WO1999014441A1

WO1999014441A1 - Screw pile anchor

Info

Publication number: WO1999014441A1
Application number: PCT/AU1998/000782
Authority: WO
Inventors: Paul Anthony Camilleri
Original assignee: Steel Foundations Limited; Steel Foundations Technology Pty. Ltd.
Priority date: 1997-09-18
Filing date: 1998-09-18
Publication date: 1999-03-25
Also published as: CA2303932A1; CN1270649A; MY122066A; ID26275A; AU9146698A; AU723287B2; BR9815375A; NZ503878A; JP2001516828A; EP1019584A1

Abstract

A screw pile anchor (10) has a tubular shaft (11) with a helical screw flyte (20) and a ground engaging bit (12) at its ground engaging end. The stabilizing assembly (30) has a plurality of fins (34 to 37) radiating from collars (31 to 33) rotatably mounted on the shaft (11). A mounting plate (51) of a lighting column assembly (50) can be attached to the fins (34 to 37) via mounting bolts (40). The stabilizing assembly (30), through the provision of the fins (34 to 37) increases the resistance of the shaft (11) to lateral movement, e.g., under wind loads.

Description

TITLE: SCREW PILE ANCHOR

BACKGROUND OF THE INVENTION

1 . Field of the Invention

THIS INVENTION relates to a screw pile anchor. The

anchor is particularly suitable for, but not limited to, supporting

lighting columns.

2. Prior Art

The use of screw pile anchors, eg., of the type

manufactured by A. B. Chance Co., Centralia, Missouri, USA, to

support a wide range of loads, is well known. The pile anchors usually

have a shaft, with a base plate at the upper end (to which is bolted or

welded a mounting plate on the lighting column or the load to be

supported), and at least one helical screw or flyte at, or adjacent, the

ground engaging end. Usually, the ground engaging end is provided

with a digging point which cuts a hole in the ground for the shaft, as

the pile anchor is rotatably driven into the ground.

Such pile anchors may only have a low lateral stability

and so may not be suitable, particularly in loose or sandy soils, to

support lighting columns or the like. This means that the speed of

installation possible with pile anchors, as supports for lighting

columns, cannot be enjoyed and conventional supports, which may

have an installation span of two weeks (while the concrete pile sets)

must be employed. One attempt to increase the lateral stability of known

screw pile anchors is disclosed in AU-A-14807/97 (VANDERFEEN). A

pair of pipes, fitted one inside the other, are mounted on the shaft via

a collar and are operable to compress the ground down onto the helical

screw or flyte. However, the increase in lateral stability due to the

vertical compression of the ground is only marginal.

SUMMARY OF THE PRESENT INVENTION

It is an object of the present invention to provide a means

to increase the lateral stability of the pile anchors.

It is a preferred object of the present invention to provide

such means immediately below the base plate.

It is a further preferred object to provide such means

where the degree of increased lateral stability can be selected

dependent on the ground in which the anchor is to be driven.

It is a still further preferred object to provide a simple,

efficient method for interconnection of respective portions of the

shaft.

It is a still further preferred object to provide a simple,

efficient method for the manufacture of the helical screws or flytes.

Other preferred objects of the present invention will

become apparent from the following description.

In one aspect, the present invention resides in a

stabilizing assembly for a screw pile anchor, of the type having a shaft with at least one helical screw or flyte at or adjacent a ground

engaging end of a shaft (and an optional base plate at or adjacent the

other end of the shaft), the stabilizing assembly including:

at least one collar or plate rotatably mountable on the

shaft; and

a plurality of fins radiating from the collar(s) or plate(s)

and adapted to be pulled into the ground as the screw pile anchor is

driven into the soil, the stabilizing assembly providing resistance

against lateral movement to at least the portion of the shaft to which

the stabilizing assembly is mounted.

Preferably, three, four or more, fins are provided on the

collar(s) or plate(s), preferably at equal spacings, about the shaft.

Preferably, the fins extend substantially radially to the

shaft, although the fins may be curved, S-shaped or other shape in

plan view.

The fins may extend from a single collar rotatably

journalled about the shaft, or from two or more vertically spaced

collars or annular plates rotatably journalled about the shaft.

