Production equipment for synthesizing calcium carbonate through continuous carbonization
Through the design of spiral ventilation tube, conical flow-guiding hollow shaft, ultrasonic vibrator and composite impeller, the problems of uneven gas distribution and slurry deposition in traditional calcium carbonate production are solved, efficient and stable carbonization reaction is achieved, and product quality and production efficiency are improved.
Patent Information
- Application Number
- CN202510842261.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-23
- Publication Date
- 2025-09-12
AI Technical Summary
In traditional calcium carbonate production equipment, lime milk is prone to sedimentation and agglomeration, and CO2 is unevenly distributed, resulting in unstable carbonization reaction and uneven particle size and crystal form of the product calcium carbonate, affecting industrial applications.
The spiral ventilation pipe is combined with the conical guide hollow shaft to form a spiral rising airflow. The ultrasonic vibrator is used to break the bubbles, the composite impeller is used for mixing, and the oblique filter and dynamic cleaning mechanism are designed to achieve uniform gas distribution and automatic slag discharge.
It significantly improves the carbonization reaction efficiency and product particle size uniformity, reduces energy consumption, and realizes continuous, efficient and stable calcium carbonate production, making it suitable for industrial large-scale production.
Smart Images
Figure CN120618397A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of calcium carbonate production, in particular to production equipment for continuous carbonization and synthesis of calcium carbonate. Background Art
[0002] In the industrial calcium carbonate production process, the continuous carbonization synthesis steps of calcium carbonate mainly include raw material preparation, carbonization reaction, process control, post-reaction treatment and tail gas recovery. Among them, the preparation and carbonization reaction of lime milk (Ca(OH)2 slurry) are key links. The traditional method usually involves the digestion reaction of quicklime (CaO) and water to produce lime milk (Ca(OH)2 slurry), which is then transported to a carbonization reactor for calcium carbonate synthesis. However, the physical and chemical properties of lime milk and process limitations have led to a series of technical difficulties, seriously affecting production efficiency and product quality.
[0003] Traditional processes usually rely on mechanical stirring or static mixers to improve slurry uniformity. Due to the difficulty in achieving dynamic optimization of gas distribution through CO2 introduction methods (such as single-point injection or simple distributors), and the easy agglomeration of Ca(OH)2 particles, lime milk is a non-Newtonian fluid, which is prone to solid-liquid separation when left standing, resulting in bottom sedimentation and thin slurry on the upper layer. Especially in large-scale production, the complex fluid dynamics further amplify the negative impact of uneven reaction, resulting in uneven slurry concentration, and then causing poor consistency in particle size and crystal form of the product calcium carbonate, affecting industrial applications and other problems.
[0004] Therefore design a kind of production equipment of continuous carbonization synthetic calcium carbonate. Summary of the Invention
[0005] The present invention addresses the deficiencies in the prior art and provides a production device for continuous carbonization synthesis of calcium carbonate, thereby solving the problems in the prior art of calcium carbonate production equipment, such as the easy sedimentation and agglomeration of lime milk, the uneven distribution of CO2, which leads to unstable carbonization reaction, and uneven particle size and crystal form of the product calcium carbonate, which affect industrial application.
[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A production device for continuous carbonization and synthesis of calcium carbonate, comprising a support frame, a production tank for preparing calcium carbonate fixedly arranged on one side of the support frame, an air intake pipe arranged inside the production tank, a flow guide hollow shaft fixedly sleeved on the outer wall of the air intake pipe, and a composite impeller fixedly arranged axially on the outer wall of the flow guide hollow shaft; An air inlet is fixedly provided on one end of the air inlet pipe located outside the production tank, and a spiral ventilation pipe connected thereto is fixedly provided on the outer wall of the air inlet pipe. The spiral ventilation pipe is located inside the guide hollow shaft, and the surfaces of the spiral ventilation pipe and the guide hollow shaft are both provided with a plurality of micro through holes for transmitting gas, and an ultrasonic vibrator is installed inside the micro through holes.
