BACKGROUND OF THE INVENTION Our proposals relate to dispenser pumps for dispensing a flowable product from a container, e. g. a container onto which the dispenser pump is attachable as a closure. The pump comprises first and second portions - typically a fixed body and a movable plunger-which between them define a pump chamber, and which are relatively reciprocably moveable in a pumping cycle which alters the volume of the pump chamber so as to dispense flowable product from the container in use. This dispensed flow is defined as being in a forward flow direction from the container, and is by way of an inlet to the pump chamber, the pump chamber itself and an outlet from the pump chamber which leads to a discharge opening, e. g. a nozzle or atomizer. The inlet, chamber

and outlet in combination make up a flow path or flow passage through the pump.

At least one directional valve is provided in this flow passage by means of a valve seat formation of the flow passage wall, bordering a valve opening of the flow passage, and a valve body in the flow passage. The valve body is operable (in use of the dispenser) in a valve mode for which it is moveable in the flow passage between a closed position, in which it bears on the valve seat formation to block the valve opening and hence prevents reverse flow in the flow passage, and an open position in which it is lifted from the valve seat by forward fluid pressure to permit forward flow in the flow passage.

This might typically be a ball valve, the valve seat being a forwardly-divergent conical formation of the flow passage wall. Typically a valve is provided at least in the inlet to the pump chamber, with a further valve at the outlet being preferred. The choice depends-in known manner-on the nature of the pump system and the material to be dispensed. Inlet and outlet valves may differ in type. It is also well known for valve bodies to be biased towards the closed position, e. g. by discrete springs. Flap valves may be used, and these may have an intrinsic closing bias.

SUMMARY OF THE INVENTION Our first novel proposal relates to a directional valve construction in a pump as described. We propose to provide the flow passage wall with a sealing detent

formation at or adjacent its valve seat formation, the detent formation being shaped to hold the valve body out of its valve mode, i. e. so that it cannot move between the mentioned closed and open positions, but is in fully sealing relation with the flow passage wall so that the flow passage is blocked. The valve body is however releasable from the sealing detent formation by forcing a relative displacement between them, so that the valve body can then operate in the valve mode described above.

A particular use of this new feature is in being able to prevent product escape and/or air ingress along the flow passage without relying on the valve mode of the valve. It is well known to prevent escape of product from a dispenser during shipping by locking a dispenser plunger down so that its tip holds a ball of the inlet valve down onto its seat. However this is reliant on the plunger remaining screwed down, and the ball valve- which can perform its pumping function without necessarily making a perfect seal-may not entirely prevent leaks.

In our proposal a distinct seating formation of the flow passage wall can be provided where the valve body, e. g. valve ball may be stably retained making a good seal and without reliance on being held in place by a relatively movable component such as the pump plunger.

Preferably the valve body makes an interference fit with the sealing detent formation. Preferably the fit that holds it in place also makes the seal. The detent

formation may have a recess between front and rear wall projections, e. g. annular projections, in which the body is stably held fixed and from which it can be released only by substantial mechanical force urging it past one of the projections.

For purposes of sealing, the detent formation may be made from a resilient material and preferably a material more resilient than neighbouring parts of the flow passage wall. In particular it may comprise elastomeric material. An elastomeric wall insert in the form of a tube or collar is suitable. The detent formation may include a pair of inward projections, e. g. one or both being annular, with a recess between them (of larger diameter, if they are annular) in which a valve body, e. g. ball can be firmly retained and make a good seal.

Alternatively, the valve body may be a simple sliding plug fit in the detent location, which may then be a plain reduced-diameter portion of the flow passage wall. Or, the valve body may be initially formed in one piece with the flow passage wall, e. g. connecting with it by an annular frangible web which is broken by an initial displacement to initiate use of the pump.

Preferably the sealing detent formation is spaced from the valve seat formation, and shaped so that the valve body will not re-engage with the detent location under ordinary pump operation pressures. For this purpose it is preferred to provide a non-sealing detent formation on the valve seat side of the sealing detent

formation, past which the valve body is forced when moving to the valve mode, and which inhibits movement of the valve body back to the sealed mode under fluid pressure arising in use.

A particular use envisaged for this proposal is in preventing reverse flows of air along the flow passage where the product to be dispensed is sensitive to air, e. g. liable to oxidative degradation. For that purpose the adapted valve construction is preferably provided at the inlet to the pump chamber. However such an adapted valve may additionally or alternatively be used as an outlet valve.

