U.S. patent application number 10/726726 was filed with the patent office on 2004-06-10 for pressure transducer.
Invention is credited to Johnson, Dwight N..
Application Number | 20040109574 10/726726 |
Document ID | / |
Family ID | 22121459 |
Filed Date | 2004-06-10 |
United States Patent
Application |
20040109574 |
Kind Code |
A1 |
Johnson, Dwight N. |
June 10, 2004 |
Pressure transducer
Abstract
A pressure transducer which has a closed chamber which is full
of oil or other non-compressible liquid. Pressure communicates with
a diaphragm which defines one side of the closed chamber and the
pressure communicates via the oil with a pressure sensor which is
mounted within the oil spaced from the diaphragm. The liquid
entered the closed chamber through a inlet hole with a selected
volume driven into the closed chamber by a ball which is forcefully
driven a selected distance into the inlet hole before stopping at
the end of the inlet hole against a physical stop.
Inventors: |
Johnson, Dwight N.;
(Carlsbad, CA) |
Correspondence
Address: |
Spencer T. Smith
53 Silver Brook Lane
North Granby
CT
06060
US
|
Family ID: |
22121459 |
Appl. No.: |
10/726726 |
Filed: |
December 3, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10726726 |
Dec 3, 2003 |
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10074748 |
Oct 29, 2001 |
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6684709 |
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Current U.S.
Class: |
381/166 ;
381/165 |
Current CPC
Class: |
G01L 19/003 20130101;
G01L 19/0645 20130101; G01L 19/0038 20130101 |
Class at
Publication: |
381/166 ;
381/165 |
International
Class: |
H04R 025/00 |
Claims
1. A method of making a pressure transducer having a closed chamber
having a flexible flat diaphragm defining one side, a support cup
including a flat base mounted within the closed chamber with the
flat base parallel to and selectively spaced from the diaphragm, a
pressure sensor mounted within the closed chamber, the closed
chamber including an inlet bore including an outer enlarged
diameter portion, a first reduced diameter portion extending a
selected distance inwardly from said enlarged diameter portion
towards said closed chamber ending at a second further reduced
diameter portion, and a pressure supply path means for delivering
fluid pressure from a hole in a pressurized pipe to the diaphragm
including a piercing needle, support means for supporting the
piercing needle for displacement into a pipe to pierce the pipe,
and bore means extending from a first location surrounding the
piercing needle to a second location communicating with the
diaphragm the method comprising applying a preload pressure to the
pressure supply path to displace the diaphragm from its relaxed
state to a deflected position against the flat base to reduce the
volume of the closed chamber by a selected volume, while
maintaining the preload pressure applying a vacuum to the inlet
bore by opening a valve to remove air from the chamber, after a
vacuum is established, closing the valve and filling the chamber
with oil at least to the juncture of the first reduced diameter
portion of the inlet bore and the enlarged diameter portion of the
inlet bore, forcing a ball smaller than the enlarged diameter
portion and larger than the first reduced diameter into said first
reduced diameter portion until the ball rests against the second
further reduced diameter portion with the volume of oil pushed into
the closed chamber being predetermined to be equal to said selected
volume so that the when the preload is removed, the diaphragm will
be at its relaxed state, and removing the preload pressure.
2. A pressure transducer comprising a closed chamber having a
diaphragm defining one side, a pressure sensor mounted within said
closed chamber with a space separating the pressure sensor and said
diaphragm, an inlet bore communicating with said closed chamber
including an outer enlarged diameter portion, a first reduced
diameter portion extending a selected distance inwardly from said
enlarged diameter portion towards said closed chamber terminating
at a second further reduced diameter portion, a ball wedged into
said first reduced diameter portion against said second further
reduced diameter portion, and a non-compressible liquid filling
said closed chamber, said diaphragm being in the relaxed state.
3. A pressure transducer according to claim 2, further comprising
support cup means including a flat base, said support cup means
being mounted within said closed chamber with said flat base
parallel to and selectively spaced from said diaphragm.
4. A pressure transducer according to claim 3, further comprising
pressure supply path means for delivering fluid pressure from a
hole in a pressurized pipe to said diaphragm including a piercing
needle, support means for supporting said piercing needle for
displacement into a pipe to pierce the pipe, and bore means
extending from a first location surrounding the piercing needle to
a second location communicating with said diaphragm.
Description
[0001] The present invention relates to pressure transducers for
sensing the pressure of a fluid being conveyed in a pipe.
BACKGROUND OF THE INVENTION
[0002] A pressure transducer conventionally includes a piercing
needle which can be advanced to engage and pierce a clamped pipe
which is carrying fluid under pressure. The pressurized fluid flows
through the pierced hole and communicates with a solid state
pressure sensor which can supply sensed pressure data to an
electronics package for computational or other use.
OBJECT OF THE INVENTION
[0003] It is an object of the present invention to provide such a
pressure transducer wherein the sensor is isolated in an inert
protective fluid which transmits the pressure to the sensor.
