GB2140707A - Impingement separator - Google Patents

Abstract

An impingement separator comprises an elongate tube 11 of rectangular cross-section, made of paper or cardboard and capable of being folded flat for storage. In use an array of such tubes forms the back wall of a spray-painting booth from which air is sucked, passing into each tube by inlets 18 and out through outlets 19. Inlets 18 and 19 may be staggered laterally and/or longitudinally of the tube to deflect the air flow, or the tube magy be internally divided by walls having holes staggered relative to the inlets and outlets. <IMAGE>

Description

SPECIFICATION Gas filter This invention relates to gas filters for use in spray painting booths.

British Patent 1507422 illustrates a first known form of gas filter comprising three interconnected sheets of stiff paper or the like which are folded in the manner of the bellows of an accordian. The three sheets are perforated and are so arranged that gas flowing through the filter from the front to the rear must follow a non-linear path whereby particles contaminating the gas impinge upon, and are retained by the surface of the sheets.

Such filters are advantageous in that they can be folded substantially flat for transportation and storage, and when so folded'occupy a volume which is only fractionally larger than the volume of material used to form the filter.

However, such filters are disadvantageous in a number of respects. Firstly such filters are relatively expensive to manufacture particularly in that relatively large areas of material (paper or the like) are used in their construction. Moreover, the apparatus which supports the filter should include means for holding the filter in tension so that the folds of the filter are opened and the filter occupies its designed maximum area. Thus in order to minimise the complexity of the installation of the filter it will generally be preferable to use filters of large area thus minimizing the ancillary apparatus necessary for supporting the filter.However, in many applications only parts of the area of the filter are subjected to high concentrations of contamination, and thus these areas will become saturated, and thus unsuitable for continued use, well before the remainder of the filter is saturated. However, since the filter is a single entity it must be replaced in its entirety when any part of it is no longer capable of satisfactory filtration.

In another known form of a gas filter, as disclosed in New Zealand Patent 915200, the replaceability problem of the first known filter has been minimised. The second known form of filter is an elongate, hollow, relatively rigid unit of rectangular cross-section, sufficient units being positioned side-by-side to constitute a filter of the required overall area. The front and rear walls of the filter units are perforated and internally each filter unit includes a plurality of corrugated paper baffles. However, while affording the possibility of replacement of smaller parts of the overall filter than is the case with the first known filter, the second known filter suffers from the very great disadvantage that it cannot be folded flat, or cannot be otherwise compressed, for transportation and storage.Thus transportation and storage of the second known form of filter entails transportation and storage of components, the volume of which is composed mainly of the internal void of the filter. Clearly any folding or compression of the box structure of each filter unit would destroy the internal corrugations thus rendering the filter subsequently unusable. Moreover it would appear that the second known form of filter is relatively complex, and therefore expensive to manufacture on a mass production basis.

It is an object of the present invention to provide a simple and convenient gas filter, wherein the disadvantages of the above-described known arrangements are minimised.

A gas filter according to the invention comprises, an elongate hollow element of rectangular cross-section having apertures in opposite walls thereof whereby gas being filtered can flow through the element, the element being capable of being folded substantially flat for transportion and storage, and when required restored to their rectangular configuration, by way of hinge-like movement at its corners and, said filter being such that the gas flow therethrough in use is deflected within the filter.

Preferably said hinge-like movement at the corners of the element is movement in the manner of a parallelogram linkage.

Alternatively a pair of opposite walls of the element include longitudinally extending fold lines and when being folded substantially flat or being subsequently restored the element undergoes hinge-like movement at its corners and about said fold lines.

Preferably said filter includes an internal baffle.

Desirably said internal baffle includes a wall which divides the interior of the hollow element into a pair of chambers which communicate by way of apertures in said wall.

Conveniently said internal baffle is parallel to and spaced from said opposite walls of the element.

Alternatively, where said opposite walls include said longitudinal fold lines, said internal baffle extends diagonally with respect to the rectangular cross-section of the element.

Preferably the apertures in a first of the walls of the element are offset with respect to the apertures in the next adjacent wall of the element, thereby ensuring that the gas flow through the element is deflected. Conveniently said apertures are offset from one another both in the direction of the length of the element and at right angles to the length of the element.

