EP2812275B1

EP2812275B1 - Device, nozzle, container and method for liquid flow control

Info

Publication number: EP2812275B1
Application number: EP13705535.6A
Authority: EP
Inventors: Richard Warrington George
Original assignee: Easy-Fill Ltd
Current assignee: Easy-Fill Ltd
Priority date: 2012-02-06
Filing date: 2013-02-06
Publication date: 2017-10-18
Anticipated expiration: 2033-02-06
Also published as: WO2013117921A1; GB2499047B; GB2499047A; EP2812275A1; GB201202026D0

Description

The present invention relates to a flow control device, and preferably but not necessarily exclusively in the form of an adaptor for insertion into a liquid-dispensing nozzle or neck of a liquid-tightly sealable container.
A movable valve which is manufactured in a nozzle to close a liquid flow path is known. However, moving parts of the valve have a shorter working life, and manufacturing the valve within a nozzle significantly increases production costs.
The use of a close- or tight-knit mesh-like perforated plate is also known from the applicant's earlier disclosure in European patent EP 2219992 B1 . Although such a mesh-like perforated plate can be made to halt the flow of certain liquids when used in conjunction with a nozzle and a fluid-tightly sealable container, the small perforations are complex to manufacture and therefore expensive.
Furthermore, the small perforations result in a higher ratio of framework to open space, thus occluding liquid flow therethrough during pouring and leading to undesirable delay.
Additionally, the small perforations have been found to block more easily and thus such a perforated plate requires cleaning more often than is desirable. The present invention therefore seeks to provide a solution to these problems.
It is also known that where a fuel container fitted with a pouring spout is used to dispense petrol or gasoline that under certain circumstances where fire or ignition occurs this flame can travel or flashback up the pouring spout causing the fuel/air mixture in the fuel container to explode causing bums, injury or death of the user.
According to a first aspect of the present invention, there is provided a flow control system for dispensing liquid from a liquid-tightly sealable container into a second container to a predetermined level, the system comprising: a liquid having a viscosity; a flow control device having a liquid flow channel having a first inlet end and a first outlet end; a fluid flow channel which is independent of the liquid flow channel and which has a second inlet end and a second outlet end; and a flow control element by which flow is prevented or substantially prevented from exiting
the first outlet end of the liquid flow channel, the flow control element being a slotted element having a plurality of elongate slots forming liquid flow apertures therethrough, the elongate slots having longitudinal extents which extend across a flow path defined by the liquid flow channel, characterised by the elongate slots being predeterminately dimensioned according to the said viscosity of the liquid to halt or substantially halt liquid flow along the liquid flow channel when the liquid flow channel is tilted to a flow condition and the fluid flow channel becomes at least in part filled with liquid, flow in the liquid flow channel remaining halted or substantially halted until the liquid flow channel is righted to an at rest condition.
Preferable and/or optional features of the first aspect of the invention are set forth in claims 2 to 12, inclusive.
According to a second aspect of the invention, there is provided a nozzle for a fluid-tightly sealable container, the nozzle comprising a flow control system in accordance with the first aspect of the invention.
According to a third aspect of the invention, there is provided a fluid-tightly sealable container comprising a neck extending from a flow outlet, and a flow control system according to the first aspect of the invention in the said neck.
In the second and third aspects, preferably the flow control device is removable.
According to a fourth aspect of the invention, there is provided a method of controlling liquid having a viscosity, dispensing from a liquid-tightly sealable container into a further container to a predetermined level and arresting flashback flame travel, the method comprising the step of providing a slotted element in a nozzle, the slotted element having a plurality of elongate slots forming liquid flow apertures, the slots having a predetermined dimension according to the viscosity of the liquid which: i) halts or substantially halts liquid flow therethrough when the slotted element is tilted to a flow condition and the predetermined level in the further container is reached, and ii) at least arrests flashback flame travel.
The present invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1a shows a diagrammatic cross-sectional view of a first embodiment of a flow control device, in accordance with the first aspect of the invention and in the form of an adaptor;
Figure 1b is an end view of the flow control device, showing a slotted flow control element and taken along line A-A in Figure 1b;
Figures 2a to 2d shows enlarged views of second through fourth embodiments of part of a fluid flow channel of the flow control device, in accordance with the first aspect of the invention, wherein a distal end is modified;
Figure 3 shows a diagrammatic cross-sectional view of the flow control device of the first embodiment, fluid-tightly inserted into a releasable liquid dispensing nozzle;
Figure 4 shows a diagrammatic cross-sectional view of the flow control device of the first embodiment, fluid-tightly inserted into a fluid-tightly sealable container;
Figure 5 is an end view of a fifth embodiment of a flow control device, showing a slotted flow control element wherein the slots are curved.

