GB2404943A

GB2404943A - Screw pile with reducing diameter flight

Info

Publication number: GB2404943A
Application number: GB0318767A
Authority: GB
Inventors: Paul Anthony Camilleri
Original assignee: Evolution International No 2 Pty Ltd
Current assignee: Evolution International No 2 Pty Ltd
Priority date: 2002-03-18
Filing date: 2003-08-09
Publication date: 2005-02-16
Anticipated expiration: 2023-08-09
Also published as: DE10337113A1; GB0318767D0; US20040076479A1; GB2404943B; AUPS115402A0

Abstract

A screw pile stem (10) includes a shank (11) having an inwardly tapered portion (12) at one end. A helical screw (18) is present on the shank (11) and on the inwardly tapered portion (12). The screw (18) is of constant pitch and the major diameter of the part of the screw on the tapered portion (12) decreases towards the small end of the tapered portion (12). There is also claimed a tapering screw pile end piece with a flight that reduces in diameter, the end piece being adapted for connection to a pile stem; a screw pile having a steel stem and a cast end piece secured thereto and a screw pile end piece formed from cast steel.

Description

r i 2404943

SCREW PILES

This invention relates to screw piles and components for screw piles.

The invention has particular application to screw piles for the construction of dwelling houses and small commercial buildings but it may be useful for larger buildings and other structures.

Screw piles for houses typically are made up of a base stem (or a screw pile stem) and a plurality of extension stems.

Typically, the base stem has a tubular steel shank with one flight (that is, one turn) of a helical screw welded thereto adjacent its lower end for screwing the pile into the ground upon rotation by suitable screw piling apparatus and a coupling portion at its upper end which is adapted to engage with a complementary coupling portion of an extension stem. Typically, a plurality of extension stems can be added, one to another, to effectively form a pile of any desired length which can be screwed into the ground to any desired depth with each extension stem having a coupling portion similar to that of the base stem.

various types of complementary coupling portions which together form a coupling are known.

The single turn helical screw is typically formed from steel plate and the minor diameter of the screw is substantially the same as the outside diameter of the steel shank to which it is welded while the major diameter is considerably greater and could be three or four times the minor diameter and possibly even more.

The helical screw of such known screw piles is the main portion which transfers the building load applied to the upper end of the pile to the founding ground. One disadvantage with such screw piles is that in some cases the load which can be applied to the tubular steel shank cannot be transferred to the ground by the large diameter steel plate screw. For example, the steel shank may have a structural capacity of say 1000 kN while It the steel plate screw may suffer unacceptable distortion under a shank load of only 500 kN or shear from the shank or deform the shank at the welded joint between the screw and the shank.

Another disadvantage with known screw piles is that in many cases the couplings by which adjacent stems are connected to each other are generally not capable of both withstanding the torsional forces required to screw the pile to the desired founding depth and transmitting the building load applied to the upper end of the top pile stem to the next pile stem and so on without an undesirable amount of failure.

Another disadvantage with known screw piles is that damaged pile stems cannot be easily removed and replaced.

One object of the present invention is to provide a screw pile which overcomes or at least ameliorates one or more of the IS aforementioned problems.

With the foregoing in view the invention resides broadly in one aspect in a screw pile stem including; a shank having an inwardly tapered portion at one end; a helical screw on said shank, said helical screw being of constant pitch and at least a part of said helical screw being on said tapered portion, the major diameter of the part of said helical screw on said tapered portion decreasing towards the small end of said tapered portion. Preferably, the part of said helical screw on said tapered portion is at least one full turn.

Preferably, a generally cylindrical portion is provided coaxial with and/or adjacent said tapered portion and part of said helical screw is on said generally cylindrical portion. In such form of the invention while it is preferred that the part of said helical screw on said cylindrical portion is about one full turn of constant major diameter, it is also preferred that the major diameter of the part of the helical screw on the tapered portion generally decreases at a constant rate. It is also preferred that such part of the helical screw generally b decreases at the same rate as the diameter of the tapered portion, that is to say the major and minor diameters decrease at the same rate such that where the diameter of the tapered portion is half that of the cylindrical portion, the major diameter of the screw is half that of the screw on the cylindrical portion.

