SEALING DEVICE IN METAL CABINETS, WHICH ARE USED TO SCREEN OFF ELECTROMAGNETIC FIELDS

Abstract: Sealing device in metal cabinets, which are used to screen off electromagnetic fields, for compressing metallic gaskets along the edges of its door. The device includes an elongate element (3, 5, 18) the length of which conforms with that of the door (1, 2) and which is pivotable about an axis (7) parallel to the pivoting axis of the door. At its pivoting axis (7) the element is provided with a first elongate contact surface (10) which presses against the gasket (12) with a leverage effect when the element is turned to its one end position. A second elongate contact surface (8) disposed on the element simultaneously engages against an abutment (9, 16) to prevent the door from warping due to the pressure exercised against the gasket.

Description: "Seailliinngg ddeevviiccee iinn mmeettaall ccaabbiinneettss,, which are used to sen•een off electromagnetic fields" TECHNICAL FIELD The invention relates to a sealing device in metal cabinets used as screens against electromagnetic fields, for compressing mettalic gaskets along the edges of the door. Electromagnetic fields occur in nature as well as those caused by electric and electronic equipment. The fields can disturb the function of other electronic equipment, and the increased use of such equipment has resulted in increasing interference or disturbance problems. Electromagnetic fields can be prevented from coming into, or departing from, electronic equipment by building such equipment into closed metallic casings. BACKGROUND ART A problem in the construction of a cabinet for electronic equipment, a so-called apparatus cabinet, is to provide an effective seal at the door of the cabinet. A previously proposed method of achieving such a seal is to implement the door and frame so that these can abut each other with metallic contact round the entire frame. This method puts great demands on tolerances in manufacture, however. Another known method is to use a metallic sealing strip along the edges of the door. Problems occur here, however, caused by large stresses on the door suspension means and by the door having a tendency to warp. Irrespective of what method is applied, there is still a further problem in achieving an effective seal between the doors to a cabinet with a pair of doors side by side, which are left- and right-hand hung. DISCLOSURE OF INVENTION The object of the present invention is to achieve a sealing device which can be used in an apparatus in the joint between door and door frame as well as in the joint between two doors. The problems is solved by a pivotable elongate element which, on being turned to its one end position for a closed door achieves that a metal gasket is compressed in the mentioned joints without the door warping or without its suspension means being appreciably loaded. The invention is characterized by the disclosures in the claims. BRIEF DESCRIPTION OF DRAWINGS The invention will now be described in detail with reference to the accompa- nying drawings, on which Figure 1 illustrates an apparatus cabinet and figures 2-4 illustrate different door joints in a cabinet, seen in cross-section from above. More specifically, Figure 2 illustrates a joint between two doors, Figure 3 a joint between door and door frame at the door suspension means and Figure 4 a joint between the closure edge of a door frame in a cabinet with only one door. Figures 5 and 6 illustrate embodiments of a gasket intended to be located in these joints. BEST MODE FOR CARRYING OUT THE INVENTION The apparatus cabinet according to Figure 1 is provided with two doors 1 and 2. Elongate elements 3, 4 and 5 are attached to the doors and extend parallel to the pivoting axes of the doors. Elements 3 and 4 are rigidly attached to the doors by fastening means, e.g. screwed joints, while the element 5 is pivotable in relation to them. A restraining means 6 may be used to keep the element 5 in an end position. Figure 2 illustrates the elongate element 5 in cross-section, and how it achieves an effective seal between the doors 1 and 2. The element is hung at one side, and pivotable about pins 7. These pins are fixed in the upper and in the lower edge portions of door 2, adjacent its vertical edge, and may be rather short. In the vicinity of its pivoting axis the element has an inwardly directed elongate contact surface 10. When the element is turned to the illustrated end position, the surface 10 is intended to engage against the outside of a through-like projection 11 thrusting out from the door 2 and containing a metallic and compressible gasket 12. When the doors are closed this gasket engages against an abutment at the vertical edge portion of the door 1, this portion having a U- shaped cross-section, so that when the element is turned to its end position pressure is exerted against the projection 11 and thereby on the gasket 12. An elongate contact surface 8 on the element, facing away from the surface 10, is intended to engage against a second abutment 9 at the edge portion of the door. A uniformly distributed pressure is provided along the entire gasket with the described device, and thereby effective sealing of the joint between both doors. This is because the gasket is compressed with relatively large pressure, due to the leverage effect of the element, which takes place without the pins on which the element is hung being loaded appreciably and without the doors warping. The doors are retained in a closed position by the element being provided with the previously mentioned restraining means 6, not illustrated in Figure 2, which may be an ordinary sliding bolt, with which the element can be restrained in the illustrated end position and by the horizontal parts of the door frame being provided with unillustrated abutments pressing against the surface 8. When the doors are to be opened, the element 5 must be first turned outwards, after which the door 2 can be opened, and then the door 1. Figure 3 illustrates how the sealing device is used in a joint between a door and a door frame. The door corresponds to door 1, with the elongate element 3 attached to it according to Figure 1. The element, which functions as hinge for the door is pivotably mounted on the door frame, and is rigidly attached to the door by fastening means 15, e.g. a screwed joint. The element otherwise corresponds to the one previously described, except that it lacks restraining means. For a closed door, the gasket 12 is pressed against an abutment 17 in an edge portion of the door frame with a U-shaped cross-section, and the surface 8 against a second abutment 16 in the edge portion. Effective sealing of a closed door is also achieved by this joint, due to the relatively large pressure, uniformly distributed along the gasket, with which the gasket is compressed. This takes place without the pins on which the door is hung being appreciably loaded and without the door warping. Figure 4 illustrates how the seal can be achieved for the joint between the closure edge of a door 19 and the door frame in a cabinet with only one door. An elongate element 18 of the same embodiment as the element 5 is pivotably suspended in the door adjacent the door frame which, as previously is denoted by 14. The seal is achieved as with the joint according to Figure 3, but with the difference that the element 18 is not rigidly attached to the door. As was the case with the elongate element 5 according to Figure 2 the abutment 18 is also provided with an unillustrated restraining means, with which the element can be kept in the illustrated end position with the door closed. The horizontal edges of the doors or the door of a cabinet are in general much shorter than the vertical edges, whereby the gaskets along the horizontal edges can be compressed without the doors warping. Different embodiments of the metallic gasket 12 are illustrated in figures 5 and 6. According to Figure 5 it consists of woven metallic net 20 around an elongate eleastic core 21 having a round cross-section. According to Figure 6, the gasket consists of a comb-like plate, the teeth of which are bent at ends and have different slope so that the gasket can fill an elongate space. Depending on what sealing capacity is desired, different metals can be selected in which to manufacture the gasket.

