Fluid sensing apparatus with a rotatable member utilizing different length light pipes for alternately transmitting a light beam

A apparatus for sensing flow and/or other characteristics of a fluid, including an emitter adapted to project a light beam, a detector adapted to transmit a signal in response to receiving the light beam and a rotatable member for transmitting the beam of light from the emitter to the detector through a quantity of the fluid. Optic fibers/light pipes may be used to transmit light to the emitter from a light source, through the rotatable member and to a processor remote from the detector. The rotatable member may also include reflective and nonreflective zones for transmitting light passing through the fluid to the detector. A plurality of light pipes, blades, emitters and detectors may be used on the rotating member depending on a particular application of the present invention.

The present invention relates generally to fluid sensors that may be 
employed in a variety of devices to include copying and printing machines, 
and more particularly concerns optical sensors capable of determining 
fluid flow rates, density, particulate content, light transmittance, 
spectral attributes and/or other fluid characteristics. 
In particular, systems involving fluid flows may require that a variety of 
components and parameters of those fluids be closely monitored. Arrays of 
various types of fluid sensors are being incorporated into a variety of 
technologically advanced machines; these sensors must be reliable and 
durable, so as to accurately monitor the requisite aspects of moving 
fluids in a variety of environments. Increased diagnostic, control and 
automation capabilities have also made it desirable to position reliable 
light emitter and receptor sensing systems in multiple locations in a flow 
path of a system. The connection of these emitters and receptors by 
power/data cables, optic fibers or other means to the remote data 
collection/analysis points can result cost savings, increased reliability 
and improved overall system performance. 
For example, copying and printing machines using liquid inks, fuser oils or 
other fluids may require sensors to accurately sense and evaluate the 
density, particulate content, light transmittance, flow rates and other 
aspects of the liquids used. In such applications, a flowing material may 
be illuminated with a collimated beam of light emitted from a light 
emitter/optical fiber, preferably provided by an infrared LED (light 
emitting diode), or by variety of light sources. A portion of the light 
directed in this fashion at a fluid can pass through a portion of the 
fluid to a light detector or other sensor, so that flow speed and other 
fluid characteristics may be monitored. 
Various sensors have been devised for sensing various fluid flow parameters 
and conditions, including those described in the following disclosures 
which appear to be relevant: 
U.S. Pat. No. 5,119,132 Patentee: Kroll et al. Issued: Mar. 9, 1993 
U.S. Pat. No. 4,981,362 Patentee: deJong et al. Issued: Jan. 1, 1991 
U.S. Pat. No. 4,793,190 Patentee: Chang Issued: Dec. 27, 1988 
U.S. Pat. No. 4,745,877 Patentee: Chang Issued: May 24, 1988 
U.S. Pat. No. 4,637,730 Patentee: Ponstingl et al. Issued: Jan. 20, 1987 
U.S. Pat. No. 4,193,694 Patentee: Smith Issued: Mar. 18, 1980 
U.S. Pat. No. 4,101,874 Patentee: Denison et al. Issued: Jul. 18, 1978 
U.S. Pat. No. 4,037,973 Patentee: Carr Issued: Jul. 26, 1977 
U.S. Pat. No. 2,599,201 Patentee: Rubenstein, et al Issued: Jun. 3, 1952 
U.S. Pat. No. 2,147,309 Patentee: Moore Issued: Feb. 14, 1939 
U.S. Pat. No. 1,998,495 Patentee: Fagan Issued: Apr. 23, 1935 
U.S. Pat. No. 1,964,784 Patentee: Nelson, et al Issued: Jul. 3, 1934 
U.S. Pat. No. 5,119,132 discloses a toner monitor which is periodically 
caused to read a simulated nominal toner concentration. A difference 
between the monitored output and the expected toner concentration is 
applied to a compensation device. The simulated nominal toner 
concentration signal is obtained by periodic alignment of the toner 
monitor with a magnetically permeable member. 
