Tendon gripping device

A tendon gripping apparatus for gripping a smooth, deformed or multiple stranded tendon having a tendon diameter, the apparatus, when secured to the tendon, preventing concrete formwork used to form a concrete structure, fitting about the tendon and contacting the apparatus, from sliding along the tendon toward the apparatus, the apparatus comprising:

• a housing with a tapered inner wall defining a chamber within the housing, the chamber being accessible on opposing ends of the housing through a front aperture and a rear aperture, the tapered inner wall defining the chamber such that the chamber increasingly narrows toward a front portion of the chamber adjoining the front aperture, the front aperture being a cylindrical bore with a helical groove on the exterior of the housing, and such that the chamber increasingly widens toward the back portion of the chamber adjoining the rear aperture, the rear aperture being a cylindrical bore with a helical groove on the interior of the housing, front aperture, the chamber, and the rear aperture being sized to permit passage of the tendon through the housing;
• a jaw cluster positioned within the chamber and sized such that the tendon may freely enter the front aperture and exit the chamber through a rear aperture, the jaw cluster comprising a plurality of elongated jaw members for securing the tendon within the apparatus, each jaw member comprising a tapered outer surface facing the tapered inner wall, a clasping inner surface facing the tendon;
• a tightening nut having a cylindrical conduit therethrough having a conduit diameter larger than the tendon diameter, the cylindrical conduit leading to a rear aperture of a diameter larger than the tendon diameter whereby the tendon may pass through the apparatus and out the rear aperture of the tightening nut, the tightening nut further comprising:
• a mechanical interface for being twisted;
• a front jaw cluster pushing surface for contacting and pushing against a rear portion of the jaw cluster;
• an intermediate threaded portion having a helical thread carried circumferentially thereabout to permit threading of the tightening nut into the helical groove on the interior and at the rear of the housing;
• wherein the tightening nut advances into the housing in response to a twisting force applied to the mechanical interface, the twisting force initiating a pushing contact between the pushing surface of the tightening nut and the rear portion of the jaw cluster, the pushing contact advancing the jaw cluster toward the front portion of the housing and thereby securing the tendon within the apparatus between the clasping inner surface of the elongated jaw members forming the jaw cluster when the tapered outer surfaces of the elongated jaw members forming the jaw cluster contact the tapered inner wall of the housing;
• and
• wherein the tightening nut withdraws from the housing in response to a counter-twisting force applied to the mechanical interface;
• and
• a tensioning nut having a cylindrical conduit therethrough having a conduit diameter larger than the tendon diameter, the cylindrical conduit leading to a front aperture of a diameter larger than the tendon diameter whereby the tendon may pass through the front aperture and into the cylindrical conduit of the tensioning nut and further in to the apparatus, the tensioning nut further comprising:
• a mechanical interface for being twisted;
• a front planar abutment surface for abutting and pushing against the concrete formwork;
• and
• an intermediate threaded portion having a helical thread carried circumferentially thereabout to permit threading of the tensioning nut onto the helical groove located on the exterior and at the front of the housing;
• wherein the tensioning nut advances forward away from the remainder of the apparatus in response to a twisting force applied to the mechanical interface, the twisting force initiating a pushing contact between the front planar abutment surface of the tensioning nut that contacts the concrete formwork and thereby adjusting the concrete formwork to a desired position.