GB2119280A

GB2119280A - Apparatus for cleaning air of paint entrained therein

Info

Publication number: GB2119280A
Application number: GB08203968A
Authority: GB
Inventors: Robert Fulton; Gerge Walker
Original assignee: FLAKT Ltd
Current assignee: FLAKT Ltd
Priority date: 1982-02-11
Filing date: 1982-02-11
Publication date: 1983-11-16
Also published as: GB2119280B

Abstract

Apparatus 1 for cleaning air of paint entrained therein, in a spray chamber 3 comprises a conduit 6 in the partition 2 open at both ends, one of which opens into the chamber 3 and the other of which opens into, and is spaced from a boundary wall 4 of, the cleaning chamber 5, the end 8 having a smaller cross-sectional area than that of the one end 7, and means to pass liquid cleaning medium over the partition 2, through the conduit 6 and into the cleaning chamber 5, whereby the paint is separated from the air and becomes mixed with the cleaning liquid. The conduit 6 may be of circular, square, rectangular or polygonal cross-section, and the smaller cross-section at end 8 may be achieved by an inwardly bent flange as shown, or by a gradual tapering of the conduit from top to bottom. Conduit 6 may stand proud of partition 2 and/or may be inclined to the vertical. <IMAGE>

Description

SPECIFICATION Apparatus for cleaning air of paint entrained therein Technical field of the invention The invention relates to apparatus for cleaning air of paint entrained therein, and to paint spray installation such as a paint spray booth in which articles such as automobile bodies are sprayed incorporating such apparatus.

The expression "paint" used herein is intended to cover paint, cellulose, lacquer, enamel and like finishes which are applied to articles such as automobile bodies to give them a protective and/or aesthetic finish.

Background art A modern water washed paint spray booth for volume production of items to be painted, typically that for painting of car bodies in the automotive industry, is not sufficiently effective to meet the environmental, operational and maintenance standards required in today's conditions. All such spray booths generally fail to give complete satisfaction in one or more of the following aspects, and particularly those spray booths which are constrained to be floor mounted as distinct from those built over deep pits or with extended projections through the flow: 1. The required degree of efficiency of removal of paint overspray from exhaust air without the use of excessive energy.

2. A sufficiently low noise level in the booth at the required overspray removal efficiency.

3. Insufficient elimination of the water carryover, causing leaking problems from exhaust ducts and fouling of roof and adjacent properties from the discharge of exhaust stacks.

4. The need to maintain ponds or sumps containing water at and below the floor of the booth leads to sedimentation of paint sludge and the need for frequent hosing and/or costly maintenance for digging out of such sedimented sludge.

5. The need to supply large quantities of gravity fed water to so called "flood sheets". Such water has to have a lower limit of dispersed paint solids above which the amount of sedimentation and drying out of such paint solids on booth surfaces becomes unacceptable from operation and maintenance aspects.

6. A system for the removal of the dispersed solids by sedimenting into sludge in a separate receptacle or pits having to be of large proportions to accommodate the required amount of water circulation dictated by the lower limit of solids in (5) above.

7. The advent of special paint spray machines and robots demands accurate control of the amount of air exhausted from particular sections of the spray booth. In the normal booth it is difficult to control the amount of such extracted air because the underpart of the booth is a complete vacuum chamber with on or more exhaust fans connected to it in parallel.

8. The devices used to remove the paint overspray from the exhaust air are all derived from the principles used in the removal of dust from exhaust air in industrial processes, typified by the mixing of the dust with water introduced into the air or the device, or other such liquids in the same manner so as to trap the dust in the water and then allowing it to be removed by sedimentation in a separate sludge tank. The relatively clean water after this operation is returned for re-use in the device. Typical wet cleaning devices are Venturi Scrubbers, Wet Impingement Collectors, Wet Inertial or Baffle Separators, Wet Cyclonic Separators, Standing Wave Collectors and certain devices which combine two or more wetting or scrubbing actions.These different devices all have disadvantages in regard to self cleaning characteristics when applied conventionally in the bottom of a spray booth chamber. Typically the fixing means contribute to water build up and sedimentation problems. In addition they are a noise source adjacent to the operators in the spray booth.

