EP3383543B1 - Method for adjusting a crushing nip - Google Patents

Description

The invention relates to a method for adjusting a crushing gap of a comminuting device, in particular an impact crusher, and a comminuting device.

Crushing devices, such as impact crushers, are used for crushing crushed material, in particular rock or ores. In an impact crusher, the crushed material is comminuted in a crushing gap formed between baffle plates and a rotor equipped with blow bars. The circumferentially mounted on the rotor blow bars, as well as the baffles are exposed during operation of the crushing device high wear, so that increases the crushing gap with progressing wear. To set a desired crushing gap, the baffle on which the baffle plates are mounted, by means of a hydraulic actuator relative to the rotor movable, so that the crushing gap and thus a desired grain size of the material to be crushed is adjustable.

The resulting from progressive wear enlargement of the crushing gap considerably complicates the exact adjustment of a desired crushing gap, since first the wear or the geometry of the crushing gap must be determined.

It is also from the DE 195 11 097 C1 It is known to adjust the crushing gap of a shredding device by first determining the zero position at which the blow bars touch the impact plates and the crushing gap assumes a value of zero. This zero position is in the DE 195 11 097 C1 determined by the baffle is moved in the direction of the rotating rotor until they touch the blow bars. The vibrations of the impact mechanism are measured and the zero position is identified when a predefinable vibration threshold value is exceeded.

In practice, however, the determination of the zero position based on the vibrations of the impact mechanism is very expensive. When moving the baffle in the direction of the rotor there is a risk of destruction of the baffle, if this is moved too far in the direction of the rotor and exceeds the zero position. Therefore, the impact work is usually gradually moved toward the rotor, whereby it is vibrated. Upon reaching the rotor, the oscillation amplitude increases, which increase is difficult to distinguish from the previous oscillation amplitudes. To identify the zero position in practice, the preceding vibrations of the impact work to be considered, with a complex calculation is necessary, which makes it difficult to accurately identify the zero position. document DE29505133U1 discloses a designated crushing machine, provided with circumferentially arranged impact tools rotor which is rotatably mounted in a crusher housing and cooperates with a baffle, which is arranged pivotably in the crusher housing and its distance to the impact tools is adjustable.

On this basis, it is an object of the present invention to provide a method for adjusting the crushing gap of a crushing device, which is simple and reliable feasible. Furthermore, it is an object of the present invention to provide a comminuting device in which the crushing gap can be adjusted easily and reliably.

This object is achieved by a method having the features of the independent method claim 1, and by a crushing device according to the independent device claim 6. Advantageous developments emerge from the dependent claims.

1. a) Rotieren des Rotors,
2. b) Bewegen des Prallwerks in Richtung des Rotors,
3. c) Ermitteln des Druckverlaufs in dem Hydraulikaktuator
4. d) Einstellen des Ventilschwellwertes des adaptiven Druckbegrenzungsventils, bei dem sich das adaptive Druckbegrenzungsventil in eine geöffnete Position bewegt, in Abhängigkeit des Drucks an dem Hydraulikaktuator,
5. e) Detektieren der Nullstellung, bei der das Prallwerk mit zumindest einem Prallelement in Kontakt kommt, wenn das adaptive Druckbegrenzungsventil in die geöffnete Position bewegt wird oder wenn die Steigung des Druckverlaufs an dem Hydraulikaktuator einen vorbestimmten Steigungsschwellwert überschreitet wobei die Position des Prallwerks über die Zeit ermittelt wird und daraus die Position des Prallwerks in der in Schritt e) detektierten Nullstellung bestimmt wird, und
6. f) Bewegen des Prallwerks in der zu Schritt b) entgegengesetzten Richtung, sodass ein gewünschter Brechspalt eingestellt wird.

