U.S. patent application number 13/555572 was filed with the patent office on 2014-01-23 for piezoelectric sensor arrangement for sensing fluid level in small volume and irregular shape reservoirs.
This patent application is currently assigned to XEROX CORPORATION. The applicant listed for this patent is Edward F. Burress, Brent R. Jones. Invention is credited to Edward F. Burress, Brent R. Jones.
Application Number | 20140022292 13/555572 |
Document ID | / |
Family ID | 49946176 |
Filed Date | 2014-01-23 |
United States Patent
Application |
20140022292 |
Kind Code |
A1 |
Jones; Brent R. ; et
al. |
January 23, 2014 |
PIEZOELECTRIC SENSOR ARRANGEMENT FOR SENSING FLUID LEVEL IN SMALL
VOLUME AND IRREGULAR SHAPE RESERVOIRS
Abstract
A fluid level sensor measures a height of a fluid in a volume
with a plurality of piezoelectric sensors arranged along at least
one wall of a container. The sensors are positioned to enable
activated sensors to interact with the materials adjacent the
sensors to produce electrical signals in more than one of the
sensors. These electrical signals are used to identify the fluid
level in the volume.
Inventors: |
Jones; Brent R.; (Sherwood,
OR) ; Burress; Edward F.; (West Linn, OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Jones; Brent R.
Burress; Edward F. |
Sherwood
West Linn |
OR
OR |
US
US |
|
|
Assignee: |
XEROX CORPORATION
Norwalk
CT
|
Family ID: |
49946176 |
Appl. No.: |
13/555572 |
Filed: |
July 23, 2012 |
Current U.S.
Class: |
347/7 |
Current CPC
Class: |
B41J 2/17566 20130101;
B41J 2002/17583 20130101; G01F 23/2968 20130101; G01F 23/2961
20130101 |
Class at
Publication: |
347/7 |
International
Class: |
B41J 2/195 20060101
B41J002/195 |
Claims
1. A fluid level sensor for measuring a height of a fluid
comprising: a container having at least one wall that forms a
volume for containing a fluid; a plurality of piezoelectric sensors
arranged along the at least one wall of the container to interact
with the fluid within the volume, two of the piezoelectric sensors
being positioned to enable fluid in the volume to cover
simultaneously a portion, but not all, of a surface area of a first
piezoelectric sensor of the two piezoelectric sensors and a
portion, but not all, of a surface area of a second piezoelectric
sensor of the two piezoelectric sensors, the portion of the surface
area of the first piezoelectric sensor covered by the fluid being
larger than the portion of the surface area of the second
piezoelectric sensor covered by the fluid; and a pair of conductors
operatively connected to each piezoelectric sensor, the conductors
configured to conduct electrical signals to and from each
piezoelectric sensor.
2. The fluid level sensor of claim 1 further comprising: a
controller operatively connected to the pair of conductors from
each of the piezoelectric sensors, the controller being configured
to activate the first and the second piezoelectric sensors through
the pair of conductors operatively connected to the first and the
second piezoelectric sensors and to identify a fluid level from a
difference between electrical signals received from the first
piezoelectric sensor and electrical signals received from the
second piezoelectric sensor.
3. The fluid level sensor of claim 1 further comprising: a third
piezoelectric sensor positioned at a location between the two
piezoelectric sensors to enable fluid in the volume to cover
simultaneously the portion of the surface area of the first
piezoelectric sensor, the portion of the surface area of the second
piezoelectric sensor, and a portion of a surface area of the third
piezoelectric sensor, the portion of the surface area of the first
piezoelectric sensor covered by the fluid being larger than the
portion of the surface area of the third piezoelectric sensor
covered by the fluid and the portion of the surface area of the
third piezoelectric sensor covered by the fluid being larger than
the portion of the surface area of the second piezoelectric sensor
covered by the fluid.
4. The fluid level sensor of claim 3 further comprising: a
controller operatively connected to the pair of conductors from
each of the piezoelectric sensors, the controller being configured
to activate the first, the second, and the third piezoelectric
sensors through the pair of conductors operatively connected to the
first, the second, and the third piezoelectric sensors,
respectively, and to identify a fluid level from a difference
between electrical signals received from the first piezoelectric
sensor, electrical signals received from the second piezoelectric
sensor, and electrical signals received from the third
piezoelectric sensor.
