The present invention relates to deployable support structures for space applications, such as deployable reflector antennas.

A low weight, compactly deployable support structure has been disclosed previously as W02012/065619 Al. This deployable structure comprises articulated struts arranged in a conical-shaped module when deployed, which can be either unique or multiply connected in a complex structure. One of the features of that invention is the deployment actuation within all of the hinged struts (V-folds) forming the upper and lower chords of the cell or ring. This actuation can be either elastically or electrically motorized. The drawback being that there is need of actuation in most of these V-fold hinges with localized actuators.

A deployable reflector antenna frame is also known from US 5,680,145 that comprises a load-bearing ring consisted of hinged rods that are capable of forming upper and lower chords; bars that connect the rods; a stretching frame consisted of flexible cellular meshes and connecting ties; and a deploying mechanism. The drawback of the above mentioned frame is the large size thereof in a stowed state, particularly its height that is caused by arrangement of the connecting bars in two rows when the rods of the upper and lower chords are stowed.

SU 429486 discloses another deployable space reflector antenna, comprising a load-bearing ring consisting of bars; a central stretching frame composed of V-fold bars hinged to the bars and being capable of forming upper and lower chords, of layers formed by elastic links, and of connecting ties; of hinges that connect the V- fold bars to the bars; and of a deploying mechanism composed of a spring that interconnects the V-fold points. The drawback of the above mentioned reflector antenna frame is a less reliable deployment of the reflector antenna and poor stability of the deployed state. Less reliable deployment of the frame is associated with the deploying mechanism made of multiple springs that connect the V-fold points of the V-fold bars. The large number of required springs and the independent actuation thereof lead to non-controllable deployment of the frame and degradation of the deployment reliability. Poor reliability of the frame deployed state is caused by elasticity of the deploying mechanism springs that is eventually reflected on non-stability of the reflector shape and degradation of its radio engineering parameters.

In view of the above problems of the prior art, the present invention seeks to improve reliability of deployment of a reflector antenna frame and enhancing its deployed state stability, mass and stiffness. It is a further object of the invention to provide a low weight, compactly deployable support structure suitable for large deployable apertures.

This object is accomplished by the subject-matter according to the subject-matter of the independent claim 1. The dependent claims refer to preferred embodiments of the invention.

In accordance with an aspect of the invention, a multi-faceted deployable antenna frame comprising a six-bar linkage structure in a lateral facet of the antenna frame is proposed. Preferably, each lateral facet comprises such a six-bar linkage structure. The six-bar linkage structure is convertible from a folded state into a de- ployed state. The six bars of the six-bar linkage structure comprises two first bars and four second bars, each bar being coupled to two others by a hinge to form a closed loop. In the deployed state, the six-bar linkage structure has substantially a quadrilateral shape. The two first bars are located at opposite sides of the quadrilateral and thus represent two opposing sides of the quadrilateral shape of the six- bar linkage when in the deployed state. Two second bars are arranged in series on each of the other two opposing sides of the quadrilateral in the deployed state. In the folded state, the second bars are pivoted around the first bars. In the folded state, the two second bars arranged in series are also pivoted relative to each other around their coupling hinge forming a V-shape (also referred to as V-fold bar). In the folded state, the first bars are arranged so that the end portions of two adjacent first bars are located side by side.

In accordance with an aspect, the deployable antenna frame comprises a deployment means for deploying the antenna frame by moving the six-bar linkage structures from the folded state (also referred to as the stowed state) into the deployed state. The deployment means comprises a flexible, elongated member of a substantially inextensible material; a guiding means provided at an end portion of one of the first bars and coupled to the elongated member; a storage means provided at the first bar that comprises the guiding means for storing a part of the elongated member; and a driving means that is coupled to the elongated member to pull the elongated member to the storing means when deploying the antenna frame.

A first end of the elongated member is attached to the storing means and a second end of the elongated member is coupled to another first bar. Thus, the other first bar that has the second end of the elongated member coupled thereto is a different first bar than the one at which the storing means and the guiding mans is provided. The elongated member is extending between said first end and said second end along a plurality of second bars. By way of example, if a further first bar is located in between the first bar that comprises the storage means and the first bar comprising the second end, the elongated member may extend along four second bars.

