Laboratory mill and grinding material filling plunger for a laboratory mill

Abstract

Laboratory mill (1) for grinding material, in particular designed as a cutting mill, impact mill, disc mill, knife mill, impact mill, centrifugal mill, rotor mill, rotor high-speed mill or mortar mill, comprising: a grinding mechanism (4) with a grinding mechanism housing (6) which defines a grinding chamber (18), and with a grinding mechanism rotor (16) which is rotatably driven in the grinding chamber (18) to grind the material to be ground with the grinding mechanism rotor (16) in the grinding chamber (18), wherein the grinding mechanism housing (6) has a material filling opening (26) which leads into the grinding chamber (18) in order to introduce the material to be ground from the outside through the material filling opening (26) into the grinding chamber (18), a drive motor for driving the grinding rotor (16) in the grinding chamber (18), a grinding material feed hopper (28) which opens into the grinding material feed opening (26), such that the grinding material can be filled into the grinding material feed hopper (28) and passes through the grinding material feed hopper (28) and the grinding material feed opening (26) into the grinding chamber (18), while the grinding rotor (16) rotates in the grinding chamber (18), a grinding material filling plunger (40) that can be inserted into the grinding material filling hopper (28), wherein the grinding material filling plunger (40) has a grinding material filling channel (50) through which the grinding material can be filled into the grinding chamber (18) when the grinding material filling plunger (40) is inserted into the grinding material filling hopper (28), wherein the grinding material filling plunger (40) has at least a section of a screw section (52) axially, in which the grinding material filling channel (50) runs in a helical or spiral manner in the grinding material filling plunger (40).

Description

Field of invention

[0001] The invention relates to a laboratory mill, in particular a cutting mill, a cross-cutter mill, a disc mill, a knife mill, an impact mill, a centrifugal mill, a rotor mill, a rotor high-speed mill and a mortar mill on a laboratory scale, which have a grinding mechanism in which the material to be ground is crushed, for example, in a gap between a grinding rotor and one or more stationary counter-elements, between two discs or by a rotor knife or impact rotor in a grinding chamber. Background and general description of the invention

[0002] Cutting mills comminute materials between a rotating cutting rotor with one or more substantially axially extending rotor blades and one or more substantially axially extending stationary counter blades, according to the scissor principle. 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 current laboratory cutting mills are, for example, the PULVERISETTE® 15, the PULVERISETTE® 19, and the PULVERISETTE® 29 of the applicant, to whose basic design reference is hereby made. Corresponding product descriptions of the PULVERISETTE® 15, PULVERISETTE® 19, and PULVERISETTE® 29 can be found, for example, at www.fritsch.de. Furthermore, reference is made to Fritsch GmbH, Idar-Oberstein: “Operating Instructions - Universal Cutting Mill - PULVERISETTE 19”, edition 11 / 2023.

[0003] In these laboratory-scale cutting mills, free-flowing bulk material is typically fed into the grinding chamber, for example via a vertical feed hopper. Inside the chamber, the cutting rotor rotates around a horizontal axis. The cutting rotor can have different geometries, such as straight cutting edges or so-called V-cutting edges. The latter have a helical shape and thus achieve good cutting performance, especially when grinding tough, elastic materials and films.

[0004] A sieve, e.g., a sieve cassette, is typically located below the cutting rotor, through which the sufficiently pulverized sample material can trickle to be collected in a container below. Regarding further design details of a laboratory cutting mill, which are generally known to those skilled in the art in this field, reference is made to the product descriptions for the applicant's PULVERISETTE® 15, PULVERISETTE® 19, and PULVERISETTE® 29 cutting mills, which were available for download at www.fritsch.de at the time of filing and publication, and which are hereby incorporated by reference with respect to the basic design of such a laboratory cutting mill. Furthermore, applications DE 196 01 594 A1, DE 10 2018 113 751 A1, DE 10 2019 108 306 A1, DE 10 2019 133 437 A1, and DE 10 2022 115 334 A1 describe laboratory cutting mills and are hereby also incorporated by reference.

[0005] Depending on the hopper size, cutting rotor, operating parameters, and material being ground, some of the material placed in the hopper may be ejected during grinding. This effect can be amplified by larger hopper diameters and higher rotational speeds. For example, this undesirable effect can become particularly significant with a feed diameter of approximately 25 mm or larger. Furthermore, uncontrolled overfeeding of the laboratory mill can occur if, for example, too much material is placed in the hopper at once. A compression plunger may be used to force the material into the hopper into the grinding chamber or against the mill rotor in short bursts. However, using a compression plunger can result in undesirably high bending forces on the motor shaft and potentially excessive pressure on the sample.Furthermore, such a tamping plunger does not prevent the material being ground from ejected at all times. These effects can potentially lead to undesirable user malfunctions, especially when the material is added while the grinder rotor is rotating.

[0006] Similar undesirable effects can also occur with impact mills (see PULVERISETTE® 16, www.fritsch.de) or disc mills (see PULVERISETTE® 13, www.fritsch.de), whose product descriptions are hereby incorporated by reference. These laboratory mills also feature a rotor grinding mechanism in which the material to be ground is crushed between a grinding rotor and stationary counter-elements of the rotor grinding mechanism, and the material is fed in from above through a hopper.

[0007] Similar undesirable effects can also occur with knife mills, in which a rotor knife rotates around a vertical axis in a grinding vessel (see PULVERISETTE® 11, www.fritsch.de), or with impact mills, sometimes also called rotor mills or rotor high-speed mills, in which a rotor, e.g., a percussion rotor in a ring sieve, rotates around a vertical axis in a grinding vessel designed as a collection vessel (see PULVERISETTE® 14, www.fritsch.de), whose product descriptions are hereby incorporated by reference. In the latter, material to be ground can be fed through an axial feed opening and thus axially fed from above to the rotating percussion rotor.

[0008] While all of these previously known laboratory mills have generally proven their worth, they can be further improved.

[0009] The invention aims to provide a laboratory mill, in particular a cutting mill, a cross-cutting mill, a disc mill, a knife mill, an impact mill, a centrifugal mill, a rotor mill, a rotor high-speed mill or a mortar mill on a laboratory scale, in which the user can conveniently, safely, in a controlled manner and evenly feed the material to be ground into the milling mechanism.

[0010] Another aspect of the task is to provide a laboratory mill in which overfeeding or excessive bending moments on the motor shaft can be avoided or at least reduced.

