Thermal exchange food processing device and method of producing same

Abstract

A thermal exchange food processing device includes a thermal conductive body, a thermal insulation layer and a phase change material. The thermal conductive body has an acting region and an inner thermal conductive region corresponding to, and in thermal connection with, the acting region. The thermal insulation layer has a lower thermal conductivity coefficient than the thermal conductive body and encapsulates, at least in part, the thermal conductive body, so that the acting region of the thermal conductive body is exposed while the remaining regions of the thermal conductive body other than the acting region are thermally insulated from ambient temperature. The thermal conductive body, alone or together with the thermal insulation layer, defines an accommodation space, and the inner thermal conductive region is situated to face the accommodation space. The phase change material is within the accommodation space.

Claims

1. A thermal exchange food processing device for processing at least one target foodstuff, comprising: a thermal conductive body comprising an acting region adapted for being in contact with and exchanging heat with the at least one target foodstuff and at least one inner thermal conductive region disposed corresponding to, and in thermal connection with, the acting region; a thermal insulation layer having a lower thermal conductivity coefficient than the thermal conductive body and encapsulating at least a portion of the thermal conductive body, so that the acting region of the thermal conductive body is exposed while remaining regions of the thermal conductive body other than the acting region are thermally insulated from the ambient environment, wherein the thermal conductive body alone or together with the thermal insulation layer defines an accommodation space and the inner thermal conductive region is disposed to face the accommodation space; and a phase change material disposed within the accommodation space and in thermal connection to the inner thermal conductive region; wherein the thermal conductive body further comprises: a processing portion comprising two side surfaces covered completely by the thermal insulation layer, wherein the acting region is a side edge connected to the two side surfaces; and a hollow handle portion extending from the processing portion and formed with the accommodation space.

2. The thermal exchange food processing device according to claim 1, wherein the thermal conductive body comprises a thermal exchange acting wall having an outer surface and an inner surface opposite to the outer surface, and wherein the acting region is the outer surface and the inner thermal conductive region is the inner surface.

3. The thermal exchange food processing device according to claim 2, wherein the thermal conductive body further comprises a surrounding wall integrally extending from the thermal exchange acting wall and cooperating with the thermal exchange acting wall to define the accommodation space.

4. The thermal exchange food processing device according to claim 2, wherein the thermal conductive body further comprises an anchor port extending from a flange of the thermal exchange acting wall, the anchor port being formed with a plurality of positioning holes, through which the thermal insulation layer is combined with the thermal conductive body.

5. The thermal exchange food processing device according to claim 2, wherein the thermal conductive body is a ceramic plate.

6. The thermal exchange food processing device according to claim 5, wherein the ceramic plate comprises the thermal exchange acting wall and downward fin portions integrally extending from the inner thermal conductive region of the thermal exchange acting wall.

7. The thermal exchange food processing device according to claim 1, further comprising a perforated corrugated metal panel disposed in the accommodation space.

8. The thermal exchange food processing device according to claim 1, wherein the thermal insulation layer extends to and covers the hollow handle portion.

9. The thermal exchange food processing device according to claim 1, wherein the inner thermal conductive region comprises a plurality of heat sink fins integrally extending into the accommodation space from the processing portion.

10. The thermal exchange food processing device according to claim 1, further comprising at least one heat pipe disposed within the accommodation space of the hollow handle portion.

11. The thermal exchange food processing device according to claim 1, wherein the processing portion is a scoop portion and the thermal insulation layer comprises a scoop inner wall and a scoop outer wall spaced apart from each other and covering the two side surfaces, respectively.

12. The thermal exchange food processing device according to claim 1, wherein the processing portion is a knife portion, and the side edge connected to the two surfaces comprises a knife blade portion and a knife back portion having a greater thickness compared with the knife blade portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The foregoing and other features and advantages of illustrated embodiments of the present invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.

(2) FIG. 1 is the schematic diagram of the invention in the first preferred embodiment, illustrating the connection between the thermal conductive body and thermal insulation layer.

(3) FIG. 2 is the sectional view of the invention in the first preferred embodiment, illustrating the phase change material in the accommodation space.

(4) FIG. 3 is the diagram of the partial structure of the invention in the first preferred embodiment, illustrating the situation of positioning holes and anchor ports of the outer flange.

