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Патент USA US2404191

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July 16,
J_ c_ QUAYLE ET AL
DIELECTRIC HEATING ELECTRODE
2,404,191
_
Filed April 9, 1945
Inventors
Joshua C. Quay/e _ 4 p¢fer Jo'nes
B
m, m? 774%A ltorneys
Patented. .iuly 16, 1946
2,404,191
UNITED STATES ‘PATENT OFFICE
2,404,191
DIELECTRIC HEATING ELECTRODE I
Joshua Creer Quayle, Helsby, and Peter Jones,
Kelsall, near Chester, England, assignors to
British Insulated Cables Limited, Prescot, Eng-L
land, a British company
Application April 9, 1945, Serial No. 587,353
In Great Britain April 22, 1944
5 Claims.
(Cl. 219—47)_
1
2
This invention relates to dielectric heating elec
.
.
be used' where the material to be heat-treated
is polyvinyl chloride or other thermoplastic hav
ing a softening action on polyvinylidene chlo
ride. Polyvinylidene chloride is sold in the form
of ?ne grains, and with the aid of heat and pres
sure may be converted into the form of a smooth,
non-porous sheet or ?lm, which may be secured
to the ?brous layer by a suitable adhesive, for
trodes for apparatus for subjecting thermoplastic
or thermosetting insulating material to pressure
whilst heat‘ is generated therein by subjecting.
it to the action of a high frequency alternating
or ?uctuating ?eld of electric force for the pur
pose of moulding or shaping or embossing the
material or welding or jointing it to other ma
terial of a similar or different nature. In the
instance, polyvinyl acetal, by pressing the sheet
improved form of apparatus in accordance with 10 or film of polyvinylidene chloride and the ?brous
theinvention, pressure is applied to the material
inner layer together after heating the adhesive
to be treated by a high frequency electrode hav
between them to its softening point.
ing a composite facing which consists of an inner
By way of example, the accompanying draw
layer of high-loss, inorganic insulating material
ing shows, diagrammatically and on an enlarged
having an open ?brous structure and of an outer 15 scale, a cross-section through a pair of electrodes
layer of high-loss, heat-stable, insulating mate
4, each provided in accordance with the inven
tion with a composite facing consisting of an in
rial having a non-?brous structure, which serves
to prevent penetration and adhesion of the ma
ner layer 3 of woven glass fabric and of a smooth~
terial to be treated.
surfaced outer layer 2 of a resin of the kind de
In the foregoing statement, and hereinafter 20 scribed. The thickness of the fabric layer 3 may
where the context permits, by “high-loss” insu
be of the order of 0.03 inch and that of the
smoothing layer 2 of 0.01 inch. Between these
lating material we mean insulating material hav
faced electrodes are shown the overlapping ends
ing a dielectric loss of the order of 0.01 as distinct
I of two strips of thermoplastic material which
from the so-called low-loss insulating materials,
such as, for instance, certain grades of steatite, 25 are to be heated and welded together by being
subjected to pressure and to the action of a high
low-loss ebonite and moisture-free, mica-?lled,
frequency electric ?eld between the electrodes 4.
borate glass, which have a dielectric loss value of
‘ The ?brous inner layer of the compositefacing
the order of 0.001, and by “heat-stable” insulat
will itself be heated by the high frequency ?eld,
ing material we mean insulating material which
is heat-stable at the temperature to which the 30 though not to the same extent as the material
material to be treated is raised during the mould
under treatment, since little heat will be gen
ing or other operation.
erated in the interstices between the fibres.
