FIELD OF INVENTION The present invention relates to an energy absorbing bollard assembly.

BACKGROUND OF THE INVENTION Energy absorbing bollards are designed, by way of example, to protect pedestrian areas such as sidewalks, pedestrian crossings, outdoor seating etc. from vehicle impacts without endangering the vehicle occupants. Energy absorbing bollards are also designed for other functions .

There are different types of bollards.

One bollard type comprises bollards that are rigid and form inflexible barriers to vehicles contacting the bollards . These bollards are constructed to cause vehicles rather than the bollards to collapse on contact with the bollards and thereby decelerate the vehicles via

absorption of energy as the vehicles collapse.

Another type of bollard comprises flexible bollards that bend and deform elastically from an upright,

typically vertical , orientation when contacted by vehicles and absorb vehicle energy via deformation of the bollards.

These flexible bollards return to their original

orientation and shape after vehicle impact.

Another type of bollard comprises bollards that are formed to selectively collapse when contacted by vehicles, with the bollards absorbing vehicle energy due to the collapse of the bollards. By way of example, the bollards may include crumple zones or other areas that can

selectively collapse and absorb energy by this mechanism.

The applicant has realised that there is a need for an alternative bollard to the bollards known to the applicant . The above description is not to be taken as an admission of the common general knowledge in Australia and elsewhere . SUMMARY OF THE INVENTION

The invention is based on a realisation of the applicant that many bollards known to the applicant tend to bend non-elastically from an original upright,

typically vertical, orientation in response to contact with vehicles and form ramps that can launch the vehicles off the ground and that this a potentially very dangerous limitation of these bollards .

In this context, the terms "vertical orientation" and "vertically" are understood to mean an original upright orientation of a bollard prior to impact by a vehicle . When a bollard assembly is located on a horizontal section of ground, the original upright orientation of the bollard is usually a vertical orientation and it is appropriate to describe the bollard as extending vertically. When the same bollard assembly is located on an inclined section of ground, the original upright orientation of the bollard is usually an orientation in which the bollard is

perpendicular to the inclined ground section.

The term "bollard" is understood to mean a post, typically a short post.

The invention provides a bollard assembly that includes (a) a bollard and (b) a support for the bollard that can be located on or in the ground and form a fixed bollard support with the bollard extending upwardly, typically vertically upwardly, from the ground. The bollard and the bollard support are formed so that the bollard can slide relative to the bollard support on impact by a vehicle, with the bollard remaining in its original orientation, typically vertical, during the sliding movement. The bollard assembly also includes an energy absorption mechanism for absorbing impact energy of the vehicle as the bollard slides relative to the bollard support and thereby contributes to decelerating the vehicle .

The bollard assembly may be formed so that the maximum length of sliding movement of the bollard relative to the bollard support is sufficient so that, in use, the amount of energy that is absorbed by both (a) the energy absorption mechanism and (b) deformation of a selected vehicle decelerates the vehicle from a selected speed to a stationary position.

In this context, the term "selected vehicle" refers to a vehicle of a selected mass and construction,

particularly the extent to which the vehicle can deform and absorb impact energy.

The bollard assembly may be formed so that, in use the bollard slides relative to the bollard support in the direction of movement of the vehicle when the vehicle impacts the bollard.

The bollard assembly may be formed so that, in use, the bollard slides relative to the bollard support in a direction that is different to the direction of movement of the vehicle when the vehicle impacts the bollard. For example, the bollard assembly may be formed so that, in use, the bollard is constrained to slide in a particular path of movement relative to the bollard support that is different to the direction of movement of the vehicle when the vehicle impacts the bollard.

The bollard assembly may be formed so that, in use the bollard slides relative to the bollard support in response to impact of the vehicle with the bollard from any direction relative to the bollard. In other words, the bollard assembly can operate effectively, with the bollard sliding relative to the bollard support, when impacted by a vehicle moving in any direction relative to the bollard assembly.

The bollard assembly may be formed so that, in use, the bollard slides relative to the bollard support in response to impact of the vehicle with the bollard from any direction in a selected arc around the bollard, such as a 180° arc around the bollard.

The bollard assembly may be formed so that, in use, the bollard slides relative to the bollard support in response to impact of the vehicle with the bollard from any direction in a 90° arc around the bollard.

