Note: Descriptions are shown in the official language in which they were submitted.
POSITIVE DISPLACEMENT FLOWMETER
BACKGROUND OF THE INVEN'.CION
Conventional type flowmeters, each of which has an
indicator unitarily attached to its body and is connected to
a pipe by means of flanges or like joining means, are
generally used for measuring and indicating the fluid's flow
by processing a flow-rate signal from a measuring partion.
There have been many applications of positive displacement
flowmeters of this type. The positive displacement
flowmeter, operating on the principle of a constant volume
of fluid discharged by a rotor rotating in a measuring
chamber of the flowmeter's body, is usually mounted with its
rotor shaft horizontally positioned so as to correctly
measure the fluid's flow-rate proportional to the rotation
of the rotor without causing any undesirable rolling
friction. Furthermore, when the flowmeter is mounted an the
piping, its indicating portion is attached to the
flowmeter's body horizontally along the axis of the
flowmeter so as to vertically dispose the indicating panel
for easily reading it.
The positive displacement flowmeter's body is attached
at its flanges to a pipeline through which a fluid to be
measured flaws. A counting portion having the function of
processing the flow-rate's signal and to indicate the value
obtained is accommodated in an outer housing which is
removably attached to the flowmeter's body through an outer
- 1 -
connecting housing with setscrews in deeply counter-bored
holes in the outer housing. However, in the case where the
flowmeter is mounted on outdoor piping, rain water may
accumulate in the deeply counter-bored holes and penetrate
through the threaded portions of the set-screws into a small
clearance between the inserted pipe of the outer indicator
housing and the inserted hole of the outer housing, which
during a long period of time may exert an adverse effect on
the inner devices of the counting portion and also make it
impossible to. remove the inserted part of the outer
indicator housing from the connecting housing due to the
rusting of its inserted part.
The outer indicator housing, accommodating therein the
circuit components such as a preamplifier for amplifying the
flow-rate signal, is composed of a body portion having a
closed bottom for placing the circuit components thereon and
a sealing cover threadably attached to the body to protect
the circuit components from moisture affection. Said
housing has at its inner bottom an integrally made and
concentrically protruding supporting portion whereto a
- circuit board with circuit components mounted thereon is
attached by using supporting columns and screws. The
circuit board with circuit components is mounted on the
supporting columns in the housing and closed by a cover
member. However, if any circuit component in the housing
has to be replaced with a new one out-of-doors in the rain,
rain water may penetrate into the housing since it takes
time for threadably mounting the circuit board onto the
supporting columns in the housing.
A reed switch is used for externally operating the
preamplifier and other circuit components on the circuit
board in the housing, since it can be switched OAT and OFF by
use of a magnet, can be simple in construction and
especially adapted for use in a drip-proof and
explosion-proof situation.
This reed switch is mounted in a housing made of
non-magnetic material and provided with a push-button
arranged on the outer surface of the housing in such a way
that the switch's body and the push-button are facing each
other across a partition wall. The push-button is normally
kept apart from the reed switch by the force of a spring in
the push-button casing on the outside of the housing and a
permanent magnet is integrally attached to the push-button
on the side adjacent to the reed switch. The reed switch is
mounted on the partition wall in such a way that it is
disposed opposite the permanent magnet parallel with the
axis therea~f. When the push-button is pressed against the
spring force to make the magnet approach the reed switch,
the magnet causes the reed switch to be ON. The push-button
has to move reciprocally in the push-button casing.
However, such problems may arise so that the mechanism
cannot realize the smooth reciprocation of the push-button
and, furthermore, the magnet directly attached to the
molding material of the face of the push-button may easily
drop off .
In the instructions on explosion-proof constructions of
- 3 -
electric equipment for factories, which have been
established in order to ensure the safety of electric
equipment installed at dangerous places with possibly
explosive atmospheres, the shroud construction of the
explosion-proof container has been standardized. The
explosion-proof container is a metal pressure-vessel capable
of withstanding the pressure specified depending an its
volume. A cover for this pressure vessel is joined to the
vessel's body thereby maintaining a specific size of the
joined surfaces. The cover is secured to the pressure
vessel by using bolts with washers in deeply counterbored
holes drilled in a plane portion of the cover. In the case
where the vessel's cover, joined thereto by use of bolts
with their heads buried deeply in counterbored holes is
installed outdoors, rain water may collect in the deeply
counterbored portions of the holes to wet the bolts' heads
and then evaporate thereby causing a gradual corrosion of
the bolts and joined metal surfaces by the repeated
atmospheric conditions.
The flowmeters are basically designed to be of an
- exglosion-proof construction since they may be frequently
used for the measurement of the flow of explosive fluids or
at places specified as having a dangerous atmosphere.
However, the manufacturing cost of the flowmeters increases
to satisfy the requirements for an explosion-proof
construction of pressure vessels in relation to a specified
volume, specified sizes of joined surfaces with a specified
allowance, lead-in wires, the separation of containers
accommodating electrical devices etc..
On the other hand, recently many flowmeters of such a
type, which process a flow-rate signal transmitted from a
flowmeter's body and indicate the calculated value, have
been adopted. The application of flowmeters incorporating a
battery as a source of energy far signal generation,
calculation and indication has also been increased. The
above-mentioned electric circuit of the flowmeter which is
of a battery-operated type requires only a small current
supply and consumes a small amount of electrical energy,
thereby being intrinsically adapted to explosion-proof
applications. The battery, adapted for intrinsically safe
circuits, is provided with a current-limiting resistance or
a like element serially connected thereto to prevent an
over-load of current from occurring across a short circuit
formed by a malfunction and furthermore it is placed in a
suitable vessel. rt is also required that the battery unit,
for use at a hazardous place, shall include a
current-limiting element and be replacable in the form of a
complete unit. Such a power supply unit is connected to the
electrical circuit by the use of a connecting means such as
a plug and connector, removably secured to a partition wall
and operated from a switch mounted on the electrical circuit
side.
The battery unit is provided with~a resistor or a like
current-limiting element connected thereto by embedding the
connections in a molded material but the other terminal of
the battery and the open terminal of the resistor are
~:onnected by a connecting means to the electrical circuit
through a switching means. Consequently, leaking current
may flow through the connecting means and circuit
components, such as a switch, even when the circuit is not
in operation. This causes an acceleration in the
deterioration of the battery. Furthermore, since the switch
mounted on the electric circuit is operated by hand each
- time it is switched OFF and ON, especially after a long OFF
period, the electric circuit may become exposed to the
atmosphere. This is undesirable from the viewpoint of
assuring the safety and durability of the device.
As mentioned above, the positive displacement flowmeter
is constructed in such a way that in a measuring chamber of
the flowmeter's body installed in a pipe line through which
the fluid flows a rotor is rotatably mounted keeping a small
clearance thereabouts and is capable of rotating therein at
a rate proportional to the flow rate of the fluid, the
rotor's rotation is sensed by a sensing means and then the
calculated .flow-rate value is indicated by an indicating
means. In many cases a system for converting a rotor's
- rotation into an electrical signal is adapted as the means
for sensing the rotor's rotation. For example, the magnetic
flux from a transmitting magnet embedded in the face of the
rotor is sensed by a magnetic sensor which in turn generates
an electric signal to be transmitted as a pulse signal of
the flow's rate. The pulse signal is processed by an
electrical transducer mounted in a counting portion made
unitarily with the flowmeter's body and then is indicated by
an indicator or transmitted to a remote place. There are
various kinds of fluids to be measured by the flowmeter in a
variety of physical or chemical conditions such as pressure,
temperature etc. For example, the temperature of a fluid
may vary in a wide range from low to high. This means that
the operating circuit of the counting portion has to operate
well at temperatures varying within a wide range. Since the
counting portion is directly connected to the flowmeter's
body, it may be effected by the thermal conduction and
radiation if the fluid is hot. Accordingly, in this case it
is necessary to protect the counting portion from the
possible effect of heat by interposing heat insulation
between the measuring portion and the counting portion. The
heat insulation is made in the form of a hollow square pipe
of mainly inorganic material having a high resistance to
heat and low thermal conductivity such as rock wool etc.
The above-mentioned positive displacement flowmeter has
heat insulation protecting it for shutting out the flow of
heat from the flowmeter's body. However, the heat
insulation provided is available to shut off heat transfer
by conduction but it cannot prevent heat transfer by
radiation. Consequently, the radiant heat from the
flowmeter's body is directly transferred to the bottom of
the counting portion wherein the temperature rises,
resulting in that air in the closed space of the counting
portion is heated and thereby expands to increase the inner
pressure. A part of the air under increased pressure is
discharged out of the counting portion through the heat
~n~ulation of the capillary-type structure. Therefore, air
from the outside flows into the counting portion after the
flowmeter stops and its temperature is lowered. Such
respiration increases the humidity of the air in the
counting portion causing the condensation of moisture
therein at a low ambient temperature. Although there are
capillaries in the heat insulation most of there are c:Losed
and cannot allow the counting portion to communicate with
the outside air. This poses the problem that the
temperature rises in the counting portion and is
irrevocable.
The measuring chamber of the positive displacement
flowmeter communicates with an inlet and an outlet of the
flowmeter and accommodates a pair of rotor shafts of the
same diameter, each of which is provided with a non-circular
gear. Each rotor shaft has one end formed in the shape of a
column having a flange secured with bolts to the outer wall
surface of the outer housing of the flowmeter's body, and
has its other end extending through a hole at the bottom of
the measuring chamber. Paired rotor shafts are arranged
parallel to each other in the measuring chamber. The rotor
shafts have gears of a non-circular shape and axe rotatably
mounted therean one by one respectively and engaged with
each other. The rotor shafts are fixed on a face plate
having two holes wherein the other ends of the shafts are
inserted respectively. The fare plate is secured to the
outer housing of the flowmeter's body by use of locating
pins. Furthermore, the face plate is enclosed by a back
g _
cover which is threadably secured to the outer housing of
the flowmeter's body with a liquid.--tight O-ring provided
there-between.
