GB2367865A

GB2367865A - Dispensing system with follower plate

Info

Publication number: GB2367865A
Application number: GB0023940A
Authority: GB
Inventors: Richard Smith; Jeffrey William Spencer
Original assignee: English Glass Co Ltd; Rieke Packaging Systems Ltd
Current assignee: English Glass Co Ltd; Rieke Packaging Systems Ltd
Priority date: 2000-03-21
Filing date: 2000-09-29
Publication date: 2002-04-17
Also published as: GB0023940D0; GB0006856D0

Abstract

A dispensing system has a container (1) to hold flowable material. A dispenser pump (2) is mounted in a cover cap at the top of the container, and receives flowable material through a stiff feed tube (3). A follower plate (5) fits around the feed tube and lies on top of the material in the container. It has a wide peripheral sealing skirt (53) enabling it to pass reduced-diameter regions of the container interior. These might be for example the narrow neck of a blow-moulded container, or finger-grip corrugations of the container wall.

Description

DISPENSING SYSTEMS

This invention relates to dispensing systems of the kind in which a follower plate is provided in a container of product, to follow the surface of the product down the container as dispensing proceeds.

BACKGROUND Dispensing systems of the above kind are well-known. The follower plate is used in conjunction with a feed tube reaching down to the base of the container from the intake of a pump at the top of the container. Preferred constructions have the pump mounted in or through a cover cap for the container. Conventionally the container is a cylindrical injection-moulded plastics container.

Follower plates are usually used where the material to be dispensed does not flow readily, e. g. as is often the case with certain cosmetic and pharmaceutical creams. To be able to dispense all the product from the container, it must be withdrawn from at or adjacent the base. Where the product is poor in flow, however, there is a tendency for a substantial part of the product to adhere to the container walls while a cavity forms around the foot of the feed tube so that the container cannot be emptied.

A follower plate, conventionally a circular flat plate, has a central hole fitting around the feed tube and lies on top of the product surface. It may make a seal against the feed tube and/or container walls, via flexible lips, depending on the properties of the product.

THE INVENTION What we now propose are new kinds of follower plates, and dispensing systems incorporating containers and follower plates, making the system able to cope with crosssectional non-uniformity of the container.

The dispensing system comprises a container to hold flowable material for dispensing, the container having a side wall and a base; a dispenser pump mounted at the top of the container; a feed tube extending in the container down from an intake of the dispenser pump to adjacent the container base, providing a conduit for flowable material to enter the dispenser pump from adjacent the container base in use of the system, and a follower plate which fits around the feed tube, extending out towards the side wall of the container, and

which is axially slidable relative to the feed tube to follow the surface of flowable material down the container as dispensing proceeds. The follower plate has a flexible sealing skirt positioned to act against the container side wall.

What we are now proposing is to use a follower plate system in a container which has one or more regions of relatively reduced internal diameter, providing the follower plate with a peripheral sealing skirt which is flexible so as to be able to pass through the reduced diameter region (s).

Such an axially-localised reduced diameter region of the container may be a circular region, coaxial with adjacent larger-diameter circular-section portions of the container. One particular possibility is a restricted neck opening of the container. Restricted neck openings are not generally encountered because follower plate systems are used with injection-moulded containers, but we have found that with the adaptations proposed herein we can use a follower plate system in a blow-moulded container. Blow-moulded containers are characteristically susceptible of being easily made with re-entrant wall portions, in addition to having neck

openings narrower than the main internal diameter of the container. In particular, it is known for blow-moulded containers to have internal surfaces which are corrugated, either circularly or in a circumferentiallylocalised way such as by"finger grip"indentations of the container wall.

We have found that, unexpectedly, if a follower plate is made with a flexible peripheral sealing skirt of sufficient radial extent to accommodate such crosssectional non-uniformities, good sealing performance and clearance of product from the container via the feed tube can nevertheless be achieved.

It is generally preferred for the follower plate to have a non-flexing central region between the peripheral skirt and feed tube in order to help maintain the orientation of the follower plate in the container. Relative stiffness for the central region can be achieved by thicker web material than used for the flexible peripheral sealing skirt, and/or stiffening structures in the central region such as angles and/or ribs. One preferred construction has a thickened reinforcement ring extending around the follower plate at the root of the flexible sealing skirt. In general, it is preferred to

have a substantial discontinuity of the follower plate thickness between the stiff central region (thicker) and the flexible peripheral region (thinner).

