Methods and apparatus for applying powder to workpieces

• US 5,474,609 A
• Filed: 06/30/1992
• Issued: 12/12/1995
• Est. Priority Date: 06/30/1992
• Status: Expired due to Fees

• Current Assignee: Nordson Corporation
• Original Assignee: Nordson Corporation
• Inventors: Matsunaga, Masafumi, Niemiec, Ronald E., Pleuse, Harald, Mulder, Douglas C., Scarbrough, Don R., Macartney, Lawrence J., Pintelon, Joseph
• Primary Examiner(s): ENGEL, JAMES J
• Application Number:
  US07/906,677
• Time in Patent Office: 1,260 Days
• Field of Search: 118/308, 118/310, 118/311, 118/314, 118/317, 118/320, 118/321, 118/323, 118/326, 118/622, 118/634, 118/319, 118/624
• US Class Current: 118/308
• CPC Class Codes: B05B 1/06 in annular, tubular or hollow conical form
• CPC Class Codes: B05B 1/265 the liquid or other fluent material being symmetrically deflected about the axis of the nozzle
• CPC Class Codes: B05B 12/004 comprising sensors for monitoring the delivery, e.g. by displaying the sensed value or generating an alarm B05B12/08 takes precedence; registering or indicating the condition or the working of machines or other apparatus in general G07C3/00
• CPC Class Codes: B05B 12/06 for effecting pulsating flow nozzles, spray head or outlet with means for generating a discharge of pulsating nature B05B1/08
• CPC Class Codes: B05B 13/0242 the objects being individually presented to the spray heads by a rotating element, e.g. turntable
• CPC Class Codes: B05B 13/0609 the hollow bodies being automatically fed to, or removed from, the machine
• CPC Class Codes: B05B 14/10 the excess material being particulate for spray booths B05B14/48
• CPC Class Codes: B05B 14/30 comprising enclosures close to, or in contact with, the object to be sprayed and surrounding or confining the discharged spray or jet but not the object to be sprayed
• CPC Class Codes: B05B 15/55 using cleaning fluids
• CPC Class Codes: B05B 5/032 for spraying particulate materials
• CPC Class Codes: B05B 5/047 using tribo-charging
• CPC Class Codes: B05B 7/1454 comprising means for supplying collected oversprayed particulate material spray booth with arrangements for collecting oversprayed material B05B14/40
• CPC Class Codes: B05B 7/1486 for spraying particulate material in dry state

Abstract

An apparatus for spraying powder coating material includes a rotatable turret which moves articles to and from a work station. A powder spray gun is operable to spray a pattern onto each of the articles in turn while the article is at the work station. The powder flows through the spray gun as a series of pulses. A diverter assembly is operable to divert a portion of each pulse of powder away from the nozzle to more sharply define the pulse. An excess powder collector draws a flow of powder away from the work station. A virgin powder container supplies powder to a powder collector container which supplies powder to a powder feed container which supplies powder to the spray gun. Sensors associated with the virgin, collector and feed containers ensure that a predetermined quantity of powder is maintained in each container. During transport of powder from the virgin and collector containers, the containers and their associated pumps are vibrated to facilitate the flow of powder. The powder spray gun is mounted on a three axis adjustment assembly to enable the powder spray gun nozzle to be accurately positioned relative to an article at the work station.

