A multi-mode low-temperature baking process for tea leaves and a special device

Abstract

This invention belongs to the field of tea processing technology, specifically a multi-mode low-temperature roasting process and dedicated equipment for tea. The process includes placement, initial roasting, re-roasting for aroma fixation, and frying stages. Initial roasting is conducted in a closed environment with periodic negative pressure, drawing moisture from the tea stems to the surface and releasing hot, humid air and aroma. The released gas is condensed and dried before being returned to the closed environment to dry the tea leaves from below. Finally, the drying gas forms a pulsed airflow, propelling the tea leaves to tumble and complete the roasting process. The dedicated equipment includes a negative pressure structure, an aroma-fixing structure, and a drying structure. The negative pressure structure changes the internal volume of the shell through the reciprocating expansion and contraction of a metal bellows, creating alternating pressure. The aroma-fixing structure includes a cooling box for condensing moisture and recovering the dried aroma. The drying structure includes an exhaust plate with vents and a disc linked to a rotating rod. This design improves the uniformity and efficiency of dehydration at low temperatures, helping to maintain the shape and aroma of the tea leaves.

Description

Technical Field

[0001] This invention relates to the field of tea processing technology, and in particular to a multi-mode low-temperature roasting process for tea and a dedicated equipment. Background Technology

[0002] Tea roasting (for aroma enhancement) is a crucial step in tea processing. Its core function is to remove excess moisture from the tea leaves through heat, promoting the thermal transformation of internal substances to create a unique aroma and fixing the tea's shape. As consumers' demands for tea quality increase, low-temperature roasting has gradually become mainstream due to its ability to effectively preserve the tea's active enzymes, chlorophyll, and volatile aromatic compounds.

[0003] However, existing low-temperature tea roasting technologies and equipment still face the following technical problems in practical applications: 1. Tea leaves are a heterogeneous porous medium. The leaves are thin with a large surface area, making moisture evaporate very easily. In contrast, tea stems have a denser structure, with moisture located deeper within the stem, resulting in greater resistance to migration. In existing low-temperature roasting methods (such as heat pump drying and static hot air roasting), the lack of a strong internal pressure gradient means that the rate of moisture migration from the center of the stem to the surface is far lower than the rate of evaporation from the leaf surface. This leads to a serious process contradiction: if leaf drying is used as the standard, the tea stems often still contain a significant amount of moisture (i.e., "false drying"), making the finished product prone to dampness and mold during storage; if stem drying is used as the standard and the roasting time is extended, the already dried leaves will lose all aroma due to prolonged heating, and may even undergo over-drying and carbonization, severely affecting quality.

[0004] 2. While some existing technologies incorporate vacuum drying or negative pressure drying to lower the boiling point of moisture, these devices typically employ industrial vacuum pumps to maintain a constant negative pressure. Although constant negative pressure lowers the boiling point, as drying progresses, the micropores inside the tea leaves shrink and close, gradually reducing the outward migration of moisture under constant pressure. The lack of periodic pressure changes to continuously "squeeze" and "draw" moisture out of the tea stems leads to a significant decrease in dehydration efficiency in the later stages. Furthermore, industrial vacuum pumps are energy-intensive and noisy, making them unsuitable for small- to medium-sized continuous tea processing.

[0005] 3. To ensure even roasting, the tea leaves must be turned over. Traditional roasting machines mostly use mechanical structures (such as spiral stirring, reciprocating rake teeth, and rotating drums). However, in the later stages of roasting, the tea leaves lose moisture and become brittle. Direct contact, compression, and friction between mechanical parts can easily cause the tea leaves to break, producing a large amount of broken tea and tea dust, thus reducing the grade of the finished tea. While airflow bed drying can avoid mechanical contact, ordinary constant airflow can easily form "channels" or "wind tunnels" in the material layer, causing airflow short-circuiting. Most of the tea leaves cannot be effectively blown up and turned over, and drying dead zones still exist.

[0006] 4. During the tea roasting process, as moisture evaporates, a large amount of low-boiling-point aromatic substances are released along with the hot and humid air. Most existing equipment directly discharges the exhaust gas into the atmosphere, which not only causes heat loss but also means that the most essential "top aroma" of the tea is wasted, resulting in insufficient aroma saturation in the final product. Summary of the Invention

[0007] This invention addresses the problem of aroma loss and morphological damage caused by traditional high-temperature roasting in tea processing. Starting with low-temperature control, it was observed that moisture migrates slowly into deeper layers, so physical negative pressure was introduced to promote dehumidification. It was also discovered that aroma is wasted during exhaust, so a closed-loop condensation and recovery system was designed. To avoid mechanical crushing during stir-frying, the principle of airflow dynamics was used to develop a pulsed airflow system that simulates manual movements. The negative pressure and recovery work together to reduce energy consumption and improve aroma adhesion. The pulsed airflow ensures uniform drying and prevents the formation of broken pieces.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A multi-mode low-temperature roasting process for tea includes the following steps: S1. Placement stage: Spread the washed and dried tea leaves evenly on the sieve, with a thickness of 2-3cm. S2, Initial Drying Stage: Place the tea leaves in a closed environment at 50-70℃ for initial drying to quickly remove surface moisture and fix the shape of the tea leaves; S2.1 During the initial roasting, reduce the air pressure in the enclosed environment in step S2 to draw the moisture inside the tea stems to the surface, and then expel the extracted hot and humid air and tea aroma for 5-10 minutes. S3, Re-drying and Aroma Fixing Stage: The temperature is reduced to 30-40℃. The hot and humid air extracted in step S2.1 and the aroma of the tea leaves are condensed and dried. Then the dried gas is reinjected into the closed environment in step S2. The dried gas dries the tea leaves in the sieve from below, and the time is extended to 15-30 minutes. S4. Stir-frying stage: The dry gas blown out in step S3 forms a pulsed airflow, which tumbles the tea leaves on the sieve, so that the tea leaves are evenly roasted. This process lasts for 1-2 hours.

