Laboratory mill

Abstract

The invention relates to a laboratory mill (1) for comminuting grinding material, in particular in the form of a cutting mill or cross beater mill, comprising: a device housing (12) with a grinding mechanism housing (16), wherein the grinding mechanism housing (16) defines a grinding chamber (32) and has an axial end side (16a); a rotor grinding mechanism (30) in the grinding chamber (32) of the grinding mechanism housing (16), wherein the rotor grinding mechanism (30) has a rotor (34) defining a rotor axis (X) and at least one counter element (36), wherein the grinding material is comminuted between the rotor (34) and the at least one counter element (36) when the rotor (34) rotates; a grinding mechanism drive (2, 4) for driving the rotor (34) in the grinding chamber (32); a grinding mechanism housing door (18) for closing the grinding mechanism housing (16) on the axial end side (16a), wherein the at least one counter element (36) can be introduced axially into the grinding mechanism housing (36) when the grinding mechanism housing door (18) is open.

Description

[0001] Laboratory mill

[0002] Area of

[0003] The invention relates to a laboratory mill, in particular a cutting mill or a cross-beam mill on a laboratory scale, which has a grinding mechanism in which material to be ground is comminuted by cutting and / or impact action, for example in a grinding gap between a grinding mechanism rotor and one or more stationary counter-elements.

[0004] Background and general description of the invention

[0005] Cutting mills comminute material to be ground between a rotating cutting rotor with one or more essentially axially extending rotor cutting edges and one or more likewise essentially axially extending stationary counter cutting edges according to the scissors principle in the grinding gap running axially between them. Such laboratory cutting mills are particularly suitable for comminuting tough or fibrous samples, e.g. biological samples such as straw, but also plastic films, to name just a few examples. Examples of current laboratory cutting mills include the PULVERISETTE® 19 and the PULVERISETTE® 15 from the applicant, to whose basic design reference is hereby made. Corresponding product descriptions of the PULVERISETTE® 19 and the PULVERISETTE® 15 can be found, for example, at www.fritsch.de.

[0006] In these laboratory-scale cutting mills, more or less free-flowing bulk material is typically fed into the grinding chamber, e.g., via a hopper, where the cutting rotor rotates around a horizontal axis. The cutting rotor can have different geometries, e.g., with straight cutting edges or so-called V-cutting edges. The latter feature a twist and thus achieve a good cutting effect, especially when comminuting tough, elastic materials and films.

[0007] Below the cutting rotor is typically a sieve, e.g., a sieve cassette, through which the sample material that has already been sufficiently comminuted can trickle to be collected in a collecting vessel below. For further design details of a cutting mill, which are generally known to those skilled in the art, reference is made to the product descriptions for the applicant's PULVERISETTE® 19 and PULVERISETTE® 15 cutting mills, which were available for download at www.fritsch.de at the time of application and its disclosure, and which are hereby incorporated by reference with regard to the basic design of such a cutting mill. Furthermore, the applications DE 196 01 594, DE 10 2018 113 751 A1, WO 2020 / 200759 A1 and DE 10 2019 133 437 A1 describe such cutting mills and are hereby also incorporated by reference.

[0008] The cutting blades are subject to wear, which can cause the cutting gap to change undesirably over time. Furthermore, the cutting blades can be damaged by hard grinding material, which may require regrinding, which also changes the width of the cutting gap. Therefore, the grinding gaps in such mills are typically adjustable for the user, and the user can readjust the blades to set the width of the cutting gap between the cutting edges of the rotor and the counter blades to the desired size and the desired parallelism. Referring to Fig. 23, in a conventional cutting mill 100, the radial positioning of the stationary counter blades 102 is typically adjusted using two threaded pins 104. The counter blades 102 are then pulled against these stops with another screw 106 to fix them.The rotor's cutting edges are typically fixed by shape and grind, or if individual cutting edges are used on the rotor, these are mounted on the rotor, and then the cutting edges of the stationary counter knives 102 are adjusted and fixed relative to the rotor cutting edges. While this adjustment of the cutting gap has proven generally effective, it also has some disadvantages.

[0009] First of all, this adjustment is not particularly easy and requires experience, which can lead to the user not always handling it optimally. Furthermore, the grinding gaps not only change due to wear but can also be adjusted after disassembly and reassembly. Especially with an undivided grinder housing, the cutting gap at the rear end near the motor is difficult to reach and measure. Another disadvantage is that the user can also set the cutting or grinding gap too small. This then results in either a grinding gap that is too small, which can lead to increased cutting edge wear, excessive heating and higher machine strain, or, even more disadvantageous, an overlap of the cutting edges. The latter can lead to damage when the grinder starts up and is not uncommon.

[0010] Another disadvantage is that the adjustment screws, threads, lock nuts, etc. used for adjustment represent additional components and are contrary to a hygienic design of the grinder.

[0011] Additionally, this type of adjustment can limit the size of the mill, as the individual elements would also have to shrink as the mill gets smaller, which would make adjustment even more difficult.

[0012] Overall, there are a lot of things that can go wrong when setting things up.

[0013] Similar disadvantages also apply to cross beater mills (see PULVERISETTE® 16, www.fritsch.de), whose product descriptions are also hereby incorporated by reference. A cross beater mill has a grinding mechanism similar to a cutting mill, but typically has a larger grinding gap than a cutting mill. This allows the comminution effect to be based more on an impact effect.

[0014] The object of the invention is to provide a laboratory mill, in particular a cutting mill or cross beater mill, which is easy to use and requires little specialist knowledge and operating effort from the user.

[0015] Another aspect of the task is to provide a laboratory mill, in particular a cutting mill or cross-beater mill, that is cost-effective, less prone to failure, and requires little maintenance. Another aspect of the task is to provide a laboratory mill, in particular a cutting mill or cross-beater mill, that is easy to clean and in which the width of the grinding gap can be adjusted very easily and reliably by the user.

[0016] Another aspect of the task is to provide a laboratory mill, in particular a cutting mill or cross beater mill, which can be built particularly small and compact.

[0017] The object of the invention is achieved by the subject matter of the independent claims. Advantageous developments of the invention are defined in the subclaims.

[0018] According to the invention, a laboratory mill for comminuting material to be ground is provided, which comprises a device housing and a grinder housing in which the rotor grinder is located. The grinder housing can be made in particular of solid metal, e.g. of aluminum or stainless steel. The grinder housing defines a grinding chamber, in particular a substantially cylindrical one, into which the rotor grinder comprising a rotor and at least one stationary counter-element is inserted. The rotor or its drive, with its axis of rotation, defines the central axis of the grinding chamber or of the grinder housing. The grinder housing can have a rear, drive-side axial end face, with which the grinder housing can be flange-mounted to a rear part of the device housing. The grinder housing has in particular a front axial end face opposite the grinder drive, from which the user gains axial access to the grinder.

