In a flow meter that works on the Coriolis principle there is provided
a single tube that is bent to have two measuring loops and a single
tube section that connects the adjacent ends of the measuring loops.
Tubular attachment end portions are respectively connected through
resilient tubular portions to the opposite ends of the two loops
and may be part of the single tube. Two blocks have tube holder
portions for having the tubular section and the measuring loops
opposite ends adjacent their juncture to the resilient portions
and the attachment portions adjacent their juncture to the resilient
portions respectively extended therethrough. The measuring loops
are oscilatable in the opposite direction while sensors are provided
adjacent to the measuring loops for measuring the relative movement
of the loops relative to one another to provide a measurement of
the fluid flow through the loops.
1. A flow meter working on the Coriolis principle for measuring
fluid flow, comprising a tubular upstream attachment end portion,
a tubular downstream attachment end portion, the attachment end
portions having adjacent ends, a tube formed from a single piece
and having a first measuring loop that has a first end and an opposite
end, a second measuring loop having a first end and an opposite
end joined to the first loop opposite end, first tubular means for
joining the upstream end portion to the first loop first end, and
second tubular means for joining the second loop first end to the
downstream end portion, each of the tubular means having a first
end remote from the respective attachment portion to which it is
joined that is joined to the first end of the respective loop, the
measuring loops having several bends and being juxtaposed, oscillator
means adjacent to the loops for oscillating the loops in the opposite
sense relative to one another, sensors means adjacent to the loops
for providing a measurement that depends on motion of the measuring
loops that are being oscillated, a first tube holder block having
the tube extended thereinto and joined to the tube adjacent to the
juncture of the first and second loop opposite ends, the juncture
of the first tubular means to the first loop first end, and the
juncture of the second tubular means to the second loop first end
for retaining each of the loop first ends in spaced relationship
to one another and to the opposite ends of the loops, and a second
tube holder block for interconnecting the attachment portions adjacent
to the juncture of the attachment means to the tubular means, and
having the attachment portions ends extending thereinto, the first
block being separate and spaced from the second block and being
carried by the tubular means.
2. A flow meter according to claim 1 characterized in that each
of the tubular means comprises a resilient connecting tube portion
that constitutes parts of the single tube for reducing forces acting
on the second block being transmitted to the first block, each block
having means defining two tube holder portions for respectively
having the attachment end portions extended thereinto and the measuring
loop first ends extended thereinto.
3. A flow meter according to claim 1 characterized in that each
of the attachment end portions is predominantly a straight tube
section, that the single tube is predominantly composed of straight
line sections that form parts of the measuring loops, the single
tube including four 180 degree bends interconnecting the single
tube straight line portions and forming parts of the measuring loops
and that each of the tubular means are arcuately bent.
4. A flow meter according to claim 3 characterized in that each
of the straight tube sections is substantially parallel to other
straight tube sections.
5. A flow meter according to claim 4 characterized in that the
second block includes means for defining a first tube holder having
the first and second loop first ends extended thereinto and second
and third tube holders that are parallel to the first tube holder
and juxtaposed to the first and second loops first ends respectively
for having the first and second loops first ends extended thereinto.
6. A flow meter according to claim 5 characterized in that the
straight tube sections are axially elongated, that the measuring
loops are of a length (L) measured in the direction of elongation
of the straight tube sections, that the 180 degree bends have a
height (H), and that the ratio of L/H is larger that 6.
7. A flow meter according to claim 6 characterized in that the
ratio of L/H is preferably about 10.
8. A flow meter according to claim 1 wherein there is provided
a protective tube that accommodates the blocks and the loops therein.
9. A flow meter according to claim 1 characterized in that the
first block has a first, a second and a third tube holder having
the tube extended thereinto, the second tube holder being intermediate
the first and third tube holders and having the first and second
loop opposite ends extended thereinto.
10. A flow meter according to claim 9 characterized in that the
measuring loops are axially elongated, and that the axial length
of the tube holders that is taken in the same direction as the elongation
of the measuring loops is less than 10% of the maximum dimension
of the measuring loops.
11. A flow meter according to claim 10 characterized in that the
axial length of the tube holders is less than 5% of the maximum
axial dimension of the measuring loops and that the dimension of
the first block in the same direction as the direction of elongation
of the measuring loops is less than 10% of the maximum axial dimension
of the measuring loops.
