ITBO20110280A1 - ICE CREAM PRODUCTION MACHINE - Google Patents

Description

DESCRIPTION

â € œMACHINE FOR THE PRODUCTION OF GELATOâ €

The present invention refers to a machine for the production of ice cream.

As is well known, a phase that is regularly carried out in the context of ice cream production is the whipping phase.

In this phase, the basic liquid or semi-liquid product is progressively cooled and, at the same time, subjected to the action of an agitator or mixer. In this way, the part of water contained in the mixture is frozen in the form of microcrystals, and at the same time air is incorporated into the product.

The result of this operation is basically ice cream, that is a low temperature product, characterized by a creamy consistency.

The quality perceived by the consumer is determined, regardless of the specific taste attributed to the ice cream, by the sensation of softness and refreshment that the consumer himself experiences when he ingests the product. These sensations are substantially due to the distribution, size and morphology of the air bubbles and ice crystals incorporated into the structure of the ice cream.

The size of the air particles gradually decreases over time during the freezing process. These dimensions are determined by the equilibrium point between the shear stresses caused by the flow field and the intersurface forces that tend to keep the air particles together.

In this context, it is very important to accurately and reliably determine the duration of the freezing process: if this operation is finished too early or too late, the characteristics of the product (expressed, for example, in terms of lightness, aroma, etc. ) can be irreparably compromised, leading to the delivery of a low quality ice cream.

Currently, the moment in which freezing is completed is determined by reading the current absorption by the motor that moves the stirrer. This control is based on the fact that, as the freezing process proceeds, the product becomes more and more dense, and the stirrer therefore encounters greater resistance to its own rotation motion. Consequently, the motor needs more power to act properly on the agitator, and therefore absorbs more current from the power supply network. Freezing is generally terminated when the absorbed current reaches a predetermined threshold, which can be, for example, between 6A and 7A.

However, this type of control has a significant operational drawback, since it is extremely sensitive to the conditions in which the engine is found. In fact, the mechanical parts of which the motor is composed are subject to wear and, with the passage of time, variations in the current absorption occur in the same way as all other conditions. In other words, the current absorption by the motor varies over time, and makes a freezing control technique that depends exclusively on this parameter at least partially unreliable.

The purpose of the present invention is to provide a machine for the production of ice cream in which the freezing process is controlled in a precise and reliable manner.

In particular, the object of the present invention is to provide a machine for the production of ice cream in which the end of the freezing process is determined in a precise and reliable manner.

Another purpose of the invention is to provide a machine in which the control over the freezing process is independent of the mechanical / structural conditions in which the motor active on the stirrer is found.

Another object of the invention is to provide a machine for the production of ice cream in which the freezing process is controlled in a simple and economical way.

These and other purposes are substantially achieved by a machine for the production of ice cream according to what is described in the appended claims.

Further features and advantages will become more apparent from the detailed description of a preferred and non-exclusive embodiment of the invention.

This description is provided below, with reference to the accompanying figures, also having purely illustrative and therefore non-limiting purposes, in which:

- figure 1 shows a block diagram of a machine for the production of ice cream in accordance with the present invention;

- figures 2a-2c, 3a-3d, 4a-4b and 5 show graphs representing the quantities used in the control of the machine of figure 1.

With reference to the accompanying figures, 1 indicates as a whole a machine for the production of ice cream in accordance with the present invention.

The machine 1 (Figure 1) first of all comprises a containment tank 2, which contains a basic liquid or semi-liquid product.

In particular, the base product can be a product or a mixture of products for the production of ice cream.

It should be noted that the aforementioned containment tank 2, depending on the needs and the type of machine in which it is used, can have a prevalent development in horizontal or vertical direction; the tank 2 can also be constituted by a box-like structure having at least one open side, or it can be constituted by a substantially â € œclosedâ € box-like structure.

To obtain ice cream from the basic product, the machine 1 comprises a treatment circuit 10.

