Food processing machine

Abstract

The invention relates to a food processing machine for processing a food product (1), comprising at least one hydraulically driven consumer (4), a hydraulic pump (7) which supplies a hydraulic fluid to drive the consumer (4) and provides a specific system pressure of the hydraulic fluid, and a control device (12) for specifying a desired mechanical power of the consumer (4), wherein a specific minimum value of the system pressure is required to achieve the desired mechanical power of the consumer (4).The invention provides that the control device (12) adjusts the system pressure supplied by the hydraulic pump (7) as required, depending on the desired mechanical power of the consumer (4), so that the hydraulic pump (7) supplies only the required minimum value of the system pressure with a certain safety margin, but no more, in order to save drive energy for driving the hydraulic pump (7).

Description

Technical field of the invention

[0001] The invention relates to a food processing machine for processing a food product, in particular for pressing the food product. Background of the invention

[0002] It is known from the prior art to shape irregularly shaped food products (e.g., raw ham, raw meat) in a pressing device before a machine slicing process in order to achieve a better slicing result. For this purpose, the food product to be shaped is placed in a pressing chamber and then pressed in the pressing chamber by several movable pressing plates in several pressing axes to bring the food product into the desired shape.

[0003] A pressing device of this type is known from US 11,412,744 B2, in which the movable pressing plates are each driven by a hydraulic drive cylinder. The drive cylinder is supplied with hydraulic oil at a specific system pressure via a supply line by a hydraulic pump, and the hydraulic oil can then be returned to a tank via a return line. The pressing process is controlled by a proportional valve, which regulates the flow of hydraulic oil through the supply and return lines. The system pressure of the hydraulic oil supplied by the hydraulic pump must be high enough to ensure that the pressing device can generate the required pressing force in all operating conditions.In many operating states of the press, the hydraulic pump therefore delivers a system pressure that is actually unnecessary at this level, but still consumes a correspondingly large amount of drive energy to power the hydraulic pump. The mechanical drive of the hydraulic pump thus leads to a relatively high energy consumption, which is undesirable. Description of the invention

[0004] The invention is therefore based on the objective of reducing the energy consumption required to drive the hydraulic pump.

[0005] This problem is solved by a food processing machine according to the invention and the main claim.

[0006] The food processing machine according to the invention initially comprises, in accordance with the prior art described above, at least one hydraulically driven consumer. This is preferably a pressing device for pressing the food product with a hydraulic drive cylinder. However, the invention is not limited to such pressing devices, but can also be implemented in principle with other types of food processing machines that have a hydraulically driven consumer.

[0007] Furthermore, the food processing machine according to the invention, in accordance with the prior art described above, has a hydraulic pump which pumps a hydraulic fluid (e.g. hydraulic oil) to drive the consumer and provides a certain system pressure of the hydraulic fluid.

[0008] Furthermore, the food processing machine according to the invention, in accordance with the prior art described above, also has a control device that specifies a desired mechanical output of the consumer. For example, the control device can specify the desired process force (i.e., the sum of pressing force, acceleration force, and friction force) of a hydraulic drive cylinder of the consumer. Pressing devices for pressing food products typically operate according to a predetermined operating profile, whereby the operating profile specifies a particular sequence of position, speed, and acceleration of the pressing plates and the resulting pressing force. However, the term "predetermined mechanical output" used within the scope of the invention is to be understood generally and is not limited to such an operating profile of a mechanical pressing device.In this context, it should be noted that a certain minimum hydraulic fluid system pressure is required to achieve the desired mechanical performance of the consumer. In the prior art described above, the hydraulic fluid system pressure is therefore chosen to be high enough to ensure the desired mechanical performance of the consumer in all operating conditions. In practice, this results in an oversized hydraulic fluid system pressure in many operating conditions, leading to a correspondingly higher fluid consumption in the mechanical drive of the hydraulic pump.

