TECHNICAL FIELD

The present invention relates to an anchor and an associated method. Embodiments of the present invention find application, though not exclusively, in providing an anchoring point, which may be used to prevent unwanted movement of objects, land formations, etc.

BACKGROUND ART

Any discussion of documents, acts, materials, devices, articles or the like which has been included in this specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed in Australia or elsewhere before the priority date of this application.

It is known to provide anchors that may be driven into the ground and which rotate when retracted, thereby lodging themselves within the ground to act as an anchor point.

Various such anchors are currently on the market; however it has been appreciated by the inventors of the present invention that aspects of the current anchors may be varied with the potential to yield desirable characteristics such as an improved strength to weight ratio, improved lodgement of the anchor within the ground, improved load carrying capacity, etc.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome, or substantially ameliorate, one or more of the disadvantages of the prior art, or to provide a useful alternative.

In one aspect of the present invention there is provided an anchor including:

a body extending between a leading end and a trailing end;

a burrowing formation being disposed at said leading end;

a drive receiving formation being disposed at said trailing end; and

a tether attachment formation being disposed intermediate said leading and said trailing ends;

wherein the body has a polygonal cross section. Preferably a number of sides of the polygonal cross section is greater than 4. More preferably the number of sides of the polygonal cross section is between 5 and 10 inclusive. Even more preferably the number of sides of the polygonal cross section is between 6 and 8 inclusive and in a preferred embodiment the polygonal cross section is hexagonal.

Preferably the cross section of the body is continuously polygonal from adjacent the leading end to adjacent the trailing end.

In an embodiment the body defines a longitudinal axis and the trailing end defines a trailing surface that is inclined at an acute angle relative to the longitudinal axis. In this embodiment the trailing surface defines a trailing edge that intersects with a side of the polygonal cross section. In a region adjacent to the trailing edge, the side that intersects with the trailing edge progressively diverges from the longitudinal axis.

In an embodiment the attachment formation is a projection defining an aperture.

Preferably the tether attachment formation is disposed along the length of the body such that there is less load bearing area between the tether attachment formation and the leading end as compared to the load bearing area between the tether attachment formation and the trailing end so as in use to promote rotation of the anchor upon the application of a retractive force to the tether attachment formation.

Preferably the tether attachment formation is for attachment of a clevis and the attachment formation includes a stop surface positioned so as to restrain a clevis attached to the attachment formation from rotating beyond a predetermined angle relative to the longitudinal axis. In one embodiment the predetermined angle is 90°.

Preferably a surface extends between the leading end and the attachment formation so as to taper the attachment portion towards the leading end.

In one embodiment at least one wing is disposed upon the body and a leading edge of the wing defines a burrowing edge. In one embodiment the wing tapers in thickness from a maximum thickness at an edge proximal to the body to a minimum thickness at an edge distal from the body. Preferably the tapering is at an angle of between 5° and 15°.

According to a second aspect of the invention there is provided a method of anchoring an object, the method including the steps of:

providing an anchor as described above with a tether attached to the tether attachment formation;

engaging a drive rod with the drive receiving formation;

exerting a force on the drive rod so as to drive the anchor into a ground;

disengaging the drive rod from the drive receiving formation;

exerting a retraction force on the tether so as to rotate the anchor into anchoring engagement with the ground; and

attaching the tether to the object.

The features and advantages of the present invention will become further apparent from the following detailed description of preferred embodiments, provided by way of example only, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Figure 1 is a front-perspective view of a first embodiment of the invention; Figure 2 is a rear-perspective view of the first embodiment;

Figure 3 A is a left side view of the first embodiment (with the right side view being a mirror image);

Figure 3B is a left side view that is identical to that of figure 3 A, except for a dotted line indicating the longitudinal axis;

Figure 4 is a plan view of the first embodiment;

Figure 5 is a front view of the first embodiment;

Figure 6A is a rear view of the first embodiment; Figure 6B is a rear view that is identical to that of figure 6A, except for a thick line marking that indicates the hexagonal cross section;

Figure 7 is a bottom view of the first embodiment;

Figure 8 is a plan view of a second embodiment of the anchor;

Figure 9 is a plan view of a third embodiment of the anchor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Referring to the figures, the anchor 1 includes a body 2 extending between a leading end 3 and a trailing end 4. The references to "leading" and "trailing" refer to the intended direction of motion when the anchor 1 is being driven into the ground. This "leading" and "trailing" naming convention is used consistently in this document regardless of whether the anchor 1 is being described as being driven into the ground or being retracted there from.

A burrowing formation 5 is disposed at the leading end. The burrowing formation 5 is modelled upon the cutting end of a rock chisel. It defines a cutting edge 6 at the intersection of a first surface 7 and a second surface 8. The included angle between the first surface 7 and the second surface 8 is approximately 70°. As can be best seen from the front view of figure 5, the length of the cutting surface 6 is approximately half of the width of the body 6 (not including the wings 9 and 10, which for these purposes are not considered to be a part of the body, despite being formed integrally therewith.).