[0011] Another aspect of the task is to provide a laboratory mill in which the material being ground can be prevented or at least reduced from jumping back out when being filled.

[0012] The object of the invention is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are defined in the dependent claims.

[0013] A laboratory mill is provided for grinding material, which is selected in particular from the group of cutting mills, impact mills, disc mills, knife mills, impact mills, centrifugal mills, rotor mills, rotor high-speed mills or mortar mills on a laboratory scale.

[0014] The laboratory mill comprises a grinding mechanism with a grinding chamber housing. The grinding mechanism also includes a grinding rotor, driven by a motor, which rotates within the grinding chamber to grind the material. The grinding chamber housing further features a material feed opening, which typically leads into the grinding chamber from above or is permanently connected to it, allowing the material to be introduced into the grinding chamber from the outside while the mill is operating. In a cutting mill, impact mill, or disc mill, the rotor axis is horizontal, and the material is preferably fed radially. In a knife mill, impact mill, centrifugal mill, rotor mill, or rotor high-speed mill, the rotor axis is vertical, and the material is preferably fed axially.

[0015] The laboratory mill has a drive motor for powering the mill rotor in the grinding chamber. The drive motor is preferably an electric motor with sufficient power and is preferably housed in the mill casing; for a mill rotor with a horizontal rotor axis, e.g., behind a vertical grinding chamber rear wall, i.e., axially behind the mill rotor, and for a mill rotor with a vertical rotor axis, e.g., under a horizontal grinding chamber floor, i.e., under the mill rotor.

[0016] The laboratory mill further comprises a material feed hopper, which can be attached to the mill. The material feed hopper can, for example, be screwed to the mill housing or be integrally formed with a mill housing door or with the mill housing itself. The material feed hopper preferably has a material feed cone and a funnel neck into which the material feed cone opens, or consists of these. The material feed hopper, or more precisely the funnel neck, opens into the material feed opening, such that the material to be ground, which is particularly free-flowing, can be filled into the material feed cone, for example, by pouring it in, and passes through the funnel neck and the material feed opening into the grinding chamber while the mill rotor rotates in the grinding chamber. The term "material feed cone" is not to be understood in a strict mathematical sense as "conical."The material feed cone can be a container that tapers from a larger cross-section at the top to a smaller cross-section at the bottom of the funnel neck. The material to be ground can be poured into the larger cross-section as a free-flowing bulk material and then slides downwards into the narrower, especially tubular, funnel neck. The material feed cone is therefore the upper, sharply tapered part of the material feed hopper that opens into the lower funnel neck. The material feed cone can be round, but also, for example, square or with another funnel-shaped taper.

[0017] The laboratory mill also includes a material filling plunger to assist in filling the grinding chamber through the material filling hopper. The material filling plunger is inserted into the material filling hopper, specifically along the central longitudinal axis of the hopper neck, which is primarily tubular.

[0018] The grinding material filling plunger has a grinding material filling channel through which the grinding material can be filled into the grinding chamber when the grinding material filling plunger is inserted into the grinding material filling funnel or into the funnel neck.

[0019] This advantageously allows for a more or less continuous and even feeding of the grinding mechanism. Furthermore, depending on the dimensions of the material feed channel, the risk of overfeeding the grinding mechanism can at least be reduced.

[0020] The material feed channel is inclined, in particular, so that the material can trickle into the grinding chamber from above due to gravity. According to claim 14, however, the material feed channel is not perpendicular and / or parallel to the central longitudinal axis of the material feed plunger or the hopper neck, at least in sections. The incline of the material feed channel therefore has, at least in sections, an angle of inclination of less than 90°, preferably less than 80°, preferably less than or equal to 70°, preferably less than or equal to 45°, and preferably greater than or equal to 10° with respect to a plane perpendicular to the central longitudinal axis of the material feed plunger or the hopper neck. The material feed plunger is preferably inserted into the material feed hopper or the hopper neck so as to be axially displaceable and / or is rotatable within the material feed hopper or the hopper neck, particularly manually.This allows the grinding material feeder to fulfill a dual function: influencing the flow of the more or less free-flowing grinding material still in the grinding material feeder cone into the grinding chamber, and simultaneously acting as a tamping plunger. For this purpose, the user can, for example, gently shake and / or rotate the grinding material feeder and, with the same movement, manually tampe down the grinding material that has already trickled down through the grinding material feeder channel towards the grinding material feeder opening of the grinder, if necessary. Even during tamping, the flow of grinding material trickling down through the grinding material feeder channel in the hopper neck is not completely interrupted, but continues at least partially.

[0021] A further advantage is that the material to be ground can be filled into the grinding chamber more or less continuously, and that the filling and, if necessary, moderate re-tamping of the material to be ground can be done with just one hand or with one and the same movement.

[0022] In a further advantageous way, the grinding material filling plunger prevents the grinding material from jumping out of the grinding material filling hopper at all times, especially since the grinding material filling plunger does not have to be pulled out of the hopper neck during the grinding process to ensure a supply of grinding material to the grinding mill, so that continuous grinding can take place.

[0023] Preferably, the material feed plunger has a lower piston section which, during operation of the laboratory mill, is inserted into the hopper neck and extends from an upper piston end to an underside at the lower end of the material feed plunger. When the material feed plunger is inserted into the material feed hopper, the upper piston end of the lower piston section is preferably located in the area of ​​the transition from the material feed cone to the hopper neck. In the inserted state, the lower end of the material feed plunger is preferably located in the area of ​​the material feed opening and may optionally project into the material feed opening in the mill housing, or extend to just before the outer circumference of the cutting rotor, with the underside at the plunger base of the material feed plunger facing the grinding chamber and the mill rotor.

[0024] The material feed channel preferably extends from the upper end of the lower piston section to the lower end of the material feed plunger, and the plunger base has a partially closed end face and a partially recessed base. The material feed channel opens into this recess, which forms a lower end face opening of the material feed channel, serving as the material outlet. This allows the material to trickle into the grinding chamber, guided through the material feed channel and the recess, and then through the material feed plunger, particularly with the aid of gravity. This allows the material feed plunger to both control the trickle of material and, if desired, to force the material into the grinding chamber.

