AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Standard Patent Applicant(s) GALLAGHER GROUP LIMITED Invention Title: Improved gate assembly The following statement is a full description of this invention, including the best method for performing it known to me/us: -2 IMPROVED GATE ASSEMBLY TECHNICAL FIELD 5 This invention relates to an improved gate assembly. More specifically this invention relates to an improved gate assembly for use with an animal processing station. BACKGROUND ART 10 Gate assemblies are commonly used to control movement of an animal or object into or out of an area. As such a gate assembly must provide a barrier sufficient to bar access when in a closed position, and to enable access 15 when in an open position. Furthermore, in many applications it is important to have a gate assembly that is easy to operate, has a quick transition between opened and closed positions, and is cost effective for the situation in which it is used. 20 For example, gate assemblies are commonly used in conjunction with animal processing stations. Animal processing stations are widely used in animal management and treatment applications. Animal processing stations 25 include stations that animals move through, or are restrained within for processing. Common processing steps include weighing, and treatment for disorders or general maintenance. 30 Animal processing stations facilitate regular processing, which can improve the health of animals, and farming efficiencies. Animal processing stations generally include at least one 35 gate assembly which controls access into and/or out of the animal processing station. N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH speci as filed.doc 13/02/08 - 3 Gate assemblies in animal processing stations generally include either swing gates or one piece sliding gates. Both these gate assemblies have a number of significant disadvantages, which are discussed below. 5 Swing gates are typically one piece gates hinged on one side to the animal processing station. Swing gates can either open away from, or towards the animal as it enters or exits the animal processing station. 10 In most instances swing gates open towards the animal on the entry to an animal processing station and away from the animal on the exit from the animal processing station. This causes significant problems in opening swing gates, 15 especially when the animals are crushed up against the gate, which is a problem often associated with moving stock through a race. A further significant problem is that if an animal is half way through the entrance gate into the animal processing station when the gate tries to 20 close the animal may become entangled with, or injure itself on the gate. This is highly undesirable as it can lead to stock panicking and severely injuring themselves, as well as damaging the gate assembly. 25 Having to fasten the swing gate in the open position to prevent this problem is not satisfactory, as it increases the time and labour required, and may result in more than one animal entering (or exiting) the animal processing station at a time. Similarly having a handler hold or 30 control the gate is labour intensive. A further disadvantage with swing gates is that if an animal is to be retained within the animal processing station the gate needs to be fastened in the closed 35 position to prevent other animals being pushed, or moving into the processing station. This again is time consuming and increases the processing time of each animal. N \Melbourne\Casea\Patent\76000-76999\P76922.AU\Specis\P76922.AU GK opeci as filed.doc 13/02/08 One piece sliding gates are also frequently used in animal processing stations. The gate blocks the entrance and/or exit to the station and is slid out to one side to allow 5 access into and/or out of the station. The main disadvantage of one piece sliding gates is that when they are in the open position they protrude from one side of the animal processing unit. This is cumbersome 10 and may interfere with the handler's ability to move and treat stock. For example an open one piece sliding gate on the entrance to an animal processing station may block and prevent easy 15 movement of the handler to encourage the next animal into the station. In this instance the handler may have to move around the barrier which is time consuming, and may lead to injury. 20 Alternatively, the one piece sliding gate could be configured to protrude out from the opposing side of the animal processing station; however this results in the same problem if a handler is required on either side of the station. 25 A further disadvantage with one piece sliding gates is that they are slow to open and close. This is undesirable as a partially open gate may result in another animal moving or being pushed into the animal processing station 30 and/or the animal in the processing station trying to back out. Another disadvantage of one piece sliding gates is that there are restrictions on where they can be placed. This 35 is due to the required clearance which is necessary to allow the gate to slide open. This restriction can prevent optimal placement of gate assemblies, or require N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specia\P76922.AU GH speci as filed.doc 13/02/08 - 5 significant and potentially costly alterations to the animal processing station and/or surrounding area. Current gate assemblies are typically made of a heavy and robust material, such as wood or metal such as steel. 5 Wooden or metal gates can be heavy, and difficult to move quickly. A further disadvantage is that is the gate is on an automated system it can require a considerable amount of power to quickly move same, resulting in increased 10 running costs. A further disadvantage of using metal for gates and/or hinges is that it can be prone to corrosion; this is increased by continued exposure to animal excrement. 15 A further disadvantage of wooden or metal gates is that they can be noisy in use, especially swing gates as they contact or bang against the sides of a race, or animal processing station. This can lead to stock panicking and 20 being difficult to handle. A further disadvantage of gates made of electrically conductive materials, (such as metals) is that they interfere with any radio frequency technology which may be 25 being used for reading electronic animal tags. This interference can cause inaccurate reading of tag information and other errors. All references, including any patents or patent 30 applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and 35 pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does 853395_4 (GHMatters) P76922.AU 14/12/12;-/4-42 -6 not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country. 