Positioning system for rotating type wheels - has permanent magnets and Hall generators for position coding using combined signals to represent particular displacement

摘要

The positioning system esp. for type wheels, comprises an electro-magnetically operated pawl arm (4) which engages with slots in the type wheel or other rotating mechanism (1). The wheel has groups of permanent magnets (2) around its periphery at certain angular displacements. These operate in conjunction with a group of Hall generators (3) to provide position-coded signals. The position detection method uses four Hall generators so that the combined signals represent a particular angular displacement, and thus position, of the wheel. The Hall outputs are fed to trigger and logic circuits. The output of the logic circuits control drivers which actuate the pawl electromagnets so that the wheel is locked in the desired position.