AU2010236105B2

AU2010236105B2 - Crack Preventing Cornice

Info

Publication number: AU2010236105B2
Application number: AU2010236105A
Authority: AU
Inventors: Richard Halbert; Peter James Levander; Bill Thompson
Original assignee: CSR Building Products Ltd
Current assignee: CSR Building Products Ltd
Priority date: 2009-10-29
Filing date: 2010-10-29
Publication date: 2016-01-14
Anticipated expiration: 2030-10-29
Also published as: AU2010236105A1; NZ588899A

Abstract

A cornice comprising a first engagement surface adapted to be fixedly installed to a ceiling and a second engagement surface having a flexible semi detached flap portion thereon. The semi-detached flap portion includes inner and outer surfaces and distally located first and second ends. The outer surface of the semi-detached flap portion is adapted to be fixedly secured to a wall surface and the inner surface of the first end of the flap portion is securely joined to the second engagement surface. Furthermore, the inner surface of the second end of the flap portion is frangibly joined to the second engagement surface and the inner surface of the flap portion between the first and second ends is unattached to the second engagement surface. BEFORE AFTER '/32 '~77JD :22 FIG 3 FIG 4

Description

mcinnes patents AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Applicant: CSR Building Products Limited Triniti 3, 39 Delhi Road North Ryde NSW 2113 Actual Inventors: Bill Thompson Peter James Levander Richard Halbert Address for Service: HODGKINSON McINNES PATENTS Patent & Trade Mark Attorneys Levels 21, 201 Elizabeth Street Sydney NSW 2000 HMcIP Ref: P21285AU01 Invention Title: Crack Preventing Cornice Details of Priority Application: Australia 2009905301 29 October 2009 P1 10AU 2 Crack Preventing Cornice TECHNICAL FIELD 5 The present invention relates generally to a cornice used for concealing the junction between a wall and a ceiling. More particularly, the present invention relates to a cornice that retains a dust seal with a wall and prevents cracking under the cornice in the event of localised movement between the wall and the ceiling. 10 BACKGROUND TO THE INVENTION Whilst there are numerous different ways in which buildings may be constructed, it is common for conventional buildings to utilise rendered 15 masonry walls and plaster ceilings. Regardless of the construction materials of the walls and the ceiling, it is typical to utilise a cornice at the junction between the wall and the ceiling in a building to provide an attractive finish. It is common for there to be some movement in a building between 20 the ceiling and the wall, particularly where the walls are of a full brick or hard rendered construction and the ceiling is of plaster. Typically, the ceiling will move downwards or partially sink with respect to the wall, which in turn applies a downward load or stress force on the cornice and particularly, the join between the wall and the cornice. 25 The stress of this downward load in many cases is sufficient for the join between the wall and a conventional cornice to fracture, thereby forming a crack between the hard wall plaster and the cornice. This results in the formation of aesthetically unpleasing cracks along the bottom edge of 30 the cornice, which is shown in FIG 1. These unsightly cracks also allow for dust and other debris located behind the cornice to fall through the space 3 between the hard wall plaster and the cornice causing further undesirable appearances on the wall surface below the cornice. In the past, it has been attempted to alleviate the unsightly 5 appearance of these cracks by incorporating a shadow line in the cornice. A shadow line is simply a portion of the cornice, which by its location, when viewed by an observer from below (as would be the typical viewing angle once the cornice is installed in between a wall structure and a ceiling), casts a shadow onto the adjoining wall, thereby concealing any small crack that 10 may be present beneath the cornice. However, shadow lines on conventional cornices only conceal relatively small cracks that may appear beneath the cornice. Also, any dust or debris that may be present behind the cornice may fall through any 15 cracks that appear, even when the cracks are small. This can result in possible unsightly stains and aesthetically unpleasing marks on the wall surface below the cornice. Therefore, it would also be desirable to provide an improved cornice 20 that ameliorates or overcomes one or more known disadvantages of existing techniques or that may provide a useful alternative to them. SUMMARY OF THE INVENTION 25 In accordance with one aspect of the present invention there is provided a cornice comprising a first engagement surface adapted to be fixedly installed to a ceiling and a second engagement surface having a flexible semi-detached flap portion thereon. The semi-detached flap portion includes inner and outer surfaces and distally located first and second ends. 30 The outer surface of the semi-detached flap portion is adapted to be fixedly secured to a wall surface; the inner surface of the first end of the flap portion is securely joined to the second engagement surface; the inner 4 surface of the second end of the flap portion is frangibly joined to the second engagement surface; and the inner surface of the flap portion between the first and second ends is unattached to the second engagement surface. 5 Preferably, the first engagement surface is adapted to be fixedly installed to the ceiling and the outer surface of the second end of the flap portion is adapted to be fixedly installed to the wall surface by way of a fixing material. A stress force applied to the cornice as a result of downward 10 movement of the ceiling with respect to the wall will result in the frangible joint between the second engagement surface and the inner surface of the second end of the flap portion to fail, thereby causing the flap portion to pull away from the second engagement surface. 15 Preferably, when the flap portion pulls away from the second engagement surface, the second end of the outer surface of the flap portion remains fixedly installed to the wall surface by way of the fixing material, thereby forming a gap between the second end of the inner surface of the flap portion and the second engagement surface. 20 Preferably, when the flap portion pulls away from the second engagement surface, a dust seal is formed between the second end of the outer surface of the flap portion and the wall surface. 25 The flap portion is substantially of flexible material, which is preferably paper and the frangible joint between the flap portion and the cornice is provided by a thin line of adhesive. However, according to another embodiment of the present invention, 30 the frangible joint between the flap portion and the cornice is provided by one or more of a score line or perforations in the flap portion.

