U.S. patent application number 12/067529 was filed with the patent office on 2008-12-11 for ground anchor.
Invention is credited to Stephen Mark Lewenhoff.
Application Number | 20080302028 12/067529 |
Document ID | / |
Family ID | 37888449 |
Filed Date | 2008-12-11 |
United States Patent
Application |
20080302028 |
Kind Code |
A1 |
Lewenhoff; Stephen Mark |
December 11, 2008 |
Ground Anchor
Abstract
A ground anchor (10) comprising an anchor shaft (11) and an
anchoring screw (13) moulded onto the anchoring shaft adjacent the
lower end thereof. The anchoring shaft (11) is of a rectangular
cross-section with four side walls (12). The anchoring shaft (11)
is configured at its bottom end (15) for ground penetration. The
upper end (19) of the anchor shaft (11) is configured to receive
torque applied thereto. The anchoring screw (13) comprises a hub
(21) and a screw flight (23) on the hub. The anchoring screw (13)
is moulded onto the anchor shaft (11), and the hub (21) is keyed to
the anchor shaft. The anchoring screw (13) is so constructed that
the spiral flight (23) is rigid yet has some resilient flexibility
which allows the flight to deflect laterally in the direction of
the screw axis. Specifically, the screw flight (23) has sufficient
rigidity to allow it to penetrate the ground in which it is
intended to be used when torque is applied to the anchor shaft
(11). Further, the screw flight (23) has sufficient rigidity in
order to retain the ground anchor (10) embedded in the ground when
subjected to the normal load conditions for which it is intended,
as is the case with conventional ground anchors. The resilient
flexibility provides the screw flight (23) with a degree of
`springiness`, so allowing the screw flight (23) to deflect
laterally in the direction of the screw axis when subjected to the
loadings to which it is exposed when winding into the ground. With
this arrangement, the pitch of the helical screw (25) is permitted
to alter during ground embedment as ground pressure increases.
Inventors: |
Lewenhoff; Stephen Mark;
(Western Australia, AU) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Family ID: |
37888449 |
Appl. No.: |
12/067529 |
Filed: |
September 20, 2006 |
PCT Filed: |
September 20, 2006 |
PCT NO: |
PCT/AU06/01374 |
371 Date: |
August 11, 2008 |
Current U.S.
Class: |
52/157 ;
52/741.1 |
Current CPC
Class: |
E02D 7/22 20130101; E04H
12/2223 20130101; E02D 5/80 20130101; E02D 5/801 20130101 |
Class at
Publication: |
52/157 ;
52/741.1 |
International
Class: |
E02D 5/80 20060101
E02D005/80 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 20, 2005 |
AU |
2005905178 |
Sep 20, 2005 |
AU |
2005905179 |
Claims
1. A ground anchor comprising an anchoring screw, the anchoring
screw comprising a screw flight winding about a screw axis, the
screw flight being generally rigid with some lateral resilient
flexibility.
2. A ground anchor according to claim 1 wherein the screw flight is
formed from a moulded non-metallic material.
3. A ground anchor according to claim 2 wherein the screw flight is
formed of a composite plastics material.
4. A ground anchor according to claim 1, wherein the screw flight
is supported on a hub.
5. A ground anchor according to claim 4 wherein the screw flight is
formed integrally with the hub.
6. A ground anchor according to claim 5 wherein the anchoring screw
is moulded from a composite plastics material.
7. A ground anchor according to claim 1 further comprising an
anchor shaft on to which the anchoring screw is mounted.
8. A ground anchor according to claim 7 wherein the anchoring screw
is moulded onto the anchoring shaft.
9. A ground anchor according to claim 8 wherein the anchoring shaft
is configured for keying the moulded anchoring screw onto the
shaft.
10. A ground anchor according to claim 7, wherein the anchoring
shaft is or a polygonal cross-section, such as hexagonal or
rectangular cross-section.
11. A ground anchor according to claim 7 wherein the anchor shaft
has a foot end configured for ground penetration.
12. A ground anchor according to claim 7 wherein the anchor shaft
has a head end adapted to receive torque to drive the anchor into
the ground.
13. A ground anchor according to claim 12 wherein the head end of
the anchor shaft incorporates at least one drive hole located
through the side of the shaft.
14. A ground anchor according to claim 1 wherein the screw flight
is adapted for selective variation of the circumference
thereof.
15. A ground anchor according to claim 14 wherein the screw flight
is adapted to be cut to vary the circumference thereof.
16. A ground anchor according to claim 15 wherein the screw flight
incorporates a guide marking radially inwardly of the outer
periphery thereof.
17. A ground anchor comprising an anchor shaft and an anchoring
screw on the anchor shaft, the anchoring screw comprising a screw
flight winding about a screw axis, the screw flight being generally
rigid with some lateral resilient flexibility.
18. A ground anchor according to claim 17 further comprising a
lateral stabilisation device adapted to be fitted onto the anchor
shaft and to engage the ground to provide lateral stabilisation to
the shaft within the ground.
19. A ground anchor according to claim 18 wherein the lateral
stabilisation device comprises a body adapted to be fitted onto the
anchor shaft for engagement with the ground to provide lateral
support for the anchor shaft with respect to the ground.
20. A ground anchor according to claim 19 wherein the body is
adapted to be rotatably supported on the shaft.
21. A ground anchor according to claim 20 wherein the body
incorporates a bearing surface and the anchor shaft is provided
with an abutment for engaging against the bearing surface for
urging the body into engagement with the ground as the ground
anchor is embedded into the ground.
