Duct coupler apparatus with compressible seals

An apparatus for joining the ends of a pair of ribbed ducts together has a collar with an interior suitable for receiving the ends of the pair of ducts therein, a first coupler element translatably secured adjacent a first end of the collar, a compressible seal disposed between a surface of the first coupler element and the first end of the collar, a second coupler element secured adjacent a second end of the collar, and a second seal disposed between a surface of the second coupler element and the second end of the collar. The coupler elements are translatable so as to compress the seal such that a surface of the seal will bear against a respective rib of the pair of ducts.

Not applicable.

REFERENCE TO MICROFICHE APPENDIX

Not applicable.

FIELD OF THE INVENTION

The present invention relates to a duct coupler, and more particularly to a coupler for providing a water-tight joint between adjacent sections of duct used to provide a channel for multi-strand post-tensioning of concrete structures.

BACKGROUND OF THE INVENTION

For many years, the design of concrete structures imitated the typical steel design of column, girder and beam. With technological advances in structural concrete, however, its own form began to evolve. Concrete has the advantages of lower cost than steel, of not requiring fireproofing, and of its plasticity, a quality that lends itself to free flowing or boldly massive architectural concepts. On the other hand, structural concrete, though quite capable of carrying almost any compressive load, is weak in carrying significant tensile loads. It becomes necessary, therefore, to add steel bars, called reinforcements, to concrete, thus allowing the concrete to carry the compressive forces and the steel to carry the tensile forces.

Structures of reinforced concrete may be constructed with load-bearing walls, but this method does not use the full potentialities of the concrete. The skeleton frame, in which the floors and roofs rest directly on exterior and interior reinforced-concrete columns, has proven to be most economic and popular. Reinforced-concrete framing is seemingly a quite simple form of construction. First, wood or steel forms are constructed in the sizes, positions, and shapes called for by engineering and design requirements. The steel reinforcing is then placed and held in position by wires at its intersections. Devices known as chairs and spacers are used to keep the reinforcing bars apart and raised off the form work. The size and number of the steel bars depends completely upon the imposed loads and the need to transfer these loads evenly throughout the building and down to the foundation. After the reinforcing is set in place, the concrete, a mixture of water, cement, sand, and stone or aggregate, of proportions calculated to produce the required strength, is placed, care being taken to prevent voids or honeycombs.

One of the simplest designs in concrete frames is the beam-and-slab. This system follows ordinary steel design that uses concrete beams that are cast integrally with the floor slabs. The beam-and-slab system is often used in apartment buildings and other structures where the beams are not visually objectionable and can be hidden. The reinforcement is simple and the forms for casting can be utilized over and over for the same shape. The system, therefore, produces an economically viable structure. With the development of flat-slab construction, exposed beams can be eliminated. In this system, reinforcing bars are projected at right angles and in two directions from every column supporting flat slabs spanning twelve or fifteen feet in both directions.

Reinforced concrete reaches its highest potentialities when it is used in pre-stressed or post-tensioned members. Spans as great as one hundred feet can be attained in members as deep as three feet for roof loads. The basic principle is simple. In pre-stressing, reinforcing rods of high tensile strength wires are stretched to a certain determined limit and then high-strength concrete is placed around them. When the concrete has set, it holds the steel in a tight grip, preventing slippage or sagging. Post-tensioning follows the same principle, but the reinforcing tendon, usually a steel cable, is held loosely in place while the concrete is placed around it. The reinforcing tendon is then stretched by hydraulic jacks and securely anchored into place. Pre-stressing is done with individual members in the shop and post-tensioning as part of the structure on the site.

In a typical tendon tensioning anchor assembly used in such post-tensioning operations, there are provided anchors for anchoring the ends of the cables suspended therebetween. In the course of tensioning the cable in a concrete structure, a hydraulic jack or the like is releasably attached to one of the exposed ends of each cable for applying a predetermined amount of tension to the tendon, which extends through the anchor. When the desired amount of tension is applied to the cable, wedges, threaded nuts, or the like, are used to capture the cable at the anchor plate and, as the jack is removed from the tendon, to prevent its relaxation and hold it in its stressed condition.

