Heat insulating door wall structure

Abstract: The present invention relates to a heat insulating door wall structure (D1) for use in a refrigerator or the like. By constituting the surface of the door with a colored glass plate (14) or the like having a transparent layer (14a) at its front surface and a colored layer (14b) at its reverse surface, deep luster is provided by the transparent glass plate (14a) located before the colored layer (14b), while owing to high rigidity of the glass plate (14a), undulation to be formed on the front surface of the door by contraction of a heat insulating material (17) filled through expansion or foaming, or by warping of the door due to temperature difference between exterior and interior of the door is advantageously prevented, and moreover, by increasing the strength of the door, reinforcing members of the door can be dispensed with for simple construction and reduction in cost.

Description: BACKGROUND OF THE INVENTION The present invention relates to a heat insulating door wall structure as described below with reference to Figs. 8 and 9. Such a door wall structure can be used in a refrigerator or the like. Recently, in order to improve design quality, a heat insulating door for a refrigerator has been increased in the number of its colors, with a luster imparted to the colors. Moreover, it has been a tendency to deepen the luster for further improvement of its design characteristics. With respect to the technique related to the door wall material as referred to above, there has conventionally been proposed an arrangement as disclosed, for example, in JP-A-61-116267 and schematically shown in Fig. 4, in which the refrigerator includes an outer casing or housing 1 of a rectangular box-like configuration, with doors 2 and 3 hingedly supported at a front portion of the housing 1 for selective closing or opening of said housing 1. The surface of each of the doors 2 and 3 is so processed that a clear paint containing a pearl pigment or metallic pigment is applied by screen printing, over the entire surface of an iron plate for subsequent baking treatment. Meanwhile, in Figs. 5 to 7, there is shown a door construction as disclosed in JP-A-54-17555, in which a door main body 4 includes an integral door frame 5 forming upper and lower sides and opposite side faces of the door, a door outer plate 6 fixed to the front face of the door frame 5, an expanded heat insulating material 7 of polyurethane foam or the like expanded into a space defined by the door frame 5 and the door outer plate 6, and a reinforcing plate 8 disposed at the reverse face side of the door frame 5 and subjected to integral expansion with the heat insulating material 7 so as to be held in place by the bonding force of said expanded heat insulating material 7. In the conventional arrangement as described with reference to Fig. 4, however, there have been such problems that, in the surfaces of the doors 2 and 3, although the degree of luster may be improved even when the printing is effected onto the iron plates owing to fine undulation or concave and convex portions on the raw material of the iron plates, such undulation can not be perfectly eliminated. In order to overcome the disadvantage as referred to above, it was considered to increase the thickness of the printed layer, but in this case, it was necessary to make the thickness of the printed layer to 1 to 2 mm for perfect elimination of the undulation on the surface, thus resulting in the high manufacturing cost. Moreover, when the above known construction is applied to the heat insulating door of the refrigerator, etc., since the inner side of the refrigerator is held at a low temperature, while the outer side of the refrigerator is maintained relatively at a high temperature, warping may be formed in the doors 2 and 3 or cracking of the printed layers is caused by the temperature difference stated above. When the reinforcing plate 8 is provided as shown in Fig. 7 for preventing warping of the door due to the temperature difference as described above, there have also been such problems that not only the higher cost may result, but waving is produced on the surface of the door outer plate 6 by the contraction arising from the expanded heat insulating material 7 between the reinforcing plate 8 and the door outer plate 6. As another conventional heat insulating door of this kind, there may be raised a heat insulating door for a refrigerator with a model number "NR-F46K1" manufactured by Matsushita Refrigeration Company and put on sale in February, 1990. Referring to Figs. 8 and 9, one example of a heat insulating door of the conventional refrigerators described so far will be explained hereinbelow. In Figs. 8 and 9, the heat insulating door generally includes an outer panel 9 formed by applying a decorative film 9d of 0.1 mm thick composed of a transparent layer 9b and a printed layer 9c, onto an iron plate 9a by a bonding agent 9e, an inner plate 10 disposed