Indicator or Bulletin (Ned E. Barnes, No. 969,592)
The patent by Ned E. Barnes of Willis, Texas, describes an Indicator or Bulletin (Patent No. 969,592, 1910). The invention is a mechanical display device designed for use in streetcars or railway coaches to exhibit station names, street crossings, or advertisements. The primary goal was to provide a reliable, manually operated system that ensures the display belt stops at exactly the right position to be read through a viewing window.
Inventor Background: Ned E. Barnes
Ned E. Barnes was an African-American inventor based in Willis, Texas.1 This 1910 patent represents one of his several contributions to railway safety and passenger convenience. Barnes was known for his practical engineering solutions to real-world problems—ranging from lubricating railway axles to this specific device for passenger information. By assigning portions of this patent to local associates (Owen A. Smith and Hervey A. McDonald), Barnes demonstrated an active involvement in the commercial and legal aspects of the burgeoning industrial South.
Invention and Mechanism (Simplified)
The device consists of a scroll-like belt housed in a casing, operated by a ratchet-and-lever system that can be switched to move the belt in either direction.
1. Housing and Display
- Casing (1): A protective housing featuring a front opening (2) protected by glass (3).
- Belt (6): A long belt containing printed matter (stations or ads). It is wound between two longitudinal shafts (4 and 5).
- Guide Rollers (7): These rollers keep the belt pressed close to the glass window so the text remains legible and doesn’t sag.
2. Propulsion System (Ratchet and Lever)
- Lever (8) and Ratchet (9): To advance the belt, a lever is mounted on one of the shafts. It features a pawl (10) that engages a ratchet wheel (9).
- Cable (13) and Spring (14): The operator pulls a cable (13) to move the lever. When released, a spring (14) pulls the lever back to its starting position. This “pumping” action rotates the shaft and winds the belt.
- Reversibility: The lever and ratchet mechanism can be removed and transferred from the upper shaft to the lower shaft. This allows the belt to be wound in the opposite direction when the train reaches the end of its route and starts the return trip.
3. Precision Stopping Mechanism (Key Innovation)
- Notched Wheel (22): A wheel with specific notches (21) is mounted on the shaft opposite the one being wound.
- Latch (18) and Detent (20): A pivotally mounted latch has a detent (20) (a small tooth) that rides on the notched wheel.
- Function: As the shaft rotates, the detent eventually drops into a notch. This locks the shafts instantly, ensuring the belt stops exactly when the next station name is centered in the window.
- Release Cable (25): Before moving the belt again, the operator pulls a separate cable to lift the latch, freeing the wheel for the next rotation.
Concepts Influenced by This Invention
Barnes’ Indicator influenced the development of early automated transit information systems and demonstrated sophisticated interlocking mechanical logic.
- Indexed Scroll Displays: The core concept of using a notched wheel to index a scroll (ensuring discrete “pages” or frames are shown) influenced early film projectors, destination signs on buses, and even early mechanical voting machines.
- Interlocking Control Logic: The requirement to lift a latch (Cable 25) before engaging the drive (Cable 13) is a precursor to modern interlock safety systems, where one action is mechanically or logically prevented until another condition is met.
- Modular Reversibility: The design’s ability to swap the drive mechanism between two shafts to change direction with minimal parts influenced the design of various reversible winding machines, from industrial looms to magnetic tape recorders.
- Public Information Design: Barnes addressed the “user experience” of early 20th-century travel, recognizing the need for consistent, legible, and synchronized information in high-vibration environments like railway cars.
