The present invention relates to an extendible mast, a method of deploying apparatus and a method of stowing apparatus.

There are many scenarios where it is desired to deploy an apparatus via an extendible structure, i.e. a mast. It is known for example to mount cameras, tools and antennas on a mast so they can be deployed in the field by extending the mast to position and support the apparatus as required in use. The mast can be retracted when not in use or for transportation or storage. Such masts can comprise, for example, telescopic elements, jointed or articulated elements, a series of elements that screw together end on end, slit tubular structures

(STEMS) that can be coiled for compact storage and driven between the coiled and extended forms. As used in the present disclosure, the term "mast" is intended to refer to any arm, mast, boom or elongate structural element.

In may scenarios, it is also necessary to provide services to the apparatus at the distal (i.e. extended) end of the mast. For instance, electrical power or control/data signals may need to be transmitted to and/or received from the apparatus at the distal end of the mast to local transmitting/receiving equipment at the distal end. Thus, transmission elements, e.g. electrical cables or hoses, may be used to connect the apparatus to local equipment. The cables or hoses require careful management so as not to interfere with the ability of the mast to extend/retract or become damages for example due to snagging or interfering with the extension/retraction mechanism. Cables or hoses can also make deploying the apparatus more time consuming and awkward. The present disclosure aims to provide improvements in extendible masts where transmission elements are required. According to a first aspect of the present invention, there is provided an extendible mast, comprising:

a member constructed and arranged so as to be configurable between a coiled form and an extended form, wherein when extended the member is resiliently biased in the form of an elongate tube having a slit along its length formed by longitudinal edges of the member and wherein when coiled the member is opened out at the longitudinal edges to a flattened form and wound about an axis extending transversely to the longitudinal extent of the member; and,

a transmission element or retaining structure for retaining a transmission element extending along at least part of the longitudinal extent of the member, wherein the transmission element or retaining structure is positioned adjacent a longitudinal edge of the member so that the transmission element forms a coil outside the interstitial spaces of the coiled member.

The transmission element allows services to be provided to apparatus supported and/or positioned by the mast by external equipment. The

transmission element is flexible to allow it to coil with the member. For instance, where the mast is used to deploy an antenna, the transmission element may provide a coaxial cable so as to transmit/receive electrical signals to/from the antenna to an external transmitter/receiver device. The resiliently biased member provides structural support to the apparatus. The transmission element coils with the member to provide a compact form for storage or transportation. The mast can be quickly and simply deployed by simply extending the mast with the transmission element extending along with the mast. When the mast is coiled, the transmission element coils with the member, but does so adjacent the side edge of the member, i.e. outside the interstitial spaces of the coiled member, so as not to interfere with the coiling of the mast. Thus, the overall thickness of the coil is not disrupted by the transmission element getting in the way.

The mast can be any desired length, e.g. more than 1 m, more than 10 m, etc. Preferably, the length of the mast is at least 5 times the flattened width of the member. In the extended form, the member has an arcuate cross section, which can subtend any desired angle from relatively shallow angles, e.g. 60 degrees or more, to more closed sections, e.g. up to 360 degrees, to provide more stiffness. If desired, the edges of the member can overlap and/or be bonded or zipped together to provide further stability. References to the near, proximal or local end of the mast 1 used herein should be taken to refer to the end from which the mast coils, whereas references to the far, distal or remote end of the mast 1 used herein should be taken to refer to the extended end of the mast 1.

The mast preferably coils about an axis transverse to the extension direction. In embodiments, the extended member is linear, although in alternative embodiments curved members can be formed. In a preferred embodiment, wherein the diameter of the transmission element or retaining structure is larger than the interstitial spaces of the coiled member; and/or wherein the diameter of the transmission element or retaining structure is smaller than the separation between the outer surfaces of adjacent coils of the coiled member. This is particularly useful when the member is resiliently biased in coiled form. I.e. the member can take its natural form without the transmission element distorting the form of the coil by forcing apart adjacent coils.

