GB2144782A

GB2144782A - Improvements relating to ceiling tiles

Info

Publication number: GB2144782A
Application number: GB08403209A
Authority: GB
Inventors: Donald George Gordon
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-03-03
Filing date: 1984-02-07
Publication date: 1985-03-13
Also published as: GB8403209D0; IE53996B1

Abstract

A ceiling tile of sheet form comprises a plaster matrix reinforced by nonwoven glass fibre scrim. The tile has ribs 14 and a peripheral rib extending transversely from the rear face giving a tile with improved fire resistance by extending the time before cracking occurs and altering the pattern of cracking. The scrim may contain glassfibre chopped strand mat, continuous filament glass fibre mat, or loose chopped fibre strands such that the impact strength of the tile is improved, and by adding ordinary portland cement, white cement or water soluble resin to the plaster mix the surface finish strength and moisture resistance of the tile is improved. <IMAGE>

Description

SPECIFICATION Improvements reiating to ceiling tiles The invention relates to ceiling tiles and more particularly to plaster ceiling tiles having an improved surface appearance and point loading and improved resistance to fire, impact and moisture.

According to the invention there is provided a ceiling tile which is of sheet form over the majority of the area thereof with a peripherally extending rib on the rear face thereof, the tile comprising plaster (which may include other added glass fibres) which is enclosed by the plaster, which extends substantially over the whole area of the tile and into the peripheraly extending rib and which is in a state of tension applied thereto by the surrounding plaster, the tile also comprising two sets of at least two ribs transversely extending across the rear face thereof so as to divide said rear face into at least nine separate areas.

The tile may be rectangular or square and the respective sets of transversely extending ribs lie parallel with the opposed sides of the tile.

There may be at least four ribs in each set of transversely extending ribs.

The peripherally extending ribs may be formed with one or more lips, tongues or grooves to facilitate inter-fitting of such tiles to form a suspended ceiling.

The foregoing and further features of the invention may be more readily understood from the following description of some preferred embodiments thereof, by way of example, with reference to the accompanying drawings, in which: Figure I is a plan view of a ceiling tile according to one embodiment of the invention, Figure 2 is a sectional view along the line 11-11 of Figure 1 on the same scale, Figures 3, 4, 5 and 6 are sectional views on an enlarged scale showing alternative edge formations, Figure 7 is a plan view of a prior art tile showing a typical cracking pattern under fire test, and Figure 8 is a plan view of the tile of Figure 1 showing a typical cracking pattern under fire test.

Referring now firstly to Figures 1 and 2 there is shown a square ceiling tile which is generally of sheet form having a lower face 10, an upper face 11 and a peripherally upwardly extending rib 12.

The tile has a non-woven glass fibre reintorcing scrim 13 which may additionally include other glass fibres (Figure 2) extending throughout the tile and into the peripheral rib 12. The reinforcing scrim is in the form of a net or mesh. The tile is also formed with two sets of ribs 14 and 15 which are transversely and upwardly extending over the upperface 11.

The tile is fabricated by moulding with plaster, and the scrim which may include other added glass fibres is introduced such that as the plaster sets it expands and applies tension to the scrim 13. This has been found to give exceptional strength to the tile and allows the overall area of the tile to be of extremely reduced thickness, substantially reducing the weight of the tile.

Figure 3 shows a sectional view of the rib 12 which is merely square and is used to form a suspended ceiling by laying the tile on a suspended inverted T-section rail.

Figure 4 shows an alternative section of rib 10 which can be used to align with a conversely formed rib on an adjacent tile.

Figures 5 and 6 show further alternative sections of rib 10 which would be formed on opposed sides of the tile to engage with inverted T-section rails which would be hidden by lip 16 (Figure 5).

Referring now to Figure 7 there is shown a plan view of a ceiling tile without ribs 14 and 15 formed on the upper face 11. When subjected to a fire test such as a tile did not achieve more than one half hour structural rating under British Standard 476 part 8.

