Manufacturing method of ceramic calcined body

Abstract

The invention discloses a manufacturing method of a ceramic calcined body, and relates to the field of ceramic manufacturing. The device mainly comprises a cylindrical tank body, a high-temperature-resistant inner tank is coaxially arranged in the cylindrical tank body, the inner tank is sleeved with a heat insulation plate, a rotating motor is installed in the center of the heat insulation plate, the output end of the rotating motor is connected with a tray through a key, a lifting mechanism comprising a lifting motor and a telescopic rod is arranged at the bottom of the tank body, and a grinding mechanism is arranged on one side of the tank body. The grinding mechanism comprises a supporting rod, a rotating frame, a grinding motor, a grinding container, a grinding head and a screen, a control panel with a feeding port and a discharging valve is installed on the edge of the grinding container, a tank cover with a temperature sensor and an unlocking mechanism are arranged at the top of a tank body, a heat exchanger is arranged on the outer side, an induction coil is arranged on the inner side, and vent holes and a sealing ring are arranged on the side wall of an inner tank; the device can realize accurate grinding of raw materials, controllable atmosphere and flexible operation of lifting and rotating, effectively improves the quality and production efficiency of a ceramic calcined body, and has important significance in the technical field of ceramic manufacturing.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic calcination, in particular to a method for manufacturing a ceramic calcined body. Background Art

[0002] As an important material, ceramics are widely used in many fields, such as construction, electronics, aerospace, etc. In the manufacturing process of ceramic calcined bodies, traditional manufacturing methods and equipment have many problems;

[0003] Traditional ceramic calcining devices usually have a single function. For example, in the raw material processing stage, they lack effective pre-processing and mixing functions. The raw materials often need to be pre-processed in other equipment before being transferred to the calcining equipment. This not only increases the production process, but also easily introduces impurities during the transfer process, affecting the quality of the ceramic. Moreover, during the calcination process, the temperature control is not precise enough, resulting in unstable physical properties of the ceramic body, such as uneven hardness, density, etc., affecting the overall performance and quality of the product. The energy utilization efficiency of traditional devices is low, and a large amount of heat energy is lost during the calcination process, which increases production costs and does not conform to the development trend of energy conservation and environmental protection. In addition, traditional equipment has a low degree of automation and requires a lot of manual intervention, from raw material loading to calcination process monitoring and finished product removal. Manual operation is not only labor-intensive, but also easily leads to unstable product quality due to human factors, and low production efficiency. In response to the above problems, the inventor proposes a method for manufacturing a ceramic calcined body to solve the above problems. Summary of the invention

[0004] In order to solve the problems of single function, inaccurate temperature control, low energy utilization efficiency and low automation in traditional methods and equipment, the purpose of the present invention is to provide a method for manufacturing a ceramic calcined body.

[0005] In order to solve the above technical problems, the present invention adopts the following technical scheme: a method for manufacturing a ceramic calcined body, comprising a tank body 1, the tank body 1 is a cylindrical structure, an inner tank 3 is coaxially arranged inside the tank body 1, the inner tank 3 is a cylindrical structure made of high-temperature resistant material, and there is a certain gap between its outer wall and the inner wall of the tank body 1, an insulation plate 43 is sleeved inside the inner tank 3, the outer edge of the insulation plate 43 is tightly fitted to the inner wall of the inner tank 3, a rotating motor 44 is fixedly installed at the center of the upper surface of the insulation plate 43, and a tray 45 is fixedly installed at the output end of the rotating motor 44 by a key connection, and the tray 45 is a circular disc-shaped structure, which is horizontally arranged inside the inner tank 3.

[0006] Preferably, a lifting mechanism is provided at the bottom of the tank body 1, and the lifting mechanism includes a lifting motor 41 and a telescopic rod 42. The lifting motor 41 is fixedly installed at the center position of the bottom of the tank body 1 by bolts, and the output end of the lifting motor 41 is installed with the telescopic rod 42, and the top of the telescopic rod 42 is fixedly connected to the lower surface of the insulation plate 43.

