Operator safety is a major concern in a nonwovens plant. To prevent operators form getting into running machinery, safety interlocks are employed to keep the doors shut until the machinery has come to a complete stop. The interlock contains an electric solenoid that will not re-lease the tang until the machine is stopped. The interlock is usually placed on the machine and the tang on the door. Additionally some interlocks may have secondary safety devices. The picture at the top right shows an interlock with a screw that must be backed out before the inter-lock will open. Since the screw is long and the threads fine, it takes a couple minutes to open the interlock thus allowing, in this instance, a doffer roll to come to a complete stop. The bot-tom right picture shows an interlock combined with a push button. The button lights when certain electrical conditions are met. Once the button is lit, it can be pushed and the interlock will open.
No one should ever attempt to electrically or mechanically defeat a safety interlock.