Abstrict The subject matter of the invention is an impeller flow-meter,
particularly for accurate measurement of the flow rate of liquid
fuel fed to an internal-combustion engine. In the flow-meter according
to the invention, an impeller chamber (1) is provided with an inlet
pipe (2), surrounded coaxially by an ante-chamber (3). A supply
pipe (4) is provided for the liquid fuel and an offtake pipe for
excess fuel, these pipes being situated in different planes along
the axis of ante-chamber (3). A space (6) is located between the
entrance end of inlet pipe (2) and the exit end of supply pipe (4).
A slot (7) is formed between the outer wall of inlet pipe (2) and
the inner wall of the coaxial ante-chamber (3). The slot (7) communicates
with space (6) and offtake pipe (5). As a result of this structure,
pulsations in the liquid supply, which would affect the impeller
accuracy, are substantially extinguished in space (6) before reaching
the impeller chamber (1).
Claims What is claimed is:
1. In an impeller flow-meter for measuring the flow rate of a liquid
impelled therethrough, including an impeller chamber for a rotary
impeller, a supply pipe for the liquid and an inlet pipe to said
chamber, and an offtake pipe for removing excess liquid not impelled
through the meter, the flow rate of the liquid being determined
by the rotational rate of the impeller, the improvement which comprises,
particularly for accurately measuring the flow rate of liquid fuel
in an internal combustion engine, incorporating in said flow-meter
the following features:
(a) an ante-chamber (3) is provided connected to said supply pipe
(4) and to said offtake pipe (5);
(b) said ante-chamber (3) has an upper portion thereof mounted
externally of an coaxially with the inlet pipe (2) to provide an
annular slot (7) therebetween, permitting passage of liquid between
the outer wall of the inlet pipe (2) and the inner wall of the ante-chamber
(3);
(c) said offtake pipe (5) is in communication with said slot (7);
and
(d) said supply pipe (4) is in communication with a space (6) within
said ante-chamber (3) below said upper portion;
whereby pulsations in the liquid supply from the supply pipe (4),
which would affect the rotational rate of the impeller, are damped
and extinguished before the liquid reaches the impeller chamber
(1) through the inlet pipe (2).
2. A flow-meter according to claim 1 in which said supply pipe
(4) and said offtake pipe (5) are situated in different planes vertically
displaced along the axis of the ante-chamber (3), so that the end
of said offtake pipe (5) enters said slot (7) and the end of said
supply pipe (4) enters said space (6) formed between the end of
inlet pipe (2) and the bottom (10) of ante-chamber (3).
3. A flow-meter according to claim 1 characterized in that in
the offtake pipe (5) of the ante-chamber (3) a constricting gland
(8) is located.
4. A flow-meter according to claim 1 characterized in that the
ante-chamber (3) is mounted on the inlet pipe (2) of the impeller
chamber (1) snugly but so that it can rotate.
5. A flow-meter according to claim 1 characterized in that the
supply pipe (4) of the ante-chamber (3) is situated in its frontal
wall (12).
6. A flow-meter according to claim 1 characterized in that the
inlet pipe (2) of the impeller chamber (1) has a retainer ring (13)
whose outer diameter is equal to the inner diameter of the ante-chamber.
7. A flow-meter according to claim 6 characterized in that at
the place of contact between the outer surface of the retainer ring
(13) and the inner surface of the ante-chamber (3) the inner wall
of the latter is provided with recesses (11) rendering possible
the flow of the liquid.
8. A flow-meter according to claim 6 characterized in that the
recesses enabling the flow of the liquid are provided in the retainer
ring (13).
9. A flow-meter according to claim 1 characterized in that the
impeller chamber (1) and its inlet pipe (2) are integrally joined.
Description The subject matter of the present invention is an impeller flow-meter,
particularly for accurately measuring the rate of flow of the liquid
fuel fed to an internal-combustion engine.
Impeller flow-meters having an impeller situated in an impeller
chamber to which a liquid is supplied, whose rate of flow is being
measured, are very sensitive to pulsations of a stream of the liquid.
Pulsations of the stream have a substantial effect on the accuracy
of the flow-meter. The phenomenon of pulsation appears especially
important in fuel feed systems of internal-combustion engines. Two
types of feed systems for internal-combustion engines are used nowadays.
The most common feed system is a system without a drain, wherein
any excess of fuel supplied by the fuel pump remains in fuel pipes
between the pump and the carburetor. The measurement of the flow
rate of the liquid in such a system by means of flow-meters in which
the liquid is supplied directly to the impeller chamber is subject
to considerable error. The other feed system for internal-combustion
engines, is a system with a drain, wherein any excess of fuel supplied
by the fuel pump is drained to a storage tank. In the said other
second system which is increasingly used in modern automotive vehicles,
offtake pipes draining the excess of fuel are provided with constricting
glands. Due to this, pulsation of the stream of the liquid is reduced,
and thus the accuracy of the measurement of the flow rate of the
liquid increases. However, this increase of the accuracy, obtained
due to glands situated in the offtake pipes for the excess of the
liquid, is not fully satisfactory. Considerable errors affecting
measurements of the flow rate of the liquid in feed systems of internal-combustion
engines cause the result that the hitherto applied instruments for
measuring the amount of fuel consumed by the internal-combustion
engine, and especially instruments for measuring an instantaneous
fuel consumption per unit of the distance covered, are subject to
considerable error and for this reason they function as indicators
and not as measuring instruments. For these reasons they also have
not found a wider application in the motor transport, despite the
fact that the necessity of economical handling of fuels requires
a continuous control of the fuel consumption in internal-combustion
engines.
