TECHNICAL FIELD

The present invention relates to a group for allowing free orientation of a sphere with respect to outside force fields.

In particular, the group of the invention finds its main field of applicability as device for experiments in microgravity.

BACKGROUND ART

Space environment exploits the advantages of the reduced gravity field to perform experiments sensitive to gravity or to reveal phenomena masked on ground by the presence of gravity. Long duration experiments however, also in reduced gravity field, may be slightly of highly affected by the effects of the residual gravity field present during the space navigation; moreover, during the navigation, the spaceships change their orientation with respect to the residual gravity field. This fact results in the presence of a disturbance, due to the residual gravity, that changes during the experiment, in modulus and orientation. Many times, this effect, that cannot be limited or eliminated, seriously affects the results of the experiments or complicates their elaboration. Therefore the need was felt to make available a device whose technical features are able to overcome the above prior art technical problems .

The concept on which the present invention is based is the physical phenomenon of permanent inhibition coalescence discovered years ago. In short, when a liquid drop is heated at a temperature higher than that of a solid surface to which the drop is approached, surface motions arise in the drop due to the variation with temperature of the liquid drop's surface tension. Studies performed have shown that such surface motions trap the air in between the drop surface and the solid one, giving rise to a soft, friction- less pillow.

Similar behavior is observed when two drops kept at different temperatures are faced each other: the two drops do not coalesce even if they are pushed one against the other.

The Applicant has exploited such a phenomenon in order to satisfy the above need.

DISCLOSURE OF INVENTION

The subject of the present invention is a device for experiments in a microgravity environment whose essential technical features are reported in claim 1, and whose preferred and/or auxiliary features are set forth in claims BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention an embodiment is given below purely by way of illustration and not of limitation with the aid of the accompanying drawings, wherein:

- Figure 1 is a partly cross section of the group according to the present invention;

- Figure 2 is a partly transparent lateral view of a first particular of the group of figure 1;

- Figure 3 is a partly transparent top perspective view of a second particular of the group of figure 1;

- Figure 4 is a partly transparent top perspective view of a third.particular of the group of figure 1;

- Figure 5 is a partly transparent top prospective view of a fourth particular of the group of figure 1.

BEST MODE FOR CARRYING OUT THE INVENTION

The group according to the present invention is indicated in Figure 1 as a whole with 1.

The group 1 basically comprises a support structure 2, a sphere 3 made of aluminium based light alloy, two locking elements 4 acting from opposite sides on the sphere 3 and useful to keep the sphere 3 in a right position during a non-operational phase of the group 1, four drop supports 5 (only three of them are shown in figure 1) located around the sphere 3 respectively on the four vertexes of a regular tetrahedron, an electrostatic discharge device 6 able to eliminate the electrostatic charge from the sphere surface, an injection device 7 able to supply liquid to the four drop supports 5 in order to realize the respective drops, and a cylindrical isolation structure 8 useful to isolate the above devices from the surrounding and to prevent dust deposition on the sphere surface and the four realized drops .

In figure 1 drop supports 5 are not shown in section for sake of clarity because of their structural complexity.

In addition group 1 comprises a cooling/filtering device not shown in figures and useful to inject cool gas, preferably nitrogen, inside the isolation structure 8 in order to cool the sphere surface as it will be explained below. The injected gas need to be filtered in order to remove the dust and, hence, prevent it from being deposited on the sphere surface and the realized drops.

The sphere 3 has been undergone to a nickel plating surface treatment and, as it is shown in figure 2, is composed of two hemisphere 9a, 9b screwed together for lodging inside the sphere itself an experimental equipment

10 and a wireless board for communication. In particular, a small engrave 11 is realized on the outer sphere surface for hosting an antenna. Such an antenna shall be glued and covered by suitable epoxy resin or similar and the roughness and smoothness after resin deposition shall be the closest possible to that of the entire sphere surface.

Differently, sphere 3 can be made of graphite- loaded polymer, which entails the advantages of a low weight and the no need to have an antenna hosted on the external surface.

The locking elements 4 are designed to allow sphere 3 locking during a non-operational phase without sticking or scratching and to be able to support the sphere load (sphere plus experimental equipment) . As it is shown in figure 3, each locking element 4 comprises a DC motor/encoder assembly 12 and a piston 13 operated by the DC motor/encoder assembly 12 in a known way.

Each piston 13 comprises a bowl shape free end 14. In particular, in each piston 13 the bowl shape free end 14 has a concavity larger than the sphere surface and has six slots 14a. These technical features have the purpose to let gas to cool the sphere also in zones covered by the bowl shape free end 14. In fact, each bowl shape free end 14, actually, contacts with the sphere surface only by a circumferential edge 15 allowing the cooling gas to reach basically all the sphere surface zone underneath the bowl shape free end 14.