22. A ground anchor according to claim 21 wherein the bearing
surface is defined by a thrust bearing in the body.
23. A ground anchor according to claim 21 wherein the abutment
provided on the anchor shaft comprises a pin projecting from the
shaft.
24. A ground anchor according to claim 19 wherein the body
comprises one or more lateral projections presenting surfaces for
engagement with the ground.
25. A ground anchor according to claim 24 wherein the lateral
projections are configured as vanes.
26. A ground anchor according to claim 25 wherein there are four
vanes arranged in an X formation when viewed in plan.
27. A ground anchor according to claim 25 wherein each vane is
configured at the lower end thereof for penetration with the
ground.
28. A ground anchor according to claim 19 wherein the body further
comprises a sleeve section defining a central passage for rotatably
receiving the anchoring shaft.
29. A ground anchor according to claim 19 wherein the body
comprises a plurality of body sections.
30. A ground anchor according to claim 19 wherein the body
incorporates a recess for accommodating the upper end of the anchor
shaft, the recess being configured to facilitate access to the
upper end of the anchor shaft when accommodated in the recess.
31. A method of manufacturing a ground anchor, the method
comprising providing an anchor shaft and moulding an anchoring
screw onto the anchor shaft.
32. A method according to claim 31 farther comprising configuring
the shaft for keying the moulded anchoring screw onto the anchor
shaft.
33. A lateral stabilisation device for a ground anchor having an
anchor shaft, the lateral stabilisation device comprising a body
adapted to be fitted onto the anchor shaft for engagement with the
ground to provide lateral support for the anchor shaft with respect
to the ground.
34. A lateral stabilisation device according to claim 33 wherein
the body is adapted to be rotatably supported on the anchor
shaft.
35. A lateral stabilisation device according to claim 34 wherein
the body incorporates a bearing surface against which an abutment
on the anchor shaft can engage for urging the body into engagement
with the ground as the ground anchor is embedded into the
ground.
36. A lateral stabilisation device according to claim 35 wherein
the bearing surface is defined by a thrust bearing in the body.
37. A lateral stabilisation device according to claim 33 wherein
the body comprises one or more lateral projections presenting
surfaces for engagement with the ground.
38. A lateral stabilisation device according to claim 37 wherein
the lateral projections are configured as vanes.
39. A lateral stabilisation device according to claim 38 wherein
there are four vanes arranged in an X formation when viewed in
plan.
40. A lateral stabilisation device according to claim 38 wherein
each vane is configured at the lower end thereof for penetration
with the ground.
41. A lateral stabilisation device according to claim 33 wherein
the body further comprises a sleeve section defining a central
passage for rotatably receiving the anchoring shaft.
42. A lateral stabilisation device according to claim 33 wherein
the body comprises a plurality of body sections.
43. A lateral stabilisation device according to claim 33 wherein
the body incorporates a recess for accommodating the upper end of
the anchor shaft, the recess being configured to facilitate access
to the upper end of the anchor shaft when accommodated in the
recess.
44. (canceled)
45. A ground anchor comprising an anchor shaft, anchoring screw
mounted on the anchor shaft, the anchoring screw comprising a screw
flight winding about a screw axis, the screw flight being generally
rigid with some lateral resilient flexibility, and a body adapted
to be fitted onto the anchor shaft for engagement with the ground
to provide lateral support for the anchor shaft with respect to the
ground.
46. A ground anchor according to claim 45 wherein the body is
adapted to be rotatably supported on the anchor shaft.
47. A ground anchor according to claim 46 wherein the body
incorporates a bearing surface against which an abutment on the
anchor shaft can engage for urging the body into engagement with
the ground as the ground anchor is embedded into the ground.
48. A ground anchor device according to claim 47 wherein the
bearing surface is defined by a thrust bearing in the body.
49. A ground anchor according to claim 45 wherein the body
comprises one or more lateral projections presenting surfaces for
engagement with the ground.
50. A ground anchor according to claim 50 wherein the lateral
projections are configured as vanes.
51. A ground anchor according to claim 50 wherein there are four
vanes arranged in an X formation when viewed in plan.
52. A ground anchor according to claim 50 wherein each vane is
configured at the lower end thereof for penetration with the
ground.
53. A ground anchor according to claim 45 wherein the body further
comprises a sleeve section defining a central passage for rotatably
receiving the anchoring shaft.
54. A lateral stabilisation device according to claim 45 wherein
the body incorporates a recess being configured to facilitate
access to the upper end of the anchor shaft when accommodated in
the recess.
55-57. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to ground anchors, and more
particularly to ground anchors employing an anchoring screw to
embed the anchor into the ground. Ground anchors are also often
referred to as earth anchors.
BACKGROUND
[0002] Anchors installed in soil are commonly utilised to provide
support, either in tension or in compression, and provide support
or a tie down point for various equipment and structures. For
example, ground anchors are commonly utilised to provide anchorage,
in tension, for guy lines used to support electrical transmission
equipment. They can also be used to provide a stable surface upon
which equipment can be mounted. When this is done, the top of the
anchor is normally encased in concrete to provide lateral (ie side
to side) stability and the equipment is mounted thereupon.
