Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Reexamination Certificate
1999-08-13
2001-03-27
Berhane, Adolf Deneke (Department: 2838)
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
C174S068300, C174S068300
Reexamination Certificate
active
06207893
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a high frequency shielded duct with a shielded cable running through the wall of an electrically conductive housing for electrical and electronic components.
The high frequency shielded duct finds application in high frequency shielded housings and cabinets of industrial electronics, in which elements and modules are accommodated. These elements and modules are sensitive to electromagnetic interfering radiation and their components can also produce interfering radiation, which must not be allowed to penetrate outward.
Increasingly components are built into housings and cabinets of electrical engineering or rather electronics. These housings necessitate an increasingly smaller noise margin due to ever lowering voltage levels and higher switching frequencies. With shielded systems it is well known that the cable ducts are the critical points at which high frequency interference currents on the cable shields are often not sufficiently drawn off and thereby the put into question the entire complex shielding of the housing or cabinet.
There are different well-known high frequency shielded ducts for use with shielded unfinished single cables (those without a plug connected), which cause a perfect electrical contacting of the cable's shield with the high frequency shielded duct. Common to all of these ducts is the lavish cost of assembly for bringing the cable into the duct. It is particularly unfavorable that the mounting of the plug connectors to the cable ends is possible often only after final assembly of the duct at the housing or cabinet. This means that additional work is expended at the place of assembly. Thus stripping, splicing, attaching the fastening piece, and soldering must be executed before the cabinet or the housing can be set up and attached to its workstation. In an electrically shielded connector with a metallic housing, according to DE 40 13 963, after removing the cable sheath, a sleeve must be put on over the cable shield. The opened shield is then brought down and fastened to the outside diameter of the case. In another design of ducts the opened cable shield is dragged through a metal pan filled with metal balls, such that the shield makes contact with the wall of the metal housing over the balls.
It is also well known, high frequency shielded cable entry housing, to fasten an assembly disk to the inside of the housing wall next to an opening for the cable passage. The duct channels are intended to have tension relievers for the cables, which are fastened to the mounting plate. The installation and attachment of the cables is however time-consuming; already made cables complete with plugs cannot be pulled through the channels (DE 40 13 886).
Further known is a switch cabinet with a high frequency shielded duct for cable consisting of two, inserted floor plates arranged at the base. These plates possess sealing strips of a flexible, electrically conductive material at bent edgings between which the cables, with their bare metal shield, are held. The assembly of the two floor plates and the use of cables is pedantic however (DE 196 04 219).
The task of the invention lies therein, to develop a high frequency shielded duct for shielded cables in such a way that a single or several cables including their plug connectors can be passed through the wall of an electrically conductive housing with the least assembly expenditure.
SUMMARY OF THE INVENTION
The solution of the task is solved by a metallic channel arranged on the wall of an electrically screened conductive housing. A cable can be led into this housing and is inserted after the spreading of its shield in the longitudinal direction, whereby, a resilient flexible contact element is then inserted into the channel and presses the shield in slightly to produce a linear shaped contact along the channel wall.
The invention makes use of the effect a high frequency electromagnetic wave has passing through a flue, as the closed channel represents here. The wave is strongly absorbed until one of the flue's dependent threshold frequency measurements is reached. It has been shown that after a suitable dimensioning of the channel, an outstanding high frequency shielded duct results and needs only an electrical connection, provided between the cable's shield and the inner wall of the channel. Here the contact pressure is not important.
The suggested duct with its resilient-flexible contact element permits the insertion of several cables next to each other and also allows different diameter cables into the channel as long as only one linear shaped contact is produced between the cable shield and an inner wall of the channel.
In relation to other well-known ducts, the invention also has the advantage that an insertion of coaxial cables leaves no junction for the characteristic impedance to occur. There is also no impairment when assembling the metallic shield—as for instance during a splicing process.
The assembly required by cables and cable bundles in connection with a duct, according to the invention, requires neither special know-how nor special processes, except when removing the sheath of a short piece of cable. Thus no special qualification demands are made on the assembly personnel. The otherwise necessary time-consuming fastening of the plug connectors is omitted on site because ready-made cables can be used.
The channel possesses a favorable u-shaped cross section. This results in easily calculable absorption rates of the flue, which is formed by the channel as well as the adjacent wall. A wave duct of rectangular cross section is thereby formed.
For attachment to the housing the channel will appropriately have mounting flanges on its open long sides and on its end wall. A channel that is equipped in such a way is cost effectively manufactured through punching and bending processes and is then screwed on to the wall of the metal housing without problems.
It is appropriate to design a tension relief for the cable at the base of the channel close to the inlet. Beyond the tension relief the position of the cable is thereby fixed at the wall of the flue.
In the simplest case a commercial cable clamp made from anticorrosive sheet metal serves as a tension relief.
The contact element can be a prismatic block from a suitable, long-lasting, and resistant foam material or from another resilient-flexible material which will evenly fill out the channel.
In order to ensure that the contact portion of the cable's shield is also at the end wall of the channel, the contact portion is upwardly curved and right-angled before it meets closely with the end wall.
Several channels can be arranged next to each other or also on top of each other on one of the outside walls of the housing.
The invention is more nearly described below by two model examples with reference to the attached drawings. Shown are:
REFERENCES:
patent: 3686607 (1972-08-01), Berry
patent: 4066837 (1978-01-01), Miura
patent: 4358632 (1982-11-01), Buch
patent: 4506224 (1985-03-01), Krause
patent: 4746866 (1988-05-01), Roschmann
patent: 5294748 (1994-03-01), Schwenk et al.
patent: 5898344 (1999-04-01), Hayashi
patent: 6093962 (2000-07-01), Ikegame
patent: 40 13 886 A1 (1991-10-01), None
patent: 40 13 963 C2 (1993-07-01), None
patent: 196 04 219 C1 (1997-06-01), None
Berhane Adolf Deneke
Merchant & Gould P.C.
Schroff GmbH
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