In an embodiment, the transmission element or retaining structure has a diameter that is greater than the thickness of the member, and wherein the mast comprises a raised portion over part or all of the inner and/or outer face of the member such that when the member is coiled, the raised portion or portions lay against the opposite face. This allows the coil to lay evenly even where the transmission element or retaining structure is bulky relative to the thickness of the member, which is often a thin sheet where made for example from Fibre

Reinforce Composites or bistable materials. In this case, an addition portion fixed or formed integrally with the member to, in effect, increase its thickness to being greater than the thickness of the transmission element/retaining structure, can be beneficial in controlling the coiling of the member. The additional portion or portions may be made from a relatively lightweight and/or compressible or extendible material compared with the member so as not to significantly affect the coiling of the member, especially where bistable materials are used. ln a preferred embodiment, the transmission element contains one or more electrical conductors for transmitting electrical power or data signals along the mast. The conductors can be co-axial cables, cables formed from wires, twisted pairs, or any other transmission elements.

In a preferred embodiment, the transmission element contains one or more optical fibres for transmitting optical power or data signals along the mast.

In a preferred embodiment, the transmission element provides a hose arranged to transmit a gas. Thus, the transmission element may transfer a propellant to the end of the mast. Xenon gas can be used in electric propulsion units for modern spacecraft for example. Alternatively, the gas can be a combustible gas for combustion at an end device, or for another chemical reaction at an end device.

In a preferred embodiment, the transmission element provides a hose arranged to transmit a fluid, gel, powder or particulate matter.

In a preferred embodiment, the transmission element provides a hose for transmitting hydraulic power along the mast.

In a preferred embodiment, the transmission element provides a fuel-line. Thus, the embodiment can provide a combustible fuel for combustion or other chemical reaction at an engine at the end of the mast.

In a preferred embodiment, the distal end of the mast has a mount adapted to attach to a tool or other device. This allows the tool or device to be removably attached to the mast. In this case, preferably a connector is provided with the mount to connect the transmission element to the tool or device.

However, in other embodiments, a tool or device can be permanently attached to the mast.

In a preferred embodiment, the mast supports or incorporates an antenna for transmitting and/or receiving electromagnetic communications. ln a preferred embodiment, the mast is constructed and arranged to support loads of at least 1 kg. In a preferred embodiment, the member comprises a reinforced composite.

In a preferred embodiment, the member comprises a bistable material. In a preferred embodiment, the mast comprises a connector on the mast for externally connecting to the transmission element. This allows external equipment to simply and conveniently attach to the apparatus supported by the mast via the transmission element. E.g. where the apparatus is an antenna supported by the mast and the transmission element is a co-axial cable, the connector can allow connection with external transmitter/receiver electrical equipment.

In a preferred embodiment, the connector is a rotatable connector. This can be useful in accommodating rotation of the coiled end of the mast as the mast is extended/retracted and helps guard against damage to the transmission means.

In an alternative embodiment, a length of the transmission element extends beyond the coiled end of the member and is in communication with the connector, wherein said length of the transmission element forms a coil wherein the tightness of the coil changes as the mast is extended and retracted. Thus, a rotatable connector is not required in this embodiment, as the movement of the coiled length of transmission element by becoming a tighter/looser coil accommodates the movement of the coiled end of the member as the mast is extended and retracted.

In a preferred embodiment, the retention structure allows the transmission element to slip relative to the member. This helps guard against damage to the transmission element as the mast is extended/retracted. For example if the transmission means is not at the bending axis of the member, it will experience a certain amount of strain if it could not slip relative to the member.

In a preferred embodiment, the retention structure is a pocket for surrounding and retaining the transmission element. This can help protect the transmission element from the environment.

In a preferred embodiment, the mast comprises a housing for containing the coiled mast and guiding the mast as it is extended. In a preferred embodiment, the housing has a winding mechanism for coiling or extending the mast, or both. This can help deploy the apparatus via the mast, for example where the apparatus is heavy or difficult to manage.

According to a second aspect of the present invention, there is provided a method of deploying apparatus, the method comprising:

extending an extendible mast, the mast supporting and/or positioning said apparatus, the mast comprising:

a member constructed and arranged so as to be configurable between a coiled form and an extended form, wherein when extended the member is resiliently biased in the form of an elongate tube having a slit along its length formed by longitudinal edges of the member and wherein when coiled the member is opened out at the longitudinal edges to a flattened form and wound about an axis extending transversely to the longitudinal extent of the member; and,

a transmission element or retaining structure for retaining a transmission element extending along at least part of the longitudinal extent of the member, wherein the transmission element or retaining structure is positioned adjacent a longitudinal edge of the member so that the transmission element forms a coil outside the interstitial spaces of the coiled member; and

providing services to the apparatus via the transmission element.

