Low temperature food storage equipment and temperature control method for such an equipment

Abstract: The low temperature food storage equipment of the present invention is provided with an icehouse (10) and a food storeroom (26) each surrounded by a heat insulator. The icehouse (10) and the storeroom (26) are connected by a detachable heat exchanger (12) disposed therebetween. In the icehouse (10) there is stored water which is frozen into ice when the outside air grows cold. In the storeroom (26) there are kept in cold storage a large amount of shippable food, for example, potatoes. In the case of shipping the food, the heat exchanger (12) is removed and the food is transported on a truck or the like while being kept in cold storage in the storeroom (26).

Description: The present invention relates to a low temperature or cold food storage equipment and to a temperature control method for such an equipment. With such a low temperature food storage equipment, it is possible to keep food in cold storage for a long period of time through utilization of low temperatures available during the winter in cold districts and to transport the food while keeping it cold in the storeroom without the necessity of transshipping it to a refrigerator truck or the like. One method that has heretofore been used to keep food in cold storage is to utilize low temperatures available during the winter in cold districts. A simple storage of this kind is a storage pit which is dug in the ground and utilizes latent and sensible heat of the surrounding frozen soil to keep food in cold storage for a long period of time. There has been proposed the use of heat pipes for quickly forming a frozen soil layer around the storage pit as disclosed in Japanese Patent Laid-Open Publication No. 233957/90, for example. The cold storage equipment described in this Japanese document is made up of a water-barrier heat insulating layer provided in the ground, a food storeroom provided inside the heat insulating layer, and heat pipes having their lower end portions inserted into the ground between the water-barrier heat insulating layer and the stockroom. However, the cold storage equipment of this kind has technical problems described below. With the cold storage equipment set forth in the above-identified Japanese document, food is kept at low temperatures in the underground storeroom during the winter, and hence in the case of shipment it must be carried out of the storeroom and loaded on a refrigerated truck or the like; this is very time-consuming and laborious work. Moreover, the frozen soil layer, which serves as a cooling or chilling source, is frozen by letting in the cold or chilly outside air through the heat pipes, and hence its frozen state varies with the outside air temperature. DE-A-2537014 discloses an arrangement with a storeroom and an icehouse, each surrounded by a heat insulator. The interior space of the icehouse is cooled by ambient air before connection to the storeroom. Connection between the storeroom and the icehouse is made by pipes provided with fans. US-A-4637222 discloses a refrigerator for vehicles comprising a cooling unit connectable to a cool-keeping container by ducts. The ducts are for supplying cold air from the cooling unit to the cool-keeping container. It is therefore an object of the present invention to provide a low temperature food storage equipment which enables food kept in cold storage to be transported without being reshipped to other transportation means and to be held in good preservation during the transportation period, for example, for at least several days. Accordingly, there is provided low temperature food storage equipment comprising an icehouse and a food storeroom each surrounded by a heat insulator, a temperature sensor disposed in said storeroom, a first heat exchanging pipe extending from the lower portion of said icehouse to the upper portion of said storeroom, a second heat exchanging pipe extending from the upper portion of said icehouse to the lower portion of said storeroom, fans provided in said pipes for circulating air between said icehouse and said storeroom, and means for selecting the air flow directions in said first and second heat exchanging pipes on the basis of the temperature detected by said temperature sensor. Moreover, there is provided a temperature control method for low temperature food storage equipment which comprises an icehouse and a food storeroom each surrounded by a heat insulator, a temperature sensor disposed in said storeroom, a first heat exchanging pipe extending from the lower portion of said icehouse to the upper portion of said storeroom, a second heat exchanging pipe extending from the upper portion of said icehouse to the lower portion of said storeroom and fans provided in said pipes for circulating air between said icehouse and said storeroom, wherein the air flow directions in said first and second heat exchanging pipes are selected on the basis of the temperature detected by said temperature sensor. The heat exchanger is formed by a first heat exchanging pipe extending from the lower portion of the icehouse to the upper portion of the food storeroom and a second heat exchanging pipe extending