U.S. patent number 3,736,937 [Application Number 05/260,873] was granted by the patent office on 1973-06-05 for cryogenic tool.
This patent grant is currently assigned to Hughes Aircraft Company. Invention is credited to Algerd Basiulis.
United States Patent |
3,736,937 |
Basiulis |
June 5, 1973 |
CRYOGENIC TOOL
Abstract
The external surface of the working tip of the cryogenic tool is
applicable to any point where cooling is desired, for example,
affected tissue in cryosurgery. An inner surface of the tip is
supplied with a cryogenic liquid thru a capillary active surface
from a reservoir. The boiled off cryogen vapor exits from the
cryogenic tool to atmosphere.
Inventors: |
Basiulis; Algerd (Redondo
Beach, CA) |
Assignee: |
Hughes Aircraft Company (Culver
City, CA)
|
Family
ID: |
22991007 |
Appl.
No.: |
05/260,873 |
Filed: |
June 8, 1972 |
Current U.S.
Class: |
606/23; 62/293;
606/116 |
Current CPC
Class: |
A61B
18/02 (20130101); A61B 2018/00095 (20130101); A61B
2218/002 (20130101); A61B 2090/0813 (20160201); F25B
19/005 (20130101) |
Current International
Class: |
A61B
18/00 (20060101); A61B 18/02 (20060101); A61B
19/00 (20060101); F25B 19/00 (20060101); A61b
017/36 (); F25d 003/00 (); A01k 011/00 () |
Field of
Search: |
;128/400,401,303.1
;119/1 ;62/293 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Medbery; Aldrich F.
Claims
What is claimed is:
1. A cryogenic tool comprising:
a reservoir for the storage of cryogenic liquid which boils at
sub-atmospheric temperatures, a lining of capillary active material
within said reservoir so that when some of said reservoir lining is
in contact with cryogenic liquid, the entire lining is wet with
cryogenic liquid;
a tubular duct extending from said reservoir, said duct having a
capillary active surface therein, and having a reservoir end and a
working end, said reservoir end of said tubular duct being open to
the atmosphere for discharge of cryogen vapor therefrom to the
atmosphere, a liquid cryogen opening between said reservoir and the
interior of said duct intermediate its end so that said lining of
capillary active material in said reservoir is in contact with the
active capillary surface in said duct and can feed liquid cryogen
through said opening into the interior of said duct to feed liquid
cryogen to the active capillary surface in said duct so that the
active capillary surface within said duct can feed liquid cryogen
toward the working end of said duct;
a working tip on the end of said duct and an evaporative surface
within said duct in thermal communication with said working tip,
said evaporative surface being fed with liquid cryogen from the
capillary active surface in said duct so that liquid cryogen is fed
to the evaporative surface whereby evaporative cooling takes place
and the cryogen vapor returns through said duct to the
atmosphere.
2. The cryogenic tool of claim 1 wherein a supplementary working
tip is positioned over said working tip, in thermal communication
therewith, so that the supplementary working tip can be removed and
interchanged.
3. The cryogenic tool of claim 1 wherein said working tip is
removable from the working end of said duct so that said working
tip can be removed and replaced.
4. The cryogenic tool of claim 3 wherein said working tip is
engaged upon said duct by screw thread engagement therebetween.
5. The cryogenic tool of claim 1 wherein said evaporative surface
in thermal communication with said working tip is substantially
conical surface with its point directed away from said working tip,
toward said duct.
6. The cryogenic tool of claim 5 wherein said capillary active
interior surface of said duct is in physical contact with said
evaporative surface.
7. The cryogenic tool of claim 6 wherein a vapor tube extends from
adjacent said working tip through said duct into said reservoir,
for the return of cryogen vapor to said reservoir.
8. The cryogenic tool of claim 7 wherein said evaporative cone has
a longitudinal groove in the surface thereof, and said vapor tube
is engaged over said evaporative cone, said groove preventing
sealing of said tube on said cone.
