Abstrict The bulk flow meter comprises a baffle plate which is arranged
inclined in the fall path of the bulk material to be measured and
is carried by a rigid support which is mounted displaceably in the
direction of a horizontal axis on at least two spring systems which
are spaced apart from each other and secured on the one hand to
the baffle plate support and on the other hand to the frame, each
spring system having at least one pair of spring members arranged
opposite each other on either side of the baffle plate support.
Each spring member is formed by a corrugated diaphragm section with
vertically extending corrugations. The corrugated diaphragms provide
a mounting of the baffle plate support with high transverse stability
so that it is possible to arrange the baffle plate without modifying
the suspension optionally in the longitudinal direction of the baffle
plate support or in the transverse direction laterally adjacent
the baffle plate support.
Claims I claim:
1. A bulk flow meter for measuring the flow of a bulk material,
the improvement comprising a main frame and at least one baffle
plate which is disposed in the flow and is connected to a rigid
support so that it is inclined with respect to the direction of
flow, said rigid support being mounted displaceably in the direction
of a horizontal axis by at least two spring systems which are in
spaced relationship with each other and are secured to both the
baffle plate support and to the main frame, each spring system comprising
two spring members disposed on opposite sides of the baffle plate
support, and each spring member being formed by a corrugated diaphragm
section which has straight, parallel, vertical corrugations and
is secured to the main frame by a vertical edge portion that is
parallel to the corrugations.
2. Bulk flow meter according to claim 1 in which the two spring
members of each pair of spring systems are formed by two corrugated
sections of a continuous corrugated diaphragm which is secured by
edge portions to the main frame and at a center portion to the baffle
plate support.
3. Bulk flow meter according to claim 1 in which each spring system
includes a plurality of corrugated diaphragms arranged parallel
to each other.
4. Bulk flow meter according to claim 1 in which the baffle plate
support comprises a support frame disposed between the corrugated
diaphragm sections and a cantilever arm attached to the support
frame and carrying the baffle plate.
5. Bulk flow meter according to claim 4 in which the cantilever
arm is adapted to be connected to the support frame along a longitudinal
axis of the support frame.
6. Bulk flow meter according to claim 5 in which the cantilever
arm comprises a bracket secured to the support frame and a support
arm secured to the bracket.
7. Bulk flow meter according to claim 1 in which the main frame
comprises at least two compensating connecting members which are
disposed parallel to the corrugated diaphragms and which have the
same temperature dependence of the change in length as the corrugated
diaphragms.
8. Bulk flow meter according to claim 7 in which each compensating
connecting member includes a pluraity of subsections which consist
of different materials.
9. Bulk flow meter according to claim 7 in which the compensating
connecting members determine the distances between the main frame
members to which the edge portions of the corrugated diaphragms
are secured.
10. Bulk flow meter according to claim 4 in which the cantilever
arm is adapted to be connected to the support frame along an axis
transverse to a longitudinal axis of the support frame.
Description The invention relates to a bulk flow meter comprising at least
one baffle plate which is connected to a rigid support which is
mounted displaceably in the direction of a horizontal axis on at
least two spring systems which are in spaced relationship with each
other and are secured on the one hand to the baffle plate support
and on the other to the frame, each spring system comprising two
spring members lying opposite each other on either side of the baffle
plate support.
As is known, the measurement of the mass throughput of bulk materials
with bulk flow meters of this type is effected in that the impact
or momentum exerted on the baffle plate by the bulk material is
converted into a displacement-proportional or force-proportional
quantity and integrated with respect to time. To keep the system
statically largely independent of the inertia and gravity forces
such as baffle plate weight, incrustation, etc., for the throughput
measurement only the horizontal force component is evaluated. This
requires that the baffle or impact plate is coupled to a mechanism
which executes at least one horizontal rectilinear or parallel movement.
Such rectilinear or parallel mechanisms are usually complicated
in their construction.
In a bulk flow meter of the type mentioned at the beginning known
from DE-PS No. 3149715 each spring member is formed by a spring
joint which has three parallel leaf spring legs which are connected
together by a cross web and which at points at equal distances from
the cross web are clamped to the support or frame respectively.
This known suspension of the baffle plate support can however only
be subjected to a limited load and further requires that the baffle
plate is arranged symmetrically with respect to the vertical plane
containing the horizontal adjustment axis because with a laterally
offset arrangement of the baffle plate a tilting moment results
which cannot be taken up by the spring joints.
