Shelter

The invention concerns a shelter device in the form of a box-like structure for the protection of electronic apparatuses against atmospheric agents. The shelter comprises walls of insulating material forming a thermal resistance, as well as an amount of material(s) having a high specific heat operating inside the structure and forming a thermal capacity, the thermal resistance and capacity being able to maintain a shelter inner temperature that is constant and is correlated to the outer mean temperature over a time period of at least 24 hours.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a device for ensuring the protection against 
atmospheric agents of electronic or similar apparatuses, in particular 
high-reliability apparatuses when installed in zones having difficult 
climatic conditions and in positions difficult to be joined and to be 
supplied with conventional energy. 
In the field of electronic apparatuses the prevailing trend is to reduce 
consumption and increase reliability, in particular for the purpose of 
reducing maintenance costs. 
These two features must be considered as essential when such apparatuses 
operate in climatically difficult zones as well as in places difficult to 
be reached, devoid of conventional energy sources without the possibility 
of human supervision. The continuous improvement of the above-mentioned 
features has introduced the problem of effectively protecting the 
apparatuses not only against atmospheric agents, but also against 
extremely high or low environmental temperatures. 
2. Description of the Prior Art 
For the protection of these electronic apparatuses so-called "shelter" 
devices are normally used essentially in the form of box-like structures 
wherein these apparatuses are housed. 
The known shelters always offer a protection against inclement weather and 
sometimes also provide a certain thermal insulation due to the thermal 
insulating material of their walls. 
However, the power dissipated by the electronic apparatuses within such 
known shelters results in a positive temperature difference between the 
inner and outer wall surfaces, but the inner temperature always follows 
the daily and seasonal environmental temperature variations. This means 
that inside the shelter maximum and minimum temperature peaks about equal 
to those of the environmental temperature plus such temperature difference 
can be detected. 
Accordingly, these known shelters are effective only if the maximum and/or 
minimum environmental temperature peaks, plus such difference, result in 
inside maximum and/or minimum temperature peaks which are compatible with 
a perfect operation of the apparatuses. 
If the outside maximum and/or minimum temperature peaks do not satisfy the 
above condition, other solutions must be found. When the shelters must 
operate in zones wherein the maximum inside temperature peak, calculated 
as hereinabove, is greater than the allowable temperature, it is possible 
to provide shelters with automatically or manually controllable openings, 
in order to reduce the inside temperature to values corresponding to 
outside temperature. However this solution, which is effective only when 
the outside temperature is compatible with the operation of the apparatus, 
shows different drawbacks, as for example a reduced protection against 
inclement weather when the shelter is open, a poor reliability when the 
shelter opening is automatically controlled, or high costs in case of a 
manual shelter opening control. 
Another solution is to provide shelters having air conditioners, heat pumps 
or other cooling or heating means. 
However this solution requires a considerable energy consumption for 
producing heat in or subtracting heat from the shelter, and involves the 
use of plants of low reliability. 
OBJECTS OF INVENTION 
An object of this invention is to provide a protection device or shelter, 
in particular for the uses as above outlined, wherein the above-stated 
problems and drawbacks of known shelters are solved and overcome and 
wherein a protection against maximum and/or minimum outside temperatures 
is ensured without using energy sources and independently from the 
reliability of temperature controlling plants. 
SUMMARY OF THE INVENTION 
According to this invention, a shelter is provided that consists in a 
closed box-like structure forming and/or cooperating with at least one 
thermal resistance and at least one thermal capacity which are calculated 
and dimensioned in such a manner as to maintain inside the structure 
substantially constant temperature values according to the mean 
environmental temperature in pre-established time periods. In particular, 
the thermal resistance is formed by a suitable insulating material forming 
the structure walls and/or cooperating therewith, while said thermal 
capacity is formed by a suitable quantity of a material having a high 
specific heat forming the box-like structure walls or cooperating 
therewith, inside the shelter. 
In other words, according to this invention, a thermal filter of suitable 
characteristics is interposed between the shelter outside and inside. This 
thermal filter operates in such a manner as to limit the heat exchange 
with the outside by means of the insulation forming the thermal 
resistance, and to prevent the heat exchange with the outside which will 
substantially affect the shelter inside temperature variations, by using 
the thermal capacity as a stabiliser. Accordingly, when for example a heat 
exchange toward the shelter inside takes place, this heat increases the 
temperature of the thermal capacity and is actually "absorbed" by the 
same, so that only a minimum increase in the thermal capacity and shelter 
inside volume temperature takes place. In the same manner, when heat 
passes outwardly from the shelter, this heat is supplied by the thermal 
capacity and causes only a minimum temperature decrease. By suitably 
selecting the thermal resistance and capacity values in relation to the 
shelter volume and surface, to the outside temperatures and to the heat 
dissipated by the electronic apparatuses, it is possible to ensure a 
substantially constant temperature inside the shelter for pre-established 
time periods. Such periods can be greater than 24 hours, and during the 
same the shelter inner temperature corresponds to the mean value of the 
outside temperatures plus the temperature differences as caused by the 
energy from the electronic apparatuses. This latter temperature difference 
is smaller than that existing in known shelters, due to the influence of 
the thermal capacity. 
Accordingly, the shelter inside temperature is no longer dependent on the 
maximum and minimimum peaks of the outside temperature, but only on the 
mean values of the outside temperature in a pre-established period of 
time, which in any case is at least equal to 24 hours. 
