Clamping assembly comprising a clamp and a strain relief guide

Abstract

A clamping assembly 10 (e.g., jumper clamping assembly for a catenary system) comprises a clamp 100 and a strain relief guide 200 (e.g., sleeve). The clamp comprises first and second clamping members

Description

FIELD OF THE INVENTION Embodiments of the present invention relate to a clamping assembly comprising a clamp and a strain relief guide. In particular, but not exclusively, they relate to a jumper clamping assembly for a catenary system. BACKGROUND TO THE INVENTION Jumpers are electrically conductive wires that electrically interconnect electrical wires, terminals, or electrodes. Jumpers have a defined purpose in the context of catenary systems for vehicles such as trains, trams, or trolleybuses. Jumpers are flexible, un-tensioned conductive lines that are used to ensure that electrical continuity is provided at overlaps between tension lengths (wire runs) of contact lines and / or catenary lines (messenger lines). Jumpers can further ensure that all wire run sections are at the same electrical potential. In catenary systems that do not have current-carrying droppers, a jumper can provide electrical current sharing between the contact line and the catenary line (messenger line). A dropper is a vertical tensioned line for suspending the contact line from the catenary line. Various types of clamps are used to connect elongate articles to each other. In the context of jumpers, clamps can connect the jumper to the catenary line and to the contact line. The jumper may extend in a C-shape rather than in a vertical line, to tolerate cyclic upwards heave (uplift) of the contact line from passing vehicle power collectors. Therefore, the jumper extends into each clamp in a horizontal orientation, parallel to the respective catenary line or contact line, and turns by 180 degrees between the clamps to define a C-shape. Railway Technical Standards may specify a minimum or target curve radius, e.g., 150mm, of the jumper as it enters the upper clamp to the catenary line. Due to cyclic heave, the radius of the jumper repeatedly changes. Where the jumper may be a wire rope, localised damage such as kinks or ‘bird caging’ of wire strands can be accelerated if the actual radius is regularly allowed to fall below the minimum curve radius. One can hang a vertical cable tie near the upper clamp, connected to the catenary line at its top end and to the jumper at its bottom end. The cable tie hoists the jumper to a required height ensuring a desired curvature of the jumper as the jumper enters the upper clamp. However, the installation of cable ties is labour-intensive, is performed at height, and is sensitive to alignment errors. Further, the above approach cannot be used to control the radius of the lower end of the jumper, as the jumper enters the lower clamp. The radius of the lower end of the jumper is generally uncontrolled. There are various topologies for connecting a jumper. In one example, a jumper may be a current-carrying jumper for electrically interconnecting a pair of contact lines and a pair of catenary lines. The jumper starts at a first contact line, extends up in a vertical C-shape to the first catenary line above the first contact line, extends laterally in a C-shape to a second catenary line horizontally adjacent the first catenary line, and then extends down in a vertical C-shape to a second contact line below the second catenary line. Alternatively, the jumper may be an equipotential jumper for electrically interconnecting one contact line and a pair of catenary lines. Alternatively, the jumper may be a single C-jumper for electrically interconnecting one contact line to one catenary line. BRIEF DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION According to various, but not necessarily all, embodiments of the invention there is provided a clamping assembly comprising a clamp and a strain relief guide, wherein the clamp comprises first and second clamping members (e.g., clamping legs) movable towards an outer side surface of an elongate article to secure the elongate article therebetween in a channel of the clamp, and wherein the strain relief guide is configured to extend from the channel and is resiliently flexible along its length. This provides the advantage of ensuring a minimum radius at which the elongate article enters or exits the clamp, with reduced installation time and error prevention. The elongate article may be an overhead line of a catenary system. The clamp may therefore be classified as an overhead line clamp. The strain relief guide may comprise a sleeve, also referred to as a boot or jacket. The strain relief guide may be shaped to surround or mostly surround the elongate article, by greater than 180 degrees or greater than 200 degrees. An advantage is that the strain relief guide retains the elongate article when flexed in any direction. This means that the strain relief guide is effective regardless of the orientation of the clamping assembly and the primary direction of flexing. The strain relief guide may be configured for side-entry installation onto the elongate article. The strain relief guide may comprise a longitudinal opening for side-entry installation onto the elongate article. The longitudinal opening may be in the form of a slit. In such examples, the strain relief guide partially surrounds but does not fully surround the elongate article. Alternatively, the longitudinal opening may be closed after installation. An advantage of side-entry installation is ease of installation because the strain relief guide does not have to be pre-attached to the elongate article before the combination is secured to the clamp. Because the strain relief doesn't need to be fed onto the elongate article from the end, the installer can install the clamping assembly, make any adjustments to ensure it is installed correctly, and then attach the strain relief guide once all geometry measurements are correct. However, if any adjustments do need to be made at a later date, the hand-operable latch (described later) on the clamping assembly can be released with the strain relief in situ and the elongate article adjusted. Another advantage of the longitudinal slit is maintenance, because if a new strain relief needs to be installed then the worker would not need to release the clamping device; a new strain relief could simply be installed. A width of the longitudinal opening may be less than an interior diameter of the strain relief guide, to enable the strain relief guide to be snap-fit connected to the outer side surface of the elongate article, through the longitudinal opening. The strain relief guide may have a first stiffness against resilient flexing in a first plane, and a second stiffness against resilient flexing in a second perpendicular plane. The first and second planes may collectively define vertical and horizontal planes, in use. The first stiffness may be approximately the same or similar to the second stiffness, e.g., less than double the second stiffness or less than triple the second stiffness. Equal flexibility in all planes is useful as disclosed in the next paragraph. However, if the strain relief guide has a longitudinal opening for side-entry installation, it may be more flexible in the vertical plane than in the horizontal plane. Likewise, the flexibility of the strain relief guide in different planes may depend on how the structural members of the strain relief guide are arranged. Hence, the first and second stiffnesses are not explicitly stated above as being equal. An advantage of the equal flexibility is that the strain relief guide can be configured to allow the elongate article to enter or exit the clamp at any of a horizontal angle, a vertical angle, or a combination thereof. When the elongate article is a jumper, some jumper topologies involve bending the jumper in multiple planes to interconnect horizontally-adjacent catenary lines as well as to interconnect each catenary line with the contact line beneath it. The strain relief guide of each clamping assembly can control the radius of each bend of the jumper, regardless of direction. The strain relief guide may comprise longitudinally-separated rows of material separated by gaps, the gaps being arranged to allow adjacent rows to resiliently flex in the first plane and to resiliently flex in the second plane. The rows of material may be rows of elongate members. The elongate members may be arcuate in form. The gaps may comprise slots and / or recesses. Bridges at the ends of the slots may interconnect the rows of elongate members. The bridges between adjacent rows may be staggered. An advantage of staggering the bridges is that the difference between the first and second stiffnesses of the strain relief guide can be reduced. The strain relief guide may be bidirectionally resiliently flexible in each of the first and second planes. Bidirectional flexibility can be defined as the stiffness in each opposite direction being approximately equal, or within 10% or within 20%. The strain relief guide may be formed from a rubber or plastics material, or a sheet spring metal or spring wire. The strain relief guide may extend coaxially with the channel when in a neutral