Multiple-leg discharge boot for slurry distribution

A multi-leg discharge boot can include an inlet conduit and first and second outlet conduits separated by a junction portion. The inlet conduit includes an entry segment, a transition segment and a heel portion disposed therebetween. The inlet conduit can include an inlet end and a junction end. A junction portion is disposed at the junction end of the inlet conduit between first and second junction openings. The junction portion includes a substantially planar wall region that is substantially perpendicular to a main flow discharge axis.

BACKGROUND

The present disclosure relates to continuous board manufacturing processes and, more particularly, to an apparatus, system and method for the distribution of a slurry in connection with the manufacture of a cementitious article.

In many types of cementitious articles, set gypsum (calcium sulfate dihydrate) is often a major constituent. For example, set gypsum is a major component of end products created by use of traditional plasters (e.g., plaster-surfaced internal building walls), and also in faced gypsum board employed in typical drywall construction of interior walls and ceilings of buildings. In addition, set gypsum is the major component of gypsum/cellulose fiber composite boards and products, as described in U.S. Pat. No. 5,320,677. Set gypsum is also included in products that fill and smooth the joints between edges of gypsum board (see, e.g., U.S. Pat. No. 3,297,601). Also, many specialty materials, such as materials useful for modeling and mold-making that are precisely machined, produce products that contain major amounts of set gypsum. Typically, such gypsum-containing cementitious products are made by preparing a mixture of calcined gypsum (calcium sulfate alpha or beta hemihydrate and/or calcium sulfate anhydrite), water, and other components, as appropriate to form a cementitious slurry. In the manufacture of cementitious articles, the cementitious slurry and desired additives are often blended in a continuous mixer, as for example described in U.S. Pat. No. 3,359,146.

For example, in a typical manufacturing process, gypsum board is produced by uniformly dispersing calcined gypsum (commonly referred to as “stucco”) in water to form an aqueous calcined gypsum slurry. The aqueous calcined gypsum slurry is typically produced in a continuous manner by inserting stucco and water and other additives into a mixer which contains means for agitating the contents to form a uniform gypsum slurry. The slurry is continuously directed toward and through a discharge outlet of the mixer and into a discharge conduit connected to the discharge outlet of the mixer. An aqueous foam can be combined with the aqueous calcined gypsum slurry in the mixer and/or in the discharge conduit. The stream of slurry passes through the discharge conduit from which it is continuously deposited onto a moving web of cover sheet material supported by a forming table.

The slurry is allowed to spread over the advancing web. A second web of cover sheet material is applied to cover the slurry and form a sandwich structure of a continuous wallboard preform, which is subjected to forming, such as at a conventional forming station, to obtain a desired thickness.

The calcined gypsum reacts with the water in the wallboard preform and sets as a conveyor moves the wallboard preform down a manufacturing line. The wallboard preform is cut into segments at a point along the line where the preform has set sufficiently. The segments are flipped over, dried (e.g., in a kiln) to drive off excess water, and processed to provide the final wallboard product of desired dimensions.

Prior devices and methods for addressing some of the operational problems associated with the production of gypsum wallboard are disclosed in commonly-assigned U.S. Pat. Nos. 5,683,635; 5,643,510; 6,494,609; 6,874,930; 7,007,914; and 7,296,919, which are incorporated by reference.

The weight proportion of water relative to stucco that is combined to form a given amount of finished product is often referred to in the art as the “water-stucco ratio” (WSR). A reduction in the WSR without a formulation change will correspondingly increase the slurry viscosity, thereby reducing the ability of the slurry to spread on the forming table. Reducing water usage (i.e., lowering the WSR) in the gypsum board manufacturing process can yield many advantages, including the opportunity to reduce the energy demand in the process. However, conveying increasingly viscous gypsum slurries through a discharge conduit mounted to the mixer and spreading such slurries uniformly on the forming table remain a great challenge.

It will be appreciated that this background description has been created by the inventors to aid the reader and is not to be taken as an indication that any of the indicated problems were themselves appreciated in the art. While the described principles can, in some aspects and embodiments, alleviate the problems inherent in other systems, it will be appreciated that the scope of the protected innovation is defined by the attached claims and not by the ability of any disclosed feature to solve any specific problem noted herein.

SUMMARY

In one aspect, the present disclosure is directed to embodiments of a multi-leg discharge boot for use in preparing a cementitious product. In embodiments, a multi-leg discharge boot can be placed in fluid communication with a slurry mixer and receive a flow of aqueous cementitious slurry therefrom. In embodiments, a multi-leg discharge boot can include an inlet conduit and first and second outlet conduits separated by a junction portion.

In one embodiment, a multi-leg discharge boot includes an inlet conduit and first and second outlet conduits separated by a junction portion. The inlet conduit includes an entry segment, a transition segment and a heel portion disposed therebetween.

The entry segment has an inlet end defining an inlet opening. The entry segment is disposed along a main flow entry axis extending between the inlet end and the heel portion. The transition segment has a junction end. The transition segment is disposed along a main flow discharge axis extending between the heel portion and the junction end. The junction end defines first and second junction openings. The first junction opening is disposed in spaced relationship to the second junction opening. The heel portion has a surface adapted to direct a flow of slurry moving from the inlet opening along the main flow entry axis through the heel portion to the transition segment along the main flow discharge axis.

