Dosing Cap For Container
Technical field
The present invention relates to a dispenser cap for a liquid container, or a container comprising the cap integrally formed therewith, which can deliver a fixed dose of liquid reliably and simply.
Background to the invention
Certain liquid compositions are intended to be dispensed and applied in specified quantities. For example cleaning products in liquid form typically instruct the end user to dose particular volumes for a desired cleaning performance to be provided.
One simple solution to this problem is to provide a measuring container with the liquid product. However, this solution, although simple, suffers from the danger of the measuring container becoming lost or separated from the liquid container.
To address this problem, dispensing caps for liquid containers have been developed which are designed to deliver fixed quantities of liquid. As the dispensing cap is integral to the container, it cannot become detached and lost.
However, most of these devices are complex to manufacture and include moving parts.
US 6,341 ,718 discloses a squeeze bottle for dispensing a liquid in a metered manner, driven by the end user squeezing the container. However, the embodiments disclosed suffer from various disadvantages such as requiring an operable valve. Such a design may not be able to cope with repeated use of certain sticky liquids, which may interfere with the proper functioning of the valve. However, omission of the valve, as also suggested in this document, results in an uncontrolled delivery of liquid.

US 6 241 129 B1 discloses a dosing head including a dosing chamber inside in which a piston is slidably fitted, a first surface of which is in communication with the interior of a container and a second surface of which is in communication with the dosing chamber. The piston is fitted so as to be able to pass from a first position in which the dosing chamber has a maximum volume to a second position in which the dosing chamber has a minimum volume. The dosing chamber includes at least one inlet which is open when the piston is in the first position and is closed when the piston is in the second position. The piston is coupled to a closure member forming at least one passage between the said closure member and an outlet for allowing a dose of the product to be expelled.
A feature of this arrangement is that air gets sucked into the container on which is fitted the dosing head. A further feature is that replenishment of the dosing chamber can only commence as the piston approaches the first position.
Thus, further improvements in this area would be highly desirable.
Summary of the invention
In a first aspect, the invention relates to a dispenser cap (10) for a liquid container having an opening, the cap comprising a means for attachment (30) to the container at the opening, a housing (12) for insertion into the opening, the housing comprising a liquid inlet (14) to receive liquid from the container, a channel and a liquid outlet (16) to expel liquid from the container, the channel comprising a moveable seal (18) defining an outlet-side liquid volume (24) and an inlet-side liquid volume (26), the moveable seal being biased to a first position towards the liquid inlet, and is moveable to a second position towards the liquid outlet by increasing the inlet-side liquid pressure, such movement thereby causing the outlet-side liquid pressure to rise and cause flow of outlet-side liquid out of the outlet, the moveable seal also comprising a liquid outlet seal means (22) which is operable to seal the liquid outlet (16) when the moveable seal is in its second position, thereby preventing further flow of liquid out of the outlet, characterised in that,

the outlet requires a difference in pressure to allow liquid to flow out of the outlet
(16),
the liquid outlet is a non-return valve, allowing only the flow of liquid out and no
backflow of atmospheric gas into the container,
the moveable seal is arranged to permit the flow of liquid from the inlet-side liquid
volume to the outlet-side liquid volume when there is a difference in pressure
across the seal,
once the pressure on the inlet-side is removed following dispensing the seal
begins to move from the second position towards the first position by action of the
biasing means such that liquid flows past the seal in response to the pressure
differences whereby once back at the first position the outlet-side liquid valve is
full of liquid.
In a second aspect, the invention relates to a container for holding a liquid, comprising a dispenser cap.
With such an arrangement, the invention allows the delivery of a fixed amount of liquid from a container, such as a squeezable container, irrespective of how much pressure is applied to the inlet-side liquid volume. Furthermore, the arrangement is mechanically simple and robust and is not prone to failure by build-up of residues from sticky liquids.
A central inventive concept is in including a seal which permits flow of liquid provided there is a sufficient pressure difference across it. This is highly counter-intuitive because, on first consideration, it would seem to be contrary to the aim of controlling or fixing the quality of liquid dispensed. The inventors have found that, surprisingly this does not prevent fixed quantities of liquid from being dispensed and also provides for a mechanically simple arrangement which is robust.
When the dispenser cap is in an unpressurised arrangement when the seal is in its first position (held there by biasing means) an outlet-side liquid volume is present and ready to be dispensed. The user increases the inlet-side liquid