In the above-mentioned conventional positive
displacement flowmeter, its rotor shafts are secured at
their flanged ends to the outer housing of the flowmeter's
body. The flanged shafts are large in size and expensive.
Furthermore, since said shafts are held at the other ends,
loosely fitted in corresponding holes of the face plate, the
liquid may leak through a minute gap formed between the
shaft and the hole of the face plate. To prevent the liquid
leakage, it is needed to add a back cover sealed with an
O-ring, thereby increasing the cost of the flowmeter.
Non-circular gears which are used in pairs as a rotor
for the positive displacement flowmeter have teeth cut by a
basic straight rack at a constant pressure angle. The
teeth's profile is an involute obtained as a trace of
rolling contact between a straight line of the basic rack
and a pitch curve of the non-circular gear, i.e. the gear
teeth are cut according to a non-circular pitch line with
partial curved centers. Accordingly, the partial curved
center of the non-circular pitch line does not coincide with
the rotating center of the non-circular gear. When the
non-circular gear is manufactured by the powder metallurgy
compression molding method, metal in a mold during the
compression process is subjected to radial outward pressure
from the rotating center of the non-circular gear.
Consequently, the powder metal density of each tooth's
g _
;surface of the molded work may be different at opposite
sides, i.e. it has a higher density at one side and a lower
density at the other side. The work is sintered to form a
non-circular gear with its teeth bent toward the surface
side of the lower powder-metal density.
When the deformed non-circular gear is compressed in a
metal mold in the next process, it receives a reverse force
to its teeth from the other side far straightening its teeth
surfaces in accordance with the mold. This poses the
problem that the gear's teeth may crack due to the
straightening force in the molding or the damaging of its
teeth's surface due to excessive friction at the time of
extruding the gear from the mold.
In the positive displacement flowmeter the rotor's
rotation is indicated mechanically through reduction gears
and electrically through a rotation sensor converting it
into an electrical signal. Many optical sensors or
magneto-electric transducer type contactless ones are
applied for directly sensing the rotation of the rotor.
There are two types of optical sensors - reflecting and
transmitting. However, these optical sensors can be applied
only tn light-transmitting fluids, the kinds which may be
limited. On the other hand, magneto-electric transducer
type sensors can be applied to many kinds of fluids and,
therefore, axe preferable for adoption in many positive
displacement flowmeters. Magnetic sensors such as a hall
device, magnetic resistance and so on are used as a
magneto-electric transducer which is capable of sensing the
- 10 -
magnetic flux from a transmitting magnet embedded in a -rotor
of the f lowmeter .
However, the above-mentioned magnetic sensors cannot be
applied to magnetic fluids affecting the distribution of
magnetic flux of the transmitting magnet and are also
limited by its working temperature. Usually, magnetic
sensors of this type can operate at relatively low
temperatures (max. working temperature of about 80 - 100°C)
and therefore in many cases cannot directly detect the
rotor's rotation. In addition, they must be provided with
respective power supply sources. This means that in the
case of the long-term measurement of fluid by a simple
method, for example, when an integrating flowmeter with
battery power is being used for the measuring of the total
flow of drinking water or of city gas, the addition of a
power supply of the sensor unit increases the manufacturing
and running costs of the flowmeter and restricts its field
of application.
The positive displacement flowmeters, wherein a
magnetic flux generated by a transmitting magnet embedded in
a rotor face is sensed by a magnetic sensor mounted on an
outer housing, are capable of directly detecting the rotor's
rotations and assures simple and accurate measurements of
the fluid's flow by virtue of its small detection load.
However, the flowmeters of this type, as well as other types
mentioned above, have the disadvantage that their bodies
must be exchanged with other bodies incorporating rotors
that are similar in form but different in size depending on
- 11 -
CA 02024083 1999-10-21
12
the specified range of the fluid's flow to beg measured.
SUN~1ARY OF THE INVENTION
According to the present invention, there is provided a
transmitting system for a positive displacement flowmeter
comprising plural types of bodies including different pairs
of rotors, which being similar in shape and different in size
for different ranges of flow measurement, each pair of rotors
rotatably mounted on respective shafts secured in a measuring
chamber and one of the rotors having a transmitting magnet
embedded in its face, a detecting cover having a magnetic
sensor mounted therein in opposite to the magnet embedded in
the rotor for detection of the rotor's rotation and a
counting potion for calculating the fluid's flow according to
a signal from the magnetic sensor and indicating the
calculation result, characterized in that the sensor is
mounted at a position on the detection cover that corresponds
to a common intersection point of different circular orbits
of transmitting magnets of rotors of different sizes in
different types of bodies.
Preferably, it is an object of the invention to provide
a positive displacement flowmeter which is no constructed as
to discharge rain water collected in counterbored bolt holes
of a flow-rate indicator, attached to the flowmeter body, by
using bolts in said holes.
Preferably it is another object of the invention to
provide a positive displacement flowmeter which is so
constructed as t:o sim,ply and quickly accommodate a circuit
board with a m_~nimum number of components to be mounted
thereon in a housing.
Preferably, it is still another object of the invention
to provide a poaitive displacement flowmeter having a reed
CA 02024083 1999-10-21
13
switch provided with a smoothly operable push-button of a
simple construction.
Preferably, it is a further object of the invention to
provide a positive displacement flowmeter wherein a first-
member having deeply counterbored through-holes drilled
therein and a second-member having threaded partially drilled
not-through holes aligned with the corresponding through-
holes in the first member are threadably connected with each
other by the uses of bolts and spring washers and a provision
is made to di~;chargE~ rain water standing in the deeply
counterbored portions of the through-holes in the first
member.
Preferably, it is still a further object of the
invention to provide a positive displacement flowmeter
wherein the electric ;system comprises an electric power unit
including a battery potted in resin together with a serially
connected thereto limiting resistance of a specified value,
an electric cir~~uit t:o be energized with current from the
electric power unit and a switch for switching the electric
power unit ON and OFF, the electric power unit and the
electric circuit being accommodated in an electric device's
housing and an internal part of the switch being also
operable (ON-OFF contl:ol) and embedded in resin with a high
insulation resistance and united with the electric power unit
to assure that there is no consumption of the battery's
charge while the battery is not in use and the electric
circuit can be switched on in its sealed state.
Preferably, it is another object of the invention to
provide a positive displacement flowmeter which is capable of
preventing heat from being transferred by conduction and
radiation from the flowmeter's body, wherein a hot fluid
flows, to a counting portion, thereby preventing a rise in
CA 02024083 1999-10-21
14
temperature of t:he electric circuit mounted in the counting
portion.
Preferably, a further object of the invention is to
provide a positive displacement flowmeter which is so
constructed as i~o be able to easily mount the shafts of a
rotor rotating a.t a rotating speed proportional to the flow
rate of the fluid flowing in a measuring chamber by
simplifying their fixed construction, thereby lowering the
cost of the flowmeter in relation to the materials used and
the assembling time.
Preferably, a further object of the invention is to
provide a positive displacement flowmeter wherein a higher
productivity is achieved through the selection of suitable
materials and a tooth profile of non-circular gears rotating
in accordance with the: flow rate of the fluid flowing inside
the measuring chamber.
Preferably, it is another object of the invention to
provide a positive displacement flowmeter which is capable of
measuring with a high reliability the flow rate of a fluid of
a high temperature by adopting an amorphous magnetic sensor
which does not require a power supply and which is capable of
generating a pulae signal of the flow-rate in response to the
magnetic flux from a magnet embedded in a rotor's face.
Preferably, it is still another object of the invention
to provide a positive displacement flowmeter which has a
rotor including a magnet embedded therein and a sensor that
is sensitive to the magnet and mounted on the outer housing,
facing the magnet and which assures a constant mounting
position of the sensor- irrespective of the flowmeter bore's
diameter
CA 02024083 1999-10-21
a
14a
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 i;s a perspective view showing a positive
displacement flow~eter according to the present invention;
Firn~re 7 shows ~ detailed portion of the embodiment of
~~~~C~
rr~ig.l;
Figure 3 is a sectional view taken along line III-III
of Fig.2;
Figure 4 is a perspective view showing the mechanism
for 'the mounting devices;
Figure 5 is a sectional view taken along line V-V of
Fig.4;
Figures 6 and 7 are sections taken on lines VI-VI and
VII-VII, respectively, in Fig.5;
Figure 8 is a sectional view taken along line VIII-VIII
of Fig.9 showing an example of a prior art for mounting
electric circuit components in a housing;
Figure 9 is a section taken on line IX-IX in Fig.8;
Figures 1Q to 13 show an embodiment of the present
invention consisting of improvements of the prior art shown
in Fig.8. Figure 13 is a section taken on line XIII-XIII in
Fig. l2;
Figure 14 is a sectional side view of a conventional
push-button switch;
Figure 15 is a sectional view taken along line XV-XV of
Fig. l4;
Figure-16 is a perspective view from the rear of the
push-button;
Figure 17 is a sectional side view showing the
construction of a push-button switch, according to the
present invention;
Figure 18 is a sectional view taken along line
XVIII-XVIII of Fig. l7;
- 15 -
rFigure 19 is a perspective view from the rear of the
push-button;
Figure 20 is a sketch showing a method of holding a
magnet;
Figure 21 is a view showing an example of a shrouding
construction of an explosion-proof vessel.
Figures 22 and 23 are illustrations of a jointing
construction according to the present invention. Figure 22
is a sectional side view taken on line XXII-XXII in Fig.23,
and Figure 23 is a sectional side view taken on line
XXIII-XXIII of Fig.22;
Figure 24 is a circuit diagram of an electric power
supply unit;
Figure 25 is a construction view of an electric power
supply unit incorporating the circuit shown in Fig.24;
Figures 26 and 27 are sketches for explaining a
conventional positive displacement flowmeter. Figure 26 is
a section taken on line XXVI-XXVI in Fig.27, and Figure 27
is a section taken on line XXVII-XXVII in Fig.26;
Figures 28 and 29 are views for explaining a positive
displacement flowmeter embodied in the present invention.
