GB2304600A

GB2304600A - Method and apparatus for cleaning an air filter

Info

Publication number: GB2304600A
Application number: GB9618389A
Authority: GB
Inventors: Patrick Joseph Butler; Geraldine Ann Butler
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-09-05
Filing date: 1996-09-04
Publication date: 1997-03-26
Anticipated expiration: 2016-09-04
Also published as: GB2304600B; GB9618389D0

Abstract

A method for cleaning a filter (2) comprises rotating the filter (2) in a cabinet (21) about its central axis by rollers (57). Nozzles (63) on air supply pipes (60,61) direct jets of high pressure air radially onto outer surfaces of inner and outer side walls (5,6) of the filter (2) for removing filtered residue from the filter (2). Subsequent to air cleaning the filter (2) is water washed in a similar type cabinet (21) where jets of high pressure water are directed from nozzles (63) at the filter (2). The filter (2) is then soaked in a water/detergent solution and then subsequently rinsed with high pressure rinse water in a similar type cabinet (21). The filter (2) is hand washed, and again rinsed in a similar type cabinet (21). The filter (2) is dried in a warm air environment.

Description

"A method and apparatus for cleaning a filter" The present invention relates to a method for cleaning a filter, and in particular, to a method for cleaning a filter of the type commonly used for filtering air, the invention also relates to an apparatus for use in carrying out the method for cleaning a filter.

Such filters, in general, are of annular cylindrical construction. In general, they comprise an inner cylindrical side wall and an outer cylindrical side wall, both of sheet metal. The inner and outer side walls are joined at their respective opposite ends by end caps also of sheet metal, which define with the inner and outer side walls an annular hollow interior region within which a paper filter is located. The inner side wall defines a central core of the filter, and one of the end caps is of annular shape having a central opening extending therethrough for facilitating axial flow of air through the central core of the filter. The inner and outer side walls are perforated for facilitating air flow radially through the annular hollow interior region, from the central core radially outwardly, or vice versa.The paper filter which is located in the annular hollow interior region is formed from a suitable filter paper type material, depending on the size of particles which are to be filtered from the air as it flows radially through the annular hollow interior region. The filter paper is pleated to form a concertina type shape, and extends completely around the annular hollow interior region, with the leaves of the pleats extending substantially radially through the annular hollow interior region, and the apices of the respective pleats substantially coinciding with the respective inner and outer side walls.

With usage such filters tend to become clogged with dust residue which has been filtered from the air. The rate at which such filters become clogged, largely depends on the environment in which they are located.

However, in general, it has been the practice to dispose of such filters when they become clogged, and replace them by a new filter. Replacing such filters after just one use, is rather an expensive exercise, and obviously, leads to a relatively high usage rate of filters. It would thus be desirable if such filters could be cleaned for reuse, at least once, and indeed, for reuse many times before the filter fails. Failure of such filters generally results from a hole forming in the filter paper, or the inner or outer side walls or end caps corroding. To date no satisfactory method for cleaning such filters is known. Additionally, there is no satisfactory apparatus for cleaning such filters.

There is therefore a need for a method and apparatus for cleaning such filters, so that the filters can be reused at least once, and preferably, many times.

The present invention is directed towards providing such a method and apparatus.

According to the invention there is provided a method for cleaning a filter of the type hereinbefore described which is of substantially annular cylindrical construction having an inner cylindrical side wall defining a core of the filter, and an outer cylindrical side wall radially spaced apart from the inner side wall, the side walls being joined by respective end caps at their respective opposite ends and the respective end caps and inner and outer side walls defining an annular hollow interior region for housing a paper filter, a central opening being formed in one of the end caps for providing access to the central core, the method comprising in the following order the steps of:: subjecting the filter to air cleaning by directing a high pressure air jet at the filter for blowing filtered residue from the filter, subjecting the filter to a first water wash by directing a jet of high pressure water at the filter for removing filtered residue remaining on the filter after the air cleaning, soaking the filter in a solution of water and detergent for cleaning the filter, subjecting the filter to a first water rinse by directing a jet of high pressure water at the filter for removing any residue of the solution of water and detergent remaining on the filter after soaking, and for removing filtered residue not already removed from the filter, and subjecting the filter to drying for drying thereof.

In one aspect of the invention the filter is subjected to air cleaning until substantially all loose filtered residue on the filter has been removed. In general, subjecting the filter to the jet of high pressure air during air cleaning for a time period in the range of 30 seconds to 180 seconds should be sufficient, and more commonly, a time period in the range of 50 seconds to 180 seconds is sufficient for removing substantially all the loose filtered residue.

In one aspect of the invention the filter is subjected to the first water wash until substantially no more filtered residue can be removed from the filter.

