Method for washing empty containers adapted to be filled with a pourable product and washing machine

Abstract

There is described a method for washing containers comprising the steps of: advancing a series of beams (5) along a washing path (P) spaced from one another by a pitch (K); spraying the containers (2) by a rotary spraying device (13) including an actuation wheel (15); actuating the actuation wheel (15) in rotation by means of contact interaction of pushing members (16), carried each by a respective beam (5); detecting the presence and position of each pushing member (16) within a detection section (18); defining an encoder main interval (19) representative of said pitch (K);the step a) of advancing comprises actuating a motor including an absolute encoder configured to provide an integer number representative of the actual position of the pushing member (16) along said pitch (K); the method comprising the steps of: reading the integer number corresponding to the position of the pushing member (16) within the detection section (18); comparing the read integer number with an expected nominal integer value representative of an expected nominal position of the pushing member (16) within the detection section (18).

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for washing empty containers adapted to be filled with a pourable product, preferably a pourable food product.

[0002] The present invention also relates to a washing machine for washing empty containers adapted to be filled with a pourable product, preferably a pourable food product.BACKGROUND ART

[0003] Washing machines are known which are configured for washing containers. Usually, a washing machine of such type is located upstream of a filling machine and a labelling machine, in which the containers are respectively filled with the pourable product and labelled with respective labels.

[0004] A washing machine is usually configured to be fed with used containers, such as returnable bottles, which have been emptied from the pourable product they are adapted to contain, so as to wash and clean the containers.

[0005] An example of washing machine is known from EP-A-2727660 in the name of the same Applicant.

[0006] A typical washing machine of the above type essentially comprises: a washing tunnel; a looped chain conveyor advancing the containers from an inlet station to an outlet station along a washing path which extends inside the washing tunnel; a feeding system for feeding containers to be treated (i.e. washed and cleaned) to the chain conveyor; a plurality of consecutive treatment zones arranged between the inlet station and the outlet station and through which the chain conveyor advances the containers.

[0007] In detail, the chain conveyor comprises a plurality of consecutive beams, which are fed at the inlet station by the feeding system with respective rows of containers to be washed.

[0008] Each beam defines one link of the chain conveyor.

[0009] In greater detail, each beam comprises a plurality of aligned pockets organized in respective rows (which are perpendicular to the washing path), each pocket being configured to receive one container to be treated at a time, to convey such container from the inlet station to the outlet station through the washing tunnel and along the washing path, and to deliver the respective washed container at the outlet station.

[0010] More precisely, each beam is discharged of the respective washed containers at the outlet station and then is conveyed along a return path back to the inlet station, where it receives new empty containers to be washed.

[0011] Typically, according to the advancing direction of the containers along the washing path and inside the washing tunnel, the treatment zones comprise, in sequence: a prewash zone, a caustic zone (or treatment zone, i.e. wherein the cleaning treatment of the containers occur) and a rinsing zone.

[0012] Each of the treatment zones may comprise an immersion zone, whereby the containers are treated by immersion in a treatment fluid, and / or a spraying zone, whereby the containers are treated by spraying the treatment fluid thereon.

[0013] For example, the caustic zone usually comprises one or more caustic baths, each defined by a respective tank which is filled with caustic chemical agents and through which the containers are advanced.

[0014] The caustic chemical agent, which thus defines the treatment fluid, is kept at a high temperature, usually around 65°C-80°C to help clean and sterilize the containers.

[0015] On the other hand, the rinsing zone usually comprises a plurality of rinsing devices. Each rinsing device comprises a rinsing nozzle, which is configured to spray or sprinkle clean fresh water towards the containers passing through the rinsing device, and a collecting rinsing basin, which is configured to collect the water sprayed on the containers.

[0016] According to a well-known solution, the nozzles or spraying devices are of the rotary type.

[0017] More specifically, a spraying device consists of a main body extending parallel to the beams, i.e. perpendicular to the washing path and to the advancing direction of the beams along the washing path, and provided with a series of nozzles or through holes, through which the treatment fluid (usually clean water) is sprayed.

