Door Controls: Perfecting the Opening and Closing Cycle

Door Controls: Perfecting the Opening and Closing Cycle

Posted by Allegion on Aug 22nd 2024

In most applications, a pedestrian manually opens a door, and a door closer controls the speed and force with which the door shuts behind them. The power to close the door is generated by the springs inside the closer. Regulated hydraulic circuits control the speed of the door’s closing swing. An ideal door closing cycle can be achieved using one of the many LCN door closers available.

Diagram: Main Stages in Correct Door Operation
  1. Opening Swing: The door closer’s function is to let the door open easily, except at the end of the swing where backcheck is applied.
    2. li>Backcheck: This feature cushions the opening swing to prevent the door from slamming into the stop. Special closers designed for potentially abusive applications, such as LCN’s Advanced Variable Backcheck (CYLAVB), begin the backcheck function much earlier (2A).
  2. Closing Arc: A uniform, reasonable (main) speed should be maintained through the long closing arc.
  3. Latching Arc: This brings the door to a quiet, secure close.

Building Up Power to Close the Door

As a controlled door is opened, the spring of the closer is compressed, building up the power to close the door. Normally, more opening force would be required as spring compression increases. However, an LCN closer changes its arm geometry while the door opens, increasing the door leverage. This offsets the spring compression, resulting in greater ease in opening the door.

In Opening: More Leverage for the Person

The changing arm geometry increases leverage over the door to overcome the growing power of the spring, allowing one to pass through the door easily.

In Closing: More Leverage for the Closer

When the person releases the door and the closer takes over, spring power is applied through the arm system to close the door. As the door closes, the spring expands, providing the power to close the door.

Special Closers for Reduced Opening Force

The 1990 Americans with Disabilities Act (ADA) and ANSI Standard A117.1 describe maximum opening force limitations for certain non-fire rated doors. The last page of each closer section in the catalog includes a section titled "Reduced Opening Force Closers." This section lists closers in that specific series that comply with a maximum opening force based on the width of the door.

Any manual door closer, including those certified by BHMA to conform to ANSI Standard A156.4, that is selected, installed, and adjusted based on ADA or other reduced opening force requirements, may not provide sufficient power to reliably close and latch the door.

Refer to the LCN Automatic Operators catalog for information on electric, pneumatic, and electromechanical systems that meet reduced opening force requirements without affecting closer power.
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