Roller set and roller mill

Abstract

One aspect of the invention relates to a roller set for a grain mill, namely a roller mill, which has a first milling roller (2) that is supported by a first bearing body (5) and a second milling roller (3) that is supported by a second bearing body (6). The second bearing body (6) can be moved relative to the first bearing body (5). Firstly, the roller set is designed to disengage the second milling roller relative to the first milling roller by moving the second bearing body, i.e., the roller set moves the second milling roller so far from the first milling roller that a milling process can no longer take place regardless of the movement state of the milling rollers and regardless of the grain size of the grain product to be milled. Secondly, the roller set is designed to set the width of the milling gap which is produced between the first and second milling roller. According to an aspect of the invention, the roller set has an electric drive which is designed to produce both the movement of the second bearing body (6) relative to the first bearing body (5) from the engaged state into the disengaged state as well as the movement of the second bearing body (6) relative to the first bearing body (5) in the engaged state in order to set the width of the milling gap on the basis of control signals.

Description

[0001] ROLLER PACK AND ROLLER HALL

[0002] The invention relates to a roller mill and a roller package for a roller mill.

[0003] Roller mills are used in grain mills or other food processing mills. A roller mill comprises at least one set—often two or four sets—of two grinding rollers each, between which a grinding gap is formed during operation. These rollers rotate—generally at different speeds—to crush the material in the grinding gap.

[0004] Common roller packages have a fixed and a movable bearing body on either side of the grinding rollers. The movable bearing body can be moved between an engaged and a disengaged position relative to the fixed bearing body for coarse gap adjustment by a generally pneumatically operated disengagement device. A comparatively rapid disengagement is achieved, particularly when finely grooved or smooth grinding rollers are used, when there is no more product in the feed system of the roller mill and the rollers would otherwise rub directly against each other, causing severe overheating in a short time. The roller mill control system therefore disengages whenever a level sensor in the feed system determines that there is no more product.In addition to the disengagement device, common roller assemblies feature an adjusting device for fine adjustment, which can be operated manually or by means of an electric motor. Furthermore, a foreign body protection device is generally present, which allows the grinding rollers to be quickly moved apart against a spring force in the event that a large, hard foreign body gets between the grinding rollers. Various solutions have been developed for the arrangement of the three elements 'disengagement device', 'adjusting device for fine adjustment', and 'foreign body protection'. WO 89703245 A1, DE 10316691 A1, EP 3597299 A1, and WO 2019 / 229014 A2 show corresponding examples. DE 27 06 166 also shows a roller assemblies with manual gap adjustment, a pneumatic engagement and disengagement device, and a foreign body protection device.As an alternative to manual gap adjustment, an electric motor is also mentioned, forming part of a control loop, i.e., a closed-loop controlled adjustment device. The controller maintains the distance between the bearing bodies constant via a proximity sensor and a comparator. The setpoint can be corrected by a temperature factor or manually via a manual input. In the schematic diagram illustrating this principle, unlike design examples of the roller mill, no release device is present.

[0005] A disadvantage of these solutions is the need for a compressed air supply for the pneumatic actuation of the disengagement device, as leaks in pneumatic systems are almost unavoidable in practice, resulting in constant energy consumption, even when the disengagement device is not actually being actuated. Furthermore, adjusting the width of the grinding gap requires considerable know-how and experience. Depending on the design, the recovery accuracy after disengaging and re-engaging the movably mounted grinding roller may be insufficient. The document IT 2020 0001 6408 describes a roller package that enables disengagement of the rollers without pneumatics. A motor is provided for this purpose. This motor drives a spindle on which a spindle nut sits. This motor moves an eccentric mechanism via a lever, which is coupled to a transmission rod.This pulls the movable bearing body toward the fixed bearing body via a spring assembly. This allows a single electric drive to be used for both gap adjustment and disengagement, eliminating the need for pneumatics.

[0006] Such an eccentric mechanism, as shown in IT 2020 0001 6408, does have the advantage that, with skillful positioning of the eccentric position, it can achieve a high force with a short travel in the fine adjustment range and a large travel with a small force in another range (coarse adjustment). However, this advantage comes with the intrinsic disadvantage that it must be adjusted very precisely during assembly and maintenance work – which results in a susceptibility to errors. The mechanism also impairs the disengagement speed, and the installation and removal of the gap adjustment mechanism is complicated and time-consuming.

[0007] It is therefore an object of the present invention to provide a roller package for grinding grain products and a roller mill with such a roller package, which overcome disadvantages of the prior art and which are advantageous with regard to energy consumption, accuracy in adjusting the grinding gap, reproducibility and / or maintenance.

[0008] This object is achieved by a roller package and a roller mill as defined in the patent claims. According to one aspect of the invention, a roller package for a grain milling machine, namely a roller mill, is provided, which has a first grinding roller which is mounted on a first bearing body, and a second grinding roller which is mounted on a second bearing body. The second bearing body is movable relative to the first bearing body. Firstly, the roller package is designed to disengage the second grinding roller relative to the first grinding roller by moving the second bearing body, i.e. to move it far enough away from the first grinding roller that no further grinding process can take place regardless of the state of movement of the grinding rollers and regardless of the grain size of the grain product to be ground. The disengaging movement can, for example,require that the second grinding roller is moved relative to the first grinding roller by at least 3 mm, often by at least 5 mm. Secondly, the roller package is configured to adjust the width of a grinding gap that results between the first and the second grinding roller. According to one aspect of the present invention, the roller package has an electric drive that is configured, based on control signals, to cause both the movement of the second bearing body relative to the first bearing body from the engaged to the disengaged state and the movement of the second bearing body in the engaged state relative to the first bearing body for adjusting the width of the grinding gap.

[0009] This allows the electric drive, for example, to move an actuator whose position provides a reliable measure of the grinding gap size at any time. Furthermore, all critical components for the grinding gap size (mechanically precise, highly stressed elements; motor; gearbox; electronics) can be installed in a single unit. This allows for pre-assembly and testing, as well as easy / quick replacement if necessary.

[0010] Another advantage is that the operator does not need to perform any initial adjustment work depending on the roller diameter, as is the case with conventional roller packages. With conventional roller packages, the fine adjustment can only travel a limited distance, so the connection of the bearing bodies (tension rod) must be adjusted to an appropriate length.

[0011] The electric drive can, for example, be part of an adjusting and disengaging device, which has an adjusting element whose position can be moved by the electric drive, and whose position, in turn, determines the position of the second bearing body relative to the first bearing body. The adjusting and disengaging device can, in particular, define an axis, wherein the electric drive causes a defined movement of the adjusting element along the axis, both for the disengagement movement and for adjusting the grinding gap.

