When the recessed mag lock is installed into the header of a sliding door opening, a shear style mag lock is installed. With a conventional magnet in this position, the door slides away from the magnet and the magnetic forces are not strong enough to secure the door. The shear style electromagnetic locks use additional holding force components to keep the door from opening.
An example is a shear lock installed into the header of a sliding door. When closed, the magnet contacts the top of the door. To stop the movement, obstacles interact between the magnetic face and the armature/strike plate. They include ball bearings or steel locking tabs built into the strike plate with receptacles in the lock housing to prevent the door from sliding. When the shear style electromagnetic lock is powered, the strike plate is drawn against the magnetic face and the ball bearings enter into recesses in the face of the magnet or the steel locking tabs enter their recesses. In this condition, the door cannot be slid open.
Shear style electromagnetic locks can have a holding force of 600 to more than 2500 pounds. Shear style electromagnetic locks are sold under different names including Camden Shear Lock, SDC Hi/Shear and Securitron Shear Aligning Magnalock (SAM/SAM2).
Another application for the shear style mag lock is a surface mount application for an inswing door. The SDC 1561TJ Series incorporates a 2,000-pound holding force electromagnetic lock with field-adjustable shear stops. The 1561TJ can be installed onto wood, hollow metal and Herculite style doors with top rails.
The challenge is properly secure the door when the electromagnetic lock is normally positioned along the header for swing door applications. For added protection, some electromagnetic lock manufacturers offer a double mag unit that provides locking near the top and bottom of the swing (lock) side of the door. Other companies offer full length housings where electromagnetic locks are installed.
One such product is the Rofu magnetic door locking device, Model 8122-002, for single-swing door applications. The 83” long bar with two 1,500 -pound electromagnets along each end is a vertically mounted onto the jamb. This device becomes the jamb stop. The Rofu 8122-002 has a door status sensor and is field adjustable 12 or 24VDC.
This type of electromagnetic lock is used in time out rooms or padded rooms of mental institutions, hospital “psych” wards and schools. This type of device eliminates the need of mechanical locks or knobs. It protects the door from major damage by securing it within the jamb. The locking mechanism is operated by a momentary button on the outside of the door. There is a small window in the door for viewing. When pressed, the momentary button provides power. When the button is released, the door can be opened. This way a person cannot be placed in the room and be left unattended.
Delayed Egress Mag Lock
Another electromagnetic lock mechanism that has become more popular is the delayed egress electromagnetic lock. The function of the delayed egress electromagnetic lock is to notify when someone is attempting to exit through a secondary door. Immediately the alarm sounds, notifying employees of an attempted exit. Once activated, the door remains locked for either 15 or 30 seconds depending upon code compliance. After the time delay, the delayed egress mag lock releases and the door can be opened. Delayed egress mag locks are connected to the fire alarm system to automatically unlock in case of a fire.
There are two types of delayed egress electromagnetic locks. One has a built-in sensor that detects when pressure is applied to push open the outswing door. The second type has a special micro-switch equipped non-latching cross bar that is sold with the delayed egress electromagnet. When the bar is pressed, the micro-switch notifies the delayed egress mag lock, sounding the siren as the 15- or 30-second delay time counts down. After the time delay, the delayed egress mag lock releases and the door can be opened.
The free-egress electromagnetic lock has a built-in passive infrared (PIR) sensor that releases the door when someone enters the sensing zone. The Dynalock 3006 Series is a 1500-pound holding force mag lock with the PIR built into the case.