[0007] Preferably, a grinding mechanism is provided on one side of the tank body, and the grinding mechanism includes a support rod, the top end of the support rod is rotatably connected to a rotating frame, a grinding motor is fixedly installed on the upper part of the rotating frame away from the support rod, a grinding container is fixedly installed on the rotating frame on the lower side of the grinding motor, the grinding container is a bowl-shaped structure, a grinding head is fixedly installed on the output end of the grinding click, and a screen is provided at the bottom of the grinding container.

[0008] Compared with the prior art, the present invention has the following beneficial effects:

[0009] 1. The present invention is provided with a lifting mechanism and a rotating mechanism, which work together. In the ceramic shaping stage, the lifting motor drives the insulation plate and the rotating motor and the tray above to rise accurately to the outside of the tank body, so that the operator can perform meticulous shaping operations on the ceramics while the rotating tray continues to rotate, which greatly improves the accuracy, flexibility and convenience of ceramic shaping;

[0010] 2. The present invention is equipped with a unique grinding mechanism, and its control panel integrates a weighing function, which can accurately measure and strictly control the amount of ceramic additives. When additives need to be added, the rotating frame can quickly rotate the grinding mechanism to a suitable position above the tank body to achieve accurate placement of additives, effectively avoiding errors that may be caused by manual weighing and addition, significantly improving the accuracy of raw material ratios, and thus improving the performance and quality stability of ceramic products;

[0011] 3. The insulation board and tray in the present invention are made of high-quality insulation materials. During the heating of the induction coil, the insulation board strongly blocks the downward conduction of heat, prevents heat loss and avoids adverse effects on the lower components, ensures that heat is efficiently concentrated on the ceramic to be calcined, greatly improves energy utilization efficiency, makes the ceramic heated more evenly and stably, and effectively promotes the optimization of the physical properties of the ceramic calcined body and the improvement of quality consistency. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 It is a schematic diagram of the structure of the present invention.

[0014] Figure 2 For the present invention Figure 2 A schematic diagram of the enlarged structure in the middle.

[0015] Figure 3 For the present invention Figure 2 Enlarged schematic diagram of the structure at point B in the middle.

[0016] Figure 4 It is a schematic diagram of the cross-sectional structure of the present invention.

[0017] Figure 5 For the present invention Figure 4 Enlarged schematic diagram of the structure at point C in the middle.

[0018] Figure 6 For the present invention Figure 4 Enlarged schematic diagram of the structure at point D in the middle.

[0019] Figure 7 It is a schematic diagram of the top view structure of the present invention.

[0020] Figure 8 For the present invention Figure 7 Enlarged schematic diagram of the structure in the middle.

[0021] In the figure: 1. tank body; 11. resistance rod; 111. shock-absorbing spring; 12. heat exchanger; 13. sealing ring; 131. vent; 14. tank cover; 141. temperature sensor; 142. buckle; 1421. hanging hole; 15. unlocking mechanism; 17. induction coil; 18. jack; 181. button; 182. rotating block; 183. first spring; 184. second spring; 2. support rod; 21. rotating frame; 22. grinding motor; 23. grinding container; 231. screen; 185. pad; 24. control panel; 241. feeding port; 242. discharge valve; 25. grinding head; 3. inner tank; 41. lifting motor; 42. telescopic rod; 43. insulation board; 44. rotating motor; 45. tray. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] like Figure 1-6As shown, the present invention provides a method for manufacturing a ceramic calcined body, including a tank body 1, which is in a cylindrical structure. An inner tank 3 is coaxially arranged inside the tank body 1. The inner tank 3 is a cylindrical structure made of high-temperature resistant material, and there is a certain gap between the outer wall thereof and the inner wall of the tank body 1. An insulation board 43 is sleeved inside the inner tank 3, and the outer edge of the insulation board 43 fits tightly against the inner wall of the inner tank 3. A rotating motor 44 is fixedly installed at the center of the upper surface of the insulation board 43, and a tray 45 is fixedly installed at the output end of the rotating motor 44 by a key connection. The tray 45 is a circular disc-shaped structure, which is horizontally arranged inside the inner tank 3.

