WO2002043953A1

WO2002043953A1 - Paper wrapped gypsum building component and manufacture thereof

Info

Publication number: WO2002043953A1
Application number: PCT/AU2001/001508
Authority: WO
Inventors: William James Thompson; Nagi Ekdawi
Original assignee: Csr Limited
Priority date: 2000-11-28
Filing date: 2001-11-21
Publication date: 2002-06-06
Also published as: AUPR173700A0; AU2002214845A1

Abstract

A paper wrapped gypsum building component, such as an elongate cornice, made in a continuous ribbon process. The component having an exposed decorative surface which is other than substantially flat or a curve having a substantially constant radius of curvature. The paper used to wrap the component is formed to provide a longitudinally extending profile of substantially constant cross section, by firstly applying a weakening agent to said paper to facilitate bending of the paper into the desired profile and then forming said paper into said desired profile.

Description

PAPER WRAPPED GYPSUM BUILDING COMPONENT AND MANUFACTURE

THEREOF

TECHNICAL FIELD

The present invention relates generally to a paper wrapped gypsum building component made in a continuous ribbon process, and more particularly to such a component which is used as a cornice.

BACKGROUND

One of the most common ways of constructing walls and ceilings includes the use of inorganic wallboard panels or sheets such as gypsum wallboard, often referred to simply as plasterboard.

The use of plasterboard is common for lining internal walls and ceilings. A product which is used in combination with plasterboard is "cornice" which is a moulded or ribbon form strip. The cornice provides an attractive finish to the junction of walls and ceilings constructed of plasterboard.

Plasterboard is conventionally produced by enclosing a core of an aqueous slurry of calcined gypsum and other materials between two large sheets of cover paper, also known as plasterboard liner (PBL). Various types of cover paper are known in the art. After the gypsum slurry has set (i.e. reacted with the water from the aqueous slurry) and dried, the sheet is transversely cut into standard sizes. This forming and cutting is typically carried out in a "continuous ribbon process".

In a similar manner to plasterboard, the large scale manufacture of gypsum cornice is also carried out in a continuous ribbon process. The process for producing gypsum cornice involves the preparation of a PBL to enable it to form an envelope by the application of a gum sealing tape to enclose a core produced by the injection of an aqueous slurry of calcined gypsum. The continuous envelope enclosing the slurry is then supported on a conveyor called a setting belt for sufficient time to gain rigidity. The continuous ribbon of cornice is then transversely cut to the finished length required and dried to remove excess moisture prior to packing and dispatch. Such gypsum cornice which is made under high speed conditions typically at 16-120 metres/minute, in a continuous ribbon process typically has a curved crossed section. The exposed or decorative surface of the conventional gypsum cornice is a simple concave surface of constant radius of curvature, which is produced by the curved profile of the conveyor or setting belt that supports the continuous envelope enclosing the slurry during the continuous ribbon production of the cornice. A newer profile of gypsum cornice also involves the production of a curved section but involving both concave and convex curves within its profile. Again such concave and convex curves are of a constant radius of curvature and are produced by the profile of the conveyor, which supports the newly made cornice for sufficient time to gain rigidity.

A problem associated with the manufacture of gypsum cornice by such a high speed continuous ribbon arrangement, is that the profiles of the cornice are limited to simple curved profiles having a constant radius of curvature as a result of reliance on the conveyor setting belt profile in order to achieve the desired cornice profile. By utilizing such a process there has been a limitation of the profiles able to be generated. A drawback of the continuous ribbon process is that when the PBL is initially formed as an envelope about a fluid core, it does not display plastic properties until the setting process is well established. Manipulation of the envelope is therefore not effective until the plastic state arises. If extensive manipulation is carried out on the envelope in its plastic state to form a complex profile, this manipulation destroys the strength of mechanical bonds being developed by the growth of plaster crystals into the PBL.

It is also known to manufacture cornices having complex profiles. Such cornices are made by moulding short lengths with intricate patterns, on the exposed decorative surface. The moulding process is generally slow and cumbersome and therefore provides a cornice product which is far more costly to produce than that capable of being produced under a continuous ribbon process.

One known method of moulding cornice is described in United States Patent No. 5,076, 978 (Blum). In this arrangement, paper is continually fed through the channel of a mould, into which slurry is poured. Excess paper is folded over using a first roller, whilst final forming is achieved by a second roller. In this arrangement the moulded slurry and paper combination cures and dries within the mould, prior to it being detached from the mould. Whilst the paper is fed continually into the mould, the process is not continuous. The arrangement requires the paper to be stationary within the mould to allow it to set. It is only once the slurry and paper combination is sufficiently set, that it can be removed from the mould. As such, this process is dissimilar to a "continuous ribbon process" where the cornice is manufactured under high-speed conditions.

