Patent project "Starting device for engines" with rubber rings (8 February 1945)

In this document

General principle

The memorandum describes a "starting device for engines" intended for starting combustion engines (or any application requiring "the release of a large amount of energy in a very short time", p. 5). The author starts from the observation that conventional electric batteries limit the starting speed, and that inertia starters used in aviation have "low efficiency and a very high unit cost price" p. 1.

The proposed solution is an "elastic" accumulation starter, the chosen element being rubber: several rubber rings moulded onto metal frames, mounted "in series", put into torsion and then released suddenly p. 1-2.

Technical description

The rings are connected to each other alternately by their outer and inner frames; the first is integral with a tensioning system (gears P and p, pawl c in fig. 1), the last with a plate locked by a latch (V) p. 2. Coupling to the engine is done by a "wedge-type roller freewheel" (RL) p. 2.

Locking system

The latch, cut "in the shape of a gear" with a pressure angle of "20° for example", is designed so that the unlocking force remains low while being cancelled "practically instantaneously" once the escape point is passed, which "eliminates any risk of breakage or wear" p. 3.

Consideration of temperature

The necessary torsion torque depends on the engine temperature: the colder it is, the greater the starting work p. 3-4. The device in fig. 10 measures this torque by the compression of a spring and the temperature by the expansion of a liquid housed in a capsule immersed "in the engine oil sump"; an electrical contact thus regulates the automatic unlocking according to these two parameters p. 4. An electrical relay (fig. 10 bis) prevents the latch from rubbing prematurely on the teeth during the sudden drop in torque p. 4-5.

Electric rewinding

A small electric motor can "rewind" the starter, which would allow keeping the ease of electric starting while significantly reducing the weight of the battery, and starting the engine "by hand" in case of a discharged battery p. 4.

Summary of claims

The text closes with three points: rubber rings in series, locking system with very low unlocking force and forces cancelled instantaneously, manual or electric torsion system p. 5.

Context

At the time of this writing, in February 1945, the French automobile industry was just emerging from the war and issues of raw material economy and mechanical reliability were central. The electric battery starter, widespread since the 1910s-1920s, remained the standard on passenger cars, while aviation used more expensive inertia starters — these two solutions are explicitly cited as points of comparison in the document itself.

Paul Magès, who joined Citroën in August 1925, wrote this memorandum while he had already moved to the design office: it was indeed on 17 February 1944, a few months before this patent, that he drew his first hydropneumatic suspension plans — the first tests on the 2 CV would only take place in May-July 1946. This 1945 patent thus testifies not to a phase prior to hydraulics, but to a mechanical research conducted in parallel, before the orientation towards hydropneumatics took hold and made his reputation with the DS presented in 1955.

Archivist's view

This typewritten memorandum, dated and signed (handwritten mention "8/2/45" and name associated with "N°178", p. 1), constitutes a relatively complete patent file document: principle, description, operation, and summary of claims follow one another rigorously, with precise references to numbered plates.

It seems that this project did not have the industrial posterity of his later work on suspension, but it illustrates an engineer's approach already focused on efficiency optimization and mechanical simplicity — concerns that will be found later in his hydropneumatic inventions.

The handwritten annotations in the margin (crosses, note mentioning names like "Joseph Bletry" or "Jean Sillomanne", p. 1 and p. 3) suggest a subsequent reading or discussion of the document, the precise nature of which remains unspecified.

To visualize the mechanisms described here, one will usefully refer to Plate n°12 — Principle diagram of the "rubber starter" and the locking and to Plate n°13 — Electric and automatic unlocking according to engine temperature, both dated the same day.