The problem underlying the invention is to provide a bulk flow
meter of the type mentioned whose spring systems are made very simply,
do not require complicated assembly and production steps and have
a high transverse stability so that there is no restriction as regards
the arrangement of the baffle plate.
According to the invention this problem is solved in that each
spring member is formed by a corrugated diaphragm section with vertically
extending corrugations.
The form of the bulk flow meter according to the invention provides
a completely rectilinear guiding of the baffle plate support in
the horizontal axis of the adjustment movement. The assembly is
very simple; in particular no complicated adjustments are necessary.
The spring systems are very robust so that they can take up high
loads but on the other hand are also sensitive to small measuring
forces. In particular, the spring members formed by corrugated diaphragm
sections have a high stability with respect to movements in the
transverse direction and against tilting movements about the axes
of the baffle plate support. This makes it possible to arrange the
baffle plate without modifying the suspension optionally in the
longitudinal direction of the baffle plate support or in the transverse
direction laterally adjacent the baffle plate support. Finally,
in simple manner compensation of the temperature-induced changes
of the spring systems is possible.
Advantageous further developments and embodiments of the invention
are characterized in the subsidiary claims.
Further features and advantages of the invention will be apparent
from the following description of an example of embodiment illustrated
in the drawings, wherein:
FIG. 1 is a very simplified schematic illustration of the bulk
flow meter for explaining the principle of the invention,
FIG. 2 is a perspective view of the bulk flow meter with one arrangement
of the baffle plate and
FIG. 3 shows the bulk flow meter of FIG. 2 with another arrangement
of the baffle plate.
The bulk flow meter illustrated very simplified and schematically
in FIG. 1 comprises a movable system 10 having an impact or baffle
plate 11 and a baffle plate support 12. The baffle plate 11 is disposed
inclined in the fall path of bulk material falling in the direction
of the arrow V. The baffle plate support 12 consists of a substantially
rectangular frame 13 and a cantilever arm 14 which is secured by
screws 15 to the upwardly bent upper longitudinal web 16 of the
frame 13. The cantilever arm 14 is shown simplified in FIG. 1 as
straight beam which carries at the end the baffle plate 11. The
frame 13 is stiffened by a plate 17 filling said frame and shown
in FIG. 1 broken away to enable the individual parts therebehind
to be seen. The construction of the frame described gives very great
stiffness with relatively low weight.
The movable system 10 is suspended by two spring systems 18 and
19 in such a manner that it is horizontally displaceable in the
direction of the longitudinal axis X of the baffle plate support
12 against the return force of the spring systems. In accordance
with the known mode of operation of bulk flow meters the bulk material
on striking the baffle plate 11 is deflected out of its falling
direction. The impact or momentum exerted on the baffle plate 11
produces a horizontal force component in the direction of the arrow
H which tends to displace the movable system 10 against the return
force of the spring systems 18 and 19. Said spring component or
the horizontal displacement travel caused thereby against the spring
force of the spring systems are a measure of the impact exerted
on the baffle plate 11 by the bulk material which in turn for a
known fall height of the bulk material is a measure of the mass
throughput of the bulk material. Thus, a force or displacement sensor
connected to the movable system 10 furnishes a signal which indicates
the mass throughput.
The two spring systems 18 and 19 are formed in the same manner
with two spring members which are independent of each other and
are arranged symmetrically to each other on either side of the baffle
plate support. In the spring system 18 the two spring members are
formed by the two halves of a corrugated diaphragm 20 which is arranged
perpendicularly to the axis X of the baffle plate support 12 in
such a manner that its parallel corrugations 21 extend vertically.
The baffle plate support 12 is secured in the centre of the corrugated
diaphragm 20. In the example illustrated for this purpose a centre
strip of the corrugated diaphragm not provided with corrugations
is clamped over the entire height thereof between a vertical web
of the frame 13 and a strip 22 by means of screws 23. The two vertical
edges of the corrugated diaphragm 20 are anchored to stationary
frame members 24a and 25a respectively which in the example illustrated
have the form of vertical posts. As shown this anchoring can be
effected in that the edge portions of the corrugated diaphragm 20
not provided with corrugations are clamped over their entire height
between the posts 24a, 25a and strips 26 27 by means of screws
28 29. Each of the two corrugated sections 20a, 20b of the corrugated
diaphragm 20 thus form one of the two spring members, independent
of each other, of the spring system 18.