[0009] A special equipment for multi-mode low-temperature roasting of tea, used to roast tea according to the above-mentioned multi-mode low-temperature roasting process, includes: The shell has a hinged door on one side; A placement frame, disposed within the housing, is used to support multiple screens. The placement frame includes two support columns and three U-shaped frames. The two support columns are rotatably connected to the top inner wall and bottom inner wall of the housing, respectively. The two ends of the three U-shaped frames are fixedly connected to the outer walls of the two support columns, respectively. Multiple vertically arranged support frames are fixedly connected between the three U-shaped frames. The support frames are used to support the screens. A negative pressure structure is used to create a negative pressure inside the housing. The negative pressure structure includes a metal bellows fixed to the top of the housing and a lifting plate fixed to the top of the metal bellows. A fragrance-fixing structure is used to dry the exhaust gas and re-inject it into the housing. The fragrance-fixing structure includes a cooling box fixed to one side of the housing and an annular plate fixed to the inner wall of the bottom of the housing. A drying structure, disposed at the bottom of the support frame, is used to dry the tea leaves from below using the drying gas discharged from the aroma-fixing structure. The drying structure includes an air outlet plate fixed to the bottom of the support frame.

[0010] In one possible design, the negative pressure structure further includes multiple vertical holes opened on the top of the housing, an annular cylinder fixed on the top of the housing, and a protective cylinder. The housing is connected to a metal bellows through the vertical holes, the lifting plate is slidably disposed in the annular cylinder, and the protective cylinder is located in the metal bellows. A rotating shaft is rotatably passed through the protective cylinder. A bevel gear I is fixedly sleeved on the outer wall of the rotating shaft. The top of the bearing column located above extends rotatably into the protective cylinder and is fixed with a bevel gear II that meshes with the bevel gear I. Cams are fixed at both ends of the rotating shaft, and pins are fixed at the eccentric positions of the cams. Two lifting frames are provided below the lifting plate, and sliding grooves are opened in the lifting frames. One end of the pin extends into the sliding groove and slides with it. The top of the lifting frame is fixedly connected to the bottom of the lifting plate through multiple connecting rods. A suction hose is fixedly inserted through the top of the lifting plate, and the bottom end of the suction hose extends into the cooling box. A one-way valve is installed inside the suction hose.

[0011] In one possible design, the fragrance fixing structure also includes an air pump and a fixing plate. The air pump is fixed to one side of the housing by a frame, and its air inlet is connected to a cooling box through a first hose. The cooling box is provided with a cooling chamber. The fixed disk is fixedly sleeved on the outer wall of the supporting column located below. The fixed disk is provided with an annular groove I. The annular plate is rotatably sleeved on the outer wall of the fixed disk. The inner wall of the annular plate and the outer wall of the fixed disk are respectively provided with an annular connecting groove, so that the annular plate and the annular groove I are connected. The air outlet of the air pump is fixedly connected to the annular plate via a second flexible hose; a conduit is fixedly passed through the top of the fixed plate, and the conduit is connected to the annular groove I; the top end of the conduit is fixedly connected to the bottom end of a vertical pipe fixed on one side of one of the U-shaped frames.

[0012] In one possible design, the drying structure further includes a connecting pipe, the two ends of which are fixedly connected to the bottom of the air outlet plate and the vertical pipe, respectively; the top of the air outlet plate is provided with multiple air outlet holes; A rotating rod is rotatably inserted inside the support frame. A support circular plate is fixed to the top of the rotating rod. The bottom of the rotating rod extends rotatably and is sealed to the air outlet plate and is fixed to a disc. The disc is rotatably and is sealed to the bottom inner wall of the air outlet plate. Multiple clearance holes are provided on the disc. When the clearance hole is aligned with the connecting pipe, the dry gas is injected into the outlet plate.

[0013] In one possible design, a screen drive structure is also included, which comprises three round rods, multiple rubber wheels, a gear ring, and three spur gears. The three round rods rotate through the three U-shaped frames and multiple support frames respectively, and the multiple rubber wheels are fixedly sleeved on the outer wall of the round rods and in contact with the outer wall of the screen. The bottom inner wall of the housing is provided with an annular groove II, and the gear ring is fixed to the bottom inner wall of the annular groove II; the three spur gears are respectively fixed to the bottom ends of the three round rods and located in the annular groove II, and mesh with the gear ring.

[0014] In one possible design, the top of the support frame is provided with a plurality of ball bearings that are rolled on a vertical rod, the top of which is flush with the top of the support circular plate.

[0015] In one possible design, the outer wall of the screen is fixed with a plurality of rubber strips, which are in contact with the rubber wheel.

[0016] One possible design also includes a drive motor, multiple heating plates, a temperature sensor, and a control panel; The drive motor is fixed to the bottom of the housing, and its output shaft is fixedly connected to the bottom end of the support column located below; the multiple heating plates are fixed to the inner wall of the housing; the temperature sensor is fixed to one side of the housing; the control panel is fixed to one side of the compartment door and is electrically connected to the heating plates, drive motor, temperature sensor and air pump.

[0017] In one possible design, a closed ring is slidably connected within the annular groove II, and the bottom ends of the plurality of round rods rotate through the closed ring.

[0018] Beneficial effects: In this invention, a segmented low-temperature baking strategy is adopted. In the initial baking stage, the temperature range of 50-70℃ can quickly remove the surface moisture of the tea leaves and fix their shape. At the same time, the negative pressure effect draws the deep moisture inside the tea stems to the surface, avoiding the problem of deep moisture being difficult to remove in traditional low-temperature baking and reducing the possibility of mold growth during tea storage. In the re-baking and aroma-fixing stages, the temperature is reduced to 30-40℃, reducing the risk of loss of tea nutrients and excessive volatilization of aroma. Meanwhile, the exhaust aroma gases are condensed and dried before being reintroduced into the baking environment to achieve aroma recovery and re-attachment, improving the aroma concentration and persistence of the tea. In the stir-frying stage, the tea leaves are tumbled by pulsed airflow, and the rotation of the screen ensures that the tea leaves are evenly exposed to airflow and heat, avoiding uneven drying or over-drying and ensuring the consistency of tea quality. In this invention, the negative pressure structure uses a combination of a metal corrugated pipe and a lifting plate. The lifting plate moves up and down reciprocally through mechanical transmission, creating physical negative pressure by utilizing volume changes. This eliminates the need for an additional vacuum pump, simplifying the structure and reducing energy consumption. The negative pressure structure and the placement rack share a drive motor, with power transmission achieved through bevel gear transmission. This allows the negative pressure operation to be synchronized with the rotation of the placement rack, improving operational coordination. The aroma-fixing structure uses a cooling box for condensation and dehydration, and an air pump for recovery and transport, creating a closed-loop airflow system to reduce aroma waste. At the same time, drying gas is blown from the bottom, specifically addressing the problem of insufficient drying at the bottom of the tea leaves. In this invention, the combination of the disc and the connecting pipe forms a pulsed airflow, eliminating the need for an additional pulse generator. This is achieved simply by the rotation of the screen driving the disc to rotate, resulting in a compact structure and stable operation. The pulsed airflow causes the tea leaves to tumble, replacing the traditional metal stirring paddle and avoiding mechanical compression that could damage the shape of the tea leaves, thus ensuring their integrity. The revolution of the placement rack, along with the cooperation of the round rod, gear ring, and spur gear, enables the screen to rotate, allowing the tea leaves to move in three-dimensional space and further improving the uniformity of roasting. In this invention, the tea aroma mixture discharged along with moisture during the initial drying stage is guided to a cooling box for condensation and drying treatment, separating the moisture and retaining the dried aroma components. Subsequently, these dried, low-temperature aromas are reinjected into the roasting cavity by an air pump and blown upwards from the bottom of the tea leaves. In the low-temperature environment of the re-drying stage, these aroma molecules that might otherwise be lost have the opportunity to re-contact and physically adsorb onto the surface of the tea leaves. This process reduces the net aroma loss rate in the entire roasting process, allowing tea made using the low-temperature process to still retain a sufficient and elegant aroma.

