Pi Day Inventions

Happy Pi Day! March 14 is known as Pi Day because 3.14 are the same first three digits as the mathematical constant pi, or π. (Because it is an irrational number and this blog will not be more specific than 3.14, here's a site with the first million digits.) 

For this year's Pi Day celebration, we are sharing some patents that use the number/mathematical constant, its concept, or the Greek letter's shape.

1. US 4,643,504 Lampholder assembly for loop-, u-, or pi-shaped gas discharge or fluorescent lamps with a single lamp cap. This one is more based on the shape of the letter pi, and uses that modified U-shape to describe part of a unique lamp. There's very little to do with the number pi, but because the letter is more commonly used than others from the Greek alphabet, the inventor used it as a descriptor that would be familiar to many.

   

   Fig. 4 seemed the most pi-shaped
   

2. US 9,444,065 π-conjugated heavy-metal polymers for organic white-light-emitting diodes. Evidently, π can also refer to an orbital of an atom, and its conjugation means it has alternating single and multiple bonds. That actually means very little to me, a person without an advanced knowledge or understanding of chemistry, so if that description is incorrect, my apologies. Please comment with a better explanation. For this invention, it refers to chemical composition and formulation rather than the number or constant. 
3. US 9,551,094 Fiber preform of π-shaped section, in particular for a fan platform made of composite material. This refers to a fan blade in an turbine engine for aviation. So there is a part of an airplane engine (maybe) that is in the shape of pi, which uses fibers to... Maybe read the patent if you understand enough about aircraft engineering.

   

   A close-up of how the fiber should be woven to form a π shape
   

   
   

   

   The fiber preformed section in a fan platform

   
   

   
   

   
   

4. US 11,161,381 Self-propelled robotic lawnmower comprising wheels arranged with a negative camber angle. π as a number and mathematical constant was used in this one! The Swedish inventors used it in a classic formula to calculate the circumference of circular wheels.

   

   Need a circumference for part 5.1? Use π