Coupling device for connecting a replaceable filter element to a conduit

A coupling device for connecting a filter element to a filter conduit has male and female couplings each having a passageway for fluid. The male coupling is secured to the filter conduit and has at least two radially projecting lugs. The female coupling is secured to the filter element and has at least two latching tabs for engaging the lugs. A spring is operatively mounted on the male coupling and interferes with the radially projecting lugs. The spring is disposed so as to engage at least one latching tab when the male and female couplings are moved toward each other. The spring urges the latching tabs to rotate in a first angular direction thereby causing the tab to latch to a lug of the male coupling.

TECHNICAL FIELD

The invention relates generally to a filter cartridge for a filter vessel in a fluid purification system, and more particularly to a coupling device used to connect a replaceable filter cartridge to an outlet tube in a filter vessel for purification of radioactive or other hazardous fluids.

BACKGROUND OF THE INVENTION

Power plants and other facilities with fluid purification processes frequently have used filter tanks or filter vessels to purify a variety of different liquids or gases, such as fluid fossil fuels, steam or water. Such filter vessels have an inlet supplying a fluid to a main filtration chamber holding a number of tubular filters. Long tubes within the filter vessel support and act as the core for the tubular filters. These long tubes extend from a tube sheet that separates the main chamber from a plenum for holding purified fluid. An outlet leads from the plenum to the exterior of the filter vessel.

In conventional practice, on the opposite end of the filters from the tube sheet, separate filter mount assemblies secure the filters to the tubes while sealing that end of the tube. The conventional filter mount assemblies contain numerous parts, which frequently fall into the filter vessel during disassembly of the mount assembly to replace the filters. Parts falling into the vessel must be removed to prevent damage to filter elements caused by motion of the loose parts during service flow. If loose parts cannot be readily located and removed with suitable “fishing” tools, filter elements must be removed to permit access to the vessel to retrieve the loose parts. U.S. Pat. No. 5,667,679 to Bozenmayer et al. attempts to solve this problem by providing a filter mount assembly that may be removed quickly without losing parts. This design, however, uses stainless steel parts that are difficult to dispose or recycle when radioactive, which condition may obtain in nuclear power plants.

Another problem associated with conventional filter mount assemblies relates to the ease of installation and removal. Rapid installation and removal of filter elements in radioactive steam systems or other hazardous environments is highly desirable to minimize worker exposure.

Referring toFIG. 1, another conventional filter vessel100has an inlet102that delivers unpurified, typically pressurized, fluids to a main chamber104. The arrows F indicate direction of flow for the fluid during normal operations.

The fluid enters replaceable filter cartridges106, as known in the art, and through known tubular filters contained thereby that remove unwanted particulate or foreign matter. The purified fluid then flows downward through tubes or pipes108that open up into a plenum110. The plenum is separated from the main chamber104by a stainless steel or a carbon steel false bottom or tube sheet112conventionally welded to the tubes108. The fluid then exits the filter vessel100through an outlet114. Conventional filter vessels100typically vary in diameter from six inches to seven feet (and three foot to eight foot heights) depending on the quantity and size of filter elements contained therein. Vessels are known to accommodate anywhere from two to over 1000 filter cartridges.

Some conventional filter cartridges106are held in place by a hold down plate116as known in the art. The filter cartridges106are single open-ended with a closed top and a protruding bolt, post, rod or other connector118to extend upward through a hole in the hold down plate116for lateral support and to maintain distances between adjacent filter cartridges. The hold down plates116are usually bolted to the perimeter of the vessel or secured to the bottom by long connecting rods (not shown). Either mechanism provides downward force to seal the cartridges106to the tube sheet112. Cartridges106that are held down by hold down plates116typically have a spigot that fits into holes in the tube sheet112, and is sealed with either a flat gasket or one or more O-rings (not shown).

Some filter cartridges106have threaded bottoms for securing the filter cartridge to the tube sheet112and effecting a liquid tight seal, and these therefore do not require a hold down plate. However, threading of the filter cartridge106onto each of the tubes108requires numerous rotations of the filter cartridge106by a robot, hand, wrench, other special tool or automatic mechanism. The threading and unthreading of the filter cartridge106is a time consuming job which undesirably prolongs the worker's exposure to a hostile environment.