The first outlet conduit is in fluid communication with the first junction opening of the inlet conduit. The first outlet conduit includes a discharge end defining a first discharge opening. The second outlet conduit is in fluid communication with the second junction opening of the inlet conduit. The second outlet conduit includes a discharge end defining a second discharge opening.

The junction portion is disposed at the junction end of the inlet conduit. The junction portion is disposed between the first junction opening and the second junction opening. The junction portion includes a substantially planar wall region. The wall region is substantially perpendicular to the main flow discharge axis.

In another embodiment, a multi-leg discharge boot includes an inlet conduit and first and second outlet conduits separated by a junction portion. The inlet conduit includes an entry segment, a transition segment and a heel portion disposed therebetween.

The entry segment has an inlet end defining an inlet opening. The entry segment is disposed along a main flow entry axis extending between the inlet end and the heel portion. The transition segment has a junction end. The transition segment is disposed along a main flow discharge axis extending between the heel portion and the junction end. The junction end defines first and second junction openings. The first junction opening is disposed in spaced relationship to the second junction opening. The heel portion has a surface adapted to direct a flow of slurry moving from the inlet opening along the main flow entry axis through the heel portion to the transition segment along the main flow discharge axis. The inlet conduit defines an inlet passage extending between the inlet opening and the first and second junction openings.

The first outlet conduit is in fluid communication with the first junction opening of the inlet conduit. The first outlet conduit includes a discharge end defining a first discharge opening. The second outlet conduit is in fluid communication with the second junction opening of the inlet conduit. The second outlet conduit includes a discharge end defining a second discharge opening.

The junction portion is disposed at the junction end of the inlet conduit. The junction portion is disposed between the first junction opening and the second junction opening. The inlet conduit includes a contoured portion that defines a flow restriction in the inlet passage adjacent the junction portion.

In another aspect of the present disclosure, embodiments of a slurry mixing and dispensing assembly are described. In one embodiment, a slurry mixing and dispensing assembly includes a mixer and a multi-leg discharge boot.

The mixer is adapted to agitate water and a cementitious material to form an aqueous cementitious slurry. The multi-leg discharge boot is in fluid communication with the mixer.

The multi-leg discharge boot includes an inlet conduit and first and second outlet conduits separated by a junction portion. The inlet conduit includes an entry segment, a transition segment and a heel portion disposed therebetween.

The entry segment has an inlet end defining an inlet opening. The entry segment is disposed along a main flow entry axis extending between the inlet end and the heel portion. The transition segment has a junction end. The transition segment is disposed along a main flow discharge axis extending between the heel portion and the junction end. The junction end defines first and second junction openings. The first junction opening is disposed in spaced relationship to the second junction opening. The heel portion has a surface adapted to direct a flow of slurry moving from the inlet opening along the main flow entry axis through the heel portion to the transition segment along the main flow discharge axis.

The first outlet conduit is in fluid communication with the first junction opening of the inlet conduit. The first outlet conduit includes a discharge end defining a first discharge opening. The second outlet conduit is in fluid communication with the second junction opening of the inlet conduit. The second outlet conduit includes a discharge end defining a second discharge opening.

The junction portion is disposed at the junction end of the inlet conduit. The junction portion is disposed between the first junction opening and the second junction opening. The junction portion includes a substantially planar wall region. The wall region is substantially perpendicular to the main flow discharge axis.

In another embodiment, a cementitious slurry mixing and dispensing assembly includes a mixer and a multi-leg discharge boot. The mixer is adapted to agitate water and a cementitious material to form an aqueous cementitious slurry. The multi-leg discharge boot is in fluid communication with the mixer.

The multi-leg discharge boot includes an inlet conduit and first and second outlet conduits separated by a junction portion. The inlet conduit includes an entry segment, a transition segment and a heel portion disposed therebetween.

The entry segment has an inlet end defining an inlet opening. The entry segment is disposed along a main flow entry axis extending between the inlet end and the heel portion. The transition segment has a junction end. The transition segment is disposed along a main flow discharge axis extending between the heel portion and the junction end. The junction end defines first and second junction openings. The first junction opening is disposed in spaced relationship to the second junction opening. The heel portion has a surface adapted to direct a flow of slurry moving from the inlet opening along the main flow entry axis through the heel portion to the transition segment along the main flow discharge axis. The inlet conduit defines an inlet passage extending between the inlet opening and the first and second junction openings.

The first outlet conduit is in fluid communication with the first junction opening of the inlet conduit. The first outlet conduit includes a discharge end defining a first discharge opening. The second outlet conduit is in fluid communication with the second junction opening of the inlet conduit. The second outlet conduit includes a discharge end defining a second discharge opening.

The junction portion is disposed at the junction end of the inlet conduit. The junction portion is disposed between the first junction opening and the second junction opening. The inlet conduit includes a contoured portion that defines a flow restriction in the inlet passage adjacent the junction portion.

