PIPE JOINT

The present invention relates to a joint for connecting tubular conduits, in particular for connecting lengths of pipe so as to form a fluid transport system.

Fluid transport systems are known for conveying materials, such as liquids and gasses, with common examples including water and fuels such as gas and oil. The systems may include oil and gas pipelines for conveying fuel over thousands of miles to domestic gas and water pipe systems. The tubular conduits used in fluid transport may be made of different materials, including steel, iron, copper, aluminium and plastic.

For small bore plastic pipes a press or screw fit joint can be used, and in copper pipe, the use of soft solder is the usual means of joint connection.

For the larger diameter pipes, typically 1 to 1.5m metres (around 40 inches) in diameter, used in the transport of fuel, welded joints are commonly used. However, welded joints have the disadvantage of requiring skilled workers as well as having negative health and safety and environmental implications. For example, construction of a gas or oil conveying pipeline, are typically made from approximately 12 metre (40 feet) long lengths of steel pipe with a diameter of 1 to 1.5 metres and conventionally use welded joints. Each joint can take a skilled team a whole day to make, when taking into consideration, the deployment of equipment at the joint location and inspection of the joint by X-ray equipment. Also, around 1 in 10 of such

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welded joints will have to be repaired after an inspection. This makes oil and gas pipelines expensive and time consuming to construct.

A further problem with press fit and welded joints is that they are difficult to disconnect, for example, for repair or maintenance, and once disconnected are not generally re-useable. Furthermore, disconnection of press fit or welded joint often results in damage to the pipe lengths.

According to the present invention, there is provided a pipe joint comprising at least one connection end wherein the or each connection end comprises: a wall defining a receiving recess for receiving an end of a pipe length; a tapered locking recess formed in an internal surface of the wall and containing a correspondingly tapered locking element; a through hole in the wall which communicates with the tapered locking recess; and a fixing element rotatable within the through hole and formed with a foot portion and wherein: in a first unlocked rotational position of the fixing element the foot is at least partially retracted from the locking recess; and in a second locked rotational position of the fixing element the foot extends into the locking recess to urge the locking element between the tapered locking recess and a pipe located within the connection end. This provides a simple yet reliable pipe joint which is easy to connect and can be disconnected in order to facilitate repair and maintenance. Each connection end may comprise a plurality of fixing elements and associated through holes. The fixing elements and associated through holes may be distributed around the receiving recess in order to facilitate an even locking effect around a circumference of a fitted pipe. The or each locking element may be resiliently biased into an unlocked position so as to facilitate disconnection of the

pipe joint for repair or maintenance. There may be more than one locking element in each connection end, again to facilitate an even locking effect around a circumference of a fitted pipe.

The locking recess may be an annular recess, in which case the locking element may be an annular ring. Again this facilitates an even locking effect around a circumference of a fitted pipe. The locking ring may be made of a resilient material and a transverse cut may be formed through the locking ring. This enables the locking ring to be compressed so that it can be passed into the receiving recess for fitment into the locking recess. The resilience of the ring also biases the ring into an unlocked position. In order to increase the engagement between the locking element and a fitted pipe, the locking element may have a radially inwardly facing face for engaging a pipe and which face may be formed with a plurality of teeth.

The foot of the or each locking element may have a variable radius forming a cam surface so that in the first unlocked rotational position of the fixing element a reduced radius portion of the foot may face the locking recess, and in the second locked rotational position of the fixing element an increased radius portion of the foot may face the locking recess. In order to smoothly urge the locking element against a fitted pipe, the foot portion may have a gradually increasing radius over at least 180°, preferably around 270° around an axis of rotation of the foot portion.

For connection to conventional cylindrical pipes, the internal surface of the wall of the receiving recess may be substantially cylindrical. In addition, each connection end may comprise a sealing arrangement for sealing between the receiving recess and

the connection end. The sealing element may be located to the side of the fixing element remote from an open end of the receiving recess. Additionally, each connection end may comprise a pipe end face abutment extending inwardly of the wall of the receiving recess.

The invention will now be described by way of example only and with reference to the accompanying schematic drawings, wherein:

Figure 1 shows a longitudinal cross-section through pipe joint according to the present invention comprising and end cap and connected to an end of a length of pipe and in an unlocked position; and

Figure 2 shows a longitudinal cross-section through the pipe joint of Figure 1 in a locked position;

Figure 3 shows a longitudinal cross-section through a connection end of a pipe joint according to the present invention;

Figure 4 shows a plan view of a pipe joint according to the present invention comprising two connections ends of Figure 3 for connecting the ends of two lengths of pipe; and

Figure 5 shows a view from below of the base of a foot of a fixing element used in the pipe joint according to the present invention.

Figure 1 shows a partial longitudinal cross-section through a pipe joint (2) connected to a length of pipe (4). Only the end of the pipe length (4) connected to the pipe joint (2) is shown in Figure 1. The pipe joint (2) comprises an open connection end (18).

As the pipe joint in Figure 1 is an end cap it comprises a single connection end having a closed end (6) for closing off an end of a pipe (4) fitted within it.

Each connection end (18) is formed with a receiving recess (8) shaped to receive an end of a pipe length (4) and so the receiving recess generally has a substantially circular transverse cross-section. As the pipe joint in Figure 1 is an end cap, the receiving recess is formed with the end face (6).

An annular recess (12) is formed in a tubular wall (14) defining the receiving recess (8) for housing an annular seal (10).