U.S. Pat. No. 4,981,362 discloses a method and apparatus for measuring the 
particle concentration in a fluid that is passed between a reciprocally 
movable window and a single photodetector. A collimated beam of light is 
directed through the window and fluid to the photodetector. The window is 
moved from a first predetermined location to a second predetermined 
location to vary the light beam path length, the ratio of the two signals 
provides the data needed to determine the particle concentration in the 
fluid. A rubber "O" ring around the cylinder seals the fluid inside the 
sensor. A single set of optics, detectors and amplifiers is used, so as to 
eliminate errors that may arise from a relative drift between two 
detectors. 
U.S. Pat. No. 4,793,190 discloses a device for measuring and indicating 
fluid flow around a flow bend which includes a housing which is connected 
with the outer side of the curvature of the flow bend. There is a rotor 
with a number of substantially radial blades which is free to rotate about 
a fixed axis in the flow cavity. The hydrodynamics of the flow around the 
bend generates a secondary circulating flow in the cavity which induces a 
vortex flow; the vortex strength increases with the rate of the bend flow. 
The rotor, which is substantially co-axial with the vortex, is driven by 
the vortex to turn in the flow cavity. The rotating speed of the turning 
rotor is monitored by an electrical sensor which provides the flow rate 
measurement through a predetermined correlation. For sight flow indication 
application a view port is provided for visual observation of the rotor 
which provides a positive indication of fluid flow in the flow band. 
U.S. Pat. No. 4,745,877 discloses a rotary sight flow indicator which 
provides a visual indication of fluid flow and of the flow direction by 
the rotation of a shrouded cross-flow rotor. The sight flow indicator 
consists of a housing with a cavity containing the rotor and its shroud, 
and at least one view window. The rotor comprises a number of radial 
blades attached to a rotatable shaft. 
U.S. Pat. No. 4,637,730 discloses an optical absorptiometer which is 
characterized by a light source unit of a broad wavelength having a source 
of constant energy which is collimated into two light beams, one of which 
is transmitted through the liquid to be measured, and another beam which 
is transmitted through a conductor and acts as a reference beam, and a 
detector unit which contains two photocells, one photocell for measuring 
the beam transmitted through the liquid to be measured, and another 
photocell which measures the reference beam. 
U.S. Pat. No. 4,193,694 discloses a color monitoring device is provided for 
measuring the concentration of a colored component in a flowing gas or 
liquid stream in which polychromatic light is passed through a frosted 
lens, then through a transparent sight tube through which the flowing 
stream passes. The light then passes through a second frosted lens, then 
through a sight mask which divides the light into two beams, one beam then 
passing through a first filter and the second beam passing through a 
second filter, the light beams passing through the filters then being 
directed to a first then second photoconductor. 
U.S. Pat. No. 4,101,874 discloses a small diameter transparent visible 
fluid flow indicator suitable for mounting behind an opening in an 
instrument panel contains a six-bladed wheel which rotates according to 
the flow of fluid passing through orifices in the indicator housing. Each 
of the six blades of the wheel contains a small magnet oppositely 
polarized from the magnets in the adjacent blades to create alternate 
magnetic fields that pass through a pickup coil embedded in the housing 
which provides both a visible indication of fluid flow and also controls 
an alarm if the fluid flow stops or varies from some predetermined value. 
U.S. Pat. No. 4,037,973 discloses a device for measuring particles in a 
liquid, utilizing a light source for the illumination of two detectors, 
one through a relatively short distance and the other through a relatively 
long distance. A reference signal produced by the first cell is supplied 
to an amplifier and indicator, and a measurement signal produced by the 
second detector is supplied to the amplifier and indicator. The two 
detectors and light source and contained in a small housing, remote from 
the amplifier and indicator. 
U.S. Pat. No. 2,599,201 discloses a fluid flow indicator and more 
particularly an axial flow turbine oil line flow indicator. The indicator 
comprises generally a tubular casing encasing an elongated rotor or vane. 
The casing is formed with an integral inwardly directed radial flange for 
providing a stop for the rotor to prevent displacement thereof from the 
casing under the influence of fluid flow and is secured within suitable 
coupling members for facilitating the insertion of the indicator in a 
fluid flow line. 