It is also particularly envisaged that the present valve construction may be used in conjunction with a collapsible container, since these are another valuable means of avoiding air contact with the product being dispensed. Another relevant container type has a rising follower piston so that the dispensed volume need not be compensated by venting.

As described, it is necessary that the valve body be displaced from the sealing detent formation to initiate ordinary operation of the pump. Preferably this is by manually-driven relative movement of the mentioned first and second body parts of the pump. For example a pump plunger may have a nose or tip which, when the plunger is fully depressed, pushes the valve body out of its sealed seating and into the space above the valve seat where it is then moveable in the valve mode.

In the light of the above, a separate aspect of the invention is a flow passage insert comprising a passage wall portion having a sealing detent formation of any kind proposed herein, with a valve body held sealingly in it. The insert wall may consist of or comprise elastomeric material, as mentioned. Such a component is useful for assembling in a dispenser pump of the kind mentioned above, or in other fluid flow apparatus or devices requiring a valve body in initially sealed condition. It can facilitate the handling of valve bodies, which are small components and present special problems of assembly, e. g. assembly of metal balls into plastic pumps. The valve body when held in a larger insert module is easier to handle and install. The module may be made symmetrical to the extent that it can be installed either way round and still be effective.

Another preferred feature is that a flow passage insert component carrying the valve body is a compression fit in its seating in the dispenser pump body, or other apparatus/device. This compression on assembly of the device enhances the seal against the valve body and the pump body.

When used with air-sensitive products, it will be understood that the use of a valve arrangement according to the invention as an inlet valve is particularly useful. The full seal at the inlet valve may protect the product in the container long-term from filling to delivery.

A further independent aspect of the invention is the provision in a dispenser of a sealed, displaceable body in the flow passage, incorporating any one or more of the features described herein but which does not function as a directional valve after displacement from its seat, e. g. having as its sole function the blocking of the flow passage e. g. for shipping.

A further aspect of our proposals relates to discharge valve arrangements at the discharge opening of such dispenser pumps, and may be combined with the aspects above.

We propose novel discharge valve arrangements for the discharge opening of a dispenser. These are particularly (but not exclusively) suitable for situations where the dispenser may be used to dispense a product which should not be exposed to the environment, e. g. because of contamination, because it is sensitive to air and/or if it is liable to dry or to thicken so as to cause a blockage.

The proposed discharge valve arrangement has a valve seat on a rigid structure at or adjacent the discharge opening, and preferably fixed in relation to the discharge channel. A valve member is provided adjacent the valve seat and includes a sealing portion which bears on the valve seat in the closed condition, a blocking portion which closes off the flow passage in that

position so that reverse flow is prevented, and a resilient biasing portion comprising or consisting of elastomeric material which in the closed position urges the sealing portion against the valve seat, but is deformable under forward flow pressure by stretching and/or bending for the sealing portion to be raised away from the valve seat to an open position permitting forward flow past the blocking portion. Preferably the elastomeric biasing portion extends at least to some extent rearwardly relative to the valve seat towards its securement, and is pre-tensioned so as to urge the sealing portion against the seat in'the closed position.

Preferably the biasing portion lies entirely behind-or at least not in front of-the sealing portion. This facilitates a construction in which the interface between the valve member and the valve seat is the last part of the discharge passage, without the need for structure forwardly of the valve seat as in a ball valve.

Preferably the biasing portion of the valve member is distributed to opposite sides, of the valve, e. g. centrosymmetrically, to increase the restoring/sealing force of the valve. Preferably the valve seat is circular and the restoring force of the biasing element centrosymmetric in relation to the circle, e. g. a central rearwardly-extending tensile element, or peripherally

distributed tensile/flap connections. One embodiment is a closed, continuous resiliently flexible annulus between a peripheral securement and a central sealing portion.

Preferably the valve element is a one-piece elastomeric entity.