[0019] The rotor grinder is therefore inserted into the grinding chamber of the grinder housing, whereby the rotor can be plugged onto a drive shaft. The at least one stationary counter element is inserted parallel to the rotor into the grinder housing in order to form a defined grinding gap between the rotor and the at least one counter element, in which grinding gap the material to be ground is comminuted when the rotor rotates relative to the at least one counter element. If appropriate, the grinder has a rotor with several, e.g. two, three, four or more cutting blades or beater bars and the laboratory mill has several, e.g. two, three, four or more counter elements, which are arranged around the rotor circumference. In the present application, “at least one” means one or more, in particular two, three, four or more such components. The laboratory mill is designed in particular as a cutting mill or cross beater mill on a laboratory scale.Thus, the rotor can be designed as a cutting rotor and the at least one counter element as a stationary counter knife of a cutting mill or the rotor can be designed as an impact rotor and the at least one counter element as a stationary counter impact bar of a cross impact mill.

[0020] The grinder drive is preferably housed in the device housing and drives the rotor via a drive shaft that extends axially into the grinding chamber. The rotor and / or the counter-element(s) extend axially within the grinding chamber, preferably from a rear end near the motor to a front end of the grinding chamber opposite the drive, in particular to the grinder housing door. The drive shaft can enter the grinding chamber, for example, through a shaft passage opening at the motor-side end of the grinding chamber.

[0021] The grinder housing or grinding chamber is open at the front end, i.e. the end opposite the motor end, thus forming an axial user access opening through which the user can insert and remove the rotor, the counter element(s) and, if necessary, other replaceable grinder components, e.g. to clean, maintain or replace them and also to clean the grinding chamber.

[0022] To operate the laboratory mill, the user access opening is closed with a grinder housing door, which is hinged, for example, to the grinder housing so that it can pivot. The grinder housing door has an open and a closed state. In the open state, the user has access to the grinder, and the laboratory mill can be operated safely with the grinder housing door closed. The laboratory mill can also have a smaller axial or radial grinding material filling opening, e.g. with a filling hopper, through which grinding material can be continuously fed during operation. The grinder housing door can have a door lock with which it can be locked in the closed state, and safety devices that ensure the locking of the grinder housing door during operation.Reference is made to the parallel patent application entitled "Laboratory Mill" filed by the same applicant on the same date, which is hereby incorporated by reference. The at least one or more stationary counter elements can advantageously be axially inserted or pushed into the grinder housing when the grinder housing door is open.

[0023] For this purpose, the grinder housing forms an axially displaceable guide with the counter element(s) with a radially acting positive connection, e.g. in the form of an axially displaceable tongue and groove guide as a linear guide.

[0024] The respective radial form fit provides support against radial inward movement of the counter element(s) toward the rotor, so that the movement of the respective counter element toward the rotor is limited. The form fit support for the corresponding counter element against radial inward movement toward the rotor is thus formed, for example, by the tongue and groove guide.

[0025] The counter element(s) are preferably only loosely inserted into the grinder housing. The radial end positions of the counter element(s) are limited in the grinder housing, in particular by a form-fitting connection, in particular against movement radially inwards, in order to define the smallest dimension of the grinding gap. The counter element(s) are therefore inserted axially into the linear guide with a radial form-fitting connection, and the grinding gap is defined by the radial form-fitting connection of the axially extending linear guide. In particular, the linear guide limits movement of the counter element(s) radially inwards. In particular, no further radial and / or axial fastening, e.g. screwing, and / or no adjusting means and / or no radial bracing, e.g. by screws, etc. is necessary. The counter element(s) are therefore inserted axially into the linear guide during operation of the laboratory mill and / or are radially fixed solely by the form-fitting connection during installation.In particular, the counter element(s) are(are) not screwed together during operation of the laboratory mill. In particular, the counter elements are not radially adjustable, e.g. with threaded pins, in order to set the grinding gap (cutting gap or impact gap) between the rotor and the at least one counter element. The width of the grinding gap is defined exclusively by the geometry of the parts and the linear guide or the radial form fit of the linear guide. The linear guide is, in particular, a single-axis linear guide. The width of the grinding gap is therefore not continuously adjustable by the user, but is fixed and manufactured by the manufacturer as a result of the design and is therefore predefined. The width of the grinding gap can be selected, for example, by using different rotors with different rotor diameters or by using counter elements of different widths, instead of by manually setting the width of the grinding gap by radial adjustment of the counter element(s).of the counter elements by the user.

[0026] This ensures very easy use of the laboratory mill, as manual adjustment of the grinding gap by radial adjustment of the counter-element(s) is no longer required and can be omitted. If the counter-element(s) become worn, they are simply replaced with new ones (the so-called single-use principle). To select the desired grinding gap width, the user maintains one, two, or more additional rotors with different diameters, which are simply exchanged to discretely change the grinding gap width. It is clear that several discrete values ​​for the grinding gap width can be selected in this way.

[0027] Incorrect operation by the user, in particular incorrect adjustment of the grinding gap, is therefore structurally impossible, which is why the laboratory mill can also be operated by less experienced users.

[0028] The invention also relates to a laboratory mill set comprising the laboratory mill and at least two, preferably at least three or more rotors with predefined different diameters or at least two or preferably at least three sets of counter elements of different widths, wherein the selection of the width of the grinding gap between the rotor currently inserted into the grinding chamber and the at least one counter element is not achieved by radial adjustment of the at least one counter element, but by exchanging the rotor or the counter elements for another rotor with a different diameter or other counter elements with a different width.

[0029] When rotors with a rotor base body and separate cutting blades or separate impact bars are used, and the cutting blades or impact bars are screwed to the rotor base body, precise radial positioning of the cutting blades or impact bars should preferably also be ensured on the rotor to precisely define the grinding gap by the manufacturer, especially since the counter element(s) are not radially adjustable but are guided by the linear guide in a single, discrete, radially predefined position. For this purpose, the rotor base body with the cutting blade or impact bars can have a tongue-and-groove connection for radial locking, and / or the cutting blades or impact bars can be screwed to the rotor base body with fitting screws.

