GB2450536A

GB2450536A - Mist generating device and control means

Info

Publication number: GB2450536A
Application number: GB0712633A
Authority: GB
Inventors: John Deal
Original assignee: JILL LABAT
Current assignee: JILL LABAT
Priority date: 2007-06-29
Filing date: 2007-06-29
Publication date: 2008-12-31
Anticipated expiration: 2027-06-29
Also published as: GB2450536B; GB0712633D0

Abstract

A mist generating device 1 (101, Fig 3) for the dispersal of liquids 13 (113A, 113B) has an ultrasonic nebuliser 9 (109) contained within a chamber 3 (137). Liquid inlet 5 provides chamber 3 via control means 7 (129). Liquid depth 15 provided above the ultrasonic nebuliser 9 may be optimised by control of the flow of liquid 13 into the main chamber 3 (127) via valve 7B and a liquid level sensor 7A. Nebulised liquid is output as a mist via outlet 11 (151). Figure 3 shows a dual container version of the invention. The arrangement allows a means of controlling the level/depth of liquid above the nebuliser 9 (109). Mist outlet 11 (151) may additional be connected to a mixing device so as to be mixed with a gas.

Description

Mist Generating Device

Field of the Invention

The present invention relates to a mist generating device having an ultrasonic nebuliser.

Background of the Invention

Mist generating devices are used for the dispersal of liquids in the form of a fine mist.

Applications include the dispersal of fragrances and sanitising chemicals within enclosed spaces, e.g. food fragrances within the premises of food retailers, and antibacterial agents in malodorous working environments.

Currently, commercially available mist generating units for the controlled dispersal of liquids work by means of a Venturi pump type of nebuliser, in which air (or other gas) is blown through a nozzle to create a partial vacuum and suck a liquid into the air flow, creating a flow that is loaded with a mist of liquid droplets. However, such devices require a high-pressure gas supply in the form of either a gas cylinder or a gas pump, making the units heavy and expensive. Further, the design and cleanliness of the nozzle is critical to high performance operation, which increases manufacturing complexity and may reduce operational reliability. Yet further, the size and rate of production of liquid droplets may not be appropriate to some applications.

Ultrasonic nebulising units have been used for uncontrolled mist generating applications, such as "pond foggers" that are used to create mist on the surfaces of garden ponds. They can be compact, inexpensive and have low requirements in terms of maintenance. However, the performance of ultrasonic nebulisers with respect to droplet size and rate of mist generation is sensitive to their operating conditions, in particular to their depth of submersion. Further, ultrasonic nebulisers are susceptible to burning out if they are operated without a covering of liquid, and so are typically fitted with a cut-out mechanism operable in response to insufficient liquid coverage.

Due to these disadvantages, the deployment of ultrasonic nebulisers for mist generation has been limited.

The mist generating performance of an ultrasonic nebuliser is a function of the depth of liquid covering the unit, and a need remains in the art for a device with an ultrasonic nebuliser that enables the depth of a liquid over the ultrasonic nebuliser to be controlled.

Summary of the Invention

It is an object of the present invention to provide a mist generating device having an ultrasonic nebuliser that seeks to overcome at least some of the above disadvantages

of the prior art.

According to the present invention there is provided a mist generating device comprising: a main chamber having an ultrasonic nebuliser within the main chamber; a liquid inlet; control means to control the flow of liquid into the main chamber through the liquid inlet; and a mist outlet.

Preferably the control means controls the level of liquid in the main chamber to a predetermined level, such that the ultrasonic nebuliser is covered by a predetermined depth of liquid. Preferably the control means is provided by an opening of the liquid inlet, such that when the opening is exposed above the level of the liquid, then further liquid may flow into the main chamber through the liquid inlet, and when the opening is beneath the level of the liquid, then further liquid may not flow into the main chamber through the liquid inlet. Alternatively the control means may comprise a liquid flow valve operable in correspondence with an output from a liquid level sensor, to control the flow of liquid through the liquid inlet. The liquid level sensor may be electrical or mechanical. Preferably a flushing gas is passed into the main chamber to flush mist out of the main chamber and through the mist outlet. The flushing gas may be drawn or blown by means of a fan or gas pump. Preferably the flushing gas may be drawn by means of a Venturi gas pump associated with the mist outlet. The mist outlet may connect to a mixing device through which gas is drawn or blown by a fan or gas pump. The mixing device may comprise a tunnel through which a mixing gas is drawn or blown.