Preferably, the stage at which no more filtered residue can be removed from the filter during the first water wash is determined by observing waste water from the first water wash, and the stage at which no more filtered residue can be removed from the filter is when the waste water from the first water wash runs clear.

In one aspect of the invention the filter is subjected to the first water wash for a time period in the range of 5 minutes to 30 minutes.

In another aspect of the invention the filter is subjected to soaking in the solution of water and detergent for a time period in the range of 5 hours to 30 hours, and preferably, for a time period in the range of 12 hours to 15 hours.

In another aspect of the invention the filter is subjected to the first water rinse until the waste water from rinsing commences to run clear.

Preferably, the filter is subjected to the first water rinse until substantially all the water and detergent solution has been removed from the filter.

In another aspect of the invention the filter is dried in a drying environment to which relatively dry air is delivered. Preferably, the filter is dried in an enclosed area having a controlled environment in which the drying air is being continuously changed. In one aspect of the invention the filter is subjected to drying for a time period of at least 10 hours, and preferably, for a time period of at least 24 hours.

Preferably, the drying air is at a temperature in the range of 1200F to 1700F, and ideally, the drying air temperature is approximately 1500F.

In another aspect of the invention the filter is subjected to a second water wash after the first water rinse, the second water wash being a manual wash whereby the filter is subjected to a jet of high pressure water from a high pressure water nozzle which is held by hand and directed by hand at the filter.

Preferably, the second water wash is provided for cleaning the outer surfaces of the side and end walls of the filter.

In a further aspect of the invention the filter is subjected to a second water rinse after the second water wash by subjecting the filter to a high pressure jet of water. Preferably, the filter is subjected to the second water rinse until waste water from the second water rinse runs clear.

In a further aspect of the invention the filter is checked for holes in the filter paper. In one aspect of the invention the check for holes in the filter paper is carried out by a visual inspection, and in another aspect of the invention the check for holes in the filter paper is carried out by determining the ability of the filter to retain air in the core thereof when immersed in water.

In one aspect of the invention the entire outer surfaces of the inner and outer side walls of the filter are subjected to air of the jets of high pressure air during air cleaning.

In another aspect of the invention the entire outer surfaces of the inner and outer side walls of the filter are subjected to water of the jets of high pressure water during the first and second water washes.

In one aspect of the invention the entire outer surfaces of the inner and outer side walls of the filter are subjected to water of the jets of high pressure water during the first and second water rinse.

Preferably, a plurality of jets of high pressure air are directed towards the filter during air cleaning, and preferably, the jets of high pressure air are provided from respective nozzles mounted at spaced apart locations along an elongated air supply pipe supplying high pressure air to the respective nozzles.

In one aspect of the invention a pair of spaced apart parallel air supply pipes are provided, and ideally, a plurality of spaced apart nozzles for providing jets of high pressure air are located on each air supply pipe.

Preferably, the filter is located relative to the air supply pipes with the axis of the filter extending substantially parallel to the air supply pipes.

Preferably, one of the air supply pipes extends into the core of the filter.

Preferably, a plurality of jets of high pressure water are directed towards the filter during the first water wash, and preferably, the jets of high pressure water are provided from respective nozzles mounted at spaced apart locations along an elongated water supply pipe supplying high pressure water to the respective nozzles.

In one aspect of the invention a pair of spaced apart parallel water supply pipes are provided, and ideally, a plurality of spaced apart nozzles for providing jets of high pressure water are located on each water supply pipe. Preferably, the filter is located relative to the water supply pipes with the axis of the filter extending substantially parallel to the water supply pipe. Preferably, one of the water supply pipes extends into the core of the filter.

Preferably, a plurality of jets of high pressure water are directed towards the filter during the first and second water rinses, and preferably, the jets of high pressure water are provided from respective nozzles mounted at spaced apart locations along an elongated rinse water supply pipe supplying high pressure water to the respective nozzles.

In one aspect of the invention a pair of spaced apart parallel rinse water supply pipes are provided, and ideally, a plurality of spaced apart nozzles for providing jets of high pressure water are located on each rinse water supply pipe. Preferably, the filter is located relative to the rinse water supply pipes with the axis of the filter extending substantially parallel to the rinse water supply pipe. Preferably, one of the rinse water supply pipes extends into the core of the filter.

