Abstract:
A babycare heating apparatus comprising a vessel ( 2;102 ) for containing water and a heating element ( 15;115 ) for heating water held in the vessel, characterized by: a temperature sensor ( 22;42,123 ) for sensing a temperature rise effected by operation of the heating element ( 15 ); and control means ( 25;125 ) for controlling the energizing of the heating element ( 15;115 ) in dependence on the output of the temperature sensor ( 22;42;123 ) and being configured to de-energize the heating element ( 15;115 ) if the change in the temperature, sensed by the sensor ( 22;42;123 ), meets a predetermined criterion. The apparatus can be used as a sterilizer or a bottle warmer, and its uses a measure of the rate of heating during operation to determine whether the apparatus has been correctly charged with water.

Description:
FIELD OF THE INVENTION 
     The present invention relates to babycare heating apparatus. 
     BACKGROUND TO THE INVENTION 
     Electric sterilisers for baby feeding bottles are well-known. Such sterilisers are designed to subject the items being sterilised to a temperature of 80° to 100° for several minutes. 
     In a known design, the operating period is set by loading the apparatus with a predetermined amount of water which evaporates during operation of a heating element. The temperature of the heating element is monitored using a bimetallic thermal switch and when the temperature of the heating element reaches a threshold temperature, indicating that all the water has evaporated or boiled off, the thermal switch opens to cut off the supply of power to the heating element. 
     A problem with this design of steriliser is that effective sterilisation is dependent on the user charging it with the correct amount of water. Additionally, the effective operational time varies according to the mains voltage and the actual values and ratings of readily available components, which can have quite wide tolerances. 
     Another heating apparatus familiar to parents is the electric feeding bottle warmer. These devices typically consist of electrically heated bains-marie. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a babycare heating apparatus comprising:
         a vessel for containing water;   a heating element for heating water held in the vessel;   a temperature sensor for sensing a temperature rise effected by operation of the heating element; and   control means for controlling the energising of the heating element in dependence on the output of the temperature sensor,   wherein the control means is configured to de-energise the heating element if the change in the temperature, sensed by the sensor, meets a predetermined criterion.       

     The control means may be configured to compare the sensed temperature, at a predetermined time after energising the heating element, with a reference value and said criterion may then comprise said sensed temperature being below said reference value, or to determine a rate of change in the temperature, sensed by the sensor, and compare said rate with a reference value and said criterion may then comprise said rate being greater than a threshold value or to determine a rate of change in the temperature, sensed by the sensor, and compare said rate with a reference value and said criterion may then comprise said rate being less than a threshold value. 
     Preferably, the control means is configured to determine a rate of change in the temperature, sensed by the sensor, and compare said rate with a reference value and said criterion comprises said rate being within a predetermined range. 
     Preferably, a metallic heat conductor is provided for conducting heat from the heating element to water in the vessel. More preferably, the temperature sensor is arranged to sense the temperature of said conductor directly. 
     Alternatively, the vessel may have a wall formed from material that is a poor heat conductor for providing thermal protection for users and the temperature sensor may then be mounted to a reduced thickness portion of said wall. Preferably, the reduced thickness portion has a thickness in the range 0.2 to 1.0 mm. 
     The present invention may be particularly embodied in a babycare product steriliser or a babycare bottle warmer. 
     According to the present invention, there is also provided a babycare bottle warmer comprising:
         a vessel for containing water and receiving a feeding bottle to be warmed;   a chamber,   a conduit between the vessel and the dumber;   a valve for opening and closing the conduit;   a heating element for heating water held in the vessel;   control means for opening the valve at the end of a bottle heating operation so that hot water in the vessel is conducted to the chamber.       

