Flexible Couplings: The Most Versatile Coupling

The flexible coupling is composed of the diaphragm shaft ends at both ends and the short section located in the middle. Its main feature is to absorb and adapt to the driving equipment and driven equipment through its unique diaphragm structure at both ends. Inevitable misalignment between the two axes. Because of its simple structure, high reliability, low maintenance requirements, easy installation, and the alignment requirements for equipment are far lower than other types of couplings, it has been widely used in many occasions, especially in the field of oil and gas. In many cases, it can completely replace rigid couplings and toothed couplings.

Features of flexible coupling

Flexible couplings have the ability to compensate for the relative offset of the axes of the two shafts. The maximum compensation amount varies with the model. Where the coaxiality of the connected two shafts is not easy to guarantee, flexible couplings should be used.

Flexible couplings have a large load-bearing capacity, but do not have cushioning and vibration reduction performance. There are shocks and noise at high speeds or unstable speeds or forward and reverse rotation. It is suitable for occasions with low speed, medium load and stable speed.

Flexible couplings have good cushioning and vibration damping performance when the speed is unstable; simply due to the low strength, short life, small bearing capacity and high tolerance, and low temperature performance of non-metallic (rubber, nylon, etc.) elastic components, so Today it is used in high-speed, light-load and normal-temperature applications.

In addition to having good cushioning and vibration damping performance, the flexible coupling has a large carrying capacity. It is suitable for occasions with large changes in speed and load and high or low temperature.

Classification of flexible coupling

1. Flange coupling

Flange coupling (also known as flange coupling) is to use bolts to connect two flanged disc half couplings. The two half couplings are respectively connected to the two shafts by keys to realize the connection of the two shafts and the transfer Moments and movements. Flange coupling is simple in structure, easy to manufacture, low in cost, reliable in operation, convenient in assembly, disassembly and maintenance, large in transmission torque, and can ensure high alignment accuracy of the two shafts, and is generally used for stable load. High-speed or high-accuracy transmission requires high shafting transmission. Flange couplings do not have the performance of radial, axial and angular compensation. If the alignment accuracy of the two shafts cannot be guaranteed during use, the service life of the coupling, transmission precision, transmission efficiency and transmission efficiency will be reduced. And cause vibration and noise.

2. Slider coupling

The structure of the slider coupling is similar to that of the cross slider coupling. The difference is that the middle cross slider is square. The middle slider is used to slide in the corresponding radial groove on the end surface of the half coupling on both sides to achieve two Half coupling coupling. The slider coupling has a loud noise, low efficiency, and fast wear. It is generally not used as much as possible, and it is only used in occasions with very low speed.

3. Chain coupling

The chain coupling utilizes a common chain and meshes with two parallel sprockets with the same number of teeth at the same time. The main difference between different types of chain couplings is the use of different chains. Common two-row roller chain couplings, single Row roller chain coupling, toothed chain coupling, nylon chain coupling, etc. The performance of the double-row roller chain coupling is better than other structural couplings. It has a simple structure, easy assembly and disassembly, no need to move the two shafts connected during disassembly, compact size, light weight, and certain compensation ability. It has the advantages of low installation accuracy, reliable operation, long life and low cost.

4.Gear coupling

The toothed coupling is composed of an internal ring gear with the same number of teeth and a flange half coupling with external teeth. The external teeth are divided into two kinds of straight teeth and drum teeth. The so-called drum teeth are the external teeth made into a spherical surface, the center of the spherical surface is on the gear axis, the tooth side clearance is larger than the general gear, the drum tooth coupling can Larger angular displacement (relative to straight tooth coupling) can improve the contact conditions of the teeth, increase the ability to transmit torque, and extend the service life. When the toothed coupling is working, the two shafts produce relative angular displacements. The tooth surfaces of the internal and external teeth periodically slide axially relative to each other, which inevitably causes tooth surface wear and power consumption. Therefore, the toothed coupling requires good lubrication and Sealed state. The toothed coupling has a small radial size and a large carrying capacity. It is often used for low-speed and heavy-duty working conditions. The high-precision and dynamically balanced toothed coupling can be used for high-speed transmission. Because the angular compensation of the drum-shaped gear coupling is greater than that of the straight gear coupling, it is widely used.

Factors to be considered when selecting a coupling

(1) The size and nature of the torque to be transmitted should be considered as well as the requirements for the cushioning and vibration reduction function. For example, for heavy-duty heavy-duty transmission, drum-shaped gear couplings can be used; for severe impact loads or requirements to be eliminated For the transmission of the torsional vibration of the shaft system, a coupling with a highly elastic element such as a tire-type coupling can be selected.