9. The cryogenic tool of claim 1 wherein said tip is an elongated
tube of larger diameter than said duct, said tube tip having a
substantial portion of its surface cooled by evaporation of cryogen
therein.
10. The cryogenic tool of claim 9 wherein the capillary active
material in said duct is in contact with capillary active material
lining said tube tip to deliver liquid cryogen for evaporation
within said tube tip.
11. The cryogenic tool of claim 10 wherein said tube tip has an
insulated nose thereon.
12. The cryogenic tool of claim 1 wherein said capillary active
material within said duct is a mass of stainless steel fibers
sintered together to form a felt-like mass.
13. The cryogenic tool of claim 1 wherein said capillary active
lining comprises a concentric annulus formed by a perforated tube
substantially concentrically positioned within said duct so that
there is a capillary space therebetween.
14. The cryogenic tool of claim 1 wherein said capillary active
surface within said duct comprises a crescent annulus formed
between a perforated tube non-concentrically positioned within said
duct and the interior of said duct.
15. The cryogenic tool of claim 1 wherein said capillary active
surface comprises a plurality of channels longitudinally directed
on the interior of said duct.
16. The cryogenic tool of claim 15 wherein a capillary active layer
is positioned within said duct interiorly of said channels.
17. The cryogenic tool of claim 1 wherein said capillary active
lining of said duct includes an artery in contact with the
capillary active surface.
18. The cryogenic tool of claim 1 wherein a heater is positioned
around said duct between said reservoir and said working tip so
that when heat is applied to said duct by said heater, liquid
cryogen flowing from said reservoir toward the working end of said
duct is evaporated before it reaches the working end of said duct
to stop cooling at the working end of said duct.
19. The cryogenic tool of claim 1 wherein a removable cap is
positionable over the end of said duct within said reservoir, so
that when said removable cap is away from said end of said duct,
vapor can escape from said duct into said reservoir and liquid
cryogen can flow through said feed opening toward said working end
of said duct, and when said cap is positioned over the end of said
duct within said reservoir, vapor pressure within said duct
prevents liquid cryogen from passing from said reservoir through
said feed opening to said duct, so that refrigeration at the
working end of said duct ceases.
20. The cryogenic tool of claim 1 wherein a trap vessel is
positioned to receive vapor from said reservoir and discharge it
toward the atmosphere, said trap vessel inhibiting the flow of
liquid cryogen to the atmosphere.
21. The cryogenic tool of claim 20 wherein said trap vessel
comprises a tube positioned within said reservoir, a vapor inlet to
said trap extending substantially half way into said trap tube, an
outlet tube from said trap reservoir extending from said trap tube
out of said reservoir.
22. The cryogenic tool of claim 1 wherein said reservoir has a
substantially truncated conical fill opening therein, a cap
detachably secured to said reservoir, a plug movably mounted with
respect to said cap engaging in said fill opening, removably close
said fill opening.
23. The cryogenic tool of claim 22 wherein said plug is resiliently
urged with respect to said cap into closure engagement within said
fill opening.
24. The cryogenic tool of claim 1 wherein a mass which is fluid at
room temperature and is solid at cryogenic temperature is
positioned on said working tip.
25. The cryogenic tool of claim 24 wherein said mass is enclosed in
a polymer composition material bag.
26. The cryogenic tool of claim 25 wherein a metallic boss engages
on said working tip and said bag engages around a portion of said
bag so that said boss is in thermal communication with said mass
and with said working tip.
Description
BACKGROUND OF THE INVENTION
This invention is directed to a cryogenic tool particularly useful
for cryosurgical techniques.
The structure presently commercially available for employment in
cryosurgical techniques comprises a large liquid cryogen reservoir,
in which liquid nitrogen is the preferred material. The liquid
cryogen is delivered under pressure thru a flexible hose to a hand
piece which has a cooled surface thereon at which film boiling
takes place. Flow is controlled by a valve at the reservoir, so
that liquid cryogen delivery for cooling the cooled surface has a
built-in delay, corresponding to the length of the structure
between the valve and the cooled surface. Thus, the prior art
structures are slow in cooling. Furthermore, liquid cryogen is
delivered for heat exchange, so that boiling from a pool of liquid
cryogen causes the cooling of the "surface". The bulk quantities of
the cryogen inhibit heat transfer because of the built up
insulative layer of vapor on the heat transfer surface. The hose
interconnecting the reservoir with the hand piece is necessarily
cumbersome, because of the needed insulation to prevent excess
cryogenic liquid boil-off.
