Apparatus for dispensing conductive coating materials including color changing capability

Abstract

An apparatus for transferring electrically conductive coating materials, such as water-based paint, from at least one source to one or more coating dispensers or spray guns for discharge onto a substrate includes two "parallel" flow paths, each having a large reservoir pump, which transmit coating material to a common valve which, in turn, switches flow to the coating dispensers from one flow path to the other. Each parallel flow path provides a voltage block between one or more sources of coating material and the electrostatically charged coating material discharged from the spray guns to ensure that there is never a completed electrical path between the source of conductive coating material and the charged coating material during a coating operation. Additionally, a rapid and efficient color change capability is provided for the entire system which permits different colored coating materials to be dispensed from the apparatus herein with minimum downtime of the coating operation.

What is claimed is: 
     
       1. A method for supplying electrically conductive coating material to at least one electrostatic coating dispenser comprising: transferring coating material from a supply through a first .Iadd.movable .Iaddend.transfer unit .Iadd.which is located at a filling position .Iaddend.to a first reservoir and through a second .Iadd.movable .Iaddend.transfer unit .Iadd.which is located at a filling position .Iaddend.to a second reservoir while electrically isolating the . .supply.!. .Iadd.reservoirs .Iaddend.from the coating dispenser;   transferring the coating material from said first and second reservoirs .Iadd.through said first and second movable transfer units when located in a discharge position .Iaddend.to a flow control means .Iadd.while electrically isolating said first and second reservoirs from said supply.Iaddend.;   alternately transferring the coating material through said flow control means to the coating dispenser from said first reservoir and said second reservoir;   moving said first transfer unit to . .a first.!. .Iadd.said discharge .Iaddend.position .Iadd.at which said first transfer unit is operative both .Iaddend.to electrically isolate said first reservoir from said supply .Iadd.and to block flow therebetween .Iaddend.while .Iadd.transferring .Iaddend.coating material . .is being transferred.!. from said first reservoir through said flow control means to the coating dispenser.Iadd., and then moving said first transfer unit to said filling position at which said first transfer unit is operative both to electrically isolate said coating dispenser from said first reservoir and to block flow therebetween while coating material is being transferred from said supply to said first reservoir.Iaddend.;   moving said second transfer unit to . .a second.!. .Iadd.said discharge .Iaddend.position .Iadd.at which said second transfer unit is operative both .Iaddend.to electrically isolate said second reservoir from said supply .Iadd.and to block flow therebetween .Iaddend.while said coating material is being transferred from said second reservoir through said flow control means to the coating dispenser.Iadd., and then moving said second transfer unit to said filling position at which said second transfer unit is operative both to electrically isolate said coating dispenser from said second reservoir and to block flow therebetween while coating material is being transferred from said supply to said second reservoir.Iaddend.; and   electrically charging the coating material sprayed from the coating dispenser.   
     
     
       2. The method of claim 1 further comprising the steps of: sensing when coating material supplied to said first and second reservoirs reaches an upper limit, and then terminating the flow of coating material from the supply into said reservoirs in response thereto;   sensing when the coating material reaches a lower limit in whichever one of said first and second reservoirs is supplying coating material through said flow control means to the coating dispenser, and then shifting said flow control valve in response thereto to begin supplying coating material from the other of said first and second reservoirs through said flow control valve to the coating dispenser.   
     
     
       3. The method of claim 2 wherein when said lower limit is sensed at said one reservoir which is supplying coating material through said flow control means to said coating dispensers, in addition to the step of shifting said flow control means, the method further comprises the step of isolating said reservoir from said electrostatic coating dispenser and refilling said reservoir from said supply in response to the sensing of said lower limit. 
     
     
       4. A method of supplying electrically conductive coating material of two or more colors to coating dispensers, comprising: transferring coating material of a first color from a first supply to first and second reservoirs;   transferring said first color of coating material from said first and second reservoirs to a first flow control valve;   transferring coating material of a second color from a second supply to third and fourth reservoirs;   transferring said second color of coating material from said third and fourth reservoirs to a second flow control valve;   transferring said first color of coating material from said first or second reservoirs through said first flow control valve to a color change manifold;   transferring said second color of coating material from said third or fourth reservoirs through said second flow control valve to said color change manifold;   operating said color change manifold to send said first or second color of coating material therethrough to said coating dispensers;   electrically isolating from their respective first or second supplies whichever of said first, second, third, or fourth reservoirs is supplying coating material to said color change manifold; and   electrostatically charging the coating material sprayed from said coating dispensers.   
     