In a further aspect of the invention the filter is rotated relative to the respective air and water supply pipes during air cleaning, the first and second water rinses and the first water wash, and preferably, is rotated about an axis extending parallel to the respective air and water supply pipes. Advantageously, the filter is rotated about its own geometrical longitudinal central axis. Ideally, the filter is supported on a pair of spaced apart rollers, at least one of the rollers being driven for rotating the filter.Ideally, one of the air and water supply pipes substantially coincides with the central axis of the central core of the filter so that jets of high pressure air and water from the respective nozzles are directed towards the inner side wall of the filter, and preferably, the other of the two air and water supply pipes is located externally of the filter and at a position radially spaced apart from the outer side wall of the filter.

Ideally, the respective air supply pipes are arranged so that the nozzles carried thereon direct the jets of air in a substantially similar direction.

Ideally, the respective water supply pipes are arranged so that the nozzles carried thereon direct the jets of water in a substantially similar direction.

Additionally the invention provides apparatus for cleaning a filter of the type hereinbefore described, the apparatus comprising a housing defining a main hollow interior region for housing the filter during cleaning, a support means located in the main hollow interior region for supporting and rotating the filter, a pair of elongated supply pipes, each supply pipe having a plurality of nozzles carried thereon and located at spaced apart intervals for directing respective jets of air or water towards outer surfaces of the inner and outer side walls of the filter, the supply pipes being spaced apart from each other and extending parallel to each other and parallel to the axis of rotation of the filter by the support means so that when the filter is supported on the support means one of the supply pipes extends into the core of the filter and directs jets of air or water radially at the outer surface of the inner side wall, and the other supply pipe extends externally of the filter with the nozzles located at a position spaced apart from the outer surface of the outer side wall for directing jets of air or water radially at the outer surface of the outer side wall, and preferably, when the support means rotates the filter, the nozzles mounted on the respective supply pipes direct air or water along the longitudinal length of the outer surface of the inner and outer side walls progressively in a circumferential direction as the filter is being rotated.

Preferably, the support means comprises a pair of spaced apart support rollers extending parallel to each other for supporting the filter with the longitudinal central axis of the filter extending parallel to the rollers, at least one of the rollers being rotated for rotating the filter about its central longitudinal axis.

The invention will be more clearly understood from the following description of an embodiment thereof which is given by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a typical filter to be cleaned using the method and apparatus according to the invention, Fig. 2 is another perspective view of the filter of Fig. 1, Fig. 3 is a block representation of the method according to the invention for cleaning the filter of Figs. 1 and 2, Fig. 4 is a partly cutaway perspective view of a cabinet of apparatus according to the invention for use in the method according to the invention for cleaning the filter of Figs. 1 and 2, Fig. 5 is a cross-sectional side elevational view of the cabinet of Fig. 4, Fig. 6 is a cross-sectional plan view of the cabinet of Fig. 4, Fig. 7 is a cross-sectional end elevational view on the line VII-VII of Fig. 5 of the cabinet of Fig. 4, and Fig. 8 is a cross-sectional elevational view of a container of apparatus also according to the invention for carrying out the method according to the invention for cleaning the filter of Figs. 1 and 2.

Referring to the drawings there is illustrated apparatus according to the invention indicated generally by the reference numeral 1 for carrying out a method, also according to the invention for cleaning filters 2. The filters 2 are of the type which are commonly used for filtering air, typically, in dust laden environments. Before describing the apparatus 1 and the method for cleaning the filters 2, a typical filter 2 will first be described with reference to Figs. 1 and 2.

The filters 2 may be of various shapes and sizes, however, each filter should be of annular construction having a central axis 3. The filters 2 comprise an inner cylindrical side wall 5 and a spaced apart outer cylindrical side wall 6 both of perforated sheet metal material having openings 4, and both being co-axial with the central axis 3. End caps 7 and 8 both of sheet metal material close the ends of the inner and outer side walls 5 and 6, and define with the inner and outer side walls 5 and 6 an annular hollow interior region 9. A paper filter 10 is located in the annular hollow interior region 9 and extends the axial length of the hollow interior region 9 and circumferentially through the hollow interior region 9. The paper filter 10 is of the appropriate type for filtering particles depending on the size of particles which are to be filtered from the air.The paper of the filter 10 is pleated into a concertina type form having a plurality of leaves 11 extending radially between respective apices 12 and 14 which are located adjacent the inner and outer side walls 5 and 6, respectively. The end cap 7 is of annular shape having a central opening 15 for communicating with a central core 17 of the filter 2 defined by the inner side wall 5 for accommodating air into the central core 17. The end cap 8 may or may not close the central core 17 at one end thereof, although, in general, the end cap 8 does close the central core 17 so that air entering axially into the central core 17 of the filter 2 through the opening 15 is directed radially through the inner and outer side walls 5 and 6 and vice versa.In this particular filter 2 a hole 18 is provided in the end cap 8 for accommodating a screw which seal ably secures the filter in a filter housing (not shown) of a duct (also not shown) of apparatus in which the air passing therethrough is to be filtered by the filter 2.

