Spacer element for guiding flowing medium

A spacer element for guiding flowing medium, especially for apparatus for separating the medium by reverse osmosis and ultrafiltration, with a respective filter element being accommodated between each two essentially plate-like spacer elements, about which the medium flows. The spacer element includes a plate member having a rim region in which is provided at least one passage for the flowing medium. The plate member has two oppositely disposed plate-like surfaces, on at least one of which are disposed a plurality of raised bosses that project from the surface, with the filter element resting on the bosses. The filter element is in the form of a diaphragm pad, with the medium flowing on both sides thereof.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a spacer element for guiding flowing 
medium, especially for apparatus for filtering and separating the flowing 
medium by microfiltration, ultrafiltration, and reverse osmosis, with a 
respective filter element being accommodated between each two essentially 
plate-like spacer elements, about which the flowing medium flows. 
2. Description of the Prior Art 
A multi-part device for accommodating filter elements is known, for 
example, from the apparatus for separating and filtering flowing medium 
disclosed in German Offenlegungsschrift 33 27 431, where each individual 
filter unit of any desired number of filter element stacks comprises a 
carrier plate, a deflector plate, and accommodated therebetween, a 
diaphragm. With this known apparatus, the periphery of the diaphragm is 
adhesively joined to the periphery of the carrier plate within an axial 
passage. 
Such a known compact construction of filter units to form a filter element 
stack is known as a so-called disk module. As a consequence of the 
individual filter units, the disks or plates have a relatively great 
inherent stability and must be provided with a relatively high pressure 
resistance since the type of diaphragm filter used there absolutely 
demands this. 
Due to the construction of the heretofore known spacer elements and of the 
apparatus in which these known spacer elements are inserted, a 
considerable partial pressure drop occurs between the inlet (unfinished 
solution, i.e. solution that is only partially treated or not treated at 
all) and the outlet (retentate) of the flowing medium into and out of the 
apparatus since the flowing medium of these apparatus generally flow 
through from the inlet to the outlet in a series-type arrangement and in a 
meander-like way along the diaphragm filters that are held by the spacer 
elements or disks. An important reason for the considerable partial 
pressure drop, which generally has a disadvantageous effect, is that the 
diaphragm rests directly upon the carrier plate and/or upon the deflector 
plate, so that the flowing medium becomes increasingly obstructed as it 
flows through the filter element stack. 
For certain applications, for such apparatus neither the known spacer 
elements, which are formed of carrier plates and deflector plates upon 
which up to now the diaphragm rests, nor the up to now conventionally used 
diaphragms, are suitable. 
An apparatus is also known (German Offenlegungsschrift 33 47 283) where 
so-called diaphragm cushions or pads are used that comprise two outer thin 
diaphragm sheets that are hermetically sealed relative to flowing medium 
along their outer edges, and where the filtrate flows to a hole that is 
provided in the diaphragm pad and that, for example, is disposed 
essentially centrally therein, although this is not absolutely necessary, 
and from where the filtrate is suitably collected and supplied to a 
filtrate outlet. 
The apparatus that have been known up to now and that have used 
conventional diaphragms are not suitable for cooperation with the 
aforementioned diaphragm pads, since with such pads it is not possible for 
the medium to flow on both sides of the diaphragm pad in order to fully 
utilize the advantages of the symmetrically constructed diaphragm pad. 
Tests have been conducted in which the diaphragm pad has been placed upon 
a carrier plate or deflector plate via the interposition of a spacer that 
is comprised of gauze or fabric. However, by using this measure the filter 
effect of one active surface of the diaphragm is practically not utilized, 
resulting in a considerable reduction in efficiency or non-utilization of 
the otherwise good separating capacity of such diaphragm pads. 
It an object of the present invention to provide a spacer element that 
permits a good circulation of medium about the filter element, which is 
disposed on the spacer element and is in the form of a diaphragm pad, so 
that it is also possible to have a parallel arrangement of diaphragm pads 
in an apparatus and/or the series arrangement of several units of 
diaphragm pads arranged in parallel, in order to minimize the pressure 
drop of the flowing medium between the inlet and the outlet, whereby the 
diaphragm pads are to be accommodated in a manner that is essentially 
resistant to pressure differentials.