    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a steriliser according to the present invention; 
         FIG. 2  is a schematic sectional view of the steriliser of  FIG. 1 ; 
         FIG. 3  is a block diagram of the control electronics of the steriliser of  FIG. 1 ; 
         FIGS. 4 to 8  are flowcharts illustrating the sterilising operation of the steriliser of  FIG. 1 ; 
         FIG. 9  is a schematic sectional view of a simplified steriliser; 
         FIG. 10  shows the control electronics of the steriliser of  FIG. 9 ; 
         FIGS. 11 to 19  are flowcharts illustrating the sterilising operation of the steriliser of  FIG. 9  to sterilise baby feeding bottles; 
         FIG. 20  is a perspective view of a feeding bottle warmer according to the present invention; 
         FIG. 21  is a schematic sectional view of the bottle warmer of  FIG. 6 ; 
         FIG. 22  is a block diagram of the control electronics of the bottle warmer of  FIG. 6 ; 
         FIGS. 23 to 27  are flowcharts illustrating the warming operation of the bottle warmer of  FIG. 20 ; 
         FIG. 28  is a schematic sectional view of another bottle warmer according to the present invention; and 
         FIG. 29  is a block diagram of the control electronics of the bottle warmer of  FIG. 28 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Referring to  FIG. 1 , a steriliser  1  comprises an opaque body  2  formed from polypropylene and a transparent plastic lid  3 , also formed from polypropylene. The body  2  comprises an upper bowl part  4  over a pedestal part  5 . Items to be sterilised are placed in the upper bowl part  4 . The pedestal part  5  contains the steriliser&#39;s electrical components. A 7-segment light emitting diode (LED) display  6  and a push button switch  7  are located in an elliptical aperture  8  in the side wall of the pedestal part  5 . 
     Referring to  FIG. 2 , which omits some structural details unnecessary for an understanding of the present invention, the floor  9  of the bowl part  4  is slightly dished and has a central roofed aperture  10 . Gaps  11  between the roof  12 , over the aperture  10 , and the surrounding part of the floor  9  open into a small cast metal trough  14 . A electric heating element  15 , rated at 500 W at 110V, is mounted to the underside of the trough  14 . The trough  14  and its heating element  15  are clamped in place by a cover  17  that is screwed to pillars (not shown) projecting from the underside of the floor  9 . A watertight seal is formed between the trough  14  and the floor  9 , preferably using an elastomeric sealing member. 
     An electronic assembly  18  is mounted in the pedestal behind the elliptical aperture  8 . The electronic assembly  18  includes a triac  19 , the purpose of which is described below. The triac  19  is thermally coupled to a planar heatsink  20  that extends below the cover  17 . 
     A small area of the floor  9 , located above the electrical assembly, is much thinner, about 0.5 mm thick, than the rest of the floor  9  forming a recess  21 . A thermistor  22  is mounted in the recess  21 . The thermistor  22  location is not covered by water when the correct amount of water has been added to the steriliser  1 . 
     Referring to  FIG. 3 , the electronic assembly  18  includes an electronic control circuit based around a microcontroller  25 . The steriliser  1  is powered from the mains and has a plug  26  for plugging into a mains outlet socket. The triac  19 , a thermal fuse  27  for protecting the steriliser  1  against overheating, and the heating element  15  are connected in series between the live and neutral pins of the plug  26 . 
     A transformer  28  and a rectifying and regulating circuit  29  provide a dc supply for powering the microcontroller  25  from the input mains. The inputs of a zero crossing detector  30  and a peak voltage detecting circuit  31  are connected to the secondary of the transformer  28 . 
     A potential divider  32 , comprising the thermistor  22  and a resistor  33 , is connected between the +V output of the rectifying and regulating circuit  29  and earth. The output of the potential divider  32 , i.e. the junction between the thermistor  22  and the resistor  29 , is connected to an analogue-to-digital converter input of the microcontroller  25 . 
     The 7-segment LED display  6  is driven from a port of the microcontroller  25 . Another port of the microcontroller  25  controls the triac  19 . Finally, the pushbutton switch  7  is connected to an interrupt port of the microcontroller  25 . A pull-up resistor  34  is connected to this interrupt port which is connected to 0V when the switch  7  is closed. 
     The operation of the steriliser  1  will now be described. 
     Referring to  FIG. 4 , when the steriliser  1  is energised from the mains, the microcontroller  25  performs an initial diagnostic routine (step s 1 ). If a fault is detected (step s 2 ), the microcontroller  25  causes the LED display  6  to flash E for “error” (step s 3 ). However, if no faults are detected, the microcontroller  25  causes the LED display  6  to display “r” for “ready” (step s 104 ). Then the microcontroller  25  determines the mains voltage and frequency from the outputs of the zero-crossing detector  30  and the peak voltage detecting circuit  31  and saves these values (step s 5 ). 
