Abstract:
The invention provides a pressure controlled device and a system for managing the heating time of a pressure controlled device. The system includes a sensing device that allows the timing of a heating period for the pressure controlled device based on temperature and/or pressure values sensed inside the pressure controlled device. A RFID tag is coupled to the sensing device and is operable for generating timing information. The sensing device and the RFID tag are powered by a nano electromechanical (NEM) device that is operable by a source of pressurized air.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to the field of temperature and pressure controlled cookers and, more particularly, to a system and method for controlling such cookers using nano electromechanical and RFID technologies. 
       RELATED ART 
       [0002]    It is known in the state of the art that pressure cooking is a method of cooking in a sealed vessel that does not permit air or liquids to escape below a preset pressure. Because the boiling point of water increases as the pressure increases, the pressure built up inside the pressure cooker allows the liquid in the pressure cooker to rise to a higher temperature before boiling. 
         [0003]    A pressure cooker is often referred to by several names, such as a steam digester, pressure canner, or pressure controlled recipe. A version of a pressure cooker used by laboratories and hospitals to sterilize materials is known as an autoclave. In the food industry, pressure cookers are often referred to as retorts. 
         [0004]    A gasket or sealing ring forms a gas-tight seal, which does not allow air or steam to escape between the pot and the cover. Normally, the only way the steam can escape is through a regulator on the cover when the pressure has built up. In case the regulator is blocked, a safety valve is provided as a backup escape route for steam. The simplest safety valve is a loose fitting rubber plug in the cover, held in place by steam pressure. If the pressure exceeds design limits, the plug pops out of its seat. 
         [0005]    The food to be cooked or the medical instruments to be sterilized are placed in the pressure cooker with a small amount of water. The vessel is then sealed and placed on a heat source. As the internal temperature rises, the pressure also rises, until the pressure reaches the design gauge pressure. However, controlling the pressure is not easy and steam production may be too important. 
         [0006]    Moreover, pressure cookers have a reputation to be dangerous with the risk of explosion. Modern pressure cookers typically have two or three independent safety valves, as well as some additional safety features, such as an interlock to prevent opening the cover while internal pressure exceeds atmospheric pressure. However there is still a risk of explosion, especially if cookers are not thoroughly and regularly maintained. 
         [0007]    U.S. 200610112834A1 discloses a controlled pressure cooker implementing a RFID tag in a cooking timer to start and stop the cooking process. A sealed cookware and serving-ware object, such as a pressure cooker, is provided. The object is temperature and pressure regulated using control technology such as Radio Frequency Identification (RFID) technology and temperature sensors associated with the objects. In a first embodiment, the temperature sensor is at least partially embedded in the base of the object. In a second embodiment, the temperature sensor extends through a tunnel in a wall of the object and includes a sealing cap to cover the tunnel and prevent air and/or liquid from escaping the interior of the object. 
         [0008]    Prior art systems based on a RFID tag require a power source to supply the RFID tag. 
         [0009]    Powering a RFID may be provided in two ways: either a constant radio frequency field is generated by an external reader as in a classic short range RFID solution or a battery is added to the pressure cooker. The first powering solution exposes the cook to a permanent high strength field in a small area such as a laboratory or a kitchen. In the second powering solution, the RFID tag presents the sensitivity of an active transponder, which then removes the problem of the high strength field. However, there is the requirement of having a battery which needs to be replaced periodically leading then to the drawbacks of battery recycling and cost. 
       SUMMARY OF THE INVENTION 
       [0010]    There is a need of a self-powering system to control pressure cookers. The present invention offers a solution to address the aforementioned needs. 
         [0011]    Accordingly, the present invention provides a system and a method for controlling a pressure cooker using a self-powered timer. 
         [0012]    The present invention further provides a battery-less system and a method for controlling a pressure cooker. 
         [0013]    According to the invention, a nano power generator, coupled to a timer and a RFID tag, are used. 
