Schematic diagram of the DS 19 hydraulic circuit (1949)

In this document

This technical drawing, referenced K.C. 65654, presents the schematic diagram of the DS 19 hydraulic circuit. The title is written vertically on the right edge of the page, and a handwritten annotation at the top right indicates "DS 19" (in red) then "1949" (in black) p. 4.

Identified components

The diagram names several components connected to each other by a dense network of pipes:

• a gearbox associated with a clutch release cylinder p. 4;
• a gear shift corrector and a corrector whose second term remains uncertain upon reading ("re-clutching" [uncertain]) p. 4;
• two brake accumulators, one at the front ("AV"), the other at the rear ("AR") p. 4;
• a pressure-setting valve p. 4.

Braking circuits

The diagram details the distribution to the brakes, with the mentions "vers frein AR" (to rear brake), "vers frein AV" (to front brake), "vers freins AR" (to rear brakes), "vers freins AV" (to front brakes), as well as "vers cylindres AR" (to rear cylinders) and "vers cylindres AV" (to front cylinders) p. 4. The drawing also shows two pairs of drum brake shoes, annotated "AR" and "AV" p. 4.

Furthermore, the diagram represents, without their precise function being named in the text, a cross-section block with pistons and springs numbered from 1 to 5, a stepped cylindrical part, and a hatched housing suggesting a reservoir or a filter p. 4.

Context

The DS 19, presented by Citroën on 6 October 1955, remained famous for its integrated hydropneumatic system, which provided suspension, braking, power steering, and gear shifting via a centralized hydraulic circuit — a technical feat of the time designed in particular by Paul Magès, who joined the Citroën design office in the late 1930s and whose first hydropneumatic suspension plans date from 17 February 1944 (differential interaction hydropneumatic suspension plans).

This type of schematic diagram, several years prior to the vehicle's commercialization, corresponds to an upstream design phase where the main functions of the circuit (braking, clutch, trajectory correction) were already thought of as interdependent within the same hydraulic network.

Archivist's perspective

Dated 1949, this document illustrates an early stage of the design of the hydraulic circuit that would make the DS's reputation, six years before its public presentation on 6 October 1955. It is in line with the research conducted by Magès since his first plans of 1944 and the first tests on 2 CV in May-July 1946 (notebook of the first tests of the 2 CV with hydropneumatic suspension), which already sought, at that date, to articulate braking, clutch, and suspension correction in a unified system.

The reference to distinct "correctors" and "brake accumulators" for the front and rear p. 4 testifies to an already advanced reflection on the differentiated distribution of braking forces, a theme found developed later, for example in the DS HP pump flow curves or in the technical note on the self-regulating pump, dated the same year. This diagram could thus come from the same "Hydraulic components" work folder as these contemporary pieces.