The bollard assembly may be formed so that, in use, the bollard slides relative to the bollard support in one direction only in response to impact of the vehicle with the bollard from any direction. By way of example, the bollard assembly may be positioned adjacent a road and separates the road and a pedestrian area, with the bollard assembly being formed so that when a vehicle travelling on the road leaves the road and impacts the bollard, the bollard slides in a direction parallel to the road and thereby prevents the vehicle moving into the pedestrian area as the vehicle decelerates.

The energy absorption mechanism may be any suitable mechanism.

In one embodiment of the invention, the energy absorption mechanism may include an energy absorption element that is positioned in a chamber within the bollard and is connected to the bollard support and, in use, the ground, so that energy of the impacting vehicle is transferred to the energy absorption element within the bollard as the bollard slides relative to the bollard support in response to vehicle impact.

By way of example, the energy absorption mechanism may include a cable of fixed length or other suitable member that connects the energy absorption element to the bollard support and, in use, the ground. With this arrangement, in use, the cable or other member makes it possible to transfer energy of the impacting vehicle to the energy absorption element within the bollard as the bollard slides relative to the bollard support.

The energy absorption element may include (a) a first part that is connected to the bollard support and in use the ground and, in use, moves axially within the bollard chamber as a consequence of the bollard sliding relative to the bollard support and the first part being connected to the bollard support and therefore not being able to move outwardly away from the connection to the bollard support and the ground and (b) a second part that is deformable within the bollard chamber and absorbs vehicle impact energy via deformation when, in use, the first part moves axially within the bollard chamber as the bollard slides relative to the bollard support. In effect, the second part resists movement of the bollard relative to the bollard support.

The second part may be a crumple zone within the bollard chamber that collapses and thereby absorbs energy when, in use, the first part moves axially within the bollard.

The crumple zone may be formed from crushable material .

The crumple zone may be formed from a structure that can collapse in response to an applied force . The structure may be a honeycomb structure. The honeycomb structure may include a continuous network of structural elements that define a plurality of cells within the bollard chamber.

The crumple zone may include a cylindrical member or a plurality of elongate elements extending axially within the bollard chamber between the first part and an end on the bollard chamber that is remote from the first part.

By way of further example, the energy absorption element may be an hydraulic shock absorber positioned within the bollard chamber.

The hydraulic shock absorber may include a

piston/cylinder assembly positioned within the bollard chamber, with the cylinder being positioned axially within the bollard chamber and the cylinder containing an hydraulic fluid, and with a piston being slidable in the cylinder and being connected to the bollard support and, in use, the ground, whereby sliding movement of the bollard relative to the bollard support causes the piston to move in the cylinder against the resistance of hydraulic fluid in the cylinder and this movement absorbs vehicle impact energy and thereby contributes to

decelerating the vehicle.

By way of further example, the energy absorption mechanism may include a deformable element that, in use, is fixed to the bollard support and the ground, and extends into the bollard chamber and is deformed and absorbs vehicle impact energy via deformation when, in use, the bollard slides relative to the bollard support.

By way of example, the deformable element may be a tube or any other suitable elongate element that extends into the bollard chamber, with the length of the element and the structural characteristics of the element determining the extent of the energy absorption and the length of sliding movement to absorb that energy.

The bollard chamber may be formed to facilitate controlled deformation of the deformable element as the bollard slides relative to the bollard support. For example, a lower section of the bollard chamber may include a throat that defines a curved surface over which the deformable element can bend as the bollard slides relative to the bollard support.

In another, although not the only other, embodiment of the invention, the energy absorption mechanism may be positioned within the bollard support and formed to selectively collapse and thereby absorb vehicle impact energy when contacted by a vehicle, while the bollard remains in its original upright orientation, typically vertical, as the bollard slides relative to the bollard support in response to vehicle impact.

The energy absorption mechanism within the bollard support may include a crumple zone that selectively collapses and thereby absorbs vehicle energy as the sliding movement continues , with the sliding movement progressively collapsing the crumple zone and decelerating the vehicle. In effect, the crumple zone resists sliding movement of the bollard relative to the bollard support.

The crumple zone within the bollard support may be any suitable form.

By way of example, the crumple zone within the bollard support may be formed from crushable material . By way of further example, the crumple zone may be formed from a structure that can collapse in response to an applied force. The structure may be a honeycomb

structure .