undeformed state. The strain relief guide may be linear when in the neutral undeformed state. An advantage is compatibility because it can be flexed in any direction, and is therefore compatible with a wide variety of clamping positions and jumper bend directions. The strain relief guide may comprise a connector arrangement to secure the strain relief guide to the clamp. The connector arrangement may be hand-securable to the clamp and hand-releasable from the clamp. An advantage is that no bolts or tools need to be handled. The connector arrangement may be shaped to cover one of the ends of the clamp. The connector arrangement may be shaped to cover a gap between the first and second clamping members. An advantage is that this helps to trap the elongate article in the channel in the gap between the first and second clamping members. The connector arrangement may be configured to fit to both the first and second clamping members. The connector arrangement may be configured to lock the first and second clamping members in a closed position, when connected to the clamp. An advantage is that the strain relief guide reduces the probability of unintentional release of the clamp during operation. The connector arrangement may comprise one or more clips. Each clip may be a snap-fit clip. An advantage is ease of installation. The connector arrangement may comprise a snap-off (quick-release) clip, a locking clip, or a combination thereof. The snap-off clip may be shaped to flexibly snap onto the clamp, in a push-fit manner. The snap-off clip may be quick-releasable by pulling it off the clamp, without intervening steps. An advantage is convenience. The locking clip may comprise an undercut. The clamp may comprise a corresponding socket for the undercut. Alternatively, the locking clip may comprise the socket and the clamp may comprise the undercut. The locking clip locks to the clamp, preventing the strain relief guide from being pulled off the clamp without first disengaging the locking clip. An advantage is improved retention, and the engagement of the undercut with the socket provides tactile feedback that the strain relief guide is properly secured. The clamping system may comprise a pair of the strain relief guides, individually securable to the clamp in alignment with opposite ends of the channel. Alternatively, a single strain relief guide may comprise a pair of sleeves extending in opposite directions from a central connector arrangement. An advantage of this double-sided strain relief arrangement is that when the clamp is a through-clamp, rather than a termination clamp, the radius of the elongate article is protected as it enters and exits the clamp. In the case of a jumper, the upper clamp connected to the catenary line may be a through-clamp, while the lower clamps connected to the contact lines may be termination clamps for the ends of the jumper. An advantage of having a pair of individually securable and releasable strain relief guides, each having its own connector arrangement to the clamp, is that a single design of strain relief guide is compatible with both through-clamps and termination clamps. When the clamp is a termination clamp, such as a contact line clamp (lower clamp), the installer can fit only one strain relief guide at the desired end, whereas when the clamp is a through-clamp, such as some catenary line clamps (upper clamps), the installer can fit a pair of opposing strain relief guides to the upper clamp of the jumper. The clamp may be configured to connect a pair of elongate articles. For a catenary system, a first elongate article of the pair may be a catenary line or a contact line, and a second elongate article of the pair may be the elongate article (e.g., jumper) referred to earlier. The clamp may comprise: a first closed position to secure the clamp to the first elongate article; and a second closed position to further secure the clamp to the second elongate article. According to various, but not necessarily all, embodiments of the invention the clamp comprises: a bias urging the first and second clamping members towards the first closed position to secure the clamp to the first elongate article; and a fastener arrangement to actuate the clamping members towards a second closed position to further secure the clamp to the second elongate article. The bias provides the advantage that the user can let go of the clamp and the clamp will stay secured to the first elongate article. This frees up the user’s hands to manipulate the second elongate article into position and then operate the fastener arrangement (fastener or fasteners). No tools are required to secure the clamp to the first elongate article. The installation time is also reduced. If the fastener is the later-described hand-operable latch, the overall installation time may be less than 10 seconds and completely tool-free. The pair of elongate articles may be electrical conductors. The pair of elongate articles may be wires. The clamp may be configured to electrically and mechanically connect the pair of elongate articles. The clamp may be compatible with both the contact line and the catenary line, despite them having different cross-section shapes. An advantage is that the clamp has a single standardised shape. The contact line may have a rounded perimeter comprising side grooves. The jumper may have a substantially circle-shaped perimeter. The catenary line may have a substantially circle-shaped perimeter. At the second closed position, the clamping members may be simultaneously secured to the substantially circle-shaped perimeter of the jumper, and either the side grooves of the contact line or the substantially circle-shaped perimeter of the catenary line. The clamping members at the second closed position may be configured to secure the first and second elongate articles substantially parallel to each other. The clamping members at the second closed position may be configured to secure the first and second elongate articles at a separation of approximately 35mm or more, measured from centre-to-centre of the first and second elongate articles. The clamp may have a first end and a second opposite end. The pair of clamping members at the first closed position may be configured to clamp the first elongate article therebetween, at or proximal to the first end of the clamp. The clamping members at the second closed position may be further configured to clamp the second elongate article therebetween, at or proximal to the second end of the clamp. Therefore, at the second closed position, the clamping members may be configured to simultaneously clamp the first and second elongate articles therebetween. The clamping members at the second closed position may be configured to clamp the second elongate article substantially parallel to the first elongate article. The clamping members actuated by the fastener arrangement may be the pair of clamping members. Therefore, at the second closed position, the pair of clamping members may be secured to the first and second elongate articles. The clamp may comprise no more clamping members than the pair of clamping members. Each of the pair of clamping members may have a first end, the first ends being at the first end of the clamp. Each of the pair of clamping members may have a second opposite end, the second ends being at the second end of the clamp. At the first closed position, the first ends of the pair of clamping members may be closer to each other than the second ends of the pair of clamping members, enabling the first elongate article to be clamped at or proximal to the first ends of the clamping members. At the second closed position, the second ends of the pair of clamping members may be closer to each other than the second ends are in the first closed position, enabling the second elongate article to be clamped at or proximal to the second ends of the clamping members. At the first closed position, the pair of clamping members may be splayed out relative to each other. At the second closed position, the pair of clamping members may be more parallel relative to each other than in the first closed position. At the second closed position, the pair of clamping members may be substantially parallel relative to each other. The degree to which the pair of clamping members are parallel may depend on any differences in the crosssections of the pair of elongate articles. The bias may be configured to apply bias force at a location between the first and second ends of the pair of clamping members. The bias may urge the first ends towards each other. The bias may urge the second ends away from each other. The bias may urge the pair of clamping members from an open position towards the first closed position. The bias may urge the one end of the clamp closed (the first end). At the open position, corresponding ends of the pair of clamping members may be separated to enable the first elongate article to be received between the corresponding ends. The corresponding ends may define a mouth therebetween for receiving the first elongate article. The corresponding ends may be the first ends of the pair of clamping members referred to above. At the open position, the corresponding ends of the pair of clamping members may be further