Patent Description:
Several industries utilize rotary drum filters to separate filtrate from residue on a large scale. A typical rotary drum filter generally comprises a cylindrical drum mounted on a rotational axis for rotation in a tank or vat filled with a slurry. The cylindrical drum comprises several divisions (i.e., cylindrical sectors) arrayed around the rotational axis. The radially outward surfaces of the divisions define a filter deck assembly. In practice, operators maintain a pressure differential between the inside and the outside of the drum. That is, the interior of the drum is generally maintained at sub-atmospheric pressure. As a given filter deck assembly on a given division rotates through the slurry, the pressure differential pulls filtrate through the filter deck assembly. The residue from the filtrate accumulate on the outer surface of the filter deck assembly. This accumulated residue may be referred to as a "pulp mat," a sediment "cake," or by other names depending upon the slurry that the rotary drum filter separates. When a division rotates above the slurry level, the pressure differential continues to pull entrapped liquid from the accumulated residue and thereby begins to dry the accumulated residue.

The filtrate flows through the filter deck assembly toward the rotational axis. The filtrate then flows out of a supportive trunnion into a drop leg. The filtrate flowing down through the drop leg creates the vacuum pressure. A stationary valve also sits in the trunnion upstream of the drop leg. The valve has a first end positioned at approximately the <NUM> o'clock position (i.e., the apex of rotation when the rotary drum filter is operational) and a second end positioned approximately between the <NUM> o'clock position (i.e., halfway along the downward rotational journey) and the <NUM> o'clock position (i.e., several degrees before the nadir of rotation). As a division rotates past the apex, the valve blocks the portion of the division that exits into the trunnion, thereby releasing vacuum pressure along the arc of the valve.

A doctor blade, roller, belt, or other apparatus removes the accumulated residue from the filter deck assembly on the now pressure-equalized division. Typically, additional equipment then collects this residue for further processing. The now cleaned filter deck assembly continues to rotate downwardly toward the slurry. As the division rotates past the end of the valve, the valve no longer blocks the portion of the division that exits into the trunnion and the sub-atmospheric pressure is again applied, thereby permitting the process to repeat as the division rotates through the slurry.

While the rotary drum filter design endures, the traditional design of the filter deck assembly contributes to problems that can lead to production loss. Traditional filter deck assemblies comprise corrugated filter plates. Each filter plate spans one or more grid supports. The respective filter plate ends engage a top hat-shaped mounting clip mounted on a grid support. Installers and servicers weld at least one end of the filter plate to a mounting clip to prevent filtrate from leaking back into the vat when the filter plate rotates downwardly. The "top hat" mounting clips also have a cap strip welded on top of (i.e., radially outward of) each mounting clip to define a generally C-shaped recess. Each end of the filter plate rests in one of these C-shaped recesses. Installers and servicers spot weld or tungsten inert gas ("TIG") weld these cap strips to the mounting clips. Installers and servicers may also weld the ends of the filter plate to the mounting clip and/or cap strip to form a secure seal and fixedly install the filter plates. The filter plates, mounting clips, and cap strips, are typically all manufactured from stainless steel.

In practice, and depending upon the application, the temperature profile of the cylindrical drum may vary significantly, at least at startup. For example, if a rotary drum filter is used to dewater a pulp slurry, the starting temperature of the pulp slurry may be in a range of <NUM> degrees Celsius (°C) (<NUM> degrees Fahrenheit (°F)) to <NUM> (<NUM> °F) in a first stage vat. The filtered pulp generally cools to about <NUM> (about <NUM> °F) by the time it is removed from the drum. Likewise, the drum divisions that start in the vat will typically have a higher average temperature than the divisions that start above the vat. As the pulp mat rotates out of the vat, washers may spray the mat with water or other fluid to displace the entrapped slurry liquid. The expansion and contraction of the stainless steel in response to temperature fluctuations can stress the filter deck assembly welds, particularly the welds engaging the filter plates, mounting clips, and cap strips. Even though rotation and the materials of the cylindrical drum may eventually reduce the temperature differential over time, any remaining temperature differential will still stress the welds. If left unaddressed, excessive or prolonged periods of stress will lead to weld failure, which will reduce the efficiency of the rotary drum filter by allowing filtrate to flow back out of the filter deck assembly and into the vat.