The six-bar linkage structures formed at the lateral facets of the antenna frame in combination with the centralizing driving means located at one of the first bars and the elongated member that couples the driving force of the centralized driving means to other first and second bars enables a particular light-weight assembly structure that can be stowed in a compact configuration. In accordance with an aspect of the invention, the guiding means is arranged on top of one of the hinges located at an end portion of the first bar comprising the storage means and projecting outwardly in a longitudinal direction of the first bar. By way of example, the guiding means may be a pulley or roller and the elongated member may be a cable.

Preferably, at least two elongate members are provided, one extending along the second bars forming the upper side of the antenna frame and one extending along the second bars forming the lower side of the antenna frame. In this case, at least a second guiding means is located at an end portion of the first bar that is opposite of the end portion comprising the first guiding means.

In accordance with an aspect, the storage means may be provided at a center portion of the first bar so that it is located at an equal distance from the two guiding means located at opposite end portions of one of the first bars.

In accordance with an aspect, a second guiding means may be provided at the hinges coupling two adjacent second bars and the elongated member may be coupled to the second guiding means. Preferably, the elongated member is coupled to the second guiding means so that, in a deployed state of the antenna frame, the elongated member extends along a broken or zigzag line between the guiding means provided at the first bars.

In accordance with an aspect, the elongated member may extend along at least four second bars. It will be appreciated that number of second bars is not restricted to a particular number as the pulling force of the centralized driving means can be coupled to a varying number of second bars by the guiding means and the hinges.

In accordance with a further aspect, the antenna frame may comprise synchronising means provided at least at some of the hinges for synchronising the pivoting movement of the second bars relative to the first bars during deployment of the six-bar linkage structures. This synchronising mechanism may be achieved, for example through an interacting pairs of gears having a toothed disc shape. According to a further example, the synchronising means may comprise a slider strut slidably coupled to two adjacent first and second bars, wherein the slider strut moves upwardly along the first bar when the antenna frame is converted from the deployed state into the folded state.

In order to stiffen the upper and lower rings of the antenna frame formed by the second bars, the antenna frame may comprise connection cables extending be- tween each adjacent first and second bars. A particular advantageous configuration of the connection cables may be achieved by attaching the connection cables to the center portions of adjacent first and second bars, so that the connection cables form a rhombic shape in the deployed state of the six bar linkage structure. In order to keep the elongated member tensioned, the second end of the elongated member may be coupled to the another first bar by a spring.

In accordance with a further aspect, the driving means may comprise an electrical motor or a plurality of motors. The storage means may comprise a drum or a plu- rality of drums. By way of example, the storage means may comprise a first and a second drum, the first drum being configured to spool an elongated member extending along the plurality of second bars arranged at an upper side of the antenna frame and the second drum being configured to spool an elongated member extending along the plurality of second bars arranged at a lower side of the anten- na frame.

In order to ensure favorable attack angles of the elongated member at the first and second bars, the first bars comprise upper and/ or lower projecting ends. Preferably, the guiding means is attached at an end portion of the projecting end. In accordance with this aspect, the projecting ends may serve as a protection mechanism to prevent the elongated member from jumping off the guiding means. In order to reduce the weight and increase the stiffness and modularity of the de- ployable reflector antenna frame and to ensure better stretching of the anterior mesh net which consists of cells, and to assume the high accuracy reflector profile, the antenna frame may have conical shape. Preferably, the conical shape is created by different lengths of the elongated member extending along the plurality of second bars arranged at an upper side of the antenna frame and the elongated member extending along the plurality of second bars arranged at a lower side of the antenna frame. It is a particular advantage of the modular frame assembly that it can serve as a basis to build deployable antennas or antenna frames of different shapes. For instance, the antenna frame may comprise any number above two of lateral facets of identical or unequal shape forming a ring structure of regular or irregular polygonal shape.

The invention is explained below in an exemplary manner with reference to the accompanying drawings, wherein

Fig. 1 shows a deployable reflector antenna frame with a cylindrical shape according to an embodiment;

Fig. 2 shows a deployable reflector antenna frame with a conical shape according to an embodiment;

Fig. 3 shows two six-bar linkage structures in a deployed state according to an embodiment- Fig. 4 shows a six-bar linkage structure in a folded state according to an embodiment- Fig. 5 shows a top view of the coupling portion between first and second bars of a six-bar linkage structure of the reflector antenna frame according to an embodiment;

Figs. 6 and 8 show front views of the coupling portion between first and second bars in the deployed state according to an embodiment; and

Figs. 7 and 9 show front views of the coupling portion between first and second bars in the folded state according to an embodiment.