In one embodiment a flow opening is defined through the valve element itself e. g. as a central hole. This has the advantage that discharge of product can be in a single, central stream. The valve seat can then be on a central body underlying a web of the valve element surrounding the central opening. Preferably the valve seat is forwardly-directed so that rearward force on the valve element increases the seal. Thus, it may be an annular region behind and surrounding the central flow opening. Additionally or alternatively, a central body behind the valve element may have a forward protuberance which only or partially occupies the flow opening when the valve is in the closed condition. This protuberance may provide all or part of the valve seat, in a sense of providing sealing. It may function to occupy the volume of the flow opening to avoid product residues there. One preferred version provides the valve member as a domed or conical elastomer part with a central hole and a rear securement (e. g. a bead or flange), fitting around in front of a central hollow insert having a front wall

whose forward surface provides an annular valve seat for the elastomeric periphery around the valve member opening, and having one or more openings through the wall radially outwardly of the annular valve seat region from an interior flow conduit of the insert, so that fluid pressure in these openings acts on the rear surface of the dome or cone to force it away from the seat. The front of the front wall may have a protuberance as mentioned above. Such an insert may be a discrete entity fitted into a nozzle mouth of a dispenser. This fitting may trap the securement of the elastomeric element between the insert and the nozzle surround.

The elastomeric element may be formed in situ on the plastics body, for example in a two-shot injection moulding process, in such a way as to cure with a degree of pre-tensioning against the valve seat.

In the first preferred development, in its closed position, the valve arrangement is configured so that the valve body seals against the valve seat substantially to prevent communication between the flow passage and a flow opening formed in the valve body.

Conversely, in the open position, the valve body is raised away from the valve seat to define a flow path between the flow passage and the valve body and through the flow opening formed in the valve body.

Preferably, the flow opening is formed approximately centrally in the valve body. The advantage of having a flow opening in the valve body (rather than simply allowing the product to flow around the valve body) is that a discharge of product from the dispenser can exit the dispenser in a relatively narrow, uniform stream.

The valve body may be approximately symmetrically formed around the flow opening. For example, the valve body (or at least those parts of the valve body which can seal against the valve seat) may be ring-shaped or collar-shaped.

The biasing means may be formed integrally with the valve body. The biasing means and the valve body are preferably an elastic, more preferably an elastomeric, element. The biasing means may be arranged annularly, or offset annularly, around the valve body. The biasing means and the valve body may together define a dome shape or curved frusto-conical shape. In that case, the biasing means is preferably arranged rearwards (with respect to the forward flow direction) from the valve body. In the open position, the product can flow in the space defined between the valve seat and the valve body and/or biasing means.

The biasing means is secured with respect to the flow passage preferably by a rear securement.

To move from the closed position to the open position, the biasing means preferably deforms by bending. Alternatively, the biasing means may deform by tension or compression.

The valve seat may be formed at an internal fixture or insert located in or adjacent the flow passage.

Typically, in use, product flows around and over the valve seat, in order to exit the valve arrangement via the flow opening in the valve body. In the case where the valve body and the biasing means together form a dome shape, the valve seat preferably has a convex surface.

In the case where the valve seat is formed at an internal fixture or insert (preferably an insert) the fixture or insert typically has an internal space along which product is flowable. The insert may have one or more subsidiary flow passages formed in it, communicating between the internal space and the valve seat, to allow product to flow from the internal space out over the valve seat.

The insert may be removably locatable in the dispenser, in a correspondingly shaped recess in or adjacent the flow passage. Preferably, an outer wall of the insert sealingly engages with this recess, in order to protect product within the dispenser from air. The insert is typically formed separately from the rest of

the dispenser. Preferably, the insert is formed from plastics materials, for example by injection moulding.

The integral valve body and biasing means may be formed in situ on the insert, for example in the second stage of a two-shot injection moulding process.

The valve seat may include a secondary sealing surface, typically the lateral surface of a projection shaped to correspond with the shape of the flow opening formed in the valve body. A front surface of the projection may be shaped to fill-in substantially smoothly the appearance of the front surface of the valve body. This allows the front surface of the valve arrangement to be wiped clean relatively easily, to avoid the problem of dried or spoiled product clogging the flow opening of the valve body. Most preferably, the projection and the flow opening combine to nip the space between them at the front extremity of the valve body.

Typically, the flow opening tapers to a smaller diameter in the forward direction sealingly to meet the lateral surface of the projection from the valve seat.

In a second version the biasing means comprises an extensible tensile connector extending behind (i. e. in the reverse direction along the flow passage relative to) the valve body to a rear securement, so that fluid pressure raising the valve body from its seat must extend

the tensile connector against a restoring force. The connector may be an elastic e. g. elastomeric, element.

It may be formed integrally with the valve body.

