Object of the present invention is a network structure that is capable of lifting and lowering, to be used as support of flexible covers or rigid panels. Further object of the present invention is a cylindrical hinge apt to connect the members of said network structure that can be lifted and lowered.

Network structures are formed by composite trusses each connected to the adjacent one by cross bracing element, that is by members able to resist to substantially axial load stress. The trusses are made of an arrangement of members laying on a plane, which at the design phase are supposed to be reciprocally connected by hinges, but in reality they are interconnected by means of rigid joints.

The conventional assembly methods of the network structures of the prior art, needs the precise definition of the point of the space whereat every joint must be mounted, thereto the members are connected, and the employment of a skilled operator able to reach that point, which can be at a considerable height from the ground, it is mandatory for carrying out the assembly.

It is understood that the lifting of a prior art network structure involves a considerable waste of time and implies also a specific equipment in order to reach every point of the structure to be assembled, with

consequent problems of danger for the operators.

Therefore, a scope of the present invention is to overcome the difficulties pointed out before and to embody a network structure that can be mounted during each of its operating phases and with relation to each of its parts at the ground level.

Such a network structure does not, therefore, demand the employment of scaffolds, or other aerial equipment suitable to lift the operator at a considerable height from the ground for carrying out the assembly.

An other object of the present invention is to embody a network structure having various shapes and dimensions without this leading to a specific design and using of provisional equipment during works.

By means of the present invention it is reached a decrease of the assembly costs of structures similar to the prior art ones.

Still an other scope of the invention is to reduce the eventuality of accidents for the assemblers.

The aforementioned scopes are reached in accordance to a first characteristic of present the invention by a network structure with means for lifting and lowering the same, suitable to be used as a support of flexible and rigid covers, formed by trusses connected each to the adjacent ones by cross bracing members, wherein said trusses being composite trusses made of linear elements

(members) connected between them in succession by means of cylindrical hinges, the ends of the successions of at least every pair of said consecutive elements being connected by means of tie members consisting of wires of a metallic alloys known as shape memory alloy, and wherein one of the extremity rods of each articulate member is provided with a sliding carriage able to slide freely on the ground.

An other characteristic is given by the fact that the cylindrical hinges of the network structure consist of -a rotating coupling between the ending extremities of a first and a second consecutive member, the first ending element of said first member including a disc-shaped portion whereas the second ending element including a fork-shaped portion or a disc-shaped portion made of a disc having a central pin or two discs being coaxial to the first portion having the shape of a disc; a hole, which lodges a rotation pivot, having a central axis and being coaxial to the disc-shaped portion and to the fork-or disc shaped one; -automatic locking means of two terminal elements of consecutive members at a desired relative angular position, including at least an eccentric coaxial hole obtained in the fork-or disc-shaped portion and at a given radial distance from the axis of the

central hole and at least a hole obtained in the portion having the ending part shaped as a disc at the same radial distance from the axis of the two eccentric holes of the portion having the ending part shaped as a fork or disc; said two eccentric holes of the fork-or disc-shaped portion and said hole of the disc-shaped portion being coaxial at a desired relative angular position of the consecutive members so to receive a locking grain housed in one of the two eccentric holes, said hole being partially threaded and loaded by a locking helical spring working by compression and insisting at the other end against a threaded closing element of said eccentric hole; -automatic unlocking means of at least two ending elements of consecutive members from a desired relative angular position including a helicoidal unlocking spring working by traction when fed by electrical current or when heated, made of a shape memory alloy, engaged at one side with the locking grain and at the other side with the threaded closing element of said eccentric hole; said locking spring being susceptible of resuming the original shape by means of heat in order to act against said locking spring, -ball joints, carrying cross bracing members, being

fixed at both sides to the ending portion shaped as fork or disc. Favourably the cylindrical hinges, being preferably of one way type and of self-locking type, warrant the automatic locking and the automatic unlocking in and from a desired angular position of the connected members thereto.

An other characteristic is given by that in the cylindrical hinges the ending element of the member including the disc-shaped ending portion exhibits at its lateral side a semi-cylindrical section member for delimiting and guiding the fork-or disc-shaped ending portion. The hinge remains guided within such a protection element.

