BACKGROUND OF THE INVENTION A well known type of dispensing system, useful with thick and viscous products such as pharmaceutical and cosmetic creams and lotions, has a plunger action dispenser pump mounted on or in the cover of a cylindrical container. A stiff feed tube for the pump extends down to the bottom of the container and a follower plate fits axially slidably around the feed tube. The follower plate lies on top of the product mass to follow it down the container as dispensing proceeds.

This helps to ensure complete clearance of the contents.

In the absence of a follower plate the formation of cavities in the product near the foot of the feed tube can make it impossible to clear the container completely.

See our EP-A-765690 and our earlier-filed UK 9718007.9 for further information about the operation of such systems and refinements thereof, for example methods for securing the feed tube against lateral displacement, and disposition of operative pump components within the feed tube itself.

With a viscous or pasty material one can fill the open container with the required weight of material,

position the follower plate in the container in contact with the material surface and then insert the foot of the feed tube, which has been pre-assembled as a sub-assembly with the cover lid and other pump components, through the central hole of the follower plate, pushing the sub- assembly down until the cover lid is fastened onto the container rim, typically with a snap fit.

As the feed tube is forced down, material may flow into it and displace air through the pump above. The extent to which this occurs depends on the shear properties of the material and the ease with which air can pass out through the pump. The latter depends on the type of pump. Most pumps have an inlet valve which will readily allow flow in the relevant direction. In many cases there is also an outlet valve from the pump chamber and this is sometimes more strict than the inlet valve since when closed its seal must be good enough to prime the pump via the inlet valve in concert with the restoring spring force provided; conversely force for opening the outlet valve is readily available from the manual operation of the device. Thus the outlet valve in particular may be reluctant to allow air to pass out as the feed tube is inserted. It is then necessary to make numerous preliminary"priming"strokes of the pump to fill the pump with material and this is a nuisance.

Certain materials are so thick that they are heated to reduce their viscosity for filling the container and here

problems are especially likely because (a) a strict outlet valve is preferred for pumping such thick material; (b) at the time of inserting the feed tube the viscosity may be reduced, and a thin material has little tendency to force air up through the pump past a strict outlet valve, and (c) subsequent priming of the pump with the re- thickened material by pumping air through the pump is very difficult.

Furthermore with materials of this kind the difficulty has been noted that the follower plate tends to fail, i. e. does not follow the product down.

SUMMARY OF THE INVENTION What we now propose is to provide a height limiting abutment arranged to act downwardly on the follower plate and prevent the follower plate from rising above a predetermined height relative to the container. In the conventional arrangement the follower plate is free to rise above the conventional fill level - it is generally the practice to leave some empty space at the top of a container to avoid spills. By providing a height limiting abutment to prevent this, at least in the assembled condition, various advantages may be obtained depending on the particular dispensing system and the particular method for filling.

By keeping the follower plate down when otherwise it

might rise under the influence of product displacement by the inserted feed tube, the flowable product can be forced up inside the feed tube. This can reduce or eliminate the difficulties with priming referred to above, even when the outlet valve is a strict one.

Where the rim region of the container includes structure dedicated to securing the cover rather than to maintaining the seal with the follower plate, the height limiting abutment can keep the follower plate in sealing engagement with the inner sealing surface proper rather than encroaching on the securing construction at the rim.

We find that this can help reduce incidences in which the follower plate fails to act. In particular, heat- expansive products which are filled in a heated state will subsequently contract so that the container must initially be filled very full to action a desired fill level/weight when cold. The initial high fill level tends to hold the follower plate too high, particularly by the feed tube.

Additionally or alternatively the more forcible contact of the follower plate with the contained material improves their mutual adhesion, which also assists the follower plate action. We have found in our investigations that, in the above-mentioned situations where the product is heated for filling, product shrinkage which occurs on cooling is apt to cause separation of the product surface from the follower plate

and the enhanced contact helps to prevent that.

In line with the explanation above, the predetermined level for the follower plate is generally one at which it makes a seal against the container wall.

