APPARATUS AND METHOD FOR FORMING A CONTAINER WITH AN INTERNAL SEPERATING WALL AND CONTAINER PRODUCED

The invention relates to a container, and in particular to a container comprising a plurality of chambers of predetermined volume.

Multi-compartment containers are known; these are typically formed as two or more separate containers which either inter-engage, or are linked by an external web. An example of a dual-compartment container including such a web is illustrated in GB 2 306 454 in the name of Polycell. An inter-engaging container is shown in the applicant's earlier application GB 2 388 097. Containers of this type have been developed to allow the storage of compositions the components of which could not he stably stored in a single compartment, or for the storage of compositions where it is undesirable for aesthetic or other reasons to mix the components prior to use.

The applicant's co-pending application, GB 0425337.3 describes a dual- compartment container and a method of forming the container comprising an entirely internal wall. This container is simpler to manufacture than the containers of GB 2 306 454 and GB 2 388 097, being obtainable ^' from a single blow moulding process, hi addition, the use of a simple internal wall reduces the amount of plastics material required to produce the container, providing economic benefits. Further, the removal of the requirement to inter-engage two separate containers, or to provide an external web, allows dual compartment containers to ¹ be produced which have different aesthetic properties to the containers above. This is because the separation of the container into two compartments is entirety internal, allowing the external surface of the container to be smooth, with no joints or linkages.

However, a possible disadvantage of the method disclosed in GB 0425337.3 is that it could sometimes difficult to control the relative size of the chambers within ■ the container. This is because the internal wall may be irregularly moulded, for instance- by becoming curved resulting in one chamber being of greater volume than intended, the second chamber being of smaller volume than may be. required.

It is therefore desirable to provide a container comprising an internal wall in which the volume of each chamber within the container is consistently and reproducibly controlled.

According to a first aspect of the invention there is provided an apparatus for forming a multi-chambered container, the apparatus comprising: a die; a pin located within the die such that there is a gap between the pin and the die, the shape of the gap corresponding to the external shape of a parison to be formed; the pin including a slot extending into a lower portion of the pin to allow the formation of an internal wall in the parison; at least two independent gas sources wherein a first source supplies gas into a first space formed between the internal wall and an external wall of the parison and a second source supplies gas into a second space formed between the internal wall and the external wall of the parison; and a control device for metering an amount of gas from each source so that the chambers formed are of predetermined size.

According to a further aspect of the invention there is provided a method of forming a container, the method comprising the steps of; locating a pin within a die such that there is a gap between the pin and the die, the shape of the gap corresponding to the external shape of a parison to be formed, wherein the pin includes a slot extending into a lower portion of the pin so that an internal wall will form in the parison; forming a parison by inserting a molten plastics material into the gap between the pin and the die under sufficient pressure that a portion of the plastics material is impelled into the slot; transferring the parison to a mould; applying a metered volume of gas to each space formed between the internal wall and an external wall of the parison so that each chamber in the container has a predetermined volume.

According to a yet further aspect of the invention there is provided a container comprising a container bod)' and an internal wall, the internal wall forming at least two separate chambers of predetermined volume within the container. Preferably there are two chambers. ViTαere there are more than two chambers, the upper limit to the total number of chambers will be determined by the size of the container (larger containers becoming necessary if several chambers are required) and the area of the upper surface of the container, as this surface must accommodate the required number of apertures.

The chambers of the container may be of different volumes or of similar volumes. For instance, there may be two chambers of substantially equal volume, or a first large chamber and a second smaller chamber. This embodiment would be of use where one of the components to be stored within the chambers is required in a smaller volume than the second. Alternatively, there may be three or more chambers of equal or differing sizes. It is essential to the invention, however, that the chambers are of a predetermined volume. Preferably, the chambers are of substantially equal volume.

As described in the applicant's co-pending British application number GB 0425337.3, the subject matter of which is incorporated by reference in its entirety, in preferred embodiments each chamber of the .container has at least one aperture to facilitate filling of the bottle and dispensing therefrom. Preferably, there will be an aperture associated with each chamber. Most preferably there will be two apertures, one associated with each of two chambers. The container may be made from any material which is both extrudable and plastically deformable. However, it is preferred that the container be formed from a plastics material, for example polypropylene, polyethylene or polyvixrylchloride. Typically, the internal wall and the container body will be of one-piece extrusion.

