In the past, glass-to-metal connection of full vacuum tubes caused problems to many manufacturers
concerning leakage and hence loss of vacuum.
So far there have been to types of glass-to-metal connections.
1. Vacuum compression connection
This glass-to-metal connection is pressed hot with air pressure
onto cladding tube like a preserving glass. Lead oxide glass serves as sealing, which melts
during this procedure.
The particular problem here are the three different materials that are interrelated and need
to ensure a vacuum seal connection. Especially if high temperature differences are operating,
the connection can lose its vacuum sealing. The closure is mechanically robust.
2. Classic glass-to-metal connection
With this method a tubular edge, which is made of metal
(e.g. copper), is pressed axially into the glass tube. The end of the glass tube is heated
up until it is soft enough for it.
If the connection is not affected by any forces, there are no problems with the vacuum.
However, there are affecting forces like wind loads the connection can break, especially
by transverse forces. This leads to vacuum loss.
NARVA is a specialist for glass, metal and vacuum.
To avoid the problems mentioned above, NARVA developed a new and very robust glass-to-metal connection.
The aim was to obviate the danger of vacuum loss with thermo compression method. This was achieved by
creating the metal connection like a barometer box in such a way that no tensile load affects the glass.
NARVA puts the glass around the metal cover and melts both together. It is not just glued as many
The NARVA solution is internationally protected by patent:
International patent application: PTC/DE2006/001244 on 13th of July 2006
Int. publication number: WO 2007/033630
AkoTec collectors have a reliable glass-to-metal sealing, 20 years warranty are an additional reliability.