U.S. patent number 3,913,581 [Application Number 05/366,004] was granted by the patent office on 1975-10-21 for cryogenic apparatus.
This patent grant is currently assigned to Spembly Limited. Invention is credited to Carl Ritson, Ernest Hilton Thomas.
United States Patent |
3,913,581 |
Ritson , et al. |
October 21, 1975 |
Cryogenic apparatus
Abstract
The invention relates to cryosurgical instruments in which gas
cooling by Joule-Thomson expansion is employed in an applicator
adapted to contact and thermally cool human tissue, the gas in the
cooling mode being carried to an orifice, for expansion
therethrough, by a first duct and led away to atmosphere after
expansion by a second duct. The invention resides in apparatus and
a method of obtaining rapid warming of the applicator by providing
valve means for connecting the second duct directly to a source of
high pressure refrigerant gas so that gas condenses within the
applicator upon any cold surface thereof.
Inventors: |
Ritson; Carl (Upavon,
EN), Thomas; Ernest Hilton (Kingston, Near
Marlborough, EN) |
Assignee: |
Spembly Limited
(EN)
|
Family
ID: |
10235329 |
Appl.
No.: |
05/366,004 |
Filed: |
June 1, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Jun 2, 1972 [GB] |
|
|
25910/72 |
|
Current U.S.
Class: |
606/23;
62/293 |
Current CPC
Class: |
A61B
18/02 (20130101); F25B 9/02 (20130101); F25D
3/10 (20130101); A61B 2018/00041 (20130101) |
Current International
Class: |
A61B
18/02 (20060101); A61B 18/00 (20060101); F25B
9/02 (20060101); F25D 3/10 (20060101); A61B
017/36 (); F25D 003/08 (); F25D 003/10 () |
Field of
Search: |
;62/293,514
;128/303.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pace; Channing L.
Attorney, Agent or Firm: Shapiro and Shapiro
Claims
We claim:
1. A cryosurgical instrument for use with a remote source of
pressurized gas and adapted to operate in a cooling mode and in a
rapid warming mode, comprising:
a body enclosing a caviyty having a wall of high thermal
conductance, said wall being shaped externally for contacting human
tissue and providing heat transfer with the tissue and being of
sufficient structural integrity to withstand the full source
pressure;
a first conduit extending through said body and connected to said
cavity terminating therein in a restricted orifice through which
pressurized gas may expand into said cavity experiencing
Joule-Thompson cooling in so doing and thereby cool said wall when
said first conduit is connected to said source of gas;
a second conduit connected to said cavity;
an exhaust passage leading to atmosphere; and
valve means for providing a cooling mode gas-flow path from said
source of pressurized gas, through said first conduit and said
orifice, into said cavity, and then through said exhaust passage,
whereby the expansion of as through said orifice cools said wall,
and for selectively providing a heating mode gas-flow path from
said source of pressurized gas, through said second conduit, and
directly to said cavity for pressurizing said cavity sufficiently
to condense said gas on the cooled wall and liberate latent heat to
warm the wall.
2. A cryosurgical instrument according to claim 1 in which said
valve means are remote from said body and comprise;
a two-position valve which in a second position provides connection
for the warming mode and in a first position provides connection
for the cooling mode;
means which prevent flow through sad first conduit in the warming
mode.
3. A cryosurgical instrument according to claim 2 in which said
means for preventing flow in said first conduit is said
two-position valve.
4. A cryosurgical instrument according to claim 2 in which said
means for preventing flow in said first conduit is a non-return
valve.
5. A cryosurgical instrument according to claim 2 in which said
valve is biased towards said second position.
6. A cryosurgical instrument according to claim 1 in which said
valve means comprise a pressure operated two-position valve
situated in said body.
7. A cryosurgical instrument according to claim 1 in which said
valve means comprise a three-position valve which, in a first
position, provides connection for the cooling mode, in a second
position provides connection for the warming mode and in a third
position isolates said source of pressurised gas.
8. A cryosurgical instrument according to claim 7 in which said
three position valve, when in said third position, also connects at
least the first conduit of said first and second conduits to said
exhaust passage.
9. A cryosurgical instrument according to claim 8 in which said
three-position valve when in said second position connects said
first conduit to said exhaust passage.
