AU785471B2 - Pipe Jointing System - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "PIPE JOINTING SYSTEM" The following statement is a full description of this invention, including the best method of performing it known to us: 2

TITLE

PIPE JOINTING SYSTEM 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 1 metre or even greater. These pipes typically have a smooth cylindrical body portion of generally constant crosssection 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 O-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.

3 While cast iron and moulded concrete pipes have a belled end 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.

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 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 4 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 to allow accurate telescopic engagement with respective adjacent ends of a pair of pipes to be joined.

Pipes having spaced annular ribs or helical ribbing give rise to difficulties in effecting fluid tight joints between adjacent lengths of pipe.

Examples of quite complex, expensive and time-consuming joints between externally ribbed pipes are to be found in International Publication WO 9211485, United States Patent 4,398,726, United States Patent 5,765,880 and French Patent No 2376986.

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.

SUMMARY OF THE INVENTION According to one aspect of the invention there is provided a pipe jointing system comprising:- 6 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; and a tubular collar adapted for sealing engagement with respective sealing members located, in use, in a respective said at least one seal locating channel adjacent a respective free end of adjacent pipes to be joined; said pipe jointing system 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.

Suitably, a reinforcing rib adjacent said respective free end of each adjacent pipe, in use, serves as a locating stop in a spigot and socket joint between a respective free end of each adjacent pipe and said collar.

If required, the seal locating channel includes at least one upright inner wall to support a seal therein during a telescopic jointing process.

Suitably, said seal locating channel may be formed between radially extending circumferential shouldered projections extending about said outer surface of said pipe.

7 Preferably, at least one of said shouldered projections tapers convergently in a direction away from said seal locating channel.

Suitably, said seal locating channels are formed as recessed channels in an outer surface of said pipe.

The seal locating channels may be formed between spaced radially extending annular circumferential rib members projecting above an outer surface of said pipe.

The resilient sealing member may comprise a generally Ushaped cross-section.

If required the resilient sealing member may include spaced flanges defining a concave recess therebetween.

Suitably said sealing member is cross-sectionally tapered.

According to another aspect of the invention there is provided a moulded plastics tubular pipe for use with the jointing system of the invention, said pipe comprising:a pipe body having a smooth bore and a plurality of radially extending annular circumferential reinforcing ribs spaced along an outer surface of said pipe body; 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 body and an adjacent reinforcing rib extending about said outer surface of said pipe body, said pipe body characterised in that, in use, said pipe body may be selectively severed along its length to provide a joinable pipe portion having at least one seal 8 locating channel formed between at least one end of said pipe body and an adjacent reinforcing rib.

Most preferably, said tubular pipe is formed by a progressive moulding process.

The tubular pipe is preferably formed by a grow-moulding 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 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 according to the invention; and 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 9 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 pipes 8,9.

As shown, a joint 10 is effected by inserting respective ends of pipes 8,9 with seals (now 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 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 13, 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 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 11 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 and 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 12 from the spirit and scope thereof.

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.

Claims (14)

1. A pipe jointing system comprising:- 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; and a tubular collar adapted for sealing engagement with respective sealing members located, in use, in a respective said at least one seal locating channel adjacent a respective free end of adjacent pipes to be joined, said pipe jointing 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 system as claimed in claim 1 wherein a reinforcing rib adjacent said respective free end of each adjacent pipe, in use, serves as a locating stop in a spigot and socket joint between a respective free end of each adjacent pipe and said collar.

3. A system as claimed in 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 system as claimed in any one of claims 1 to 3 wherein, said 14 seal locating channel is be formed between radially extending circumferential shouldered projections extending about said outer surface of said pipe.

A system as claimed in claim 4 wherein, at least one of said shouldered projections tapers convergently in a direction away from said seal locating channel.

6. A system as claimed in any one of claims 1 to 3 wherein, said seal locating channels are formed as recessed channels in an outer surface of said pipe.

7. A system as claimed in any preceding claim wherein, the resilient sealing member comprises a generally U-shaped cross-section.

8. A system as claimed in any preceding claim wherein, the resilient sealing member includes spaced flanges defining a concave recess therebetween.

9. A system as claimed in any preceding claim wherein, said sealing member is cross-sectionally tapered.

A moulded plastics tubular pipe for use with the jointing system of any preceding claim, said pipe comprising: a pipe body having a smooth bore and a plurality of radially extending annular circumferential reinforcing ribs spaced along an outer surface of said pipe body; 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 body and an adjacent reinforcing rib extending about said outer surface of said pipe body, said pipe body characterised in that, in use, said pipe body 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 body and an adjacent reinforcing rib.

11. A pipe as claimed in claim 10 whenever formed by a progressive moulding process.

12. A pipe as claimed in claim 10 or claim 11 wherein, the tubular pipe is formed by a grow-moulding process.

13. A system as hereinbefore described with reference to the accompanying drawings.

14. A pipe as hereinbefore described with reference to the accompanying drawings. DATED this Fourth day of June 2002. EVERHARD INDUSTRIES PTY LTD By Its Patent Attorneys FISHER ADAMS KELLY