pressure, e.g. by squeezing the container. Initially this rise in pressure is not transmitted to the outlet-side liquid volume and the arrangement can respond to this difference in pressure in one of two ways.
Firstly, liquid may flow from the inlet-side liquid volume past the seal (because there is a pressure difference) until the outlet-side liquid is at the same pressure as the inlet-side liquid. Secondly, the seal can physically move from its first position towards its second position, driven by the difference in pressure on either side of the seal. It is to be noted that only a very small movement of the seal would be sufficient for the reduction in volume available for the outlet-side liquid volume to translate into an increase in pressure, as liquids are highly incompressible.
The inventors have discovered that any difference in pressure between the inlet-side liquid volume and outlet-side liquid volume is very quickly eliminated by a small movement of the seal. Thus, practically no liquid passes the seal, despite large pressure differences being introduced across it.
Once the outlet side liquid volume increases in pressure due to the movement of the seal, liquid can flow out of the outlet and dispensing of liquid begins.
Such dispensing will have the effect of a drop in pressure on the outlet-side liquid volume. This may also coincide with a continuous or increased induced pressure on the inlet-side liquid volume as the end user squeezes the container during dosing.
Such a difference in pressure is however quickly eliminated by further movement of the seal in the direction of its second position.
This balancing of pressure is maintained during dispensing so that both the inlet-side and outlet-side have elevated pressure due to squeezing, but the pressures

are essentially the same, so no liquid can flow past the seal and into the outlet-side liquid volume.
Eventually the seal arrives at its second position. Once in the second position the liquid outlet seal means closes off the liquid outlet, e.g. by covering it. Further increases in inlet side liquid volume can no longer cause the seal to move and so no rebalancing of pressure between outside liquid volume and inlet-side liquid volume can occur. Thus, further squeezing establishes a pressure difference across the seal which has the effect of pressing the liquid outlet seal means with a force directly in proportion to the pressure difference.
Thus, even if a small amount of liquid flows past the seal, it cannot be dispersed because the outlet is sealed. Furthermore, the strength of the seal is proportional to the pressure applied, so responds exactly enough to prevent further dispensing.
Thus, a fixed dose of liquid is dispensed regardless of the magnitude and duration of squeezing applied.
Once the pressure on the inlet-side is removed following dispensing the seal can begin to move from the second position towards the first position by action of the biasing means. This will have the initial effect of reducing the pressure on the outlet-side liquid volume (for not all of the outlet-side liquid volume is dispersed). This results in liquid flowing past the seal in response to the pressure difference. This flow acts to rebalance the pressure differences, allowing the biasing means to overcome the reduced pressure difference and continue to move the seal to its first position.
Thus, once back at the first position the outlet-side liquid valve is full of liquid and the whole process can begin again if a second dose is required.
As discussed, the means for increasing the inlet-side pressure is preferably in the form of the container being squeezable. This is the simplest and most convenient

form. However alternatives are possible, and the container can be collapsible, for example. Alternatively the container may comprise a syringe wherein injection of a body into the container reduces the volume available and thus raises the pressure accordingly.
The dispenser cap may be attachable to the body of the container in a variety of ways known in the art. Typically this is simply by means of a screw thread, although other arrangements such as snap-on or similar can be employed as desired. Alternatively, the dispenser cap and container body may be unitary i.e be of a one-piece construction.
The liquid outlet may be a non-return valve, allowing only the flow of liquid out and no backflow of atmospheric gas into the container. It is thus desirable to have some means for introducing atmospheric gas into the container to replace the liquid which has been dosed. Thus, in a preferred embodiment, the dosing cap comprises a channel providing gaseous communication between the inlet-side liquid valve and the atmosphere outside the container.
Typically the housing will be cylindrical and the seal means being a circular arrangement within the cylindrical housing. However, other shapes are possible.
The seal means separates the inlet-side liquid volume from the outlet-side liquid volume. At the same time it is capable of allowing liquid to flow from the inlet-side to the outlet-side provided a sufficient pressure difference across the seal exists. Thus, the seal is effectively designed to " fail" as a seal when a pressure difference exists.
In a preferred embodiment the seal comprises a resilient material which forms its seal by pressing onto the inside walls of the housing. Once a sufficient pressure difference is established, the resilient material can deform to move away from the wall of the housing and to allow liquid to pass. Once the pressure difference is removed, the seal is re-established to prevent any further flow. For example, a

