Harmonic Drive
Coating Unit Linear Actuator
Special actuator
Harmonic Drive gears can be used to drive linear actuators for applications demanding high linear forces and exceptionally high accuracy. An interesting application of this type of actuator is in the coating section of a paper machine. The linear actuator is used to accurately control the thickness of varnish applied to the surface of the paper. The actuator positions the coater blade relative to the paper and so controls the coating thickness.
The coater blade is pre-loaded and the actuator must apply adjustment forces of up to 10 kN in both tension and compression. The drawing shows the basic design of this special actuator. The actuator is driven by a stepping motor and the motor rotation is transmitted to a precision ballscrew via a specially developed HDUR component set. The ballscrew converts the rotary motion at the gear output into a precise linear motion which is guided by means of a pre-loaded ballspline.
The stainless steel housing enables reliable operation in humid or chemically corrosive environments. The gear is specially designed to provide the actuator with self-locking characteristics, which allow the motor to be switched off when the actuator is at a stand-still, even under load.
