Abstract:
A switch for a domestic appliance, such as a cooking range, that includes a radiation emitter, an auxiliary radiation emitter and a radiation receiver, the radiation receiver adapted to receive at least part of the radiation emitted from the radiation emitter and auxiliary radiation emitter and to generate one or more reception signals whose values depend on the radiation received. A controller associated with the switch generates a periodic control pulse (Pc) at a first time interval to cause the radiation emitter to emit radiation for a duration of time and a periodic test pulse (Pt) at a second time interval different than the first time interval to cause the auxiliary radiation emitter to emit radiation for a duration of time. The controller configured to evaluate the one or more reception signals to determine if an error or malfunction exists in the switch.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to Spanish Patent Application ES-P200702211, filed Aug. 6, 2007. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to a tactile switch, and more specifically to a tactile switch used in domestic appliances, such as a cooking appliance. 
       BACKGROUND 
       [0003]    Contact switches are widely used in domestic appliances, such as cooking appliances. The contact switches are disposed beneath a cover on the appliance and a user acts on them by exerting pressure on or pressing the cover, the pressing action being detected thanks to the contact switches. 
         [0004]    Different types of contact switches, such as capacitive or optical switches, are known. In optical switches an optical sensor is disposed beneath the cover, the optical sensor generally comprising a radiation emitter that emits radiation (light) and a receiver that may receive at least part of the radiation emitted by the emitter. When a user exerts pressure on the cover that covers the switch, the radiation emitted by the emitter that the receiver receives varies, the pressing action being detected. 
         [0005]    In conventional optical switches it is not possible to detect if the optical sensor is working correctly or not, which could cause serious safety problems. If the switch is activated and this is not detected by the optical sensor, this is extremely serious, the result being that the deactivation of the switch is not detected when the user presses it again. For example, United States Patent Application published as US2006/0282070A1 discloses the use of an evaluation circuit for evaluating the functioning of the optical sensor and thereby identify any faults in it, the circuit enabling the evaluation of the value of an input signal in a microprocessor for a preset period of time. The period is divided into a first and a second time interval, the values of the input signal being obtained in one or the other interval. Thus, in the first interval the value mainly depends on the radiation emitted by a light emitter whereas in the second interval it mainly depends on a signal emitted by the microprocessor itself. 
       SUMMARY OF THE DISCLOSURE 
       [0006]    It is an object of the invention to provide a tactile switch as described in the claims. 
         [0007]    The tactile switch of the invention is used in domestic appliances. In one embodiment, the switch comprises an optical sensor that comprises at least a radiation emitter and reception means/radiation receiver adapted to receive at least part of the emitter radiation emitted by the emitter and which generates at least a reception signal, the value of which depends on the radiation received, and a controller/control means for evaluating the reception signal. 
         [0008]    The optical sensor also comprises an auxiliary radiation emitter and the reception means/radiation receiver is also adapted to receive at least part of the auxiliary emitter radiation emitted by the auxiliary emitter, the reception signal generated by the reception means/radiation receiver also depending on the auxiliary emitter radiation received from the auxiliary emitter. The controller/control means generates a periodic control pulse so that the emitter may emit emitter radiation, and a periodic test pulse so that the auxiliary emitter may emit auxiliary emitter radiation, the controller/control means generating the pulses during different time intervals so that they do not coincide. 
         [0009]    In this way, depending on the reception signal, the controller/control means may determine if the switch has been pressed or not depending on the emitter radiation received by the reception means/radiation receiver, and whether the optical sensor is malfunctioning or not depending on the auxiliary emitter radiation received by the reception means/radiation receiver. 
         [0010]    Thus, it is possible to determine whether the optical sensor is malfunctioning or not, thereby reducing the risk of a fault not being detected when the switch is pressed to activate a function such as, for example, the switching on of a burner on a cooking appliance. In this case, if a fault is detected in the switch the function can be switched off automatically without having to wait for the switch to be pressed again, which in this case would also be impossible to detect. 
         [0011]    These and other advantages and characteristics of the invention will be made evident in the light of the drawings and the detailed description thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a cross-sectional view of a switch in an embodiment of the present invention. 
           [0013]      FIG. 2  shows a reception signal in normal lighting conditions. 
