GEARX Logo The Invention of Double Enveloping Worm Gear Drives

The invention of the double enveloping worm gear drive is a breathtaking story with two dramatic personae, Friedrich Wilhelm Lorenz and Samuel I. Cone, each acting in distant parts of the world-one in Germany and the other in the United States.
Initially, the author intended to find a photograph of Samuel Cone (1865– 1949), the American inventor of the drive that carries the name of Cone Drive Co., the main producer of the aforementioned drives in the United States. Unfortunately, the photograph disappeared from the company files but was finally located in the family archives with the help of Cone’s granddaughter Mrs. Mary Bell Kluge (nee Taylor). The search ended happily, but it was not the end of the story because during our visit to the Lorenz Co. in Ettingen, Germany, we learned that Dr. Lorenz had invented methods to generate the worm and the gear of the double-enveloping worm gear drive and that he had received two patents for this work in 1891.

Dr. Lorenz’ invention was unknown to Samuel Cone, a modest draftsman to whom the idea of a double enveloping worm gear drive came independently, as seen in the following statement from the archives of the Cone Drive Co. in 1924:
About 15 years ago, Mr. Samuel I. Cone of Portsmouth, Virginia, manufactured at the Norfolk Navy Yard the first Cone Type Worm. It is believed that this was the first instance in which Double Throated or Double Enveloping Worm Gears, having area contact, were ever made.
Even though such worm-gear drives were manufactured at the Lorenz Co., the value of Cone’s contribution cannot be diminished when one considers his courage and strong will. Cone acted as a lone inventor whereas Lorenz used the skills of his many employees. Still, it took a long time and required much effort before the Cone drive technology became applicable in the United States. We must pay credit to the Lorenz invention, but the father of the American invention was Samuel I. Cone. Despite these facts, the question of who should claim exclusive rights for the double enveloping worm gear remains unanswered. Our opinion is that we have to credit both Lorenz and Cone.

Wilhelm Lorenz and Samuel Cone understood very well the advantages of the drives they had invented, particularly, the increased load capacity due to the higher contact ratio in comparison with that of conventional worm gear drives. Although the geometry of the Lorenz and Cone drives differs, both types offer this advantage. Later, investigations showed that the double enveloping worm gear drive’s higher efficiency results from the existence of more favorable lubrication conditions.

The complex geometry of the double enveloping worm gear drive, the specific conditions of lubrication (found later), and the formation of the worm-gear tooth surface as a two-part surface inspired many researchers to develop the analytical aspects of the meshing of the worm and the worm-gear tooth surfaces. Among such researchers are N. I. Kolchin, B.A. Gessen, and P.S. Zak in Russia, Sakai in Japan, and Litvin in the United States, whose investigation and results are presented in Litvin (1968,1994). The primary manufacturer of double enveloping worm gear drives in the United States is the Cone Drive Textron Co. Presently, the Lorenz Co. does not produce these gear drives.

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