Apparatus for dispensing conductive coating materials including color changing capability

• US 5,326,031 A
• Filed: 10/15/1992
• Issued: 07/05/1994
• Est. Priority Date: 10/15/1992
• Status: Expired

• Current Assignee: Nordson Corporation
• Original Assignee: Nordson Corporation
• Inventors: Konieczynski, Ronald D.
• Primary Examiner(s): Kashnikow, Andres
• Assistant Examiner(s): Morris, Lesley D.
• Application Number:
  US07/961,156
• Time in Patent Office: 628 Days
• Field of Search: 118/302, 118/626, 118/629, 427/475, 427/483, 239/690, 239/691, 239/695, 239/708, 239/3
• US Class Current: 239/3
• CPC Class Codes: B05B 12/14 for supplying a selected one of a plurality of liquids or other fluent materials or several in selected proportions to a spray apparatus, e.g. to a single spray outlet
• CPC Class Codes: B05B 12/149 characterised by colour change manifolds or valves therefor B05B12/1409 takes precedence
• CPC Class Codes: B05B 5/1625 the insulating means comprising an intermediate container alternately connected to the grounded material source for filling, and then disconnected and electrically insulated therefrom
• CPC Class Codes: B05B 5/1633 the arrangement comprising several supply lines arranged in parallel, each comprising such an intermediate container

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.

Claims

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 transfer unit to a first reservoir and through a second transfer unit to a second reservoir while electrically isolating the supply from the coating dispenser;

transferring the coating material from said first and second reservoirs to a flow control means;

alternatively 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 position to electrically isolate said first reservoir from said supply while coating material is being transferred from said first reservoir through said flow control means to the coating dispenser;

moving said second transfer unit to a second position to electrically isolate said second reservoir from said supply while said coating material is being transferred from said second reservoir through said flow control means to the coating dispenser; 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 is 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 signal 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 actuators 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 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, 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 a 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.