Furthermore, processes that expose the welds to electronegative ions can also weaken the welds over time. For example, in bleach plant applications, the chlorine in bleach will attack the protective oxide layer of the stainless steel, and then attack the steel itself. Because substantially all structural components of the cylindrical drum are manufactured from stainless steel, all the steel in the drum will be attacked. Unlike rust, chloride-induced corrosion is not bulk corrosion. That is, once the chlorine wears through the protective oxide layer, the chlorine will concentrate in that area and continue to corrode the exposed steel. The induced stresses from welding, combined with built-in mechanical stresses from manufacturing and thermal cycling, make welds in particular a weakened initiation point for the corrosion. Once the corrosion starts, the reactive chloride ions tend to concentrate in these areas, thereby accelerating further corrosion. As a result, these welds create a greater potential for loose cap strips and deck panels (i.e., filter plates), torn or otherwise damaged face wire, and damage to doctor blades caused by the blades impacting the cap strips.

Deactivating the rotary drum filter to fix these problems results in production loss. Removing the welds to repair or rebuild the rotary drum filter can be time consuming and costly, which motivates some mill operators to delay shutdowns until there is a risk of imminent equipment failure. This practice results in reduced equipment production as the problems continue to develop. Furthermore, it takes more time to repair or rebuild a severely damaged rotary drum filter, thereby further exacerbating production loss.

Previously, others attempted to improve installation time such as with the design described in <CIT>(hereinafter, "Giasson"), a document that discloses features falling under the preamble of claim <NUM>. This design requires welding, gluing, or otherwise affixing the "top hat" mounting clips to the support grids and having a "snap in" cap strip. However, the "snap in" cap strip comprises a U-shaped piece and a generally planar top piece (i.e., a traditional cap strip) that is welded, glued, or otherwise fixedly engaged to the U-shaped piece. Furthermore, after installation, Giasson recommends welding or otherwise permanently engaging the removable cap strip into place. The presence of welds to secure: the mounting clips to the support grids, the components of the cap strip to one another, and optionally, the cap strip to the mounting clip does nothing to address the problem of weld failure in the filter deck assembly. <CIT> discloses a filter division strip.

The present invention provides an engagement assembly as recited in claim <NUM>. The present disclosure relates generally to rotary drum filters configured to filter slurries, and more particularly to filter plates in rotary vacuum drum washers, thickeners, and filters used in the pulp and paper, chemical recovery, waste separation, and mining industries. The problem of production loss due to weld fatigue in welds between filter plates and mounting clips in a filter plate assembly of a rotary drum filter can be mitigated by aspects of the present disclosure.

According to various aspects there is provided an engagement assembly for a rotary drum filter. In some aspects, the engagement assembly may include: a retaining clip having a body, a first shelf extending outwardly from the body in a first direction and a second shelf extending outwardly from the body in a direction opposite the first direction; and an S-clip having a major concave area configured to receive a leading end or a trailing end of a filter plate, and a minor concave area configured to receive the first shelf or the second shelf of the retaining clip.

According to various aspects there is provided a filter deck assembly for a rotary drum filter. In some aspects, the filter deck assembly may include: a filter plate having a leading end distally disposed from a trailing end; and an engagement assembly configured to engage the filter plate. The engagement assembly may include a retaining clip having a body, a first shelf extending outwardly from the body in a first direction and a second shelf extending outwardly from the body in a direction opposite the first direction. The engagement assembly may include an S-clip having a major concave area configured to receive the leading end or the trailing end of the filter plate, and a minor concave area configured to receive the first shelf or the second shelf of the retaining clip.

