Filter silencer

Abstract

The present application provides a filter muffler having a filter cartridge (12) formed at an upper edge thereof with a circumferentially outwardly projecting lug (18) configured to form a bayonet fit with a slot (42) at a top edge (36) of a receiving cage (28) that forms part of a housing of a filter. The housing may also include a filter bowl (46) having an upper rim formed with a protruding lug (48) configured to form a bayonet fit with a slot (44) at a bottom rim (40) of the receiving cage. If the filter cartridge and the filter bowl each have four lugs, the filter bowl may be fixed to or removed from the cage by rotating a quarter of a circle, and the filter cartridge may also be mounted into or removed from the cage by rotating a quarter of a circle.

Description

Technical Field

[0001] The invention relates to a filter silencer for compressed air streams contaminated with atomized oil, in particular compressed air systems, and to a removable filter element for fitting into the housing of such a silencer. Background Art

[0002] GB-B-2033247 explains that it is very rare for compressed air not to be restored to its original ambient conditions, and in industry, when compressed air is discharged to atmospheric pressure through a control valve, a lot of noise is usually generated. Not only is noise generated, but any pollutants in the air pipeline are discharged to the atmosphere. Noise levels can be over 125 decibels, which is very harmful to hearing, and pollutants such as oil aerosols can harm the respiratory system. Health and safety organizations around the world are implementing strict controls on working conditions and are particularly concerned about reducing noise and air pollution levels in industry.

[0003] For example, when using pneumatic equipment, it is generally accepted that lubricators should be installed to ensure that moving parts are lubricated. As an example, pneumatic piston and cylinder assemblies require lubrication on the cylinder wall to prevent the piston from scratching the cylinder bore and to extend the life of the piston seal. In the case of an oil-lubricated air compressor, a certain amount of oil is atomized and carried downstream. This means that the oil concentration level in the exhaust air is high. Similarly, on the exhaust side of an oil-lubricated vacuum pump, the air needs to be filtered and silenced.

[0004] Prior to the '247 invention, when noise control became necessary, attachments were fixed to the exhaust ports to reduce the noise level of the escaping air. However, these attachments did not reduce the pollution level, and in some cases where sintered materials were used, they increased the pollution by atomizing the lubricating oil so that it was sprayed into the atmosphere. Recently, however, filter silencers have been produced that provide a 30 dB to 35 dB reduction in noise levels. It has been determined that the filtration efficiency of these attachments using the DOP method is as good as 99.9%, and the worst is less than 10%.

[0005] The primary object of the '247 invention is to provide a filter-muffler that is substantially more efficient than any muffler heretofore proposed because it provides a DOP efficiency of at least 99.95%, typically in the region of 99.999%, and an oil removal efficiency of about 99.999%, while being capable of noise reduction of 50 dB to 60 dB. Another object is to effectively accommodate pulsating flow patterns that occur when an air source is turned on and off.

[0006] The '247 invention provides, in a related aspect, a filter-muffler for treating a compressed gas stream contaminated with dust, water, oil or aerosolized oil, the filter-muffler comprising: a housing containing at least one vertically hollow filter element; and a guide device for guiding the gas stream from the interior of the filter element outwardly through the wall of the filter element, whereby when the filter-muffler is in use, the noise level of the gas stream is reduced, solid dust particles are captured by the filter element, and the oil aerosol agglomerates and travels through the filter element in the form of bulk oil, wherein any water flows to the outside of the filter element to be discharged into a filter bowl forming part of the housing, and further the gas is directed entirely through the housing wall to the atmosphere, the housing wall having pores large enough to allow the gas to travel through the pores substantially at atmospheric pressure, and a spacing space is provided between the filter element and the housing wall, the size of which is sufficient to substantially eliminate any oil carryover to one or more of the muffler elements or the housing wall.

