The present invention generally relates to fluid filtration. More particularly, the present invention relates to indicators for providing a warning when a filter element of a filter assembly is missing, of an incorrect size, or improperly installed, and to filter assemblies incorporating such indicators.
Fluid cleanliness is an important factor in the health of a fluidic/hydraulic system. Engine oil lubrication systems, for example, which are typical of many fluidic systems, frequently include a filter assembly for removing damaging particles from the lubricating oil utilized in the system. Mechanical wear within the engine, the outside environment, and contaminants accidentally introduced during normal servicing provide a source of large particles which may plug lubricating nozzles or severely damage parts and create excessive wear on surfaces that may rely on a thin film of the lubricating oil for protection.
Clearly, the level of undesirable contaminants in the fluid affects not only the quality of system performance, but also the useful life of substantially all of the working components within the system. All moving components in contact with the fluid are vulnerable to wear and, therefore, the resultant premature failure, if such contaminants are not removed from the system. Consequently, proper cleaning of the fluid to remove undesirable contaminants can significantly lengthen the life of the system components, as well as reduce maintenance and its attendant costs. Further, effective cleanliness control can result in significant improvements in the overall reliability and performance of the system.
Filter assemblies, or modules, have been used for this purpose in a variety of applications and fluidic environments. In typical filter assemblies, a filter element is encased within a filter body, or casing (e.g., a filter bowl). One or more filter manifolds may be attached to the filter body to feed unfiltered medium to the upstream side of the filter element (e.g., where the filter element is cylindrical, the outside of the filter element). As the medium passes through the membrane material to the downstream side of the filter element, contaminants are removed from the medium. Filtered medium is then collected from the downstream side of the filter element (e.g., where the filter element is cylindrical, the inside of the filter element).
During the filter element's service life, an increasing amount of removed contaminant will collect on one side of the filter element, which causes the pressure difference between the upstream and downstream sides of the filter element to increase, thereby lowering the filtration efficiency of the filter element. If the differential pressure exceeds a certain pre-determined value that is dependent upon the filter element material, design, etc., the filter element may be damaged. Additionally, at high differential pressures, particle breakthrough (i.e., contaminant particles passing through the pores in the filter element) may occur. Timely cleaning or replacement of the filter element is therefore of utmost importance.
To this end, in existing filter assemblies, the filter head may contain pressure transducers, temperature detectors, or other similar means to measure characteristics of fluid flow and filter performance. These components are used to sense the differential pressure across the filter element to determine whether the filter element is sufficiently clogged with contaminant removed from the fluid flow to require replacement. Thus, once the differential pressure across the filter element reaches the pre-determined threshold, an indication may be provided (e.g., by causing a part to pop up out of the exterior of the filter head) to signal the need to replace the filter element.
Still, such devices only signal the need for replacement of the filter element. However, once a filter element has been removed from the filter assembly, it must be ensured that a replacement filter, of the correct size/configuration, is properly re-installed into the filter assembly prior to placing the assembly back into service. In aircraft applications, for example, on numerous prior occasions, maintenance personnel have failed to install a filter element into the filter assembly after the used filter element was removed. With no provisions for detecting and indicating a missing-element condition, the aircraft was then placed back into service and flown without proper filtration, thereby causing severe damage to down-stream components.
There is therefore a need for a means of detecting situations in which a filter element is absent, of an incorrect size, improperly installed, etc., and providing a warning signal to alert personnel prior to re-deployment of the filter assembly.
The present invention addresses the above-mentioned shortcomings by way of indicator devices, and filter assemblies incorporating such devices, that provide a visual and/or electrical (remote) indication of a missing filter element. It is noted that, in the instant application, the term “missing” is used to refer generally to situations where no filter element is installed, or a filter element of an incorrect size is installed, or a filter element is mis-aligned/improperly installed, etc. In addition, although specific situations may be referred to herein, such references are made by way of example only, and the present invention is applicable to all aerospace/aircraft, marine, and land-based filtration systems involving oil, fuel, water, and/or other fluid filtration.
In a preferred embodiment, the indicator device 50 has a generally cylindrical configuration, and includes a housing 52 having a top end 52a and a bottom end 52b. Towards its upper portion, the housing 52 includes a first passage 54 that is separated from a second passage 56 by a solid transverse section 53, where the wall of each of the passages 54, 56 is defined by a respective portion of the radially-inner surface of the housing 52. Thus, the first passage 54 extends from the solid transverse section 53 to the top end 52a of the housing 52, while the second passage 56 extends from the solid transverse section 53 to the bottom end 52b of the housing 52.
As shown in
The indicator 50 includes a piston 58 that is disposed so as to slide axially within the first passage 54, and a button 62 that is disposed so as to slide axially within the second passage 56. In embodiments of the invention, the piston 58 is generally T-shaped, including an upper end 58a that may form the horizontal portion of the “T”. The T-shaped piston 58 also includes a (unitary) central vertical portion 90, which extends axially downwards a distance from the upper end 58a, and then becomes hollow, with the hollow portion having an annular wall 91 and a top end 58b. As shown in
The upper end 58a of the piston 58 is also unitary with an annular outer wall 88 that extends axially downwards from the upper end's periphery and is disposed such that its sliding movement is guided by the wall of the first passage 54. In addition, a (second) annular compartment 92 is formed between the central vertical portion 90 and the annular outer wall 88, and is bounded on top by the underside of the piston's upper end 58a. Preferably, the piston 58 is retained in place by an upper annular cap (or retainer) 70 that is disposed between the annular outer wall 88 and the wall of the first passage 54. In this regard, the annular outer wall 88 may have a lip 89 that abuts the upper annular cap 70 when the piston 58 is fully extended outwards.
