GB2112259A

GB2112259A - Microwave sealing arrangement

Info

Publication number: GB2112259A
Application number: GB08236430A
Authority: GB
Inventors: David W Brashears; John R Kraus
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1981-12-24
Filing date: 1982-12-22
Publication date: 1983-07-13
Also published as: CA1213967A

Abstract

A sealing arrangement for preventing electromagnetic radiation from passing an access opening in a sheet of electromagnetically opaque material, having a closure of similarly opaque material with a surface urged against the surface of the sheet at the opening, the arrangement comprising strip 24 of wire mesh construction extending around the opening in contact with edge surfaces thereof, and in cross-section having a bulbous portion 25 with a fin portion 26 extending laterally therefrom toward and through the opening. Wear strips 37 are provided to secure the fin to the edge surfaces of the opening. <IMAGE>

Description

SPECIFICATION Sealing arrangement This invention relates to sealing arrangements and particularly to the sealing of housings for electrical equipment producing electromagnetic radiation so as to confine the radiation and prevent its spread outside the housing.

Much present-day electronic equipment produces electromagnetic radiation, either intentionally or inadvertently, and the housings of such equipment function not only to protect the internal complements physically, but to prevent radiation generated within the housing from escaping. A problem arises, when, as is usually the case, the housing must have access openings or other openings. Closures for the openings are of course provided, but radiation at the higher frequencies now common is found to escape from the housing around the openings, and various precautions must be taken to prevent this.

One avaiiable procedure is to install a frame gasket at the opening. This procedure has the disadvantages of requiring close tolerance mounting holes and of calling for relatively skilled labour for installation, in addition to its considerable cost. It also requires that sufficient lead time be allowed, in the production of equipment, for the acquisition of the frame gaskets, and that a supply of frame gaskets of suitable shapes and sizes be maintained in inventory.

It is an aim of the present invention to provide an improved sealing arrangement for preventing the escape of electromagnetic radiation from an enclosure having an access opening closed by a closure member, the enclosure and closure member being of a electromagnetically opaque material, the arrangement comprising a strip of wire mesh construction extending around the opening, the strip in cross-section having a bulbous portion which in use seals the gap between the closure member and enclosure and a fin portion which in use surrounds an edge or edges of the enclosure defining the access opening; and elongate securing means which in use surround the fin portion of the strip to secure it to said edge or edges.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a radiation sealing arrangement according to the present invention installed around an access opening in a housing, Figure 2 is a fragmentary section of the sealing arrangement of Figure 1, and Figure 3 is an enlarged, detailed view of a portion of Figure 1.

As is shown in the drawings, a cabinet or housing for equipment producing electromagnetic radiation includes a wall 20 having an access opening 21, with which a closure 22 cooperates by hinging, clamping, or other appropriate measures (not shown).

A strip 24 of woven wire construction is mounted to surround opening 21. In crosssection, gasket strip 24 comprises a bulbous, generally circular, portion 25 from which a fin 26 extends laterally toward and through opening 21, being folded over the edge 27 of the opening.

Strip 24 may be preformed in the exact size to fit around opening 21, or may be made on the spot from a length of material, the adjacent ends being mutually twisted and intertwined to form a continuous bond, and the joint preferably being located at a site other than a corner of the opening. In order to give a more perfect configuration, fin 26 only of strip 24 may be mitred at the corners, as shown at 30 in Figure 3.

In order to secure strip 24 in position, a set of strips are of slightly less length than the sides of opening 21, and may be of nylon or other suitable plastics material. They are of U-shaped configuration in cross-section, comprising first and second legs 35 and 36 extending in the same direction from a bight 37. The spacing between the legs is substantially the same as the thickness of wall 20 plus twice the thickness of fin 26, see Figure 2.

To install the sealing arrangement, seal strip 24 is placed at opening 21 and fin 26 is passed through the opening and folded along the surfaces of wall 20. Starting near one corner, a wear strip such as 34 is pressed over the fin and the end of the wall, and this is continued until the entire length of the wear strip is tightly engaged.

This is repeated at the other edges of the opening, until the seal strip is firmly secured all around the opening. The wear strips come sufficiently close to the corners to give adequate holding of the seal strip, but a mitered corner is not found necessary.

Figure 2 shows that the diameter of the seal strip is greater than the thickness of the wear strip, so that the seal strip can be compressed between door surface 40 and housing surface 41, while the wear strip acts as a mechanical stop to prevent undue compression of the seal strip.

In one embodiment of the invention, the seal strip was of Monel Mesh material supplied by Tecknit, and the wear strip was of molybdenum disulfide Filled Nylon, supplied by Polymer Corp.

For a housing of 1.5 to 2.25 mm thick gauge metal the diameter of the seal strip 24 was 4.69 mm and the width of fin 26 was 18.75 mm. The dimensions of wear strips 31 to 34 were 5.75x8.00 mm.

While the seal has been shown as applied to the housing around the opening, it can with equal satisfaction be applied to the edge of a closure of proper dimensions.

From the above description it will be evident that a sealing arrangement for sealing an opening against passage of electromagnetic radiation has been provided which does not require frames or fasteners and which can be assembled readily and inexpensively by relatively unskilled labour.

