U.S. patent application number 10/683409 was filed with the patent office on 2004-04-22 for screw piles.
Invention is credited to Camilleri, Paul Anthony.
Application Number | 20040076479 10/683409 |
Document ID | / |
Family ID | 34381463 |
Filed Date | 2004-04-22 |
United States Patent
Application |
20040076479 |
Kind Code |
A1 |
Camilleri, Paul Anthony |
April 22, 2004 |
Screw piles
Abstract
A screw pile stem includes a shank having an inwardly tapered
portion at one end, and a helical screw on the shank, with the
helical screw being of constant pitch and at least a part of the
helical screw being on the tapered portion, and with a major
diameter of the part of the helical screw on the tapered portion
decreasing towards a small end of the tapered portion.
Inventors: |
Camilleri, Paul Anthony;
(Mermaid Beach, AU) |
Correspondence
Address: |
ABELMAN, FRAYNE & SCHWAB
150 EAST 42ND STREET
NEW YORK
NY
10017-5612
US
|
Family ID: |
34381463 |
Appl. No.: |
10/683409 |
Filed: |
October 9, 2003 |
Current U.S.
Class: |
405/252.1 ;
405/251; 52/169.13 |
Current CPC
Class: |
E02D 5/56 20130101; E02D
27/16 20130101 |
Class at
Publication: |
405/252.1 ;
405/251; 052/169.13 |
International
Class: |
E02D 005/08; E02D
027/42 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 2002 |
AU |
PS1154 |
Claims
What is claimed is:
1. A screw pile stem comprising: a shank having an inwardly tapered
portion at one end; and a helical screw on the shank, the helical
screw being of constant pitch and at least a part of the helical
screw being on the tapered portion, a major diameter of the part of
the helical screw on the tapered portion decreasing towards a small
end of the tapered portion.
2. The screw pile stem according to claim 1, wherein the shank has
a generally cylindrical portion coaxial with and/or adjacent to the
tapered portion and a part of the helical screw is on the generally
cylindrical portion.
3. The screw pile stem according to claim 2, wherein the part of
the helical screw on the cylindrical portion extends about one full
turn.
4. The screw pile stem according to claim 1, wherein the part of
the helical screw on the tapered portion extends at least one full
turn.
5. The screw pile stem according to claim 1, wherein the major
diameter of the part of the helical screw on the tapered portion
generally decreases at a constant rate.
6. The screw pile stem according to claim 1, 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. The screw pile stem according to claim 1, wherein the shank
includes: a body portion; and an end portion coupled to the body
portion at one end thereof.
8. The screw pile stem according to claim 7, wherein the tapered
portion is on the end portion.
9. The screw pile stem according to claim 7, wherein the end
portion includes a cylindrical portion and a part of the helical
screw is on the cylindrical portion.
10. The screw pile stem according to claim 7, wherein all of the
helical screw is on the end portion.
11. The screw pile stem according to claim 7, wherein the body
portion and the end portion include complementary coupling means by
which the end portion is detachably coupled to the body
portion.
12. The screw pile stem according to claim 11, wherein the
complementary coupling means are adapted to transmit forward and
reverse rotational drive from the body portion to the end
portion.
13. The screw pile stem according to claim 12, wherein the
cylindrical portion forms a socket on the end portion; and wherein
the body portion includes a spigot which is engaged in the socket,
one of the socket and the spigot having a side wall with a
protuberance thereon and the other of the socket and the spigot
having a side wall with a complementary recess therein adapted to
receive the protuberance, the protuberance being adapted to engage
in the recess so as to transmit forward and reverse drive to the
end portion.
14. The screw pile stem according to claim 12, wherein the
cylindrical portion forms a spigot on the end portion, the body
portion includes a socket, and the spigot is engaged in the socket,
one of the socket and the spigot having a side wall with a
protuberance thereon and the other of the socket and the spigot
having a side wall with a complementary recess therein adapted to
receive the protuberance, the protuberance being adapted to engage
in the recess so as to transmit forward and reverse drive to the
end portion.
15. The screw pile stem according to claim 13, wherein one of the
socket and the spigot has a side wall with a plurality of
protuberances thereon, and the other of the socket and the spigot
has a side wall with a complementary recess therein adapted to
receive the protuberances, the protuberances being adapted to
engage in the recess so as to transmit forward and reverse drive to
the end portion.
16. The screw pile stem according to claim 13, wherein each of the
spigot and the socket terminates at a free end, the recess opens to
a respective one of the free ends, and each protuberance is adapted
to enter and exit the recess through the opening to the free end
upon relative axial movement of the spigot and socket.
