Mat sensor
First Claim
1. A mat sensor comprising:
- mat shaped body detection means including a plurality of sensor portions, wherein each sensor portion includes a pair of mutually facing electrode plates which are contacted when the pressure from a body acts from above, thus producing a body present detection signal, and which are separated when the pressure is released, thus producing a body absent detection signal, agreement or disagreement detection means for detecting agreement or disagreement between detection signals from the sensor portions of said body detection means,judgment means for generating a normal judgment signal for said body detection means when agreement detection information is input from said agreement or disagreement detection means, and stopping said normal judgment signal when disagreement detection information is input from said agreement or disagreement detection means, andsensor output generating means for generating, on the condition that the normal judgment signal is being generated from said judgment means, a sensor output signal indicating the absence of the body, only when all said detection signals from said respective sensor portions of said body detection means are body absent detection signals.
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Accused Products
Abstract
The invention relates to a highly reliable mat sensor which can also detect temporary faults in a sensor portion. Two sensor portions are provided, and agreement or disagreement of an ON/OFF condition of the output from the two sensor portions is detected, and when the output conditions of the two sensor portions are in agreement, then a normal judgment signal for both sensor portions is generated. When the normal judgment signal is generated and the two sensor portions are OFF, an operation permit signal for a movable portion of a machine is generated. Moreover, the presence or absence of a body is detected from a change in value of the electrostatic capacity of one sensor portion. In this way, a temporary poor contact attributable to deterioration of the sensor portion can also be detected, and the movable portion of the machine can be stopped.
33 Citations
39 Claims
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1. A mat sensor comprising:
- mat shaped body detection means including a plurality of sensor portions, wherein each sensor portion includes a pair of mutually facing electrode plates which are contacted when the pressure from a body acts from above, thus producing a body present detection signal, and which are separated when the pressure is released, thus producing a body absent detection signal, agreement or disagreement detection means for detecting agreement or disagreement between detection signals from the sensor portions of said body detection means,
judgment means for generating a normal judgment signal for said body detection means when agreement detection information is input from said agreement or disagreement detection means, and stopping said normal judgment signal when disagreement detection information is input from said agreement or disagreement detection means, and sensor output generating means for generating, on the condition that the normal judgment signal is being generated from said judgment means, a sensor output signal indicating the absence of the body, only when all said detection signals from said respective sensor portions of said body detection means are body absent detection signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
- mat shaped body detection means including a plurality of sensor portions, wherein each sensor portion includes a pair of mutually facing electrode plates which are contacted when the pressure from a body acts from above, thus producing a body present detection signal, and which are separated when the pressure is released, thus producing a body absent detection signal, agreement or disagreement detection means for detecting agreement or disagreement between detection signals from the sensor portions of said body detection means,
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25. A mat sensor comprising mat shaped body detection means including a sensor portion with a pair of mutually facing electrode plates which are contacted when the pressure from a body acts from above, and which are separated when the pressure is released,
electrostatic capacitance value detection means for detecting a change in electrostatic capacitance value based on a change in spacing between the electrode plates of the sensor portion of said body detection means, said electrostatic capacitance value detection means including a first transformer with an AC input signal applied to a primary side coil and a secondary side coil connected in series to the electrode plates of said sensor portion, and sensor output generating means for generating a sensor output indicating the presence or absence of the body based on detection results from said electrostatic capacitance value detection means wherein said electrostatic capacitance value detection means comprises a parallel resonance circuit including said first transformer with the electrode plates of said sensor portion as a capacitor, which resonates in parallel when the electrode plates of said sensor portion are separated; wherein said sensor output generating means comprising; a first rectifying means for rectifying an output from said parallel resonance circuit; a first level detection means for generating an output of logic value 1 when a rectified output from said first rectifying means is equal to or greater than a predetermined level; a first AC amplifying means for amplifying the rectified output from said first rectifying means and for magnifying along a time axis the change in the rectified output from said first rectifying means when the electrode plates of said sensor portion change from a separated condition to a contacted condition; a second level detection means for generating an output when an amplified output from said first AC amplifying means is equal to or greater than a predetermined level; and a first logical product operating means for carrying out a logical product operation on both of the outputs from said first and second level detection means, and an output of logic value 1 from said first logical product operating means is made the sensor output indicating the absence of the body. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
Specification