Abstrict The present invention relates to a flow meter, particularly for
liquids, having an impeller wheel arranged in a vertical tubular
measurement bore and acted on by a flow stream. The impeller wheel
has a bearing shaft, the ends of which are rotatably mounted in
axially and radially guiding bearings respectively. The impeller
wheel has one or more vanes, the flow-on attack surfaces of which
are inclined to the direction of oncoming flow of the stream. A
sensor detects the rotary frequency of the impeller wheel. A movable
wall subdivides a chamber into two chamber halves, one of which
communicates with an inlet connection and the measurement bore upstream
of the impeller and the other one of which communicates with an
outlet connection and the measurement bore downstream of the impeller.
In order, with such a flow meter, to make possible in simple manner
and at low cost of manufacture a high precision of measurement over
the entire measurement range, the bearing shaft is arranged with
axial play between the bearings and the impeller wheel is acted
on from below by the flow. In this connection, the attack surfaces
are so inclined with respect to the direction of flow that the force
component, directed in the approach direction, of the force exerted
by the flow stream on the impeller wheel is equal to or greater
than the weight of the impeller wheel.
Claims We claim:
1. In a flow meter, particularly for liquids, having an impeller
which is arranged in a measurement bore and is drivable by a flow
stream of oncoming flow flowing through the measurement bore, the
improvement comprising
a housing forming a chamber with an inlet connection and an outlet
connection,
a movable wall subdividing said chamber into two chamber halves,
one of said chamber halves is in communication with said inlet
connection and the measurement bore upstream of said impeller,
the other of said chamber halves is in communication with said
outlet connection and the measurement bore downstream of said impeller,
the impeller has a bearing shaft, the ends of said bearing shaft
being rotatably mounted in an axially and radially guiding bearing,
at least one vane of the impeller having a flow-on surface inclined
to the direction of the oncoming flow, and
sensor means for detecting the rotary frequency of said impeller.
2. The flow meter as set forth in claim 1 wherein
the flow-on attack surfaces have an inclination to the direction
of the flow between 45 degrees and 65 degrees.
3. The flow meter as set forth in claim 2 wherein
said inclination is 52 degrees.
4. The flow meter as set forth in claim 1 wherein
said impeller is a turbine wheel.
5. The flow meter as set forth in claim 1 further comprising
flow straighteners arranged in said line in front of and behind
the impeller as seen in the direction of the flow, and
said bearings are arranged in front sides of said flow straighteners
facing said impeller.
6. The flow meter as set forth in claim 5 further comprising
a housing block,
said line is a continuous measurement bore formed within said housing
block, said impeller and said straighteners are axially inserted
in said bore.
7. The flow meter as set forth in claim 6 wherein
said straighteners are mounted in a forced-fit into said measurement
bore.
8. The flow meter as set forth in claim 1 wherein
an upstream rear of said bearings is a conical bearing.
9. The flow meter as set forth in claim 1 wherein
a downstream front of said bearings is a journal bearing.
10. The flow meter as set forth in claim 1 wherein
the impeller comprises a vaned body mounted on the bearing shaft.
11. The flow meter as set forth in claim 10 wherein
said vaned body is a plastic part and said bearing shaft is a metal
part.
12. The flow meter as set forth in claim 11 wherein
said vaned body is a part injection molded to said bearing shaft.
13. The flow meter as set forth in claim 11 wherein
said bearing shaft has a cylindrical outer surface surrounded by
said vaned body, said cylindrical outer surface is formed with recesses
in which said vaned body engages.
14. The flow meter as set forth in claim 1 wherein said sensor
means comprises
means comprising a radiation transmitter for sending radiation
along a radiation path intersecting said at least one vane of said
impeller,
a radiation receiver means for receiving said radiation beyond
said impeller, the radiation being adapted to be interrupted intermittently
by rotation of the at least one vane.
15. The flow meter as set forth in claim 14 wherein
said radiation transmitter is a source of light and said radiation
receiver means is a light-sensitive element constituting means for
producing electric signals.
