Tunnels and subways have often been used as conduits through which cables, such as communication or power cables, can be passed. Typically, such cables have been mounted by metal cable supports, such as cable hooks or ladders, attached on the walls or ceilings.

However, such supports are not convenient for laying radiating feeders as the supports and/or their close proximity to the walls can reduce the efficiency of a radiating feeder by breaking the integrity of the radiation field around the feeder. Though breaking the integrity of the radiation field around a feeder may not be too problematical under normal circumstances (mobile phone users will be very familiar with the loss of signal as they pass through a particular section of a tunnel, which signal then reconnects either automatically or by redialing, for example when signal strength permits within the given area or by entering a different section further along the tunnel), the effective lack of a radio signal (radio black spots) in a section of the tunnel can cause severe problems to the emergency services should, for example, an incident or accident occur in that section.

To overcome the problems of radio black spots in tunnels and subways, it has been determined that radio signal cables should be mounted away from the wall of the tunnel or from any metal support. This has lead to the introduction of a new cable mounting system, especially designed to mount radio signal cables and comprising a thermoplastic stand-off base having two ends separated from each other by at least 50mm, wherein one end of said stand-off base is connected to a

thermoplastic cable cleat/clamp/tie and wherein the opposite end of said stand-off base is connected to a thermoplastic connector suitable for interlocking attachment of the base to a support, such as a cable tray or Uni-StrutTM type support, secured to the tunnel wall or ceiling. Though this system enables radio blackspots to be substantially eliminated in a tunnel, cable tray and UnistrutTM type supports are not commonly found in tunnels used for underground rail transportation systems.

In tunnels used for underground rail transportation systems it is more common to find communication and power cables supported on an hook-type cable support system.

A universal cable mounting device, comprising a thermoplastic stand-off base, a thermoplastic cable/cleat/clamp/tie, and a thermoplastic connector having a channel which passes through said connector, such as described in my co-pending British Application Number 9810929.1 (published under number 2 330 458), may be used for mounting radio signal cables upon an hook-type cable support system. In mounting this device, the channel of the connector is engaged with the hook of said cable support such that said support passes completely through the channel, and the stand-off base and cable cleat/clamp/tie extend away from the wall on which said support is attached towards the centre of the tunnel.

In some tunnels, particularly where space is very limited between the passing trains and the existing cable support systems, it is not possible to use cable mounting devices which would position the radio signal cables closer to the centre of the tunnel than the existing cable support system.

Accordingly, it is an object of the present invention to provide a cable mounting device which in use neither significantly encroaches into the space between the passing trains and an existing hook-type cable support

system mounted on the wall of the tunnel nor significantly reduces the integrity of the radiation field around the radio signal cable. It is a further object of the present invention, that the device can be fitted at least as quickly as, if not quicker than, the prior art devices used for mounting radio signal cables on hook- type cable supports. It is yet a further object of the present invention that, once fitted, the device and mounted radio signal cable do not impede access to the existing cable support system.

In accordance with the present invention, there is provided a cable mounting device, suitable for use in mounting radio signal cables on a hook-type cable support mounted on the wall or ceiling of a tunnel, wherein the device comprises a thermoplastic stand-off base (1) having two ends separated from each other; a thermoplastic cable cleat/clamp/tie (2) connected to one of said ends; and a thermoplastic connector (3), suitable for attaching said base to said hook-type cable support, connected to the other said end or one of the sides of the device, wherein said thermoplastic connector (3) comprises female connection means for receiving and tightly engaging with the free-end of the hook of said support, and wherein said means is orientated such that, in use, the cable is mounted substantially over and above the tip of the hook.

In accordance with another aspect of the present invention, there is provided a method of mounting a radio signal cable on a hook-type cable support mounted on a wall or ceiling of a tunnel, said method comprising the steps of: (a) attaching a cable mounting device to said hook-type cable support, which device comprises a thermoplastic stand-off base (1) having two ends separated from each other; a thermoplastic cable cleat/clamp/tie (2) connected to one of said ends; and a thermoplastic connector (3), suitable for attaching said base to said hook-type cable support, connected to the other said end or one of the

sides of the device and comprising female connection means for receiving and tightly engaging with the free- end of the hook of said support, and wherein said means is orientated such that, in use, the cable is mounted substantially over and above the tip of the hook; and (b) fastening said cleat/clamp/tie (2) around said radio signal cable.

(In practice, the free-end of the hook of the support and the female receiving means of the connector together act as corresponding male and female parts) The mounting device of the present invention advantageously offers the cable layer the ability to quickly mount radio signal cables in tunnels where space is very limited between passing trains and an existing hook-type cable support system, and without substantially impairing access to said existing cable support.