Figure 28 i.s a section taken on line XXVIII-XXVIII in
Fig.29, and Figure 29 is a section taken on line XXIX-XXIX
in Fig.28;
Figure 30 is a view showing the construction of a
measuring portion of a conventional positive displacement
flowmeter, and Figure 31 is a sectional view of a measuring
portion of a positive displacement flowmeter according the
16
present invention;
Figure 32 is a view shawing in detail a shaft's
construction. Figure 33 is a view showing an example of a
shaft fixture, and Figure 34 is a section taken along line
XXXIV-XXXIV of Fig.32;
Figure 35 is a view for explaining an example of a
non-circular gear used in a conventional positive
displacement flowmeter, and Figure 36 is a view for
explaining an example of a non-circular gear used in a
positive displacement flowmeter according to the present
invention;
Figure 37 shows the magnetic characteristics of a
magnetic sensor. Figure 38 is a construction view of a
magnetic sensor used in a positive displacement flowmeter,
according to the present invention;
Figure 39 is a view for explaining an outline of a
positive displacement flowmeter wherein non-circular gears
are adopted;
Figure 40 and 41 are views f or explaining flow-rate
transmitters according to the present invention. Figures 42
to 45 are views showing other embodiments of flaw-rate
transmitters;
Figure 46 is a view showing an example of a positive
displacement flowmeter to which the present invention
applies and is a section taken along line XLVI-XLVI of
Fig.47. Figure 47 is a section taken along line XLVII-XLVII
of Fig.46;
Figures 48 to 51 are views for explaining a
- i7 _
~~ ~ t~
::onventional transmitting system;
Figures 52 to 55 are views for explaining the relative
positions of a transmitting magnet and a magnetic sensor in
a transmitting system of a positive displacernent flowmeter,
according to the present invention; and
Figures 56 to 58 are views for explaining other
embodiments of the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Fig.l shows an example of a flowmeter which is composed
of a body 30 having flanges 30a and 30b for connecting to a
pipeline (not shown), a counting portion 10 incorporating
therein a counting unit capable of processing a flow-rate
signal to be indicated on a flow-rate indicating unit 10a,
and a connector housing 20 for removably connecting the
device housing 10 to the body 30 of the flow meter. As
shown in Fig.2, the device housing 10 is secured to the
connector housing by means of set screws 3 screwed into
counterbored threaded holes 4 in the connector housing.
Fig.2 is a detailed view showing an example of
attaching the device housing 10 to the connector housing.
As shown in Fig.2, the device housing has an inserting
cylindrical portion 1 extending concentrically and
outwardly, which is inserted into a receiving hole 20a
concentrically drilled in the connector housing 20, and
which is clamped therein by set screws 3 screwed through the
counterbored holes 4, two (upper and lower) pairs, arranged
_ 18 _
~~~~fl~3~
symmetrically to each other along line III-III of Fig.2 at
both sides of the connector housing 20. Since the connector
housing 20 is made in the sarne form as the device hauling
10, they can be unitarily connected as shown in Fig.l. The
inserting cylindrical portion 1 of the device housing arid
the receiving hole 20a of the connector housing do not
always need to be concentric with their housings
respectively, i.e. if both housings may be connected with
each other to form a unit of the same form.
Fig.3 shows a cross-section of the unitarily connected
portion of both housings 20 and 10, which is taken along
line III-III of Fig.2. When the flowmeter is mounted on the
outdoor pipeline, rain water "W" may collect in the
counterbared holes 4, as illustrated, gradually penetrating
through the threaded portions of the setscrews 3 into a
small clearance "g" between the receiving hole of the
connector housing 20 and the insert portion 1 of the device
housing 10 as shown by the letters Wa resulting in that the
inner components of the device housing are subjected to
deterioration from humidity and after a long period it
becomes impossible. to remove the insertion part of the
device housing from the connector housing due to the rusting
of its inserted portion.
Fig.4 is a perspective view showing a method far
connecting the device housing 10 to the connector housing
20. Fig.S is a view taken in the direction of the arrows
along line V-V of Fig.4. In these drawings, like parts, as
those of Fig.2, are indicated by like reference characters.
- 19 -
The connector housing 20 has a receiving ring (hole) 20a
which is secured concentrically in the connector housing 20
by means of inner walls 6. In other words, the connector
housing 20 is separated by the inner walls 6 from the
receiving hole 20a and its counterbored holes 4 communicate
with the receiving ring 20a through corresponding columned
ribs 2b. Fach counterbored hole 4, drilled through the
columned rib 2b to an opening in the receiving ring 2a, has
a thread 5 cut therein. Through-holes 9 made in the
reinforcing ribs 2c between the housing 20 and the receiving
ring 2a are provided for allowing the rain water to flow
out.
Fig.6 is a sectional view taken in the direction of the
arrow along line VI-VI of Fig.5 showing the columned rib 2b.
Fig.7 is a sectional view taken in the direction of the
arrows along line VII-VII of Fig.S. In these drawings, a
drain ditch 7 is drilled toward the inner wall 6 from the
circumference of the columned rib 2b at the bottom of the
counterbored hole 4. Since said drain ditch 7 is intended
to discharge the rain water collected in the corresponding
counterbored hole 4 through the columned rib, it is
preferable to make the lower portion of the ditch deeper so
as to completely drain out the rain water therethrough. A
drain hole 8 is drilled through in the vicinity of the
connector housing 20 above the counterbored hole 4 in the
lower columned rib 2b. The above-mentioned drain system
realizes the draining of the rain water collected in each of
the upper counterbored holes 4 in such a way that, as shown
- 20 -
~9~4~8~
by arrows Q in Fig. S, the rain water flows along the wall's
surface 6 between the receiving ring 2a and the connector
housing 20, passes through the passage hole 9 and the drain
hole 8 and reaches the lower counterbored hole 4 wherefrom
it is then discharged out of the connector housing. The
clearance between the connector housing and the device
housing is sealed with a flexible plate such. as a rubber
plate to prevent the penetration of the rain water into the
device housing. Although the above--mentioned rain water
draining system is applied to two pairs of the upper and
lower counterbored holes at the opposite sides along line
V-V in the Fig.4, the method described can be applied not
only to flow meters, but also to any object which has
counterbored holes at its upper portion, shroudings at their
upper and lower portions and inner chambers allowing liquid
to flow therethrough. Since according to the
above-mentioned mounting methad rain water can run along the
vertically provided draining channel in the housing from the
upper counterbored hole to the lower counterbored hole
wherefrom it is discharged, there will be no effect by the
rain water on the insulation of the electric circuit
components in the device housing. Furthermore, the
inserting and receiving portions can be prevented from
rusting and the outside surface of the housing can be kept
unstained by the effect of rain water making the maintenance
of the flow meter easier.
Fig.B is a view showing a mechanism for easily locking
a circuit board with components mounted thereon in the
- 21 -
~~~~~~~J
device housing. The electric circuit components such as a
preamplifier etc. are usually accommodated in a housing and
secured therein by means of the device shown in Fig. B.
Fig.8 is a section taken along line VIII-VIII of Fig.9,
while Fig.9 is a section taken along line IX-IX of Fig.8.
In the drawings, a housing 41 for accommodating the circuit
components 43 has a bottom 41c whereon supporting aprons 41a
are formed unitarily with the inner wall of the housing 41,
protruding inwardly toward the axis of the bottom 41c. A
sealing cover 42 is threadably secured at its threaded part
42a to the housing 41 to prevent the humidity from entering
therein and effecting the circuit components 43 mounted on a
circuit board 44. The circuit board 44 with the circuit
components are secured to the supporting aprons 41a through
corresponding supporting columns 45 by placing screws 46
into the threaded holes 41b in the supporting aprons 41a.
The circuit board 44 with the circuit components mounted
thereon is thus secured to the supporting aprons 41a by
means of supporting columns 45 in the housing closed with a
cover 42. However, since in the above-mentioned housing the
circuit board 44 together with supporting columns 45 are
threadably secured to the supporting aprons 41a, it takes
considerable time to replace any circuit component with a
new one and therefore, if the replacement is made outdoors
in the rain, the rain water may penetrate into the housing
41.
An embodiment shown in Figs. l0 to 11 was made in order
to eliminate the above-mentioned drawbacks by minimizing the
- 22 -
number of elements to be incorporated into the housing 41
and by improving the locking structure making it capable of
easily and quickly mounting the circuit board. Parts
similar to those of the prior art shown in Fig.8 are
indicated by corresponding characters and excluded from
further description. In Fig.lO, numeral 51 indicates a
cylindrical housing having a bottom 51c, which is provided
with a ring seat 51a at its inner cylindrical surface. Said
ring seat 51a has vertical slots 51b of a specified length
drilled in a portion thereof toward the bottom 51c. A
circuit board 54 is shown in detail in Figs.l2 and 13.
Fig. l2 is a plane view, and Fig. l3 is a section taken along
line XIII-XIII of Fig. l2. The circuit board 54 is a plate
having notches 54b cut parallel to each other in a radial
direction from the centre 0 in such a way as to form a
rectangular tongue 54a which is bent downwards at its base
portion 54c. Electrical parts 43 are secured onto the
circuit board 54 which in turn is mounted on the ring seat
51a made at the inner wall of the housing 51 in such a way
that the bent rectangular tongue 54a of the circuit board
54a is inserted in the vertical slot 51a made on the inner
wall of the housing.
Fig.l1 is an enlarged detail of the inserted portion of
the circuit board 54. In Fig.ll, the bent rectangular
tongue 54a is locked in the vertical slot 51b not to allow
the circuit board to move in a circumferential direction.
However, since in this condition the circuit board 54 may
still move in a vertical direction, a cover 42 is threadably
- 23 -
l
attached to the housing so as to fix the circuit board
between said cover 42 arid the ring seat 51a. As rnentioned
above, the circuit board 54 is locked in place by the ring
seat 51a and the vertical slot 51b so as to become
immobilized in both circumferential and vertical directions.