[0018] The main body thus extends along a longitudinal axis parallel to the beams and is rotatable on itself about such longitudinal axis.

[0019] In particular, the main body is not self-motorized. Conversely, the main body is actuated in rotation by the movement of the beams.

[0020] More precisely: the spraying device includes an actuation wheel, normally a star wheel, mounted to an axial end of the main body. The actuation wheel has a plurality of arms angularly distributed about the longitudinal axis.

[0021] Each beam includes a pushing member, opportunely arranged at an extremity of the beam, configured to cooperate in contact with one arm of the actuation wheel, so as to determine a rotation of a certain angle of the actuation wheel, and therefore of the main body.

[0022] Being the beams spaced from one another of a constant pitch, the continuous interaction of successive pushing members with respective arms of the actuation wheel determines a sort of continuous rotation of the main body.

[0023] In practice, a sort of rack and pinion gear mechanism is defined, whereby the beams correspond to the rack, the teeth of the rack being the pushing members, and the actuation wheel corresponds to the pinion, the teeth of the pinion being the arms of the actuation wheel.

[0024] Although the known washing machines and method for washing containers work satisfyingly well, the Applicant has noted that they are still prone to further improvement, in particular as per the efficiency of the washing and cleaning process, as per avoiding undesired stops and jammings, and as per reducing the total costs and time of maintenance.DISCLOSURE OF INVENTION

[0025] It is therefore an object of the present invention to provide a method for washing containers which is designed to meet at least one of the above-mentioned needs in a straightforward and low-cost manner.

[0026] This object is achieved by a method for washing containers as claimed in claim 1.

[0027] A further object of the invention is to provide a washing machine for washing containers which is designed to meet at least one of the above-mentioned needs in a straightforward and low-cost manner.

[0028] This object is achieved by a method for washing containers as claimed in claim 13.

[0029] Preferred embodiments of the present invention are laid down in the appended dependent claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic lateral view, partially sectioned, and with parts removed for clarity of a washing machine according to the invention; Figure 2 is a larger-scale, schematic lateral view, with parts removed for clarity, of a particular zone of the washing machine including a spraying device and a sensor device; and Figure 3 is a diagram illustrating some quantities used for controlling the sensor device in a method for washing containers according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

[0031] With reference to Figure 1, number 1 indicates as a whole a washing machine configured to wash empty containers 2 adapted to be filled with a pourable product, preferably a pourable food product, such as beer, wine, water, juice, soft drinks, milk or the like.

[0032] In particular, containers 2 are defined by respective empty bottles (for example, returnable glass bottles) intended to be filled with the pourable product.

[0033] Washing machine 1 comprises: a washing tunnel 3 into which empty containers 2 are fed and accordingly washed; and a conveyor 4 configured to convey a plurality of containers 2 along a washing path P in an advancement direction D.

[0034] Preferably, the conveyor 4 comprises a looped chain conveyor (of the type known and only schematically shown) for advancing containers 2 along washing path P inside washing tunnel 3, so as to convey containers 2 from one end of the tunnel 3 to the other end along a general direction D, preferably horizontal with respect to gravity.

[0035] In detail, conveyor 4 may be of the type described in WO-A-2020119958 and comprises: a pair of elongated chains (not shown) parallel to path P and parallel to one another; and a series of successive conveying beams 5 (laterally shown), which extend between the chains in a transversal and, more in detail, orthogonal manner to the chains and to path P.

[0036] Specifically, each beam 5 comprises a row of pockets 6 (laterally shown) aligned orthogonally to path P and configured to receive corresponding containers 2.

[0037] In such a manner, containers 2 carried by a corresponding beam 5 are aligned orthogonally to path P and housed inside the respective pockets 6, individually.

[0038] Beams 5 are spaced from one another by a fixed distance defining a pitch or step K of the series of beams 5 along path P.

[0039] In light of the above, each beam 5 defines a link of the looped chain.