     
       5. The method of claim 4 in which said step of transferring said first color of coating material further comprises switching the flow of said first color of coating material transferred to the color change manifold from one of the first and second reservoirs to the other when said one reservoir is depleted of coating material. 
     
     
       6. The method of claim 4 in which said step of transferring said second color of coating material further comprises switching the flow of said second color of coating material transferred to the color change manifold from one of the third and fourth reservoirs to the other when said one reservoir s depleted of coating material. 
     
     
       7. The method of transmitting electrically conductive coating material to at least one electrostatic coating dispenser, comprising: supplying coating material to a first holding means from a first transfer unit which is connected to the source of coating material and to the coating dispenser, said transfer unit maintaining the first holding means electrically isolated from the coating dispenser which coating material is supplied to the first holding means;   supplying a second holding means with coating material from a second transfer unit which is connected to the source of coating material and to the coating dispenser, said transfer unit maintaining the second holding means electrically isolated from the coating dispenser while coating material is supplied to the second holding means;   transferring coating material from one of the first and second holding means to the coating dispenser while maintaining said one holding means electrically isolated from the source; and   switching the flow of coating material transferred to the coating dispenser to the other of the first and second holding means when said one holding means is depleted of coating material.   
     
     
       8. The method of claim 7 in which said step of supplying coating material to the first holding means comprises moving a first shuttle into coupling engagement with a first filling station connected to the source of coating material, and transferring the coating material from the first filling station through the first shuttle into the reservoir of a first pump. 
     
     
       9. The method of claim 8 in which said step of supplying coating material to the second holding means comprises moving a second shuttle into coupling engagement with a second filling station connected to the source of coating material, and transferring the coating material from the second filling station through the second shuttle into the reservoir of a second pump. 
     
     
       10. The method of claim 9 in which said step of transferring coating material comprises moving said first shuttle into coupling engagement with a first discharge station which communicates with the coating dispenser, and then transmitting coating material from the reservoir of said first pump through said first shuttle and said first discharge station to the coating dispenser, and wherein said step of switching the flow of coating material comprises moving said second shuttle into coupling engagement with a second discharge station which communicates with the coating dispenser and transmitting coating material from said second pump through said second shuttle and said second discharge station to the coating dispenser while terminating the flow of coating material from said first pump.   
     
     
       11. The method of claim 7 further comprising the steps of: producing a signal representative of a depleted condition of said one of said first and second holding means; and   switching the flow of coating material transferred to the coating dispenser to the other of said first and second holding means in response to production of said signal.   
     
     
       12. The method of claim 11 in which said step of transferring coating material comprises transmitting coating material from the reservoir of one of a first and second pumps to the coating dispenser by movement of a piston within the reservoir of said one pump, and wherein said step of producing a signal comprises sensing the movement of the piston within the reservoir of said one of said first and second pumps, and generating a signal when the piston reaches a predetermined position.   
     
     
       13. The method of claim 7 further comprising the steps of: terminating the supply of coating material to each of said first and second holding means,   transmitting coating material remaining in the first and second holding means back to the source; and then   transmitting a flushing fluid through each of said first and second holding means and the coating dispenser to remove the coating material therefrom.   
     
     
       14. The method of transmitting electrically conductive coating material to at least one electrostatic coating dispenser, comprising: supplying coating material to a first pump from a source of coating material while maintaining the first pump electrically isolated from the coating dispenser, the first pump having a reservoir and a piston movable within the reservoir;   supplying a second pump with coating material from the source while maintaining the second pump electrically isolated from the coating dispenser, the second pump having a reservoir and a piston movable within the reservoir;   transferring coating material from one of the first and second pumps to the coating dispenser while maintaining said one pump electrically isolated from the source;   switching the flow of coating material transferred to the coating dispenser to the other of the first and second pumps when said one pump is depleted of coating material;   terminating the supply of coating material to each of the first and second pumps, and the transmitting a flushing fluid to the first and second pumps; and   alternately moving the piston of each of the first and second pumps in one direction and then in the opposite direction while flushing fluid is present within the reservoirs thereof to clean coating material from the reservoirs.   
     