The indicator 50 also includes a first magnet 60, which may be, e.g., a pin magnet. As shown in
In embodiments of the invention, the magnet 60 is epoxy bonded to the top end 58b. In addition, the piston 58 may include a longitudinal bore 58c that allows for bleeding of air during the epoxy bonding process. The bore 58c also helps to reduce the overall weight of the indicator 50.
As shown in the embodiment of
In embodiments of the invention, a second magnet 64, such as, e.g., a pin magnet, lies within the U-shaped lower portion 74 and extends into the upper portion of the button 62. In the embodiment shown in
In a preferred embodiment, a piston 158 is disposed so as to slide axially within the first passage 154. As with other embodiments of the present invention, the piston 158 is generally T-shaped, including an upper end 158a that may form the horizontal portion of the “T”. The T-shaped piston 158 also includes a (unitary) central vertical portion 190, which extends axially downwards from the upper end 158a, and then becomes hollow, with the hollow portion having an annular wall 191 and a top end 58b. As shown in
The upper end 158a of the piston 158 is also unitary with an annular outer wall 188 that extends axially downwards from the upper end's periphery and is disposed such that its sliding movement is guided by the wall of the first passage 154. In addition, a (second) annular compartment 192 is formed between the central vertical portion 190 and the annular outer wall 188, and is bounded on top by the underside of the piston's upper end 158a. Preferably, the piston 158 is retained in place by an upper annular cap (or retainer) 170 that is disposed between the annular outer wall 188 and the wall of the first passage 154. In this regard, the annular outer wall 188 may have a lip 189 that abuts the upper annular cap 170 when the piston 158 is fully extended outwards.
The indicator 100 also includes a first magnet 160, which may be, e.g., a pin magnet. As shown in
In embodiments of the invention, the magnet 160 is epoxy bonded to the top end 158b. In addition, the piston 158 may include a longitudinal bore 158c that allows for bleeding of air during the epoxy bonding process. The bore 158c also helps to reduce the overall weight of the indicator 100.
The indicator 100 also includes a button 162 that is disposed so as to slide axially within the annular compartment 156. As shown
In the embodiment of
With reference to
In practice, the devices 50, 100 are used to indicate a missing filter element, where the term “missing” refers generally to situations where no filter element is installed, or a filter element of an incorrect size is installed, or a filter element is mis-aligned/improperly installed, etc. As shown in
When indicator 50 is used in the filter assembly 1, the first magnet 60 and second magnet 64 are positioned such that they face one another with respective opposite poles. Thus, when a filter element 5 of correct size/shape is properly installed within the bowl 10, the filter element 5 rests on the upper end 58a of the piston 58. The weight of the filter element 5 then causes the piston assembly (i.e., the piston 58 and the first magnet 60) to slide downwards, i.e., inwards. Given the polar configuration of the two magnets 60, 64, the inward motion of the piston assembly creates a magnetic force that overcomes the spring force of the second spring 68, thereby attracting the button assembly (i.e., the button 62 and the second magnet 64) to move upwards, i.e., inwards. In this way, when a filter element 5 is properly installed, the button is pulled all the way in such that it is substantially flush with the bottom end 18 of the annular wall 16 and the bottom end 52b of the housing 52 (see
However, when the filter element 5 is missing (see, e.g.,
In embodiments of the invention, the visual signal/warning may be replaced by, and/or supplemented with, an electrical indication. Thus, in one embodiment, means may be provided for generating an electrical signal to indicate a missing filter element. See, e.g.,
As shown in
When, on the other hand, the filter element 5 is properly installed, the button 62, 162 is retracted inwards. As a result, the magnet 64, 164 (and corresponding magnetic field) is no longer within actuating proximity of the Hall Effect sensor 600, which causes the sensor 600 to deactivate (e.g., open the electrical circuit) and indicate an “off” condition.
It is noted that other means for generating an electrical signal may also be used. For example, in the embodiment of
As mentioned previously, the indicator 100 shown in
However, when the filter element 5 is missing, the spring 166 pushes the piston assembly outwards, thereby reducing the force of attraction between the two magnets 160, 164, and positioning them to repulse one another. This repulsion, in turn, urges the button assembly outwards, thereby providing a visual signal that indicates a missing filter element.
As with the indicator 50, in this embodiment, the U-shaped lower portion 174 of the button 162, or a visible section thereof, may be colored (e.g., red) to enhance visibility. In addition, the visual signal/warning may be replaced by, and/or supplemented with, an electrical signal for (normal and wireless) remote indication as described previously.
While the description above refers to particular embodiments of the present invention (the presently disclosed embodiments are to be considered in all respects as illustrative and not restrictive), it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention. All changes that come within the meaning, and range of equivalency, of the claims are intended to be embraced therein.