A fluid flow meter of the positive displacement rotary kind where
a housing defines an annular passage coupling input and output ports,
a rotor has depending blades which are driven around the passage
by the flow of fluid and an idler has pockets which accommodate
the rotor blades in sealed relationship as the blades pass from
outlet to inlet, the invention being characterized in the provision
of two rotors each having blades and pockets and two annular passages
accommodating respectively the blades of the different rotors, and
each rotor constitutes the idler for the other rotor.
1. A fluid flow metering device comprising:
a housing, said housing having an inlet port, and an outlet port,
and a plurality of annular passages coupling said inlet and outlet
a plurality of rotor means rotatably fitted in said annular passageway
for rotating as fluid flows through said passageways from said inlet
to said outlet, each rotor means being comprised of:
a rotor body rotatably fitted in said annular passageways, said
rotor body having at least one blade portion depending therefrom
fitting in one of said annular passages in a sealing relationship
therewith, so that the fluid passing between the inlet and outlet
ports through the passageway causes the rotor body to rotate by
forcing against said blade portion, said rotor body further having
at least one longitudinal pocket therein accommodating a blade portion
of another rotor body in said passageways as the blade portion of
the other rotor body rotates from the outlet to the inlet, said
pocket forming a liquid seal for said blade portions; and
gear means coupled to said rotor means for causing said plurality
of rotor means to rotate together in opposite directions.
2. A device as claimed in claim 1 wherein said rotor bodies are
of the same size and have the same number of blade portions and
3. A device as claimed in claim 2 wherein there are two blade
portions and two pockets in each rotor body.
4. A device as claimed in claim 2 wherein one of the rotating
structures comprised of the rotor means and the gear means has at
least one magnetically salient part; and
said device further comprises a magnetic proximity switch means
fitted within said housing adjacent said magnetically salient part
for responding to the passage thereby of said magnetically salient
The invention relates to a fluid flow meter of a rotary positive-displacement
The invention is particularly concerned with a fluid flow meter
of the kind comprising a housing defining an annular cylindrical
passage communicating with inlet and outlet ports; a rotor comprising
a rotor body from which depend a number of blades which fit the
annular passage in sealing relationship so that fluid passing from
the inlet to the outlet around the passage drives the rotor by way
of the blades; and an idler geared to rotate with the rotor about
an axis parallel with and offset from the rotor axis, the idler
being basically cylindrical with longitudinal pockets in its side,
the pockets each accommodating a rotor blade as the blade returns
from the outlet to the inlet and the pocket giving a liquid seal
for the rotor blade, the idler running in sealing relationship with
a fixed part of the housing. Such a meter will hereinafter be referred
to as a flow meter of the kind referred to. The present invention
seeks to provide a flow meter of the kind referred to which is particularly
compact for a given capacity.
According to the present invention there is provided a flow meter
of the kind referred to comprising two rotors, each rotor body being
provided with longitudinal pockets and being arranged to constitute
the idler for the blades of the other rotor, there being two annular
passages coupling the inlet and outlet ports at opposite sides of
the housing and offset to accommodate the respective rotor blades.
The flow meter may be used in a household to measure, for example
the flow of gas used in domestic gas heating and cooking. Another
application is in the measurement of the flow of domestic water.
Other applications may include measurement of the flow of liquid
fuel in dispensing operations.
It is possible to arrange for the rotors to be of different diameters
so that they rotate at different speeds and have appropriately different
numbers of blades and pockets. However, it is preferred that the
rotors be of the same size and have the same number of blades and
pockets as each other. In a preferred embodiment there are two blades
and two pockets on each rotor.
Preferably the housing accommodates timing gears which are mounted
on axial shafts of the rotors and which mesh together to ensure
appropriate timing. In order to give a volume output from the meter
it is convenient to use a magnetic proximity switch fixed in the
housing and responsive to the passage of a magnetically salient
part or parts of one of the rotating structures. Conveniently, this
is one or more tangs on one of the timing gears.
