GB2131344A

GB2131344A - Blow moulding bottles

Info

Publication number: GB2131344A
Application number: GB08332672A
Authority: GB
Inventors: Geoffrey Alan Giles; Brian Alec Furnell; Christopher John Griffin
Original assignee: Metal Box PLC
Current assignee: Crown Packaging UK Ltd
Priority date: 1982-12-08
Filing date: 1983-12-07
Publication date: 1984-06-20
Also published as: GB8332672D0; GB2131344B

Abstract

A bottle (10) for a jigger-style closure cap is formed by blow moulding an injection moulded preform, the bottle having a neck portion (14) with a cylindrical part (14A) on which is formed a screw thread 12. The neck portion further includes a flared skirt (20) which carries a ring (18) formed with ratchet teeth (16) adapted for co- operation with complementary ratchet teeth on a tamper proofing ring around the free edge of the jigger cap (not shown). The skirt (20) overlies an intermediate portion (24') which joins the neck portion (14) with the body portion (26') of the bottle. The neck portion (14) is given substantially its final form at the preform stage, whereas the intermediate (24') and body portions (26') are expanded by the blow mouldings operation. The expansion of the intermediate portion (24') brings it into firm engagement with the bottom of the skirt (20) so as to locate the ratchet teeth (16) radially and render the skirt solid with the remainder of the bottle. Alternatively, portion (24') may engage skirt (20) over substantially the whole of its length, and the skirt may be provided with circumferentially spaced apertures, Figures 6, 7 (not shown). <IMAGE>

Description

SPECIFICATION Bottles and a method of making them This invention relates to bottles formed by blow moulding from a preform, and a method of making them.

It is well known to blow mould bottles from plastics material which, immediately prior to the blow moulding operation, is in the form of a plain extruded tubular parison. Bottles normally require specific features such as threads on their neck portions, and when certain plastics such as PVC or high density polyethylene are being used these formations can be satisfactorily formed during the blow moulding operation because these plastics will stretch and flow satisfactorily into appropriately formed recesses in the interior of the blow mould. A further type of formation sometimes required is a plurality of ratchet teeth located on the neck portion of the bottle below the threads, for engagement with complementary ratchet teeth formed on the periphery of a cap which is to be screwed onto the bottle threads.The cap teeth are carried on a ring which is arranged to break away from the remainder of the cap when the cap is unscrewed from the bottle, this breaking being caused by the attempt to move the ratchet teeth over one another in a reverse direction. These ratchet teeth on a bottle neck can also be satisfactorily formed from the a bovementioned plastics during the blow moulding operation.

However, other plastics such as PET (polyethylene-terephthalate) do not stretch and flow well into constricted internal blow mould recesses, and satisfactory definition of, for example, screw threads or ratchet teeth is difficult or impossible to achieve. To overcome this problem when using such plastics, it has been usual to use, instead of a tubular parison, an injection moulded preform on which the neck features such as threads and ratchet teeth have been moulded to their final form during the injection moulding process. The preform is then subjected to a blow moulding operation which leaves the neck portion of the preform and its injection moulded features substantially unchanged but which expands the remainder of the preform so as to form the main body of the bottle.

There is no special difficulty in forming PET bottles in this manner which have ratchet teeth located at substantially the same radius as their screw threads.

However, there is a demand for bottles which accept a "jigger" type cap closure which flares downwardly and outwardly, this type of closure serving as a measure for the bottle contents after the bottle has been opened. It will be appreciated that, when the periphery of such a cap is provided with an internally toothed tamper proofing ring, the complementary ratchet teeth on the bottle need to be located at a substantial distance axially away from the bottle threads and also at a substantially greater radial distance from the bottle axis than are the threads themselves. These requirements for the location of the ratchet teeth on the bottle arise because the extra height and flared shape of the jigger cap make its periphery of substantially greater radius than its neck portion at the screw threads.

In order to use the standard injection moulded preform technique in the manufacture of bottles to accept a jigger cap, that part of the preform in the vicinity of the neck portion which is to carry the ratchet teeth would have to be made very thick because the requirements of extracting the preform from the injection mould dictate that the bore of the neck portion should not increase in diameter in the direction towards the body portion, whereas the required positioning of the ratchet teeth on the neck portion means that the teeth need to lie on a substantially greater external radius of the neck portion than its external radius at the screw threads.

