GB2096485A - Air filter apparatus - Google Patents

Abstract

An air filter apparatus for removing particles from air, particularly for removing powdered plastics from air extracted from an electrostatic spray booth, comprises a first unit (10) having an open-ended through duct (13) which carries the particle laden air and a separate duct (14) through which filtered air flows to a suction fan 15 and outlet 17. Detachably connected to the first unit (10) is a second unit (11) having an inlet (22) for receiving air from duct (13) and filter bags (24) whose outlets (25) deliver filtered air to duct (14). The unit 11 can be readily detached from the unit 10 and moved on wheels (21) so that another similar unit (11) can be connected to the unit (10). The apparatus enables the units (11) to be quickly and easily changed when changing from one type and/or colour of powdered material to another and prevents different types and/or colour becoming mixed together and facilitates reclamation of the material removed from the air. Unit (10) carries nozzles (19) by which reverse flow cleaning air is periodically delivered to the filter bags. <IMAGE>

Description

SPECIFICATION Air filter apparatus This invention relates to an air filter apparatus for removing particles from air, and particularly, but not exclusively, air filter apparatus for removing particles of powdered material from air.

In the coating of articles with electrostically charged powdered material, such as powdered plastics material, a considerable proportion of the powder from a spray unit does not remain in contact with the article during application of the powder to the article and the excess powder is extracted with air from the spray booth or cabinet by an air extraction and filter unit and the powder is removed from the air in a filter unit before the cleaned air is exhausted to atmosphere.

In known filter units the powder extracted from the air can be reclaimed for re-use by cleaning the filter unit, which is important due to the high cost of the powdered material, but the cleaning is laborious and time consuming and results in the spray booth or cabinet being out of use for long periods. Also the cleaning of a filter unit is not always satisfactory and particles of the powdered material remain in the unit even after cleaning has taken place. Such a system is satisfactory if the filter unit always receives the same type of powder and the same colour of powder. If a change in the type of powder or colour of powder is made then the filter unit can contain a mixture of two powders of different type and/or colour and the reclaimed powder is unusable.

There is a need for a filter apparatus in which the filter unit can be readily detached from the filter apparatus and replaced by another filter unit.

According to the present invention there is provided an air filter apparatus for removing particles from air, comprising a first unit which includes a first duct for receiving airto be filtered, a second duct for receiving air which has been filtered, a fan for drawing air through said ducts, and a discharge duct through which filtered air is discharged from said first unit, and a second unit which includes an inlet for receiving air from the first duct of said first unit and a filter through which air can flow from said second unit into the second duct of said first unit, said second unit being readily detachable from said first unit so as to be removable therefrom and replaceable by another second unit.

With an air filter apparatus of the present invention the first unit can be fixed in its operative position and the second unit which is portable can be replaced by another second unit whenever a change is made in the type and/or colour of a powder being removed from the air. Therefore the air filter system will comprise one first unit and a plurality of second units, each second unit being associated with one particular type or colour of powder and connected to the first unit whenever that particular type and colour of powder is being used. The powder collected in the second unit is always the same and can be reclaimed for further use and the cleaning does not have to be as thorough as when one filter unit is used for different types and/or colour of powder.

An embodiment of the present invention will now be described by way of an example, with reference to the accompanying drawing in which: Figure 1 is a diagrammatic side elevation, partly in section, of the units of an air filter apparatus according to the present invention, Figure 2 is a diagrammatic perspective view of the units of the air filter apparatus shown in Figure 1, and Figure 3 is a diagrammatic section through the filter pads and compressed air discharge conduits taken along the line 3-3 indicated on Figure 1.

The airfilter apparatus comprises a unit 10 and a plurality of units 11 (only one of which is shown) each of which can be individually connected to the unit 10. The unit 10 comprises a casing 12 which is divided into a duct 13 and a duct 14 which are sealed with respect to one another. The duct 13 has an inlet end 13a and an outlet end 13b. The inlet end 13a of duct 13 is connected to ducting (not shown) to receive air to be cleaned. In this particular embodiment the ducting connected to inlet end 13a receives air from a spray booth or cabinet (not shown) where electrostatically charged particles of a powdered plastics material are sprayed onto a workpiece.