[0012] The position of the actuating element relative to a stop element can define the position of the second bearing body relative to the first bearing body. For this purpose, a stop structure is each assigned to the stop element and the actuating element, wherein the stop structure of the actuating element follows a movement of the actuating element relative to the stop element, i.e., the stop structure of the actuating element moves relative to the stop structure of the stop element along the axis, by the same distance as the actuating element relative to the stop element.

[0013] The stop structures are in engagement with a stop section of the first bearing body and the second bearing body, respectively.

[0014] Such an actuating element can, for example, be moved by a spindle drive in such a way that the axial position is clearly determined by the revolutions of the spindle and ultimately of the electric drive (especially a servo motor). Such a spindle drive can, in particular, have a bearing that defines the position of the spindle axis, but also absorbs axial forces. An example of a bearing that both defines the position of the spindle axis and absorbs axial forces is a bearing with interacting conical structures, e.g., a tapered roller bearing. In addition to such a bearing, the spindle drive can also have a conventional bearing, e.g., a ball bearing, to ensure high positioning accuracy of the axis. Other solutions are also conceivable, in which, for example, the functions of "definition of the spindle axis" and "absorption of axial forces" are completely separate and distributed among different components of the bearing.

[0015] The first and second grinding rollers are each supported on both sides relative to the roller axes. In particular, it can be provided that an assembly consisting of a first bearing body, a second bearing body, and an adjusting and disengaging device is present on each side. This means that the statements in this text regarding the bearing body and the adjusting and disengaging device apply to both sides of the roller assembly. However, a common control unit can be provided for the adjusting and disengaging devices on both sides and possibly also for other roller assemblies of the roller mill.

[0016] A common control unit of this type can be a dedicated roller stack control unit, or it can be fully or partially integrated into a control module of the entire roller mill and / or partially also into at least one external component – ​​e.g., a universal computer connected via an interface, a mobile device, and / or a higher-level controller for controlling multiple devices of a grain mill. It can also, if necessary, be formed at least partially by an integrated electronics unit of an electronic handwheel (or the like), as described below. The roller stack thus has an electric drive for moving the second bearing body relative to the first bearing body, with this electric drive being the only active drive for this movement, i.e., the only actuator that can move the second bearing body relative to the first bearing body.The electric drive is therefore the only active drive per side for influencing the position of the second bearing body relative to the first bearing body - ie the roller package is free of an automated release device in addition to the setting and release device.

[0017] However, the control device can be configured to interact with a level sensor of the roller mill to which the roller set belongs, in order to initiate an immediate disengagement movement by the adjusting and disengaging device as soon as the level monitoring detects that there is no more product or insufficient product in the feeding device via which the product to be processed is fed to the roller set.

[0018] An 'active drive' in this sense is a drive in which an actuator causes a movement based on a control signal, which in at least one direction of movement involves the absorption of electrical energy (directly or indirectly) and its conversion into movement. Merely passive, resilient elements and the like, on the other hand, do not constitute an active drive. An 'electric drive' in this context is a drive that has an electric motor whose mechanical power is directly converted into the desired movement via mechanical means (gearbox, spindle drive, etc.). Accordingly, a hydraulic or pneumatic drive is an active drive, but not an electric drive in the sense of this text. A 'roller package' in the sense of this text can, in particular, form a unit that can be removed as a whole from a roller mill and inserted into it, thus forming an independent module.This means that maintenance and, under certain circumstances, certain calibration and testing steps can be carried out on the insulated roller package and do not have to be carried out on the machine while it is still installed. The roller package serving as such a module can also form a closed load frame, i.e. the forces occurring during grinding and in the event of disruptions to the grinding process can be absorbed by the roller package itself, apart from any possible twisting of the roller package due to roller overdrive. A roller mill frame then only has to carry the roller package and, if necessary, absorb the belt force of the rotary drive of the rollers as well as any possible twisting due to roller overdrive, but does not have to absorb any of the forces between the grinding rollers, which are disproportionately greater in relation to the weight and can occur during grinding or in the event of disruptions to the grinding process.

[0019] Alternatively, it cannot be ruled out that the elements of the roller package are not assembled as a module and are, for example, mounted at least partially individually or as a sub-module in the roller mill and also have to be removed at least partially individually or as a sub-module.

[0020] The electric drive can be formed by an electric motor and, if necessary, a gearbox. The electric motor can, in particular, be a servomotor. A 'servomotor' here is understood to be a motor that, through a sensor and possibly a control circuit, allows the control of the revolutions and, in many embodiments, also the angular position of the electric motor. The sensor does not necessarily have to be installed with the actual electric motor, but can also be present separately, for example, on a shaft driven by the gearbox, e.g., the spindle described below. During the grinding process, the grinding rollers are pushed apart by the material to be ground. The adjusting and disengaging device can form a counterforce arrangement - optionally with the foreign body protection - which exerts the appropriate counterforce to define the grinding gap during the grinding process.For example, the roller assembly can be preloaded, with the preload preloading the second bearing body relative to the first bearing body in the direction that moves the second grinding roller away from the first grinding roller (preload in the disengagement direction). For this purpose, a preload spring can be present, which permanently presses the first and second grinding rollers apart in order to preload the first and second bearing bodies against the counterforce arrangement formed by the adjusting and disengaging device. Such a preload spring can, for example, act on the first and second bearing bodies, i.e., there can be a preload spring on either side of the roller assembly.

[0021] With such a configuration, the adjusting and disengaging device can have a first stop structure against which the first bearing body - more precisely: a stop section of the first bearing body - is pressed outwards, as well as a second stop structure that engages with the second bearing body and against which the second bearing body (or: a stop section of the second bearing body) is pressed outwards. The bearing bodies therefore tend to move outwards, away from each other - due to the material being ground between the grinding rollers and also due to the preload. One of the two stop structures is assigned to the stop element and moves with it if necessary, and the other of the stop structures is assigned to the adjusting element and follows movements of the adjusting element relative to the stop element.The distance between the stop element and the adjusting element therefore determines the position of the second bearing body relative to the first bearing body, namely directly, in that, as mentioned, the stop parts of the first bearing body and the second bearing body follow the movement of the stop element or the adjusting element, which excludes, for example, a deflection movement.

[0022] This also means, for example, that the first stop structure and the second stop structure and accordingly also the stop parts of the first bearing body and the second bearing body are centered on the axis along which the actuating element moves relative to the stop element - for example the spindle axis.

