FIELD OF THE INVENTION

The present invention relates to a device and method for retaining a growth medium such as soil on a sloped surface, such as a hill. The retained growth medium forms a platform for growing plants which can also be useful for reducing erosion and/or stabilising the sloped surface.

BACKGROUND

It can be difficult to cultivate plants on sloped surfaces:- the topsoil can be shallow, which limits the choice of plants able to be grown, or the surface can become unstable and/or susceptible to erosion when the existing covering is disturbed. To overcome this problem one possible solution is to grow the plants in pots; this is however limiting, in that the size of pots available limits the size of plants. It is difficult to grow a pine tree in a pot unless it is a bonsai. In addition, each plant often requires a separate pot; this is not practical or economical for large numbers of plants. A trough can be used to allow a number of plants to be grown. If the sloped surface is subject to earthworks, then pots and troughs do little to stabilise the surface, as the roots of the plants within are not normally growing in the sloped surface's topsoil. Troughs and pots are normally made of concrete or a similar material, these can be heavy and/or expensive. To allow the roots to grow into the topsoil open bottom pots or troughs can be used, though even these limit the size of the plant able to be grown. Open bottom troughs and pots can also be heavy and/or expensive.

Terraced blockwork, crib walling and retaining walls can be used to form a retaining structure for the sloped surface topsoil which can then be backfilled to create growing platforms. All of these are made up of bricks or blocks, generally of concrete or a similar material. This makes the structures heavy when complete, which means they often require firm bearing to be used. This may necessitate excavating the slope to provide this firm bearing, which adds to the cost and, due to the earthworks, can further destabilise the sloped surface. Each of these solutions requires the construction of a wall, this takes time and requires some skill to do properly. In the case of a retaining wall, it must also meet council or local authority's requirements, which often means it needs to be approved prior to construction and inspected during and after construction. Once these structures are built it can be difficult to quickly extend them, which may limit their usefulness. All of these structures require some form of drainage system to allow water to drain from the retained material. These drainage systems often involve the installation of channels and pipes to avoid disturbing the firm bearing or wall itself; this can further increase the cost and time required to construct. Another method of creating a growing platform is using concrete half rounds, these are put in place and backfilled with soil to create the growing platform. These often require a crane or other machine to put in place due to their weight and/or size. If the sloped surface is inaccessible to cranes then it is unlikely this particular solution can be used. In addition, in some cases, a hole must be excavated to retain the half pipe to prevent it moving in the future

A further alternative is to use one of the mat products which are rolled over the sloped surface to prevent the loss of topsoil. Plants are sown on the surface of the mats and as they grow they penetrate through the mat and into the topsoil below. Some of these mats are prone to UV degradation and so they can break down in a relatively short time. If water seeps through the mat, or comes up from behind the mat, then the surface behind the mat can be eroded.

To provide a quickly erected alternative to an engineered and constructed retaining wall a silt fence can be used. A silt fence consists of a wire mesh fence with a woven sheet material retained on the inner surface held in place with a series of posts. A silt fence is not a permanent solution as the woven material eventually breaks down when exposed to UV. The posts must be properly driven into the ground at the right spacing to be effective, the mesh then needs to be installed and finally the silt retaining material needs to be applied. All of this can make the construction of the silt fence expensive. Aesthetically a silt fence can look messy and temporary, so although often required by councils to prevent silt runoff during construction projects they are not intended to be a long term solution. OBJECT OF THE INVENTION

An object of the present invention is to provide a soil retention device that can be used to create one or more growing platforms for plants that overcome one or more of the deficiencies highlighted above, or at least provide the consumer with a useful choice.

The present invention provides a soil retention device including a planar crescent shaped central section with a first edge and a second, opposite, edge, the first edge being shorter than the second edge.

Preferably the central section includes one or more apertures or perforations configured to allow water to drain when the soil retention device is in use. Preferably there are a multitude of apertures or perforations evenly distributed over the surface of the central section.

In a preferred form the soil retention device is made of a resilient material. In a further preferred form the resilient material is a plastic material. In a highly preferred form the plastic material is wholly or partially recycled material. Preferably the central section includes an engagement aperture, and at one, or both distal ends, of the central section there is a tab. In a highly preferred form there is a tab at each distal end. In a highly preferred form the or each tab includes an engagement section configured to be inserted into the engagement aperture of a second soil retention device. In a still more preferred form the or each tab includes a transition section which connects the engagement section to the central section.