In a preferred embodiment of the present invention, the female connection means comprises a mortise formed in the base of the connector and of such dimensions so as to receive and tightly engage the free-end of the hook of the support. (In practice, in this embodiment the free-end of the hook of the support and the female connection means together constitute a mortise and tenon joint) In another embodiment, the female connection means comprises at least one set of four walls (8,9,10, 11), which together define a channel which passes through said connector. Preferably, the device also comprises a stop, located on the connector or the stand- off base and which is a protrusion which, in use, abuts the tip of the hook.

In yet another embodiment, the female connection means comprises two legs having"U-shaped"cross- sectional profiles, the legs being orientated so that together they receive and tightly engage the free-end of the hook.

The stand-off base (1), cleat/clamp/tie (2) and the connector (3) are preferably formed integrally, or they

may be formed as two or three separate parts which can be fitted together prior to use.

Preferably, the cleat/clamp/tie (2) is a zip-strap fastener.

In a preferred embodiment, the cleat/clamp/tie comprises a zip-strap fastener which may be received by a channel defined by a set of walls formed in the stand- off base at the end of the stand-off base remote from the connector (3), or formed on one side of the connector (3).

The mounting device is assembled by threading one zip- strap through the channel at the end of the base.

Preferably, all components of the mounting device are moulded from a low-smoke thermoplastic material.

Preferably, all components of the mounting device are moulded from a zero-halogen material. Thermoplastic materials which are"Low-smoke"and/or"zero-halogen" are well known to the specialist plastics compounder.

The invention will now be further described by way of exemplification and with reference to the accompanying drawings, in which: FIG 1 is a schematic view of a radio signal cable mounted by a first embodiment of a clamping device in accordance with the present invention upon a hook-type cable support; FIG 2 is a schematic view of a second embodiment of a clamping device in accordance with the present invention secured upon a hook-type cable support; and FIG 3 is a schematic view of a third embodiment of a clamping device in accordance with the present invention secured upon a hook-type cable support.

Referring now to FIG 1, a first embodiment of a clamping device in accordance with the present invention consists of a stand-off base (1) having a thermoplastic cable cleat/clamp/tie in the form of a zip- strap (2) connected to one end of said base (1) and a connector (3) connected to the other end of said base.

The stand-off base (1) comprises a set of four walls, (4), (5), (6) and (7), which together define a channel (12)

which passes substantially perpendicular to the longest dimension of the cable (100) through the stand-off base (1), close to the end used for securing the cable. The channel (12) has a rectangular cross-section and dimensions suitable for receiving said zip-strap (2) which is of conventional design and is of such length that it may be threaded through the channel (12) in the stand- off base (1) and fastened around the cable. The connector (3) comprises a set of walls, (8), (8a), (9), (10) and (11), which defines a mortise formed within the connector and having a cross-sectional profile of such dimensions so as to receive and tightly engage with the end of a hook-type cable support. In use, the device is attached to the hook-type cable support by aligning the mortise with the end of the hook-type cable support (13), and pushing down on the device until a tight fit is achieved. Once the device is secured to the cable support, the radio signal cable (100) is mounted upon the device and held in position by fastening the zip-strap (2) around the cable. As is illustrated, the radio signal cable is mounted over and above the tip of the hook.

Referring now to FIG 2, a second embodiment of a clamping device in accordance with the present invention consists of a stand-off base (1) having a thermoplastic cable cleat/clamp/tie in the form of a zip- strap (2) connected to and formed integrally with one end of said base close to the end used for securing the cable, and a connector (3) connected to and formed integrally with one side of said base. Said zip-strap (2), although integral, is formed of conventional design and is of such length that it may fastened around the cable (100). The connector (3) comprises a set of four walls, (8), (9), (10) and (11), which defines a channel formed in the connector which in use, securely engages on to a hook- type cable support (13). A stop (14) is formed in the wall of the device against which the tip (15) of the hook abuts.

As is illustrated, the radio signal cable is mounted over and above the tip of the hook.

Referring now to FIG 3, a third embodiment of a clamping device in accordance with the invention consists of a stand-off base (1) having a thermoplastic cable cleat/clamp/tie in the form of a zip-strap (2) connected to one end of said base and a connector (3) connected to the other end of said base. The stand-off base (1) comprises a set of four walls, (4), (5), (6) and (7), which together define a channel (12) which passes substantially perpendicular to the longest dimension of the cable (100) through the stand-off base (1), close to the end used for securing the cable. The channel (12) has a rectangular cross-section and dimensions suitable for receiving said zip-strap (2) which is of conventional design and is of such length that it may be threaded through the channel (12) in the stand-off base (1) and fastened around the cable. The connector (3) comprises a pair of legs (16,17) of U-shaped cross-section which, in use, securely engage on to a hook-type cable support (13).

Stops (18,19) formed on the insides of the legs against which the tip (15) of the hook abuts. As is illustrated, the cable is mounted over and above the tip of the hook.