage of the present invention is to provide an annular wall that extends outwardly from the turbine device defining a seat for engaging the housing thereby forming a rigidly stabilized connection between the turbine device and the housing, which have proven to maintain a fixed gap between the shaft of the rotational bell unit and the paint line for keeping the shaft at a fixed distance relative to the paint line to prevent contact between the paint line and the shaft. 
     Another advantage of the present invention is to provide the turbine device having an improved surface-to-surface contacts between the potential member and the turbine device to improve ionization of the atomized fluid particles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG. 1  illustrates a rotating atomizer on a robotic arm positioned next to a vehicle body in a paint shop; 
         FIG. 2  is a cross sectional view of a turbine device installed in a turbine housing; 
         FIG. 3  is a perspective and exploded view of the turbine device shown in  FIG. 2 ; 
         FIG. 4  is a perspective and exploded view of the turbine device; 
         FIG. 5  is a cross sectional view of a neck portion of the turbine device; 
         FIG. 6  is an end view of one of the ring plates of the housing of the turbine device illustrating a brake nozzle and at least two inlets; 
         FIG. 7  is a cross sectional and fragmental view of a biasing device disposed in the housing of the turbine device; and 
         FIG. 8  is a cross sectional and fragmental view of the biasing device of  FIG. 7  shown in compressed mode and biased against an air shaping ring to provide surface-to-surface contact. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the  FIGS. 1 and 2 , wherein like numerals indicate like or corresponding parts, an inventive atomizer assembly is generally shown at  10 . A paint circulation system (not shown) supplies paint to a paint booth  12  where the paint is applied to a production part, such as, for example, a vehicle body  14 . In a typical automobile assembly plant the vehicle body  14  is transported through the paint spray booth  12  by conveying equipment  16  where the paint is applied to the vehicle body  14  and subsequently cured in a paint oven (not shown) as is known to those skilled in the art. The paint is applied by automated application equipment, such as a robotic device  18  that includes the atomizer assembly  10  that is connected to an arm  20  of the robotic device  18 . Alternatively, the atomizer assembly  10  is operably connected to an overhead or side reciprocator (not shown). 
     Referring to  FIGS. 2 through 4 , the atomizer assembly  10  includes a housing, generally indicated at  22  in  FIG. 2 , having a curved configuration. The housing  22  is defined by a plurality of detachable components with one of these components, i.e. core member  24 , as shown in  FIG. 2 , surrounding an axis A. The core member  24  is disposed in the housing for engaging at least one paint delivery line or a feed unit  26  fluidly communicated with a paint source (not shown). The core member  24  presents in interior surface  28  defined between annular side wall  30  of the core member  24 . A turbine device, generally shown at  40 , is the actual drive element of the high speed atomizer assembly  10  and is disposed in the core member  26 . 
     As best shown in  FIGS. 3 and 4 , the turbine device  40  include a front plate  42 , a neck portion, generally indicated at  44 , and defining a tubular body  46  and a base plate  48  having a diameter larger than a diameter of the tubular body  46 . The turbine device  40  includes a pair of core plates  50 ,  52  disposed between the front plate  42  and the neck portion  44 . The core plates  50  and  52  and the base plate  48  form a chamber, partially shown at  54  in  FIG. 5 . An annular intermediate chamber  56  is defined by a cavity formed in one of the plates  50  and covered by the other plate  52  to form the annular intermediate chamber  56 . A first inlet  58  is defined in the annular intermediate chamber  56  for delivering fluid, such as, for example gas or air, into the annular intermediate chamber  56  from a fluid source (not shown). The turbine device  40  defines a proximal end  59  and a distal end  60 . At least one second inlet  61  is defined in the annular intermediate chamber  56  for delivering fluid into the annular intermediate chamber  56  thereby increasing amount of fluid in the annular intermediate chamber  56  to increase a rotational speed of an atomizing bell unit, generally indicated at  62  and best shown in  FIGS. 3 and 4 . The atomizing bell unit  62  will be described in great details as the description of the present invention proceeds. The atomizing bell unit  62  is rotated as increased amount of fluid is introduced thereto through a plurality of nozzles, such as, for example Lavalle nozzles  64 ,  66 , and  68  defined in the core plate  52  as best shown in  FIG. 6 . 
