Gas separation – Flexible or collapsible bag type – With securing or supporting means
Reexamination Certificate
2000-07-21
2002-09-17
Hopkins, Robert A. (Department: 1724)
Gas separation
Flexible or collapsible bag type
With securing or supporting means
C055S483000, C055S484000, C055S492000, C055S506000, C055S508000, C055SDIG001, C055SDIG003
Reexamination Certificate
active
06451079
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a pocket filter having an outer frame made of plastics material and several adjacent filter elements arranged in the outer frame.
BACKGROUND OF THE INVENTION
A known pocket filter of this type disclosed in German patent publication DE 44 43 144 C1 makes use of an outer frame of which the profiles exhibit a U-shaped inwardly opened cross section. At the end of each of the limbs of this cross section, a web extends inwardly at right angles. The clear distance between webs is smaller than the height of the profiles of the inner frame. Each of these profiles is rotated elastically around its longitudinal axis before it can be manipulated with the free border of the pocket into the interior space of the profile of the outer frame. To this end, the deformation resistance of the longitudinal and front profiles of each inner frame must be reduced by means of end notches, which has a disadvantageous effect on the rigidity of the inner frame. Longitudinal profiles of the inner frame are provided with holes and accompanying complementary, projecting parts protruding outwards. Each projecting part penetrates two pocket borders and one aligned hole in the adjacent inner frame and is finally welded to a rivet head. Transverse walls are arranged between the longitudinal profiles and between adjacent protruding parts and holes of each longitudinal profile. The low level of rigidity of the inner frame and the high assembly costs are disadvantageous.
The design of the outer frame in one piece in the form of a grid with a longitudinal opening for each filter pocket is known per se from U.S. Pat. No. 4,300,927 A. Each inner frame is designed as a funnel shape and, at the inlet side, is interlocked by means of teeth with an inner border of the outer frame.
An additional clamping ring presses the free border of the filter pocket against the outer surface of the inner frame.
U.S. Pat. No. 4,312,648 A shows as known per se a one-piece outer frame onto which outer flanges of funnel-shaped inner frames are placed in an overlapping manner. An additional clamping ring is also required here in accordance with U.S. Pat. No. 4,300,927 A.
One-piece inner frames made of plastics material with transverse walls between the longitudinal profiles are known per se from U.S. Pat. No. 5,298,044 A. The transverse walls laterally limit open-passages; in each case, a projecting part is arranged in the longitudinal center of one longitudinal profile, and a hole is arranged in the other longitudinal profile. The free border of two filter pockets in each case is clamped between adjacent inner frames and their projecting part/hole pairings. Each inner frame is supported with a continuous longitudinal flange in a continuous longitudinal groove of the adjacent inner frame. The facing profiles of the inner frame are held with projecting parts and the free borders of the filter pockets in an outer frame of U-shaped cross section.
Bending the outer frame from a metal strip with notches along the border is known per se from German patent publication DE 87 16 251 U1. In this context, overlapping areas with sections of the sheet metal folded at right angles are produced at the corners of the outer frame in order to achieve the most level outer facing surface of the outer frame possible. The outer frame ultimately has a U-shaped cross section.
In the case of a pocket filter known per se and disclosed in German patent publication DE 93 00 732 U1 all the profiles of the outer frame have a purely U-shaped, inwardly open cross section into which extensions of the corner connectors also exhibiting a U-shaped cross-section are adhered. The border of the filter pockets can be held firmly sealed in the interior space of the profiles of the outer frame with a sealing strip made of PU-foam or cellular rubber. This design is not sufficiently stable especially with relatively high pressure differences and larger filter-pocket sizes. The holding and sealing of the filter pockets in the outer frame are unreliable.
Designing all profiles of the outer frame with a U-shaped, inwardly opened cross section is known per se from U.S. Pat. No. 4,356,011 A. In the interior space, a stopping strip projects from approximately half of every limb; on closing the outer frame, the said stopping strips are placed against the free border of the filter pocket. This free border is inserted together with a bar of the inner frame into the outer frame. Longitudinal bars of adjacent inner frames are attached to one another by rivets with pocket borders clamped between them.
SUMMARY AND OBJECTS OF THE INVENTION
The present invention is based on the object of designing the inner frame to be more stable, and simplifying and improving the installation of the filter elements into the outer frame.
This object is resolved by a pocket filter according to the invention having an outer frame made of plastics material and several adjacent filter elements arranged in the outer frame. The outer frame is composed of opposing limb profiles, a base profile and a closing profile, each of which have an essentially U-shaped cross section with an inwardly opened interior space. Each of these elements can be joined to one another at the corners of the outer frame, wherein each profile of the outer frame exhibits a base wall and limbs extending from the base wall. Holding ribs extend from the free end of each limb and are spaced at a clear distance from one another.
An inner frame made of plastics material of the accompanying filter element is arranged within a free border of each filter pocket. Each inner frame exhibits two opposing longitudinal profiles and two opposing end profiles attached at the ends of the longitudinal profiles.
In a transverse plane of each inner frame at least two holes are spaced from one another and at least two, outwardly extending, complementary projecting parts are arranged alternately in each longitudinal profile, whereby each hole in one longitudinal profile is opposed by a projecting part in the other longitudinal profile. Transverse walls are fastened on the accompanying longitudinal profile and extend into an inlet of the inner frame. Each projecting part of the inner frame penetrates the free border of the accompanying filter pocket and the free border of an adjacent filter pocket and engages into the complementary hole of the inner frame belonging to the adjacent filter pocket. Each filter element engages with the free border of its filter pocket in a sealed manner into the interior space of the adjacent profiles of the outer frame, and one of the transverse walls extends at least approximately in alignment with each hole and each projecting part of the longitudinal profiles of each inner frame.
The pocket filter is especially intended for filtering air and other gases. All the profiles of the outer frame are preferably made of extruded plastics material, for example, highly impact-resistant polystyrene or other plastics materials capable of incineration. The inner frame can be readily manufactured and connected in a form-locking manner with the free border of the accompanying filter pocket. The transverse walls form a desirable stiffening of the inner frame and, moreover, define lines of action for the assembly forces which will have to be applied in order to fit the filter elements into the outer frame. The penetration of the projecting parts through the free border of the filter pocket is also made easier. Additionally, the free ends of each of the projecting parts can be pointed. Fitting together the projecting part and the hole produces an additional mutual stiffening of the joint between adjacent filter elements. The holes and projecting parts are preferably spaced from one another at the same distance.
Inner frames designed in one piece can be manufactured in a particularly cost-favorable and robust manner.
Each inner frame can be designed in two parts so that the transverse walls and the end profiles of both parts of the inner frame overlap and so that the mutually overlapping transverse walls and
Lange Michael
Westphal Uwe
Camfil KG
Hopkins Robert A.
Synnestvedt & Lechner LLP
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