apart from each other than when the pair of clamping members are at the first closed position, to enable the first elongate article to be received between the corresponding ends. At the first closed position, the corresponding ends of the pair of clamping members may be close enough to each other for the bias to secure the first elongate article between the pair of clamping members. The pair of clamping members may be actuatable from the first closed position to the open position by actuation against a force of the bias. The actuation may separate the corresponding ends of the pair of clamping members to enable the first elongate article to be received between the corresponding ends. A position of the actuation may be at or proximal to opposite ends of the pair of clamping members, opposite the corresponding ends. The opposite ends may be the second ends of the pair of clamping members referred to earlier. The actuation to the open position may comprise squeezing the pair of clamping members together at the position at or proximal to the opposite ends of the pair of clamping members. The bias may have a stiffness low enough that the actuation can be effected by a user’s digits, such as a thumb and fingers, to actuate the pair of clamping members to the open position. The clamp can therefore be defined as a hand- operable clamp. The clamp may be hand-actuatable between the open position and the first closed position. The fastener arrangement may have discrete states including an unlocked position and a locked position. This obviates the need for a torque specification for the user to manually check and adhere to. The fastener arrangement may be in the unlocked position when the clamp is open for receiving the first elongate article. The clamping members may be in the open position described above. The fastener arrangement may be in the unlocked position when the pair of clamping members are at the first closed position securing the first elongate article. The fastener arrangement may be in the locked position when the clamping members are at the second closed position. The fastener arrangement may move the pair of clamping members from the first closed position to the second closed position, when the fastener arrangement is moved / tightened from the unlocked position to the locked position. The fastener arrangement may be configured to actuate (force) the clamping members towards each other. The fastener arrangement may be configured to actuate the clamping members towards each other when the fastener arrangement is moved from the unlocked position to the locked position. This may make the clamping members more parallel as described earlier. While the fastener arrangement is at the unlocked position, the clamping members may be openable to receive the first elongate article therebetween, then releasable to enable the bias to move the pair of clamping members to the first closed position to secure the first elongate article while the second elongate article is inserted between the clamping members. When the fastener arrangement is moved to the locked position, the fastener arrangement may move the clamping members closer together to further secure the second elongate article therebetween such that both the first and second elongate articles are simultaneously clamped. The fastener arrangement may comprise a hand-operable latch. The hand-operable latch provides the advantage of enabling rapid securing of the elongate articles, and for rapid adjustment of the clamp position to correct the positioning of the elongate articles. This is because the hand-operable latch obviates the requirement for tools. The clamp can therefore be described as hand-actuatable between the first and second closed positions, via the fastener arrangement. The hand-operable latch may comprise a hand-operable lever. One end of a stroke of the hand-operable lever may define the unlocked position of the fastener arrangement. An opposite end of the stroke of the hand-operable lever may define the locked position of the fastener arrangement. Rotating the hand-operable lever towards the locked position may translate and / or rotate move the clamping members closer together. The clamping members may be forced together to become more parallel to each other and to simultaneously clamp the pair of elongate articles. The fastener arrangement may define a bistable latch mechanism. For example, the hand-operable latch may be an over-centre latch. The over-centre latch may comprise the hand-operable lever configured to rotate a cam to actuate the clamping members. An advantage is that toggle-like feedback is provided to the user, indicating that the clamping members are at the second closed position. This obviates the need for a torque specification for the user to manually check and adhere to. The fastener arrangement may comprise a shaft extending through apertures in the clamping members, connecting the hand-operable latch at one end of the shaft with an anchor (e.g., nut) at the other end of the shaft. The clamping members may be slidable towards or away from each other along the shaft. The shaft may enable the pair of clamping members to splay out relative to each other, in the first closed position. The shaft and the apertures may be shaped to secure the clamping members and fastener arrangement in a fixed orientation relative to the shaft. This advantageously prevents the fastener arrangement from rotating, meaning it is always in the correct orientation and leaves no room for user error. The shaft and the apertures may be noncircular in cross-section shape, to enable the fixed orientation. The strain relief guide may be connectable to the clamp when the clamping members are at the second closed position. The strain relief guide, when so connected, may inhibit movement of the clamping members away from the second closed position. The clip(s) of the earlier-described connector arrangement may secure the clamping members at the second closed position. An advantage is that the fastener arrangement is resistant against being worked loose, for example as a result of noise, vibration and harshness of passing vehicles, or wind-induced oscillation of the line, among other things. The strain relief guide may be shaped (e.g., the clip(s) of the connector arrangement of the strain relief guide) to cover the second end of the clamp. The strain relief guide may be shaped to cover the earlier-described gap between the clamping members. Each end of the gap may comprise a mouth through which a corresponding one of the pair of elongate articles is received. The mouths may include the mouth referred to earlier. The strain relief guide may be shaped to cover one of the mouths. The mouth may be at the second end of the clamp. The mouth may be defined between the second ends of the clamping members. The strain relief guide may therefore cover the second ends of the clamping members to cover the second elongate article. An advantage of the strain relief guide covering the second ends of the clamping members is that the strain relief guide further prevents the bias from moving the second ends apart, and further encloses the second elongate article within the channel while providing strain relief to the second elongate article outside the channel. The clamping members may be in the form of plates. The clamp may comprise electrically conductive material to form an electrical connection between the first and second elongate articles. The clamping members may be formed from the electrically conductive material such as copper, silver, tin, aluminium, or an alloy thereof. The clamping members may comprise pincer formations (pincers) shaped to fit within grooves of the first elongate article. The grooves may be the side grooves of the contact line. The clamping members may have pincer-shaped ends to define the pincer formations. The pincer-shaped ends may each comprise an edge shaped to fit within a corresponding one of the contact-line side grooves. The pincer-shaped ends may be the first ends referred to earlier. The clamping members may define a first channel to receive at least part of the first elongate article. The first channel may be a rounded channel. Each of the pair of clamping members may define a portion of the first channel. For example, each of the pair of clamping members may have a first section defining a respective portion of the first channel. The first sections may comprise rounded curves / bends to define the portions of the first channel. The first channel may be located proximal to the first end of the clamp. The first channel may be located proximal to the first ends of the clamping members. The first channel may be shaped to receive the first elongate article. When the first elongate article comprises a catenary line, the first channel may enable the catenary line to be seated substantially within the first channel. When the first elongate article comprises a contact line, the contact line may be seated within a channel mouth of the first channel and mostly outside the first channel. The channel mouth may be one of the mouths referred to earlier. The clamping members may define a second channel to receive at least part of the second elongate article. The second channel may