BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a control system for a clothes dryer and, more particularly, to a clothes dryer control system incorporating a moisture sensor used to terminate a drying process when the amount of moisture present in the clothes inside the dryer reaches a desired level as selected by a user.  
           [0003]    2. Discussion of the Prior Art  
           [0004]    It is well known in the art to provide a clothes dryer with a simple time-dry control, in addition to a sensor-dry mode. When the time-dry control is used, the user simply places wet articles inside the dryer and selects the duration for the drying process. Because there is little or no automatic control or adjustment during the process, the drying process simply continues until the time expires. The result can be inefficient, because it is difficult for a user to accurately estimate the time required to reach a desired, final moisture level prior to operating the machine.  
           [0005]    In comparison, sensor-dry modes are provided to automatically control a drying operation. Specifically, when a sensor-dry mode is selected, the user places wet articles inside the dryer drum and selects a desired final dryness level. Instead of forcing the user to guess as to how long the process should take, the machine stops when the desired dryness level is reached. For this purpose, the machine includes at least one moisture sensor for detecting the level of moisture of the articles. The machine simply operates until the moisture sensor detects the final desired dryness level selected by the user. By terminating the process upon achieving the desired final dryness level, there is no need to re-start the process to finish incomplete drying. In addition, extra energy is not expended to dry the articles beyond the desired dryness level.  
           [0006]    Electronic controls have been developed to assist in the operation of such an automatic drying processes. For example, U.S. Pat. No. 3,762,064, to Offut, discloses a system for automatic operation of a dryer in which extra time is added to a drying process according to a predetermined table. A selection of a dryness level beyond a predetermined level (e.g. damp-dry) results in the addition of extra time. The duration of this extra time is dependent upon the length of time required to reach the predetermined dryness level and the desired final dryness level selected by the user. While this system incorporates a moisture sensor for making a drying operation more efficient, this system is nevertheless highly inefficient, because only one threshold dryness level is detected and the final dryness level is never actually measured, as the time to reach that level is simply estimated. Therefore, just as in time dry modes, the articles will often either be under-dried and still wet, or over-dried.  
           [0007]    U.S. Pat. No. 4,477,892, to Cotton, represents an improvement over the system disclosed in the &#39;064 patent and includes sensors or electrodes which contact the wet articles to determine the current moisture level contained therein. Through the system of this patent, the current moisture level inside the machine can be measured at a variety of continuous levels. By comparing the number of conductive electrode “hits” during a given time period, it is possible to estimate the current degree of dryness.  
           [0008]    However, there still remains a concern regarding the programming of the operation controller. U.S. Pat. No. 6,020,698 to Stenger et al. discloses the use of multiple binary switches to program an electromechanical timer and an electronic control circuit. A plurality of timer switches are included in relation to a control knob to provide control input, and changing from one control position to an adjacent control position results in a switch either being opened or closed. However, this system only allows a small number of different settings to the microprocessor or electronic control circuit, dependent upon the number of timer switches. Increasing the variability, therefore, requires increasing the number of timer switches and, accordingly, greatly increasing the cost.  
           [0009]    Based on the above, there exists a need in the art to provide a control system for a clothes dryer which allows for programming of a wide range of final desired dryness levels, while efficiently drying the clothes contained therein, in a cost efficient manner. Additionally, there exists a need for a clothes dryer which quickly recognizes a dry condition upon commencing a drying cycle and powers down without running a heater.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention is particularly directed to a control system for a clothes dryer including a timer used to calculate an initial position of a dial or control knob. For instance, during operation of the control system of the invention, the user can select a sensor-dry mode by rotating the dial to a position indicating the final desired dryness level of the articles contained within the dryer. Upon pressing a start button, an internal motor quickly rotates the dial to a preset position, and the time to do so is measured. Because the control system of the invention is programmed with the speed at which the dial is rotated, the initial position of the knob can be quickly and easily determined by multiplying the rotational speed by the time required to rotate the knob. The result is compared to the output from a typical moisture sensor, and drying operation is halted when the detected moisture level reaches the selected level.  