     
       15. The method of transmitting electrically conductive coating material to at least one electrostatic coating dispenser, comprising: supplying coating material to a first holding means from a source of coating material while maintaining the first holding means electrically isolated from the coating dispenser;   supplying a second holding means with coating material from the source while maintaining the second holding means electrically isolated from the coating dispenser;   transferring coating material from one of the first and second holding means to the coating dispenser while maintaining said one holding means electrically isolated from the source;   switching the flow of coating material transferred to the coating dispenser to the other of the first and second holding means when said one holding means is depleted of coating material; and   circulating coating material through the first and second holding means to and from the source when the coating material is not being discharged from the coating dispensers.   
     
     
       16. Apparatus for transmitting electrically conductive coating material to at least one electrostatic coating dispenser, comprising: a first transfer unit and a second transfer unit each having an inlet adapted to be connected to at least one common source of electrically conductive coating material, an outlet, and, a holding means for receiving coating material from said inlet and for transmitting coating material to said outlet;   voltage block means, associated with each of said first and second transfer units, which is movable to a first position for electrically isolating said holding means from said outlet while said holding means receives coating material, and which is movable to a second position for electrically isolating said holding means from said inlet while said holding means transmits coating material to said outlet;   flow control means, connected to said outlet of each of said first and second transfer units, for sequentially supplying coating material from said first transfer unit and from said second transfer unit to at least one electrostatic coating dispenser.   
     
     
       17. The apparatus of claim 16 further including sensor means, associated with each of said first and second transfer units, for producing a representative of a low level condition of said holding means. 
     
     
       18. The apparatus of claim 17 in which each of said holding means is a pump formed with a reservoir, said pumps each including a piston movable within said reservoir and a piston rod which is connected to said piston and extends outwardly from said reservoir. 
     
     
       19. The apparatus of claim 18 in which said flow control means includes a sync valve having a valve body formed with a central bore connected to an outlet which is adapted to communicate with said at least one coating dispenser, a first inlet connected to said central bore and to said outlet of said first transfer unit, a second inlet connected to said central bore and to said outlet of said second transfer unit, a first valve carried within said first inlet which is movable between an open and closed position relative to the intersection of said first inlet and said central bore, and a second valve carried within said second inlet which is movable between an open and closed position relative to the intersection of said second inlet and said central bore. 
     
     
       20. The apparatus of claim 19 in which each said sensor means is a limit valve engageable with said piston rod of said pump associated with one of said first and second transfer units, each of said limit valves being effective in response to movement of their associated piston rods to a predetermined, lowermost position to produce said signal and cause one of said first and second valves to move from a closed position to an open position. 
     
     
       21. The apparatus of claim 20 in which said first and second valves of the synch valve each include a piston at one end and a ball engageable with a seat located at the intersection of said first and second inlets and said central bore, respectively, said flow control means further comprising a pilot valve connected to said limit valve of each of said first and second transfer means and to said sync valve, said pilot valve being effective upon receipt of said signal from said limit valve associated with one of said first and second transfer means to cause said valve within said sync valve associated with the other of said first and second transfer means to open. 
     
     
       22. The apparatus of claim 16 in which each of said first and second transfer units includes a filling station formed with said inlet, and a discharge station formed with said outlet said discharge station being spaced from said filling station. 
     
     
       23. The apparatus of claim 22 in which said voltage block means of each of said first and second transfer units comprises a shuttle movable between said filling station and said discharge station, said shuttle being connected to said holding means so that upon movement of said shuttle to said filling station the coating material is transmitted into said holding means and upon movement of said shuttle to said discharge station the coating material is transmitted from said holding means to said outlet. 
     
     
       24. The apparatus of claim 16 in which said flow control means is adapted to communicate with a coating dispenser and includes means for switching the flow of coating material to the coating dispenser from said holding means of one of said first and second transfer units to said holding means of the other of said first and second transfer units without interrupting the flow of coating material to the coating dispenser. 
     
     
       25. The apparatus of claim 24 in which said flow control means includes a sync valve, including: a first inlet connected to said outlet of said first transfer unit and communicating with said holding means thereof;   a second inlet connected to said outlet of said second transfer unit and communicating with said holding means thereof;   an outlet internally connected to each of said first and second inlets; and   check means for closing one of said first and second inlets while opening the other.   
     
     
       26. The apparatus of claim 25 in which said flow control means further includes a pilot valve connected to said check means of said sync valve and communicating with each of said holding means, said pilot valve being effective to operate said check means when the coating material within one of said holding means is at a low level so that said inlet of said sync valve communicating with the other of said holding means is opened while said inlet of said one holding means is being closed, whereby a substantially continuous flow of coating material through said sync valve to the coating dispenser is maintained. 
     
