A flow meter, particularly for warm water heating systems, includes
a measuring element and an indicator element. The indicator element
has a basic component with a cylindrical attachment extending into
the collector pipe. An indicator rod with a rebounding plate extends
into the measuring element and vertically slidable. According to
the invention, a filter is installed ahead of the rebounding plate
in the flow direction of the heating medium. Where the basic component
extends to a cylindrical attachment affecting the flow against the
rebounding plate, it is suitable to provide a number of slits in
the cylindrical external wall of the lower portion of the attachment,
the slits being distributed around the perimeter parallel to the
axis. In this manner, dirt particles, which could impair the function
of the indicator, are virtually filtered out.
What is claimed is:
1. A flow meter comprising: a measuring element for measuring a
flow of a medium; and an indicator element for indicating a flow
of the medium, wherein the indicator element includes a basic component
having a cylindrical portion extending into a distribution pipe
through which an indicator rod having a rebounding plate extends
into the measuring element and is vertically movable therein, and
wherein a filter is provided upstream of the rebounding plate in
the flow direction of the medium.
2. The flow meter according to claim 1 wherein the basic component
extends into a cylindrical attachment that influences the flow towards
the rebounding plate, and wherein a lower portion of the cylindrical
attachment is designed as the filter.
3. The flow meter according to claim 2 wherein the lower portion
of the cylindrical attachment is provided with a plurality of slits
that are distributed around a circumference of the lower portion
and are parallel to an axis formed by the flow direction of the
medium through the measuring element.
4. The flow meter according to claim 3 wherein the slits are evenly
distributed around the circumference of the lower portion of the
5. The flow meter according to claim 3 wherein a width of the
slits increases in the direction of the flow.
6. The flow meter according to claim 3 wherein at a point of entry
of the medium, the slits have a width of 0.5 to 1.0 mm.
7. The flow meter according to claim 2 wherein the lower portion
of the attachment is designed as an insert, which is connectable
to the attachment by insertion into the cylindrical attachment.
8. The flow meter according to claim 7 wherein the indicator rod
is guided in the insert vertically slidable.
9. The flow meter according to claim 2 wherein the lower portion
is made of plastic.
10. The flow meter according to claim 1 wherein the flow meter
is used for warm water heating systems.
11. The flow meter according to claim 6 wherein the slits have
a width of 0.8 mm.
12. The flow meter according to claim 1 wherein the filter is
between the indicator element and the measuring element.
13. A flow meter comprising: an indicator element for indicating
a flow rate of a medium through the flow meter via a rebounding
plate that is slidably attached to the indicator element; a measuring
element having a measuring bore extending along an axis, the axis
being substantially parallel to a flow direction of the medium,
the rebounding plate slidably extending into the measuring bore
of the measuring element; and a cylindrical attachment being provided
between the indicator element and the measuring element, the cylindrical
attachment having an internal bore for enabling the rebounding plate
to extend slidably therethrough from the indicator element to the
measuring element, the internal bore of the cylindrical attachment
having a diameter that is adapted to fixedly receive an insert,
the insert having a plurality of apertures provided therein for
filtering dirt particles from the medium.
14. The flow meter according to claim 13 wherein the apertures
that are provided in the insert for filtering dirt particles from
the medium have a greater width on an inner circumference of the
insert than on an outer circumference of the insert.
15. The flow meter according to claim 13 wherein a mesh screen
is provided to substantially cover a medium entrance of the apertures,
which are provided on the insert.
16. The flow meter according to claim 13 wherein the insert has
two apertures on a circumferential side of the insert.
17. The flow meter according to claim 16 wherein the two apertures
are substantially across from one another on the circumferential
side of the insert.
18. The flow meter according to claim 13 wherein the flow meter
is a forward-flow flow meter.
 This nonprovisional application claims priority under 35
U.S.C. .sctn. 119 on German Patent Application No. DE 203 07 977.9
filed in Germany on May 22 2003 which is herein incorporated by
BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a flow meter, particularly
for warm water heating systems.
 2. Description of the Background Art
 Flow meters of this type for flowing liquids are generally
known. They are frequently used in warm water heating systems to
register partial flows of a heating medium in various pipe lines,
or branch lines, and to be able to monitor them during operation.
