Process and installation for cleaning partially de-leafed leafy salad vegetables and removing small foreign bodies therefrom

An installation for cleaning pieces of partially deleafed leafy salad vegetables and for removing particles of small foreign bodies therefrom includes a bath for receiving the pieces to be cleaned and a means for causing the pieces to circulate in the bath. A deflector, which is permeable to the particles, deflects the pieces below the level of the bath. A source of gas bubbles emits gas bubbles below the deflector so that the gas bubbles entrain the particles and cause the particles to rise through the deflector to separate the particles from the pieces. A particle collector recovers and removes the particles which have risen through the deflector and are floating on the surface of the bath.

FIELD OF THE INVENTION 
The present invention relates to a process and an installation for cleaning 
partially de-leafed leafy salad vegetables, which are in piece-form, in 
order to remove small foreign bodies, such as small pieces of plants, 
earth, dirt or small insects, which remain attached to the pieces of 
partially de-leafed leafy salad vegetables already cleaned by being 
floated in a bath. 
The development of partially de-leafed leafy salad vegetables, that is to 
say, leafy salad vegetables prepared and packaged in packets under an 
inert atmosphere, in a state practically ready to be seasoned, requires 
improvements in the preparation chain, especially in the cleaning of the 
partially de-leafed leafy salad vegetables. The prepared pieces of leafy 
salad vegetables are generally cleaned by being floated in a bath of 
salted water in order to cause the small animals, such as snails or the 
like which remain attached to the salad leaves, to fall to the bottom of 
the bath. This cleaning process is not, however, sufficient to eliminate 
the small, very light, foreign bodies which are not sensitive to this 
cleaning bath and can at present be removed only by hand. These foreign 
bodies are, for example, small animals, small spiders, ants, etc. . . or 
grains of sand or small pieces of straw or leafy salad vegetables which 
remain attached to the prepared pieces. 
At present, the pieces of leafy salad vegetables are inspected visually and 
those on which such foreign bodies appear are cleaned. Unfortunately, in 
addition to their laborious and expensive nature, these checking and 
cleaning operations allow a large number of foreign bodies through so 
that, when the prepared leafy salad vegetables are used, a second 
meticulous cleaning operation has to be carried out. 
SUMMARY OF THE INVENTION 
The aim of the present invention is to overcome these disadvantages and to 
provide a cleaning process and installation enabling the small foreign 
bodies to be removed from the pieces of partially de-leafed leafy salad 
vegetables before those leafy salad vegetables are packaged for sale. 
To that end, the invention relates to a process which is characterised in 
that: 
the pieces are maintained below the level of the water; 
a stream of gas bubbles is passed through them in order to entrain the 
particles and cause them to rise to the surface of the bath separately 
from the pieces; 
the particles are removed. 
The invention relates also to a cleaning installation, especially for 
implementing the process. This installation is characterised in that it 
comprises a bath receiving the pieces to be cleaned, a means for causing 
the pieces to circulate in the bath, a deflector, which is permeable to 
the particles, for deflecting the pieces below the level of the bath, and 
a source of gas bubbles emitting gas bubbles below the deflector so that 
they rise through the deflector and separate the particles attached to the 
pieces in order to entrain them. 
The process and the installation enable the low density of the small 
foreign bodies to be used in order to subject the pieces to be cleaned to 
agitation and "sweeping" by the stream of liquid and gas bubbles below the 
level of the bath so that the particles are detached from the pieces and 
entrained in the ascending current formed by liquid and gas in order to 
separate them from the pieces and recover them at the surface of the bath. 
This cleaning operation treats the partially de-leafed pieces of leafy 
salad vegetables gently because the entrainment of the pieces below the 
level of the bath is effected gently. The agitation by circulation of the 
bath (relative circulation), and the gas bubbles, in particular air or an 
inert gas, produce a very efficient agitation of the fluid on the surface 
of the pieces, possibly with turning and agitation of the pieces, with the 
result that the two faces of the pieces are exposed to this ascending 
stream entraining the small particles. 
The deflector guiding the pieces below the level of the bath comprises 
passages or perforations which are of a size sufficient to allow the 
liquid/gas stream charged with particles to pass through while the pieces 
are retained. The deflector may thus be formed by a piece of perforated 
sheet metal or by a network of wires preferably directed in the direction 
of flow of the bath. 
It may also be advantageous to direct these wires in the transverse 
direction in order to create areas of roughness to which the pieces become 
attached in such a manner as to promote their rolling or turning movement 
during their circulation below the level of the bath. 