In another aspect of the present disclosure, embodiments of a method of preparing a cementitious product are described. In one embodiment of a method of preparing cementitious product, a main flow of aqueous cementitious slurry is discharged from a mixer. The main flow of aqueous cementitious slurry is redirected in an inlet conduit of a multi-leg discharge boot from a main flow entry axis to a main flow discharge axis by a change in direction angle within a range of about ten degrees to about one hundred thirty-five degrees. The main flow of aqueous cementitious slurry is moved past a flow restriction in the inlet conduit upstream of a junction portion separating first and second outlet conduits of the multi-leg discharge boot. The main flow of aqueous cementitious slurry moving along the main flow discharge axis is split into a first discharge flow of aqueous slurry and a second discharge flow of aqueous slurry in the multi-leg discharge boot. The first and second discharge flows are discharged from the first and second outlet conduits.

Further and alternative aspects and features of the disclosed principles will be appreciated from the following detailed description and the accompanying drawings. As will be appreciated, the multi-leg discharge boots disclosed herein are capable of being carried out and used in other and different embodiments, and capable of being modified in various respects. Accordingly, it is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and do not restrict the scope of the appended claims.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present disclosure provides various embodiments of a cementitious slurry mixing and dispensing assembly that can be used in the manufacture of products, including cementitious products such as gypsum wallboard, for example. Embodiments of a cementitious slurry mixing and dispensing assembly constructed in accordance with principles of the present disclosure can be used in a manufacturing process that includes a multi-leg discharge boot in a discharge conduit mounted to a mixer to effectively split a single flow of a slurry—such as an aqueous foamed gypsum slurry containing air and liquid phases, for example—entering the multi-leg discharge boot from the mixer such that at least two independent flows of the slurry exit from the multi-leg discharge boot.

Embodiments of a cementitious slurry mixing and dispensing assembly constructed in accordance with principles of the present disclosure can be used to mix and distribute a cementitious slurry (e.g., an aqueous calcined gypsum slurry) onto an advancing web (e.g., paper or mat) moving on a conveyor during a continuous board (e.g., wallboard) manufacturing process. In one aspect, a multi-leg discharge boot constructed in accordance with principles of the present disclosure can be used in a conventional gypsum drywall manufacturing process as, or as a part of, a discharge conduit attached to a mixer adapted to agitate calcined gypsum and water to form an aqueous calcined gypsum slurry.

A cementitious slurry mixing and dispensing assembly according to principles of the present disclosure can be used to form any type of cementitious product, such as a board, for example. In some embodiments, a cementitious board, such as a gypsum drywall, a Portland cement board or an acoustical panel, for example, can be formed.

The cementitious slurry can be any conventional cementitious slurry, for example any cementitious slurry commonly used to produce gypsum wallboard, acoustical panels including, for example, acoustical panels described in U.S. Patent Application Publication No. 2004/0231916, or Portland cement board. As such, the cementitious slurry can optionally further comprise any additives commonly used to produce cementitious board products. Such additives include structural additives including mineral wool, continuous or chopped glass fibers (also referred to as fiberglass), perlite, clay, vermiculite, calcium carbonate, polyester, and paper fiber, as well as chemical additives such as foaming agents, fillers, accelerators, sugar, enhancing agents such as phosphates, phosphonates, borates and the like, retarders, binders (e.g., starch and latex), colorants, fungicides, biocides, hydrophobic agent, such as a silicone-based material (e.g., a silane, siloxane, or silicone-resin matrix), and the like. Examples of the use of some of these and other additives are described, for instance, in U.S. Pat. Nos. 6,342,284; 6,632,550; 6,800,131; 5,643,510; 5,714,001; and 6,774,146; and U.S. Patent Application Publication Nos. 2004/0231916; 2002/0045074; 2005/0019618; 2006/0035112; and 2007/0022913.

Non-limiting examples of cementitious materials include Portland cement, sorrel cement, slag cement, fly ash cement, calcium alumina cement, water-soluble calcium sulfate anhydrite, calcium sulfate α-hemihydrate, calcium sulfate β-hemihydrate, natural, synthetic or chemically modified calcium sulfate hemihydrate, calcium sulfate dihydrate (“gypsum,” “set gypsum,” or “hydrated gypsum”), and mixtures thereof. In one aspect, the cementitious material desirably comprises calcined gypsum, such as in the form of calcium sulfate alpha hemihydrate, calcium sulfate beta hemihydrate, and/or calcium sulfate anhydrite. In embodiments, the calcined gypsum can be fibrous in some embodiments and nonfibrous in others. The calcined gypsum can include at least about 50% beta calcium sulfate hemihydrate. In other embodiments, the calcined gypsum can include at least about 86% beta calcium sulfate hemihydrate. The weight ratio of water to calcined gypsum can be any suitable ratio, although, as one of ordinary skill in the art will appreciate, lower ratios can be more efficient because less excess water must be driven off during manufacture, thereby conserving energy. In some embodiments, the cementitious slurry can be prepared by combining water and calcined gypsum in a range from about a 1:6 ratio by weight respectively to about 1:1 ratio, such as about 2:3, for board production depending on products.