Claims

1. An apparatus for use in sequentially applying an annular band of powder to a surface of each can lid of a plurality of can lids, said apparatus comprising a conveyor having can lid retainers to hold can lids, said conveyor being operable to move each of said can lids in turn to and from a work station, a spray device disposed adjacent to said conveyor, said spray device being operable to spray an annular band of powder on one surface of each of said can lids in turn while each of said can lids is at said work station in a spaced apart relationship with said spray device, said spray device including a body section in which a flow of air with powder entrained therein is conducted, a charging apparatus connected with said body section to electrostatically charge powder entrained in said flow of air in said body section, a nozzle connected with said body section and spaced apart from said one surface of each of said can lids during movement of each of said can lids in turn to and from said work station and during spraying of an annular band of powder onto each of said can lids at said work station, a diverter connected with said body section at a location between said charging apparatus and said nozzle and operable to divert a flow of air and electrostatically charged powder being conducted in said body section away from said nozzle to interrupt a flow of powder from said nozzle toward said can lid at said work station, and an excess powder collector at least partially enclosing said nozzle to draw a flow of excess powder away from said one surface of a can lid at said work station and into said excess powder collector, said excess powder collector being spaced apart from said one surface of said can lid at said work station during flow of the stream of air and powder through said space between said nozzle and said one surface of said can lid at said work station and during a flow of excess powder away from said one surface of said can lid at said work station into said excess powder collector, a source of powder, a pump connected in communication with said source of powder and said nozzle to induce a flow of powder from said source of powder toward said nozzle, said pump being operable between an active condition in which said pump is effective to induce a flow of powder from said source of powder and an inactive condition in which said pump is ineffective to induce a flow of powder from said source of powder, and control means for effecting operation of said pump between the active condition and the inactive condition to produce pulses of air with powder entrained therein, said diverter being operable between an active condition in which said diverter is effective to divert a flow of air and powder away from said nozzle and an inactive condition in which said diverter is ineffective to divert a flow of air and powder, said control means being operable to effect operation of said diverter between said inactive condition and said active condition to divert a portion of each pulse of powder away from said nozzle.

2. An apparatus as set forth in claim 1 wherein said source of powder includes a container which holds powder, a screen through which powder entering said container is conducted, said screen being connected with said container by a single cantilever arm to enable said screen to vibrate, and a vibrator which is connected with said container and is operable to vibrate said container and said screen.

3. An apparatus as set forth in claim 1 wherein a conduit connected with said spray device and said source of powder to conduct a flow of powder between said source of powder and said spray device, a heat sensitive element disposed in said conduit in a path of flow of powder through said conduit between said source of powder and said spray device, and means connected with said heat sensitive element for providing an output signal in response to exposure of said heat sensitive element to excessive heat.

4. An apparatus as set forth in claim 1 further including a first adjustment connected with said nozzle and operable to move said nozzle relative to said conveyor along a first axis which is coincident with a longitudinal central axis of said body section, a second adjustment connected with said nozzle and operable to move said nozzle relative to said turret along a second axis which is perpendicular to said first axis, and a third adjustment connected with said nozzle and operable to move said nozzle along a third axis which is perpendicular to said first and second axes.