17. The screw pile stem according to claim 16, wherein the recess
includes two circumferentially spaced-apart securing portions
adapted to selectively receive therein a protuberance in which
relative axial movement between the spigot and the socket is
prevented.
18. The screw pile stem according to claim 17, wherein the opening
is between the circumferentially spaced-apart securing
portions.
19. The screw pile stem according to claim 18, wherein the recess
has a plurality of spaced-apart axially-aligned securing portions,
one of the spigot and the socket has a plurality of axially-aligned
protuberances, and the protuberances are arranged to coincidentally
locate in respective ones of the securing portions to prevent
relative axial movement between the spigot and the socket.
20. The screw pile stem according to claim 13, wherein at least one
of the recesses is formed by pressing a portion of the side wall
inwards.
21. The screw pile stem according to claim 13, wherein partial
relative rotation of the spigot and socket causes each protuberance
to locate in one of the respective securing portions.
22. The screw pile stem according to claim 21, wherein each
protuberance and recess are arranged such that partial relative
rotation of the spigot and the socket urges the end portion and the
body portion axially together.
23. The screw pile stem according to claim 13, further comprising:
a plurality of complementary circumferentially spaced-apart
protuberances and recesses.
24. The screw pile stem according to claim 13, wherein the socket
has a shoulder therein, and the end of the spigot is adapted to
abut the shoulder, whereby downward loads applied to the upper end
of the shank are transmitted to the helical screw by the
shoulder.
25. The screw pile stem according to claim 1, wherein the shank
includes extension coupling means at its other end for coupling
thereto an extension stem.
26. The screw pile stem according to claim 25, wherein the
extension coupling means is adapted to engage complementary
coupling means on an extension stem corresponding to the coupling
means on the one end.
27. A screw pile end piece adapted to be connected to a pile stem,
the screw pile end piece comprising: an inwardly tapered portion
with at least a part of a helical screw thereon, the helical screw
on the tapered portion being of constant pitch and a major diameter
of the helical screw decreasing towards a small end of the tapered
portion.
28. The screw pile end piece according to claim 27, further
comprising: a generally cylindrical portion coaxial with and
adjacent to the tapered portion; and wherein part of the helical
screw is on the generally cylindrical portion.
29. The screw pile end piece according to claim 28, wherein the
part of the helical screw on the cylindrical portion extends about
one full turn.
30. The screw pile end piece according to claim 27, wherein the
part of the helical screw on the tapered portion extends at least
one full turn.
31. The screw pile end piece according to claim 27, wherein the
major diameter of the part of the helical screw on the tapered
portion generally decreases at a constant rate.
32. The screw pile end piece according to claim 27, 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. The screw pile end piece according to claim 27, further
comprising: coupling means adapted to engage complementary coupling
means on a pile stem to which the end piece is to be attached for
coupling the screw pile end piece thereto, with the coupling means
being adapted to receive forward and reverse rotational drive from
the complementary coupling means of the pile stem.
34. The screw pile end piece according to claim 33, wherein the
cylindrical portion forms a socket which is adapted to receive
therein a complementary spigot on the pile stem to which the end
piece is to be coupled, with the 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. The screw pile end piece according to claim 33, wherein the
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, the spigot having a recess therein adapted to receive a
complementary protuberance in the socket, or the 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. The screw pile end piece according to claim 34, wherein the
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. The screw pile end piece according to claim 34, wherein the
spigot terminates at a free end and the recess opens to the free
end, the opening being adapted to receive therethrough the
protuberance of the pile stem to which the end piece is to be
coupled.
38. The screw pile end piece according to claim 34, wherein the
socket terminates at a free end and the recess opens to the free
end, the opening being adapted to receive therethrough the
protuberance of the pile stem to which the end piece is to be
coupled.
39. The screw pile end piece according to claim 37, wherein the
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 the end
piece is prevented.
40. The screw pile end piece according to claim 39, wherein the
opening is between the circumferentially spaced-apart
axially-aligned securing portions.
41. The screw pile end piece according to claim 40, wherein the
recess has a plurality of spaced-apart axially-aligned securing
portions.
42. The screw pile end piece according to claim 34, wherein the
recess extends only partway through the side wall of the
socket.
43. The screw pile end piece according to claim 35, wherein the
recess extends only partway through the spigot.
44. The screw pile end piece according to claim 36, wherein the
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. The screw pile end piece according to claim 34, wherein the
socket has a shoulder therein adapted to be engaged by the free end
of the pile stem to which the shoulder is to be attached and to
receive bearing loads therefrom.
