Force applicators

A hydraulic nut for applying a load to a threaded tensile member relative to a clamping surface through which the threaded tensile member projects, said hydraulic nut including:

• an annular housing having a stepped annular recess extending inwardly from an end face of the annular housing opposite to the clamping surface, the stepped annular recess defining a central bore for the tensile member and forming a cylinder for a piston member, the annular housing having an exterior threaded peripheral locking surface;
• a piston having an axial bore therethrough which is threaded to engage, in use, about the threaded tensile member, said piston being of complementary stepped configuration to said stepped recess of said housing whereby said piston is slidably engaged in said housing, the diameter of said piston being greater than the diameter of said housing so as to provide a peripheral flange radially outwardly of the peripheral locking surface of said housing, said flange having a bottom surface which defines a locking face,
• sealing means provided between the relatively movable surfaces of said housing and said piston,
• a locking collar having an internal thread engageable with the threaded peripheral locking surface of said housing, said locking collar having an upper end surface engageable with said locking face of said piston member when said locking collar is moved upwardly toward said piston following pressure application;
• said stepped annular recess of said housing and said stepped piston member having opposed pressure faces which define therebetween an annular chamber the volume of which depends upon the relative displacement of the piston member relative to the annular housing;
• and
• pressure application means communicating through said piston to said annular chamber whereby pressurized fluid may be applied to and expand said annular chamber to displace said piston relative to the said housing and tension said tensile member,
• whereby, said locking collar can be screwed against said locking face of said piston member so that the expanded annular chamber can be maintained, thus maintaining tension in the tensile member when said pressure is released.