12. A flow meter according to claim 1 characterized in that the
loops are axially elongated, have intermediate portions along the
length of the tube intermediate the junctures of the loops first
ends and opposite ends of the loops to the first block, and have
axial portions along the tube that extend along the tube toward
the intermediate portions and away from first block in opposite
axial directions from the first block and that the oscillator is
located adjacent to the intermediate portions.
13. A flow meter according to claim 10 characterized in that the
axial dimension of the second block is many times less than the
dimension of one of the measuring loops.
The invention relates to a flow meter working on the Coriolis principle,
comprising an attachment apparatus connected on one side to an upstream
and a downstream final tube and on the other side to two juxtaposed
measuring tube loops which can be oscillated in opposite directions
by an oscillator and are provided with sensors for receiving a measurement
depending on the relative movement.
In a known device of this kind (EP-OS No. 0 239 679 A1), a large
solid block serves to interconnect the attachment tubes and the
two measuring tube loops. For this purpose, three connecting orifices
at the corners of a triangle are provided at each of two opposed
ends. The ends of the attachment tubes and the measuring tube loops
are fixed in these orifices. The connecting orifices for the attachment
tubes and the two ends of each measuring tube loop are axially aligned.
Within the block there are passages which interconnect the connecting
orifices in such a way that the two measuring tube loops lie in
series and are traversed in the same sense by the fluid to be measured.
The production of such a flow meter is expensive because a multiplicity
of tube sections has to be prefabricated and connected to the block.
It is the object of the invention to provide a flow meter of the
aforementioned kind with a simpler construction and simpler to assemble.
This problem is solved according to the invention in that the two
measuring tube loops are formed by a single tube bent several times
and that the attachment apparatus has a tube holder for receiving
a throughgoing single tube section connecting the two measuring
The use of the single tube leads to considerable simplifications
in production because the entire measuring loop arrangement is no
longer put together from individual pieces but can be bent from
a throughgoing tube which need then only be joined to the tube holders.
At the transition from the one measuring tube to the other, the
flow section remains constant. Nor is it unfavourably influenced
by solder points and the like and it presents no sealing problems.
No pocket is formed in which dirt can collect. There is no fear
of reactions between the medium to be measured and the solder material.
One can expect a uniform strength of the tube throughout.
The aforementioned advantages apply to the entire measuring device
if the attachment tubes are likewise formed by the single tube and
the attachment apparatus comprises tube holders for receiving two
throughgoing single tube sections adjoining the connecting tubes.
In this construction, only a single tube is employed in the entire
measuring device and it is fixed at particular points by the tube
holders. A constant throughflow cross-section is available everywhere.
Nowhere need one fear pockets, interfering solder points and the
like. The meter is "hygienically created" and retains
this property. Since no solder points or the like are provided along
the entire length of measuring loop, there is also no danger of
overstressing such points during oscillation of the loops.
In a preferred embodiment, the attachment apparatus comprises a
first block connected to the attachment tubes and at least one pair
of resilient connecting tubes between the two blocks, the connecting
tubes are also formed by the single tube, and both blocks each comprise
two tube holders for receiving throughgoing single tube sections
which adjoin the connecting tubes. The resilient connecting tubes
can be taken into account without difficulty during bending of the
individual tube. They ensure that the second block remains substantially
free from external influences such as clamping forces and clamping
torques, vibrations and the like. Consequently, the use of a very
strong block of large mass that was hitherto conventional can be
dispensed with. Upon a change in temperature of the medium, the
small blocks rapidly adapt to the changed temperature. All this
increases the measuring accuracy.
In the simplest case, the tube holders are divided for inserting
the tube sections. After insertion, the two parts need merely be
placed on each other and connected, which can be effected by adhesion,
soldering, welding, screws or a simple frictional connection.
The attachment apparatus may comprise at least one divided block
of which the parting gap passes through at least two tube holders.
Such blocks are easy to assemble and manipulate.
Alternatively, the blocks may be cast or extruded around the appropriate
The use of the throughgoing single tube also permits a block for
receiving the measuring tube ends to have tube holders of an extremely
short axial length. In particular, the length can be less than the
largest width of the block. This short length keeps the thermal
expansion in the direction of the tube extremely low during temperature
changes. The measuring tube loops are therefore at most subjected
to thermal stresses to a negligible extent. This likewise increases
the measuring accuracy.
