Rotational angle control of screw tightening
First Claim
1. A threaded coupling tightening device, comprising:
- motor means having a shaft for operatively connecting to the coupling and for rotating said shaft with a velocity that decreases as shaft angular rotation increases during tightening of the threaded coupling;
measuring means responsive to the rotation of said shaft for providing plural shaft angle/time data with respect to a plurality of shaft angular positions; and
means for controlling said motor means to rotate said shaft from a starting point of tightening based solely on said angle/time data inputted from said measuring means, through a fixed rotation angle.
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Accused Products
Abstract
The turn-of-nut tightening method that is improved by determining the starting point only through measurements of the angle and time relationship to determine the linear portion of the tightening curve, which is extended to the previous free running speed point where the corresponding angle is determined as the starting angle, to which is added a fixed turning amount to control the end of the tightening. As a specific embodiment, the turning angle is chosen as the variable and measured with specific time intervals. Using fixed time intervals, time is removed as a variable. Therefore, with a simple and economical angle measuring device, such as a shaft encoder, tightening is accurately controlled.
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Citations
23 Claims
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1. A threaded coupling tightening device, comprising:
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motor means having a shaft for operatively connecting to the coupling and for rotating said shaft with a velocity that decreases as shaft angular rotation increases during tightening of the threaded coupling; measuring means responsive to the rotation of said shaft for providing plural shaft angle/time data with respect to a plurality of shaft angular positions; and means for controlling said motor means to rotate said shaft from a starting point of tightening based solely on said angle/time data inputted from said measuring means, through a fixed rotation angle. - View Dependent Claims (2, 4)
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3. A threaded coupling tightening device, comprising:
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motor means having a shaft for operatively connecting to the coupling and for rotating said shaft with a velocity that decreases as shaft angular rotation increases during tightening of the threaded coupling; measuring means responsive to the rotation of said shaft for providing plural shaft angle/time data with respect to a plurality of shaft positions; and
means for controlling said motor to rotate said motor shaft for a fixed rotational angle based only upon said angle/time data from said means for measuring.
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5. A method of tightening a threaded coupling member, comprising the steps of:
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rotating a threaded coupling member by a motor and simultaneously measuring plural motor shaft rotation angle/time data, determining a linear portion of said data only from said angle/time data and decreasing motor speed in response to said determining; extending said linear portion of said data backward in time to estimate starting angle of shaft rotation wherein the threaded coupling member first started to tighten; and
thereafter tightening the threshold coupling only for a fixed angular relationship from said starting angle. - View Dependent Claims (6)
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7. A threaded rotary coupling tightening device, comprising:
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shaft means for engaging said coupling; motor means for rotating said shaft means with a speed characteristic that decreases linearly with tightening at least during a linear portion of said tightening; measuring means for providing a plurality of shaft angle/time data; controlling means for determining the linear portion of said shaft angle/time data; said controlling means stopping said motor and correspondingly stopping the tightening of said coupling based solely on said angle/time data. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A threaded coupling tightening device, the tightening of which is controlled through a rotational angle, comprising:
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means for discriminating roughly whether a tightening is started or not, including means for collecting data of a tightening angle and a tightening rotational speed; means for discriminating whether a relation between the tightening angle and the tightening rotational speed is linear; means for calculating a linear relationship between the tightening angle and the tightening rotational speed through a method of least squares; and means for calculating a tightening start point in view of said linear relation, including means for discriminating whether the tightening start point has reached a predetermined tightening angle; and
means for stopping the tightening of the threaded coupling tightening device when the predetermined tightening angle is reached.
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Specification