Method for rejecting products

Abstract

A method for rejecting products comprising the steps of: conveying the products along a conveyance line (2); inspecting the products in transit along the conveyance line (2); removing a first product having at least one defect detected during the inspection of the products; wherein the step of removing the first product comprises the step of hitting said first product with a fluid jet delivered by a first nozzle (31) controlled by a first solenoid valve (41); the step of hitting the first product being determined by a removal procedure comprising in turn the following steps: making electric current pass through an electric conductor (410) in the first solenoid valve (41) and which opens a switch (411) that alternatively would prevent the passage of a fluid flow through the first solenoid valve (41);-making the fluid flow pass through the first solenoid valve (41); the step of making the fluid flow pass through the first solenoid valve (41) placing the fluid flow in thermal contact with said conductor (410) to cool or heat it; performing a diagnostic check to verify the actual passage of the fluid flow through the first solenoid valve (41); wherein the step of performing said diagnostic check comprises the sub-step of determining a parameter associated with a temperature of the conductor (410) of the first solenoid valve (41).

Description

[0001] DESCRIPTION METHOD FOR REJECTING PRODUCTS

[0002] Technical field

[0003] The object of the present invention is a method for rejecting products having any defects.

[0004] Prior art

[0005] Solutions are known illustrating a conveyance line for conveying products along which inspection means for inspecting the products to search for a detectable defect are arranged.

[0006] Along the transport line, downstream of the inspection means, the products undergo a jump and, while they are airborne, pass underneath a plurality of nozzles positioned side by side. The nozzles are controlled by the inspection means. They are capable of delivering a fluid jet in the direction of a product having a defect. By hitting the product, this jet causes a diversion in trajectory and the product is therefore recovered and rejected.

[0007] Each nozzle is fed by a corresponding solenoid valve located upstream. Each solenoid valve comprises an electromagnet which, if electrically powered, allows the feed to the corresponding nozzle downstream to be opened. Control systems that check electrically whether the solenoid valve has opened are known.

[0008] A drawback of such a solution is linked to the fact that the operator does not have feedback on the actual passage of air through the solenoid valve which could possibly even open to no purpose. For example, blockages present along the line upstream would not be detectable. Opening of the solenoid valve would therefore not effectively be associated with passage of a gaseous flow.

[0009] Object of the invention

[0010] The object of the present invention is to provide a rejection method that allows simple and effective diagnostics.

[0011] The technical task set and the objects specified are substantially attained by a method comprising the technical features as set out in one or more of the appended claims.

[0012] Brief description of the drawings

[0013] Further features and advantages of the present invention will become more apparent from the indicative and thus non-limiting description of a preferred but non-exclusive embodiment of a method as illustrated in the appended drawings, in which:

[0014] - Figure 1 shows a schematic view of a system implementing the method according to the present invention;

[0015] - Figure 2 shows a detail of the system of Figure 1 .

[0016] Detailed description of preferred embodiments of the invention

[0017] The object of the present invention is a method for rejecting products. The products are, for example, food products, such as vegetables or fruit. However, they could also be non-food products. Application to food products is particularly important, as they are perishable products.

[0018] Such method comprises the step of conveying the products along a conveyance line 2. For example, such conveyance line 2 can comprise one or more conveyors. The conveyance line 2 also defines one or more jumps along which the product is not directly supported by a supporting element. In this / these zone / s, the product is “falling” through the air (see dashed portion in Figure 1 ).

[0019] The method comprises the step of inspecting the products in transit along the conveyance line 2.

[0020] The step of inspecting the products occurs through visual inspection means 6, typically video cameras and / or spectroscopic analysis means. In this regard, advantageously the conveyance line 2 comprises a conveyor (for example a conveyor belt) and the visual inspection means 6 surmounts such conveyor.

[0021] The method comprises the step of removing a first product having at least one defect detected in the step of inspecting the products. The first product forms part of said products. The step of removing the first product provides for removing said first product from the conveyance line 2. In particular, this occurs at an end section of the conveyance line 2 (at the jump).

[0022] The step of removing the first product comprises the step of delivering a fluid jet from a first nozzle 31 to divert the trajectory of said first product. The step of delivering the fluid jet from the first nozzle 31 is controlled by a first solenoid valve 41 . The first solenoid valve 41 is, in fact, interposed between a pressurised sleeve and the first nozzle 31 .

[0023] The fluid jet is typically a pressurised gaseous jet. By interacting with the first product, the fluid jet determines a diversion thereof with respect to the planned trajectory. Consequently, the first product can be recovered in a rejection zone 21 to which the rejected products are directed. The nonrejected products, on the other hand, will be in a receiving zone 22 (which is typically a collection zone). The zone 22 is usually the end of the conveyance line 2. The zone 21 and the zone 22 are located underneath the jump, in an end zone of the conveyance line 2.

