CO.sub.2 Snow Forming Header With Triple Point Feature

1. Field of the Invention

The instant invention relates to an improved apparatus and method for forming CO.sub.2 snow within a tank provided therefor and to be contained within insulated shipping containers, railway cars, vehicle bodies and even stationary containers. The instant apparatus is somewhat more efficient than the apparatus disclosed in my co-pending U.S. application Ser. No. 702,888 in that the liquid CO.sub.2 discharged from opposing nozzles is supplied to the latter through a header pipe disposed midway between and in alignment with the opposing nozzles thereby enabling the liquid CO.sub.2 to be chilled substantially to the triple point temperature (approximately minus 69 degrees F.) immediately before the liquid CO.sub.2 under pressure is expanded by discharge from the opposing nozzles.

2. Description of Related Art

Various different forms of apparatus heretofore have been provided for forming CO.sub.2 snow within a container therefor by the discharging of liquids CO.sub.2 under pressure into such a container through conventional snow forming nozzles.

Various different forms of CO.sub.2 snow forming devices heretofore have been provided such as those disclosed in U.S. Pat. Nos. 2,475,755, 3,807,187, 4,111,362, 4,367,511, 4,381,649 and 4,462,423. However, these previously known forms of CO.sub.2 snow forming devices, for the most part, are not primarily concerned with forming the maximum amount of CO.sub.2 snow from a given quantity of liquid CO.sub.2.

Further, although my prior U.S. Pat. No. 4,381,649 discloses a means by which liquid CO.sub.2 to be discharged under pressure from snow forming nozzles is chilled to approximately the triple point temperature, the means by which this previous chilling of the liquid CO.sub.2 immediately prior to its expansion by being discharged from snow forming nozzles is cumbersome and requires the use of an eutectic solution within a tank of considerable volume.

Under substantially ideal conditions it is generally accepted that the formation of an amount of CO.sub.2 snow equivalent to 46% of the weight of liquid CO.sub.2 utilized to form that snow is the maximum amount of snow that may be formed from a given quantity of liquid CO.sub.2. Accordingly, a need exists for a means by which the forming of CO.sub.2 snow is rendered more effective so that a higher percentage in weight of CO.sub.2 snow for a given weight quantity of liquid CO.sub.2 used to form that snow may be obtained.

The CO.sub.2 snow forming header of the instant invention utilizes an apparatus by which CO.sub.2 snow can be produced with the weight of the snow equalling more than 54% of the weight of the liquid CO.sub.2 utilized to form that snow. This actually represents an increase of greater than 17% in the weight of CO.sub.2 snow being formed from a given quantity of liquid CO.sub.2. Accordingly, considerable savings in materials as well as time can be realized through the utilization of the instant invention.

The use of liquified carbon dioxide for refrigerating shipping containers is generally limited to containers in which cooling or moderately low freezing temperatures are required and the liquified carbon dioxide is, in most cases, utilized to form carbon dioxide snow which is approximately minus 69 degrees F. at the triple point temperature of 75 pounds per square inch absolute, but which drops from minus 69 degrees F. to minus 109 degrees F. at atmospheric pressure. Further, CO.sub.2 snow is conventionally formed by discharging chilled liquid carbon dioxide from spray nozzles. In such instance, the liquid carbon dioxide is supplied to the spray nozzles at approximately zero degrees F. with the result that one pound of liquid carbon dioxide will yield approximately 0.40 to 0.45 pounds of carbon dioxide snow. However, if the temperature of the liquid carbon dioxide can be maintained at the triple point temperature, one pound of liquid carbon dioxide will yield approximately 0.46 to 0.51 pounds of carbon dioxide snow. Further, it has been found that if, instead of merely discharging liquified carbon dioxide from snow forming nozzles into the ambient atmosphere or onto a chilled surface, a pair of nozzles are disposed in spaced opposing relation and have liquid CO.sub.2 supplied thereto at approximately 300 psi, the simultaneous discharge of liquified CO.sub.2 from the nozzles, each toward the other with the spacing between the outlet ends of the nozzles being approximately 121/2 inches the production of CO.sub.2 snow from a given quantity of liquified CO.sub.2 is even further increased.