be the earlier-described channel. The second channel may be opposite the first channel. The second channel may be located proximal to the second end of the clamp. The pair of clamping members may further define the second channel to receive the second elongate article. The second channel may be located proximal to the second ends of the pair of clamping members. The first and second channels may be located towards opposite ends of the same gap between the clamping members. The second channel may be substantially parallel to the first channel. The second channel may be approximately 35mm from the first channel, or more. The second channel may be a rounded channel. Each of the pair of clamping members may define a portion of the second channel. For example, each of the pair of clamping members may have a second section defining a respective portion of the second channel. The second sections may comprise rounded curves / bends to define the portions of the second channel. When the second elongate article comprises a jumper, the second channel may enable the jumper to be seated substantially within the second channel. Each of the pair of clamping members may comprise a middle section. The middle sections may be between the first and second sections, wherein the first and second sections may be shaped relative to the middle section to define the first and second channels. The middle sections of the pair of clamping members may provide surfaces for mounting the bias. The middle sections of the pair of clamping members may be substantially parallel to each other. The middle sections of the pair of clamping members may be substantially flat in a direction extending between the first and second ends of the clamp. The middle sections of the pair of clamping members may each comprise an aperture through which the shaft of the fastener arrangement can extend. The bias may be in the form of a spring, such as a V-spring. Each end of the spring may act as a stop to prevent the elongate articles from being inserted beyond the first and second channels. The bias may be between the pair of clamping members. The bias may be located between the middle sections of the pair of clamping members. The bias may be in the form of a spring, such as a V-spring. The spring may comprise a pair of spring legs connected to each other at a hinge. One of the spring legs may bias against one of the clamping members while the other of the spring legs may bias against the other of the clamping members. The spring legs may extend substantially parallel to the clamping members. The bias may be secured to the pair of clamping members by the shaft of the fastener arrangement. Each spring leg of the bias may have a corresponding aperture therethrough, through which the shaft of the fastener arrangement can extend. According to various, but not necessarily all, embodiments of the invention there is provided a catenary system comprising a pair of the clamps, and a set of elongate articles. The set of elongate articles may comprise the jumper, the contact line, and the catenary line. One of the clamps may connect the jumper to the contact line, in the second closed position. The contact line may be the first elongate article and the jumper may be the second elongate article. The other of the clamps may connect the jumper to the catenary line, in the second closed position. The catenary line may be the first elongate article and the jumper may be the second elongate article, or vice versa. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of various examples of embodiments of the present invention reference will now be made by way of example only to the accompanying drawings in which: FIG. 1 illustrates an example of a catenary system; FIG. 2 illustrates a cross-section of a contact line; FIG. 3 illustrates a perspective view of an example clamp; FIG. 4 illustrates a side view of the clamp in a first closed position; FIG. 5 illustrates a side view of the clamp in a second closed position; FIG. 6 illustrates a perspective view of another example clamp; FIG. 7 illustrates a perspective view of another example clamp; FIG. 8 illustrates a cross-section view of part of the clamp of FIG. 7; FIG. 9 illustrates a clamping assembly comprising a clamp and a strain relief guide; FIG. 10 illustrates the strain relief guide; FIG. 11 illustrates the clamping assembly with a strain relief guide flexed vertically; FIG. 12 illustrates the clamping assembly with a strain relief guide flexed horizontally; and FIGS. 13A-13C illustrate various jumper topologies. DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION FIG. 1 illustrates an example catenary system 1 for transportation. The illustrated catenary system 1 defines an electrified overhead line system for a vehicle power collector (e.g., pantograph) of a vehicle such as a train, tram, or trolleybus. The catenary system 1 comprises tensioned lines including: an upper, catenary line 3; a lower, contact line 2; and periodically spaced droppers 4 suspending the contact line 2 from the catenary line 3. The catenary system 1 further comprises un-tensioned lines in the form of jumpers 5. C-jumpers are shown, electrically connecting the catenary line 3 to the contact line 2. In this example, C-jumpers may be used when the droppers 4 are non-current carrying. However, in other examples, the jumpers 5 may be current-carrying jumpers or equipotential jumpers as defined earlier. The contact line 2 is an electrically conductive line configured to contact the overhead device of the vehicle, forming an electrical connection. The contact line 2 is suspended at a substantially constant vertical height above the rails / roadway, to maintain constant contact with a vehicle power collector of the vehicle such as a pantograph, bow collector or trolley pole. The catenary line 3 is an electrically conductive line attached at intervals to support structures such as masts or buildings. The catenary line 3 extends parallel to and above the contact line 2. The catenary line 3 droops at each midspan, due to its own weight and the weight of the droppers 4 and contact line 2 suspended therefrom. The catenary line 3 can be a stranded wire of circular cross-section. The droppers 4 are upright electrically conductive lines, such as generally vertical wires, for hanging the contact line 2 from the catenary line 3. Droppers 4 which are connected to the mid-spans of the catenary line 3 are typically shorter than those connected towards the end spans of the catenary line 3, to compensate for the droop of the catenary line 3 and ensure that the contact line 2 is a constant height. The jumpers 5 are flexible and connected to the lines 2, 3 in a curved manner to provide some slack. The bend radius of the jumper 5 at each connection may be approximately 150mm or more. The jumper 5 can be a stranded wire of circular cross-section. The illustrated example system 1 is suitable for a heavy-rail implementation, over a permanent way. However, the clamp of the present invention is also useable in other types of catenary systems, such as a light rail / tram electrified overhead line system. The latter system may have spaced support lines perpendicular to the contact line 2, which connect to the contact line 2 directly or via a short dropper 4. FIG. 2 illustrates an example of a cross-section of a contact line 2. Without limitation, the contact line 2 may be a single-core wire such as a cold drawn solid wire made of copper, silver, tin, or an alloy thereof, or another electrically conductive metal. The contact line 2 has a rounded but non-circle cross-section. The contact line 2 has a curved base 22, a curved crown 24 (anvil), and side grooves 20 at its left and right sides. The side grooves 20 provide a clamping surface for clamps, enabling an interference clamping fit in which clamping members slot into the side grooves 20 and laterally compress the contact line 2. The base 22 is uncovered and exposed for continuous contact with a vehicle power collector. The crown 24 is wider than the side grooves 20, so that when the contact line 2 is clamped it cannot be pulled out. The exact dimensions of the contact line 2 may be standardised, but may differ globally depending on the railway standard applicable to the region. FIGS. 13A-13C illustrate various topologies for connecting a jumper 5. In FIG. 13A, jumper is a current-carrying jumper 5A for electrically interconnecting a pair of contact lines 2A, 2B and a pair of catenary lines 3A, 3B. The jumper 5A starts at a first contact line 2A, extends up in a vertical C-shape to the first catenary line 3A above the first contact line 2A, extends laterally in a C-shape to a second catenary line 3B horizontally adjacent the first catenary line 3A, and then extends down in a vertical C-shape to a second contact line 2B below the second catenary line 3B. In FIG. 13B, the jumper is an equipotential jumper 5B for electrically interconnecting one contact line 2A and a pair of catenary lines 3A, 3B. In FIG. 13C, the jumper is a single C-jumper 5C for electrically interconnecting one contact line 2 to one catenary line 3. FIGS. 3-5 illustrate an example implementation of the clamp 100. The clamp 100 is a jumper clamp that can connect the jumper 5 to the