DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Referring now to FIGS. 1 to 4, there is shown a bottle-type plastic container according to one embodiment of the present invention. The container includes a barrel portion 1 and an opening 2 in one end region of the barrel 1, for allowing liquid contents to be charged into the container and discharged therefrom.

[0020] The container according to the present invention may be comprised of appropriate synthetic resin, typically polyethylene terephthalate (PET) resin. Alternatively, however, the container may be comprised of polyamid resin, polycarbonate resin, polyacetal resin, polybuthylene terephthalate resin or other synthetic resin having a sufficient resistance to chemicals. The container may be formed by known molding process, such as a biaxial orientation blow molding process or a direct blow molding process.

[0021] The barrel portion 1 has a generally polygonal cross-section, i.e., a square cross-section in the illustrated embodiment. The polygonal cross-section of the barrel portion 1 is defined by a plurality of substantially flat walls 3, as well as a plurality of part-cylindrical corner walls 4 extending contiguously between the flat walls 3.

[0022] Each flat wall 3 has a shape that is deflected inwards, i.e., toward the longitudinal axis of the container, as the liquid contents charged into the container at a high temperature is cooled to a room temperature. Such deflection of the flat walls 3 serves to absorb a pressure drop within the container. It is preferred that each flat wall 3 has at least one reinforcing rib 5 that extends horizontally when the container is standing on a support, such as a conveyor in a beverage factory or a table at home. These reinforcing ribs 5 effectively prevent bulging out of the flat walls 3 when the container is charged with contents, and serve to maintain the shape of the barrel portion 1 upon the pressure drop within the container.

[0023] Further, each corner wall 4 has a center line of curvature that extends in parallel with a longitudinal direction of the container, and a radius of curvature R that decreases to a smaller radius R′ as the pressure drop is absorbed by the deflection of the flat walls 3.

[0024] The square cross-sectional geometry of the container includes two pairs of flat walls 3 forming part of the barrel portion 1, wherein opposed flat walls 3 of the adjacent containers are parallel to each other. It is thus possible to ensure that, when a series of containers are successively transferred along a conveyor in a beverage factory, neighboring containers are brought into a stable contact with each other to realize an improved alignment stability.

[0025] With reference to FIG. 5, when the container shown in FIGS. 1 to 4 is charged with liquid contents at a high temperature of 80-95° C., for example, and the contents then undergo a gradual cooling to a room temperature, the flat walls 3 of the barrel portion 1 are deflected inwards as shown by arrows, to thereby absorb a pressure drop within the container. Simultaneously, the radius of curvature R of the corner walls 4 between these flat walls 3 is decreased to a smaller radius R′ so that the corner walls 4 serve as a reinforcing column to provide an improved buckling strength of the container.

[0026] The unique cross-sectional geometry of the container according to the present invention, wherein at least two of the flat walls forming part of the barrel portion are parallel to each other, also provides a practical advantage that, when a series of containers are successively transferred along a conveyor in a beverage factory, neighboring containers are brought into a stable contact with each other to realize an improved alignment stability.

[0027] With reference to FIGS. 6A and 6B, when a series of conventional bottle-type plastic containers are successively transferred along a conveyor in a beverage factory, adjacent containers, of which the flat walls have been more or less subjected to bulging out, tend to be brought into a single line contact with each other thereby generating side forces as shown by arrows in FIG. 6A. As a result, the containers tend to be rotated about the respective center axes as shown in FIG. 6B, making it difficult to achieve an orderly alignment of the containers. On the other hand, according to the present invention, adjacent containers while being transferred along a conveyor are brought into contact with each other along two lines at the opposite corner walls 4, as shown in FIG. 6C, so that the orientation of the containers about the respective longitudinal axes can be maintained stably, thereby facilitating further processing and/or handling of the containers at a beverage factory.

[0028] A modified embodiment of the present invention is shown in FIG. 7, wherein the barrel portion of a plastic container is enclosed by a heat shrink label 6. In this instance, when the container is subjected to a pressure drop upon cooling of high temperature liquid contents, the part-cylindrical corner wall 4 of the barrel portion 1 are directly connected to each other by the shrink label 6 whereby the corner walls 4 functioning as reinforcing columns are further reinforced by the beams that are formed by the heat shrink label 6. It is thus possible to realize a further improved bucking strength of the container.

[0029] It will be appreciated that the present invention provides an improved bottle-type plastic container that can be charged with liquid contents at a high temperature, and that exhibits a sufficient buckling strength against a load applied to the container in its longitudinal direction, even after the cooling of the contents and the resultant pressure drop within the container. The improved container according to the present invention can be highly efficiently produced at a low cost, without requiring substantial changes to existing facilities.

[0030] While the present invention has been described above with reference to specific embodiments, it is needless to say that various changes and/or modifications are possible without departing from the scope of the invention.