Flow meters of this kind have an indicator scale, of which the respective
position of an indicator rod, having a rebounding plate that is
influenced by the flowing medium, can be read. Conventionally, the
indicator scale is usually arranged on a surface of an inspection
glass along a line.
 In a conventional flow meter of this type, for example,
as described in EP 0 884 514 B1 the indicator element as well as
the measuring element are screwed opposite of each other with cylindrical
attachments into a collector pipe, whereby a gap is formed between
the lower end of the indicator element and the upper end of the
measuring element. If such a flow meter is not used in the return
flow, as taught in EP 0 884 514 B1 where the rebounding plate of
the indicator rod is slidable in the internal bore of the measuring
element and is exposed to direct flow, but is used in the forward
flow, then it is necessary to influence the flow against the rebounding
plate in order to avoid any turbulence of the flow against the rebounding
plate. This is accomplished, for example, by arranging a pipe-shaped
attachment in the area between the lower end of the indicator element
and the upper end of the measuring element, which bridges this gap
for the most part and is provided with openings, which influence
 It was found in actual operation that in warm water heating
systems, particularly after operation of the system was started
or after the system was serviced, sharp-edged dirt particles are
often transported with the heating medium. Since the annular gap
between the outer perimeter of the rebounding plate and the internal
bore of the measuring element is, for flow-technical reasons, very
narrow, the danger exists that such dirt particles can get jammed
or clogged in this annular gap, thereby blocking the function of
SUMMARY OF THE INVENTION
 It is therefore an object of the present invention to provide
a flow meter that avoids an impairment of the measuring process
by dirt particles without disturbing the steady flow against the
 The invention is based on the idea to install a filter ahead,
e.g., upstream, of the rebounding plate in the flow direction of
the heating medium to filter out dirt particles that could impair
the function of the indicator. It is advantageous, for practical
purposes, to design this filter in the form of longitudinal slits
in the external wall of the cylindrical attachment, which is an
extension of the cylindrical part of the basic component of the
indicator element extending in the direction of the measuring element.
 It is considered particularly beneficial to design this
attachment as an insert, which can be made of metal or, in particular,
of plastic, and can be installed by insertion into the internal
bore of the cylindrical part of the basic component.
 Further scope of applicability of the present invention
will become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the invention
will become apparent to those skilled in the art from this detailed
BRIEF DESCRIPTION OF THE DRAWINGS
 The present invention will become more fully understood
from the detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus,
are not limitive of the present invention, and wherein:
 FIG. 1 is a partial cross-section of a side view of a flow
meter mounted on a collector pipe according to a preferred embodiment
of the invention;
 FIG. 2 is a cross section through the flow meter along the
line II-II in FIG. 1;
 FIGS. 3a-d show various illustrations of a basic component
of an indicator element of the flow meter;
 FIG. 4 is an illustration of an alternate embodiment of
the flow meter of FIG. 1; and
 FIG. 5 is a cross section through the flow meter along the
line V-V in FIG. 4.
 The flow meter 1 which is illustrated in FIG. 1 including
a measuring element 2 and an indicator element 3 is mounted on
a forward-flow distribution pipe 4 of a warm water heating system
and measures the forward flow, in the direction of arrow 7 in an
individual branch line 5. It is common practice to arrange several
such flow meters next to one another on the distribution pipe 4
for various branch lines.
 The measuring element 2 which is tightly screwed into the
distribution pipe 4 by an external screw thread 6 has a connecting
branch line 5 which is not actually illustrated but only indicated
by the arrow 7 which is pointing in the flow direction. As is principally
standard practice, a rebounding plate 10 which is supported by
an indicator rod 9 is located in a measuring bore 8 of the measuring
element 2. The measuring bore 8 is conically enlarged towards the
branch line 5 whereby the position of the rebounding plate 10 along
the measuring bore 8 depends on the respective flow-through.
