GB2421282A

GB2421282A - Method and apparatus for expelling contents of container

Info

Publication number: GB2421282A
Application number: GB0427594A
Authority: GB
Inventors: James Patrick Dale
Original assignee: RPC Containers Ltd
Current assignee: RPC Containers Ltd
Priority date: 2004-12-16
Filing date: 2004-12-16
Publication date: 2006-06-21
Anticipated expiration: 2024-12-16
Also published as: GB0427594D0; GB2421282B

Abstract

Apparatus for expelling the viscous contents of a container 10 includes a piston 40, which is used to compress the container 10 and expel the contents. The piston has an outer annular part 50, and an inner part 60, slidable within the annular part. When the piston is used to compress the container, the outer part compresses the radially outer part of the container (which may be formed with concertina pleats 14). When the outer part is fully compressed, the inner part 60 of the piston forces the viscous fluid from the radially inner part of the container. The radially inner part of the container may be cup-shaped, and the inner part of the piston may serve to evert the cup-shaped portion so that it projects into the container.

Description

METHOD AND APPARATUS FOR EXPELLING

CONTENTS OF CONTAINER The present invention relates to a method and apparatus for expelling the contents of a container, and more particularly to a method and apparatus allowing substantially the entire contents of the container to be expelled therefrom. The invention is particularly applicable to dispensing viscous fluids. It is well known that dispensing viscous fluids from containers can involve difficulties. Since the fluid does not flow easily, it is usually necessary to compress the container to expel the fluid, and it can be difficult to fully expel the contents of the container, as the container must be fully collapsed in order to do this. Further, if the container is resilient, it can spring back to its original shape if released, and suck the viscous product back into the container. These problems are not acute if the viscous fluid being dispensed is a low-value product (such as toothpaste). However, for higher-value products, total expulsion of the contents of a container is much more important, as any fluid which cannot be expelled from the container is wasted. A further problem can arise if the contents of the container are sensitive to air (for example, if the contents spoil or degrade on contact with air). It is then necessary to ensure that air is not sucked back into the container after the contents have been partially expelled, and this may require the container to be subjected to a constant compressive force during expulsion of the contents. The compressive force may be incrementally increased to expel more product from the container. A number of containers are known which allow at least a large proportion of a viscous fluid held therein to be dispensed. For example, US 5913342 (McGill) discloses a collapsible container for a viscous or semisolid product, whose circumferential wall is formed with concertina pleats. The container is compressed by a plunger, which is shaped to push the base of the container up into the body of the container as an initial step. The plunger then continues to compress the container, to close up the pleats and expel product. Because the base of the container is pushed into the container as a first step, it is possible that material may be become trapped in the lowermost pleat of the container during this step. This can be a problem if the container is used for a high-value product. According to a first aspect of the invention, there is provided an apparatus for expelling viscous fluid from a container, comprising: means for retaining the container; and a piston, adapted to compress the container as it is retained in the retaining means, wherein the piston is formed from: an outer annular part, which contacts and compresses a radially outer part of the container; and an inner part, slidable within the outer annular part, which contacts a radially inner part of the container to expel fluid from the radially inner part of the container, this expulsion taking place after the radially outer part of the container has been compressed. Such an apparatus allows a container of viscous fluid to be compressed in a "two-step" method. In a first step, the radially outer part of the container is compressed. This serves to expel some of the product from the container, and also urges any product in the radially inner part of the container into the central region of the container. Then, the material in the central region of the container is forced out of the container. Such a two-step method allows a very large amount of the product in the container to be expelled. Of course, the container can have any form, but uncontrolled compression can lead to some of the product being trapped. In a preferred form, the container has a radially outer wall formed with concertina pleats, which are caused to close up by the compression of the radially outer part of the container by the outer annular part of the piston. The concertina pleats allow the container to collapse in a controlled and predictable manner. It is further preferred for the radially inner part of the container to be a base projecting from the container, and for the inner part of the piston to cause the projecting base to evert so that it projects into said container. Once the concertina pleats have closed, product which was originally present within the pleats will have been pushed into the central region of the container. Everting the projecting base of the container allows this material to be expelled, and thus the amount of wasted product (product remaining in the container at the end of the expulsion process) is further reduced. The outer annular part and the inner part of the piston can be driven separately. However, this arrangement can be complex, and so in a preferred form, the outer annular part of the piston and the inner part of the piston are biassed away from each other by a resilient means such as a spring. With such an arrangement, it is only necessary to drive one part of the piston; the force will be transmitted to the other part through the spring. In a particularly preferred form, the force needed to compress the spring is more than the force needed to collapse the concertina pleats of the container. After the base of the container has been everted into the container, the inner part of the piston will project into the container. In order to further reduce the amount of wasted product, in a preferred form, a part of the profile of the inner part of the piston closely matches a part of the inner profile of the container. This reduces the internal volume of the compressed container still further. The inner part of the piston may be provided with means for positively engaging with a base of the container. This allows the piston to be drawn back after the container has been compressed, and allows the container to be refilled. According to a second aspect of the invention, there is provided a method of expelling viscous fluid from a container, comprising the steps of: retaining a container in a retaining means; compressing a radially outer part of the container with an annular piston; and then expelling material from a radially inner part