[0003] Ground anchors typically include a helix formed in a spiral
configuration around a hub. The helix is rigid and most commonly of
metal. Some designs have used a cast iron type helix whereas other
designs have the metal helix welded to a metal hub. When the ground
anchor is to be installed into the ground, a torque tube is coupled
to the hub of the anchor so that the torque applied to the torque
tube is transferred through the hub from the torque tube to the
helix. The torque tube is controlled to then apply both a downward
force and a rotational force to the ground anchor. The combination
of forces (at least initially) causes the helix to bore into the
ground.
[0004] Since it is primarily the helix of the ground anchor that
absorbs the load exerted on the earth, the strength and diameter of
the helix must be designed to withstand its expected load.
Typically different sized anchors are provided for different
intended purposes (taking into account expected loads and ground
conditions).
[0005] There have been various prior art proposals for ground
anchors. U.S. Pat. No. 3,1487,510 (Sullivan) discloses a method of
driving a screw anchor into the ground. The anchor itself is of a
conventional design and uses a rigid shaft and a rigid helical
screw. The method of inserting the anchor is depicted by way of
specialised industrial equipment. U.S. Pat. No. 4,316,350 (Watson)
discloses a ground having a helical screw with an increasing radial
extent from the tip of the screw towards the top of the anchor.
U.S. Pat. No. Re 32,076 (U.S. Pat. No. 4,334,392--Dziedzic)
discloses a helical screw type anchor for industrial applications
wherein the anchor comprises individual components adapted to be
assembled together. Specialised equipment is used to install such
anchors. U.S. Pat. No. 5,156,369 (Tizoni) discloses a helical screw
applied to the lower part of an beach umbrella stand. The umbrella
stand is adapted at its upper part to receive a tool for rotating
the stand and thereby embedding the helical screw into the ground.
U.S. Pat. No. 5,265,982 (Burtelson) discloses a ground anchor in
which the hub carrying the helical screw is adapted to engage a
torque tube for transferring torque from the torque tube to the
helix. The design is said to allow a greater torque to be applied
to the helical screw for a lower manufactured cost, and the helix
is typically attached to the hub by welding.
[0006] The anchors described in the prior art all teach of the use
of rigid helical screws and all are of metal.
[0007] The torque required to install a helical screw ground anchor
into a given ground condition will be, dependent on the size of the
helical screw. A low torque is particularly desirable for helical
screw ground anchors intended for manual operation and therefore
smaller (rather than larger) helical screws are desirable.
[0008] Reducing the friction between the helical screw and the
earth would also reduce the torque required for installation or
removal.
[0009] Further in all of the above prior art cases, the width of
the anchor shaft is relatively narrow as compared to the diameter
of the helical screw. Therefore the ability of the ground anchor to
resist lateral loads (ie transverse to the longitudinal direction
of the anchor shaft) is limited in comparison to the ground holding
ability of the helical screw.
[0010] In order to provide lateral stability to the top of such
ground anchors, concrete can be poured in-situ to encapsulate the
top of the anchor and provide a mounting point for equipment or
other hardware.
[0011] Such in-situ stabilisation is time consuming and labour and
material intensive.
[0012] It is against background, and the problems and difficulties
associated therewith, that the present invention has been
developed.
DISCLOSURE OF THE INVENTION
[0013] According to a first aspect of the invention there is
provided a ground anchor comprising an anchoring screw, the
anchoring screw comprising a screw flight winding about a screw
axis, the screw flight being generally rigid with some lateral
resilient flexibility.
[0014] With this arrangement, the rigid nature of the screw flight
allows it to move through the ground during rotation while also
allowing some lateral deflection in response to loading on the
screw flight to change the pitch of the flight.
[0015] Such an arrangement offers an increased loading capacity
compared to prior art designs of a similar size.
[0016] The degree of resilient flexibility desirable for a
particular ground anchor according to the invention may be
dependent, amongst other things, on the nature of the ground into
which it will be inserted (eg sandy loose soil would require a more
flexible helical screw than say, hard compacted soil). Simple
application engineering techniques, either mathematical, model
based or routine trial and experimentation, would identify suitable
flexibility requirements for any particular application.
[0017] Preferably, the screw flight is formed from a moulded
non-metallic material, such as a semi-rigid composite material or
other plastics material. More preferably, the entire anchoring
screw formed on such material. Such materials are inherently more
flexible then the metal helical screws typically used in the prior
art.
[0018] The anchoring screw may be made of a composite plastics
materials The desired flexibility of the screw flight can be
conveniently controlled by suitable choice of materials, and/or the
thickness of the screw flight.
[0019] Use of such materials also reduces the friction between the
screw flight and the earth, and thus can provide benefits in
reducing the insertion torque.
[0020] Preferably the non-metallic material is corrosion resistant.
As such the torque required to remove an anchor that has been in
the ground for a period of time is reduced. Such ground anchors are
therefore well suited for re-usable applications.
[0021] Preferably the screw flight is formed of a material that can
be cut (such as by sawing) for selectively varying the
circumference thereof. Further, the screw flight may have a
circumferential guide marking radially inwardly of the outer
periphery of the helical screw, such guide marking providing a
visual guide for cutting off an outer section of the screw flight.
Preferably the screw flight can be so cut manually.
[0022] With such an arrangement, a user of such ground anchor, upon
determining that a smaller diameter screw flight is desirable for a
particular application (for instance, where the ground is
hard/compacted and therefore the insertion torques would be
exceedingly high for a large diameter screw flight) can
conveniently reduce the radial extent of the screw flight, thus
reducing the torque and loads required to embed the ground
anchor.
