US 5,871,258 · Granted 1999-02-16
How Steelcase Engineered the Office Chair That Actually Fits Your Back
Imagine an office chair that adjusts not just up and down, but where the seat slides forward as you recline, and the backrest reshapes itself to support your spine exactly where you need it. This patent describes a chair engineered so the seat and back work together like they're reading your body's needs, with a clever spring system that prevents the whole thing from breaking when you adjust it.
The plain-English version
What it protects
The patent covers a chair design where the seat platform slides forward independently of the back frame while also pivoting, creating a synchronized reclining motion where both the seat and backrest move in concert. It specifically protects the combination of: a flexible back with adjustable lumbar support zones, a two-part seat structure where the front cushion flexes while the rear section bears most of your weight, seat depth adjustment mechanics, and a spring-tension system (the 'moment arm shift adjuster') that lets users change recline resistance without overtorquing or damaging internal components.
Why it matters
Office chairs are one of the most-used pieces of furniture in the developed world, and back pain from poor seating is a costly workplace health issue. By patenting this integrated system of moving parts that keep the spine supported through multiple adjustment positions, Steelcase locked down a category of ergonomic seating that competitors couldn't simply copy. The patent reflects a shift in furniture design away from static forms toward dynamic support — chairs that move with you rather than forcing you into fixed postures.
Real-world use
Every time someone leans back in an ergonomic office chair and feels the seat slide forward while the backrest pivots and reshapes, they're experiencing the mechanics this patent protects — it's why modern task chairs feel so different from the rigid chairs of the 1980s and early 90s.
Original USPTO abstract
A chair is provided having a base assembly, a back frame pivoted to the base assembly for movement between upright and reclined positions, and a seat slidably supported on the base frame and pivoted to the back assembly so that the seat moves forwardly and its rear moves forwardly and downwardly with the back frame upon recline. A flexible back is connected to the back frame at top and bottom locations and is provided with lumbar adjustment for improved lumbar force/support and shape. A seat is provided with seat depth adjustment and with active and passive thigh flex support. The seat includes a front section adjustably and/or flexibly supported on a rear section for optimal comfort while supporting a seated adult user's thighs, with the rear section being configured to carry a majority of the weight of a typical seated adult user. A novel energy mechanism is provided that includes a moment arm shift adjuster for adjusting the spring tension on the back frame. The moment arm shift adjuster is readily adjustable and includes an overtorque device to prevent damage to components of the energy mechanism.
Patent details
- Publication number
- US 5,871,258
- Filing date
- 1997-10-24
- Grant date
- 1999-02-16
- Assignee
- Steelcase Inc.
- Inventor(s)
- BATTEY; ROBERT J., KNOBLOCK; GLENN A., DEKRAKER; LARRY, HEIDMANN; KURT R., JOHNSON; MICHELLE R., SCHEPER; ROBERT M.
- CPC class
- A47C1/023
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