In one preferred embodiment, a one-piece elastomeric element has a front portion constituting the valve body, a central linking portion constituting the tensile connector, e. g. extending coaxially of the centre of the flow passage, and a rear securing portion shaped to engage a wall of the flow passage to restrain it against forward movement. The surrounding flow passage wall may be provided with one or more circumferentially-localised recesses (or, alternatively considered, one or more circumferentially-localised radial projections) allowing fluid pressure to access the rear of the valve body to lift it from its seat. Other types of clearances may be provided for this purpose, and to allow product to flow around the rear securement and intermediate connector portions of the tensile constructions. One preferred embodiment has a central valve opening with a surrounding annular valve seat, the valve body and a tensile connector being central. However, it is also possible to have the valve body annular, sealing (radially) both inwardly and outwardly against elements of the flow passage relative to which it is movable. In this case the tensile connector (which may comprise more than one

axially-extending element) may be peripherally disposed in relation to the flow passage.

These aspects of the invention provide new valve constructions which are useful in dispenser pumps, particularly but not exclusively as discharge valves.

Some embodiments of the first version and all embodiments of the second version have the potential advantage that the restoring element (of the biasing means) lies behind the discharge valve body, unlike a conventional sprung ball valve in which the spring is in front of the valve body. In these embodiments, it becomes possible to position the valve body at the extremity of the discharge opening. Closure of the discharge valve isolates the entire pump interior and flow passage from the outside air, avoiding drying or degradation of product in a nozzle portion immediately adjacent to the discharge opening.

BREIF DESCRIPTION OF THE DRAWINGS An embodiment of the present proposals is now described by way of example, with reference to the accompanying drawings in which: Fig. 1 is an axial cross-section through a twin-pump hand-held dispenser system; Fig. 2 is an enlarged axial cross-section showing the inlet valve construction of each pump;

Fig. 3 is a cross-section of the same dispenser system, transverse to that of Fig. 1 and taken axially with respect to one of the outlet valves; Fig. 4 is a front view of the dispensing system from the outside, with a cap removed to show the twin outlets; Fig. 5 is a cross-section of the dispenser system of Fig. 1, transverse to the view of Fig. 1 and taken axially with respect to one version of discharge valve ; Fig. 6 is an enlarged view of the discharge valve construction of Fig. 5; Fig. 7 is a perspective view of the dispenser system of Fig. 1, with a discharge valve insert removed; Fig. 8 is a front perspective view of the dispenser system of Fig. 7, and Fig. 9 is an enlarged view of a second embodiment of discharge valve construction, seen also in Fig. 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS With reference to the drawings, the present proposals are exemplified with reference to a twin dispenser designed to dispense two different products simultaneously through adjacent outlets. This feature has no particular association with the inventive proposals, which may equally well be implemented in a single dispenser, or indeed in one with two pumps which feed a common mixer outlet, or with more than two pumps. The

following description refers to only one pump arrangement of the pair, for clarity's sake.

With reference to Fig. 1, a bag container 3 is of flexible plastics material and has a thicker integral collar 31 at its upper end which fits sealingly (by an 0- ring) over the downward plug or spigot 13 of a fixed pump body 1. The pump body is supported in the top opening of a stiff plastics outer container shell 32 which encloses the bag container 3 and provides support, to hold the neck collar 31 of the bag container 3 up in place on the pump body spigot 13.

The pump body 1 includes an upwardly-extending cylinder 11 which is open at the top to receive the piston stem 21 of a reciprocable plunger 2. The lower end of the piston stem 21 carries a resilient seal element 22 which wipes the inner surface of the cylinder 11, and extends down beyond the seal with a central nose 23. Alternatively the seal and stem may be in one piece.

The nose 23 is cylindrical and has a central bore 24 which is the discharge channel for the pump. This leads up through the plunger stem 21 to a junction 25 with a generally horizontal discharge channel portion 26 leading in turn to a valved outlet 7 indicated in Fig. 3.

The bottom end of the pump cylinder 11 has a valve inlet construction which is now described in detail with reference to Fig. 2.

The pump body provides a circular inlet opening 61 through the middle of the plug or spigot 13. This leads

up into the cylinder 11 via a conically divergent portion 62 which constitutes a valve seat, and a cylindrical detent seat portion 63 in which a rubber sealing detent 5 is fitted. This sealing detent 5 is an elastomeric sleeve dimensioned to make a compressive, sealing fit in the cylindrical seat 63 at the base of the cylinder 11.