SUMMARY OF THE INVENTION 
The spacer element of the present invention is characterized primarily in 
that it comprises a plate member having a rim region in which is provided 
at least one passage for the flowing medium, with the plate member having 
two oppositely disposed plate-like surfaces, on at least one of which are 
disposed a plurality of raised projections or bosses that project from 
this surface, with the filter element resting on the bosses whereby the 
filter element is in the form of a diaphragm pad, with the flowing medium 
flowing on both sides thereof. 
The advantage of the inventive spacer element is essentially that the 
flowing medium, which passes over both sides of the diaphragm pad as 
unfinished solution over essentially the entire surface from one side to 
the other, has a practically non-obstructed flow, since the bosses have an 
only infinitesimally small contact surface with the diaphragm pads and 
therefore do not obstruct the flow of the medium, as a result of which 
similarly no inorganic deposits can form that prevent the flow of the 
medium and the filtering effect of the diaphragm pad, and the build-up of 
which, as was known up to now with contact surfaces of carriers for the 
diaphragm device, is prevented. 
In order to be able to fixedly hold the diaphragm pads, which are generally 
fused together along the outer periphery, between the spacer elements, it 
is advantageous that the bosses have different heights, i.e. to make them 
higher in the rim region where the weld seam of the diaphragm pad is 
provided, so that at that location the diaphragm pad could also be 
reliably fixed. 
Pursuant to one advantageous specific embodiment of the present invention, 
in a plane parallel to the surfaces of the filter element, the bosses are 
provided with an essentially circular cross-sectional configuration. 
Pursuant to an alternative advantageous specific embodiment, in a plane 
parallel to the surfaces of the filter elements, the bosses have an 
essentially spherical cross-sectional configuration, which can, however, 
also preferably be essentially tear-shaped, whereby such a tear-shaped 
cross-sectional configuration to a large extent prevents turbulence in the 
medium that is flowing past, and reduces a pressure loss. 
Pursuant to another advantageous specific embodiment of the inventive 
spacer element, the latter is provided with an outer, essentially 
circumferential rim on both of its surfaces, whereby preferably one of the 
rims is raised from the surface by at least the thickness of a filter 
element. 
In this connection, it should be noted that the spacer element need in no 
way be limited to a disk or plate having an essentially circular 
configuration. Rather, the design of the outer contours of the spacer 
element, i.e. as a circle, as any other suitable polygon, etc., depends 
upon the type of application of the spacer element in the apparatus. The 
filter element, which is embodied as a diaphragm pad, can also have any 
desired suitable outer contour, for example a circle, polygon, etc., 
whereby the outer contour of the selected spacer element need not 
necessarily coincide with the outer contour of the diaphragm pad 
accommodated therein. 
For example, it has been shown to be advantageous to provide the spacer 
element with an essentially circular disk-like configuration, whereas the 
diaphragm pad accommodated therein, for example, advantageously can have 
an octagonal contour. 
The spacer element itself, in principle, can be made of any desired 
suitable material that imparts to the spacer element a low weight, a high 
strength, and an ease of fabrication. 
The spacer element is advantageously made of plastic, preferably ABS, which 
is particularly suitable where a high quality of the filtrate, for example 
drinking water quality or also high-purity water, is required. 
The spacer element can also be made of standard polystyrene, SAN, or 
Luran(Polystyrol). 
Further specific features of the present invention will be described in 
detail subsequently. 
DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring now to the drawings in detail, the apparatus 10 for filtering and 
separating flowing medium 11 by reverse osmosis and ultrafiltration is 
illustrated by way of example in FIG. 4, which will subsequently be 
discussed first. A number of filter elements 12 and spacer elements 11 are 
stacked together in the apparatus 10 to form a filter element stack of 
predetermined length. 
