Trapezoidal screw jack has self-locking function which means when the rotational force on the screw is removed, it will remain motionless where it was left and will not rotate backwards, regardless of how much load it is supporting. Self-locking function is very important for some applications.

Self-locking and back-driving conditions are defined in the following 4 situations:

This condition happens when the direct efficiency value is lower than 0.30.

• Working screw jack with a load opposite the motion: by interrupting the motor power supply the screw jack stops.This condition happens when the direct efficiency value is lower than 0.25.

• Working screw jack with a load applied on the same direction of the motion: the screw jack’s stop is not guaranteed by interrupting the motor power supply. The screw jack stops only if the direct efficiency value is lower than 0.20 and, anyway, it stops in an unrepeatable position.

In  this  case,  we  recommend  to  use  a  brake  motor  to  stop  the  load  and  keep  it  in  position, avoiding the motion start in case of pushes or vibrations.

with direct efficiency values between 0.30 and 0.50, the screw jacks are in  an  uncertain  self-locking  condition.  The  self-locking  depends  on  the  load  and  the  inertia  of  the system. In  this  case  we  recommend  to  use  a  brake  motor  to  guarantee  the  self-locking  condition  or  to  contact Lude Transmission to evaluate the application.

We remind you that, in any case, also to start a not self-locking screw jack a certain minimum load must be applied. To define this load value please contact Lude Transmission.

Learn more about self locking screw jacks at www.ludetransmission.com. (Screw jacks supplier China)