Tensioner

A tensioner for threaded members, the tensioner comprising:

• a base and a piston defining a pressure space therebetween, the base and piston being arranged to be urged apart along an axis upon introduction of a fluid into the pressure space;
• and
• a thread-engaging member, comprising a body portion having a threaded interior for engagement with a threaded member, a piston engaging portion carrying a protrusion, and a sleeve surrounding the body portion;
• in which the piston bears against the protrusion such that the piston exerts a force on the protrusion when urged apart from the base by the introduction of fluid into the pressure space;
• the tensioner further comprising a displacement sensor arranged for determining the relative position of the body portion of the thread-engaging member and the base, the displacement sensor comprising a first part carried on the base and a second part carried on the sleeve of the thread-engaging member;
• in which the displacement sensor is a linear encoder, in which the second part comprises a scale that encodes a position and the first part is a transducer that reads the scale.

A combination, comprising:

• a tensioner;
• and
• a threaded member,
• in which the tensioner comprises:
• a base and a piston defining a pressure space therebetween, the base and piston being arranged to be urged apart along an axis upon introduction of a fluid into the pressure space;
• and
• a thread-engaging member, comprising a body portion having a threaded interior for engagement with a threaded member, a piston engaging portion carrying a protrusion, and a sleeve surrounding the body portion;
• in which the piston bears against the protrusion such that the piston exerts a force on the protrusion when urged apart from the base by the introduction of fluid into the pressure space;
• the tensioner further comprising a displacement sensor arranged for determining the relative position of the body portion of the thread-engaging member and the base, the displacement sensor comprising a first part carried on the base and a second part carried on the sleeve of the thread-engaging member;
• in which the sleeve is free to rotate around the body portion, but a stop is provided to prevent linear movement of the sleeve along the axis relative to the body portion;
• and
• in which the thread-engaging member is engaged with a thread of the threaded member.

A combination, comprising:

• a tensioner;
• and
• a threaded member,
• in which the tensioner comprises:
• a base and a piston defining a pressure space therebetween, the base and piston being arranged to be urged apart along an axis upon introduction of a fluid into the pressure space;
• and
• a thread-engaging member, comprising a body portion having a threaded interior for engagement with a threaded member, a piston engaging portion carrying a protrusion, and a sleeve surrounding the body portion;
• in which the piston bears against the protrusion such that the piston exerts a force on the protrusion when urged apart from the base by the introduction of fluid into the pressure space;
• the tensioner further comprising a displacement sensor arranged for determining the relative position of the body portion of the thread-engaging member and the base, the displacement sensor comprising a first part carried on the base and a second part carried on the sleeve of the thread-engaging member;
• in which the displacement sensor is a linear encoder, in which the second part comprises a scale that encodes a position and the first part is a transducer that reads the scale;
• and
• in which the thread-engaging member is engaged with a thread of the threaded member.