Automatic temperature and humidity regulation – Mixing fluid of dissimilar temperature – Mixing valve with temperature motive means
Reexamination Certificate
2002-11-19
2004-04-20
Tapolcai, William E. (Department: 3744)
Automatic temperature and humidity regulation
Mixing fluid of dissimilar temperature
Mixing valve with temperature motive means
C004S676000
Reexamination Certificate
active
06722575
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to water temperature regulation, and in particular to controllable mixing valves and associated control for water temperature regulation for appliance usage.
BACKGROUND OF THE INVENTION
In the consumer and commercial appliance industry, and with particular applicability to clothes washing machines, water temperature regulation is accomplished primarily through the timed mixing of hot and cold water inputs. The hot water input is typically provided from a consumer or commercial hot water heater which supplies hot water for various uses throughout the home or establishment. Depending on its other utilizations, the hot water is typically provided at a temperature of approximately 140° Fahrenheit, although this temperature may be set by the user. The cold water input is typically provided at the tap from the cold water input into the home or establishment. While this cold water input is not typically temperature adjustable, common cold water inputs are approximately 60° F. However, this temperature may vary depending upon location, installation, utility supply, etc.
While the hot and cold water are typically supplied at the above-described temperatures, seldom is the use for water at these particular temperatures. That is, most usages of the water require mixing of the hot and cold water inputs to accommodate a particular usage. For example, commercial and consumer clothes washers provide different washing cycles with user selectable water temperatures from hot, to warm, to cold. However, water at 140° F. may damage some fabrics. Further, stringent consumer energy standards for these appliances limit the amount of hot water that may be used therein. Further, while cold water detergents are available and are in wide usage, particular for brightly colored fabrics, these detergents do not perform particularly well as the water temperature drops below, for example, 70° F. As such, even clothes washing machines that provide hot and cold washing cycles do not typically utilize only water from either the hot or the cold input directly.
In such clothes washing machines, electronically controlled temperature mixing valves are typically employed to provide a combination flow of hot and cold water inputs to the washing drum. The control of the individual hot and cold water inputs to the mixing valve traditionally has been provided by an electromechanical timer circuit, although more modern controllers may replace the electromechanical timer function with an electronic timer control circuit. In either event, the operation of these two timing mechanisms is effectively the same from the mixing valve standpoint. As an example, the timer circuit may operate to provide a one-minute fill time of the washing tub. During that one-minute fill time, the timer may energize the electrically controlled valve for the hot water input to allow a flow of the hot water into the washing tub from the beginning of the fill cycle. The timer circuit may then energize the cold water input control valve after, for example, approximately 30 seconds of the fill cycle. In this way, the temperature of the water in the washing tub is reduced below that which would result if only the hot water valve were used. Different operating fill timing schemes are typically employed by the timer circuits to control the time during which each of the hot and cold water inputs are energized to provide the various water temperature cycles allowed by the washing machine.
While the timer control of both the hot and cold water inputs to the mixing valve operates satisfactorily for a majority of applications, various factors may exist in particular installations that do not provide satisfactory results for that particular installation. These problems relate to a breakdown of the primary assumption under which a timer controller may be utilized for temperature control of the water in the washing tub. Specifically, the timer relationships of a period of time for which each of the hot and cold water inputs allow the flow of their respective temperature water is based upon a generalized assumption of what the hot water temperatures and cold water temperatures are. However, in installations where the washing machine is remotely located from the hot water heater, for example, the temperature of the hot water input may initially be quite a bit lower than the typically assumed temperature of the hot water input.
As such, allowing the hot water valve to be opened for only a pre-selected period of time before the cold water valve is opened may result in a washing tub water temperature significantly below that which is desired and which would have resulted had the hot water input to the mixing valve been at its assumed temperature. In other words, if the temperature of the hot water input is only 120° F. for the first 30 seconds of the fill cycle as controlled by the timer, opening the cold water input and closing the hot water input for the second half of the fill cycle will result in the water temperature of the washing tub being cool instead of warm as would have been the case if the hot water input were actually at its assumed 140° F. temperature during the first 30 seconds of the exemplary one minute fill cycle.
Similarly, the temperature of the cold water input is likely to be higher than the steady state water input from the utility during the initial period of water flow, until the water in the pipe between the utility input and the washing machine is used up. This results from the ambient heating of the pipe and water when no water is flowing. As such, utilizing timed fill cycle control may well result in the washtub water temperature being much warmer than desired for a cold water wash where the hot water control valve is turned on for some timed period during the fill cycle time. Each of these problems is exacerbated by physical location of the washing machine in each particular location in relation to the utility cold water input and the location of the hot water heater, as well as the user temperature setting of the hot water heater itself.
Recognizing the problem that reliance on assumed water temperatures with a timer circuit presented, systems were developed to operate in conjunction with the water valve timer control to add an element of temperature sensing. One such system is described in U.S. Pat. No. 5,984,194 to Francalanci, entitled “Valve for Controlling the Temperature of the Water in a Washing Machine or Dishwasher, Methods of Treating Water in These Machines Which Can be Implemented by Means of Said Valve and Machines for Washing Using This Valve.” In such systems, a specialty mixing valve is required that includes a thermostat placed in proximity to a thinned portion of an exterior wall of the valve to sense the water temperature therein. When the temperature of the water flowing through the valve increases above or drops below the set point of the thermostat, an internal switch closes or opens. In the system of the '194 patent, this thermostat is used in line with the timer control circuit to hold off the timed closure of the cold water solenoid until the hot water flowing through the valve increases to its assumed or expected temperature. Specifically, the system of the '194 patent prevents the timer control circuit from opening the cold water valve until and unless the hot water has reached the temperature set point of the switch. Indeed, for the one minute fill cycle example discussed above where the cold water solenoid is energized 30 seconds into the fill cycle, if the hot water never reaches the temperature set point of the thermostat, the cold water valve will be prevented from turning on during its 30 second timed cycle.
Unfortunately, while such systems address the problem of cool water in the hot water pipe during the initial period of a fill cycle, their operation is still fundamentally governed by the timer control circuit. As these systems cannot adjust for temperature excursions on the outside of the normally anticipated temperature limits. The
Gagne Kelly S.
Hawken Philip C.
Pearson James E.
Leydig , Voit & Mayer, Ltd.
Robertshaw Controls Company
Tapolcai William E.
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