Technical characteristics and application of tea color sorter

Picking stems and removing miscellaneous items in tea processing is a labor-consuming and time-consuming and very critical process. Picking and picking has become a bottleneck in the quality and cost control of tea refining. Due to mechanical performance and other reasons, conventional equipment such as stepped stem picking machine and electrostatic picking machine, the picking effect is not ideal. If Gongfu black tea is sorted through multiple machines and statically, it still needs to be assisted by manual sorting. The cost of manual tea sorting accounts for 10%-15% of the cost of refined black tea. In recent years, the quality of manual picking of fresh tea leaves has declined and the number of mechanical tea picking has increased, and the amount of stems picked during tea processing has increased accordingly. The industry has been looking forward to technological breakthroughs in tea picking equipment. Color sorting technology refers to the use of a special recognition lens to capture the image element signals on the surface of the material, collect the material transmittance signal and other component information, and use PLC control and CPU processing to achieve photoelectric signal exchange, and compare and analyze the material with the standard signal The color sorting equipment has been widely used in agriculture, food industry, industry and mining and other fields. In recent years, some enterprises in Anhui and other provinces have successfully used color sorters to pick

Inclusions such as tea stalks have high picking quality and high work efficiency. The cost of tea production is reduced, and the extraction rate is significantly improved. It can be widely used in the picking operation in the refining of green tea, black tea, and oolong tea, and the selection of famous and high-quality teas for removing slices and stalks. Processing etc.

1. Technical characteristics of tea color sorter

Color sorters are mainly multi-purpose and general-purpose color sorting equipment. When used in different industries and products, some components and operating modes must be subjected to corresponding technical research and testing to achieve the desired quality requirements.

1.1 The working principle of tea color sorter

The tea color sorter uses photoelectric technology to specifically remove heterochromatic materials, and analyzes the appearance and color of the tea material surface through the photoelectric system to distinguish tea, stems and non-tea inclusions. It can solve the conventional use of screening, winnowing and picking equipment. Unachievable separation of tea stems. There are several long and narrow passages in the sorting room of the color sorter. The exit of the passage is equipped with a highly stable light source. When the tea material enters the sorting area evenly through the chute channel through the vibrating feeding system, the material must be heavy before passing through the detection area.

The force and the falling speed make each tea leaf arranged in a straight line and fall into the photoelectric detection chamber one by one. Each trough has 2 high-resolution cameras, plus data processing hardware. When the material passes through, it can be checked from both sides to determine the heterochromatic product. The photoelectric sensor measures the reflected light and the amount of light projected and compares it with the reference color. The amount of light reflected by the plates is compared, and the difference signal is amplified and processed. When the signal is greater than a predetermined value, the spray system (the nozzle at the end of the trough) is driven to blow out the heterochromatic materials with compressed air. The tea color sorter adopts a new generation of digital signal processor (DSP) instead of traditional industrial computer, and adopts fuzzy logic algorithm and support vector machine (SVM) algorithm to automatically adjust the angle of the background board and the feeding speed, which truly realizes the color The automatic control of the selection machine also makes the performance of the machine automatically reach the optimal state when working.

1.2 The basic structure of tea color sorter 

The main components of the tea color sorter are: feed hopper, vibrating feeder, chute, light source, background board, photoelectric detector, digital camera, by-product tank, genuine tank, jet valve, air compressor, air purifier and filter Controllers, signal conditioning components, timing components and microcomputer control systems, etc. Feeding system: It consists of a feed hopper, a vibrating feeder and a chute. The tea material to be sorted enters the vibrating feeder from the hopper, and the material is automatically arranged into a continuous linear beam through the vibration and guiding mechanism, and then accelerated through the trough and thrown at a constant speed into the detection of the photoelectric system In order to ensure that the tea material is accurately presented in the optical zone and spray zone.

Photoelectric system: The photoelectric system is the core part of the color sorter, which is mainly composed of light source, background board, digital camera and related auxiliary devices. The light source provides stable and uniform illumination for the tested material and the background board. The photodetector converts the reflected light of the measured material into an electrical signal in the detection area. The background board provides a reference signal for the electronic control system, and its reflective characteristics are basically equivalent to those of qualified products, but are quite different from the rejected objects.

Sorting system: The sorting system is composed of auxiliary product tank, finished product tank, jet valve, air compressor, filter and other related accessories. The pneumatic nozzle is equipped with nearly 200 nozzles as standard, with a diameter of only 2-3mm, high resolution, long life, and accurate spraying.

Electronic control system: The electronic control system is composed of signal conditioning components, timing components, and microcomputer control systems. The electronic control system amplifies the color difference voltage from the photoelectric system and compares it with the set color difference threshold. The core technology is the product heterochromatic tracking module to control the brightness of the backlight of the optical system of the color sorter, dust cleaning and automatic correction, etc., to track and eliminate heterochromatic objects.

Operating system: Different color tracking software can track the quality of finished products at any time to ensure that the color sorter can maintain the stability of performance even during long-term uninterrupted continuous production. The Chinese touch screen operation interface can retain more than 20 preset sample modes and save 100 user-confirmed samples

Mode, the conversion between sample modes can be completed in an instant.