In the accompanyings drawings, Figure 1 is a diagrammatic front elevational view of the rear wall of a spraybooth incorporating a filter in accordance with one example of the present invention; Figure 2 is a diagrammatic perspective representation of a filter element of the filter seen in Figure 1; Figure 3 is a front elevational view of a more practical embodiment of the filter ele ment of Figure 2; Figure 4 is a sectional view on the line 4-4 in Figure 3; Figure 5 is a sectional view to an enlarged scale of the element seen in Figure 3, but in an almost flat configuration; Figure 6 is a view similar to Figure 3 of a modification thereof; Figure 7 is a cross-sectional view of a filter element in accordance with a second example of the present invention; Figure 8 is a view in the direction of arrow A in Figure 7;; Figure 9 is a view similar to Figure 5 but of the element of Figure 7; Figure 10 is a diagrammatic representation of a modification of the element of Figure 7; Figure 11 is a diagrammatic representation of a further modification of the element of Figure 7; Figure 12 is a diagrammatic representation of a still further modification; Figure 13 is a diagrammatic representation of the element of Figure 12 in a collapsed condition; and Figure 14 is a diagrammatic representation of a yet further modification.

Although the examples of the present invention are described herein with reference to use in a spray painting booth it is to be understood that examples of filters in accordance with the present invention may be utilized in other environments.

Referring first to Figure 1 it can be seen that the rear wall of the spraybooth is composed of a plurality of filter elements 11 of elongate form arranged with their length extending vertically. The upper and lower ends of each of the elements 11 are received in transversely extending channel members 12, 13 which support the filter elements 1 1, and the side edges of the filter elements 11 are held in abutment with one another by virtue of the elements 11 being trapped between end frame members 1 4, 1 5. Preferably at ieast one of the frame members 14, 15 is detachable to facilitate insertion and removal of elements 11.

Each of the elements 11 is a filter in its own right, but the combination of elements 11 with the supporting structure 12, 13, 14, 15 constitutes a large area filter forming a rear wall of the paint spraying booth. An operator stands in front of the rear wall and operates the spray gun towards the rear wall.

Behind the rear wall is an enclosure from which air is drawn by means of a fan. Thus air is drawn through the wall from the region where spraying is taking place, and thus air contaminated with paint droplets or particles is drawn through the wall of filter elements 11.

Each of the filter elements can take a number of different forms, Figure 2 illustrating the basic configuration. It can be seen from Figure 2 that each filter element 11 is elongate, hollow, and of rectangular cross-section. It is not clear from Figure 2 how the element 11 is constructed, and reference to the remaining Figures will illustrate a number of different methods of construction.

The front wall 16 of each element 11 is formed adjacent one vertical edge with a row of apertures 18 while the rear wall 17 is formed with a similar vertical row of apertures 1 9 disposed adjacent the opposite edge of the element. It will be recognised therefore that air drawn through the element 11 enters the element 11 by way of the apertures 18 and leaves the element by way of the apertures 19. In passing through the element the air flow is deflected and paint particles or dropiets carried by the air flow through the apertures 1 8 will be deposited on the inner surface of the rear wall 17 so that the air flow passing out through the apertures 19 is substantially free of contaminating paint droplets or particles.

It will be recognised that the element 11 occupies a significant volume when in an operative configuration.

It is however vital that the volume of the element 11 is minimised for transportation and storage. Thus the element is capable of being folded flat substantially as shown in Figure 5 by pressing a diagonally opposed pair of vertical edges or corners of the element towards one another. The four corners of the element thus bend, or move in a hinged manner, the four faces of the element 11 moving in the manner of the elements of a parallelogram linkage. In this manner the element 11 can be rendered substantially flat and of course will then occupy a volume which is only marginally greater than the volume of material used in its construction.

The element 11 can be formed from a wide range of materials but conveniently is formed from a stiff paper or light card.

