GB2477845A

GB2477845A - Coupling of tubular sections

Info

Publication number: GB2477845A
Application number: GB201101552A
Authority: GB
Inventors: Peter Dunn
Original assignee: Screwfast Foundations Ltd
Current assignee: Screwfast Foundations Ltd
Priority date: 2010-02-11
Filing date: 2011-01-31
Publication date: 2011-08-17
Anticipated expiration: 2031-01-31
Also published as: GB201002310D0; GB2477845B; GB201101552D0

Abstract

Tubular sections, for example of ground penetrating metal foundation piles, are connectable end to end, by a coupling comprising a first tubular section (20) having an end portion providing a socket (22) and a second tubular section (10) having an end portion providing a spigot (12) for insertion into the socket. The socket end section (20) has opposing slots (24) extending longitudinally from the open end of the socket, each slot including a lateral recess (26) remote from the open end of the socket, and the spigot end section has at least one bar (30) extending across its diameter and projecting radially outwards at each end for location axially into the opposing slots (24) of the socket (22) and for engagement into the respective lateral recesses (26) upon relative rotation of the tubular sections (20, 10), in the manner of a bayonet joint. A collar (40) is fixedly mounted around the exterior of the socket end section (20). The collar (40) has an axial length shorter than the longitudinal extent of the slots (24) so that a gap remains below the collar to enable access to the slots at their inner ends. Separate strips of material (42) are provided of a size and shape for fitting into the slots (24) after engagement of the bar (30) into the lateral recesses (26). The strips (42) are each provided with a formation, such as a notch (43), adjacent their insertion end, which can be accessed via aforesaid gap to facilitate their removal from the slots and enable disengagement of the coupling. Additional formations, such as apertures (44), may also be provided to facilitate engagement of a tool and removal of a strip after initial lifting by means of the notch.

Description

COUPLING OF TUBULAR SECTIONS

This invention relates to a coupling arrangement for joining tubular elements or tubular parts of larger bodies end to end.

BACKGROUND

Helical piles, which are also frequently referred to as "screw piles" by technicians in this field, are driven into the ground by rotary action to serve as ground penetrating foundations and anchors. They are conventionally extended in length by means of welding or bolting on additional sections. These connection methods have draw backs, particularly when installing large diameter helical piles subjected to big loads and installed with heavy piling rigs.

The current trend is to use bigger helical piles than were generally used a few years ago, namely larger diameter, length and thickness. During the last decade some leading helical pile specialists have developed bigger machinery to install bigger piles up to 5000 kN in vertical bearing.

Welding of joints requires manufacturing skills not normally acquired by ground workers and piling operatives and in many cases requires the issuance of a test certificate to verify the quality of the welds which are subject to enormous torsional loads.

Bolting the sections together normally necessitates a group of at least three bolts spaced around the circumference in a spigot and socket arrangement. Locating the bolts through the concentric components is fiddly and time consuming, especially if there is any inaccuracy in the alignment of the piles during installation. A heavy rig may have to be rotated back and forth and inched up and down several times to align each bolt through the spigot and socket of the pile connection.

A further disadvantage associated with bolts is the not infrequent shearing of bolts or tearing of bolt holes when subjected to high shear loads during installation. Often, the bolt holes are elongated during installation and bolts are frequently over stressed resulting in weakened areas which occasionally lead to pile breakage during installation.

A further disadvantage to using bolts or site welding for the connections of pile extensions is encountered when trying to remove the piles should this be required. In this respect helical piles are frequently used for temporary structures because of their ability to be installed and later removed and relocated. Upon removal, welded connections have to be cut and the piles are often not reusable afterwards. Bolted connections can be very difficult to remove when bolt threads have corroded or been damaged during installation by contact with rocks or abrasive soils while being driven into the ground.

Others have attempted to produce alternative methods for connecting helical piles in such a way that the connections are capable of transmitting reverse rotation and tension from one section to the other, but none have so far achieved a generally practical alternative to bolting or on site welding. Consequently, these two methods are still used to the exclusion of virtually all other methods.