(2) The working speed of the coupling and the magnitude of the centrifugal force caused by the coupling should be considered. The allowable speed range of the coupling is determined by calculation according to the allowable linear speed and maximum outer edge size of different materials of the coupling. The allowable speed range of the coupling is different for different materials, varieties and specifications. Changing the material of the coupling can increase the allowable speed range of the coupling. For high-speed transmission shafts, couplings with high balance accuracy should be used, such as diaphragm couplings, etc., and slider couplings with eccentricity should not be used.

(3) The size and direction of the relative displacement of the two shafts should be considered. After installation and adjustment, it is still difficult to maintain strict and accurate alignment of the two shafts, or when the two shafts will produce a large additional relative displacement during the work, the flexible coupling should be used. Device. For example, when the radial displacement is large, the slider coupling can be selected, and if the angular displacement is large and the two shafts intersect, a universal coupling can be used.

(4) The reliability of the coupling should be considered. Generally, the drum tooth coupling does not need lubrication and is more reliable;

The performance of the coupling to be lubricated is susceptible to the degree of lubrication perfection and may pollute the environment. Drum-shaped gear couplings containing rubber and other non-metals are more sensitive to temperature, corrosive media and strong light

Feeling, and easy to age.

(5) The load category of the coupling should be considered

Due to the different structure and materials, the coupling capacity of the coupling used in the transmission system of each mechanical product varies greatly, mainly for the impact, vibration, positive and negative rotation, braking, frequent starting and other reasons of the working load of the working machine. Form different types of loads.

(6) The transmission accuracy of the coupling should be considered

Low torque and shafting transmission based on power transmission require couplings with high transmission accuracy. Flexible couplings with metal elastic elements should be used. High-torque shaft power transmission also requires transmission accuracy. At high speeds, flexible couplings with gaps between non-metallic elastic components and movable components should be avoided, and diaphragm couplings with high transmission accuracy should be used.

(7) Coupling size should be considered for installation and maintenance

The external dimensions of the coupling, ie the maximum radial and axial dimensions, must be within the installation space allowed by the machine. Choose a coupling that is easy to assemble and disassemble, does not require maintenance, has a long maintenance period or is easy to maintain, replaces wearing parts without moving the two shafts, and is easy to align and adjust. Large machines and equipment are difficult to adjust the alignment of the two shafts, and you should choose a coupling that is durable and convenient to replace wearing parts. Flexible couplings with metal elastic elements generally have a longer service life than flexible couplings with non-metallic elastic elements. The need to seal lubrication and use of durable couplings will inevitably increase the maintenance workload. For the occasions of long-term continuous operation and high economic benefits, the drum tooth coupling is generally used at present. The toothed coupling has large torque transmission, good lubrication and sealing, and can work for a long time. The sealing condition needs to be checked frequently. Fill with oil or grease.

The difference between couplings with and without elastic elements

Because this type of coupling is equipped with elastic elements, it can not only compensate for the relative displacement between the two shafts, but also have the ability to cushion the vibration. The more energy the elastic element can store, the stronger the buffering capacity of the coupling; the greater the frictional performance between the parts of the elastic element after the elastic band and the elastic deformation, the better the vibration damping ability of the coupling . This type of coupling is currently widely used and has many varieties.

More and more.

Non-elastic element couplings have good ability to compensate the relative offset of the two shafts and have a large load-bearing capacity; but they do not have cushioning and vibration reduction performance, gear joints need lubrication, complex structure and high cost. Suitable for medium load and low speed occasions

Selection of elastic elements of flexible couplings

The elastic element in the coupling can produce significant elastic deformation when loaded, which is used to compensate for the relative displacement of the two shafts. At the same time, the stored elastic deformation can relieve the impact, and can also change the rigidity of the coupling and adjust the shaft. To avoid the resonance of the natural frequency, at present, in the flexible coupling, the material of the elastic element is metal and non-metal, which can make the coupling have torsional elasticity, axial elasticity and radial elasticity. The general requirements for elastic components are as follows:

1. With high elasticity and damping, the rigidity is constant and durable

2. Store larger deformation energy under the same conditions, which can achieve better buffering and eliminate vibration effects

3. Reasonable structure and good craftsmanship

4. Small size and light weight

Compared with non-metallic elastic elements, metal elastic elements have the following characteristics:

1. High fatigue strength, large bearing capacity, compact structure, small size and light weight

2. The performance of the coupling is relatively stable, the working range is wide, suitable for high speed, heavy load, and also suitable for precision servo system and data transmission system.

3. Good durability, long service life, no aging and deterioration

4. The elastic modulus is large and stable, making the kinetic energy characteristics of the coupling easy to control