     Referring to  FIG. 5 , when the user operates the switch  7 , the microcontroller  25  first checks that “r” or “S” is being displayed (step s 11 ). If neither “r” or “S” is being displayed, the microcontroller  25  reads the stored mains voltage and frequency values and determines switching times for the triac  18  (step s 12 ). For instance, if the mains supply is 110V at 60 Hz, the triac  19  needs to be turned on at the start of each half-cycle which requires a pulse every 16.7 ms. However, if the mains supply is 220V at 50 Hz, the triac needs to be turned on halfway through each half-cycle which requires a pulse 5 ms after each zero-crossing at a rate of one every 20 ms. At substantially the same time, the microprocessor  25  starts first and second timers with respectively 40 seconds and 60 seconds durations (step s 13 ). 
     The microcontroller  25  then begins to output the necessary triac control pulses (step s 14 ) and causes the LED display  6  to display “O” for operating (step s 15 ). 
     Referring to  FIG. 6 , when the first timer has timed out, the microcontroller  25  reads and stores the output of the potential divider  32 , which represents the temperature in the bowl part  4  of the steriliser  1  (step s 21 ). 
     Referring to  FIG. 7 , when the second timer times out, the microcontroller  25  reads the output of the potential divider (step s 31 ). The first value is then subtracted from the new, second value (step s 32 ) and the result compared with upper and lower thresholds (steps  33  and  34 ). The upper and lower thresholds correspond to the rate of heating to be expected with the minimum and maximum acceptable amounts of water in the steriliser  1  under normal domestic operating conditions. 
     If the difference between the first and second values is above the upper threshold, the user has placed insufficient water in the steriliser  1 . The microcontroller  25  responds to this by causing the LED display to flash “L” for “water level too low” (step s 36 ) and ceasing to send pulses to the triac  18  to de-energise the electric heating element  15  (step s 37 ). If the difference between the first and second values is below the lower threshold, the user has placed too much water in the steriliser  1 . The microcontroller  25  responds to this by causing the LED display  6  to flash “H” for “water level too high” (step s 38 ) and ceasing to send pulses to the triac  18  to de-energise the electric heating element  15  (step s 37 ). 
     If the difference between the first and second values is within the range bounded by the upper and lower thresholds, the microcontroller  25  continues to supply pulses to the triac  18  while monitoring the output of the potential divider  32 . 
     When the monitored voltage reaches a level, corresponding to a temperature of 90° in the upper bowl pan  4  of the steriliser  1  (step s 39 ), a four-minute timer is started in the microcontroller  25  (step s 40 ). 
     The microprocessor  25  then enters a loop (steps s 41  to s 44 ) to perform simple on off control of the temperature in the steriliser  1 . The temperature is controlled by de-energising the heating element  15  when the temperature rises above 90° and energising the heating element when the temperature falls below 90°. 
     Referring to  FIG. 8 , when the four-minute timer times out, the microcontroller  25  ceases to send pulses to the triac  19  to de-energise the heating element  15  (step s 51 ) and causes the LED display to display “S” for sterilised (step s 52 ). At substantially the same time, a sterilised time timer is started in the microcontroller  25  (step s 53 ) and the “S” continues to be displayed until the sterilised time timer expires after 3 hours, when it is replaced by “r”. 
     Referring to  FIG. 9 , in a simplified steriliser, a thermistor  42  is mounted to the cast trough  14  instead of in the floor  9  as in the preceding embodiment. The heatsink  20  is also absent, a floor  5   a  has been added to the pedestal part  5  and the cover  17  modified to extend from the floor  5   a  of the pedestal part  5  to the cast trough  14 . A central locating finger  14   a  projects downwards from the cast trough  14  and is received in a hole in the cover  17 . 
