The "amphibious" breathing apparatus GC 42/47
By Dr.-Ing. Lothar Seveke

In [Sev1] I presented the range of breathing and diving apparatuses of the French company Commeinhes, which already from 1942 contained innovative and practicable submersible apparatuses (diving world record 1943 with the GC42) and anticipated many performance features of the apparatuses of Gagnan/Cousteau (CG45), which were introduced later, and partly went beyond them.
Relatively little is known about the internal technology of the GC42/47 devices that was actually realised in accordance with Georges Commeinhes' patents, although they are contained in many collections. It was therefore necessary to close the documentation gap after the GC39 until before the C58. 
David Dekker kindly provided a GC42 for this purpose.

The so-called container device GC 42, for "George Commeinhes 1942", by the Commeinhes company from St. Maur near Paris is a compressed air device for use in toxic atmospheres or under water, therefore amphibious.
It was designed by George Commeinhes in his father René's company after France's armistice with the German aggressor in 1941. The company had been building tank breathing apparatus for the fire brigade and the military since the 1930s (RC 35, MC 39, ...). George had also already converted his father's RC 35, which he had converted from a rebreather into a tank breathing apparatus with compressed air cylinders, into an amphibious apparatus, as he was interested in diving through spearfishing.
George filed the patent [Com1] in 1942 to match the GC 42, although the regulator with bellows designed there was probably never produced with the device, or only in very small numbers, but rather the regulator with a large flat diaphragm, as it was later used for the GC 47, possibly also with compensation, and is laid down in the patent [Com3] (variant 1 of the two regulators shown there).
Many collectors incomprehensibly hardly give out details about their Commeinhes devices (or don't know them?). For example, it is not clear whether the GC 42 ever used the regulator with bellows (Fig. 23) or the version as pendulum breather without VGM from the patent [Com2], or whether the GC 47 ever used the compensated regulator according to patent [Com3] Fig. 23.
The pendulum breathing version with mouthpiece and normal half mask (no VGM with exhalation valve as in [Com3]) is significant insofar as it anticipates the attachment of the exhalation valve close to the regulator diaphragm, which Gagnan and Cousteau later had explicitly patented again. In any case, the pendulum breathing hose offered the possibility of using the diving apparatus with a half mask, or one could mount an exhalation hose, see Fig. 24, Galerne from 1949.
Whether the exhalation valve was placed in the immediate vicinity of the regulator diaphragm rather accidentally or intentionally is no longer comprehensible today. Rouquayrol & Denayrouze had also done the same.

Complete unit

The GC 42/47 has already been presented in detail in [Sev1], so here are just a few pictures of the real device. 

The device does not deny its origins in respiratory protection technology, recognisable by the small bottles and their interchangeability during use, and by the leather strapping. 
Whether the amphibious usability was an intended development goal is doubtful. The fact that it could ALSO be used for diving came about and was useful at a time when no or too few real diving devices were available. The valves were not standardised for INT, and you could not mount 7 or 10 litre cylinders in the carrying frame. The regulator was fixed and so could not be used in other configurations.
On the other hand, the TG was small and very compact and thus well suited for special short-duration operations in the navy, in wrecks or caves.

Picture 07: Carrying frame made of folded sheet metal

Picture 05: Full-face mask (VGM) with adjustable exhalation valve

The full face mask has a very modern design, minimal volume, flat front screen, nose notch for pressure equalisation, adjustable exhalation valve, swivel for the inhalation hose.
The cylinder bridge had non-return valves so that the hanging cylinders, which were only screwed on hand-tight, could be changed by the user during operation without having to set the unit down. Very useful for long dry rescue operations. But under water, one would probably rather change the complete unit, right?

Pictures 07 & 08: Bridge with check valves

Also the quick release for the bottles is not really relevant for our underwater use, but it is so interesting that I want to show it at least, see pictures 10 -12.

So there are many nice, innovative details on this unit, which dates from around 1940 and was certainly one of the most practical breathing apparatus container units of its time.

Pictures 10, 11, 12: Quick-release cylinder coupling of the GC 42/47

It was also purchased in very large numbers by the French military and rescue organisations. After the war, it helped to bridge the gap in the supply of diving equipment.
Among many others, the non-modularity of such devices , special cylinder connection, fixed regulator, single-purpose carrying frame,... was probably the reason for their disappearance from the market.

The regulator
of the GC42 and its classification among the inventions of demand-controlled compressed air diving apparatuses was the reason to consider this member of the Commeinhes apparatus family again separately.
In my opinion, the following inventions, which led to practical devices and were produced in large numbers, are the true forerunners of our present-day diving regulators:

- 1870 Rouquayrol/Denayrouze, 1-stage, automatically demand-controlled,
- 1918 Ogushi, non-automatic bite control,
- 1925 Fernez/Le Prieur, PTG with Freeflow,
- 1933 Le Prieur, manual flow control,
- 1937 G. Commeinhes, adapted respirator, demand-controlled regulator,
- 1941 Victor Berge, mouth regulator, 2-stage, automatic demand-controlled.
- 1942 G. Commeinhes, amphibian device GC42, 1-stage, demand-controlled,
- 1943 Gagnan/Cousteau, 2-stage, automatic,

If we consider only swim diving, in a very narrow time range, the last three inventions remain as essential and fundamental to our regulators today.
Strangely, but probably caused by the events of the war, they came about independently of each other. Each of the three invented on the basis of his basic knowledge of physics and technology and came up with the solution that was so obvious: a membrane acted upon by the depth-dependent water pressure reacts to the diver's inhalation negative pressure and opens a valve.
They solved the problem of exhalation somewhat differently:
- Berge worked with the familiar mouth regulator and exhaled close to it through the cuff of the ORCO mask,
- Commeinhes placed his exhalation valve (by chance or copied from Rouquayrol?) next to the regulator membrane (pendulum tube according to Fig. 23, having previously used an adjustable exhalation valve on the VGM),
- Gagnan brought his exhalation valve OBJECTIVELY into the pressure range of the regulator diaphragm and needed the second hose for this.

