AU2007202505B2

AU2007202505B2 - Improved Cornice

Info

Publication number: AU2007202505B2
Application number: AU2007202505A
Authority: AU
Inventors: Bill Thompson; Serge Zappone
Original assignee: CSR Building Products Ltd
Current assignee: CSR Building Products Ltd
Priority date: 2006-06-02
Filing date: 2007-05-31
Publication date: 2012-01-19
Anticipated expiration: 2027-05-31
Also published as: AU2007202505A1

Abstract

The present invention relates generally to a cornice having a longitudinally extending profile of constant cross section. The cornice has a substantially rectangular main body portion having opposed first and second faces. The first face is adapted to be concealed and the second face is adapted to be an exposed decorative surface, when the cornice is installed to a junction of a wall and ceiling. A stepped projection extends along one side of the main body portion of the cornice, such that the projection has opposed third and fourth faces offset from the main body portion. The cornice is adapted to be installed to the junction with the projection running adjacent to the wall. In this way, the cornice thus forms a recess between the wall and the main body portion. The cornice is composed of a substantially gypsum core with a paper lining and is made in a continuous process. Figure to accompany Abstract = Figure 2

Description

AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Applicant: CSR Building Products Limited Level 4, 9 Help Street Chatswood NSW 2067 Actual Inventors: Bill Thompson Serge Zappone Address for Service: HODGKINSON McINNES PATENTS Patent & Trade Mark Attorneys Level 21, 201 Elizabeth Street Sydney NSW 2000 HMP Ref: P20536AU01 Invention Title: Improved Cornice Details of Associated Provisional 2006903014 dated 2 June 2006 Application: The following statement is a full description of this invention, including the best method of performing it known to us: PII OKPAU 2 IMPROVED CORNICE TECHNICAL FIELD s The present invention relates generally to cornice used ornamentally and for concealing the junction between a wall and a ceiling, and more particularly to a cornice composed of gypsum plaster encased by a liner and made in a continuous ribbon process. 10 BACKGROUND One of the most common ways of constructing walls and ceilings includes use of inorganic wallboard panels or sheets such as gypsum wallboard, often referred to simply as plasterboard. 15 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. 20 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. The continuous envelope enclosing the aqueous slurry is then supported on a conveyor 25 called a "setting belt" for sufficient time to gain rigidity. 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". 30 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 3 aqueous slurry of calcined gypsum. The continuous envelope enclosing the slurry is then supported on 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. 5 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 10 of the conveyor or setting belt that supports the continuous envelope enclosing the slurry during the continuous ribbon production of the cornice. This type of cornice, shown in Fig 1(a) and marketed under the trade mark GYPROCK* COVE by CSR Building Products Limited is widely used and is simple and effective in providing an ornamental finish and concealing the junction of a wall and ceiling. However, its wide use detracts 15 from its aesthetic appeal. Cornices with more complex decorative surfaces are also made in a continuous process as described in International Patent publication No. WO 02/43953 in the name of CSR Limited. For example, two such cornices are marketed under GYPROCK* JAZZTM and GYPROCK* CONCERTOTM by CSR Building Products Limited and shown in Figs 1(b) and 1(c). The "step" in the decorative surface of the 20 cornice of Fig 1 (c) creates a shadow effect. One disadvantage of conventional cornices is that sometimes after their installation to a wall-ceiling junction movement occurs between the wall and ceiling thus visibly forming a crack, which in many instances is aesthetically undesirable. 25 Whilst the abovementioned conventional gypsum cornices are made in a cost effective continuous ribbon process, it is desirable to offer home-builders and renovators with alternative cornices that are more flexible in their application, easy to install, and offer solutions to camouflaging cracks formed by wall-ceiling movement. 30 It would also be desirable to provide an improved cornice that ameliorates or overcomes one or more known disadvantages of existing techniques or that may provide a useful alternative to them.

