Abstract:
An apparatus and method for infinitely variable adjustment of temperature range of a device in multiple selected temperature ranges. The method includes providing a plurality of operational temperature ranges of the device, selection of a desired temperature range, and infinitely variable selection of a specific temperature within a selected range. The apparatus includes a temperature range mechanism limiting operational temperature to first and second temperature ranges, and a control mechanism to select one of the first and second temperature ranges and then infinitely adjusting temperature within the selected range. In the example of a clothes dryer, the invention allows the selection of a higher or lower temperature range for the clothes dryer and, once the range is selected, infinitely variable temperature control within the selected range.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to temperature control of a system or device that generates heated air, and in particular, to a temperature control that has multiple selectable temperature ranges. 
     2. Problems in the Art 
     A variety of devices utilize heated air. One example is a clothes dryer. A conventional drying mode uses internal means to heat air and supplies the heated air to the clothes in the clothes dryer for a pre-selected time period. The amount of heat provided to dry the clothes is primarily a function of the temperature of the heated air and the amount of drying time manually selected by the user. For example, if a relatively small amount of heat is needed, a shorter time period is selected. Increased amounts of heat are achieved by lengthening the time period. 
     However, the wide variety of available fabric types has resulted in an expansion of desired drying options for clothes dryers. For example, it can be detrimental to some fabrics to be exposed to normal dryer temperatures. It can also be detrimental to some fabrics to be exposed to normal dryer temperatures for extended periods of time, but such fabrics could sustain higher dryer temperatures during shorter periods. 
     Economic considerations also come into play. As is obvious, a single temperature clothes dryer requires energy to produce the heated air for drying. The single temperature must be selected to accommodate a wide variety of drying tasks. However, some drying tasks can be accomplished effectively at lower temperatures. In those cases a single temperature dryer would provide more heat than needed and consequently consume excessive amounts of energy. Most drying applications require the combination of heated air and tumbling for good results. Similarly, other applications require relatively low temperatures. In these cases, lack of flexible temperature control can result in unneeded consumption of energy. As discussed above, there are also situations where higher temperatures may be needed. Again lack of temperature flexibility may result in un-needed expenditure of energy or time during a drying application. 
     As a result, attempts have been made to provide for different drying temperatures in clothes dryers. See, for example, U.S. Pat. No. 4,226,026 to Deming et al and U.S. Pat. No. 3,031,768 to Kurouski. While these patents recognize that different temperatures can be advantageous for different fabrics and drying applications, their solutions are to provide multiple fixed levels of heat selectable by the user. Instead of having one dryer temperature, these patents allow selection between several fixed temperature levels. 
     While such a solution provides more temperature options for a user, there is still room for improvement in the art. It would be advantageous to have more flexibility in the control of heated air temperature for devices utilizing heated air. It is therefore a principal object of the present invention to provide an apparatus and method for multiple temperature range control which improves over or solves the problems and deficiencies in the art. 
     It is a further object of the present invention to provide an apparatus and method as above described which provides for not only multiple temperature ranges of heated air, but infinitely variable control of the temperature of the heated air within each range. 
     A further object of the present invention is to provide an apparatus and method as above described which provides more temperature control options for the user. 
     Another object of the present invention is to provide an apparatus and method as above described which is more economical with regard to energy use. 
     A still further object of the present invention is to provide an apparatus and method as above described which is efficient, economical, and durable. 
     These and other objects, features, and advantages of the present invention will become more apparent with reference to the accompanying specification and claims. 
     SUMMARY OF THE INVENTION 
     The invention includes an apparatus and method for infinitely variable control of heated air temperature within multiple temperature ranges. The method includes providing a plurality of temperature ranges within normal operating temperatures of a heated air application or device. The user is allowed to select one of the plurality of temperature ranges. The user is additionally allowed infinitely variable control of temperature within the selected range. 
     The apparatus according to the present invention includes a temperature range mechanism which thermostatically limits the temperature of the heated air to a plurality of temperature ranges. A control mechanism allows a user to select between the temperature ranges and then infinitely variably adjust the temperature within the selected range. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an electrical schematic of control circuitry according to a preferred embodiment of the present invention. 