The function of the permeable deflector is not only to cause the pieces to 
descend below the level of the bath but also to separate the pieces from 
the particles which have been detached, in order to prevent the latter 
from reattaching themselves to the pieces. 
Although the use of a simple deflector, that is to say, a static member, 
has surprisingly yielded excellent results, it is also possible to replace 
the deflector and the bath-circulating means by a single means formed, for 
example, by a rotating cylinder equipped with blades or a conveyor belt 
descending below the level of the bath or a disc with blades or cups 
entraining the pieces below the level of the bath, through the ascending 
stream of liquid and gas bubbles. 
In the case of a stationary deflector, it is advantageous to cause the bath 
to circulate, especially in a closed circuit. This circulation may be 
effected by pumps. 
According to an advantageous feature, the deflector is a surface in the 
form of a ramp descending below the level of the bath. This surface may be 
a flat surface or a curved surface. 
In order to promote the effect of turning the pieces and the creation of 
shocks promoting the separation of the particles, the deflector may be 
produced by assembling a succession of ramps maintaining the pieces below 
the level of the bath but causing them to travel ascending and descending 
paths with breaks. 
In the case of a single ramp or a plurality of ramps, it is advantageous to 
follow this (these) ramp(s) with a substantially horizontal surface, which 
is permeable to the particles, in order to cause the pieces which are to 
be cleaned to circulate below the surface of the bath over a certain 
distance which can also be controlled as a function of the speed of 
circulation of the bath, depending on the nature of the pieces to be 
cleaned. The removal of the particles, which become attached to the 
bubbles and float on the surface of the bath owing to their light weight 
or to surface-tension effects, is effected by a collecting element, for 
example a static collecting element, such as a chute, which uses the 
circulation of the liquid and evacuates the particles to the exterior of 
the bath. The collecting element may also be a conveyor belt or an 
equivalent means which skims the surface of the bath.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
According to FIGS. 1 and 2, the invention relates to a process and an 
installation for cleaning partially de-leafed leafy salad vegetables, 
referred to in the description hereinafter as "pieces", in order to remove 
the small foreign bodies which are referred to by convention as 
"particles". As already indicated, these foreign bodies may be plant 
pieces, mineral products, small stones, grains of sand, etc. . . . or 
small insects or small animals which have escaped previous cleaning 
operations for separating large foreign bodies (snails, slugs, larger 
plant pieces, stones, etc . . .). 
According to the invention, a bath 1 is used in which the pieces 2 to be 
cleaned are immersed. The bath 1 is equipped with a means 3 for causing 
the liquid of the bath to circulate in the direction of arrow B. 
This circulation means is formed, for example, by an injector fed by a 
pump. 
The pieces 2 are thus entrained in the direction of arrow B and arrive at a 
deflector 4 which causes them to descend in the direction of arrow C below 
the level 5 of the bath. Usually, the pieces 2 float on the surface of the 
bath. 
The deflector 4 is in this case extended by a horizontal portion 6 which 
passes over a source of gas bubbles 7 arranged at the base of the tank of 
the bath 1. The gas source 7 emits fine bubbles which rise through the 
bath while agitating the pieces 2 (arrow E), turning them and sweeping 
over all their faces. 
The deflector 4 and, above all, the extension 6 of the deflector are 
equipped with perforations or meshes which are of a size sufficient to 
permit the passage of the foreign bodies, indicated by the asterisks 8, 
which are entrained by the stream of liquid/gas bubbles so that they are 
separated from the pieces 2 and arrive at the surface 5 of the bath, on 
the other side of the deflector 4 and its extension 6. 
The pieces 2 continue their circulation and, at the end of the portion 6, 
the pieces 2 rise to the surface of the bath (arrow G) from where they are 
removed (arrow H). 
The particles 8 are collected by means of a collector 9, for example in the 
form of a chute, which skims the surface 5 of the bath above the deflector 
4 and its extension 6. The particles are removed from the bath either by 
liquid entrainment or by a mechanical means not shown in this Figure. 
The bath 1 is generally water, optionally with an additive compatible with 
food regulations. The gas used to entrain the particles is generally air. 
It may also be nitrogen in the case of fragile products in order to avoid 
too rapid an oxidation. 
FIG. 2 is a diagram of the structure of the installation described above 
with reference to FIG. 1. This Figure shows, in particular, the tank 
constituting the bath 1 and the means 3 for causing the liquid to 
circulate. This means is represented diagrammatically in the form of a 
nozzle, but without showing the connections to the pump and the pipes 
drawing the liquid, preferably on the side where the products are 
discharged, in order to create a circulation of liquid entraining the 
pieces. 