5. The fluid level sensor of claim 3 further comprising: a
controller operatively connected to the pair of conductors from
each of the piezoelectric sensors, the controller being configured
to activate at least one of the first, the second, and the third
piezoelectric sensors through the pair of conductors operatively
connected to the activated sensor, and to identify a fluid level
from a difference between electrical signals received from the
first piezoelectric sensor, electrical signals received from the
second piezoelectric sensor, and electrical signals received from
the third piezoelectric sensor.
6. The fluid sensor of claim 3 wherein a distance between the third
piezoelectric sensor from the first piezoelectric sensor is equal
to a distance between the third piezoelectric sensor and the second
piezoelectric sensor.
7. The fluid sensor of claim 3 wherein a distance between the third
piezoelectric sensor and the first piezoelectric sensor is
different than a distance between the third piezoelectric sensor
and the second piezoelectric sensor.
8. The fluid sensor of claim 1 wherein the plurality of
piezoelectric sensors are configured in a non-linear
arrangement.
9. The fluid sensor of claim 2, the controller being further
configured to identify a second orientation of the container that
is different than a first orientation of the container from a
difference between electrical signals received from the first and
second piezoelectric sensors at the first orientation and
electrical signals received from the first and second piezoelectric
sensors at the second orientation.
10. An inkjet printer comprising: an inkjet printing apparatus
having a plurality of inkjet ejectors, the inkjet printing
apparatus being configured to eject ink from the inkjet ejectors
onto a substrate; an ink reservoir configured to supply ink to the
plurality of inkjet ejectors, the ink reservoir having at least one
wall that forms a volume for containing the ink; a plurality of
piezoelectric sensors arranged along the at least one wall of the
ink reservoir to interact with the ink within the volume, two of
the piezoelectric sensors being positioned to enable the ink in the
volume to cover simultaneously a portion, but not all, of a surface
area of a first piezoelectric sensor of the two piezoelectric
sensors and a portion, but not all, of a surface area of a second
piezoelectric sensor of the two piezoelectric sensors, the portion
of the surface area of the first piezoelectric sensor covered by
the ink being larger than the portion of the surface area of the
second piezoelectric sensor covered by the ink; and a pair of
conductors operatively connected to each piezoelectric sensor, the
conductors configured to conduct electrical signals to and from
each piezoelectric sensor.
11. The inkjet printer of claim 10 wherein the ink reservoir is
integrated within the inkjet printing apparatus and ink within the
ink reservoir is in direct fluid communication with the inkjet
ejectors.
12. The inkjet printer of claim 10 further comprising: a controller
operatively connected to the pair of conductors from each of the
piezoelectric sensors, the controller being configured to activate
the first and the second piezoelectric sensors through the pair of
conductors operatively connected to the first and the second
piezoelectric sensors and to identify an ink level from a
difference between electrical signals received from the first
piezoelectric sensor and electrical signals received from the
second piezoelectric sensor.
13. The inkjet printer of claim 10 further comprising: a third
piezoelectric sensor positioned between the two piezoelectric
sensors to enable ink in the volume to cover simultaneously the
portion of the surface area of the first piezoelectric sensor, the
portion of the surface area of the second piezoelectric sensor, and
a portion of a surface area of the third piezoelectric sensor, the
portion of the surface area of the first piezoelectric sensor
covered by the ink being larger than the portion of the surface
area of the third piezoelectric sensor covered by the ink and the
portion of the surface area of the third piezoelectric sensor
covered by the ink being larger than the portion of the surface
area of the second piezoelectric sensor covered by the ink.
14. The printer of claim 13 further comprising: a controller
operatively connected to the pair of conductors from each of the
piezoelectric sensors, the controller being configured to activate
the first, the second, and the third piezoelectric sensors through
the pair of conductors operatively connected to the first, the
second, and the third piezoelectric sensors, respectively, and to
identify an ink level from a difference between electrical signals
received from the first piezoelectric sensor, electrical signals
received from the second piezoelectric sensor, and electrical
signals received from the third piezoelectric sensor.
15. The printer of claim 13 further comprising: a controller
operatively connected to the pair of conductors from each of the
piezoelectric sensors, the controller being configured to activate
at least one of the first, the second, and the third piezoelectric
sensors through the pair of conductors operatively connected to the
activated sensor, and to identify an ink level from a difference
between electrical signals received from the first piezoelectric
sensor, electrical signals received from the second piezoelectric
sensor, and electrical signals received from the third
piezoelectric sensor.