According to a first preferred embodiment of the present invention there is provided a mist generating device having a main chamber comprising a filling chamber and a nebulising chamber, having a liquid inlet associated with the filling chamber, control means within the filling chamber to control a flow of liquid into a chamber through the liquid inlet, an ultrasonic nebuliser in the nebulising chamber, and a mist outlet associated with the nebulising chamber, wherein the filling and nebulising chambers are connected by a fluid interconnection, through which at least liquid may flow.

Both liquid and gas may pass through the fluid interconnection between the filling and nebulising chambers. A gas interconnection may additionally be provided through which gas may flow between the filling and nebulising chambers.

According to a second preferred embodiment of the present invention there is provided a mist generating device comprising a main chamber having a filling and a nebulising portion, a liquid inlet associated with the filling portion, control means in the filling portion to control a flow of liquid into the main chamber through the liquid inlet, an ultrasonic nebuliser in the nebulising portion, and a mist outlet associated with the nebulising portion, wherein the main chamber is shaped such that liquid within the filling portion is at least partially isolated from disturbance of liquid within the nebulising portion of the main chamber.

The at least partial isolation may comprise a constriction in the width of the main chamber between the filling and nebulising portions. Further the main chamber may be shaped such that the at least partial isolation is provided by means of a bend in the main chamber between the filling and nebulising portions.

According to a third preferred embodiment of the present invention there is provided a mist generating device having a main chamber and a mist outlet chamber, the main chamber having an ultrasonic nebuliser within the main chamber, a liquid inlet, control means to control a flow of liquid into the main chamber through the liquid inlet, wherein the mist outlet chamber has a mist outlet and is connected with the main chamber by a mist interconnection through which mist output may flow.

Preferably the design of the mist outlet chamber and/or mist interconnection provides at least a partial filtering of large droplets from the mist output. The main chamber and mist outlet chamber may be separated by a plate, and the interconnection may be provided by means of holes through the plate.

Brief Description of the Drawings

For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which: Figure 1 is a schematic cross sectional view of a mist generating device according a preferred embodiment of the present invention.

Figure 2 is a schematic plan view of a mist generating device according to a preferred embodiment of the present invention.

Figure 3 is a schematic cross sectional view of a further mist generating device according to a further preferred embodiment of the present invention.

Detailed Description of Preferred Embodiments

Referring to Figure 1 of the accompanying drawings, a mist generating device I according to a preferred embodiment of the present invention is illustrated. The mist generating device 1 has a main chamber, within which are provided a liquid inlet 5 and a control means 7, an ultrasonic nebuliser 9 and a mist outlet 11. The control means 7 comprises a liquid level sensor 7A to sense a level of the liquid 13 and a valve 7B to control the flow of liquid through the liquid outlet 5. The mist outlet 11 may comprise an open top of the main chamber 3 or an output pipe (not illustrated).

When the liquid level sensor 7A senses that the level of the liquid 13 is below a predetermined level the valve 7B is opened and allows further liquid to flow into the main chamber 3 through the liquid inlet 5. When the liquid level sensor 7A senses that the liquid 13 has reached the correct level the valve 7B is closed and no further liquid flows into the main chamber 3. In this way the control means 7 ensures that a predetermined, substantially constant depth 15 of liquid 13 is maintained above the ultrasonic nebuliser 9, which may optimise the generation of mist with respect of droplet size and/or rate of mist generation. In operation the main chamber 3 contains liquid 13 and the ultrasonic nebuliser 9 generates a mist of droplets of the liquid above the surface of the liquid, which exits the main chamber by the mist outlet 11.

