The Invention
The patent, US385034A, granted to Granville T. Woods of Cincinnati, Ohio, on June 26, 1888, is for a complex and innovative system for powering an electric railway. This patent describes an entire system, including the power delivery, track layout, and control mechanisms. Its primary goal was to improve the efficiency and safety of early electric streetcar systems.
Key Features of the System:
- Two-Branch Conductor System: The system uses a unique outgoing conductor that is split into two parallel branches, A and B, of the same electrical polarity.
- Divided into Blocks: The entire railway is divided into sections, or “blocks,” of a specific length. At the start of each block, a “normally-closed switch” (E) connects the two branches.
- Alternating Resistances: A crucial part of the invention is the placement of an electrical resistance (
r) in one of the branches at the end of each block. This resistance is alternated from one branch to the other in successive blocks. - How the System Works:
- Normally, with no train on a block, the current flows through the path of least resistance, which is through the switches and past the resistances.
- When a streetcar enters a block, a “traveling contact-brush” on the car completes a local circuit that energizes a magnet (m).
- This magnet then opens the switch (E) for that block.
- With the switch open, the current is forced to flow through the resistance in one of the branches, creating a large difference in electrical potential (an “unequal pressure”) between the two branches.
- The streetcar’s motor, which acts as a “traveling contact-bridge,” then draws current from the high-potential branch and shunts it to the low-potential branch, using the power to propel the car forward.
- Auxiliary Systems: The patent also describes methods for handling side tracks and switches, using auxiliary generators for more power, and even a way to use the motor current to power signal lamps along the line.
- Conduit System: Woods also provides a detailed design for an underground conduit (F) to protect the electrical conductors from the elements, as this was a major challenge for electric railways at the time. The conductors themselves are designed to be sheltered within the conduit.
Significance of the Invention and Inventor
Granville T. Woods was one of the most important inventors in the history of electrical and railway technology. This patent is a testament to his engineering genius.
- Solving a Core Engineering Challenge: The biggest obstacle to early electric railways was efficiently and safely delivering power to a moving vehicle. Woods’s system was a groundbreaking solution that allowed for multiple streetcars to be powered from a single source without interfering with one another. His use of “blocks” and the “traveling contact-bridge” was a significant advance over earlier, less-reliable systems.
- Foundation of Modern Systems: Woods’s work on segmented tracks and automatic switching was a direct precursor to modern railway signaling and power control systems. While the specific technology of his patents has been superseded, the underlying principles of isolating sections of track and using a controlled current to power moving vehicles remain fundamental to railway engineering today.
- A Prolific Innovator: This is just one of many significant patents held by Woods. He was a trailblazer in his field, and his work was so advanced that he was often a target of litigation from larger, more established companies like those of Thomas Edison. Despite facing intense prejudice and legal battles as an African-American inventor, Woods consistently defended his work and proved his ingenuity. This patent stands as a clear example of his vision and his crucial role in the development of electrified transportation.