Preferably, said shank includes a body portion and an end portion, and said end portion is connected to maid body portion at one end. In such form it is preferred that the end portion is lo cast steel or other suitable material.

In another aspect the invention resides broadly in a screw pile end piece adapted to be connected to a pile stem, the screw pile end piece having an inwardly tapered portion with at least a part of a helical screw thereon, said helical screw on said tapered portion being of constant pitch and the mayor diameter of said helical screw decreasing towards the small end of said tapered portion. Preferably, the end piece includes a generally cylindrical portion coaxial with and/or adjacent said tapered portion and part of said helical screw is on said generally cylindrical portion. It will be appreciated that such a screw pile end piece may be connected to a pile stem to form a screw pile stem as previously described. Advantageously, in a preferred form, all of said helical screw is on said end piece which allows the pile stem which forms the shank to be a simple tubular stem with connecting means at one end for connecting to the end piece.

Such a stem can be a pile extension stem adapted to couple to other like extension stems thus limiting the type of stock to be held. Further, such arrangement allows the stems to be stored and transported as a bundle of tubes with the end pieces as separate components, thus allowing easier and closer stacking making transport easier and more efficient.

Preferably, said end piece and the pile stem to which it is to be connected include complementary coupling means which allow the pile stem to be detachably coupled to the end piece.

Advantageously, such arrangement has the further advantage that a damaged pile stem can be detached from an end piece and withdrawn from a pile hole during installation while leaving the end piece in situ and then a new pile stem may be fitted to the end piece down the hole.

In another aspect the invention resides broadly in the combination of an end piece as previously described and a pile stem adapted to be detachably coupled to said end piece.

Preferably, said complementary coupling means are adapted to transmit forward and reverse rotational drive from said pile stem to said end portion.

In a preferred form, said Cylindrical portion forms a socket on said end piece and said pile stem includes a spigot which is adapted to be engaged in said socket, one of said socket and said spigot having a side wall with a protuberance thereon and the other of said socket and said spigot having a side wall with a complementary recess therein adapted to receive said protuberance, said protuberance being adapted to engage in said recess so as to transmit forward and reverse drive to said end piece. However, in another form the spigot and socket are reversed so that the Cylindrical portion forms the spigot on said end piece and said pile stem includes the socket.

In one form, said socket has a side wall with a plurality of protuberances thereon adapted to engage in a complementary recess in the spigot. In such form said spigot terminates at a free end and said recess opens to said free end, said opening being adapted to receive therethrough the protuberance on the side wall of the socket as the spigot and socket move into axial engagement. However, in another form, said recess is formed in a wall of said socket which terminates at a free end and said recess opens to said free end, said opening being adapted to receive therethrough the protuberance which is provided on a side of the spigot.

Preferably, said recess includes two circumferentially spaced apart securing portions adapted to selectively receive therein a protuberance such that relative axial movement between the pile stem and said end piece is prevented. In such form it is preferred that said opening is between said circumferentially spaced apart securing portions. It is also preferred that said recess has a plurality of spaced apart axially aligned securing portions. In the case where the recess is provided in the side wall of the socket it is preferred that said recess extends only partway through the side wall of said socket. In a preferred form, the recess is formed by pressing the wall of the socket inwards thus maintaining the full wall thickness of the socket through the full extent of its circumference.

Preferably, said plurality of spaced apart protuberances are axially aligned and adapted to engage in complementary securing portions of the recess.

Preferably, said socket has a shoulder therein adapted to be engaged by the free end of the spigot so that bearing loads can be transferred from the pile stem to the end piece by the shoulder. In one form where the socket is provided on the end piece, the shoulder is in the end piece while in another form in which the socket is provided on the pile stem, the shoulder is in the pile stem. Preferably, the coupling means are arranged to urge the free end of the spigot into engagement with the shoulder upon relative movement of the pile stem and the end piece into the coupled position.