5 The fixing material is preferably cornice cement and the cornice preferably has a core body substantially of gypsum plaster, which is paper wrapped and is made in a continuous ribbon process. 5 Preferably, the flap portion overlaps with a portion of the paper wrapping and the cornice has a profile that includes a shadow line detail to assist in concealing any movement of the cornice with respect to the wall. In this specification, unless the context clearly indicates otherwise, 10 the term "comprising" has the non-exclusive meaning of the word, in the sense of "including at least" rather than the exclusive meaning in the sense of "consisting only of". The same applies with corresponding grammatical changes to other forms of the word such as "comprise", "comprises" and so on. 15 BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in 20 which: FIG 1 is a photograph of a conventional prior art cornice installed at a junction between a wall and a ceiling showing a plurality of cracks that have formed below the cornice; FIG 2 is a schematic plan view of a cornice according to an 25 embodiment of the present invention; FIG 3 is a schematic plan view of the cornice of FIG 2 installed at a junction between a ceiling and a wall; FIG 4 is a schematic plan view of the cornice of FIG 3 after the ceiling has moved downwardly.

6 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The present invention generally relates to a cornice 10 used for concealing the junction 30 between a wall 34 and a ceiling 32. More 5 particularly, the present invention relates to a cornice 10 that retains a dust seal with a wall 34, and prevents cracking under the cornice in the event of localised movement between the wall and the ceiling 32. FIG 1 shows a conventional cornice 1 installed at the junction 10 between walls 34a and 34b and a ceiling 32. The ceiling 32 has moved downwardly with respect to the walls 34a, 34b, whereby the stress of this downward load has caused the join between the walls and the cornice 1 to fracture, forming a plurality of cracks 40 along the bottom edge of the cornice. These unsightly cracks 40 also allow for dust and other debris 15 located behind the cornice 1 to fall through the space between the hard wall plaster and the cornice causing further undesirable appearances on the wall surfaces below the cornice. FIG 2 shows an embodiment of the present invention which provides 20 a cornice 10 comprising a core body 14 of gypsum plaster covered with a wrapping 16 of paper. Typically, the paper wrapped cornice 10 of the present invention is made in a continuous ribbon process. The cornice 10 has at least one surface layer 12 for attaching the 25 cornice to a wall surface. This surface layer 12 includes a flexible semi detached flap portion, being a sheet of flexible material 18, such as paper. The flexible semi-detached flap portion 18 is securely joined with the wrapping 16 at one end thereof and is frangibly joined to the wrapping at a lower end 20 thereof by adhesive 22. 30 The adhesive 22 is only applied in a thin line at the lower end 20 of the cornice 10. In this way, one end of the flexible material 18 is securely joined to the wrapping 16 of the cornice 10 and the other end of the flexible 7 material, which is distally located at the lower end 20 of the cornice is attached to the wrapping only by way of the thin line of adhesive 22. In other words, the flexible sheet of material 18 overlaps with a 5 portion of the wrapping 16 at an overlapping area generally identified as item 24 and is securely fixed to the wrapping at one end thereof, with its other lower end 20, being only frangibly joined to the wrapping by a thin line of adhesive 22. 10 FIG 3 shows the cornice 10 attached to a junction formed between a ceiling 32 and a side wall 34. The cornice 10 is securely attached to both the ceiling 32 and the wall 34 by a suitable fixing material 36, such as cornice cement. When installed, the cornice 10 serves to conceal the junction between the ceiling 32 and the wall 34. 15 Where the cornice 10 is fixedly installed to the ceiling 32, it is by way of the wrapping 16 being secured to the ceiling by way of the fixing material 36. However, where the cornice 10 is fixedly secured to the wall 34, it is by way of the flexible material 18 being secured to the wall surface 34 by way 20 of the fixing material 36. In this way, the weakest component in the joint between the cornice 10 and the wall 34 is the frangible joint between the thin line of adhesive 22 and the flexible material 18 rather than the joint between the flexible 25 material and the wall. In the event that the ceiling 32 downwardly moves with respect to the wall, a stress load force will be applied on the joint between the cornice 10 and the wall 34. In this case, it is the thin line of adhesive 22 securing 30 the flexible material 18 to the gypsum core body of the cornice that will fail, rather than the joint between the wall 34, the flexible material 18 and the fixing material 36.