It therefore follows that in order to accommodate this difference in internal and external radial dimensions, the injection moulded material of the preform mould, with conventional techniques, need to be thick in that region where the ratchet teeth are required. This is a considerable disadvantage because a considerable extra quantity of plastics material then has to be used, and additional time has to be allowed during each moulding cycle for the thick injection moulded portion to cool sufficiently for the moulding to be released from the mould.

Both aspects are, of course, economically unfavourable.

From a first aspect, the present invention provides a bottle formed by blow moulding from a preform, the bottle comprising a neck portion adapted to receive a closure cap for the bottle, a body portion, and an intermediate portion integrally joining the neck and body portions, the neck portion comprising a skirt which lies in surrounding relation to the intermediate portion, and the neck portion having been given substantially its final form in the formation of the preform.

From another aspect, the invention provides a method of making a plastics bottle, which comprises preparing a preform having first and second portions for respectively providing the bottle neck adapted to receive a closure cap for the bottle, and the bottle body, and a third portion integrally joining the first and second portions, the first portion having a skirt which lies in surrounding relation to the third portion, the method further comprising blow moulding the preform to expand the second and third portions but to leave the first portion substantially unchanged, the second portion being thereby formed as the bottle body.

From a further aspect, the invention provides a preform for a plastics bottle, which has first and second portions for respectively providing the bottle neck adapted to receive a closure cap for the bottle, and the bottle body, and a third portion integrally joining the first and second portions, the first portion having a skirt which lies in surrounding relation to the third portion, the preform being adapted, when heat-softened and subjected to a blow moulding operation, for the second and third portions to be expanded so as to form the second portion as the bottle body.

It will be appreciated that the invention in any of its aspects is applicable to bottles made from materials other than PET, and to the provision of other external formations than ratchet teeth; moreover, although particularly described in relation to preforms which are injection moulded, the invention may employ preforms prepared by other moulding methods.

However, despite such broader applications, it will be appreciated that the invention substantially improves the economics of manufacturing injection and blow moulded bottles from PET in which ratchet teeth are provided at a relatively large radius for co-operation with flared jigger type caps.

The term "blow moulding" as used herein comprehends processes wherein the preform is mechanically elongated prior to its expansion by pressurised gas. Such a process is often referred to as "stretch-blow moulding".

In order that the invention may be more clearly understood an embodiment thereof will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 shows an injection and blow moulded bottle in accordance with the invention; Figure 2 shows an injection moulded preform from which the bottle of Figure 1 is formed by blow moulding; Figure 3 shows a top plan view of the preform of Figure 2; Figure4shows a jigger type cap forthe bottle of Figure 1, partly in cross-section and partly in side elevation; and Figure 5 shows a plan view from below, of the cap shown in Figure 4.

Figure 6shows a further injection and blow moulded bottle in accordance with the invention;and Figure 7shows an injection moulded preform from which the bottle of Figure 6 is formed by blow moulding.

It is convenient first to refer two Figures 4 and 5, showing the jigger cap, in conjunction with Figure 1.

The cap shown in Figures 4 and 5 is of known design and will not be described in great detail. However, it is to be noted that the cap flares downwardly and outwardly, is internally formed with a thread 2 at its narrower end and at its lower periphery, of greater radius, it is provided with a tamper proof ring 4 which is attached by means of nine thin webs 6 to the lower edge of the main part of the cap. On its inside, the ring 4 is provided with nine ratchet teeth 8.

Referring now to Figure 1, when the cap of Figures 4 and 5 is screwed onto the bottle 10 of Figure 1 the internal threads 2 of the cap engaged with the external thread 12 on the neck portion 14 of the bottle and eventually the internal ratchet teeth 8 on the tamper proof ring 4 of the cap engage with and click over eight ratchet teeth 16 (to be described further below with reference to Figures 2 and 3) which are provided by way of a formation below, and at some distance from, the thread 12. The cap is of course screwed down until it is tight.During the initial unscrewing movement of the cap from the bottle, the teeth 8 and 16, because they are angled in ratchet fashion, will not click over each other but firmly engage with each other and this causes sufficient strain to be applied to the webs 6 that the tamper proof ring 4 breaks away from the remainder of the cap and the cap can be unscrewed in the normal way. The broken webs 6 provide an indication that a filled and factory-closed bottle has had its cap at least partly unscrewed.