10. A cryosurgical instrument according to claim 7 in which said
three position valve passes through said second position at least
when changing from the first to the third position.
11. A cryosurgical instrument according to claim 10 in which delay
means are provided which temporarily maintain said three-position
valve in said second position when it is urged from said first
position towards said third position.
12. A cryosurgical instrument according to claim 11 in which said
delay means comprise; a pressure operated detent including a bleed
orifice through which any gas pressure in said detent may leak away
when said detent is fluidly isolated; in which cryosurgical
instrument said three-position valve is adapted to (a) operate said
detent by connecting it to said source only when in said first
position; and (b) to be maintained in said second position by said
operated detent, when changing from said first to said third
position, for a period determined by the rate of bleed of gas from
said detent when fluidly isolated; means which fluidly isolate said
detent from said source when said three-position valve is in said
second position.
13. A cryosurgical instrument according to claim 12 in which said
detent isolation means is a non-return valve connecting said detent
to said first conduit and said three-position valve when in its
second position connects said first conduit to said exhaust
passage.
14. A cryosurgical instrument according to claim 1 in which said
restricted orifice includes a non-return valve such that, in the
cooling mode, gas flow is restricted but that gas flow is
relatively unrestricted in the reverse sense of flow.
15. A cryosurgical instrument according to claim 14 in which said
first conduit terminates in a portion of reduced diameter and in
which said non-return valve comprises a free ball of smaller
diameter than that of the first conduit bore but greater than that
portion of reduced diameter and which seats on the reduced portion
under the action of pressure within said first conduit, and is
released upon reversal of pressure; in which said restricted
orifice is formed in the wall of said reduced portion.
16. A method of cooling and then warming the highly thermally
conductive wall of an expension chamber in a cryosurgical
instrument, the external surface of the wall providing the
applicator surface of the instrument, the method comprising:
introducing a pressurized gaseous refrigerant from a source thereof
into said chamber through flow-restricting means while connecting
said chamber to a region of pressure lower than the pressure of
said source, thereby cooling said wall and said applicator surface
by the Joule-Thomson effect; and then
pressurizing said chamber from said source of pressurized gaseous
refrigerant through a flow path separate from said flow-restricting
means so that said refrigerant condenses on said wall and liberates
latent heat thereto, thereby warming said wall and said applicator
surface.
17. A method as described in claim 16 wherein the gaseous
refrigerant is carbon dioxide.
18. A method as described in claim 16 wherein the gaseous
refrigerant gas is nitrous oxide.
19. A method as set forth in claim 16, wherein said introducing is
effected through a conduit having said flow-restricting means
therein.
20. A method as set forth in claim 19, wherein said conduit is
blocked during said warming.
21. A method as set forth in claim 19, wherein said conduit is
connected to said source during said warming.
22. A method as set forth in claim 19, wherein said conduit is
connected to atmosphere during said warming.
23. A cryosurgical instrument according to claim 1, in which said
body is a hollow cylindrical body having said first conduit
extending therethrough from one end of the body and into said
cavity at the opposite end, said second conduit and said exhaust
passage being connected to said body at said one end, said valve
means comprising a valve member slidably mounted in said body at
said one end of said body and having means for connecting said
second conduit and said exhaust passage to said cavity alternately
in response to gas pressure in said second conduit, said valve
means further comprising a control valve for selectively connecting
said second conduit to said source or to atmosphere.
Description
This invention relates to cryogenic apparatus and in particular to
cryosurgical instruments of the type in which pressurised
refrigerant gas, such as nitrous oxide for example, is expanded
through an orifice to thereby produce a cooling effect by
Joule-Thomson expansion, the cooled gas impinging upon the internal
surfaces of a hollow working tip, applicator or probe whereby
animal tissue in contact therewith may be frozen. Such instruments
are described in U.S. Pat. No. 3,502,081 which also shows
electrical heaters associated with the probes for the purpose of
rapidly heating a working tip so that it may be readily detached
from frozen tissue when so desired.
Such instruments have an exhaust passage leading from the hollow
working tip to atmosphere whereby the refrigerant after expansion
is ducted away, and may use the bottled refrigerant in the liquid
phase, drawing-off the refrigerant as a gas from above the liquid
surface.