Multi-strand tensioning is used when forming especially long post-tensioned concrete structures, or those which must carry especially heavy loads, such as elongated concrete beams for buildings, bridges, highway overpasses, etc. Multiple axially aligned strands of cable are used in order to achieve the required compressive forces for offsetting the anticipated loads. Special multi-strand anchors are utilized, with ports for the desired number of tensioning cables. Individual cables are then strung between the anchors, tensioned and locked as described above for the conventional monofilament post-tensioning system.

As with monofilament installations, it is highly desirable to protect the tensioned steel cables from corrosive elements, such as de-icing chemicals, sea water, brackish water, and even rain water which could enter through cracks or pores in the concrete and eventually cause corrosion and loss of tension of the cables. In multi-strand applications, the cables typically are protected against exposure to corrosive elements by surrounding them with a metal duct or, more recently, with a flexible duct made of an impermeable material, such as plastic. The protective duct extends between the anchors and in surrounding relationship to the bundle of tensioning cables. Flexible duct, which typically is provided in 20 to 40 foot sections is sealed at each end to an anchor and between adjacent sections of duct to provide a water-tight channel. Grout then may be pumped into the interior of the duct in surrounding relationship to the cables to provide further protection.

Several approaches have been tried to solve the problem of quickly, inexpensively and securely sealing the joints between adjacent sections of duct used in multi-strand post-tensioned applications. However, all prior art devices have utilized a plurality of arcuate sections which must be assembled at a joint around the ends of adjacent duct sections. Wedges, compression bolts or the like then are used to compress the joined sections into sealing engagement with the duct and with each other. Such prior art devices have been cumbersome to use and have proved somewhat unreliable in their ability to exclude moisture or other corrosive elements from the interior of the ducts.

Several patents have issued relating to duct couplers. For example, U.S. Pat. No. 5,320,319, issued on Jun. 14, 1994, to K. Luthi describes a coupling element which is fitted with chamfered flanges. The sheaths of the coupler have protrusions which are inserted into the coupling element with a tubular element which forms the end of the sheaths. A sealing ring is inserted between each of the flanges and protrusions of the sheaths. The flanges and the protrusions are held together by sloping surfaces and by a groove worked within each socket. Also, U.S. Pat. No. 5,474,335, issued on Dec. 12, 1995, to the present inventor, describes a duct coupler for joining and sealing between adjacent sections of the duct. The coupler includes a body, flexible cantilevered sections on the end of the body adapted to pass over annular protrusions on the duct and locking rings for locking the cantilevered flexible sections into position, so as to lock the coupler onto the duct.

U.S. Pat. No. 5,775,849, issued on Jul. 7, 1998 to the present inventor, describes a coupler as used for ducts in post-tension anchorage systems. This duct system includes a first duct having a plurality of corrugations extending radially outwardly therefrom, a second duct having a plurality of corrugations extending radially outwardly therefrom, and a tubular body threadedly receiving the first duct at one end and threadedly receiving the second duct at the opposite end. The tubular body has a first threaded section formed on an inner wall of the tubular body adjacent one end of the tubular body and a second threaded section formed on the inner wall of the tubular body adjacent an opposite end of the tubular body. The threaded sections are formed of a harder polymeric material than the polymeric material of the first and second ducts. The tubular body has an outer diameter which is less than the diameter of the ducts at the corrugations. The first and second threaded sections have a maximum inner diameter which is less than the outer diameter of the ducts at the end of the ducts. First and second elastomeric seals are affixed to opposite end of the tubular body and juxtaposed against a surface of a corrugation of the first and second ducts.

