Filling machine for food products in cans, particularly of the type with product density control

Abstract

A filling machine for food products in cans, including a supporting frame which forms a chamber and a feeding tunnel which is adapted to convey a food product into the chamber that is provided with a plunger which can move along the chamber, along a predefined compression direction; the chamber being provided with an expulsion piston configured to move transversely with respect to the compression direction for the expulsion of at least one preset shape in the direction of a station for canning the food product; a motor being provided which is associated with the plunger for a movement along the compression direction; and elements for measuring the density of the food product compressed in the chamber in order to control the driving torque of the motor as a function of the achievement of a predetermined density value.

Description

[0001] The present invention relates to a filling machine for food products in cans, particularly of the type with product density control.

[0002] In the field of food product canning, both for humans and for animals, automatic machines are known which are used for processing the food product and for its subsequent packing into metal boxes and / or cans in tablet form.

[0003] These filling machines have the particularity of performing the cutting, forming, compression and canning operations in a single process. This process is pre-configured by the operator and takes place without discontinuities within a single operating station constituted by the machine itself.

[0004] This allows to have the fastest possible transformation of the food product, for example tuna, salmon, and chicken, whether pre-cooked fillet products or precooked quarters of food products cleaned, frozen and wrapped in a shrink-wrap film, into tablets contained in metal boxes.

[0005] At the outlet of the machine there are metal boxes containing the food product tablets ready to be subjected to the subsequent steps: addition of seasonings, preserving liquid, seaming, and finally sterilization.

[0006] Currently, particularly in the tuna canning sector, most filling machines use a mechanical cam system, coupled with a spring, with a pneumatic system or with an actuator, in order to achieve a thrust value that is predetermined by the operator.

[0007] In greater detail, by means of a plunger connected to the systems mentioned above, the thrust value predetermined by the operator is reached in order to compress the food product inside a chamber, forming the tablets.

[0008] Only the predetermined value of the thrust can be changed, and only manually, by the operator who, due to the speed of the machine, has no control over the individual cycle. This does not allow to have the precise control over the density of the product.

[0009] During this step, in order to obtain a good efficiency of the machine, a greater quantity of product than actually needed to form the tablets is “loaded” into the compression chamber. In this manner the excess product is subjected to various compressions before being transformed into a tablet and then inserted in the box.

[0010] Such filling machines of the known type are not free from drawbacks, which include the fact that these very compressions pulp and squeeze the product, compromising its quality and lowering the performance of said machine.

[0011] Another drawback of filling machines of the known type resides in that they entail variations of the weight of the canned tablets due to the generation of a slurry that causes the compression plunger to stick, lowering the efficiency, known in the jargon as “pasting”; to speed variations of the machine that change the inertia forces acting on the product, which, added to the increased compression time, cause liquid to leak out, known in the jargon as “squeeze loss”; and / or to mechanical wear, especially in systems provided with a pneumatic cylinder, intense work cycles produce early wear of the seals.

[0012] A further drawback of filling machines of the known type is the impossibility to vary and / or control the thrust at each individual cycle, thus generating the problems described above and not allowing furthermore to have active control over the density of the product converted into a tablet because it is not possible to vary and / or control the thrust value of the plunger at each individual cycle.

[0013] All these drawbacks are inherent in the “cam +cylinder” or “cam +spring” or “actuators” mechanisms, since these mechanisms work by following a mechanical rule of motion, which is determined by the cam, and impart the thrust value predetermined by the operator, compressing the product throughout the operating cycle, regardless of the amount of residual product left in the compression chamber, thereby continuing to squeeze and / or overcompress said product, compromising its quality.

[0014] The aim of the present invention is to provide a filling machine for food products in cans that is capable of obviating the drawbacks described above.

[0015] Within this aim, an object of the present invention is to provide a filling machine capable of controlling the thrust of the plunger at each individual cycle and thus avoiding squeezing and / or over-compression of the food product and, consequently, ensuring the uniform quality of the canned product.

