Abstract:
A method for operating an appliance includes (1) turning on the appliance, (2) determining if the appliance is moving with sufficient velocity with an optical motion sensor, and (3) if the appliance is not moving with sufficient velocity, turning off the appliance. An appliance includes an optical motion sensor for detecting motion of the appliance and a controller coupled to the optical motion sensor, wherein the controller turns off the appliance if the appliance is not moving with sufficient velocity.

Description:
DESCRIPTION OF RELATED ART  
       [0001]     A flat iron is a useful home appliance for pressing wrinkled fabrics. However, a problem occurs if a hot flat iron is left resting on a piece of fabric. The fabric may be damaged or even set on fire. A piece of fabric that catches fire represents a danger to both people and property.  
         [0002]     One existing solution is to use a timer. To use the iron, the timer must be set. When the timer expires, the iron shuts off until the timer is set again. A disadvantage of this solution is that a short timeout period provides increasing safety but it is also inconvenient because the timer must be reset often. If a long timeout period is used, the iron may rest on a piece of fabric for a long time before shutting off and therefore cause damage to the fabric or even a fire.  
         [0003]     Another existing solution is to use a motion sensor. However, a single motion sensor in an iron cannot determine both the motion of the iron and the orientation of the iron (e.g., determining if the iron is sitting flat against a surface or on its heel and away from the surface). Thus, both a motion sensor and a tilt sensor would have to be used, thereby increasing the cost of the iron. Some motion sensors also use a mercury tilt switch, which is difficult to dispose after the useful life of the iron.  
         [0004]     Yet another existing solution is an iron that uses only steam. As the temperature of steam is below the ignition temperature of most fabrics, such an iron will not cause fabric to catch fire even if it is left in contact with the fabric for an extended period of time. A disadvantage of this solution is that a steam-only iron does not remove wrinkles as well as a conventional flat iron.  
         [0005]     Thus, what is needed is an iron that addresses the above-described disadvantages.  
       SUMMARY  
       [0006]     In one embodiment of the invention, a method for operating an appliance includes (1) turning on the appliance, (2) determining if the appliance is moving with sufficient velocity with an optical motion sensor, and (3) if the appliance is not moving with sufficient velocity, turning off the appliance.  
         [0007]     In one embodiment of the invention, an appliance includes an optical motion sensor for detecting motion of the appliance and a controller coupled to the optical motion sensor, wherein the controller turns off the appliance if the appliance is not moving with sufficient velocity. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  illustrates a schematic of an electric flat-iron in one embodiment of the invention.  
         [0009]      FIG. 2  illustrates a schematic of an optical sensor for the iron of  FIG. 1  in one embodiment of the invention.  
         [0010]      FIG. 3  is a flowchart of a method to operate the iron of  FIG. 1  in one embodiment of the invention.  
         [0011]      FIG. 4  is a flowchart of a method to operate the iron of  FIG. 1  in another embodiment of the invention.  
         [0012]      FIG. 5  illustrates a schematic of another optical sensor for the iron of  FIG. 1  in another embodiment of the invention. 
     
    
       [0013]     Use of the same reference numbers in different figures indicates similar or identical elements.  
       DETAILED DESCRIPTION  
       [0014]      FIG. 1  illustrates an electric flat iron  100  in embodiment of the invention. Iron  100  has a heated sole plate  102  that is pressed against fabric to remove wrinkles. Sole plate  102  has an electrical resistance heating element  104 . Heating element  104  is coupled by a power switch  106  to a power supply  108 . Power supply  108  in turn coupled to a power cord  110 .  
         [0015]     A microcontroller  112  is coupled to an optical motion sensor  114  mounted on the heel of iron  100 . Sensor  114  may be mounted away from sole plate  102  to avoid heat damage. Sensor  114  is able to detect the motion of iron  100  over a working surface  116  as well as the orientation of iron  100  (e.g., flat against or lifted away from surface  116 ). Sensor  114  is also ore sensitive to motion than conventional motion sensors used in irons. Depending on the motion of iron  100 , microcontroller  112  closes or opens switch  106  to turn on or off heating element  104 .  
         [0016]      FIG. 2  illustrates one implementation of optical motion sensor  114  in one embodiment of the invention. In one embodiment, sensor  114  is an optical navigation sensor for optical mouse available from Agilent Technologies, Inc. of Palo Alto, Calif.  
         [0017]     Sensor  114  includes a light source  202  (e.g., a light emitting diode) that illuminates surface  116 . Light source  202  may generate a light that is not visible, such as infrared and ultraviolet. A lens  203  directs the light from light source  202  onto an area on surface  116 . The light reflects off microscopic textural features in the area. A lens  204  collects the reflected light and forms an image on an optical sensor chip  206 .  
         [0018]     Light source  202  can also be an indicator of the state of iron  100  to the user. For example, light source  202  can generate a continuous light when iron  100  is against surface  116  and moving (during use), a fast flashing light when iron  100  is against surface  116  but not moving (during nonuse), and a slow flashing light when iron  100  is not against surface  116  (during liftoff).  
         [0019]     Sensor chip  206  captures surface images sequentially and uses common features in these image to determine the movement of iron  100 . Sensor chip  206  writes the X and Y displacements over surface  116  in registers Delta_X and Delta_Y, respectively.  