As can be best seen from the side view of figure 3 A, the first and second surfaces 7 and 8 extend for only a short proportion of the total length of the anchor 1. The first surface 7 intersects with a third surface 11, a fourth surface 12 and a fifth surface 13. The third surface 1 1 and the fifth surface 13 are inclined at an angle of approximately 16° relative to the longitudinal axis 14. The fourth surface 12 is inclined at an angle of approximately 30° relative to the longitudinal axis 14 and extends between the leading end 3 and the attachment formation 20 so as to taper the attachment portion 20 towards the leading end 3. This continuous tapering from the tether attachment formation 20 all the way to the burrowing foraiation 5 contributes additional strength to the anchor and helps to minimise the burrowing forces that act upon the tether attachment formation 20. Whilst burrowing, the first, third, fourth and fifth surfaces 7, 11, 12 and 13 displace soil and other detritus perpendicularly away from the cutting edge 6 towards the top of the anchor 1 as it is depicted in the drawings.

The second surface 8 intersects with a sixth surface 15, which is inclined at an angle of approximately 16° relative to the longitudinal axis 14. Whilst burrowing, the second and sixth surfaces 8 and 15 displace soil and other detritus perpendicularly away from the cutting edge 6 towards the bottom of the anchor 1 as it is depicted in the drawings.

The seventh and eight surfaces 16 and 17 are chamfers that act to displace soil and other detritus to either side of the cutting edge 6 during burrowing. When viewed in plan, the seventh and eight surfaces 16 and 17 are inclined at approximately 24° relative to the longitudinal axis 14. Together, the first, second, third, fourth, fifth, sixth, seventh and eighth surfaces 7, 8, 1 1, 12, 13, 15, 16 and 17 form the burrowing formation 5. It is believed by the inventors (although has not yet been experimentally verified) that the burrowing formation 5 of the preferred embodiment of the anchor 1 will have the potential to allow less force to be used when burrowing the anchor into hard ground as compared to the known prior art anchors.

The burrowing formation 5 that is modelled upon the cutting end of a rock chisel is believed by the inventors to be less susceptible to chipping as compared to the stepped heads of some of the prior art anchors.

As best shown in figures 2, 4 and 6, a drive receiving formation 18 in the form of an aperture 19 is disposed at the trailing end 4. This aperture 1 extends longitudinally along a proportion of the body 2, for example between approximately 40% to 70% of the total length of the anchor 1. The aperture 19 is sized to receive a drive rod (not illustrated). The aperture 19 is centred upon the longitudinal axis 14 of the body 2 (although the ramped portion 24 that is formed by the lower surface 27 at the trailing end 4 of the body 2 is ignored for the purposes of this centering). The presence of the end of the rod within the aperture 19 keeps the anchor 1 pointing in the desired direction whilst it is being burrowed into the ground.

When viewed from the side, such as shown in figure 3A for example, a tether attachment formation 20 is disposed intermediate of the leading end 3 and the trailing end 4. The tether attachment formation 20 is in the form of a hole 21 defined within projection 22 to which a tether (not illustrated) is attachable. In one embodiment the tether is in the form of a rope, cord, cable or wire that is looped through the hole 21. In another embodiment, the tether is in the form of an elongate rod that is attached to the hole by a clevis. In yet another embodiment the tether is in the form of a bar that attaches directly to the tether attachment formation 20. In a further embodiment the tether is in the form of a shackle attaching a chain to the tether attachment formation 20. As will be appreciated, the tether attachment, and tether, may take yet other forms.

To anchor an object using the anchor 1, the user commences by attaching a tether, such as a cable, bar or rod and clevis, to the tether attachment formation 20. Alternatively, the anchor 1 may be supplied to the end user with the tether pre-attached by the supplier. Next the anchor 1 is placed on the ground in the intended deployment area and a drive rod is inserted into the aperture 19 of the drive receiving formation 18. Then a driver, such as a sledge hammer or a small jackhammer, is used to exert a force on the drive rod so as to drive the anchor 1 into the ground. Once the anchor 1 has been burrowed a sufficient distance into the ground, the drive rod is removed and a retraction force is exerted on the tether as if to pull the anchor back out of the ground. However, as will be described in more detail below, the geometry of the anchor 1 is such that it would typically only retract a very short distance before starting to rotate into anchoring engagement with the ground. Once rotated, the anchor is embedded within the ground and the tether may be attached to the object that is to be anchored.

