Electrostatic rotary atomizing spray device with improved atomizer cup

Abstract

An electrostatic, liquid spray, rotary atomizer has an atomizer housing, a power supply within the housing and an atomizer cup at a front end of the housing. The atomizer cup, which is formed of a non-conductive material, has several elongate conductive pathways embedded in the body of the cup. Each conductive pathway has one end exiting an outer surface at a rear end of the cup for receiving the charge from the power supply and another end exiting an inner surface at a front end of the cup for conveying an electrical charge from the power supply to the liquid (paint) particles passing through the atomizer cup. An electrode is provided for maintaining a small voltage at the access hole. The rotary atomizer with the improved charge ring and rotary cup can be mounted to a robot and connected to the liquid supply by an elongated spiral passageway to increase the electrical resistance between the atomizer and the liquid supply so that a very small electrical charge, if any, will be present in the passageway carrying paint to the rotary cup.

We claim:  
     
       1. An atomizer cup for an electrostatic rotary atomizing spray device for spraying a liquid coating material, comprising: 
       a body formed primarily of a non-conductive material, having a one end, an other opposite end, a bore extending therethrough from the one end to the other end, an outer surface, a rear section and a generally frustro-conically shaped forward section, the forward section having a front surface; and  
       a conductive pathway embedded within the body for conducting an electrical charge from the outer surface to the front surface , the conductive pathway having two ends, a first end extending to the front surface and further comprising an extension portion which extends within the body from the conductive pathway to one of  terminating proximate a source of electrical energy and a second end terminating at the outer or front surfaces  surface of the body of the atomizer cup.  
     
     
       2. The atomizer cup of  claim 1  wherein the extension portion extends within the body from the conductive pathway to both the outer surface and the front surface of the body of the atomizer cup. 
     
     
       3. The atomizer cup of  claim 2  further including a plurality of the conductive pathways embedded within the body for conducting the electrical charge wherein the conductive pathways are provided as two sets of conductive pathways: 
       a first set of conductive pathways having two ends, a first end exiting the outer surface of the rear section and a second end, opposite the first end, exiting the inner surface of the frustroconically shaped end section; and  
       a second set of conductive pathways having two ends, a first end exiting the outer surface of the rear section and a second end, opposite the first end, exiting the inner surface of the frustroconically shaped end section and further comprising extension portions which extend within the body of the frustroconically shaped end section from the second ends of the second conductive pathways and branch off to exit both the outer and inner surfaces of the frustroconically shaped end section of the atomizer cup.  
     
     
       4. An electrostatic rotary atomizing spray device, comprising: 
       an atomizer housing defining an interior chamber therein;  
       a rotary drive shaft extending at least partially through the interior chamber of the atomizing housing, the rotary drive shaft mounted at a first end to a motor disposed in the atomizer housing and at a second end to an atomizing cup located outside of the atomizer housing, the atomizer cup comprising:  
       a body formed primarily of a non-conductive material, having a one end, an other opposite end, a bore extending therethrough from the one end to the other end, an outer surface, a rear section and a generally frustroconically shaped forward section, the forward section having a front surface; and  
       a conductive pathway embedded within the body for conducting an electrical charge from the outer surface to the front surface, the conductive pathway having two ends, a first end extending to the front surface and further comprising an extension portion which extends within the body from the conductive pathway to one of the outer or front surfaces of the body of the atomizer cup; and  
       a circuit for transferring a high voltage electrostatic charge from a power supply to an electrode which projects out of the forward end of the atomizer housing, the electrode having an end positioned proximate to the first end of the conductive pathway to transfer electrical charge to the conductive pathway.  
     
     
       5. The atomizer cup of  claim 4  wherein the extension portion extends within the body from the conductive pathway to both the outer surface and the front surface of the body of the atomizer cup. 
     
     
       6. An atomizer cup for an electrostatic rotary atomizing spray device for spraying a liquid coating material, comprising: 
       a body formed primarily of a non-conductive material, having an outer surface and an inner surface; and  
       at least one elongate conductive pathway embedded within the body for conducting an electrical charge from a first end of the conductive pathway at an outer surface of the cup  terminating proximate a source of electrical energy through the body of the cup to an opposite end of the conductive pathway having first and second opposite ends, wherein said first opposite end  which terminates at said outer surface of the body and said second opposite end terminates at said inner surface of the body .  
     
     
       7. The atomizer cup of  claim 6  wherein the conductive pathway carries the electrical charge from a position on a rear section to a frustoconically shaped end section of the atomizes cup. 
     
     
       8. The atomizer cup of  claim 6  wherein the conductive pathway is disposed within the body of the atomizer cup at evenly-spaced intervals about a longitudinal axis of the atomizer cup. 
     
     
       9. The atomizer cup of  claim 6  wherein a second end portion of each conductive pathway is of increased cross-dimension. 
     
