AU2001100668B4 - Joinable pipe - Google Patents

Description

Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION INNOVATION PATENT Invention Title: "JOINABLE PIPE The following statement is a full description of this invention, including the best method of performing it known to me/us:

TITLE

JOINABLE PIPE FIELD OF THE INVENTION This invention is concerned with improvements in pipe joints of the type employing a resilient gasket to effect a fluid tight seal between adjacent pipe members.

The invention is particularly although not exclusively concerned with pipe joints in plastics pipes.

BACKGROUND OF THE INVENTION Pipes or conduits for waste water or storm water conveyance typically may be formed from cast iron, moulded concrete, fibre reinforced cement or extruded plastics and generally are provided in discrete lengths with a diameter of from 150mm to 1metre or even greater. These pipes typically have a smooth cylindrical body portion of generally constant cross section along the length of the body portion and a belled or expanded diameter portion on one end with an internal diameter slightly greater than the external diameter of the pipe at its other end.

A liquid tight joint is formed between adjacent lengths of pipe by placement of a resilient rubber 0-ring adjacent one end of a pipe opposite the belled end and then that end, bearing the O-ring, is forced into the belled end of an adjacent length of pipe. As the smaller diameter pipe end enters the belled end cavity, the rubber O-ring is compressed in a radial direction to form a liquid tight seal between the respective ends of adjacent pipes when they are fully telescopically engaged.

While cast iron, moulded concrete pipes and rotationally moulded pipes have a belled end or collar integrally formed during a rotational casting process, the belled end of an extruded plastics pipe is usually formed in a post extrusion operation with a heated mandrel to expand one end of the pipe and shape it to a predetermined internal diameter to receive a free end of an adjacent pipe.

Another method of joining plastics pipe of uniform cross section along its length is to fuse adjacent ends of respective pipes with a heated metal plate and then urge the respective molten pipe ends together to form a fused joint.

Still another method is to use plastics, fibre reinforced cement, concrete or cast iron pipes of uniform cross section with a tubular jointing collar and rubber O-rings located on respective pipe ends which are urged into the jointing collar.

A disadvantage associated with rubber O-rings is that as a pipe end is urged into a belled pipe end or jointing collar, the O-ring rolls along the respective inner and outer surfaces of the telescopic joint. In some cases, manufacturing tolerances in dimensions and surface finish variations cause uneven rolling and twisting in the O-ring with the result that fluid tightness of the joint is compromised but this does not become apparent until after the pipe laying exercise is complete and the pipe I -1 4 trench is filled in. Clearly, repairs of such compromised joints are an expensive and time consuming exercise.

In an endeavour to improve the reliability of fluid tight joints in fibre reinforced cement (FRC) pipes it has been proposed to machine a shallow groove in the outer surface of the pipe adjacent one end thereof to receive a resilient "slip" seal. The slip seal is a continuous ring of a solid resiliently compressible material such as neoprene and has a flat base with upstanding sidewalls to engage in the machined groove to prevent slipping.

A pipe end having a slip seal located in the machined groove is able to be urged into a jointing collar with some confidence that the seal will remain in place in the machined groove.

While generally effective for its intended purpose, the location of a slip seal in a machined groove of a pipe, whether made from cast iron, FRC, reinforced concrete or extruded plastics materials does suffer a number of disadvantages.

The machining process is labour intensive and adds substantially to the cost of the pipes. Moreover, the seal groove forms a localised reduction in wall thickness of a pipe which can compromise its internal pressure rating or its ability to withstand externally applied loads due to vehicular traffic or the like. A still further disadvantage arises from the requirement of an internal abutment or stop in the jointing collar or a belled pipe end to allow accurate telescopic engagement with respective adjacent ends of a pair of pipes to be joined.

Of more recent times, plastics pipes have been produced by a progressive injection moulding process known as "grow-moulding".

