Liquid purification or separation – Filter – Within flow line or flow line connected close casing
Reexamination Certificate
1999-08-06
2001-09-04
Savage, Matthew O. (Department: 1723)
Liquid purification or separation
Filter
Within flow line or flow line connected close casing
C210S491000, C210S504000, C210S505000
Reexamination Certificate
active
06283307
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This patent pertains to the technological sector of filtration in general, and relates in particular to fluid filtration in the engine field.
2. Description of the Background Art
In both Diesel cycle and Otto cycle internal combustion engines, it is well known that the lubricating oil must be kept filtered.
The problem of effective lubricating oil filtration is not easy to solve, as it involves opposing requirements.
European patent 341349 in the name of the present applicant offers a solution to the problem, consisting of locating within a filter of commonly known type, such as a full-flow filter, three filter cartridges, two of which are connected in series with each other, the combination being connected in parallel with the third.
By carefully coordinating the porosity of the three cartridges, with the parallel cartridge having a porosity between that of the two series-connected cartridges and the most porous cartridge being located externally, the filter of the said patent attains an efficiency not achievable by other full-flow filters, and achievable only by the most costly and complicated known filters such as double filtration filters.
The problem inherent in the various filtration systems will be more apparent on reading said European patent 341349, the entire content of which is hereby incorporated by reference.
The present patent relates in particular to filters the subject of said European patent.
Although said filters have proved very effective operationally, they present certain constructional difficulties which considerably increase their cost.
In this respect they use three separate filter cartridges of different type, of both paper and unwoven fabric, which not only have to be manufactured separately and then individually mounted in the filter, but require the filter to be provided with an inner metal reinforcement to maintain them in their operating position.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a filter medium from which a single filter cartridge can be formed having the characteristics of the combined three said filter cartridges of the said European patent and which can be manufactured in a single piece for insertion into the filter device as it is.
A further object of the present invention is to provide a filter medium having better filtration and mechanical characteristics than known materials.
A further object is to enable filter devices of “cup” type to be formed presenting improved filtration characteristics, within the framework of a simplified construction.
The above objects are obtained, according to the process of the present invention, by:
forming, on a web for oil filters, at least one first filtering region (A) made of a layer (A) of cellulose pulp and at least a second filtering region (AB) made of a layer (A) of cellulose pulp to which is adhered superposed at least one layer (B) of cellulose pulp and a fiber material selected from the group consisting of glass, polyester, polyethylene and polyamide fibers;
pressing the resulting web, said layers (A, B) of said at least one second filtering region (AB) being subjected to a lesser pressure than the layer (A) of said at least one first filtering region, this latter thus being positioned lying on the same plane as the layer (B) of the adjacent second filtering region (AB); and
folding the pressed web in a single filter cartridge for oil filters comprising three separate filter regions, two of which are in series and the third one is in parallel with the first two.
A multilayer filter sheet, the characteristics of which will be apparent from the ensuing description of its method of manufacture, is then cut into strips and folded to form a filter cartridge of the well known toroidal form.
The technology employed in the manufacture of the filter medium is that typically used in paper manufacture.
According to the invention the process is carried out in a paper manufacturing plant for processing synthetic cellulose fibres.
At least two pulpers are provided in said plant.
One of these is used for preparing the cellulose fibre suspension in the manner known in paper manufacture.
In the present case, the cellulose fibres are provided in sheets and are processed to a concentration of between 3% and 5% at a pH of between 5 and 7.
According to the invention, the cellulose fibres have a high alpha-cellulose content to ensure sufficient inter-fibre bonds without having to use extensive beating.
In this respect, it is known that beating modifies the fibre dimensions, to create inter-fibre bonds which are so close as to compromise porosity and hence the filtering characteristics of the paper.
The other pulper is provided to disperse bales of staple glass fibre or the like in water by opening their fibres.
According to the invention, the glass fibres are processed at very low fibre concentration, of between 0.5 and 1.2%, in an acid environment of pH between 2.8 and 3.8, maintained within said range by adding sulphuric acid.
Starting from the resultant materials, two separate pulps are prepared, one containing only cellulose fibres, the other containing both cellulose fibres and glass fibres.
A proportion generally suitable for achieving good results is 50% of glass fibres and 50% of cellulose fibres, it being apparent that the glass fibre percentage influences the filtering effectiveness in a directly proportional manner, in this respect it being the glass fibres which provide the lowest porosity.
The two pulps are then purified of undesirable particles by treatment in known cleaners or cyclones, which exploit the specific gravity differences between the treated particles and the particles of dirt.
Before the formation stage a moisture-resistant resin of known type, such as an acrylic resin or an epoxy resin, is added to each pulp to increase the physical-mechanical characteristics of the fibre and make it suitable for the subsequent forming and drying stages.
The forming stage is effected in the manner well known in paper works by conveying the two pulps separately in succession onto a temporary support, substantially a plastic web, which grazes a mesh-forming cylinder dipping into a forming box containing the desired pulp.
The web firstly collects the pulp formed only of cellulose fibres, which are to form the substrate of the filter medium.
On the first layer there is then applied a second layer using the pulp containing both the cellulose fibres and the glass fibres.
This second layer can conveniently be formed as strips, by suitably masking the forming roller.
The two layers formed and combined in this manner are collected by a synthetic felt web which acts as a conveyor belt and absorbs the two pulps by capillarity, so joining them together.
According to the invention, the glass microfibres, used for the most severe filtration stage, have a size of between 0.5 and 14 microns and retain the contaminating particles while allowing the liquid undergoing filtration to pass, they also retaining particles smaller than the pore size by virtue of known phenomena such as Brownian motion.
Combining glass fibres with cellulose fibres prevents the glass fibres releasing miniparticles, commonly known as shots, which are extremely damaging if they reach the hydraulic lubrication circuits, and which up to the present time have greatly limited the use of glass fibres in filter media.
The two pulps, which are initially simply laid one on the other, are then pressed to a pressure of between 0.1 and 1 kg/cm
2
, for example between facing rollers.
The sheet obtained in this manner is then dried, generally by a mixed method using rollers heated to about 120° C. by steam, and hot air drying ovens of adjustable temperature.
After drying, the material is impregnated with acrylic latex in a 50% solution (percentage of dry material) to give the sheet material to form the filter plate sufficient mechanical strength to resist subsequent folding of the sheet, and to withstand operating pressures of the order of between 100 and 800 kPa (kilopa
Birch & Stewart Kolasch & Birch, LLP
Savage Matthew O.
UFI Universal Filter Intenational S.p.A.
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