For orientation it is normally preferable to form the centre of the follower plate with an axially-extending sleeve which fits around the feed tube. Like the peripheral skirt, this sleeve may be formed integrally in one piece with the rest of the follower plate, by injection moulding of suitable plastics material e. g. low-density polyethylene (LDPE).

The radial extent of the flexible skirt will naturally depend on the variation or range of container internal cross-section that is to be accommodated. However it can be said in general that the radial extent of the flexible skirt will be usually substantially greater than in conventional resiliently-sealing follower plates. In conventional sealed plates, e. g. as in our EP-A-765690, the peripheral sealing lip extends nearly perpendicular to the plane of the follower plate; tolerances in the injection-moulded container's interior surface are accommodated by bending over a very small distance of radial action. By contrast in the present systems the radial extent of the flexible skirt may be typically at

least 10%, at least 15%, at least 20% or at least 25% of the total radial extent of the follower plate. With reference to the container, the reduction or variation of its internal diameter may likewise be at least 5%, at least 10%, at least 15% or at least 20% of the largest internal container diameter encountered by the follower plate.

Because the follower plate is intended to move downwardly past cross-sectional restrictions, its outer edge is preferably inclined upwardly. Thus, the flexible peripheral skirt region may be upwardly concave. However it may or may not have a significant upward extent relative to the level of the central region of the follower plate. For example it may have a region spaced inwardly from the outer edge where it inclines downwardly and outwardly from the centre. These inclinationswhich may be provided by curvature of the peripheral skirt in an axial plane-can assist flexing. Because of its resilient flexibility, the skirt can project relatively directly towards the container wall, unlike peripheral sealing lips in conventional sealed follower plates. For example the angle (in an axial plane) between the feed tube axis and a line joining the root of the flexible skirt to its outer edge is preferably at

least 45 , more preferably at least 60 .

A feature of both injection moulded and blow-moulded containers is that their base interior surfaces may not be flat, i. e. may be 3-dimensionally contoured. One common shape has an annular peripheral trough around a central platform. In the present system the lower surface of the follower plate is preferably shaped to complement or conform with the upward contour of the container base. Where there is a peripheral trough in the base, it is easy to shape the peripheral skirt of the follower plate with a corresponding downward bulge (which can correspond with downwardly and upwardly inclining skirt portions mentioned above). A practical significance of this is the ability to clear substantially all the product from the container via the pump, without trapping substantial volumes in pockets between non-conforming parts of the follower plate and base surface.

A possible variation within the present proposals is to provide the flexible sealing skirt with plural structural discontinuities (in the circumferential sense) distributed around it. These enable the skirt to collapse circumferentially with less buckling or folding

of the skirt periphery. The forced diminution in circumference caused by passing a decrease in container wall diameter can be taken up by preferential circumferential collapse at the location (s) of the collapsable structures in the skirt, which in some situations may avoid or reduce peripheral buckling and help to maintain sealing.

A particularly preferred form of discontinuity is a slot or slit extending radially or substantially radially in from the edge of the skirt, so that circumferential compression can be accommodated by portions of the skirt to either side of the slit overlapping one another.

Slots and slits have the advantage of being easy to make, requiring no complicated shaping of the flexible skirt.

Embodiments of the present proposals are now described by way of example, with reference to the accompanying drawings in which: Fig. 1 is an axial cross-section of a first embodiment of dispensing system ; Fig. 2 is a plan view of the follower plate from the Fig. 1 system; Figs. 3 and 4 are diametral sections of the follower plate at III-III, IV-IV respectively;

Fig. 5 is an enlarged cross-section near the edge of the follower plate, taken at V-V of Fig. 3 ; Fig. 6 is a top view of a second embodiment of follower plate, with Fig 6. A showing a peripheral detail; Fig. 7 is a side view of the second embodiment, partially radially sectioned at VII-VII; Fig. 8 is a schematic axial sectional view showing the second embodiment of the follower plate at two different positions in a dispenser system, and Fig. 9 is a top view showing schematically a non circular cross-section region of the container of the second embodiment, at IX-IX of Fig. 8.