[0030] Inserting the stationary counter element(s) into a linear guide with radial form-fit offers another advantage. This allows the counter element(s), and thus the grinder and the entire laboratory mill, to be designed very compactly, as adjustment elements such as threaded pins and screws on the counter elements can be eliminated, thus achieving a synergy effect of simplicity, cost-effectiveness, and compactness.

[0031] The grinder housing preferably has at least one or more receiving and guide slots for the counter-element(s), which extend axially along the rotor and radially. The receiving and guide slots are open radially inwards towards the rotor and on the axial end face of the grinder housing. The associated counter-element can be manually inserted or pushed axially into the associated receiving and guide slot through the end face opening of the receiving and guide slot. The counter-element(s) protrude radially inwards with at least one axial edge (counter-cutting edge or counter-impact edge) from the respective receiving and guide slot into the grinding chamber in order to comminute the material to be ground between the rotor and the at least one axial edge in a peripheral casing region of the grinding chamber. The axial linear guide between the counter-element(s) preferably forms a...the receiving and guide slots and the associated counter element(s) provide an inner radial support for the respective associated counter element, so that their movement radially inwards towards the rotor is limited and a precisely defined grinding gap is ensured. The receiving and guide slot(s) can each have at least one guide groove extending axially and transversely to the receiving and guide slot as a guide rail, and the counter element(s) can each have at least one spring element displaceable in the at least one guide groove. The groove and spring of the axially displaceable tongue and groove guide formed in this way could, however, also be designed the other way around, ie the groove(s) in the counter elements and the spring(s) in the receiving and guide slots. The tongue and groove guide therefore forms guide rails for the linear guide.

[0032] Preferably, symmetrical axial guide grooves extend on both sides of the receiving and guide slot(s). The receiving and guide slot(s) can thus, together with the guide grooves on both sides, have a substantially cross-shaped cross-section. The linear guides or the receiving and guide slots and / or the guide grooves each extend axially and linearly from a rear drive-side end to a front door-side end. The linear guide(s) for the counter element(s) or the guide groove(s) are preferably provided transversely on both sides of the receiving and guide slots.

[0033] Such linear guides, receiving and guide slots as well as guide grooves can be incorporated into a solid metal grinder housing with reasonable effort.

[0034] Preferably, the counter element(s) each have two flat sides which extend axially and radially in the respectively associated receiving and guide slot and rest against this when the counter element(s) is(are) inserted into the respectively associated receiving and guide slot. The terms “radial” or “extension in the radial direction” are not to be understood in a strictly mathematical sense here, but rather mean a direction which is “essentially” radial, i.e. inwards towards or outwards away from the rotor axis. The “radial” direction in this sense does not necessarily have to intersect the rotor axis mathematically exactly. According to one exemplary embodiment, at least one, preferably at least two or more transverse bores are provided through the two flat sides of the counter element(s), in each of which a transverse pin is fastened, e.g. with a press fit. The transverse pin(s) form(s) theThe spring elements are radially guided in the corresponding guide groove and axially displaceable to form the respective linear sliding guide. Preferably, tongue-and-groove guides are provided on both sides of the counter element(s).

[0035] The radial limitation of the movement to form a fixed, defined width of the grinding gap can be designed as follows: To limit the radially inward movement, the counter element(s) can be supported radially inward toward the rotor on a radially inner side wall of the respective guide groove of the tongue-and-groove guide, so that the movement of the counter element(s) is limited radially inward toward the rotor.

[0036] To limit the radial outward movement, the counter element(s) can be supported radially outwards in the direction away from the rotor on a radially outer side wall of the respective associated guide groove of the tongue and groove guide, so that the radial outward movement of the counter element(s) is limited, or a long side of the counter element(s) facing away from the rotor can be supported directly or indirectly on a radially outer base of the respective associated receiving and guide slot, so that the movement of the counter element(s) is also limited radially outwards in the direction away from the rotor. In this way, a clearance fit of the linear guide can be formed with little clearance in the radial direction, e.g. from close to zero to a maximum of + / - one tenth, preferably -V- a few hundredths, in order to structurally define the width of the grinding gap.

[0037] In particular, the receiving and guide slot(s) can each have an axial bore at a radially outer base into which an axially extending support pin is inserted. A longitudinal side of the counter-element(s) facing away from the rotor is then supported on the support pin, and the support pin is supported in the axial bore on the grinder housing in order to limit the movement of the at least one counter-element radially outwards in the direction away from the rotor. This has the advantage that the loads acting radially outwards during grinding can be transferred via a long line along the longitudinal pin, wherein the axial support pin can be designed, for example, as a hardened steel pin, which in turn then has a large surface area within the axial bore available for load transfer to the grinder housing. This is particularly advantageous for small laboratory mills.

[0038] The two end faces or narrow end faces of the counter element(s) extend in particular in a plane transverse to the rotor axis when the counter element is inserted into the associated receiving and guide slot. A pulling opening can be provided in the counter element near at least one of the two end faces, e.g. a transverse bore through the flat sides, so that a pulling tool, e.g. a pulling hook, can be brought into positive engagement, in particular hooked, into the pulling opening in order to pull the counter element axially out of the grinder housing or from the associated receiving and guide slot using the pulling tool when the grinder housing door is open. This allows the user to easily remove the counter element(s) from the grinder housing, e.g. to clean, turn or replace them.

[0039] It is particularly easy to position the drawing opening in the radial direction on the guide groove so that the drawing opening can be reached with the drawing tool through the guide groove that is already present.

[0040] Preferably, the counter element(s) each comprise base bodies in the form of elongated, flat plates or strips. The base bodies are, in particular, substantially cuboid-shaped. The counter element(s) thus comprise two axially and radially extending flat sides, two longitudinal sides extending axially and transversely to the flat sides, and two end faces extending transversely to the flat sides and longitudinal sides, i.e., in a plane transverse to the rotor axis and, in particular, substantially parallel to the axial end face of the grinder housing. The aspect ratio between the width and thickness of the base bodies is preferably at least 2 or at least 3.

[0041] At least one longitudinal edge between a flat side and an adjacent longitudinal side forms a cutting edge or striking edge of the respective counter-element, which cooperates with the cutting edges or striking edges of the rotor in order to crush the material to be ground therebetween, wherein said longitudinal edge runs axially in the interior of the grinding chamber when the at least one counter-element is inserted into the at least one receiving and guide slot of the grinder housing.

