BIAXIALLY STRETCHED BLOW MOLDED BOTTLE

Abstract: This invention relates to a biaxially stretched, blow molded bottle (1) made of a synthetic resin. The bottle includes a square pillar body (2) and a panel wall (3) for resisting a reduced pressure occurring inside the bottle is disposed on a flat wall portion of each surface of the body. A plurality of transverse grooves (5) are juxtaposed with predetermined gaps between them at ridge portions interposed between the panel walls (3). The corners of the body (2) are rounded to form a longitudinally elongated flat surface (4) and a plurality of transverse grooves may be juxtaposed with predetermined gaps between them on the flat surface (4).

Description: The present invention relates to a biaxially blow-moulded bottle-shaped container made of synthetic resin, especially but not exclusively to a construction of a body portion of a biaxially blow-moulded bottle-shaped container made of polyethene terephthalate resin. There has hitherto been widely used a bottle-shaped container which is produced by biaxially blow-moulding a preformed parison of a synthetic resin, such as polyethene terephthalate resin. Such a bottle-shaped container has excellent material properties with regard to its contents which is provided by appropriately orienting the preformed parison. The bottle-shaped container is formed with a thin, light wall. The container has excellent shock resistance and can be inexpensively produced by mass production. However, there is a problem that when the bottle-shaped container is filled with a hot liquid content and subsequently cooled, the wall of the body portion of the bottle-shaped container is deformed owing o a reduced pressure in the container. Accordingly, it has been known to provide panel walls in the body portion to absorb the reduced pressure by elastic deformation of the panel walls. It is required that each panel wall is of a relatively large flat wall construction due to the following reasons: (1) the panel wall is more deformable by the reduced pressure than other parts of the body; (2) the deformation produced on the panel wall is an elastic deformation; and (3) only a little depression-deformation decreases the volume of the container by a relatively large amount. A large biaxially blow-moulded bottle-shaped container, having a cylindrical body portion of a circular section, can be provided with reduced-pressure absorbing panels only by forming vertically extended flat portions on the peripheral surface portion of the body portion. Therefore, the shape of the panel walls on the body portion of the container is vertically elongated and as the result the panel walls of the container can not be greatly deformed. Therefore, the volume of the bottle-shaped container is not greatly varied by the depression-deformation of the panel walls on the body portion of the bottle-shaped container. A large biaxially blow-moulded bottle-shaped container having a cylindrical body of a square section can be provided with reduced-pressure absorbing panels by forming a flat portion on each side of the square cylindrical body portion. Each flat portion can be easily and sufficiently deformed and has a large flat area, so that the volume of the container can be greatly varied by the deformation of the flat portions. Thus, each flat portion effectively acts as a panel wall for absorbing the reduced pressure. Figure 3 illustrates a conventional bottle-shaped container 1' having a square cylindrical body portion 2'. Each side surface of the body portion 2' respectively continues adjacent to both side surfaces through ridge line portions. Each side surface of the body portion is provided with a reduced-pressure absorbing panel wall 3' for absorbing the deformation of the wall of the bottle-shaped container caused by the reduction of the pressure in the container. When the pressure in the bottle-shaped container 1' is reduced, the panel walls 3' are deformed and bent inwardly to cause internal stress extending to the ridge line portions. The ridge portions are pillar portions for maintaining the shape of the bottle-shaped container and must have a high mechanical strength. If the ridge portions are deformed by the internal stress, the mode of bending of the panel walls 3' is not constant and the body portion of the square cylindrical shape is deformed. In particular, large bottle-shaped containers are greatly deformed by the reduced pressure, because the large bottle-shaped containers have a thin wall owing to relatively deep orientation and relatively great height thereof. Thus, the large bottle-shaped containers are required to have ridge line portions having a high mechanical strength. In order to obviate the aforementioned problems, these containers have been designed to provide elongated grooves 5' in the ridge line portions. Such an elongated groove 5' acts as a reinforcing rib to increase the mechanical strength in the ridge line portion thereby to prevent the ridge line portion from undue strain deformation owing to the deformation of the panel wall 3'. Generally, biaxially blow-moulded bottle-shaped containers produced in a factory are packed in cases made of a corrugated cardboard and transported to other factories for filling the bottle-shaped containers with liquid. The bottle-shaped container is light, but is bulky. Consequently, in order to efficiently transport the bottle-shaped containers, it is desirable that a number of bottle-shaped containers are closely packed in each cardboard case. However, when uncapped bottle-shaped containers, as