Technical Field

The invention relates to a heat-shrinkable sleeve for making an enclosure of an elongated article like an electrical cable, a cable connection, or the like, the collar comprising a heat-shrinkable sheet dimensioned to overlappingly enwrap the article, the sheet having interlocking elements on two opposite marginal portions destin¬ ed for mutual overlapping, which elements are adapted to be brought into positive interengagement after the sheet has been wrapped around the article and which then form a closure that holds the sleeve to¬ gether against the forces which will arise in the shrinking.

Background Art

The prior art includes the heat-shrinkable sleeve of U.S. Patent No. 3,379,219 in which the interlocking elements consist of button-like protrusions and holes mating therewith. It has been found that a closure buttoned in this way will too easily become inadvertently disengaged upon shrinking under the influence of the high shrinking forces and as a consequence of the softening of the sheet material. Moreover, sheets having button-like protrusions cannot be manufactured by extruding as well as cutting and/or stamp¬ ing. That mode of manufacture, however, is highly desirable because of the much reduced cost, particularly for the extruding. Therefore, extruded sheets without button-like protrusions are employed in other known sleeves. The closure is then formed, for instance, by clamps clamped onto the edges of the sheet as in U.S. Patents Nos. 3,455,336 and 4,123,047 and German disclosure 2938 270. In these embodiments, it is necessary to have clamps of suitable size available at the site of application. The manufacture of the sleeves requires a con- siderable expense of labor at the site of operation; moreover the result obtained is highly dependent upon the care and skill of the manufacturing personnel.

The heat-shrinkable sleeve of U.S. Patent No. 3,574,313 is formed by inwardly folded, mutually overlaid marginal portions, with the one marginal portion having pre-shrunk tabs which are in¬ serted into slots of the other marginal portion. Such a closure

is difficult to close and has little strength; in particular, the tabs can be easily drawn out of the slots in the circumferential direction under the action of the high shrinking forces.

In the heat-shrinkable sleeve of U.S. Patent No. 3,530,898 the marginal portions have mutual y staggered rows of round holes, and when laying the sheet around, the marginal portions are folded back inwardly along folding lines extending through the rows of holes so that the areas left between the holes, which form flat bends, interfit and can be interconnected by a bar inserted through them. The manufacture of such a closure is time consuming and requires great care, particularly in the case of relatively long sleeves. As with other embodiments in which additional metallic elements are employed, corrosion problems may arise.

In German disclosure 2938270 the overlapping marginal portions are provided with pressure sensitive adhesive tape and adher¬ ed to each other by pressing together. In this case, the subsequent shrinking must not include the marginal portions. With such a foil section of material which shrinks only partly, it is difficult to obtain a smooth closure seam. Also, the manufacture of such partly shrinkable sheets is relatively expensive.

Disclosure of Invention

The present invention provides a heat-shrinkable sleeve formed from an extruded sheet in which the interlocking elements comprise, in the one marginal portion, a row of tabs cut from the edge, each tab having a base portion and a lock portion extending therefrom, the lock portion having a greater length in the direction of the edge than the base portion, and in the other marginal portion, a row of longitudinal slots associated one with each of the tabs in the first row and being dimensioned and arranged for the passage therethrough of the base portions of the tabs, and in that the longi¬ tudinal slot is accessible.via a transverse slot extending from the edge.

Brief Description of Drawings In the drawing-: Figure 1 is a perspective partial view of a heat-shrinkable sleeve according to the invention prior to the closing and shrinking thereof;

Figure 2 is a partial view of the sleeve shown in Figure 1 after.the closing thereof;

Figure 3 is a view similar to that of Figure 1 , of a second embodiment; Figure 4 is an extruded heat-shrinkable sheet for a third embodiment of a sleeve according to the invention;

Figure 5 is a perspective view of a sleeve made from the sheet of Figure 4;

Figure 6 is a perspective view of an enclosure made from the sleeve of Figure 5 by heat-shrinking;

Figure 7 is a perspective view of a fourth embodiment of a heat-shrinkable sheet for a sleeve according to the invention;

Figure 8 is a cross-sectional view, along line VI11-VI11 of Figure 7 of a sleeve made from the sheet of Figure 7, wherein a reinforcing strip has been added;

Figure 9 is a transverse cross-sectional view of a fifth embodiment, similar to that of Figure 7, but having reinforced margi¬ nal areas;

Figure 10 is a partial cross-sectional view like that of Figure 8, of a sleeve made from the sheet of Figure 9;

Figure 11 is a cross-sectional view of a sixth embodiment which is basically similar to that of Figure 7 but has reinforced marginal areas of a cross-section different from that shown in Figure 9; Figure 12 is a partial cross-sectional view of a sleeve made with the sheet of Figure 11;

Figure 13 is a cross-sectional view of a seventh embodiment of a heat-shrinkable sheet which is similar to that of Figure 11; and Figure 14 is a partial cross-sectional view of a sleeve made from the sheet of Figure 13.