     
       27. Apparatus for transmitting electrically conductive coating material to at least one electrostatic coating dispenser, comprising: first and second pumps each having a reservoir formed with an inlet and an outlet;   first transfer means for supplying coating material to said first pump, said first transfer means including: (i) a filling station adapted to be connected to a source of coating material;   (ii) a discharge station spaced from said filling station; and   (iii) a first shuttle movable between said filling station and said discharge station, said first shuttle being connected to said inlet and outlet of said first pump and being releasably couplable to each of said filling and discharge stations, said shuttle being effective to permit the transfer of coating material into said reservoir of said first pump when coupled to said filling station and to permit the transfer of coating material from said pump reservoir when coupled to said discharge station;     second transfer means for supplying coating material to said second pump, said second transfer means including: (i) a filling station adapted to be connected to a source of coating material;   (ii) a discharge station spaced from said filling station;   (iii) a second shuttle movable between said filling station and said discharge station, said second shuttle being connected to said inlet and outlet of said second pump and being releasably couplable to each of said filling and discharge stations, said shuttle being effective to permit the transfer of coating material into said reservoir of said second pump when coupled to said filling station and to permit the transfer of coating material from said pump reservoir when coupled to said discharge station;     flow control means, connected to said discharge station of each of said first and second transfer means, for sequentially transmitting coating material supplied from said first pump and said second pump through their associated discharge stations to at least one coating dispenser.   
     
     
       28. The apparatus of claim 27 in which said filling station of each of said first and second transfer units is connected to a source of flushing liquid, said apparatus further comprising flushing means for simultaneously transmitting a flushing fluid from said source of flushing fluid through said first and second pumps, said first and second transfer units, said flow control means and said at least one coating dispenser in preparation for changing to a coating material of different color. 
     
     
       29. The apparatus of claim 28 in which said flushing means includes means for connecting said source of flushing fluid to a first discharge line which interconnects said discharge station of said first transfer unit with said flow control means, and for connecting said source of flushing fluid to a second discharge line which interconnects said discharge station of said second transfer unit with said flow control means, whereby a flow path for the flushing fluid is created from each of said discharge stations, through said flow control means and to said at least one coating dispenser. 
     
     
       30. The apparatus of claim 29 in which said means for connecting said source of flushing fluid comprises: a circulation shuttle having a discharge station connected to said source of flushing fluid and a filling station connected to each of said first and second discharge lines;   actuator means for moving said filling station of said circulation shuttle in and out of coupling engagement with said discharge station thereof;   a flush switch connected to said actuator means, said flush switch being effective to cause said actuator means to move said filling station into coupling engagement with said discharge station to create a continuous flow path from said source of flushing fluid, through said circulation shuttle to said flow control means and then to said at least one coating dispenser.   
     
     
       31. The apparatus of claim 30 in which said actuator means includes a linear actuator connected to said filing station, and a switch for operating said linear actuator. 
     
     
       32. The apparatus of claim 28 in which said flushing fluid is water, air, or, water and air. 
     
     
       33. The apparatus of claim 28 in which said flushing means includes dump means, connected to each of said first and second shuttles, for moving each of said first and second shuttles into coupling engagement with their respective filling stations so that flushing fluid is transmitted into said reservoir of each of said first and second pumps, through said filling stations and back to said source of flushing fluid. 
     
     
       34. The apparatus of claim 28 in which said flushing means includes pump agitation means for alternately introducing a flushing fluid into said reservoir of each of said first and second pumps from said source of flushing fluid so that said piston therein moves in a first direction, and for then causing said pistons to move in an opposite, second direction to force the flushing fluid from said first and second pumps, through said discharge stations, through said flow control means and back to said source of flushing fluid. 
     
     
       35. The apparatus of claim 27 in which each of said first and second pumps has a piston movable within said reservoir thereof, said apparatus further comprising pump agitation means for introducing a flushing liquid into said reservoir of each of said first and second pumps so that said piston therein moves in a first direction, and for then causing said pistons to move in an opposite, second direction to force the flushing liquid from said reservoir of said first and second pumps. 
     
