US 3406503 A
Description (OCR text may contain errors)
c. 22, 1968 F, FLQYD AUTOMATIC FABRIC AIR FILTER 5 Sheets-Sheet l Filed July 23, 1965 FIG.1.
INVENTOR 5w E/c/ ATTORNEY c. 22, i968 F, FLQYD 3,406,503
AUTOMATIC FABRIC AIR FILTER Filed July 215, 1965 5 Sheets-Sheet 2 INVENTOR Pyze/c/f HLW@ BY ATTORNEY A oct. 22, 1968 F. FLOYD 3,406,503
AUTOMATIC FABRIC AIR FILTER Filed July 23, 1965 5 Sheets-Sheet 5 ATTORNEY Unted States Patent "s 3,406,503 AUTOMATIC FABRIC AIR FILTER Frederick Floyd, Strood, Kent, England, assignor to Ozonair Engineering Company Ltd., Kent, England, a corporation of England Filed July 23, 1965, Ser. No. 474,418 1 Claim. (Cl. 55-354) ABSTRACT F THE DISCLOSURE A filter web consisting of compressible material reinforced with cotton netting is moved across the path of air or fiuid to be cleansed in a zigzag fashion, guided by a series of rollers. The edges of the web are provided with a bead or piping =held in position by tapes. Channels are provided along the sides of the path of the web having a recess in which the bead may slide, with inturned lips to contact the web inside of the bead and form an air or liuidtight enclosure. This effectively seals the web and prevents bypassage of the material around the edges of the web.
This invention relates to improvements in automatic fabric air filters, and includes filters employed in the cleaning of other gases.
It is well known to provide a filter having a casing with a supply roll at the top, a take-up roll at the bottom, and a web of filter material led between the two rolls in an eX- tended path, such path being vertical and horizontal serpentine or zigzag, and the edges of the filter material being sealed against the sides -of the casing so that the air to be cleaned can only pass from the dirty air side tothe clean air side through the filter material. The material is wound from the supply roll to the take-up roll at a speed depending on the use to which the filter is being put, so that clean material is being presented at one end and dirty or clogged material is being removed from the airstream at the other end.
Various methods of ensuring adequate edge sealing of the filter material have been attempted and it is an object of the present invention to provide an improved sealing means which will enable a filter to be operated continuously and give adequate edge sealing without imposing undue stresses on the filter material or requiring as much power as has heretofore been needed to draw the material along its path.
According to the invention an automatic continuous filter for `air or other gases, having a casing and a web of filter material fed therethrough along an extended path, and edge sealing means to prevent the passage of air between the filter material and the adjacent casing wall, has edge sealing means which comprise a bead extending along each edge of the web and rigid guide tracks on the casing walls embracing the beads in Huid-tight manner where there is a pressure differential across the filter material, while permitting sliding of the web relatively to and along the tracks.
Each track may have a passage to accommodate the bead, and in-turned rigid lips arranged to bear upon the filter material adjacent to t-he bead.
Alternatively each track may have a passage to accommodate the bead and in-turned rigid lips arranged to bear against the bead at its junction with the filter material.
Each track may be formed where abrupt changes of direction occur, with a pulley constituting the inner side of the track, and co-operatng with a fixed outer side of the track.
The invention also includes a filter material for such a filter, wherein the bead and the adjacent material are united by and covered by a tape.
3,406,503 Patented Oct. 22, 1968 vEmbodiments of the invention will be described with reference to the accompanying drawings, in which:
FIGURE 1 is a fragmentary diagrammatic side elevation of a filter having one side of the casing omitted to show the interior, illustrating the general arrangement of a filter,
FIGURE 2 is a fragmentary cross-section on the line II-II, to an enlarged scale, showing the details of one form of edge seal,
lIGURE 3 is a similar view of another form of edge sea FIGURE 4 is a similar view o-f yet another form of edge sea FIGURE 5 is a fragmentary diagrammatic side elevation, to a greatly enlarged scale, of a portion of track in the neighbourhood of a roller,
FIGURE 6 is a sectional elevation thereof on the line VI--VI, FIGURE 5,
FIGURE 7 is a section thereof on the line VII-VII, FIGURE 5,
FIGURE 8 is a view similar to FIGURE 5, but of another embodiment, and
FIGURE 9 is a section thereof on the line IX-IX, FIG- URE 8.
Referring to FIGURE 1, a filter casing 20 has at the top thereof a receptacle 21 containing unused filter material 22 which is drawn downwards in an extended path consisting of a zig-zag comprising straight sections 23 connected by arcuate sections 24 where the filter material passes around rollers 25. The inside of each side wall of the casing carries a track of this configuration from a point just below the filter material supply receptacle 21 at the top of the filter casing to a point near the bottom of the casing just above a take-up device (not shown) for the filter material. Each track consists of an aluminium extrusion formed from straight pieces and curved pieces so aligned and diS- posed relatively to one another as to give a zig-zag path as described above, the straights and the curves blending smoothly into one another. The aluminium extrusions are conveniently screwed to the walls -of the casing.
Referring to FIGURE 2, a simple cr-oss-section for such an extruded track consists of a rectangular bar 26 having a circular passage 27 therein `communicating with the outside in one wall of the track through the medium of a narrow slot 28 defined by two in-turned lips 29, 30. There is thus provided -a rigid track secured to the casing 20 by screws 19, that will resist deformation as a result tof any forces likely to be encountered.