16. The flow meter as set forth in claim 15 further comprising
an electronic measurement means for receiving said electric signals
and converting said electric signals into an electric value, the
latter constituting a flow measurement value.
17. The flow meter as set forth in claim 16 further comprising
members comprising channels and chambers operatively communicating
with the impeller in which the flow passes,
a temperature sensor is arranged in one of said members and constitutes
means for producing an electrical variable which corresponds to
the temperature of the flow stream and for feeding said electric
variable to said measurement means in order to affect the measurement
value.
18. The flow meter as set forth in claim 1 wherein
the shaft is disposed with axial play between said bearings,
the impeller is arranged in said measurement bore such that it
is acted on by the flow stream from below, and
the flow-on surface of the impeller is inclined relative to the
direction of the oncoming flow in such a manner that the force component
in the direction of the flow of the force exerted by the flow stream
on the impeller is at least equal to the weight of the impeller.
19. The flow meter as set forth in claim 1 wherein
said movable wall is a diaphragm.
20. The flow meter as set forth in claim 19 mounted in a vehicle,
wherein
said movable wall defines a plane disposed at an angle of between
45 degrees and 90 degrees to the longitudinal axis of the vehicle.
21. In a flow meter, particularly for liquids, having an impeller
which is arranged in a vertical line and can be driven by a flow
stream flowing through the line, the impeller having a bearing shaft
the ends of which are rotatably mounted in an axially and radially
guiding bearing, at least one vane of the impeller having a flow-on
surface inclined to the direction of the oncoming flow, and a sensor
which detects the rotary frequency of the impeller, the improvement
wherein
the shaft is disposed with axial play between said bearings,
the impeller is arranged in the line such that it is acted on by
the flow stream from below,
the flow-on surface of the impeller is inclined relative to the
direction of the oncoming flow in such a manner that the force component
in the direction of the flow of the force exerted by the flow stream
on the impeller is at least equal to the weight of the impeller,
flow straighteners arranged in said line in front of and behind
the impeller as seen in the direction of the flow,
said bearings are arranged in front sides of said flow straighteners
facing said impeller,
a housing block,
said line is a continuous measurement bore formed within and completely
through said housing block, said impeller and said straighteners
being axially inserted in said bore, and
means comprising closures for closing outer ends of said measurement
bore, respectively.
22. The flow meter as set forth in claim 21 wherein
an upstream one of said closures and an adjacent of said straighteners
form a single one-piece component.
23. In a flow meter, particularly for liquids, having an impeller
which is arranged in a vertical line and can be driven by a flow
stream flowing through the line, the impeller having a bearing shaft
the ends of which are rotatably mounted in an axially and radially
guiding bearing, at least one vane of the impeller having a flow-on
surface inclined to the direction of the oncoming flow, and a sensor
which detects the rotary frequency of the impeller, the improvement
wherein
the shaft is disposed with axial play between said bearings,
the impeller is arranged in the line such that it is acted on by
the flow stream from below,
the flow-on surface of the impeller is inclined relative to the
direction of the oncoming flow in such a manner that the force component
in the direction of the flow of the force exerted by the flow stream
on the impeller is at least equal to the weight of the impeller,
flow straighteners arranged in said line in front of and behind
the impeller as seen in the direction of the flow,
said bearings are arranged in front sides of said flow straighteners
facing said impeller,
a housing block,
said line is a continuous measurement bore formed within said housing
block, said impeller and said straighteners are axially inserted
in said bore, and
said housing block is formed with an inlet bore and an outlet bore
communicating with said measurement bore in a radial direction relative
thereto.
24. The flow meter as set forth in claim 23 wherein
said housing block is formed with a chamber,
a movable wall is mounted in said housing block and subdivides
said chamber into two chamber halves communicating respectively
with said inlet bore and said outlet bore.
25. The flow meter as set forth in claim 24 wherein
said movable wall is a diaphragm.