           [0011]    Preferably, the control system, via the motor, is capable of driving the dial at different speeds. The first, or fast speed, is used during the initial programming procedure, as described above. A second, or slower speed, is used during the remainder of the sense dry cycle. By providing these varying rotational speeds, greater control and variability is permitted.  
           [0012]    Additional objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment thereof, when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a front perspective view of a clothes dryer incorporating a dryness level detection and display system according to the invention;  
         [0014]    [0014]FIG. 2 is a front view of a control panel provided on the clothes dryer of FIG. 1; and  
         [0015]    [0015]FIG. 3 is a diagrammatic representation of a typical control sequence of a sensor dry mode according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    A clothes dryer  1  of the current invention is shown in FIG. 1 and generally includes an outer cabinet  10 , having an opening leading to a rotatable drum  14  and a door  18  for closing the opening. Disposed on the upper surface of the outer cabinet is a control panel  22  for establishing a desired operational sequence for programming the clothes dryer  1  of the invention.  
         [0017]    [0017]FIG. 2 depicts a close-up view of control panel  22  and includes a plurality of buttons and other elements for controlling clothes dryer  1 . Although control panel  22  is described below in a specific arrangement, it should be understood that the particular arrangement is only exemplary, as a wide range of layouts would suffice. Accordingly, disposed on the left side of control panel  22  is a temperature selector  40 , which includes buttons for determining the heat output of the clothes dryer  1 . In the most preferred embodiment, temperature selector  40  includes an air fluff button  42 , a delicate button  44 , a medium button  46  and a regular button  48 .  
         [0018]    Next to temperature selector  40  is a moisture monitor  55  for displaying the current moisture state of articles contained within clothes dryer  1 . Moisture monitor  55  is shown as including a set of LEDs  58  for indicating the specific moisture level. Because the LEDs  58  are vertically arranged, individual LEDs  58   a - f  can be illuminated to indicate a current moisture level. For example, a low moisture level can be signified by illuminating only LED  58   a , while a higher moisture level can be shown by illuminating LED  58   d  alone or LEDs  58   a ,  58   b ,  58   c  and  58   d  simultaneously.  
         [0019]    Proximate to moisture monitor  55  is a signal controller  62 . Signal controller  62  is provided to selectively regulate the operation of a buzzer (not shown), and includes an OFF button  64  and an ON button  66 . The selection of ON button  66  causes the buzzer to sound upon completion of the drying operation, while selection of OFF button  64  prevents the buzzer from sounding upon completion of the drying operation. Additionally, control panel  22  includes a start button  70  for commencing operation of clothes dryer  1 .  
         [0020]    Finally, control panel  22  includes a control dial  100  for programming clothes dryer  1 . Disposed on the periphery of the center surface of dial  100  is a location pointer  101  which indicates an established setting for dial  100 . Annularly disposed about the periphery of dial  100  is indicia  103  which illustrates the various settings. Specifically, indicia  103  includes a first sense dry zone  105 , a second sense dry zone  110  and a time-dry zone  113 , each defining a portion of indicia  103  and designed to indicate the mode of dryer operation, i.e. a sense dry mode, or a time dry mode. Sense dry zones  105  and  110  each include a MORE DRY setting  120   a ,  120   b  and a LESS DRY setting  125   a ,  125   b  with continuous levels therebetween. First sense dry zone  105  also includes a press care setting  128 . Each zone  103 ,  105  and  113  includes a cool down sequence at the end of the desired cycle, although not specifically labeled in each zone  103 ,  105  and  113 . A plurality of time increments  130  are defined by indicia  103  in time-dry zone  113 . Finally, disposed between each of zones  105 ,  110  and  113  are OFF positions  132   a - c . Depending upon the operational state of clothes dryer  1 , dial  100 , and hence location pointer  101 , will reference the appropriate indicia  103 .  
