WO2012080319A1

WO2012080319A1 - Self-acting supply air terminal device

Info

Publication number: WO2012080319A1
Application number: PCT/EP2011/072737
Authority: WO
Inventors: Herman Lindborg
Original assignee: Lindinvent Ab
Priority date: 2010-12-14
Filing date: 2011-12-14
Publication date: 2012-06-21
Also published as: SE1051318A1; EP2652412A1; SE535779C2

Abstract

The invention is related to a device (100) for variable restriction of flows, comprising a feed end (120) and a delivery end (122), a first restriction means (136) which has a first restrictive surface (135) against said delivery end (122) to regulate the flow through said device, the restrictive surface (135) being at least as large as the cross-section (150) of the delivery end (122), and the first restriction means (136) being suspended via more than one first lever arm (112, 162, 172, 182), whereby the first restriction means (136) is vertically movably arranged in relation to the delivery end (122) such that the distance between the first restriction means (136) and the delivery end (122) increases when the flow increases and inclinably arranged in relation to the delivery end (122).

Description

SELF-ACTING SUPPLY AIR TERMINAL DEVICE

TECHNICAL FIELD

The invention relates to the field of devices for regulation of air flows. More specifically, the invention pertains to the field of devices for variable restriction of flows in different types of spaces. BACKGROUND

It is beginning to be increasingly important in today's society to reduce human impact upon the environment, not least in relation to the ongoing debate about climate change and population growth. In this context, technical solutions which utilise less of the earth's resources will become increasingly popular. A field in which such technical solutions are likely to be applied is more efficient use of heat and electricity.

In ventilation of premises there is particularly great potential scope for energy saving.

Existing solutions in premises have long used constant air flows in the ventilation installation and have resorted to district heating to warm the air to appropriate temperatures. Large energy savings (up to 90%) can be achieved by the air in the respective rooms being warmed by human occupants, lighting, computers (jointly representing about 350 W) instead of using external energy (e.g. district heating) to raise the air temperature from 14-15°C (degrees Celsius) to 22°C at the fan unit. Modern fan units utilise up to 70% of exhaust air energy, resulting in a supply air temperature of 14°C on an annual basis. This air is distributed to each room via duct systems. The flow is adapted by a flow regulator to achieve a balance at, for example, 22°C. This means that when "warming starts" the flow increases and when "warming stops" (departing personnel, lighting switching off automatically and computers going on standby) the flow decreases to 4 litres/second. In the winter months with their greater transmission of heat through walls and windows, only 100 W is used to heat 10 litres/second of air (human presence flow) and the remaining 250 W reduces the heat needed from radiators. If thermal loads in the room (solar input) rise, the flow of 15°C air increases. (Comfort donation without cooling baffles.) An absolute requirement for being able to use this method is the supply air device being able to provide 15°C air in a draught-free way throughout the flow range. This is by far the most cost-effective energy saving measure in premises. For some years the applicant has been patenting devices with vane technology, built-in electronics and motors which control the flow in premises as above with very good results.

Two such solutions are described in Swedish patents SE 520 293 C2 and SE 520 294 C2.

The first solution (SE 520 293 C2) involves a device with a pipeline, a feed aperture, a delivery aperture and a restriction means with a restrictive surface. The restriction means and the delivery aperture are situated in relation to one another in such a way that the restriction means can be set to different distances from the delivery aperture. This may be done either manually or by powered means. Altering the distance between the restriction means and the delivery end of the pipeline regulates the air flow through the device.

The second solution (SE 520 294 C3) to some extent resembles the first but adds two or more vanes to serve as restrictive surfaces for the air leaving the delivery end of the pipeline. Given a constant air flow through the delivery end, the shorter the distance between these restrictive surfaces the lower the noise level in the space in which the device is situated. These vanes are also connected to one another by suspension means which make it possible to vary the distance between them depending on whether the air flow decreases or increases.

However, this solution is relatively expensive for open-plan offices, conference rooms, school halls and shopping centres where many devices operate in conjunction.

In the case of flexible areas, however, in which walls are added or altered from time to time, the applicant's present solution (as described above) is cost-effective. For office rooms it is always cost-effective.