The main object of this invention is to provide an improved method of more efficiently producing carbon dioxide snow for cooling the interiors of insulated containers.

Another object of this invention is to provide a method and apparatus in accordance with the immediately preceding object and wherein the structure required to carry out the method is maintained extremely simple and thus quite inexpensive.

A still further object of this invention is to provide a method and apparatus for converting liquid carbon dioxide to carbon dioxide snow wherein the production of the desired amount of carbon dioxide snow may be accomplished at a rapid rate.

Another object of this invention is to provide a CO.sub.2 snow forming apparatus which will be capable of forming a quantity of CO.sub.2 having a weight value considerably greater than 50% of the weight value of the liquid CO.sub.2 used to form that snow.

A final object of this invention to be specifically enumerated herein is to provide a method and apparatus in accordance with the preceding objects and which will conform to conventional forms of manufacture, be of simple construction and easy to use so as to provide a method and apparatus which will be economically feasible and extremely dependable.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part thereof, wherein like numerals refer to like parts throughout.

FIG. 1 is a side elevational view of a tank in which liquid CO.sub.2 is discharged under pressure through snow forming nozzles in order to form CO.sub.2 snow within the tank and with portions of the tank being broken away and illustrated in vertical section;

FIG. 2 is an enlarged fragmentary horizontal sectional view taken substantially upon the plane indicated by the section line 2--2 of FIG. 1;

FIG. 3 is an enlarged fragmentary vertical sectional view taken substantially upon the plane indicated by the section line 3--3 of FIG. 2;

FIG. 4 is an enlarged vertical sectional view illustrating the type of nozzle by which liquid CO.sub.2 is discharged in order to form CO.sub.2 snow; and

FIG. 5 is a fragmentary perspective view of a modified form of manifold assembly by which liquid CO.sub.2 may be utilized to produce CO.sub.2 snow in accordance with the present invention.

With reference now more specifically to the drawings, the numeral 10 generally designates a vented substantially closed tank constructed of good heat conducting material and in which liquid CO.sub.2 snow 12 is to be formed. The tank 10 includes opposite end walls 14 and opposite side walls 16 as well as top and bottom walls 18 and 20. The top wall 18, one of the side walls 16 or portions of the side walls 16 may be removed in order to gain access to the interior of the tank for maintenance purposes, should maintenance become necessary.

The tank 10 includes three horizontal U-shaped manifolds 22 mounted therein and each of the manifolds 22 includes a pair of opposite side tubes 24 and 26 interconnected at one pair of corresponding ends by an end tube extending therebetween and communicating therewith. The end tube 28 includes a T-fitting 30 connected therein and a supply pipe 32 has its discharge end supported from an opening into the T-fitting 30, the inlet end of the supply pipe 32 having the discharge end of a supply hose 34 removably coupled thereto. The inlet end of the supply hose 34 is suitably connected to a valved discharge (not shown) of a suitable supply of liquid CO.sub.2 under pressure.

From FIGS. 2 and 4 of the drawings it may be seen that each of the tubes 24 and 26 includes a pair of tubular nozzles 36 spaced longitudinally therealong. Each of the nozzles 36 includes a diametrically reduced inlet end 38 and a larger diameter outlet end 40. The inlet ends 38 are contoured to abut against the side of the corresponding pipe and are secured thereto in any convenient manner such as by welding 42. In addition, each of the pipes 24 and 26 includes a small diameter outlet port 44 formed therein opening into the inlet end 38 of the corresponding nozzle 36. The inlet ends 38 are approximately 5/8 inch in diameter and 3/4 inch long and the outlet ends are 3/4 inch in diameter and approximately 4 inches long. Further, the outlet ports 44 are approximately 5/32 inch in diameter. Also, it will be noted from FIGS. 2 and 3 of the drawings that corresponding nozzles 36 carried by the pipes 24 and 26 are aligned with and directly oppose each other, the spacing between the opposing outlet ends 40 being approximately 121/2 inches.