[0007] Preferably, the air inlet pipe passes through the top of the production tank, and a motor is fixedly provided on the top of the air inlet pipe. The motor is fixedly connected to the production tank, and the motor is used to drive the air inlet pipe to rotate.
[0008] Preferably, the bottom of the flow-guiding hollow shaft is conical in shape, and the diameter of the bottom gradually increases, so as to convert the concentrated airflow into a radially uniform distribution to avoid slurry deposition.
[0009] Preferably, the compound impeller includes a propeller impeller, a sawtooth disc turbine and a pitched blade turbine, and the three are distributed from bottom to top on the guide hollow shaft.
[0010] Preferably, the propulsion impeller has swept-back blades and is used to promote macroscopic mixing of the slurry, the serrated disc turbine is provided with a plurality of radial serrations and is used to saw-cut and microscopically break bubbles, and the blades of the pitched blade turbine are beveled and are used to stabilize the liquid surface and prevent vortices.
[0011] Preferably, a feed port and a slag discharge pipe are respectively provided on the top and side wall of the production tank, a circular plate is fixedly provided on the inner wall of the production tank, a filter is provided on the top of the circular plate, and the filter is used to filter the introduced lime milk slurry.
[0012] Preferably, an insertion groove is provided on one side of the circular plate, and a partition ring is fixedly provided on the bottom of the circular plate, and the partition ring is used to isolate the slurry.
[0013] Preferably, the filter screen is arranged obliquely, and the lower side is close to the slag discharge pipe. A rubber ring is fixedly provided on the outer wall of the filter screen. The side of the rubber ring away from the insertion groove is hinged to the inner wall of the production tank, and the side of the rubber ring close to the insertion groove is in contact with the circular ring plate.
[0014] Preferably, a connecting rod is fixedly provided on the top of the inclined-blade turbine, a driving inclined block is fixedly installed on the top of the connecting rod, one side of the inclined surface of the driving inclined block abuts against an extrusion rod, a movable plate is fixedly provided on the bottom of the extrusion rod, a return spring fixedly connected to the inner wall of the production tank is fixedly installed on the movable plate, and the side of the extrusion rod away from the driving inclined block abuts against a lifting inclined block.
[0015] Preferably, a limiting slide is fixedly provided on the inner wall of the production tank, and the movable plate is slidably connected to the limiting slide.
[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention forms a spiral rising airflow through the synergistic effect of the spiral vent pipe and the conical guide hollow shaft, prolongs the gas residence time and achieves radially uniform distribution. After the CO2 gas enters the air inlet pipe from the air inlet, a spiral rising airflow is formed inside the guide hollow shaft through the spiral vent pipe. Compared with the traditional straight-through air intake method, this spiral airflow path significantly prolongs the residence time of the gas in the system and improves the gas utilization rate. The conical expansion design at the bottom of the guide hollow shaft converts the concentrated airflow into a radially uniformly distributed flow field, effectively avoiding the slurry deposition problem common in traditional equipment. Combined with the ultrasonic vibrator, the bubbles are broken into micron level, which increases the gas-liquid contact area by 3-5 times. This structure solves the traditional problems of uneven gas distribution and slurry deposition, significantly improves the carbonization efficiency, makes the product particle size more uniform, and greatly reduces the energy consumption, providing an efficient and stable technical solution for the industrial production of high-quality calcium carbonate. The present invention integrates three impellers with different functions (propeller impeller, serrated disc turbine, and pitched blade turbine) on the same hollow guide shaft through the design of a composite impeller, forming a synergistic mixing system that simultaneously meets the requirements of mixing, crushing, and stabilization. The radial serrated structure of the serrated disc turbine improves the bubble crushing efficiency by more than 50% compared to the traditional smooth disc turbine, and the serration spacing is optimized to ensure uniform distribution of bubble size. The three-stage impeller adopts a bottom-up functional gradient arrangement, which conforms to the principles of fluid mechanics and solves technical problems such as uneven mixing, excessive bubble size, and high energy consumption in the traditional calcium carbonate production process. In particular, the synergistic effect of the serrated disc turbine and the ultrasonic vibrator has significant advantages in the generation of micro-nano bubbles, which is a prominent feature not possessed by the existing technology. The present invention realizes automatic slag discharge and anti-blocking through the combination of an oblique filter screen and a dynamic cleaning mechanism. The driving oblique block and the return spring are linked to each other to automatically trigger the vibration of the filter screen in conjunction with the stirring power. No additional energy input is required, which is energy-saving and efficient. At the same time, the rubber ring hinge and abutment structure not only ensure the sealing, but also allow the filter screen to swing slightly to assist in slag discharge. Compared with rigid fixation, it is more suitable for high-solid content slurry, realizes the continuity and automation of filtration and slag discharge in the calcium carbonate production process, reduces equipment maintenance costs, and improves production stability. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. 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 any creative work.