[0025] Preferably, the material feed channel is formed as a groove in the circumferential surface of the material feed plunger or the lower piston section and is open radially outwards. The outer diameter A of the lower piston section is only slightly smaller than the inner diameter of the funnel neck. The funnel neck thus forms a guide sleeve for the lower piston section, and the material feed channel is bounded radially outwards by the inner surface of the funnel neck when the lower piston section is inserted into the funnel neck as a piston housing. In other words, the material feed channel runs between the channel surface of the lower piston section and the inner surface of the funnel neck when the lower piston section is inserted into the funnel neck. Advantageously, the material feed plunger or the material feed channel can preferably be CNC-milled. This allows the surface to be manufactured to a relatively smooth finish.This makes the grinding material filling plunger hygienic and easy to clean. However, the grinding material filling plunger can also be manufactured as an injection-molded part or 3D-printed.

[0026] The outer diameter A of the lower piston section is preferably greater than or equal to 10 mm, more particularly greater than or equal to 20 mm, more particularly less than or equal to 50 mm, more particularly less than or equal to 40 mm, or preferably 25 mm ± 5 mm or ± 2 mm, or 40 mm ± 5 mm or ± 2 mm. The inner diameter of the funnel neck is preferably only slightly larger than the outer diameter A of the lower piston section, e.g., about 1 mm larger. The distance from the upper end of the funnel neck or the lower end of the material feed cone to the outer circumference of the cutting rotor is preferably greater than or equal to 120 mm, more preferably less than or equal to 500 mm.

[0027] This can advantageously influence the prevention or reduction of ground material jumping out of the hopper neck.

[0028] According to one embodiment, the closed end-face bottom surface of the grinding material filling plunger is at least 25%, preferably at least 30%, preferably at least 40%, preferably a maximum of 80%, preferably a maximum of 75%, preferably a maximum of 70%, preferably in the range between 40% and 70% of the cross-sectional area Pi*(A / 2) 2 of the lower piston section.

[0029] According to one embodiment, the closed end-face bottom surface is larger than the radial cross-sectional area of ​​the grinding material outlet or the end-face opening.

[0030] This allows for a good packing effect to be achieved to a significant advantage. Furthermore, this helps to prevent the contents from being ejected.

[0031] According to claim 1, the material feed channel is configured as a helical or spiral channel, at least in sections. The material feed plunger thus has an axially defined screw or screw section, at least in sections, in which the material feed channel runs helically or spirally around the longitudinal axis of the material feed plunger in the lower piston section. The material feed channel preferably forms a helix in the screw section. In other words, the material feed plunger or lower piston section is configured as a screw conveyor, at least in sections, and the lower piston section, together with the hopper neck, forms a screw conveyor. In other words, the lower piston section forms an Archimedean screw, which preferably operates with gravity (rather than against gravity).

[0032] This may initially seem counterintuitive, since the material feed channel already has a slope, allowing the material to trickle downwards more or less independently due to gravity, depending on the type of material. However, the auger allows the user to assist this gravitational flow of the material as needed, in particular by increasing it, but also by slowing it down if necessary.

[0033] The material feed channel for the ground material preferably extends as a spiral groove in the circumferential surface of the lower piston section within the screw section. However, the spiral groove preferably does not extend, or at least not completely, to the lower end of the material feed ram or conveying ram, or not, or at least not completely, to the lower bottom surface, so that a foot section of the lower piston section has more material or more "fat" in cross-section compared to the helix.

[0034] This allows for improved guidance in the funnel neck, control of the flow rate, and the packing effect.

[0035] According to a preferred embodiment, the lower piston section has at its upper piston end a head section, at its lower piston end a foot section, and A screw section or a conveying screw extending axially between the head section and the foot section. Preferably, the material feed channel in the screw section extends helically or spirally around the central longitudinal axis of the material feed plunger. Furthermore, preferably, the material feed channel extends axially in the head section. Even more preferably, the material feed channel extends axially in the foot section.

[0036] The material feed channel is therefore preferably designed in the head section as an axially extending head groove and / or in the foot section as an axially extending foot groove, wherein the axially extending head groove transitions into the spiral groove of the screw section at the lower end of the head section and / or wherein the spiral groove of the screw section transitions into the axially extending foot groove at the upper end of the foot section, so that the material to be ground can successively trickle axially through the head groove, spirally through the spiral groove and / or axially through the foot groove and subsequently through the material feed opening of the grinding chamber into the grinding chamber.

[0037] According to a preferred embodiment, the material feed plunger can be inserted axially into the funnel neck, the material feed hopper in particular forming an axial stop for inserting the material feed plunger. More preferably, the material feed plunger is rotatably mounted in the funnel neck when inserted.

[0038] This allows the user to influence the conveying of the material being ground as needed, depending on the situation.

[0039] The grinding material feed plunger has a material cross-sectional area FS in the screw section (i.e., total cross-sectional area of ​​the lower piston section (Pi*(A / 2)) 2) minus the cross-sectional area of ​​the spiral groove). The closed end face bottom surface is preferably larger than the material cross-sectional area FS in the screw section, preferably at least twice as large. In other words, the foot section of the lower piston section is more closed in terms of its radial cross-section than the spiral of the screw section, or has more material in its cross-section, which in turn can improve the plugging action.

[0040] Preferably, the snail segment is designed as a single-ended helix, meaning it has only one canal.

[0041] It has been shown that for most users it is advantageous to wind the screw section or spiral groove counterclockwise, so that a clockwise rotation can increase the downward conveyance of the ground material.

[0042] According to one embodiment, the screw section has at least half a screw turn, preferably between one and 10, preferably between one and 5, preferably between 2 and 4 screw turns.

[0043] According to one embodiment, the spiral material feed channel in the screw section has a pitch P in the range of 10 mm to 120 mm, preferably in the range of 20 mm to 80 mm, preferably 40 mm ± 20 mm or ± 10 mm. This has proven advantageous in preventing the sample from being ejected.

[0044] According to one embodiment, the grinding material feed channel in the screw section has a slope angle β in the range between 5° and 70°, preferably in the range between 10° and 50°, preferably between 15° and 40°, preferably 25° + / - 10° or + / - 5°.

[0045] According to one embodiment, the grinding material feed channel in the screw section has a groove width N, i.e. an axial width of the groove between two adjacent turns, in the range between 10 mm and 100 mm, preferably in the range between 20 mm and 75 mm, preferably 40 mm + / - 15 mm or + / - 10 mm.