According to a first aspect, the invention comprises a method for adjusting a breaking gap of a comminution device, in particular an impact crusher, wherein the comminution device comprises a rotor rotatable about its center axis with collision elements arranged peripherally thereon and an impact mechanism movably mounted relative to the rotor by means of a hydraulic actuator. The hydraulic actuator is connected to an adaptive pressure limiting valve and a crushing gap is formed between the impact mechanism and the impact elements. The method comprises the steps:

1. a) rotating the rotor,
2. b) moving the impact mechanism in the direction of the rotor,
3. c) determining the pressure curve in the hydraulic actuator
4. d) adjusting the valve threshold of the adaptive pressure relief valve, wherein the adaptive pressure relief valve moves to an open position, in response to the pressure at the hydraulic actuator,
5. e) detecting the zero position where the impactor contacts at least one baffle when the adaptive pressure relief valve is moved to the open position or when the slope of the pressure waveform on the hydraulic actuator exceeds a predetermined threshold threshold, the position of the impaction over time and from this the position of the impact mechanism is determined in the zero position detected in step e), and
6. f) moving the impact mechanism in the opposite direction to step b), so that a desired crushing gap is set.

To set the crushing gap of the shredding device, the zero position is determined in particular first. The zero position is the position of the baffle in which the baffle contacts at least one baffle element of the rotor, so that the crushing gap assumes a value of zero in this position. Starting from the determined zero position, the crushing gap is adjusted, wherein the impact mechanism is moved away from the rotor, so that the desired crushing gap is set. In the zero position, one of the baffle elements in rotation of the rotor touches the baffle, in particular the Impact force is applied, which results in a pressure increase in the hydraulic actuator.

In particular, the hydraulic actuator has a hydraulic cylinder with a piston arranged movably therein. The piston divides the hydraulic cylinder into two chambers and is connected at one end to the impact mechanism, so that a movement of the piston results in a movement of the impact work. If pressure is applied to the cylinder chamber facing away from the impact mechanism, the impact mechanism moves in the direction of the rotor. In the zero position, in particular, the cylinder chamber facing away from the impact mechanism is subjected to a pressure.

The impact elements are, for example, blow bars, crusher teeth or hammer tools, which are mounted circumferentially on a rotor.

The hydraulic actuator is in particular connected to a pressure measuring device which determines the pressure profile in the cylinder chambers of the hydraulic cylinder over time. Preferably, the pressure profile determined with the pressure measuring device is transmitted to the adaptive pressure limiting valve.

The adaptive pressure relief valve preferably has a valve threshold corresponding to a predetermined differential pressure at the adaptive pressure relief valve. Upon reaching the valve threshold, the adaptive pressure relief valve is moved to an open position in which hydraulic fluid flows through the adaptive pressure relief valve and the pressure on the hydraulic actuator, particularly in the cylinder chamber facing away from the impactor, is reduced. The adaptive pressure limiting valve is preferably designed such that the valve threshold value adjusts as a function of the pressure at the hydraulic actuator, in particular in the cylinder chambers.

The adaptive pressure limiting valve has in particular at least two surfaces which are pressurized. The first surface is acted upon by the pressure applied to the hydraulic actuator, in particular in the cylinder chamber facing away from the impact mechanism, wherein the second surface is acted upon by a reference pressure, in particular the pressure applied by means of a hydraulic pump of the hydraulic system. When the difference between the pressure applied to the hydraulic cylinder and the reference pressure exceeds the valve threshold, the adaptive pressure relief valve is moved to the open position. The valve threshold value is in particular a threshold value of the pressure difference from the pressure applied to the hydraulic cylinder and the reference pressure.

For example, the valve threshold is about 5 - 10 bar, in particular 7 bar, so that the adaptive pressure relief valve is moved to the open position when the pressure at the hydraulic actuator about 5-10 bar, in particular 7 bar higher than the reference pressure. The reference pressure is preferably independent of the achievement of the zero position of the impact mechanism, so that it does not change at all by a blow to the baffle or only by the subsequent opening of the adaptive pressure relief valve.

The adaptive pressure limiting valve has, for example, a spring of variable spring constant, via which the valve threshold value can be set. Preferably, the spring acts on the adaptive pressure limiting valve in the direction of the closed position.

