Patent Publication Number: US-10309052-B2

Title: Air flow pressure compensator system for clothes dryers

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to International Application No. PCT/US2014/047363, filed Jul. 21, 2014, which claims priority to U.S. Application Ser. No. 61/856,259, filed Jul. 19, 2013, the entirety of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present disclosure relates to air flow pressure compensator systems incorporated into clothes dryers to increase air flow and improve clothes drying efficiency. 
     Multiple factors affect the drying efficiency of clothes dryers and particularly how air flows through a dryer. These factors include, but are not limited to, the positioning and arrangement of exhaust ducting and the blockage of air exiting the tumbler. 
     When a clothes dryer system is installed, exhaust ducting is coupled to the system and then positioned and arranged to a vent the dryer to the outside. However, frequently during installation, exhaust ducting is particularly lengthy due to the long distance between the outer dryer vent and outside venting. Depending on where the installation is placed, exhaust ducting may also be arranged to have a large number of twists and turns in order reach outside venting. What results from arranging exhaust ducting in this manner is a ducting environment that affects the overall efficiency of the clothes dryer. For example, high static pressure will likely develop within in the exhaust ducting, reducing air flow in system and extending drying times for clothes. 
     Also, as a cycle of a clothes dryer progresses, the removal of moisture from clothing causes clothes to impede air flow in the system. As clothes dry, the nature of clothing materials change. Some materials tend to fan or spread out and block air from exiting the tumbler. This reduces air flow through the clothing material and also negatively affects drying times. 
     For these reasons, among others, there is a clear need for air flow pressure compensator systems incorporated into clothes dryers to increase air flow and improve clothes drying efficiency. The present invention fulfills this need and provides further related advantages, as described below. 
     BRIEF SUMMARY OF THE INVENTION 
     Disclosed herein is an air flow pressure compensator system used to maintain substantially constants air flow within a clothes dryer system. Specifically, the compensator system adjusts the speed of one or more exhaust fans by monitoring one or more sensors/transmitters positioned in one or more exhaust ducts and/or one or more incoming air ducts. Real-time monitoring of the sensors/transmitters allow for system adjustments which improve clothing drying time and dryer efficiency. These adjustments, therefore, compensate for inefficiencies in the clothes dryer and enhance overall dryer performance. 
     A more complete understanding of the air flow pressure compensator system will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by consideration of the following detailed description. Reference will be made to the appended sheets of the drawings, which will first be described briefly. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. 
       In the drawings: 
         FIG. 1  shows a perspective view of an exemplary dryer that incorporates an air flow pressure compensator system; 
         FIG. 2  show a front elevated view of an exemplary controller panel used to operate the air flow pressure compensator system and other dryer controls; 
         FIG. 3  shows perspective view of a first schematic of air flow in a clothes dryer system; 
         FIG. 4  shows perspective view of a second schematic of air flow in a clothes dryer system; 
         FIG. 5  shows a schematic showing an air flow pressure compensator system; 
         FIG. 6  shows an exemplary exhaust fan incorporated into an air flow pressure compensator system; 
         FIG. 7  shows a rear elevated view of an exemplary sensor/transmitter for monitoring pressure and air velocity in an air flow pressure compensator system; 
         FIGS. 8A and 8B  show perspective views of exemplary sensors/transmitters used in an air flow pressure compensator system; and 
         FIG. 9  shows front elevated views of exemplary circuitry and variable frequency drives used in an air flow pressure compensator system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning in detail to the drawings,  FIG. 1  shows one embodiment of a clothes dryer  100  that incorporates an air flow pressure compensator system  10  ( FIG. 5 ). Clothes dryers that incorporate the air flow compensator systems disclosed herein include those manufactured by American Dryer Corporation (ADC) and particularly air flow compensator systems included in ADC Intelligent Dryer Series (id-series) Dryer Models. The id-series of dryer models is manufactured to achieve higher performance, improved efficiency, shorter clothes dry times, safe and reliable operation, among other benefits. 