5 It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it 10 will be taken to mean an inclusion of not only the listed components it directly references, but also other non specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or 15 process. DISCLOSURE OF INVENTION According to one aspect of the present invention there is provided a gate element for use with a sliding gate 20 assembly, the gate element including: an open section unbounded on at least one side; a blocking structure adjacent to the open section; and at least one mounting structure extending laterally 25 from a side of the blocking structure, wherein the mounting structure is configured to interact with a track of the sliding gate assembly, such that the gate element may slide along the track According to another aspect of the present invention there 30 is provided a gate assembly including at least two gate elements substantially as described above. The gate elements of the gate assembly may be mounted in the gate assembly such that the gate elements can slide 35 relative to each other such that when the gate assembly is in an open position the open 853395_4 (GHMatters) P76922.AU 14/12/12-1344244-2 -7 sections of each gate element are substantially adjacent one another to allow access through the gate assembly, and when the gate assembly is in a closed position the 5 blocking structures of each gate element are substantially adjacent one another to block access through the gate assembly. Reference to a gate assembly throughout this specification 10 should be understood to refer to a gate including two or more gate elements. According to a further aspect of the present invention there is provided an animal processing station including a 15 sliding gate assembly as described above. Reference to an open section throughout this specification should be understood to mean a space in a gate element which forms an opening which, when placed adjacent to the 20 open space of another gate element, provides a space through which an animal or object may pass. In a preferred embodiment the gate element is configured such that the open section is unbounded on at least one 25 side. 853395_4 (GHMatters) P76922.AU 14/12/12-1-/4--/44 - 8 An object having an open section which is unbounded should be understood to refer to an object defining an open space in which the object does not fully enclose the open space. An open section, as used throughout this specification, 5 may be illustrated by reference to a rectangle, in which the four sides of the rectangle enclose an open space. If one side of the rectangle is removed the remaining three sides define an unbounded open space. Similarly, an open section may be formed by removing two adjacent sides from 10 a rectangle, to form an 'L' shape. Preferably the blocking structure is an elongate member. An elongate blocking structure is preferred as it is a 15 relatively simple configuration to make and use to block access. However, it will be appreciated that a blocking structure may be any shape, provided it performs the function of blocking thoroughfare, and therefore reference to an elongate blocking structure only should not be seen 20 as limiting. A blocking portion may be an elongate solid panel or it may be a panel (or frame) having one or more apertures where the size of any aperture is such that an animal to 25 be processed cannot move through the blocking portion. Preferably the blocking portion may include one or more apertures. For example, a blocking structure may include at least one elongated aperture, such that it may appear 30 as two (or more) bars, the bars being connected together at each end of the elongated aperture. A blocking portion may also be formed from a mesh-like structure, provided the mesh size is appropriate to the 35 size of an animal to be processed, and that the construction has sufficient rigidity to block access through the blocking structure. N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH speci as filed.doc 13/02/08 - 9 An advantage of a blocking portion having at least one aperture is that it may be lighter and use less materials to make than a solid panel blocking portion, making it 5 easier to move and less expensive to make. In a preferred embodiment the gate element includes at least one mounting structure extending laterally from a side of a blocking structure. 10 Reference to a mounting structure should be taken as meaning a part of a gate element extending laterally from a side of a blocking structure, the mounting structure being configured to interact with a track. 15 More generally, reference to a mounting section should be understood to refer to a section of a gate element configured to interact with a track. Thus, both a blocking structure and a mounting structure may include 20 mounting sections. In a preferred embodiment an edge of the mounting structure is substantially aligned with an edge of the blocking structure. 25 In this arrangement a mounting section may extend continuously along the aligned edges of the blocking structure and the mounting structure. 30 An advantage of having a mounting structure extending from a side of a blocking structure as described above is that it may provide a mounting for a gate element of greater length than a width of a blocking structure. This may assist a gate element to move smoothly along a track 35 without jamming, as may happen if a mounting section was restricted to a width of a relatively narrow elongate blocking structure. N:\Melbourne\Casea\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH apeci as filed.doc 13/02/08 - 10 Such an arrangement may also reduce the effect of any force applied to a gate element that creates a bending moment to the gate element on a track, in comparison with 5 shorter mounting structures. Such forces may arise for example if an animal obstructs the gate elements during the closing movement. A mounting structure extending from a side of a blocking 10 structure of a gate element defines an unbounded open section, being the space defined by an edge of the blocking structure and an adjacent edge of the extended mounting structure, and unbounded otherwise. 15 In a preferred embodiment the blocking structure and the mounting structure are configured in the shape of the letter 'L'. Preferably, an 'L'-shaped gate element may be oriented 20 such that when a longitudinal axis of the elongate blocking structure lies substantially in a vertical direction a mounting structure extends from the blocking structure in a substantially horizontal direction. 