Fig. 1 shows the general layout of a dispensing system consisting of a blow-moulded plastics container 1 with a generally cylindrical side wall 11, a snap-fit cover cap 6 and a dispenser pump 2 mounted through a hole in the cover cap 6. The nature of the pump 2 is not critical.

It may be any kind of suitable dispenser pump, e. g. a plunger-action moveable-nozzle pump of a type in itself well-known, where the vertical reciprocation of a plunger 21 incorporating a nozzle (not shown) moves a piston 24 in a pump cylinder connected to a valve inlet. A stiff cylindrical feed tube 3 extends down to the base of the

container, and the foot of the feed tube has openings 31 for product to enter and rise to the inlet of the pump.

In this particular embodiment we show a preferred arrangement of a pump as described in our EP-A-899206 i. e. in which the interior of the upper part of the feed tube 3 itself constitutes the pump cylinder, and the pump inlet valve structure 23 is formed integrally with the feed tube interior. As mentioned, however, other kinds of pump with conventional feed tubes may be used. A feature of the blow-moulded container-as with blowmoulded containers in general-is that the neck opening 15 is narrower than the main internal diameter. In this embodiment the radius of the top cylindrical neck portion 15 is about 10% less than that of the main container wall 11, with a smooth taper portion 16 linking the two.

The base of a container has a flat circular central platform 13 on which the foot of the feed tube 3 rests, surrounded by an annular depression or channel 14 with a curved concave interior surface.

A follower plate 5 is provided in the container interior to lie on top of the mass of product (not shown) and follow the product surface down the container. The

follower plate 5 is a generally flat disc formed in one piece of plastics material by injection moulding. It includes a central rigid axial sleeve 51 defining a central opening 56 through which the feed tube 3 fits reasonably closely. This combination of fit and axial length of the sleeve 51 assures correct alignment of the follower plate 5 transversely to the feed tube as it moves down the container. There is however no particular limitation on the construction of the follower plate at this region. Around the central sleeve 51 the plate extends as a stiff, flat central zone consisting of a planar web 52 stiffened by integral radial stiffening ribs 521 extending out to meet a circumferential stiffening ring 522. The circumferential ring 522 marks the boundary of the stiff central region 52. Outwardly of the ring 522 the follower plate 52 has a flexible sealing skirt 53, extending out to an extreme peripheral edge 532.

The entire follower plate 5 is moulded in one piece of LDPE, because of the need for flexibility. The following thickness dimensions exemplify how stiffness of the central region 52-necessary for proper functioning of the follower plate-can be combined with flexibility of the sealing skirt 53 for the special functions described

below. In this embodiment the central web 52 is about 1mm thick, its stiffening ribs 521, 522 are 1mm high while the sealing skirt 53 is about 0. 5mm thick from its root 531 to its edge 532.

The flexible sealing skirt 53 is specially shaped as shown in the drawings. Proceeding radially outwardly from the root 531 immediately beyond the stiffening ring 522, it has a planar region 541, a conical downward inclination 542, a further substantially planar region 543 curving into an upwardly inclined edge part 544 leading to the extreme edge 532 which engages the container wall.

The total diameter of the follower plate is about 100mm and the skirt 53 in this embodiment is about 16mm radially from root to tip (contributions about a third of the total diameter).

What are the special functions? Firstly, the flexible and upwardly-curved periphery 53 of the follower plate is easily inserted through the neck restriction of the container on assembling the system. Secondly, it is found to seal satisfactorily against the container wall as dispensing proceeds. Thirdly, its shape is matched to

the shape of the peripheral channel 14 of the container base, so that when the follower plate reaches the base substantially all fluid can be cleared. It may be desirable to provide some slight discontinuity of the opposed follower plate/container base surfaces towards the central region, so that the last residues of material can flow inward from the periphery as the surfaces move together.

It is an unexpected finding that a follower plate fringe sufficiently flexible to pass through a blow-moulded container neck is able to seal satisfactorily in this way.

In this embodiment the angle a between the follower plate axis and a cone surface containing the root and the tip of the skirt 53 is about 80 degrees (in the free condition of the plate 5).

