Cutting mill for cutting and shredding samples

Description

Field of invention

[0001] The invention relates to a cutting mill for the cutting and comminution of samples, particularly on a laboratory scale, with a cutting rotor rotating about a horizontally extending axis. Background of the invention

[0002] Cutting mills comminute samples by means of a scissor-like cutting effect, typically between a rotating cutting rotor with one or more substantially axially extending cutting edges and one or more substantially axially extending stationary counter-cutting edges. Such laboratory cutting mills are particularly suitable for comminuting tough or fibrous samples, e.g., biological samples such as straw, but also, for example, plastic films, to name just a few examples. Examples of such laboratory cutting mills are, for example, the Pulverisette®< 19 and the Pulverisette®< 25 of the applicant, to whose basic design reference is hereby made. Corresponding product descriptions of the Pulverisette®< 19 and the Pulverisette®< 25 can be found, for example, at [link to product description]. www.fritsch.de.

[0003] In these cutting mills, free-flowing bulk material is typically fed into the grinding chamber, possibly via a hopper, where the cutting rotor rotates horizontally. The cutting rotor can have different geometries, for example, so-called V-cutting blades, which have a helix and thus provide good cutting action, especially for the comminution of tough-elastic materials and films. This illustrates that the definition of an essentially axially oriented cutting edge is not limited to the cutting edge running strictly parallel to the axis of rotation, but should also include angled cutting edges with an axially parallel component. Essentially axially oriented cutting edges can therefore also run at an angle to the axis of rotation, which in principle corresponds to a helix. A screen is typically located below the cutting rotor, e.g.,A sieve cassette through which the sample material, which has already been sufficiently pulverized, can trickle to be collected in a collection vessel below. Such a laboratory mill is described in utility model DE 297 13 097 U1. Regarding further design details, which are generally known to those skilled in the art in this field, reference is made to the product descriptions for the Pulverisette®< 19 and Pulverisette®< 25 cutting mills of the applicant, which were available at the time of filing and publication under [website address missing]. www.fritsch.de are downloadable, and which are hereby referenced in relation to the basic construction of such a cutting mill.

[0004] In such a cutting mill, the torque is transmitted from the motor shaft to a rotor mount, for example, by means of a key. In previous cutting mills, this rotor mount was typically permanently installed and could only be removed by extensive disassembly of the device. The rotor mount in these laboratory cutting mills was typically sealed with felt rings.

[0005] While the use of a separate rotor mount allows for easy manual insertion of the cutting rotor, the torque transmission in some previously known cutting mills is achieved relatively far outboard via drive pins, which in turn has resulted in a relatively large sealing diameter. At a predefined rotational speed, a large seal diameter means a relatively high circumferential speed at the seal, which is associated with relatively high heat generation. Furthermore, the rotor mount in previous cutting mills was typically not easily removable for cleaning. In addition, the felt rings used were also not easily replaceable. Although the seal using felt rings has generally proven effective, substances such as waxes, oils, or resins could penetrate the seal and potentially impair its sealing function.

[0006] These felt seals have proven their worth and have therefore been used for decades. Nevertheless, the sealing concept in a cutting mill can be improved. In particular, the accessibility of the seal can be further enhanced.

[0007] German patent DE 35 09 698 A1 and EP 1 510 257 A2 disclose cutters for the production of sausage meat or sausage stuffing, in which cutter blades rotate in a working chamber. US patent 4,353,559 discloses a labyrinth seal for the rotor of a granulator. CN 107 486 308 A1 discloses a high-temperature dry roasting machine for decomposing animal carcasses. General description of the invention

[0008] It is therefore an object of the invention to provide a cutting mill of the type mentioned at the outset, which is easy to maintain and / or which can be cleaned well, particularly in the area of ​​the grinding chamber rear wall and the drive shaft.

[0009] Another aspect of the object of the invention is to provide a cutting mill which exhibits low heat generation in the area of ​​the drive shaft, despite a potentially high circumferential speed at sealing points.

[0010] Another aspect of the object of the invention is to provide a cutting mill which has a good sealing effect between the grinding chamber and the area of ​​the drive motor.

[0011] Another aspect of the object of the invention is to provide a cutting mill which allows improved access to the seal of the drive shaft in the grinding chamber rear wall.

[0012] The object of the invention is solved by the subject matter of the independent patent claims. Advantageous further developments of the invention are the subject matter of the dependent patent claims.

[0013] The invention relates to a cutting mill for the cutting and comminution of samples, particularly on a laboratory scale. Such cutting mills for the cutting and comminution of samples operate on the scissor principle. The cutting edges of the cutting rotor and the counter-cutting edges are substantially axially and radially offset from the axis of rotation of the cutting rotor. The grinding chamber therefore preferably has counter-cutting edges that are axially offset circumferentially and substantially axially extending, which interact with the cutting edges of the cutting rotor such that the samples are cut between the cutting edges of the cutting rotor and the counter-cutting edges according to the scissor principle when the cutting edges of the cutting rotor and the stationary cutting edges slide past each other.