[0009] The invention therefore provides that the control unit adjusts the system pressure supplied by the hydraulic pump according to the required mechanical power of the consumer, ensuring that the hydraulic pump delivers only the required minimum system pressure with a certain safety margin, and no more, in order to conserve drive energy for the hydraulic pump. Thus, if only a low process force is required from the pressing device during a pressing operation, the system pressure of the hydraulic fluid can be reduced. Conversely, if a very high process force is required during a pressing operation, the system pressure can be increased accordingly so that the drive cylinder of a pressing device can generate the required process force. The demand-based setting and reduction of the system pressure therefore enables energy savings in the drive of the hydraulic pump.

[0010] The aforementioned concept of a safety margin is preferably implemented using a safety factor. For example, the hydraulic fluid system pressure can be set to exceed the calculated minimum value by 30%. Alternatively, the safety margin can also be an absolute value, i.e., a specific pressure differential added to the calculated minimum system pressure.

[0011] In one embodiment of the invention, the hydraulic pump has an adjustable speed, with the control device adjusting the speed of the hydraulic pump to regulate the system pressure of the hydraulic fluid supplied by the hydraulic pump. However, such variable-speed hydraulic pumps are relatively sluggish and therefore react only slowly to changes in the desired speed or system pressure.

[0012] Preferably, the hydraulic pump is therefore not a variable-speed pump, but a pump with an adjustable displacement volume ("variable displacement pump"), whereby the control device for adjusting the system pressure supplied by the hydraulic pump then adjusts the displacement volume of the hydraulic pump.

[0013] In a preferred embodiment of the invention, an axial piston pump is used, for example, a swashplate pump or a swashplate pump. Such axial piston pumps are known per se from the prior art and therefore do not need to be described in detail. However, it should be mentioned that the axial piston pump has several pistons, each of which is axially displaceable along a piston axis and is axially displaced by a sliding disk. The sliding disk is inclined with its disk axis at an angle of attack relative to the piston axis of the pistons, and this angle of attack of the sliding disk determines the displacement volume of the axial piston pump. To adjust the displacement volume of the axial piston pump, and thus also to adjust the system pressure of the hydraulic fluid supplied by the axial piston pump, the control device then adjusts the angle of attack of the sliding disk of the axial piston pump accordingly.This adjustment of the angle of attack of the sliding disc of the axial piston pump can be carried out with significantly greater dynamics and correspondingly lower inertia than the adjustment of the speed in a variable speed hydraulic pump.

[0014] In the preferred embodiment of the invention, the hydraulically driven consumer is a pressing device for pressing the food product, as briefly mentioned above. Depending on the type of food product to be pressed (e.g., raw ham, raw meat), the control unit specifies a particular operating profile for the pressing device according to a predetermined pressing recipe. This profile includes a specific time course for the position, speed, and acceleration of a pressing plate and the associated pressing force of the pressing device. For example, a specific pressing force should be maintained for a certain duration during a pressing process to achieve a good pressing result.The control unit then calculates, based on the product-specific operating profile of the pressing unit, the required minimum system pressure that the hydraulic pump must supply to perform the desired pressing operation. The control unit then regulates the hydraulic pump so that, with a certain safety margin, it delivers only the required minimum system pressure, and no more. With an axial piston pump, this system pressure can be set by adjusting the hydraulic pump's displacement volume.

[0015] In the preferred embodiment of the invention, the hydraulic pump (e.g., axial piston pump) is connected to the hydraulically driven consumer (e.g., drive cylinder of a pressing device) via a supply line. A return line runs from the hydraulically driven consumer to a return line (e.g., hydraulic oil tank). The hydraulically driven consumer is controlled by a valve (e.g., proportional valve), which regulates both the hydraulic flow from the hydraulic pump through the supply line to the consumer and the hydraulic flow from the consumer through the return line to the return line. The control unit then adjusts this valve so that the actual process force of the pressing device corresponds as closely as possible to the desired process force.

[0016] Furthermore, it should be mentioned that a pressure measuring device is preferably provided which measures at least one hydraulic pressure at the pressing device. The food processing machine according to the invention preferably has two separate control loops, namely a first control loop for controlling the desired process force and a second control loop for controlling the system pressure of the hydraulic fluid.