Turning now to the apparatus 1 and the method for cleaning the filter 2, before describing the apparatus 1 in detail, a broad outline of the method employed in cleaning the filter 2 using the apparatus 1 will first be described with reference to Fig. 3 which illustrates the method according to the invention in block representation. Each filter 2 is initially subjected to an air clean, namely, block 20 which requires directing jets of high pressure air at the outer surfaces of the inner and outer side walls 5 and 6 for blowing loose filtered residue from the filter 2, both from the side walls 5 and 6 and the paper filter 10.

The filter 2 is placed in a cabinet 21 which will be described in detail below within which the jets of high pressure air are directed at the filter 2. The filter is subjected to the jets of high pressure air which are radially directed at the respective side wall 5 and 6 until substantially all loose particles of filtered residue have been dislodged from the filter 2, including the paper filter 10. Typically this may require from 50 seconds to 300 seconds, but more commonly 50 seconds to 180 seconds.

On the loose particles of filtered residue having been removed from the filter 2, the filter 2 is then subjected to a first water wash, namely, block 24. The first water wash comprises directing a plurality of jets of high pressure water radially at the outer surfaces of the inner and outer side walls 5 and 6.

The first water wash is carried out in a cabinet which is similar to the cabinet 21 as will be described below. Each filter 2 is subjected to the first water wash 24 until no more particles of filtered residue can be removed from the filter 2. This is determined by inspecting waste water from the first water wash, and on the waste water running clear the first water wash is terminated. Typically, depending on the state of the filter, the first water wash may last for a time period of anywhere between 1 minute and 30 minutes, but more typically, will last for a time period in the range of 1 minute to 6 minutes.

On termination of the first water wash, each filter 2 is then subjected to soaking in a solution of water and detergent, namely, block 26 for removing further dirt from the filter, and in particular for cleaning the paper filter 10. The solution of water and detergent is contained in a container (not shown), and each filter 2 is soaked by immersing the filter 2 in the solution of water and detergent for a period in the range of 12 to 15 hours.The solution of water and detergent comprises a solution of water and a detergent, in this case, a non-foaming biodegradable detergent, which are mixed in appropriate proportions depending on the strength of the detergent, typical proportions being: water 10 parts by volume detergent 1 part by volume After each filter has been subjected to soaking in the solution of water and detergent, the filter 2 is subjected to a first visual inspection, namely, block 27 to ascertain if the paper filter 10 is adequately cleaned. The paper filter 10 is inspected through the openings 4 in the inner and outer side walls 5 and 6, respectively. If the paper filter 10 still looks dirty, the filter 2 is returned for further soaking, and so on until the paper filter 10 visually appears to be clean.

On each filter 2 passing the first inspection of block 27, the filter 2 is subjected to a first water rinse which is represented by block 28. During the first water rinse the filter 2 is subjected to a plurality of jets of high pressure water which are directed radially at the outer surfaces of the inner and outer side walls 5 and 6 for rinsing any residue of the solution of water and detergent from the filter 2, and in particular, from the paper filter 10. Any loose particles of filtered residue still remaining on the filter 2 are also removed during the first water rinse.

The first water rinse is carried out in a cabinet which is similar to the cabinet 21 which is described in detail below. The filter 2 is continuously subjected to the first water rinse until substantially all residue of the solution of water and detergent has been removed from the filter. This is determined by visual inspection of the waste water from the first water rinse, and on the waste water from the first water rinse running clear, the first water rinse is terminated.

On completion of the first water rinse of block 28 the filter 2 is subjected to a second water wash, namely, block 32 which in this case, is a manual type wash.

The filter 2 is placed in a container 33, see Fig. 8, which contains water. A nozzle (not shown) from which a single jet of high pressure water issues is located at the end of a hand held lance (also not shown). The lance is held by an operator and the nozzle is directed at the filter 2 for directing the jet of high pressure water at the filter. By holding the filter 2 in one hand and the lance in the other, the filter may be oriented and rotated by hand and the lance may be moved for progressively subjecting the entire outer surfaces of the inner and outer side walls 5 and 6 to the jet of high pressure water. The filter 2 is also oriented relative to the nozzle for directing the jet of high pressure water during the second water wash at the respective end caps 7 and 8 for cleaning the end caps 7 and 8.The filter 2 is continuously inspected by the operator during the second water wash, and the second water wash is terminated on the outer surfaces of the inner and outer side walls and the end caps 7 and 8 being cleaned to a desired standard.

