Patent Grant
7360671
This application is the national phase of PCT/GB2001/01602, filed Apr. 6, 2001, which claims priority to European patent application 00303037.6, filed Apr. 11, 2000, both of which are incorporated by reference in their entirety.
The present invention relates to reservoirs for liquids, in particular, although not necessarily exclusively to reservoirs for supplying a liquid at a constant flow rate and/or on the demand of a load.
One known form of liquid reservoir system works on the so called “chicken-feeder” principle. A main reservoir containing the liquid has an outlet conduit in its base and is otherwise closed. The outlet conduit opens into a secondary reservoir open to atmosphere at its top, such that atmospheric pressure acts on a free surface of liquid in the secondary reservoir. Liquid flows from the main reservoir through the outlet conduit into the secondary reservoir and air is drawn into the main reservoir through the same conduit. Once the liquid level in the secondary reservoir rises to cover the end of the outlet conduit, it is no longer possible for air to be drawn back into the main reservoir to replace the liquid flowing from it. Consequently, there is a drop in pressure in the air space at the closed upper end of the main reservoir and the system quickly reaches a state of equilibrium where the head of liquid in the main reservoir is balanced by atmospheric pressure acting on the surface of the liquid in the secondary reservoir, and the flow of liquid from the main reservoir ceases.
In use, when liquid is drawn from the secondary reservoir, the outlet conduit is uncovered once more, air can again be drawn into the main reservoir and flow commences, to top up the secondary reservoir. In this manner, a substantially constant head of liquid is maintained in the secondary reservoir.
This basic “chicken-feeder” arrangement is, however, rather unwieldy and relatively complex to manufacture as a consequence of the need for two reservoirs and the connection between them. It is also necessary to shield the free surface of the liquid in the secondary reservoir when it is desired to prevent human contact with the liquid, for example because it comprises a toxic or other potentially harmful substance. An example of this (though not for a toxic liquid) is seen in WO-A-96/14788, which is equivalent to U.S. Pat. No. 5,590,817, where the secondary reservoir is in the form of a cup positioned round and below a liquid outlet at the bottom of a flexible closed chamber.
In EP-A-0203744 a dynamic device for dispensing syrups has a permanently open mouth in the floor of a container. The container is fillable through a removable lid which is then sealed in airtight manner to the container. There is an air bleed hole in the lid, the size of which determines the rate at which syrup may pass out of the mouth. The bleed hole communicates with a tube which terminates above the mouth: this structure does not give a constant head.
In contrast, the invention provides an essentially constant-head liquid reservoir. It has a chamber for holding liquid and being for orientation in use with an upper end and a lower end, the chamber having a closed upper end, and an air inlet duct with an upper end at the upper end of the chamber and extending through the chamber to a lower end of the duct through which air can enter the lower end of the chamber. To obtain the constant-head effect, the liquid outlet from the chamber is above the level of the bottom of the air inlet duct.
The invention also provides a liquid reservoir having a chamber with an upper and a lower end, an internal duct communicating to the outside of the chamber at the upper end, the chamber containing liquid, a frangible seal preventing egress of the liquid through the internal duct and closing the chamber, a liquid outlet portion separate from the chamber, the liquid outlet portion having a liquid output duct, the outlet portion and the chamber being complable together such that the liquid outlet duct can break the frangible seal and contact the liquid at a level below that of the lower end of the internal duct; and a cartridge containing liquid and comprising a closed chamber with two ends, an internal duct in the chamber leading from one of the two ends, where it is open to the outside of the chamber, to adjacent the other of the two ends, and a frangible seal across the duct and closing the chamber against egress of liquid.
In a similar manner to the traditional “chicken-feeder” those reservoirs find an equilibrium position in which, due to a reduction in pressure in an air space formed above the liquid at the closed, upper end of the chamber, the column of liquid in the chamber is supported by atmospheric pressure acting at the liquid/air interface present at the opening of the air supply port to the lower end of the chamber, as explained in more detail below. This is especially valuable for fragrances because of the comparatively small air volume that is found above the level of the liquid; there is less opportunity for fractionation of different elements of the fragrance into the air with consequential distortion of the perceived effect of the fragrance when dispensed.