[0040] Washing machine 1 comprises also a feeding system 7 of the known type (only schematically shown in Figure 1) for feeding a sequence of empty containers 2 along direction D and at an inlet station I of washing tunnel 3. Expediently, containers 2 are fed by feeding system 7 along direction D arranged in rows orthogonal to path P.

[0041] In use, the most forward containers 2 of each row of containers 2 are transferred by feeding system 7 to the respective pockets 6 of the beam 5 that is travelling at inlet station I.

[0042] Washing machine 1 further comprises an outfeed system 8, which receives rows of cleaned containers 2 from conveyor 4 at an outlet station 0 of washing tunnel 3.

[0043] In view of the above, path P comprises: a washing branch P1, which extends from inlet station I to outlet station O and along which containers 2 are advanced by chain conveyor 4; and a return branch P2, which extends from outlet station O to inlet station I and defines a return path along which beams 5 return towards inlet station I after having discharged containers 2.

[0044] Washing machine comprises a plurality of consecutive treatment zones arranged between the inlet station I and the outlet station O and through which the chain conveyor 4 advances the containers 2.

[0045] According to a preferred embodiment and to the aforementioned advancing direction of the containers 2 along path P, washing machine 1 comprises in sequence along washing branch P1: a prewash zone C1; a cleaning zone C2 arranged downstream prewash zone C1; and a final rinsing zone C3 arranged downstream cleaning zone C2.

[0046] The operation of washing machine 1 at the prewash zone C1, cleaning zone C2 and rinsing zone C3 is well-known, for example from WO-A-2020119958, and therefore will not be described in detail herein.

[0047] In particular, cleaning zone C2 comprises at least one cleaning tank 12, in particular a plurality of cleaning tanks 12, in the embodiment shown two successive cleaning tanks 12.

[0048] Each tank 12 is configured for holding a treating solution, such as a detergent chemical solution made of several chemical agents.

[0049] In one embodiment, the treating solution comprises basic aqueous solutions that include, in particular, sodium hydroxide.

[0050] In use, the containers 2, carried by beams 5 and advanced by conveyor 4 along path P, pass through baths 12, thereby undergoing a cleaning treatment.

[0051] Then, the containers 2 are conveyed through rinsing zone C3 wherein they are sprinkled with a rinsing fluid, normally clean fresh water.

[0052] Thus, the containers 2 are treated along washing path P both by immersion and by spraying a treatment fluid thereon.

[0053] To this end, washing machine 1 includes at least one, and in particular a plurality of, spraying devices 13 which are arranged (distributed) along the washing path P and are configured for spraying the containers 2 with a treatment fluid.

[0054] In particular, prewash zone C1 and rinsing zone C3 are provided with one or more spraying device 13.

[0055] For the sake of brevity, reference will be made in the following to a single spraying device 13. However, the structural and functional features described hereinafter for such spraying device may apply to all spraying devices of washing machine 1.

[0056] As better visible in Figure 2, spraying device 13 includes a main body 14, which extends along a central axis A parallel to the beams 5 and has a plurality of spraying nozzles (not shown), and an actuation wheel 15 mounted at an axial end of the main body 14.

[0057] In particular, the actuation wheel 15 is a star wheel and includes a plurality of radial arms 15a.

[0058] More in particular, the actuation wheel 15 is rigidly fixed to main body 14. In practice, actuation wheel 15 is rotationally integral with main body 14.

[0059] Each beam 5 comprises a pushing member 16, preferably mounted at an end portion thereof.

[0060] In particular, each pushing member 16 is defined by a shaped bracket which is rigidly mounted to the respective beam 5.

[0061] The pushing members 16 are configured to sequentially cooperate in contact with, and in other words to push, respective arms 15a of the actuation wheel 15, so that a linear motion of the pushing members 16 along the washing path P is transformed into a rotary motion of the actuation wheel 15 and of the main body 14 about the central axis A.

[0062] Therefore, spraying device 13 is a rotary spraying device.

[0063] This configuration is schematized in Figure 2.

[0064] Washing machine 1 further comprises a control unit (known per se and not shown).