To reduce their cost, many installations have been based on conventional devices which share a single flow regulator controlling the flow to a number of devices. The problem with such solutions is that any supply of below-temperature air will cause "cold zones" resulting in draughts if the flow is less than 40-50% of the maximum flow for the specific device. The energy saving becomes quite small if the flow cannot be reduced by more than 50% (the radiator has to warm the surplus cold air). If the maximum flow of the device is greater than the maximum flow used, the potential saving becomes still smaller.

There is on the market a device (Flipper) which opens gaps progressively as the flow increases, in order to avoid "cold zones". That device is described in international published patent application WO03/001 124. The cost of installing it would be relatively high because the duct system would be quite extensive, since each device cannot provide an air flow of more than 40 litres/second with low noise level. Moreover, equal distribution of the air flow among many devices involves obvious difficulty in requiring a low duct pressure. With low duct pressure and high air velocity in the main duct, the air molecules cannot sufficiently diverge into branches to individual units.

There is therefore a need for an energy-efficient device for regulation of air flows to different spaces which is compatible with existing ventilation installations, cost- effective and capable of regulating large air flows through the ventilation system.

SUMMARY OF THE INVENTION

These and other problems are solved by a device for regulation of flows according to claim 1.

More specifically, the present invention is related to a device for variable restriction of flows, comprising a feed end and a delivery end, a first restriction means which has a first restrictive surface against said delivery end to regulate the flow through said device, the restrictive surface being at least as large as the cross-section of the delivery end, and the first restriction means being suspended via more than one first lever arm, whereby the first restriction means is vertically movably arranged in relation to the delivery end such that the distance between the first restriction means and the delivery end increases when the flow increases and inclinably arranged in relation to the delivery end.

The advantage of the solution according to the invention is that the flow velocity from the device is maintained even at small flows so that no "cold zones" occur.

Another advantage of the device according to the invention is that if the supply air temperature is 15°C, it rises to 21 °C within 1.5 m as the air moves along the ceiling from the edge of the device, irrespective of flow volume. Devices cater for a flow range of from 4 to 100 litres/second with a maximum noise level of 27 dB(A).

The air outlet velocity is high throughout the flow range, resulting in a large amount of co-injection of room air which warms outflowing air. The flow volume is regulated so that there is temperature equilibrium in the room at the given temperature set-point value.

For open-plan offices, conference rooms, school halls and shopping centres where many devices operate in conjunction, it is thus possible to reduce installation costs by having a flow regulator which controls the flow to a number of self-acting devices which can provide 15°C air in a draught-free way throughout the flow range in an inexpensive configuration (without motor, electronics and cable connections).

DESCRIPTION OF DRAWINGS

Fig. 1 depicts a first embodiment of the present invention in a side view with maximum distance between the ring and the restriction means. Fig. 2 depicts the same embodiment as Fig. 1 but with minimum distance between the ring and the restriction means.

Fig. 3 depicts a second embodiment of the present invention in a side view with minimum distance between the ring and the restriction means.

Fig. 4 depicts the embodiment from Fig. 3 as seen from below.

Fig. 5 depicts a third embodiment of the invention in a side view.

DESCRIPTION OF EMBODIMENTS It should be noted that the following description relates to embodiments which are intended to illustrate the function of the invention and not to restrict it solely to these examples. In the final analysis, the invention is only limited by the protective scope of the attached claims.

Fig. 1 depicts a first embodiment of the device 100 according to the present invention. The device 100 comprises a connecting sleeve 130 (to the box in which the device is situated) which is connected to the inner edge of a planar ring 132. The concept is that the whole of the box in which the device is situated should be connectable to the ceiling of the space in which the device is intended to regulate the air flow. The connecting sleeve 130 should then be insertable in the ceiling recess intended for the ventilation. It is however perfectly possible to connect the device to an existing ventilation hole in the ceiling without the sleeve 130.

Below the sleeve 130 and the ring 132 there is a disc-like restriction means 136 with a restrictive surface 135 which is at least as large as the cross-section 150 of the connecting sleeve 130. In the embodiment illustrated in figure 1 , the restrictive surface 135 of the restriction means 136 is as large as the surface defined by the planar ring 132 plus the cross-section 150 of the connecting sleeve 130. Although the restrictive surface 135 may be larger or smaller, it is normally larger than the cross-section 150 of the connecting sleeve 130.

The advantage of a restrictive surface 135 of such a size is that it creates a large flow surface for the air flow which passes through the sleeve 130 and the restrictive surface 135, and a large gap between them, which makes greater air flows possible when needed.