[0019] In this invention, the negative pressure structure utilizes volume change to improve deep dehydration efficiency, quickly removes surface moisture and fixes the shape; the aroma-fixing structure re-injects the dried humid air and aroma to prevent aroma loss and also dries the tea leaves from the bottom; the drying structure forms a pulsed airflow to ensure uniform roasting of the tea leaves, simulating the action of hand-stirring tea, avoiding mechanical crushing, and improving the uniformity and quality of tea roasting as a whole, meeting the roasting needs of different teas. Attached Figure Description

[0020] Figure 1 A three-dimensional structural schematic diagram of a special equipment for multi-mode low-temperature roasting of tea provided by the present invention; Figure 2 This is a three-dimensional exploded structural diagram of a special equipment for multi-mode low-temperature roasting of tea provided by the present invention. Figure 3 A three-dimensional structural diagram of the U-shaped frame, cooling box, and annular plate of a special equipment for multi-mode low-temperature roasting of tea provided by the present invention; Figure 4 A three-dimensional structural diagram of the U-shaped frame, support frame, and support column of a special equipment for multi-mode low-temperature roasting of tea provided by the present invention; Figure 5 A three-dimensional exploded view of the screen, support frame, and air outlet plate of a special equipment for multi-mode low-temperature roasting of tea provided by the present invention; Figure 6 This is a partial three-dimensional cross-sectional view of the support frame and air outlet plate of a special equipment for multi-mode low-temperature tea roasting provided by the present invention. Figure 7 This is a three-dimensional cross-sectional view of the shell and annular cylinder of a special equipment for multi-mode low-temperature roasting of tea provided by the present invention; Figure 8 This is a three-dimensional exploded structural diagram of the cam, lifting frame, and supporting column of a special equipment for multi-mode low-temperature roasting of tea provided by the present invention. Figure 9 A three-dimensional exploded structural diagram of the fixed plate, air pump, and cooling box of a special equipment for multi-mode low-temperature roasting of tea provided by the present invention; Figure 10 This is a three-dimensional cross-sectional view of the fixed plate and the annular plate of a special equipment for multi-mode low-temperature roasting of tea provided by the present invention. Figure 11 A three-dimensional exploded structural diagram of the closed ring, spur gear, and gear ring of a special equipment for multi-mode low-temperature roasting of tea provided by the present invention; Figure 12 This is a physical image of a special equipment for multi-mode low-temperature roasting of tea provided by the present invention.

[0021] In the diagram: 1. Shell; 2. Door; 3. Control panel; 4. Sealing ring; 5. Support column; 6. U-shaped frame; 7. Support frame; 8. Screen; 9. Annular cylinder; 10. Lifting plate; 11. Corrugated metal pipe; 12. Protective cylinder; 13. Rotating shaft; 14. Bevel gear I; 15. Bevel gear II; 16. Cam; 17. Pin; 18. Lifting frame; 19. Sliding groove; 20. Connecting rod; 21. Suction hose; 22. Cooling box; 23. Air pump; 24. 25. Fixed plate; 26. Annular groove I; 27. Annular plate; 28. Annular connecting groove; 29. ​​Vertical pipe; 30. Conduit; 31. Air outlet plate; 32. Air outlet hole; 33. Rotating rod; 34. Bearing circular plate; 35. Ball bearing; 36. Disc; 37. Clearance hole; 38. Connecting pipe; 39. Round rod; 40. Rubber wheel; 41. Rubber strip; 42. Annular groove II; 43. Closed ring; 44. Gear ring; 45. Spur gear; 46. Drive motor; 47. Heating plate. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0023] In one embodiment: a multi-mode low-temperature roasting process for tea includes the following steps: S1. Placement stage: The tea leaves to be roasted, which have been washed and thoroughly dried, are evenly spread on the sieve 8 of the special equipment. The thickness of the tea layer is controlled between 2-3 cm. This thickness range ensures that the airflow in the subsequent stage can effectively penetrate the tea layer, while avoiding incomplete drying of the tea leaves inside due to excessive thickness. S2. Initial drying stage: The sieve 8 carrying the tea leaves is placed inside a closed shell 1. The heating plate 46 is activated to raise the ambient temperature inside the shell 1 and maintain it between 50 and 70 degrees Celsius. At this temperature, the tea leaves are initially dried. The main purpose of this stage is to quickly remove the moisture attached to the surface of the tea leaves and use heat to initially fix the shape of the tea leaves to prevent excessive deformation of the tea leaves in subsequent processes. S2.1 Depressurization and Dehumidification Stage: After the initial roasting begins, the negative pressure structure of the equipment is activated. This structure creates a physical negative pressure environment below atmospheric pressure inside the shell 1 by periodically changing the internal volume of the shell 1. This periodically changing negative pressure acts on the tea leaves, especially the tea stems. Under the action of negative pressure, the moisture inside the tea leaves, especially inside the tea stems, is accelerated and driven to the surface of the tea leaves. At the same time, the humid and hot air generated inside the shell 1 due to the initial roasting and the tea aroma that begins to volatilize are forcibly expelled from the shell 1 as the negative pressure structure exhausts. This depressurization and dehumidification process lasts for 9 minutes. S3. Re-drying and Aroma Fixation Stage: After the initial drying and dehumidification, the temperature inside the shell 1 is lowered to a low-temperature range of 30 to 40 degrees Celsius. At this time, the discharged hot and humid air and aroma mixture are guided to a cooling box 22. The circulating cooling water in the cooling box 22 causes the temperature of the mixed gas to drop sharply, and the water vapor in it condenses into liquid water, thus obtaining a mixture of dry cold air and tea aroma with most of the moisture removed. This is referred to as dry aroma. Subsequently, this dry aroma is reinjected into the shell 1 through an air pump 23. The dry aroma is then processed through a specific... The pipeline delivers the air to the air outlet plate 30 located at the bottom of the screen 8. The air outlet plate 30 has multiple air outlet holes 31. The drying aroma passes through the screen 8 from bottom to top, drying the tea leaves laid on the screen 8 from bottom to top. This method of introducing the drying low-temperature aroma from the bottom can specifically treat the tea leaves that have accumulated at the bottom due to gravity, promoting the uniformity of overall drying. At the same time, the tea aroma substances carried in the drying aroma have the opportunity to re-contact and adhere to the surface of the tea leaves. The time for this re-drying and aroma fixation stage is extended to 25 minutes to ensure the effect of low-temperature drying and aroma re-attachment. S4. Stir-frying stage: Based on the re-drying and aroma-fixing stage, the equipment further regulates the delivery method of the dried aroma. Through a valve structure that can be opened and closed periodically, the dried aroma blown out from the air outlet 31 forms an intermittent pulse airflow. The sudden impact force of the pulse airflow acts on the tea leaves on the screen 8, which is enough to lift the tea leaves and make them tumble and move in the air. With the interval of the pulse, the tea leaves fall back to the screen 8. This process is repeated, and the tea leaves are constantly tossed up, tumbled, and fall back in the screen 8, achieving a uniform heating effect similar to hand stir-frying. This stir-frying stage lasts for 1.5 hours. Throughout the entire low-temperature baking cycle, the final drying and shaping of the tea leaves are completed through the physical action of the airflow, completely avoiding physical contact and damage to the tea leaves by the mechanical stirring blades.