[0024] In the preferred solution, a battery 40 of aligned nozzles is present along the conveyance line 2 (in particular at the end thereof). The nozzles typically extend along a straight line oriented along a direction transverse to the conveyance line 2. Advantageously, from 96 to 288 side-by-side nozzles are present. Based on the information detected by the step of inspecting the products, the nozzle / s suited to removing the product concerned is / are activated. The first nozzle 31 forms part of the battery 40. The step of delivering a fluid jet from the first nozzle 31 is determined by a procedure comprising in turn a step of modifying the transit of electric current through an electric conductor 410 which is present in the first solenoid valve 41. Said conductor 410 is responsible for whether or not there is the passage of the fluid flow through the first solenoid valve 41 .

[0025] Modifying the transit of electric current provides for making an electric current transit through an electric conductor 410 present in the first solenoid valve 41. The conductor 410, if crossed by a suitable electric current, generates an electromagnetic field. The conductor 410 (if crossed by a suitable electric current) therefore opens a switch 411 that alternatively prevents the passage of the fluid flow through the first solenoid valve 41 .

[0026] The conductor 410 is typically a solenoid. Opportunely, an air gap is present inside the coils of the solenoid.

[0027] The conductor 410 comprises / defines an electromagnet which is energised to move said switch 411 and allow the passage of the fluid flow through the first solenoid valve 41 . Energising the electromagnet provides for the passage of electric current in the conductor 410.

[0028] In particular, the first solenoid valve 41 can comprise an inlet 401 for the fluid, a zone 402 for housing the conductor 410, an outlet 403 for the fluid. Opportunely, said switch 411 is intended to occlude the outlet 403 for the fluid.

[0029] The switch 411 is a shutter. Typically, the switch 411 comprises a metal element. Advantageously, the switch 411 comprises fluid dynamic sealing means 404 which prevent the transit of the fluid flow (or rather, prevent the fluid flow from entering the outlet 403). The fluid dynamic sealing means 404 comprises, for example, a gasket located on the metal element. The sealing means 404 comprises, in particular, a rubber portion applied onto the metal element. Opportunely, the switch 411 (or rather, the metal element) comprises a blade. This has a constrained portion and a cantilevered portion. The cantilevered portion is moved by the conductor 410. The constrained portion is intended to remain fixed.

[0030] When energised, the conductor 410 moves the cantilevered portion of the switch 411 , taking it into a configuration in which it allows the passage of a fluid flow. If not energised, the switch 411 is in a configuration in which it prevents the transit of the fluid flow through the first solenoid valve 41 . In particular, elastic means 405 (a spring) can be present which presses on the switch 411 so as to occlude the outlet 403 of the fluid.

[0031] The method comprises a step of making the fluid flow pass through the first solenoid valve 41 .

[0032] The step of making the fluid flow pass through the first solenoid valve 41 places the fluid flow in thermal contact with said conductor 410 to cool or heat it. Passage of the fluid flow usually determines cooling of the conductor 410. The conductor could, however, also be located in a cold environment (for example, in a controlled temperature environment) and the fluid flow taken from an environment in which the temperature is higher; in that case, the passage of the fluid flow determines a heating of the conductor 410. The step of placing the fluid flow in thermal contact with the conductor 410 can occur by placing in contact and lapping the conductor 410 directly with the fluid flow, or indirectly (for example, by transferring the heat with interposed elements).

[0033] The above method (or possibly the procedure) also provides for verifying the actual passage of the fluid flow through the first solenoid valve 41 . This is therefore a case of performing a diagnostic check. The step of verifying the actual passage of the fluid flow through the first solenoid valve 41 comprises a sub-step of determining a parameter associated with a temperature of the conductor 410 of the first solenoid valve 41. In this description, the expression “determining a parameter associated with” means the value of said parameter.

[0034] The step of verifying the actual passage of the fluid flow through the first solenoid valve 41 provides, in fact, for determining the variation in temperature of the conductor 410 induced by passage of the fluid flow through the first solenoid valve 41 . In fact, the pressurised fluid flow, by passing inside the first solenoid valve 41 , determines the cooling of the conductor 410 (or its heating, as explained above).

[0035] The step of determining a parameter associated with a temperature of the conductor 410 of the first solenoid valve 41 comprises the step of determining an electrical quantity. In particular, an electrical quantity of the conductor 410. Such electrical quantity could be:

[0036] - an electrical resistance of the conductor 410 of the first solenoid valve 41 (or a parameter associated with the electrical resistance of the conductor 410); or

[0037] - the voltage across the conductor 410 maintaining a constant intensity of the electric current through the conductor 410 (or a parameter associated with said voltage); based on Ohm's law, the voltage across the conductor 410 is equal to the product of the resistance of the conductor and the current intensity. Therefore, if the current intensity (maintained constant) is known and the voltage across the conductor 410 is read, the resistance is immediately known.