The restriction means 136 is suspended and connected via a first lever arm 112 with a weight 1 10. The first lever arm 112 is suspended from mountings (not depicted) and may be situated above (Fig. 1) or below (Fig. 3) the restriction means 136. It should be noted that the device 100 in Fig. 1 only is shown with one such first lever arm 112 and weight 1 10, but the restriction means 136 is connected to more than one lever arm and more than one weight as depicted in Fig. 4. The restriction means 136 is suspended via at least two first lever arms 1 12, 162, 172, 182. Since the first restriction means 136 is suspended via more than one first lever arm 1 12, 162, 172, 182, the first restriction means 136 is vertically movably arranged in relation to the delivery end such that the distance between the first restriction means 136 and the delivery end 122 increases when the flow increases. In addition, since the first restriction means 136 is suspended via more than one first lever arm 1 12, 162, 172, 182, the first restriction means 136 is vertically movably arranged in relation to the delivery end such that the distance between the first restriction means 136 and the delivery end 122 decreases when the flow decreases. In addition, since the first restriction means 136 is suspended via more than one first lever arm 112, 162, 172, 182, the restriction means 136 is inclinably arranged in relation to the delivery end 122. The first restriction means 136 is inclinably arranged in relation to the delivery end 122 such that the distance between the first restriction means 136 and the delivery end 122 may be different for different portions of the first restriction means 136.

By suspending the first restriction means 136 in more than one first lever arm

1 12, 162, 172, 182, a construction which is sensible to variations in the flow is obtained. This is achieved since suspension in a plurality of lever arms results in almost negligible frictional forces. The almost negligible frictional forces resulting in that the device 100 reacts to very small variations of the air flow implies that the restriction means reacts directly when the flow through the device 100 varies. Since the restriction means reacts without delay when the flow varies, the restriction means will be in the same position at a particular flow irrespective of if the flow has been reduced to the particular flow from a higher level or if the flow has been increased to the particular flow from a lower level. Thereby, a principally hysteresis free operation of the device 100 is obtained. As a result of the fact that the restriction means will be in the same position at a particular flow, the air velocity through the device 100 is principally constant irrespective of the air flow.

As stated above, the suspension of the first restriction means 136 via a plurality of first lever arms 112, 162, 172, 182 results in the first restriction means being vertically movably arranged in relation to the delivery end 122 such that the distance between the first restriction means 136 and the delivery end 122 increases when the flow increases. Thereby, the first restriction means 136 moves downwards when the flow increases. Since the distance between the first restriction means 136 and the delivery end 122 thereby is adapted to the flow "cold zones" are avoided. The flow affects the first restriction means 136 such that the first restriction means 136 moves downwards when the flow increases and upwards when the flow decreases.

Since the distance between the first restriction means 136 and the delivery end 122 is adapted to the flow, the device 100 is a device with a self-acting valve. Because of the suspension of the first restriction means 136 via a plurality of first lever arms each lever arm may move independent of the other lever arms. Thereby, different portions, such as different suspension points, of the restriction means may move vertically independently of each other. Thus, the different portions, such as different suspension points, of the restriction means may move downwards to different extent. Consequently, the first restriction means is inclinable in relation to the delivery end. Thereby, creation of "cold zones" is further reduced.

In one embodiment, the first restriction means 136 is suspended via at least three first lever arms 112, 162, 172, 182. By suspending the restriction means via at least three first lever arms, the suspension of the restriction means is balanced. Thereby, the inclination of the restriction means is controllable and it is secured that the restriction means may be in a horizontal position when in rest, e.g. when the flow through the device is zero. The three first lever arms may be positioned in a triangular pattern and thereby the suspension of the restriction means is further balanced. In one embodiment, the first restriction means 136 is suspended via at least four first lever arms 1 12, 162, 172, 182 as shown in Fig. 4. Even though the suspension of the restriction means is further balanced when the number of lever arms increases, the number of restriction means is preferably not too large, since a large number of lever arms increases the friction forces and increases the number of operations for adjusting the reaction of the device in relation to the flow through the device. Since an adjustment means may be present for each first lever arm, the number of adjustment means and thereby the number of adjustment operations increases when the number of first lever arms increases. In one embodiment, the restriction means is not suspended via more than 4 first lever arms. In one embodiment, the restriction means is suspended via 2-4 first lever arms. In one embodiment, the restriction means is suspended via 3 or 4 first lever arms. In one embodiment, the restriction means is not suspended via more than 3 first lever arms. In one embodiment, the restriction means is suspended via 3 first lever arms.