9. Frequently the use of wet devices described above produce water elimination problems. The introduction of dewatering devices frequently reduces or prevents the possibility of constructing the booth with a high proportion of glass surfaces in the booth walls. The incorporation of a high proportion of glass in the walls has become occupationally desirable for the operators inside the booths and for equipment inspections to see what is being done, particularly by automatic machines, from the outside of the booth.

It is an object of the invention to seek to mitigate the adverse features of the prior art mentioned above.

Accordingly, the invention in one of its aspects provides apparatus for cleaning air of paint entrained therein, comprising a partition on one side of which in use there is a spray chamber in which the paint is entrained in the air and on the other side of which there is a cleaning chamber in which the air and paint are separated, air exhaust means connected with the cleaning chamber by an extraction duct for extracting air cleaned of paint from the cleaning chamber, and a conduit in the partition open only at both ends and one of which opens into the chamber and the other of which opens into, and is spaced from a boundary wall of, the cleaning chamber, the boundary wall being spaced from the partition at least adjacent the other end of the conduit, the other end having a smaller crosssectional area than that of the one end, and means to pass liquid cleaning medium over the partition through the conduit and into the cleaning chamber, the arrangement solely of the conduit with respect to the two chambers being such that in use of the apparatus the cleaning liquid forms a plurality of curtains through which paint laden air passes whereby the paint is separated from the air and becomes mixed with the cleaning liquid.

Accordingly, the invention in another of its aspects provides a paint spray installation such as a paint spraying booth for spray painting of automobile bodies, including apparatus as hereinbefore defined in the immediately preceding paragraph.

Using the invention it is possible to provide an enhanced efficiency of paint removal from air at a relatively low energy expenditure and noise genera tion as compared to prior devices.

The conduit may comprise a cylindrical tube, or may be polygonal in transverse cross-section, for example triangular or rectangular. In all these embodiments, the conduit provides a simple yet efficient apparatus for providing thorough mixing of cleaning liquid and paint-laden air, whereby the paint is transferred from the air to the water.

The conduit may include an internal baffle over which cleaning liquid can flow from the one to the other end. This arrangement provides for more points or positions at which the paint laden air penetrates the cleaning liquid and can thus enhance the cleaning action.

The conduit may have a boundary wall which at the other end may be turned inwardly to provide a flange and thus the smaller cross-sectional area.

Alternatively the boundary wall(s) of the conduit may converge from the one end to the other end to provide the other opening of smaller cross-sectional area. Both constructions are relatively simple, yet effective.

The one end of the conduit may be proud of the surface of the partition facing into the chamber. This provides a distinct sharp edge over which the cleaning liquid flows in use into the conduit, and this constructions, while relatively simple provides for efficient mixing of the paint-laden air and cleaning liquid.

The one end of the conduit may be adjustable in position in a direction transverse to the plane of the partition. This construction provides a relatively simple means for adjusting the depth of water flowing over the partition prior to entering the conduit at the one end without adjusting the height of the other end of the conduit above the boundary surface of the cleaning chamber. The adjustment may be effected by shims and/or screw jacks, for example three screw jacks round the periphery of a cylindrical tubular conduit.

The partition may be substantially horizontal; this provides for ease of passage of cleaning liquid thereover.

The conduit may have at least a part adjacent the other end which may be inclined with respect to the part thereof adjacent the one end, and the boundary wall of the cleaning chamber adjacent the other end ffay be arranged so that liquid and air exiting the other end in use may strike the boundary wall at substantially right angles. Alternatively, the whole of the conduit may be inclined with respect to the partition.

There may be drain means for draining cleaning liquid and entrained paint from the cleaning chamber.

There may be means to clean the liquid of paint and means to direct the cleaned water over the partition towards the conduit.

There may be means to flood cleaning liquid over the boundary wall of the cleaning chamber, which means may comprise the second - mentioned means of the immediately preceding paragraph. This construction provides a relatively simple way of providing for cleaning liquid circulation.

The drain means may be disposed at one or more sides of the cleaning chamber. Where the apparatus is in combination with a spray painting installation, the partition may provide a flood plate beneath a (perforated) floor of the installation and there may be a plurality of discrete, spaced, conduits in the flood plate. The conduits may be spaced longitudinally of the flood plate, or alternatively they may be spaced transversely of the flood plate. The latter arrangement provides for the flood plate itself to be formed from a plurality of modular flood plate sections assembled together and each of which may include a plurality of the conduits spaced apart transversely of the assembled flood plate, and each plurality of conduits may lead to a separate cleaning chamber.This construction provides for an efficient cleaning action with relatively little or no carry over of liquid with the air, and with low noise.