[0017] The first control loop for force regulation starts at the pressure measuring device and proceeds to a first controller, which actuates the valve in the supply and return lines based on the hydraulic pressure measured by the pressure measuring device. This control is such that the actual process force of the pressing device corresponds as closely as possible to the desired process force. For this purpose, the pressure measuring device preferably uses two pressure sensors to measure the hydraulic pressure in the supply and return lines and calculates the pressure difference acting on a movable piston in the drive cylinder. From this pressure difference, the process force applied by the drive cylinder can then be calculated.

[0018] The second control loop for regulating the system pressure of the hydraulic fluid also starts from the pressure measuring device at the consumer and goes to a second controller, which adjusts the displacement volume of the hydraulic pump as required, depending on the hydraulic pressure measured by the pressure measuring device, so that the hydraulic pump delivers only the required minimum value of the system pressure with a certain safety margin, but no more.

[0019] The second control loop ensures that sufficient system pressure of the hydraulic fluid is always available as needed, while the first control loop ensures that the desired process force is set.

[0020] The valve (e.g., a proportional valve) in the supply or return line is typically controlled according to a valve characteristic curve or a characteristic curve field, where the valve characteristic curve or characteristic curve field is based on a specific system pressure of the hydraulic fluid. Therefore, if the system pressure changes, the valve characteristic curve or characteristic curve field must also be adjusted accordingly. The second control loop preferably also includes an actuator that adjusts the valve characteristic curve or characteristic curve field of the first controller in the first control loop based on the system pressure supplied by the hydraulic pump. This ensures that the proportional valve is controlled correctly even when the system pressure of the hydraulic fluid changes.

[0021] In the preferred embodiment of the invention, the pressing device has at least one pressing chamber to hold the food product during a pressing operation. During a pressing operation, at least one pressing plate is moved by a drive cylinder, wherein a piston is displaceable within the hydraulic drive cylinder and acts on the pressing plate via a piston rod. It should be noted that the piston rod of the hydraulic drive cylinder can act directly on the pressing plate. However, it is also possible for the piston rod of the drive cylinder to act indirectly on the pressing plate via a kinematic mechanism. The previously mentioned supply line opens into the drive cylinder at the bottom to extend the piston rod. The previously mentioned return line, on the other hand, opens into the drive cylinder on the rod side, i.e., on the side of the piston rod.The pressure measuring device preferably has two pressure sensors: a first pressure sensor that measures the hydraulic pressure in the drive cylinder at the bottom or in the supply line, and a second pressure sensor that measures the hydraulic pressure in the drive cylinder at the rod end or in the return line. The control unit can then calculate the differential pressure acting on the piston of the drive cylinder from the two pressure readings of the two pressure sensors, from which the process force that the drive cylinder can generate can then be calculated. It should be noted that the process force of the drive cylinder includes the frictional force, the acceleration force (inertial force), and the actual pressing force with which the food product is pressed.The second controller in the control loop then adjusts the displacement volume of the hydraulic pump so that the hydraulic pump, with a certain safety margin, only delivers the required minimum value of the system pressure as needed, but no more.

[0022] It should also be mentioned that the hydraulic pump can be driven by an electric motor.

[0023] The control unit can then include a pulse-width modulator (PWM) that receives a setpoint value for the hydraulic pressure and outputs a pulse-width modulated control signal. For example, such a PWM can also include a dither circuit that adds a dither signal to the PWM control signal to prevent the disruptive stick-slip effect. Furthermore, the PWM can include an output current regulator that outputs the PWM control signal as a current signal.

[0024] Furthermore, it should be mentioned that the control unit of the food processing machine according to the invention can have an electromechanical actuator, wherein the electromechanical actuator receives the pulse-width modulated control signal from the pulse-width modulator and adjusts the displacement volume of the hydraulic pump according to the pulse-width modulated control signal in order to adjust the system pressure. For example, the electromechanical actuator can adjust the angle of attack of the sliding disc of the axial piston pump, as already briefly described above.