The container may have any shape into which it is possible to make a blow mould. In particular, the container may have, for example, different cross-sectional configurations (round, square, circular, elliptical, non-uniform); a height which is either greater or smaller than the width and/or depth; tapering to .produce cones,

pyramids, tetrahedrons or frusto-conical configurations; stepping between different cross-sectional areas; or rotation of the cross-section smoothly around the central vertical axis to produce a 'twisted' appearance to the outer surface of the container.

Dependent upon the relative configuration of the pin and die, and shape of the consequent gap between the pin and the die; the parison may be annular, ellipsoid or oval. Typically, the gap between the pin and die will be annular, resulting in the production of an annular parison.

The apparatus of the invention may be used to produce the containers of the first aspect of the invention. The slot in the pin may be such that a single internal wall will form in the parison. ^" Where a single internal wall is to be formed, the slot extends across the width of a lower portion of the pin. Alternatively, there may be more than one slot arranged to produce three or more chambers in series. Where this is the case, it is preferred, but not essential, _. that the walls are substantially parallel. As a further alternative, the slot or slots may be arranged so that they do not extend across the entire width of the pin, but meet in the interior of the pin to form a parison incorporating segments which may be equally or differently sized. Accordingly, there may be any number of segments, providing the container is large enough to accommodate these. Preferably, there will be between two and six chambers, more preferably two or three, most preferably two chambers. The person skilled in the art would appreciate that as the number of chambers is increased, more precision in the handling of the parison and other processing may become necessary to prevent collapse of the parison and adherence of the walls to one another.

The apparatus includes a control device for metering an amount of gas into each side of the internal wall of the parison during the blowing cycle of the process. The control device ensures that the internal volume of each chamber is both known and precisely controlled. The gas may be metered using any control device known in the art, however it is preferred that the control device be an electronic control device or a pneumatic cylinder. .In embodiments comprising two

chambers, there will be either two electronic control devices, one linked to each of two gas sources; or two pneumatic cjdinders, both linked either to a single gas source or one linked to each gas source. It will be immediately apparent that where more chambers are to be formed, additional control devices will become necessary.

Where an electronic control device is used, this will monitor one or more properties which are representative of the amount of gas passing into the mould. For instance, properties such as gas flow which allow the amount of gas passing into the mould to be calculated. Where flow meters are used they ma}', for example, be placed between the gas source and the blow pin or hi the apparatus itself. Where electronic metering is used, more than one property of the gas may be monitored at any time, for instance not only may the gas flow and the air pressure be monitored separately but both of these properties may be monitored in combination.

Where pneumatic cylinders control the gas metered into the mould, it is preferred that each cylinder is of known volume because this allows the volume of each chamber within the container to be precisely determined. It is further preferred that the capacity of the cylinders be adjustable so that any difference in the volume of the path length between the cylinders and the blow pin, for instance in the capacity of the piping linking the cylinders to the blow pin, may be accounted for. hi embodiments where two chambers are formed, a pair of cylinders will be completely discharged during each moulding (i.e. during the formation of each container) and recharged prior the next moulding. It is, preferred that a single pair of cylinders be used with each apparatus to reduce the operational costs of the machine.

An embodiment of the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 a is a front view of a container according to the invention; Figure Ib is a side view of the container .of Figure Ia;

Figure Ic is apian view from above of the container of Figure Ia: Figure Id is a cross-sectional view through. X-X of the container of Figure Ia; Figure 2a is a cross-sectional view through the die of the invention; Figure 2b is a perpendicular cross-sectional view through the die of Figure 2a; Figures 3a to 3e are cross-sectional views through the die of Figures 2a and 2b taken at points A-A to E-E;

Figure 4 is a schematic representation of an electronically metered apparatus; Figures 5a to 5d are schematic representations of a pneumatically metered apparatus at different stages of the cylinder discharge and recharge cycle.