from the upper portion of the icehouse to the lower portion of the food storeroom. Each of the first and second heat exchanging pipes may have a pair of branch lines, wherein flow-direction switching means and air supply means may be provided. With the low temperature food storage equipment of the above construction, the temperature in the icehouse is substantially free from the influence of a change in the outside air temperature, because the icehouse is surrounded by the insulator. The heat source for cooling the storeroom is ice frozen by the outside air, and hence is stable in temperature and humidity. The temperature in the storeroom wherein perishable foods are stocked is controlled to stay within a predetermined temperature range on the basis of a detected value of a temperature sensor. Moreover, the heat exchanger interposed between the icehouse and the storeroom is detachable, and when it is removed, the storeroom can be loaded on a truck or the like, with foods stocked therein. While the specification concludes with claims 1 and 5 which define the subject-matter of the invention, it is believed the invention will be better understood from the following description taken in connection with the accompanying drawings. Fig. 1 is a longitudinal-sectional view of low temperature storage equipment according to an embodiment of the present invention; Fig. 2 is a cross-sectional view of the low temperature storage equipment shown in Fig. 1; Figs. 3 and 4 are schematic diagrams for explaining an icehouse of the storage equipment; Fig. 5 is a schematic diagram for explaining a food storeroom of the storage equipment; Figs. 6A and 6B are schematic diagrams for explaining the principal parts of heat exchanging pipes for use in the storage equipment; Fig. 7 is a schematic diagram for explaining the arrangement of temperature switches in the food storeroom of the storage equipment; Fig. 8 is a table for explaining ON-OFF control of electromagnetic shutters and fans for controlling the temperature in the food storeroom; A description will be given, with reference to the drawings, of preferred embodiments of the present invention. Figs. 1 through 8 illustrates an embodiment of the low temperature food storage equipment according to the present invention, which has an icehouse 10 and a food storeroom 26 each enveloped by a heat insulator. The icehouse 10 and the storeroom 26 are interconnected by a detachable heat exchanger 12 disposed between them. The icehouse 10 is rectangular parallelepipedic in shape and is composed of an icehouse body 16 having a door 14 at one end and entirely surrounded by a heat insulator and trays 18 placed therein. As shown in Figs. 3 and 4, the trays 18 are mounted on shelves 20 provided one above another at predetermined intervals in the icehouse body 16. The trays 18 are each inverted trapezoidal in cross section and constructed so that it will not break even when water contained therein freezes. The water to be contained in such a tray 18 is water that has dissolved therein a predetermined amount of salt, for instance. The water is cooled and frozen into ice by the cold outside air which is admitted into the icehouse body 16 by opening the door 14. When the water in each tray 18 is thus frozen into ice, the door 14 is closed. The storeroom 26 for storing perishable foods is provided adjacent the icehouse 10, and in this embodiment the former has about the same shape as that of the latter. Fig. 5 is a cross-sectional view of the storeroom 26, which is surrounded by a heat insulator and in which foods (potatoes, for example) 26a packed in cardboard boxes or similar containers are placed one above another. The heat exchanger 12 comprises, in this embodiment, a first heat exchanging pipe 22 which extends along the bottom of the icehouse body 16 and thence to and along the ceiling of the storeroom 26 and a second heat exchanging pipe 24 which extends along the ceiling of the icehouse body 16 and thence to and along the bottom of the storeroom 26. The heat exchanging pipes 22 and 24 are made of vinyl chloride and each portion extending in the icehouse body 16 and the storeroom 26 has a number of perforations. The sum total of the areas of such perforations made in each pipe is nearly equal to the cross-sectional area of the pipe. The heat exchanging pipes 22 and 24 are detachably connected to the storeroom 26 by means of, for instance, couplings composed of bolts and nuts and disposed between branch lines 28 of the pipes 22 and 24 and the storeroom 26 in such a manner that the pipes 22 and 24 are partly left in the storeroom 26 when they are disconnected from the icehouse 10. Of course, the pipes 22 and 24 are adapted so that they can be pulled out of the storeroom 26 entirely. The first and second heat exchanging pipes 22 and 24 each have its intermediate portion forked into two branches 28 which join again. In the branches 28 there are provided electromagnetic shutters D1 to D4 and fans F1 to F4 as shown in Fig. 6. The electromagnetic shutters D1 to D4 and the fans F1 to F4 are connected in series as depicted in Fig. 7 and they are controlled by thermostats TH1 to TH4 (see Fig. 1) disposed at upper and lower positions in the storeroom 26. Fig. 