You can freely build on Interchangeable Blades for Folding Pocket Tools

What this patent covers

This patent describes a folding multi-tool with two U-shaped handles that swing around to enclose or expose a central blade. It features a mechanism to swap in different tools, such as a saw blade, using a pivoting block with a split (bifurcated) end on one handle. When the handles are closed, a pin on the second handle slides into this split end, locking the interchangeable tool securely in the middle. To prevent the blades from wobbling, built-in centering guides inside each handle hold the tool perfectly aligned. Additionally, the design uses soft aluminum handles with press-fit pivot pins and reinforcing spacers, allowing the user to use the folded tool as a heavy-duty, right-angle screwdriver without scratching or damaging the metal.

What is now free to use

All 0 claims of US 4669140 are in the public domain. Specifically:

The 0 dependent claims add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Does not cover multi-tools with single, solid handles where blades fold out like a traditional Swiss Army knife.

• Does not cover interchangeable blade systems that do not use a bifurcated pivoting block and mating pin to lock the tool.

• Does not cover tools that lack centering guides built inside the U-channel of the handles.

• Does not cover folding knives with steel or titanium handles that do not require protective press-fit reinforcing spacers.

Who is building on this today

While modern multi-tool giants like Leatherman and Gerber dominate the market, they typically use proprietary slide-locks or button-releases for interchangeable blades rather than this specific bifurcated block and pin system. However, specialty outdoor tool makers still utilize similar split-handle folding mechanisms for compact saws and survival implements.

Products built on expired version of this technology

How to cite this patent in your documentation

Individual. US Patent 4669140. Pocket folding tool and knife system. Granted 1987, expired 2004. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.