[0014] The term "essentially axial" here does not refer to cutting edges that are strictly parallel to the axis of rotation. Rather, the cutting edges can also be inclined, for example, along a helical path or exhibit a helix. For instance, cutting rotors with so-called V-cutting edges can be used, in which the cutting edges are axially offset from the axis of rotation and essentially axial, but inclined along a helical path, so that the cutting edges exhibit a helix. Such laboratory cutting mills are generally known to those skilled in the art; see, for example, [reference to relevant source]. www.fritsch.de .

[0015] The cutting mill includes a device housing, a drive motor arranged in particular in the device housing and a drive shaft which may include the motor shaft and possibly further shaft elements such as a rotor mounting element placed on the motor shaft, a grinding chamber with a cutting rotor arranged therein for cutting and crushing the samples in the grinding chamber.

[0016] The cutting rotor, driven by the drive shaft, rotates about an axis of rotation within the grinding chamber. The grinding chamber is bounded axially on the motor side, i.e., axially with respect to the axis of rotation or at the motor end face, by a grinding chamber rear wall. The cutting rotor is preferably cylindrical overall, and the motor-side end face of the cylindrical cutting rotor runs parallel to the grinding chamber rear wall. The grinding chamber rear wall has a shaft opening through which the cutting rotor can be driven by the drive shaft. In particular, the drive shaft extends through the shaft opening to drive the cutting rotor in rotation within the grinding chamber. Preferably, the drive shaft and / or the axis of rotation of the cutting rotor are horizontal, and / or the grinding chamber rear wall is vertical.

[0017] Unlike earlier cutting mills, the shaft opening in the grinding chamber's rear wall is now sealed by a labyrinth seal. Labyrinth seals are sometimes also called gap seals because they provide a non-contact shaft seal. The sealing effect is based on the lengthening of the flow path through the sealing gap, which increases flow resistance. This path lengthening can be achieved, for example, by interlocking elements of the rotor and stator, a process known as interlocking.

[0018] The rotational speed of the cutting rotor in the granulator can, for example, range from 20 rpm to 5000 rpm, preferably between 50 and 3000 rpm. It has now been observed that in some granulators, the radius or circumference of the seals on the rear wall of the grinding chamber is relatively large due to the design, resulting in a relatively high peripheral speed at the seal. The use of a labyrinth seal is advantageous, among other things, because it can reduce heat generation at the rear wall of the grinding chamber.

[0019] Another advantage of using a labyrinth seal at this point is that it allows improved access to the area inside and behind the shaft opening in the grinding chamber rear wall. This makes the cutting mill easier to maintain and, in particular, simplifies and improves cleaning in the area of ​​the shaft opening in the grinding chamber rear wall. This can be helpful, for example, when grinding oily or resinous samples, as conventional cutting mills could potentially allow oily and / or resinous residues to diffuse into the area of ​​the shaft opening seal during the grinding process.

[0020] Another advantage of using a labyrinth seal lies in its durability and ease of maintenance. Furthermore, the labyrinth seal can be easily installed and removed, for example, for cleaning, inspection, and / or replacement.

[0021] The grinding chamber of the cutting mill has at least in some areas, preferably at least at the bottom, a circumferential screen wall which separates the grinding chamber from a collection container, such that the screen wall allows sample particles that have been reduced below a particle size predefined by the screen openings to pass directly through the screen openings into the collection container during the cutting process of the samples.

[0022] Preferably, the sieve wall is designed as part of a sieve cassette, wherein the sieve cassette can be inserted as a unit below the cutting rotor into the grinding chamber.

[0023] Preferably, the device housing includes a closure cover located axially at the end face with respect to the axis of rotation. The closure cover is positioned on the side of the grinding chamber opposite the rear wall and can be opened to access the grinding chamber. With the grinding chamber open, the cutting rotor and / or any other components, such as the screen cartridge and / or the labyrinth seal, can be removed. This allows the components to be replaced, for example, with a different cutting rotor and / or a different screen cartridge.

[0024] The cutting rotor is mounted on the drive shaft and thus supported on the motor side via the drive shaft. It is also preferably supported on the side opposite the motor or the labyrinth seal in the openable cover when the cover is closed. For this purpose, the cover can include, for example, a conical counter bearing. This design allows for easy removal of the components, e.g., for cleaning and replacement.

[0025] The cutting rotor is preferably designed to be manually attached to and removed from the drive shaft in a coaxial or concentric manner when the cover or grinding chamber is open. Opening the cover releases the counter bearing, allowing the cutting rotor to be manually removed from the drive shaft. For this purpose, the cutting rotor is simply, for example, attached to the drive shaft.

[0026] The torque is preferably transmitted from the drive shaft to the cutting rotor via a positive-locking coupling when the grinding chamber is closed. This includes, for example, drive elements that engage positively with the cutting rotor when the cutting rotor is mounted on the drive shaft, in order to transmit the torque to the cutting rotor via the drive elements.

[0027] According to a preferred embodiment of the invention, the drive shaft is multi-part and comprises at least one primary shaft, which can, for example, be the motor shaft itself, and an intermediate piece, the so-called rotor mounting element, which is mounted coaxially on the primary shaft. The rotor mounting element is then coaxially fitted onto the primary shaft, and coupling means are included between the primary shaft and the rotor mounting element, which effect the torque transmission from the primary shaft to the rotor mounting element, for example, a key. The cutting rotor is fitted onto the rotor mounting element and can be easily removed from the rotor mounting element manually without tools when the grinding chamber is open. The rotor mounting element can also be removed from the primary shaft, whereby a removal tool may be required, for example, a central screw for pressing the rotor mounting element off the primary shaft.Parts of the labyrinth seal are automatically pulled away from the back wall of the grinding chamber.