At least one through hole (20) is formed through the tubular wall (14) of the receiving recess (8) from the external surface (13) of the tubular wall through to the internal surface (15). A major part of the bore of the through hole (20) is substantially concentric with a line (22) extending substantially radially from the longitudinal axis (24) of the connection end (18). In the example shown in Figure 1 , two such through holes are formed in the connection end (18). The annular seal (10) is located to the side of the through holes remote from the open end of the receiving recess (8). Each through hole (20) is formed with a main portion (20a) of reduced radius as compared to an inner end (20c) of increased radius as compared to the main portion (20a). The inner end (20c) communicates with an annular locking recess (26) for receiving an annular locking ring (28).

The fixing element has a central stem portion (30b) with a radius matching that of the main portion (20a) of the through hole. An outer surface of the stem portion (30b) is

formed with a recess (40) for receiving a screwing tool. The fixing element (30) can be pushed into the through hole (20) from the inside of the receiving recess (8) and a snap fit connection holds the fixing element (30) within the through hole (20) so that the fixing element is rotatable within the through hole. The snap fit connection comprises an annular recess formed around the stem portion (30b), close to the outer surface of the fixing element and a facing annular recess is formed in the main portion (20a) of the through hole (20). A metal snap ring (31) is fitted within the recess in the through hole (20). Then when the fixing element (30) is pushed into the through hole (20) the snap ring (31) moves into the recess in the stem portion of the fixing element to releaseably hold the fixing element there. Other types of releaseable connections, such as friction connections or snap fit connections will be apparent to a person skilled in the art which could be used to releaseably hold the fixing elements (30) within the through holes (20).

The fixing element also has a foot portion (30c), shown in more detail in Figure 5. The foot portion (30c) increases smoothly in radius (with respect to the axis (22)) to form a cam surface, from a first radius η equal to the radius of the stem portion (30b) to a second larger radius r ₂ matching the radius of the inner end (20c) of the through hole. The radii of the portions (20a, 20c) of the through hole match the radii of the portions (30b, 30c) of the fixing element so as to facilitate rotation of the fixing element (30) within the through hole.

The annular locking recess (26) is terminated at its end remote from the open end of the receiving recess by an annular wall which is aligned with the sides (32) of the main portions (20a) of the through holes proximal the open end of the receiving

recess (8). The annular recess is formed with an intermediate annular wall (34) which is aligned with the sides of the inner portions (20c) of the through holes proximal the open end of the receiving recess (8). The annular wall (34) forms a step to a sloping portion (37) of the annular recess which tapers from the step (34) to the internal surface (15) of the tubular wall- (14) towards the open end of the receiving recess (8).

The annular locking ring (28) has a shape matching the shape of the sloping portion (36) of the annular recess (26). The locking ring (28) has a radially inwardly facing locking surface which has a substantially constant radius on which is formed a plurality of annular locking teeth (36). The radially outer surface (28c) of the locking ring (28) tapers to a thin edge (28a) in a direction towards the open end of the receiving recess (8). The locking ring (28) may be made of a resilient material, for example metal, and may be cut so as to allow the locking ring to be contracted so as to fit the locking ring (28) within the annular locking recess (28). The locking ring (28) is fitted within the annular locking recess (26) after the fixing elements (30) have been assembled into the through holes (20) and due to its resilience the locking ring expands into the locking recess into the position of the locking ring shown in Figure 1. The fixing elements (30) are assembled into the through holes (20) in the rotational position of the fixing elements shown in Figure 1 in which the reduced radius portions of the fixing elements are racing towards the open end of the receiving recess (8).

To fit a pipe end (4) into the connection end (18) of the pipe joint of Figures 1 and 2, the pipe end (4) is slideably located within the receiving recess (8) with the end face

of the pipe abutting the end face (6) of the receiving recess. With the pipe in this position the annular seal (10) seals around the outer surface of the pipe (4) so forming a seal between the pipe (4) and the connection end (18). This position is shown in Figure 1.

A screwing tool (not shown) is then used to rotate each fixing element (30) within its associated through hole (20) by engaging the screwing tool within the recess (40) in the outer face of the fixing element. The fixing element (30) is rotated to its position in Figure 2 and during this rotation the increasing radius portions of the foot (30c) of the fixing element pushes against the locking ring (28) to urge the locking ring in a direction towards the open end of the receiving recess (8). This forces the locking ring (28) into the tapered portion of the annular locking recess (26). When the fixing element arrives in the position shown in Figure 2, the large diameter portion of the foot (30c) of the fixing element engages the locking ring to lock it tightly within the tapered portion of the annular locking recess. Engagement between the tapered upper face (28c) of the locking ring and the sloping portion (37) of the annular locking recess urges the teeth (36) of the locking ring (28) to engage the outer surface of the pipe end (4). In this way, the pipe end is locked within the connection end (18) due to the engagement of the locking ring (28).

Alternatively, the locking ring (28) could be replaced with a series of locking wedges, one associated with each locking element (30).

The pipe joint according to the present invention is not restricted to an end cap, as is shown in Figure 1. Alternatively, the pipe joint may comprise more then one

connection ends (18) of the type shown in Figure 3, in which the end face (6) is replaced by an annular abutment (16) against which an end face of a pipe (4) can be seated. As shown in Figures 3 and 4 the pipe joint may (18) comprise two connection ends connected by any length or shape of conduit (3) and so can be used for connecting two or more pipe ends together, as is shown in Figure 4. In addition, the pipe joint comprising one or more connection ends of the type shown in Figure 3 might include a valve or other element, which are typically included in such pipe joints.