BOTTLES

Abstract: A plastics bottle, particularly for use in a carbonating machine, with a weakness (6) in the neck for the bottle to burst at a selected internal pressure and in a controlled manner.

Description: Bottles This invention relates to bottles, and in particular to bottles which in use are intended to be subjected to internal pressures, such as bottles for use in liquid carbonating machines to prepare carbonated beverages " There is known- e.g. from patent specification No. GB 1453363} a type of liquid carbonating machine in which the liquid, generally water, is placed in a bottle and the bottle is then loaded into the machine . During the carbonation process the bottle is pressurised by the gas introduced into the liquid. Sometimes a defective or damaged bottle can shatter under this pressure. For this reason it is usual for the bottle to be housed within a strong shield to prevent injury to a person using the machine. Hitherto it has been the usual practice to use glass bottles since glass is non-porous, enabling carbonated drinks to be stored for lengthy periods, and the glass surface is very smooth which facilitates the carbonating process. Although many plastics materials are quite unsuitable, there are available plastics materials having such properties that they could be used for bottles to be used in a carbonating machine. Examples of such materials include polyethyleneterephthalate (PET), which is widely used for bottles for carbonated beverages, certain grades of nylon,polycarbonate and.PVDC. Other materials are also possible and will occur to readers skilled in the art. T If a plastics bottle is pressurised until it bursts the material will normally split open to release the pressure, and it has been suggested that use of a plastics bottle in a carbonating machine would obviate the need for the protective shield since there would be no danger from flying bottle material. However, tests have shown that even some plastics bottles with a rigid moulded neck portion will in some instances burst with the neck shattering. The present invention aims at a solution to the above problem and resides in a bottle made of plastics material and including an integral portion of reduced thickness defining a predetermined weakness at which the bottle will burst upon over-pressurisation to release the pressure in a controlled manner. In a preferred embodiment of the invention the reduced thickness portion is provided in the region of the bottle neck, preferably above the normal level of liquid in the bottle, and is formed during moulding of the bottle neck. In this way the thickness of the weakened portion is conveniently predetermined so that it will fracture by splitting at a desired pressure avoiding any danger of shattering. By locating the weakened portion above the normal level of liquid it is ensured that liquid is not sprayed out under pressure when a burst does occur, which would happen if the body of the bottle split open. The configuration of the reduced thickness portion is variable and as described in more detail below can, for example, take the form of a flat surface portion on the outside of the body, a disc of thinner material, or a groove in the external surface . Three particular embodiments of the invention applied to bottles made of PET will now be described with reference to the accompanying drawing in which:- Figure 1 is a front view of a bottle neck; OMPI Figure 2 is a side view of the bottle neck; Figure 3 is a part section along the line X-X of Figure 2; Figure 4 is a front view of another bottle neck; Figure 5 is a side view of the bottle neck; Figure 6 is a part section taken along the line Y-Y of Figure 5; Figure 7 is a front view of a further bottle neck; and Figure 8 is a section taken along the line Z-Z in Figure 7 • A method often adopted in the manufacture of plastics bottles,e.g.PET,consists of producing by injection moulding a preform including a neck part and a body and subsequently blowing out the body into the final shape. During the step of blowing out the body the material is stretched substantially and . its thickness is reduced. The shape and form of the oocc-Ie neck are unchanged by the blowing process and as a result the material at the neck of the finished bottle is relatively brittle despite being much thicker than the bod . Figures 1 to 3 show the neck portion of a PET bottle manufactured by the above method. The neck is formed with its final shape during production of the preform by injection moulding. As illustrated the neck includes a screw thread 1 and an integral ring 2 but these features are not essential to the invention. The neck includes also a weakened portion 3 of reduced thickness provided by a flat on the outside of the neck below the ring 2. The minimum thickness of the neck material at the portion 3 ma be in the order of 0.1 to 0.25 mm. Some bottles of this form were made and tested and the portion 3 ruptured at between 200 and 250 p.s.i. in each case and always before a shattering of K OMPI the neck or splitting of the body. The bottle illustrated in Figures to 6 is essentially the same as that of Figures 1 to 3 except that „ in this case the weakened portion takes the form of a circular disc or membrane approximately 8 mm in diameter and ofa uniform thickness which is selected in accordance with the required burst pressure. The disc 4 is formed by a cylindrical recess 5 moulded into the neck and ensures a controlled burst at a pressure which is safely below that ε. v.iic the body could split or the neck shatter. Typically a carbonating machine bottle which would burst at 300 psi should have a membrane which would burst at a pressure of between 200 and 240 psi and it has been found that a membrane thickness of the order of 0.1 to 0.15 z>-~ ~ is appropriate in the. case of PET. The bottle shown in Figures 7 and 8 differs from the earlier embodiments in that the weakened portion comprises a groove 6 in the external surface of the bottle neck. The groove is V-shaped in cross-section and extends around a substantially closed path of square rectangular configuration. The groove is formed in the bottle neck during injection moulding of this bottle part. For the weakened portion to rupture at a desired pressure in the region of 200-240 psi the thickness of the PET material at the bottom of the groove should be about 0.05 to 0.15 tm. ' Tests with this form of bottle embodying the invention have shown that the weakened portion will initially burst at one of the corners between adjacent portions of the groove 6. Although specifically described in relation to bottles made of PET the invention is also applicable to bottles made of other plastics materials, including laminates. It is believed that the different forms of weakened neck portion described above will be practical for other materials although dimensions may need to be adjusted to achieve the desired bursting pressure. A carbonating bottle made in accordance with the - invention obviates the need for a strong protective shield in a carbonating machine by eliminating the risk of flying material in the event of the bottle bursting. If a burst does occur the pressure is released gradually in a controlled fashion rather than suddenly in an explosion. For a bottle to be used in carbonating machines the reduced thickness portion will be arranged to rupture at a pressure greater than the normal operating pressure of the machine, preferably by about 20-60psi. While the invention has been described specifically in relation to bottles for carbonating machines it should nevertheless be understood that the invention is capable of a much wider application and will be of advantage in other plastics bottles which are intended or liable to be subjected to internal pressures. OMPI ^ WIPO

