Electricity: conductors and insulators – Conduits – cables or conductors – Accessories
Patent
1994-09-14
1996-12-31
Sough, Hyung S.
Electricity: conductors and insulators
Conduits, cables or conductors
Accessories
174DIG8, H01B 700
Patent
active
055896677
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pre-stretched elastomeric tubing (hereinafter PST) mounted on a plastic core which can be removed to allow the PST to contract into contact with an object to be covered by the tube.
BACKGROUND OF THE INVENTION
One method of insulating and environmentally protecting a connector for a power cable or other cable is by use of a contractible insulating tube expanded to fit over the outer surface of a hollow cylindrical core. The tube and core are slid over one cable end and the cables connected by means of the connector. The tube and core are then repositioned over the connector area and the hollow cylindrical core is pulled out so that the expanded insulating tube may contract into contact with the connector and cables.
U.S. Pat. No.3,515,798, assigned to the assignee of the present invention and incorporated by reference herein, describes a one-piece, rigid, plastic core having interconnected adjacent coils in a closed helix configuration. One end of the core is partially unwound and led back through the core so that pulling on this end will cause the core to unwind and allow the tube to contract. Because the core is helically wound, the core length as it is extracted through the space between the core and the object over which the core has been positioned must be rotated around the object as the core end is pulled. This is cumbersome and does not permit the use of automation to remove the core as the machine cannot release the core on one side of the object and regrasp it on the other side of the object.
Japanese Utility Model Unexamined publication No. 3-28387 describes a straight pull-out core which overcomes the aforesaid drawback. The core, however, poses problems in that the core ribbon to be broken when pulled out straight is secured with multiple thin ribs. Therefore, when a tightening force is increased due to contraction of a rubber elastic body mounted on the core or an ambient temperature rises, the material strength is lowered, and thus the shallow ribs may break and crush the core. When the ribs are made thicker to increase the strength, the core ribbon becomes harder to pull out, and this deteriorates the workability.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a PST core that is difficult to crush and which may be removed without the necessity of rotating the core end around the object over which the core and the tube were positioned.
In an effort to achieve the above object, the present invention provides a core having hairpin return sections for reversing the direction of separation of the core strip as it is withdrawn. Thus, the core strip unwinds from the core in one direction for a portion of the circumference of the core and then reverses direction to unwind from the core in the opposite direction for an equal portion of the circumference of the core. This arrangement thereby permits the entire core to be withdrawn from the tube without releasing the core strip once pulling has begun or rotating the core strip around the object to be covered by the tube.
More particularly, the present invention provides a removable core for supporting a pre-stretched elastomeric tube in a radially-expanded condition which includes a flexible sheet having opposite edges which include means for interlocking the opposite edges to maintain the sheet in a cylinder; the sheet having a series of substantially parallel lines of localized weakening extending from one of the opposite edges to a point near but short of the other of the opposite edges, with successive lines extending from alternate edges of the sheet to define a strip beginning at a free end and continuing in a serpentine length between and around consecutive lines so that pulling the free end will cause the strip to separate along the lines and permit the core to be removed from the tube without coiling of the strip.
One removable core according to the present invention includes a Joint formed by matching multiple projections which alternately
REFERENCES:
patent: 3515798 (1970-06-01), Sievert
patent: 4735836 (1988-04-01), Giebel et al.
Nakamura Tsunehisa
Tsukazaki Tomio
Griswold Gary L.
Kirn Walter N.
Minnesota Mining and Manufacturing Company
Musgrove Jack V.
Sough Hyung S.
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