Gas separation – Flexible or collapsible bag type – Seaming – reinforcing or bag structure
Reexamination Certificate
1999-04-06
2001-10-23
Smith, Duane S. (Department: 1724)
Gas separation
Flexible or collapsible bag type
Seaming, reinforcing or bag structure
C055SDIG005
Reexamination Certificate
active
06306188
ABSTRACT:
BACKGROUND OF THE INVENTION
In order to be able to filter large amounts of air in for instance, air conditioning installations, it is known to use folded filters with a very great depth. These filters are sometimes called bag-filters since they can be considered as a group of bags located adjacent one another. In addition to achieving a large area for the filter material in this way, the filter bags can be folded for transport and storage, which in particular results in transport savings since the filter in the shape when used is particularly bulky. As a result of the large area of the separate bags these however have a tendency to inflate so that the triangular cross section shape desired for a good flow is easily lost. In order to counteract this it is known to sew fast threads cross-wise through the bag. While this has no negative effect on the foldability of the filters, the sewing of threads in the filter material may however easily lead to damage either during sewing or later when the filter is subjected to a load. Primarily these damages may result in leakages, which is why glue usually is applied as a sealant. In other words the number of steps required for the fabrication of these filters and in particular the manual effort involved is comparatively large. Furthermore, the use of glue makes the material non-homogeneous which is a disadvantage when it comes to recycling.
In view of the above problems of filters of this kind the object of the invention is to achieve a filter and a fabrication method that can be executed simpler, faster, and with a more complete homogeneity of material.
BRIEF SUMMARY OF THE INVENTION
In accordance with the invention the above is achieved by welding distance elements between the opposed filter material sides of the filter bag, that upon use of the filter can be extended to different degrees at different locations in the filter. In one embodiment the distance elements can consist of sheet material with openings, for instance in the shape of a ladder but where the separate steps rather than being entirely straight across become increasingly bent or V-shaped. Since the connecting steps are longer in one end the longitudinal parts of the ladder can be pulled apart to different degrees so that a narrowing or widening ladder is obtained, dependent on in which direction it is viewed. By welding one longitudinal part of the ladder to the filter material on one side of the filter bag and the other longitudinal part of the ladder to the other, the distance elements can during welding be arranged with the longitudinal parts at the same distance, while upon erection of the filter the separate steps or connections are extended so that the intended shape of the filter is defined and maintained. The welding of the distance elements can take place with the filter material and the distance elements lying essentially flat and close to one another which facilitates relative positioning before welding. In addition to the simple welding method obtained in this way for the welding of the distance elements it is also easy to adapt the fabrication method to different width bags since one quite simply changes the distance elements to one with shorter or longer extendable connections.
By arrangement of a distance element over the entire depth of the filter bag it also is possible to arrange the desired number of connections between the opposed sides of the bag by connecting alternating “longitudinal ladder parts” to the sides of the filter bag. In this way the distance element connection will not extend perpendicular to the filter material but instead a zigzag shaped framework will be obtained with obliquely or angled connections or bridges between the sides of the filter fold.
In known filters where the distance elements extend straight through the filters, and against the filter material, when the filter is subjected to a load, depressions are easily obtained corresponding to the locations of the cross connections. This means that the outlet channels for the filter become somewhat more narrow than the inlet channels, which possibly must be compensated by making the transverse distances shorter. It is possible according to the present invention possible to control deviation from the desired plane areas due to the flexibility of the filter material. Since the distances elements of the invention run in zigzag fashion the filter has a tendency to form a wave shape but with a more constant width in the cross section. This wave shape can be used to stiffen the filter and is preferably arranged cross-wise in relation to the flow direction. By making the bags in this way the flow conditions on the inlet side as well as on the outlet side can be made very uniform. The wave shape can also be used to increase the filter area.
In accordance with one aspect of the invention the welded distance elements are arranged in relation to the filter material either running lengthwise or cross-wise in the filter or in other directions or patterns or only in the shape of points. In all cases the connections can be made shorter close to the bottom and longer in the upper ends of the filter bags despite the welding being carried out with the filter material webs on a constant distance from each other.
The material forming the distance elements may have the same chemical composition as the filter material but may be constituted by a comparatively thin foil from which material has been punched so that bent, V-shaped or zigzag shaped foil bands are formed. Also, other shapes may give the same result.
Since the invented method allows continuous machine fabrication of filter bags by means of welding, good quality is obtained at a low cost with a minimum of manual work.
While welding is preferred, other types of binding, as for instance gluing, seaming, heat treatment, etc., may be employed. Likewise the distance elements may have different shape as long as they in use result in the desired differing length connections. The welding of the distance elements to the sides of the filter need to be along lines but may instead be in points. If the number of cross connections that are required are few in number or if the cross connections are widely spread the distance elements or the web also may include parts that via easily separable extra connections are connected to the parts that are to be welded to the filter material and thereby maintain the distance elements in the right position until its welded. When the welding has taken place the separable part may be drawn loose from the welded parts and removed from the filter.
The distance elements can be comprised of filter material, thin foil, net or a nonwoven material from which has been punched, cut, burnt, or in some other suitable way connections with different lengths have been achieved.
REFERENCES:
patent: 5156661 (1992-10-01), Adiletta
patent: 5215609 (1993-06-01), Sanders
patent: 5891208 (1999-04-01), Gil
patent: 5928396 (1999-07-01), Choi
patent: 6010548 (2000-01-01), Burkhead et al.
Camfil AB
Hayes Soloway Hennessey Grossman & Hage PC
Smith Duane S.
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