For this reason, the shelter according to this invention will have a range 
of application much greater than that of the known common shelters, in 
particular when the pre-established period of time is extended by suitably 
selecting the thermal resistance and thermal capacity values, with the use 
of more than one thermal filter (each consisting of one resistance and one 
capacity) with a cascade connection. In addition, the shelter according to 
this invention may also be used in combination with heating and/or cooling 
devices for conditioning the inside of the shelter when the mean outside 
temperature conditions require such plants. In this case, a further 
advantage is given by a substantial reduction of the load and intervention 
periods of these plants.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, a shelter according to this invention essentially and 
diagrammatically consists of a box-like carrying structure 10 with a 
suitable layer 14 of a heat-insulating material, for example polystyrene 
or foamed polyurethane or any other material having good insulation 
properties and, if possible, low weight. In the embodiment of FIG. 1, the 
insulating layer is interposed between two supporting and containing 
layers 10 and 12, but it is to be understood that the same may be 
positioned and arranged in any other manner, or even form itself the 
box-like structure, provided that it could ensure a satisfactory thermal 
insulation of the shelter inside space 16 that is sealed against the 
outside environment 18. 
Under these conditions, as known, heat exchange in both directions between 
the inside space 16 and the outside environment 18 depends on different 
factors and mainly on the temperature difference between the two spaces 
and the insulating capacity or thermal resistance of the shelter walls. It 
is obvious that the amount of heat that is admitted to or subtracted from 
the inside space 16 directly influences the inside space temperature in a 
substantial manner. In order to reduce this effect, the invention 
provides, inside the shelter, a suitable thermal capacity, that is a 
suitable amount of a material having a high thermal capacity or high 
specific heat, as shown for example by the water containers 20 in FIG. 1, 
this material being in thermal heat exchange relationship with the space 
16. Thus the heat exchange between the two spaces results in a much 
smaller effect on the temperature of the space 16, because the heat is in 
part supplied to or absorbed by the capacity 20, acting as a thermal 
stabilizer. 
Accordingly, the shelters of this invention show the combination of two 
main features, i.e. to limit on one hand the heat exchanged with the 
outside space by means of a thermal resistance, and to reduce on the other 
hand the effect of this heat exchange on the inside shelter temperature by 
means of a thermal capacity or stabilizer. Further, by means of a suitable 
selection of such resistance and capacity, it is possible to obtain a 
substantially constant temperature within inside space 16 during 
preestablished time periods, usually in excess of 24 hours. 
For example, assuming that the outside temperature flow is according to the 
curve Te of FIG. 2, by suitably sizing the thermal resistance and 
capacity, a substantially constant inside temperature T.sub.i1 may be 
ensured, such temperature corresponding to the mean outside temperature 
within the considered 36 hour period. If the shelter houses a heat source, 
for instance formed by a heating device or by the same protected 
electronic apparatuses, the inside temperature will increase to T.sub.i2, 
but will remain always constant. It must be observed that the temperature 
gap T.sub.i2 -T.sub.i1, for example caused by the heat emission of the 
protected apparatuses, is reduced due to the presence of the thermal 
capacity 20, when compared to known shelters without such thermal 
capacity. 
As already mentioned, the thermal capacity 20 consists of a suitable amount 
of a substance having a high specific heat, for instance water. For 
reasons of constructional convenience, other materials can be used and it 
is possible to foresee very high thermal capacities at given temperature 
ranges by choosing materials that undergo a change of state in such 
ranges. 
FIGS. 3 and 4 show an embodiment according to this invention, wherein the 
overheating effect of solar radiation on the shelter walls has been 
considered. 
Such radiation may considerably increase the heat exchange in a 
discontinuous manner only statically foreseeable in view of the type of 
heat supply, thus changing all the calculation values and increasing the 
overall size and weight of the thermal capacity. 
It is thus suitable to provide a solar radiation screen. In particular, 
according to the embodiment of FIGS. 3 and 4 a double outer solar screen 
22,24 is provided, such screen being cooled by the natural air circulation 
induced by the wall heating, as shown by the arrows. A natural draft is 
ensured by the chimney effect for the outside screen 22 and by the chimney 
effect improved by a short stack 26 for the inner screen 24. The double 
screen makes it possible to protect the shelter against atmospheric 
agents. The walls of the double screen are made of a reflecting material 
in order to reduce heat transmission. 
The shelter is still further protected by an upper sheet slide 28 against 
the possible accumulation of sand or the like. The upper wall carries a 
through bolt with a hook 30 at the inside of the shelter for an assembly 
winch for the electronic material. 
At the shelter bottom a door 32 opens toward the outside with air-tight 
seals, such door being made of a frame with a heat-insulating packing. The 
shelter insulating layer 34 is made of foamed polyurethane, polystyrene or 
similar heat-insulating material. 
The thermal capacity is fixed to the shelter inside walls. It consists of a 
set of plastic square tubes 36, slightly shorter than the total height of 
the wall and filled with a suitable liquid and sealed at the top and 
bottom. 
In less severe climates and with higher admissible inner temperatures, it 
is possible to avoid the outer screen and, in case of minor requirements 
or improvements in the climatic conditions, also the inner solar screen. 
In a tested screenless embodiment, the sizes of the inner cell were 
1.70.times.1.70.times.2 m with an insulation formed by a 30 cm thick 
foamed polystyrene layer. The thermal capacity was formed by 220 l. of 
water contained in 24 round plastic tubes 1.90 m height, inner diameter 80 
mm. The results of tests carried-out with an inner dissipated power of 40 
and 30 W are shown in the diagram of FIG. 5, wherein the upper curve 
indicates the shelter inside temperature (point A indicates a reduction of 
the dissipated power from 40 to 30 W) while the lower curve indicates the 
values of the outside temperatures. 
The values of the thermal capacity shall be proportional to the desired 
damping of the outside temperature variations and to the thermal 
resistance of the walls. 
It is to be understood that the illustrated embodiments may undergo 
modifications, in particular according to the operational requirements, 
without departing from the spirit and scope of this invention.