16. The printer of claim 13 wherein a distance between the third
piezoelectric sensor and the first piezoelectric sensor is equal to
a distance between the third piezoelectric sensor and the second
piezoelectric sensor.
17. The printer of claim 13 wherein a distance between the third
piezoelectric sensor and the first piezoelectric sensor is
different than a distance between the third piezoelectric sensor
and the second piezoelectric sensor.
18. An ink cartridge for containing liquid ink comprising: an ink
reservoir formed within the cartridge, the ink reservoir having at
least one wall that forms a volume for containing the liquid ink; a
plurality of piezoelectric sensors arranged along the at least one
wall of the ink reservoir to interact with the liquid ink within
the volume, two of the piezoelectric sensors being positioned to
enable the liquid ink in the volume to cover simultaneously a
portion, but not all, of a surface area of a first piezoelectric
sensor of the two piezoelectric sensors and a portion, but not all,
of a surface area of a second piezoelectric sensor of the two
piezoelectric sensors, the portion of the surface area of the first
piezoelectric sensor covered by the liquid ink being larger than
the portion of the surface area of the second piezoelectric sensor
covered by the liquid ink; and a pair of conductors operatively
connected to each piezoelectric sensor, the conductors configured
to conduct electrical signals to and from each piezoelectric
sensor.
19. The ink cartridge of claim 18 further comprising: a controller
operatively connected to the pair of conductors from each of the
piezoelectric sensors, the controller being configured to activate
the first and the second piezoelectric sensors through the pair of
conductors operatively connected to the first and the second
piezoelectric sensors and to identify a liquid ink level from a
difference between electrical signals received from the first
piezoelectric sensor and electrical signals received from the
second piezoelectric sensor.
Description
TECHNICAL FIELD
[0001] This disclosure relates generally to fluid level sensing
and, in particular, to fluid level sensing in on-board ink
reservoirs of printheads associated with phase change ink imaging
devices.
BACKGROUND
[0002] In general, inkjet printers include at least one printhead
that ejects drops of liquid ink onto an image receiving surface. A
phase change inkjet printer employs phase change inks that are
solid at ambient temperature, but transition to a liquid phase at
an elevated temperature. The melted ink can then be ejected onto an
image receiving surface by a printhead. The image receiving surface
may be a media substrate or an intermediate imaging member. The
image on the intermediate imaging member is later transferred to an
image receiving substrate. Once the ejected ink is on the image
receiving surface, the ink droplets quickly solidify to form an
image.
[0003] Printers store a variety of fluids to enable ink imaging and
ensure reliable printer operation. In some cases, monitoring of the
volume or the head height of the stored fluids is important.
Accurate monitoring of the head height is especially important
where the head height of a stored fluid affects the mechanism or
system that draws or uses the fluid. For example, restricting the
head height range within an ink reservoir and precisely controlling
the replenishment to an on-board ink reservoir of a printhead are
often needed to prevent overfill-caused dripping of ink from the
printhead jet orifices and to prevent the introduction of air if
the fluid level is depleted below tolerable levels.
[0004] Currently available fluid sensing systems suffer from a
number of drawbacks. For instance, applications in which small
reservoirs or holding tanks are needed to store a fluid may not
offer the space or fluid height required to accommodate known fluid
sensing systems, such as float-based systems. Also, many "sense and
fill" systems suffer from significant hysteresis problems in that
these systems tend to respond late or overfill before flow is
stopped. Moreover, fluid sensing systems that sense fluid materials
by detecting a resistance change upon attaining a liquid level are
dependent on consistent material properties, which may change over
the life of the mechanism or system that uses the fluid. For
example, the properties of a fluid may deteriorate over time due to
age degradation, or the fluid may be replaced with a fluid having
different properties. Therefore, improvements to sensing systems
that enable fluid sensing in small and irregular shape reservoirs
and that can detect fluids with varying properties are desired.
Improvements to sensing systems that can respond to small, short
term fluid level changes and longer term, continuous changes where
the initial fluid level may be at any point in the usable volume
range are also desirable.
