GB1589853A - Method and device for collecting surplus spray material at spray coating operations - Google Patents

Description

(54) METHOD AND DEVICE FOR COLLECTING SURPLUS SPRAY MATERIAL AT SPRAY COATING OPERATIONS (71) We, ATLAS COPCO AKTIEBOLAG, a Swedish Company, of Nacka, Sweden, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of and a device for use in collecting surplus atomized spray material in spary coating operations.

In most conventional spray coating operations significant quantities of atomized spray material pass by the article desired to be sprayed and are surplus to the material actually used in coating the article. It is desirable that this material should be collected in a simple and economic manner.

The present invention provides a method of collecting surplus atomized spray material from a spray coating operation, in which method a collector liquid is exposed at a spraying location for taking up in suspension air-borne spray material, and the collector liquid carrying said spray material is circulated upwardly through a rotating separator drum journalled for rotation about a substantially vertical axis to separate by centrifugal forces the spray material suspended in the collector liquid from said collector liquid, and the separated spray material is collected on the peripheral wall of the separator drum, said collector liquid having a lower density than said spray material.

The present invention also provides a device for use in collecting surplus atomized spray material from a spray coating operation, said device comprising liquid exposure means arranged for exposing at a spraying location, in use of the device, a spray material collector liquid, a separator drum, drive means for rotating said separator drum about a substantially vertical axis, and circulating means arranged for circulating said spray material collector liquid, in use of the device, upwardly through the rotating separator drum, whereby spray material is separated from the collector liquid by centrifugal forces and collected at the peripheral wall of said separator drum, the collector liquid used having a lower density than said spray material.

Further preferred features and advantages of the invention will appear from the following description given by way of example of a preferred embodiment illustrated with reference to the accompanying drawing which is a partly sectioned side elevation of a device for use in collecting surplus spray material in accordance with the present invention.

In the drawing is shown a spray cabin 1 comprising three walls and a roof and in which there is supported an object 2 to be sprayed and a spray gun 3. The cabin 1 is provided with a ventilation passage 4 which at its upper end 5 is connected to a suction means (not shown) and which at its lower end communicates with a spray compartment 9 (in which the object 2 and spray gun 3 are located) of the cabin 1 via an elongate horizontally extending opening 6. In the ventilation passage 4 there are mounted a number of transverse deflectors or baffles 7 for catching particles of spray material carried over by the ventilation air flow, whilst a vertical partition wall 8 separates the ventilation passage 4 from the spray compartment 9.

The upper horizontal edge 10 of the vertical partition wall 8 constitutes a spillway from a channel 11 extending alongside said edge 10 whereas the lower edge 12 of said partition wall 8 defines, together with the upper face of a lower wall member 13 which extends generally parallel thereto and has a generally 'T'-shaped cross-section, the elongate opening 6.

In the lower part of the spray cabin 1 there is provided a tank 15 for the collector liquid.

The lower wall member 13 acts as a partition wall in the tank 15 and is provided with an opening 14 to permit communication between the two parts of the tank on either side of the wall member 13. The tank 15 is in communication with the channel 11 via a collector liquid circulation pump 16 and a conduit 17.

Most conveniently water is used as the collector liquid and in order to simplify the following description the collector liquid will be simply referred to as water.

In operation, there is maintained an air flow through the spray compartment 9 of the cabin 1, the elongate opening 6 and the passage 4 to ventilate the cabin 1. The channel 11 is continuously supplied with water from the tank 15 by the pump 16 and the conduit 17.

Water flows over the upper edge 10 of the vertical partition wall 8 and forms a curtain of falling water over the front surface of the wall 8. Through the opening 6 the air velocity is normally so high that the water curtain will be substantially atomized and mixed intimately with the air-borne spray material particles. The surplus spray material resulting from the spray coating operation, i.e. the amount of spray material which is emitted from the spray gun 3 but does not hit the object 2, is partly absorbed by the water curtain exposed to it on the wall 8 and partly by the atomized water exposed to it in or downstrcam of the elongate opening 6. As a matter of fact, the main part of the air-borne spray material particles is absorbed by the collector liquid water in atomized form just behind the opening 6.

Together, the pump 16, conduit 17, partition wall 8, elongate opening 6, and channel 11, constitute a liquid exposure means for exposing the water circulating therearound to the surplus atomized spray material.

After having settled 017 the walls and deflectors 7 in the ventilation passage 4, the water returns to the tank 15 under the influence of gravity and is recirculated to the channel 11.