[0018] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a schematic diagram of the three-dimensional structure of the production tank of the present invention; Figure 3 This is a schematic diagram of the cross-sectional three-dimensional structure of the production tank of the present invention; Figure 4 For the present invention Figure 3 A magnified schematic diagram of the local structure at center A; Figure 5 Schematic diagram of the structural coordination relationship between the air intake pipe and the flow guide hollow shaft of the present invention; Figure 6 Schematic diagram of the composite impeller structure of the present invention; Figure 7 Schematic diagram of the structure coordination between the filter screen and the circular ring plate of the present invention; Figure 8 It is a schematic diagram of the structural coordination relationship between the driving inclined block and the lifting inclined block of the present invention.
[0019] Explanation of the figure numbers: 1. Support frame; 2. Production tank; 21. Feed port; 22. Slag discharge pipe; 23. Circular ring plate; 231. Insertion groove; 232. Partition ring; 24. Limit slide; 3. Inlet pipe; 31. Inlet port; 32. Spiral vent pipe; 33. Motor; 4. Diversion hollow shaft; 5. Compound impeller; 51. Propeller impeller; 52. Sawtooth disc turbine; 53. Pitched blade turbine; 531. Driving ramp; 532. Extrusion rod; 533. Return spring; 534. Lifting ramp; 6. Filter; 61. Rubber ring. DETAILED DESCRIPTION
[0020] The present invention will be described in further detail below with reference to the accompanying drawings.
[0021] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are for illustrative purposes only, and those skilled in the art will readily appreciate other obvious variations. The basic principles of the present invention defined in the following description may be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present invention.
[0022] Those skilled in the art should understand that, in the disclosure of the present invention, the terms "longitudinal", "transverse", "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like to indicate directions or positions are based on the directions or positional relationships shown in the accompanying drawings, which are merely simplified descriptions for the convenience of describing the present invention, and do not indicate or imply that the device or component referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the above terms should not be understood as limiting the present invention.
[0023] It is understandable that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.
[0024] See also Figure 1-8 A production device for continuous carbonization and synthesis of calcium carbonate, comprising a support frame 1, a production tank 2 for preparing calcium carbonate fixedly mounted on one side of the support frame 1, an air inlet pipe 3 disposed inside the production tank 2, a flow guide hollow shaft 4 fixedly sleeved on the outer wall of the flow guide hollow shaft 4, and a composite impeller 5 fixedly mounted along the axial direction on the outer wall of the flow guide hollow shaft 4; An air inlet 31 is fixedly provided on one end of the air inlet pipe 3 located outside the production tank 2, and a spiral vent pipe 32 connected thereto is fixedly provided on the outer wall of the air inlet pipe 3, and the spiral vent pipe 32 is located inside the guide hollow shaft 4. The surfaces of the spiral vent pipe 32 and the guide hollow shaft 4 are both provided with a plurality of micro through holes for transmitting gas, and an ultrasonic vibrator is installed inside the micro through holes. The air inlet pipe 3 passes through the top of the production tank 2, and a motor 33 is fixedly provided on the top of the air inlet pipe 3. The motor 33 is fixedly connected to the production tank 2, and the motor 33 is used to drive the air inlet pipe 3 to rotate. The bottom of the guide hollow shaft 4 is conical, and the bottom diameter gradually increases, which is used to convert the concentrated airflow into a radially uniform distribution to avoid slurry deposition. The production equipment for continuous carbonization and synthesis of calcium carbonate described in the present application significantly improves the carbonization efficiency and product quality of calcium carbonate by optimizing the gas distribution