US 5,482,100 · Granted 1996-01-09
The Spring That Lets You Raise Blinds Without Pulling a Cord
Imagine a venetian blind that you can lift and lower just by gently pushing the bottom bar—no dangling cords to tangle or get stuck. Inside, a special spring that gets thicker or thinner as it winds up automatically balances the weight of the blind, so it doesn't feel heavy or light at different heights.
The plain-English version
What it protects
The claim covers a cordless window blind system that uses a variable force spring motor to lift and lower blinds and shades. What's protected here is the specific design where the spring changes thickness or width along its length as it winds around a storage drum, which automatically adjusts the lifting force as the blind rises or falls. The patent also protects the coupling of a cord spool to this spring drum, allowing simple manipulation of the blind's bottom bar to raise or lower it without external hanging cords or separate locking mechanisms.
Why it matters
This patent solved a real consumer frustration: tangled cords on blinds. By eliminating the need for exposed lifting cords, the design made window coverings safer around children and pets while also simplifying the mechanism itself. The variable force spring was the clever engineering trick that made cordless operation practical—it compensates automatically so the blind doesn't feel like it's fighting you at the top or dropping on its own at the bottom. This became a foundational technology for the modern cordless blind market.
Real-world use
When you push up on the bottom rail of a modern cordless roller shade or venetian blind in a hotel room or newer home, you're benefiting from this spring-balancing technology that keeps it from feeling jerky or unbalanced.
Original USPTO abstract
A cordless, balanced venetian blind or shade with a constant variable spring motor includes conventional window covering components without the outside hanging lifting cords or cord locking mechanisms. One or more constant variable force spring motors are employed, preferably comprising springs which vary in thickness or in width along their length as they are wound around storage drums. A cord spool, in the preferred embodiment, is coupled to one of the spring drums to serve to wind the cords to cause the blind to be raised or lowered, simply by manipulation of the bottom bar of the blind system. Due to the difference in thickness or width of the spring, the system compensates for the increasing weight on the cords as the window covering is raised and for the decreasing weight as it is lowered.
Patent details
- Publication number
- US 5,482,100
- Filing date
- 1994-04-06
- Grant date
- 1996-01-09
- Assignee
- Newell Operating Company
- Inventor(s)
- KUHAR; OTTO
- CPC class
- E06B9/32
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