For the avoidance of doubt it should be noted that in this specification reference to 'up', 'down', 'upper', 'lower', 'vertical', 'horizontal', 'top', 'bottom' and related terms refers to the orientation that the components of the apparatus adopt when in normal use, as they are shown in the figures.

Figures Ia to Id show an embodiment of a polypropylene container 10 according to the invention. The container has an internal wall 15 defining, with the container body 20, a container 10 with, in this instance, two equally sized chambers 25. Each chamber 25 is associated with one aperture 30 at the top of the container 10. In this embodiment, the apertures 30 are positioned offset from centre towards two opposing corners of the container 10 and the internal wall 15 is substantially central within the container 10.

The container of Figures Ia to Id is formed by an apparatus 35 shown in Figures 2 - 5 comprising a die 40, a pin 45 located within the die 40, a mould 75 for receiving an extruded parison 60 and two control devices 80 for metering an amount of compressed air via a twin blow pin assembly 100 into the mould 75.

In the embodiment of Figures 2a, 2b and 3a to 3e, there is an annular gap 50 between the pin 45 and the die 40, a parison 60 being extruded into this gap 50

(Figures 2a and 2b). Both the pin 45 and die 40 are metallic. The pin 45 includes

^• two graduated slots 55 at diametrically opposing points around the annular surface of phi 45. The slots 55 become increasingly elongate ^' as shown in Figure 2b and

Figures 3a - 3e, from the top to the bottom along the length of the pin 45. At the distance of approximately one sixth the total length of the pin 45 from the bottom of the pin 45. the slots 55 meet to form a single slot 55. From this point to the bottom of the pin 45, the slot 55 extends across the width of the pin 45 allowing the formation of an internal wall 115 in the parison 60 (this internal wall 115 becoming the internal wall 15 of the container 10 upon moulding). The extruded pofypropylene is forced into the slot 55 as it passes along the pin 45 from the top to the bottom of the die 40. Where the slot 55 extends across the entire width of the pin 45, the extruded polypropylene meets and forms the internal wall of the parison 115. Figures 3a - 3e illustrate the graduation of the slot 55 from the top to the bottom of the pin 45 and the formation of the internal wall 115 of the parison 60 therein.

Mould 75 is positioned, in this embodiment, below the die 40 so that the extruded parison 60 can pass from the die 40 into the mould 75 for subsequent blow moulding.

In the example of Figures 2a, 2b and 3a to 3e, there are two channels 65, 70 in the phi 45 wherein a first channel 65 supplies air into a space on a first side of the internal wall 115 of the parison 60 and a second channel 70 supplies air into a space on a second side of the internal wall 115 of the parison 60. The air flow prevents the annular walls 120 of the parison 60 from coming into contact with and/or adhering to the internal wall 115 and deforming the parison 60.

Prior to blow moulding, parison 60 is transferred to mould 75. Blow pin 100 is brought into alignment with the mould 75.

In general, the control devices 80 meter the air flowing from air source 95, via the blow pin assembly 100 into the mould 75. For clarity, only one of the two control devices 80 is illustrated in each of Figures 4 and 5a - 5d. Air is metered, in this embodiment, from two air sources 95, via separate piping 105, to each of the two control devices 80. After passing through the control devices 80, the air

then flows to blow pin 100. Blow pin 100 includes two passages (not shown) one linked to each air source 95.

As illustrated in Figure 4, in one embodiment the control device 80 is an electronic control device 80 including a flow and pressure meter. Air flow is controlled by a valve Vl. The air flow path is linear from air source 95, through piping 105 and valve Vl ₅ then the electronic control device 80 to the blow pin 100.

In an alternative embodiment, the control device 80 is a pair of pneumatic cylinders 80 one half of which is shown schematically in Figures 5 a to 5d. Air flow into the cylinder 80 is via valve V2 when charging, and Vl when discharging. Flow to the blow pin 100 is controlled using valve V4, and air flow displaced from the cylinder flows out through valve V3.

In use, the pin 45 is located within the die 40 such that, in this example, there is an annular gap 50 therebetween. Molten polypropylene is extruded into the gap 50 under sufficient pressure that a portion of the polypropylene is impelled into the slots 55. The graduation of the slots 55 and pressure applied to the molten polypropylene ensures that where the slots 55 meet an internal wall 115 is formed as a single extrusion in the parison 60.

