Food-processing machine

1 . A food-processing machine for processing a food product, with

a) at least one hydraulically driven consumer,

b) a hydraulic pump which is adapted to deliver a hydraulic fluid for driving the consumer and to supply a specific system pressure of the hydraulic fluid, and

c) a control device for specifying a desired mechanical power of the consumer, wherein a specific minimum value of the system pressure is required to achieve the desired mechanical power of the consumer,

d) wherein the control device is adapted to adjust the system pressure supplied by the hydraulic pump as a function of the desired mechanical power of the consumer as required in such a way that the hydraulic pump 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.

2 . The food-processing machine according to claim 1 , wherein

a) the hydraulic pump has an adjustable displacement volume, and

b) the control device is adapted to adjust the displacement volume of the hydraulic pump in order to set the system pressure of the hydraulic fluid supplied by the hydraulic pump.

3 . The food-processing machine according to claim 1 , wherein

a) the hydraulic pump has an adjustable rotary speed, and

b) the control device is adapted to adjust the rotary speed of the hydraulic pump in order to set the system pressure of the hydraulic fluid supplied by the hydraulic pump.

4 . The food-processing machine according to claim 2 , wherein

a) the hydraulic pump is an axial piston pump, with

a1) several pistons, each of which is axially displaceable along a piston axis and

a2) a sliding disk that moves the pistons axially,

a3) wherein the sliding disk is inclined with its disk axis by a setting angle relative to the piston axis of the pistons and the setting angle of the sliding disk determines the displacement volume of the axial piston pump, and

b) the control device is adapted to adjust the setting angle of the sliding disk of the axial piston pump in order to set the displacement volume of the axial piston pump and thus to set the system pressure of the hydraulic fluid supplied by the axial piston pump.

5 . The food-processing machine according to claim 1 , wherein

a) the hydraulically driven consumer is a pressing device for pressing the food product, and

b) the control device, depending on the type of food product to be pressed, specifies a specific travel profile of the pressing device in accordance with a predetermined pressing recipe, with a specific progression of position, speed and acceleration of a pressing plate and/or a pressing force of the pressing device,

c) the control device is adapted to calculate the required minimum value of the system pressure, which must be supplied by the hydraulic pump, as a function of the predetermined travel profile of the pressing device, and

d) the control device is adapted to control the hydraulic pump in such a way that the hydraulic pump only supplies the required minimum value of the system pressure as required with a specific safety margin, but no more.

6 . The Food-processing machine according to claim 5 , further comprising

a) a return for receiving recirculated hydraulic fluid,

b) a supply line from the hydraulic pump to the hydraulically driven consumer,

c) a return line from the hydraulically driven consumer into the return, and

d) a valve for controlling the hydraulic flow

d1) from the hydraulic pump through the supply line to the consumer and

d2) from the consumer through the return line into the return,

e) wherein the control device is adapted to actuate the valve in such a way that the actual process force of the pressing device matches the desired process force as precisely as possible.

7 . The food-processing machine according to claim 6 , further comprising

a) a pressure measuring device for measuring at least one hydraulic pressure at the pressing device,

b) a first control loop for controlling the process force generated by the pressing device, the first control loop extends from the pressure measuring device to a first controller which actuates the valve as a function of the hydraulic pressure measured by the pressure measuring device in such a way that the actual process force of the pressing device matches the desired process force as precisely as possible, and

c) a second control loop for controlling the system pressure of the hydraulic fluid supplied by the hydraulic pump, wherein the second control loop extends from the pressure measuring device to a second controller, which is adapted to adjust the displacement volume of the hydraulic pump as required as a function of the hydraulic pressure measured by the pressure measuring device in such a way that the hydraulic pump supplies only the required minimum value of the system pressure with a certain safety margin, but no more.

8 . The food-processing machine according to claim 6 , wherein

a) the first controller in the first control loop is adapted to control the valve as a function of the hydraulic pressure measured by the pressure measuring device in accordance with a valve characteristic curve or in accordance with a characteristic curve map, and

b) the second control loop contains an actuator which is adapted to adjust the valve characteristic curve or the characteristic curve field of the first controller in the first control loop as a function of the system pressure supplied by the hydraulic pump.

9 . The food-processing machine according to claim 6 , wherein

a) the pressing device comprises at least one pressing chamber for receiving the food product during a pressing operation,

b) the pressing device comprises at least one drive cylinder with a piston which can be displaced in the drive cylinder and acts on a pressing plate via a piston rod in order to press the food product in the pressing chamber,

c) the piston rod of the drive cylinder optionally acts directly on the pressing plate or indirectly via kinematics,

d) the supply line opens into the drive cylinder at the bottom in order to extend the piston rod,

e) the return line opens into the drive cylinder on the rod side,

f) the pressure measuring device comprises a first pressure sensor which measures the hydraulic pressure in the drive cylinder on the base side or in the inlet line,

g) the pressure measuring device comprises a second pressure sensor which measures the hydraulic pressure in the drive cylinder on the rod side or in the return line,

h) the control device uses the hydraulic pressures measured in the drive cylinder on the base side and on the rod side and the desired process force of the drive cylinder to calculate the minimum required system pressure, which must be supplied by the hydraulic pump so that the pressing device can apply the predetermined process force, and

i) the second controller in the second control loop is adapted to adjust the displacement volume of the hydraulic pump such that the hydraulic pump only supplies the required minimum value of the system pressure as required with a certain safety margin, but no more.

10 . The food-processing machine according to claim 1 , wherein the hydraulic pump is driven by an electric motor.

11 . The food-processing machine according to claim 1 , wherein the control device comprises a pulse-width modulator which is adapted to receive a setpoint value for the hydraulic pressure and to output a pulse-width modulated control signal on the output side.

12 . The food-processing machine according to claim 11 , wherein the pulse-width modulator comprises a dither element which is adapted to impose a dither signal on the pulse-width modulated control signal in order to avoid a stick-slip effect.

13 . The food-processing machine according to claim 11 , wherein the pulse-width modulator preferably comprises a current controller on the output side, which is adapted to output the pulse-width modulated control signal as a current signal.

14 . The food-processing machine according to claim 11 , wherein the control device comprises an electromechanical actuator, wherein the electromechanical actuator is adapted to receive the pulse-width modulated control signal from the pulse-width modulator and to adjust the displacement volume of the hydraulic pump according to the pulse-width modulated control signal in order to adjust the hydraulic pressure.

15 . The food-processing machine according to claim 1 , wherein the control device comprises a limiting member which is adapted to limit the rate of pressure change of the system pressure of the hydraulic fluid.

16 . The food-processing machine according to claim 1 , wherein

a) the food-processing machine is a pressing device and comprises a phase controller which is adapted to recognize and distinguish several of the following phases of a pressing process:

a1) Loading phase in which a food product is loaded into a pressing chamber,

a2) Press positioning phase, in which at least one pressing plate is moved towards the food product in the pressing chamber,

a3) Force build-up phase, in which a predetermined pressing force is built up to act on the food product,

a4) Force holding phase, in which a predetermined pressing force is maintained, which acts on the food product,

a5) a release phase in which the pressing force acting on the food product is reduced, and

a6) an unloading phase in which the pressed food product is removed from the pressing chamber, and

b) the phase controller is adapted to specify a minimum value for the system pressure in each of the individual phases of the pressing process.

17 . The food-processing machine according to claim 1 , wherein the food-processing machine is a food forming machine for forming the food product.

18 . The food processing machine according to claim 1 , wherein the food-processing machine is a food separating machine for separating food products.