It has a central bore whose diameter varies in the following manner. At the end of the sleeve there is a cylindrical bore portion 51, matching the bore of the body's inlet opening above the conical divergence 62.

Above this, the bore of the rubber insert has a conically convergent portion 52 leading to a first restriction 56 which has the minimum diameter of the bore. Above the restriction 56, half way up the sleeve insert 5, there is an annular groove 53 with a curved inward surface complementing a valve ball 9 or other valve body which is gripped firmly and stably in this recess 53. The valve ball 9 may be of any material appropriate to the product being dispensed, e. g. steel, nylon, glass. The upper portion of the sleeve 5 is a mirror image of the lower, so that it can be fitted either way up (facilitating assembly) and the ball 9 is equally retained from above and below against axial movement. At the same time it makes a fluid-tight seal of the bottom of the cylinder, enhanced by the compression of the sleeve on assembly.

The sleeves 5 with the balls 9 already fitted can be fed to the assembly machinery for fitting into the cylinders 11.

The dispenser is designed to be packaged and\shipped with the plunger 2 in the up position. The tight a\nd continuous seal between the ball 9 and the surrounding valve collar recess 53 assures complete exclusion of air from the contents of the container 3 after filling and assembly. The ball 9 is self-maintaining in its sealed condition, requiring no force from the plunger above as in prior art down-shippers.

To initiate use the user pushes the plunger 2 down forcibly. The tip of the nose 23 on the plunger stem applies this manual force directly to the ball 9, forcing it down out of its elastomeric seat 53 and into the space 65 below where it lies in conventional fashion on the conical valve seat 62.

Because the central eminence of the sleeve 5 is made circumferentially continuous in order to seal, its lower conical surface 52 would be capable of acting as a valve seat for the ball 9 in the wrong direction, i. e. so as to prevent necessary forward flow of product into the pump chamber 69 on the upstroke of the plunger 2. To avoid this, the bore of the sleeve 5 features a set of circumferentially-localised inwardly-projecting lugs 55.

The manual force that initially displaces the ball 9 from the sleeve 5 also pushes it past these lugs 55.

Subsequently, the lugs 55 present an obstacle to prevent the ball 9 from being carried up under flow pressure and seating sealingly in the wrong direction.

This particular version of the pump is designed to be suitable for use with materials which need to be isolated against contamination e. g. from the environment. The use of a collapsible bag container in conjunction with the special inlet valve described above protects the material in the container. After the initial use however the pump chamber 69 and discharge passage 24 will also be full of material, and it may be desirable to prevent or minimise exposure of this material, although for a frequently-used product this requirement may be less stringent than that for sealing the container long-term at the inlet.

With reference to Fig. 1, the pump body 1 includes an upwardly-extending cylinder 11 which is open at the top to receive the piston stem 21 of a reciprocable cap portion 2.

Depression of cap portion 2, after a priming stage, forces product from the bag container 3 upwards through the pump and along the flow passage to a junction 25 with a generally horizontal discharge channel portion 26 leading in turn to a valved discharge outlet.

Embodiments of the valved discharge outlet are described below.

Figs. 5 and 6 show a first embodiment of a discharge valve arrangement. The pump body 1 extends upwards to define a pressable surface 150 which a user can press to

reciprocate the cap portion 2. Junction 25 in Fig. 1 communicates with passage 52 (part of discharge channel portion 26) in Fig. 5 which in turn leads to a discharge valve arrangement encircled and indicated in Fig. 5 by reference numeral 154. This is shown in more detail in Fig. 6.

Passage 152 leads into an enlarged cylindrical socket or recess 154 formed in cap portion 2. An insert 156 is shaped to be held tightly in recess 154.

Insert 156 is of generally cylindrical form. It is formed by injection moulding of plastics. A support portion is formed from a relatively rigid plastics material and has a cylindrical bore 158. A flexible portion is formed as a valve cap 160 over one end of the first portion. Valve cap 160 is dome-shaped with a circular opening 162 formed at its centre. Valve cap 160 is formed in the second stage of a two-shot moulding operation, from any suitable elastomeric material e. g. rubber.

Subsidiary passages 164 are formed in the insert which communicate from the cylindrical bore 158 to a space between valve cap 160 and the support portion of the insert 156.