[0024] Reference Figure 1 and Figure 2A special equipment for multi-mode low-temperature roasting of tea, relating to the field of tea processing technology, mainly includes a housing 1. A rectangular opening is provided on one side of the housing 1. A door 2, matching the size of the opening, is hinged and mounted on one edge of the opening, allowing the door 2 to rotate around the hinge axis to open or close the opening. The door 2 is made of metal sheet, and an annular sealing ring 4 is fixedly installed on its side facing inwards from the housing 1. The sealing ring 4 is made of high-temperature resistant silicone rubber. When the door 2 is closed, the sealing ring 4 is tightly pressed against the sealing surface of the opening edge of the housing 1, thereby ensuring the airtightness of the working chamber inside the housing 1. The sealing ring 4 has a support spring embedded inside, and the elastic coefficient of the support spring ranges from 5N / mm to 15N / mm to ensure that the sealing ring 4 can maintain a stable sealing pressure at different temperatures. A heat insulation mounting base is fixed on one side of the door 2, and the control panel 3 is embedded in the heat insulation mounting base. The heat insulation mounting base is made of ceramic fiber heat insulation material with a thickness of 10-15mm. The outer shell of the control panel is equipped with heat dissipation fins, and a heat dissipation gap of 5-8mm is reserved between the heat insulation mounting base and the door 2. The control panel 3 is equipped with a temperature setting button, a time setting knob, a process mode selection switch, a power switch, and a status indicator light.

[0025] Furthermore, referring to Figures 2-5 The interior of the housing 1 is equipped with a support frame for supporting multiple layers of screens 8. The support frame includes two vertically arranged support columns 5, the axes of which are parallel to the central axis of the housing 1. The upper end of the upper support column 5 is rotatably connected to the center of the top inner wall of the housing 1 via a bearing, and the lower end of the lower support column 5 is also rotatably connected to the center of the bottom inner wall of the housing 1 via a bearing. Three U-shaped frames 6 are fixedly connected between the two support columns 5. The three U-shaped frames 6 are evenly distributed circumferentially around the axis of the support column 5. The two ends of each U-shaped frame 6 are welded and fixed to the outer walls of the upper and lower support columns 5, respectively, so that the three... A U-shaped frame 6 and two supporting columns 5 together form a stable frame structure. Between two adjacent U-shaped frames 6, multiple supporting frames 7 are horizontally fixed and installed. The multiple supporting frames 7 are arranged at equal intervals in the vertical direction and fixed between the three U-shaped frames 6. The upper surface of the supporting frame 7 is used to place the sieve 8. The sieve 8 is a circular mesh structure woven from stainless steel wire. The mesh diameter is smaller than the minimum size of the tea leaves to be roasted to ensure that the tea leaves will not fall. The outer diameter of the sieve 8 is slightly smaller than the outer diameter of the supporting frame 7, so that the sieve 8 can be placed stably on the supporting frame 7 and can rotate relative to the supporting frame 7 under a certain external force.