[0024] By adopting the above technical scheme, by adopting the above technical scheme, the tank body 1 serves as the outer shell of the overall structure to provide protection and support. The inner tank 3 is used to contain ceramic raw materials and related components. The high-temperature resistant material ensures the stability of the structure during the calcination process. The gap between it and the outer wall of the tank body 1 can play a certain heat insulation role. The insulation plate 43 further reduces the downward transfer of heat to ensure the normal operation of the components below the device and energy saving. The rotating motor 44 provides rotational power for the tray 45, so that the ceramic raw materials on the tray 45 can be evenly heated during the calcination process, which helps to improve the quality uniformity of the ceramic calcined body. The tray 45 is used to place the ceramic raw materials, and its horizontal setting ensures the stability of the raw materials during rotation.

[0025] A lifting mechanism is provided at the bottom of the tank body 1, and the lifting mechanism includes a lifting motor 41 and a telescopic rod 42. The lifting motor 41 is fixedly installed at the center position of the bottom of the tank body 1 by bolts, and the telescopic rod 42 is installed at the output end of the lifting motor 41. The top of the telescopic rod 42 is fixedly connected to the lower surface of the insulation board 43.

[0026] By adopting the above technical solution, the lifting motor 41 serves as a power source to drive the telescopic rod 42 to extend and retract. The telescopic rod 42 is connected to the insulation plate 43, thereby realizing the lifting and lowering functions of the insulation plate 43 and upper components such as the rotating motor and the tray. During the ceramic calcination process, the height of the components can be accurately adjusted according to the needs of different process stages. For example, the rotating mechanism can be raised to the outside of the tank body for easy operation during the shaping stage, and lowered during the heating stage to ensure uniform heating, etc., thereby improving the functionality and operational flexibility of the device.

[0027] A grinding mechanism is provided on one side of the tank body, and the grinding mechanism includes a support rod 2, the top end of the support rod 2 is rotatably connected to a rotating frame 21, a grinding motor 22 is fixedly installed on the upper part of the rotating frame 21 away from the support rod 2, a grinding container 23 is fixedly installed on the rotating frame 21 on the lower side of the grinding motor 22, and the grinding container 23 is a bowl-shaped structure. A grinding head 25 is fixedly installed on the output end of the grinding motor 22, and a screen 231 is provided at the bottom of the grinding container 23.

[0028] By adopting the above technical solution, the support rod 2 provides support for the rotating frame 21 so that it can rotate stably. The rotating frame 21 can realize the position adjustment of the grinding motor 22 and the grinding container 23, which is convenient for operation. The grinding motor 22 drives the grinding head 25 to rotate to grind the raw materials, so that the raw material particles are more refined and uniform, which is beneficial to improving the quality of ceramics. The grinding container 23 is used to accommodate the raw materials to be ground. The bowl-shaped structure facilitates the concentration and grinding of raw materials. The screen 231 can screen the raw materials during the grinding process to ensure that the particles that meet the requirements enter the subsequent process, remove oversized or unqualified particles, and further optimize the quality of the raw materials.

[0029] A tank cover 14 is provided on the top of the tank body 1 . The tank cover 14 is a circular plate-shaped structure, and its edge extends downward to form a skirt that matches the top opening of the tank body 1 . A temperature sensor 141 is fixedly installed on the lower surface of the tank cover 14 .

[0030] By adopting the above technical solution, the skirt structure of the tank cover 14 is adapted to the top opening of the tank body 1 to ensure the sealing of the tank body 1 and reduce heat loss and the entry of external impurities. The temperature sensor 141 is installed on the lower surface of the tank cover 14, which can monitor the temperature in the tank body in real time and provide data support for the precise control of the calcination temperature, so as to timely adjust the heating power or take other temperature control measures to ensure that the ceramic calcination process is carried out within a suitable temperature range, thereby improving the quality stability of the ceramic calcined body.

[0031] An unlocking mechanism 15 is provided on the tank body 1, and the unlocking mechanism 15 includes a socket 18, and the socket 18 is opened on the outer wall of the tank body 1. A button 181 is slidably connected in the socket 18, and a rotating block 182 is rotatably connected to the lower end of the button 181. The lower end of the rotating block 182 is fixedly connected to a first spring 183. A cushion block 185 is also provided in the socket 18, and the lower end of the cushion block 185 is fixedly connected to a second spring 184. The lower ends of the first spring 183 and the second spring 184 are fixedly connected to the outer wall of the tank body 1.

