LEGO patents improved brick principle in 1958

LEGO GmbH submitted a patent application for "a toy building element" on January 28, 1958. This application detailed a new design incorporating internal tubes, addressing the stability issues reported with earlier hollow brick designs and greatly improving the interlocking capability.

The development stemmed from market feedback indicating that hollow LEGO bricks led to unstable constructions. Godtfred Kirk Christiansen devised a solution by introducing tubes inside the bricks. When combined with the external studs, these tubes created a stronger "clutch power," enabling the construction of more complex and stable models.

The design, featuring the stud and tube principle, was patented just days after Christiansen sketched the concept with Axel Thomsen. The patent application was a critical step in protecting the product and securing the future of the LEGO System in Play.

Following the patent filing, the improved bricks with studs and tubes began appearing on the exterior of new LEGO sets. This innovation was fundamental to the evolution of the LEGO System, allowing for endless combinations and improved structural integrity.