The extrusion process is then continued so that the parison 60 flows downwards hanging below the pin 45 and die 40. The mould 75 is then closed around the parison 60 and the required length of parison 60 is severed, as the mould is closed, from the continuous extrusion using a knife (not shown), the length severed is greater than the length of the mould cavity (not shown) to ensure that when the mould 75 is closed the bottom of the mould 75 grips the distal end of the parison 60, sealing this end so that blow moulding forms a sealed base of the container 10. Similarly, the proximal end of the parison 60 is gripped by the upper edge of the mould cavity 75, so that an upper surface 12 of the container 10 will be formed. However, at this upper edge of the mould 75, gaps occur in the sealed parison 60

at the portion of the mould 75 that forms the apertures 30 of the container 10. This ensures a clear passageway into the retained parison 60, for the blow pin 100.

In the embodiment described a metered volume of air is then dispensed from a first air source 95 into a space on the first side of the internal wall 115 of the parison 60, and substantially simultaneously from a second air source 95 into a space on the second side of the internal wall 115. The air passes from blow pin

100 into the mould 75 where the parison 60 is blow moulded to match the internal shape of mould 75. The technique of blow moulding is well known to the person skilled in the art and need not be discussed further.

The amount of gas is metered using the control device 80 so that each chamber 25 has a predetermined volume, in this example, the volume is 155 ml, to accommodate 150 ml of a composition in each chamber 25 whilst retaining a workable head space. In order to produce a container 10 in which the chambers 25 are of equal volume, it is necessary (in accordance with Boyle's Law) to equalise the pressure in each chamber 25 during moulding. Boyle's Law states that at a given temperature the volume of a fixed amount of gas is inversely proportional to the total amount of pressure applied, i.e. that P ₁ V ₁ = PoV ₂ (where 'P' represents pressure and 'V represents volume). In this embodiment the blow moulding pressure is 90 psi (620 kPa), although any pressure in the range of 75 - 120 psi (517 kPa- 827 kPa) would be appropriate.

In the embodiment where the control device 80 is an electronic device 80 including a flow and pressure meter, volume control in the mould 75 is achieved through a continuous feedback mechanism wherein, in this instance, the flow of air and the air pressure are monitored and the volume of air in the chamber 25 calculated during the moulding process every few milliseconds. If at any point in time the volume in either of the piping systems 105 and attached chamber 25 rises beyond that predetermined for that time valve Vl, related to that system, is fully or partly closed to reduce the air flow and subsequent pressure and volume, where the volume in one piping system 105 and attached chamber 25 falls below that predetermined for that time valve Vl is opened more fully. Where the chambers

25 are of substantially equal volume then the predetermined volumes at any point in time should be substantially the same after taking into account any difference in the volume of the piping 105 linking the control device 80 to the chamber 25.

Where the control device 80 is a pneumatic C3 ^f linder 80 the pressure in the mould 75 is controlled by connecting each passage of the blow pin assembhy 100 to an individually calibrated air cylinder 80. As shown in Figure 5a, the cylinder 80 of this example is then charged with air by opening valves V2 and V3 and closing valves Vl and V4. This configuration of open and closed valves allows any air in the uncalibrated portion of the C3'linder 80 to be ejected, and the calibrated portion of the cylinder 80 to be filled with a known volume of air. Once the cylinder 80 has been charged, valves V2 and V3 are closed (Figure 5b). and valves Vl and V4 opened when the moulding cycle is read)? for the main blow. The metered volume of air is then discharged, via the blow pin 100, into the mould 75. Because the volume of air is known, and calibrated for the system in which it is being used, the pressure applied to each side of the internal wall of the parison 115 is the same. Should one chamber 25 become larger than the other, a pressure differential will arise. However, the pressures in the chambers 25 will equalise (Bθ3 ^r le's Law) by distorting the internal wall 115. This process will also equalise the volume of each chamber 25. At the end of the discharge step valves Vl and V4 are once again closed, to allow the recharge phase of the cycle to begin.

Once blow moulding is complete, the blow pin assembly 100 and mould 75 are separated and the container 10 is ejected from the mould 75.