GB1583776A - Oil-bath air filters - Google Patents

Description

(54) OIL-BATH AIR FILTERS (71) We, DELBAG-LUFTFILTER GmbH, a Joint Stock Company organised under the laws of Germany (Fed. Rep.) of Schweidnitzer Strasse 11-16, 1 Berlin 31, Germany (Fed.

Rep.) do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- The invention relates to oil-bath air filters for cleaning air containing dust with a variable rate of air flow, in which a centrifuging device or device imparting a spin is provided, which guides the dust-laden air stream to be cleaned and centrifuged through an oil drip bath or oil-bath reservoir and after wetting and intensive contact with a filtering element, discharges a purified air stream.

Oil-bath air filters of this type are necessary in order to provide the best possible cleaning of the intake air of internal combustion engines and compressors or the exhaust air of sand blasting installations or cast iron processing installations or similar installations with considerable dust contamination.

It is known to use single or multi-stage oilbath air filters or inertial dust separators, which have an adequate effect for this purpose, as has been shown, to obtain dust-free exhaust air or intake air in the areas of application mentioned by way of example. It is also known that almost all oil-bath air filters of this type operate according to the same or a similar principle.

For this, either centrifugal devices and oilbaths are used as wetting or precipitation devices in conjunction with filtering layers of wire cloth of the additional oil circulating pumps are used, which supply predetermined quantities of wetting agent in the circulating system to the filtering layers in the housings, in order to obtain, in this way, effective purification of the dust-laden air with simultaneous rinsing of the filtering layers.

With air filters or dust separators of this type, it is generally necessary that the degree of dust removal does not deteriorate substantially even with smaller quantities of air. This is particularly true for the intake air of internal combustion engines for example used in heavily dust-laden areas.

In this respect, the state of the art contains a series of constructions by way of example US Patent Specification 1 926 841, German Auslegeschrift 1 295 520, German Auslegeschrift 1 242 568, German Auslegeschrift 1 227 428, German Patent 1 086 946, German Auslegeschrift 1 421 329, German Auslegeschrift 1 298 507, German Patent 1 671 402, US Patent Specification 813 327, German Offenlegungsschrift 2 131 657, US Patent Specification 1 926 841.

Criticism of the present state of the art is directed primarily to the fact that in emergency situations, most of these air filters are not able to clean a fraction of the throughput of air over a longer period of time, with the same effect as when under full load.

This is necessary for example for the intake air of diesel power stations, which are operated with a continuously alternating load, for supplying generating sets or pumping stations on pipe lines. However, this necessity also exists in various other suction devices used industrially, particularly if, for various reasons, a predetermined partial load must always be maintained, whereas the peak load is only required temporarily.

A further complaint is that in the case of most oil-bath filters, before coming into contact with or reaching the actual filtering element, the dust-laden air is firstly passed deep into the liquid of the oil-bath, which amounts to an inevitable shift in the level of liquid and in the case of oil which has become thick and is no longer able to flow, as a result of dust deposits, can be a problem for the wetting and rinsing of the filtering element on account of the danger of blocking.

However, an essential point is the wetting of the filtering element, which in many constructions is either inadequate or excessive, but whose controlled function is necessary for removing the dust and for cleaning or for rinsing the filter element.

If the wetting of the filtering element is excessive, the wetting oil mixed with dust is drawn through onto the clean air side and causes damage at this point.

If the wetting of the filtering element by the oil is inadequate, then the separating principle, which is based on the inertial and adhesion effect, can be compromised owing to the absence of an adequate capillary action. In this case, the filter no longer cleans itself automatically and the degree of dust removal is low. The result of the latter is generally rapidly increasing clogging of the filtering element until it is completely impermeable to air with the resulting damage.

From this account, it is clear that a regulating mechanism is lacking, which ensures adequate wetting, rinsing and elimination of dust at any time, irrespective of the throughput of air, without in any way jeopardising the required high degree of dust removal.

A further drawback of the known oil-bath air filters consists in that due to the absence of preliminary coarse dust separators, in the case of excessive contamination with sand and dust, such as for example in sand storms or in the case of the sudden discharge of industrial accumulations of dust, the oil-baths and filtering elements enlarge rapidly and lead to interruption of the air supply for the machines. For diesel power stations, whose output is required continuously, such a state of affairs would be intolerable unless the station is equipped with changeover units. This in turn requires a higher outlay for investment and maintenance.

