How the Modern LEGO Brick Design Works
The 1958 patent that defined the iconic LEGO brick with hollow tubes inside, allowing bricks to lock together firmly.
Original patent title: “Toy building brick”
The 1958 patent that defined the iconic LEGO brick with hollow tubes inside, allowing bricks to lock together firmly. Granted to Interlego AG in 1961 with 374 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
This patent describes the structural design of a toy building brick that features hollow cylindrical tubes on its underside. These tubes are positioned to frictionally engage the walls of other bricks when pressed together. This specific arrangement allows for a stable, interlocking connection that remains secure even when the structure is moved or turned upside down. It transformed simple plastic blocks into a versatile construction system.
The gap
What does this patent NOT cover?
- Does not cover bricks without the specific hollow tube configuration on the underside
- Does not cover non-plastic materials or different geometric shapes like spheres or pyramids
- Does not cover the specific chemical composition of the plastic used
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The innovation was placing hollow tubes inside the brick to create a friction-fit with the studs above, rather than relying on simple gravity or loose stacking.
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
Standard 2x4 LEGO bricks
LEGO Technic beams
LEGO Duplo blocks
Why it matters
The bigger picture
This design is the foundation of the entire LEGO brand. By solving the problem of structural instability in early plastic blocks, it enabled the creation of complex, multi-story models that do not fall apart during play.
Filed
July 28, 1958
Granted
October 24, 1961
Market context
Who's building on this
Companies in this space
The LEGO Group remains the primary developer of this system, continuously refining the tolerances and material science of the bricks. Many compatible 'brick-compatible' toy manufacturers have emerged since the original patent expired, building on this fundamental geometry.
Market impact
This patent effectively created the modern construction toy category. It allowed for the standardization of parts, which is essential for the massive, interoperable ecosystem of sets that LEGO sells today.
Claim 1 — Plain English
What this patent covers
This patent describes the structural design of a toy building brick that features hollow cylindrical tubes on its underside. These tubes are positioned to frictionally engage the walls of other bricks when pressed together. This specific arrangement allows for a stable, interlocking connection that remains secure even when the structure is moved or turned upside down. It transformed simple plastic blocks into a versatile construction system.
The clever bit
The innovation was placing hollow tubes inside the brick to create a friction-fit with the studs above, rather than relying on simple gravity or loose stacking.
What it does not cover
- Does not cover bricks without the specific hollow tube configuration on the underside
- Does not cover non-plastic materials or different geometric shapes like spheres or pyramids
- Does not cover the specific chemical composition of the plastic used
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Moderate
Citation count
40/40
Highly cited
Claim breadth
0/20
Narrow 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
$79K – $253K
Midpoint $158K · expired or expiring · industry ×2.2
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
Concepts involved
Citations
Patent lineage
Cite this patent
Kirk, C. G. (1961). How the Modern LEGO Brick Design Works (U.S. Patent No. 3,005,282). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/3005282/lego-toy-brick
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 How the Modern LEGO Brick Design Works cover?
The 1958 patent that defined the iconic LEGO brick with hollow tubes inside, allowing bricks to lock together firmly.
Who owns patent US 3005282?
Interlego AG owns this patent, granted in 1961.
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 3005282 cited by?
This patent has been cited by 374 later patents that build on its ideas.
What problem does this patent solve?
This design is the foundation of the entire LEGO brand. By solving the problem of structural instability in early plastic blocks, it enabled the creation of complex, multi-story models that do not fall apart during play.
What does this patent NOT cover?
Does not cover bricks without the specific hollow tube configuration on the underside
Patent monitoring