           [0014]      FIG. 3  shows a reception signal when the reception means/radiation receiver receives a lot of radiation from an external source. 
           [0015]      FIG. 4  is a perspective view of a switch in an embodiment of the present invention. 
           [0016]      FIG. 5  is a perspective view of a switch in another embodiment of the present invention. 
           [0017]      FIG. 6  shows the control and test pulses generated by the controller/control means of a switch in an embodiment of the present invention. 
           [0018]      FIG. 7  schematically shows the switches of  FIG. 4  and  FIG. 5 . 
           [0019]      FIG. 8  is a perspective view of a switch in another embodiment of the present invention. 
           [0020]      FIG. 9  is a perspective view of a switch in another embodiment of the present invention. 
           [0021]      FIG. 10  schematically shows the switches of  FIG. 8  and  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]      FIG. 1  shows a tactile switch  100  in an embodiment of the present invention. The switch  100  comprises a cover  1  on which a user touches or otherwise exerts pressure, generally with their finger, in order to press the switch  100 , and preferably an optical sensor  2  disposed beneath the cover  1  and a controller/control means  3  that may comprise, for example, a microcontroller, which may determine if the switch  100  has been pressed or not depending on at least a reception signal  4 ,  5  generated by the optical sensor  2 . The optical sensor  2  comprises at least a radiation emitter  21  and reception means/radiation receiver  22  adapted to receive at least part of the emitter radiation emitted by the emitter  21  by reflection, the reception means/radiation receiver  22  generating the reception signal  4 ,  5  that reaches the controller/control means  3 , the value of which depends on the radiation it receives. 
         [0023]    Part of the emitter radiation emitted by the emitter  21  is reflected on the cover  1  and the rest passes through the cover  1 , with only the light that is reflected on the cover  1  reaching the reception means  22 . When a user acts on the switch  100  by pressing or touching the cover  1 , at least part of the light that passes through the cover  1  is reflected on the finger of the user and reaches the reception means  22 , the reception signal  4 ,  5  generated by the reception means  22  thereby being modified and the control means  3  detecting the pressing action thanks to the reception signal  4 ,  5 . 
         [0024]      FIG. 2  shows an embodiment of the reception signal  4 ,  5  in normal lighting conditions when a user presses or touches the switch  100  during a time interval t 1 -t 4  with their finger, for example. Up to the instant t 1  and from the instant t 4 , time intervals in which a user does not press the switch  100 , part of the emitter radiation emitted by the emitter  21  is reflected on the cover  1  and the vast majority of it passes through the cover  1  and is not reflected, the reflected part being detected by the detection means  22 . In this situation, the controller/control means  3  does not detect any pressing of the switch  100 . During the time intervals t 1 -t 2  and t 3 -t 4 , the user&#39;s finger moves towards the cover  1  of the switch  100  (or away from it) reflecting part of the radiation that passes through the cover  1  on it, the radiation reaching the reception means  22 . The interval t 2 -t 3  corresponds with the time interval during which the finger presses down on the cover  1  of the switch  100 , a large part of the radiation that passes through the cover  1  being reflected on the finger and reaching the reception means  22 . When receiving a reception signal  4 ,  5  of these characteristics, the control means  3  detects that the switch  100  has been pressed. 
         [0025]      FIG. 3  shows an embodiment of the reception signal  4  when the reception means/radiation receiver  22  receives a lot of radiation from an external source, such as fluorescent or solar radiation, for example. Up to the instant t 1  and from the instant t 4 , the reception means  22  generate a reception signal  4  with great intensity (or maximum intensity) as they are receiving a lot of radiation, a sign that may indicate a saturation of the reception means  22 . During the intervals t 1 -t 2  and t 3 -t 4 , the user&#39;s finger moves towards the cover  1  of the switch  100  (or away from it) and blocks at least part of the external radiation, all or a portion of the radiation not reaching the reception means  22 , the reception means  22  being reached by the emitter radiation emitted by the emitter  21  that is reflected on the cover  1  and the part of the emitter radiation emitted by the emitter  21 , which, after passing through the cover  1  is reflected on the finger. The interval t 2 -t 3  corresponds with the time interval during which the finger exerts pressure on or presses down the switch  100 , a large part of the emitter radiation emitted by the emitter  21  being reflected on the finger, and with the reception means  22  only being reached by the reflected radiation, this being detected by the control means  3 . 
