A method and apparatus to manufacture gypsum board that directs an aqueous gypsum slurry to a second cover sheet, and passes the second cover sheet over a roller spaced above a first cover sheet so that a majority of the aqueous gypsum slurry of falls off the second cover sheet to deposit over the first cover sheet. Another aqueous gypsum slurry of a different density than the deposited slurry is applied over the first cover sheet before and/or after the deposited slurry. A gypsum board having layers of different densities is made by the method and apparatus.

A method and apparatus to manufacture gypsum board that directs an aqueous gypsum slurry to a second cover sheet, and passes the second cover sheet over a roller spaced above a first cover sheet so that a majority of the aqueous gypsum slurry of falls off the second cover sheet to deposit over the first cover sheet. Another aqueous gypsum slurry of a different density than the deposited slurry is applied over the first cover sheet before and/or after the deposited slurry. A gypsum board having layers of different densities is made by the method and apparatus.

Turning motion of gypsum slurry spouting onto a sheet of paper for a gypsum board liner is restricted for preventing maldistribution, deviation or irregular dispersion from occurring in the density distribution of the slurry on the sheet of paper. A mixing and stirring device for gypsum slurry has a circular casing forming a mixing area, a rotary disc positioned in the casing, and a tubular passage for feeding the slurry onto the sheet of paper for the gypsum board liner. A chute has a fluid passage portion with its cross section being non-axisymmetric with respect to a center axis of the tubular passage, or a fluid passage portion varying a position of the center axis of the tubular passage by a change or lateralization of the cross section of fluid passage.

Turning motion of gypsum slurry spouting onto a sheet of paper for a gypsum board liner is restricted for preventing maldistribution, deviation or irregular dispersion from occurring in the density distribution of the slurry on the sheet of paper. A mixing and stirring device for gypsum slurry has a circular casing forming a mixing area, a rotary disc positioned in the casing, and a tubular passage for feeding the slurry onto the sheet of paper for the gypsum board liner. A chute has a fluid passage portion with its cross section being non-axisymmetric with respect to a center axis of the tubular passage, or a fluid passage portion varying a position of the center axis of the tubular passage by a change or lateralization of the cross section of fluid passage.

Gypsum panels, sheathing systems, and methods of making and using the same are provided. A gypsum panel includes a gypsum core associated with a first fiberglass mat having a continuous barrier coating, the coating penetrating a portion of the first fiberglass mat opposite the gypsum core, wherein gypsum penetrates a remaining fibrous portion of the first fiberglass mat such that voids in the first fiberglass mat are substantially eliminated. A building sheathing system includes at least two gypsum panels and a seaming component to provide a seam at an interface between the gypsum panels.

The instant invention is concerned with the post-treatment of -hemihydrate plasters for the purpose of stabilization. The invention relies in the addition of a retardant to the calcined -hemihydrate. It is also the purpose of the invention to provide stabilized -hemihydrate plasters which exhibit advantageous properties.

An apparatus for production of a gypsum product is provided which comprises a conveyer comprising a conveyer belt and means for rotating the conveyer belt; means for forming a gypsum product; and at least one laser scanner positioned over the conveyer belt at the location where the scanner scans at least one edge of the gypsum product which is at least partially set; and the laser scanner is in communication with a processor. Methods for forming a gypsum product with the apparatus are provided as well.

An apparatus for production of a gypsum product is provided which comprises a conveyer comprising a conveyer belt and means for rotating the conveyer belt; means for forming a gypsum product; and at least one laser scanner positioned over the conveyer belt at the location where the scanner scans at least one edge of the gypsum product which is at least partially set; and the laser scanner is in communication with a processor. Methods for forming a gypsum product with the apparatus are provided as well.

A constrictor valve can be associated with a conduit in fluid communication with a mixer to control a flow of cementitious slurry discharged from the mixer through the conduit. The constrictor valve can include a constrictor housing, a webbing constriction assembly, and a drive mechanism. The webbing constriction assembly includes a pair of rotatable members rotatably mounted to the constrictor housing and a plurality of webbing straps connected to the rotatable members and wrapped around the conduit. The drive mechanism includes a drive shaft and a gear assembly configured to rotate the rotatable members in opposing winding directions in response to the drive shaft rotating in a tighten direction to wrap the webbing straps tighter around the conduit to compress it and to rotate in opposing unwinding directions in response to the drive shaft rotating in a loosen direction to loosen the grip of the webbing straps on the conduit.

A constrictor valve can be associated with a conduit in fluid communication with a mixer to control a flow of cementitious slurry discharged from the mixer through the conduit. The constrictor valve can include a constrictor housing, a webbing constriction assembly, and a drive mechanism. The webbing constriction assembly includes a pair of rotatable members rotatably mounted to the constrictor housing and a plurality of webbing straps connected to the rotatable members and wrapped around the conduit. The drive mechanism includes a drive shaft and a gear assembly configured to rotate the rotatable members in opposing winding directions in response to the drive shaft rotating in a tighten direction to wrap the webbing straps tighter around the conduit to compress it and to rotate in opposing unwinding directions in response to the drive shaft rotating in a loosen direction to loosen the grip of the webbing straps on the conduit.