5. An apparatus for use in sequentially applying an annular band of powder to a surface of each can lid of a plurality of can lids, said apparatus comprising a rotatable turret having a circular array of can lid retainers to hold can lids in a spaced apart relationship with one surface of each of said can lids facing outwardly away from an axis of rotation of said turret, said turret being rotatable to move each of said can lids in turn to and from a work station along an arcuate path, and a spray device disposed adjacent to said turret, said spray device being operable to spray an annular band of powder on one surface of each of said can lids in turn while each of said can lids is held at said work station by said turret in a spaced apart relationship with said spray assembly, said spray device including a body section in which a flow of air with powder entrained therein is conducted, a charging apparatus connected with said body section to electrostatically charge powder entrained in said flow of air in said body section, a nozzle connected with said body section and spaced apart from said one surface of each of said can lids during movement of each of said can lids in turn to and from said work station ant during spraying of an annular band of powder onto each of said can lids at said work station, said nozzle including an inner deflector element which has an outer side surface which flares outwardly in the direction of flow of the stream of air with electrostatically charged powder entrained therein and which is engaged by the flow of the stream of air with electrostatically charged powder entrained therein, said nozzle including an outer deflector element having an inner side surface which flares outwardly in the direction of flow of the stream of air with electrostatically charged powder entrained therein and which circumscribes at least a part of said outer side surface of said inner deflector element and is engaged by the flow of the stream of air with electrostatically charged powder entrained therein, said outer side surface of said inner deflector element and said inner side surface of said outer deflector element cooperating to define a flow path which has an annular cross sectional configuration and which flares outwardly in the direction of flow of the stream of air with electrostatically charged powder entrained therein, an excess powder collector at least partially enclosing said nozzle to draw a flow of excess powder away from said one surface of a can lid held at said work station by said turret and into said excess powder collector, said excess powder collector being spaced apart from said one surface of said can lid at said work station during flow of the stream of air and powder through said space between said nozzle and said one surface of said can lid at said work station and during a flow of excess powder away from said one surface of said can lid at said work station into said excess powder collector, a diverter located between said charging apparatus and said nozzle and connected with said body section to divert a flow of air and electrostatically charged powder being conducted in said body section away from said nozzle to interrupt a flow of powder from said nozzle toward said can lid at said work station while the flow path between the outer side surface of the inner deflector element and the inner side surface of the outer deflector element remains open to facilitate spraying an annular band of powder on a next succeeding can lid, a source of powder, a pump connected in communication with said source of powder and said nozzle to induce a flow of powder from said source of powder toward said nozzle, said pump being operable between an active condition in which said pump is effective to induce a flow of powder from said source of powder and an inactive condition in which said pump is ineffective to induce a flow of powder from said source of powder, and control means for effecting operation of said pump between the active condition and the inactive condition to produce pulses of air with powder entrained therein, said diverter being operable between an active condition in which said diverter is effective to divert a flow of air and powder away from said nozzle and an inactive condition in which said diverter is ineffective to divert a flow of air and powder, said control means being operable to effect operation of said diverter between said inactive condition and said active condition to divert a trailing end portion of each of said pulses of powder away from said nozzle.

6. An apparatus as set forth in claim 5 further including a first adjustment connected with said nozzle and operable to move said nozzle relative to said turret along a first axis which is coincident with a longitudinal central axis of said body section, a second adjustment connected with said nozzle and operable to move said nozzle relative to said turret along a second axis which is perpendicular to said first axis, and a third adjustment connected with said nozzle and operable to move said nozzle along a third axis which is perpendicular to said first and second axes.

7. An apparatus as set forth in claim 6 further including indicia disposed adjacent to said first, second and third adjustments to indicate the position of said nozzle relative to said axes.

8. An apparatus for use in sequentially applying an annular band of powder to a surface of each can lid of a plurality of can lids, said apparatus comprising a rotatable turret having a circular array of can lid retainers to hold can lids in a spaced apart relationship with one surface of each of said can lids facing outwardly away from an axis of rotation of said turret, said turret being rotatable to move each of said can lids in turn to and from a work station along an arcuate path, and a spray device disposed adjacent to said turret, said spray device being operable to spray an annular band of powder on one surface of each of said can lids in turn while each of said can lids is held at said work station by said turret in a spaced apart relationship with said spray assembly, said spray device including a body section in which a flow of air with powder entrained therein is conducted, a charging apparatus connected with said body section to electrostatically charge powder entrained in said flow of air in said body section, a nozzle connected with said body section and spaced apart from said one surface of each of said can lids during movement of each of said can lids in turn to and from said work station and during spraying of an annular band of powder onto each of said can lids at said work station, said nozzle including an inner deflector element which has an outer side surface which flares outwardly in the direction of flow of the stream of air with electrostatically charged powder entrained therein and which is engaged by the flow of the stream of air with electrostatically charged powder entrained therein, said nozzle including an outer deflector element having an inner side surface which flares outwardly in the direction of flow of the stream of air with electrostatically charged powder entrained therein and which circumscribes at least a part of said outer side surface of said inner deflector element and is engaged by the flow of the stream of air with electrostatically charged powder entrained therein, said outer side surface of said inner deflector element and said inner side surface of said outer deflector element cooperating to define a flow path which has an annular cross sectional configuration and which flares outwardly in the direction of flow of the stream of air with electrostatically charged powder entrained therein, and an excess powder collector at least partially enclosing said nozzle to draw a flow of excess powder away from said one surface of a can lid held at said work station by said turret and into said excess powder collector, said excess powder collector being spaced apart from said one surface of said can lid at said work station during flow of the stream of air and powder through said space between said nozzle and said one surface of said can lid at said work station and during a flow of excess powder away from said one surface of said can lid at said work station into said excess powder collector, a powder supply to hold powder to be sprayed by said spray device, a pump connected in communication with said powder supply and operable between an active condition inducing a flow of powder from said powder supply toward said nozzle and an inactive condition in which said pump is ineffective to induce a flow of powder from said powder supply toward said nozzle, a diverter connected with said body section and operable between an active condition in which said diverter is effective to divert a flow of powder away from said nozzle and an inactive condition in which said diverter is ineffective to divert a flow of powder away from said nozzle, and control means for effecting operation of said pump to its inactive condition and for contemporaneously therewith effecting operation of said diverter to its active condition.