[0023] Preferably, the screw flight is configured as a helical
screw.
[0024] Preferably, the screw flight is supported on a hub.
[0025] Preferably, the screw flight is formed integrally with the
hub.
[0026] Preferably, the ground anchor further comprises an anchor
shaft on to which the anchoring screw is mounted.
[0027] The anchor shaft may be of hollow construction or solid
construction.
[0028] The tensile strength of the anchor shaft may be such that
sufficient torsional capacity is available to effectively wind the
anchor into the ground. Thus a separate torque tube need not be
necessary.
[0029] The anchor shaft may be of one-piece construction or
alternatively it may comprise a plurality of sections adapted to be
fitted together. The latter arrangement is advantageous in that it
provides for selective variation of the length of the anchor
shaft.
[0030] Preferably, the anchoring screw is secured in position on
the anchoring shaft. Conveniently, the anchoring screw may be
moulded onto the anchoring shaft. The anchoring shaft may have
provision for keying the moulded anchoring screw onto the
shaft.
[0031] Conveniently, the anchoring shaft is of a cross-sectional
shape other than circular in order to facilitate torque
transmission between the anchoring shaft and the anchoring screw
without relying totally on the bond therebetween. Conveniently, the
anchoring shaft is of a polygonal cross-section, such as hexagonal
or rectangular cross-section.
[0032] Without wishing to be limited as to the technical
correctness of such beliefs, the inventor believes that reasons as
to why the use of a resiliently flexible screw flight provides an
improvement in the ground holding ability of a ground anchor,
resides in the fact that the pitch of the helical shape is
permitted to alter during ground embedment as ground pressure
increases. It is believed that the change in pitch effectively
compresses the soil in a given zone. Such compression effectively
extends the zone of influence of the helical screw beyond the
diameter of the helical screw itself. Thus the effective diameter
of the screw flight is increased. Put another way, the action of
the resiliently deformed helical shape creates increased soil
pressure providing additional breakout threshold capacity in
shallow anchoring applications, thus improving the effectiveness of
the anchor for a given helix size.
[0033] Furthermore, it has been found that flexibility provided by
the flexible helical shape material behaves as a shock absorber in
cyclic tensile load conditions, reducing the snatch effect upon
connections to the ground anchor (such as connecting tendons or guy
wires).
[0034] The transfer of the downward and rotational forces to the
screw flight via the anchor shaft, and the subsequent transfer of
those forces into the ground effects anchor embedment. These forces
allow simultaneous embedment of the helical shape and the anchor
shaft. The configuration of the screw flight pulls the complete
assembly into the ground to the required depth.
[0035] Preferably, the anchor shaft has a foot end configured for
ground penetration. The end may also be configured to displace the
soil around the shaft.
[0036] Preferably, the head end of the anchor shaft is utilised to
drive the anchor into the ground. Typically the head end is square
or hexagonal to accept drive adaptors.
[0037] The head end of the anchor shaft may have at least one drive
hole located through the side of the shaft. The drive hole may
accept a drive pin.
[0038] The invention lends itself particularly well to ground
anchors that can be manually inserted, or inserted with the use of
conventional and readily available tools, such as wrenches,
spanners or hand operated power tools (eg battery operated drills).
The ground anchor may, for example, be wound into the ground
manually using a tool such as a T-bar arrangement.
[0039] The ground anchor may be removable by reversing the
direction of embedment rotation force. The opposite rotation force
required to withdraw the ground anchor is typically less than the
original installation force due to the behaviour of the flexible
screw. Specifically, tension induced in the screw flight as it
resiliently deflects during installation of the ground anchor is of
assistance in the unwinding action.
[0040] Preferably, the ground anchor is intended for reusable
use.
[0041] According to a second aspect of the invention there is
provided a ground anchor comprising an anchor shaft and an
anchoring screw on the anchor shaft, the anchoring screw comprising
a screw flight winding about a screw axis, the screw flight being
generally rigid with some lateral resilient flexibility.
[0042] The ground anchor according to the invention may be used in
conjunction with a lateral stabilisation device adapted to be
fitted onto the anchor shaft and to engage the ground to provide
lateral stabilisation to the shaft within the ground.
[0043] Preferably the lateral stabilisation device comprises a body
adapted to be fitted onto the anchor shaft for engagement with the
ground to provide lateral support for the anchor shaft with respect
to the ground.
[0044] Preferably, the body is adapted to be rotatably supported on
the shaft. In this way, the body can be drawn into engagement with
the ground surface as the ground anchor is embedded into the
ground. Because the body is rotatably supported with respect to the
anchor shaft, the anchor shaft can rotate as the anchor is embedded
into the ground while the body does not rotate.
[0045] Preferably, the body incorporates a bearing surface and the
shaft is provided with an abutment for engaging against the bearing
surface for urging the body into engagement with the ground as the
ground anchor is embedded into the ground. The bearing surface may
be defined by a thrust bearing in the body. Typically, the thrust
bearing is of metal. The abutment provided on the anchor shaft may
comprise a pin projecting from the shaft.
[0046] The body may comprise one or more lateral projections
presenting surfaces for engagement with the ground.
[0047] Preferably there are a plurality of the lateral projections.
The lateral projections may be configured as vanes. Conveniently
there are four vanes arranged in an X formation when viewed in
plan.
[0048] Each vane may be configured at the lower end thereof for
penetration with the ground.
[0049] Preferably, the body further comprises a sleeve section
defining a central passage for rotatably receiving the anchoring
shaft.