[0038] The electrical resistance of the conductor 410 is, in fact, variable with the temperature. Therefore, the electrical resistance of the conductor 410 is associated with the temperature of the conductor 410.

[0039] The step of determining the parameter associated with a temperature of the conductor 410 is performed by an electronic central control unit 5 as a function of said electrical quantity and of the temperature of the fluid flow. In fact, a higher or lower temperature of the fluid flow will vary to a lower or higher extent the temperature of the conductor 410 and this consequently also influences the resistance assumed instantaneously by the conductor 410.

[0040] The method further comprises the step of comparing such parameter or such electrical quantity with predetermined values. This is to check for any anomalies if such electrical quantity were to have values outside the expected ranges.

[0041] In addition or as an alternative, the step of verifying the actual passage of the fluid flow through the first solenoid valve 41 comprises the sub-step of comparing said parameter associated with the temperature of the conductor 410 with a same parameter determined for solenoid valves associated with corresponding nozzles arranged in a row with said first nozzle 31. One or more of the features or operating methods indicated above for the first solenoid valve 41 can also be repeated for the other solenoid valves. Said solenoid valves form part of the same battery 40. For example, it is possible to compare the electrical resistance (or a parameter associated with the electrical resistance) of the conductor 410 of the first nozzle 31 in a given instant with the electrical resistance or a parameter associated with the electrical resistance of the conductor which determines the opening of the solenoid valves associated with the corresponding nozzles arranged in a row with said first nozzle 31. In this manner, any deviations between the values of one nozzle and those of the others can be identified. Such a condition is probably associated with an anomaly.

[0042] The step of determining the electrical quantity of the first solenoid valve 41 occurs with the switch 411 which allows passage of the fluid. In other words, the aforementioned electrical quantity is determined simultaneously with delivery of the fluid flow.

[0043] The step of performing a diagnostic check therefore occurs simultaneously with at last a part of the passage of the flow through the first solenoid valve 41 .

[0044] In the preferred version, the step of determining the electrical quantity of the first solenoid valve 41 associated with passage of the fluid flow takes place only during a first portion of the time associated with the stroke of the switch 411 ; said first portion excluding an initial length, evaluated in time, of the stroke of the switch 411 . This is to avoid any initial current peaks that occur at the start of the stroke of the switch 411 .

[0045] In summary, operation of a particular solution according to the present invention provides for the following:

[0046] - conveying the products along a conveyance line 2;

[0047] - identifying, by means of the inspection means 6, a first product having a defect;

[0048] - delivering a fluid jet to remove said first product; this occurring while the first product is falling, in an end zone of the conveyance line 2;

[0049] - recovering the first product in a rejection zone 21 separate from a zone 22 towards which the products without defects are directed (in the absence of intervention of a fluid jet). What is described for the first product can also be repeated for the other products. A first nozzle 31 intervenes to remove the first product; in order to remove any other products having defects, the first nozzle 31 can intervene again or other nozzles of the same battery 40.

[0050] In order to ensure that the first nozzle 31 actually delivers the fluid jet correctly, a control is performed on the temperature of an electric conductor 410 responsible for opening the first solenoid valve 41 . In fact, if the first solenoid valve 41 is crossed by the gaseous fluid, there is a variation in the temperature thereof, due to passage of the fluid (typically a cooling). In this regard, the first solenoid valve 41 is shaped to allow thermal contact between the conductor 410 and the gaseous fluid. An electric quantity is therefore measured in order to determine a parameter associated with the temperature of the conductor 410. Such electric quantity is measured with a dedicated circuit or by using Ohm's law (measuring the voltage at constant current). The result is then compared with expected predetermined values or with values detected for the adjacent nozzles. Clear misalignments therefore signal an anomaly.

[0051] The present invention achieves important advantages.

[0052] In the first place, it allows any malfunctions that prevent actual delivery of the fluid jet, independently or not of opening of the solenoid valve, to be detected. In fact, at the first solenoid valve, there could be an insufficient flow rate due to blockages of the nozzle, intrusions of foreign bodies, blockage of the conduits, manufacturing defects of the solenoid valve or the conduits, oxidation of the ferromagnetic parts due to inclusions of humidity by the nozzle and of air that is not perfectly dried and coming from the factory network.