Usually this is spaced below the container rim, and especially where the container rim has a radially recessed band adjacent the rim for cover securement purposes.

Typically the follower plate takes the form of a generally level continuous web with an upwardly projecting sealing lip around its outer edge, making sealing contact at or near its upper extremity. The centre of the follower plate has a hole for the feed tube, and a sealing construction at the inner periphery desirably has a downwardly-directed (downwardly convergent) sealing lip to facilitate feed tube insertion. However the downwardly-directed inner sealing lip is generally provided on a central upwardly- projecting construction so that the underside of the follower plate can descend unobstructed right to the floor of the container. Or, an upward lip may be used e. g. if the feed tube can be inserted up through the follower plate.

The structure and disposition of the height limiting abutment can be chosen from a variety of options. One approach would be to provide one or more internal projections of the container side wall. This is least

preferred because of the need for a special container and the requirement that while the projection (s) will adequately prevent rise of the follower plate, the follower plate must nevertheless be conveniently insertable down past the projection (s) during assembly.

Thus, it is more preferred that engagement by the height limiting abutment acts against a component other than the container, i. e. one or more of the feed tube, other pump components (where present at the underside of the cover) and the cover itself.

Preferably the height limiting abutment engagement for the follower plate is distributed around the feed tube. This levels the follower plate as the abutment counters the pressure of material beneath the plate. The arrangement can effectively function as a spacer between the general level of the follower plate and the general level of the cover. To this end it may comprise one or both of an upward projection on the follower plate and a downward projection on the cover. Or it may be on one of the pump components mounted thereto.

A preferred form of abutment is annular, and most preferably immediately adjacent the feed tube exterior either as an integral projection thereof or as a discrete spacer element which can fit around the feed tube. We prefer to use a discrete element because of the design flexibility enabling different axial sizes of abutment to be chosen.

Desirably an air vent is provided through the cover adjacent the top of the feed tube/pump body, e. g. as one or more small openings into or past the pump body. The height limiting construction of the present proposals preferably engages the follower plate below the air vent arrangement, leaving clearance for venting above the engagement. The abutment, e. g. annular spacer, may itself include one or more vent openings for this purpose.

In an annular spacer this may be one or more vent openings from the inside to the outside of the annulus, and/or one or more vent openings from the top to the bottom of the annulus. Such openings are conveniently provided as recessed portions of the top/bottom/inner surfaces of the spacer, as appropriate.

It should be understood that a filled dispensing system of the kind described, in which the height limiting abutment holds the follower plate down at a predetermined level as described above, is one aspect of the invention. A further aspect is a method of filling a dispensing system of the kind described, including filling the material into the container (optionally with heating to reduce its viscosity), positioning the follower plate and inserting the feed tube. The order of operations first explained need not necessarily be followed. That is, the steps of positioning the follower plate on the material surface

and of pushing the feed tube down into the material maybe interchanged or may overlap. The height limiting abutment can serve a useful effect even when the follower plate is introduced into the container as part of an assembly with the feed tube.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention is now described in detail with reference to the accompanying drawings, in which: Fig 1 is an axial cross-section of a dispensing system; Fig 2 is a relatively enlarged axial cross-section of the upper part of a dispensing system, showing a height limiting arrangement in accordance with the invention; and Figs 3 and 4 show plans and radial sections at two kinds of annular height limiting spacer.

DETAILED DESCRIPTION OF EMBODIMENTS Note that the present discussion adopts the terms "top"and"bottom"for ease of description, but unless the context requires otherwise these are not to be taken as limiting the actual orientation in use.

A container 1 for material (M) to be dispensed has a cylindrical side wall 12 and a generally flat base 11.

The top opening of the container is closed by a top cover cap 2 having a downward peripheral skirt 23 with internal circumferential ribs 24 making a secure and air-tight

snap engagement over corresponding outwardly directed ribs 14 around the rim of the container wall.

