U.S. patent application number 09/987689 was filed with the patent office on 2002-06-06 for apparatus and method for compressing a gas, and cryosurgery system and method utilizing same.
Invention is credited to Zvuloni, Roni.
Application Number | 20020068929 09/987689 |
Document ID | / |
Family ID | 38135555 |
Filed Date | 2002-06-06 |
United States Patent
Application |
20020068929 |
Kind Code |
A1 |
Zvuloni, Roni |
June 6, 2002 |
Apparatus and method for compressing a gas, and cryosurgery system
and method utilizing same
Abstract
An apparatus for compressing a gas and its uses are disclosed.
The apparatus comprises a fixed-volume container having a hollow
and a moveable element subdividing said hollow into a first
variable-volume portion and a second variable-volume portion, the
second variable-volume portion having an opening for introducing
therein a hydraulic and/or pneumatic fluid under pressure, for
causing an increase in the volume of said second variable-portion
by moving said moveable element, thereby, consequently, decreasing
the volume of the first variable-volume portion and compressing a
gas contained therein.
Inventors: |
Zvuloni, Roni; (Haifa,
IL) |
Correspondence
Address: |
G.E. EHRLICH (1995) LTD.
c/o ANTHONY CASTORINA
SUITE 207
2001 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Family ID: |
38135555 |
Appl. No.: |
09/987689 |
Filed: |
November 15, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09987689 |
Nov 15, 2001 |
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09860486 |
May 21, 2001 |
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60242455 |
Oct 24, 2000 |
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Current U.S.
Class: |
606/22 |
Current CPC
Class: |
A61B 90/36 20160201;
A61B 2018/00041 20130101; A61B 2017/00092 20130101; A61B 2018/0262
20130101; F17C 2201/019 20130101; A61B 2018/0268 20130101; F17C
2201/018 20130101; A61B 2018/0287 20130101; F17C 2201/0185
20130101; A61B 2017/00867 20130101; A61B 18/02 20130101 |
Class at
Publication: |
606/22 |
International
Class: |
A61B 018/02 |
Claims
What is claimed is:
1. An apparatus for compressing a gas, comprising a fixed-volume
container having a hollow and a moveable element subdividing said
hollow into a first variable-volume portion and a second
variable-volume portion, said second variable-volume portion having
an opening for introducing therein a hydraulic and/or pneumatic
fluid under pressure, for causing an increase in a volume of said
second variable-portion by moving said moveable element, thereby,
consequently, decreasing a volume of said first variable-volume
portion and compressing a gas contained therein.
2. The apparatus of claim 1, wherein said first variable-volume
portion is designed and constructed so as to be couplable during a
first phase of operation to a mechanism for introducing a gas into
said first variable-volume portion, and to be couplable during a
second phase of operation to a mechanism for transporting a
compressed gas from said first variable-volume portion to a
compressed gas utilizing application, for supplying a compressed
gas to said compressed gas utilizing application.
3. The apparatus of claim 2, wherein said first variable-volume
portion is coupled during said first phase of operation to a source
of a gas.
4. The apparatus of claim 2, wherein said first variable-volume
portion is coupled during said second phase of operation to a
mechanism for transporting a compressed gas from said first
variable-volume portion to a compressed gas utilizing
application.
5. The apparatus of claim 1, wherein said second variable-volume
portion is designed and constructed to be couplable during said
second phase of operation to a source of hydraulic and/or pneumatic
fluid under pressure.
6. The apparatus of claim 5, wherein said second variable-volume
portion is coupled during said second phase of operation to a
source of hydraulic and/or pneumatic fluid under pressure.
7. The apparatus of claim 1, wherein said moveable element is
constructed of a rigid material.
8. The apparatus of claim 7, wherein said moveable element is a
piston.
9. The apparatus of claim 1, wherein said moveable element is at
least partially constructed of a flexible material.
10. The apparatus of claim 9, wherein said flexible material is an
elastomer.
11. The apparatus of claim 9, wherein said flexible material is
reinforced rubber.
12. The apparatus of claim 9, wherein said moveable element is a
diaphragm.
13. The apparatus of claim 9, wherein said moveable element is a
bladder.
14. The apparatus of claim 13, wherein said first variable-volume
portion forms a portion of said hollow and is defined by said
bladder.
15. The apparatus of claim 13, wherein said first variable-volume
portion forms a portion of said hollow and is defined by said fixed
volume container and outside said bladder.
16. A method for compressing a gas, utilizing a fixed-volume
container having a hollow and a moveable element subdividing said
hollow into a first variable-volume portion and a second
variable-volume portion, comprising: (a) introducing a gas into
said first variable-volume portion of said hollow during a first
phase of operation; and (b) introducing a hydraulic and/or
pneumatic fluid under pressure into said second variable-volume
portion of said hollow during a second phase of operation, thereby
increasing a volume of said second variable-volume portion by
moving said moveable element, thereby, consequently decreasing a
volume of said first variable-volume portion and compressing said
gas contained therein.
17. A method for supplying a compressed gas to a compressed gas
utilizing application, utilizing a fixed-volume container having a
hollow and a moveable element subdividing said hollow into a first
variable-volume portion and a second variable-volume portion,
comprising: (a) introducing a gas into said first variable-volume
portion of said hollow during a first phase of operation; (b)
introducing a hydraulic and/or pneumatic fluid under pressure into
said second variable-volume portion of said hollow during a second
phase of operation, thereby increasing a volume of said second
variable-volume portion by moving said moveable element, thereby
consequently decreasing a volume of said first variable-volume
portion and compressing said gas contained therein; and (c)
transferring a gas during said second phase of operation from said
first variable-volume portion of said hollow to said compressed gas
utilizing application.
18. A compressed gas utilization system comprising: (a) a first gas
compression apparatus for compressing a gas, including a
fixed-volume container having a hollow and a moveable element
subdividing said hollow into a first variable-volume portion and a
second variable-volume portion, said second variable-volume portion
having an opening for introducing therein a hydraulic and/or
pneumatic fluid under pressure, for causing an increase in a volume
of said second variable-volume portion by moving said moveable
element, thereby consequently decreasing a volume of said first
variable-volume portion and compressing a gas contained therein;
(b) a compressed gas utilizing application utilizing compressed
gas; and (c) a first mechanism for transporting a compressed gas
from said first variable-volume portion of said first gas
compression apparatus to said compressed gas utilizing
application.
19. The system of claim 18, wherein said first mechanism for
transporting a compressed gas comprises a valve for controlling
flow of gas.
20. The system of claim 18, wherein said first mechanism for
transporting a compressed gas comprises a gas manifold.
21. The system of claim 18, wherein said first mechanism for
transporting a compressed gas comprises a control module for
controlling said transporting of compressed gas.
22. The system of claim 21, wherein said control module comprises a
feedback sensor.
23. The system of claim 22, wherein said feedback sensor is a
temperature sensor.
24. The system of claim 22, wherein said feedback sensor is a
pressure sensor.
25. The system if claim 22, wherein said feedback sensor is a mass
flow sensor.
26. The system of claim 21, wherein said control module comprises a
processor and a memory, said processor being operable according to
a set of programmed instructions stored in said memory.
27. The system of claim 21, wherein said control module comprises a
console for receiving commands from a user.
28. The system of claim 21, wherein said control module comprises a
remote command module incorporating a telecommunications
device.
29. The system of claim 21, wherein said control module comprises a
remote command module incorporating an infrared communications
device.
30. The system of claim 18, wherein said first variable-volume
portion of said first gas compression apparatus is coupled during a
first phase of operation to a mechanism for introducing a gas into
said first variable-volume portion of said first gas compression
apparatus, and said first variable-volume portion of said first gas
compression apparatus is coupled during a second phase of operation
to said mechanism for transporting a compressed gas from said first
variable-volume portion of said first gas compression apparatus to
said compressed gas utilizing application.
31. The system of claim 30, further comprising: (d) a second gas
compression apparatus including a fixed-volume container having a
hollow and a moveable element subdividing said hollow into a first
variable-volume portion and a second variable-volume portion, said
second variable-volume portion having an opening for introducing
therein a hydraulic and/or pneumatic fluid under pressure, for
causing an increase in a volume of said second variable-volume
portion by moving said moveable element, thereby consequently
decreasing a volume of said first variable-volume portion and
compressing a gas contained therein; and (e) a second mechanism for
transporting a compressed gas from said first variable-volume
portion of said second gas compression apparatus to said compressed
gas utilizing application.
32. The system of claim 31, designed and constructed so as to
enable said first gas compression apparatus to be in said first
phase of operation while said second gas compression apparatus is
in said second phase of operation, and said first gas compression
apparatus to be in said second phase of operation while said second
gas compression apparatus is in said first phase of operation.
33. The system of claim 32, designed and constructed so that said
first gas compression apparatus is in said first phase of operation
when said second gas compression apparatus is in said second phase
of operation, and said first gas apparatus is in said second phase
of operation when said second gas compression apparatus is in said
first phase of operation.
34. A cryosurgery system comprising: (a) a first gas compressor for
compressing gas; (b) a cryoablation apparatus utilizing compressed
gas; and (c) a mechanism for transporting compressed gas from said
gas compressor to said cryoablation apparatus during use.
35. The system of claim 34, wherein said cryoablation apparatus
comprises a Joule-Thomson heat exchanger for cooling a portion of
said cryoablation apparatus.