46. The screw pile end piece according to claim 35, wherein the
spigot has a shoulder thereon adapted to be engaged by the free end
of the pile stem to which the shoulder is to be attached and to
receive bearing loads therefrom.
47. The screw pile end piece according to claim 34, wherein the
recess is formed by pressing a portion of the side wall
inwards.
48. A pile stem for screw piles, the pile stem comprising: a body
portion; and two opposite end portions, with: a first end portion
being adapted to engage a first screw pile end piece having an
inwardly tapered portion with at least a part of a helical screw
thereon, the helical screw on the tapered portion being of constant
pitch and a major diameter of the helical screw decreasing towards
the small end of the tapered portion; and a second end portion
being adapted to engage a second like pile stem.
49. In combination, a screw pile assembly comprising: a screw pile
end piece having an inwardly tapered portion with at least a part
of a helical screw thereon, the helical screw on the tapered
portion being of constant pitch and a major diameter of the helical
screw decreasing towards a small end of the tapered portion; and a
pile stem adapted to be detachably coupled to the screw pile end
piece.
50. A screw pile stem comprising: a steel stem; and a cast end
piece secured thereto.
51. A screw pile end piece comprising: a body formed of cast steel.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] 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.
[0003] 2. Description of the Related Art
[0004] 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 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.
[0005] 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.
[0006] 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 about 1,000 kN. while the steel plate
screw may suffer unacceptable distortion under a shank load of only
500 kN. or shear from the shank or deformation of the shank at the
welded joint between the screw and the shank.
[0007] 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.
[0008] Another disadvantage with known screw piles is that damaged
pile stems cannot be easily removed and replaced.
BRIEF SUMMARY OF THE INVENTION
[0009] One object of the present invention is to provide a screw
pile which overcomes or at least ameliorates one or more of the
aforementioned problems.
[0010] With the foregoing in view the invention resides broadly in
one aspect in a screw pile stem including:
[0011] a shank having an inwardly tapered portion at one end;
and
[0012] a helical screw on the shank, the helical screw being of
constant pitch and at least a part of the helical screw being on
the tapered portion, the major diameter of the part of the helical
screw on the tapered portion decreasing towards the small end of
the tapered portion. Preferably, the part of the helical screw on
the tapered portion extends at least one full turn.
[0013] Preferably, a generally cylindrical portion is provided
coaxial with and/or adjacent to the tapered portion and part of the
helical screw is on the generally cylindrical portion. In such form
of the invention, while it is preferred that the part of the
helical screw on the cylindrical portion extends 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 decreases
at the same rate as the diameter of the tapered portion, that is,
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.
[0014] Preferably, said shank includes a body portion and an end
portion, and the end portion is connected to the body portion at
one end. In such form it is preferred that the end portion is cast
steel or other suitable material.
[0015] In another aspect the invention resides broadly in a screw
pile end piece adapted to be connected to the pile stem, the screw
pile end piece having an inwardly tapered portion with at least a
part of a helical screw thereon, the helical screw on the tapered
portion being of constant pitch and the major diameter of the
helical screw decreasing towards the small end of the tapered
portion. Preferably, the end piece includes a generally cylindrical
portion coaxial with and/or adjacent to the tapered portion and
part of the helical screw is on the 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 the helical
screw is on the 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.
[0016] Preferably, the 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.
[0017] 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 the end piece. Preferably, the
complementary coupling means are adapted to transmit forward and
reverse rotational drive from the pile stem to the end portion.
[0018] In a preferred form, the cylindrical portion forms a socket
on the end piece, and the pile stem includes a spigot which is
adapted to be engaged in the socket, one of the socket and the
spigot having a side wall with a protuberance thereon and the other
of the socket and the spigot having a side wall with a
complementary recess therein adapted to receive the protuberance,
the protuberance being adapted to engage in the recess so as to
transmit forward and reverse drive to the end piece. However, in
another form the spigot and socket are reversed so that the
cylindrical portion forms the spigot on the end piece and the pile
stem includes the socket.
[0019] In one form, the socket has a side wall with a plurality of
protuberances thereon adapted to engage in a complementary recess
in the spigot. In such form the spigot terminates at a free end and
the recess opens to the free end, the 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, the recess is formed in a wall of the
socket which terminates at a free end and the recess opens to the
free end, the opening being adapted to receive therethrough the
protuberance which is provided on a side of the spigot.
[0020] Preferably, the 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 the end piece is prevented. In such form it is preferred
that the opening is between the circumferentially spaced apart
securing portions. It is also preferred that the 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 the recess extends only partway through the side
wall of the 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.