[0065] According to a first aspect of the invention, washing machine 1 comprises a single sensor device 17 configured to sequentially detect the presence and position of each pushing member 16 within a detection section 18 along the washing path P.

[0066] In other words, as shown in Figure 2 and as schematized in Figure 3, detection section 18 is the area along washing path P wherein sensor device 17 detects the position / presence of pushing members 16.

[0067] More in particular, detection section 18 is arranged within a predetermined control area X (schematized in Figure 3) having a length (as measured along washing path P) corresponding with pitch K.

[0068] In detail, such control area X defines an area along washing path P along which the control performed by the control unit according to the present invention occurs, as better explained below.

[0069] Conveyor 4 comprises a motor (for example an electric motor, not shown) including an absolute encoder (known per se and not shown).

[0070] The encoder is configured to provide, for each pushing member 16, an integer number representative of the actual position of the pushing member 16 along the pitch K and within control area X.

[0071] More in detail, the integer number increments, in use, during advancing of the pushing member 16 along the pitch K, so that the integer number zeroes at the beginning of the control area X and reaches its maximum value at the end of control area X.

[0072] More precisely, when a pushing member 16 is advanced by conveyor 4 within control area X (which contains the detection section 18 as schematized in Figure 3), the integer number as provided by the encoder starts to increment, up to a maximum value reached when the pushing member 16 exits the control area X. Opportunely, as said, the control area X has a length along the washing path P which is equal to said pitch K.

[0073] At that point, being the length of control area X equal to pitch K, the successive pushing member 16 enters control area X, and therefore the integer number zeroes again.

[0074] This cycle is repeated sequentially for each pushing member 16.

[0075] According to an aspect of the invention, the control unit is configured to define a numeric main interval 19 representative of said pitch K and having a plurality of integer values representative of respective nominal positions of the pushing member 16 within the control area X.

[0076] For example, the integer values of main interval 19 range from 0 to 100.

[0077] Reference will be made in the following to a single pushing member 16 and to the detection of such single pushing member 16 by the sensor device 17.

[0078] According to a third aspect of the invention, the control unit is configured to: read the integer number provided by the encoder corresponding to the detected position of the pushing member 16 within the detection section 18; compare the read integer number with an expected nominal integer value of the main interval 19 representative of an expected nominal position of the pushing member 16 within the control area X.

[0079] Furthermore, according to another aspect of the invention, the control unit is configured to generate a warning signal if the read integer number differs from the nominal integer value.

[0080] In one embodiment, the control unit is configured to generate a stop signal for interrupting the advancement of the beams 5 along the washing path P if the read integer number differs from the nominal integer value.

[0081] Advantageously, the control unit defines at least one numeric sub-interval 20, 21 having a sub-plurality of integer values which is smaller than the plurality of integer values of the main interval 19, so that the sub-interval 20, 21 is comprised within the main interval 19.

[0082] As a non-limiting example, the integer values of the sub-interval 20, 21 may range from 20 to 30, or from 50 to 70.

[0083] Accordingly, the control unit is configured to: read the integer number provided by the encoder corresponding to the detected position of the pushing member 16 within the detection section 18; compare the read integer number with the sub-interval 20, 21 to check whether the read integer value is within the sub-interval 20, 21.

[0084] Conveniently, the control unit is configured to generate the warning signal or the stop signal if the read integer number is not within (i.e. is outside) the sub-interval 20, 21.

[0085] According to a preferred embodiment of the present invention, the control unit defines a first numeric sub-interval 20 having a first sub-plurality of integer values and a second encoder sub-interval 21 having a second sub-plurality of integer values, both the first and second sub-intervals 20, 21 being comprised within the main interval 19.

[0086] In detail, the first sub-plurality of integer values does not overlap the second sub-plurality of integer values.

[0087] In greater detail, the first sub-interval 20 does not overlap the second sub-interval 21.

[0088] More precisely, the highest integer value of the first sub-interval 20 is lower than the lowest integer value of the second sub-interval 21, so that, within the main interval 19, the first sub-interval 20 is upstream of the second sub-interval 21 with respect to the value of the integer values.