9. An apparatus for use in sequentially applying powder to each workpiece of a plurality of workpieces, said apparatus comprising a spray device which sprays powder on each of said workpieces in turn while said workpiece is at a work station, said spray device including components which produce pulses of air with powder entrained therein, a body section connected with said components which produce pulses of air and in which a flow of pulses of air with powder entrained therein is conducted, charging elements which are connected with said body section and electrostatically charge powder entrained in the flow of pulses of air in said body section, a nozzle connected with said body section to spray powder onto each of said workpieces in turn at said work station, said nozzle being effective to spray powder in one of said pulses of air with powder entrained therein onto one of said workpieces and to spray powder in a pulse of air with powder entrained therein next succeeding said one pulse of air with powder entrained therein onto a workpiece next succeeding said one workpiece, and a diverter located upstream of said nozzle and connected with said body section to divert away from said nozzle a portion of at least some of the pulses of air with powder entrained therein, said components which produce pulses of air with powder entrained therein includes a source of powder, a pump connected with the source of powder to induce a flow of powder from said source of powder toward said nozzle, said pump being operable between an active condition in which said pump is effective to induce a flow of powder from said source of powder and an inactive condition in which said pump is ineffective to induce a flow of powder from said source of powder, and control means for effecting operation of said pump between said inactive condition and said active condition, said diverter being operable between an active condition in which said diverter is effective to divert a flow of air and powder away from said nozzle and an inactive condition in which said diverter is ineffective to divert a flow of air and powder, said control means being operable to effect operation of said diverter between said inactive condition and said active condition in a predetermined relationship with operation of said pump between said inactive condition and said active condition to enable said diverter to sequentially divert the same portion of each of said pulses of air with powder entrained therein.

10. An apparatus as set forth in claim 9 wherein the portion of each of said pulses which is diverted is a trailing end portion of each of said pulses.

11. An apparatus as set forth in claim 9 further including an excess powder collector at least partially enclosing said nozzle and operable to induce a flow of excess powder away from said workpieces into said excess powder collector.

12. An apparatus as set forth in claim 9 wherein said components which produce pulses of air with powder entrained therein includes a pressurized container and means to maintain a relatively constant air pressure in said container.

13. An apparatus as set forth in claim 12 further including means for maintaining a minimum level of powder in said container.

14. An apparatus as set forth in claim 9 wherein said diverter is located between said charging elements and said nozzle to enable said diverter to divert a portion of each pulse of air with powder entrained therein away from said nozzle after said portion of each pulse of air with powder entrained therein has been electrostatically charged by said charging elements and immediately before said portion of each pulse of air with powder entrained therein enters said nozzle.

