Importance

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Abstract

The present invention relates to hydraulic prestressing nuts for setting a tensile stress in a bolt whereon the nut of the present invention is turned. The invention involves a nut body wherein an annular piston is arranged to be hydraulically extended from a bottom face thereof against a plate, head, platen, or the like, elevating the nut and extending the bolt therewith. A concentric loading ring is arranged with the nut body for turning into engagement with the place, such that when the loading ring is so extended, it provides a rigid columnar support to the annular piston. Tensile stress on the bolt is maintained by the loading ring. The nut of the present invention further involves a failsafe arrangement for providing a backup repressurization capability consisting of a second piston arrangement that can be independently pressurized at a primary seal failure, extending the primary piston therewith. The present invention also provides manually and hydraulically operated arrangements for breaking apart the loading ring should reextension of the piston arrangement become impossible for any reason.

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First Claim