GB2047369A - Releasable coupling - Google Patents

Abstract

A high strength releasable coupling particularly adapted for quick and simple interconnection of piling sections has mating cylindrical male and female members (18, 20) releasably interlocked by multiple locking pins (22) passing tangentially through the members. The pins (22) are received within spaced sets (42a,42b,42c) of complemental bores (44) in the female member (20) and extend partially through a corresponding annular groove (26a,26b,26c) formed in the male member (18) whereby the members (18, 20) may be locked together in axial alignment without requiring rotation about their axes. The arrangement of the bores (44) in each set (42a,42b,42c) is such that the axes of the pins (22) circumscribe the male member (18) when the members (18, 20) are interlocked thereby evenly distributing axial loads on the coupling while also providing superior endurance to bending loads. In preferred forms each set (42a,42b,42c) of bores (44) is angularly offset about the axes of the members (18, 20) relative to the other bore sets for improved loading. <IMAGE>

Description

SPECIFICATION Releasable coupling This invention relates to releasable couplings and is particularly concerned with a high strength releasable coupling for securely connecting piling sections in end-to-end alignment.

It has long been the practice in the setting of large pilings to initially fabricate the piling in a number of elongate sections which are sequentially assembled in end-to-end alignment at the construction site as the piling is driven into the ground. This well known and widely practiced technique permits extremely long pilings to be driven into the ground without the need for correspondingly large driving equipment.

A problem associated with the aforementioned pile driving technique is that of providing a coupling which is sufficiently strong to securely interconnect the piling sections and withstand loads which may be transmitted to the joint formed therebetween, yet at the same time having assembly characteristics which do not place unacceptable burdens on the driving operations. For example, one type of coupling for use in this field is disclosed in United States Letters Patent No. 3,974,875.

While the coupling there disclosed is certainly adequate to withstand any load which might reasonably be expected to be transmitted to the joint between the sections, it is unacceptable from the standpoint of difficulty of assembly. In this connection, the use of the coupling requires that the sections first be brought into end-to-end alignment, then oriented angularly to permit interfit of the thread segments, shifted axially, and subsequently reoriented about their longitudinal axes to bring the thread segments into locking engagement. Such complicated manipulation of the piling sections to effect interlocking thereof is extremely undesirable primarily because of the massive nature of such piling sections. Typically these piling sections must be positioned using heavy construction equipment such that excessive manoeuvering of the sections may become extremely time consuming.

Another approach to the problem of interconnecting piling sections is shown in United States Patent No. 3,422,630. There, mating male and female members are locked together by deformable retainer pins which are complementally received within aligned annular grooves formed in the respective members.

This approach eliminates much of the cumbersome manipulation in assembly of the piling sections, requiring only that the sections be brought into end-to-end alignment and shifted axially toward one another. However, since the locking pins must be sufficiently deformable to follow the curvature of the complemental grooves, the strength of the joint obtained in the coupling is somewhat limited. This is of particular concern in instances where the coupling is placed under axial tension as when the piling is withdrawn for example. Moreover, in larger couplings, considerable force would be required to drive the pins into position and similarly to remove them, thereby detracting from the releasable feature of the coupling.

Yet another coupling suited for interconnecting piling sections is shown in United States Patent No. 3,503,636, wherein com- plementally tapered male and female sections captively receive a retaining ring therebetween to effect interlocking. While this coupling has some advantages, it certainly is not readily releasable as is often desired in pile driving applications.

Other related devices for coupling pipe sections are disclosed in United States Letters Patents Nos. 1,298,878 and 3,154,327, as well as in British Patent No. 1,230,857.

These patents show various quick release couplings for pipe sections though such couplings would not be well suited for pile driving applications due to their limited strength characteristics.

The object of the present invention is to provide a high strength coupling which may be quickly and easily engaged and disengaged for facilitating the interconnection of piling sections.

The present invention provides a releasable coupling for interconnecting elongate piling sections, said coupling comprising: a generally cylindrical male member adapted for securement to one end of a first of said sections in coaxial alignment therewith, said member having an annular concentric groove formed in its outer periphery, a female member having a central cylindrical cavity and adapted for securement to an end of a second of said sections with said central cylindrical cavity in coaxial alignment with said second piling section for complementally receiving said male member, stop means limiting the interengagement of said members to thereby define a maximum engagement position therefor, said female member being provided with a coplanar set of at least three transverse bores each having its axis extending tangentially of said cavity, said set of bores being arranged such that said axes circumscribe said cavity, the plane of said set being coincident with said groove when said members are in said maximum engagement position, and an elongate locking pin for each bore, said pins being adapted to be inserted within respective said bores when said members are in said maximum engagement position, each pin extending through a portion of said groove when received within its respective bore such that said members are securely interlocked.