According to a third aspect of the present invention, there is provided a method of stowing apparatus, the method comprising: retracting an extendible mast, the mast supporting and/or positioning said apparatus, the mast comprising:

a member constructed and arranged so as to be configurable between a coiled form and an extended form, wherein when extended the member is resiliently biased in the form of an elongate tube having a slit along its length formed by longitudinal edges of the member and wherein when coiled the member is opened out at the longitudinal edges to a flattened form and wound about an axis extending transversely to the longitudinal extent of the member; and,

a transmission element or retaining structure for retaining a transmission element extending along at least part of the longitudinal extent of the member, wherein the transmission element or retaining structure is positioned adjacent a longitudinal edge of the member so that the transmission element forms a coil outside the interstitial spaces of the coiled member.

In other aspects, a method of manufacturing an extendible mast as described above is provided. The method may comprise attaching a

transmission element to retaining means of the mast prior to deploying the mast. It will be appreciated that any features expressed herein as being provided

"in one example" or "in an embodiment" or as being "preferable" may be provided in combination with any one or more other such features together with any one or more of the aspects of the present invention. Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows a perspective view of an example of an extendible mast according to an embodiment of the present invention;

Figure 2 shows a perspective view of an example of a coilable and extendible member suitable for use with the mast of Figure 1 ; Figure 3 shows in plan view an example of a mast according to an embodiment of the present invention;

Figure 4 shows in cross section the mast of Figure 3 across section A-A;

Figure 5 shows in cross section the mast of Figure 3 across section B— B;

Figure 6 shows in cross section a housing for dispensing a mast; Figure 7 shows in cross section another housing for dispensing a mast;

Figure 8 shows another example of a mast according of an embodiment of the present invention; and, Figure 9 shows another example of a mast according of an embodiment of the present invention.

Figure 1 shows an example of an extendible mast 1 for deploying apparatus 6. The mast comprises a member 2 and a transmission element 18 used to connect the apparatus 6 to transmitting and/or receiving equipment. In the present example, the mast 1 is used to support an antenna 6 and transmit and receive electromagnetic signals to and from the antenna 6 via a co-axial cable 18 connected to suitable radio equipment 18. However, it will be apparent from the following description, that the mast can be used for supporting and positioning apparatus other than an antenna, such as tools, cameras, sensing apparatus, etc, and for providing other services via the transmission element 18.

The mast 1 of Figure 1 comprises a member 2 incorporating an integral antenna 6 formed from one or more antenna elements along some or all of its length (shown in broken line in the example of Figure 1 ). References made herein to the longitudinal or axial direction of the mast 1 or member 2 generally refer to the direction in which the mast is extended. The mast 6 has a top cap 3 and a bottom cap 4 which attach to the ends of the mast. Optionally, tethers 5 are attached the top of the mast or to the top cap 3 and are pinned to the ground to help anchor the mast 1 in place. Alternatively, the mast 1 can be self supporting.

The mast 1 has a connector 7 by which connection can be made at a convenient point to the mast 1 by a cable 8, e.g. a co-axial cable, for connecting the mast 1 to a communication system 9. A cable 8 is used to connect the connector 7 to the antenna 6.

The member 2 has the form of a STEM (slit tubular extendible member). Thus, as shown in more detail in Figure 2, the member 2 is formed of an elongate member of sheet-like material, i.e. the member is thin in cross section, e.g.

typically between 1 mm and 5mm. The member can be opened out into a flat form allowing it to be wound into a coil 11. The extended portion 12 is resiliently biased to have a cross section that is curved, in this example, in the form of a circle or partial circle. Thus when fully extended, the member is resiliently biased in the form of a slit tube. The sides of the tube may meet or overlap to form a full tube, or a gap may be left. Cross sections other than circular may be used. For example, ovals and other continuous, non-circular arcs for the cross section can also be produced. The cross section may have straight portions between curved portions whilst being generally curved. The antenna 6 is integral with the member 2 so as to be able to coil and uncoil with the member 2. Various techniques for doing this are described in the following disclosure.