and stirring structure. Specifically, the gas first enters the axial cavity of the guide hollow shaft 4 through the wall hole of the spiral vent pipe 32, and then diffuses through the upper wall hole of the guide hollow shaft 4. The air inlet pipe 3 passes through the top of the production tank 2 and is connected to the motor 33 to drive the guide hollow shaft 4 and the composite impeller 5 to rotate, thereby realizing efficient mixing of the slurry. The surfaces of the spiral vent pipe 32 and the guide hollow shaft 4 are both provided with micro through holes and ultrasonic vibrators are installed to form micro-nano bubbles of CO2 gas in the slurry, greatly increasing the gas-liquid contact area and enhancing the carbonization reaction rate. The spiral vent pipe 32 extends the gas flow path, so that CO2 can be pre-distributed in the shaft to avoid concentrated injection. Compared with the prior art, the main distinguishing features and advantages of the present application are: The bottom of the guide hollow shaft 4 is conical and the diameter gradually increases, so that the airflow changes from concentrated distribution to radial uniform diffusion, avoiding slurry deposition and improving reaction uniformity; the spiral ventilation tube 32 and the guide hollow shaft 4 are combined with an ultrasonic vibrator, which can produce smaller bubbles than traditional aeration methods, reduce gas escape, and improve carbonization efficiency. The rotary gas distribution effectively prevents slurry deposition and ensures the stability of continuous production. This design increases the carbonization reaction efficiency by more than 40%, makes the product particle size distribution more uniform, and reduces energy consumption by more than 30%, providing a reliable technical solution for the industrial production of high-quality calcium carbonate. Through the above-mentioned innovative design, this application solves the problems of uneven gas distribution, low mixing efficiency, and easy deposition in the traditional calcium carbonate production process, and realizes a continuous, efficient and stable carbonization reaction, which is suitable for industrial large-scale production.
[0025] See also Figure 6 The compound impeller 5 includes a propeller impeller 51, a sawtooth disc turbine 52 and a pitched blade turbine 53, and the three are distributed from bottom to top on the guide hollow shaft 4. The propeller impeller 51 has swept blades and is used to promote macroscopic mixing of the slurry. The sawtooth disc turbine 52 is provided with multiple radial saw teeth and is used to sawtooth cut and break microscopic bubbles. The blades of the pitched blade turbine 53 are inclined and are used to stabilize the liquid surface and prevent vortexes. This application achieves the integration of multiple functions of slurry mixing, bubble breaking and flow field stabilization through the innovative structural design of the composite impeller 5, significantly improving the efficiency and uniformity of the carbonization reaction. The specific working principle is as follows: through the synergistic mechanism of the three-stage impeller, the mixing efficiency is improved. The propulsion impeller 51 adopts a swept-back blade design and is located at the bottom end of the guide hollow shaft 4. It mainly generates axial flow, promotes macroscopic mixing of the slurry, and ensures sufficient circulation of the reaction materials in the vertical direction. Its unique swept-back blades can reduce energy consumption and save more than 15% energy compared to traditional straight-blade impellers; the serrated disc turbine 52 is located in the middle position. Its radial serrated structure generates strong shear force when rotating at high speed, which can cut the introduced CO2 bubbles into micron-sized bubbles, increase the gas-liquid contact area by 3-5 times, and significantly improve the carbonization reaction rate. The sharp angle design of the sawtooth (preferably 45-60 degrees) can further enhance the bubble breaking effect; the inclined blade turbine 53 is arranged at the top end, and its inclined blades can effectively suppress the formation of liquid surface vortexes and maintain a stable flow field of the reaction system. Compared with a single impeller mechanism, this arrangement can reduce liquid surface fluctuations by more than 30%.
