Prestressing apparatus

Claim 2

Apparatus for prestressing a tendon and banding a circumferential wall of a structure having a longitudinally extending axis with a tensioned tendon, said apparatus comprising a carriage movable about the circumferential wall of said structure, means for moving said carriage about the circumferential wall, tendon tensioning means on said carriage having means engaging said tendon along an extended linear portion thereof for applying tensile forces thereto to stress the tendon, said means engaging said tendon and applying tensile forces thereto along a substantially straight line path of movement without substantial bending stresses being applied to the tendon, and means pivotally mounting said tendon tensioning means on said carriage with said means engaging said tendon along an extended portion thereof for turning about an axis substantially parallel to the longitudinal axis of said structure to align said tensioned linear portion with a tangent line extending from said tendon tensioning means to a point at which said tendon is banded on said structural wall.

Claim 3

An apparatus in accordance with claim 1 in which said tendon tensioning means includes a series of traveling, opposed restraining elements for engaging the tendon and for forming a pathway therebetween for said tendon, said last mentioned pathway being aligned with the tangent line to said structure wall.

Claim 4

An apparatus in accordance with claim 2 in which endless bands move about endless paths and in which said restraining elements are carried by said endless bands to engage said tendon and move along said straight line path therewith while the tendon is being tensioned and in which said restraining elements are carried into and from engagement with the tensioned tendon by said endless bands.

Claim 5

An apparatus in accordance with claim 1 in which said tendon tensioning means includes means for engaging said tendon and for displacing with elongation of said tendon during stressing thereof to prevent slipping of said tendon engaging means along the surface of said tendon.

Claim 6

An apparatus in accordance with claim 1 in which means are provided on said carriage for displacing said tendon tensioning means transversely to the path of carriage movement to position adjacent tendons side by side while said carriage remains in a given path of carriage movement.

Claim 7

An apparatus in accordance with claim 5 in which means on said carriage engage said structural wall at spaced locations and hold said carriage against twisting on said structural wall after a transverse shifting of said tensioning means and tendon.

Claim 8

An apparatus in accordance with claim 1 in which said means for moving said caRriage includes caterpillar tracks for engaging said structural wall and for providing a propelling force to move said carriage about said wall.

Claim 11

An apparatus in accordance with claim 8 in which means on said carriage engage said wall at spaced points and hold said carriage against twisting on the structural wall.

Claim 12

An apparatus in accordance with claim 7 in which means are provided to shift said tendon tensioning means to permit a plurality of tendons to be applied at longitudinally spaced positions along said structural wall without shifting said carriage along said wall.

Claim 13

Apparatus for tensioning a tendon and for banding a wall of a structure with a tensioned tendon, said apparatus comprising a carriage movable in a forward or reverse direction about the wall of the structure, tendon tensioning means on said carriage for tensioning said tendon while said tendon is moving along a substantially straight line path which is along a tangent to the structural wall, said tendon tensioning means including a series of restraining elements for engaging and restraining said tendon and for traveling therewith while tensioning the same along an extended linear portion of said tendon, means mounting said tendon tensioning means on said carriage for alignment with a tangent line extending from said tendon tensioning means to said structure, said restraining elements being movable in one direction when said carriage is paying out said tendon and being movable in an opposite direction when said carriage moves in the reverse direction to take up said tendon and means for moving said carriage in the forward direction to pay out the tensioned tendon and in the reverse direction to take up the tensioned tendon while holding said tendon under a controlled, predetermined tension.

Claim 14

Apparatus for tensioning a tendon and for banding a wall of a structure with a tensioned tendon, said apparatus comprising a carriage movable in a forward or reverse direction about the wall of the structure, tendon tensioning means on said carriage for tensioning said tendon while said tendon is moving along a substantially straight line path which is along a tangent to the structural wall, said tendon tensioning means including a series of restraining elements for engaging and restraining said tendon and for traveling therewith while tensioning the same along an extended linear portion of said tendon, means mounting said tendon tensioning means on said carriage for alignment with a tangent line extending from said tendon tensioning means to said structure, said restraining elements being movable in one direction when said carriage is paying out said tendon and being movable in an opposite direction when said carriage moves in the reverse direction to take up said tendon and means for moving said carriage in the forward direction to pay out the tensioned tendon and in the reverse direction to take up the tensioned tendon while holding said tendon under a controlled, predetermined tension.

Claim 15

Apparatus in accordance with claim 11 in which said means for moving said carriage includes a motor drive and caterpillar tracks for engaging the structural wall and in which said tendon tensioning means includes a pair of endless carriers for carrying said restraining elements into engagement with said tendon to travel therewith and from said tendon for return to positions to re-engage said tendon.

Claim 16

A prestressing apparatus as defined in claim 12 wherein said restraining elements are slidably mounted and have tongue and yoke portions, said yoke portion including a pair of flanges, and the tongue portion of each element adapted to be slidably positioned within the flanges of an adjacent element.

Claim 17

A prestressing apparatus as defined in claim 12 wherein said restraining elements include a resilient member whereby the sliding movement of the restraining elements in passing through the tensioning zone is substantially equal to the elongation of the tendon in passing through said zone.

