Overhead line support structure

Abstract

An overhead line support structure 10 suitable for an overhead line equipment (OLE) installation (figure 1, 100). The overhead line support structure 10 comprises a support mast 20 having a first end

Description

FIELD OF THE INVENTION The present invention relates to an overhead line support structure for an overhead line equipment (OLE) installation, to a linear drive mechanism for said overhead line support structure, to an overhead line equipment (OLE) installation comprising said overhead line support structure, and to a method of adjusting a gradient of a contact wire of said overhead line equipment (OLE) installation. BACKGROUND OF THE INVENTION Rail electrification is the process of powering rail vehicles (e.g., locomotives) by electricity from an external source, such as overhead lines or conductor rails. Rail electrification has several benefits compared to more traditional methods of powering rail vehicles, such as diesel or steam. Firstly, rail electrification reduces greenhouse gas emissions and air pollution by replacing fossil fuels with cleaner sources of energy. This can help mitigate the effects of climate change and improve public health. Secondly, rail electrification improves energy efficiency and lowers operating costs by reducing fuel consumption and maintenance needs. More particularly, electrically-powered rail vehicles typically have higher power-to-weight ratios and can accelerate and brake more quickly than diesel or steam alternatives, which saves energy and time. Furthermore, electric rail vehicles are also capable of regenerative braking, meaning that some of the motive energy lost during braking can be recovered. Thirdly, rail electrification also increases reliability and performance by eliminating the risk of mechanical failures or fuel shortages that can disrupt service. Electric rail vehicles also tend to have better traction and can operate on steeper gradients and curves when compared to their steam or diesel-powered equivalents, which further enhances rail vehicle safety and flexibility. As such, the aforementioned benefits make rail electrification a desirable option for modernizing and upgrading rail systems around the world. However, electrifying existing track can also present several challenges. In particular, overhead lines need to have a flat or shallow gradient to provide a smooth “pantograph to contact wire” interface to ensure a continuous flow of electricity is provided from the contact wire to the pantograph of the electric rail vehicle. Notably, rapid changes in the gradient of the overhead line can lead to poor mechanical performance, and can also result in poor contact, or even detachment, of the pantograph from the contact wire during use. The need for flat or shallow gradients can be particularly challenging when installing overhead lines in built-up areas (e.g., stations) where changes in the height of the overhead line may be required to avoid obstacles (e.g., bridges, buildings, pedestrian walkways, level crossings etc.) and / or to comply with local height restrictions. When designing railway infrastructure, it is conventional for designers and engineers to follow a “simulate and build” methodology in which a proposed design is first simulated (or modelled) using suitable computational software to assess its viability before being implemented in a final “built” product. However, it has been found that this approach can often lead to overly “conservative” (or shallow) gradient angles being implemented which may lead to unnecessary and expensive civil interventions (such as the demolition of existing infrastructure) and / or speed restrictions in areas where a more aggressive (or steeper) gradient angle may have allowed the overhead line infrastructure to avoid the obstacle (thereby avoiding the need for such interventions). It is the aim of the present invention to provide a solution to this issue. SUMMARY OF THE INVENTION The present teachings provide an overhead line equipment (OLE) installation and a method of adjusting a gradient of a contact wire for an overhead line equipment (OLE) installation according to the appended claims According to a first aspect of the present invention, there is provided an overhead line equipment (OLE) installation for transmitting electrical power to an electric rail vehicle comprising: a plurality of overhead line support structures each comprising: a support mast having a first end mounted to a foundation, a second end opposite the first end, and a longitudinal axis defined between said first and second ends; a cantilever arm arranged transverse to the longitudinal axis of the support mast; and a linear drive mechanism configured to adjust a vertical position of the cantilever arm relative to the support mast; a catenary wire suspended from and / or supported by the respective cantilever arms of the plurality of overhead line support structures; and a contact wire suspended from the catenary wire, said contact wire being configured for carrying an electric current for transmitting electrical power to an electric rail vehicle, wherein each linear drive mechanism comprises: a carriage