[0042] Preferably, the counter element(s) are(are) designed in principle as single-use components, i.e. they are not reground, since otherwise the width of the grinding gap would no longer be correct, but the counter element(s) can be designed to be reversible and thus suitable for multiple use. For this purpose, the receiving and guide slot(s) can be mirror-symmetrical. Furthermore, the counter element(s) can each be designed to be rotationally symmetrical by 180° or reversible with respect to at least one, two or three of the following axes: around an axis running transversely to the flat side, around an axis running transversely to the long side, and / or around an axis running transversely to the end face, so that the counter element(s) can be inserted into the associated receiving and guide slot not just in one, but in at least two, three or four orientations.

[0043] The counter element(s) can therefore preferably be inserted into the grinder housing in a first orientation and a second orientation facing the first orientation, and / or in a third orientation facing the first and second orientations, and / or in a fourth orientation facing the first, second, and third orientations, in order to use a first and second and / or third and / or fourth longitudinal edge of the at least one counter element as a cutting or striking edge. In other words, the counter element(s) can be turned at least once, twice, or three times, and can be used at least twice, three times, or four times by turning them.

[0044] Preferably, at least four, in particular axially collinear, transverse bores can be provided through the flat sides of the at least one counter element for turning, wherein a continuous transverse pin protruding to both sides as a spring element is fastened in each of the two axially inner transverse bores, e.g. with a press fit, and wherein the two axially outer bores remain free as drawing openings. The counter elements inserted with the single-axis linear guide can advantageously be designed to be relatively small, in particular since the counter elements are not screwed and more complex components such as threaded pins and screws for adjustment and tightening can be omitted. However, they can also be designed larger.Preferably, the base body of the axially insertable counter-elements can have a length between 20 mm and 200 mm, preferably between 30 mm and 60 mm, a width between 8 mm and 60 mm, preferably between 15 mm and 30 mm and / or a thickness between 3 mm and 25 mm, preferably between 4 mm and 8 mm.

[0045] An elastomeric pressure element, e.g., in the form of an elastomeric seal, can be attached to the inside of the grinder housing door. This element clamps the counter element(s) axially against the axial end of the receiving and guiding slot on the motor side when the grinder housing door is closed. This prevents residual movement due to play in the linear guide.

[0046] The elastomeric pressure element can be designed as an O-ring, for example, and can be mounted in an annular groove on the inside of the grinder housing door. The elastomeric seal can serve a dual function: on the one hand, it can provide a ring-shaped seal on the front side of the guide grooves and / or the grinding chamber, and on the other hand, it can clamp the counter element(s).

[0047] Preferably, the grinding chamber can be formed as a substantially cylindrical, in particular substantially round-cylindrical cavity in the grinder housing and can transition radially downwards into a grinding material outlet channel through which the comminuted grinding material can trickle into a grinding material collecting container. The grinding chamber and the grinding material outlet channel can be separated by an arcuate sieve plate, in particular without a stable sieve cassette, through which the comminuted grinding material can trickle downwards from the grinding chamber into the grinding material outlet channel. The arcuate sieve plate and the rotor can be removed axially from the grinder housing with the grinder housing door open. For this purpose, the arcuate sieve plate can be inserted into the grinder housing and rest there between the grinding chamber and the grinding material outlet channel.Advantageously, the grinder housing is particularly free of webs on its front door-side face in the area below the screen plate, meaning it has no web spanning the grinding material outlet channel. This allows the grinding chamber and the grinding material outlet channel to be brushed out together from the front of the grinder housing without obstructions for cleaning when the grinder housing door is opened and the rotor and the curved screen plate are removed. The grinding chamber and the grinding material outlet channel thus share a uniform front face opening.

[0048] According to one aspect of the present invention, the laboratory mill, which is particularly designed as a cutting mill or cross-beater mill, can comprise the following: a device housing with a grinder housing, wherein the grinder housing defines a substantially cylindrical grinding chamber and has a front axial end opposite the grinder drive, a rotor grinder in the grinding chamber of the grinder housing, wherein the rotor grinder has a rotor defining a rotor axis and at least one stationary counter-element, preferably several, in particular two, three, four or more stationary counter-elements, wherein the material to be ground is comminuted between the rotor and the stationary counter-element(s), which are preferably arranged along a circumferential line around the rotor, when the rotor rotates, a grinder drive in the device housing for driving the rotor in the grinding chamber,a grinder housing door for closing the grinder housing on the axial end face, wherein the grinder housing door has an open and a closed state, wherein the user has axial access to the grinder in the open state of the grinder housing door, wherein the grinding chamber is formed in the form of a substantially cylindrical cavity in the grinder housing and merges downwards into a grinding material outlet channel through which the comminuted grinding material can trickle into a grinding material collecting container, wherein the grinding chamber and the grinding material outlet channel are separated by an arcuate sieve plate, in particular without a sieve cassette, through which the comminuted grinding material can trickle downwards from the grinding chamber into the grinding material outlet channel, and wherein at least one or more, preferably at least two or at least three axial conical pins protrude from the grinder housing door, which, when the grinder housing door is closed, by a pivoting movement,be swung under the curved sieve plate and support it downwards when the grinder housing door is closed.

[0049] Advantageously, a simple, flat screen plate, e.g., punched from a perforated sheet and subsequently bent, can be guided without a screen cassette and without any other transverse reinforcement in two lateral grooves in the grinder housing and supported at the front edge facing the grinder housing cover by the conical pins at the bottom. Using the conical pins as the lower support on the grinder housing door, it can be ensured that the door swings shut without jamming.

[0050] In the following, the invention is explained in more detail using exemplary embodiments and with reference to the figures, wherein identical and similar elements are partly provided with the same reference numerals and the features of the various exemplary embodiments can be combined with one another.

[0051] They show:

[0052] Fig. 1 is a three-dimensional representation of a cutting mill according to an embodiment of the invention,

[0053] Fig. 2 as Fig. 1 with transparent grinder housing,

[0054] Fig. 3 as Fig. 1 with grinder housing door open,

[0055] Fig. 4 a front view of the cutting mill from Fig. 1 without the grinder housing door,

[0056] Fig. 5 is an enlargement of section A from Fig. 4,

[0057] Fig. 6 is a three-dimensional representation of a cutting mill according to a further embodiment of the invention without a grinding mechanism housing door,

[0058] Fig. 7 is a front view of the cutting mill from Fig. 6,

[0059] Fig. 8 Enlargement of section A from Fig. 7,

[0060] Fig. 9 a longitudinal section through the cutting mill from Fig. 1 ,

[0061] Fig. 10 a three-dimensional representation of the stationary counter element,

[0062] Fig. 11 is a plan view of a flat side of the counter element from Fig. 10,

[0063] Fig. 12 is a front view of a longitudinal side of the counter element from Fig. 10, Fig. 13 is a view of an end face of the counter element from Fig. 10,

[0064] Fig. 14 is a three-dimensional representation of a rotor according to an embodiment of the invention,

[0065] Fig. 15 is a three-dimensional representation of a rotor according to a further embodiment of the invention,

[0066] Fig. 16 shows a horizontal section through the grinder housing, Fig. 17 shows a vertical section through the grinder housing, Fig. 18 shows a three-dimensional representation of a cutting mill without a grinder housing door according to a further embodiment of the invention,

[0067] Fig. 19 is a front view of the cutting mill from Fig. 18,

[0068] Fig. 20 is an enlargement of section A in Fig. 19,

[0069] Fig. 21 a three-dimensional view from the bottom left of the main body of the cutting mill from Fig. 6,

[0070] Fig. 22 a three-dimensional view from diagonally above right of the main body of the cutting mill from Fig. 6,

[0071] Fig. 23 is an exploded view of parts of a conventional cutting mill.