Preferably, the lower edges of the fins are inclined to the

horizontal, so that they will progressively cut into the ground as the

screw pile anchor is driven into the ground. Where the fins have

ground engaging points distal from the shaft, they will tend to

vertically stabilize the pile anchor before it is fully driven into the ground.

Preferably, one or more bolts are provided on the fins,

collar(s) and/or annular plates and extend upwardly for releasable

engagement with a mounting on a lighting column or other load to be

supported.

In a second aspect, the present invention resides in a

screw pile anchor including:

a shaft;

at least one helical screw or flyte at or adjacent a ground

engaging end of the shaft;

an optional base plate at or adjacent the other end of the

shaft; and

a stabilizing assembly, having at least one collar or plate

rotatably mounted on the shaft, and a plurality of fins radiating from

the shaft and adapted to be pulled into the ground as the screw pile

anchor is driven into the soil, the stabilizing assembly providing

resistance against lateral movement to at least the portion of the shaft

on which the stabilizing assembly is mounted.

The screw pile anchor may be provided with two or more

of the stabilizing assemblies at spaced intervals along the shaft.

Preferably, a cable entry slot is provided in the wall of the

tubular shaft below the fins.

In a third aspect, the present invention resides in a method of coupling respective portions of a tubular shaft of a screw

pile anchor, where one end of one of the portions is telescopically

interfitted into an adjacent end of the other of the portions, wherein:

the one end of the one portion has a first coupling zone

having an angular inclination (relative to the longitudinal axis of the

shaft) greater than the inclination of a second coupling zone, the

coupling first and second coupling zones being engageable in

complementary coupling zones at the adjacent end of the other

portion.

Preferably, the one coupling zone and complementary

zone provide coupling of the portions in a direction longitudinal of the

shaft; and the second coupling zone and its complementary zone

provide coupling of the portions for rotation of the shaft.

In a fourth aspect, the present invention resides in a

coupling between two portions of a tubular shaft for a screw pile

anchor of the type where one end of one of the portions is

telescopically interfitted in an adjacent end of the other of the

portions, wherein:

the one end of the one portion has a first coupling zone

having an angular inclination (relative to the longitudinal axis of the

shaft) greater than the angular inclination of a second coupling zone,

the first and second coupling zones being engageable in

complementary coupling zones at the adjacent end of the other portion.

In a fifth aspect, the present invention resides in a helical

flyte of a screw pile anchor including:

a pair of flyte plates, each of substantially helical

configuration, mountable on the shaft at spaced locations and

convergent at a peripheral rim.

The leading and trailing portions of the flyte plates may

be convergent to respective leading and trailing edges. One or more

flanges may be formed integrally with the flyte plates to enable

mounting of the flyte plates on the shaft; and the flanges and flyte

plates may be formed integrally from a single piece of sheet metal.

BRIEF DESCRIPTION OF THE DRAWINGS

To enable the invention to be fully understood, preferred

embodiments will now be described with reference to the

accompanying drawings in which:

FIG. 1 is a view of a typical installation of a lighting

column on a first embodiment of a screw pile anchor in accordance

with the present invention;

FIG. 2 is a perspective (exploded) view of the mounting

of the lighting column on the screw pile anchor in more detail;

FIG. 3 is a perspective view of the screw pile anchor of

FIGS. 1 and 2;

FIGS. 4 and 5 are perspective views of second and third embodiments of the screw pile anchor;

FIG . 6 is a plan view illustrating how the stabilizing

assembly of the present invention operates;

FIG. 7 is a sectional side view corresponding to FIG. 6;

FIG . 8 is a similar view to FIG. 7, the screw pile anchor

having a pair of the stabilizing assemblies of the present invention;

FIG . 9 is an (exploded) perspective view of a fourth

embodiment of the screw pile anchor;

FIG. 1 0 is a perspective view of a first embodiment of the

coupling between two shaft portions;

FIG. 1 1 is a sectional side view of a second embodiment

of the coupling between two shaft portions;

FIG. 1 2 is a perspective view of a first embodiment of a

helical flyte; and

FIG . 1 3 is a similar view of a second embodiment of the

helical flyte.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, this shows a typical

installation of a lighting column on a screw pile anchor in accordance

with the present invention.