Referring firstly to Figures 1a and 1b of the drawings, there is shown a first embodiment of a flow control device 10, in this case being in the form of a flow control adaptor for adapting a nozzle or spout of a fluid-tightly closable and openable liquid container. The flow control device 10 comprises a hollow and substantially tubular body 12, an elongate liquid flow passage or channel 14, an elongate air flow passage or channel 16 which is independent of the liquid flow channel 14, and a slotted flow control element 18.
Herein throughout, 'elongate' is intended to mean having a greater length than width or, in other words, a greater longitudinal extent than a lateral extent.
The hollow body 12 is formed integrally with the air flow channel 16, whereby the liquid flow channel 14 is defined by the remaining bore 20 of the body 12. Preferably though not necessarily exclusively, the body 12 and air flow channel 16 are one-piece, for example, being moulded plastics. A partitioning wall 22 of the air flow channel 16 partitions the bore 20 of the body 12, whereby the liquid flow channel 14 is defined by the wall 24 of the bore 20 and the exterior surface 26 of the air flow channel 16.
The shared partitioning wall 22, in this embodiment, extends the length of the body 12.
Preferably, the body 12 is a generally tubular and, typically, cylindrical push-fit insert adaptor for a neck, nozzle or spout, but may be the neck, nozzle or spout itself.
The slotted flow control element 18 can be any form of material. By way of example, the slotted flow control element 18 is a slotted plate or disk, and may be made from a solid material, such as metal or plastics.
Advantageously, in this embodiment, the slotted flow control element 18 is provided integrally at a distal end of the body 12. However, the slotted flow control element 18 can be formed at any point along a flow path defined by the liquid flow channel 14, as necessity dictates.
Beneficially, the slotted flow control element 18 can be integrally moulded with the body 12 at the time of manufacture. Consequently, the device 10 in adaptor form can be easily and cheaply formed as a single one-piece moulding incorporating the slotted flow control element 18.
The adaptor 10 may also optionally incorporate a sealing element 28 located circumferentially around the body 12 such that, when the adaptor 10 is inserted in to an outlet opening of a nozzle or neck of a container, a fluid tight seal is achieved between the adaptor 10 and the container. The sealing element 28 is typically made from a rubber or other suitable compressible material, and is preferably seated in a continuous circumferential recess in an exterior surface of the body 12.
Although only one sealing element 28 is shown, two or more, preferably spaced, sealing elements can be provided to improve a seal.
The air flow channel 16 may be a separate pipe or tube that is formed in the body 12 forming a fluid flow path 30 in parallel with a liquid flow path 32 of the liquid flow channel 14. However, preferably, the air flow channel 16 is integrally formed as one-piece with the body 12, as shown in Figure 1a.
The liquid flow channel 14 has a liquid-inlet end 34 and a liquid-outlet end 36 at opposite ends of the body 12. The liquid flow path 32 is thus defined therebetween. Similarly, the air flow channel 16 has an air-inlet end 38 at one end of the of the body 12, and an air-outlet end 40 which is spaced from the opposite end of the body 12 so as to be remote from the bore 20 of the body 12. An air flow path 42 is similarly defined between the air-inlet end 38 and the air-outlet end 40.
Referring to Figure 1b, the slotted flow control element 18 is shown from the front. As can be understood, the flow control element 18 is a stationary or substantially stationary slotted element having a plurality of elongate slots 42 forming liquid flow apertures 44 therethrough. Each elongate slot 42 extends to or adjacent to a perimeter edge portion of a body 46 of the flow control element 18. As such, each elongate slot 42 extends across at least a majority of the body 46.