Accordingly, the commercially available structures are slow in
response from the time the liquid cryogen valve is opened to the
time the cooled surface is at operating temperature. Furthermore,
it is difficult to maneuver the end piece with its cooled surface
because of the needed complexity of the cryogen liquid delivery
hose. The hose is limited in length and therefore the radius of
operation from the liquid cryogen reservoir is restricted. In view
of the heat transfer condition at the cooled tip, film boiling, the
cooled tip does not substantially reach the liquid cryogen boiling
temperature. The disadvantages can be overcome by providing
cryogenic tool which is sufficiently light and small to be
hand-held and employs liquid cryogen delivery and heat transfer
characteristics which permit the working tip to quickly reach a
temperature approaching that of the evaporating liquid cryogen.
SUMMARY OF THE INVENTION
To aid in the understanding of this invention, it can be stated in
an essentially summary form that it is directed to a cryogenic tool
which employs capillary delivery of liquid cryogen from the
interior of a reservoir to a surface in such quantities as to
permit film boiling on the surface.
Accordingly, it is an object of this invention to provide a
cryogenic tool which has a working tip which is supplied with
cryogenic liquid from a reservoir thru a capillary delivery means
so that the supply is controlled to prevent flooding so that
evaporative cooling occurs for cooling the working tip. It is
another object to provide a cryogenic tool which is hand-held, with
a probe carrying a working tip on the outer end thereof, and a
reservoir on the upper end. It is a further object to provide a
reservoir containing a capillary active surface which feeds liquid
cryogen to the probe in various reservoir positions. It is another
object to provide a reservoir for liquid which has capillary means
on the interior surface thereof so that the capillary means can
feed liquid cryogen thru the probe into the heat exchange
relationship with the working tip.
Other objects and advantages of this invention will become apparent
from the study of the following portions of this specification, the
claims, and the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal section thru the cryogenic tool of this
invention.
FIG. 2 shows an alternative replaceable tip positioned on the
permanent tip of the cryogenic tool of FIG. 1.
FIG. 2A shows another type of thermal applicator tip.
FIG. 2B shows a further type of thermal applicator tip.
FIG. 3 is a longitudinal section of the probe portion of another
species of the cryogenic tool showing a different tip attachment
means.
FIG. 4 is a longitudinal section thru the end of the probe of
another species of the cryogenic tool, showing a prostatic probe
termination.
FIG. 5 is a transverse section thru a species of the probe wherein
a fibrous mat is used for capillary flow.
FIG. 6 is a section through another species of the probe, wherein
concentric tubes are used for capillary flow.
FIG. 7 is a section through a further species of the probe wherein
a crescent annulus is used for capillary flow.
FIG. 8 is a section through another species of the probe wherein
longitudinal channel corrugations covered with screen are used for
capillary flow.
FIG. 9 is a section through a further species of the probe wherein
a stainless steel fibrous wicking with an artery is used for
capillary flow.
FIG. 10 is a longitudinal section through another species tip
wherein an electrical heater is used to stop cryogen liquid flow to
the working tip.
FIG. 11 is a longitudinal section through another species of
reservoir, wherein liquid cryogen flow is controlled by a valve cap
on the vent tube.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a generally central longitudinal section through
preferred embodiment of the cryogenic tool 10 of this invention.
The cryogenic tool 10 has a tubular duct 12 which serves as the
main cryogen conduit in the cryogenic tool. The upper open end 14
of the duct 12 may carry a cap 16 from which a vapor vent tube 18
extends. The upper open end 14 is positioned within a reservoir 20.
