Patent ID: 6470636
Filing Date: 2002-10-29
Classification: E04C,E04G,Y10S

Abstract:
A detensioning apparatus, for use during a process of fabricating prestressed concrete, during which process a region in which concrete is to be poured includes at least two opposing abutments, and one or more prestressing strands are run between opposing abutments, tensioned and held in tension, by clamps that engage the strands and bear against the opposing abutments, while concrete is poured into the region and cured,wherein each clamp includes a chuck having one or more jaws, and a surrounding strand chuck barrel, configured so that tension in the strand, between opposing abutments, prompts the one or more jaws of the chuck to be pressed against the strand to frictionally engage the strand, while preventing movement of the strand in a first direction relative to the strand clamp; the detensioning apparatus comprising: a collar member, operably configured to be placed onto a prestressing strand that has been tensioned and to which a strand clamp is affixed, the collar member having a central bore, a first portion of which is operably configured to surround and insertingly receive the strand chuck barrel of the strand clamp which is affixed to the prestressing strand, and a second portion of which is provided with a smaller inner diameter than the first portion, defining a shoulder configured to bear against at least a portion of an end of the strand chuck barrel of the strand clamp which is affixed to the prestressing strand; a separation member housing, operably configured to be insertingly received in the second portion of the central bore of the collar member; at least one separation member supported on the separation member housing, and operably configured for separating a chuck from a prestressing strand, after the tension in the strand causing the chuck to be prompted against the strand is balanced, to permit movement of the strand in the first direction and in a second direction relative to the one or more chuck jaws, said second direction being substantially opposite to the first direction; the collar member being operably configured to be slid onto a free end of a prestressing strand, to a position surrounding a strand chuck barrel that is holding a strand in tension, such that upon exertion of tension between a free end of the strand and a strand chuck barrel, the collar member bears against the strand chuck barrel and prevents its movement, so that additional tension in the strand will cause the chuck to be drawn toward the at least one separation member contained within the collar member.