The or each conduit may be removable. This provides for relatively easy repair and/or maintenance.

Apparatus embodying the invention is hereinafter described, by way of example, with reference to the accompanying drawings.

Brief description of the drawings Figure 1 is part a perspective view of a paint spray installation in the form of a paint spray booth for spray painting car bodies, including apparatus according to the invention; Figure 2 is an enlarged sectional view of a conduit of Figure 1; Figure 3 is a sectional view to the same scale as Figure 2 of a further embodiment of conduit; Figure 4 is to a larger scale still, a perspective view of the one end of the conduit of Figure 3; Figure 5 is a sectional view showing a further embodiment of conduit to the same scale as that of Figures 2 and 3; Figure 6 is to a larger scale than Figure 3, a schematic perspective view from the one end of the conduit of that Figure;; Figures 7, 8 and 9 show schematic perspective views of other embodiments of conduit, that of Figure 9 being similar to that of Figure 5 but having its boundary walls converging over their whole length; Figures 10, 11 and 12 are respectively side elevational views of further embodiments of conduit according to the invention; Figure 13 isaside elevational view of a yet further embodiment of conduit according to the invention; and Figures 14 and 15show respectively a longitudinal sectional sectional view and a plan view of flood sheets of a paint spray booth embodying the invention.

In the drawings like parts are referred to by like numerals.

Referring firstly to Figures 1 and 2 of the drawings, the apparatus 1 shown therein has a partition on the form of a flood sheet 2 which is substantially parallel to and below a perforated floor (not shown) of the paint spray booth on which floor operatives (also not shown) stand to paint objects, in this case car bodies, as they move continuously or intermittently :hrough a spray painting chamber 3. The flood sheet 2 is spaced above a drain sheet 4 which forms a Joundary wall of a cleaning chamber 5.In the flood sheet 2 there is a plurality of conduits spaced along the longitudinal centre line of the flood sheet each conduit comprising a right cylindrical tube 6 which is open at one end 7 which projects about 3cm to 6cm above the flood sheet 2, to form a lip 7a, and which is open at the other end 8 which is spaced above the drain sheet 4 and has a smaller cross-sectional area than the one end 7. The other end 8 is formed by turning in the material of the tube to form a flange 9 as shown.

In the embodiment shown, the distance OA, the diameter of the one end 7, is a maximum of 400mm, while OB, the diameter of the other end 8 is a maximum of 300mm. The distance "C" of the other end 8 from the drain sheet 4 is a maximum of 300mm, while centre-to-centre spacing "D", of adjacent tubes 6 is a maximum of 1 M.

In use to clean air laden with paint particles exciting the chamber 3 cleaning liquid in the form of water and a "killing" agent flow from circulating means adjacent the side walls of the chamber 3 across the flood sheet 2 to the tubes 6. Because of the lip 7a, a "pond" of liquid shown by a dashed line above the flood sheet 2 builds up and this then flows over the edge of each tube 6 at the one end 7, which edge is a sharp edge, into the tubes with the air and paint.The air, paint and liquid mix in the respective tubes where there is a first tubulent mixing at X, and mix again in the cleaning chamber Sat R, Sand T externally of each tube 6 below the other end 8 the water entrapping the paint particles and flowing across the drain sheet 4 to drainage means 10 in the form of channels, whence it is passed to cleansing means to remove the paint prior to being recirculated to the paint spray chamber 3 with make-up liquid. The air cleaned of paint, passes out of the apparatus to one or more exhaust stacks which could be at one or both sides or at the end(s) of the apparatus 1.Using a cleansing liquid flow rate of 300 1/mien per metre length of booth and with a pressure drop of 1100 Pascal across each tube 6 a cleaning efficiency of 99.87% has been achieved, in other words 99.87% of all paint overspray carried in the air has been removed from the air and transferred to the cleaning liquid.The pressure drop combined with the turbulance of air/paint and cleaning liquid causes the efficient entrapment of the paint in the cleaning liquid the embodiment of apparatus 20 Figures 3 and 4 is similarto that of Figures 1 and 2, except that the tube 21 tapers or converges as a whole from the one end 7 to the other end 8 and there is in inner tube 22 held internally of the main tube 21 by bridges or channels 23 connected to the flood sheet, forming a toroidal path 24 and which have upstanding lips 25 standing above the level of the flood sheet 2 like the lips 7a of the main tube 21. This arrangement allows for more cleaning liquid curtains in the tube 21 and externally thereof in the cleaning chamber 5.The cleaning liquid flows over the edge of the main tube, like in Figure 1, and also over the lips 25 of the bridges 23 and of the inner tube 22 so that there is a liquid curtain formed inside the inner tube and between the inner and main tubes. Figure 5 shows a modification in which the tube 6 of Figures 1 and 2 has a central partition 30 supported from the flood plate 2 by a bridge or channel 31 which has upstanding lips 32 over which cleaning liquid flows to provide multi-curtains on both sides of the partition 30 and hence a plurality of positions at which penetration or mixing of the air and cleaning liquid mix.