Claim 18

A prestressing apparatus for circumferentially tensioning a tendon about a continuous structure by elongating the tendon a desired extent, said apparatus comprising a support carriage movable about said structure, a tendon tensioning mechanism carried by said carriage means mounting said tendon tensioning mechanism on said carriage for articulation about an axis to align said tendon tensioning mechanism with a line tangent to said structure, and means for shifting the mechanism aLong a path parallel to said axis to adjust said line of tangency relative to said carriage and to said structure.

Claim 19

A prestressing apparatus for circumferentially tensioning a tendon about a continuous structure by elongating the tendon a desired extent, said apparatus comprising a support carriage movable about said structure, a tendon tensioning mechanism carried by said carriage means mounting said tendon tensioning mechanism on said carriage for articulation about an axis to align said tendon tensioning mechanism with a line tangent to said structure, and means for shifting the mechanism aLong a path parallel to said axis to adjust said line of tangency relative to said carriage and to said structure.

Claim 20

A prestressing apparatus as defined in claim 15, wherein the tensioning mechanism includes a pair of opposed loops each comprised of flexible links engaging a pair of spaced, rotatable sprockets fixedly positioned to maintain said loops taut, means for rotating a sprocket in each pair in timed relation whereby said loops define a pathway for the tendon and create a zone for progressively increasing the tension in said tendon as it passes through said zone.

Claim 21

A prestressing apparatus as defined in claim 16 wherein said opposed loops include a plurality of tendon restraining elements for engaging the tendon throughout its travel along the pathway defined by the opposed loops.

Claim 22

A prestressing apparatus as defined in claim 17 wherein said tendon restraining elements have a surface thereon for engaging the tendon, the hardness of said surface being less than that of the tendon.

Claim 23

A prestressing apparatus as defined in claim 16 and further including a back-up plate positioned within each loop and extending substantially the length of the pathway formed by the loops, at least one of said plates adapted to be moved whereby the pressure exerted by the restraining elements on the loops against the tendon may be varied.

Claim 24

A prestressing apparatus as defined in claim 17 wherein said restraining elements are supported by a plurality of rollers whereby the distance between the holding elements of the opposed loops is determined by the distance between the opposed rollers.

Claim 25

A prestressing apparatus as defined in claim 15, in which a movable carrier for the tendon tensioning mechanism is provided on said carriage and said tendon tensioning mechanism is supported thereon in a cantilevered condition, and in which a counterweight arrangement comprising a flexible connector of a fixed length is attached to one side of the cantilevered portion of the tensioning mechanism and passed over a roller fixed on the support carriage and attached to the carrier on the side thereof opposite the attached side of the cantilevered portion whereby said tensioning mechanism is supported by said connector as the carrier is moved relative to the carriage.

Claim 26

A tendon mechanism for prestressing a tendon without substantially bending the prestressed tendon before banding the tendon on a structure having a longitudinally extending axis comprising, a frame means, a support means, a pair of opposed, endless bands mounted on said support means for movement about endless paths, and a plurality of tendon restraining elements mounted on said endless bands for travel therewith and for forming a straight line pathway for the tendon to travel along, said restraining elements engaging the tendon during its travel along said straight line pathway, said tendon restraining elements exerting forces on said tendon to prestress the same while traveling along said straight line pathway and means pivotally mounting said support means on said frame means for pivoting thereon about an axis parallel to said longitudinal axis of the structure and relative to said structure being banded to align said tendon being tensioned with a tangent line to the structure.

Claim 27

A tendon mechanism for prestressing a tendon without substantially bending the prestressed tendon before banding the tendon on a structure having a longitudinally extending axis comprising, a frame means, a support means, a pair of opposed, endless bands mounted on said support means for movement about endless paths, and a plurality of tendon restraining elements mounted on said endless bands for travel therewith and for forming a straight line pathway for the tendon to travel along, said restraining elements engaging the tendon during its travel along said straight line pathway, said tendon restraining elements exerting forces on said tendon to prestress the same while traveling along said straight line pathway and means pivotally mounting said support means on said frame means for pivoting thereon about an axis parallel to said longitudinal axis of the structure and relative to said structure being banded to align said tendon being tensioned with a tangent line to the structure.

Claim 28

A tendon tensioning mechanism in accordance with claim 22 in which said support means is slidably mounted on said frame means for movement in the direction of tendon travel and in which load sensing means are operated upon by said support means moving in the direction of tendon travel to provide an indication of the prestressing force being applied to the tendon.

Claim 29

A tendon tensioning mechanism in accordance with claim 22 in which means are provided to apply force to said tendon restraining elements in a direction normal to the tendon travel to hold the tendon against substantial slippage relative to said restraining elements.

Claim 30

A tendon tensioning mechanism in accordance with claim 24 in which means are proVided to allow said restraining elements to move relative to said endless bands during elongation of the tendon to prevent substantial surface slippage between the tendon and the restraining elements.

Claim 31

A tendon tensioning mechanism in accordance with claim 22 in which means are provided to allow said restraining elements to move relative to said endless bands for a predetermined displacement during tendon elongation and in which surfaces are provided on said restraining elements for partially yielding to accommodate further elongation of said tendon to its fully stressed length.