Pipes and tubular conduits – Spirally seamed
Patent
1988-03-03
1990-12-18
Bryant, III, James E.
Pipes and tubular conduits
Spirally seamed
138122, 138129, 138174, F16L 1111
Patent
active
049779311
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of and means for producing reinforced ribbed structures, particularly tubes but has application also to panels, but in particular it relates to structures of the type in which a strip having a series of upstanding ribs on at least one face and interengaging edge means is used.
This form of helically wound tube is already well known and is described in patents by the same Inventor relating both to the form of the strip and the form of the machine by means of which the tubes are produced from such strips.
It is a well established fact that a helical, sometimes referred to as a spiral, tube of a plastics material with a ribbed configuration forms an attractive method of producing low cost tubes for water, sewers and the like.
One problem with such tubes is that because such tubes are made from thermoplastic materials, they have a low modulus of elasticity to the point that to meet the deflection criteria when buried in a trench or subject to high earth loads, such tubes need to have relatively high ribs and a substantial wall thickness.
The object of the present invention is to provide certain improvements to the method of manufacture and the tube itself formed according to this invention and this improvement is achieved according to this invention by reinforcing members associated with the tube so formed, which reinforcing members may comprise relatively rigid members in strip form of selected cross section, which reinforcing members locked on to or placed between or embedded in the structure in such a manner that the deflection resistance of such a tubular object is materially increased.
It is of course already known to reinforce tubing, such for instance as used in vacuum lines, by steel springs or the like wound into the wall of the tube during manufacture or associated with the tube after manufacture by embedding the wire spring material or the like in a groove in the material, but the object of the present invention is to stiffen the ribs in at least a generally radial direction, although some lateral stiffening may also be necessary.
It has been found that when a helically wound plastic tube is placed in a trench and backfilled with sand or gravel and a load is applied on top of the backfilled tube, the load can be a wheel of a laden truck or by simply a force from a hydraulic jack on to a steel plate, which in turn deflects the buried test pipe to destruction, the failure mode is one which deforms the crown of the pipe, leaving the rest of the pipe in good order. The particular failure point is when the tube is deformed beyond its elastic limit the helical seam springs open and the sand backfill under load then quickly flows to the failure point further exaggerating the problem as the `domino effect` takes over because the ribbed configuration then collapses sideways.
One of the problems of course of winding a strip or the like into such a structure, such as by engaging it to be upstanding along the wall of T-shaped ribs or the like, is to be able to achieve the required circular configuration when the face of such material is radially disposed and to still allow the strip to be closely accommodated to the ribs when the strip from which they are formed is bent into a helical formation to form the tube, and the invention therefore is designed so that while withstanding generally radial loads the reinforcing ribbon or the like may be corrugated laterally or so formed that it can be bent to a circular configuration. The invention is however not limited to tubular structures but applies also to panels having a similar rib structure.
The reinforcing member can be locked on to or placed between ribs in such a manner that the member considerably increases the deflection resistance of such objects but instead of using a metal reinforcing member, a strip of fiberglass, saturated with a plastic resin such as epoxy or polyester, may be used.
The steel or other reinforcing member can be encased in a resilient or a plastic sheath to avoid corrosion or absorb shocks, or the reinfo
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Bryant III James E.
Peterson Gordon L.
Rib Loc Australia Pty. Ltd.
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