     
       36. The apparatus of claim 35 in which each of said first and second transfer units includes a linear actuator which is effective to move said shuttles associated therewith between said filling station and said discharge station: said pump agitation means includes: (i) a first switch connected to a source of pressurized air;   (ii) a pressure regulator connected to said switch to receive pressurized air therefrom and to discharge a stream of reduced pressure air; and   (iii) a control valve associated with each of said first and second transfer units, each of said control valves being connected to said pressure regulator, to said linear actuator associated with their respective first and second transfer units, and to one of said first and second pumps, each of said control valves being effective in response to receipt of said stream of reduced pressure air from said pressure regulator to operate one of said linear actuation such that said first and second shuttles are moved into coupling engagement with their respective discharge stations, and such control valves being effective to move said piston within each of said first and second piston pumps in a first direction;     a switch associated with each of said first and second piston pumps, each of said switches being operative in response to movement of said pistons to a predetermined location in said first direction to operate said linear actuators so that said first and second shuttles are moved into coupling engagement with their respective filling stations to permit the transmission of flushing liquid into said reservoirs of said first and second pumps.   
     
     
       37. The apparatus of claim 36 in which said circulation means includes: a circulation shuttle having a discharge station connected to the source of coating material, and a filling station connected to said flow control means; and   actuator means for moving said filling station of said circulation shuttle in and out of coupling engagement with said discharge station.   
     
     
       38. The apparatus of claim 27 further including pump emptying means for moving each of said first and second shuttles into coupling engagement with their respective discharge stations so that coating material contained within said reservoir of each of said first and second pumps is transmitted through said flow control means without supplying new coating material to either of said first and second pumps. 
     
     
       39. The apparatus of claim 38 in which each of first and second transfer units includes: a linear actuator which is effective to move said shuttle associated therewith between said filling station and said discharge station; and   an actuator valve which controls the operation of said linear actuators;   said pump emptying means including a switch operative to produce a signal, whereby each of said actuator valves is effective upon receipt of said signal to cause said linear actuators of their associated first and second transfer units to move said shuttles to said discharge stations.   
     
     
       40. The apparatus of claim 27 in which said filling station is connected by a supply line and by a return line to the source of coating material, said apparatus further including dump means for moving each of said first and second shuttles into coupling engagement with their respective filling stations so that coating material contained within said reservoir of each of said first and second pumps is transmitted to said filling stations and through said return line to the source of coating material. 
     
     
       41. The apparatus of claim 40 in which each of said first and second transfer units includes a linear actuator which is effective to move said shuttles associated therewith between said filling station and said discharge station, and wherein said dump means comprises a switch operative to produce a signal which operates each of said linear actuators to move their respective shuttles into coupling engagement with said discharge stations of said first and second transfer units. 
     
     
       42. The apparatus of claim 27 in which said flow control means includes a sync valve having a valve body formed with a central bore connected to an outlet which is adapted to communicate with said at least one coating dispenser, a first inlet connected to said central bore and to said discharge station of said first transfer unit, a second inlet connected to said central bore and to said discharge station of said second transfer unit, a first valve carried within said first inlet and movable between an open and closed position relative to the intersection of said first inlet and said central bore, and a second valve carried within said second inlet and movable between an open and closed position relative to the intersection of said second inlet and said central bore. 
     
     
       43. Apparatus for transmitting electrically conductive coating material to at least one electrostatic coating dispenser, comprising: first and second pumps each having a reservoir formed with an inlet and an outlet;   a first transfer unit for supplying coating material to said first pump, said first transfer unit including: (i) a filling station connected to a source of coating material;   (ii) a discharge station spaced from said filling station; and   (iii) a first shuttle releasably couplable to said filling station and to said discharge station, said shuttle being connected to said inlet and to said outlet of said first pump;     a second transfer unit for supplying coating material to said second pump, (i) a filling station connected to the source of coating material;   (ii) a discharge station spaced from said filling station; and   (iii) a second shuttle releasably couplable to said filling station and to said discharge station, said second shuttle being connected to said inlet and to said outlet of said second pump;     filling control means, associated with each of said first and second transfer means, for moving said shuttle of each of said first and second transfer means to their respective filling stations in response to depletion of coating material from said reservoir of said first and second pumps, respectively;   discharge control means, associated with each of said first and second transfer means, for moving said shuttle of each of said first and second transfer means to their respective discharge stations in response to filling of said reservoir of said first and second pumps, respectively, with coating material;   flow control means, connected to said discharge station of each of said first and second transfer means and to at least one coating dispenser, for sequentially transmitting coating material to the coating dispenser from said reservoir of said first pump through said discharge station of said first transfer means, and then to the coating dispenser from said reservoir of said second pump through said discharge station of said second transfer means.   
     