In a preferred embodiment, the axial length of the tube holders
is less than 10%, preferably less than 5%, of the largest measurement
of the measuring loops measured in the same direction.
It is particularly advisable for the single tube to consist predominantly
of straight tube sections which are interconnected by way of four
180.degree. bends to form the two measuring tube loops and by way
of further bends to extend them to the connecting tubes. This simplifies
production because one can make do with a total of six bends.
Preferably, the straight tube sections are substantially parallel.
This results in an elongate meter requiring a small cross-section
in a plane perpendicular to the tube sections and therefore capable
of being accommodated, for example in a protective tube.
It is in this case recommended that the tube holders for the ends
of the measuring tubes be juxtaposed and receive parallel tube sections.
This very simple construction leads to the measuring tube loops
being slightly spirally deformed. However, since this deformation
takes place equally in both measuring tube loops, it does not detrimentally
It is also advantageous for the length of the measuring tube loops
measured in the direction of the straight tube sections to have
a ratio L/H larger than 6 preferably about 10 to the height prescribed
by the 180.degree. bends. This dimensioning leads to a meter which
not only has a small total cross-section but also possesses a high
measuring sensitivity and mechanical strength. This is because a
substantial part of the oscillation movement is received by torsion
on the measuring tubes and this gives less mechanical stress than
Preferred examples of the invention will now be described in more
detail with reference to the drawing, wherein:
FIG. 1 is a diagrammatic representation of a flow meter according
to the invention,
FIG. 2 is the diagrammatic representation of a modified embodiment,
FIG. 3 is a perspective view of one constructional solution,
FIG. 4 shows a first block,
FIG. 5 shows a second block,
FIG. 6 shows a modification of the second block,
FIG. 7 is a perspective view of a second constructional solution,
FIG. 8 is a perspective view of a third constructional solution,
FIG. 9 is a perspective view of a fourth constructional solution,
FIG. 10 is a side elevation of the FIG. 9 construction,
FIG. 11 is a perspective view of a fifth constructional solution,
FIG. 12 is a perspective view of a sixth constructional solution,
FIG. 13 is a perspective view of a seventh constructional solution,
FIG. 14 is a perspective view of an eight constructional solution,
FIG. 15 shows a further alternative for the second block.
FIG. 1 illustrates a flow meter 1 which works on the Coriolis principle
and can be accommodated in a protective tube 2. Only the two flanges
3 and 4 project outwardly for connection to a tube system. The flanges
are connected to an upstream attachment conduit 5 and a downstream
attachment conduit 6 respectively. The confronting ends are received
by a first block 7. The latter is connected to a second block 10
by way of two resilient connecting tubes 8 and 9 which are each
in series with one attachment tube 5 or 6. The second block carries
two measuring tube loops 13 and 14 each formed by one measuring
tube 11 12. The loops extend to both sides of the second block
10 by substantially the same length, are connected in series and
are connected at their ends to a respective connecting tube 8 9.
In the middle of the measuring tube loops, there are parts of a
diagrammatically indicated oscillator 15 which oscillates the measuring
tube loops 13 and 14 in opposite senses. Sensors 16 and 17 which
are likewise only diagrammatically indicated provide a measurement
depending on the relative motion of the tubes, for example a stress
which is proportional to the relative speed.
The resilient connecting tubes 8 and 9 ensure that the second block
10 and the measuring tube loops 13 and 14 carried thereby are substantially
free from external influences such as clamping forces and torques,
vibrations and the like.
Since the measuring tube loops 13 and 14 consisting of straight
and semi-circularly bent tube sections have a long length L relatively
to the height H, the measuring tubes are to a lesser extend loaded
in bending and to an increased extent by torsion, which reduces
stressing of the material. In addition, one obtains a high sensitivity
during measurement of the amount flowing through.
In the illustrated example, the measuring tube loops have a length
L of 34 cm and a height H of 6 cm. In an alterative construction,
L=37 cm and H=4 cm. If necessary, the measurements can also be larger.
