Liquid purification or separation – Processes – Separating
Reexamination Certificate
2000-05-24
2001-06-19
Savage, Matthew O. (Department: 1723)
Liquid purification or separation
Processes
Separating
C210S340000, C210S411000, C210S425000
Reexamination Certificate
active
06248246
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a filtering apparatus, comprising a plurality of parallel-connected filtering units, having a common inlet channel for a flow to be filtered, a common outlet channel for a filtered flow, as well as a common, movable valve element provided with flow connections attachable to the inlet and outlet flow channels for directing the flow to the filtering units for activating the filtering units one by one. The invention further relates to the use of such a filtering apparatus in an engine as an automatic filter for filtering fuel and lubricant, as well as to a continuous-action filtering method applying the apparatus.
U.S. Pat. No. 4,256,583 describes a filter apparatus, comprising a rotary valve for directing a flow to be filtered alternately into two parallel filter chambers. In addition, the apparatus includes means for cleaning the filter chambers with a backflush between filtering cycles. Thus, the apparatus is a continuous-action unit and intended to be self-cleaning in order to avoid the necessity of replacing the filter elements present in the chambers.
The most important application for automatic filters, of which the U.S. Pat. No. 4,256,583 is one example, comprises fuel and lubrication systems in diesel engines, wherein filtering is used for removing mostly solid, engine-wearing impurities. Despite repeated flushings, the filtering capacity of automatic filters nonetheless deteriorates in time as a result of wear and contamination of filter elements, which manifests itself as a shorter interval between flushings, i.e. an increased need for flushing. At some point, the filter elements must be replaced with new ones and, e.g. in the diesel engines of ships, this must be done with no interruption of filtration. The inconvenience of service is a problem in presently available automatic filters, since the successive operating cycles of filtering chambers or the like filtering units are too short for the replacement of filter elements therebetween, particularly if the cycles have become shorter by the time the replacement of elements becomes necessary.
This problem has been addressed by using a separate backup filter for directing the flow to be filtered thereto while the actual filtering units of an apparatus are being serviced. However, such an extra-apparatus solution, which requires separate flow control valves and channels, is bulky and impractical.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a filtering apparatus, wherein it is possible to direct a flow to be filtered to various filtering units, such that servicing the units becomes easier and is possible to carry out within the framework of a structurally compact and integral apparatus. A filtering apparatus of the invention is characterized in that it comprises three filtering units, that a valve element is adapted to rotate around its axis and furthermore to move between two different positions, and that the valve element is provided with inlet and outlet connections for two filtering units for operating the units alternately by rotating the valve element, as well as with inlet and outlet connections for a third filtering unit which can be set in operation by moving the valve element.
Thus, the filtering apparatus of the present invention includes two filtering units which, in a normal operation of the apparatus, are able to take care of filtering and whose operation preferably consists of alternating filtering and flushing cycles controlled by a valve element. Hence, the third filtering unit of the apparatus constitutes a backup unit, to which a flow to be filtered can be directed as the two first-mentioned units are being serviced. According to the invention, the third unit is integrated as a structural part of the filtering apparatus and its operation is controlled by the same valve element as the other two filtering units of the apparatus. The third filtering unit can be provided with a filter element, which is clean, has a large filtering surface and a capacity which is sufficient for the duration of servicing the other two units, such as for the replacement of filter elements included therein. As the filtering process then continues with serviced filtering units, it is possible to replace the soiled filter element of the third filtering unit to make it ready for action for the next servicing period of the regular filtering units.
In accordance with the present invention, the actions required of a valve element are performed by a spindle with a preferably circular cross-section, which is both movable in the direction of its longitudinal axis and rotatable around its longitudinal axis, the actions being independent of each other. The spindle may be provided with flow deflecting ports located in a plane normal to its axial direction or with recesses bounded by the side of the spindle, which function as common inlet and outlet connections for the two filtering units normally used in the apparatus. By rotating the spindle, the flow can be preferably directed alternately to these units through the same flow connections. On the other hand, the inlet and outlet connections for the third filtering unit may be constituted by ports extending directly through the spindle in a plane normal to the spindle axis. These are positioned in the spindle alongside the inlet and outlet connections for the other two filtering units and are coupled with inlet and outlet channels common to the filtering units of the apparatus by moving the spindle in the axial direction and possibly by rotating it at the same time.
The operation of the two filtering units normally employed in the apparatus is based on alternating filtering and cleaning cycles in each unit. Cleaning is preferably effected by a backflush, the filtering units being thus provided with channels for delivering a flushing medium as well as for discharging a fluid contained in the unit at the start of a flushing, any loose impurities, as well as the flushing medium. The third filtering unit can preferably employ filter elements that are replaceable, disposable, or cleanable at the time of a replacement, whereby this unit does not require any flushing channels.
The invention comprises particularly the use of a filtering apparatus as described above in engines, such as diesel engines for ships, as an automatic filter for filtering fuel or lubricant. However, the apparatus is good for other applications as well, e.g., in power plants and in paper and process industries.
In a filtering method of the invention, a flow is filtered in continuous action by using alternately a plurality of filtering units, having a common inlet channel for a flow to be filtered, a common outlet channel for a filtered flow, as well as a common, movable valve element provided with flow connections to be coupled with the inlet and outlet flow channels for directing the flow to pass through the filtering units, such that the units are in operation one at a time. The method is characterized in that it employs two filtering units provided with preferably common inlet and outlet connections included in the valve element, by directing a flow to the units alternately by rotating the valve element around its axis, and that the flow is occasionally directed, by moving the valve element, to a third filtering unit, the valve element being provided with separate inlet and outlet connections therefor.
It is preferable that the filtering process is based on the two alternately used filtering units discussed above, as far as its operation is concerned. It is during any given operating cycle of one filtering unit that the other unit is subjected to cleaning, which is performed preferably by a compressed-air driven backflush. The third filtering unit constitutes a backup unit, which is primarily used during the replacement of filter elements in the other two units, or other such service procedures.
REFERENCES:
patent: 1189077 (1916-06-01), Elliott
patent: 1213764 (1917-01-01), Elliott
patent: 1699680 (1929-01-01), Sweetland
patent: 35982
Hunter Christopher H.
Parker Hannifin Oy
Savage Matthew O.
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