4 DISCLOSURE OF INVENTION According to a first aspect the present invention consists in a cornice having a longitudinally extending profile of constant cross section, the cornice having a s substantially rectangular main body portion with opposed first and second faces, the first face adapted to be concealed and the second face adapted to be an exposed decorative surface when the cornice is installed to a junction of a wall and ceiling, wherein a stepped projection extends along one side of the main body portion such that the projection has opposed third and fourth faces offset from the main body portion, and the cornice adapted 10 to be installed to the junction with the projection running adjacent the wall, thus forming a recess between the wall and the main body portion and wherein the cornice is composed of a substantially gypsum core with a paper lining and is made in a continuous process. Preferably the recess provides a shadow effect along the wall, thereby at least is partially camouflaging a crack that may occur in the junction. Preferably the cornice is adapted for at least two types of installation, the first type being where a portion of the first face is abutted against at least one ceiling sheet of the ceiling, the second type being where both the cornice and the at least one ceiling sheet are 20 both suspended from ceiling joists such that the second face of the body portion of the cornice is substantially flush with the exposed face of the ceiling sheet. Preferably the third and fourth faces are each flat and equidistantly spaced from each other. 25 Preferably the cornice has elongate tensile elements embedded within the gypsum core. Preferably the elongate tensile elements are glass rovings. 30 Preferably, the elongate tensile elements are off-set from the centre of the core.

5 Preferably, the elongate tensile elements are embedded within the gypsum core near an interface between the gypsum core and a paper lining. According to a second aspect the present invention consists in a cornice adapted to 5 be fitted to the junction of a wall and ceiling, the cornice is composed of a substantially gypsum core and paper lining and made in a continuous process such that it has a longitudinally extending profile of constant cross section, the cornice comprising a plank like main body portion having opposed first and second faces in such a manner that when the cornice is installed the first face is concealed and the second face is exposed, the 10 cornice further comprising a stepped projection extending from the main body portion in such a manner that when the cornice is installed the projection is adjacent to the wall and vertically closer to ceiling joists supporting the ceiling than is the main body portion, thereby forming a recess between the main body portion and the wall and wherein the cornice is composed of a substantially gypsum core with a paper lining and is made in a 15 continuous process. Preferably the recess provides a shadow effect along the wall, thereby at least partially camouflaging a crack that may occur in the junction. 20 Preferably the cornice is adapted for either plant-on installation or flush installation. Preferably in the plant-on installation a substantial portion of the first face is abutted against at least one ceiling sheet of the ceiling. 25 Preferably in the flush installation the cornice and at least one ceiling sheet of the ceiling are both suspended from ceiling joists by furring channels such that the projection is accommodated above the ceiling sheet and the main body portion is in the same plane as the ceiling sheet. 30 Preferably the cornice has elongate tensile elements embedded within the gypsum core. Preferably the elongate tensile elements are glass rovings.