The spring system 19 comprises in similar manner a corrugated diaphragm
30 with parallel corrugations 31 which is arranged perpendicularly
to the axis X in such a manner that its corrugations 31 extend vertically.
The two corrugated diaphragms 20 and 30 thus lie parallel to each
other. The vertical centre strip of the corrugated diaphragm 30
is clamped between the other vertical web of the frame 13 and a
strip 32 and the vertical edge portions of the corrugated diaphragm
30 are clamped between stationary frame members 24b, 25b and strips
36 37. The two corrugated sections 30a, 30b of the corrugated diaphragm
30 form the two spring members, independent of each other, of the
spring system 19.
The arrangement illustrated of the spring systems 18 19 with vertical
corrugated diaphragms 20 30 permits horizontal movement of the
movable system 10 against a defined return force but offers a high
resistance to any movement or deflection of the movable system in
any other direction. In particular the corrugated diaphragms 20
and 30 provide great stiffness against movements in the vertical
direction and against tilting movements about the three axes of
the system. This gives a very precise rectilinear or parallel guiding
of the movable system 10 which is required for exact measurement
of the mass throughput. Vertical inertia or gravity forces such
as the baffle plate weight and any settlements of bulk material
do not impair the measurement accuracy.
It is further not necessary for the baffle plate 11 to be arranged
symmetrically with respect to the vertical plane containing the
axis X. This makes it possible in particular to arrange the baffle
plate 11 laterally adjacent the spring systems 18 19 as is desired
in many uses. To do this it suffices to arrange the cantilever arm
14 not parallel as shown in FIG. 1 but transversely of the frame
13 the connection between the baffle plate 11 and the cantilever
arm 14 then of course having to be altered so that the direction
H of the horizontal force component again extends parallel to the
axis X.
These various possibilities are apparent from the example of embodiment
of a bulk flow meter illustrated in FIGS. 2 and 3 in detail.
Apparent in FIGS. 2 and 3 are again the components illustrated
schematically in FIG. 1 of the bulk flow meter which are provided
with the same reference numerals as in said Figure but which differ
therefrom in the details of the constructional form described below.
The frame members 24a, 24b are the vertical webs of a very robust
rectangular profile frame 24 and in the same manner the frame members
25a, 25b are the vertical webs of a profile frame 25 formed in the
same manner. The two profile frames 24 25 are connected together
at the four corners by four cylindrical connecting members 40 41
42 43. In this manner a very robust and strong twist-resistant
frame 45 is formed which has the shape of a right parallelepiped
or cube. The profile frames 24 and 25 are preferably aluminium castings.
The cylindrical connecting members 40 41 42 43 lie parallel to
the corrugated diaphragms 20 30. This construction of the frame
45 permits in simple manner the adjustment of the pretensioning
of the corrugated diaphragms and the compensation of temperature-induced
length changes of the corrugated diaphragms in a manner which will
be explained in detail hereinafter.
The illustrations of FIGS. 2 and 3 also show the purpose of the
bending of the upper longitudinal web 16 of the frame 13: this bending
is so dimensioned that the cantilever arm 14 for any securing projects
freely beyond the upper edge of the frame 45.
The upper longitudinal web 16 has the form of a cross with transverse
arms 46 which project in the centre towards both sides and of which
in FIG. 2 only the forwardly projecting transverse arm 46 can be
seen. The transverse arms 46 permit a secure mounting of the cantilever
arm 14 both in the longitudinal direction (FIG. 2) and in the transverse
direction (FIG. 3).
The cantilever arm 14 consists of two parts, that is a horizontal
bracket 50 and a support arm 60. The bracket is a one-piece casting,
preferably of aluminium, comprising two superimposed spaced apart
plates 52 53 of substantially triangular cross-section which are
connected together at the narrow ends projecting beyond the frame
45 by a vertical flange 54. The widest points of the plates 52
53 have substantially the width of the transverse arms 46 and are
connected together by a transverse web 55 and by a rearwardly projecting
U-shaped stirrup member 56. The bracket 50 formed in this way has
with relatively low weight a very great stiffness and strength.
It further permits a very reliable securing on the frame 13 both
in the longitudinal direction and in the transverse direction, the
widest point of the bracket 50 bearing either on the bent longitudinal
support 16 (FIG. 3) or on the transverse arms 46 (FIG. 2) thereof.
The support arm 60 serves to secure the baffle plate 11 to the
bracket 50. Depending on whether the baffle plate 11 is to be arranged
in the longitudinal direction of the baffle plate support 12 (FIG.