     
       44. The apparatus of claim 43 in which each of first and second transfer units includes a linear actuator which is effective to move said shuttles associated therewith between said filling station and said discharge station, and an actuator valve which controls the operation of said linear actuators. 
     
     
       45. The apparatus of claim 44 in which said filling control means of each of said first and second transfer units includes a second sensor operative to produce a second signal in response to movement of said piston to said retracted, depleted position, said actuator valve being operative in response to receipt of said second-signal to activate said linear actuator so that said shuttle moves to said filling station. 
     
     
       46. The apparatus of claim 45 further including a control valve operatively connected to said second sensor of each of said first and second transfer units and to said flow control means, said control valve being effective in response to receipt of said second signal from said second sensor of one of said first and second transfer units to operate said flow control means such that flow of coating material from said reservoir of one of said pumps to the coating dispenser is terminated while flow of coating material from said reservoir of the other of said pumps to the coating dispenser is initiated. 
     
     
       47. The apparatus of claim 44 in which said first and second pumps each include a piston movable within said reservoir thereof between and extended, filled position and a retracted, depleted position, said discharge control means of each of said first and second transfer units including a first sensor operative to produce a first signal in response to movement of said piston to said extended position, said actuator valve being operative in response to receipt of said first signal produced by said first sensor to actuate said linear actuator so that said shuttle moves to said discharge station. 
     
     
       48. Apparatus for supplying electrically conductive coating material, comprising: a first reservoir and a second reservoir each adapted to connect to a source of electrically conductive coating material;   flow control means for connecting said first and second reservoirs to at least one coating dispenser;   means for alternatively transmitting coating material from said first reservoir and from said second reservoir through said flow control means to the coating dispenser for discharge onto a substrate;   means for charging the coating material discharged from the coating dispenser;   first means movable to a first position for electrically isolating said first reservoir from the source of electrically conductive coating material when said first reservoir is receiving coating material from the source, and second means movable to a second position for electrically isolating said second reservoir from the source of electrically conductive coating material when said second reservoir is receiving coating material from the source.   
     
     
       49. The system of claim 48 wherein said first and second reservoirs have upper limit indicating means and lower limit indicating means for controlling the transfer of coating material therein. 
     
     
       50. The system of claim 49 wherein when said upper limit means of the first reservoir is triggered, coating material flow is shut off, and when said lower limit means of the first reservoir is triggered, said flow control means shifts the supply of paint to the coating dispenser from the first reservoir to the second reservoir. 
     
     
       51. The apparatus of claim 48 further including means for circulating the coating material to and from the source of electrically conductive coating material when said at least one coating dispenser is not operating. 
     
     
       52. Apparatus for transmitting electrically conductive coating material to at least one electrostatic coating dispenser, comprising: first a second pumps each having a reservoir formed with an inlet and an outlet;   a first transfer unit for supplying coating material to said first pump, said first transfer unit including: (i) a filling station connected to a source of coating material;   (ii) a discharge station spaced from said filling station; and   (iii) a first shuttle releasably couplable to said filling station and to said discharge station, said shuttle being connected to said inlet and to said outlet of said first pump;     a second transfer unit for supplying coating material to said second pump, said second transfer unit including: (i) a filling station connected to the source of coating material;   (ii) a discharge station spaced from said filling station; and   (iii) a second shuttle releasably couplable to said filling station and to said discharge station, said second shuttle being connected to said inlet and to said outlet of said second pump;     flow control means, connected to said discharge station of each of said first and second transfer units and to a coating dispenser, for sequentially supplying coating material from said first pump and then from said second pump to said coating dispenser for deposition onto a substrate;   circulation means for circulating coating material from the source of coating material, through each of said first and second transfer units, and back to said source, when said coating dispenser is not dispensing coating material.   
     
     
       53. Apparatus for supplying electrically conductive coating material to at least one coating dispenser, comprising: a color changer connected to at least one coating dispenser;   a number of parallel, voltage block systems each connected to said color changer and to separate source of electrically conductive coating material, each of said voltage block systems including: (i) a first reservoir and a second reservoir each adapted to connect to a source of electrically conductive coating material;   (ii) flow control means for connecting said first and second reservoirs to at least one coating dispenser;   (iii) means for alternatively transmitting coating material from said first reservoir and said second reservoir through said flow control means to the coating dispenser for discharge onto a substrate;   (iv) means for charging the coating material discharged from the coating dispenser; and   (v) means for electrically isolating said first reservoir from the source of electrically conductive coating material when said first reservoir is supplying coating material through said flow control means to the coating dispenser, and means for electrically isolating said second reservoir from the source of electrically conductive coating material when said second reservoir is supplying coating material through said flow control means to the coating dispenser. .Iadd.     
     