[0089] For example, the integer values of the first sub-interval may range from 20 to 30, whereas the integer values of the second sub-interval 21 may range from 50 to 70, the main interval 19 ranging from 0 to 100.

[0090] According to an aspect of the invention, the control unit is configured for: comparing the read integer number with the first sub-interval 20 to check whether the read integer number is within the first sub-interval 20; and comparing the read integer number with the second sub-interval 21 to check whether the read integer number is within the second sub-interval 21.

[0091] Furthermore, the control unit is advantageously configured to generate the warning signal or the stop signal if, in use, the read integer number is not within the first sub-interval 20.

[0092] Moreover, if in use the read integer number is in fact within the first sub-interval 20, the control unit is advantageously configured to generate the warning signal or the stop signal if the read integer number is not within the second sub-interval 21.

[0093] From the foregoing, it is clear how the washing machine 1 according to the present invention allows to implement a method for washing empty containers 2 adapted to contain a pourable product, the method comprising the steps of: a) advancing a series of beams 5 along a washing path P and through treatment zones C1, C2, C3, each beam 5 having a plurality of pockets 6 for receiving the containers 2, the beams 5 being spaced from one another by a fixed distance defining a pitch or step K of the series of beams 5 along the washing path P; b) spraying the containers 2 carried by the pockets 6 of each beam 5 with a treatment fluid by means of at least one rotary spraying device 13 including a main body 14, which extends along a central axis A parallel to the beams 5 and has a plurality of spraying nozzles, and an actuation wheel 15 mounted at an axial end of the main body 14; c) actuating the actuation wheel 15 in rotation by means of contact interaction of pushing members 16, carried each by a respective beam 5, with respective arms 15a of the actuation wheel 15, so that a linear motion of the pushing members 16 along the washing path P is transformed into a rotary motion of the actuation wheel 15 and of the main body 14 about the central axis A; wherein the method further comprises the steps of, for each pushing member 16: d) detecting the presence and position of the pushing member 16 within a detection section 18 along the washing path P by means of a sensor 17, the detection section 18 being arranged within a predetermined control area X having a length corresponding with said pitch K; e) defining a main numeric interval 19 representative of said pitch K and having a plurality of integer values representative of respective nominal positions of the pushing member 16 within the control area X; wherein the step a) of advancing comprises actuating a motor including an absolute encoder, the encoder being configured to provide an integer number representative of the actual position of the pushing member 16 along said pitch K and within the control area X, the integer number incrementing during advancing of the pushing member 16 along the pitch K, so that the integer number zeroes at the beginning of the control area X and reaches its maximum value at the end of the control area X; and wherein the method further comprises the steps of: f) reading the integer number provided by the encoder corresponding to the detection position of the pushing member 16 within the detection section 18 detected during the step d) of detecting; g) comparing the read integer number with an expected nominal integer value of the main interval 19 representative of an expected nominal position of the pushing member 16 within the control area X.

[0094] Conveniently, the method comprises the steps of: h) generating a warning signal if during the step g) of comparing the read integer number differs from the nominal integer value; and / or i) generating a stop signal for interrupting the step a) of advancing if during the step g) of comparing the read integer number differs from the nominal integer value.

[0095] Preferably, the method comprises the steps of: j) defining at least one numeric sub-interval 20, 21 having a sub-plurality of integer values which is smaller than the plurality of integer values of the main interval 19, so that the sub-interval 20, 21 is comprised within the main interval 19; k) reading the integer number provided by the encoder corresponding to the detection position of the pushing member 16 within the detection section 18 detected during the step d) of detecting; m) comparing the read integer number with the sub-interval 20, 21 to check whether the read integer number is within the sub-interval 20, 21.

[0096] Conveniently, the method comprises the step of: n) generating a warning signal, or a stop signal for interrupting the step a) of advancing, if during the step m) of comparing the read integer number is not within the sub-interval 20, 21.

