Top is a rotary limit switch used to control the movement of industrial machinery. It operates as an auxiliary controller of electrical motors through a power interface, such as a contactor or PLC. Suitable for heavy duty, its shaft is connected to the motor and, after a set number of revolutions, the cams operate the switches, thus starting the predetermined movement. A worm gear and a helical toothed gear combined with one or more pairs of straight toothed gears are used for the transmission of the movement from the input shaft to the output shaft.
Top is used on wind turbines to control the position of the nacelle or the pitch angle of the blades. The motor that controls the rotation of a wind turbine on the yaw axis (or of the blade around its longitudinal axis) transfers the movement to the limit switch. A rotary encoder reads the rotation of the shaft, and its pulses are sent to a PLC which controls the position of the nacelle or of the blade. The movement of the shaft is also transferred, through a gearmotor, to a series of cam switches: the appropriate setting of the actuating point of the cams can signal up to four critical positions of the movement of the nacelle or of the blade.
Revolution ratios, ranging from 1:1 to 1:9400, result from the use of different combinations of gear wheels between the input shaft and the output shaft, which is connected to the cams operating the switches. Each output of the limit switch can be set with a different revolution ratio to allow for a diversified control of the machinery to meet special requirements.
Each cam can be set with great accuracy thanks to the cam adjusting screws.
The auxiliary switches are of a positive opening type, thus suitable for safety functions.