An object of the present invention is to provide such an alternative manner of end to end connection of helical piles which does not have the aforesaid disadvantages associated with the conventional welding and bolting methods just described and also offer a means to readily disconnect the sections when removing them from temporary installations.

SUMMARY OF INVENTION

The present invention provides a coupling whereby tubular sections are connectable end to end, the coupling comprising a first tubular section having an end portion providing a socket and a second tubular section having an end portion providing a spigot for insertion into the socket, the socket end section having opposing slots extending longitudinally from the open end of the socket, each slot including a lateral recess remote from the open end of the socket, and the spigot end section having at least one bar extending across its diameter and projecting radially outwards at each end for location axially into the opposing slots of the socket and for engagement into the respective lateral recesses upon relative rotation of the tubular sections, a collar fixedly mounted around the exterior of the socket end section and separate strips of material of a size and shape for fitting into the slots of the socket end section after engagement of the bar into the lateral recesses of these slots.

The aforesaid coupling is similar to a conventional bayonet connection as known for attachment of a cylindrical body or portion into a tubular socket in respect of small-scale items, but has been adapted by use of the diametric bar and by provision of the additional collar which overlies the slot of the socket and the strips which fill in the cut out region of the slot after the connection has been made. These features together make the coupling effective for connecting helical pile sections. They allow large torsional loads to be distributed over a larger contact area than would be possible using bolts and they maintain tension resistance over the joint, that is to say they minimise weakness of the pile assembly at the joint between sections (such weakness inevitably resulting from the provision of slots).

The location of the strips into the slots after interconnection of the tubular end portions serves to maintain the bar in the recessed part of the slots. Each of the strips is preferably slightly bowed (curved) or slightly tapered in a longitudinal direction, that is in the direction of insertion of the strip into the slot, such that the strips have to be driven into the slots by force, typically using a hammer. This ensures they are reliably and securely fitted, minimising any risk of loosening by friction with surrounding soil/ground, thus minimising risk of disconnection, during the further rotatory ground penetration procedure, or during reversal of torsion if the pile is to be lifted or removed.

In addition, in accordance with the present invention the collar has an axial length shorter than the longitudinal extent of the slots so that a gap remains below the collar to enable access to the inner end of each slot, and the strips are each provided with a formation adjacent at least one of their ends to facilitate their removal from the slots, by engagement through aforesaid gap. Therefore, if the pile is to be subsequently removed, the infill strips can be lifted out to allow disconnection of the pile sections with minimal risk of damage, and consequent possibility of later reuse.

In practical embodiments according to the invention the respective strips of material have, as aforesaid formations, which enable engagement by a tool, notches at the intended insertion end which is fitted into the inner or closed end of the slot in use.

In some embodiments according to the invention the respective strips of material have additional formations adjacent the other end thereof, which also enable engagement by a tool, to further facilitate subsequent removal of the strips. These additional formations may suitably be in the form of recesses or apertures adjacent the trailing end of the strips.

In other embodiments other suitable formations may enable purchase by an inserted tool to enable lifting out of the respective strips and disengagement of the coupling.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described further, by way of example, with reference to the accompanying drawings in which: Figure 1 is a perspective exploded view of respective end portions of two tubular pile sections which are to be connected together end-to-end by a preferred practical embodiment of the coupling of the present invention; and Figure 2 is a corresponding view of the end portions of the tubular piles shown in figure 1 after these have been connected together.

DETAILED DESCRIPTION

As shown, two generally vertically oriented pile sections 10, 20 are to be connected by a coupling arrangement in accordance with the invention. An upper end portion of the lower pile section 20, which will typically already be partially installed into the ground, provides a socket 22 into which a spigot 12 at the lower end of the upper pile section 10 is to be inserted. The socket 22 is provided as a cylinder of larger diameter than the sections 10, 20, which is mounted, and typically secured by welding, to the upper end of the lower pile section 20.

