Rubber ring from Siebe Gorman Merlin Mark 6 twin hose SCUBA regulator / demand valve

Maker Siebe, Gorman and Company Limited (British, 1880 - 1998)

Date1966

Object number00048280

NameDemand valve ring

MediumRubber

DimensionsOverall: 3 x 22 mm, 1 g

ClassificationsTools and equipment

Credit LineANMM Collection Gift from Dr John Penrose

Terms

DescriptionThis rubber ring belongs to a Siebe Gorman Merlin Mark VI SCUBA air regulator. When it was first manufactured in 1966 the Siebe Gorman Mark VI demand valve was at the zenith of diving equipment. Rugged and dependable it became the demand valve or air regulator of choice for the Royal Navy as well as for commercial and scientific divers such as Dr John Penrose.HistoryAugustus Siebe (1788-1872) the inventor of the standard dress diving suit and acknowledged as the 'Father of Diving' (Kemp, 1986) was born in Saxony in 1788 before moving to Berlin where he took up an apprenticeship as a metal caster and watch maker. After serving in and being invalided out of the Prussian Army he migrated to London, England in 1814 where he continued his profession as watch maker, metal chaser (engraver of metal) and later a gun maker. In 1834 he met Charles Deane who had developed a smoke and fire hood and Siebe combined Deane's hood with an air pump to produce the 'open dress' diving suit. In 1838 Siebe adapted the ideas of Deane's engineer, George Edwards, to enclose the suit to stop it from flooding by clamping the top of the canvas suit to the bottom of the helmet creating the first closed dress or standard dress diving suit. Over the next few years Siebe made a number of significant changes to the suit and helmet introducing inlet and outlet valves, a separate bonnet and breastplate joined by a waterproof thread and regulating valves. The standard dress diving equipment became a commercial success and after the successful salvage of the ROYAL GEORGE at Spithead in 1840 the suit was adopted for use by the Royal Navy. Following Augustus Siebe's retirement in 1868 the company was handed over to his son Henry and son-in-law William Augustus Gorman and the company commenced trading as Siebe & Gorman in 1870 and then Siebe Gorman & Co Ltd in 1881. With the development of commercial diving in the latter half of the 19th century and the pearl diving industry in the early half of the 20th century the company prospered and, working out of its Neptune Engineering and Instrument Works at Chessington in Surrey, the company went on to produce a wide range of general breathing apparatus, underwater cameras and submarine equipment. During WWII Siebe Gorman Co. Ltd started to move away from standard dress diving equipment and branched out into smaller more portable re-breather units. The first was the Salvus, used in mines and for fire fighting, but it was later adapted for underwater use by the British military services. After WWII the increasing demand for recreational diving equipment saw Siebe Gorman Co. Ltd develop an open circuit scuba unit, which they called an 'aqua lung', consisting of two inverted 26 cu ft tanks, an air pressure reduction valve and a demand valve. The Company then obtained a license from the French company La Spirotechnique to first manufacture the CG-45 demand valve (the demand valve invented by Captain Jacques-Yves Cousteau and Emile Gagnan in 1943) and then later the twin hose Mistral demand valve which they called the eeSGee or the Siebe Gorman Mk1. The other major British manufacturer of diving equipment at the time C.E. Heinke & Company were denied trade access to the CG-45 and Mistral demand valves and tried to get around the various patents by developing a slightly modified twin hose demand valve which they called the Heinke Lung or Mk I in the mid 1950s. Heinke made a number of modifications (Mk II- Mk VI) and by the time Siebe Gorman bought out C.E. Heinke in 1961 the companies demand valves were more or less interchangeable and early examples of the Merlin Mk VI, like Dr. Penrose's, are found with both Heinke and Siebe Gorman markings. The Merlin Mk VI was the heir of the original and efficient Heinke regulators, it had a piston first stage, an optional built in reserve, was also capable of being used as a hookah and could be adapted to take a contents pressure gauge. Its ruggedness and dependability saw it adopted as the standard twin hose regulator used by the British Royal Navy for more than two decades. The Siebe Gorman company continued to trade under its own name until 1999 when it merged with another company to form the breathing apparatus manufacturer Invensys. SignificanceDivers working underwater need a dependable demand valve or regulator that can not only control the delivery of air from the diver's cylinders but also reduce and balance the air so that it compensated for the pressure of the water around them. The Merlin Mark VI was the demand valve of choice for Royal Navy and commercial and scientific divers in the 1960s.