Turning now to the Figures, Referring toFIGS. 1-7, an embodiment of the multi-leg discharge boot200, which is constructed according to principles of the present disclosure, is shown. An embodiment of a multi-leg discharge boot constructed in accordance with principles of the present disclosure can advantageously be configured as a retrofit component in an existing wallboard manufacturing system, for example. The multi-leg discharge boot200can be placed in fluid communication with a slurry mixer102, for example, as shown inFIGS. 11 and 12, to deliver separated flows of slurry therefrom. In embodiments, the multi-leg discharge boot comprises a terminal portion of a discharge conduit in fluid communication with the mixer.

The multi-leg discharge boot200can be made from any suitable material, such as a flexible material, including poly vinyl chloride (PVC), urethane, or any other suitable resiliently flexible material. In other embodiments, the multi-leg discharge boot200can be made from other materials, such as a substantially rigid material (e.g., aluminum, stainless steel, etc.).

The multi-leg discharge boot200includes an inlet conduit202and first and second outlet conduits204,206separated by a junction portion210. The inlet conduit202can be adapted to receive a main flow of slurry from a mixer. The pair of outlet conduits204,206are substantially cylindrical in the illustrated embodiment and each are in fluid communication with the inlet conduit202. The outlet conduits204,206can be adapted to dispense two separate outlet flows of slurry from the multi-leg discharge boot200.

Although the illustrated embodiment of the discharge boot200includes two outlet conduits or “legs”204,206, it should be understood that in other embodiments, a discharge boot according to principles of the present disclosure can have more than two outlet conduits. In embodiments including more than two legs, a junction and/or a contoured portion as described herein can be provided between each pair of adjacent legs.

Referring toFIG. 1, the inlet conduit202includes an entry segment221, a transition segment223, and a heel portion225disposed therebetween. The entry segment221has an inlet end203defining an inlet opening207. The entry segment221is disposed along a main flow entry axis75extending between the inlet end203and the heel portion225(seeFIG. 5also). The inlet opening207of the inlet end203can be adapted to be placed in fluid communication with a slurry mixer and to receive a main flow of slurry therefrom.

The transition segment223has a junction end205. The transition segment223is disposed along a main flow discharge axis85extending between the heel portion225and the junction end205(seeFIG. 5also).

Referring toFIG. 5, the entry segment221is disposed at a feed angle θ with respect to the transition segment223and the first and second outlet conduits204,206. The feed angle θ can be in a range from about forty five degrees to about one hundred seventy degrees in some embodiments, from about sixty degrees to one hundred twenty degrees in other embodiments, and from about seventy degrees to about one hundred ten degrees in yet other embodiments. The illustrated entry segment221is substantially perpendicular to the transition segment223and to the first and second outlet conduits204,206.

Referring toFIG. 6, the junction end205defines first and second junction openings209,211. The first junction opening209is disposed in spaced relationship to the second junction opening211. The first and second junction openings209,211are adapted to split the main flow of aqueous cementitious slurry into a first discharge flow of aqueous slurry and a second discharge flow of aqueous slurry.

Referring toFIG. 7, the heel portion225has a surface241adapted to direct a flow of slurry moving from the inlet opening207along the main flow entry axis75through the heel portion225to the transition segment223along the main flow discharge axis85. The heel portion225can be adapted to redirect the main flow of slurry from the main flow entry axis75to the main flow discharge axis85by a change in direction angle α. In some embodiments, the change in direction angle α can be in a range of about ten degrees to about one hundred thirty-five degrees, from about sixty degrees to one hundred twenty degrees in other embodiments, and from about seventy degrees to about one hundred ten degrees in yet other embodiments.

Referring toFIG. 3, the first outlet conduit204is in fluid communication with the first junction opening209of the inlet conduit202. The first outlet conduit204includes a discharge end215defining a first discharge opening217. The first outlet conduit204is adapted to receive the first discharge flow of aqueous slurry from the inlet conduit202and to dispense the first discharge flow from the first discharge opening217.

The second outlet conduit206is in fluid communication with the second junction opening211of the inlet conduit202. The second outlet conduit206includes a discharge end225defining a second discharge opening227. The second outlet conduit206is adapted to receive the second discharge flow of aqueous slurry from the inlet conduit202and to dispense the second discharge flow from the second discharge end225.

Referring toFIGS. 1 and 2, the junction portion210is disposed at the junction end205of the inlet conduit202. Referring toFIG. 6, the junction portion210is disposed between the first junction opening209and the second junction opening211. The junction portion210includes a substantially planar wall region219(seeFIG. 7also). Referring toFIG. 7, the wall region219is substantially perpendicular to the main flow discharge axis85.

Referring toFIGS. 3 and 4, the first discharge opening217of the first outlet conduit204and the second discharge opening227of the second outlet conduit206each can have a cross-sectional area less than or about equal to the cross-section area of the inlet opening207of the inlet conduit202. In embodiments, the cross-sectional area of the first discharge opening217of the first outlet conduit204and the cross-sectional area of the second discharge opening227of the second outlet conduit206each is less than about 85% of the cross-section area of the inlet opening207of the inlet conduit202. In some embodiments, the cross-sectional area of the first discharge opening217of the first outlet conduit204is substantially the same as the cross-sectional area of the second discharge opening227of the second outlet conduit206.