In many constructions of oil-bath separators, the obstacle of these drawbacks has led partly to complicated and expensive additional apparatus, which can no longer be dismantled or is not easily accessible for general cleaning.

The partly customary and constantly regular wetting of filtering elements in dust separator housings by pump units and distribution systems requires mechallisms which are doubtful on account of their circulating action, due to their susceptibility to disturbances, for example for use in very dusty locations or even in desert areas. Excluding the parts which are subject to wear, such as motors, moving pump parts and jets, which have to be exchanged from time to time and for this reason require a store for replacement parts, filters of this type cannot be maintained without expenditure for maintenance.

However, the most serious drawback is that many of these known oil-bath separator constructions are not designed such that an oilbath separator system taking in air freely can be converted with simple building aids by the modular building method, into a closed system for the passage of air, by adding a low cost additional part, as required. Or, for example, free air and closed air intake systems cannot be subsequently equipped with a simple but effective additional preliminary separator in order to absorb considerable dust contaminations which occur suddenly and were not calculated for previously, in order to relieve the filtering element and the oil-bath.

A further drawback is to be seen in that with a greater throughput of air, oil-bath filters of this type assume dimensions as regards height and width which, if they cannot be broken down into their individual parts in a manner involving considerable expenditure, must cause considerable difficulties as regards transportation.

It is inevitable that the construction and dimensions of such filters are influenced greatly by the fact that the air intake speeds at a peripheral rain apron should not be greater than 2 to 2.2 metres/sec. in order to prevent dripping or driving rainwater from being drawn into the oil-bath.

However, many constructions exceed this value by far, for this reason, whereby it is made clear that water must collect in the oil-bath, which water can considerably reduce the separating capacity of the oil-bath filter by thinning down the oil and finally by forming an emulsion of low wetting capacity.

An object of the invention is to reduce or completely eliminate the many afore-mentioned drawback and to provide a compact oilbath filter which can be completely dismantled and is protected against corrosion, according to the modular construction system, in which the action of several dust separators which are resistant to wear, require no maintenance and operate completely automatically one behind the other, is realised in one apparatus with relatively simple devices, without the assistance of electromechanical equipment and which can be combined in the simplest manner by the exchange or alternate incorporation of various individual unit parts one below the other or one after the other so as to be able to cope with various applications and considerable dust contamination without impairing the degree of efficiency.

According to the present invention there is provided an oil bath air filter comprising a housing vertically adjustably mounted on supports, an air inlet funnel inserted in the lower end of the housing with its narrow end directed upwardly so as to define an annular oil bath between the outside of the inlet funnel and the housing, an air deflecting member vertically adjustably suspended in the housing above the inlet funnel and including a peaked roof with a downwardly directed cone-shaped deflector on its underside and with a smooth outer surface sloping down to a slotted rim at the upper edge of a perforate, cylindrical wall from which depends an apron with circumferentially arranged flaps adapted to impart an axis-symmetrical centrifugal motion to air passing therethrough and hence to the surface of the oil bath, the narrow upper end of the air inlet funnel extending into the lower end of the air deflecting member, an axial flow filter element mounted in the housing above the air deflecting member, and an air outlet funnel disposed above the filter element with its wide end directed downwardly, the arrangement being such that, in use, air flows in a generally upward axial direction through the housing.

A second air inlet funnel may be provided upstream of the aforementioned air inlet funnel and engages with its narrow upper end in the wide lower end of the first funnel. The air inlet defined by the lower end of the funnel or the lower funnel is preferably fitted with a vane system for imparting a centrifugal motion to incoming air and/or with a wire gauze screen.

Preferably, the apron of the air deflecting member is divided by axial slits into rectangular sections each fixed at one upper corner to said cylindrical wall and at the diagonally opposite lower corner to an apertured ring so as to produce said flaps.

The air deflecting member may be suspended from at least three points on the housing by inwardly and downwardly bent hangers whereof each lower end is provided with a series of alternative fixing holes permitting vertical adjustment of said member in the housing.

Preferably, the axle flow filter element comprises sheet expanded metal strip rolled with obliquely corrugated metallic knitted wire gauze into a disc shape coaxial with the air outlet funnel.

Several embodiments of the invention are illustrated in the drawings and are described as follows: Figure 1 is a section C-C through the upright basic construction with all details, the flow pattern with the air circulation and the surface movement of the oil-bath.

