A FILTER FRAME

Abstract: The present invention relates to a filter frame (10, 12, 14 and 16) having an interior which contains a granular filter medium (22) when the filter frame is in use, a first main aperture across which a first screen part (18) extends, and a second main aperture across which a second screen part (20) extends, so that a fluid which is to be filtered can pass into the frame interior through one of the screens (18 or 20) and out through the other (20 or 18). The filter frame is provided with further aperture means (24, 26) to enable such a medium (22) to be removed from and/or fed into the interior of the filter frame (10, 12, 14 and 16) whilst the latter is installed for use, without the need to dismantle it.

Description: A filter frame The present invention relates to a filter frame having an interior which contains a granular filter medium when the filter frame is in use, a first main aperture across which a first screen part extends, and a second main aperture across which a second screen part extends, so that a fluid which is to be filtered can pass into the frame interior through one of the screens and out through the other. The granular filter medium may for example comprise activated carbon. This has the property of absorbing gaseous pollutants for example, so that air which is passed through the filter frame has such pollutants filtered out of it. After an extended period of use, the granular filter medium may be become saturated with the substance which it is intended to absorb, or so nearly saturated that the filter frame and its contents become ineffective. It is therefore then desirable to replace the filter medium. Hitherto, this has been done by removing the filter frame from its installed position, dismantling it at least to some degree, removing the used granular filter medium, replacing it with fresh granular filter medium, re- assembling the frame and finally re-installing it. A disadvantage of this procedure is the time and labour involved, and sometimes the difficulty it creates in handling a filter medium which has been absorbing a toxic or otherwise hazardous substance. The present invention seeks to provide a remedy. Accordingly a first aspect of the present invention is directed towards a filter frame having the construction set out in the opening paragraph of the present specification, in which the filter frame is provided with further aperture means to enable such a medium to be removed from and/or fed into the interior of the filter frame whilst the latter is installed for use, without the need to dismantle it. The screens are preferably on opposite main faces of the filter f ame. It is desirable for the further aperture means to be constituted by a lower aperture to facilitate removal of such a medium, and an upper aperture to facilitate filling of the filter frame with such a medium. The filter frame may be generally quadrilateral, or it may be composed of a combination of interconnected quadrilateral parts, the combination having such further aperture means common to all the quadrilateral parts, the interiors of the latter being in communication with one another. In one useful configuration, four four-sided filter cells are connected together to form a combination which is of a hollow cylindrical quadrilateral-section form. The further aperture means may be provided with at least one readily removable cap. This may so fit the further aperture means as to seal the latter. According to a second aspect of the present invention, there is provided extractor means for removing such a medium from the interior of a filter frame having a construction in accordance with the first aspect of the present invention, comprising a passageway having one end which is insertable through or attachable to the further aperture means, collector means at the other end of the passageway, and suction means to draw air from the filter frame interior to facilitate the flow of such a medium from the filter frame interior into the collector means. The collector means may comprise an air-permeable bag. The extractor means may be provided with filter means downstream of the bag to remove any toxic or other hazardous substances form the air expelled by the suction means. Weighing means may be provided to weigh the contents of the collector means, thus to provide an indication of when the collector means are full. Automatic cut-off means may also be provided to switch off the suction means directly a predetermined value, corresponding to full collector means, is indicated by the weighing means. According to a third aspect of the present invention there is provided feed means for filling a filter frame having a construction in accordance with the first aspect of the present invention, comprising a passageway having one end which is insertable through or attachable to the further aperture means of the filter frame and another end connected to a blower which directs an air stream through the passageway into the filter frame interior when the feed means are in use, and entraining means connected to the passageway to enable such a medium to be entrained in the air stream and thus fed into the filter frame interior. The entraining means may comprise wall means defining a generally circular cavity containing a wheel device with a plurality of paddles spaced apart around its axis of rotation and extending from a hub of the wheel device outwardly as far as the inner