In preferred forms, the pins are somewhat shorter than the length of their corresponding bores such that the ends of the bores may be blocked to capture the pins therewith in.

The provision of multiple, axially spaced sets of bores in the female member, each having a corresponding annular groove on the male member, significantly enhances the bending strength of the joint formed by the coupling as well as increasing the axial loads which may be withstood. Further enhancement of load bearing characteristics may be obtained by angularly offsetting successive bore sets about the axis of the female member.

The invention will be more particularly described with reference to the accompanying drawings, in which:~ Figure 1 is a perspective view of a releasable coupling constructed in accordance with the present invention, with portions shown in section to review details of construction; Figure 2 is an enlarged end view of the coupling with portions thereof broken away to reveal the location of the locking pins; and Figure 3 is an enlarged side elevational view of the coupling shown partially in cross section.

In Fig. 1 there is shown a releasable coupling 10 intermediate a pair of elongate piling sections 12, 14. Though not shown, it is to be understood that sections 12, 14 are to be permanently secured to appropriate members of the coupling 10 by welding, and to this end, each of the sections 12, 14 is provided with beveled ends 16.

The coupling 10 comprises a generally cylindrical male member 18 attached to the section 14, a mating female member 20 attached to the section 12, and a number of rigid locking pins 22 adapted to releasably retain the members 18, 20 in a mated position as will be described. In preferred forms, the members 18, 20 are constructed of standard carbon steel, through virtually any material compatible with the sections 12, 14 may be used.

The male member 18 #is generally tubular having a cylindrical body 24 carried in coaxial alignment with the axis of the section 14.

Three annular grooves 26a, 26b, and 26coy semicircular transverse cross-section are axially spaced along the outer cylindrical periphery of the body 24 in concentric relation thereto. A circular shoulder 28 is presented on the piling-engaging end of the member 18 while an inwardly beveled face 30 is formed in the opposite end of the member 18, each for a purpose to be explained.

As best shown in Fig. 1, the female member 20 is also generally tubular and presents a cylindrical central cavity 32 carried in coaxial alignment with the piling section 12 for com- plementally receiving the body 24 of member 18. The outermost end of the member 20 has an outwardly tapered annular face 34 adapted to butt against the shoulder 28 to limit the maximum interengagement of the members 18, 20. Similarly, the piling-engaging end of the member 20 has a shoulder 36 configured to mate with the annular face 30 on the member 18 for also limiting the degree of engagement between the members. It is noted that the faces 34, 30 and their abutting shoulders 28, 36 respectively are beveled in such a manner that axially directed compression loads tend to clamp the members together more tightly rather than spreading them apart.The member 20 has a pair of spaced O-ring grooves 38 circumscribing the cavity 32 for receiving respective resilient 0rings 40 when the members 18, 20 are mated as shown, for example, in Fig. 3.

As best illustrated when viewing Figs. 2 and 3 conjointly, the female member 20 is provided with three coplanar sets 42a, 42b and 42c of rectilinear bores 44 extending through the member 20 tangentially of the cavity 32. Each bore set 42 comprises four bores 44 symmetrically arranged around the axis of the member 20 such that the axes of the bores 44 in each set 42 fully circumscribe the cavity 32. When considering Fig. 2 in more detail, it will be appreciated that the arrangement of the bores 44 in each set forms a square, though it is contemplated that a circumscribing triangle might be presented if only three bores were used in a set. Moreover, each of the bore sets are angularly offset about the axis of member 20 relative to the other sets. In the embodiment shown for example, the sets 42a, 42b and 42c are angularly shifted 30 relative to one another.

Each bore set 42a, 42b and 42c, is adapted to align with a corresponding annular groove 26a, 26b and 26 c respectively when the member 18, 20 are fully mated as shown in Fig. 3. In this regard, it is noted that the bores 44, by virtue of their position in the member 20, each partially open into the cavity 32 (this is best illustrated in Fig. 1). When the members 18, 20 are mated, the grooves 26 provide the missing portion of the bores 44 as shown in Fig. 3.

