Temperature sensing automatic faucet

An automatic temperature regulating system for a faucet, especially an automatic faucet in which water flow is activated by a touchless switch, is constructed to operate so as to compensate for lag time of hot water arriving from the hot water supply. The apparatus includes at least one temperature sensor, this first sensor being disposed in the hot water supply line upstream of the hot water valve. A more sophisticated apparatus includes a second-temperature sensor disposed for sensing the temperature of the outlet water. Methods of automatically regulating temperature of output water from a remote-activated or touchless-switch-activated outlet to compensate for lag in arrival of hot water from the hot water source, are also described.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to automatic faucets and particularly to improved 
temperature control of the water flow from such faucets. 
2. State of the Art 
Automatic faucets, in which the water flow is started and stopped according 
to the presence of a user's hands near the faucet, are known. Examples 
include the following U.S. Pat. Nos. 5,074,520, 5,062,164, and 4,886,207 
to Lee et al., U.S. Pat. No. 5,309,940 to Delabie et al., U.S. Pat. No. 
4,682,628 to Hill, U.S. Pat. No. 5,095,941 to Betz, U.S. Pat. No. 
4,928,732 to Hu, U.S. Pat. No. 5,050,641 to Shwu-Fen, U.S. Pat. No. 
4,688,277 to Kakinoki et at., U.S. Pat. No. 4,767,922 to Stauffer, U.S. 
Pat. No. 3,480,787 to Johansen, and U.S. Pat. No. 3,576,277 to Blackmon. 
Additionally, UK patent publications Nos. 2 226 105 A by Wu, 2 226 104 A 
by Wu, and 2 255 625 A by Bosch, and European patent publication No. 0 387 
471 A2 by Nilsson and Maattanen also disclose automatic faucets. 
However, most prior art automatic faucets have disadvantages. In some 
cases, installation of the faucet requires construction of additional 
plumbing and/or electrical lines, making retrofitting of conventional 
faucets expensive and tedious. In other cases, the temperature of the 
water from the faucet is not satisfactorily regulated. 
First, the water standing in a hot water line prior to the faucet being 
turned on will typically be cooler in temperature than the hot water 
supply. Thus, if the desired outlet water temperature is warm or hot, a 
higher proportion of flow from the hot water valve is needed to produce 
outlet water of the desired set temperature when the faucet is first 
turned on. In a conventional manually operated faucet, the user 
compensates by first opening the hot water all the way, and then as the 
temperature of the outlet water rises, reducing the hot water flow and 
opening the cold water valve. However, in a faucet which is activated by a 
touchless switch, the user cannot, or does not wish, to manually adjust 
the flows of hot and cold water. 
In many automatic faucets, the relative flows of hot and cold water are 
fixed over the period of activation. That is, when the faucet is turned 
on, the hot and cold valves open to respective positions computed to 
provide water of the set temperature assuming that the hot water is at the 
temperature of the hot supply. Thus, the water which initially leaves the 
outlet is usually colder than the set temperature. Especially in winter, 
or if the plumbing is proximal to air-conditioning or refrigeration units, 
this temperature can be unpleasantly cold. If the period of use is brief, 
the water at the outlet may never reach the set temperature. If the user 
tries to wait for hotter water to arrive, water is wasted. In many areas 
of the country water conservation is a high priority. Or, if the user 
removes his hands from the faucet area while waiting for warmer water to 
arrive, the flow of water may be turned off by the automatic sensor. 
Further, most such faucets have temperature sensors only in the mixing area 
downstream of both the cold and hot inputs. A sensor so located will sense 
a cool or cold temperature when the water flow is activated, and typically 
the faucet will respond by increasing the proportion of hot water coming 
to the mixing area. This can result in an overshoot in temperature of the 
water delivered from the spout, to a temperature that is painfully hot and 
even scalding. Again responding only to the temperature of the mixing 
area, the faucet may overcompensate downward, delivering water that is 
cooler than the set or desired temperature. Thus, the temperature of the 
water at the output of the faucet may fluctuate initially between too hot 
and too cold, before finally achieving the set output temperature. 
