Granita production machine

A machine for the production of granita and in particular of the type called Sicilian granita comprising a container with a predominately horizontal development in which rotate motorized means for stirring the mixture contained therein in contact with a wall chilled by a refrigerating circuit and means of delivery of said mixture from said container. Said chilled wall is cylindrical in form and said means of stirring the mixture comprise a first rotating cylindrical screw propeller placed inside and axially with said cylinder and a second rotating cylindrical screw propeller placed axially with and wound externally around said cylinder, said screw propellers being rotated by a motor to impart opposed thrusts to the mixture so as to bring about circulation of the liquid in one direction inside the cylinder and the opposite direction outside thereof. The mixture container is accomplished in a single piece preferably of transparent material and completely removable from the machine to facilitate cleaning.

DESCRIPTION 
Machines for the production of granita, in particular the so-called 
"Sicilian granita", wherein formation of ice in the acqueous solution and 
maintenance thereof in a pasty consistency is secured through the combined 
action of a refrigerating circuit and a rotating agitator immersed in the 
mixture. 
Such machines exist at present in two main types, to wit with the tank and 
its agitator developing vertically or horizontally. 
The invention relates more specifically to this second type of machine, 
which prepares a high-quality granita and delivers it under thrust to one 
end of the horizontal tank where an outlet with a tap is provided. 
A known form of embodiment of granita machines provides an essentially 
cylindrical chamber, the wall of which is entirely metal, in contact with 
the evaporator of a refrigerator circuit. In this embodiment the heat 
exchange surface is very large with the resulting benefits for the 
capacity of the machine regarding the quantity of granita produced. 
However this type of machine does not allow ready cleaning of the chamber, 
which is necessarily fixed and accessible only by removal of the front 
wall. In addition it is impossible to see the contents, i.e. the granita 
in the course of preparation, as would be desirable to attract consumers. 
To allow in particular placing in view the horizontal tank in which the 
granita is prepared, there has been proposed the formation thereof in two 
parts, to wit a lower metallic part for heat exchange and an upper part of 
transparent material. In this embodiment the upper part is removable to 
provide access to the agitator and permit cleaning of the tank by an 
operation which is not, however, quite easy. Reduction of the area of the 
exchange wall lowers the efficiency of the machine and the visibility of 
the contents is also limited. 
The object of the present invention is to obviate the drawbacks of the 
known art, in particular providing a machine with high surface area for 
heat exchange while the granita is forming and with complete visibility of 
the mixing chamber and complete and easy cleaning of the parts in contact 
with the foodstuff. 
In view of these objects it was thought to realize a granita production 
machine, in particular of the type of granita called "Sicilian granita", 
comprising a container in which rotate motorized means for stirring of the 
liquid mixture contained therein in contact with a wall chilled by a 
refrigerator circuit and mean$ of delivering said mixture from said 
container characterized in that said chilled wall has a cylindrical form 
and that said stirring means of the mixture consist of a first rotating 
cylindrical screw propeller placed inside said cylinder and axially 
therewith and a second cylindrical screw propeller rotating axially 
therewith and coiling around said cylinder externally, the screw 
propellers being rotated by a motor to impart opposed thrusts to the 
mixture.

