Claims
- 1. A spray coating apparatus (10) of the type for applying a coating material composed of a controlled mixture of at least two liquid components onto a workpart, comprising: first pump means (12) for pumping an adjustable volumetric flow rate of the first component to an applicator (14), said first pump means (12) including a first motor (16) having an adjustable speed for controlling the rate of fluid pumped by said first pump means (12) and providing feedback signals in response to the instantaneous speed thereof; second pump means (18) for pumping an adjustable volumetric flow rate of the second component to the applicator (14), said second pump means (18) including a second motor (20) having an adjustable speed for controlling the rate of fluid pumped by said second pump means (18) and providing feedback signals in response to the instantaneous speed thereof; and characterized by automatic adjustor means (24) responsive to said feedback signals from said first (16) and second (20) motors for computing an instantaneous ratio of the volumetric flow rates of the first and second components and comparing said instantaneous ratio with a reference ratio of the volumetric flow rates of the first and second components and individually adjusting the speeds of said first (16) and second (20) motors to continually adjust said instantaneous ratio into conformity with said reference ratio.
- 2. An apparatus (10) as set forth in claim 1 further characterized by each of said first (16) and second (20) motors including a tachometer (26, 28) for sending motor speed feedback signals, and motor drive means (22) for receiving the feedback signals from said tachometers (26, 28) and continuously readjusting the instantaneous speed of each of said first (16) and second (20) motors into conformity with a reference speed.
- 3. An apparatus (10) as set forth in claim 2 further characterized by said first pump means (12) including a first gear pump (32) having intermeshing rotors supported within a first housing (34) and operatively connected to said first motor (16), and said second pump means (18) including a second gear pump (36) having intermeshing rotors supported within a second housing (38) and operatively connected to said second motor (20).
- 4. An apparatus (10) as set forth in claim 3 further characterized by including a spray booth (30) defining an isolated internal spray zone.
- 5. An apparatus (10) as set forth in claim 4 further characterized by said first (32) and second (36) gear pumps disposed inside said spray booth (30) and said first (16) and second (20) motors disposed outside of said spray booth (30).
- 6. An apparatus (10) as set forth in claim 5 wherein said apparatus (10) includes a plurality of pneumatically actuated valves (78, 80) disposed in said spray booth (30) for opening and closing fluid flow passages, further characterized by including valve actuator means (76) for individually actuating said valves (78,80) at predetermined times in the workpiece coating process.
- 7. An apparatus (10) as Set forth in claim 6 further characterized by including mixer means (40) disposed in said spray booth (30) for mixing the first and second components of the coating material and discharging the mixture from an output (42) thereof.
- 8. An apparatus (10) as set forth in claim 7 further characterized by including a first conduit (46) associated with said first gear pump (32) and extending from a first component supply outside of said spray booth (30) to said mixer means (40), and a second conduit (48) associated with said second gear pump (36) and extending from a second component supply outside of said spray booth (30) to said mixer means (40).
- 9. An apparatus (10) as set forth in claim 8 further characterized by including applicator means (14) communicating with said output (42) from said mixer means (40) for applying the mixed first and second components of the coating material onto the workpart.
- 10. An apparatus (10) as set forth in claim 9 wherein said first (32) and second (36) gear pump housings each include an upstream inlet (50, 52) and a downstream outlet (54, 56), further characterized by said first conduit (46) including a recirculation line (58) disposed between the first component supply and said first housing inlet (50), and said second conduit (48) including a recirculation line (60) disposed between the second component supply and said second housing inlet (52).
- 11. An apparatus (10) as set forth in claim 10 further characterized by each of said first (12) and second (18) pump means including upstream pressure sensing means (66, 68) disposed adjacent said upstream inlet (50, 52) of respective said first (32) and second (34) housings for sensing when the static pressure in respective said first (46) and second (48) conduits upstream of said inlets (50, 52) falls below a predetermined value.