Preferably the treatment circuit 10 comprises a pasteurizer 60, adapted to pasteurize the basic product. Pasteurization preferably consists in a rapid heating of the base product up to a predetermined temperature (for example between 80 ° C and 90 ° C, reached in less than 60 minutes), in maintaining this temperature for a predetermined time interval ( in the order of a few minutes), and in a subsequent rapid cooling (again, in less than 60 minutes) until reaching a temperature of about 4 ° C.

The purpose of pasteurization is to free the mixture from pathogenic bacteria, to facilitate the mixing of the ingredients, and to improve the flavor, quality and uniformity of the product.

Pasteurizer 60 is, in itself, known, and is therefore not described in further detail.

The treatment circuit 10 comprises a batch freezer 20 for carrying out a freezing of said base product.

As schematically shown in figure 1, the batch freezer 20 comprises a container 21, suitable for receiving the product contained in the containment tank 2.

The containment tank 2 and the container 21 can be connected to each other by means of suitable rigid or flexible ducts. The flow of product from the tank 2 to the container 21 can be obtained by gravity, by positioning the tank 2 at a greater height than the container 21, and / or through the use of suitable pump means, known per se and therefore not further described.

The batch freezer 20 also comprises a stirrer 22, housed inside the container 21.

Preferably, the agitator 22 is rotatably mounted inside the container 21, so as to be able to rotate around a longitudinal axis X.

Preferably, the aforementioned longitudinal axis X coincides with a prevalent development axis of the container 21; the latter may present, by way of example, a cylindrical shape, and its prevailing axis of development is substantially the central axis of this cylindrical shape.

In one embodiment, the agitator 22 is provided with a central shaft, arranged along the axis of rotation X. In a different embodiment, the agitator 22 has no central shaft, and is supported by the lateral surface of the container 21.

The agitator 22 is rotated by a motor 23.

Preferably the motor 23 is an electric motor, and even more preferably it is a brushless motor.

The batch freezer 20 also comprises heat exchange means 24, active on the product contained in the container 21 to supply to or subtract heat from said product in the container 21.

In a preferred embodiment, the heat exchange means 24 can comprise a coil, arranged around the container 21. A cooling fluid preferably flows in this coil, such as for example a fluid of the R-404A type.

The heat exchange means 24 are advantageously associated with a refrigerating system, known per se and therefore not further described, which allows the heat absorbed by the refrigerating fluid to be disposed of so as to maintain it at the temperature necessary for carrying out the freezing process. .

As mentioned, the heat exchange means 24 have the task of supplying heat to the product in the container 21, or of subtracting heat from the product (therefore, cooling the product) in the container 21.

In particular, during the freezing process, the heat exchange means 24 cool the product in the container 21 while the stirrer 22 is being moved.

Advantageously, the machine 1 further comprises a sensor 30 positioned inside the container 21 and suitable for detecting a main parameter P. The main parameter P is representative of an electrical impedance of the product present in the container 21.

Preferably, the sensor 30 comprises a pair of electrodes 31. In a preferred embodiment, the electrodes are made of stainless steel. Preferably the main parameter P is representative of one or more of the following quantities: modulo | Z | the electrical impedance of the product; Arg (Z) argument of the electrical impedance of the product. In addition or alternatively, the main parameter P can be representative of a difference ∠† Arg (Z) between consecutive measurements of the argument Arg (Z) of the electrical impedance of the product present in the container 21.

In practice, the main parameter P can comprise several values, each representative of a different quantity relating to the electrical impedance Z of the product contained in the container 21.

Preferably, as will become clearer later, the impedance Z, of which the main parameter P is representative, has an imaginary part (reactive component) other than zero.

Preferably, the sensor 30 comprises a detection module 32. In the preferred embodiment, the detection module 32 is connected to the aforementioned electrodes 31.

The detection module 30 is configured to make a test signal T flow in the product contained in the container 21.

Preferably, the test signal T signal is a time-varying voltage signal.