Best Mode For Carrying Out the Invention

Figure 1 illustrates a heat-shrinkable sleeve 1 for making an enclosure of an elongated article 3, such as an electrical cable, comprising a heat-shrinkable sheet 5 dimensioned to overlappingly enclose the article 3, the sheet having interlocking elements on

two opposite marginal portions 7 and 9 destined for mutual overlap¬ ping. The interlocking elements on one marginal portion 7 consist of a row of tabs 11 cut from the edge, each having a base portion 13 and a lock portion 15 extending therefrom. The lock portion 15 has, in the direction 17 of the edge, a greater length than the base portion 13. On the other marginal portion 9, the interlocking ele¬ ments consist of a row of longitudinal slots 19, one slot correspond¬ ing to each tab in the first row. Each of the longitudinal slots 19 is accessible through a transverse slot 21 extending from the edge. The longitudinal slots 19 are dimensioned and arranged so as to be transversed by the base portions 13 of the opposed related interlocking tabs 11. The longitudinal slots 19 each have a width b measured transversely of the edge, which is smaller than the width B of the lock portion 15 as measured transversely of the edge. The width b of the longitudinal slot is the same as, or slightly greater than, the sheet thickness of the base portion 13.

Figure 2 illustrates the sleeve of Figure 1 in the closed condition. As can be seen, in order to close the sleeve, the row of tabs 15 has to be inserted, one after the other, each through the associated transverse slot 21 and longitudinal slot 19 by flexing the sheet material. As can be seen from Figure 1 the marginal areas of the marginal portion 9 between adjacent slots 19 form tabs 23 which have the same function as the tabs 15.

Figure 3 illustrates a second embodiment of a sleeve 301 in which tabs 315, 323 are provided on both margianl portions 307 and 309. In this case, a particularly complete overlapping is achiev¬ ed in that on both edges a row of tabs 315, 323, a row of longitudinal slots 319 and 325, respectively, and a row of transverse slots 321 and 327, respectively, is formed due to the fact that the marginal areas left between the longitudinal and transverse slots from tabs 315 and 323, respectively.

Figures 4 through 6 illustrate a third embodiment of a sleeve 401 according to the invention, in which again both marginal portions 407 and 409 are the same and each comprises a row of tabs and longitudinal and transverse slots 419, 425. The longitudinal slots 419, 425 have rounded contours; thereby, the assembly is facili¬ tated, and the sleeve adapts itself better to local differences in thickness of the article to be enclosed. In the embodiment illustrat-

ed, the longitudinal slots are provided in the form of circular open¬ ings. In this embodiment, the sheet is reinforced along each edge by each a unitary marginal ledge 429 and 431, respectively. As is shown particularly in Figure 6, the bar-like sections of the marginal ledges left between the transverse slots 421 and 427, respectively, will overlappingly and inter!ockingly back against each other upon the heat-shrinking and thus form a closure which can securely with¬ stand even high shrinking forces in the circumferential direction of the sleeve despite the softening of the sheet material occurring during the heat-shrinking. In Figure 6, a three-core cable 403 is indicated as an example of an enclosed article.

Figures 7 and 8 illustrate a fourth embodiment in which the sleeve is formed from a sheet 705 of uniform thickness. When the closure has been formed, a reinforcement is formed in the area of the tabs and longitudinal slots by a reinforcing strip 733 attached to the sheet (see Figure 8). The reinforcing strip 733, which must be heat-resistant and for instance may have a fiber glass reinforce¬ ment, may be adhesively attached on the closure area 735, for instance by means of a ther osetting plastic adhesive. Figures 9 and 10 illustrate a fifth embodiment wherein the sheet 905 is similar to the sheet 705 of Figure 7, but differs in that it is reinforced by thickenings 939 and 941 in the area of the tabs and longitudinal slots. The thickening is appropriately dimensioned so that it about compensates for the reduction in strength caused by the slots in the marginal portion of the sheet 905.

Figures 11 and 12 illustrate a sixth embodiment of a sheet 1105 which again is similar to that of Figure 7, and like that of Figures 9 and 10 is reinforced in its marginal portions by thickenings 1139 and 1141. These, however, are formed so that an essentially round, bead-like seam will result in the connection area 1135 upon the closing of the sleeve (see Figure 12).

Figure 13 and 14 illustrate an embodiment like that of Figures 11 and 12 except that the sheet 1305 has been extruded to include a unitary sealing lip 1343 which underlies the one marginal portion 1341. When making the tabs and longitudinal and transverse slots, that sealing lip 1343 is left unchanged so that a continuously satisfactory sealing will result in the connecting area 1335 in the closed condition of the sleeve 1301 (see Figure 14) due to the fact that the whole closure is underlaid by the sealing lip 1343.

In the manufacture of a heat-shrinkable sleeve according to the invention, a heat-shrinkable sheet material is extruded, heated for purposes of cross-linking, stretched and cooled in the stretched condition, _, the sheet being cut out and being provided with the inter- locking elements in the form of the tabs and the longitudinal and transverse slots by means of cutting and/or stamping. In doing so, it is preferred to perform the cutting only after the heating, stretch¬ ing, and cooling because the stretching of a larger section of the sheet material can be performed more eas ly and more uniformly than with a smaller sheet. In doing so, it is furthermore preferred that the cutting and/or stamping of the longitudinal and transverse slots be done after the heating, stretching, and cooling. Thereby, the stretching can be performed without being disturbed by already present slots. The same is also true for the tabs. Furthermore, it is ad- vantageous if the cross-linking heating and the stretching are perform¬ ed directly after the extrusion because then, the heat which is still contained in the sheet material due to the extrusion can be utilized for the cross-linking heating, and the temperature rise due to the heating can be utilized for the subsequent stretching. For sleeves according to the invention, extrudable sheet materials of different kind are suited. Normally, cross-linked poly¬ ethylene is particularly well suited, which can be stretched and shrunk by about 300 to 400%. Materials of that kind have good emer¬ gency proeprties, i.e. they can withstand overheating up to 250° for short periods of time without becoming damaged or permanently deformed. Moreover, materials of that kind are available at a rela¬ tively low price.