The screw pile anchor 1 0 has a tubular shaft 1 1

terminating at its ground engaging end in a removal drilling point or bit

1 2. A base plate 1 3 is welded (or otherwise fixed) to the upper end of the shaft 1 1 and may be provided with slots or recesses 14.

The stabilizing assembly 30 has three, vertically spaced,

collars 31 , 32, 33 rotatably journalled on the shaft, the collar 31 being

immediately below the base plate 1 3, and a locating ring (not shown)

is provided adjacent the lower collar 33 to limit movement of the

stabilizing assembly along the shaft 1 1 .

Four fins 34, 35, 36, 37 extend radially from the collars

31 to 33 at equal, angular spacings.

Each fin 34, 35, 36, 37 has a lower, cutting edge 38

which is inclined downwardly in a radially-outward direction and

terminates in a ground engaging point 39 distal from the collar 33.

A respective mounting bolt or stud 40 extends vertically

from the top edge 41 of each of the fins 34 to 37 and may be

provided with nuts 42 to secure a mounting plate 51 of a lighting

column assembly 50 to the screw pile anchor 1 0 after the latter has

been installed.

Referring to FIG. 3, the screw pile anchor 1 0 is provided

with an alternative helical screw or flyte 20a, to be hereinafter

described in more detail and an alternative drilling point or bit 1 2a.

A cable hole 52 is provided in a locating ring 33a, below

the lower collar 33, enabling electrical cables to be fed to the interior

of the tubular shaft 1 1 for connection to cables (not shown) for the

light assembly 52 mounted on the lighting column 53 (see FIG. 1 ). Referring to FIG. 4, the screw pile anchor 1 1 0 is modified

in that the stabilizing assembly 1 30 only has three fins 1 34 to 1 36

spaced at 1 20° intervals. This embodiment may be preferred where

the ground into which the screw pile 1 1 0 is to be driven has a higher

mechanical strength than the ground where the screw pile anchor 1 0

is to be employed. It will also be noted that the screw pile anchor 1 1 0

can only provide three mounting bolts 140 for the mounting plate of

the lighting column assembly or other load to be supported.

In the embodiment of FIG. 5, the screw pile anchor 21 0

has eight fins 234 to 237, 234a to 237a, where the four primary fins

234 to 237 are provided at 90° intervals and are bisected by a

respective one of the secondary fins 234a to 237a. In addition, the

primary fins 234 are deeper and extend from the upper collar 231 to

the lower collar 233, while the secondary fins 234a to 237a extend

from the upper collar 231 only to the central collar 232. It will be

noted that both the primary and secondary fins have inclined cutting

edges 238, 238a terminating in ground engaging points 239, 239a

distal from the shaft 21 1 .

The screw pile anchors 1 0, 1 1 0, 21 0 are driven into the

ground using a standard power driving head, the drilling bits 1 2, 1 1 2,

21 2 cutting a hole for the tubular shafts 1 1 , 1 1 1 , 21 1 . The screw

pile anchors 10, 1 10, 210 pull themselves into the ground until the

ground engaging points 39, 1 39, 239 engage the ground surface. The stabilizing assemblies 30, 1 30, 230, which have tended to rotate with

the shafts 1 1 , 1 1 1 , 21 1 , cease rotation and the cutting edges 38,

1 38, 238 (and 238a) on the fins 34 to 37, 1 34 to 1 36, 234 to 237

cut downwardly into the soil. In the embodiment of FIG. 5, the

cutting edges 238a will enable the secondary fins 234a to 237a to

enter the ground when their digging points 239a engage the soil.

The screw pile anchors 1 0, 1 1 0, 21 0 are driven into the

ground until their respective base plates 1 3, 1 1 3, 21 3 are at, or just

above, the ground surface.

Referring to FIGS. 5 and 6, where a cable trench 60 has

been cut in the ground 61 , back-filling 62 of the trench will result in

reduced resistance to lateral movement of the upper end of the screw

pier 1 0, particularly when medium to high wind loads 70 are applied to

the light column assembly 50 in the direction of the arrow in FIG. 6.

