Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2001-05-16
2003-07-29
Martin, David (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S818000, C361S800000, C174S034000
Reexamination Certificate
active
06600664
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a housing of a switchgear cabinet for a printing machine, with housing elements formed of electrically conductive material, which have an electrically insulating surface layer, and which include at least one door, one body and one electrically conductive elastic seal disposed therebetween.
The cabinet includes a body, at least one door and at least one electrically conductive seal that is disposed therebetween for the purpose of sealing and shielding the housing elements. The body is formed of various housing elements, such as ceilings, floors, walls, and detachable accessories or insertion parts for receiving the components or subassemblies of the electronic control.
The housing elements are produced from electrically conductive material. Steel or steel plate are preferably utilized for this purpose. They are protected against corrosion by an appropriate surface treatment such as varnishing, coating or surface tempering. In this process, the housing elements are individually surface-treated and then assembled into the switchgear cabinet.
To ensure undisturbed operation, it is necessary to satisfy electromagnetic compatibility (EMC) requirements, whereby electromagnetic fields must be shielded. On one hand, the interior of the switchgear cabinet must be kept free of electromagnetic fields, and on the other hand, the environment must be protected from electromagnetic fields which arise in the interior of the cabinet. It is also possible to provide separate electromagnetic shielding for individual compartments in the interior of the cabinet.
It is particularly important that the surface of the cabinet or of the individual compartments be completely electrically conductive. An electrical field acts upon the conductive surface to the effect that charge displacements are generated in the conductive housing material, which produces a charging of the surface. These charges of the cabinet, known as surface charges, generate a field which precisely counteracts the field acting upon the surface. The interior of the cabinet is then ideally entirely free of fields. The functional principle that is used therein is based on what is known as the Faraday effect, with the cabinet forming a so-called Faraday cage.
To achieve complete shielding, the cabinet must be produced with an optimally uniformly conductive surface, so that disturbances stemming from various properties or thicknesses of the materials or other instabilities in the surface can be avoided. Particularly in moving parts such as the door, all edges must be conductively connected to the body, because unstable points of the surface will emerge there otherwise, at which a transfer of electromagnetic fields could occur.
In addition, the housing of the switchgear cabinet must be sealed against dust, oil vapors, and moisture (IP) and against other environmental influences in the vicinity of the machine operation.
German Patent 196 10 045 thus proposes the disposing of an EMC seal between the body and the door. The EMC seal is electrically conductive and elastic, and connects the housing elements which are allocated to one another. To this end, seals made of conductive plastic material, plastic-material seals having electrically conductive coverings, or electrically conductive metal nettings and braidings (for example, sheet covers having contact locations or points at the adjoining housing element) are proposed. Additional EMC seals which serve various functions such as sealing a window or a mountable coverplate are known from German Patents 9107917 and 296 09 873.
A disadvantage of these seals is that the insulating surface treatment renders the connections between the mounted housing elements, i.e., between the seal and the body or the door, insufficiently conductive. As a result, the housing of the cabinet has the required thorough and stable electrical conductivity only accidentally, if at all.
In addition, so-called two-chamber systems have become known, which have an inner housing made of conductive material, e.g., hot-galvanized sheet and state-of-the-art EMC seals, and an outer housing wherein the inner housing is disposed. The outer housing is produced from varnished sheetmetal or plastic material with corresponding seals against dust and moisture. A disadvantage of this arrangement is in the production outlay and the associated cost disadvantages, as well as poor accessibility, because the various housings impede access to the electronic components or subassemblies in the interior of the cabinet.
An additional measure is to provide a varnished housing having two seals, one of which is provided against dust and moisture (IP), and the other of which is provided as an EMC shield. What poses the biggest problem here is obtaining good and reliable conductivity over the course of several years, as well as the high outlay in production.
The published German Patent Document DE 42 07 308 C2 teaches a method for producing a sheetmetal housing from a housing body having at least one sealing part wherein the housing body and an opening can be connected to one another in an electrically and magnetically conductive manner. To this end, the housing body is greased, and a contact surface is then placed on the housing body in a flame injection procedure and covered with a cover strip. Next, the housing body is cleaned and varnished, and the cover strip is removed. The sealing part is either chromated or is formed of rustproof material, or it is provided with a contact surface in the same manner. Next, the housing body and the sealing part are connected to an elastic HF sealing element. This method is disadvantageous due to the great outlay and the associated costs.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to overcome the above mentioned disadvantages by providing a shielded switchgear cabinet housing with surface-treated housing elements with which it is possible to obtain an optimal shielding against electromagnetic fields, in particular by producing considerably uniform conductivity of the overall switchgear cabinet.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a housing of a switchgear cabinet for a printing machine, with housing elements formed of electrically conductive material having an electrically insulating surface layer, comprising at least one door, one body and one electrically conductive elastic seal disposed therebetween, respective mutually allocated elements of the housing elements having corresponding electrically conductive contact locations at electrically conductive strip material connected to the conductive material of the housing elements; each of the contact locations being covered by a protective layer which is removable during assembly of the cabinet, for the purpose of electrically conductively connecting the housing elements and the seal.
In accordance with another feature of the invention, the protective layer is formed of at least one material selected from the group consisting of paper, plastic material, metal and a composite material.
In accordance with a further feature of the invention, the contact locations are elevations which are embossed and/or stamped in the conductive material of the respective housing element.
In accordance with an added feature of the invention, the contact locations form a contact surface.
In accordance with an additional feature of the invention, the strip material is covered with a removable film.
In accordance with yet another feature of the invention, mutually corresponding contact locations are constructed at the housing elements, which are to be connected as a borehole into which a self-cutting conductive screw with a cutting thread is screwable, the self-cutting screw, when tightened, serving for cutting into the conductive material and for gas-tightly sealing the borehole.
In accordance with yet a further feature of the invention, the self-cutting screw has at least one cutting element on an inner surface of a screw he
Dörr Wolfgang
Glaunsinger Georg
Schunn Johann
Bui Hung
Greenberg Laurence A.
Heidelberger Druckmaschinen AG
Locher Ralph E.
Martin David
LandOfFree
Shielded switchgear cabinet housing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Shielded switchgear cabinet housing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Shielded switchgear cabinet housing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3039717