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FIELD OF THE INVENTION

The present invention relates to a vertical batch freezer. In particular, this batch freezer is specifically used to produce pasty food products such as, for example, ice creams and similar products.

KNOWN PRIOR ART

According to the prior art, vertical batch freezers comprise a tub open on top and provided with a base on which a through hole is obtained, a refrigeration cylinder provided with a cavity inside which the tub is removably housed, a pair of paddles, or scraping blades, to stir the food product, and actuating means to rotate the two paddles within the tub. Usually, the actuating means comprise a motor equipped with a drive shaft for transmitting the rotary motion to the two stirring paddles. Alternatively, there are batch freezers, especially of industrial type, having no removable tub and having, therefore, a tub integral with either the frame of the batch freezer or the batch freezing cylinder. The food product to be batch frozen consists of a liquid mixture prepared to be then subjected, inside the batch freezer tub, to a process of cooling and simultaneously mixing the liquid product obtained by rotating the paddles inside the tub. After about 16-18 minutes, the liquid preparation turns into a pasty substance just like the ice cream.

Still according to known art, the batch freezer, either with removable and nonremovable tubs, further comprises heat adjusting means arranged inside the refrigeration cylinder and near the tub, in order to adjust the temperature of the food product being processed. These temperature adjusting means comprise refrigeration means and controlling means to control the temperature in the tub containing the product to be batch frozen. In particular, the cooling means comprises, in known manner, a tube having circular section and bended to helix-shape, inside which the cavity of the refrigeration cylinder is thus defined so that an outer surface zone of this tube is in front of the tub at least when the tub is housed in the aforementioned cavity. For example, US4538427A in the name of Cavalli describes a batch freezer whose cooling means are made from one or more circular section tubes which are U-shaped

l and define the aforesaid cavity of the cooling cylinder.

The document US4583863A in the name of Brevetti Gaggia Spa also describes a batch freezer whose cooling means are made from one or more tubes having circular section and being helically arranged to form the cavity of the refrigeration cylinder.

The coolant usually running through this tube of the cooling means is generally Freon 404.

It should also be noted that the cooling means further comprise a closed refrigeration circuit which comprises, in known manner, a compressor, a thermal expansion valve and a condenser. The helical tube of the cooling means operates in the closed circuit as evaporator. In practice, the coolant passing through the tube changes from the liquid state to the gaseous state by absorbing heat from the outside and thereby cooling the tub placed inside the aforementioned cavity and, as a result, also the food product contained therein. Then, the coolant follows the typical refrigeration cycle along the aforementioned closed circuit, passing from the compressor to the condenser, then to the thermal expansion valve and, finally, back to the aforementioned helical tube.

However, this batch freezer of known art is not free from drawbacks. In fact, the tub is not efficiently refrigerated and, therefore, not only the batch freezing time is greater, but the power consumption in the batch freezing process is significantly more sizable. Therefore, object of the present invention is to implement a batch freezer which allows greater efficiency in refrigerating the product inside the tub of the batch freezer to be guaranteed.

Further object of the present invention is to implement a batch freezer which is therefore faster than the batch freezers of known art in carrying out the batch freezing process to batch freeze the product inside the tub.

SUMMARY OF THE INVENTION

These and other objects are achieved by a vertical batch freezer for preparing a pasty food product, comprising at least one tub containing said pasty food product, the tub being open on top and having a side wall and a lower base, at least one refrigeration cylinder provided with a cavity inside which said tub is at least partially housed, said refrigeration cylinder further comprising cooling means to cool said pasty food product contained in said tub, said cooling means comprising at least one tubular duct for passing a coolant, which extends along a curvilinear longitudinal axis arranged around and/or underneath said at least one tub, said duct comprising at least one outer perimetrical surface having a heat exchange zone facing said side wall and/or said lower base of said tub, characterized in that said heat exchange zone has, for at least one portion of said duct, along said curvilinear longitudinal axis, cross section having a substantially straight length facing said side wall and/or said lower base of said tub. In practice, said heat exchange zone is therefore defined by the translation of said straight length along said curvilinear longitudinal axis of said duct. In this way, this heat exchange zone substantially takes the shape of the tub surface, or side wall and/or base which it faces. It should be noted that, hereinafter, substantially straight length means a length whose curvature is basically close to zero. Therefore, a length having a non-zero, but close to zero, curvature would therefore fall within the protection scope of the present invention.