There are other known methods and devices for moulding cornices, one of which is described in International Patent publication No. WO 00/47382 (Dudley). This method utilizes first and second elongate members to form an open topped cavity and an end stop to form a seal between the elongate members. This method is not a "continuous ribbon process", but one in which the cornice is set within the mould, prior to its removal.

International Patent publication No. WO95/27110 (Dreamtank Pty Limited) discloses a device and method for producing a cornice having a polystyrene core in a continuous process. Whilst the process is capable of producing cornice of varied shapes and sizes, the process and device is not suited to manufacturing cornice having a "gypsum" core.

The present invention is directed towards a method of manufacturing a paper wrapped gypsum building component such as cornice, utilising a high speed continuous ribbon process, in which the building component has some form of intricacy contained therein.

SUMMARY OF INVENTION

In accordance with a first aspect of the present invention there is disclosed a paper wrapped gypsum building component made in a continuous ribbon process, characterised in that said component having an exposed decorative surface which is other than substantially flat or a curve having a substantially constant radius of curvature.

In one embodiment, said paper wrapped gypsum building component is an elongate cornice. In accordance with a second aspect of the present invention there is disclosed a paper wrapped gypsum building component made in a continuous ribbon process, said component having an exposed decorative surface characterised in that said decorative surface has at least one longitudinally extending peak or valley thereon.

In one embodiment said paper wrapped gypsum building component is an elongate cornice.

In a second embodiment said paper wrapped gypsum building component is a wallboard.

In accordance with a third aspect of the present invention there is disclosed a continuous ribbon process in which paper is formed to provide a longitudinally extending profile of substantially constant cross section, said method comprising the steps of (i) applying a weakening agent to said paper to facilitate bending of the paper into the desired profile and (ii) forming said paper into said desired profile.

Preferably said paper is used to form a paper wrapped gypsum building component having at least one exposed decorative surface.

Preferably said exposed decorative surface is other than substantially flat or a curve having a substantially constant radius of curvature.

Preferably said paper wrapped gypsum building component is a cornice component.

Preferably said weakening agent is a water based solution containing one or more volatile organic additives.

In accordance with a fourth aspect of the present invention there is disclosed an apparatus for making a paper wrapped gypsum building component in a continuous ribbon process, said apparatus comprising a depositing means for depositing an aqueous slurry of calcined gypsum onto a continuous sheet of paper traveling therepast, characterised in that said apparatus further comprising a manipulation means for manipulating the profile of said sheet of paper prior to said sheet of paper reaching said depositing means, and a delivery means for delivering a weakening agent to said paper upstream of said manipulation means to assist in the manipulation of said paper.

Preferably said manipulation means is a forming tray with a profile having a transition from a substantially flat form to a desired profile.

Preferably said forming tray has a plurality of openings therein fruidally connected to a vacuum system to create a vacuum to assist in holding said paper against the forming tray as it is moves therealong and is manipulated.

Preferably said delivery means delivers a weakening agent which is a water based solution containing one or more volatile organic additives.

Preferably said water based solution is any one of ethanol 20-80%, n-butanol 2-10% or iso- propyl alcohol.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will now be described with reference to the drawings in which:

Fig. 1 is an elevation view of an embodiment of an apparatus for manufacturing a paper wrapped gypsum building component in a continuous ribbon process in accordance with the present invention,

Fig. 2 is a plan view of the apparatus of Fig. 1,

Fig. 3 is an enlarged plan view of the forming tray of the apparatus shown in FigJ,

Fig. 4 is an elevation view of the forming tray shown in Fig. 3,

Fig 5. is a transverse cross-sectional view of an embodiment of a paper wrapped gypsum building component which can be manufactured in accordance with present invention, and Fig. 6 depicts eight profiles or cross sections of paper wrapped gypsum building components which can be manufactured in accordance with present invention.

MODE OF CARRYING OUT THE INVENTION

Figs. 1 and 2 depict an embodiment of an apparatus for manufacturing a paper wrapped gypsum building component in a continuous ribbon process, which in this embodiment is cornice. The apparatus is laid out in an elongate configuration in a conventional manner. For reason of ease of illustration the apparatus is shown without the plasterboard liner, gypsum slurry and other additives traveling therealong.

