Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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APPARATUS FOR PREVE~1TING AIR FLOW THROUGH Q METER
This invention is in the field of liquid handling equipment, and in particular
meters for
s measuring liquid flow.
BACKGROUND
Liquids are commonly dispensed by a pump from storage tanks through a meter
that
to measures the amount dispensed. For~example fuel is pumped from storage
tanks at retail
gas stations, card locks, and tike facilities. Fuel is also transported in
bulk tanker vehicles
which stop at customers Locations such as farms, retail gas stations, card-
lock facilities,
and the like and deliver a portion of their total load into tanks at each
stop. The amount
delivered in each dispensing event is measured by a flow meter.
Such fuel delivery facilities often comprise a plurality of tanks or
compartments. Tanker
vehicles comprises a tank divided into a plurality of compartments. Each
individual
compartment is connected to the pump intake by a pipe network, and valves are
manipulated to connect the pump intake to the desired compartment. When a
compartment is empty, the valve or valves connecting the empty compartment to
the
pump intake are closed, and other valves are manipulated to connect a full
compartment
to the pump intake.
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In fuel delivery facilities and vehicles, the pump output is connected to a
meter, and
typically a solenoid operated shut-off valve is provided at the output of the
meter and
before the output conduit to the customer's tanks. The shut-off valve is
typically set up
such that if power to the solenoid is cut off, the valve closes and no further
fuel can pass
from the pump output through the meter. This shut-off valve is also commonly
connected to the meter so that the system can be programmed to pump off a set
amount
of fuel, and when this amount has been measured by the meter, the shut-off
valve will
close. The meter, with temperature compensation built in, and shut-off valve
are thus
to configured to provide an Electronic Fuel Delivery (EF'D) system.
When a compartment is Bumped dry, air is drawn into the pump intake, and
through the
pump to the meter. In order to maintain an accurate meter measurement of the
liquid
delivered, this air must be prevented from passing through the meter. Air
passing
through the meter will be measured as liquid, and the measured amount of
liquid will be
inaccurate.
In fuel delivery facilities and vehicles, an air eliminator is therefore
provided between the
pump output and the meter. The air eliminator is not required on all systems,
such as
2o those using a submersible pump. Essentially the air eliminator comprises a
housing
connected to the pipe between the pump output and the meter. A float and seal
are
provided in the housing and a vent is provided above the float. So long as
liquid is
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present in the housing from the pump output pipe, the float is maintained
against the seal
and liquid escape through the vent is prevented. Once the liquid level in the
housing
drops, or the fuel becomes less dense because of air bubbles, the float moves
away from
the sea! and air rises through the liquid in the lower part of the housing and
is exhausted
through the vent. Thus air is prevented from passing through the meter and
rendering the
meter measurements inaccurate.
For maximum efficiency, it is desirable to minimize the time spent dispensing
fuel. Thus
pump capacities are increased to move the liquid faster, and in doing so the
capacity of
the air eliminator is sometimes exceeded. Fuel and air is moving through the
pipe so fast
that all air is not removed from the liquid, with the result that air passes
through the meter
and renders the measurement inaccurate.
The amount of fuel or the like measured by the meters is paid for by the
customer, and so
in most jurisdictions the meters must be certified as legal for trade, and are
inspected and
tested from time to time. Such testing typically includes running a
compartment dry to
see if air is passed through the meter. If the air eliminator capacity is
exceeded, the meter
can be rejected and the vehicle prevented from further deliveries until the
jurisdiction
inspectors are satisfied that it is metering accurately. A small amount of
air, typically
two to three liters for a bulk fuel delivery vehicle, is usually allowable as
an error during
such tests without causing rejection.
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SUMMARY OF THE INVENTION
It is an object of the present invention to provide an air transfer control
for bulk liquid
delivery facilities and vehicles, such as for fuel delivery, that prevents air
from passing
through the liquid meter.
The air transfer control provides a sensor, such as an optical sensor,
positioned in the
housing of the air eliminator to sense whether there is liquid covering the
sensor. The
sensor is connected to a switch that operates the solenoid shut-off valve in a
typical EFD
to system on a fuel delivery vehicle for example. When the sensor senses that
the level of
liquid in the housing is below the sensor, or that air bubbles are present in
the liquid in
the housing, the switch is opened and the shut-off closes. Thus air is
prevented from
entering the meter, and instead the air is exhausted through the vent in the
air eliminator.
When a new compartment is opened, and fuel fills the piping again, the sensor
toms the
t5 switch on and the shut-off valve opens and delivery continues.
The design of the air transfer control of the invention is such that even if
the air
eliminator failed and stayed closed not allowing any air to escape, the system
would still
not allow any airflow through the meter. Thus the EFD system would pass
accuracy tests.
2o In a normally operating system, all air would be exhausted though the air
eliminator ports
with, again, none passing through the metering system.
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Conveniently the air transfer control can include an adjustable time delay
such that
timing of closing the shut-off valve can be set for each system individually,
during the
calibration process, to fme tune the system and transfer the maximum amount of
product
without transferring any air. It is desired to completely empty each
compartment in order
to avoid needlessly hauling fuel or the like back to the source. In a typical
EFD system
there is some space between the air eliminator and the meter, such that fuel
is still present
in the pipe to the meter that could be pumped off without having any air pass
through the
meter. It may be desirable to have the sensor delay closing the shut-off valve
briefly to
allow this fuel to pass through the meter and be unloaded prior to closing the
shut-off
to valve. Such a delay also allows prevents the switch from rapidly turning on
and off when
air bubbles contact the sensor.
