| United States Patent | 3,889,488 |
| Maeda , et al. | June 17, 1975 |
Refrigerating apparatus
Abstract
A refrigerating apparatus having a tank for containing liquefied gas and a vibrator for vibrating the tank. Articles are fed to the tank from one side thereof, placed into the liquefied gas for refrigeration, sent to the other side by virtue of the vibration of the tank and taken out from the liquefied gas.
| Inventors: | Maeda; Hiroyuki (Nishinomiya, JA), Matsuda; Takuma (Kobe, JA) |
| Assignee: |
Osaka Gas Kabushiki Kaisha
(Osaka,
JA)
|
| Appl. No.: | 05/427,685 |
| Filed: | December 26, 1973 |
| Dec 27, 1972 [JA] | 48-940 | |||
| Current U.S. Class: | 62/218 ; 62/374; 62/378 |
| Current International Class: | F25D 3/11 (20060101); F25D 25/00 (20060101); F25D 25/04 (20060101); F25D 3/10 (20060101); G01F 23/24 (20060101); G01F 23/22 (20060101); F25b 041/04 () |
| Field of Search: | 62/63,64,374,375,378,380,218 |
| 3413818 | December 1968 | Pelmulder |
| 3558105 | January 1971 | Moritz |
| 3733839 | May 1973 | Waldin |
Assistant Examiner: Capossela; Ronald C.
Attorney, Agent or Firm:
What is claimed is:
1. A refrigerating apparatus comprising, in combination:
a. a tank for containing liquefied gas for refrigerating articles, said tank having an inlet end and an outlet end; and
b. means for advancing articles as placed in the liquefied gas within said tank from said inlet end to said outlet end to remove advanced articles from the liquefied gas, said means for advancing articles including
1. an article carrying member disposed at least partially beneath said liquefied gas in said tank and having a conveying surface for conveying such articles as may be placed thereon, said conveying surface extending substantially over the entire length of the distance between said inlet end and said outlet end and having at least a portion toward said outlet end gradually rising above a level of the liquefied gas within said tank, and
2. vibrating means moving said tank from outside thereof to move said conveying surface back and forth along a path, which is inclined upwardly toward said outlet end, for flinging the articles upwardly and toward said outlet end;
whereby articles introduced into the tank at the inlet end are moved toward the outlet end in a series of motions of the conveying surface which flings the articles upwardly out of the liquefied gas and forwardly toward the outlet end a number of times and finally to the outlet end.
2. An improved apparatus as set forth in claim 1, wherein said tank is formed of a tubular body having a generally horizontal longitudinal axis and said article carrying member is the interior bottom wall of said tubular body, said tubular body being substantially closed except for an opening at said inlet end for feeding the articles into the interior thereof and another opening at said outlet end for discharging the articles therefrom, the apparatus further comprising at least one containing member for storing the articles to be fed into the interior of said tubular body, means for feeding the articles from said containing member into the liquefied gas within said tubular body at an approximately constant rate, liquefied gas supplying means for supplying the liquefied gas to said interior of said tubular body, a controller for controlling said liquefied gas supplying means to keep the liquid level of the liquefied gas within said tubular body substantially constant and conduit means for supplying the gas from within said tubular body to said containing member and to said feeding means to cool the articles before they are fed into said tank.
3. An improved apparatus as set forth in claim 1, further comprising at least one containing member for storing the articles to be fed to said tank and means for feeding the articles from said containing member into the liquefied gas within said tank at an approximately constant rate.
4. An improved apparatus as set forth in claim 3, wherein said tank is substantially closed except for an opening for feeding in the articles at said inlet end, another opening for discharging the articles at said outlet end and conduit means for providing gas from said tank to said containing member and said feeding means to cool the articles before they are fed into said tank.
5. An improved apparatus as set forth in claim 1, further comprising means for supplying the liquefied gas to the interior of said tank and a controller for controlling the liquefied gas supplying means to keep the liquid level of the liquefied gas in said tank substantially constant.
6. An improved apparatus as set forth in claim 5, further comprising a sensor for detecting the liquid level of the liquefied gas to sense whether or not the liquid level is within a predetermined range based on a change in ambient temperature dependent on whether said sensor is immersed in the liquefied gas or not, said sensor being disposed within a tubular member whose upper end is exposed to an atmosphere having a temperature higher than the condensation temperature of the ambient gas thereof, and said tubular member having a lower end positioned below the liquid level of the liquefied gas within said tank.