36. The system of claim 35, further comprising: (d) a mechanism for
re-pressurizing a gas depressurized by use in said Joule-Thomson
heat exchanger.
37. The system of claim 36, further including a mechanism for
transporting a gas depressurized by use in a Joule-Thomson heat
exchanger from said cryoablation apparatus to said gas
compressor.
38. The system of claim 37, wherein said mechanism for transporting
a gas includes a second gas compressor.
39. The system of claim 37, wherein said mechanism for transporting
a gas includes a gas reservoir.
40. The system of claim 34, wherein said gas compressor comprises a
fixed-volume container having a hollow and a moveable element
subdividing said hollow into a first variable-volume portion and a
second variable-volume portion, said second variable-volume portion
having an opening for introducing therein a hydraulic and/or
pneumatic fluid under pressure, for causing an increase in a volume
of said second variable-volume portion by moving said moveable
element, thereby consequently decreasing a volume of said first
variable-volume portion and compressing a gas contained
therein.
41. The system of claim 40, wherein said first variable-volume
portion of said first gas compression apparatus is coupled during a
first phase of operation to a mechanism for introducing a gas into
said first variable-volume portion of said first gas compression
apparatus, and said first variable-volume portion of said first gas
compression apparatus is coupled during a second phase of operation
to said mechanism for transporting a compressed gas from said first
variable-volume portion of said first gas compression apparatus to
said compressed gas utilizing application.
42. A method for cryosurgery, involving in situ compression of gas,
comprising: (a) using a first in situ gas compressor to compress a
gas, thereby transforming said gas into a first compressed gas at a
first gas pressure; (b) transferring said first compressed gas at
said first gas pressure from said first gas compressor to a
cryoablation apparatus utilizing said first compressed gas at said
first gas pressure; and (c) using said cryoablation apparatus to
perform cryoablation, thereby creating a decompressed gas at a
second gas pressure.
43. The method of claim 42, further comprising: (d) transferring
said depressurized gas at said second gas pressure to said first
gas compressor, for recompression and reuse; and (e) recompressing
and reusing said depressurized gas.
44. The method of claim 42, further comprising: (d) transferring
said depressurized gas at said second gas pressure to a second gas
compressor, for recompression and reuse; and (e) recompressing and
reusing said depressurized gas.
Description
[0001] This is a continuation-in-part of U.S. patent application
Ser. No. 09/860,486, filed May 21, 2001, which claims the benefit
of priority from U.S. Provisional Patent Application No. US
60/242,455, filed Oct. 24, 2000, now expired.
FIELD AND BACKGROUND OF THE INVENTION
[0002] The present invention relates to apparatus and method for
compressing and/or re-compressing gas and further to the use of in
situ gas compression as a source of compressed gas to a compressed
gas utilizing application, such as a cryoablation apparatus.
[0003] Many methods are known in the art for mechanically
compressing (pressurizing) gas, for storing compressed
(pressurized) gas in containers, for transporting compressed gas to
sites where the compressed gas is to be used, and for utilizing
compressed gasses for a variety of purposes in a variety of utility
applications.
[0004] Gas compression is most typically accomplished using single
stage or multiple stage reciprocating piston systems powered by
independent power sources such as electric motors or internal
combustion engines.
[0005] Alternatively, low and medium pressure gasses are sometimes
raised to a higher pressure via the use of what is known in the art
as "booster" pumps. One popular form of a booster pump does not
require external power sources. In these pumps the pressure of the
input gas itself is applied over the surface of a large area piston
which, by mechanical linkage, induces movement in a small area
piston. The small area piston is used to compress a portion of the
input gas to a higher level of compression.
[0006] In many usages of compressed gas, heavy-duty equipment for
pressurizing gas is located at a gas supply facility distant from
the utilization site itself. Pressurized gas is typically
transported to the utilization site in pressurized gas containers
such as gas cylinders. At the utilization site, the gas containers
are coupled to the application that utilizes the compressed gas.
During utilization, the gas containers are gradually emptied until
the residual pressure of the gas in the containers becomes too low
for the particular application. The containers are then typically
uncoupled from the application and returned to the gas supply
facility, where they are refilled and re-pressurized.
[0007] For many industrial, domestic, recreational, and other uses,
these prior art methods are adequate. With respect to some
applications, however, limitations and disadvantages of these prior
art methods are apparent.
[0008] Reciprocating piston compression systems typically require
lubrication, and volatilization of the lubricants can compromise
the purity of the compressed gas.
[0009] Thus there is a widely recognized need for, and it would be
highly advantageous to have, a method and apparatus for gas
compression not involving the large rapid and continuous mechanical
movements typical of reciprocating piston systems, and not
requiring lubrication of the moving parts.
[0010] The phrases "medium pressure" and "medium pressure gas" are
used herein to refer to gasses in a range of pressures customarily
used in industrial processes, and customarily supplied by
industrial supply sources. Compressed argon, used for a variety of
industrial purposes, is typically supplied at a pressure of about
2500 PSI. For argon, pressures in this range are referred to herein
as "medium" pressures.
[0011] The phrases "high pressure" and "high pressure gas" are used
herein to refer to gasses in a range of pressures above medium
pressure. Various compressed gas utilizing applications require the
use of high pressure gas. Compressed argon for use in cryosurgery
applications, for example, is typically required to be in the range
of 3000-4500 PSI and above.
[0012] The prior art methods of supplying high pressure gas to high
pressure gas applications are problematic in several respects.
[0013] One practical problem encountered in using high pressure gas
in applications is that some high pressure gasses are simply not
commercially available in many regions of the world. This problem
exists even in some highly industrialized regions. In Japan, for
example, argon gas, which is used in welding and other industrial
processes, is available in popular industrial medium-pressure
concentrations, yet high pressure argon gas is not commercially
available in Japan. A Japanese utilization site, such as a
cryosurgery site, requiring high pressure argon gas, must import
this gas from outside the country.
[0014] A second practical problem in the use of prior art methods
for supplying high pressure gas to a high pressure gas application
is that transporting high pressurize gas can be inconvenient and/or
dangerous. High pressure gas requires containers that are stronger
and heavier than containers used for housing moderate pressurize
gas. Transportation is more problematic as well. It may be
considered more dangerous to transport high pressurize gas by air
transportation, for example.
[0015] Thus, there is a widely recognized need for, and it would be
highly advantageous to have, a method and apparatus for supplying
high pressurize gas to a high pressurize gas application, using gas
from popularly available medium pressure sources. Such an apparatus
and method would overcome the practical difficulties of acquiring
high pressure gas and the practical difficulties of transporting
high pressurize gas.
[0016] A third problem in the use of prior art methods for
supplying gas to high pressure gas applications is that a
significant portion of gas so supplied cannot be used for its
intended purpose. When gas is supplied in pressurized containers
connected directly to the utilization mechanisms, the pressure of
the gas in the supplied container gradually falls as the gas is
used. Gas pressure in the container eventually drops to a point
where it is lower than the minimum pressure required for the
high-pressure application. At this point, considerable gas still
remains in the container. This situation has the practical
disadvantage that the container must then be returned to the gas
supplier for refilling while still containing a significant
quantity of unused gas, which is inconvenient. It also has the
commercial disadvantage that in many cases suppliers do not credit
their customers for the returned gas, so that the customer often
pays for gas which was supplied to him but which he could not
use.
[0017] There is, thus, also a widely recognized need for, and it
would be highly advantageous to have, a method and apparatus for
utilizing compressed gas which enables full use of all, or at least
substantially most, of the gas supplied in a gas supply
container.
[0018] There are, of course, some compressed gas utilizing
applications in which re-pressurization and re-use of gasses is
impractical. In some uses of compressed gas the cost of
pressurizing and transporting the gas is relatively greater than
the cost of manufacturing or isolating the gas. Pressurized air
provides an example. For such gasses there would be little point in
recycling the gas after use. In other cases, a pressurized gas is
chemically transformed during utilization. Flammable gasses used
for combustion are an example. Here too, recycling the gas is not
generally practical.
[0019] In some applications, however, recycling is possible and in
many cases eminently desirable. This is the case, for example, in
compressed gas utilizing applications utilizing a gas which is
rare, or is expensive to produce or to isolate, and in which the
gas is not chemically transformed when utilized. A cryosurgery
system utilizing krypton gas is an example of such an
application.
[0020] Cryosurgery systems based on Joule-Thomson heat exchangers
(also commonly referred to as Joule-Thomson devices) use compressed
gas for heating and intense cooling of therapeutic cryoprobes used
to ablate tissues within the body. The design of such applications
is based on the fact that a compressed gas changes temperature as
it moves from a region of high pressure to a region of low
pressure. The gasses used do not enter into chemical interactions
with their environment, they simply expand and contract, liquefy
and evaporate.
[0021] Krypton presents advantages over the more popular argon gas
for this application. For reasons connected with the physical
characteristics of the gas, a krypton-based cryosurgery system can
function at a lower pressure than an argon-based system,
consequently is easier to build, maintain, and use. Yet krypton is
considerably more expensive than argon, on the order of one hundred
times more expensive in today's market. In a prior art system,
where the compressed gas used in cryosurgery is, after
decompression through use, simply vented to the atmosphere, use of
the otherwise desirable krypton gas would be wasteful and
expensive.