[0032] By adopting the above technical solution, the unlocking mechanism 15 is used to control the locking and unlocking of the tank cover 14. The socket 18 provides installation space for components such as the button 181 and the rotating block 182. The button 181 realizes a specific unlocking action through the rotational connection with the rotating block 182 and the elastic action of the first spring 183. The pad 185 and the second spring 184 work together to ensure the stability and reliability of the unlocking mechanism 15 during the locking and unlocking process, which facilitates the operator to open and close the tank cover 14 safely and conveniently, and ensures the smooth progress of the ceramic calcination process.

[0033] A control panel 24 is fixedly mounted on the edge of the grinding container 23 . A feeding port 241 is provided on an inner side of the control panel 24 . A discharge valve 242 is rotatably connected to the feeding port 241 .

[0034] By adopting the above technical solution, the control panel 24 allows the operator to control and set parameters of the grinding mechanism, such as the speed of the grinding motor 22, etc. The feeding port 241 is used to add raw materials into the grinding container 23, and the rotating connected discharge valve 242 can control the amount and timing of the raw materials, thereby achieving precise addition of raw materials and ensuring accurate raw material ratios, which helps to improve the performance and quality stability of ceramic products and facilitates raw material management during operation.

[0035] A heat exchanger 12 is disposed outside the tank body 1 . The heat exchanger 12 is fixedly mounted on the outer wall of the tank body 1 by welding, and an internal pipe thereof is communicated with the interior of the tank body 1 .

[0036] By adopting the above technical solution, the heat exchanger 12 is fixed to the outer wall of the tank body 1 by welding to ensure the firmness of the connection. Its internal pipeline is connected to the inside of the tank body 1 to realize heat exchange. During the ceramic calcination process, the heat exchanger 12 can adjust the temperature inside the tank body as needed, such as rapid heating in the heating stage and auxiliary heat dissipation in the cooling stage, ensuring that the ceramic calcined body is processed in a suitable temperature environment, improving the accuracy and efficiency of temperature control, and helping to improve the quality of ceramic products.

[0037] The side wall of the inner tank is provided with a plurality of vent holes 131 , the internal pipes of the vent holes 131 are connected with the inside of the tank body 1 , and the vent holes 131 are connected to the outside of the tank body and a sealing ring 13 is fixedly installed thereon.

[0038] By adopting the above technical scheme, the several air vents 131 on the side wall of the inner tank provide channels for connecting various gases such as inert gases. During the ceramic calcination process, the introduction of different gases can be accurately controlled according to the process requirements. For example, the introduction of inert gases can effectively prevent the raw materials from oxidizing at high temperatures and protect the raw material composition and performance. The air vents 131 are connected to the inside of the tank body 1 to ensure that the gas can be evenly distributed in the tank, so that the ceramic raw materials can be calcined in a specific atmosphere. The air vents 131 are connected to the outside of the tank body and a sealing ring 13 is installed. The sealing ring 13 plays a vital sealing role. It strictly prevents gas leakage, maintains the stability and purity of the gas environment in the tank, and ensures the effectiveness and reliability of the gas regulation function, thereby creating favorable conditions for manufacturing high-quality ceramic calcined bodies, ensuring that the performance of ceramic products is not interfered by external gases, and effectively improving product quality.

[0039] An induction coil 17 is arranged inside the tank body 1, and a plurality of resistance rods 11 distributed in a circular array are fixedly connected to the bottom of the tank body by welding. A shock-absorbing spring 111 surrounds the resistance rod 11, and the upper end of the shock-absorbing spring 111 is fixedly installed on the bottom of the tank body, and the lower end of the shock-absorbing spring 111 is fixedly installed on the ground.