SUMMARY
[0005] A fluid level sensor has been developed that enables
measurement of a height of fluid in small volume and irregular
shape reservoirs. The fluid level sensor includes a container
having at least one wall that forms a volume for containing a
fluid, a plurality of piezoelectric sensors arranged along the at
least one wall of the container to interact with the fluid within
the volume, two of the piezoelectric sensors being positioned to
enable fluid in the volume to cover simultaneously a portion, but
not all, of a surface area of a first piezoelectric sensor of the
two piezoelectric sensors and a portion, but not all, of a surface
area of a second piezoelectric sensor of the two piezoelectric
sensors, the portion of the surface area of the first piezoelectric
sensor covered by the fluid being larger than the portion of the
surface area of the second piezoelectric sensor covered by the
fluid, and a pair of conductors operatively connected to each
piezoelectric sensor, the conductors configured to conduct
electrical signals to and from each piezoelectric sensor.
[0006] A printer incorporates the fluid level sensor in a printhead
of the printer to improve the measurement accuracy of ink head
height within the printhead. The printer includes an inkjet
printing apparatus having a plurality of inkjet ejectors, the
inkjet printing apparatus being configured to eject ink from the
inkjet ejectors onto a substrate, an ink reservoir configured to
supply ink to the plurality of inkjet ejectors, the ink reservoir
having at least one wall that forms a volume for containing the
ink, a plurality of piezoelectric sensors arranged along the at
least one wall of the ink reservoir to interact with the ink within
the volume, two of the piezoelectric sensors being positioned to
enable the ink in the volume to cover simultaneously a portion, but
not all, of a surface area of a first piezoelectric sensor of the
two piezoelectric sensors and a portion, but not all, of a surface
area of a second piezoelectric sensor of the two piezoelectric
sensors, the portion of the surface area of the first piezoelectric
sensor covered by the ink being larger than the portion of the
surface area of the second piezoelectric sensor covered by the ink,
and a pair of conductors operatively connected to each
piezoelectric sensor, the conductors configured to conduct
electrical signals to and from each piezoelectric sensor.
[0007] In another embodiment, an ink cartridge incorporates the
fluid level sensor to enable measurement of a height of aqueous or
emulsified ink contained within the ink cartridge. The ink
cartridge includes an ink reservoir formed within the cartridge,
the ink reservoir having at least one wall that forms a volume for
containing the liquid ink, a plurality of piezoelectric sensors
arranged along the at least one wall of the ink reservoir to
interact with the liquid ink within the volume, two of the
piezoelectric sensors being positioned to enable the liquid ink in
the volume to cover simultaneously a portion, but not all, of a
surface area of a first piezoelectric sensor of the two
piezoelectric sensors and a portion, but not all, of a surface area
of a second piezoelectric sensor of the two piezoelectric sensors,
the portion of the surface area of the first piezoelectric sensor
covered by the liquid ink being larger than the portion of the
surface area of the second piezoelectric sensor covered by the
liquid ink, and a pair of conductors operatively connected to each
piezoelectric sensor, the conductors configured to conduct
electrical signals to and from each piezoelectric sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The foregoing aspects and other features of a fluid sensor
configured to measure a height of a fluid are explained in the
following description, taken in connection with the accompanying
drawings.
[0009] FIG. 1 is a section view of a printhead that includes at
least one on-board reservoir and that incorporates the fluid sensor
for measuring the height of ink within the printhead.
[0010] FIG. 2 is a partial view of two of a plurality of
piezoelectric sensors positioned relative to one another.
[0011] FIG. 3 is a partial view of a third piezoelectric sensor
positioned between the two piezoelectric sensors of FIG. 2 at a
first distance and a second distance from the two piezoelectric
sensors.
[0012] FIG. 4 is a schematic block diagram of an embodiment of an
inkjet printer.
[0013] FIG. 5 is a schematic block diagram of an embodiment of an
inkjet printer that is similar to the embodiment of FIG. 4.
DETAILED DESCRIPTION
[0014] For a general understanding of the present embodiments,
reference is made to the drawings. In the drawings, like reference
numerals have been used throughout to designate like elements.
FIGS. 4 and 5 are schematic block diagrams of an embodiment of an
inkjet printer that includes a controller 10 and at least one
printhead 20. The printhead 20 includes a plurality of inkjets
configured to eject drops of ink 33 either directly onto a print
medium 15 (FIG. 4) or onto an intermediate transfer surface 30
(FIG. 5). A print medium transport mechanism 40 moves the print
medium relative to the printhead 20, which can be stationary or can
move in a transverse direction.
