Patent Application
20250222386
This invention relates to filter silencers for compressed gas streams, particularly compressed air systems, contaminated by atomised oil, and to removable cartridges for fitting into housings of such silencers.
GB-B-2033247 explains that it is very rare for compressed air not to return to its original ambient conditions and often in industry when compressed air exhausts to atmospheric pressure through a control valve a great deal of noise is created. Not only is noise created but any contamination within the airline is exhausted into the atmosphere. The noise levels can be above 125 decibels which is very damaging to the sense of hearing and contamination such as oil aerosol can be damaging to the respiratory system. Health and safety organisations throughout the world were implementing stringent controls covering working conditions and a particular interest was being taken in the reduction of noise and air pollution levels in industry.
For example, when pneumatic equipment is used it is generally accepted that a lubricator should be fitted to ensure that the moving parts receive lubrication. As an example, a pneumatic piston and cylinder assembly requires lubrication on the cylinder wall to stop the piston scoring the bore and to increase the life of the piston seal. In the case of an oil lubricated air compressor, a certain amount of oil is atomised and carried downstream. This means a high oil level concentration in the exhausting air. Similarly on the exhaust side of an oil lubricated vacuum pump the air needs to be filtered and silenced.
Prior to the '247 invention, when noise control had been necessary, attachments had been fixed to exhaust ports to reduce the noise level of the escaping air. However, these attachments did not reduce the contamination level and in some cases where sintered material was used, these increased this pollution by atomising lubricating oil so that it was sprayed into the atmosphere. Recently, however, filter silencers had been produced which provided a 30 to 35 decibel reduction in noise level. So far as could be ascertained, the filtration efficiency of these attachments by DOP methods was for the best 99.9% and for the worst less than 10%.
A main object of the '247 invention was to provide a filter silencer that was substantially more effective than any heretofore proposed in that it provided a DOP efficiency of at least 99.95% and generally in the order of 99.999% having an oil removal efficiency of the same order with a noise reduction that could be as great as 50 to 60 decibels. A further object was effectively to accommodate pulsating flow patterns that occurred when the air supply was switched on and off.
The '247 invention provided, so far as is relevant, a filter silencer for compressed gas streams contaminated by dirt, water, oil or atomised oil aerosol comprising a casing containing at least one vertical hollow filter element, and means for directing a gas stream to pass outwards from inside the filter element through the wall of the filter element whereby, when the filter silencer is in use, the noise level of the gas stream is reduced and solid dirt particles are trapped by the filter element while oil aerosol is coalesced and passes through the filter element as bulk oil with any water to the outside-of the filter element to drain into a bowl forming part of the casing and for further directing the gas to atmosphere wholly through a casing wall having apertures sufficiently large to pass the gas therethrough substantially at atmospheric pressure, an intervening space of a size sufficient substantially to eliminate any carryover of oil to the silencing element or elements or casing wall being provided between the filter element and the casing wall.
In the applicants' current product, the gas stream is introduced through an aperture in the top surface of the casing and passes into the filter element through an inlet tube extending downwardly through an aperture in a top cap of the filter element. The lower end of the inlet tube is threaded and the filter element has a lower end cap provided on its inner surface with a threaded bar for insertion into the inlet tube, rotation of the filter element relative to the casing engaging the threads and securing the filter element in position within the casing.
An object of the invention is to provide a more rapid and convenient arrangement for fitting the filter element into and removing the filter element from the housing.
In one aspect the invention provides a filter silencer having a cartridge formed with circumferentially directed outwardly projecting lugs at its upper rim configured for forming a bayonet fit into slots at a top rim of a receiving cage forming part of a housing for the filter. The filter housing may further comprise a bowl having an upper rim formed with projecting lugs configured for forming a bayonet fit into slots at a bottom rim of the receiving cage. In each case, if there are four such lugs, the cartridge and the bowl may each be fastened and released by a quarter turn. Advantageously each lug of the cartridge and/or bowl has a tapered leading edge for facilitating insertion into a slot and a downwardly projecting tab at its trailing end for abutment with an adjacent region of the housing to define a fully inserted rotational position.
Advantageously the slots in the top rim of the receiving cage extend radially through the rim and open to the exterior surface thereof so that the lugs of the cartridge are visible from the exterior of the filter silencer when the cartridge has been fitted into position. Similarly, the upper end of the bowl may be formed with projecting lugs for fitting into slots in a lower rim of the depending wall. The receiving cage may be of a plastics material, for example nylon. The bowl may also be of plastics material e.g. polypropylene.
In another aspect the invention provides a housing for a cartridge of a filter silencer comprising a cage for accommodating the cartridge and a bowl removably connectable to the cartridge to permit insertion and removal of the cartridge and also to collect coalesced oil, wherein a top rim of the cage is formed with a plurality of slots for receiving protuberant lugs at the top of the cartridge and providing a removable bayonet fit between them. In an embodiment, a bottom rim of the cage is also provided with a plurality of slots to receive protuberant lugs at the top of the bowl for providing a removable bayonet fit between the cage and the bowl.
