Office Chair Base

The formal name for the office chair base is the chassis or swivel base, which serves as the core support and adjustment mechanism for office chairs. It primarily undertakes the following functions:

1. Enabling Horizontal Rotation
The base utilizes built-in bearing structures to allow the chair seat (including cushion and backrest) to rotate 360 degrees horizontally around the axis of the gas lift. This function enables users to easily turn around to retrieve items, communicate with colleagues behind or to the side, or slightly adjust their angle facing the computer without getting up, significantly enhancing flexibility and efficiency in office settings. The smoothness of rotation depends on the precision and lubrication of the base bearings, with high-end bases potentially employing silent bearings to reduce friction noise.

2. Controlling Recline Adjustment
The base integrates mechanical structures for recline functionality, including springs, dampers, or fiberglass springs. By operating the control lever on the right side of the chair or the knob at the bottom of the base, users can lock the recline angle (e.g., 100°-135°) or adjust the backrest rebound force. Depending on the recline method, bases are categorized into three types:

• Back Recline: Only the backrest reclines, with the seat remaining horizontal;
• Seat Recline: The seat and backrest recline simultaneously, but with a fixed angle ratio;
• Synchronous Recline: The backrest and seat move in tandem according to ergonomic proportions (e.g., when the backrest reclines 15°, the seat tilts forward 2°), providing a more natural lying position and reducing lumbar pressure.

3. Bearing and Connecting Functions
The upper end of the base connects to the seat frame via bolts or clips, directly bearing the user's weight (typically designed to support a range of 100-150kg); the lower end connects to the top of the piston rod of the gas lift (gas spring) through a central hole or sleeve. The nitrogen pressure difference inside the gas lift drives the piston rod to extend or retract, with the lifting action transmitted to the seat through the base to achieve height adjustment (typically ranging from 40-55cm). The connection strength between the base and the gas lift directly affects the chair's safety, with poor-quality bases potentially causing the seat to tip over due to loose connections.

Structural Composition
The base consists of two main modules:

• Control Mechanism: Includes the control lever on the right (for locking/unlocking recline) and the bottom knob (for adjusting rebound force), with some high-end models employing wired or electric controls;
• Connecting and Mechanical Structure: Comprises a metal frame (providing structural support), rotating shafts (enabling rotation and recline), springs/dampers (controlling recline resistance), and a plastic or metal housing (protecting internal components and enhancing aesthetics).

The design of the base must balance strength, durability, and ergonomics, with its materials (such as cold-rolled steel, engineering plastics) and processes (such as stamping, injection molding) directly influencing the chair's lifespan and user experience.