While in the container 33 in which the second water wash is carried out, the filter 2 is subjected to a second inspection for checking if the paper filter 10 is holed. This second inspection is represented by block 36 and is carried out by immersing each filter 2 in water in the container 33 as illustrated in Fig. 8.

However, when immersing the filter 2 in the water in the container 33 air is entrapped in the central core 17 of the filter 2. This is achieved by entering the filter 2 into the water in the container 33 with the end cap 7 facing downwardly and the central axis 3 of the filter 2 extending substantially vertically. If the end cap 8 is provided with a hole 18, the hole 18 is sealed by the operator placing a thumb or finger over the hole 18, or by other suitable sealing means.

The filter with the central axis 3 extending vertically is then lowered into the water until the filter 2 is substantially fully immersed in the water. With the filter 2 with its central axis 3 inclined to the vertical the filter 2 is rotated about its central axis 3 in the water in the container 33, and the water is inspected for air bubbles escaping from the filter 2 which would indicate a hole in the paper filter 10.

Should a hole be detected in the paper filter 10, the filter 2 is scrapped.

Those filters 2 which pass the second inspection of block 36 are then subjected to a second water rinse which is represented by block 38 for finally rinsing any remaining residue of the solution of water and detergent and any remaining particles of filtered residue from the filter. The second water rinse is carried out in a cabinet which is similar to the cabinet 21 which will be described below. During the second water rinse each filter 2 is subjected to a plurality of jets of high pressure water which are directed radially towards the outer surface of the inner and outer side wall 5 and 6, respectively, for removing the respective residues from the filter 2, including the paper filter 10.Each filter 2 is subjected to the second water rinse until the waste water from the second water rinse runs clear and shows no traces of the solution of water and detergent and particles of filtered residue.

The filters 2 are then transferred into a drying oven (not shown) the environment of which is controlled for drying, namely, block 40. Air in the oven is heated to a temperature of approximately 1500F, and the air is continuously changed. In general, drying takes approximately 24 hours.

On being adequately dried each filter 2 is removed from the drying oven, and is subjected to a third inspection, namely, block 41 which is a visual inspection for holes in the paper filter 10. To carry out the third inspection a light bulb is placed in the central core 17 of the filter 2, which is then rotated about the bulb. By visually inspecting the filter 2 along the outer side wall 6 a change in the light intensity seen through the paper filter 10 indicates a hole in the paper filter 2.

Turning now to Figs. 4 to 7 the cabinet 21 within which the filters 2 are subjected to the air clean, namely, block 20, will now be described. The cabinets (not shown) within which the first water wash and the first and second water rinses are carried out, as discussed above are similar to the cabinet 21, and will be briefly discussed below. The cabinet 21 comprises a framework 45, which supports a base panel 46 secured thereto. A rear panel 47 and a side panel 48 are also secured to the framework 45. A front panel 49 is hinged to the framework 45 by a hinge 50 as is a side panel 51 also hinged to the framework 45 by a hinge 52.

A top panel 53 extends across the top of the framework 45. The base panel 46, rear panel 47, side panel 48, front panel 49, side panel 51 and top panel together define a main hollow interior region 54 within which each filter 2 is subjected to the jets of high pressure air.

A support means for supporting each filter 2 in the hollow interior region 54 of the cabinet 21 comprises a pair of roller shafts 55 which are rotatably carried in bearings 56 which are carried in suitable mountings (not shown) mounted on the framework 45. The roller shafts 55 extend parallel to and are spaced apart from each other. Rollers 57 are mounted fast on the shafts 55 for supporting each filter 2 thereon at spaced apart locations with the central axis 3 of the filter 2 extending parallel to the shafts 55. A motor 58 mounted on a platform 62 which is supported on the framework 45 drives one of the shafts 55, and a chain and sprocket drive 59 transfers drive from the driven shaft 55 to the other shaft 55 so that both shafts rotate at the same speed, and in the same direction for rotating the filter 2 about its central axis 3.