periphery of the wall means, with an inlet and an outlet at positions spaced apart around the wall means, preferably diametrically opposite one other, whereby rotation of the wheel device enables material to pass from the inlet to the outlet. There may be a seal formed between the paddles and the wall means to inhibit air from the blower escaping through the circular cavity. The inlet may be positioned above the outlet so that a granular filter medium may be fed via the generally circular cavity to the said passageway by gravity feed. According to a fourth aspect of the present invention there is provided feed means for filling a filter frame having a construction in accordance with the first aspect of the present invention, comprising coaxial tubes through one of which is fed such a medium and through the other of which can pass air from the filter frame interior during such filling. This is particularly useful in conjunction with feed means in accordance with the third aspect of the present invention, because it enables dust in the filter frame interior to be collected as the latter is being filled with the granular filter medium. Blocking means may extend across that passageway provided by the coaxial tubes through which passes air from the filter frame interior, to inhibit granules of the filter medium passing into that passageway. The latter passageway may have an end further from the filter frame closed by dust-trap filter means to trap any dust or other fine particles from the filter frame interior. Preferably the dust-trap filter means comprise an air-permeable bag. In addition it may have further filter means for removing any toxic or hazardous pollutants or contaminants from the filter frame interior. Suction means may also be provided to draw air from the filter frame interior. A problem encountered in the filling, or the emptying and re-filling of the filter frame, is spillage of the filter medium. A fifth aspect of the present invention seeks to provide a remedy. Accordingly, the fifth aspect of the present invention is directed towards a filter frame having an interior which contains a granular filter medium when the filter frame is in use, a first main aperture across which a first screen part extends, and a second main aperture across which a second screen part extends, so that a fluid which is to be filtered can pass into the frame interior through one of the screens and out through the other, in which the filter frame is provided with further aperture means to enable such a medium to be removed from and/or fed into the interior of the filter frame, whilst the latter is installed for use, without the need to dismantle it, in which the further aperture means comprises at least one tube. The interior of the tube is preferably longer than it is wide. The tube may be L-shaped. It has been found that a granular medium inside a tube will tend to pile up at an angle of about 45° to the horizontal. Therefore, if a filter frame made in accordance with the fifth aspect of the present invention is held such that the tubular further aperture means extends in a generally horizontal direction. Thus, if the tubular further aperture means is longer than it is wide as regards its interior, it will inhibit the likelihood of spillage from the filter frame when the latter is being filled or re-filled. This reduces wastage and dirt. It is desirable for the further aperture means to be constituted by a lower tubular aperture to facilitate removal of such a medium, and an upper tubular aperture to facilitate filling of the filter frame of such a medium, the tubes of both apertures, so far as their interiors are concerned, being longer than they are wide. The or each aperture tube may be provided with a stopper or cap having a portion which fits closely into the interior of the tube of the aperture. That portion may be of the same length as the interior of the tube. It is particularly desirable that at least the lower aperture should be provided with such a stopper or cap. this will reduce the likelihood of any voids being formed within the filter frame. The upper aperture may be provided with a cap comprising a first part having the same shape and dimensions as an interior cross-section of the aperture tube, a second part which is wider than the said interior to be able to effect total closure thereof, and a spring connecting the first and second parts together. The spring may, for example, be a helical spring. Preferably, the aperture tube or tubes are straight . The present invention also extends to a method of emptying a granular filter medium from a filter frame interior. It also extends to a method of filling a filter frame with a granular filter medium. According to a sixth aspect of the present invention, there is provided feed means for use in filling a filter frame having a construction in accordance with the first aspect of the present invention, comprising a hopper or other reservoir which serves to hold such a medium, and at least an inlet thereto which is sealable by a ball valve. The ball of the ball valve may tend to be seated in a sealing position by means of gravity. According to a seventh aspect of the present invention, there is provided feed means for use in filling a filter frame having a construction in accordance with the first aspect of the present invention, comprising a passageway which is connected to the filter frame when in use and which serves to feed such