Figure 2 represents a bisected plan view on the section line A-A with the axially-located rotational guide vane system, whereas the section B-B corresponds to a bisected plan view of the cylindrical perforated sheet metal member with the vertically adjustable supports.

Figure 3 is a view of the five main parts exploded in axial direction of the oil-bath air filter on both sides, with partial sections.

Figure 4 corresponds essentially to figure 1 and according to the flow pattern is an oil-bath air filter protected from the rain and having its intake on the underside, with the indicated oil filler and oil drain connections and the cleaning apertures in partial sectional view.

Figure 5 is a partial sectional view of the oilbath air filter as in figure 4, but with an upper and a lower pipe connection to a selectively cylindrical or funnel-shaped transfer pipe with a flange connection and laterally guided intake air pipe as a closed system for the passage of air.

Figure 6 corresponds to figures 1 and 4, but with an additional preliminary separator system incorporated on the underside and lateral cleaning apertures as a free air intake member according to the flow lines indicated.

Figure 7 is shown as a closed system for the passage of air, similar in its construction to figure 5, but with an additionally incorporated preliminary dust separator and a pipe connection, which leads by way of a funnel-shaped transfer connection to a pipe or to a concrete channel let into the ground.

Figure 8 is a perspective view of the cylindrical perforated sheet metal member, provided with a slotted rim, with the conical cap and the internal truncated cone and the slotted flexible apron with the simultaneous illustration of an adjustable offset support mounted on the latter by way of example. The directions of the arrows represent the guide paths for the air stream and the oil drainage.

Figure 9 shows the cylindrical perforated sheet metal member with the sporadically slotted rim in sectional view to illustrate the arrangement of the internal truncated cone and the arrangement of the offset supports adjustable in the holes.

Figure 10 shows the disc-shaped filtering layer cartridge in section with the angle iron rings and reinforcements including the handles bent towards the inside.

Figure 11 is a perspective view of a rolled-up filtering layer to illustrate the individual layers of the filter made from expanded metal and obliquely corrugated galvanised knitted steel or aluminium wire gauze with a core stopper at the centre.

In the embodiment according to Figure 1, the basic construction consists firstly of the upper conical funnel-shaped connecting piece 2 with the narrowed-down cylindrical neck and flange 22 and a pipe 22a which can be attached to the latter for example. Located below the latter is the disc-shaped filtering layer cartridge 19 which is sealed and clamped by the peripheral housing flange 25. Suspended below this disc-shaped filtering layer cartridge 19 in the housing body 1 and so that it is vertically adjustable on supports 18 is the perforated sheet metal body 15 with the upper cone 3 and the internal cone 36 and the slotted rim 37 as well as the flexible apron attachment 31 secured to the perforated sheet metal body 15 and provided with parallel vertical slots, with the triangular flaps 59. Located below the latter coaxially with respect to the axis of the housing member 1 is the funnel member 34, penetrating the perforated body 15 somewhat, with the axial rotational guide vane system 7 and the wire gauze screen cover 8, for example as a sheet of paper and bird protection device. A disc 9 which is impermeable to air is located in the centre of the vane system 7 for securing the latter. The entire funnel member 34 is either screwed or welded in a fixed air-tight manner in the oil-bath air filter housing 1. The housing member 1 is attached to three support legs 11 with bottom flange plates 35 so that it is vertically adjustable. The guidance of the air stream in the oil-bath air filter 1 is indicated by the direction arrows. According to the latter, the dust-laden air 55 is sucked-in centrifugally from below at a suitable distance from the ground, protected from the rain, at a speed of approximately 2 metres per second, through the funnel member 34 with the vane system 7 and the wire gauze screen 8 into the housing member 1, provided that the rigid vane system is present. Due to the perforated sheet metal body 15 which is placed over the funnel member 34, the dust-laden air is deflected towards the oil-bath la as a result of the internally incorporated truncated cone 36 and sets the surface of the latter in a movement rotating about the central axis, with considerable formation of waves. The flexible apron 31 illustrated with the inclined triangular flaps 59, which can be raised by the intake air, is provided in addition to the vane system 7.