Non-electrical methods have been proposed for reheating the working
tips of similar instruments, which methods do not suffer from the
need to regulate the heating, or to monitor the tip temperature
when so doing, as with electrical methods. Such a non-electrical
method is disclosed in U.S. Pat. No. 3,696,813 and involves
restricting or completely closing the exhaust passage so that
refrigerant fluid, still flowing through the orifice, raises the
pressure within the working tip to that, or nearly so, of the
refrigerant source. In the case of a Joule-Thomson, gas-cooled
instrument, as the pressure of gas rises within the working tip,
gas begins to condense on the cold surfaces, the latent heat of
condensation serving to warm the surfaces and bring about a rapid
"defrost" as it is generally known.
Although the method described may be satisfactory in small
instruments, it is believed that the rate of warming can be
accelerated in larger instruments by by-passing the orifice and
pressurising the interior of a working tip directly from the source
of refrigerant thus avoiding delays due to exponential rates of
pressure rise arising from the restriction to flow of an
orifice.
The rate of pressure rise in a working tip is also affected by the
size of the isolated volume and the size of orifice (which however
is normally fixed to produce the required cooling power). It is
believed that U.S. Pat. No. 3,696,813 seeks to minimise the
restricted or isolated volume by providing a manually operated
valve within the normally hand-held instrument so that the surgeon
may initiate cooling and reheating of the working tip by
respectively depressing and releasing the valve with his finger/s.
In view of the high refrigerant pressures employed, for example 700
p.s.i. in the case of nitrous oxide, such a valve requires either a
large force, or an exaggerated finger movement if levers are
employed to reduce the force for operation thereof, and which may
make precise movements or manipulations of the instrument difficult
during surgery. By removing the valve and placing it remote from
the instrument, although permitting the surgeon greater sensitivity
of operation, the isolated volume in the warming mode would be
greatly increased resulting in slower defrost.
It is therefore an aim of the invention to provide a method for
initiating a cooling mode and for causing the cooled working tip of
a cryosurgical instrument to rapidly rewarm sufficiently for
detachment from tissue frozen theret, i.e., a warming mode, in
which the rate of warming is independent of any isolated volume;
and it is also an aim to provide apparatus in which such cooling
and rewarming is achieved by valve or other control means which may
be either within or separate from the instrument.
Accordingly the invention provides a cryosurgical instrument for
use with a remote source of pressurised gas and adapted to operate
in a cooling mode and in a rapid warming mode, comprising:
a body enclosing a cavity having a wall of high thermal
conductance, said wall being shaped externally for contacting human
tissue and being of sufficient structural integrity to withstand
the full source pressure and providing heat transfer with the
tissue;
a first conduit extending through said body and connected to said
cavity terminating therein in a restricted orifice through which
pressurised gas may expand into said cavity, experiencing
Joule-Thomson cooling in so doing, and thereby cool said wall when
said first conduit is connected to said source of gas;
a second conduit connected to said cavity; cross-over valve means
to which connects said first and second conduits, said source of
pressurised gas and an exhaust passage leading to atmosphere, which
valve means, in the cooling mode connect said source to said first
conduit and connect said second conduit to said exhaust passage,
and in the warming mode connect said source to said second
conduit;
all such that, in the cooling mode, pressurised gas from said
source expands through said orifice and into said cavity wherefrom
it is ducted to atmosphere via said second conduit and said exhaust
passage and, that in the warming mode, gas from said source is fed
via said second conduit directly into said cavity wherein, if the
wall is cold it condenses thereupon, thus liberating latent heat
and warming said wall in consequence.
The valve means may conveniently comprise a two position valve,
either within or remote from said body, which in a second position
provides connection for the warming mode and in a first position
provides connection for a cooling mode. Such a valve may be biased,
by a spring for example, towards said second position, and may be
adapted for foot, hand or pressure control.
When such a two-position valve is used it is preferable to include
means, such as for example a non-return valve in series with said
first conduit, in order to prevent continuous reversal of flow when
in the warming mode. The valve itself, when in its second position,
may be adapted to close said first conduit, or the conduit may be
permitted to remain connected to said source since no flow will
occur when the pressure in said first and second conduits is
equal.