a medium into the filter frame, and a blower connected to the passageway to create a stream of fluid flowing through the passageway towards the filter frame, and a constant flow device connected between the blower and the passageway to maintain a substantially constant flow of fluid in the passageway irrespective of the pressure therein. In the second aspect of the present invention, in which the collector means comprise an air-permeable bag, the latter may be held in place by quick-release means. The latter may comprise two generally frusto-conical rings one of which can be nested in the other, whereby the mouth of the bag can be held between the rings, in a quick- release manner. Examples of a filter frame, feed means, and extractor means made in accordance with the various aspects of the present invention are illustrated in the accompanying drawings in which: Figure la shows a perspective view of a filter frame in accordance with a first aspect of the present invention; Figure lb shows a perspective cross-sectional view of the filter frame shown in Figure lb; Figure 2 shows an alternative construction of filter frame enclosed within a box; Figure 3 is an elevational diagrammatic view of a filter frame and extractor means connected thereto; Figure 4 is an elevational diagrammatic view of a filter frame and feed means connected thereto; Figure 5 is an elevational diagrammatic view of a modification to the feed means shown in Figure 4; Figure 6 shows entraining means of the feed means of Figure 4 on a larger scale; Figures 7 and 8 show respective modified forms of filter frames; Figure 9 is a diagrammatic sectional view of a filter frame in a plane which is generally parallel thereto, the frame being in accordance with the fifth aspect of the present invention; Figure 10 shows, on a larger scale, details of a lower part of the filter frame shown in Figure 9, filled with a granular filter medium and being provided with a closure stopper or cap; Figure 11 shows, on the same scale as Figure 10, an upper part of the filter frame shown in Figure 9, again filled with a granular filter medium and again provided with a closure stopper or cap; Figure 12 shows that part of the filter frame shown in Figure 11, with the closure cap or stopper in place; Figure 13 is an elevational diagrammatic view of a modification to the feed means shown in Figure 4; Figure 14 is an elevational diagrammatic somewhat exploded view on a larger scale of part of a modification of the extractor means shown in Figure 3; and Figure 15 is a further elevational diagrammatic view of a further modification of the extractor means shown in Figure 3. The filter frame shown in Figures la and lb comprises two elongate strip plates 10 and 12. Respective ends of the strip plates 10 and 12 are connected to opposite ends of a C-sectioned elongate frame part 14. The opposite ends of the strip plates 10 and 12 are correspondingly connected to an opposite C-sectioned frame part 16. The concave sides of the parts 14 and 16 face towards one other, and the ends of the strip plates 10 and 12 are rounded so as to be flush with the outer surfaces of the parts 14 and 16. The plates 10 and 12 together with the parts 14 and 16 thereby constitute a generally rectangular frame. The depth of the frame is determined by the width of the strips 10 and 12, and is about 50mm. Respective rectangular perforated screens 18 and 20 extend across the main faces of the filter frame. The interior of the frame between the screens 18 and 20 is filled with course granules of activated carbon 22. It will be seen that the edges of the plates 10 and 12 and the edges of the parts 14 and 16 on one side of the filter frame define a first aperture across which the screen 18 extends, and the edges of those parts on the other side of the frame define a second aperture across which the other screen 20 extends. When the frame is in use, air or other fluid which is to be filtered is directed through the first screen 18, through the activated carbon 22 into which pollutants or contaminants are absorbed from the air or other fluid, and out of the frame interior through the second screen 20. In addition, the plate 10 has further aperture means constituted by an intended upper aperture 24 at an intended upper end of the plate 10 and an intended lower aperture 26 at an intended lower end of the plate 10. These apertures 24 and 26 are normally sealed by means of readily removable caps 28 and 30 respectively. The lower aperture 26 is for use in removing the granular activated carbon from the filter frame interior, and the upper aperture 24 is for use in filling the filter frame interior with fresh granular activated carbon. The filter frame shown in Figure 2 is a more complex configuration comprising a series of filter cells 32. Each cell 32 has the same general configuration as the filter frame shown in Figures la and lb. Four cells are connected together to form a combination which is of a hollow cylindrical quadrilateral-section form 34. A pair of such forms are arranged end-to-end, and a further such pair is arranged alongside the first. Each pair has an upper frame part 36 which is common to all the cells of the pair and in one end of which is provided an upper aperture 38 sealed by a readily removable cap 40, and correspondingly each pair has a lower frame part 42 formed with a lower aperture 44 in one of its ends, sealed by a cap 46. Thus all the cells of each pair can