The first preliminary deposition of dust according to the flow pattern takes place at the time of the two-stage deflection of the dustladen air by the funnel-shaped member 34 to the oil-bath la. Part of the air escapes unwetted through the holes of the perforated sheet metal member 15, whereas the major proportion of the air flows with the entrained oil droplets from the oil-bath la, which was set in a rotational movement symmetrically with respect to the axis, by the rigid vane system 7 and the flexible skirt flap system 59 to the disc-shaped filtering layer cartridge 19, in which the heavy oil and the oil-laden residual dust is separated positively from the air.

Due to the flow around the perforated sheet metal member 15 and due to the action of the conically shaped axial air inlet 55 and the conically shaped coaxial air outlet in the pipe 22a, according to the development of rotational energy and centrifugal forces in the housing 1, as a result of the interposed flow resistance of the disc-shaped filtering layer cartridge 19 with the centre plug 19c, a slowing down or rebound effect of the axis symmetrical flow path occurs.

Since the purified air leaves the filter 1 in the centre, an exchange movement of the forces occurs at this point, i.e. the upwardly directed centrifugally accelerated air stream produces an action of centripetal force directed partly downstream on the underside of the filter cartridge 19.

In this operation, a major part of the oil 58 mixed with dust, thrown at the filter cartridge 19, is collected, concentrated at the centre of the cartridge 19c and flows downwards towards the cone 3 of the perforated sheet metal member 15 due to the suctional forces of the centripetal acceleration and forces of gravity.

After this, the oil 56 and 58 flows back once more through the sporadic slots 29 in the rim 37 of the perforated sheet metal member in the direction of the oil-bath la and in this way once more enters the circuit. A part of the oil 58, which has reached the inner wall of the housing member 1 due to centrifugal forces, flows back into the oil-bath In with rotational movements, influenced by forces of gravity, together with the wetted dust.

The vertical adjustment of the filter housing 1 in the support legs 11 serves for simpler and occasional dismantling of the disc-shaped filtering layer cartridge 19. For this purpose, the screws on the upper housing flange 25 are released and the housing member 1 is lowered.

The funnel-shaped connecting part 2 thus remains suspended from the upper pipe 22a for example. Due to this, it is simple to remove the filter cartridge 19 for a cleaning operation, without the entire filter housing having to be separated and moved away from the pipe section 22a, as previously.

The embodiment according to figure 3 is intended to illustrate the oil-bath air filter broken down into its individual parts. Thus, the funnel-shaped connection 2 on the upper side is provided with the cylindrical narroweddown neck and flange 22. Provided on the inclined sides are sporadic circular detachable observation and cleaning openings 38 with a screw-thread of at least 100 mm.

A peripheral seal 24 of oil resistant material is trapped by an internal retaining ring 23 inside the funnel part 2. The screws 21 can be inserted through the peripheral angular flange 25.

The disc-shaped filtering layer cartridge according to Figure 3 consists of a peripheral endless circular upright sheet metal strip 20 with the inserted filtering layer 19 and the angle steel rings 27 penetrating the sheet metal strip 20 on the upper and lower side, for support and reinforcement. Located below the cartridge 19 are transverse angle steel reinforcements 28, which serve for simultaneously supporting the filtering layer 19.

In this respect, figure 11 shows in detail how the disc-shaped filtering layer 19 is produced from alternate layers of rolled up strips of expanded metal l9a and obliquely corrugated metallic knitted wire gauze 19b, inserted in whose centre is a tightly rolled knitted gauze made of metal, as a core stopper 19c.

The cylindrical perforated sheet metal member 15 according to figures 3,8 and 9, which preferably has a round construction, consists of the upper smooth sheet metal cone 3 with the inner truncated cone 36 and the peripheral rim 37 provided sporadically with slots 29, to which the endless peripheral perforated sheet metal cylindrical casing 15 is attached, to whose underside a flexible apron 31 provided on its periphery with vertical slots 32 is attached, which apron is secured by a lower perforated ring 39 between the slots with screws or rivets 30 and 31a such that the loose apron flaps having an inclined triangular shape 59 bend sideways and towards the outside in the manner of vanes solely when air under pressure flows towards the latter from inside. This produces an axis-symmetrical rotational flow 57 (Figure 8) in the housing body. The drainage of oil is indicated by the flow lines 56 and 58.

Figure 9 shows the vertically adjustable supports 18 which are bent at two points and per forated several times, with the screws 16, which supports retain the perforated metal sheet member 15 at the centre by screws 16a, fixed in the housing 1 which is not shown.