[0046] According to one embodiment, the screw section has a web width S, i.e. an axial width of the web between two adjacent turns, in the range between 1 mm and 30 mm, preferably in the range between 2 mm and 20 mm, preferably in the range between 3 mm and 15 mm, preferably 6 mm + / - 4 mm or + / - 2 mm.

[0047] According to one embodiment, the screw section has a core diameter K or a core with a diameter K in the range between 2 mm and 20 mm, preferably in the range between 3 mm and 15 mm, preferably in the range between 4 mm and 10 mm, preferably 6 mm + / - 2 mm or + / - 1 mm.

[0048] Depending on the material being ground, this allows the effect of preventing or reducing the ejection of the material from the hopper neck to be advantageously balanced with the gravitational trickling or controlled conveying of the material being ground.

[0049] Preferably, a stop is formed between the material feed plunger and the material feed hopper to prevent axial downward movement and thus prevent the material feed plunger from contacting the grinding rotor. For this purpose, the head section can have a ridge which, in the area of ​​the transition from the material feed cone to the hopper neck, forms the lower stop for the material feed plunger within the material feed hopper. The material feed channel can then extend through a cutout in the ridge. The cutout in the ridge preferably covers a sector angle in the range of 30° to 330°, more preferably in the range of 60° to 300°, and more preferably 180° ±90° or ±45°, in order to allow the material to be fed into the material feed channel. This advantageously enables well-controlled conveying of samples with varying free-flowing properties.

[0050] According to one embodiment, the material feed plunger comprises an extension stem that extends the material feed plunger from the upper piston end away from the grinding chamber to an upper or distal plunger end extending upwards out of the material feed hopper. A handle can be arranged at the distal plunger end, allowing the user to grip the material feed plunger for rotation and / or re-tamping.

[0051] The extension handle can have a smaller outer diameter than the lower piston section. Conversely, the handle can have a larger outer diameter than the extension handle.

[0052] The subject of the application also includes the material feed plunger or conveying plunger, designed for insertion into the material feed hopper of a laboratory mill described herein, wherein the material feed plunger has a material feed channel through which the material can be fed into the grinding chamber when the material feed plunger is inserted into the hopper neck. The material feed plunger is a separately marketable product, which can be offered, for example, for different materials and with differently sized material feed channels. Therefore, the material feed plunger is also claimed, if applicable, with one, several, or all of the features described above.

[0053] 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

[0054] They show: Fig. 1 a three-dimensional representation of a cutting mill according to an embodiment of the invention, Fig. 2 a front view of the cutting mill Fig. 1, Fig. 3 a partially cutaway three-dimensional representation of the cutting mill made of Fig. 1, Fig. 4 a partially cut-out front view of the cutting mill made of Fig. 1, Fig. 5 a sectional view of the cutting mill made of Fig. 1, cut by the mill, Fig. 6 a side view of a grinding material filling plunger according to an embodiment of the invention, Fig. 7 a longitudinal section through the grinding material filling plunger Fig. 6, Fig. 8 a cross-section through the grinding material filling plunger along line 8 - 8 in Fig. 6, Fig. 9 a cross-section through the grinding material filling plunger along line 9 - 9 in Fig. 6, Fig. 10 an axial view of the underside of the grinding material filling plunger made of Fig. 6, Fig. 11 a three-dimensional representation of the grinding material filling plunger made of Fig. 6, Fig. 12 another three-dimensional representation of the grinding material filling plunger made of Fig. 6, Fig. 13 a three-dimensional longitudinal section along the central longitudinal axis X of the grinding material filling plunger made of Fig. 6, Fig. 14 a three-dimensional representation of an upper part of the grinding material filling plunger made of Fig. 6, Fig. 15 a three-dimensional representation of a lower part of the grinding material filling plunger made of Fig. 6, Fig. 16 like Fig. 15, but rotated around the central longitudinal axis X. Detailed description of the invention

[0055] Referring to the Fig. Figure 1-5 shows that the laboratory mill 1, in the form of a cutting mill, has a mill housing 2, on the front 2a of which a grinding mechanism 4, in the form of a cutting mill, is mounted. The grinding mechanism 4 comprises a separate grinding mechanism housing 6, which in the illustrated example is arranged on the front 2a of the mill housing 2. The grinding mechanism housing 6 has a grinding mechanism body 8 and a grinding mechanism door 10, which is attached to the grinding mechanism housing body 8, for example, by hinges 12, and can thus be pivoted open and closed to open and close the grinding mechanism housing 6. For this purpose, the grinding mechanism door 10 can be unlocked with a locking button 14 and locked again after closing.

[0056] The grinding housing 6 defines a grinding chamber 18 in which a grinding rotor 16 rotates about a rotor axis 20. When the front axial grinding door 10 is open, the user has axial access to the grinding chamber 18, allowing the grinding rotor 16 to be removed from the grinding chamber 18, in particular by pulling it axially out, e.g., to replace the grinding rotor 16. In the present cutting mill 1, the grinding rotor 16 is designed as a cutting rotor and comprises, for example, four axially extending cutting blades 22. These blades are arranged around the circumference of the rotor axis 20.Axially and radially extending counter-cutting knives 24 are arranged around the grinding chamber 18 and the cutting rotor 16, such that when the cutting rotor 16 rotates, the material to be ground is introduced into the grinding chamber 18 is comminuted between the cutting knives 22 of the rotating cutting rotor 16 and the stationary counter-cutting knives 24 by a cutting action based on the scissor principle. In the illustrated embodiment, the material to be ground is fed radially from above onto the rotating grinding rotor 16 during the grinding process. The grinding mechanism 4, or the grinding rotor 16, is driven by an electric drive motor 5, preferably arranged coaxially to the rotor axis 20, in the mill housing 2.

[0057] The grinding mechanism 4 has a material feed opening 26 on its upper surface 4a, which extends radially with respect to the rotor axis 20 and, in this example, vertically from the upper surface 6a of the grinding mechanism housing 6 into the grinding chamber 18. In this example, the material feed opening 26 is designed as a channel in the grinding mechanism housing 6, e.g., in the form of a cylindrical bore through the grinding mechanism housing body 8, with the channel opening into the grinding chamber 18. Thus, the material to be ground can trickle from above, conveyed by gravity, through the material feed opening 26 into the grinding chamber 18 or radially from above onto the grinding rotor 16.