8 Conversely, where a conventional cornice has been installed, in the event that the ceiling 32 downwardly moves with respect to the wall, causing a stress load force being applied on the joint between the cornice and the wall, it is the fixing material that is used to fixedly install the 5 cornice to a wall surface that will fail. This results in unsightly cracks appearing below the cornice, as best shown in FIG 1. FIG 4 shows the cornice of the present invention installed to conceal a joint between a ceiling 32 and a wall 34 after the ceiling has moved 10 downwardly with respect to the wall by a distance of approximately 3 mm. As can be seen in FIG 4, the thin line of adhesive 22 has failed as a result of the stress load force resulting from the downward movement of the ceiling 32 with respect to the wall being applied on the joint between 15 the cornice 10 and the wall 34. In this way, as the cornice 10 moves downwardly and drops away from the wall surface, the now free end of the flexible material 18 is pulled clear of the corresponding portion of the wrapping 16 of the cornice. The 20 amount of movement between the flexible material 18 and the cornice will be determined by the amount of movement of the ceiling 32 relative to the wall 34. In other words, the more the ceiling 32 moves relative to the wall 34, the wider the gap between the flexible material 18 and the overlapping area 24 of the cornice will become. 25 The outer side of the flexible material 18 remains fixedly installed to the wall surface 34 by way of the fixing material 36. This seal between the flexible material 18 and the wall surface 34 prevents any dust and debris that may be located behind the cornice 10 from falling through any gaps in 30 the joint between the cornice and the wall. In this way, the flexible material 18 can be thought of as a "flap", which is pulled clear of the unbonded surface of the wrapping 16 in the 9 event that the ceiling 32 moves downwardly with respect to the wall 34. The "flap" arrangement of flexible material 18 thereby forms a dust sealing membrane to prevent any dust and debris that may be located behind the cornice 10 from falling through any gaps in the joint between the cornice 5 and the wall 34. The cornice 10 of the present invention prevents the formation of unsightly cracks below the cornice as a result of downward ceiling 32 movement, which are caused by the fracturing of the joint between 10 conventional cornices and the wall surface by a rigid bond such as that provided by cornice cement 36. This is achieved by providing the cornice 10 of the present invention with the overlapping layer of the flexible material 18, which allows for some 15 movement of the cornice with respect to the wall 34, without fracturing the rigid bond that fixedly secures the cornice to the wall, typically by way of cornice cement or the like 36. In this way, the flexible material 18 is fixedly installed to the wall 20 surface by way of fixing material 36 and where the ceiling 32 moves downwardly with respect to the wall 34, the thin line of adhesive 22 will fail, thereby allowing the flexible material to pull away from the unbonded surface of the wrapping 16, which allows the joint between the flexible material and the wall to be maintained and also allows for some movement 25 of the cornice relative to the wall and the flexible material. In order that the movement of the cornice 10 relative to the wall 34 and the flexible material 18 can be disguised, the profile of the cornice is such that it includes a shadow line detail 26. Where the ceiling 32 has 30 moved downwardly, causing a corresponding movement of the cornice 10 and resultant pulling away of the flexible material 18 from the unbonded surface of the wrapping 16, the shadow line detail 26 will prevent the movement of the cornice 10 away from the wall 34 from being noticeable to 10 an observer from below (as would be the typical viewing angle once the cornice is installed in between a wall structure and a ceiling). Whilst it is preferable for the sheet of flexible material 18 to overlap 5 with the wrapping 16 in the overlapping area 24, it is also within the scope of the present invention for the sheet of flexible material 18 to be an integral part of the wrapping 16. In this alternative embodiment, the wrapping 16 would be fastened to the core body 14 at or near the lower end 20 only by way of a thin line of adhesive 22. 10 Whilst this alternative embodiment is within the scope of the present invention, it is not preferred. This is because when the thin line of adhesive fails under the stress of any movement of the ceiling 32, the now free end of the wrapping 16 would pull away from the core body of the cornice, 15 thereby exposing the core body. Whilst the function of the free end of the wrapping at the lower end 20 would serve an identical function to the flexible material 18 in so far as retaining the joint with the hard wall surface, the disadvantage is that the core body 14 of the cornice 10 would now be exposed. 20 Conversely, in the more preferred embodiment of the invention, when the thin line of adhesive 22 fails under the stress of any movement of the ceiling 32, the now free end of the flexible material 18 retains the joint with the hard wall surface but the core body 14 of the cornice 10 is not 25 exposed because of the wrapping 16 located in the overlapping area 24. Whilst it is preferred that the fixing material 36 is cornice cement, it is envisaged that other suitable materials can be utilised. Other suitable materials include different types of adhesives. It is also envisaged that 30 mechanical fixings such as nails, screws or the like may also be utilised to secure the cornice to the wall and the ceiling.