Claims

1. A sealing arrangement for preventing the escape of electromagnetic radiation from an

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Sealing arrangement This invention relates to sealing arrangements and particularly to the sealing of housings for electrical equipment producing electromagnetic radiation so as to confine the radiation and prevent its spread outside the housing. Much present-day electronic equipment produces electromagnetic radiation, either intentionally or inadvertently, and the housings of such equipment function not only to protect the internal complements physically, but to prevent radiation generated within the housing from escaping. A problem arises, when, as is usually the case, the housing must have access openings or other openings. Closures for the openings are of course provided, but radiation at the higher frequencies now common is found to escape from the housing around the openings, and various precautions must be taken to prevent this. One avaiiable procedure is to install a frame gasket at the opening. This procedure has the disadvantages of requiring close tolerance mounting holes and of calling for relatively skilled labour for installation, in addition to its considerable cost. It also requires that sufficient lead time be allowed, in the production of equipment, for the acquisition of the frame gaskets, and that a supply of frame gaskets of suitable shapes and sizes be maintained in inventory. It is an aim of the present invention to provide an improved sealing arrangement for preventing the escape of electromagnetic radiation from an enclosure having an access opening closed by a closure member, the enclosure and closure member being of a electromagnetically opaque material, the arrangement comprising a strip of wire mesh construction extending around the opening, the strip in cross-section having a bulbous portion which in use seals the gap between the closure member and enclosure and a fin portion which in use surrounds an edge or edges of the enclosure defining the access opening; and elongate securing means which in use surround the fin portion of the strip to secure it to said edge or edges. An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a radiation sealing arrangement according to the present invention installed around an access opening in a housing, Figure 2 is a fragmentary section of the sealing arrangement of Figure 1, and Figure 3 is an enlarged, detailed view of a portion of Figure 1. As is shown in the drawings, a cabinet or housing for equipment producing electromagnetic radiation includes a wall 20 having an access opening 21, with which a closure 22 cooperates by hinging, clamping, or other appropriate measures (not shown). A strip 24 of woven wire construction is mounted to surround opening 21. In crosssection, gasket strip 24 comprises a bulbous, generally circular, portion 25 from which a fin 26 extends laterally toward and through opening 21, being folded over the edge 27 of the opening. Strip 24 may be preformed in the exact size to fit around opening 21, or may be made on the spot from a length of material, the adjacent ends being mutually twisted and intertwined to form a continuous bond, and the joint preferably being located at a site other than a corner of the opening. In order to give a more perfect configuration, fin 26 only of strip 24 may be mitred at the corners, as shown at 30 in Figure 3. In order to secure strip 24 in position, a set of strips are of slightly less length than the sides of opening 21, and may be of nylon or other suitable plastics material. They are of U-shaped configuration in cross-section, comprising first and second legs 35 and 36 extending in the same direction from a bight 37. The spacing between the legs is substantially the same as the thickness of wall 20 plus twice the thickness of fin 26, see Figure 2. To install the sealing arrangement, seal strip 24 is placed at opening 21 and fin 26 is passed through the opening and folded along the surfaces of wall 20. Starting near one corner, a wear strip such as 34 is pressed over the fin and the end of the wall, and this is continued until the entire length of the wear strip is tightly engaged. This is repeated at the other edges of the opening, until the seal strip is firmly secured all around the opening. The wear strips come sufficiently close to the corners to give adequate holding of the seal strip, but a mitered corner is not found necessary. Figure 2 shows that the diameter of the seal strip is greater than the thickness of the wear strip, so that the seal strip can be compressed between door surface 40 and housing surface 41, while the wear strip acts as a mechanical stop to prevent undue compression of the seal strip. In one embodiment of the invention, the seal strip was of Monel Mesh material supplied by Tecknit, and the wear strip was of molybdenum disulfide Filled Nylon, supplied by Polymer Corp. For a housing of 1.5 to 2.25 mm thick gauge metal the diameter of the seal strip 24 was 4.69 mm and the width of fin 26 was 18.75 mm. The dimensions of wear strips 31 to 34 were 5.75x8.00 mm. While the seal has been shown as applied to the housing around the opening, it can with equal satisfaction be applied to the edge of a closure of proper dimensions. From the above description it will be evident that a sealing arrangement for sealing an opening against passage of electromagnetic radiation has been provided which does not require frames or fasteners and which can be assembled readily and inexpensively by relatively unskilled labour. Claims

1. A sealing arrangement for preventing the escape of electromagnetic radiation from an enclosure having an access opening closed by a closure member, the enclosure and closure member being of a electromagnetically opaque material, the arrangement comprising a strip of wire mesh construction extending around the opening, the strip in cross-section having a bulbous portion which in use seals the gap between the closure member and enclosure and a fin portion which in use surrounds an edge or edges of the enclosure defining the access opening; and elongate securing means which in use surround the fin portion of the strip to secure it to said edge or edges.

2. The sealing arrangement of Claim 1, wherein the securing means is of generally Ushaped cross-section and of a plastics material.

3. A sealing arrangement substantially as herein described with reference to the accompanying drawings.

4. In combination an electromagnetically opaque enclosure sealed by a sealing arrangement according to any one of Claims 1 to 3.

5. The combination of Claim 4, wherein the access opening of the enclosure is rectangular in shape wherein the sealing strip is continuous around the opening with adjacent ends mutually twisted and interwoven, and wherein four securing means, one for each edge, secure the fin portion of the strip to respective edges of the opening.

6. The combination of sealing arrangement and enclosure, substantially as herein described with reference to the accompanying drawings.