 The indicator element 3 is mounted opposite the measuring
element 2 on top of the distribution pipe 4. The indicator element
3 includes a basic component 11 that is tightly screwed together
with the distribution pipe 4 and has a tube-shaped inspection glass
12 that is made of, for example, transparent material. The indicator
rod 9 is guided in the indicator element 3 so that it can slide
vertically, e.g., in the flow direction, and has a disk-shaped pointer
13 close to its upper end, which moves up and down in the bore of
the inspection glass 12 depending on the position of the rebounding
plate 10. Across from the bottom of the bore of the inspection glass
12 and the pointer 13 that is, the indicator rod 9 a pressure
spring 14 is supported. The scale for reading the respective flow
quantity is located in a sleeve-shaped scale carrier 15 which is
arranged around the inspection glass 12. The principle construction
and function of such a flow meter are known to those skilled in
the art and do not need to be described any further.
 As can be seen in FIG. 1 the basic component 11 of the
indicator element 3 which is screwed into the distribution pipe
4 by an external screw thread 16 extends within the cross section
of the distribution pipe 4 into a cylindrical attachment 17. The
cylindrical attachment 17 features an internal bore, through which
the indicator rod 9 is vertically slidable. According to the invention,
a lower portion 18 of the cylindrical attachment 17 which has limited
play towards an upper front edge 19 of a connecting pipe 20 of the
measuring element 2 extending into the distribution pipe 4 is designed
as a filter. In the illustrated embodiment, the lower portion 18
has a number of slits 21 extending parallel to an axis, e.g., the
flow direction, of the flow meter and are evenly distributed around
the perimeter of the attachment 18.
 The distribution of the longitudinal slits 21 and the flow
through the lower portion 18 thus achieved is illustrated in FIG.
2 in a cross section through the lower portion 18 along line II-II
shown in FIG. 1. It can also be seen here that the width of the
longitudinal slits increases in the direction of the flow, that
is, from the outside to the inside, to enforce the effectiveness
of the filter and to keep out potential dirt particles. A suitable
size of the longitudinal slits is approximately 0.8.times.6.0 mm
so that particles measuring less than 0.8 mm can potentially pass
into the measuring zone, which reduces the risk of blocking the
Indicator rod considerably.
 In FIG. 3 the basic component 11 of the indicator element
3 is shown in several different illustrations. While FIG. 3a shows
the basic component 11--much like in FIG. 1--in (full) view and
FIG. 3d in diagonal view, the insertion of the filter element into
the basic component is described with reference to FIGS. 3b and
 The lower portion 18 of the cylindrical attachment 17 having
the longitudinal slits 21 is, for practical purposes, designed as
an insert, which can be inserted from below into an internal bore
22 of the cylindrical attachment 17 of the basic component 11. Thus,
the lower portion 18 can be made of materials, which can be different
from the material that the basic component 11 is made of, for example,
plastic of suitably robust consistency. On its outer perimeter,
the lower portion 18 can have a ring bulge 23 or protrusions that
are provided across from each other, and which pliably lock into
a groove when inserted into a lower area 22a of the internal bore
22 and thus assure firm engagement. It goes without saying that
other means of installation are possible, for example, screwing
(the insert) into position.
 The lower portion 18 can also include a guide (not shown)
for the indicator rod 9 namely in a central bore 24. Among other
things, it makes sense for installation reasons to practically assemble
the complete indicator element 3 from below so that first the inspection
glass 12 including a suitable O-Ring seal is inserted into the internal
bore 22 of the cylindrical attachment 17 and by inserting the lower
portion 18 with the indicator rod 9 and the rebounding plate 10
the indicator element 3 is fixed into position.
 From a flow-technical standpoint, designing the filter to
be installed ahead, e.g. upstream, of the rebounding plate as longitudinal
slits 21 has the advantage that the flow is divided into individual
flow threads thus smoothing the turbulent flow so that the indicator
is calmer and, therefore, more precise. In this way, the filter
also has a noise-reducing effect.
 In FIGS. 4 and 5 an alternate embodiment is illustrated,
whereby a lower portion 18a of the attachment 17 is designed as
an insert for the attachment, as described above. In this embodiment,
the filter is installed ahead of the rebounding plate 10 and is
designed as a close-meshed screen 25 encircling the lower portion
18a. The lower portion 18a of this embodiment has openings 26 that
are provided on opposite sides of the lower portion 18a, with the
heating medium flowing in the direction of the arrows.
 The invention being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to
be regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are to be included within the scope of the following claims.