Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1995-12-22
2001-02-27
Ryan, Patrick (Department: 1725)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S227000, C156S210000, C156S218000, C156S073100, C210S494200, C210S494300
Reexamination Certificate
active
06193830
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a filter insert, configured as a pleated pack and made of thermoplastically bondable nonwoven material, such as fiber material, and a method of its manufacture.
Such a filter pack and method are known from EP 0 438 639 B1, corresponding to U.S. Pat. No. 5,167,740, which is incorporated herein by reference.
In particular, the invention, like that disclosed in U.S. Pat. No. 5,167,740, relates to a filter insert comprising a planar filter medium folded and then set in its folded (pleated) form at a specific fold spacing.
In U.S. Pat. No. 5,167,740, after the process step of creating a defined fold spacing, the two outer edges of the filter insert are clamped into comb-like profiles, having profiles substantially corresponding to the fold pattern to engage in toothed fashion into the top and bottom of the folds. The spacing between the comb-like profiles is chosen to be the same as or slightly less than the thickness of the nonwoven material.
In U.S. Pat. No. 5,167,740, the filter material is allowed to project beyond the comb-like profiles, on each long side of the folded pack, a distance equal to 1.5 to 2.5 times the fold spacing. Subsequently, the resulting excess-length material is folded by means of a pressure element acting laterally thereon, until the excess-length material lies against the adjacent fold end so that the edges overlap. The overlap zone is simultaneously thermally bonded by means of energy delivered via the pressure element.
A filter insert produced in this manner possesses great inherent stability, so that an additional receiving frame can be omitted for installation in a filter housing. A further advantage of the filter insert manufactured with this known method is its good recycling capability, since the filter insert is made of only one material, namely the nonwoven material. The known filter insert is flexurally strong in three coordinate axes, the flexural strength resulting from bonding of the excess-length material of each fold to the adjacent folds. The consolidated side surfaces thus perform the function of a frame. Because of the large excess length, which equals 1.5 to 2.5 times the fold spacing, creasing and overlapping of all adjacent folds in one direction results in a closed side surface which imparts three-dimensional rigidity to the known filter.
SUMMARY OF THE INVENTION
It is an object of the invention to develop further a manufacturing method for a filter insert, configured as a folded pack, of the aforesaid type, in such a way that the filter insert is flexurally and torsionally movable and that the manufacturing method can be implemented easily with few operations.
In accordance with the present invention, during manufacture the folded filter material projects beyond the comb-like profiles at each outer edge a distance less than the distance of the fold spacing. A sealing band, having a width corresponding substantially to the height of the folds, is laid on the outer edges on the long sides. The sealing bands are then compressed by pressure elements acting laterally thereon and at the same time thermally bonded, with energy delivered via the pressure elements, to the outer edges of the filter material. The bond points so formed are pressed together and immobilized until they cool. The comb-like profiles are then removed, and the folded pack is cut to length.
In the context of this specification, and the claims hereto, the “fold spacing” is understood to be the distance between adjacent fold peaks. Preferably, during manufacture, the outer edges of the folded filter material project beyond the comb-like profiles at a distance of 0.1 to 0.5 times the fold spacing. At this length, folding the excess length does not result in the extent of overlap taught in the prior art U.S. Pat. No. 5,167,740. Accordingly, and advantageously, a filter insert manufactured in accordance with the invention is flexurally and torsionally movable in the lengthwise direction, transverse to the folds of the folded pack. This type of movability of the filter insert is advantageous especially when the latter is to be mounted in filter housings that enclose a rounded, domed, or internally contorted installation space.
The sealing bands are also preferably made of a nonwoven material. Thus, thermal bonding of the sealing bands to the filter material is facilitated. The pressure elements are heated to a temperature that is above the melting range of the bondable constituents of the sealing bands and/or the nonwoven material of the folded pack. In order to avoid impairing the sealing regions other than the points to be bonded, the pressure elements preferably consist of ultrasonic sonotrodes. Ultrasonic sonotrodes allow localized bonding of the sealing bands to the outer edges of the filter material. Thus, by means of the pressure elements, the sealing bands are sealed only at spots or lines, and adhesively joined to the outer edge of the filter material by the meltable constituents. Outside the regions in which the sealing bands are bonded, the sealing bands have a comparatively uncompressed structure, which facilitates sealing the periphery of the folded pack with respect to a filter housing.
The invention also relates to a filter insert in the form of a folded pack manufactured according to the method described above. The sealing bands consist of a nonwoven material and each has a height corresponding to the height of the folded pack. The sealing bands are preferably bonded to the outer edges of the folded pack. Each sealing band is preferably bonded by at least two straight-line bonding beads, running parallel to one another, preferably extending along each outer edge of the folded pack, and bounding at least one substantially uncompressed section of the sealing band. With an embodiment of this kind, it is advantageous that the sealing bands form, in the direction of the pressure differential and transverse to the direction of the bonding beads, a labyrinth seal with the adjacent housing, since only the uncompressed regions of the sealing bands contact the housing in the form of sealing lips.
REFERENCES:
patent: 2663660 (1953-12-01), Layte
Elve M. Alexandra
Firma Carl Freudenberg
Kenyon & Kenyon
Ryan Patrick
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