In practice, therefore, unlike the ducts of the known art cooling means made in the form of cylindrical tube, this tubular duct, or even a portion thereof, has a shape such as to have at least one substantially straight length in a generic cross section of the curvilinear longitudinal axis of the duct. In this way, the heat exchange zone of that duct portion containing this straight length turns out to have the shape of a surface band which follows the tub surface in front thereof and which is, therefore, complementary to the surface of the tub itself. It is to be understood that shape substantially complementary to the tub means a surface having a shape which in practice follows the shape of the surface in front thereof. Therefore, the heat exchange zone turns out to be a sort of translation surface of the tub surface region in front thereof.

This provides the undeniable advantage of guaranteeing a heat exchange surface much larger than that given by a cylindrical duct having the same size and length. In fact, in this last case, the heat exchange zone of the outer perimetrical surface of a cylindrical duct extends in helical semi-cylindrical shape whose portion closest to the tub is a curvilinear generatrix of said helical semi-cylindrical surface. Between two adjacent coils of this duct of known art there is also space or air which, in cross section, takes the form of a triangle with the two vertex sides each represented by an arc of a circle having of about 90° width, wherein the circle is that of the cross section of the two cylindrical ducts of the two adjacent coils. Obviously, in such a solution the heat exchange between the duct and the tub is not very efficient.

Still according to the invention, said straight length is either vertical, at least when it faces said side wall of said tub, and horizontal at least when it faces said lower base of said tub. In practice, the heat exchange zone is either of a substantially cylindrical type, in case it faces the side wall of the tub, i.e. it can be depicted by a partial surface superimposable to the shell of a cylinder, or a horizontal plane type in case it faces the lower base of the tub.

Still according to the invention, the outer perimetrical surface of said portion of said duct has, along said curvilinear longitudinal axis, a substantially semicircle-shaped cross section. In practice, therefore, the outer perimetrical surface of the duct portion consists of both the heat exchange zone, i.e. the part of the external perimetrical surface which comprises the chord of the semicircle depicted in cross section, and an inner surface opposite the first one, i.e. the part of the perimetrical surface which comprises the 180° arc of the semicircle depicted in cross section.

Furthermore, said portion of said duct is helically wound around at least part of the side wall of the tub. Furthermore, two or more adjacent intermediate coils of said at least one helical portion of said duct are in contact to one another at least next to the end of the respective substantially straight length. This gives the advantage of allowing the elimination of vacuum or air areas which would exist, by contrast, between two intermediate coils adjacent to each other when they are formed by a perfectly cylindrical duct, even when the coils are in contact to one another along the generatrix of the cylindrical duct. Therefore, in practice, at the end of said at least one straight length, the cross section of the aforementioned portion of said duct substantially has a sharp edge precisely to prevent vacuum between two consecutive coils. In the light of this, the heat exchange zone, i.e. the part of the perimetrical surface comprising the chord of the semicircle, i.e. the straight length, between one coil and the other is continuous, i.e. with no recesses.

It should be noted that, in other embodiments, this portion of said duct is also spirally wound under the tub, in this case, however, the curvilinear longitudinal axis of the duct lies substantially on a plane lower than the base of the tub.

Again, according to a further embodiment of the invention, said cooling means comprise a heat transfer, or heat exchange, body comprising at least one sleeve whose outer surface is arranged in front of said heat exchange zone of said at least one portion of said duct. Still according to this embodiment, this heat transfer body may further comprise a lower closing element couplable, on the bottom, to said sleeve, and arranged between said lower base of said tub and said at least one duct.

Specifically, said sleeve and/or said closing element has/have thickness from 0.1 to 1 mm, preferably 0.2 mm.

Moreover, said at least one tubular duct and/or said at least one heat transfer body is/are made of copper.

According to a peculiar aspect of the invention, said at least one portion of said at least one duct is obtained from a tube having a circular cross section having outer diameter between 7 and 15 mm, preferably 10 mm, preferably whose wall has constant thickness. Again, said at least one portion of said duct is obtained by lathe drawing said at least one tube having circular section.

BRIEF DESCRIPTION OF THE FIGURES

These and other aspects of the present invention will become more clear thanks to the following detailed description of a preferred embodiment, provided herein by way of example only and without limitations, with reference to the accompanying figures, in which:

figure 1A is a top axonometric view of the batch freezer according to the invention;

figure IB is another top view of the batch freezer of figure 1 A;

figure 2 is a longitudinal sectional view of the batch freezer of figure 1A, in which the tub has not yet been introduced;

figure 3 A is a longitudinal sectional view of the batch freezer of figure 1 A, the tub being introduced inside the refrigeration cylinder.

figure 3B is a side section view of the batch freezer according to the invention. figure 4 is a cross sectional view of three coils of a portion of duct through which the coolant passes; figure 5 is an axonometric view of the duct portion for passing the coolant having a cross section provided with a substantially straight length.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PRESENT INVENTION