Figs. 6-9 relate to a second embodiment; Fig. 8 shows the general layout of the dispensing system. The reference numbers generally correspond to those in the first embodiment. Here a different design of the follower plate is used, as follows

The skirt region 53 decreases in thickness from adjacent the stiffening rib 522 to a minimum thickness at its outer edge 532. In this example the stiffening ribs 521, 522 are lmm high, the central web 52 is 1.5mm thick, the sealing skirt 53 is. 6mm thick at its root 531 tapering to. 3mm thick at its sealing edge 532.

The plate is made from low density polyethylene to provide resilient flexibility in the sealing skirt 53.

The radial extent of the sealing skirt is 30% of the total radius of the plate. It is curved upwardly for ease of insertion in the container ; the angle between the axis and a cone surface containing the root 531 and edge 532 of the skirt being about 70 degrees. Figs. 1 and 2 show the free condition; when installed the sealing skirt deforms slightly further upwardly. In this embodiment the container has a plain bottom and the skirt 53 does not bulge downwardly.

A particular feature of the container 1 is the presence of finger grip grooves 12 in its outer surface. As indicated in Fig. 9, these correspond to opposite inward projections of the interior surface of the wall. Fig. 8 shows a follower plate in two positions 5, 5' in the first

of which it makes sealing contact with the full circular diameter of the container and in the second of which it is passing the internal projections 12.

The sealing skirt 53 is interrupted by three equiangularly spaced slits 54 extending radially from root 531 to edge 532. When the follower plate 5 passes the container finger grooves 12, opposed sides of the sealing skirt 53 must flex to ride over this irregularity. This flexion is possible owing to the large radial extent of the flexible skirt 53. At the same time, the portions of the skirt bordering the slits 54 ride over one another-as indicated in Fig. 6A-in order to accommodate the circumferential contraction forced by the inward projection of the wall. We have found in tests that this avoids or reduces general buckling or crumpling of the skirt circumference may occur when passing inward projections of certain shapes and sizes, the seal between the skirt 53 and the container wall 11 is essentially maintained. In turn, this reduces a tendency for the follower plate 5 to become detached from the product surface as it passes the internal bulges 12. The number and disposition of slits can be determined by trial and error for a given system. In the present case we prefer not more than five slits, to minimise leakage at the slits. In other cases the slits may be nonuniformly distributed.

Other variations will occur to the skilled person.

Claims

Claims 1. A dispensing system comprising a container to hold flowable material for dispensing, the container having a side wall and a base; a dispenser pump mounted at the top of the container; a feed tube extending in the container down from an intake of the dispenser pump to adjacent the container base, providing a conduit for flowable material to enter the dispenser pump from adjacent to the container base in use of the system, and a follower plate which fits around the feed tube, extending out towards the side wall of the container and which is axially slidable along the feed tube to follow the surface of flowable material down the container as dispensing proceeds; wherein the container has one or more regions of a relatively reduced internal diameter, and the follower plate has a peripheral sealing skirt which is sufficiently flexible for the follower plate to slide through the reduced diameter region (s).
2. A dispensing system according to claim 1 in which a said reduced diameter region of the container is a restricted neck opening thereof.
3. A dispensing system according to claim 1 or claim 2 in which a said reduced diameter region of the container is a corrugation or inward projection of the side wall thereof.
4. A dispensing system according to any one of claims 1 to 3 in which the container is a blow-moulded container.
5. A dispensing system according to any one of the preceding claims in which the follower plate has a nonflexing central region, and the radial extent of the

flexible skirt is at least 10% of the total of radius of the follower plate.
6. A dispensing system according to claim 5 in which the radial extent of the flexible skirt is at least 20% of the total radius of the follower plate.
7. A dispensing system according to any one of the preceding claims in which the base interior surface of the container is three-dimensionally contoured and the lower surface of the follower plate is shaped to complement or conform with the upward contour of the container base.
8. A dispensing system according to claim 7 in which the container base has an annular peripheral trough, and the follower plate's peripheral skirt has a corresponding downward annular bulge.
9. A dispensing system according to any one of the preceding claims in which the flexible sealing skirt has plural structural discontinuities distributed around it circumferentially, at which the skirt can collapse circumferentially.
10. A dispensing system according to claim 9 in which the discontinuities are radial slits in the skirt.
11. A follower plate having a flexible sealing skirt, for a system as defined in any one of the preceding claims.
12. A dispensing system or a follower plate for a dispensing system, substantially as described herein with reference to the accompanying drawings.