     The nozzles  64  through  68  are exposed from the annular intermediate chamber  56  and are asymmetrically disposed relative the axis A. The nozzles  64  through  68  are angularly and vortecaly spaced relative to the axis A for rotating the atomizing bell unit  62 . Preferably, one of the nozzles  64  through  68  is defined between the first inlet  58  and the second inlet  61  defined in the core plate  52 . The nozzles  64  through  68  drive fluid in unison from the annular intermediate chamber  56  for facilitating uniformed application of fluid onto the atomizing bell unit  62 . Preferably, the nozzles  64  through  68  are oriented in the circumferential direction over an angle range of approximately 130°, relative to the axis A. 
     Alluding to the above, the first inlet  58  and the second inlet  61  discharge fluids axially into the intermediate annular chamber  56 . Preferably, the first and second inlets  58  and  61  present a circular cross-section with a diameter of 5 mm. The first inlet  58  and the second inlet  61  are exposed to the intermediate chamber  56  to discharge fluid from the intermediate chamber  56 . As shown in  FIG. 6 , the first and second inlets  58  and  61  are located in the upper half of the annular intermediate chamber  56 , as best shown in  FIG. 6 . A brake nozzle  69  is defined in the core plate  52  for driving fluid onto the atomizer bell unit  62  in a direction reverse to the angular direction of fluid driven through the nozzles  64  through  68  thereby decreasing a rotational speed of the atomizer bell unit  62 . 
     As best shown in  FIG. 4 , the front plate  42  includes connections for bearing air  80 , a connection port for breaking air  84 , a pair of connection ports for turbine air or turbine air ducts  86 ,  88 , and a connection port for shaping air  90 . The aforementioned connection ports  80  through  90  are independently or separately connected to the fluid source. The turbine air ducts  86 ,  88 , which are independent connected to another fluid source (not shown), supply compressed air to a turbine wheel  102  of the atomizing bell unit  62  for driving a shaft  104  connected to the wheel  102 . By using two ducts  86 ,  88  for the turbine air, the performance of the turbine device  40  is improved and more precisely controlled. 
     The aforementioned connection ports  80  through  90  are radially spaced around a stabilizing member defined by an annular wall  94 . The annular wall  94  extends outwardly from the proximal end  59  of the turbine device  40  circumscribing the atomizing bell unit  62  to define a seat, generally indicated at  96  in  FIG. 2 , for engaging the core member  24  to form a rigidly stabilized connection between the turbine device  40  and the core member  24 . The annular wall  94  includes a plurality of air exhaust apertures  98  radially defined in the annular wall  94  and at least one cut-out portion  100  defined therein. 
     As best illustrated in  FIGS. 3 and 4 , the shaft  104  of the atomizing bell unit  62  holds and drives an atomizing bell or bell cup  108  disposed at one of the extremities  112  of the shaft  104 . The aforementioned turbine wheel  102  is rigidly connected to and circumscribes the shaft  104  at another extremity  114  of the shaft  104 . A plurality of U-shaped cut out portions  115  are defined at the extremity  114  of the shaft  104 . Each U-shaped cut out portion  115  is aligned with the cut out portion  100  defined in the annular wall  94  to receive a fastener  117  extending through the housing  22  to prevent rotational movement of the shaft  104  during cleaning of the turbine device  40 . The shaft  104  is hollow to receive the paint line  26  guided therethrough and exposed through the bell cup  108  to the body of the automotive vehicle. The shaft  104  includes an annular groove  109  defined therein to form an air bearing. Preferably, the annular groove  109  is exposed to an air channel  119  defined in the neck portion  46  to receive the bearing air and to drive the bearing air to the annular groove  109  thereby distributing the bearing air evenly along the shaft  104  to improve alignment of the axial rotation of the shaft  104 . 
