Heat-shrinkable article

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The foregoing and other objects of the invention will become apparent upon referring to the following detailed description and the accompanying drawings, in which: FIG.
1 is a transverse section of a tubular article formed from a heat-shrinkable sheet embodying the invention prior to closure; FIG.
2 is a transverse section of the tubular article of FIG.
1 after closure and after recovery; and FIG.
3 is a detail of a transverse section similar to that of FIG.
1 showing a preferred embodiment of the invention.
Referring to the drawings, and first to FIG.
1 thereof, a sheet 1 of appropriate material, such as polyethylene, is extruded, cross-linked and expanded by conventional techniques.
The extruder is so constructed as to give a profile to the sheet, so that the extruded sheet 1 has edges 2, 3 which are half the thickness of the body 4 of the sheet.
The extruded sheet 1 is then expanded preferentially; that is, the body 4 is expanded and made heat unstable while the edges 2, 3 remain unexpanded and are therefore heat stable.
Such expansion lengthens the body 4 of the sheet 1 and in so doing, reduces its thickness, so that the thickness of the heat-unstable body 4 of the sheet 1 becomes about the same as that of the heat-stable edges 2, 3.
Pressure sensitive adhesive tapes 5, 6 with release papers 7, 8 are located on the heat-stable edges 2, 3.
Referring now to FIG.
2, therein is shown the heat-unstable wrap-around sleeve of FIG.
1 after recovery.
During recovery the length of the body 4 of the sheet 1 shortens and, in so doing, increases its thickness, so that the thickness of the heat-stable edges 2, 3 is now about one-half the thickness of the recovered body 4.
Consequently, the recovered sleeve has essentially uniform thickness, and a raised edge which might catch or lift during use is avoided.
FIG.
3 shows an embodiment of the invention in which the substrate is so designed that an aligning and holding device is built into it.
To that end, a raised ridge 9 is produced on the end of heat-stable edge 3'