What is it?
Coupling is a device that connects two shafts together at their ends with the purpose of transmitting power. They normally do not allow disconnection of shafts during operation, however there is torque limiting them which can slip or disconnect when some torque limit is exceeded.
To join two pieces of rotating devices while permitting some degree of misalignment or end movement or both is the couplings primary purpose. By careful selection, servicing and of installation them, substantial savings can be made in reduced maintenance costs and downtime.
What is gear coupling?
It is a mechanical device for transmitting torque between two shafts that are not collinear. It consists of a flexible joint fixed to each shaft. The two joints are connected by a third shaft, called the spindle.
Each joint consists of a 1:1 gear ratio internal/external gear pair. The tooth flanks and outer diameter of the external gear are crowned to allow for angular displacement between the two gears. Mechanically, the gears are equivalent to rotating splines with modified profiles. They are called gears because of the relatively big size of the teet possess higher torque densities than common joints designed to fit a given space while common joints induce lower vibrations. The limit on torque density in common joints is due to the limited cross sections of the cross and yoke. The gear teeth in a gear coupling have high backlash to allow for angular misalignment. The excess backlash can contribute to vibration.
Gear couplings are generally limited to angular misalignment, we.e., the angle of the spindle relative to the axes of the connected shafts, of 4-5°. Universal joints are capable of higher misalignment.
Single joint gear couplings are also used to connect two nominally coaxial shafts. In this software the device is called a gear-type or flexible coupling. The single joint allows for small misalignment such as installation errors and modifications in shaft alignment due to operating conditions. These types of gear couplings are limited to angular misalignment of 1/4-1/2° generally. Check – Cardan Shaft Manufacturers.
It is generally observed that even with the most exacting precision in the original installation, subsequent misalignment can rarely be avoided over a period of time, foundations may settle, bearings ultimately wear and measurements change with heat range.
The misalignment also takes place due to vibrations. These Flexible Gear couplings are available in two configurations – Full Geared and Half Geared Half Rigid.
Full Geared Coupling: Here both the halves are identical and consist of two Hubs and two outer Flanges Sleeves bolted collectively. This type of Coupling is capable of accommodating both Offset as well as Angular misalignment.
Half Geared Half Rigid Coupling: Here instead of two identical halves one half is geared and the other half is rigid. There exists a single Hub in this type since the other aspect is rigid. This type is used for taking care and attention of only Angular misalignment.