(5) FIG. 4 is the schematic diagram of the invention in the first preferred embodiment, illustrating the situation of the perforated corrugated metal panel disposed in the accommodation space.

(6) FIG. 5 is the sectional view of the invention in the second preferred embodiment, illustrating the structure of the downward fin portions.

(7) FIG. 6 is the perspective diagram of the invention in the third preferred embodiment, illustrating the situation of the technology of this case applied in the structure of thermos.

(8) FIG. 7 is the schematic diagram of the invention in the third preferred embodiment.

(9) FIG. 8 is the perspective diagram of the invention in the fourth preferred embodiment, illustrating the situation of the technology of this case applied in the structure of the thermal box.

(10) FIG. 9 is the flowchart of the production method in the invention.

(11) FIG. 10 is the vertical sectional view of the invention in the fifth preferred embodiment, illustrating the situation of the technology of this case applied in an ice cream scoop.

(12) FIG. 11 is the transverse sectional view of the invention in the fifth preferred embodiment, illustrating the interaction among the hollow accommodation space, phase change material and the heat sink fins in the ice cream scoop.

(13) FIG. 12 is the vertical sectional view of the invention in the sixth preferred embodiment, illustrating the structure of the hollow handle portion.

(14) FIG. 13 is the vertical sectional view of the invention in the seventh preferred embodiment, illustrating the situation of the hollow handle portion formed with sealed ends on both ends.

(15) FIG. 14 is the schematic diagram of the invention in the eighth preferred embodiment, illustrating the situation of the technology of this case applied in the butter knife.

(16) FIG. 15 is the front view of the invention in the eighth preferred embodiment, illustrating the situation of the thermal insulation layer encapsulating two side surfaces.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

(17) The above statements related to the invention, other technical contents, features and benefits will be clearly presented in the detailed illustration for the preferred embodiments as shown in the diagrams. Besides, the same assembly in these embodiments will be represented by similar symbols.

(18) The thermal exchange food processing device according to the first preferred embodiment of the invention is shown in FIGS. 14. The thermal exchange food processing device disclosed herein is a foodstuff board, mainly comprising a thermal conductive body 1 and a thermal insulation layer 2, as well as the phase change material 5 providing latent heat for temperature control. According to the manufacturing method shown in FIG. 9, a hollow thermal conductive body 1 having openings 15 at two opposite ends is initially formed in Step 71. In this embodiment, the thermal conductive body is tailored to extend along a single direction by an aluminum extrusion molding process. Taking advantage of the ductility of aluminum power, a thermal conductive body having a large surface area can be easily produced by extrusion molding. For example, with a 10-inch wide mold, aluminum powder can be easily extrusion molded into a hollow thermal conductive body having a length of 15 inches, 17 inches or even 30 inches, which is in turn cut into a desired length to meet the market demand. For the purpose of clarity and illustration, the direction extending from upper left to lower right in FIG. 1 is designated as the length direction and the direction from lower left to upper right is designated as the width direction.

(19) For the purpose of clarity and illustration, the top plate of the thermal conductive body 1 shown in FIG. 2 is denoted as the thermal exchange acting wall 11, and the bottom plate opposite to the thermal exchange acting wall 11 is denoted as the bottom wall 12 of the thermal conductive body 1. An accommodation space 14 is thus defined between the thermal exchange acting wall 11 and the bottom wall 12. In this embodiment, the thermal conductive body 11 includes an inner thermal conductive region 111 which is illustrated as the inner surface of the inner thermal conductive region 11 facing the accommodation space 14, whereas the acting region 112 is the outer surface of the thermal exchange acting wall 11 exposed outside. Two outer flanges 13 are extended from the thermal exchange acting wall 11 along the width direction. In Step 72, anchor ports 132 with a plurality of positioning holes 131 are formed on the outer flanges 13 by stamping. As shown in FIG. 3, the anchor ports 132 are fixed to the thermal insulation layer through the positioning holes 131. The thermal conductive body is the media for heat exchange, thus, it could be substituted by other metal conductive plates with a high conductivity coefficient, such as copper plates and aluminum plates, so as to provide good and stable thermal exchange efficiency.

(20) Next, in Step 73 shown in FIG. 4, the opening 15 of the thermal conductive body 1 shown in the upper left side of the Figure is sealed, and the accommodation space 14 is then inserted with a piece of corrugated metal panel formed with multiple perforations, which is therefore called perforated corrugated metal panel 16. Besides, the perforated corrugated metal panel 16 may be substituted by other material capable of improving thermal conductivity, such as metal mesh fabrics or plastic fabrics added with graphite.

