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Патент USA US2138224

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.NOV. 29, 1938.
H_ P~ BARASCH
2,138,224
METHOD OF SEALING ELECTRICAL CONDUCTORS INTO VITREOUS ENVELOPES
Filed Jan. ll, 1958
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Patented Nov. 29, 1938
2,138,224
PATENT OFFICE
UNITED- STATES
2,138,224
METHOD OF SEALING ELECTRICAL CON
DUCTORS INTO VITREOUSr ENVELOPES
Hans Pius Barasch, Kensington, London, Eng,
land
Application January 11, 1938, Señal No. 184,484
In Great Britain January 12, 1937
4 Claims.
(Cl. 176-126)
The present invention relates to methods of
sealing electrical conductors into envelopes of
quartz or other refractory vitreous materials, and
is particularly applicable to the sealing of lead
ing-in wires into the quartz envelopes of the
so-called super-pressure mercury vapour lumi
nous discharge tubes.
It has been proposed, in order to obtain a
satisfactory seal, to employ as the leading-in
wire for a discharge tube with a quartz envelope
> a very thin strip or ribbon of molybdenum.
Ow
tubes, each rod carrying at one end an electrode
and at the other end an electrical conductor,
the conductor and electrode being connected by
a very thin metallic ribbon wound round the @1
rod in the form of a helix, each rod being fused
into a capillary tube so `that the two electrodes
face one another in the envelope which is
evacuated and ñlled with a suitable gas.
The invention will now be described by way
of example with reference to the accompanying
drawing in which
vention;
rounding the leading-in molybdenum strip has
and
the cross-section of the strip. ,For example, it
is customary to employ for this portion of the
envelope a capillary tube having a substantially
rectangular cross-section, the length of the rec
25 tangle being very large compared with the width.
One object of the present invention is to avoid
the necessity for any such specially shaped en
velopes or parts thereof when employing a thin
strip or ribbon of metal as the leading-in con
ductor.
v
Another object of the invention is to provid
a highly efficient seal capable of withstanding the
very high pressures and temperatures employed
in super-pressure mercury vapour discharge
tubes.
'
`
'
’
`
A further object of the invention is to provide
a simple and efficient method of constructing
such super-pressure mercury vapour discharge
tubes.
According to the present invention a method
of sealing an electrical conductor in the form of ’
a very thin metallic ribbon into a refractory
' vitreous envelope comprises wrapping the con
ductor into the form of a helix around a rod of a
45 material having substantially the same coef
ilcient of expansion as the material of the enve
lope, the cross-section of the rod being very
slightly smaller than the inner cross-section of
a portion of the envelope, inserting the rod with
the ribbon into the said portion, and‘fusing to
gether said rod and said portion.
»
According to the invention in another aspect,
a luminous electrical discharge tube comprises a
quartz envelope having two end portions in the
55 form of capillary tubes, a pair of quartz rods
.
which ñt closely into the bore of the capillary
ing to the extreme thinness of the ribbon, the
amount of its expansion due to heating is too
small to produce any fracture of the surround
ing quartz. At the same time, in order to‘ ob
tain a satisfactory seal, it has been hitherto
necessary to employ an envelope which is so
shaped that the portion of the envelope sur
20 a cross-section which more or less conforms to
30
'
Fig. l'is a perspective diagram showing the
method of sealing according to the present in
-
Fig. 2 shows in part section a luminous dis
charge tube in which the leading-in wires are
sealed by the method of the present invention;
'
Fig. 3 shows in section an alternative form 20
of electrode unit for use in a luminous discharge
tube.
-
Referring to Fig, 1, the quartz envelope I of
the vessel into which a leading-in Wire is to be
sealed is formed with a constricted portion 2 of
circular cross section and small bore. 'I'he lead
ing-in wire 3 is in the form of a very thin rib
bon of molybdenum having a thickness of the
order of 15a which is wound helically round a
quartz rod 4 having a cross-section which is 30
very slightly smaller than the inner cross-sec
tion of the portion 2, so that the rod with the
ribbon will just fit into the bore of the portion
2. The rod is pushed into the bore of the por-r
tion 2 and the two are fused together along the 35
whole of their length, thereby enclosing' the
ribbon 3 to form a perfect seal.l
The application of the inventionto the manu
facture of a superpressure mercury vapour lu
minous discharge tube will now be described with 40
reference to Fig. 2.