2) or laterally adjacent the baffle plate support 12 (FIG. 3), two
different support arms 60 are used. In both cases the support arm
60 has the form of a bent rod whose vertical leg is secured by means
of screws 61 to the flange 54 of the support plate 50 whilst the
free end of the horizontal leg is connected via a serrated rotary
joint coupling 62 to the baffle plate 11. The rotary joint coupling
62 permits adjustment of the angle of attack of the baffle plate
11. The two support arms 60 for the longitudinal securing (FIG.
2) and for the transverse securing (FIG. 3) differ essentially only
in that the rotation axis of the rotary joint coupling 62 for the
transverse securing lies coaxial to the axis of the horizontal leg
of the support arm 60 whilst for the longitudinal securing it lies
transversely of said axis.
The division of the cantilever arm 14 into the bracket 50 and the
support arm 60 has the advantage that the same bracket 50 can be
used for the longitudinal securing and for the transverse securing
so that for changing the type of securing only the relatively simple
and cheap support arm 60 need be changed.
On the frame 45 the auxiliary means necessary for operating the
bulk flow meter are also disposed. Thus, FIG. 2 shows a force or
displacement sensor 70 which is secured by means of an angle member
71 to the profile frame 24. An arm 72 secured to the plate 17 of
the frame 13 is connected to the actuating pin 73 of the sensor
70 so that the horizontal force component exerted on the baffle
plate 11 or the horizontal displacement of the baffle plate support
12 caused thereby can be directly transmitted to the sensor 70.
The force or displacement sensor can of course be of any type known
or suitable for bulk flow meters.
Also secured to the profile arm 24 is a damper 75 which is connected
via an arm 76 to the baffle plate support 12 for damping the movements
of the movable system 10.
The corrugated diaphragms 20 and 30 may be made from any suitable
spring metal, for example from spring steel sheet of 0.2 mm thickness
or also of bronze spring sheet. The corrugations may be made relatively
flat, for example with an amplitude of 2.5 mm on either side of
the centre plane, because the maximum deflection of the spring systems
is very small; for example, it is about 2.4 mm when using an inductive
displacement sensor. By corresponding dimensioning of the corrugated
diaphragms (for example about 320.times.170 mm) it is readily possible
to obtain measuring force/transverse force ratios which are greater
than 1:100.
As already mentioned the construction of the frame 45 with cylindrical
connecting members 40 41 42 43 lying parallel to the corrugated
diaphragms 20 30 permits adjustment of the pretensioning of the
corrugated diaphragms in simple manner. The pretensioning of the
corrugated diaphragms 20 30 depends on the distance between the
profile frames 24 and 25. This distance can easily be varied by
varying the length of the cylindrical connecting members or by inserting
disc-shaped spacers. In this manner an exact calibration of the
bulk flow meter is possible.
Temperature-induced length changes of the corrugated diaphragms
20 30 also influence the pretensioning thereof and thus the measurement
result. This temperature dependence can be completely compensated
by suitable construction of the cylindrical connecting members 40
41 42 43. For this purpose they are so constructed that their
length varies in dependence upon the temperature in the same manner
as the length of the corrugated diaphragms 20 30. This can be done
in particular in that they are made up of sub-sections which consist
of different materials. Thus, in FIG. 3 the cylindrical connecting
member 40 consists of two sub-sections 40a and 40b, the sub-section
40a consisting for example of aluminium and the sub-section 40b
of brass. The remaining connecting members 41 42 43 are of course
formed in the same manner. By suitable dimensioning of the sub-sections
and choice of the materials adaptation of the temperature compensation
to the particular type of corrugated diaphragms used is possible.
The measurement range of the bulk flow meter depends on the properties
of the corrugated diaphragms. By the dimensioning of the corrugated
diaphragms the bulk flow meter can be designed for specific measurement
ranges.
A change of the measurement range is possible by replacing the
corrugated diaphragms. Another possibility for changing the measurement
range is to connect several corrugated diaphragms in parallel in
each spring system. The corrugated diaphragms of each system are
arranged for this purpose parallel to each other slightly spaced
apart with interposition of spacing strips and jointly clamped at
the frame 45 and the frame 13 of the baffle plate support 12.
Various modifications of the bulk flow meter described will readily
be apparent to the expert. Thus, it is possible to form each corrugated
diaphragm from two separate halves which are joined together by
the clamping at the baffle plate support. Also, the baffle plate
support could be connected via more than two spring systems to the
frame. |