GB2043489A - Rotary atomiser - Google Patents

Abstract

In a rotary atomiser having a dished rotary dispersion member 2 with a planar central region 7 and a peripheral frusto-conical wall 8 along which liquid migrates to be thrown off as droplets, liquid is fed to the central region along one or more filaments 11 extending from a source of liquid supply to the central region. The filaments may be in the form of a brush or wick, e.g. a brush of 5-30 solid, non-porous, nylon filaments of 50-200 microns diameter. The use of filaments ensures an even supply of liquid to the dispersion member and is particularly suitable for small atomisers with a liquid supply rate of less than 30 ml/minute. <IMAGE>

Description

SPECIFICATION Rotary atomiser This invention relates to rotary atomisers of the kind which include a rotary dispersion member on to which liquid to be atomised is fed, rotation of the dispersion member resulting in migration of the liquid to the periphery of the dispersion member and the issuance of a stream of droplets from said periphery.

The rotary dispersion member may have a substantially planar circular central region with a peripheral frusto-conical wall inclined outwardly from the central region. One example of this type of frusto-conical member is shown in my UK Patent Specification No. 1515511.

Liquid may be fed to the central region which, in effect, acts as a reservoir for the liquid. For smaller atomisers the feed may be a simple gravity feed through a tube having a suitably dimensioned outlet connected to a container for the liquid, (e.g. a bottle). A transfer from the outlet to the dispersion member should be a ligament so that the supply of the spray liquid to the member is completely even. If, however, very small amounts of liquid are being used the ligament formation may stop and single droplets may issue from the orifice giving alternate overfeeding and underfeeding. The present invention is, therefore, concerned with further improving the supply of liquid to the dispersion member of a rotary atomiser by using one or more filaments to effect the transfer. The liquid flows along the filaments and a steady run of supply, even of very small quantities, is assured.

According to the present invention a rotary atomiser comprising a dished rotary dispersion member having a substantially planar central region with a peripheral frusto-conical wall inclined outwardly from the central region and means for supplying liquid to the central region, is characterised in that the means for supplying liquid is one or more filaments extending between a source of liquid supply and the central region.

The filaments are preferably solid and nonporous so that the liquid flows down the outside of the filaments. Preferably there are a number of parallel filaments forming a brush.

Alternatively the filaments may be in woven or knitted form acting as a wick. They may be formed of any suitable material, e.g. nylon.

The filaments may be attached at one end to a suitable fixed part of the atomiser close to the liquid supply source. The other end may be free and in contact with the central region of the dispersion member. In a preferred embodiment the liquid supply source may be a tube with a restricted outlet with the filaments embedded in the wall of the tube close to the outlet.

Other features of the rotary atomiser may follow known practice, particularly as described in UK Patent Specification No.

1515511 and in the specification of UK Patent Specification No. 2004383 (Case 4424).

Thus, the inner surface of the frusto-conical wall may have grooves extending radially outwardly from the central region to the periphery of the wall, which may be toothed. The teeth and grooves may be radially symmetrical or asymmetrical and the grooves may lead to the gaps between the teeth or to the apices of the teeth.

The invention is illustrated with reference to the accompanying drawing which is a section through a rotary atomiser head.

In the drawing, the rotary atomiser head has a fixed portion 1 and a rotating disc 2.

The fixed portion has an electric motor 3 which drives a spindle 4 to which disc 2 is attached. The motor may be driven by batteries housed in the compartment or in a handle (not shown) attached to the fixed portion of the head. The fixed portion also has a tube 5 with a restricted outlet 6.

The rotating disc 2 has a planar central portion 7 and a frusto-conical wall 8, having radial grooves 9 on its inner surface. The periphery of the wall has radially symmetrical teeth. For example, there may be 360 teeth and 360 grooves, each groove leading to a tooth.

The clearance between the centre of the rotating disc 2 and the centre of the fixed portion is small and is in the form of a labyrinth 10, which acts as a liquid seal.

Tube 5 is connected to a source of liquid supply, e.g. an inverted bottle of liquid (not shown). Set into the wall of the tube 5 near the restricted outlet 6 is a bundle of filaments 11 which extend downwardly so that the free ends of the filaments are in contact with the central region 7 of disc 2. The bundle may contain 5 to 30 filaments of nylon having a diameter of 50 to 200 microns.

In operation disc 2 is rotated. Liquid is fed by gravity through tube 5 and outlet 6 and is transferred to the central region 7 to disc 2 via the bundle of filaments 11. From the central region 7 the liquid is fed by centrifugal force along grooves 9 to the periphery of wall 8 and is discharged from the apex of each tooth as a spray of fine droplets.

As compared with a similar atomiser head without the bundle of filaments and in which the liquid was transferred to the rotating disc as droplets falling from the outlet 6 onto the disc, the transfer using the bundle of filaments was smoother and more regular. Consequently, the supply of liquid to the teeth of the rotating disc was also smoother and more regular giving a regular spray of uniform-sized droplets.

The object is to achieve an even flow by avoiding drop formation at the liquid outlet 6.

The feed onto the disc should not be intermit tent. The lowest feed achievabie with a single outlet fed by gravity is 30 ml per minute, without intermittent feed being obtained owing to droplet formulation. For feeds less than this, it is, therefore, desirable to transfer the liquid according to the present invention.

As can be seen, the material flows down through the normal restricted outlet but instead of feeding in an uncontrolled fashion onto the disc. it is taken along the filament which is in direct contact with the disc, giving a smooth even transfer to the atomiser.

Rotary atomisers of the present invention may be used for any of the uses for which such atomisers are known. Thus they are particularly suitable for applying biocides (e.g.

herbicides, insecticides, fungicides, etc.) or preservatives to arable land or to growing or harvested crops.

Claims (6)

1. A rotary atomiser comprising a dished rotary dispersion member having a substantially planar central region with a peripheral frusto-conical wall inclined outwardly from the central region and means for supplying liquid to the central region, characterised in that the means for supplying liquid is one or more filaments extending between a source of liquid supply and the central region.

2. A rotary atomiser as claimed in claim 1 wherein there are a number of parallel filaments forming a brush.

3. A rotary atomiser as claimed in claim 1 or 2 wherein the filament or filaments are solid and non-porous.

4. A rotary atomiser as claimed in claims 2 or 3 wherein the brush comprises 5 to 30 filaments having a diameter of from 50 to 200 microns.

5. A rotary atomiser as claimed in any of claims 1 to 4 wherein the source of liquid supply is of a size such that the rate of feed of liquid is less than 30 ml per minute.

6. A rotary atomiser as claimed in claim 1 substantially as described with reference to the drawing.