8 is a table showing combinations of the electromagnetic shutters D1 to D4 and the fans F1 to F4 which are driven or stopped in accordance with the state of the thermostats TH1 to TH4. In this example the thermostats TH1 and TH2 arranged at the upper positions in the storeroom 26 are set so that they turn ON at 4C° and OFF at 2C°. The thermostats TH3 and TH4 at the lower positions are set so that they turn OFF at 2C° and ON at 0C°. The electromagnetic shutters D1, D4 and the fans F1, F4 are driven or stopped by the ON-OFF operation of the thermostats TH1 and TH2 disposed at the upper positions, whereas the electromagnetic shutters D2, D3 and the fans F2, F3 are driven or stopped by the ON-OFF operation of the thermostats TH3 and TH4 disposed at the lower positions. When the temperature at the upper portion in the storeroom 26 is higher than 4 C°, the electromagnetic shutters D1, D4 and the fans F1, F4 are driven. In this instance, the first heat exchanging pipe 22 takes therein chilly air at the lower portion in the icehouse 10 and supplies it to the upper portion of the storeroom 26. The second heat exchanging pipe 24 takes therein air at the lower portion in the storeroom 26 and discharges it into the upper portion of the icehouse 10. Thus the chilly air in the icehouse 10 circulates via the route: lower portion of icehouse 10 → upper portion of storeroom 26 → lower portion of storeroom 26 → upper portion of icehouse 10 → lower portion of icehouse 10. When the temperature at the lower side in the storeroom 26 is below 0C°, the electromagnetic shutters D2, D3 and the fans F2, F3 are driven. In this case, the first heat exchanging pipe 22 takes therein the air at the upper portion in the storeroom 26 and discharges it into the lower portion of the icehouse 10. The second heat exchanging pipe 24 takes therein at the upper portion in the icehouse 10 chilly air with relatively higher temperature than that of the air at the lower portion in the icehouse 10 and supplies it to the lower portion in the storeroom 26. Thus the chilly air in the icehouse 10 circulates via the route: upper portion of storeroom 26 → lower portion of icehouse 10 → upper portion of icehouse 10 → lower portion of storeroom 26 → upper portion of storeroom 26. In this way, the temperature in the storeroom 26 is held in the range of between 0 and 4C° and the humidity is held at about 95%.

Claims: Low temperature food storage equipment comprising an icehouse (10) and a food storeroom (26) each surrounded by a heat insulator, a temperature sensor (TH1, TH2, TH3, TH4) disposed in said storeroom (26), a first heat exchanging pipe (22) extending from the lower portion of said icehouse (10) to the upper portion of said storeroom (26), a second heat exchanging pipe (24) extending from the upper portion of said icehouse (10) to the lower portion of said storeroom (26), fans (F1, F2, F3, F4) provided in said pipes for circulating air between said icehouse (10) and said storeroom (26), and means for selecting the air flow directions in said first and second heat exchanging pipes (22,24) on the basis of the temperature detected by said temperature sensor (TH1, TH2, TH3, TH4). Low temperature food storage equipment as claimed in claim 1, wherein each of said first and second heat exchanging pipes (22,24) has in an intermediate portion a pair of branches (28), a direction switching means and one of said fans (F1, F2, F3, F4) being provided in each of said branches. Low temperature food storage equipment as claimed in claim 2, wherein each said direction switching means comprises an electromagnetic shutter (D1, D2, D3, D4). Low temperature food storage equipment as claimed in any preceding claim, wherein said icehouse (10) comprises an icehouse body (16) provided with a door (14), and a plurality of trays (18) placed one above another in said icehouse body (16), wherein said trays (18) are for containing water to be frozen at an outside air temperature. A temperature control method for low temperature food storage equipment which comprises an icehouse (10) and a food storeroom (26) each surrounded by a heat insulator, a temperature sensor (TH1, TH2, TH3, TH4) disposed in said storeroom (26), a first heat exchanging pipe (22) extending from the lower portion of said icehouse (10) to the upper portion of said storeroom (26), a second heat exchanging pipe (24) extending from the upper portion of said icehouse (10) to the lower portion of said storeroom (26) and fans (F1, F2, F3, F4) provided in said pipes for circulating air between said icehouse (10) and said storeroom (26), wherein the air flow directions in said first and second heat exchanging pipes (22,24) are selected on the basis of the temperature detected by said temperature sensor (TH1, TH2, TH3, TH4).

Inventors: HACHINOHE YUTAKA, IMAMURA AKIHIDE, OUCHI KAZUYUKI, SASAKI MASATOSHI, YOKOCHI SHOICHI, HACHINOHE, YUTAKA, IMAMURA, AKIHIDE, OUCHI, KAZUYUKI, SASAKI, MASATOSHI, YOKOCHI, SHOICHI
Applicants: HAZAMA GUMI, MITSUI O S K LINES LTD, OHBAYASHI CORP, TAIHEI SANGYO CO LTD, HAZAMA CORPORATION, MITSUI O.S.K. LINES, LTD., OBAYASHI CORPORATION, TAIHEI SANGYO CO., LTD.
Application year: 1992
Main classification: F25D3
IPC codes: F25D3, F25D13, F25D29