[0058] To fill the milling material into the laboratory mill 1 during operation, i.e., while the grinding rotor 16 is rotating, a material filling hopper 28 is attached to the top 4a of the grinding mechanism 4 or to the top 6a of the grinding mechanism housing 6, e.g., screwed in place. The material filling hopper 28 can consist of a material filling cone 30 and a funnel neck 32. The material filling cone 30 has a funnel opening 34 at an upper cone end 30a and tapers downwards to a lower cone end 30b. At the tapered lower cone end 30b, the material filling cone 30 transitions into the funnel neck 32. In this example, the funnel neck 32 is designed as a cylindrical tube.The user can thus pour the material to be ground through the filling opening 34 into the upwardly open material filling cone 30, so that the material can then trickle or fall by gravity into the funnel neck 32, through the funnel neck 32 and the material filling opening 26 into the grinding chamber 18, where it is ground by the grinding mechanism 4. The ground material then trickles out of the grinding mechanism housing 6 through a ring sieve 35, a lower grinding mechanism outlet 36, and, if applicable, an outlet grid 38. A collection container (not shown) can be positioned below the grinding mechanism housing 6 or below the outlet grid 38 to collect the ground material. Therefore, the material can be poured into the material filling funnel 28 or through the material filling opening 26 into the grinding chamber 18 while the grinding mechanism housing 6 remains otherwise closed during the grinding process.during the rotation of the grinding rotor 16, so that the material to be ground can be continuously crushed.

[0059] In a conventional cutting mill, the material to be ground was poured more or less uncontrolled into the open material feed hopper 28 by the user. Depending on the material and grinding parameters, this could lead to a blockage in the material feed hopper 28 or to an overfilling of the cutting mill 1. Sometimes, after pouring, the material was pressed into the grinding chamber with a cylindrical ram. This could lead to an overfeeding of the grinding mechanism 4. Furthermore, the ram could undesirably stress the axis 20 of the cutting rotor 16. In addition, there was a risk that individual particles of the material to be ground would jump back out of the open material feed hopper during filling.This is now taken into account by inserting a novel material filling plunger 40 into the material filling hopper 28, which supports the filling of the material by allowing the material to be fed into the grinding chamber 18 or to the grinding mechanism 4 in a more controlled manner and, if necessary, influenced by the user.

[0060] Referring to the Fig. In the example 3-16, the grinding material filling plunger 40 has a lower piston section 42 that extends axially from the transition area 28a between the grinding material filling cone 30 and the funnel neck 32 downwards to the grinding material filling opening 26 in the grinding material filling hopper 28. In the present example, the lower piston section 42 extends downwards into the grinding material filling opening 26, i.e., into the grinding mechanism housing 6. A space 19 remains between the outer circumference of the grinding mechanism rotor 16 and the underside 40a of the grinding material filling plunger 40 or the lower piston section 42, in which a small amount of grinding material can collect above the grinding mechanism rotor 16.At the upper piston end 42a of the lower piston section 42 there is a partially interrupted circumferential bead 44 on the grinding material filling plunger 40, which forms a stop of the grinding material filling plunger 40 against the tapered lower cone end 30b of the grinding material filling cone 30, so that the grinding material filling plunger 40 cannot slide further downwards.

[0061] In the operating state, i.e., when the grinding material filling plunger 40 is inserted fully into the grinding material filling hopper 28, the radial distance between the outer circumference of the grinding rotor 16 and the underside 42a of the grinding material filling plunger 40, or to the closed lower bottom surface 60 forming the gap 19, is approximately 1 mm in the present embodiment. Generally, this radial distance in the operating state should preferably be less than or equal to 25 mm, preferably between 0.2 mm and 10 mm, and preferably between 0.5 mm and 6 mm. This ensures that even smaller sample particles can still be effectively fed into the grinding material filling plunger 40.

[0062] In its upper region, the material filling plunger 40 has an extension stem 46, which in this example is integrally formed with the bead 44 or the lower piston section 42. At the upper end 46a of the extension stem 46, a handle 48 is integrally formed with the material filling plunger 40, so that the user can grasp the material filling plunger 40 by the handle 48, pull it out of the material filling hopper 28, and / or rotate it about the central longitudinal axis X of the material filling plunger 40. The material filling plunger 40 can be inserted axially by the user from above through the material filling cone 30 into the hopper neck 32 along the longitudinal axis X of the material filling plunger 40 and the material filling hopper 28, and can also be pulled out axially upwards.The downward axial movement of the grinding material filling plunger 40 is limited by the stop of the bead 44, so that the grinding material filling plunger 40 cannot collide with the grinding rotor 16, but the gap 19 is maintained.

[0063] The material feed plunger 40 is loosely rotatable within the material feed hopper 28, allowing the user to easily rotate it with their fingers during the grinding process. This directs the material downwards towards the grinding mechanism 4 and / or simultaneously lifts the plunger slightly, allowing more material to trickle into the slightly enlarged space 19. The user can then also use the plunger 40 for tamping by pressing it axially downwards against the increased quantity of material that has trickled into the space 19, thus pushing it into the grinding chamber 18 or against the grinding rotor 16.The illustrated material filling plunger 40 thus fulfills an advantageous multiple function, namely, on the one hand, in the example shown, to be able to influence the conveying speed of the material being ground in the material filling hopper 28 by rotating the material filling plunger; furthermore, to be able to push the material being ground into the grinding chamber 18 in the space 19 or the material filling opening 26; and to effectively prevent the sample from being ejected. The proposed material filling plunger 40 can therefore provide several advantages in synergistic combination.

[0064] In the cutting mill 1 shown here, the grinding rotor 16 runs horizontally and rotates around the horizontal rotor axis 20, so the mill 4 can be described as horizontal. The material to be ground is fed radially from above, i.e., transversely to the rotor axis 20. This is also the case, for example, with a cross-head mill or a disc mill, for which the material feeding plunger 40 can also be used. In a knife mill or an impact mill, sometimes also called a rotor mill, rotor high-speed mill, or centrifugal mill, the grinding rotor 16 typically rotates around a vertical rotor axis. However, here too, the material to be ground is fed into the grinding chamber from above, conveyed by gravity; i.e., axially in these laboratory mills.The grinding material filling plunger 40 described here can also be used in laboratory mills with axial material feed, where the controlled conveyance of the grinding material and the prevention of the sample being ejected are paramount, rather than re-stuffing.