contact line 2, and that can connect the jumper 5 to the catenary line 3. The clamp 100 is compatible with both the contact line 2 and the catenary line 3. FIGS. 3 and 5 show a perspective view and a side view of the clamp 100 in the second closed position, while FIG. 4 shows a side view of the clamp 100 in the first closed position. The clamp 100 comprises a pair of clamping members 102 in the form of electrically-conductive plates, acting as clamping legs of the clamp 100. The clamp 100 further comprises a bias 104, which is a V-spring in this example (pair of spring legs 144 connected at an acute hinge / fold 146). The clamp 100 further comprises a fastener arrangement in the form of a single fastener 106, which comprises a hand-operable latch 108 in this example. The hand-operable latch 108 comprises a hand-operable lever 112 having a catch 122 secured to its end. The clamping members 102 and the bias 104 are mounted to a shaft 118 of the fastener 106. The shaft 118 interconnects a nut (or equivalent anchor 120) and the hand-operable latch 108, at opposite ends of the shaft 118. The clamping members 102, and spring legs 144 of the bias 104, comprise aligned through-hole apertures through which the shaft 118 extends. The shaft 118 and the apertures each have a Double-D shape (double-flat), to prevent the assembly from rotating about the shaft 118. The clamping members 102 are secured between the anchor 120 and the hand-operable latch 108, with the bias 104 mounted in the central gap 124 between the clamping members 102. The bias 104 urges the clamping members 102 into the splayed position shown in FIG. 4, analogous to a clothes peg (spring peg). This position is referred to herein as a first closed position. This enables the clamp 100 to hold on to a first elongate article, which is the contact line 2 in the illustrated example. This frees up both of the user’s hands to manipulate the second elongate article, in this example the jumper 5, into the clamp 100. When the user has inserted the jumper 5 into the clamp 100, the user can then turn the hand-operable lever 112 through an obtuse or reflex angle, to force the clamping members 102 together into the second closed position shown in FIGS. 3 and 5, trapping the contact line 2 and the jumper 5 between the clamping members 102. Although not shown, the clamp 100 can also be used as an upper clamp to connect the jumper 5 with the catenary line 3 instead of the contact line 2. The contact line 2 and the jumper 5 are held apart from each other by the clamp 100, by a spacing of approximately 35mm (between wire centres), or another spacing required by the implementation. Each clamping member 102 has a first end 114 and a second end 116 vertically opposite the first end 114. A clamp 100 that connects the jumper 5 to the contact line 2 is in an upright orientation so that the first end 114 is the bottom end and the second end 116 is the top end. This orientation holds the jumper 5 above the contact line 2, so that the jumper 5 cannot foul on vehicle power collectors. A clamp 100 that connects the jumper 5 to the catenary line 3 can be used either way up. Each clamping member 102 is bent or formed into a shape that defines a variable-width gap 124 between the clamping members 102. As a result, each clamping member 102 has a curved first section 136, a straight middle section 140, and a curved second section 138. The middle sections 140 of the clamping members 102 are between the first and second sections 136, 138 and provide flat surfaces comprising the apertures for the shaft 118 of the fastener 106, as well as flat inner surfaces for the spring legs 144 of the bias 104 to urge against. The curved first sections 136 of the clamping members 102 define a circular first channel 132 between said sections, and the curved second sections 138 of the clamping members 102 define a circular second channel 134 between said sections. The circular first and second channels 132, 134 extend in a parallel horizontal direction, parallel to the contact line 2. The circular first and second channels 132, 134 are each of a diameter large enough to hold the jumper 5 and the catenary line 3. The bias 104 is located between the middle sections 140 of the clamping members 102 and acts as a spacer 142 between the first and second channels 132, 134, because the bias 104 extends as far as the perimeters of the first and second channels 132, 134. This ensures a minimum vertical spacing of the contact line 2 and the jumper 5. The hinge 146 of the bias 104 is at the perimeter of the first channel 132, and the end of one of the spring legs 144 is folded into an angled tip 148 that extends across the gap 124 and extends at least partially tangentially along the perimeter of the second channel 134. The first channel 132 is open at the first ends 114 of the clamping members 102, and the second channel 134 is open at the second ends 116 of the clamping members 102. The gap between the first ends 114 of the clamping members 102, specifically between inner edges 130 of the first ends 114 of the clamping members 102, define a variable-width first mouth 126 enabling access to the first channel 132. The corresponding gap between the inner edges 130 of the second ends 116 of the clamping members 102 define a variable-width second mouth 128 enabling access to the second channel 134. The bias 104 can pivot the clamping members 102 about the shaft 118, and urges the first mouth 126 closed while urging the second mouth 128 open. To open the first mouth 126 wide enough to accept the contact line 2, the user squeezes the clamping members 102 at or near the second ends 116 of the clamping members 102, between their thumb and fingers. This flexes the clamping members 102, against the urging force of the bias 104, into an open position (not shown) at which the first ends 114 of the clamping members 102 are separated by a large enough distance that the crown 24 of the contact line 2 is insertable into the first channel 132 through the wider first mouth 126. The user aligns the side grooves of the contact line 2 with the sides of the first mouth 126, which are the inner edges 130 of the first ends 114 of the clamping members 102. The user then releases their squeezing force. This enables the bias 104 to urge the inner edges 130 of the first ends 114 of the clamping members 102 against the side grooves of the contact line 2. This traps the contact line 2 in the first mouth 126 of the clamp. This represents the first closed position of the clamping members 102. The crown 24 of the contact line 2 (above the side grooves) protrudes slightly into the first channel 132. The crown 24 of the contact line 2 is wider than the side grooves. Therefore, the clamp 100 cannot be pulled off the contact line 2. The base 22 of the contact line 2 is exposed to form a continuous uncovered connection to a vehicle power collector. The inner edges 130 of the first ends 114 of the clamping members 102 have an internal angle (e.g., 90 degrees) matching the internal angle of the V-shaped side grooves, to function as pincer formations. This enables the first ends 114 of the clamping members 102 to act as pincer-shaped ends that snugly fit in the side grooves of the contact line 2. Once the clamp 100 is holding the contact line 2 in the first channel 132, the clamping members 102 in the first closed position may still be slightly splayed out such that the second mouth 128 is wide enough to accept the jumper 5. The user lowers the jumper 5 through the second mouth 128 into the second channel 134. The angled tip 148 of one of the spring legs 144 of the bias 104 prevents the jumper 5 from being inserted beyond the second channel 134 into the space between the middle sections 140 of the clamping members 102. In some examples, the user may have the alternative choice of axially sliding an end of the jumper 5 into the second channel 134. Once the jumper 5 is positioned within the second channel 134, the user can rotate the hand-operable lever 112 from the unlocked position of FIG. 4 to the locked position of FIG. 5, to engage the hand-operable latch 108. The stroke length of the hand-operable lever 112 may be an obtuse or reflex angle. The illustrated hand-operable latch 108 comprises a cam 110 connected to the hand-operable lever 112. The hand-operable latch 108 exhibits bistability, toggling between stable positions as it is moved ‘over-centre’ of the cam 110. The hand-operable lever 112 has a mechanical advantage of greater than two or greater than three or greater than four. As the hand-operable lever 112 is rotated, the cam 110 pushes one clamping member 102 towards the other along the shaft 118. This causes the clamping members 102 to become more parallel from their previous splayed orientations. The hand-operable lever 112 is able to travel at least a short distance past the over-centre position (maximum lift of the cam 110), to settle in a stable locked position. Specifically, as the hand-operable lever 112 is rotated to the locked position, the second ends 116 of the clamping members 102 are brought together until the second mouth 128 therebetween is less wide than the diameter of the jumper 5. This traps the jumper 5 within the second channel 134. Meanwhile, the crown 24 