In another aspect the invention resides broadly in a pile stem for screw piles, the pile stem having a body portion and two opposite end portions, one end portion being adapted to engage with a screw pile end piece as previously described and the other end being adapted to engage with another like pile stem.

In another aspect the invention resides broadly in the combination of an end piece and a pile stem as previously described.

The terms "upper", Plowers, "tops, "bottom', 'sides, Forwards, "reverses and the like are used herein to describe screw pile stems and components therefor in their normal in-use position and are not intended to limit the use of the invention to any particular orientation. Further the terms "forwards and "reverse. are used to describe the direction of rotation of the screw piles into and out of the ground respectively.

Several embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: Fig. 1 is an elevation of a screw pile stem and extension stem according to the invention in-line for assembly; Fig. 2 is an end view of the screw pile stem shown in Fig. 1; Fig. 3 is an end view of the extension stem shown in Fig. 1; Fig. 4 is a sectional elevation of the upper end portion of the screw pile stem shown in Fig. 1 along line 4-4 in cut away; Fig. 5 is a sectional elevation of the lower end portion of the extension stem shown in Fig. 1 along line 5-5 in cut away; Fig. 6 is a pictorial representation of a screw pile end piece according to the invention; Fig. 7 is an elevation of the screw pile end piece of Fig. 6 from one side; Fig. 8 is an elevation of the screw pile end piece of Fig. 6 at 90 degrees to the elevation of Fig. 7; Fig. 9 is a top end view of the screw pile end piece of Fig. 6; Fig. 10 is a sectional elevation of the screw pile end piece of Fig. 6 along line 10-10; Fig. 11 is a pictorial representation of an extension stem according to the invention; Fig. 12 is an upper end view of the extension stem of Fig. 11; Fig. 13 is a lower end view of the extension stem of Fig. 11; Fig. 14a is an elevation of the upper end portion of the extension stem of Fig. 11; Fig. 14b is a sectional elevation of the upper end portion of the extension stem of Fig. 11 along line 14-14; Fig. 15a is an elevation of the lower end portion of the extension stem of Fig. 11; Fig. 15b is a sectional elevation of the lower end portion of the extension stem of Fig. 11 along line 15-15; Fig. 16 is a pictorial representation of another screw pile end piece according to the invention; Fig. 17 is an elevation of the screw pile end piece of Fig. 16 from one side; Fig. 18 is an elevation of the screw pile end piece of Fig. 16 at 90 degrees to the elevation of Fig. 17; Fig. 19 is a top end view of the screw pile end piece of Fig. 16; Fig. 20 is a sectional elevation of the screw pile end piece of Fig. 16 along line 20-20.

The screw pile stem 10 shown in Fig. 1 has a shank 11 with an inwardly tapered portion 12 at its lower end and a socket 13 at its upper end and a hollow cylindrical body portion 15 there between, the socket being adapted to receive therein the spigot 14 at the lower end of the extension stem 16 shown in-line for assembly, as will be described more fully later. A helical screw 18 formed of cast steel is welded to the shank with part of the helical screw being on the tapered portion and part on the cylindrical portion immediately adjacent the tapered portion.

Although the screw pile stem of this embodiment is circular in cross section, it is to be understood that the term "cylindrical used herein is to be understood as including elongate bodies of cross sectional shapes other than circular and could for example be octagonal.

The part of the helical screw on the tapered portion is approximately two and one quarter turns and only one quarter turn is on the cylindrical portion of the shank. However, in other embodiments, at least one full turn is on the cylindrical portion of the shank.

Socket 13 is defined by the upper end portion of the socket wall 22 which has been expanded to a suitable diameter to receive therein the spigot 14. Similarly the spigot 14 has been formed by expanding the lower end portion 24 of the hollow extension stem wall 17 to a suitable diameter which is an easy sliding fit in the socket 13, the spigot and socket being sized to transmit the desired torsional loads for installation and the desired bearing loads once installed.

Two opposite rows of three recesses 26 are formed in the socket wall 22 but not through the wall, each recess having an axially extending recess portion 27 which opens to the upper end of the socket through opening 28 and three axially spaced apart circumferentially extending recess portions 29, 30 and 31 which are bisected by the axial portion 27 to form a securing portions at each end, 29a and 2sb, 30a and sob, and 31a and 31b, respectively.