[0022] Thus, there is a widely recognized need for, and it would be
highly advantageous to have, system and method for re-pressurizing
and reusing gasses utilized in compressed gas utilizing
applications, cryosurgery applications in particular.
[0023] The limitations and disadvantages of the prior art in the
field of gas compression and the use of compressed gasses are
particularly clear in the context of cryosurgery. Various medical
conditions require the ablation of unhealthy tissues within the
body. Techniques for cryoablation developed in recent years present
various advantages over other ablation techniques, in particular
the advantage of causing less damage to healthy tissues in
proximity to the tissues whose removal or destruction is desired.
Invasive surgical procedures require cutting or destroying tissues
between the exterior of the body and the particular site whose
destruction is desired. Less invasive procedures have been used,
which bring about the destruction of selected tissues using probes
which penetrate to the area to be operated and destroy the selected
tissue by transferring energy to those tissues. RF energy, light
(laser) energy, microwave energy, and high-frequency ultra-sound
energy have been used in this context. However all such methods
have the common disadvantage that while they raise the temperature
of the tissues whose destruction is intended, they transfer heat to
healthy tissues as well, causing their destruction, partial
destruction, or functional impairment. Moreover, in some cases
tissues exposed to thermal energy or other forms of energy that
raise their temperatures secrete substances toxic to adjacent
healthy tissues. For these and other reasons, cryoablation has
become a popular method for certain types of ablation procedures.
Examples are the treatment of prostate tumors and of benign
prostate hyperplasia (BPH), and the creation of trans-myocardial
channels to effect trans-myocardial revascularization.
[0024] According to a popular cryosurgical methodology, highly
compressed gas is employed to cool and to heat surgical probes used
for cryoablation of tissues. A preferred technology for effecting
cryoablation involves the use of Joule-Thomson heat exchangers
(also popularly known as "Joule-Thomson devices") for cooling and
for heating of cryoprobes at the site of tissues to be cryoablated.
U.S. Pat. No. 6,142,991 to Schatzberger and U.S. Pat. No. 5,978,697
to Maytal, et al., provide examples of systems using such
devices.
[0025] To cool a cryosurgical apparatus utilizing a Joule-Thomson
heat exchanger, a gas such as argon, nitrogen, air, krypton,
CF.sub.4, xenon, N.sub.2O, or a mixture of similar gasses, under
high pressure, is allowed to pass through an orifice into a chamber
where the gas can expand. Expansion of the gas causes it to cool
and may cause it to liquefy, or further liquefy. This process cools
the chamber. Gasses which cool such a chamber after passing through
such an orifice from an area of high pressure to an area of lower
pressure are referred to herein as "cooling gasses." If the chamber
is constructed of thermally conductive material such as a metal,
cooling the chamber cools materials in proximity to the chamber as
well. Cryoprobes for cryoablation are typically designed and
constructed according to this principle. Cryoprobes using expansion
of a high-pressure cooling gas through a Joule-Thomson orifice into
a chamber constructed of thermally conductive material are used to
cool body tissues in close proximity to the cryoprobe, to effect
cryoablation.
[0026] Cryosurgical procedures sometimes also require heating of
cryoprobes. Tissues undergoing cryoablation tend to adhere to the
cold cryoprobe. Heating the cryoprobe subsequent to cryoablation
causes melting at areas of contact between the cryoprobe and the
tissues, thereby eliminating adherence of the tissues to the
cryoprobe and allowing the cryoprobe to be easily removed from the
cryoablation site. Cryoprobes may be heated, as well as cooled,
using a Joule-Thomson heat exchanger. High-pressure helium or a
similar gas passing through a Joule-Thomson orifice and expanding
in a chamber, heats the chamber. Gasses which heat such a chamber
after passing through such an orifice from an area of high pressure
to an area of lower pressure are referred to herein as "heating
gasses." If the chamber is constructed of thermally conductive
material such as a metal, heating the chamber has the effect of
heating materials in proximity to the chamber. This effect is used
in the construction and utilization of cryoprobes to melt material
adjacent to a cryoprobe subsequent to cryoablation, thereby
enabling disengagement of the cryoprobe from the operated
tissues.
[0027] Cryosurgical equipment using Joule-Thomson heat exchangers
and utilizing popular and easily available cooling gasses, such as
argon, require for their efficient operation a source of high
pressure cooling gas, typically in the pressure range of 3000 PSI
to 4500 PSI.
[0028] The need for high pressure gasses for efficient operation of
cryosurgical equipment raises the several practical problems
discussed hereinabove. Argon, for example, is a preferred gas for
cooling in cryosurgical equipment based on Joule-Thomson devices.
High pressure argon is more expensive than argon at standard
industrial pressures, and in some locations, such as Japan, high
pressure argon is not available at all. Argon can of course be
purchased from standard industrial supply sources, but only at the
medium pressures customarily used in industrial processes,
typically around 2500 PSI. The pressure of easily commercially
available industrial compressed argon is lower than the pressures
required for efficient cooling of cryosurgical equipment using
argon in a Joule-Thomson heat exchanger.
[0029] Thus, there is a widely recognized need for, and it would be
highly advantageous to have, a method and apparatus for
cryoablation wherein containers of gas pressurized to moderate
pressure, such as are available from standard industrial sources of
supply, are used to supply gas to a cryosurgury apparatus requiring
gas of high pressure to effect cryogenic cooling.
[0030] An additional problem connected with the high-pressure
requirements of cryosurgery is that even in regions of the world
where high-pressure cooling and heating gasses are commercially
available, their utilization is awkward and expensive. Gasses
supplied in a high-pressure container can be utilized only until
the pressure of gas in the container falls to the minimum pressure
usable in cryosurgery. According to the methods of prior art, once
pressure in a gas supply container falls below the minimum pressure
required for cryosurgery, the gas supply container can no longer be
utilized as a cryosurgery gas source, despite the fact that a
considerable amount of cooling (or heating) gas may yet remain in
the tank. If for example a cryoprobe requires a pressure of 4500
PSI (a typical figure) and a full container of gas is initially
pressured to 6000 PSI, then only 25% of the supplied gas can be
used for cryosurgery. As soon as more than one fourth of the gas
initially contained in the container has been used, pressure in the
container falls below the 4500 PSI minimum required by such a
cryoprobe. In the case of a cryoprobe operating at 3250 PSI the
situation is only slightly better: only approximately 46% of the
gas contained in a 6000 PSI container can be used before pressure
in the container falls below the minimum pressure required for
operation of the cryoprobe.
[0031] Once pressure in a gas supply container falls below the
minimum required for operation of a cryoprobe, the container must
be returned to a gas supplier re-filling. In practice, some
suppliers credit users for the unused gas returned to them in such
a container. Other suppliers do not. In either case, the expense
and bother occasioned by the necessity of switching containers, and
the necessity of returning containers to a supplier for refilling
while they yet contain substantial amounts of useful gas, are
significant disadvantages of cryosurgical equipment and procedures,
according to the known methods of prior art.
[0032] Thus, it would be desirable and advantageous to have a
method and system for utilization of compressed gas in cryosurgery,
and in similar applications, permitting utilization of
substantially all or most of the contents of each container of
supplied gas.
[0033] Prior art cryosurgery systems also suffer from the
disadvantage that they do not re-use pressurized gas. The
advantages (lower pressure requirements) of krypton gas over argon
gas for use in cryosurgery systems are well known. Yet, it is
largely impractical to use Krypton gas in prior art cryogenic
systems, wherein the cooling gas is used for cryogenic cooling only
once, and then is allowed to escape to the atmosphere.
[0034] Thus, there is a widely recognized need for, and it would be
highly advantageous to have, an apparatus and method for
re-pressurizing and re-utilizing the pressurized gasses in some
compressed gas systems, particularly systems which utilize gasses
that are rare or expensive to produce or isolate, and in which the
gasses are not chemically altered when used. In cryosurgery there
is a particular need for such methods and systems.
SUMMARY OF THE INVENTION
[0035] According to one aspect of the present invention there is
provided an apparatus for compressing a gas, including a
fixed-volume container having a hollow and a moveable element
subdividing the hollow into a first variable-volume portion and a
second variable-volume portion, the second variable-volume portion
having an opening for introducing therein a hydraulic and/or
pneumatic fluid under pressure, for causing an increase in the
volume of the second variable-portion by moving the moveable
element, thereby, consequently, decreasing the volume of the first
variable-volume portion and compressing a gas contained
therein.
[0036] According to further features in preferred embodiments of
the invention described below, the first variable-volume portion is
designed and constructed so as to be couplable during a first phase
of operation to a mechanism for introducing a gas into the first
variable-volume portion, and to be couplable during a second phase
of operation to a mechanism for transporting a compressed gas from
the first variable-volume portion to a compressed gas utilizing
application, for supplying a compressed gas to said compressed gas
utilizing application.
[0037] According to still further features in the described
preferred embodiments, the first variable-volume portion is coupled
during the first phase of operation to a source of a gas, and is
coupled during a second phase of operation to a mechanism for
transporting a compressed gas from the first variable-volume
portion to a compressed gas utilizing application.
[0038] According to still further features in the described
preferred embodiments, the second variable-volume portion is
designed and constructed to be couplable during the second phase of
operation to a source of hydraulic and/or pneumatic fluid under
pressure.
[0039] According to still further features in the described
preferred embodiments, the second variable-volume portion is
coupled during the second phase of operation to a source of
hydraulic and/or pneumatic fluid under pressure.