     
       54.  A system for supplying electrically conductive material from a source to at least one electrostatic coating dispenser comprising: a power supply for electrically charging the coating material;   a pump; and   a movable transfer unit having a filling position connecting the source to said pump to fill said pump with coating material while simultaneously creating a voltage block between said pump and the dispenser, and a discharge position connecting said pump to the dispenser to permit the flow of coating material from said pump to the dispenser while simultaneously creating a voltage block between the source and said pump..Iaddend..Iadd.55. The system of claim 54 in which said pump is a first pump and said movable transfer unit is a first movable transfer unit, said system further including:   a second pump;   a second movable transfer unit having a filling position connecting the source to said second pump to fill said second pump with coating material while simultaneously creating a voltage block between said second pump and the dispenser, and a discharge position connecting said second pump to the dispenser to permit the flow of coating material from said second pump to the dispenser while simultaneously creating a voltage block between the source and said second pump; and   a flow control device associated with said first and second movable transfer units, said flow control device being operative to sequentially shift the flow of coating material from one of said first pump and said   
     
     
        second pump to the other..Iaddend..Iadd.56.  A method for supplying electrically conductive material to at least one electrostatic coating dispenser comprising: applying high voltage to the conductive coating material;   selectively directing coating material from a supply through a movable transfer unit in a filling position to a pump while utilizing the movable transfer unit in the filling position for both blocking flow of the conductive material from the pump to the dispenser and creating a voltage block therebetween; and   selectively directing the coating material from the pump through the movable transfer unit in a discharge position to the dispenser while utilizing the transfer unit in the discharge position for both blocking flow of the conductive material from the supply to the pump and creating a   
     
     
        voltage block therebetween..Iaddend..Iadd.57.  The method of claim 56 further comprising the steps of: selectively directing coating material from a supply through a second movable transfer unit in a filling position to a second pump while utilizing the movable transfer unit in the filling position for both blocking flow of the conductive material from the second pump to the dispenser and creating a voltage block therebetween;   selectively directing the coating material from the second pump through the second movable transfer unit in a discharge position to the dispenser while utilizing the transfer unit in the discharge position for both blocking flow of the conductive material from the supply to the second pump and creating a voltage block therebetween; and   controlling the operation of the movable transfer units so that flow of coating material can be shifted from said pump and said second pump to said dispenser..Iaddend..Iadd.58. The method of claim 57 further including the steps of:   sequentially shifting the flow of coating material from said pump and said second pump through a flow control device to the dispenser; and   controlling the operation of the movable transfer units and the flow control device so that both said movable transfer unit and said second movable transfer unit are located at their discharge positions at the same time to permit an overlap in the flow of coating material from said pump and said second pump to said dispenser during the shifting of flow from   
     
     
        one of said pump and said second pump to the other..Iaddend..Iadd.59.  A system for supplying electrically conductive coating material from a supply to at least one dispenser, comprising: a first flow path and a second flow path each having an inlet adapted to be connected to the source of coating material, an outlet, and, a pump for receiving coating material from said inlet and delivering coating material to said outlet;   a voltage block device associated with each of said first and second flow paths, said voltage block device being movable to a filling position at which coating material passes to said pump while a voltage block is created between said pump and the dispenser, said voltage block device being movable to a discharge position at which coating material passes from said pump to the dispenser while a voltage block is created between the supply and said pump;   a flow control device associated with each of said first and second flow paths, said flow control device being operative to sequentially shift the flow of coating material from one of said first and second flow paths to the other while maintaining a substantially uninterrupted flow of coating   
     
     
        material to the dispenser..Iaddend..Iadd.60.  The apparatus of claim 59 in which said flow control device includes a synchronizing valve comprising a synchronizing valve body having a first inlet connected by a line to said outlet of said first flow path, a second inlet connected by a line to said outlet of said second flow path, an outlet internally connected to each of said first and second inlets and being adapted to connect to at least one dispenser, and, a first valve and a second valve for selectively closing and opening said first and second inlets..Iaddend..Iadd.61. The apparatus of claim 60 further including a control system connected to said first and second valves of said synchronizing valve and operative in response to material levels in each of said pumps, said control system being effective to open one of said first and second valves while the other of said first and second valves is still closing to have an overlap in flow through said synchronizing valve from both pumps, whereby a substantially uninterrupted flow of coating material through said synchronizing valve to at least one 
     