unit for coupling the cantilever arm to the support mast, said carriage unit being moveable along the longitudinal axis of the support mast; and an electric motor for adjusting the vertical position of the carriage unit relative to the support mast, and wherein the overhead line equipment (OLE) installation further comprises at least one control system configured to adjust a gradient of the contact wire via operating one or more of the electric motors. Advantageously, the provision of a linear drive mechanism for adjusting a vertical position of the cantilever arm relative to the support mast allows the gradient of the contact wire (suspended from said cantilever arm when the overhead line support structure is used as part of an overhead line equipment (OLE) installation) to be adjusted by a user. As such, the claimed invention allows users to rapidly replicate current and proposed electrification gradients as part of a real-life test rig before construction of a final “built” product has begun. This enables engineers and designers to perform testing on proposed overhead line equipment (OLE) installations featuring sharp gradient changes to assess their viability which, if found to be viable, may reduce the need for expensive civil interventions and / or speed restriction in order to realise the final “built” product in a real-world civil infrastructure project. Optionally, the support mast may comprise a web and at least one flange, and the carriage unit may comprise a plurality of rollers configured to engage with said flange. Optionally, the plurality of rollers may be formed of a hardened steel material. Optionally, the carriage unit may comprise a first set of rollers configured to engage with a trackside face of the flange, and a second set of rollers configured to engage with a rear-side face of the flange. Optionally, at least one of the first and / or second sets of rollers may be adjustably mounted to the carriage unit. Optionally, the carriage unit may comprise a first plate, a second plate arranged substantially parallel to the first plate, and at least one support bracket extending transversely between the first and second plates. Optionally, the linear drive mechanism may comprise a screw drive assembly (e.g., a screw jack) operably connected to an output of the at least one actuator for converting rotational motion of the at least one actuator into linear motion for moving the carriage unit along the longitudinal axis of the support mast. Optionally, the screw drive assembly may comprise a stationary element which is fixed relative to the support mast and a moving element, which is extendable relative to the stationary element, said moving element having a first end which is contained within a body of the stationary element and a second end which is coupled to the carriage unit. Optionally, the screw drive assembly may be configured such that extension of the moving element out of the body of the stationary element causes the carriage unit to descend down the longitudinal axis of the support mast. Optionally, the screw drive assembly may be further configured such that retraction of the moving element into the body of the stationary element causes the carriage unit to ascend up the longitudinal axis of the support mast. Optionally, the linear drive mechanism may be configured to move the cantilever arm between a maximum height position, in which the cantilever arm is positioned proximate to the second end of the support mast, and a minimum height position, in which the cantilever arm is positioned approximately mid-way between the first and second ends of the support mast. Optionally, the cantilever arm may be pivotally mounted to the carriage unit so as to permit yawwise rotation of the cantilever arm relative to the carriage unit. Optionally, the linear drive mechanism may be contained within a housing formed of a weatherproof material. Optionally, the weatherproof material may be selected from one, or a combination, of stainless steel; aluminium, fiberglass, polycarbonate (PC), polyethylene (PE), polyvinyl chloride (PVC), and / or acrylic. Optionally, the housing may comprise an elongate slot extending in a direction substantially parallel to the longitudinal axis of the support mast for facilitating connection of the cantilever arm to the carriage unit. Optionally, the overhead line support structure may further comprise a height gauge extending vertically along an exterior surface of the housing. Optionally, the at least one control system may be configured to adjust the gradient of the contact wire via operating a plurality of the electric motors in unison. Optionally, the control system may further comprise a plurality of sensors configured to calculate the respective heights of each cantilever arm. Optionally, the plurality of overhead line support structures may each comprise a screw drive assembly (e.g., a screwjack), each screw drive assembly may be operably connected to a respective one of the electric motors, and the plurality of sensors may be configured to calculate the respective heights of the cantilever arms based on the rotational positions of the screw drive assemblies. Optionally, the