[0097] According to a preferred embodiment of the invention, the step j) of defining includes defining a first numeric sub-interval 20 having a first sub-plurality of integer values and a second numeric sub-interval 21 having a second sub-plurality of integer values, both the first and second sub-intervals 20, 21 being comprised within the main interval 19, the first sub-plurality of integer values not overlapping the second sub-plurality of integer values; and wherein the step m) of comparing includes the steps of: m1) comparing the read integer number with the first sub-interval 20 to check whether the read integer number is within the first sub-interval 20; and m2) comparing the read integer number with the second sub-interval 21 to check whether the read integer number is within the second sub-interval 21.

[0098] Conveniently, the method comprises the step of: o) generating a warning signal, or a stop signal for interrupting the step a) of advancing, if during the step m1) of comparing the read integer number is not within the first sub-interval 20.

[0099] Conveniently, if during step m1) of comparing the read integer number is within the first sub-interval 20, the method further comprises the step of: p) generating a warning signal, or a stop signal for interrupting the step a) of advancing, if during the step m2) of comparing the read integer number is not within the second sub-interval 21.

[0100] Appropriately, the step m1) of comparing is performed prior to the step m2) of comparing.

[0101] Advantageously, the method may further comprise the steps of: q) detecting at least a quantity representative of an operative condition of the washing process; r) determining a quality level of the washing process based on the step q) of detecting; s) updating the extreme integer values of the sub-interval 20, 21 as a function of the quality level determined at step r) of determining.

[0102] Advantageously, the step d) of detecting is carried out by means of a single sensor device 17 arranged along the washing path P at said detection section 18.

[0103] The advantages of washing machine 1 and of the related method for washing containers according to the present invention will be clear from the foregoing description.

[0104] In particular, an effective control of the nominal condition and positioning of each pushing member 16 can be continuously performed, so that the risk of undesired jammings or impacts or damages is significantly reduced.

[0105] More precisely, a more precise check of the nominal condition of each pushing member 16 independently of the advancing speed of the beams 5 is performed.

[0106] In fact, thanks to such peculiar and advantageous control strategy, the control is based on the pitch K, which is clearly constant throughout the washing process, unlike the advancing speed of beams 5.

[0107] Moreover, the control of the nominal condition and positioning of each pushing member 16 can be performed not only effectively, as explained above, but also efficiently, since only a single sensor device 17 is needed.

[0108] In addition, since the check on the read integer number is advantageously performed relatively to intervals, and not to a punctual single value, the control takes into account for possible deformations and structural abnormalities in and between each pushing member 16, which are anyway within the accepted structural tolerances thereof.

[0109] In this way, repeated and undesired stops of the washing machine 1 can be avoided, thereby leading to a more streamlined washing process.

[0110] On the other hand, thanks to the effective control on each pushing member 16, if a pushing member 16 is structurally compromised well above the admitted structural tolerance range, the machine 1 is promptly stopped, thereby avoiding jammings and also damages on the other pushing members 16 or on the actuation wheels 15.

[0111] Moreover, since the sub-intervals 20, 21 are preferably updated based on the actual operative condition of the washing machine 1, the precision of the control is further improved and does not decrease with time and usage of the washing machine.

[0112] In addition, the control is highly flexible and adaptable to various formats of containers 2 and / or to different pitches K, since it is sufficient to vary the extension of the control area X adapting it to the new pitch K.

[0113] Clearly, changes may be made to washing machine 1 and to the related method as described herein without, however, departing from the scope of protection as defined in the accompanying claims.