Although in the above-mentioned case the cover 42 is
threadably attached to the housing 41, it is also possible
to adopt another means for fixing the cover 42 to the
housing, as for example, by using the ring seat and bolts.
As is apparent from the foregoing description,
according to the present invention, it is possible to easily
lock the circuit board in the housing by adopting a low cost
and easy-to-use fixing structure wherein the circuit board,
including the circuit components mounted thereon and having
the rectangular tongue simply made in a radial direction at
its circumference, is placed on the ring seat by inserting
its tongue in the vertical slot and then being secured by
the cover which is threadably secured to the housing to
firmly abut the circumference of the circuit board against
the ring seat.
A reed switch is usually adopted for operating
thus-mounted circuit components from the outside of the
housing. Since the reed switch can be switched ON and OFF
by use of a magnet and is simple in construction, it is
especially adapted for use in drip-proof and explosion-proof
applications.
Fig. l4 shows a conventional push-button switch.
Numeral 61 indicates a cross-section of a main portion of
_ 24 -
the housing made of a non-magnetic material, whereirx the
circuit board is mounted. Fig. l5 is a section taken along
line XV-XV of Fig. l4. The housing 61 includes a reed switch
chamber 60 and push-button chamber 63 which are separated
from each other by a partition 6$. A push-button 62 made of
a non-magnetic material is mounted as being extended by the
force of a spring 64 in the push°button chamber 63. A plate
72 is used for abutting the spring 64 against the outer
surface of the collar 62a of the push-button 62.
~ig.l6 is a perspective view showing the push-button 62
from its back side. The collar 62a of the push-button is a
guide ring having a pin 66 which at one end is fitted in the
cylindrical side wall of the collar and at the ather end is
inserted into a guide slot 65 vertically made on the inner
wall of the push-button chamber. The push-button 62 is
inserted in the push-button chamber 63 keeping a small gap
there-between. A square-rod magnet 67, magnetized in its
axial direction, is embedded with molding material 62b, e.q.
resin, in an upper ring 62d of the push-button 62 in such a
way that the upper surface of the magnet is substantially
flush with the upper ring face 62d of the push-button. A
reed switch 70 is potted with resin 69a in a holder 69 made
of a non-magnetic material, which is secured to the
partition wall 61 in such a way that it is disposed opposite
the magnet 67 in parallel with the axis thereof. When the
push-button 62 is pressed against the force of the spring 64
to move the pin 66 along the guide slot 65, the magnet 67
approaches the reed switch 70 and puts the reed switch ON.
- 25 -
The reed switch 70 is provided with terminals 70a and 70b.
The above-mentioned structure makes it possible to control
the reed switch 70 in a state of being separated from the
outside by the partition wall 61. In order to ensure the
smooth movement of the pin 66 fitted in the collar 62a along
the guide slot 65 when the push-button 62 is pressed and
released, it is necessary to correctly fit the pin 66 in the
side wall of the collar 62a without bending and also to
always keep a constant angle of positioning the pin 66
against the magnet 67. However, the above-mentioned
conditions were hardly achieved, since the push-button 62
and its collar 62a have a slight gap there-around in the
cylindrical cavity of the push-button chamber. Furthermore,
there was the problem that the magnet 67, directly attached
to the molding material of the face of the push-button,
easily dropped off.
Fig.l7 is a view for explaining an example of a
push-button which is designed to be free from the
above-mentioned drawbacks of the prior art by eliminating
the necessity of fitting the pin 66 in the cylindrical outer
surface of the collar 62a and also of cutting the guide slot
in the inner wall of the housing, thereby achieving its
smooth reciprocal movement. In Fig.l7, elements similar to
those of the prior art shown in Fig.l~ are indicated by the
same corresponding characters and excluded from further
description. The push-button chamber 75, as. shown in Fig. l8
(a section taken along line XVIII-XVIII of Fig.l7), has a
rectangular cross-section of '°1" in width and "m" in length
- 26 -
(1=m). The push-button 76 is provided with a flange 76a
which is slightly smaller in diameter than the push-button
chamber 75 and therefore is loosely insertable into the
chamber 75.
Fig.l9 is a perspective view showing 'the push-button 76
from its back side. The push-button comprises a center
flange 76a receiving the force of the pressure-spring 64 and
abutting to a plate 72, a push-button body 76b projecting
outwardly from the plate 72, and an inserted portion 76c
having embedded therein a magnet 67 inserted in the
push-button chamber 75. The inserted portion 76c of the
push-button is a cone-shaped frustum which has a smaller
diameter at its face 62d to enable it to be smoothly pushed
into the cylindrical compression spring 64 without causing
any interference to the spring in its compressed state. In
the embodiment shown, the magnet 67 is fixed on a holding
column 74 to prevent the magnet from falling and is embedded
in a molding material 62b in the frustum in such a way as to
be flush with the face 62d thereof.
Fig.20 shows the relationship between the magnet 67 and
the holding column 74 consisting of a column 74b and a
holding portion 74a which is of a larger diameter than that
of the column 74b and which has a groove 74c cut into its
plane for adhesively fitting therein the square-pole shaped
magnet 67. The depth of the groove 74c is smaller than the
thickness of the square-pole shaped magnet 67, and the
holding portion 74a is completely embedded in the layer of
molding material 62b in order not to allow the magnet 67 to
- 27 -
fall out of the molded layer 62b.
The push-button chamber 75 shaped in a rectangular
cross-section and the push-button 76 having a flange portion
76a of a like rectangular cross-section, can be instantly
formed respectively through die-casting or resin-molding
methods with no additional need for machining of the
push-button 76, thereby the manufacturing cost of the
push-button switch is lowered. Furthermore, the push-button
can be correctly mounted in the push-button chamber by
pos~.tioning its rectangular flange 76a so as to correctly
dispose the magnet 67 parallel with and opposite to the reed
switch 70. The magnet 67 together with the holding column
is unitarily potted in the push-button so as to eliminate
the possibility of its falling out from the push-button.
Such a constructed push-button switch is reliable,
easy-to-make, low cost and adaptable to water-proof and
explosion-proof use.
In the regulations on 'the explosion-proof construction
of electric equipment for use in factories, established to
ensure the safety of electric Pquipment installed at
hazardous places where there exists an explosive atmosphere,
the locking construction for the explosion-proof vessels is
standardized.
Fig.21 shows an example of the locking mechanism for an
explosion-proof vessel. Numeral 80 designates a pressurized
metal vessel designed for a specific pressure and a specific
volume and which has a cover 81 which is attached to the
cylindrical portion 81a and the plane portion 81b of the
- 28 -
pressure vessel 80. The clearances betoreen the matched
surfaces of the vessel's body and the cover correspond in
size and clearance to the requirements specified by the
regulations. The cover 81 has a ring slot 85 for fitting
therein an O-ring to seal against the penetration of rain
water into the vessel. The cover 81 is secured at its plane
portion 81b to the pressure vessel 80 by use of a bolt 83
(with like numeral 83 in Fig.1) provided with a spring
washer 88 through respective holes 81d having a deeply
counterbored part 81a drilled in said plane portion 81b.
each hole has a thread 84 to engage with the bolt 83.
Although the above-mentioned structure relates to a method
for locking the cover 81 to the explosion-proof vessel 80,
in many ordinary structures like locking methods are applied
for jointing the members' surfaces with counterbored holes
by using bolts.
In cases where the vessel, having the cover jointed
thereto by the use of bolts with their heads sunk deeply in
counterbored holes as shown in Fig.21 is installed outdoors,
rain water 87 may collect in the deeply counterbored
portions 81c of the holes, evaporate on a fine day with this
cycle repeating itself causing a gradual propagation of
corrosion of the bolts 83 and the jointed metal surfaces
81b.
Figs.22 and 23 show an example of a jointing structure
wherein the first-element having a counterbored hole made
therein and a second-element having a threaded blind hole
matching with said counterbored hole are connected with each
- 29 -
other by the use of a bolt, and wherein at least one of t'ne
jointed surfaces of the first and the second elements has a
groove made thereon starting from the caunterbored hole and
terminating at the external surface of the housing exposed
to the outside atmosphere in order to solve the
above-mentioned problems. Construction elements similar to
those shown in Fig.21 are indicated by corresponding like
numerals and will not be further explained. Fig.22 is a
sectional side view taken on line XXII-XXII of Fig.23, and
Fig.23 is a section taken on line XXIII-XXIII cf Fig.22. In
these drawings, numeral 81 is a first-element (base element)
having a flat surface 81f and numeral 80 is a second-element
(pressure vessel) having a flat surface 80b to be joined
with the flat surface of the first element. A blind hole
with an internal thread 84 is provided in the flat surface
80b of the second element 80, and a groove 81e communicating
with a bolt hole 81c and an end face B exposed to the
atmosphere is provided in the first element 81. The first
element 81 and the second element 80 are coupled with each
other at their flat surfaces 81e and 80b and secured to each
other by screwing a bolt 83 into the threaded hole 84
through a spring washer 88.
The above-mentioned jointed portion works as follows:
When rain water flows into the deeply counterbored
portion 81c, it does not remain there but runs along a
groove 88a provided, opposite the spring washer 88 and the
groove 81e (with a like reference number 81e in Fig.1) into
the atmosphere. Although, in the above-mentioned case, the
- 30 -
groove 81e is made in the direction of the bolt hole 81d of
the first element 81, to the atmasphere side B, it may be
provided in either of the first elements 81 and 80,
Furthermore, it is also possible to make a plurality of
grooves 81e which may take any form on its cross-section.
In case of a pressure vessel the groove size may be limited
so as to have less than the allowable clearance value.
The above-mentioned jointed structure, wherein two
elements are joined by screwing a bolt into a deeply
counterbored hole with a groove provided therein, assures
that the rain water collected in the deeply caunterbored
hole will be discharged into the atmosphere through the slot
opposite the spring washer, the bolt hole and the groove,
the deeply counterbored portion may be free from corrosion
as for example, the bolt sticking because of rust in the
locking portion of the explosion vessel.