[0072] Detailed description of the invention

[0073] 1-9, a laboratory mill 1 is shown, in the present example in the form of a cutting mill. The laboratory mill 1 has a device housing 12 with a user display 14 for the user to enter grinding parameters into a control device (not shown) of the laboratory mill 1. On the front 12a of the device housing 12, a grinder housing 16 is arranged, which can be closed at the front (axially) with a grinder housing door 18. The grinder housing door 18 is designed as a swing door and can be pivoted open and closed about hinges 20. The grinder housing door 18 can be locked with a door lock 22 when the grinder housing door 18 is closed, as shown in Fig. 1. When the grinder housing 16 is closed, the material to be ground can be fed into the grinding mill via a filling hopper 24 and a radial material filling opening 26 in this example (Fig.21-22) so that material to be ground can be continuously fed and comminuted during operation of the cutting mill 1. When the locking element 22 is unlocked, the user can pivot open the grinder housing door 18 to gain access to the rotor grinder 30, which is located in the interior or grinding chamber 32 of the grinder housing 16. When the grinder housing door 18 is fully pivoted open, the user thus gains axial access through an axial user access opening 38 to the essentially round-cylindrical grinding chamber 32 and the rotor grinder 30 arranged therein, which has a rotor 34 rotating coaxially to the drive axis or rotor axis X and a plurality of axially extending stationary counter-elements 36 arranged in a ring around the rotor 34. The example shows a cutting mill such that the rotor 34 is designed as a cutting rotor and the stationary counter-elements 36 are designed as stationary counter-blades.In a correspondingly constructed cross beater mill, the rotor 34 is designed as a beater rotor with beater bars and the stationary counter elements 36 are designed as counter beater bars.

[0074] The rotor 34 is preferably mounted and axially screwed onto a drive shaft 2, which is driven at the rear by a drive motor 4, and is driven via a positive-locking element. For this purpose, the drive shaft 2 extends through a central opening 6 between the rear part 12b of the device housing 12 and the grinder housing 16 flanged to the front, and also defines the coaxial rotor axis X (Fig. 9).

[0075] When the grinder housing door 18 is fully open, the user can loosen the rotor 34 and pull it axially off the drive shaft 2 and pull it out axially through the front axial user access opening 38 of the grinder housing 16. During operation, the rotor 34 rotates, and the ground material is fed via the feed hopper 24 through the radial ground material filling opening 26 to the rotor grinder 30 and comminuted between rotor blades 40 or impact bars of the rotor 34 and the stationary counter elements 36 by cutting and / or impact action. The comminuted ground material then trickles downwards, e.g., through a sieve 42, into a ground material collection container 44.

[0076] The stationary counter elements 36 are fixed in the grinder housing 16, i.e. they are not radially adjustable and are therefore radially fixed. In the present example, they can be used four times in that they are designed to be rotationally symmetrical in several ways, so that they can be turned in four different orientations and inserted into the grinder housing 16 in a turned position. To ensure that the user can still select different grinding gap widths depending on the material to be ground, the laboratory mills 1 can be offered, for example, with different rotors 34 with different diameters. For example, each laboratory mill 1 is offered with a set of three different rotors 34 which, in conjunction with the radially non-adjustable counter elements 36, provide three grinding gap widths of, for example, 0.2 mm, 0.6 mm and 1 mm. Identical cutting knives 40 orBlow bars can be used, which can also be turned twice. Only the rotor bodies 35, which are easy to manufacture, each have different radial dimensions. These radial dimensions of the rotor base bodies 35 ultimately determine the different discrete widths of the grinding gap, so that the selectable widths of the grinding gap do not come from dimensions undefined by the user, but are dimensionally clearly defined by the production from the rotor body 35, for example by machining. The rotor blades 40 or blow bars are clearly and precisely defined in their position on the rotor 34, for example via an axially running tongue and groove connection 46 or via fitting screws 48. The rotor blades 40 or blow bars are machined with geometric precision, which is easy and cost-effective to achieve, since they have to be ground anyway and can therefore be machined with high precision in a final operation.

[0077] Thus, the laboratory mill 1 does not allow for continuous radial adjustment of the counter elements 36 and thus of the grinding gap width. However, it does provide a discrete number of, for example, two, three, or more discrete values ​​for the grinding gap width, which can be selected, for example, using rotors 34 with different diameters, i.e., from the supplier's catalog. Alternatively, the discrete values ​​for the grinding gap width can also be provided using different sets of counter elements 36 with different widths.

[0078] The rotor 34 is axially inserted onto the drive shaft 2 through the user access opening 38. The laboratory mills 1 according to the present exemplary embodiments have, for example, four stationary counter-elements 36 which, when the grinder housing door 18 is open, are inserted from a front axial end face 16a into four long axial receiving and guide slots 52 in the grinder housing 16. The receiving and guide slots 52 form a uniaxial, axially extending linear guide for the stationary counter-elements 36. Referring to Figs. 10-13, the counter-elements 36 consist of a cuboid-shaped base body 54 with two flat sides 54a, two long sides 54b and two end faces 54c and are made in one piece, e.g. from hardened steel, tungsten carbide or a ceramic material. In this example, four transverse bores 56 extend through the flat sides 54a, which can be identical for the sake of simplicity.A guide or spring pin 58 is press-fitted into each of the two axially inner transverse bores 56a. Thus, the axial linear guide 62 for the counter elements 36 in the grinder housing 16 is designed in the form of a tongue-and-groove linear guide, in this example with two plain bearings. The two axially outer bores 56b remain open and serve as pulling openings 60 for pulling the counter elements 36 out of the receiving and guide slots 52, for example, using a pulling tool (not shown) that is hooked into the respective front target opening 60.