[0025] Furthermore, it should be mentioned that the control device may include a limiting element that restricts the rate of change of the hydraulic fluid system pressure. This dampens excessively rapid pressure changes.

[0026] Furthermore, the pressing device can have a so-called phase controller, which can distinguish between different phases of a pressing process. For example, the following phases of a pressing process can be distinguished: • Loading phase, in which a food product is loaded into a press chamber, • Press positioning phase, in which at least one press plate is moved towards the food product in the press chamber, • Force build-up phase, in which a predetermined pressing force is built up that is intended to act on the food product, • Force holding phase, in which a predetermined pressing force is maintained, acting on the food product, • Relief phase, in which the pressing force acting on the food product is reduced, and • Unloading phase, in which the pressed food product is removed from the pressing chamber.

[0027] The phase controller can then specify a minimum value for the system pressure in each phase of the pressing process, which must not be undercut under any circumstances, regardless of the demand-based calculation of the system pressure.

[0028] As already described above, the food processing machine is preferably a pressing device. However, the principle according to the invention can also be used in other types of food processing machines, for example, in food processing machines for forming or separating food products.

[0029] In a forming machine for forming so-called patties for hamburgers, the hydraulics move the forming plate (quickly) in and out, and the raw material (e.g. minced meat) is pumped towards the forming cavities (in the so-called pump box) by two hydraulic cylinders.

[0030] In a separation machine, on the other hand, meat and bone remnants are pressed through a perforated plate using a hydraulic cylinder.

[0031] Both machines (forming machines and separation machines) are driven by a hydraulic pump, so that the principle according to the invention can also be used in these types of machines.

[0032] Other advantageous embodiments of the invention are characterized in the dependent claims or are explained in more detail below together with the description of the preferred embodiments of the invention with reference to the figures. Brief description of the drawings Fig. Figure 1 shows a schematic representation of a pressing device according to the invention for pressing food products. Fig. Figure 2 shows a control engineering equivalent circuit diagram of the pressing device. Fig. 1. Fig. 3A and Fig. Figure 3B shows further details of the control of the press device according to the invention. Fig. Figure 4 shows a time diagram with the time profiles of the regulated system pressure and the position of the press plates of the press device during a pressing operation. Detailed description of the drawings

[0033] The following describes the exemplary embodiment of a pressing device according to the invention, as shown in the drawings, which serves to press a food product 1 (e.g. raw ham, raw meat) as is known from the prior art.

[0034] The pressing device has a pressing chamber 2 into which the food product 1 to be pressed can be placed during a pressing process. In the pressing chamber 2, the food product 1 can be pressed by at least one pressing plate 3, which can be moved in the direction of the double arrow by a hydraulic drive cylinder 4. A piston 5 is movable within the drive cylinder 4, and the piston 5 is connected to the pressing plate 3 via a piston rod 6, thus moving the plate. It should be noted that the piston rod 6 can also be indirectly connected to the pressing plate 3 via a kinematic mechanism not shown. Furthermore, it should be noted that for the sake of simplicity, the drawing shows only a single pressing axis with the pressing plate 3. In practice, however, the food product 1 is usually pressed along three axes (length, height, width), which is not shown here for the sake of simplicity.

[0035] The hydraulic pressure for operating the drive cylinder 4 is generated by an axial piston pump 7, which pumps hydraulic oil into the drive cylinder 4 via a supply line 8, specifically at the bottom of the piston 5. The hydraulic pressure generated in the drive cylinder 4 via the supply line 8 thus causes the piston rod 6 to extend, resulting in a pressing operation.

[0036] A return line 9 branches off from the drive cylinder 4 on the rod side of the piston 5, which leads into a hydraulic oil tank 10 to receive returned hydraulic oil.