15. An apparatus as set forth in claim 9 further including an excess powder collector disposed adjacent to said nozzle and operable to induce a flow of excess powder away from the work station, and a first conduit which conducts a flow of air with powder entrained therein from said excess powder collector to said source of powder, said source of powder includes a first container for holding powder, said first conduit being connected with said first container to conduct powder to said first container, a second container for holding virgin powder, a second conduit which conducts a flow of air with virgin powder entrained therein from said second container to said first container, a third conduit which conducts a flow of air with powder entrained therein along a flow path from said first container toward said spray device and a vibrator connected to said first container and operable to vibrate said first container to promote a flow of powder from said first container to said third conduit.

16. An apparatus as set forth in claim 15 wherein said source of powder further includes a third container connected with said spray device, said third conduit being connected with said third container to enable said third conduit to conduct a flow of air with powder entrained therein from said first container to said third container, a sensor disposed adjacent to said third container and operable to sense the quantity of powder in said third container, and a pump connected with said first container and said third conduit and operable to establish a flow of air with powder entrained therein from said first container through said third conduit to said third container in response to said sensor sensing that the quantity of powder in said third container is less than a predetermined quantity.

17. An apparatus as set forth in claim 16 further including a second vibrator connected with said second container and operable to vibrate said second container and promote a flow of powder from said second container through said second conduit.

18. An apparatus as set forth in claim 15 wherein said first container includes an open upper end portion and means for inducing a flow of air into said first container through said open upper end portion of said first container.

19. An apparatus as set forth in claim 15 wherein said second conduit means conducts a flow of air with virgin powder entrained therein from a lower portion of said second container, said source of powder further including a fourth conduit for conducting a flow of air with virgin powder entrained therein from an upper portion of said second container to said first container during filling of said second container with virgin powder.

20. An apparatus as set forth in claim 9 further including an excess powder collector at least partially enclosing said nozzle and operable to draw a flow of excess powder away from a workpiece at said work station, a conduit extending between said excess powder collector and said source of powder for conducting a flow of air with powder entrained therein from said excess powder collector to said source of powder, said source of powder including a container having an open upper portion connected with said conduit, a filter disposed in said container between said open upper portion of said container and a lower portion of said container for removing powder from the flow of air and powder conducted from said excess powder collector to said open upper portion of said container by said conduit, and a fan connected with said container and operable to induce a continuous flow of ambient air into said container through said open upper portion of said container and through said filter.

21. An apparatus as set forth in claim 20 further including a heat sensitive element connected with said conduit, and means for providing an output signal in response to said heat sensitive element being exposed to excessive heat in said conduit.

22. An apparatus as set forth in claim 20 further including means for holding a supply of virgin powder and a conduit extending between said means for holding a supply of virgin powder and said container for conducting a flow of air with virgin powder entrained therein from said means for holding a supply of virgin powder to said container.

23. An apparatus as set forth in claim 20 further including a fusible element disposed in a path of flow of air with powder entrained therein through said conduit from said excess powder collector, and means for providing an output signal in response to said fusible element being fused by exposure to excessive heat in said conduit.

24. An apparatus as set forth in claim 9 wherein said components which produce pulses of air with powder entrained therein include a container which holds powder, a screen connected with said container and through which powder entering said container is conducted, said screen being connected with said container by a single cantilever arm to enable said screen to vibrate, and a vibrator which is operable to vibrate said container and said screen.

25. An apparatus for use in sequentially applying powder to each workpiece of a plurality of workpieces, said apparatus comprising a spray device which sprays powder on each of said workpieces in turn while said workpiece is at a work station, said spray device including components which produce pulses of air with powder entrained therein, a body section connected with said components which produce pulses of air and in which a flow of pulses of air with powder entrained therein is conducted, charging elements which are connected with said body section and electrostatically charges powder entrained in the flow of pulses of air in said body section, a nozzle connected with said body section to spray powder onto each of said workpieces in turn at said work station, said nozzle being effective to spray powder in one of said pulses of air with powder entrained therein onto one of said workpieces and to spray powder in a pulse of air with powder entrained therein next succeeding said one pulse of air with powder entrained therein onto a workpiece next succeeding said one workpiece, and a diverter located upstream of said nozzle and connected with said body section to divert away from said nozzle a portion of at least some of the pulses of air with powder entrained therein, the portion of each of said pulses which is diverted being a trailing end portion of each of said pulses.

