In the support structures used in knitting circular machines, rolling bearings are commonly categorized into two main types: ball-type and steel-track type. Ball-type bearings were predominantly used in Japanese circular knitting machines before the 1980s, while steel-track bearings became widely adopted globally after that period.
The ball rolling bearing is the simplest form of rolling bearing used in these machines. It consists of a set of rolling elements (such as balls) housed within a large raceway groove, which are radially supported against a cylindrical surface. These bearings can be lubricated using either grease or an oil bath, with the latter being more suitable for high-speed operation, reduced noise, and better maintenance of motion accuracy. The primary advantage of this design is its simplicity, leading to lower manufacturing and installation costs. However, compared to steel-track bearings, it has slightly less wear resistance.
Steel-track bearings, on the other hand, are the most widely used and technologically advanced support system in modern knitting circular machines. They feature a compact cross-section, available in both metric and imperial sizes. A nylon spacer separates the steel balls, allowing them to roll along a fixed circular track positioned at four corners. This compact design makes it ideal for integration into tight spaces within the machine. One of the key advantages of steel-track bearings is their suitability for large-diameter rotating components and low-energy applications, which aligns well with the operational needs of circular knitting machines.
The most common configuration of a steel-track bearing is the three-body-enclosed structure. This design typically includes a fixed top housing, a movable pinch gear, and a compression ring that encloses a square-section steel-track bearing in the center. Depending on the position of the compression ring relative to the steel balls and the housing, the structure can be classified into several types, such as upper inner pressure ring, upper outer pressure ring, lower inner pressure ring, and lower outer pressure ring.
One of the major benefits of this enclosed structure is its ease of adjustment and replacement. It allows for simple gap adjustments by loosening screws and replacing gaskets. When it’s time to replace the bearing, the compression ring can be removed without disturbing other components, making the process quick and efficient. This design significantly enhances maintenance convenience and reduces downtime.
Piston and Rod Seals
Piston Seals and Rod Seals are important seals used in mechanical equipment. Their main function is to prevent liquid and gas leaks and ensure the normal operation of mechanical equipment. Piston seals and rod seals are usually used in hydraulic and Pressure system, such as hydraulic cylinders and Pneumatic cylinder. The quality and performance of these seals directly affect the efficiency and lifespan of mechanical equipment.
The classification of piston seals and rod seals is mainly based on their material and design structure. According to the different materials, they can be divided into rubber seals, polyurethane seals, polytetrafluoroethylene seals, metal seals, etc. According to the different design structures, they can be divided into unidirectional seals, bidirectional seals, rotary seals, etc.
Rubber seals are a common type of seal, and their main material is rubber. Rubber seals have good sealing performance and wear resistance, and are suitable for medium and low pressure hydraulic systems and Pressure system. Polyurethane sealing element is a high-performance sealing element, and its main material is polyurethane. Polyurethane seals have high wear resistance, high temperature performance and high pressure performance, and are suitable for high-pressure hydraulic systems and Pressure system. PTFE sealing element is a corrosion-resistant sealing element, and its main material is PTFE. PTFE seals have excellent corrosion resistance and high temperature resistance, making them suitable for fields such as chemical and food processing. Metal seals are a type of high-temperature and high-pressure seal, mainly made of metal. Metal seals have high temperature and high pressure performance and corrosion resistance, and are suitable for high temperature and high pressure hydraulic systems and Pressure system.
Unidirectional seals and bidirectional seals are classified based on different sealing directions. A unidirectional seal can only prevent the leakage of liquid or gas from one direction, while a bidirectional seal can prevent the leakage of liquid or gas from both directions. Rotating seal is a type of seal that can rotate and is mainly used for sealing rotating shafts. Rotary seals are divided into unidirectional rotary seals and bidirectional rotary seals.
Overall, piston seals and rod seals play a very important role in mechanical equipment. Choosing appropriate seals can improve the efficiency and lifespan of mechanical equipment, reduce maintenance costs and downtime. When selecting seals, it is necessary to comprehensively consider factors such as the working environment, pressure, and temperature of the mechanical equipment to choose a suitable seal.
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