The crumple zone within the bollard support may be positioned in the path of sliding movement of the bollard relative to the bollard support.

In another, although not the only other, embodiment of the invention, the energy absorption mechanism may include two separate mechanisms, one positioned within the bollard chamber and the other positioned within the bollard support, with both parts being formed to

selectively collapse and thereby absorb vehicle impact energy when contacted by a vehicle, while the bollard remains in its original upright orientation, typically vertical, as the bollard slides relative to the bollard support in response to vehicle impact.

By way of example, one mechanism may be a deformable element that extends into the bollard chamber, with the length of the element and the structural characteristics of the element determining the extent of the energy absorption and the length of sliding movement to absorb that energy.

By way of example, the other mechanism may include a crumple zone positioned within the bollard support.

The combination of two separate mechanisms may be useful in situations where it is necessary to accommodate higher speed collisions with bollard assemblies and there is a need for a longer length of sliding movement of the bollard relative to the bollard support.

The bollard may include a base and a post extending from the bollard base, and the bollard support may include a chamber, with the bollard base being positioned within the bollard support chamber, and the bollard base and the bollard support chamber being formed so that the base can slide within the chamber in a direction that is

perpendicular to the upright axis of the bollard, with the bollard remaining in its original upright orientation during the sliding movement. When the bollard has an original vertical orientation, the sliding movement is horizontal .

The bollard base may be a flat plate. With this arrangement, the bollard extends perpendicular to the base plate.

The bollard support chamber may be defined by a lower wall , a side wall , and an upper wall , with upper wall including an opening. The opening may be formed to define the direction of movement of the bollard relative to the bollard support. By way of example, the opening may be an elongate slot so that, in use, the bollard slides relative to the bollard support in one direction only in response to impact of the vehicle with the bollard from any direction. By way of further example, the opening may be a semi-circular opening so that, in use, the bollard slides relative to the bollard support in response to impact of the vehicle with the bollard from any direction in a 180° arc around the bollard.

There may be a gap between an outer edge of the base and the side wall that defines the bollard support chamber, and the bollard support crumple zone may be positioned in the gap, whereby sliding movement of the bollard relative to the bollard support brings the base into contact with the crumple zone and sliding movement can only continue via progressive collapsing of the crumple zone, thereby absorbing vehicle energy and decelerating the vehicle. The bollard may be any suitable shape and size and be formed from any suitable material.

The invention also provides a ground-mounted bollard assembly that comprises the bollard assembly described above and a foundation that fixes the bollard support in the ground.

DESCRIPTION OF FIGURES The invention is described further by way of example only with reference to the drawings, of which:

Figure 1 is a perspective view of one embodiment of a bollard assembly in accordance with the invention, with the bollard assembly shown in an initial position prior to being contacted by a vehicle;

Figure 2 is a vertical cross-section through one embodiment of a ground-mounted bollard assembly in accordance with the invention, which includes the bollard assembly shown in Figure 1 and a foundation that fixes the bollard assembly to the ground and with the bollard assembly in the initial position shown in Figure 2 prior to being contacted by a vehicle;

Figure 3 is the same vertical cross-section shown in Figure 2 after the bollard assembly has been contacted by a vehicle and has moved via sliding movement from the position shown in Figure 2 to the position shown in the Figure ;

Figure 4 is a perspective view of another, although not the only other, embodiment of a bollard assembly in accordance with the invention, with the bollard assembly shown in an initial position prior to being contacted by a vehicle ;

Figure 5 is a vertical cross-section through an embodiment of a ground-mounted bollard assembly in accordance with the invention, which includes the bollard assembly shown in Figure 4 in the initial position shown in Figure 4 prior to being contacted by a vehicle; Figure 6 is a perspective view of another, although not the only other, embodiment of a bollard assembly in accordance with the invention, with the bollard assembly shown in an initial position prior to being contacted by a vehicle;

Figure 7 is a vertical cross-section through an embodiment of a ground-mounted bollard assembly in accordance with the invention, which includes the bollard assembly shown in Figure 6 in the initial position shown in Figure 4 prior to being contacted by a vehicle; and Figure 8 is a vertical cross-section through an embodiment of a ground-mounted bollard assembly in accordance with the invention, which includes the bollard assembly shown in Figure 6 after the bollard assembly has been contacted by a vehicle and has moved via sliding movement from the position shown in Figure 7 to the position shown in the Figure.

