Stock material or miscellaneous articles – Hollow or container type article – Shrinkable or shrunk
Patent
1995-07-19
1997-12-23
Dye, Rena
Stock material or miscellaneous articles
Hollow or container type article
Shrinkable or shrunk
428 351, 428 369, 428913, 2853814, 285909, 264230, 174DIG8, B65B 5302, F16B 400, B29C 6102
Patent
active
057005281
DESCRIPTION:
BRIEF SUMMARY
This invention relates to dimensionally heat-recoverable polymeric articles, such articles made, for example, of cross-linked polyolefin plastics, being generally well known. Methods and materials for making such articles have been described, for example, in U.S. Pat. Nos. 3,086,242 and 3,597,372.
SUMMARY OF THE INVENTION
The present invention provides a special form of such article, which is particularly convenient to use in certain situations. The invention accordingly provides a resiliently flexible ring of dimensionally heat-recoverable polymeric material formed so that it inherently maintains a non-circular open configuration enabling it to grip resiliently an object around which it is placed in use prior to heat-recovery, the maximum transverse dimension of the said object being at least 2.5% less, preferably at least 5% less, than the notional circular diameter of the ring.
References herein to a "ring" will be understood to mean open-ended tubular articles whose length is less than their notional circular diameter (the length of their perimeter divided by pi). The invention is especially advantageous with rings whose length is less than half, or less than one quarter, or less than one eighth, of their notional circular diameter.
By providing such a ring in non-circular open configuration, the invention ingeniously enables the ring to grip a circular object, about which such rings may be fitted, prior to heat recovery to shrink the ring tightly onto the object. The open configuration enables the ring to be fitted onto the object without difficulty, unlike a flattened tubular configuration which would be difficult to hold open during fitting. However, the resilient grip provided by the non-circular configuration according to the present invention reduces the irritating problem of the ring falling off the object between the initial fitting and the heat-recovery operation. This problem is more severe with axially shorter rings especially those whose tubular or axial length is less than one eighth of their notional circular diameter, when applying them close to the end of objects such as shafts or hoses. One particularly relevant case is that in which the length of an object available to receive a short ring is little greater than, or equal to, the short tubular length of the ring.
The non-circular open configuration of the ring according to this invention could be simply eliptical having two equal "ends" of relatively small radius of curvature, or possibly pear-shaped having one smaller and one larger "end". However, it is preferred to provide the ring with at least three "corners" of relatively small radius of curvature (relative to the notional circular diameter), preferably evenly spaced around its circumference. The longer portions of the ring extending between these corners may be curved with a larger radius than the corners, or may be substantially straight, giving the ring a triangular, square, pentagonal, or hexagonal configuration, depending on the number of corners provided. It will be realised that the usefulness of the gripping effect will diminish as the number of corners increases beyond about six, and it is thought that fewer than ten, preferably fewer than eight, corners will be desirable in most cases. Three or four corners, most preferably three, will tend to give a more positive grip for locating the ring on a round object. The radius of curvature of the "corners" will preferably be less than 1/4, more preferably less than one eighth, and especially preferably less than one tenth or less than one twentieth, of the notional circular diameter of the ring. Sharp-pointed corners are not excluded, but are likely to be less convenient in practice. Rounded corners are preferred.
The rings according to the invention may be made by known techniques, for example by individual moulding, or by extrusion of a tube which is cut to length. The non-circular open configuration will preferably be imparted after the moulding or extrusion of a substantially circular shape, for example during the usua
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patent: 5224903 (1993-07-01), Langhof et al.
patent: 5340167 (1994-08-01), Morse
patent: 5360378 (1994-11-01), Susuki et al.
Burkard Herbert G.
Dye Rena
Novack Sheri M.
Raychem Limited
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