Patent Application
20100012350
This application claims the benefit of the filing date under 35 U.S.C. §119(a)-(d) of German Patent Application No. DE 10 2008 033157.0, filed Jul. 15, 2008.
The present invention relates to a support element for a resilient sheath, in particular to a holdout for a cable sleeve.
Cold-shrink sleeves or cover tubes are often used when connecting cables or repairing defective locations, or at junctions. They are made from a resilient material, for example a silicone rubber, which is positioned over the region to be covered, for example the connection region of two cables, in a pre-expanded state and then returned from the pre-expanded state to the original size thereof, which is selected in such a way that the cold-shrink sleeve can be sealed off for example from a cable jacket.
To hold a resilient sheath of this type in the pre-expanded state, it is known to mount the sheath in the expanded state on a substantially tubular support, which is known as a holdout. The support, for example, may consist of a helically wound strip, which is wound in such a way as to form a tube having a diameter greater than a diameter of the resilient sheath in the relaxed state. In this radially expanded state, the resilient sheath is positioned over the cable, which may be a power cable or a telecommunications cable, and the support is removed from the inside of the sheath by continuously pulling out the strip. It is, as a practical matter worthwhile, to form the wound holdout to be as thin as possible, because a lot of waste is produced during the removal. This minimizes increases in the cost of assembly, while also minimizing an increase in the expansion rate due to wall thickness.
Moreover, the internal diameter of the pre-expanded sheath should be as small as possible, in order to minimize the stretching forces exerted on the sheath. This means that the internal diameter of the support is selected in such a way that it just fits over the external diameter of the arrangement to be covered.
However, these known spiral holdouts present a problem, in that the internal diameter of the holdout deforms from the original circular cross-section to an oval cross-section after the resilient sheath has been mounted. This means that the internal cross-section, as in the case of an ellipse, now has a semi-major axis distance greater than the desired original radius, and a semi-minor axis distance smaller than the original radius plus the space required for pulling the strip through.
This means that the construction set can no longer be slid over the outer diameter of the round region to be covered. This described effect occurs directly after the pre-expanded sheath is mounted on the holdout, even at room temperature. It may thus be observed that an inner diameter of known holdouts may reduce from an original 84 mm to between 75 and 78 mm as a result of this type of flattening effect. Further, deformation increases over time. For many applications, a minimum value of 80 mm is required for example.
To avoid deformations in spiral holdouts of this type, it is known from U.S. Pat. No. 5,844,170 to provide a second spiral holdout which is arranged in the interior of the primary holdout in order to support it. This secondary holdout, as it is known, is only removed just before assembly.
The known solution has a disadvantage, in that the secondary holdout is also a spiral which must be removed by being pulled out and thus produces a comparatively large amount of waste. Secondly, a comparatively stable and therefore expensive spiral is used to provide sufficient support. Furthermore, the required disassembly of the secondary holdout spiral significantly increases assembly times if very long regions are to be supported. Therefore, in the known arrangement, a secondary spiral is also not provided over the entire region, but only in a tightly delimited region with an increased load.
Therefore, there is a need to provide a support element for a resilient sheath, in particular for application in cable sleeve construction sets, which is dimensionally stable and can be produced at low cost and keeps the assembly time as low as possible. There is furthermore a need for a solution which produces little waste, and is therefore environmentally friendly.
The invention has been made in view of the above problems, and provides a cable sleeve construction set in which a cable sleeve is held in the pre-expanded state by a support sleeve having an expansion element which is further supported by a reinforcing member.
The support element for a resilient sheath includes a tubular expansion element and a reinforcing member. The expansion element can be brought into contact with an inner wall of the resilient sheath and is formed in such a way as to hold the resilient sheath in a pre-assembled radially expanded state. The reinforcing member, which in the pre-assembled state of the resilient sheath, is at least partially received in the expansion element to reinforce and support the internal diameter of the expansion element, is constructed in such a way that it can be removed from the expansion element before the assembly of the resilient sheath without being destroyed.
The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like components will be provided with like reference numerals and like component names. Furthermore, some features or combinations of features from the various embodiments shown and described may be independent inventive solutions or solutions according to the invention. Therefore, respective elements of the embodiment may be exaggerated in the drawings.
The reinforcing member 102 can be produced from plastic material, being extruded at a particularly low cost and cut to an appropriate length.
The external diameter 110 is selected in such a way that the necessary minimum internal diameter of the expansion element 116 (
According to an embodiment of the present invention, the expansion element 116, which produces the actual expansion of the resilient sheath 202 (
The shape of the reinforcing member 102, shown in
According to the invention, the reinforcing member 102 is constructed in such a way that it can be removed from an expansion element 116 before the assembly of a cable sleeve, without being destroyed. This prevents the support element 100 from deforming, and it further ensures that the pre-expanded cable sleeve can quickly be brought into a state such that it can be assembled. The intact reinforcing member 102 can then be used again for a new application.
According to the invention, the contact surface along the outer circumference 108 is kept as small as possible, so that the reinforcing member 102 can be removed immediately before the actual assembly without being destroyed. Additionally, the surface configuration of this contact surface with the expansion element 116 is optimized accordingly. It has been found that a surface quality “as extruded” delivers better results if there is subsequent lubrication with grease, with the grease being the type used in conventional connection elements and rejacketing sleeves.
To minimize the amount of material used for the reinforcing member 102, an optimum value for the following parameters must be found in combination with the respective expansion element 116 to be supported: the number of reinforcing ribs 106: the wall thickness and the length of the reinforcing ribs 106, the internal diameter of the annular element 114, the effective contact surface between the reinforcing ribs 106 and the inner surface of the annular element 114, the surface structure in these assembly regions and the possibility of lubrication between the elements in the contact regions.
