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Патент USA US2126765

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mg., ` m, wm.
Filed March 4, 1937
Patented Aug. 1e, 193s. "
` 2,126,765
Paul B. Freemanrlndianapolis, Ind., assigner to. l
P. B. Mallory ds Co., Inc», Indianapolis, Ind., a._
corporation. of Delaware
Application March 4, 1931, serial No.' 128.953
s claims.
(ci. ris-aes)
This invention relates to dry >disc rectiners.
ing the internal space surrounding the clamp
ing bolt. The sole purpose of such sealing has 5
been to protect the junctions from the deleterious
Other objects of the invention will be apparent
from. the following ldescription vand accompany
ing drawing _taken in connection with the ap
Beaded claims.
effects of moisture.
means, such as insulating varnish.
protected by insulating varnish on both the in‘
safely deliver 100 amperes D. C. when connected` .
in a 3-phase bridge rectifier. The same junction
' sealed in the conventional manner by cork wash- 25
ers at the end of the rectifier so as to adequately
exclude moisture is unable, onthe other hand, '
to deliver more than approximately 30 to 50 am
peres without such serious sparking across the
flergwhereby its performance> is materially iin-_
J'ner and the outer edges of therectiñer discs will
In its preferred form the present invention in
volves a novel sealing means_for a drydisc recti
Vity is remarkable. It has been found, for exam
' ple. that a rectifier junction 1%" in diameter, 20
_ Figure 3 shows a modified form of bolt for the
- The improvement in current rectifying capac
- Figure 2 is an end view of the rectifier with
parts- broken away; and
The sealing I propose appears to. ma- 16
istics of the rectiñer.
terially affect the electric breakdown character-A
Figure 1 is a longitudinal section `through a dry
. _disc recti?er embodying features of the present
This improvement in performance extends far
beyond a mere improvement in sealing against
_16 set forth, including the illustrations in the draw- moisture.
In the
the rectifier elements with _ a suitable- sealing
yof parts. and methods of manufacture and op
eration referred to above or which will be brought
vout and exemplified inthe disclosure hereinafter
_I have now discovered that the performance
of the rectifier can be materially improved _by
sealing both the inside and the outside edges of -10
V:lil \ The invention comprises the features of con
. struction, combination- of elements, arrangement
washer or gasket to prevent moisture from enter- '
Another object is to improve the sealing means
5 for a dry disc rectiñer.
ternal sealing means and the ends ofthe assem
bly have been provided with a cork or rubber
An object 'of the invention is to improve a rec
_tifler of the dry disc-type.
While a preferred embodiment of the inven
30 tion is described herein, it is contemplated that junction as would cause complete breakdown of- 3d
considerable variation may be made in the meth ythe rectifier in a relatively few-hours of opera
-od of procedure and’thefconstruction of parts
without departingfrom the spirit of the inven
While Ido _not wish to belimited to any par
tion. In the following description and in the ticular theory of operation it is my lpresent opin
'35 claims, parts will be identißed by specific names ion that the following theory might explain the 35
Vfor convenience, _but they are intended- tobe as ' phenomenon: In making the copper sulñde rec
generic in their applicationto similar parts as tiñer the magnesium disc is pressed firmly against
the art will permit.
the cupric sulñde disc and an intermediate film
,The present invention isV particularly applica
is _formed by the passage of electric current
40 ble to rectiilers of the type set forth in Samuel- through“ a dielectric film previously created' on
Ruben Patents 1,751,359.' v1,751,361 and 1,751,363 the magnesium by a chemical process. »The elec
tric forming process is continued until al1 of the
issued March 18, 1930 and others. , One co‘mmer
cial form of the rectifier comprises ,copper sulfide . magnesium area in _sufficiently close contact with
washers each having> one face in contact with a -the cupric sulfide washer isv formed into the rec
‘45 magnesium washer andthe opposite face in con
tifyfng ñlm. Since thereis a‘ curvature at the
tact with a non-polarizing layer such as a washer inner and outer edges of the cupric sulñdewasher
.or carbonized nickel. The washers are arranged there is obviously an ‘irregular line extending
in face to face contact‘in proper sequence with around both the inner and outer edges at which
>larger radiating fins at suitable intervals and a the cupric sulfide surface becomes-tangent to the
50 bolt passing'through the center for clamping the magnesium surface. Immediately adjacent the
.groups of discs together.~
Heretofore such rectifl'ers have been sealed ex
ternally against the effects of moisture by coat
ing the outer edges of the-washers with some
56 sort of protecting varnish or by some other ex
outermost formed portion of theiunction there
will be a point at which the cupric sulfide and
the magnesium are separated by an extremely
small gap. Assuming this gap to be air ñlled,
the presence of`a minute hot spot in the formed 5s
2 .
2,126,765 '
material at the edge of the gap or an increase ' slots or'aperturesl 2| in the end washers. The
in voltage across the Junction due to the passage
of high currents or a.\combination of these two
`causes probably results in ionization of the air
in this very narrow gap, which in turn produces
an arc. The' destructive or erosive e?ect of this
are with high currents will cause the point of
assembly may then be baked to solidify and
harden the varnish.