[0040] According to still further features in the described
preferred embodiments, the moveable element is constructed of a
rigid material.
[0041] According to still further features in the described
preferred embodiments, the moveable element is a piston.
[0042] According to still further features in the described
preferred embodiments, the moveable element is at least partially
constructed of a flexible material, such as an elastomer, or a
reinforced rubber.
[0043] According to still further features in the described
preferred embodiments, the moveable element is a diaphragm.
[0044] According to still further features in the described
preferred embodiments, the moveable element is a bladder. The first
variable-volume portion forms a portion of said hollow and may be
defined by the bladder, or it may be defined by the fixed volume
container and outside the bladder.
[0045] According to another aspect of the present invention there
is provided a method for compressing a gas, utilizing a
fixed-volume container having a hollow and a moveable element
subdividing the hollow into a first variable-volume portion and a
second variable-volume portion, including the steps of introducing
a gas into the first variable-volume portion of the hollow during a
first phase of operation; and introducing a hydraulic and/or
pneumatic fluid under pressure into the second variable-volume
portion of the hollow during a second phase of operation, thereby
increasing the volume of the second variable-volume portion by
moving the moveable element, thereby, consequently decreasing the
volume of the first variable-volume portion and compressing the gas
contained therein.
[0046] According to yet another aspect of the present invention
there is provided a method for supplying a compressed gas to a
compressed gas utilizing application, utilizing a fixed-volume
container having a hollow and a moveable element subdividing the
hollow into a first variable-volume portion and a second
variable-volume portion, including the steps of introducing a gas
into the first variable-volume portion of the hollow during a first
phase of operation; introducing a hydraulic and/or pneumatic fluid
under pressure into the second variable-volume portion of the
hollow during a second phase of operation, thereby increasing the
volume of the second variable-volume portion by moving the moveable
element, thereby consequently decreasing the volume of the first
variable-volume portion and compressing the gas contained therein,
and transferring a gas during the second phase of operation from
the first variable-volume portion of the hollow to the compressed
gas utilizing application.
[0047] According to still another aspect of the present invention
there is provided a compressed gas utilization system including a
first gas compression apparatus for compressing a gas, including a
fixed-volume container having a hollow and a moveable element
subdividing the hollow into a first variable-volume portion and a
second variable-volume portion, the second variable-volume portion
having an opening for introducing therein a hydraulic and/or
pneumatic fluid under pressure, for causing an increase in the
volume of the second variable-volume portion by moving the moveable
element, thereby consequently decreasing the volume of the first
variable-volume portion and compressing a gas contained therein,
the system further including a compressed gas utilizing application
utilizing compressed gas, and a first mechanism for transporting a
compressed gas from the first variable-volume portion of the first
gas compression apparatus to the compressed gas utilizing
application.
[0048] According to further features in preferred embodiments of
the invention described below, the first variable-volume portion of
the first gas compression apparatus is coupled during a first phase
of operation to a mechanism for introducing a gas into the first
variable-volume portion of the first gas compression apparatus, and
the first variable-volume portion of the first gas compression
apparatus is coupled during a second phase of operation to the
mechanism for transporting a compressed gas from the first
variable-volume portion of the first gas compression apparatus to
the compressed gas utilizing application.
[0049] According to still further features in the described
preferred embodiments, the system further includes a second gas
compression apparatus including a fixed-volume container having a
hollow and a moveable element subdividing the hollow into a first
variable-volume portion and a second variable-volume portion, the
second variable-volume portion having an opening for introducing
therein a hydraulic and/or pneumatic fluid under pressure, for
causing an increase in the volume of the second variable-volume
portion by moving the moveable element, thereby consequently
decreasing a volume of the first variable-volume portion and
compressing a gas contained therein, and further includes a second
mechanism for transporting a compressed gas from the first
variable-volume portion of the second gas compression apparatus to
the compressed gas utilizing application.
[0050] According to still further features in the described
preferred embodiments, the system is designed and constructed so as
to enable the first gas compression apparatus to be in the first
phase of operation while the second gas compression apparatus is in
the second phase of operation, and the first gas compression
apparatus to be in the second phase of operation while the second
gas compression apparatus is in the first phase of operation.
[0051] According to still further features in the described
preferred embodiments, the system is designed and constructed so
that the first gas compression apparatus is in the first phase of
operation when the second gas compression apparatus is in the
second phase of operation, and the first gas compression apparatus
is in the second phase of operation when the second gas compression
apparatus is in the first phase of operation.
[0052] According to an additional aspect of the present invention
there is provided a cryosurgery system including a first gas
compressor for compressing gas, a cryoablation apparatus utilizing
compressed gas, and a mechanism for transporting compressed gas
from the gas compressor to the cryoablation apparatus during
use.
[0053] According to further features in the described preferred
embodiments, the cryoablation apparatus includes a Joule-Thomson
heat exchanger for cooling a portion of the cryoablation
apparatus.
[0054] According to still further features in the described
preferred embodiments, the system includes a mechanism for
re-pressurizing a gas depressurized by use in the Joule-Thomson
heat exchanger.
[0055] According to still further features in the described
preferred embodiments, the system further includes a mechanism for
transporting a gas depressurized by use in a Joule-Thomson heat
exchanger from the cryoablation apparatus to the gas compressor.
The mechanism may include a second gas compressor, and may also
include a gas reservoir.
[0056] According to still further features in the described
preferred embodiments, the first gas compressor includes a
fixed-volume container having a hollow and a moveable element
subdividing the hollow into a first variable-volume portion and a
second variable-volume portion, the second variable-volume portion
having an opening for introducing therein a hydraulic and/or
pneumatic fluid under pressure, for causing an increase in a volume
of the second variable-volume portion by moving the moveable
element, thereby consequently decreasing a volume of the first
variable-volume portion and compressing a gas contained
therein.
[0057] According to still further features in the described
preferred embodiments, the first variable-volume portion of the
first gas compression apparatus is coupled during a first phase of
operation to a mechanism for introducing a gas into the first
variable-volume portion of the first gas compression apparatus, and
the first variable-volume portion of the first gas compression
apparatus is coupled during a second phase of operation to the
mechanism for transporting a compressed gas from the first
variable-volume portion of the first gas compression apparatus to
the compressed gas utilizing application.
[0058] According to yet an additional aspect of the present
invention there is provided a method for cryosurgery, involving in
situ compression of gas, including using a first in situ gas
compressor to compress a gas, thereby transforming the gas into a
first compressed gas at a first gas pressure, transferring the
first compressed gas at the first gas pressure from the first gas
compressor to a cryoablation apparatus utilizing the first
compressed gas at the first gas pressure; and using the
cryoablation apparatus to perform cryoablation, thereby creating a
decompressed gas at a second gas pressure.
[0059] According to further features in the described preferred
embodiments, the method further includes the steps of transferring
the depressurized gas at the second gas pressure to the first gas
compressor, for recompression and reuse, and recompressing and
reusing the depressurized gas.
[0060] According to still further features in the described
preferred embodiments, the method further includes the steps of
transferring said depressurized gas at the second gas pressure to a
second gas compressor, for recompression and reuse, and
recompressing and reusing the depressurized gas.
[0061] The present invention successfully addresses the
shortcomings of the presently known configurations by providing a
method and apparatus for compressing gas which does not depend on a
rapidly moving reciprocating piston system, and therefore does not
require lubrication which might contaminate the purity of the
compressed gas.
[0062] The present invention further successfully addresses the
shortcomings of the presently known configurations by providing a
method and apparatus for supplying gas of substantially constant
pressure to a compressed-gas application, using standard cylinders
of compressed gas as a source of gas.
[0063] The present invention further successfully addresses the
shortcomings of the presently known configurations by providing a
method and apparatus for supplying gas of high pressure to an
application using high-pressure compressed gas, utilizing standard
cylinders of moderate pressure compressed gas as a source of gas.
In particular, the present invention successfully addresses the
shortcomings of the presently known configurations of cryosurgery
systems by providing a method and apparatus for cryoablation that
efficiently uses gas for Joule-Thomson cooling (or heating) from a
gas source whose initial pressure is lower than that required for
efficient operation of a Joule-Thomson device, and is in the range
of gas pressures available from standard industrial gas sources.
This is in sharp distinction to methods of prior art, which require
specialized high-pressure gas sources for operation of a
cryosurgery device.
[0064] The present invention further successfully addresses the
shortcomings of the presently known configurations by providing a
method and apparatus for supplying gas of high pressure while
nevertheless utilizing substantially most or all of the compressed
gas supplied in standard compressed gas cylinders. In particular,
the present invention successfully addresses the shortcomings of
the presently known configurations of cryosurgery systems by
providing a method and apparatus for cryoablation in which
substantially most of the cooling gasses supplied in a tank of
cooling gas can be used for cooling a cryoprobe, and substantially
most of the heating gasses supplied in a tank of heating gas can be
used for heating a cryoprobe. This is in distinction to methods of
prior art wherein a substantial portion of the contents of each
tank of cooling gas cannot be used for cooling a cryoprobe, and a
substantial portion of the contents of each tank of heating gas
cannot be used for used for heating a cryoprobe.