Furthermore, accarding to the ministerial ordinances
for securing the safety of electrical machinery and
apparatus for use in explosive gas atmospheres, the
hazardous places are specified with due consideration to
explosion-hazard characteristics such as the flammability
limits and the flashing point of explosive gas atmospheres,
vapor-generating conditions and the ignition point, fire
spreading limits, the minimum ignition current and so an,
and guidance is given for explosion-proof constructions for
electrical machinery and apparatus in accordance with
corresponding explasion-hazardous installation places. The
flowmeters are basically designed to be of an
- 31 -
explosion-proof construction since they may be frequently
used fox measuring the flow of explosive fluids or at places
where an explosive gas atmosphere exists. However, the
flowmeters of explosion-proof constructions may be higher in
cost since the requirements for explosion-proof vessels in
relation to their volume, joint sizes and allowances, lead-
in wires, separation of containers accommodating electrical
devices and so on should be considered.
On the other hand, recently many flowmeters, wherein a
flow-rate signal transmitted from a flowmeter body is
processed and the result indicated, have been adopted. The
application of flowmeters incorporating a battery as a
source of supply for signal generation, calculation and
indication has also been increased. The above-mentioned
battery-operated electrical circuit requires only a small
supply of current and consumes a small amount of electric
energy thereby being intrinsically adaptable to
explosion-proof applications. The battery adapted for
intrinsically safe circuits is provided with a
current-limiting resistance or a like element, serially
connected thereto to prevent an overcurrent from occurring
across a short circuit caused by a mis-operation, and
furthermore it is potted or included in a suitable vessel.
It is also necessary that the battery unit for use at a
hazardous place should include a current-limiting element
and be replacable as a complete unit. A thus-formed power
supply unit is connected to the electric circuit by use of a
connecting means such as a plug and connector which is
- ~2
removably secured to a partition wall and is operated from a
switch mounted an the electric circuit side.
In the above-mentioned prior art, the battery unit is
provided with a resistance or a like current-limiting
element connected thereto by embedding the connections in a
molded material but the other terminal of the battery and an
open terminal of the resistance are connected by a
connecting means to the electrical circuit through the
switching means. Consequently, leaking current may flow
through the connecting means and circuit components such as
a switch even when the circuit is riot in operation. This
causes the accelerated deterioration of the battery.
Furthermore, since the switch mounted on the electric
circuit is operated by hand each time the power supply is
switched OFF or ON, to stop and restart the circuit after a
long period of stoppage, the electric circuit may become
exposed to the atmosphere. This is undesirable from the
standpoint of assuring the safety and durability of the
device.
Figs.24 and 25 show a method adopted in order to solve
the above-mentioned problems. Fig.24 is a circuit diagram
of a power supply unit. Fig.25 is an assembly diagram of
said power supply unit. In these drawings, numeral 90 is a
power supply unit which includes batteries E1, E2 of a
specific voltage, resistances R1, R2 are selected so as to
get a specific battery short-circuit current, e.q. 30mA, and
resin material 93 for unitarily molding therein resistances
R1, R2 and switches 91, 92. In this case the resistances R1
- 33 -
and R2, the switches 91 and 92, the batteries E1 and E2 and
a connecting portion 95a are molded all tagether to form a
complete unit. The connecting portion 95a may be a socket
or a connector for making a removable electrical connection,
and has the terminals T1, T2, T3 and T4. Numeral 100
designates an electric circuit and numeral 101 indicates a
partition which separates the power supply unit 90 from the
electric circuit 100 arid has a connecting portion 95b
mounted thereon. The connection portions 95a and 95b are
connected to each other at their corresponding terminals
(T1, T11), (T2, T21), (T3, T31) and (T4, T41) to supply
electric energy to the electric circuit 100. The terminal
T4 is used when the total voltage of the batteries E1 and E2
is supplied through the terminal Tl, and the terminal T3 is
used when the voltage from the battery E2 is supplied
through the terminal T2. As shown in Fig.25, the switches
91 and 92 are composed of reed switches 91a and 92a and a
magnet 99 for magnetically (contactlessly from the outside)
closing and opening the contacts of the reed switches 91a
and 92a. The reed switches 91, 92 together with. the
resistances R1, R2 axe disposed parallel to each other at
the same surface of a circuit board 96 and are connected to
the circuit according to the circuit diagram shown in
Fig.24. Circuit boards 97 and 98 are of the same size as
that of the circuit board 96, and are secured to each other
to form a pile. However, a rectangular opening 98a is made
in the board 98 and magnets 98b and 98c, magnetized in the
same langitudinal direction, are secured respectively to the
-- 34 -
opposite ends of the board 98. The magnet 99, magnetized in
the same direction with the magnets 98a and 98c, is used for
driving the reed switches that axe arranged parallel to each
other at the same time. The magnet 99 is a plate magnet
which has a substantially same length as those of the reed
switches 91a and 92a, and has a suitable width to move
within the opening 98a of the board 98. A non-magnetic
guide plate 99a has the magnet 99 secured thereto, and
movably covers the piled boards 97 and 98. A handle 99b is
also fixed to the board 99. the boards 97 and 98 are
secured to the molded resin 93 or 96 closely being opposite
and parallel to the reed switches. When the handle 99b is
positioned in the direction M as shown in Fig.25, the
driving magnet 99 is attractively locked by the magnet 98c
and turns ON the reed switches 91a and 92a. When the handle
99b is moved in the direction L against the attractive force
of the magnet 98c, the reed switches 91a and 92a are turned
OFF and the driving magnet 99 is attractively locked by the
magnet 98b. The reed switches can be turned ON and OFF by
moving the driving magnet without making contact with the
reed switches. In the case shown two power supply batteries
E1 and E2 are used but the power supply unit may be camposed
of one battery or a plurality of them.
As is apparent from the foregoing description, the
above-mentianed power supply unit is so constructed that the
batteries, the current limiting resistances and reed
switches are unitarily molded in resin and the reed switches
are turned ON and OFF by use of the driving magnet which can
- 35 -
~~~~~~~d~
Lravel between two positions and be reliably locked in
corresponding positions by the small stationary magnets.
Since the circuit elements are completely buried in the
molded resin not to be exposed to the atmosphere and to
satisfy the requirements for intrinsically safe devices and
since the reed switches with a high insulation resistance
are applied to eliminate the possibility of current leaking
when the circuit is open and there is no need to touch or
expose any part of the electric circuit, according to the
present invention, it is possible to provide a power unit
which can operate with a high degree of reliability and
stability for a long period of use.
Fig.26 shows a positive displacement flowmeter which is
mounted on a pipeline for measuring the flow rate of a hot
fluid and is provided with a heat insulating means for
preventing the transfer of heat to its counting portion. In
many positive displacement flowmeters a system for
converting a rotor's rotations into an electrical signal is
adopted as a means for sensing the rotor's rotation. For
example, a magnetic flux from a transmitting magnet embedded
in the face of the rotor is sensed by a magnetic sensor
which in turn generates an electrical signal to be
transmitted as a pulse signal [flow rate]. The pulse signal
is processed by an electric' transducer mounted in a counting
portion combined unitarily with the flowmeter's body and is
indicated by an indicator or transmitted to a remote place.
There are various kinds of fluids to be measured by the
flowmeter in a variety of their physical or chemical
- 36 -
conditions such as pressure, temperature and so on. For
example, the temperature of a fluid may wary in a wide range
from low to high. This means that 'the operational circuit
of the counting portion has to operate well at temperatures
varying within a wide range. Since the counting portion is
directly connected to the flowmeter body, it rnay be affected
by thermal conduction, radiation or convection if the fluid
is hot. Accordingly, in this case it is necessary to
protect the counting portion from possibly being effected by
heat. Fig.26 is a sectional view (taken on line XXVI-XXVI
of Fig.27) for explaining an example of the prior art.
Fig.27 is a view taken along line XXVII-XXVII in Fig.26. In
Figs.26 and 27, numeral 111 is a flowmeter body, 112 is a
counting portion incorporating the operational circuit, and
113 is a skirt for connecting therethrough the flowmeter
body 111 with the counting portion 112. The counting
portion 112 has a ringed groo~re 112a for fitting therein a
ring portion 113a of the skirt 113 with an O-ring 118 for
air-tight sealing. A magnetic sensor 114 is applied for
magnetically detecting the rotation of the flowmeter's rotor
(not shown). A heat insulation 115, which is made in the
form of a hollow square plate of mainly inorganic material
having a high resistance to heat and low thermal
conductivity such as rock wool and the like, is secured to
the flowmeter body by the use of a bolt 117 to reduce the
heat transfer of heat from the flowmeter body 111 to the
counting portion 112.
The above-mentioned positive displacement flowmeter has
- 37 -
a heat insulation 115 cutting off the flow of heat from the
flowmeter body 111. ~zowever, the heat insulation 115 having
a high resistance to heat is capable of protecting against
heat transfer by conduction but it cannot prevent heat
transfer by radiation. Consequently, the radiant heat from
the flowmeter body 111 is directly transferred to the bottom
112b of the counting portion 112 wherein the temperature
rises, resulting in that air in a closed space 119 of the
counting portion 112 is heated and thereby expands to
increase inner pressure. A part of the air under increased
pressure is forced out of the counting portion 119 through
the heat insulation 115 of the capillary structure.
Therefore, air from the outside reversely enters into the
counting potion when the flowmeter stops with no hot fluid
in the piping and its temperature is lowered. Such repeated
respirations increase the humidity of the air in the
counting portion, causing dew condensation therein at a low
ambient temperature. Although. there are capillaries in the
heat insulation, most of them are closed and cannot allow
the counting portion to communicate with the outside air,
thereby irrevocably causing a rise in temperature of the
counting portion.