[0065] Referring to the Fig. A material feed channel 50 runs through the lower piston section 42, through which the material to be ground can pass from the upper end 32a of the hopper neck 32 to the material feed opening 26 of the grinder 4. In the present example, the material feed channel 50 is largely spiral-shaped. This has the advantage that the user can increase or decrease the conveyance of the material to be ground towards the grinding chamber 18 by rotating the material feed ram or conveying ram 40, similar to a screw conveyor, depending on the direction in which the material feed ram 40 is rotated.

[0066] In the present example, the lower piston section 42 is essentially designed as a screw section 52 with a spiral 53. The material feed channel 50 is thus formed by a spiral groove 54, which winds helically around the central longitudinal axis X of the material feed plunger 40. Between two adjacent turns of the spiral groove 54 is a spiral web 56, which has the outer diameter A of the piston section 42. In this example, the spiral 53 of the screw section 52 is designed as a single-start helix with approximately 2 to 3 screw turns. The spiral 53 is left-handed, which has the advantage that the conveyance of the material to be ground can be increased by a clockwise rotation of the material feed plunger 40, which is ergonomically advantageous for most users.

[0067] When the grinding material filling plunger 40 is turned clockwise, the flow of the grinding material from top to bottom through the funnel neck 42 towards the grinding chamber 18, which may already be driven by gravity, is thus intensified, whereby the turning in the conveying direction also creates a certain packing effect, but advantageously - unlike with a conventional plunger - without exerting undesirably large forces on the rotor axis 20 and without undesirably large pressure on the sample, thereby reducing wear and ensuring gentle grinding.

[0068] The screw section 52, or spiral 53, extends from an upper region 42a of the lower piston section 42, or approximately from the bead 44, to a lower region 42b of the lower piston section 42, such that the material feed channel 50 runs largely in a spiral shape in this area. However, the material feed channel 50 begins at its upper end 50a with an upper axial channel section 51a as a head groove, which extends axially through the bead 44. An axial channel section 51b is also formed as a foot groove at the lower end 50b of the material feed channel 50. The axial channel sections 51a, 51b help to ensure that the recess or milling in the bead 44 and the axial outlet opening, which forms the lower grinding material outlet 62 of the grinding material feed channel 50 in the foot section 58 at the lower end 42b of the lower piston section 42, do not become too large.This is advantageous with regard to the guidance of the grinding material filling plunger 40 in the funnel neck 32 and also ensures that the closed bottom surface 60 of the grinding material filling plunger 40 remains relatively large in order to have a correspondingly large area for repacking.

[0069] Referring to the Fig. In the following example, the lower axial channel section 51b can be milled into the foot section 58 of the grinding material filling plunger 40 as a foot groove with a crescent-shaped cross-section. The cross-sectional area of ​​the axial foot groove 51b is considerably smaller than the closed lower bottom surface 60 of the lower piston section 42 or foot section 58. In the present example, the closed end-face bottom surface 60 is approximately 61% of the cross-sectional area of ​​the lower piston section 42. Thus, the ratio between the cross-section of the lower axial channel section 51b and the closed lower bottom surface 60 is approximately 1 to 1.56. However, this ratio between the cross-section of the lower axial channel section 51b and the closed lower bottom surface 60 is exemplary and can be adjusted depending on the embodiment, preferably in the range of 1 to 0.33 to 1 to 4, and preferably in the range of 1 to 0.6 to 1 to 3.The lower closed bottom surface 60 should preferably not be too small. The lower axial channel section 51b thus forms the lower material outlet 62 from the material feed channel 50 in the form of a recess in the bottom, from which the material can trickle gravitationally into the space 19 or into the grinding chamber 18. Accordingly, the cross-sectional area of ​​the material outlet 62 in this embodiment is smaller than the closed lower bottom surface 60.

[0070] It is evident that the cross-sectional area of ​​the material feed channel 50, or of the upper axial channel section 51a, the spiral groove 54, and the lower axial channel section 51b, can already define a certain gravity-driven base flow of the material through the material feed hopper 28 or the hopper neck 32, depending on the material being ground. On the other hand, this base flow can be increased or decreased by the user by rotating the material feed plunger 40 in order to control the material flow into the grinder 4 individually and situationally.

[0071] Referring to a comparison of the Fig. 9 and Fig. As can be seen in Figure 10, the cross-sectional area of ​​the material FS in the area of ​​the spiral 53 in the lower piston section 42 is also considerably smaller than the closed lower bottom surface 60. This can be achieved by not milling the spiral groove 54 completely through to the lower end of the material feed plunger 40, but rather by extending it into the lower axially milled channel section 51b. As a result, the outer surface area 59, which has the outer diameter A of the lower piston section 42 adapted to the inner diameter of the funnel neck 32, is larger in the base section 58 than the outer surface area of ​​a spiral with a completely milled spiral groove 54. Thus, the base section 58 is less deeply cut out in cross-section by the material feed channel 50 than the axially central area of ​​the spiral 53. This is advantageous with regard to the interaction between material conveyance and the packing effect.

[0072] Referring to Fig. 8 and Fig. In section 12, the bead 44 is circumferentially cut out to form an upper inlet opening 64 into the material feed channel 50. In this example, the cutout extends over a circumference of approximately 180°. This is achieved, among other things, by the upper axial channel section 51a. Thus, the head section 57 of the lower piston section 42 is also less deeply cut out by the material feed channel 50 than the axially central area of ​​the spiral 53, or compared to a spiral groove milled completely through the bead 44.

[0073] In other words, the spiral groove 54 does not extend completely upwards through the bead 44 and / or downwards through the base section 58, in order to avoid excessive hollowing out of it. The material feed channel 50, or the material feed groove, therefore runs, viewed from top to bottom, first axially 51a for a short distance, then spirally 54, and then axially again 51b.

[0074] Furthermore, the less deeply milled base section 58 and / or the less deeply milled head section 57 can counteract a potential tilting of the grinding material filling plunger 40.

[0075] Referring to the Fig. 6 and Fig. In the present embodiment, the spiral 53 has a groove width N of approximately 33 mm, a web width S of approximately 7 mm, and a pitch P of approximately 40 mm. The pitch angle β is approximately 22°. The core diameter K, or the diameter of the inner surface of the spiral 53, is approximately 6 mm. The length of the axial channels 51a and 51b is approximately 20 mm in this example.