In order to isolate the source of gas and/or to vent said first and
second conduits when the instrument is not in use, the valve means
may comprise a three-position valve having the same first and
second positions as the aforementioned two-position valve but
having a third position whereat the source is isolated and, if so
desired, at least the first conduit of said first and second
conduits may be connected to said exhaust passage.
If the valve is adapted to pass through the second position when
changing from the first to third positions, and vice versa and is
biased normally towards said third position, the instrument may
then be operated by a single movement, automatically passing
through the warming mode in each direction of valve movement.
Should the time of transit through the second position be
insufficient for thorough warming to take place, the invention
provides for delay means which temporarily maintain the valve in
its second position when changing from first to third positions.
Such delay means in its simplest form may comprise a dashpot
operatively connected to the movable member of the valve, or may,
in a preferred form, comprise a pressure operated detent which
includes a bleed orifice through which any gas pressure in the
detent may leak away when the detent is fluidly isolated. The
detent may be operated by said three-position valve which may be
adapted to connect the detent to said source of gas only when in
said first position, and means may be provided to fluidly isolate
the detent when the valve is in said second position, the valve,
when changing from first to third positions, being maintained in
its second position by said detent for a period determined by the
rate of bleed of gas from the now fluidly isolated detent. The
detent isolation means may comprise a non-return valve, or be part
of said three-position valve. The three-position valve may be
adapted for hand, foot or pressure operation.
When a three-position valve is used, said first conduit when a
warming mode is selected, may be either closed, open to atmosphere
and shut off from the source, or remain connected to said source.
If open to atmosphere, reverse flow through said restricted orifice
being only for such time that the valve is maintained in its second
position. It is therefore within the scope of the invention to
connect said first conduit to atmosphere by said three-position
valve when in its second position particularly when delay means are
incorporated which ensure such connection holds for only a brief
period. Such momentary reversal of gas flow is advantageous in that
contaminants may be flushed out of said first conduit.
It has been found in practice that when cryosurgical instruments
according to the invention are used in the cooling mode for
excessively long periods, such as for example when freezing a large
volume of human tissue, the second conduit, and even the valve
means when remote, are cooled by the effluent gas to such an extent
that they fill or partially fill with condensed liquid when
pressurised in the warming mode. With a three-position valve which
when in the third position, vents the second conduit, such liquid
is expelled. However, by including a pressure operated shuttle
valve within said instrument body, cold effluent may be vented to
atmosphere directly from said body thus minimising the regions
which may be cooled by such gas flow.
Accordingly the invention provides a cryosurgical instrument for
use with a remote source of pressurised gas and adapted to operate
in a cooling mode and in a rapid warming mode, comprising:
a body defining a chamber and enclosing a cavity having a wall of
high thermal conductance, said wall being shaped externally for
contacting human tissue and providing heat transfer with the tissue
and being of sufficient structural integrity to withstand the full
source pressure, a wall of which chamber is provided with an
exhaust passage leading to atmosphere adjacent a first end
thereof;
a first conduit connecting with said remote source of pressurised
gas, extending through said body and into said cavity terminating
therein in a restricted orifice through which gas from said source
may expand into said cavity and thereby cool said wall;
a second conduit leading from said cavity into said first end of
said chamber;
a valve member slidably mounted in said chamber movable therein
under the action of pressure and having an axially aligned fluid
passage therethrough, said exhaust passage being closeable by said
valve member;
a control valve connected to said source and a third conduit
leading from said control valve to a second end of said
chamber;
all such that; when the control valve is operated for the cooling
mode, said third conduit is connected by said valve to atmosphere
so that gas entering and expanding in said cavity is ducted to said
first end of said chamber thrusting said valve member towards said
chamber second end thus opening said exhaust passage and permitting
said expanded gas to escape to atmosphere therethrough; when the
control valve is released for the warming mode, said third conduit
is connected to said source so that said valve member is thrust
towards said chamber first end thus closing said exhaust passage
and ducting high pressure gas from said third conduit through said
fluid passage and into said cavity, via said second passage,
wherein said gas will condense upon the wall, if this be cold,
giving up latent heat in so doing.
The control valve may be adapted for hand, foot or pressure
operation.
