FILTER UNIT

Abstract: A sheet 14 of filter medium is fitted on a frame 16 by turning over the margins of the sheet and shaping by heat and pressure or by securing the turned-over margins by adhesive. An inner frame 18 of the same or slightly smaller dimensions is pressed through the outer frame, stretching the sheet 14, until it lies between the frame 16 and the main extent of the filter sheet. Cross braces 24 strengthen the frame 18 and have locating lugs 26 (not visible) at their ends.

Description: FILTER UNIT This invention relates to a filter unit. The following specification also describes a method of mounting, stretching and supporting a filtering material in the form of a sheet or laminate, on a supporting and tightening frame in order to constitute an air filter unit, easily assembled and disassembled to replace the filtering fabric or material when the same becomes torn down or damaged or soiled. There has been in the field related to the manufacture of filter units, the need to manufacture the same in such a manner that, in case of wearing out of said filtering material, the same can be replaced without the disposal of the entire filter unit being necessary. Furthermore, said replacement must constitute a simple operation, requiring no special tools nor specialized workmanship. A substantial amount of time and money has been invested until now in the continuous search for a suitable solution, so as to lower the costs of said filter units, make easier the assembling of the filtering fabric and provide a product with utmost suitable characteristics. However, until now no satisfactory results have been obtained since although certain filter panels are efficient the costs thereof are quite high and conversely, those lower priced filter units are of quality and efficiency substantially under the range acceptable for the good fulfilment of their purpose. Another further negative characteristic suffered by the present filters is the relatively difficult assembling thereof, as well as their high costs of manufacture. The filter unit of this application satisfactorily solves the problems inherent to the assembling and disassembling of said units as well as those relating the mounting of said filtering fabric on the assembling frame In accordance with the present invention there is provided a filter unit comprising a sheet of filter medium attached to a frame by turned-over margins of the sheet and by a stretching member having substantially the same peripheral outline as the frame and located between the frame and the main extent of the filter sheet such that the turned-over margins of the sheet are gripped between the frame and the stretching member. In one embodiment of the invention the stretching member is of reduced dimensions-relative to the assembly frame and has one of its corners deformed or cut-away to facilitate insertion. The filter sheet is mounted on the frame by preforming the same through the application of heat, pressure and steam to those areas previously-bent over or through the use of an adhesive material previously adhered to the peripheral edge of said filtering material. The mounting, stretching and supporting of the filtering fabric is thus made easier. Replacement of the filtering material can be effected in a relatively short period of time and without the requirement of specialized workmanship. The costs of assembling a filter unit are lowered, through the reduction of the time required therefor, without involving in said action assembling techniques other than those already employed in the prior art. The manufacture and assembling of air filtering panels can be carried out with a minimum amount of stages, at a lower cost and with reliable sealing characteristics, construction and assembling which provide for the avoiding of the non-filtered air leaks between the structural parts thereof and also between the mounting or assembling frame of said filtering panels. In the drawings: Figure 1 is a perspective view of a filter unit in accordance with this invention completely assembled. Figure 2 is a frontal view showing the configuration of the filtering fabric according to one embodiment of the invention. Figure 3 shows in a frontal view the filtering material arranged on the assembling frame prior to the attachment of said filtering material to said frame. Figures 4a and 4b are perspective vieusof the two frames employed for the assembling, stretching and supporting of said filtering material, according to two embodiments of this invention Figures 5a to 5c are sectional views according to the embodiment as shown in Figure 4a, of the various assembling stages or integration stages of said filter unit; and Figures 6a to 6c are sectional views according to the embodiment as shown in Figure 4b, of the various assembling stages or integration stages of the filter unit. In the accompanying drawings the same reference numbers are employed to illustrate similar parts in the two embodiments. As shown in the annexed figures, mainly in Figures 1 to 3, 4a and 4b, the filter unit 10 of this invention is comprised of a composite frame 12 and a filtering material sheet 14 wherein said composite frame 12 is constituted by two independent frames -16 and 18. According to one embodiment as shown in Figure 4a, said frame 18 is of dimensions slightly smaller than said frame 16 and made up from wire or any other suitable material to provide a filter unit with a structural strength suitable to provide said filtering material 14 with the tensioning and support needed for the good performance thereof. In the embodiment of Figure 4b, said frames 16' and 18' are of substantially equal dimensions. As can be seen in Figures 4aand4b, the stretching and supporting frame 18 is provided with cross braces 24 in such a number and arrangement that the same strengthen the longitudinal elements 23 thereof and, at the same time, serve as supports for the filtering fabric 14 when the same has been assembled as a part of the filter unit 10. The above mentioned braces 24 are extended slightly above the elements 23, thus forming small ears 26 contributing to the alignment of the frame 16 and the filtering material 14 with the stretching and supporting frame 18. As one of the objects of the frame 18 is to stretch and support the filtering material 14, it is to be understood that, instead of the braces 24, the frame can be provided with a mesh sized to the frame 18 and even could be replaced by an apertured plate which will comply with the purposes of the frame 18. The frame 18, in the embodiment of Figure 4a has at least one of the vertexes thereof 20 flattened or cut-away in order to facilitate the assembling or integration of said filter unit 10. The frame 16 for the assembling of the filtering material -14-is made with longitudinal and transversal dimensions slightly greater than those of the frame 18. Both the greater sizes and the flattened vertex 20 of the frame 18 are for the purpose of facilitating the assembling of said filtering unit, as can be deduced from Figures 5a to 5c to be discussed later herein, although the frames 16 and 18 also can be made with similar dimensions and even without said flattened vertex 20, according to the showing of Figures 4b and 6a to 6c. There has been illustrated in Figure 2 the shape of the filtering material 14, the corners 22 of which have been trimmed at 450. The trimming 22 serves to avoid the accumulation of material at the corners of the frames 16 and 18. On one of the surfaces of the filtering material sheet 14, there are doublesided adhesive strips 21 joined to said filtering material through a contact adhesive and the free surface of which is provided with a tearoff paper protecting the adhesive on the strip 21 when said filtering material is in its position non-assembled on the frame 16. In accordance with the preferred embodiment of the invention, as shown in Figure 3 of the accompanying drawings, the filtering material 14 is shaped on the frame 16 by bending the flanges 17 thereof onto the structural elements 15 and 19 forming the sides of the frame 16, by applying heat, pressure and steam, and with no other expedient being needed; said solution facilitating and making cheaper the assembling costs for said filtering material. Referring to Figures 5a to 5c, particularly Figure 5a, there can be seen the arrangement of the filtering material 14 on the frame 16 and also the first stage of assembling the two frames 16 and 18. As will be understood, when the frame 18 is of smaller size than the frame 16, the assembling of the frames is easier, especially when the cut-away 20 is provided on the frame 18. In the embodiments of Figures 6a to 6c, said assembling is also obtained, although with a certain degree of difficulty due to the fact that both frames 16 and 18 are of substantially the same dimensions. Said difficulty is overcome thanks to the flexibility of the material of which said frames are made. On the other side, the stretching and supporting actions of the frame 18 are obvious, as well as the effect of said ears 26 avoiding the displacement of the frame 16 relative to the frame 18, when the filter unit 10 is assembled. As can be seen in Figures 3, 5a to 5c and 6a to 6c, the assembling of said filter unit is started when the filtering material is arranged on the frame 16, either by means of heat, pressure and steam or by means of an adhesive strip 21. Thereafter, the frame 18 is inserted by arranging the same over the frame 16, and starting to fit closely one of the sides thereof into the corresponding side of the frame 16, and thus stretching said filtering material 14, and finally inserting the end of the frame 18 provided with the cutdown or trimmed vertex 20. In the embodiment of Figures 6a to 6c which side of the frame 18 is inserted first becomes irrelevant. The assembling of the frame 18 is also expedited if the structural characteristics of the frame 18 are taken into consideration. In fact, the frame 18 can be slightly bent without a substantial , deformation, thus providing adequate shaping and stretching of the filtering material 14.