         [0026]    The optical sensor  2  of the switch  100  of the invention also comprises an auxiliary radiation emitter  23 , shown in  FIGS. 4 and 5 , which is preferably adapted to emit auxiliary emitter radiation directly towards the reception means  22 . Through an emitter signal  6  the controller/control means  3  transmits a periodic control pulse Pc (See  FIG. 6 ) to the emitter  21  shown in  FIG. 7  so that the emitter  21  emits emitter radiation, and through an auxiliary emitter signal  7  the controller/control means  3  transmits a periodic test pulse Pt (See  FIG. 6 ) to the auxiliary emitter  23 , as shown in  FIG. 7 , so that the auxiliary emitter  23  emits auxiliary emitter radiation, the pulses Pc and Pt being generated during different time intervals. Thus, the control pulses Pc and the test pulses Pt do not coincide, the control means  3  being capable of determining if the value of the reception signal  4 ,  5  corresponds with the emitter radiation emitted by the emitter  21  or with the auxiliary emitter radiation emitted by the auxiliary emitter  23 . 
         [0027]    When the value of the reception signal  4 ,  5  depends on the emission radiation emitted by the emitter  21 , the control means  3  evaluates the reception signal  4 ,  5  to determine if the switch  100  has been pressed or not. When the control means  3  generates the test pulses Pt, the value of the reception signal  4 ,  5  depends on the auxiliary emission radiation emitted by the auxiliary emitter  23 , and the control means  3  evaluates the reception signal  4 ,  5  to determine if the optical sensor  2  is malfunctioning or not. When the reception means  22  receive the auxiliary emitter radiation directly, they receive substantially all the radiation emitted by the auxiliary emitter  23  generating a reception signal  4 ,  5  with a high value. As a result, thanks to the value, the control means  3  may also determine if the reading is correct or not. Thus, in one embodiment in normal lighting conditions, when the auxiliary emitter  23  receives a test pulse Pt it generates auxiliary emitter radiation for a time interval preferably equal or substantially equal to the duration of the test pulse Pt, and the reception means  22  receives at least part of the radiation and generates the corresponding reception signal  4 , which is received by the control means  3 . If the reception means  22  malfunction, the reception signal  4  comprises a null value or a maximum value that corresponds with the saturation of the reception means  22  (in the event of the short-circuit of the reception means  22 , for example), the control means  3  determining an error or malfunction in the optical sensor  2 . 
         [0028]    In one embodiment, the emitter  21  is also adapted to generate a safety signal  8 , as shown in  FIG. 7 , that reproduces, at least in part, the control pulses Pc it receives. The safety signal  8  reaches the control means  3 , the control means  3  being capable of evaluating the safety signal  8 . Thus, if when a control pulse Pc is generated it does not receive a pulse through the safety signal  8 , the control means  3  may determine that there is an error in the emitter, for example. 
         [0029]    In the embodiments of  FIGS. 4 ,  5  and  7 , the reception means  22  comprises a single radiation receiver  22   a.  The receiver  22  and the auxiliary emitter  23  may be built into a single unit or element  24 , as shown in  FIG. 4 , or into different elements  30  and  31  as shown in  FIG. 5 , the emitter  21  forming a single element  25  in both cases. The receiver  22  is adapted to receive at least part of the emitter radiation emitted by the emitter  21  by reflection and to receive part or substantially all the auxiliary emitter radiation emitted by the auxiliary emitter  23  directly, generating the reception signal  4  depending on the radiation it receives at each moment. For this reason, the switch  100  comprises, in one embodiment, at least an insulating element  101  disposed between the emitter  21 , and the auxiliary emitter  23  and the receiver  22   a.  It is appreciated that switch  100  may comprise multiple radiation emitters and/or multiple auxiliary radiation emitters  23  and/or multiple radiation reception means  22 . 
