US 3305623 A
Description (OCR text may contain errors)
1967 w. F. BAKKER ETAL 3,305,623
SHIELDED WINDOW CONSTRUCTION Filed Oct. 19, 1964 l l Ill/III!!! I P wF M WM? i 3 Jo Q J W M y B a 3,305,623 SHIELDED WINDOW CONSTRUCTION Willem F. Bakker, Clark, Arthur J. Johnson, Newark, and Joseph P. Kosiarski, Freehold, N.J., assignors to Metex Corporation, a corporation of Delaware Filed on. 19, 1964, Ser. No. 404,801 6 Claims. (Cl. 17435) This invention relates to shielded observation windows or similar devices for electrical or electronic devices.
At present the prevention of radio frequency leakage through relatively large openings which require an undistorted view of some form of visual read out, is accomplished by means of a coated glass commonly called conductive glass. Such material affords poor shielding effectiveness against radio frequency loss; the glass is heavy and relatively high in cost and diffic-ulty is encountered in making proper contact between the conductive glass and the surrounding enclosure frame work.
It is an object of the present invention to provide a construction which will eliminate the above objections and other objections arising from the use of the conductive glass, and the present invention contemplates the provision of a window which employs a pair of overlying panes of transparent plastic material such as Plexiglas between which is sandwiched a layer of foraminous metallic mesh that extends co-planar with the panes, the edges of the plastic panes and the edges of the metallic mesh being enclosed in a metallic mounting frame or rim.
In numerous types of electronic equipment which is totally enclosed or confined in shielded boxes, it is frequently necessary or at least desirable that some means be provided to observe certain instruments, the functioning of parts of the apparatus or other features having a bearing on the proper operation of the equipment.
It is accordingly, one of the objects of the invention to provide an observation window for apparatus of this character, which can be made in almost any shape and size to suit special equipment, and which will be provided with shielding material to suppress or exclude radio frequency interference.
It is another object of the invention to provide means for attaching the observation window to the equipmentcontaining enclosure and in such a manner that no objectionable radio frequency leaks will occur around the periphery of the observation panel.
With these and other objects to be hereinafter set forth in view, we have devised the arrangement of parts to be described and more particularly pointed out in the claims appended hereto.
In the accompanying drawing, wherein an illustrative embodiment of the invention is disclosed,
FIG. 1 is a perspective view, with some parts fragmentarily shown, of a shielded observation window constructed according to the invention;
FIG. 2 is a transverse sectional view, taken substantially on the line 2-2 of FIG. 1, looking in the direction of the arrows;
FIG. 3 is a face view of a part of the metallic knit mesh and a part of the metallic binding strip applied thereto; and
FIG. 4 shows an alternate form of metallic mesh.
Referring to the drawing, 1 and 2 respectively indicate a pair of sheets or panes composed of a transparent plastic material, such as Plexiglas or another material of similar characteristics. Sandwiched between the sheets or panes 1 and 2 and lying co-planar therewith, is a layer 3 of foraminous conductive material, such as metallic mesh. Such material may be composed of wire in the knitted form shown in FIG. 3 or it might be of the woven Wire type shown in FIG. 4 or of some other known wire mesh.
Such metallic shielding material while in the form of United States Patent 3,305,623 Patented Feb. 21, 1967 I CC an independent layer disposed between the Plexiglas panes glas or other transparent plastic.
The layer 3 of shielding material, has its peripheral edge enclosed in a binding consisting of a channel strip 5 of metal, such as stainless steel foil, and to which the mesh 3 or 4 is spot welded as shown at 6, thereby providing a metallic enclosing rim or frame for the metal mesh. Both the metallic mesh, framed as above described, and the Plexiglas sheets or panes 1 and 2 are confined in a surrounding frame 7 composed of metal or one which is both conductive and compressively resilient so that it acts gasket-like when secured around an opening in a metallic enclosure as shown in FIG. 2.
The inner edge of the frame 7 is properly grooved, as shown at 9 for the reception of the edges of the Plexiglas panes and also grooved as shown at 10 to snugly receive the binding 5 that extends around the edges of the metal mesh 3, 4.
The result of the structure described is a shielded window which is of sturdy construction; one which provides for complete visibility and one which is very effective to prevent radio frequency leakage. The window constructed as described, is attached over an opening in an enclosure by means of the bolts 11 or equivalent fastening means which pass through the frame 7 and through the marginal edge area defining the opening in the enclosure 8. The frame 7, being to a certain degree compressible, serves as a gasket against the face of the enclosure 8 and establishes good contact between the metallic mesh insert and the body of the enclosure.
While we have herein shown the shielding insert and window as being substantially rectangular in shape, it will be understood that it may be made in various other shapes according to the shape of the opening over which it is fitted. Also while we have suggested that the panes 1 and 2 shall be of a plastic material such as Plexiglas, these panes can, if desired, be composed of glass.
The wire mesh may be replaced with a perforated metal element, photo-etched foil and/or a honeycomb construction with results which are improved over those of the prior art. In addition, a plurality of layers of mesh or the like may be used, as for example, a multiple layer sandwich having a layer of Plexiglas, then mesh, then a second Plexiglas layer, then a second mesh, completed by a third layer of Plexiglas.
Having thus described the invention, it is obvious that the same is not to be restricted thereto, but is broad enough to cover all structures coming within the scope of the annexed claims.
What we claim is:
1. A shielded window for electronic apparatus comprising an enclosure having an opening, a window fitted thereover and closing said opening, said window including a resilient and conductive frame, a pair of transparent panes mounted in said frame, a layer of metallic foraminous mesh confined between the panes, with the edges of the mesh disposed in the frame and in contact therewith, and wherein the edges of the metal mesh are enclosed in a metallic binding strip and said strip is fitted within and in contact with the resilient and conductive frame.
2. A shielded window comprising an enclosure having an opening, a window fitted thereover and closing said opening, said wind-ow including a resilient and conductive frame, a pair of transparent panes mounted in said frame, a layer of metallc foraminous mesh confined between the panes, with the edges of the mesh disposed in the frame and in contact therewith, and wherein grooves are provided in the inside edge of the frame receiving the panes and the metal mesh layer located between them.
3. A shielded window as provided for in claim 1, wherein the metal mesh is composed of wire in knitted form having its edge contained in a binding strip of metal and said strip is fitted in the frame.
4. A shielded window as provided in claim 1, and wherein the metal mesh is composed of wire in woven form and has its edge enclosed in and Welded to a metallic binding strip which is enclosed in the frame.
5-. A shielded window'for a metal enclosure for electronic equipment'comprising a substantially flat layer of foraminous metal, a binding strip around the edges thereof and gripping both faces of said layer, at least one sheet of transparent plastic material contacting a face of said layer, a conductive frame surrounding the edge of said layer, sheet and strip, and in contact with said sheet and strip, and means attached to said frame for anchoring said shielded window into an opening in said enclosure.
References Cited by the Examiner UNITED STATES PATENTS 2/ 1947 Naumann 317-2 l/l960 Hahn.
LEWIS H. MYERS, Primary Examiner.
D. L., CLAY, Assistant Examiner.