26. An apparatus as set forth in claim 25 further including an excess powder collector at least partially enclosing said nozzle and operable to induce a flow of excess powder away from said workpieces into said excess powder collector.

27. An apparatus as set forth in claim 25 wherein said components which produce pulses of air with powder entrained therein include a pressurized container and means to maintain a relatively constant air pressure in said container.

28. An apparatus as set forth in claim 27 further including means for maintaining a minimum level of powder in said container.

29. An apparatus as set forth in claim 25 wherein said diverter is located between said charging elements and said nozzle to enable said diverter to divert a portion of each pulse of air with powder entrained therein away from said nozzle after said portion of each pulse of air with powder entrained therein has been electrostatically charged by said charging elements and immediately before said portion of each pulse of air with powder entrained therein enters said nozzle.

30. An apparatus as set forth in claim 25 wherein said components which produce pulses of air with powder entrained therein include a container which holds powder, a screen connected with said container and through which powder entering said container is conducted, said screen being connected with said container by a single cantilever arm to enable said screen to vibrate, and a vibrator which is operable to vibrate said container and said screen.

31. An apparatus for use in sequentially applying powder to each workpiece of a plurality of workpieces at a work station, said apparatus comprising a conveyor which is operable to move each of the workpieces in turn to and from the work station, a spray device which is disposed adjacent to said conveyor and is operable to spray at least a portion of a pulse of air with electrostatically charged powder entrained therein onto each of the workpieces in turn at the work station, said spray device including pulse producing means for producing pulses of air with powder entrained therein, a body section connected with said pulse producing means and in which a flow of pulses of air with powder entrained therein is conducted, charging apparatus connected with said body section and operable to electrostatically charge powder entrained in each of the pulses of air in the flow of pulses of air with powder entrained therein, a diverter connected with said body section and operable to divert a portion of each of said pulses of air with powder entrained therein away from said body section, said diverter being operable between an active condition in which said diverter is effective to divert a flow of air and powder away from said body section and an inactive condition in which said diverter is ineffective to divert a flow of air and powder away from said body section, a nozzle connected with said body section to direct a flow of at least a portion of each of the pulses of air with powder entrained therein toward each of the workpieces in turn at the work station, and control means for effecting operation of said diverter from the active condition to the inactive condition to enable at least a portion of one of said pulses of air with powder entrained therein to be conducted through said nozzle toward one of said workpieces at the work station, for effecting operation of said diverter from the inactive condition to the active condition to divert a trailing end portion of the one pulse of air with powder entrained therein away from said body section, and for effecting operation of said diverter from the active condition to the inactive condition to enable at least a portion of a pulse of air with powder entrained therein next succeeding the one pulse to be conducted through said nozzle toward the workpiece next succeeding the one workpiece at the work station.

32. An apparatus as set forth in claim 31 further including a powder supply connected with said spray device, said powder supply including a container which holds powder, a screen through which powder entering said container is conducted, said screen being connected with said container by a single cantilever arm to enable said screen to vibrate, and a vibrator which is connected with said container and is operable to vibrate said container and said screen.

33. An apparatus as set forth in claim 31 further including a powder supply connected with said spray device, a conduit connected with said spray device and said powder supply to conduct a flow of powder between said powder supply and said spray device, a heat sensitive element disposed in said conduit in a path of flow of powder through said conduit between said powder supply and said spray device, and means connected with said heat sensitive element for providing an output signal in response to said heat sensitive element being exposed to excessive heat in said conduit.

