Power tool safety mechanisms

A protection mechanism for protecting a drive system of a power tool upon a rapid stop event of an active portion of the power tool;

• comprising:
• an active portion detachably coupled by a clamp to a drive member, wherein the clamp maintains the active portion in fixed relation to the drive member in a first operating mode and disengages from at least one of the active portion and the drive member to thereby enable the drive member to operate independently of the active portion in a second operating mode;
• a drive motor configured to drive the drive member;
• a stopping mechanism configured to engage the active portion of the power tool in response to an activation signal and thereby cause a rapid stop event of the active portion and trigger the second operating mode of the clamp;
• a transmitter capacitively coupled to the active portion of the power tool and operable to transmit an electrical signal to the active portion of the power tool;
• a receiver capacitively coupled to the active portion of the power tool and operable to receive said electrical signal transmitted to the active portion of the power tool;
• and
• a controller connected to said receiver, said controller operable to detect a variation in said electrical signal and to generate the activation signal when said variation in said electrical signal exceeds a threshold value.

A power tool;

• comprising:
• a frame structure;
• a blade mounted on a spindle that is supported by the frame structure;
• a clamp detachably couples the blade to the spindle, the clamp configured to maintain the blade in fixed relation to the spindle during a first operating mode and to disengage from at least one of the blade and the spindle during a second operating mode such that the spindle rotates independently of the blade;
• a drive motor mounted to the frame structure and configured to drive the spindle;
• a stopping mechanism mounted to the frame structure and configured to engage the blade of the power tool in response to an activation signal and thereby trigger the second operating mode of the clamp;
• a transmitter capacitively coupled to the active portion of the power tool and operable to transmit an electrical signal to the active portion of the power tool;
• a receiver capacitively coupled to the active portion of the power tool and operable to receive said electrical signal transmitted to the active portion of the power tool;
• and
• a controller connected to said receiver, said controller operable to detect a variation in said electrical signal and to generate the activation signal when said variation in said electrical signal exceeds said threshold value.

A table saw comprising:

• a frame structure with a generally flat work surface;
• a blade mounted on a spindle and being adapted to have at least a portion of the blade extending above the work surface;
• a drive motor mounted to the frame structure and configured to drive the spindle;
• a braking mechanism mounted to the frame structure and configured to brake the blade of the power tool in response to an activation signal;
• a clamp detachably couples the blade to the spindle, the clamp having at least one tab in mesh with a complimentary bore formed in the spindle, where the tab maintains the blade in fixed relation to the spindle during normal operation of the saw but shears away from remainder of the clamp upon occurrence of a rapid stop event of the blade by the brake mechanism;
• a transmitter capacitively coupled to the blade and operable to transmit an electrical signal to the blade;
• a receiver capacitively coupled to the blade and operable to receive said electrical signal transmitted to the blade;
• and
• a controller connected to said receiver, said controller operable to detect a variation in said electrical signal and send an activation signal to the braking mechanism when said variation in said electrical signal exceeds said threshold value, where said detection circuit adjusts said threshold value based on an electrical load associated with the operation of the blade of the power tool.