- 12. An apparatus (10) as set forth in claim 11 further characterized by each of said first (12) and second (18) pump means including downstream pressure sensing (72, 74) means disposed adjacent said downstream outlet (54, 56) of respective said first (34) and second (36) housings for sensing when the static pressure in respective said first (46) and second (48) conduits downstream of said outlets (54, 56) rises above a predetermined value.
- 13. An apparatus (10) as set forth in claim 12 further characterized by including first coupler means (37) for providing an electrically insulated mechanical coupling through said spray booth (30) between said first motor (16) and said first gear pump (32).
- 14. An apparatus (10) as set forth in claim 13 further characterized by including second coupler means (39) for providing an electrically insulated mechanical coupling through said spray booth (30) between said second motor (20) and said second gear pump (36).
- 15. An apparatus (10) as set forth in either of claims 7 or 14 further characterized by including a host controller means (23) disposed outside of said spray booth (30) for supplying reference values to said motor drive means (22) and said adjustor means (24) and controlling said valve actuator means (76) in response to preprogrammed commands.
- 16. An apparatus (10) as set forth in claim 15 further characterized by including flushing means (88) associated with said mixer means (40) for flushing residual coating material from said mixer means (40) and said applicator means (14).
- 17. An apparatus (10) as set forth in claim 16 further characterized by said applicator means (14) including a rotary atomizer (92) fixedly mounted in said spray booth (30).
- 18. An apparatus (10) as set forth in claim 17 further characterized by including electrostatic charging means (94) associated with said applicator means (14) for applying an electrostatic charge to the sprayed coating material.
- 19. An apparatus (10) as set forth in claim 18 further characterized by said applicator means (14) including a manually controllable atomizer.
- 20. An apparatus (10) as set forth in claim 19 further characterized by said host controller means (23) including a fault indicator (70) associated with each of said first (66) and second (68) upstream sensing means and said first (72) and second (74) downstream sensing means.
- 21. A method for spray coating workparts with a coating material composed of a controlled mixture of at least two liquid components, comprising the steps of: pumping a first component to an applicator (14); controlling the flow rate of the first component with an adjustable speed first motor (16); sending feedback signals in response to the instantaneous speed of the first motor (16); pumping a second component to the applicator (14); controlling the flow rate of the second component with an adjustable speed second motor (20); sending feedback signals in response to the instantaneous speed of the second motor (20); and characterized by computing an instantaneous ratio of the volumetric flow rate of the first and second components and comparing the instantaneous ratio to a reference ratio of the volumetric flow rate of the first and second components and individually adjusting the speeds of the first (16) and second (20) motors to continuously adjust the instantaneous ratio between the flow rates of the first and second components into conformity with the reference ratio.
- 22. A method as set forth in claim 21 further characterized by electrostatically charging the sprayed coating material.
- 23. A method as set forth in claim 22 further characterized by continuously readjusting the instantaneous speed of each of the first (16) and second (20) motors to a reference speed.
- 24. A method as set forth in claim 23 wherein a first gear pump (32) pumps the first component and a second gear pump (36) pumps the second component, further characterized by measuring the static pressure of the first and second components at positions upstream and downstream of the respective first (32) and second (36) gear pumps.
- 25. A method as set forth in claim 24 further characterized by signaling a fault indicator (70) in the event the static pressure of at least one of the first and second components upstream of the respective first (32) and second (36) gear pumps falls below a predetermined value.
- 26. A method as set forth in claim 25 further characterized by signaling a fault indicator (70) in the event the static pressure of at least one of the first and second components downstream of the respective first (32) and second (36) gear pumps rises above a predetermined value.
- 27. A method as set forth in claim 26 further characterized by mixing the first and second components at a position upstream of the applicator (14).
- 28. A method as set forth in claim 27 further characterized by circulating the first and second coating materials to and from respective supplies during periods when the first (32) and second (36) gear pumps are not operating.
Parent Case Info
This is a continuation in part of U.S. Ser. No. 07/332,557, filed Mar. 13, 1989, abandoned.
US Referenced Citations (5)
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
322557 |
Mar 1989 |
|