     Referring to  FIG. 10 , the circuit of the simplified steriliser comprises a transformerless dc power supply  43 , a microcontroller  44 , a 7-segment LED display  45 , a relay  46 , a fuse  47 , a piezo sounder  48 , a pushbutton switch  49  and a potential divider consisting of the thermistor  42  and a resistor  50 . The microcontroller  44  is powered from the dc power supply  43  which rectifies and reduces the mains voltage received via a mains plug  51 . The potential divider has the resistor  50  connected to the +V output of the dc power supply  43  and the thermistor  42  connected to the earth/−V output of the dc power supply  43 . The node between the thermistor  42  and the resistor  50  is connected to an analogue-to-digital converter input of the microcontroller  44 . The piezo sounder  48  is driven directly from outputs of the microcontroller  44 . The segments of the LED display  45  and the coil of the relay  46  are also energised directly by the microcontroller  44 . The pushbutton switch  49  is connected between an interrupt port of the microcontroller  44  and earth. 
     The fuse  47  and the switch of the relay  46  are connected in series between the to mains live input and one end of the heating element  15 . The other end of the heating element  15  is connected to the mains neutral input. 
     The operation of the simplified steriliser will now be described. 
     Referring to  FIG. 11 , when the simplified steriliser is powered up, the microcontroller  44  causes to LED display  45  to display “ 0 ” (step s 60 ). 
     Referring to  FIG. 12 , closing the pushbutton switch  49  generates an interrupt. If responding to the switch closing is not enabled (step s 61 ) nothing happens. However, if responding to the switch  49  closing is enabled, which is the case when the steriliser has been energised and the switch  49  has not yet been closed, the switch closing is responded to. If a sterilising operation is in progress (step s 62 ), the steriliser is reset to its initial powered but not operating state (step s 63 ). However, if a sterilising operation is not in progress, a 2-minute timer is started and the relay  46  is closed to energise the heating element  15  (step s 64 ). 
     Once the heating element  15  has been energised, the temperature of the cast trough  14  is monitored using the output of the potential divider (step s 65 ) and, if the temperature exceeds 110° C., it is determined that the steriliser has boiled dry and the relay  46  is opened to de-energise the heating element  15  (step s 66 ) and an alert is signalled by operating the piezo sounder  48  and flashing “d” on the LED display  45  five times (step s 67 ). Responding to the switch  49  being closed is then enabled (step s 67 ) and the signalling of the alarm continued (step s 68 ). If the switch  49  is now closed, step s 63  will be performed and the steriliser reset. 
     Referring to  FIG. 13 , when the 2 minute timer times out, the temperature of the cast trough  14  is tested (step s 70 ) and, if it is over 80° C., a 1-minute timer is started (step s 71 ) and then monitoring of the temperature of the cast trough  14  is performed (step  972 ). If the temperature is determined to exceed 110° C. at step s 72 , the flow moves to step s 66  of  FIG. 12 . 
     However, if the temperature of the cast trough  14  is found not to be above 80° C. at step s 70 , it is determined that the steriliser has been overfilled and the relay  46  is opened to de-energise the heating element  15  (step s 73 ) and an alert is signalled by operating the piezo sounder  48  and flashing “F” on the LED display  45  five times (step s 74 ). Responding to the switch  49  being closed is then enabled (step s 75 ) and the signalling of the alarm continued (step s 76 ). If the switch  49  is now closed, step s 63  will be performed and the steriliser reset. 
     Referring to  FIG. 14 , when the 1-minute timer times out, a 7-minute timer is started and ‘ 9 ’ is displayed by the LED display  45  (step s 77 ). The temperature of the cast trough  14  is then monitored (step s 78 ) and, if it exceeds 110° C., flow moves to step s 66  in  FIG. 12 . 
     Referring to  FIG. 15 , when the 7-minute timer times out, the microcontroller  44  starts a second 2-minute timer (step s 79 ) and performs simple on/off closed loop control of the heating element  15  to maintain the temperature of the cast trough  14  at about 110° C. (step s 80 ). 
     Referring to  FIG. 16 , when the second 2-minute time times out, the heating element  15  is de-energised (step s 81 ) and an alert signalled to indicate the completion of the sterilising process (step s 82 ). The alert signalling comprises energising the piezo sounder  48  five times while flashing “O” on the LED display  45 . When the alert is complete, “≡” is displayed by the led display  45  (step s 83 ) and a first 1-hour timer is started (step s 84 ). 
     Referring to  FIG. 17 , when the first 1-hour timer times out, the displayed symbol on the LED display  45  is changed to “=” (step s 85 ) and a second 1-hour timer is started (step s 86 ). 