In particular, the test signal T has a non-zero frequency.

In particular, the test signal T is substantially periodic, preferably substantially sinusoidal. Preferably the test signal T has a frequency comprised between 20Hz and 10KHz, preferably less than 300Hz, and in particular less than 100Hz. By way of example, the test signal T can have a frequency substantially equal to about 20Hz.

Preferably the test signal T has an amplitude comprised between 50mV and 150mV, preferably between 80mV and 120mV and in particular comprised between 95mV and 105mV. By way of example, the test signal T can have an amplitude substantially equal to about 100mV.

The detection module 32 then detects, in the product contained in the container 21, a detection signal R. This detection signal R is detected while the test signal T passes through the product.

In practice, as mentioned, the test signal T is a sinusoidal voltage signal. The sense signal R is preferably representative of the current flowing in the product when the test signal voltage T is applied.

As a function of the detection signal R, the detection module 32 determines the aforementioned main parameter P. Preferably, this main parameter P is also determined as a function of the test signal T.

Preferably, the detection module 32 cooperates with the aforementioned electrodes 31 for the application of the test signal T and for the detection of the corresponding detection signal R.

In a preferred embodiment, the detection module 32 can be realized as an impedance analyzer, and determine one or more of the aforementioned quantities | Z |, Arg (Z), ∠† Arg (Z) as a function of the test signal T and the detection signal R.

As mentioned, the value of the imaginary part of the detected impedance Z is different from zero.

In particular, the test signal T is generated so as to be able to detect not only the purely resistive component of the mixture, but also the reactive component.

Advantageously, the machine 1 also comprises a control unit 40 connected to the sensor 30.

The control unit 40 receives the main parameter P sent by the sensor 30, and in particular it receives the main parameter P determined by the detection module 32 and sent by the latter to the control unit 40.

The control unit 40 compares the received main parameter P with at least one preset value. The preset value can be, by way of example, a threshold value calculated in advance, or a value determined on the basis of previous measurements of the sensor 30.

In one embodiment, the preset value is a maximum threshold, representative of the value that is assumed by the electrical parameters of the product present in the container 21 when it reaches the desired consistency.

For example, the threshold value can be determined experimentally, by detecting the electrical parameters of a product that has reached an optimal level of consistency and for which, therefore, the freezing process is concluded.

In practice, to determine the aforementioned reference value, a known type system can be used, such as the control technique based on the current absorption by the motor, after checking the optimal operating conditions of the motor used: when the known system, placed in optimal operating conditions, indicates that the product has reached the desired consistency, the values assumed in this circumstance by the electrical parameters of the product itself are detected and stored. These values can then be used to define the reference value to be used in the application of the present invention. According to the comparison made between the main parameter P and the preset reference value, the control unit 40 generates an electrical signal S representative of a conclusion of the freezing process.

Note that, in the present context, the detection module 32 and the control unit 40 have been presented separately; however, they can be realized as a single electronic device, suitably programmed and configured to perform the functions described here.

In one embodiment, the electrical signal S can be destined to the heat exchange means 24, to interrupt the cooling that they apply to the product present in the container 21.

In addition or alternatively, the electric signal S can be destined to the motor 23, so that the latter interrupts the movement of the agitator 22, since the freezing process is finished.

In addition or alternatively, the electrical signal S can be a notification signal, intended for a signaling device 50, preferably of the acoustic and / or visual type, suitable for signaling to an operator the completion of freezing. In this way, the operator is appropriately alerted at the end of freezing and can proceed manually to set the subsequent processing / dispensing phases of the product.

In addition or alternatively, the electric signal S can be destined to a transfer / dispensing system 70 which, since the ice cream production is substantially completed, removes the ice cream from the container 21.

Note that, depending on the device or equipment for which it is intended, the electrical signal S can be suitably pre-processed, before transmission, so that it can be understood and correctly interpreted by the recipient.