The slotted flow control element 18 is preferably a thin plate or disk, which is planar or substantially planar. Each elongate slot 42 in this embodiment is straight, having a uniform or substantially uniform lateral extent along at least a majority of its longitudinal extent. Due to the bore 20 of the fluid flow channel 16 being preferably circular or substantially circular, each or at least a majority of the elongate slots 42 have different longitudinal extents. However, although feasible to provide two or more coaxially aligned said elongate slots arranged substantially end to end across the body 46, this would likely only negatively impact the fluid flow rate through the slotted flow control element 18 due to the body 46 forming effectively a central spar, and thus is not thought to be preferable at this time.
Although the slotted flow control element 18 is a disk or plate, it is possible that the flow control element 18 can be a slotted block having a greater thickness. Due to the increase in material, this would increase production costs, but a similar flow control would be achievable, since it understood to be the lateral extents of the elongate slots 42 perpendicular to the direction of the liquid flow path that govern the operation of the flow control device 10.
In this embodiment, the elongate slots 42 extend in or substantially in parallel with each other.
The slotted flow control device 10 is preferably unitarily formed as one-piece and therefore without moving parts. The elongate slots 42 in this case have fixed lateral and longitudinal extents, as well as fixed depths or thicknesses.
When the flow control device 10 is used with liquids of low viscosity it is sometimes necessary, as shown in the second to fourth embodiments of Figures 2a to 2d, to modify the air-outlet end 40 of the air flow channel 16 to prevent the air flow channel 16 becoming rapidly filled with liquid before liquid flow is established in the liquid flow channel 14. Once the air flow channel 16 becomes filled with liquid, liquid flow along the liquid flow channel 14 ceases and thus pouring from the flow control device 10 stops.
Referring to Figure 2a, a second embodiment of the flow control device 10 seals the air-outlet end 40 of the air flow channel 16, and provides one or more vent holes 48 laterally through the side of the air flow channel 16 adjacent to the air-outlet end 40.
Figure 2b shows a third embodiment of the flow control device 10, wherein a mesh or perforated flow restriction element 50 may be provided across the air-outlet end 40 of the air flow channel 16.
A fourth embodiment of the flow control device 10 is shown in Figure 2c, and this includes a U-shaped bend 52 at the distal end portion 54 of the air-outlet end 40 of the air flow channel 16. Liquid flow therefore does not impinge directly on the air-outlet end 40 of the air flow channel 16, during use and when the flow control device 10 is tilted to a pouring or dispensing condition.
A fifth embodiment of the flow control device 10 is shown in Figure 2d, and this comprises a one-way ball or check valve 56. The valve 56 includes a ball 58 provided in an enlarged end portion 60 of the air flow channel 16. The ball 58 is seatable on or adjacent to a narrowed bore portion 62 which is spaced from the air-outlet end 40. Once seated, the ball 58 closes off the air flow path 30 to liquid flow into the air flow channel 16 from the air-outlet end 40. Thus, air or liquid can flow in to the air flow channel 16 via the air flow channel inlet end 38, but liquid cannot or substantially cannot enter the air flow channel 16 from the closable air outlet end 40.
The second to fourth embodiments are given by way of examples only, and other means to prevent or limit liquid flow ingress into the air flow channel 16 from the air-outlet end 40 can be used with low viscosity liquids, as necessity dictates. With higher viscosity liquids, the liquid flow ingress means may be dispensed with.
Figure 1a shows the flow control device 10 in the form of an adaptor and which preferably includes a depth stop 64. In this embodiment, the depth stop 64 is a radially outwardly extending lip or flange at the proximal end of the body 12. The depth stop 64 may be continuous or discontinuous around the body 12. The geometry of the depth stop 64 is such that when the flow control device 10 is used to fill a container of known capacity and/or geometry and the depth stop 64 is resting against the front lip or rim of the container being filled, only a measured amount of liquid is dispensed before the slotted flow control element 18 halts the flow of liquid.
Although provided on the body 12, the depth stop could be included on the liquid tightly sealable container or a nozzle, spout or neck into which the device 10 in adaptor form is insertable.
The elongate slots 42 in the slotted flow control element 18 are dimensioned such that, when the liquid is flowing through the liquid flow channel 14 and air flows through the air flow channel 16, the liquid flow rate through the slotted flow control element 18 is high. However, once a level of dispensed liquid results in back flow into the air flow channel 16 via the air flow inlet 38, the liquid flow through the slotted flow control element 18 is stopped or substantially stopped due to the slotted flow control element 18.