1.3 Performance index of tea color sorter

The main performance indicators of the tea color sorter are measured under the conditions of the content of the foreign color and the rated flow rate, and are related to the type, color and density of the foreign color. Generally, when the content of different colors is the same and the output is rated at the time, the higher the color sorting accuracy, the lower the take-out ratio, which indicates the better the process performance of the color sorter.

Hourly output: Tea color sorting machine has great innovation. It adopts dual-lens double-sided search. The processing capacity of each channel is increased, and the output and color sorting accuracy are greatly improved. The processing capacity per stage is 0.8-1.0t?h. This number is only about dozens of times that of conventional tea picking equipment, but the selection effect is far incomparable with conventional equipment.

Sorting rate: the sorting rate (stem sorting rate) refers to the weight percentage of the number of impurities selected to the impurity content in the tea raw materials after color sorting of tea containing heterochromatic substances. The impurity sorting of tea color sorting The rate is determined by the tea's impurity ratio, and theoretically eliminates the special requirements for the length, shape, and specific gravity of the impurity. Different color selection processes can be determined according to the clarity requirements of different tea grades.

Take-out ratio: The take-out ratio (misselection ratio) refers to the ratio of the weight of the foreign-colored matter in the by-products to the weight of the qualified tea after the tea has been color sorted. That is, how many units of qualified products are brought out for each unit of impurity sprayed out, generally up to about 1:0.6. The higher the purity requirement of genuine tea, the more qualified tea may be brought out. If the take-out ratio is particularly low, it will affect the accuracy of the secondary color sorting. If it is too high, the selected materials will be difficult to handle, and the tea leaves in the by-products will be out of material.

Color sorting accuracy: The color sorting accuracy refers to the weight percentage of the authentic and qualified tea with the selected tea raw materials after the selected tea raw materials containing foreign colors are color sorted. Conventional tea picking equipment is mainly stepped stalk picking machine and electrostatic stalk picking machine. The stepped stalk picking machine can only pick thick and long stalks. The sorting rate of the tea planting machine is low, and the mis-sorting ratio is high. The identification of impurities in tea color selection is only in the depth of the color regardless of its shape and specific gravity, eliminating the interference of many other unfavorable factors.

2. Technical regulation of tea color sorter

The tea color sorter has higher requirements for the installation and use environment, supporting compressed air system, and cleaning system. It also has the characteristics of photoelectric detection elements, light source spectral characteristics, double-sided color sorting, jet valve performance, control system anti-interference ability, and the overall average Improve and optimize the failure time and other aspects.

2.1 Feeding system design

Since the shape and specifications of tea materials are quite different from those of rice, wheat, soybeans, etc., the feeding device of a general-purpose color sorter cannot meet the technical requirements of tea color sorting. The tea color sorter has an innovative design of the hopper device, which can achieve the flat direct flow of tea materials instead of columnar flow. The flat direct current can make the logistics evenly and continuously sent to the oscillating plate, and realize

Now it is self-cleaning, all tea materials flow at the same speed, while the conventional color sorting machine mostly flows in a columnar shape. If the tea is selected, the flow rate is fast in the middle and the speed on both sides is slow, which is prone to potential dead ends and blockages. When the hopper sends the tea raw materials to the oscillating plate, two screws can be used to adjust the material door up and down to ensure that the raw materials are transported to the oscillating plate in a straight line. In addition, the parts of the entire feeding system are made of stainless steel, which is strong and wear-resistant. Special anodized channel troughs are used for color selection, which has a high selection rate and increased output.

2.2 Photoelectric and sorting system control

The new digital imaging technology allows users to simultaneously set multi-level thresholds and multiple parameters for impurities and heterochromatic substances. Through the analysis of the spectral characteristics of qualified products and impurities in tea materials, and according to the average color of tea materials, the accepts can be separated And rejects, the use of light sources with specific spectral characteristics makes the reflected light of qualified products and impurities have a greater difference. By adopting double-sided color sorting technology, the detection area of the picked materials is increased, and more comprehensive information is obtained to improve the selection rate of picking stems and tendons. The tea color sorter sprays tea materials along the flow from back to front, and the flow in contact with the edge of the trough remains relatively stable, so that the nozzle can be as close to the flow as possible, and the flow is naturally divided when the nozzle blows. And set up a channel type trough, each channel has one nozzle, one nozzle is aimed at one material, and the carry-out ratio is extremely low. When the nozzle is sprayed horizontally, it can ensure the maximum control of gas diffusion, and the nozzle valve is opened or closed when the nozzle is sprayed vertically. Control, its special switching frequency speed is up to several hundred nanoseconds, and the nozzle speed can reach 300 times per second. Material tracking and automatic correction make the color sorter maintain high accuracy and output.

