U.S. patent application number 11/842695 was filed with the patent office on 2007-12-27 for liquid level and density measurement device.
This patent application is currently assigned to Franklin Fueling Systems Inc.. Invention is credited to Vitaliy Demin.
Application Number | 20070295085 11/842695 |
Document ID | / |
Family ID | 38562020 |
Filed Date | 2007-12-27 |
United States Patent
Application |
20070295085 |
Kind Code |
A1 |
Demin; Vitaliy |
December 27, 2007 |
Liquid Level and Density Measurement Device
Abstract
A liquid level and density measurement device is disclosed. The
device comprises an elongated magnetostrictive transducer and at
least two transducer magnets embedded into floats that can freely
move along a transducer. One float is relatively more sensitive to
liquid density variation than the other float. The less sensitive
float is used for liquid level measurement and the more sensitive
float is used for liquid density measurement. The liquid density
float has a lower part completely immersed into a liquid and an
upper part partially immersed into a liquid. The upper part is made
substantially in the form of a hollow cylinder with an internal
diameter larger than the external diameter of the liquid level
float. Therefore the liquid density float can move up and down
without touching the liquid level float.
Inventors: |
Demin; Vitaliy; (Saco,
ME) |
Correspondence
Address: |
MARSHALL, GERSTEIN & BORUN LLP
233 S. WACKER DRIVE, SUITE 6300
SEARS TOWER
CHICAGO
IL
60606
US
|
Assignee: |
Franklin Fueling Systems
Inc.
Madison
WI
53718
|
Family ID: |
38562020 |
Appl. No.: |
11/842695 |
Filed: |
August 21, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11472897 |
Jun 22, 2006 |
7278311 |
|
|
11842695 |
Aug 21, 2007 |
|
|
|
Current U.S.
Class: |
73/447 |
Current CPC
Class: |
G01F 23/72 20130101;
G01F 23/76 20130101; G01N 9/12 20130101 |
Class at
Publication: |
073/447 |
International
Class: |
G01N 9/18 20060101
G01N009/18 |
Claims
1. A device for placement in a tank of liquid for determining the
level and density of the liquid in the tank, the device comprising:
a liquid density sensing float having a lower base portion and an
upper portion extending substantially continuously about a
periphery of the base portion and defining a cavity; a liquid level
sensing float disposed in the cavity; and circuitry for determining
the height of the density sensing float and the level sensing
float.
2. The device of claim 1 wherein the density sensing float and the
level sensing float include a magnet and the circuitry includes a
magnetostrictive transducer.
3. The device of claim 2 wherein the density sensing float and the
level sensing float include an aperture to slidably receive the
magnetostrictive transducer.
4. The device of claim 1 wherein the density sensing float is
dimensioned to fit through a four inch opening into the tank.
5. The device of claim 1 wherein the upper portion is substantially
cylindrical.
6. A device for placement in an underground liquid storage tank,
the device to determine the level and density of liquid in the
tank, the device comprising: a magnetostrictive transducer to be
generally vertically disposed in the tank; a liquid density sensing
float having a lower base portion and a generally cylindrical upper
portion extending substantially continuously about a periphery of
the base portion and defining a cavity, wherein the density sensing
float includes a magnet and the base portion has a bore to slidably
receive the transducer; a liquid level sensing float slidably
disposed in the cavity and having a bore to slidably receive the
transducer, wherein the level sensing float includes a magnet; and
circuitry coupled to the transducer for determining the position of
the magnets relative to the transducer.
7. A system for measuring the height and density of a liquid
comprising: an underground storage tank containing the liquid and
having a nominally four inch opening; a magnetostrictive transducer
generally vertically disposed in the tank; a liquid density sensing
float having a lower base portion and a generally cylindrical upper
portion extending substantially continuously about a periphery of
the base portion and defining a cavity, wherein the density sensing
float includes a magnet and the base portion has a bore slidably
receiving the transducer; a liquid level sensing float slidably
disposed in the cavity and having a bore slidably receiving the
transducer, wherein the level sensing float includes a magnet; and
circuitry coupled to the transducer for determining the position of
the magnets relative to the transducer.
8. A liquid level and density measurement device comprising an
elongated magnetostrictive transducer and at least two transducer
magnets embedded into a liquid density float and a liquid level
float and spaced along a transducer, wherein the liquid density
float is more sensitive to liquid density variations than the
liquid level float, and the liquid density float has a lower part
completely immersed into a liquid wherein the improvement
comprises: an upper part of the liquid density float partially
immersed into the liquid is made substantially in the form of
hollow cylinder with an internal diameter larger than the external
diameter of the liquid level float.
Description
THE FIELD OF THE INVENTION
[0001] This invention relates to a device for measuring the level
and density of a liquid in a tank, such as an underground petroleum
storage tank.
BACKGROUND OF THE INVENTION
[0002] Magnetostrictive transducers are widely used for the liquid
level measurement. See, for example, Koski et al., U.S. Pat. No.
4,839,590. Koski et al., discloses a measurement device for
precision measurement of a liquid level in an underground storage
tank that, in combination with a temperature measurement, allows
detecting very small leaks from the tank. There is also a need for
an accurate product density measurement in the same containers
where the level is being measured.
