Von Duprin: The Sound of Silence

Inventions usually happen because somebody recognizes a need and tries to find a solution. It is said that door closers were invented after churchgoers complained about the noise caused by slamming doors. At one time door closers were called door checks which is probably a referral to a device which stopped or checked a door from moving too quickly and slamming against the door stop.  

Exit devices supposedly had a similar cause and effect beginning. A Chicago theatre locked their exit doors from the inside in order to prevent unpaid guests from entering. When a fire broke out during a performance,  many people were killed. This event prompted an Indianapolis hardware dealer to invent a way to secure exit doors while still allowing ease of egress during an emergency.  As a result, Von Duprin exit devices were invented. 

While the basic push-bar-to-exit design has remained the same for over 100 years,  improvements on the original design continue to be made.  One improvement is the Quiet Electric Latch (QEL) feature.  As electronic access control increases market share, electrified latch retraction has become commonplace.   Von Duprin exit devices have had an electric latch retraction option (EL) for many years.  Electric latch retraction usually consists of a solenoid which exerts rapid push bar motion and a notable sound as the push bar is stopped at the unlocked position.   

Situations such at hospitals, libraries, museums and theatres often require a quiet atmosphere. Noises can be disruptive. Von Duprin has an answer with their Quiet Electric Latch Retraction kit (QEL).   Von Duprin QEL kits uses electric motor operation in place of a solenoid. Electric motors using screw drivers can be calibrated to minimize any sounds caused by latch or pushbar movements.

QEL conversion kits are available for Von Duprin 98/99 and 33a/35a series exit devices. QEL wiring must be attached to the fire alarm system if installed on fire exit hardware.  The conversion kit consists of a baseplate assembly wich replaces the existing assembly. Different kits are required for a three foot wide device or a four foot wide device. The device must be removed from the door for conversion.

Installation Steps:

1. Remove case cover and pushbar.
2. Remove manual dogging assembly. The manual dogging assembly may have been fastened either with screws or rivets.
3. Install new Install QEL motor assembly. 
4. Attach pushbar and reinstall case cover. 

QEL operation is controlled by an 871-2Q logic board. A Von Duprin PS873 power supply furnishes 4 amps at 12VDC or 2 amps at 24VDC which can operate up to four Von Duprin QEL-equipped devices (photo 5).  QEL automatically calibrates pushbar movement replacing the need for adjusting vertical rod components.  Complete QEL conversion kit instructions are and other information can be downloaded at at: http://us.allegion.com/industries/custom/quiet/Pages/default.aspx