GB1599533A

GB1599533A - Liquid dispensing apparatus

Info

Publication number: GB1599533A
Application number: GB12988/78A
Authority: GB
Original assignee: Frigitronics Inc
Current assignee: Frigitronics Inc
Priority date: 1977-04-04
Filing date: 1978-04-03
Publication date: 1981-10-07
Also published as: ES465743A1; CA1062142A; DE2758893A1; JPS6133587B2; FR2386773A1; IT1106975B; FR2386773B1; JPS53122921A; IT7867098A0; DE2758893C2; BR7800465A; MX146492A

Description

(54) IMPROVEMENTS IN OR RELATING TO LIQUID DISPENSING APPARATUS (71) We, FRIGITRONICS OF CONN., INC., a corporation organised under the laws of the State of Connecticut, United States of America, of 770 River Road, Shelton, Connecticut, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement; Liquid nitrogen is commonly used by dermatologists and other medical practitioners for the treatment of various tumors and lesions. Such treatment is well accepted and has been utilized for a number of years. The methods of application vary widely. Some physicians, for example, apply the liquid nitrogen with a cotton swab. Others utilize a more sophisticated approach, using specially designed selfpressurizing flasks such as those shown in United States patents 3,702,114 and 3,739,956.

The latter method, while effective, is somewhat limited by the relatively small volume of liquid nitrogen which can be contained in the flask.

Furthermore, the self-pressurizing nature of the flask means that pressure drops considerably upon use so that sustained dispensing of the liquid nitrogen cannot be achieved.

In many larger liquid nitrogen systems, such as those for use in neurosurgery, the pressure problem has been overcome by the insertion of heaters into the liquid nitrogen containers.

This has the obvious disadvantage of requiring an external power supply and also of introducing additional electrical circuitry into the operating room atmosphere. Still another problem encountered with these larger capacity liquid nitrogen systems, is that the valves controlling the liquid nitrogen flow are highly susceptible to freezing and become inoperable.

There are also certain circumstances wherein it would be highly desirable to be able to transport a liquid nitrogen treatment facility into the field. For example, liquid nitrogen has been used quite successfully by veterinarians for the treatment of certain diseases of cattle.

To be successfully used for this purpose, the apparatus should be light in weight, of relatively high capacity, and not require any external power supply.

Other features, which are difficult to achieve in prior art systems but are highly desirable, are simple regulation of the liquid nitrogen discharge velocity, accurate control with abrupt termination of liquid nitrogen flow when desired, and a pulsed spray rather than a continuous stream.

A pulsed spray reduces dripping of sprayed liquid and improves visibility at the site.

Accordingly, it is an object of the present invention to provide a simplified apparatus for dispensing a liquid cryogen. Other objects are to provide such apparatus which does not require an electrical power supply; wherein valving is not exposed to liquid cryogen; which may have a large capacity of cryogen; which may have sustained dispensing ability; which may permit either continuous flow or pulsed flow; and which may have improved accuracy of control.

The present invention consists in apparatus for dispensing a liquid, which comprises a pressure vessel containing a quantity of pressurizing liquid having a boiling point below ambient temperature and a vapor space, a ballast chamber having its interior in heat transfer relationship with the ambient atmosphere, a first transfer conduit having a first end positioned within said pressure vessel below the normal level of pressurizing liquid therein and a second end positioned in said ballast chamber, a supply vessel containing a quantity of liquid to be dispensed, a liquid dispensing line having a first end positioned within said supply vessel below the normal level of liquid therein and a second, discharge, end at a liquid utilization device, and means for selectively interconnecting the interior of said ballast chamber with the interior of said supply vessel to pressurize said supply vessel and dispense liquid therefrom.

In order that the present invention may be more readily understood, reference will now be made to the accompanying drawings, in which: Figure 1 illustrates apparatus constructed in accordance with the present invention in partial cross section to illustrate its internal construction; Figure 2 is a schematic diagram of the apparatus of Figure 1 showing the apparatus in its static mode; and Figure 3 is an illustration similar to Figure 2, showing the apparatus in its dispensing mode.

With particular reference to Figure 1, there is illustrated an apparatus in accordance with the present invention, comprising a pressure vessel 10 and a liquid storage vessel 12, interconnected through a ballast chamber 14, to supply a spray gun 16 through an insulated delivery line 18. Delivery line 18 maybe con- structed in any of avariety of ways. One suitable form of construction is disclosed in U.S. Patent 3,907,339. Pressure vessel 10 and storage vessel 12 are substantially identical and, accordingly, similar parts thereof will be assigned similar reference numerals. Each is a conventional Dewar comprising an internal flask 20 and an outer casing 22 defining a vacuum space 24 therebetween.The mouth 26 of each vessel is closed by a conventional cap assembly 28, having inlet port 30 and outlet port 32. The pressure vessel 10 encloses a cryogenic liquid 34 and a vapor space 36. Similarly, the storage vessel 12 encloses a cryogenic liquid 38 and a vapor space 40. In the described embodiment, the cryogenic liquids 34 and 38, are both liquid nitrogen. However, it is not essential that the same liquid be enclosed in each of the vessels. The inlet port 30 of vessel 10 may be connected through a pressure relief valve 42 to a pressure vent valve 44 and a vent 46.