The duct 14 has an inlet 14a and an outlet 14b in which is housed a fan 15 driven by an electric motor 16, the fan 15 discharging into an outlet duct 17 which can exhaust to atmosphere. Extending down wardly across the inlet 14a are a plurality of tubes 18 provided with jet nozzles 19 which are directed away from the inlet 14a. The tubes 18 are connected to a source of compressed air through a control valve (not shown).

Each unit 11 comprises a casing 20 forming a cabinet which is mounted on wheels 21. The front face of the casing 20 has an inlet 22 and an outlet 23.

Mounted in the outlet 23 are a plurality of filter bags 24 which extend horizontally. Each filter bag 24 is carried in support structure and the open end of each bag 24 is connected to metal plates which define a flaired outlet 25. The front face of the casing 19 is provided with seals 26.

Each unit 11 can be attached to the unit 10 with the seals 26 forming an air-tight seal between the units 10 and 11. The units 10 and 11 are held together by manually releasable clamping members 27 provided on the unit 10. When a unit 11 is attached to the unit 10 the nozzles 18 of the tubes 17 lie in the flared outlets 25.

In use of the apparatus the fan 15 pulls air through the apparatus so that air laden with particles of the powdered material is drawn into the duct 13 through its inlet 13a and the particle laden air flows out of the outlet 13b of duct 13 into the interior of the cabinet 20 and it then flows through the walls of the filter bags 24 where the particles are removed and the cleaned air flows out of each filter bag 24 through the flaired outlets 25 and into the duct 14 of unit 10 and is discharged to atmosphere via the outlet duct 17.

Any particles which fall off the filter bags 23 is collected in the bottom of the cabinet 20 of unit 11. In order to prevent the filter bags 24 becoming glogged with particles of the powder compressed air is periodically supplied to the tubes 18 by the control valve and is directed by the nozzles 19 into the interior of the filter bags 24 to remove powder from the exterior of the filter bags 24.

The unit 11 can easily be disconnected from the unit 10 by releasing the clamping members 27 and the unit 11 is then moved away from the unit 10 and can easily be cleaned and serviced. Whilst cleaning and servicing a unit 11 anothersimilar unit can be connected to the unit 10 so that the air filter apparatus can be kept in operation with a minimum of down-time.

Preferably a unit 11 is provided for each type and/or colour of powdered plastics material used in the spray booth or cabinet and therefore a change over from one type and/or colour of powder to a different type and/or colour of powder can be quickly carried out without there being any possibility of mixxing types and/or colours. When a change of type and/or colour of powder is made the duct 13 can easily be cleaned and if there happened to be any particles in the duct 14 they will not flow into the unit 11.

There is thus provided a flexible air filter apparatus which overcomes the problems associated with known air filter apparatus used in the coating of workpieces with electrostactically charged powdered material.

Claims (7)

1. An air filter apparatus for removing particles from air, comprising a first unit which includes a first duct for receiving air to be filtered, a second duct for receiving air which has been filtered, a fan for drawing air through said ducts, and a discharge duct through which filtered air is discharged from said first unit, and a second unit which includes an inlet for receiving air from the first duct of said first unit and a filter through which air can flow from the second unit into the second duct of said first unit, said second unit being readily detachable from the first unit so as to be removable therefrom and replaceable by another second unit.

2. An air filter apparatus as claimed in claim 1, in which the filter of the second unit comprises a plurality of filter bags each of which has an open end connected to a flaired outlet.

3. An air filter apparatus as claimed in claim 2, in which the inlet end of said second duct of said first unit is provided with nozzles through which compressed air can periodically be discharged into the filter bags to remove particles from the outer surfaces of said filter bags.

4. An air filter apparatus as claimed in any preceding claim in which said first unit is provided with manually releasable means for fastening a second unit thereto.

5. An air filter apparatus as claimed in any preceding claim, in which the second unit is provided with wheels on which the unit can be moved.

6. An air filter apparatus as claimed in any preceding claim, including means for sealing the abutting faces of the units.

7. An air filter apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.