26. The flow meter as set forth in claim 25 mounted in a vehicle,
wherein
said movable wall defines a plane disposed at an angle of between
45 degrees and 90 degrees to the longitudinal axis of the vehicle.
27. In a flow meter, particularly for liquids, having an impeller
which is arranged in a vertical line and can be driven by a flow
stream flowing through the line, the impeller having a bearing shaft
the ends of which are rotatably mounted in an axially and radially
guiding bearing, at least one vane of the impeller having a flow-on
surface inclined to the direction of the oncoming flow, and a sensor
which detects the rotary frequency of the impeller, the improvement
wherein
the shaft is disposed with axial play between said bearings,
the impeller is arranged in the line such that it is acted on by
the flow stream from below,
the flow-on surface of the impeller is inclined relative to the
direction of the oncoming flow in such a manner that the force component
in the direction of the flow of the force exerted by the flow stream
on the impeller is at least equal to the weight of the impeller,
flow straighteners arranged in said line in front of and behind
the impeller as seen in the direction of the flow,
said bearings are arranged in front sides of said flow straighteners
facing said impeller,
a housing block,
said line is a continuous measurement bore formed within said housing
block, said impeller and said straighteners are axially inserted
in said bore,
said housing block comprises two housing halves, each of said housing
halves forms a chamber half having the shape of a pot, defining
an opening, said openings of said chamber halves are directed towards
each other,
a diaphragm has a circumferential edge arranged between surfaces
of said housing halves adjacent said openings,
means for clamping together said surfaces of said housing halves
with said diaphragm therebetween, and
said chamber halves communicate with said measurement bore upstream
and downstream of said impeller, respectively.
28. The flow meter as set forth in claim 27 further comprising
a circumferential packing is arranged between one of said surfaces
of said housing halves and a side of a circumferential edge region
of said diaphragm facing one of said surfaces of said housing halves.
29. The flow meter as set forth in claim 28 wherein
said packing is a sealing ring.
30. The flow meter as set forth in claim 29 wherein
said impregnation is fuel-repellent.
31. The flow meter as set forth in claim 28 wherein
said diaphragm has a liquid-tight impregnation on said edge region
of said diaphragm located between said surfaces of said housing
halves which are clamped together.
32. In a flow meter, particularly for liquids, having an impeller
which is arranged in a vertical line and can be driven by a flow
stream flowing through the line, the impeller having a bearing shaft
the ends of which are rotatably mounted in an axially and radially
guiding bearing, at least one vane of the impeller having a flow-on
surface inclined to the direction of the oncoming flow, and a sensor
which detects the rotary frequency of the impeller, the improvement
wherein
the shaft is disposed with axial play between said bearings,
the impeller is arranged in the line such that it is acted on by
the flow stream from below,
the flow-on surface of the impeller is inclined relative to the
direction of the oncoming flow in such a manner that the force component
in the direction of the flow of the force exerted by the flow stream
on the impeller is at least equal to the weight of the impeller,
an inlet chamber half,
an inlet bore communicating with said inlet chamber half and said
line, and
a gas separation valve is connected to an upwardly directed region
of said inlet bore or of said said inlet chamber half.
33. The flow meter as set forth in claim 32 wherein
said gas separation valve includes a float valve.
34. The flow meter as set forth in claim 33 wherein
said float valve includes a float and a closure member rigidly
connected together.
35. The flow meter as set forth in claim 33 wherein
said float valve includes,
a valve chamber having a lower region,
an inlet is in communication with said lower region of said valve
chamber and with said inlet bore or said inlet chamber half,
said valve chamber has an upper region defining an outlet,
a closure means for closing said outlet, and
a float arranged in said valve chamber and actuatingly connected
to said closure means.
36. The flow meter as set forth in claim 35 wherein
said gas separation valve is a seat valve and a mouth of said outlet
in said valve chamber constitutes a valve seat, said seat valve
is coordinated to said valve seat.
37. The flow meter as set forth in claim 35 wherein
said closure means and/or said float is guided in a direction of
actuation of the valve.
