Electricity: conductors and insulators – Overhead – Towers – poles or posts
Reexamination Certificate
1999-07-14
2001-09-11
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Overhead
Towers, poles or posts
C174S066000, C220S241000
Reexamination Certificate
active
06288331
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a cable duct made up of plastic troughs, which can be lined up in a row next to one another, and to an elevated cable duct, and to covers therefor.
2. Discussion of the Prior Art
Plastic cable ducts with approximately U-shaped troughs which are provided with a cover are known from WO 94/21018. These troughs, which can be endlessly lined up in a row next to one another and are provided with connectors, are injection molded, predominantly from recycled plastic, such as polyester, polyurethane or polyethylene, in lengths measuring approximately 1 m. These troughs are equipped with special ribs and protrusions which allow such ducts to be buried in the ground, in particular along railroad routes. It is possible to walk on the cover.
A brochure published by Krupp, DE, and entitled “Der Kunststoffkabelkanal DRAE-KA” discloses the practice of elevating such cable ducts in marshland. The brochure sets forth a wood pile with boards which extend thereon from pile to pile and serve as a supporting structure for the cable duct. Of course, exposure to weathering means that such a supporting structure has only a very short service life.
German references DE 39 36 003 C2 and DE 34 47 836 A1 disclose elevated cable ducts in the case of which trough-like sheet-metal cable-duct elements are screwed to metal supports and transverse securing means provided thereon. Both the supports and the transverse load-bearing members as well as the troughs, which are all screwed to one another, are connected at short spacings to the parallel rail track by corresponding grounding cables. This measure is necessary both because it is possible for the cables in the trough to become defective, and thus for the entire cable duct to become conductive, and because, in the case of a contact wire of an electric railroad rupturing, the formation of parasitic voltages is possible, and this has to be prevented. Nevertheless, in the meantime, the railroad companies no longer allow such sheet-metal ducts on electrified stretches of track. Operators who happen to be present could be put in danger by current surges and corresponding conduction of the ducts; moreover, problems may arise as far as signalling is concerned, in particular for the presence-of-trains indicating system.
Although cable ducts which are known from WO 94/21018 have been used successfully when buried in the ground, their application area is limited, e.g. in tunnels or where water build-up is to be expected and in cases of flush out and stretches where embankment slippage is to be expected.
SUMMARY OF THE INVENTION
The problem on which the invention is based is thus to provide improved plastic troughs which can be elevated, and covers which are suitable therefor. It is a further object to provide, for corresponding cable ducts, a means of elevation which takes into consideration of the previously mentioned boundary conditions for such ducts and can be installed both on ground supports and on wall supports.
The invention takes as its departure point, in principle, the cable ducts set forth in WO 94/21018 and, for this purpose, uses, inter aila, the example of the elevated-pile trough according to DE 34 47 836 A1. However, the cable ducts can only be produced in short lengths on extremely large injection-molding machines, with the result that there is no question of straightforward transfer of the solution which is known per se, because such a small support spacing would not be cost-effective in most cases; in addition, the support spacing would always have to match up exactly with the parting joint of the ducts, in order for it to be possible to secure adjacent troughs of the cable ducts.
For this reason, in a variant according to the invention, first of all the support is provided with a load-bearing member, which extends in the longitudinal direction of the cable duct and on which the troughs are then fitted without also having to be fastened separately on the load-bearing members. For this purpose, the troughs are provided, according to the invention, with recesses which are configured precisely such that they can accommodate the load-bearing members as soon as the trough is fitted over the load-bearing members. Ideally, the recesses are configured such that, after having been fitted on, the troughs retain with a friction fit or grip round the load-bearing members, or parts of the load-bearing members, in the manner of a clamp-action or snap-action closure. A slight capacity for longitudinal displacement on the load-bearing members is quite desirable here in order for it to be possible to line up the troughs in a row next to one another without any sizeable joints. The trough connectors which can be used for this purpose are set forth in WO 94/21018, but may be dispensed with in the case of the invention. Instead of such clamp-action or snap-action closures directly on the recesses, it is also possible for parts of the trough to be configured, preferably on the sides or beneath the base thereof, such that they grasp with a friction fit, or grip round, the load-bearing member. For an effective transition from trough to trough, and in order also to limit even slight torsion of the troughs with respect to one another, the trough ends may be provided with tongues, which may in each case be part of the inner wall of the following trough. Alternatively, or in addition, the troughs are connected to the load-bearing members by screws, e.g. self-tapping metal screws. After the troughs have been fitted and positioned, such screws can be drilled into the load-bearing members from above by way of the trough borders, it being possible for corresponding guides to be injection molded into the trough borders as an aid.
In order to escape the risk of disruption to presence-of-trains indicating systems or else to avoid an undesired short circuit due to a contact wire falling down, the recesses are configured, according to the invention, such that the load-bearing member is essentially concealed within the shape of the trough. In other words, the recesses are shaped on the outside such that, when the trough is installed, the load-bearing members are located within the contours of the trough, said contours being defined by the outsides of the trough, i.e. the trough has, at the same time, an apron which is connected integrally to the trough.
This means that no current-carrying part can reach the load-bearing members. This applies equally for the damaged cables which may be located within the trough. In some cases, it may be expedient first of all to produce, and install, plastic troughs which are of relatively straightforward configuration, and can thus be injection molded relatively inexpensively, and only to provide means for covering the load-bearing members subsequently as required, if no other grounding arrangement is possible. These means are, for example, aprons which are made of insulating materials and can be provided on the trough, the load-bearing member or a support by, for example, adhesive bonding or screw-connection such that the load-bearing members are concealed. The load-bearing members are usually formed from metal profiles, preferably from steel profiles. In a preferred embodiment, these are rectangular tubes or round tubes which, for reasons of corrosion prevention or for a better friction fit with the trough, may additionally be coated with plastic. However, it is also possible for T-profiles or L-profiles or U-profiles of corresponding design and arrangement to be used, in principle, even if these may involve disadvantages—as a result of production—in terms of dimensional stability, torsion and/or surface protection.
Such metal profiles can easily absorb loads of 100 kg per meter or more, as is conventionally required of cable ducts on railroads.
Ideally, each trough rests on two parallel load-bearing members which are arranged at a horizontal spacing apart in the bottom part of the trough when the trough is in its use position.
However, it is also possible, for relativel
Kaulbersch Otto
Michel Jurgen
Wirthwein Udo
Cohen & Pontani, Lieberman & Pavane
Estrada Angel R.
Reichard Dean A.
Udo Wirthwein
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