Thus, with the end cap 3 and bottom cap 4 removed, the mast 1 can be progressively wound/unwound around an axis perpendicular to its longitudinal extent between a fully coiled form and a fully extended form. If desired, as described below, a housing can be provided to contain the coiled mast and to help guide the extension of the mast. The material base used for the member 2 is not such as to interfere with the RF requirements of the antenna 6, it is anticipated that implementation will in many cases use composites, Fibre Reinforced Plastics (or Polymers) (FRPs) or Bistable Reelable Composite type devices, as their characteristics are well suited to this type of use. Other material, such as polymers with good elastic properties or metals may be used but in general FRP produce a product of superior performance.

FRPs are known per se and are not described in detail herein. However, in brief, FRPs are composite materials made of a polymer matrix reinforced with fibres. The fibres are usually fiberglass, carbon, or aramid, while the polymer is usually an epoxy, vinylester or polyester thermosetting plastic or thermoplastic, such as polypropylene, polyethylene nylon or poly-ether-ether-ketone. Although the use of thermosetting resins has formed the traditional basis for FRP manufacture, thermoplastic matrix polymers are increasingly being used, due to their speed of production and often superior mechanical performance. The use of fibrous materials mechanically enhances the strength and elasticity of the plastics. The original plastic material without fibre reinforcement is known as the matrix. The matrix is a tough but relatively weak plastic that is reinforced by stronger stiffer reinforcing filaments or fibres. The extent that strength and elasticity are enhanced in a fibre reinforced plastic depends on the mechanical properties of both the fibre and the matrix, their volume relative to one another, and the fibre length and orientation within the matrix. Often FRPs are manufactured by consolidating or laminating different layers of material together. As described below, this layering technique can be used to integrally couple the antenna to the mast by placing the antenna within the laminate.

In one example, the material used for the member 2 is a BRC comprising bistable member, whether made of FRP or otherwise. Such a bistable member has a first stable state in the coiled form, wherein the cross section of the member is generally flat and a second stable state in the extended form, wherein the cross section of the member is curved as previously described. Preferably, the bistable member is capable of reversible configuration between its coiled and extended forms a plurality of times. Suitable structures are disclosed in the following international patent applications, each of which is incorporated here by reference: WO-A-88/08620, WO-A-97/35706, WO-A-99/6281 1 , and WO- A-99/62812. Such bistable structures are available from RolaTube Technology Limited of Lymington, United Kingdom. As described in the above-referenced patent applications, such a bistable member generally comprises material that creates a bias towards configuring the material in the extended form (e.g. having a circular cross-section in this example), as well as material that creates a bias opposite to the first bias (e.g. one that biases the member towards its flattened, retracted or coiled form). The member can comprise a resilient substrate, made of metal for example, which is biased toward the extended form (e.g. biased toward making the member have a circular cross-section), laminated with a plastic layer that tends to bias the member towards the retracted form (e.g. having a flattened cross-section).

Alternatively, the member can comprise a strip or sheet of a thermoplastic material having prestressing means attached thereto or embedded therein. One particular example is a thermoplastic strip having prestressed fibres therein (such as fibres of glass, carbon, or polymeric materials). The fibres can be located at different angles relative to each other in the plane of the coiled member, such as comprising one set of fibres that are longitudinally extending and a second set of fibres that are transversely extending. Such fibres-reinforced composite members (e.g. a thermoplastic resin, such as polyethylene or polypropylene, with fibres of another material, such as glass, carbon, or aramid, embedded therein) are preferred for use in the present invention.

If the antenna 6 is small, for example the 2 to 4 GHz type described above, a simple conductive foil antenna can be bonded to the member 2, or embedded within the lamina of a composite (e.g. FRC or BRC) mast. If the material of the STEM is conductive, an insulating layer must be placed to act as a barrier between the STEM 2 and the antenna element 6 or elements.

