ZA200207567B

ZA200207567B - Filter medium.

Info

Publication number: ZA200207567B
Application number: ZA200207567A
Authority: ZA
Inventors: Nicolas Form; Dennill William Mark
Original assignee: Nicolas Form; Dennill William Mark
Priority date: 2000-03-31
Filing date: 2002-09-20
Publication date: 2004-03-29

Description

FILTER MEDIUM

FIELD OF THE INVENTION oo :

This invention relates to a filter medium for use in air filters.

BACKGROUND TO THE INVENTION

Air filter media are widely used as a washable and replaceable components in building air conditioning plants. A common medium is a pleated panel of the medium in the form of a mat of fibre material. These mats of synthetic resin material are mounted in frames which are positioned in air ducting.

The mats are located in a suitable frame to enable them to be located in airflow ducting. Disposable mats are also widely used and these are generally retained in cardboard frames. However galvanized steel frames are used for both washable and disposable filter media mats.

The mats should be made to provide progressive density to effect their best filtering and dust holding ability but single ply media are difficult to manufacture with progressive density.

The mats also usually lack rigidity in a direction transverse to the length of the i pleats and require some form of stiffening. This has heretofore been effected by the application of an excessive amount of resin impregnated into the medium which seriously reduces the filter area or the mats are wire backed with wire grids. This latter requires expensive machinery to form the grids and the oo ~~ CONFIRMATION COPY E oo

. © WO001/72397 PCT/IB01/00324 product is expensive. Where used in disposable mats these grids are not easily disposed of.

OBJECT OF THE INVENTION it is an object of this invention to provide a filter medium suitable for air filters which will at least mitigate some of the disadvantages inherent in the kinds of media presently in general use.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a filter medium comprising a panel of pleated fibrous material characterized in that the panel! is reinforced with wire strands along the apices of the pleats.

Further features of the invention provide for the fibrous material to be synthetic 0 resin filaments, preferably suitable polyester and polypropylene resin fibre materials, and for the wire strands to be located between a pair of panels secured together. Co

The invention also provides for the mats to be secured together by adhesive coating the wires and fixing the panels to the wires, by needling the panels between the wires, by stitching the panels together around the wires or by heat welding the panels to the wire. :

Other methods of fixing the wire strands could also be used within the scope of this invention.

The panels will preferably be of different density to provide different filter 0 capabilities.

oo wo 01/72397 PCT/IB01/00324

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention is described below, by way of example only, , and with reference to the accompanying drawings in which: [}

FIG. 1 is a diagrammatic drawing showing one form of assembly of the panels and wire;

FIG. 2 illustrates a cross-section of the finalized filter medium; and

FIG. 3 illustrates a framed panel of filter media for insertion in an air flow duct.

DETAILED DESCRIPTION OF THE INVENTION

As shown in Fig 1 an air filter medium is manufactured by drawing panels to provide mats (2) of different density polyester and polypropylene resin fibre ) material from supply rolls (3) and (4).

This can be effected by having the first stage of the filter media, that is the upstream mat of an installed filter media, needled to give a low density relative to the second stage of filter media. The latter will be a continuous strand mat to which about thirty percent by weight of acrylic binder has been added. The fibrous synthetic resin materials are well known.

To form the mats (2) into a handleable material for pleating and providing adequate strength against deformation when subject to an airflow to be cleaned the first and second stage mats (2) are joined together. . As shown in Fig 1 the lengths of wire (5) are drawn from a series of rolls (6) and ) the wire (5) guided to be coated with adhesive in an adhesive bath (7). From : there the wire (5) is drawn between the mats (22) at distances spaced apart determined by the depth of the pleats (8) shown in Fig 2.

The mats (2) are then drawn together between rolls (9) sandwiching the wire strands (5) between them to secure the wire strands (5) to each mat and thus secure the mats (2) to each other.

Other methods of securing the wires (5) between the mats (2) can of course be used. For example the wires (5) may be needled to cause inter-engagement of the fibres from each mat (2). Further alternatively, stitching may be used through the mats (2) around the wires (5).

Also heat welding by heating the wires (5) and melting the fibres of the mats to adhere to the wires (5) can be effectively used. ) The composite panel will be cut to the desired length for pleating in known manner into the final filter medium. The pleated panels are then fixed in surrounding frames indicated at (10) in Figure 2.

The panels made in the manner above described result in several advantages over the panels presently made and used. They are considerably cheaper to > manufacture than the conventional wire backed panels and they do not delaminate during use.

Because the mats 2) are separately made to different density real effective progressive density can be achieved through the thickness of the panel.

The strands of wire (5) give the desired rigidity to the panels where it is needed ) without adversely reducing the filter area provided and this results in the panels acting effectively as filter material and, where intended to be reusable, also withstanding the rigours of removal from and replacement in the air conditioning ducting and the washing operation to remove collected contaminants from the air which has passed through the filter.

oo wo 01/72397 PCT/1B01/00324

RX It will be appreciated that the above embodiment is not to be considered as limiting the scope of the invention. Many variations may be made to the embodiment described. For example, the fibre material is not limited to

E] polyester and polypropylene is particularly suited for fine filtration because of the nature of the fibres which can be drawn from this material.

Further the medium can be made as a single mat with the wire support attached to the apices of a single series of pleats and different filter stages of the filter may be spaced apart along the direction of air flow. This enables coarse and fine filters to be separately treated or replaced and also enables different materials to 0 be used for these different filter stages.

Claims

1. A filter medium comprising a panel of pleated fibrous material characterized in that the panel is reinforced with wire strands along the apices of the pleats.

2. A filter medium as claimed in claim 1 characterized in that a plurality of panels are used to form the medium.

3. A filter medium as claimed in daim 2 characterized in that the wire strands are located between pairs of panels secured together.

4, A filter medium as claimed in claim 2 in which the panels are spaced apart and each is provided with its own reinforcing wire strands.

5. A filter medium as claimed in claim 2 characterized in that the fibrous material is of synthetic resin filaments.

6. A filter medium as claimed in claim 5 characterized in that the synthetic resin filaments are suitable polyester or polypropylene resin fibre material.

7. A filter medium as claimed in claim 6 characterized in that two panels are formed into mats having different densities with the mat located upstream in use in an air flow being the mat of lower density.

8. A filter medium as claimed in claim 7 characterized in that the mat of lower . density is a needled fibre mat.

9. A filter medium as claimed in claim 7 characterized in that the mat of higher density is a continuous stand mat and includes up to thirty per cent by weight of acrylic binder.

10. A filter medium as claimed in claim 7 characterized in that the two mats are adhesively secured to the wire strands.

11. A filter medium as claimed in claim 1 in which the medium is located in a metal frame.

12. A filter medium substantially as described with reference to the accompanying drawings. :