[0076] The outer diameter A of the lower piston section 42 is approximately A = 25 mm in this example. The lower piston section 42 is guided more or less precisely by the funnel neck 32, so that the inner diameter of the funnel neck 32 (approximately 26 mm in this example) is only slightly larger than the outer diameter A. Therefore, the lower piston section 42, or the screw section 52 of the material feed ram 40, and the funnel neck 32, acting as a conveying tube, form a screw conveyor for the material being ground. It may initially seem counterintuitive to use a vertical screw conveyor to convey the material being ground vertically or almost vertically downwards, since without the screw conveyor the material being ground would simply trickle or fall into the grinding chamber 18 due to gravity, at least if no ram were used at all.The inventors have discovered, however, that in a laboratory mill, such a material filling plunger 40 with an integral material filling channel 50 can prevent unwanted upward ejection of material particles from the filling hopper 28. Furthermore, such a material filling plunger 40 with an integral material filling channel 50 can produce two opposing effects: firstly, it reduces the gravity-driven trickle, and secondly, it can, if necessary, facilitate controlled conveyance, for example, by a screw conveyor, which has proven highly advantageous for a laboratory cutting mill.

[0077] The material feed plunger 40 can optionally be machined, e.g., CNC milled. The material feed plunger 40, especially with a spiral 53, can act like a baffle plate and also serve as a dust guard. The material to be ground does not fall directly downwards, but slides along the surface of the material feed channel 50 or the spiral groove 54. Depending on the material being ground, this results in a slow, continuous or a controlled feed. This effect occurs particularly with materials that do not slide well on the surface and can be triggered or influenced by kinematic forces such as rotation, vibration, or vertical movement of the plunger. The material feed plunger 40 does not necessarily have to be raised and lowered during grinding to convey the material into the grinding chamber 18, as is the case with a conventional ram, although this is not excluded.In any case, excessive impact forces on the sample and greater bending forces on the motor shaft can be avoided.

[0078] The size of the grinding particles is somewhat limited depending on the design of the grinding material feed channel 50, e.g., groove width and pitch, so that possibly only smaller samples up to a particle size of, for example, approximately Ø10×10, e.g., beans, feed pellets, rice, etc., can be fed in. The use of the spiral plunger 40 as a tamper for pushing down may also be somewhat limited, but is still possible, especially if its lower shape has a sufficiently large surface area 60.

[0079] However, handling and grinding with the material feeder 40 is advantageously quieter and more relaxed. Constant lifting and lowering, as with a conventional plunger, is avoided, preventing the material from jumping out. If necessary, the user can pour the entire sample into the feed hopper 28 at once, eliminating the need to use both hands. Overfeeding the machine can be avoided or at least the risk is reduced. The user can also better hear the grinding or cutting process and, if needed, adjust the material feeder 40 slightly when the workload decreases to increase the feed rate.

[0080] Similarly, the material filling plunger 40 can also be used for other laboratory mills, in particular for impact mills, disc mills, knife mills, impact mills, centrifugal mills, rotor mills, high-speed rotor mills, or mortar mills. Furthermore, the material filling plunger 40 can be easily retrofitted to existing laboratory mills and is therefore also available as a separate retrofit part.

