Adjourned patent: three-way valve with adjustable overlap length (22 Dec. 1959)

In this document

This is the full text of an adjourned patent application, filed by the Société Anonyme André Citroën via the Blétry Office, concerning a "three-way valve with adjustable overlap length", stamped "ADJOURNÉ" (ADJOURNED) and dated 22 December 1959 p. 22.

The problem posed

The described valve comprises a body pierced with three channels (intake, exhaust, component to be operated) and a sliding spool. The document explains that in high-pressure regulation systems, settings must be achieved "to within a few hundredths of a millimetre" p. 23, which makes the adjustment of the overlap (the spool travel between intake and exhaust) particularly delicate.

The claimed solution

The invention proposes that this overlap be adjustable by simple angular rotation of the spool within its body, without requiring re-machining — useful both for initial adaptation and for correcting wear during prolonged service p. 23.

Comparison with known models

The text details two existing valves (figures 1 and 2): one with a single groove where the overlap L-l depends on the centre distance of the channels, the other with two grooves where L and l "are easy to produce directly with precision" p. 25. The document then lists the limiting factors not covered by these models: spool/bore clearance, blunted edges, erosion wear p. 26.

The claimed variants (fig. 3 to 6)

The final Summary p. 27-28 synthesises these four claims, specifying in particular the application to "open-centre" valves p. 27. The plate p. 29 illustrates the six cited figures.

Context

This type of three-way valve is a key component of the hydropneumatic regulation systems developed by Citroën at that time for the suspension and power steering of the DS, launched in 1955. The concern for precision to the hundredth of a millimetre mentioned here is characteristic of the requirements specific to the high-pressure circuits of these vehicles — but this link remains general knowledge outside the document, which does not explicitly mention the DS.

Archivist's perspective

The "ADJOURNÉ" stamp p. 22 indicates that this application was likely not granted as it stood; the handwritten annotation "modify sketch" and "see 6 line 6" p. 22 suggests that a revision of the drawing was required before continuing the procedure.

This document clearly illustrates the engineering approach of Paul Magès and his teams: starting from an existing and documented component (figures 1 and 2, presented as "known models") to propose a targeted improvement, adjustable without heavy mechanical reworking. It is in the same vein as other items in the "Hydraulic components" file, such as the Principle of the hydraulic pressure regulator or the 2nd addition to patent P.685.691 on a flow regulator, which testify to a continuous effort to optimise hydraulic regulation components at Citroën during this period.