The arrangement of such an adaptive pressure limiting valve offers the advantage of a simple and reliable determination of the zero position of the impact mechanism, wherein the pressure in the actuator is automatically lowered upon reaching the zero position and a further method of the impact mechanism in the direction of the rotor is reliably prevented.

The step d) of adjusting the adaptive pressure relief valve valve threshold at which the adaptive pressure relief valve moves to an open position in response to the pressure at the hydraulic actuator allows the valve threshold to be approached upon movement of the impactor towards the rotor The zeroing is prevented, although the pressure in the actuator, for example, rises slightly. At a high pressure rise in the actuator, in which the gradient threshold value according to step e) is exceeded, in particular by about 5 bar / sec, the valve threshold value is reached and the adaptive pressure relief valve is opened.

This dependence of the valve threshold value of the pressure, in particular the pressure curve, on the actuator reliable detection of the zero position and a subsequent automatic movement of the baffle is made possible away from the rotor, with only a touch of the baffle with the blow bars is sufficient to the adaptive To move the pressure relief valve to the open position. The measurement of an entire oscillation or even several oscillations and thus also several contacts of the impact mechanism with the rotor are therefore not necessary. This is particularly gentle on material, since only a blow of the baffles of the rotor to the baffle is necessary to detect the zero position.

In particular, the valve threshold is adjusted such that the adaptive pressure relief valve is in the closed position when the pressure curve of the hydraulic actuator falls below the gradient threshold and the adaptive pressure relief valve is in the open position when the pressure curve of the hydraulic actuator exceeds the gradient threshold.

The position of the impact mechanism is determined over time and from this the position of the impact mechanism is determined in the zero position detected in step e). In particular, the step f) of moving the impactor away from the rotor is carried out in response to the determined position of the impact mechanism in the zero position, so that a desired crushing gap is set relative to the determined zero position. The determination of the position of the baffle in the zero position offers the possibility of adjusting the crushing gap with respect to the zero position. Furthermore, it is possible to determine the further operation of the comminution device, the wear of the impact mechanism and the baffle elements on the rotor, wherein over the time determined positions of the impact mechanism are compared in the zero position.

The baffle is moved in the direction of the rotor according to a further embodiment with a constant speed. According to a further embodiment, step f) takes place after the first contact of the impact mechanism with a baffle element of the rotor, so that the impact mechanism and the baffle element have exactly one contact.

The gradient threshold value of the pressure rise in the actuator, according to a further embodiment, has a value of about 3-8 bar / sec, in particular about 4-6 bar / sec, preferably about 5 bar / sec. In particular, the zero position of the impact mechanism is detected when the slope of the pressure curve on the actuator exceeds the gradient threshold value for a period of <1 second.

The invention further comprises a shredding device comprising a rotatable about its central axis rotor with circumferentially arranged thereon baffle elements, a baffle, which is movably mounted by means of a Hydraulikaktuators relative to the rotor, formed between the baffle and the baffles crushing gap and a pressure measuring device for determining the Pressure curve in the hydraulic actuator, wherein the hydraulic actuator is connected to an adaptive pressure relief valve. The shredding device has a displacement measuring device for determining the position of the impact work and a control device for controlling the hydraulic actuator, which is designed such that it determines the slope of the pressure curve and detects a zero position of the impact mechanism, wherein the impact mechanism touches a baffle element of the rotor, if the adaptive pressure relief valve is moved to the open position or when a predetermined pressure threshold is exceeded.

The advantages mentioned above with respect to the method for adjusting a crushing gap of a crusher apply to the crusher in a conforming manner.

In particular, the adaptive pressure relief valve is connected to the pressure measuring device. In particular, the pressure measuring device transmits the determined pressure profile at the hydraulic actuator to the adaptive pressure limiting valve, so that, for example, the valve threshold value corresponds to the pressure threshold determined pressure is set. For example, the adaptive pressure relief valve is opened or closed as a function of the determined pressure curve.