(21) Then, the accommodation space 14 is filled with a phase change material 5 through the opening 15. In this embodiment, the phase change material 5 is paraffin particles in solid state, which is filled in the accommodation space 14 until it is thermally connected to the inner thermal conductive region 111. In Step 74, the opening 15 at the lower right side is sealed. From then on, the phase exchange material 5 is taken as a temperature control source that acts to absorb or release heat for food processing. It is apparent to those skilled in the art that the paraffin particles illustrated herein can be substituted by various organic or inorganic phase change materials, such as esters, polyols, crystalline hydrates, molten salts, aqueous solutions of salts, and a mixture thereof.

(22) Finally, as shown in Step 75, a complete thermal insulation layer 2 is formed by injection molding, so that the bottom wall 12 and the outer flanges 13 of the thermal conductive body 1 are insulatively covered by the thermal insulation layer, with the acting region 112 being exposed outside and serving as an acting region for receiving and processing foodstuff. The outer flanges 13 are formed with a plurality of positioning holes 131, so that the thermal-resistant plastics used in the injection molding process would flow into the positioning holes 131. After cooling, the cured thermal insulation layer 2 is meshed and tightly engaged with the thermal conductive body 1 and sealed the openings 15 to a greater extent. The thermal exchange food processing device disclosed herein is produced accordingly.

(23) The thermal insulation layer 2 may include an additional thermal insulation film made from different materials (not shown), thereby increasing the thermal insulation effect. It should be noted that Step 72 and Step 75 in this embodiment are interchangeable. In other words, the formation of the thermal insulation layer can be carried out prior to the filling of the phase change material and the sealing of openings.

(24) Of course, the metal conductive plate used for the thermal conductive body according to the embodiment above can also be replaced by a ceramic plate with high thermal conductivity. FIG. 5 is the sectional view of the thermal exchange food processing device according to the second preferred embodiment of the invention. Different from the first preferred embodiment, the second preferred embodiment described herein uses the ceramic plate as the thermal conductive body 1.sub.2. Moreover, a plurality of downward fin portions 17.sub.2 extend downwardly from the lower side of the inner thermal conductive region 111.sub.2 opposite to the thermal exchange acting wall 112.sub.2. The downward fin portions 17.sub.2 may extend to the accommodation space 14.sub.2 to increase the thermal exchange surface area between the thermal conductive body 1.sub.2 and the phase change material 5.sub.2 in the accommodation space 14.sub.2, thereby improving the thermal exchange efficiency for food processing. Moreover, the downward fin portions 17.sub.2 may further serve as a support frame. When the user applies force on the acting region 112.sub.2, such as stirring a juice solution on the acting region 112.sub.2 with a turner, or pressing the foodstuff with tableware, the force can be countered by the integrally formed downward fin portions 17.sub.2, so as to avoid deformation or damage of the thermal conductive body 1.sub.2 and increase the reliability of the device. In addition, the accommodation space 14.sub.2 is defined by the thermal conductive body 1.sub.2 together with the thermal insulation layer 2.sub.2.

(25) This embodiment is for processing the ice treats and, therefore, an aqueous solution of table salt is filled within the accommodation space 14.sub.2 to serve as the phase change material 5.sub.2. In the case of preparing smoothies, the device is cooled in a freezer for a period of time to transform the aqueous solution into ice at 20. Then a liquid juice is poured on the acting region of the thermal exchange food processing device and stirred with a turner, so that the phase change material absorbs the heat of the liquid juice continuously to solidify the liquid juice. The device disclosed herein allows the user to make ice treats in an extremely simple way and further greatly prolongs the frozen period of the ice treats once it is made. Thus, the consumers don't have to concern with the problems of immediate melting of the ice treats. Moreover, the thermal exchange food processing device disclosed herein is of a simple structure, which is not equipped with complicated electronic parts for heat dissipation. It is cost effective to manufacture and highly durable. Especially, since it is easy-to-operate, people could learn to use it very quickly. Besides, the phase change material inside is paraffin or an aqueous solution of table salt which is safe and non-poisonous. Even if the shell is cracked or broken, it will not pose high risks.