[0007] In the applicant's current product, airflow is introduced through a hole in the top surface of the housing and enters the filter element through an inlet tube extending downwardly through a hole in the top cover of the filter element. The lower end of the inlet tube is threaded, and the filter element has a lower end cover with a threaded rod on the inner surface of the lower end cover for insertion into the inlet tube, and rotation of the filter element relative to the housing engages the threads and secures the filter element in place within the housing.

[0008] It is an object of the present invention to provide a faster and more convenient arrangement for fitting and removing a filter element into and from a housing. Summary of the invention

[0009] In one aspect, the invention provides a filter silencer having a filter element, the filter element having a circumferentially outwardly projecting lug formed at its upper edge, the lug being configured to form a bayonet fit with a slot at the top edge of a receiving cage, the receiving cage forming part of a housing for the filter. The housing of the filter may also include a filter bowl having an upper edge formed with a projecting lug, the projecting lug being configured to form a bayonet fit with a slot at the bottom edge of the receiving cage. In each case, if there are four such lugs, the filter element and the filter bowl can be tightened and released by a quarter turn. Advantageously, each lug of the filter element and / or the filter bowl has: a tapered front edge to facilitate insertion into the slot; and a downwardly projecting tab at the rear end of the lug for abutting against an adjacent area of ​​the housing to define a fully inserted rotational position.

[0010] Advantageously, the slots in the top edge of the receiving cage extend radially through the top edge and open to the outer surface of the receiving cage so that the lugs of the filter element are visible from the exterior of the filter silencer when the filter element is already in place. Similarly, the upper end of the filter bowl may be formed with projecting lugs for fitting into the slots in the lower edge of the overhanging wall. The receiving cage may be made of a plastic material such as nylon. The filter bowl may also be made of a plastic material such as polypropylene.

[0011] In another aspect, the present invention provides a housing for a filter cartridge of a filter silencer, the housing comprising: a cage to house the filter cartridge; and a filter bowl removably connected to the filter cartridge to allow insertion and removal of the filter cartridge and also to collect coalesced oil, wherein a top edge of the cage is formed with a plurality of slots for receiving protruding lugs at the top of the cage and providing a removable bayonet fit between the plurality of slots and the protruding lugs. In an embodiment, a bottom edge of the cage is also provided with a plurality of slots to receive the protruding lugs at the top of the filter bowl, thereby providing a removable bayonet fit between the cage and the filter bowl.

[0012] In another aspect, a filter element is provided for a filter muffler for a compressed air stream that can be contaminated by aerosolized oil.

[0013] The filter element includes an upper end cap, a lower end cap and a tubular coalescing filter, the upper end cap and the lower end cap are made of glass-filled nylon, the tubular coalescing filter extends between the upper end cap and the lower end cap and is adhered to the upper end cap and the lower end cap,

[0014] A tubular coalescing filter includes a filter element made of resin-bonded glass fibers and used to coalesce oil in a compressed air stream, and a drainage layer for collecting the coalesced oil and allowing the coalesced oil to flow through or past a lower end cap,

[0015] The edge of the upper end cover is formed with a radially outwardly protruding lug, which can be rotatably assembled into a circumferential narrow groove located directly below the upper end of the shell in the filter housing when in use, so as to hold the filter element in the shell and the upper end of the filter element is located below the upper end of the shell.

[0016] The invention also provides a filter silencer for a compressed air stream that can be contaminated by aerosolized oil, the filter silencer comprising a housing and a filter element as defined above, the housing comprising a cage in which the filter element can be removably mounted and a filter bowl, the filter bowl being removably attachable to the lower end of the cage for collecting oil coalesced by the filter element,

[0017] The cage has a cage top and an overhanging wall, the overhanging wall having an annular top edge and a hole located below the top edge, the hole being used to discharge air that has passed through the filter element, the cage top being formed with a central hole and provided with a connecting piece for receiving a compressed air flow and allowing the compressed air flow to pass through the central hole to reach an air inlet pipe on its inner surface, for guiding the compressed air flow into the filter element and toward the lower end of the filter element, and the top edge being formed with a circumferential slot for slidably inserting the lug into and removing it from the end cover when the filter element rotates relative to the end cover.