Three sets of complementary axially aligned protuberances 36, 37 and 38 are provided on the spigot and the recess is adapted to receive therein the protuberances through the opening 28, each protuberance being adapted to locate in a respective one of the securing portions of the recess upon relative partial rotation of the spigot and the socket to prevent relative axial movement there between. Thus, it can be seen that the extension stem can be fitted to the screw pile stem by aligning the protuberances with the opening 28 and sliding the spigot into the socket in an axial movement until the protuberances align with the securing portions of the recess whereupon the spigot can be partially rotated to locate the protuberances in the respective securing portions. It will be appreciated that in other embodiments the spigot and socket could be reversed so that the spigot is on the screw pile stem. Similarly, the recess could be lo provided on the spigot and the protuberances on the socket if desired. It will also be appreciated that in other embodiments there could be more or less circumferential recess portions, for example, four, and in that case an equal number protuberances would be provided. Further, while this embodiment has the axial recess portion bisecting the circumferential recess portions, in other embodiments, the axial recess portion dissects it offset from the centre. : The screw pile end piece 50 illustrated in Fig. 6 has a shank 51 with an inwardly tapered lower portion 52a which depends from a cylindrical upper portion s2(b). The upper portion defines an upwardly open socket 63 adapted to receive therein the spigot 54 at the lower end of the pile stem 56 shown in Fig. 11. A helical screw 58 is integrally formed with the shank and about one full turn of the screw is on the cylindrical portion while about one and a half turns is on the tapered portion, the helical screw terminating a short distance from the tip 59 of the tapered portion. The major diameter of the helical screw on the cylindrical portion remains constant for the full turn. Bowever, the major diameter of the helical screw on the tapered portion decreases constantly towards the tip at the same rate as the diameter of the tapered portion decreases. A notch 60 is formed in the tapered portion adjacent the tip to provide a cutting edge 61 for initiating a drill hole for the pile.

As can be more clearly seen in Fig. 10, two opposed pairs of axially aligned protuberances or lugs 62 and 63 extend radially into the socket from the cylindrical wall and are adapted to engage in a recess 66 provided in the wall of the spigot 54 of the pile stem 56 as will be described more fully later. It will be appreciated that the lugs cooperate with the recess in a similar manner to the protuberances and recesses described in relation to the screw pile stem of Fig. 1. Each recess 66 is pressed into the spigot wall thus maintaining the full wall thickness and the integrity of the spigot whereby it can transfer the torsional loads required to install the screw pile. Each recess 66 has an axially extending recess portion 67 which opens to the lower end of the spigot through opening 68 and two axially spaced apart circumferentially extending recess portions 69 and 70 which are bisected by the axial portion 67 to form opposed securing portions at their ends 69 (a) and 69 (b), and 70(a) and 70 (b) respectively.

It can be seen that at one end the extension stem 56 has the expanded spigot 54 and at the other end it has a complementary expanded socket portion 80 with the stem between the spigot portion and the socket portion being an unexpanded cylindrical tube 57. It can also be seen that the extension stem can be fitted to the screw pile end piece 50 in much the same manner as the extension stem 16 is fitted to the screw pile stem of Fig. 1, that is, by aligning the lugs or protuberances with the opening 68 and sliding the spigot into the socket in an axial movement until the protuberances align circumferentially with the circumferential portions of the recess whereupon the spigot can be partially rotated to locate the protuberances in the respective securing portions. It will be appreciated that for forward drive, the protuberances locate in securing portions 69(b) and 70 (b) and upon reverse drive being commenced, the pile stem 56 rotates relative to the screw pile end piece 50 until the protuberances locate at the other end of the circumferential recess portions in securing portions 69(a) and 70(a) respectively and engage against the wall at the edge of the recess securing portions to cause reverse drive to be applied to the screw pile end piece 50.