control system may further comprise at least one limit switch configured to deactivate the electric motor when the cantilever arm reaches a minimum height position and / or a maximum height position. Optionally, the overhead line equipment (OLE) installation may be an overhead line equipment testing rig. According to a second aspect of the present invention, there is provided a method of adjusting a gradient of a contact wire for an overhead line equipment (OLE) installation comprising the steps of: a) providing an overhead line equipment (OLE) installation according to the first aspect of the invention; and b) operating at least one of the linear drive mechanisms so as to adjust a vertical position of at least one of the cantilever arms relative to the support mast to which said at least one cantilever arm is attached. Optionally, step b) may comprise operating a plurality of the linear drive mechanisms in unison. According to a third aspect of the present invention, there is provided a linear drive mechanism for an overhead line support structure having a support mast and a cantilever arm, said linear drive mechanism comprising: a carriage unit for coupling a cantilever arm to a support mast of an overhead line support structure, said carriage unit comprising a plurality of rollers configured for engaging with the support mast so as to permit vertical movement of the carriage unit along a longitudinal axis of the support mast; and a screw drive mechanism for adjusting the vertical position of the carriage unit relative to the support mast, said screw drive mechanism comprising a stationary element, and a moving element which is extendable relative to the stationary element, said moving element having a first end which is contained within a body of the stationary element and a second end which is coupled to the carriage unit. It shall be appreciated that optional features of the first aspect of the invention may be combined with the second and / or third aspects of the invention. It shall be appreciated that the term “electric rail vehicle” is defined herein as a vehicle that runs on rails and which is powered primarily via electricity obtained from either a conductor rail or from an overhead contact wire. It shall also be appreciated that the term “electric rail vehicle” encompasses both locomotives (e.g., electric trains) and also light rail vehicles such as trams or streetcars. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of an overhead line equipment (OLE) installation according to an embodiment of the present invention; Figure 2 is a schematic illustration of an overhead line support structure of the overhead line equipment (OLE) installation illustrated in Figure 1; Figure 3A is a side view of the carriage unit of the overhead line support structure illustrated in Figure 2; Figure 3B is a top view of the carriage unit of the overhead line support structure illustrated in Figure 2; Figure 4A is a schematic illustration of the overhead line support structure illustrated in Figure 2 in which the cantilever arm is at a maximum height position; Figure 4B is a schematic illustration of the overhead line support structure illustrated in Figure 2 in which the cantilever arm is at a minimum height position; Figure 5 is a schematic illustration of an overhead line support structure according to an alternative embodiment of the present invention, in which the vertical position of the carriage unit can be adjusted via a manually-operated actuator; and Figure 6 is a schematic illustration of a housing suitable for use with the overhead line support structures illustrated in Figures 2 and 4. DETAILED DESCRIPTION OF EMBODIMENT(S) Figure 1 shows an overhead line equipment (OLE) installation 100 in accordance with an embodiment of the present invention. In the illustrated embodiment, the overhead line equipment (OLE) installation 100 is an overhead line equipment (OLE) testing rig which is designed to mimic real-life civil infrastructure to enable realistic testing of sharp (or steep) contact wire gradients. However, it shall be appreciated that in other embodiments, the overhead line equipment (OLE) installation may be used on a live section of rail track. As shown in Figure 1, the overhead line equipment (OLE) installation 100 comprises a plurality of overhead line support structures 10, at least one catenary wire 12 suspended from and / or supported by respective cantilever arms 30 of the plurality of overhead line support structures 10 and at least one contact wire 14 suspended from the at least one catenary wire 12. The contact wire 14 is configured for carrying an electric current and for transmitting electrical power to electric rail vehicles travelling along a rail track (not shown) adjacent to the overhead line equipment (OLE) installation 100. As such, the contact wire 14 is typically formed of an electrically conductive material (e.g., copper) and is connected at one or both ends to an associated power supply (not shown). Meanwhile, the catenary wire 12 is configured to hold the contact wire 14 at a substantially consistent height and / or gradient relative to the overhead line support structures 10 to