Only one of the two locking elements 4 comprises a helicoidal spring 16 wounded around a stem of the respective piston 13. In this way, the pressure against the sphere surface is reduced at minimum without jeopardizing the locking power of the two locking elements 4.

As it is shown in figure 4, each drop supports 5 comprises a DC motor/encoder assembly 17 and a piston 18 operated by the DC motor/encoder assembly 17 in a known way.

Furthermore, the piston 18 comprises at one of its ends an internal structure 19 made of copper and hosting a heater and a thermistor used as a temperature sensor. The internal structure 19 comprises an external tip 20 from which the drop is formed and which is sharp edged, machined in a truncated cone shape and with lateral surface inclined by 45°. In addition, each drop support 5 comprises a liquid inlet 21, a liquid outlet 22, a remotely controlled 2 -valve 23 in order to allow the liquid circuit to be closed, and a remotely controlled 3 -valve 24 in order to switch from injection and viceversa. The controlled liquid inlet 21 and liquid outlet 22 are obviously hydraulically connected with the internal structure 19.

The electrostatic discharge device 6 comprises a DC motor/encoder assembly 25, a thin tungsten wire 26 which is laid in a loop shape in order to improve the contact with the sphere surface, and a secondary metal wire 27 able to connect the thin metal wire 26 with a lug 28 which is fixed to the support structure 2. The purpose of the secondary metal wire 27 is to perform a ground connection through a dedicated electric harness.

In order to know when the electrostatic discharge device 6 has to be used, the group 1 comprises an electric potential meter (not shown in the Figures) for measuring the electrostatic charge on the sphere 3.

As it is shown in figure 5, the injection device 7 comprises a DC motor/encoder assembly 29 and a liquid reservoir 30 wherein a piston 31 operated by the DC motor/encoder assembly 29 is able to move. The injection device comprises a filling valve 32 and a liquid outlet 33 facing both into the liquid reservoir 30. The liquid outlet 33 is connected with the liquid inlet 21 of the drop supports 5 by a hose. Drops shall be formed or sucked only by means of piston 31 movement and drop volume shall be controlled. Preferably, the liquids to be used for drops formation are silicon oils of different viscosity and chain length.

In use, the sphere 3 is blocked in its right position inside the. isolation structure 8 by the two locking elements 4 as it is shown in figure 1. Starting from this situation, the injection device 6 injects a silicon oil into the four drop supports 5 which proceed to form respective drops. The drops shall of course be heated with the heater hosted into the copper internal structure 21. The temperature of the heater should be settable and controllable. In particular, once the drop is formed, the heater starts heating it up to 55°C-60°C. A sensor, not shown in the Figures, monitoring the temperature of the drop will help understanding when the set temperature is reached. In the same time, the sphere 3 is brought at a temperature lower that of the drop by means of the cooling/filtering device.

After having verified that the thermal condition are satisfied, the operator moves the drop supports to approach slowly the drop to the sphere surface until the contact is established. In particular, every DC motor/encoder 17 brings the respective formed drop into contact with the sphere surface. Actually, the drops only apparently touch the sphere surface.

At this point, the operator moves back the locking elements to release the sphere, which is now free to move with respect to the drops being supported by them without friction.

This invention may reveal particularly useful as a new device that could be embarked onboard microgravity platforms to perform experiments sensitive to rotating force fields that could compromise the experimental results. Indeed, while orbiting around Earth, platforms offer an environment with reduced gravity levels (i.e. the microgravity environment) ; however such desired condition is accompanied by several undesired effects that may sometime affect seriously the results of the experiment under study.

Differently of what is described above, the number of drops can be also higher than four, placed in a symmetrical way around the sphere .

Normally on ground it is easily to form drops by 3-4 mm in diameter. An upper limit may be set to 5 mm in diameter, larger sizes becoming unstable due to the gravity field. In an environment with reduced gravity levels it is possible to generate stable larger drops (of 20 mm in diameter or larger) necessary to sustain the load, whose amount will depend upon the number of drops foreseen for the facility.

The group of the present invention can also solve the problems related to the presence of vibrations that are transmitted to the experimental devices, and the presence of the residual gravity vector, that cannot be eliminated because of the intrinsic characteristics of the space flights.

The peculiarity of the group of the present invention is not only the capability of orienting the sphere and the h/w located inside it with respect to any rotating field imposed to the sphere itself, but also the possibility to adapt the sphere without friction, i.e. without any inertial effect due to the presence of mechanical joints (like those, for instance, of a gyroscope) .

In conclusion, the group of the present invention offers an innovative solution of allowing the free orientation, i.e. without friction and physical or mechanical constraints, of spherical masses with respect to a force field (the residual gravity for instance) acting on the sphere itself.