6 Preferably, the elongate tensile elements are off-set from the centre of the core. Preferably, the elongate tensile elements are embedded within the gypsum core near 5 an interface between the gypsum core and a paper lining. BRIEF DESCRIPTION OF THE DRAWINGS The invention is now discussed with reference to drawings, where: 10 Figs 1 (a)-(c) depict cross-sectional views of three prior art cornices. Fig 2 is a schematic perspective view of a first embodiment of a cornice in accordance with the present invention. 15 Fig 3 depicts a cross-sectional view of the cornice shown in Fig 2. Fig 4 is a schematic elevation view of the cornice of Fig 2 in a plant-on installation to a junction of a wall and ceiling. 20 Fig 5 is a schematic elevation view of the cornice of Fig 2 in a flush installation to a junction of a wall and ceiling. Fig 6 is a schematic perspective view of a second embodiment of a cornice in 25 accordance with the present invention. BEST MODE OF CARRYING OUT INVENTION Figs 1(a)-(c) depict three prior art cornices marketed by CSR Building Products 30 Limited. Fig 1(a) is a simple curved cornice (scotia section with square edges) of the type marketed under GYPROCK* COVE. Figs 1(b) and 1(c) are cornices with decorative surfaces that are marketed under the GYPROCK* JAZZ T M and GYPROCK* CONCERTO brands. All of these three prior art cornices are typically affixed in a "plant- 7 on" installation where they are affixed to the wall and ceiling. Where movement occurs between the wall and ceiling at a later stage, a crack at the wall interface may appear and be undesirable. 5 Figs 2 and 3 depict a cornice 1 adapted to be fitted to the junction of a wall and ceiling in accordance with a first embodiment. Preferably, the cornice is composed of a substantially gypsum core and paper lining and made in a continuous process such that it has a longitudinally extending profile of constant cross section. The cornice 1 is preferably used in conjunction with walls covered with plasterboard wall lining 9 and 10 plasterboard ceiling lining 10. Cornice I has a rectangular (plank-like) main body portion 2 and a stepped projection 3 extending therefrom. The main body portion 2 has a first upper face 4 and a second lower face 5. The projection 3 has a third upper face 7 and a fourth lower face 8. 15 A longitudinal notch 20 exists at the junction of body portion 2 and projection 3. The dimensions shown in Fig 2 are preferred dimensions where the cornice I is used with 10mm ceiling sheets. However, it should be understood that in other embodiments the dimensions may differ. 20 In use, when the cornice I is installed, the upper face 4 of body portion 2 and upper face 7 of projection 3 are both concealed whilst the lower face 5, body portion 2 and lower face 8 of projection 3 are exposed. 25 In use, cornice I can be installed in at least two installation types, the first being "plant-on installation" and the second being "flush installation". Fig 4 depicts cornice I when it is used in a "plant-on installation". In this installation, the cornice 1 is installed on the plasterboard ceiling lining (ceiling sheets) 10 30 such that the upper face 4 of body portion 2 is abutted against ceiling sheets 10. In such a plant-on installation the plasterboard wall lining (wall sheets) 9 are preferably installed first, and they finish close to the ceiling joist I I to produce a neat 8 shadow recess. The ceiling sheets 10 are preferably installed next, and preferably finish a minimum of about 30mm from the wall sheet to accommodate the projection 3 of cornice 1. Next, cornice I is fixed in place using conventional cornice cement, such as that marketed under the GYPROCK* brand. Enough cement must be applied to upper 5 face 4 of cornice I to support the cornice. Screws (not shown) may be used to temporarily hold the profile in place before the cement sets. All gaps 15 between the wall sheet 9 and the edge of the cornice I should preferably be filled with a flexible and paintable sealant, such as for example, GYPROCK* Wet Area Acrylic Sealant. 10 Fig 5 depicts an alternative, "flush installation" where the cornice I is installed directly onto a furring channel 13 before the ceiling sheets 10 are also installed on similar furring channels 13. Preferably, the main body portion 2 has a thickness identical to that of the ceiling sheets 10, thereby ensuring that the main body portion 3 of cornice 1 is flush with the ceiling sheet 10. 15 The furring channels 13 are installed into the ceiling joists 11. Next, cornice I is fixed to furring channel 13 using conventional plasterboard screws 16. Any gaps between wall sheet 10 and the edge of the cornice I may then be filled with a flexible and paintable sealant similar to that of the earlier described "plant-on installation". The 20 ceiling sheet 10 may have its edge butted up to the edge of cornice 1, forming a joint 30 similar to a butt joint between two sheets of plasterboard. This joint 30 may be taped and set in a similar fashion as a plasterboard butt joint. A decorative paint finish may then be applied as for conventional plasterboard. 25 In both of the abovementioned installation methods, flexible and paintable sealant may be applied into the gaps 15 between cornice I and wall sheets 9. In both installation methods, a recess 25 is formed by the notch 20 of cornice I in combination with wall sheet 9. 30 An advantage of the cornice I of the present invention is that it can be installed in either of the abovementioned "plant-on" or "flush" installations, and at the same is able to form longitudinally extending recess 25 in the region between cornice I and wall 9, in the region of projection 3. This recess 25 provides a shadow effect along wall sheet 10, 9 thereby camouflaging or at least partially camouflaging any cracks that may occur as a result of relative movement between the ceiling and wall, at the junction of the cornice 1 and wall sheet 10. 5 Fig 6 depicts a second embodiment of a cornice 21 in accordance with the present invention. In this embodiment, the cornice 21 has a shape like that of the first embodiment and also has a gypsum core enclosed by a paperboard liner. In addition, the cornice 21 has a plurality of continuous fibreglass rovings 14 extending in a lengthwise direction from one end of the cornice to the other. The use of such continuous fibreglass 10 rovings and their advantages are fully described in co-pending Australian Patent Application No. 2007201188 entitled: "Paper Wrapped Gypsum Building Component" and filed on 19 March 2007. Australian Patent Application No. 2007201188 is incorporated herein by reference. 15 Unless the context indicates otherwise, the words "comprise" or "comprising" and the like terms should be construed in an inclusive sense, as contrasted to an exclusive or exhaustive sense. These words normally mean "including but not limited to". It will be apparent that obvious variations or modifications may be made in 20 accordance with the spirit of the invention that are intended to be part of the invention, and any such obvious variations or modification are therefore within the scope of the invention. 25