The socket 22 is formed with opposing slots 24 extending longitudinally from the open end of the socket 22, each slot 24 having, at its inner closed end (as shown the lower end) a lateral recess 26. Each recess 26 is generally rectangular in shape, providing an undercut shoulder 27, which extends in circumferential direction and a lateral edge 28, which extends longitudinally of the pile section 20 and socket 22. As illustrated, the respective lateral recesses 26 of each slot are in the same clockwise direction around the socket 22.

The spigot 12 is formed with opposing notches 14 in its lower face 11 and a box section bar 30 is secured diametrically across the outer, lower end of the spigot 12, by fitting into these notches 14 and again typically being welded in place. The outer surface of the bar 30 is preferably generally flush with the lower face 11 of the spigot 12. The respective ends of the bar 30 extend radially beyond the exterior of the spigot 12 in order to locate into the respective slots 24 in the socket 22 as the spigot 12 is lowered into the socket 22.

A collar 40 is permanently welded (or otherwise permanently fixed) to the exterior of the socket 22. Separate strips 42 are provided for driving into the slots 24 after the spigot 12 has been lowered into the socket 22 and turned to engage ends of the drive bar 30 into the respective recesses 26.

As is evident from the drawings, the pile sections 10, 20 are connected by lowering the upper pile section 10 so that the spigot 12 enters the socket 22 with the projecting ends of the bar 30 locating into the slots 24. The upper pile section 10 is then turned clockwise, as indicated by the arrow at the top of figure 1, 50 that the projecting ends of the bar 30 engage into the respective recesses 26, each bar end engaging fully behind the respective shoulder 27 and bearing against the lateral edge 28, as shown in figure 2.

The bar 30 may be termed a drive bar since it transmits force between the upper and lower pile sections 10, 20 during subsequent rotation of the coupled pile sections. It is important that the ends of the bar 30 project sufficiently beyond the spigot 12 to engage into the slots 24, for locking into the recesses 26 and subsequent force transmission, but not so far as to jam against the external collar 40 that is attached externally of the socket 22.

The collar 40 is fixed over the socket 22 at such a position as to leave open the closed (lower) end of the slots 24 and the recesses 26 so that during coupling it is possible for operatives to check visually that the bar 30 has correctly engaged into the recesses 26. Equally important, this opening at the bottom allows for insertion of a tool for lifting out the strips 42 if the pile sections 10, 20 are to be subsequently disconnected. The strips 42 are formed with notches 43 in their lower ends in order to facilitate lifting out by insertion of a tool through said opening.

Although not apparent in the drawings, each of the strips 42 is initially preferably slightly bowed (curved) or slightly tapered in a longitudinal direction, that is in the direction of insertion of the strip 42 into the slot 24. Accordingly, once the bar 30 is correctly in place, engaged into the lateral recesses 26, the strips 42 are driven into the slots 24 by force, typically using a hammer, and preferably until they are below or at the level of the upper edge of the collar 40. This ensures that the strips 42 are reliably and securely fitted, minimising any risk of loosening by friction with surrounding soil/ground, thus minimising risk of disconnection of the coupling, during the further rotatory ground penetration procedure, or during reversal of torsion if the pile is to be lifted or removed.

The strips 42 are also formed with apertures 44 near their upper ends. If the strips 42 are of appropriate length and have been driven down to a level below the upper edge of the collar 40, as just described, these apertures 44 are not accessible once the coupling is formed. However, in circumstances where the pile assembly is subsequently to be removed and it is desired to disconnect the pile sections 10, 20, the strips 42 are first of all slightly lifted by engagement of a tool, by way of the opening below the collar, with the notches 43, as described above. Once the strips 42 are slightly lifted in this way, these apertures 44 become accessible above the level of the upper edge of the collar 40 and may then additionally be used to enable lifting out of the strips 42 by insertion of a tool therein. Of course, if the strips 42 already project above the upper edge of the collar 40 after having been driven into the slots 24, i.e. less than the preferred optimum position, the apertures 44 will already be accessible for engagement to facilitate lifting of the strips 42.

After lifting out the strips 42, the pile sections 10, 20 can be disconnected by anti clockwise rotation of the upper pile section 10 and lifting of same to remove the spigot 12 from the socket 22.

