Method and apparatus for pretensioning screw joints

Details Method and apparatus for pretensioning screw joints Method and apparatus for pretensioning screw joints

1977-11-17

1979-07-17

Staab, Lawrence J.

Tool driving or impacting

Processes

173 12, B23Q 1906

Patent

active

041612213

ABSTRACT:
A method and apparatus for tightening a screw joint to a predetermined axial load F.sub.p providing the spring constant k=(F/.phi.) of the joint is known, wherein the torque/rotation relationship M (.phi.) is determined during the linear, elastic deformation part of the tightening process by calculating the joint stiffness (dM/d.phi.) at an arbitrarily chosen torque level M.sub.2. A theoretical, tensionless angular position .phi..sub.0 of the joint is calculated by extrapolating the determined torque/rotation relationship M (.phi.), and the tightening process is interrupted as an angular interval .DELTA..phi. from said theoretical, tensionless position .phi..sub.0 has been passed, which interval according to the spring constant k of the joint corresponds to the predetermined axial load F.sub.p.

REFERENCES:
patent: 3939920 (1976-02-01), Hardiman et al.
patent: 3974685 (1976-08-01), Walker
patent: 3974883 (1976-08-01), Sigmund
patent: 3982419 (1976-08-01), Boys
patent: 4014208 (1977-03-01), Moore et al.
patent: 4016938 (1977-04-01), Rice
patent: 4026369 (1977-05-01), Vliet

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