According to various aspects there is provided a rotary drum filter. In some aspects, the rotary drum filter may include a filter deck assembly, and grid supports configured to support the filter deck assembly. The filter deck assembly may include a filter plate having a leading end distally disposed from a trailing end, and an engagement assembly configured to engage the filter plate. The engagement assembly may include a retaining clip having a body, a first shelf extending outwardly from the body in a first direction and a second shelf extending outwardly from the body in a direction opposite the first direction, and an S-clip having a major concave area configured to receive the leading end or the trailing end of the filter plate, and a minor concave area configured to receive the first shelf or the second shelf of the retaining clip.

The foregoing will be apparent from the following more particular description of exemplary embodiments of the disclosure, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, with emphasis instead being placed upon illustrating the disclosed embodiments.

The following detailed description of the preferred embodiments is presented only for illustrative and descriptive purposes and is not intended to be exhaustive or to limit the scope and spirit of the invention. The embodiments were selected and described to explain the principles and practical applications. Many variations can be made to the embodiments disclosed in this specification without departing from the scope of protection.

Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of various features and components according to the present disclosure, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate embodiments of the present disclosure, and such exemplifications are not to be construed as limiting the scope of the present disclosure in any manner.

References in the specification to "one embodiment," "an embodiment," "an exemplary embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic.

Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiment selected for illustration in the drawings, and are not intended to define or limit the scope of the disclosure.

Numerical values should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the states value by less than the experimental error of conventional measurement technique of the type described in the present application to determine the value.

All ranges disclosed herein are inclusive of the recited endpoint and are independently combinable (for example, the range "from <NUM> grams to <NUM> grams" is inclusive of the endpoints, <NUM> grams and <NUM> grams, and all intermediate values.

As used herein, approximating language may be applied to modify any quantitative representation that may vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as "about," "approximately," and "substantially," may not be limited to the precise values specified. The modifier "about" should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression "from about <NUM> °F to about <NUM> °F" also discloses the range "from <NUM> °F to <NUM> °F.

It should be noted that many of the terms used herein are relative terms. For example, the terms "upper" and "lower" are relative to each other in location, i.e., an upper component is located at a higher elevation than a lower component in a given orientation, but these terms can change if the device is flipped. The terms "inlet' and "outlet" are relative to a fluid flowing through them with respect to a given structure, e.g., a fluid flows through the inlet into the structure and flows through the outlet out of the structure. The terms "upstream" and "downstream" are relative to the direction in which a fluid flows through various components, i.e., the flow of fluids through an upstream component prior to flowing through the downstream component.

The terms "horizontal" and "vertical" are used to indicate direction relative to an absolute reference, e.g., ground level. However, these terms should not be construed to require structure to be absolutely parallel or absolutely perpendicular to each other. For example, a first vertical structure and a second vertical structure are not necessarily parallel to each other. The terms "top" and "bottom" or "base" are used to refer to locations/surfaces where the top is always higher than the bottom/base relative to an absolute reference, e.g., the surface of the earth. The terms "upwards" and "downwards" are also relative to an absolute reference; an upwards flow is always against the gravity of the earth.

<FIG> is a perspective view of a rotary drum filter <NUM>. The rotary drum filter <NUM> may be, for example, a vacuum washer used in the pulp and paper industry. Although designs can vary, a typical rotary drum filter <NUM> includes a cylindrical drum <NUM> disposed in a vat (not shown). Closure plates <NUM> bound each end <NUM>, <NUM> of the drum <NUM>. Support ribs <NUM> extend generally radially outward from structures surrounding the axis of rotation toward the outer circumference of the drum <NUM>. Multiple ring supports <NUM> support the filter deck assembly <NUM>. A trunnion <NUM> extends from each end <NUM>, <NUM> of the drum <NUM> and rotatably mounts the drum <NUM> to adjacent bearing and pedestal assemblies <NUM>. One of the trunnions 16a is hollow and connects to a drop leg (not shown). During operation, the drop leg pulls air through the drum and thereby draws filtrate <NUM> through the rotary drum filter <NUM> under vacuum. A number of filtrate conduits <NUM> disposed between the hollow trunnion 16a and the filtrate chambers <NUM> allow filtrate <NUM> to fluidly communicate with the drop leg.