In order to achieve cessation of liquid flow, the viscosity of the liquid being dispensed governs a lateral extent of the elongate slots 42. By way of example, it has been determined through investigation that liquids with a kinematic viscosity range of or substantially of 0 to 20 mm² s^-1 [cSt (centi Stokes)], the preferred slot width is or substantially is 1.5mm or less. However, for liquids with a kinematic viscosity in the range of or substantially of 20 to 1500 mm² s^-1 [cSt], the preferred slot width is in the range of or substantially of 1.5 to 2.0 mm. For liquids having a kinematic viscosity in the range of or substantially of 1500 to 3000 mm² s^-1 [cSt], the preferred slot width is in the range of or substantially of 2.0 to 3.0 mm, and for liquids with a kinematic viscosity which is greater than or substantially greater than 3000 mm² s^-1 [cSt], the preferred slot width can be greater than 3.0 mm. Obviously, the slotted flow control element 18 inevitably provides an occlusion to or restriction of fluid flow therethrough, and consequently it is beneficial to have the greatest width of the elongate slots 42 as possible for a given viscosity of liquid to be dispensed.
Referring to Figure 3, there is shown the flow control device 10 of the first embodiment, in adaptor form, inserted into a distal end 66 of a liquid dispensing nozzle 68. The nozzle 68 includes a screw-threaded attachment 70 at its proximal end 72 for fluid-tight releasable engagement with a neck of a fluid-tightly sealable container not shown.
Preferably, the nozzle 68 includes a flexible portion 74 partway between its distal and proximal ends 66, 72, allowing directional orientation of the distal end 66.
The body 12 is insertable up to the depth stop 64, which thus positions the fixed slotted flow control element 18 at the exact position required to automatically halt the dispensing of liquid once the dispensed liquid reaches or substantially reaches the distal end 66 of the nozzle 68 and dispensed liquid flows into the air flow channel 16.
The screw-threaded attachment 70 may conveniently include a threaded collar 76 which is independently received on the nozzle body to simplify engagement with the mating screw-threaded neck of the dispensing container.
Preferably, to provide a fluid-tight seal, a further seal element 78 is provided at or adjacent to the proximal end 72 of the nozzle 68. For operation of the slotted flow control element 18 to be successful, the nozzle must be fluid-tightly sealable to the container, and the container in all other respects bar the opening at the neck must be fluid-tight.
The nozzle may be other shapes, as necessity dictates, and may be a spout or an extended neck in which the flow control device 10 is received.
In other modifications, the nozzle, spout or neck may be part of the flow control device 10, whereby the slotted flow control element 18 is integrally formed as part of the nozzle, spout or neck instead of being provided as part of an adaptor.
When in the form of an adaptor, the flow control device 10 is insertable and also preferably removable, so that the spout, neck or nozzle 68 can be used in its standard unadapted form, if required.
Referring to Figure 4, there is shown the flow control device 10 of the first embodiment inserted into a mouth and neck 80 of a fluid-tightly sealable container 82. An outside diameter B of the device 10 is typically such that it is an interference or friction fit within the inside diameter of the outlet 84 of the liquid tightly sealable container 82, thereby ensuring that it forms a fluid-tight seal to the container 82 and remains in place when the container 82 is inverted. The seal 32 of the device 10, if utilised, also improves the fluid-tight engagement.
With the flow control device 10 in use and thus tilted or even substantially inverted to a pouring or dispensing position, the partial or total back filling of the air flow channel 16 with liquid entering via the air-inlet end 38 due to the rising level of the dispensed liquid results in a state whereby, once the air-inlet end 38 of the air flow channel 16 is withdrawn or removed from the dispensed liquid, air in significant volume is not drawn into the air flow channel 16 via its air-inlet end 38. The blocking of the air flow channel 16 with dispensed liquid along with the predetermined widths or lateral extents of the elongate slots 42 of the slotted flow control element 18 based on the kinematic viscosity of the dispensed liquid causes further flow through the slotted elongate element 18 to be halted or substantially halted. The flow control device 10 can thus be withdrawn from the dispensed liquid in the container being filled without further or substantial further liquid flow occurring from the liquid-outlet end 36 of the liquid flow channel 14.
The flow control device 10 can then be reset for further use by uprighting the liquid-sealable container on which the device 10 is provided. The liquid in the flow control device 10 thus flows back in to the dispensing container under gravity.