         [0014]    Further aspects of the invention will now be described, by way of implementation and examples, with reference to the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The above and other items, features and advantages of the invention will be better understood by reading the following more particular description of the invention in conjunction with the figures. 
           [0016]      FIG. 1  is a schematic view of a pressure cooker according to an embodiment of the present invention. 
           [0017]      FIG. 2  details a nano electromechanical system in accordance with an embodiment of the present invention. 
           [0018]      FIG. 3  illustrates several temperature ramp-up curves. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Embodiments of the invention are described hereinafter by way of examples with reference to the accompanying figures and drawings. 
         [0020]      FIG. 1  is a schematic illustration of a pressure cooker  100  in accordance with an embodiment of the present invention. The pressure cooker  100  comprises typical pieces of standard pressure cookers such as a housing  102  closed by a housing cover  104  equipped with a safety valve and pressure regulator  106 . Additional typical components are omitted from the figure and description for sake of clarity. An air/pressure system located on top of the housing cover  104  includes an enclosure  108  that contains a membrane  110 , a nano electromechanical system  112 , and a Radio Frequency IDentification (RFID) tag  114 . 
         [0021]    The membrane  110  in the enclosure  108  is subject to a deformation proportional to the pressure ramp up in the pressure cooker  100 . The pressure is transmitted through a conduit  105  between the housing cover  104  and the enclosure  108 . The membrane  110  further acts to prevent steam from passing through nano electromechanical system  112 , thereby avoiding damaging it. The membrane  110  also allows pressurizing in the enclosure  108  the space  109  located above the membrane  110 . The air contained in this cavity  109  provides energy required to power the nano electromechanical system  112 . As the air consumption of the nano electromechanical system  112  is very low, the pressure value in the cavity is not affected. 
         [0022]    In an alternate embodiment, a safety valve (not shown on  FIG. 1 ) is added on the enclosure to balance air pressure at the end of cooking time. When the pressure increases in the cavity  109  the nano electromechanical system  112  is activated, starting a heating timing duration transmitted to the RFID tag  114 . 
         [0023]      FIG. 2  depicts an embodiment of the nano electromechanical system  112 , namely nano electromechanical system  200 , including a nano power generator  206 , timer  214 , and RFID tag  114 . 
         [0024]    Whereas a long and detailed description on nanotechnology is not provided herein, some general concepts are described for clarity and understanding of the present invention. However, it is to be appreciated that any variations in the implementation, material, or form of the nano electromechanical system  112 , may be made herein without departing from the spirit and scope of the invention. 
         [0025]    Nano electromechanical systems, often abbreviated as NEMS, encompass devices integrating electrical and mechanical functionality on the a nano scale. NEMS typically integrate transistor-like nano electronics with mechanical actuators, pumps, or motors. 
         [0026]    The nano electromechanical system  200  comprises an air path  204  allowing circulation of compressed air. The air path  204  receives from enclosure  108  compressed air flux on an inlet air path ( 204 - a ), generated by the deformation of the membrane  110 , and outputs compressed air flux at an outlet air path ( 204 - b ). 
         [0027]    The nano power generator  206  is composed of a nano wheel  206 - 1  and a nano dynamo  206 - 2 . The compressed air flux arriving at the inlet air path  204 - a  initiates the rotation of nano wheel  206 - 1 . The rotation of nano wheel  206 - 1  generates the rotation of the nano dynamo  206 - 2 . 
         [0028]    The nano dynamo  206 - 2  includes a rotor  203  with magnetized pole and coils  205 . The rotor  203  with the coils  205  operates as a miniaturized dynamo that generates energy. 
         [0029]    A capacitive device  210  stores the energy generated by the nano dynamo  206 - 2  and operates as a temporary battery in case of a failure of the nano power generator  206 . The power thus generated supplies the timer  214  and the RFID tag  114 . 
