Accordion filter with a protective mask

Gas separation – With nonliquid cleaning means for separating media – Relatively movable pneumatic nozzle

Reexamination Certificate

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Details

C055S497000, C055S499000, C055S500000, C055S502000

Reexamination Certificate

active

06299660

ABSTRACT:

BACKGROUND OF INVENTION
1. Field of the Invention
The invention relates to a filter element of the accordion fold pack type that can be sealingly secured in position in a filter housing.
2. Description of Related Art
Such a filter element is known from the German Patent 21 37 309. The filter element comprises an accordion fold block made of an impregnated filter-paper strip that is folded zigzagged, in the case of which a protective metal net is arranged in front of the accordion fold block in the air-filtering direction and is joined to the sealing frame. The metal screen grid is comparatively wide-meshed and—relative to the folds of the accordion fold block—is provided with rhombic meshes.
Methods for cleaning filter elements are known from the printed documents DE 43 43 160 and DE 44 34 625.
SUMMARY OF THE INVENTION
The problem underlying the invention is to further develop a filter element of the previously known type in such a way that it can be cleaned by compressed air repeatedly during its service life without damage to the accordion fold pack.
In accordance with the present invention, a filter element comprises an accordion fold pack wherein the flow-off side (i.e., the clean-air side) of the accordion fold pack is covered by a latticed protective mask (preferably having a lattice of slots) and the protective mask is sealingly joined to all of the fold backs of the accordion fold pack on the clean-air side. An advantage of this structural approach is that the delicate fold backs of the filter material of the accordion fold pack are protected from damage and destruction by the protective mask (which preferably consists of a tough material).
After being covered with dust during normal operation, the filter element is cleaned by compressed air blown into the filter element opposite to the air-filtering direction from the clean-air side of the filter element. This causes the dust accumulated during the use of the filter to be blown out from the filter element. Subsequently the filter element is again operated in the normal manner as a filter until reaching a specific pressure difference between the oncoming-flow side and the flow-off side, or until some other indication that there has been an amount of dust covering. The filter can then again be dedusted by compressed air. The sealing connection between the protective mask and the fold backs of the accordion fold pack is provided in order to avoid a loss of compressed air caused by leakage during the cleaning of the filter element and thereby to permit an efficient cleaning.
According to one embodiment, the slotted mask and the fold backs are cemented to one another. The sealing connection between the slotted mask and the fold backs is thereby easily and cost-effectively produced.
The width of the slots of the slotted mask is no greater than the width of the fold openings between the fold backs. The ratio of the width of the slots and the width of the fold openings amounts to 0.6 to 1, preferably 0.7 to 0.9. This refinement ensures that when the individual fold openings are acted upon, one after the other by compressed air, that only the individual fold opening, and not the adjacent fold openings, are acted upon by compressed air. Thus, the compressed air is concentrated in only one fold opening—the fold openings preferably being blown free individually, one after the other. Furthermore, with such an embodiment it is advantageous that, even given comparatively generous manufacturing tolerances of the accordion fold pack and/or the slotted mask, the slots are always arranged over the fold openings between the fold backs.
The slotted mask may be, for instance, a rustproof, metallic material. Since the slotted mask is mounted on the accordion fold pack on the clean-air side, corrosion of the slotted mask is minimized even during a long service life of the filter element.
According to another embodiment, the slotted mask may be a nonmetallic material, such as a woven fabric. In a further embodiment, the slotted mask may be, for example, polystyrene.
Preferably, the accordion fold pack and the slotted mask form a unit that can be preassembled, thus advantageously simplifying manufacture of the filter element. The unit which can be preassembled, including an accordion fold pack and a slotted mask, can be provided with a sealing device and subsequently inserted as a whole into a filter housing.
The slotted mask can be enclosed by a frame which completely covers the filter element. The slotted mask may advantageously extend over the frame of the filter element, so that a plane surface is formed, across which a cleaning rod passes.
In addition, the oncoming-flow side of the accordion fold pack can be covered by a further latticed protective mask that is sealingly joined to all fold backs of the accordion fold pack on the oncoming-flow side. The protective mask on the oncoming-flow side is constructed in correspondence to the protective mask on the clean-air side, and is joined to the accordion fold pack. An advantage of this approach is that it serves to mechanically stabilize and protect the filter element as a whole by shielding the delicate accordion fold pack from external contacts.
The filter element according to the invention may be used as a high efficiency submicron particulate air filter for gaseous media.


REFERENCES:
patent: 2019213 (1935-10-01), Dahlman
patent: 2395449 (1946-02-01), Briggs
patent: 2895174 (1959-07-01), Hockett
patent: 3151962 (1964-10-01), O'Dell
patent: 3216578 (1965-11-01), Wright et al.
patent: 4678578 (1987-07-01), Nodes et al.
patent: 2137309 (1798-11-01), None
patent: 1367226 (1974-09-01), None
patent: 60-137454 (1985-07-01), None
patent: 60-193518 (1985-10-01), None
patent: 4267914 (1992-09-01), None

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