With the possible exception of the aspect of the invention in which
reverse flow is permitted in the warming mode, it is also
advantageous to provide a non-return valve in said restricted
orifice being such that, in the cooling mode gas flow is restricted
and that, in the reverse sense of flow, gas flow is relatively
unrestricted. Such an arrangement permits said first conduit to be
flushed if so desired and therefore constitutes a facility for
unblocking a blocked restricted orifice.
The invention contemplates a method for controlling the cooling and
subsequent reheating of the working tip of a cryosurgical
instrument of the type described in which an exhaust passage leads
normally to atmosphere from the interior of the working tip, which
method involves connecting by valve means the exhaust passage to
atmosphere during a cooling operation, and directly to a source of
gaseous refrigerant during a reheating operation. The refrigerant
leading to the orifice in operation, may be permanently connected
to its source, since all flow through that orifice will cease as
the pressure difference thereacross equalises. However, it is
within the scope of the invention to interrupt the supply of
refrigerant to the orifice during a warming mode, and even to
connect the supply side of the thus isolated orifice briefly to
atmosphere so that a modicum of reverse flow occurs therethrough,
thus clearing the supply passages of liquid refrigerant which may
condense therein, or of contaminants.
The invention will now be exemplified with reference to the
accompanying drawings which are as follows:
FIG. 1 illustrates a simple cryosurgical probe or applicator having
the general features referred to in the invention;
FIGS. 2 and 3 show, in sectional elevation and end view
respectively, a restricted orifice fitted with a ball valve;
FIGS. 4 and 5 are schematic diagrams of cryosurgical instruments
which incorporate remote, two-position control valves and such an
applicator as illustrated in FIG. 1;
FIG. 6 is a schematic diagram of a cryosurgical instrument having a
remote, three-position, control valve and an applicator such as
illustrated in FIG. 1.
FIG. 7 shows schematically a cryosurgical instrument, of the type
illustrated in FIG. 6, in which a pneumatic delay is provided;
FIGS. 8, 8A and 8B illustrate respectively the three-control
positions of an instrument similar to the kind depicted in FIG.
6;
FIG. 9 shows in section a cryosurgical applicator, in the body of
which is provided a two-position, pressure operated, shuttle valve;
and
FIG. 10 is a schematic diagram of an instrument which incorporates
an applicator such as illustrated in FIG. 9.
Referring to FIG. 1, the cryosurgical applicator illustrated
comprises a hollow, cylindrical body 1 of stainless steel, closed
at one end and having a bore 1H recessed at 1A, into which recess
is brazed end 2B of a thin-walled stainless steel tube 2. The other
end 2A of tube 2 is closed to define a cavity and constitutes the
working tip of the applicator, the external surface of end 2A
being, in operation, applied to human tissue in order to extract
heat therefrom. The wall of end 2A is thin so that the thermal
conductance thereof is high but is sufficient structural integrity
to withstand the full source pressure.
A first conduit 3 extends co-axially and sealedly through the wall
of the closed end of body 1, extending through bore 1H and tube 2
wherein it terminates in an orifice 3A such that any gas issuing
from orifice 3A is directed towards the internal surface of the end
2A. The orifice 3A is restricted in the sense that its
cross-sectional area is smaller than that of the bore of conduit 3
leading up to the orifice.
End 3B of conduit 3 is adapted to receive a flexible hose 4 through
which a high pressure gaseous refrigerant is, in the cooling
operation, ducted to the applicator. Such a refrigerant may, for
example, be a polyatomic gas such as carbon dioxide or nitrous
oxide and which has an inversion temperature above normal room
temperature, normally stored in bottles as a liquid at high
pressure (around 700 p.s.i.).
A second conduit 7 also leads sealedly through the wall of the
closed end of body 1, opening within a recess 1J of bore 1H. The
outer end 7A of the second conduit 7 is adapted to receive a
flexible hose 8 through which, in operation, gases expanded from
orifice 3A into tube 2 are exhausted away to a region of low
pressure, such as the atmosphere.
Body 1 is threaded externally to engagedly receive a thermally
insulative handle 9, suitably threaded internally at 9B for this
purpose.