25 In alternate embodiments a gate element may be configured in the shape of the letter 'C'. Preferably, when used in a gate assembly, a 'C'-shaped gate element may be oriented such that a longitudinal axis 30 of the elongate blocking structure lies substantially in a vertical direction and a mounting structure extends from each end of the blocking structure in a substantially horizontal direction. In this embodiment the open section corresponds to the unbounded space defined by an edge of 35 each extended mounting structure and an adjacent edge of the blocking structure. Nr\Melbourne\CaueB\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH epeci as filed-doc 13/02/08 - 11 In a preferred embodiment the mounting structure is offset from the blocking structure. A mounting structure that is offset from a blocking 5 structure should be understood to mean that the mounting structure lies substantially in a place to a side of a plane of the blocking structure when viewed side on. Preferably the gate element is formed integrally. 10 Forming a gate element integrally, including a mounting structure and a blocking structure, may save manufacturing cost as no further assembly of parts is required. It may also provide an improved gate element as the relative 15 orientation of the blocking structure and mounting structure are fixed and therefore do not move relative to one another during operation, as can occur if the gate element is made from a number of parts which come loose following repeated use. 20 In a prefered embodiment the gate element is formed from a plastics material. A gate element formed from a moulded plastics material may 25 be relatively inexpensive to manufacture in large quantities. A plastic gate element may be lightweight in comparison to gate elements made from other materials such as wood or metal. This may provide a gate element which is easy to operate and can be moved quickly and relatively 30 quietly. Further advantages of a gate element as described above will become more apparent from the ensuing description of a gate assembly including two or more gate elements. 35 Throughout this specification a gate assembly will be discussed with reference to its use with an animal N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH speci as filed.doc 13/02/08 - 12 processing station which has a controlled entry point. However, it is envisaged that a gate assembly according to the present invention may be used in a wide variety of situations where controlled access is required, and 5 reference to a gate assembly used with an animal processing station only throughout this specification should not be seen as limiting. An animal processing station may be a restricted area 10 where one or more animals may be isolated for processing, such as an animal crate or an animal pen. Alternatively, and more generally, an animal processing station may be a place where selection of animals takes place, for example a gateway in an animal race which is opened or closed to 15 allow or deny access to the other side of the gateway to one or more selected animals. For clarity of description a gate assembly will be described throughout this specification in connection with 20 an animal processing station in the form of an animal crate. However, this should not be seen as limiting as many other uses are also envisaged, such as (without limitation) with an animal race, pen, stadium or indeed in any situation when controlled access for animals, humans 25 or objects is desired. A gate assembly positioned at an entry to the animal crate may be used to allow the desired number of animals to enter and to prevent other animals from moving or being 30 pushed into the animal crate. A gate assembly will therefore be discussed with reference to it being positioned at an entry to an animal crate, thereby controlling animal access into the crate. It should be appreciated however, that a gate assembly could also be 35 used to control both entry and exit points of an animal crate, or the controlled entry or exit into other parts of a stockyard or shed. Having gate assemblies at both an N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH speci as filed.doc 13/02/08 - 13 entry and an exit of the animal crate is beneficial where multiple or more time consuming processing or treatment is required and an animal or animals need to be contained in the crate for a period of time before release. 5 Reference to directions, such as upper, lower, front, back, right or left etc, throughout this specification should be understood to refer to directions as viewed from outside an animal crate when in its normal operating 10 position. A gate assembly controlling access into or out of an animal crate will normally be oriented substantially in a vertical plane. 15 Throughout this specification reference will be made to a gate assembly having two gate elements. However this should not be seen as limiting as gate assemblies having more than two gate elements are also envisaged. 20 In a gate assembly according to the present invention, the blocking structures of the two gate elements are substantially adjacent to one another when in a closed position. In the closed position, the blocking structure 25 of one gate element substantially blocks one half of the entry into the animal processing station and the blocking structure of the other gate element substantially blocks the other half of the entry. 30 In a preferred embodiment the two gate elements, when in an open, closed, or any intermediate position, are located substantially symmetrically about a centre point between the two gate elements. 35 To move from the closed position to the open position, the two gate elements are moved in opposite directions away from one another, while remaining positioned substantially N:\Melbourne\Case8\Patent\76000-76999\P?6922.AU\Speci\P76922.AU CH speci as filed.doc 13/02/08 - 14 symmetrically about the centre point between the two gate elements. To move from the open position to the closed position, the 5 two gate elements are moved in opposite directions towards one another, while remaining positioned substantially symmetrically about the centre point between the two gate elements. 10 Preferably at least some portion of the two gate elements, whether closed, open or moving between the two, are positioned in, and remain on, substantially the same vertical plane. 