The tube comprises a quartz envelope having
two end portions in the form of capillary tubes
5.0i circular cross-section. A quartz rod 6 of
circular cross section with an external diameter
of very slightly less than internal diameter of
the tubes 5 is provided with a short axial hole
at each end, the diameter of the hole being 1
mm. At one end of the rod 6 a tungsten rod 1
of 1 mm. diameter is inserted into the hole and "
at the other end of the rod 6, one end of a
tungsten wire 8 is inserted into the other hole.
Around the rod 6 is tightly wrapped in the form
of a helix a length of very thin molybdenum
ribbon -9. One end of the ribbon is wrapped
2
2,188,224
tightly round the tungsten rod 1 and is further
and wire I 8 are connected by the ribbon I9 the
secured thereto by a quartz sleeve l0 which is ' ends of which are wrapped round the electrode
slipped over the tungsten rod 1.
The tungsten
rod serves as an electrode, and the quartz sleeve
acts as a shield to prevent the discharge from
and wire respectively.
I claim as my invention:
1. In an electrical discharge device, an en
velope and a seal for a leading-in conductor com
reaching the molybdenum ribbon. The other
end of the molybdenum ribbon is secured to the
prising a tube of refractory vitreous material
tungsten wire 8. The complete unit consisting
of the quartz rod and attached electrode mem
forming a continuation of the envelope of said
device, a rod of the same material as said tube
10. ber, molybdenum ribbon, and tungsten wire is
inserted into the bore of a capillary tube 5, the
electrode being nearest to the centre of the tube.
An exactly similar unit Il is inserted into the
inserted in the bore of said tube and fused there 10
to, and a thin metallic ribbon wrapped helically
around said rod between said rod and said tube.
2. In an electric discharge device, an envelope
and a seal for a leading-in _conductor com
bore of the other capillary tube 5 from the other
end, with its electrode facing the electrode of the
ñrst mentioned unit. The wall of the capillary
tube is then fused to the quartz rods along the
whole length of the latter and also to the quartz
sleeves, thus providing a long seal around'the
prising a quartz tube forming a continuation of
the envelope of said device, a quartz rod in
serted in the bore of said quartz tube and fused
thereto, and a thin molybdenum ribbon wrapped
helically around said rod between said rod and
molybdenum strip. The portion i_ 2 of the bore
said quartz tube.
surrounding the tWo electrodes is then evacuated
and filled with mercury vapour at the required
pressure. The lengths of the quartz rods are so
chosen that the total length of each seal is
25 greater than the length of the discharge space.
If the discharge tube is to work on direct cur
rent one electrode is coated with a suitable elec
tron emitting material, Whilst if the tube is to
work on alternating current, both electrodes
will be so coated.
An alternative form of electrode unit is shown
in Fig. 3. A quartz rod I3 has a fine bore run
ning along the whole of its length, the bore be~
ing provided with a constriction I4 near one end.
A tungsten electrode i5 carrying a quartz sleeve
20
3. A luminous electrical discharge tube com‘
prising a quartz envelope, two end portions of
said envelope in the form of quartz capilliary
tubes, a pair of quartz rods fitting closely into
the bore of said capillary tubes, each of said rods 25
carrying at one end an electrode and at the other
end an electrical conductor, said electrode and
conductor being connected by a thin metallic
ribbon wound round the rod in the form of a
helix, each of said rods being fused into one of 30
said capillary tubes so that said electrodes face
one another in said envelope.
4. A luminous electrical discharge tube ac
cording to claim 3 wherein each of said elec
trodes carries a quartz sleeve between the opera
i6 is pushed into one end of the bore until its
tive end thereof and the junction of said elec
tip reaches the constriction I4. A thin quartz
rod il ñlls the remainder of the bore with the
trode and said ribbon, each of said sleeves being
fused in the bore of one of said capillary tubes.
exception of an end portion into which is in
serted the tungsten wire I8. The electrode l5
HANS PIUS BARASCH.
40
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