Accordingly, a need remains for an automatic mixing faucet apparatus which 
delivers water at a uniform preset temperature throughout the period of 
activation, without large over- or under-shoots and which follows changes 
in the temperature of water in the hot water line immediately upstream of 
the mixing area. A need also remains for a temperature regulating system 
for an automatic faucet, which compensates for the lag time of arrival of 
hot water. It is desirable that the automatic faucet apparatus and the 
temperature regulating system should be easily retrofitted to a 
conventional faucet. 
SUMMARY 
The invention comprises an automatic temperature regulating system for a 
faucet in which water flow is activated by a touchless switch, and an 
automatic faucet apparatus including the automatic temperature regulating 
capabilities. The invention also provides a method of automatically 
regulating temperature of output water from a remote-activated or 
touchless-switch-activated outlet, which compensates for lag time of hot 
water arriving from the hot water supply. In a preferred embodiment, the 
automatic temperature regulating system provides for selection of the 
preset temperature of the output water by a user. 
A basic automatic faucet system includes a hot water line, a cold water 
line, a mixing region to which the hot and cold water lines are connected, 
and a spout or outlet connected downstream of the mixing region, which 
delivers a flow of water to a user location such as a basin. A hot water 
valve controls the flow of hot water into the mixing region, and a cold 
water valve similarly controls the flow of cold water. A touchless switch 
sensor is disposed for sensing an object such as a user's hands in a 
command location. The sensor location will typically, though not 
necessarily, be proximal to or identical to the user location. 
In the temperature regulating system of the invention, a first temperature 
sensor is located to sense the temperature of water in the hot water line 
just upstream of the mixing region. A controller is connected to receive 
signals from the first temperature sensor and the touchless switch, and to 
control the hot and cold water valves. The controller computes hot and 
cold water valve settings to achieve a preselected temperature, and 
activates the hot and cold water valves to the appropriate settings. The 
controller is further constructed to determine the hot and cold water 
valve settings according to whether the temperature at the first 
temperature sensor is within an acceptable range of the expected hot water 
source temperature. If not, due to cool water standing in the pipes, the 
controller reduces or stops the cold water flow until the first 
temperature reaches the expected hot water temperature. 
Optionally but desirably, a second temperature sensor is located to sense 
the temperature of water in the mixing region. In this embodiment, the 
controller is further constructed to vary the respective flows of hot and 
cold water to bring the second temperature to the preset outlet 
temperature, using the temperature information provided by both 
temperature sensors. The controller is particularly constructed to 
compensate for the lag time of arrival of hot water in the mixing zone 
from the hot water source. 
In a preferred embodiment the automatic temperature regulating faucet 
apparatus, including hot and cold water valves, temperature sensors, 
touchless switch and controller, is constructed for retrofitting to a 
conventional faucet installation without requiting additional water lines 
or electrical lines other than standard 120 volt AC.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
As shown in FIG. 1, a preferred embodiment of an automatic faucet system 
with adjustable automatic temperature regulating capability includes an 
outlet or spout 100 connected to a hot water line 102 and a cold water 
line 104. Hot water line 102 and cold water line 104 connect at a "T" 
junction 105 to an outlet segment 106, which terminates in the spout 100. 
Junction 105 and outlet segment 106 together constitute a mixing zone, in 
which flows of water from the hot and cold water lines combine before 
exiting the spout. A hot water control valve 108 controls a flow of water 
from a hot water supply (not shown), and a cold water control valve 110 
controls a flow of water from a cold water supply (also not shown). A 
touchless switch 112 is positioned for activation by a user whose hands 
are in the vicinity of the spout 100. A water temperature selector 114 is 
positioned near the user location or sink (not shown) into which water 
flows from the spout 100. A first temperature sensor 116 is disposed in 
the hot water line 102 upstream of the hot water control valve 108. A 
second temperature sensor 118 is disposed in the mixing zone downstream of 
the junction 105. 
A controller 120 is communicatively connected to receive and/or read 
signals from the touchless switch 112, from the temperature selector 114, 
and from both temperature sensors 116, 118. Controller 120 is also 
connected to control the hot water valve 108 and the cold water valve 110, 
and to receive electrical power from an electrical power source which is 
here embodied as a conventional 120-volt AC outlet 122, modified with a 24 
volt AC transformer 124. 