34. An apparatus as set forth in claim 31 further including a first adjustment connected with said nozzle and operable to move said nozzle relative to said work station along a first axis which is coincident with a longitudinal central axis of said body section, a second adjustment connected with said nozzle and operable to move said nozzle relative to said work station along a second axis which is perpendicular to said first axis, and a third adjustment connected with said nozzle and operable to move said nozzle along a third axis which is perpendicular to said first and second axes.

35. An apparatus as set forth in claim 31 further including an excess powder collector at least partially enclosing said nozzle to draw a flow of excess powder away from a workpiece at the work station and into said excess powder collector, said excess powder collector and said nozzle being spaced apart from the workpiece at the work station during flow of a pulse of air with powder entrained therein through space between said nozzle and the workpiece at the work station and during a flow of excess powder away from the workpiece at the work station into said excess powder collector.

36. An apparatus for use in sequentially applying powder to a surface of each workpiece of a plurality of workpieces, said apparatus comprising a conveyor which is operable to sequentially move said plurality of workpieces to and from a work station, a source of powder, a pump connected with said source of powder, said pump being operable between an active condition in which said pump is effective to induce a flow of air with powder from the source of powder entrained therein and an inactive condition in which said pump is ineffective to induce a flow of air with powder entrained therein, control means for effecting operation of said pump between the active condition and the inactive condition to produce pulses of air with powder entrained therein, and a spray device which is disposed adjacent to said conveyor and is operable to spray powder on said surface of each of said workpieces in turn while each of said workpieces is at said work station, said spray device including a body section connected with said pump and which receives pulses of air with powder entrained therein from said pump, a charging apparatus connected with said body section to electrostatically charge powder entrained in the pulses of air in said body section, a nozzle connected with said body section and spaced apart from said surface of each of said workpieces during movement of each of said workpieces in turn to and from said work station and during spraying of powder onto each of said workpieces at said work station, a diverter connected with said body section at a location between said charging apparatus and said nozzle and operable to divert a flow of air with powder entrained therein away from said nozzle, an excess powder collector at least partially enclosing said nozzle and operable to draw a flow of excess powder away from said surface of a workpiece at the work station and into said excess powder collector, said excess powder collector being spaced apart from said surface of said workpiece at said work station and during a flow of excess powder away from said surface of said workpiece at said work station into said excess powder collector, said control means being operable to effect operation of said diverter to divert a trailing end portion of each of said pulses of air with powder entrained therein away from said nozzle.

37. An apparatus as set forth in claim 36 wherein said source of powder includes a first container for holding powder, a first conduit connected with said excess powder collector and said first container to conduct a flow of air with powder entrained therein from said excess powder collector to said first container, a second container for holding powder, a second conduit connected with said second container and said first container to conduct a flow of air with powder entrained therein from said second container to said first container, a third container connected with said spray device, a third conduit connected with said first container and said third container to conduct a flow of air with powder entrained therein from said first container to said third container, a sensor disposed adjacent to said third container and operable to sense the quantity of powder in said third container, a first pump connected with said first container and said third conduit and operable to establish a flow of air with powder entrained therein through said third conduit to said third container in response to said sensor sensing that the quantity of powder in said third container is less than a predetermined quantity, a second pump connected with said second container and said second conduit and operable to establish a flow of air with powder entrained therein through said second conduit to said first container, a first vibrator connected with said first container and operable to vibrate said first container and promote a flow of powder from said first container through said third conduit to said third container, and a second vibrator connected with said second container and operable to vibrate said second container and promote a flow of powder from said second container through said second conduit to said first container.

38. An apparatus as set forth in claim 37 wherein said source of powder includes a fourth conduit for conducting a flow of air and powder diverted by said diverter to said first container.