It is to be understood that references to clockwise, anticlockwise, upper and lower refer specifically to the orientation illustrated in the accompanying drawings and pile sections to which the invention is applied may instead be installed upwardly or horizontally, for example in mining applications, or indeed in any orientation.

The foregoing is illustrative and not limitative of the scope of the invention. In other words, the invention is not restricted to the details of the foregoing embodiment and variations are possible within the scope of the appended claims. In particular, no limitation is intended with respect to the number of bars or the configuration of the or each bar. In other embodiments a plurality of bars may be provided in different orientations. Also, the bar or bars may be mounted proud of the spigot end face instead of flush or below the level thereof as described in respect of the first illustrated embodiment. Further, the formations at or near respective ends of the strip, to facilitate engagement by tool for lifting out, may be different to notches and/or apertures, such as recesses, slits, depressions or the like.

The invention of course covers the coupling arrangement, both when the parts are separated and when the parts are connected.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other components. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Claims

CLAIMS1. A coupling whereby tubular sections are connectable end to end, the coupling comprising a first tubular section having an end portion providing a socket and a second tubular section having an end portion providing a spigot for insertion into the socket, the socket end section having opposing slots extending longitudinally from the open end of the socket, each slot including a lateral recess remote from the open end of the socket, and the spigot end section having at least one bar extending across its diameter and projecting radially outwards at each end for location axially into the opposing slots of the socket and for engagement into the respective lateral recesses upon relative rotation of the tubular sections, a collar fixedly mounted around the exterior of the socket end section and separate strips of material of a size and shape for fitting into the slots of the socket end section after engagement of the bar into the lateral recesses of these slots, characterised in that the collar has an axial length shorter than the longitudinal extent of the slots so that a gap remains below the collar to enable access to the slots at their inner end, and the strips are each provided with a formation adjacent at least one of their ends to facilitate their removal from the slots.
2. A coupling as claimed in claim 1 wherein each lateral recess provides both an undercut shoulder and a recess lateral edge.
3. A coupling as claimed in claim 1 or claim 2 wherein the strips are each curved or tapered in a direction longitudinally of the respective slots prior to insertion into the slots.
4. A coupling comprising a first tubular section having an end portion providing a socket and a second tubular section having an end portion providing a spigot which is inserted into the socket, the socket end section having opposing slots extending longitudinally from the open end of the socket, each slot including a lateral recess remote from the open end of the socket, and the spigot end section having at least one bar extending across its diameter and projecting radially outwards at each end, the bar end margins being located into the opposing slots of the socket and being engaged into the respective lateral recesses, a collar fixedly mounted around the exterior of the socket end section and respective strips of material fitted into the slots of the socket end section characterised in that the collar has an axial length shorter than the longitudinal extent of the slots so that a gap remains below the collar to enable access to each of the slots at its inner end, and the strips are each provided with a formation adjacent the inner end thereof, which formation is accessible via the gap to facilitate the removal of the strips from the slots.
5. A coupling as claimed in claim 4 wherein each lateral recess provides both an undercut shoulder and a recess lateral edge, and the bar at each end engages behind the respective undercut shoulder and bears against the respective recess lateral edge.
6. A coupling as claimed in claim 2 or claim 4 wherein the undercut shoulder extends annularly of the socket portion and the recess lateral edge extends longitudinally of the socket portion.
7. A coupling as claimed in any preceding claim wherein the formation adjacent one end of each strip is in the form of a notch in the material of each strip.
8. A coupling as claimed in any preceding claim wherein the respective strips of material are provided with an additional engagement formation in the form of a recess or aperture adjacent the other end thereof.
9. A coupling as claimed in any preceding claim wherein the bar is countersunk into notches in the end of the spigot end portion so as to have its outer surface flush with or below an end face of the spigot portion.
10. A coupling as claimed in any preceding claim wherein the tubular sections are ground penetrating metal foundation piles or anchors.
11. A coupling whereby tubular sections are connectable or connected end to end substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.