Abstract
A nonconventional application of worm gears exploits the irreversibility of these power transmission devices in order to realize fast emergency braking. This application can be used to secure lifting devices. A limiting factor in the design of these instantaneous braking systems is the residual deformations of the worm/wheel contacting teeth, due to the impact between them at each emergency stop. The prediction of these residual displacements requires solving of an elastic–plastic, multi-scale and multi-contact problem. Original numerical tools were developed in this study to solve the problem at global and local scales. The method has been validated by comparing the obtained results with 3D measurements on new and deformed worm/wheel pairs. In order to predict the issue of the worm gear after an impact, a criterion based on kinematic errors is proposed. Applying this criterion gives the maximal admissible torque for the braking system to be operational after the impact.
Highlights
Worm gears are one of the most important devices used for power transmission between spatial crossed axes
The semi-analytical solver allows overcoming difficulties of finite element method in dealing with nodal forces. – In steps 6–8, the bending and the contact residual displacement fields resulting from the plastic deformation at the local and global scales are transferred to ROUVISLAM, in order to compute the kinematic errors, and to predict whether the worm gear will be able to continue to ensure the safety of the lifting system
Numerical simulations are compared to measurements in order to validate the method presented above to solve the elastic–plastic, multi-scale and multi-contact problem encountered in the worm gear used in the Fastbrake© system
Summary
Worm gears are one of the most important devices used for power transmission between spatial crossed axes They are employed in applications requiring high reduction ratio, relatively low speed drive and compactness. Worm gears are widely employed in industrial applications such as automotive applications (mainly for actuators), steam turbines, lifts, conveyor belts and stringed musical instruments They present some disadvantages compared to parallel axis gearing, such as delicate assembling, or high wear rate and lower efficiency due to the sliding between the contacting teeth. A nonconventional application of worm gears exploits this latter feature in order to secure lifting devices during uncontrolled movements, such as over-speed, backwashing and gear failure This feature is used in the Fastbrake© system developed by FOC Transmissions.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