The reservoir has a lower wall 22 which is secured to tube 12. It
has an outer wall 24, which is conveniently cylindrical.
Furthermore, reservoir 20 has an upper wall 26 to which is secured
filler funnel 28.
Liquid feed openings 30 and 32 are orifices or perforations in
tubular duct 12 within reservoir 20, at the lower end adjacent
lower wall 22. The inside of outer wall 24, and the interior of
lower wall 22 are lined with capillary active material 34. This
material extends up over the exterior of tubular duct 12 to cover
feed openings 30 and 32 and extend through them to touch the lining
36 in duct 38. The capillary active lining 34 can be of suitable
nature for the liquid that it is intended to feed. In the specific
example, liquid nitrogen or other liquid cryogen is the liquid
which is to be fed, and therefore a lining of stainless steel
fibers deposited to form random mat and sintered together is a
suitable working material. As referred to in this specification,
stainless steel means those grades of stainless steel which are not
subject to embrittlement at cryogenic temperature. Rather than a
sintered mat of fibers, the capillary material 34 can be in the
form of one or more layers of woven metal screen, with the screen
preferably being of stainless steel material.
The interior of tubular duct 12 is also provided with a lining 36
of capillary active material. FIG. 5 is a section through preferred
embodiment of the capillary active material, and again, it is a
random deposited mass or mat of stainless steel fibers which are
sintered together to form a felt-like mass. It lines the entire
interior tubular duct 12.
FIG. 6 illustrates a tubular duct 38, which corresponds to tubular
duct 12, which contains a perforated inner tube 40 which is
concentrically arranged within duct 38, with a spacing of such size
as to produce the capillary liquid feed force for feeding the
liquid cryogen through tubular duct 38. Perforations are required
to permit the vapor of boiled-off liquid cryogen to pass into the
central space. The liquid cryogen passes through concentric
capillary space while the vapor passes through tube 40 and out
vapor vent tube 18.
FIG. 7 is a tubular duct 42, which corresponds to tubular duct 12,
and which has perforated inner tube 44 therein. Inner tube 44 is
positioned against one wall of the duct to define a crescent space
therebetween. The crescent space provides the capillary spacing
which provides capillary feed force for the liquid cryogen. Tube 40
is perforated to permit the return of cryogen vapor.
FIG. 8 is another embodiment of a suitable tubular duct for the
feeding of liquid cryogen, and the return of boiled-off cryogen
vapor. Tubular duct 46, which corresponds to duct 12, has
longitudinal grooved channels or interior corrugations 48 therein.
These channels extend from one end to the other of the duct, and
are of such size as to provide capillary force. While open channels
are considered to be satisfactory, a screen or mask of sintered
metallic fibers 50 is preferably to enhance liquid feed by
capillarity. Another configuration of a suitable tubular duct is
illustrated in FIG. 9, with tubular duct 52, which is equivalent to
duct 12. Duct 52 contains capillary feed means 54, which may be a
felt-like sintered mass of metallic fibers, or may be a woven
screen of one or several layers. In this case, the capillary feed
means 54 is provided with an artery 56, which reduces the pressure
drop in the capillary feed. Any one of these tubular ducts can be
employed to supply liquid cryogen from the reservoir 20 to the
closed lower end thereof. The capillary lining 34 is in
communication through liquid feed openings 30 and 32 with the
capillary lining 36 interiorly of the tubular duct. Therefore,
liquid from anywhere in reservoir 20 is fed to the interior of the
duct. The upper end of the duct is closed by cap 16 to prevent
liquid escape from the upper end thereof back to the reservoir.
However, vapor vent tube 18 permits the escape of vapor from the
interior channel of the tubular duct back into the reservoir.
The exterior of reservoir 20 and exterior of most of the length of
tubular duct 12 are prevented from substantial heat leak by dewar
envelope 58. The envelope extends around and is spaced from the
reservoir, and extends around and is spaced from tube 12. As seen
in FIG. 1, the lower end of tube 12 is enclosed by the tube 60,
which forms the portion of dewar envelope 58 extending down around
tube 12. The lower end of tubes 12 and 60 are joined by conical
transition pieces 62 and 64 and tube 66, which prevent the coolest
part of the transition between duct 12 and tube 60 from being
engageable with hand, so that the entire tube 60 can be comfortably
and manually engaged.