[0028] Preferably, a drive flange is also included, which extends around the drive shaft and has a significantly larger diameter than the motor shaft. The drive elements, e.g., drive pins, engage on one side in the drive flange and on the other side in the cutting rotor to effect the torque transmission from the drive shaft to the cutting rotor over the largest possible radius.

[0029] The gap dimension of the labyrinth seal is preferably between 0.05 mm and 2 mm, more preferably between 0.1 mm and 0.5 mm, radially preferably in the range of 0.2 mm, axially possibly slightly more due to bearing clearance.

[0030] The drive elements are preferably designed as axially extending drive pins, wherein their radially outer limit is at least 10 mm, preferably at least 15 mm, preferably at least 20 mm or preferably at least 25 mm, e.g. 31.5 mm radially away from the axis of rotation, thereby enabling the transmission of a high torque.

[0031] Preferably, the drive flange is designed as part of the rotor mounting element, and the rotor mounting element and drive flange can be mounted as a unit onto the primary shaft. This has proven effective for transmitting the required torques in the cutting mill.

[0032] According to a preferred embodiment of the invention, the drive flange is arranged at least partially within the shaft opening. This has proven advantageous with regard to size. While this requires a relatively large shaft opening, this is easily manageable with a labyrinth seal.

[0033] Preferably, the labyrinth seal comprises an inner labyrinth ring rotating with the drive shaft and a labyrinth ring cover on the grinding chamber side, wherein an axial end face of the inner labyrinth ring on the grinding chamber side is interlocked with an axial end face of the labyrinth ring cover on the grinding chamber side.

[0034] Furthermore, preferably the labyrinth seal comprises the inner labyrinth ring rotating with the drive shaft and a motor-side labyrinth ring cover, wherein a motor-side axial end face of the inner labyrinth ring is interlocked with an axial end face of the motor-side labyrinth ring cover.

[0035] Such an axially end-face interlocking is advantageous with regard to the disassembly of the labyrinth seal.

[0036] Preferably, the rear wall of the grinding chamber has an annular recess on the grinding chamber side, in which the labyrinth ring cover on the grinding chamber side is secured. It is particularly advantageous if the grinding chamber-side end surface of the labyrinth ring cover is flush with the rear wall of the grinding chamber.

[0037] Preferably, the labyrinth ring cover on the grinding chamber side is clamped in the annular recess on the grinding chamber side, so that the labyrinth seal remains assembled when the cutting rotor is pulled off the drive shaft or the rotor mounting element. However, the inner labyrinth ring can be pulled off in the direction from the motor to the grinding chamber if the clamping of the labyrinth ring cover on the grinding chamber side in the annular recess is overcome and the cover, along with the inner labyrinth ring, is pulled off the drive shaft. Preferably, the rotor mounting element is pulled off the primary shaft by overcoming a certain clamping force, thereby also pulling the inner labyrinth ring and the labyrinth ring cover on the grinding chamber side off the drive shaft, e.g., supported on the motor side by the drive flange.

[0038] The labyrinth ring cover on the grinding chamber side can be clamped in the grinding chamber rear wall or in the grinding chamber-side annular recess of the grinding chamber rear wall by means of an O-ring, preferably inserted in a form-fitting manner, and can be removed by overcoming the clamping force caused by this.

[0039] Preferably, the inner labyrinth ring is arranged radially outside on the rotor mounting element, in particular radially outside on the drive flange.

[0040] According to a further embodiment, an airflow generation device is included which generates an airflow through the gap of the labyrinth seal, preferably from the motor towards the grinding chamber. This improves the effectiveness of the labyrinth seal by reducing the diffusion of dirt from the grinding chamber towards the motor area through the shaft passage opening.

[0041] For this purpose, the inner labyrinth ring can have fan blades which, when the inner labyrinth ring rotates, generate an airflow through the gap of the labyrinth seal. The large radius of the seal, which initially appears disadvantageous for the seal itself, proves to be advantageous, as the associated high circumferential speed can have a positive effect on generating an airflow.

[0042] For example, the fan blades are conveniently arranged on the radially outer circumferential wall of the inner labyrinth ring.

[0043] Preferably, an air supply ventilation channel is provided between the grinding chamber rear wall and the drive motor, e.g. in the motor side of the grinding chamber rear wall, through which the airflow is guided towards the grinding chamber through the labyrinth seal.

[0044] Alternatively or additionally, a circumferential "open labyrinth" or so-called see-through labyrinth can also be provided. The labyrinth seal again comprises an inner labyrinth ring that rotates with the drive shaft, and the shaft passage opening has an inner radial ring wall within which the inner labyrinth ring is arranged, such that the inner radial ring wall encloses the inner labyrinth ring in a ring-like fashion. The open labyrinth or see-through labyrinth is characterized in that either the inner radial ring wall or the outer radial ring wall of the inner labyrinth ring defines a meandering shape in axial cross-section, but the inner radial ring wall and the outer radial ring wall of the inner labyrinth ring are not interlocked with each other, so that the inner labyrinth ring can nevertheless be pulled axially out of the shaft passage opening.