A further characteristic is given by the fact that the rotating pin of the cylindrical hinge is formed by a prisoner whose threaded ends are suitable to be screwed into counter threaded seats of said ball joints.

An other characteristic is given by the fact that the rotating pin of the cylindrical hinge is made of a couple of screws having respectively an inner and outer threading and provided of screwing heads suitable to be screwed in counter threaded seats of said ball joints.

The present invention allows to embody a process for assembling network structures comprising the following lifting steps: -assembling along a plane the members of each truss

by means of the respective cylindrical hinges; -connecting the cylindrical hinges facing the adjacent truss by means of cross bracing members with ball joints, in order to form the flat network structure; -connecting between the endings of at least two consecutive members the cylindrical hinges of the same truss by means of respective tie members made of shape memory alloys, said tie members being lengthened beforehand in the martensitic state at ambient temperature of the necessary length for connecting said cylindrical hinges on a plane, said plane being at a higher level than the plane of the tie members; -heating by Joule effect each tie member till the required temperature for its relative shortening to the original length (austenitic phase), in order to obtain the desired angular position of the erected structure for each couple of members delimited by the cylindrical hinges constraining each tie member; -automatic locking of the cylindrical hinges in the angular position of erected structure by means of a conventional spring, -releasing the bracing members, bound to the endings of the locked cylindrical hinges, by means of their cooling at ambient temperature till the

reaching of the aforesaid length of connection of said cylindrical hinges on a plane; and from the fact that comprises the following lowering steps: -Supplying current to the tie members of shape memory alloy, in order to avoid the collapse of the structure; -unlocking the cylindrical hinges from the angular position of erected structure, by means of heating; -flattening the network structure also by means just of its weight; -disassembling along a plane the ball joints of the cross bracing members between the trusses and the cylindrical hinges of the members of each composite trusses.

Other characteristics and advantages of the invention will become clear from the description of some embodiments given as a not limiting example by figures 1, 12,13 and 14.

Figure 1 represents a top view on a plane of the network structure with a polygonal plant according to the invention; Figure 2 represents a top view on a plane of the network structure with a square plant according to the invention; Figure 3 represents a schematic side view of the

structure of figure 2 in the assembling phase accomplished at the ground level; Figure 4 represents a side schematic view of the structure of figure 2 in the intermediate phase of elevation from the ground level; Figure 5 represents a side schematic view of the structure of figure 2 at the ending phase of elevation after the locking of the cylindrical hinges between the members; Figure 6 represents a magnified schematic side view of a portion of the structure of figure 5; Figure 7 represents a perspective schematic view of one section of the structure of figure 1 in relative phases of elevation corresponding to those of the figures from 3 to 5; Figure 8 represents a perspective schematic view of the structure of the figure 1 in the phase of completed elevation; Figure 9 represents a perspective partial cross-section view of a cylindrical hinge according to the invention; Figure 10 represents an exploded perspective partial cross-section; Figure 11 represents a schematic side view of the hinge according to the invention in a flat angle arrangement; Figure 12 represents a cross-section obtained along lines A-A of figure 11;

Figure 13 represents a schematic side view of the hinge according to the invention in an angular position of the erected structure.

Figure 14 represents a schematic side view of the hinge according to the invention in an angular position of the flattened structure.

With reference to figures 1 and 2 two examples of plants of a network structure according to the present invention are shown.

In figure 1 is shown a central polygonal plant of a network structure which in figures 7 and 8 is shown during the elevation phase while in figure 2 is shown a plant with four sides, in particular a square, while the elevation phases of such a structure are shown in figures from 3 to 6.

It is understood however that other configurations of plants can be adopted.

With reference to figure 1 the assembled, but laying on a plane, network structure is indicated as a whole by (1), the members of composite trusses along the diameters are marked with (10) and the cross bracing or cross bracing members along the circumference with (11).

In figure 7 is shown a section of plant 12 (figure 1) in a perspective magnified scale with the same reference number, whereas with (12') and respectively (12") are indicated two subsequent phases of lifting of the network

structure (1).

Members (10) are interconnected by means of cylindrical hinges whose endings are marked with (13). The cross bracing members (11) are fixed to the facing terminal hinges by means of ball joints.