         [0020]     Sensor chip  206  also tracks the number of visible features in the surface images in order to detect liftoff of iron  100  from surface  116 . A high number of visible features indicates that iron  100  is flat against surface  116  so that sensor chip  206  is receiving in-focus images. On the other hand, a low number of visible features indicates the iron is lifted away from surface  116  so that sensor chip  206  is receiving out-of-focus images. Sensor chip  206  writes the number of visible features in a register SQUAL (Surface QUALity).  
         [0021]     Microcontroller  112  is coupled to sensor  114  to read the values in registers Delta_X, Delta_Y, and SQUAL. Note that when light source is also used as an indicator, microcontroller  112  should only read the values in these registers when the light is on because the values are invalid when the light is off.  
         [0022]      FIG. 3  illustrates a flowchart of a method  300  for operating an appliance, such as iron  100 , in one embodiment of the invention.  
         [0023]     In step  302 , iron  100  is turned on by a user. In response, microcontroller  112  closes switch  106  to turn on heating element  104 . Heating element then brings sole plate  102  up to a working temperature for removing wrinkles from fabric. Step  302  is followed by step  304 .  
         [0024]     In step  304 , microcontroller  112  determines if iron  100  is flat against surface  116 . Specifically, microcontroller  112  reads the surface quality value from register SQUAL in sensor chip  206 . Microcontroller  112  determines if the surface quality value is greater than a threshold value that indicates iron  100  is flat against surface  116 . If so, then step  304  is followed by step  306 . If the surface quality value is less than or equal to the threshold value, then step  304  is followed by step  314 .  
         [0025]     In step  306 , microcontroller  112  starts a timer. This timer tracks a time period deemed safe for iron  100  to be motionless and flat against surface  116 . Step  306  is followed by step  308 .  
         [0026]     In step  308 , microcontroller  112  determines if iron  100  is moving with a velocity sufficient to prevent fabric damage and/or fire hazard prior to timing out. Specifically, microcontroller  112  continuously reads the displacement values from registers Delta_X and Delta_Y in sensor chip  206 . Microcontroller then determines the velocity of iron  100  from the displacement values. If the velocity of iron  100  is greater than a threshold value prior to timing out, then step  308  is followed by step  304  and repeats the above-described steps. If the velocity of iron  100  not greater than the threshold value prior to timing out, then step  308  is followed by step  310 .  
         [0027]     In step  310 , microcontroller  112  opens switch  106  to turn off heating element  104  in order to prevent fabric damage and/or fire hazard. Step  310  is followed by step  312 .  
         [0028]     In step  312 , microcontroller  112  determines if iron  100  is flat against surface  116  and moving with sufficient velocity. Specifically, microcontroller  112  determines if the surface quality value from register SQUAL is greater than its threshold, and determines if the displacement values from registers Delta_X and Delta_Y result in a velocity greater than its threshold. If iron  100  is flat against surface  116  and moving with sufficient velocity, then step  312  is followed by step  302  where microcontroller  112  turns on heating element  104  and the above-described steps are repeated. Otherwise step  312  loops until iron  100  is flat against surface  116  and moving with sufficient velocity or the user turns off iron  100  completely.  
         [0029]     In step  314 , microcontroller  112  puts iron  100  into a power saving mode. In the power saving mode, heating element  104  operates at a lower temperature. This allows iron  100  to return to the working temperature more quickly when it is used again (e.g., flat against surface  116 ). Iron  100  exits the power saving mode and brings iron  100  back to the working temperature when microcontroller  112  detects that iron  100  is again flat against surface  116 . At this point, step  314  is followed by step  304  and the above-described steps are repeated. If microcontroller  112  does not detect that iron  100  is flat against surface  116  with in a period of time, microcontroller  112  can also completely turn off heating element  104 .  
         [0030]      FIG. 4  illustrates a flowchart of a method  400  for operating iron  100  in one embodiment of the invention. Method  400  is similar to method  300  except that steps  306  and  308  are deleted and step  309  is added. In method  400 , microcontroller  112  turns off heating element  104  whenever iron  100  is not moving with sufficient velocity. Method  400  relies on the thermal inertia of heating element  104  and sole plate  102  to smooth out minor variations in temperature.  
         [0031]     Specifically, step  309  follows step  304  if iron  100  is flat against surface  116 . In step  309 , microcontroller  112  determines if iron  100  is moving with sufficient velocity. If so, step  309  is followed by step  304 . If iron  100  is not moving with sufficient velocity, then step  309  is followed by step  310 .  
         [0032]      FIG. 5  illustrates another implementation of optical motion sensor  114  in another embodiment of the invention. Instead of having registers where the displacement and liftoff values are stored, optical sensor chip  506  has a velocity signal line  508  and a liftoff signal line  510 . When iron  100  is moving with velocity greater than the velocity threshold value, sensor chip  506  puts one logical state (e.g., a logic “1”) on velocity signal line  508 , and vice versa. When iron  100  is flat against surface  116  (i.e., when the surface quality value is greater than the liftoff threshold value), sensor chip  506  puts one logic state (e.g., a logic “1”) on liftoff signal line  510 , and vice versa.  
         [0033]     This implementation of sensor  114  would use an internal circuitry, such as a digital signal processor, to determine the velocity of iron  100  from the displacement values and whether the velocity and liftoff conditions are met. When using this implementation of sensor  114  in method  300  or  400 , microcontroller  112  would simply read the logic states on displacement signal line  508  and liftoff signal line  510  instead of a register in the sensor.  
         [0034]     Various other adaptations and combinations of features of the embodiments disclosed are within the scope of the invention. For example, the concepts described can be applied to other appliances. Numerous embodiments are encompassed by the following claims.