     FIG. 2 is a diagrammatic view of mechanical, manually operated control switches according to a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     To achieve a better understanding of the invention, a preferred embodiment according to the invention will now be described in detail. Frequent reference will be taken to the drawings. Reference numbers and letters will be utilized in the drawings to indicate certain parts and locations in the drawings. The same reference numerals and/or letters will be used to indicate the same parts or locations throughout the drawings, unless otherwise indicated. 
     FIG. 1 schematically illustrates a control circuit which will be referred to generally by reference numeral  10 . Circuit  10  has a first electrical connection L 1  to line voltage, and a second connection L 2  to line voltage. In the preferred embodiment, control circuit  10  is operatively installed in an electric clothes dryer and line voltage between L 1  and L 2  is 220 volts. 
     Circuit  10  comprises two main sections. A control mechanism section  12  includes infinite temperature switch  14  and option switch  16 . A temperature range mechanism  18  is the second principle portion of circuit  10 . 
     As shown in FIG. 1, a timer contact TC 3 , such as well known in the art, controls the actuation of circuit  10 . The user manually sets the timer to a desired time period. Circuit  10  is thus connected to line voltage for that period. In this example, an electrical heater  20  is included in circuit  10  between L 1  and L 2 . Heater  20  is such as is conventional and well known within the art, converting a portion of electrical current through circuit  10  into thermal energy when current is passed through heater  20 . This thermal energy is utilized to heat the air which is then channeled into the clothes drying chamber of the dryer by conventional methods and apparatus. 
     As shown in FIG. 1, a high limit thermostatic switch  22  is also installed in circuit  10  between L 1  and L 2 . Switch  22  is used in many clothes dryers and serves as a safe guard back-up or cut-out switch in case dryer temperature for some reason exceeds a safety limit and other thermostatic controls do not prevent such a temperature. 
     FIG. 1 additionally shows centrifugal switch  24  associated with a drive motor (not shown) for rotating the dryer drum (also not shown), also well known in the art. Switch  24  is closed as long as the drive motor is energized and the dryer drum is rotating. Upon cessation of dryer drum rotation, switch  24  opens and thus prevents heating of the dryer chamber. 
     Temperature range mechanism  18  includes what are referred to here as “normal” thermostat  26  and “gentle” thermostat  28 . Operation of these elements of circuit  10  will be discussed in detail below. 
     FIG. 2 illustrates the manual controls on the external control panel or dryer fascia of a dryer  30  that are associated with circuit  10  of FIG.  1 . “Options” switch  16  has a manual push button  32  to select a “normal temperature range” for dryer  30  and a manual push button  34  to select a “gentle temperature range” for dryer  30 . Buttons  32  and  34  are exclusive of each other. When one is selected, the other one is deselected and vice versa. As can be seen in FIG. 1, this is accomplished by option switch  16  being a double pole, double throw switch. When push button  32  is selected, option switch  16  would be in the position shown in FIG. 1 with conductors  57  and  129  contacting poles  58  and  132  respectively. On the other hand, when push button  34  is selected, option switch  16  in FIG. 1 would be changed so that the current path would flow to the poles  60  and  130  of switch  16  labeled “GENT” instead of “NORM”. 
     Thus, the user manually selects a desired temperature range between normal temperature range and gentle range by pushing button  32  or  34  corresponding to the indicia (“Normal” or “Gentle”) on the facia of dryer  30 . In the preferred embodiment, a normal temperature range can be 150° Fahrenheit to 140° Fahrenheit. The gentle range, lower than normal range, could be 130° Fahrenheit to 120° Fahrenheit. These ranges can vary according to desire and need. They can be separated or could overlap. 