In the illustrated embodiment, the inside diameter Ø1of the inlet opening207of the inlet conduit202is larger than the inside diameters Ø2, Ø3of the first discharge opening217of the first outlet conduit204and the second discharge opening227of the second outlet conduit206, respectively. In the illustrated embodiment, the respective inside diameters Ø2, Ø3of the first discharge opening217of the first outlet conduit204and the second discharge opening227of the second outlet conduit206are substantially the same.

The inside diameters Ø1, Ø2, Ø3(and, thus, the cross-sectional areas) of the inlet opening207and the first and second discharge openings217,227can vary depending on the desired average flow velocity. Higher average flow velocity can reduce the chance of set material buildup resulting from solidification of slurry residing in the discharge boot200. The inside diameter Ø2, Ø3of the first and second discharge openings217,227can be made smaller than the inside diameter Ø1of the inlet opening207in order to maintain a relatively high flow velocity throughout the multi-leg discharge boot200. When the inside diameters Ø2, Ø3of the first and second discharge openings217,227are substantially equal to the inside diameter Ø1of the inlet opening207, the average flow velocity of the slurry will be reduced by about 50% through the outlet conduits204,206if the volumetric flow rate through the inlet and both outlets is substantially the same. When the inside diameters of the outlet conduits204,206are smaller than the inside diameter of the inlet conduit, however, the flow velocity can be maintained in the outlet conduits204,206or at least reduced to a lesser extent than if the discharge conduits204,206and the inlet conduit202have substantially equal inside diameters Ø1, Ø2, Ø3.

The multi-leg discharge boot200also includes a central contoured portion208. Referring toFIGS. 6 and 7, the inlet conduit202defines an inlet passage231extending between the inlet opening207and the first and second junction openings209,211. The inlet conduit202includes the contoured portion208which defines a flow restriction235in the inlet passage231adjacent the junction portion210.

The contoured portion208includes an upper convex region212and an opposing lower convex region213. The upper and lower convex regions212,213project toward each other in the inlet passage231to define the flow restriction235therebetween.

Referring toFIG. 6, the contoured portion208defines first and second guide channels218,220. The flow restriction235is disposed laterally between the first and second guide channels218,220along a transverse axis95substantially perpendicular to the main flow discharge axis85. The first and second guide channels218,220are disposed laterally outwardly relative to the upper and lower convex regions212,213, respectively. The first and second guide channels218,220each have a cross-sectional area greater than the cross-sectional area of the flow restriction235. The first and second guide channels218,220are substantially aligned with the first and second junction openings209,211, respectively.

The flow restriction235has a maximum height H1along a height axis which coincides with the main flow entry axis75in this embodiment. The height axis75is perpendicular to both the main flow discharge axis85and the transverse axis95. The first and second guide channels218,220each have a maximum height H2, H3along the height axis75which is larger than the maximum height H1of the flow restriction235. In the illustrated embodiment, the first and second guide channels218,220have substantially the same maximum height H2, H3along the height axis75.

The contour portion208includes the upper depression212in the top of the multi-leg discharge boot200and the lower depression213in the bottom of the multi-leg discharge boot200that helps promote flow to outer lateral edges214,216of the multi-leg discharge boot to reduce the occurrence of slurry buildup at the junction210. As shown in the Figures, the shape of the central contoured portion208results in large channels218,220disposed adjacent respective outer edges214,216thereof. The depressions212,213in the central portion208define the flow restriction235which has a smaller cross-sectional area than the cross-sectional area at the outer edges214,216and a smaller height H2, H3than found adjacent the outer edges H2, H3. As a result, the slurry flowing along the main flow discharge axis85toward the junction210encounters less flow resistance in the guide channels218,220disposed at the outer edges214,216. Therefore, flow is directed toward the large channels218,220at the multi-leg discharge boot's200outer edges214,216and away from the central portion208and the junction210.

The junction210is disposed between the two outlet conduits204,206. The junction210is made up of the planar wall219that is substantially perpendicular to the main flow discharge axis85along which slurry will flow when entering the inlet opening207of the inlet conduit202. The planar wall219is sized such that fibers and other additives in the cementitious slurry are impeded from wrapping around the junction210and building up at that site (a process also referred to as “stapling”). The planar wall219can be configured to help prevent slurry from adhering to the junction210, building up, and eventually breaking off to cause lump formation. Depending on the line speed and volumes passing through the multi-leg discharge boot200and the boot legs204,206, the configuration of the junction210and the central contoured portion208can be varied to achieve the desired results.

The junction210can be configured to help prevent slurry buildup in a region just upstream of the junction210. If this buildup does occur, however, it can disrupt the flow of slurry, which can cause the split of slurry flow to become uneven and/or interrupted. The trapped buildup of slurry can harden and set, that in time can eventually break away, causing hard lumps to be carried in the slurry flow which can cause process problems and interruptions, such as paper breaks at the forming station.