[0026] Furthermore, referring to Figure 7 and Figure 8A negative pressure structure is provided at the top of the housing 1 to periodically change the air pressure inside the housing 1. The core component of the negative pressure structure is a vertically arranged metal bellows 11. The lower flange of the metal bellows 11 is fixedly connected to the top of the housing 1 by bolts. The top of the housing 1 has multiple vertical holes, and the housing 1 is connected to the metal bellows 11 through the vertical holes. A circular lifting plate 10 is fixedly connected to the upper flange of the metal bellows 11. In order to guide the lifting plate 10 to make stable vertical reciprocating motion, a cylindrical annular cylinder 9 is also fixedly installed on the top wall of the housing 1. The annular cylinder 9 is coaxially sleeved on the outside of the metal bellows 11. The outer edge of the lifting plate 10 maintains a sliding fit with the inner wall of the annular cylinder 9. Inside the metal bellows 11, a vertical protective cylinder 12 is fixedly installed. The lower end of the protective cylinder 12 is fixed to the top wall of the housing 1, located at the top of the supporting column 5 above. The end extends upward, passes through the bearing on the top wall of the housing 1, and further extends into the interior of the protective cylinder 12. Inside the protective cylinder 12, a bevel gear II 15 is fixedly installed at the top of the bearing column 5. A rotating shaft 13 horizontally passes through the side wall of the protective cylinder 12 and is rotatably connected to the protective cylinder 12 through a bearing. A bevel gear I 14 is fixedly sleeved on a section of the outer wall inside the protective cylinder 12. The bevel gear I 14 and the bevel gear II 15 mesh with each other. When the bearing column 5 rotates, the rotating shaft 13 can be driven to rotate around its own axis through the transmission of the bevel gear pair. The two ends of the rotating shaft 13 extend to the outside of the protective cylinder 12, and a cam 16 is fixedly installed at each end. The two cams 16 have the same profile and are installed in the same phase. At the position away from the center of each cam 16, a pin 17 is fixed. The axis of the pin 17 is parallel to the rotation axis of the cam 16.

[0027] Furthermore, referring to Figure 7 and Figure 8Below the lifting plate 10, two lifting frames 18 are provided. Each lifting frame 18 has a rectangular frame structure, and a horizontal sliding groove 19 is provided on the inner side of each lifting frame 18. One end of the pin 17 is in rolling engagement with the inner wall of the sliding groove 19 via a rolling bearing (such as a needle roller bearing). (Those skilled in the art should understand that the pin 17 and the sliding groove 19 are consumable parts and require regular inspection, lubrication, or replacement.) The tops of the two lifting frames 18 are fixedly connected to the bottom of the lifting plate 10 via multiple vertical connecting rods 20. When the rotating shaft 13 drives the cam 16 and the pin 17 to rotate, due to… The pin 17 slides in the sliding groove 19, and the contour change of the cam 16 is converted into the up-and-down reciprocating motion of the lifting frame 18. The lifting frame 18 then drives the upper end of the lifting plate 10 and the metal bellows 11 to move up and down together through the connecting rod 20. A suction hose 21 is fixedly inserted through the top center of the lifting plate 10. The lower end of the suction hose 21 extends downward. A one-way valve that only allows gas to flow in one direction is installed inside the suction hose 21. When the lifting plate 10 moves downward, the gas in the housing 1 can be discharged through the suction hose 21 and the one-way valve inside.

[0028] Furthermore, referring to Figure 2 A cooling box 22 is fixedly installed on the outer side of the shell 1. The cooling box 22 has a double-layer structure, with the inner layer being a gas channel and the outer layer being a cooling water jacket for introducing circulating cooling water. The lower end of the suction hose 21 extends into the gas channel of the cooling box 22 and is fixed. The shell 1 is also provided with a fragrance-fixing structure for treating the gas discharged from the shell 1 and reintroducing it.

[0029] Furthermore, referring to Figure 2 , Figure 4 , Figure 9 and Figure 10The fragrance fixing structure includes an air pump 23 fixed to the side wall of the housing 1. The air inlet of the air pump 23 is connected to the outlet of the gas channel of the cooling box 22 through a first hose. In the central area of ​​the bottom inner wall of the housing 1, an annular fixing plate 24 is rotatably mounted. The lower end of the supporting column 5 located below passes through the central hole of the fixing plate 24 and is fixedly connected to it. An annular plate 26 is rotatably fitted on the outer circumference of the fixing plate 24 through a bearing. The annular plate 26 has a cavity inside. The fixing plate 24 has an annular groove I 25 inside. On the contact surface between the annular plate 26 and the fixing plate 24, and on the contact surface between the fixing plate 24 and the annular plate 26... On the top, each has an annular connecting groove 27. The two annular connecting grooves 27 are connected to each other, so that the internal cavity of the annular plate 26 is connected to the annular groove I 25 inside the fixed plate 24. The air outlet of the air pump 23 is fixedly connected to the air inlet on the annular plate 26 through the second hose. At the top of the fixed plate 24, a conduit 29 is vertically fixed through it. The lower end of the conduit 29 is connected to the annular groove I 25, and the upper end extends upward. On the side of one of the U-shaped frames 6, a vertical pipe 28 is fixedly installed. The lower end of the vertical pipe 28 is connected to the upper end of the conduit 29 through a flexible pipe to realize the gas passage connection between the rotating part and the fixed part.

[0030] Furthermore, referring to Figures 3-6 A drying structure is provided at the bottom of the support frame 7. This structure includes an air outlet plate 30 fixed to the lower surface of the support frame 7. The bottom of the air outlet plate 30 is connected and fixed to the vertical pipe 28 through a connecting pipe 37. On the top plane of the air outlet plate 30, a plurality of small air outlet holes 31 are evenly distributed. At the center of the support frame 7, a rotating rod 32 is vertically rotatable via a bearing. The upper end of the rotating rod 32 is fixedly connected to a circular support plate 33. A plurality of vertical rods are evenly fixed to the top of the support frame 7. The top of each vertical rod is welded with an arc-shaped ball seat. The balls 34 are embedded in the ball seats and can roll freely. The top of the balls 34 is flush with the top of the support plate 33. The screen 8 is placed directly on the support plate 33 and these balls 34, which can reduce the friction during rotation. The lower end of the rotating rod 32 extends downwards, passes through the top plate of the air outlet plate 30 in a sealed manner, and extends into the internal cavity of the air outlet plate 30. Inside the air outlet plate 30, a disc 35 is fixedly installed at the bottom end of the rotating rod 32. The disc 35 maintains a small gap with the bottom inner wall of the air outlet plate 30 and can rotate relative to it to seal the connecting pipe 37. The disc 35 has multiple clearance holes 36, the diameter of which is the same as the inner diameter of the connecting pipe 37. The disc 35 rotates synchronously with the screen 8. Through the periodic alignment and misalignment of the clearance holes 36 with the connecting pipe 37, the dry gas forms a stable pulse airflow that is injected into the air outlet plate 30 and then ejected through the air outlet 31. When the disc 35 rotates and the clearance holes 36 are misaligned with the connecting pipe 37, the solid part of the disc 35 will block the outlet of the connecting pipe 37, and the gas will stop being ejected.