[0045] Preferably, the meander shape of the open labyrinth or see-through labyrinth is radially tapered in the axial cross-section, e.g. triangular in the axial cross-section, possibly tapering to a triangular point.

[0046] Experiments have shown that such an open labyrinth or see-through labyrinth, or such geometries, can create vortices that can cause air cushions and thus make it more difficult for dirt to pass through the labyrinth seal.

[0047] The invention will now be explained in more detail with reference to exemplary embodiments and the figures, whereby identical and similar elements are partially provided with the same reference numerals and the features of the different exemplary embodiments can be combined with one another. Brief description of the characters

[0048] They show: Fig. 1 a three-dimensional view of a cutting mill on a stand according to a first embodiment of the invention, Fig. 2 a three-dimensional view of the cutting mill made of Fig. 1 with the grinding chamber open, Fig. 3 a three-dimensional view of the cutting mill made of Fig. 1 with the grinding chamber open and the cutting rotor removed, the sieve cassette removed and the grinding chamber cover removed, Fig. 4 shows a three-dimensional view of the cutting rotor and the sieve cassette for the cutting mill made of Fig. 1 , Fig. 5 a partial three-dimensional view, partially cut away, of the shaft passage through the grinding chamber rear wall of the cutting mill made of Fig. 1 , Fig. 6 a detail enlargement from Fig. 5 In the area of ​​the labyrinth seal, Fig. 7 shows a cross-sectional view of the closed grinding chamber with cutting rotor of the cutting mill. Fig. 1 , Fig. 8 a cross-sectional view of an enlarged section from Fig. 7in the area of ​​the labyrinth seal, Fig. 9 a view of the drive motor for the cutting mill made of Fig. 1 , Fig. 10 a view from below of the rotor mounting element of the cutting mill made of Fig. 1 , Fig. 11 a cross-sectional view of the rotor mounting element made of Fig. 10 along line 11-11, Fig. 12 a cross-sectional view of the labyrinth seal according to a further embodiment of the invention, Fig. 13 an enlarged view of section A13 in Fig. 12 . Detailed description of the invention

[0049] Referring to the Figs. 1-3 The cutting mill 10 has a housing 12 which contains the parts of the cutting mill. The housing 12 of the laboratory-scale cutting mill can, for example, be placed on a stand 8 ( Fig. 1 ). In the right part 12a of the device housing 12 there is a commercially available electric drive motor 14 (see Fig. 7 , 9). In the present example, the one in Fig. 9The drive motor 14 shown is a geared motor for a cutting mill 10 with a speed range of 50 to 700 rpm. Another embodiment of the cutting mill 10 operates with a drive motor 14 without a gearbox for a speed range of 300 to 3000 rpm (not shown). The grinding chamber 16 is located in the left part 12b of the device housing. Samples to be ground or the material to be ground can be added to this chamber during operation via a filling funnel 18 through a filling opening 19. The grinding chamber 16 can be opened from the side by opening the grinding chamber cover 20. Furthermore, the grinding chamber 16 can be opened even further by folding open a side wall of the grinding chamber, sometimes also referred to as the housing top or grinding chamber top, in this example the side wall 21 to which the filling funnel 18 is attached.It should be noted that terms such as "front", "back" or "side" refer to the point of view and are therefore not to be understood as absolute.

[0050] Referring to Fig. 7 The drive motor 14 is flanged to the motor side 24a of the grinding chamber rear wall 24 by means of a motor flange 22. The motor shaft 26, as the primary shaft, runs horizontally and extends through a through-opening 28 in the grinding chamber rear wall 24 and into the grinding chamber 16. A shaft extension, which forms the rotor mounting element 30, is mounted on the motor shaft 26. The torque transmission between the motor shaft 26 and the rotor mounting element 30 is effected by a key 32. In this example, the torque is therefore transmitted directly from the motor shaft 26 to the rotor mounting element 30 by means of the key 32.

[0051] The rotor mounting element 30 has a drive flange 34 on the motor side, the diameter of which is considerably larger than the diameter of the motor shaft 26. Eccentrically arranged drive pins 36 are mounted in the drive flange 34, by means of which the torque is transmitted to the cutting rotor 38. Due to the relatively large distance of the drive pins 36 from the axis of rotation A, a large torque can be transmitted to the cutting rotor 38. The cutting rotor 38 has corresponding receiving bores 40 for the positive engagement of the drive pins 36 in the cutting rotor 38. In this example, the rotor mounting element 30 and the motor shaft 26 (which can also be referred to as the primary shaft) together form the drive shaft 42 for the cutting rotor 38.

[0052] The drive flange 34 of the rotor mounting element 30 or the drive shaft 42 runs at least partially within the grinding chamber rear wall 24 or within the passage opening 28. Therefore, in this example, the diameter d of the passage opening 28 is also relatively large, which in turn requires a relatively large diameter for the seal of the passage opening 28.

[0053] In the present embodiment, the grinding chamber rear wall 24 is designed in two parts and consists of a body part 44 made of aluminum and a plate 46 made of stainless steel which is mounted on or inserted into the grinding chamber. This allows weight to be saved on the one hand and aluminum abrasion in the grinding chamber 16 to be largely avoided on the other.

