Loris E. Mitchell

Biography
Loris E. Mitchell (13 October 1890 - 11 March 1960) was a native of Warren, Ohio and was the son of George and Laura (Longmore) Mitchell. He graduated from the Warren Public Schools in the class of 1909.

In 1910 Mitchell worked in the Trumbull Mazda Lamp Works in Warren. Later, he was associated with Arthur James White and after they developed the tipless lamp at Nela Park in 1919 he became known as "Tipless Mitch."

Mitchell joined the Radiotron Division of RCA when it was organized in Cleveland in 1929. He was the manager of tube development in Harrison, New Jersey for nine years before moving, in 1942, to Lancaster, Pennsylvania. In Lancaster Mitchell was credited with considerable cost savings as a result of his plan for reorganizing training and work programs for RCA's electronic tube division. He retired in 1955 after being manager of the Manufacturing Standards Department for fourteen years.

Mitchell was granted nine patents between the years 1922 and 1942. He married Laura Gardner in 1916 and they had two sons, George G. and Robert.

Loris Mitchell passed away in his home in Lancaster as a result of a coronary occlusion. Interment was in Pine Knoll Cemetery in the Warren area.

Development of the Tipless Lamp
A feature of the electric incandescent lamp since its inception in 1879 was a glass tip at the crown of the bulb. The tip was a remnant of the glass tubing through which the lamp was exhausted of its air (as well as filled with inert gases after the invention of the gas-filled lamp in 1912). Visible exhaust tips are commonplace again today on tungsten-halogen lamps. In the early years of production such a protuberance could be the reason for lamp breakage as well as personal injury. The glass tip also affected light distribution. For these reasons it was very desirable to eliminate the tip.

Tipless lamps did appear early in the manufacture of the incandescent lamp but the techniques used were expensive in one way or another. Some of them were practical for certain lamp types but could not be considered for a commodity product that had to be produced at high rates of speed. The seamless butt seal, common on flashlight bulbs, was one such technique. Such lamps had no stem to support the filament; it was held by two lead wires which were embedded in the glass. Higher voltage lamps could not be constructed in that manner.

One of the methods most used to make a tipless lamp utilized a construction that was patented by Herman J. Jaeger in 1903 (U.S. Patent 729,182). It consisted of an "L" shaped exhaust tube that was sealed to the inside of the stem tube after the pinch had been made. A lamp employing this exhaust procedure was marketed for many years by the Tipless Lamp Company.

The General Electric Company marketed a premium lamp from 1906 to 1911 that was tipless. It was a large globular lamp known as the Meridian. The construction was patented by H. D. Burnett and Samuel E. Doane in 1894 (U.S. Patent 516,800). Their idea couldn't be used, however, until 1906, after Mark H. Branin of the Edison Lamp Works made a machine improvement that allowed the stem structure to be made. The Meridian was a decorative lamp and was manufactured to compete with the popular Nernst lamp, which employed metal oxides instead of a filament. The Jaeger and Meridian methods of exhaust were too expensive for general use. A variety of these different exhaust methods are shown below.

An inexpensive method of construction, which eliminated the tip from view and exposure, was invented at Nela Park in 1919. It was Loris E. Mitchell and Arthur J. White who applied for a patent for their construction and procedure and received it in 1922 (U.S. Patent 1,423,956, July 25 1922). It would appear that their invention stopped any further attempts to exhaust lamps differently. Their construction was quickly adopted throughout the world and is still used today.

The Mitchell and White construction permitted the exhaust tube to be inserted when the stem was being made. During the stem-making process, when the glass could still flow, air was blown from the outside at that location where the exhaust tube was sealed into the stem. A hole resulted which could then be used later to exhaust the lamp from the base end. The exhaust tip was then hidden from view by the lamp base. The new tipless lamp was economical, stronger, safer, aesthetically more appealing and also gave a better distribution of light.

Mitchell and White were awarded the Charles A. Coffin Foundation Award in 1924 for their invention of the tipless lamp. From the records of the Foundation the following excerpt gives an account of the achievement:

"Louis Edwin Mitchell and Arthur James White, both foreman in Nela Lamp Division, Nela Park, developed the method and type of equipment which makes possible on a commercial scale the manufacture of tipless Mazda lamps - one of the greatest advances in incandescent lamp manufacture in years. Neither of these men is employed as an engineer, a laboratory man, or a 'researcher.' Mr. White has been with the company twenty-one years and Mr. Mitchell fourteen. They conceived the idea that they could make the tipless lamps of which their manager so often spoke, and they proceeded to do so, after considering, and one by one discarding, all previous efforts as being uncommercial. Their invention, whereby the exhaust tube of the lamp is attached at the seal, has eliminated operations, wrought greater production, made less skill necessary on the part of operators, and reduced shrinkage. Today, nearly 100% of the Mazda lamps manufactured are made by their method. Among the many desirable things it has accomplished, perhaps the most recent is in connection with automobile headlight lamps. Here it has introduced such accuracy in axial alignment and over-all length as was never dreamed of before - accuracy which is of the utmost importance in focussing."