Controller 120 is constructed to activate hot water valve 108 and cold 
water valve 110 in response to receipt of an "on" signal from the 
touchless switch 112. Controller 120 is further constructed to regulate 
the temperature of the outlet water by varying the respective amounts of 
water flowing through hot water valve 108 and cold water valve 110 in 
accordance with the values of hot water temperature and outlet water 
temperature read respectively by the hot water sensor 116 and the outlet 
water sensor 118. The controller varies the relative flows from the hot 
and cold water valves so as to compensate for the lag time of hot water 
arriving from the hot water supply. 
The controller determines the initial hot and cold valve settings using the 
temperatures detected in the hot water fine by sensor 116 and in the 
mixing zone by sensor 118. As the faucet stays on and hotter water from 
the hot water supply reaches the sensor 116, the controller changes the 
valve settings to decrease the proportion of hot water flow. The 
temperature regulation process which the controller is constructed to 
follow also includes a feedback-loop-type process based on the temperature 
sensed by sensor 118 near the outlet. The operation of controller 120 is 
described in greater detail subsequently, with reference to the flow chart 
of FIG. 2. 
Desirably, the faucet apparatus further includes a water temperature 
display 126, which displays the temperature detected by sensor 118 near 
the spout 100. The temperature display may be connected to the controller 
as shown in FIG. 1, or alternatively may be connected directly to the 
sensor 118. By observing the temperature reading of the display 126, a 
user can wait until the water temperature reaches a comfortable level 
before immersing his hands. 
The hot water and cold water valves 108, 110 are variable-flow valves 
constructed to provide selectable flow rates. In a working model of the 
embodiment of FIG. 1, the VA-8051 solenoid-actuated valve from Johnson 
Controls, 2255 South Technology Parkway, West Valley City, Utah 84119, is 
used. However, variations of the apparatus using other types of valves 
such as continuous, duty-cycle, or incrementally-controlled valves, are 
within contemplation. 
The touchless switch 112 can be any suitable touchless switch compatible 
with the environment of the faucet, as known in the art. Known types of 
touchless switches include active infrared switches, in which the user's 
hand reflects a standing infrared beam into an infrared light detector; 
passive infrared switches, in which a user's hand blocks an infrared beam 
from reaching an infrared detector; and inductive triggers. In a working 
model of the system of FIG. 1, a Radio Shack Invisible Beam Entry Alert, 
catalog #49-311 switch is used. Another suitable Radio Shack switch is the 
Pulsed Infrared Invisible Beam Intrusion Sensor, catalog #49-551A. A 
touchless switch with a sensor which may be attached directly to the 
faucet outlet is another useful choice. 
The controller can be any suitable logic chip having the necessary inputs 
and outputs for communicating with the temperature sensors, valves, and 
touchless switch, and programmable to execute the functions as outlined. 
The controller has code directing execution of temperature regulation 
physically embedded within it, as known to those of skill in the art. In 
the present working embodiment, the controller is a DS5000 microcontroller 
chip available from Systronix, Inc, Salt Lake City, Utah. However, other 
types of chip such as a discrete logic chip, or a custom-designed chip, 
could be used. 
FIG. 2 outlines the steps of one embodiment of a temperature regulating 
method or process which the controller 120 may be constructed to execute. 
The process is initiated by the controller upon receipt of an "on" signal 
from the touchless switch indicating that water flow is to be activated 
(step 200). The controller then reads temperatures A and B from sensors 
116 and 118, respectively, and also reads the temperature set point from 
the water temperature selector 114 (steps 202 and 204). Steps 202 and 204 
may be performed in the reverse order. Next, the controller determines 
initial valve settings H and C, which respectively are the settings for 
the hot water valve and for the cold water valve which should result in 
the mixed, output water having the desired set point temperature, based on 
the temperatures A and B (step 206). The controller then signals the hot 
and cold valves to open to their respective initial valve settings (step 
208). 
In step 210, the controller reads the temperatures A of the hot water and B 
of the output water. The controller then asks whether B differs 
significantly from the set temperature (step 212), and if "Yes", the 
controller goes on to determine new valve settings H and C using the new 
readings of A and B (step 214). Continuing on this branch, the controller 
then signals the hot and cold valves to operate according to the new valve 
settings (step 216). Following step 216, the controller returns to step 
210. 