     
       10. The atomizer cup of  claim 6  wherein a plurality of elongate conductive pathways are disposed within the body of the atomizer cup at evenly-spaced intervals about a longitudinal axis of the atomizer cup at a first distance from the longitudinal axis and the conductive pathways each have two ends; 
       a first end exiting the outer surface of a bottom section of the atomizer cup at evenly-spaced intervals at a second distance from the longitudinal axis; and  
       a second end, opposite the first end, exiting the inner surface of a frustoconically shaped end section of the atomizer cup at evenly-spaced intervals at a third distance from the longitudinal axis which is approximately equal to the first distance.  
     
     
       11. The atomizer cup of  claim 6  wherein at least five elongate conductive pathways are embedded within the body. 
     
     
       12. The atomizer cup of  claim 11  wherein ten elongate conductive pathways are embedded within the body. 
     
     
       13. The atomizer cup of  claim 6  wherein a plurality of conductive pathways are provided as two sets of conductive pathways: 
       a first set of conductive pathways having two ends, a first end exiting the outer surface of a rear section of the atomizer cup and a second end, opposite the first end, exiting the inner surface of a frustoconically shaped end section of the atomizer cup; and  
       a second set of conductive pathways having two ends, a first end exiting the outer surface of the rear section and a second end, opposite the first end, exiting the inner surface of the frustoconically shaped end section and further comprising extension portions which extend within the body of the frustoconically shaped end section from the second ends of the second conductive pathways and branch off to exit both the outer and inner surfaces of the frustoconically shaped end section of the atomizer cup.  
     
     
       14. The atomizer cup of  claim 13  wherein: 
       the first set of conductive pathways are disposed at evenly-spaced intervals about a longitudinal axis of the atomizer cup; and  
       the second set of conductive pathways are disposed at evenly-spaced intervals about the longitudinal axis.  
     
     
       15. The atomizer cup of  claim 14  wherein the second set of conductive pathways are disposed between adjacent ones of the first set of conductive pathways. 
     
     
       16. The atomizer cup of  claim 15  wherein at least five of the first set of elongate conductive pathways and at least five of the second set of elongate conductive pathways are embedded within the body. 
     
     
       17. The atomizer cup of  claim 13  wherein the extension portions have first ends which are contiguous with the second ends of the second elongate conductive pathways, a first opposite end portion which exits the outer surface of the frustroconically shaped end section of the atomizer cup, and a second opposite end portion which exits a forward flow surface of the frustroconically shaped end section of the atomizer cup. 
     
     
       18. The atomizer cup of  claim 17  wherein the first opposite end portions of the extension portions exit the outer surface of the frustoconically shaped end section at a fourth distance from a longitudinal axis of the atomizer cup, and the second opposite end portions of the extension portions exit the forward flow surface of the frustoconically shaped end section at a fifth distance from the longitudinal axis. 
     
     
       19. The atomizer cup of  claim 6  wherein said inner surface comprises a frustroconically shaped section, a forward flow surface section and a front edge section, said second opposite end of said conductive pathway terminates at one of said inner surface sections. 
     
     
       20. An electrostatic rotary atomizing spray device for spraying a liquid coating material, comprising: 
       an atomizer housing which defines an interior chamber therein;  
       a charging ring having a front wall with a circular bore therethrough mounted to the atomizer housing;  
       a drive shaft within the interior chamber of the atomizer housing and extending exterior of the atomizer housing through the circular bore of the charging ring, the drive shaft being attached at a first end to a motor within the atomizer housing and at a second opposite end to a rotary atomizer head; and  
       an access hole extending through the charge ring to create an approach way to reach the drive shaft within the interior of the atomizer housing.  
     
     
       21. The electrostatic rotary atomizing spray device of  claim 20  further comprising a check valve disposed within the access hole. 
     
     
       22. The electrostatic rotary atomizing spray device of  claim 20  further comprising an electrode disposed near the access hole for providing a low voltage at the access hole. 
     
     
       23. The electrostatic rotary atomizing spray device of  claim 20  further comprising: 
       the atomizing head at least partially extending into the circular bore of the charge ring to define an air gap between the atomizing head and the circular bore; and  
       a circuit for transferring a high voltage electrostatic charge from a power supply, through the charge ring and across the air gap into the atomizing head, the circuit including a first resistor connected to the charge ring for transferring the high voltage electrostatic charge from the power supply to the charge ring, a plurality of second resistors mounted in the charge ring and connected to the first resistor, and a third resistor mounted in the charge ring and connected to the first resistor;  
       a plurality of first electrodes which project out of the front wall of the charge ring for providing concentrated charge on an outer surface of the charge ring, the plurality of first electrodes being electrically connected to the second resistors for lowering the spark potential of the electrodes; and  
       a second electrode which projects into the access hole extending through the charge ring.  
     
