Office Chair Base

The “round disc” beneath an office chair is formally known as the base or swivel base. It serves as the core support and adjustment mechanism of the office chair, responsible for three key functions: horizontal rotation, backrest tilt adjustment, and load-bearing connection.

I. Core Function Analysis

1. Horizontal Rotation Function
   The base connects to the gas lift via a central spindle, enabling the seat (including cushion and backrest) to rotate horizontally around the axis of the gas lift. This design allows users to turn around to retrieve items, communicate with colleagues behind or to the side, or slightly adjust their angle toward the computer without moving their body, significantly enhancing office flexibility. For example, in collaborative work scenarios, the rotation function reduces the need to stand up frequently, improving communication efficiency.

2. Backrest Tilt Adjustment Function
   The base incorporates mechanical structures such as springs, dampers, or fiberglass springs internally. Backrest tilt locking and tension adjustment are achieved by operating the right-side control lever or the bottom knob. Based on the tilt method, bases are categorized into three types:

• Back Tilt: Only the backrest reclines, suitable for short rest periods.
• Seat Tilt: Only the seat cushion tilts backward, distributing pressure on the lower back.
• Synchronous Tilt: The backrest and seat cushion move synchronously at an angular displacement, providing a more ergonomic natural reclining position and reducing fatigue from prolonged sitting.

3. Load-Bearing and Connection Function
   The upper end of the base is secured to the seat frame with screws, directly bearing the user's weight. The lower end connects to the top of the gas lift piston rod through a central hole or sleeve. The nitrogen pressure difference inside the gas lift drives the piston rod to extend or retract, with the base transmitting this motion to adjust the chair's height, ensuring stable and reliable functionality.

II. Structural Composition

1. Control Mechanism

• Right-side control lever: Responsible for height adjustment (press the lever and apply body weight) and backrest tilt locking (move the lever to a fixed position).
• Bottom cylindrical knob: Adjusts backrest tilt tension, increasing resistance when turned clockwise and decreasing it when turned counterclockwise to accommodate users of different weights.

2. Connection and Mechanical Structure
   Includes components such as a metal frame, spindle, springs, and dampers. The metal frame provides structural support, the spindle ensures smooth rotation, and the springs and dampers work together to control the tilt force and rebound speed. For example, fiberglass springs, known for their fatigue resistance, are often used in high-end bases to extend service life.

III. Installation Points

When installing the base, align the tray (the part connecting the base to the seat cushion) with the screw holes on the seat cushion, secure it with screws, and tighten them to ensure a stable connection. After installation, check that the rotation and backrest tilt functions operate smoothly to avoid abnormal noises or functional failures caused by loose screws.