Pyrotechnic drop mechanism for power tools

A saw comprising a working surface having an opening defined therein, the saw comprising:

• a plate structure configured to be attached to the saw at least partially below the working surface;
• an arm pivotally attached to the plate structure about a first shaft, the arm comprising a surface having at least two teeth;
• a blade engaged with the arm at a location spaced from the first shaft, the blade positioned within the opening such that at least a portion of the blade extends through the opening and is situated to cut a work piece when the saw is in a normal operating position;
• and
• a firing mechanism comprising
• a barrel end portion having a bore defined therein, wherein the barrel end portion is attached to the plate structure, and
• an extendable piston at least partially positioned within the bore, the extendable piston engaging the arm during its extension and causing the arm to pivot about the first shaft when the firing mechanism is activated by an activation signal, the pivoting of the arm causing the blade to be moved downwardly below the working surface;
• and
• a ratchet assembly comprising a ratchet member biased toward the at least two teeth and configured to engage at least one of the teeth to counter kick back of the arm.

A saw comprising a working surface having an opening defined therein, the saw comprising:

• a plate structure configured to be attached to the saw below the working surface;
• an arm movably attached to the plate structure about a first shaft, the arm comprising at least two teeth;
• wherein a blade is configured to be engaged with the arm at a location spaced from the first shaft, the blade configured to be positioned within the opening such that at least a portion of the blade extends through the opening and is situated to cut a work piece when the saw is in a normal operating position;
• a firing mechanism comprising
• a barrel end portion having a bore defined therein, wherein the barrel end portion is attached to the plate structure, and
• a firable piston configured to be at least partially positioned within the bore, the firable piston movable between a first unfired position, where the blade is in the normal operating position, and a second fired position, where the blade is moved into a position below the working surface of the saw, the firable piston in communication with an activation signal and
• a ratchet assembly comprising a ratchet member biased toward the at least two teeth and configured to engage at least one of the teeth to counter kick back of the arm.

A saw of the type that has a top with an opening in the top through which a saw blade can extend, the height and angular orientation of which can be adjusted, and also configured to be retracted in response to an activation signal being applied, the saw comprising:

• a plate structure configured to be mounted to the saw below the top;
• an arm pivotally mounted to the plate structure about a first shaft;
• a rotatable circular blade having an arbor mounted to the arm at a location spaced from the first shaft, and configured so that at least a portion of the blade can extend through the top opening and be in a position to cut a work piece when the blade is in its normal operating position;
• a drive motor with an output shaft operatively connected to power the blade;
• a firing mechanism having a barrel end portion with a cylindrical bore mounted to the plate structure and an extendable piston positioned in the bore, the extendable piston engaging the arm during its extension and causing the arm to pivot about the first shaft when the firing mechanism is activated by the activation signal being applied, the pivoting of the arm causing the blade to be moved downwardly below the top toward its retracted position;
• wherein the first shaft and the arbor are generally horizontally aligned with one another when the blade is in its normal operating position, the arm having a lower extension with an anvil portion spaced from the first shaft and the arbor for being engaged by an outer portion of the extendable piston, wherein the extendable piston has a hammer located at its outer end portion for contacting the anvil portion, the hammer moving the arm through an arc sufficient to lower the blade below the top, and wherein the lower portion of the arm has a curved outer surface at a curvature that is defined by a constant radius about the first shaft that extends from the arbor through an arc of about 90 degrees, the outer surface having a plurality of teeth configured to engage a ratchet member;
• and
• a ratchet assembly having a ratchet member biased toward the teeth and configured to engage the teeth to counter kick back of the arm.

A saw of the type that has a top with an opening in the top through which a saw blade can extend, the height and angular orientation of which can be adjusted, and also configured to be retracted in response to an activation signal being applied, the saw comprising:

• a plate structure configured to be mounted to the saw at least partially below the top;
• an arm pivotally mounted to the plate structure about a first shaft;
• wherein a blade having an arbor is configured to be mounted to the arm at a location spaced from the first shaft, and is configured so that at least a portion of the blade can extend through the top opening and be in a position to cut a work piece when the blade is in its normal operating position;
• a firing mechanism having a barrel end portion defining a bore mounted to the plate structure and an extendable piston positioned within the bore, the extendable piston engaging the arm during its extension and causing the arm to pivot about the first shaft when the firing mechanism is activated by the activation signal being applied, the pivoting of the arm causing the blade to be moved downwardly below the top toward its retracted position;
• wherein the first shaft and the arbor are generally horizontally aligned with one another when the blade is in its normal operating position, the arm having a lower extension with an anvil portion spaced from the first shaft and the arbor configured to be engaged by an outer portion of the extendable piston, wherein the extendable piston has a hammer located at its outer end portion for contacting the anvil portion, the hammer moving the arm through an arc sufficient to lower the blade below the top, and wherein the lower portion of the arm has a curved outer surface at a curvature that is defined by a constant radius about the first shaft that extends from the arbor through an arc of about 90 degrees, the outer surface having a plurality of teeth configured to engage a ratchet member;
• and
• a ratchet assembly having a ratchet member biased toward the teeth and configured to engage the teeth to counter kick back of the arm.