Compact filter cells
United States Patent [191 Gustavsson et at.  
 ( Apr. 29, 1975 COMPACT FILTER CELLS [75] Inventors: Karl-Axel G. Gustavsson; Holger A.  
 Persson, both of Enkoping, Sweden AB Bahco Ventilation Corporation, Enkoping. Sweden 221 Filed: May 31, 1974 [2!] Appl.No.:47-l.963  
 {73] Assignee:  
 Primary l:.\&#39;aminw&#39;l3ernard Nozick Attorney. Agent, or Firm-Stevens. Davis. Miller &amp; Mosher [57] ABSTRACT A securing and guiding arrangement for compact filter cells of the type comprising a web of textile material folded into a number of deep, transversely extending folds and having longitudinally extending seams at each fold to provide a predetermined number of mutually and identical passages for purified gas. All of the passages are open in one and the same mutual direction and are closed in the opposite direction (at the bottom of the fold). and each of the passages are provided with a shaping member which imparts thereto a particular cross-sectional shape which may be a square shape. The member has a diagonal which coincides with the direction in which the row of passages extends. and the two remaining corners of the member lie against corresponding corners of passages in adjacent rows of passages. and each of the rows of passages for purified gas is surrounded by rows of mutually parallel crude-gas passages formed between the folds and having the same square cross-sectional shape as the purified-gas passages. The crude-gas passages are open in one and the same mutual direction which is opposite to that of the purified-gas passages. and are closed in the opposite direction in an upper frame which comprises part of a rightangled parallel epipedic filter cassette. This frame is arranged to be brought. through the intermediary of an intermediate packing member into scaling abutment with a connecting frame arranged in a common filter housing suitable for accommodating a plurality of cassettes. the cassettes. in addition to the upper frame. is provided with a corresponding lower frame and with frame portions which connect the upper and lower frames at the corners thereof. The upper frame has the form of an upwardly open U-shaped section. suitably having slightly converging flanges whose edge portion are folded inwardly through an angle of zip proximately 180. and which is provided with a number of transverse support stays having rounded upper edges. The stays are securely connected to the upper frame in positions which coincide with a central plane in the crude-gas passages The lower frame is provided with transverse distance stays arranged in the central plane of the crude-gas passage rows, which distance stays together with the shaping member fix the passages against lateral movement in that the compact filter cell along all side edges at the side where the puri fled gas passages are open is provided with a fold edge of such width that it can be folded in and shaped along at least the inner flange and the bottom of the U- shaped section of the upper cassette frame and be retained in position by means of a resilient sealing strip which when seen in cross section, is rectangular of frusto-triangular in shape and which has a greater height than the flanges. The sealing strip subsequent to the filter cassette is connected to the connecting frame of the filter housing and arranged to provide sealing between the cassette and the filter housing and between the filter cell and the cassette frame and to increase the securing forces of the folding edges in the U-shaped section so as to provide an operably reliable filter unit.  
 1 Claim. 4 Drawing Figures COMPACT FILTER CELLS The present invention relates to a securing and guiding arrangement for compact filter cells of the type comprising a web of textile material folded into a number of deep, transversely extending folds and having longitudinally extending seams at each fold to provide a predetermined number of mutually parallel and identical passages for purified gas, all of said passages being open in one and the same mutual direction and being closed in the opposite direction (at the bottom of the fold), and each of said passages being provided with a shaping member imparts thereto a particular crosssectional shape, which may be a square shape, said member having a diagonal which coincides with the direction in which the row of passages extends, and wherein the two remaining corners of said member lie against corresponding corners of passages in adjacent rows of passages, and wherein each of said rows of passages for purified gas is surrounded by rows of mutually parallel crudegas passages formed between the folds and having the same square cross-sectional shape as said purified-gas passages, said crude gas passages being open in one and the same mutual direction which is opposite to that of the purified-gas passages, and are closed in the opposite direction in an upper frame which comprises part of a right-angled parallelepipedic filter cassette, which frame is arranged to be brought, through the intermediary of an intermediate packing member, into sealing abutment with a connecting frame arranged in a common filter housing suitable for accommodating a plurality of cassettes, said cassettes, in addition to the upper frame, being provided with a corresponding lower frame and with frame portions which connect the upper and lower frames at the corners thereof.  
