BACKGROUND It has been known for years that dispensing liquid products from a collapsible flexible bag, e. g. as in a wine box, is one way of protecting the product from the air. Because the bag container can reduce its volume, there is no need for air to be vented into the container to compensate for the volume of product dispensed. In pump dispensers, such as are well-established for use on household and medical products such as creams, lotions, soaps and more recently toothpaste, earlier practice was to provide a follower piston in a cylindrical container enabling the container volume to reduce without venting.

More recently, collapsible bags are being used in this kind of dispenser too. A variety of film materials is becoming available for making bags impermeable to a corresponding range of bag contents.

There are however some issues with collapsible bag dispensers, notably the complication of assembling them in a dispenser with adequate sealing but controllable

expense (since they are frequently single-use products).

Also, the issue of achieving adequate collapse of the bag. In previous proposals, product clearance has been improved by providing finned stems projecting down inside the bag, but these raise the component count and are hard to attach. Prior art bags have been sealed onto pump inlets-a significant function, since the bag contents are frequently highly penetrating or permeating-by bonding the bag rim to a rigid plastics collar and sealing the collar around a pump inlet spigot by a rubber 0-ring in between. Again, this is expensive and troublesome.

SUMMARY OF THE INVENTION A first aspect proposed here relates to adapting a collapsible bag for connection to a dispenser inlet, typically a dispenser pump inlet. In our proposal the collapsible bag is formed in one piece with a thickened neck or collar, preferably by a blow moulding technique such as extrusion blow moulding or injection blow moulding. This can eliminate a troublesome step of attaching a discrete hard collar component. Preferably the thickened neck region of the bag includes an outwardly-projecting flange portion assisting axial location of the container relative to the connection.

The neck portion desirably includes an inner and/or outer smooth cylindrical surface, optionally with a slight taper, for pushing into sealing engagement with a

complementary sealing surface of the adjacent dispenser inlet structure.

The connection to the dispenser inlet structure may be by way of a spigot or socket into/onto which the container neck slides. This may have a supplementary seal such as an 0-ring. However we have found that when the stiff neck ring is formed integrally of the same material as the collapsible bag, its (relatively) more flexible and resilient material can give a good seal even without a supplementary sealing member, by a simple push fit into or onto a socket or spigot. Also, because of the greater deformability of the material compared with prior art neck rings, it is practical to form the socket/spigot and/or the sealing surface of the neck ring with one or more annular projections to enhance the grip and/or seal between the two components. The relatively flexible neck material can deform sufficiently for these features to act, enhancing sealing without requiring a discrete sealing component.

The material of the bag needs to be selected so that the bag will collapse under the prevailing dispensing conditions while being sufficiently impermeable to the material being dispensed. This selection is generally a routine matter for a skilled person. Suitable materials include those based on polyethylene (PE), e. g. low- density polyethylene (LDPE). Materials e. g. PE materials may contain modifiers or blend ingredients to adapt them to the purpose in hand as regards impermeability,

flexibility and suitability for the moulding process used. Thermoplastic elastomers (TPEs) are useful, e. g. those based on PE such as Santoprene.

A further feature proposed herein is a particular conformation of collapsible bag. With collapsible containers measures are needed to prevent uncontrolled collapse of the container leading to bodies of product becoming isolated from the pump inlet by folds of the container wall. One conventional arrangement has a central finned rod extending down into the container from the centre of the pump body, keeping the container longitudinally extended and providing riser channels for the product even when nearly exhausted. This is not easily combined with some constructions of pump inlet.

One proposal here is instead to provide the wall of the collapsible container with a longitudinally extending preformed corrugation which can stiffen the wall of the bag longitudinally at one or a few parts of its circumference: other parts may be plain. In the collapsed condition, the corrugation helps to keep open a flow channel to the pump inlet.

Additionally or alternatively, the collapsible bag wall may have a longitudinally-graduated wall thickness.

Thus, it may be more readily collapsible at its base than nearer the top, encouraging a gradual turning of the bag inside out from the bottom as dispensing proceeds, rather than"waisting"higher up as is otherwise the tendency.

A further proposal herein, which like the previous proposal is preferably embodied in bags with integral neck rings but may be embodied in other types, also relates to promoting satisfactory collapse of the bag.

In this proposal the collapsible main part of the bag has a pre-formed shape which is flattened in one direction, i. e. with local"folds", which need not be actual folds but have a sharper curvature than the wall portions directed transverse to them. Preferably this flattened conformation persists for at least 25%, more preferably at least 40% of the height of the bag from its end (i. e. the end removed from the neck). Preferably a side"fold" extends squarely or in an arc around the bottom of the bag end, which may therefore be spatulate in form.

The present invention encompasses both the novel forms of bag themselves, and bags with any or all of the above features installed in a dispenser, especially a pump dispenser. The dispenser may have an inlet construction with a socket or spigot, preferably engaging the bag neck ring solely frictionally with gripping projections as mentioned above, i. e. without supplementary sealing rings, although these may be used.