The ballast chamber 14, which interconnects the vessels 10 and 12, is exposed to the temperature of the ambient atmosphere and is constructed of a material, such as aluminium, having relatively high heat conductivity. A line 48 extends from within the pressure vessel 10 and below the level of the liquid 34, to within the interior of the ballast chamber 14. A pressure gauge 50 permits monitoring of the internal pressure ofthe chamber 14.

A control line 52 extends from within the ballast chamber 14, and passes between the outer sheath 54 and inner tube 56 of the delivery line 18 to one port of a three waxy valve 58 mounted in the pistol grip 60 of spray gun 16, where it may be actuated by a trigger 62.

Another line 64 extends from the three way valve 58, and beneath sheath 54, to the operating port of a piloted three-way main valve 66.

A pressure line 68 extends from the ballast chamber 14 and passes through a pressure regulator 70 and main valve 66, to the inlet port 30 of storage vessel 12. Intermediate the pressure regulator 70 and main valve 66, there is mounted a pressure gauge 72.

A dip tube 74 extends from below the level of the liquid 38 in the storage vessel 12, and connects to the inner tube 56 of the delivery line 18 and into fluid flow communication with a nozzle 76 on spray gun 16. It is to be understood that the apparatus of this invention is not limited to use with a gun for spraying liquid nitrogen. The open nozzle, for example, could be replaced by a cryosurgical probe having suitable means for venting exhaust gas.

The operation of the apparatus of this invention will now be explained, with particular reference to the schematic diagrams of Figures 2 and 3. In these diagrams, elements similar to those illustrated in Figure 1 are given similar reference numerals. In these illustrations, the three-way valves 58, 66, are shown as substantially identical slide valves. Three-way valve 58 is illustrated as including a housing 78 and an inner slide 80 operable by the trigger 62 against the force of a spring 82. The inner slide 80 defines a pair of passages 84, 86, which are alignable with ports 88,90,92 in the housing 78. Main valve 66 is similarly constructed and the parts are given similar reference numerals. The primary distinction between valves 66 and 58 is that main valve 66 is operated pneumatically within the housing 78 by pressure exerted through line 64.

Figure 2 illustrates the apparatus in its static condition. In this condition liquid nitrogen exists in the pressure vessel 10, the vapor space above the liquid being filled with nitrogen gas.

Nitrogen gas alone exists within the ballast chamber 14, which is at ambient atmospheric temperature considerably above the boiling point of liquid nitrogen. The control line 52 and the pressure line 68 are both snubbed off by the respective three-way valves 58, 66 and, accordingly, the pressures within the pressure vessel 10 and the ballast chamber 14 are equalized. The liquid storage vessel 12 also contains liquid nitrogen, but the vapor space above the liquid is vented to atmosphere through pressure line 68 and passage 84 of main valve 66.

In order to dispense liquid nitrogen from the apparatus, the trigger 62 is pressed, causing actuation of three-way valve 58 to the condition illustrated in Figure 3. The reservoir of pressurized gas within the ballast chamber 14 is now connected through the passage 86 of valve 58 and through line 64 to main valve 66, which is thereby actuated to the illustrated position. In this position, the gas within the ballast chamber 14 is also supplied through the pressure regulator 70, and the passage 86 of main valve 66 to the vapor space within the liquid storage vessel 12. The increased pressure causes liquid nitrogen to be forced outwardly through tube 56 to the spray nozzle or other device. The pressure within ballast chamber 14 is self-replenishing. As the gas pressure therein is released, the imbalance is the pressures within pressure vessel 10 and chamber 14 causes additional liquid nitrogen to pass into the chamber 14 via line 48. This liquid nitrogen immediately flash vaporizes upon entering the chamber 14 thereby continually replenishing the pressure as required. Upon release of the trigger 62, the valves 58,66, return to the positions illustrated in Figure 2. This immediately vents the storage vessel 12 to atmosphere through passage 84 of main valve 66, thereby immediately terminating the flow of liquid nitrogen.

The pressure regulator 70 serves an important function in permitting sustained pulsating flow of cryogen from a spray nozzle. This is a valuable feature as it prevents liquid dripping or running from the operative site and also provides better visibility of the site. The pulsing is caused by the formation of bubbles of gas in the cryogenic liquid due to heat absorbed as it flows through the delivery line 18. A higher flow rate exceeds the heat transfer capability of the delivery line insulation, resulting in a continuous liquid stream being ejected. A lower flow rate would result in vaporization of a greater quantity of cryogen with increased gas and decreased liquid delivery. The pressure regulator 70 permits the liquid flow to be precisely matched to the heat transfer through the delivery line 18 for optimal pulsing action.