     
       24. A method of constructing a rotary atomizer cup, comprising the steps of: 
       forming the rotary atomizer cup of a non-conductive material;  
       embedding a plurality of conductive pathways within the rotary atomizer cup, with a first end of each conductive pathway exiting an outer surface of the one end of the rotary atomizer cup and a second end of each conductive pathway exiting an inner surface of the opposite end of the rotary atomizer cup; and  
       embedding a plurality of elongate conductive extension portions within the rotary atomizer cup, each extension portion having a first end which is contiguous with the opposite end of at least a portion of the plurality of conductive pathways and a second opposite end which branches off to exit both the outer and inner surfaces of the opposite end of the rotary atomizer cup.  
     
     
       25. A method of removing a rotary cup from an electrostatic rotary atomizing spray device, the spray device having an atomizer housing which defines an interior chamber therein, a drive shaft within the interior chamber of the atomizer housing, the drive shaft being attached at a first end to a motor within the atomizer housing and at a second opposite end to the rotary atomizer cup, comprising the steps of: 
       inserting a rigid elongate tool through an access hole in the atomizer housing so that an end of the rigid elongate tool enters a recess in the drive shaft, thereby preventing the drive shaft from freely rotating; and  
       unscrewing the rotary atomizer cup from the drive shaft with the rigid elongate tool preventing the drive shaft from freely rotating.  
     
     
       26. A rotary atomizer system including a rotary atomizer and a robot mounting, the system comprising: 
       an atomizer housing defining an interior chamber therein having a rotary drive shaft extending therethrough and mounted to an atomizing cup located outside of the atomizer housing, the cup having a high voltage electrostatic charge transferred thereto, a fluid type being disposed within the drive shaft for directing a flow of the liquid coating material to the atomizer head where electrical charge is transferred to the liquid coating material passing through the atomizer cup, a robot mounting ring having an electrically grounded liquid supply control device by an elongated spiral passageway to increase the electrical resistance between the atomizer and the liquid supply so that a very small electrical charge will be present in the passageway carrying paint to the rotary cup.  
     
     
       27. A rotary atomizer system, the system comprising: 
       a rotary atomizer having an atomizing cup projecting outward thereof, a fluid tube being disposed within the rotary atomizer for directing a flow of the liquid coating material to the atomizer head where the liquid coating material is electrically charged as it passes through the atomizer cup;  
       a robot mounting arm having an electrically grounded, liquid supply control device attached thereto; and  
       a voltage isolator connecting the fluid tube in the rotary atomizer to the electrically grounded, liquid supply control device to prevent electrical current from being transferred through the liquid coating material being charged at the rotary cup to the control device.  
     
     
       28. The rotary atomizer system of  claim 27  wherein: 
       the rotary atomizer is a low capacitance rotary atomizer; and  
       the voltage isolator is a spiral tube.  
     
     
       29. An atomizer cup for an electrostatic rotary atomizing spray device for spraying liquid coating material, the cup being comprised of a first material and a second material which is electrically more conductive than the first material, the cup being principally comprised of the first material and having and outer surface and an inner flow surface, the cup being embedded with elongated pathways of the second material, one or more of the pathways having a first end which terminates proximate a source of electrical energy and a second end which terminates at the outer surface of the cup. 
     
     
       30. The atomizer cup of  claim 29  wherein one or more of the conductive pathways has a first end which terminates proximate the source of electrical energy and a second end which terminates at the inner flow surface. 
     
     
       31. The atomizer cup of  claim 29  wherein one or more of the conductive pathways has a first end which terminates proximate a source of electrical energy and a second and which is split into first and second portions, the first portion terminating at the outer surface and the second portion terminating at the inner flow surface. 
     
     
       32. A rotary atomizer, comprising: a housing formed of an electrically nonconductive material having an interior chamber, and air turbine disclosed within the interior chamber, the air turbine having a output shaft, an atomizer cup mounted on the output shaft, a paint feed tube which supplies paint to the atomizer cup, the cup being comprised of a first material and a second material which is electrically more conductive than the first material, the cup being principally comprised of the first material and having and outer surface and an inner flow surface, the cup being embedded with elongated pathways of the second material, one or more of the pathways having a first end which terminates proximate a source of electrical energy and a second end which terminates at the outer surface of the cup. 
     
     
       33. The rotary atomizer of  claim 32  wherein one or more of the conductive pathways of the atomizer cup has a first end which terminates proximate the source of electrical energy and a second end which terminates at the inner flow surface. 
     
     
       34. The rotary atomizer of  claim 32  wherein one or more of the conductive pathways of the atomizer cup has a first end which terminates proximate a source of electrical energy and a second and which is split into first and second portions, the first portion terminating at the outer surface and the second portion terminating at the inner flow surface.