Method and apparatus for tightening and/or slackening bolts
First Claim
1. A method of tightening and/or slackening of a bolt, in which a mechanical stress is applied in order to cause a suitable strain of said bolt and a nut is displaced on said bolt, wherein after execution of a first program of verification of interconnection and positioning of tightening/ slackening systems on a nut-and-bolt said method consists in:
- displaying, for an operator, a table indicative of initial values of strain and pressures and programmed design values of strain and pressure,testing via a test program for proper functioning of transducers and elements permitting of a process of tightening and/or slackening as such,carrying out said tightening and/or slackening as such with analysis of values received from said transducers of strain of said bolt and of pressure applied for causing said strain, said tightening and/or slackening being carried out by servo-control of said strain imposed on said bolt via a mechanical stress applied to the latter, to a design value and a control being carried out by correlation between said display strain and said applied pressure in order to cause said strain,display and memorisation of values of maximum strain and final pressure obtained for said bolt in question,displacing said nut by screwing and/or unscrewing with respect to a tightening surface on said corresponding bolt,releasing said applied stress.
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Accused Products
Abstract
The invention relates to a method and to apparatus for tightening and slackening bolts by hydraulic tensioning. The apparatus comprises a tightening system (60) applied to the bolts to be tightened and/or slackened, controlled by a central unit (24), via the intermediary of a control device (26) and a hydraulic pump (28). Transducers (19 and 18) permit respectively measurement of the effective strain of the bolt and the pressure effectively applied to the tightening system (60). A correlation between the effective strain of the bolt and the pressure effectively applied is thus effected for obtaining a very good precision of the strain. Application is to mechanical construction in the nuclear environment.
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Citations
13 Claims
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1. A method of tightening and/or slackening of a bolt, in which a mechanical stress is applied in order to cause a suitable strain of said bolt and a nut is displaced on said bolt, wherein after execution of a first program of verification of interconnection and positioning of tightening/ slackening systems on a nut-and-bolt said method consists in:
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displaying, for an operator, a table indicative of initial values of strain and pressures and programmed design values of strain and pressure, testing via a test program for proper functioning of transducers and elements permitting of a process of tightening and/or slackening as such, carrying out said tightening and/or slackening as such with analysis of values received from said transducers of strain of said bolt and of pressure applied for causing said strain, said tightening and/or slackening being carried out by servo-control of said strain imposed on said bolt via a mechanical stress applied to the latter, to a design value and a control being carried out by correlation between said display strain and said applied pressure in order to cause said strain, display and memorisation of values of maximum strain and final pressure obtained for said bolt in question, displacing said nut by screwing and/or unscrewing with respect to a tightening surface on said corresponding bolt, releasing said applied stress. - View Dependent Claims (2, 3, 4, 5)
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6. An apparatus for the tightening and slackening of a bolt, wherein a mechanical stress is applied in order to cause a suitable strain of said bolt and a nut is displaced on said bolt with respect to a tightening surface, said apparatus comprises:
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means including an annular jack for tightening and slackening said bolt; a control device for pressurizing said annular jack; a transducer for measurement of said strain of said bolt arranged at an end of said bolt and of which the output is connected to said control device for pressurizing said annular jack; a transducer for measurement of pressure applied to said annular jack in a manner to permit a control by correlation between effective strain and said pressure applied, wherein said pressure applied causes said strain of said bolt; and an automatic control circuit to which the output of said transducers for strain and pressure is connected, said automatic control circuit comprising particularly; a central unit for inputting a predetermined value of said strain of said bolt and for controlling the pressurization, stabilization and release of said pressure on said annular jack. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13)
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Specification