         [0021]    With reference to FIG. 1, clothes dryer  1  also includes a control circuit generally indicated at  200 . Specifically a CPU  210  is provided with a timer  215 , and a dryness level determination circuit  220 . A motor  225  is provided to drive timer  215  upon direction from CPU  210 . A moisture sensor  230  is provided as an additional input to CPU  210 . Moisture sensor  230  may be any conventional moisture sensor known in the art, such as the moisture sensor described in U.S. Pat. No. 4,477,982, to Cotton, which is hereby incorporated in its entirety by reference. A series of drum and heater controls are collectively represented at  240  which, when directed by CPU  210  through timer  215 , operate a drum rotation motor (not shown) and a heating element (not shown) in response to a drying profile set by the elements on control panel  22  and the output from CPU  210 .  
         [0022]    After wet articles are placed within drum  14 , a user selects an operation in a generally conventional manner. First, temperature selector  42  is used to chose a desired operating temperature for clothes dryer  1 . While selection regular button  48  uses the highest temperature setting and results in the fastest drying time, the “regular” setting may be too hot for some articles. Therefore, additional temperature levels are provided. Before pressing start button  70  and beginning operation of clothes dryer  1 , the user rotates dial  100  from OFF setting  132  into time-dry zone  113 , first sense dry zone  105  or second sense dry zone  110 .  
         [0023]    If dial  100  is rotated such that location pointer  101  is in time-dry zone  113 , clothes dryer  1  is in time-dry mode, and simply operates until the time indicated by time increment  130  expires. CPU  210  directs motor  225  to rotate dial  100  at a relatively slow speed through a reduced duty cycle coinciding to time increments  130 , and operates the heater at the temperature chosen via temperature selector  42 . Rotation of drum  14  continues until location pointer  101  reaches OFF setting  132   c . If desired, moisture sensor  230  could be designed to operate during the time-dry mode to display to the user the current moisture level via moisture monitor  55 , even though the sense dry mode was not selected.  
         [0024]    The present invention is particularly directed to the operation of clothes dryer  1  in one of sense dry zones  105  or  110 . Second sense dry zone  110  is provided for automatic operation of clothes dryer  1  in most situations. However, first sense dry zone  105  is generally provided for use with permanent press articles or when the user wants wrinkles prevented. The two sense dry zones  105  and  110  operate in substantially the same manner, as commonly known in the art, with their differences not forming part of the present invention. First sense dry zone  105  directs a “wrinkle-free” cycle and therefore, includes press care setting  128  and operates at a lower temperature with an extended period of no added heat, i.e. an air fluff mode, than the cycle directed by second sense dry zone  110  so as to extend tumbling to limit creasing of articles. Because operation of clothes dryer  1  is substantially the same for first sense dry zone  105  and second sense dry zone  110  in accordance with the invention, only one description follows, making specific reference to first sense dry zone  105 .  
         [0025]    With reference to the drawings and particularly FIG. 3, just as when time-dry zone  113  is used, when a sense dry mode of clothes dryer  1  is called for, the user places the wet articles inside drum  14 , chooses a drying temperature with temperature selector  40  (Step  300 ), selects signal ON or OFF ( 302 ), and indicates the desired, final dryness level by rotating dial  100  until location pointer  101  points to the desired level (Step  304 ). Specifically, the desired setting may be either MORE DRY setting  120 , LESS DRY setting  125  or somewhere between. After start button  70  is pressed (Step  306 ), CPU  210  through timer  215  begins tumbling of drum  14  (Step  308 ).  
         [0026]    In a preferred embodiment, CPU  210  measures the current moisture level within drum  14  via moisture sensor  230  upon commencing tumbling of drum  14  (Step  310 ). Timer  215  is then activated by CPU  210  (Step  316 ) to rotate dial  100  to determine its position or setting (Step  318 ). Specifically, dial  100  is rotated at a relatively fast rate, e.g. 8°/minute, as opposed to the slower speed of 2°/minute. Although in a preferred embodiment, dial  100  rotates at the same speed internally and externally, it is contemplated to rotate dial  100  at the slower speed externally, while moving four times as fast internally, as to maintain a substantially constant rotation as viewed by the user. More specifically, timer  215  rotates dial  100  at a constant known rate from its initial position to LESS DRY setting  125  (Step  320 ). Because the rotational velocity is known, CPU  210  calculates the arc length traveled by dial  100  during this period. By multiplying the preset rotational velocity by the rotation duration of timer  215 , the arc length traversed can be calculated (Step  324 ). For example, if dial  100  is set in close proximity to LESS DRY setting  125 , the rotation period will be substantially less than if dial  100  were set closer to MORE DRY setting  120 . CPU  210  converts this distance value into a dryness level, to be compared to the result from moisture sensor  230  by dryness level determination circuit  220 . At Step  328 , timer  215  is stopped, which halts rotation of dial  100  until later in the cycle.  