Referring to Figure 5, a fifth embodiment of a flow control device 10 is shown. Again, like references refer to parts which are the same as or similar to those of the previous embodiments, and further detailed description is thus omitted. In this embodiment, the flow control device 10 comprises the liquid flow channel 14, the fluid flow channel 16, and the slotted flow control element 18.
In this embodiment, elongate slots 142 of the slotted flow control element 18 have an at least in part arcuate longitudinal extent, and more preferably the elongate slots 142 are semi-circular.
The semi- or part-circular elongate slots 142 may advantageously be concentric with each other, so that they extend in or substantially in parallel. It is beneficial from a cost-effective production perspective to centre a radius of each elongate slot 142 on the fluid flow channel 16.
The benefit of the arcuate elongate slots 142 is that a longitudinal extent of one or more of the elongate slots 142a is greater than a lateral extent of the liquid flow channel 14. This provides an increase in open surface area to framework 94 for liquid flow therethrough, whilst maintaining the required uniform lateral extent of each elongate slot 42.
Although not shown in the drawings, a discrete or independent filter or mesh may be positioned across the liquid flow path to filter the liquid as it is poured. The filter or mesh may be at or adjacent to the slotted flow control element 14, at an end of the liquid flow channel 14 remote from the slotted flow control element 16, or partway therebetween.
In an additional benefit of the present invention, the flow control device 10 also forms a flame arrestor, thereby preventing or limiting back travel or flashback along the tubular body 12 and into the connected container.
It has been determined that there are two criteria for successful operation of a flame arrestor using the flow control device 10. The dimensions of the apertures of the slotted flow control element 18 must be less than a critical dimension and the critical velocity through the apertures must be higher than the impinging flame velocity where the critical velocity through the mesh is a function of the mesh geometry.
By virtue of the geometry and dimensions of the flow control device 10 and the slotted flow control element 18, along with the inherent latent heat of vaporisation of the fuel coating the preferably moulded slots 42, a thermoplastic material can be beneficially utilised without resulting in melting during direct short term flame exposure as experienced with accidental petrol ignition or explosion in the vicinity of the plurality of apertures. The use of a plastics as opposed to a metal significantly reduces manufacturing costs and thus allows greater exposure to potential consumers.
During an ignition situation, for example, with a user refilling a tank of a gasoline powered lawnmower that has just been in use and is thus up to running temperature, the appropriately dimensioned slots 42 effectively break up any travelling flame mass into flamelets. This is sufficient to prevent flashback and explosion of the fuel air mixture in the fuel container.
It has been determined that, for flashback to be prevented or limited, the slots 42 should be no more than 1.5 mm or less for 0 to 20 mm² s^-1 [cSt] viscosity.
With the present invention, the slots 42 are preferably 7 mm in length and 1.5 mm in width, thereby achieving the required flame arrestor characteristic as well as enabling flow control including shutoff during a pouring or dispensing operation, without requiring any moving parts.
Although the nozzle described above is preferably removably engagable with the fluid-tightly sealable container, it may be permanently attached once inserted or become an integral part of the nozzle and/or container.
Preferably, the liquid flow channel and the fluid flow channel have uniform lateral dimensions or bores along at least a majority of their longitudinal extents.
Although the fluid flow channel has a greater longitudinal extent than the body of the liquid flow channel, it may feasibly be received fully within the body.
The body of the liquid flow channel may be formed with an opening or longitudinal subsidiary bore for receiving an independent fluid flow channel as, for example, a tight push fit. This may ease or simplify manufacturing and would allow a length of the fluid flow channel to be easily adapted dependent on intended use.
The flow control device may be used with any kind of liquid to be dispensed and a gas other than air. The air flow channel mentioned in the previous embodiments may therefore be generically termed a fluid flow channel, and/or a gas-flow channel, even though it may receive, as mentioned above, some dispensed liquid.
The flow control device may be utilised solely as a flame arrestor, and in this case the flow control aspect would be dispensed with. It would still be preferable to utilise the elongate slots, but the slots may be dispensed with in favour of apertures of other dimensions. Providing the dimension of 1.5 mm is retained, flashback of flame travel into the associated container can be prevented or limited.