39. An apparatus as set forth in claim 37 wherein said first container includes an open upper end portion and means for inducing a flow of air into said first container through said open upper end portion of said first container.

40. An apparatus as set forth in claim 37 wherein said second conduit means conducts a flow of air with powder entrained therein from a lower portion of said second container, said source of powder further including a fourth conduit for conducting a flow of air with powder entrained therein from an upper portion of said second container to said first container during filling of said second container with powder.

41. An apparatus as set forth in claim 37 wherein said source of powder includes a heat sensitive element disposed in one of said conduits, and means for providing an output signal in response to said heat sensitive element being exposed to excessive heat in said one of said conduits.

42. An apparatus for use in sequentially applying powder to a surface of each can lid of a plurality of can lids, said apparatus comprising a conveyor which is operable to move can lids in a spaced apart relationship to and from a work station, and a spray device disposed adjacent to said conveyor and operable to spray powder onto a surface of each of the can lids in turn while each of the can lids is positioned at the work station by said conveyor, said spray device including a pump operable between an active condition in which said pump is operable to produce a flow of air with powder entrained therein and an inactive condition in which said pump is ineffective to produce a flow of air with powder entrained therein, a body section connected with said pump and in which a flow of air with powder entrained therein from said pump is conducted, charging elements which electrostatically charge powder entrained in the flow of air in said body section, a nozzle connected with said body section and spaced apart from the surface of each of the can lids during movement of each of the can lids in turn to and from the work station and during spraying of powder onto each of the can lids at the work station, an excess powder collector at least partially enclosing said nozzle and operable to draw a flow of excess powder away from the surface of a can lid held at the work station by said conveyor and into said excess powder collector, said excess powder collector being spaced apart from the surface of the can lid at the work station during flow of the stream of air and powder through the space between said nozzle and the surface of the can lid at the work station and during a flow of excess powder away from the surface of the can lid at the work station into said excess powder collector, a diverter connected with said body section and operable between an active condition diverting a flow of air and powder entrained therein away from said nozzle and an inactive condition in which said diverter is ineffective to divert a flow of air and powder entrained therein away from said nozzle, and control apparatus which effects repetitive operation of said pump between the active and inactive conditions to produce a series of pulses of air with powder entrained therein which also effects operation of said diverter from the inactive condition to the active condition to divert a trailing end portion of each pulse of air with powder entrained therein and to effect operation of said diverter from the active condition to the inactive condition before a leading end portion of a next succeeding pulse of air with powder entrained therein is conducted to said diverter to enable the powder in the leading end portion of each pulse of air with powder entrained therein to be applied to one of the can lids while the powder in the trailing end portion of each pulse of air with powder entrained therein is diverted by said diverter before the powder in the trailing end portion of each pulse of air with powder entrained therein can be applied to one of the can lids.

43. An apparatus as set forth in claim 42 further including a source of powder connected with said pump, said source of powder including a pressurized container and means to maintain a relatively constant air pressure in said container.

44. An apparatus as set forth in claim 42 wherein said conveyor includes a rotatable turret having a circular array of workpiece retaining elements for holding can lids, said turret being rotatable to move each of the can lids in turn to and from the work station along an arcuate path.

45. An apparatus as set forth in claim 42 further including a powder supply connected with said spray device, said powder supply including a container which holds powder, a screen connected with said container and through which powder entering said container is conducted, said screen being connected with said container by a single cantilever arm to enable said screen to vibrate, a second pump which is operable to induce a flow of air with powder entrained therein away from said container, and a vibrator which is operable to vibrate said container and said screen.

46. An apparatus as set forth in claim 45 further including means for drawing air and powder from around an opening through which powder enters said container during filling of said container with powder, said powder supply means further including a secondary container, first conduit means for conducting a flow of air with powder entrained therein from said second pump to said secondary container, and second conduit means for conducting a flow of air with powder entrained therein from said means for drawing air and powder from around the opening through which powder enters said container to said secondary container.