The upper end of dewar envelope 58 joins with filler funnel 28 and
has threads 68 on the exterior thereof for the removable attachment
of cap 70. Cap 70 engages upon threads 68 and has an annular recess
72 which is open facing the upper shoulder 74 of dewar envelope 58.
Annular recess 72 is vented through vent holes 76.
Cap 70 carries truncated closure plug 76. Spring 78 urges plug 76
to the left, while cap screw 80 prevents plug 76 from moving
totally free of the cap. Thus, plug 76 can rotate with respect to
the cap, and is spring thrust into filler funnel 28 to close the
filler funnel. The main body of cap 70, plug 76 and cap screw 80
are preferably made of low thermal conductive material which is
capable of withstanding cryogenic temperature. Polymer composition
materials which fall into this category include nylon and
teflon.
Liquid cryogen trap 82 is in the form of a closed end tube secured
on the inside of reservoir 20, preferably against the outer wall
thereof. It is connected by means of vapor outlet tube 84 through
upper shoulder 74 into annular recess 72 in the cap. Inlet from
reservoir 20 to trap 82 is by means of vapor inlet tube 86 which is
open from the upper end of trap 82 to approximately the center of
the trap. Thus, cryogen vapor coming from the upper end of tubular
duct 12 passes out through vapor vent tube 18, through trap 82 and
is vented to atmosphere vent through cap 70. Trap 82 is configured
so that if the cryogenic tool 10 is turned with cap 70 down, liquid
cryogen will not be immediately expelled.
Liquid cryogen in reservoir 20 is fed from the reservoir into
tubular duct 12 through the continuous active capillary lining
material to the tip end of the duct. This feed is gravity
independent. At the tip end, tip 88 is secured to the duct 12, and
the lining 36 extends into recess 90 in the tip so that it is in
direct engagement with the material of the tip. The material of tip
88 is preferably of high thermal conductivity, and it is not
embrittled at cryogenic temperatures. Copper is suitable material.
Liquid cryogen is thus delivered by capillary action to the base of
recess 90 directly beneath the working end 92 of the tip. The
working end 92 is illustrated in FIGS. 1 and 2 as a pointed end.
With a flat bottom in the recess 90, evaporative cooling will occur
without flooding, which would cause film boiling, because of the
controlled flow of liquid cryogen through capillary lining.
However, in order to enhance heat transfer, the area over which
evaporative cooling is accomplished is enlarged by providing
inwardly directed point 94, of high thermal conductivity material
which is in thermally conductive relationship with the main body 88
of the tip. Thus, liquid cryogen is delivered to the surface of the
inwardly directed point and evaporates therefrom. The resulting
cryogen vapor is delivered up the hollow interior of tubular duct
12.
It is convenient to confine returning cryogen by installing a vapor
duct 96 interiorly of capillary lining, with a space between the
capillary lining and vapor duct, as illustrated in FIGS. 1 and 5.
The vapor duct 96 terminates adjacent vapor vent tube 18 so that
the cryogenic vapor both within and without vapor duct 96 can exit
from vapor vent tube 18. In order to prevent vapor duct 19 from
sealing on the inwardly directed point 94, the point 94 carries
vapor channels 98 cut into the sides thereof.
FIG. 2 illustrates the installation of an interchangeable and
replaceable tip 100 directly over the exterior of the permanently
installed tip 88. Replaceable tip 100 is of high thermal
conductivity, preferably of a sterilizable material and has a
suitable working face 102. As an example, FIG. 2 shows a large area
face such as is suitable for dermatological techniques.
FIG. 2A shows a tip 140 which is formed as a flexible plastic bag
142 containing a freezable solution 144. The solution can be water
or jelly, containing metal particles to enhance thermal
conductivity. The bag is shaped to the proper surface contour, then
frozen and used as a cryogenic applicator tip.