Figs.28 and 29 show a positive displacement flowmeter
which is so constructed as to solve the above-mentioned
problems. Fig.28 is a sectional side view taken on line
XXVIII-XXVIII of Fig.29, while Fig.29 is a view taken in the
direction of the arrows along line XXIX-XXIX of Fig.28. In
these drawings, the elements similar to those of Figs.26 and
- 38 -
27 are indicated by corresponding like numerals and need no
further explanation. 2n Figs.28 and 29, a heat insulating
washer 122, made of a heat insulating material, is fitted
onto a bolt 117 fox threadably connecting a flowrneter body
111 with a skirt 113 and is urged between the body 111 and
the skirt 113, thereby a clearance 122 is also created
there-between which serves as a blow hole 123 for directly
exhausting the heated air from the flocnneter body 111 into
the atmosphere. The temperature's rising in the counting
portion 122 is effectively prevented. A radiation shield
116 made of heat insulating material is also provided far
reflecting the radiant heat and has a preferably
light-reflecting surface against the flowmeter body 111.
The radiant shield 116 is fitted at its periphery in a
ringed groove 121 made in the inner wall's surface of the
skirt 113, maintaining a gap between the radiant shield and
the bottom 112b of the counting portion 112 in the space 119
so as to improve the radiant ray-reflecting effect of the
radiant shield 116. Tests have proven that the heat
insulating effect of the present invention is considerably
higher than that of the prior art shown in Fig.26, that is,
the temperature of the counting portion of the flawmeter,
according to the present invention, rose to 60°C during the
flowmeter's operation with a hat fluid of 120°C and at a
normal ambient temperature, whereas the temperature of the
counting portion of the flowmeter, according to the prier
art (Fig.26), rose further to 100°C under the same operating
conditions.
- 39 -
In the above-mentioned positive displacement flowmeter,
an effective and low-cost heat insulation is realised by
applying a heat insulating washer, instead of the plate
type, which not only prevents the transfer of heat by
conduction but also it produces a blowout hole allowing not
air to escape from the space between the flowmeter body and
the skirt, and by additionally providing a radiant shield
for preventing a rise in temperature of the air in the space
due to radiatian heat. Furthermore, no moisture appears in
the space by virtue of the existence of said blowout hole.
Fig.30 shows an example of a construction of a
conventional positive displacement flowmeter. In Fig.30, a
circle 140 indicated by a dotted line is an inlet or outlet
port. The housing 1.30 of the flowmeter's body includes a
measuring chamber 131 which has a recess communicating with
the inlet/outlet port 140. In said measuring chamber 131 a
pair of rotor shafts 132, 132 of the same diameters are
placed parallel with each other: each rotor shaft is secured
at its flanged end 141, by use of bolts 142, to the .autside
wall surface of the flowmeter body's housing 130 through the
bottom hole of the measuring chamber and is fitted at its
other end in the through hole of the chamber cover. 134. A
pair of rotors 133, 133 are shown as non-circular gears
engaged with each other 133a. Each rotor (non-circular
gear) 133 is provided with a bearing 143 by which it is
rotatably mounted on the shaft 132. The paired rotors 133,
133 rotate, keeping a small clearance from the inner wall of
the measuring chamber. The chamber is closed with the cover
40 _
i34 having two through holes 145, 145 for fitting therein
the corresponding shafts' ends. Said cover is secured to
the flowmeter body's housing 130 by the use of a locating
pin 135. A back cover 136 is provided with an O-ring 138
for liquid-tight sealing and secured to the flowmeter body's
housing 130 by the use of a bolt 137. A counter housing 139
accommodates a counting portion (not shown) for sensing the
rotors' revolutions and for indicating the measured flow
rate.
In the above-mentioned conventional positive
displacement flowmeter, its rotor shafts 132 are secured at
their flanged ends to the housing of the flowmeter body's
housing 130. The flanged shafts are large in size and
relatively expensive to manufacture. Furthermore, since
said shafts 132 are fitted to the other ends in the
corresponding holes 145 of the face plate 134, the liquid
may leak through a minute gap formed between each shaft 132
and the hole 145 of the face plate. To prevent the liquid
from leaking, it is necessary to add to the back cover 136 a
liquid-tight seal 138, thereby increasing the cost of the
flowmeter.
Figs.31 to 34 are views for explaining an embodiment
whicr. was made in order to solve the above-rnentioned
problems. Fig.31 is a sectional view showing a positive
displacement flowmeter according to the present invention.
The same components as those shown in Fig.30 are indicated
by the same numerals and will not be explained further. In
Fig.3l, the rotor shaft 150 is a uniformly round
- 41 -
cross-section and as shown in Fig.32, it has a stopping pin
151 eccentrically driven into one end face and a pin hale
150a eccentrically drilled into the other end face. Fig.32
is an enlarged detail of the rotor shaft construction.
Fig.34 is a sectional view taken in the direction of the
arrows along line XXXIV-XXXIV of Fig.32. In the bottom of
the measuring chamber 131 of the body housing 130, two blind
hales 130a of a specified depth are drilled for fitting
therein the rotor shafts, and, furthermore, at the bottom of
each hole 130a a hole 130b is also made by spot facing at an
eccentric distance from "d" from the axis of the hole 130a.
A back cover 152 has two blind holes 152a for inserting
therein the other ends of the rotor shafts, a through hole
152b for fitting therein a locating pin 153 and a through
hole 152c for screwing a bolt 137 for securing the back
cover 152 to the body's housing 130.
In the above-mentioned positive displacement flowmeter
each rotor shaft 150 is secured to the body's housing 130 by
use of the shaft mounting jig 160 shown in Fig.33. The
shaft mounting jig 160 comprises a columnar body 161 which
has a recessed face portion 161a for inserting therein one
end of the rotor shaft 150 and has a pin 162 embedded at one
end in a hole made in the bottom of said recessed face
portion 161a at a position corresponding to the position of
the pin fitting hole 150a at the bottom end of each rotor
shaft 150. The end of the shaft 150 is inserted into the
recessed face portion 161a of the columnar body 161 of the
shaft mounting jig 160 so as to receive the pin 162 in its
- 42 -
hole 150a. In this case the stopping pin 151 is placed at
position A in the off-centered (eccentric) hole 130b. The
shaft 150 is then turned in the direction of the arrows R.
The shaft is bound when the stopping pin 151 is urged to its
side surface against 'the inner wall of the off-centered hole
130a at the position B. At this time both shafts 150 are
fitted at their other ends in the corresponding holes 152a,
152a provided in the back cover 152 fixed in position by the
locating pin 153. The shafts are thus secured at both ends.
Since the shaft holes 152a, 152a and 130a, 130a and the
off-centered holes 130b, 130b are not drilled through the
back cover 152 and the body housing 130, it is unnecessary
to use the face plate 134 applied in the prior art.
According to the present invention, it is possible to
provide an inexpensive positive displacement flowmeter in
which its rotor shafts 150 are of a uniformly round
cross-section and can be secured simply by turning them
until the stopping pins 151 are urged against the inner wall
of the corresponding off-centered holes 130b the body
housing 130, which does not require a face plate 134.
Non-circular gears which are used in pairs as rotors of
the positive displacement flowmeter have teeth usually cut
by use of a basic straight rack at a constant pressure
angle. The tooth profile is an involute obtained as a 'trace
of rolling contact between a straight line of the basic rack
and a pitch curve of the non-circular gear, i.e. the gear
teeth are cut according to an approximately non-circular
pitch line with which each partial curvature centers.
- 43
Accordingly, a partially curved center of the non-circular
pitch line does not coincide with the rotating center of the
non-circular gear.
Fig.35 shows the upper half, taken on a minor axis X-X,
of the above-mentioned conventional non-circular gear 133.
In Fig.35, the rotating axis of the non-circular gear and
its pitch line (curve) are indicated by characters O and Pc
respectively. A tooth profile Ti (i=1,2,..., i,.., n) of
the gear can be obtained by cutting the teeth in a circle
having a partial profile center O' and including a part of
the partial pitch line Pci. Since the partial pitch line
center O' is apart. from the rotating center of the
non-circular gear 133, an angle 8 is formed between the
center of the partial pitch line Pci of the teeth profile,
the center O' of said teeth profile and the rotating center
O of the non-circular gear 133. The angle 8 varies its
value for every part of the pitch line (i.e. for each tooth
profile position). Accordingly, the profiling of each tooth
is made according to a line passing through the partial
profile center O' and by not passing through the rotating
center O of the non-circular gear.
The above-mentioned conventional non-circular gear is
manufactured by the powder metallurgy compression, molding
method that includes the following process:
(1) An amount of prepared metal powder is placed into a
mold for molding a non--circular gear from powdered metal by
means of compression. The powdered metal is compressed in
the mold from both top and bottom into the shape of a
_ 44
non-circular gear which is then taken out of the mold.
(2) The compressed metal powder is then heated in order. to
get a sintered metal powder, non-circular gear.
(3) The sintered metal powder is compressed into a
reforming mold from both top and bottom sides in order to
obtain a highly precise and a highly dense metal powder
sintered non-circular gear.
In general, when powdered metal is compressed in a mold
from the top and bottom sides, the metal flows or is
deformed radially from the mold's center in a direction
perpendicular to the d~:rection~ of the compressing force,
thereby being densely pressed against the inner wall of the
mold to be formed into the desired shape. In the case of
the compression molding of the non-circular gear, the
powdered metal flows radially from the gear's rotating
center and is formed into the shape of the non-circular gear
according to the shape of the mold's inner wall. However,
in the case of compression molding of the conventional
non-circular gear shown in Fig.35, a tooth's surface A is
subjected to pressure in the direction of arrow C, but the
tooth's surface B scarcely receives the pressure in the
direction of arrow C since it has a part that is at a
negative angle to the direction of arrow C. Consequently,
the work molded by compression has a higher powder metal
density at the tooth's surface A than at the tooth's surface
B, i.e. the powder metal's density varies between the
tooth's surfaces A and B.
