Longitudinally divided sleeve of shrinkable material

A longitudinally divided sleeve of shrinkable material has a lock closure along longitudinal edges. One of the longitudinal edges includes a closure element having a locking groove formed by two longitudinally extending leg portions, a second longitudinal edge being provided with a locking element having a longitudinally extending hook part having a resilient projection which is received in the locking groove to form the lock closure. The resilient projection prevents the accidental removal of the hook part from the locking groove and preferably the material forming the two elements has a higher cross-linking than the remaining portions of the heat-shrinkable sleeve.

BACKGROUND OF THE INVENTION 
The present invention is directed to a longitudinally divided sleeve of 
shrinkable material comprising a closure element along each of the 
longitudinal edges to form a lock closure. The lock closure comprises one 
of the elements having a longitudinal locking groove along one 
longitudinal edge of the divided sleeve and a second closure element being 
a lock element which mates with the longitudinal locking groove and is 
provided along the other longitudinal edge. 
A method for covering connections of electrical cables and pipes wherein a 
cladding, which is shrinkable under an influence of heat, is applied over 
the location of the connection, is then closed by engaging lock elements 
along the edges and is finally shrunken down onto the enclosed article is 
disclosed by German OS No. 1,947,057. The closure elements are composed of 
a longitudinal groove along one longitudinal edge and of a lock element 
mating with the groove along the second longitudinal edge. Both elements 
are arranged so that a bead will project outwardly from the cladding. 
Particularly given high shrinking forces, this has the disadvantage that 
the closing region is pulled apart so that a longitudinal gap, which will 
cause a loss of tightness, can occur. The risk also exists that given high 
shrinking forces, the closure can become undone again since the lock 
element is engaged in the groove in the same direction as the forces 
created by the shrinking which are in a circumferential direction. 
Moreover, the insertion of the lock element in the groove requires greater 
closing forces if it is to be guaranteed that the closure is also suitable 
given greater stressing particularly during the shrinking operation. 
SUMMARY OF THE INVENTION 
An object of the present invention is to create a closure for a 
longitudinally divided sleeve which is suitable for high-closing forces 
and which can nonetheless be closed in a simple and easy way so that the 
distribution of forces in the closing region is to be designed such that 
it is torque-free as possible and thus sure to remain closed under the 
influence of the forces created during a shrinking operation. 
This object is achieved with an improvement in a longitudinally divided 
sleeve of heat-shrinkable material having a lock closure along its 
longitudinal edges, which lock closure comprises a longitudinal locking 
groove along one longitudinal edge and a lock element mating with the 
longitudinal groove being provided along the second longitudinal edge. The 
improvements are that the closing region formed by the lock closure has a 
higher degree of cross-linking than the rest of the shrinkable sleeve, 
that the longitudinal locking groove of the one closure element is formed 
by two longitudinally extending leg portions which are inclined one toward 
the other to form a groove having a base or root wider than the mouth of 
the groove, the lock element along the other side is shaped in the form of 
a hook shape having an angle of the hook part which is engaged in the 
longitudinal locking groove matching the angle of inclination of one of 
the undercut legs forming the groove, the lock element also includes a 
resilient projection which with the hook is matched to the width of the 
root or base of the groove and the longitudinal gap of the locking groove 
is selected such that the lock element of the hook and projection can be 
forced or squeezed into the longitudinal groove in a locking fashion. 
Advantages given the sleeve of the invention particularly occur wherein the 
latching mechanism can be actuated in a reliable and simple way so that 
unintentional opening cannot occur. Due to dimensioning of the closure 
elements, an optimal torque-free closing region is created and this will 
guarantee a reliable closure even during the critical heat-shrinking 
operation. In selecting the cross-linking ratio between the shrinking part 
of the sleeve and the non-shrinking closure region, it is also achieved 
that the susceptibility to tearing is reduced particularly given large 
diameters. This ratio is selected so that the closure region stretches 
within a certain limit given excessive shrinking forces. As a consequence 
of this stretching, the shrinking force will decrease and the walls of the 
shrinking part of the sleeve is protected against tears. It is noted that 
this wall is very thin per se particularly given large diameters. The 
influencing variables coming into consideration therefore are the 
thickness of the closure region, the thickness of the hook part, the 
degree of cross-linking of these elements and the temperature prevailing 
during the heat-shrinking operation. Within certain limits, the shrinkage 
factor can also be influenced by these quantities since the closure region 
is to be viewed as being an expansion member. It is thereby also innocuous 
that the locking mechanism becomes ineffective as a result of the 
stretching since at the moment in which the expansion begins in the 
closure region, the part to be enveloped is already firmly surrounded by 
the sleeve and is already adequately secured by the hook-like part of the 
closure elements so that unintentional opening is not possible. 