Failure is due to cracking whilst under test, cracks 17 occur as shown in Figure 7 and can open up to about 2 mm allowing direct heat onto the glass fibre reinforcing scrim. The glass reinforcement will melt at about 600"C and since the furnace temperature is around 1000"C the glass reinforcement melts when in direct contact with furnace heat and a segment of tile falls out bringing about failure of the test at that point.

Indicative tests have shown that a tile made according to Figure 8 with ribs 14 and 15 on the upper face of the tile will achieve up to a two hour structural fire rating under British Standard 476 part 8, which is a considerable improvement. This is due to a reduction in the width of the cracks which occur during testing and it will be seen by studying Figures 7 and 8 and that ribs 14 and 15 confine the cracks to the flat area within the ribs. Because the tile with the ribs 14 and 15 is divided into 25 separate areas by the ribs, the cracks are reduced in width by a factor of about 25.

The hairline cracks which result under test (shown in Figure 8) are not wide enough to allow direct contact between the glass fibre reinforcing scrim 13 and the furnace heat and thus the scrim 13 which may include other glass fibres is insulated by the plaster matrix and produces a greatly improved structural fire rating performance.

The ribs 14 and 15 do not have a critical width, height or distance between them or any particular pattern, but the more ribs that are introduced the smaller the flat areas between which in turn will reduce the width of the cracks that occur during a fire and allow the tile to last longer.

To improve impact and point load strength of the tile the glass fibre scrim may be additionally reinforced by any one of the following:- (a) loose glass fibre strands, (b) glass fibre chopped strand mat, (c) continuous glass fibre strand mat.

To improve plaster strength, surface appearance and moisture resistance of the tile the plaster/water mix may include any one of the following: (a) ordinary portland cement, (b) white cement, (c) water soluble resin.

