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Патент USA US2513115

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June 27, 1950
2,513,114
D. W. SMITH
LIQUID AIR TRAP
Filed Oct. 19, 1944 -
75 [on Gauge
/
(722 Vacuum Pump
INVENTOR
Douglas W. Smith.
BY
.
WZM
ATTORNEY
Patented June 27, 1950
2,513,114
orFicE.
mmiflii?ap
'’
‘
Douglasrlw. Smith, Stevensville, Micha, assignor,‘
by mesne'assignments, tof=tlfe=UnitedrStatéS 50f ‘
America‘: as represented by the United States
Atomic Energy Commission»
Application October 19, 1944§Serial N15. 559;4e7 "
1
2'Claims.
This invention-relates to cold traps and par
(Cl.257=-'-29) >
.
2*
.
is-‘cap‘abl'e ‘of being maintained in operation for
ticularly to liquid air traps for condensing water
substantial ' periods » of time without replenishing
and other vapors, such as mercury vapors, pres’
the refrigerant.
ent‘in ‘a vacuum‘ line.
Other and further objects‘ will be apparent
from-‘the following description taken in connec
tion with the drawing, in which:
Fig. 1 is a‘ crossfsectional viewof my improved
Irr- high" vacuum-systems‘ it " is customary to
attach ‘an ion gauge‘to the “system for measuring
the“ degree " of vacuunr'andso" detect any ‘leaks
that may develop: thereiniu In order to prevent
wateror' other vapors, such asv mercury vapors,
liquid air trap, and
Y
'
Fig?‘ 25‘ ‘is ar-viewin' cross section taken along
from entering the ion gauge, _.it is the practice 10 IineZQ-ZcfFig. 1'. _
‘
to freeze out lsuchv vapors .in a cold trap made by
-My invention consists in- providng a cold trap
inserting a‘ dewar, or double-walled vacuum ?ask,
integral with" a-‘tubular‘conduit and designed to
in the vacuum line and ?lling the ?ask with
surround the conduit with a cylindrical pool of
liquid air. Such a construction is illustrated in
liquid air; a double-Walled, evacuated chamber
Fig. 8 of United States Letters Patent No. 15 being provided to insulate the liquid air from
1,367,865 to Crawford and in Fig. 19, examples 0',
the atmosphere.
c" appearing on page 122 of “Procedures in Ex
With reference to the drawings, my improved
perimental Physics” by John Strong, New York
cold trap comprises a unitary structure includ
(1943). The vacuum line is thus made to pass
ing a pair of co-axially arranged conduits, one
between the inner and outer walls of the dewar.
being an intake conduit I0, and the other an ex
In such an arrangement the inner wall of the
haust conduit II. The intake conduit is sur
dewar is chilled by the liquid air, while the outer
rounded by a suitable refrigerant, such as liquid
wall is exposed to the atmosphere and is not
air, carried in an annular well I2 co-axial with
chilled. Any vapors in the vacuum line coming
conduit 10 and de?ned by the outer surface of
in contact with the inner or chilled wall con
said conduit and‘inner Wall portion [3 of the
dense and adhere thereto, but vapors contact
?ask. An insulating chamber 14, of generally
ing the outer unchilled wall are not condensed
cylindrical con?guration, circumscribes the re
and may pass into the ion gauge. As a result,
frigerant well and is de?ned by wall portion I3
removal of undesired vapors is not complete.
and an outer wall portion 15 co-axial and paral
Also, traps of the sort heretofore used have 30 lel therewith. Chamber I A communicates with
the disadvantage of presenting a large surface of
exhaust conduit II at 16 and is maintained in
liquid air to the atmosphere thus causing rapid
evaporation and loss of refrigerant. Further
more, loss of refrigerant creates misleading data
an evacuated condition by a vacuum pump (not
illustrated). Being evacuated, the chamber 14
serves to insulate the refrigerant in well 12 from
at the ion gauge. In a vacuum system of known 35 the atmosphere and hence reduces loss of re
pressure if the liquid air level drops no more
frigerant through evaporation.