[0023] The roller package of the type described above can therefore in particular have an adjusting and disengaging device with the electric drive, an adjusting element and a stop element, wherein the electric drive is designed to move the adjusting element relative to the stop element along an axis in order to effect the movements of the second bearing body relative to the first bearing body from the engaged to the disengaged state and to adjust the width of the grinding gap, and wherein a distance between the adjusting element and the stop element determines a position of the second bearing body relative to the first bearing body, wherein the adjusting and disengaging device has two stop structures, namely a first stop structure and a second stop structure,wherein one of the stop structures is assigned to the stop element and accompanies movements of the stop element, and the other of the stop structures is assigned to the adjusting element and accompanies movements of the adjusting element, and the first bearing body and the second bearing body are pressed outward in the axial direction with respect to the axis against the first stop structure and the second stop structure, respectively, when the first grinding roller and the second grinding roller are pressed apart, and wherein the first stop structure and the second stop structure are centered on the axis. In this case, the adjusting and disengaging device can, in particular, comprise a spindle drive with a spindle axis, wherein the spindle drive is driven by the electric drive and the adjusting element is moved relative to the stop element along the spindle axis, and the first stop structure and the second stop structure are centered on the spindle axis.ie the axis corresponds to the spindle axis.,

[0024] This "everything on one axis" concept has, firstly, the major advantage of eliminating the need for deflection devices or the like, which, due to tolerances, etc., introduce additional small degrees of freedom and thus imprecision. Secondly, no adjustment of deflection devices is necessary. Thirdly, assembly and disassembly are particularly simple, as the actuating and disengaging device as a whole can simply be positioned and engaged with the stop sections or removed.

[0025] The stop element can be stationary with respect to a frame or housing of the actuating and disengaging device, or it can also be movable like the actuating element, in particular along the axis.

[0026] In one group of embodiments, the adjusting and disengaging device also has a foreign body protection device. This allows the two grinding rollers to be moved apart against a comparatively strong spring force in order to prevent the grinding rollers from being damaged or other elements from being overstressed if a hard foreign body, for example a metal part, gets between the grinding rollers. Foreign body protection devices, for example with disc spring assemblies, are known per se. However, the present group of embodiments is characterized by the fact that such a foreign body protection device is present on the adjusting and disengaging device. It can therefore be provided that a preloaded spring device is present between the adjusting element and the (second or first) stop structure assigned to it and / or between the stop element and the (first or second) stop structure assigned to it.The preload of the spring device is so great that, during normal operation, the axial distance between the adjusting element and the second stop structure, or between the stop element and the first stop structure, remains constant and independent of the forces between the grinding rollers. The spring force with which the spring device is preloaded can therefore be greater than the maximum force prevailing between the rollers during normal operation, e.g., at least 40 kN, at least 50 kN, e.g., approximately 55 kN.

[0027] In particular, it can be provided that the relative movement of the bearing bodies when the grinding rollers move apart due to a foreign body is qualitatively the same as during disengagement and adjustment of the grinding gap. In particular, it can be provided that there is only a single degree of freedom for relative movements of the bearing bodies. Thus, the stop structures of the adjusting and disengaging device are moved apart along the same axis when a foreign body passes through as during the disengagement movement or fine adjustment.

[0028] Providing only a single degree of freedom offers significant advantages in terms of defining the position of the rollers. In contrast to the prior art, there is no accumulation of inaccuracies resulting from play for each degree of freedom. Rather, the bearing bodies can be preloaded against each other along the single degree of freedom, ensuring a precise and reproducible position. In particular, it can be provided that the first stop structure and the second stop structure are moved apart relative to each other even when the two grinding rollers move apart due to a foreign body.For this purpose, the first stop structure or the second stop structure (or both) can be movable outwards along the axis against a spring force of the prestressed spring device, for example a disc spring assembly, without influencing the relative position of the actuating element and the stop element, and thus also without influencing the electric drive.

[0029] In embodiments of this group, all movements to which the bearing bodies—or the stop sections of the bearing bodies—may be subjected correspond to a movement along a single axis, namely the axis of the actuating and disengaging device. This axis can also correspond to the axis of the motor (e.g., servomotor) of the electric drive or, if a gearbox is used, be at least parallel to it.

[0030] In some embodiments, the first and second bearing bodies are mounted in a housing-mounted manner with respect to a frame of the roller assembly. In particular, it can be provided that the first bearing body is fixed in its position and orientation relative to the frame, i.e., immobile, while the second bearing body is pivotable about a pivot axis that is fixed relative to the frame, immobile, and parallel to the roller axes. The first bearing body can, for example, be integral with the frame, i.e., can be formed by the frame.

[0031] The adjusting and disengaging device can, for example, be located on the top side of the roller assembly (i.e., there can be an adjusting and disengaging device on each side of the roller assembly), while the second bearing body can pivot on the bottom side about a pivot axis parallel to the roller axes. The axis of the adjusting and disengaging device is accordingly located in a plane perpendicular to this pivot axis and the roller axes.

[0032] In addition to the grinding rollers, the roller package can have a scraper, which during operation scraps off any grinding material that adheres to the grinding rollers after passing through the grinding gap. It can also be provided that the scraper is automatically lifted off the grinding rollers when the grinding rollers are disengaged. This can prevent the idle grinding rollers from becoming worn or damaged, and prevent overheating. In one group of embodiments, the roller package can be configured to automatically lift the scraper through the disengaging movement, specifically in such a way that lifting is brought about by the bearing bodies moving apart (directly or indirectly, via elements of the adjusting and disengaging device connected to the bearing bodies).

[0033] In one group of embodiments, this is achieved in such a way that the scraper lifts off upon disengagement, but the scraper is not affected by a – generally very rapid – relative movement of the grinding rollers caused by a foreign body. This also applies when, as described above, relative movements between the bearing bodies have only a single degree of freedom.

[0034] According to a first possibility, a lifting mechanism is designed such that a movement of the second bearing body relative to the first bearing body is only transmitted to the lifting mechanism during the final section of the disengagement process, i.e., just before the grinding rollers have moved apart as far as possible. This way, both small movements, such as adjusting the grinding gap, and very rapid movements out of the engaged position (if a foreign object gets between the grinding rollers during operation) leave the scraper unaffected.

[0035] Such a configuration according to the first possibility can be achieved, for example, by having the lifting mechanism with a transmission element with a slotted hole. Depending on the arrangement, this ensures that the transmission element is only driven at the end of its travel (when a driving structure reaches the end of the slotted hole) and / or that the transmission element only drives a structure to be driven at the end of its travel through the transmission element (when the structure to be driven reaches the end of the slotted hole). The transmission element can be a pivoting lever, for example. Other mechanical solutions with a similar effect are also conceivable, e.g., using a guide curve.

[0036] This first option has the further advantage that the lifting mechanism is not unaffected by coarse adjustments, such as those made due to different roller diameters.

[0037] According to a second possibility, the lifting mechanism can also be coupled to the actuating element of the actuating and disengaging device instead of to the second bearing body, so that only movements caused by the electric drive are detected by the lifting mechanism, but not movements of the second bearing body relative to the first bearing body, which occur against a spring force of the foreign body securing device.