As Can be more clearly seen in Fig. 10, a shoulder 75 is provided at the inner end of the socket 53, the shoulder being adapted to abut the free end face 72 of the pile stem so that downloads Can be transmitted directly from the pile stem to the screw pile end piece via the shoulder. In order to ensure that the free end positively engages against the shoulder, the lowermost edges 69(c) and 70 (e) of the securing portions of the recess 66 taper away from the free end face 72 whereby engagement of the protuberances 62 and 62 thereagainst urges the spigot 54 further into the socket 53.

The socket portion 80 of the pile stem 56 is similar to the Cylindrical portion of the screw pile end piece 50 to the extent that it has opposed pairs of axially aligned lugs 82 and 83 therein which correspond with lugs 62 and 63 in shape and position and a shoulder 85 which corresponds to shoulder 75 in the screw pile end piece. It will be understood that the socket portion is adapted to receive therein the spigot portion 54 of a like pile stem so that any number of pile stems can be added one after another to create a pile of any desired length adapted to be installed to any desired depth.

It is believed that a screw pile having a screw pile end piece of the type illustrated in Fig. 6 has the Capacity to Carry the desired structural load without unacceptable distortion while the arrangement of socket and spigot for coupling pile stems to each other and to the screw pile end piece has the capacity to transmit the torsional forces necessary to screw a pile with such an end piece to the desired depth. Additionally, the coupling arrangement allows removal of damaged stems from the screw pile end piece or from other stems by simply partially rotating the screw pile stems in reverse until the lugs align with the axial portion 67 of the recess 66 and then lifting the pile stem from the screw pile end piece or from the adjacent pile stem as the case requires.

The screw pile end piece 150 illustrated in Fig. 16 is intended to be permanently secured to a hollow pile stem, for example, by welding or pinning and includes a shank 151 having a tapered portion 152(a) at its lower end and a cylindrical portion 152(b) at its upper end, the Cylindrical portion being adapted to engage in the hollow of the pile stem to which it is to be attached. A helical screw 158 is integrally formed with the shank, the whole of the helical screw being on the tapered portion. The first turn of the helical screw (that is, the uppermost turn) has a constant major diameter but its minor diameter, being the outer diameter of the tapered portion of the shank, decreases constantly over the turn. The major diameter and the minor diameter of subsequent turns decrease constantly towards the tip 159 of the tapered portion. : While the foregoing description has been given by way of illustrative example of the invention, it will be understood that the invention may be embodied in many other forms and all such forms are deemed to fall within the broad scope and ambit of the invention as defined by the appended claims.