The relative positioning of the ports may be selected to give some control over the characteristics of the device. For example, if the liquid outlet from the container is no lower than the lower end of the air conduit where it opens into the chamber and is a simple open port, no liquid will flow from the container through the outlet port under equilibrium conditions.
Thus, in one form of the device having separate liquid outlet and air inlet, the outlet and the lower end of the air conduit are disposed substantially at the same level as one another in the container. In this manner, the hydrostatic pressure at the outlet will be substantially equal to the atmospheric (i.e. ambient) pressure outside the container, ensuring that no flow takes place until demanded by e.g. a load connected to the outlet. However, the outlet from the container may be in a wick or other device which raises the liquid from the lower end of the container.
In any case, the “chicken feeder” effect assists a regular and controlled rate of output which may both be more linear, and at a lower level, than has been possible in the past.
Then, a volatile liquid, as for an air freshener, may be led to an emanator from which it will evaporate. This may be a simple exposed wick, but preferably is a porous or high-surface-area member which lies mainly below the level at which it is fed from the outlet. In this way “heavy” fragrance elements, which tend to be of lower volatility than “top note” elements, are swept chromatographically over the emanator giving a maximum area for their dispersion into the atmosphere and hence a more level and true effect.
To compensate for temperature variations, which it has been found can give rise to a significant expansion in the volume of the air pocket trapped at the upper end of the chamber, means are preferably provided to accommodate liquid displaced as a result of this expansion.
Embodiments of the invention are described below, by way of example, with reference to the accompanying drawings, in which:
Referring initially to
An air supply conduit 5 extends through the reservoir, and in this example is disposed centrally, coaxially with the axis of the cylindrical container 1. Normally, the axis of the container will be vertical or approximately so, in use. An upper end of this conduit 5 protrudes, in this embodiment, from the top wall 3 of the container 1 and is open to the surrounding atmosphere. An air permeable plug 9, for example a sintered element, is disposed in the opening at the upper end of the conduit. This plug 9 does not present any significant resistance to the passage of air through the conduit 5, but serves as a barrier to liquid.
The other end of the air supply conduit 5 opens into the interior of the container close to its base 4. As can be clearly seen in
Although it is possible for the air supply conduit to have a constant cross-section along its entire length, the preferred configuration is that illustrated, in which there is an increase in the cross-sectional area of the conduit 5 towards its lower end. specifically, a portion 10 running for most of the length of the conduit 5 has a constant, circular cross-section of relatively small diameter. However, at its lower end there is a step increase in this cross-section so that the conduit 5 terminates in a considerably larger-diameter, cylindrical portion 6, also of circular section, and having a lower edge 11 forming the lower end of the duct.
The basic mode of the operation of the reservoir will now be explained, still referring to
The air in this space 12 is at below atmospheric pressure. Specifically, in the equilibrium condition illustrated, the pressure in this space is equal to atmospheric pressure less the hydrostatic pressure attributable to the head (h) of liquid 14 above the lowest edge 11 of portion 6 of the air supply conduit 5 where it opens into the reservoir. The air supply conduit 5 is, as mentioned above, effectively open to atmosphere at its upper end, which of course means that the air in this conduit is at atmospheric pressure. In this way, atmospheric pressure acts on the surface 15 of the liquid 14 at the air/liquid interface at the lower end of the air supply conduit. Thus, a pressure balance is achieved between atmospheric pressure acting at this liquid/air interface formed at surface 15 on the one hand, and the below-atmospheric pressure in air space 12 combined with the hydrostatic pressure due to the head (h) of liquid 14 above the liquid/air interface 15 on the other. In this equilibrium state, the relative levels of the two free liquid surfaces, namely the surface 13 at air space 12 and the surface 15 at the lower end of the air conduit 5, are maintained.
