Rotary cutting blade control system

A control system for a rotary cutting blade, comprising:

• rotary drive means for rotating the cutting blade,
• positioning means for moving said blade in a cutting cycle into and out of a workpiece,
• reference means for continuously producing during said cutting cycle a position reference indicative of the position of the center of said blade,
• sample and hold means for recording as a contact reference the position reference produced at initial contact of the blade with the workpiece during said cutting cycle, and
• comparator means continuously receiving the position reference and the output of said sample and hold means for continuously producing a comparator output corresponding to the difference between said position reference and said contact reference during said cutting cycle, thereby continuously determining the position of the center of the blade after initial contact of the blade with the workpiece relative to the position of the center of the blade at said initial contact.

A method of making successive cuts through a workpiece with a rotary blade, having a periphery which wears during use comprising:

• commencing a first cutting cycle by moving said blade toward the workpiece from a first start position wherein the periphery of said blade is close to the workpiece,
• sensing as a first contact reference the position of the center of said blade at initial contact of the blade with the workpiece,
• completing the first cutting cycle by returning the blade to a second start position established by a predetermined relationship to the first contact reference,
• commencing a second cutting cycle by moving said blade toward the workpiece from said second start position,
• sensing as a second contact reference the position of the center of said blade at initial contact of the blade with the workpiece,
• completing the second cutting cycle by returning the blade to a third start position established by a predetermined relationship to the second contact reference whereby the third start position is closer to the workpiece than the second start position to thereby compensate for wear of said blade during the first cutting cycle.

A method of making successive cuts through a workpiece with a rotary blade, having a periphery which wears during use comprising:

• commencing a first cutting cycle by moving said blade toward the workpiece from a home position wherein the periphery of said blade is relatively remote from the workpiece,
• sensing as a first contact reference the position of the center of said blade at initial contact of the blade with the workpiece,
• completing the first cutting cycle by returning the blade to a first start position established by a predetermined relationship to the first contact reference,
• commencing a second cutting cycle by moving said blade toward the workpiece from said first start position,
• sensing as a second contact reference the position of the center of said blade at initial contact of the blade with the workpiece, and
• completing the second cutting cycle by returning the blade to a second start position established by a predetermined relationship to the second contact reference whereby the second start position is closer to the workpiece than the first start position to thereby compensate for wear of said blade during the first cutting cycle.

In combination with a control system for a rotary cutting blade having a periphery which wears during use including rotary drive means for rotating said blade, positioning means for positioning the center of said blade during a plurality of cutting cycles from a start position wherein the periphery of said blade is close to the surface of a workpiece, past a blade contact position wherein the periphery of said blade contacts said workpiece, to a cutting position within the workpiece, and back to a subsequent start position;

• a blade position comparator system, comprising:
• reference means for continuously producing during said cutting cycle a position reference indicative of the position of the center of said blade,
• sample and hold means for recording the position reference produced at said blade contact position responsive to said blade contacting said workpiece, and for retaining said position reference in said sample and hold means until said blade reaches a blade contact position during a subsequent cutting cycle, and
• comparator means receiving said position reference and the output of said sample and hold means for producing an output corresponding to the difference between said position reference and said sample and hold output such that said comparator output indicates the difference between the position of the center of said blade at said blade contact position and the instantaneous position of the center of said blade, said difference being, at the blade contact position for said subsequent cutting cyle, an indication of the wear of said blade during the previous cutting cycle.