be emptied via the lower aperture 44 which is therefore common to all the cells, and all the cells may be filled by means of the aperture 38, which is therefore common to all the cells of the pair of quadrilateral forms. The filter construction shown in Figure 2 is enclosed in a box 48 and a supporting structure (not shown) and baffles (not shown) are used to direct the air flow through the cells 32. A particulate filter 50 is positioned downstream of the filter cells to remove dust which escapes from them for a short period after they have been filled or re¬ filled. This may subsequently be removed or simply left in place. An extractor for removing the activated granular carbon 22 from the filter frame is shown in Figure 3. It comprises an elongate tubular lance 52 which is inserted into the filter frame via its lower aperture 26 after the sealing cap 30 has been removed therefrom. The lance 52 is connected to a collector tube 54 via flexible hosing 56. The collector tube 54 extends downwardly through the top 58 of a housing 60. An air-permeable collector bag 62 has its mouth connected to the lower end of the collector tube 54. It will thus be appreciated that the bag 62 is inside the housing 60. An outlet 64 therefrom is connected to a suction inlet 66 of a blower 68 the outlet from which is covered by a carbon filter 70 and a particulate filter 72 positioned downstream of the carbon filter 70. The bag 62 rests on a weighing device 74 within the housing 60. Vibration means 73 may be provided under or adjacent to the filter frame to brake up any granular medium that has cloyed. The extractor shown in Figure 3 is operated in the following manner. The sealing cap 30 is removed from the lower aperture 26 of the filter frame and the free end of the lance 32 is inserted a little way into the interior of the frame. The blower 68 is switched on by means not shown to form an air stream which passes from the filter frame interior, along the inside of the lance 52, through the hose 56, into the bag 62 via the collector tube 64, out through the bag wall and thence out through the housing 64 from the housing 60 into the blower 68 via its suction inlet 66 and finally out of the blower 68 via the filters 70 and 72. This air stream assists a gravity feed of the granular activated carbon 22 from the filter frame interior into the bag 62. The filters 70 and 72 prevent any toxic or otherwise hazardous substances escaping from the blower 68. As the extraction process progresses, the lance 52 is inserted further and further into the filter frame interior so as to remove substantially all the filter medium. When the weighing device 64 indicates that the bag 62 is full, it automatically cuts off the blower 68 by a cut-off means (not shown) . The filter frame may be re-filled by feed means shown in Figure 4. These comprise a feed lance 75 inserted through the upper aperture 24 of the filter frame. The outlet 76 of a blower 78 is connected to the lance 75 via flexible hosing 80. Entraining means 82 are connected at a lower end thereof to the blower outlet 76. Upwardly from this point of connection, the entraining means 82 comprise a connecting tube 84, wall means 86 defining a circular cavity 88, and a hopper 90. The lower narrower end of the hopper 90 has its interior in communication with the cavity 88 via an inlet 92 thereof, and the interior of the connecting tube 84 is in communication with the cavity 88 via an outlet 94 thereof. The interior of the connecting tube 84 is also at its other end in communication with the interior of the outlet 76 of the blower 78 by means of a T- piece 95. This has an inlet 95a, being of the same internal diameter as the tube 84, greater than its outlet 95b for good carbon flow. Air enters the T-piece through the side inlet 95c. A wheel device 96 is held within the cavity 88 so that its hub 98 is positioned centrally in the cavity 88. Paddles 100 are uniformly spaced around and extend radially outwardly from the hub 96 so that their outer ends just touch the interior of the wall means 86. When in operation, the blower 78 is switched on and the hopper 90 is filled with fresh granular activated carbon. The carbon granules fall into the upright part of the T-piece 95 via the paddles 100. The wheel device 96 is rotated by means of a motor 101 to maintain a steady feed of granules to the T-piece 95. The granules are entrained in the air stream form the blower 78, and pass into the filter frame via the hosing 80 and the lance 75. The rate of feed of granules into the air stream may be adjusted by altering the speed of rotation of the motor 101. The paddles 100 form a seal with the wall means 86 to prevent reverse flow of air. The lance 75 is initially inserted far within the filter frame, and is gradually withdrawn as the filter frame fills with the granules to reduce the likelihood of voids forming and to ensure that the filter frame is completely filled. In the modified form shown in Figure 5, the lance 75 is surrounded by the suction tube 102. Optional blocking means in the form of an annular mesh 104 at the free ends of the lance 75 and the suction tube 102 covers the annular entrance into the passageway between the suction tube 102 and the lance 75 to prevent loss of granules from the frame interior. The suction tube 102 extends beyond the outlet end of the lance 75 by preferably 50mm, to reduce the likelihood of dust which issues from the lance 75 being deposited in