[0031] Furthermore, referring to Figure 4 , Figure 5 , Figure 7 and Figure 11 To drive the screen 8 to rotate, a transmission mechanism is provided on each of the three U-shaped frames 6. Specifically, a round rod 38 is vertically rotatably mounted on each U-shaped frame 6. The lower end of the round rod 38 passes through the corresponding through holes on each layer of the support frame 7. At the corresponding position on each layer of the support frame 7, a rubber wheel 39 is fixedly fitted on the outer wall of the round rod 38. The outer circumferential surface of the rubber wheel 39 contacts the outer circumferential surface of the screen 8 placed on the support frame 7. On the bottom inner wall of the housing 1, an annular groove II 41 is opened around the fixed disk 24. A gear ring 43 is fixedly installed in the annular groove II 41. The lower ends of the three round rods 38 extend downward into the annular groove II 41, and a spur gear 44 is fixedly installed in each of them. All three spur gears 44 mesh with the fixed gear ring 43.

[0032] Furthermore, referring to Figure 5 Multiple rubber strips 40 are fixed to the outer wall of the screen 8, and the rubber strips 40 cooperate with the rubber wheel 39 to increase the friction between the rubber wheel 39 and the outer wall of the screen 8. The outer circumferential surface of the rubber wheel 39 and the contact surface of the rubber strips 40 are both made with patterns to increase the friction. In addition, those skilled in the art should understand that the rubber wheel 39 and the rubber strips 40 are consumables and need to be replaced after long-term use to maintain the transmission effect.

[0033] Furthermore, referring to Figure 2 and Figure 3 A drive motor 45 is fixedly installed on the bottom outer side of the housing 1. The output axis of the drive motor 45 passes through the bottom wall of the housing 1 and is fixedly connected to the bottom end of the support column 5 located below. Multiple heating plates 46 are evenly installed on the inner wall of the housing 1. A temperature sensor is also installed on the inner wall of the housing 1. The heating plates 46, drive motor 45, temperature sensor and air pump 23 are all electrically connected to the control panel 3 through wires and are controlled by it.

[0034] The control panel 3 is connected to a programmable logic controller (PLC), which has a pre-set control program corresponding to the multi-mode low-temperature roasting process steps of tea. This program coordinates the sequential operation of each component: In the initial roasting stage, the heating plate 46 is heated to 50-70°C and maintained, while the drive motor 45 is started to drive the placement rack to rotate; In the depressurization and dehumidification stage, the heating temperature is maintained, and the drive motor 45 is kept running to drive the negative pressure structure to operate periodically; In the re-roasting and aroma-fixing stage, the heating plate 46 is cooled to 30-40°C, the air pump 23 is started, and the drive motor 45 is kept running; In the stir-frying stage, the air pump 23 and the drive motor 45 are kept running until the process is completed.

[0035] In another embodiment: Refer to Figure 7 and Figure 11 An annular sealing ring 42 is also provided in the annular groove II 41. The inner wall of the sealing ring 42 is provided with an annular sealing groove, and a non-woven dustproof ring is embedded in the sealing groove. The sealing ring 42 slides and seals with the side wall and bottom wall of the annular groove II 41. The lower ends of the three round rods 38 extend downward and pass through the through hole on the sealing ring 42 and are press-fitted with the non-woven dustproof ring. The sealing ring 42 can prevent dust from entering the gear meshing area. Multiple chip removal holes are opened at the bottom of the annular groove II 41. The chip removal holes are threaded with sealing plugs, and the sealing plugs can be disassembled periodically to clean the tea leaves accumulated in the groove.