Referring toFIGS. 8-10, an embodiment of a compressing device or automatic squeezing apparatus300for compressing the multi-leg discharge boot200at adjustable and regular time intervals can be provided to help prevent slurry from building up inside the multi-leg discharge boot. The squeezing apparatus300addresses potential cleanliness issues associated with the multi-leg discharge boot200as it splits a main flow of incoming cementitious slurry into two outlet flow streams. The squeezing apparatus300squeezes a central portion208of the multi-leg discharge boot200to help reduce buildup of set slurry at the junction210.

The compressing device300includes first and second compressing members302,304disposed in spaced relationship to each other. The junction portion210of the multi-leg discharge boot200is disposed between the first and second compressing members302,304. At least one of the first and second compressing members302,304is movable over a range of travel relative to the other compressing member304along a compressing axis75, which is substantially perpendicular to the main flow discharge axis85, between a normal position and a compressed position (see second compressing member304shown in phantom inFIG. 9). In the compressed position, a portion of at least one of the inlet conduit202and the first and second outlet conduits204,206adjacent the junction portion210is compressed relative to the normal position. In embodiments, the junction portion210is compressed when the compressing members302,304are in the compressed position relative to the normal position.

The compressing members302,304each comprise a substantially planar compressing surface303,305. The compressing surfaces303,305are in substantially parallel relationship to each other and to the main flow discharge axis75.

Referring toFIG. 9, the compressing device300includes at least one actuator306adapted to selectively move the first compressing member302relative to the second compressing member304. In the illustrated embodiment, the second compressing member304, which is disposed below the multi-leg discharge boot200, is movable, and the first compressing member302is stationary. In other embodiments, other movement arrangements are possible.

The compressing device300can include a controller320adapted to control each actuator306such that the actuator306is periodically actuated according to a predetermined frequency to periodically compress the junction portion. The controller320can be adapted to control each actuator306such that the actuator306is actuated to move the first and second compressing members302,304toward each other by a predetermined stroke length L1(seeFIG. 10).

As shown inFIGS. 8-10, the squeezing apparatus300is disposed adjacent the junction210of the multi-leg discharge boot200. The first and second compressing members are in the form of an upper plate302and a lower plate304. The upper plate302is positioned on the top of the multi-leg discharge boot200, and the lower plate304is positioned below the multi-leg discharge boot200. As best shown inFIG. 9, the illustrated squeezing apparatus300includes a pair of actuators306in the form of a pneumatic cylinder308with a reciprocally movable piston310. Each actuator306is mounted to the upper plate302and the lower plate304such that, when the actuator is actuated, the piston310retracts and the lower plate304moves toward the upper plate302over a defined stroke length L1along the height axis75which is substantially perpendicular to the main flow discharge axis75. A pair of pneumatic lines312is connected to the pneumatic chamber308of each actuator306and to a source of pressurized air322. The controller320is adapted to selectively control the source of pressurized air322, such as with suitable electrically-operated valves, for example, to selectively operate the actuators306to retract the pistons310to compress the squeezing apparatus and to extend the pistons to return the plates302,304to the normal position. The actuator306can be operated either automatically or selectively to move the plates302,304together relative to each other to apply a compressive force upon the multi-leg discharge boot200at the recessed central portion208and the junction210. Moving the upper and lower plates302,304closer to each other applies a compressive force that can cause the multi-leg discharge boot200to flex inwardly at the junction210to discourage slurry build up.

When the squeezing apparatus300squeezes the multi-leg discharge boot200, the squeezing action applies compressive force to the multi-leg discharge boot, which flexes inwardly in response. This force helps prevent buildup of solids that can disrupt the flow of slurry through the outlet conduits204,206of the multi-leg discharge boot200. In some embodiments, the squeezing apparatus300is designed to automatically pulse through the use of a programmable controller operably arranged with the actuators306. The squeezing apparatus300can be configured such that it actuates at varying stroke lengths and frequencies, which can be adjusted depending on production conditions. The squeezing apparatus300can also provide support for the multi-leg discharge boot200to help maintain the internal geometry of the multi-leg discharge boot and help prevent unwanted distortion, which can help maintain proper velocity and flow characteristics when slurry flows through the multi-leg discharge boot200.

Referring toFIGS. 11 and 12, an embodiment of a slurry mixing and dispensing assembly100is shown that includes a slurry mixer102in fluid communication with a multi-leg discharge boot200constructed in accordance with principles of the present disclosure. The slurry mixer102can be adapted to agitate water and a cementitious material to form an aqueous cementitious slurry. Both the water and the cementitious material can be supplied to the mixer102via one or more inlets as is known in the art. Any suitable mixer (e.g., a pin mixer) can be used with the slurry mixing and dispensing assembly100.

The multi-leg discharge boot200illustrated inFIG. 11is adapted to separate an incoming main flow of slurry from the slurry mixer102into two substantially even discharge flows. The multi-leg discharge boot200has an inlet conduit202adapted to receive the main flow of slurry from the mixer102and a pair of outlet conduits204,206each in fluid communication with the inlet conduit202and adapted to dispense two outlet flows of slurry from the multi-leg discharge boot200.