the filter frame instead of being sucked into the tube 102 as it should be, whilst at the same time allowing heavier granules issuing from the lance 75 to pass freely into the frame interior. The flow of air through the suction tube 102 exceeds that through the lance 75 to facilitate this. The other end of the tube 102 is connected to a collector tube 106 to the lower end of which is attached a permeable bag 108 in suction apparatus 110 which is as shown in Figure 3 but without the need for a weighing device 74. In fact, it is possible to use the very same apparatus as is illustrated in Figure 3, with the lance 52 thereof being replaced by the suction tube 102. The modification shown in Figure 5 is thus able to remove fine dust particles from the frame interior as it is being filled. Such particles which are collected in the bag 108 may be recycled. In the modification shown in Figure 7, the lower and upper apertures are extended by -shaped tubing 112 to facilitate insertion of the lances 52 and 75 in a direction at right angles to the plane of the frame for installations in which there is no such access available within the plane of the frame. In this case, it is necessary for the lance to be made of a resilient material, such as hard rubber, so that it can negotiate the bend in the tubular portions 112. In the modification shown in Figure 8, comprising a simple single-cell frame, L-shaped tubing 114 is also used to extend the lower and upper apertures. In this case, however, since the frame is relatively small, it is possible to empty and fill the frame without lances, using the blow and suction of an air stream to reach the frame interior. The L-shaped tubing 114 may be straight instead, or indeed it may be any shape. The filter frame 210 shown in Figure 9 comprises a generally rectangular frame 212, across opposite main sides of which extends respective screens, only one of which, labelled 214, is shown in Figure 9. The rectangular frame 212 and the two screens together within them define an interior 216. A lower tube 218 constitutes a lower aperture to the interior 216. It is fixed to an intended lower end of one of the longer uprights of the rectangular frame 212 and opens at one end into the interior 216 where the tube 218 meets the frame 212 and, in Figure 9, its opposite end opens into the exterior. Similarly, an intended upper tube 220 constitutes an upper aperture of the frame. It is secured to an upper end of the same upright of the rectangular tube 212 to which the tube 218 is attached. It also opens into the interior 216 where it meets the frame 212 at one end and, at its other end, is open to the exterior. Preferably, both tubes 218 and 220 have an internal diameter of about 60mm and both tubes are about 85mm long, although larger and smaller tubes are naturally possible. Both tubes 218 and 220 are short, straight and of generally circular aperture and their interiors are generally longer in the axial direction than they are wide (that is to say their length is greater than their internal cross-sectional diameter) . When the filter frame 210 is filled or re-filled, it contains a granular filter medium 222 which forms a pile in the lower tube 218 with a surface 224 which is generally at 45° to the horizontal. The lower tube 218 is provided with a cap or stopper 226. This has a main cylindrical body 228 having an external diameter just less than the internal diameter of the tube 218 so as to form a close fit therewith. The body 228 is of the same length as the tube 218. The stopper or cap 226 is provided with a flange 230 at its intended outer end which has a cross-sectional diameter greater than the internal diameter of the tube 218 so as to form a closure therefor. As can be seen from Figures 11 and 12, the upper tube 220 is also provided with a stopper or cap 232. In this case the stopper or cap 232 comprises a disc 234 having a diameter which is just less than the internal diameter of the tube 220 so as to form a close fit therewith. It also has a flange 236 which is of larger diameter than the internal diameter of the pipe 220 to form a closure therewith. The disc 234 and the flange 236 are interconnected by a helical spring 238. In operation, the stopper or cap 226 is removed from the lower tube 218 as a result of which spent filter medium 222 in the filter frame 210 tips into the tube 218 until it forms a sloping surface 224, making an angle of about 45° to the horizontal. Because the tube 218 is longer than it is wide, this does not result in spillage. An extraction lance is then inserted through the tube 218, and the granular filter medium 222 extracted from the filter frame 210, whereafter the stopper or cap 226 is replaced. It will be appreciated that the fact that its main body is of substantially the same length as the tube 218, reduces the likelihood of voids being formed in the filter frame interior 222 when the latter is filled or re¬ filled. Such re-filling occurs through the tube 220, and after that re-filling, the filter medium 222 forms a sloping surface 224 which is generally at 45° horizontal within the tube 220. Again, because the tube 220 is longer than it is wide, the filter medium 222 does not spill out from the tube 220. When the stopper or cap 232 is inserted into the tube 220, the disc 234 pushes the granular filter medium 222, which naturally rests with a surface slope 224 having an angle generally at 45° to the horizontal, so that the