U.S. Pat. No. 5,954,373, issued on Sep. 21, 1999 to the present inventor, describes a different type of duct coupler apparatus. The duct coupler apparatus of this patent includes a tubular body with an interior passageway between a first open end and a second open end. A shoulder is formed within the tubular body between the open ends. A seal is connected to the shoulder so as to form a liquid-tight seal with a duct received within one of the open ends. A compression device is hingedly connected to the tubular body for urging the duct into compressive contact with the seal. The compression device has a portion extending exterior of the tubular body. The compression device includes an arm with an end hingedly connected to the tubular body and having an abutment surface adjacent the end. The arm is movable between a first position extending outwardly of an exterior of the tubular body and a second position aligned with an exterior surface of the tubular body. A latching member is connected to an opposite end of the arm and serves to affix the arm in the second position. The abutment surface of the arm serves to push a corrugation of the duct against the seal and against the shoulder so as to form a liquid-tight seal between the duct and the interior of the coupler.

It is an object of the present invention to provide a coupler for sealing between adjacent sections of an elongated duct.

It is another object of the present invention to provide a coupler which facilitates installation by the user and which, when engaged with the opposed ends, will securely seal against the intrusion of corrosive elements and to prevent the leakage of sealing materials from the interior of the duct.

It is a further object of the present invention to provide a coupler which includes compressible seals for securely engaging coupler sections together and for conforming the seals to the surfaces of the duct.

It is another object of the present invention to provide a coupler which is easy to use, easy to manufacture and relatively inexpensive.

It is still a further object of the present invention to provide a duct coupler apparatus which maintains the integrity of an annular seal in the area of the connections between the coupler and the duct.

It is still another object of the present invention to provide a duct coupler apparatus which prevents the ducts from longitudinally separating from each other.

BRIEF SUMMARY OF THE INVENTION

The present invention is an apparatus for joining the ends of a pair of ducts together. The apparatus of the present invention has a collar with an interior suitable for receiving the pair of ducts therein in end-to-end relationship. The collar has a first end and a second end. A first coupler element is translatably secured to an exterior of the collar adjacent a first end. This first coupler element has a lip at an outer end thereof. A compressible first seal is disposed between the first end of the collar and the lip of the first coupler element. The first coupler element is translatable so as to compress the first seal such that the first seal extends toward the interior of the collar. A second coupler element is secured to the exterior of the collar adjacent the second end. The second coupler element also has a lip at an outer end thereof. A second seal is disposed between the lip of the second coupler element and the second end of the collar.

In the present invention, the first seal is affixed to the first end of the collar and the second seal is affixed to the second end of the collar. The second seal is also compressible. The second coupler element is translatable so as to compress the seal such that the second seal extends toward the interior of the collar. The first coupler element is threadedly translatable on the collar. The first coupler element is rotatable so as to move the lip thereof so as to compress the first seal. The second coupler element is also threadedly translatable on the collar. The second coupler element is rotatable so as to move the lip thereof so as to compress the second seal.

In the present invention, the first end of the collar has a notch formed on an outer surface thereof. The first seal has an extended portion received in this notch. Similarly, the second end of the collar has a notch formed at an outer surface thereof. The second seal has an extended portion received in this notch at the second end of the collar. The first seal has a surface that is flush with the inner wall of the collar when uncompressed. Similarly, the second seal has a surface that is flush with the inner wall of the collar when uncompressed. The lip of the first coupler element extends radially inwardly therefrom. Similarly, the lip of the second coupler element extends radially inwardly therefrom. The first seal is interposed between an inner surface of the lip of the first coupler element and the first end of the collar. The second seal is interposed between the inner surface of the lip of the second coupler element and the second end of the collar.

In the present invention, each of the collar and the first and second coupler elements are formed of a polymeric material. The first and second seals are formed of an elastomeric material.

Each of the first and second coupler elements has a plurality of ribs formed on an exterior surface thereof. Each of the plurality of ribs extends longitudinally for at least a portion of a length of the coupler element. This plurality of ribs are radially spaced from each other around the diameter of the coupler element. The collar has a constant inner diameter extending entirely between the first end and the second end of the collar.