to confront said outer panel 9, a frame member 11 having an outer panel inserting portion lla of a generally U-shaped cross section for application over an entire outer peripheral portion of the outer panel 11, an insulating material 12 filled through expansion into a space defined by the outer panel 9, the inner plate 10 and the frame member 11, and a reinforcing member 13 of a U-shaped cross section inserted in the frame member 11 at the side of the heat insulating material 12. In the known arrangement as described above, however, although the luster is given by the decorative film, a sufficient depth is not provided in the luster, since the decorative film can not be made thick. Moreover, the surface of the outer panel tends to be formed with undulation instead of being flat, due to the facts that when the decorative film is applied onto the iron plate, bubbles and dust, etc. are apt to be confined, concave and convex portions of the bonding agent or undulation on the surface of the iron plate, etc. tend to be undesirably picked up. Meanwhile, when the heat insulating door is subjected to cooling or heating, the bonding agent is separated to be raised due to difference in the linear expansion coefficients between the iron plate and the decorative film, thus forming the undulation on the surface of the heat insulating door. Another disadvantage of the conventional arrangements is that the outer panel for the insulating door tends to be formed with undulation by the heat insulating material filled through expansion in the door. SUMMARY OF THE INVENTION Accordingly, an essential object of the present invention is to provide a heat insulating door wall structure for a refrigerator or the like, in which formation of very small undulation, waving or the like on the surface of the heat insulating door is prevented to provide a door construction with a high degree of luster. Another object of the present invention is to provide a heat insulating door wall structure of the above described type which is simple in construction with a high durability, and can be readily manufactured at low cost. In accomplishing these objects, according to the present invention, there is provided a heat insulating door wall structure which comprises an outer face plate member consisting of a transparent layer and a colored layer, a frame member provided on an entire peripheral portion of said outer face plate member, an inner plate provided to confront said outer face plate member through a predetermined distance therefrom, and a heat insulating material filled, through expansion, in a space defined by said outer face plate member, said frame member and said inner plate, said transparent layer being made of glass, and the colored layer being disposed on the side of said transparent glass layer which faces said heat insulating material. Further advantageous embodiments are defined in the subclaims. More specifically, by constituting the surface of the door with a colored glass plate or the like having a transparent layer at its front surface and a colored layer at its reverse surface, deep luster is provided by the transparent glass plate located before the colored layer, while owing to high rigidity of the glass plate, undulation to be formed on the front surface of the door by contraction of an insulating material filled through expansion or foaming or by warping of the door due to temperature difference between exterior and interior of the door, is advantageously prevented and moreover, by increasing the strength of the door, reinforcing members for the door can be dispensed with for simple construction and reduction in cost. BRIEF DESCRIPTION OF THE DRAWINGS These advantages of the present invention will become apparent from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a heat insulating door according to one preferred embodiment of the present invention, Fig. 2 is a fragmentary cross sectional view showing an enlarged scale, part of the heat insulating door of Fig. 1, Fig. 3 is a cross sectional view similar to Fig. 2, which particularly relates to a second embodiment of the present invention, Fig. 4 is a perspective view of a refrigerator provided with conventional heat insulating doors (already referred to), Fig. 5 is a perspective view showing one example of a conventional heat insulating door (already referred to), Fig. 6 is an expoded perspective view of the conventional heat insulating door (already referred to), Fig. 7 is a cross section taken along the line XIX-XIX in Fig. 6 (already referred to), Fig. 8 is a perspective view of another conventional heat insulating door (already referred to), and Fig. 9 is a fragmentary cross sectional view showing on an enlarged scale, part of the conventional heat insulating door of Fig. 8 (already referred to). DETAILED DESCRIPTION OF THE INVENTION Before the description of the present invention proceeds, it is to be noted that like parts are designated by like reference numerals