Internal Structure of Office Chairs
The internal structure of an office chair mainly consists of five parts: the base frame, support and adjustment system, seat and backrest, additional components, and pivot design, which work together to provide support, adjustability, and comfort for the chair.
The base frame is the load-bearing core of the office chair, typically formed by bending 14-gauge steel tubes to create the frame structure for the bottom cushion. It connects the end heads and welds horizontal steel bars to form a stable support system, while also providing an installation base for the seat adjustment mechanism. S-shaped steel springs are suspended from the front to the back of the seat frame, dispersing pressure through elastic deformation, while the horizontal bars enhance overall stability. The backrest frame includes a spinal support structure and armrest attachments, with the steel surface needing to be deburred to avoid scratches. Some high-end models adopt ergonomic curve designs that fit the natural curvature of the back.
The support and adjustment system centers around the gas lift (pneumatic rod), which enables seat height adjustment and 360-degree rotation by compressing gas. The chassis connects the gas lift to the seat, with some high-end models employing dynamic support technologies. For instance, dual dynamic lumbar support systems automatically adjust support intensity with changes in sitting posture through the cooperation of elastic materials and mechanical structures; flexible back-following designs maintain continuous contact with the lumbar spine through a deformable back frame.
The seat and backrest directly affect user comfort. The seat consists of a three-layer structure of wood, foam, and fabric, with the front end of the cushion adopting a downward-sloping waterfall curve design to reduce pressure on the thigh veins and promote blood circulation. The backrest typically includes adjustable lumbar and head pillows, with the position and support intensity of the lumbar pillow adjustable via mechanical or pneumatic devices. Some models employ a hip-axis following system (such as the Yongyi Flow550), which aligns the backrest's rotation axis with the human hip joint to achieve synchronous movement between the backrest and lumbar spine, avoiding the "empty waist" phenomenon.
Additional components include casters, chair legs, and armrests. Casters are often made of nylon or polyurethane materials, balancing wear resistance and quiet operation; chair legs are usually five-pointed star-shaped structures that enhance load-bearing capacity through reinforcing ribs; armrests are adjustable in height and angle, with some models equipped with 4D adjustment functions (up and down, front and back, left and right, rotation) to suit different usage scenarios. High-elasticity mesh fabric has become the mainstream material for seats and backrests due to its good breathability and moderate elasticity.
The pivot design affects the่ๅจ (coordinated movement) effect between the backrest and seat. Traditional bottom-axis structures have pivots hidden beneath the seat cushion, which are misaligned with the human hip joint's pivot point, causing the backrest movement to lag behind the lumbar spine; hip-axis structures (such as the FLOW hip-axis following lumbar support system) align the rotation axis with the human hip joint, making the backrest's movement trajectory consistent with the natural curvature of the lumbar spine, significantly improving comfort during prolonged sitting.