     The rigidly stabilized connection defined between the turbine device  40  and the core member  24  maintains a fixed gap between the paint line  26  and the shaft  104  of the atomizing bell unit thereby keeping the shaft  104  at a fixed distance relative to the paint line  26  as the shaft  104  rotates about the axis A, as best shown in  FIG. 2 . This fixed gap prevents contact between the paint line  26  and the shaft  106  and reduces chances of wear and tear of the paint line  26  by the shaft  104  rotatable at a high speed. The shaft  104  is driven by the turbine air. 
     A reflector disk, generally indicated at  116 , is attached to the turbine wheel  102  to monitor the rotational speed of the bell cup  108 . The speed of the bell cup  108  presents an important parameter for atomization of the paint. The speed of the bell cup  108  is measured at the turbine device  40  through the use of the aforementioned reflector disk  116 , a fiber-optic cable (not shown), and an opto-electronic converter (not shown). The reflector disk  116  has four reflective surfaces  122  through  128  and four alternating blackened surfaces  130  through  136 . This configuration provides for four light pulses being reflected back to the fiber-optic cable with each rotation of the shaft  104 . The opto-electronic converter changes these pulses of light into electric signals which are processed by a speed transducer (not shown). The speed transducer compares the current speed of the shaft  104  with the present value by means of the signals and regulates the supply of the turbine air accordingly. 
     A plurality of blades  130  are connected to and extend outwardly and axially from the turbine wheel  102  to receive bearing air. Each turbine blade  130  is curved, as shown in  FIG. 3 . Alternatively, (not shown), each turbine blade  130  is non-curved and radially extends from the axis A. A second wheel  132  has a frostoconical configuration and is connected to the shaft  104  below the turbine blades  130 . The second wheel  132  includes a vortexly shaped outer surface  134  which produces air turbulence as the shaft  104  is rotated about the axis. 
     A potential member, such as, for example, an air shaping ring  140  provides a source of direct atomization of the atomized paint particles. The air shaping ring  140  is disposed around one of the terminal ends  118  at the neck portion  46  of turbine device  40  about the bell cup  108 . The air shaping ring  140  is known to those skilled in the art and is designed for concentrating the paint as the paint is applied to the body  14  of the automotive vehicle by injecting air from annular channels  141  defined in the neck portion  46  air to the bell cup  108  through annular apertures  143 . To improve contact between the neck portion  46  and the air shaping ring  140 , a biasing device, generally indicated at  150 , is disposed in the neck portion  46  of the turbine device  40  to interconnect the turbine device  40  with the air shaping ring  140  to improve path of continuity and for providing constant surface to surface contact between the turbine device  40  and the air shaping ring  140 . In alternative embodiment of the present invention, the potential member is defined by a source of indirect atomization, such as, for example, a plurality of electrostatic probes (not shown). 
     The biasing device  150  is disposed in a cavity  152  defined in the neck portion  46 . The biasing device  150  includes a tubular housing  154 , a ball  156 , and a spring  158  extending from the cavity  152  to the ball  156  for forcing the ball  156  away from the tubular housing  154  as the air shaping ring  140  is disposed about the neck portion  46  of the turbine device  40 . 
     The atomizer assembly  10  presents an air tight enclosure. To preserve the air inside the atomizer assembly  10  a cover  180  is mechanically connected with the annular wall  30  of the core member  24  extending between the core member  24  and the air shaping ring  140 . The turbine device  40  includes a plurality of O-rings  160  disposed respective annular grooves  162 . To keep the front plate  42 , the neck portion  44 , the base plate  48 , the core plates  50 ,  52  at least one centering pin  166  and a pair screw  168  extend through the front plate  42 , the neck portion  44 , the base plate  48 , the core plates  50 ,  52  to hold the front plate  42 , the neck portion  44 , the base plate  48 , the core plates  50 ,  52  together. 
     While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teaching of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not to be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the invention, but that the invention will include all embodiments falling within the scope of the appended claims.