According to a further embodiment, the adaptive pressure limiting valve is configured such that the valve threshold value at which the adaptive pressure limiting valve moves into an open position adjusts in dependence on the pressure, in particular the pressure curve in the hydraulic actuator.

The valve threshold is according to another embodiment in about 5- 10 bar, in particular 7 bar.

The shredding device comprises a path measuring device for determining the position of the impact work and a control device for controlling the hydraulic actuator, which is designed such that it determines the slope of the pressure curve and detects a zero position of the impact mechanism, wherein the impact mechanism contacts a baffle element of the rotor, if adaptive pressure relief valve is moved to the open position or when the slope of the pressure in the hydraulic actuator exceeds the slope threshold.

The hydraulic actuator has according to a further embodiment, a hydraulic cylinder and a piston arranged therein, wherein the piston is connected to the baffle and the displacement measuring device is attached to the piston.

The pressure measuring device is arranged according to a further embodiment such that it determines the pressure in the cylinder chamber of the hydraulic actuator facing away from the impact mechanism.

Description of the drawings

• Fig. 1 zeigt eine schematische Darstellung einer Zerkleinerungseinrichtung gemäß einem Ausführungsbeispiel.
• Fig. 2 zeigt ein Diagramm eines Druckverlaufs an einem Hydraulikzylinder der Zerkleinerungseinrichtung gemäß Fig. 1.

The invention is explained in more detail below with reference to several possible embodiments with reference to the accompanying figures.

• Fig. 1 shows a schematic representation of a crushing device according to an embodiment.
• Fig. 2 shows a diagram of a pressure curve on a hydraulic cylinder of the crusher according to Fig. 1 ,

In Fig. 1 shows a crushing device 10, in particular an impact crusher, with a rotor 14 and a baffle 12. The rotor 14 is substantially cylindrical and formed around its Central axis rotatable. On its lateral surface, the rotor 14 has a plurality of circumferentially arranged impact elements 16. In particular, it is in the in Fig. 1 illustrated embodiment of the baffles 16 to blow bars. The baffles 16 are arranged in a radial recess in the lateral surface of the rotor 14 and extend in the radial direction to about half of their length from the rotor 14 out. The direction of rotation is indicated by an arrow in Fig. 1 characterized.

The baffle 12 is disposed adjacent to the rotor 14 and has a plurality of baffles 34 which are arranged facing in the direction of the rotor 14. Between the baffles 34 of the baffle 12 and the baffles 16 of the rotor 14, a crushing gap 38 is formed. The baffles 34 of the baffle 12 are arranged one behind the other in the rotational direction, wherein the distance of the baffles 34 reduced to the blow bars 16 of the rotor 14 in the direction of rotation to the in Fig. 1 lowest of the baffles 34 with the rotating baffles 16 forms the crushing gap 38. The baffle 12 is rotatably mounted about a pivot axis 32 so that the baffles 34 can be aligned relative to the rotor 14. Furthermore, the baffle 12 is arranged on the pivot axis 32 with a hydraulic actuator 18 in the direction of the rotor 14 movable. The hydraulic actuator 18 has a hydraulic cylinder 40 with a piston 20 movable therein, which divides the hydraulic cylinder 40 into two cylinder chambers. The piston 20 is attached at its one end to the baffle 12 and has a displacement measuring device 22 for detecting the movement of the piston 20 in the hydraulic cylinder 40. On the actuator 18, a pressure measuring device 24 is further attached, the pressure in the baffle 12th determined cylinder chamber of the actuator.

The actuator 18 is connected to an adaptive pressure limiting valve 26. Furthermore, the actuator 18 is connected via a directional control valve 42 to a hydropump 30. Between the directional control valve 42 and the adaptive pressure relief valve 26, a pilot-operated check valve 27 is arranged. The check valve 27 prevents hydraulic flow from the adaptive pressure relief valve 26 back to the directional control valve 42. Upon reaching a predetermined pressure in the line B from the hydraulic actuator 18 to the directional control valve 42, the check valve 27 is unlocked.