         [0027]    As indicated above, motor  225  rotates dial  100  at a different rate when in a sensor-dry zone  105  or  110  as compared to time-dry zone  113 . This allows for a greater degree of selection and flexibility in the layout of indicia  103  in the sensor dry zones  105  and  110 . By advancing dial  100  at a faster rate, in effect, more gradations are possible in the sensor-dry zone. In a preferred embodiment, motor  225  rotates dial  100  at a rate of 8° per minute when in sensor-dry zone  105  or  110  and advances dial  100  at a rate of 2° per minute when in time dry zone  113 . Preferably, this is accomplished by advancing dial  100  for 15 seconds out of every 60 seconds.  
         [0028]    The heater is then energized (Step  330 ) and clothes dryer  1  operates with dial  100  in LESS DRY selection  125  until the final dryness level is reached (Step  332 ). By continually monitoring the output from moisture sensor  230 , and comparing the output to the desired, final dryness level, dryness level determination circuit  220  causes CPU  210  to advance to the next step when the final dryness level is reached. Essentially, the rotational movement of dial  100  is halted until the desired dryness level is achieved by cycling between Steps  328 - 332 . When the final desired dryness level is achieved, CPU  210 , through timer  215 , restarts timer  215  at the slower speed (Step  333 ), and de-energizes the heater, but permits the continuation of tumbling of drum  14  (Step  334 ). Once the heater is de-energized, clothes dryer  1  enters cool-down mode (Step  338 ).  
         [0029]    If ON button  66  of signal controller  62  is depressed (Step  340 ), CPU  210  sounds the buzzer or other notification device to alert the user of the completion of the drying cycle (Step  342 ). If, however, OFF button  64  is depressed, CPU  210  does not actuate the buzzer and proceeds to the next step. Finally, CPU  210  and drum and heater controls  240  stop tumbling of drum  14  and shuts down clothes dryer  1  (Step  344 ).  
         [0030]    The particular arrangement of CPU  210  within dryer  1  is designed to prevent excessive heating of articles contained in drum  14  if a dry condition is realized at the initiation of a drying cycle. If dyer  1  is started with an already dry load (or no load at all) therein, this will be detected by moisture sensor  230  in Step  310 . Because this reading will be below any desired dryness level calculated in Step  324 , when CPU  210  progresses to Step  332 , CPU  210  will quickly move through Steps  330 - 334  and almost immediately stop the heater. Therefore, in the event that an already dry load is placed within drum  14 , the heater will only remain energized for a short duration.  
         [0031]    With this arrangement, the actual operator established setting between MORE DRY and LESS DRY in either of sense dry zone  105  or  110  is determined by CPU  210  well in advance of reaching a LESS DRY status for the clothes. Although not shown, CPU  210  could be used to control a visual numeric or other type of read-out (not shown) provided on control panel  22  or elsewhere, to indicate to the user the amount of time to an end of cycle. Therefore, although described with reference to preferred embodiments, it should readily understood that various changes and/or modifications could be made to the invention without departing from the spirit thereof. For example, selection element  100  need not be a dial, as one of ordinary skill in the art would recognize that using a slidable element would be within the scope of this invention. Additionally, indicia  103  may include a variety of additional dryer cycles, or simply a single sense dry zone. In any event, the invention is only intended to be limited by the scope of the following claims.
A method of programming and controlling an automatic cycle of a clothes dryer provides that, after positioning of a selection dial, a motor associated with the selection dial is rapidly moved to a predetermined location at a constant speed, while the time to do so is measured. With the rotational velocity being known, the exact, initially setting position of the dial is determined in advance.