[0054] The cutting rotor 38 has a cutting rotor core 48, which is mounted on the drive shaft 42 and has axially extending rotor cutting edges 50 on its circumferential side. In the present example, the rotor cutting edges 50 are integrally formed. However, the rotor cutting edges 50 can also be manufactured as separate cutting strips, possibly made of a different material than the cutting rotor core 48, and connected to the cutting rotor core 48. The cutting rotor core 48 can also be designed in two or more parts (not shown). The cutting rotor 38 can also be designed as a disc rotor, possibly with indexable inserts (not shown). The cutting rotor 38 rotates horizontally, i.e. about a horizontal axis A. On the motor side, the cutting rotor 38 is mounted on the drive shaft 42 and is mounted on the opposite side by a conical bearing 54, which in turn is rotatably mounted in the grinding chamber closure cover 20 via ball bearings 56.The cutting rotor 38 can include a conical bearing receptacle 55, which can be attached to the cutting rotor 38 by a central screw 57.

[0055] Referring again to the Figs. 2-4 The cutting mill comminutes the material or sample by a cutting action between the essentially axially oriented cutting edges 50 of the cutting rotor 38 and the also essentially axially oriented stationary counter-cutting edges 52. The cutting mill 10 thus operates on the scissor principle, in which the sample is cut between a pair of cutting edges 50, 52. Here, "essentially axially oriented" or "axially oriented" cutting edge does not necessarily mean that the cutting edges 50, 52 must be exactly parallel to the axis of rotation A; the cutting edges 50, 52 can also be axially inclined (with a helix), as in the example shown in the Fig. 2 , 4 The example of a cutting rotor 38 shown. The one in the Fig. 2 , 4The example shown depicts a cutting rotor 38 with so-called V-shaped cutting edges 50. In the context of a cutting mill, these cutting edges 50, while inclined (with a helix), are nevertheless axial or essentially axial, meaning they are not transverse or perpendicular to the axis of rotation A. The V-shaped cutting edges 50 of the cutting rotor 38 essentially follow an acute-angled helix, which can still be defined as axial or essentially axial in general. Below the cutting rotor 38 is a sieve cassette 92, through which the sufficiently finely ground material can trickle into the collection container 94.

[0056] The grinding chamber cover 20 can be opened, allowing access to the front of the grinding chamber 16 for removal of the cutting rotor 38 when the cover 20 is open. Folding back the side wall or top 21 of the grinding chamber further improves access to the open grinding chamber 16. With the grinding chamber 16 open, the cutting rotor 38 can be manually pulled horizontally off the drive shaft 42. For this purpose, the cutting rotor 38 is simply axially mounted onto the drive shaft 42 and, apart from the axial fixation by the conical bearing 54 when the grinding chamber cover 20 is closed, is not axially secured. The cutting rotor 38 is only positively and rotationally coupled to the drive shaft 42 via the drive pins 36, but can be pulled off the drive shaft 42 without tools after opening the grinding chamber cover 20.

[0057] Although the rotor mounting element 30 facilitates simple manual insertion of the cutting rotor 38 onto its mounting, in this exemplary design the torque transmission via the drive pins 36 is located relatively far to the outside, which means that sealing takes place over a fairly large diameter (cf. Fig. 3 , 5 , 7 , 8 , 10-11 The diameter d of the circular ring on which the drive pins 36 are arranged is d = 55 mm in this example; therefore, with a drive pin diameter of 8 mm, the outer torque-transmitting diameter D = 63 mm. In other words, the radially outer boundary of the drive pins 36 is 31.5 mm radially from the axis of rotation (A).

[0058] At constant rotational speed, a large diameter, while detrimental to the seal, results in a relatively high circumferential speed compared to a seal hypothetically positioned closer to the axis of rotation A. Furthermore, in previous cutting mills, the rotor housing could only be removed with considerable effort and typically not for regular cleaning. The seal was formerly achieved, for example, with felt rings, which were cumbersome to replace. These felt rings could become stuck, for example, due to waxes, oils, or resins that might be released from the material being ground.

[0059] Referring to Figs. 5-8The cutting mill 10 according to the invention now has a labyrinth seal 60, which can be easily removed by the user, e.g., for cleaning. In the illustrated example, the labyrinth seal 60 has an inner labyrinth ring 62, which in this example is mounted as a separate part on the drive shaft 42, more precisely on the drive flange 34. The inner labyrinth ring 62 extends completely around the drive shaft 42 or the drive flange 34 and has a projection on its motor-side rear side 62a in the simplest form of a meander shape 64a. Furthermore, the inner labyrinth ring 62 also has a meander shape 64b on its grinding chamber-side front side 62b. The inner labyrinth ring 62 lies radially outside the torque-transmitting drive pins 36.

[0060] However, it is also possible to design the rotor mounting element 30, or the drive flange 34, directly with corresponding labyrinth shapes or meanders on the grinding chamber side and / or motor side, i.e., to manufacture the rotor mounting element 30 and the inner labyrinth ring 62 in one piece.