U.S. Pat. No. 2,147,309 discloses a flow indicating device and more 
particularly to that type of indicating device used in connection with 
gasoline pumps and commonly called a spinner. The present invention 
provides a flow indicator in which the indicating member will rotate at a 
substantially uniform speed regardless of the total amount of flow of the 
fluid through the discharge line so long as said total amount does not 
decrease below a predetermined minimum quantity. 
U.S. Pat. No. 1,998,495 discloses a liquid flow indicator and more 
particularly a device for use with gasoline dispensing stations. The 
present invention in preferred form comprises the provision of a removable 
top carrying the top bearing for a vertical shaft of the indicator symbol 
and wherein the vertical shaft comprises a tubular member with one end 
terminating above the line of vision through the transparent chamber and 
the other end terminating in the line of flow of the gasoline in such 
manner as to provide an aspirating action through the tubular member which 
at all times withdraws the fluids from the upper end of the transparent 
chamber whereby the entrapment of air in the transparent chamber is 
completely avoided. 
U.S. Pat. No. 1,964,784 discloses a device adapted to be interposed in a 
liquid circuit and containing an element which is rotatable by the moving 
liquid and visible through a transparent portion of a housing. More 
specifically, the invention is directed to a particular type of rotatable 
member which is devised to operate in coaxial relation to the liquid 
stream. The housing for this member is specially formed so that its 
removal may be accomplished without disturbing or dismantling the housing. 
In accordance with one aspect of the present invention, there is provided 
an apparatus for sensing a fluid, including an emitter adapted to project 
a light beam, a detector adapted to transmit a signal in response to 
receiving the light beam and a rotatable member for transmitting the beam 
of light from the emitter to the detector through a quantity of the fluid. 
Other aspects and features of the present invention will become apparent as 
the following description proceeds and upon reference to the drawings, in 
which: 
FIG. 1 is an elevational view, partially in section, showing a sensor 
arrangement in accordance with the present invention; 
FIG. 2 is an elevational view, partially in section, showing another 
embodiment of a sensor in accordance with the present invention; 
FIG. 3A is an elevational view, partially in section, showing a sensor in 
accordance with the present invention; 
FIG. 3B is a sectional elevational view taken along the line in the 
direction of the arrow 3B of FIG. 3A; 
FIG. 3C is an elevational view, partially in section, showing a sensor in 
accordance with the present invention; 
FIG. 3D is a sectional elevational view taken along the line in the 
direction of the arrow 3D of FIG. 3C; 
FIG. 4A is an elevational view, partially in section, showing another 
embodiment of a sensor of the present invention; 
FIG. 4B is a perspective view, partially in section, showing a sensor 
arrangement shown in FIG. 4A; 
FIG. 5 is an elevational view, partially in section, showing another 
embodiment of a sensor of the present invention; 
FIG. 6 is a perspective view, partially in section, showing another 
embodiment of a sensor of the present invention; and 
FIG. 7 is a perspective view, partially in section, showing another 
embodiment of a sensor of the present invention.

While the present invention will hereinafter be described in connection 
with preferred embodiments thereof, it will be understood that it is not 
intended to limit the invention to these embodiments. On the contrary, it 
is intended to cover all alternatives, modifications and equivalents, as 
may be included within the spirit and scope of the invention as defined by 
the appended claims. 
For a general understanding of the features of the present invention, 
reference is made to the drawings. In the drawings, like reference 
numerals have been used throughout to identify identical elements. 
FIG. 1 shows a cross sectional view of combined flow rate and fluid density 
sensor 1. Support member 4 is shown connected to flow tube 3 at two 
positions. A rotatably mounted member, prop 6, is mounted on axle 8. Axle 
8 is rotatably attached to support 4, such that prop 6 turns freely 
according to fluid flow through blow tube 3. Light pipes 10 and 12 are 
formed within interior areas of prop 6, and pass through the blades or 
fins of prop 6 as shown. Emitter 14 emits light such that when light pipe 
10 or 12 aligns with emitter 14 and detector 16, light is transmitted 
through the fluid across the gap between the light pipe ends. 