Claims: CLAIMS: t. A filter unit suitable for filtering and/or purification of air, comprising two superimposed frames of which the first frame carries a filtering material and the second frame, which is designed to stretch and support it, is inserted between said filtering material and said first frame, and a sheet of filtering material of greater size than said frames, with the vertexes thereof cutdown and with peripheral portions thereof bendable on said first frame, said filtering material being conformed to the dimensions of said first frame by means of heat, pressure and steam or by means of an adhesive. 2. The filter unit of claim 1, wherein said second frame is dimensioned slightly smaller than said first frame and with at least one of the vertexes thereof cutdown. 3. The filter unit of claim l wherein said second frame is provided transversely to the longest sides thereof one or more reinforcing elements the ends of which can be projected beyond the perimeter of said second frame and constitute ears serving as stops contributing to the superimposed arrangement of said frames; with said reinforcement elements providing a support for said filtering material. 4. A filter unit of claim 1, wherein said filtering material is provided peripherally with a strip of adhesive material for mounting the same into said first frame. 5. A filter unit according to the prior claims, wherein said supporting and reinforcing elements are substituted by a mesh or said frame can be constituted by an apertured sheet. 6. A filter unit comprising a sheet of filter medium attached to a frame by turned-over margins of the sheet and by a stretching member having substantially the same peripheral outline as the frame and located between the frame and the main extent of the filter sheet such that the turned-over margins of the sheet are gripped between the frame and the stretching member.

Inventors: LUNDBERG, BO ERIK HOLLSTEN
Applicants: LUNDBERG, BO ERIK HOLLSTEN
Application year: 1983
Main classification: B01D46
IPC codes: B01D46