[0016] Another object of the present invention is to provide a filling machine capable of obtaining tablets of constant density, regardless of the mechanism of the cam.

[0017] Another object of the present invention is to provide a filling machine that uses per se known technologies and is thus economically competitive.

[0018] This aim and these and other objects that will become better apparent hereinafter are achieved by a filling machine for food products in cans, particularly of the type with product density control, comprising a supporting frame which forms a chamber and a feeding tunnel which is adapted to convey a food product or the like into said chamber; said chamber being provided with a plunger which can move along said chamber, along a predefined compression direction, between a bottom dead center position, in which said chamber is free from said plunger in order to feed said food product or the like into said chamber, and a top dead center position, in which said plunger occupies at least partially said chamber for the compression of said food product or the like into at least one preset shape; said chamber being provided with at least one expulsion piston which can move transversely with respect to said compression direction for the expulsion of said at least one preset shape in the direction of a station for canning said food product or the like; motor means being further comprised which are associated with said plunger for its movement along said compression direction; characterized in that it comprises means for measuring the density of said food product or the like compressed in said chamber in order to control the driving torque of said motor means as a function of the achievement of a predetermined density value.

[0019] Further characteristics and advantages will become better apparent from the description of a preferred but not exclusive embodiment of a filling machine for food products in cans, particularly of the type with product density control, illustrated by way of non-limiting example with the aid of the accompanying drawings, wherein:

[0020] FIG. 1 is an exploded perspective view of the internal components of a filling machine according to the present invention;

[0021] FIG. 2 is a chart which plots the position and torque curves of the plunger of the filling machine shown in FIG. 1, without the product in the chamber;

[0022] FIG. 3 is a chart which plots the position and torque curves of the plunger of the filling machine shown in FIG. 1, with the product in the chamber;

[0023] FIG. 4 is a block diagram of the control logic of the filling machine.

[0024] With particular reference to FIG. 1, the filling machine for food products in cans, particularly of the type with product density control, generally designated by the reference numeral 1, comprises a supporting frame, not shown for the sake of graphic simplicity, which forms a chamber 2 and a feeding tunnel 3 which is adapted to convey a food product or the like 4 into the chamber 2.

[0025] In greater detail, the supporting frame comprises two lateral guides 5 and 6 that delimit laterally the chamber 2 inside which a plunger 7 slides, along a predefined compression direction 8, between a bottom dead center position PMI, in which the chamber 2 is free from the plunger 7 in order to feed the food product or the like 4 into the chamber 2, and a top dead center position “PMS”, in which the plunger 7 occupies at least partially the chamber 2 for the compression of the food product or the like 4 into at least one preset shape, called in the jargon “tablet”.

[0026] Conveniently, the plunger 7 is associated with motor means 9 for its movement along the compression direction 8.

[0027] In greater detail, said motor means 9 comprise a mechatronic system constituted by a control unit 31 (MAC or PLC or the like), on which dedicated software is installed which contains an algorithm developed for this purpose, which manages a rotary servo motor of the brushless type 10 provided with an encoder 34, and a high-performance speed reduction unit 11 such as, for example, a constant-speed globoid cam positioning device, an epicyclic reduction unit or the like, and are associated with the plunger 7 by means of a first rod-and-crank mechanism 12.

[0028] According to the invention, the filling machine 1 comprises means 30 for measuring the density of the food product or the like 4 compressed in the chamber 2 in order to control the driving torque of the motor means 9, which are capable of detecting actively, during the compression step of each individual cycle, the density of the product and of adjusting accordingly the thrust values in order to achieve the predetermined density value.

[0029] More specifically, the density measuring means 30 comprise a distributed control architecture wherein the control unit 31 is connected to a servo-actuator 32 provided with a dedicated memory 32a for processing in real time.

[0030] The control occurs by way of mode switching: a first stage of position control for rapid approach, and a second stage of torque control managed directly by a program resident in the memory of the servo-actuator 32.