shown in Figure 3, are closely packed within the cardboard case and are subjected to an external pressure over a limit of the mechanical resistance of the ridge line portions having a mechanical strength sustained by the elongated grooves 5', the ridge line portions are inwardly bent to cause a bending deformation. This bending-deformation is semi-permanently retained since the elongated grooves 5 act as reinforcing ribs in the condition of bending deformation thus preventing the ridge line portions from elastically returning back to their original form. JP-U-61-117,109 shows a blow-moulded bottle-shaped container made of synthetic resin. The container has a series of parallel depressions in one of its curved walls to reduce the likelihood of deformation. However this is not particularly effective as a considerable external pressure is required because of the curved nature of the walls. Thus any deformation is likely to be permanent. A further similar container is described in EP-A-0,324,305 which has a series of parallel depressions in each one of its four curved corners and suffers the same disadvantages. It is an aim of the present invention to obviate the aforementioned problems and disadvantages in the prior art and to provide a bottle-shaped container adapted for preventing the ridge line portions from inwardly bending and being semi-permanently deformed by the external pressure applied on the body portion of the bottle-shaped container, whilst also maintaining a necessary mechanical strength. Accordingly the present invention is directed to a biaxially blow-moulded bottle-shaped container of synthetic resin including a generally square cylindrical body portion, in which a panel wall for absorbing a reduced pressure in the bottle-shaped container is provided as a flat wall portion at each side of the body portion, and depressed cross grooves are provided spaced apart in parallel in a ridge line portion between the adjacent panel walls, in which the ridge line portions comprise generally longitudinally extending elongated flat surfaces provided by corners of the body portion which have a cut-off form, so that the depressed cross grooves may be provided spaced apart in parallel in each flat surface. When the pressure in the bottle-shaped container is reduced by cooling after the container is filled with a hot liquid, the reduction of the pressure is sufficiently absorbed by elastic depression-deformation of the panel walls of the body portion. When the panel walls are elastically depression-deformed to cause an internal stress, this internal stress acts on the ridge line portions between adjacent panel walls. The internal stress comprises a component of force drawing the ridge line portions inwardly and a component of force acting on each ridge line portion from the opposite sides thereof. The cross grooves depressed in the ridge line portion will effect inward bending of the ridge line portion against the force drawing the ridge line portion inwardly. The ridge line portion is subjected to the inwardly drawing force as well as the forces acting from the opposite sides thereof as mentioned above. The ridge line portion tends to protrude radially and outwardly owing to the forces acting on the ridge line portion from the opposite sides thereof. Thus, the ridge line portions act as reinforcing ribs against the inwardly drawing force and provide a high mechanical strength. Accordingly, when uncapped bottle-shaped containers closely packed within the cardboard case are subjected to a force acting sidewardly on the body portion and the force increases higher than a predetermined value, the ridge line portions are all similarly elastically deformed inwardly owing to the cross grooves which are transversely depressed in the ridge line portion. Thus, the external force or pressure is absorbed by the elastic bending-deformation of the ridge line portion all over the same. In this case, since the deformation of the ridge line portions is an elastic deformation, the deformed ridge line portions are elastically returned to the original form when the external force or pressure is released. Accordingly the ridge line portions are not semi-permanently deformed. A corner of the body portion is cut-off to provide flat ridge line portions. Thus, each ridge line portion has corners formed at its opposite sides and each cross groove also has corners formed at its opposite sides. These corners arranged at the opposite sides of the each ridge line portion can act as reinforcing ribs against an elastically bent deformation of the central portion of the ridge line portion. Thus, the opposite side portions of the ridge line portion have a stress to extrude radially and outwardly from the ridge line portion by a force pressing the ridge portion from the opposite sides thereof due to the deformation of the panel wall. As a result, the mechanically support for the ridge line portion in the deformation of the panel wall is increased. Since the central portion of the ridge line portion is flat, the ridge line portion can be elastically deformed by the external force or pressure. Consequently, when the body portion of the bottle-shaped container which is not filled with liquid is subjected to a large external force or pressure, the whole ridge line portion can be more greatly elastically deformed without semi-permanent bending-deformation and as a result the faculty of absorbing the external force or pressure is increased by the elastic deformation of the whole ridge line portions and also a sufficient mechanical strength