15 In a preferred embodiment the two gate elements move between the closed and open position, and vice versa, along at least one track. Throughout this specification the term track should be 20 taken as meaning a guide which defines a line of travel for an object located on it. Common forms of track include (without limitation) a rail or a groove, in each case configured to engage with another body for locating the body on the track and for guiding the other body along 25 it. The gate elements move along at least one track in a sliding motion. A sliding motion should be taken as meaning that the same part of the gate element maintains 30 continuous contact with the track during movement. In a preferred embodiment the gate assembly includes at least one track configured to interact with an upper mounting section of the gate elements, and at least one 35 track configured to interact with a lower mounting section of the gate elements. N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH speci au filed.doc 13/02/08 - 15 This arrangement of tracks may provide a robust gate assembly that is unlikely to buckle or come off the track if an animal leans on, runs into, kicks or otherwise places a larger than usual force onto the gate assembly. 5 In a particularly preferred embodiment the upper mounting sections of the gate elements interact with and move along at least one fully enclosed track guide bushing. 10 Reference to a fully enclosed track guide bushing should be understood to refer to a cylindrical shaped bearing enclosed within an end of a mounting structure and/or an end of a mounting section. The bearing typically travels on a rod or tube. 15 Such an enclosed track guide bushing may provide a compact housing for a bearing, be readily manufactured as part of a gate element and provide a seal and protection for a bearing enclosed in the track guide bushing. 20 This arrangement may also allow smooth, quiet movement of the doors along the track, which may provide a robust connection to the track as well as a reduction in noise. Any reduction in noise is of considerable benefit as it 25 may reduce agitation of an animal in the vicinity of the gate as well as providing an improved operating environment for people working around the gate assembly. In alternate embodiments other types of track guide may be 30 used as are well known in the art for mounting a panel on a track. In a preferred embodiment a lower mounting section of a gate element includes at least one lower track guide. 35 Reference to a lower track guide throughout this specification should be understood to refer to a device N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH speci as filed.doc 13/02/08 - 16 attached to a lower mounting section of a gate element and configured to retain and guide the gate element on a track. 5 In preferred embodiments of a gate assembly a lower track may be configured as an elongate member extending across the base of the gate assembly, the elongate member being oriented on an edge. In such embodiments a prefered lower track guide may be configured to attach to the lower 10 mounting section of a blocking structure, for example into an aperture on the base edge of the blocking structure, and to sit over and to each side of the elongate member. Such a lower track guide may be configured at the track engaging end as a two-pronged fork (or 'C' shape) for 15 example. Preferably each gate element includes one lower track guide only. A single lower track guide may be prefered as it allows considerable freedom for a gate element to 20 adjust for any distortions in a lower track. The upper track guides may be configured to provide a robust connection to an upper track, this track being less likely to be deformed by the action of animals. 25 Preferably each lower track guide is configured to rotate about an axis in a plane of the gate element and lower track. In such embodiments the lower track guide may be mounted 30 to a blocking structure such that it may rotate and move up and down with respect to the blocking structure, thus enabling the track guide to move to align itself with the track as it travels along it. In this way if the track does become bent, as may happen if kicked or trodden on by 35 an animal, then the lower track guide may adjust for the deformation and keep the gate element engaged with the lower track. 853395_4 (GHMatters) P76922.AU _4/_lj2M-/+ 2 - 17 Preferably a leading edge of a lower track guide is configured to assist removal of debris from the lower track as it moves along it. 5 This may reduce jamming of a gate element due to accumulated debris, as may be common with other forms of sliding gate when used with animals. In other embodiments a track may be configured as a 10 channel, in which case a suitable track guide may have an end in the form of a plug configured to fit into the channel and to resist lateral movement of the gate with respect to the channel. 15 Use of a gate guide may provide smooth and quiet movement of the gate elements along a track. This may cause less stress to both animals and operators of an animal processing station. 20 A gate guide configured to locate and hold a gate element on a track may reduce down time caused by a gate element being dislodged from the track, for example if pushed by an animal, thus saving processing time and costs. 25 In a preferred embodiment the gate assembly is configured such that, when the gate assembly is in a closed position, there is a gap between an outer edge of a blocking structure and an inner edge of the animal processing station. 30 In a preferred embodiment, the gate assembly is configured such that, when the gate assembly is in a closed position, there is a gap between the inner edges of the two blocking structures. 35 An aspect of some embodiments of the present invention is that the blocking 853395_4 (GHMatters) P76922.AU 14/12/12 - 18 structure of each gate element may be of significantly less width than half the width of the opening into the animal crate. 5 Having each gate element acting to block substantially half the entry when in the closed position may increase the speed at which the gate assembly can be opened and closed. This is due to each gate element having to move only half of the width of the gate assembly to either 10 allow or restrict access to the animal crate. This is highly desirable, especially when a quick and simple processing step is being undertaken, for instance when weighing animals. 