Abstract:
A touch switch includes a touch input section, a metal piece provided to the touch input section at a surface thereof, and at least two induction-type proximity sensors so provided as to face the metal piece. The induction-type proximity sensors are arranged in parallel to each other and each have an LC oscillation circuit that output signals that changes in accordance with the distance to the metal piece. A duplicated touch switch that requires no stroke and achieves switch duplication is thus provided.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a duplicated touch switch that requires no stroke and achieves switch duplication. 
         [0003]    2. Description of the Related Art 
         [0004]    Some switches provided on the operation board of a machine tool and other apparatus are used to command the machine to start and stop operation and emergently stop a driven section in case of emergency. The reliability and safety of such a switch itself are regarded as important features, and the switch is duplicated (two switch systems are provided) for improvement in the reliability and safety. 
         [0005]      FIG. 5  is a schematic configuration diagram showing an example of the duplicated switch. 
         [0006]    A duplicated switch  1  shown in  FIG. 5  has a structure in which an operation button  2  is pressed down in the direction indicated by the arrow in  FIG. 5  to apply pressure onto a contact  21  on a first switch system and a contact  22  on a second switch system so that the contacts  21  and  22  are closed. Therefore, even when one of the switch systems formed of the contacts  21  and  22  fails, the duplicated switch  1  can be used with no problem as long as the other switch system normally functions. 
         [0007]    As a related-art technology of a duplicated switch configured in consideration of reliability and safety, for example, Japanese Registered Utility Model No. 3,179,471 (JP 3,179,471 U) discloses, for example, a membrane switch in which contacts on a plurality of switch systems are provided in each layer. The duplicated switch of the related art is a switch that requires a fixed stroke. 
         [0008]    The duplicated switch of the related art, which requires a fixed stroke as described above, cannot be formed of a touch switch. A keyboard or an operation board using the duplicated switch therefore has a problem of restricted operability and exterior appearance. 
       SUMMARY OF THE INVENTION 
       [0009]    An object of the present invention is to provide a duplicated touch switch that is a touch switch that achieves switch duplication. 
         [0010]    A first aspect of a touch switch according to the present invention includes a touch input section, a metal piece provided to the touch input section at a surface thereof, and at least two induction-type proximity sensors facing the metal piece and arranged in parallel to each other. And each of the induction-type proximity sensors has an LC oscillation circuit that provides an output that changes in accordance with a distance to the metal piece. 
         [0011]    A second aspect of a touch switch according to the present invention includes a touch input section, a first metal piece provided to the touch input section at a surface thereof, a second metal piece provided in a position separated from the touch input section via a linkage section, and first and second induction-type proximity sensors that include LC oscillation circuits so provided as to face the first and second metal pieces and outputting signals that change in accordance with distances to the metal pieces. 
         [0012]    A third aspect of a touch switch according to the present invention includes a touch input section, a metal piece so provided as to be separate from the touch input section via a linkage section, and first and second induction-type proximity sensors that include first and second LC oscillation circuits so provided on opposite sides of the metal piece as to face the metal piece and outputting signals that change in accordance with a distance to the metal piece. 
         [0013]    The present invention, in which a duplicated switch keyboard using a touch switch can be achieved by using induction-type proximity sensors, allows improvement in operability of the keyboard and an increase in design flexibility. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The object and feature of the present invention described above and other objects and features thereof will be apparent from the description of the following embodiments with reference to the accompanying drawings: 
           [0015]      FIG. 1  is a schematic configuration diagram showing an example of an induction-type proximity sensor; 
           [0016]      FIG. 2  is a schematic configuration diagram of a duplicated touch switch according to a first embodiment of the present invention; 
           [0017]      FIG. 3  is a schematic configuration diagram of a duplicated touch switch according to a second embodiment of the present invention; 
           [0018]      FIG. 4  is a schematic configuration diagram of a duplicated touch switch according to a third embodiment of the present invention; and 
           [0019]      FIG. 5  is a schematic configuration diagram showing an example of a duplicated switch. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    According to the present invention, a duplicated switch using a touch switch based on an induction-type proximity sensor is provided. 
         [0021]    An example of an induction-type proximity sensor will first be described with reference to  FIG. 1 . 
         [0022]    An induction-type proximity sensor  10  is formed of an LC oscillation circuit, which is formed of a coil  12  and a capacitor  13 , and a sensor IC  11 , which senses the oscillation state of the LC oscillation circuit, as shown in  FIG. 1 . When a metal piece  30 , which is an object to be detected, is brought into proximity to, but not in contact with, the LC oscillation circuit of the induction-type proximity sensor  10 , the sensor IC  11  can sense attenuation or pause of the oscillation of the LC oscillation circuit that occurs when the metal piece  30  is displaced in the direction indicated by the arrow A or A′ in  FIG. 1 . 