     As shown in  FIGS. 1 and 2 , a clothes dryer  100  includes a control panel  110 , having dryer controllers  112  that are electrically coupled to various sub-systems, one of which is the air flow pressure compensator system  10  ( FIG. 5 ). The air flow pressure compensator system  10  is coupled to the control panel  110  by a compensator controller  12 , as shown in  FIG. 5 . The controllers  112  and the control panel  110  are designed to be user-friendly, self-diagnostic, and programmable. 
     The id-series dryer models sold by American Dryer Corporation also incorporate features that complement the air flow pressure compensator system  10 . As illustrated particularly in  FIG. 3 , these features include a tumbler  114 , which allows trans-axial air flow  116  in the dryer  100  and, as shown in  FIG. 4 , a unique two-shell design of the id-series burner  118 , which forces incoming air  120  (indicated by arrows) in a first pass to sides  122  of an oven housing  124  to pre-heat incoming air  120  and thereafter introduce warmed and heated air into the tumbler (warmed air indicated by arrows  126  and heated air indicated by arrows  128 ). Each of these features improves dryer efficiency. 
     Another feature incorporated into the id-series is ADC&#39;s patented SENSOR ACTIVATED FIRE EXTINGUISHING (S.A.F.E)™ system, as described in U.S. Pat. Nos. 5,197,203, 6,505,418, and 6,725,570, which are incorporated herein by reference. Some models, which incorporate the air flow pressure compensator systems, include the id35, id50, id80, id120, id30x2, and id45x2 models. Other dryers and dryer systems, however, may incorporate the air flow pressure compensator systems disclosed herein. 
       FIG. 5  schematically shows one embodiment of an air flow pressure compensator system  10 . The system  10  includes a compensator controller  12 , circuitry  14 , a variable frequency drive  16  (VFD), an anemometer or a differential pressure sensor/transmitter  18 , and at least one exhaust fan  20  incorporated into a fan housing  22 . The variable frequency drive  16  is incorporated into the system  10  to control motor speed of the dryer blower based on inputs received from one or more differential pressure sensors/transmitters  18 . The variable frequency drive  16  is programmed to control the running frequency of the blower motor. One type of drive suitable for use in the system has the following specifications: 0.33-200 hp (0.25 kW-132 kW); 115V/208-240V/380-480V/575V/690V. 
     Programming controls  24  ( FIG. 9 ) may be located on the variable frequency drive  16  or incorporated elsewhere within the system. In one alternative embodiment, the drive can be programmed by a microcontroller (not shown) on a system board, where programming code resides on the microcontroller. In this alternative embodiment, program code can be downloaded to the variable frequency drive. 
     Referring back to  FIG. 5 , an exhaust fan  20  is coupled to the variable frequency drive  16  and one or more anemometers or differential pressure sensor/transmitters  18  such that pressure differentials DPA, DPB, DPC and air velocities V 1 , V 2 , V 3  can be monitored at various points in the system  10 . Suitable measurement points within the system  10  for air flow velocity include points for make-up air (V 3 ), exhaust air (V 2 ), and clothing/lint build up points (V 1 ), i.e. where clothing is positioned in a tumbler or where lint build ups. 
     The anemometers or differential pressure sensor/transmitters  18  are used in the system  10  to measure pressure and convert the pressure to an electrical signal (I.E. 0-10 volt, 4-20 ma, serial data, and/or another means of transferring a measured output). Output signals  26  are then interpreted by the compensator controller  12  and/or the variable frequency drive (VFD) to increase or decrease fan speed such that substantially constant airflow is maintained during dryer operation. As airflow is impeded, as indicated by measurements taken at V 1 , V 2  and/or V 3 , fan speed will be increased or decreased to maintain substantially constant airflow. Airflow velocity will generally range from 0 to 1 inch water column. 
     Suitable sensors/transmitters for use in the system include MAGNESENSE® Differential Pressure Transmitters sold by Dwyer Instruments Inc. In a preferred configuration, specifications for the variable frequency drive include the following: 
     Accuracy: ±1% for 0.25″ (50 Pa), 0.5″ (100 Pa), 2″ (500 Pa), 5″ (1250 Pa), 10″ (2 kPa), 15″ (3 kPa), 25″ (5 kPa) 12% for 0.1″ (25 Pa), 1″ (250 Pa) and all bidirectional ranges.
         Stability: ±1% F.S./year.   Temperature Limits: 0 to 150° F. (−18 to 66° C.).   Pressure Limits: 1 psi maximum, operation; 10 psi, burst.   Power Requirements: 10 to 35 VDC (2-wire); 17 to 36 VDC or isolated 21.6 to 33 VAC (3-wire).   Output Signals: 4 to 20 mA (2-wire); 0 to 5 V, 0 to 10 V (3-wire).   Response Time: Field adjustable 0.5 to 15 sec. time constant. Provides a 95% response time of 1.5 to 45 seconds.   Zero &amp; Span Adjustments: Digital push button.   Loop Resistance: Current output: 0-1250Ω max; Voltage output: min. load resistance 1 kΩ.   Current Consumption: 40 mA max.   Electrical Connections: 4-20 mA, 2-wire: European Style Terminal Block for 16 to 26 AWG. 0-10 V, 3-wire: European Style Terminal Block 16 to 22 AWG.       