[0026] See also Figure 7-8 , a feed port 21 and a slag discharge pipe 22 are respectively provided on the top and side wall of the production tank 2, a circular plate 23 is fixedly provided on the inner wall of the production tank 2, a filter screen 6 is provided on the top of the circular plate 23, and the filter screen 6 is used to filter the introduced lime milk slurry, a placement groove 231 is provided on one side of the circular plate 23, a partition ring 232 is fixedly provided on the bottom of the circular plate 23, and the partition ring 232 is used to isolate the slurry, the filter screen 6 is arranged obliquely, and the lower side is close to the slag discharge pipe 22, and a rubber ring 61 is fixedly provided on the outer wall of the filter screen 6, the side of the rubber ring 61 away from the placement groove 231 is hinged to the inner wall of the production tank 2, and the side of the rubber ring 61 close to the placement groove 231 is in contact with the circular plate 23; Through the innovative filtering and slag discharge structure and dynamic cleaning mechanism, the problems of easy clogging of filter screen 6 and incomplete slag discharge in the traditional carbonization reaction process are effectively solved, which significantly improves production efficiency and product quality. Specifically, in the calcium carbonate production process, filtering the slurry when stirring the lime milk is a key pretreatment step. When low-grade limestone is used or the digestion process is imperfect, the slurry may contain undigested CaO particles, insoluble matter such as sand and gravel, fly ash, and metal impurities such as rust, which affect the purity of the subsequent calcium carbonate preparation. Therefore, it is particularly important to filter and discharge the slurry before mixing it with carbon dioxide. Through the hinged design of the inclined filter screen 6 and the rubber ring 61, the filter screen 6 can automatically clean the sediment. When the lime milk slurry enters from the feed port 21, the filter screen 6 filters out large particles of impurities, and the inclined setting makes its lower end close to the slag discharge pipe 22. Impurities naturally slide to the slag discharge port under the action of gravity, reducing the probability of accumulation and blockage. The design of the insertion groove 231 and the partition ring 232 ensures that the filter screen 6 fits tightly with the circular ring plate 23, while allowing the filter screen 6 to be maintained or replaced when necessary, which is easier to operate than traditional fixed filters.
[0027] A connecting rod is fixedly provided on the top of the inclined-blade turbine 53, and a driving inclined block 531 is fixedly installed on the top of the connecting rod. An extrusion rod 532 abuts on one side of the inclined surface of the driving inclined block 531. A movable plate is fixedly provided on the bottom of the extrusion rod 532. A return spring 533 fixedly connected to the inner wall of the production tank 2 is fixedly installed on the movable plate. A lifting inclined block 534 abuts on the side of the extrusion rod 532 away from the driving inclined block 531. A limiting slide 24 is fixedly provided on the inner wall of the production tank 2, and the movable plate is slidably connected to the limiting slide 24. A dynamic anti-blocking mechanism is used to reduce the probability of blockage of the filter 6. When the inclined-blade turbine 53 rotates, the driving inclined block 531 is driven to rotate through the connecting rod. The inclined surface of the driving inclined block 531 periodically pushes the extrusion rod 532, causing the movable plate to slide along the limiting slide 24, thereby compressing the reset spring 533. When the driving inclined block 531 is disengaged from the extrusion rod 532, the reset spring 533 pushes the movable plate to reset, causing the lifting inclined block 534 to act in the opposite direction, forming a reciprocating motion. This mechanism can indirectly vibrate the filter 6 to prevent the filter holes from being blocked. Compared with traditional static filtration methods, the frequency of manual cleaning is greatly reduced.
[0028] Those skilled in the art will appreciate that the embodiments of the present invention described above and shown in the accompanying drawings are intended only as examples and are not intended to limit the present invention. The objectives of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and illustrated in the embodiments. Any variations or modifications may be made to the embodiments of the present invention without departing from the principles described.
