GB2025889A

GB2025889A - Longitudinally extending thin- wall bottle formed from synthetic resin

Info

Publication number: GB2025889A
Application number: GB7923496A
Authority: GB
Original assignee: Yoshino Kogyosho Co Ltd
Current assignee: Yoshino Kogyosho Co Ltd
Priority date: 1978-07-10
Filing date: 1979-07-05
Publication date: 1980-01-30
Also published as: CH639040A5; JPS5512422U; NL7905297A; CA1157785A; JPS6128736Y2; FR2430891A1; IT1193207B; DE2927822A1; IT7922033V0; AU537100B2; DE2927822C2; AU4875879A; IT7924133A0

Abstract

The side wall (2) of a thin-wall blow moulded bottle of synthetic resin, particularly poly(ethylene terephthalate) resin, is inwardly and curvedly depressed around its periphery at its mid-portion to form a constriction (3), and the base portion of the constriction is slightly peripherally and curvedly protruded outwardly to form a peripheral protrusion (4). The bottle has increased strength without the need for thickening the wall of the whole body (2). <IMAGE>

Description

SPECIFICATION Longitudinally extending thin-wall bottle formed from synthetic resin, and method of its manufacture The present invention relates to a longitudinally extending blow-molded thin-wall bottle formed from synthetic resin, and to a method of making such a bottle. The invention is applicable more particularly to a longitudinally extending biaxial stretch blow-molded thin-wall bottle formed from poly(ethyleneterephthalate) resin.

Recently, a number of longitudinally extending blow-moulded thin-wall bottles formed from synthetic resin have been used in particular as bottles for storing liquids.

This results from the perception that such bottles themselves are light in weight, simple to mold, of good appearance, low in production cost, etc. Because of the use of blowing or blow molding in the molding process, the wall thickness of the peripheral body of the bottle inevitably becomes thin.

Particularly, in the case where the bottles are molded from polyethylene terephthalate resin as the synthetic resin material and which has the property of resisting chemicals such as acids, has mechanical durability, and has various other properties, the articles must be subjected to sufficient biaxial stretch molding. For this reason, the wall thickness of the peripheral body, to which the greatest biaxial stretch molding is applied becomes relatively thin.

This gives rise to a problem in that the peripheral body portion is less secure against internal pressure, and has reduced mechanical strength in connection with the durability against pressure from above.

In particular, the external forces against the peripheral body mainly tend to act concentrically on the middle portion in height of the peripheral body. Thus, in the event that an even external force acts on the entire peripheral body, the external force will principally act concentrically on a specific limited portion even if the peripheral body can exhibit sufficient durability, thereby resulting in inconveniences such as deformation and even damage.

In the past, therefore, the wall thickness of the entire peripheral body has been made thick to the extent that the peripheral body can withstand the external force acting thereon in order to compensate for the lack of mechanical strength of the peripheral body portion. As a consequence, the quantity of synthetic resin material used to mold one bottle considerably increases as compared to the theoretical quantity of synthetic resin material required for the bottle to serve as a container, which is extremely uneconomical.

Further, if the wall thickness of the peripheral body is increased as described above, the pressure of the pressurized fluid (usually pressurized air) required for blow molding increases. Accordingly, it is necessary to increase the pressure resisting value of the pressurized fluid flow passage system due to said increased pressure and to increase the mold-fastening force of the mold as well as the capacity of the compressor.

Furthermore, particularly, in the event that polyethyleneterephthalate resin is used, it is necessary for the article to be molded and cooled in a primary step, after which the piece has to be evenly reheated up to a temperature capable of achieving blow molding for biaxial stretch blow molding. In reheating the piece up to a temperature of capable of achieving the biaxial stretch blow molding, however, the whole piece of increased wall thickness must be reheated to a uniform predetermined temperature, and thus, it takes a long period of time for such reheating, which results in a lowering of the molding rate.

The increase in wall thickness of the peripheral body for the purpose of compensating for the lack of mechanical strength thereof, as described above, gives rise to various inconveniences in view of economy, equipment capacity of the molding apparatus, and molding rate. Thus, the emergence of means to overcome these difficulties has been desired earnestly.