The adaptive pressure relief valve 26 has in the embodiment of Fig. 1 a movable piston comprising four surfaces A, B, AP and BP. The surfaces A and B point in the direction of the lines connected to the hydraulic actuator, the surfaces AP and BP pointing in the direction of a control line shown in broken lines, which leads from the adaptive pressure relief valve to the line between the directional control valve 42 and the pump 30. The area AP minus the area BP corresponds approximately to the area A together with the area B. The area AP is acted upon by a spring in the direction of the closed position.

During operation of the impact crusher, the rotor 14 rotates in the direction of the arrow, wherein crushing material is fed onto the rotor 14, which are thrown by the rotation of the rotor 14 against the baffle plates 34 of the baffle 12. To set the refractive gap 38, the baffle 12 is moved in the direction of the rotor 14 or away from the rotor 14. For this purpose, the directional control valve 42 is moved to the position shown on the left, in which the directional control valve 42 is opened, so that hydraulic fluid is pressed into the impact mechanism 12 remotely located cylinder chamber of the actuator 18 via the pump 30, whereby the piston 20 in the direction of the rotor 14 moves and the crushing gap 38 is reduced. To move the baffle 12 away from the rotor 14 to increase the crushing gap 38, the directional control valve 42 is in the in Fig. 1 moved right position in which the valve is opened so that the supply and return line are crossed, so that the piston 20 is moved in the direction away from the rotor 14. In the in Fig. 1 shown valve position, the piston 20 is not moved.

The pressure relief valve 26 is connected to both cylinder chambers of the actuator 18. If the pressure at the pressure limiting valve 26 exceeds a predetermined valve threshold value, the pressure limiting valve 26 opens and the hydraulic fluid flows from line A via the open seat of the pressure limiting valve into the line B. The valve threshold value of the pressure limiting valve 26, from which the pressure relief valve 26 opens, depends on the on the hydraulic actuator 18, applied pressure. If the same pressure acts on the hydraulic actuator 18 and the control line connected to the pump 30, an equilibrium of forces is applied to the surfaces A, B, AP and BP of the cylinder of the adaptive pressure limiting valve 26, so that the piston is moved into the closed position by the spring is charged. The applied pressure in the control line is also referred to as the reference pressure. In an applied to the piston of the adaptive pressure limiting valve 26 balance of forces, the valve threshold is determined by the spring force, so that it is always higher by the spring force than the voltage applied to the hydraulic actuator pressure. The valve threshold value is, for example, approximately 5 to 10 bar, in particular 7 bar, higher than the pressure applied to the actuator 18.

However, if the pressure in the actuator 18 rises sharply due to a blow on the impact device 12 connected to the piston 20, the surface A is subjected to a higher pressure than the areas AP and BP acted upon by the pressure of the pump 30. The pressure on surface B is preferably very low or almost zero. If this pressure difference exceeds the spring force, the adaptive pressure relief valve 26 is moved to an open position.

To adjust the crushing gap 38, the rotor 14 is rotated about its axis of rotation, wherein during the adjustment of the crushing gap no material to be crushed is fed into the crushing gap. Subsequently, the pump 30 is started and the directional control valve 42 is moved to the left, parallel position, so that the impact mechanism 12 facing away from the cylinder chamber is pressurized and the Piston 20 moves at approximately constant speed in the direction of the rotor 14. Between the hydraulic pump 30 and the directional valve 42, a throttle check valve 29 is arranged, via which the speed of the piston 20 is adjusted, so that the piston 20 is moved at a constant speed in the direction of the rotor 14. To secure the maximum system pressure, another pressure limiting valve 36 is arranged parallel to the throttle check valve 29. Furthermore, a buffer 28 serving as a buffer 28 is arranged between the pump 30 and the throttle check valve 29. The pressure measuring device 24 determines the pressure on the actuator 18, in particular in the cylinder chamber facing away from the baffle 12, over time, wherein the displacement measuring device 22 determines the position of the piston 20 over time. Upon contact of at least one of the baffles 34 of the baffle 12 with one of the blow bars 16, the pressure in the actuator 18 increases such that the adaptive pressure relief valve 26 opens so that the piston 20 moves in an opposite direction away from the rotor 14. By means of the pressure profile determined by the pressure measuring device 24, the time of contact between the baffle plate 34 of the baffle 12 is determined with the blow bar 16. The position of the zero position of the baffle 12 is determined by means of the determined by the path measuring device 22 position of the piston 20 at the time of pressure rise. If the slope of the pressure curve exceeds a certain gradient threshold, the zero position of the impact mechanism 12 is detected. The zero position is also detected, for example, when the adaptive pressure relief valve 26 is moved to the open position.