FIG. 2B is similar and shows a tip 146 which is a similar solution
molded to shape, then frozen and used for cryogenic surface
application. Both of these tips can be used with tip 88, as
shown.
FIG. 3 illustrates a tip 104 replaceably screw threaded onto the
lower end of tubular duct 106. The tip and duct are respectively
the same as tip 88 and duct 12, except for the screw thread
interengagement therebetween which permits the removal and
replacement of tip 104. The interengaging structure between the tip
and duct are such that the tip is guided onto the lining of active
capillary material so that the material is in direct contact with
the interior of replaceable tip 104.
FIG. 4 illustrates a prostatic tip 108 which is formed as a tube
110 having a lining of capillary active material 112. Tubular duct
114 is the same as duct 12, and is supplied with a liquid cryogen
from a reservoir. Duct 114 is surrounded by insulation layer, such
as an evacuated dewar, or a vacuum space filled with multiple foil
super insulation, or the like. Tube 110 is formed as an expanded
part of the duct 114, and there is continuity between the capillary
lining material of the duct and the capillary lining 112. Thus,
liquid cryogen is supplied to the inside wall of tube 110, and
evaporates therefrom to fill the interior space 118 of tip 108 with
boiled-off cryogen vapor. Vapor tube 120, preferably perforated in
the interior space 118, extends up the tubular duct to discharge
the vapor to the reservoir as previously described. The lower end
of prostatic tip 108 has an insulated tip 122 which can be supplied
with heat from any convenient source, such as from the outer tube
forming the exterior of insulation 116. By this means, there is
evaporative cooling of the interior surface of tube 110 to permit
it to be used in prostatic cryosurgery.
In cryosurgery it is desirable to effectively cease refrigeration
when desired to stop the cryogenic cooling action at the point of
application. This can be accomplished either by stopping the inflow
of liquid cryogen or by boiling off liquid cryogen before it
reaches the tip. FIG. 10 illustrates an electric heater coil 124 on
a tubular duct similar to duct 12, between the insulator housing on
the duct and the tip secured on the end thereof. Upon the
application of electric current to the heater, electrically derived
heat is directly applied to the duct, so that the liquid cryogen is
evaporated in that portion of capillary active material directly
therein. None of it reaches the tip. By this means, refrigeration
ceases at the tip. The electric heater coil 124 can be controlled
at any convenient point.
FIG. 11 illustrates a duct 126, the same as duct 12, at its upper
end within reservoir 20. Cap 128 is similar to cap 70 as to its
structure and positioning. It carries a slide rod 130 therethrough
which carries a cap 132 on its inner end. By manually depressing
the slide rod through cap 128, cap 132 engages over the outer end
duct 126, thereby closing off the vapor exit therefrom. Vapor
pressure builds up to block inflow of liquid cryogen into the duct
126, through its liquid feed openings corresponding to feed
openings 30 and 32. With no more liquid feed, evaporation at the
tip ceases, to stop refrigeration
The particular cryogen used is dependent upon several factors.
Liquid nitrogen is inert and is conveniently and inexpensively
available. It evaporates at a sufficiently low temperature to
provide for proper cryosurgery. The evaporative cooling technique
achieved by feeding the liquid cryogen by capillary action to the
evaporative surface permits the inner surface of the tip upon which
the evaporation is taking place to reach temperatures within about
1.degree. C of the evaporating cryogen temperature. Thus, low
temperatures are achieved. Liquid argon is also a suitable liquid
cryogen, but is expensive. Liquid oxygen is less expensive than
liquid argon, but has the disadvantage of combustion danger. Freon
type compounds are relatively expensive, and if economic loss was
not objectable, and the temperature provided by one of the freons
was required, it could be employed.
This invention having been described in its preferred embodiment,
and several additional embodiments also described, it is clear that
this invention is susceptible to numerous modifications and
embodiments within the ability of those skilled in the art. Thus,
the scope of the invention is defined by the scope of the following
claims.
* * * * *