A pair of supply pipes, namely, a lower supply pipe 60 and an upper supply pipe 61 extend into the main hollow interior region 54 of the cabinet 21 for delivering jets of high pressure air to the filters 2. The supply pipes 60 and 61 are secured to the side panel 48 by mounting flanges 64. Each supply pipe 60 and 61 is provided with a plurality of spaced apart nozzles 63 which direct jets of air radially at the outer surfaces of the inner and outer side walls 5 and 6, respectively of the filters 20. The lower supply pipe 60 is located relative to the shafts 55 so that the lower supply pipe 60 extends into the central core 17 of the filter 2 adjacent, but not necessarily coinciding with the central axis 3 of the filter 2. Whether the central axis 3 of the filter 2 coincides with the lower supply pipe 60 will depend on the outer diameter of the filter 2. However, in general, the central axis of each filter 2 and the lower supply pipe 60 should lie in the same vertical axis. The nozzles 63 on the lower supply pipe 60 are directed radially downwardly for directing the jets of high pressure air radially downwardly towards the outer surface of the inner side wall 5, so that the jets impinge perpendicularly on the outer surface of the inner side wall 5. The upper supply pipe 61 is located above the filter 2, and is arranged so that the nozzles 63 are directed radially downwardly towards the filter 2 so that jets of high pressure air from the nozzle 63 are directed radially downwardly towards the outer surface of the outer side wall 6 so that the jets of high pressure air impinge substantially perpendicularly on the outer surface of the side wall 6.The jets of high pressure air are accommodated through the openings 4 in the inner and outer side walls 5 and 6 for blowing loose filtered residue from the paper filter 10 of the filter 2, and needless to say, the jets of high pressure air from the nozzle 63 also blow any loose particles of filtered residue from both the inner and outer surfaces of the inner and outer side walls 5 and 6. Air from a high pressure source (not shown) but typically a compressor, in this embodiment of the invention at approximately 1001bs per square inch is supplied to the lower and upper supply pipes 60 and 61 for delivery through the nozzles 63.

Air and particles of filtered residue blown from the filter 2 are extracted from the main hollow interior region 54 during the air cleaning operation through an extraction outlet 65 extending from the top panel 53.

In use, with the front panel 49 and the side panel 51 hinged open as illustrated in Fig. 4, the filter 2 is placed on the rollers 57 of the roller shafts 55 with the lower supply pipe 60 extending into the central core 17 of the filter 2. This is achieved by entering the filter 2 with its end cap 7 first into the hollow interior region 54, through the side of the cabinet 21, which is normally closed by the side panel 51 and with the central axis 3 of the filter 2 substantially horizontal. The filter 2 is entered into the main hollow interior region 54 until the lower supply pipe 60 just abuts the end cap 8, so that the lower supply pipe 60 extends the full length of the central core 17 of the filter 2, the lower supply pipe 60 being accommodated into the central core 17 through the opening 15 in the end cap 7.The filter 2 is then placed on the rollers 57 where it is supported thereon.

The front panel 49 and the side panel 51 are hinged into the closed position to close the hollow interior region 54, and high pressure air at 1001bs per square inch is supplied to the lower and upper supply pipes 60 and 61, respectively. The motor 58 is activated for driving the two shafts 55 for in turn rotating the filter 2 in the direction of the arrow A about its central axis 3. As the filter 2 is being rotated about its central axis 3, the outer surfaces of the inner and outer side walls 5 and 6, respectively, are progressively subjected to the jets of high pressure air exiting from the nozzles 63. The filter 2 is continuously rotated by the rollers 57, and high pressure air is continuously supplied to the lower and upper supply pipe 60 and 61, respectively, until substantially all loose particles of filtered residue have been blown from the filter 2.

The cabinets for carrying out the first wash and the first and second rinses are substantially similar to the cabinet 21 just described. The main difference between these cabinets and the cabinet 21 is that instead of being supplied with high pressure air the lower and upper supply pipes 60 and 61 are supplied with high pressure water at approximately 80lbs per square inch, which is delivered through the nozzles 63 and impinges substantially perpendicularly on the outer surface of the inner and outer side walls 5 and 6. A drain outlet 67 is provided from the base panel 46 for waste water. The waste water delivered through the drain outlet 67 is passed through an inspection glass for facilitating visual inspection of the waste water for determining when the first water wash and first and second water rinses have been completed. In practice, the cabinet 21 for carrying out the air cleaning is provided with an extraction outlet 65 only, and the cabinets (not shown) for carrying out the first water wash and the first and second water rinses are provided with a drain outlet 67 only.

In this embodiment of the invention the motor rotates the roller shafts in the respective cabinets at a similar speeds of approximately 40 revs per minute.

Claims

1. A method for cleaning a filter of the type hereinbefore described which is of substantially annular cylindrical construction having an inner cylindrical side wall defining a core of the filter, and an outer cylindrical side wall radially spaced apart from the inner side wall, the side walls being joined by respective end caps at their respective opposite ends, and the respective end caps and inner and outer side walls defining an annular hollow interior region for housing a paper filter, a central opening being formed in one of the end caps for providing access to the central core, the method comprising in the following order the steps of:: subjecting the filter to air cleaning by directing a high pressure air jet at the filter for blowing filtered residue from the filter, subjecting the filter to a first water wash by directing a jet of high pressure water at the filter for removing filtered residue remaining on the filter after the air cleaning, soaking the filter in a solution of water and detergent for cleaning the filter, subjecting the filter to a first water rinse by directing a jet of high pressure water at the filter for removing any residue of the solution of water and detergent remaining on the filter after soaking, and for removing filtered residue not already removed from the filter, and subjecting the filter to drying for drying thereof.