It is believed that the many advantages of this invention will now be apparent to those skilled in the art. One such advantage is that no valve throughout the apparatus is exposed to liquid nitrogen, thus obviating the freeze up problem encountered in many prior art designs.

Furthermore, the apparatus operates completely without any electrical power requirement, thereby increasing its safety and making it practical for portable field work.

In the foregoing description, the apparatus has been described as operable with liquid nitrogen. However, it will be understood that other fluids may be employed. In fact, two different liquids may be utilized, a low boiling (below ambient) temperature fluid within the pressure vessel 10 for providing the motive force, and any other desired liquid within the storage vessel 12 which is to be dispensed. Also, the ballast chamber has been described as a relatively large volume chamber. Other configurations such as, a coiled metal tube could be utilized. Furthermore, the apparatus is not limited to medical or surgical applications but may have other uses as well.

WHAT WE CLAIM IS: 1. Apparatus for dispensing a liquid, which comprises a pressure vessel containing a quantity of pressurizing liquid having a boiling point below ambient temperature and a vapor space, a ballast chamber having its interior in heat transfer relationship with the ambient atmosphere, a first transfer conduit having a first end positioned within said pressure vessel below the normal level of pressurizing liquid therein and a second end positioned in said ballast chamber, a supply vessel containing a quantity of liquid to be dispensed, a liquid dispensing line having a first end positioned within said supply vessel below the normal level of liquid therein and a second, discharge, end at a liquid utilization device, and means for selectively interconnecting the interior of said ballast chamber with the interior of said supply vessel to pressurize said supply vessel and dispense liquid therefrom.

2. Apparatus as claimed in Claim 1, wherein the pressurizing liquid is liquid nitrogen.

3. Apparatus as claimed in Claim 1 or 2, wherein the liquid to be dispensed is liquid nitrogen.

4. Apparatus as claimed in Claim 1, 2 or 3, wherein the interconnecting means comprises a pressure regulator for maintaining a preselected pressure within the supply vessel when the ballast chamber is interconnected with the supply vessel.

5. Apparatus as claimed in any one of the preceding claims, wherein the selective interconnecting means comprises a pressurizing conduit between the ballast chamber and the supply vessel, and means for selectively opening and closing said pressurizing conduit to fluid flow.

6. Apparatus as claimed in Claims 4 and 5 wherein the pressurizing conduit includes the pressure regulator.

7. Apparatus as claimed in Claim 5 or 6, wherein the opening and closing means comprises a main valve in the pressurizing conduit, and means for remotely actuating said main valve.

8. Apparatus as claimed in Claim 7, wherein the remote actuating means comprises a pilot valve, and a control line connected between the ballast chamber and the main valve through said pilot valve.

9. Apparatus as claimed in Claim 8, wherein the utilization device is a cryosurgical instrument and the pilot valve is mounted on said instrument.

10. Apparatus for dispensing a liquid substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. function in permitting sustained pulsating flow of cryogen from a spray nozzle. This is a valuable feature as it prevents liquid dripping or running from the operative site and also provides better visibility of the site. The pulsing is caused by the formation of bubbles of gas in the cryogenic liquid due to heat absorbed as it flows through the delivery line 18. A higher flow rate exceeds the heat transfer capability of the delivery line insulation, resulting in a continuous liquid stream being ejected. A lower flow rate would result in vaporization of a greater quantity of cryogen with increased gas and decreased liquid delivery. The pressure regulator 70 permits the liquid flow to be precisely matched to the heat transfer through the delivery line 18 for optimal pulsing action. It is believed that the many advantages of this invention will now be apparent to those skilled in the art. One such advantage is that no valve throughout the apparatus is exposed to liquid nitrogen, thus obviating the freeze up problem encountered in many prior art designs. Furthermore, the apparatus operates completely without any electrical power requirement, thereby increasing its safety and making it practical for portable field work. In the foregoing description, the apparatus has been described as operable with liquid nitrogen. However, it will be understood that other fluids may be employed. In fact, two different liquids may be utilized, a low boiling (below ambient) temperature fluid within the pressure vessel 10 for providing the motive force, and any other desired liquid within the storage vessel 12 which is to be dispensed. Also, the ballast chamber has been described as a relatively large volume chamber. Other configurations such as, a coiled metal tube could be utilized. Furthermore, the apparatus is not limited to medical or surgical applications but may have other uses as well. WHAT WE CLAIM IS:

1. Apparatus for dispensing a liquid, which comprises a pressure vessel containing a quantity of pressurizing liquid having a boiling point below ambient temperature and a vapor space, a ballast chamber having its interior in heat transfer relationship with the ambient atmosphere, a first transfer conduit having a first end positioned within said pressure vessel below the normal level of pressurizing liquid therein and a second end positioned in said ballast chamber, a supply vessel containing a quantity of liquid to be dispensed, a liquid dispensing line having a first end positioned within said supply vessel below the normal level of liquid therein and a second, discharge, end at a liquid utilization device, and means for selectively interconnecting the interior of said ballast chamber with the interior of said supply vessel to pressurize said supply vessel and dispense liquid therefrom.