15 Opening and closing the gate assembly quickly may also restrict the ability of unwanted animals entering the animal processing station at one time. There are a number of well-known methods for locating the 20 gate elements onto at least one track, as is well known in the art. For example a gate element may include at least one roller which runs along the track, or channel therein. Another example may be a gate element including a recess configured to engage with a complementary protrusion in a 25 track along which the gate element can move or slide. It will be appreciated that various other arrangements may be use, such as those commonly used to locate and guide sliding panels, such methods being well known in the art. 30 The split sideways movement of the gate elements is also highly advantageous. As well as increasing the speed of opening and closing the gate elements it minimises problems with animals becoming entangled with, injuring 35 themselves on or damaging the gate element. In a preferred embodiment, when the gate assembly is in an N:\Melbourne\Caees\Patent\76000-76999\P76922.AU\Specio\P76922.AU GH speci as filed.doc 13/02/08 - 19 open position, neither gate element extends beyond any side wall of the animal processing station. In a preferred embodiment when each gate element is in the 5 closed position the peripheral end of the mounting structure is positioned at substantially the side edge of the animal processing station, but not protruding beyond same. 10 In a preferred embodiment at least a portion of the gate elements may overlap one another. Hereinafter reference will be made to the two gate elements being a 'front' and 'rear' gate element. It 15 should be appreciated that the front gate refers to the gate element which overlaps over the front of the rear gate element. In one preferred embodiment the front gate element is 20 configured and positioned such that the blocking portion is positioned in the right hand side of the entrance to the animal processing station, and the mounting structure extends to the left hand side of the gate assembly. 25 In one preferred embodiment the rear gate element is configured and positioned such that the blocking portion is positioned in the left hand side of the entrance to the animal processing station, and the mounting structure extends to the right hand side of the gate assembly. 30 Reference will herein be made to the front and rear gate elements being in the above configuration and position. It should be appreciated however that the position of the blocking and mounting structures of the front and rear 35 gate elements may be the other way around. In a preferred embodiment when the gate elements are moved N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH speci as filed.doc 13/02/08 - 20 from the closed position to the open position, the front gate element moves towards the far right hand side of the gate assembly and the rear gate element moves to the far left of the gate assembly. 5 Having the gate elements positioned and moving as described above means that the mounting structures of each gate element move inwards from the sides of the gate assembly as the gate elements move from the closed to the 10 open position. In this way the mounting structures never extend or protrude past the sides of the gate assembly at any stage in the closed to open to closed movement of the gate 15 elements. Preventing the mounting or any other portion of the gate elements protruding beyond the gate assembly is highly advantageous. It increases safety and usability of the 20 gate assembly for an operator working around the animal processing station. The area around an animal processing station (or race) does not have to be configured to provide additional room for the mounting structures or whole gate elements to protrude beyond the sides of the 25 animal processing station. In a preferred embodiment the blocking portions of the two gate elements are positioned in substantially the same vertical plane. 30 In a preferred embodiment the mounting structures of the two gate elements are positioned in vertical planes offset from the plane of the blocking portions. This allows the overlap and movement of the gate elements in opposing 35 directions as described in more detail below. In a preferred embodiment the blocking portions of the N.\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH speci as filed.doc 13/02/08 - 21 front and rear gates are in substantially the same vertical plane. For example, the blocking portion of the rear gate element 5 may protrude further forward from its mounting structure than does the blocking portion of the front gate element from its mounting structure. The configuration may be such that when in the gate assembly both the blocking portions of the front and rear gates may be in substantially the 10 same vertical plane. Having the blocking portions in the same vertical plane may ensure that the two gate elements provide a robust and efficient gate blocking the entrance to the animal processing station . 15 In a preferred embodiment the mounting structure of each gate element move along different tracks. In general each mounting structure may be located and guided along one of a pair of tracks, running 20 substantially parallel to one another. The tracks may be offset from each other sufficiently to allow the mounting structure of the rear gate to be sandwiched between the animal processing station and the mounting structure of the front gate element and such that the blocking portions 25 of each gate element lie substantially in the same vertical plane. In a preferred embodiment the blocking portions of both gate elements move along a single track. 30 In a typical example of the gate assembly according to the preferred embodiment, two gate elements are configured to move together and apart along a single track below the blocking portion of each gate element, and along a pair of 35 tracks in the vicinity of the top of the gate elements, one for each mounting structure. N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH speci as filed.doc 13/02/08 - 22 In some embodiments a base or lower portion of a blocking portion of each of the two gate elements may be configured to engage with and move along a single track. 5 In a preferred embodiment the gate assembly includes a drive mechanism to move the gate elements. In a preferred embodiment the drive mechanism includes an actuator. 10 In a preferred embodiment the drive mechanism includes a single actuator. The drive mechanism may be configured to drive open and 15 close both gate elements. A drive mechanism may be configured such that activation of a single drive actuator results in synchronised motion of the gate elements during either opening or closing, and decreases the time required to drive the gate elements between the open and closed 20 position, and vice versa. In one preferred embodiment the actuator is a pneumatic drive system. 