Bolt tightening method and bolt tightening apparatus
First Claim
1. A bolt tightening method applicable to a bolt having bolt tightening torque properties, in which a torque gradient expressed in terms of the ratio of an additional tightening torque exerted on a bolt to its additional turning angle has a first torque gradient in an initial bolt tightening stage and a second torque gradient in a late bolt tightening stage subsequent to the initial bolt tightening stage, a magnitude of the second torque gradient being greater than that of the first torque gradient, the method comprising the steps of. tightening the bolt with a predetermined snug torque;
- and turning the bolt subsequently by a total turning angle that is equivalent to the sum of a predetermined initial-set turning angle and a corrective additional-turning angle, wherein said corrective additional-turning angle is the sum of a first corrective additional-turning angle and a second corrective additional-turning angle, said first corrective additional-turning angle being to compensate for a situation in which a bolt turning angle corresponding to said snug torque on an extension line of said bolt tightening torque properties with the second torque gradient is greater than a bolt turning angle corresponding to said snug torque on a line of said bolt tightening torque properties with the first torque gradient, said second corrective additional-turning angle being to compensate for a decrease of an effective bolt axial force that is caused by an existence of said bolt tightening torque properties with the first torque gradient.
1 Assignment
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Accused Products
Abstract
After it is tightened with a snug torque TA, a bolt is tuned by a total turning angle θS equivalent to the sum of an initial-set turning angle θA and a corrective additional-turning angle (θB+θC). The corrective additional-turning angle (θB+θC) is the sum of a first corrective additional-turning angle θB and a second corrective additional-turning angle θC, the first corrective additional-turning angle θB being to compensate for a situation where a bolt turning angle θ22 corresponding to the snug torque θA on an extension line of the bolt tightening torque properties C2 in a late tightening stage II is different from a bolt turning angle θ11 corresponding to the actual snug torque TA, the second corrective additional-turning angle θC being to compensate for a decrease of an effective bolt axial force that is caused by an existence of the initial tightening stage I.
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Citations
13 Claims
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1. A bolt tightening method applicable to a bolt having bolt tightening torque properties, in which a torque gradient expressed in terms of the ratio of an additional tightening torque exerted on a bolt to its additional turning angle has a first torque gradient in an initial bolt tightening stage and a second torque gradient in a late bolt tightening stage subsequent to the initial bolt tightening stage, a magnitude of the second torque gradient being greater than that of the first torque gradient, the method comprising the steps of.
tightening the bolt with a predetermined snug torque; - and
turning the bolt subsequently by a total turning angle that is equivalent to the sum of a predetermined initial-set turning angle and a corrective additional-turning angle, wherein said corrective additional-turning angle is the sum of a first corrective additional-turning angle and a second corrective additional-turning angle, said first corrective additional-turning angle being to compensate for a situation in which a bolt turning angle corresponding to said snug torque on an extension line of said bolt tightening torque properties with the second torque gradient is greater than a bolt turning angle corresponding to said snug torque on a line of said bolt tightening torque properties with the first torque gradient, said second corrective additional-turning angle being to compensate for a decrease of an effective bolt axial force that is caused by an existence of said bolt tightening torque properties with the first torque gradient. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A bolt tightening apparatus applicable to a bolt having bolt tightening torque properties, in which a torque gradient expressed in terms of the ratio of an additional tightening torque exerted on a bolt to its additional turning angle has a first torque gradient in an initial bolt tightening stage and a second torque gradient in a late bolt tightening stage subsequent to the initial bolt tightening stage, a magnitude of the second torque gradient being greater than that of the first torque gradient, the apparatus comprising:
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a bolt turning device operative to turn the bolt around a bolt axis;
a torque detecting device operative to detect a torque applied to the bolt;
a bolt turning angle detecting device operative to detect a bolt turning angle;
a control device operative to control an operation of said bolt turning device; and
a corrective additional-turning angle calculating device operative to calculate a corrective additional-turning angle that is equivalent to an amount of additional tightening of the bolt to be added to a predetermined amount of initial tightening of the bolt, wherein said control device is configured so to operate said bolt turning device until a bolt tightening torque detected by said torque detecting device becomes a predetermined snug torque and subsequently operate said bolt turning device until a bolt turning angle detected by said bolt turning angle detecting device becomes a total turning angle that is equivalent to the sum of a predetermined initial-set turning angle and the corrective additional-turning angle calculated by said corrective additional-turning angle calculating device, and said corrective additional-turning angle calculating device is configured so as to calculate a first corrective additional-turning angle and a second corrective additional-turning angle, the first corrective additional-turning angle being to compensate for a situation in which a bolt turning angle corresponding to said snug torque on an extension line of said bolt tightening torque properties with the second torque gradient is greater than a bolt turning angle corresponding to said snug torque on a line of said bolt tightening torque properties with the first torque gradient, and said second corrective additional-turning angle being to compensate for a decrease of an effective bolt axial force that is caused by an existence of said bolt tightening torque properties with the first torque gradient, the sum of the first corrective additional-turning angle and the second corrective additional-turning angle being said corrective additional-turning angle. - View Dependent Claims (10, 11, 12, 13)
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Specification