By way of example, the electrical signal S sent to the heat exchange means 24 may have a substantially identical meaning to the electrical signal S sent to the motor 23 (ie, interruption of operation); however, the two signals may have different formats, precisely because the recipients (heat exchange means 24, motor 23) are different from each other and can use different communication protocols.

In order to further clarify the contents of the present invention, some experimental data relating to the invention are reported below.

Figure 2a shows the trend as a function of time of the impedance module Z (indicated as | Z |), that is an example of implementation of the aforementioned main parameter P, measured at different frequencies of the test signal T.

Figure 2b shows the trend as a function of time of the impedance argument Z (indicated as Arg (Z)), i.e. a different embodiment of the aforementioned main parameter P, measured at different frequencies of the test signal T .

Figure 2c shows the current absorption by the motor 23 as a function of time, determined in the same conditions in which the data represented in Figures 2a and 2b were collected.

Figure 3a shows the trend of the impedance module | Z | as a function of the measured current absorption.

As can be seen, a substantially linear relationship was verified between the two variables. The dispersion around the expected value is not uniform throughout the current absorption range: for currents greater than 5A an increase in the dispersion is noted.

Figure 3b shows the trend of the Arg (Z) impedance argument as a function of the measured current absorption, in a range between 0A and 8A.

Figure 3c shows in greater detail a part of the results of Figure 3b, relating to the range 3.5A -7.5A.

At the beginning of the freezing process, when the temperature is not yet very low and the mixture is still substantially liquid, Arg (Z) grows very rapidly. Subsequently, the freezing process progresses and the density of the mixture increases, causing first a slower increase of Arg (Z), and subsequently a saturation. For currents greater than 4 A (process already started) the relationship between Arg (Z) and the absorbed current is substantially linear. This aspect is clearly visible in figure 3c, where, as mentioned, Arg (Z) is represented as a function of the current absorption in the range 3.5A -7.5A. The linear regression line and the determination factor R <2> are also indicated. From the data shown it also emerges that the dispersion with respect to the expected value of Arg (Z) is substantially uniform for the different absorption values.

Figure 3d shows the trend of the ∠† Arg (Z) parameter, defined as the difference between consecutive readings of Arg (Z), as a function of the measured current absorption.

The value of ∠† Arg (Z) increases rapidly at the beginning of the freezing process (low current absorption), reaching a maximum when the current is approximately 2.5A; then ∠† Arg (Z) decreases as the process progresses.

Figure 3d shows the trend of ∠† Arg (Z) as a function of the absorbed current, in the range 3A -7.5A; both the linear regression line and the determination factor R <2> are indicated. As you can see, the dispersion is greater at the beginning of the process and decreases subsequently.

Figures 4a and 4b show, respectively, the trend of | Z | and Arg (Z) as a function of the measured current absorption, detected in distinct and consecutive freezing processes, in which different products were used. Between each process and the next the container 21 was not cleaned.

The values of | Z | they are not significantly affected by the container not being cleaned. Arg (Z) exhibits a non-reproducible behavior only for low values of the absorbed current (beginning of the freezing process). Arg (Z) has significantly higher values at the beginning of the freezing process, when the container 21 has not been cleaned. This result may be linked to the presence of frozen ice cream residues between the electrodes 31. However, these differences substantially occur only at the beginning of the freezing process (low current absorption), while for higher values the behavior of Arg (Z) it has no differences.

Therefore, the fact that the container is not cleaned between one process and another does not affect the reliability of the detection of the useful values of the main parameter P, and of the consequent determination of the term of freezing, since the correlation between the electrical parameters detected and the current absorption remains unchanged in the final phase of the process.

Figure 5 shows the trend of Arg (Z) in two processes in which a different quantity of product was used (3 liters in one case, 7 liters in the other).

As can be seen, the behavior of Arg (Z) is substantially independent of the quantity of product contained in the container 21. Both in the case in which 3 liters of product have been used, and in the case in which 7 liters of it have been used, Arg (Z) presented a substantially equal trend and reached the same values at the end of the freezing process.

