Filter assembly and cartridge therefor

#This invention relates to a filter assembly and to a filter cartridge adapted to form part of such an assembly.

#It is well known in the gas and liquid filtration art to provide a filter housing in the form of a filter bowl and a filter head and to provide a separate consumable filter cartridge for fitting into the bowl. For assembling the filter, the cartridge is conventionally attached first to the filter head, followed by the filter bowl. But this conventional method of assembly is wasteful of space because the filter bowl has to be slid axially over the cartridge before it can engage the filter head, subsequent removal requiring the reverse procedure. A free space has to be provided beneath the filter head whose length equals the sum of the lengths of the the cartridge and the filter bowl. Where compactness is desired, or where the filter assembly forms part of a crowded installation, this waste space can be a disadvantage.

#It is therefore an object of the invention to provide an assembly of filter bowl, cartridge and head in which the filter bowl can be removed within a "freeboard" which is only a part, and preferably only a minor part, of the length of the filter cartridge.

#An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

#FIG. 1 is a view of a filter head in horizontal section;

#FIG. 2 is a view of the filter head and upper portions of a filter bowl and of a filter cartridge in the bowl, the view being taken in vertical composite section on the lines 0-A and 0-A' of FIG. 1;

#In the drawings, a filter bowl 10 is mountable to and demountable from a filter head 11 and houses a consumable filter element or cartridge 12 which may be a vapour coalescing filter of the general kind described in our Pat. No. GB-A-1603519 and 1557821 or may be an activated carbon filter element as described in our Pat. No. GB-B-2109268 or may be a dust removal filter or may be a combined filter and adsorption element. The working parts of the cartridge 12 are housed in a casing of plastics or other suitable material having an upper portion 14 attached by adhesive or other suitable means to a lower portion 16. The upper portion 14 is formed with a flange 18 projecting radially outwards therefrom and reinforced at intervals about the periphery of the upper portion 14 by upper and lower vertical webs 22,24 of triangular form extending part-way across the flange 18. It is also reinforced on its upper face with four generally rectangular top webs 20 extending the full distance across the flange 18. As seen in FIGS. 4a, 4b, the flange 18 is formed with a first cut-out 26 of relatively large angular extent and with three second cut-outs 28 of relatively small angular extent, the four cut-outs being disposed symmetrically at equi-angular intervals about the periphery of the flange 18. The relatively large first cut-out 26 is to allow the cartridge to enter a bowl having a pressure relief valve generally indicated by the reference numeral 38. The four rectangular top webs 20 occur at the ends of the first cut-out 26 and midway between each pair of second cut-outs 28 (FIGS. 4a,4b). However, if the valve 38 were omitted, the cut-outs could all be of the same angular extent, and there could be three such cut-outs or more than four with corresponding formations (described below) in the inner face of the filter bowl 10.

#As seen in FIG. 2, the filter bowl 10 has a lower region 30 connected at a transition region 31 to a radially enlarged top region 32 by a horizontal step 34 which defines a seat on which the flange 18 rests and thereby supports the cartridge 12 in an intended axial position relative to the bowl 10. The outer face of the top region 32 is formed with a groove 40 in which an O-ring 42 fits and is retained during mounting of the bowl 10 to and during demounting of the bowl 10 from the filter head 11. Internally of the top region 32 there are formed three vertically directed horizontally interrupted buttresses 44 disposed at 90.degree. intervals about the axis of the bowl 10. Each buttress 44 is formed with a lower part 44b that arises at a small clearance above the horizontal step 34 and acts firstly as an abutment limiting axial travel of flange 18 and secondly as a physical stop limiting angular travel of the bowl 10. Each buttress 44 is also formed with an upper part 44a that acts as a bayonet ramp follower. A first groove 46 is defined between the buttress lower parts 44b and the step 34 and receives the flange 18. Thus the second cut-outs 28 are dimensioned and positioned so that when the cartridge 12 is in an angular position such that they align with the buttresses 44 the cartridge 12 can pass axially downwards into the bowl 10 until flange 18 seats onto step 34. Displacement of the cartridge 12 in either angular direction engages flange 18 into groove 46 and the lower part 44b of each buttress then limits upward travel of the cartridge 12 which is therefore mounted to and demounted from the filter head 11 as a unit with the bowl 10. It is understood that the groove 46 at each buttress 44 is of the same height, has a common datum with that at each other buttress 44 and is directed parallel to the step 34. The upper part 44a of each buttress acts as a bayonet ramp follower and defines a second groove 48 with the lower part 44b. Again the second groove 48 at each buttress 44 is of the same height, has a common datum with that at each other buttress 44 and is directed parallel to the step 34. Each buttress 44 has a relatively small angular extent (about 24.degree.), the corresponding intervals being relatively large (about 66.degree.), these intervals not being critical but being selected to provide an effective and robust interface.

#Referring now to the the structure of the filter head 11, a first threaded or bayoneted port 50 leads to the interior of the cartridge 12 via a vertical port 52 which receives a spigot 54 upstanding from the upper casing portion 14. The port 52 is stepped at 60. An upper cartridge O-ring 56 seals against an upper smaller diameter portion 62 of the port 52 and a lower cartridge O-ring 58 seals against a lower larger diameter portion 64 thereof. When the cartridge 12 is correctly fitted to the filter head 11 the O-rings 56, 58 define an annular space 65 bounded by spigot 54 and vertical port 52 that is isolated from the prevailing pressure of fluid (usually gas) within the bowl 10 and head 11. A port 66 which conveniently is formed by post-drilling downwardly at a small angle communicates with the space 65 and may be threaded as shown for connection thereto of a pressure transducer (not shown) or other pressure-sensitive device. In the absence of a cartridge 12 in the bowl 10 or if the cartridge 12 is incorrectly fitted the state of the transducer or other device connected to the port 66 is determined by line pressure, and differs from the state when a cartridge is present. By this means an indication of the presence or absence of the cartridge 12 may be given either on the side of the filter head 11 or at a remote location. An outer chamber 68 is defined between the cartridge 12 and the bowl 10 and leads via a radially offset vertical port 70 in the filter head 11 to a second threaded or bayonet port 72. The ports 50, 72 are interchangeably inlets and outlets to the cartridge 12 depending on the intended direction of fluid flow.