It is thus possible to provide a flow control device, which may be in the form of an adaptor and which can be easily inserted, typically by being push-fitted, into a nozzle or mouth and neck of a container. The flow control device utilises no moving parts, and thus has a long working life and is not prone to failure. The device utilises a slotted flow control element, preferably being a plate, disk or even flexible or rigid membrane, which may be positioned arbitrarily along the liquid flow channel. In the case of the device being an adaptor, it may also be removable, and can thus be used with a variety of different nozzles, spouts, and/or containers. It is also possible to utilise the flow control device as a flame arrestor to achieve further functionality, provided the elongate slots are dimensioned appropriately.
The embodiments described above are provided by way of examples only, and various other modifications will be apparent to persons skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims

A flow control system for dispensing liquid from a liquid-tightly sealable container into a second container to a predetermined level, the system comprising: a liquid having a viscosity; a flow control device (10) having a liquid flow channel (14) having a first inlet end (34) and a first outlet end (36); a fluid flow channel (16) which is independent of the liquid flow channel (14) and which has a second inlet end (38) and a second outlet end (40); and a flow control element (18) by which flow is prevented or substantially prevented from exiting the first outlet end (36) of the liquid flow channel (14), the flow control element (18) being a slotted element (18) having a plurality of elongate slots (42) forming liquid flow apertures (44) therethrough, the elongate slots (42) having longitudinal extents which extend across a flow path defined by the liquid flow channel (14), characterised by the elongate slots (42) being predeterminately dimensioned according to the said viscosity of the liquid to halt or substantially halt liquid flow along the liquid flow channel (14) when the liquid flow channel is tilted to a flow condition and the fluid flow channel (16) becomes at least in part filled with liquid, flow in the liquid flow channel (14) remaining halted or substantially halted until the liquid flow channel (14) is righted to an at rest condition.
A flow control system as claimed in claim 1, wherein the elongate slots (42) have a lateral extent of or substantially of 1.5 mm or less for a liquid having a viscosity up to or substantially up to 20 mm² s^-1 [cSt].
A flow control system as claimed in claim 1, wherein the elongate slots (42) have a lateral extent of or substantially of 3 mm for a liquid having a viscosity between or substantially between 20 mm² s^-1 [cSt] and 1500 mm² s^-1 [cSt].
A flow control system as claimed in any one of claims 1 to 3, wherein the elongate slots (42) of the slotted element (18) are straight.
A flow control system as claimed in any one of claims 1 to 3, wherein the elongate slots (42) of the slotted element (18) have an at least in part arcuate longitudinal extent.
A flow control system as claimed in any one of claims 1 to 5, wherein the elongate slots (42) of the slotted element (18) extend in or substantially in parallel with each other.
A flow control system as claimed in any one of claims 1 to 6, wherein the slotted element (18) extends across the liquid flow channel (14).
A flow control system as claimed in any one of claims 1 to 7, wherein the slotted element (18) is rigid or substantially rigid and devoid of movable parts.
A flow control system as claimed in any one of claims 1 to 8, wherein the slotted element (18) is at or adjacent to the first inlet end (34) of the liquid flow channel (14).
A flow control system as claimed in any one of claims 1 to 9, wherein the flow control device (10) is an adaptor for insertion into a liquid-dispensing nozzle or neck of a fluid-tightly sealable container.
A flow control system as claimed in claim 10, the flow control device (10) further comprising a stop (64) for the insertion of the in use adaptor a preset distance into the liquid-dispensing nozzle, such that the container is fillable repeatedly to a fixed predetermined level.
A flow control system as claimed in any one of the preceding claims, wherein the elongate slots (42) have a lateral extent which in use form a flame arrestor.
A nozzle for a fluid-tightly sealable container, the nozzle comprising a flow control system as claimed in any one of claims 1 to 12.
A fluid-tightly sealable container comprising a neck extending from a flow outlet, and a flow control system as claimed in any one of claims 1 to 12 in the said neck.
A method of controlling liquid having a viscosity, dispensing from a liquid-tightly sealable container into a further container to a predetermined level and arresting flashback flame travel, the method comprising the step of providing a slotted element (18) in a nozzle, the slotted element (18) having a plurality of elongate slots (42) forming liquid flow apertures (44), the slots (42) having a predetermined dimension according to the said viscosity of the liquid which: i) halts or substantially halts liquid flow therethrough when the slotted element (18) is tilted to a flow condition and the predetermined level in the further container is reached, and ii) at least arrests flashback flame travel.