In one embodiment, the first restriction means 136 is suspended via first lever arms 1 12, 162, 172, 182 attached to the first restriction means 136 at a distance from the centre of the first restriction means 136. Thereby, the suspension of the restriction means is further balanced.

The first lever arms 1 12, 162, 172, 182 may be pivotably fastened to the sleeve 130 or the planar ring 132.

The first restriction means 136, which in Fig. 1 is disc-like, may be of any desired shape. It may for example be rectangular. The restrictive surface 135 may be smooth, planar or curving. The weight 1 10 may be fixed or movable. The object of a movable weight 1 10 is to be able to set the sensitivity of the first restriction means 136 to changes in air flows through the device by setting the turning moment of the first lever arm 1 12. With advantage, the turning moment may be set by the weight 110 being movably arranged on a slide rail 116. If the weight 1 10 is moved nearer to the suspension point of the first lever arm 112, the resulting smaller turning moment will cause the first restriction means 136 to be more sensitive to variations in the air flow through the delivery end 122 of the sleeve 130.

In the same way, the further the weight 1 10 is moved from the suspension point of the level arm 112, the less sensitive to changes in the air flow through the delivery end 122 of the sleeve 130 the restriction means 136 will become, owing to the greater turning moment.

Between the ring 132 and the first restriction means 136 there is an intermediate ring 134 which is also suspended from the first lever arm 112 but at a shorter distance from the lower surface of the planar ring 132 than the distance between the restrictive surface 135 and the lower surface of the planar ring 132. This means that the intermediate ring 134 will always be midway between the planar ring 132 and the disc-like restriction means 136.

The intermediate ring 134 serves also as a second restriction means for the flow through the delivery end 122 of the valve 100 whereby the restriction of the flow takes place along the restrictive surface 133 of the intermediate ring 134 and the spaces between the planar ring 132 and the intermediate ring 134 and between the intermediate ring 134 and the first restriction means 136.

An intermediate ring between the first restriction means 136 and the planar ring 132 reduces the noise level significantly. At 100 litres/second, the noise level 1 m below the device is 1 dB(A) higher than the background noise level. Without the intermediate ring 134, the noise level increases by about 2.5 dB(A) despite the aperture increasing by about 50% and thereby reducing the air velocity (the trajectory length). The applicant has at present no good theoretical explanation why the intermediate ring 134 reduces the noise level, but notes that all experimental trials have shown that the vane technique, i.e. intermediate ring 134 and a first restriction means 136 which defines a horizontal air gap, works well.

It should however be mentioned in this context that the invention also works without the intermediate ring 134 but then with higher noise level and shorter trajectory length.

The second restriction means 134 may be suspended via second lever arms 1 14, 164, 174, 184.

The number of second lever arms 114, 164, 174, 184 may be equal to the number of first lever arms 112, 162, 172, 182 according to above. In one embodiment, the second restriction means 134 is suspended via second lever arms 1 14, 164, 174, 184 attached to the second restriction means 134 at a distance from the centre of the second restriction means 134. Thereby, the suspension of the restriction means is further balanced.

The second lever arms 114, 164, 174, 184 may be pivotably fastened to the sleeve 130 or the planar ring 132.

The device 100 further comprises a boundary means in the form of an underplate 138 connected to the ring 132 by a number of suspension means 140. The boundary means 138 provides protection and stability for movable parts and limits the range of movement of the first restriction means 136.

The air flow through the feed end 120, the sleeve 130 and the delivery end 122 pushes the disc-like restriction means 136 down, causing a balanced air pressure which drives the air out along the ceiling of a room at good velocity. The air pressure is settable by means of the weights 1 10 as described above. The weights 1 10 can be set so that the device is minimally open at zero flow or very low flows (say 4 l/s) through the delivery end 122 and maximally open at large flows (say near to 100 l/s). After being set, the device reacts passively to changes in the flow through the delivery end 122, i.e. the device is self- acting.

The large restrictive surface 135 of the first restriction means 136 and almost negligible friction forces on the first lever arm 1 12 result in the air velocity being almost constant throughout the flow range. This flow range may be defined as flows between 4 and 100 litres/second. This solution meets requirements for very low noise levels at large flows, which in the applicant's view is not achieved by devices available on the market.