boundary of the filter medium in the tube 220 subsequently assumes a substantially vertical surface abutting the disc 234. Again, the presence of the spring 238 reduces the likelihood of any voids forming inside the filter frame 210. Numerous variations and modifications to the apparatus illustrated in the drawings will readily occur to the reader of ordinary skill the art without taking such modifications and variations outside the scope of the present invention. To give one example, at least the lower frame part 116 in the frame shown in Figure la may curve upwardly at its end further from the lower aperture 26. This would facilitate the insertion of a resilient filling lance through the lower aperture 26 far enough for its free end to follow the curve of the lower part 16 of the frame so that further insertion of the lance will push its free end upwardly to the top of the filter frame interior. Indeed, if the upper frame part 14 is correspondingly curved, the free end of the lance could end up immediately adjacent to the upper aperture 24. As a result, that upper aperture 24 would become otiose, and only the aperture at the bottom of the filter frame would be necessary. The filter frame may be filled with impregnated activated alumina, or a molecular sieve material, or any other granular filter medium, instead of activated carbon. If the filter frame is sufficiently small, it may not be necessary for a lance to be inserted far into its interior for it to be filled, since the speed of the airstream can be sufficient to carry granules to the far end of the frame interior before falling any significant distance. Any bagged used filter medium can be dumped or recycled. The frames can be of substantially any size. The C-sectioned frame parts 14 and 16 may instead be generally U-sectioned, including sections where the base of the U is substantially straight, and the arms thereof meet that base at substantially right-angled turns. The depth of the frame is preferably 50mm, but may be of any depth in the range from 25mm to 100mm, and may even be above or below this range. Whilst the configuration shown in Figure 2 comprises sixteen filter cells, it may alternatively comprise any number of cells arranged to act in combination as a filter. The tubes 218 and 220 could have their outer mouths flush with the frame 212, even though this is less desirable because, with the tubes themselves then being in the frame interior, they interfere with the flow of fluid which passes through the filter frame to be filtered, when the latter is in use. Nonetheless, it does provide the advantage that there are no protuberances from the filter frame. It will be appreciated that the fifth aspect of the present invention may be incorporated into any of the constructions shown in Figures 1, 2, 3 and 4. Instead of having the paddles 100 forming a seal with the wall means 86 to prevent reverse flow of air, the top of the hopper 90 may be sealed with a lid 332 as shown in Figure 13. In this case, the paddles 100 simply control the flow of carbon from the sealed hopper. In the lid 332 there is a central inlet 314 comprising a sealable large ball valve 315 and an exhaust 316 which is close to the rim of the lid 332 and which is also sealable by a large ball valve 317. Hoses 340 and 342 can be connected respectively to the inlet 314 and the exhaust 316, and fresh carbon 318 can be sucked from a bag 320 in which it is contained, via the hose 340, to fill the hopper 90. Alternatively, the lid 332 can be of simple construction, without any inlet or exhaust, and can be made readily removable so that the fresh carbon can be poured directly into the hopper 90. As also shown in Figure 13, a constant flow device 344 may be connected between the blower 78 and the T-piece 95 to maintain a constant flow of air irrespective of the pressure in the T-piece. The mesh 104 is optional, although it is definitely preferable under fault conditions. Where used, the permeable bag 62 shown in Figure 3 may fill up very quickly when a filter frame is being emptied and several such bags are used in quick succession. For this reason it is desirable for the bag to be changeable quickly. A quick release holder for the bag is shown in Figure 14. At the top of the housing 60, the mouth of the bag 62 is held between two frusto-conical rings, one 350 of which is fixed to a lower lid 354 of the housing 60 and the other 352 of which is free. The weight of the ring 352, much amplified by the leverage provided by the cone, holds the rim of the bag 62 in place. The seal between the rings need not be perfect. The upper lid 356 is held onto the lower lid 354 by the reduced air pressure inside the housing 60. It seals using a soft material 358 onto the ring 360 which is part of the lower lid 354. The reduced pressure also holds the lower lid onto the sides 362 of the housing. When the bag 62 is full, the suction is switched off and the whole apparatus can be disassembled and reassembled with a fresh bag 62 in less than two minutes. The weighing device 74 shown in Figure 3 may instead be outside the housing 60 in which case it weighs the whole housing including its contents, as shown in Figure 15. In that case, when the filter frame is being emptied, the permeable bag 108 may be omitted and the housing itself used as the collection box. When the filter frame is being filled, the permeable bag 108 or some other filter means is still used to trap the dust.