25 In a preferred embodiment the actuator is a single cylinder system. In such embodiments the two gate elements are connected together such that operation of a single pneumatic cylinder connected to one of the gate elements may be used to control the movement of both gate 30 elements. In a preferred embodiment the drive mechanism includes a drive link connected to the two gate elements and to an actuator. A drive link may preferably be a wire, rope or 35 cable. However, this should not be seen as limiting, as one skilled in the art would be aware that other means could also be used to connect the two gate elements, for N:\Melbourne\Caaes\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH speci as filed.doc 13/02/08 - 23 example using a mechanical linkage, to ensure synchronised motion. Preferably a drive link is formed as a continuous loop, 5 the loop being connected to each mounting structure and to the actuator. The link drive may also be located around a pair of pulley wheels, one at each side of the gate assembly. In this way when the actuator is operated it moves the drive link which results in the gate elements 10 moving synchronously. In an alternative embodiment the actuator may be a double pneumatic cylinder system, wherein each cylinder is configured to interact with and control the movement of 15 one gate element. The pressure to the cylinders may be supplied from a single source, each cylinder being configured to move one or other of the gate elements such that they move in opposite directions either away or towards one another. 20 However, this should not be seen as limiting as any other drive system may be utilised with the present invention. For example geared, electrical or petrol driven drive systems may be used. 25 In a preferred embodiment the drive system may be configured such that each gate element is moved at substantially the same time, and at substantially the same speed. This may avoid a problem that could arise if one 30 gate element opened before the other, leaving a gap that an animal could try to push through. This may lead to an animal being caught between the partially opened gate elements and potentially causing damage to the gate assembly or injury to the animal, in either case causing 35 increased costs during processing. In some embodiments the drive mechanism may be activated Ns\Melbourne\Case\Patent\76000-76999\P6922.AU\Speci\P6922.AU GH speci as filed.doc 13/02/08 - 24 manually. Manual activation of the drive mechanism may be completed via a user operable switch. It should be appreciated that 5 the position of the switch may vary depending on the use and position of the gate assembly, and common treatment procedures. In a preferred embodiment the drive mechanism is activated 10 by at least one sensor. For example, a sensor may be positioned on the gate assembly. However, this should not be seen as limiting as the sensor may in alternative embodiments be positioned on 15 the animal processing station or in any other location capable of sensing the presence of an animal, or the exit of the animal in the animal processing station from same. In such embodiments the sensor may sense when an animal 20 has been processed, treated or has exited the animal processing station. The drive mechanism may then be activated to open the gate assembly to allow access into the animal processing station for the next animal. 25 In some embodiments the sensor may also sense an animal in or moving along a race towards the gate assembly, and through it. The drive mechanism may then be activated to close the gate assembly after one animal has entered the station, and before the next animal. 30 It should be appreciated that, if gate assemblies are positioned on both the entry and exit to the animal processing station, then a separate drive mechanism and/or sensor system may be used in conjunction with each gate 35 assembly. In a preferred embodiment the gate assembly includes an N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Speci\P76922.AU GH speci as filed.doc 13/02/08 - 25 opening control system. Reference to an opening control system throughout this specification should be understood to mean a system that 5 controls how far the gate elements are displaced from one another in the open position. Being able to control the displacement of the two gate elements from one another when in the open position is 10 highly beneficial. This is especially the case when animals are small, and the full width (open position) of the gate elements is not required to allow an animal to pass. As the size of individual animals increases the displacement between the two gate elements when in the 15 open position can also be increased to provide a wider opening. Control of the width or displacement of the gate elements in the open position reduces the possibility of two small animals entering the animal processing station at the same time. 20 In a preferred embodiment the opening control system includes a braking system. Preferably at least one brake is integrated into, or 25 associated with at least one of the gate elements. The brake acts to stop the movement of the gate elements at a selected position when the brake is applied. In a preferred embodiment at least one brake may include 30 at least one pneumatic (or other power/driving force) brake control and at least one contact brake pad surface. Preferably when the brake is applied or activated the brake pad is moved towards and against the mounting 35 structure of the gate element to which it is not attached. The subsequent friction is used to stop relative movement of the gate elements. N3\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH epeci as filed.doc 13/02/08 - 26 In a preferred embodiment the braking system is automatically controlled. 5 However, this should not be seen as limiting, as in an alternative embodiment the average size or weight of the animals in a group may be manually assessed by the operator, and the braking system set manually to the desired position. 10 In a preferred embodiment the opening control system includes a sensor and feed back driven control system. In a preferred embodiment the displacement between the 15 gate elements in an open position is based on the average weight of animals in the group to be processed in relation to animal width for that particular weight and/or specific RFID data. 20 In a preferred embodiment data from an animal can be used to automatically optimise the displacement between the gate elements. This may be done, for example, by using an RFID reader to collect data from each animal as it approaches the animal processing station. 