     FIG. 2 illustrates that infinite temperature switch  14  includes a manually operated slide control  36 . Indicia on the fascia around slide control  36  provides the user with visual information regarding different positions of control  14 . If normal temperature range button  32  is selected on switch  16 , the indicia on the left side of slide  36  is operative. The user would have infinitely variable selection of the temperature within the normal temperature range (between the high end of the range denoted by the top-most arrow and the label “regular”, down to the lowest part of the range denoted by the arrow and labeled “delicate”). 
     If push button  34  of switch  16  is selected, the gentle temperature range (i.e. a lower temperature range) would be in operation. The user would have infinitely variable adjustment of temperature within the gentle temperature range as noted on the right side indicia of slide control  36  in FIG.  2 . This would include the upper end of gentle temperature range denoted by the arrow and label “delicate” down to the lowest end of that range denoted by the arrow and label “ultra care”. 
     Switch  14  presents an additional dryer mode of operation. An “air fluff” mode, which would not utilize any heated air, can be invoked at any time during the timed drying operation by moving slide control  36  to the very bottom of its travel in FIG. 2 (into alignment with the arrows and labels “air fluff”). Referring to FIG. 1, this movement of slide control  36  would mechanically move air fluff switch  38  from the position shown in FIG. 1 to its other state toward pole  48 . This would cut out heater operation from the circuitry but allow rotation of the dryer drum and continue delivery of air flow through the dryer for the process of air fluffing, such as is well known within the art. 
     Therefore, as can be seen by referring to FIGS. 1 and 2, the user can select between a higher “normal temperature range” and a lower “gentle temperature range”. Once the range is selected, the user then additionally has infinitely variable adjustable control over the temperature within the selected range. For example, if normal temperature range is selected at options switch  16 , slide  36  of infinite temperature switch  14  then allows the user to adjust temperature within a range from a high of 150° Fahrenheit to a low of 140° Fahrenheit, or any temperature in between. If the “gentle” temperature range is selected, infinite adjustability between 130° Fahrenheit and 120° Fahrenheit is possible. The user thus has the ability to either save energy by utilizing the least amount of heat energy for the given range, or very minutely tailor temperature within the range for a given fabric or drying strategy. The user is not simply provided with two or three fixed temperatures to select from. Rather a normal dryer operating range is first segmented into multiple temperature ranges. Then, within each of those ranges, the user is provided with infinitely variable temperature adjustablility. 
     Operation of circuit  10  of FIG. 1 is as follows. The user selects between buttons  32  and  34  for normal or gentle temperature range. This determines the position of conductors  57  and  129  in double-pole, double-throw “options” switch  16  (e.g. 864 Series double pole, double throw switch, ARK-LES Corporation of Boston, Mass.). If the normal temperature range is selected, conductors  57  and  129  would be in the position shown in FIG. 1 contacting poles  58  and  132 . If slide  36  (FIG. 2) is in a position other than “air fluff”, conductor  45  in air fluff switch  38  (FIG. 1) would be in the position contacting pole  46  as shown in FIG. 1, namely in the “INF” or infinite temperature control state. Once the operator sets timer contact TC 3  to a drying time period and the dryer drum begins rotating, conductor  108  of centrifugal switch  24  would close contacting pole  106  and creating a conducting pathway between L 1  and L 2 . Resistive element  100  of heater  20  would then begin to produce heat. 
     An electrical pathway would then form, beginning at line input L 1  and through timer contact TC 3 , through conductor  40  and to infinite temperature switch  14 . The current path would then flow through conductors  42 ,  45 ,  50 ,  52 ,  54 ,  57 ,  62 , and  66  to “normal” thermostat  26 . Normal thermostat  26  comprises a thermally sensitive switch (e.g. Thermodisc, division of Emerson Electronics, St. Louis, Mo., model number 60T11) between poles  70  and  76 . A bi-metal member  72  would have characteristics predetermined to separate from electrical contact  74  upon reaching a given temperature (e.g. 150° Fahrenheit). Normal thermostat  26  also includes an internal biasing resistor  148 . The bi-metal member  72  is positioned to react to the temperature of heated air created by heater  20  in dryer  30 . 