BACKGROUND OF THE INVENTION
The present invention relates to a refrigerating apparatus comprising a tank for containing liquefied gas for refrigerating articles and conveying means by which the articles placed in the liquefied gas within the tank are conveyed through the liquefied gas from one side of the tank to the other side and the conveyed articles are then taken out from the liquefied gas.
Apparatuses for refrigerating articles by immersing them in a low-temperature liquefied gas such as Freon, liquefied carbonic acid, liquefied nitrogen or the like find versatile applications, for example, for refrigerating and freezing foodstuffs, for refrigerating plastic materials such as rubbers and plastics as pretreatment for crushing these materials and for sub-zero treatment of metals, inasmuch as immersion of articles in liquefied gas is advantageous in that both the sensible heat of liquefied gas and the latent heat due to vaporization of the gas can be utilized for the refrigeration of articles and further in that the thermal conductivity in the case of contact between liquid and solid is more than ten times higher than that involved in the contact between gas and solid, making it possible to effectively utilize expensive refrigerating energy and to achieve rapid refrigeration.
Further for efficient refrigeration of large quantities of articles through continuous operation, it has been practiced in the above-mentioned various applications to take out the articles from liquefied gas after they have been conveyed as immersed therein. The conveying means heretofore used or proposed for this purpose are belt conveyors, chain conveyors, roller conveyors and/or screw conveyors.
However, it is not too much to say that none of conventional apparatuses have proved very satisfactory for use on an industrial scale because of the following problems encountered:
1. Since the conveying means is in contact with liquefied gas with any of the conventional apparatuses, the conveying means is very likely to become inoperative due to freezing. For instance, freezing frequently takes place where the rotary shaft of roller conveyor or screw conveyor is supported on the bearing, where the belt or chain of belt conveyor or chain conveyor is in sliding contact with the guide rail or where the screw of screw conveyor is in sliding contact with the outer cylinder.
2. For the same reason as above, the conveying means undergoes marked thermal contraction, rendering the parts susceptible to damage and failure and consequently making it difficult to ensure trouble-free operation.
3. For the same reason as given under paragraph (1), the heat of friction caused by the conveying means is transferred to the liquefied gas, resulting in a waste of liquefied gas due to vaporization.
4. Since the conventional conveying means are all designed to convey articles generally at a constant velocity, gaseous films tend to be formed around the articles due to vaporization of liquefied gas, with the result that the refrigeration efficiency will be impaired.
5. In the any of the conventional apparatuses, not only a tank but also a conveying means must be refrigerated by liquefied gas in the initial stage of operation. Thus, component parts of the conventional apparatus to be refrigerated in the initial stage of operation are high in heat capacity so that there is waste of refrigerating energy in the initial stage of operation.
SUMMARY OF THE INVENTION
The present invention relates to a refrigerating apparatus comprising a tank for containing liquefied gas for refrigerating articles, conveying means for conveying the articles as placed in the liquefied gas within the tank from one side of the tank to the other side thereof to take out the conveyed articles from the liquefied gas, the apparatus being characterized in that the conveying means comprises a member disposed in the liquefied gas within the tank to carry the articles thereon and means for vibrating the tank and conveying surface from outside the tank in a direction along the article conveying direction and inclined with respect to the conveying surface, the article carrying member extending over the entire length of path of conveyance of the articles through the liquefied gas and having a gently slanting upper surface extending upward above the liquid level of liquefied gas within the tank toward the terminal end of the path of conveyance.
Technically, the present invention is characterized in that the tank in its entirety is vibrated from outside to convey articles through liquefied gas and to take out refrigerated articles thereform without permitting the liquefied gas to contact the article conveying means. Accordingly, the refrigerating apparatus of this invention has the following outstanding advantages:
1. The vibrating means which is disposed outside the tank is least affected by the temperature of low-temperature liquefied gas, this rendering the apparatus operable almost free from troubles owing to freezing and thermal contraction already described. Moreover, the heat to be generated by the operation of the vibrating means will hardly be transferred to the low-temperature liquefied gas to nearly obviate the foregoing objections such as waste of liquefied gas and impaired refrigerating efficiency which have conventionally been attributable to the heat of friction caused by the conveying means.