As can be seen in the attached figures, according to the embodiment of the invention, the vertical batch freezer 1 for preparing a pasty food product, such as for example ice cream, comprises a tub 2 for containing the food product to be batch frozen, and a refrigeration cylinder 3, the tub being open on top and having a side wall 2a and a lower base 2b, and the cylinder being provided with a cavity 3 a inside which the tub 2 can be housed. This refrigeration cylinder 3 further comprises means 4 for cooling the pasty food product during the operation of the batch freezer 1. The cooling means 4 comprise a tubular duct 5 made of copper and where a coolant, for example of the Freon 404 type, runs through. This tubular duct 5 extends along a curvilinear longitudinal axis Z around at least part of the tub 2. It should be noted that the cooling means 4, as generally shown in figure 3B, further comprise a closed refrigeration circuit not shown herein but known to the field technician, which comprises a compressor, a thermal expansion valve and a condenser. The tubular duct 5 described in more detail below operates as evaporator in the closed circuit. In practice, the coolant running through the duct 5 changes from the liquid state to the gaseous state thereby absorbing heat from the outside and thus cooling the tub 2 placed inside the aforementioned cavity 3 a. Then, the fluid follows the classic refrigeration cycle along the aforementioned closed circuit, passing from the compressor to the condenser, then to the thermal expansion valve. Moreover the batch freezer 1, in a known manner, comprises temperature adjusting means which comprise, in turn, controlling means 101 to control the temperature inside the containing tub 3.

According to the invention the duct 5, as better shown in detail in figures 4 and 5, comprises an outer perimetrical surface 7 having a heat exchange zone 7a facing the wall 2a of the tub 2 to exchange heat with the product contained in the tub 2.

According to the invention, the heat exchange zone 7a of a portion 5 a of the duct 5 has, along the aforementioned curvilinear longitudinal axis Z, a cross section provided with a substantially straight length 10 facing the side wall 2a of the tub 2. As better shown in figure 5, the heat exchange zone 7a is therefore defined by the translation of the straight length 10 along the curvilinear longitudinal axis Z of the duct 5. Therefore, it will take the form of a surface band. In particular, according to the embodiment described herein, this straight length 10 is substantially vertical since the heat exchange zone 7a faces the side wall 2a of the tub 2, wherein this side wall is substantially represented by the shell of a cylinder. In the light of this, such straight length 10 has a direction substantially parallel to the longitudinal axis Y of the tub 2. If the heat exchange zone 7a was facing the lower base 2a of the tub 2, the straight length 10 would be horizontal. On the contrary, in the embodiment shown herein the duct 5, under the base 2b of the tub 2, has known cylindrical shape.

According to the particular embodiment described herein, the portion 5 a of the duct 5 has, along the curvilinear longitudinal axis Z, substantially semicircle-shaped cross section. It is clear that the chord of this semicircle corresponds to the straight length 10 lying on the heat exchange zone 7a, whereas the arc of this semicircle corresponds to the arc-shaped length lying on the inner perimetrical surface 7b of the outer surface 7 of the duct 5.

It should be noted that, although an embodiment in which the duct 5 has a cross section provided with a substantially straight length 10 further arranged in front of the base 2b of the tub 2, therefore arranged horizontally, is never shown hereinafter, however such an embodiment in which the duct 5 has a portion 5a having a cross section provided with a substantially straight length 10 facing the side wall 2a of the tub 2 and a further portion 5a having a cross section provided with a straight length 10 facing the lower base 2b of the tub 2, would fall within the protection scope of the present invention. In particular, as described above, this heat exchange zone 7a of the portion 5a of the duct 5 has a shape substantially complementary to the shape of the side wall 2a of the tub 2 in front of this heat exchange zone 7a. Thus, the heat exchange zone 7a thus obtained follows the shape of the zone, in front thereof, of the outer surface of the tub 2, although being translated with respect to the latter zone by a few millimeters. This solution makes it possible to exploit as much as possible the effective heat exchange surface between the duct 5 and the tub 2. It is clear that this solution, compared to that of known art with a cylindrical-shaped duct, provides immediately evident advantages in terms of improvement of the efficiency and performance of the refrigeration cycle. In fact, in this way, the heat exchange area can be extended to a surface uniformly placed around the tub 2 thereby lowering the freezing time from 16-18 minutes to about 12 minutes, the volume and type of product to be batch frozen being unchanged. Moreover, in the embodiment shown herein, the tub 2 is removable from the cavity 3 a and fixed to the frame 50 of the batch freezer by means of fastening means 20 so as to reversibly lock the rotation and/or translation of the tub 2 with respect to both the frame 2 of the batch freezer 1 and, as a result, the refrigeration cylinder 3, at least when the tub 3 is housed within the cavity 3 a of the refrigeration cylinder 3.

Furthermore, a through hole 2d is obtained on the lower base 2b of the tub 2 which is provided, at the through hole 2d, with a tubular sleeve 45 sealingly arranged on the base 2b of the tub 2. Furthermore, the tub 2 is provided with a pair of stirring paddles or scraping blades 21 to stir the food product by rotating inside the tub 2 around the sleeve 45. The actuation means for the two paddles 21 comprise an electric motor 46 as well as a drive shaft 22 for transmitting the rotary motion to the two stirring paddles 21. Furthermore, the batch freezer 1 also comprises means 23 for the integral and removable connection of the two paddles 21 to the drive shaft 22. It should be noted that the two paddles 21 mentioned above are not further described here since they are known to the field technician. They can be made in very different geometries and sizes without departing from the protection scope of the present invention.

Moreover the tub 2, in order to be introduced/removed into/from the cavity 3a of the refrigeration cylinder 3, has substantially frustoconical shape. In particular, the angle between the side walls 2a and the base 2b of the tub 2, with respect to the longitudinal axis Y, is between 0.5 and 3°, where the area of the base 2b is smaller than the area of the top opening 2e of the tub 3.

In other embodiments, the tub 2 can be perfectly cylindrical as well, without thereby departing from the protection scope of the present invention.

However, it should be noted that although a batch freezer 1 has been described so far with a removable tub 2, a batch freezer 1 with a non-removable tub 2, therefore fixed within the cavity 3a of the cooling cylinder 3 and having a perfectly cylindrical shape, would fall any way in the protection scope of the present invention. Still according to the invention, this portion 5a of the duct 5 is helically wound around the side wall 2a of the tub 2, along the longitudinal axis Y of the tub 2 itself. In particular, as better shown in Figure 4, the adjacent intermediate coils 40 of the portion 5 a of the duct 5 are in contact to one another at least next to the ends 30 and 31 of the respective substantially straight length 10 comprised in the heat exchange zone 7a. In practice, therefore, the pitch of this helix is substantially equal to the extent of the straight length 10 of the cross section of the portion 5a of duct 5. Moreover, in the embodiment shown herein, the helix radius is constant. In other embodiments, as the duct portion 5a extends along the axis Y of the tub, the helix radius could also be slightly different, for example slightly decreasing if the shape of the tub 2 is frustoconical rather than cylindrical.

In practice, according to the embodiment shown herein, the outer perimetrical surface 7 of the portion 5a of the duct 5, which comprises the straight length 10, describes a band of cylindrical surface being helically wound around the vertical longitudinal axis Y of the tub 2, thereby forming the side surface of a cylinder, the surface following the shape of the tub 2 with no discontinuity. In this way, a perfectly uniform heat exchange surface can be obtained in front of the wall 2a of the tub 2.

Therefore, in practice, at the ends 30 and 31 of the straight length 10 of an intermediate coil 40, the cross section of the aforementioned portion 5a of the duct 5 substantially has a sharp edge precisely to prevent vacuum between two consecutive coils 40, which would obviously result in reduced heat exchange. In the light of this, the heat exchange zone 7a between a coil and the other is continuous, i.e. a cylindrical surface without recesses.

Furthermore, according to the embodiment of the invention described herein, the cooling means 4 comprise a heat transfer, or heat exchange, body 70. This heat transfer, or heat exchange, body 70 comprises a sleeve 71 whose first outer surface 71a is arranged in front of the heat exchange zone 7a of the aforementioned portion 5a of the duct 5 and whose second outer surface 71b is in front of the side wall 2a of the tub 2.

This heat transfer, or heat exchange, body 70 further comprises a lower closing element 72 couplable, on the bottom, to the sleeve 71 and arranged between the lower base 2b of the tub 2 and the duct 5.

Still according to the invention, both the sleeve 71 and the lower closing element 72 are made of copper and have thickness of 0.2 mm. However, in other embodiments, their thickness may be between 0.1 and 1 mm, even different from one another, such as for example the sleeve 71 being of 0.2 mm and the lower closing element being of 0.6 mm, without thereby departing from the protection scope of the invention.

It should be noted that the portion 5a of the duct 5, which comprises a cross section having a straight length 10, is obtained starting from a tube having outer diameter of 10 mm. An embodiment in which such cylindrical tube has a diameter between 7 and 15 mm would however fall within the protection scope of the present invention. Finally, the aforementioned portion 5 a of duct 5 is obtained by lathe drawing the afore mentioned tube having circular section with diameter of 10 mm. In practice, the tube having circular cross section is wound on a cylinder which is mounted on the lathe. This tube, during its winding around the cylinder, is simultaneously passed through a template having the shape of the cross section to be given to the final product, i.e. the portion 5a of the duct 5.