help achieve a smooth and consistent contact between the contact wire 14 and the pantograph of an electric rail vehicle (not shown) as it travels along the adjacent rail track. The catenary wire 12 is typically formed of the same or similar materials (e.g., copper) as that of the contact wire 14 and is held under tension via a suitable tensioning apparatus (such as a spring or a weight) to maintain a constant tension on the catenary wire 12 which helps prevent unwanted sagging or dropping of the contact wire 14 during use. In some embodiments, the overhead line equipment (OLE) installation 100 may also comprise a plurality of droppers 16 extending at regular intervals between the catenary wire 12 and the contact wire 14 to help further ensure a consistent contact wire height and / or gradient is maintained along the overhead line equipment (OLE) installation 100. It shall also be appreciated that in some embodiments, the overhead line equipment (OLE) installation 100 may also comprise one or more auxiliary wires, such as an additional catenary wire or a feeder wire, to provide further mechanical and / or electrical support to the contact wire 14. Figure 2 shows a more detailed view of one of the overhead line support structures 10 of the overhead line equipment (OLE) installation 100 illustrated in Figure 1. Whilst only one of the overhead line support structures 10 is depicted in Figure 2, it shall be appreciated that the remaining overhead line support structures 10 of the overhead line equipment (OLE) installation 100 are of a substantially identical construction and so, for the sake of conciseness, shall not be described further within this application. As shown in Figure 2, the overhead line support structure 10 comprises a support mast 20, a cantilever arm 30 arranged transverse to said support mast 20, and a linear drive mechanism 50 for adjusting a vertical position of the cantilever arm 30 relative to the support mast 20. Considering firstly the support mast 20, as shown in Figure 2, the support mast 20 has a first end 22 which is mounted to a foundation 24 (e.g., the ground) and a second end 26 which is provided opposite (or distal) to the first end 22. The support mast 20 has a longitudinal (X-X) axis which is defined between the first 22 and second 26 ends of the support mast 20. In the illustrated embodiment, the longitudinal (X-X) axis extends in a substantially vertical direction. In the illustrated embodiment, the support mast 20 is an I-beam (sometimes referred to as an “H-beam”) and hence comprises a pair of flanges 21, 23 which are connected via a web 25 which extends along the longitudinal (X-X) axis of the support mast 20. However, it shall be appreciated that in other embodiments, the support mast 20 may comprise a different structure such as a T-beam, a box beam, U-beam, or a cylindrical pipe structure. It shall also be appreciated that the support mast 20 may be made of metal, composite, or any other suitable material depending on the design and requirements of the overhead line equipment (OLE) installation 100. Considering now the cantilever arm 30, as mentioned above, the cantilever arm 30 is arranged transverse to the longitudinal (X-X) axis of the support mast 20 and is configured for supporting the catenary 12 and contact 14 wires of the overhead line equipment (OLE) installation 100. As shown in Figure 2, the cantilever arm 30 comprises a base portion 31 for coupling the cantilever arm 30 to the support mast 20 and a stay arm 32 (sometimes referred to as a “top anchor”) extending outwardly away from the base portion 31 in a direction transverse to the longitudinal (X-X) axis of the support mast 20. In the illustrated embodiment, the cantilever arm 30 also comprises an angled bracket portion 33 which extends obliquely between the base portion 31 and the stay arm 32 for providing additional structural support to the cantilever arm 30. However, it shall be appreciated that in other embodiments, the angled bracket portion 33 may be omitted. The cantilever arm 30 also comprises a stay arm insulator 34 which is configured to insulate the support mast 20 and other components of the overhead line support structure 10 from electrical currents passing through the contact wire 14 during use. In the illustrated embodiment, the stay arm insulator 34 is located approximately mid-way along a length of the stay arm 32. However, it shall be appreciated that in other embodiments, the stay arm insulator 34 may instead be provided at other locations along the length of the stay arm 32. For example, in some embodiments, the stay arm insulator 34 may be provided at a position proximate to the base portion 31. Furthermore, in embodiments in which the cantilever arm is a “Type C” or “Bonomi” cantilever, the cantilever arm may comprise multiple (e.g., two) insulators provided proximate to the support mast 20. The cantilever arm 30 also comprises a catenary support 35 for receiving and supporting a catenary wire 12 when the overhead line support structure 10 is utilised as part of an overhead line equipment (OLE) installation 100. As shown in Figure 2, the catenary support 35 is provided at a distal end of stay arm 