Berge and Gagnan used actual industrial regulators, Gagnan's being so large (1st and 2nd stage of a car gas regulator) that it had to be attached to the cylinder valve and connected to the mouthpiece with a corrugated hose. 
Berges, on the other hand, was so small (thanks to the us aircraft industry) that he could wear it on his mouth. His intermediate pressure came either by hose from above or from a bottle on his back where there was a reducer [Will].
Commeinhes used a 1-stage regulator with a large diaphragm and a 2-lever mechanism, which was not common in industrial regulators, to replace the water-sensitive "control bag" from his father's MC37 [Sev1]. He also invented a compensation for the regulator piston, which made the breathing resistance independent of the cylinder pressure and only became common in diving regulators decades later.
Who now wants to judge where the greatest inventive achievement lay?
We know who the economic winner was!

Picture 20: Flat diaphragm regulator from the GC42

Picture 21: Controller with compensation

What does the Commeinhes regulator look like?
The diaphragm is very large, corrugated at the edge and firmly coupled to the lever mechanism, which promises very good efficiency. The lever mechanism consists of two levers, but they are unfavourably short, for which there is actually no reason. 

It is very solidly built (pictures 18&19 below), so that hardly any wear is to be expected there.
The basic body of the lever is adjustable in height, which makes the regulator adjustable. 

Pictures 18 & 19

The plunger moved by the levers penetrates a sealing body and presses on the sealing cone against a spring (picture 20 left).
Incidentally, there is still a residual pressure whistle in the inhalation port for the corrugated hose (here exhalation via the VGM), i.e. in air, although there is a manometer on the unit that can be read by the diver (picture 07 front).

A key innovative feature of the regulator is its compensation (Fig. 21). The piston of the high-pressure stage remains unaffected by the ambient pressure, as this can act from both sides. The aim is to keep the inhalation resistance independent of the cylinder pressure. This is the first compensation in a single-stage diving regulator that I have heard of. Later it was successfully used in other regulators, e.g. USD's Royal Mistral and Poland's Kajman. However, it is unknown to me whether the principle shown in the patent in Fig. 21 was widely used in the GC42/47 produced. I would be grateful to the reader for any useful information on this. 
In any case, it could easily be retrofitted under the screw cap in any regulator.
The regulator with the flat diaphragm was housed in a heavy, solid case, but this did not bother me because there was enough space between the two bottles.
Without exhalation problems, it could only be used with the VGM (single tube), as there was no exhalation valve on the regulator.
The version with the exhalation valve on the mouthpiece, as in the swimming pool photo on the left, might not have been comfortable due to the strong position dependency. But as Cousteau is reported to have once said, "Breathing need not be easy, it is commanded."

The version of the GC42/47 with a pendulum bellows hose with mouthpiece (but with bellows instead of flat menbran) is shown in the photo above right. 
The exhalation valve is close to the regulating bellows.

After the war, new diving equipment was scarce, and for strenuous underwater work, the restrictive pendulum hose with VGM was replaced by two hoses with mouthpiece, as was later common practice. To do this, one only had to redesign the hose port as shown in the sketch on the right (regulator with bellows).
The well-known French diving work group Galerne used modified GC47s with flat diaphragm regulators from the fire brigade until the 1950s with a duckbill valve at the end of the additionally attached exhalation hose in the housing, picture on the right.

It is probably pointless to argue about who invented the diving regulator, Emile, René or Victor.
But this analysis of the R. Commeinhes devices GC42/47 shows the exposed position they have in Genesis.
The early death of their developer on the one hand, and the capital power and marketing strength of the competition on the other, have meant that their role is hardly respected today.

Sources:
[Com1] Commeinhes, G., Pat. fr0976590, 1942, GC42 with bellows t1p.de/lih3 
Com2] Commeinhes, G., Pat. ch230369,1942, a.o. bridge with check valves, pendulum breathing apparatus o. VGM t1p.de/acsv 
Com3] Commeinhes, G., Pat. fr0989153, 1944, flat diaphragm regulator with compensation t1p.de/cu1e 
Com4] Commeinhes, G., Pat. fr0989164, 1944, bottle connection t1p.de/mxdt 
[Com5] Commeinhes, G., Manuel GC42 t1p.en/9kf2 
[Com6] Commeinhes, catalogue breathing protection, 196x, franz & eng t1p.de/stch 
[Roc] Rockwell, K., SCUBA WORKSHOP PROJECT ELEVEN- G.C. 42 AMPHIBIAN Georges Commeinhes Scuba,
	HIST. DIVER Vol. 13, Issue 3, Number 44, p. 44, 2005, t1p.en/lv5z 
Rou1] Rousseau, Ph.,, Georges Commeinhes: A Very Discreet Pioneer, HIST.  DIVER Vol.13, Issue 3, No. 44, t1p.de/zxtg 
[Sev1] Seveke, L., George Commeinhes - forgotten too soon! TH 09, 2018, pp. 24-32 t1p.en/y2kl 
[Will] Williams, Des, The ORCO full-face mask, TH 09, 2018, t1p.en/yfjt