A screen <NUM>, typically a wire mesh (also referred to as a "face wire"), cloth, synthetic textile, or plastic screen encircles the drum <NUM>. In operation, the vat is filled with a slurry. In <FIG>, the drum <NUM> rotates in rotational direction R, which in this example is counter-clockwise. As divisions of the drum <NUM> rotate through the vat, the vacuum pressure facilitates the accumulation of residue <NUM> on the screen <NUM>. As the drum division continues to rotate above the slurry level, filtrate <NUM> percolates through the filter deck assembly <NUM> and eventually flows through the filtrate conduits <NUM> into the drop leg. As the drum <NUM> continues to rotate, the residue <NUM> begins to dry and a doctor blade, belt, roller, or other device (not shown) eventually scrapes the residue <NUM> from the screen <NUM> before that section of the screen <NUM> rotates back into the slurry to repeat the process.

When the rotary drum filter <NUM> is a vacuum washer used in the pulp and paper industry, the slurry is a typically a mixture of pulp and water called a "pulp stock. " The residue <NUM> on the screen are typically known as a "pulp mat. " In mineral processing, the rotary drum filter may be known as a thickener. The residue <NUM> is typically cakes of mineral sediment. For example, lime mud filters are typically used to recover lime from spent pulp and paper liquors. In a lime mud filter, the filtrate <NUM> typically comprises water and the residue <NUM> comprises lime mud.

<FIG> is a detailed perspective view of a portion of the filter deck assembly <NUM> of <FIG>. The screen <NUM> rests atop an array of filter plates <NUM>. The filter plates <NUM> are typically corrugated filter plates 4a having a plurality of ridges <NUM> and channels <NUM>. Corrugated filter plates 4a are generally preferred because the corrugations increase the surface area available for holding excess filtrate <NUM> and thereby permit the rotary drum filter <NUM> to rotate at higher speeds than would typically be achievable in a rotary drum filter <NUM> having a comparatively flat filter plate (i.e., a filter plate that curves slightly to match the arc of the drum, but that is otherwise flat). Furthermore, the corrugations easily expand or contract slightly to accommodate thermal expansion. Each filter plate <NUM> has a width W and a length L. The filter plate <NUM> has areas defining multiple drainage slots <NUM> disposed throughout the filter plate <NUM>. When the filter plate <NUM> is a corrugated filter plate 4a, the multiple drainage slots <NUM> are disposed in the channels <NUM>. The drainage slots <NUM> may be louvered to collect pools of filtrate <NUM> on the downturn.

The filter plate <NUM> spans one or more grid supports <NUM>. Adjacent grid supports <NUM> and the filter plate <NUM> define one or more filtrate chambers <NUM>. In operation, filtrate <NUM> flows through the screen <NUM> and through the drainage slots <NUM> on the upturn and part of the downturn. The filtrate <NUM> then flows through the filtrate chambers <NUM> before flowing further to the filtrate conduits <NUM> and drop leg.

The filter plate <NUM> further comprises a leading end <NUM> and a trailing end <NUM>. The leading end <NUM> is the end that first exits the slurry when the particular section of the filter plate <NUM> is moving upward toward the apex of rotation and the leading end <NUM> is likewise the first end to fall back under the level of the slurry when the section of the filter plate <NUM> is moving downward toward the nadir of rotation. Similarly, the trailing end <NUM> is distally disposed from the leading end <NUM>. The trailing end <NUM> is the second end to exit the slurry when the filter plate <NUM> is moving toward the apex of rotation. It will be understood that if an operator reverses the direction of rotation, the "leading ends" and the "trailing ends" designations will likewise reverse.

The respective ends <NUM>, <NUM> of the filter plates <NUM> engage a "top hat"-shaped mounting clip <NUM> mounted on a grid support <NUM>. In the past, installers and servicers have welded or otherwise rigidly affixed at least one end <NUM> or <NUM> of the filter plate <NUM> to a mounting clip <NUM> to prevent filtrate <NUM> from leaking back out of the filter plate <NUM> when the filter plate <NUM> is on the downturn. The top hat mounting clips <NUM> also have a cap strip <NUM> welded or otherwise rigidly affixed to each mounting clip <NUM>. In practice, installers and services spot weld or TIG weld these cap strips <NUM> to the mounting clips <NUM>. The recess <NUM> (i.e., the generally C-shaped feature) created by the mounting clip <NUM> and the cap strip <NUM> also secures the ends <NUM>, <NUM> of the filter plates <NUM> to the drum <NUM>.