At one end of the apparatus, a roll of plasterboard liner (PBL) 1 is supported for delivery to a PBL tensioning mechanism 2 in a conventional manner. The PBL 1 is adapted to travel continuously in a ribbon-like conventional manner along the apparatus towards a mixer 4 where an aqueous slurry of calcined gypsum (plaster of paris) and other materials are injected onto the PBL 1 to provide a fluid core. As the PBL 1 passes mixer 4, the edges of the PBL 1 are bent over and towards each other and a gummed sealing tape 5 is applied to form an envelope around the fluid core, also in a conventional manner. The sealing tape 5 is applied by a sealing tape mechanism 6. The continuous envelope which encapsulates the slurry is then supported on a conveyor (setting belt) 7, for sufficient time to gain rigidity. The continuous envelope is then transversely cut to the finished length required, and dried to remove excess moisture prior to packing and dispatch.

An important new feature of the apparatus in this embodiment is the provision of a forming tray 3 located between the tensioning apparatus 2 and the mixer 4 as shown in enlarged detail in Figs. 3 and 4. Also new is the provision of a weakening agent delivery system 8 at the upstream end of forming tray 3.

The weakening agent delivery system 8 takes the form of a plurality of delivery nozzles 9 adapted to continuously deliver a water based "conditioning" or "weakening" solution to specific longitudinally arranged regions of the PBL 1 as it passes below the delivery nozzles 9. One preferable embodiment of delivery nozzles 9, is the use of hypodermic tubing, with the weakening solution applied under gravity. The hypodermic tube ends are placed close to the PBL 1 to enable a continuous stream of weakening solution to be applied without drops forming on the PBL 1.

A number of suitable weakening agents are those containing volatile organic additives. Examples of suitable water based solutions may be ethanol 20-80% (by weight), n-butanol 2-10% (by weight) or iso-propyl alcohol. The use of such volatile organic additives decrease the surface tension of the water in the weakening solution and allow it to penetrate the PBL 1 at a desired fast rate. The use of such weakening agents enables the PBL 1 to be manipulated about the specific regions where it has been applied, but allows the PBL 1 to regain its strength properties once the weakening solution has evaporated. As the volatile organic additives in the weakening solution evaporate, no substances harmful to a satisfactory bond between the PBL and plaster core remain. There is also no deleterious environmental consequence.

The forming tray 3 is provided with a profile having a transition from a substantially flat form to a desired profile, hi Fig. 3 this profile is represented by lines 10 disposed longitudinally therealong. A plurality of openings 11 in the forming tray 3, are fluidally connected to a vacuum system 12 shown in phantom lines. A vacuum is applied to the openings 11, which holds the PBL 1 to the form of the tray 3, as it passes over it.

As mentioned earlier, the weakening agent which is being applied to the paper board liner 1 ensures that it can be manipulated as it passes over the tray 3. The use of the vacuum ensures that the PBL 1 can be shaped in a way that minimises extraneous stresses which could otherwise cause undesired deformation and instability. The profile of the tray 3 is derived from the natural geometry of the PBL sheet material progressing in transition from a flat form to the desired profile. Thus the profile ensures that the geometry is a series of related conical elements without any spherical components which develop tensile or compressive forces within the PBL 1. As the PBL 1 is manipulated to a desired shape as it passes over the tray 3, the width of the manipulated PBL narrows, as does the width of the forming part of the tray 3 in the direction of travel Y.

The forming tray 3 of the apparatus of Figs. 1 to 4 is used to manipulate the PBL 1 to form the lower portion of profile 13 shown in Fig 5. In particular, the forming tray 3 is used to form the decorative peaks 14 and valleys 15 on the PBL 1 which appear on the profile 13. The peaks 14 and valleys 15 longitudinally extend along the decorative (lower) surface of the profile.

As the PBL 1 leaves the tray 3 it passes through roller mechanism 16, prior to reaching mixer 4 (Fig. 2) where it has the aqueous slurry of calcined gypsum (plaster of paris) and other materials injected onto it to provide a fluid core. The bed 17 supporting the travelling PBL 1 immediately after the mixer 4, as well as the conveyor 7 are both profiled in a complementary manner to the manipulated profile of the PBL to allow for ease of support whilst the fluid plaster core sets.

The edges of the PBL 1 may be scored in the conventional manner to allow the envelope to be formed about the plaster core prior to sealing tape 5 being applied. It is however preferable to weaken specific regions of the PBL 1 with the earlier applied weakening agent to allow for folding of the edges to form the envelope. Use of the weakening agent is able to be used to replace scoring.

Once the envelope is sealed by tape 5 at the sealing tape mechanism 6, it continues onto the conveyor 7. An upper belt mechanism 18 is applied to envelope back (reverse side to the decorative surface) of the envelope and assists in the formation of the finished profile, prior to continuing along the conveyor 7 towards a cutting station (not illustrated).