         [0030]    The timer  214  senses/measures temperature and/or pressure and calculates the quantity of heat received in the pressure cooker. Based on cooking/sterilization settings given by the operator, through the RFID tag  114 , the timer  214  determines the cooking/sterilization time duration. 
         [0031]    Time duration information is then available for the RFID tag  114 . At the end of the time duration, the timer  214  sends the end of cooking/sterilization information to the RFID tag  114 . The RFID tag  114  generates, for a tag reader, an order to stop heating the pressure cooker. 
         [0032]    In alternate embodiments, the RFID tag  114  may provide various timing information. For example, the RFID tag  114  may provide cooking/sterilization time duration or pressure and temperature at given time intervals to allow, for example, a remote software device coupled to the tag reader to compute its own cooking/sterilization time duration. Further, the tag reader can be embedded into a control board of a heating device to automatically stop the heating of the pressure cooker. 
         [0033]    As already mentioned, in order to balance pressure in the cavity  109 , the nano electromechanical system  200  may be further equipped with a safety valve  212  which opens at the end of cooking/sterilization time. 
         [0034]    It will be appreciated that the present invention may be used with a pressure cooker made with any material and heat on any heating source, including induction, gas, electric, etc. 
         [0035]      FIG. 3  shows several examples of time-temperature ramp-up curves that take advantage of the system of the present invention. 
         [0036]    As already explained before, cooking or sterilization conditions depend on the quantity of heat received by the food or by the medical materials in the pressure cooker. The pressure cooker stabilizes the temperature by regulating the internal pressure. To control the duration of the cooking/sterilization time in a standard pressure cooker, a cooking/sterilization time is applied when the pressure regulator starts to operate. This has two effects. Firstly, cooking/sterilization is not precise because the shape of the temperature ramp-up is not considered. However, this parameter depends on the heat source used to heat the pressure cooker. Secondly, as the temperature ramp-up is not controlled, and moreover as it is not possible to precisely control the heat source used to heat the pressure cooker, it becomes not possible to set the pressure regulator to a value that is not achievable even by the worst heat source. 
         [0037]    One of the advantages of the present invention is that the system is able to record in the timer  214  both the temperature and the pressure as soon as the temperature increases, generating a variation of pressure which allows the nano power generator  206  to operate, even if the variation of pressure is small. 
         [0038]    On FIG.  3 - a , a temperature ramp-up is shown for a conventional cooking where the pressure regulator operates when a maximum temperature is reached. In prior art systems, cooking time is manually determined by measuring pressure regulator operating time. On the contrary, with the present invention, there is no need to wait for the pressure regulator to set the cooking time duration. 
         [0039]    FIG.  3 - b  illustrates the case where no pressure regulation is used. The temperature increases over a temperature limit. With the present invention, the source heating is stopped when the necessary quantity of heat is reached. No steam leaks out of the cooker, thereby saving energy. 
         [0040]    On FIG.  3 - c , the temperature ram-up shows the case where a temperature limit is never reached due to an insufficient heating source. Nevertheless with the system of the present invention, end of cooking is determined by considering the quantity of energy applied inside the pressure cooker. 
         [0041]    Thus, any shape of temperature ramp-up as shown on  FIG. 3  or any variation from those, is integrated for the calculation of cooking time even if the pressure limit provided by the pressure regulator is never reached. To this extent, the system of the present invention allows designing faster pressure cookers because pressure limitation remains only a security feature. It is thus not anymore required to wait for the pressure regulator to start operating to measure the cooking time. Moreover, on top of the cooking time benefit, the system of the present invention limits or suppresses steam emission. Thus, less energy is required to obtain the same cooking/sterilization conditions. 
         [0042]    It should be appreciated that while the invention has been shown and described with reference to various embodiment(s), various changes in form and detail may be made therein without departing from the spirit, and scope of the invention. Particularly, no specific description has been made of the process to build the nano electromechanical generator which can be adapted in shape, size to the existing and upcoming nano scale technologies.