In this process, a finite length of pipe having an external reinforcing rib located intermediate the ends of an otherwise tubular body is initially formed about a mandrel in an injection moulding die. After the body has cooled sufficiently to enable it to be removed from the die, it is slid along the mandrel, which extends out through one side of the die, whereby one end of the tubular body remains located in an end of the closable die to form a closure about the mandrel extending through the side of the die. A charge of molten plastics material is introduced under pressure into the die cavity and where the molten mass contacts the free end of the tubular body extending into the die cavity, it fuses therewith to form an integral tubular body now twice the length of the originally formed body. That process is repeated as required to produce an integrally formed plastics pipe having a smooth internal bore and spaced, radially protruding external reinforcing ribs.

This pipe forming process has significant advantages over a conventional large bore pipe extrusion process as substantially less floor space and capital expenditure for equipment that otherwise was occupied by vacuum sizing equipment, cooling troughs and a travelling saw to sever a continuously produced pipe into predetermined lengths.

It is an aim of he present invention to provide a pipe jointing 6 process and a pipe which overcome or alleviate at least some of the problems associated with prior art pipe joints.

SUMMARY OF THE INVENTION According to one aspect of the invention there is provided a joinable moulded plastics tubular pipe, said pipe comprising:a plurality of radially extending annular circumferential reinforcing ribs spaced along an outer surface of said pipe; at least one circumferential seal locating channel located between adjacent reinforcing ribs and at least one seal locating channel being formed between at least one end of said pipe and an adjacent reinforcing rib extending about said outer surface of said pipe, said pipe characterised in that in use said pipe may be selectively severed along its length to provide a joinable pipe portion having at least one seal locating channel formed between at least one end of said pipe and an adjacent reinforcing rib.

If required said reinforcing rib, in use, may serve as a locating stop in a spigot and socket joint between adjacent pipes.

If required, two or more spaced seal locating channels may be located between adjacent reinforcing ribs.

The seal locating channel may be located between radially extending circumferential ribs.

Preferably said seal locating channel may be formed by spaced radially extending circumferential ribs projecting from an outer wall of said pipe.

The seal locating channel preferably includes at least one upright 4 L jr 7 inner wall to support a seal therein during a telescopic jointing process.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be more fully understood and put into practical effect, reference will now be made to a preferred embodiment illustrated in the accompanying drawings in which:- FIG 1 shows a moulded element of a pipe produced by the grow moulding process.

FIG 2 shows a schematic side elevational view of a pipe jointing system.

FIG 3 shows an enlarged part cross-sectional view of the joint system of FIG 2.

DETAILED DESCRIPTION OF THE DRAWINGS Throughout the description of the preferred embodiment with reference to the accompanying drawings, like reference numerals are used for like features for the sake of clarity.

In FIG 1 an injection moulded plastics pipe element 1 produced by a grow moulding cycle is shown.

The element comprises a tubular body portion 2, spaced reinforcing ribs 3 and seal locating channels 4 formed by spaced radially extending circumferential ribs 5. The plastics material utilised in the moulded pipe product may be any suitable polymeric material such as PVC, polyethylene, polypropylene, ABS or any other mouldable thermoplastic polymer, co-polymer or mixed polymer species.

As previously explained, the pipe element 1 is produced during a moulding cycle and after the die (not shown) is opened, the element 1 is advanced along a mandrel 6, which extends into the die cavity (not shown), a predetermined distance with an end portion of the pipe element overlapping an interior portion of the die cavity. When the die is closed that end portion of the element 1 is clamped between the die end wall and the mandrel to form a closure to the die cavity. When a charge of molten plastics material is injected into the die cavity to form a further pipe element, the molten plastics charge fuses with the internally protruding end portion of the preceding element to form an integral structure. The process is repeated to form a solid, integrally formed reinforced plastics pipe of any desirable length and ideally, the pipe is severed in the region shown at 7 between adjacent seal channels 4.

FIG 2 shows schematically a part cross sectional view of a joint between adjacent lengths of grow moulded pipe 8, 9.

As shown, a joint 10, is effected by inserting respective ends of pipes 8, 9 with seals (not shown) located in respective seal channels (represented by numerals 4 in FIG 1) into a sealing collar 11 until opposite edges of the collar abut facing upright walls of ribs 3. The ribs 3 serve as locating stops to align the collar 11 centrally over the abutment 12 of the free ends of pipes 8 and 9.

