Tightening method and system
First Claim
1. A tightening system for tightening a fastener to a desired axial load, said system comprising:
- wrench means for applying torque and imparting rotation to said fastener;
said wrench means including means for measuring one of the input characteristics experienced by said fastener as it is being tightened;
said wrench means further including means for determining when the yield point of said fastener has been reached and for stopping the application of torque;
means responsive to said yield point determining means and said measuring means for calculating said measured input characteristic required to develop the desired axial load in said fastener; and
,control means operatively connected between said wrench means and said means for calculating said measured input characteristic for reapplying torque to said fastener until said measured input characteristic substantially equals said calculated input characteristic.
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Abstract
A tightening method and system for practicing same are disclosed herein for tightening a fastener to a desired axial load. According to the method, torque is applied to the fastener until it is tightened to its yield point and either the torque applied at the yield point or the angular rotation of the fastener at the yield point are determined and are used to determine the axial load acting on the joint assembly and these determined characteristics are used to determine either the torque or angular rotation required to tighten the fastener to the desired load. Thereafter, torque is again applied to the fastener and when the actual torque being applied or actual angular rotation of the fastener substantially equals that required to tighten the fastener to the desired load, the application of torque is discontinued.
The tightening system disclosed for practicing the method includes a wrench for applying torque to a fastener and including means for developing a signal representative of the torque applied to or angular rotation of the fastener and means for developing an actuating signal when the fastener has been tightened to its yield point. The actuating signal shuts off the wrench and feeds the signal representative of torque or angular rotation at the yield point to a memory device including predetermined load-torque relationships or a predetermined load-angular rotation relationship for the fastener. From these relationships the torque or angular rotation required to tighten the fastener to the desired load can be determined and a signal representative thereof is developed and stored for comparison with a signal representative of the actual torque or angular displacement of the fastener as the wrench again applies torque to the fastener. When the compared signals are substantially equal, a control signal is developed for shutting off the wrench.
78 Citations
27 Claims
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1. A tightening system for tightening a fastener to a desired axial load, said system comprising:
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wrench means for applying torque and imparting rotation to said fastener; said wrench means including means for measuring one of the input characteristics experienced by said fastener as it is being tightened; said wrench means further including means for determining when the yield point of said fastener has been reached and for stopping the application of torque; means responsive to said yield point determining means and said measuring means for calculating said measured input characteristic required to develop the desired axial load in said fastener; and
,control means operatively connected between said wrench means and said means for calculating said measured input characteristic for reapplying torque to said fastener until said measured input characteristic substantially equals said calculated input characteristic. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of tightening a fastener to a desired axial load comprising;
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applying torque and imparting rotation to said fastener and tightening said fastener to its yield point; measuring one of the input characteristics experienced by said fastener at its yield point; determining the magnitude of a parameter related to said measured input characteristic and thereafter calculating the magnitude of said measured input characteristic required to develop said desired axial load in said fastener using said parameter; and reapplying torque to said fastener while measuring said input characteristic and stopping the reapplication of torque when said measured input characteristic approximately equals said calculated input characteristic. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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Specification