2. The articles are conveyed through the liquefied gas with frequently repeated intermittent motion at invariably varying high velocities relative to the liquefied gas. Consequently, although marked bubbling takes place around the articles due to the vaporization of liquefied gas caused by the heat of articles, the resulting gaseous films formed around the articles can be reduced in thickness as compared with conventional apparatuses or such gaseous films can be almost eliminated under favorable conditions, making it possible to effectively utilize satisfactory heat transfer between liquid and solid for efficient refrigeration as already described.
An object of this invention is to provide a refrigerating apparatus which is less susceptible to troubles during conveyance to be caused when the means for conveying articles to be refrigerated becomes refrigerated with liquefied gas.
Another object of this invention is to provide a refrigerating apparatus in which impaired heat transfer attributable to the vaporization of liquefied gas is remedied to make it possible to refrigerate articles rapidly and to thereby refrigerate articles in continuous operation and which is therefore compact relative to its ability.
Another project of this invention is to provide a refrigerating apparatus which is capable of preventing vaporization of liquefied gas due to the heat of friction caused by the operation of means for conveying articles to be refrigerated.
Another object of this invention is to provide a refrigerating apparatus which is designed to effectively utilize the refrigerating energy of expensive liquefied gas and which is therefore inexpensive to operate.
Still another object of this invention is to provide a refrigerating apparatus in which the component part to be refrigerated in the initial stage of operation are low in heat capacity so as to mitigate waste of refrigerating energy in the initial stage of operation.
Other objects and advantages of this invention will become apparatent from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic side elevation partly broken away and showing an apparatus in its entirety;
FIG. 2 is a view in section taken along the line II--II in FIG. 1; and
FIG. 3 is a view illustrating the mode of conveyance of articles.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Articles stored in a container 1 are supplied by a feeder 2 to a tank 3 through an inlet 4 upwardly open at one end of the tank 3 in an almost constant amount per unit hour. The tank 3 contains a liquefied gas 5 suitable to refrigerate the articles placed therein. As will be described later, the articles supplied to the tank 3 through the inlet 4 are conveyed through the liquefied gas 5 and discharged from the tank 3 through an outlet 6 open downward at the other end of the tank 3. The tank 3 is in the form of a cylindrical body 12 having a substantially horizontal longitudinal axis 7. The cylindrical body 12 includes a first tubular member 8 forming an inner wall surface and a second tubular member 9 forming an outer wall surface, the tubular members 8 and 9 being spaced apart and disposed coaxially. To impart to the wall of the cylindrical body 12 an ability to thermally insulate the interior space of the first tubular member 8, the space between the first and second tubular members 8 and 9 is filled with a suitable known insulating material and/or is reduced in pressure. Preferably, the space may contain a vacuum. The first tubular member 8 is gently inclined upward toward the outlet 6. To take out the articles in the liquefied gas 5 therefrom, the bottom portion of the first tubular member 8 is gently inclined upward as at 11 and extends upward above the liquid level of the liquefied gas 5 within the tank 3.
The cylindrical body 12 is mounted on a base 17 by three sets of support means 16 each comprising two inclined plate springs 13 and 14 substantially in parallel to each other and a coiled spring 15 stretchable approximately perpendicular to the plate springs 13 and 14. The plate springs 13 and 14 act to regulate the vibration of the cylindrical body 12, the cylindrical body 12 being rockable in one direction along its longitudinal axis 7. A crank shaft 18 mounted on the base 17 is driven by an electric motor 19 on the base 17 through pulleys 20, 21 and a belt 22. The crank shaft 18 is further connected to the cylindrical body 12 by a connecting rod 23 and shock absorber 24 comprising an elastic body as of hard rubber. Thus the electric motor 19 rocks the cylindrical body 12 in a direction along the direction of longitudinal axis 7, namely along the article conveying direction, the direction of rocking being inclined with respect to a horizontal plane.