In order to keep the amount of suspended spray material particles in the water below a certain level, the tank 15 is connected to a separating unit 20 through supply and return conduits 21 and 22, respectively. The separating unit 20 comprises a frame 23 which supports a rotatable separator drum 24 and a collector housing 25 surrounding the separator drum. The frame 23 also supports a feed pump 26 and a motor 27. The latter is arranged to serve as a drive means to rotate the separator drum 24 as well as the feed pump 26 by means of a belt transmission 28 At its suction end, the feed pump 26 communicates with the tank 15 via supply conduit 21. At its pressure end, the feed pump 26 communicates with a supply valve 29 and a supply conduit 30. The supply conduit 30 extends through a central discharge opening 32 in the upper end 31 of the separator drum 24 into the lower part of the separator drum 24 and has its outlet end located eccentrically relative to the rotation axis of the separator drum 24.

The separator drum 24 has the form of a circular cylinder the rotation axis of which is vertically directed. The upper end wall 31 of the drum 24 is provided with a central circular discharge opening 32. Through this discharge opening there is insertable as well as removable a plastics material sack 33 which is intended to form a lining to the peripheral wall of the separator drum 24. This plastics sack 33, which is shown in dotted lines in the drawing, is intended to facilitate removal of collected spray material from the separator drum 24.

The collector housing 25, which entirely encloses the separator drum 24, is intended to collect the purified water which continuously leaves the drum 24 through the discharge opening 32. Thus the feed pump 26, conduit 30 and discharge outlet 32 together serve as a circulation means for circulating water through the separator drum 24. At its bottom, the collector housing 25 is connected to the tank 15 via the return conduit 22.

In operation, the separator drum 24 as well as the feed pump 26 are both driven by the motor 27. Spray material carrying water is conveyed from the tank 15 to the separator drum 24 via the conduits 21 and 30. Because of the drum rotation and the resulting centrifugal forces acting upon the water in the separator drum 24, this water is pressed against the peripheral wall of the drum 24 and forms a substantially tube-shaped layer having an internal water surface 34. Due to the fact though that the spray material particles suspended in the water are of higher density than water, they will be forced outwardly towards the peripheral wall and the plastics sack 33. This means that that part of the water which is closest to the cylindrical water surface 34 will become completely free from spray material particles.

As water is continuously supplied to the lower part of the separator drum 24 through the supply conduit 30, the thickness of the water layer is increased which means that the diameter of the cylindrical water surface 34 will become less than the diameter of the discharge opening 32. This means that the water at this cylindrical surface 34 will begin to leave the separator drum 24 through the discharge opening 32 and be collected in the housing 25 from where it is returned to the tank 15 via the return conduit 22.

The spray material particles are gradually separated from the water as the latter is circulated upwards through the separator drum 24, from the outlet end of the supply conduit 30 in the lower part of the drum to the discharge opening 32 in the upper end wall 31 of the drum 24.

After a given period of operation a layer of spray material particles will have accumulated at the peripheral wall of the drum 24.

This layer should not exceed a given thickness if the effectiveness of the device is to be fully maintained. Because of this, it is neces sary to remove the collected spray material from time to time. This is carried out very simply by removing the plastics sack 33 from the drum 24 through the discharge opening 32. The removed sack is readily replaced by a new one.

The above described method of and device for use in surplus atomized spray material collection is particularly advantageous in that the spray material is recovered in a concentrated form substantially free of any other material, which makes it much easier to store or destroy the material. By utilizing a separator unit of the centrifugal type, it is also possible to entirely avoid operational breakdowns such as those due to clogging of filters.

The above described embodiments may be readily modified without departing from the scope of the present invention as defined in the claims. Thus, for example, the arrangement of the separator unit 20 could be modified e.g. instead of connecting it in parallel with the circulation pump 16 of the liquid exposure means it could be connected in series therewith.

WHAT WE CLAIM IS: 1. A method of collecting surplus atomized spray material from a spray coating operation in which method a collector liquid is exposed at a spraying location for taking up in suspension air-borne spray material, and the collector liquid carrying said spray material is circulated upwardly through a rotating separator drum journalled for rotation about a substantially vertical axis to separate by centrifugal forces the spray material suspended in the collector liquid from said collector liquid, and the separated spray material is collected on the peripheral wall of the separator drum, said collector liquid having a lower density than said spray material.

2. A method according to claim 1, wherein the spray material is removed from the separator drum by interrupting circulation of the collector liquid through the drum and rotation of the separator drum, and removing a replaceable drum lining.

3. A method according to claim 1 or claim 2 wherein the collector liquid is water.

4. A device for use in collecting surplus atomized spray material from a spray coating operation, said device comprising liquid exposure means arranged for exposing at a spraying location, in use of the device, a spray material collector liquid, a separator drum, means for rotating said separator drum about a substantially vertical axis, and circulating means arranged for circulating said spray material collector liquid, in use of the device, upwardly through the rotating separator drum, whereby spray material is separated from the collector liquid by centrifugal forces and collected at the peripheral wall of said separator drum, the collector liquid used having a lower density than said spray material.