[0004] Other objects and advantages of the present invention will
become apparent from the following portion of this specification
and from the accompanying drawings which illustrate, in accordance
with the mandate of the patent statutes, a presently preferred
embodiment incorporating the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is an oblique view, partly in section, of a
temperature/pressure transducer, made in accordance with the
teachings of the present invention, clamped to a water pipe;
[0006] FIG. 2 is another oblique view, partly in section of the
temperature/pressure transducer shown in FIG. 1;
[0007] FIG. 3 is a cross sectional view of the pressure/temperature
sensing module schematically assembled with structure for loading
the module with oil;
[0008] FIG. 4 is an oblique view of the diaphragm as shown in FIG.
3,
[0009] FIG. 5 is an oblique view of the support cup shown in FIG.
3;
BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT
[0010] FIGS. 1 and 2 illustrate a pressure/temperature transducer
P/T 14 which is clamped onto a water pipe 31 much like a saddle
valve, by tightening a clamping bolt 32 to advance a jaw 33 to
clamp the housing 34 to the water pipe proximate a piercing needle
35. Once clamped, the piercing needle can be extended until the
pipe wall is pierced, by rotating the body 38 of the piercing
needle, which is threadedly received by an internally threaded
sleeve 39 in the housing 34 of the pressure sensing device.
Surrounding the piercing needle, proximate the pipe is an annular
compression seal 40, which effectively seals the pierced hole 42.
The compression seal 40 has a through hole 41 larger than the
piercing needle. A second seal 44 seals the body 38 of the piercing
needle and the housing bore 45 in which the body moves. When the
piercing needle is retracted, water will pass through the pierced
hole 42, through the hole in the compression seal 41, through a
needle guide hole 43 in the housing, into the housing bore 45 along
the piercing needle and through a hole 49 (FIG. 2) into a chamber
47 between the housing 34 and a flexible diaphragm 46, which also
defines the bottom of an upper sealed chamber 48 in which a solid
state pressure sensor 50 is located. The housing additionally
supports a temperature sensor (thermistor, for example) 56 that is
clamped against the pipe wall when the housing is clamped in
position.
[0011] Oil, such as silicone oil, is permanently captured within
this chamber in the manner shown in FIG. 3. A first port 70 is
connected to the housing 34 at the compression seal bore 41 by
establishing a suitable face seal, for example. This port is
connected to a source of diaphragm preload pressure P1/72 (10-20
PSI) and the pressure source can be turned on and off with a
suitable valve 74. A chuck 76 is also connected to the housing 34
at the fill hole 54 by establishing a suitable face seal, for
example. The chuck has a first port 78 which is connected to a
source of oil under pressure P2/80 and this pressure source can be
turned on and off with a suitable valve 82. The chuck has a second
port 84 which is connected to a source of vacuum P3/86 and the
vacuum source can be turned on and off with a suitable valve 88.
The chuck has an exit bore 90 for receiving a metallic sealing ball
92 which is sized to be larger than the reduced diameter portion 93
of the oil inlet hole. The juncture of the reduced diameter portion
and an enlarged diameter portion 94 of the oil inlet hole defines
the location in the hole where the reduced diameter portion will be
sealed by the ball. The chuck also supports a displaceable plunger
96 which is sealed within its hole 98 and which will not move when
P2 is applied (rearward displacement past the shown position may be
prevented with a key/keyway interconnection, for example).
[0012] With valves 82 and 88 closed and valve 74 open P1 is applied
to deflect the top of the diaphragm 46 down against a support cup
100. FIG. 4 illustrates the diaphragm at this time and FIG. 5
illustrates the support cup. Now, valve 88 is opened and vacuum is
applied to eliminate all the air intermediate the diaphragm and the
valve. When this is complete valve 88 is closed and valve 82 is
opened to fill the space between the diaphragm and the valve with
oil. P2 is less than P1 so that the top of the diaphragm will not
move off the support cup. When this is complete, valve 82 is closed
and the plunger is displaced axially by an air cylinder, for
example, to forcefully displace the ball to its final position at
the end of the reduced diameter of the oil inlet hole against the
tapered surface 106. The volume of oil pushed into the system as
the ball is displaced from the juncture of the enlarged and reduced
diameter portions to the end of its displacement is a defined
volume which is chosen to deflect the top of the diaphragm to its
original flat neutral condition (oil will flow through holes 110 in
the support cup and a number of nubs 108 will facilitate the
separation of the diaphragm from the support cup). When the pre
load inlet and chuck are removed, the diaphragm will be ideally
neutral and no pressure will be transmitted from the diaphragm,
across the oil to the pressure sensor. The module can be calibrated
by determining the sensed pressure after assembly. The spacing
between the neutral diaphragm and the support cup is sufficient so
that any sensed pressure will not be sufficient to push the
diaphragm against the support cup. Accordingly, any pressure
applied to the diaphragm will be transmitted through the
noncompressible oil to the sensor and will be read by the
system.
* * * * *