A COUPLING AND RIGID PIPE

FIELD OF THE INVENTION

This invention relates to a connector and coupling for pipes, in particular rigid pipes which are used in mining operations. The invention also relates to pipes and to a pipe connecting system.

BACKGROUND TO THE INVENTION

A number of couplings for rigid pipes are known. One type of coupling includes a pair of connectors, each of which can engage over the end of a pipe. Once secured to adjacent ends of a pair of pipes, the connectors can be engaged with each other to provide the coupling. Securing a connector to a plastics pipe can be difficult. With a steel pipe this is normally done by welding.

A large part of the effectiveness of a pipeline, especially one that has a relatively high operational pressure, depends on the couplings. It is also desirable to have pipes which are suited to operate under harsh conditions.

OBJECT OF THE INVENTION

It is an object of this invention to provide a novel pipe connector and coupling, as well as a novel pipe, and a system of these components.

SUMMARY OF THE INVENTION

In accordance with a first aspect of this invention there is provided a pipe connector having an outer coupling formation and a longitudinal bore from a first end to a second end, the bore adapted to engage over the end of a pipe at the second end and having a reduced diameter at the first end, with a first sealing formation provided at the first end to establish a seal axially inwardly from the diameter of the bore at the second end.

The invention further provides for the bore to have a second sealing formation to establish a seal about the end of a pipe axially outwardly from the first seal.

Further features of the invention provide for the bore to have an inward step adjacent the first end; for the sealing formations to be annular grooves for seals; for the groove of the second sealing formation to be on a surface of the step facing the second end; and for the bore to be screw-threaded adjacent the second end.

In accordance with another aspect of this invention there is provided a pipe connector having an outer coupling formation at a first end and a second end internally screw-threaded to engage corresponding screw-threads on the end of a metal sleeve on a plastics pipe.

Further features of both mentioned aspects of the invention provide for the coupling formation to be a tapered flange for a clamp or a perforated flange for bolting together.

The invention extends to a coupling including a pair of connectors as defined in either or both of the aspects above.

In accordance with still another aspect of this invention there is provided a plastics pipe having a metal sleeve secured along its length with the sleeve outwardly screw-threaded adjacent its ends.

The invention further provides for the pipe to be Unplasticized Polyvinyl Chloride (UPVC) and for the sleeve to be steel. The pipe may be provided with a lining as defined in the aspect below.

In accordance with yet another aspect of this invention there is provided a pipe for conveying backfill having an inner lining selected from the group comprising Polytetrafluroethylene (PTFE), Ultra High Molecular Weight Polyethylene (UHMW-PE), High Molecular Weight Polyethylene (HMW-PE), High Density Polyethylene (HDPE) and Polypropylene.

Further features of the invention provide for the pipe to be of plastics material or steel; and for the pipe to be of a plastics material with a steel sleeve. The plastics material of the pipe will preferably be Unplasticized Polyvinyl Chloride (UPVC).

Another aspect of the invention provides for a pipe connecting system which includes the couplings comprising connectors and the pipes as defined above. This system is preferably for conveying backfill, usually in mining applications.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will become apparent from the following description of one embodiment of the invention, by way of example only, with reference to the drawings in which:

Figure 1 shows a cross-section of a coupling connecting a pair of pipes; Figure 2 shows a perspective view of a connector of the coupling; and Figure 3 shows a perspective view of the coupling.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to the drawings, a pipe coupling (1 ) comprising a pair of connectors (2) and an annular clamp (3) are shown. The coupling (1 ) is of the type sometimes referred to as a "tapered end" coupling. This name derives from the feature of an annular flange (4) on each connecter (2) which tapers outwardly towards the join or middle of a coupling (1 ). The tapered flanges (4) of two connectors (2) provide engaging surfaces for a channel (3.1 ) with correspondingly inclined sidewalls formed inside the clamp (3). This arrangement is not on its own new.

In the embodiment shown, the flange (4) of each connector (2) provides an outer coupling formation (4) at a first end (5). The second end (6) of the connector (2) is adapted to engage over the end of a pipe (7). More particularly, an internal screw-threaded portion (8) is provided to engage corresponding screw-threads (9) on the end of a pipe (7).

A longitudinal bore (10) through the connector (2) has a reduced diameter at the first end (5). The reduced diameter of the bore (10) is provided by an inward step (1 1 ). A first sealing formation (12) is provided at the first end (5) of the connector (2). This sealing formation is a groove (12) for an annular seal (13) to establish a

first seal (13) axially inwardly from the diameter of the bore (10) at the second end (6). Another annular groove (14) for a seal (15) forms a second sealing formation on the surface of the inward step (1 1 ) facing the second end (6). The second groove (14) is to establish a seal (15) at the end of a pipe (7) axially outwardly from the first seal (13). The significance of the relative diameters of the first (13) and second (15) seals will be discussed below.