32 at a location laterally outboard of the stay arm insulator 34. The cantilever arm 30 also comprises a registration arm 36 having a first end which is coupled (e.g., via a drop bracket) to the distal end of stay arm 32 at a location laterally outboard of the stay arm insulator 34 and a second end which is coupled to a steady arm 37 which supports the contact wire 14 when the overhead line support structure 10 is utilised as part of an overhead line equipment (OLE) installation 100. It shall be appreciated that the cantilever arm 30 depicted in Figure 2 is a standard (Series 1) type of electrification cantilever arm which is commonly used within the rail industry and so, for the sake of conciseness, shall not be described in further detail. However, it shall also be appreciated that, in other embodiments, the overhead line support structure 10 may comprise other types of cantilever arm such as “Type C” cantilever arms, “Bonomi” cantilever arms and / or “UKMS” cantilever arms. Considering now the linear drive mechanism 50, the linear drive mechanism 50 comprises a carriage unit 60 for coupling the cantilever arm 30 to the support mast 20 and an actuator 70 for adjusting the vertical position of the carriage unit 60 relative to the support mast 20. As shown in Figure 2, in the illustrated embodiment the base portion 31 of the cantilever arm 30 is mounted to the carriage unit 60 via a pivot joint so as to permit yaw-wise rotation of the cantilever arm 30 relative to the carriage unit 60. However, it shall be appreciated that in other embodiments, the cantilever arm 30 may be fixed relative to the carriage unit 30. For example, in some embodiments, the carriage unit 60 may be integrally formed as part of the cantilever arm 30. Figures 3A and 3B show side and top views of the carriage unit 60 of the overhead line support structure 10 illustrated in Figure 2. Referring to Figure 3A, the carriage unit 60 comprises a body 61 to which a plurality of rollers 62, 63 are mounted. The plurality of rollers 62, 63 are configured to engage with the front (or track-side) flange 23 of the support mast 20 thereby coupling the carriage unit 60 to the support mast 20 whilst also permitting vertical movement of the carriage unit 60 along the longitudinal (X-X) axis of the support mast 20. In the illustrated embodiment, the plurality of rollers 62, 63 are formed of a hardened steel material to allow for substantially frictionless movement of the carriage unit 60 along the front (or track-side) flange 23 of the support mast 20. However, it shall be appreciated that in other embodiments, other suitable materials may be used. As shown in Figure 3A, the plurality of rollers comprise a first set of rollers 62 which are configured to engage with a front (or track-side) face of the flange 23 and a second set of rollers 63 positioned rearward of the first set of rollers 62 which are configured to engage with a rear face of the flange 23. In the illustrated embodiment, the second set of rollers 63 are adjustably mounted to the carriage unit 60 such that the size of the gap (not shown) defined between the first 62 and second 63 sets of rollers can be adjusted to account for manufacturing tolerances in the front (or track-side) flange 23 of the support mast 20. This helps to ensure that a consistent and continuous contact can be maintained between the rollers 62,63 and the support mast 20 during use. However, it shall be appreciated that in other embodiments, the first set of rollers 62 may be adjustably mounted to the carriage unit 60 in addition to, or instead of, the second set of rollers 63. Furthermore, it shall also be appreciated that in further embodiments, the first 62 and second 63 sets of rollers may be mounted at a fixed position relative to the carriage unit 60. Referring now to Figure 3B, the body 61 of the carriage unit 60 is formed of a pair of first and second plates 64, 65 which are arranged substantially parallel to each another, and which are spaced apart in the lateral direction such that a space (A) is defined therebetween. As shown in Figure 3B, the plurality of rollers 62, 63 are mounted to the first 64 and second 65 plates in an equal distribution such that one half of the first 62 and second 63 sets of rollers are mounted to the first plate 64 and such that the other half of the first 62 and second 63 sets of rollers are mounted to the second plate 65. However, it shall be appreciated that in other embodiments, the plurality of rollers 62, 63 may be unequally distributed between the first 64 and second 65 plates. In the illustrated embodiment, the carriage unit 60 also comprises a pair of upper and lower support brackets 66a, 66b which extend transversely across the carriage unit 60 between the first 64 and second 65 plates. In other words, the pair of upper 66a and lower 66b support brackets extend laterally across the space (A) defined between the first 64 and second 65 plates. The upper 66a and lower 66b support brackets are configured to provided bracing to the body 61 of the carriage unit 60 to help prevent buckling or bending of the carriage unit 60 during use, which may cause misalignment of the rollers 62, 63. It