2. A method as claimed in Claim 1 in which the filter is subjected to air cleaning until substantially all loose filtered residue on the filter has been removed.

3. A method as claimed in Claim 1 or 2 in which the filter is subjected to the jet of high pressure air during air cleaning for a time period in the range of 30 seconds to 180.

4. A method as claimed in Claim 3 in which the filter is subjected to the jet of high pressure air during air cleaning for a time period in the range of 50 seconds to 180 seconds.

5. A method as claimed in any preceding claim in which the filter is subjected to the first water wash until substantially no more filtered residue can be removed from the filter.

6. A method as claimed in any preceding claim in which waste water from the first water wash is observed for determining the stage at which substantially no more filtered residue can be removed from the filter.

7. A method as claimed in any preceding claim in which the filter is subjected to the first water wash for a time period in the range of 5 minutes to 30 minutes.

8. A method as claimed in any preceding claim in which the filter is subjected to soaking in the solution of water and detergent for a time period in the range of 5 hours to 30 hours.

9. A method as claimed in Claim 8 in which the filter is subjected to soaking in the solution of water and detergent for a time period in the range of 12 hours to 15 hours.

10. A method as claimed in any preceding claim in which the filter is subjected to the first water rinse until substantially all the water and detergent solution has been removed from the filter.

11. A method as claimed in any preceding claim in which waste water from the first water rinse is observed for determining when the first water rinse may be terminated.

12. A method as claimed in any preceding claim in which the filter is located in a drying environment during drying, and relatively dry air is delivered to the drying environment.

13. A method as claimed in any preceding claim in which the drying environment is a controlled environment located in an enclosed area, and drying air is continuously changed in the enclosed area during drying.

14. A method as claimed in Claim 12 or 13 in which the drying air delivered to the drying environment is at a temperature in the range of 1200F to 1700F.

15. A method as claimed in Claim 14 in which the drying air temperature is approximately 1500F.

16. A method as claimed in any preceding claim in which the filter is subjected to drying for a time period of at least 10 hours.

17. A method as claimed in Claim 16 in which the filter is subjected to drying for a time period of at least 24 hours.

18. A method as claimed in any preceding claim in which the filter is subjected to a second water wash after the first water rinse, the second water wash being a manual wash whereby the filter is subjected to a jet of high pressure water from a high pressure water nozzle which is held by hand and directed by hand at the filter.

19. A method as claimed in Claim 18 in which the second water wash is provided for cleaning the outer surfaces of the side and end walls of the filter.

20. A method as claimed in Claim 18 or 19 in which the filter is subjected to a second water rinse after the second water wash by subjecting the filter to a high pressure jet of water.

21. A method as claimed in Claim 20 in which waste water from the second water rinse is observed for determining when the second water rinse may be terminated.

22. A method as claimed in any preceding claim in which the filter is checked for holes in the filter paper.

23. A method as claimed in Claim 22 in which the check for holes in the filter paper is carried out by determining the ability of the filter to retain air in the core thereof when immersed in water.

24. A method as claimed in Claim 22 or 23 in which the check for holes in the filter paper is carried out by a visual inspection.

25. A method as claimed in any preceding claim in which the entire outer surfaces of the inner and outer side walls of the filter are subjected to air of a plurality of jets of the high pressure air during air cleaning.

26. A method as claimed in Claim 25 in which the jets of high pressure air are provided from respective nozzles mounted at spaced apart locations along an elongated air supply pipe supplying high pressure air to the respective nozzles.

27. A method as claimed in Claim 26 in which a pair of spaced apart parallel air supply pipes are provided, each air supply pipe having a plurality of the spaced apart nozzles for providing jets of high pressure air.

28. A method as claimed in Claim 27 in which the filter is located relative to the air supply pipes with the axis of the filter extending substantially parallel to the air supply pipes.

29. A method as claimed in Claim 27 or 28 in which one of the air supply pipes extends into the core of the filter for directing the jets of air at the inner side wall, and the other air supply pipe is located externally of the filter for diverting the jets of air at the outer side wall.

30. A method as claimed in any of Claims 27 to 29 in which the respective air supply pipes are arranged so that the nozzles carried thereon direct the jets of air in a substantially similar direction.

31. A method as claimed in any preceding claim in which each jet of air is directed in a substantially radial direction towards the adjacent inner or outer side wall.