Fig. 2 shows the pressure profile determined by the pressure measuring device 24 during the process for adjusting the crushing gap 38, wherein the baffle 12 is moved in the direction of the rotor 14, while the rotor 14 rotates about its axis of rotation. With the solid line, the pressure on the actuator 18, in particular in the cylinder chamber facing away from the baffle 12, shown over time. The broken line shows the valve threshold set on the adaptive pressure relief valve 26 over time. During the process of adjusting the crushing gap 38, the displacement sensor detects the position of the piston 20 in the hydraulic cylinder 40 over time. At 0 seconds, the pump 30 is turned on, while the directional control valve 42 in the in Fig.1 shown locked position and the pressure in the actuator 18 is constant. After about 3 seconds, the directional control valve 42 is moved to the parallel position, so that the cylinder chamber facing away from the baffle 12 is pressurized and the piston 20 moves at approximately constant speed in the direction of the rotor 14. The pressure on the actuator 18, in particular in the cylinder chamber facing away from the baffle 12, increases approximately linearly, wherein the slope is for example about 2-3 bar per second. The valve threshold value of the adaptive pressure limiting valve 26 runs approximately parallel to the pressure curve of the actuator 18, wherein the valve threshold value is higher by about 5 bar than the actuator pressure. The increase in pressure in the actuator 18 is due to, for example, that the baffle 12 is raised against gravity. After about 11 seconds, one of the baffle elements 16 touches a baffle plate 34 of the baffle 12 and the pressure curve has a pitch that is significantly greater than the slope of the pressure curve during the movement of the impact mechanism 12 in the direction of the rotor 14. By way of example, the slope is about 100 bar per second. The pressure on the actuator 18 rises to a value of about 70 bar, wherein the valve threshold of the adaptive pressure relief valve 26 is exceeded and the pressure relief valve 26 is opened, so that the piston 20 moves in the opposite direction away from the rotor 14. The pressure in the actuator 18 decreases to a value that approximately corresponds to the output pressure value in the actuator 18, wherein the pressure limiting valve 26 is closed and has a threshold which is higher than the actuator pressure by about 5 bar.

The pressure on the actuator 18 increases significantly when touching one of the baffle elements 16 with a baffle plate 34, so that the time of contact of the beater bar 16 with the baffle plate 34 is clearly determined from the pressure curve. In the in Fig. 2 illustrated exemplary pressure profile is the time of contact 11 seconds. In particular, a contact between one of the blow bars 16 is detected with a baffle plate 34 when the pressure increase of the actuator pressure exceeds a predetermined value. In particular, this gradient threshold is about 5 bar / sec.

In order to determine the zero position of the piston, in which one of the baffle elements 16 is in contact with a baffle plate 34, the position of the piston 20 in the cylinder 40 determined by the displacement measuring device 22 is determined at 11 seconds. With known zero position of the piston, the crushing gap 38 is then adjusted.