[0031] The arrest of the plunger 7 is determined by the detection of a peak of current absorbed by the servomotor 10 upon contact of the plunger with the product, so ensuring an immediate response time which prevents over-compression. So, in substance, once the density of the product has been set, the control unit 31 intervenes at each cycle by checking and adjusting the thrust of the motor means 9 so that when the desired density has been reached the thrust stops, locking and maintaining the plunger in position.

[0032] In order to determine the correct thrust value of the motor means 9 for reaching the desired density, various parameters are monitored including, by way of non-limiting example, the force, the position, the time, the frictions, the temperature and the inertias of the operating cycle.

[0033] The means for measuring 30 are a distributed mechatronic system:

[0034] Control Hardware: The system comprises the PLC connected to the servo-actuator which is provided with local memory.

[0035] Measurement Components: Measurement of torque (and therefore of density) occurs by real-time monitoring of the current absorbed by the brushless servomotor 10 and by the memory 32a of the servo-actuator 32 in order to ensure execution in real-time.

[0036] The encoder 34 integrated in the servomotor 10 makes it possible to read the position and speed and, by means of the servo-actuator 32, to correlate these data with the absorbed current.

[0037] Program Distribution: The partial allocation of the program in the servo-actuator 32 is an essential technical characteristic to minimize latency times, enabling a level of control of the response speed that a standard PLC cannot provide.

[0038] The architecture described enables:

[0039] Position to Torque: the present method entails a step of acceleration in the position control stage, followed by a dynamic switching in the torque control stage once operating speed is reached.

[0040] Dynamic Product Detection: The “stop” command is not based on a fixed position, but on the variation in the absorbed current at the exact moment when the plunger meets the product 4.

[0041] Real-Time Execution: Using the memory 32a of the servo-actuator 32 to execute the stop commands eliminates the PLC scan delays, so ensuring that the set density is achieved with a precision to one tenth of a millimeter, avoiding over-compression.

[0042] The measurement is an intrinsic function of the servo-actuator hardware, which acts as a virtual sensor, analyzing the current of the brushless motor 10 in real time.

[0043] The transition from position control to torque control during the same cycle is a key characteristic of the present invention.

[0044] The latency of communication between a PLC and a motor (typical of the prior art) would impede the immediate arrest required in order not to damage the delicate product 4. Using the servo-actuator memory for the arrest is the specific technical solution to a latency problem.

[0045] In this manner, the drawbacks of known machines are eliminated, since the invention allows to have the active control of the thrust of the plunger at each cycle, ensuring the achievement of the desired density and, consequently, a qualitatively superior product.

[0046] Advantageously, the chamber 2 is delimited, on the opposite side with respect to the plunger 7 proximate to the top dead center, by an abutment element 13 which is contoured, on the side directed toward the inside of the chamber 2, with a geometric profile 14 which reproduces in negative form a portion of said at least one preset shape or tablet.

[0047] Furthermore, the chamber 2 is provided with at least one expulsion piston 15 which can move transversely with respect to the compression direction 8 for the expulsion of said at least one preset shape or tablet in the direction of a station for canning the food product or the like 4.

[0048] More specifically, in the proposed embodiment, the abutment element 13 is shaped in order to define at least two preset shapes or tablets, and there are at least two expulsion pistons 15 which correspond to said geometric profile 14 of the abutment element 13.

[0049] In a variation of the proposed embodiment that is not shown, the abutment element 13 can be shaped to form multiple preset shapes or tablets, for example three or four. Accordingly, a matching number of expulsion pistons, which are mutually independent or integral with each other and correspond to the geometric profile of the abutment element 13, is provided.

[0050] Advantageously, means 16 for adjusting the position of the abutment element 13 along the compression direction 8 are provided which comprise a servomotor 17 which is associated with the abutment element 13 by means of a second rod-and-crank mechanism 18 in a cascade arrangement with respect to a guiding and adjustment device 19.

[0051] In the proposed embodiment, the feeding tunnel 3 comprises a plurality of conveyor belts which are oriented parallel to each other so as to form a passage channel interposed between them.

[0052] In greater detail, the conveyor belts comprise an upper conveyor belt 20, a lower conveyor belt 21, and two lateral conveyor belts 22, of which only one is shown for the sake of simplicity in illustration.