For a better understanding of the construction of the spacer element, the 
apparatus 10 will be explained in conjunction with filter elements 12 in 
the form of diaphragm cushions or pads. The apparatus 10 essentially 
comprises a tubular casing 101. Spacer elements 11 and filter elements 12 
are alternately disposed in the casing 101, i.e. a filter element 12 is 
disposed between each two spacer elements 11. Only at the two ends of a 
filter element stack that is formed in this way does the spacer element 
have no filter element 12. At the connection end of the filter element 
stack a connection flange 104 is provided; at the opposite end of the 
filter element stack, a terminal flange 105 is provided. The filter 
element stack and the two flanges 104, 105 are held together by a central 
clamping bolt 102 that extends through appropriate central holes of all of 
the aforementioned elements, whereby at both ends of the filter element 
stack the clamping bolt 102 is provided with nuts 103 that hold the filter 
element stack together; for the sake of simplification, merely one of the 
nuts 103 is shown in FIG. 4. The filter element stack is sealed off in a 
known manner via gaskets or other seals 109 relative to the tubular casing 
101 into which the filter element stack is placed. 
Provided in the connection flange 104 is an opening or inlet 106 for the 
introduction of the flowing medium 19, which represents an unfinished 
solution that is to be separated (i.e. a solution that has not been 
treated at all or has not been completely treated), as well as an outlet 
108 for the filtrate and an outlet 107 for the retentate. 
Via the inlet opening 106 provided in the connection flange 104, the 
flowing medium 19 enters the interior of the casing 101, and in particular 
into the gap between the filter element stack and the inner wall of the 
casing 101. In this gap, the flowing medium 19 passes into the space 
formed between the terminal flange 105 and the adjacent spacer element 11. 
The flowing medium 19 is symbolized within the apparatus 10 by arrows. 
In the apparatus 10 illustrated in FIG. 4, the uppermost spacer element 11 
has only a single passage 18 for the flowing medium, with this passage 
being provided in the rim region 16 in the disk member. The flowing medium 
19 passes through this passage 18 into a chamber 23 formed between two 
spacer elements 11 and, since several spacer elements 11 are disposed in 
such a way that the passages 18 are arranged one above the other, the 
flowing medium 19 passes into the chambers 23 of respectively adjacent 
spacer elements 11 disposed therebelow. 
In the illustrated embodiment of FIG. 4, a unit is formed of five spacer 
elements 11 that are connected with one another in this manner. 
As will be described in greater detail subsequently, a respective filter 
element 12 is disposed in each chamber 23. The flowing medium 19 that is 
in the chambers 23 sweeps or passes over both sides of a respective filter 
element 12 that is disposed in the chamber 23. In FIG. 4, the flow is from 
right to left flowing toward the left side of the spacer element 11, 
whereby in the rim portion in the disk member there is similarly formed a 
passage 182 for the flowing medium 19. 
In the filter elements 12, which are disposed in the chambers 23 and are in 
the form of diaphragm pads, the filtrate is conveyed to an opening 
provided in the filter element 12, i.e. in the diaphragm pad. In the 
apparatus illustrated in FIG. 4, i.e. in the diaphragm pad 12 used 
therein, the aforementioned opening is a central opening. The filter 
elements 12, i.e. diaphragm pads, accommodated in the chambers 23 are 
sealed off relative to the spacer elements that confine them in a known 
manner in the region toward the filtrate outlet opening, which is 
symbolized by the central hole 15. 
The spacer element 111 that in the illustration of FIG. 4 delimits the 
bottom of the aforementioned unit that is formed of five spacer elements 
11 is provided, just as was the case with the uppermost spacer element 11, 
with merely a single passage 18 for the flowing medium 19, with this 
passage being provided in the rim region 16 in the disk member 17. As a 
result, as shown in FIG. 4, the flowing medium 19 can pass through the 
aforementioned spacer element 11 through only the single passage 18. 