25 It should be appreciated that a sensor or sensor system used to control the open position of the gate elements may be distinct from the sensor system used to control the opening and closing of the gate elements. However, this 30 should not be seen as limiting as these two sensor purposes may be combined. In a preferred embodiment a plurality of position defining inserts are moulded into the top surface of one gate 35 element, which along with a sensor positioned on a stationary part of the gate assembly are used for determining the position of the gate elements. N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH speci as filed.doc 13/02/08 - 27 In a preferred embodiment the inserts are metal. In a preferred embodiment a proximity sensor is used for 5 determining the position of the gates relative to the final desired opening position. In this embodiment the proximity sensor mounted on the gate assembly senses the metal inserts moulded into the 10 gate element and by counting or determining the number of inserts which have been traversed the position of the gate elements relative to the desired opening position can be determined. The brake can then be applied at the correct time to ensure the desired displacement between the gate 15 elements when in the open position. Alternatively, the metal inserts may be moulded in at different depths and the proximity sensor may determine the gate position by the distance to each metal insert. 20 In a preferred embodiment when the gate assembly is in the open position each gate element is substantially aligned with a different side wall of the animal processing station. 25 In a preferred embodiment the blocking portions of the gate elements is substantially the same width as the thickness of the side walls of the animal crate. The thickness of the side walls of an animal crate according to the present invention is the same as the width of an 30 end wall of the animal crate when viewed from in front of a gate assembly on the animal crate. This configuration prevents the gate elements from protruding into the entrance way of the animal processing 35 station when the gate elements are in the open position. Again, this prevents or limits the chance of an animal getting entangled with or injuring itself on the gate N:\Melbourne\Casea\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH apeci as filed.doc 13/02/08 - 28 elements. In a preferred embodiment the gate assembly also includes a fault sensing system which detects if the gate elements 5 are blocked or stopped prior to when anticipated. A fault sensing system may detect if an animal is in the entrance when the gate elements close. This is desirable as it may prevent an animal becoming caught in the gate 10 elements, panicking and potentially injuring itself or damaging the gate assembly. In one embodiment a fault sensing system may incorporate a hydraulic or pneumatic fluid pressure sensor. 15 However this should not be seen as limiting, as one skilled in the art would realise that other methods could be used to detect an animal blocking the entrance of the gate assembly when this is in the open position or moving 20 between the open and closed positions. Such alternate methods may include optical sensors for example. Alternatively, a sensor for the braking system or a sensor that detects the approach of an animal and activates the 25 gate elements to open or closed may be used. The gate assembly of the present invention provides a number of significant advantages over present gate systems, which can include: 30 e The use of gate elements made from plastics material means that the gate assembly is relatively lightweight and quiet. This allows quick and easy opening and closing of the gate elements. It also minimises noise, thereby lessening the risk of panicking of stock 35 due to loud noises which can be associated with metal or wooden gates opening and closing suddenly. N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specio\P76922.AU GH speci as filed.doc 13/02/08 - 29 e Having each gate element acting to block substantially half the entry when in the closed position increases the speed at which the gate assembly can be opened and closed. 5 e Increased speed of the gate assembly opening and closing minimises the ability of more than one animal entering the animal processing station at one time. 10 0 Preventing the mounting or other portion of the gate elements protruding beyond the gate assembly means that the gate assembly is safe and has high user friendliness. 15 e The use of a synchronized drive mechanism increases the speed with which the gate elements can be opened and closed. e The use of an automatically adjustable open 20 position for the gate assembly enables this setting to be adjusted as animals grow or for a user to alternate the opening position quickly between groupings of different sized animals. 25 BRIEF DESCRIPTION OF DRAWINGS Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying 30 drawings in which: Figure 1A shows a schematic view of a gate element according to one embodiment of the current invention; and 35 Figure 1B shows another schematic view of the gate element shown in Figure 1A; and Nc\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specio\P76922.AU GH speci as filed.doc 13/02/08 - 30 Figure 2 shows a schematic view of a gate assembly in the closed position according to one embodiment of the present invention; and 5 Figure 3A shows a schematic view of the gate assembly of Figure 2 in the open position; and Figure 3B shows another schematic view of the gate assembly of Figure 2 in the open position; and 10 Figure 3C shows another schematic view of the gate assembly of Figure 2 in the open position; and Figure 4A shows a schematic view of a gate assembly 15 including a brake for controlling the open position of the gate elements according to one embodiment of the present invention; and Figure 4B shows another schematic view of the gate assembly 20 shown in Figure 4A. BEST MODES FOR CARRYING OUT THE INVENTION A gate element according to one embodiment of the present 25 invention is generally indicted by arrow 40 in Figure 1. The gate element (40) is formed integrally from plastics material. The gate element (40) includes a blocking structure (41) 30 in the form of a planar, elongate element. The blocking structure includes an aperture (43) The gate element (40) also includes a mounting structure (42) extending from a side of the blocking structure (41). 