Liquid purification or separation – With repair or assembling means
Reexamination Certificate
2000-08-28
2002-05-21
Drodge, Joseph (Department: 1723)
Liquid purification or separation
With repair or assembling means
C210S455000, C210S095000, C055S426000, C055S395000, C055S398000
Reexamination Certificate
active
06391197
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a filter assembly for collecting material that is entrained in a gas stream such as particulate solid material or liquid in an aerosol form, and to a tubular filter element for location in a housing to collect such material.
2. Present State of the Art
Filtration of gas in a compressed gas system is generally required so that the gas is sufficiently clean for a subsequent application or to minimize adverse effects of impurities on components of the system. For example removal of compressor oil can be required to minimize chemical contamination and accumulation on valves which might lead to malfunction of the valves and removal of particulate solid material can be required to minimize abrasion.
A known filter assembly for use in compressed gas systems is sold by Domnick Hunter Limited under the trade mark OIL-X. It comprises a housing having inlet and outlet ports for the gas stream that is to be filtered and a tubular filter element which can be located in the housing and is configured for the gas stream to flow through its wall, for example generally outwardly from the inside of the filter element to the outside. When the assembly is used to collect liquid in the gas stream (for example which is carried in the stream as an aerosol), the filter element will cause the liquid to coalesce. Coalesced liquid then drains from the filter element and collects in the housing for discharge. For such applications, the housing will include an outlet for discharge of any collected liquid.
The housing of such a filter assembly comprises a body section in which the filter element is located and a head end cap with the inlet and outlet ports for the gas stream. The end cap includes appropriate conduits within it for the gas stream to flow between the ports and the filter element. The body section is closed at its base and therefore provides a reservoir in Which coalesced liquid that has been filtered from the gas stream can collect. The formation of the body section housing with a closed base means that each body section must be made individually, for example by a moulding or casting process. Different tools for use in such processes are required for each configuration of product.
SUMMARY OF THE INVENTION
The present invention provides a filter assembly in which the housing comprises a body section with a constant cross-section along its length and at least one separable end cap.
Accordingly, in one aspect, the invention provides a filter assembly for collecting material that is entrained in a gas stream, which comprises a housing for a tubular filter element the housing having an inlet and an outlet for the gas that is to be filtered, and comprising a body section and a separable end cap, the body section having at least one longitudinally extending formation in its internal wall and its cross-section being substantially constant along its length, the body section having a generally transverse groove formed in its internal wall which can be engaged by the end cap to connect it to the body section, the transverse groove having a discontinuity at a longitudinally extending edge of the longitudinally extending formation.
The constant cross-section of the body section is such that its cross-section at any two spaced apart points taken on parallel planes are similar and equal figures, apart from features by which te cross-section is specifically modified for example to provide fixation points for other components of the assembly or to provide seals to other components. The constant cross-section is such as might be formed by an extrusion process. It is an advantage of the present invention that the body section of the housing can be formed by extrusion, allowing the body section effectively to be formed continuously.
The filter assembly of the present invention has the advantage that the holding can be constructed with a size suitable for the filter element that is to be used in it and for the location in which te assembly is to be used, by cutting the body section to an appropriate length. Common end caps can be used for housings with a range of capacities. Details of a housing which with a body section having a constant cross-section and separable end caps are disclosed in WO-A-30803 (which claims priority from UK patent applications nos. 9726419.6 and 9815963.5 and which has the same filing, priority and publication dates as the present application). Subject matter that is disclosed in that document is incorporated in the specification of the present application by this reference. The flexibility of design that arises from use of a constant cross-section body section Las advantages for he user because products can be built to meet the requirements of his application. The flexibility has advantages for the manufacturer of the housing because a range of products can be made without the need to make different moulds for each product. The inventory of parts that the manufacturer is required to maintain for manufacture of a range of products is also minimised. Maintenance is facilitated since parts of a housing that have failed can be replaced without having to replace all of the housing.
In another aspect, the invention provides a method of making a housing for a filter for collecting material that is entrained in a gas stream, which comprises forming a body section with at least one longitudinally extending formation in its internal wall by extrusion, cutting the body section to an appropriate length, and fastening the body section at each of its ends to respective end caps.
It is an advantage of the constant cross-section of the body section that it can be made conveniently by extrusion with formations present in the wall. The internal formation in the body section might stand proud of the internal surface in the manner of a rib. It might be in the form of a groove. A combination of one or more ribs and one or more grooves might be incorporated.
It has been found that an internal longitudinal formation can facilitate drainage of liquid that has coalesced in the housing into the bottom of the housing for discharge. This can be important to prevent reentrainment of the liquid in the gas stream as it is discharged from the assembly. It is a particular advantage when the gas stream passes through the wall of the filter element from the internal cavity for discharge from the annular space between the filter element and the internal wall of the housing.
The internal formation can be used to incorporate a generally transverse groove into the body section in its internal wall for engaging one or more end caps. For example, when the longitudinally extending formation comprises a rib, the generally transverse groove can be formed in the rib. When the longitudinally extending formation comprises a groove, the generally transverse groove can be formed in the wall of the body section, communicating with the longitudinal groove. When the groove is provided in the rib, it can extend around the full width of the rib or just a part of the width of the groove. When the groove is provided in the wall of the body section to communicate with the longitudinally extending groove, it can extend around substantially all of the perimeter of the body section (apart from that part occupied by the longitudinally extending groove unless it is deeper than that groove) or just a part of the perimeter of the body section, for example less than 70%, less than 50%, less than 40% or less than 20%.
Preferably, the width of the internal formation, measured as the proportion of the perimeter of the body section that it occupies, is at least about 3%, more preferably at least about 7%, for example at least about 10%. The width is preferably not more than about 20%, more preferably not more than about 15%. When the body section has a generally circular cross-section, the width of the formation can be expressed in terms of angle of arc. The formation will therefore preferably have a width of at least about 5°, more preferably at least about 10°, especially
Cecil Terry K.
Domnick Hunter Limited
Drodge Joseph
Workman & Nydegger & Seeley
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