The schematic diagram in FIG. 4 shows how such an applicator 16 may
be connected to a control valve VI and thereby to a source of
gaseous refrigerant 12, the combination of applicator, valve and
source constituting a practical embodiment of the invention.
The control valve VI is a two-position, foot-operated, two-way,
cross-over valve, shown in FIG. 4 in the defrost or warming mode
position. When the valve VI is depressed, gaseous refrigerant from
gas bottle 12 is ducted to the applicator 16 via isolation valve
14, duct 13, flexible hose 4 and non-return valve 4A, leaving the
applicator via hose 8 and escaping to atmosphere via valve port
15.
High pressure gas expands through orifice 3A, cooling as it does so
as a result of the Joule-Thomson effect, thus cooling application
surface 2A, the expanded gas being led away by hose 8 as described
above.
When the valve VI is released, refrigerant gas from gas bottle 12
is ducted into hose 8 thus immediately pressurising the bore of
tube 2 of the applicator so that gas condenses on the cold inner
surfaces thereof, thus liberating latent heat and rapidly rewarming
the surfaces including application surface 2A. The non-return valve
4A, in this particular embodiment, prevents a reversal of gas
flow.
It is to be noted that in this last-described case, while there is
reversal of the sense of direction of the pressurized gas supply,
there is reversal of gas flow only to the extent required to charge
the cavity and connected spaces with the pressurized gas. The valve
provisions may be such that, as in the case where there is a valve
4A, there is no continuous reverse flow in the warming mode; or it
may be such that the valve port 15 is so restricted that virtually
the whole of the source pressure is applied within the cavity and
connected spaces, there being only a very reduced continuous flow.
The device of FIGS. 2 and 3 (described in full below) may be used
in either case.
The system illustrated in FIG. 5 is similar to that of FIG. 4, but
has a different control valve, now V2, which achieves the same
result as follows:
In the warming mode position as illustrated, hoses 8, 4 and gas
bottle 12 are all connected together so that, when the pressures in
hoses 4 and 8 have equalised, no reverse flow can occur. When the
valve V2 is depressed, the applicator 16 is connected as
before.
A three-position valve V3 is used in the instrument of FIG. 6, and
is shown in its intermediate position corresponding to the warming
mode, but is naturally biased towards the "OFF" position whereat
gas bottle 12 is isolated. When valve V3 is fully depressed, and as
illustrated it is foot operated, applicator 16 receives high
pressure gas as described before, via duct 13, isolation valve 14
which may now comprise the gas bottle valve and be normally left
open, and duct 4. Hose 8 is connected to atmosphere via valve port
15.
As valve V3 is released, it passes through the intermediate
position illustrated, and if necessary may be momentarily checked
in this position by the operator, whereat hose 4 is isolated and
hose 8 connected to bottle 12. When valve V3 reaches its final, or
"OFF" position, bottle 12 is isolated and applicator 16 vented of
high pressure through valve-port 15.
In order to ensure that valve V3 dwells in the intermediate
position long enough for adequate warming of the application
surface 2A, means may be provided for detaining the valve in the
intermediate position when it is released. Such an arrangement is
shown in FIG. 7 in which the control valve V4, a foot-operated,
three-position valve, normally biased towards the "OFF" position,
is illustrated in the intermediate position. The plunger 19 by
which the valve is operated, is provided with a collar 20 which
acts as a stop in co-operation with a pneumatically operated detent
18, such that when bellows 17 are inflated by high pressure gas,
detent 18 is thrust into the path of the collar 20.
Valve V4 has ports and associated passages such that: it behaves as
valve V3 of FIG. 6 as regards controlling applicator 16; in the
intermediate position, duct 22, which connects bellows 17 to the
valve, is closed; in the first or operating position, bellows 17 is
connected to the gas bottle 12. The bellow 17 is also provided with
a bleed valve 21, through which gas is bled from the bellows at a
rate determined by the valve 21 setting.
When valve V4 is fully depressed, applicator 16 is put into the
cooling mode and bellows 17 are pressurised thus extending detent
18 into the path of collar 20 which is now below and spaced from
the detent 18. Upon releasing the valve V4, it moves into the
intermediate position whereat it is held by detent 18. In this
position, the applicator 16 is put into the warming mode, and the
pressure in the now isolated bellows 17 falls at a rate determined
by the now setting of bleed valve 21, until the detent 18 moves
clear of collar 20 and permits the valve to move to the "OFF"
position whereat both applicator and bellows are vented to
atmosphere. By adjusting bleed valve 21, the length of the warming
mode period may be varied.