The air transfer control is conveniently provided in kit form so that it may
be readily
installed on existing fuel delivery or like vehicles.
DESCRIPTION OF THE DRr~~~S:
While the invention is claimed in the concluding portions hereof, preferred
embodiments
are grovided in the accompanying detailed description which may be best
understood in
conjunction with the accompanying diagrams where like parts in each of the
several
diagrams are labeled with like numbers, and where:
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Fig. I is a schematic drawing of an electronic fuel delivery system with the
air
transfer contml of the present invention installed;
Fig. 2 is a schematic sectional view of the air eliminator when the pump is
pumping liquid fuel;
Fig. 3 is a schematic sectional view of the air eliminator when the pump is
P~P~ ~'.
DETAILED ~gN O~ THE II~USTRATED EMBODI~~NTS:
Fig. 1 schematically illustrates a typical FrFD system in a fuel delivery
facility or vehicle
with the air transfer control 1 of the invention installed thereon. The system
comprises a
pump 3 having an intake operatively connected by a network of pipes 5 to a
plurality of
tank compartments 7. Compartment valves 9 can be opened or closed to
selectively
direct fuel from any compartment 7 to the pump intake.
Conduit 11 connects the output of the pump 3 to a meter 13, and an sir
eliminator 15 is
teed into the conduit I1. The output of the meter 13 is connected by a pipe to
a solenoid
shut-off valve 17 and a delivery hose 19 is typically connected to the shut-
off valve I7 to
carry the fuel to the customer's tank.
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As schematically illustrated in Figs. 2 and 3, the air eliminator 15 comprises
a housing 21
oortnected to the conduit 11 between the output of the pump 3 and the meter
13. A float
23 and seal 25 are provided in the housing 21 and a vent 27 is provided above
the float
23. The illustration is schematic only, and such floats and seals are
configtued in variety
of ways. As illustrated in Fig. 2, when pumping fuel from one of the
compartments 7,
liquid 29 from the pump output conduit 11 flows up into the housing 21 and the
float 23
is pushed against the seal 25, and liquid escape through the vent 27 is
prevented. Once
the compartment 7 is empty, the pump 3 will draw air instead of liquid fuel,
and the level
of liquid 29 in the housing will drop. The float 23 then moves away from the
seal 25 and
air A rises through the liquid 29 in the lower part of the housing 21 and is
exhausted
through the vent 27. The air is thus vented off and prevented from passing
through the
meter 13 and rendering the meter measurements inaccurate.
The air transfer control of the present invention provides a control element
30 positioned
in the housing 21 of the air eliminator 15. The control element 30 comprises a
sensor 31
operative to detect whether there is liquid 29 covering the sensor 32, as is
the case in the
illustration of Fig. 2. The sensor 31 illustrated is an optical sensor that
uses optics to
detoct liquid. The sensor 31 is connected to a switch 33, located in an
electrical box 44
and the control is configured such that when liquid 29 is detected at the
sensor 31, as
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illustrated in Fig. 2, the switch 33 is closed. When the liquid 29 in the
housing 21 falls
below the sensor 31, as illustrated in Fig. 3, the switch 33 is opened.
The solenoid shut-off valve 17 is powered from an electrical source 44
supplying a
voltage V, as seen in Fig. 1. The shut-off valve 17 is conventionally
configured such that
when voltage V is connected, the shut-off valve 17 is open, and when the
voltage V is
disconnected the shut-off valve 17 is closed.
In the present invention the power wire 42 from the voltage source 40 to the
shut-off
valve 17 is connected through the switch 33 to the shut-off valve 17. Thus
when the
liquid fuel level in the housing 21 drops below the sensor 31, as illustrated
in Fig. 3, the
switch 33 is open and the voltage V is disconnected from the shut-off valve 17
and it
closes, preventing any flow of air through the meter 13. All air A then
escapes up
through the vent 27. When valves 9 are manipulated to connect a new
compartment 7
that contains fuel, fuel fills the conduit 11 again, the sensor 31 senses the
liquid 29 in the
housing and turns the switch 33 on and the shut-off valve 17 opens and
delivery can
continue.
The control element 30 containing the sensor 31 is conveniently provided by a
High
Pressure Optical Liquid Level Sensor - OS-150B Glass - Metal Optical Level
Sensor as
supplied by Strain Measurement Devices of Meriden, CT. This sensor is
configured to
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be "off' when liquid is present covering the sensor. When liquid falls below
the sensor,
or when a bubble contacts the surface of the sensor, the sensor turns "on" and
activates
the switch 33 to turn off.
The control element 30 conveniently is threaded into a port drilled and tapped
into the
housing 21 of the air eliminator 15 of a conventional EFD system, and wired
into the
switch 33 through the electrical box 44. The wiring in the boa 44 also shows
the power
wire 42 connected through the meter 13, as is common in order to allow a
selected
metered amount of fuel to be delivered, and then close the shut-off valve 17.
A timer delay element 45 can be included in the box 44 and incorporated to
delay the
time between when the sensor 31 senses a lack of liquid or bubbles in the
fuel, and when
the switch 33 is opened. The air transfer control is conveniently provided as
a kit for
installation on existing EFD systems and comprising the control element 30,
and box 44
containing the switch 33 and delay 46, and appropriate wiring.
The foregoing is considered as illustrative only of the principles of the
invention.
Further, since numerous changes and modifications will readily occur to those
skilled in
the art, it is not desired to limit the invention to the exact construction
and operation
shown and described, and accordingly, all such suitable changes or
modifications in
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structwe or operation which may be resorted to are intended to fall within the
scope of
the claimed invention.
