Sensor apparatus and safety apparatus for protecting approach to machines

A safety apparatus for detecting entrance of at least a part of human body in a predetermined area of a machine grounded electrically, to thereby actuate safety securing means, said safety apparatus, comprising:

• at least one electrode plate disposed relative to said machine with said area being interposed between said machine and said electrode plate;
• an auxiliary electrode disposed in opposition to a portion of said at least one electrode plate;
• a capacitance change detecting circuit for detecting whether a part of the human body exists or not in said area on the basis of change of capacitance between said at least one electrode plate and said machine;
• and
• monitor for monitoring normality of human body detecting operation of said sensor apparatus by electrically connecting periodically said auxiliary electrode to said capacitance change detecting circuit.

A sensor apparatus, comprising:

• a pair of electrode plates disposed in opposition to each other with a predetermined space being interposed therebetween;
• an auxiliary electrode disposed in opposition to a portion of either one of said electrode plates;
• a capacitance change detecting circuit for detecting whether a predetermined dielectric exists or not within said space on the basis of change of capacitance between said pair of electrode plates;
• and
• monitor for monitoring normality of dielectric detecting operation of said sensor apparatus by electrically connecting periodically said auxiliary electrode to said capacitance change detecting circuit.

A safety apparatus for detecting entrance of at least a part of human body in a predetermined area of a machine grounded electrically, to thereby actuate safety securing means, said safety apparatus, comprising:

• a pair of electrode plates disposed in opposition to each other with said area being interposed between said pair of electrode plates;
• an auxiliary electrode disposed in opposition to a portion of either one of said electrode plates;
• a capacitance change detecting circuit for detecting whether at least a part of the human body exists or not in said area on the basis of change of capacitance between said pair of electrode plates;
• and
• monitor for monitoring normality of human body detecting operation of said sensor apparatus by electrically connecting periodically said auxiliary electrode to said capacitance change detecting circuit.