The Invention
The patent, US386282A, granted to Granville T. Woods of Cincinnati, Ohio, on July 17, 1888, is for an improved method of constructing an underground tunnel for electric railway conductors.1 This invention addresses the practical challenge of protecting electrical power lines from the elements while still allowing a streetcar to draw power from them. The system is designed to be efficient, durable, and safe.2
Key Features of the Construction:
- Protective Tunnel (Conduit): The entire system is housed in a tunnel built beneath the road. The tunnel is designed to keep water and debris away from the electrical conductors. The base is preferably made of concrete to act as a gutter and includes drainage openings.3
- Yoke Support System: The conductors are supported by a series of yokes (A), preferably made of cast iron.4 These yokes are bolted to a cross-tie underneath the road and provide a sturdy structure for the entire system. Each yoke is made of three parts: a base piece and two “jaw-pieces” that support the slot rails and the conductors.5
- Conductor and Slot Rails: The yoke’s jaws support two slot-rails (D), which form a narrow opening, or slot, at the surface of the roadway. Immediately below these rails are the electrical conductors (F F).
- Insulated Conductors: The conductors are designed to be insulated from the yokes and the rest of the tunnel. They are supported by a wooden or other insulating plug (e) inside a bracket on each yoke.6 The conductors themselves are strips of metal, preferably copper, with a unique inverted U-shape that helps to shelter the electrical components.
- Parallel Conductors: The system uses two continuous, parallel conductors.7 A key part of the invention is that both conductors carry current of the same polarity.8 This reduces the electrical leakage (or power loss) that would occur if they were of opposite polarities. The current is then drawn from one or both of these conductors and returned to the system via the track rails or slot rails, which are grounded.9
Significance of the Invention and Inventor
Granville T. Woods was a visionary and prolific African American inventor who made immense contributions to electrical and railway technology.10 This patent is a prime example of his work, which focused on solving fundamental engineering problems of the late 19th century.
- Practical Engineering Solution: Early electric railway systems faced significant problems with power delivery, especially in wet conditions. Woods’s tunnel design was a practical and robust solution that addressed these issues. By protecting the conductors from rain, snow, and debris, his invention made electric streetcar systems more reliable and safer for the public.
- Efficiency and Safety: The use of two parallel conductors of the same polarity was a clever innovation that improved the system’s electrical efficiency.11 This detail demonstrates Woods’s deep understanding of electrical principles. The entire design, with its focus on durability and protection, was a major step forward in the safety of electric transit.
- A Prolific Legacy: This is one of many patents held by Woods in the field of electric railways.12 His work was highly regarded and often licensed to major companies. Despite the racial prejudice he faced as an African American inventor, his technical genius was undeniable. His contributions were essential to the development of modern electrical transit and helped pave the way for a more reliable, efficient, and widespread use of electricity in public transportation.