The cover cap 2 has a flat horizontal main web 21 with a central circular opening 22 through which a pump construction is mounted as described below. The manner in which the cap 2 fits onto the container 1 is not critical and may be varied as desired, e. g. by using a screw thread. The top rim of the container has a reduced-thickness zone 15 to facilitate the deformation required for snap fitting; here the container's inner diameter is radially enlarged relative to the otherwise uniform cylindrical inner surface 16.

A stiff cylindrical feed tube 3 extends vertically from the top to the bottom of the container. At the bottom it rests against the container base 11, with lateral openings 38 for material to enter. The present embodiment locates the foot of the feed tube over a cruciform spike 13, as discussed in our EP-A-765690. At the top of the container an integral tubular threaded extension 33 of the feed tube 3 projects up through the cover opening 22 and is held in place by a threaded-on fixing collar and plunger guide component 6. The feed tube component has an integral annular flange 34 projecting out radially immediately below the top extension 33, and the web 21 of the cover cap is trapped between this and the downward skirt 61 of the guide component 6 to hold the feed tube 3 and cover 2 together

as a single assembly.

The outer surface 36 of the feed tube 3 is a uniform smooth cylinder from the top to the bottom of the container and serves as an inner guide for a follower plate 5. This is a generally flat annular plate having a continuous horizontal web 51 with a central opening 52 through which the feed tube passes. Its function, as known from earlier disclosures, is to lie on top of the mass of product in the container. As the product level in the container falls the follower plate 5 moves down the container, guided by the feed tube 3, to assure full clearance of material from the container space.

The central opening 52 has an upwardly-projecting stiff tubular seal construction 54 supporting a downwardly convergent inner flexible sealing lip 55 which bears against the feed tube surface 36. The periphery of the plate has a flexible upwardly-divergent sealing lip 56 to bear against the container's inner surface 16.

The cover/feed tube assembly also includes a pump 8.

This may take any of a variety of relatively conventional forms, e. g. as shown in our EP-A-765690 where the pump body (cylinder) fits down inside the top of the feed tube. The present embodiment is a more sophisticated construction in which the feed tube 3 itself acts as the pump cylinder. The active component of the pump is a <BR> <BR> <BR> manually reciprocable plunger 7 having a. bottom piston 73 working sealingly in the upper region of the feed tube 3

and a top plunger head 81 with a laterally-directed discharge spout 82 communicating with the pump chamber via a central discharge channel 72 within the plunger itself. The pump chamber has an inlet valve to assure unidirectional flow up the feed tube 3. In this embodiment the inlet valve 4 is a flap insert 45 supported on an inward flange 44 formed integrally in the interior of the feed tube 3, but other constructions are possible: a ball valve may be used, or the valve construction may be in a discrete pump body component inserted in the feed tube.

A discharge valve 9 is provided in the discharge channel of the plunger 8 so that product is drawn into the pump chamber as the plunger 8 rises after a pumping stroke. The discharge valve 9 may take a variety of forms as is well known, for example a ball or flap valve.

In the present embodiment, designed for situations in which the material to be dispensed is reluctant to flow, we adopt a flap valve with a flap of resilient material e. g. nitrile rubber which in its rest position is urged with a sealing force against the stiff counter surface.

For ease of construction the rubber flap is provided as a disc with a central hole, trapped in the enlarged bottom opening of the discharge channel 72 by an insert component which snaps into place. Such a valve provides high-efficiency sealing. It also requires an appreciable pressure to open it; greater than that required for the

inlet valve 4.

The operation of the pump as such is completely conventional and need not be explained further; there is a pump spring 65 for restoring the plunger 7 to its rest condition after each stroke.

Dispensing systems of this kind conventionally require a vent arrangement so that air can enter the container to compensate for the volume of product dispensed. The venting system must be proof against leaks, however. In the present proposal, as in some previous proposals, one or more small vent openings 35 (see Figure 2) are provided through the wall of the feed tube 3 immediately below its locating flange 34. Air can leak into the container through the vent opening (s) 35 from above via a tortuous path through the pump construction.