FIGS. 8, 8A and 8B depict schematically a variation of the
instrument of FIG. 7 in which the control valve is so modified that
the valve may be changed directly from the "OFF" to the first, or
operational position, without passing through the intermediate
position, but does pass through temporarily and is held in the
intermediate position when changing in the reverse sense.
Applicator 16 is connected to control valve assembly generally
indicated as V5, hose 4 connecting with two-position valve V5A and
hose 8 connecting with another two position valve V5B which has a
ported body 31 moveable axially relative to the fixed body of valve
V5A, the valve member 32 of V5B being connected by rod 33 to member
30 of V5A.
A lever 35, pivotally mounted at 37, extends through a slot 34 in
rod 33 such that when button 35A on the lever is pressed, i.e., the
lever is urged in a clockwise direction, valve members 30 and 32
are moved to the left against the action of the valve biasing
spring 36. Valve body 31 may be moved axially against the action of
compression springs 43 by means of a bellows 38 which, when
pressurised, extends and thrusts upon end 31B of the valve body 31.
The bellows fluidly connect with hose 4 via a spring loaded
non-return valve, and a bleed valve 39 permits any pressurised gas
within the bellows 38 to gradually bleed to atmosphere.
A gas-bottle 12 is connected to valve V5A via duct 13 and to
valve-body 31 of valve V5B via a duct 13A which has sufficient
flexibility to permit movement of body 31, likewise hose 8 is
sufficiently flexible.
FIG. 8 illustrates the "OFF" position and FIG. 8A the operational
position. Referring then to FIG. 8A, when button 35A is depressed,
V5A takes up the position shown in which duct 13 connects with hose
4, V5B remains unchanged, the valve body 31 not having moved
relative to member 32 which engaged with end stops 31A, both member
32 and body 31 having moved to the left. Hose 8, in this position
of valve V5B, is connected to atmosphere via port 15. As hose 4
received gas from bottle 12, the pressure therein was communicated
via duct 41 of non-return valve 40 to bellows 38 which extended
leftwards to engage with end 31B of body 31, thus preventing return
of the body to its original position, whilst not impeding any
subsequent rightwards movement of member 32. When button 35A is
released, members 30 and 32 move to the right under the action of
spring 36, body 31 remaining held to the left by bellows 38, and
FIG. 8B illustrates this, the warming mode position. Hose 4 is now
vented to atmosphere via valve V5A and port 42, hose 8 is connected
by valve V5B to gas bottle 12 via duct 13A, so that rapid warming
of the applicator 16 occurs. Some reverse flow results through
orifice 3A of the applicator, but as the warming period is short,
this flow is unimportant. Because hose 4 is vented to atmosphere,
non-return valve 40 isolates bellows 38 which, after a
pre-determined period of time (according to the adjustment of bleed
valve 39) retract, permitting body 31 to move to its original "OFF"
position (as in FIG. 8) under the action of springs 43.
It has been found that, in some particular surgical operations
where prolonged cooling is required, cold effluent gas may cool
hose 8 and the associated control valve (such as valve V1 of FIG. 1
for example) sufficiently for condensation of refrigerant gas to
occur within these members during a warming mode, thus tending to
flood the instrument. FIG. 9 therefore shows an applicator in which
a pneumatically operated shuttle valve is included which permits
the effluent gas to escape to atmosphere at the applicator and not
at some remote point. The total mass that can be cooled is
therefore reduced.
Referring to FIG. 9, the cryosurgical instrument illustrated
comprises a valve body 51 of stainless steel which is in the form
of a hollow chamber having a cylindrical bore 51G in which is a
shuttle valve member 55 in axially slidable sealed engagement
therewith.
A passing 51D leads axially from the bore 51G, opening thereinto,
terminating in a spigot 51B to which is soldered or welded end 52B
of a stainless steel tube 52, the other end 52A of which is closed.