DETAILED DESCRIPTION

The Figures illustrate three of many possible embodiments of the bollard assembly of the invention.

The bollard assembly shown in Figures 1 to 3 includes a bollard generally identified by the numeral 3. The bollard 3 includes a base 11 in the form of a horizontal flat plate and a cylindrical , hollow post 9 that extends upwardly, specifically perpendicularly, from an upper surface of the base 11. In a situation in which the bollard assembly is located on or in a horizontal section of ground, the original upright orientation of the bollard

3 is a vertical orientation.

The bollard assembly also includes a support 5 for the bollard 3. The bollard support 5 includes a chamber 13 that receives and houses the bollard base 11 and determines the maximum limit of sliding movement of the bollard assembly. The bollard support 5 includes a lower wall 17 (see Figures 2 and 3) , a side wall 21, and an upper wall 19 that define the chamber 13. The upper wall 19 includes an elongate opening 25 through which the bollard post 9 extends upwardly from the base 11.

The bollard base 11 and the bollard support chamber 13 are formed so that the bollard 3 can slide relative to the bollard support 5 on impact by a vehicle (not shown) , with the bollard post 9 remaining in the original upright orientation during the sliding movement. In particular, the chamber 13 , and more particularly the lower and upper walls 17 and 19, respectively, confines the bollard base 11 for movement horizontally as shown in the Figures and with the bollard post 9 being in a vertical orientation as shown in the Figures — assuming that, in use, the bollard assembly is located on or in a horizontal section of ground.

As can be seen in the Figures, the shape of the opening 25 defines the directions of sliding movement of the bollard 3 relative to the bollard support 5 from the set-up position of the bollard 3. As can best be seen in Figure 1, the opening 25 is semi-circular, with a straight section 31 and a semi-circular section 33. Figure 1 shows the bollard 3 in the initial set-up position prior to being contacted by a vehicle . It can be appreciated that, when in this position, the bollard 9 can slide in any direction towards the perimeter wall that defines the semi-circular section 33 of the opening 9. Therefore, the bollard assembly can respond to vehicle impact from any direction in a 180° arc.

The bollard base 5 also includes a series of openings 23 extending through the side wall 21 at spaced intervals around the perimeter of the support base 5 for receiving bolts to secure the bollard assembly to a foundation 7 shown in Figures 2 and 3. The foundation 7 may be any suitable foundation, such as a concrete block embedded in the ground. In use, in order to install the bollard assembly, the foundation 7 is poured and allowed to set in a required location for the bollard assembly and the bollard assembly 5 is bolted (or otherwise mounted) to the foundation 7.

The bollard assembly also includes an energy

absorption mechanism for absorbing the energy of a vehicle (not shown) when the vehicle contacts the bollard 3 and the bollard 3 slides relative to the bollard support 5 in response to the vehicle contact and thereby decelerates the vehicle to a stationary position.

With reference to Figures 2 and 3, the energy absorption mechanism includes (a) an hydraulic shock absorber generally identified by the numeral 37 coupled to the bollard post 9 and (b) a cable 43 of fixed length or other suitable member connected at one end to the

hydraulic shock absorber 37 and at the other end to the bollard support 5 and the foundation 7. The connection point to the bollard support 5 and the foundation 7 is identified by the numeral 61 in Figures 2 and 3.

Basically, the cable 43 extends through an opening 85 in the base 11 of the bollard 3 and is connected to the foundation 7 at the location 61.

The hydraulic shock absorber 37 is positioned in and completely occupies a hollow chamber of the bollard post 9 and includes a piston/cylinder assembly. The

piston/cylinder assembly includes an axially extending cylinder 39 that contains a suitable hydraulic fluid and a piston 41 that divides the cylinder into an upper chamber 81 and a lower chamber 83 and is slidable in the cylinder 39. The piston 41 includes flow valves 45 (Figures 2 and 3) that allow hydraulic fluid to flow between the chambers 81. 83 and control the flow rate of hydraulic fluid between the chambers 81, 83.

The dimensions of the bollard post 9 and the

piston/cylinder assembly may be selected as required for the operational requirements of the bollard assembly. For example, for typical applications, the stroke length for the piston 41 may be 250-900 mm, the post diameter may be 100-300 mm and the post length may be 0.9-1.2 m. It is emphasised that the embodiment, and the invention, are not limited to these dimensions .