2.3 Electric control and operating system control

Using tea color as a sorting basis can realize functions that other conventional sorting methods cannot. After color sorting, the color of the tea is uniform, the appearance is improved, the quality is greatly improved, and the market competitiveness of the product is significantly enhanced. In order to solve the problems of unstable light source of the existing color sorter, low impurity removal rate and low degree of automation, blue high-brightness light-emitting diodes are used as the light source of the color sorter instead of traditional lamps, and the method of automatically adjusting the dynamic threshold value is adopted. Threshold of color sorter. The dynamic threshold method avoids manual intervention and helps to improve the degree of automation of the color selection system. It initially verifies the feasibility of high-brightness LEDs as the light source and the dynamic threshold method. The product different color tracking module used in the tea color sorter controls the brightness of the backlight of the optical system of the color sorter, dust cleaning and automatic correction, etc., to track and eliminate foreign color objects. And using DSP, PLC and other components as the control core of the electronic control system, it can automatically monitor the operating status of the system during operation, and automatically adjust the feeding system, sorting system, photoelectric system, etc., so that the color sorter can keep the most Good working condition.

3. Technical application of tea color sorting

The color selection of tea has created favorable conditions for the improvement of work efficiency and cost control of tea processing, especially for export tea processing. At the same time, the purchase and use of tea color sorting machines are very cautious. In practice, it is necessary to correctly master and apply tea color sorting technology.

3.1 Raw material control of tea color selection

The size and specification requirements of the raw material tea of the tea color sorting machine are the basic conditions for determining the tea color sorting process and the tea refining process. The leaves of Maocha have long stalks and high stalk content. If Maocha is used as raw material to enter the vibrating feeder, it is easy to block the feeder outlet, and the material cannot be automatically arranged into a row of continuous linear bundles through the vibration and guiding mechanism. It is even more unable to smoothly pass through the trough and then toss at a constant speed into the detection area of the photoelectric system. Although the semi-column tea in the process of drum sieve and other processes has been roughly divided into sizes and not cut too much, it still has a long leaf body, a large number of large stems, a large amount of impurities, and poor fluidity. Therefore, red (green) Maocha, Maochatou and large sieve tea are not suitable as tea raw materials for color sorters. The technical indicators of tea color sorting, such as the selection rate, the take-out ratio and the output per hour, mainly depend on the content of the stalk and the end of the tea. The results of the study showed that the selection rate of the sieve tea behind the fine fan was high, the take-out ratio was low, and the output was high when it was set, and the color selection effect was the best.

3.2 Clarity control of tea color selection

The content of impurities such as tea stems in different grades of tea materials varies greatly. The lower the tea grade, the more tendons in the tea raw materials. The high-grade tea with fine tendons and tender stems has low impurity content, and the degree of heterochromia of tendon stems is also low. It is more difficult to select. Low-grade teas with thick stems and stems have high impurity content and high degree of impurity heterochromia. , The difficulty of selecting is relatively easy. In addition, the clarity requirements of different grades of commercial teas are also very different, with high-grade teas requiring high purity and low-grade teas having low purity requirements. Therefore, the work efficiency of tea color selection and selection is opposite to grain color selection. High-end tea with less impurities and high purity requirements has low work efficiency and technical difficulty, and low-grade tea with many impurities and low clarity requirements has high work efficiency. And the technical difficulty is small. For tea raw materials of the same grade or with similar impurities (gluten stalks), the higher the purity requirements of commercial teas, when the take-out ratio remains the same or the change is small, the flow of the selected tea can only be reduced or more. Secondly, the output of the tea color sorter will be reduced accordingly. Otherwise, the take-out ratio of the tea color selection will increase, and the most taboo phenomenon of material running and feeding will appear in tea refining. In tea refining, through the selection, fine-tuning and determination of the technical mode of the tea color sorting machine workstation, the maximum output of the tea color sorting machine is realized under the premise that the tea picking and picking ratio and the sorting rate meet the technological requirements.

4. Conclusion 

Traditional tea stem picking uses a combination of machine picking and hand picking, which has a high error picking ratio and consumes a lot of manpower and financial resources. The quality and efficiency of picking stems cannot meet the requirements of clean and engineered processing. By systematically using a color sorter to pick out tea stalks and other inclusions in tea processing, there is no need to over-standardize the length and thickness of the sieve tea delivered for color sorting, which not only has a good impurity removal effect, but also optimizes the refining process to reduce repeated cutting and shaking. The sieve manufacturing industry avoids excessive breakage and bluntness of tea, and achieves the processing effects of high picking quality, high work efficiency, reduced tea production costs, and improved extraction rate, which basically solves the poor quality of tea picking in the past. And the defects of low efficiency. What's more, the tea stems picked by conventional machinery or manually bring out the noodles tea with tight, sharp edges, and the by-products of the tea color selection bring out the different-color tea of inferior quality. The processing capacity of a tea color sorter can be equivalent to hundreds of tea pickers, the production capacity of the enterprise is effectively activated, and the processing cycle is greatly shortened. In addition, the tea leaves are not touched by manual tea picking, which avoids the potential pollution of manual picking, so that it is more hygienic and clean, and achieves clean and standardized processing.