of the contact line 2 is trapped within the first channel 132 between the pincer formations (inner edges 130 of the first ends 114 of the clamping members 102). This defines the second closed position (FIG. 5) of the clamping members 102, where the clamping members 102 trap both the contact line 2 and the jumper 5 therebetween. To provide further security, a distal end of the hand-operable lever 112 supports an optional hook-shaped snap-fit catch 122, which is shaped to cover the second mouth 128 and snap-fit to the second section 138 of the clamping member 102 on the opposite side of the gap 124. This prevents the hand-operable lever 112 from being worked loose and also covers the second channel 134. The catch 122 automatically engages with the hand-operable lever 108 reaches the locked position. The catch 122 cannot be used to cover the contact line 2, to avoid interfering with. If the clamp 100 is used the wrong way up, the catch 122 will interfere with the base 22 of the contact line 2, preventing the catch 122 from engaging. FIGS. 4 and 5 only illustrate a clamp 100 holding a jumper 5 to a contact line 2. If the clamp 100 is instead holding the jumper 5 to the catenary line 3, then the orientation does not matter. The first and second channels 132,134 would each receive one of the jumper 5 and the catenary line 3. FIG. 6 illustrates a perspective view of another example clamp 100A, demonstrating that additional clamping members and fasteners may be provided. The clamp 100A comprises a first clamping member 102A, a second clamping member 102B, and a third clamping member 102C. The first channel 132 is defined between the first and second clamping members 102A, 102B. The second channel is defined between the first and third clamping members 102A, 102C. The channels 132, 134 of FIG. 6 are suitable for connecting a jumper 5 to a catenary line 3. A modified version of FIG. 6 may comprise pincer formations for compatibility with a contact line 2. In FIG. 6, the fastener arrangement comprises a first fastener 106A and a second fastener 106B. The first fastener 106A secures the first and second clamping members 102A, 102B together to define a first closed position of the clamp 100A. In FIG. 6, a second fastener 106B secures the first and third clamping members 102A, 102C together to define the second closed position. The first and second fasteners 106A, 106B are bolted fasteners rather than hand-operable latches. In other examples, hand-operable latches are used. Without a bias, the first fastener 106A is instead used to hold the clamp 100A onto the first elongate article. If a bias is provided, it may urge a pair of the clamping members 102A-102B or 102A-102C towards a first closed position, in a similar manner to the clamp 100 of FIGS. 3-5. This enables the clamping members 102A, 102B to hold on to the first elongate article 5. The user can then lock the first fastener 106A and then secure the second elongate article to the other pair ofclamping members 102A, 102C via the second fastener 106B. A second bias may optionally be provided for the other pair of clamping members 102A, 102C. In other respects, the clamp 100A may have the same features as described in relation to FIGS. 3-5. FIGS. 7-8 illustrates views of a further example clamp 100B. The axis of rotation of the lever 112 of the clamp 100B is in a different direction than in the earlier FIGS, non-parallel with an upstream-downstream direction of the channels 132, 134 of the clamp 100. As a result, the catch 122 no longer covers the second channel 134. The axis of rotation is no longer transverse and is at least partially parallel to the channels 132, 134. If the clamp 100B is unintentionally inserted upside down such that the contact line 2 is in the second channel 134, the catch 122 will not interfere with the ability of the passing vehicle power collector to maintain continuous contact with the contact line 2. FIG. 8 is a cross-sectional area of the area labelled ‘CSA’ in FIG. 7. As shown in FIG. 8, the catch 122 of the lever 112 of the clamp 100B can engage with an upstream end or downstream end of the middle section 140 of the same clamping member 102 to which the hand-operable latch 108 is mounted, the upstream and downstream ends of the middle section 140 being upright and extending between the curved sections 136, 138. In some examples, the catch 122 may be omitted. A further modification in FIG. 7 is that each clamping member 102 has a structurally-reinforcing variable cross-section geometry from its upstream end to its downstream end. This relates to any variations in shape and / or thickness that increase the rigidity of the clamping member 102 against flexing about its minor axis. This provides resistance to pull-out forces. High pull-out forces may occur during installation, or in-use as a result of significant upwards thrusting of the catenary system 1 by passing vehicle power collectors. In examples, the structurally-reinforcing variable cross-section geometry is achieved by variations in shape without substantial variations in thickness. Each clamping member 102 comprises one or more bends in a downstream direction from its upstream end to its downstream end. In FIG. 7, such bends define a flared upstream portal 150 and a flared downstream portal 152, formed in each clamping member 102. Each flared portal 150, 152 may comprise a bend extending continuously or discontinuously between the first and second ends 114, 116. In FIG. 7, the bend extends through the curved first section 136, through the middle section 140, and through the curved second section 138. Where the flared portals 150, 152 intersect the curved sections 136, 138, approximately-conical flared entrances and exits for the lines 2, 5 are defined. A further advantage of flaring at upstream and / or downstream ends is to tolerate some flexing of the lines 2, 5 as they enter or leave the clamp 100. A further modification in FIG. 7 is the provision of bends 154 in the downstream direction in a central region of the middle section 140 of each clamping member 102. The bends 154 have a raised section 156 (e.g. raised flat platform) therebetween, which is contacted by a washer 158 (e.g., saddle washer) of the hand-operable latch 108. The through-hole aperture through which the shaft 118 extends is located in the raised section 156. During manufacture, if the assembler places one of the clamping members 102 facing the wrong direction (i.e., both facing the same way rather than facing each other), then the raised section 156 will instead be a sunken section. As a consequence, too much shank of the protruding shaft 118 will be exposed, so it will not be possible to properly assemble the hand-operable latch. Therefore, an advantage of the bends 154 is a reduced likelihood of incorrect assembly during manufacture, ensuring that the clamping members 102 are always assembled facing each other. A further advantage is that the bends 154 and raised section 156 provide reinforcement about the same axis as the flared portals 150, 152. FIGS. 9-12 illustrate a clamping assembly 10 comprising a clamp 100 and a strain relief guide 200 attached to the clamp. The illustrated clamp is the clamp 100B, but may alternatively be one of the other clamps 100, 100A described earlier. The strain relief guide 200 comprises at least one sleeve 202 which is resiliently flexible along the sleeve’s length, to control the minimum radius of the jumper 5 entering or leaving the clamp 100, as described earlier. The strain relief guide 200 is connectable to the clamp 100, and when connected the sleeve 202 is aligned with the entrance or exit of the second channel 134 of the clamp 100. FIG. 9 illustrates a double-sided strain relief guide 200A for securing to the outside of a through-clamp 100 that the jumper 5 extends through without terminating. The strain relief guide 200A comprises a central connector arrangement 212 for connecting the strain relief guide 200A to the clamp 100, and a pair of sleeves 202A, 202B extending from opposite ends of the central connector arrangement 212. The first sleeve 202A is aligned with the entrance of the second channel 134, and the second sleeve 202B is aligned with the opposite exit of the second channel 134. A through-clamp 100 may be an upper clamp with a catenary line 3 in the first channel 132, when the jumper 5 is a current-carrying jumper 5A (FIG. 13A) or an equipotential jumper 5B (FIG. 13B) extending through the second channel 134 of the clamp 100. FIGS. 10-12 illustrate a single-sided strain relief guide 200B, having a connector arrangement 212 and a single sleeve 202 extending from one side of the connector arrangement 212. In use, the sleeve 202 is aligned with the entrance or exit of the second channel 134. A single-sided strain relief guide 200B is useful for both through-clamps and termination clamps, for jumpers 5A, 5B, 5C (FIGS. 13A-13C). A termination clamp 100 requires strain relief at only one side. For a through-clamp 100 requiring strain relief at both sides, a pair of single-sided strain relief guides 200B may be connected to the through-clamp 100, facing opposite directions. The lower clamp(s) 100 secured to the contact line(s) may be termination clamps (FIGS. 13A-13C). The upper clamp(s) 