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Panel smoothing process and apparatus for forming a smooth continuous surface on fiber-reinforced structural cement panels

a technology of fiber reinforced structural cement and smoothing process, which is applied in the direction of surface layering apparatus, sustainable waste treatment, manufacturing tools, etc., can solve the problems of insufficient structural strength, and achieve the effect of removing pock marks or grooves

Inactive Publication Date: 2008-05-01
UNITED STATES GYPSUM CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0019]The present invention features a flexible smoothing device or shroud apparatus designed to apply a light uniform pressure to the entire top surface of a formed fiber reinforced gypsum-cement panel as it exits the embedment device of the final slurry forming station to smooth the surface of the panel and remove pock marks or grooves without damaging the panel.
[0022]Only the surface of a downstream end portion of the flexible sheet contacts the top surface of the formed panel and the flexible sheet of the smoothing device is curved so a small angle of entry, e.g., less than 150, preferably less than 50, is provided at the nip point and preferably the angle tapers to zero. This allows for a very gradual, or zero, change in the height of the SCP panel as it contacts the smoothing sheet.
[0023]The smoothing device with its pivoting mounting is designed to have the downstream end portion of the flexible sheet “float” up and down over the surface of the freshly formed gypsum-cement panel. Thus, only a low pre-determined pressure is exerted on the top surface to smooth out the surface and fill in grooves or pock marks in the panel surface. This avoids scratching or tearing the panel surface. Furthermore, the flexible sheet can be pivoted up and away from the panel production line when it is not in use. In addition to permitting it to be moved out of the way when not in use, the ability to pivot the flexible sheet up makes it easier to maintain and clean the device.
[0026]In a preferred embodiment, multiple layers of chopped individual loose fibers are deposited relative to each layer of deposited slurry. The preferred sequence is that a layer of loose fibers are deposited, upon either the moving web or existing slurry, followed by a layer of slurry, then another layer of fibers. Next, the fiber / slurry / fiber combination is subjected to embedding to thoroughly mix the fibers in the slurry. This procedure has been found to permit the incorporation and distribution of a relatively larger amount of slurry fibers throughout the slurry using fewer slurry layers. Thus, panel production equipment and processing time can be reduced, while providing an SCP panel with enhanced strength characteristics.

Problems solved by technology

However, a drawback of such conventional panels is that they do not have sufficient structural strength to the extent that such panels may be comparable to, if not stronger than, structural plywood or oriented strand board (OSB).

Method used

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  • Panel smoothing process and apparatus for forming a smooth continuous surface on fiber-reinforced structural cement panels
  • Panel smoothing process and apparatus for forming a smooth continuous surface on fiber-reinforced structural cement panels
  • Panel smoothing process and apparatus for forming a smooth continuous surface on fiber-reinforced structural cement panels

Examples

Experimental program
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Effect test

second embodiment

of a Production Line

[0149]The incorporation of a volume fraction of loose fibers distributed throughout the slurry 46 is an important factor in obtaining desired panel strength. Thus, improved efficiency in incorporating such fibers is desirable. It is believed the system depicted in FIGS. 1-5 in some cases requires excessive numbers of slurry layers to obtain an SCP panel having sufficient fiber volume fraction.

[0150]Accordingly, an alternate SCP panel production line or system is illustrated in FIG. 6 and is generally designated 130 for producing high-performance, fiber reinforced SCP panels incorporating a relatively high volume of fibers per slurry layer. In many cases, increased levels of fibers per panel are obtained using this system. While the system of FIGS. 1-5 discloses depositing a single discrete layer of fibers into each subsequent discrete layer of slurry deposited after the initial layer, the production line 130 includes a method of building up multiple discrete rein...

example 1

[0214]Referring now to FIG. 1C, a fragment of the SCP panel 92 made from fibers and a slurry. The cements portion of the slurry comprises 65 wt. % Calcium sulfate alpha hemihydrate, 22 wt. % Type III Portland cement, 12 wt. % Silica Fume, and 1 wt. % hydrated lime. The liquid portion of the slurry comprises 99.19 wt. % water and 0.81 wt. % ADVACAST superplasticizer by W.R. Grace and Co. The liquid:cement weight ratio was 0.55 and the Aggregate (EXTENDOSPHERES SG microspheres):Cement weight ratio was 0.445.