[0065] The present invention further successfully addresses the
shortcomings of the presently known configurations by providing a
method and apparatus for re-pressurizing and reusing gas supplied
from a high-pressure source and depressurized by utilization in an
application. In particular, the present invention successfully
addresses the shortcomings of presently known configurations of
cryosurgery systems by providing a method and apparatus for the
practical and economical use of rare and expensive gasses in such
systems through the use of method and apparatus for re-pressurizing
and reusing such gasses.
BRIEF DESCRIPTION OF THE DRAWINGS
[0066] The invention is herein described, by way of example only,
with reference to the accompanying drawings. With specific
reference now to drawings in detail, it is stressed that the
particulars shown are by way of example and for purposes of
illustrative discussion of the preferred embodiments of the present
invention only, and are presented in the cause of providing what is
believed to be the most useful and readily understood description
of the principles and conceptual aspects of the invention. In this
regard, no attempt is made to show structural details of the
invention in more detail than is necessary for a fundamental
understanding of the invention, the description taken with the
drawings making apparent to those skilled in the art how the
several forms of the invention may be embodied in practice.
[0067] In the drawings:
[0068] FIG. 1 is a gas compression apparatus utilizing a piston,
according to the present invention;
[0069] FIG. 2 is a gas compression apparatus utilizing a diaphragm,
according to the present invention;
[0070] FIG. 3 is a gas compression apparatus utilizing a bladder,
according to the present invention;
[0071] FIG. 4 is an alternative construction of a gas compression
apparatus utilizing a bladder, according to the present
invention;
[0072] FIG. 5 is an exemplary compressed gas utilization system in
the form of a cryosurgery apparatus utilizing in situ compressed
gas, according to the present invention;
[0073] FIG. 6 is a compressed gas delivery module, according to the
present invention;
[0074] FIG. 7 is a compressed gas utilization system incorporating
a rechargeable gas compression apparatus, according to the present
invention; and
[0075] FIG. 8 is a compressed gas utilization system utilizing a
plurality of gas compression apparati.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0076] The present invention is of apparatus and method for
compressing and/or re-compressing gas which can be used for in situ
gas compression as a method of supplying compressed gas to a
compressed gas utilizing application, such as a cryoablation
apparatus. More specifically, the present invention can be used to
compress a gas for use in a compressed gas utilizing application.
The present invention can further be used to raise the pressure of
a compressed gas, to thereby supply high pressure gas to a
compressed gas utilizing application using medium pressure gas
sources. It can further be used to supply compressed gas at a
constant selected pressure to a compressed gas utilizing
application. It can further be used to supply compressed gas to a
compressed gas utilizing application, while utilizing all or
substantially most of the gas supplied in conventional gas
cylinders or similar containers.
[0077] In one particular and presently preferred embodiment, the
present invention is used to supply high pressure gas to a
cryosurgery apparatus and enables re-pressurization and re-use of a
compressed gas used in a Joule-Thomson heat exchanger for heating
and cryogenic cooling.
[0078] To enhance clarity of the following descriptions, the
following terms and phrases will first be defined:
[0079] The terms "compression" and "pressurization" are used herein
interchangeably. A "compressed gas" is a pressurized gas, a gas
held under a pressure higher than atmospheric pressure.
[0080] A "compressed gas utilizing application" is a device,
apparatus, or system utilizing compressed gas while operating.
[0081] The phrase "medium pressure" is used herein to refer to a
degree of pressurization in or near the range of pressurization
typical of gasses sold by industrial supply sources when supplying
gasses used for common industrial purposes. By way of example,
compressed argon is commonly sold by industrial supply sources
pressurized to about 2500 PSI. It is noted that other particular
types of gasses may be typically available in other pressure
ranges. The term "medium pressure", as used herein, is not limited
to a particular pressure, but is used generally to refer to a
pressure range typically commercially available for each type of
gas, and is contrasted with "high pressure" defined
hereinbelow.
[0082] The phrase "high pressure" is used herein to refer to a
degree of pressurization higher than the range of pressurization
typical of gasses sold by industrial supply houses when supplying
gasses used for common industrial purposes. By way of example,
compressed argon used in cryosurgery apparatus is typically
pressurized to the range of 3000-4500 PSI, which range, for argon,
is referred to herein as a high pressure, and argon gasses at such
pressure are referred to herein as high pressure gasses. The term
"high pressure" as used herein is not, however, limited to that
particular pressure range. Rather, the term "high pressure" is used
herein to refer to that pressure which, for any particular type of
gas, is higher than the "medium pressure" at which that particular
type of gas is typically easily and economically commercially
available.
[0083] The phrase "low pressure" is used herein to refer to a
degree of pressurization lower than the range of pressurization
typical of gasses sold for use in compressed gas utilizing
applications. A gas may be at "low pressure", and yet be at a
pressure higher than atmospheric pressure.
[0084] The phrase "depressurized gas" and the term
"depressurization" are used herein to refer particularly to the
pressurization state of a gas which has been used by a compressed
gas utilizing application, and which is consequently at a low
pressure subsequent to having been so used.
[0085] The phrase "Joule-Thomson heat exchanger" refers, in
general, to any device used for cryogenic cooling or for heating,
in which a gas is passed from a first region of the device, wherein
it is held under higher pressure, to a second region of the device,
wherein it is enabled to expand to lower pressure. Such devices are
also commonly referred to as Joule-Thomson devices. A Joule-Thomson
heat exchanger may be a simple conduit, or it may include an
orifice through which gas passes from the first, higher pressure,
region of the device to the second, lower pressure, region of the
device. The expansion of certain gasses (referred to herein as
"cooling gasses") in a Joule-Thomson heat exchanger, when passing
from a region of higher pressure to a region of lower pressure,
causes these gasses to cool and may cause them to liquefy, creating
a cryogenic pool of liquefied gas. This process cools the
Joule-Thomson heat exchanger itself, and also cools any thermally
conductive materials in contact therewith. The expansion of certain
other gasses (referred to herein as "heating gasses") in a
Joule-Thomson heat exchanger causes the gasses to heat, thereby
heating the Joule-Thomson heat exchanger itself and also heating
any thermally conductive materials in contact therewith.
[0086] The principles and operation of a gas compression apparatus
and of a compressed gas utilization system according to the present
invention may be better understood with reference to the drawings
and accompanying descriptions.
[0087] Before explaining at least one embodiment of the invention
in detail, it is to be understood that the invention is not limited
in its application to the details of construction and the
arrangement of the components set forth in the following
description or illustrated in the drawings. The invention is
capable of other embodiments or of being practiced or carried out
in various ways. Also, it is to be understood that the phraseology
and terminology employed herein is for the purpose of description
and should not be regarded as limiting.
[0088] Referring now to the drawings, FIG. 1 presents a preferred
embodiment of a gas compression apparatus according to the present
invention. For convenience and clarity, a gas compression apparatus
according to the present invention will be referred to hereinbelow
as a "bi-pump" 18.
[0089] In FIG. 1, bi-pump 18 comprises a container 20, rigidly
constructed of a strong material such as a metal and designed to
withstand high pressures. Container 20 is optionally surrounded by
a thermally insulating layer 16. Container 20 has a hollow 22 and a
moveable element 28. Moveable element 28 serves to divide hollow 22
into a first variable-volume portion, referred to herein as gas
portion 24, and a second variable-volume portion, referred to
herein as fluid portion 26.
[0090] Gas portion 24 is for receiving, holding, and compressing a
gas. A gas to be compressed is introduced into gas portion 24
through a gas input coupling 46. Gas input coupling 46 is for
coupling bi-pump 18 to a source of gas which is to undergo
compression. The input gas introduced into bi-pump 18 may be an
uncompressed gas, or may be a pressurized gas at a pressure lower
than a pressure which is desired to be obtained, e.g., for use in a
compressed gas utilizing application 42. A gas output coupling 40
is provided for coupling gas portion 24 to compressed gas utilizing
application 42, or to some other destination for the compressed
gas. Thus, compressed gas may be transferred to compressed gas
utilizing application 42 or to any other destination through gas
output coupling 40. Optionally, gas input coupling 46 includes a
gas input valve 41 for controlling flow of input gas. Optionally,
gas output couping 40 includes a gas output valve 43 for
controlling flow of output gas.
[0091] The gas introduced into gas portion 24 can be any gas,
including, but not limited to argon, nitrogen, air, krypton,
CF.sub.4, N.sub.2O, CO.sub.2, and helium. Fluid portion 26 is for
receiving and holding a pressurizing fluid 32. Pressurizing fluid
32 enters fluid portion 26 through a pressurizing fluid input
coupling 48, and can be drained from the apparatus through
pressurizing fluid output coupling 50.
[0092] During a first phase of operation, a gas is introduced into
gas portion 24 through input gas coupling 46. Also during the first
phase of operation, pressurizing fluid 32 present in fluid portion
26 as a result of previous iterations of the process is allowed to
drain from fluid portion 26 through pressurizing fluid output
coupling 50.
[0093] During a second phase of operation, pressurizing fluid 32 is
introduced into fluid portion 26 in order to exert pressure on
moveable element 28. Pressurizing fluid 32 is any fluid capable of
exerting such pressure, such as a hydraulic fluid such as oil or
water, or such as a pneumatic fluid such as a compressed gas, or
such as a mixture of a hydraulic fluid such as oil mixed with a
pneumatic fluid such as a compressed gas. Use of a hydraulic liquid
as pressurizing fluid 32 is the currently preferred choice in
preferred embodiments of the invention.