In addition, the flow in a certain direction may be limited to avoid "flow clashes" with other devices, so that draughts do not occur. One or more spacers 142 placed on the lower plate 138 will prevent the first restriction means 136 from opening more than the spacers allow. The restriction means 136 may slope with respect to its position of rest in which it is parallel with the cross-section 150 of the sleeve 130. When one or more spacers 142 are put in place as depicted in Fig. 1 , larger flows through the delivery end will thus cause the restriction means 136 to slope more on the side where there are no spacers, since that is where the flow will mainly pass. The advantage of the spacers is that they are easy to arrange even after the valve 100 has been fitted in the ceiling of the space being ventilated.

The device 100 is in particular suitable and effective when a plurality of devices 100, such as at least two devices 100, interact. The flow may be centrally controlled and conveyed to the devices 100. The opening of each device is thereby automatically adapted to the flow by means of the suspension of the first restriction means 136 in a plurality of first lever arms 1 12, 162, 172, 182. No operation of each device is needed and a high flexibility is achieved. When a spacer 142 is present, the first restriction means 136 is automatically tilted, i.e. inclined, when the flow increases. Thereby, the flexibility is further increased. In addition, "cold zones", which may result from "flow clashes" of below-temperature air from different devices 100, are avoided.

Fig. 1 depicts the situation where the device 100 is in a state somewhere between closed and fully open. This situation results in a flow of about 100 litres/second. The remaining distance is used to be able to tilt the restriction means 136 without increasing the noise level.

Fig. 2 depicts the same device 100 in an almost closed state. A closed state of the device 100 may be defined as when the air flow through the delivery end 122 of the sleeve 130 is zero or very small. The device 100 may then be set so that the vertical distance between the first restriction means 136 and the ring 132 is zero in cases where an intermediate ring 134 is not used. In cases where there is an intermediate ring 134 inserted between the ring 132 and the first restriction means 136, the device is closed when this distance is equal to the thickness of the intermediate ring 134.

It is similarly possible to define a fully open position for the device 100 as when the air flow through the delivery end 122 of the sleeve 130 is maximum. The distance between the first restriction means 136 and the boundary means 138 will then be zero.

Fig. 3 depicts a second embodiment of the device 100 wherein the weight 110 is situated below the boundary means 138. The device is protected by a cover 160 which also has an aesthetic function in concealing the weight 110.

In Fig. 3 the device is in a state near to the closed state defined above.

The advantage of this embodiment is that the sensitivity of the restriction means 136 to varying air flows through the delivery end 122 of the sleeve 130 can easily be set without having to take the whole device 100 down from the ceiling.

The embodiment in Fig. 1 might then be used in cases where only one adjustment of the sensitivity of the restriction means 136 is needed or where this adjustment is not needed particularly often.

Fig. 4 depicts the embodiment from Fig. 3 as seen from below.

In figure 4 four weights 1 10, 160, 170 and 180 and four pairs of lever arms 1 12, 114; 162, 164; 172, 174; 182, 184 belonging to the respective weights are shown. The weights may be fixed or movably arranged on respective rails in the same way as described above with respect to Fig. 1. The weights 1 10, 160, 170 and 180 have the same function as described above with reference to Fig. 1 , viz. to set the respective lever arm's turning moment and thereby adjust the sensitivity of the restriction means 136 to changes in the flow through the delivery end 122 of the device 100. Further, the weights and the lever arms may also be situated on the upper side of the restriction means 136 (as illustrated in Fig. 1) or below it (see Fig. 3). The invention is not confined to any specific geometrical shape of the device 100, so shapes other than simply annular or circular are conceivable for the restriction means 136, the intermediate ring 134 and the planar ring 132. They might be square, triangular, trapezoidal or polygonal.

In one embodiment, the device 100 spreads the flow omnidirectional. Thereby, the device spreads the air flow in all directions principally parallel to the first restriction means 136. The omnidirectional spreading of the flow may be achieved by a restriction means having any geometrical shape as discussed above. However, the omnidirectional spreading of the flow is in particular pronounced for an annular shaped restriction means. In one embodiment, the first restriction means 136 is annular. In one embodiment, the second restriction means 134 is annular. In one embodiment, the planar ring 132 is annular. In one embodiment, the first restrictive surface 135 is annular. In one embodiment, the second restrictive surface 133 is annular. In one embodiment, the first restriction means 136, the second restriction means 134 and the planar ring 132 are annular. In one embodiment, the first restrictive surface 135 and the second restrictive surface 133 are annular. The omnidirectional spreading of the flow may be regulated and controlled in certain directions by means of a spacer 142 as discussed above. Fig. 5 depicts a third embodiment of the invention in which a device 200 is fitted against a sidewall 230 and the flow from the device 200 passes through the sidewall to the space which is to be ventilated.