(26) In addition to being applied for preparing smoothies, the device can also serve as a stable heat source for warming foodstuff by using a phase change material that releases heat continuously, such as paraffin having a melting point of 60. For example, when the device is applied in a common steakhouse, the steak may be put on the device and serve to the consumer. The phase change material inside can keep the steak warm. In this way, it could maintain the temperature of steak longer than by just merely relying on the heat remaining in the dish, making the consumer enjoy the best taste of the food. It is a piece of good news especially for those who like eating slowly, because they could enjoy the food slowly without worrying about the original flavor being lost once the food cools down. Moreover, the device disclosed herein makes the steakhouse more competitive in the market.

(27) The third preferred embodiment of the invention is shown in FIGS. 6 and 7. The thermal exchange food processing device disclosed herein is in the form of a thermos bottle, comprising an insulated cover 6.sub.3 axially combining with the thermal insulation layer 2.sub.3. The thermal conductive body 1.sub.3 is fabricated to include a thermal exchange acting wall 11.sub.3, which is a metal plate formed by drawing and having a central recessed area, rather than the planar structure disclosed in the embodiments above. A surrounding wall 18.sub.3 integrally extending from the thermal exchange acting wall 11.sub.3 defines an accommodation space 14.sub.3 together with the thermal exchange acting wall 11.sub.3. The thermal insulation layer 2.sub.3 is illustrated as a cup body encapsulating the surrounding wall 18.sub.3 from the outside. The insulated cover 6.sub.3 is illustrated as a cup cover which, when combined with the cup body, can effectively block the thermal exchange with the outside. In this way, the inner heat could be fully utilized.

(28) Similarly, when it is applied to the iced drink, the device is put in a freezer for a period of time before pouring the drink into it. The phase change material in solid phase absorbs the heat in the drink and transforms into liquid phase, so that the drink is cooled. The user could even shake the thermal exchange food processing device to have the heat in the drink be absorbed by the device, thereby producing a smoothie rapidly.

(29) The structural design of the thermal exchange food processing device may vary depending on the sizes of the food items to be processed. According to the fourth preferred embodiment of the invention shown in FIG. 8, the thermal insulation layer 2.sub.4 and the insulated cover 6.sub.4 are tailored in rectangular shape. It can be used as thermal insulated containers for storing variety of food items, which are not restricted to the liquid items stated in the above embodiments. When storing fresh food items, such as vegetables and fruits, it could keep them fresh under low temperatures for a long time. In this way, it prevents food from being spoiled or becoming a breeding ground for bacteria, and further increases the usage of the invention.

(30) The invention can be also used for local temperature control. For example, when a frozen food item which may soften or liquefy under ambient temperature, such as butter or ice cream, is to be processed, it may require applying heat to a limited region to help cut or scoop a part of the frozen food item, while avoiding melting of the entire frozen food item. As shown in FIG. 10, the thermal exchange food processing device according to the fifth preferred embodiment of the invention is an ice cream scoop, which comprises a thermal conductive body 1.sub.5 and a thermal insulation layer 2.sub.5 encapsulating at least in part the thermal conductive body 1.sub.5. The thermal conductive body 1.sub.5 is a scoop-shaped thermal conductive metal comprising a hollow handle portion 10.sub.5 and a processing portion 19.sub.5. The hollow handle portion 10.sub.5 is a generally cylindrical-shaped metal handle covered by the thermal insulation layer 2.sub.5. For the purpose of clarity and illustration, the axial direction in which the handle extends is defined as the longitudinal direction.

(31) A processing portion 19.sub.5 extending from the front end of the thermal conductive body 1.sub.5 is a scoop which may serve to take ice cream. The processing portion 19.sub.5 is integrally formed with the thermal conductive body 1.sub.5 by aluminum casting and includes two side surface portions 31.sub.5, namely the concave portion and convex portion, both being coated with the thermal insulation layer 2.sub.5 having a lower thermal conductivity coefficient compared with the thermal conductive body 1.sub.5. For the purpose of illustration, the thermal insulation layer 2.sub.5 in the concave portion is called scoop inner wall 21.sub.5, while the thermal insulation layer 2.sub.5 in the convex portion is called scoop outer wall 22.sub.5. The side edge of the scoop connecting the scoop inner wall 21.sub.5 and the scoop outer wall 22.sub.5 is the acting region 112.sub.5 not covered by the thermal insulation layer 2.sub.5. The exposed acting region 112.sub.5 has a high conductivity coefficient and constitutes a part of the thermal conductive body 1.sub.5 and is adapted for thermal connection with ice cream.

