The brakes: Perrot's French patents, Adiel Dodge's duo-servo, and the NoRoL hill holder

1922–1936 · THE PRIORITY QUESTION, ANSWERED FROM THE RECORD

The French thread: The Bendix brake business began with a death and a purchase. In 1922 Bendix's father was killed in a Chicago street accident blamed on inadequate brakes; in France in 1924 Bendix met Henri Perrot, the French engineer whose patents covered the internal-expanding drum brake of modern pattern, and acquired the American rights — the accounts date the license to 1923–24. This is the documented French priority question in the Bendix line, and the record answers it without romance: the four-wheel brake system that made the company was a French invention, licensed, not a South Bend or Chicago invention. Bendix's first brake company said so on its own door: the firm organized in South Bend in November 1923 began as the Perrot Brake Company. What Bendix's organization added was American manufacture and selling — 650,000 brake sets shipped in 1926, 3.6 million in 1928 — and a genuine inventive line of its own, part of which does stand on South Bend paper.

Vincent Bendix's own brake patent, No. 1,757,071, "Fluid-Operated Brake," filed 15 June 1925 and granted 6 May 1930, is again Chicago-faced on its document, Vincent Bendix of Chicago, assignor to the Bendix Brake Company of Chicago. The South Bend inventor of the brake line is a quieter man: Adiel Y. Dodge of South Bend, whose two brake patents assigned to the Bendix companies here contain the self-energizing principle the industry came to call duo-servo. No. 1,982,798, filed 25 August 1928 and granted 4 December 1934, assignor to the Bendix Brake Company of South Bend, states its object as "a simple and inexpensive brake which has a powerful servo action"; No. 1,978,699, first filed 30 October 1926 and granted 30 October 1934, assignor to the Bendix Aviation Corporation of South Bend, describes in its own specification shoes "arranged to form a brake of the 'duo servo' type, that is, the shoe 16 applies the shoe 14 when the drum is turning" — the primary shoe, dragged by the drum's rotation, wedging the secondary shoe into harder contact, so the brake amplifies itself.

An Ottawa inventor assigns into the same file: Walter H. Delahaye of Ottawa, Ontario, No. 1,936,870, filed 2 December 1929 and granted 28 November 1933, assignor to the Bendix Brake Company of South Bend, for a servo-shoe brake guided at both ends by a floating link. British trade press of 2 December 1930 was describing the Bendix "Turbrake," British Patent No. 337,268, on the same self-energizing principle. Two famous brake devices of the era close the entry at their exact shares. The hill holder — the valve that held a car's brakes on a grade until the clutch engaged, sold under Bendix's name as the "NoRoL" — was invented by the Wagner Electric Corporation and manufactured by the Bendix Brake Company in South Bend; it was first offered in 1936 as an option on the Studebaker President, this city's two great firms crossing one more time, and reached Hudson, Nash and others by 1937. And when the Avanti needed disc brakes a generation later, it was Bendix that built the Dunlop-licensed calipers in the entry above. The brake record, summed honestly: licensed French foundations, a Chicago-faced founder's patent, and the servo principle's clearest patent statement drawn by a man of this city.

Sources:

1. The Perrot record — Britannica and the Bendix company histories: the 1922 death of Bendix's father; the 1924 meeting with Henri Perrot and the acquisition of the French patent rights (dated 1923–24 across accounts); the Perrot Brake Company, South Bend, November 1923; 650,000 brake sets in 1926 and 3.6 million in 1928.
2. U.S. Patents Nos. 1,757,071 (Bendix, fluid-operated brake), 1,978,699 and 1,982,798 (Dodge of South Bend, assignors to the Bendix Aviation Corporation and the Bendix Brake Company of South Bend), and 1,936,870 (Delahaye of Ottawa, assignor to the Bendix Brake Company, South Bend) — the patents themselves, via the Patent Office images and Google Patents; the duo-servo language quoted from No. 1,978,699's specification.
3. The Commercial Motor, 2 December 1930 — the Bendix "Turbrake" self-energizing brake, British Patent No. 337,268.
4. The Wagner Electric / Bendix "NoRoL" record as carried in the Studebaker and Hudson-Nash literature — Wagner's invention, Bendix Brake Company manufacture at South Bend, first offered on the 1936 Studebaker President.