The filter material 22 consists of a web 31 of compressible material reinforced with cotton netting 32 and having running along each of its edges a bead or piping 33 and two tapes 34, 35 which are secured to the bead 33 and extend over the edges of the filter material 31 and cotton netting 32 and are stitched thereto by two lines of stitching 36, 37 extending parallel with the longitudinal edge of the filter material web 22. The dimensions of the passage 27 and the slot 28 in the track, and of the bead 33 and the filter material where it is covered by the tape, are arranged so that there is ample clearance within the passage 27 for the bead but that the width of the slot 28 causes the in-turned lips 29, 30 to compress the filter material to a considerable extent. The 'width of the slot is related to the diameter of the bead at the edge of the filter material, i.e., slot width should be no greater than half the diameter of the bead. For example, if 1A diameter bead is used then the slot should be l wide. The exact dimensions may easily -be ascertained for any given fil-ter so as to ensure that the material 22 slides smoothly with the bead 33 in the passage 27 of the track, while at the same time the filter material is gripped by the inturned lips 29, 30 sufficiently to resist anyforces tend-AA ing to draw'it away from the'v track.
Referring to FIGURE 3, in an alternative construction the track consists of an extrusion 38 of approximately D-shaped cross-section, the flat side of the D facing against the wall 20 of the casing Iand there being a narrow slot 39 along the centre of the curved part of the D. This again affords rigid lips which resist any tendency of the 'bead 33 to ybe drawn out of the passage 40 within the D.
In yet another alternative illustrated in FIGURE 4, the track consists of a channel-shaped member 41 having in-tumed lips 42, 43 extending inwardly at approximately 45 to the top and bottom sides of the channel from which they spring, said lips terminating in free edges rounded, and if necessary slightly enlarged in thickness, in order to give a smooth seating `for the bead 33, which as before extends in the passage 44 inside the track but in this embodiment seats on the lips 42, 43. The resistance to unwanted movement of the filter material is in this embodiment afforded by the bead itself, and no appreciable compression of the filter material 22 adjacent to the bead 33 takes place.
In any of these arrangements, the arcuate sections of track which connect the straight sections of a zig-zag may cause an undesirably high drag. This may be reduced by providing at each apex of the zig-zag a pulley or its equivalent, having an external peripheral crosssection similar to that of one side (the inner side) of the track. One such arrangement is illustrated in FIG- U'RES 5, 6 and 7. An extruded angle section 4S constituting the track consists of a backplate 46 from which project two walls 47, 48 the wall 47 having a lip 49 and the wall 48 having a lip 50. Between them there extends a web 22 of filter material having a bead 33 constrained by the lips 49, k50 in the manner hereinbefore described. Where the track passes through a relatively acute angle around the apex of one of the zig-zags, a roller 51 is accommodated in a cut-out portion of the track indicated at 52, the wall 47 and lip 49, and the neighboring part of the backplate 46, being cut away. This allows the roller 51 to rotate easily in its bearing and the outside flange of the backplate 46 is slotted as at 52 to allow the metal to be stretched where it passes around the bend.
As will be seen yfrom FIGURE 6, in the neighborhood of the bend, the Ibead 33 of the filter material 22 is constrained on the one hand Iby the remaining lip 50 on the wall 48 of the track and on the other hand by the roller 51. The track therefore remains effectively continuous, but the provision of what is in effect a pulley gap between the lip 50 and the roller 5.1'is atthis'point arranged to 'be the same as the slot width in the straight portions of the track. With a bead of 1z-inch diameter a suitable gap would be 1/s-inch.
FIGURES 8 and 9 show lanother way of achieving a continuous track around an apex joining ytwo straights in a zig-zag track. The cross-section 0f the track and its general lay-out are the same as that of 'FIGURE 5, except that the 4apical portion of the trackis not cut away as before. Instead, the roller 53 is shouldered as at 54 near its ends, and, as will be seen in FIGURE 9, the bea-d 33 continues to be gripped between the lips 49, of the track without any interference by the roller. The shaded area S5 represents a slot cut in the track to facilitate bending of the extruded metal of which it is formed. This slot is also to :be identified in FIGURE 9.
1. A web filter for cleansing and removing dirt and impurities from air and other fluids, having a casing with a supply means at one side thereof and side walls with open inlet and outlet ends to define a path for the air being cleansed, a filter web extending from the supply means across the path of the air with its lateral edges closely adjacent the interior faces of the side walls and means for preventing escape of air around the edges of the filter web 'between the filter web and the interior faces of the side walls, said last mentioned means including tracks mounted in air-tight Vfashion on the interior faces defining the location of the lateral edges of the web across the path, beads mounted on the lateral edges of said filter web, said tracks including base portions mounted on said interior faces and inwardly extending lips engaging the lateral edges inside of said beads to prevent bypassing of air, said -web being formed of compressible material, a reinforcing cotton netting associated with said compressible material and tapes stitched to the later-al edges to bold the beads in position on said lateral edges.
References Cited UNITED STATES PATENTS 187,894 2/1877 Osgood 160--273 2,133,931 10/ 1938 Walker et al 55--354 2,800,194 7/1957 Peek 55-382 2,869,680 1/1959 Fields 55-354 3,019,855 2/ 1962 Engle 55-352 HARRY B. THORNTON, Primary Examiner. B. NOZICK, Assistant Examiner.