  The main problem associated with such filter cells is that because when mounting the filter cells in position in the housing the edge band of the filter cells becomes wrinkled, giving rise to leakages, it is difficult to secure said edge band to the upper frame portion in a manner to obtain a seal which is satisfactory at the high pres sure drops occurring with such filters. Furthermore, the rows of purified gas passages tend to become displaced in relation to each other as the filter is fitted to the housing, thereby causing the cross-sectional areas of the crude gas passages located between said purifiedgas passages to vary and the filter cell to become unbalanced as a consequence thereof.  
  These disadvantages are at least substantially eliminated by means of the arrangement according to the invention, which is mainly characterized in that the upper frame has the form of an upwardly open U- shaped section, suitably having slightly converging flanges whose edge portions are folded inwardly through an angle of approximately 180, and which is provided with a number of transverse support stays having rounded upper edges, said stays being securely connected to said upper frame in positions which coincide with a central plane in the crude-gas passages; in that the lower frame is provided with transverse distance stays arranged in the central plane of the crudegas passage rows, which distance stays together with said shaping member fix the passages against lateral movement in that the compact filter cell along all side edges at the side where the purified-gas passages are open is provided with a fold edge of such width that it can be folded in and shaped along at least the inner flange and the bottom of the U-shaped section of the upper cassette frame and be retained in position by means of a resilient sealing strip which, when seen in cross section, is rectangular or frusto-triangular in shape and which has a greater height than the flanges; and in that said sealing strip subsequent to said filter cassette being connected to the connecting frame of the filter housing, is arranged to provide sealing be tween the cassette and the filter housing and between the filter cell and the cassette frame and to increase the securing forces of the folding edges in the U-shaped section so as to provide an operably reliable filter unit.  
  Owing to the fact that the upper frame and the lower frame are respectively provided with support stays and distance stays, and since, when mounting a compact filter of the folded-web type in position, said stays are located on both sides of each row of purified-gas passages in the filter, the rows of purified-gas passages cannot be displaced towards each other so as to disturb the desired array of purified-gas passages of square cross section and the crude-gas passages of square cross section surrounding said purified-gas passages, in other words cannot cause the compact filter to become unbalanced with respect to its treatment of contaminated gas being filtered therein. Furthermore, the support stays serve to take-up the high pressure load acting on the filter cell, which load occurs at the exit end of the filter cell, i.e., at the upper frame, when the filter is being blown clean.  
  The invention will now be described in more detail with reference to the accompanying drawings, in which FIG. I is a perspective view of a filter cassette frame according to the invention, having a compact filter of the folded-web type mounted therein.  
  FIG. 2 is an enlarged, cross-sectional view of part of the upper frame shown in FIG. 1.  
  FIG. 3 is an enlarged view of part of the upper frame shown in FIG. 1, and illustrates the manner in which a supporting stay is secured in said upper frame, and  
  FIG. 4 is an enlarged view of a corner of the cassette frame shown in FIG. 1 from beneath.  
  The cassette frame shown in FIG. 1 comprises a rectangular upper frame 1 and a rectangular lower frame 2 having the same size as the upper frame 1. The corners of the upper and lower frames are connected together by means of straight rods 3 which are of equal length and which extend normal to the frames.  
  As will be seen from FIG. 2, secured to the upper frame is a compact filter of the folded web type 4. The compact filter is provided with inserts 5 which are arranged to impart to the gas passages arranged in the filter a square-sectional shape.  
  The upper frame is provided between two opposing sides thereof with a number of parallel support stays 6 for supporting the folds in the compact filter. Conveniently, there is one support stay arranged for each fold and said stay is preferably in the form of a sheet-metal strip having edge portions folded through to strengthen said strip, as disclosed in FIG. 3. The support stays are preferably secured to the upper frame as by welding.  
  Mounted on the under frame between two opposing sides thereof is a number of straight, distance stays 7 which extend parallel with the support stays 6, as shown more clearly in FIG. 4.  