The gas source 7 may be formed by a compressor (not shown) which supplies 
the source 7 formed by a box placed at the bottom of the bath. This box is 
provided with perforations and, optionally, registers in order to control 
the flow of gas and the size of the bubbles. 
The deflector is composed of a principal portion 4, followed by an 
extension 6. In the case of FIGS. 1 and 2, the portions 4 and 6 are formed 
by two flat surfaces which adjoin one another. Other forms may, however, 
be envisaged, as will be seen later. 
The deflector 4, 6 is generally formed by a piece of perforated sheet metal 
but it may also be a structure of stainless steel wires, the size of the 
apertures and meshes of which is selected in order to permit the passage 
of the particles to be removed. 
Finally, FIG. 2 shows the particle-collector 9. 
The extension 6 of the deflector 4 is preferably followed by a partition 10 
which is usually at least permeable to the liquid of the bath in order to 
facilitate circulation. The only requirement is that the partition 10 
should be of a permeability which does not permit the passage of the 
particles to be removed. However, the partition 9 may also be impermeable. 
FIG. 3 shows a first variant of the deflector arranged relative to the 
level 5 of the bath, the liquid of which circulates in accordance with 
arrow B. The deflector is composed of an assembly of deflectors 41, 42, 43 
in the form of an inclined plane, followed in each case by an extension 
61, 62, 63. The ramps 41, 42, 43 and the extensions 61, 62, 63 are 
perforated or permeable to the particles. 
FIG. 4 shows another variant of the deflectors which are likewise formed by 
assembling a succession of deflector elements 41', 42', 43'. . . , which 
are formed by a curved surface corresponding to the combination of the 
flat surfaces 4, 6 or 41, 61, etc . . . 
These deflectors 41'-43' are also permeable to the small particles to be 
removed. 
FIG. 4 shows another variant of a single deflector which may also be joined 
in an assembly in order to form a succession of deflectors. This single 
deflector 41' is a curved surface of which the curvature of the upstream 
side (arrow B) is very great, and diminishes progressively. 
It should be noted that in the various Figures discussed above (FIGS. 1 to 
5) the deflectors 4 . . . 41', 6 . . . 63 are formed by cylindrical 
elements of which only the cross-section has been shown. 
It has been assumed that the bath 1 is subjected to a circulation of liquid 
and consequently to an entrainment of the particles from right to left. 
It is also possible to provide circular installations with a bath in the 
form of a ring. The structures explained above then apply to one or more 
individual segments of the ring which are occupied transversely by 
deflectors. 
This facilitates the circulation of the bath because the advance of the 
liquid takes place inside this ring shape. 
FIG. 6 shows a variant of the means for entraining the pieces below the 
level of the liquid. This means is formed by a cylinder 104 which is 
partially immersed in the bath 101 below the level 105. The cylinder 104 
is equipped with blades 1041 projecting towards the outside and towards 
the inside of the cylinder and also blades 1042 projecting only towards 
the inside of the cylinder. The cylinder is perforated in the same manner 
as the deflectors in order to permit the passage of the particles 108 
which become separated from the pieces 102 entrained below the level of 
the bath by the blades 1041. The blades 1042 are used to skim the 
particles 108 from the surface of the bath, inside the cylinder 104, in 
order to lift them and drop them onto the removal means 109 which is 
formed, for example, by a conveyor belt. 
The sense of rotation of the cylinder is indicated by the arrow i. 
This installation comprises a source of gas bubbles 107 which is shown 
diagrammatically. 
At the outlet, the pieces 102 rise to the surface, become separated from 
the cylinder 104 and are recovered as before. 
FIG. 7 shows another variant of the invention which provides for a 
deflector 204 descending below the level of the bath 205 in order to cause 
the pieces 202 to descend there. At the outlet of the deflector, a means 
209 is provided for collecting the particles 208. This means 209 is a type 
of conveyor belt equipped with scrapers or bars for skimming the surface 
205 of the bath and entraining the particles 208. The particles 208 fall 
from the other side of the belt 209 onto a belt 2090 which removes them. 
To the left of the belt 209, the pieces 202 rise to the surface and are 
removed as before. 
The present invention has been described above in its preferred application 
of cleaning pieces of partially de-leafed leafy salad vegetables in an 
industrial manufacturing chain before packaging. However, the process and 
the installation may also be used for cleaning other products, whether or 
not they are foodstuffs, which are in the same physical state and pieces 
of flat products which have a very irregular shape and to which particles 
to be removed are attached.