Power tool driving systems

In a method of cutting reinforced concrete with a concrete cutting tool rotated by an electric drive motor and advanced in said reinforced concrete by an electric tool advance, the improvement comprising in combination:

• sensing obstacles to cutting in said reinforced concrete including reinforcing bars by sensing an increasing draw of electric power of said electric drive motor in rotating said concrete cutting tool in said reinforced concrete;
• automatically slowing down said electric tool advance in response to said increasing draw of electric power;
• cutting through a sensed obstacle in said reinforced concrete with said concrete cutting tool by driving said concrete cutting tool with the slowed-down electric tool advance;
• automatically restoring the speed of the slowed-down electric tool advance in response to a decrease in the sensed draw of electric power of said electric drive motor in rotating said concrete cutting tool in said reinforced concrete;
• and
• advancing said concrete cutting tool in said reinforced concrete with said electric tool advance at the restored speed.

In apparatus for cutting a workpiece with a cutting tool rotated relative to the workpiece by an electric drive motor and advanced in said workpiece by an electric tool advance, the improvement comprising in combination:

• means for sensing obstacles to cutting in said workpiece, including means for sensing an increasing draw of electric power of said electric drive motor in rotating said cutting tool relative to said workpiece;
• means between said means for sensing an increasing draw of electric power and said electric tool advance for automatically slowing down said electric tool advance in response to said increasing draw of electric power so that said cutting tool cuts through a sensed obstacle in said workpiece while being driven with the slowed-down electric tool advance;
• and
• means for automatically restoring the speed of the slowed-down electric tool advance in response to a decrease in the sensed draw of electric power of said electric drive motor in rotating said cutting tool relative to said workpiece so that said cutting tool is advanced in said workpiece with said electric tool advance at the restored speed.

In apparatus for cutting reinforced concrete with a concrete cutting tool rotated by an electric drive motor and advanced in said reinforced concrete by an electric tool advance, the improvement comprising in combination:

• means for sensing obstacles to cutting in said reinforced concrete including reinforcing bars, including means for sensing an increasing draw of electric power of said electric drive motor in rotating said concrete cutting tool relative to said reinforced concrete;
• means between said means for sensing an increasing draw of electric power and said electric tool advance for automatically slowing down said electric tool advance in response to said increasing draw of electric power so that said concrete cutting tool cuts through a sensed obstacle in said reinforced concrete while being driven with the slowed-down electric tool advance;
• and
• means for automatically restoring the speed of the slowed-down electric tool advance in response to a decrease in the sensed draw of electric power of said electric drive motor in rotating said concrete cutting tool in said reinforced concrete so that said concrete cutting tool is advanced in said reinforced concrete with said electric tool advance at the restored speed.