to maintain the shape of the bottle-shaped container is sustained. A preferred example of a biaxially blow-moulded bottle-shaped container made in accordance with the present invention is illustrated in Figures 1 and 2 of the accompanying drawings, in which: Figure 1 is a front view of an embodiment of a biaxially blow-moulded bottle-shaped container according to the present invention; and Figure 2 is an enlarged cross-sectional view of the lower portion of the bottle-shaped container shown in Figure 1. A bottle-shaped container 1 shown in Figures 1 and 2 is a large bottle having a thin wall which is produced by biaxially blow-moulding a preformed parison made of a synthetic resin. In this embodiment, the bottle-shaped container 1 is made of a polyethene terephthalate resin. The bottle-shaped container 1 has a generally square cylindrical body portion 2. This body portion 2 is provided at each side of the container for about the two-thirds of the lower portion thereof, with panel walls 3 for absorbing deformation caused by reduced pressure in the container. Each panel wall 3 may be provided at its central portion with one or more depressed portions 3a which absorb the reduced pressure in the container. The depressed portion 3a effectively permits the whole panel wall 3 to deform owing to the reduced pressure without unduly straining it. In the illustrated embodiment, two depressed portions 3a, 3a are formed at positions vertically spaced apart in each panel wall on each side of the body portion, but an elongated depressed portion may be provided in each panel wall 3. A ridge line portion at each corner of the square cylindrical body portion 2 is cut off to provide an elongated flat surface 4, which extends vertically at each corner. Corner portions 7 are formed at the opposite sides of the flat surface 4. The flat surface 4 is provided with a plurality of depressed cross grooves 5 spaced apart in parallel. A cross ridge 6 is formed between adjacent cross grooves 5, 5 as a remaining portion of the flat surface 4. The cross groove 5 extends in the circumferential direction of the body portion over the width of the flat surface 4. The cross groove 5 has corners 7a formed therein. These corners 7a respectively correspond to the corners 7. Vertical ribs 5a are respectively formed between the opposite ends of the cross grooves and the corners 7a. The upper and lower ends of each cross groove 5 act as cross ribs 5b. The corners 7 and 7a continuously form a vertical rib which resists internal stress in the ridge line portion when the panel wall 3 absorbs the reduced pressure generated within the bottle-shaped container 1. The vertical ribs 5a and cross ribs 5b together with the cross ridge 6 absorb the external force or pressure applied to the bottle-shaped container 1 to deform the flat surface 4 elastically. The bottle-shaped container having the aforementioned construction can exhibit the following effects. Since each ridge line portion stably and rigidly supports the panel wall, which is elastically depression deformed owing to the reduced pressure to resist the internal stress caused by the depression-deformation of the panel wall, each panel wall for absorbing the reduced pressure in the bottle-shaped container is elastically depression-deformed. Accordingly, the configuration of the bottle-shaped container can be maintained in a better form when deforming due to the reduced pressure generated within the bottle-shaped container. When the body portion of the bottle-shaped container which is not filled with any contents is subjected to a high external force or pressure in the lateral direction, the whole ridge line portions are greatly elastically deformed, so that the external force or pressure can be absorbed by the elastic deformation of the ridge line portions. Thus, the ridge line portions are not permanently deformed in the form of a buckling- or bending-deformation by the external force or pressure. As a result, the occurance of a bottle-shaped container of inferior quality owing to the permanent buckling-deformation of the ridge line portions is obivated. Since the ridge line portions in the corners of the square cylindrical body portion are provided with depressed cross grooves, fingers are snugly fitted in the cross grooves when the body portion is gripped by one hand. Therefore, such a large bottle-shaped container can be safely handled by one hand. Since the cross grooves are simply depressed in the ridge line portions, the construction is simple and can be easily moulded in the conventional manner without the necessity for any particularly special moulding technique.

Claims: A biaxially blow-moulded bottle-shaped container (1) of synthetic resin including a generally square cylindrical body portion (2), in which a panel wall (3) for absorbing a reduced pressure in the bottle-shaped container is provided as a flat wall portion at each side of the body portion, and depressed cross grooves (5) are provided spaced apart in parallel in a ridge line portion between the adjacent panel walls (3, 3), characterised in that the ridge line portions comprise generally longitudinally extending elongate flat surfaces (4) provided by corners of the body portion which have a cut-off form, so that the depressed cross grooves (5) are provided spaced apart in parallel in each flat surface (4).

Inventors: HAYASHI YOSHIAKI YOSHINO KOGYO, HAYASHI, YOSHIAKI YOSHINO KOGYOSHO CO.; LTD.
Applicants: YOSHINO KOGYOSHO CO LTD, YOSHINO KOGYOSHO CO., LTD.
Application year: 1989
Main classification: B65D1
IPC codes: B65D1