Figure 4 shows the formation of an element 11 a similar to the element 11 of Figure 2 from a single sheet of material. The starting sheet is of rectangular form and is stamped to produce apertures 18 which will be in the front wall 16 of the element 11 a and apertures 19 which will be in the rear wall 17 of the element. The stamping of the apertures 19 is arranged to leave the material still attached to the sheet to form a partcircular tongue 19a. The sheet is then folded about three parallel lines to form the element 11 of rectangular cross-section and the tongues 19 are bent downwardly internally of the element 11 a and are secured to the adjacent side wall of the element 11 a in any convenient manner, for example by means of an adhesive or by stapling.

It is the element 11 a shown in Figures 3 and 4 which is illustrated in Figure 5 in its collapsed configuration.

In the elements 11 and 11 a illustrated in Figures 1 to 5 the apertures 18 in the front wall and the apertures 19 in the rear wall are offset from one another in a direction at right angles to the length of the element. As an alternative, although preferably in addition to this latter offsetting the apertures 18, 19 can also be offset from one another in the direction of the length of the element. Figure 6 illustrates an element 11 b where the apertures 19 and the apertures 18 are offset from one another both in the direction of the length of the element 11 b and transverse to the length of the element.

As mentioned previously the simple rectangular crosssection configuration is a basic configuration for the filter element. However, a more practical and in many applications more preferable form of filter element ?s illustrated in Figures 7, 8 and 9 wherein the element llc has an internal wall 21 parallel with the external front and rear walls 16, 17. The internal wall 21 divides the element 11 c into front and rear vertically extending compartments which communicate by way of apertures 22 provided in the wall 21. As is evident from Figures 7 and 8 the apertures 18 in the front wail 16 are aligned with the apertures 19 in the rear wall 17 but the apertures 22 in the internal wall 21 are offset from the apertures 18, 19 in a direction transverse to the length of the element.Figure 8 shows a minor, preferential modification, in which the apertures 22 of the wall 21 are also offset from the apertures 18, 19 in the direction of the length of the element 11 C.

The presence of the internal wall 21 does not prevent the collapse of the element in the parallelogram linkage manner As can be seen from Figure 9 the element 11 c can be folded substantially flat, it being understood that Figure 9 does not show the completely flat configuration in the interests of clarity.

The element 11 c again is formed from a single sheet of material which has first been stamped to provide the apertures 18. 19, 22 in the appropriate places. As is evident from Figure 7 the sheet is bent about six parallel fold lines and adhesive or staples or some other convenient form of securing is provided where appropriate, for example at 23 and 24 in Figure 7. It will be recognised that when the sheet is stamped to produce the apertures 22 then a similar approach to that used in Figure 4 can be used in that the material stamped from the apertures 22 can remain attached to the sheet and can form integral securing tongues whereby one end of the internal wall 21 is anchored in position by means of the adhesive or the like at 24.

Figure 10 illustrates diagrammatically a modification of the element 11 c wherein the front and rear walls 16, 17 have their respective apertures 18, 19 disposed along the centre lines of the walls and the internal wall 21 has two rows of apertures 22, each row being adjacent a respective vertical edge of the wall 22. Since Figure 10 shows the walls of the element by means of a single thickness line, gaps have been left in the drawing for clarity where sections of walls overlap. It will be recognised that there will not be gaps at this point in the practical realisation of the element.

Figure 11 illustrates the manner in which a single sheet may be folded to provide front and rear walls 16, 17 and a pair of parallel internal walls 21, 21 a (again where wall sections overlap at the sides of the element gaps have been left for clarity in Figure 11). The arrangement of apertures in the walls 16, 17, 21, 21 a can take any suitable form provided that the apertures in adjacent walls are offset laterally and/or lengthwise of the element to ensure deflection of the air flow.

Figures 12 and 13 illustrate an element 11 e similar to the element 11 c of Figure 7 but wherein the internal wall 31 is located diagonally rather than parallel to the front and rear walls of the element. The diagonal internal wall 31 prevents collapse of the element in the manner of a parallelogram linkage but the element 11 e can be folded flat for transport and storage by appropriate bending of the end walls of the element, as shown in Figure 13. Thus each end wall has a longitudinal fold line whereby the wall bends to Vshape as the element is collapsed, the walls 16, 17 hinging about their junction with the wall 31 to lie substantially in facial contact with the wall 31.It will be understood that the side walls can bend about their londitudinal fold line either such that the apical edges so formed lie between the wall 31 and the front and rear walls 16, 17 respectively, or lie externally in which case the collapsed thickness of the element 11 e is reduced but its collapsed area is increased by comparison with the collapsed condition where the apical edges are internal.

