Mechanical entrapment prevention for sliding and hinged doors

• Posted on 18 June 2025
• 0

The ALPHA, mechanical entrapment prevention for sliding and hinged doors

The ALPHA is a mechanical entrapment prevention for sliding and hinged doors on machinery. The ALPHA prevents unexpected machine restart during maintenance or cleaning, and protects operators against being trapped when entering the safeguarded area with their whole body.

The ALPHA is used as an additional safety measure on existing interlocks and provides protection in line with the Lockout-Tagout (LOTO) principle, without requiring any electrical modifications.

How does the ALPHA work?

ALPHA for hinged doors
When the machine is running, the door is closed and the safety contacts of the existing safety interlock are closed.

When the door is opened, the safety interlock disables the machine. The ALPHA prevents the door from being fully opened until the key is turned and removed.

Turning and removing the key serves two functions:
- The front blocking plate is released, allowing the door to be fully opened.
- The rear blocking plate is rotated, mechanically preventing the door from being closed.

The operator takes the key as a personal safety key into the safeguarded area. Without this key, the door cannot be closed and the machine cannot be restarted.

ALPHA for sliding doors
When the machine is running, the sliding door is closed and the safety contacts of the existing safety interlock are closed.

When the door is opened, the safety interlock disables the machine. The ALPHA also prevents the sliding door from being fully opened until the key is turned and removed.

By turning and removing the key:
- The front blocking plate is released, allowing the sliding door to be fully opened.
- The rear blocking plate is rotated, preventing the sliding door from being closed.

Again, the operator takes the key as a personal safety key into the safeguarded area. As long as the key is not returned, the door cannot be closed and the machine remains locked out.

Lockout-Tagout application
The ALPHA can optionally be fitted with two Lockout-Tagout safety padlock points. This allows multiple operators to mechanically secure their presence in line with applicable LOTO procedures.

Technical features
- Mechanical trapped key interlock for sliding and hinged doors
- Prevents unexpected restart during whole body access
- Fully mechanical, no wiring or programming required
- Easy to integrate with existing interlock systems or light curtains
- Stainless steel construction, suitable for heavy industrial use
- Mounting with only two fixings
- Suitable for dusty, dirty or wet environments, and installations requiring regular washdown
- Two padlockable points for additional Lockout-Tagout safety padlocks

Typical applications
- Safeguarded areas with sliding or hinged doors
- Access points where operators enter the hazardous area with their whole body
- Additional protection on existing interlock systems or light curtains (BRAVO for light curtains)
- Environments with Lockout-Tagout procedures

For technical specifications or application advice about the ALPHA, please contact Lockout-tagout-shop.com.