The difference in metal density adversely affects the
- 45 -
2Q~4~~~
accuracy of the tooth's profile and the tooth's strength, as
for example, in the sintering process (2) the work is
subjected to the deformation of the teeth due to the
differences in the thermal expansion of the metal, i.e. each
tooth is bent toward the tooth's surface B of a lower
powder-metal density. When the deformed non-circular gear
is compressed in a re-forming mold in the next process, it
receives a reverse force applied to each tooth from its
surface B for correcting the deformed tooth in the mold,
thereby cracking may be caused at the flanks of the gear's
teeth. The difference in molding pressures at the teeth's
surfaces may shorten the lifetime of the mold or cause
damage to the mold in an extreme case. In the post, it was
very hard to effectively produce low cost non-circular gears
with a high accuracy and a high density by compressing and
sintering highly shrinkable powdered metal such as stainless
alloys or the like.
In the case of forming the above-mentioned conventional
non-circular gear by plastic molding, heat extrusion and
cold drawing, the same problem mentioned above in powder
metal compression molding exists.
Fig.36 is a view showing, by way of example, a
non-circular gear which is free from the above-mentioned
problem. Fig.36 shows the upper half, taken on the minor
axis X-X, of the above-mentioned non-circular gear. A
tooth's profile Ti (i=1,2,., i, .., n) formed with a pitch
line Pc' of the non-circular gear 133' has the axis line
O-Y' passing through the rotating center O. Consequently,
- 46 -
~~~~~e~
when an amount of powdered metal is compressed in a
compression mold, both surfaces, ~ and B, of each tooth,
having the profile Ti' receive substantially an even force
and, therefore, the metal can be compressed to an even
density. Therefore, in the primary sintering process, the
compressed powdered metal of the non-circular gear can
almost uniformly shrink toward the rotating center O. Since
the shrunk non-circular gear has a scarcely deformed tooth
profile, in the secondary compression process it can be
reformed uniformly in a mold. The reforming force effecting
the gear teeth is very small in comparison with the
conventional non-circular gear, and therefore the production
yields are improved.
The non-circular gear shown in Fig.36 is also suitable
to be formed by resin molding and can be made effectively by
hot extrusion and cold drawing.
In the positive displacement flowmeter the rotor's
rotation is indicated mechanically through a reduction
gearing and electrically through a rotation sensor
converting it into an electrical signal. Many optical
sensors and magneto-electric transducer-type contactless
sensors are applied for directly sensing the rotation of the
rotor. There are two types of optical sensors - reflecting
and transmitting. However, these optical sensors can be
applied only for light-transmitting fluids, the kinds of
which may be limited, On the other hand, magneto-electric
transducer type sensors can be applied for many kinds of
fluids and, therefore, they are preferable fox adoption in
~~~~~~e~7
many positive displacement flowcneters. F4agnetic sensors
such as a hall device, magnetic resistors and so on are used
as a magneto-electric transducer which is capable of sensing
a magnetic flux from a transmitting magnet embedded in a
rotor of the flowmeter.
However, the above-mentioned magnetic sensors cannot be
apglied to magnetic fluids effecting the distribution of
magnetic flux of the transmitting magnet arid they are also
limited by its working temperature. Usually, magnetic
sensors of this type can operate at relatively low
temperatures (max. warking temperature of about 80-100°C)
and therefore in many cases they cannot directly detect the
rotor's rotation. In addition, they must be provided with
alternate power supply sources. This means that in the case
of the long-term measurement of fluid by a simple method,
for example, when an integrating flowmeter with a battery
power supply being used for the measurement of the total
flow of city water or city gas, an additional power supply
for the sensor unit increased both the manufacturing and
running costs of the flowmeter and restricted its
application field.
The present invention is intended to provide a magnetic
sensor which utilizes the characteristics of amorphous metal
and does not need a battery powered supply of energy.
Amorphous metal is obtained by quenching the molten
metal into a solid state at the high cooling speed of
1000°/msec. Amorphous metal is available in the form of
thin plates, thin wire, powder etc.. When a metal from its
- 48 _
molten state (i.e. a state of active molecular movement) is
rapidly cooled with no time to be crystallized, it becomes
amorphous, i.e. a solid that has no crystals and which is
homogeneous and easy to become an alloy. For this reason
many amorphous alloys, having excellent mechanical
properties, being resistant to corrosion and having magnetic
characteristics, are produced. Especially, a Fe-Si.-B system
amorphous fiber (hereinafter called as AMF) has a small
coercive force He of 0.4 oe (oersteds) and is featured by
its magnetic hysteresis curve. Accordingly, when the
magnetic intensity exceeds 0.4 oe, there arises an abrupt
change in magnetic flux density, i.e. a Barkhousen jump
according to the magnetic hysteresis curve.
Fig.38 shows an example of a magnetic sensor utilizing
the above-mentioned effect. As shown in Fig.38, the
magnetic sensor 170 is composed of a magnetically sensing
element 171 made of a single piece or a bundle of AMF, a
coil 172 wound around the sending element and a protecting
case 173 made of a non-magnetic material for accommodating
therein the coil-wound sensing element. The magnetic sensor
170 produces an output at terminals 172a and 172b of the
coil 172. In Fig.38, when a magnet is approached to a face
173a of the case 173, the AMF and produces the Barkhausen
jump, i.e. it instantly changes the magnetic flux density
into /2Bm/ at a coercive force of aver ~Hc, thereby a
voltage corresponding to the change of the magnetic flux
density is produced at the coil 172.
Fig.39 shows an outline of a positive displacement
- 49 -
.~iowmeter provided with the above-mentioned, AMF magnetic
sensor 170. In a measuring chamber 179 of the floumteter
body housing 176 having a flow inlet 174 and a flow outlet
175 there is a pair of non-circular gears 177 and 178
(hereinafter referred to as rotors 177 and 178) which are
fitted onto shafts 177a and 178a respectively and which
engage with each other. The difference of inlet 174 and
outlet 175 pressures causes the rotors 177 and 178 to rotate
in the direction of R when fluid flows in the direction of
the arrow Q. Since a flow rate is proportional to the
rotations of the rotors 177, 178, it can be measured by
sensing the rotation of either rotor 177 or 178.
Fig.40 is a view showing an embodiment of the present
invention. Rotors 177 and 178 rotate, engaging with each
other in the same way as the rotors shown in Fig.39, and
they are indicated by corresponding like numerals. The body
housing 176 and other construction elements shown in Fig.39
are omitted in Fig.40. A magnetic sensor is indicated by a
like reference numeral (170). Fig.40 shows a basic
construction of the embodiment. A rotor 177 has two
transmitting magnets 180a and 180b which are embedded flush
with the face of the rotor at opposite points where a major
axis of the rotor (non-circular gear) is intersected by a
concentric circle having a common center 177a. The exposed
surface (north pole) of the transmitting magnet 180a is
indicated by a small black circle, and the exposed surface
(south pole) of the transmitting magnet 180b is indicated by
a small white circle. the magnetic sensor 170 is mounted on
- 50 -
2~~4~8~
the housing 176 or like suitable element at a place where it
can oppose the transmitting magnets 180a and 180b by turns
when the rotors 177 and 178 rotate. 2 pulses per rotation
of the rotor 177 are transmitted as flow rate signals.
Fig.41 shows another embodiment wherein a rotor 177 has
two magnets 180a and 180a' embedded with like north poles
exposed at opposite paints whereat a major axis of the rotor
177 is intersected by a concentric circle having a common
center 177a, and a rotor 178 has two magnets 181a and 181b
embedded with like south poles exposed at opposite points
where a major axis of the rotor 178 is intersected by a
concentric circle having a common center 178a. 4 pulses per
rotation of the rotors are generated as flow rate signals,
i.e., the resolution of the pulse signals of this embodiment
is two times higher than that of the basic embodiment shown
in Fig.40.
Fig.42 shows another embodiment_wherein a yoke 182 of
highly permeable material such as permalloy is provided
between a rotor 177 having two magnets 180a and 180b (in the
same way as shown in Fig.40) and a magnetic sensor 170.
Since a signal from the transmitting magnet 180a or 180b may
be attenuated by a leakage flux at the yoke 182 in the way
of the magnetic sensor 170, the yoke 182 is formed as being
larger in diameter than the magnets 180a, 180b for the
purpose of decreasing magnetic resistance (reluctance) and
to have tapered ends 182a facing the magnetic sensor 170.
Fig.43 shows another embodiment wherein a ring magnet
183 is embedded in the f ace of a rotor 177 to form a
- 51 -
concentric ring having a common center 177a and being flush
with the rotor's face. The ring magnet 183 is composed of a
plurality of magnets (segments) arranged in a circle arid
magnetized with unlike poles next to each other. The
purpose of this embodiment is to increase the number of
pulse signals per rotation of the rotor 177.
Figs.44 and 45 show embodiments wherein a plurality of
magnetic sensors 170 are provided in order to achieve the
same purpose as that of the embodiment of Fig.43, i.e. to
obtain an increased number of pulse signals for one rotation
of the rotor 177.
In Fig.44, a rotor 177 has a transmitting magnet 179a
embedded therein with its narth pole exposed and a plurality
of magnetic sensors 1701, 1702, 1703, 1704,..., 170n. A
circular magnet 184 has substantially the same diameter as
that of the orbiting circle of the magnet 179a and is
opposite to its unlike south pole to the magnet 179a.
In Fig.45, a rotor 177 has two transmitting magnets
179a and 179b embedded therein (the same as shown in Fig.40)
and plurality of magnetic sensors 1701 , 1702 , 1703 , ...,
170n are disposed opposite along a rotating circle of the
transmitting magnet 179a and 179b. Since the magnetic
sensors 170 have a high sensitivity, the transmitting
magnets of a compact size can be used and each sensar is
capable of producing pulse signals of the flow rate at its
terminals 172a and 172b with no power supply.
As is apparent from the foregoing description, since
all of the above-mentioned magnetic sensors according to the
- 52 -
present invention can transmit the flow-rate pulse signals
without power being supplied and are sensitive enough to
detect magnetism of simple and compact magnets, it is
possible to provide a highly sensitive flowmeter having
light .rotors. By virtue of the excellent performance of the
magnetic sensors at high temperatures, the application range
of the flo~~rneter is also widened to various kinds of fluids
with high temperatures.