The tether attachment formation 20 is disposed along the length of the body 2 such that when viewed in plan there is slightly less load bearing area between the tether attachment formation 20 and the leading end 3 as compared to the load bearing area between the tether attachment formation 20 and the trailing end 4. That is, when the anchor 1 is viewed in plan, a line may be drawn through the centre of the hole 21 perpendicular to the longitudinal axis 14 and the surface area from the plan perspective computed on either side of the line. The surface area on the leading end 3 side of the line should be slightly less than the surface area on the trailing end 4 side of the line. This positioning creates a slight imbalance when a retraction force is being applied to the tether, which desirably promotes rotation of the anchor 1 when a force is applied to the tether attachment formation 20 in an attempt to retract the anchor 1 from the ground. The rotational effect arises because the trailing half of the anchor 1 can present a slightly greater surface area to resist withdrawal as compared to the surface area presented by the leading half of the anchor 1.

For applications in which the tether attachment is via a clevis the tether attachment formation 20 includes a pair of stop surfaces 28 that are positioned so as to restrain the clevis from rotating beyond a predetermined angle, such as 90°, relative to the longitudinal axis 14. This prevents the anchor from over rotating in response to the application of a retractive force via the tether. Otherwise, such over rotation could allow the anchor to rotate through 180° and it would then be free to retract from the ground rather than to lodge into the ground in the desired fashion. It also inhibits the anchor from rotating to some angle between 90° and 180°, which may still allow the anchor to lodge into the ground, but in a manner that presents less surface area upon which an anchoring frustum of soil may act.

The cross section of the body 2 is continuously polygonal from the leading end 3 to the trailing end 4. The number of sides of the polygonal cross section of the body 2 is preferably greater than four. In this document, including within the claims, phrases such as "the cross section of the body", and the like, are to be assessed without reference to addenda such as the burrowing formation 5, the tether attachment formation 20 or the wings 9 and 10. This is so even if those addenda are integrally formed with the body 2. Consistent with this approach, the cross section of the body 2 of the preferred embodiment illustrated in figure 6A would be assessed to be hexagonally shaped. For ease of reference, this hexagonal shape is shown in the thicker outline as marked on figure 6B. The six surfaces that together define the external boundary of the hexagonal cross section of the body 2 are: the upper surface 34; the upper left surface 35; the upper right surface 36; the lower surface 27; the lower left surface 37; and the lower right surface 38. (Note: the references to "upper" and "lower" are merely relative to the orientation of the anchor as depicted in the drawings; in practice the anchor 1 may be used in any desired orientation.)

Computerised simulated analysis of the preferred embodiment having a body 2 with a hexagonal cross section yielded an approximately 10% greater resistance to bending or breakage as compared to the simulated strength properties of a similarly sized anchor having a cylindrical body. A hexagonal cross sectional shape is considered by the inventors to strike a desirable balance between strength and weight. In particular, the hexagonal cross sectional shape yields an anchor with desirable strength properties relative to the amount of material from which it is manufactured. It is believed by the inventors (although has not yet been experimentally verified) that the hexagonal cross sectional body 2 of the preferred

embodiment of the anchor 1 will have the potential to exhibit less deflection along its length when it is being forced into hard ground as compared to the deflection typically exhibited by known cylindrical bodied prior art anchors.

Additionally, the hexagonal cross sectional shape neatly accommodates the central circular aperture 19 of the drive receiving formation 20. However, it will be appreciated that other embodiments may utilise a differing number of sides, such as between five and ten inclusive and more preferably between six and eight inclusive.

The improved strength-to -weight ratio given by the polygonal cross section of the preferred embodiment provides options such as providing a lighter anchor that is nevertheless of equal strength compared to the prior art cylindrical bodied anchors. Another option, which is favoured by the inventors, is to take some of the material from the body 2 that is freed up by the improved strength characteristics and apply it to other areas of the anchor that would benefit from additional strengthening, such as the tether attachment formation 20 and/or the burrowing formation 5. In particular, an important aspect of the anchor is the strength properties of the tether attachment because breakage of the tether attachment is one of the failure modes of such anchors. Hence, in the preferred embodiment at least some of the material that is freed up by use of the hexagonal cross sectioned body 2 is reallocated to provide additional strengthening of the tether attachment formation 20. This approach yields an anchor that has a total weight that is roughly the same as a comparable prior art cylindrical bodied anchor. However, such an embodiment has a lighter hexagonal body 2 of

approximately equal strength to that of the prior art cylindrical bodied anchor, along with a heavier and stronger tether attachment. One example of such an embodiment (as illustrated in figures 1 to 7) is referred to internally by the inventors by model designation Ή50'. The properties of the H50 may be compared to an example cylindrical bodied prior art product, known as the DB88, which is sold by a competitor to the applicant. The overall dimensions of the H50 are generally comparable to those of the DB88. The holding capacity of the DB88, including a 2: 1 safety factor, in coarse gravel and cobbles is rated at 1365 kg. This is the rating at which the tether attachment may fail. In contrast, the holding capacity of the H50, including a 2: 1 safety factor, in coarse gravel and cobbles is rated at 2250 kg. Once again, this is the rating at which the tether attachment may fail, however as mentioned above, the present invention allows for the tether attachment formation 20 to be heavier and stronger.