In a still more preferred form the engagement section is a flat strip, and the transition section is a planar curved strip the same width as the engagement section; in this form, at each end of the first edge, where it joins the respective transition section, there is a first engagement notch which is an indentation in the first edge; at each end of the second edge, where it joins the respective transition section, there is a first notch; the linear distance between the base of the first notch and the base of the respective engagement notch is approximately the same as the length of the major axis of the engagement aperture. Preferably the central section includes at least one fixing point configured to engage with a peg, each said peg is configured to connect the or each soil retention device to the ground. Preferably there are at least two fixing points, with one fixing point located close to each distal end of the central section. Preferably the or each fixing point is an indentation in the first edge. Preferably the cross section of the peg, at the point where it is configured to engage the respective fixing point, is approximately the same as the profile of the fixing point.

Preferably one end of the or each peg is bent to form a U-shaped section which is configured to engage with the respective fixing point. In an alternative preferred form the or each peg is U-shaped, with the base of the U configured to engage with the surface of the respective fixing point.

In an alternative form the central section of the soil retention device includes one or more fixing tabs, where the or each fixing tab is a strip extending from the second edge. In a preferred form the or each fixing tab includes a fixing hole. In a highly preferred form there are three fixing tabs, two side fixing tabs which divide the central section approximately into thirds, and a central fixing tab that is located approximately midway along the second edge. Preferably the or each fixing hole is configured to engage with a fixing peg when in use.

In a preferred form the soil retention device includes zero or more fixing tabs and/or zero or more fixing points. The present invention also includes a method of using the soil retention device to form a growing platform, which includes the following steps in order: a. bend the soil retention device into shape by bringing of the tabs closer together;

b. place on the ground so that the second edge is in contact with the ground ;

c. place a first peg over the soil retention device in line with a first fixing point;

d. drive the first peg into the ground until it fully engages with the fixing point ;

e. allow the soil retention device to spring out to the desired shape; f. place a second peg over the soil retention device in line with the remaining fixing point;

g. drive the second peg into the ground until it fully engages with the remaining fixing point;

h. back fill the soil retention device with soil to form the growing platform.

The present invention also includes a system of linked soil retention devices, such that each soil retention device in the system is attached to at least one other soil retention device. Preferably these linked soil retention devices form a fishscale pattern when viewed from above. Preferably the or each soil retention device is configured to be connected by inserting a tab from at least one soil retention device into the engagement aperture of another soil retention device. In a further preferred form, where there are two adjacent soil retention devices, the first tab of one soil retention device and the second tab of the adjacent soil retention device are both inserted into the engagement aperture of a third soil retention device.

The present invention also includes a kit which includes two or more soil retention devices and two or more pegs. By way of example only a preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings in which:

Figure 1 is a plan view of the soil retention device;

Figure 2 is a pictorial view of a single soil retention device forming a growing platform; Figure 3 is plan view of a number of soil retention devices in use forming a number of growing platforms;

Figure 4 is a plan view of a second embodiment of the soil retention device;

Figure 5 is a pictorial view of the second embodiment of the single soil retention device forming a growing platform.

Referring to figure 1 a soil retention device (1 ) including a central section (2) and two tabs (5,6) is shown. The soil retention device (1 ) is an essentially crescent shaped flat piece of flexible and resilient material, such as plastic, treated timber or spring steel. The first tab (5) is at one distal end (7) of the central section (2) and the second tab (6) is at the opposite distal end (8). The central section (2) includes an engagement aperture (9), a first edge (10) and a second, opposite, edge (1 1 ), the second edge (1 1 ) being longer than the first edge (10). The engagement aperture (9) is a rectangular hole located in the centre of the central section (2) with its major axis lying perpendicular to the edges (10,1 1 ) at that point.

