Safety system for machine tools
OwnerDavid J Butlerinventor
Life of this patent
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Abstract
A safety system for a rotary saw or other dangerous machine tools features a flesh-sensing circuit (14, 19), located on a safety guard (16) surrounding a dangerous machine part, which generates an electronic signal to trigger emergency stopping of the machine before the operator can contact the dangerous machine part. The stopping means preferably employs DC injection, winding current direction reversal and/or electromagnetic motor braking, in the event of detection of operator contact with the safety guarding device. The system is adapted to be used both with newly-manufactured machine tools and by retrofitting onto previously-manufactured machine tools, by in-the-field modifications.
Claims18
A machine tool safety system adapted for electrical connection to an electric-motor-driven machine tool, comprising:
- a substantially transparent safety guard (16), shaped to surround at least one dangerous part of a machine tool, and fixed in place to prevent a portion of a human operator's body from contacting said dangerous part;
- at least one electrical element (14), forming part of said safety guard, and coupled to
- an electronic flesh-sensing response circuit (19) which detects any capacitance change of at least 10 picofarads resulting when an operator contacts said electrical element (14), and generates a corresponding output signal;
- an electrical control circuit connected to the flesh-sensing circuit (19) in such a way as to sense bodily contact;
- and
- an electrical control circuit which, upon receiving said output signal from the flesh-sensing circuit (19), generates a current burst, on a winding of a motor of said electric-motor-driven machine tool, having a duration of at least 200 milliseconds to brake motion of a rotor of said motor, to a negligible speed, quickly enough to avoid injury to a body part of said operator.
Dependencies are inferred from the claim text.