     
        dispenser can be maintained..Iaddend..Iadd.62.  The apparatus of claim 59 wherein said substantially uninterrupted flow is maintained by said flow control device permitting flow from both of said pumps through said flow control device simultaneously for a period of time during the shift from one flow path to the other..Iaddend..Iadd.63. The apparatus of claim 62 wherein said flow control device includes a first valve communicating with said outlet of said first flow path, and a second valve communicating with said outlet of said second flow path, said flow control device permitting said first and second valves to be simultaneously open for said period of 
     
     
        time..Iaddend..Iadd.64.  A method for supplying electrically conductive coating material to at least one coating dispenser comprising: transferring coating material from a supply through a first transfer unit which is located in a filling position to a first reservoir and through a second movable transfer unit which is located in a filling position to a second reservoir while electrically isolating the first and second reservoirs from the coating dispenser;   transferring the coating material from said first and second reservoirs through said first and second movable transfer units which are located in discharge positions to a flow control means while electrically isolating the first and second reservoirs from said supply;   alternately transferring the coating material through said flow control means to the coating dispenser from said first reservoir and from said second reservoir while providing an overlap in flow from both reservoirs during changeover from one to the other;   moving said first transfer unit to the discharge position at which the first transfer unit is operative both to electrically isolate said first reservoir from said supply and to block flow therebetween while coating material is being transferred from said first reservoir through said flow control means to the coating dispenser, and then moving the first transfer unit to the filling position at which the first transfer unit is operative both to electrically isolate said coating dispenser from said first reservoir and to block flow therebetween while coating material is being transferred from said supply to said first reservoir;   moving said second transfer unit to the discharge position which is operative both to electrically isolate said second reservoir from said supply and to block flow therebetween while said coating material is being transferred from said second reservoir through said flow control means to the coating dispenser, and then moving the second transfer unit to a filling position at which the second transfer unit is operative both to electrically isolate said coating dispenser from said second reservoir and to block flow therebetween while coating material is being transferred from said supply to said second reservoir; and   electrically charging the coating material sprayed from the coating   
     
     
        dispenser..Iaddend..Iadd.65.  A method for supplying electrically conductive coating material to at least one coating dispenser comprising: transferring coating material from a supply through a first transfer unit to a first reservoir to fill said first reservoir to a high level while electrically isolating the first reservoir from the coating dispenser;   when said first reservoir is filled to said high level, connecting said first reservoir to a flow control valve and operating said flow control valve to transfer coating material from said first reservoir to the coating dispenser while electrically isolating the first reservoir from the supply;   transferring coating material from the supply through a second transfer unit to a second reservoir to fill said second reservoir to a high level while electrically isolating the second reservoir from the coating dispenser;   when said second reservoir is filled to said high level connecting said second reservoir to said flow control valve while coating material is still being transferred to the flow control valve from the first reservoir;   when said coating material in said first reservoir reaches a low level, operating said flow control valve to transfer coating material simultaneously from said first reservoir and said second reservoir to the coating dispenser while electrically isolating said first and second reservoirs from the supply thereby simultaneously transferring coating material through said flow control means to the coating dispenser from both said first reservoir and said second reservoir while both of said reservoirs are isolated from said supply;   terminating the flow of coating material through said flow control means to the coating dispenser from said first reservoir while maintaining the flow of coating material through said flow control means to the coating dispenser from said second reservoir;   transferring coating material from the supply through the first transfer unit to the first reservoir to fill said first reservoir to said high level while electrically isolating said first reservoir from the coating dispenser; and   when said first reservoir is filled to said high level connecting said first reservoir to said flow control valve so that said first reservoir is ready to supply coating material through said flow control valve to said dispenser when the coating material in said second reservoir reaches said low level..Iaddend..Iadd.66. The method of claim 65 wherein the flow control valve comprises a first valve communicating with the first reservoir and a second valve communicating with the second reservoir, and wherein said first and second valves are simultaneously open for a period of time while coating material is being simultaneously transferred from said first and second reservoirs to said dispenser..Iaddend..Iadd.67. The method of claim 65 wherein at least a part of the period of time when said first and second valves are simultaneously open occurs while said first valve is opening and said second valve is closing, and while said second valve is opening and said first valve is closing..Iaddend.