Significantly, since there is atmospheric pressure acting at the liquid/air interface at surface 15 at the lower end of the air supply conduit 5, then in the equilibrium condition shown the hydrostatic pressure of the liquid at the level of this interface is equal to atmospheric pressure. By locating the outlet 8 from the reservoir substantially at the same level as the lower edge of the air conduit but slightly above it, as illustrated, a balance is also achieved between the hydrostatic pressure of the liquid at this outlet 8 and atmospheric pressure acting at the outer end of the outlet 8. Consequently, there is no flow of liquid through the outlet until some external force is applied to upset this equilibrium.
As seen in
To prime the reservoir initially, in order to set up the equilibrium condition described above, it can be inverted and filled either through the outlet 8 (as in the illustrated example) or a sealable filling port may be provided at or near the lower end of the container for this purpose. The container 1 is inverted and can be filled up to the level of the lower end 11 of the air supply conduit (which of course is uppermost during inversion). During this operation it is preferable to avoid any liquid entering the air supply conduit 5, but any liquid that should inadvertently find its ways into the conduit 5 is retained in the reservoir by virtue of the plug 9. Once the container has been filled, it is turned back to its upright orientation (seen in the Figures) creating the space 12 at the top of the container 1, giving rise to the equilibrium condition in the manner already explained.
Let us now assume that a quantity of liquid is drawn off at the outlet 8. This will cause a drop in the level of the liquid surface 13 at the top of the container 1. This results in an increase of the volume of the sealed air space 12 and a consequential drop in the air pressure in this space 12. This in turn creates an imbalance between the pressures acting on the two free liquid surfaces 13,15 within the reservoir. This imbalance causes air to flow into the container 1 through the air supply conduit 5, the air passing into the container around the lower edge of the enlarged lower end 11 of the conduit to bubble upwardly through the liquid 14 to the air space 12—see FIG. 2—to increase the pressure in that space until an equilibrium is once again restored.
Once the equilibrium is restored, the hydrostatic pressure of the liquid at the level of the lower end 11 of the air supply conduit 5, and hence at the level of the reservoir outlet 8, is equal to atmospheric pressure once more.
It will be appreciated, therefore, that the reservoir in effect presents a substantially constant hydrostatic pressure at its outlet 8 (in this case equal to atmospheric pressure, that is to say the pressure of the local environment surrounding the device) irrespective of the level of the liquid in the container. In this sense, it is similar in effect to the traditional “chicken-feeder” design discussed above, but achieves this effect in a very compact, less complex device. What is more, since the only liquid surface exposed to the outside of the device is that of the meniscus at the outlet 8, the device is inherently safer than the “chicken-feeder” with its exposed secondary reservoir, and can therefore be more readily used in systems for dispensing toxic or otherwise hazardous liquids.
One factor which has been found to disturb the equilibrium of the fluid air system in embodiments of the reservoir of the present invention is temperature. Specifically, with a rise in ambient temperature the liquid, and to a much greater extent the air trapped in air space 12, will expand. This expansion, in particular of air in space 12, is accommodated by the liquid moving part way up the air supply conduit 5. If this conduit 5 were of a relatively small diameter along its entire length, the displaced liquid would be driven a considerable distance up the conduit 5. This in turn could create a significant head of liquid in the conduit 5 above the level of the outlet 8, causing an undesired flow of liquid through this outlet 8.
However, in the illustrated embodiment, the liquid displaced as a result of a temperature change is accommodated in the much larger diameter, lowermost portion 6 of the conduit 5. In this way, the displaced liquid only causes a very small rise of the level of the air/liquid interface 15 at the lower end 11 of the air conduit 5, creating only a negligible increase in the hydrostatic pressure at the outlet 8, and the undesirable effect of the temperature rise is thus negated or at least made minimal.