Alternatingly, light thereafter passes through each light pipe 10 or 12 
and across the gaps at the ends of each light pipe and into detector 16. 
Light pipe 12 is shown in FIG. 1 as being slightly shorter than light pipe 
10, such that when light pipe 12 is aligned with emitter 14 and detector 
16, the light beam must pass through a greater fluid gap or distance than 
when light pipe 10 is aligned with emitter 12 and detector 16. In certain 
applications, it may be desirable to maintain uniform or laminar flow 
through tube 3. In other applications, fluid mixing according to movement 
of prop 6 may be desired. 
As the fluid moves through flow tube 3, pressure on the blades of prop 6 
causes prop 6 to rotate. As prop 6 rotates, the light pipes 10 and 12 will 
alternately align with emitter 14 and detector 16. The total fluid gap 
will be different in each case due to a difference in the length of light 
pipes 10 and 12. The sensed fluid gap includes the gaps at each end of 
each light pipe; thus, the total fluid gap is the length of the light pipe 
minus the distance between the source and detector. This two-gap system 
allows for some variation in the exact position of the light pipes while 
maintaining a constant total fluid gap, thus relaxing the tolerances on 
the bearing system for prop 6 while maintaining accurate measurement. As 
fluid flows through sensor 1, prop 6 is forced to rotate such that flow 
rate, density, particulate content and a variety of other fluid attributes 
may be detected, such as described in U.S. Pat. No. 4,981,363 to deJong et 
al., incorporated herein by reference. Prop 6 may be cast plastic, rubber, 
nylon, metal or other material affixed about the light pipes. Prop 6 may 
be fabricated of two halves or portions, and then coupled, heat cast or 
otherwise mated about light pipes 10 and 12. Alternatively, prop 6 may be 
cast from a translucent or transparent material and coated with a 
light-retaining material, so as to transmit light from emitter 14 to 
detector 16. Data/power lead 18 connects emitter 14 to remote power and/or 
data analysis devices (not shown); data and power lead 20 may likewise 
provide a signal from detector 16 (which may be a photosensor) to a 
processor, power source, data analysis sensor, controller or other device 
(not shown), such as described in U.S. Pat. No. 4,981,363 to deJong et al. 
or in U.S. Pat. No. 4,037,973 to Carr Fiber optic members (not shown in 
FIG. 1) may be used to transmit light from a remote light source to 
emitter 14 and from detector 16 to remotely positioned signal or light 
sensors/processors (also not shown in FIG. 1). 
The concentration of absorbing and/or scattering particles in a fluid can 
be measured optically using a detector coupled with the sensors of the 
present invention using Beer's law; T/T.sub.0 =exp(a.times.c.times.l), 
where "T.sub.0 " is the transmitted light intensity at zero concentration, 
"T" is the transmittance at the unknown concentration ("c"), "l" is the 
distance through the fluid that the transmitted light travels and "a" is 
the absorption coefficient. T.sub.0 can be determined only once when 
continuous concentration sensing is conducted; light source intensity 
variations or other extraneous mechanisms and factors such as 
transmittance reduction, optical filming and others can cause erroneous 
measurements of concentration. The varied length, multi-light 
pipe/reflective area embodiments of the present invention can effectively 
employ such a single detector and amplifying circuit. In the embodiment of 
the present invention shown in FIG. 1, a single light source, emitter 14, 
illuminates two light pipes positioned so that the light travels through 
two different distances in the fluid. A single light detector provides all 
necessary data such that a comparison of the ratio of the two detected 
signals can eliminate T.sub.0 from the equation, thus providing a signal 
that is relatively insensitive to light source intensity, accumulation of 
material on the optical surfaces and other factors. (Other embodiments of 
the present invention, such as those shown and described in conjunction 
with FIGS. 3A, 4A and 5-7, also can rely on intermittent use of single 
emitter and detector systems.) When two or more detectors are used (each 
with their own amplifier circuits), these detectors may drift with respect 
to each other and cause an error in the ratio of the transmittance. 