     Referring to  FIG. 18 , when the second 1-hour timer times out, the displayed symbol on the LED display  45  is changed to “=” (step s 87 ) and a third 1-hour timer is started (step s 88 ). 
     Referring to  FIG. 19 , when the third 1-hour timer times out, the microcontroller  44  causes “≡” to be flashed by the LED display  45  (step s 89 ) and responding to closing of the switch  49  is enabled (step s 90 ) to allow the steriliser to be reset. 
     Bottle warmers according to the present invention will now be described. 
     Referring to  FIG. 20 , a bottle warmer  101  comprises a body  102  formed from an opaque plastics material e.g. polypropylene. The body  102  comprises an upper bowl part  104  over a base part  105 . A basket  103  is removably received in the bowl part  104  and provides a secure resting place for feeding bottles  106  during warming. 
     The pedestal part  105  contains the warmer&#39;s electrical components. A 7-segment LED display  107 , a push button switch  108  and a power control knob  109  are provided on the side of the base part  105 . 
     Referring to  FIG. 21 , which omits some structural details unnecessary for an understanding of the present invention, the floor  110  of the bowl part  104  has a roofed central aperture  111  which opens into a small cast metal trough  114 . A electric heating element  115 , rated at 200 W at 110V, is mounted to the underside of the trough  114 . The trough  114  and its heating element  115  are clamped in place by a cover  117  that is screwed to pillars (not shown) projecting from the underside of the floor  110 . The side of the bowl part  104  is hollow. 
     An electronic assembly  118  is mounted in the hollow side of the bowl part  104  and extends into the base part  105 . The electronic assembly includes the switch  107 , a three-position rotary switch  119  (see  FIG. 11 ), operated by means of the knob  109 , and the LED display  107 . The electronic assembly  118  includes a triac  120  ( FIG. 22 ), the purpose of which is described below. The triac  120  is thermally coupled to a heatsink (not shown). 
     A small area of the inner wall of the side of the bowl portion  104  is much thinner, about 0.5 mm thick, than the rest of the inner wall. A recess  122  is formed where the wall  110  is thinned and a thermistor  123  is mounted in the recess  122 . 
     For use, water is placed between the bowl part  104  so that the basket  103  is partial submerged. The water is heated by the heating element  15  and heat is transferred from the water to the bottle  106  in the basket  103 . 
     Referring to  FIG. 22 , the electronic assembly  118  includes an electronic control circuit based around a microcontroller  125 . The warmer  101  is powered from the mains and has a plug  126  for plugging into a mains outlet socket. The triac  120 , a thermal fuse  128  for protecting the warmer  101  against overheating, and the heating element  115  are connected in series between the live and neutral pins of the plug  126 . 
     A transformer  129  and a rectifying and regulating circuit  130  provide a dc supply for powering the microprocessor  125  from the input mains. The inputs of a zero crossing detector  131  and a peak voltage detecting circuit  132  are connected to the secondary of the transformer  129 . 
     The rotary switch  119  has its terminal connected to the +V output of the rectifying and regulating circuit  130  and its other terminals connected to respective input pins of an input port of the microcontroller  125 . Pull-down resistors (not shown) are connected between these pins and 0V. Thus, the three positions of the switch  119  provide three different 3-bit values to the microcontroller  125 . 
     A potential divider  133 , comprising the thermistor  123  and a resistor  134 , is connected between the +V output of the rectifying and regulating circuit  130  and earth. The output of the potential divider  133 , i.e. the junction between the thermistor  123  and the resistor  134 , is connected to a analogue-to-digital converter input of the microcontroller  125 . 
     The 7-segment LED display  107  is driven from a port of the microcontroller  125 . Another port of the microcontroller  125  controls the triac  120 . Finally, the pushbutton switch  108  is connected to an interrupt port of the microcontroller  125 . A pull-up resistor  135  is connected to this interrupt port which is connected to 0V when the switch  108  is closed. 
     The operation of the bottle warmer  101  will now be described. 