Claims: Claims : 1. A filter frame having an interior which contains a granular filter medium when the filter frame is in use, a first main aperture across which a first screen part extends, and a second main aperture across which a second screen part extends, so that a fluid which is to be filtered can pass into the frame interior through one of the screens and out through the other, in which the filter frame is provided with further aperture means to enable such a medium to be removed from and/or fed into the interior of the filter frame whilst the latter is installed for use, without the need to dismantle it. 2. A filter frame according to claim 1, in which the screens are on opposite main faces of the filter frame. 3. A filter frame according to claim 1 or claim 2, in which the further aperture means are constituted by a lower aperture to facilitate removal of such a medium, and an upper aperture to facilitate filling of the filter frame with such a medium. 4. A filter frame according to any preceding claim, being generally quadrilateral. 5. A filter frame according to any one of claims 1 to 4 , in which it is composed of a combination of interconnected quadrilateral parts, the combination having such further aperture means common to all the quadrilateral parts, the interiors of the latter being in communication with one another. 6. A filter frame according to claim 5, in which the quadrilateral parts are connected together to form a combination which is of a hollow cylindrical quadrilateral- section form. 7. A filter frame according to any preceding claim, in which the further aperture means are provided with at least one readily removable cap. 8. A filter frame according to claim 8, in which the cap so fits the further aperture means as to seal the latter. 9. Extractor means for use in removing such a medium from the interior of a filter frame having a construction as claimed in claim 1, comprising a passageway having one end which is insertable through or attachable to the further aperture means, collector means at the other end of the passageway, and suction means to draw air from the filter frame interior to facilitate the flow of such a medium from the filter frame interior into the collector means. 10. Extractor means according to claim 9, in which the said collector means comprise an air-permeable bag. 11. Extractor means according to claim 9 or claim 10, further comprising filter means downstream of the collector means to remove any toxic or other hazardous substances from the air expelled by the suction means. 12. Extractor means according to and one of claims 9 to 11, in which weighing means are provided to weigh the contents of the collector means, thus to provide an indication of when the collector means are full. 13. Extractor means according to claim 12, further comprising cut-off means to switch off the suction means directly a predetermined value, corresponding to full collector means, is indicated by the weighing means. 14. Feed means for use in filling a filter frame having a construction in accordance with claim 1, comprising a passageway having one end which is insertable through or attachable to the further aperture means of the filter frame and another end connected to a blower which directs an air stream through the passageway into the filter frame interior when the feed means are in use, and entraining means connected to the passageway to enable such a medium to be entrained in the air stream and thus fed into the filter frame interior. 15. Feed means according to claim 14, in which the entraining means comprise wall means defining a generally circular cavity containing a wheel device with a plurality of paddles spaced apart around its axis of rotation and extending from a hub of the wheel device outwardly as far as the inner periphery of the wall means, with an inlet and an outlet at positions spaced apart around the wall means, whereby rotation of the wheel device enables material to pass from the inlet to the outlet. 16. Feed means according to claim 15, in which the positions of the said inlet and the said outlet are diametrically opposite one another. 17. Feed means according to claim 15 or claim 16, in which there is a seal formed between the paddles and the wall means to inhibit air from the blower escaping through the circular cavity. 18. Feed means according to any one of claims 15 to 17, in which the inlet is positioned above the outlet so that a granular filter medium may be fed via the generally circular cavity to the said passageway by gravity feed. 19. Feed means for use in filling a filter frame as claimed in claim 1, comprising coaxial tubes through one of which is fed such a medium and through the other of which can pass air from the filter frame interior during such filling. 