[0050] Preferably, the sleeve and the vanes are formed of a
plastics material.
[0051] The body may be of one-piece construction or it may be
assembled from a plurality of body sections. The latter arrangement
is particular convenient as it allows the length of the
stabilisation device to be selected according to the requirements
of the installation site.
[0052] Where the body is formed of a plurality of sections, the
sections preferably comprise a lowermost section and an uppermost
section. There may also be one or more intermediate sections
adapted for location between the lowermost and uppermost
sections.
[0053] Preferably, the lowermost section is configured for
penetrating the ground.
[0054] Preferably, the uppermost section preferably incorporates
the bearing surface.
[0055] The uppermost section may be adapted to receive a fitting to
which an object to be anchored by the ground anchor can be
attached. The fitting may comprise a plate adapted to be releasably
attached to an upper surface of the upper most body section. The
plate may carry a coupling element.
[0056] According to a third aspect of the invention there is
provided a method of manufacturing a ground anchor, the method
comprising providing an anchor shaft, and moulding an anchoring
screw onto the anchor shaft.
[0057] Preferably, the method further comprises configuring the
shaft for keying the moulded anchoring screw onto the shaft.
[0058] According to a fourth aspect of the invention there is
provided a lateral stabilisation device for a ground anchor having
an anchor shaft, the lateral stabilisation device comprising a body
adapted to be fitted onto the anchor shaft for engagement with the
ground to provide lateral support for the anchor shaft with respect
to the ground. Preferably, the body is adapted to be rotatably
supported on the shaft.
[0059] Preferably, the body incorporates a bearing surface against
which an abutment on the anchor shaft engages for urging the body
into engagement with the ground as the ground anchor is embedded
into the ground.
[0060] The body may be configured to present one or more lateral
surfaces for engagement with the ground.
BRIEF DESCRIPTION OF THE DRAWINGS
[0061] The invention will be better understood by reference to the
following description of several specific embodiments thereof as
shown in the accompanying drawings in which:
[0062] FIG. 1 is a schematic perspective view of a ground anchor
according to a first embodiment;
[0063] FIG. 2 is a side elevational view of the ground anchor of
the first embodiment;
[0064] FIG. 3 is a fragmentary perspective view of the lower end of
the ground anchor showing in particular the anchoring screw;
[0065] FIG. 4 is a view similar to FIG. 3 but viewed from a
different position;
[0066] FIG. 5 is a side elevational view of the anchoring
screw;
[0067] FIG. 6 is a plan view of the anchoring screw;
[0068] FIG. 7 is a side view of a ground anchor according to a
second embodiment;
[0069] FIG. 8 is a plan view of an anchoring screw for a ground
anchor according to a third embodiment;
[0070] FIG. 9 is a plan view of an anchoring screw for a ground
anchor according to as fourth embodiment;
[0071] FIG. 10 is a plan view of an anchoring screw according to a
fifth embodiment;
[0072] FIG. 11 is a fragmentary side elevational view of a ground
anchor according to a sixth embodiment, with the ground anchor
incorporating a lateral stabilisation device;
[0073] FIG. 12 is a view similar to FIG. 11 with the exception that
the lateral stabilization device is shown in section;
[0074] FIG. 13 is a perspective view of the ground anchor shown in
FIG. 11, but with the lateral stabilisation device shown in an
exploded condition;
[0075] FIG. 14 is an exploded perspective view of the lateral
stabilisation device;
[0076] FIG. 15 is a side elevational view of a ground anchor
according to a seventh embodiment for supporting a pole;
[0077] FIG. 16 is a fragmentary view of the ground anchor of FIG.
15, with the ground anchor being shown supporting a pole in a
tilted condition; and
[0078] FIG. 17 is a fragmentary view of the ground anchor of FIG.
15 shown in a condition for installation.
BEST MODE(S) FOR CARRYING OUT THE INVENTION
[0079] Referring to FIGS. 1 to 6, there is shown a ground anchor 10
according to a first embodiment. The ground anchor 10 comprises an
anchor shaft 11 and an anchoring screw 13 fitted onto the anchoring
shaft adjacent the lower end thereof. The anchoring shaft 11 is of
polygonal cross-sectional, and in the arrangement shown is of
rectangular cross-section with four side walls 12. The anchoring
shaft 11 is configured at its bottom end 15 for ground penetration.
In the arrangement shown, the bottom end is provided with a point
17 generated by an angular cut on the shaft. The point 17 serves to
penetrate the ground and also displace soil sidewardly as it
advances through the ground.
[0080] The upper end 19 of the anchor shaft 11 is configured to
receive torque applied thereto. The upper end 19 may be configured
to receive a tool such as a torque tube through which torque may be
applied to the anchor shaft 11. The torque may be applied manually
or through a power device, such as for example, a portable electric
drill.
[0081] The upper end 19 also incorporates at least one transverse
hole 20 which can receive a drive pin or provide an attachment
point.
[0082] The anchoring screw 13 comprises a hub 21 and a screw flight
23 on the hub. In this embodiment, the screw flight 23 is formed
integrally with the hub 21. The screw flight 23 comprises a helical
screw 26 having a leading end 27 and a trailing end 29 extending
outwardly of the hub 21. The screw flight 23 presents a spiralling
upper surface 31 and a spiralling lower surface 32. The upper and
lower surfaces 31, 32 taper inwardly with respect to each other in
the radially outer direction and terminate at a peripheral edge
33.
