History
3M branched off into the traffic signal industry partly as the result of product innovation and secondly as the result of an increase in complex intersections requiring specific traffic control. In late 1964, 3M began developing a line of beacon-type devices that were designed to feature the capability of being "optically limited" to a certain viewing area. The original design, invented by Roger H. Appledorn, was filed with the United States Patent Office on August 10, 1966. The original design consisted of a beacon-type device utilizing a fresnel lens, and several different combinations of light sources (the original source of light being a flashlight bulb), and all featured a light diffusing method and a method of masking the signal. In the patent application, Appledorn described the device as being able to be used as a traffic signal device, an airport beacon lamp, as well as a water navigation aid. After the patent was filed, 3M further enhanced the development, focusing solely on its traffic signal capabilities, and released the 3M Model 123., a prototype traffic signal that advertised the capability of being "visibly programmed" where certain lanes of traffic could view the indication. The prototype Model 123 was very crude in design, featuring a large door at the rear of the signal for replacing the lamp and allowing access to the signal's optics. In addition to masking the signal, it could also be vertically aimed about the axis via a series of alignment pins in 2-degree increments. These pins were located on the top of each signal housing, and could allow the tilt to be adjusted from as little as zero to as much as ten degrees. Vertical axis alignment was performed initially by loosening the pins, and a retainer inside the signal housing. In July 1969, nearly three years after the patent was applied for, 3M was issued the patent on July 22, 1969. After the patent was issued, 3M further enhanced the signal and introduced the Model 131, which featured a few enhancements over the 123 signal. Improvements over the 123 that were incorporated into the Model 131 signal were largely to make the signal easier to service. Those improvements included the ability to align the signal much more easily than the 123, and make signal maintenance easier.
Read more about this topic: 3M High Visibility Signals
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