The pipe (7) is of a composite nature having an inner plasties pipe (16) fitted with a steel sleeve (17). This will normally be done by heating a sleeve (17) of suitable diameter and inserting the plastics pipe (16) while it is in an expanded condition. The sleeve (17) carries the screw-threads (9) adjacent its ends to engage the screw-threads (8) in the end of the connector (2). The ends of the sleeve (17) are, once properly in place, spaced inwardly along the pipe (7) from the ends of the inner plastics pipe (16). The plastics material is selected from UPVC and HDPE, however, other suitable types may also be used.

The components (2) and (7) described provide, in combination, a system for connecting pipes which is further described in what follows. In use, the connectors (2) are fitted to the pipes (7) by engaging the respective screw- threads (8) and (9). An additional groove (18) for a third seal (19) is provided to locate around the exposed outer surface adjacent the end of the plastics pipe (16). The end itself locates against the surface of the step (1 1 ) facing the second end (6) and the second annular seal (15) is established.

With two adjacent pipe ends having connectors (2) fitted thereto, a coupling (1 ) between the pipes (7) is provided. Bolts (not shown) are used in the normal way to close the clamp (3) into position and bias the ends (5) of the connectors (2) against each other. The first seal (13) is established.

An assembled coupling (1 ) will normally contain fluid under a given working pressure. Two bleed passages (20) and (21 ), for each connector (2), are

provided from the bore (10) to the first seal (13) and the second seal (15), respectively. It will be appreciated that these passages result in two annular effective areas (A) and (B) on either side of the step (1 1 ) whereon forces due to the pressure in the pipe act. These forces will also be referred to as (A) and (B).

The force (A) acts against the step (1 1 ) to separate the connectors (2). This force (A) must be resisted by the clamp (3). The force (B), which is greater than (A), acts on the step (1 1 ) in the opposite direction, to hold the connectors (2) together. This force (B) assists the clamp (3) and alleviates the opening stresses it needs to resist. A counter-force to (B) will act on the end of the inner pipe (16). This force (B) will, however, generally be balanced by equal force acting at the opposite end of the inner pipe (16), at the next coupling. The inner pipe (16) is thus subjected to compression stresses but these are not transferred to the sleeve (17) which has its ends screw-threaded into the connectors (2).

A smooth transition from bore of the pipe (7) over the inward steps (1 1 ) in the coupling (1 ) to bore of the next pipe (7) is generally desirable for unobstructed flow. This is important when conveying slurries or suspensions of particulate material.

It will be appreciated that the force (A) can be reduced by positioning the first seal (13) closer to the bore (10) at the first end (5). The force (B) can similarly be increased by moving the second seal (15) to a position of larger diameter in the bore (10).

The steel sleeve (17) of the pipe (7) increases the safe working pressures obtainable with such a pipeline and also provides a protective shell to the plastics pipe (16) inside. Such protection against mechanical impact can be useful, for example, in underground mining operations. Where plastics pipes are used to convey salt water to recycling plants, they are often buried for protection. Again,

in these conditions, the protection afforded by the steel sleeve (17) will be beneficial.

It is also anticipated that an alternative embodiment of the coupling will be used with connectors that have a bore of constant diameter. The arrangement will allow the ends of the plasties pipes to abut, under bias applied through the screw-threaded engagement to the sleeves. The ends of the pipes may be grooved for an annular seal, or some other suitable seal, for example a sealing collar around the outside of the pipe end, can form part of the coupling. Such an arrangement is beneficial when conveying salt water which corrodes metal components and also suspensions of particulate material which may wear at the metal.

The screw-threads (9) can also be cut into a plastics pipe, where the benefits of a steel sleeve are not essential, for example, in lower pressure applications.

It will be also be appreciated that the coupling formation of each connector may, instead of a tapered flange for a clamp, be a perforated flange for bolting the connectors together.

A further aspect of this invention provides a rigid pipe (not shown) with an inner wear lining selected from Polytetrafluroethylene (PTFE), Ultra High Molecular Weight Polyethylene (UHMW-PE), High Molecular Weight Polyethylene (HMW- PE), High Density Polyethylene (HDPE) and Polypropylene. The pipe may have the features of the one described above. The lining is however directed to application in the conveying of backfill in mining operations.

The pipe may be made of plastics material or of steel and alternatively as a steel sleeve and plastics composite of the type already described. The selected linings generally have desirable resistance to abrasion, corrosive chemicals and heat. They can also be used at elevated temperatures without substantially any

denaturing of the plastic. The combination of such a lining within a UPVC, HDPE or steel pipe, which enables high working pressures and provide a protective outer shell, will prove advantageous in underground applications of the kind mentioned.

The specific thickness of the lining in relation to that of the material from which the outer pipe or sleeve is made will be within the design competence of a suitably skilled person and will vary for different applications. This will extend to a system which uses the connectors already described above. It will also be understood that the described variations from the components of the illustrated embodiment will equally apply to the mentioned system for connecting pipes.

A suitably skilled person will appreciate that a number of other variations may be made to features of the described embodiments without departing from the scope of the current invention.