circular flap of siliconised material or other resilient material with a diameter a little greater than that of the inside walls of the housing, provides a suitable seal.
The liquid outlet seal means is another essential element of the invention. This acts to prevent flow out of the liquid outlet when the seal is in its second position. In a preferred embodiment, this is established by surrounding the outlet or otherwise covering it. In a further preferred embodiment, this is established by the liquid outlet seal means comprising a region which forms a seal around the outlet with a defined thickness.
In this way, further increases in pressure applied merely act to press the outlet seal more strongly, thus making the seal stronger. Thus, no liquid can leave the outlet by squeezing done when the seal is in its second position.
Thus the liquid outlet seal means may comprise a resilient material adapted to engage a portion of the housing surrounding the liquid outlet. Preferably the engagement involves the liquid outlet seal means to engage a face parallel to a face of the housing to provide the seal.
The invention will now be illustrated, by way of example only, and with reference
to the following figures, in which:
Figure 1 is a cut-away perspective view of a dispensing cap according to the
present invention.
Figures 2a to 2d show cut-away perspective views of the dosing cap shown in
Figure 1 in use according to the invention.
Turning to the figures, Figure 1 shows a dispensing cap 10 according to the invention in its first position. The dispensing cap 10 comprises a cylindrical housing 12 comprising a liquid inlet 14 and a liquid outlet 16. The liquid outlet comprises a non-return valve 17 to prevent the ingress of atmospheric gas.

Contained within the housing 12 is a moveable seal 18 attached to a plunger 20. The seal 18 also comprises a liquid outlet seal means 22. The seal 18 defines an outlet-side liquid volume 24 and an inlet-side liquid volume 26.
Attached to the plunger 20 are two elastic bands 28 which are also attached to the outside of housing 12.
The dispensing cap 10 can be attached to any suitable liquid container by screw thread 30. To facilitate the introduction of atmospheric gas into the container following liquid dosing an air inlet 32 is provided in the cap.
When it is desired to dose liquid from a container, the container is inverted. If the container was inverted following a previous use, then the outlet-side volume 24 should be all liquid and no gas. However, for a first application, one charging stroke may be necessary to expel any gas in the outlet volume 24.
As is shown in Figure 2a the container (not shown) to which the cap 10 is attached, is squeezed, resulting in an increase in inlet-side liquid volume 14. This establishes a force 34 on plunger 20. The force 34 moves the plunger 20 and its seal 18 sufficiently to increase the outlet side 24 pressure. This rebalancing of pressure prevents any flow of liquid past seal 18. The increased pressure on the outlet liquid volume 24 causes outflow of liquid from outlet 16.
The end user continues to squeeze the container (not shown) and the plunger 20 and seal 18 gradually move towards the second position, as shown in Figure 2b. As the plunger moves, it maintains approximate equality of pressure between the inlet-side liquid volume and the outlet-side liquid volume.
As can be seen, elastic bands 28 begin to stretch as the plunger 20 and seal 18 move.