[0037] The insertion of the piston rod 6 with the pressure plate 3 is carried out in reverse, by the proportional valve 11 introducing the hydraulic oil via the return line 9 on the rod side of the piston 5 into the drive cylinder 4, so that the piston 5 is pushed to the left in the drawing.

[0038] The pressing process is controlled by a proportional valve 11, which controls the hydraulic flow through the supply line 8 and through the return line 9.

[0039] The valve position of the proportional valve 11 is hereby predetermined by a control device 12 in the manner according to the invention, as will be described in detail below.

[0040] A pressure sensor 13 is located in the supply line 8, which measures a hydraulic pressure p Zulauf in the supply line 8. The measured hydraulic pressure p Zulauf is essentially equal to the hydraulic pressure in the drive cylinder 4 at the bottom of the piston 5.

[0041] Furthermore, another pressure sensor 14 for measuring a hydraulic pressure p is located in the return line 9. Rücklauf in the return line 9. The measured hydraulic pressure p Rücklaufis essentially equal to the hydraulic pressure in the drive cylinder 4 on the rod side of the piston 5.

[0042] The control unit 12 can use the two pressure measurements p Zulauf , p Rücklauf Calculate the pressure difference acting on piston 5. From this, and taking into account the different pressure application areas of piston 5 on the bottom side and on the rod side, the process force F exerted by the drive cylinder 4 can be calculated. This process force F is the sum of the frictional force, the acceleration force, and the actual pressing force acting on the food product 1.

[0043] Furthermore, the press device shown has a position sensor 15 which measures the position of the piston 5 and thus also of the press plate 3 and reports a corresponding position value x to the control unit 12.

[0044] The following is a simplified equivalent circuit diagram for control engineering according to Fig. 2 described, where this equivalent circuit diagram represents the control processes in the control unit 12 according to Fig. 1 illustrates.

[0045] The control device 12 has two control loops 16, 17, whereby control loop 16 serves to control the process force F, while the other control loop 17 serves to control the system pressure p. SYSTEM serves, which is supplied by the axial piston pump 7.

[0046] Control loop 16 measures the hydraulic pressure p for force control. Zulauf in the supply line 8 and the hydraulic pressure p Rücklauf in the return line 9 and reports these pressure measurements to a proportional valve controller 18, which controls the proportional valve 11 according to a stored characteristic curve or according to a characteristic curve field so that the drive cylinder 4 generates the desired process force F.

[0047] The second control loop 17 has a system pressure controller 19, which has the task of controlling the system pressure p SYSTEM to regulate the hydraulic oil as needed, pursuing two control objectives. Firstly, the system pressure p must be controlled. SYSTEM It should be large enough to allow the required process force F to be applied by the drive cylinder 4. Secondly, the system pressure p should be... SYSTEM However, it should be as low as possible to ensure the most energy-efficient mechanical drive of the axial piston pump 7. The system pressure controller 19 therefore adjusts the adjustable displacement volume of the axial piston pump 7 to achieve both control objectives. This is done by adjusting the angle of attack of the sliding disk of the axial piston pump 7, which results in a corresponding change in the displacement volume of the axial piston pump 7.

[0048] When the system pressure p changes SYSTEMIt must be ensured that the proportional valve controller 18 still correctly controls the proportional valve 11, since this control is adapted for a specific system pressure. The second control loop 17 therefore has an actuator 20 which, when the system pressure p is adjusted, SYSTEM also adapts the valve characteristic curve or characteristic curve field stored in the proportional valve controller 18 so that the force control in the first control loop 16 also when the system pressure p is adjusted SYSTEM continues to function correctly.

[0049] The following will now refer to the Fig. 3A and Fig. 3B further details of the control system and regulation technology of the control unit 12 are described.

[0050] The control unit 12 has a control module 21 which calculates the required system pressure for each of the three press axes (length, width, height) and outputs the minimum required system pressure p by means of a comparator unit 22.

[0051] In a second control module 23, a safety factor is first multiplied by the calculated minimum system pressure using a gain element 24. This gain is intended to ensure that the subsequently set system pressure is sufficient in any case to apply the desired process force.