[0079] The counter elements 36 shown here are extremely simple in design and do not have any adjusting elements, such as threaded holes for fastening screws, since they are positioned radially precisely in the grinder housing 16 by means of the linear guide 62 to a dimension determined during production (which cannot be changed by the user). The counter elements 36 can be manufactured easily and designed to be relatively small, so that relatively compact laboratory mills 1 can be built with them. In this exemplary embodiment, the length of the counter elements 36 is only 40 mm, the width is 20 mm, and the thickness is 5 mm. The diameter of the spring pins 58 is 5 mm, and their projection on both sides, i.e. the engagement depth of the tongue-and-groove linear guide, is 2.5 mm.

[0080] The cuboid-shaped base body 54 of the counter elements 36 is made in one piece from a cutting edge material, e.g., hardened steel, and the counter elements 36 are rotationally symmetrical by 180° about all three surface normals. All four longitudinal edges 54d between the flat sides 54a and the longitudinal sides 54b are designed as identical cutting edges. Thus, the counter elements 36 can be turned three times and axially inserted into the receiving and guide slots 52 in four different orientations, i.e., can be used four times. The axial receiving and guide slots 52 are each open towards the grinding chamber 32 and have guide grooves 64 extending transversely from the receiving and guide slots 52 on both sides, which guide grooves 64, together with the spring elements or spring pins 58 of the counter elements 36, form a linear guide 62 in the form of a tongue and groove linear guide.

[0081] 4 - 5, the fit between the spring pins 58 and the guide grooves 64 is manufactured as a clearance fit, for example with a clearance of + / - 5 / 100, so that the spring elements 58 form the radial support of the counter elements 36 both radially inward and radially outward. The spring elements 58 engage behind a radially inner running surface 64a of the associated guide groove 64 and are supported radially inward against it. The radially inner surface line 58a of the spring element 58 thus forms an inward-acting stop with the running surface 64a, and the radially outward-pointing surface line 58b of the spring element 58 forms an outward-acting stop of the linear guide 62 for the counter element 36 with the radially outer running surface 64b. A radially outer free space 68 is therefore kept free in the receiving and guide slot 52. This saves additional undercuts during milling.

[0082] On the other hand, the outwardly acting load is dissipated via the relatively short surface lines 58b of the spring pins 58. The linear guide 62, in the present example, therefore has two axially spaced radial load transfer points. If at least two axially spaced radial load transfer points are used, tilting moments can be avoided and high gap parallelism can be ensured.

[0083] 6 - 8, the axially extending guide groove 64 can also be manufactured with a significant radial oversize for a radially outer free space 69. In this case, only the radially inward-acting stop is formed between the spring elements 58 and the guide groove 64. The radially outward-acting stop is formed here by the radially outer longitudinal side 54b. In this example, the radially outer counter-stop is formed by a support pin 72, e.g. a hardened steel pin 72, running in an axial bore 70. Although this variant requires an additional bore 70 and an additional support pin 72, the radially outward-acting load is carried over a greater length, preferably over the entire length of the radially outer longitudinal side 54b of the counter element 36 or of the support pin 72.Nevertheless, additional undercuts in the milling of the receiving and guide slots 52 can be omitted. This allows the groove geometries to be kept simple. The support pins 72 can be press-fitted into the corresponding axial bore 70, since they do not need to be removed by the user.

[0084] The stationary counter-elements 36 are thus secured against radial inward movement, i.e., toward the rotor 34, in both embodiments by means of the tongue-and-groove linear guide, or more precisely by means of the spring elements 58 guided in the guide grooves 64. The axial linear guide 62 therefore has at least no degree of freedom of movement in the radial direction toward the rotor 34 for the inserted counter-element 36.

[0085] In the embodiment shown in Figs. 4-5, the spring elements 58 and the guide groove 64 also act as a limiting stop away from the rotor. In the embodiment shown in Figs. 6-8, the stop acting against a movement directed radially outward or away from the rotor 34 is formed by the support pins 72. Therefore, the axial linear guide 62 preferably also has no degree of freedom of movement in the radial direction away from the rotor 34 for the inserted counter-element 36.

[0086] In both cases, the loosely inserted counter-elements 36 are therefore preferably radially fixed in both directions radially inwards and radially outwards, except for the radial play predetermined by the manufacturing tolerances, in the associated receiving and guide slots 52, so that the width of the grinding gap is fixed and predefined and / or no longer needs to be adjusted.

[0087] A further advantage of dispensing with the radial adjustment of the counter-elements 36 arises from the fact that in conventional cutting mills, such an adjustment requires that the rotor is rotated for adjustment so that the rotor blades 40 and the counter-elements 36 are exactly opposite one another in order to adjust the cutting gap. This can be omitted with the present invention. Therefore, the rotation drive of the rotor 34 can even be positively locked as a safety function when the grinder housing door 18 is open. The present invention can therefore be particularly advantageous in combination with a positive locking of the grinder drive, as described in the patent application filed on the same day by the same applicant under the title "Laboratory Mill", although this is not necessary. The laboratory mill 1 can, for example,have a positive-locking coupling, which is actuated by the door lock 22 via a mechanical manipulation chain and positively locks the grinder when the grinder housing door 18 is open. For further details, reference is made to the aforementioned parallel patent application.

[0088] Advantageously, the counter elements 36 can be easily rotated and / or replaced by inserting and pulling them into and out of the receiving and guide slots 52 or into and out of the linear guide 62, particularly since no threaded pins or screws are required for adjustment and / or tightening. Furthermore, all parts of the rotor grinder 30, in particular the rotor 34 and the counter elements 36 as well as the curved sieve 42, can be easily pulled axially out of the grinding chamber 32 when the grinder housing door 18 is open, so that the grinding chamber 32 can be easily cleaned of grinding dust, e.g., by brushing it out. Even if grinding dust should become stuck to the counter elements 36, it can be pulled out with sufficient pull-out force using the pull-out openings 60. The laboratory mill 1 is therefore dirt-tolerant in this regard.