In this example the diameter of the enlarged lower end of the conduit is about 5 times that of the upper portion of the conduit. Generally, however, the cross-sectional area of the lower end can be selected depending on the variation in temperature that the reservoir can be expected to undergo, in order to accommodate the resulting expansion without a significant rise in the liquid head. Typically, the cross-sectional area at the lower end will be at least 10 times, or better still 20 times greater than the area at the upper end.
Other temperature compensation measures may be employed as an alternative to the enlarged lower end of the air supply conduit, or to supplement it. For instance, one or more ballast tubes may be provided, these tubes opening into the chamber substantially at the level at which the air supply port opens into the chamber, and being open to atmosphere at their other, upper end. In this way, the displaced liquid rises up these tubes as well as the air conduit. The effect is similar, in that the volume of liquid displaced is spread across a wider cross-sectional area, minimising the rise in liquid head in the air supply conduit.
Turning now to
In use, liquid from the reservoir is drawn into the wick by capillary action until the wick becomes saturated, at which point the flow stops. If subsequently an external load is connected to the wick to draw liquid from it, or liquid is drawn from the wick in any other manner, flow will commence, only to stop again as soon as the load is removed. This arrangement therefor relies primarily on capillary action to deliver liquid from the reservoir outlet to a load.
The container body is essentially rigid; that is, it is not intended to allow or cause descent of liquid by becoming deformed or being squeezed.
This modified wick 17′ therefore serves in the manner of a siphon to draw liquid from the reservoir. What is more, the siphon is self-priming, the capillary nature of the wick drawing liquid from the reservoir along its length to initiate the siphon effect. Once the siphon is flowing, liquid is drawn off from the reservoir at a constant flow rate due to the constant hydrostatic pressure maintained at the outlet 8 by virtue of the design of the reservoir.
As will be readily appreciated, the reservoir has wide applicability and may be used to advantage in a great variety of applications. The reservoir is particularly useful for applications where there is a desire to provide a constant flow rate to a ‘load’ or other element. For example, the reservoir can be used to supply a constant flow of a liquid fragrance to an emanating element from which the fragrance is dispersed into the surrounding environment, e.g. a screen of the form described in co-pending WO-A-01/66158.
Embodiments of the reservoir can also be advantageously employed where there is a desire to present a liquid in an easily accessible manner to an animal, whilst ensuring that the liquid does not escape from the reservoir until demanded by the animal. Such an arrangement might be useful, for example, for baiting poison, where it is clearly undesirable that the liquid should escape into the environment. An arrangement of the form illustrated in
A second embodiment is described with reference to
This has many features in common with the first, and in particular a feature of an inlet air conduit which extends coaxially through a rigid container of the reservoir, but it also has the important and inventive feature that the container and its liquid contents can form a cartridge-like sealed entity, a seal of which is broken by a discrete liquid output portion. Because of this, the liquid output portion may be completely separable from, and insertable into, replacement liquid containers.
In
The container 20 and the duct 30 are then assembled together as seen in the lower part of
Seal 32 remains intact so that liquid 27 in the container is displaced to a level 34, air above the liquid being displaced progressively with the insertion of the duct 30 so that at the time of the formation of the seal at 33 pressure in air gap 29 below the upper wall 23 of the container is atmospheric. Thus we have, as seen in the lower part of
For additional security, the cartridge may be sent out with a temporary closure or cap over the open upper end of the duct 30, the closure or cap fitting over the outside of the cylindrical wall 25.
A liquid outlet portion of the second embodiment is seen firstly in
An output tube 35 is a hollow cylinder filled with wicking material 36 which has a wicking action in the axial direction of the tube.
At the head of the tube 35 there is a circular head 37 of larger diameter than the tube and the container 20, with an annular ridge 45 at the junction between the tube and head.
Radial ports 38 distributed circumferentially around this head contain wicking material 39 arranged to wick in a horizontal (radial) direction. Alternatively an annular disc of wicking material may be used. In either case the wicking material is arranged so as to have intimate contact at interfaces 40,41 with the wicking material 36 in the output tube.
