Fire door electromagnetic releaser, referred to as fire door releaser for short, is a normally open fire door positioning device, which has the function of keeping the fire door normally open and automatically releasing the fire door, and automatically closing the fire door under the action of ordinary door closer after release. So as to completely solve the inconvenience caused by the normal closing of the fire door to the passage of people and the man-made damage caused by frequent opening and closing, and ensure the fire safety at the same time, and is widely used in the normally open fire door on the fire evacuation passage of buildings.
The first generation product is called electromagnetic release (see figure 1), which consists of an electromagnetic iron absorber, a lever, a valve plate and a spring. Usually, the lock is manually inserted into the electromagnetic release and stuck. In case of fire, the electromagnet is energized to act, and the lock is released under the action of pulling force. However, due to the complex internal mechanical structure, easy deformation and high failure rate, and the control mode of "power supply closing", it does not meet the fire protection requirements, so it is gradually eliminated by the market. The second generation product is called electromagnetic door stopper releaser (see Figure 2). When pushing the door, electromagnetic door stopper will hold the door tightly and position it automatically without manual operation. The principle and structure are simple and reliable, and the service life can reach decades or even hundreds of years, which meets the fire protection requirements of "power failure and door closing". Therefore, electromagnetic door stopper releaser is mainly used for fire doors of buildings.