35 The gate element (40) is configured in the shape of the letter 'L'. An unbounded open area, bounded on two sides Na\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specia\P76922.AU GH speci aa filed.doc 13/02/08 - 31 by the blocking structure (41) and the mounting structure (42), is indicated by the arrow 39. A plane of the mounting structure (42) is offset from a 5 plane of the blocking structure (41) as shown in Figure 1B. Figure 2 shows a front schematic view of a gate assembly including a front gate element (1) and a rear gate element 10 (2) according to one embodiment of the present invention. The gate assembly is shown attached to an animal processing station in the form of an animal crate, generally indicated by arrow (10) 15 Each of the gate elements (1) and (2) include a blocking structure (3) and (4) respectively and a mounting structure (5) and (6) respectively. Figure 2 shows the gate elements (1) and (2) in a closed 20 position blocking access to the animal crate (10). In this position the blocking structures (3, 4) are substantially adjacent one another, and the peripheral ends (50, 51) of the mounting structures (5, 6) are positioned substantially at a side edge (52, 53) of the 25 animal crate (10). The gate assembly is configured such that, when the gate assembly is in a closed position as shown in Figure 2, there is a gap between an outer edge (44, 46) of a 30 blocking structure (3, 4) and an inner edge (45, 47) of the animal crate (10). The gate assembly is also configured such that, when the gate assembly is in a closed position, there is a gap 35 between the inner edges (48, 49) of the two blocking structures (3, 4). N:\Melbourne\Casee\Patent\76000-76999\P76922.AU\Specia\P76922.AU GH speci as filed.doc 13/02/08 - 32 Further, when each gate element (1, 2) is in the closed position the peripheral end (50, 51) of the mounting structure (5, 6) is positioned at substantially the side edge (52, 53) of the animal crate (10), but not protruding 5 beyond same. The gate assembly includes one lower track (7), along which the base of the gate elements (1) and (2) move. The gate assembly also includes two upper tracks (13) (only 10 one visible in this figure). The mounting structures (5, 6) of the gate elements are positioned on offset vertical planes, or one in front of the other, the offset being such that the blocking structures (3, 4) of each gate element lie substantially in the same vertical plane. The 15 two upper tracks are similarly offset. When moving from the closed to the open position the front gate element (1) moves to the right as indicated by arrow (8) and the rear gate element (2) moves to the left as 20 indicated by arrow (9). This direction of movement means that the mounting structures (5) and (6) respectively move do not protrude beyond the sides of the animal processing station. 25 The animal crate (10) in this embodiment has sides (11) and (12) of a width substantially equivalent to the width of the gate element blocking portion (3) and (4) respectively. This means that the blocking portions do 30 not extend into the entry of the animal crate (10) when the gate assembly is in an open position. Figures 3A, 3B and 3C show a front, a top and a side view of the gate assembly when the gate elements are in the 35 open position. Figure 3 shows the two gate elements (14) and (15) - in N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specia\P76922.AU GH speci as filed.doc 13/02/08 - 33 this figure (15) indicates the front gate element and (14) indicates the rear gate element. Figure 3A shows the upper and lower tracks along which the 5 gate elements move. In this embodiment the animal processing station includes one lower track (16), to which the gate elements (14) and (15) run via the gate guides (17) and (18) respectively. 10 As can be seen in Figure 3C each of the gate guides (17 in this Figure) has a slot (19) that fits over the lower track (16) and thereby provides a secure connection between the track (16) and the gate elements (14) and (15). 15 The mounting structures of gate elements (14) and (15) move along upper tracks (20) and (21) respectively. The two gate elements (14) and (15) are moved between the 20 open and closed position by an actuator in the form of a single pneumatic cylinder (22) attached in this Figure to the rear gate element (14) by an attachment portion (23) The two gate elements (14) an (15) are connected together 25 via a link drive in the form of a continuous wire cable (24) which is also connected to each gate element at points (23) and (25) respectively. The wire cable (24) moves around two cable guide pulleys (26) and (27). 30 As the pneumatic cylinder (22) moves along the shaft into the direction of arrow (28), the portion (23) to which the pneumatic cylinder is connected to the gate element (14) also moves in the same direction, pulling the cable around the pulleys (26) and (27) resulting in portion (25) 35 pulling gate element (15) in the opposite direction. This movement results in the gate elements moving from the open to the closed position. Similarly the opposite action of N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH speci as filed.doc 13/02/08 - 34 the pneumatic cylinder will result in the gate elements moving from the closed to the open position. Figures 4A and 4B show an embodiment of the present 5 invention including an opening control system including a brake (30) that can be used to control the width to which the gate elements open to in the open position. Figure 4A shows the two gate elements, (28) being the rear 10 gate element and (29) being the front gate element. The front gate element (29) includes a pneumatic brake (30) which acts between the mounting structures of the front and rear gate elements. 15 The brake (30) is positioned within and extending from a moulded cavity in the front gate element (31). When the brake (30) is applied it applies pressure to the rear gate element in the direction of arrows (32), 20 providing friction to stop and lock the two gate elements in position when the brake is applied. Figure 4A also shows the wire cable (33) and pulleys (34) and (35) as discussed in relation to Figure 3. 25 The rear gate element (28) also includes a number of metal inserts (38) which determine the position of the gate elements relative to one another in conjunction with a sensor (37). The sensor may be configured to determine how 30 many inserts have been traversed, and therefore the displacement of the gate elements (28, 29) from one another. The brake (30) can then be applied at the correct time to ensure that the gate elements in the open position are at the desired displacement from one another. 35 Figure 4A also shows an air port (36) for the pneumatic brake. N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH speci as filed.doc 13/02/08 - 35 Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope of the appended claims. 5 In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as 10 "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. 15 It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country. N:\Melbourne\Cases\Patent\76000-76999\P76922.AU\Specis\P76922.AU GH speci as filed.doc 13/02/08