[0053] Conveniently, the feeding tunnel 3, which has a longitudinal extension that is substantially perpendicular to the compression direction 8, comprises a plurality of skimming elements 23, 24 and 25, one for each conveyor belt, arranged at the inlet of the chamber 2 for the optimum conveyance of the food product or the like 4 into the chamber 2.

[0054] In the proposed embodiment, the inlet is formed by a front plate 26 arranged so as to close the chamber 2.

[0055] The general operation of the filling machine 1 is clear and evident from what has been described so far.

[0056] With particular reference to FIGS. 2 and 3, the torque behavior of the motor means 9 as a function of the position of the plunger 7, without and with the food product or the like 4 placed in the chamber 2 respectively, is described hereinafter.

[0057] More specifically, the algorithm allows control of the movement of the plunger 7 along the chamber 2, a movement which can be divided into three steps.

[0058] In the first step, the algorithm gives the command to the motor means to raise the plunger 7 from the bottom dead center “PMI” to the vicinity of the top dead center “PMS”.

[0059] In the second step, the algorithm commands the motor means to reverse the motion of the plunger 7 proximate to or at the top dead center “PMS”, and the third step represents the descent of the plunger 7 from the top dead center “PMS” until it returns to the initial position, i.e., at the bottom dead center “PMI.”

[0060] Subsequently, there is a fourth step which corresponds to a waiting step, in which the food product or the like 4 is loaded into the chamber 2 in order to then start again with the first step.

[0061] With particular reference to FIG. 2, without the food product 4 or the like placed in the chamber 2, in the first step the algorithm commands the motor means 9 to impart a positive driving torque, correspondingly to the step for accelerating the plunger 7; then, by way of indication halfway through the rising step, the algorithm commands a reversal of the driving torque, so as to correspond to the deceleration step of the plunger 7, until the top dead center “PMS” is reached, which, in the absence of the product, by detecting the failure to reach the pre-configured torque limit value, corresponds to a predetermined plunger stroke limit value, at which the driving torque becomes zero, partially completing the second step.

[0062] Again in the second step, the algorithm commands the motor means 9 to impart a negative driving torque, so as to correspond to the acceleration step of the plunger 7 in the step for recalling the plunger 7; subsequently, in the third step, which corresponds by way of indication to halfway along the path of the descending step, the algorithm commands an inversion of driving torque, so as to correspond to the deceleration step of the plunger 7, until the bottom dead center “PMI” is reached, which even in the absence of the product corresponds to a predetermined limit value of the stroke of the plunger, at which the driving torque becomes zero again.

[0063] With particular reference to FIG. 3, with the food product or the like 4 placed in the chamber 2, in the first step the algorithm commands the motor means 9 to impart a positive driving torque, in a manner that corresponds to the acceleration step of the plunger 7; subsequently, by way of indication halfway along the path of the rising step, a reversal of driving torque occurs which is managed by the algorithm in a manner that corresponds to the deceleration step of the plunger 7.

[0064] The plunger 7 rises along the compression direction without reaching the top dead center “PMS” due to the presence of the food product or the like 4 which inevitably creates thickness.

[0065] The algorithm, for each individual cycle, detects the achievement of the predetermined density of the product by measuring the torque of the motor means 9 and commands the motor means 9 to stop, locking and maintaining the plunger in position.

[0066] Upon achieving at each individual cycle, the predetermined density of the food product or the like 4, the algorithm commands the motors to stabilize the plunger in position.

[0067] In this manner, the plunger 7, for each individual cycle, is brought and kept in different positions without over-compressions by virtue of the algorithm that manages the driving torque of the motor means 9, which is controlled so as not to impart additional thrust force to the product.

[0068] At this point, the expulsion pistons 15 intervene and remove the tablets of food product or the like 4 from the chamber 2.

[0069] In this case, the second step is substantially constituted by the parking of the plunger 7 at an intermediate height between the bottom dead center “PMI” and the top dead center “PMS” proximate to the top dead center and at the preset density value.

