Based on the provided patent information, here is a breakdown of Granville T. Woods’s “Overhead Conducting System for Electric Railways” from 1888.
The Invention
The patent, US383844A, granted to Granville T. Woods of Cincinnati, Ohio, on May 29, 1888, is for a novel overhead power delivery system for electric railways. The invention addresses the critical challenge of efficiently and reliably transferring electricity from a stationary power source to a moving streetcar.
The core of the invention lies in a specific arrangement of multiple wires and a unique “traveling contact” or carriage that connects the streetcar to the power lines.
Key Features of the System:
- Three-Wire Conductor Path: Woods’s system uses a three-wire design:
- A central copper wire (3) that carries the main, high-voltage current from the power generator.
- Two outer iron wires (1 and 2) that serve as the physical rails for the traveling contact carriage.
- Insulated Metallic Brackets: All three wires are supported by insulated hangers or brackets. The central copper wire is insulated, while the outer iron wires are held on metallic arms of the same bracket. This is a crucial design point, as the electricity from the central wire is intentionally transmitted through the bracket’s metallic arms to the outer wires. This allows the outer wires to also become current-carrying conductors.
- Traveling Contact Carriage: The streetcar connects to the overhead system via a small wheeled carriage.
- The carriage has three grooved wheels (10, 11, 12) that ride on the three wires.
- The two outer wheels ride on the iron wires (1 and 2), while the central wheel rides on the central copper wire (3).
- This design ensures a “constant electrical contact without danger of interruption,” even if there are irregularities in the wires.
- Car Connection: A flexible cable (14) connects the traveling carriage to the streetcar below. This cable includes a special “spring-clamp” (13) designed to release the carriage from the car if it gets snagged or if the car stops suddenly. This prevents damage to the conducting lines.
Significance of the Invention and Inventor
Granville T. Woods was a pioneering African American inventor who made significant contributions to the fields of rail and electrical technology. His work, including this patent, was instrumental in advancing electric railway systems.
- Pioneer in Electric Railways: In the 1880s, the development of electric streetcars was a major technological race. The biggest challenge was creating a reliable method of power transfer. This patent represents one of the most innovative and practical solutions of the time. Woods’s system provided a robust and safe way to power the streetcars, an improvement over earlier, less-reliable designs.
- Efficiency and Reliability: By having a separate, lighter carriage that rides on the wires, the invention provided a more stable connection than a single trolley wheel pushing up on a wire. The three-wire system also allowed for greater power capacity with lighter, cheaper wires by using the supporting wires to carry the current as well. The “instantaneous release” clamp was a critical safety and durability feature.
- Overcoming Obstacles: As an African American inventor in the late 19th century, Woods faced significant racial discrimination. Despite these challenges, he was incredibly prolific, holding dozens of patents. His work was so groundbreaking that he was often sued by larger companies (like Thomas Edison’s) who claimed his inventions infringed on theirs. Woods successfully defended his patents in court and became a celebrated figure for his scientific and engineering achievements. This patent is just one example of his genius and determination.
- Legacy: Woods’s contributions helped lay the groundwork for modern electric public transit systems. His inventions in railway telegraphy and power distribution were fundamental to the development of electrified train and streetcar networks worldwide.