As may be seen from, for example, FIG. 1 the maximum axial dimension
of the first block is many times less than the axial length L of
the a measuring loop.
The blocks 7 and 10 can be light in weight so that their temperature
rapidly follows any temperature changes in the medium. In the direction
of the length L of the measuring tube loop, the block 10 can be
kept short so that temperature elongation in this direction is small
and no thermal stresses are exerted on the measuring tube loops
13 and 14. This gives a high measuring accuracy and temperature
In the FIG. 2 embodiment, corresponding parts are given reference
numerals increased by 100. Between the first block 107 and the second
block 110 there are two further blocks 118 and 119. Consequently,
resilient connecting tubes 108 and 109 extend between the first
block 107 and the further block 118 resilient connecting tubes
108a and 109a between the two further blocks 118 and 119 and resilient
connecting tubes 108b and 109b between the further block 119 and
the second block 110. The following tube circuit is obtained: Attachment
tube 105 - connecting tube 108 - connecting tube - 109a - connecting
tube 108b - measuring tube loop 113 - measuring tube loop 114 -connecting
tube 109b - connecting tube 108a - connecting tube 109 -attachment
In this construction, the external influences are still better
avoided by the second block 110 and the measuring tube loops 113
In all the following embodiments, the attachment tubes, connecting
tubes and measuring tubes consist of a single tube R built several
times. In the representations, the oscillators and sensors have
been omitted for the sake of simplicity. They are located in substantially
that position of the measuring tube loops as shown in FIG. 1. Depending
on the type of sensor, different arrangements are also possible.
In the embodiment of FIGS. 3 to 5 corresponding parts have reference
numerals increased by 200 relatively to FIG. 1. The first block
207 consist of an upper portion 220 and a lower portion 221 which,
in the assembled condition, form two tube holders 222 and 223. The
tube holders each extend from one end face to one side face of the
The second block 210 likewise consist of an upper portion 224 and
a lower portion 225 which together form three tube holders 226
227 and 228 in the form of parallel apertures. In the alternative
of FIG. 6 the block 210a is provided with grooves 229 230 and
231 closable by a respective insert 232 to leave tube holders 226a,
227a and 228a in the form of parallel apertures.
The single tube R is bent several times and placed at predetermined
positions in the tube holders 222 223 226 227 and 228 which are
closed by bringing the upper portion and lower portion together.
The upper and lower portions are then interconnected and connected
to the appropriate tube sections by the first and second blocks
respectively, the nature of the connection depending on the materials.
The tube can be of steel, brass or the like. The blocks can be of
steel, brass or some other metal. The connection is desirably by
soldering or welding. However, adhesion or simple clamping are also
The end effect is a structure in which the attachment tubes 205
and 206 enter the first block 207 at opposite ends and the connecting
tubes, such as the tube 208 leave at opposite side faces of this
block 207. The connecting tubes have a deflecting bend with which
they merge with a straight tube section 233 which is received by
the tube holder 228 and forms the end section of the measuring tube
212. There follows a semicircular bend 234 which is connected to
a straight tube section 235 extending over the entire length of
the measuring tube loop 214. There follows a semicircular bend 236
which again adjoins a straight tube section 237 which extends over
practically the entire length, is held at the middle in the tube
holder 227 forms part of the measuring tube loop 213 at one side
and part of the measuring tube loop 214 on the other side. There
again follows a semi-circular bend 238 a straight section 239
a semicircular bend 240 and a straight section 241 which is held
in the tube holder 226 and merges with a connecting tube corresponding
to the connecting tube 208. The two measuring tube loops 213 214
are therefore suspended at the middle of their axial length by a
comparatively narrow block 210. If one regards each measuring tube
loop as a formation put together from two hair clips, the limbs
of each hair clip are practically of equal length.
A single tube R thus formed can be readily produced from a straight
tube because it is only necessary to produce the semi-circular bends
234 236 238 and 240 and the bends located in the vicinity of the
connecting tubes 208. Since the straight tube sections 233 237
and 241 are inserted in the parallel tube holders 226 227 and 228
the measuring tube loops 213 and 214 are slightly spiral. However,
their associated tube sections are parallel to each other. Since
we are merely concerned with the fixing of the tubes, the tube holders
need not be long. In particular, in the case of the second block
210 the tube holder length can be selected to be so short that
temperature elongations in the direction of the tube play practically
no role. These tube holders have a length of only a few cm. It is
desired to keep this length as short as possible, for example 2
As shown in FIG. 3 the first block 207 lies between the two measuring
tube loops 213 and 214. The two attachment tubes 205 and 206 are
disposed between the two measuring tube loops. This gives an extraordinarly
compact construction of which the entire height is only slightly
more than the height H of the measuring tube loops.