[0094] During a second phase of operation, fluid pressurizer 33
supplies pressurizing fluid 32 under pressure. Pressurized
pressurizing fluid 32 is introduced into fluid portion 26 through
pressurizing fluid input coupling 48. In a preferred embodiment,
fluid pressurizer 33 is a hydraulic unit 35, capable of supplying a
hydraulic liquid at a selected pressure, according to methods well
known in the art. Pressurizing fluid 32 exerts pressure on moveable
element 28, causing moveable element 28 to move.
[0095] The movement of moveable element 28 in response to pressure
exerted by pressurizing fluid 32 causes the volume of fluid portion
26 of hollow 22 to increase. Gas portion 24 and fluid portion 26
share the same fixed total volume, which is the volume of hollow 22
exclusive of the volume of moveable element 28, which in preferred
embodiments is relatively non-compressible.
[0096] Consequently, an increase in the volume of fluid portion 26
coincides with a decrease in the volume of gas portion 24. Thus,
the movement of moveable element 28 forces the gas contained in gas
portion 24 into a smaller volume, and the gas is thereby compressed
proportionally.
[0097] Moreover, moveable element 28 moves relatively freely, hence
moveable element 28 will tend to move in such a manner as to
equalize pressure between gas portion 24 and fluid portion 26. In
consequence, changes in pressure of pressurizing fluid 32 as
supplied by fluid pressurizer 33 are rapidly reflected as
corresponding changes in pressure of the gas being compressed
within gas portion 24. Thus, pressure of gas compressed in gas
portion 24 is substantially controlled by pressure of pressurizing
fluid 32. Fluid pressurizer 33 is capable of supplying fluid at a
selected pressure, using techniques well known to one schooled in
the art. Control of output pressure of fluid pressurizer 33
constitutes control of pressure of gas compressed by gas portion
24. Thus, bi-pump 18 can compress gas to a selected and controlled
pressurize.
[0098] Thus, according to another aspect of the present invention
there is provided a method for compressing a gas, utilizing a
fixed-volume container having a hollow and a moveable element
subdividing the hollow into a first variable-volume portion and a
second variable-volume portion. The method according to this aspect
of the invention is effected by introducing a gas into the first
variable-volume portion of the hollow during a first phase of
operation; and thereafter introducing a hydraulic or pneumatic
fluid under pressure into the second variable-volume portion of the
hollow during a second phase of operation, thereby increasing a
volume of the second variable-volume portion by moving the moveable
element, thereby, consequently decreasing a volume of the first
variable-volume portion and compressing the gas contained
therein.
[0099] According to methods of use in currently preferred
embodiments of the present invention, during a second phase of
operation, compressed gas from gas portion 24 is allowed to pass
through gas output coupling 40, from where it can serve as a supply
of compressed gas to compressed gas utilizing application 42 or
other needs.
[0100] Gas input coupling 46 and gas output coupling 40 are shown
as different couplings, yet in an optional construction they may be
a combined input/output gas coupling. Similarly, pressurizing fluid
input coupling 48 and pressurizing fluid output coupling 50 are
shown as different couplings, yet in an optional construction they
may be a combined pressurizing fluid input/output coupling.
[0101] Moveable element 28 will either move rigidly, changing
position within container 20, or else it will move elastically,
changing shape. An example of rigid movement is presented by the
embodiment of FIG. 1. Examples of elastic movement are given by the
embodiments presented by FIGS. 2, 3 and 4.
[0102] In a preferred embodiment of the present invention,
specifically shown in FIG. 1, moveable element 28 is constructed of
a rigid material, such as a metal or a hard non-deformable
polymeric material or composite material. In this preferred
embodiment container 20 is cylindrical, and moveable element 28 is
designed and constructed in the form of a piston 34. Piston 34 is
able to move longitudinally within cylindrical container 20. During
a second phase of operation, when pressurized pressurizing fluid 32
is introduced into fluid portion 26 it exerts pressure on piston
34. Piston 34 responds to the pressure by moving longitudinally in
container 20 towards gas portion 24. The volume of gas portion 24
is thereby reduced and the gas contained therein is compressed.
[0103] FIGS. 2, 3 and 4 present preferred embodiments in which at
least a part of moveable element 28 is constructed of flexible
material, such as a reinforced rubber or an elastomer.
[0104] In a preferred embodiment of the present invention shown in
FIG. 2, moveable element 28 is a diaphragm 36. Diaphragm 36 is
anchored at a fixed in position within container 20, yet flexible
area 38 of diaphragm 36 is constructed of an elastic material.
During the second phase of operation, high-pressure pressurizing
fluid 32 is introduced into fluid portion 26. Pressure exerted by
pressurizing fluid 32 on diaphragm 36 causes flexible area 38 of
diaphragm 36 to distend towards gas portion 24. The volume of gas
portion 24 is thereby reduced and the gas contained therein is
compressed.
[0105] In preferred embodiments of the present invention shown in
FIGS. 3 and 4, moveable element 28 is a bladder 44. Bladder 44 is
preferably constructed of a strong but very flexible material, and
has a shape something similar to the shape of a child's balloon. At
its maximum expansion, bladder 44 extends to fill substantially all
of the volume of hollow 22. At its minimum expansion, bladder 44
takes up little more volume than the volume of the materials of
which bladder 44 is composed. In a preferred embodiment the volume
of bladder 44 at minimum expansion is typically approximately 15%
of the volume of hollow 22.
[0106] In a preferred embodiment of the present invention shown in
FIG. 3, gas portion 24 is the interior volume of bladder 44 and
fluid portion 26 is the volume within hollow 22 of container 20
which is outside of bladder 44. During the first phase of
operation, gas is introduced into the interior of bladder 44
through gas input coupling 46. During the second phase of operation
pressurizing fluid 32 is introduced into the volume within hollow
22 of container 20 which is outside bladder 44. Pressure exerted by
pressurizing fluid 32 on bladder 44 causes bladder 44 to contract,
thereby exerting pressure on gas contained within bladder 44, and
consequently compressing it.
[0107] In a preferred embodiment of the present invention shown in
FIG. 4, gas portion 24 is the volume within hollow 22 of container
20 which is outside of bladder 44. In this embodiment, fluid
portion 26 is the interior volume of bladder 44. During the first
phase of operation gas is introduced into the portion of hollow 22
which is exterior to bladder 44, through gas input coupling 46,
causing bladder 44 to collapse. During the second phase of
operation pressurizing fluid 32 is introduced into the interior
volume of bladder 44. Pressure exerted by pressurizing fluid 32 on
the interior of bladder 44 causes bladder 44 to expand. Since gas
portion 24 is the volume of hollow 22 exterior to bladder 44,
expansion of bladder 44 causes a reduction of volume of gas portion
24, thereby compressing a gas therein.
[0108] It is to be noted that a configuration reversed with respect
to those presented in FIG. 3 and in FIG. 4 is known in prior art,
yet according to the teachings of the prior art the configuration
is used to fulfill quite a different function. A device known in
the art as an "accumulator" is used to pressurize a liquid, such as
a hydraulic liquid, e.g., water or oil. An example is provided by
the accumulator sold by Accumulators Inc. of 9042 Long Point Road,
Huston Tex. 77055, part number A56100, or that sold by Ballas
Engineering & Mechanization Ltd. of 4 HaManor Street, Tel Aviv,
Israel, and identified by part number SB800/1000. The function of
this accumulator, and of all know usages of "accumulators" of
similar design, according to the teachings of the prior art, is to
pressurize a hydraulic liquid. For this purpose, a compressed gas
is used. In other words, the usage of an accumulator according to
the prior art is just the reverse of the usage presented herein. In
a prior art accumulator, gas is introduced under pressure into a
portion of the device, for the purpose of exerting a force on an
extensible bladder in order to pressurize a liquid such as a
hydraulic liquid like water or oil, which is then subsequently used
in an application requiring a pressurized hydraulic liquid for
operation. This is, of course, in sharp contrast to the
configuration, purpose, and usages of the present invention,
wherein a pressurizing fluid is used to compress a gas for use by a
compressed gas utilizing application.
[0109] An advantage of an apparatus constructed in accordance with
the teachings of the present invention is in the ability of the
apparatus to supply gas at a constant and selected pressure. In
each of the embodiments presented in FIGS. 1-4, pressure of a
compressed gas held under pressure in gas portion 24 will, during
the second phase of operation, be substantially similar to pressure
exerted by pressurizing fluid 32 on moveable element 28. In a
preferred mode of operation, pressurizing fluid 32 is supplied by
fluid pressurizer 33 through pressurizing fluid input coupling 48
at a constant pressure chosen to be an optimal pressure for a
selected gas application. Bi-pump 18 is thus enabled to supply
compressed gas to compressed gas utilizing application 42 at a
substantially constant and optimized pressure. This is in sharp
contrast to the configurations of prior art, in which compressed
gas is typically supplied to compressed gas utilizing applications
in the form of compressed gas containers, such as cylinders, of
constant geometry. In such configurations, the pressure of
compressed gas supplied to the application typically depends on the
amount of gas remaining in the supplied container of gas. That
pressure varies over time, pressure in the gas supply containers
gradually falling as gas in the container is gradually used by the
compressed gas utilizing application.
[0110] For some compressed gas utilizing applications, for example
for the cryosurgery application discussed more fully hereinbelow,
it is advantageous, for efficient operation of the application, to
have a supply of compressed gas at a substantially constant
pressure. Thus, the ability of a gas compression apparatus
according to the present invention to supply compressed gas to a
compressed gas utilizing application at a substantially constant
and optimized pressure is an important advantage of the present
invention over the configurations of the prior art.
