A mass flow meter for flowing media that works on the Coriolis
Principle includes at least one oscillating Coriolis line carrying
the flowing medium and at least one housing holding the Coriolis
line, and attachments to the housing. The mass flow meter is characterized
by the fact that at least some of the attachments are connected
to the housing via means of oscillation decoupling.
What is claimed is:
1. The mass flow meter for flowing media that works on the Coriolis
Principle, said flow meter comprising a Coriolis line having a first
axis; a housing holding the Coriolis line, said housing having an
exterior wall and a natural frequency of vibration; an attachment
disposed adjacent to said exterior wall; cooperating connection
means on said attachment and said exterior wall for connecting the
attachment to the exterior wall while allowing relative motion thereof
along a second axis perpendicular to said first axis, and biasing
means disposed between the attachment and said exterior wall for
biasing the attachment in one direction along said second axis,
whereby when the mass flow meter is in operation, the natural frequency
of the housing is substantially the same as if the attachment were
not connected to the housing.
2. The mass flow meter defined in claim 1 wherein the biasing
means comprises a spring.
3. The mass flow meter defined in claim 1 wherein the attachment
is an evaluation unit.
4. The mass flow meter defined in claim 3 wherein the cooperating
connection means comprise
a first flange extending from the attachment, and
a base has one end anchored to said exterior wall and has a second
end defining a second flange, said first and second flanges interfitting
so as to permit relative movement of said attachment and said base
only along said second axis.
The invention concerns a mass flow meter for flowing media that
works on the Coriolis Principle, with at least one oscillating Coriolis
line carrying the flowing medium and at least one housing holding
the Coriolis line and attachments to the housing.
BACKGROUND OF THE INVENTION
A large number of designs are known for mass flow meters for flowing
media that work on the Coriolis Principle. The number of proposals
for making the Coriolis line run optimally is almost impossible
to review. For the flowing medium to bring about the desired Coriolis
effect in the Coriolis line, the Coriolis line must be in oscillation.
An oscillator, or frequently several oscillators, is generally used
for this purpose. In conventional flow meters, the mass flow of
the flowing medium through the Coriolis line is determined by quantitative
analysis of the Coriolis force acting on the oscillating Coriolis
line. Since the Coriolis forces that occur are generally very small,
conventional flow meters are particularly sensitive to the output
and input of mechanical energy between the mass flow meter and its
environment. In the past, the mechanical coupling between the flow
meter and the pipelines connected to the flow meter received a lot
of attention, and a great many suggestions have been made for solutions
that attempt to reduce this mechanical coupling.
The coupling between the Coriolis line and the housing holding
generally the Coriolis line, the oscillator or oscillators and the
transducer or transducers that senses the motion of the Coriolis
line has already been the subject of improvements as well. The common
approach to this is to guarantee very strong decoupling between
the Coriolis line and the housing by making the inherent frequency
of the housing as different as possible from the oscillation frequency
of the Coriolis line. To do so, the housing is generally designed
to be very rigid to oscillation.
In the past, no attention was paid to the problem of the mechanical
coupling between the Coriolis line and the housing, on one hand,
and the flow meter's various attachments to the housing, on the
Frequently, a basic device, i.e., a unit consisting of the Coriolis
line, an oscillator, a transducer and a housing, is used as the
basis for a large number of mass flow meters for different purposes.
Depending on the purpose for which the flow meter is used, various
attachments are connected to the flow meter, respectively to its
housing. Because these attachments are connected to the housing
in a way that is generally undefined, mechanical couplings are created
in systems capable of oscillation that can have a major influence
on the measurement precision of the flow meter. These unwanted influences
frequently cannot be prevented by the corresponding layout of the
attachments, since the mechanical coupling is frequently also influenced
by the specific on-site installation situation, whose design understandably
cannot be considered. As a result, on the known flow meters, the
influences determining the oscillation properties of the device
cannot be determined in advance by a corresponding design, so that
the measurement precision of the mass flow meter is already affected
by inadequate definition of the whole mass flow meter as a system
capable of oscillation.
The object of the invention is thus based on improving the known
mass flow meters for flowing media that work on the Coriolis Principle
in such a way that the technical oscillation properties of the whole
device remain basically constant regardless of the different attachments,
so that high measurement precision is guaranteed.
SUMMARY OF THE INVENTION
The object already presented and described is solved according
to the invention by having at least a part of the attachments connected
to the housing via means of oscillation decoupling. The measure
in the invention guarantees a defined oscillation behavior of the
mass flow meter, since the undefined influences of the attachments
have very little or no effect on the oscillation behavior as a whole.
According to known physical laws, the means of oscillation decoupling
are designed so that, if possible, there is no, or only slight,
oscillation coupling between the attachments and the housing.
Springs are especially good as means of oscillation decoupling
for economic reasons. They are simple to make and synchronize and
are available in a large number of forms of embodiment, adapted
to the respective purpose for which they are used.
Oscillation decoupling between the attachments and the housing
is advantageous, particularly for large-sized attachments, like
for example electronic evaluation units, attachments with an outer
abutment, like for example cables or pipe-type cables, and attachments
with particularly defined oscillation properties, like for example
means for heating the mass flow meter.
Now there are many different ways of designing and developing the
mass flow meter according to the invention for flowing media that
works on the Coriolis Principle. In this connection, please refer
to the patent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
For a fuller understanding of the nature and objects of the invention,
reference should be had to the following detailed description taken
in connection with the accompanying drawings, in which:
FIG. 1 is a schematic diagram to explain the principle of the invention,
FIG. 2 is a sectional view of one embodiment of a connection according
to the invention between a housing and an electronic evaluation
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows a mass flow meter for flowing media that works on
the Coriolis Principle. The schematic drawing shows only the housing
1 holding a Coriolis line C, an attachment 2 not further specified,
and a means 3 of oscillation decoupling according to the invention
which connects the housing 1 to the attachment 2. By choosing spring
and damping properties of the means 3 of oscillation decoupling
that are tailored to the housing 1 and the attachment 2 the oscillation
decoupling according to the invention between the housing 1 and
the attachment 2 is guaranteed.
FIG. 2 shows a special example of an embodiment of a mass flow
meter for flowing media according to the invention that works on
the Coriolis Principle. FIG. 2 shows only a cutout of this example
of embodiment in cross section. A base 4 having a flange 4a is attached
to the wall 1a of housing 1 via a solder connection 5. An attachment
in the form of an electronic evaluation unit 6 shown only in section
has a flange 6a that interfits with flange 4a forming a connection
that allows relative movement of base 4 and electronic evaluation
unit 6 only in the axial direction. A spring unit, shown generally
at 7 forms a central element of this connection. Depending on the
requirement, this spring unit 7 can be composed of one or more spring
washers, one or more coil springs or one or more leaf springs. The
spring unit 7 is thus designed to guarantee maximum oscillation
decoupling of housing 1 and evaluation unit 6.
The measure according to the invention justifies the expense connected
with it only in a case where the attachment in question has a substantial
influence on the measurement precision of the mass flow meter. It
is, therefore, not always necessary to connect all attachments to
the housing via means of oscillation decoupling.
It will thus be seen that the objects set forth above, among those
made apparent from the preceding description, are efficiently attained
and, since certain changes may be made in the above construction
without departing from the scope of the invention, it is intended
that all matter contained in the above description or shown in the
accompanying drawings shall be interpreted as illustrative and not
in a limiting sense.
It is also to be understood that the following claims are intended
to cover all of the generic and specific features of the invention