         [0023]    The induction-type proximity sensor  10  can sense the state of the oscillation even when the distance between the metal piece  30  and the LC oscillation circuit changes by as small as about 5 μm and can therefore be used as a touch switch in an application in which bending of an operation surface operated by an operator or a minute change in the position of the operation surface need to be sensed. In the present invention, a duplicated touch switch is achieved by using this induction-type proximity sensor  10 . 
         [0024]    A duplicated touch switch according to a first embodiment of the present invention will next be described with reference to  FIG. 2 . 
         [0025]    A duplicated touch switch  3  according to the present embodiment includes a touch input section  5 , which is formed of the metal piece  30  bonded to part of an operation board enclosure  4 , and at least two induction-type proximity sensors  10   a,    10   b,  . . . , which are located in the vicinity of the enclosure interior side of the touch input section  5 , as shown in  FIG. 2 . 
         [0026]    The touch input section  5  is formed by fitting the metal piece  30  to, burying the metal piece  30  in, or attaching the metal piece  30  to, cover of the operation board enclosure  4 . The cover that is part of the operation board enclosure  4  and forms the touch input section  5  is made of a resin or any other elastic material and is therefore elastically deformed by a small amount in the direction indicated by the arrow C in  FIG. 2  when the bonded metal piece  30  receives pressure produced by contact of a fingertip or any other object with the touch input section  5  and oriented in the direction indicated by the arrow B in  FIG. 2 . The elastic deformation changes the distance between the metal piece  30  and LC oscillation circuits ( 12   a,    13   a;    12   b,    13   b ) provided in the induction-type proximity sensors  10   a,    10   b,  . . . , and sensor ICs  11   a,    11   b,  . . . sense attenuation or pause of the oscillation of the LC oscillation circuits that occurs due to the change in the distance. Contact of a fingertip or any other object with the touch input section  5  is thus sensed. 
         [0027]    The number of induction-type proximity sensors  10   a,    10   b,  . . . provided in one duplicated touch switch  3  is at least two, and the sensor ICs  11   a,    11   b,  . . . , provided in the induction-type proximity sensors  10   a,    10   b,  . . . respectively are connected to different switch systems. Further, the LC oscillation circuits formed of the coils  12   a,    12   b,  . . . , and the capacitors  13   a,    13   b,  . . . in the induction-type proximity sensors  10   a,    10   b,  . . . are disposed in the vicinity of, but not in contact with the metal piece  30 , the enclosure interior side of the touch input section  5 . Therefore, even when one of the switch systems fails or otherwise malfunctions, the other switch system that works normally can sense that the operator has touched the touch input section  5 . Further, even when the position where the operator touches the touch input section  5  is slightly off-center to the periphery, one of the induction-type proximity sensors  10   a,    10   b,  . . . senses the operator&#39;s contact operation, whereby the operation can be stably sensed. 
         [0028]    A duplicated touch switch according to a second embodiment of the present invention will next be described with reference to  FIG. 3 . 
         [0029]    In a duplicated touch switch  3  according to the present embodiment, the induction-type proximity sensor  10   a  is disposed in the vicinity of the enclosure interior side of the touch input section  5  including a metal piece  30   a,  and an auxiliary sensing section  7  is disposed on the enclosure interior side of the induction-type proximity sensor  10   a,  as shown in  FIG. 3 . The auxiliary sensing section  7  is then linked with the touch input section  5  via a linkage section  6 , and the induction-type proximity sensor  10   b  is disposed in the vicinity of on the enclosure interior side of the auxiliary sensing section  7 . The auxiliary sensing section  7  includes a metal piece  30   b,  as the touch input section  5  does. The linkage section  6  is made of a material rigid enough to withstand against external pressure, and when the touch input section  5  is displaced in the direction indicated by the arrow E in  FIG. 3 , the displacement is transmitted to the auxiliary sensing section  7  via the linkage section  6 . 
         [0030]    The LC oscillation circuit provided in the induction-type proximity sensor  10   a  is disposed in the vicinity of, but not in contact with, the enclosure interior side of the touch input section  5 , and a change in the distance to the metal piece  30   a  allows the sensor IC  11   a  to sense attenuation or pause of the oscillation of the LC oscillation circuit. 
         [0031]    Similarly, the LC oscillation circuit provided in the induction-type proximity sensor  10   b  is disposed in the vicinity of, but is not in contact with, the enclosure interior side of the auxiliary sensing section  7 , and a change in the distance to the metal piece  30   b  allows the sensor IC  11   b  to sense attenuation or pause of the oscillation of the LC oscillation circuit. 
         [0032]    The sensor ICs  11   a  and  11   b  provided in the induction-type proximity sensors  10   a  and  10   b  are connected to different switch systems. 
