Pipe joints or couplings – With fluid pressure seal – Flexible lip
Reexamination Certificate
1997-04-28
2003-06-24
Browne, Lynne H. (Department: 3679)
Pipe joints or couplings
With fluid pressure seal
Flexible lip
C285S373000, C285S368000, C285S419000
Reexamination Certificate
active
06581977
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to segmented pipe couplings, such couplings being comprised of two or more arcuate coupling segments having bolting pads at their respective ends enabling the coupling segments to be bolted to each other in encircling relation with a pipe or a fitting, the segmented pipe coupling being employed to connect adjacent ends of pipes to each other, or, to connect a fitting to a pipe, or to another fitting.
While not limited thereto, the present invention finds particular application in segmented pipe couplings that are employed to interconnect lengths of high-density polyurethane pipe, the present invention also finding application in segmented pipe couplings employed for interconnecting lengths of cut or roll grooved metal pipe, in which it is intended that the keys of the coupling segments engage the bottom wall of the groove throughout the entire arcuate extent of the respective coupling segments.
BACKGROUND OF THE INVENTION
Segmented pipe couplings are well-known in the art, including segmented pipe couplings having teeth extending circumferentially of the inner periphery thereof for biting and gripping engagement with the outer surface of a pipe.
The usual manner of securing the coupling segments to one another is by the use of traction bolts, which extend through apertures in adjacent bolting pads of a pair of coupling segments, the traction bolts having a head at one end that engages a bolting face of the associated bolting pad, the bolting face extending on a radius of the coupling segment, and either parallel to, or at an angle to a radial plane that includes the longitudinal axis of the coupling segment.
The other end of the traction bolt is threaded, for it to receive a nut, which similarly engages the associated bolting face of the next adjacent coupling segment, that bolting face extending either parallel to the bolting face of the next adjacent coupling segment, or, extending at an angle thereto, for the respective bolting faces to diverge and to define and include angle, and be other than truly parallel to one another.
Commonly bolt holes are provided in the bolting pads for the reception of a shank of the traction bolt, the shank of the traction bolt being inserted through the bolt holes in the adjacent bolting pads, subsequent to which the nut is applied to the shank of the traction bolt, and, the nut is then torqued down to draw the bolting pads of the respective coupling segments towards each other, and, in turn, to draw the assembled segmented pipe coupling into clamping engagement with the exterior of the associated pipes or fittings.
The coupling segments, while essentially being rigid, are capable of flexure to a limited extent in a direction to reduce the arcuate radius of the coupling segment, and, permit the coupling segment to extend in continuous engagement with the outer surface of the associated pipe or fitting.
This flexing movement is of particular value in segmented pipe couplings employed for interconnecting lengths of high-density polyurethane pipe [HDPE], the coupling segments being provided with teeth on their inner periphery which are to bite into the outer surface of the pipe, and thus anchor the segmented pipe coupling against movement axially of the associated pipe.
This capability of flexing of the coupling segments is employed to advantage in segmented pipe couplings that incorporate only two coupling segments, which each subtend an arc of a semi-circle. Provision must be made for positioning the internal teeth of the coupling segments over the pipe periphery prior to torquing down of the traction bolts, i.e., the radially inner surfaces of the teeth at the ends of the coupling segments must be spaced radially outwardly of the axis of the coupling segment by a distance that is equal to the radius of the outer surface of the pipe, in order to permit the coupling segment to be assembled over the pipe periphery. On torquing down of the pipe coupling, the respective ends of the respective coupling segments flex inwardly and are caused to move towards each other, in order to move the teeth at the ends of the coupling segments into biting engagement with the pipe exterior, the only other option being to relieve the teeth at the opposite ends of the coupling segment in a direction tangential to the radius of the coupling.
Segmented pipe couplings are known in which one end of the traction bolt is pivotally secured within the bolting pads of one of the coupling segments, and which can be swung into a position in which the nuts can be engaged with the bolting pads of the next adjacent coupling segment. Such a construction is disclosed in Stillwagon U.S. Pat. No. 2,459,251 issued Jan. 18, 1949, which, while intended for use with metal piping, also would find use in the coupling of high-density polyurethane piping.
In that construction, the ends of the bolts are pivotally mounted within the bolting pads of the associated coupling segment by providing hinge pins that extend through the bolt heads, and which are secured within the associated bolting pads.
In that construction, while the traction bolts and the bolting pads can hinge relative to each other, no provision is made for corresponding movement of the bolts relative to the bolting pads of the next adjacent coupling segment. Thus, in the event that the bolting face of the next adjacent coupling segment is not truly perpendicular to the axis of the shank of the bolt, but is inclined thereto, the nut will engage the bolting face of the associated bolting pad in essentially line contact extending radially of the bolt axis, i.e., the nuts will not be in continuous end face engagement with the bolting face of the bolting pad. This gives rise to the tensional forces existing in the bolt acting in a direction that is other than co-axial with the shank of the bolt, and which results in bending or attempted bending of the shank of the bolt.
Further problems arise as a result of the nut attempting to spiral along the associated bolting face as the nut is torqued down to the required value. However, at that time, the nut is attempting to bite into the associated bolting face at the location of line engagement, a circumstance which again militates against the nut reaching true parallelism with the associated bolting face.
The result is that under mechanical or thermal loading of the assembled pipes and segmented pipe coupling, the nut can move relative to its associated bolting face, and, it will attempt to do so in order to bring the operative face of the nut into continuous face engagement with the associated bolting face. This movement of the nut in an attempt to reach parallelism with the bolting face will result in a reduction in the tensile stress in the shank of the bolt, and in turn will result in a reduction in the clamping force exerted by the segmented pipe coupling on the associated pipes.
The positioning of a washer under the nut in no way removes this problem, in that the washer, during torquing down of the nut, becomes engaged with the associated bolting face with a very considerable resistance to movement of the washer relative to the bolting face.
It is also known to provide T-bolts in which the head of the bolt is integral with the shank instead of being pivotally interconnected with the shank. Such a construction is disclosed in Skelly U.S. Pat. No. 2,837,383 issued Jun. 3, 1958.
While the bolt of this reference overcomes the inherent requirement of providing a pivot pin at the bolt head, as is essential to the Stillwagon construction, the teachings of Skelly are not directly related to the employment of the Skelly construction in a segmented pipe coupling. While Skelly teaches a T-bolt having an integral head, a nut applied to the shank of the bolt, and a saddle that is capable of rotation relative to its supporting member, Skelly also requires that the saddle be channelled for it to extend around one half of the circumference of the bolt shank, which can result in the trunnions of the saddle moving out of axial alignment with one a
Dole Douglas R.
Mason Dennis A.
Stone Jon T.
Abelman ,Frayne & Schwab
Browne Lynne H.
Victaulic Company of America
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