FIG. 1 includes a movable prop 6 that requires no external electrical or 
other hook-ups to the emitter or detector to vary the fluid gaps. No 
mechanical fluid seals that may develop leaks over time are required, as 
flow tube 3 completely contain the fluid without the need for "O" rings or 
other such seals. In addition to measuring the concentration of light 
absorbing and/or scattering particles in a fluid, the embodiment shown in 
FIG. 1 also provides for flow measurement, according to the frequency of 
the intermittent passing of light from emitter 14 to detector 16 by light 
pipes 10 and 12. Again, a remote processor, controller or other device 
(not shown) can monitor for peaks in voltage caused by the various levels 
of transmitted light; each peak signal by detector 16 would correspond to 
light passing through one of the light pipes. Again, the frequency of the 
voltage peaks indicates how rapidly the wheel is turning so as to provide 
a measure of fluid flow. 
FIG. 2 shows an elevational view of another embodiment of the combined 
fluid flow rate and density sensor of the present invention. Sensor 50 is 
shown with an upper tube wall portion 62 and lower tube wall portion 60; 
shaft 52 is mounted on trailing shaft support 54 and leading shaft support 
56. Fins 58 on shaft 52 cause shaft 52 to rotate in the direction 
indicated in response to the flow of fluid through sensor 50. As shaft 52 
rotates, the ends of light pipe 64 moves past light emitter 66 and light 
detector 68 such that the flow rate and density of the fluid flowing 
through sensor 50 may be determined by a remote sensor or detector (not 
shown). Sensor 50 is shown in FIG. 2 using a single pipe 64 as shown; 
other single light pipe (FIG. 3C) or multiple light pipe (FIGS. 1, 3A or 
5) configurations may also be used to detect flow rate and/or fluid 
characteristics. 
FIG. 3A shows a 6 blade, 3 light pipe assembly. Blades 272, 274 and 276 are 
shown fixed on light transmissive shaft 52, so as to make up a 6 blade 
prop 264. An emitter 66 intermittently projects light through each of 
blades 272, 274 and 276 as they rotate past, such that detector 68 
receives light as it passes through the transparent interior portion of 
each blade. FIG. 3B shows a cross-section of blade 276 taken in the 
direction of the arrows shown in FIG. 3A, in which a hollow or light 
transparent, translucent or otherwise transmissive portion 278 is 
surrounded by a opaque area 280. The 6 blade configuration of prop 264 as 
shown in FIGS. 3A and 3B permits accurate detection of slower moving fluid 
flows. The length of one (or more) blades of the sensor may vary as 
described in conjunction with FIG. 1, or may be the same. 
FIG. 3C shows another embodiment of a fluid flow sensor of the present 
invention. Blade members 372 and 376 are shown with a fiber optic member 
368 extending therethrough. Each blade 372 and 374 is affixed to shaft 52 
so as to form prop 250. As each light pipe 368 passes emitter 66, light is 
transmitted therethrough so as to be detected by detector 68. FIG. 3D 
shown a cross-sectional view of blade 374 of FIG. 3C taken in the 
direction of the arrows shown. Optic fiber 368 passes through the solid 
portion 373 of blade 374. The embodiment of the present invention shown in 
FIGS. 3C and 3D is well suited to rapid fluid flow, due to its 
fluid-dynamically formed blades 272 and 274. 
FIG. 4A shows another embodiment of the flow sensor of the present 
invention. Blades 154 are mounted to a shaft 156 which rotates in flow 
sensor 150. Light emitters 162 and 166 emit light into the ends of blades 
154 such that light can be detected and analyzed by light receptors 164 
and 168. Fluid flows into the interior body area 152 of sensor 150 via 
conduit 158, where it causes blades 154 to rotate about pivot 156. Fluid 
is thereafter released from interior body area 152 from sensor 150 by 
conduit 160 in the direction of the arrow shown. FIG. 4B shows a 
perspective view of the flow sensor of the present invention, in which 
fluid flows into sensor 150 via conduit 158 in the direction of arrow 
shown. Fluid then circulates through the central body portion 152 in the 
direction the of arrow shown, exerting pressure on blades 154 so as to 
rotate them about pivot 156 in the direction of fluid flow. Fluid is 
thereafter released from sensor 150 by conduit 160 in the direction of the 
arrow shown. 