1. A ceiling tile which is of sheet form over the majority of the area thereof with a peripheral rib

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements reiating to ceiling tiles The invention relates to ceiling tiles and more particularly to plaster ceiling tiles having an improved surface appearance and point loading and improved resistance to fire, impact and moisture. According to the invention there is provided a ceiling tile which is of sheet form over the majority of the area thereof with a peripherally extending rib on the rear face thereof, the tile comprising plaster (which may include other added glass fibres) which is enclosed by the plaster, which extends substantially over the whole area of the tile and into the peripheraly extending rib and which is in a state of tension applied thereto by the surrounding plaster, the tile also comprising two sets of at least two ribs transversely extending across the rear face thereof so as to divide said rear face into at least nine separate areas. The tile may be rectangular or square and the respective sets of transversely extending ribs lie parallel with the opposed sides of the tile. There may be at least four ribs in each set of transversely extending ribs. The peripherally extending ribs may be formed with one or more lips, tongues or grooves to facilitate inter-fitting of such tiles to form a suspended ceiling. The foregoing and further features of the invention may be more readily understood from the following description of some preferred embodiments thereof, by way of example, with reference to the accompanying drawings, in which: Figure I is a plan view of a ceiling tile according to one embodiment of the invention, Figure 2 is a sectional view along the line 11-11 of Figure 1 on the same scale, Figures 3, 4, 5 and 6 are sectional views on an enlarged scale showing alternative edge formations, Figure 7 is a plan view of a prior art tile showing a typical cracking pattern under fire test, and Figure 8 is a plan view of the tile of Figure 1 showing a typical cracking pattern under fire test. Referring now firstly to Figures 1 and 2 there is shown a square ceiling tile which is generally of sheet form having a lower face 10, an upper face 11 and a peripherally upwardly extending rib 12. The tile has a non-woven glass fibre reintorcing scrim 13 which may additionally include other glass fibres (Figure 2) extending throughout the tile and into the peripheral rib 12. The reinforcing scrim is in the form of a net or mesh. The tile is also formed with two sets of ribs 14 and 15 which are transversely and upwardly extending over the upperface 11. The tile is fabricated by moulding with plaster, and the scrim which may include other added glass fibres is introduced such that as the plaster sets it expands and applies tension to the scrim 13. This has been found to give exceptional strength to the tile and allows the overall area of the tile to be of extremely reduced thickness, substantially reducing the weight of the tile. Figure 3 shows a sectional view of the rib 12 which is merely square and is used to form a suspended ceiling by laying the tile on a suspended inverted T-section rail. Figure 4 shows an alternative section of rib 10 which can be used to align with a conversely formed rib on an adjacent tile. Figures 5 and 6 show further alternative sections of rib 10 which would be formed on opposed sides of the tile to engage with inverted T-section rails which would be hidden by lip 16 (Figure 5). Referring now to Figure 7 there is shown a plan view of a ceiling tile without ribs 14 and 15 formed on the upper face 11. When subjected to a fire test such as a tile did not achieve more than one half hour structural rating under British Standard 476 part 8. Failure is due to cracking whilst under test, cracks 17 occur as shown in Figure 7 and can open up to about 2 mm allowing direct heat onto the glass fibre reinforcing scrim. The glass reinforcement will melt at about 600"C and since the furnace temperature is around 1000"C the glass reinforcement melts when in direct contact with furnace heat and a segment of tile falls out bringing about failure of the test at that point. Indicative tests have shown that a tile made according to Figure 8 with ribs 14 and 15 on the upper face of the tile will achieve up to a two hour structural fire rating under British Standard 476 part 8, which is a considerable improvement. This is due to a reduction in the width of the cracks which occur during testing and it will be seen by studying Figures 7 and 8 and that ribs 14 and 15 confine the cracks to the flat area within the ribs. Because the tile with the ribs 14 and 15 is divided into 25 separate areas by the ribs, the cracks are reduced in width by a factor of about 25. The hairline cracks which result under test (shown in Figure 8) are not wide enough to allow direct contact between the glass fibre reinforcing scrim 13 and the furnace heat and thus the scrim 13 which may include other glass fibres is insulated by the plaster matrix and produces a greatly improved structural fire rating performance. The ribs 14 and 15 do not have a critical width, height or distance between them or any particular pattern, but the more ribs that are introduced the smaller the flat areas between which in turn will reduce the width of the cracks that occur during a fire and allow the tile to last longer. To improve impact and point load strength of the tile the glass fibre scrim may be additionally reinforced by any one of the following:- (a) loose glass fibre strands, (b) glass fibre chopped strand mat, (c) continuous glass fibre strand mat. To improve plaster strength, surface appearance and moisture resistance of the tile the plaster/water mix may include any one of the following: (a) ordinary portland cement, (b) white cement, (c) water soluble resin. CLAIMS

1. A ceiling tile which is of sheet form over the majority of the area thereof with a peripheral rib extending from the rear face thereof, the tile comprising a plaster matrix reinforced by a non-woven glass fibre scrim which is enclosed by the plaster matrix, which extends substantially over the whole area of the tile and into the peripheral rib, and which is in a state of tension applied thereto by the surrounding plaster matrix, the tile also comprising two sets of at least two ribs transversely extending across the rear face of the tile so as to divide said rear face into at least nine separate areas.

2. A ceiling tile as claimed in claim 1, wherein said tile is rectangular or square and the respective sets of transversely extending ribs lie parallel with the opposed sides of the tile and cross each other substantially at right angles.

3. A ceiling tile as claimed in claim 1, wherein said tile is rectangular or square and said transversely extending ribs are located diagonally thereof.

4. A ceiling tile as claimed in any preceding claim wherein there are at least four ribs in each set of transversely extending ribs.

5. A ceiling tile as claimed in any of the preceding claims, wherein the glass fibre scrim is in the form of a net or mesh.

6. A ceiling tile as claimed in claim 5, wherein additional glass fibres are added to the scrim.

7. A ceiling tile as claimed in claim 6, wherein the additional glass fibres may be in the form of loose fibre strands, glass fibre chopped strand net, or continuous glass fibre strand net.

8. A ceiling tile as claimed in any of the preceding claims wherein the plaster includes one or more additives comprising portland cement and/orwhite cement, andlor water soluble resin.

9. A ceiling tile substantially as hereinbefore described with reference to any one of the embodiments shown in Figures 1 to 6 of the accompanying drawings.