[0052] Furthermore, the control module 23 has a phase controller 25 that can distinguish between different phases of a pressing process and specifies a minimum required system pressure for each pressing phase. This minimum required system pressure is then taken into account by a processing unit 26; that is, regardless of the actual system pressure required, the minimum system pressure specified by the phase controller 25 is always maintained.

[0053] Furthermore, the control module 23 has a limiting element 27 that limits the maximum rate of change of the system pressure in order to prevent jerky changes.

[0054] Next comes a linearizer 28, which transmits the required system pressure to a dither element 29. The dither element 29 is designed to prevent the disruptive stick-slip effect.

[0055] Next comes a current controller 30, which, via an electromechanical actuator 31, controls a servomotor 32 to adjust the angle of attack of the sliding disc of the axial piston pump 7, thereby adjusting the displacement volume of the axial piston pump 7.

[0056] Furthermore, the control module contains 23 additional details, which, however, are not essential to the invention and therefore do not need to be described in more detail. Fig. 3A are immediately apparent.

[0057] The following are the time diagrams according to Fig. 4 described, which show different temporal phases of a pressing process.

[0058] The upper time diagram shows the time course of the position x of the respective press plates in the press axes with respect to length, width and height.

[0059] The lower diagram shows the corresponding time course of the required system pressure p. SYSTEM, where the system pressure p SYSTEM The process force F is adjusted according to the required specifications. The period between t=t3 and t=t4 is a force-holding phase, during which a relatively high pressing force F must be maintained, requiring a correspondingly high system pressure p. SYSTEM is required. Before the actual pressing process, however, a relatively low process force F is required, so that the system pressure p SYSTEM then it can be lowered accordingly to save drive energy for driving the axial piston pump 7.

[0060] The invention is not limited to the preferred embodiment described above. Rather, a multitude of variants and modifications are possible, which also make use of the inventive concept and therefore fall within the scope of protection. In particular, the invention also claims protection for the subject matter and the features of the dependent claims independently of the respective referenced claims and especially also without the features of the main claim. The invention thus comprises various aspects of the invention that enjoy independent protection. Reference symbol list 1 food product in the pressing chamber 2 Press chambers 3 Pressing plates for pressing the food product in the pressing chamber 4 drive cylinders for moving the press plate 5 pistons in the drive cylinder 6 Piston rod of the drive cylinder 7 Axial piston pump 8. Supply line from the axial piston pump to the drive cylinder 9 Return line from the drive cylinder to the tank 10 Hydraulic oil tank for recirculated hydraulic oil 11 Proportional valve 12 Control unit for controlling the proportional valve and the axial piston pump 13 Pressure sensor for measuring the hydraulic pressure in the supply line 14 Pressure sensor for measuring the hydraulic pressure in the return line 15 Position sensor for measuring the position of the piston 16 Control loop for regulating the process force 17 Control loop for regulating the system pressure of the hydraulic oil supplied by the axial piston pump 18 Proportional valve controllers for controlling the proportional valve 19 System pressure regulator for adjusting the system pressure by adjusting the angle of attack of the sliding disc of the axial piston pump 20 Actuator for adapting the valve characteristic curve or characteristic curve field of the proportional valve controller to the system pressure 21 Control module for determining the required system pressure of the three press axes 22 Comparator unit for determining the maximum required system pressure in the three press axes 23 Control module 24 Reinforcing element to increase the required system pressure with a safety factor 25-phase controller 26 computing units 27 Limiting element for limiting the dynamic change in system pressure 28 linearizers 29 dither links to prevent the slip-stick effect 30 current regulators 31 Actuator 32 Actuator for adjusting the angle of attack of the sliding disc of the axial piston pump F Process force of the drive cylinder (press force + friction force + acceleration force) p SYSTEM Hydraulic oil system pressure p Zulauf Hydraulic pressure in the supply line p Rücklauf Hydraulic pressure in the return line x Position of the piston in the drive cylinder QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 11,412,744 B2

[0003]

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