Drill feed control utilizing a variable overcenter valve
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United States of America Patent
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Dec 8, 1992
Grant Date -
N/A
app pub date -
Oct 2, 1991
filing date -
Oct 2, 1991
priority date (Note) -
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status (Latency Note)
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Abstract
An apparatus includes a feed cylinder having a first end port and a second end port. A feed cylinder is located within the feed cylinder and is movable in a drive direction in response to fluid pressure applied to the first end port, and is movable in a return direction in response to fluid pressure applied to the second end port. A feed pump selectively displaces fluid between the first and the second end ports. A variable overcenter device controls fluid pressure offset, independent of the feed pump, between the first end port and the second end port. An adjustment device automatically adjusts the variable overcenter device during travel of the feed cylinder in the drive direction to a value corresponding to an amount of force required to displace the feed cylinder in the return direction. The variable overcenter device may be either microprocessor based or mechanically based including an accumulator reservoir which builds to a certain pressure based upon the amount of weight of the drill string when the feed cylinder was last displaced in the return direction.
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