         [0030]    In the embodiments of the switch  100  shown in  FIGS. 8 to 10  the reception means  22  comprises a radiation receiver  22   a  and an auxiliary radiation receiver  22   b.  The receiver  22   a  is adapted to receive at least part of the emitter radiation emitted by the emitter  21  by reflection and to receive part or substantially all the auxiliary emitter radiation emitted by the auxiliary emitter  23  directly, and the auxiliary receiver  22   b  is adapted to receive at least part of the auxiliary emitter radiation emitted by the auxiliary emitter  23  by reflection and to receive part or substantially all the emitter radiation emitted by the emitter  21  directly. For this reason, the switch  100  preferably comprises at least a second insulating element  102  disposed between the emitter  21  and the auxiliary receiver  22   b,  and the auxiliary emitter  23  and the receiver  22   a.  Each receiver  22   a  and  22   b  generates a reception signal  4  and  5  whose value depends on the radiation received by the corresponding receiver  22   a,    22   b,  both reception signals  4  and  5  reaching the control means  3  which may determine that the switch  100  has been pressed, by means of both reception signals  4  and  5 . In the second embodiment, the control means  3  transmits the control pulses Pc for the emitter  21  through the emitter signal  6  and the test pulse Pt for the auxiliary emitter  23  through auxiliary emitter signal  7 , thereby determining if there is an error or not in the optical sensor  2  depending on the reception signals  4  and  5  received. In these embodiments the emitter  21  and the auxiliary receiver  22   b  may be built into a first single unit/element  27  of the optical sensor  2 , and the auxiliary emitter  23  and the receiver  22   a  may be built into a second single unit/element  26  of the optical sensor  2  as shown in  FIG. 8 , or they may be independent to each other to form four elements  33 ,  34 ,  35  and  36  as shown in  FIG. 9 . In one embodiment, radiation emitter  21  and/or auxiliary radiation emitter  23  generate a safety signal  8  and  9 , respectively, that reproduces the control pulses Pc and the test pulses Pt they receive, respectively. If the safety signals  8  and/or  9  reach the controller/control means  3 , the control means  3  is capable of evaluating one or both of safety signals  8  and  9 . Thus, if when a control pulse Pc or a test pulse Pt is generated it does not receive a pulse through the corresponding safety signal  8  and/or  9 , the control means  3  may determine that there is an error in the emitter, for example. In alternative embodiments switch  100  comprises multiple radiation emitters  21  and/or multiple radiation receivers  22   a  and/or multiple auxiliary radiation emitters  23  and/or multiple auxiliary radiation receivers  22   b.    
         [0031]    In a brightly lit environment in which the reception means  22  receives a lot of radiation from an external source, such as solar radiation or radiation originating from a fluorescent light, the reception means  22  may be saturated generating a reception signal  4  and/or  5  corresponding with the saturation (the maximum possible value). In the event that the optical sensor  2  malfunctions (a malfunction in the receiver  22  for example), the reception signal  4  and/or  5  may be equal to that of the saturation due to a short in the radiation receiver, for example, the control means  3  being unable to distinguish between the malfunction and the saturation due to the high external radiation. In such a case, the control means  3  is adapted to evaluate whether the optical sensor  2  suffers a malfunction or not when the switch  100  is pressed. In the embodiments of  FIGS. 4 ,  5  and  7 , when the switch  100  is pressed in a brightly lit environment, if the optical sensor  2  malfunctions in a way that produces a maximum reception signal  4  (as a result of a short in radiation receiver  22   a,  for example) the control means  3  is not adapted to identify this type of error. In the embodiments of  FIGS. 8 to 10 , when switch  100  is pressed the pressing action may be determined by the control means  3  by means of both reception signals  4  and  5 . Thus, if one of the elements  21 ,  22   a,    22   b,    23 ,  26  or  27  malfunctions (a malfunction in the optical sensor  2 ), the control means  3  may determine the malfunction as, by means of one of the reception signals  4  or  5 , they will detect that the switch  100  has been pressed, thereby reducing the risk of a malfunction not being detected in the optical sensor  2 , and consequently, in the switch  100 . For example, in one embodiment, reception signals  4  and  5  are made to be equal or substantially equal when both receivers  22   a  and  22   b  are functioning properly. In such an embodiment, a malfunction of one or the other of receivers  22   a  or  22   b  is detectable by comparing the reception signals  4  and  5  to determine if the signals are equal.