[0083] The screw flight 23 winds about a screw axis through
approximately one revolution such that the trailing edge 29 is
located approximately above the leading edge 27 at a spacing
corresponding to the pitch of the spiral flight. The screw axis is
coincident with the central longitudinal axis of the anchor shaft
11.
[0084] The anchoring screw 13 is moulded onto the anchor shaft 11,
and the hub 21 is keyed to the anchor shaft. This is achieved by
the provision of keys (not shown) configured as transverse channels
in at least some of the side walls 12 of the anchor shaft. Further,
one or more of the side walls 12 may be deformed in order to
promote keying with the hub 21. With this arrangement, the
anchoring screw 13 is keyed to the anchor shaft 11 when it is
moulded into position onto the anchor shaft.
[0085] The anchoring screw 13 is formed of a composite plastics
material, having a high stiffness, such as Nylon 66 incorporating
reinforcing fibres.
[0086] The anchoring screw 13 is so constructed that the spiral
flight 23 is rigid yet has some resilient flexibility which allows
the flight to deflect laterally in the direction of the screw axis.
Specifically, the screw flight 23 has sufficient rigidity to allow
it to penetrate the ground in which it is intended to be used when
torque is applied to the anchor shaft 11. Further, the screw flight
23 has sufficient rigidity in order to retain the ground anchor 10
embedded in the ground when subjected to the normal load conditions
for which it is intended, as is the case, with conventional ground
anchors.
[0087] The resilient flexibility provides the screw flight 23 with
a degree of "springiness", so allowing the screw flight to deflect
laterally in the direction of the screw axis when subjected to the
loadings to which it is exposed when winding into the ground. With
this arrangement, the pitch of the helical screw is permitted to
after during ground embedment as ground pressure increases. It is
believed that the change in pitch effectively compresses the soil
in a given zone. Such compression effectively extends the zone of
influence of the anchoring screw 13 beyond the diameter of the
anchoring screw itself. Thus the effective diameter of the
anchoring screw is increased. Furthermore, the resilient
flexibility of the screw flight 23 can function to absorb shock in
cyclic tensile load conditions, thereby reducing the snatch effect
upon connections to the ground anchor.
[0088] The extent of resilient deflection of the screw flight 23
can depend upon various factors, including the density of the soil,
the size and configuration of the helical screw 25, the size of the
anchor shaft 11, and the size of the helical screw 25 in proportion
to the size of the anchor shaft 11.
[0089] The pitch change can be in the order of about 1 mm or less
in certain cases. In other cases, it may be up to 20 mm or
more.
[0090] The screw flight 23 is adapted for selective variation of
the circumference thereof. In this embodiment, markings 40 are
provided on one side of the spirally flight 29, typically the
underside 32. The markings 40 may comprise guide lines 41 along
which the spiral flight 23 can be out in order to reduce the outer
diameter of the spiral flight 23 if desired. In the arrangement
shown, there are two guide lines 41, so offering two alternative
sizes for the helix. Typically, the spiral flight 23 would be cut
along the inner mark for dense soil conditions and along the outer
mark for firm soil conditions. The spiral flight would be retained
at its original size for loose soil conditions.
[0091] The ground anchor 10 is wound into the ground in the
conventional way; that is, by application of embedment torque to
the upper end 19 thereof. The torque can be applied in any
appropriate way, such as manually using a tool such as a T-bar
arrangement or using a power assisted means such as an electric or
battery operated hand drill coupled to the anchoring shaft through
a connecting socket.
[0092] The ground anchor 10 is removable by reversing the direction
of the embedment torque. The reverse torque required to withdraw
the ground anchor is likely to be less (and possibly considerably
less) than the original installation force due to the behaviour of
the resiliently flexible spiral flight 23.
[0093] Referring now to FIG. 7 of the drawings, there is shown a
ground anchor 50 according to a second embodiment. The ground
anchor 50 according to the second embodiment is similar in many
respects to the ground anchor 10 according to the first embodiment
and so corresponding reference numerals are used to identify
corresponding parts. In this second embodiment, the ground anchor
50 is provided with a second anchoring screw 51. The second
anchoring screw 51 is of a similar construction to the first
anchoring screw 13 and is spaced therefrom along the anchoring
shaft 11. More anchoring screws may also be provided on the
anchoring shaft for certain applications, if desired.
[0094] In the first and second embodiments, the leading and
trailing edges 27, 29 of the screw flight 23 extend outwardly from
the hub 21 in a generally radially direction. Other arrangements
are, of course, possible. Several possible variations are
illustrated in FIGS. 8, 9 and 10 of the drawings. As each anchoring
screw is of a somewhat similar configuration to the anchoring screw
13 of the first embodiment, corresponding reference numerals will
be used to identified corresponding parts.
[0095] Referring now to FIG. 8, there is shown an anchoring screw
60 for a ground anchor according to a third embodiment. In this
embodiment, the leading edge 27 of the spiral flight 23 is not
generally straight (as was the case with the previous embodiments)
but rather it is configured to present a curved profile 61 towards
the radially outer end thereof. The curved profile 61 comprises a
curve which merges with the outer circumference 33. The curved
configuration serves to displace rock and debris in the path of the
leading edge 27 outwardly away from the rotating helix as it winds
into the ground.
