U.S. patent number 3,759,391 [Application Number 05/293,997] was granted by the patent office on 1973-09-18 for coiled filter element and method of manufacturing the same.
This patent grant is currently assigned to Robert Bosch GmbH. Invention is credited to Adolf Dreher.
United States Patent |
3,759,391 |
Dreher |
September 18, 1973 |
COILED FILTER ELEMENT AND METHOD OF MANUFACTURING THE SAME
Abstract
An elongated strip of filter material is wound into a coil and
consists of two superimposed strip portions connected to each other
at their one side and spaced from each other at their opposite
side. The strip portions, in consecutive windings of the strip, are
spaced from each other at their connected sides and connected at
their spaced sides to respectively form first and second parallel
adjoining filter pockets of substantially V-shaped cross section,
open at the opposite end faces of the coil. Transverse corrugations
are provided in the strip portions and afford adjustments in the
length of the respective strip portions to the extent such
adjustments are necessary during the convoluting of the strip
portions into coil shape.
Inventors: |
Dreher; Adolf (Unterhausen,
DT) |
Assignee: |
Robert Bosch GmbH (Stuttgart,
DT)
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Family
ID: |
5746587 |
Appl.
No.: |
05/293,997 |
Filed: |
October 2, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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74605 |
Sep 23, 1970 |
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Foreign Application Priority Data
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Sep 26, 1969 [DT] |
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P 19 48 704.8 |
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Current U.S.
Class: |
210/494.1;
210/497.2 |
Current CPC
Class: |
B01D
25/24 (20130101) |
Current International
Class: |
B01D
25/00 (20060101); B01D 25/24 (20060101); B01d
027/06 () |
Field of
Search: |
;210/494,497
;55/520 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Zaharna; Samih N.
Assistant Examiner: Calvetti; F. F.
Parent Case Text
This is a continuation, of application Ser. No. 74,605, filed Sept.
23, 1970, now abandoned.
Claims
What is claimed as new and desired to be protected by Letters
Patent is set forth in the appended claims:
1. A coiled filter element, comprising a coil of an elongated strip
of filter material transversely folded upon itself so as to produce
superimposed longitudinally coextensive strip portions each having
two longitudinally extending margins respectively located at one
and at another lateral side of said strip, said strip portions
being of one piece with one another along said margins of said
other lateral side of said strip; a plurality of at least
substantially parallel corrugations provided in each of said strip
portions and extending transversely to the elongation of said
strip, the convolutions of said strip defining two spirally
convoluted internal filter pockets one of which is open at one
axial end of the coil and the other of which is open at the other
axial end of the coil, and said corrugations enabling compensation
of length variations which occur due to convoluting of said strip
in one of said strip portions with reference to the other strip
portion with which said one strip portion is of one piece along
said margins at said other lateral side; and sealing means
sealingly connected consecutive convolutions of said coil in the
region of one of said axial ends of the coil, which end lies
opposite to said other lateral side of said strip at which said
strip portions are of one piece with one another.
2. A filter element as defined in claim 1, and further comprising
spacing means extending along said margins in the region of one of
said axial ends of the coil.
3. A filter element as defined in claim 2, wherein said spacing
means extending along said margins at said other lateral side and
spaces said margins apart.
4. A filter element as defined in claim 2, wherein said spacing
means comprises a spacing strip having a width substantially
smaller than the width of said strip portions and extending along
at least substantially the entire length of the latter.
5. A filter element as defined in claim 4, wherein said spacing
strip has longitudinally adjacent transverse corrugations spaced
and configurated differently from said corrugations of said strip
portions for preventing interengagement therewith.
6. A filter element as defined in claim 1, and further comprising
first spacing means extending between the margins of said strip
portions at said one lateral side and spacing said margins apart;
and second spacing means extending along the margins at said other
lateral side and spacing apart consecutive convolutions of the
coil.
7. A filter element as defined in claim 1, wherein said
corrugations are spaced at identical distances longitudinally of
said strip.
8. A filter element as defined in claim 1, wherein said
corrugations extend over the entire width of said strip
portions.
9. A filter element as defined in claim 1, wherein said
corrugations extend over only part of the width of said strip
portions, and wherein said margins of said strip portions are free
from said corrugations at least at one of said lateral sides.
10. Method of manufacturing a coiled filter element, comprising the
steps of forming an elongated strip of filter material transversely
folded upon itself so as to produce superimposed longitudinally
coextensive strip portions extending lengthwise of said strip and
each having two longitudinally extending margins located at
opposite lateral sides of said strip, with the margins at one
lateral side of said strip portions being of one piece with each
other; forming a plurality of at least substantially parallel
transverse corrugations in each of said strip portions of said
elongated strip; providing adhesive means on said strip portions
along said margins at the other lateral side of said strip; and
convoluting said strip to form a coiled element having a plurality
of convolutions forming a pair of spirally convoluted filter
pockets one of which is open at one axial end of said coiled
element and the other of which is open at the other axial end of
said coiled filter element.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a coiled filter element,
particularly for liquids, and a method of manufacturing the
same.
Conventional coiled filter elements in the art are made of an
elongated strip of filter material and consist of two superimposed
strip portions which, lengthwise, are connected at their one side
and open at their opposite side and which, in wound condition, are
collectively interconnected at their open sides and spaced at their
connected sides so as to respectively define first and second
parallel adjoining filter pockets in the coil with the filter
pockets open at the opposite end faces of the coil.
One such known coiled filter element comprises consecutively wound
strip portions of a paper filter material and which, in conjunction
with a spacer strip arranged at the opposite longitudinal sides of
the strip portions, define a substantially V-shaped cross
section.