         [0033]    In the thus configured duplicated touch switch  3 , when the touch input section  5  receives pressure produced by contact of a fingertip or any other object with the touch input section  5  and oriented in the direction indicated by the arrow D in  FIG. 3 , the touch input section  5  is elastically deformed by a small amount in the direction indicated by the arrow E in  FIG. 3 , and the displacement of the touch input section  5  due to the elastic deformation is transmitted to the auxiliary sensing section  7  via the linkage section  6 . As a result, the auxiliary sensing section  7  is slightly displaced in the direction indicated by the arrow F in  FIG. 3 , and the distance between the metal piece  30   a  and the LC oscillation circuit provided in the induction-type proximity sensor  10   a  and the distance between the metal piece  30   b  and the LC oscillation circuit provided in the induction-type proximity sensor  10   b  change, respectively. Sensing attenuation or pause of the oscillation of the LC oscillation circuits due to the changes in the distances, the sensor ICs  11   a  and  11   b  can sense that a fingertip or any other object has touched the touch input section  5 . 
         [0034]    Therefore, even when one of the switch systems fails or otherwise malfunctions, the other switch system that works normally can sense that the operator has touched the touch input section  5 . Further, in the embodiment, the plurality of induction-type proximity sensors  10   a,    10   b,  . . . are not required to be arranged in parallel to each other, as compared with the first embodiment described above with reference to  FIG. 2 , the area of the touch input section  5  can be reduced. 
         [0035]    A duplicated touch switch according to a third embodiment of the present invention will next be described with reference to  FIG. 4 . 
         [0036]    In a duplicated touch switch  3  according to the present embodiment, the auxiliary sensing section  7  is disposed on the enclosure interior side of the touch input section  5 , the auxiliary sensing section  7  is linked with the touch input section  5  via the linkage section  6 , and the induction-type proximity sensors  10   a  and  10   b  are disposed in the vicinity of the enclosure exterior side and in the vicinity of the enclosure interior side of the auxiliary sensing section  7 , respectively, as shown in  FIG. 4 . The auxiliary sensing section  7  includes the metal piece  30 . The linkage section  6  is made of a material rigid enough to withstand against external pressure, and when the touch input section  5  is displaced in the direction indicated by the arrow H in  FIG. 4 , the displacement is transmitted to the auxiliary sensing section  7  via the linkage section  6 . 
         [0037]    The LC oscillation circuit provided in the induction-type proximity sensor  10   a  is disposed in the vicinity of, but not in contact with, the enclosure exterior side of the auxiliary sensing section  7 , and a change in the distance to the metal  30  allows the sensor IC  11   a  to sense attenuation or pause of the oscillation of the LC oscillation circuit. 
         [0038]    Similarly, the LC oscillation circuit provided in the induction-type proximity sensor  10   b  is disposed in the vicinity of, but not in contact with, the enclosure interior side of the auxiliary sensing section  7 , and the change in the distance to the metal  30  allows the sensor IC  11   b  to sense attenuation or pause of the oscillation of the LC oscillation circuit. 
         [0039]    The sensor ICs  11   a  and  11   b  provided in the induction-type proximity sensors  10   a  and  10   b  are connected to different switch systems. 
         [0040]    In the thus configured duplicated touch switch  3 , when the touch input section  5  receives pressure produced by contact of a fingertip or any other object with the touch input section  5  and oriented in the direction indicated by the arrow G in  FIG. 4 , the touch input section  5  is elastically deformed by a small amount in the direction indicated by the arrow H in  FIG. 4 . The displacement of the touch input section  5  due to the elastic deformation is transmitted to the auxiliary sensing section  7  via the linkage section  6 , and the auxiliary sensing section  7  is slightly displaced in the direction indicated by the arrow J in  FIG. 4 . As a result, the distance between the metal piece  30  and the LC oscillation circuit provided in the induction-type proximity sensor  10   a  changes, and the distance between the metal piece  30  and the LC oscillation circuit provided in the induction-type proximity sensor  10   b  changes. Sensing attenuation or pause of the oscillation of the LC oscillation circuits due to the changes in the distances, the sensor ICs  11   a  and  11   b  can sense that a fingertip or any other object has touched the touch input section  5 . 
         [0041]    Therefore, even when one of the switch systems fails or otherwise malfunctions, the other switch system that works normally can sense that the operator has touched the touch input section  5 . Further, the induction-type proximity sensors  10   a  and  10   b  are not required to be arranged in parallel to each other, as compared with the first embodiment, the area of the touch input section  5  can be reduced. 
         [0042]    The embodiments of the present invention have been described above, but the present invention is not limited only to the embodiments described above and can be implemented in a variety of aspects with appropriate changes made to the embodiments.