A particular feature of the construction is a height limiting abutment in the form of a discrete, annular spacer insert 100 best seen in Fig 2. The spacer insert 100 which (like the rest of the pump) may conveniently be moulded in plastics material fits closely (but slidably) around the top of the feed tube 3. It presents a generally flat radial lower surface 101, radially aligned with the upwardly-projecting inner seal construction 54 of the follower plate 5 so that the top of that seal construction makes an engagement around the spacer 100 defining an uppermost limit position for the follower

plate 5. The upper surface 102 of the insert 100 bears upwardly against the bottom of the locking flange 34 of the feed tube, i. e. effectively up against the bottom of the cover. One or more radially-extending vent channels 103 penetrate the spacer 100; in this embodiment they are provided as simple recesses in its upper surface 102.

The inner surface 105 of the insert 100, which otherwise fits closely against the feed tube, has at its upper portion an annular recess 104 providing a manifold to assure communication of the (circumferentially localised) vent openings 35 in the feed tube 3 with the (circumferentially localised) venting channels 103 in the insert 100.

In use the discrete spacer insert 100 is pushed onto the feed tube 3 before the cover cap, pump and feed tube components are put on the container. The container having been filled and the follower plate 5 positioned on the material surface in the container (the follower plate may alternatively be put first onto the feed tube), the feed tube is then pushed down into the container until the cover cap locks onto the container rim. As already discussed, displacement by the feed tube requires that the material surface will rise in the container and/or that the material will rise up inside the feed tube. The latter tendency is strongly inhibited by the discharge valve 9, which is reluctant to open. The tendency therefore would be for the material surface to rise,

lifting the follower plate 5 to the condition shown at the left-hand side of Fig 2. This would compromise the seal made at the outside of the follower plate, because the outer sealing lip 56 would be at the recessed rim zone 15 of the container. When this happens with flow- resistant materials which have been heated for filling, and which then shrink as they cool, we find that the descending surface of the shrinking material leaves the follower plate 5 behind owing to the loose contact at the compromised outer seal. This is a likely cause of follower plate failure. Furthermore the feed tube would be full of air which is difficult to pump through the system so that many priming strokes are required.

In the present construction however the presence of the spacer insert 100 as now proposed forces the follower plate in the assembled condition to adopt the predetermined lower level as seen on the right hand side of Figure 2, with its outer seal properly in contact with the container's inner sealing surface. This enhances contact of the follower plate with the material surface too, so that the follower plate reliably follows the material surface even when there is shrinkage. The height (axial size) of the insert can easily be varied in relation to the volume of material filled so that the forced movement of the follower plate 5 to the predetermined level as shown will force an appropriate quantity of material up the feed tube 3 to prime the

pump.

The skilled person will appreciate that the mechanical height-limiting effect of the spacer insert 100 can be achieved in a number of ways. A discrete insert is not strictly necessary. The same height- limiting effect can be achieved with integral projections on any of the follower plate, feed tube, pump body and cover, for example. However the use of a discrete component has the advantage of enabling ready variation of the predetermined level by providing a range of inserts of different axial extent. This helps to control the priming and sealing situation in accordance with the volume and heat expansivity of the material concerned.

By having an annular engagement with the follower plate 5, tilting of the plate is prevented. Again, the skilled person will appreciate that this effect can be achieved with other kinds of mechnical abutment provided that the engagement is appropriately distributed around the feed tube axis.

Figs 3 and 4 show details of variants and refinements of the height controlling spacer 100. The version shown in Fig 3 corresponds in essence to that shown in Fig 2, with a pair of radially-extending recesses 103 enabling venting from the inside to the outside of the ring passed the bearing surface 102, and an internal manifold recess 104 to assure vent communication. The refinement here is that the top and

bottom surfaces of the annular spacer are formed identically, as seen to the left of Fig 3, so that the orientation of the spacer does not need to be controlled during assembly. In the Fig 4 version the top and bottom bearing surfaces of the spacer are flat and entire. The possibility of venting is provided instead by a series of inwardly-directed teeth 109 on the spacer which fit against the feed tube surface and leave a corresponding circumferential series of top-to-bottom clearances 106 between them.