Subsequently disposed is again a unit that is comprised of five spacer 
elements 11, whereby essentially oppositely disposed openings 18, 182 are 
provided for the flowing medium 19, so that, as described in conjunction 
with the upper unit, also in this second unit flowing medium 19 again 
passes over both sides of a plurality of filter elements 12 that are 
embodied as diaphragm pads. In the apparatus 10 illustrated in FIG. 4, the 
bottom of this unit is delimited by a spacer element 111 that again is 
provided with only a single passage 18 embodied in the rim region 16 in 
the disk member 17, so that through this passage 18, all of the 
concentrated flowing medium 19 (retentate) that leaves the apparatus 10 
can leave the same through the outlet 107 that is formed in the connection 
flange 104. 
The inventive spacer element 11 or 111 is illustrated in FIG. 1. In this 
embodiment, the spacer element is essentially formed by a circular disk 
member 17 that on two oppositely disposed sides is delimited in a 
chord-like manner, i.e. at these locations the disk member 17 deviates 
from a strictly circular shape. 
The disk member 17 is provided with two essentially parallel disk-like 
surfaces 20, 21. The spacer element 11 or 111 is essentially formed by the 
disk member 17 and is provided on both sides of the disk-like surface 20, 
21 with a rim 13, 14, which essentially completely defines the spacer 
element 11, 111. Formed in a region 16 of the rim of the spacer element 
11, 111 that is, for example, formed by an imaginary chord and the rim 13, 
14 that delimits the chord, is at least one passage 18 in the disk member 
17 through which passes the flowing medium 19, as previously described. 
The passage of the flowing medium 19 through the passage 18 is symbolized 
in FIG. 1 by the arrows 19. In the illustrated embodiment of the spacer 
element 11, several of which are respectively disposed in the middle of 
the unit of the apparatus 10 of FIG. 4, formed on that side of the disk 
member 17 that is essentially opposite the one passage 18 is a further 
passage 182 which the flowing medium 19 again enters after it has passed 
over both sides of the octagonal filter element 11 that is indicated by 
dashed lines in FIG. 1. A plurality of further passages 180, 181 or 183, 
184 can be disposed not only in the rim region 16 of the spacer element 11 
in which the one passage 18 is provided, but also in the other rim region 
16 in which the second passage 182 is disposed. These additional passages 
180, 181 and 183, 184 ensure that the flowing medium 19 very uniformly 
sweeps across the filter element 12 that rests upon the spacer element 11, 
111. 
To definitely ensure that on the one hand the filter element 12 securely 
rests upon the spacer element 11, 111 while the flowing medium 19 passes 
by, and on the other hand, due to the support of the filter element 12 on 
the spacer element 11, 111, the contacted support surface is 
infinitesimally small, a number of raised projections or bosses 22 are 
provided on the disk-like surfaces 20, 21 and project therefrom, so that 
the diaphragm pad, about both sides of which the flowing medium 19 passes, 
rests merely on these bosses 22. In the plane parallel to the surfaces 20, 
21, the bosses 22 can have any desired cross-sectional shape, although 
this shape is preferably circular and/or spherical. The highest portion of 
the bosses 22 that projects from the surfaces 20, 21 has a semicircular 
cross-sectional configuration, so that, as desired, even during operation 
of the apparatus 10 with the inventive spacer elements 11, 111 as well as 
the inserted diaphragm pads, these in fact rest only with an 
infinitesimally small surface upon the tips of the bosses. The plurality 
of bosses 22 disposed on the surface 20, 21 are disposed thereon in such a 
way that the flow of the medium 19 is not interrupted, so that the 
disadvantageous inorganic and organic diaphragm coatings or deposits, 
which have to be watched with other apparatus or filter elements, are also 
completely prevented by the suitably selected type and location for the 
disposition of the bosses 22 on the surfaces 20, 21. 
The spacer element 11, 111 can be made of any suitable material, for 
example plastic such as polystyrene, acrylonitrile-butadiene-styrene 
(ABS), styrene-acrylonitrile polymer (SAN), Luran, or the like. It should 
be noted that in principle stainless steel is also suitable for the 
production of such spacer elements 11, 111. 
The present invention is, of course, in no way restricted to the specific 
disclosure of the specification and drawings, but also encompasses any 
modifications within the scope of the appended claims.