Deflection Sheaves for Elevator Application in Lightweight Design

Current elevators are mostly designed as rope-dependent elevators. Main components in the roping system are the deflection sheaves which are conventional manufactured of grey cast iron. Due to the high weight of cast iron sheaves there is a high potential for reducing mass, especially when regarding aspects of effort, safety and ergonomics while assembly and maintenance in the elevator shaft. Within the framework of a R&D co-operation the Chemnitz University of Technology and the AMB Oberlungwitz GmbH developed a fibre-reinforced plastic sheave that comply with the requirements of lightweight design. The technological basic approach to realize that development is compression molding of glass-mat-reinforced thermoplastics (GMT). The project includes the whole development-chain, consisting of part design, tool design, process chain arrangement, parameter studies as well as validation of specimen. In the course of the project appeared a high potential for improvement of the part properties by alternative design solutions. In this context current activities are focused on multi material design methods such as combining GMT with other thermoplastic prepregs. In this manner it is possible to equip every local area with the specific properties that are required. For example the ribs of the sheave, that receive highest values of stress, can be made of materials with continuous-fibre-reinforcement while the basic part body consists of GMT, which is long-fibre-reinforced. This method also enables to avoid process influenced effects like the segregation of the fibre-matrix distribution in GMT. Additionally the input of different materials offers chances to inlay non-preheated prepreg blanks into the compression mould, so that the amount of the preheated material volume can be reduced. In this way cycle times and also lost of temperature due to transfer times of the heated blanks to the mould can be reduced.