Abstract:
Egg cooking apparatus comprises a cradle ( 13, 14 ) for the egg including resistance means ( 22 ), and control circuitry for heating the resistance means. The cradle comprises flexible sheet means wrappable round the egg, mounted in a pair of half-shell units ( 10, 11 ) mounted for opening and closing around the egg. The half-shell units are of a silicone elastomer with crimped resistance wire incorporated therein, and each backed by a set of resilient fingers. The control circuitry includes temperature sensing means adjacent to the resistance means, and means ( 15 ) for setting the desired temperature and cooking time.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to egg cooking apparatus and the like. 
     TECHNICAL FIELD 
     A boiled egg is a traditional option for breakfast. Boiling eggs is relatively straightforward, but nevertheless can be a somewhat awkward and slightly stressful matter, requiring a saucepan, water, and cooking on a cooker with careful attention to correct timing. Various proposals have therefore been made for automating the boiling of eggs to some degree. The object of the present invention is to provide an improved apparatus for cooking eggs. 
     SUMMARY OF THE INVENTION 
     According to the invention there is provided cooking apparatus for food items such as eggs and the like comprising a cradle for the food item including resistance means, and control circuitry for heating the resistance means. 
     Preferably the cradle comprises flexible sheet means wrappable round the food item, preferably comprising a pair of half-shell units mounted for opening and closing around the item. Preferably the half-shell units are of a silicone elastomer with crimped resistance wire incorporated therein, and each backed by a set of resilient fingers. Preferably the control circuitry includes temperature sensing means adjacent to the resistance means, and means for setting the desired temperature and cooking time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An egg cooking apparatus embodying the invention will now be described, by way of example and with reference to the drawings, in which: 
         FIG. 1  is a perspective view of the apparatus; 
         FIG. 2  shows the two half-shell heating units and one set of resilient fingers; and 
         FIG. 3  shows the control circuitry. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , the apparatus comprises a base  10  and a lid  11  hinged together at  12 . The base  10  includes a half-shell  13 ; the lid  11  contains a matching half-shell  14 . The base also includes control circuitry (described with reference to  FIG. 3 ) and has various control knobs, switches, and indicators  15  thereon. 
       FIG. 2  shows the half-shells  13  and  14  in more detail. Each half-shell is a sheet of silicone elastomer formed as a flat sheet  20  with a half-egg depression  21  in it (the depression in half-shell  14  is reversed). Each depression has a nickel chromium resistance wire  22  embedded in the elastomer; this wire is generally in the form of a large spiral (which can conveniently be a double spiral, so that both ends are at the outer edge of the depression), and is of crimped or zig-zag form so that the half-shell can deform as an egg is placed in it. The ends of the resistance wires are terminated in contacts  23 . 
     In use, an egg is placed in the depression in half-shell  13 , and half-shell  14  is closed on it. The depressions  21  are slightly smaller than the size of a small egg when relaxed, so that closing them over the egg causes them to expand to accommodate the egg. The depressions therefore mold themselves to the egg, ensuring good thermal contact. 
     To assist in this molding, depression  21  may be backed by a gripping element  24  comprising a set of fingers  25 . Element  24  is of flexible and resilient material. A spring (not shown) may be provided behind the centre of element  24  to urge it towards the egg. The half-shell  14  is preferably provided with a similar gripping element (not shown). 
       FIG. 3  shows the circuitry of the apparatus in block form. The circuitry is fed with mains power via a power supply unit  30  which transforms the mains voltage down to a safe and suitable value or values. The PSU  30  feeds a control unit  31 , which drives the resistance wires (heater elements)  22 . One or both of the depressions  21  also has a thermistor or other temperature sensor  35  embedded in it, feeding the control unit  31 . 
     The control unit is fed with suitable control signals from control elements  32 - 34 . In a simple version, there may be a single control  33  (in addition to an on-off switch) which sets the time of cooking Preferably however element  34  is used to set the desired cooking temp and element  32  is used to set the size of egg. The signal from the size of egg control is used to adjust the actual cooking time from the nominal value set by element  33 , so that a large or small egg is cooked for a slightly longer or shorter time than the time used for a standard egg. If desired, a further control may be provided to set the desired cooking temperature. The controls may be potentiometers, multi-position switches, or of digital form with each being selectable in turn by a suitable menu system. 
     The control unit controls the current fed to the heater elements to cook the egg in the desired manner. The time of cooking is set by element  33 ; typical times used for boiling an egg are 3, 4, or 5 minutes. The larger the egg, the longer is takes to cook; element  32  enables the cooking time to be adjusted to compensate automatically for the egg size. 
     As an alternative, the rate of rise of temperature as cooking starts can be measured. The rate at which heat is generated is fixed while the larger the egg, the larger the surface area over which it is applied. A large egg will therefore heat up less rapidly than a small one. The size of the egg can thus be estimated from the rate of temperature rise, as measured by the sensor  35 , and the cooking time is automatically adjusted accordingly. 
     The sensor  35  also enables the temperature of cooking to be controlled to a desired level. In a simple system, this level will be set to the temperature of boiling water, approximately 100° C., to match the effect of boiling the egg. If the temperature control  34  is provided, however, then the temperature of cooking can be controlled; this enables the consistency of the yolk relative to that of the white to be controlled. The control unit either adjusts the level of the heater current or pulses the current with a variable duty ratio. 
     When cooking is complete, the control unit turns off the heater current and sends a signal which is here shown as being fed to an alarm unit  36 , which can conveniently generate an audible signal and/or turn an indicator light on or off. The apparatus can also be arranged to open automatically or to cause the cooked egg to pop up or out somewhat like a pop-up toaster. For this, it is desirable to provide a wire skeleton holder to hold the egg and enable it to be lowered into and raised out of the cradle  16 . 
     Means for weighing the egg can also be provided, coupled to the control unit so as to adjust the cooking time automatically in dependence on the weight of the egg. This can be done relatively easily if a wire skeleton holder is provided as just discussed, with a strain gauge or other weight sensing unit attached to the skeleton. Alternatively, the size of the egg may be measured. 
     Means may also be provided for sensing the changing properties of the egg as it cooks, eg by sensing its optical or ultrasound transmitting properties, and controlling the cooking time accordingly. 
     If desired, the apparatus can be provided with a plurality of cradles so that several eggs can be cooked at once. Preferably the various cradles have independent control circuits so that different eggs can be cooked differently. Micro-switches can be provided so that only occupied cradles are energized. 
     The control unit preferably turns the heater on only when the lid is closed on the base. Optionally, the on-off switch may be omitted, with the closure of the lid automatically initiating cooking. Preferably, means are provided for detecting the presence of an egg in a cradle, so that only an occupied cradle is energized. (This function can be performed by weighing means if those are provided.) 
     It is clear that the present apparatus can be used to cook eggs in a manner directly equivalent to boiling, but without the need for a saucepan and water, and without the need for the cook to time the operation. There is no lime scale build-up and nothing to be washed after use. The apparatus is also quicker, as the time delay required to heat and boil water is eliminated, and for the same reason it uses less energy than conventional boiling. Further, since the temperature can be set to various values, different methods of cooking are provided—for example, by using a lower temperature, the egg can effectively be poached.