US 6,609,755 · Granted 2003-08-26
The Four-Bar Linkage That Made Office Chairs Actually Comfortable
Imagine a chair where leaning back doesn't slide you forward or cut off blood flow to your legs. This patent uses a clever four-bar mechanical linkage—basically connected bars that work together—so when you tilt the backrest, the seat tilts up at the back just enough to keep your feet flat and your thighs pressure-free. It's engineering that feels like magic.
The plain-English version
What it protects
The claim covers a specific mechanical arrangement in an ergonomic chair: a lower frame with front and rear rigid supports, a seat pivoted to the front support, a backrest connected to the rear support, and a link member that bridges the seat and backrest. What's protected here is this exact four-bar linkage geometry and how it coordinates the simultaneous tilting of both the backrest and the seat to achieve the ergonomic benefit. Anyone making a chair with this same mechanical relationship would be infringing.
Why it matters
Office chairs are used by millions of people every day, and poor chair design causes real pain and long-term health problems. This patent addresses a genuine mechanical problem: traditional chairs either trap your thighs when you recline, or they slide you forward uncomfortably. By patenting this specific linkage solution, Hon Technology protected a design that actually solves the problem. For a furniture manufacturer, this kind of ergonomic innovation can become a key selling point and competitive advantage in a crowded market.
Real-world use
Every office worker who leans back in their chair and feels their seat tilt up slightly—keeping their feet planted while relieving pressure on their thighs—is experiencing this patented mechanism in action.
Original USPTO abstract
An ergonomic chair includes a four-bar linkage arrangement wherein a lower frame member is provided with a rigid front support and a rigid rear support with a seat member pivotably connected to the front support. A back rest has an upper support pivotably connected at an upper end of the rear support of the lower frame member. A link member pivotably connects at a first end to a rear support of the seat member and at second end to a lower support of the back rest. This novel arrangement permits tilting movement of the backrest rearwardly relative to the lower frame member causing elevation of a rear portion of the seat member, permitting the feet to remain on the floor and alleviating pressure on the user's thighs.
Patent details
- Publication number
- US 6,609,755
- Filing date
- 2001-06-15
- Grant date
- 2003-08-26
- Assignee
- Hon Technology Inc.
- Inventor(s)
- KOEPKE MARCUS C., KRULL JAMIE, MACHAEL JAY R.
- CPC class
- A47C31/126
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