Handle Under Office Chair

The handle (or knob, lever) under an office chair is mainly used to adjust the backrest firmness, chair height, and locking or unlocking functions. Some chairs also have a handle for adjusting the forward and backward tilt of the seat. Here are the specific functions:

1. Adjusting Backrest Firmness
The handle controls the support strength of the backrest through rotation. When rotated clockwise, the internal mechanical structure (such as springs or pneumatic devices) tightens, making the backrest firmer and providing stronger support, suitable for scenarios where a straight sitting posture needs to be maintained for a long time. Rotating counterclockwise relaxes the internal structure, making the backrest softer and providing more flexible support, suitable for relaxation or leaning back for rest. This function is achieved by adjusting the friction between the backrest and the chair back frame or the compression degree of the elastic elements.

2. Adjusting Chair Height
Height adjustment is usually accomplished by rotating the lever up or down. Rotating upward raises the chair; rotating downward lowers it. The core principle relies on a pneumatic rod (filled with high-pressure nitrogen gas inside) or a mechanical screw device:

• Pneumatic rod: It generates elastic force by utilizing the difference in gas pressure and piston cross-sectional area. When the lever triggers the valve, nitrogen flows inside the pneumatic rod, pushing the piston to move and achieving stepless height adjustment.
• Mechanical screw: It rotates to lift or lower through a threaded structure, with a fixed adjustment range and requiring continuous force application.
  Some chairs need to be adjusted in height while in a sitting position to ensure the normal operation of the pneumatic rod or screw device.

3. Locking and Unlocking Functions
The handle controls the fixed state of the chair through pushing and pulling actions:

• Pushing the lever inward: It activates the internal locking mechanism (such as a catch or friction plate), fixing the current angle or height of the chair to prevent accidental movement, suitable for scenarios where a stable sitting posture is required.
• Pulling the lever outward: It releases the locking mechanism, restoring the chair's adjustment function and allowing the user to readjust the angle or height.

4. Adjusting Seat Forward and Backward Tilt (Some Models)
Some office chairs have an independent handle for controlling the tilt angle of the seat surface. By rotating the handle, the angle between the seat and the horizontal plane can be adjusted:

• Forward tilt mode: The seat surface tilts forward, suitable for scenarios where one needs to work close to the desktop (such as drawing or writing), reducing waist pressure.
• Backward tilt mode: The seat surface tilts backward, forming a lying posture with the backrest, suitable for short breaks.
  This function is usually achieved through a synchronous tilt mechanism, that is, the seat surface and the backrest move in tandem at a fixed ratio to maintain the stability of the body's center of gravity.

Usage Tips: Before adjustment, confirm the function of the handle (which can be distinguished by markings or the instruction manual) to avoid misoperation. When adjusting the pneumatic rod, avoid rapid pressing to prevent damage caused by sudden internal pressure changes. After long-term use, regularly check whether the connection of the handle is loose to ensure normal function.