Conduit systems

Details Conduit systems Conduit systems

1999-10-07

2001-06-19

Brinson, Patrick (Department: 3752)

Pipes and tubular conduits

Longitudinally seamed

Sectional

C138S162000, C138S166000, C285S373000

Reexamination Certificate

active

06247500

ABSTRACT:

This invention is concerned with an improved modular plastics conduit system for electrical cabling fluid conduits and the like.
The invention also relates to a repair system for existing damaged conduits.
Hitherto there have been many attempts over the last forty years or so to provide modular conduits and fittings therefor, particularly for in-situ repairs to damaged conduit systems.
The absence from the marketplace of such systems and the increasing number of patents sought for such systems is a clear illustration of their infeasibility, either in terms of functional adequacy or in terms of manufacturing costs.
Australian Patent Application No. 18343/83 and Australian Patent Application No. 70072/91 respectively describe multi-part, longitudinally divided plastics conduits which are readily assembled on site and avoid the need to thread cables or wires through a conventional one-piece tubular conduit. Each describes a snap in tongue and groove connection between a longitudinally extending rib having an enlarged bead on its free edge and a longitudinally extending groove having a cross sectional shape complementary to the cross sectional shape of the rib, the free edges of the groove being resiliently deformable to receive the enlarged bead.
While generally effective for their intended purpose, they are not adapted for mechanical or fluid tight engagement with a suite of couplings such as tees, elbows, inspection ports or the like.
Moreover, neither of the above conduit systems lends itself to in situ repair of existing damaged conduits nor are either suited to in situ repairs, branching or the like short of complete removal and replacement of an entire length of damaged conduit member.
U.S. Pat. No. 4,967,800 describes a secondary confinement pipe assembled from identical segments of extruded plastics material.
The opposite edges of semi-circular pipe sections include longitudinally extending beaded ribs and complementary narrow mouthed grooves, at least one of which includes a co-extruded resilient plastics material to enhance fluid sealing in the opposed tongue and groove joints.
This confinement pipe is designed for fitment only about a straight length of primary pipe for the purpose of monitoring leakage between the primary and secondary pipes. No mention is made of confinement of fittings such as tees, elbows etc.
Australian Patent No. 236968, Australian Patent Application No. 73044/81 and U.S. Pat. Nos. 3,204,668, 3,126,035, 4,304,267 and 4,576,846 each disclose thermal sheathing systems for is straight lengths of pipe which permit in-situ fitting to an existing pipe.
With the exception of U.S. Pat. No. 4,304,267, which relates to interlocking refractory elements, each of these thermal sheathing patent documents discloses longitudinally extending tongue and groove joints to secure the sheathing in situ around a straight length of pipe.
Again these patent documents are silent as to complementary fittings for tees, elbows and inspection ports in the pipe to be insulated.
Australian Registered Design No. 117052 describes a one piece moulded tee coupling split longitudinally but connected by an integrally formed hinge so that it may be closed and secured by bolts or screws through fillets at the junction between the upright and transverse portions. The edges of one half portion are formed with upstanding ribs which locate in corresponding channels in the edges of the other portion when the two halves are abutted.
U.S. Pat. Nos. 3,944,260, 4,109,944, 4,260,181, 4,374,596, 4,652,023 and 5,443,096 each describe pipe couplings or pipe repair couplings formed in two longitudinally split half sections and designed for fitment about a leaking pipe coupling, a damaged straight pipe or otherwise facilitate electrical trunking systems.
U.S. Pat. Nos. 3,944,260 and 4,652,023 describe flange bolted repair couplers for damaged fittings and straight pipe sections respectively.
U.S. Pat. Nos. 4,109,944 and 4,260,181 describe repair couplers for adhesive bonding to plastics piping. Overlapping tabs and grooves with interengaging teeth mechanically lock the two halves of the fittings while the adhesive sets.
Electrical duct fittings comprising longitudinally split halves are disclosed in U.S. Pat. No. 4,374,596. One half includes a non beaded discontinuous rib on each free edge while the other half includes parallel sided discontinuous channels on each free edge while the other half includes parallel sided discontinuous channels on each free edge to mate with the ribs of the other half. Resilient lips protruding from the outer surface of the fittings engage in slots in conduits which engage over the ends of the fittings.
U.S. Pat. No. 5,443,096 describes a repair coupling for straight pipes, the coupling comprising similar halves which snap together by resilient deformation of interengaging hooked lips to mechanically retain the fitting under compression while an adhesive bond is formed between the coupling and the pipe.
A tongue and groove snap-fit pipe coupling for joining and or repairing thermoplastic pipes by mechanical and adhesive bonding is described in U.S. Pat. No. 5,007,666. This patent discloses straight couplings for repair or jointing of plastics conduits as well as elbows, tees and cruciform couplings having a tongue and groove edge joint wherein the tongue is slotted to permit contraction to enter the groove and expansion to lock within the groove.
In my Australian Patent No. 648818 and copending Australian Patent Application No. 68918/94 there is described a modular conduit system wherein elongate conduit elements and conduit fitting elements are provided on opposed free edges with a beaded rib and a recessed channel in to which the beaded rib locates.
Although generally satisfactory for their intended purpose these element suffer a number of practical disadvantages.
While the elongate conduit elements may be extruded satisfactorily, difficulties have been encountered in economical production of the conduit fitting elements by injection moulding.
From the outset, separate dies or die cavities must be formed to fabricate the interengaging halves of the fittings as they are not true mirror images of each other.
Moreover the formation of the beaded rim portion of the conduit elements requires compound dies to enable release of the rib portions after moulding. This has not been practically achievable with the undercut groove portions even with a compound die assembly due to “hang-ups” and distortion upon release from the die. These problems are exacerbated by the relatively small proportions and close proximity of the beaded rim and undercut channel on opposed free edges of the fittings.
While all of the prior art conduits, pipe couplings and repair couplings are satisfactory for their respective intended purposes, all suffer from one or more disadvantages including high tooling costs, incompatibility between conduit structures and coupling structures and a lack of modularity. In other words none of the prior art permits a complete conduit system comprising a split conduit and a suite of complementary split fittings which enables an initial conduit installation, repairs to a damaged installation or ready modification to an existing conduit installation.
It is an aim of the present invention to overcome or alleviate at least some of the disadvantages of prior art conduit systems and to provide a modular conduit system applicable to a wide range of circumstances.
According to one aspect of the invention there is provided a modular conduit system comprising:
longitudinally divided elements engagable to form a hollow conduit having a smooth bore of substantially circular cross section, said elements characterised in the provision of one or more interengageable complementary tongue and groove formations along opposed free edges thereof, said tongue formation and said groove formation each having at least one radial curvature with the same radial origin when opposing elements are interengaged, said opposing elements being engagable or disengagable against radial deformation forces

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