The nozzles 36 are operative to form the CO.sub.2 snow 12 within the tank 10 as liquid CO.sub.2 is supplied to the manifold 22 under pressure from the supply hose 34 and the supply pipe 32. The liquid CO.sub.2 is discharged into the nozzles 36 through the outlet ports 44. The liquid CO.sub.2 is supplied to the hose 34 at approximately 300 psi and the discharge of CO.sub.2 through the opposing outlet ports 44 and nozzles 36 results in the spray jets 46 from the nozzles 36, see FIG. 3, directly opposing each other.

However, the supply pipe 32 extends along a straight path connecting the points at which the spray discharges from the nozzles 36 impinge with each other. Accordingly, the CO.sub.2 snow being formed as a result of operation of nozzles 36 not only impinges with the snow being discharged from the opposite nozzles but also impinges upon the discharge end of the supply pipe 32. Thus, the liquid CO.sub.2 passing through the supply pipe 32 is chilled to approximately the triple point temperature of the liquid CO.sub.2 at 300 psi, the size of the ports 44 and the number of pairs of nozzles 36 disposed along the supply pipe 32 as well as the pressure of the liquid CO.sub.2 passing through the supply pipe 32 and thus supplied to the ports 44 all functioning together to accomplish the desired chilling of the liquid CO.sub.2 within the supply pipe 32 to approximately the triple point temperature of the liquid CO.sub.2 therein at 300 psi.

While some of the expansion of the liquid CO.sub.2 from the nozzles results in a small portion of the liquid CO.sub.2 being directly transformed into CO.sub.2 gas, by discharging the jets 46 not only directly toward each other in the manner illustrated in FIG. 3 but also upon the supply pipe 32 and with the nozzles spaced approximately 121/2 inches apart, less of the liquid CO.sub.2 is transformed directly into CO.sub.2 gas with the result that the CO.sub.2 snow 12 formed within the tank has a weight equal to more than 54% of the weight of the liquid CO.sub.2 utilized to form the snow. Actually, by using the arrangement of the instant invention more than 54% of the weight of the liquid CO.sub.2 used is transformed into snow, whereas conventional methods of forming CO.sub.2 snow result in the snow being formed weighing approximately only 46% of the weight of the liquid CO.sub.2 utilized to form that snow. This of course translates into a greater than 17% increase in the amount of CO.sub.2 snow which may be formed from a given amount of liquid CO.sub.2.

With attention now invited more specifically to FIG. 5 of the drawings, there may be seen a modified form of manifold referred to in general by the reference numeral 22' and which is generally U-shaped in configuration and includes a pair of tubular legs 24' and 26' corresponding to the tubes 24 and 26. The ends of the legs 24' and 26' remote from the end tube 28' corresponding to the end tube 28 are capped as at 27', the tubes 24 and 26 being capped as at 27.

Only one pair of nozzles 36' are supported from the legs 24' and 26' and discharge end of the supply of pipe 32' corresponding to the supply pipe 32 opens into a T-fitting 30' corresponding to the T-fitting 30. Therefore, it may be seen that the manifold 22' is substantially identical to the manifold 22, except that the manifold 22' includes only one pair of nozzles 36' as opposed to two pairs of nozzles 36.

With attention again invited to FIGS. 2 and 3, it may be seen that the mid-portions of the tubes 24 and 26 disposed between the corresponding nozzles 36 have a brace 50 extending and secured therebetween. The brace 50 as well as a similar brace 50' shown in FIG. 5, is needed to prevent the jet action of the high pressure discharge of liquid CO.sub.2 through the ports 44 from generating sufficient thrust to spread the free end portions of the tubes 24 and 26 apart and the nozzles 36 to be shifted out of direct opposing relation with each other.

From FIG. 3 of the drawings it may be seen that the spray jets 46 from the outlet ends 40 impact in opposing relation in an area 54 spaced centrally between the outlet ends 40 and that the supply of pipe 32 includes an intermediate length portion thereof passing centrally through the area 54.

Accordingly, not only is an increase in the CO.sub.2 snow produced realized by the directly opposing impacting of the discharges 46 in the area 54 but also by the cooling of the intermediate portion of the supply of pipe 32 which passes centrally through the area 54, this cooling of the intermediate portion of the supply of pipe 32 serving to chill the liquid CO.sub.2 passing through the supply of pipe 32 to substantially the triple point temperature of liquid CO.sub.2 at 300 psi.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.