[0040] By adopting the above-mentioned technical scheme, the induction coil 17 is arranged on the inner side of the tank body 1, which can provide wireless power supply for the rotating motor 44 and other components in the tank, reducing the inconvenience of line connection and safety hazards brought by the traditional wired power supply method, and improving the stability and operational convenience of the device. The combination of the resistance rod 11 and the shock-absorbing spring 111 is fixed to the bottom of the tank body by welding, which can effectively reduce the vibration of the tank body during operation, improve the stability of the device, prevent the vibration from affecting the ceramic raw materials, components and measuring equipment such as the temperature sensor 141, etc., ensure the smooth progress of the ceramic calcination process, and help to improve the quality of the ceramic calcined body.

[0041] The shape of the grinding head 25 is such that the gap between its bottom and the grinding container 23 gradually decreases from top to bottom.

[0042] By adopting the above-mentioned technical solution, the special shape design of the grinding head 25 makes it possible for the raw material particles to be gradually subjected to a stronger grinding action in the grinding container 23 during the raw material grinding process. As the gap decreases, the squeezing force and friction force on the raw material increase, so that the raw material can be more effectively ground to a finer particle size, thereby improving the grinding efficiency and quality, making the raw material more uniformly refined, and facilitating the subsequent ceramic forming and performance improvement.

[0043] Working principle: When the present invention is used, the lifting motor 41 is first started to drive the telescopic rod 42 to extend, and the insulation board 43 and the upper rotating motor 44 and the tray 45 are lifted to a suitable position on the upper part of the tank body cavity. Thereafter, a proper amount of ceramic clay raw materials are placed on the tray 45, and ceramic additives are placed in the grinding container 23 through the feeding port 241 on the control panel 24 at the edge of the grinding container 23. After being weighed at the feeding port 241, the discharge valve 242 of the feeding port 241 is closed, and the grinding motor 22 is started. The grinding motor 22 drives the grinding head 25 to rotate. The gap between the bottom of the head 25 and the grinding container 23 gradually decreases from top to bottom, and the raw material is gradually ground and refined in the grinding container 23. After being screened by the screen 231, the qualified particles fall into the clay raw material on the tray 45 below. At this time, the rotating motor 44 is then started to drive the tray 45 to rotate, and the operator shapes the rotating ceramic raw material. After completion, the lifting motor 41 reverses to lower the insulation plate 43 and the upper components back to the initial position, and then the tank cover 14 is closed and locked with the tank body 1 through the buckle 142. The hanging hole 1421 of the buckle 142 corresponds to the tank body 1 The structure is matched to ensure sealing. The temperature sensor 141 on the lower surface of the tank cover 14 monitors the temperature inside the tank in real time. The heat exchanger 12 outside the tank body 1 adjusts the temperature inside the tank body according to the feedback of the temperature sensor 141. Its internal pipeline is connected with the inside of the tank body 1 to realize heat exchange. During baking, the rotating motor 44 can be started in time according to the process requirements to drive the tray 45 to rotate so that the raw materials are heated evenly. The vent hole 131 on the side wall of the inner tank can be connected to various gases such as inert gas as needed. The gas enters the inside of the tank body 1 through the vent hole 131. The sealing ring 13 ensures that the vent hole 131 is sealed to prevent gas leakage. Leakage. After calcination is completed, the tank cover 14 is unlocked through the unlocking mechanism 15, and the button 181 in the socket 18 is pressed. The lower end of the button 181 is rotated to connect the rotating block 182 to overcome the elastic force of the first spring 183 and rotate to release the locking structure of the tank cover 14. The tank cover 14 is opened, and the lifting motor 41 is started again to lift the tray 45 with the ceramic calcined body for easy removal. The resistance rod 11 is welded to the bottom of the tank body 1 and the shock-absorbing spring 111 is surrounded by it. The vibration of the tank body 1 is reduced during the whole process, ensuring the stable operation of each component and the smooth progress of the ceramic calcined body manufacturing process.

[0044] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for manufacturing a ceramic calcined body, comprising a can body (1), characterized in that: The tank body (1) is of cylindrical structure. An inner tank (3) is coaxially arranged inside the tank body (1). The inner tank (3) is of cylindrical structure made of high temperature resistant material. There is a certain gap between the outer wall of the inner tank (3) and the inner wall of the tank body (1). An insulation board (43) is sleeved inside the inner tank (3). The outer edge of the insulation board (43) is tightly fitted to the inner wall of the inner tank (3). A rotating motor (44) is fixedly installed at the center of the upper surface of the insulation board (43). A tray (45) is fixedly installed at the output end of the rotating motor (44) by key connection. The tray (45) is of circular disc structure and is horizontally arranged inside the inner tank (3).

