Gear Coupling

The gear coupling is a type of movable rigid coupling. It utilizes the meshing of internal and external teeth to transmit torque and rotational motion between the two halves of the coupling. It is suitable for connecting the transmission shafting of two concentric shafts and has the capability to compensate for the relative displacement of the two shafts to a certain extent. The gear coupling is composed of main components such as an internal gear ring, a gear sleeve, and end caps. Generally, for small-sized gear couplings, the end cap and the internal gear ring can be integrated into a sigle unit.

Owing to its characteristics including compact structure, high load-bearing capacity, wide operating speed range, and reliable performance, the gear coupling is widely applied in various mechanical industries such as metallurgy, mining, lifting and transportation, petroleum, and shipbuilding.

Based on the differences in the axial tooth profile of their external gear sleeves, gear couplings can be divided into three types: straight-tooth gear couplings, crowned-tooth gear couplings, and special crowned-tooth gear couplings. Regardless of the type, the internal gear ring is identical to the involute straight-tooth internal gear in all aspects except for the selection of the tooth tip clearance coefficient.

The axial tooth blanks of the external gear sleeves in straight tooth gear couplings can be processed into two forms: straight-line and circular-arc. However, both the reference circle and the root circle are straight lines. The meshing form of this type of coupling is completely the same as that of the internal and external meshing of involute cylindrical gears. It compensates for the relative displacement between the two shafts by increasing the tooth side clearance of the internal and external teeth, but the compensation amount is limited.

The tooth tips of the external gear sleeves in crowned-tooth gear couplings are processed into circular arcs, meaning the tooth blanks are processed into spherical shapes. In the cross-section that lies on the tooth center plane and is tangent to the pitch cylinder surface, the tooth profile takes on a crowned shape—hence the name "crowned-tooth gear coupling". Its characteristics are as follows:

High load-bearing capacity: Calculated based on bending strength, under the same conditions, it can transmit 15% to 30% more torque than straight-tooth gear couplings.

Reasonable structure and reliable performance: Due to the crowned shape of the tooth sides, when the axes are at a certain angle, the contact condition is improved. This reduces the contact stress, eliminates the load concentration at the tooth ends of straight-tooth couplings (i.e., eliminates edge extrusion), and enhances the working performance.

Excellent compensation performance: The crowned tooth profile of the external gear sleeve increases the allowable relative offset of the two connected shafts. The maximum allowable inclination angle can reach up to 6 degrees, and the generally recommended range is 1.5 degrees to 2.5 degrees.