[0003] A widely known method of density measurement is based on the
hydrostatic principle that the weight loss of an object in a liquid
equals the weight of the liquid displaced. The method is used in
hydrometers where a relatively large weighted lower portion of a
body is completely immersed into a liquid and a tall narrow upper
section with a scale sticks out above the surface. The immersion
depth of the hydrometer is in an inverse proportion to the liquid
density. The hydrometer will float higher in a heavy liquid and
lower in a light liquid. The sensitivity of the hydrometer is in an
inverse proportion with a cross section of the upper section. The
narrower this part is, the more sensitive the hydrometer is. The
measurement range of the hydrometer is in direct proportion with
the height of upper part. The taller that part is, the larger
measurement range is.
[0004] There are also devices that combine level and density
measurement in one magnetostrictive transducer. See, for example,
Nyce et al., U.S. Pat. No. 5,253,522, and Russian patent RU
2138028.
[0005] The device disclosed in the Russian patent, and as generally
illustrated in FIGS. 1a, 1b and 1c, includes a liquid density float
17, and a liquid level measurement float (not shown). The level
measurement float is relatively less sensitive to liquid density
variation and the liquid density float 17 is relatively more
sensitive to liquid density variation. The liquid density float 17
is made in the form of an immersed cylinder 16 and four narrow
vertical rods 15 that are located on top of the cylinder around its
perimeter and extend above the surface. In essence, it is a group
of four hydrometers connected together. The diameter of the density
float 17 should be large enough to allow the liquid level float to
freely move between the rods 15.
[0006] Size is one drawback of such a device. As discussed above,
magnetostrictive transducers are widely used for leak detection in
underground tanks. Such leak detection requires reliable
measurement of very small changes of the liquid level, in the range
of 0.001 inches (0.025 mm) or less. To achieve this type of
resolution, the float for the level measurement should be heavy
enough and therefore large enough to overcome the friction between
the float and the body of the transducer, otherwise an effect known
as "stiction" can mask a leak. At the same time, standard openings
in the tanks for the transducer installation are typically four
inches (100 mm) in diameter or less, which limits the permitted
diameter of the float. To increase the tank opening size would be
expensive.
[0007] To be able to combine level and density measurement into one
transducer installed into a standard tank opening, without
compromising leak detection capabilities, requires a density float
to take as small portion of the opening diameter as possible and
leave sufficient room for the level float.
SUMMARY OF THE INVENTION
[0008] In accordance with the invention, shape of the density
measurement float allows minimizing its diameter. This is achieved
by making the upper part of the density float substantially in the
form of a hollow cylinder with an external diameter smaller than
the opening diameter of the tank and an internal diameter larger
than external diameter of the level float.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIGS. 1a, 1b and 1c are respective top, side and perspective
views of a prior art liquid density measurement device.
[0010] FIGS. 2a, 2b and 2c are respective top, side and perspective
views of a density float of the liquid level and density
measurement device according to the invention.
[0011] FIGS. 3a and 3b are side sectional views of the liquid level
and density measurement device of FIGS. 2a and 2b, illustrating the
float positions in liquids of different densities.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0012] While this invention is susceptible of embodiment in many
different forms, there will be described herein in detail, a
specific embodiment thereof with the understanding that the present
disclosure is to be considered as an exemplification of the
principles of the invention and is not intended to limit the
invention to the specific embodiment illustrated.
[0013] A liquid level and density measurement device, generally
designated 20, is illustrated in FIGS. 2a, 2b, 2c, 3a and 3b. The
liquid level and density measurement device 20 comprises a
conventional, elongated magnetostrictive transducer 21 and first
and second transducer magnets 24a and 24b. The first transducer
magnet 24a is embedded into a liquid density float 22, which is
relatively more sensitive to liquid density variations. The second
transducer magnet 24b is embedded in a liquid level float 23, which
is relatively less sensitive to liquid density variations. The
floats 22, 23 can freely move along the transducer 21. The liquid
level float 23 is used for liquid level measurement, and the liquid
density 22 is used for liquid density measurement.
[0014] The liquid density float 22 has a lower part 26 completely
immersed into a liquid 28 and an upper part 30 partially immersed
into the liquid 28. The upper part 30 is made substantially in the
form of a hollow cylinder, with an internal diameter defining a
cavity 30a. The internal diameter of the cavity 30a is dimensioned
larger than the external diameter of the liquid level float 23.
Therefore the liquid density float 22 can move up and down without
touching the liquid level float 23.
[0015] The liquid density float 22 is shown in a relatively more
dense liquid in FIG. 3a and in a relatively less dense liquid in
FIG. 3b. The difference in height "d" is indicative of the relative
difference of the densities of the two liquids.
[0016] The liquid density float 22 preferably is made of a low
density material with a ballast at the bottom. The lower part 26
preferably has a diameter of approximately 95 mm. The upper part
preferably has an outer diameter of 95 mm and an inner diameter of
approximately 72 mm.
[0017] The liquid level float is preferably made of a low density
material. It has a diameter preferably of approximately 72 mm.
[0018] Openings 34 are provided through the upper part 30 to permit
fluid to flow into the cavity 30a.
[0019] Because the generally cylindrical upper part 30 of the
liquid density float 22 has circumferentially more mass than does
the prior art liquid density float, its diameter can be reduced to
permit insertion through a typical four inch tank opening.
[0020] The upper part 30 of the liquid density float 22 may be
other than cylindrical. For example it may have a taper due to its
formation during a molding process.
[0021] From the foregoing, it will be observed that numerous
variations and modifications may be effected without departing from
the spirit and scope of the invention. It is to be understood that
no limitation with respect to the specific apparatus illustrated
herein is intended or should be inferred. It is, of course,
intended to cover by the appended claims all such modifications as
fall within the scope of the Claims.
* * * * *