In most cases, the antenna 6 will terminate electrically some distance from either end of the supporting STEM member 2. Although electrical connection can be made to a separate cable 8 at the feed point of the antenna 6, it is clearly desirable to be able to make this connection at some point convenient to the user. To this end, a cable 18 is embodied in the STEM member 2 to connect the antenna 2 to the connector 7. Figures 3, 4 and 5 show the cable 18 running within a pocket 16 along an edge 17 of the STEM member 2. This is particularly well suited to use with coaxial cables or others that require a significant diameter in order to function. By positioning the cable 2 at the edge of the member 2, it can coil with the member 2, but is not caught up within the coils of the member. Thus, any increase in the overall thickness of the structure can be eliminated or kept to a minimum, so its affect on the ability of the member 2 to coil is minimised. In contrast, if the cable was positioned on the face of the member 2, the whole structure will distort during coiling as one part of it is separated by the additional cable gap and other parts are not. It would then be necessary to increase the thickness of the STEM elsewhere to compensate, leading to a large, unmanageable coil.

The diameter D of the pocket 16 (or the diameter of the cable 18 if no pocket is used), is preferably greater than the size of the interstitial spaces (denoted "a" in Figure 4) (which may be zero wherein the member is closely coiled) and preferably less than the separation of the outer surfaces of two adjacent coils (denoted "b" in Figure 4). Thus, the cable 18 is larger than the space normally available within the coil, but can be accommodated outside the coiled member without increasing the normal size of the coil.

In some cases, it will be preferable to have no gap between the coils of the member, i.e. "a" = 0. Often the STEM member 2 is a relatively thin sheet (thickness denoted "c") which if tightly coiled leaves little space for bulky pockets 16 or transmission elements 18 at the side. In cases where the diameter D of the transmission element 18, inclusive of the diameter of any material in which it is housed, i.e. retaining structure 16, is such that there is a gap "a" between the faces of the STEM member 2 when coiled it may be desirable to provide some or all of the face of the STEM member 2 that is raised, on one or both sides, such that it lies in contact with the opposite face in the coil. Figure 4 shows an example of this in which the inner faces have an optional raised portion 15 (in broken line) which contacts the opposite outer face when coiled. This has the advantage that the coil will be better able to lay evenly. In contrast, if the coiling takes place such that the thicker section D at the transmission element prevents contact between the faces of the STEM and no provision is made to constrain the edges on coiling there will be a tendency for the coil to offset, layer on layer, to one or both sides, producing a distorted and uneven pattern of coiling.

The mast 1 may be provided with a housing 50 which contains the coiled mast 2 from which it can be extended wholly or partially. The housing 50 may form a base for supporting the extended antenna assembly when deployed. Figure 6 shows a housing 50 that provides a simple "push-pull" cassette, which holds the coil 1 1 in place and allows the mast 2 to be push-pull extended and retracted. The housing 50 may include a releasable mechanism that constrains the coiled portion 1 1 of the mast 2, such that releasing the mechanism allows the mast 2 to self coil. The housing 50 may include a hand-operated or motor driven mechanism for winding/extending the mast 2 that is arranged such as to drive the mast 2 between extended 12 and coiled 11 states. For example, Figure 7 shows a housing 50 comprising a pinch-wheel 51 operable to drive the mast 2.

As will be appreciated many other means are available to provide the housing 50 and drive to the member 2. The housing 50 may provide complete containment or be composed of rods or rollers arranged around the coil 1 1 , closely enough spaced to prevent it going in between the rods or rollers when in use, but thus reducing friction on the surface of the coil.

The housing 50 may comprise a rotatable connector 22 aligned with the axis about which the member coils which is connected by a length of cable 22 to the cable 18 within the pocket of the member 2. This allows the mast 1 to coil without the cable 8 being twisted, which may be undesirable and lead to damage of the cable where for example the degree of rotation is large or the cable 8 is stiff or delicate. Suitable rotatable connectors for electrical connectors or fluid connections are known per se and are not described in detail herein. Figure 9 shows an alternative arrangement for managing the connection to the transmission element 18 at the coiled end 1 b of the mast 1 which does not rely on using a rotatable connector as in Figures 6 and 7. Provision is made for a length 18b of the transmission element 18 to be coiled beyond the near end 2b of the STEM member 2 and terminated to a hub 19 lying inboard of the internal diameter of the coiled STEM member 2. As the STEM member 2 is extended, the extra length 18b of the transmission element 18 will tend to coil towards the hub 19, as it is retracted it will tend to uncoil to its original diameter. In other words, the extra length 18b forms a coil which becomes tighter when the mast 1 is extended and looser when the mast 1 is retracted. In this manner a connection can be made that is non-rotating at the hub and provides continuity for a cable, pipe of other transmission element 18 without the need for any slip ring or similar sliding or rotary sliding device. This has the advantages of removing sliding electrical connections that may wear or create electrical interference and allowing a pressurised transmission element to be free of seals that may leak.