[0021] Preferably, the plurality of spaced apart protuberances are
axially aligned and adapted to engage in complementary securing
portions of the recess.
[0022] Preferably, the 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.
[0023] 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 a
screw pile end piece as previously described and the other end
being adapted to engage another like pile stem.
[0024] In another aspect the invention resides broadly in the
combination of an end piece and a pile stem as previously
described.
[0025] The terms "upper", "lower", "top", "bottom", "side",
"forward", "reverse" 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 "forward" and "reverse"
are used to describe the direction of rotation of the screw piles
into and out of the ground respectively.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0026] In order that the invention can be more easily understood
and put into practical effect, reference will now be made to the
accompanying drawings, wherein:
[0027] FIG. 1 is an elevational view of a screw pile stem and
extension stem according to the invention in-line for assembly,
with inserts A and B shown in greater detail in FIGS. 1A-1B,
respectively;
[0028] FIG. 2 is an end view of the screw pile stem shown in FIG.
1;
[0029] FIG. 3 is an end view of the extension stem shown in FIG.
1;
[0030] FIG. 4 is a sectional elevational view of the upper end
portion of the screw pile stem shown in FIG. 2 along lines 4-4 in
cut-away;
[0031] FIG. 5 is a sectional elevational view of the lower end
portion of the extension stem shown in FIG. 3 along lines 5-5 in
cut-away;
[0032] FIG. 6 is a pictorial representation of a screw pile end
piece according to the invention;
[0033] FIG. 7 is an elevational view of the screw pile end piece of
FIG. 6 from one side;
[0034] FIG. 8 is an elevational view of the screw pile of FIG. 6 at
90 degrees to the elevational view of FIG. 7;
[0035] FIG. 9 is a top end view of the screw pile end piece of FIG.
6, with insert A shown in greater detail in FIG. 9A;
[0036] FIG. 10 is a sectional elevational view of the screw pile
end piece of FIG. 6 along lines 10-10;
[0037] FIG. 11 is a pictorial representation of an extension stem
according to the invention;
[0038] FIG. 12 is an upper end view of the extension stem of FIG.
11;
[0039] FIG. 13 is a lower end view of the extension stem of FIG.
11;
[0040] FIG. 14a is an elevational view of the upper end portion of
the extension stem of FIG. 11;
[0041] FIG. 14b is a sectional elevational view of the upper end
portion of the extension stem of FIG. 11 along lines 14-14;
[0042] FIG. 15a is an elevational view of the lower end portion of
the extension stem of FIG. 11;
[0043] FIG. 15b is a sectional elevational view of the lower end
portion of the extension stem of FIG. 11 along lines 15-15;
[0044] FIG. 16 is pictorial representation of another screw pile
end piece according to the invention;
[0045] FIG. 17 is an elevational view of the screw pile end piece
of FIG. 16 from one side;
[0046] FIG. 18 is an elevational view of the screw pile end piece
of FIG. 16 at 90 degrees to the elevational view of FIG. 17;
[0047] FIG. 19 is a top end view of the screw pile end piece of
FIG. 16; and
[0048] FIG. 20 is a sectional elevational view of the screw pile
end piece of FIG. 16 along lines 20-20 in FIG. 17.
DETAILED DESCRIPTION OF THE INVENTION
[0049] Referring to FIGS. 1-20, 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 therebetween, 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 of
the cylindrical portion immediately adjacent to 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.
[0050] The part of the helical screw on the tapered portion extends
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.
[0051] The 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.
[0052] 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 the 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 securing portions at each
end 29a and 29b, 30a and 30b, and 31a and 31b, respectively.
[0053] 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
therebetween. 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 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 of 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 center.
[0054] 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 52b. 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. However, 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 to
the tip to provide a cutting edge 61 for initiating a drill hole
for the pile.
[0055] 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 for 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 69a and 69b, and 70a and 70b respectively.
[0056] 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 69b and 70b 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 69a and 70a
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.
[0057] 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
downward loads 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 69c and 70c of the securing portions of the recess 66 taper
away from the free end face 72 whereby engagement of the
protuberances 62 and 63 thereagainst urges the spigot 54 further
into the socket 53.
[0058] 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 the 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.
[0059] 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.
[0060] The screw pile end piece 150 illustrated in FIG. 16 is
intended to be permanently secured to the hollow pile stem, for
example, by welding or pinning and includes a shank 151 having a
tapered portion 152a at its lower end and a cylindrical portion
152b 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.
[0061] 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.
* * * * *