[0089] The grinder housing door 18 can additionally have an elastomeric seal 74 on its inner side 18a facing the grinding chamber 32, for example an annular seal in a circumferential groove 76. The annular seal 74, e.g. an O-ring, seals the user access opening 38 or the grinding chamber 32 in a ring-shaped manner when the grinder housing door 18 is closed, so that no grinding dust can escape. Advantageously, the annular seal 74 runs radially circumferentially between the grinding chamber 32 and the guide grooves 64 of the receiving and guide slots 52. This allows the guide grooves 64 to be largely kept free of grinding dust. For this purpose, the front end faces 54c of the counter elements 36 are essentially flush with the front side 16a of the grinder housing 16 or with a slight oversize.The elastomer seal 74 clamps the counter elements 36 in the receiving and guide slots 52 against a rear end of the receiving and guide slots 52, so that even with slight fit play of the linear guide 62, the counter elements 36 are firmly fixed and do not rattle when the grinder housing 16 is closed. Referring to Figs. 18 - 20, the elastomer seal 74 can also be designed as a special flat seal 74' and have ears 78 that can axially overlap and completely close the front end faces of the guide grooves 64. Due to the larger surface area of ​​the ears 78, more force can also be applied axially to the counter elements 36.

[0090] Three conical pins 80 are attached to the grinder housing door 18 slightly below the grinding chamber 32. These pins protrude from the inner side 18a of the grinder housing door 18. When the grinder housing door 18 is closed, in particular by a pivoting movement about the hinges 20, the conical pins 80 pivot in a pivoting trajectory beneath the curved screen plate 42 and ultimately support it downwards. This eliminates the need for a support web for the screen plate 42 that is firmly attached to the grinder housing 16 and spans the user access opening 38 transversely. The use of conical pins 80 has proven particularly advantageous with regard to the pivoting trajectory in combination with the shape of the curved screen plate 42.

[0091] Referring to Figs. 21-22, the grinder housing 16 can comprise a one-piece base body or housing block 17, and can be milled in one piece from a metal block, for example. The receiving and guide slots 52, the guide grooves 64, the grinding chamber 32, and / or a grinding material outlet channel 82 adjoining the grinding chamber at the bottom are machined from the metal block as a uniform, communicating cavity 84. The cavity 84 is preferably milled cylindrically with a complex surface line 84a. The front end of the cylindrical cavity 84 is preferably completely open.In other words, the uniform cylindrical cavity 84, consisting of communicating receiving and guide slots 52, guide grooves 64, grinding chamber 32 and / or the grinding material outlet channel 82 adjoining the grinding chamber at the bottom, opens completely with a uniform common opening area, which is delimited by the surface line 84a of the cylindrical cavity 84, on the front end face 17a of the housing block 17. This allows, on the one hand, the grinder housing to be milled cost-effectively, e.g., from an aluminum or stainless steel block, and, on the other hand, a compact, small laboratory mill 1 with a small grinder 30 can be constructed. The screen plate 42 can be manufactured relatively simply and flexibly from a simple perforated sheet, since it allows cross-web-free access despite the wide, uniform user access opening 38, which allows access to both the essentially round-cylindrical grinding chamber 32 and the relatively wide grinding material outlet channel 82.The entire cavity 84, consisting of the grinding chamber 32 and the uniformly formed grinding material outlet channel 82, is open without obstruction at the front end 16a of the grinder housing 16 when the grinder housing door 18 is open. The conical pins 80 prevent deflection of the screen plate 42 during operation. The screen plate 42 is inserted between the counter elements 36 and a support surface 86 between the grinding chamber 32 and the grinding material outlet channel 82.

[0092] It will be apparent to those skilled in the art that the embodiments described above are to be understood as examples, and the invention is not limited to them, but can be varied in many ways without departing from the scope of the claims. Components described in the singular are also to be understood in the plural, and vice versa. Furthermore, it is clear 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

Laboratory mill (1) for grinding material, in particular designed as a cutting mill or impact mill, comprising a device housing (12) with a grinding unit housing (16), wherein the grinding unit housing (16) defines a grinding chamber (32) and has an axial end face (16a), a rotor grinding unit (30) in the grinding chamber (32) of the grinding unit housing (16), wherein the rotor grinding unit (30) has a rotor (34) defining a rotor axis (X) and at least one counter element (36), wherein the material is ground between the rotor (34) and the at least one counter element (36) when the rotor (34) rotates, a grinding unit drive (2, 4) for driving the rotor (34) in the grinding chamber (32), a grinding unit housing door (18) for closing the grinding unit housing (16) at the axial end face (16a), wherein the at least one counter element (36) can be inserted axially into the grinder housing (36) when the grinder housing door (18) is open.Laboratory mill (1) according to claim 1, wherein the at least one counter element (36) is axially guided in the mill housing (16) by a radial positive fit. Laboratory mill (1) according to claim 2, wherein the radial positive fit provides support against movement of the at least one counter element (36) at least radially inwards towards the rotor (34). Laboratory mill (1) according to any one of the preceding claims, wherein the mill housing (16) has at least one axially extending receiving and guide slot (52) for the at least one counter element (36), wherein the receiving and guide slot (52) is open radially inwards towards the rotor (34) and at the axial end face (16a) of the mill housing (16). A counter element (36) can be inserted axially through the open end face (16a) into the at least one receiving and guide slot (52), and wherein an axial linear guide (62) is formed between the at least one receiving and guide slot (52) and the at least one counter element (36). Laboratory mill (1) according to claim 4, wherein the at least one receiving and guide slot (52) has at least one guide groove (64) extending axially and transversely to the receiving and guide slot (52), and the at least one counter element (36) has at least one spring element (58) displaceable in the at least one guide groove (64), or conversely, such that the axial linear guide (62) is designed as an axially displaceable tongue-and-groove guide.Laboratory mill (1) according to claim 5, wherein the at least one counter element (36) has two flat sides (54a) which extend axially into the at least one receiving and guide slot (52) when the at least one counter element (36) is inserted into the at least one receiving and guide slot (52), wherein at least one transverse bore (56) is provided through the flat sides (54a) of the at least one counter element (36) in which a transverse pin is fastened which is axially displaceable and radially guided as a spring element (58) in the at least one guide groove (64).Laboratory mill (1) according to one of claims 5 to 6, wherein the at least one counter element (36) is supported radially inwards towards the rotor on a side wall (64a) of the guide groove (64) of the tongue-and-groove guide and / or wherein the at least one counter element (36) is supported radially outwards towards the rotor (34) on a side wall (64b) of the guide groove (64) of the tongue-and-groove guide or wherein a longitudinal side (54b) of the at least one counter element (36) facing away from the rotor (34) is supported directly or indirectly on a radially outward base of the receiving and guide slot (52).

8. Laboratory mill (1 ) according to one of claims 4 to 7, wherein the receiving and guide slot (52) has an axial bore (70) at a radially outer base, into which an axially extending support pin (72) is inserted, and wherein a longitudinal side (54b) of the at least one counter element (36) facing away from the rotor (34) is supported on the support pin (72), and wherein the support pin (72) is supported in the axial bore (70) on the mill housing (16).

