Fleming - valves; GB

Thomas Edison demonstrated several of his "Edison Effect" lamps at the International electrical Exhibition which was held in Philadelphia from September 2nd to October 11th, 1884. One of the attendees was William Henry Preece from England. Preece was, at the time, Chief Engineer at the British Post Ofice. Edison gave him at least nine of his lamps and these were not identical. Preece returned to England where he presented a paper entitled "On a Peculiar Behaviour of Glow Lamps when raised to High Incandescence" on March 18th, 1885. This papr followed extensive experiments Preece carried out on his Edison lamps.

Nine of these lamps have been traced and five have been found in a private collection in the UK, three in the Cragside Museum, in England and one in a private collection in the US. Preece apparently put them in a cupboard in his work area and nothing more was done with them. John Ambrose Fleming was aware of them and they were to be the basis of his experiments in wireless telegraphy while working for the Marconi Wireless Telegraph Co Ltd in 1904.,. 

J. A. Fleming was born on November 29th, 1849 and died April 18th, 1945. He grew up in Lancaster where he attended Lancaster Royal Grammar School and later University College School  and University College, where he graduated in 1870. He obtained his BA while at St John's College, Cambridge in 1881. He lectured at several other universities during the late 1880's. He was a consultant for the Marconi Wireless Telegrapg Co, as well as the Swan Company, Ferranti, Edison Telephone Company and later the Edison Electric Light Company. He rejoined University College, taking the Chair of Electrical Technology. 

Original Fleming valves were somewhat crude and samples have been seen which have the electrical connections coming through the butt seal pinch of the glass bulb and in turn being connected to a solid wire for each of the three terminals. The Science Museum in London has some of these.

In 1904 while working at the Marconi Company, he invented the first thermionic vacuum tube (or valve). This was known as the Fleming Valve. The valve was the subject of patents including UK patent no 24850 granted September 21st, 1905  and filed earlier the same year. A patent was applied for in the US and Patent no 803684 was granted on the valve on November 7th, 1905.

It is recorded in several reference books that the Edison Swan United Electric Company made valves for Fleming and a range of four valves listed in the Marconi catalog of 1910 show that they were branded "Royal Ediswan" and "Fleming Oscillation Valve" and filament volts (depending on the type - either 4 or 12 volts). One valve has been located which has a serial number stamped into the brass base.

It was obvious to Fleming that performance of detector devices of the day were not good. The coherer, for example, was insensitive and slow. He tried electrolytic detectors for a while but turned to the lamps he had developed. The first experiment was carried out in October 1904 and the transmitting circuit involved a tuning coil, inductance coil and two Leyden Jars (batteries) and one of his lamps. He had done further work on these lamps and discovered that a cylindrical anode surrounding the filament was better that a single sheet plate between the "legs" of the filament. Twelve lamps of the new design were made for him by Edward Gimingham, manager of the Edison Swan lamp Factory. These had 12 volt carbon filaments operating at 2.7 - 3.7 amps. The cylindrical anode was made of aluminium.  

The anode was changed to nickel in 1906 and the carbon filament was replaced by Tungsten in 1908. These valves were mounted in wooden frames for a while but this was changed to the bayonet cap (B22 today) and in some cases Edison Screw (E27). By 1910 there were four types and these were given Marconi type numbers: 132R, 133R, 134R and 135R. The134R was also available with the smaller Edison screw E14 base. The 135R was fitted with an outer copper gauze screen to to protect it from transmitted waves.     

Later Fleming Valves were made with the small "S14" sized bulb, possibly  and different anodes have been used in this style. They had B22 bases. Several of these have been found in US museums and tube collections. The US Marconi Company made a tubular Fleming Valve around 1910. One of these is pictured on page 14 of the Harold Greenwood book "A Pictorial Album of wireless and radio 1905 -1928" . In the 1950's/60/s Phil. Weingarten, a US collector, made replicas of this type as well as de Forest Audions. A few different tubular Fleming Valves have been located in US collections and may not be reproductions.

As a detector, the Fleming Valve was many years ahead of its time and it wasn't untill the early 1930's that diode detectors came back into use.

References;

1) John Ambrose Fleming biography, Wikipedia

2) British Radio Valves, the Vintage Years, 199, pages 7 -16

3) MWTCO catalog 1910

4) A Pictorial Album of Wireless andRadio 1905 -1928, page 14