US 6,523,898 · Granted 2003-02-25
The Synchrotilt Chair Patent That Redefined Office Ergonomics
This is a blueprint for an office chair where the backrest tilts in a unique way—it moves more backward and less downward when you recline, which feels more natural and comfortable. The armrests and lumbar support (lower back cushioning) move with you too, all synchronized so your whole body stays supported as you lean back.
The plain-English version
What it protects
The claim covers a chair design where the back tilt pivot point is positioned rearward of the seat's rear edge, creating synchronized movement between the seat, backrest, and armrests during recline. What's protected here is the specific four-bar linkage arrangement that connects the extension, back tilt bracket, and backrest frame, plus the adjustable lumbar support system with a sliding lumbar section that can change both vertical and horizontal shape independently. The synchronized movement that causes armrests to pivot at a rate between the seat and back motion is also covered.
Why it matters
This patent addresses a real comfort problem: most office chairs tilt the back straight down when you recline, which can feel unstable or strain your neck. By moving the tilt axis rearward and creating synchronized armrest movement, this design keeps your body better supported and aligned throughout the recline motion. The adjustable lumbar support adds another layer of personalization, letting different body types find their ideal lower-back support. For Steelcase, a major office furniture manufacturer, this kind of ergonomic innovation is central to competing in the premium chair market where comfort and health claims drive purchasing decisions.
Real-world use
Every office worker who leans back in a high-end task chair and notices the armrests moving smoothly with them, or who adjusts the lumbar support dial to fit the curve of their lower back, is experiencing the mechanics this patent locks down.
Original USPTO abstract
A chair includes a base having a control, and a seat and a back tilt bracket pivoted to the control for synchronous movement. An extension is adjustably supported on the back tilt bracket and is pivotally connected to a back support structure and a backrest frame in a four-bar linkage arrangement. The extension is adjustable to change the angular position of the back when in the rest position, and further provides a back tilt axis that is located rearward of a rear edge of the seat, which provides a unique back movement upon recline that is more rearward and less downward than most synchrotilt chairs. The back support structure includes a spine assembly pivoted to a rear end of the extension and extends upwardly. Armrests are operably supported on the spine assembly for vertical adjustment by an armrest mount, and a handle on the armrests is operably connected to a latch on the armrest mount for easy adjustment of the armrests. The arrangement of the backrest frame, the spine assembly, the back tilt bracket and the seat with side supports provides a unique synchronous movement that, among other things, pivots the armrests at an angular rate between a rate of the seat and the back during recline of the back. The back includes a flexible back shell having a lumbar section, a lumbar slide slidably engaging a rear surface of the back shell and operably supported thereagainst for changing a vertical shape of the lumbar section, and lumbar side arms engaging a rear surface of the back shell and also operably supported thereagainst for changing a horizontal shape of the lumbar section. A method related to the above is also contemplated.
Patent details
- Publication number
- US 6,523,898
- Filing date
- 2000-05-25
- Grant date
- 2003-02-25
- Assignee
- Steelcase Development Corporation
- Inventor(s)
- BALL DOUGLAS C., GOLDICK LEON, DESLAURIERS ALAIN, SOKALSKI JEFF G.
- CPC class
- A47C1/023
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