Fig. 1 shows a deployable reflector antenna frame 1 having a cylindrical shape in the deployed state whereas Fig. 2 shows a different embodiment of a deployable reflector antenna frame having a conical shape.

The deployable reflector antenna frame 1 comprises a load-bearing ring 2 with vertical bars 3, V-fold bars 5 that are hinged with a revolute joint 4 to the vertical bars 3 and that form upper and lower chords, and interacting deployment synchronising means 6 provided at the coupling portions between vertical bars 3 and the V-fold bars 5. The V-fold bars 5 comprise two bars arranged in series and coupled by a center hinge 20 (not shown in Figs 1 and 2, cf. Fig. 3).

Each closed loop of vertical bars 3 and V-fold bars 5 forms a planar six-bar linkage occupying a facet of the frame structure. The deployable reflector antenna frame 1 is provided with a stretching frame 7 comprising an anterior net 8 having triangular cells, a rear net 9 having triangular cells, and connecting ties 10. The net 8 which consists of triangular cells is intended for forming the reflector profile and fastening the elastic reflective surface. Connection cables 11 are extended between each adjacent vertical 3 and horizontal 5 bars to stiffen the stable load- bearing ring 2. In order to reduce the weight and increase the stiffness and modularity of the deployable reflector antenna frame 1 and to ensure better stretching of the anterior net 8 which consists of cells, and to assume the high accuracy reflector profile respectively, it is preferably made in the form of a cone, as shown in Fig. 2.

Fig. 3 shows two lateral facets of the antenna reflector frame. A lateral facet is formed by a six-bar linkage structure 100. The six-bar linkage structure 100 is convertible from a folded state (shown in Fig. 4) into a deployed state (shown in Fig. 3). The six-bar linkage structure comprises two vertical bars 3 and four horizontal bars 5 (the terms "vertical" and "horizontal" relate to the illustration of the deployed state, as shown in Fig. 3). Each of the bars 3, 5 is coupled to two others by a hinge 4, 20 to form a closed loop. Reference number 20 denotes the hinge that couples two horizontal bars 5, whereas reference number 4 denotes the hinge that couples the horizontal bar 5 to a vertical bar 3. In the deployed state, the six-bar linkage structure 100 has a quadrilateral shape, wherein the two vertical ba s 3 are located at opposing sides of the quadrilateral and two horizontal bars 5 are arranged in series on each of the other opposing sides at the upper and lower end of the load-bearing ring 2. In the folded (stowed) state, the reflector assembly occupies a smaller volume than when in the deployed state. The deploying mechanism of the frame 1 comprises rollers 13 arranged on one side in the load-bearing ring 2 sections and of cables 14 that are guided by the rollers 13 so that the cables extend along the vertical 3 and horizontal 5 bars, respectively. One end portion of the cables 14 are connected to the vertical bars 3 at one section of the antenna frame 1 by means of springs 15, and the other end portion of the cables 14 are attached to drums 16 that are driven by electrical motors (not shown) and disposed in the middle of a vertical bar 3 of another section of the antenna frame with the capability of being rolled up on the drums 16.

The connections 11 of the load-bearing ring 2 are made in the form of cables connected in the middle parts 17 of the vertical bars 3 and in sites 18 adjacent to folding points of the V-fold bars 5, whereby a rhomb like structure is created in each ring 2 cell that ensures better stability of the ring in the deployed state. The load-bearing ring 2 vertical bars 3 are provided with upper and lower projecting ends 19. The cables 14 of the deploying mechanism 12 mounted in the load- bearing ring 2 sections are passed over the rollers 13 connected to the projecting ends 19 of the posts 3 and are passed over the rollers 21 connected to the hinges 20 of the V-fold bars 5. The rollers 21 located at the V-fold bars hinges are similar to rollers 13 on the vertical bars 3.