[0018] The upper end cap of the filter element may have a central hole configured to receive an airflow tube suspended from the upper end of the housing and to fit airtightly around the airflow tube. The end cap may be made of a plastic material, which is suitably a glass-filled plastic material, such as 15% glass-filled nylon 6.

[0019] The glass fibers of the filter element may be bonded by a water-soluble acid-based resin binder including a carboxylic acrylic polymer and a multifunctional alcohol. The drainage layer may be made of polyester fibers coated with fluorocarbon. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0021] Figure 1 is an exploded view of a filter cartridge and a cage for removably receiving the filter cartridge;

[0022] Figure 2 is a side view of the filter silencer showing the filter element seated in the filter cage with a removable filter bowl attached at a lower end of the filter element for receiving coalesced oil;

[0023] Figure 3 is a detailed cross-sectional view near the upper edge of the filter silencer, showing a lug forming part of the filter upper end cap, the lug being received in a slot in the upper end of the cage;

[0024] Figure 4 is a side view of the housing with the filter bowl removed from beneath the filter cage;

[0025] Figure 5 is a side view of an embodiment of a filter silencer viewed from slightly above;

[0026] Figure 6 is formed Figure 6 a perspective view of a filter in a portion of a filter silencer; and

[0027] Figure 7 is a vertical cross-section of the filter silencer. DETAILED DESCRIPTION

[0028] The filter silencer of the present invention adopts Figure 1 The filter element shown includes an upper end cap 10 , a cylindrical filter medium 12 and a lower end cap 14 .

[0029] In contrast to previous coalescing filter cartridges that have employed metal end caps, both 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 available from Oceanworks (11828 Grange Avenue, 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 four lugs 18 in this example for bayonet-type connection to slots 42 in the top rim 36 of the filter cage 28. It can be seen that each lug has: a tapered leading edge 20 to facilitate insertion into one of the slots; a central region 22 of constant depth for resting in the slot; and a downwardly projecting tab 24 at the rear end of the lug for abutting against an adjacent region of the housing to define a fully inserted rotational position.

[0030] The cylindrical coalesced filter media 12 is attached at its upper end to an upper end cap 10 and at its lower end to a lower end cap 14 which is also made of 15% glass filled nylon 6 and has a raised center region 26 which fits within and encloses the center region of the filter media 12. Figure 7 As seen in FIG. 1 , filter media 12 includes an inner filter element 72 where coalescing occurs and a surrounding drainage layer 74 .

[0031] The filter element 72 may be made in the manner 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 the fibers are composed of glass microfibers (e.g., borosilicate glass microfibers), the aqueous dispersion further comprising a heat-curable water-soluble acid-based resin binder comprising a carboxylated acrylic polymer and a polyfunctional alcohol, the aqueous dispersion having a pH of about 3; (b) forming a tubular article from the aqueous dispersion by feeding the aqueous dispersion into a tubular forming space; and (c) heating the tubular article to successively remove water and cure the resin.

[0032] 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 of 600-4000 mPas at 23°C. The resin is said to crosslink at a temperature of 180°C, with a recommended temperature of 200°C, and is an aqueous solution of a substituted polycarboxylic acid containing a polyol as a crosslinking agent. The polycarboxylic acid is a carboxylated acrylic acid polymer and the polyol is triethanolamine. The formulation is in the form of a 50% solids aqueous solution with a viscosity of 1000-4500 cps and a specific gravity of 1.2. It can be used in a dispersion, for example at a concentration of about 40-80 g / l, depending on the desired mechanical properties of the filter, and the concentration of the resin in the dispersion has a relatively small effect on the pressure drop of the resulting filter medium.