FIG. 5 shows another embodiment of flow sensor 200 of the present 
invention. Shaft 202 is rotatably mounted in flow sensor 200 by brackets 
204 and 206. Prop members 208 are positioned in a narrow portion of flow 
sensor 200; the positioning of props 208 in such a constricted flow zone 
of flow sensor 200 causes shaft 202 to rotate more rapidly according to 
the increased flow rate in this zone. The use of multiple props 208 
rotates light pipes 210 and 211 past light emitter 214 and light detector 
216 in even highly viscous fluids. As shaft 202 rotates, light pipes 210 
and 211 rotate pass emitter 214 and detector 216, so as to permit flow 
rate sensing, particulate component detection, specular analysis and other 
sensing operations. 
FIG. 6 shown another embodiment of the flow sensor 280 of the present 
invention. Shaft 286 of sensor 280 is rotatably mounted on support member 
288; prop member 290 rotates in direction "R" according to fluid flow in 
direction "F" as shown. Ring 284 is attached as shown to the ends of prop 
290, and includes on its outer circumference reflective areas 291 and 
nonreflective timing marks 292. Light from a remote light source (not 
shown) is emitted from emitter optic fiber 294 towards the circumference 
of ring 284. As ring 284 rotates with prop 290 in response to fluid flow, 
receptor optic fiber 296 transmits light reflected by reflective areas 291 
from emitter optic fiber 294, and similarly, detects the appearance of 
timing marks 292. A remote sensor (not shown) evaluates the pulses of 
light provided by receptor optic fiber 296. Further, according to the 
frequency of timing marks 292, the flow rate of the fluid through sensor 
280 is detected. 
In alternative embodiments (not shown in FIG. 6), selected or alternating 
reflective areas 291 may be recessed into ring 284 such that the fluid gap 
through which light passes can be uniformly varied, such as with the 
multiple light pipes shown in FIG. 1 of the present invention. In another 
embodiment, timing marks 292 may be holes or apertures in ring 284 that do 
not reflect light from emitter optic fiber 294 to receptor optic fiber 
296. As is also adaptable to other embodiments of the present invention 
such as those shown in FIGS. 1-5 and 7, emitter optic fiber 294 and 
receptor optic fiber 296 may direct light from the LED light, infrared, 
ultraviolet, white, spectral or other light source through the fluid. As 
shown in FIG. 6, sensor 280 precisely positions optic fiber 294 to direct 
columnated light towards photoreceptor ring 284. In alternative 
embodiments, blades (such shown in FIGS. 3A and 3C) may be equipped with 
reflective tip facets similar to reflective areas 291 shown in FIG. 6 to 
reflect light to receptor optic fiber 296. 
FIG. 7 shows another embodiment of the sensor/mixing chamber of the present 
invention. Sensor/mixing chamber 300 includes a mixing prop 310, with 
light pipes 312 and 314 extending therethrough. Prop 310 is mounted on 
shaft 316, rotatably held in position on support member 320. Shaft 316 is 
rotated by motor 318, which is fixed by supports (not shown) to 
sensor/mixing chamber 300. As the ends of light pipes 312 and 314 pass 
emitter 322 and detector 324, a variety of the attributes of the fluid 
being mixed by prop 310 can be evaluated, as previously described in 
association with FIG. 1. The sensors shown and described in conjunction 
with FIGS. 1-7 may be optically connected with fiber optic tubes to 
centralized and/or remote emitter and receptor assemblies capable of 
servicing a plurality of light emitters and receptors. 
While the invention has been described in conjunction with a specific 
embodiment thereof, it is evident that many alternatives, modifications, 
and variations will be apparent to those skilled in the art. Accordingly, 
it is intended to embrace all such alternatives, modifications and 
variations that fall within the spirit and scope of the appended claims.