[0096] With the arrangement shown in FIG. 8, the curved profile 61
can increase the horizontal component of separation between the
leading and trailing edges of the screw. In certain circumstances,
such separation may be undesirable as it may disrupt the uniformity
of loading on the anchoring screw. With a view to addressing this
deficiency, the anchoring screw may be configured so that there is
some vertical overlap between the leading and trailing edges. Such
an arrangement is provided by the next embodiment. Referring now to
FIG. 9, there is shown an anchoring screw 70 for a ground anchor
according to a fourth embodiment. In this embodiment, the leading
edge 27 incorporates the rounded profile 61 of the previous
embodiment but the relative positions of the leading and trailing
edges are moved angularly such that there is overlap
therebetween.
[0097] There may be some situations where there is no need to
provide overlap between the leading and trailing edges 27, 29 of
the this anchoring screw. Such an arrangement is provided by the
next embodiment. Referring now to FIG. 10 of the drawings, there is
shown an anchoring screw 80 for such a ground anchor according to a
fifth embodiment. As can be seen in FIG. 10, the spacing between
the leading and training edges 27, 29 has a horizontal
component.
[0098] With regard to the arrangements shown in FIGS. 8, 9 and 10,
it should be understood that the profile of the rounded leading
edge can vary.
[0099] In certain applications, it may be desirable or necessary to
provide the anchoring shaft with lateral stability when embedded in
the ground. Referring now to FIGS. 11 to 14, there is shown a
ground anchor 100 having provision for lateral support at the upper
end thereof.
[0100] The ground anchor 100 according to this embodiment is
similar to the ground anchor 10 according to the first embodiment,
and so corresponding reference numerals are used to identify
corresponding parts. In this embodiment, the provision for lateral
support comprises a device 110 adapted for location on the anchor
shaft 13. The device 110 comprises a body 111 adapted to be fitted
onto the upper end portion of the anchor shaft 11. The body 111
comprises a central sleeve 113 which is of cylindrical
configuration and which defines a central passage 115 into which
the anchor shaft 11 can be received. The central passage 115 is so
dimensioned that the anchor shaft can rotate within the passage.
The central passage 115 has an enlarged section 117 adjacent its
upper end. The enlarged section 117 opens onto the top end 119 of
the body defined by a top wall 120. A shoulder 121 is defined at
the inner end of the enlarged section 117.
[0101] The shoulder 121 provides a seat 123 for a thrust bearing
125. In this embodiment, the thrust bearing 125 comprises a washer
which is located on the seat 123. The thrust bearing 125 is adapted
to present a rigid surface against which an abutment 127 on the
anchor shaft 13 can bear to transmit an axial force from the anchor
shaft 11 to the body 111. In this embodiment, the abutment 127
comprises a drive pin 129 accommodated in the transverse hole 20 in
the shaft.
[0102] The enlarged section 117 defines a recess 131 in which the
drive pin 129 and the end portion of the anchor shaft 13 thereabove
can be accommodated. A cap 133 is provided for closing the upper
end of the recess 131. The cap 133 may be of tamper-proof
construction. The cap 133 presents an outer surface 135 which
locates within the plane of the surface 137 at the top end 119 of
the body.
[0103] The body 111 is provided with a plurality of vanes 141
projecting radially outwardly from the central sleeve portion 113.
Each vane 141 presents two opposed broad side surfaces 143, 144 and
an outer edge 145. In the arrangement shown, there are four vanes
141, arranged in an X configuration when viewed in plan.
[0104] The vanes 141 are formed integrally at their upper end 151
with the top wall 120 of the body. Further, the vanes 141 are
configured at their lower ends 153 to penetrate the ground. In this
regard, the lower ends 163 are provided with angled corners 155
which provide a somewhat pointed configuration to the lower end of
the body 111 for ground penetration.
[0105] While the body 111 can be of one piece construction, it
comprises a plurality of sections 160 in this embodiment. The
sections 160 comprise a lowermost section 161, an uppermost section
162 and an intermediate section 163 between the lowermost and
uppermost sections. The lowermost section 161 is configured to
incorporate the angled corners 155. The uppermost section 162 is
configured to incorporate the recess 131. With this arrangement,
each vane 141 also comprises three vane sections.
[0106] The three body sections 161, 162 and 163 are adapted to be
connected one with respect to another to restrain relative rotation
therebetween. The connection is by way of locating spigots 171
provided on one body section for location in matching sockets 173
provided on an adjacent body section. Specifically, the bottom edge
of each vane section of the upper body section 163 is provided with
a spigot 173 for location in a corresponding socket 173 on the
upper edge of the adjacent intermediate vane section. Further, the
lower edge of the intermediate vane section is provided with a
spigot 171 for location in a corresponding socket 173 on the upper
edge of the adjacent lower vane section.
[0107] The top wall 120 of the body 111 is adapted to support a
plate (not shown) which can be secured thereto by a fasteners such
as screws threadedly engaging holes 185 incorporated in the vanes
141. The vanes 141 incorporate boss sections 185 at their upper
ends to accommodate the holes. The plate supports at coupling 185
which a device to be anchored with respect to the ground by way of
the ground anchor 100 can be tethered. The coupling may comprise a
coupling pin upstanding from the plate and secured to in a manner
permitting axial rotation of the pin with respect to the plate. The
coupling may further comprise a shackle connected to the pin.
[0108] In this embodiment, the body 111 is moulded from a plastics
material.