2. The method for manufacturing a ceramic calcined body according to claim 1, characterized in that: A lifting mechanism is provided at the bottom of the tank body (1), the lifting mechanism comprising a lifting motor (41) and a telescopic rod (42), the lifting motor (41) being fixedly mounted at the center position of the bottom of the tank body (1) by means of bolts, the output end of the lifting motor (41) being mounted with the telescopic rod (42), the top of the telescopic rod (42) being fixedly connected to the lower surface of the insulation board (43).

3. The method for manufacturing a ceramic calcined body according to claim 1, characterized in that: A grinding mechanism is provided on one side of the tank body (1), the grinding mechanism comprising a support rod (2), the top end of the support rod (2) being rotatably connected to a rotating frame (21), a grinding motor (22) being fixedly mounted on the upper portion of an end of the rotating frame (21) away from the support rod (2), a grinding container (23) being fixedly mounted on the rotating frame (21) at the lower side of the grinding motor (22), the grinding container (23) being a bowl-shaped structure, a grinding head (25) being fixedly mounted on the output end of the grinding motor (22), and a screen (231) being provided at the bottom of the grinding container (23).

4. The method for manufacturing a ceramic calcined body according to claim 1, characterized in that: A tank cover (14) is arranged on the top of the tank body (1); the tank cover (14) is a circular plate-shaped structure, the edge of which extends downward to form a skirt that matches the top opening of the tank body (1); and a temperature sensor (141) is fixedly mounted on the lower surface of the tank cover (14).

5. The method for manufacturing a ceramic calcined body according to claim 1, characterized in that: The tank body (1) is provided with an unlocking mechanism (15), the unlocking mechanism (15) comprising a socket (18), the socket (18) being opened on the outer wall of the tank body (1), a button (181) being slidably connected in the socket (18), a rotating block (182) being rotatably connected at the lower end of the button (181), a first spring (183) being fixedly connected at the lower end of the rotating block (182), a cushion block (185) being further provided in the socket (18), a second spring (184) being fixedly connected at the lower end of the cushion block (185), the lower ends of the first spring (183) and the second spring (184) being fixedly connected to the outer wall of the tank body (1).

6. The method for manufacturing a ceramic calcined body according to claim 3, characterized in that: A control panel (24) is fixedly mounted on the edge of the grinding container (23); a feeding port (241) is provided on the inner side of the control panel (24); and a discharge valve (242) is rotatably connected to the feeding port (241).

7. The method for manufacturing a ceramic calcined body according to claim 1, characterized in that: A heat exchanger (12) is arranged on the outside of the tank body (1); the heat exchanger (12) is fixedly mounted on the outer wall of the tank body (1) by welding, and an internal pipe of the heat exchanger (12) is connected to the inside of the tank body (1).

8. The method for manufacturing a ceramic calcined body according to claim 1, characterized in that: The side wall of the inner tank (3) is provided with a plurality of vent holes (131), the internal pipes of the vent holes (131) are connected to the inside of the tank body (1), and the vent holes (131) are connected to the outside of the tank body (1) and are fixedly provided with a sealing ring (13).

9. The method for manufacturing a ceramic calcined body according to claim 1, characterized in that: An induction coil (17) is arranged inside the tank body (1), and a plurality of resistance rods (11) distributed in a ring array are fixedly connected to the bottom of the tank body (1) by welding, and a shock absorbing spring (111) surrounds the resistance rod (11), and the upper end of the shock absorbing spring (111) is fixedly installed on the bottom of the tank body (1), and the lower end of the shock absorbing spring (111) is fixedly installed on the ground.

10. The method for manufacturing a ceramic calcined body according to claim 3, characterized in that: The shape of the grinding head (25) is such that the gap between its bottom and the grinding container (23) gradually decreases from top to bottom.

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