38. The flow meter as set forth in claim 37 further comprising
a guide rod connects said float to said closure means, said guide
rod is guided in a guide fixed in a housing.
39. The flow meter as set forth in claim 35 wherein
said outlet is connected with an outlet bore.
40. The flow meter as set forth in claim 35 wherein
said outlet is connected with a flow return line.
41. The flow meter as set forth in claim 35 wherein
said valve chamber has a pot shape,
a closure screw is screwed into said valve chamber,
said outlet is formed in said closure screw.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flow meter, particularly for
liquids, having an impeller which is arranged in a vertical line
or measurement bore and can be driven by a flow stream, the impeller
having a bearing shaft, the ends of which are rotatably mounted
in an axially and radially guiding bearing, and one or more vanes
of the impeller having their flow-on or attack surfaces inclined
to the direction of the oncoming flow, and having a sensor which
detects the rotary frequency of the impeller.
2. Description of the Prior Art
In such flow meters it is known to manufacture the impeller of
a material whose density corresponds to that of the flowing fluid.
In this way the result is obtained that the impeller floats in the
flow fluid so that the friction of the mounting shaft in its bearings
which must be overcome is kept as small as possible. This is necessary
in order to keep measurement inaccuracies due to frictional losses
as low as possible, particularly in the range of low velocities
of flow.
The development of the impeller with a density equal to that of
the flow medium, however, affords great difficulty since, on the
one hand, the mounting shaft must consist of metal due to the high
resistance to wear which is required while, on the other hand, the
selection of the material for the vane part is very limited. This
is of great disadvantage in particular when, for instance, a corrosive
flow fluid permits the use of only very specific materials for the
impeller, for instance metallic materials.
SUMMARY OF THE INVENTION
The object of the invention is, therefore to create a flow meter
of the above-indicated type which while simple and cheap to manufacture
has a high accuracy of measurement over the entire measurement range.
This object is achieved in accordance with the present invention
by a movable wall (e.g. 33 FIGS. 2 3) subdividing a chamber into
two chamber halves (28 31), one of which communicates with an inlet
connection and the measurement bore upstream of the impeller and
the other one of which communicates with an outlet connection and
the measurement bore downstream of the impeller. This arrangement
sees to it that pulsations in the flow fluid which may come, for
instance, from a pump are absorbed before reaching the flow meter
proper. In this case, the movable wall is preferably a diaphragm
(33), since this diaphragm by its deformation contributes to absorption
of the pulsations.
If the flow meter is arranged in a vehicle it is of particular
advantage if the plane of the movable wall is arranged at an angle
of between 45.degree. and 90.degree. to the longitudinal axis of
the vehicle. In this way, movements caused in the liquid by accelerations
or decelerations of the vehicle are taken up substantially in the
chamber which is divided by the movable wall and in this way preventing
a reverse flow of flow fluid which cannot be processed by the flow
meter. An erroneous reading is thus not produced.
It is further advantageous in accordance with the invention to
arrange the bearing shaft (13) with axial play between the bearings
(14 and 15) and the impeller is acted on by the flow from below,
the flow-on surfaces (20) being inclined to the oncoming direction
of flow (21) in such a manner that the component of force in the
direction of flow of the force exerted by the flow stream on the
impeller is equal to or greater than the weight of the impeller.
This development leads to the result that the impeller is lifted
from its lower axial bearing point by the fluid flowing through
it even upon a flow within the lower measurement range, so that
the greatest part of the bearing friction is eliminated. Only in
the upper part of the measurement range of the flow meter does the
shaft come to rest axially against the upper bearing. Since, however,
a high velocity of approach of the fluid and thus a large attack
of force on the impeller are present, the axial bearing friction
produced thereby can no longer have any substantial influence on
the measured values.