     However, current flow through internal biasing resistor  148  would supply additional heat locally to bi-metal member  72  and thus cause a break in current to heater  20  at dryer temperatures lower than 150° Fahrenheit, depending on the amount of additional heat generated by internal biasing resistor  148 . The more current through biasing resistor  148 , the more heat it generates. The more heat it generates, the more heat is experienced by bi-metal member  72  (in addition to the heat generated by heater  20 ). This effectively creates an operating range for normal thermostat  26  between a high temperature (e.g. 150° Fahrenheit) and a lower dryer air temperature (e.g. 140° Fahrenheit). 
     As long as bi-metal member  72  is in electrical communication with contact  74 , current would flow from pole  76  through conductor  86  to pole  84 , and through conductor  88  to pole  90  of high limit thermostat switch  22 . As long as bi-metal member  92  of high limit thermostat  22  is in electrical communication with contact  94  (e.g. up to a limit determined by the characteristics of member  92 ), current would continue through pole  96 , conductor  98 , heater resistive element  100 , conductor  102 , conductor  104 , and switch conductor  108 . 
     At the same time, current would flow in a parallel circuit through conductor  112  to a potentiometer including resistive element  118  in infinite temperature switch  14  then through conductors  122 ,  124 ,  126 ,  129 ,  138 , and  142 , through internal biasing resistor  148 , and through conductor  152  to pole  76  of normal thermostat  26 . Slide control  36  would include a mechanical linkage (not shown) to variable connection  114  of the potentiometer. Movement of slide  36  would adjust the amount of resistance in the above described parallel circuit that is in series with internal biasing resistor  148 . 
     As is well known in the art, if slide  36  is positioned at the top of its range of travel (at the “regular” setting for normal temperature range), variable connection  114  would provide the most resistance to internal biasing resistor  148  and thus, conversely, internal biasing resistor  148  would create the least amount of heat energy that would influence bi-metal member  72  of normal thermostat  26 . On the other hand, movement of slide  36  to the “delicate” position of the normal temperature range (see FIG. 2) would provide the least electrical resistance through resistance element  118  and thus cause the highest heat output from internal biasing resistor  148 , which in turn would create the most influence on bi-metal member  72  of normal thermostat  26 . 
     Thus, in the above-described normal temperature range setting for option switch  16 , adjustment of infinite temperature slide  36  of infinite temperature switch  14  would provide infinitely variable control of dryer air temperature within the higher “normal temperature range” for the dryer. Options switch  16  would set the range for drying (150° F. to 140° F.) by selecting the maximum temperature trip point of normal thermostat  26  (150° F). Infinite temperature switch  14  would bias or adjust the trip point of normal thermostat  26  including and between 150° F. to 140° F. by proportionally adding to the amount of heat sensed at bi-metal member  72 . This effectively provides a 150° F. to 140° F. range and infinite selection of operating temperature of the dryer within that range. Heater  20  would heat such air to the selected temperature within the “normal range” until temperature exceeded the trip point of bi-metal member  72  of normal thermostat  26 , the timer associated with contact TC 3  times out, high limit thermostat  22  tripped, or the drive motor discontinued operation and opened centrifugal switch  24 . 
     If the heater  20  heated air beyond the trip point for normal thermostat  26 , the circuit would open and heater  20  would be turned off until dryer air temperature fell below the trip temperature. At that point bi-metal member  72  would close and become conducting again. Heater  20  would heat dryer air again. The control circuit would thus keep dryer air at or near the infinitely adjustable selected temperature within the selected temperature range. 
     At any time, the user could change the trip point of normal thermostat  26  by altering the position of slide control  36 , thus changing the resistance value of the potentiometer and consequently the amount of heat generated by internal biasing resistor  148 . This would adjust the dryer operating temperature within the normal temperature range. 
