[0002] All vacuum cleaners known up to now use more or less efficient filtration systems
which lead to disadvantages of various types; they require units with high power,
they consume a large amount of energy and emit noise, they return air which is not
completely clean, and they have various practical disadvantages. In particular, given
the large quantity of air set in motion (30 - 70 l/sec.), filtration quality is connected
with energy consumption and with the need to use very powerful units, and therefore
has a practical limitation. The invention avoids these disadvantages by arranging
for the expelled air to be returned into the suction region of the vacuum cleaner
in order to be recirculated; the atmosphere is thus not affected by the air-flow containing
dust residues. In an advantageous embodiment of the invention, the vacuum cleaner
comprises a special opening which takes in the dust/air mixture, a filter which retains
and collects the dust, a turbine with radial/tangential discharge, a duct which conveys
the discharge air to the output opening which injects the air into the suction region,
and a dispenser for modifying the physical/chemical characteristics of the air without
superfluous dispersal of additives into the atmosphere.
[0004] Figure 1 shows the principle of operation of the invention; the air and the dust
are drawn in from the opening 1 and pass through the filter 2 which retains a large
portion of the dust. In the system of the invention, the filtering of the air can
be coarse; this permits a considerable reduction in the power of the suction unit
and hence in its consumption and noise. The noise connected with the emerging air-flow
is attenuated owing to the fact that the discharge air-flow is no longer admitted
freely to the atmosphere. The filter 2, which may be equipped with a dust-collection
box 21, is cleaned periodically, manually or automatically, by the methods known in
the prior art. After the air has left the filter 2, it is drawn in and compressed
by the turbine 3 and is not expelled to the exterior (as in the prior art) but is
conveyed to the output opening 4 where its mechanical energy renders the dust removal
more efficient since it acts in the manner of a rotating brush, helping to remove
the dirt and, finally, the mechanical compression energy of the discharge air is recovered.
As a result of the recirculation, in addition to the recovery of the mechanical compression
energy, there is a further advantage due to the recovery of the thermal energy of
the process air which thus tends to be heated considerably. The fact that, in the
present invention, the expelled air is conveyed back into the region to be cleaned,
provides the opportunity for the air to be treated by a device 5 which is constituted
by any dispenser known in the art which enables the output air to be enriched with
liquid or solid detergents and disinfectants, water, steam, ozone, foam, ions, heat,
etc. As a result of the recirculation of the air, the additives are not dispersed
and both the perceptible heat and the latent heat contained in the steam are recovered.
The motor 6 which drives the turbine 3 is not affected by the treated air but has
its own independent cooling system. Figures 2 and 3 show embodiments of the suction
and output openings; before the compressed air is expelled into the working region,
it undergoes a reduction in cross-section and, for the same air subsequently drawn
in, the cross-section then increases progressively. In practice, in the dust-removal
region, in which the cross-section is smallest, a large increase in the air speed
is brought about in the same manner as in a Venturi tube and in the suction openings
of currently available vacuum cleaners. Again with reference to Figures 2 and 3, the
suction duct, indicated 1, is the diverging portion of the Venturi tube which has
its smallest cross-section in the dust-removal region, with the purpose of recovering
the kinetic energy of the air-flow coming from the duct 4 which constitutes the converging
portion; the diverging portion must be designed in a manner such as to favour the
conversion of the kinetic energy into pressure energy with great efficiency in order
thus to achieve energy and noise advantages. Figure 4 shows another advantageous application
of the invention and indicates, by way of example, a possible configuration of the
suction and output openings which operate effectively on a battery-operated "robot"
vacuum cleaner. This device takes advantage particularly of the reduction in power
absorbed and in noise permitted by the invention. The "robot" structure also helps
to reduce flow resistance since it avoids the long hoses of the conventional structure.
Moreover, the expulsion of air into the atmosphere is prevented according to the present
invention; in practice, the "robot" vacuum cleaner takes in dusty air from the opening
1, conveys it directly, that is, without long connecting hoses, through the filter
to the turbine and, from there, discharges it again directly, under pressure, from
the opening 4 where it contributes to the exertion of a mechanical dirt-removal action.
In practice, the details of construction may vary without, however, departing from
the scope of the invention and hence from the scope of the patent of invention.