By virtue of the rocking of the cylindrical body 12, the first tubular member 8 reciprocally moves with an amplitude of L in the directions of dot-line arrows in FIG. 3 to send the articles 25 forward in the direction of longitudinal axis 7 of the cylindrical body 12 (in the direction of solid-line arrow) as if throwing them away obliquely upward within the liquefied gas 5. Through repetition of such minute forward motion, the articles 25 are progressively sent from inlet 4 to outlet 6. Toward the outlet 6, the articles ascend the gently upwardly slanting surface 11, where the articles 25 are separated from the liquefied gas 5 and the articles refrigerated with the liquefied gas 5 are thereafter discharged from the outlet 6. Accordingly, if the articles 25 are supplied through the inlet 4 successively, the refrigerated articles 25 will be taken out from the outlet 6 in succession, hence efficient refrigeration. The refrigerated articles discharged from the outlet 6 are sent to a subsequent process such as crushing process by suitable conveying means (not shown), detailed description of which will be herein omitted.
One end of a pipe 26 connected to liquefied gas supply means (not shown) extends into the interior space of the first tubular member 8, whilst there is provided means 27 for detecting the liquid level of liquefied gas 5 in the first tubular member 8. A signal from the liquid level detecting means 27 is fed to a controller 28, which in turn emits a signal to open and close an electromagnetic valve 29 mounted on the pipe 26 and to thereby keep the liquid level of the liquefied gas 5 nearly constant within the cylindrical body 12.
The liquid level detecting means 27 comprises a pipe 30 and a sensor 31 housed in the pipe 30. One end of the pipe 30 is positioned outside the cylindrical body 12, while the other end thereof is positioned in the liquefied gas 5. The upper and lower ends of the pipe 30 communicate with each other through the interior thereof. The lower end of the pipe 30 is placed sufficiently deep in the liquefied gas 5 so as not to position above the liquid level of the liquefied gas 5 in the event of variation of the liquid level of the liquefied gas 5. The inner diameter of the pipe 30 is small enough to prevent access of atmospheric air to the position of the sensor 31. The sensor 31 is made for example of carbon or gallium arsenide through which feable current is passed, the construction being such that the variation of feable current is detected which will be caused by a change in temperature depending on whether the sensor is located in the liquefied gas or not. Alternatively, the sensor comprises a sealed container made of a material of good thermal conductivity and a gas enclosed in the container and capable of undergoing condensation and vaporization depending on whether the sensor is positioned in the liquefied gas or not so that the gas pressure can be detected. A gas enclosed in the container may be selected dependent on the liquefied gas as an object; for example, a gas mixture of argon and oxygen may be used as a gas for liquefied nitrogen. Thus the sensor is one which is adapted to detect the liquid level of liquefied gas by detecting various physical changes resulting from changes in temperature. Although the sensor 31 may fail to detect the liquid level correctly in the event of freezing of water or condensation of various gases taking place around the sensor 31, such failure due to freezing or condensation will be prevented by the construction that the sensor 31 is housed in the pipe 30 and is therefore enclosed with the gas vaporized from the liquefied gas 5. Furthermore, changes in the liquid level caused by the supply of articles through the inlet 4 into the liquefied gas 5, bubbling in liquefied gas 5 and/or vibration of cylindrical body 12 do not appreciably affect the liquid level within the pipe 30, so that the detecting means is suitable for use in the present apparatus in which the liquid level of liquefied gas is liable to change.
A pipe 32 has one end which is open to the interior of the first tubular member 8 at an upper portion thereof and the other end open to the interior of the feeder 2. A low-temperature gas vaporized from the liquefied gas within the cylindrical body 12 is supplied to the feeder via the pipe 32 by a blower 33 mounted thereon so as to cool the articles before they are fed to the cylindrical body 12. The cylindrical body 12 is almost closed except at the inlet 4 and outlet 6, permitting the low-temperature gas to be led through the pipe 32 to the feeder 2 easily while rendering the atmospheric air inaccessible to the interior of the cylindrical body 12. It is preferably to close the inlet 4 and outlet 6 as with gas curtains.
Usable as the feeder 2 are various known conveyor means such as roller conveyor, chain conveyor, belt conveyor and screw conveyor. Gravity feed means is likewise employable which is equipped with a damper or the like to control the amount of supply. Briefly, suitable means may be selected for use in accordance with the kind, size and properties of articles to be refrigerated. Although the container 1 and feeder 2 are convenient for continuous refrigeration, the articles may be fed to the cylindrical body 12 manually without departing from the technical concept of this invention, instead of employing the container 1 and/or feeder 2.