[0109] In operation, the device 110 is embedded into the ground by
the driving and pulling forces exerted on it by the ground anchor
100 as the latter is embedded in the ground. The recess 131 at the
upper end of the body 111 provides access to the upper end 19 of
the anchor shaft 13 for application of embedment torque to the
ground anchor. More particularly, the recess provides access for a
torque tube to be fitted onto the upper end of the ground anchor
100. Further, the recess 131 provides access for anchoring onto the
anchor shaft 11, if required.
[0110] As the ground anchor 100 is installed into the ground, the
drive pin 129 engages against the thrust bearing 125 and applies a
downward force onto the body 111, so urging the body into contact
with the ground. Once the body 111 contacts the ground it is
restrained against rotation because of the engagement with the
ground. However, this does not interfere with continued rotation of
the anchor shaft 11 which can freely rotate within the central
sleeve portion 113 of the body 111 and the thrust bearing 125 as
previously explained. The drive pin 129 rotates with the anchor
shaft 13 and is in sliding contact with the thrust bearing 125. The
continued downward movement of the anchor shaft 13 applies an
ongoing downward force to the body 111 through engagement between
the drive pin 129. The leading (lower) end of the body 111 engages
and cuts the ground during downward movement of the body. At
completion of the installation process, both the ground anchor 100
and the device 110 are locked into the ground. Typically,
installation is complete when the upper end of the device 110 is at
ground level.
[0111] Once the device 100 is in the ground, it provides lateral
support for the anchor shaft 13. The lateral support is afforded by
the presence of the vanes 141 which project outwardly and present
broad opposed surfaces to the ground. With this arrangement, the
device 110 can transfer any horizontal load exerted on the anchor
to the surrounding ground and in this way utilise the passive
resistance properties of the ground to transfer these loads. This
action limits the sideways movement of the ground anchor when
subjected to such horizontal loads.
[0112] The body 111 is locked into the ground by the drive pin 129
pushing down on the bearing 125 and the passive resistance of the
soil against the body 111 (including against top wall 120), as well
as the increased resistance of the soil pressure against the ground
anchor helical shape as it changes in helical plane pitch.
[0113] The length of the body 111 is selected according to the load
to be anchored and the characteristics of the installation site.
The length can be varied as necessary by incorporating one or more
of the intermediate body sections 163, or alternatively omitting
the intermediate body section 163 when a short length be required.
Indeed, in certain applications, it may be appropriate to use only
the uppermost section 162.
[0114] The device 110 is automatically installed in the ground at
the same installation angle as the ground anchor.
[0115] Referring now to FIGS. 15, 16 and 17, there is shown an
anchoring arrangement 180 designed particularly to support an
upstanding elongate element such as a pole 181. The pole 181 may
comprise, for example, the shaft of a beach umbrella.
[0116] The anchoring arrangement 180 comprises a ground anchor 135
of similar construction to the ground anchor 10 according to the
first embodiment and a coupling 187 at the upper end of the ground
anchor for receiving and supporting the pole 181.
[0117] The coupling 187 comprises a sleeve 189 for receiving and
supporting the lower end of the pole and locking means 191 for
releaseably locking the pole 181 within the sleeve. In the
arrangement shown, the looking means 191 comprises a hand screw 193
operable to bear at its inner end against the pole 181 and thereby
clampingly retain it within the sleeve 189. The sleeve 189 is
connected to the anchor shaft 13 by way of hinge mechanism 195
incorporating hinge pin 197. With this arrangement, sleeve 189 can
be rotated through 90 degrees, between an upright condition (as
shown in FIG. 15) to support the pole in an upright position, and a
generally horizontal condition in which the sleeve 189 can function
as a handle for turning the anchoring shaft 11 for manual
installation of the ground anchor 10 (as shown in FIG. 11).
[0118] A releasable locking mechanism 199 for locking the sleeve
189 in the upright condition. The locking mechanism 199 also has
provision for locking the sleeve 189 in a selected one or more of
available angular conditions between the upright condition and the
horizontal condition, one such angular conditions being the angular
position shown in FIG. 17. The locking mechanism 199 may also look
the sleeve 189 in the horizontal condition.
[0119] From the foregoing, it is evident that the present
embodiment provides a simple yet highly effective ground anchor
which has improved performance characteristics arising from the
substantially rigid yet resiliently flexible characteristics of the
spiral flight.
[0120] The ground anchor according to the invention can be used in
a wide range of applications, as would be apparent to a skilled
addressee. The ground anchor is, however, particularly suitable for
applications where temporary anchoring is required. By way of
example, the ground anchor can be particularly suitable for
tethering of animals, and for anchoring boats and other water craft
at shore. In such applications, the ground anchor is particularly
advantageous as it can be embedded entirely, or almost entirely,
into the ground and therefore not present an obstacle to persons in
the vicinity, and also be subsequently removed. Ground anchors
according to the invention can be used for anchoring tents and
other structures, as well as for guy wires and the like. Further,
ground anchors according to the invention can be used as footings
for structures.
[0121] The ground anchors according to the invention can be used
either with or without the lateral stabilisation devices.
[0122] Further, the lateral stabilisation devices may have
application to ground anchors other than ground anchors of the type
according to the present invention.
[0123] It should be appreciated that the scope of the invention is
not limited to the scope of the various embodiments described.
[0124] Modifications and improvements can be made without departing
from the scope of the invention.
[0125] Throughout the specification, unless the context requires
otherwise, the word "comprise" or variations such as "comprises" or
"comprising", will be understood to imply the inclusion of a stated
integer or group of integers but not the exclusion of any other
integer or group of integers.
* * * * *