[0036] A method for using a special equipment for multi-mode low-temperature roasting of tea includes the following steps: S1. Spread the washed and naturally dried tea leaves evenly on the sieve 8, with the thickness controlled between 2 cm and 3 cm. Place multiple sieves 8 loaded with tea leaves on each layer of support frame 7 in sequence. Close the door 2 and ensure that the sealing ring 4 is pressed tightly and sealed. Set the process parameters through the control panel 3. S2. The control panel 3 activates the heating plate 46, raising and maintaining the temperature of the enclosed environment inside the housing 1 between 50 and 70 degrees Celsius. At this temperature, the tea leaves undergo preliminary roasting, and the free moisture on their surface is quickly removed, thus initially fixing the shape of the tea leaves. At the same time, the drive motor 45 starts, causing the lower support column 5 to rotate slowly. The lower support column 5 drives the upper support column 5 and the entire placement rack, including all the support racks 7 and the screens 8, to revolve around the axis of the support column 5 through the U-shaped frame 6. The revolve of the placement rack allows the tea leaves on the multi-layer screens 8 to receive more even radiant heat and hot air convection from the surrounding heating plate 46. S3. After the initial baking begins, the negative pressure structure operates synchronously. Due to the rotation of the bearing column 5, the rotating shaft 13 is driven to rotate through the meshing transmission of bevel gear II 15 and bevel gear I 14. The rotating shaft 13 drives the cams 16 at both ends to rotate. The pins 17 on the cams 16 move in the sliding grooves 19 of the lifting frame 18, converting the rotational motion of the cams 16 into the reciprocating linear motion of the lifting frame 18. The lifting frame 18 drives the upper end of the lifting plate 10 and the metal bellows 11 to reciprocate through the connecting rod 20. When the lifting plate 10 moves upward, the metal bellows 11 is stretched, and its internal volume increases. Since the metal bellows 11 is connected to the inside of the shell 1, the total volume inside the shell 1 increases instantaneously, and the air pressure drops. The low pressure creates a physical negative pressure, which acts on the tea leaves and draws the bound moisture inside the tea leaves, especially inside the tea stems, to the surface of the tea leaves. When the lifting plate 10 moves downward, the metal bellows 11 is compressed, the internal volume of the shell 1 decreases, and the air pressure increases. At this time, the hot and humid air inside the shell 1, containing a large amount of moisture and volatile aroma of tea leaves, opens the one-way valve in the suction hose 21 under the action of air pressure and is discharged into the gas channel of the cooling box 22 through the suction hose 21. This breathing action, simulated by the periodic expansion and contraction of the metal bellows 11, continues for 5 to 10 minutes. The negative pressure promotes deep dehydration, and the positive pressure discharges hot and humid waste gas, improving the efficiency of moisture migration and removal under low temperature conditions. S4. Control panel 3 controls heating plate 46 to reduce the internal temperature of shell 1 to between 30 and 40 degrees Celsius. The mixture of high-temperature and high-humidity air and tea aroma discharged from shell 1 enters cooling box 22. Cooling box 22 has circulating cooling water in its jacket layer, and the temperature is usually controlled between 5 and 15 degrees Celsius. When the high-temperature and humid air flows through the tortuous gas channel in cooling box 22, it exchanges heat with the low-temperature box wall. Water vapor in the air condenses into liquid water droplets when it encounters the condenser and is separated from the gas. After condensation and dehumidification, the relative humidity of the gas is greatly reduced. At the same time, due to the high boiling point of tea aroma components, most of them are still retained in the gas, forming a dry gas rich in tea aroma. S5. Air pump 23 starts, extracting the dried gas from cooling box 22 and pumping it into the cavity of annular plate 26 through the second hose. The gas passes sequentially through annular connecting groove 27, annular groove I 25, then enters conduit 29, and then ascends into vertical pipe 28. Since vertical pipe 28 is fixed on a U-shaped frame 6 and revolves with the placement frame, the gas is distributed to the inlet of each air outlet plate 30 through connecting pipe 37. The gas attempts to enter the air outlet plate 30 through connecting pipe 37, but due to the screen 8... Driven by friction, the rubber wheel 39 slowly rotates. This rotation is achieved as follows: when the mounting frame revolves, the stationary gear ring 43 and the spur gear 44 mounted on the lower end of the round rod 38 generate relative motion. Since the gear ring 43 is fixed, the spur gear 44 is forced to rotate around its own axis, thereby driving the round rod 38 and the rubber wheel 39 on it to rotate. The rotating rubber wheel 39 drives the outer edge of the screen 8 in contact with it through friction, causing the screen 8 to rotate on the support of the bearing plate 33 and the ball bearings 34. The support rotates around its own center. The rotation of the screen 8 causes the supporting circular plate 33 and the rotating rod 32 at its bottom to rotate together, which in turn causes the disc 35 inside the air outlet plate 30 to rotate. The rotation of the disc 35 causes the clearance hole 36 on it to periodically align or misalign with the outlet of the connecting pipe 37. When the clearance hole 36 aligns with the connecting pipe 37, the dry aroma gas can flow into the cavity of the air outlet plate 30 and be sprayed upward from the air outlet 31 at the top, blowing onto the tea leaves on the screen 8. When the pipe 37 is staggered, the gas supply is blocked by the disc 35, and the air outlet 31 stops spraying. This process is repeated. The air outlet 31 blows out intermittent pulse airflow. These pulse airflows impact upward from the bottom of the tea leaves, which can penetrate the tea leaf layer and dry the tea leaves piled up at the bottom. At the same time, the tea aroma carried in the gas re-contacts and adheres to the surface of the tea leaves. The time for this re-drying and aroma fixation stage is extended to 15 to 30 minutes, realizing low-temperature slow drying and aroma refilling. S6. The equipment continues to operate, with the drive motor 45 maintaining operation to make the screen 8 revolve. At the same time, the meshing of the gear ring and spur gear ensures the rotation of the screen 8. The air pump 23 continues to work, pumping the drying aroma gas into the system. Due to the periodic opening and closing of the disc 35, the intensity and frequency of the pulse airflow ejected from the air outlet 31 are related to the rotation speed of the screen 8. The strong pulse airflow impacts the tea layer upwards in an instant, which can slightly throw some of the tea leaves up. Since the screen 8 itself is also rotating slowly, the tea leaves that are thrown up will fall to different positions on the screen 8 when they fall back down. This process of throwing up and falling back, combined with the rotation of the screen 8, achieves uniform tumbling and repositioning of the tea leaves on the screen surface. The entire frying process lasts for 1 to 2 hours. During this process, the tea leaves are continuously subjected to uniform low-temperature drying airflow and are constantly and gently turned over, avoiding local overheating or uneven drying, and completely avoiding the squeezing and crushing of the tea leaves by the mechanical stirring blades. After all steps are completed, the equipment is turned off, the chamber door 2 is opened, and the roasted tea leaves are taken out.

[0037] It should be understood that the rubber wheels 39, rubber strips 40, and sealing rings 4 involved in this equipment are all consumable parts. To ensure the long-term stable operation of the equipment, users need to regularly inspect, lubricate, or replace them according to the frequency of use. The above maintenance is a routine operation in this technical field.

[0038] However, as is well known to those skilled in the art, the working principles and wiring methods of the air pump 23, drive motor 45, control panel 3 and heating plate 46 are all conventional means or common knowledge, and will not be described in detail here. Those skilled in the art can make any selections according to their needs or convenience.

[0039] The accompanying drawings in this application are for illustrative purposes only. The dimensions and shapes of the components shown are not actual limitations but are merely schematic representations. In actual implementation, the components can be reasonably configured and adjusted according to specific needs and actual conditions.

[0040] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A multi-modal low temperature roasting process for tea leaves, characterized in that, Includes the following steps: S1, Placement stage: After washing and drying, the tea leaves are evenly spread on the sieve (8), with a thickness of 2-3cm; S2, Initial Drying Stage: Place the tea leaves in a closed environment at 50-70℃ for initial drying to quickly remove surface moisture and fix the shape of the tea leaves; S2.

1. Reduce the air pressure in the enclosed environment in step S2 to draw the moisture inside the tea stems to the surface, and then expel the extracted hot and humid air and tea aroma for 5-10 minutes. S3, Re-drying and Aroma Fixing Stage: The temperature is reduced to 30-40℃. The hot and humid air extracted in step S2.1 and the aroma of the tea leaves are condensed and dried. Then the dried gas is reinjected into the closed environment in step S2. The dried gas is used to dry the tea leaves in the sieve (8) from below. The time is extended to 15-30 minutes. S4, Stir-frying stage: The dry gas blown out in step S3 forms a pulse airflow to tumble the tea leaves on the sieve (8) so that the tea leaves are evenly roasted for 1-2 hours.