Each tab (5,6) includes an engagement section (12,13) and a transition section (14,15). Each engagement section (12,13) is a short strip of material that extends from the respective transition section (14,15) of the first edge (10). Each engagement section (12,13) forms an exposed end of the soil retention device (1 ). Each transition section (14,15) is a planar curved strip the same width as the respective engagement section (12,13) that joins that engagement section (12,13) to the central section (2). At each end of the first edge (10), where it joins the respective transition section (14,15), there is a first engagement notch (18,19). Each first engagement notch (18,19) is a semi circular indentation in the first edge (10) approximately the same diameter as the thickness of the engagement section (12,13). At each end of the second edge (1 1 ), where it joins the respective transition section (14,15), there is a first notch (20,21 ). The linear distance between the base of the first notch (20,21 ) and the base of the respective engagement notch (18,19) is approximately the same as the length of the major axis of the engagement aperture (9).

The central section (2) also includes two fixing points (24,25), each fixing point (24,25) is a semi circular indentation in the first edge (10). Each fixing point (24,25) is located closer to centre of the central section (2) than any of the notches (18,19,20,21 ).

The central section (2) also includes a number of holes (30) that allow any water in the soil being retained by the soil retention device (1 ) to drain away. These holes (30) can be circular, rectangular, thin slits or any other shape that allows the water to drain, whilst minimising the soil loss.

Referring to Figure 2 a single soil retention device (1 ) is shown in use forming a growing platform (40) is shown, a preferred method of constructing this follows this description. The soil retention device (1 ) is curved and each end (7,8) is held in place by peg (41 ,41 a) driven into the ground (42). Each peg (41 ,41 a) is engaged with a fixing point (24,25). Each peg (41 ,41 a) is a piece of round stock approximately the same diameter as a fixing point (24,25); such that, in use, each peg (41.41 a) closely engages with the exposed surface of the respective fixing point (24.25). One preferred method of using a single soil retention device (1 ) to create a growing platform (40) includes the following steps in order: a. bend the soil retention device (1 ) into shape by bringing the tabs (5,6) closer together;

b. place on the ground (42) so that the second edge (1 1 ) is in contact with the ground (42);

c. place a first peg (41 )over the soil retention device (1 ) in line with a first fixing point (24);

d. drive the first peg (41 ) into the ground until it fully engages with the fixing point (24);

e. allow the soil retention device (1 ) to spring out to the desired shape; f. place a second u-shaped peg (41 ,41 a) over the soil retention device in line with the remaining fixing point (25);

g. drive the second peg (41 a) into the ground (42) until it fully engages with the remaining fixing point (25);

h. back fill the soil retention device (1 ) with soil to form the growing platform (40).

As shown in Figure 3, by using more than one soil retention device (1 ,1 a,1 b,1c,1d,1 e), it is possible to create a series of interlinked terraced growing platforms (40,40a,40b,40c,40d,40e). This forms a fishscale pattern, when viewed from above, which is particularly successful at stabilising the slope whilst providing a number of terraced growing platforms (40,40a,40b,40c,40d,40e). Referring to figure 3 a first soil retention device (1 ) is shown connected to a second soil retention device (1 a) by its first tab (5) which is inserted into the second soil retention device's (1 a) engagement aperture (9a). The second soil retention device (1 a) is directly adjacent a third soil retention device (1 b). The third soil retention device (1 b) is connected to a fourth soil retention device (1c) by its first tab (5b) which is inserted into the fourth soil retention device's (1c) engagement aperture (9c). The fourth soil retention device (1c) is directly adjacent a fifth soil retention device (1d), and the fifth soil retention device (1d) is also directly adjacent a sixth soil retention device (1 e). The third soil retention device's (1 b) second tab (6b) and the second soil retention device's first tab (5a) are inserted into the fifth soil retention device's (1d) engagement aperture (9d) to connect them together. The second soil retention device's (1 a) second tab (6a) is inserted into the sixth soil retention device's (1 e) engagement aperture (9e) to connect them together.

Each soil retention device (1 ,1 a,1 b,1c,1d,1 e) is held in place by pegs (41 ,41 a) which engage with their fixing points (24,25) as the pegs (41 ,41 a) are driven into the ground (42). It is preferred that each of the soil retention devices (1 ,1 a,1 b,1c,1d,1 e) is a resilient plastic material which has good UV stability. However, it is possible that they are made of a biodegradable material which breaks down over a period of time leaving the or each growing platform (40,40a,40b,40c,40d,40e) self supporting. Though the pegs (41 ) and fixing points (24,25) are described as circular in cross- section, square, rectangular and other cross-section are equally applicable.