     Referring to  FIG. 23 , when the steriliser  1  is energised from the mains, the microcontroller  125  performs an initial diagnostic routine (step s 101 ). If a fault is detected (step s 102 ), the microcontroller  125  causes the LED display  107  to flash E for “error” (step s 103 ). However, if no faults are detected, the microcontroller  125  causes the LED display  6  to display “r” for “ready” (step s 104 ). Then the microcontroller  25  determines the mains voltage and frequency from the outputs of the zero-crossing detector  30  and the peak voltage detecting circuit  31  and saves these values (step s 5 ). 
     Referring to  FIG. 24 , when the user operates the switch  108  with a single push, the microcontroller  125  first checks that “r” is being displayed (step s 111 ). If “r” is not being displayed, the microcontroller  125  reads the stored mains voltage and frequency values and determines switching times for the triac  120  on the basis of these and the power level indicated by the position of the three-way switch  199  (step s 112 ). At substantially the same time, the microprocessor  25  starts first and second timers with respectively 40 s and 60 s durations (step s 113 ). 
     The microcontroller  25  then begins to output the necessary triac control pulses (step s 114 ) and causes the LED display  107  to display “O” for operating (step s 115 ). 
     Refuting to  FIG. 25 , when the first timer has timed out, the microcontroller  25  reads and stores the output of the potential divider  133 , which represents the temperature in the bowl part  104  of the warmer  101  (step s 121 ). 
     Referring to  FIG. 26 , when the second timer times out, the microcontroller  25  read the output of the potential divider (step s 131 ). The first value is then subtracted from the new, second value (step s 132 ) and the result compared with upper and lower thresholds (steps  133  and  134 ). The upper and lower thresholds to correspond to the range of rates of heating consistent with safe and effective heating of milk. If the rate of heating is too high, the target temperature may be overshot and the milk overheated. If the rate of heating is too low, the milk may not reach the required temperature. 
     If the difference between the first and second values is above the upper threshold, the user has placed insufficient water and/or milk in the warmer  101 , or selected too high a power level. The microcontroller  125  responds to this by causing the LED display to flash “L” for contents too low (step s 135 ) and ceasing to send pulses to the triac  120  to de-energise the electric heating element  115  (step s 136 ). If the difference between the first and second values is below the lower threshold, the user has placed too much water and/or milk in the warmer  101  or selected too low a power level. The microcontroller  125  responds to this by causing the LED display  6  to flash “H” for “contents too high” (step s 137 ) and ceasing to send pulses to the triac  120  to de-energise the electric heating element  115  (step s 136 ). 
     If the difference between the first and second values is in the range bounded by the upper and lower thresholds, the microcontroller  125  continues to supply pulses to the triac  120  while monitoring the output of the potential divider  133 . 
     When the monitored voltage reaches a level, corresponding to a temperature of 37° in the milk being heated (step s 138 ), “F” for finished is displayed by the LED display  107  (step s 140 ). 
     A second mode of operation is started by a double push on the pushbutton switch  107 . 
     Referring to  FIG. 27 , the heating element  115  is energised at full power (step s 201 ) until the water in the warmer  101  is at 37° (step s 202 ). The power supply to the heating element  115  is then turned off and on by the microprocessor  125  to keep the water at 37° (steps s 201  to s 204 ). Keeping the water at 37° ensures that the milk being warmed will eventually reach 37° without risk of overheating. 
     Referring to  FIG. 28 , a second bottle warmer  201  according to the present invention is similar to that shown in  FIG. 20 . However, it differs in that a chamber  202  is provided within its base  105 . A passageway  203  extends from the interior of the bowl part  104  to the chamber  202 . A solenoid valve  205  is provided for opening and closing the passageway  203 . A plug  206  can be removed from the bottom of the chamber  202  so that its contents can be drained. 
     Referring to  FIG. 29 , die control circuit is the same as that of the first bottle warmer  101  described above except that an output of the microcontroller  125  is used to control the solenoid valve  205 . 
     The operation of the second bottle warmer  201  is the same as the operation of the first bottle warmer  101  with the addition of the control of the solenoid value  205 . Under normal circumstance, the solenoid valve  205  is closed. However, the microcontroller  125  outputs a signal to open it in step s 140  so that the hot water can drain into the chamber  202 . 
     It will be appreciated that many modifications may be made to the embodiments described above. For example, heating elements having different power and voltage ratings could be used. Additionally, a bottle warmer may use the same temperature control arrangements as the simplified steriliser.