[0061] On the motor-side rear side 24a of the grinding chamber rear wall 24, there is a motor-side labyrinth ring cover 66, which interlocks with the motor-side rear side 62a or meander shape 64a of the inner labyrinth ring 62 to form a corresponding labyrinth. In the present example, the motor-side labyrinth ring cover 66 is formed integrally with the grinding chamber rear wall 24 (see Figure 1). Fig. 7 , 8 The motor-side labyrinth ring cover 66 can also be designed as a separate part from the grinding chamber rear wall 24.

[0062] On the front surface 24b of the rear wall 24 of the grinding chamber, specifically on the stainless steel cover plate 46, a labyrinth ring cover 67 is recessed into a corresponding recess 68 in the rear wall 24 of the grinding chamber or the stainless steel cover plate 46. In the illustrated example, the labyrinth ring cover 67 and the rear wall 24 of the grinding chamber or the stainless steel plate 46 are flush, so that together they form a substantially flat inner surface 24b of the rear wall of the grinding chamber in the area of ​​the cutting rotors 38.

[0063] In the present embodiment, the rotor mounting element 30 is fastened to the motor shaft 26 by means of a central screw 31, although this is not strictly necessary depending on the embodiment. Although the rotor mounting element 30 sits on the motor shaft or primary shaft 26 with a typical transition fit, i.e., a tight clamping fit, it can nevertheless be pulled axially off the primary shaft 26 in the direction of the open grinding chamber cover 20 by overcoming the clamping force, provided the screw 31, if present, has been loosened. In the Fig. 7 , 8In the sections shown, the rotor mounting element 30 has a central bore 33 for the central fastening screw 31. To overcome the clamping force of the transition fit for removing the rotor mounting element 30, the bore 33 can be designed as a threaded bore with a larger thread diameter. Then, for example, a suitable threaded screw can be used in the threaded bore 33 for removal (not shown).

[0064] The rotor mounting element 30 also removes the inner labyrinth ring 62 and, with it, the labyrinth ring cover 67 on the grinding chamber side, so that the passage opening 28 in the rear wall 24 of the grinding chamber is then relatively easily accessible around the primary shaft 26, for example, for cleaning. In other words, when the rotor mounting element 30 is removed from the primary shaft 26, it automatically takes the labyrinth ring cover 67 on the grinding chamber side with it. Afterwards, the rotor mounting element 30, the inner labyrinth ring 62, and / or the labyrinth ring cover 67 on the grinding chamber side can be cleaned, for example, in an ultrasonic bath. The labyrinth ring groove 66a on the grinding chamber side in the motor-side labyrinth ring cover 66 is also easily accessible from the open grinding chamber 16 after the rotor mounting element 30, along with the inner labyrinth ring 62 and the labyrinth ring cover 67 on the grinding chamber side, and can likewise be cleaned.

[0065] The labyrinth seal 60 designed in this way is therefore advantageously maintenance-friendly, as it is easy to clean and very durable. This is because the rotating parts of the labyrinth seal – the inner labyrinth ring 62 rotating with the cutting rotor and the stationary labyrinth ring covers 66, 67 on the motor and grinding chamber sides – do not touch each other, but operate on the principle of a gap seal, i.e., an air gap exists between the interlocking structures. Therefore, heat generation at the labyrinth seal is low at this point, despite the relatively large seal diameter, since the labyrinth seal is a non-contacting gap seal and, as long as the gaps remain clean, no increased friction is generated here. Nevertheless, the seal, which is mounted on the rotor mounting element 30, canThe drive flange 34 runs far to the outside, as with previous seals, thus maintaining compatibility with existing cutting mills. Furthermore, the parts of the grinding chamber rear wall 24 that directly adjoin the grinding chamber 16, i.e., at least the plate 46 and the labyrinth ring cover 67 embedded therein, can be made of stainless steel, thus enabling FDA compliance.

[0066] The sealing effect of the labyrinth seal 60 can now be further improved by additional measures.

[0067] Referring to the Fig. 5 , 6One possible measure for further improving the sealing effect of the labyrinth seal 60 lies in generating an airflow from the motor side towards the grinding chamber 16. For example, fan blades 72 can be provided on the outer circumferential surface 62c of the inner labyrinth ring 62. These fan blades 72 can, for example, be milled relatively easily. The airflow, or rather a dynamic pressure, is thus generated by the rotor mounting element 30 or the inner labyrinth ring 62 mounted on it. In this respect, the large diameter, which is rather problematic for the seal due to the high circumferential speeds, can be used synergistically to a positive effect on the airflow generation of the labyrinth seal 60.

[0068] When the inner labyrinth ring 62 rotates, the fan blades 72 generate an airflow and therefore form an airflow generation device 73. However, an external pump could also be used as an airflow generation device 73.

[0069] Referring to Fig. 7 The air supply is ensured by an air duct 74 in the motor side 24a of the grinding chamber rear wall 24. The airflow is visualized by the arrow 76. This allows the relatively large motor flange 22 of a standard drive motor 14 to still be flanged to the grinding chamber rear wall 24.

[0070] The airflow 76 enters the grinding chamber 16 from the space surrounding the drive motor 14 outside the grinding chamber 16 through the ventilation duct 74 and through the labyrinth seal 60. This airflow 76, forced by the airflow generation device 73, further improves the sealing effect of the labyrinth or gap seal 60.