of the container with an inner piston sliding within the annular piston. In a preferred form, the container has a radially outer wall formed with concertina pleats, and the compression of the radially outer part of the container by the annular piston causes the pleats to close. In a further preferred form, the radially inner part of said container is a base projecting from said container, and the inner piston causes the projecting base to evert so that it projects into the container. A preferred embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of an apparatus for discharging the contents of a container of viscous fluid, with such a container mounted on the apparatus, before the container is compressed; Figure 2 is a schematic illustration of the container in its uncompressed state; Figure 3 is a schematic illustration of an apparatus for discharging the contents of a container of viscous fluid, with such a container mounted on the apparatus, with the container fully compressed; and Figure 4 is a schematic illustration of the container in its fully compressed state. As can be seen from Figures 1 and 2, the container 10 to be used in connection with the discharging apparatus and method of the present invention is generally cylindrical, and its peripheral wall 12 is formed with concertina pleats 14. The neck 16 of the container 10 is formed with a screw thread 18 for engaging with a standard screw top, but other forms of closure can also be used. The base 20 of the container 10 is generally cup-shaped. At the centre of the base of the container is a projection 22, which can be positively engaged by a part of the discharging apparatus; however, the projection is not a necessary feature, and may be omitted. The discharging apparatus 20 includes a retaining means 32, which is adapted to engage with the region of the container near the neck 16, so that the container can be held in position while it is compressed. It will be appreciated that any suitable means for preventing the container from moving as it is compressed could be used. The base of the container is contacted by a piston 40, which is free to move axially. The piston is formed from two parts; an outer annular part 50, which fits around the cup-shaped base 20 of the container 10 and contacts the concertina pleats 14, and an inner part 60, which contacts the cup-shaped base 20. The profile 62 of the inner part 60 is shaped so as to match the inner profile of the neck region of the container. The inner part can have a recess 64 to engage with the projection 22 on the base of the container, if one is provided. The inner part 60 of the piston is sized to fit closely within the outer annular part 50, and can slide therein. Disposed between the outer annular part 50 and the inner part 60 of the piston 40 is a spring 42, which biases the inner part 60 and the annular part 50 away from each other. The strength of the spring 42 depends on the particular container from which fluid is to be expelled, and is such that the force needed to compress the spring 42 disposed between the outer annular part 50 and the inner part 60 is greater than the force needed to compress the concertina pleats 14 of the container 10. The method of discharging contents from the container will now be described. Firstly, the container 10 is fitted into the retaining means 32. If there is a projection 22 on the base 20, then this can be engaged with the recess 64 on the inner part 60 of the piston 40. The retaining means 32 is engaged with the region of the container 10 near the neck 16, to prevent the container from being pushed from the apparatus when the piston 40 moves. The piston 40 is then pressed into the container, by pushing the inner part 60 towards the neck region 16 of the container 10. As mentioned above, the force needed to compress the spring 42 disposed between the outer annular part 50 and the inner part 60 is greater than the force needed to compress the concertina pleats 14 of the container 10. As a result, the spring 42 is not compressed at this stage; instead, the compressing force is transmitted through the spring 42 to the outer annular part 50 of the piston 40, which presses on the concertina pleats 14, and these start to close up. As they close, product disposed in the pleats is forced into the central part of the container, rather than being trapped therein. The closing of the pleats also reduces the length of the container, and so product is expelled from the container. Compression of the container in this way continues until the pleats 14 are fully closed, by which time a large amount of material has been expelled from the container. However, there is still product in the central part of the container, and in the base 20 of the container. The inner part 60 of the piston 40 continues to be pushed towards the neck region 16 of the container 10. However, as the pleats 14 are now fully closed, the outer annular part 50 cannot move, and so the inner part 60 of the piston 40 moves within the outer annular part 50, compressing the spring 42. This motion of the inner part 60 pushes the base 20 of the container 10 into the central part of the container 10, everting it, and expelling product both from the central part and the base of the container. The cup-shaped base of the container is of such a size and shape that, once it is fully everted, it leaves hardly any free space within the container. This helps to expel as much material as possible from the container. In addition, as the profile 62 of the inner part 60 of the piston 40 matches the inner profile of the neck region 16 of the container 10, the everted base of the container is pressed against the inner part of the neck region by the inner part of the piston, which further reduces the free space within the container. As can be seen from Figure 4, the only free space left in the container is in the neck itself, and adjacent to the topmost concertina pleat. Thus, very little material can remain in the container, and so there is very little wastage. The contents of the container can be expelled in one single process, as described above; alternatively, the contents can be expelled in discrete amounts. It is preferred for the container to remain under compression after each discrete amount has been dispensed, to prevent the container from resiling to its original shape. After the material has been expelled, the container 10 can be removed from the sleeve 32 and discarded. Alternatively, if the base 20 of the container 10 is engaged with the recess 64 on the inner part 60 of the piston 40, the container can be reused and refilled. This can be done by pulling the inner part 60 of the piston 40 away from the neck region 16 of the container 10, using the engagement of the projection 22 on the base 20 and the recess 64 on the inner part 60 of the piston 40. It is necessary for the mouth of the container to be immersed in a supply of the product with which the container is to be filled, and for the neck 16 to be restrained (perhaps by the retaining means 32) to prevent the entire container 10 from being pulled backwards. The pulling of the inner part 60 of the piston 40 will tend to un-evert the base 20 of the container 10 and re-open the pleats 14, increasing the internal volume of the container and sucking the product back into the container.