Eventually the seal 18 reaches its second position, as shown in Figure 2c. Force 34 may still be present as the end user does not know in advance that the seal 18 is at its second position.
It can be seen that a portion 23 of the outlet seal means 22 has connected with the inside walls of the housing 12. This has the effect of sealing off the liquid outlet 16 thus preventing any further flow of liquid. It can also be seen that a portion of the outlet-side liquid volume 24 remains undispensed. Further application of force 34 cannot cause movement of plunger 20 and seal 18 in view of the contact made between the liquid outlet seal 22 and the housing 12. The pressure difference established may therefore result in a small flow of liquid into volume 24. However, the pressure applied also forces the seal 23 to be tight, preventing any flow of liquid out of the outlet.
Once liquid flow out of the outlet stops, the end user notices this and stops squeezing, removing force 34. As the container is squeezable, it will now tend to resume its uncompressed state, establishing a reduction in pressure on the inlet-side. This exhibits itself as a force 36 acting to move the plunger 20 and seal 18 to move away from its second position, as can be seen in Figure 2d.
Such movement results in a drop in pressure on the outlet-side and as no gas can enter through outlet 16, liquid passes seal 18 to rebalance the pressure difference. Such rebalancing allows the force 36, assisted by elastic bands 28, to move the plunger 20 and seal 18 back to the first position. It is to be noted that the outlet side volume will be full of liquid and ready to deliver another dose of liquid.
Once completed the container can be put into a non-inverted state and the liquid will remain in the outlet-side liquid volume as it cannot pass valve 18, despite a difference in pressure. Thus, when another dose is required, the container can be inverted and the sequence shown in Figures 2a to 2d followed again.

Claims
1. A dispenser cap (10) for a liquid container having an opening, the cap
comprising a means for attachment (30) to the container at the opening, a
housing (12) for insertion into the opening, the housing comprising a liquid
inlet (14) to receive liquid from the container, a channel and a liquid outlet (16)
to expel liquid from the container, the channel comprising a moveable seal
(18) defining an outlet-side liquid volume (24) and an inlet-side liquid volume
(26), the moveable seal being biased to a first position towards the liquid inlet,
and is moveable to a second position towards the liquid outlet by increasing
the inlet-side liquid pressure, such movement thereby causing the outlet-side
liquid pressure to rise and cause flow of outlet-side liquid out of the outlet, the
moveable seal also comprising a liquid outlet seal means (22) which is
operable to seal the liquid outlet (16) when the moveable seal is in its second
position, thereby preventing further flow of liquid out of the outlet,
characterised in that,
the outlet requires a difference in pressure to allow liquid to flow out of the
outlet (16),
the liquid outlet is a non-return valve, allowing only the flow of liquid out and no
backflow of atmospheric gas into the container,
the moveable seal is arranged to permit the flow of liquid from the inlet-side
liquid volume to the outlet-side liquid volume when there is a difference in
pressure across the seal,
once the pressure on the inlet-side is removed following dispensing the seal
begins to move from the second position towards the first position by action of
the biasing means such that liquid flows past the seal in response to the
pressure differences whereby once back at the first position the outlet-side
liquid valve is full of liquid.
2. A dispenser cap according to claim 1, wherein the dispenser cap comprises a
channel providing gaseous communication between the inlet-side liquid and
the atmosphere outside the container.

3. A dispenser cap according to claim 1 or claim 2 wherein the housing is cylindrical and the seal means is a circular arrangement within the cylindrical housing.
4. A dispenser cap according to any one of the preceding claims, wherein the moveable seal comprises a resilient material which forms its seal by pressing onto the inside walls of the housing.
5. A dispenser cap according to any one of the preceding claims, wherein the moveable seal comprises a circular flap of resilient material with a diameter a little greater than that of the inside walls of the housing.
6. A dispenser cap according to any one of the preceding claims, wherein the liquid outlet seal means operates by surrounding the outlet or otherwise covering it.
7. A dispenser cap according to claim 6, wherein the engagement involves the liquid outlet seal means to engage a face parallel to a face of the housing to provide the seal.
8. A container for holding a liquid comprising the dispensing cap of any one of the preceding claims.
9. A container according to claim 8, wherein the means for increasing the inlet-side pressure is in the form of a squeezable body.
10. A container according to claim 8 or claim 9, wherein the dispenser cap is attachable to the container body by means of a screw thread.
11. A container according to claim 8 or claim 9, wherein the dispenser cap and container body are unitary.