subject: Types and Applications of Fluid Couplings [print this page] A fluid coupling is a hydrodynamic device used to transmit rotating mechanical power. It offers the advantages of soft starting of the load, torque limitation, and mechanical shock absorption which are all with minimal energy loss.
Addition to the hydraulic fluid, a fluid coupling consists of three components. Those are the housing and two turbines. As to these two turbines, one is known as the pump or impellor that is connected to the input shaft; the other is known as output turbine or runner that is connected to the output shaft. In its simplest form, a fluid coupling consists of two hollow bowls with radial vanes. One bowl is connected to the input shaft and the other to the output shaft of the coupling. When the input bowl is filled with fluid and rotated by the prime mover, centrifugal force causes the fluid to be flung outwards. And then the high velocity fluid impinges on the vanes of the output bowl, transferring torque to rotate the bowl and output shaft. The production of them is rather simple. For instance, the turbines can be aluminum castings or steel stampings, and the housing can also be a casting or made from stamped or forged steel.
Fluid couplings can be further divided into various types. There are constant-fill couplings, delayed-fill couplings, variable-fill couplings, and centrifugal lockup couplings, etc. The first category is the most common type of fluid couplings. The second type is designed with a delayed filling chamber, where a portion of the total fluid in the coupling is stored in a reservoir while the motor is starting. As to the third type, the drive motor can be started and run without any load until fluid is introduced to the coupling by the operation of an external lever.
Addition to the various categories, there are also various applications of the fluid couplings. It has been used in automobile transmissions as an alternative to a mechanical clutch. It also has a wide range of application in industries and rail transportation. Besides, they are also used in automotive applications. As in this application, the turbine is connected to the input shaft of the transmission. While the transmission is in gear, as engine speed increases torque is transferred from the engine to the input shaft by the motion of the fluid, propelling the vehicle. The fluid couplings can even be applied in the aviation.
All in all, the fluid coupling is a rather important component. It is quite useful in various places.
