Electricity: conductors and insulators – Conduits – cables or conductors – Single duct conduits
Patent
1995-09-21
1997-12-30
Sough, Hyung S.
Electricity: conductors and insulators
Conduits, cables or conductors
Single duct conduits
220 36, H02G 318
Patent
active
057033285
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a cable lead-in mounted in an opening in a wall of a casing for current conductors, the cable lead-in comprising an outer part and an inner part, wherein the outer part includes a portion passed through said opening and a through duct through which an electric cable may be run for connection with the current conductors, at least a section of said duct being formed as a funnel, and wherein the outer part is provided with a flange which engages one side of said wall around said opening, the inner part being assembled with the outer part to clamp the outer part in the opening of the casing wall.
BACKGROUND OF THE INVENTION
According to present heavy current regulations stripped current conductors in e.g. a terminal block have to be duly shielded against unintentional touch by means of a suitable casing, e.g. a box. When the current conductors are to be connected to other current conductors outside the casing via an electric cable, the cable must therefore be drawn through an opening in the wall of the casing. To prevent the cable from being damaged by the edge of the opening and/or being disconnected from the current conductors during this operation, this opening is normally provided with a threaded cable clamp including a strain relief member and usually also a sealing ring as well as a break preventing funnel which is provided on the outermost end part of the threaded joint opposite the current conductors.
A cable lead-in of this type is known from U.S. Pat. No. 2,118,672. This cable lead-in has an outer part 5 and an inner part 26 for mounting in an opening in a wall 3. The upper part has a duct 9 which is formed as a funnel and a flange 23 whose height is smaller than the length of the funnel. The flange engages the outer side of the wall around the opening with the funnel converging in the direction of she conductors.
This known cable lead-in is thus composed of several coaxial components which are arranged successively in the longitudinal direction. The cable entry is therefore relatively long, and since it is moreover fixed freely cantilevered in the wall of the casing, it is very liable to be broken off completely or partly. This applies especially to cable entries to mobile machinery, such as e.g. industrial vacuum cleaners, welding units and measuring tables, which are often relatively low with low cable entries which will easily abut obstacles when the machine in question is moved, just as the cable entry may be broken if a person steps on it.
If the cable entry is broken, the cable relief member is usually rendered inoperative, involving the risk of the cable being torn loose from its connection to the current conductors such that the power supply to the machine is interrupted. Since the stripped conductor ends of the cable are now exposed, this may moreover result in shortcircuiting and current leakage to machine parts which will thereby become conductive. The latter situation is extremely dangerous, since a person touching the conducting parts may be injured and in some cases even so seriously that it may proove fatal.
Accordingly, there is a need for an improved cable lead-in of the type mentioned in the opening paragraph, which, when mounted on even mobile machinery, cannot in practice be broken by arbitrary impacts, or because a person steps on it.
SUMMARY OF THE INVENTION
The novel and unique features of the invention achieving this object are that said flange engages the outer side of said wall such that only the flange is present on the outer side of the wall, said funnel is formed in at least the outermost section of said duct and converges inwardly in a direction toward the inside of the casing, and said flange has a smaller height than the axial extent of the funnel. In contrast to the conventional structures, the major part of the cable lead-in is now protected behind the casing, while actual flange which is present on the outer side of the casing. However, the flange per se is so low that it cannot be broken off by arbitrary impacts
REFERENCES:
patent: 2118672 (1938-05-01), Green
patent: 4789759 (1988-12-01), Jones
Patel Dhiru R.
Sough Hyung S.
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