The present invention is applied to said second type of system
above referred to comprising an impeller flow-meter for measuring
the flow rate of a liquid impelled therethrough, in which a rotary
impeller is located in an impeller chamber, the liquid is supplied
through a supply pipe and an inlet pipe to said chamber and excess
fluid not impelled through the meter is removed by an offtake pipe,
the rotational rate of the impeller being utilized to determine
the flow rate of the liquid, for example, by a conventional electric
circuit converting impeller rotations to a signal proportional to
the liquid flow rate.
In accordance with the invention, an improvement to said impeller
flow-meter is provided, particularly for accurately measuring the
flow rate of liquid fuel in an internal combustion engine, which
improvement comprises incorporating in said flow-meter the following
features:
(a) an ante-chamber is provided connected to the supply pipe and
to the offtake pipe;
(b) said ante-chamber has an upper portion thereof mounted externally
of and coaxially with the inlet pipe to provide an annular slot
therebetween, permitting passage of liquid between the outerwall
of the inlet pipe and the inner wall of the ante-chamber;
(c) the offtake pipe is in communication with said slot; and
(d) the supply pipe is in communication with a space within said
ante-chamber below said upper portion.
As a result, pulsations in the liquid supply from the supply pipe
which would affect the rotational rate of the impeller, damped and
extinguished before the liquid reaches the impeller chamber through
the inlet pipe.
The inlet pipe and the offtake pipe of the ante-chamber are situated
in different planes perpendicular to said ante-chamber and displaced
along its axis, whereby the offtake pipe is located adjacent said
slot, and the supply pipe is located adjacent the space formed between
the entrance end the inlet pipe of the impeller chamber and the
bottom of the ante-chamber. The ante-chamber is mounted snugly on
the inlet pipe of the ante-chamber, so that it can rotate. In the
offtake pipe of the ante-chamber a constricting gland is located.
The supply pipe of the ante-chamber can be situated in its frontal
wall. For the purpose of better fixing the ante-chamber on the inlet
pipe of the impeller chamber, the said inlet pipe has a retainer
ring whose outer diameter is equal to the inner diameter of the
ante-chamber. In order to enable the flow of the liquid through
the slot to the offtake pipe of the ante-chamber, at the place of
contact between the outer wall of the retainer ring and the inner
surface of the ante-chamber, the inner wall of the latter is provided
with recesses. Recesses enabling the flow of the liquid through
the slot can be made in the retainer ring. The impeller chamber
and its inlet pipe can be joined integrally.
Due to the use of the ante-chamber a high degree of accuracy of
the flow rate of the liquid is rendered possible. This results from
the fact that the stream of the liquid is damped down and its pulsation
is completely extinguished.
The subject matter of the invention is presented in the accompanying
drawing, wherein FIG. 1 shows a longitudinal section of the flow-meter
according to the invention, and FIG. 2 shows a longitudinal section
of a portion of the flow-meter with a retainer ring on the inlet
pipe of the impeller chamber.
The flow-meter has an impeller chamber 1 in which an impeller is
situated, which is not shown in the drawing. The impeller chamber
1 has an inlet pipe 2 which can be integrally joined therewith.
On the inlet pipe 2 an ante-chamber 3 is mounted co-axially and
snugly but so that it can rotate, said ante-chamber having a supply
pipe 4 and an offtake pipe 5 communicating with an annular slot
7 formed between the inner wall of the ante-chamber 3 and the outer
wall of the inlet pipe 2 of the impeller chamber 1. In the offtake
pipe 5 a constricting gland 8 is situated. Between the bottom 10
of the ante-chamber 3 and the entrance end 9 of the inlet pipe 2
a space 6 is formed, communicating with the inlet pipe 4 and to
which a liquid is supplied, whose flow rate is being measured. The
inlet pipe 4 and the offtake pipe 5 of the ante-chamber 3 are situated
in different planes displaced along the axis of the ante-chamber
3 and perpendicular to said axis. The supply pipe 4 can be situated
in the frontal wall 12 of the ante-chamber 3. The inlet pipe 2 of
the impeller chamber 1 can be provided with a retainer ring 13 whose
outer diameter is equal to the inner diameter of the ante-chamber
3. In this case, instead of contact between the outer surface of
the retainer ring 13 and the inner surface of the ante-chamber 3
the inner wall of the latter is provided with recesses 11 rendering
possible the flow of the liquid. These recesses can be made also
in the retainer ring 13.
The liquid is fed by the supply pipe 4 to the space 6 of the ante-chamber
3. In said space the stream of the liquid is damped down and the
pulsation thereof is extinguished. A part of the stream of the liquid
is fed by the inlet pipe 2 to the impeller chamber 2 wherein it
drives the impeller, and then it is taken off to a receiver which
can be, for example, the carburettor of an internal-combustion engine.
The part of the stream of the liquid, which is not collected by
the receiver, is drained through the slot 7 and the offtake pipe
5 to a storage tank.
As has been proved in tests, the measurement of the flow rate by
means of the flow-meter according to the invention is characterized
by a very high accuracy. For this reason flow-meters of this type
can be used for measurements of and accounting for amounts of the
fuel consumed by internal-combustion engines of automotive vehicles
as well as by stationary engines. |