The motors are used for the transformation of the structure from the stowed state (Fig. 4) to the deployed state (Fig. 3) by spooling the cable 14 into the drums 16. In this spooling process the cable is pulled and travels over the rollers 13 and 21, transferring the motor action into a tensioning force. The resultant of tensioning forces on the rollers 21 and consequently on the hinge 20 is the cause of a lifting force of the V-fold bars 5, which results in the necessary moment to rotate them around their hinges 4 and to unfold the six-bar linkage 100 present in each facet of the ring structure. A minimum of one motor is provided, driving two drums 16, one for the upper chord 14 and one for the lower chord 14. More motors can be used for redundancy. Fig. 4 shows a different cut-out portion of the antenna frame as Fig. 3. For instance Fig. 4 shows only the right and middle vertical bars 3 shown in Fig. 3, but not the left vertical bar 3. The wiggly line 11 illustrates the cables 11 in the folded state when the cables are not tensioned. In the folded state, the vertical bars 5 are aligned parallel to each other and their end portions are positioned next to each other. The V-fold bars 5 are folded to an acute V-form, wherein the center hinges 20 of the upper ring are located in between the vertical bars 3 along a straight line, wherein center hinges 20 of the same six-bar linkage structure are located opposite to each other.

Fig. 5 shows a top view of the hinge 4 comprising deployment synchronising means 6 which couples two end portions of the horizontal bars 5. The deployment synchronising means 6 also couples the vertical bar 3 with the vertical bars 5 as shown in the front view of Fig. 6. The deployment synchronising means 6 comprises the interacting pairs of gears 22 having teeth 23 and seats 24 with rounded surfaces for ensuring rolling over one another during the deployment process both in vertical and horizontal planes simultaneously and for inclining thereof outwardly. The hinge which connects the gears 22 to the vertical bars 3 is made in the form of brackets 25 and 26 having turning handles. Besides, the gears 22 are connected to the brackets 25 and 26 by means of rotary axes 27. In the embodiment where the load-bearing ring 12 has a structure of twelve equal facets, the brackets 25 and 26 are connected to the vertical bars 3 making an angle of 150 degrees between them, and the teeth 23 and seats 24 of the interacting pair of gears 22 that connect the V-fold bars 5 have the capability of rolling over one another by their surfaces rounded by approximately 3 degrees to create the maximum angles of 153 degrees and minimum angles of 147 degrees between them and to enhance the frame deployment reliability by compensating the inequal forces produced during the load-bearing ring 2 deployment. The load-bearing ring 2 vertical bars 3 are made in two portions and are connected to each other by means of the brackets 25 and 26 of the pair of gears 22, to create free spaces 28 between the portions of the vertical bars 3 at the levels of the pair of the gears 22 for interacting the teeth 23 and seats 24.

Both Figs. 6 and 8 show a detailed view of the coupling portion comprising the synchronisation means 6 between the bars 3 and 5 in the deployed state. Fig. 6 shows a detailed view of the upper portion of the middle vertical bar 3 shown in Fig. 4, i.e. the vertical bar 3 that is shared by the two shown six-bar linkage structures 100. This vertical bar has no drums 16 or motor attached thereto. Fig. 8 shows a detailed view of the upper portion of the vertical bar 3 located on the right shown in Fig. 4. This vertical bar has drums 16 and a motor (not shown Fig. 4) attached thereto at its center portion. As shown in Fig. 6, the cable 14 extends horizontally to the right and left since it extends along the unfolded two upper horizontal bars 5. By contrast, as shown in Fig. 8, the cable 14 is guided by the pulley 13 to change its direction to extend downwards along the right vertical bar 3 to the drum 16.

Figs. 7 shows the upper portion of the vertical bar 3 shown in Fig. 6 in the folded state, and Fig. 9 shows the upper portion of the vertical bar 3 shown in Fig. 8 in the folded state. The angle of the cable 14 to the vertical bar 3 is narrower in Fig. 9 than in Fig. 7 since the cable 14 as shown in Fig. 9 extends towards the drum 19 located at the center portion of the right vertical bar 3 (cf. Fig. 3), whereas the cable 14 as shown in Fig. 7 extends along the bar 5 to the roller 21 of the center hinge 20 (cf. Fig. 4). Features, components and specific details of the structures of the above- described embodiments may be exchanged or combined to form further embodiments optimized for the respective application. As far as those modifications are readily apparent for an expert skilled in the art they shall be disclosed implicitly by the above description without specifying explicitly every possible combination, for the sake of conciseness of the present description.