20. Feed means according to claim 19, in which the end thereof which is connected to or inserted in the filter frame is such that the end of the outer tube extends beyond the end of the inner tube. 21. Feed means according to claim 19 or claim 20 in combination with feed means according to any one of claims 14 to 18. 22. Feed means according to any one of claim 19 to 21, in which blocking means extend across the passageway provided by the coaxial tubes through which passes air from the filter frame interior, to inhibit granules of the filter medium passing into that passageway. 23. Feed means according to claim 22, in which the said passageway has an end further from the filter frame closed by dust-trap filter means to trap any dust or other fine particles from the filter frame interior. 24. Feed means according to claim 23, in which the dust-trap filter means comprise an air-permeable bag. 25. Feed means according to claim 23 or claim 24, in which the end further from the filter frame is further provided with further filter means for removing any toxic or hazardous pollutants or contaminants from the filter frame interior. 26. Feed means according to any one of claims 19 to 25, further comprising suction means to draw air from the filter frame interior. 27. A filter frame according to any one of claims 1 to 8, in which the further aperture means comprising at least one tube. 28. A filter frame according to claim 27, in which the interior of the said at least one tube is longer that it is wide. 29. A filter frame according to claim 27 or claim 28, in which the said at least one tube is L-shaped. 30. A filter frame according to any one of claims 27 to 29, in which the further aperture means are constituted by a lower tubular aperture to facilitate removal of such a medium, and an upper tubular aperture to facilitate filling of the filter frame of such a medium, the tubes of both apertures, so far as their interiors are concerned, being longer than they are wide. 31. A filter frame according to any one of claims 27 to 30, in which the or at least one of the aperture tubes is provided with a stopper or cap having a portion which fits closely into the interior of the tube of the aperture. 32. A filter frame according to claim 31, in which the said portion is of the same length as the interior of the tube. 33. A filter frame according to claim 31 or claim 32, in which at least the lower aperture is provided with such a stopper or cap. 34. A filter frame according to any one of claims 31 to 33, in which the upper aperture is provided with a cap comprising a first part having the same shape and dimensions as an interior cross-section of the aperture tube, a second part which is wider than the said interior to be able to effect total closure thereof, and a spring connecting the first and second parts together. 35. A filter frame according to claim 34, in which the spring is a helical spring. 36. A filter frame according to any one of claims 27 to 35, in which the aperture tube or tubes are straight. 37. A method of emptying a granular filter medium from a filter frame interior, using extractor means according to any one of claims 9 to 13. 38. A method of fitting a granular filter medium into a filter frame interior, using feed means according to any one of claims 14 to 26. 39. Feed means for use in filling a filter frame having a construction in accordance with claim 1, comprising a hopper or other reservoir which serves to hold such a medium, and at least an inlet thereto which is sealable by a ball valve. 40. Feed means according to claim 39, in which the ball of the ball valve tends to be seated in a sealing position by means of gravity. 41. Feed means for use in filling a filter frame having a construction in accordance with claim 1, comprising a passageway which is connected, to the filter frame when in use and which serves to feed such a medium into the filter frame, and a blower connected to the passageway to create a stream of fluid flowing through the passageway towards the filter frame, and a constant flow device connected between the blower and the passageway to maintain a substantially constant flow of fluid in the passageway irrespective of the pressure therein. 42. Extractor means according any one of claims 10 to 13, in which the bag is held in place by quick-release means . 43. Extractor means according to claim 42, in which the quick-release means comprise two generally frusto- conical rings one of which can be nested in the other, whereby the mouth of the bag can be held between the rings, in a quick-release manner.

Inventors: MARSHALL DENNIS ALBERT GEORGE, MARSHALL, DENNIS, ALBERT, GEORGE
Applicants: MARSHALL D A G, MARSHALL, DENNIS, ALBERT, GEORGE
Application year: 1996
Main classification: B01D53
IPC codes: B01D46, B01D53, B01J8