Citroën patent of 8 July 1960: regulating device for hydraulic motors (file 4387)

In this document

Nature and filing

This file is a patent application filed by the Office Josse on behalf of the Société Anonyme André Citroën, under provisional no. 832.505, with a stamp indicating the filing date "8 July 1960" and the mention "DELIVRANCE AJOURNEE" p. 103. The file bears the handwritten number "4387" and the annotation "TH 60" p. 103. The text itself mentions "the French patent application filed on 6 July 1960" for a related device entitled "process and device for regulating hydraulic motors" p. 104 — this patent is therefore its direct complement.

Object of the invention

The patent concerns a regulating device for hydraulic motors of the barrel and swashplate type p. 103-104. It aims to correct a defect in existing devices: these draw high-pressure fluid to actuate the regulating distributor, which leads to "a permanent loss of fluid entirely diverted from the motor's operation" p. 104.

The invention proposes using "the entire flow of the motor to be regulated but with a very low pressure drop," taken from the exhaust rather than the intake, thanks to an effort amplification obtained by the action of low pressure on a mobile element of appropriate surface area p. 104.

Described operation

The regulator is based on two variable capacities (6 and 7) whose mobile walls (membranes or pistons depending on the figures) drive the spool of a hydraulic distributor (11), which in turn connects a piston (12) controlling the inclination of the motor's swashplate (13) p. 103-106. A mobile part (3), positioned between two exhausts (4 and 5), regulates the differential pressure between the two capacities according to the input variable to be controlled p. 105.

Two control modes for part 3 are described:

• Figure 1: an electromagnet (19) excited by the flow of an electric generator, in antagonism with a spring p. 105-107.
• Figure 3: a centrifugal governor (21) keyed directly onto the motor shaft p. 106-107.

The document specifies the intended application: "the control, for example, of the power or speed of a hydraulic motor 1 coupled to an electric generator 2" p. 105.

Claims and abstract

Six numbered claims detail the device and its variants p. 106-107. The Descriptive Abstract summarizes the invention in one sentence using the same numbered elements p. 108. Three figures accompany the text: cross-sectional diagrams of the complete device (Fig. 1), detail of the capacity distributor (Fig. 2), and variant with centrifugal governor (Fig. 3) p. 109-110.

Context

This patent is part of the research conducted at Citroën on hydrostatic transmission, a technology intended to replace conventional mechanical transmissions with a high/low-pressure hydraulic circuit. Paul Magès, known primarily for the hydropneumatic suspension of the DS, also worked on these swashplate hydraulic motors, a parallel line of research explored by Citroën in the 1960s-1970s.

The filing via the Office Josse, a Parisian firm specializing in patents, was a common practice for large industrial companies of the time to legally secure their technical innovations.

Archivist's view

This document appears to be one of the early milestones of the "Hydrostatic Transmission" program at Citroën, dated from the very beginning of the 1960s — the handwritten annotation "TH 60" p. 103 confirms this and explicitly links it to this broader file.

It complements, one day apart, an earlier application from 6 July 1960 concerning the same type of motor p. 104, which suggests a strategy of grouped filings to successively protect several aspects of the same invention.

The mention "délivrance ajournée" p. 103 probably indicates an administrative procedure still in progress at the time of the digitization of this file, without it being possible to draw a definitive conclusion about its outcome.

This patent sheds light on a technical stage probably prior to the more advanced developments documented in later pieces of the same collection, such as the Handwritten notes "Presentation T.H. 50 CV" at the B.E.A. or the Note on the endurance of 2.2 cm³ hydraulic motors, which testify to the continuation of tests on this same type of component.