[0070] In greater detail, during the first step, while the motor means 9, for each individual cycle, perform the positioning of the plunger 7 at the height that allows to achieve the predetermined density, if the algorithm detects that a preset determined torque value has been exceeded, due to the compression of the food product or the like 4, positioning is stopped in order to then move on to the second step while waiting for the third step. Subsequently, the motor means 9 impart a negative driving torque, in a manner that corresponds to the acceleration step of the plunger 7 in the step for recalling the plunger 7 and, in the third step that corresponds by way of indication to halfway along the descending step, an inversion of driving torque occurs, in a manner that corresponds to the deceleration step of the plunger 7, until the bottom dead center “PMI” is reached at which the driving torque becomes zero again.

[0071] Therefore, to sum up, the means for measuring 30 constitute a specific, integrated hardware architecture dedicated to real-time execution:

[0072] Hardware Configuration: The system is made up of the PLC (Programmable Logic Controller) connected to the servo-actuator provided with dedicated local memory for executing commands in real time, operating on the brushless servomotor with encoder.

[0073] Distribution of Control: The control program is strategically allocated partially in the PLC and partially in the memory of the servo-actuator, to minimize communication latency (scan time).

[0074] Physical Operation: Measurement of the torque and the density occurs by physically monitoring the current absorbed by the motor, detected at that exact moment by the servo-actuator. This structure ensures immediate cessation of motion upon contact with the product, a function that cannot be performed by a generic algorithm that is not integrated in the actuation system.

[0075] Hybrid Control (Position / Torque): The present system implements a cycle divided into separate stages: a first stage of acceleration, under position control, and a subsequent switch to torque control.

[0076] Dynamic Stop Trigger: the invention uses the memory of the servo-actuator to launch a stop command based on the current peak upon actual contact with the product. This solves the problem of variability of density of the natural product, so ensuring real-time precision.

[0077] In practice it has been found that the filling machine for food products in cans, particularly of the type with product density control, according to the present invention, achieves the intended aim and objects, since it allows to:

[0078] determine precisely at each individual cycle the density of the product with each consequent effect;

[0079] reduce the squeezing time of the food product or the like to the minimum necessary to achieve the desired density, regardless of the speed of the filling machine;

[0080] make the machine work at the maximum allowed speed without affecting product quality and, consequently, make production processes more efficient;

[0081] increase the number of the cycles of compression of the food product or the like without damaging it, ensuring its quality;

[0082] avoid thrust variations with respect to traditional systems (such as spring systems, pneumatic cylinder systems, or actuator systems), which would lead to pressure increments as the plunger position varies and therefore do not allow to obtain tablets with constant density;

[0083] eliminate weight fluctuations of the tablets even just as the speed of the filling machine varies, compensating for the incidence of the forces generated by the inertias of the mechanism;

[0084] control for each cycle the exact position of the plunger, so as to ensure good operation even in the event of “pasting”;

[0085] control for each cycle the exact position of the plunger, eliminating external sensors, by virtue of a system directly integrated in the motor means;

[0086] determine for each cycle the exact quantity of food product or the like inside the chamber;

[0087] interact in real time and for each cycle, by means of a signal, with: the motorized chamber volume control system, the feeding tunnel, as well as the inlet section of the feeding port;

[0088] compensate for any weight variations for each cycle by means of an external signal, such as for example a remote weighing device, arranged in a position that lies after the tablet generation step, which interacts with the system, varying automatically the working parameters of said system;

[0089] simplify the mechanical complexity by using a mechatronic system.

[0090] The filling machine thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the accompanying claims.

[0091] All the details may furthermore be replaced with other technically equivalent elements.

[0092] In practice, the materials used, so long as they are compatible with the specific use, as well as the contingent shapes and dimensions, may be any according to the requirements and the state of the art.

[0093] The disclosures in Italian Invention Patent Application No. 102021000021224, from which this application claims priority, are incorporated by reference.