100 that connect to the catenary line 3 can be either through-clamps or termination clamps depending on the topology used (FIG. 13A or 13B). The sleeve 202 of the strain relief guide 200 can be formed from a plastics or rubber material, or formed from spring sheet metal or spring wire, to provide flexibility. The sleeve 202 is tubular, defining a passage therethrough for the jumper 5. The illustrated sleeve 202 is shaped to mostly surround the jumper 5, by greater than 180 degrees or greater than 200 degrees, except for a longitudinal opening 204 (slit) extending along the length of the sleeve 202. The sleeve 202 is U-shaped in cross-section, the longitudinal opening 204 being slightly narrower than the diameter of the jumper 5 and narrower than the interior diameter of the passage within the sleeve 202. The flexibility of the sleeve 202 allows snap-on fitment of the strain relief guide 200 to the outer side surface 6 (FIG. 4) of the jumper 5, via the longitudinal opening 204. In other words, the strain relief guide 200 can be side loaded onto the jumper 5, rather than end fed. To assist with alignment and fitting, the longitudinal opening 204 may comprise a tapered throat proximal to the narrowest point of the longitudinal opening 204, to feed in the jumper 5. The flexibility of the sleeve 202 also allows snap-off removal (quick-release) from the jumper 5 by pulling the strain relief guide 200 out of the longitudinal opening 204 with sufficient force. It would be appreciated that the longitudinal opening 204 is not essential. The sleeve 202 could alternatively be end-fed. As a further variant, the single sleeve 202 with a single snap-on longitudinal opening 204 may be replaced with a multi-part sleeve assembly that hinges or self-attaches to form a flexible enclosure over the jumper 5. The sleeve 202 is no more than twice as stiff, or no more than three times as stiff, against bending in a vertical plane as the sleeve 202 is against bending in a horizontal plane. Therefore, the sleeve 202 can be resiliently flexed vertically as shown in FIG. 11, and resiliently flexed horizontally as shown in FIG. 12. This is useful for the jumper topologies illustrated in FIGS. 13A and 13B, where the jumper 5 is bent vertically and horizontally. The stiffness may be characterised by the second moment of area of the cross-section of the sleeve 202. As shown in FIG. 10, the stiffness of the sleeve 202 can be further controlled by forming gaps 208, such as perforations, in the material. FIG. 10 illustrates the sleeve 202 comprising a plurality of longitudinally-separated rows of elongate members 206 separated by gaps 208, wherein the gaps 208 comprise slots, edge recesses, or a combination thereof. Each adjacent row is connected to each adjacent other row by a bridge 210, the bridge 210 being between the ends of a pair of gaps 208. Each elongate member (row) 206 may be connected to each adjacent row by two or three bridges 210. The elongate members 206 and gaps 208 may extend transverse to the longitudinal direction of the sleeve 202. The gaps 208 may extend generally parallel to the elongate members 206. The rows of elongate members 206 may be defined by the gaps 208. The bridges 210 may extend between the elongate members 206, generally in the longitudinal direction. In another implementation, the sleeve 202 has a helical form, and may be a wound coil or spiral rather than a perforated tubular form. In still further implementations, the sleeve 202 is a simple rubber or foam tube without a spiral form and without gaps 208. The gaps 208 of the illustrated sleeve 202 are distributed over multiple sides of the sleeve 202, in cross-section, therefore controlling the stiffness of the sleeve 202 against flexing in both vertical and horizontal planes. Individual gaps 208 may be elongate, extending over more than one side of the sleeve 202. The bridges 210 between adjacent rows or groups of rows of elongate members 206 may be alternately staggered (offset). The offset of the bridges 210 distributes the forces around the whole cross section, and configures flexibility in both vertical and horizontal planes. As shown in FIG. 10, a first bridge 210 connecting a first row (elongate member 206) to a second row (elongate member 206) adjacent the first row is aligned between, e.g., halfway between, a pair of bridges 210 connecting the second row to a third row (elongate member 206) adjacent the second row and opposite the first row. The sleeve 202 in FIG. 10 is bidirectionally vertically flexible (up and down) and bidirectionally horizontally flexible (left and right). Therefore, the sleeve 202 is suitable for every clamp position shown in FIGS. 13A-13C, just as the clamp 100 is compatible with every clamp position shown in FIGS. 13A-13C. Therefore, a single clamping assembly 10 can be used for all the jumper connections. As shown in FIG. 9, the sleeve 202 extends coaxially with the second channel 134 when in a neutral undeformed state. It can be flexed in any direction, and is therefore compatible with a wide variety of clamping positions and jumper bend directions. In alternative implementations, the sleeve 202 may be curved in a particular direction in its neutral undeformed state. The connector arrangement 212 of the strain relief guide 200 is best illustrated in FIG. 9. The illustrated connector arrangement 212 is optionally hand-securable to the clamp 100, and may be hand-releasable without tools. The connector arrangement 212 firstly comprises a rounded flexible snap-fit clip configured as a snap-off (quick-release) clip 214. The snap-off clip 214 is U-shaped (hook shaped) and connects / covers the second ends 116 of the clamping members 102 (the second end of the clamp 100), to cover the gap 124 between the clamping members 102 and enclose the second channel 134 in the same manner as the catch 122 of FIG. 5. The connector arrangement 212 therefore traps / encloses the jumper 5 in the second channel 134. In examples, the snap-off clip 214 does not lock to the clamp 100 and therefore can be pulled off with enough force to spread the sides of the snap-off clip 214. The flared portals 150, 152 (FIG. 7) of the clamping members 102 of the clamp 100 may prevent the snap-off clip 214 from sliding off the rim of the clamp 100. The connector arrangement 212 of the strain relief guide 200 can be connected to the clamp 100 when the clamp 100 is in the second closed position of FIGS. 3, 5, 7, 9, 11, 12. When the clamp 100 is in the first closed position of FIG. 4, the second ends 116 of the clamping members 102 are splayed apart, therefore the strain relief guide 200 may not be connectable to the second ends of the clamping members 102. Therefore, the installer may perform the following sequence of operations: - secure the clamp 100 to the contact line 2 or catenary line 3, leaving it in the first closed position; - align the jumper 5 with the second channel 134 of the clamp 100; - use the lever 112 to actuate the clamp 100 to the second closed position, bringing the clamping members 102 together to secure the jumper 5 in the second channel 134; and - secure the strain relief guide(s) 200 to the combined jumper 5 and clamp 100. As shown in the circular detail view of FIG. 9, the illustrated connector arrangement 212 additionally, or alternatively, comprises a second snap-fit clip in the form of a locking clip 216. The locking clip 216 comprises a flexible tab having an undercut 218, which snaps into a socket 160 formed in the exterior side of one of the clamping members 102. This locks the strain relief guide 200 to prevent unintentional removal because the user would need to simultaneously bend the tab and undercut 218 away from the socket 160, while pulling the strain relief guide 200 away from the clamp 100. Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. For example, instead of having a connector arrangement 212, the strain relief guide could be permanently secured or integrally formed with the clamp. Or, a separate connector may secure the strain relief guide to the clamp. For example, it would be appreciated that the catch 122 is not limited to the specific example shown. It would also be appreciated that the hand-operable latch 108 may be replaced with a different type of fastener 106, including a nut and bolt fastener requiring a tool to operate. Other examples include, but are not limited to: - a hand-operable crank such as a threaded screw with a hand-operable crank lever at one end; - a rotary button clamp such as a quarter-turn clamp, a half-turn clamp or a full-turn clamp; - a scissor mechanism clamp or other push-pull clamp. The strain relief guide may be usable with different types of clamp and different types of elongate articles. Further modifications include: - The clamping members 102 may slide linearly rather than being rotatable; - The clamping members 102 may have one closed position; - The clamp 100 may be for securing a single elongate article to another body. Features described in the preceding description may be used in combinations other than the combinations explicitly described. Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. 5 Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not particular emphasis has been placed thereon. 10