With reference to the figures a granita production machine comprises a base 
10 containing the electric circuits for control of the machine and a 
refrigerating device of the known art the evaporator of which is 
accomplished in the form of a hollow cylinder 11 fixed in a projecting 
manner by means of a hollow support 12 having openings to a vertical body 
13 projecting from the upper part of the base 10 in such a manner that 
said cylinder is horizontal and extends along the upper surface of the 
base 10. 
The refrigerating circuit with all the control devices connected therewith 
and the entire electrical part of the machine, which can be of any type in 
the known art, will not be further described herein as they are easy to 
immagine by those skilled in the art. 
The connections between the evaporator in the cylinder 11 and the rest of 
the refrigerating circuit pass within the support 12 and the body 13. 
An electric ratiomotor unit 14 is connected to the body 13 in such a manner 
that the output shaft 17 is axial with the axis of the cylinder 11 and 
passes in a sealed manner through a hole 18. 
To the output shaft 17 is connected in a removable manner a cylindrical 
screw propeller 19 with its axis parallel to the axis of the cylinder and 
diameter slightly smaller than said cylinder. 
To protect the motor against excessive loads in case the mixture becomes 
too dense, there can be placed, as is known to those skilled in the art, a 
torque limiter, e.g. the friction type between the screw propellers and 
the geared motor, or consisting of a current limiting device of known type 
in the motor. 
A second cylindrical screw propeller 20 consisting of a strip arranged 
helically 21 with winding direction opposite that of the screw propeller 
19, can be advantageously supported and held in shape by a frame 
consisting of a ring 22 and a crosspiece 23 connected together and to the 
screw propeller by rods 24. 
The crosspiece 23 has a central hole 32 for engagement in a removable 
manner on the appropriately shaped free end 33 of the central shaft of the 
screw propeller 19 in such a manner as to form a rigid assembly therewith 
upon engagement. 
As can be seen in FIG. 2 once assembled the components described above form 
a structure in which the screw propeller 19 is completely inserted in the 
cylinder 11 so as to graze the inner wall thereof while the screw 
propeller 20 is arranged around the cylinder so as to graze the outer wall 
thereof. 
A container 25 made of transparent material and having low heat conduction 
(e.g. plastic) consisting of a cylindrical section from which there 
extends in the upward part an extension open at the top and optionally 
equipped with a removable cover 26 is fitted on the assembly consisting of 
the cylinder 11 and the screw propellers 19, 20 in such a manner as to 
receive it, through a side opening 15, in the cylindrical section which 
has an internal diameter slightly larger than the outside diameter of the 
second screw propeller 21 and a length such that, when the container 25 is 
secured and sealed to the body 13 (by means of any system of the known 
art, with screws, fixed end etc. and therefore not shown in detail) the 
assembly formed by the two screw propellers grazes the opposite end of the 
container. 
As may be seen in FIG. 2, once the container is fixed, the screw propeller 
grazes the internal cylindrical walls thereof. 
A gasket 16 placed in a seat corresponding with the edge of the opening 15 
of the container ensures sealing of the connection between the container 
25 and the body 13. 
The container 25 bears on the end of the cylindrical section opposite the 
opening for insertion of the agitator-refrigerator unit a delivery tap 27 
which can be of any known type in the known art. For example a sliding 
cylinder 28 moved by means of a lever 29 moving in an inclined slot 30 in 
such a manner as to open or close a hole 31 in the wall of the container 
25 placed level with the lower part of the external screw propeller. 
The machine operates as follows. 
With the container installed on the machine and the mixture to be converted 
to granita placed therein, when the machine starts the refrigerator will 
begin to chill the mixture by means of the evaporator cylinder 11 while 
the ratiomotor 14 will put in motion the screw propeller 19 which will 
transmit the motion of the outer screw propeller 20 integral therewith. 
The two screw propellers being wound in opposite directions, within the 
cylinder the mixture will move in one direction while externally it will 
move in the opposite direction, giving rise to a continuous stirring of 
the mixture and reaching all points thereof. 
The direction of rotation of the screw propellers is preferably the 
direction which brings about a movement of the mixture from left to right 
(seen from the machhine in FIG. 2) to the outside of the cylinder 11 and 
vice versa inside, in such a manner as to aid flow of the mixture through 
the hole 31 upon opening of the tap 27. 
The action of the two screw propellers along the walls of the cylinder 11 
also prevents formation of ice thereon so as to not limit the chilling 
action and prevent blockage of the screw propellers. 
It is noted that said chilling action is particularly effective because the 
contact surface between the evaporator and the mixture is much larger than 
that of a machine of the same container size but accomplished according to 
the known art, especially the types where only the lower wall of the 
mixture container effects the heat exchange, being in contact externally 
with the evaporator of the refrigerating circuit. 
Finally the possibility of completely separating the container from the 
rest of the machine and of removing the screw propellers from the cylinder 
11 permits very thorough cleaning of all the parts in contact with the 
mixture. 
The general form of the machine and in particular of the container 25 and 
the base 10 is shown here only as an example as is the form of embodiment 
of the screw propeller 20 and the support 12 and should not be considered 
limiting within the scope of the present invention. 
However rational the use of a direct coupling of the screw propeller 19 
with the screw propeller 20 may be and hence producing opposite flow of 
the mixture by means of opposite winding directions of the two screw 
propellers, it is of course possible to accomplish a machine applying the 
innovative principles of the present invention having screw propellers 
wound in the same direction but counter-rotated by using appropriate 
motors easy to immagine for anyone skilled in the art.