U.S. Pat. No. 3,279,608 to Soriente et al. discloses a guide rod and hook design used to mount a filter cartridge onto a tube welded to a tube sheet such as an Aegis™ Fossil Assembly as is known in the art. The filter cartridge has a guide rod welded to a plate with an end having a hook. A coil spring and nut are used to seal the top of the filter while compressing the filter cartridge against the tube to hold it in place against an adapter threaded permanently to the tube.

The upper end of the guide rod is used to attach to a positioning lattice for lateral stabilization. This design, however, still requires the unthreading of the nut to remove the filter cartridge from the tube, and the rivet hook is not considered to be of adequate strength for high pressure and highly corrosive nuclear power plant applications.

Another known filter cartridge and filter vessel eliminates the need for threading the filter cartridge to a tube on a tube sheet. As shown onFIGS. 2A-2D, a filter cartridge500has a steel adapter502that connects a filter504to a stainless steel filter vessel tube506. As shown inFIGS. 2C-2D, a spring508applying forces of 50-60 pounds is located between a support ring510welded to the exterior of the tube506and two pins512also welded to the exterior of the tube506. Referring toFIGS. 2B and 2C, the adapter502has two opposing slots514(only one shown) for receiving the pins512and has an annular groove516that slides over the pins512as the adapter502is rotated about the tube506. Once the adapter is rotated 90°, as shown inFIG. 2D, the pins512are positioned in two opposing locking apertures518.

In order to position a filter cartridge500on the tube506, the filter cartridge must be pushed downward (axially) to engage the pins512and spring508, and then rotated a full ninety degrees to place the pins512in the locking apertures518. The spring508biases the adapter502upward to hold the pins512against the bottoms520of the locking apertures518, which further stabilizes and secures the filter cartridge500on the tube506.

In some nuclear power plant filter vessel applications, during backwashing (fluid flow in the upward direction onFIGS. 2A-2D) the spring and fluid can combine to form an axial force of over 100 pounds that impacts the filter cartridge500. The adapter502must be made of steel to withstand this force, which is transmitted through the circular pins512. Otherwise, the high axial forces will cause the pins512to rip through an adapter502made of a weaker material, such as plastic, and disengage the filter cartridge500during backwashing operations.

Radioactive steel hardware, however, is dangerous, difficult and expensive to handle when replacing filter cartridges. Steel hardware cannot be recycled or incinerated using present technology. Re-use of the hardware with new filter cartridges is not practical due to the amount of radiation to which the operator is exposed. For this reason alone, the hardware is often replaced rather than re-used. The discarded hardware that is disposed of as radioactive waste will incur a disposal cost that is ten times or more its initial cost.

Accordingly, what is needed is an inexpensive, easy to use filter mount assembly constructed of easily and economically disposable materials.

SUMMARY OF THE INVENTION

The present invention is directed to a coupling device for connecting a filter element to a fluid conduit. The coupling device includes a male and a female coupling member with each member having a passageway for fluid. The male coupling member has at least two radially projecting lugs. The female coupling member has at least two latching tabs that engage the radially projecting lugs of the male coupling member. A spring is operatively mounted on the male coupling member. The spring is disposed to engage at least one latching tab when the male and female coupling members are moved toward each other. The spring urges the latching tab to rotate in an axial direction thereby causing the latching tab to latch to the lug of the male coupling member.

Another aspect of the present invention is directed to a fluid coupling element with a first and second coupling member formed around an axis. The second coupling member is sealably matable to the first coupling member for the transmission of fluid therethrough. The first coupling member has a free end and a sidewall with a lug extending laterally from the sidewall. The lug has a latch surface formed at an angle to the axis. The lug also has a guide surface that extends from the latch surface toward the free end of the first coupling member. The second coupling member has a sidewall that terminates in a free end. The second coupling member also has a latch tab that terminates in an enlargement portion. A means for indexing, is mounted on the first coupling member, leads the enlargement of the latch tab to the guide surface of the lug. A spring is mounted on the first coupling member and is disposed to engage the second coupling member when the first coupling member is coupled to the second coupling member. The enlargement portion of the latch tab is urged against the guide surface of the lug by the spring. The enlargement portion of the latch tab clears the second surface of the lug when the first coupling member is mated to the second coupling member. The spring rotates the enlargement portion of the latch tab relative to the axis of the first coupling member so that the enlargement portion of the latch tab abuts the latch surface of the lug after the enlargement portion of the latch tab clears the guide surface of the lug.

