16.2.1 CAT Valve Construction
Robert’s involvement with the CAT can be traced back to as early as 1922
when in November of that year public broadcasting in the UK began with the
creation of the British Broadcasting ‘Company’.
5 The first daily broadcasts,
(radio only) included news, politics and music. A GEC laboratory report of
May that year entitled, ‘Valves for broadcasting sets’,
6 signaled the laboratories’ engagement with the new medium. In that year, experiments were
started on large water cooled valves
7 and Robert’s initial involvement
addressed the various glass-to-metal joints that they depended on—one of the
most important being the integration of the cylindrical anode plate with the
glass envelope. In this way an outer jacket containing coolant could surround
the envelope and come into direct contact with it—heat at the anode being
dissipated through the glass to the circulating coolant. Robert was later joined
by his friend and fellow chemist Ralph Chirnside, and together they attended
to the problems with coolants, but between 1922-3 Robert, together with C.
A. Morton, were the first to successfully ‘glass’ pieces of nickel-iron (anode)
tube to the envelope, the first specimen of which was christened by them, ‘the
Great Seal of England!’
8
Much work had already been done in America regarding metal-glass
bonding by William G. Houskeeper (no ‘e’) of the Western Electric
Company, which he patented in the USA in 1919.
9 Houskeeper was able to
make robust glass-to-glass joints between hard and soft glasses, and to hermetically seal metal conductors into vacuum tubes by simultaneously welding
glass to the opposite sides of an intermediate metal disc, usually of copper.
The disk was very thin (sometimes thicker, but with very thin chamfered or
‘feathered’ edges) and the distortion caused by the differential cooling was
accommodated by the flexibility of the disc (or rather the disc’s edge). In this
way the glass expansion predominates and the disk is forced to adopt the
thermal expansion coefficient of the glass. Subsequently in 1923, the ‘art’ of
hermetically sealing the anode tube to the valve envelope was described by
Houskeeper in a second publication, (Chap. 15), but for many the process
remained a mystery, achievable only by the most talented of glass blowers.
Progress could only be made with the new cooled anode valves therefore if
this technique could be mastered and devolved to the laboratory craftsmen
who had to build the valves. It was here that Robert made a fundamental
contribution by using a variation on an already known process. Alloys of
nickel and iron could be made which had approximately the same coefficients
of expansion as the glass envelope and which could be joined directly to the
368
D. Sheppard
Robert’s involvement with the CAT can be traced back to as early as 1922
when in November of that year public broadcasting in the UK began with the
creation of the British Broadcasting ‘Company’.
5 The first daily broadcasts,
(radio only) included news, politics and music. A GEC laboratory report of
May that year entitled, ‘Valves for broadcasting sets’,
6 signaled the laboratories’ engagement with the new medium. In that year, experiments were
started on large water cooled valves
7 and Robert’s initial involvement
addressed the various glass-to-metal joints that they depended on—one of the
most important being the integration of the cylindrical anode plate with the
glass envelope. In this way an outer jacket containing coolant could surround
the envelope and come into direct contact with it—heat at the anode being
dissipated through the glass to the circulating coolant. Robert was later joined
by his friend and fellow chemist Ralph Chirnside, and together they attended
to the problems with coolants, but between 1922-3 Robert, together with C.
A. Morton, were the first to successfully ‘glass’ pieces of nickel-iron (anode)
tube to the envelope, the first specimen of which was christened by them, ‘the
Great Seal of England!’
8
Much work had already been done in America regarding metal-glass
bonding by William G. Houskeeper (no ‘e’) of the Western Electric
Company, which he patented in the USA in 1919.
9 Houskeeper was able to
make robust glass-to-glass joints between hard and soft glasses, and to hermetically seal metal conductors into vacuum tubes by simultaneously welding
glass to the opposite sides of an intermediate metal disc, usually of copper.
The disk was very thin (sometimes thicker, but with very thin chamfered or
‘feathered’ edges) and the distortion caused by the differential cooling was
accommodated by the flexibility of the disc (or rather the disc’s edge). In this
way the glass expansion predominates and the disk is forced to adopt the
thermal expansion coefficient of the glass. Subsequently in 1923, the ‘art’ of
hermetically sealing the anode tube to the valve envelope was described by
Houskeeper in a second publication, (Chap. 15), but for many the process
remained a mystery, achievable only by the most talented of glass blowers.
Progress could only be made with the new cooled anode valves therefore if
this technique could be mastered and devolved to the laboratory craftsmen
who had to build the valves. It was here that Robert made a fundamental
contribution by using a variation on an already known process. Alloys of
nickel and iron could be made which had approximately the same coefficients
of expansion as the glass envelope and which could be joined directly to the
368
D. Sheppard