The invention will further be described with reference to the accompanying
drawings, of which:
FIG. 1 is a side elevation of a flow meter in accordance with the
FIG. 2 is a plan view of the meter of FIG. 1;
FIG. 3 is a cross-sectional view taken at C--C of FIG. 2;
FIG. 4 is a cross-sectional view taken at A--A of FIG. 3; and
FIG. 5 is a cross-sectional view taken at B--B of FIG. 4.
Referring to the drawings, the flow meter comprises a housing 1
which is cast from aluminum alloy. The housing has two ports at
opposite sides which will be designated as inlet port 2 and outlet
port 3 although it will be appreciated that the flow meter will
operate to measure flow in either direction. Referring particularly
to FIG. 1 the housing has a timing case cover 4 which houses timing
gears 5 and 6 (FIG. 2). A proximity switch 7 is fixed to the timing
cover and gives an output pulse, when energised, for each unit of
revolution of the rotors of the meter.
Referring now to FIGS. 3 to 5 the internal structure of the meter
is shown. The meter has two rotors 9 and 10 the rotor 9 having
a body 9a and blades 9b depending therefrom. Rotor 10 has a body
10a and blades 10b depending therefrom. The two rotors are identical
and are fixed on respective shafts 11 and 12 which have fixed on
their ends the timing gears 6 and 5 respectively. The timing gears
are of the same diameter and are meshed with each other so as to
ensure that the two rotors rotate at the same speed and in opposite
In rotating, blades 9b move in sealing relationship in an annular
passage 13 defined between the outer wall 14 of the housing 1 and
an inner fixed block 15. Movement of fluid from the inlet port 2
to the outlet port 3 drives the rotor 9 by way of the rotor blades
9b in passage 13 in a counterclockwise direction as seen in FIG.
4. Blades 10b of rotor 10 are accommodated in sealing relationship
in a similar annular passage 16 defined between the outer wall 14
of the housing and another fixed internal block 17. The action of
fluid passing from the inlet port to the outlet port through the
passage 16 turns the rotor 10 in a clockwise direction.
In order to return the rotor blades from the outlet side of the
meter to the inlet side without experiencing the in-flowing pressure
of the fluid, the blades are returned in sealed pockets formed in
the idler portion of the rotor. Thus, for example, FIG. 4 shows
one of the blades 9b being returned in a pocket 18 formed in portion
10a. The body 10a co-operates in sealing relationship with the fixed
block 15 so that the pocket 18 which is a cylindrical recess in
the wall of portion 10a is sealed and embraces blade 9b as the blade
returns from outlet to inlet. Another pocket 19 diametrically opposite
to pocket 18 accommodates the other blade 9b in a similar way. Pockets
20 in portion 9a accommodates the blades 10b.
It will be seen that the meter can be regarded as two similar meters
of the positive displacement rotary kind disposed adjacent to each
other. The bisecting plane of the rotors is shown at P in FIGS.
3 and 5 so that one meter may be regarded as lying to the lefthand
side of plane P in FIG. 3 (beneath the plane in FIG. 5) and the
other meter to the right-hand side of plane P in FIG. 3 (above the
plane in FIG. 5).
The arrangement described has the advantage that the two rotors
can be cast as identical components, as can the stationary blocks
15 and 17. The material of the rotors and blocks is conveniently
aluminum alloy which is anodized.
The output from the meter is taken as a series of pulses from proximity
switch 7 which responds to the passage past the switch of each of
a number of tangs 21 mounted on timing gear 6. These projecting
tangs are of ferromagnetic material and represent magnetically salient
features to which the switch 7 responds. Thus, the switch is closed
to give an output pulse, when energized, for each unit of rotation
of gear 6. The output pulses are counted, sealed in accordance with
the calibration of the meter and fed to drive a digital volume indicator
by conventional electronic techniques.
The invention is not restricted to the details of the embodiment
described above with reference to the drawing. For example, it is
envisaged that instead of being made of metal some or all of the
parts may be moulded in plastics materials. The detector for giving
a volume output may be other than a magnetic proximity switch. For
example, an optical detector may be used, or there may be provided
a mechanical counter which can be operated by a sealed shaft. In
another arrangement a mechanical counter may be housed within the
body of the meter, being visible through a pressure-tight window.