The mast 1 may be provided with a housing 50 which contains the coiled member 2 from which it can be extended wholly or partially. The housing 50 may form a base for supporting the extended mast 1 when deployed. Figure 6 shows a housing 50 that provides a simple "push-pull" cassette, which holds the coil 1 1 in place and allows the member 2 to be push-pull extended and retracted. The housing 50 may include a releasable mechanism that constrains the coiled portion 1 1 of the member 2, such that releasing the mechanism allows the member 2 to self coil.

The housing 50 may include a hand-operated or motor driven mechanism for winding/extending the member 2 that is arranged such as to drive the member 2 between extended 12 and coiled 1 1 states. For example, Figure 7 shows a housing 50 comprising a pinch-wheel 51 operable to drive the member 2.

As previously described, the mast 1 can be used to deploy other apparatus than antennas 6 which require other flexible transmission elements 6 than cables. It will be appreciated that the principles described in relation to antennas and cables apply to these other scenarios. The mast 1 may comprise mount 24 (shown in Figures 6 and 7), e.g. at the distal end, for removably mounting a tool, camera or other apparatus 6. In this case, a connector 26 is preferably provided at the mount 24 for connecting the transmission element to the removable apparatus 6. The transmission element 18 may comprise a co-axial cable or cables or other arrangements of one or more conductive elements for transmission of electrical power, data, or control signals. Additionally or alternatively, the transmission element 18 may provide fibre optic means for optical

communications with the apparatus 6. Additionally or alternatively, the transmission element 18 may provide a hose for transmitting a fluid, gel or particular matter to the apparatus 6. For instance, the transmission element 18 may comprise a hose for providing hydraulic power to the apparatus 6. The transmission element 18 may comprise a hose for providing liquid or gaseous fuel to the apparatus 6.

As described, the mast 1 may comprise a pocket 16 for containing the transmission element 18. However, other retention structure 16 can be used to attach the transmission element to the member 2. It can be convenient for the retention structure 16 to allow some degree of slip between the member 2 and the transmission element 18. It can also allow the transmission element to be removed and replaced according to the apparatus being deployed or to deal with wear or damage to the transmission means over time. The retention structure 16 can be a continuous pocket which completely surrounds the transmission element 18, and thus helps protect it from the environment or provide insulation. Alternatively, discrete clips or other retention structure can be used. In other embodiments, the transmission element 18 itself may be directly bonded to the member 2, i.e. no pocket or retention structure 18 is provided. The transmission element 18 and retention structure 16 can be provided at one or both side edges of the member 2. For instance, where the transmission elements 18 are hydraulic hoses, one side can be used to supply hydraulic fluid to the apparatus 6 and the other side can be used for the return path.

Alternatively or additionally, more than one transmission element may be provided on a single side.

The transmission element 18 may be used to provide fuel or propellant to an engine or thruster mounted at the end of the mast, where the mast 1 is mounted to a vehicle and used to deploy the engine when required. For instance, Figure 9 shows a form of electric propulsion, an ion thruster, used for spacecraft propulsion that creates thrust in accordance with momentum conservation by accelerating ions or plasma using either electrostatic or electromagnetic force. Xenon and other gases can be used for propulsion. The operation of such devices is known per se, and a detailed description of their operation is therefore not given herein.

The thrusters 41 are mounted on the distal end of respective masts 1 with the coiled ends mounted to the vehicle 40, such that extending the mast 1 by a powered mechanism (not shown in Figure 9 for clarity) deploys the thrusters 41 to the desired position for propulsion 42. The transmission elements 18 in this example are in the form of hoses or tubes for transmitting the gas 44 supply to the thrusters 41 from a gas source 42. The mast 1 provides an advantageous means of providing for the gas supply without the need to provide additional umbilical pipes which might interfere with the ability of the mast 1 to extend and coil.

It will be appreciated that other types of fuel or propellant may be used with different types of engine or thruster deployed with the mast 1 disclosed herein.

Embodiments of the present invention have been described with particular reference to the example illustrated. However, it will be appreciated that variations and modifications may be made to the examples described within the scope of the present invention.