Alternatively, if in step 212 the answer is "No", the controller asks 
whether the new value of A differs significantly from the immediately 
previous value of A (step 220). If "Yes", the controller goes on to steps 
214 and 216, determining new valve settings and setting the hot and cold 
water valves to those settings. The controller thus cycles through the 
steps of checking the temperatures of the two sensors and comparing output 
temperature B to the temperature set point, until an "off" signal is 
received from the touchless switch indicating that the water flow is to be 
terminated. The manner by which triggering of the "off" signal is 
accomplished varies according to the type of touchless switch used and the 
specific instructions embedded in the microcontroller, as will be apparent 
to those of skill in the art. In response to the "off" signal, the 
controller closes both the hot and cold water valves. 
The steps 206 and 214 of determining valve settings can be performed in 
different ways. For example, the settings can be determined from a 
two-dimensional temperature table which cross-correlates the hot water 
temperature (temperature A), the cold water temperature and the 
temperature set point (the desired output temperature), with the settings 
for both the hot and cold water valves. The cold water temperature could 
be assumed to be a typical "room temperature water" value, a different 
value according to the local environment, such as 55.degree. F. which is 
an average normal temperature of underground waterlines. Or the initial 
temperature of water standing in the mixing zone (temperature B.sub.o 
sensed by sensor 118 at the time the "on" signal is received) could be 
used as the cold water temperature. The look-up table can be constructed 
empirically, or by using an algorithm which takes into account the volumes 
of hot and cold water flow for particular valve settings, as will be 
apparent to the typical skilled artisan. A temperature table constructed 
using an algorithm could also be refined by empirically testing the 
system. 
In a highly refined embodiment, there could be a third temperature sensor 
disposed in the cold water line, and the controller would be connected to 
read this third temperature sensor. An algorithm for this situation would 
use the cold water temperature in addition to the hot water temperature 
and the set point temperature. A temperature table for such an embodiment 
would be a three-dimensional look-up table. 
Alternatively, the controller could itself be constructed to compute the 
valve settings from the set point temperature and hot water temperature A 
using an appropriate algorithm. The algorithm could be refined for systems 
having different water flow volumes and by empirical tests. Extension to 
the more sophisticated version having the third temperature sensor in the 
cold water line would be a simple matter for the skilled artisan. However, 
at present the two-sensor system is preferred, as it is less expensive and 
will produce adequate temperature regulation in most faucet systems. 
FIG. 3 illustrates an alternate, less expensive embodiment substitutes a 
proportioning or mixing valve 300 in combination with hot water and cold 
water binary valves (valves operable only between an "on" state and an 
"off" state) for the temperature selector 114 and the variable-flow hot 
and cold water valves 108, 110 (FIG. 1). Also, this embodiment lacks an 
outlet water temperature display. Further, the controller 306 of the 
embodiment of FIG. 3 is constructed somewhat differently. The 
proportioning valve 300 is in a permanently open state, and the relative 
flows of hot and cold water are fixed at the time of installation to 
provide a satisfactory mixture based on the average temperatures of water 
from the hot water supply (when the hot water is "up") and water from the 
cold water supply. For example, when both hot and cold water are "up", a 
mixture of 50% hot water and 50% cold water may produce outlet water which 
is comfortably warm. Since the proportion of hot to cold water flow is 
fixed, the controller compensates for the lag time of hot water arriving 
from the hot supply by opening only the hot water binary valve when either 
of temperatures A or B is too low. Once temperature A reaches the maximum 
temperature of water from the hot supply, or temperature B reaches the set 
temperature for which the proportioning valve is set, the controller opens 
the cold water valve 304, while keeping open the hot water binary valve 
302. 
In an alternate embodiment, the proportioning valve 300 could be eliminated 
and the controller 306 would then be constructed to operate the cold and 
hot water binary valves according to a duty cycle, the specific duty cycle 
being computed according to the sensed temperatures A or B. Still another 
embodiment would substitute a three-way control valve for the two binary 
valves. 
In another alternate embodiment, the outlet water sensor is eliminated, and 
the controller only compares temperature A to the temperature of the hot 
water supply which is specified in the controller's memory. In this 
embodiment, the outlet temperature sensor 118 may be eliminated, or may 
function as a fail-safe. In the latter case, if temperature B rose above 
the preset temperature, as might occur if there were a failure of cold 
water flow, the controller would shut off hot water flow to prevent 
scalding of the user. A controller for the simplified embodiment which 
controls the valves only according to temperature A may operate according 
to the flow chart of FIG. 4. 
