Ogura permanent magnet hysteresis clutch and brake are used to control tension in rewinding application.
Ogura's PHT series.
Description of Operation
A single motor drives a pulley which is attached to the OD of the PHT30. The PHT30 drives the winding roll which draws the material across a flat surface so the operator can inspect it. On the opposite unwinding roll, the PHT30 is also used to control tension on the material.
Reason for Selection of the Ogura PHT Clutch and Brake
Since this is a relatively small diameter, there is not a substantial amount of difference from the tension on the center of the roll to the tension on the OD of the roll. Typically in rewind and unwind applications you want to have a varying torque applied to the shaft so that your tension remains constant. However, if the over all diameter does not differ greatly, a constant drag (or tension) can be used. The PHT units is ideal for this function because there is no frictional contact internally, and there is no wearing parts. Since the PHT can be manually adjusted to different tension amounts, the operator can make a simple adjustment to arrive at the torque required for different types of material. Also, since the PHT units are not speed dependent, the operator can accelerate or decelerate the motor and the PHT units will always deliver a preset torque.
This application is for an inspection table for a wall paper manufacturer. Besides wall paper, other materials such as textiles, foil and film could also use the PHT clutches and brakes for controlling tension. (The difference between a PHT clutch and a brake is only that in a brake, the body is mounted solid, in a clutch, the body rotates freely.) Tension control applications are also critical for wire or film winding applications. In some tensioning applications that are operating at slower speeds, the OPL is also a good alternative. The OPL units from Ogura deliver the same type of hysteresis drag with no wear at a very inexpensive price. (For other information on the OPL and PHT please see the data sheets.)