[0015] FIG. 5 is a schematic block diagram of an embodiment of an
inkjet printer that is similar to the embodiment of FIG. 4. The
printer includes a transfer drum 30 for receiving the drops ejected
by the printhead 20. A print media transport mechanism 40
transports a print medium 15 to a position proximate the transfer
drum 30 where a transfix roller (not shown) forms a nip with the
drum 30. The medium 15 enters the nip where the image printed on
the transfer drum 30 is transferred to the print medium 15 and the
transport mechanism carries the medium to a tray for retrieval or
subsequent processing.
[0016] The printer depicted in FIGS. 4 and 5 includes an ink
delivery system 25 that is configured to supply ink to a plurality
of on-board ink reservoirs 61, 62, 63, 64 associated with the at
least one printhead 20. Respective ink supply channels 71, 72, 73,
74 operatively connect the ink delivery system 25 to the on-board
ink reservoirs of the printhead 20. The printer can further include
remote ink containers (not shown) that are configured to
communicate melted phase change ink held therein to the on-board
reservoirs 61, 62, 63, 64. The ink supply channels 71, 72, 73, 74
can be conduits for molten ink or can be drip paths as typically
implemented with an ink supply system that deposits ink directly
into printhead reservoirs 61, 62, 63, 64 as ink is melted.
[0017] In one embodiment, the printer is a phase change ink imaging
device. Accordingly, the ink delivery system comprises a phase
change ink delivery system that has at least one source of at least
one color of phase change ink in solid form. The phase change ink
delivery system also includes a melting and supply apparatus (not
shown) for melting the solid form of the phase change ink into a
liquid form and delivering the melted ink to the respective
on-board ink reservoir 61, 62, 63, 64.
[0018] The on-board ink reservoirs 61-64 are configured to contain
the melted solid ink and can be heated to maintain the ink in
liquid form. The ink supply channels 71-74 can similarly be heated.
The melted solid ink can be supplied to the on-board ink reservoirs
61-64 by any known fluid transport technique. For example, the ink
delivery system 25 can drip melted ink into the reservoirs or, if
delivered through a conduit, can generate a pressure differential
to enable ink to flow from an ink source to the on-board ink
reservoirs 61-64. Once the pressurized ink reaches the printhead
via an ink supply channel, the ink is collected in the on-board
reservoir.
[0019] FIG. 1 shows an embodiment of a printhead 20 that includes
at least one on-board reservoir 61. The on-board reservoir 61 is
configured to communicate ink 154 to a jet stack 100 that includes
a plurality of inkjets 108. The jet stack 100 can be formed in many
ways, but in this example, the stack 100 is formed of multiple
laminated sheets or plates, such as stainless steel plates.
Cavities etched into each plate align to form channels and
passageways that define the inkjets 108 for the printhead. Larger
cavities align to form larger passageways that run the length of
the jet stack. These larger passageways define ink manifolds 104
that are arranged to supply ink to the inkjets 108. The plates of
the jet stack 100 are stacked in face-to-face registration with one
another and then brazed or otherwise bonded together to form a
mechanically unitary and operational jet stack.
[0020] In one embodiment, each inkjet 108 has an inlet channel that
receives ink from the manifold 104, a reservoir, or other ink
containing structure. The ink flows from the inlet channel into a
pressure chamber or body chamber that is bounded on one side, for
example, by a flexible diaphragm. An electromechanical transducer
is attached to the flexible diaphragm overlying the body chamber.
The electromechanical transducer can be a piezoelectric transducer
that includes a piezo element disposed, for example, between
electrodes that enable firing signals to be received from the
controller 10. Actuation of the piezoelectric transducer with a
firing signal causes the transducer to distend the diaphragm and
urge ink from the pressure chamber to an outlet channel. The outlet
channel includes an aperture 134 formed in a jet stack aperture
plate 140 through which ink drops are ejected.
[0021] During operation, capillary action causes the ink 154 from
the on-board printhead reservoir 61 to fill the ink manifolds 104,
inlet channels, pressure chambers, and outlet channels of the
inkjets 108 and form a meniscus (not shown) at each aperture 134
prior to being expelled from the apertures 134 in the form of a
droplet. The size of the apertures and channels of the inkjets
enable the ink meniscus to be pinned at the aperture 134 until the
inkjet 108 is actuated while preventing air from entering the
printhead 20 through the apertures 134.