Figures 4, 5, 6 and 7 relate to various versions of the filter and are illustrations of the oilbath air filter on a smaller scale. Like figure 1, figure 4 shows the basic design of the oil inlet opening 41 and the outlet opening 42 and the cleaning apertures 61 for removing the dust slurry on the outer casing 39 of the housing. As shown by the flow lines, this oil-bath air filter is designed to draw in air freely from below.

Figure 5 shows the same oil-bath filter construction as in figure 4, but as a closed system 40 and not a system drawing in air freely, between the pipes 22a and 45, constructed with a selectively lower cylindrical connecting piece 44 or with a conical funnel-shaped connection 43 as a transition member to the flange connector 62 for a flange connection to a bent pipe 45 for example.

Figure 6 shows an oil-bath air filter 46 drawing in air freely from below, with an incorporated axial rotational guide vane preliminary separator system 34 for the preliminary separation of dust mounted with a gap 60 from the upper funnel member for the purpose of the centrifugal separation of dry dust or sand 47, which can be removed from the openings 52.

This function takes place automatically at the air inlet 55, in that the mixture of dust and air is set in rotation by the guide vane system 7, whereby the centrifuged dust is thrown through the gap 60 over the edge of the funnel-shaped member 34 and is then deposited in the cavity 47 of the funnel 34 without a whirling action.

In contrast to figure 5, in figure 7, the oilbath air filter 48 is solely equipped with an additional preliminary dust separator 34 at the dust/air or intake side, which consists essentially of the funnel member according to figure 3 and with the function according to figure 6 with the parts 4, 5, 7, 8, 9 and 34 and the angle steel ring member 6 welded to the funnel body 34, which can be inserted in the housing members of all the figures. Adjoining the latter is a funnel-shaped connecting part 50 with the flange or pipe connection 62 and the associated pipe 51 for example, which opens into a concrete channel or terminates in a pipe 53, which can be let into the ground.

The advantages of these oil-bath air filter constructions according to the invention shown in the drawings by way of example, lie in the fact that it is possible to produce different filter assemblies according to the modular construction system, from the same parts by arranging the latter selectively one after the other.

Finally, it is also an advantage that it is possible to adjust the internal perforated sheet metal member with the cone and the flexible apron suspended in the latter, vertically such that the spacing between the oil-bath and the lower edge of the apron can be small or large depending on the permanent air throughput, which naturally influences the degree of efficiency and wetting of the dust-laden air with the oil and the pressure loss in a lasting manner.

As an advantage with respect to the state of the art, it can also be stated that even with a slight pressure difference, i.e. with a low throughput of air, it is still possible with both vane systems to convert centrifugal forces from a predetermined point below the disc-shaped filtering layer cartridge into centripetal forces acting in a downwards direction, in order to convey the major part of the oil located in the disc-shaped filtering layer cartridge downwards over the cone of the perforated sheet metal member.

Finally, it is also of significance that with this construction according to the invention, it is immaterial to the high degree of dust removal to be achieved, with which quantity of air and at which speed of passage this oil-bath air filter is acted upon, when both vane systems are present. This is particularly true when the peripheral slotted flexible apron penetrates the oilbath somewhat, in order that with small quantities of air the air stream is guided in a positive manner through the oil-bath, whereas with a larger throughput of air, the individual inclined triangular apron flaps are raised outwards and clear the path for the air. In this way, an axissymmetrical rotational flow is simultaneously produced, which develops centrifugal forces. In this case, the oil entrained is mixed intensively with dust, and thrown partly outwards towards the inner wall of the housing. The simple regulation mechanism due to this separator and functional kinematics of the flexible apron, whose flaps divide the air into many individual air streams, which is set in rotation according to the tangential outlet, serves as a particular advantage for throughput quantities of air which vary suddenly, such as in diesel power stations for example.

The rigid axial rotational guide vane system in the enlarged conical funnel member as the enlarged inlet cross section of the housing en sures that due to a relatively low inlet speed of the air into the vanes, only a low surface fric tion occurs, which in the last analysis is an advantage as regards the durability.

Finally, a further advantage with regard to the prior art is the construction of the lower intake on the funnel member, in which an ex pensive apron repelling rain can be dispensed with.