However, by providing the stabilizing assembly 30, the

fins 34 to 37 tend to compress the ground in the area generally

indicated by the triangular shaded area 63 in FIG . 6. Tests have

shown that the compression of the ground may increase the resistance

of the upper end of the shaft 1 1 (and thereby the screw pile anchor

1 0) against lateral movement by a factor of five to ten times, more

generally six times. The rate of degree of resistance depends on

factors such as the number of fins provided on the stabilizing

assembly, the depth and the width of the fins, and the structure of the surrounding soil. Where the ground has a low mechanical strength, it

is preferable to use the screw pile anchors 1 0, 21 0, illustrated in FIGS.

3 and 5 over the screw pile anchor 1 10 of FIG. 4, as greater lateral

resistance is provided by increasing the number of fins.

By use of the stabilizing assemblies 30, 1 30, 230, it is

possible to use thinner gauge material in the manufacture of the

tubular shafts 1 1 , 1 1 1 , 21 1 without loss of vertical load capacity or

reduction in lateral bending resistance below prescribed limits.

FIG. 8 shows a modified embodiment of the screw pile

anchor of FIG. 7 which is suitable for use in soils which have stratas

having different mechanical strengths. In this embodiment, a pair of

the stabilizing assemblies 30 are provided at spaced intervals along the

shaft 1 1 of the screw pile anchor 1 0, where the upper end of the

shaft 1 1 and the lower end of the shaft 1 1 are in ground stratas 64,

65 of relatively low mechanical strength, and are separated by a

ground strata 66 of relatively higher mechanical strength.

It will be readily apparent to the skilled addressee that

where any soils strata is of relatively low mechanical strength, two or

more of the stabilizing assemblies 30 may be provided along the shaft

1 1 to increase the resistance of the shaft 1 1 to lateral movement

within that strata or stratas.

In the preferred embodiments shown in FIGS. 1 to 8, the

cutting edges 38, 1 38, 238 (and 238a) have been shown to be downwardly inclined to the ground engaging points, 39, 1 39, 239

(and 239a) distal from the shafts 1 1 , 1 1 1 , 21 1 . In alternative

embodiments (see FIG. 9), the cutting edges 338a may be upwardly

inclined radially outwardly (as shown in dashed lines) so that they

initially cut the ground adjacent the lower collar 33, 1 33, 233.

In a further alternative embodiment (not shown), the

spaced collars 31 to 33, 1 31 to 1 33, 231 to 233 may be substituted

by a single tubular collar or by one or more annular plates rotatably

journalled about the shafts 1 1 , 1 1 1 , 21 1 .

Referring to FIG. 9, it is possible to provide the stabilizing

assembly 330 as a kit for mounting on the tubular shaft of an existing

screw pile anchor (eg., of the type manufactured by A. B. Chance

Co.); or on tubular shaft portions not especially adapted to receive the

stabilizing assemblies 330. An example of such a kit is illustrated

where the fins 334 to 336 are radially mounted on spaced collars 331

to 333 dimensioned to be rotatably journalled on a tubular shaft

portion 31 1 a, adapted to be coupled to a second tubular shaft portion

31 1 b fitted with the helical flyte 320 and, in turn, adapted to be

coupled to a third tubular shaft portion 31 1 c having the digging point

31 2.

A method of coupling the respective tubular shaft

portions 31 1 a to 31 1 b and 31 1 b to 31 1 c will hereinafter be described

with reference to FIGS. 1 0 and 1 1 . Locating rings 331 a and 333a are provided with locking

screws (not shown) to enable them to be secured to the tubular shaft

portion 31 1 a to locate the stabilizing assembly 330 along the tubular

shaft portion 31 1 a while permitting rotation of the stabilizing assembly

330 about the shaft portion.