A discharge conduit104is in fluid communication with the slurry mixer102and comprises the multi-leg discharge boot200. The delivery conduit104can be made from any suitable material and can have different shapes. In some embodiments, the delivery conduit104can comprise a flexible conduit.

An aqueous foam supply conduit108can be in fluid communication with at least one of the slurry mixer102and the delivery conduit104. An aqueous foam from a source can be added to the constituent materials through the foam supply conduit108at any suitable location downstream of the mixer102and/or in the mixer102itself to form a foamed cementitious slurry that is provided to the multi-leg discharge boot200. In the illustrated embodiment, the foam supply conduit108is disposed downstream of the slurry mixer112. In the illustrated embodiment, the aqueous foam supply conduit108has a manifold-type arrangement for supplying foam to an injection ring or block associated with the delivery conduit104as described in U.S. Pat. No. 6,874,930, for example.

In other embodiments, one or more secondary foam supply conduits can be provided that are in fluid communication with the mixer102. In yet other embodiments, the aqueous foam supply conduit(s) can be in fluid communication with the slurry mixer alone102. As will be appreciated by those skilled in the art, the means for introducing aqueous foam into the cementitious slurry in the slurry mixing and dispensing assembly100, including its relative location in the assembly, can be varied and/or optimized to provide a uniform dispersion of aqueous foam in the cementitious slurry to produce board that is fit for its intended purpose.

Any suitable foaming agent can be used. Preferably, the aqueous foam is produced in a continuous manner in which a stream of the mix of foaming agent and water is directed to a foam generator, and a stream of the resultant aqueous foam leaves the generator and is directed to and mixed with the cementitious slurry. Some examples of suitable foaming agents are described in U.S. Pat. Nos. 5,683,635 and 5,643,510, for example.

When the foamed cementitious slurry sets and is dried, the foam dispersed in the slurry produces air voids therein which act to lower the overall density of the wallboard. The amount of foam and/or amount of air in the foam can be varied to adjust the dry board density such that the resulting product is within a desired weight range.

One or more flow-modifying elements106can be associated with the delivery conduit104and adapted to control a main flow of slurry discharged from the slurry mixer102. The flow-modifying element(s)106can be used to control an operating characteristic of the main flow of aqueous cementitious slurry. In the illustrated embodiment ofFIGS. 11 and 12, the flow-modifying element(s)106is associated with the discharge conduit104. Examples of suitable flow-modifying elements include volume restrictors, pressure reducers, constrictor valves, canisters etc., including those described in U.S. Pat. Nos. 6,494,609; 6,874,930; 7,007,914; and 7,296,919, for example.

In use, a main flow of slurry is discharged from the mixer102into the delivery conduit104, aqueous foam is inserted into the main flow through the foam supply conduit108, and the flow-modifying element(s)106controls an operating characteristic of the main flow of slurry. The main flow of slurry is directed into the inlet conduit202of the multi-leg discharge boot200. The main flow of slurry from the mixer102is redirected in the inlet conduit202and split in the multi-leg discharge boot200into a first discharge flow of slurry and a second discharge flow of slurry which are discharged therefrom via the first and second outlet conduits204,206, respectively. The multi-leg discharge boot200can separate the incoming main flow of slurry from the mixer102into two substantially even discharge flows that can be discharged from the multi-leg discharge boot200upon an advancing web of cover sheet material, for example, moving along a machine axis50.

The multi-leg discharge boot200can act to slow down the slurry flow and help spread the slurry in a cross-machine axis60, which is substantially perpendicular to the machine direction50, across the width of the advancing web of cover sheet material. In various embodiments, the multi-leg discharge boot200can have various configurations and sizes depending on the intended slurry volume and the line speed of the board line. Board lines running at higher speeds can use the multiple leg boots to help overcome problems with spreading the slurry along the cross-machine axis60in these applications.

Referring toFIG. 12, an exemplary embodiment of a wet end150of a gypsum wallboard manufacturing line is shown. The illustrated wet end150includes the cementitious slurry mixing and dispensing assembly100including the multi-leg discharge boot200, a hard edge/face skim coat roller152disposed upstream of the multi-leg discharge boot200and supported over a forming table154such that a first moving web156of cover sheet material is disposed therebetween, a back skim coat roller158disposed over a support element160such that a second moving web162of cover sheet material is disposed therebetween, and a forming station164adapted to shape the preform into a desired thickness. The skim coat rollers152,158, the forming table154, the support element160, and the forming station164can all comprise conventional equipment suitable for their intended purposes as is known in the art. The wet end150can be equipped with other conventional equipment as is known in the art.

Water and calcined gypsum can be mixed in the mixer102to form an aqueous calcined gypsum slurry. In some embodiments, the water and calcined gypsum can be continuously added to the mixer in a water-to-calcined gypsum ratio from about 0.5 to about 1.3, and in other embodiments of about 0.75 or less.

Gypsum board products are typically formed “face down” such that the advancing web156serves as the “face” cover sheet of the finished board. A face skim coat/hard edge stream166(a layer of denser aqueous calcined gypsum slurry relative to at least one of the first and second flows of aqueous calcined gypsum slurry) can be applied to the first moving web156upstream of the hard edge/face skim coat roller152, relative to the machine direction168, to apply a skim coat layer to the first web156and to define hard edges of the board.

