BACKGROUND OF THE INVENTION Vessels are often filled with substances, which soil insides of the vessels, with the result that the vessels need to be cleaned. For example, paint trays are typically partly filled with paint, from where the paint is applied by using paintbrushes or rollers. When painting is temporarily ceased, such as at the end of a workday, paint remaining in the paint tray is often discarded, and the paint tray has to be cleaned. This prevents paint from drying inside the paint tray, from where it will be difficult to remove the paint, and from where it can hamper further use of the paint tray, e. g. by becoming dissolved or dislodged when the paint tray is subsequently filled with paint.

Cleaning of vessels such as paint trays requires time and effort, and usually involves the use of solvents, such as water, organic solvents, detergents, or the like. Once paint has been dissolved in these detergents, the solution typically goes to waste, often at risk of polluting the environment.

SUMMARY OF THE INVENTION According to a first aspect of the invention, there is provided a liner for a vessel, said liner comprising: a sheet of flexible material, having an outline which defines at least one corner ; and shrink means, which extends near the periphery of the sheet, the shrink means being under tension when the sheet is generally flat, and the shrink means exerting a contracting load on the sheet along at least one shrink zone.

The term"flat"refers to an extended, smooth condition of the sheet, irrespective of its orientation. The phrase"spanning a corner"refers to a location extending between the vicinities of two sides, disposed on either side of the corner. The term"corner"includes a corner that is rounded.

The shrink means may be attached to the sheet, or may be integrally formed with the sheet.

The sheet may be of a substantially liquid-impermeable material such as a plastics material, e. g. polyethylene.

The sheet may have a rectangular outline, and may include four shrink zones, each spanning a corner of the sheet.

The shrink means may include at least one resilient elongate element, attached to the sheet. Each resilient elongate element may be an elastic element, such as a length of elastomeric material, e. g. rubber, and <BR> <BR> may be attached to the sheet by stitching, gluing, welding, etc. , or the resilient elongate element may be a resilient thread, stitched to the sheet.

Each shrink zone may extend along a curve spanning at least one corner of the sheet, with ends proximate two edges of the sheet, the two edges being disposed on either side of the corner.

According to another aspect of the invention, there is provided a method of lining a vessel, said method comprising: placing a liner over a polygonal opening of the vessel, the liner comprising a sheet of flexible material and shrink means exerting a contracting load on the sheet near its periphery, in the region of at least one of its corners; and engaging an outer periphery of the vessel with the shrink means, to hold the liner in position.

The periphery of the vessel may be engaged by hooking the shrink means over a ridge, extending outwardly from a periphery of the opening.

The sheet may take the shape of an inside of the vessel, to act as a liner. The sheet may be urged under gravity into abutment with the inside of the vessel, by a substance placed on the sheet, within the vessel.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: Figure 1 shows a top plan view of a liner for a vessel in accordance with a first embodiment of the invention; Figure 2 shows a three-dimensional view of the liner of Figure 1, lining a vessel ; and Figure 3 shows a top plan view of a liner for a vessel in accordance with a second embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to the drawings, a liner in accordance with the invention is generally indicated by reference numeral 10.

Referring to Figure 1 of the drawings, according to a first embodiment of the invention, the liner 10 includes a thin rectangular sheet 12 of polyethylene, defining four curved shrink zones 14, each extending near the periphery of the sheet, and each spanning a corner 16 of the sheet.

Shrink means in the form of an elongate resilient element in the form of an elastic rubber band 18 is stitched or glued to the sheet 12 in each shrink zone. Each rubber band 18 extends along a curve and is under tension, when the sheet is generally in a flat condition such as that shown in Figure 1 of the drawings. The tension in each rubber band 18 causes it to exert a contracting load on the sheet 12 in its associated shrink zone 14.

Referring to Figure 2 of the drawings, in use, a vessel such as a paint tray 20, which is to be lined by the liner 10 according to the first embodiment of the invention, is covered by placing the liner over a rectangular opening 22 of the paint tray, and engaging an outer periphery of the paint tray by hooking the shrink zones 14 of the liner over corners 24 of the paint tray. Paint 28 is poured on top of the liner 10 and urges the liner under gravitational load of the paint, to abut an inside of the paint tray 20.

A ridge 26 extends outwardly from a periphery of the opening 22, and allows the shrink zones 14 to engage the periphery of the paint tray 20 more securely by being hooked over the ridge, each rubber band 18 placing the sheet 12 under tension in a region below the ridge 26.

When the paint tray 20 is required to be emptied and cleaned, excess paint 28 may be poured off, and the liner 10 which is soiled with paint is removed from the paint tray 20 by unhooking the shrink zones 14 from the corners 24, and is discarded.

Referring to Figure 3 of the drawings, a liner 10 in accordance with a second embodiment of the invention, includes a rectangular sheet 12 which has four rounded corners 16, and which defines a single shrink zone 14 extending generally around a periphery of the sheet, in a spaced arrangement. An elastic rubber band 18 is stitched or glued to the sheet 12, in similar fashion, to the rubber band shown in Figures 1 and 2 of the drawings, and is under tension when the sheet is in a flat condition, such as that shown in Figure 3 of the drawings. The tension in the rubber band 18 causes it to exert a contracting load on the sheet 12 in the shrink zone 14.

The liner 10 shown in Figure 3 of the drawings, is used generally in the same way as the liner shown in Figures 1 and 2 of the drawings, by placing the liner over the opening 22 of a paint tray 20, and engaging the outer periphery of the paint tray by hooking the shrink zone 14 over the corners 24.

In an alternative embodiment (not shown), the shrink means comprises an elasticised thread stitched to the sheet 12 along each shrink zone.

The invention illustrated holds the advantage of avoiding the cleaning of vessels such as paint trays 20. It holds another advantage of being capable of lining a contaminated vessel, to prevent contamination of contents of the vessel placed within the liner, e. g. the liner 10 may be placed inside a dirty paint tray 20, and paint 28 may be poured on top of the liner 10 and used, without fouling of the paint on top of the liner, by the dirty paint tray. The invention illustrated holds the further advantage that the liner 10 can be used as a cover for a vessel such as a paint tray 20, to isolate contents of the vessel from the atmosphere. The invention illustrated also holds the advantages of quick and easy application of the liner 10 to a paint tray 20, low cost of the liner 10, and avoiding waste and environmental disadvantages of discarding detergents and/or solvents.