Claims

1. A cornice having a longitudinally extending profile of constant cross section, the cornice having a substantially rectangular main body portion with opposed first and second faces, the first face adapted to be concealed and the second face adapted to be an exposed decorative surface when the cornice is installed to ajunction of a wall and ceiling, wherein a stepped projection extends along one side of the main body portion such that the projection has opposed third and fourth faces offset from the main body portion, and the cornice is adapted to be installed to the junction with the projection running adjacent the wall, thus forming a recess between the wall and the main body portion.

2. A cornice as defined in claim 1, wherein the cornice is composed of a substantially gypsum core with a paper lining.

3. A cornice as defined in claim 1, wherein the recess casts a shadow along the wall, thereby at least partially camouflaging a crack that may occur in the junction.

4. A cornice as defined in claim 1, wherein the cornice is adapted for at least two types of installation, the first type being where a portion of the first face is abutted against at least one ceiling sheet of the ceiling, the second type being where both the cornice and the at least one ceiling sheet are both suspended from ceiling joists such that the second face of the body portion of the cornice is substantially flush with the exposed face of the ceiling sheet.

5. A cornice as defined in claim 1, wherein the third and fourth faces are each flat and equidistantly spaced from each other.

6. A cornice as defined in claim 1, wherein the cornice has elongate tensile elements embedded within the gypsum core.

7. A cornice as defined in claim 6, wherein the elongate tensile elements are glass rovings.

8. A cornice as defined in claim 6 wherein the elongate tensile elements are off-set from the centre of the core.

9. A cornice as defined in claim 6, wherein the elongate tensile elements are embedded within the gypsum core near an interface between the gypsum core and a paper lining.

10. A cornice having a longitudinally extending profile of constant cross section substantially as hereinbefore described with reference to any one or more of Figures 2 to 6.

11. A method for camouflaging a crack that may appear at the junction of a wall and a ceiling, using a cornice as defined in any one of the preceding claims, said cornice having at least a main body and a stepped projection extending along one side of the main body portion to create a recess, said method comprising the steps of: installing the cornice at the junction; so that a recess between the main body of the cornice and the wall casts a shadow along the wall; thereby at least partially camouflaging a crack that may occur in the junction.

12. A method for manufacturing a cornice as defined in any one of claims 1 to 10, said method comprising the steps of: firstly forming a continuous paper lining envelope; injecting an aqueous slurry of gypsum within the envelope and then supporting the envelope for sufficient time to gain rigidity.

13. A cornice substantially as herein described with reference to any one or more of Figures 2 - 6 of the drawings. * * * *