Claims: CLAIMS 1. Sealing device in metal cabinets, which are used to screen off electromag¬ netic fields, for compressing metallic gaskets along the edges of its door, characterized in that the device includes an elongate element (3,5,18) the length of which at least nearly agrees with the length of an adjacent door edge, and which is pivotable about an axis (7) parallel to the pivoting axis of the door, adjacent the former axis the element being provided with a first elongate contact surface (10) which, when the element is pivoted to one end position, presses against the gasket 12 with a leverage effect, a second elongate contact surface (8) disposed on the strip element simultaneously engaging against an abutment (9,16) to prevent the door from warping due to the pressure exercised on the gasket. 2. Device as claimed in claim 1, characterized in that the element (5) is suspended at the closure edge of the door (2), and that the abutment (9) comprises an elongate, projection thrusting out from the closure edge of an adjacent door (1). 3. Device as claimed in claim 2, characterized in that the element (5) is provided with a restraining means (6) with which the element can be restrained in said end position. 4. Device as claimed in claim 1, characterized in that the element 3 is rigidly attached to the door (1) and constitutes a hinge for suspending the door on a door frame (14) of the cabinet. 5. Device as claimed in any one of the preceding claims, characterized in that the gasket (12) comprises an elastic core (21) surrounded by a metallic net (20). 6. Device as claimed in any one of the preceding claims, characterized in that the gasket (12) comprises a comb-like means of metal, its teeth being bent at the ends and forming a least two groups with different slope.

Inventors: EKDAHL PER ANDERS ALLAN, EKDAHL, PER, ANDERS, ALLAN
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET LM ERICSSON
Application year: 1985
Main classification: H05K9
IPC codes: H05K9