[0215]The slurry was produced according to the present process, using the present system, and is shown to have four slurry layers, 77, 80, 88 and 90. This panel should be considered exemplary only in that a panel 92 produced under the present system may have one or more layers. By using the above mathematical relationships, the slurry layers 77, 80, 88 and 90 can have different fiber volume fractions. For example, skin or face layers 77, 90 have a designated fiber volume fraction V...

example 2

[0219]The residence time of the wet slurry in various embodiments of a vertical mixing chamber have been empirically determined by determining the residence time of a red dye tracer added to the slurry to completely exit the vertical chamber. Tests were conducted to determine residence time in the vertical mixing chambers using a red dye tracer added to the water and powder slurry as it enters the vertical chamber. The cementitious slurry had substantially the same composition as described above for Example 1.

[0220]The equipment used was a digital scale to weigh the slurry, a bucket to catch the slurry and a stop watch to measure the elapsed time of the various points. A mixer was used with three different mixing chamber designs as listed in Tables 2-4 as a 12 inch Mixer, an 8 inch Extended Mixer, and an 8 inch Stock Mixer.

[0221]The 8 inch Stock Mixer is a DUO MIX 2000 mixer which is similar to that of FIG. 3A of U.S. patent application Ser. No. ______ (Attorney Docket No. APV31962 / ...

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Abstract

A vibrating flexible smoothing sheet or shroud disposed transversely of a direction of travel of a formed fiber panel including gypsum-cementitious slurry and embedded chopped fibers. The sheet is used to smooth the surface of the panel as it exits a fiber embedment station of a structural cementitious panel production line to remove grooves and other non-uniform surface imperfections to reduce the need for costly finishing after the panels are cured and cut to size. The flexible sheet is designed to float over the surface of the formed panel without tearing or otherwise damaging the surface of the heavily fiber reinforced surface layers of the panel. The vibrating sheet is pivotally mounted on the side dams of the web production line so it can float over the panel surface during use, but be raised off the line when not in use.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is related to co-pending:[0002]U.S. patent application Ser. No. ______ (Attorney Docket No. APV31960 / 3991), entitled PROCESS AND APPARATUS FOR FEEDING CEMENTITIOUS SLURRY FOR FIBER-REINFORCED STRUCTURAL CEMENT PANELS, filed concurrently with the present application;[0003]U.S. patent application Ser. No. ______ (Attorney Docket No. APV31962 / 3993), entitled METHOD FOR WET MIXING CEMENTITIOUS SLURRY FOR FIBER-REINFORCED STRUCTURAL CEMENT PANELS, filed concurrently with the present application;[0004]U.S. patent application Ser. No. ______ (Attorney Docket No. APV31963 / 3994), entitled APPARATUS AND METHOD FOR WET MIXING CEMENTITIOUS SLURRY FOR FIBER-REINFORCED STRUCTURAL CEMENT PANELS, filed concurrently with the present application;[0005]U.S. patent application Ser. No. ______ (Attorney Docket No. APV31965 / 3845), entitled WET SLURRY THICKNESS GAUGE AND METHOD FOR USE OF SAME, filed concurrently with the present application;[0...

Claims

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Application Information

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IPC IPC(8): B29C47/00
CPCB01F3/1221B01F3/1271B01F7/00583B01F15/0251B28C7/0418B28B19/0092B28C5/1284B28C5/404B28B11/0845B01F23/59B01F23/53B01F27/13B01F35/71775Y02W30/91
Inventor STIVENDER, EUGENE SCOTT
Owner UNITED STATES GYPSUM CO
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