What is a Friction Torque Limiter?

Friction torque limiter is a protective device that restricts torque transfer in the drive system by sliding when the torque needs exceed a preset value due to shock load, overload, overload, or machine jamming. The minimum to have low-cost protection. Torque Limiter is operated with a spring friction surface that adjusts the spring force to provide slip torque. Recca friction type torque limiter can be mounted on a shaft, capable of transmission with a sprocket, gear, pulley, roller chain, or flange as a centerpiece and sandwiched between two friction lining plates. It enables the safe operation of protective equipment at the lowest possible cost.

How Does A Torque Limiter work?

Selection Guide

1. Determine the required slip torque from the loading conditions or from the design strength of the machine. If the loading conditions of the machine are unknown, set the required slip torque of the Torque limiter to 1.5 to 2 times of the torque that the motor produces on the shaft where the Torque limiter is mounted.
2. Select a Torque limiter which has enough torque range and bore range.
3. Determine the proper bushing length from the thickness of the center member to be inserted between the friction facings. Always choose the largest bushing which does not exceed the width of the center member. Maximum thickness of the center member is shown as ’ S(max)’ in the dimension table.

Torque Limiters’ Center Part

1. Process the friction face of center parts to ensure the rated torque, planeness and parallelism in line with the bore and protect the partsfrom the rust and oil. The recommended surface roughness (Ra) is1.6. The sliding torque will be not stable if the center part is defected.
2. Please process the bore of center parts according to the followingTable and, select sprocket with min. teeth number and lining ringlength.

How To Set the Torque for A friction torque Limiter? 

Tight and loose the adjusting bolts or nuts to set the torque of the Torque Limiter. The Limiter from size RTL50 to RTL89 depend upon theadjusting nuts, whereas RTL127 and RTL178 depends upon the adjusting bolts. Set the torque after mounting the Limiter upon the shaft as follow:

For sizes from RTL50 to RTL89
Rotate to tight the adjusting nuts by hands to fix thedisc spring and plate. Then, try to tight the nuts (about 60C) by wrench.

For sizes from RTL127 to RTL178
First, rotate the nuts to tight the disc spring and pressure plate.Then tight all the adjusting bolts (about 60°)

If the Limiter slides with normal loading, please tight the nuts (for sizes from RTL50 to RTL89) or bolts (from RTL127 to RTL178) generally until the Limiters stop sliding. Please ensure that each bolt is tightened or lossened averagely.
Find out the setting torque appropriate for the equipments aftertests. Please refer the following Table that shows the relationship between the effective rotation angle and torque setting.
To make torque setting precisely, we recommend you to use Torque Limiter for trial once. For example, while the rotation speed is 50~60 rpm with 500 circles, rotate the adjusting nuts or bolts around 45°.

Frition Torque Limiters Rotation Angle and Torque Setting Chart

Dimensions Chart For RTL50~RTL178           

Dimensions In mm