[0094] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. A filling machine for food products in cans, particularly of the type with product density control, comprising a supporting frame which forms a chamber and a feeding tunnel which is adapted to convey a food product into said chamber; said chamber being provided with a plunger which can move along said chamber, along a predefined compression direction, between a bottom dead center position (PMI), in which said chamber is free from said plunger in order to feed said food product into said chamber, and a top dead center position (PMS), in which said plunger occupies at least partially said chamber for a compression of said food product into at least one preset shape; said chamber being provided with at least one expulsion piston which is configured to move transversely with respect to said compression direction for an expulsion of said at least one preset shape in a direction of a station for canning said food product; motor means being further provided which are associated with said plunger for a movement thereof along said compression direction; and further comprising means for measuring a density of said food product compressed in said chamber by said plunger in order to control a driving torque of said motor means as a function of an achievement of a predetermined density value, the thrust of said motor means being stopped when the predetermined density value has been reached, locking and maintaining the plunger in position, said motor means comprising a control unit and a servomotor, the arrest of the plunger being determined by detection of a peak of current absorbed by the servomotor upon contact of the plunger with the product, so ensuring an immediate response time which prevents over-compression.

2. The filling machine according to claim 1, wherein said means for measuring the density of said food product compressed in said chamber comprise means for measuring a driving torque of said motor means.

3. The filling machine according to claim 1, wherein said motor means comprise a mechatronic system constituted by a control unit, a rotary servo motor of the brushless type provided with an encoder, and a speed reduction unit.

4. The filling machine according to claim 1, wherein said motor means are associated with said plunger by virtue of a first rod-and-crank mechanism.

5. The filling machine according to claim 1, wherein said feeding tunnel comprises a plurality of conveyor belts which are oriented parallel to each other so as to form a passage channel interposed between said conveyor belts; said conveyor belts comprising an upper conveyor belt, a lower conveyor belt, and two lateral conveyor belts.

6. The filling machine according to claim 1, wherein said feeding tunnel comprises a plurality of skimming elements which are arranged at an inlet of said chamber for an optimum conveyance of said food product into said chamber.

7. The filling machine according to claim 1, wherein said feeding tunnel has a longitudinal extension that is substantially perpendicular to said compression direction.

8. The filling machine according to claim 4, wherein said chamber is delimited, on an opposite side with respect to said plunger proximate to said top dead center, by an abutment element which is contoured, on a side directed toward an inside of said chamber, with a geometric profile which reproduces in negative form a portion of said at least one preset shape.

9. The filling machine according to claim 8, wherein said abutment element is shaped to form at least two predefined shapes; said at least one expulsion piston comprising at least two expulsion pistons which correspond to said geometric profile of said abutment element.

10. The filling machine according to claim 8, further comprising adjustment means for adjusting a position of said abutment element along said compression direction.

11. The filling machine according to claim 10, wherein said adjustment means comprise a servomotor which is associated with said abutment element by means of a second rod-and-crank mechanism in a cascade arrangement with respect to a guiding and adjustment device.

12. A method for the filling of food products in metallic boxes, cans, comprising the steps of:feeding a food product to a chamber provided with a plunger which is configured to move along said chamber, along a predefined compression direction, between a bottom dead center position (PMI), in which said chamber is free from said plunger in order to feed said food product into said chamber, and a top dead center position (PMS), in which said plunger occupies at least partially said chamber for a compression of said food product into at least one preset shape;setting up a predetermined density value of said food product;compressing said food product by means of said plunger;measuring a density of said food product compressed by said plunger in said chamber;actively controlling, during the compression of each single compression cycle, a driving torque of the motor means adapted to move said plunger, said driving torque being controlled by detecting a density of the food product compressed and adjusting said driving torque in order to achieve said predetermined density value of said food product;upon achieving said predetermined density value of said food product stopping a stroke of said plunger in a position that corresponds to said predetermined density value and maintaining that position, thus avoiding compressing further said food product, the stop of the stroke of the plunger being based on the variation in an absorbed current of a servomotor of the motor means at an exact moment when the plunger meets the product.

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