In use, a first duct and a second duct have respective ends received within the interior of the collar. The first and second coupler elements are suitably translatable such that the surface on the lip of each of the coupler elements bears against a surface of the respective first and second seals. With further movement of the first and second coupler elements, the first and second seals suitably compress so as to extend toward the interior of the collar and bear against the respective ribs on the first and second ducts so as to lock the ducts in a proper end-to-end longitudinally aligned position. In particular, the first and second coupler elements can be rotated with respect to the collar so as to apply pressure on the edges of the seal so as to suitably compress the seal and to cause the seals to extend downwardly in a bearing relationship against opposed surfaces of respective ribs on the first and second ducts. A plurality of tendons extend longitudinally through the interior of the ducts and through the interior of the collar. A grout material fills the interior of the first and second ducts. The collar and the first and second coupler elements form a liquid-tight seal with the first and second ducts respectively so as to prevent grout from flowing outwardly of the first and second ducts and to prevent grout from flowing outwardly of the first and second ducts, to prevent liquids from intruding into the interior of the first and second ducts, and to prevent the first and second ducts from moving longitudinally from each other.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIG. 1, there is shown the coupler apparatus10in accordance of the preferred embodiment of the present invention. The coupler apparatus10includes a collar12, a first coupler element14and a second coupler element16. A first duct18is received within the interior of the collar12and within the interior of the first coupler element14. A second duct20is received within the collar12and within the interior of the second coupler element16. The collar12has an interior suitable for receiving the ducts18and20in end-to-end relationship and in generally longitudinal alignment. The first coupler element14is translatably secured to the exterior of the collar12. The first coupler element14is translatable so as to suitably compress a seal (to be described hereinafter) between a first position spaced from the exterior of the duct18and a second position which would bear against a rib26of the duct18. The second coupler element16is also translatably secured to the exterior of the collar12. The second coupler element16is translatable so as to move the seal (to be shown hereinafter) between a first position spaced from the exterior of the duct12to a second position bearing against a surface of one of the ribs32of the duct20.

As can be seen inFIG. 1, the first duct18has a plurality of ribs26formed thereon. Longitudinal channels28extend between the ribs26and allow liquid and grout therein to communicate between the ribs26. Longitudinal channels28have an outer edge which is flush with the outer diameter of the ribs26. The first duct18has an outer wall30which extends between the ribs26and defines the interior of the duct18. The second duct20similarly has a plurality of ribs32, longitudinal channels34and wall36. The first duct18is identical in construction to the second duct20. In normal use, ducts18and20will receive tendons therein and allow a grout material to fill the interior thereof. The respective channels28and34allow grout to fill the interior of the respective ducts18and20and to flow into the ribs26and32, respectively.

In past practice, it has been somewhat difficult to join the respective ends of the ducts18and20in a properly sealed end-to-end relationship. It is important to provide both the liquid-tight sealing of the ducts18and20and to prevent the separation of the ducts18and20from each other. Since time of installation is an important requirement for construction, the coupler apparatus10should be sufficiently usable so as to quickly allow the joining of the ends of ducts18and20together. Since the quality of labor at construction sites can be poor at times, the coupler apparatus10should have the ability to be easily installed in a simple and effective manner without complex training or procedures.

The coupler element14is translatable about one end of the collar12. The translating motion in the preferred embodiment of the present invention is established by a threaded relationship between the exterior surface of the collar12and the interior surface of the coupler14. In other embodiments of the present invention, the coupler element14can be translatable by slidable or ratcheting motion. Suitable hinging mechanisms or other lever actions can be incorporated with the apparatus10so as to facilitate proper translatable motion of the coupler elements14and16on the collar12. Coupler element16will have a configuration similar to that of coupler element14and will translate in the same manner as coupler element14. Each of the coupler elements14and16has a plurality of ribs64formed on an exterior surface thereof. Each of the plurality of ribs64extends longitudinally for a portion of the length of the respective coupler elements14and16. The plurality of ribs are radially spaced from each other around the diameter of the respective coupler elements14and16. Ribs64facilitate the ability of a worker to grasp the exterior surface of the coupler elements14and16and to provide the necessary translatable motion with respect to movement of the coupler elements14and16onto the respective seals.