[0033] The aqueous dispersion can be fed into the molding space under pressure, and the formation of the tubular product can generally include: introducing the aqueous dispersion under pressure into the top of the annular molding space, the molding space being defined between a central core, a vertical cylindrical screen and a support, the cylindrical screen being spaced apart from the central core and outside the central core, the support defining the lower boundary for the molding space, so that the fiber body is compacted on the cylindrical screen and the liquid is discharged from the molding space through the cylindrical screen; gradually increasing the height of the effective opening area of ​​the cylindrical screen by moving a sleeve in sliding contact with the cylindrical screen upward at a rate substantially equal to the rate at which the fiber body height increases above the support; and removing the resulting tubular fiber body from the molding space.

[0034] The drainage layer 74 may be a butt-welded tubular structure, for example made of non-woven polyester fabric, wherein the ends of the drainage layer are welded together without overlapping so that there are no "dead zones" on the filter surface, see WO 2008 / 1146045 (Spence). The drainage layer may be coated with fluorocarbon.

[0035] The filter housing includes a cage 28 having a top surface 30 formed with a central aperture 32 provided with a connector, such as a brass insert with internal threads, for attachment to an air line or other source of compressed air flow to be processed. The top surface 30 carries a depending air inlet tube 34 which, when in use, extends through a majority of the depth of the filter media 12 for directing air to a lower region of the filter element. The air inlet tube 34 is open at its lower end and may also have side apertures. The generally cylindrical sidewall has a top edge 36 adjacent the top surface 30 and a plurality of depending ribs defining apertures 38 for exhausting air from the filter therebetween and leading to a lower edge 40 formed with a circumferential slot 44 for attaching a filter bowl as described below.

[0036] Figure 2 is a side view of an embodiment of a filter silencer showing the filter media 12 mounted within the cage 28 with the lugs mounted within and visible through the slots 42 and the lower end cap 14 slightly below the lower rim 40 of the cage. A clear polypropylene filter bowl 46 is shown attached to the lower rim 40 for preventing air from escaping from the housing except through the holes and for collecting coalesced oil and having a removable polypropylene plug 50 at the lower end of the filter bowl to allow the oil to drain from the filter bowl.

[0037] Figure 3 is a partial cross-sectional view of the filter silencer near the edge, which shows the lugs 22 of the upper end cap 10 engaged in the slots 42. It can be seen that the slots have short inward extensions 52 for additional support of the lugs 22, and the upper end cap of the filter has short overhanging walls 54 that abut against the inner end of each of the inward extensions 52 for positioning and centering the filter element relative to the housing.

[0038] exist Figure 4 , the filter bowl 46 is shown below the cage, and it can be seen that the rim of the filter bowl has four lugs 48, each of which has: a tapered front edge 56 to facilitate insertion into one of the slots 44; a central region 58 of constant depth for resting in the slot; and a downwardly projecting tab 60 at the rear end of the lug for abutting against an adjacent region of the housing to define a fully inserted rotational position. In this manner, the filter bowl 46 can be secured to and removed from the cage in the same manner as the filter media 12, with a quarter turn motion. The filter bowl has a hole 62 at its lower end for attachment of the polypropylene plug 50.

[0039] Figure 5 A prototype filter silencer is shown which is similar to that shown in the previous figures except that the top surface of the cage has a plurality of reinforcing ribs on its outer surface to assist the nylon of the top surface in resisting the internal pressure of compressed air when the filter silencer is in use. Figure 6 A prototype of the filter media 12 is shown with the underside of the lower end cap 14 having a central raised area 68 provided with a plurality of radial reinforcing ribs 70 to assist the nylon in the central raised area of ​​the lower end cap in withstanding the internal pressure of the compressed air. The central raised area 68 and the reinforcing ribs are also present. Figure 7 in the cross-sectional view.