Examples of articles 25 are various foodstuffs, rubbers, plastics and like plastic materials, metals and versatile other articles. In fact, the present apparatus is usable for many of known refrigerating processes.
Exemplary of the liquefied gas 5 are Freon, liquefied carbonic acid, liquefied nitrogen and various liquefied gases heretofore used as refrigerants. A suitable gas may be selected in accordance with the properties of articles to be refrigerated, purpose of refrigeration, economy and various conditions involved. The amount and depth of the liquefied gas 5 within the cylindrical body 12 may be determined appropriately, depending on the size and refrigeration characteristics of articles to be refrigerated.
Although the tank 3 for containing the liquefied gas 5 in the embodiment is the cylindrical body 12 of circular section, the present invention can be practiced without departing from its technical concept by using tanks of elliptical, square and various other sections, or one having an upper opening although inferior in preventing waste of liquefied gas. However, to keep the liquefied gas within the tank thermally insulated, the tank is preferably in the form of a double-layer tube containing a vacuum in the space between the inner and outer walls of the tube. To assure strength, the tube is then preferably of circular or elliptical section. It is further desired to minimize the opening of the tank 3 so that the low-temperature gas resulting from vaporization of the liquefied gas 5 will not escape from the interior of the tank 3. Moreover, the use of low-temperature gas in the tank 3 to previously cool the articles serves to effectively utilize the refrigerating energy of liquefied gas 5 (e.g., a saving of 20% of liquefied gas as ascertained by an experiment), but the pre-cooling means can be omitted without departing from the spirit of this invention.
The means for vibrating the tank 3 containing the liquefied gas 5 may be of various types conventionally employed in vibrating conveyors. The velocity of conveyance of articles by vibration is adapted for the refrigeration characteristics of articles to be treated, the desired refrigerating temperature and/or length of conveying path for the articles in the liquefied gas, by suitably determining the direction in which the tank 3 is vibrated, frequency and/or amplitude of vibration. Conveniently, the article conveying velocity is made variable as desired so as to assure satisfactory refrigeration all the time.
To simplify the construction, it is convenient to utilize the inner bottom wall of the tank 3 as the member for carrying articles in the liquefied gas. Alternatively, a special guide plate or the like may be disposed in the liquefied gas 5 within the tank 3. The article carrying member need not necessarily be one which provides a rectilinear path for conveying articles but may be designed to convey the articles along a curved path. If a curved path is employed, the tank 3 is vibrated in a direction along the conveying direction of the curved path, the direction of vibration being inclined with respect to the conveying surface, whereby the articles can be conveyed smoothly. Especially if a helical conveying path is formed about a generally vertical axis to convey the articles upward along the path, the apparatus will require a floor space which is small relative to the length of the conveying path, hence convenient.
Various means heretofore employed for liquefied gases are usable as the liquid level detecting means 27 and/or controller 28. Alternatively, such means may be dispensed with, in which case the amount of gas vaporized from the liquefied gas will be automatically or manually supplied to the tank.
Given below is an example of refrigerating operation.
A tank having a double-layer construction of circular section was used, the space between its inner and outer walls being packed with granular perlite and rendered substantially vacuum. The tank was installed in place with its longitudinal axis positioned generally horizontally. The tank measured about 355.6 mm in the diameter of its interior space and contained liquefied nitrogen to a maximum depth of about 30 mm over a length of about 5,200 mm in the article conveying direction. The interior bottom wall of the tank toward the outlet had an angle of inclination of about 4.degree. with respect to a horizontal plane and was positioned above the liquid level of liquefied nitrogen at the outlet. The tank was vibrated minutely in a direction at about 6.degree. with respect to a vertical plane, substantially in parallel to the article conveying direction, such that it would be brought to an increasingly higher level toward the conveying direction, permitting articles to be discharged from the outlet about 7 minutes after they were fed through the inlet. At room temperature, fragments of waste tires measuring about 100 mm .times. 100 mm .times. 10 mm were supplied to the tank through the inlet, with the result that they were found refrigerated to -180.degree.C when discharged from the tank and were crushable as intended in the subsequent crushing process.
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