Favorable expansion factors can be obtained for the closure region when the 
wall thicknesses of the legs of the longitudinal groove are selected in 
the range of 1 through 1.8 mm and those of the hook part are selected in a 
range of 2 to 3 mm. It is therefore expedient to select overall 
cross-linking in the closure region to be two through six times greater 
than in the stretchable region which is the remaining portion of the 
sleeve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The principles of the present invention are particularly useful in a 
longitudinally divided sleeve of a heat-shrinkable material generally 
indicated at 1 in FIG. 1. The sleeve 1 has a widened sleeve region 2 which 
along one edge has a closure or element 3 which has a longitudinally 
extending hook element 4. Along the opposite edge of the sleeve region 2 
is a second closure or lock element 20 which has a pair of longitudinally 
extending leg portions 8 and 9 which create a locking groove 10 for 
receiving the hook element 4. The legs 8 of the element 20 and the element 
3 each have outwardly extending projections 7 which can be engaged by a 
tool utilized for closing the closure device. 
The element 20 on a free edge is provided with an inside flap 12, which 
extends underneath the lock element 3 and improves the sealing condition 
along the longitudinal gap. The inside surface of the sleeve 1 is provided 
with a coating of a hot-melt adhesive 13 in both the wide sleeve region 2 
and in the closure region to form a reliable seal relative to the 
enveloped article as a result of the heat-meltable adhesive. It should be 
pointed out that the plastic material employed for the closure region is 
subjected to a higher cross-linking than the material of the shrinkable 
sleeve region 2 which is ultimately shrunk onto the articles to be 
enveloped or enclosed within the sleeve 1. The material for both the 
sleeve region 2 and the closure region is a thermoplastic material, for 
example, polyethylene. This material can be cross-linked by various 
conventional treatments such as by irradiation with various energy of 
electrons from an electron beam. Also, chemical methods for cross-linking 
can be used. 
The closure region is best illustrated in FIG. 2. As illustrated, the 
groove 10 has a keyway shape due to the sloping of the legs 8 and 9 toward 
each other. Thus, the base or root of the groove 10 is wider than the 
mouth. As mentioned, the legs 8 and 9 slope toward each other with a 
suitable angle so that undercuts will occur. The lock element 3, which has 
a bent back but likewise longitudinally proceeding hook part 4, extends at 
an angle substantially the same as the angle of the surface of the leg 9. 
The hook part 4, in addition, has a resiliently protruding lip-like 
projection 5, which has a dimension so that it will fill out the width of 
the base or root of the groove 10 when the hook part 4 is inserted into 
the groove 10 to form the closure. The projection or lip 5 thus acts to 
prevent accidental disengagement of the hook part 4 from the groove. 
At its end directed adjacent the shrinkable sleeve region 2, the lock 
element 3 is provided with a supporting element 6 with which the lock 
element 3 is supported against an inside flap 12 of the other element 20 
after closing. As a result thereof, the force condition in the closed 
region can be compensated so that the torsions hardly will occur. It is 
the aim of the invention that the degree of offset "a" between a middle 
force transfer point 11 on the surface of the hook part 4 and the middle 
of the wall plane of the region 2 adjacent the supporting element 6 is as 
low as possible and preferably equal to zero. This would be the ideal case 
and corresponds to a uniaxial state of stress where no additional torque 
will deteriorate the sealing or respectively closing conditions acting on 
the closure region proceeding from the point at which the force is 
applied. As illustrated, the inner surface of the element 20 including the 
flap 12 is provided with the coating 13 of the adhesive and also a portion 
of the lock element 3 is provided with a coating in at least the area of 
the portion 6. 
The longitudinal leg 8 has a greater height than the leg 9 so that the 
outer surface is substantially in the same plane as the outer surface of 
the lock element 3. The leg 9 adjacent its outer surface is provided with 
the longitudinal projection 7 which protrudes laterally and opposite to 
the projection 7 of the element 3 as illustrated in FIG. 2. These 
projections 7 respectively form longitudinally extending outside grooves 
18 which serve for the guidance of a simple closing tool which has a shape 
to press the elements 3 and 20 together and press the hook part 4 into the 
longitudinal groove 10. The closing tool is a simple auxiliary item and 
facilitates the closing operation particularly given larger and thus 
stiffer closure elements and long sleeves. 
A closure tool is generally indicated at 14 in FIG. 3 and essentially 
consists of a pair of wedge-shaped pressure elements 16 combined in a U 
shape which is introduced into the above-mentioned outside grooves 18. By 
drawing the closing tool 14 in a direction indicated by the arrow 17 along 
the outside grooves 18 of the closure region, which grooves serve as a 
guide, the lock element 3 is pressed into the longitudinal groove 10 as a 
consequence of indentation or depression 19 in the middle region of the 
tool 14. The spacing of the U-shaped lateral legs 15 corresponds to the 
spacing of the two outside lateral projections 7 of the closure when in a 
closed condition. 
Although various minor modifications may be suggested by those versed in 
the art, it should be understood that we wish to embody within the scope 
of the patent granted hereon, all such modifications as reasonably and 
properly come within the scope of our contribution to the art.