Claims

CLAhNS 1. A screw pile stem including: a shank having an inwardly tapered

portion at one end; a helical screw on said shank, said helical screw being of constant pitch and at least a part of said helical screw being on said tapered portion, the major diameter of the part of said helical screw on said tapered portion decreasing towards the small end of said tapered portion.
2. A screw pile stem according to Claim 1, wherein said shank also has a generally cylindrical portion coaxial with and/or adjacent said tapered portion and a part of said helical screw is on said generally cylindrical portion.
3. A screw pile stem according to Claim 2, wherein the part of said helical screw on said cylindrical portion is about one full turn.
4. A screw pile stem according to any one of the preceding claims, wherein the part of said helical screw on said tapered portion is at least one full turn.
5. A screw pile stem according to any one of the preceding claims wherein the major diameter of the part of the helical screw on the tapered portion generally decreases at a constant rate.
6. A screw pile stem according to any one of the preceding claims wherein the major diameter of the part of the helical screw on the tapered portion generally decreases at the same rate as the diameter of the tapered portion.
7. A screw pile stem according to any one of the preceding claims, wherein said shank includes a body portion and an end portion, and said end portion is coupled to said body portion at one end.
8. A screw pile stem according to Claim 7, wherein said tapered portion is on said end portion.
9. A screw pile stem according to Claim 7 or Claim 8, wherein said end portion includes a cylindrical portion and part of said helical screw is on said cylindrical portion.
lo. A screw pile stem according to any one of Claims 7, 8 and 9, wherein all of said helical screw is on said end portion.
11. A screw pile stem according to Claim 7, wherein said body portion and said end portion include complementary coupling means by which said end portion is detachably coupled to said body portion.
12. A screw pile stem according to Claim 11, wherein said complementary coupling means are adapted to transmit forward and reverse rotational drive from said body portion to said end portion.
13. A screw pile stem according to Claim 12, wherein said cylindrical portion forms a socket on said end portion and said body portion includes a spigot which is engaged in said socket, one of said socket and said spigot having a side wall with a protuberance thereon and the other of said socket and.said spigot having a side wall with a complementary recess therein adapted to receive said protuberance, said protuberance being adapted to engage in said recess so as to transmit forward and reverse drive to said end portion.
14. A screw pile stem according to Claim 12, wherein said cylindrical portion forms a spigot on said end portion and said body portion includes a socket and said spigot is engaged in said socket, one of said socket and said spigot having a side wall with a protuberance thereon and the other of said socket and said spigot having a side wall with a complementary recess therein adapted to receive said protuberance, said protuberance being adapted to engage in said recess so as to transmit forward and reverse drive to said end portion.
15. A screw pile stem according to Claim 13 or Claim 14, wherein one of said socket and said spigot has a side wall with a plurality of protuberances thereon and the other of said socket i and said spigot has a side wall with a complementary recess therein adapted to receive said protuberances, said protuberances being adapted to engage in said recess so as to transmit forward and reverse drive to said end portion.
16. A screw pile stem according to any one of Claims 13 to 15, wherein each of said spigot and said socket terminates at a free end and said recess opens to a respective one of said free ends and the or each protuberance is adapted to enter and exit said recess through the opening to said free end upon relative axial movement of said spigot and socket.
17. A screw pile stem according to Claim 16, wherein said recess includes two circumferentially spaced apart securing portions adapted to selectively receive therein a protuberance in which relative axial movement between said spigot and said socket is prevented.
18. A screw pile stem according to Claim 17, wherein said opening is between said circumferentially spaced apart securing portions.
19. A screw pile stem according to Claim 18, wherein said recess has a plurality of spaced apart axially aligned securing portions and one of said spigot and socket has a plurality of axially aligned protuberances and said protuberances are arranged to coincidentally locate in respective ones of said securing portions to prevent relative axial movement between said spigot and said socket.
20. A screw pile stem according to any one of Claims 13 to 19, wherein said recess or recesses are formed by pressing a portion of said side wall inwards.
21. A screw pile stem according to any one of Claims 13 to 20, wherein partial relative rotation of said spigot and socket causes the or each protuberance to locate in one of said respective securing portions.
22. A screw pile stem according to Claim 21, wherein the or each . protuberance and recess are arranged such that partial relative rotation of said spigot and socket urges said end portion and said body portion axially together.
23. A screw pile stem according to any one of Claims 13 to 22, including a plurality of complementary circumferentially spaced apart protuberances and recesses.
24. A screw pile stem according to any one of Claims 13 to 23, wherein said socket has a shoulder therein and the end of said spigot is adapted to abut said shoulder whereby downward loads applied to the upper end of said shank may be transmitted to said helical screw by said shoulder.
25. A screw pile stem according to any one of the preceding claims, wherein said shank includes extension coupling means at its other end for coupling thereto an extension stem.