As shown in figure 7 with reference to the positions (12') and (12") of a section of the structure, below the members (10) there are tie members (14) connected, in the shown embodiment, to the alternate couples of hinges (13); as aforesaid, the tie members (14) can also be connected to the ends of groups composed by more than two consecutive members, the limits in the number of members being fixed by the load, by the coefficients of traction of said tie members (14) and by the strength coefficient.

According to the present invention the members are made of metallic alloys known as shape memory. As it is known these alloys (binary of nickel and titanium or ternary of copper, zinc and aluminium, but also of other metals) have the property to vary their characteristics (dimensions, shape, resistance) according to the conditions of use (temperature, electric potential, mechanical deformations); in brief, the items built with these alloys once deformed, according to the martensitic and austenitic states, at a certain temperature they maintai-n their deformation until they are electrically heated or stressed. Then they recover their original shape and take

back the state (dimensions, shapes, property) they assumed when were forged.

The network structure is built by connecting members (10) by means of cylindrical hinges (13), as shown in figure 9. Cross bracing members (11)- (11) are connected from opposite sides (figure 10) to the same hinge (13), the bracing members (11) being suitable to absorb substantially horizontal forces in the network structure.

In the hinge (13), moreover, concur the tie members (14)- (14), suitable to arrange consecutive members (10)- (10) in accordance to desired angular positions of the erected structure.

Two ending elements (120) and (125) of consecutive members (10) are connected to the hinge (13). Ending element (125) includes a portion with shape of fork or disc (130), (140) of two coaxial discs while ending element (120) includes one portion with shape of disc (121) presenting at the lateral side, a semi-cylindrical section member (122) confining and guiding the fork shaped portion (130), (140). In the disc-shaped portion (121) and in the fork-shaped portion (130), (140) a hole (110) is obtained with a central axis for a rotation pin (112). At least two eccentric holes (150) and (160), biased from the central axis hole (110), are coaxially drilled in the fork-shaped portion at a certain radial distance from the axis of the central hole and at least a

hole (100) is drilled in the disc-shaped portion (121) at the same radial distance than the two eccentric holes (150) and (160) of the fork-shaped portion (130), (140).

In the figures are shown two couples of eccentric holes (150) and (160) for the fork-shaped portion (130) and (140) and two holes (100) for the disc-shaped portion (121).

As illustrated in figure 9, the eccentric holes (150) e (160) of the fork-shaped portion (130), (140) and hole (100) of the disc-shaped portion (121) are coaxial at a desired angular position of consecutive members (10)- (10) (figures 13 and 14) in order to receive a locking grain (40). When eccentric holes (150) and (160) are not coaxial with the hole (100) (figures 11 and 12) the locking grain (40) is lodged in one of two eccentric holes (150).

Hole (150) is partially threaded for being closed by a threaded closing element (70). Between the threaded closing element (70) and the grain (40) is placed an helicoidal locking spring (60). The locking spring (60) of conventional type works by compression on grain (40). To the inner of the same hole (150) an helicoidal unlocking spring (50) is housed, engaged by a side with the threaded closing element (70) and from the other side with the grain (40). The helicoidal spring (50) is made of a shape memory alloy of the type at one or two ways.

That means that said spring is by norm deformed and

exercise a small antagonist force to the traditional spring (60). When the helicoidal unlocking spring (50) of the memory shape type is heated or is otherwise stressed in order to take back its original shape, said helicoidal spring exceeds the force of the helicoidal locking spring and attracts towards itself the locking grain (40).

The cross bracing members (11) and (11) (figure 10) are connected to the cylindrical hinge by means of two ball joints (170), forming a seat (80) for a ball joint (180) having a connecting threaded portion with the respective cross bracing member. Ball joints (170) are connected to cylindrical hinge (20) by means of a prisoner, with which is embodied the rotation pin (figure 10) suitable to be screwed with its threaded ends into counter threaded seats of ball joints (170). As alternative, as shown in figure 9, the rotation pin (110) is constituted by a couple of screws with respectively inner and outer threading having threaded heads that are screwed in the counter threaded seats of the ball joints (170).