     If the user would like a lower temperature range for a given drying batch, the gentle temperature range (e.g. 120° Fahrenheit to 130° Fahrenheit) would be selected by pushing button  34  of “options” switch  16 . This in turn would move switch conductors  57  and  129  to the “GENT” or “gentle” positions of options switch  16  in FIG. 1 (conducting to switch poles  60  and  130  instead of poles  58  and  132 ). Circuit  10  would operate essentially in the same manner as described above except that the current path from pole  56  of option switch  16  would go to pole  60 , through conductors  64 ,  68 , to pole  78  of gentle thermostat  28 , through bi-metal member  80  and contact  82  to pole  84  of gentle thermostat  28 , and then through conductor  88 , high limit thermostat  22 , heater  20 , and centrifugal switch  24 . 
     Also, current flow from potentiometer ( 114 ,  116 ,  118 ,  120 ) would then go from pole  128  of option switch  16  through conductor  129  to pole  130 , through conductors  136  and  140 , and through internal biasing resistor  144  of gentle thermostat  28 , then through conductor  146  to pole  150 , through conductor  152  to pole  76 , and finally through conductor  86  to pole  84 , to place the potentiometer and the internal biasing resistor  144  in parallel with the other circuitry of circuit  10 . Bi-metal member  80  of gentle thermostat  28  would function to trip at a lower temperature (e.g. 130° Fahrenheit) than bi-metal member  72  of normal thermostat  26 , thus effectively creating a lower or “gentle” temperature range. Internal biasing resistor  144  would function to allow infinitely variable adjustability within the lower temperature range based on resistance selected at potentiometer ( 114 ,  116 ,  118 ,  120 ). In the present example, setting slide  36  at “delicate” in FIG. 2 would maximize the amount of resistance of the potentiometer at  118  and thus minimize the amount of influencing heat generated by internal biasing resistor  144 , thus effectively causing the 130° Fahrenheit trip temperature of bi-metal member  80  to be the maximum gentle range temperature for dryer air. On the other hand, moving slide  36  to the “ultra care” position would minimize resistance through the potentiometer at  118  and maximize the amount of influencing heat generated by internal biasing resistor  144 . This would effectively cause bi-metal member  80  to trip when dryer air was at a temperature lower than 130° (120° Fahrenheit) because of the cumulative effect of heat from the internal biasing resistor  144  with the actual dryer air temperature sensed by gentle thermostat  28 . Slide  36  can be placed at any position in between “delicate” and “ultra care” and thus infinitely variably change the resistance of the potentiometer within its range, thus infinitely variably changing the heat generated by internal biasing resister  144  within its range, and thus infinitely variably changing the trip point of gentle thermostat  28  within its range (120°-130° F.). 
     Therefore, the user not only has a different and lower temperature range available for such things as delicate fabrics, but within that lower range has infinitely variable control of the temperature. 
     It will be appreciated that the present invention can take many forms and embodiments. The included preferred embodiment is given by way of example only, and not by way of limitation to the invention, which is solely described by the claims herein. Variations obvious to one skilled in the art will be included within the invention defined by the claims. 
     For example, precise construction and operation of the manual controls for the dual ranges of temperature and the infinitely variable adjustment within a selected range, can vary. They do not have to be push button and slide controls. It is possible for the manual controls to be consolidated into one control. 
     Furthermore, it is possible for there to be infinitely variable adjustable control in any one of the temperature ranges or in all of the temperatures ranges. It is furthermore possible to have greater than two selectable temperature ranges with infinite variable adjustment of air temperature within any or all of the ranges. 
     Still further, the temperature ranges can be separate and segregated along the temperature scale or could have some overlap. Temperature ranges can be predesigned by selection of the components and specifications of the thermostats and the potentiometer. 
     Still further, the above description is made with respect to an electric clothes dryer. The invention is equally applicable to gas dryers. Instead of having the current of circuit  10  control an electric heater  20 , heater  20  can be substituted by an electrical component that would operate a gas supply valve. When current flows through the electrical component, the electrical component would open the supply of gas which would be ignited and serve to heat dryer air. 
     The control system described above is not limited to use with a clothes dryer. By way of example and not limitation, the control system could be utilized for ovens, home or building heating, or water heaters. Other uses are possible.