Another aspect of the present invention is directed to a method of joining a first fluid carrying member to a second fluid carrying member so as to define a fluid path therebetween. A terminal portion of at least one latch tab of the first fluid carrying member is indexed to a guide surface of a lug extending from the sidewall of the second fluid carrying member. One of the first or second fluid carrying members is inserted into a second of the first or second fluid carrying members. The terminal portion of the latch tab is slid along the guide surface of the lug until an enlarged portion of the latch tab has moved axially farther away from the free end of the second fluid carrying member than a retaining surface of the lug. A spring is used to rotate the latch tab of the first fluid carrying member around the axis such that the enlarged portion of the latch tab becomes located adjacent the retaining surface of the lug.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIG. 3A, a filter vessel12has a fluid inlet14, an outlet16, a main filtration chamber18and a plenum20separated from the main chamber by a tube sheet or false bottom22. While the filter vessel12is shown holding three filter elements or cartridges24, it will be appreciated that filter vessels may be designed to accommodate any number of filter cartridges depending on the particular filtration requirements of the fluid system.

Each filter cartridge24has a top portion26, preferably designed to be free standing, but alternatively supported laterally and/or vertically by a hold down plate or positioning lattice28as known in the art. The hold down plate or positioning lattice28may include spaced dimples (not shown) to mate with indents (not shown) on the top portion26of the filter cartridges24, or posts or bolts (not shown) may extend from the top portion26to be inserted through holes in the hold down plate or positioning lattice28as known in the art.

Each filter cartridge24includes a housing29which holds a tubular filter30, as known in the art, that includes yarn and/or pleated non-woven membrane surrounding a perforated core.

For radioactive filtering applications it is desirable to form the housing29from a material which can be readily shredded and incinerated. Preferably, the housing29is formed from a thermoplastic material such as polypropylene which may be reinforced with glass fiber or another filler.

Referring now toFIG. 3B, a coupling device10according to the invention mounts each filter cartridge24onto a steel filter conduit or tube32integrally formed with, or welded to, the tube sheet22. Each coupling device10includes a preferably stainless steel adapter or male coupling34and a non-steel adapter or female coupling36which is formed as part of the filter cartridge24. The male coupling34is permanently attached to the filter conduit32, as explained below.

It will be appreciated that the male coupling34may be made of any corrosion-resistant material of suitable strength as long as it is compatible with the hazardous or radioactive environment of the fluid process.

To facilitate disposal, the female coupling36may be formed of any material which is amenable to be shredded and incinerated. Preferably, the female coupling36is formed of a polymeric material, such as thermoplastic and thermosetting plastics, polymers and resins, that have sufficient structural strength to withstand, in the structures shown, at least 70 to 100 pounds in axial force without shearing, tearing or otherwise failing. A particularly preferred material includes injection molded polypropylene which may be reinforced.

The female coupling36may be continuously formed with the housing29, or may be integrally attached thereto using any known method of attachment. For example, the female coupling36may be attached to the housing29by thermo-bonding, welding, chemical bonding, threading, pinning, or any other mechanical mechanism that provides an adequate seal between the housing29and the female coupling36while permitting the core of the filter to communicate with the core74of the female coupling36.

It will be appreciated, however, when recycling or handling is not a concern, the female coupling36could be made of metal, such as stainless steel, as long as it is strong enough to withstand the impact of axial forces distributed by the lugs54.

Referring toFIGS. 4A and 4B, in the preferred embodiment, the male coupling34has a generally cylindrical shape defining a hollow core40to be used as a fluid passageway and defining an axial direction or axis ‘a’. The male coupling34also includes a cylindrical first upper portion42with a free end41that connects to the female coupling36, and a second lower portion44that connects to the filter conduit32, preferably by welding or threaded connection.