Since components of force of different values acting in the direction
of flow on the impeller can be obtained by different inclination
of the attack surfaces with respect to the direction of approach
of the flow, the impeller wheel can be readily made of a material
which has a substantially higher density than the flow fluid. By
suitable inclination of the attack surfaces even such an impeller
can be used without disadvantage. The inclination of the attack
surfaces (20) to the direction of approach (21) can be between 45.degree.
and 65.degree., preferably having an inclination of 52.degree..
With these angles of inclination a sufficiently large lifting force
acts on the impeller without a negatively large influence on the
velocity of flow of the fluid acting.
The impeller can be a turbine wheel (12).
A structurally simple arrangement having only a few structural
parts can be obtained by forming the bearings (14 and 15) in the
front sides, facing the impeller, of flow straighteners (10 and
11) arranged in the tube line in front of and behind the impeller
as seen in the direction of approach.
Since in the flow meter of the invention, axial support of the
impeller wheel during operation is necessary only at the rear bearing,
as seen in the direction of flow, this bearing is preferably developed
as a conical bearing in order to reduce the bearing losses in the
upper measurement range of the flow meter. As to the front bearing,
as seen in the direction of flow, it is entirely sufficient for
it to be developed as a journal bearing.
One simple construction of the flow meter, which can therefore
be manufactured economically, consists therein that the tube line
is a continuous measurement bore (5) within a housing block (1)
into which the impeller and the straighteners (10 and 11) can be
axially inserted. A simple mounting of the straighteners and the
impeller can be obtained here if the straighteners (10 and 11) can
be inserted with forced-fit into the measurement bore (5). The outward
directed ends of the measurement bore (5) can be closed in simple
fashion by a closure (6 and 7), closure (6) and straightener (10)
preferably forming a single one-piece part.
Simple production of the impeller results when the impeller comprises
a vaned body (18) placed on the supporting shaft (13), in which
connection the vaned body may be a plastic part and the shaft a
metal part. For this, in simplest fashion the vaned body can be
formed by injection molding on the supporting shaft, so that said
body does not require any additional machining.
In order to avoid the vaned body shifting on the supporting shaft
as a result of the axial forces acting on it from the flow fluid,
the supporting shaft (13) preferably has recesses (19) on the cylindrical
outer surface thereof which is surrounded by the vaned body (8).
In this way a positive form-locking is produced between vaned body
and supporting shaft.
If an inlet bore (8) and an outlet bore (9) are developed in the
housing block (1) so as to debouch radially into the measurement
bore (5), all of these bores can be produced by simple means by
clamping the housing block in a drill and producing the bores.
The inlet bore (8) is connected with one half (28) of the chamber
and the outlet bore (9) with the other chamber half (31) of a chamber
(28 and 31) subdivided into two chamber halves by a movable wall.
This arrangement sees to it that pulsations in the flow fluid which
may come, for instance, from a pump are absorbed before reaching
the flow meter proper. In this case, the movable wall is preferably
a diaphragm (33) since this by its deformation contributes to the
absorption of the pulsation.
If the flow meter is arranged in a vehicle it is of particular
advantage if the plane of the movable wall is arranged at an angle
of between 45.degree. and 90.degree. to the longitudinal axis of
the vehicle. In this way, movements caused in the liquid by accelerations
or decelerations of the vehicle are taken up substantially in the
chamber which is divided by the movable wall and in this way a reverse
flow of flow fluid which cannot be processed by the flow meter is
prevented. An erroneous reading is thus not produced.
A construction which is easily produced and furthermore readily
mounted is obtained if the housing block (1) consists of two housing
halves (2 and 3) in each of which housing halves (2 and 3) there
is developed, in pot shape, a chamber half (28 and 31), the openings
of said chamber halves being directed towards each other, and if
the diaphragm (33) has its circumferential edge arranged between
the surfaces of the housing halves (2 and 3) which are clamped together.
In this way, both the different bores and the chamber halves can
be developed by simple means. In this connection, a circumferential
packing (34) is preferably arranged between one of the surfaces
and the side facing it of the circumferential edge region of the
diaphragm (33). This packing (34) can be a sealing ring.
