AB key lock, it has two kinds of A. B keys. It is a kind of lock made up of the structure of the bullet and so on. The depth of the pit is different from that of the tooth of the flat key. The function of AB key is that when people install the lock, the owner can give a key to the house fitters for them to use when they enter and exit the house, so it is also called 'fitment key'. When the decoration is finished, the owner does not need the decorator to enter the room. After the owner inserts the B key into the lock hole and turns the lock cylinder, the a key loses the function of unlocking. Therefore, the B key is also called 'the owner key'. A. The advantage of B key lock is that it can meet the needs of people to decorate the house, so as to avoid losing the key to open the door when the decoration is busy, or the person who has a bad intention to copy the key to open the door when the decoration is busy, which may avoid the unsafe factors to the owner after the decoration, and also avoid the trouble and cost caused by changing the lock for safety after the decoration, so it is welcomed by people. The difference between two kinds of AB keys and the working principle of lock 1. For the sake of people's easy to distinguish, 6 B keys are sealed in transparent hard shell, and 2 a keys are hung outside. Some AB keys are different in color. Two a keys are yellow and six B keys are white. The back of the 6 B keys is provided with the instruction manual. The owner should read it clearly before use, recognize the use methods of the two keys, do not mix them up, and avoid improper use of the two keys. 2. If the two kinds of AB keys are carefully observed, experienced people will find that there is a difference in one of the seven pits on the key. I think the expert must have some ideas in mind. It's not convenient for us to say the specific differences too carefully, so I remind the owner of the room to take back the key a after use, and properly store or destroy it 3. The structure of the marbles in the marbles chamber corresponding to the pits with different depths of AB key is special, and a φ 1mm steel ball is installed between the upper and lower marbles. When key a is used, the height of the downball in the chamber plus the height of the small steel ball is exactly flush with the lock cylinder, so key a can turn the lock cylinder to unlock; when key B is used, the small steel ball can be pushed out of the lock cylinder, that is to say, the downball is flush with the lock cylinder at this time, so key B can also turn the lock cylinder to unlock. This principle is the same as that of the parent-child key system After the lock cylinder rotates at a certain angle, the small steel ball will fall into the blind hole cleverly designed on the lock cylinder in advance under the effect of the spring loaded on it. Some people call this small blind hole a trap, which is very appropriate. The diameter of the blind hole is larger than that of the small steel ball, but smaller than that of the bullet. Otherwise, the bullet will fall down and lock the lock cylinder. Once the small steel ball falls into the blind hole, it can only rotate with the lock cylinder, and will not run out of the blind hole, which will not affect the use of key B. However, when using key a, because there is no small steel ball, the lower shell in this billiard chamber cannot be flush with the lock cylinder, and the lock cylinder cannot be turned to open the lock. Two unlock 1. The lock cylinder is designed to be lockable both inside and outside the door, so the middle part of the inside and outside lock cylinder is equipped with a clutch device. When one side of the lock cylinder is inserted into the key, the front end of the key will push the plug-in device on this side into the joint groove in the middle cam, and at the same time, the plug-in device in the slot on the other side can be pushed out of the groove. When the lock cylinder is rotated, the plug-in device drives the cam to move the lock tongue to unlock. There are two ways to locate the depth of 2Ab key inserted into the lock cylinder, one is to locate with the root of the key, the other is to locate with the front end of the key. The positioning function is that when the key is inserted, not only can each lower bead fall into a suitable pit, but also can make the front end of the key connect the plug-in device with the cam, and drive the cam to rotate.