Metal working – Method of mechanical manufacture – Assembling or joining
Reexamination Certificate
1999-06-07
2001-03-20
Hughes, S. Thomas (Department: 3726)
Metal working
Method of mechanical manufacture
Assembling or joining
C403S362000, C052S749100
Reexamination Certificate
active
06202282
ABSTRACT:
BACKGROUND OF THE INVENTION
In the art of joining the adjacent end portions of two generally aligned concrete reinforcing bars or “rebars”, it is known to use a tubular steel coupling body or sleeve which receives the end portions of the bars. The coupling sleeve is crimped or swaged with substantial force against the reinforcing bars with the aid of a hydraulically actuated press and die set, for example, as disclosed in U.S. Pat. Nos. 3,551,999 and 4,241,490. It is also known to form tapered or non-tapered threads on the end portions of each reinforcing bar, and to join the end portions together with a coupling sleeve having internal tapered or non-tapered threads, for example, as disclosed in U.S. Pat. Nos. 197,509 and 3,415,552.
In order to avoid the need for a hydraulically actuated press, a hydraulic pump and power source and a crimping die set, or to avoid the threading operation and protection of the threaded end portions of the reinforcing bars, it is also known to use a tubular coupler sleeve with longitudinally spaced and radially extending screws. According to one coupler as disclosed in U.S. Pat. Nos. 4,666,326 and 5,046,878, each of the screws has a hex shaped outer end portion and a threaded inner portion integrally connected by a reduced neck portion. The screws are tightened through the coupling sleeve into the reinforcing bars until the torque is sufficient to shear the hexagonal head portions from the threaded inner portions at the neck portions generally flush with the outer surface of the sleeve. This tubular coupling sleeve is also provided with a pair of elongated racks or hardened strips with inwardly and outwardly projecting teeth, and the ends of the strips are welded to the coupling sleeve. It has also been proposed to inject an epoxy material into these coupling sleeves after the screws are tightened for further increasing the gripping strength of the coupler sleeve with the opposing end portions of the connected reinforcing bars.
The forming of threads on the end portions of the reinforcing bars and the protection of the threads during handling and shipping of the bars add significantly to the cost of the reinforcing bars. In addition, the forming of internal threads within the tubular coupling sleeve adds to the cost of the coupling sleeve. In regard to the above described coupler with inner strips having teeth, the use of longitudinally spaced special screws increases the cost of the coupling sleeve, and the cost of the sleeve is further increased by the cost of forming the internal hardened strips with teeth on opposite sides and the cost for welding the strips within the coupling sleeve. Also, during installation, the strips of teeth sometimes bind upon the reinforcing bars as they are being inserted. This difficulty creates additional field labor. Further, once the heads of the special screws have been sheared off there is no provision to loosen the screws to reposition the coupler if it has been misinstalled. Another problem with special screws is that if the screws are not precisely formed, they are sometimes unreliable because the heads do not shear off at the prescribed torque.
Another form of tubular coupling with longitudinally spaced radial screws is disclosed in U.S. Pat. No. 4,314,771. However, this coupling sleeve is designed for connecting the opposing end portions of rods or shafts which do not require a high strength connection of the rods or shafts, as is required when joining reinforcing bars.
SUMMARY OF THE INVENTION
The present invention is directed to an improved and relatively inexpensive tubular coupler for positively coupling the adjacent end portions of two concrete reinforcing bars, and which coupler provides a high tensile strength which is equal to or greater than the tensile strength of the reinforcing bar or exceeds other strength requirements for reinforcing bar connections which may be mandated by building codes. The coupler of the invention is also adapted to be installed in the field without the need for power operated presses or special equipment and without the need for preparing or threading the end portions of the reinforcing bars. Additionally, the coupler is designed for sliding smoothly onto the reinforcing bars.
In accordance with one embodiment of the invention, a tubular coupler sleeve or body is produced by deforming or cold forging a section of generally seamless cylindrical tubing of ductile steel to provide the body with a generally diamond-shaped cross-sectional configuration. The coupler body includes a longitudinally extending wedge portion having converging inner surfaces disposed at an included angle of about 60°. Thus when an end portion of a reinforcing rod is inserted into the tubular body, the circumferential ribs on the bar engage the inner surfaces of the wedge portion. Longitudinally spaced threaded holes are formed within the tubular body in opposing relation to the wedge portion of the body, and a standard socket head and cone point set screw is threaded into each hole.
In accordance with another embodiment of the invention, the tubular coupler sleeve or body is formed by extruding or cold-drawing a steel tube so that the body has a generally cylindrical outer surface and an inner chamber defined by three uniformly spaced part-cylindrical concave surfaces connected by three convex surfaces to form a clover leaf cross-sectional configuration. The part-cylindrical concave surfaces have a radius which is generally about 70% to 90% of the radius of the concrete reinforcing bar to provide the body with a wedging portion with longitudinally extending and opposing wedging seats or surfaces which receive the ribs on the reinforcing bar. The cross-sectional configuration of the tubular body also provides the body with portions having a heavier wall thickness where desirable. That is, the thicker wall portions form the wedging surfaces and the opposing portion where threaded holes are formed for receiving corresponding locking screws having pointed ends for penetrating and deforming the reinforcing bar. In this embodiment, the locking screws have hexagonal head portions which shear from the threaded portion of the screw in response to a predetermined torque up to several hundred foot pounds.
When the locking screws are tightened against a reinforcing bar to a prescribed or preset torque, depending upon the size of the reinforcing bar, the conical or pointed tips of the screws penetrate the reinforcing bar and also force the circumferential ribs on the reinforcing bar into the inner wedging surfaces of the wedge portion. This forms a positive lock of the coupler body onto the end portion of the reinforcing bar. The penetration of the circumferential ribs into the wedge portion of the coupler body, and the penetration of the cone point screws into the reinforcing bar, result in forming a connection or coupling with a tensile strength higher than the tensile strength of the reinforcing bar or higher than the building code requirements to which the coupler is designed. The coupler of the invention is also economical to produce and may be provided with longitudinally spaced and outwardly projecting ribs which cooperate to provide interlocking of the body with surrounding concrete.
Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.
REFERENCES:
patent: 197509 (1877-11-01), Abbott
patent: 2938698 (1960-05-01), Johnson
patent: 3415552 (1968-12-01), Howlett
patent: 3551999 (1971-01-01), Gutmann
patent: 4040757 (1977-08-01), Pauli
patent: 4241490 (1980-12-01), Edwards
patent: 4314771 (1982-02-01), Lambert
patent: 4666326 (1987-05-01), Hope
patent: 5046878 (1991-09-01), Young
patent: 5419217 (1995-05-01), Umezawa et al.
patent: 5468524 (1995-11-01), Albrigo et al.
patent: 5681126 (1997-10-01), Lin
patent: 5689923 (1997-11-01), Winkeljann et al.
patent: 5797696 (1998-08-01), Baynes et al.
Barsplice Products, Inc.
Hong John C.
Hughes S. Thomas
Jacox Meckstroth & Jenkins
LandOfFree
Method of making a tubular coupler for concrete reinforcing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of making a tubular coupler for concrete reinforcing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of making a tubular coupler for concrete reinforcing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2487768