Double-leaf Hinges are the most common type of hinge used on doors, cabinets, and windows. Their name comes from the fact that when a door or cabinet is closed, the two metal plates “lie flush” against each other.

Core Structure:

A standard double-leaf hinge consists of three main parts:

· Hinge plates: Two flat metal plates with screw holes. One plate is attached to the movable door, and the other is attached to the fixed door frame.

· Hinge rings: Hollow, interlocking ring-shaped structures located on the inner edges of each hinge plate.

· Hinge pin: A solid metal rod inserted downward through the centers of the aligned hinge rings, used to secure the two hinge plates together while allowing them to rotate.

Working Principle and Key Features

1. Tongue-and-groove installation: In traditional installation, a small groove (called a tongue-and-groove) is cut into the edges of both the door panel and the door frame. The hinge is embedded flush with these grooves, ensuring a tight seal between the door panel and the door frame when the door is closed.

2. Heavy-Duty Support: Since the weight of the door panel acts directly on the hinge pin, double-leaf hinges provide robust structural support, making them ideal for heavy solid wood or metal doors.

3. Common Types:

· Standard Bearings: Suitable for basic designs of light- to medium-duty interior doors.

· Ball Bearings: Small bearings are installed between the hinge joints, making them suitable for heavy-duty or high-traffic exterior doors, ensuring smooth and quiet operation.

· Spring-Loaded: Automatically pulls the door shut after it is opened (commonly used for fire doors).