Whilst the present invention has been described with reference to the manufacture of a cornice profile as shown in Fig. 5, it should be understood that the apparatus and method of the earlier described embodiment can be used to manufacture other profiles whose exposed decorative surface is other than substantially flat or a curve having a substantially constant radius of curvature. Figures 6(a)-(h) are a representative selection of a number of cornice profiles which can be manufactured. In the case of profiles 6(a)-(f) they can be manufactured in a like manner described above, however the tray 3 would have to be replaced by a tray to suit the specific profile, as would the positioning of the weakening agent delivery nozzles 9. In the case of profiles 6(g) and (h) additional formation is required on the envelope back (non-decorative side). This can be achieved by applying weakening solution to these specific regions of the PBL 1 that form the envelope back. This envelope back can then be manipulated as part of an extrusion process as the envelope passes between the upper belt mechanism 18 and conveyor 7. In order to achieve the profiles 6(g) and 6(h) the upper belt of upper belt mechanism 18 has a profile complementary to that being formed in the back of the envelope.

It should be readily understood that whilst the embodiment described above is directed towards the formation of cornice having a complex decorative surface using a continuous ribbon process, the present invention can be applied to other paper wrapped gypsum building components having complex profiles.

It will be recognised by persons skilled in the art that numerous variations and modifications may be made to the invention without departing from the spirit and scope of the invention.

The term "comprising" as used herein is used in the inclusive sense of "including" or "having" and not in the exclusive sense of "consisting only of.

Claims

CLAIMSThe claims defining the invention are as follows:

1. A paper wrapped gypsum building component made in a continuous ribbon process, characterised in that said component having an exposed decorative surface which is other than substantially flat or a curve having a substantially constant radius of curvature.

2. A paper wrapped gypsum building component made in a continuous ribbon process as claimed in claim 1, wherein said paper wrapped gypsum building component is an elongate cornice.

3. A paper wrapped gypsum building component made in a continuous ribbon process, said component having an exposed decorative surface characterised in that said decorative surface has at least one longitudinally extending peak or valley thereon.

4. A paper wrapped gypsum building component made in a continuous ribbon process as claimed in claim 3, wherein said paper wrapped gypsum building component is an elongate cornice.

5. A paper wrapped gypsum building component made in a continuous ribbon process as claimed in claim 3, said paper wrapped gypsum building component is a wallboard.

A continuous ribbon process in which paper is formed to provide a longitudinally extending profile of substantially constant cross section, said method comprising the steps of (i) applying a weakening agent to said paper to facilitate bending of the paper into the desired profile and (ii) forming said paper into said desired profile.

A continuous ribbon process in which paper is formed to provide a longitudinally extending profile of substantially constant cross section as claimed in claim 6, wherein said paper is used to form a paper wrapped gypsum building component having at least one exposed decorative surface.

8. A continuous ribbon process in which paper is formed to provide a longitudinally extending profile of substantially constant cross section as claimed in claim 7, wherein said exposed decorative surface is other than substantially flat or a curve having a substantially constant radius of curvature.

9. A continuous ribbon process in which paper is formed to provide a longitudinally extending profile of substantially constant cross section as claimed in claim 7, wherein said paper wrapped gypsum building component is a cornice component.

10. A continuous ribbon process in which paper is formed to provide a longitudinally extending profile of substantially constant cross section as claimed in any one of claims 6 to 9, wherein said weakening agent is a water based solution containing one or more volatile organic additives.

11. An apparatus for making a paper wrapped gypsum building component in a continuous ribbon process, said apparatus comprising a depositing means for depositing an aqueous slurry of calcined gypsum onto a continuous sheet of paper traveling therepast, characterised in that said apparatus further comprising a manipulation means for manipulating the profile of said sheet of paper prior to said sheet of paper reaching said depositing means, and a delivery means for delivering a weakening agent to said paper upstream of said manipulation means to assist in the manipulation of said paper.

12. An apparatus for making a paper wrapped gypsum building component in a continuous ribbon process as claimed in claim 11, wherein said manipulation means is a forming tray with a profile having a transition from a substantially flat form to a desired profile.

13. An apparatus for making a paper wrapped gypsum building component in a continuous ribbon process as claimed in claim 12, wherein said forming tray has a plurality of openings therein fluidally connected to a vacuum system to create a vacuum to assist in holding said paper against the forming tray as it is moves therealong and is manipulated.

14. An apparatus for making a paper wrapped gypsum building component in a continuous ribbon process as claimed in any one of claims 11 to 13, wherein said delivery means delivers a weakening agent which is a water based solution containing one or more volatile organic additives.

15. An apparatus for making a paper wrapped gypsum building component in a continuous ribbon process as claimed in claim 15, wherein said water based solution is any one of ethanol 20-80%, n-butanol 2-10% or iso-propyl alcohol.