It is thought by the inventors that the polygonal cross section of the body 2 of the preferred embodiment, and in particular the hexagonal cross sectional shape, will yield further advantages over the prior art cylindrical bodied anchors such as improved fixation within the ground once the anchor has been deployed. Additionally, the polygonal cross sectioned body 2 is likely to be more amenable to being manufactured by casting techniques because it is believed to allow for easier removal of slag as compared to prior art cylindrical bodied anchors. Some embodiments are manufactured from AS 1831 grade ductile iron and preferably from the 400-250-12 variant. Other embodiments are manufactured from stainless steel, aluminium, plastics and/or phosphor bronze.

As shown for example in figures 2 and 3 A, the body 2 defines trailing surface 25 at the trailing end 4 of the anchor 1 that is inclined at an acute angle relative to the longitudinal axis 14. In the preferred embodiment the acute angle is approx 38°. The trailing surface 25 defines a straight trailing edge 26 that intersects with the lower side 27 of the polygonal cross section of the body 2. The length of the straight trailing edge 26 is approximately half of the width of the body 2. When a retractive force is applied via the tether, the straight trailing edge 26 bites into the ground so as to commence rotation of the anchor 1. Cylindrical bodied prior art anchors have an analogous curved trailing edge that fulfils a similar role. However, it has been appreciated by the inventors of the present invention that the curved trailing edge of the prior art anchors can sometimes fail to bite into the ground, thereby failing to commence rotation and undesirably allowing the anchor to be retracted from the ground. This problem is particularly prevalent when attempting to lodge the prior art anchors into hard ground. In contrast, the straight length of the trailing edge 26 of the preferred embodiment of the present invention provides more opportunities for the trailing edge 26 to engage with harder surfaces when the anchor 1 is being retracted so as to promote rotation (as compared to the prior art anchors having a cylindrical body and defining a curved trailing edge.). As shown for example in figure 3 A, the side that intersects with the trailing edge 26 (i.e. the lower side 27) progressively diverges from the longitudinal axis 14 so as to form ramped portion 24. The provision of this ramped portion 24 promotes rotation of the anchor 1 in response to the application of a retractive force via the tether by positioning the trailing edge 26 so as to promote biting of the trailing edge 26 into the ground during retraction.

The wings 9 and 10 are disposed upon opposite sides of the body 2. Various embodiments offer wings 9 and 10 of differing widths. Generally, a wing having a shorter width is suitable for anchoring into harder ground and vice versa. The leading edges 29 and 30 of each respective wing 9 and 10 defines a burrowing edge to assist with penetration into the ground. As can be seen for example in figure 6A, each of the wings taper in thickness from a maximum thickness at an edge 31 proximal to the body 2 to a minimum thickness at an edge distal 32 from the body 2. The tapering is preferably at an angle of between 5° and 15° and in the preferred embodiment it is 9°. It is believed that this tapering may increase the frustum upon which the embedded anchor bears, which has the potential to increase the maximum load rating of the anchor 1.

As shown in figure 7 a hole 33 this is disposed in the lower surface 27. This hole allows gasses to escape from within the aperture 19 during coating of the anchor. Various embodiments may feature differing coatings, such as galvanising (including thermal diffusion galvanising), friction reducing coating or coating with zinc aluminium. An example of a commercially available coating is DACROMET®, which is a water-based inorganic metal finishing system that is available from the NOF Metal Coatings Group. It is also possible to apply combinations of the aforementioned coatings. Typically, it is the soil conditions into which the anchor 1 is proposed to be embedded that will determine the particular coating or coatings required.

Figure 8 is a plan view of a second embodiment of the invention that has some slight alterations to assist with manufacture. This embodiment has slight radiusing instead of shaip corners to assist with the casting process. The radiusing of the corners also contributes improved strength characteristics. Additionally, some of the straight edges have a minimal divergence from straight, which is known as a draft angle, to assist with casting or moulding of the anchor 1. Hence, in this embodiment the trailing edge 40 is not straight. Nevertheless, it is composed of two essentially straight portions, which are anticipated to give an improved 'bite' into the ground upon retraction as compared to the curved trailing edges of the cylindrical bodied prior art anchors.

Another difference between the first embodiment as illustrated in figures 1 to 7 and the second embodiment is the width of the wings 41 and 42, which is substantially longer in the second embodiment, and therefore more suited to use with softer ground. As can be seen in figure 9, the width of the wings 50 and 51 of the third embodiment is longer as compared to the corresponding dimension of the wings on the first and second embodiments.

While a number of preferred embodiments have been described, it will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.