However, it is also possible for the diaphragm (33) to have a liquid-tight
impregnation on its edge region located between the surfaces of
the housing halves (2 and 3) which are clamped together, the impregnation
being preferably fuel-repellent when the flow meter is used as a
fuel meter. This impregnation prevents the flow fluid from passing
along the fiber fabric of the diaphragm to outside the housing block.
Measurement errors which result from the fact that in the case
of a liquid flow fluid, bubbles of gas are contained in said fluid
are preferably eliminated by connecting a gas separation valve (39)
to the upward directed region of the inlet bore (8) or the chamber
half (28) connected to it. Since the gas bubbles move along this
upward directed region, they are removed from the stream of liquid
at the gas separation valve and do not reach the impeller, so that
liquid volumes which are falsified by gas bubbles cannot be measured
there.
The gas separation valve (39) is preferably developed as a float
valve. In such case, the gas separation valve (39) can have a valve
chamber (40) into the lower region of which there discharges an
inlet (43) which is in communication with the inlet bore (8) or
the chamber half (28) connected with it, and within the upper region
of which there debouches an outlet (44) which can be closed by a
closure member (42) which can be actuated by a float (41) arranged
in the valve chamber (40). The gas bubbles present in the upward
directed region of the inlet bore or the chamber half connected
with it travel in this connection into the normally liquid-filled
valve chamber and collect in the upper region thereof. The float
is normally pushed upward by the liquid and in this way presses
the closure member into the closed position of the gas separation
valve. By the increase in the gas volume, the liquid volume is reduced
and thus also the liquid level in the valve chamber. The float also
drops in this connection and thus opens the outlet of the gas separation
valve so that the gas present in the valve chamber can flow out.
Due to the rise in the level of the liquid in the valve chamber
which is caused thereby, the float and thus also the closure member
are again moved into the closed position and remain there until
once again sufficient gas has collected in the valve chamber to
effect a new opening process.
The float can be rigidly connected with the closure member. A simple
development, while at the same time obtaining dependable closure,
is obtained in the manner that the gas separation valve (39) is
a seat valve and the mouth of the outlet (44) in the valve chamber
(40) is the valve seat. Valve member (42) and/or float (41) can
be guided in valve actuation direction, the float being preferably
connected in this connection to the valve member by a guide rod
which is guided in a guide fixed in the housing.
The outlet can either be connected with the outlet bore and the
gas thus returned again to the stream of liquid after the volumetric
measurement thereof. However, it is also possible for the outlet
(44) to be connected with a return, which can lead, for instance,
to a liquid tank.
One simple development comprises forming the valve chamber (40)
in pot shape and closing the opening by a closure screw, the outlet
(44) being developed in the closure screw. Such a development can
be produced without the use of special tools.
In order to determine the rotary frequency of the impeller, a beam
is or can be sent preferably by a radiation transmitter along a
radiation path to a radiation receiver, the radiation being adapted
to be interrupted intermittently by the rotating vanes (26). The
number of interruptions of the radiation is then a measure of the
volume of flow fluid which has passed through the flow meter. In
this connection, the radiation transmitter is preferably a source
of light (24) and the radiation receiver a light-sensitive element
(23) by which electric signals can be produced. The electric signals
can be conducted for processing to an electronic measurement system
and be converted into an electrical value.
In order to avoid having increases and decreases in temperature
of the flow fluid affect the measurement values of the flow meter,
since the volume of the flow fluid varies as a function of the temperature,
a temperature sensor can be arranged in one of the channels or chambers
of the flow meter, the sensor producing an electrical variable which
corresponds to the temperature of the flow fluid and can be fed
to the measurement electronic system in order to affect the measurement
value. In this way, the measurement value given off by the measurement
electronic system relates, in principle, in all cases to a very
specific temperature and is thus a generally valid, objective measurement
value.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown in the drawing
and will be described in further detail with reference to the drawings,
in which
FIG. 1 is a front view of a flow meter in accordance with the invention
partly in section;
FIG. 1a is a view similar to FIG. 1 but showing another embodiment;
FIG. 2 is a section along the line II--II of FIG. 1 or 1a;
FIG. 3 is a section along the line III--III of FIG. 1 or 2;
FIG. 4 is a section along the line IV--IV of FIG. 1 or 2;
FIG. 5 shows the turbine wheel of the flow meter of FIG. 1 or 2
in partial section;
FIG. 6 is a partial section along the line VI--VI of FIG. 1 or
2; and
FIG. 7 is a longitudinal section through a straightener with bearing
in accordance with FIG. 1 or 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The flow meter shown in the figures, which is intended for liquids,
is to be used in particular as a fuel consumption meter for automotive
vehicles.