Where passage 51D opens into bore 51G, a valve seat 51C, comprising
a lip, is provided with which valve member 55 may sealedly engage.
Holes 51E are provided in the valve body wall adjacent the valve
seat, leading from the bore 51G into an annular space 59A existing
between a handle 59 of insulating material which substantially
encloses the instrument, except for a length of tube 52 and the
enclosed end 52A thereof which extends from the handle 59 and which
constitutes the working tip or application surface of the
instrument, i.e., that portion which may be used to contact and
cool human tissue.
The handle 59 is in threaded engagement with threaded portion 51F
of valve body 51, and the annulus 59A opens to atmosphere.
A conduit extends co-axially and sealedly through the left hand end
wall of the valve body 51, it extends through bore 51G and valve
member 55 (which has a bore 55A extending therethrough), passage
51D and tube 52 where it terminates in an orifice of chosen
diameter or area adjacent closed end 52A. A nylon hose 54 is shown
connected to the external end of conduit 53, and leads to a
gas-bottle 12 as will be explained in relation to FIG. 10. Another
conduit 57 also extends sealedly through the left hand end wall of
valve body 51, and opens into bore 51G. Another nylon hose 58
connected to the external end of conduit 57 leads to a control
valve V6 as shown in FIG. 10.
The valve member 55, which is provided with an annular seal 56 in
slideable contact with bore 51G, may be moved from one end of the
bore 51G to the other by the use of pressurised gaseous refrigerant
in the following manner: when conduit 57 is, via hose 58, open to
atmosphere, and pressurised refrigerant is supplied to conduit 53,
the refrigerant issues from orifice 53A, impinges upon the internal
wall of tube end 52A which it cools, and exhausts along tube 52,
passage 51D, and pushes valve-member 55 into the position
illustrated. The exhaust gas may now pass through holes 51E and
annulus 59A to atmosphere.
If, now, gaseous refrigerant, from the same gas-bottle 12 is
connected via hose 58 to conduit 57, valve member 55 is thrust
towards valve seat 51C which it sealedly contacts thus closing the
exhaust passage but permitting the gaseous refrigerant to flow
through the annulus bounded by conduit 53 and valve member 55A,
thus to rapidly raise the pressure within the working tip to that
of the source.
Although the annulus extending through the valve member must not be
so large that it prevents operation of the valve member, its area
can be very much greater than that of the orifice 53A without
affecting such operation.
In the arrangement of FIG. 10, valve member 5 is controlled
directly from a foot operated valve V6. No reverse flow is
contemplated therefore it is sufficient to move valve-member 55
onto seat 51C so that gas is supplied directly from bottle 12 to
the interior of tube 52. Flow through orifice 53A ceases as the
pressure difference thereacross disappears.
Instruments according to the invention may also be provided with
means for clearing a blocked expansion orifice, such blocking
occuring occasionally in practice due to the presence in the first
conduit of particulate matter which has either escaped the gas
filter, if such be provided, or is due to failure to adequately
clean the conduit during manufacture.
Such means are illustrated in FIGS. 2 and 3 and comprise a ball 11
situated within tubular conduit 3 in the vicinity of end 3C thereof
which has been reduced in diameter (by spinning for example) to
form a seat for the ball. The ball 11 is retained within conduit 3
by a stop 3B welded or soldered into the wall thereof. A small nick
3D in the reduced end 3C constitutes the restricted orifice when
the ball 11 is seated as shown in FIG. 2.
In operation, when high pressure gas is introduced into conduit 3,
the ball is thrust thereby onto its seat, thus closing end 3C with
the exception of orifice 3D through which the gas then expands.
When the pressure across ball 11 is equalised, or when a reverse
flow occurs, the ball 11 either drops away from end 3C or is lifted
by the reverse flow.
So that a blocked orifice may readily be cleared, a further valve
may be provided (such as that shown in dotted line in FIG. 6 and
annotated 60) which, when the applicator is in the warming mode,
may be briefly opened to atmosphere thus flushing conduit 3 and
lifting ball 11 clear of its seat permitting particulate matter
trapped in orifice 3D to be blown away.
While particular embodiments of the invention have been described,
various modifications may be made thereto by practitioners in the
art without departing from the spirit of the invention and the
scope of the appended claims.
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