It will be recognised that each of the alternative elements described above has the advantage that it can be folded substantially flat for transportation and storage, and additionally can be used with a number of substantially identical filter elements to form a large filter panel of the kind shown in Figure 1. Of course where only regions of the filter panel are subject to heavy contamination then the elements in those regions can be replaced without the need to replace the whole of the filter panel. Moreover, if part of a filter element is subject to heavy contamination then that particular filter element can, if desired, be inverted to change the region of the element which is undergoing heavy contamination.

Although it is extremely desirable for the elements to separate from one another, it will be understood that an interconnected series of similar elements can be produced by folding a single sheet of appropriate material. Such an arrangement is illustrated in Figure 1 4 wherein three elements 11 d, each having front and rear walls and an internal wall are formed by appropriate folding of a single sheet of material. As with Figures 10 and 11 the wall thicknesses are shown by a single line in Figure 14 and thus gaps are left for clarity in the drawing where side walls overlap.

Again the positioning of apertures will be determined by the application which the filter element is to serve. However, the aperture arrangement of Figure 7 or Figure 10 could be utilized if desired. While the arrangement illustrated in Figure 14 does not exhibit the advantage of individual replaceability of elements it nevertheless does provide a construction which can be folded flat for transportation and storage. In addition of course it would not be essential to provide the whole of the panel in one continuous series of elements 11 d and the panel could be provided by a plurality of sections each of which contains two or more integrally formed elements 11 d. Thus although each individual element would not readily be replaceable, discrete sections of the overall panel would be replaceable without the need to replace the whole filter panel.

Claims (16)

1. A gas filter comprising an elongate hollow element of rectangular cross-section having apertures in opposite walls thereof whereby gas being filtered can flow through the element, the element being capable of being folded substantially flat for transportion and storage, and when required restored to their rectangular configuration, by way of hinge-like movement at its corners and, said filter being such that the gas flow therethrough in use is deflected within the filter.

2. A filter as claimed in claim 1 wherein said hinge-like movement at the corners of the element is movement in the manner of a parallelogram linkage.

3. A filter as claimed in claim 1 wherein a pair of opposite walls of the element include longitudinally extending fold lines and when being folded substantially flat or being subsequently restored the element undergoes hinge-like movement at its corners and about said fold lines.

4. A filter as claimed in any one of claims 1 to 3 wherein said filter includes an internal baffle.

5. A filter as claimed in claim 4 wherein said internal baffle includes a wall which divides the interior of the hollow element into a pair of chambers which communicate by way of apertures in said wall.

6. A filter as claimed in claim 4 or claim 5 where dependent upon claim 2 wherein said internal baffle is parallel to and spaced from said opposite walls of the element.

7. A filter as claimed in claim 4 or claim 5 where dependent upon claim 3 wherein said opposite walls include said longitudinal fold lines, said internal baffle extends diagonally with respect to the rectangular cross-section of the element.

8. A filter as claimed in any one of claims 1 to 7 wherein the apertures in a first of the walls of the element are offset with respect to the apertures in the next adjacent wall of the element, thereby ensuring that the gas flow through the element is deflected.

9. A filter as claimed in claim 8 wherein said apertures are offset from one another both in the direction of the length of the element and at right angles to the length of the element.

10. A gas filter substantially as hereinbefore described with reference to Figures 1 to 5 of the accompanying drawings.

11. A gas filter as claimed in claim 10 modified substantially as hereinbefore described with reference to Figure 6 of the accompanying drawings.

12. A gas filter substantially as hereinbefore described with reference to Figures 7 to 9 of the accompanying drawings.

13. A gas filter as claimed in claim 12 modified substantially as hereinbefore described with reference to Figure 10 of the accompanying drawings.

14. A gas filter as claimed in claim 1 2 modified substantially as hereinbefore described with reference to Figure 11 of the accompanying drawings.

15. A gas filter substantially as hereinbefore described with reference to Figures 12 and 13 of the accompanying drawings.

16. A gas filter substantially as hereinbefore described with reference to Figure 14 of the accompanying drawings.