In use, forward flow pressure forces product along the cylindrical bore 158 and through the subsidiary

passages 154 to deform an offset annular valve collar 166 (part of the valve cap) away from valve seat 168. There is a restoring force back to the original position due to the resilience of valve cap 160. In the open configuration, product can flow, and a forward flow pressure out of the discharge valve arrangement via opening 162.

Opening 162 has tapering side walls 170 through the valve cap 160. In contrast, a projection 172 is formed from valve seat 168, extending through opening 162, and the side walls of projection 172 that are more approximately cylindrical. Tapering opening 162 meets the lateral side wall of projection 172 at the extremity of projection 172. This forms a nip point which gives a secondary seal, in order to protect product between the valve seat and the nip point. The tapering of opening 162 allows more volume of product to be dispensed for a small movement of the valve collar 166 than would be the case if the opening 162 had cylindrical side walls to match the shape of projection 172.

Insert 156 is releasably locatable in recess 154.

The insert 156 typically forms a tight seal with recess 154 in order to force product to flow only through the discharge valve arrangement. The seal may be enhanced by

the elastomeric nature of valve cap 160, which can be deformed slightly to give a better seal.

The rigidity of the support portion of insert 156 gives the valve seat 168 its firmness. This means that the valve collar 166 can bear tightly against the valve seat 168 to give a tight seal. This may be supplemented by some secondary sealing at the nip point between the opening 162 and projection 172. Furthermore, the approximately smooth surface presented by the outer surfaces of cap 160 and projection 172 give a wipeable discharge opening to the dispenser which is easily cleaned by a user to remove excess product.

The tight seal formed by the discharge valve arrangement allows the valve arrangement to act also as an outlet valve for the pump itself, negating the need for an extra valve to be included in the flow passage between the pump chamber and the discharge opening. A requirement of a pump outlet valve is that it has good sealing against reverse flow, e. g. of air or product.

Figs. 7 and 8 show external views of the embodiment illustrated in Figs. 5 and 6. In Figs. 7 and 8, one insert 156 has been removed to show the recess 154.

An alternative, second embodiment of a suitable discharge valve arrangement is shown in Figs. 3 and 9.

In Figs. 3 and 9, the downstream part 26 of the flow passage opens into a recess (an enlarged cylindrical socket 129) formed in the cap module 2. A discrete outlet valve module 18 is fitted into socket 129/and consists essentially of a hollow plastic cylinder with a central bore which converges from rear to front as indicated by the broken lines in Fig. 9, with inwardly radially projecting fins 181 along the convergent portion. The front opening of the bore diverges again at a conical sealing surface (valve seat 182).

Structural similarities can be seen here with respect to the discharge valve embodiment described above. In particular, the discharge valve arrangement is a discrete module which can be fitted into recess 129.

As will be described in more detail below, the seal formed by the valve arrangement is formed at the extreme downstream part of the discharge opening. However, in this, second, embodiment, the valve seat 182 is an inwardly facing surface, rather than an outwardly facing surface of an insert in the discharge opening.

A rubber element 14 is captive in the plastics module 18. This element has a front sealing head 141 (i. e. the valve body) with a conical rear surface 149, a narrow central stem 142 and rear enlargement 143. As manufactured, its tail 144 has a rearward extension 144a

(shown by broken lines). The module is assembled using the tail to pull the rubber element rearwardly through the front opening of the plastics module. Its rear enlargement 143 has a gentle rear taper to facilitate this. Once the rear enlargement 143 is pulled past the rear abutment ends of the plastic fins 181, it can be released and the tail extension 144a cut off. The rubber element 14 is dimensioned so that its central portion 142 is held in tension between the sealing surface 182 at the front and the ends of the fins 181 at the back. Thus, the front opening is positively sealed. At the back, fluid can pass the enlargement 143 via the clearances between the ribs 181. In use, therefore, forward pressurised flow of the material along the discharge channel 126 applies this pressure to the rear of the rubber head 141 and forces it off its seat to dispense the product. When the pressure relaxes at the end of the stroke, the tension in the rubber stem 142 pulls the head 141 back into sealing relationship with surface 182.

Again, because the seal is at the extreme end of the discharged channel, it protect the entire contents of the pump from the atmosphere. The front surface of the head 141 is shaped to align with the front surface 188 of the surrounding module 18 so that any residue can easily be wiped away.

As with the first embodiment, this valve arrangement of the second embodiment performs the function of an outlet valve for the pump.