It will now be seen that the shape of the cap shown in Figures 4 and 5 requires that the ratchet teeth 16 on the bottle be rooted on a radius which is substantially greater than that of the neck portion at the thread 12, and it is this requirement which presents the problems already referred to, particularly when such bottles are to be blow moulded from injection moulded preforms in PET. For the purposes of this description the part of the neck portion on which the thread 12 is formed is particularly denoted 14A in the drawings. It will be seen that it is generally cylindrical.

Referring now to Figures 2 and 3, which show the injection moulded preform from which the bottle 10 of Figure 1 has been blow moulded, it can be seen that the neck portion 14 with its thread 12 is injection moulded in the preform to its final shape as required in the finished bottle. In addition to the thread 12 the neck portion also includes a ring 18 which is carried at the lower periphery of a skirt 20 and which is externally formed with the ratchet teeth 16. The skirt 20 flares outwardly and downwardly as shown in Figure 2 from a root 22 which merges with the bottom of the part l4Aofthe neck portion 14.

The skirt 20 completely encircles and overlies an intermediate cylindrical portion 24 of the preform.

The intermediate portion 24 forms a continuation of the neck part 14A below the attachment of the skirt 20, and serves to join the neck portion 14 to the top end of a conventional body portion 26 of the preform. As will be seen from Figure 2, the part 14A and intermediate portion 24 share common internal and external diameters. The body portion 26 has a major, generally cylindrical part 28 with a rounded and closed bottom end 29, and a minor, downwardly tapering part 30. The part 30 is joined at its top end to the intermediate portion 24. In this manner, the interior of the preform has a shape which is well suited for injection moulding and yet at the same time the teeth on ring 16 lie substantially further away from the preform axis than the thread 12 without there being any excessively thick injection moulded wall portion.

Figure 3 shows that the ratchet teeth 16 on ring 18 are provided in two groups of four disposed diametrically opposite each other.

The preform of Figures 2 and 3 is blow moulded substantially in the normal mannerwhilethe neck portion 14 including the skirt 20 is firmly restrained against deformation. The blow-moulding pressure expands the main body portion 26 of the bottle 10, now denoted 26'. The skirt 20 remains undeformed but the intermediate tubular portion 24 of the preform which is overlain by the skirt 20 expands and becomes flared outwardly as shown at 24' in Figure 1 so as to considerably close up the space which previously existed beneath the skirt. The radial expansion of the portion 24' is limited by contact with the inner, smoothly curved lower periphery of the ring 18, which effectively serves as part of the blow mould so far as this portion of the expanding preform is concerned.

It will be appreciated from Figure 1 that in the completed bottle it is not evident to the consumer that the external surface of the bottle has any discontinuity, although in fact a discontinuity exists where the ring 18 contacts the outside of the wall portion 24'; moreover, the wall portion 24' serves to provide radial location for the skirt 20 and, thereby, the ratchet teeth 16, so that in all essential respects the ratchet teeth are immovable in relation to the remainder of the bottle.

In a modification of the bottle shown in Figure 1, the skirt 20 is formed with apertures 32, for example as illustrated in Figure 6, so as to save material.

The bottle shown in Figure 6 is similar to that of Figure 1 apart from the modifications in the skirt, and the same reference numerals are used for similar parts. likewise, the preform which is shown in Figure 7 and from which the bottle of Figure 6 is made is like that of Figure 2 except for the variations in the skirt.

As shown, the apertures 32 in this instance are in the part of the skirt 20 linking the ring 18 to the rest of the neck portion 14, the ring 18 being intact. They are spaced circumferentially around the skirt 20 and extend axially to separate the body of the skirt into a number of wall portions 34. The provision of the illustrated apertures 32 allows a substantial reuction in the material employed in the skirt 20 to be obtained.

Alternative shapes and arrangements for the apertures may also beneficially be employed. They may be of any size and number consistent with the skirt 20 retaining the necessary strength to carry the ring 18, even to the point where the skirt wall portions 34 are reduced to form a number of relatively widely spaced ribs between the ring 18 and the rest of the neck portion 14. In this latter case, the thickness of the wall portions 34 in the radial direction may be increased for added strength, which has the advantage of providing less restricted flowpaths for the plastic during injection moulding whilst still saving on material content.

Although in Figures 1 and 6, the wall portion 24' is shown to engage the skirt 20 only at the ring 18, the portion 24' may be expanded by the blow moulding operation so as to engage the skirt 20 over substantially the whole length of the skirt 20. In this way the rigidity and location of the skirt is further improved, and the additional liquid capacity provided in the bottle neck by the portion 24' may be employed to reduce variations of the filling level of the bottle due to dimensional tolerances of the bottle or inaccuracy of the filling apparatus; the filling operation is therefore facilitated, and product consistency is improved.