In Figure 3 is shown a modified form of bolt
21 having a hollow core 28 and a pair of radial
openings 28 and 30 in the wall thereof. When
this bolt is -used in place of bolt I8 the slotted
actual contact between. discs to move inwardly ` washers are not required as the varnish 26 may
and the next point of arcing would be farther
in from the edge of the Junction. Thus the arc
ing will be a progressive process which will rapid
ly destroy the rectifying property of the entire
It will be obvious that even by changing the
be introduced through the hollow core. and radial
openings. This form of bolt is particularly ap 10
plicable to the larger sizes of rectiiiers.
-While the present invention, as to its lobjects
and advantages has been described herein as car
ried out in specific embodiments thereof, it is not
shape of the rectiner elements this borderline
desired to be limited thereby but it is intended to 15
cover the invention broadly within the spirit and
scope of the appended claims.
According to the present invention, the narrow ' What is claimed is:
aretzdof small air gap cannot be‘ entirely elimi
' gap between the edges of the discs is illled with
a dielectric material which excludes air from the
gap whereby no ionization can take place and
there can be no arc created from this cause.
The drawing illustrates a rectifier sealed in
the preferred manner of the present invention.
Each cupric sulnde washer .l0 is in contact on
one face with a magnesium washer Il between
1. A dry disc rectifier comprising a plurality of '
rectifier discs in face-to-face contact said discs 20
having inner and outer edges and an insulating
sealing material in solid adherent form’covering
all the edges of saiddiscs so as to exclude air from
the .edge surfacesy of said discs. A
, 2. A dry disc rectifier comprising a'series of
rectifier discs having central apertures therein,
lwhich a suitable rectifying layerv is formed by
passage of an/electric current as mentioned above.
said discs being in face-to-face contact withthe
-The otherface of the copper sulfide washer I0 is
a solid adherent insulating sealing material coat
in contact with a non-polarizing layer I2, such
as a carbonized nickel disc or one of pure-iron,
or nickel plated steel, and the like. Two groups
of these rectifying units are interposed between
each pair of radiating plates i3' which- may be
of any suitable metal, such as steel.
In the present instance the rectifier is intended
for full wave operation and accordingly five
spaced radiating plates I3 are used providing four
rectifier sections.
'I'hese sections can be con
central apertures of all said discs in, register, and
,ing the inner and outer edges of said discs. '
3. A dry disc rectifier comprising a series'l of
rectifier discs having central apertures therein
said discs being in face-to-fa_ce contact with the ,
central apertures of all said discs in register, and
a solid adherent insulating sealing material coat 35
ing the inner and outer edges of said discs so as
to seal all the edge surfaces thereof.
4. A dry disc rectifier comprising a series of
rectifier discs having central 'apertures therein ~
nected in the fourarms of the bridge by four
terminals I4, l5, I6 and i1., The rectiñer' plates
said'discs being in face-to-face contact with ‘the 40
central apertures of all said discs in register, and
in each section are arranged in such polarity as to `
a'n insulating varnish coating the inner and outer
provide DC across terminals I5 and I1 when AC
is imposed across terminals I4 and I6.
edges of said discs.
5. A_ dry disc rectifier comprising a series of
The rectifier assembly is held together by bolt
rectifier discs having central ' apertures therein
I8 passing through the holes in the center of the
rectifier disc members. A pair of end washers
22, 24 and 23, 25 are included at each end of the
and discs being in face-to-face contact with the
central apertures of all said discs in register, and
an insulating varnish coating the inner and outer
assembly. Washers 22 and 23 are disposed di
rectly on top of the end plates and are slotted to
faces thereof. .
permit introduction of the insulating varnish.
The assembly is held under compression by spring
washer 20 which is tightened against the end of
the assembly by nut I9 on bolt I8.
According to the invention a sealing varnish
26 is coated over the internal and external edges
of the rectifier washers. 'I'he .varnish used should
preferably have a low surface tension when ap-'
edges of said discs so as to seal all the edge sur
6. A dry disc rectifier comprising a pair of rec
tifier discs having central apertures therein',- said
discs being in face-to-face contact with the cen
- tral apertures of said discs in register,'said discs
thereby providing a rectifying junction between _
them, and a solid adherent insulating sealing ma
terial covering the inner and outer edges of the
junction of said discs so as to excludeair from
plied so as to flow into the narrow spaces at the the edge surfaces of said junction.
edge of the discs and completely exclude air from "
7. A dry disc rectifier comprising a. pair ofrec
contact with the disc edges. Air pockets should 1 tiñer discs having central apertures therein, said
be carefully avoided. The varnish should also disc being in face-to-face contact with the central
preferably have a Vhigh dielectric strength. One apertures of said discs in register, said discs lthere
varnish which has been found very satisfactory by providing a ,rectifying junction between them,
is made according to the following procedure: 100 and a solid adherent insulating varnish covering
pounds Robertson's wax, 12 gallons of raw tung the inner and outer edges of the junction of said '
oil and 5 pounds manganese resinate are cooked. discs so as to ,excludeair from the edge surfaces
together at approximately 250° C. until the mix
of said junction., ,
. _
ture is ready to yJell and then allowed to cool.
8. A dry plate rectifier comprising a Aser-ies of
70 While it is cooling 31 gallons of petroleum naptha rectifier plates having an aperture therethrough,
>are added as »rapidly as possible to complete the said plates being in face-to-facè contact anda
solid adherent sealing material coating the inner
The varnish may be applied to the clamped and outer edges of said plates.
assembly before the end washers and nut are put
75 on but preferably may be introduced through' the
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