[0022] The ink 154 can be purged from the printhead 20 by applying
a positive pressure source or a negative pressure source to ink 154
in the on-board printhead reservoir 61. For example, a positive
pressure applied can be applied through an opening or vent 144 in
the reservoir 61. This positive pressure causes the ink 154 to
discharge through the plurality of inkjets 108 in the jet stack 100
and out of the corresponding plurality of apertures 134 in the
aperture plate 140. A scraper or wiper blade 148 can also be drawn
across the aperture plate 140 to squeegee away any excess liquid
phase change ink, as well as any paper, dust, or other debris that
has collected on the aperture plate 140. The waste ink wiped-off or
otherwise removed from the face of the printhead is typically
caught by a gutter, which ultimately channels or otherwise directs
the ink toward a waste ink collection container (not shown) for
later disposal.
[0023] Referring still to FIG. 1, a piezoelectric sensor
arrangement 50 for sensing fluid level in small volume and
irregular shape reservoirs is shown in operative association with
the printhead 20. The sensor arrangement includes a container that,
in this example, is shown as the on-board ink reservoir 61 of the
printhead 20. The ink reservoir 61 has at least one wall 150 that
forms a volume for containing a fluid, such as the liquid phase
change ink 154. In at least one additional embodiment, the
container is an ink reservoir formed within a liquid ink cartridge.
In this embodiment, the cartridge is configured to store aqueous or
emulsified ink within the ink reservoir and to supply the ink to a
plurality of inkjets when the cartridge is operatively associated
with a printer. In another embodiment, the liquid ink cartridge can
contain ink that is nominally solid at non-elevated temperatures
but is liquid in a functional state when heated with an internal or
external heater.
[0024] The sensor arrangement 50 further includes a plurality of
piezoelectric sensors 160 that are arranged along the at least one
wall 150 of the ink reservoir 61 to interact with the ink 154
within the volume. Note that the printhead illustrated in FIG. 1 is
simplified and not necessarily to scale. The acceptable upper and
lower fluid levels in the printhead are not illustrated, but a
typical sensor arrangement can span such a range. The sensors are
illustrated from the side view, but for a greater level range, the
sensor array can be oriented in the transverse direction.
[0025] Arranging the sensors 160 along the at least one wall 150
can be accomplished by any method that provides fixed spacing
between the plurality of sensors 160. For example, in one
embodiment, the sensors 160 can be fastened to the wall 150 by
using adhesive. In another embodiment, the sensors 160 can be
incorporated in a planar member that is attached to the wall by
using rigid fasteners, such as screws. In yet another embodiment,
the sensors 160 can be attached to the wall by providing a feature
in the wall 150 that enables an interference fit between the sensor
160 and the wall 150 of the ink reservoir 61. In yet another
embodiment, the sensors 160 can be suspended from a cover or panel
above or extended from a shelf or floor below the fluid. The
distance or offset between successive sensors of the plurality of
piezoelectric sensors 160 is discussed in more detail below.
[0026] The sensors 160 can be constructed using piezoelectric film
products or using ceramic resonator material. In the latter
construction, the ceramic resonator materials are coated with
conductive layers to form the piezoelectric element and an
electrical ground return path. A pair of conductors 164 is
operatively connected to each piezoelectric sensor 160. The
conductors 164 are configured to conduct electrical signals to and
from each piezoelectric sensor. For simplicity, a single line is
used to depict the pair of conductors 164 for each sensor 160 of
FIG. 1. The controller 10 is operatively connected to the pair of
conductors 164 from each of the piezoelectric sensors 160 and
configured to activate the sensors through the conductors
operatively connected to each of the sensors. Activation of the
sensors through the conductors enables the controller to identify a
fluid level 168 of the ink 154 from differences between electrical
signals received from each sensor in the plurality of sensors. The
activation of the plurality of sensors is discussed in more detail
below.
[0027] FIGS. 2 and 3 show two embodiments of the distances or
offsets between successive sensors of the sensor arrangement 50.
For simplicity, the figures depict the smallest number of
successive sensors needed to describe the distances and positions
of the sensors relative to one another and the resulting positional
relationship of the sensors near the fluid level 168 of the ink
154.