The difference with this embodiment is that it is suited to fitting in sidewalls as is sometimes the case with ventilation devices in certain European countries. Figure 5 depicts a connecting duct 220 by which the device 200 is connected to the rest of the ventilation system (not depicted). The device 200 further comprises a restriction means 236 and an intermediate ring 234 which are very similar to the restriction means and the intermediate rings depicted in Figs. 1-4. Whereas the restriction means 236 and the intermediate ring are connected to weights 282 and 262 via respective lever arms 284 and 264, the outflow from the device is in only one direction, i.e. the direction through the aperture in the sidewall 230, which direction is indicated by the arrows in Fig. 5. It should be noted that the device 200 is with advantage installed close to the ceiling of the space which is to be ventilated by it, as depicted in figure 5. In other respects the function of the device 200 is in principle identical with the device 100 depicted in the previous figures and will not be explained in more detail.

Claims

1. A device (100) for variable restriction of flows, comprising a feed end (120) and a delivery end (122), a first restriction means (136) which has a first restrictive surface

(135) against said delivery end (122) to regulate the flow through said device, the restrictive surface (135) being at least as large as the cross-section (150) of the delivery end (122), and the first restriction means (136) being suspended via more than one first lever arm (1 12, 162, 172, 182), whereby the first restriction means (136) is vertically movably arranged in relation to the delivery end (122) such that the distance between the first restriction means (136) and the delivery end (122) increases when the flow increases and inclinably arranged in relation to the delivery end (122).

2. A device according to claim 1 , wherein the first restriction means (136) is suspended via at least three first lever arms (1 12, 162, 172, 182).

3. A device according to claim 1 or 2, further comprising an adjusting means for each first lever arm (1 12, 162, 172, 182) for variable setting of the inertia of the movement of the first restriction means (136) caused by the flow through the delivery end (122).

4. A device according to claim 3, wherein each said adjusting means comprises at least one weight (110, 160, 170, 180) for setting the centre of gravity of the adjusting means.

5. A device according to claim 4, wherein each said adjusting means comprises a rail (1 16) and the weight (110, 160, 170, 180) is movably arranged on the rail (1 16).

6. A device according to any one of claims 1-5, further comprising a second restriction means (134) between the delivery end (122) and the first restriction means (136), which second restriction means (134) is movably arranged in relation to the delivery end (122) and the first restriction means (136) and comprises a second restrictive surface (133) which is smaller than the first restrictive surface (135) of the first restriction means (136).

7. A device according to any one of the preceding claims, wherein the device spreads the flow omnidirectional.

8. A device according to any one of claims 3-7, wherein the first restriction means (136) is connected to said adjusting means via said first lever arms (1 12, 162, 172, 182).

9. A device according to any one of claims 6-8, wherein the second restriction means (134) is connected to said adjusting means via second lever arms (114, 164, 174, 184).

10. A device according to any one of claims 4-9, wherein each lever arm (112, 162, 172, 182, 114, 164, 174, 184) is settable via the weight (110, 160, 170, 180).

1 1. A device according to any one of claims 3-10, wherein said adjusting means are situated below the first restriction means (136).

12. A device according to any one of claims 3-10, wherein the adjusting means is situated above the first restriction means (136).

13. A device according to any one of claims 6-12, wherein the device (100) is adapted to being in a closed state at a certain minimum flow through the delivery end (122) in which closed state the distance between the first restriction means (136) and the second restriction means (134) is minimum.

14. A device according to claim 13, wherein the device (100) is adapted to being in an open state when the flow through the delivery end (122) is greater than the minimum flow.

15. A device according to any one of claims 1-14, further comprising a boundary means (138) adapted to defining the maximum distance between the first restriction means (136) and the delivery end (122).

16. A device according to claim 15, further comprising at least one spacer (142) situated between the boundary means (138) and the first restriction means (136) to limit the flow between the delivery end (122) and the first restriction means (136) in a predefined direction.