Claims

1. Method for washing empty containers (2) adapted to contain a pourable product, the method comprising the steps of: a) advancing a series of beams (5) along a washing path (P) and through treatment zones (C1, C2, C3), each beam (5) having a plurality of pockets (6) for receiving the containers (2), the beams (5) being spaced from one another by a fixed distance (K) defining a pitch or step of the series of beams (5) along the washing path (P); b) spraying the containers (2) carried by the pockets (6) of each beam (5) with a treatment fluid by means of at least one rotary spraying device (13) including a main body (14), which extends along a central axis (A) parallel to the beams (5) and has a plurality of spraying nozzles, and an actuation wheel (15) mounted at an axial end of the main body (14); c) actuating the actuation wheel (15) in rotation by means of contact interaction of pushing members (16), carried each by a respective beam (5), with respective arms (15a) of the actuation wheel (15), so that a linear motion of the pushing members (16) along the washing path (P) is transformed into a rotary motion of the actuation wheel (15) and of the main body (14) about the central axis (A); wherein the method further comprises the steps of, for each pushing member (16): d) detecting the presence and position of the pushing member (16) within a detection section (18) along the washing path (P)by means of a sensor (17), the detection section (18) being arranged within a predetermined control area (X) having a length corresponding with said pitch (K); e) defining a main numeric interval (19) representative of said pitch (K) and having a plurality of integer values representative of respective nominal positions of the pushing member (16) within the control area (X); wherein the step a) of advancing comprises actuating a motor including an absolute encoder, the encoder being configured to provide an integer number representative of the actual position of the pushing member (16) along said pitch (K) and within the control area (X), the integer number incrementing during advancing of the pushing member (16) along the pitch (K), so that the integer number zeroes at the beginning of the control area (X) and reaches its maximum value at the end of the control area (X); and wherein the method further comprises the steps of: f) reading the integer number provided by the encoder corresponding to the detection position of the pushing member (16) within the detection section (18) detected during the step d) of detecting; g) comparing the read integer number with an expected nominal integer value of the main interval (19) representative of an expected nominal position of the pushing member (16) within the control area (X).

2. Method as claimed in claim 1, and comprising the step of: h) generating a warning signal if during the step g) of comparing the read integer number differs from the nominal integer value.

3. Method as claimed in claim 1 or 2, and comprising the step of: i) generating a stop signal for interrupting the step a) of advancing if during the step g) of comparing the read integer number differs from the nominal integer value.

4. Method as claimed in any of the preceding claims, and comprising the steps of: j) defining at least one numeric sub-interval (20, 21) having a sub-plurality of integer values which is smaller than the plurality of integer values of the main interval (19), so that the sub-interval (20, 21) is comprised within the main interval (19); k) reading the integer number provided by the encoder corresponding to the detection position of the pushing member (16) within the detection section (18) detected during the step d) of detecting; m) comparing the read integer number with the sub-interval (20, 21) to check whether the read integer number is within the sub-interval (20, 21).

5. Method as claimed in claim 4, and comprising the step of: n) generating a warning signal, or a stop signal for interrupting the step a) of advancing, if during the step m) of comparing the read integer number is not within the sub-interval (20, 21).

6. Method as claimed in claim 4 or 5, wherein the step j) of defining includes defining a first numeric sub-interval (20) having a first sub-plurality of integer values and a second numeric sub-interval (21) having a second sub-plurality of integer values, both the first and second sub-intervals (20, 21) being comprised within the main interval (19), the first sub-plurality of integer values not overlapping the second sub-plurality of integer values; and wherein the step m) of comparing includes the steps of: m1) comparing the read integer number with the first sub-interval (20) to check whether the read integer number is within the first sub-interval (20); and m2) comparing the read integer number with the second sub-interval (21) to check whether the read integer number is within the second sub-interval (21).

7. Method as claimed in claim 6, and comprising the step of: o) generating a warning signal, or a stop signal for interrupting the step a) of advancing, if during the step m1) of comparing the read integer number is not within the first sub-interval (20).

8. Method as claimed in claim 7, wherein, if during step m1) of comparing the read integer number is within the first sub-interval (20), the method further comprises the step of: p) generating a warning signal, or a stop signal for interrupting the step a) of advancing, if during the step m2) of comparing the read integer number is not within the second sub-interval (21).

9. Method as claimed in any of the claims 6 to 8, wherein the highest integer value of the first sub-interval (20) is lower than the lowest integer value of the second sub-interval (21), so that, within the main interval (19), the first sub-interval (20) is upstream of the second sub-interval (21) with respect to the value of the integer values.

10. Method as claimed in any of the claims 6 to 9, wherein the step m1) of comparing is performed prior to the step m2) of comparing.