Figure 2 shows the bollard assembly in a set-up position, with the bollard 3 in a central position, i.e. equidistant from the ends of the opening 25. Figure 3 shows the bollard assembly after impact by a vehicle (not shown) moving in the direction of the arrow A in Figure 3. The vehicle has moved the bollard 3 to the left of the Figure. This movement is sliding movement of the bollard 3 relative to the bollard support 5 (and the foundation 7) . The bollard assembly absorbs impact energy of the vehicle as the bollard 3 slides in the bollard support 5 and contributes to decelerating the vehicle, as described below .

As noted above, the cable 43 is attached to the piston 41. As a consequence, and given that the opposite end of the cable 43 is fixed to the foundation 7 at location 61 (and also to the bollard support 5) by virtue of the cable 43 extending through the opening 85 in the base 11 of the bollard 3, sliding movement of the bollard 3 away from location 61 of the foundation 7 extends a section of the cable 43 horizontally in the bollard support chamber 13 and this movement causes the piston 41 to be moved downwardly in the cylinder 39 against the resistance of hydraulic fluid in the cylinder 39 and the permissible flow rate of hydraulic fluid from the lower chamber 81 to the upper chamber 83 of the cylinder 39 via the flow valves 43. This movement absorbs impact energy of the vehicle and thereby contributes to decelerating the vehicle.

The flow valves 45 control the movement of the piston 41 to be at the same speed within the cylinder regardless of the impact force of the vehicle on the bollard 3.

The bollard assembly shown in Figures 4 and 5 has the same basic components as the bollard assembly shown in

Figures 1 to 3 and the same reference numerals are used to describe the same components . With reference to Figures 4 and 5, the bollard base 11 and the bollard support chamber 13, and more

particularly the opening 25, allow the bollard 3 to slide relative to the bollard support 5 in one direction only in response to impact by a vehicle (not shown) from any direction, with the bollard post 9 remaining in its original orientation, typically vertical, during the sliding movement. In particular, the bollard support chamber 13, and more particularly the lower and upper walls 17 and 19, respectively, of the chamber 13 confines the bollard base 11 for movement horizontally and with the bollard post 9 being in a vertical orientation — as viewed in the orientation of the bollard assembly with respect to the ground shown in Figures 4 and 5.

As can best be seen in Figure 4, the opening 25 is an elongate slot. Figures 4 and 5 show the bollard 3 in the initial position prior to being contacted by a vehicle. It can be appreciated that, when in this position, the bollard 9 can slide only in the elongate direction of the slot-shaped opening 25. Therefore, the bollard assembly can respond to vehicle impact from any direction by sliding movement of the bollard 3 in one direction only. This is an important feature when it is desirable to prevent any incursion of a vehicle into a pedestrian area. By way of example, when the bollard assembly is positioned adjacent a road and separates the road and a pedestrian area, with the bollard assembly positioned so that the slot-shaped opening 25 is parallel to the road, when a vehicle travelling on the road leaves the road and impacts the bollard 3 in any direction from the road, the slot- shaped opening 25 confines the bollard 3 to slide in a direction parallel to the road and thereby prevents the vehicle moving into the pedestrian area as the vehicle decelerates .

With further reference to Figures 4 and 5, the energy absorption mechanism is positioned in a hollow chamber 63 of the bollard post 9. The bollard chamber 63 extends substantially the length of the bollard post 9.

The energy absorption mechanism includes a first part that is connected to the bollard support 5 and the ground at a connection location 61 (see Figure 5) . The first part is in the form of a plate 51 that, in the initial position shown in the Figures , is at an upper end of the bollard chamber 63.

The energy absorption mechanism also includes a second part in the form of a cylindrical member 53 extending vertically within the bollard chamber 63 between the plate 51 and a lower end on the bollard chamber 63. In use, downward axial movement of the plate 51 causes the cylindrical member 53 to collapse, i.e. deform, within the bollard chamber 63 and thereby absorb vehicle impact energy .

The bollard assembly shown in Figures 6 to 8 has the same basic components as the bollard assemblies shown in Figures 1 to 3 and Figures 4 and 5 and the same reference numerals are used to describe the same components.