Claims

1. A clamping assembly comprising a clamp and a strain relief guide, wherein the clamp comprises first and second clamping members movable towards an outer side surface of an elongate article to secure the elongate article therebetween in a channel of the clamp, andwherein the strain relief guide is configured to extend from the channel and is resiliently flexible along its length.

2. The clamping assembly of claim 1, wherein the strain relief guide comprises a sleeve.

3. The clamping assembly of claim 1 or 2, wherein the strain relief guide is configured for side-entry installation onto the elongate article.

4. The clamping assembly of claim 1,2, or 3, wherein the strain relief guide has a first stiffness against resilient flexing in a first plane, and a second stiffness against resilient flexing in a second perpendicular plane, wherein the strain relief guide comprises longitudinally-separated rows of material separated by gaps, the gaps being arranged to allow adjacent rows to resiliently flex in the first plane and to resiliently flex in the second plane.

5. The clamping assembly of any preceding claim, wherein the strain relief guide comprises a connector arrangement to secure the strain relief guide to the clamp, and wherein the connector arrangement is hand-securable to the clamp and hand-releasable from the clamp.

6. The clamping assembly of claim 5, wherein the connector arrangement is shaped to cover one of the ends of the clamp, and wherein the connector arrangement is shaped to cover a gap between the first and second clamping members.

7. The clamping assembly of claim 6, wherein the connector arrangement is configured to fit to both the first and second clamping members, and lock the first and second clamping members in a closed position, when connected to the clamp.

8. The clamping assembly of claim 5, 6, or 7, wherein the connector arrangement comprises one or more clips, and wherein each clip is a snap-fit clip.

9. The clamping assembly of claim 8, wherein the connector arrangement comprises a snap-off clip.

10. The clamping assembly of claim 8 or 9, wherein the connector arrangement comprises a locking clip.

11. The clamping assembly of any preceding claim, comprising a pair of the strain relief guides individually securable to the clamp in alignment with opposite ends of the channel, or a single strain relief guide comprising a pair of sleeves extending in opposite directions from a central connector arrangement.

12. The clamping assembly of any preceding claim, wherein the clamp is configured to connect a pair of elongate articles.

13. The clamping assembly of claim 12, wherein the clamp comprises: a first closed position to secure the clamp to the first elongate article; and a second closed position to further secure the clamp to the second elongate article.

14. The clamping assembly of claim 12 or 13, wherein the clamp comprises: a bias urging the first and second clamping members towards the first closed position to secure the clamp to the first elongate article; anda fastener arrangement to actuate the clamping members towards a second closed position to further secure the clamp to the second elongate article.

15. The clamping assembly of claim 14, wherein the strain relief guide is connectable to the clamp when the clamping members are at the second closed position, and wherein the strain relief guide, when so connected, inhibits movement of the clamping members away from the second closed position.

16. The clamping assembly of claim 14 or 15, wherein the fastener arrangement comprises a hand-operable latch.

17. The clamping assembly of any one of claims 12 to 16, wherein the clamp comprises electrically conductive material to form an electrical connection between the first and second elongate articles.

18. The clamping assembly of any one of claims 12 to 17, wherein the clamping members comprises pincer formations shaped to fit within grooves of the first elongate article.

19. The clamping assembly of any one of claims 12 to 18, wherein the clamping members define a first channel to receive at least part of the first elongate article, and a second channel to receive at least part of the second elongate article.

20. The clamping assembly of claim 19, wherein the second channel is opposite the first channel, and substantially parallel to the first channel.

21. The clamping assembly of any preceding claim, wherein the clamping members are in the form of plates.

22. A catenary system comprising a pair of the clamps each as claimed in any one of the preceding claims, and a set of elongate articles.

23. The catenary system of claim 22, wherein the set of elongate articles 5 comprises a jumper, a contact line, and a catenary line.

24. The catenary system of claim 23, dependent through claim 14, wherein a first one of the clamps connects the jumper to the contact line, in the second position, and wherein the second one of the clamps connects the jumper to the 10 catenary line, in the second closed position.

25. The catenary system of claim 24, dependent through claim 18, wherein the pincer formations of the first one of the clamps fits within side grooves of the contact line.15

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