In practice, Applicant has discovered that the rigidly affixed cap strips <NUM> create ongoing maintenance problems. The rigidly affixed cap strip <NUM> prevent a servicer from easily accessing and removing or replacing the filter plate <NUM>. Additionally, if the cap strips <NUM> have been welded to the mounting clips <NUM>, the environment within the rotary drum filter <NUM> can lead to weld fatigue and corrosion. In extreme cases, broken welds create loose cap strips <NUM> and filter plates <NUM>, which can damage the doctor blades, rollers, belts, or other device configured to remove the residue <NUM> from the screen <NUM>. The loose cap strips <NUM> or filter plates <NUM> can likewise tear or otherwise damage the screen <NUM>. This permits filtrate <NUM> to flow both between drum divisions and back out of filter plate <NUM> and screen <NUM>, thereby reducing the overall efficiency of the system. To address these problems, several exemplary embodiments, combinations of which are all considered to be within the scope of in this disclosure, are presented.

<FIG> is a perspective view of an exemplary filter plate and an exemplary engagement assembly comprising an S-clip at both the leading end and the trailing end of the filter plate according to some aspects of the present disclosure. Referring to <FIG>, the filter deck assembly <NUM> may include a filter plate <NUM> having a leading end <NUM> distally disposed from a trailing end <NUM>, an engagement assembly <NUM> configured to engage the filter plate. The engagement assembly <NUM> may include an "S" shaped clip <NUM> (also referred to herein as an S-clip), and a retaining clip <NUM>.

<FIG> is a detailed view of the exemplary engagement assembly <NUM> shown in <FIG> according to some aspects of the present disclosure. Referring to <FIG>, the retaining clip <NUM> may include a body <NUM>, a first shelf <NUM>, and a second shelf <NUM>. Both the first shelf <NUM> and the second shelf <NUM> may extend outwardly from the body <NUM>. A major concave area "M" of the S-clip <NUM> may be configured to receive the leading end <NUM> or the trailing end <NUM> of the filter plate <NUM>. A minor concave area "m" of the S-clip <NUM> may be configured to receive the first shelf <NUM> or the second shelf <NUM> of the retaining clip <NUM>.

As illustrated in <FIG>, the exemplary S-clip <NUM> defines the major concave area M adjacently disposed to the minor concave area m. The minor concave area m may be separated from the major concave area M by a horizontal body strip <NUM> of the S-clip <NUM>. The minor concave area m may be disposed in a direction that is opposite of a direction of the major concave area M. That is, the opening of the minor concave area m may face the opposite direction from the opening of the major concave area M.

The S-clip <NUM> may include a first horizontal strip <NUM> configured to engage a first vertical strip <NUM> at a first end <NUM> of the first vertical strip <NUM>. A second end <NUM> of the first vertical strip <NUM> may be configured to engage a first end <NUM> of a horizontal body strip <NUM>. The first end <NUM> of the first vertical strip <NUM> may be distally disposed from the second end <NUM> of the first vertical strip <NUM>. The first horizontal strip <NUM>, the first vertical strip <NUM>, and the first horizontal body strip <NUM> may define the major concave area M.

The S-clip <NUM> may further include a second horizontal strip <NUM> configured to engage a second vertical strip <NUM> at a first end <NUM> of the second vertical strip <NUM>. A second end <NUM> of the second vertical strip <NUM> may be configured to engage a second end <NUM> of the horizontal body strip <NUM>, wherein the second end <NUM> of the horizontal body strip <NUM> may be distally disposed from the first end <NUM> of the horizontal body strip <NUM>. The second end <NUM> of the second vertical strip <NUM> may be distally disposed from the first end <NUM> of the second vertical strip. The second horizontal strip <NUM>, the second vertical strip <NUM>, and the horizontal body strip <NUM> may define the minor concave area m.

