1998 Scientific and Technological Development Key Project (Contract No.: Gui-Kexin 9810001) The author is responsible for the design and commissioning of the TF-1350 automatic centrifuge pneumatic system. Combining with the production conditions, process and action requirements, reliability, safety, and economics of the centrifuge, we introduce some features of the pneumatic system circuit design and component selection.
The 2TF-1350 automatic centrifuge is driven by the production cycle and operating characteristics, and can be in the form of inverter DC stepless speed regulation. The PLC accepts the signals sent from the on-site command signal and speed detection unit, position sensor, etc., and then judges according to logic, and then issues instructions according to a programmed procedure to control the rotation speed of the motor and each actuator to realize automatic cycle operation. Diagram of the typical speed of the machine.
It can be seen that the motor reaches different process speeds in different time periods 1) t0 ~ t2, the system starts, the motor speed is accelerated to the lowest speed of the automatic cycle that is the discharge speed 50r/min, after the normal continuous cycle such as the t0 ~ t1 section of the start process No longer repeat.
170r/min, and in t3 ~ t4 stage by the cylinder drive feed door opening and closing to complete the feeding action. The feeding door cylinder can be stopped at any position of the stroke (by adjusting the position of the sensor) to control the opening of the feeding door and achieve the purpose of controlling the feeding speed. At this time, the cylinder drip-proof door is placed in the open state, the feed amount detector is placed in the measurement position by the cylinder drive, and is placed in the reset position after the material is full. The honey water separation mechanism is set by the cylinder to be the "raw honey" collection state (the centrifuge has two different sugar content honey juices during the production cycle and needs to collect the raw honey with higher sugar content before being washed and washed. The honey water separation mechanism is set by the cylinder as honey, and the honey water separation mechanism is located in the "wash honey" collection state).
The water wash action is completed in ~t6 stage. At this time, the honey water separation mechanism is changed from the cylinder position to the “wash honey†collection state.
4) After t6~t8, after the washing is completed, the motor speed is accelerated to the separation speed of 1200r/min. At this time, the cylinder-driven anti-drip door is placed in the closed state to prevent the color value of white sugar from exceeding the standard due to the leakage of honey.
After the deceleration to the unloading speed 50r/min. In the 50r/min speed corps, mainly engaged in hydraulic, pneumatic research and teaching work.
Hydraulic and pneumatic drive by the cylinder to complete the unloading sugar action: sugar unloading cover lifts, exposes the sugar unloading mouth, unloads the sugar shovel to turn, the radial cutting edge moves the radial sugar along the screen basket, after the unloading sugar shovel rotates in place, stays for about 2s (to guarantee Radial shovel sugar can shovel a complete circle) down, by the axial cutting blade shovel sugar. After the sugar unloading is completed, the sugar unloading shovel is lifted upwards, and the sugar unloading cover is put down to reset the unloading sugar mechanism. The honey water separation mechanism also resets the “raw honey†state and the machine enters the next cycle.
Since the TF-1350 automatic centrifuge adopts the form of dragging with variable direct current stepless speed regulation, the speed control feature is good, and no mechanical brake is needed during normal circulation. Therefore, the mechanical brake system driven by the cylinder only operates in abnormal conditions.
3 Pneumatic system design and characteristics The logic relationship of the cylinder in the system can be completed by software. The design of pneumatic system is simple, reliable and practical. In order to ensure the safety performance of the machine, the circuit design and component selection of the pneumatic system are combined with the production conditions and technological features of the machine. Schematic diagram of the TF-1350 automatic centrifuge pneumatic system.
The characteristics of the pneumatic system circuit and its components are as follows: 1) Proximity switches are installed at the start and end positions of each cylinder-driven mechanism, and the PLC monitors the position of the mechanism and the completion of the movement according to the signals of these proximity switches.
2) Air pressure sensor, check valve and gas tank are installed at the air supply port. When the air supply is interrupted or the pressure is insufficient, the electronic control system will reset the machine according to the signal sent from the pressure sensor. The compressed air in the air tank can ensure The machine performs the necessary reset cycle or reset action to avoid the destructive conditions such as the leakage of sugar and the retention of sugar paste.
3) Anti-drip door cylinders, feed door cylinders, feed detector cylinders, sugar relief valve cylinders, sugar shovel rotary cylinders, honey water separation cylinders, brake cylinders, etc., all use common exhaust throttling. The unloading scoop lift cylinder uses the throttle throttle, mainly considering the action characteristics when unloading sugar: First of all, the unloading sugar shovel rotation, rotation in place, stay 2s and then down the sugar shovel, if the use of exhaust throttle Speed ​​regulation, due to the established hysteresis of the throttling relationship of the throttle valve, when the cylinder descends, there will be a phenomenon of rapid forward punching at the beginning of a short stroke, resulting in unsweetened unloading sugar (the unloading shovel only cuts out a spiral groove). The use of air intake throttling can reliably control the movement speed of the sugar shovel when it starts to descend. At the same time, the supply air of the control valve V7 of the shovel lift cylinder is taken from the output port of the sugar dump cover control valve V5, and it is ensured from the pneumatic aspect that the unloading sugar shovel can move only after the sugar cane is opened.
1. Air source 2 pressure sensor 3. Check valve 4 Air tank 5 Water separator 6 air source adjusting device 7 Oil mister V1-V6 Two-position five-way valve V7, V8 Three-position five-way valve T1-T16 Unidirectional Throttle TF-1350 Centrifuge Pneumatic System Principle) The selection of pneumatic components fully considers the strong corrosive characteristics of the sugar paste in the sugar process. All cylinders are made of aluminum alloy type, and all gas valves are metal-sealed. For the mechanism with only two operating states (pure water separation, anti-drip gate, feed detection, brake, shovel rotation, sugar unloading hood), in order to reduce the PLC output points, the cylinder's control valve adopts spring return, single electromagnet The 2 position valve. The feeding and sugar shovel lifting mechanism, because the required mechanism can stay at any position in the journey, so the choice of double electromagnets, the middle position closed three valve. The valve is selected from Japan's SMC company VFS series products, the use of plate structure, all installed on the same bus board, simple and reliable.
4 Conclusion The successful development of the TF-1350 automatic centrifuge was performed in a sugar factory for two crop seasons (tests). Its pneumatic system is flexible and reliable with low failure rate. Practice has proved that the pneumatic system design is successful. â–¡
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