The tubes may not be cylindrical as described.

They may be triangular 40 (Figure 7) or rectangular 50 (Figure 8) with an inwardly directly flange 9 at the other end 8 to provide the smaller cross-sectional area, or rectangular with converging boundary walls 70, Figures 6 and 9, the tube 70 of Figure 6 having an inner tube 71 similar to that of Figures 3 and 4 and functioning in a similar manner while that of Figure 9 has a partition 72 similar to that of Figure 5 and functioning in a similar manner.

The tubes may not be upright in other words with their longitudinal axis substantially at 90 to the plane of the flood sheet. Figure 10 shows a tube 80 which is wholly inclined to the vertical, while Figures 11 and 12 show embodiments in which only part 81 of the tube 90 or 100 carrying the other end 8 is inclined. In every embodiment, though, the plane of the other end 8 lies generally parallel to the plane of the immediately adjacent part of the drain sheet 4. In this way, the air, cleaning liquid mixture exiting the other end in use strikes the adjacent part of the drain sheet 4 with considerable velocity so enhancing ultimate separation of the liquid and air which can then pass to their respective, separate, destinations.

In every embodiment the or each tube can be removable, for cleaning or repair, or adjustable in position in relation to the flood sheet, for example by shims 110, Figure 13. Also, the upper (as viewed) edge can be adjusted in height without altering the distance "C", Figure 1, by using screw jacks 112 in this case three for a cylindrical tube, two of which are shown and which are fixed to a sleeve or ring 113 movable with respect to the rest of the tube 6.

In every embodiment efficient cleaning of the air is achieved in apparatus 1 which occupies only about 1 metre of space from the base of the spray painting chamber 3, (the perforated floor) to the drain sheets 4 and in which the noise level is acceptable. The low height ensures that expensive, deep, foundations or pits are not required, and the whole booth can be of relatively low height as compared with existing booths. Although a sharp edge of the tubes at the one end 7 has been described, it will be understood that a smooth edge could be used. Also the one end 7, whether sharp or smooth, may be flush with the flood sheet 2 instead of standing proud of it as shown.

Figures 14 and 15 show an embodiment 200 in which the tubes 6 be in rows which extend transversely to the length of the booth. In this case, the flood sheet 2 and its tubes 6 could be formed as a series of modules 201,202,203 etc each with an upstanding wall 204 at opposite longitudinal ends by which one module is secured to another. The depth of cleaning liquid circulated across the flood sheets is the same along the whole length of the booth at the walls, so any variation in height between individual modules is irrelevant. The cleaning liquid will always flow to the tubes 6. The exhaust air turns through approximately 900 as shown by the arrows "Y" in its passage from the cleaning chamber, so de-celerating rapidly and threby reducing the likelihood of liquid-spray carry over.All the embodiments of tube described with respect to Figures 1 to 13 are, it will be understood, applicable for the embodiment of Figures 14and 15.

It will also be understood that the invention may be applicable to a spray painting chamber for a single object, in which case there may be only a single tube, rather than a plurality as shown and described. Also, in every embodiment, the drain sheets 4 may be flooded with cleaning liquid, either as a film or sheet orto a certain depth to provide a pond. Also, there may be means to prevent or hinder build up of sludge deposits on the flood sheets. This means may comprise a jet or jets of water or other liquid which is or are directed into the water flooding over the sheets, the jet(s) preferably entering the water from below the level of the flood water. This means may be adjustable to control the flow of water from the jet(s).