Referring now to FIGS. 1-4 and particularly FIG. 2 the housing
block 1 of the flow meter is formed of two housing halves 2 and
3 which are firmly connected to each other by bolts 4. Within the
housing half 2 there is developed a continuous measurement bore
5 whose outwardly directed ends are closed by closures 6 and 7.
Into one end region of the measurement bore 5 communicating radially
therewith is an inlet bore 8 while the other end region of the
measurement bore 5 radially communicates with an outlet bore 9.
The measurement bore 5 extends vertically in such a manner that
the inlet bore 8 opens within the lower region of the measurement
bore 5 and the outlet bore 9 in the upper region.
Within the measurement bore 5 between the inlet bore 8 and the
outlet bore 9 two flow rectifiers or flow straighteners 10 and 11
are inserted by forced fit via their blades 10a, 11a, a turbine
wheel 12 being arranged between the flow straighteners 10 11. The
turbine wheel 12 which is shown on a larger scale in FIGS. 2a and
5 has a bearing shaft 13 the free ends of which are rotatably
supported on axially and radially guiding bearings 14 (also see
FIG. 7) and 15 which are disposed in the front sides of the rectifiers
10 and 11 which face the turbine wheel 12.
The flow rectifier 10 is formed as a one-piece structural part
with the closure 6 (FIG. 2).
The support of the turbine wheel 12 in the bearings 14 and 15 is
of such a nature that the turbine wheel 12 has axial play.
At the bearing 14 one journal pin 13a of the bearing shaft 13 which
is made of steel is guided radially in a bearing jewel 16 and limited
in its axial movement by a cap jewel 17 the jewels 16 17 being
mounted in the flow straightener 10 by members 50 51.
At the bearing 15 (FIG. 2a) which is a bottom conical bearing the
second journal pin 13a of the bearing shaft 13 is guided radially
and limited in its axial movement by a cap jewel 17a which is mounted
in the flow straightener 11 by member 50.
The vaned body 18 (FIG. 5) of the turbine wheel 12 is a plastic
part which is mounted on the support shaft 13. So that the vaned
body 18 cannot shift on the bearing support shaft 13 the latter
is provided on its cylindrical surface surrounded by the vaned body
18 with recesses 19 into which the material of the vaned body 18
engages.
The flow-on surfaces 20 of the turbine wheel 12 are inclined by
a given angle 22 with resepct to the flow direction 21. This angle
22 which is preferably 52.degree., is so selected that the force
component directed in the flow direction 21 of the force exerted
by the flow stream on the turbine wheel 12 is equal to or greater
than the weight of the turbine wheel 12. Thus, upon the flow against
the turbine wheel 12 the latter is lifted upward from the lower
cap jewel 17 of the bearing 14 (FIGS. 2 2a, 7) and turns freely
in floating manner. If the flow-on speed increases, the journal
pin 13a of the bearing shaft 13 comes axially against the cap jewel
17a of the upper bearing 15. Due to the fact that with higher velocity
of flow a high rotating force also acts on the turbine wheel 12
the frictional forces due to the axial supporting of the shaft 13
at the bearing 15 have practically no influence on the precision
of measurement of the flow meter.
