Saw sharpening machine with pitch pre-measurement and feedback control for saw blade indexing

A machine for sharpening a saw blade having multiple teeth spaced apart along the saw blade, comprising:

• a saw blade support adapted to movably support a saw blade;
• a grinding wheel driven for reciprocating movement relative to the saw blade for plunging toward and sharpening the teeth of the saw blade;
• and
• a indexing mechanism for indexing the saw blade so that its teeth are successively positioned for sharpening by the grinding wheel, the indexing mechanism including:
• an indexing actuator,
• a feed finger driven by the indexing actuator to reciprocate for multiple indexing cycles, each indexing cycle comprising a feed stroke and a retraction stroke, the feed stroke including movement of the feed finger in a first direction for advancing the saw blade and the retraction stroke including movement of the feed finger in a second direction opposite the first direction for resetting the index mechanism, the feed finger contacting a first tooth of a the saw blade during movement in the first direction and retracting past a second tooth of the saw blade adjacent the first tooth during movement in the second direction,
• a caliper finger mechanically linked to the feed finger for reciprocating movement therewith,
• a drag mechanism mechanically linked to the caliper finger, the drag mechanism urging the caliper finger closer to the feed finger during movement of the feed finger in the first direction so that the caliper finger presses against the second tooth during advancement of the saw blade,
• a sensor coupled to the caliper finger and the feed finger for measuring a pitch distance between the first and second teeth during movement in the first direction, and
• a control unit coupled to the sensor and the indexing actuator, the control unit including a feedback loop for control the feed stroke based on the pitch distance measured during a previous feed stroke, and to thereby accurately position the teeth of the saw blade for sharpening by the grinding wheel.

A method of sharpening a saw blade having multiple spaced apart teeth having a profile, comprising:

• movably supporting the saw blade;
• providing a grinding wheel mounted for reciprocating movement relative to the saw blade;
• providing a feed finger sized to contact the teeth of the saw blade;
• driving the feed finger to reciprocate for multiple indexing cycles, each indexing cycle comprising a feed stroke and a retraction stroke, the feed stroke including moving the feed finger in a first direction for advancing the saw blade and the retraction stroke including moving the feed finger in a second direction opposite the first direction, the feed finger contacting a first tooth of a the saw blade during movement in the first direction and retracting past a second tooth of the saw blade adjacent the first tooth during movement in the second direction;
• providing a caliper finger mechanically linked to the feed finger for reciprocating movement therewith;
• urging the caliper finger closer to the feed finger during the feed stroke so that the caliper finger presses against the second tooth as the saw blade is advanced;
• during the feed stroke of each indexing cycle, measuring the position of the feed finger relative to the caliper finger to determine a pitch distance between the first and second teeth;
• providing a feedback loop for controlling the feed stroke based on the pitch distance determined during a previous feed stroke, to thereby accurately advance the teeth into position for sharpening by the grinding wheel;
• and
• moving the grinding wheel in concert with advancing of the saw blade to thereby sharpen the profile of the teeth of the saw blade.

A device for machining a band saw blade, comprising:

• a machining tool;
• a drive assembly for driving the machining tool to reciprocate relative to a band saw blade;
• a reciprocating indexing mechanism for advancing the band saw blade in a feed stroke so that it is positioned for machining by the machining tool;
• a measurement mechanism mechanically coupled to the indexing mechanism for measuring a dimension of the band saw during the feed stroke of the indexing mechanism;
• a computer control unit coupled to the measurement mechanism, the computer control unit providing feedback to one of the drive assembly, the indexing mechanism, or both, in response to the dimension measured by the measurement mechanism, and to thereby accurately advance the band saw into position for sharpening by the grinding wheel based on a pre-measurement of the dimension of the band saw blade.