Method and apparatus for scrim embedment into wet processed panels
AssigneeUnited States Gypsum Company
InventorDavid Paul MILLER
Life of this patent
Estimating the term…
Abstract
A method of producing a paperless gypsum/fiber board from a mixture including reinforcing material particles, calcined gypsum and water. A headbox feeds the mixture into a panel forming area (forming pond) over the upper surface of a continuous forming fabric to form a panel mat. Also, a reinforcing mesh is fed over a transverse member, located over a portion of the forming fabric, and into the forming pond to embed the mesh in the mixture. At least a portion of a downstream end of the transverse member is under a downstream portion of the headbox or downstream of the headbox. Then the panel mat is pressed, the calcined gypsum of the pressed panel mat is rehydrated, and the resulting board is dried.
Claims23
A method of producing a gypsum/fiber board comprising the steps of:
- mixing ground gypsum and host particles of a fibrous reinforcing material and sufficient liquid comprising water to make a slurry having at least 60% liquid by weight;
- calcining the gypsum in the presence of the host particles and the water, by heating the slurry under pressure, to form a slurry mixture comprising water and calcium sulfate alpha hemihydrate crystals;
- feeding the slurry mixture through a headbox to a panel forming area over the upper surface of a flat porous forming fabric;
- providing a transverse member over a portion of the forming fabric, wherein a downstream portion of the transverse member is under a downstream portion of the headbox or downstream of the headbox;
- passing a reinforcing mesh under the headbox, over the transverse member, and into the forming pond to embed the reinforcing mesh in the slurry mixture in the forming pond, wherein the transverse member extends transverse to a direction of movement of the mesh;
- removing water from the slurry mixture to form a panel mat with the mesh embedded in the panel mat;
- pressing the panel mat having the embedded mesh;
- rehydrating the calcined gypsum of the pressed panel mat to form a board comprising bonded host particles and gypsum with the mesh embedded in the board;
- and
- drying the board to provide a finished board with the mesh embedded in the finished board.
An apparatus for producing a gypsum/fiber board comprising:
- a mixer for mixing ground gypsum and host particles of a fibrous reinforcing material and sufficient liquid comprising water to make a slurry having at least 60% liquid by weight;
- a reactor for calcining the gypsum in the presence of the host particles and the water, by heating the slurry under pressure, to form a slurry mixture comprising water and acicular calcium sulfate alpha hemihydrate crystals;
- a headbox for feeding the slurry mixture through the headbox into a forming pond of a panel forming area over the upper surface of a flat porous forming fabric;
- a transverse member over a portion of the forming fabric, wherein a downstream portion of the transverse member is under a downstream portion of the headbox or downstream of the headbox;
- a space between the headbox and the transverse member for feeding a reinforcing mesh between the transverse member and the headbox and then into the forming pond to embed the reinforcing mesh in the slurry mixture in the forming pond;
- vacuum means for removing water from the slurry mixture to form a panel mat with the mesh embedded in the panel mat;
- a first press for pressing the panel mat having the embedded mesh;
- a second press for permitting rehydrating of the calcined gypsum of the pressed panel mat to form a board comprising bonded host particles and gypsum with the mesh embedded in the board;
- and
- a drier for drying the board to remove free water and provide a finished board with the mesh embedded in the finished board.
The apparatus of claim 21, wherein the transverse member comprises a sheet located over a portion of the forming fabric, the sheet having an upstream portion, a downstream portion and a middle portion between the upstream portion and downstream portion,
- wherein the upstream portion is upstream of an upstream lip of the head box,
- wherein the middle portion is under the headbox,
- wherein sheet is spaced from the headbox to form the space for passing therethrough the reinforcing mesh.
The apparatus of claim 22, wherein the downstream end of the sheet forms a bend having an upwards angle of at most about 20 degrees relative to a horizontal plane upon which the middle portion lies.
Dependencies are inferred from the claim text.