-The present invention is defined in the appended claims, to which reference shouid now be made.

The invention will be described in more detail, by way of example, with reference to the drawing in which: Figure 1 is a front view showing the external appearance of a bottle embodying the present invention; and Figure 2 is an enlarged longitudinal sectional view of a portion within the circle II in Figure 1.

The drawing shows a longitudinally extending blow-molded thin-wall bottle formed from synthetic resin, and more particularly a longitudinally extending biaxial stretch blow molded thin-wall bottle formed from polyethyleneterephthalate resin. In a substantially middle portion in height of a fully biaxial-stretched thin wall peripheral body 2 of a longitudinally extending molded bottle 1, a constricted part 3 curvedly depressed over the whole periphery of the said middle portion is molded in the form of a peripheral groove, and a bottom or base portion of the constriction 3 is curvedly protruded oppositely to form a peripheral protrusion 4. The protrusion does not extend outwardly beyond the. periphery of the upper and lower portions of the body'2..

When the bottle 1 is filled with liquid, the relatively largely depressed constriction 3 molded in the substantially middle portion height of the peripheral body 2 serves to disperse the internal pressure concentrically acting on the middle portion in the direction of the height of the peripheral body 2 towards portions in both the upper and lower directions of the peripheral body 2 along both the inclined side walls, whereby the internal pressure does not concentrically act on the middle portion in height of the peripheral body 2 but dispersively acts over a wide range of the peripheral body 2.

For this reason, the internal pressure per unit area of the peripheral body 2 is somewhat higher than the case wherein the constriction 3 is not included, but the internal pressure per unit area acting on the construction 3 is a value much smaller than the case wherein the constriction 3 is not provided.

Namely, the internal pressure acts substantially evenly on the whole region of the peripheral body 2 by the provision of the constriction 3, and accordingly, it is not now necessary to increase the wall thickness of the whole peripheral body 2 in order to increase the strength of a limited portion of the peripheral body 2. Thus, it is possible to permit the whole body of the peripheral body 2 to have the thin wall thickness that can withstand the above-mentioned substantially even internal pressure.

It is also designed so that the constriction 3 molded in an inwardly curvedly depressed manner is subjected to easy elastic deformation by a biasing force acting in the axial direction of the bottle 1.

When receiving the aforesaid biasing force, the constriction 3 is readily elastically-deformed to absorb and bear the biasing force before deformation of the rst of the peripheral body 2 occurs. The capability of the constriction 3 to bear the biasing force due to the elastic deformation is of course limited, and hence, as the biasing force is permitted to be increased gradually to increase the amount of elastic deformation of the constriction 3, the deformation finally concentrates on the bottom of the constriction 3 to buckle and break the bottom of the constriction 3.

Accordingly, the peripheral protrusion 4 is molded in the bottom of the constriction 3 in order to increase the buckling strength of the constriction 3.

As is apparent from the whole construction of the constriction 3 and the peripheral protrusion 4, the peripheral protrusion 4 does not materially influence the elastic deformation of the constriction 3 under the effect of a biasing force along the axis of the bottle 1 , but as the amount of elastic deformation increases, the peripheral profusion 4 itself elastically deforms so as to impede the increase in elastic deformation.

That is, the elastic deformation of the constriction 3 as a whole proceeds to displace inwardly the bottom of the constriction 3, whereas the deformation of the peripheral protrusion 4 itself proceeds in a direction of its outward protrusion. Consequently, the elastic deformation of the constriction 3 cannot concentrate on the bottom or the peripheral protrusion 4, and the whole constriction 3 including the peripheral protrusion 4 is substantially evenly deformed.

As described above, since the constriction 3 including the peripheral protrusion 4 is subjected to uniform elastic deformation as a whole against the biasing force in a longitudinal direction without permitting deformation of the elastic deformation to be concentrated on a specific portion, it is possible to exhibit extremely powerful buckling strength.