Referring to Figure 4 a second embodiment of the soil retention device (1 ) is shown, in this embodiment there are no fixing points (24,25) present instead there are three fixing tabs (50,51 52), two side fixing tabs (50,51 ) and a central fixing tab (52). Each fixing tab (50,51 ,52) is a strip of material extending from the second edge (1 1 ). Each fixing tab (50,51 ,52) is coplanar with the central section (2) and has an approximately parabolic profile, this allows the or each fixing tab (50,51 ,52) to be directly inserted into the ground (42), if necessary. It should be noted that although shown with a parabolic profile, the or each fixing tab (50,51 ,52) could be any suitable shape, and may not even be coplanar with the central section (2) In some forms.

The central fixing tab (52) is located close to or at the centre of the second edge (1 1 ), each of the side fixing tabs (50,51 ) is equidistant from the central fixing tab (52) and approximately divide the second edge (1 1 ) into thirds. Each fixing tab (50,51 ,52) includes a fixing hole (55). It should be noted that although only three fixing tabs (50, 51 , 52) are shown for the second embodiment there may be more or less of them. In addition, though not shown Figure 4, the fixing points (24,25) may also be present in some configurations.

Referring to Figure 5 a single soil retention device (1 ) according to the second embodiment is shown in use. In this embodiment each of the fixing tabs (50, 51 , 52) can be used in one of two ways, either bent away from the plane of the soil retention device (1 ) and a tab peg (60, 61 ) driven through the fixing hole (55), or, if the soil/ground is soft enough, pushed directly into the ground. In Figure 5 only the side fixing tabs (50,51 ) are shown bent and held in place with tab pegs (60,61 ), though it could also include fixing hole (55) in the centre fixing tab (52). In either case the fixing tabs (50, 51 , 52), when in use, act to fix the soil retention device (1 ) in place. In further embodiments (not shown) the tabs (5,6) are connectors of an alternative but known design. For example an expanded section of a tab (5,6) is bent to reduce its width; the tab (5,6) is then inserted into the engagement aperture (9) and allowed to expand. An alternative is that the tabs (5,6) include one or more mushroom shaped heads that are inserted into one or more round engagement apertures (9), the engagement aperture (9) deforms to allow the shaped head to be inserted but then returns to its original shape preventing the shaped head from being removed.

In a further embodiment (not shown) there is only one tab (5,6) on the soil retention device (1 ), or, when using a single soil retention device (1 ), no tabs (5,6).

In a still further embodiment (not shown) there are no fixing points (24,25) or fixing tabs (50,51 ,52) formed into the soil retention device (1 ). In this embodiment each peg (41 ,41 a) includes a cutting section configured to cut into the first edge (10) of the soil retention device (1 ) to form a strong but releasable connection with the soil retention device (1 ). In a further embodiment (not shown) this connection is permanent.

In a further embodiment the tabs (5,6,5a,6a,5b,6b), once inserted into the respective engagement aperture (9,9a,9c,9d,9e), are permanently or semi permanently connected to the next soil retention device (1 ,1 a,1 b,1 c,1d,1 e) by a known means such as gluing, riveting, screws, nuts/bolts and welding for example. This may be in addition to the tabs (5,6,5a,6a,5b,6b) or instead of. In a further embodiment (not shown) the exposed end of the or each engagement section (12,13) is narrower in width than the respective transition section (14,15), so that it can be easily inserted into the respective engagement aperture (9,9a,9c,9d,9e).

The soil retention device (1 ) can be used to protect, maintain or establish stable riparian strips as well as stabilise banks, hillsides, and other sloped ground surfaces. It should also be noted that after installation the soil retention devices (1 ) may be covered with soil as the underlying land has been stabilised.

It is preferable that the soil retention device (1 ) is made of a resilient material so that, in use, it can be bent to form a smooth curve. The resilient material of choice is a recycled plastic, which for some purposes may be biodegradable. By being resilient the soil retention device (1 ) can be transported flat and formed into shape on installation.

Any discussion of the prior art throughout the specification is not an admission that such prior art is widely known or forms part of the common general knowledge in the field.