In order to facilitate easier grip for an operator, the reinforcing member 102 includes two apertures 112, which may lie opposite one another, in the vicinity of an edge region of the annular element 114. As is evident from viewing these figures in conjunction with
If a smaller external diameter 110 is required, the number of reinforcing ribs 106 can be reduced. Depending on the mechanical load exerted by the pre-stretched elements of a cable sleeve, the width of the reinforcing ribs 106 can also be reduced.
An example of a further embodiment of this type of reinforcing member 102 is shown in
This arrangement is well-suited to outer diameters 110 of approximately 30 mm, for example. It is important in any case for the contact surface, between the reinforcing ribs 106 and the inner wall of the expansion element 116, to be large enough in order to prevent penetration of the reinforcing ribs 106 through the expansion element 116, or unintentionally opening the seam regions. At very small external diameters 110 of the reinforcing member 102, the annular element 114 can even be minimized, as long as it is not possible that the reinforcing ribs 106 could buckle. In such a situation, the reinforcing ribs 106 have a rounding of for example R 0.5 mm at the corners. This makes it possible to prevent buckling by the reinforcing rib 106 by the expansion element 116. The ratio between the height and wall thickness of the reinforcing ribs 106 is to be set in such a way, taking into account the transition radius R3 in
Apertures 112, into which a suitable pull-strip 118 can be threaded in order to remove the reinforcing member 102 before assembly, are also provided in the embodiment shown here. According to the invention, two identical reinforcing members 102 may be introduced into a pre-expanded sheath from two sides, and be removed before assembly by being pulled in two mutually opposed directions. This reduces the frictional forces for each individual reinforcing member 102, because the effective length of the contact between the reinforcing member 102 and the expansion element 116 only accounts for half of the necessary total length in each case.
The diameter of the circumference 108 may be approximately the same size as, or in the alternative, smaller than a diameter of the expansion element 116. What is important is that the boundary values for the minimum internal diameter, as required for assembly, of the expansion element 116 are not exceeded and compromised. Specifically, if the diameter of the circumference 108 is too close to the internal diameter of the expansion element 116, it is possible that over time, the tensile forces which are required to remove the reinforcing member 102, before assembly, will become too high. For example, with an original expansion element 116 internal diameter of 83 mm, the diameter of the circumference 108 of the reinforcing member 102 may advantageously be approximately 80 mm.
The various shapes shown are respectively prepared in order to optimize different force ratios and lengths of sheaths to be expanded.
It is important on the one hand that the internal diameter of the expansion element 116 is maintained, but on the other hand that the tensile forces used when removing the reinforcing member 102 are low enough that an assembler can perform this task a number of times each day without difficulty.
To facilitate the removal of the reinforcing member 102, a removal mechanism may be arranged on the reinforcing member 102. This may, for example, be a pull-strip 118 which is guided through corresponding apertures 112 in the reinforcing member 102. A pull-strip 118 of this type provides a comparatively simple and low-cost type of removal mechanism.
To facilitate the removal of the reinforcing member 102, the reinforcing member 102 may be provided with a lubricant on the outer wall thereof so as to reduce the friction with the inner wall of the expansion element 116.
The arrangement shown in this case is dimensionally stable as a construction set 200 for at least three years even at elevated temperature.
The preparation for assembly will now be described with reference to
To reduce the frictional forces which come into effect when the reinforcing member 102 is removed from the expansion element 116, various modifications can be made to the reinforcing member 102 and will be explained in detail in the following with reference to
To reduce the friction between the outer surface of the reinforcing member 102 and the inner wall of the expansion element 116 before removing the reinforcing member 102, one or more reinforcing ribs 106 may, as is shown in
Before the removal of the reinforcing member 102, it is now possible for the reinforcing finger 109 to be removed either alone or together with the adapter 111 by pulling in the longitudinal direction, significantly reducing the friction as in the case of
In
A further possibility for reducing the forces required to pull out the reinforcing member 102 involves dividing up the reinforcing member 102 in the longitudinal direction. This is shown schematically by means of the cross-sectional schematic, shown in
The reinforcing member 102 is formed by three interconnected reinforcing member segments 115. The friction between the internal contact surfaces 117 at which these segments 115 are interconnected can be reduced by a lubricant. By pulling in the longitudinal direction, each segment 115 can be removed, one after another, and the forces to be applied remain low provided that the internal contact surfaces 117 between the segments have sufficiently low friction.
In the embodiment shown in
The internal contact surfaces 117, at which these segments 115 are interconnected, must not lie against one another fully in a positive connection over the entire contact surface, but may contact one another only at the lugs in order to reduce the frictional forces. The friction between them may also be reduced using a lubricant. Moreover, the segments 115 need not necessarily be identical. In particular, at least one element may include contact surfaces at an angle deviating from the radial direction, so as additionally to reduce the frictional forces and thus the tensile forces on this element. Non-identical segments 115 may also differ as regards the number and formation of the ribs for the purposes of reducing the tensile forces.
To prevent, what is known as cold welding, between the reinforcing member 102 and the expansion element 116, it is advantageous to produce these two components from different materials. The reinforcing member 102 may be produced using a low-cost thermoplastic material, such as acrylonitrile butadiene styrene (ABS). This extruded reinforcing member 102 may in addition be co-extruded with an outer layer of a low-friction material. One material of this type is polytetrafluoroethylene (PTFE, “Teflon”), for example.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2008 033157.0 | Jul 2008 | DE | national |