shall also be appreciated that providing the carriage unit 60 as a pair of first 64 and second 65 plates helps to minimise the weight of the overhead line support structure 10. However, in alternative embodiments, the carriage unit 60 may be of a different construction, and hence the upper 66a and lower 66b support brackets may be omitted in some embodiments. Referring back to Figure 2, in the illustrated embodiment, the linear drive mechanism 50 also comprises a screw drive assembly (e.g., a screw jack) 80 which is configured to convert rotational motion of the at least one actuator 70 into linear motion for moving the carriage unit 60 relative to the support mast 20. However, it shall be appreciated that the screw drive assembly may be omitted in embodiments in which a linear actuator, rather than a rotary actuator, is utilised. As shown in Figures 4A and 4B, the linear drive mechanism 50 is configured to move the cantilever arm 30 between a maximum height position (shown in Figure 4A), in which the cantilever arm 30 is positioned proximate to the second end 26 of the support mast 20, and a minimum height position (shown in Figure 4B), in which the cantilever arm 30 is positioned approximately mid-way between the first 22 and second 26 ends of the support mast 20 in the longitudinal (X-X) direction. In the illustrated embodiment, the maximum height position is approximately 6m above the foundation 24 of the support mast 20, whilst the minimum height position is approximately 4m above the foundation of the support mast 20. As such, in the illustrated embodiment, the minimum and maximum height positions are separated by a distance of approximately 2m. The screw drive assembly 80 is made up of stationary element 82 (which may alternatively be referred to as a lead screw housing) which is fixed relative to the support mast 20 via a mounting bracket, and a moving element 84 which is extendable relative to the stationary element 82. As shown in Figure 2, the screw drive assembly 80 is fixed to the support mast 20 such that both the stationary element 82 and the moving element 84 extend in a direction substantially parallel to the longitudinal (X-X) axis of the support mast 20. Referring now to Figure 4B, the moving element 84 has a first end (not shown) which is contained within a body of the stationary element 82 and comprises a threaded outer surface (not shown) which is configured to engage with a correspondingly threaded surface provided on an inner surface (not shown) of the stationary element 82. The moving element 84 also comprises a second end which is coupled to the carriage unit 60. The moving element 84 is operably connected to an output of the at least one actuator 70 such that when the actuator 70 is activated, a rotational force is imparted on the moving element 84 thereby causing the moving element 84 to rotate about its axis. As the moving element 84 rotates about its axis, the engagement between the threaded outer surface (not shown) of the moving element 84 and the threaded inner surface (not shown) of the stationary element 82 also causes the moving element 84 to translate in the longitudinal (X-X) axis direction relative to the stationary element 82. As such, rotation of the moving element 84 in a first (e.g., clockwise) direction will cause the moving element 84 to extend out of the body of the stationary element 82 (shown in Figure 4B) and hence push the carriage unit 60 in a first (e.g., descending) direction along the longitudinal (X-X) axis of the support mast 20. Conversely, rotation of the moving element 84 in the opposite (e.g., anti-clockwise) direction will cause the moving element 84 to retract back into the body of the stationary element 82 (shown in Figure 4A) and hence pull the carriage unit 60 in the opposite (e.g., ascending) direction along the longitudinal (X-X) of the support mast 20. In this manner, the screw drive assembly 80 is able to convert rotational motion from the at least one actuator 70 into linear motion which can be used to effect translation of the carriage unit 60 in the ascending and / or descending directions along the longitudinal (X-X) axis of the support mast 20 thereby allowing the vertical position of the cantilever arm 30, and hence the gradient of the contact wire 14 suspended therefrom, to be adjusted. In particular, the claimed invention allows users to rapidly replicate current and proposed contact wire gradients as part of a real-life test rig before construction of a final “built” product has begun. This enables designers and engineers to perform testing on installations having sharp contact wire gradients to assess their viability which, if found to be viable, may reduce the need for expensive civil interventions or unnecessary speed restrictions in order to realise the final “built” product. It shall be appreciated that in the illustrated embodiment, the maximum height position (shown in Figure 4A) corresponds to the position of the cantilever arm 30 when the moving element 84 of the screw drive assembly 80 is fully retracted, whilst the minimum height position (shown in Figure 4B) corresponds to the position of the cantilever arm 30 when the moving element 