In winding the strip portions to form a coil, a linear differential
between the length of the inner strip portion relative to that of
the outer strip portion necessarily develops, and it has been found
that even by using strip portions made of crepe paper, it is
impossible to provide sufficient compensation to maintain the edges
of both strip portions in overlapping relationship.
A paper strip folded in itself to V-shaped configuration in order
to obtain the inner and outer strip portions, could under these
circumstances be wound into a coil only under the application of
considerable tensile forces; this, however, would prevent the
formation of satisfactory filter pockets in the coil.
Consequently, although the use of such coiled filter elements is
theoretically known, they have not been actually made and used
heretofore because of these manufacturing problems.
Further known are coiled filter constructions which, in order to
overcome the above disadvantages, employ two spirally wound paper
strips whose longitudinal margins extending at the axially opposite
end faces of the filter element, are alternately connected in
permeable and impermeable relationship.
Even though this latter type of filter construction avoids the
above-discussed length-differential problem, it has the
disadvantage that it requires adhesive seams or connections which
are twice as long as those needed in the first mentioned type,
which is uneconomical and expensive as regards the costs of
manufacturing and of materials, not to mention the greater
likelihood of leaks along these longer seams.
Further known is coiled filter element which, in order to provide a
length compensation of one strip portion relative to the other,
utilizes two filter material strip portions of unequal length. This
avoids the above-discussed problem, but such a construction cannot
be economically manufactured.
SUMMARY OF THE INVENTION
Object of the present invention is to overcome the above
disadvantages and to provide a simple but effectively and
economically constructed coiled filter element which is designed in
such a way as to afford a simple but effective compensation for the
length differential which develops between the inner and outer
strip portions when they are wound into the form of a coil.
A further object of the present invention is to provide a method of
manufacturing such a coiled filter element according to the
invention.
The coiled filter element according to the invention comprises a
spirally wound elongated strip of filter material consisting of two
superimposed strip portions extending lengthwise of the strip and
each having two longitudinally extending margins located at
opposite lateral sides of the strip. Each of the strip portions is
provided with a plurality of at least substantially parallel
corrugations extending transversely to the elongation of the strip.
First spacing means are interposed between the strip portions and
extend along and space apart the margins thereof at one lateral
side of the strip, and second spacing means are disposed on and
extend along the margins of the strip portions at the other lateral
side of the strip for spacing apart the consecutive convolutions of
the coiled filter element. During winding of the superposed strip
portions the corrugations of the other strip portion "flatten" as
they permit the other strip portions to be sufficiently
longitudinally stretched to compensate for the length differential
which would otherwise develop between it and the inner strip
portion.
The novel features which are considered as characteristic for the
invention are set forth in particular in the appended claims. The
invention itself, however, both as to its construction and its
method of operation, together with additional objects and
advantages thereof, will be best understood from the following
description of specific embodiments when read in connection with
the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
The single FIGURE of the drawings illustrates in perspective view
the winding construction of the coiled filter element according to
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The filter element coil 1, particularly for use with liquids,
essentially comprises a crepe paper strip 2 which is folded upon
itself in substantially V-shaped configuration to provide the strip
portions 2a and 2b which are superimposed and longitudinally
coextensive. Two spacing strips 3, 4 and adhesive filaments 5, 6,
are spirally wound to the shape of the coil 1 together with the
strip 2 onto core tube 7.
The two strip portions 2a, 2b are provided with a plurality of
transverse corrugations 8 which are adjacent one another
longitudinally of the strip 2. The folded crepe paper strip 2 can
most easily be formed with such corrugations by advancing it
through a pair of loosely intermeshing spur gears, not shown, to
thereby form the closely arranged, parallel corrugations 8 in the
strip sections 2a and 2b. Aside from their length-compensating
function, the corrugations also reinforce the paper and
consequently improve the pressure resistance of the filter element
coil 1.
Provided between the margins 9 and 10 at the open side of the
substantially V-shaped paper strip 2, is a first corrugated spacer
strip 3, to maintain these margins slightly spaced apart from one
another. A similar corrugated spacer strip 4 extends along the
margin 11 at that side of the strip portion 2a which faces the
interior of the coil 1.
On the same side of the strip portion i l convolutions. provided
two adhesive filaments 5 and 6 which extend along the margin 9 and
serve to maintain consecutive convolutions of the coil 1 slightly
spaced as well as to provide a seal between such consecutive
voconvolutions.
In this manner, the coil 1 is provided, when the strip 2 is
convoluted, with two spirally intercalated filter pockets 12 and 13
of which pocket 12 is open for entry of fluid at the axial end 14
of the coil while the pocket 13 is open for the same purpose at the
other axial end 15 of the coil 1.
If the material of the strip 2 is relatively readily stretchable,
either inherently or because of its creping, it may be advantageous
not to provide the margins 9 and 10 -- where the filaments 5 and 6
are located -- with the grooves or corrugations 8. Instead, these
margins 9 and 10 could be flat or almost flat, thus reducing the
quantity of adhesive filament required to obtain the desired
effects.
The present invention, compared to what is known from the art,
requires adhesive seams which are approximately only half as long
as known from the art. This is not only reflected in a saving of
material, but also permits much more rapid and economic manufacture
of the novel filter element and at the same time increases the
reliability of operation of the element, the latter factor being
aided by the fact that the novel element has a larger active
surface area available for filtration purposes. According to
another concept of the invention it is also possible to omit one of
the spacer strips 3 and 4.
Without further analysis, the foregoing will so fully reveal the
gist of the present invention that others can by applying current
knowledge readily adapt it for various applications without
omitting features that, from the standpoint of prior art, fairly
constitute essential characteristics of the generic or specific
aspects of this invention and, therefore, such adaptations should
and are intended to be comprehended within the meaning and range of
equivalence of the following claims.
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