throughout the accompanying drawings. Referring now to the drawings, there is shown in Figs. 1 and 2, a heat insulating door D1 according to a first embodiment of the present invention, which includes a door surface colored plate member or colored glass plate 14 having a transparent layer 14a at a front surface and a colored layer 14b fused onto a reverse surface of the transparent layer 14a, a frame member 16 having a colored glass plate inserting portion 16a formed on an entire peripheral portion thereof, an inner plate 15 provided to confront the colored glass plate 14 through a space, and a heat insulating material 17 filled, through expansion, in the space defined by the colored glass plate 14, the inner plate 15 and the frame member 16. By the heat insulating door D1 according to the first embodiment as described above, effects as follows can be obtained. (1) Luster is provided by the colored glass plate 14 having the transparent layer 14a on its front surface, and the colored layer 14b at the reverse surface, while depth may be imparted to the luster. (2) Since the surface of the door D1 is constituted by a single part, it is not necessary to apply a decorative film onto the iron plate as in the conventional practice, and thus, there in no possibility of confining bubbles, dust, etc., or forming undulation or concave and convex portions on the surface of the iron plate by the bonding agent, and therefore, the surface of the heat insulating door D1 is free from undulation. (3) Owing to the fact that the surface of the door D1 is made of the single part, there is no possibility that the bonding agent is separated and raised by the difference of linear expansion coefficients upon application of cooling and heating to the heat insulating door. (4) Since the surface of the heat insulating door D1 made of the glass plate 14 has rigidity, it is not subjected to undulation by the heat insulating material 17 filled through expansion, and thus, the surface of the heat insulating door D1 is free from concave and convex portions. (5) Although there is a possibility that the surface of the heat insulating door D1 made of the glass plate is broken, the expanded heat insulating material 17 provided at reverse face side of the glass plate absorbs shock when external force is applied to the glass plate, while the edges of the glass plate which are the weakest portion are protected by the frame member 16 so as to be free from breakage. (6) When the heat insulating material 17 is to be expanded, it slides along the back face of the colored layer 14b of the glass plate 14 for efficient filling. (7) Since the glass plate 14 has rigidity, the reinforcing plate conventionally provided in the heat insulating door may be dispensed with. In a heat insulating door D2 in Fig. 3 according to a second embodiment of the present invention, the colored glass plate 14 in the first embodiment of Figs. 1 and 2 has been replaced by a reinforced colored glass plate 19 having a transparent reinforced glass layer 19a at the front surface, and a colored layer 19b at the reverse surface, while other constructions are generally similar to those in the door D1 of the first embodiment, with like parts being designated by like reference numerals for brevity. In the heat insulating door D2 according to the second embodiment of the present invention, in addition to the effect available from the door D1 in the first embodiment, durability is further improved by using the reinforced glass, while safety is achieved even when the glass should be broken.

Claims: A heat insulating door wall structure which comprises an outer face plate member (14; 19) consisting of a transparent layer (14a; 19a) and a colored layer (14b; 19b), a frame member (16) provided on an entire peripheral portion of said outer face plate member (14; 19), an inner plate (15) provided to confront said outer face plate member (14; 19) through a predetermined distance therefrom, and a heat insulating material (17) filled, through expansion, in a space defined by said outer face plate member (14; 19), said frame member (16) and said inner plate (15), said transparent layer (14a; 19a;) being made of glass, and the colored layer (14b; 19b) being disposed on the side of said transparent glass layer (14a; 19a) which faces said heat insulating material (17). A heat insulating door wall structure as claimed in Claim 1, wherein said outer face plate member (14; 19) is a colored glass plate (14; 19) including the transparent layer (14a; 19a) and the colored layer (14b; 19b). A heat insulating door wall structure as claimed in Claim 2, wherein said colored glass plate is a colored reinforced glass plate (19).

Inventors: AOKI TAKASHI, MAEDA KOUJI, MATSUMOTO TAKUYA, YAMAMOTO KOUJI, AOKI, TAKASHI, MAEDA, KOUJI, MATSUMOTO, TAKUYA, YAMAMOTO, KOUJI
Applicants: MATSUSHITA REFRIGERATION, MATSUSHITA REFRIGERATION COMPANY
Application year: 1992
Main classification: F25D23
IPC codes: E06B3, E06B5, F25D23