84 of the screw drive assembly 80 is fully extended. In the illustrated embodiment, the at least one actuator 70 is an electric motor which is operably connected to a control system (not shown) which allows a user to operate (or activate) the electric motor, and hence adjust the vertical position of the cantilever arm 30, as may be required to adjust the gradient of the contact wire 14 of the overhead line equipment (OLE) installation 100. It shall be appreciated that a separate control system may be provided for each electric motor of the overhead line equipment (OLE) installation 100, or a single control system may be provided for operating the electric motors of the overhead line equipment (OLE) installation 100 in unison in order to achieve faster adjustment of the contact wire gradient. The one or more control systems (not shown) may be operably connected to the electric motors via a wired or wireless connection. In some embodiments, the control system (not shown) may further comprise a plurality of sensors configured to calculate the respective heights of each cantilever arm 30 of the overhead line equipment (OLE) installation which may be fed back to the user (e.g., via a visual display or indicator). For example, in some embodiments, the plurality of sensors may be configured to calculate the heights of the respective cantilever arms 30 based on the rotational position of the moving element 84 of the screw drive assembly 80. In other embodiments, a linear encoder may be attached to the stationary element 82. The linear encoder may comprise a wire which is attached to the carriage unit 60 such that movement of the carriage unit 60 down the support mast 20 causes the encoder to turn thereby enabling the position of the cantilever arm 30 to be accurately calculated. In the illustrated embodiment, the control system comprises a pair of limit switches 86, 88 which are positioned along the stationary element 82 at positions corresponding to the desired minimum and maximum heights of the cantilever arm 30. As shown in Figures 4A and 4B, a first limit switch 86 is positioned along the stationary element 82 at a position corresponding to the desired maximum height of the cantilever arm 30 and a second limit switch 88 is positioned along the stationary element 82 at a position corresponding to the desired minimum height of the cantilever arm 30. The first 86 and second 88 limit switches are operably connected to the electric motor and are configured to automatically de-activate the electric motor when the moving element 84 reaches a position which corresponds to the minimum or maximum height positions of the cantilever arm 30 along the support mast 20 thereby preventing further operation which could potentially damage the screw drive assembly 80 (or other components of the linear drive mechanism 50). Referring now to Figure 5, an overhead line support structure 200 according to an alternative embodiment of the present invention is provided in which the at least one actuator 270 is a manually-operated crank-handle. It shall be appreciated that in embodiments in which the linear drive mechanism comprises a manually-operated actuator 270, components such as the plurality of sensors, limit switches and the one or more control systems may be omitted. The overhead line support structure 200 illustrated in Figure 5 is otherwise of a substantially identical construction to those illustrated in Figures 1 and 2 and so, for the sake of conciseness, shall not be described further within this application. Like reference numerals denote equivalent parts. Figure 6 depicts a housing 90 suitable for use with the overhead line support structures illustrated in Figures 2 and 4. As shown in Figure 6, the housing 90 comprises a body 92 formed of a weatherproof material which is configured for containing components of the linear drive mechanism 50, such as the actuator 70 and the screw drive assembly 80, so as to protect said components from rain or dirt. The weatherproof material may be selected from one, or a combination of, stainless steel, aluminium, fibreglass, polycarbonate, polyethylene, polyvinyl chloride and / or acrylic, or, in other embodiments, may comprise any othersuitable weatherproof material. As shown in Figure 6, the housing 90 is mounted to the support mast 20 (e.g., via suitable connectors or fasteners) and comprises an elongate slot 94 which extends through a thickness of the housing 90 in a direction substantially parallel to the longitudinal axis (X-X) of the support mast 20 for facilitating connection between the cantilever arm 30 and the carriage unit 60 contained within the housing 90. In some embodiments, a height gauge 96 may be provided extending vertically along an exterior surface of the housing 90 to assist a user in determining the height of the cantilever arm 30. However, it shall be appreciated that in other embodiments, for example those in which the at least one actuator is electrically controlled and operated, the aforementioned height gauge 96 may be omitted. It shall also be appreciated that the housing 90 may be omitted in some embodiments. Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims

Claims

1. An overhead line equipment (OLE) installation for transmitting electrical power to an electric rail vehicle comprising:a plurality of overhead line support structures each comprising:a support mast having a first end mounted to a foundation, a second end opposite the first end, and a longitudinal axis defined between said first and second ends;a cantilever arm arranged transverse to the longitudinal axis of the support mast; anda linear drive mechanism configured to adjust a vertical position of the cantilever arm relative to the support mast;a catenary wire suspended from and / or supported by the respective cantilever arms of the plurality of overhead line support structures; anda contact wire suspended from the catenary wire, said contact wire being configured for carrying an electric current for transmitting electrical power to an electric rail vehicle,wherein each linear drive mechanism comprises:a carriage unit for coupling the cantilever arm to the support mast, said carriage unit being moveable along the longitudinal axis of the support mast; andan electric motor for adjusting the vertical position of the carriage unit relative to the support mast, andwherein the overhead line equipment (OLE) installation further comprises at least one control system configured to adjust a gradient of the contact wire via operating one or more of the electric motors.

2. The overhead line equipment (OLE) installation according to claim 1, wherein the support mast comprises a web and at least one flange, and wherein the carriage unit comprises a plurality of rollers configured to engage with said flange.

3. The overhead line equipment (OLE) installation according to claim 2, wherein the plurality of rollers are formed of a hardened steel material.

4. The overhead line equipment (OLE) installation according to claim 2 or 3, wherein the carriage unit comprises a first set of rollers configured to engage with a track-side face of the flange, and a second set of rollers configured to engage with a rear-side face of the flange.

5. The overhead line equipment (OLE) installation according to claim 4, wherein at least one of the first and / or second sets of rollers is adjustably mounted to the carriage unit.

6. The overhead line equipment (OLE) installation according to any preceding claim, wherein the carriage unit comprises:a first plate;a second plate arranged substantially parallel to the first plate; andat least one support bracket extending transversely between the first and second plates.

7. The overhead line equipment (OLE) installation according to any preceding claim, wherein each linear drive mechanism comprises a screw drive assembly operably connected to an output of the electric motor for converting rotational motion of the electric motor into linear motion for moving the carriage unit along the longitudinal axis of the support mast.

8. The overhead line equipment (OLE) installation according to claim 7, wherein the screw drive assembly comprises:a stationary element which is fixed relative to the support mast; anda moving element, which is extendable relative to the stationary element, said moving element having a first end which is contained within a body of the stationary element and a second end which is coupled to the carriage unit.

9. The overhead line equipment (OLE) installation according to claim 8, wherein the screw drive assembly is configured such that extension of the moving element out of the body of the stationary element causes the carriage unit to descend down the longitudinal axis of the support mast; andwherein the screw drive assembly is further configured such that retraction of the moving element into the body of the stationary element causes the carriage unit to ascend up the longitudinal axis of the support mast.

10. The overhead line equipment (OLE) installation according to any preceding claim, wherein the linear drive mechanism is configured to move the cantilever arm between a maximum height position, in which the cantilever arm is positioned proximate to the second end of the support mast, and a minimum height position, in which the cantilever arm is positioned approximately mid-way between the first and second ends of the support mast.

11. The overhead line equipment (OLE) installation according to any preceding claim, wherein the cantilever arm is pivotally mounted to the carriage unit so as to permit yaw-wise rotation of the cantilever arm relative to the carriage unit.

12. The overhead line equipment (OLE) installation according to any preceding claim, wherein the linear drive mechanism is contained within a housing formed of a weatherproof material.

13. The overhead line equipment (OLE) installation according to claim 12, wherein the housing comprises an elongate slot extending in a direction substantially parallel to the longitudinal axis of the support mast for facilitating connection of the cantilever arm to the carriage unit.

14. The overhead line equipment (OLE) installation according to claim 12 or 13, wherein the overhead line support structure further comprises a height gauge extending vertically along an exterior surface of the housing.

15. The overhead line equipment (OLE) installation according to any preceding claim, wherein the at least one control system is configured to adjust the gradient of the contact wire via operating a plurality of the electric motors in unison.

16. The overhead line equipment (OLE) installation according to any preceding claim, wherein the control system further comprises a plurality of sensors configured to calculate the respective heights of each cantilever arm.

17. The overhead line equipment (OLE) installation according to claim 16 when dependent on claim 7, wherein each screw drive assembly is operably connected to a respective one of the electric motors, andwherein the plurality of sensors are configured to calculate the respective heights of the cantilever arms based on the rotational positions of the screw drive assemblies.

18. The overhead line equipment (OLE) installation according to any preceding claim, wherein the control system further comprises at least one limit switch configured to de-activate the electric motor when the cantilever arm reaches a minimum height position and / or a maximum height position.

19. The overhead line equipment installation (OLE) according to any preceding claim, wherein the overhead line equipment (OLE) installation is an overhead line equipment testing rig.

20. A method of adjusting a gradient of a contact wire for an overhead line equipment (OLE) installation comprising the steps of:a) providing an overhead line equipment (OLE) installation according to any one of the preceding claims, andb) operating at least one of the linear drive mechanisms so as to adjust a vertical position of at least one of the cantilever arms relative to the support mast to which said at least one cantilever arm is attached.

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