Claims

1. A filter element for a filter silencer of a compressed air stream that can be contaminated by atomized oil aerosols, The filter element includes an upper end cap, a lower end cap and a tubular coalescing filter, the upper end cap and the lower end cap are made of glass-filled nylon, the tubular coalescing filter extends between the upper end cap and the lower end cap and is adhered to the upper end cap and the lower end cap, The tubular coalescing filter includes a filter element made of resin-bonded glass fibers and configured to coalesce oil in the compressed air flow, and a drainage layer configured to collect the coalesced oil and allow the coalesced oil to flow through or past the lower end cap, in, The edge of the upper end cover is formed with a radially outwardly protruding lug, which is rotatably assembled into a circumferential narrow groove located in the shell of the tubular coalescing filter just below the upper end of the shell when in use, so as to hold the filter element in the shell and the upper end of the filter element is located below the upper end of the shell.

2. The filter element of claim 1 having four lugs symmetrically spaced apart that allow insertion and removal of the filter element by a quarter turn.

3. The filter element according to claim 1 or 2, wherein: Each lug has a tapered leading edge to facilitate insertion into the slot and a downwardly projecting tab at a trailing end of the lug for abutting against an adjacent area of ​​the housing to define a fully inserted rotational position.

4. A filter element according to any one of the preceding claims, wherein The upper end cap has a central hole configured to receive an airflow tube depending from an upper end of the housing and to be airtightly fitted around the airflow tube.

5. A filter element according to any one of the preceding claims, wherein The upper and lower end caps are made of 15% glass-filled nylon 6.

6. A filter element according to any one of the preceding claims, wherein The glass fibers of the filter element are bonded by a water-soluble acid-based resin binder comprising a carboxylated acrylic polymer and a multifunctional alcohol.

7. A filter element according to any one of the preceding claims, wherein The drainage layer is made of polyester fiber coated with fluorocarbon.

8. A filter silencer for a compressed air stream that can be contaminated by aerosolized oil, the filter silencer comprising a housing and a filter element according to any one of claims 1 to 8, the housing comprising a cage into which the filter element can be removably mounted and a filter bowl removably attached to the lower end of the cage for collecting oil coalesced by the filter element, The cage has a cage top and an overhanging wall, the overhanging wall has an annular top edge and a hole located below the top edge, the hole is used to discharge air that has passed through the filter element, the cage top is formed with a central hole and is provided with a connecting piece, which is used to receive a compressed air flow and transmit the compressed air flow through the central hole to an air inlet pipe on the inner surface of the central hole, which is used to guide the compressed air flow into the filter element and to the lower end of the filter element, and the top edge is formed with a circumferential narrow groove, which is used to enable the lug to be slidably inserted into and removed from the end cover when the filter element is rotated relative to the end cover.

9. The filter silencer according to claim 8, wherein: The circumferential slot extends radially through the top rim and opens to an outer surface of the top rim.

10. The filter silencer according to claim 8 or 9, wherein: The upper end of the filter bowl is formed with a protruding lug for fitting into a slot in the lower edge of the overhanging wall.

11. The filter silencer according to claim 8, 9 or 10, wherein: The cage is made of nylon.

12. The filter silencer according to any one of claims 8 to 11, wherein: The filter bowl is made of polypropylene.

13. A filter silencer, the filter silencer having a filter element, the filter element having a circumferentially outwardly protruding lug formed at an upper edge of the filter element, the lug being configured to form a bayonet fit with a narrow groove at a top edge of a receiving cage, the receiving cage forming a part of a housing of the filter.

14. The filter silencer according to claim 13, wherein: The housing also includes a filter bowl having an upper rim formed with a protruding lug configured to form a bayonet fit with a slot at a bottom rim of the receiving cage.

15. A housing for a filter cartridge of a filter silencer, the housing comprising a cage for housing the filter cartridge and a filter bowl removably connected to the filter cartridge to allow insertion and removal of the filter cartridge and also for collecting coalesced oil, wherein The top edge of the cage is formed with a plurality of slots for receiving the protruding lugs at the top of the filter element and providing a bayonet fit between the plurality of slots and the protruding lugs.

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