The rotary frequency of the turbine wheel 12 and thus the flow
stream is determined by a photosensitive element 23 (FIG. 6) which
cooperates with a source of light 24. Element 23 and the source
of light 24 are arranged opposite each other in a bore 25 which
intersects the measurement bore 5 in the region of the turbine wheel
12 which is in the bore 5 (but not drawn in FIG. 6 for clarity)
in such a manner that the beam of light directed from the source
of light 24 onto the element 23 is interrupted during the rotation
of the turbine wheel by the vanes 26 of the latter, but can pass
through the spaces between two vanes 26. In this way, the element
23 detects a frequency of light pulses which is proportional to
the rotary frequency of the turbine wheel 12 which pulses are transmitted
further via connections 27 to a measurement electronic system (not
shown).
The inlet bore 8 (FIG. 2) leads from the measurement bore 5 to
a chamber half 28 which is formed in that face wall of the housing
half 2 which is directed towards the half 3. Via an inlet connection
29 which debouches centrally into the chamber half 28 (FIG. 4),
the chamber half 28 is connected with an inlet connection 30 (FIG.
3).
Corresponding to the chamber half 28 (FIG. 2), there is developed
in the front side of the housing part 3 facing the housing part
2 a second chamber half 31 into which the outlet bore 9 debouches
and from which a connection leads to an outlet connection 32. Between
the surfaces of the housing halves 2 and 3 which are clamped together,
there is interposed a membrane 33 which separates the chamber halves
28 and 31 from each other. A seal 34 is inserted for purposes of
sealing between the housing half 3 and the diaphragm 33.
The possibility of movement of the diaphragm 33 in the two chamber
halves 28 and 31 is limited on the one hand by the inlet connection
29 and on the other hand by stops 35 which are rigidly connected
to the housing half 3 and against which the diaphragm 33 comes to
rest via a stiffening part 36 which is connected with it.
The flow meter is so installed in an automotive vehicle that the
plane of the diaphragm 33 which corresponds to the plane in which
the housing halves 2 and 3 rest against each other is arranged at
an angle of between 45.degree. and 90.degree. to the longitudinal
axis of the vehicle. As can be noted from FIG. 3 a connection 37
extends from the inlet connection 29 directly to the outlet connection
32. The cross section of passage of this connection 37 can be closed
off to a greater or lesser extent by a shut-off screw 38. By means
of this shut-off screw 38 calibration of the flow meter can be
effected after it has been installed. Calibration is necessary in
order, for instance, to compensate for measurement errors caused
by machining tolerances of the individual parts.
FIG. 4 is a horizontal cross-sectional view through a valve chamber
40. A vertical sectional view of a valve chamber 40 of the gas separation
valve 39 is shown in FIG. 1 and FIG. 1a. The valve chamber 40 is
closed by closure screw. The closure screw is formed as a connection
in which an outlet 44 is formed. The upper region of the chamber
half 28 is connected via an inlet 43 with the valve chamber 40 in
which a float 41 is arranged. The float 41 carries at its upper
end a closure member 42 by which the outlet 44 which debouches in
the upper region of the valve chamber 40 can be closed. The mouth
of the outlet 44 in the valve chamber 40 forms a valve seat.
The outlet 44 leads to a connection 45 which is connected with
a return (not shown) which leads to a fuel tank of the vehicle.
Due to the fact that the inlet 43 debouches in the upper region
of the chamber half 28 bubbles of gas present in the liquid pass
through the inlet 43 into the valve chamber 40 and collect in the
upper region of the latter. Since the valve chamber 40 is normally
filled with liquid, the float 41 is in its upper position so that
the closure member 42 closes off the outlet 44. If the amount of
gas which has accumulated is so great and the level of liquid in
the valve chamber has dropped so far that the float 41 descends,
the outlet 44 is opened and the gas can flow out. The increase in
the level of liquid produced thereby in the valve chamber 40 now
lifts the float 41 so that the outlet 44 is again shut off. Due
to the fact that the gas bubbles are removed from the liquid in
front of the measurement bore 5 they cannot affect the measurement
at the turbine wheel 12 or lead to measurement errors. |