For the inner layer of the composite facing we
Owing to its open ?brous structure, this inner
layer will considerably restrict ?ow of heat to the
may use a woven fabric, or a felted fabric. The
preferred material is a woven glass fabric, but
electrode. In the smooth outer layer which
serves to prevent penetration and adhesion of
we may use a felted fabric of glass, asbestos or
slag wool. For the outer sealing or smoothing
the material to be treated, heat will be generated
layer that will engage the material to be sub
more rapidly than in the heat-insulating ?brous
Jected to the high frequency and pressure treat
layer. By selecting for the outer layer of the
ment, we may use a thermosetting plastic ma 40 facing, a material having a dielectric loss value
terial, for instance, a resin of the phenol-, cresol-,
of the same order as that of the material to be
‘ »melamine- or urea-formaldehyde type. The res
treated, the temperature of its surface in contact
in, in varnish form, may be calendered on to the
with that of the material to be treated may be
woven or felted fabric of inorganic ?brous ma
' made to approximate that of the said material.
terial and subsequently baked, or it may be ap 45
plied to a sheet of paper and the resin-coated
paper may be applied, if necessary,‘ with the aid
of an adhesive, to the woven or felted fabric.‘
Alternatively, we may use as the smoothing layer
a thin sheet of a thermoplastic‘ material that has 60
a sufficiently high softening point and is not plas
ticised by the material under treatment. Poly
vinylldene chloride is considered at present to be
the most satisfactory thermoplastic material for
the smooth outer layer, but this material cannot
Thus by the provision of the composite insulating
layer, chilling of the material to be treated due
to the presence of the electrode may be very much
reduced or even completely avoided.
We have found such chilling to be a disad
vantage in many cases, particularly in making
lap welds in thermoplastic strip material with
out increasing the thickness of the strip. Here
the. provision of the composite facing on each
electrode enables the weld to be made without
55 the formation at each end thereof of a surface
’
2,404,191
3
/
.
4
groove which locally reduces the mechanical
inorganic, ?brous materials consisting of ‘glass
strength of the welded strip.
?bre, asbestos ?bre and slag wool, and of an outer
layer of high-loss, heat-stable‘ insulating material
having a non-?brous structure, by ‘which pres
_
'
What we claim as .our invention is:
1. In apparatus for subjecting thermoplastic
or thermosetting insulating material to pressure
whilst generating heat therein by _the action of a
sure is applied to the material to be treated.
4. In apparatus for subjectingv thermoplastic
dr thermosetting insulating material to pressure
high frequency ?eld of electric force, a high fre
whilst generating heat therein by the action of
quency electrode having a composite facing con
a high frequency ?eld of electric force,,a high
sisting of an inner layer of high-loss, inorganic,
insulating material having an open ?brous struc ML frequency electrode having a composite facing
ture and of an outer layer of high-loss‘, heat-w
stable, insulating material having a non-?brous
consisting ofan inner layer of high-loss, inor
ganic, insulating material having an open ?brous
structure and of an outer layer of a resin of the
structure, by which pressure is applied to the
type selected from the group consisting of phenol
material to be treated:
2. In apparatus for subjecting thermoplastic 18 iormaldehyde type resins, cresol-formaldehyde
type resins, melamine-formaldehyde type resins
or thermosetting insulating material to pressure
and urea-formaldehyde type resins, by which
whilst generating heat therein by the action of a
pressure is applied to the material to be treated.
high frequency ?eld of electric force, a high fre
5. In apparatus‘ for subjecting'thermopla‘stic
quency electrode having a composite facing con
sisting or an inner layer of woven glass fabric and 20 or thermosetting insulating material to pressure
of an outer layer of high-loss, heat-stable insu-' . whilst generating heat therein by the action of a
lating material having a non-?brous structure, by
high frequency ?eld-oi electric force, a high fre
which pressure is applied to the material to be
quency electrode having a composite facing con
sisting of an inner layer of high-loss, inorganic,
_
3. In apparatus for subjecting thermoplastic 25 insulating material having an open ?brous struc
ture and of an outer layer of polyvlnylidene chlo
or thermosetting insulating material to pressure
ride, by which pressure is applied to the material
whilst generating heat therein by the action of
to be treated.
'
,
a high frequency ?eld of electric force, a high
frequency electrode having a composite facing
JOSHUA CHEER QUAYLE.
PETER. JONES.
consisting of an inner layer of felted fabric of 80
a material selected from the group of high-loss,
treated.
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