Computer controlled automatic shift drill
First Claim
1. A mechanism for forming a workpiece with a tool comprising:
- a means for rotationally driving the tool at one of two speeds;
a means for sensing a force applied to the tool;
a first means for comparing the sensed force to a first threshold value;
means for shifting the speed of said means for driving in response to the first means for comparing; and
means, responsive to the sensed force, for periodically redefining the first threshold value.
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Accused Products
Abstract
The trust exerted on a drill bit is sensed and employed to determine the speed at which the bit is driven. A controller for the drill compares the thrust to a predetermined threshold value and in response to the comparison emits a control signal which shifts a transmission in the drill into high or low speed. After each shift, a number of thrust samples are taken in order to compute an average thrust for different strata of the material being drilled. At the completion of drilling each hole, the average thrusts for the hole are used to recalibrate the shift threshold value. In this manner, the shift threshold is adjusted to compensate for drill bit wear. The sensed thrust is also compared to a bit reject threshold value to determine when the bit is too dull for proper drilling.
148 Citations
20 Claims
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1. A mechanism for forming a workpiece with a tool comprising:
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a means for rotationally driving the tool at one of two speeds; a means for sensing a force applied to the tool; a first means for comparing the sensed force to a first threshold value; means for shifting the speed of said means for driving in response to the first means for comparing; and means, responsive to the sensed force, for periodically redefining the first threshold value. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for controlling the speed of a tool driven by a machine having a first speed that is faster than a second speed, said method comprising:
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sensing a force exerted on the tool; comparing the sensed force to a first threshold value; shifting the speed of the machine to the second speed in response to the sensed force exceeding the first threshold value, and to the first speed in response to the sensed force being below the first threshold value; determining the average force exerted on the tool during a given period of time after a shift in speed; and employing the determined average force to redefine the first threshold value. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A drill for rotationally driving a bit into a workpiece to form a hole comprising:
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a prime mover; a transmission, coupled to said prime mover, for selectively driving the bit at either a first or a second speed; means for sensing a force applied to the bit; means for comparing the sensed force to a plurality of threshold values; means, responsive to the means for comparing, for shifting the speed of the transmission (1) to the first speed for a first interval upon the sensed force exceeding a first threshold value, (2) thereafter shifting the speed of the transmission to the first speed in response to the sensed force being above a second threshold value and to the second speed in response to the sensed force being below the second threshold value, and (3) shifting the speed of the transmission to the first speed whenever the sensed force is below a third threshold value; means for determining the value of the average force exerted on the bit during a second interval of time after each shift in speed in response to the force crossing the second threshold value; and means, responsive to the average force values, for redefining the second threshold value. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A drill having a bit for forming a hole in a workpiece comprising:
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a means for selectively rotationally driving the bit at either a first or a second speed; means for sensing a force applied to the bit; means for comparing the sensed force to a threshold value; means, responsive to the means for comparing, for shifting the speed of said means for driving (1) to the first speed in response to the sensed force being above the threshold value, and (2) to the second speed in response to the force being below the threshold value for a first predetermined period of time. - View Dependent Claims (20)
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Specification