FIG. 2illustrates the collar12as having a first end40and a second end42. The collar12is a tubular member that defines an interior passageway44. The interior of the collar12should have a suitable diameter so as to receive the ducts18and20therein. The collar12has a constant interior diameter extending between end40and end42. As can be seen inFIG. 2, the end40has a notch46formed on an exterior surface thereof. Similarly, the end42also has a notch48formed on an exterior surface thereof. An exterior threaded portion50is formed on the exterior of the collar12adjacent end40. Another threaded section52is formed on the exterior of collar12adjacent end42.

The first coupler element14has a lip54formed at one end thereof. As used herein, the term “lip” can pertain to an inwardly extending surface, a projection, a shoulder, or similar structure. The lip54extends in spaced relationship from the end40of the collar12. The first coupler element14also has an internally threaded section56in threadedly translatable relationship with the exterior threaded section50of the collar12. As such, a rotation of first coupler element14will cause the coupler element to move relative to the collar12.

A seal58is interposed between the inner surface of the lip54and the end40of collar12. The seal58can be formed of an elastomeric material. The seal58should be suitably compressible so as to move toward the interior44of the collar12when the lip54of first coupler element14applies pressure thereon. The seal58has an extended portion60which is received with the notch46at the end40of the collar12. The receipt of the extended portion60within the notch46facilitates the ability of seal58to “flip” downwardly and, ultimately, bear against the rib26of the duct18.

In the position illustrated inFIG. 2, the seal58has a surface extending generally flush with the inner wall62of the collar12. Similarly, the inwardmost surface66of the lip54will also be generally flush with the inner wall62of the collar12. This relationship allows the duct18to be easily pushed into the interior44of the collar12without obstruction or interference by either the seal58or the lip54.

InFIG. 2, it can be seen that the second coupler element16has interior threads70which are threadedly received by the exterior threads52of the collar12. Similarly, a lip72extends downwardly at an outer end of the coupler element16. A seal74is affixed so as to have an extended portion78received within the notch48at the end42of collar12. The lip72will bear against the end of the seal74in the same manner that the lip54of coupler element14bears against the seal58. The second coupler element16will operate in a similar manner as coupler element14such that a rotation of the coupler element16will cause the seal74to be compressed and flip slightly downwardly toward the interior44of the collar12and to ultimately bear against a surface of the rib32of duct20.

InFIG. 2, it can be seen that a plurality of tendons80extends through the interior of the ducts18and20. A grout material fills the interior of the ducts18and20. As a result, when the seals58and74exert compressive contact against the respective ribs26and32of the ducts18and20, the grout82will be retained within the interior of the collar12and the interior of the respective ducts18and20. Additionally, the ducts18and20will be prevented from being moved longitudinally apart.

FIG. 3shows a detailed view of how the seal74is suitably compressible so as to bear against a surface90of the rib32of duct20. The same relationship will occur with respect to the seal58. InFIG. 3, the second coupler element16has been suitably rotated about the exterior threaded section52on the collar12. As a result, the lip72exerts a compressive force on the seal74. This compressive force causes the seal74to move toward the interior44of the collar12and to ultimately bear against the surface90of rib32. The receipt of the extended portion78within the notch48further facilitates the ability of the elastomeric seal74to “flip” downwardly and, hence, bear against the rib32. As a result of this relationship, a strong sealing contact is established with the seal74. Additionally, the seal74will somewhat extrude outwardly and downwardly so as to bear strongly against the flat top surface92of rib32. As a result, the seal74establishes two methods of protection. First, longitudinal separation of the ducts18and20is prevented because of the strong bearing contact between the seal74and the surface90of rib32. Additionally, liquid infiltration and exfiltration is prevented because of the strong sealing contact between the surface of the seal74and the flat surface92at the outer portion of the rib32.