The pins 22 are adapted to be inserted into the bores 44 and through respective portions of grooves 26 when the members 18, 20 are fully mated. When properly seated, the pins 22 preclude relative axial movement between the members 18, 20 and thus serve to lock the coupling 10 in its connected position. The opposed ends of each bore 44 are threaded for receiving retaining set screws 46 to preclude inadvertent removal of the pins 22 from their nested locking position within the bores 44. The pins 22 are, of course, shorter than the length of the bores 44 but at the same time are long enough to fully span the inter section of the bores 44 and the cavity 32.

The use and advantages of the releasable coupling of the present invention are clearly explained hereinabove. The coupling 10 is especially suited for forming a releasable, high strength connection between piling sections without requiring cumbersome manipulation during assembly thereof.

In use, it is contemplated that each piling section be provided with a male and female member at opposite ends thereof to facilitate successive driving of the sections. As explained, the members 18, 20 are configured to be readily welded to the ends of piling sections 12, 14, thereby permitting full utilization of the advantages offered by the coupling 10.

Of particular note is the fact that the sections 12, 14 may be quickly interconnected by the coupling 10 without requiring axial rotation of either section. Further in this regard, the construction of the members 18, 20 is such that the two are aligned for insertion of the pins 22 when face 34 abuts shoulder 28 to define the fully mated position for the members.

The unique design of the coupling 10 permits expeditious assembly as described above while at the same time providing a joint of superior strength. In this connection, tests on actual models indicate that the coupling may develop strength far in excess of the strength of the sections to be joined. Specifically, in a "pull out" test, a piling coupling according to the invention designed for API 5LX-46 pipe failed under a load 1.65 times greater than the calculated failure load of the pipe. This unexpected result is believed to be the result of the uniform load distribution through the coupling 10 created by the unique arrangement of the bores 44 and the offset relation of the bore sets 42.

Claims (14)

1. A releasable coupling for interconnecting elongate piling sections, said coupling comprising: a generally cylindrical male member adapted for securement to one end of a first of said sections in coaxial alignment therewith, said member having an annular concentric groove formed in its outer periphery.

a female member having a central cylindrical cavity and adapted for securement to an end of a second of said sections with said central cylindrical cavity in coaxial alignment with said second piling section for complementally receiving said male member, stop means limiting the interengagement of said members to thereby define a maximum engagement position therefore, said female member being provided with a coplanar set of at least three transverse bores each having its axis extending tangentially of said cavity, said set of bores being arranged such that said axes circumscribe said cavity, the plane of said set being coincident with said groove when said members are in said maximum engagement position, and an elongate locking pin for each bore, said pins being adapted to be inserted within respective said bores when said members are in said maximum engagement position, each pin extending through a portion of said groove when received within its respective bore such that said members are securely interlocked.

2. A coupling according to claim 1, there being multiple sets of said bores, said sets being disposed in parallel, axially offset planes, there being a corresponding number of annular grooves on said male member disposed for alignment with respective said sets when said members are in said maximum engagement position, each of said bores having a removable said locking pin for interlocking said members.

3. A coupling according to claim 2, the bores in each set being equal in size and symmetrically arranged around the axis of said cavity.

4. A coupling according to claim 2 or 3, there being the same number of bores in each of said sets.

5. A coupling according to claim 2, 3 or 4, each set of bores being angularly offset about the axis of said cavity relative to the other sets of bores.

6. A coupling according to any one of claims 2 to 5, the plane of each of said sets being axially equispaced from the planes of adjacent sets.

7. A coupling according to claim 5, there being three of said bore sets, the latter being arranged in offset angular increments of 30 about the axis of said cavity.

8. A coupling according to any one of the preceding claims, and means for sealing the ends of said bores when said pins are disposed therewithin.

9. A coupling according to any one of the preceding claims, each of said bores being configured and sized to complementally receive its respective locking pin.

10. A coupling according to any one of the preceding claims, said stop means comprising an annular shoulder on one of said members and a complemental shoulder-abutting face on the other of said members.

11. A coupling according to any one of the preceding claims, said members being tubular, there being seal means between the members.

12. A coupling according to any one of the preceding claims, said bores having a circular transverse cross-section, said groove being semicircular in transverse cross section, and said pins being cylindrical.

13. A releasable coupling for interconnect ing elongate piling sections, substantially as herein described with reference to the accompanying drawings.

14. An elongate piling section having secured to opposite ends thereof in coaxial alignment therewith male and female members of a coupling according to any one of the preceding claims.