The dispenser may also incorporate valve constructions adapted for air tightness, e. g. as disclosed in our PCT application filed on the same day as this one entitled"Dispenser Pumps and Valve Arrangements"and claiming two priorities in common with the present filing.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention are now described by way of example, with reference to the accompanying drawings in which Fig. 1 is an axial cross-section of a pump dispenser for toothpaste, showing the connection of a collapsible bag to a dispenser; Figs. 2 to 5 are first and second side elevations, a top view and a section at 0-0 (see Fig. 3) of the collapsible bag shown alone; Fig. 6 is a cross-sectional view showing a different kind of collapsible bag used in a twin dispenser, and Figs. 7 and 8 are an axial sectional view and bottom end view respectively of a variant bag construction suitable for the Fig. 6 dispenser.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Fig. 1 shows a toothpaste dispenser incorporating a piston and cylinder pump whose particulars are not critical for present purposes, but having a base plate 11 defining an inlet opening 112 with a valve 113 whose nature, like that of the remainder of the pump, is not important for present purposes.

Fig. 1 also shows an outer casing 9 which, in common with most dispensers of the relevant kind, provides the structural support and protection for the product that the thin bag container 8 cannot provide.

The bag 8 is a one-piece blow-moulded construction and includes an essentially rigid (through being much

thicker) top neck portion 81. The thicker portion includes an upright plug 811, with smooth cylindrical inner and outer surfaces, and an outwardly-projecting locating flange 82.

The base plate 111 of the pump provides a plug engagement by an outer cylindrical skirt 114 and an inner flexible sealing skirt 115, with an annular space between them. The cylindrical bag neck is a push fit into this annular space, the degree of insertion being limited by the flange 82 and a full seal being made without the need for discrete sealing components.

Figs. 2-5 show the bag 8 complete, illustrating various refinements. The lower, collapsible part of the bag may feature a gradual decrease in wall thickness from the top to the bottom of the bag, to promote collapse of the bag from the bottom upwards as product is gradually dispensed. This is a first measure to reduce the chance of a body of product becoming trapped at the bottom of the bag as the upper regions collapse. A second feature shown here, which may be an additional or an alternative to the graduated wall thickness, is a corrugated formation 83 extending down one side of the bag, for most of the length of the collapsible part. As shown in Fig. 9, this corrugation provides rib projections 84 running side by side up the back with a recess 85 between. As the bag collapses, the rib projections 84 tend to keep the clearance 85 open as a communication

channel, reducing the possibility of bodies of product becoming isolated from the pump intake.

Fig. 6 shows a different kind of dispenser with a different bag container. This is a twin dispenser adapted for dispensing a two-component medicament; the two components need to be mixed at the time of application to avoid deterioration. So, the outer casing 19 houses a double pump 102, with twin plungers actuated by the same plunger cap, and a pair of collapsible bag containers 18 housed side-by-side in the casing 19. Each pump has a connection spigot 103 penetrated by the pump inlet passage 104, and having a cylindrical outer surface onto which the thickened integral neck 181 of the bag container 18 is pushed. This embodiment shows the use of a rubber 0-ring seal 191 to enhance the sealing. Here the locating flange 182 of the bag neck is supported from beneath by surround structure 96 in the lower casing 19, holding it up in position on the spigot 103.

Figs. 7,8 show a varied construction for a collapsible bag, e. g. useful in a dispenser of the kind shown in Fig. 6. Here the wall of the bag 208 gradually decreases in thickness, from a thick portion 207 close beneath the neck flange 82 to a thinner side wall 209 lower down. The neck of the bag is not re-entrant, i. e. it has the same internal diameter as the rest.

Preferably it is made by injection blow-moulding using an elastomer-modified PE, e. g. using Elvaloy 1224 from DuPont. The pump base 211 has an integral downwardly-

projecting spigot skirt 203 with a series of sharp annular ridges 231 over which the neck 82 of the bag 208 is forced. It may further be held in place by a support frame 296 having a flange engageable beneath the bag neck flange 82. In the embodiment shown the outer bag surface, at the thick portion close beneath the flange 82, has a further annular bead 228 to locate it positively in the support frame 296; this allows the bags held in the frame to be handled separately as a unit during assembly.

We find that because of the level of deformability introduced into the stiff collar component 82 by its material, being the same material as the collapsible bag, a long term gas tight seal is achieved over the spigot 203, particularly by virtue of the barbed beads 231. The pump inlet 201 is also shown.

Figs. 7 and 8 show further features of this embodiment which promote effective collapse of the bag even when made in small sizes. Firstly, from about half way down a creased or more acute portion 238 is introduced in opposing sides of the bag, extending down and around the closed end of the bag in an arc, at a relatively acute angle of fold, as a flattened or folded tip 239. It is roughly semicircular when seen from the transverse direction (Fig. 7 (b)).

The same design functions well in ordinary LDPE provided that it can withstand the contents chemically.