5. A device according to claim 4, wherein said circulation means comprises a feed pump, a supply conduit leading to the lower part of the separator drum, and a discharge opening located in the central part of the upper end wall of said separator drum.

6. A device according to claim 5, wherein said separator drum and said feed pump of the circulation means are driven by a common motor.

7. A device according to claim 5 or claim 6 wherein said separator drum is substantially surrounded by a collector housing which is arranged to receive the collector liquid leaving said separator drum through said discharge opening.

8. A device according to any one of claims 5 to 7, wherein said supply conduit extends into said separator drum through said discharge opening.

9. A device according to any one of claims 5 to 8, wherein the outlet end of said supply conduit is located eccentrically relative to said separator drum.

10. A device according to any one of claims 4 to 9, wherein said separator drum is lined with a sack of a plastics material which is insertable and removable through said discharge opening.

11. A device according to any one of claims 4 to 10 wherein the liquid exposure means comprises a liquid circulation means arranged for conducting a curtain of the collector liquid past the downstream side of the spraying location with respect to the spraying direction.

12. A method of collecting surplus atomized spray material, substantially as hereinbefore described with reference to the accompanying drawing.

13. A device for collecting surplus atomized spray material, substantially as hereinbefore described with particular reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. sary to remove the collected spray material from time to time. This is carried out very simply by removing the plastics sack 33 from the drum 24 through the discharge opening 32. The removed sack is readily replaced by a new one. The above described method of and device for use in surplus atomized spray material collection is particularly advantageous in that the spray material is recovered in a concentrated form substantially free of any other material, which makes it much easier to store or destroy the material. By utilizing a separator unit of the centrifugal type, it is also possible to entirely avoid operational breakdowns such as those due to clogging of filters. The above described embodiments may be readily modified without departing from the scope of the present invention as defined in the claims. Thus, for example, the arrangement of the separator unit 20 could be modified e.g. instead of connecting it in parallel with the circulation pump 16 of the liquid exposure means it could be connected in series therewith. WHAT WE CLAIM IS:

1. A method of collecting surplus atomized spray material from a spray coating operation in which method a collector liquid is exposed at a spraying location for taking up in suspension air-borne spray material, and the collector liquid carrying said spray material is circulated upwardly through a rotating separator drum journalled for rotation about a substantially vertical axis to separate by centrifugal forces the spray material suspended in the collector liquid from said collector liquid, and the separated spray material is collected on the peripheral wall of the separator drum, said collector liquid having a lower density than said spray material.

2. A method according to claim 1, wherein the spray material is removed from the separator drum by interrupting circulation of the collector liquid through the drum and rotation of the separator drum, and removing a replaceable drum lining.

3. A method according to claim 1 or claim 2 wherein the collector liquid is water.

4. A device for use in collecting surplus atomized spray material from a spray coating operation, said device comprising liquid exposure means arranged for exposing at a spraying location, in use of the device, a spray material collector liquid, a separator drum, means for rotating said separator drum about a substantially vertical axis, and circulating means arranged for circulating said spray material collector liquid, in use of the device, upwardly through the rotating separator drum, whereby spray material is separated from the collector liquid by centrifugal forces and collected at the peripheral wall of said separator drum, the collector liquid used having a lower density than said spray material.

5. A device according to claim 4, wherein said circulation means comprises a feed pump, a supply conduit leading to the lower part of the separator drum, and a discharge opening located in the central part of the upper end wall of said separator drum.

6. A device according to claim 5, wherein said separator drum and said feed pump of the circulation means are driven by a common motor.

7. A device according to claim 5 or claim 6 wherein said separator drum is substantially surrounded by a collector housing which is arranged to receive the collector liquid leaving said separator drum through said discharge opening.

8. A device according to any one of claims 5 to 7, wherein said supply conduit extends into said separator drum through said discharge opening.

9. A device according to any one of claims 5 to 8, wherein the outlet end of said supply conduit is located eccentrically relative to said separator drum.

10. A device according to any one of claims 4 to 9, wherein said separator drum is lined with a sack of a plastics material which is insertable and removable through said discharge opening.

11. A device according to any one of claims 4 to 10 wherein the liquid exposure means comprises a liquid circulation means arranged for conducting a curtain of the collector liquid past the downstream side of the spraying location with respect to the spraying direction.

12. A method of collecting surplus atomized spray material, substantially as hereinbefore described with reference to the accompanying drawing.

13. A device for collecting surplus atomized spray material, substantially as hereinbefore described with particular reference to the accompanying drawing.