Although for aesthetic and functional reasons it is desirable for the wall portion 24' to be expanded into contact with the skirt 20 as specifically described, within the ambit of the invention are bottles wherein the expansion of the intermediate portion is insufficent to bring it into contact with the skirt.

Claims

1. A bottle formed by blow moulding from a preform, the bottle comprising a neck portion adapted to receive a closure cap for the bottle, a body portion, and an intermediate portion integrally joining the neck and body portions, the neck portion comprising a skirt which lies in surrounding relation to the intermediate portion, and the neck portion having been given substantially its final form in the formation of the preform.

2. A bottle as claimed in claim 1, wherein the intermediate portion has been expanded by the blow moulding operation into engagement with the inside of the skirt.

3. A bottle as claimed in claim 1 or claim 2, in which the skirt is flared outwardly and downwardly from its attachment to the preform to a periphery which carries a formation for engagement with a said closure cap.

4. A bottle as claimed in claim 3, wherein the formation comprises teeth for engagement with complementary teeth on a tamper proofing ring of the closure cap.

5. A bottle as claimed in any preceding claim, wherein in addition to said skirt said neck portion comprises a generally cylindrical part which defines the bottle mouth and which has an external thread for engagement with a complementary thread on a said closure cap.

6. A bottle as claimed in claims 3,4 and 5, having a downwardly and outwardly flared closure cap screwed on to said thread, the lower end of the closure cap being formed as a tamper proofing ring having teeth which are in ratchet engagement with the teeth on said skirt, the upper end of the closure cap having a thread in threaded engagement with the thread on said generally cylindrical part.

7. A bottle as claimed in any preceding claim, in which the skirt is provided with apertures.

8. A bottle as claimed in claim 7, in which the apertures are spaced circumferentially around the skirt.

9. A bottle as claimed in claim 8, in which the skirt comprises a plurality of axially extending ribs between the apertures.

10. A bottle as claimed in claim 2, wherein the intermediate portion engages the skirt over substantially the whole length of the skirt.

11. A bottle as claimed in claim 2, wherein the intermediate portion engages the skirt only adjacent the free edge of the skirt.

12. A bottle as claimed in any preceding claim, made of PET.

13. A method of making a plastics bottle, which comprises preparing a preform having first and second portions for respectively providing the bottle neck adapted to receive a closure cap for the bottle, and the bottle body, and a third portion integrally joining the first and second portions, the first portion having a skirt which lies in surrounding relation to the third portion, the method further comprising blow moulding the preform to expand the second and third portions but to leave the first portion substantially unchanged, the second portion being thereby formed as the bottle body.

14. A method as claimed in claim 13, wherein the third portion is expanded into engagement with the inside of the skirt.

15. A method of making a bottle as claimed in claim 14, wherein the third portion is expanded into engagement with the skirt over substantially the whole length of the skirt.

16. A method of making a bottle as claimed in claim 14, wherein the third portion is expanded into engagement with the skirt only adjacent the free edge of the skirt.

17. A method as claimed in any of claims 13 to 16, in which the skirt of the first portion of the preform is formed with apertures.

18. A method as claimed in claim 17, in which the apertures are spaced circumferentially around the skirt.

19. A method as claimed in claim 18, in which the skirt is formed into a plurality of axially extending ribs between the apertures.

20. A method as claimed in any of claims 13 to 19 of making a bottle from PET.

21. A bottle, substantially as hereinbefore described with reference to the accompanying drawings.

22. A method of making a bottle, substantially as hereinbefore described.

23. A preform for a plastics bottle, which has first and second portions for respectively providing the bottle neck adapted to receive a closure cap for the bottle, and the bottle body, and a third portion integrally joining the first and second portions, the first portion having a skirt which lies in surrounding relation to the third portion, the preform being adapted, when heat-softened and subjected to a blow moulding operation, for the second and third portions to be expanded so as to form the second portions as the bottle body.

24. A preform as claimed in claim 23, in which the skirt is provided with apertures.

25. A preform as claimed in claim 24, in which the apertures are spaced circumferentially around the skirt.

26. A preform as claimed in claim 25, in which the skirt comprises a plurality of axially extending ribs between the apertures.

27. A preform, substantially as hereinbefore described with reference to Figure 2 or Figure 7 of the accompanying drawings.