Claims: ^ Claims : 1. A bottle intended for or liable to internal pressurisation and made of plastics material, characterised in that an integral portion (3j 4; 6) of the bottle has reduced thickness and defines a predetermined weakness at which the bottle will burst upon over- pressurisation to release the pressure in a controlled manner. 2. A bottle according to claim 1, wherein the reduced thickness portion is provided in a moulded part of the bottle and is formed during the moulding of said part . 3. A bottle according to claim 2, wherein said part is produced by injection moulding. 4. A bottle according to claim 1, 2 or 3j wherein the reduced thickness part is provided in the region of the bottle neck above the intended level of liquid in the bottle . 5. A bottle according to any one of the preceding claims wherein said reduced thickness portion is provided by a flat (3) on the exterior surface of the bottle. 6. A bottle according to any one of claims 1 to Δ. , wherein the reduced thickness portion comprises a membrane (4) formed by an external recess (5) in the bottle. 1 - A bottle according to any one of claims 1 to A , wherein the reduced thickness portion is provided by a groove (6) in the external surface of the bottle. "8. A bottle according to claim 7 wherein the groove has a substantially V-shaped cross-section. 9. A bottle according to claim 7 or δ, wherein the ' groove includes two portions which meet at an angle. 10. A bottle according to claim 9 , wherein the groove extends around a substantially rectangular path. 11. A bottle according to any one of the preceding claims, intended for use in a carbonating machine, wherein the reduced thickness portion is arranged to rupture at a pressure gre ' a ' er ' t ar. the normal operating pressure of the machine, preferably by about 20-60 psi.

Inventors: MABB KENNETH GEORGE, MABB, KENNETH, GEORGE
Applicants: SODASTREAM LTD, SODASTREAM LIMITED
Application year: 1983
Main classification: B65D23
IPC codes: B65D1, B65D23, B65D51