The leading end <NUM> of the filter plate <NUM> or the trailing end <NUM> of the filter plate <NUM> may be inserted into the major concave area M of the S-clip <NUM>, and the major concave area M of the S-clip <NUM> may be configured to receive the leading end <NUM> of the filter plate <NUM> or the trailing end <NUM> of the filter plate <NUM>. For example, the leading end <NUM> and the trailing end <NUM> of the filter plate <NUM> may be tapered such that the leading end <NUM> is retained within the major concave area M of the S-clip <NUM> while being supported by a horizontal body strip <NUM> of the S-clip <NUM>. The minor concave area m of the S-clip <NUM> that supports the trailing end <NUM> of the filter plate <NUM> may engage the first shelf <NUM> of the retaining clip <NUM> such that the horizontal body strip <NUM> of the S-clip <NUM> and the second horizontal strip <NUM> of the S-clip <NUM> contact the first shelf <NUM> of the retaining clip <NUM>. Similarly, The minor concave area m of the S-clip <NUM> that supports the leading end <NUM> of the filter plate <NUM> may engage the second shelf <NUM> of the retaining clip <NUM> such that the horizontal body strip <NUM> of the S-clip <NUM> and the second horizontal strip <NUM> of the S-clip <NUM> contact the second shelf <NUM> of the retaining clip <NUM>. During installation of the filter plate <NUM>, the leading end <NUM> filter plate <NUM> or the trailing end <NUM> of the filter plate <NUM> may be slid into the major concave area M of the S-clip <NUM>. Alternatively, the leading end <NUM> or the trailing end <NUM> of the filter plate <NUM> may be angled into the major concave area M of the S-clip <NUM> laterally.

The height of the major concave area M may be greater than the height of the leading end <NUM> of the filter plate <NUM> and the trailing end <NUM> of the filter plate <NUM> so as to secure the leading end <NUM> of the filter plate <NUM> and the trailing end <NUM> of the filter plate <NUM> into the major concave area M of the S-clip <NUM> when the filter plate <NUM> is installed in the filter deck assembly <NUM>. The major concave area M may surround the top, lateral end, and bottom portions of the leading end <NUM> of the filter plate <NUM> and/or the trailing end <NUM> of the filter plate <NUM>, and may prevent edges of the leading end <NUM> and/or the trailing end <NUM> from contacting the screen <NUM> thereby preventing such edges from piecing holes in the screen <NUM>. Holes in the screen <NUM> contribute to production loss. The deepest portion of the minor concave area m may extend beyond the end of the horizontal strip <NUM> defining the major concave area M, and the deepest portion of the major concave area M may extend beyond the second horizontal strip <NUM> defining minor concave area m.

In conventional rotary drum filters, the "top hat" mounting clip <NUM> is welded to a grid support <NUM>. The S-clip <NUM> of the present disclosure slides onto one of the shelves (e.g., the first shelf <NUM> or the second shelf <NUM>) of the retaining clip <NUM> without the use of welds or other fastener. Another advantage of the present disclosure is that there is no longer a need for cap strips, thereby reducing the overall welds in the filter deck assembly and potentially extending the useful life of the assembly. The minor concave area m of the S-clip <NUM> is configured to receive first shelf <NUM> or the second shelf <NUM> of the retaining clip <NUM>. Alternatively, the first shelf <NUM> or the second shelf <NUM> of the retaining clip <NUM> may be pushed into the minor concave area m of the S-clip <NUM> laterally. In this manner, the minor concave area m of the S-clip <NUM> is also configured to receive the first shelf <NUM> or the second shelf <NUM> of the retaining clip <NUM>.

The height of the minor concave area m may be greater than the height of the first shelf <NUM> or the second shelf <NUM> of the retaining clip <NUM> so as to secure the first shelf <NUM> or the second shelf <NUM> of the retaining clip <NUM> into the minor concave area m when the S-clip <NUM> is installed in the filter deck assembly <NUM>.