The invention achieves important advantages.

First of all, in the machine according to the invention, the freezing process is controlled in a precise and reliable way.

In particular, the end of the freezing process is determined in a precise and reliable way.

Furthermore, the control over the freezing process implemented in the machine according to the invention is independent of the mechanical / structural conditions in which the motor active on the stirrer is found.

A further advantage is that the freezing process is controlled in a simple and economical way.

Another advantage is found in the fact that the freezing process control technique described and claimed here is able to operate reliably even when the container of the batch freezer is not cleaned when the product to be creamed is changed.

Claims (15)

CLAIMS 1. Machine for the production of ice cream comprising: - a containment tank (2) for a basic liquid or semi-liquid product; - a treatment circuit (10) of said basic product, to obtain ice cream; wherein said treatment circuit (10) comprises a batch freezer (20) for carrying out a freezing of said product, said batch freezer (20) being provided with: - a container (21) adapted to receive the product contained in said containment tank (2); - an agitator (22), housed in said container (21); - a motor (23), active on said agitator (22) to move it inside said container (21); - heat exchange means (24) active on the product contained in said container (21) to supply or subtract heat to said product in the container (21) during the movement of said stirrer (22) characterized in that it further comprises: - a sensor (30) positioned in said container (21) and suitable for detecting a main parameter (P) representative of an electrical impedance of the product in said container (21); - a control unit (40) connected to said sensor (30) and configured for: - receiving said main parameter (P); - comparing said main parameter (P) with at least one preset value; - generating, as a function of said comparison, an electrical signal (S) representative of a conclusion of said freezing. 2. Machine according to claim 1 wherein said sensor (30) comprises a pair of electrodes (31), preferably made of stainless steel. 3. Machine according to any one of the preceding claims, in which said main parameter (P) is representative of one or more of the following quantities: electrical impedance module; argument of electrical impedance; difference between consecutive measurements of the electrical impedance argument. 4. Machine according to claim 3 in which the impedance of which said main parameter (P) is representative has an imaginary part having a non-zero value. Machine according to any one of the preceding claims, wherein said sensor (30) comprises a detection module (32) suitable for: - making a test signal (T) flow into the product in said container (21); - detecting in said product a detection signal (R) in correspondence with the test signal (T) through said product; - determining said main parameter (P) as a function of said detection signal (R); - sending said main parameter (P) determined to said control unit (40). 6. Machine according to claim 5 wherein said test signal (T) is a time-varying voltage signal. 7. Machine according to claim 6 wherein said test signal (T) has a frequency other than zero. 8. Machine according to claim 6 or 7 wherein said test signal (T) is substantially periodic, preferably substantially sinusoidal. Method according to claim 8 wherein said test signal (T) has a frequency comprised between 20Hz and 10KHz, preferably less than 300Hz, and in particular less than 100Hz. 10. Machine according to any one of claims 6 to 9, wherein said test signal (T) has an amplitude between 50mV and 150mV, preferably between 80mV and 120mV and in particular between 95mV and 105mV. 11. Machine according to any one of the preceding claims, in which said reference value is a maximum threshold, and said control unit (40) is configured to generate said electrical signal (S) when said main parameter (P) is greater or equal to said maximum threshold. Machine according to any one of the preceding claims, in which said electrical signal (S) is intended for said heat exchange means (24) to terminate a cooling of the product in said container (21). 13. Machine according to any one of the preceding claims, in which said electrical signal (S) is intended for said motor (23) to terminate a movement of said agitator (22). 14. Machine according to any one of the preceding claims, in which said electrical signal (S) is intended for a signaling device (50), preferably of the acoustic and / or visual type, suitable for signaling to an operator the completion of freezing. Machine according to any one of the preceding claims, wherein said electrical signal (S) is intended for a transfer / dispensing system (70) associated with said container (21) to remove the product from said container (21).