  With the embodiment shown in FIG. 2 the upper frame 1 has the form of a U-shaped sheet-metal bar into which the edge band 8 of the compact filter 4 is inserted so that said band extends over practically the entire bottom surface of a groove 9 located in the bar. The band is held securely in this position by means of a scaling strip 10 which presses said band against the bottom of the groove 9 and against one flange of the bar or upper frame 1. The sealing strip 10 is suitably made of sponge rubber or some other appropriate resilient material. The sealing strip 10 provides a fully satisfactory seal. despite the fact that the band cannot be inserted into the bar or upper frame without said band becoming wrinkled. This sealing effect of the strip 10 can be facilitated by causing the flanges of the upper frame 1 to converge slightly, as shown in FIG. 2.  
  In accordance with the invention a distance stay 7 is passed through a hole 11 located in the under frame 2 so as to hold apart the rows of purified-gas passages 12, so that intermediate crude-gas passages 13 retain their square cross-sectional shape. This is illustrated more clearly in FIG. 4, which shows a corner of the cassette frame according to FIG. 1 from beneath. The distance stays 7 are secured to the under frame 2 by bending the edges of said stays around adjacent portions of the frame. The distance stays, however, may be secured to the frame in another manner, such as by welding for example.  
  Although the invention has been described and illustrated with respect to a particular embodiment thereof, this embodiment is not restrive of the invention. The under frame may comprise bars of U-shaped cross section, while the rods connecting the upper and lower frames may comprise L-shaped rods welded to said frames.  
 We claim:  
  1. A securing and guiding arrangement for compact filter cells of the type comprising a web of textile material folded into a number of deep, transversely extending folds and having longitudinally extending seams at each fold to provide a predetermined number of mutually and identical passages for purified gas, all of said passages being open in one and the same mutual direction and being closed in the opposite direction (at the bottom of the fold), and each of said passages being provided with a shaping member which imparts thereto a particular cross-sectional shape which may be a square shape, said member having a diagonal which coincides with the direction in which the row of passages extends, and wherein two remaining corners of said member lie against corresponding corners of passages in adjacent rows of passages, and wherein each of said rows of passages for purified gas is surrounded by rows of mutually parallel crude-gas passages formed between the folds and having the same square crosssectional shape as said purified-gas passages, said crude-gas passages being open in one and the same mutual direction which is opposite to that of the purifiedgas passages, and are closed in the opposite direction in an upper frame which comprises part of a rightangled parallelepipedic filter cassette, which frame is arranged to be brought, through the intermediary of an intermediate packing member into sealing abutment with a connecting frame arranged in a common filter housing suitable for accommodating a plurality of cassettes, said cassettes, in addition to the upper frame, being provided with a corresponding lower frame and with frame portions which connect the upper and lower frames at the corners thereof, characterized in that the upper frame has the form of an upwardly open U- shaped section, suitably having slightly converging flanges whose edge portion are folded inwardly through an angle of approximately and which is provided with a number of transverse support stays having rounded upper edges, said stays being securely connected to said upper frame in positions which coincide with a central plane in the crude-gas passages; in that the lower frame is provided with transverse distance stays arranged in the central plane of the crude-gas pas sage rows, which distance stays together with said shaping member fix the passages against lateral movement in that the compact filter cell along all side edges at the side where the purified gas passages are open is provided with a fold edge of such width that it can be folded in and shaped along at least the inner flange and the bottom of the U-shaped section of the upper cassette frame and be retained in position by means of a resilient sealing strip which when seen in cross section, is rectangular of &#39;frusto-triangular in shape and which has a greater height than the flanges; and in that said sealing strip subsequent to said filter cassette being connected to the connecting frame of the filter housing, is arranged to provide sealing between the cassette and the filter housing and between the filter cell and the cassette frame and to increase the securing forces of the folding edges in the U-shaped section so as to provide an operably reliable filter unit.  
  UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3,880,628  
 DATED :April 29, 1975 INVENTOR(S) Karl-Axel G. GUSTAVSSON; Holger A. PERSSON It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:  
 [73] Cancel &#34;Corporation.&#34;  
 Signed and Sealed this fourth D ay Of November 1 9 75 [SEAL] Arrest.-  
 RUTH C. MASON C. MARSHALL DANN&#39; Arresting Officer (bmmissimrer oflatents and Trademarks