     Electrical Entry: ½″ NPS Thread. Accessory: Cable Gland for 5 to 10 mm diameter cable.
         Process Connection: 3/16″ (5 mm) ID tubing. Maximum Outer diameter 9 mm.   Enclosure Rating: NEMA 4X (IP66).       

     The sensors/transmitters may be connected directly to the variable frequency drive or connected directly to a microcontroller. When a sensor is connected directly to the variable frequency drive, a control decision point is made in the variable frequency drive. When a sensor/transmitter is connected directly to the microcontroller, the control decision point is made in the controller. Decision points are determined by the differential pressure sensor in conjunction with the variable speed drive (VFD). As the sensor detects changes in pressure between 0 and 1 in of WC (Water Column), one or more sensors/transmitters will output a signal between 4 and 20 ma, where 4 ma corresponds to 0 inches WC and 20 ma corresponds to 1 in WC. The variable frequency drive then will use the 4 to 20 ma signal from the sensors/transmitters to change the frequency of the motor and either increase or decrease the fan speed, thereby increasing or decreasing airflow. The variable frequency drive uses a percentage of the 4 to 20 MA, where 4 ma is 0% and 20 ma is 100% to make the adjustment(s). 
     An alternative method of adjusting fan speed without sensors is to monitor fan motor current. As static pressure increases, fan motor current decreases as the fan pushes less air. Conversely, as static pressure decreases, fan motor current increases as the fan pushes more air. 
     Using the variable frequency drive to control the fan motor and using fan motor current, particularly symmetrical fan motor current limits function of the variable frequency drive such that one can control the speed of the fan by (1) setting a maximum symmetrical current to a desired percentage of maximum fan motor current, where the maximum symmetrical current will allow the fan motor to run at its maximum current based on a predetermined percentage parameter. Setting a thermal protection parameter to “on” and presetting the variable frequency drive to a maximum desired frequency. When using this control method, as the static pressure increases and the current begin to drop, the variable frequency drive increases the frequency to the motor, and thereby increase motor fan speed until the maximum predetermined percentage parameter has been, thus stabilizing the fan speed. 
     Conversely, as the static pressure decreases and the motor current begins to rise, the variable frequency drive decreases motor frequency, thereby slowing motor fan speed until the frequency is lowered such that motor current is below a maximum symmetrical current percentage of the motor current. This method also provides a real time fan response, which corresponds to different levels of static pressure. 
     Examples 
     The following examples were performed on an ADC Intelligent Dryer Model id120 to assess dryer performance at varying exhaust fan frequencies. Static pressures were set to either 0.6″ w.c. or 1.5″ w.c. @ 60 Hz while the dryer was empty. 
     
       
         
           
               
            
               
                   
               
               
                 ADC id120 Performance Testing at Varying Fan Frequencies 
               
            
           
           
               
               
            
               
                   
                 Test # 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Fan Frequency 
                 40 Hz 
                 45 Hz 
                 50 Hz 
                 60 Hz 
                 70 Hz 
                 50 Hz 
                 60 Hz 
                 70 Hz 
               
               
                 Empty Static Pressure 
                 0.6″ w.c.     
                 0.6″ w.c.  
                 0.6″ w.c.  
                 0.6″ w.c.  
                 0.6″ w.c.  
                 1.5″ w.c.  
                 1.5″ w.c.  
                 1.5″ w.c.  
               
               
                 Load Size (in Lbs) 
                 120 
                 120 
                 120 
                 120 
                 120 
                 120 
                 120 
                 120 
               
               
                 Fan Motor Speed (in RPM&#39;s) 
                 1200 
                 1350 
                 1500 
                 1800 
                 2100 
                 1500 
                 1800 
                 2100 
               
               
                 Fan Motor Volts (VAC) 
                 117 
                 139 
                 165 
                 212 
                 230 
                 162 
                 221 
                 230 
               
               
                 Fan Motor Start Amps 
                 1.7 
                 1.92 
                 2.18 
                 2.74 
                 3.68 
                 2.11 
                 2.74 
                 3.53 
               
               
                 Fan Motor End Amps 
                 N/A 
                 1.73 
                 1.98 
                 N/A 
                 3.25 
                 1.91 
                 2.43 
                 3.08 
               
               
                 CFM @ .6″ Static &amp; 60 Hz Empty 
                 738 
                 1053 
                 1251 
                 1600 
                 1800 
                 1251 
                 1600 
                 1800 
               
               
                   
               
            
           
         
       
     
     The disclosure has been illustrated by detailed description and examples of particular embodiments. Various changes in form and detail may be made to the illustrative embodiments without departing from the spirit and scope of the present invention. It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that the present invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.