Referring to FIG. 1 0, a first embodiment of a coupling

between the adjacent tubular shaft portions, eg., 31 1 a and 31 1 b, the

lower end of tubular shaft portion 31 1 a has a first coupling zone 380

and a second coupling zone 381 adapted to be telescopically

interfitted with, and engaged with, complementary first and second

coupling zones 390 and 391 at the upper end of the tubular shaft

portion 31 1 b. It will be noted that the angular inclination of the first

coupling zone 380, eg., of 2-5 ° relative to the longitudinal axis of the

tubular shaft portion 31 1 a, is less than the angular inclination of the

second coupling zone 381 , eg., 5-1 5 °, more preferably 5-1 0° . The

shallow angle of inclination, and large surface area, of the

complementary first zones 380, 390 enables a larger driving torque to

be provided down the shaft portions 31 1 a, 31 1 b, to enable the drill bit

31 2 and helical flyte 320 to cut respective pathways down the soil.

The higher angle of inclination of the second coupling zones 381 , 391

provides longitudinal location between the respective tubular shaft

portions 31 1 a, 31 1 b, to resist the downward force on the shaft

portions supplied by the driving head. In the alternative embodiment shown in FIG. 1 1 , the first

driving zones 380a, 390a have the increased angular inclination

relative to their longitudinal axis of the tubular shaft portions and the

secondary coupling zones 381 a, 31 9a may be inclined in the range of

0-5 ° , more preferably, 0-2° to the longitudinal axis.

Referring to FIG . 1 2, this illustrates a first embodiment of

the helical flyte or screw in accordance with the present invention.

The helical flyte 320 is formed from two helical flyte

plates 321 , 322 which are each cut from a steel sheet and are

deformed into a substantially helical shape. Each plate 321 , 322 is

welded, brazed or otherwise fixed to the tubular shaft portion 31 1 and

is oppositely inclined so that the two plates 321 , 322 are convergent

at the peripheral rim 323 of the helical flyte. The plates are joined by

welding, brazing or other suitable fixing means, and the "triangulation"

formed by the inclination of the two plates to each other results in a

helical flyte which is easily manufactured but which has a high

mechanical strength.

In use, the space between the plates is quickly filled with

soil, which forms a "plug" which pushes other ground out of the way

as the helical screw flyte 320 is rotatably driven into the ground.

In the second embodiment shown in FIG. 1 3, the two

helical plates 321 a, 322a are formed integrally (eg., by folding) from a

single piece of sheet metal, and flanges 324a and 325a enable the helical flyte 320a to be welded, brazed or otherwise fixed to the

tubular shaft portion 31 1 . (Reinforcing ribs 329a can be formed

integrally in the helical plates 321 a, 322a to increase the strength

thereof.)

It will be readily apparent to the skilled addressee that the

helical screw flytes 320, 320a illustrated in FIGS. 1 2 and 1 3 can be

manufactured from thinner section steel than would otherwise be

required for a conventional helical screw flyte having the same load

characteristics.

It will be readily apparent to the skilled addressee that the

stabilizing assembly, and associated features hereinbefore described

for the screw pile anchors, enable anchors to be manufactured with

the same, or higher, resistance to lateral movement, and the same or

higher vertical loadings, than conventional screw pile anchors using

thicker section, and thereby heavier, components. For example, the

stiffness of the composite section of the anchor which comprises the

stabilizing assembly and shaft is approximately 50% more than the

shaft stiffness alone.

The stabilizing assembly can provide resistance to lateral

movement of the shaft of the screw pile anchor which can be many

times greater than the resistance of a conventional unrestrained (or

unstabilized) anchor. The use of the fins increases the effective area

of the ground restraining the shaft against lateral movement, not only to many times greater than the diameter of the shaft, but also many

times greater than the width of the fins.

Various changes and modifications may be made to the

embodiments described and illustrated without departing from the

present invention as defined in the claims.

Claims

1 . A stabilizing assembly for a screw pile anchor, of the type

having a shaft with at least one helical screw or flyte at or adjacent a

ground engaging end of a shaft (and an optional base plate at or

adjacent the other end of the shaft), the stabilizing assembly including:

at least one collar or plate rotatably mountable on the

shaft; and

a plurality of fins radiating from the collar(s) or plate(s)

and adapted to be pulled into the ground as the screw pile anchor is

driven into the soil, the stabilizing assembly providing resistance

against lateral movement to at least the portion of the shaft to which

the stabilizing assembly is mounted.