A large majority of positive displacement flowmeters
are intended to carry out measurements of flow by detecting
the rotations of a pair of rotors, which rotate in
accordance with the flow rate of a fluid in a measuring
chamber provided between an inlet port and an outlet port of
the flowmeter's body, and also to employ such a detection
system that magnetic flux, generated by a transmitting
magnet embedded in the face of the rotar, is sensed by a
magnetic sensor mounted on a housing.
Figs.46 and 47 show an example of a construction of
said positive displacement flowmeter. Fig.46 is a section
taken in the direction of the arrows XLVI-XLVI in Fig.47,
and Fig:48 is a section taken in the direction of arrows
XLVII-XLVII. in Fig.46. In Figs.46 and 47, numeral 200
indicates a flowmeter's body composed of a housing 191,
rotor shafts (hereinafter called "shaft") 193a, 193b and
rotating non-circular gears (hereinafter called "rotor")
192a, 192b. The rotors 192a and 192b are rotatably mounted
onto the shafts 193a and 193b respectively and disposed in
the measuring chamber 191a and recessed in the housing 191,
- 53 -
in such a way that they may rotatably mesh. with each other.
Column-shaped transmitting magnets 194, 194 magnetized in an
axial direction are embedded in the face 192aa of the rotor
192 at opposite planes on 'the major axis of the rotor 192a
at an equi-distance from the rotating center 193a. L~umeral
196 indicates inlet and outlet ports made in the body 200
for leading the fluid's flow into/from the measuring chamber
191a, and the numeral 195 indicates a sensor mounting cover
which closes the measuring chamber 191a in such a way as to
obtain the smooth rotation of the rotors 192a and 192b by
providing a minute clearance from the tips of the teeth of
the rotors 192a and 192b rotating in the measuring chamber
191a, which is also used for mounting thereon a sensor 197
placed opposite to the rotor 192 having the transmitting
magnets 194 and 194. The sensor 197 includes a magnetic
sensor such as a magnetic resistor, a hall element and the
like in its bottom portion 197a whereto the transmitting
magnets 194 and 194 can approach when the rotors rotate. A
lead wire 197b, for transmitting therethrough a detection
signal from the magnetic sensor 197 to a counting portion
199, is laid in a mounting column 198 which is secured to
the sensor mounting cover 195 and supports the counting
portion 199. The counting portion 199 receives rotor
rotation signals from the magnetic sensor through the lead
wire 197b and calculates the momentary flow, total flow etc.
and indicates the calculation results, e.g. in the
above-mentioned positive displacement flowmeter, when a
fluid flows in the measuring chamber in the direction of
54 _
arrow Q, paired rotors 192a and 192b rotate in the
directions indicated by arrows +R and -R .respectively by the
action of the differential torque appearing alternately
through every 90° of their rotation about the shafts 193a
and 193b. The rotations of the paired rotars are detected
by the sensor 197 which detects a magnetic flux from the
magnets 194 and 195 rotating about the rotor's shaft and
alternately appraaching thereto, generates a signal
proportional to the flow rate and transmits it to the
counting portion 199.
The above-mentioned positive displacement flowmeter is
capable of directly detecting the rotor's rotations and is
featured by simple and accurate measurements of the fluid's
flow by virtue of a small load for the flow's detection.
However, a flowmeter of this type, in common with other
types, have the disadvantage that, in order to cover a wide
range of flaw measurements, it is necessary to prepare
variations of bodies which incorporate rotors being similar
in form but different in size and which are selectively used
depending on the required measurement range of fluid flow to
be measured.
Figs.48 to 50 are views showing mutual arrangements of
sensors and transmitting magnets of a variety of rotors.
Fig.48 shows pitch curves Aa, Ab of rotors for small
flow measurements, and Figs.49 and 50 show pitch curves Ba,
Bb and Ca, Cb respectively for middle and large flow
measurements. A plurality of transmitting magnets (194A1,
194A2,..., 194An), (194B1, 194B2,..., 194Bn) a.nd (194C1,
- 55 -
19402,..., 194Cn) are embedded in faces of corresponding
rotors Aa, Ba arid Ca in such a way that they are arranged on
a circle having corresponding rotation centers OA, OB, OC at
pitch intervals proportional to rotation speeds of
corresponding pairs of rotors (non-circular gears) engaging
with each other. The positions of the magnetic sensors
corresponding to the above-mentioned transmitting magnets
are indicated by numerals 197A, 197B, 1970 respectively.
Each of the sensors (197A, 1978, 1970) is disposed on a
major axis (ra-ra, rb-rb, rc-rc) of a rotor (Aa, Ba, Ca)
being apart at a specified distance (YA, YB, YC) from the
intersection of the major axis (ra-ra, rb-rb, rc-rc) and the
pitch circle (Aa, Ba, Ca).
Fig.51 shows a saver 195 whereon the sensors' positions
197A, 197B, 1970 shown in Figs.48 to 50 axe indicated. As
is apparent from Fig.5l, if the sensor mounting cover 195
and the counting portion 199 are made in the same sizes for
variations of flowmeter bodies, it is also necessary to
prepare respective covers that are the same size but differ
from each other by the sensor mounting positions (i.q. 197A,
197B, 1970).
Figs.52 to 54 are views showing the mutual arrangements
of rotors (transmitting magnets) and sensors according to
the present invention, wherein the sensors' mounting
positians are changed from those of the conventional
flowmeters shown in Fig.46. Variations of flowmeters shown
in Figs.52 to 54 are similar to those shown in Figs.48 to 50
respectively. Pairs of rotors are indicated by their pitch
- 56 --
f~
circles (Aa, Ab), (Ba, Bb), (Ca, Cb) respectively. rn order
to increase the resolution of each flowmeter a number "n" of
transmitting magnets [(194A1, 194A2,.., 194An), (194B1,
194B2,.., 194Bn), (194C1, 194C2,.., 194Cn)] are embedded in
the faces of the rotor (Aa, Ba, Ca) in such a manner that
they are arranged an a circle having a common center (OA,
OB, OC) with the rotor. Magnetic sensors corresponding to
the above-mentioned transmitting magnets are mounted on
corresponding covers and their positions are indicated by
numerals 197A1, 197B1, 197C1 respectively. The position of
each sensor (197A1, 197B1, 197C1) is defined by a constant
distance 13 between a point (PA, PB, PC) whereat the rotor
(Aa, Ba, Ca) engages at its major axis with a matching rotor
(Ab, Bb, Cb) and a point whereat an axial line L-L of the
sensor intersects with the rotor's major axis at light
angles, and by a constant distance a. from a point whereat
the sensor°s axial line L-L perpendicularly intersects with
the rotor's major axis, and by that the line (MA-MA, MB-MB,
MC-MC) passing the sensor's center and being perpendicular
to a minor axis of the rotor and a rotation circle (CA, CB,
CC) of the transmitting magnets have an intersection being
on a common. trace of the rotation of the magnets of rotors
rotating in a variety of bodies. Accordingly, a cover with
a sensor mounted thereon at the point corresponding to a
common point of rotation cifcles of the magnets of different
type rotors are used commonly for variations of rotors, that
is, for variations of flowmeter bodies. Although in the
above-mentioned embodiments rotors with a plurality of
- 57 -
transmitting magnets are used, it is also possible to use
rotors having a single rnagnet embedded therein.
Fig.55 shows a sensor mounting cover 195 with a sensor
197 secured thereon at a position of -b and -a relative to
the orthogonal lines X-X' and Y-Y' passing a center O of the
cover. Rotation axes of rotors Aa, Ab, Ac are indicated by
the characters OA, OB, OC respectively and they are at
angles of 81, 92, 93 to the sensor position and the line
Y-Y'. Rotation circles CA, CB, CC of transmitting magnets
are indicated by dotted lines. The cover 195 having the
sensor 197 thus positioned thereon can be commonly used for
a variety of flowmeters. This cover is also used with the
same counting portion 199, that is, the sensor-mounted cover
provided with the counting portion 199 is adopted as a
common unit adapted f or a variety of f lowmeter bodies . The
above-mentioned sensor-mounted cover 195 cannot be applied
for flowmeters' bodies including small sized rotors and,
more particularly, for rotors being so small in size as to
obtain no common intersection of the lines L-L and M-M and
the rotation circles of the transmitting magnets.
Fig.56 shows another embodiment of the present
invention made to provide a cover applicable for the
above-mentioned small flowmeters' bodies. In Fig.56, an
auxiliary sensing cover 201 is a disc having as its center
O-O at a half of a line connecting a center of the sensor
197 mounted thereon with the center O of the cover 195,
This auxiliary cover 201 is mounted on the cover 195 in such
a way as to be rotatable by 18~° about the center O-O, that
~~~~~~3
is, turning the auxiliary cover allows the sensor 197 to be
placed at the center O whereat the sensor can be opposed to
a rotating circle Cs of a transmitting magnet of a small
type flowmeter. Practically, the auxiliary sensor-mounted
cover 201 is turned about the center O-O to the opposite
position and fixed to the cover 195 by use of screws or the
like as shown in Fig.57 and 58. Although the
above-mentioned cover 195 serves to cover the flawmeter's
body arid also to mount thereon a magnetic sensor, it is also
possible to assemble separate plates - a cover and a sensor
mounting plate. The purpose of the present invention is to
obtain a constant mutual arrangement of magnets embedded in
a rotor and a sensor mounted on a flowmeter's body
independent of a variety of flawmeters. Accordingly.
transmitting elements are not limited to only magnets but
may be optical reflecting elements.
As is apparent from the foregoing description, the
transmitting system of the positive displacement flowmeter,
according to present invention, makes it possible to use the
same cover and the same counting portion for a variety of
the flowmeters' bodies of different measurement .ranges, and
therefore to reduce a number of component parts, simplify
the manufacturing process and reduce the number of
assembling steps of the flowmeters. Furthermore, it
produces many other effects such as an increased
interchangeability of the flowmeters etc..
- 59 --