32. A method as claimed in any preceding claim in which the entire outer surfaces of the inner and outer side walls of the filter are subjected to water of a plurality of jets of the high pressure water during the first and second water washes.

33. A method as claimed in Claim 32 in which the jets of high pressure water are provided from respective nozzles mounted at spaced apart locations along an elongated water supply pipe supplying high pressure water to the respective nozzles.

34. A method as claimed in Claim 33 in which a pair of spaced apart parallel water supply pipes are provided, each water supply pipe having a plurality of the spaced apart nozzles for providing jets of high pressure water.

35. A method as claimed in Claim 34 in which the filter is located relative to the water supply pipes with the axis of the filter extending substantially parallel to the water supply pipes.

36. A method as claimed in Claim 34 or 35 in which one of the water supply pipes extends into the core of the filter for directing the jets of water at the inner side wall, and the other water supply pipe is located externally of the filter for directing the jets of water at the outer side wall.

37. A method as claimed in any of Claims 34 to 36 in which the respective water supply pipes are arranged so that the nozzles carried thereon direct the jets of water in a substantially similar direction.

38. A method as claimed in any preceding claim in which each jet of water is directed in a substantially radial direction towards the adjacent inner or outer side wall.

39. A method as claimed in any preceding claim in which the entire outer surfaces of the inner and outer side walls of the filter are subjected to water of a plurality of jets of the high pressure water during the first and second water rinses.

40. A method as claimed in Claim 39 in which the jets of high pressure rinse water are provided from respective nozzles mounted at spaced apart locations along an elongated rinse water supply pipe supplying high pressure water to the respective nozzles.

41. A method as claimed in Claim 40 in which a pair of spaced apart parallel rinse water supply pipes are provided, each rinse water supply pipe having a plurality of the spaced apart nozzles for providing jets of high pressure rinse water.

42. A method as claimed in Claim 41 in which the filter is located relative to the rinse water supply pipes with the axis of the filter extending substantially parallel to the rinse water supply pipe.

43. A method as claimed in Claim 41 or 42 in which one of the rinse water supply pipes extends into the core of the filter for directing the jets of rinse water at the inner side wall, and the other rinse water supply pipe is located externally of the filter for directing the jets of rinse water at the outer side wall.

44. A method as claimed in any of Claims 41 to 43 in which the respective rinse water supply pipes are arranged so that the nozzles carried thereon direct the jets of rinse water in a substantially similar direction.

45. A method as claimed in any preceding claim in which each jet of rinse water is directed in a substantially radial direction towards the adjacent inner or outer side wall.

46. A method as claimed in any preceding claim in which the filter is rotated relative to the respective air and water supply pipes during air cleaning, the first and second water rinses and the first water wash.

47. A method as claimed in Claim 46 in which the filter is rotated about an axis extending parallel to the respective air and water supply pipes.

48. A method as claimed in Claim 46 or 47 in which the filter is rotated about its own geometrical longitudinal central axis.

49. A method as claimed in any of Claims 46 to 48 in which the filter is supported on a pair of spaced apart rollers, at least one of the rollers being driven for rotating the filter.

50. A method for cleaning a filter of the type hereinbefore described, the method being substantially as described herein with reference to and as illustrated in the accompanying drawings.

51. Apparatus for cleaning a filter of the type hereinbefore described, the apparatus comprising a housing defining a main hollow interior region for housing the filter during cleaning, a support means located in the main hollow interior region for supporting and rotating the filter, a pair of elongated supply pipes, each supply pipe having a plurality of nozzles carried thereon and located at spaced apart intervals for directing respective jets of air or water towards outer surfaces of inner and outer side walls of the filter, the supply pipes being spaced apart and extending parallel to each other and parallel to the axis of rotation of the filter by the support means so that when the filter is supported on the support means one of the supply pipes extends into the core of the filter and directs jets of air or water radially at the outer surface of the inner side wall, and the other supply pipe extends externally of the filter with the nozzles located at a position spaced apart from the outer surface of the outer side wall for directing jets of air or water radially at the outer surface of the outer side wall.

52. Apparatus as claimed in Claim 51 in which the nozzles are mounted on the respective supply pipes for directing air or water along the longitudinal length of the outer surface of the inner and outer side walls progressively in a circumferential direction as the filter is being rotated.

53. Apparatus as claimed in Claim 51 or 52 in which the support means comprises a pair of spaced apart support rollers extending parallel to each other for supporting the filter with the longitudinal central axis of the filter extending parallel to the rollers, at least one of the rollers being rotated for rotating the filter about its central longitudinal axis.

54. Apparatus for cleaning a filter of the type hereinbefore described, the apparatus being substantially as described herein with reference to and as illustrated in the accompanying drawings.