[0111] An additional advantage of an apparatus according to the
present invention lies in the ability of the apparatus to utilize,
during the second phase of operation, substantially all of the gas
supplied to gas portion 24 during the first phase of operation.
Since the pressure of compressed gas supplied to compressed gas
utilizing application 42 through gas output connector 40 is not
dependent on the amount of gas remaining in the apparatus, the
second phase of operation can be continued until substantially all
of the gas present in gas portion 24 has been transferred through
gas output coupling 40 to compressed gas utilizing application 42.
This is in sharp contrast to the typical situation of prior art,
wherein the pressure of gas supplied in a gas cylinder or similar
container gradually falls over time as gas is used. In such a
system a point is reached at which the pressure of the gas supplied
falls below the minimum pressure required by compressed gas
utilizing application 42. At that point the gas supply container
must typically be returned for refilling by a supplier, despite the
fact that a significant amount of valuable gas is still contained
in the container. In a cryosurgery system, for example, the
required gas pressure is typically so high that gas supply
cylinders used by conventional cryosurgery systems are typically
returned to a supplier for refilling with more than half the
supplied gas still in the cylinder.
[0112] FIG. 5 presents a compressed gas utilization system
according to the present invention.
[0113] At least one gas source 100 supplies gas to an input gas
manifold 102. Gas from input gas manifold 102 is compressed by gas
compression apparatus 104, then passes through an optional
compressed gas manifold 106 to a compressed gas delivery module
108. In a preferred embodiment, compressed gas delivery module 108
is a control module for controlling delivery of compressed gas to
compressed gas utilizing application 42, which utilizes the
compressed gas.
[0114] Gas source 100 is a source of any gas. In a preferred
embodiment of the present invention, a plurality of gas sources 100
are enabled to input gas to input gas manifold 102.
[0115] Gas source 100 may be a source of uncompressed gas, such as
air. Gas source 100 may also be a source of compressed gas at a low
pressure, at a medium pressure, or at a high pressure. In a
preferred embodiment, gas sources 100 typically supply gas at a
pressure lower than a pressure desired for a particular compressed
gas utilizing application 42. Examples of compressed gas sources
100 include an industrial `always on` compressed gas supply line,
an external gas cylinder or similar gas container, a plurality of
external gas cylinders or similar gas containers, an internal gas
cylinder or similar gas container, and a plurality of internal gas
cylinders or similar gas containers.
[0116] Gas from gas sources 100 is supplied through input gas
manifold 102 to gas compression apparatus 104. Gas compression
apparatus 104 is for raising the pressure of a gas from a first
pressure, the gas pressure supplied by gas sources 100, to a second
pressure, a pressure appropriate for use by compressed gas
utilizing application 42. In a preferred embodiment, gas
compression apparatus 104 is a bi-pump 18, described
hereinabove.
[0117] Compressed gas from gas compression apparatus 104 passes
through optional compressed gas manifold 106 to compressed gas
delivery module 108, which controls delivery of compressed gas to
compressed gas utilizing application 42, where it is used.
[0118] An optional gas recycling module 118 is for recycling gas
that is depressurized in consequence of having been utilized by
compressed gas utilizing application 42. Decompressed gas is
recovered from compressed gas utilizing application 42 or from
compressed gas delivery module 108 to a gas recovery manifold 120.
Gas from gas recovery manifold 120 may optionally be repressurized
or partially repressurized by an optional recycling gas
pre-compressor 122, and may further optionally be stored in a
recovered gas reservoir 126. The recovered and repressurized gas is
ultimately transported or guided to compressed gas utilizing
application 42, where it is re-used. In a preferred embodiment of
the present invention presented in FIG. 5, the recovered gas, after
optional pre-compression by recycling gas pre-compressor 122 and
optional intermediate storage in recovered gas reservoir 126, is
ultimately transported or guided to input gas manifold 102 for
further repressurization by gas compression apparatus 104, whence
it is supplied for re-use by compressed gas utilizing application
42.
[0119] A preferred embodiment of a compressed gas utilization
system according to the present invention, wherein compressed gas
utilizing application 42 is a cryosurgery application 110,
constitutes a departure from prior art, and presents several
advantages over prior art configurations using compressed gas for
cooling portions of a cryosurgery apparatus.
[0120] Referring again to FIG. 5, compressed gas utilizing
application 42 is cryosurgery application 110, in which compressed
gas is supplied to at least one cryoprobe 112, preferably a
plurality of cryoprobes 112. Cryoprobes 112 utilize compressed gas
in Joule-Thomson heat exchangers 114 for cooling and optionally
also for heating cryoprobes 112. In a preferred embodiment,
compressed cooling gasses are supplied to cryosurgery application
110 to cool cryoprobes 112, generally to affect cryoablation of
tissues, and compressed heating gasses are supplied to cryosurgery
application 110 to heat cryoprobes 112, generally to melt frozen
tissues touching cryoprobes 112 so as to facilitate the
disengagement of cryoprobes 112 from body tissues subsequent to
cryoablation. In a preferred embodiment, gas decompressed by
utilization in cryoprobes 112 is conducted, either directly or by
way of application 42, to gas recovery manifold 120, for
recompression and reuse as described hereinabove.
[0121] Prior art cryosurgery systems participate in the
disadvantages of high pressure gas systems recited hereinabove.
These disadvantages include the expense and inconvenience of
acquiring high pressure gas for use in the systems, an inability to
utilize substantially most of the high pressure gas supplied in
high pressure gas cylinders or other gas containers, and the
expense and wastefulness of systems which vent expensive gasses to
the atmosphere after a single use.
[0122] A compressed gas utilization system according to the present
invention, wherein compressed gas utilizing application 42 is
cryosurgery application 110, overcomes these and other advantages
of prior art systems.
[0123] Cryosurgery applications typically require high pressure gas
for effective heating and cooling of cryoprobes 112. Argon, for
example, is often used as a compressed gas for cryosurgery
applications, and is optimally used at pressures in the range of
3000-4500 PSI. Industrial supply sources of compressed argon
typically supply compressed argon at pressures of about 2500 PSI.
Thus, a preferred embodiment of a compressed gas utilization system
of the present invention enables to use argon gas compressed to
medium pressure, which can conveniently be purchased from standard
industrial sources, as a gas source 100, yet supplies high pressure
argon to a compressed gas utilizing application 42 such as a
cryosurgery application 110. This ability constitutes a significant
improvement over prior art.
[0124] In another preferred embodiment, also including a
cryosurgery application 110 utilizing cryoprobes 112, krypton gas
is used as the compressed gas. Use of krypton gas instead of argon
enables efficient cooling of cryoprobes 112 at lower pressures than
those required for efficient cooling utilizing argon gas. Krypton
gas enables efficient cooling at pressures in the neighborhood of
2,500 PSI, considerably lower than the pressures required for
argon. Consequently, cryosurgery systems designed and constructed
to be used with compressed krypton rather than compressed argon
present various advantages, including relatively simplicity of
construction and convenience of use.
[0125] In prior art cryosurgery systems compressed gas used for
cooling a cryoprobe is typically subsequently vented to atmosphere
rather than being recovered and recycled. Krypton gas, however, is
expensive, and cannot be conveniently and economically used in such
a prior art system. Thus a preferred embodiment of a compressed gas
utilization system according to the present invention, wherein
compressed gas utilizing application 42 is cryosurgery application
110, the embodiment further incorporating optional gas recycling
module 118, enables efficient and economical use of compressed
krypton in a cryosurgery application, thereby constituting a
further significant improvement over prior art.
[0126] Thus, according to another aspect of the present invention
there is provided a method for cryosurgery involving in situ
compression of gas. The method according to this aspect of the
invention is effected by using a first in situ gas compressor to
compress a gas, thereby transforming the gas into a first
compressed gas at a first gas pressure, transferring the first
compressed gas at the first gas pressure from the first gas
compressor to a cryoablation apparatus which utilizes the first
compressed gas at the first gas pressure, and using the
cryoablation apparatus to perform cryoablation.
[0127] According to yet another aspect of the present invention
there is provided a method for cryosurgery, involving in situ
compression of gas and further providing for re-compression and
re-utilization of the gas. The method according to this aspect of
the invention is effected by using a first in situ gas compressor
to compress a gas, thereby transforming the gas into a first
compressed gas at a first gas pressure, transferring the first
compressed gas at the first gas pressure from the first gas
compressor to a cryoablation apparatus which utilizes the first
compressed gas at the first gas pressure, using the cryoablation
apparatus to perform cryoablation, thereby creating a decompressed
gas at a second gas pressure, transferring the depressurized gas at
the second gas pressure either to the first gas compressor or to a
second gas compressor for recompression and reuse, and
recompressing and reusing the depressurized gas.
[0128] Still further advantages of a compressed gas utilization
system according to the present invention may be particularly noted
in preferred embodiments wherein gas compression apparatus 104 is a
bi-pump 18, bi-pump 18 being a gas compression apparatus according
to the present invention.
[0129] Use of bi-pump 18 enables to supply compressed gas at a
continuous, even, selected pressure to compressed gas utilizing
application 42, irrespective of pressure levels in gas sources 100.