The inner diameters of the upper and lower portions are also different lengths to accommodate the sizes of the filter cartridge24and the filter conduit32. The filter conduit32comes in a range of sizes from 1″ to 6″ outer diameter, but typically is provided with approximately 1½″ outer diameter for both nuclear and fossil fuel applications, while the filter cartridges themselves are provided in the 2-2½″ outer diameter range for most applications. The upper portion42of the male coupling34typically has inner diameter of 1¼to 1½″ for filter cartridges24spaced within the filter vessel12at 3 to3½″ centers.

In the preferred configuration, lugs54are welded to, or more preferably integrally formed with, the exterior sidewall50of the male coupling34so that the core40is not blocked by any support mechanism for the lugs54. The lugs54project outwardly from the exterior sidewall50of the male coupling34, preferably at right angles to axis a. The lugs54include an upper surface53, a lower, retaining or latch surface56, a guide surface58and a sloped, angled or concavely arcuate surface59.

While the illustrated embodiment shows lugs54disposed about a single plane that is orthogonal to axis a, in an alternative embodiment the lugs can occupy segments of helical paths. In this alternative embodiment, each lug54would tilt upward from the junction of the guide surface58and the latching surface56.

It will be appreciated that while lugs54are shown at diametrically opposite positions, many positions at angles to the axis ‘a’ are possible. Additionally, three, four or more lugs can be used rather than just the two lugs shown.

The male coupling34is fitted with one or more springs65, preferably torsional, that are mounted to respective mounting posts or shanks55which extend from the exterior sidewall50of the male coupling34in a direction generally normal to the axis ‘a’. SeeFIGS. 4A and 4B. Spring65defines an opening67which fits snugly into shank55. In an assembled condition, the spring65is press fit onto the shank55.

According to the embodiment illustrated inFIG. 4A, the shank55may be of circular cross-section and include a through hole or channel57formed proximate a terminal end thereof. The spring65may include a terminal loop end portion69adapted to snugly fit within the through channel57. In this manner the through channel57and loop end portion69cooperatively prevent rotation of the spring65relative to the shank55.

The shanks55are axially positioned to be near the lugs54such that each spring65contacts a lug54when installed on a shank55. The spring65includes an elongated sloped portion65awhich, as will be described below, aids in orienting the female coupling36relative to the male coupling34. The spring65also includes a free end65b. As shown inFIG. 3B, when the spring65is positioned on the shank55, a gap or indexing notch60is formed between the spring65and the guide surface58of each lug54.

Alternatively, as illustrated inFIG. 4C, the shank has a non-circular cross-section to inhibit rotation of the spring relative to the shank.

Referring now toFIGS. 5-7, in the illustrated embodiment the female coupling36has a preferably cylindrical body70with an interior cylindrical surface or side wall72that ends in a free end71and defines a hollow core74that provides a passageway for fluid and defines an axial direction or second axis ‘a’ in the general direction of flow through the female coupling36.

The female coupling36features a latch ring76having a pair of preferably integrally formed latching tabs78which are sized to engage the lugs54(see FIG.7). According to a preferred embodiment, the latch ring76is continuously and integrally formed with the female coupling36from the same material used to form the female coupling36. Alternatively, the latch ring76may be formed separately from the female coupling36, and press fit, glued or otherwise bonded to the hollow core74of the female coupling36.

The latching tabs78are configured to engage and partially surround the lugs54. The latching tabs78include an enlargement portion84defined by a bottom sloped surface79, a side surface80and a top surfaces81. The latching tabs78also include a leg83that extends downwardly from the latch ring76into the enlargement portion84of each latching tab78. The top surfaces81of the latching tabs78are configured to engage the retaining or latching surfaces56of the lugs54, and a lower surface77of the latching ring76engages an upper surfaces53of the lugs54.

The retaining surface56of the lugs54may be formed at a slight angle relative to horizontal, in which case the top surface81of the latching tabs78would be formed at a complimentary angle to promote engagement therebetween.

The lugs54are extended circumferentially around the male coupling34, leaving an opening sized to permit operation of the spring65and passage of the latching tabs78. The free end65bof each spring65is shaped to interfere with the lugs54. Moreover, each lug54and spring65cooperatively defines a uniform path around which the latching tabs78may travel when the female coupling36is rotated.

