Interchangeable Blades for Folding Pocket Tools
A 1987 patent for a folding pocket knife with split handles that can securely swap out different tools, like saw blades, using a locking pivot block and protective aluminum handles.
Original patent title: “Pocket folding tool and knife system”
A 1987 patent for a folding pocket knife with split handles that can securely swap out different tools, like saw blades, using a locking pivot block and protective aluminum handles. Granted to Individual in 1987 with 21 claims and 57 forward citations, and it is now in the public domain.
Key facts
Coverage
What does this patent actually cover?
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.
The gap
What does this patent NOT cover?
- 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.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
Instead of using a complex latch, the tool uses the natural closing action of the two handles to lock the interchangeable blade. The split end of the pivot block on one handle is physically pinned shut by a post on the opposing handle when they meet.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Modular pocket knives with interchangeable saw and knife blades
Early butterfly-style multi-tools
Aluminum-handled folding utility knives
Why it matters
The bigger picture
This patent represents an early innovation in the consumer multi-tool market of the 1980s, trying to solve the problem of carrying multiple heavy tools. By allowing a single handle system to swap out saws, files, and blades, it paved the way for modern modular pocket tools. It also addressed the manufacturing challenge of using lightweight, cheap aluminum instead of heavy steel for the handles.
Filed
June 25, 1984
Granted
June 2, 1987
Market context
Who's building on this
Companies in this space
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.
Market impact
This design contributed to the evolution of lightweight, pocketable multi-tools in the late 1980s. By demonstrating how to construct durable pivot joints in soft aluminum without scratching the metal, it helped manufacturers transition away from heavier, more expensive steel-lined handles.
Claim 1 — Plain English
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.
The clever bit
Instead of using a complex latch, the tool uses the natural closing action of the two handles to lock the interchangeable blade. The split end of the pivot block on one handle is physically pinned shut by a post on the opposing handle when they meet.
What it does not cover
- 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.
Patent Journey
From filing to expiry
PatentBrief Score
Impact Score
Moderate
Citation count
35/40
Highly cited
Claim breadth
14/20
Broad claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$32K – $101K
Midpoint $63K · expired or expiring · industry ×0.9
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
The original legal language
Original claims
21 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Miceli, P. V. (1987). Interchangeable Blades for Folding Pocket Tools (U.S. Patent No. 4,669,140). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/4669140/leatherman-multitool
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does Interchangeable Blades for Folding Pocket Tools cover?
A 1987 patent for a folding pocket knife with split handles that can securely swap out different tools, like saw blades, using a locking pivot block and protective aluminum handles.
Who owns patent US 4669140?
Individual owns this patent, granted in 1987.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 4669140 cited by?
This patent has been cited by 57 later patents that build on its ideas.
What problem does this patent solve?
This patent represents an early innovation in the consumer multi-tool market of the 1980s, trying to solve the problem of carrying multiple heavy tools. By allowing a single handle system to swap out saws, files, and blades, it paved the way for modern modular pocket tools. It also addressed the manufacturing challenge of using lightweight, cheap aluminum instead of heavy steel for the handles.
What does this patent NOT cover?
Does not cover multi-tools with single, solid handles where blades fold out like a traditional Swiss Army knife.
Same assignee
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