The optimum depth 15 of liquid 13 above the ultrasonic nebuliser 9 may be a function of properties of the liquid, e.g. density, viscosity, surface tension and temperature.

The operation of the sensor 7A or ultrasonic nebuliser 9 may be calibrated with respect to properties of the liquid 13.

Referring to Figure 2 of the accompanying drawings, a plan view of a mist generating device 1 according to an embodiment of the present invention is illustrated. In operation the ultrasonic nebuliser 9 generates a disturbance 17 of the surface of the liquid 13 within the main chamber 3, for example in the form of waves on the surface of the liquid 13, which spread out from the ultrasonic nebuliser. Such disturbance 17 in the level of the liquid 13 may interfere with the operation of the liquid inlet control means 7. The main chamber 3 may be shaped to reduce the exposure of the control means 7 to the disturbance 17. For example the main chamber 3 may have a filling portion 19 and a nebulising portion 21, between which a bend 23 or constriction (not illustrated) is advantageously provided to reduce the transmission of disturbance 17 of the liquid 13 between the portions.

Referring to Figure 3 of the accompanying drawings, a cross sectional view of a mist generating device 101 according to a further preferred embodiment of the present invention is illustrated. In the figure, like features to those of Figure 1 have been labelled with like numerals, incremented by one hundred. The mist generating device 101 comprises a main chamber 103 and a mist outlet chamber 131. The main chamber 103 comprises a filling chamber 125 and a nebulisation chamber 127.

The filling chamber 125 and nebulisation chamber 127 contain liquids I 13A and 11 3B respectively, which are in communication through a fluid interconnection 133 that is at least partially beneath the common level of the liquids, such that liquid may flow from the filling chamber to the nebulisation chamber. The two chambers 125 and 127 are also in communication through a gas interconnection 135 provided above the common level of the liquids, such that gas may flow between the chambers 1 25 and 127.

I

An ultrasonic nebuliser 109 is provided within the nebulising chamber 127. A combined liquid inlet and control means 129 is provided within the filling chamber 125. The combined liquid inlet and control means 129 comprises a pipe 137 (e.g. a filling needle) having an opening, and being coupled to a vessel 139 (e.g. a filling bottle) containing a reservoir of further liquid 141. The coupling may be provided by means of a ZellerTM type of valve in the neck of the vessel 139. When the level of the liquid 11 3A falls beneath the level of the, opening of the combined liquid inlet and control means 129, gas may flow into the pipe 137 and vessel 139, enabling further liquid 141 to be displaced and to flow out into the filling chamber 125, until the level of the liquid 1 13A has risen to cover the opening, at which point further liquid 141 ceases to flow out into the filling chamber.

The filling chamber 125 and the nebulisation chamber 127 may be separated by means of a baffle 143, through which the fluid interconnection 133 andlor gas interconnection 135 may be provided.

As discussed with respect to Figure 2, in the device of Figure 3 it is also desirable to at least partially isolate the control means 129 from disturbance of the level of the liquid 113B created by the ultrasonic nebuliser 109. Thus the control means 129 and ultrasonic nebuliser 109 are advantageously provided within different chambers 125 and 127.

The nebulisation chamber 127 and mist outlet chamber 131 are in communication by means of at least one mist interconnection 149, through which mist may pass. As well as producing a mist of fine droplets, the ultrasonic nebuliser 1 09 typically produces a spray of larger droplets above it (e.g. on axis with a mode of vibration). Preferably the opening of the at least one mist interconnection 149 is provided other than directly above (or on axis with) the ultrasonic nebuliser 109. The interconnection 149 connects to the mist outlet chamber 131, which is provided with a mist outlet 151.

The design of the mist outlet chamber andlor mist interconnection 149 is preferably such that larger droplets may be at least partially, and preferably substantially, filtered from a mist output.

The nebulisation chamber 127 and mist outlet chamber 131 are separated by a plate 153 through which the mist interconnection 149 is formed.