LIST OF REFERENCE NUMBERS

10

comminution device

12

pounding device

14

rotor

16

Baffle elements blow bars

18

hydraulic actuator

20

piston

22

displacement measuring system

24

Pressure measuring device

26

adaptive pressure relief valve

27

unlockable check valve

28

hydraulic accumulator

29

Speed Controller

30

hydraulic pump

32

swivel axis

34

Flapper

36

Pressure relief valve

38

crushing gap

40

hydraulic cylinders

42

way valve

Claims (9)

1. Method for adjusting a crushing gap (38) of a comminution device (10), in particular of an impact crusher, comprising a rotor (14) which can be rotated about its centre axis and has impact elements (16) which are arranged over its circumference,
   an impact mechanism (12) which is fitted such that it can be moved relative to the rotor (14) by means of a hydraulic actuator (18), wherein the hydraulic actuator (18) is connected to an adaptive pressure-limiting valve (26), and
   a crushing gap (38) which is formed between the impact mechanism (12) and the impact elements (16), wherein the method has the following steps:

   a) rotating the rotor (14),

   b) moving the impact mechanism (12) in the direction of the rotor (14),

   c) ascertaining the pressure profile in the hydraulic actuator (18),

   d) adjusting the valve threshold value of the adaptive pressure-limiting valve (26) at which the adaptive pressure-limiting valve (26) moves into an open position, depending on the pressure on the hydraulic actuator (18),

   e) detecting the neutral position, in which the impact mechanism (12) comes into contact with at least one impact element (16) when the adaptive pressure-limiting valve is moved into the open position or when the gradient of the pressure profile on the hydraulic actuator (18) exceeds a predetermined gradient threshold value, wherein the position of the impact mechanism (12) over time is ascertained and from which the position of the impact mechanism (12) in the neutral position detected in step e) is determined, and

   f) moving the impact mechanism (12) in the opposite direction to step b), so that a desired crushing gap (38) is established.
2. Method according to Claim 1,
   wherein the impact mechanism (12) is moved in the direction of the rotor (14) at constant speed.
3. Method according to one of the preceding claims,
   wherein step f) is carried out following the first contact of the impact mechanism (12) with an impact element (16) of the rotor (14), so that the impact mechanism (12) and the impact element (16) have exactly one contact.
4. Method according to one of the preceding claims,
   wherein the gradient threshold value has a value of about 3-8 bar/sec, in particular about 4-6 bar/sec, preferably about 5 bar/sec.
5. Comminution device (10) comprising
   a rotor (14) which can be rotated about its centre axis and has impact elements (16) which are arranged over its circumference,
   an impact mechanism (12) which is fitted such that it can be moved relative to the rotor (14) by means of a hydraulic actuator (18),
   a crushing gap (38) formed between the impact mechanism (12) and the impact elements (16), and
   a pressure measuring device (24) for ascertaining the pressure profile in the hydraulic actuator (18), the hydraulic actuator (18) being connected to an adaptive pressure-limiting valve (26), characterized in that the comminution device (10) comprises a displacement measuring device (22) for ascertaining the position of the impact mechanism (12) and a control device for controlling the hydraulic actuator (18), which is formed in such a way that it ascertains the gradient of the pressure profile and detects a neutral position of the impact mechanism (12), in which the impact mechanism (12) touches an impact element (16) of the rotor (14) when the adaptive pressure-limiting valve is moved into the open position or when a predetermined pressure threshold value is exceeded.
6. Comminution device (10) according to Claim 5,
   wherein the adaptive pressure-limiting valve (26) is formed in such a way that the valve threshold value at which the adaptive pressure-limiting valve (26) moves into an open position is adjusted, depending on the pressure in the hydraulic actuator (18).
7. Comminution device (10) according to Claim 6,
   wherein the valve threshold value is about 5-10 bar, in particular 7 bar.
8. Comminution device (10) according to one of Claims 5 to 7, wherein the hydraulic actuator (18) comprises a hydraulic cylinder (40) and a piston (20) arranged therein, wherein the piston (20) is connected to the impact mechanism (12) and the displacement measuring device (22) is fitted to the piston (20).
9. Comminution device (10) according to one of Claims 5 to 8, wherein the pressure measuring device (24) is arranged in such a way that it ascertains the pressure in that cylinder chamber of the hydraulic actuator (18) which faces away from the impact mechanism (12).

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