[0038] In embodiments, the force transmission between the stop element and one bearing body (e.g. the first bearing body) and / or the force transmission between the actuating element and the other bearing body (e.g. the second bearing body) takes place via a universal joint-like connection, which enables a transmission of forces in the axial direction, but allows tilting in two different planes leading through the axis - generally perpendicular to one another.

[0039] It turns out that a connection that allows tilting not only in one plane, but in both, is advantageous. This prevents unwanted distortion due to movement of the bearing bodies, thermal expansion (for example, of the grinding rollers), manufacturing tolerances, etc.

[0040] Particularly preferably, both the first bearing body and the second bearing body are connected to the actuating and disengaging device via a universal joint. Tilting in two planes is thus possible on both sides in such embodiments, which is particularly advantageous for avoiding unwanted distortion.

[0041] The design of the universal joint-like connection can, for example, be such that a force transmission element and an intermediate element are present on the side of the stop element and / or on the side of the actuating element. The first bearing body or second bearing body engages with the intermediate element in a joint-like manner, i.e. in such a way that relative tilting is possible. There is also an articulated connection between the intermediate element and the force transmission element, with the possibility of relative tilting about a different tilting axis. The respective articulated connections, which must transmit compressive forces in the axial direction (but not tensile forces due to the preload), can, for example, be formed by cutting edges engaging in beads. In designs of the type mentioned, one force transmission element can simultaneously form the stop element and / or the other force transmission element can form the actuating element.However, it can also be provided in particular that the pre-tensioned spring device, which forms the foreign body protection, is arranged between the stop element and the force transmission member assigned thereto or between the actuating element and the force transmission member assigned thereto.

[0042] In one group of embodiments, the roller set also has an optional bearing preload. This is designed to permanently preload the grinding rollers relative to their bearing bodies, i.e., the first grinding roller is preloaded relative to the first bearing body, and the second grinding roller is preloaded relative to the second bearing body. The grinding rollers are preloaded such that they are pushed away from each other and upward by a spring force. As a result, the grinding rollers are displaced away from each other by the radial clearance of their bearings, into the position they assume relative to their bearing body when they are pressed apart with great force during the grinding process.This has the advantage that not only is the position of the bearing bodies relative to each other always defined by the adjusting and disengaging device, regardless of any possible play, but also the position of the grinding rollers relative to their bearing bodies, regardless of the bearing clearance and the load currently acting.

[0043] In addition to the robustness of the grinding gap and the increased accuracy, further advantages of bearing preload are that the rollers cannot collapse in the bearing in the event of feed problems, and that vibrations are reduced - which has a positive effect on the load on components. The unavoidable difference between the relative positions of the grinding rollers under load, during the grinding process, on the one hand, and when unloaded, on the other hand, can be taken into account when adjusting the grinding gap based on experience. However, the bearing preload approach has the advantage of even better possible accuracy, also because without the bearing preload the relative position can still change slightly depending on the size of the load and the load distribution along the grinding rollers. Secondly, the bearing preload approach has the advantage of enabling a very precise calibration procedure, which is described below.Especially for grinding to very fine products, with smooth rollers or finely grooved rollers with at least approx. 1 groove per mm of circumferential length, e.g. with a roller diameter of 250 mm 850 to 1200 grooves per circumference, the procedure with bearing preload is of substantial advantage, while the accuracy for the rather coarse grinding can be sufficient even without bearing preload.

[0044] In addition to the roller package, a roller mill is also part of the subject matter of the present invention. The roller mill has at least one roller package of the type described here. The roller package can be present as a module in the sense that the roller package as a whole can be removed from the roller mill, for example, for maintenance purposes or when it needs to be replaced. However, the term "roller package" does not necessarily mean that this must be the case: a roller package within the meaning of this text also exists when two rollers as well as the other elements defined here (first bearing bodies, second bearing bodies, etc.) are present and interact, even if the rollers are mounted, for example, on a roller mill support structure and must be removed individually.

[0045] In a conventional manner, the roller mill may also comprise, in addition to the roller stack, a feed device for feeding the grinding material into the grinding gap between the rollers. The roller mill may comprise several pairs of rollers, which may include, for example, at least two roller stacks of the type described here. These may be arranged one above the other and / or back to back.

[0046] The roller mill is configured to disengage the grinding rollers relative to each other as soon as there is no more product or too little product in the feed device. For this purpose, the feed device—as is known per se—has a level sensor for detecting a level in the feed device. The roller mill is configured to move the second grinding roller relative to the first grinding roller from the engaged state to the disengaged state as soon as the level sensor detects that there is no more product or too little product in the feed device.

[0047] The level sensor can be designed as described in WO 2023 / 198735, or it can be designed in another way, for example with a weight force sensor, capacitive and / or optical.

[0048] The feeding device can optionally be designed as a whole as described in WO 2024 / 013179 or as in the prior art discussed therein.

[0049] In embodiments, the roller mill is configured so that the electric drive(s) automatically move the grinding rollers apart in the event of a power failure. Complete disengagement is not necessary - a moving apart of, for example, approximately 1 mm may be sufficient. The roller mill can therefore be configured, in particular, to detect a power failure and, in response, immediately issue the necessary control commands for moving the rollers apart. The energy required for moving the rollers apart in the event of a power failure, as well as for the control commands required for this, can be stored in at least one dedicated energy storage device; in embodiments, residual energy available in the electronics (in capacities already present, etc.) can also be sufficient for this purpose. Since the inventive procedure makes pneumatics superfluous, it is also advantageous in emergency situations.For example, pneumatics can be problematic in the event of a fire, as the compressed air can create a very disruptive draft.

[0050] In embodiments, the roller mill has an electronically readable physical control element, for example a handwheel, which can effect a manual adjustment of the width of the grinding gap in parallel operation by parallel (coordinated and simultaneous, synchronous) operation of both electric drives when operating the physical control element.

[0051] A physical control element, in contrast to, for example, a touch-sensitive screen, is an element that is physically movable relative to a housing. The physical control element is electronically readable in that it is designed so that its position and / or movement is electronically recorded and can be used for electronic evaluation, for example, by outputting the position or movement as a digital signal. An example of an electronically readable, physical control element is a so-called electronic handwheel, i.e., a handwheel together with an electronic rotary movement and / or rotary position detection device. Electronic handwheels are known, for example, for CNC machine tools and are commercially available. The roller mill - i.e.,in particular its control unit - can further be configured, in addition to parallel operation in single-sided operation, to also enable manual adjustment of the width of the grinding gap on one side only, by operating only one of the electrical drives when operating the physical control element. For example, it is possible to switch between a first state (parallel operation) and a second state (single-sided operation, only one electrical drive is controlled via the physical control element, e.g., only the drive to the left of the grinding rollers) and, for example, a third state (single-sided operation, only the other electrical drive is controlled via the physical control element, e.g., only the drive to the right of the grinding rollers). In a roller mill with several roller packages, each with a pair of rollers, the same physical control element can also be used to adjust the width of several grinding gaps, i.e.The user can switch not only between parallel and single-sided operation, if necessary, but also between different roller pairs. In particular, an eight-roller roller mill can have exactly one physical control element (e.g., handwheel) at the front and rear, each of which can be used to adjust the grinding gaps of two superimposed roller pairs. Then, for example, at least six operating modes can be selected per control element (e.g., per handwheel): upper roller pair parallel, left, right; lower roller pair parallel, left, right.

[0052] The physical operating element, e.g. handwheel, can in particular be designed to generate physical feedback during operation, which depends in particular on the current position of the bearing bodies, i.e. on the current width of the grinding gap. Physical feedback is feedback that the user feels on the handwheel itself, in particular so-called force feedback, sometimes also referred to as 'haptic feedback'. Such physical feedback can include a controlled counter-torque and / or pulses ('ticks'), whereby the counter-torque or the number of pulses per traveled distance can depend on the current width of the grinding gap. It can also be provided that when a certain minimum gap width is reached, a stop is formed by which the physical operating element can no longer be moved, e.g. rotated, in the direction of the "smaller grinding gap".

[0053] In particular, in contrast to the prior art, the roller mill can be configured to allow adjustment of the grinding gap from both a smaller and a larger grinding gap. This means that a certain gap width can be set by moving the grinding rollers towards each other after the grinding gap was previously larger than the value to be set, or conversely by moving the grinding rollers away from each other after the grinding gap was previously smaller. In this case, with a given calibration and a given operating mode, i.e., without intermediate switching, for example, between parallel and single-side operation, it can be provided that a specific (rotational) position of the physical control element corresponds to a specific distance between the first and second bearing bodies of the grinding rollers, regardless of the (rotational) direction of the last movement of the control element, i.e.When the control element is moved away from one position and back to it, the grinding rollers return to the same position, regardless of their previous position. In particular, a value for the grinding gap width stored in a data memory or manually entered can also be approached from a different grinding gap width.

[0054] This independence of the grinding gap width adjustment from the direction is made possible in particular by the combination of an electric servo drive with the provision of the adjusting element and stop element, which clearly define the position of the bearing bodies relative to one another. In embodiments, the roller mill is also configured, optionally independently of the physical operating element, to display an absolute reference. An absolute reference is the indication of the current position of the grinding rollers relative to one another. According to the prior art, such an absolute reference display is linked to the handwheels themselves, for example, by providing them with a pointer display similar to an analog clock.Such an absolute reference is often a requirement of the operators - however, in the state of the art it is associated with the inaccuracies described above, and in addition, its reading is only possible with experience and knowledge of the calibration carried out.

[0055] In contrast, in embodiments of the present invention, the display is provided via an output unit (e.g., a display) or an external device, whereby, for example, the width of the grinding gap can be displayed in absolute values ​​and in physically meaningful units, e.g., in millimeters. Due to the principle that the gap width is adjusted using electric drives, particularly servomotors, the roller mill never loses the absolute reference setting with a given calibration – it is retained even after extended periods of operation.

[0056] In embodiments, the roller mill is configured for automatic calibration. It is programmed such that, during calibration operation, the second grinding roller is moved relative to the first grinding roller, in particular without the grinding rollers rotating. This occurs until a contact criterion is reached, which indicates that the second grinding roller is touching the first grinding roller. For example, the torque applied by the servomotor can be measured and compared with a threshold value. Reaching the threshold value is considered the contact criterion. The rotational position of the electric drives (or, if applicable, equivalently: the position of the actuators) that applies when the contact criterion is met is stored and serves as a reference, for example, as a zero position.

[0057] Due to the inventive design of the roller assembly, the roller mill can be free of any drive means other than electric ones, meaning, in particular, no compressed air supply for pneumatics is required. Furthermore, the grinding gap can be adjusted in a single way, namely by the electric drive, in particular a servomotor.

[0058] The advantages of the present invention are particularly great when the roller mill is set up for grinding the material to be ground into a relatively fine product, for example when the grinding rollers are smooth rollers or rollers with at most fine corrugation, i.e. with a corrugation of, for example, at least one corrugation per mm of circumference, for example with a roller with a diameter of 250 mm of 850... 1200 corrugations / circumference. The roller mill is associated with this - in particular set up for grinding under large forces of, for example, up to 30, up to 40 or even up to 50 kN. The length of the grinding rollers is typically at least 0.8 m, in particular between 0.8 m and 1.5 m. The adjustable gap width can be down to 0 mm or less (set without load), i.e. the rollers can be positioned so that they come into contact without material to be ground and, for example, are also pressed against one another.

[0059] Embodiments of the invention are described below with reference to drawings. In the drawings, like reference numerals designate like or similar elements. The drawings are partly schematic and not to scale. They show partly corresponding elements in different sizes from figure to figure. They show: Fig. 1: A partial view of a roll package for a roll mill;

[0060] Fig. 2 is a top view of part of the roller package of Fig. 1;

[0061] Fig. 3 a side view of the roller package;

[0062] Fig. 4 and 5 the roller package cut along the plane IV-IV and the plane VV in Fig. 2 respectively;

[0063] Fig. 6 a view of the adjusting and disengaging device of the roller package;

[0064] Fig. 7 is a sectional view of the actuating and releasing device;

[0065] Fig. 8 is a schematic representation of the displacement of the rollers relative to the bearing bodies with or without bearing preload; Fig. 9 is a schematic view of a roller mill according to the invention;

[0066] Fig. 10 a diagram with control unit;

[0067] Fig. 11 shows a force-position characteristic for a handwheel as the physical control element; and

[0068] Fig. 12 Characteristic curves for the calibration process. Figure 1 shows a view of a roller pack 1, of which only one side is shown. Figure 2 shows a view of one side of the roller pack from above, and Figure 3 shows a side view of the roller pack. Figures 4 and 5 show the roller pack sectioned along planes IV-IV and VV, respectively, with a drive housing of the adjusting and disengaging device shown in elevation. The roller pack has a first grinding roller 2 and a second grinding roller 3. The first and second grinding rollers each have a roller stub 21, 31 on the side, which is rotatably mounted by a first bearing 22 and a second bearing 32, respectively.

[0069] A frame 4 forms a supporting structure and can be attached to a roller mill frame or forms part thereof. A first bearing body 5 and a second bearing body 6 are present or mounted on the frame 4. In the illustrated embodiment, the first bearing body 5 is formed by the frame itself, thus forming part of it. The second bearing body 6 is pivotally mounted on the frame 4, with the pivot axis defined by a pivot pin 7 and being fixed to the frame and thus also to the housing with respect to the roller mill.

[0070] The first bearing body 5 and the second bearing body 6 are pressed apart by a preload spring 10, so that they are permanently preloaded. An adjusting and disengaging device 40 exerts a counterforce against this spring force and, during the grinding process, also against the force exerted by the material to be ground and transmitted from the grinding rollers to the bearing bodies, which pushes the grinding rollers apart. For this purpose, the adjusting and disengaging device 40 has a stop structure on each of its two sides with force transmission elements described below. An electric drive can exert a force between the two stop structures and move the stop structures towards each other against the aforementioned forces pushing the first bearing body 5 and the second bearing body 6 apart, thus moving them from a disengaged position to an engaged position.The electric drive can also enable and / or actively drive a reverse movement of the bearing bodies away from each other. - TI -.

[0071] The actuating and disengaging device 40 is shown somewhat enlarged in Figures 6 and 7. It has a drive housing 41 with an electric drive motor, namely a servomotor (42), which is only shown schematically in the figures. This drives a spindle 44, which is arranged in a spindle housing 47, via an optional gear 43, which is also only shown schematically. A spindle nut 45, which interacts with the spindle 44, is thereby moved in the axial direction together with a shaft 46, which is firmly connected to the spindle nut. A fixing device 48 is provided on the end of the shaft, which is screwed to the shaft, for example, and can also be glued, to secure the screw.

[0072] The unit comprising spindle nut 45, shaft 46, and fixation 48 together forms an actuating element within the meaning of this text, i.e., the position of this unit along axis 70 relative to the stop element is uniquely determined by the electric drive, namely the drive motor 42. The connection between spindle nut 45 and shaft 46 can be a screw connection, possibly with additional bonding; other connections are also possible.

[0073] Between the fixation 48 and a second force transmission member 49 there is a disc spring arrangement 55 which is compressed between the fixation 48 and the second force transmission member 49, whereby it is preloaded and presses the second force transmission member 49 permanently against a stop 58 formed by the spindle housing 47.

[0074] In addition to the second force transmission member 49, the actuating and disengaging device 40 has a second intermediate member 50 cooperating with the second intermediate member 50, as well as, toward the other end, a first force transmission member 52 and a first intermediate member 53. The first force transmission member 52 is firmly connected to the spindle housing 47 and, in the illustrated embodiment, is even integral with it, so that the spindle housing 47 and the first force transmission member 52 are formed by a common component.

[0075] The first force transmission element 52 acts - in the example shown together with the spindle housing 47 - as a stop element in the sense of the present text.

[0076] The first intermediate member 53 interacts with the first force transmission member 52. The first and second intermediate members 50, 53 are permanently pressed away from each other and against the first and second force transmission members 52, 49 by the preload of the roller stack and, during operation, also by the grinding rollers themselves. They have the second stop structure and the first stop structure, respectively, in the illustrated embodiment in the form of the first cutting edges 71 and second sheaths 72, respectively, which will be described below.

[0077] Inside the spindle housing 47, the adjusting and disengaging device 40 has a tapered roller bearing 61, which can absorb high axial forces and tensile forces acting on the spindle. These tensile forces arise between the spindle and spindle nut, counteracting the forces coupled via the first force transmission element 52 and the second force transmission element 49, respectively, by pushing the first and second bearing bodies apart.

[0078] An optional deep groove ball bearing 62 is provided for additional radial guidance. A supplementary radial guide, which acts independently of the tapered roller bearing 61, has proven advantageous under certain circumstances and contributes to defining a precise radial position of the spindle while ensuring uniform absorption of the axial forces by the tapered roller bearing. A grease chamber 63 is formed on both sides of the tapered roller bearing 61. This chamber ensures permanent lubrication of the tapered roller bearing 61. It is delimited on the motor side by a radial shaft seal 64 with axial locking and on the other side (spindle nut side) by the deep groove ball bearing 62.

[0079] Between the spindle 44 and the spindle nut 45, there is a trapezoidal thread, which is designed, for example, to be self-locking. The air space 51 around the spindle 44 and spindle nut 45 is delimited on the motor side by the deep groove ball bearing 62 and on the other side by a double wiper 66 and a felt seal 67 to protect against the ingress of dirt. Since the volume of the air space 51 is not constant during axial movements of the spindle nut 45 relative to the spindle 44, at least one vent screw 59 is provided, which allows the inlet and outlet of air and prevents the lubricating grease present in the air space 51 for lubricating the spindle from escaping.

[0080] As an alternative to a spindle and spindle nut with thread, especially a trapezoidal thread, a low-friction ball screw or, for example, a roller screw drive can also be considered.

[0081] The force transmission between the first and second bearing bodies 5, 6 on the one hand and the actuating and disengaging device 40 on the other hand takes place via the first and second force transmission element as well as the first and second intermediate element, in an angularly movable manner in the manner of a universal joint on each side.

[0082] The connection between the first bearing body 5 and the first intermediate link 53, as well as the connection between the second bearing body 6 and the second intermediate link 50, allows for relative tilting in the vertical plane. The possibility of such relative tilting in the vertical plane (i.e., about a first tilting axis perpendicular to the vertical plane) is necessary because the second bearing body 6 is fixed in position on its underside and is consequently subject to a pivoting movement during engagement and disengagement, changing its orientation in the vertical plane relative to the first bearing body 5.

[0083] In addition, the described arrangement with the universal joint-like connections also allows tilting about a second tilting axis, which is approximately vertical in the illustrated configuration. This is achieved by the design of the connection between the first force transmission member 52 and the first intermediate member 53 and / or the connection between the second force transmission member 49 and the second intermediate member 50.

[0084] Specifically, the universal joint-like connection has first cutting edges 71 formed on the first intermediate member 53, which engage in corresponding beads 81 in the first bearing body 5 - more precisely: in the stop part 83 of the first bearing body 5. Correspondingly, second cutting edges 72 are present on the second intermediate member 50, which engage in beads 82 in the second bearing body 6 - or in the stop part 84 of the second bearing body 6. In addition, third cutting edges 73 and fourth cutting edges 74 are present on the first and second intermediate members 53, 50, respectively, which engage in beads on the first force transmission member 52 and the second force transmission member 49, respectively. The third cutting edges and fourth cutting edges 73, 74 are arranged at a position relative to the first cutting edges 71 andsecond cutting edges 72 are arranged in a position offset by 90° (relative to the axis 70 of the adjusting and disengaging device 40), so that they allow slight tilting out of the vertical plane leading through the axis 70, i.e. tilting about the approximately vertical second tilting axis perpendicular to the axis 70. If a foreign body gets between the grinding rollers and thereby briefly pushes the first and second grinding rollers apart with great force, the second bearing body 6 can move the second force transmission member together with the first force transmission member 49 away from the stop 58 against the spring force of the disc spring arrangement 55. The drive train with servo motor, if applicable, gearbox, spindle and spindle nut remains unaffected.