9. Laboratory mill (1) according to one of the preceding claims, wherein the at least one counter element (36) has at least one draw opening (60) such that a draw tool can be brought into the draw opening (60) in a form-fitting manner in order to draw the at least one counter element (36) axially out of the mill housing (16) using the draw tool when the mill housing door (18) is open.

10. Laboratory mill (1) according to one of the preceding claims, wherein the at least one counter element (36) has a base body (54) in the form of an elongated plate or strip.

11. Laboratory mill (1) according to claim 10, wherein the length of the base body (54) is between 20 mm and 200 mm, the width of the base body (54) is between 8 mm and 60 mm and / or the thickness of the base body (54) is between 3 mm and 25 mm.

12. Laboratory mill (1) according to one of the preceding claims, wherein the at least one counter element (36) has at least one flat side (54a) and at least one longitudinal side (54b) which abut each other at a longitudinal edge (54d), wherein the longitudinal edge (54d) forms a cutting edge or striking edge of the at least one counter element (36) which interacts with cutting edges or striking edges of the rotor (34) to crush the material to be ground between them.

13. Laboratory mill (1) according to claim 12, wherein the at least one longitudinal edge (54d) extends axially in the grinding chamber (32) when the at least one counter element (36) is in the at least one receiving and is inserted into the guide slot (52) of the grinder housing (16).

14. Laboratory mill (1) according to one of the preceding claims, wherein the at least one counter element (36) has a base body (54) in the form of an elongated plate or strip, which has two flat sides (54a), two longitudinal sides (54b) extending axially and transversely to the flat sides (54a), and / or two end faces (54c) extending transversely to the flat sides (54a) and longitudinal sides (54b), and wherein the at least one counter element (36) is designed to be reversible by 180° in particular with respect to at least one, two, or three of the following axes: about an axis extending transversely to the flat side (54a), about an axis extending transversely to the longitudinal side (54b), and / or about an axis extending transversely to the end face (54c), such that the at least one counter element (36) is in a first orientation and a second orientation reversed with respect to the first orientation, and / or in a third orientation reversed with respect to the first and second orientations. and / or in a first,The second and third orientations can be inserted into the grinding mechanism housing (16) in order to use a first and second and / or third and / or fourth longitudinal edge (54d) of the at least one counter element (36) as a cutting edge or striking edge.

15. Laboratory mill (1) according to one of claims 4-14, wherein the at least one counter element (36) has two flat sides (54a) which extend axially into the at least one receiving and guide slot (52) when the at least one counter element (36) is inserted into the at least one receiving and guide slot (52), wherein at least four transverse bores (56) are provided through the flat sides (54a) of the at least one counter element (36), wherein a through transverse pin projecting to both sides as a spring element (58) is fastened in each of the two axially inner transverse bores (56), and wherein the two axially outer transverse bores (56) form draw-outlets (60).

16. Laboratory mill (1) according to one of claims 4-15, wherein an elastic pressure element is attached to the mill housing door (18) which forms an axial end face (54c) of the at least one counter element (36) a laboratory mill (1) according to one of claims 4-16, wherein a ring seal (74) is included which is attached to the mill housing door (18) and seals against the axial end face (16a) of the mill housing, thereby sealing the grinding chamber (32) in an annular manner, and wherein the ring seal (74) presses an axial end face (54c) of the at least one counter element (36) axially against an axial motor-side end of the receiving and guide slot when the mill housing door (18) is closed. Laboratory mill (1) according to one of the preceding claims, wherein the grinding chamber (32) is formed as a substantially cylindrical cavity in the mill housing (16) and extends radially downwards into a grinding material outlet channel (82), wherein the grinding chamber (32) and the grinding material outlet channel (82) are separated by a sieve plate (42),through which the crushed material can trickle downwards from the grinding chamber (32) into the material discharge channel (82) and into a material collection container (44), wherein the sieve plate (42) and the rotor (34) can be removed axially from the grinding housing (16) when the grinding housing door (18) is open, and wherein the grinding housing (16) does not have a web spanning the material discharge channel (82) transversely on its end face (16a) in the area below the sieve plate (42), such that the grinding chamber (32) and the material discharge channel (82) can be brushed out together without obstruction from the end face (16a) of the grinding housing (16) when the grinding housing door (18) is open and the rotor (34) and the sieve plate (42) have been removed. Laboratory mill (1) for grinding material, in particular designed as a cutting mill or impact mill, in particular according to one of the preceding claims, comprising a device housing (12) with a grinding unit housing (16),wherein the grinding housing (16) defines a grinding chamber (32) and has an axial end face (16a), a rotor mill (30) in the grinding chamber (32) of the mill housing (16), wherein the rotor mill (30) comprises a rotor (34) defining a rotor axis (X) and at least one counter element (36), wherein the material to be ground is crushed between the rotor (34) and the at least one counter element (36) when the rotor (34) rotates, a mill drive (2, 4) for driving the rotor (34) in the grinding chamber (32), a mill housing door (18) for closing the mill housing (16) at the axial end face (16a), wherein the grinding chamber (32) is formed in the form of a substantially cylindrical cavity in the mill housing (16) and transitions downwards into a material outlet channel (82), wherein the grinding chamber (32) and the material outlet channel (82) are separated by a screen plate (42) through which the The ground material can trickle down from the grinding chamber (32) into the grinding material outlet channel (82) and into a grinding material collection container (44),and wherein at least one or more projecting conical pins (80) are attached to the grinder housing door (18), which are pivoted under the sieve plate (42) when the grinder housing door (18) is closed and support the sieve plate downwards when the grinder housing door (18) is closed.

20. Laboratory mill set consisting of the laboratory mill (1) according to one of the preceding claims and at least two, preferably at least three, rotors (34) with predefined different diameters, wherein the selection of the width of the grinding gap between the rotor (34) inserted into the grinding chamber (32) and the at least one counter element (36) is not achieved by radial adjustment of the at least one counter element (36), but by replacing the rotor (34) with another rotor (34) with a different diameter.

21. Laboratory mill set consisting of the laboratory mill (1) according to one of the preceding claims and at least two, preferably at least three, sets of counter elements (36) of different widths, wherein the selection of the width of the grinding gap between the counter elements (36) inserted into the mill housing (16) and the rotor (34) is not made by radial adjustment of the counter elements (36), but by exchanging the Counter elements (36) against other counter elements (36) with a different width is achieved.

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