# Ralph Teetor's Speed Control Device for Automobiles

> A 1948 invention by Ralph Teetor that introduced the mechanical foundation for modern cruise control by creating a system to resist accelerator pedal movement at a set speed.

- **Patent:** US 2519859
- **Original title:** Speed control device for resisting operation of the accelerator
- **Owner:** Individual
- **Granted:** 1950
- **Status:** Public domain (expired)
- **Times cited:** 23
- **Field:** automotive, mechanical

## What it does

The device acts as a mechanical governor for an automobile's accelerator pedal. It uses a speed-sensing mechanism connected to the vehicle's drivetrain to monitor velocity. When the car reaches a pre-selected speed, the device engages a resistance mechanism that pushes back against the driver's foot on the gas pedal. This provides tactile feedback to the driver, effectively signaling or maintaining a constant speed by making it physically difficult to accelerate further without intentional effort.

## What it does NOT cover

- Does not cover fully electronic drive-by-wire throttle systems.
- Does not cover automatic braking or collision avoidance systems.
- Does not cover systems that maintain speed without providing physical feedback to the pedal.

## The clever bit

The innovation lies in using the accelerator pedal itself as a communication interface, providing tactile feedback to the driver rather than just disconnecting the throttle.

## Real-world examples

1. Early mechanical cruise control systems in 1950s and 60s Chrysler vehicles
2. Speedostat systems

## Why it matters

This invention is the direct ancestor of modern cruise control. Ralph Teetor, who was blind, was inspired to invent the system after experiencing the frustration of his driver constantly slowing down and speeding up while talking. It transformed long-distance driving by reducing driver fatigue.

## Frequently asked questions

### What does Ralph Teetor's Speed Control Device for Automobiles cover?

A 1948 invention by Ralph Teetor that introduced the mechanical foundation for modern cruise control by creating a system to resist accelerator pedal movement at a set speed.

### Who owns patent US 2519859?

Individual owns this patent, granted in 1950.

### When does this patent expire?

This patent has expired and is now in the public domain — anyone can use the invention freely.

### What is patent US 2519859 cited by?

This patent has been cited by 23 later patents that build on its ideas.

### What problem does this patent solve?

This invention is the direct ancestor of modern cruise control. Ralph Teetor, who was blind, was inspired to invent the system after experiencing the frustration of his driver constantly slowing down and speeding up while talking. It transformed long-distance driving by reducing driver fatigue.

### What does this patent NOT cover?

Does not cover fully electronic drive-by-wire throttle systems.

**Full plain-English explainer:** https://patentbrief.org/patent/us/2519859/cruise-control-teetor

**Original patent:** https://patents.google.com/patent/US2519859

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._


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- [George Selden's 1895 Patent for a Road Engine](https://patentbrief.org/patent/us/549160/selden-automobile-patent) — George Selden's 1895 patent describes a 'road engine,' a precursor to the automobile, focusing on a combined engine and vehicle design.