26. A screw pile stem according to Claim 25, wherein said extension coupling means is adapted to engage with complementary coupling means on an extension stem corresponding to the coupling means on said one end.
27. A screw pile end piece adapted to be connected to a pile stem, the screw pile end piece having an inwardly tapered portion with at least a part of a helical screw thereon, said helical screw on said tapered portion being of constant pitch and the major diameter of said helical screw decreasing towards the small end of said tapered portion.
28. A screw pile end piece according to Claim 27, including a generally cylindrical portion coaxial with and/or adjacent said tapered portion and wherein part of said helical screw is on said generally cylindrical portion.
29. A screw pile end piece according to Claim 28, wherein the part of said helical screw on said cylindrical portion is about one full turn.
30. A screw pile end piece according to any one of Claims 27 to 29, wherein the part of said helical screw on said tapered portion is at least one full turn.
31. A screw pile end piece according to any one of Claims 27 to 30, wherein the major diameter of the part of the helical screw on the tapered portion generally decreases at a constant rate.
32. A screw pile end piece according to any one of Claims 27 to 31, wherein the major diameter of the part of the helical screw on the tapered portion generally decreases at the same rate as the diameter of the tapered portion.
33. A screw pile end piece according to any one of Claims 27 to 32, including coupling means adapted to engage with complementary coupling means on a pile stem to which the end piece is to be attached for coupling said screw pile end piece thereto, said coupling means being adapted to receive forward and reverse rotational drive from the complementary coupling means of the pile stem.
34. A screw pile end piece according to Claim 33, wherein said cylindrical portion forms a socket which is adaptedto receive therein a complementary spigot on the pile stem to which the end piece is to be coupled, said socket having a side wall with a protuberance thereon adapted to engage in a complementary recess in the pile stem, or a recess therein adapted to receive a complementary protuberance on the pile stem so as to receive forward and reverse drive therefrom.
35. A screw pile end piece according to Claim 33, wherein said cylindrical portion forms a spigot which is adapted to engage in a complementary socket on the pile stem to which the end piece is to be coupled, said spigot having a recess therein adapted to receive a complementary protuberance in the socket, or said spigot having a protuberance thereon; adapted to engage in a complementary recess in the socket of the pile stem, so as to receive forward and reverse drive therefrom.
36. A screw pile end piece according to Claim 34, wherein said socket has a side wall with a plurality of protuberances thereon adapted to engage in a complementary recess in the pile stem so as to receive forward and reverse drive therefrom.
37. A screw pile end piece according to Claim 34 or Claim 35, wherein said spigot terminates at a free end and said recess opens to said free end, said opening being adapted to receive therethrough the protuberance of the pile stem to which the end piece is to be coupled.
38. A screw pile end piece according to Claim 34 or Claim 35, wherein said socket terminates at a free end and said recess opens to said free end, said opening being adapted to receive therethrough the protuberance of the pile stem to which the end piece is to be coupled.
39. A screw pile end piece according to Claim 37 or Claim 38, wherein said recess includes two circumferentially spaced apart securing portions adapted to selectively receive therein a protuberance such that relative axial movement between the pile stem and said end piece is prevented. ;
40. A screw pile end piece according to Claim 39, wherein said opening is between said circumferentially spaced apart securing portions.
41. A screw pile end piece according to Claim 40, wherein said recess has a plurality of spaced apart axially aligned securing portions.
42. A screw pile end piece according to Claim 34, wherein said recess extends only partway through the side wall of said socket.
43. A screw pile end piece according to Claim 35, wherein said recess extends only partway through said spigot.
44. A screw pile end piece according to Claim 36, wherein said plurality of spaced apart protuberances are axially aligned and adapted to engage in complementary securing portions of a recess in the pile stem to which it is to be coupled.
45. A screw pile end piece according to Claim 34, wherein said socket has a shoulder therein adapted to be engaged by the free end of the pile stem to which it in to be attached and to receive bearing loads therefrom.
46. A screw pile end piece according to Claim 35, wherein said spigot has a shoulder thereon adapted to be engaged by the free end of the pile stem to which it is to be attached and to receive bearing loads therefrom.
47. A screw pile end piece according to Claim 34 or Claim 35, wherein said recess is formed by pressing a portion of said side wall inwards.
48. A pile stem for screw piles, the pile stem having a body portion and two opposite end portions, one end portion being adapted to engage with a screw pile end piece as defined by any one of Claims 27 to 46 and the other end being adapted to engage with another like pile stem.
49. In combination, a screw pile end piece as defined by any one of Claims 27 to 46 and a pile stem adapted to be detachably coupled to said end piece. ;
50. A screw pile stem having a steel stem and a cast end piece secured thereto.
51. A screw pile end piece formed of cast steel.
52. A screw pile stem as hereinbefore described with reference to the accompanying drawings.
53. A screw pile end piece as hereinbefore described with reference to the accompanying drawings.
54. A pile stem as hereinbefore described with reference to the accompanying drawings.