The powerful internal pressure acts on the portion of the peripheral protrusion 4, by the provision of the peripheral protrusion 4, as compared to the case wherein the peripheral protrusion 4 is not provided. However, since most of internal pressures acting on the middle portion in height of the peripheral body-2 in which the constriction 3 is provided are dispersed in both the upper and lower directions by the inclined side walls of the constriction 3, the increment of internal pressure acting thereupon is small.

To increase further the buckling strength of the peripheral body 2 as a whole against the longitudinalbiasing force, it is advantageous to provide a number of small depressed recesses 5 in the peripheral direction over substantially the entire height of the peripheral body 2, as shown in the drawing.

However, these recesses 5 are not affected by the usual longitudinal biasing force but merely perform their function to a degree that there is a possible capability of preventing breakage of the bottle 1, depending upon the magnitude of the biasing force when the excessive biasing force is applied.

The reason is that in that state wherein the portion of.the recess 5 needs to be subjected to elastic deformation, even elastic deformation of the constriction 3 as a whole including the peripheral protrusion 4 has already reached its limit, and the durability against so powerful a biasing force as to cause the elastic deformation is not required in the design of the bottle 1.

Accordingly, to increase the buckling strength of the peripheral body 2 is a secondary object of the recesses 5, and a primary object thereof is to provide ornamental effects achieved by giving variety to the external appearance of the bottle 1 as a whole.

In view of the above-mentioned construction, it is possible substantially evenly and dispersively to exert the external forces such as pressure from the interior of the bottle 1 and the longitudinal biasing force on the entire peripheral body 2, elastic deformation due to the action of external forces readily occurs and local occurrence of such elastic deformation can be avoided. Thus, it is possible for the bottle to bear extremely effectively such external forces so as to exhibit an.extremely powerful mechanical durability.

Furthermore, since local concentration of external forces and location deformation can be avoided positively, it is possible to make the wall thickness of the peripheral body 2 thinner than that of prior art bottles of the type as described, thereby reducing the quantity of synthetic resin material required to mold bottles of the same capacity and size as the latter.

This indicates considerable improvements in pressure resistance of pressure fluid system, heating speed and molding speed required in blow molding, thereby considerably reducing equipment cost and considerably increasing production rate and efficiency.

Moreover, since the largely depressed constriction 3 is molded in a middle portion in height of the peripheral body 2, it is possible, in handling the bottle 1 by one hand, to put the fingers around the constriction 3, whereby the bottle 1 may be handled safely without permitting the bottle to slip and a variety may be given by the constriction 3 to external appearance of likely monotonous bottle 1 thereby heightening the ornamental effect of the bottle 1.

Claims

1. A longitudinally extending stretch blowmolded thin-wall bottle formed from synthetic resin in which at a substantially middle portion in height of the peripheral body the bottle is inwardly and curvedly depressed around its periphery to form a constriction and the base of the constriction is slightly outwardly and curvedly protruded around the periphery to form a peripheral protrusion.

2. The longitudinally extending thin-wall bottle as claimed in claim 1, wherein said synthetic resin material comprises poly(ethylene terephthalate).

resin, and wherein said bottle is molded by biaxial.

stretch blow molding.

3. The longitudinally extending thin-wall bottle as claimed in claim 1 or 2, in which the peripheral protrusion does not extend outwardly beyond the periphery of the major part of the rest of the bottle.

4. A longitudinally-extending stretch blowmolded thin-wall bottle, substantially as herein described with reference to the drawing.

5. A method of making a longitudinallyextending bottle comprising blow-molding a thinwall bottle from synthetic resin, the blow-molding operation including a stretch blow molding step, in which at a substantially middle portion in height of the peripheral body of the bottle is inwardly and curvedly depressed around its periphery to form a constriction, and the base of the constriction is slightly outwardly and curvedly protruded around the periphery to form a peripheral protrusion.

6. A method according to claim 5, in which the synthetic resin comprises poly (ethylene terephthalate) resin or an obvious chemical equivalent thereof.

7 A method of making a longitudinally extending stretch blow-molded thin-wall bottie, substantially as herein described with reference to the drawing.