The FIG. 7 embodiment corresponds to FIG. 1 the meter merely being
inverted. The same reference numerals as in FIG. 1 are therefore
The FIG. 8 embodiment corresponds to that of FIG. 3. The same reference
numerals are therefore employed. The only difference is that the
connecting tube 208a is connected to the upstream attachment tube
205 and leaves at the underside of the first block 207a. The same
applies to the other connecting tube. This enables comparatively
short and therefore stiff resilient connections to be achieved.
In the embodiment of FIGS. 9 and 10 reference numerals are employed
which are increased by 300 relatively to FIG. 1. In this case, the
two measuring tube loops 313 and 314 are superposed because the
tube holders 326 327 and 328 likewise lie in a vertical plane.
By reason of the spiral shape, the straight tube sections 333 335
337 339 and 341 have a continuous inclination towards the downstream
attachment conduit 306. This meter is arranged between a 3-way change-over
valve 342 and 3-way change-over valve 343. The change-over valve
342 selectively connects the attachment tube 305 to a conduit 344
conveying the medium to be measured or to atmosphere 345. The change-over
valve 343 selectively connects the attachment tube 306 to the conduit
346 for the medium to be measured or to a discharge 347. Now, if
in the case of the valve 342 the path to atmosphere 345 and for
the valve 343 the path to the discharge 347 are opened, the entire
system can empty itself automatically. If, subsequently, a different
medium of which the throughflow is to be measured is carried by
the conduits 344 and 346 there will be no mixing with residues
of the preceding medium. In this construction, the first block 307
is located in the projection of the measuring tube loops 313 and
FIG. 11 illustrates an embodiment with reference numerals increased
by 400. Again, the second block 410 is vertical. The first block
407 lies beyond the vertical projection of the measuring tube loops
413 and 414. It is disposed at half the height of the second block
410 so that substantially straight connecting tube sections can
In the FIG. 12 embodiment, where reference numerals increased by
500 are employed, the peculiarity is that the longitudinal extent
of the first block 507 is parallel to the longitudinal extent of
the second block 510. In this way, the axis of the attachment tubes
505 and 506 can be disposed perpendicular to the planes of the measuring
tube loops 513 and 514.
In the FIG. 13 embodiment, reference numerals increased by 600
are employed. Here, the measuring tubes are again applied to opposite
ends of the second block 610. On the other hand, the connecting
tubes 608 leave from the upper side face of this block. In this
way, the measuring tube loops 613 and 614 can be accommodated in
two parallel planes. The connecting tubes 608 give a 180.degree.
As shown in FIG. 14 with reference numerals increased by 700 the
parallel arrangement of the measuring tube loops 713 and 714 can
also be realised in that the connecting tubes 708 do not provide
a 180.degree. deflection.
As may be clearly seen from, for example, FIGS. 1 11 and 12
the adjacent ends of a first and a second attachment tube are respectively
fluidly connected to the first ends of the first and second connecting
tubes and interconnected by the first block while adjacent to the
juncture of the first connecting tube to the first end portion of
the first loop, the juncture of the loops opposite end portions
and the juncture of the first end of the second loop and the second
end of the second connecting tube, there is an interconnection provided
by a second block that is joined thereto.
In these cases, however, a somewhat differently formed second block
has to be used, as is shown for the block 610 in FIG. 15. It contains
three grooves 629 630 and 631 which are covered by corresponding
fillers 632 632a and 632b to leave tube holders 626 627 and 628.
These tube holders are adapted to the shape of the bent tube sections.
For further particulars, attention is drawn to the applicants'
applications similarly entitled "Flow meter working on the
Coriolis principle" (I), (III) and (IV).
The resilient connecting tubes can also be employed in conjunction
with measuring tube loops shaped differently from those illustrated
in the drawings, for example circular loops.