[0028] FIG. 2 shows a partial view of two sensors in the plurality
of piezoelectric sensors 160 positioned relative to one another at
a distance 202 from one another. The distance 202 enables ink 154
in the volume to cover simultaneously a portion, but not all, of a
surface area 204 of a first piezoelectric sensor 206 of the two
piezoelectric sensors and a portion, but not all, of a surface area
208 of a second piezoelectric sensor 210 of the two piezoelectric
sensors. The portion of the surface area of the first piezoelectric
sensor 206 covered by the fluid 154 is larger than the second
portion of the surface area 208 of the second piezoelectric sensor
210 covered by the fluid 154. In this embodiment, the surface areas
204, 208 of the first and second piezoelectric sensors 206, 210 are
those surfaces that interact with the ink 154 to exploit the
piezoelectric effect of the activated sensors on the materials
adjacent the surfaces of the sensors.
[0029] In the embodiment of FIG. 2, the controller is configured to
activate or excite the first and second piezoelectric sensors 206,
210 through the pair of conductors 164 operatively connected to the
first and second piezoelectric sensors 206, 210. When the first and
second piezoelectric sensors 206, 210 are first excited with an
activation signal from the controller, these sensors distend into
the volume adjacent the sensors to perturb the substance occupying
that volume. The effect of an activated sensor on air in the volume
is different than the effect of the activated sensor on ink in that
volume. Similarly, the effect of the activated sensor on that
volume differs for a sensor almost completely covered by ink and
one that is only partially covered by ink. The substance or
proportions of different substances perturbed by the sensor also
produces a responsive effect in the sensor. This effect generates
an electrical signal in the conductor between the controller and
the sensor that varies in frequency and/or amplitude with regard to
the substance or substance proportions perturbed by the sensor.
These signatures that differ with respect to the response of the
sensor to the material(s) perturbed by an activated sensor can be
obtained empirically for different sensor configurations and types
of sensors and/or inks. Each of these signatures is correlated with
an ink level in the reservoir to enable the controller 10 to
capture a signal from the conductor connecting the controller to a
sensor and identify an ink level at the sensor.
[0030] For example, the activation or excitation of the first and
second piezoelectric sensors 206, 210 enables the controller 10 to
identify a fluid level 168 from a difference between the electrical
signals received as a return or echo from the first piezoelectric
sensor 206 and the electrical signals received as a return or echo
from the second piezoelectric sensor 210. The piezoelectric sensors
can be excited independently where the vibrations induced by the
activated sensor generate a signal from an adjacent non-activated
sensor. Repeating this process with the other sensor establishes
"return" signals that can be compared, enabling determination of
fluid submersion differences that can be translated to a determined
fluid level. This cycle can be repeated any number of times and can
be utilized with any number of sensors excited one at a time or in
any combination. Return or echo signal evaluation is a process that
is generally known in the art.
[0031] FIG. 3 shows a partial view of a third piezoelectric sensor
302 positioned between the first and second piezoelectric sensors
206, 210. The third piezoelectric sensor 302 is positioned at a
first distance 304 to the first piezoelectric sensor 206 and at a
second distance 306 to the second piezoelectric sensor 210. The
first and second distances 304, 306 enable the ink 154 in the
volume to cover simultaneously the portion of the surface area 204
of the first piezoelectric sensor 206, the portion of the surface
area 208 of the second piezoelectric sensor 210, and a portion of a
surface area 308 of the third piezoelectric sensor 302. The portion
of the surface area 204 of the first piezoelectric sensor 206
covered by the ink 154 is larger than the portion of the surface
area 308 of the third piezoelectric sensor 302 covered by the ink
154. The portion of the surface area 308 of the third piezoelectric
sensor 302 covered by the ink 154 is larger than the portion of the
surface area 208 of the second piezoelectric sensor 210 covered by
the ink 154. In this embodiment, the surface areas 204, 208, 308 of
the first, second, and third piezoelectric sensors 206, 210, 302
are those surfaces that interact with the ink 154 to exploit the
piezoelectric effect of the activated sensors on the materials
adjacent to the surfaces of the sensors.