[0081] It is evident to the 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] Laboratory mill (1) for grinding material, in particular designed as a cutting mill, impact mill, disc mill, knife mill, impact mill, centrifugal mill, rotor mill, rotor high-speed mill or mortar mill, comprising: a grinding mechanism (4) with a grinding mechanism housing (6) which defines a grinding chamber (18), and with a grinding mechanism rotor (16) which is rotatably driven in the grinding chamber (18) to grind the material to be ground with the grinding mechanism rotor (16) in the grinding chamber (18), wherein the grinding mechanism housing (6) has a material filling opening (26) which leads into the grinding chamber (18) in order to introduce the material to be ground from the outside through the material filling opening (26) into the grinding chamber (18), a drive motor for driving the grinding rotor (16) in the grinding chamber (18), a grinding material feed hopper (28) which opens into the grinding material feed opening (26), such that the grinding material can be filled into the grinding material feed hopper (28) and passes through the grinding material feed hopper (28) and the grinding material feed opening (26) into the grinding chamber (18), while the grinding rotor (16) rotates in the grinding chamber (18), a grinding material filling plunger (40) that can be inserted into the grinding material filling hopper (28), wherein the grinding material filling plunger (40) has a grinding material filling channel (50) through which the grinding material can be filled into the grinding chamber (18) when the grinding material filling plunger (40) is inserted into the grinding material filling hopper (28), wherein the grinding material filling plunger (40) has at least a section of a screw section (52) axially, in which the grinding material filling channel (50) runs in a helical or spiral manner in the grinding material filling plunger (40). [2] Laboratory mill (1) according to claim 1, wherein the grinding material feed hopper (28) has a grinding material feed cone (30) and a funnel neck (32) and the funnel neck (32) opens into the grinding material feed opening (26), such that the grinding material can be filled into the grinding material feed cone (30) and passes through the funnel neck (32) and the grinding material feed opening (26) into the grinding chamber (18), while the grinding rotor (16) rotates in the grinding chamber (18) and wherein the material to be ground can be filled into the grinding chamber (18) through the material filling channel (50) when the material filling plunger (40) is inserted into the funnel neck (32). [3] Laboratory mill (1) according to claim 2, wherein the grinding material feed channel (50) is formed in the form of a groove (54) in the circumferential surface of the grinding material feed plunger (40) and is open radially outwards, so that the grinding material feed channel (50) is limited radially outwards by the funnel neck (32) when the grinding material feed plunger (40) is inserted into the funnel neck (32). [4] Laboratory mill (1) according to one of the preceding claims, wherein the grinding material feed channel (50) runs at least sectionally with a gradient of less than 90°, preferably less than 80°, preferably less than or equal to 70°, preferably less than or equal to 45°, preferably greater than or equal to 10° in the grinding material feed plunger (40). [5] Laboratory mill (1) according to any one of the preceding claims, wherein the grinding material filling plunger (40) has a lower piston section (42) which extends from an upper piston end (42a) to a plunger base at a lower end of the grinding material filling plunger (40), wherein the plunger base faces the grinding chamber (18) when the grinding material filling plunger (40) is inserted into the grinding material filling hopper (28), wherein the grinding material feed channel (50) extends from the upper piston end (42a) to the lower end of the grinding material feed plunger (40), and wherein the stamp base has partly a closed end-face base surface (60) and partly a base recess into which the grinding material feed channel (50) opens, as a grinding material outlet (62), such that the grinding material can trickle through the grinding material feed channel (50) and the base recess into the grinding chamber (18). [6] Laboratory mill (1) according to claim 5, wherein the closed end face bottom surface (60) comprises at least 25%, preferably at least 30%, preferably at least 40%, preferably a maximum of 80%, preferably 75%, preferably a maximum of 70%, preferably in the range between 40% and 70% of the cross-sectional area of ​​the lower piston section (42). [7] Laboratory mill (1) according to one of claims 5-6, wherein the closed end face bottom surface (60) is larger than the radial cross-sectional area of ​​the grinding outlet (62). [8] Laboratory mill (1) according to claim 1, wherein the grinding material feed channel (50) extends in the screw section (52) as a spiral groove (54) in the circumferential surface of the lower piston section (42) and the spiral groove (54) does not extend or at least does not extend completely to the lower end of the grinding material feed plunger (40). [9] Laboratory mill (1) according to one of claims 5-8, wherein the lower piston section (42) at its upper piston end (42a) a head section (57), at its lower piston end (42b) has a foot section (58), and a worm section (52) extending axially between the head section (57) and the foot section (58), and wherein the grinding material feed channel (50) extends axially in the head section (57), helically or spirally around the longitudinal axis (X) of the grinding material feed plunger (40) in the screw section (52) and / or axially in the foot section (58). [10] Laboratory mill (1) according to any of the preceding claims, wherein the laboratory mill (1) has at least one, several or all of the following features: The material feed plunger (40) has a material cross-sectional area (FS) in the screw section (52) and the closed end face bottom surface (60) is larger than the material cross-sectional area (FS) in the screw section (52), preferably at least twice as large as the material cross-sectional area (FS) in the screw section (52), and / or the cochlear segment (52) is formed as a single-start helix, and / or the cochlear segment (52) is left-handed, and / or the screw section (52) has at least half a screw turn, preferably between one and 10, preferably between one and 5, preferably between 2 and 4 screw turns, and / or The material feed channel (50) has a slope (P) in the screw section (52) in the range between 10 mm and 120 mm, preferably in the range between 20 mm and 80 mm, preferably 40 mm + / - 20 mm or + / - 10 mm, and / or The material feed channel (50) in the screw section (52) has a slope angle (β) in the range between 5° and 70°, preferably in the range between 10° and 50°, preferably between 15° and 40°, preferably 25° + / - 10° or + / - 5°, and / or The material feed channel (50) in the screw section (52) has a groove width (N) in the range between 10 mm and 100 mm, preferably in the range between 20 mm and 75 mm, preferably 40 mm + / - 15 mm or + / - 10 mm, and / or The screw section (52) has a web width (S) in the range between 1 mm and 30 mm, preferably in the range between 2 mm and 20 mm, preferably in the range between 3 mm and 15 mm, preferably 6 mm + / - 4 mm or + / - 2 mm, and / or the screw section (52) has a core diameter (K) in the range between 2 mm and 20 mm, preferably in the range between 3 mm and 15 mm, preferably in the range between 4 mm and 10 mm, preferably 6 mm + / - 2 mm or + / - 1 mm. [11] Laboratory mill (1) according to one of claims 5-10, wherein the lower piston section (42) has a bead (44) at its upper piston end (42a) which forms a lower stop for the grinding material filling plunger (40) in the grinding material filling hopper (28) in the transition area (28a) between the grinding material filling cone (30) and the hopper neck (32). [12] Laboratory mill (1) according to one of the preceding claims, wherein the material filling plunger (40) comprises an extension stem (46) which extends the material filling plunger (40) from an upper piston end (42a) in the direction away from the grinding chamber (18) to an upper plunger end and wherein a handle (48) is arranged at the upper plunger end by which the user can grasp the material filling plunger (40). [13] Laboratory mill (1) according to one of claims 2-12, wherein the grinding material filling plunger (40) is insertable into the funnel neck (32) and is rotatable in the funnel neck (32) when inserted. [14] Laboratory mill (1) for grinding material, in particular designed as a cutting mill, impact mill, disc mill, knife mill, impact mill, centrifugal mill, rotor mill, rotor high-speed mill or mortar mill, comprising: a grinding mechanism (4) with a grinding mechanism housing (6) which defines a grinding chamber (18), and with a grinding mechanism rotor (16) which is rotatably driven in the grinding chamber (18) to grind the material to be ground with the grinding mechanism rotor (16) in the grinding chamber (18), wherein the grinding mechanism housing (6) has a material filling opening (26) which leads into the grinding chamber (18) in order to introduce the material to be ground from the outside through the material filling opening (26) into the grinding chamber (18), a drive motor for driving the grinding rotor (16) in the grinding chamber (18), a grinding material feed hopper (28) which opens into the grinding material feed opening (26), such that the grinding material can be filled into the grinding material feed hopper (28) and passes through the grinding material feed hopper (28) and the grinding material feed opening (26) into the grinding chamber (18), while the grinding rotor (16) rotates in the grinding chamber (18), a grinding material filling plunger (40) that can be inserted into the grinding material filling hopper (28), wherein the grinding material filling plunger (40) has a grinding material filling channel (50) through which the grinding material can be filled into the grinding chamber (18) when the grinding material filling plunger (40) is inserted into the grinding material filling hopper (28), wherein the grinding material feed channel (50) runs at least in sections with a gradient of less than 90° in the grinding material feed plunger (40). [15] Grinding material filling plunger (40), prepared for insertion into the grinding material filling hopper (28) of the laboratory mill according to one of the preceding claims, wherein the grinding material filling plunger (40) has a grinding material filling channel (50) through which the grinding material can be filled into the grinding chamber (18) when the grinding material filling plunger (40) is inserted into the grinding material filling hopper (28), wherein the grinding material feed channel (50) runs at least partially with a gradient of less than 90° in the grinding material feed plunger (40) or wherein the grinding material feed plunger (40) has axially at least partially a screw section (52) in which the grinding material feed channel (50) runs helically or spirally in the grinding material feed plunger (40).

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