[0053] A further important advantage is linked to optimisation of the number of components needed and consequently the associated overall dimensions. The information is, in fact, obtained without needing a complex circuit board and a sensor for measuring the flow rate. It is, in fact, sufficient to measure the voltage across the conductor 410 when the solenoid valve is operated at constant current.

[0054] Furthermore, the system could be used to signal an excessive overheating of a solenoid valve. In this regard, at least two types of electromagnets are known (which form part of the first solenoid valve referred to above):

[0055] 1) those that operate with a fixed voltage for the entire excitation time; and

[0056] 2) those that operate with two different voltages, a higher one for switching it on and a lower one for maintaining it switched on.

[0057] Type 2 equips high-speed solenoid valves, those that are normally used in electronic selectors. Type 1 electromagnets, although slower, also continue to operate with a lower voltage once they are switched on. This aspect can be exploited to reduce consumption. Type 2 electromagnets, if controlled incorrectly or too frequently, can be subject to melting of the insulator of the coils, and consequently to a short circuit or to melting of the internal plastic parts, due to the higher dissipated power caused by the lower electrical resistance of the winding. The present invention would allow, in both cases, the status to be checked and both overheating and irreversible damage to be prevented.

[0058] A further advantage could be that of using software based on artificial intelligence to concatenate the various pieces of information available with each other.

[0059] The invention thus conceived is susceptible of numerous modifications and variants, all falling within the scope of the inventive concept that characterises it. Moreover, all the details may be replaced by other technically equivalent elements. All the materials used, as well the dimensions, may in practice be any whatsoever, according to needs.

Claims

CLAIMS1 .A method for rejecting products comprising the steps of: i) conveying the products along a conveyance line (2); ii) inspecting the products in transit along the conveyance line (2); iii) removing a first product having at least one defect detected during the inspection of the products; the step of removing the first product comprising the step of delivering a fluid jet from a first nozzle (31 ) to divert the trajectory of said first product; the step of delivering the fluid jet from the first nozzle (31 ) being controlled by a first solenoid valve (41 ); the step of delivering a fluid jet from the first nozzle (31 ) being determined by a procedure comprising in turn the following steps:-modifying the transit of electric current through an electric conductor (410) which is present in the first solenoid valve (41) and which is responsible for whether or not there is a passage of a fluid flow through the first solenoid valve (41 );-making the fluid flow pass through the first solenoid valve (41 ); the step of making the fluid flow pass through the first solenoid valve (41 ) placing the fluid flow in thermal contact with said conductor (410) to cool or heat it; iv) verifying the actual passage of the fluid flow through the first solenoid valve (41 ); the step of verifying the actual passage of the fluid flow through the first solenoid valve (41 ) comprising a sub-step of determining a parameter associated with a temperature of the conductor (410) of the first solenoid valve (41 ).

2. The method according to claim 1 , characterised in that the step of determining said parameter associated with a temperature of the conductor (410) of the first solenoid valve (41 ) comprises the step of determining an electrical quantity.

3. The method according to claim 2, characterised in that said electrical quantity is:- an electrical resistance of the conductor (410) of the first solenoid valve (41 ); or- a voltage across the conductor (410), maintaining a constant intensity of the electric current through the conductor (410).

4. The method according to claim 2 or 3, characterised in that the step of determining said parameter associated with said temperature of the conductor (410) of the first solenoid valve (41 ) is performed by an electronic central control unit (5) as a function of said electrical quantity and of the temperature of the fluid.

5. The method according to claim 2 or 3 or 4, characterised in that the step of determining said electric quantity takes place with the switch (411 ) allowing the passage of the fluid.

6. The method according to any one of claims 2 to 5, characterised in that the step of determining said electric quantity takes place simultaneously with at least a part of the passage of the fluid flow through the first solenoid valve (41 ).

7. The method according to any one of claims 2 to 6, characterised in that the step of determining said electric quantity takes place only during a portion of the time in which the stroke of the switch (411 ) takes place; said portion excluding an initial length of the stroke of the switch (411 ).

8. The method according to any one of the preceding claims, characterised in that the step of verifying the actual passage of the fluid flow through the first solenoid valve (41 ) comprises a sub-step of comparing said parameter associated with the temperature of the conductor (410) with predetermined values.

9. The method according to any one of the preceding claims, characterised in that the step of verifying the actual passage of the fluid flow through the first solenoid valve (41 ) comprises the sub-step of comparing said parameter associated with the temperature of the conductor (410) with a same parameter determined for solenoid valves associated with corresponding nozzles arranged in a row with said first nozzle (31 ).

10. The method according to any one of the preceding claims,characterised in that said conductor (410) is a solenoid and defines an electromagnet which is energised to move said switch (411 ) and allow the passage of the fluid flow through the first solenoid valve (41 ).

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