Note "Fluid distribution spool" (18 November 1959)

In this document

This handwritten note dated 18 November 1959, referenced P 2247_1, deals with the fluid distribution spool, a key component of hydraulic regulation systems.

At the top of the page is an annotation that is still uncertain to read ("Paubrever [uncertain: Bibby] requested from... on 18/11/59"), accompanied by a handwritten arrow p. 38.

The general principle

Magès poses the central problem: when a distribution spool is used in a regulation system, the travel required to move from intake to exhaust (and vice versa) must be as small as possible, sometimes even a well-determined value p. 38.

He highlights the difficulty specific to high-pressure fluid: at very small spool openings, flow rates remain significant, which imposes adjustment and dimensioning tolerances of the order of "a few hundredths of a millimetre" p. 38.

Three compared figures

• Fig. 1: the overlap depends on the difference between L and l. If l is easy to obtain with precision, L — distance between the generatrices of two holes — depends on the precision of the centre distance A and the diameters B and C p. 38.
• Fig. 2: the overlap also comes from the difference L-l, but here L (length of the generatrix of the central part of the spool) and l (diameter of the communication hole) are both "easy to achieve with precision". Magès notes that this solution "is satisfactory in most cases" p. 38.
• Fig. 3: three views of a spool with a "pressure balancing groove", responding to the need, mentioned at the end of the note, for the overlap to be adjustable for the most demanding regulation applications p. 38.

Context

The hydraulic distribution spool is a classic component of servocontrols and regulators: a sliding cylinder that opens or closes pressurised fluid intake and exhaust ports.

At Citroën, in the late 1950s, these components equipped the high-pressure hydraulic circuits of the DS, notably the regulators and distributors associated with the suspension and power steering — although this document does not itself specify its exact application.

Archivist's perspective

This note is a matter of fundamental design reflection rather than a test report: Magès reasons as an engineer on the geometric tolerances (centre distance, diameters) that condition the precision of an overlap, before proposing an adjustable solution via a balancing groove p. 38.

It appears to be a preparatory study for a regulation component, probably linked to the work on high-pressure pumps and regulators conducted at the same time, such as the DS high-pressure pump plan no. E 401.8444 or the Principle of the hydraulic pressure regulator, documents from the same "Hydraulic components" collection.

The handwritten annotation at the top of the page, still difficult to read, suggests a request addressed to a third party, but its exact recipient remains unspecified.