The particularly advantageous manner of production and construction of the disc-shaped filtering layer cartridge is not only money saving, but also of light weight with large dimensions so that it can be handled by the oper ators at the time of assembly, without the assistance of a crane.

Furthermore, the vertical adjustment of the entire housing member in the support legs en sures that the filtering cartridge can be removed at any time without having to detach the upper funnel from the connecting pipe or shift the entire housing.

Furthermore, this construction facilitates complete dismantling of each individual part if the latter need to be exchanged after a prolonged period of time. Finally, the economical assembly from the afore-described five main parts according to the modular building system can be regarded as the greatest advantage.

WHAT WE CLAIM IS: 1. An oil bath air filter comprising a housing vertically adjustably mounted on supports, an air inlet funnel inserted in the lower end of the housing with its narrow end directed upwardly so as to define an annular oil bath between the outside of the inlet funnel and the housing, an air deflecting member vertically adjustably suspended in the housing above the inlet funnel and including a peaked roof with a downwardly directed cone-shaped deflector on its underside and with a smooth outer surface sloping down to a slotted rim at the upper edge of a perforate, cylindrical wall from which depends an apron with circumferentially arranged flaps adapted to impart an axis-symmetrical centrifugal motion to air passing therethrough and hence to the surface of the oil bath, the narrow upper end of the air inlet funnel extending into the lower end of the air deflecting member, an axial flow filter element mounted in the housing above the air deflecting member, and an air outlet funnel disposed above the filter element with its wide end directed downwardly, the arrangement being such that, in use, air flows in a generally upward axial direction through the housing.

2. An oil bath air filter as claimed in claim 1, wherein a second air inlet funnel is provided upstream of the aforementioned air inlet funnel and engages with its narrow upper end in the wide lower end of the first funnel.

3. An oil bath air filter as claimed in claim 1 or 2, wherein the air inlet defined

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. sures that the filtering cartridge can be removed at any time without having to detach the upper funnel from the connecting pipe or shift the entire housing. Furthermore, this construction facilitates complete dismantling of each individual part if the latter need to be exchanged after a prolonged period of time. Finally, the economical assembly from the afore-described five main parts according to the modular building system can be regarded as the greatest advantage. WHAT WE CLAIM IS:

1. An oil bath air filter comprising a housing vertically adjustably mounted on supports, an air inlet funnel inserted in the lower end of the housing with its narrow end directed upwardly so as to define an annular oil bath between the outside of the inlet funnel and the housing, an air deflecting member vertically adjustably suspended in the housing above the inlet funnel and including a peaked roof with a downwardly directed cone-shaped deflector on its underside and with a smooth outer surface sloping down to a slotted rim at the upper edge of a perforate, cylindrical wall from which depends an apron with circumferentially arranged flaps adapted to impart an axis-symmetrical centrifugal motion to air passing therethrough and hence to the surface of the oil bath, the narrow upper end of the air inlet funnel extending into the lower end of the air deflecting member, an axial flow filter element mounted in the housing above the air deflecting member, and an air outlet funnel disposed above the filter element with its wide end directed downwardly, the arrangement being such that, in use, air flows in a generally upward axial direction through the housing.

2. An oil bath air filter as claimed in claim 1, wherein a second air inlet funnel is provided upstream of the aforementioned air inlet funnel and engages with its narrow upper end in the wide lower end of the first funnel.

3. An oil bath air filter as claimed in claim 1 or 2, wherein the air inlet defined by the lower end of the funnel or the lower funnel is fitted with a vane system for imparting a centrifugal motion to incoming air and/or with a wire gauze screen.

4. An oil bath air filter as claimed in any one of the preceding claims, wherein the apron of the air deflecting member is divided by axial slits into rectangular sections each fixed at one upper corner to said cylindrical wall and at the diagonally opposite lower comer to an apertured ring so as to produce said flaps.

5. An oil bath air filter as claimed in any one of the preceding claims, wherein the air deflecting member is suspended from at least three points on the housing by inwardly and downwardly bent hangers whereof each lower end is provided with a series of alternative fixing holes permitting vertical adjustment of said member in the housing.

6. An oil bath air filter as claimed in any one of the preceding claims, wherein the axial flow filter element comprises sheet expanded metal strip rolled with obliquely corrugated metallic knitted wire gauze into a disc shape coaxial with the air outlet funnel.

7. An oil bath air filter substantially as herein described with reference to and as illustrated in the accompanying drawings.