In some exemplary embodiments, the S-clip <NUM> may be constructed from stainless steel or a polymer configured to be resistant to heat up to <NUM> (<NUM> °F). Other shapes for the clip that fix the retaining clip <NUM> to the filter plate <NUM> without the use of a top hat clip (e.g., the top hat mounting clip <NUM>) and without exposing the ends <NUM>, <NUM> of the filter plate <NUM> to the screen <NUM> may be used without departing from the scope of the present disclosure. An optional seal can be made from a gasket material to prevent leaking around the ends <NUM>, <NUM> of the filter plate <NUM>. The seal may have a rectangular shape and may be disposed between a surface of the major concave area M and the leading end <NUM> of the filter plate <NUM>. Other shapes, materials, and orientations may be used to provide the optional seal. For example, a shaped seal or an adhesive material such as RTV silicone may be applied between the bottom of the leading end <NUM> of the filter plate <NUM> and the horizontal body strip <NUM> of the S-clip <NUM> to create the seal. The seal strip may positioned on the leading end of the filter plate to minimize filtrate leakage from under the filter plate and rewetting the pulp mat once the vacuum to the filter plate is cut off.

It will be understood that the terms: "first horizontal strip <NUM>," "first vertical strip <NUM>," "first end <NUM> of the first vertical strip <NUM>," "second end <NUM> of the first vertical strip <NUM>," "horizontal body strip <NUM>," "first end <NUM> of the horizontal body strip <NUM>," "second end <NUM> of the horizontal body strip <NUM>," "second vertical strip <NUM>," "first end <NUM> of the second vertical strip <NUM>," "second end <NUM> of the second vertical strip <NUM>," and "a second horizontal strip <NUM>" are used to refer to parts of the S-clip <NUM> regardless of how the S-clip <NUM> is manufactured. For example, an exemplary S-clip <NUM> can be fabricated from multiple strips of material. By way of another example, an exemplary S-clip <NUM> can be manufactured by bending a plate of material to adopt the "S" shaped form as described in this disclosure. For example, a second vertical strip <NUM> may be created by bending a plate of material back over itself. In such a case, the second vertical strip <NUM> is the section of plate connecting the substantially parallel horizontal body strip <NUM> and second horizontal strip <NUM>.

<FIG> is a cross-sectional side view of an exemplary filter deck assembly <NUM> including the exemplary engagement assembly <NUM> according to some aspects of the present disclosure. As illustrated in <FIG>, two S-clips 45a, 45b may be disposed on each retaining clip <NUM>. A first S-clip 45a engages the first shelf <NUM> of the retaining clip <NUM> and a trailing end <NUM> of an adjacent filter plate <NUM>. A second S-clip 45b engages the second shelf <NUM> of the retaining clip <NUM> and engages a leading end <NUM> of a second adjacent filter plate <NUM>'. The filter plates <NUM> and <NUM>' may be corrugated filter plates 4a.

Claim 1:
An engagement assembly (<NUM>) for engaging a filter plate (<NUM>) that spans at least one grid support (<NUM>) of a rotary drum filter (<NUM>), the engagement assembly (<NUM>) comprising:
a retaining clip (<NUM>) configured to be mounted on the grid support (<NUM>), the retaining clip (<NUM>) having a body (<NUM>), a first shelf (<NUM>) extending outwardly from the body (<NUM>) in a first direction and a second shelf (<NUM>) extending outwardly from the body (<NUM>) in a direction opposite the first direction;
characterized in that
the engagement assembly (<NUM>) further comprises an S-clip (<NUM>) for fixing the retaining clip (<NUM>) to the filter plate (<NUM>), the S-clip (<NUM>) having a major concave area (M) configured to receive a leading end (<NUM>) or a trailing end (<NUM>) of a filter plate (<NUM>), and a minor concave area (m) configured to receive the first shelf (<NUM>) or the second shelf (<NUM>) of the retaining clip (<NUM>) , wherein:
the major concave area (M) is disposed adjacent to the minor concave area (m),
the minor concave area (m) is separated from the major concave area by a body strip (<NUM>) of the S-clip (<NUM>), and
wherein the minor concave area (m) is disposed in a direction that is opposite of a direction of the major concave area (M).