[0071] Referring to Figs. 12, 13 Below, another possibility for improving the labyrinth seal 60 is proposed, whereby the basic structure is the same as in the Figs. 1-11 , so that reference can be made to the relevant description here to avoid repetition.

[0072] The difference to the embodiment in the Figs. 1-11 The reason for the airflow generation device 73 is that the embodiment of the Figs. 12, 13 The device contains additional labyrinth elements 82 (instead of fan blades 72 to generate a forced airflow 76). The inner labyrinth ring 62 used here has meandering projections 82 on its radial outer circumference 62c. In the present example, the meandering projections 82 are formed by two rings 84, 86 that are triangular in axial cross-section. As shown in the sectional view of the Fig. 12As can be seen, the cylindrical outer surface 62c of the inner labyrinth ring 62 is provided with sharp-edged points. The rotation of the inner labyrinth ring 62 can cause this geometry to form vortices, which can create air pockets and thus impede or prevent the passage of particles from the grinding chamber 16 towards the area surrounding the motor 14. An advantage of this inner labyrinth ring 62 is that it can be manufactured as a purely turned part and does not require milling. In the present example, the inner labyrinth ring 62 has meandering projections on its radial outer circumferential side 62c, for example in the form of two radially outwardly tapering, axially offset rings 84, 86.The inner ring wall 28d of the passage opening 28, surrounding the inner labyrinth ring 62, does not have any counter-labyrinth rings engaging in the spaces between the projections 84, 86, so that it can be described as an open labyrinth on the circumferential side or a see-through labyrinth. In other words, the radially outwardly extending annular projections 84, 86 are not interlocked with corresponding counter-labyrinth elements. Advantageously, the inner labyrinth ring 62 remains axially retractable from the passage opening 28.

[0073] Referring to the Fig. 7 , 8 , 12The grinding chamber-side labyrinth ring cover 67 is positively engaged with an O-ring 88, clamping it into the recess 68 in the plate 46. The elastic O-ring 88 ensures a secure clamping hold of the labyrinth ring cover 67 in the grinding chamber rear wall 24, while also allowing the rotor mounting element 30, along with the inner labyrinth ring 62 and the grinding chamber-side labyrinth ring cover 67, to be axially pulled out by overcoming the clamping force exerted by the O-ring 88. Thus, by applying sufficient axial force to overcome the clamping force, the user can pull parts 30, 62, and 67 out of the through-opening 28, making the through-opening 28 and the motor-side labyrinth ring cover 66 at least partially accessible from the front for cleaning. In other words, the labyrinth seal 60 can be relatively easily pulled apart axially, especially manually, to allow access for cleaning.

[0074] In summary, the sealing concept presented here offers a number of advantages, e.g. compared to previously used felt seals.

[0075] The sealing concept is maintenance-friendly and requires very little maintenance. Despite this, the sealing concept effectively keeps dust in the grinding chamber and allows only a small amount of dust to pass through the labyrinth seal into the area of ​​the drive motor 14. Furthermore, the sealing concept generates little heat. Nevertheless, the labyrinth seal 60 can be positioned relatively far out on an existing rotor mounting element 30, thus maintaining compatibility with earlier types of cutting mills.

[0076] A particular advantage is the prevention of material abrasion (with a clean labyrinth) and the possibility of FDA approval, especially if, for example, parts 62, 66, and 67 of the labyrinth seal 60 and the plate 46 are made of stainless steel. Despite its relatively large diameter, the production of such a labyrinth seal 60 has proven technologically feasible and even offers some surprising advantages. Currently, for example, efforts are underway in some regions of the world to increasingly legalize cannabis products for various applications. This has led to increased demand for shredders in cannabis processing. Particularly in the shredding of oily cannabis flowers, and to some extent also cannabis leaves, it has been shown that the labyrinth seal proposed here can effectively prevent oiling or resinification of the seal in a shredder, or at least significantly improve cleaning capabilities.

[0077] It is evident to a person skilled in the art that the embodiments described above are to be understood as examples and that the invention is not limited to them, but can be varied in many ways without departing from the scope of protection of the claims. Furthermore, it is evident that the features, regardless of whether they are disclosed in the description, the claims, the figures, or otherwise, also individually define essential components of the invention, even if they are described together with other features.

Claims

1. A cutting mill (10) in laboratory scale for cutting down samples according to the shearing principle, comprising: a device housing (12); a drive motor (14) and a drive shaft (42), a grinding chamber (16) with a cutting rotor (38) arranged therein for cutting down the samples in the grinding chamber (16); wherein the cutting rotor (38) defines a rotational axis (A) and wherein the cutting rotor (38) has rotor cutting edges (50), wherein counter blades (52) having a stationary counter cutting edge (52) are arranged circumferentially in the grinding chamber (16), such that the sample is cut, according to the shearing principle, between a pair of cutting edges consisting of a rotor cutting edge (50) and a counter cutting edge (52) when the rotor cutting edges (50) and the stationary counter cutting edges (52) slide past one another; wherein the grinding chamber (16) is bounded axially on the motor side by a grinding chamber rear wall (24), the grinding chamber rear wall (24) having a shaft passage opening (28) through which the cutting rotor (38) can be driven by the drive shaft (42); characterised in that the cutting rotor (38) can be slid onto the drive shaft (42); and the shaft passage opening (28) in the grinding chamber rear wall (24) is sealed by a labyrinth seal (60).

2. The cutting mill (10) according to claim 1, wherein the device housing (12) comprises an axially front-end closure lid (20) which can be opened to open the grinding chamber (16), and in which the cutting rotor (38) is mounted for rotation (54, 56) on the axial side opposite the drive motor (14) when the closure lid (20) is closed.

3. The cutting mill (10) according to any one of the preceding claims, wherein drive elements (36) are provided which engage in a positive-locking manner in the cutting rotor (38) when the cutting rotor (38) is placed on the drive shaft (42) in order to transmit the torque to the cutting rotor (38) by means of the drive elements (36).

4. The cutting mill (10) according to any one of the preceding claims, wherein the drive shaft (42) is of multi-part design and comprises at least one primary shaft (26) and a rotor mounting element (30) mounted coaxially on the primary shaft (26), and wherein coupling means (32) are provided between the primary shaft (26) and the rotor mounting element (30) which effect the torque transmission from the primary shaft (26) to the rotor mounting element (30).

5. The cutting mill (10) according to any one of the preceding claims, wherein the drive shaft (42) comprises a drive flange (34) which extends around the drive shaft (42), and wherein drive elements (36) engage on the one hand in the drive flange (34) and on the other hand in the cutting rotor (38).

6. The cutting mill (10) according to any one of claims 3 or 5, wherein the drive elements (36) are in the form of axially extending drive pins whose radially outer boundary is spaced apart radially from the rotational axis (A) by at least 15 mm.

7. The cutting mill (10) according to claim 4, wherein a drive flange (34) is formed as part of the rotor mounting element (30) and the rotor mounting element (30) with the drive flange (34) can be slid onto the primary shaft (26) as a unit.

8. The cutting mill (10) according to any one of claims 5 to 7, wherein the drive flange (34) is arranged at least partially within the shaft passage opening (28).

9. The cutting mill (10) according to any one of the preceding claims, wherein the labyrinth seal (60) comprises an inner labyrinth ring (62) and a grinding-chamber-side labyrinth ring cover (67), and wherein a grinding-chamber-side axial end face (62b) of the inner labyrinth ring (62) is intermeshed with an axial end face of the grinding-chamber-side labyrinth ring cover (67); and / or wherein the labyrinth seal (60) comprises an inner labyrinth ring (62) and a motor-side labyrinth ring cover (66), and wherein a motor-side axial end face (62a) of the inner labyrinth ring (62) is intermeshed with an axial end face of the motor-side labyrinth ring cover (66); and wherein, preferably, the grinding chamber rear wall (24) has a grinding-chamber-side annular recess (68) in which the grinding-chamber-side labyrinth ring cover (67) is fixed, and wherein, preferably, the inner labyrinth ring (62) is removable in the direction from the motor (14) to the grinding chamber (16), and the grinding-chamber-side labyrinth ring cover (67) is clamped in the grinding chamber rear wall (24) and, when the inner labyrinth ring (62) is retracted, the grinding-chamber-side labyrinth ring cover (67) is released from the clamping in the grinding chamber rear wall (24) and can be withdrawn from the drive shaft (42) together with the inner labyrinth ring (62), and wherein, preferably, the grinding-chamber-side labyrinth ring cover (67) is clamped by means of a positive-locking inserted O-ring (88) in the grinding-chamber-side annular recess (68).

10. The cutting mill (10) according to claim 9, wherein the inner labyrinth ring (62) is arranged radially outside on a rotor mounting element (30), in particular radially outside on a drive flange (34).

11. The cutting mill (10) according to any one of the preceding claims, wherein an air flow generating means (73) is provided, which generates an air flow (76) through the gap of the labyrinth seal (60).

12. The cutting mill (10) according to any one of claims 9 to 11, wherein the inner labyrinth ring (62) comprises fan blades (72) which, upon rotation of the inner labyrinth ring (62), generate an air flow through the gap of the labyrinth seal (60); and wherein, preferably, the fan blades (72) are arranged on a radially outer peripheral wall (62c) of the inner labyrinth ring (62).

13. The cutting mill (10) according to any one of the preceding claims, wherein a ventilation passage (74) is provided between the grinding chamber rear wall (24) and the drive motor (14), through which an air flow (76) is guided through the labyrinth seal (60).

14. The cutting mill (10) according to any one of the preceding claims, wherein the labyrinth seal (60) comprises an inner labyrinth ring (62), wherein the shaft passage opening (28) has an inner radial annular wall (28d) within which the inner labyrinth ring (62) is arranged so that the inner radial annular wall (28d) annularly surrounds the inner labyrinth ring (62), wherein either the inner radial annular wall (28d) or the outer radial annular wall (62c) of the inner labyrinth ring (62) defines a meandering shape (82, 84, 86) in axial cross-section, but without the inner radial annular wall (28d) intermeshing with the outer radial annular wall (62c) of the inner labyrinth ring (62), such that the inner labyrinth ring (62) can nevertheless be axially withdrawn from the shaft passage opening (28); and wherein, preferably, the meandering shape (82, 84, 86) is formed so as to radially taper in axial cross-section; and wherein, preferably, the meandering shape is formed so as to taper in a triangular shape in axial cross-section, optionally acutely triangular (84, 86).