As shown in the part cross sectional view of FIG 2, the pipes 8 and 9 are smooth bored and the joint between adjacent pipes is such as to minimise any disruption to fluid flow therein.

FIG 3 shows an enlarged part cross sectional view of a joint between abutting pipes 8 and 9 as shown in FIG 2.

Prior to effecting a joint between adjacent pipes 8 and 9, a resilient polymeric seal 13 is located in a respective seal channel 4 of adjacent ends of pipes 8 and 9 with a convergently tapering face 14 facing towards the end of a respective pipe.

A tubular plastics sealing collar 11 having an outwardly divergent tapered inner edge 15 is then aligned with one of the pipe ends and is urged over the compressible seal until an edge of the collar engages against a side wall of rib 3.

As shown, seals 1 3, typically of a solid or cellular neoprene rubber or the like, are in a relaxed, uncompromised state but when collar 11 is urged over the seals, they are compressed between a floor of seal channel 5 and an inner surface 16 of collar 11.

The adjacent end of the other pipe is then urged into the free end of collar 11 until it engages against rib 3 of the other pipe.

The jointing system of the present invention provides a convenient and cost efficient means for in-situ jointing of waste water and storm water drains and the like and even in confined spaces such as a deep trench, pipes are simply and reliably joined with confidence that the seal has not become displaced or distorted with a resultant risk of leakage.

Grow moulded pipes and jointing systems according to the invention offer substantial advantages over prior art pipes and jointing systems.

For example, pipes produced by a grow moulding process possess far superior dimensional tolerances than extruded plastics pipes in terms of wall thickness variations (both circumferentially and longitudinally), inner and outer diameter variations while at the same time permitting a reduced wall thickness as a result of the reinforcing ribs and a small reinforcing contribution by the ribs forming the edges of the seal retaining channels. This greater control of manufacturing tolerances gives rise to a high level of confidence in the integrity of sealed joints between adjacent pipes.

Apart from the above advantages when compared with prior art plastics pipe jointing systems, the grow moulded pipes and the jointing system according to the invention offer further advantages over prior art waste and storm water pipes and jointing systems therefor.

As the grow moulded pipes according to the invention are relatively thin walled compared to prior art plastics, FRC, reinforced concrete or cast iron pipes, they do not require heavy lifting nd transportation equipment and generally can be handled and installed with far less labour than hitherto required.

It readily will be apparent to a skilled addressee that many modifications and variations may be made to the invention without departing from the spirit and scope thereof.

11 Throughout this specification and claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.

DATED this Twenty-First day of December 2001.

EVERHARD INDUSTRIES PTY LTD By Its Patent Attorneys FISHER ADAMS KELLY

Claims (4)

1. A joinable moulded plastics tubular pipe, said pipe comprising:- a plurality of radially extending annular circumferential reinforcing ribs spaced along an outer surface of said pipe; at least one circumferential seal locating channel located between adjacent reinforcing ribs and at least one seal locating channel being formed between at least one end of said pipe and an adjacent reinforcing rib extending about said outer surface of said pipe, said pipe characterised in that in use said pipe may be selectively severed along its length to provide a joinable pipe portion having at least one seal locating channel formed between at least one end of said pipe and an adjacent reinforcing rib.

2. A tubular pipe as claimed in claim 1 wherein said reinforcing rib, in use, serves as a locating stop in a spigot and socket joint between adjacent pipes.

3. A tubular pipe according to claim 1 or claim 2 wherein said seal locating channel includes at least one upright inner wall to support a seal therein during a telescopic jointing process.

4. A tubular pipe as claimed in any one of claims 1 to 3 wherein said seal locating channel is formed between radially extending circumferential shouldered projections extending about said outer surface of said pipe. A tubular pipe as claimed in claim 4 wherein at least one of said shouldered projections tapers convergently in a direction away from said seal locating channel.