In another aspect, there is provided a cartridge for a filter silencer for a compressed air stream that may be contaminated by atomised oil aerosol,
The invention further provides a filter silencer for a compressed air stream that may be contaminated by atomised oil aerosol comprising a cartridge as defined above and a housing comprising a cage into which the cartridge can be removably fitted and a bowl that can be removably attached to a lower end of the cage for collecting oil coalesced by the cartridge,
The upper end cap of the cartridge may have a central aperture configured to receive and fit gas-tightly around an air flow tube depending from the upper end of the housing. The end caps may be of plastics material, suitably a glass-filled plastics material, for example 15% glass-filled nylon 6.
The glass fibres of the filter element may be bonded by a water-soluble acid-based resin binder comprising a carboxylated acrylic polymer and a polyfunctional alcohol. The drainage layer may be of polyester fibres coated with fluorocarbon.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
The filter silencer of the invention employs a filter cartridge as shown in
In contrast to previous coalescing filter cartridges that employ metal end caps, the upper and lower end caps are formed of 15% glass-filled nylon 6 (e.g. Nearshore (15% Glass Fiber) nylon 201272 which is recycled and is available from Oceanworks, 11828 La Grange Ave, Los Angeles, CA, 90025, USA). The upper end cap 10 has a central aperture 16 through which air can enter the cartridge, and is formed with, in this instance, four lugs 18 for bayonet-type connection into slots 42 in a top rim 36 of the filter cage 28. It will be seen that each lug has a tapered leading edge 20 for facilitating insertion into one of the slots, a constant depth central region 22 for resting in the slot and a downwardly projecting tab 24 at its trailing end for abutment with an adjacent region of the housing to define a fully inserted rotational position.
The cylindrical coalescing filter medium 12 is attached at its upper end to end cap 10 and at its lower end to end cap 14 which is also of 15% glass-filled nylon 6 and which has a raised central region 26 that fits within and closes the central region of the medium 12. As seen in
The filter element 72 may be made as described in EP-B-1979067 (Waltl et al.), the disclosure of which is incorporated herein by reference. The disclosed method comprises (a) forming an aqueous dispersion comprising fibers, wherein said fibers consist of glass micro-fibers (e.g. borosilicate glass microfibres), said dispersion further comprising a thermally curable water-soluble acid-based resin binder comprising a carboxylated acrylic polymer and a polyfunctional alcohol, the dispersion having a pH of about 3; (b) forming a tubular article from the aqueous dispersion by feeding said dispersion to a tubular molding space; and (c) heating the article to successively drive off water and cure the resin.
A preferred resin is Acrodur 950 L (BASF) which has a pH of 3.5, a molecular weight of about 80,000 and a Brookfield viscosity at 23° C. of 600-4000 mPas. It has been stated to crosslink at temperatures as low as 180° C., with a recommended temperature of 200° C. and is an aqueous solution of a substituted polycarboxylic acid containing a polybasic alcohol as the crosslinking agent. The polycarboxylic acid is a carboxylated acrylic polymer and the polybasic alcohol is triethanolamine. The preparation is presented as a 50% solids solution in water with viscosity of 1000-4500 cps, specific gravity of 1.2. It may be used in the dispersion at e.g. a concentration of about 40-80 g/liter depending on the desired mechanical properties of the filter, the effect of resin concentration in the dispersion on pressure drop of the resulting filter medium being relatively small.
The aqueous dispersion may be fed under pressure to the moulding space, and formation of a tubular article may typically comprise introducing the dispersion under pressure into the top of an annular molding space defined between a central core, a vertical cylindrical screen spaced from and outward of said core and a support defining a lower boundary for the molding space so that a mass of fibers becomes compacted on the screen and liquid is discharged from the molding space through the screen; progressively increasing the height of the effective open area of the cylindrical screen by moving upwardly a sleeve in sliding contact with the cylindrical screen at a rate substantially equal to the rate at which the height of the mass of fibers increases above the support; and removing the resulting tubular mass of fibers from the molding space.
The drainage layer 74 may be a butt-welded tubular structure e.g. of non-woven polyester fibres with ends of the drainage layer welded together without overlap so that there is no “dead area” on the filter surface, see WO 2008/1146045 (Spence). The layer may be coated with a fluorocarbon.
The filter housing includes a cage 28 having a top face 30 formed with a central aperture 32 provided with a connector e.g. a, internally threaded brass insert for attachment to an airline or other source of the compressed air stream to be treated. The top face 30 carries a depending inlet tube 34 which in use extends for most of the depth of the filter medium 12 for leading air to lower regions of the cartridge. The inlet tube 34 is open at its lower end and may also have side apertures. A generally cylindrical side wall has a top rim 36 adjacent the top face 30 and a multiplicity of depending ribs with apertures 38 defined between them for discharge of air from the filter and leading to a lower rim 40 formed with circumferentially directed slot 44 for attachment of the filter bowl as described below.
In
| Number | Date | Country | Kind |
|---|---|---|---|
| 2209575.6 | Jun 2022 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2023/051682 | 6/28/2023 | WO |