Claims

1. Apparatus for cleaning air of paint entrained therein, comprising a partition on one side of which in use there is a spray chamber in which the paint is entrained in the air and on the other side of which there is a cleaning chamber in which the air and paint are separated, air exhaust means connected with the cleaning chamber by an extraction duct for extracting air cleaned of paint from the cleaning chamber, and a conduit in the partition open only at both ends and one of which opens into the chamber and the other of which opens into, and is spaced from a boundary wall of, the cleaning chamber, the boundary wall being spaced from the partition at least adjacent the other end of the conduit the other end having a smaller cross-sectional area than that of the one end, and means to pass liquid cleaning medium over the partition, through the conduit and into the cleaning chamber, the arrangement solely of the conduit with respect to the two chambers being such that in use of the apparatus the cleaning liquid forms a plurality of curtains through which paint laden air passes whereby the paint is separated from the air and becomes mixed with the cleaning liquid.

2. Apparatus according to Claim 1, the conduit comprising a cylindrical tube.

3. Apparatus according to Claim 1, the conduit being polygenal in transverse cross-section.

4. Apparatus according to Claim 3, the conduit being triangular in transverse cross-section.

6. Apparatus according to Claim 1, the conduit being rectangular in transverse cross-section.

6. Apparatus according to any of Claims 2 to 5, the conduit including an internal baffle over which cleaning liquid can flow from the one to the other end.

7. Apparatus according to any preceding Claim, in which the conduit has a boundary wall which at the other end is turned inwardly to provide the smaller cross-section.

8. Apparatus according to any of Claims 1 to 6, in which the boundary walls of the conduit converge(s) from the one end to the other end to provide said other opening of smaller cross-sectional area.

9. Apparatus according to any one of the preceding Claims, in which the one end is proud of the surface of the partition facing into the chamber.

10. Apparatus according to any of Claims 1 to 9, in which the one end is flush with the surface if the partition facing into the chamber.

11. Apparatus according to Claim 9 or Claim 10, the one end of the conduit providing a sharp edge over which the cleaning liquid flows.

12. Apparatus according to any preceding Claim, in which the one end of the conduit is adjustable in position in a direction transverse to the plane of the partition.

13. Apparatus according to any preceding Claim, the partition being substantially horizontal.

14. Apparatus according to Claim 13, the conduit having at least a part adjacent the other end which is inclined with respect to the part thereof adjacent the one end, the boundary wall of the cleaning chamber adjacent the other end being arranged so that liquid and air exiting the other end in use strike the boundary wall at substantially rightangles.

15. Apparatus according to Claim 14, the whole of the conduit being inclined with respect to the partition.

16. Apparatus according to any preceding Claim, including drain means for draining cleaning liquid and entrained paint from the cleaning chamber.

17. Apparatus according to Claim 16, including means to clean the liquid of paint and means to direct the cleaned water over the partition towards the conduit.

18. Apparatus according to any preceding Claim, including means to flood cleaning liquid overthe boundary wall of the cleaning chamber.

19. Apparatus according to Claim 18, the means comprising the second mentioned means of Claim 17.

20. Apparatus according to any of Claims 16 to 19, the drain means being disposed at one or more sides of the cleaning chamber.

21. A paint spray installation such as paint spraying booth for spray painting of automobile bodies, including apparatus according to any preceding Claim.

22. A paint spray installation according to Claim 21, in which the partition comprises a flood plate of the apparatus and in which the cleaning apparatus includes a plurality of spaced conduits in the flood plate.

23. A paint spray installation according to Claim 22, in which the conduits are spaced longitudinally of the flood plate.

24. A paint spray installation according to Claim 22, in which the spaced conduits are spaced transversely of the flood plate.

25. A paint spray installation according to Claim 24, in which the flood plate is comprised of a plurality of modular flood plate sections assembled together and each of which includes a plurality of the conduits spaced apart transversely of the assembled flood plate, each plurality of conduits leading to a separate cleaning chamber.

26. A paint spray apparatus according to any of Claims 21 to 25, in which the or each conduit is removable.