11 Whilst the preferred embodiment of the present invention utilises a thin line of adhesive to frangibly secure the flexible material 18 to the wrapping 16 of the cornice 10, in another embodiment that is not shown in the accompanying drawings, the flexible material may incorporate a line of 5 weakness that is adapted to tear when predetermined stress load is applied to the cornice. The line of weakness may include either a score line or a row of perforations in the flexible material 18. It will be apparent that obvious variations or modifications may be 10 made which are in accordance with the spirit of the invention and which are intended to be part of the invention, and any such obvious variations or modifications are therefore within the scope of the invention. 15 INDUSTRIAL APPLICABILITY The invention can be utilised in the construction of buildings to provide an attractive finish to the junction between a wall and ceiling. Specifically, the cornice of present invention can be used to conceal the 20 junction between a wall and a ceiling in a building where localised movement between the wall and the ceiling is likely and so the cornice will retain a dust seal with the wall even in the event of ceiling movement.

Claims

1. A cornice comprising: a first engagement surface adapted to be fixedly installed to a ceiling and a second engagement surface having a flexible semi-detached flap portion thereon; the semi-detached flap portion includes inner and outer surfaces and distally located first and second ends; the outer surface of the semi-detached flap portion is adapted to be fixedly secured to a wall surface; the inner surface of the first end of the flap portion is securely joined to the second engagement surface; the inner surface of the second end of the flap portion is frangibly joined to the second engagement surface; and the inner surface of the flap portion between the first and second ends is unattached to the second engagement surface.

2. A cornice of claim 1 wherein the first engagement surface is adapted to be fixedly installed to the ceiling and the outer surface of the second end of the flap portion is adapted to be fixedly installed to the wall surface by way of a fixing material, wherein a stress force applied to the cornice as a result of downward movement of the ceiling with respect to the wall will result in the frangible joint between the second engagement surface and the inner surface of the second end of the flap portion to fail, thereby causing the flap portion to pull away from the second engagement surface. 13

3. A cornice of claim 2 wherein when the flap portion pulls away from the second engagement surface, the second end of the outer surface of the flap portion remains fixedly installed to the wall surface by way of the fixing material, thereby forming a gap between the second end of the inner surface of the flap portion and the second engagement surface.

4. A cornice of claim 3 wherein when the flap portion pulls away from the second engagement surface, a dust seal is formed between the second end of the outer surface of the flap portion and the wall surface.

5. A cornice of claim 1 wherein the flap portion is substantially of flexible material.

6. A cornice of claim 5 wherein the flexible material is paper.

7. A cornice of claim 1 wherein the frangible joint between the flap portion and the cornice is provided by a thin line of adhesive.

8. A cornice of claim 1 wherein the frangible joint between the flap portion and the cornice is provided by one or more of a score line or perforations in the flap portion.

9. A cornice of claim 2 wherein the fixing material is cornice cement. 14

10. A cornice of claim 1 having a core body substantially of gypsum plaster, which is paper wrapped and is made in a continuous ribbon process.

11. A cornice of claim 10 wherein the flap portion overlaps with a portion of the paper wrapping.

12. A cornice of claim 1 having a profile that includes a shadow line detail to assist in concealing any movement of the cornice with respect to the wall. * * * * * * *