4L55/4L56 - Mechanical Slam Action Cell Lock



To provide secure locking of swinging cell doors, under conventional key control where automatic deadlocking is a requirement.


The 4L55 and 4L56 are surface mounted locks of robust construction based on the Chubb Lock Custodial Services standard cell lock footprint. The main bolt is automatically extended providing a throw of 32mm and deadlocked on closure of the door.

The 4L55 is designed to be mounted flush with the door skin whereas the 4L56 is designed to be mounted on the door skin itself.

Note: An alternative fixing method can be used to enable mounting of the 4L56 variant flush with the door skin.

Secure locking is achieved as follows:

  • Unlocking is achieved by a partial turn of the key which lifts the internal blocking mechanism enabling the withdrawal of the main bolt by the handle. The bolt is then retained automatically when fully retracted and door is out of frame.
  • Locking is achieved automatically; on closure of the door the brass snib bolt is depressed on contact with the strike plate mounted to the frame this then releases the main bolt. Deadlocking occurs when the main bolt is fully extended allowing the internal blocking mechanism to engage.
  • The lock has an external visual indicator mechanism, which enables staff to verify the status of the lock.



  • Solid Case Technology; Lock case machined from single piece carbon steel.
  • Steel main bolt, with carbide anti-cutting rollers and 32mm throw.
  • Brass quick acting stud release mechanism.
  • External visual locking status indication.
  • Independent 7-lever locking mechanism.
  • Factory restricted key section.
  • 5 bolt secure fixing.
  • Integral baffle arrangements to resist interference via the keyhole.
  • Escutcheon designed to give positive key alignment.


  • Mechanical locking mechanism tested to a minimum of 100,000 operations.
  • Handle mechanism tested to a minimum of 300,000 bolt operations.
  • Stud release mechanism tested to a minimum of 300,000 operations
  • Saw attack 12 hours
  • End load 20 kN
  • Side Load 25 kN

Additional Features

  • Range of Anti-Ligature or 'T' handle furniture options available.
  • Range of fixings including backplates, stud fixings, locking plate and keeps.
  • Available in alternative paint / furniture finishes on request.
  • External handle designed to shear under excessive load to prevent damage to internal lock mechanism.
  • Interchangeable mechanical inner locking unit to enable re-coding.
  • Can be configured to differ or to pass.

Total Range

  • The lock is available in left or right hand variants for opening in or opening out doors and can be fitted to steel or wooden doors. A range of backplate stud lengths is available to suit door thicknesses from 25 to 70mm.
  • Fully dimensioned customer drawings are available on request to assist with door preparation.

Dimensions & Weights

Case Height286mm
Case Length267mm
Case Thickness30mm
Bolt Throw32mm
Bolt Depth45mm
Bolt Thickness22mm
Weight (lock only) 4L5510.5kg
Weight (lock only) 4L5612.0kg



  • Lock case - carbon steel electro-plated and powder coated exterior.
  • Main bolt - carbon steel electro-plated.
  • Main bolt follower high tensile brass.
  • Keys - Hardened Steel
  • Levers and springs - Brass / phosphor Bronze.