2. A tea multi-mode low-temperature baking dedicated equipment for carrying out the tea multi-mode low-temperature baking process according to claim 1, characterized in that, include: The shell (1) has a door (2) hinged to one side. A placement frame is set inside the housing (1) to support multiple screens (8). The placement frame includes two support columns (5) and three U-shaped frames (6). The two support columns (5) are rotatably connected to the top inner wall and bottom inner wall of the housing (1) respectively. The two ends of the three U-shaped frames (6) are fixedly connected to the outer walls of the two support columns (5) respectively. Multiple vertically arranged support frames (7) are fixedly connected between the three U-shaped frames (6). The support frames (7) are used to support the screens (8). A negative pressure structure is used to create a negative pressure inside the housing (1). The negative pressure structure includes a metal bellows (11) fixed to the top of the housing (1) and a lifting plate (10) fixed to the top of the metal bellows (11). The aroma-fixing structure is used to dry the exhaust gas and re-inject it into the housing (1). The aroma-fixing structure includes a cooling box (22) fixed on one side of the housing (1) and an annular plate (26) fixed on the inner wall of the bottom of the housing (1). A drying structure, located at the bottom of the support frame (7), is used to dry the tea leaves from below using the drying gas discharged from the aroma-fixing structure. The drying structure includes an air outlet plate (30) fixed to the bottom of the support frame (7).

3. A multi-modal low temperature roasting apparatus for tea leaves as claimed in claim 2 wherein, The negative pressure structure also includes multiple vertical holes opened on the top of the housing (1), an annular cylinder (9) fixed on the top of the housing (1), and a protective cylinder (12). The housing (1) is connected to the metal bellows (11) through the vertical holes. The lifting plate (10) is slidably disposed in the annular cylinder (9), and the protective cylinder (12) is located in the metal bellows (11). The protective cylinder (12) has a rotating shaft (13) that rotates through it. The outer wall of the rotating shaft (13) is fixedly fitted with a bevel gear I (14). The top of the bearing column (5) located above extends rotatably into the protective cylinder (12) and is fixed with a bevel gear II (15) that meshes with the bevel gear I (14). Both ends of the rotating shaft (13) are fixed with cams (16), and pins (17) are fixed at the eccentric position of the cams (16). Two lifting frames (18) are provided below the lifting plate (10). A sliding groove (19) is provided in the lifting frame (18). One end of the pin (17) extends into the sliding groove (19) and slides with it. The top of the lifting frame (18) is fixedly connected to the bottom of the lifting plate (10) through multiple connecting rods (20). The top of the lifting plate (10) is fixedly connected to a suction hose (21), the bottom end of which extends into the cooling box (22), and a one-way valve is provided inside the suction hose (21).

4. A multi-modal low temperature roasting apparatus for tea leaves as claimed in claim 3 wherein, The fragrance fixing structure also includes an air pump (23) and a fixing plate (24). The air pump (23) is fixed to one side of the housing (1) by a frame, and its air inlet is connected to the cooling box (22) through a first hose. The cooling box (22) is provided with a cooling chamber. The fixed disk (24) is fixedly sleeved on the outer wall of the supporting column (5) located below. The fixed disk (24) is provided with an annular groove I (25). The annular plate (26) is sealed and rotatedly sleeved on the outer wall of the fixed disk (24). The inner wall of the annular plate (26) and the outer wall of the fixed disk (24) are respectively provided with an annular connecting groove (27) so that the annular plate (26) and the annular groove I (25) are connected. The air outlet of the air pump (23) is fixedly connected to the annular plate (26) through the second hose; the top of the fixed plate (24) is fixedly connected to the conduit (29), which is connected to the annular groove I (25); the top of the conduit (29) is fixedly connected to the bottom of the vertical pipe (28) fixed on one side of one of the U-shaped frames (6).

5. A multi-modal low temperature roasting apparatus for tea leaves as claimed in claim 4 wherein, The drying structure also includes a connecting pipe (37), the two ends of which are fixedly connected to the bottom of the air outlet plate (30) and the vertical pipe (28), respectively; the top of the air outlet plate (30) is provided with multiple air outlet holes (31). A rotating rod (32) is rotatably passed through the support frame (7). A support circular plate (33) is fixed at the top of the rotating rod (32). The bottom end of the rotating rod (32) extends in a sealed rotational manner into the air outlet plate (30) and is fixed with a disc (35). The disc (35) is rotatably and sealedly disposed on the bottom inner wall of the air outlet plate (30). Multiple clearance holes (36) are provided on the disc (35). When the clearance hole (36) is aligned with the connecting pipe (37), the dry gas is injected into the outlet plate (30).

6. A multi-modal low temperature roasting apparatus for tea leaves as claimed in claim 5 wherein, It also includes a screen drive structure, which includes three round rods (38), multiple rubber wheels (39), a gear ring (43) and three spur gears (44). The three round rods (38) rotate through the three U-shaped frames (6) and multiple support frames (7) respectively, and multiple rubber wheels (39) are fixedly sleeved on the outer wall of the round rods (38) and in contact with the outer wall of the screen (8); The bottom inner wall of the housing (1) is provided with an annular groove II (41), and the gear ring (43) is fixed to the bottom inner wall of the annular groove II (41); the three spur gears (44) are respectively fixed to the bottom ends of the three round rods (38) and located in the annular groove II (41), meshing with the gear ring (43).

7. A multi-modal low temperature roasting apparatus for tea leaves as claimed in claim 6 wherein, The top of the support frame (7) is provided with multiple balls (34) that are rolled by a vertical rod, and the top of the balls (34) is flush with the top of the support circular plate (33).

8. A multi-modal low temperature roasting apparatus for tea leaves as claimed in claim 7 wherein, The outer wall of the screen (8) is fixed with a plurality of rubber strips (40), which are in contact with the rubber wheel (39).

9. A multi-modal low temperature roasting apparatus for tea leaves as claimed in claim 8 wherein, It also includes a drive motor (45), multiple heating plates (46), a temperature sensor, and a control panel (3); The drive motor (45) is fixed to the bottom of the housing (1), and its output shaft is fixedly connected to the bottom end of the support column (5) located below; the multiple heating plates (46) are fixed to the inner wall of the housing (1); the temperature sensor is fixed to one side of the housing (1); the control panel (3) is fixed to one side of the door (2) and is electrically connected to the heating plate (46), drive motor (45), temperature sensor and air pump (23).

10. A multi-modal low temperature roasting apparatus for tea leaves as claimed in claim 9 wherein, The annular groove II (41) is sealed and slidably connected with a closed ring (42), and the bottom ends of the multiple round rods (38) rotate through the closed ring (42).

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