(32) As shown in FIG. 11, the cylindrical chamber of the hollow handle portion 10.sub.5 includes an inner thermal conductive region 111.sub.5 surrounding an accommodation space 14.sub.5 along the longitudinal direction. The accommodation space 14.sub.5 is filled with phase change material 5.sub.5. In this embodiment, the phase change material 5.sub.5 is distilled water thermally connected with the inner thermal conductive region 111.sub.5. Moreover, in the processing portion 19.sub.5, the inner thermal conductive region 111.sub.5 is formed with a gap 30.sub.5 connecting to the accommodation space 14.sub.5, so that distilled water could flow into it. A plurality of heat sink fins 4.sub.5 extending from the hollow handle portion 10.sub.5 into the accommodation space 14.sub.5 are integrally formed with the thermal conductive body 1.sub.5, so as to effectively increase the thermal exchange area between distilled water and the thermal conductive body 1.sub.5.

(33) When the user uses the thermal exchange food processing device disclosed herein to scoop some ice cream, the scoop inner wall 21.sub.5, scoop outer wall 22.sub.5 and acting region 112.sub.5 of the ice cream scoop at room temperature are brought in contact with the frozen ice cream. Since the scoop inner wall 21.sub.5 and scoop outer wall 22.sub.5 have low thermal conductivity, the acting region 112.sub.5 is the only portion to conduct thermal exchange with the ice cream. The acting region 112.sub.5 will transfer the heat stored in the processing portion 19.sub.5 and the thermal conductive body 1.sub.5 to the ice cream, so as to slightly soften the ice cream. However, due to the low thermal capacity of aluminum, the metal portion of the ice cream scoop will be cooled instantly. Then, distilled water in the gap 30.sub.5 of the processing portion 19.sub.5 and the accommodation space 14.sub.5 of the hollow handle portion 10.sub.5 will further provide heat to the inner thermal conductive region 111.sub.5. The heat will be transferred from the inner thermal conductive region 111.sub.5 to the acting region 112.sub.5. In this way, the acting region 112.sub.5 could continue to conduct thermal exchange with the frozen foodstuff 112.sub.5, so as to slightly melt the solid frozen foodstuff for scooping.

(34) When the ice cream scoop is used by many people continuously, the phase change material, namely distilled water, will be gradually cooled down to 0. At this time, as affected by the ice cream below 0, distilled water will undergo a phase change from liquid water to solid ice at 0. Through this phase change, the phase change material can release latent heat which is in turn delivered to the acting region 112.sub.5 of the processing portion 19.sub.5, and then to the position for scooping the ice cream. Therefore, with the heat from the metal portion and distilled water and the heat released from the phase change of distilled water, the ice cream contacting the acting region 112.sub.5 will thaw easily for cutting or scooping.

(35) The outer side of the hollow handle portion 10.sub.5 of the thermal conductive body 1.sub.5 may also be covered by the thermal insulation layer 2.sub.5. Therefore, even if the metal portion and distilled water are cooled down to 0, or even during the phase change process, the heat on the user's hand will not be significantly absorbed by the device and will not make the user feel uncomfortable. In the meantime, the processing portion 19.sub.5 covered by the thermal insulation layer 2.sub.5 will only slightly melt the target part of the ice cream, but will not affect the remaining parts. In this way, it keeps the food item at a frozen state. When taken out from the freezer, the food item will not be melted quickly due to absorbing large amounts of heat from the ice cream scoop.

(36) Therefore, when the user scoops ice cream with the thermal exchange food processing device disclosed herein, it will be very easy to operate on one hand, and the user could get a complete scoop of ice cream rather than some melted cream in liquid state, on the other hand. In particular, it protects the ice cream remaining in the bucket from melting due to the temperature of the ice cream scoop. Moreover, the user's hand will not be chilled due to the low temperature of the ice cream. After using, the user just need to place the thermal exchange food processing device in ambient temperature, allowing it to absorb heat from the ambient air to conduct thermal exchange with the thermal conductive body, scoop portion and the heat sink fins. Furthermore, the distilled water would undergo a phase change from solid to liquid, through which it will achieve the effect of absorbing/releasing heat without a power supply, so as to save energy effectively.