The multi-leg discharge boot200can be used to distribute an aqueous calcined gypsum slurry upon the first advancing web156. A main flow121of aqueous calcined gypsum slurry is discharged from the mixer102into the discharge conduit104including the multi-leg discharge boot200. The main flow of aqueous calcined gypsum slurry enters the inlet conduit202of the multi-leg discharge boot200is directed downwardly in the inlet conduit202toward an advancing web of cover sheet material156moving in a machine direction168upon the forming table154, is redirected in the inlet conduit202such that the main flow of aqueous calcined gypsum slurry is moving substantially along the machine direction168, and is split therein between the first outlet conduit204and the second outlet conduit206to define first and second discharge flows180,182, respectively. The first and second discharge flows180,182of aqueous calcined gypsum slurry can be discharged from the multi-leg discharge boot200upon the first moving web156.

In embodiments, the first discharge flow180of aqueous calcined gypsum and the second discharge flow182of aqueous calcined gypsum slurry each has an average velocity that is at least about 50% of the average velocity of the main flow121of aqueous calcined gypsum slurry entering the inlet conduit202of the multi-leg discharge boot200. In embodiments, the first discharge flow180of aqueous calcined gypsum and the second first discharge flow182of aqueous calcined gypsum slurry each has an average velocity that is at least about 70% of the average velocity of the main flow121of aqueous calcined gypsum slurry entering the multi-leg discharge boot200. In embodiments, the first and second discharge flows180,182of aqueous calcined gypsum slurry can have at least one flow characteristic that is substantially similar, such as average velocity, for example.

The face skim coat/hard edge stream166can be deposited from the mixer102at a point upstream, relative to the direction of movement of the first moving web156in the machine direction168, of where the first and second flows180,182of aqueous calcined gypsum slurry are discharged from the multi-leg discharge boot200upon the first moving web156. The first and second flows180,182of aqueous calcined gypsum slurry can be discharged from the slurry distributor with a reduced average velocity to help prevent “washout” of the face skim coat/hard edge stream166deposited on the first moving web156(i.e., the situation where a portion of the deposited skim coat layer is displaced from its position upon the moving web156in response to the impact of the slurry being deposited upon it).

A back skim coat stream184(a layer of denser aqueous calcined gypsum slurry relative to at least one of the first and second flows180,182of aqueous calcined gypsum slurry) can be applied to the second moving web162. The back skim coat stream184can be deposited from the mixer102at a point upstream, relative to the direction of movement of the second moving web162, of the back skim coat roller158. The second moving web162of cover sheet material can be placed upon the slurry discharged from the multi-leg discharge boot200upon the advancing first web156to for a sandwiched wallboard preform that is fed to the forming station164to shape the preform to a desired thickness.

In another aspect of the present disclosure, a multi-leg discharge boot constructed in accordance with principles of the present disclosure can be used in a variety of manufacturing processes. For example, in one embodiment, a multi-leg discharge boot can be used in a method of preparing a gypsum product. A multi-leg discharge boot can be used to split a main flow of aqueous calcined gypsum slurry discharged from a mixer into at least two discharge flows of aqueous calcined gypsum slurry which are discharged from the multi-leg discharge boot.

In embodiments of a method of preparing a cementitious product, a main flow of aqueous slurry can be discharged from a mixer. The main flow of slurry is redirected in an inlet conduit of a multi-leg discharge boot from a main flow entry axis to a main flow discharge axis by a change in direction angle within a range of about ten degrees to about one hundred thirty-five degrees. The main flow of aqueous slurry is moved past a flow restriction in the inlet conduit upstream of a junction portion separating first and second outlet conduits of the multi-leg discharge boot. The main flow of aqueous slurry moving along the main flow discharge axis is split into a first discharge flow of aqueous slurry and a second discharge flow of aqueous slurry in the multi-leg discharge boot. The first and second discharge flows are discharged from the first and second outlet conduits.

In embodiments, first and second guide channels are disposed in flanking relationship to the flow restriction. The first and second guide channels can be in substantial respective alignment with first and second junction openings leading to the first and second outlet conduits, respectively.

In embodiments, the first discharge flow of aqueous slurry and the second feed flow of slurry each has an average velocity that is at least about 50% of the average velocity of the main flow of slurry entering the inlet conduit of the multi-leg discharge boot. In embodiments, the first and second discharge flows of aqueous slurry each has an average velocity that is at least about 75% of the average velocity of the main flow of aqueous slurry entering the inlet conduit of the multi-leg discharge boot. In embodiments, a method of preparing a cementitious product can include discharging the first and second discharge flows of aqueous slurry from the slurry distributor upon a web of cover sheet material moving along a machine direction.

In embodiments, a method of preparing a cementitious product can include compressing a junction portion of the multi-leg discharge boot. The junction portion can be disposed between a first outlet conduit and a second outlet conduit of the multi-leg discharge boot. In embodiments, the junction portion can be compressed periodically according to a predetermined frequency. In embodiments, compressing the junction portion includes moving first and second compressing members toward each other by a predetermined stroke length.