Customers often ask, “what is the difference between an ELR and ALR?” They are referring to two types of retractors used in Seat Belts. An Automatic Locking Retractor (ALR) locks when the continuous motion of spooling the belt out is stopped. Once the occupant has pulled the lap belt into place and the seat belt tongue is inserted into the buckle, the ALR allows the extra seat belt webbing to retract into the retractor until the webbing is tight around the occupant’s hips and all slack in the belt is removed. At this point a bar locks into a spool with gears, and prevents any further webbing from being released. The limitation of an ALR is that once the webbing is locked in place, it can become uncomfortable and tight for the occupant if they try to move, because more webbing cannot be withdrawn from the retractor. This function is also called child restraint mode, as the ALR function can be used for securing child seats. ALRs are an older design, though still popular today.
An Emergency Locking Retractor (ELR) is a seat belt retractor that locks only in response to the rapid deceleration of a vehicle or rapid spooling out of the seat belt webbing from the retractor, and increases the comfort of the seat belt assembly compared to an ALR. The ELR was designed to allow the seat belt webbing to move freely once the seat belt is in place, but locking the webbing instantly in the event of a crash. The locking sensitivity of the device has been an important issue given the need to assure that the retractor would lock very early during a collision, but not be so sensitive as to cause nuisance locking during normal driving conditions.
There are two types of ELR functions, the sensitivity to the webbing withdrawal rate and the sensitivity to vehicle deceleration. The vehicle sensibility function of an ELR responds directly to a 0.7 g acceleration pulse and lock-up usually occurs within a short period of time. If the occupant wears a seat belt with an ELR properly and makes sure there isn’t a lot of slack in the belt, it will restrain the occupant correctly during a rapid deceleration of the vehicle.
One of the limitations of a seat belt with only an ELR is that it cannot be used to hold a child seat in place. The belt will still lock in a crash, but the child seat could have moved enough to hit some part of the vehicle during the crash or upon impact. New retractors have been designed that have both ELR/ALR function, so that maximum comfort can be offered to the occupant, but if a child seat must be secured, the ALR function will make sure the belt is automatically locked.
GWR Safety Systems’ mission is 100 percent safety because the value of life is crucial and customer’s safety means the world to us. Therefore, we design and manufacture Emergency Locking Retractors (ELRs) and Automatic Locking Retractors (ALRs) for seat belt systems used to improve both passenger and driver safety and reduce injury and deaths from accidents.