The liquid outlet portion will include also an emanator 42 which is a cylinder of cardboard, felt, papier maché or similar wicking material. It has an axial height x.
The outlet portion is assembled together as seen in the upper part of
A cap 46 is fitted over the top of the plate and within the uppermost edges of the emanator 42.
The liquid outlet portion seen in the upper part of
The axial length of the tube 35 is such that when the plate 37 fits closely over the flange 31 of the air inlet tube the lower end of the tube 35 is near the floor of the container.
The annular ridge 45 fits within the uppermost end of the duct 30. However, it does not do so in an airtight fashion. As a result an annular air inlet conduit 47 formed between tubes 35 and 30 is maintained at ambient pressure. To assist this there may be grooves or ports in the ridge 45 and grooves in the upper surface of the flange 31.
The load on this reservoir is represented by the evaporation surface of the emanator 42 from which liquid evaporates as schematically indicated by arrows B.
By selection of the length x of the emanator 42 and/or of its setting in relation to the plate 37, the relationship of the bottom end 48 of the emanator with the bottom end of the tube 35 may be adjusted so as to regulate (either fixedly or variably) the rate of flow and hence of evaporation. If the end 48 went below the end of the tube 35 there would be a siphon established.
However, the effect of the construction of the reservoir and in particular the positioning of the air inlet duct 30 within it means that there is a substantially constant head, exactly in the manner as described for the first embodiment, of liquid pressure at the bottom of the tube 35. Bubbles to replenish the air gap 29 may escape at the broken edges of the seal 32.
A third embodiment shown in
In
In
In
The liquid outlet portion includes an output tube 60 which is filled with axially-acting wicking material 61. At its head the tube 60 has the axial arm of an L-shaped fitting 62, the radial arm of which is occupied with a tube 63 forming a socket by which a wick, siphon, emanator or the like—in particular a screen-type emanator as seen in my U.S. Pat. No. 6,631,891—may be brought into contact with and ultimately take liquid, which has left the chamber at outlet 8″, from the top surface 64 of the wicking material 61. Alternatively, the arm 63 may have a capillary tube, wicking material or the like which will draw liquid, when available, radially away from the wicking material 61.
To activate the embodiment, the liquid outlet portion is pushed axially downwardly either directly or with the aid of screw-threading (not shown) so that the bottom end 65 of the tube 60 breaks the seal 55 and the wicking material 61 is brought into contact with liquid 51.
The axial arm of the coupling 62 is not a tight fit in the bung 54 such that an annular air inlet conduit 66 is formed between tubes 53 and 60. Air ingress may be assisted by axial grooves in the arm 62 and/or the bung 54.
These examples of possible applications for the reservoir are of course only some of a great many possibilities, and go some way to illustrating the applicability of the reservoir in many diverse applications. As such, they are intended to be illustrative rather than in any way limiting on the scope of the present application.
It will also be appreciated that many variations from the specifically described embodiments are possible.
| Number | Date | Country | Kind |
|---|---|---|---|
| 00303037 | Apr 2000 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB01/01602 | 4/6/2001 | WO | 00 | 2/6/2003 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO01/77004 | 10/18/2001 | WO | A |
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|---|---|---|---|
| 1938151 | O'Connor | Dec 1933 | A |
| 3862701 | Strunc et al. | Jan 1975 | A |
| 4121507 | Kuckens | Oct 1978 | A |
| 4982875 | Pozzi et al. | Jan 1991 | A |
| 5971009 | Schuetz et al. | Oct 1999 | A |
| 6708897 | Hart et al. | Mar 2004 | B1 |
| Number | Date | Country |
|---|---|---|
| 44 33 954 | Mar 1996 | DE |
| 0 203 744 | Dec 1986 | EP |
| WO 0123008 | Apr 2001 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20030150518 A1 | Aug 2003 | US |