[0085] It is a characteristic of the roller package described in this text that the disengagement or engagement movement, the fine adjustment of the width of the grinding gap and the foreign body protection all take place on a common axis - the axis 70 of the adjusting and disengaging device 40, which can in particular correspond to the spindle axis - i.e. during all these movements, elements of the adjusting and disengaging device 40 (namely the stop structures with the force transmission members) move towards or away from each other along the axis 70 while they are in engagement with the first or second bearing body 6.

[0086] As is known per se, the stripper, which acts on the grinding roller(s) during operation to strip off adhering ground material, is also to be lifted off the grinding rollers during the disengagement process. For this purpose, the roller package has a lifting mechanism with a pivoting lever 91 that can be pivoted about a pivot point 92 and is connected to the second bearing body 6 via a joint 93 and a flat lever 94. If the second bearing body 6 is moved away from the first bearing body, the pivoting lever 91 is accordingly taken along and pivoted about the pivot point 92. On the underside, the pivoting lever 91 has an elongated hole 95 into which a driving pin 96 engages. The movement of this hole - to the left in Figure 3 - lifts the stripper off the grinding rollers 5, 6 against a spring force. The stripper can, for example, be designed as described in Swiss patent application 000831 / 2022.When the grinding rollers are moved away from each other, the driving pin 96 is initially not driven along by the resulting pivoting movement of the pivot lever 91, since the elongated hole is dimensioned and arranged such that the pivot lever can move relative to the driving pin 96. Only towards the end of the pivoting movement of the pivot lever 91 does the driving pin 96 strike a driving surface (in Fig. 3, on the right at the elongated hole 95) and is driven along to lift the scraper. This mechanism ensures that the scraper is not impaired during a fine adjustment of the grinding gap and, in particular, during a very rapid movement of the second bearing body due to a foreign object between the grinding rollers. The scraper is therefore only lifted when the grinding rollers are disengaged, in that the adjusting and disengaging device 40 causes the two stop structures to move completely apart into the disengaged position.

[0087] In embodiments, the roller assembly also has a bearing preload. This is designed to permanently push the grinding rollers 2, 3 outward relative to their bearing bodies 5, 6, i.e., away from each other, and upward. The grinding rollers are therefore permanently in the position relative to their bearing bodies in which they are as far apart as possible. This is schematically shown – for the first grinding roller 2 – in Figure 8, in which the circle shown schematically represents the radial play for the roller stub in its bearing. Without bearing preload, when the roller mill is not in operation, a first, underside position 111 is assumed due to the grinding rollers' own weight. When the grinding rollers are pushed apart during operation, however, they are in a second, lateral position 112 relative to their bearing.The bearing preload forces the grinding rollers in the direction of the arrow shown, i.e., into the second position 112, even when stationary. This is why their position is always defined and essentially unchangeable relative to the bearing and thus to the bearing body, even during a calibration process. The bearing preload thus prevents the position of the grinding rollers 2, 3 relative to their bearing bodies from changing due to the unavoidable radial bearing clearance as soon as the grinding process begins, which would force the grinding rollers apart with great force.

[0088] In the illustrated embodiment, the bearing preload is achieved as follows: An additional bearing preload ball bearing is provided on each side of each roller (in addition to the one that supports the shaft stub relative to its bearing body), e.g., a deep groove ball bearing. A plurality of spring assemblies 101, each with a stop surface 102 oriented radially inward by a spring force, push the outer ring of the bearing preload ball bearing outward and upward—directly or indirectly, e.g., via a sleeve 103, 104.

[0089] As an alternative to the illustrated design with pressure-loaded disc spring assemblies, the bearing preload could also be such an additional bearing preload ball bearing pulled outwards and upwards by a spring device.

[0090] Figure 9 shows a very schematic view of the entire roller mill 201 with at least one roller assembly. A handwheel 202 serves as an electronically readable physical control element. Additional input and output options may be present, which are indicated in Fig. 9 by a schematic display panel 203—which may be touch-sensitive—, an input panel 204, and an interface to a mobile phone 205. It is also possible for additional physical control elements to be present on the roller mill and / or for additional or different interfaces to be available. The handwheel 202 can be a rotary-push control element, meaning that in addition to rotation, an axial movement of the handwheel is also possible and is recorded electronically.

[0091] Figure 10 shows a very schematic view of a control unit 210 of the roller mill, which is configured to individually control the servomotors 42 of the two actuating and disengaging devices of the roller stack—and, if multiple roller stacks are present, corresponding to the servomotors of each actuating and disengaging device. Control is performed based on the user input on the handwheel 202, which is read electronically. However, it also occurs—additionally or alternatively—based on further inputs, e.g., a setting 221 between the operating modes "left" (only the first servomotor M1 is controlled), "parallel" (both servomotors are controlled), and "right" (only the second servomotor M2 is controlled), based on stored data 222, e.g., so-called "recipes," and / or based on user inputs, e.g., via an external device (mobile phone 205).

[0092] The roller mill also has a roller mill feed system, to which the product to be processed is fed. This can have at least one feed roller, through which the product to be processed—processing material, present as bulk material—is metered and fed to the grinding rollers of the roller stack(s). Furthermore, a level monitor 225 is provided, which monitors the level of the product present in the roller mill feed system above the feed roller(s). The data acquired by the level monitor can be used to control the roller mill—for example, among other things, the speed of the feed roller and / or the grinding rollers—and / or to control the equipment upstream of the roller mill.The control unit 210 of the roller mill is connected to the level monitoring device 225 in such a way that it immediately causes a disengagement movement of the type discussed above as soon as the level monitoring device determines that there is no or insufficient product available to feed the grinding rollers.

[0093] Figure 11 shows a possible force-position characteristic to which the handwheel can be programmed. Depending on the width b of the grinding gap (in single-sided operation, depending on the width b on the corresponding side), the force (torque) F with which the user must operate the handwheel to move the rollers towards each other increases segment-by-segment linearly, i.e., proportional to (c s -b), where c s is a constant that can vary from segment to segment.

[0094] In the illustrated embodiment, the dimensions of the segments 230 decrease with a smaller width b of the grinding gap. Furthermore, the curves become steeper when the grinding rollers are close to each other or even touch each other, i.e., for segments 230 corresponding to smaller widths b, the proportionality constant is larger.

[0095] Furthermore, the number of pulses per angle of rotation—that is, per unit length by which the grinding gap is adjusted—can also depend on the width b of the grinding gap and, for example, vary from segment to segment. In particular, more pulses per angle of rotation can be generated for segments 230, which correspond to smaller grinding gap widths (left in Fig. 11).

[0096] In addition to the segments 230, an electronically adjusted stop 231 can also be provided for the rotational movement of the handwheel, beyond which rotation of the handwheel is no longer possible without the application of excessive force. A calibration process can provide for the non-rotating grinding rollers to be slowly moved toward each other, starting from a pre-position in which they are safely spaced apart, until a predetermined criterion (contact criterion) that is significant for physical contact between the grinding rollers is met—for example, exceeding a threshold value Ms for the required drive torque of the servomotors. Figure 12 shows this schematically for a first characteristic curve 241, as is characteristic of an embodiment with bearing preload, and a flatter second characteristic curve 242, as can result when no bearing preload is present.The position of the servo drives when the contact criterion is reached is saved and remains valid even after subsequent processes, such as the disengagement and re-engagement of the grinding rollers, as well as grinding processes with potentially different products. The calibration process only needs to be repeated after extended operation, during which the grinding rollers may wear out, or after replacing the grinding rollers, e.g., for maintenance purposes.

Claims

PATENT CLAIMS 1. A roller assembly for a grain milling machine, comprising a first grinding roller (2) and a second grinding roller (3), wherein the first grinding roller (2) is mounted on both sides by a first bearing body (5) and the second grinding roller (3) is mounted on both sides by a second bearing body (6), wherein the second bearing body (6) is movable relative to the first bearing body (5), wherein the roller assembly is configured to move the second grinding roller (3) relative to the first grinding roller (2) from an engaged state, in which a grinding gap is formed between the first and second rollers, to a disengaged state, in which no grinding process is possible between the first and second rollers, and wherein the roller assembly is further configured to adjust a width of the grinding gap in the engaged state, characterized by an electric drive which is configuredto effect, based on control signals, both the movement of the second bearing body (6) relative to the first bearing body (5) from the engaged to the disengaged state and the movement of the second bearing body (6) relative to the first bearing body (5) in the engaged state for adjusting the width of the grinding gap.

2. Roller package according to claim 1, wherein the electric drive comprises a servo motor (42).

3. Roller package according to claim 1 or 2, which forms a closed load frame except for possible torsional forces due to roller overdrive.

4. Roller package according to one of the preceding claims, wherein there is only a single degree of freedom for movements of the second bearing body (6) relative to the first bearing body (5).

5. Roller package according to one of the preceding claims, which is prestressed in that the second bearing body is prestressed in relation to the first bearing body in the direction which moves the second grinding roller (3) away from the first grinding roller (2) 6. Roller package according to one of the preceding claims, characterized by an adjusting and disengaging device (40) with the electric drive, an adjusting element and a stop element, wherein the electric drive is designed to move the adjusting element relative to the stop element in order to effect the movements of the second bearing body relative to the first bearing body from the engaged to the disengaged state and to adjust the width, and wherein a distance between the adjusting element and the stop element determines a position of the second bearing body relative to the first bearing body.

7. Roller package according to claim 6, wherein the adjusting element is movable relative to the stop element along a single axis (70).

8. Roller package according to claim 6 or 7, wherein the adjusting and disengaging device (40) has a spindle drive which is driven by the electric drive and adjusts the adjusting element relative to the stop element.

9. Roller package according to one of claims 6 to 8, wherein the adjusting and disengaging device (40) has two stop structures, namely a first stop structure and a second stop structure, and the first bearing body (5) and the second bearing body (6) are pressed outwards in the axial direction with respect to the axis (70) against the first stop structure and the second stop structure, respectively, when the first grinding roller (2) and the second grinding roller (3) are pressed apart.

10. Roller package according to claim 9, wherein one of the stop structures is assigned to the stop element and the other of the stop structures is assigned to the adjusting element, wherein a prestressed spring device is arranged between the stop element and the stop structure assigned to it or between the adjusting element and the stop structure assigned to it, which spring device effects a foreign body protection by allowing a relative movement of the stop structures along the axis (70) against a spring force of the spring device, whereby the spring device acts as a foreign body protection by enabling evasion in the presence of large forces between the first grinding roller (2) and the second grinding roller (3).

11. Roller package according to claim 9 or 10, wherein one of the stop structures is assigned to the stop element and the other of the stop structures is assigned to the actuating element, wherein the stop structure of the actuating element follows a movement of the actuating element relative to the stop element.

12. Roller package according to one of claims 9-11, wherein the first stop structure and the second stop structure are centered on the axis (70).

13. Roller package according to one of claims 6-12, wherein a force transmission between the stop element and the one bearing body and / or the force transmission between the adjusting element and the other bearing body takes place via a universal joint-like connection which enables a transmission of forces in the axial direction, but enables tilting in two different planes.

14. Roller package according to one of the preceding claims, comprising a scraper which, during operation, scrapes ground material from the first grinding roller (2) and the second grinding roller (3), wherein the roller package is designed to automatically lift the scraper from the grinding rollers during a movement from the engaged to the disengaged state, and wherein the roller package is further designed to leave the scraper unaffected during a relative movement of the second grinding roller (3) relative to the first grinding roller (2) due to a foreign body entering the grinding gap.

15. Roller package according to claim 14, wherein the roller package is configured such that a movement of the second bearing body relative to the first bearing body from the engaged to the disengaged state is only transmitted over a final section to a lifting mechanism causing the scraper to lift off.

16. Roller package according to one of the preceding claims, comprising a bearing preload which is designed to permanently preload the first grinding roller (2) relative to the first bearing body (5) and / or to permanently preload the second grinding roller (3) relative to the second bearing body (6).

17. Roller mill comprising at least one roller package according to one of the preceding claims and a feeding device for feeding a grinding material to the rollers of the first roller package.

18. Roller mill according to claim 17, which is designed to allow the electric drive or drives to automatically move the grinding rollers apart in the event of a power failure.

19. Roller mill according to claim 17 or 18, comprising an electronically readable physical operating element which, in parallel operation, can effect a manual adjustment of the width of the grinding gap by parallel (coordinated and simultaneous, synchronous) operation of both electric drives when operating the physical operating element.

20. Roller mill according to claim 19, which is further configured to enable, in a single-side operation, manual adjustment of the width of the grinding gap only on one side by operating only one of the electric drives when operating the physical control element.

21. Roller mill according to claim 19 or 20, wherein the physical operating element is configured to generate a physical feedback during operation which is dependent on a current width of the grinding gap.

22. Roller mill according to one of claims 17-21, which is arranged to move the second grinding roller (3) relative to the first grinding roller (2) in a calibration operation until a contact criterion is reached which indicates that the second grinding roller (3) touches the first grinding roller (2), and that a rotational position of the electrical drives when the contact criterion is reached can be saved to serve as a reference.

23. Roller mill according to one of claims 17-22, comprising a level sensor (225) for detecting a level in the feed device, wherein the roller mill is arranged to move the second grinding roller (3) relative to the first To move the grinding roller (2) from the engaged state to the disengaged state as soon as the level sensor detects that there is no more product or too little product in the feed device.

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