Preferably tie members (14)- (14) are made of shape memory alloy of the type at one or two ways and are associated to the consecutive members to bring into the desired angular position.

With reference to the figures 11 and 12 members (10), (10) are shown in a flat angular position. As schematically shown in this position, eccentric holes

(150) and (160) of the fork-shaped portion are not coaxial with hole (100) of the disc-shaped portion (121), for this reason grain (40), even if pressed from traditional spring (60), cannot be pushed between the disc-shaped portion (121) and the fork-shaped portion (130), (140) in order to lockingly engage one with the other.

When, as shown in figures 13 and 14, tie members (14)- (14) bear members (10)- (10) at the desired angular position, that is the one of an erected network structure, the grain (40) pushed by the spring (60) can partially enter in hole (100) of the disc-shaped portion (121) in order to engage this last one with the fork-shaped portion (130), (140).

The members (10)- (10), after having supplied again the tie members (14) for avoiding the collapse, are locked in their turn at such angular position. At the moment in which they must be unlocked in order to obtain the flattening of the structure, the spring (50) of a metallic alloy with memory shape is brought in its antagonist retracting position by winning the force of the traditional spring (60). Therefore, metallic grain 40, as shown in figure 14 it is extracted from hole (100) of the disc-shaped portion (121) and the hinge (13) brings back members (10)- (10) at the flat position. For this happens at the same time for all the cylindrical hinges

of the network structure, this flattens to the ground thanks only to its weight.

In the method according to the invention tie members (14) are made of metallic alloys with shape memory of a one or a two ways type, so that said tie members (14) once cooled or after expiring of the electric effect, they tend to release in order to return to the shape, dimensions and other typical property of their deformed state; tie members (14) can also be of a shape memory sort of a one way type, in such case when the structure comes down it is creates martensite induced by stress and the tie member returns at its initial state. Therefore, the network structure is mounted flat at the ground level by connecting the members (10) of each truss by means of the respective cylindrical hinges. The cylindrical hinges (13) facing the adjacent trusses are connected by means of cross bracing members (11) through ball joints in order to form a flat network structure. The cylindrical hinges (13) at the ends of a succession of two or more consecutive members of a same truss are connected by means of the relative tie members (14) made of shape memory alloys at one or two ways and preventively lengthened, by martensitic deformation at ambient temperature, of the necessary length for the connection of the cylindrical hinges on a plane. Every tie member (14) is heated at the temperature required for the

relative shortening to the original length. The desired angular position of the erected structure (12') of each couple of members delimited by the cylindrical hinges binding each tie member is then obtained. Once this erected structure is made, the cylindrical hinges (13) are locked depending from the type either manually or automatically at the reached angular position.

Since tie members (14) are of metallic shape memory alloys of the type at one or two ways, after their cooling at ambient temperature they will be unstressed, forming arches as shown in figure 6 with reference to the structure with a square plant (1); in the method according to the present invention the lowering of the network structure happens after the manual or the automatic unlocking of the cylindrical hinges from the angular position of the erected structure. Since tie members (14) are in their unstressed position, the structure flattens also only because of its weight and it is therefore easy to proceed to the disassembling on a plane of the ball joints, of the cross bracing members between the trusses and of the cylindrical hinges from the members of each composite truss. In the example of figure 2 in the network structure (2), analogously assembled but placed on a plane as the structure (1), composite trusses with cross-sectional course are generically marked (20) and with (21) the cross bracing

members with longitudinal course. With reference to the figures from 3 to 6 it is shown a truss subordinate to one operation of elevation like the one previously described for the network structure of a central polygonal plant. At an end of each truss there is provided a carriage (15) (not shown but present also in the network structure of the figures 7 and 8) free to move on the soil; the cylindrical hinges are marked with (13). For the structure shown in figure 2 are worth the same considerations for the elevation and the lowering made for the structure of figure 1.

The cross bracing members or of the sections are of a telescopic type for the automatic locking and unlocking by means of a spring. The invention, understandably, is not limited to the representation given in the figures but it can be susceptible of modifications by the man skilled in the art without exiting however the boundaries of what is protected by the claims.

The present invention contributes to numerous advantages and overcomes difficulties that could not be won with the systems currently known.