[0032] In a first embodiment of the sensor arrangement depicted in
FIG. 3, the controller is configured to activate or excite the
first, the second, and the third piezoelectric sensors 206, 210,
302 through the pair of conductors 164 operatively connected to the
first, the second, and the third piezoelectric sensors 206, 210,
302, respectively. In this embodiment, the controller sequentially
excites each of the piezoelectric sensors 206, 210, 302 with an
adequate interval pause therebetween that allows the un-powered
sensors to generate signal responses due to the ink motion and
damping characteristics produced during active excitation. The
activation of the first, second, and third piezoelectric sensors
206, 210, 302 enables the controller to identify the fluid level
168 from a difference between the electrical signals received from
the first piezoelectric sensor 206, the electrical signals received
from the second piezoelectric sensor 210, and electrical signals
received from the third piezoelectric sensor 302. In particular,
analysis of the output signals of each sensor based on the ink
motion due to resonance as influenced by the fluid level and the
degree to which fluid covers the surface area of each sensor can be
interpolated as volume level.
[0033] In a second embodiment of the sensor arrangement depicted in
FIG. 3, the controller is configured to activate one of the first,
the second, and the third piezoelectric sensors through the pair of
conductors operatively connected to the activated sensor. For
example, the controller can excite a lower piezoelectric sensor,
i.e., a sensor that is more likely to be submerged in a fluid than
the other sensors in the sensor arrangement, and then monitor all
or some of the nearby sensors and determine from the
characteristics of the signals received from those sensors the
fluid level in the reservoir. The activation of the sensor enables
the controller to identify the fluid level 168 from a difference
between the electrical signals received from the first
piezoelectric sensor 206, the electrical signals received from the
second piezoelectric sensor 210, and the electrical signals
received from the third piezoelectric sensor 302.
[0034] In at least one embodiment of the sensor arrangement
depicted in FIG. 3, the first distance 304 of the third
piezoelectric sensor 302 from the first piezoelectric sensor 206 is
equal to the second distance 306 of the third piezoelectric sensor
302 from the second piezoelectric sensor 210. In an alternative
embodiment, the first distance 304 of the third piezoelectric
sensor 302 from the first piezoelectric sensor 206 is different
than the second distance 306 of the third piezoelectric sensor 302
from the second piezoelectric sensor 210.
[0035] Although only two successive piezoelectric sensors are shown
in FIG. 2 and three successive sensors are depicted in FIG. 3, any
quantity of sensors greater than that depicted in FIGS. 2 and 3 can
be incorporated to achieve a desired fluid sensing resolution. In
embodiments incorporating this greater quantity of piezoelectric
sensors, the distances between successive sensors can be equal,
different, or any combination thereof as long as the surface areas
of the successive sensors interact with the ink fluid level at
least in the manner depicted in FIGS. 2 and 3.
[0036] The piezoelectric sensors of the sensor arrangement are
small enough to allow multiple elements to be used in small and
irregular shape spaces. The spacing and/or angle of the line or
series of piezoelectric sensors establish the resolution capability
of the sensor arrangement. In FIGS. 1-3, the piezoelectric sensor
arrangement is shown as a straight line, but in alternative
embodiments, the arrangement of the sensors can be non-linear. For
example, the sensors can be arranged in a variable radial curve or
other geometric shapes based on the structure of the delivery
system, such as a reservoir in which the container shape is
non-uniform in area or volume at different heights.
[0037] Various attributes of the reservoir or chamber volume to be
measured, such as shape, area to height ratio, and being vented or
un-vented, can influence signal generation and processing to
achieve desired sensor performance. The sensor arrangement
disclosed herein accommodates these variations by enabling
excitation and response signal generation to be optimized for the
application, for example, by optimizing amplitude, frequency,
timing, repetitions, and so forth. Nominal fluid level detection is
correlated to known or calibrated fluid volumes or levels relative
to the sensors when the device is in an expected or nominal
orientation relative to gravity. A sufficient number of sensors in
known positions can also be utilized to determine tilt angle in the
sensor array axis as fewer sensors are fully or partially immersed
when tilted in one direction and a greater number of sensors are
fully or partially immersed in another direction relative to the
nominal fluid level detection. These differences can be correlated
to device or product angle.
[0038] Those skilled in the art will recognize that numerous
modifications can be made to the specific implementations described
above. Therefore, the following claims are not to be limited to the
specific embodiments illustrated and described above. The claims,
as originally presented and as they may be amended, encompass
variations, alternatives, modifications, improvements, equivalents,
and substantial equivalents of the embodiments and teachings
disclosed herein, including those that are presently unforeseen or
unappreciated, and that, for example, may arise from
applicants/patentees and others.
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