than half an inch, less vapor will be frozen from
In operation, my improved cold trap is inserted
the line and the degree of vacuum indicated at
in a vacuum line intermediate an ion gauge and
the ion gauge will be lower than is actually the
a vacuum pump, and well 12 is ?lled with liquid
case. Similarly, if the liquid air is replenished 40 air. Water and other vapors, such as mercury
more vapor will be frozen out and the pressure
vapors originating in a diffusion pump connected,
shown by the ion gauge will indicate a mislead
for example, to the conduit ll, condense and
ingly high degree of vacuum.
freeze to the Walls of the conduit l0. Such va
An object of this invention is to provide a cold
pors are thus con?ned to the conduit I0 and
trap that completely surrounds a fluid conduit 45 can not enter the ion gauge that is connected
and requires a minimum of refrigerant.
thereto. Chamber l4, being evacuated, insulates
A further object is to provide a cold trap that
is integral with a conduit in a vacuum system
the pool of liquid air which is protected thereby
from exposure to the atmosphere except for a
and utilizes the vacuum to insulate the refriger
relatively small annular surface l1.
ant from the atmosphere.
50
While my cold trap is especially designed for
A further object is to provide a cold trap that
use in a vacuum system and uses the vacuum
is designed to expose only a relatively small an
system to provide an evacuated insulating cham
nular surface of refrigerant directly to the at
ber for the refrigerant, it is apparent that the
mosphere.
trap can be used in any ?uid line, although with
A further object is to provide a cold trap that
reduced efficiency.
2,513,114
4
duit and adapted to insulate the well from the
I prefer a design in which the refrigerant
chamber and the insulating chamber are gen
atmosphere.
may be adopted for this purpose without de
parting from the scope of this invention, the es
sential features of which consist in making the
means de?ning a well surrounding the inlet con
trap integral with the vacuum line, completely
surrounding the line with refrigerant, and in
sulating the refrigerant from the atmosphere. 10
My improved cold trap may be made of glass,‘v 7
although it is to be understood that the material
used is not critical and numerous other suitable
materials will readily suggest themselves to one
skilled in the art.
'
"'
'
'
2. A cold trap for removing vapors from a
vacuum line comprising a unitary structure in
cluding an inlet conduit and an exhaust conduit,
erally cylindrical in shape and concentric with
the conduit to be cooled. However, other shapes
duit, 'said well being adapted to receive a re
frigerant, and means de?ning a chamber circum
scribing said well, the chamber communicating
with both the inlet conduit and the exhaust con
duit and adapted to insulate the well from the
atmosphere, said inlet conduit and said well and
said chamber being disposed in co-axial relation,
and said well and said chamber being substan
16 tially co-extensive in length.
DOUGLAS W. SMITH.
The present construction marks a distinct ad
vance over the prior art and has demonstrated
REFERENCES CITED
its superiority thereover in actual use. Modi?- '
cation of the foregoing invention may suggest ‘
The vfollowing references are of record in the
themselves to those skilled in the art, and such 20 ?le of this patent:
,
modi?cations as fall within the scope of the
appended: claims are contemplated as forming
part of my'invention.
I claim:
'
1
UNITED ' STATES PATENTS
Number .
'
'
l. A cold trap for removing vapor fromv a 25
vacuum line comprising a unitary structure in
cluding an inlet conduit and. an exhaust conduit,
means de?ning a well surrounding the inlet con
duit,jsaid well. being adapted to receive a re
frigerant, and means de?ning a chamber circum
scribing said well, the chamber communicating
with both the inlet-conduit and the exhaust ccn- ,
Name ‘
Date
'
1,529,597
Langmuir ______ __;__ Mar. 10, 1925
1,845,247 >
Davidson ________ __ Feb. -16, 1932
2,317,814
Schuchmann et a1. __ Apr. 27, 1943
2,370,703
Zaikowsky ________ __ Mar. .6, 1945
-
:
FOREIGN PATENTS
Number
30
201,321
Country
7
Date a
Germany '_; ______ __ Sept. 8, 1908
, 433,770
Great Britain __v____ Aug. 20, 19,35
’
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