2. A stabilizing assembly as claimed in Claim 1 , wherein:

three, four or more fins are provided on the collar(s) or

plate(s) at equal spacings, about the shaft.

3. A stabilizing assembly as claimed in Claim 1 or Claim 2

wherein:

the fins extend substantially radially to the shaft, or are

curved, S-shaped or other shape in plan view.

4. A stabilizing assembly as claimed in any one of Claims 1

to 3 wherein:

the fins extend from a single collar rotatably journalled

about the shaft, or from two or more vertically spaced collars or annular plates rotatably journalled about the shaft.

5. A stabilizing assembly as claimed in any one of Claims 1

to 4 wherein:

the lower edges of the fins are inclined to the horizontal,

so that the lower edges will progressively cut into the ground as the

screw pile anchor is driven into the ground.

6. A stabilizing assembly as claimed in Claim 5 wherein:

the lower edges are downwardly inclined outwardly from

the shaft and terminate in ground engaging points distal from the

shaft, the ground engaging points tending to vertically stabilize the

screw pile anchor before the screw pile anchor is fully driven into the

soil.

7. A stabilizing assembly as claimed in any one of Claims 1

to 6 wherein:

one or more bolts are provided on the fins, collar(s)

and/or annular plate(s) and extend upwardly for releasable engagement

with a mounting plate on a lighting column or other load to be

supported.

8. A screw pile anchor including:

a shaft;

at least one helical screw or flyte at or adjacent a ground

engaging end of the shaft;

an optional base plate at or adjacent the other end of the shaft; and

a stabilizing assembly having at least one collar or plate

rotatably mounted on the shaft, and a plurality of fins radiating from

the shaft and adapted to be pulled into the ground as the screw pile

anchor is driven into the soil, the stabilizing assembly providing

resistance against lateral movement to at least the portion of the shaft

on which the stabilizing assembly is mounted.

9. A screw pile anchor as claimed in Claim 8 wherein the

stabilizing assembly is as claimed in any one of Claims 1 to 7.

1 0. A screw pile anchor as claimed in Claim 8 with two or

more of the stabilizing assemblies as claimed in any one of Claims 1 to

7 at spaced intervals along the shaft.

1 1 . A screw pile anchor as claimed in any one of Claims 8 to

1 1 wherein:

a cable entry slot is provided in the wall of the shaft

below the fins.

1 2. A method of coupling respective portions of a tubular

shaft of a screw pile anchor, where one end of one of the portions is

telescopically interfitted into an adjacent end of the other of the

portions, wherein:

the one end of the one portion has a first coupling zone

having an angular inclination (relative to the longitudinal axis of the

shaft) greater than the angular inclination of a second coupling zone, the first and second coupling zones being engageable in

complementary coupling zones at the adjacent end of the other

portion.

1 3. A method of coupling as claimed in Claim 1 2, wherein:

the one coupling zone and complementary zone provide

coupling of the portions in a direction longitudinal of the shaft; and the

second coupling zone and its complementary zone provide coupling of

the portions for rotation of the shaft.

1 4. A coupling between two portions of a tubular shaft for a

screw pile anchor of the type where one end of the portions is

telescopically interfitted in an adjacent end of the other of the

portions, wherein:

the one end of the one portion has a first coupling zone

having an angular inclination (relative to the longitudinal axis of the

shaft) greater than the angular inclination of a second coupling zone,

the first and second coupling zones being engageable in

complementary coupling zones at the adjacent end of the other

portion.

1 5. A helical flyte for a screw pile anchor including:

a pair of flyte plates, each of substantially helical

configuration, mountable on the shaft at spaced locations and

convergent at a peripheral rim.

1 6. A helical flyte as claimed in Claim 1 5 wherein: the leading and trailing portions of the flyte plates are

convergent to respective leading and trailing edges.

1 7. A helical flyte as claimed in Claim 1 5 or 1 6 wherein:

one or more flanges are formed integrally with the flyte

plates to enable mounting of the flyte plates on the shaft.

1 8. A helical flyte as claimed in Claim 1 7 wherein:

the flanges and flyte plates are formed integrally from a

single piece of sheet metal.