Claims
1. A production equipment for continuous carbonization synthesis of calcium carbonate, characterized in that, It comprises a support frame (1), a production tank (2) for preparing calcium carbonate fixedly arranged on one side of the support frame (1), an air intake pipe (3) arranged inside the production tank (2), a flow guide hollow shaft (4) fixedly sleeved on the outer wall of the flow guide hollow shaft (3), and a composite impeller (5) fixedly arranged on the outer wall of the flow guide hollow shaft (4) in the axial direction; An air inlet (31) is fixedly provided on one end of the air inlet pipe (3) located outside the production tank (2), and a spiral vent pipe (32) connected thereto is fixedly provided on the outer wall of the air inlet pipe (3). The spiral vent pipe (32) is located inside the guide hollow shaft (4), and a plurality of micro-through holes for transmitting gas are provided on the surfaces of the spiral vent pipe (32) and the guide hollow shaft (4), and an ultrasonic vibrator is installed inside the micro-through holes.
2. The production equipment for continuous carbonization and synthetic calcium carbonate according to claim 1, characterized in that: The air intake pipe (3) passes through the top of the production tank (2). A motor (33) is fixedly provided on the top of the air intake pipe (3). The motor (33) is fixedly connected to the production tank (2). The motor (33) is used to drive the air intake pipe (3) to rotate.
3. The production equipment for continuous carbonization and synthesis of calcium carbonate according to claim 2, characterized in that: The bottom of the flow-guiding hollow shaft (4) is in a conical shape, and the bottom diameter gradually increases, so as to convert the concentrated airflow into a radially uniform distribution and avoid slurry deposition.
4. The production equipment for continuous carbonization and synthesis of calcium carbonate according to claim 3, characterized in that: The composite impeller (5) comprises a propulsion impeller (51), a sawtooth disc turbine (52) and a pitched blade turbine (53), and the three are distributed from bottom to top on the guide hollow shaft (4).
5. The production equipment for continuous carbonization and synthetic calcium carbonate according to claim 4, characterized in that: The propulsion impeller (51) has swept-back blades and is used to promote macroscopic mixing of the slurry. The sawtooth disc turbine (52) is provided with a plurality of radial saw teeth and is used to sawtooth cut and break up microscopic bubbles. The blades of the pitched blade turbine (53) are in the shape of a slope and are used to stabilize the liquid surface and prevent vortexes.
6. The production equipment for continuous carbonization and synthetic calcium carbonate according to claim 5, characterized in that: A feed port (21) and a slag discharge pipe (22) are respectively provided on the top and side wall of the production tank (2), a circular plate (23) is fixedly provided on the inner wall of the production tank (2), and a filter screen (6) is provided on the top of the circular plate (23), and the filter screen (6) is used to filter the introduced lime milk slurry.
7. The production equipment for continuous carbonization and synthesis of calcium carbonate according to claim 6, characterized in that: An insertion groove (231) is provided on one side of the circular ring plate (23), and a partition ring (232) is fixedly provided on the bottom of the circular ring plate (23), and the partition ring (232) is used to isolate the slurry.
8. The production equipment for continuous carbonization and synthetic calcium carbonate according to claim 7, characterized in that: The filter screen (6) is arranged obliquely, and the lower side is close to the slag discharge pipe (22). A rubber ring (61) is fixedly arranged on the outer wall of the filter screen (6). The side of the rubber ring (61) away from the insertion groove (231) is hinged to the inner wall of the production tank (2), and the side of the rubber ring (61) close to the insertion groove (231) is in contact with the circular ring plate (23).
9. The production equipment for continuous carbonization and synthetic calcium carbonate according to claim 4, characterized in that: A connecting rod is fixedly provided on the top of the inclined blade turbine (53), a driving inclined block (531) is fixedly installed on the top of the connecting rod, an extrusion rod (532) is abutted on one side of the inclined surface of the driving inclined block (531), a movable plate is fixedly provided on the bottom of the extrusion rod (532), a return spring (533) fixedly connected to the inner wall of the production tank (2) is fixedly installed on the movable plate, and a lifting inclined block (534) is abutted on the side of the extrusion rod (532) away from the driving inclined block (531).
10. The production equipment for continuous carbonization and synthetic calcium carbonate according to claim 9, characterized in that: A limiting slideway (24) is fixedly provided on the inner wall of the production tank (2), and the movable plate is slidably connected to the limiting slideway (24).