Method and a device for sensing the distance between a first object and a second object
First Claim
1. A method for sensing the distance between a first object and a second object being moved relative to each other and for-activating or facilitating a predetermined action or predetermined actions when said distance has attained a value including zero, the method comprising the steps oftransmitting a capacitive proximity signal between a transmitting system and a receiving system,the first object and the second object each constituting an integral part of a respective one of the systems and a part of the signal path of the proximity signal, andthe proximity signal providing indication of distance between the first object and the second object, andmonitoring the proximity signal for sensing variations of the signal as the first object and the second object are moved relative to each other, andactivating the predetermined action when the signal has attained a predetermined condition.
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Abstract
A method and device for sensing the distance between a first object and a second object so as to activate or facilitate predetermined actions when the distance has attained a certain value. A person (1) (first object) holds a handle (2) of a power tool, the handle being connected to a function generator (6) for a signal in turn connected to a unit (7) for encoding or modulating the signal. A capacitance (C1) exists between the hand of a person (1) and the handle (2). A capacitance (C2) exists between the person (1) and the active portion (4) (second object) of the tool connected to a demodulator or tone decoder (8) in turn connected to a control unit (9) incorporating the control circuitry. The control unit (9) controls the security system (10) in turn controlling the protective measures such as braking or power cut-off (11). The control unit (9) also controls an alarm and self-testing circuitry (11a).
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Citations
38 Claims
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1. A method for sensing the distance between a first object and a second object being moved relative to each other and for-activating or facilitating a predetermined action or predetermined actions when said distance has attained a value including zero, the method comprising the steps of
transmitting a capacitive proximity signal between a transmitting system and a receiving system, the first object and the second object each constituting an integral part of a respective one of the systems and a part of the signal path of the proximity signal, and the proximity signal providing indication of distance between the first object and the second object, and monitoring the proximity signal for sensing variations of the signal as the first object and the second object are moved relative to each other, and activating the predetermined action when the signal has attained a predetermined condition.
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17. A device for protecting an object from interaction with an active portion of an apparatus, having an electronic circuit comprising
the object and the active portion capacitively connected in series, generating means for generating an alternating voltage and connected in series with the object and the active portion, monitoring means for detecting alternating current flowing through the object in response to the alternating voltage and for generating an output signal when a parameter of the alternating current attains a predetermined reference value, and protecting means for preventing the object from interaction with the active portion and activated in response to the output signal.
Specification