Fluid, gas or mist interconnections may alternatively be provided by means of pipes connected between separate chambers.

Flushing gas may be drawn into the main chamber of the mist generating device by a reduction in pressure at the mist outlet, causing mist to be flushed out of the mist outlet. The reduction in pressure at the mist outlet may be generated by any suitable known means, such as a fan or gas pump, particularly a Venturi gas pump.

Alternatively flushing gas may be blown into the main chamber of the mist generating device to flush mist out of the mist outlet. The gas may be blown by any suitable means, such as a fan or gas pump. The gas may preferably be drawn or blown into a filling chamber of the main chamber.

The mist outlet may be connected to a mixing device (not illustrated), through which a mixing gas (e.g. air) is drawn or blown in order to better disperse generated mist throughout a room. The mixing gas may be drawn or blown through the mixing device by means of a fan or gas pump.

The ultrasonic nebuliser may be a piezoelectric component. A plurality of nebulisers may be provided within the main chamber of a mist generating device. The main chamber may be provided with a cut-out mechanism, such that the ultrasonic nebuliser cannot operate if the depth of liquid above the ultrasonic nebuliser is less than a minimum depth.

Claims

Claims 1. A mist generating device comprising: a main chamber having an

ultrasonic nebuliser within the main chaniber; a liquid inlet; control means for controlling the flow of liquid through the liquid inlet; and a mist outlet.
2. A mist generating device according to claim I wherein a flow of liquid into the main chamber is controlled to provide a predetermined level of liquid within the chamber.
3. A mist generating device according to one of claims I or 2 wherein the control means comprises an opening of the liquid inlet, and control of the flow of liquid through the liquid inlet is a function of whether the opening is exposed or obscured by a liquid within the main chamber.
4. A mist generating device according to claim 3 wherein the liquid inlet is a pipe having an opening, and the pipe is coupled to an opening of a vessel containing a reservoir of liquid.
5. A mist generating device according to one of claims I or 2 wherein the control means comprises a liquid level sensor and an inlet flow valve, such that the inlet flow valve is operable in correspondence with an output from the liquid level sensor.
6. A mist generating device according to any preceding claim, wherein the main chamber comprises a filling chamber and a nebulising chamber, the control means is provided within the filling chamber and the ultrasonic nebuliser is provided within the nebulising chamber, and a fluid interconnection is provided such that at least liquid may flow between the filling and nebulising chambers.
7. A mist generating device according to claim 7 wherein a gas interconnection is provided through which gas may flow between the two chambers.
8. A mist generating device according to any of claims 6 and 7 wherein the filling and nebulising chambers are separated by a baffle through which the fluid interconnection is provided.
9. A mist generating device according to any of claims 1 to 5 wherein the main chamber is shaped and provided with a filling portion and a nebulising portion, the control means is disposed within the filling portion and the ultrasonic nebuliser is disposed within the nebulising portion, the main chamber being shaped such that when a liquid is provided within the main chamber the control means is at least partially isolated from disturbance of the liquid by the ultrasonic nebuliser.
10. A mist generating device according to any preceding claim wherein the device comprises a mist outlet chamber disposed to receive a mist output from the main chamber through a mist interconnection, and associated with the mist outlet.
11. A mist generating device according to claim 10 wherein the design of the mist outlet chamber and/or mist interconnection provides at least a partial filtering of large droplets from the mist output.
12. A mist generating device according to one of claims 10 or 11 wherein the main chamber and mist outlet chamber are separated by means of a plate through which the mist interconnection is provided.
13. A mist generating device according to any preceding claim wherein a flushing gas is drawn or blown through the main chamber to flush mist through the mist outlet.
14. A mist generating device according to any preceding claim wherein the mist outlet connects to a mixing device and a mist output through the mist outlet is mixed with a mixing gas drawn or blown through the mixing device.
15. A mist generating device substantially as herein before described and as illustrated in any of the accompanying drawings.