The gap or indexing notch60is defined by the elongated sloped portion65aof each spring65and the guide surface58of each lug54. The gap or indexing notch60is configured to receive a point82of a respective latching tab78(see FIGS.8A-8C).

The exterior side wall50has a portion68that defines a first surface of rotation around axis a that fits within the female coupling36. The first surface of rotation68is provided with a generally smooth finish for slidably engaging a sealing member92within the female coupling36. The first surface of rotation68is, in the illustrated embodiment, cylindrical, but could otherwise conform to conical, spherical, ellipsoidal or paraboloidal shapes, or other forms.

In operation, as illustrated inFIGS. 8A-8C, the female coupling36is coupled to the male coupling34by suspending the female coupling36vertically above the male coupling34with the latching tabs78resting on the lugs54of the male coupling34. The female coupling36is then rotated until the point82of each latching tab78drops into the gap or indexing notch60cooperatively formed by the spring65and the lug54(see FIG.8A).

An axial force is then applied to the female coupling36and attached filter cartridge24to push the female coupling36down onto the male coupling34against the spring65(see FIG.8B). As a result of the interference between the point82of the latching tab78, the lug54and the spring65causes the spring65to rotate counterclockwise (as viewed from above) to permit passage of the enlargement portion84of the latching tab78. During this passage, guide surface80of the latch tab78slides by guide surface58of lug54(FIG.4A).

Once enlarged portion84of the latching tab78has cleared the latching surface56of the lug54, the spring65pushes against the female coupling36causing the top surface81of the latching tabs78to rotate clockwise (as viewed from above) into engagement with the latching surface56of each lug54(see FIG.8C). Thereafter, the spring65provides a biasing force which deters inadvertent disengagement of the latching tab78from the lug54.

To disengage the female coupling36from the male coupling24, a user simply rotates the female coupling36in a counterclockwise direction (as viewed from above) until the top surface81of the latching tab78clears the retaining or latching surface56of the lug54, and then lifts the female coupling36and attached filter cartridge24.

Referring toFIGS. 5 and 6, the female coupling36also has an annular groove90opening on the interior side wall or second surface of rotation72. The second surface of rotation72matches the first surface of rotation68of the male coupling34. A sealing member92(FIGS.8A-8C), such as an O-ring, fits snugly in the groove90(see FIG.3B and FIG.6). When the coupling device10is assembled, the sealing member92engages the first surface of rotation68on the male coupling34, forming a tight seal that prevents unpurified material from bypassing the filter cartridge24.

The number of latching tabs78(and lugs54) dictate the maximum rotational displacement of the filter cartridge24until the point82of the latching tabs78finds a corresponding indexing notch60. In the embodiment depicted, two latching tabs78are provided. Thus, the maximum rotational displacement until the point82of the latching tabs78falls into engagement with the indexing notch60is approximately 180 degrees. Providing additional latching tabs (and a corresponding number of lugs54) will reduce the rotational displacement by a proportional amount. For example, the use of four latching tabs will reduce the maximum rotational displacement to approximately 90 degrees (¼ turn).

It will be appreciated that many alternative configurations fall within the scope of the present invention contemplated by the inventors. For instance, the filter cartridges24may hang down from an upper tube sheet32. Additionally, a filter-side coupling may be a polymeric adapter or male coupling instead of the female coupling while a steel coupling may be permanently attached to the filter conduit as the conduit-side coupling.

The coupling device10has a polymeric female coupling36that can be incinerated or shredded along with other parts of the filter cartridge24for disposal after the female coupling36is used in hazardous or radioactive material processes. Incineration and shredding reduces volume of radioactive material which must be contained in secure containers at monitored storage facilities.

Also, the male coupling34has lugs54designed to spread an axial separation force laterally, by providing a generally flat predetermined retaining surface56on each lug54for impacting the top surface81of the latching tab78so the full force is not directed to a single point on the female coupling36. The lugs54, latching tabs78and springs65are configured so that only an axial force is needed to fully engage the female coupling36on the male coupling34.

While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims.