ANOTHER

The present invention relates to apparatus for mechanically isolating a first object above a second object. For example, the invention is particularly applicable to ships design.

Sensitive electronic equipments installed on board of a navy ship, such as sensors, antennas, radars and other Radio-Frequency equipments (RF), require measures to cope with severe shocks and vibrations. However, it is a challenge not to compromise the performance of the primary RF functions of the electronic equipments.

A first solution is to harden the equipments on component level, as specified in military standards. However, this leads to unacceptable increasing of mass and volume, and prevents from using cost-effective Components Off The Shelves (COTS).

In an attempt to overcome these drawbacks, the prior art teaches isolating from mechanical loads each equipment individually. For example, the European patent EP 1 424 507 discloses a coupling device consisting in a combination of rod-mechanisms and dampers to suspend a sensitive electronic equipment. The patent discloses the use of such elementary coupling devices for locally isolating from mechanical loads each radar, each antenna and each optical sensor on a navy ship.

A major drawback of these coupling devices is that they require additional protection shielding against other environmental effects, especially against weather conditions and electromagnetic fields. Unfortunately, the additional flexible shields and radomes have a negative influence on the performance of the primary RF functions. For example, the variable spacing of radomes induce negative effects on RF performances. Moreover, the re- enforcing of radomes increases RF transmission losses. Furthermore, each individual coupling device requires freedom that induces a gap in EMC shielding. Finally, the mast structure requires a large opening, which degrades the mechanical integrity. The space in between radome and antenna needs to be sufficient to deal with displacements of antenna and deformations of the radome. Consequence is a large radome which contradicts with compact packaging of antenna systems.

Yet another drawback of these coupling devices is that repeating the same solution for each component individually requires a huge amount of provisions, thus increasing assembling and maintenance costs up to a very high level. As an example, the flexible sealing used to accompany the movements of each component is very costly and has limited lifetime, especially when exposed to severe weather conditions.

Yet another drawback of these coupling devices is that they require high global stiffness and high global and local interface flatness to meet the accuracy requirements.

Yet another drawback of these coupling devices is that they provide three degrees of freedom in translations, while rotations are restrained by the rod-mechanisms. As a consequence, they do not provide isolation from rotations induced by vibrations, slamming and shocks.

In other respects, local suspended antennas from the prior art, which allow six degrees of freedom in rotations and in translations, require lots of additional measurement devices to compensate deviations in rotation, hereby lowering the reliability aspects.

The present invention aims to provide an apparatus which may be used to overcome at least some of the technical problems described above. In particular, the invention aims at a global uncoupling, so as to reduce dynamic loads in rotation induced by ship rotations and thus at improving sensors accuracy. For that purpose, the invention proposes an integrated suspension solution based on combined spring-damper elements only and that has six degrees of freedom : three in translation and three in rotation. At its most general, the invention proposes an apparatus for mechanically isolating a first object above a second object. The apparatus comprises a plurality of spring-dampers. Each spring-damper is arranged so that one of its end is attached to the second object and its other end is attached to the first object and headed to a point which is substancially in the horizontal plane containing the centre of gravity of the first object, so as to minimise the rotation movements of the first object when the second object is driven into a rotation movement.

For example, the second object may a Cabinet Module of a ship and the first object may be an Integrated Sensor Arrangement Module of a ship.

The top side of the second object may have four corners and the first object may have four side walls.

Each corner of the top side of the second object may have ends of two spring-dampers attached to, the other ends of these two spring-dampers being attached to two adjacent side walls of the first object.

Thus, an advantage provided by the present invention in any of its aspects is that it requires less provisions, thus reducing assembling and maintenance costs. Moreover, the invention enables having a fixed distance between radiator and radome, thus allowing optimum RF performance. Furthermore, the invention provides the ability to minimise the required built- in space, which results in compact packaging arrangements with a minimal amount of mass. Finally, the invention allows a flexible interface to the ship deck.

Non-limiting examples of the invention are described below with reference to the accompanying drawings in which :

- figure 1 schematically illustrates by a front section view an exemplary suspension layer according to the invention; - figure 2, schematically illustrates the same exemplary suspension layer according to the invention. In the figures, like reference signs are assigned to like items.

Figure 1 schematically illustrates by a front section view an exemplary suspension layer 23 according to the invention. An Integrated Sensor Arrangement Module 21 (ISAM) of a height H| _S AM contains antennas and radar electronics/optics that are not represented on Figure 1 . A Cabinet Module 22 (CM) of a height H _C M is supported by the deck 24 of a navy ship. The CM 22 contains all back-end electronics 25, 26, 27, 28 and 29 of the antennas and radar electronics/optics contained in ISAM 21 . The ISAM 21 is suspended above the CM 22 by the single suspension layer 23 of a height HSL according to the invention. The suspension layer 23 comprises a typical constellation composed of spring-dampers, depicted configuration shows eight spring-dampers 1 , 2, 3, 4, 5, 6, 7 and 8. The number however can vary depending on the design constraints. Only spring-dampers 1 and 2 can be viewed on Figure 1 , as it is a front view. However, spring-dampers 3, 4, 5, 6, 7 and 8 can be viewed on Figure 2. The interface between the ISAM 21 and the CM 22 has fixed dimensions Fl (Fixed Interface), while the footprint of the CM 22 on the deck 24 has variable dimensions FP (Flexible Footprint).

Figure 2 schematically illustrates by a top view, a front view and a side view the same exemplary suspension layer 23 according to the invention. These views represent the arrangement of the eight spring- dampers 1 , 2, 3, 4, 5, 6, 7 and 8 in order to suspend the ISAM 21 above the CM 22. To understand the arrangement of the spring-dampers 1 , 2, 3, 4, 5, 6, 7 and 8, the three views must be considered at a same time.

Due to the relative arrangement of the spring-dampers 7 and 8, their representations are merged on the front view. Due to the relative arrangement of the spring-dampers 1 and 6, their representations are merged on the front view. Due to the relative arrangement of the spring- dampers 2 and 5, their representations are merged on the front view. Due to the relative arrangement of the spring-dampers 3 and 4, their representations are merged on the front view.

Due to the relative arrangement of the spring-dampers 1 and 2, their representations are merged on the side view. Due to the relative arrangement of the spring-dampers 3 and 8, their representations are merged on the side view. Due to the relative arrangement of the spring- dampers 7 and 4, their representations are merged on the side view. Due to the relative arrangement of the spring-dampers 5 and 6, their representations are merged on the side view. The bottom side of the ISAM 21 is depicted as a squared shaped, as well as the top side of the CM 22. Shape can vary depending on the design constraints.

The first end of the spring-damper 1 is attached to a first corner of the top side of the CM 22. The second end of the spring-damper 1 is headed to a point VSC 1 (Virtual Spring Centre). The point VSC 1 is located at the intersection of the vertical symmetry axis of a first side wall of the ISAM 21 , said first side wall being adjacent to the first corner to which the first end of the spring-damper 1 is attached, with the horizontal plane PCOG which contains the centre of gravity COG of the ISAM 21 . The first end of the spring-damper 8 is attached to the same first corner of the top side of the CM 22 as the spring-damper 1 . The second end of the spring-damper 8 is headed to a point VSC 8. The point VSC 8 is located at the intersection of the vertical symmetry axis of a fourth side wall of the ISAM 21 , said fourth side wall being the other side wall of the ISAM 21 adjacent to the first corner to which the first end of the spring-damper 1 and the first end of the spring- damper 8 are headed, with the horizontal plane P COG which contains the centre of gravity COG of the ISAM 21 .

The first end of the spring-damper 2 is attached to a second corner of the top side of the CM 22, the first side wall containing VSC 1 being also adjacent to this second corner. The second end of the spring-damper 2 is headed to a point VSC 2, which is at the same location as the point VSC 1 . The first end of the spring-damper 3 is attached to the same second corner of the top side of the CM 22 as the spring-damper 2. The second end of the spring-damper 3 is headed to a point VSC 3. The point VSC 3 is located at the intersection of the vertical symmetry axis of a second side wall of the ISAM 21 adjacent to the second corner to which the first end of the spring- damper 3 and the first end of the spring-damper 2 are headed, with the horizontal plane P _C OG which contains the centre of gravity COG of the ISAM 21 .

The first end of the spring-damper 4 is attached to a third corner of the top side of the CM 22, the second side wall containing VSC 3 being also adjacent to this third corner. The second end of the spring-damper 4 is headed to a point VSC 4, which is at the same location as the point VSC 3. The first end of the spring-damper 5 is attached to the same third corner of the top side of the CM 22 as the spring-damper 4. The second end of the spring-damper 5 is headed to a point VSC 5. The point VSC 5 is located at the intersection of the vertical symmetry axis of a third side wall of the ISAM 21 adjacent to the third corner to which the first end of the spring-damper 5 and the first end of the spring-damper 4 are headed, with the horizontal plane PCOG which contains the centre of gravity COG of the ISAM 21 .

The first end of the spring-damper 6 is attached to a fourth corner of the top side of the CM 22, the third side wall containing VSC 5 being also adjacent to this fourth corner. The second end of the spring-damper 6 is headed to a point VSC 6, which is at the same location as the point VSC 5. The first end of the spring-damper 7 is attached to the same fourth corner of the top side of the CM 22 as the spring-damper 6. The second end of the spring-damper 7 is headed to a point VSC 7, which is at the same location as the point VSC 8.

By virtue of its spring-dampers 1 to 8 and in the absence of rod- mechanisms, the suspension layer 23 allows not only for translation movements of the ISAM 21 along any axis, but it also allows for rotation movements of the ISAM 21 around any axis. Moreover, because the virtual spring centres VSC 1 to VSC 4 are in the same plane P _C OG as the centre of gravity COG, the rotation movements of the suspended ISAM 21 are minimised.

Depending on the accuracy requirements, no attitude measurement device might be required to correct for the attitude of the ship. For highest attitude accuracy demanding systems, only one attitude measurement device may be required, as all the sensitive antennas and radars are supported by the single suspension layer 23. The suspension layer 23 provides a globally optimised solution minimising volume and mass of the ISAM 21 . Indeed, no free space is required inside the suspended ISAM 21 for individual suspensions between the sensors. Antenna and radar systems can be simply hard mounted within the suspended ISAM 21 , thus reducing the volume and mass of each piece of equipment and allowing a low centre of gravity of the suspended ISAM 21 . This is especially important for ship's top side design, as it allows for maximizing installation height and therefore performances for each radar and sensor system.

The suspended ISAM 21 can be fully implemented by use of cost- effective COTS, which can be simply integrated based on hard mounted techniques.

In the absence of cavities and highly reflecting structures between the sensors inside the suspended ISAM 21 , the RCS signature is reduced.

No large mast window is required, as the structural integrity of the ship's structure is not compromised by the free field of view required for the antennas, radars and optical systems. The mast opening can be mechanically closed using the antenna structure. This allows for a higher integration level where structural parts of sensors are integrated with the structure of the suspended ISAM 1 . This provides a higher structural integrity to the mast in terms of strength and stiffness. The mass of the suspended ISAM 1 is dynamically uncoupled from the ship's super structure. This reduces the dynamic design constraints to ship's superstructure in terms of stiffness, strength and fatigue.

The single suspension layer 23 provides natural uncoupling between the ISAM 21 and the CM 22. This allows for different thermal expansions of the ISAM 21 and the CM 22, as well as for the use of different materials for building the ISAM 21 and the CM 22. Moreover, the design of the suspension layer 23 can be globally optimised so as to provide a standard solution for most of the ships. However, depending on specific requirements on a ship, the design of the suspension layer 23 may be tailored while keeping the same equipment interfaces. Indeed, the suspension layer 23 enables keeping stable interfaces to the ISAM 21 , while offering freedom to design interfaces to the CM 22. Thus, even in case of later modifications of the CM 22, modifications of the suspension layer 23 may be limited to a few components.

The natural uncoupling between the ISAM 21 and the CM 22 provided by the suspension layer 23 may be regarded as a natural separation between an integrated mast, which comprises sensor equipments, and a standard cabinet module. This allows for easy and flexible adaptation of an integrated mast to various ship classes and sizes, while maintaining a stable configuration of the ISAM 21 . All back-end electronics may be packaged in the standard cabinet module, so as to keep the overall centre of gravity as low as possible and thus provide roll stability and good sea keeping ability.

The use of the single suspension layer 23 instead of multiple local suspensions inside the ISAM 21 provides a single combined suspended structure for both the ship structure and the antenna structure. This is a more reliable design, that is to say with a lower failure rate and lower repair times, as it requires less components. The redundancy can be ensured with minimised amount of provisions. For example, all equipments above the suspension layer 23 have the benefit of the hard mounting without the need for flexible EMI sealings and attitude measurement devices.

The invention allows uncoupling the ISAM 21 from the dynamic loads from the ships deck 24. The invention allows uncoupling the material selection for the ISAM 21 and the CM22. The invention allows uncoupling the dimensioning of the ISAM21 and the CM22.