As seen in FIG. 4, when an "on" signal from the touchless switch is 
received by the controller (step 400), the controller first reads the 
temperature of the hot water line sensor 116, that is, temperature A (step 
402), and asks whether temperature A is more than X degrees Fahrenheit 
below the temperature Y of the hot water supply specified in the 
controller's memory (step 404). If the answer is "yes", the controller 
opens only the hot water valve (step 406). The controller then reads 
temperature A again and again asks whether temperature A is more than X 
degrees lower than temperature Y (step 410). If the answer is "no", the 
controller opens the cold water valve (step 412). After step 412, the 
controller continues to hold both the hot and cold water binary valves 
open until an "off" signal is received (step 414), after which both the 
hot and cold valves are closed (step 416). If the answer in step 410 is 
"yes", the controller repeats steps 408 and 410 in sequence until the 
answer in step 410 is "no". 
If in step 404 the answer is "no", the controller opens both the hot and 
cold water valves (step 420). The controller then goes to steps 414 and 
416. 
An "off" signal may be a signal generated by the touchless switch, or it 
may be generated by a timer associated with the controller which begins to 
count a preset interval when an "on" signal is received from the touchless 
switch. An "off" signal may comprise one of the following conditions: a) 
the infra-red signal does not sense the presence of a user and b) the 
indicated temperature set point has been reached, or c) a preset time 
limit has been reached. 
In still another embodiment, the controller is constructed to first open 
both the hot and cold water valves upon receiving an "on" signal, and then 
performs the temperature checking functions. Both controller 120 and 
controller 306 can be configured to execute the temperature control 
functions according to this method; FIG. 5 depicts the method as it would 
be executed by controller 120 of the apparatus shown in FIG. 1. In this 
control path, the first step 502 following the receipt of an "on" signal 
is to check the selected output temperature, and open the hot and cold 
valves to the baseline settings for that selected temperature (step 504). 
Next, the controller checks the hot water temperature A, and asks whether 
it is more than 2 degrees below the expected hot water source temperature 
to achieve temperature B (steps 506, 508). If "yes", the controller rams 
the cold water valve off (step 510), and continues with only the hot water 
valve, open to its original setting, for a preset interval of two minutes 
(step 512). 
The preset interval need not be two minutes. The hot-only flow interval may 
be based on the time usually required for hot water to reach sensor A from 
the hot water source, and in preferred embodiments may be user-selectable 
at the time of manufacture or installation. For example, an interval as 
short as a few milliseconds, or less. Or, the controller could be 
constructed to keep the cold water valve closed until temperature B 
reaches the set temperature for the outlet water. 
After step 5 12, the controller then again asks whether temperature A is 
more than 2 degrees below the expected hot water source temperature (step 
514), and if "no", the controller opens the cold water valve to the 
original setting (step 516). The controller then reads temperature B, and 
asks if temperature B is within 2 degrees of the set temperature (steps 
518, 520). If yes, the controller continues to operate at the original 
settings until an "off" signal is received. If the answer is "no", the 
controller goes through a sequence of calculating new valve settings, 
setting the valves to the new settings, and rechecking temperature B, 
until temperature B reaches the set temperature. 
It is desirable that a fail-safe mechanism be built into either the 
controller programming, or as a separate, outside mechanism, which will 
cause all water to shut off if temperature B reaches a temperature of more 
than 5 degrees above the set temperature, or a selected upper limit 
temperature, to prevent scalding incidents. 
Of course this same computer logic may be used to mix gases as well as 
liquids by simply using control values specifically designed for use with 
gases by volume rather than liquids by temperature and modifying the 
sensors accordingly. For instance mixing nitrous oxide (N.sub.2 O) with 
oxygen (O.sub.2) by use of this system at a predetermined level might be 
efficacious in dentistry and surgery as well as beneficial in preventing 
needless death if the device was preset to never allow a setting centering 
less than 20% oxygen to occur. 
The device could even be designed to occur within one canister or tank 
which accurately mixed the oxygen and nitrous oxide at a preset level 
rather than the two separate tank systems containing either pure nitrous 
oxide and pure oxygen which are used today. 
It will be apparent that numerous modifications may be made to the 
apparatus, to the construction of the controller, and to the method of 
temperature regulation without departing from the concepts embodied in 
this application. The claims themselves define the scope of that which the 
inventor regards as his invention.