Claims

1. An apparatus for expelling viscous fluid from a container, comprising: means for retaining the container; and a piston, adapted to compress the container as it is retained in the retaining means, wherein the piston is formed from: an outer annular part, which contacts and compresses a radially outer part of the container; and an inner part, slidable within the outer annular part, which contacts a radially inner part of the container to expel fluid from the radially inner part of the container, this expulsion taking place after the radially outer part of the container has been compressed.

2. An apparatus for expelling viscous fluid from a container as claimed in claim 1, wherein said container has a radially outer wall formed with concertina pleats, and wherein the compression of the radially outer part of the container by said outer annular part of the piston causes the pleats to close.

3. An apparatus for expelling viscous fluid from a container as claimed in claim 2, wherein said radially inner part of said container is a base projecting from said container, and wherein the inner part of the piston causes the projecting base to evert so that it projects into said container.

4. An apparatus as claimed in any preceding claim, wherein the outer annular part of the piston and the inner part of the piston are biassed away from each other by a resilient means such as a spring.

5. An apparatus as claimed in any preceding claim, wherein a part of the profile of the inner part of the piston closely matches a part of the inner profile of the container.

6. An apparatus as claimed in any preceding claim, wherein the inner part of the piston is provided with means for positively engaging with a base of the container.

7. A method of expelling viscous fluid from a container, comprising the steps of: retaining a container in a retaining means; compressing a radially outer part of the container with an annular piston; and then expelling material from a radially inner part of the container with an inner piston sliding within the annular piston.

8. A method as claimed in claim 7, wherein said container has a radially outer wall formed with concertina pleats, and wherein the compression of the radially outer part of the container by said annular piston causes the pleats to close.

9. A method as claimed in claim 8, wherein said radially inner part of said container is a base projecting from said container, and wherein the inner piston causes the projecting base to evert so that it projects into said container.

10. Apparatus for expelling viscous fluid from a container substantially as described herein with reference to Figures 1 to 4.

11. A method of expelling viscous fluid from a container substantially as described herein with reference to Figures 1 to 4.