Use of bi-pump 18 further enables utilizing all or substantially
most of a gas supplied in internal or external gas cylinders or
other containers used as gas sources 100. Use of bi-pump 18
presents the further advantage that bi-pump 18 is not a rapidly
reciprocating pump, therefore requires no lubrication and does not
risk contamination of compressed gas by volatile lubricating
materials.
[0130] Thus, according to another aspect of the present invention
there is provided a method for supplying a compressed gas to a
compressed gas utilizing application, utilizing a fixed-volume
container having a hollow, and a moveable element subdividing the
hollow into a first variable-volume portion and a second
variable-volume portion. The method according to this aspect of the
invention is effected by introducing a gas into the first
variable-volume portion of the hollow during a first phase of
operation, then introducing a hydraulic and/or pneumatic fluid
under pressure into the second variable-volume portion of the
hollow during a second phase of operation, thereby increasing a
volume of the second variable-volume portion by moving the moveable
element, thereby consequently decreasing a volume of the first
variable-volume portion and compressing a gas contained therein,
and transferring the compressed gas during the second phase of
operation from the first variable-volume portion of the hollow to a
compressed gas utilizing application.
[0131] Compressed gas delivery module 108 may include various
mechanisms such as valves, one-way valves, pressure re, dryers,
filters and measuring devices for temperature and pressure, for
managing the delivery of compressed gas to compressed gas utilizing
application 42, according to methods well known in the art.
[0132] In a preferred embodiment presented in FIG. 6, compressed
gas delivery module 108 further includes control elements for
managing gas compression. A control unit 130 receives information
from application feedback element 132. In the case a preferred
embodiment in which compressed gas utilizing application 42 is a
cryosurgery system 110, application feedback element 132 is
plurality of thermal sensors 133, reporting on temperatures within
various parts of cryosurgery application 110, such as within
cryoprobes 112. Other optional sensors included in feedback element
132 are a pressure sensor 135 and a mass flow sensor 137.
[0133] Control unit 130 also receives information from internal
sensors 136, which typically include pressure sensors and other,
e.g., temperature sensors.
[0134] Control unit 130 also receives information and commands from
an optional command console 134 for receiving commands from a user,
and from optional remote command module 136, which is a data source
such as an infrared remote control unit or other telecommunications
device.
[0135] Control unit 130 optionally includes a processor 140 and
memory 142, used to coordinate and control various parts of the
system. In a preferred embodiment, processor 140 is operable to
control gas compression and gas flow according to a set of
programmed instructions stored in memory 142. Output from control
unit 130 goes to control elements of gas delivery control system
108, such as valves controlling flow of gas. In a preferred
embodiment utilizing bi-pump 18, output from control until 130 also
goes to control elements of fluid pressurizer 33 of bi-pump 18, for
controlling the output pressure of fluid pressurer 33 and thereby
controlling a compressed gas pressure of a compressed gas supplied
by bi-pump 18 through compressed gas manifold 106 to compressed gas
delivery module 108.
[0136] Yet another embodiment of a compressed gas utilization
system according to the present invention is presented by FIG. 7.
In this preferred embodiment, gas source 100 and bi-pump 18 are
combined into a single element, a rechargeable bi-pump 150. In a
first phase of operation, rechargeable bi-pump 150 is disconnected
from fluid pressurizer 33 and from compressed gas manifold 106, and
is typically transported to a source of medium pressure gas, such
as an industrial gas supply source, where rechargeable bi-pump 150
is recharged with medium pressure gas in much the same way that
classical gas cylinders are recharged with compressed gas.
[0137] In a second phase of operation, recharged rechargeable
bi-pump 150 is re-connected to fluid pressurizer 33 and to gas
output manifold 106. Fluid pressurizer 33 then applies pressure to
pressurizing fluid 32, as described hereinabove, further
pressurizing gas in gas portion 24 of rechargeable bi-pump 150,
raising the pressure of a gas contained therein up to a pressure
required by compressed gas utilizing application 42. Compressed gas
is then supplied through gas output manifold 106 and gas delivery
control module 108 to compressed gas utilizing application 42.
[0138] The embodiment of FIG. 7 has several advantages over prior
art, in particular the advantage that rechargeable bi-pump 150 can
be charged to medium pressure at an industrial gas supply source,
yet can supply high pressure gas to compressed gas utilizing
application 42. The embodiment presents the further advantage that
substantially all the gas supplied in a charged rechargeable
bi-pump 150 can be delivered at high pressure to compressed gas
utilizing application 42, in distinct contrast to prior art systems
in which a substantial portion of the gas supplied in a traditional
gas supply cylinder or similar container cannot be so used.
Further, the embodiment of FIG. 7 presents the additional advantage
of simplicity.
[0139] Yet, the embodiment of FIG. 7 does present a disadvantage,
in that rechargeable bi-pump 150 must contain sufficient gas to
effect the entire operation of compressed gas utilizing application
42, or else operation of compressed gas utilizing application 42
must be interrupted while an emptied rechargeable bi-pump 150 is
replaced by a recharged rechargeable bi-pump 150.
[0140] FIG. 8 presents an alternative construction of another
preferred embodiment of the present invention, one which allows for
continuous operation of compressed gas utilizing application 42. In
this embodiment gas input manifold 102 supplies gas to a plurality
of bi-pumps 18, represented in FIG. 8 by bi-pumps 18a and 18b. Gas
input manifold 102 supplies gas to bi-pumps 18a and 18b through
one-way filters 152 which allow gas to flow from gas input manifold
102 towards bi-pumps 18a and 18b, but do not allow gas to flow from
bi-pumps 18 towards gas input manifold 102. Control unit 130 of gas
delivery module 108 controls fluid pressurizers 33a and 33b in such
a manner that when bi-pump 18a is in its first phase of operation
bi-pump 18b is in its second phase of operation, and vice
versa.
[0141] Thus, during a first period, bi-pump 18a is in a first phase
of operation, during which pressurizing fluid 32a in fluid portion
26a is not under pressure, and is indeed allowed to drain from
bi-pump 18a into fluid pressurizer 33a. Gas pressure from gas input
manifold 102, under pressure from at least one gas source 100,
exerts pressure on moving partition 18a, causing gas portion 24a to
expand and allowing gas portion 24a to fill with gas from gas input
manifold 102. Movement of moveable element 28a also causes or
assists pressurizing fluid 32a to drain from fluid portion 26a.
Also during this first period, bi-pump 18b is in its second phase
of operation, during which pressurizing fluid 32b is supplied by
fluid pressurizer 33b under pressure, compressing gas in gas
portion 24b, which is then supplied through gas output coupling 40b
to output gas manifold 106 and thence to compressed gas delivery
module 108 and thence to compressed gas utilizing application
42.
[0142] During a second period, the roles of bi-pump 18a and of
bi-pump 18b are reversed. Bi-pump 18a enters into its second phase
of operation, fluid pressurizer 33a pressurizes pressurizing fluid
32a, thereby compressing a gas in gas portion 24a of bi-pump 18a.
Compressed gas from gas portion 24a is supplied through gas output
coupling 40a to gas output manifold 106 and then to compressed gas
delivery module 108 and thereafter to compressed gas utilizing
application 42. Also during this second period, bi-pump 18b, which
was partially or completely emptied of gas during the first period,
is refilled: pressure from fluid pressurizer 33b is relaxed,
pressurizing fluid 32b is allowed to drain from fluid portion 26b
of bi-pump 18b, and the relaxed pressure in fluid portion 24b
allows gas pressure from input gas manifold 102 to move moveable
element 28b, expanding gas portion 24b and filling gas portion 24b
with gas, while assisting in draining pressurizing fluid 32b from
fluid portion 26b.
[0143] Alternating first periods and second periods enables the
system of FIG. 8 to provide a continuous supply of pressurized gas
to compressed gas utilizing application 42. In the first period
bi-pump 18a fills with gas while bi-pump 18b supplies compressed
gas for compressed gas utilizing application 42, then in the second
period bi-pump 18b fills with gas while bi-pump 18a supplies
compressed gas for compressed gas utilizing application 42. The
process then repeats, and can be repeated indefinitely, so long as
a gas source 100 is available to supply gas to gas input manifold
102. An external or internal gas cylinder or other gas supply
container can supply gas as many as several times to fill a bi-pump
18, the gas being supplied each time at somewhat lower pressure as
the supply cylinder gradually empties. Moreover multiple gas
sources 100, multiple gas supply cylinders for example, may be
connected to gas input manifold 102, hence it is possible to
replace an empty gas source 100 such as an empty gas supply
cylinder with a full gas source 100 such as a charged gas supply
cylinder, without interrupting a flow of gas from at least one gas
supply source 100 to gas input manifold 102. Thus, the embodiment
of FIG. 8 enables continuous gas compression and continuous supply
of compressed gas to compressed gas utilizing application 42.
[0144] It is appreciated that certain features of the invention,
which are, for clarity, described in the context of separate
embodiments, may also be provided in combination in a single
embodiment. Conversely, various features of the invention, which
are, for brevity, described in the context of a single embodiment,
may also be provided separately or in any suitable
subcombination.
[0145] Although the invention has been described in conjunction
with specific embodiments thereof, it is evident that many
alternatives, modifications and variations will be apparent to
those skilled in the art. Accordingly, it is intended to embrace
all such alternatives, modifications and variations that fall
within the spirit and broad scope of the appended claims.
* * * * *