With reference to Figures 6 to 8 , the energy

absorption mechanism is a combination of two separate mechanisms, with one positioned within the bollard chamber 63 of the bollard 9 and the other positioned within the bollard support chamber 13 of the bollard support 5. Both mechanisms are formed to selectively collapse and thereby absorb vehicle impact energy when contacted by a vehicle, while the bollard 9 remains in its original upright orientation, typically vertical, as the bollard 9 slides relative to the bollard support 5 in response to vehicle impact.

One energy absorption mechanism comprises a

deformable element 71 in the form of a tube that, in use, is fixed to the bollard support 5 and the ground (via the foundation 7) , and extends into the bollard chamber 63. The arrangement is such that, in use, the deformable tube 71 is bent and collapsed and thereby deformed and absorbs vehicle impact energy via deformation when, in use, the bollard 9 slides relative to the bollard support 5 in response to vehicle impact. The progressive bending and collapsing of the deformable tube 71 is evident from Figures 7 and 8. It is noted that in Figure 8, the deformable tube 71 is completely bent and collapsed and is clear of the bollard chamber 63 and extends within the bollard support chamber 13. The length of the deformable tube 71 and the structural characteristics of the tube determine the extent of the energy absorption and the length of sliding movement to absorb that energy.

The bollard chamber 63 formed to facilitate

controlled deformation of the deformable tube 71 as the bollard 9 slides relative to the bollard support 5.

Specifically, a lower section of the bollard chamber 63 include a throat 73 that defines a curved surface over which the deformable element can bend as the bollard 9 slides relative to the bollard support 5.

The energy absorption mechanism also comprises a crumple zone 75 in the form of crushable plates positioned in the bollard support chamber 13 at the end of the opposite end of the chamber 13 to the initial set-up position of the bollard 9. The crushable plates 75 are formed to selectively collapse and thereby absorb vehicle impact energy as the sliding movement continues, with the sliding movement progressively collapsing the crushable plates 75 and decelerating the vehicle. The extent of the crushable plates 75 and the structural characteristics of the plates determine the extent of the energy absorption and the length of sliding movement to absorb that energy.

The combination of the energy absorption mechanisms shown in Figures 6 to 8 is useful in situations where it is necessary to accommodate higher speed collisions with bollard assemblies and there is a need for a longer length of sliding movement of the bollard relative to the bollard support .

In this regard, it is noted that the embodiment shown in Figures 6 to 8 is formed so that the deformable tube 71 absorbs vehicle impact energy first and the crushable plates 75 absorb vehicle impact energy second. The invention is not confined to this arrangement and the two mechanisms may operate simultaneously or with some overlap .

In any given situation with the embodiments described with reference to Figures 1 to 3, Figures 4 and 5, and Figures 6 to 8 , the extent of the sliding movement of the bollard 3 that is required to decelerate a vehicle that contacts the bollard assembly from a given impact speed to a stationary position will depend on a number of factors .

These factors include, by way of example, the impact speed, the mass of the vehicle, and the characteristics of the energy absorption mechanism.

In the case of the energy absorption mechanism shown in Figures 1 to 3, the relevant characteristics are the stroke length of the piston 41, the cylinder volume, the hydraulic fluid, and the flow rate control provided by the flow valves 43.

In the case of the energy absorption mechanism shown in Figures 4 and 5 the relevant characteristics are the maximum length the plate 51 can move axially within the bollard chamber 63 and the structural characteristics of the cylindrical member 53, more particularly the energy required to collapse the cylindrical member 53.

The applicant has considered these factors in the context of designing the bollard assemblies of the type shown in the Figures to comply with requirements for crash barriers in European Standard EN1317 and the US Manual for Assessing Safety Hardware (MASH) . The requirements in

EN1317 and the MASH are followed in Australia and

elsewhere .

The use of the energy absorption mechanisms in the bollard assemblies shown in the Figures allows the resistive force to be automatically adjusted in an impact to account for various vehicle masses and provide the lowest possible impact severity in various conditions. A vehicle of any mass will stop in the same distance with the same deceleration rate . Vehicles exceeding these guidelines such as trucks will be contained by the steel footing, still safely protecting pedestrians.

Many modifications may be made to the embodiment of the method and the apparatus of the present invention shown in the drawings without departing from the spirit and scope of the invention.

Throughout this specification the word "comprise" , or variations such as "comprises" or "comprising" , will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.