(37) The sixth preferred embodiment of the invention is shown in FIG. 12, wherein the phase change material 5.sub.6 is distilled water. In this embodiment, the heat sink fins 4.sub.6 extend from the processing portion 19.sub.6 into the accommodation space 14.sub.6. When the thermal conductive body 1.sub.6 of the thermal exchange food processing device is brought in contact with the ice cream, the heat sink fins 4.sub.6 will transfer heat from the ice cream to the distilled water. Through the simple phase change of the distilled water, the invention applies heat to slightly melt a part of the ice cream for scooping. In addition, the lower half of the hollow handle portion 10.sub.6 is made of metal and integrally formed with the processing portion 19.sub.6, and the upper half thereof is med of transparent plastic material. On one hand, the user's hand would provide some heat for melting the ice cream that is in contact with the acting region. On the other hand, the upper half of the hollow handle portion 10.sub.6 allows the user to watch the phase change process of the phase change material 5.sub.6 filled in the accommodation space 14.sub.6.

(38) The seventh preferred embodiment of the invention is shown in FIG. 13. One of the two opposite ends of the hollow handle portion 10.sub.7 is a sealed end 33.sub.7. A heat pipe 32.sub.7 is disposed in the accommodation space 14.sub.7 and connects the processing portion 19.sub.7 to the sealed end 33.sub.7. During the manufacture of the device disclosed herein, the pressure of the accommodation space is reduced, and the accommodation space is filled with the phase change material. The liquid phase fluid (not denoted with numeral) in the heat pipe will change into vapor phase at room temperature and low pressure. Moreover, the low pressure environment in the chamber will make the vapor (not denoted with numeral) fill up the chamber. When the ice cream absorbs heat, the vapor is cooled to liquid and then flows to the sealed end 33.sub.7 due to the vacuum and capillary effect. After that, the liquid will absorb heat from the sealed end 33.sub.7 and then return to its vapor state. The continuous cycle of liquid-vapor phase change achieves the purpose of softening the ice cream to be scooped. In this embodiment, a low-temperature fluid having the working temperature ranging from 70 C.200 C. is employed, and the preferred is water, methanol, ethanol and acetone.

(39) In the eighth preferred embodiment of the invention, the solid frozen foodstuff is a frozen butter block (not shown) stored under low temperature, and the thermal exchange food processing device is illustrated as a butter knife. As shown in FIGS. 14 and 15, the processing portion 19.sub.8 is a knife portion comprising two side surfaces covered by the thermal insulation layer 2.sub.8, an acting region 112.sub.8 connected to the two side surfaces 31.sub.8 and configured in the form of a knife blade portion, and a knife back portion 113.sub.8 having a greater thickness compared with the knife blade portion.

(40) The acting region 112.sub.8 in the form of a knife blade portion has a small area for applying stress. The force applied by the user will be concentrated along the blade due to the shape and structure of the acting region 112.sub.8. When the acting region 112.sub.8 is pressed on the butter, it will easily slice a piece of butter. The side surfaces 31.sub.8 are covered by the thermal insulation layer, so that they will not release heat to further melt the butter remaining on the side surfaces 31.sub.8 after cutting. The user could also easily spread the cut butter on a toast slice.

(41) The thermal exchange food processing device of the invention is applicable in food processing which requires local temperature control, such as the solid frozen foodstuff. Whether the invention is fabricated in the form of a butter knife or an ice cream scoop, it could easily cut and separate the clotted butter or ice cream, increasing the convenience in use. In addition, by virtue of the thermal insulation layer, the invention is adapted to prevent the solid frozen foodstuff from liquefying on the thermal exchange food processing device directly. Thus, the user could spread the butter or eat the ice cream more easily or neatly. Even if the structure of the thermal exchange food processing device is damaged accidentally, causing the leakage of the phase change material, there is no occurrence of contamination in the foodstuff because the invention uses distilled water as the phase change material in the fifth-eighth embodiments. Moreover, distilled water is cheap and easily available, which reduces the manufacturing cost. The invention achieving all the above purposes accordingly.

(42) While the invention has been described with reference to the preferred embodiments above, it should be recognized that the preferred embodiments are given for the purpose of illustration only and are not intended to limit the scope of the present invention, and various modifications as well as changes, which will be apparent to those skilled in the relevant art, may be made without departing from the spirit and scope of the invention.