11. Method as claimed in any one of the claims 4 to 10, and comprising the steps of: q) detecting at least a quantity representative of an operative condition of the washing process; r) determining a quality level of the washing process based on the step q) of detecting; s) updating the extreme integer values of the sub-interval (20, 21) as a function of the quality level determined at step r) of determining.

12. Method as claimed in any one of the foregoing claims, wherein the step d) of detecting is carried out by means of a single sensor device (17) arranged along the washing path (P) at said detection section (18).

13. Washing machine (1) configured to wash empty containers (2) adapted to be filled with a pourable product, the washing machine (1) comprising: - a series of beams (5) distributed along a washing path (P) and spaced from one another by a fixed distance (K) defining a pitch or step of the series of beams (5) along the washing path (P), each beam (5) having a plurality of pockets (6) for receiving the containers (2) and carrying a pushing member (16); - at least one rotary spraying device (13) for spraying the containers (2) with a treatment fluid, the spraying device (13) being arranged along the washing path (P) and including a main body (14), which extends along a central axis (A) parallel to the beams (5) and has a plurality of spraying nozzles, and an actuation wheel (15) mounted at an axial end of the main body (14); wherein the pushing members (16) are configured to sequentially cooperate in contact with respective arms (15a) of the actuation wheel (15), so that a linear motion of the pushing members (16) along the washing path (P) is transformed into a rotary motion of the actuation wheel (15) and of the main body (14) about the central axis (A) ; - a single sensor device (17) configured to sequentially detect the presence and position of each pushing member (16) within a detection section (18) along the washing path (P), the detection section (18) being arranged within a predetermined control area (X) having a length corresponding with said pitch (K); - a conveyor (4) configured to advance the beams (5) along the washing path (P), the conveyor (4) comprising a motor including an absolute encoder, the encoder being configured to provide, for each pushing member (16) an integer number representative of the actual position of the pushing member (16) along said pitch (K) and within the control area (X), the integer number incrementing during advancing of the pushing member (16) along the pitch (K), so that the integer number zeroes at the beginning of the control area (X) and reaches its maximum value at the end of the control area (X); - a control unit; wherein the control unit is configured to: - define a numeric main interval (19) representative of said pitch (K) and having a plurality of integer values representative of respective nominal positions of the pushing member (16) within the control area (X); - read the integer number provided by the encoder corresponding to the detected position of the pushing member (16) within the detection section (18); - compare the read integer number with an expected nominal integer value of the main interval (19) representative of an expected nominal position of the pushing member (16) within the control area (X).

14. Washing machine as claimed in claim 13, wherein the control unit defines at least one numeric sub-interval (20, 21) having a sub-plurality of integer values which is smaller than the plurality of integer values of the main interval (19, so that the sub-interval (20, 21) is comprised within the main interval (19); and wherein the control unit is configured to: - read the integer number provided by the encoder corresponding to the detected position of the pushing member (16) within the detection section (18); - compare the read integer number with the sub-interval (20, 21) to check whether the read integer number is within the sub-interval (20, 21).

15. Washing machine as claimed in claim 14, wherein the control unit defines a first numeric sub-interval (20) having a first sub-plurality of integer values and a second numeric sub-interval (21) having a second sub-plurality of integer values, both the first and second sub-intervals (20, 21) being comprised within the main interval (19), the first sub-plurality of integer values not overlapping the second sub-plurality of integer values; and wherein the control unit is configured for: - compare the read integer number with the first sub-interval (20) to check whether the read integer number is within the first sub-interval (20); and - comparing the read integer number with the second sub-interval (21) to check whether the read integer number is within the second sub-interval (21).

16. Washing machine as claimed in claim 15, wherein the control unit is configured to generate a warning signal, or a stop signal for interrupting the advancement of the beams along the washing path, if in use the read integer number is not within the first sub-interval (20); and wherein, if in use the read integer number is within the first sub-interval (20), the control unit is configured to generate a warning signal, or a stop signal for interrupting the advancement of the beams (5) along the washing path (P), if the read integer number is not within the second sub-interval (21).

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