Capacitively coupled machine tool safety system having a digital quantizer

Claim 2

A machine tool safety system comprising an electric field generator for generating an electric field having a predetermined recurrence rate; a capacitive receptor antenna cooperable with the electric field generator to form a capacitive coupled transmission arrangement operative to induce in the capacitive antenna a signal having a corresponding recurrence rate; a receiver for detecting the induced signal, the receiver comprising: a network responsive to a first command for asynchronously sampling the induced signal a predetermined number of sample times during each period of the induced signal; an analog-to-digital converter connected to the sampling network for quantizing the magnitude of the sampled signal at each sample time; and a network responsive to a second command to remove the sampled signal value from the sampling network prior to the occurrence of the next sample time.

Claim 3

A machine tool safety system comprising an electric field generator for generating an electric field having a predetermined recurrence rate; a capacitive receptor antenna cooperable with the electric field generator to form a capacitive coupled transmission arrangement operative to induce in the capacitive antenna a signal having a corresponding recurrence rate; a receiver for detecting the induced signal, the receiver comprising a plurality of serally connected amplifier stages each of which includes a linear limiting amplifier with fast recovery; a sampling network connected to the output of each amplifier stage for asynchronously sampling, in response to a first command, the signal at the output of each amplifier stage; an analog-to-digital converter connected to each sampling network for quantizing the signal level of the first of the amplifier stages not saturated; and, a network associated with each amplifier stage and responsive to a second command to remove the sampled signal value from its associated amplifier stage prior to the occurrence of the next sample time.

Claim 4

A machine tool safety system comprising an electric field generator for generating an electric field having a predetermined recurrence rate; a capacitive receptor antenna cooperable with the electric field generator to form a capacitive coupled transmission arrangement operative to induce in the capacitive antenna a signal having a corresponding recurrence rate; a receiver for detecting the induced signal, the receiver comprising a plurality of serally connected amplifier stages each of which includes a linear limiting amplifier with fast recovery; a sampling network connected to the output of each amplifier stage for asynchronously sampling, in response to a first command, the signal at the output of each amplifier stage; an analog-to-digital converter connected to each sampling network for quantizing the signal level of the first of the amplifier stages not saturated; and, a network associated with each amplifier stage and responsive to a second command to remove the sampled signal value from its associated amplifier stage prior to the occurrence of the next sample time.