Door Assembly For An Enclosure Having A Tight Shielding For High Frequency Emissions

Abstract

A door assembly having a casing member surrounding a door opening, a door mounted on the casing member for closing the opening with electrical sealing means disposed therebetween. The improvement is the provision of magnetic means for clamping the door and casing against the electrical sealing means to insure a minimum transitional resistance therebetween. In one embodiment of the invention, the magnets are electromagnets which require deenergizing to enable opening of the door. Another embodiment of the invention, the magnets are permanent magnets with associated pole pieces which are shifted relative thereto to reduce the magnitude of the magnetic force to enable opening of the door. The third embodiment of the invention, is a provision of two groups of magnets with their poles aligned with or without pole pieces interposed therebetween with the groups of magnets being moved relative to each other to enable reducing the magnetic force to enable opening the door.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a door assembly for an enclosure having a tight shielding for high frequency emissions.

2. Description of the Prior Art

Enclosures which have a shielding for high frequency emissions comprising a metal foil lining on the walls of a room are well known in the art. In such arrangements, a door assembly comprising a door member pivotally mounted on a casing or frame member, which is connected to the shielding, and an electrical sealing member such as cords of metal fabric or contact springs which are provided between the door and frame. The door is held against the frame to insure contact through the electrical sealing member by mechanical means to insure a faultless electrical connection around a periphery of the opening. In many instances, due to misalignment between the door and the casing, gaps do occur in the electrical connection which create an unhomogeneous shielding for the room due to the difference in the transitional resistance at the electrical sealing member. To insure a faultless electrical connection around the periphery of the opening the prior art assembly uses a heavy rigid structure for the door so that the mechanical clamping forces applied thereto would provide the desired uniform contact pressure on the sealing member around the periphery of the opening.

It has been suggested to utilize a shielding foil on one side of the door which is held or pressed by an elastically secured magnetic band or strip against the casing frame. However, the magnetic forces of the magnetic band is very small and the foil does not have a spring like characteristic to provide a self-cleaning feature and may develop imperfect electrical connections. Since the attraction of the magnetic bands is so slight that it will not twist the door to correct any misalignment therebetween, both the door and frame must be mechanically rigid and very accurately adjusted for alignment to insure equally applied force between the door and frame. The proposed magnetic system of the prior art have such a weak magnetic force that the door can easily be opened by hand and in some cases is inadvertently opened.

SUMMARY OF THE INVENTION

The present invention is directed to an improved door assembly in which magnets are disposed around a periphery of the door opening in the casing member to pull the door member against the casing member with sufficient force to twist the door member if necessary to apply an equal contact pressure around the opening between the members and with such sufficient force that the door cannot be opened by hand. In one embodiment of the invention, electromagnets are distributed about the opening of the casing and must be deenergized to enable the door to be opened. In a second embodiment of the invention, permanent magnets with a pole piece for each magnet are distributed around the opening of the door with relative movements between the pole pieces and the associated poles of the magnets to increase and decrease the magnetic force clamping the door to enable opening of a closed door. A third embodiment of the invention, provides two groups of permanent magnets mounted on the door with or without pole pieces with either group of magnets being movable so that the poles thereof are in alignment for attracting the poles of the other group or opposing the poles to enable clamping and unclamping of the door. The fourth embodiment of the invention is the provision of two groups of magnets with each group fixedly mounted on the door and casing member with their poles in alignment for attraction and with pole pieces interdisposed therebetween which are movable relative to the groups of magnets to increase and decrease the magnetic force clamping the door against the casing member.

Accordingly, an object of the present invention is to provide an improved door assembly for an enclosure having a tight shielding for high frequency emissions.

Another object of the present invention is to provide a door assembly for an enclosure having tight shielding for high frequency emissions which assembly utilizes magnetic forces to clamp the door against the casing with twisting if necessary to compensate for misalignment therebetween.

A still further object of the present invention is to provide a door assembly for an enclosure having tight shielding for high frequency emissions in which the door can be of a thinner and less rigid structure.

Yet another object of the present invention is to provide a door assembly for an enclosure having a tight shielding for high frequency emission utilizing magnetic force from permanent magnets for clamping the door tightly against the casing which force is adjustable to enable opening of the door.

Other objects, features and advantages of the invention will be readily apparent from the following description of the preferred embodiments thereof taken in conjunction with the accompanying drawings although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of the door assembly of the prior art;

FIG. 2 is a cross sectional view taken on lines II--II of FIG. 1;

FIG. 3 is a side elevational view of the door assembly of the present invention;

FIG. 4 is a cross-sectional view taken on lines IV--IV of FIG. 3;

FIG. 5 is a side elevational view with portions of the door removed for purposes of illustration of an embodiment of the door assembly of the present invention;

FIG. 6 is a cross sectional view of another embodiment of the door assembly of the present invention illustrating the positioning of the permanent magnets in a clamping position; and

FIG. 7 is a view similar to FIG. 6 illustrating the placement of the permanent magnets in an unclamping position.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A prior art door assembly for enclosures such as rooms having tight shielding for high frequency emissions is illustrated in FIGS. 1 and 2 and includes a door member 1 and a frame or casing member 2. The casing member 2 has portions such as tubular pieces joined together such as by welded joints in a rectangular arrangement to define a door opening which is closed by the door member 1. To insure an electrical connection between the door member 1 and casing member 2, electrical sealing means 3 such as contact springs or a metal fabric cord is placed on either of the members 1 or 2 to surround the opening and to be pressed between the casing member 2 and a contact surface 4 of the door member 1 as the door member is clamped in the closed position illustrated. The door member 1 is mounted on the casing member 2 by a pair of hinge members 6 and is clamped in the closed position by a mechanically actuated latching mechanism having thrust bars 5.

The assembly was utilized in a shielded enclosure such as a room having a shielding formed by a non-magnetic metal foil 7 such as copper, which foil is electrically connected to the casing member 2 or to a foil provided on the casing member 2. The door member 1 could have a similar foil provided on its contact surface 4 to provide the desired shielding characteristics for the door assembly.

Since the clamping force was provided by the thrust rods or pins 5, the door member 1 in the prior art device illustrated in FIGS. 1 and 2 was of a heavy, rigid structure to prevent twisting and to apply the clamping force equally around the periphery of the opening in the casing member 2. If the door member 1 was not perfectly aligned with the casing member 2, either due to imperfections in the structure of the door member 1 or the casing member 2 or the hinge members 6 which imperfections cause a misalignment, the door could not twist to insure an equal contact pressure applied to the sealing members 3 disposed between the door 1 and casing 2. Furthermore, if the clamping mechanism were misaligned, the door would not twist to compensate for unequal application forced by the clamping members such as the thrust rods 5 to provide the equal clamping pressure on the sealing means 3.

In the present invention, as illustrated in FIG. 3, the door assembly comprises the door member 1', the frame member 2 with electrical contact sealing means 3 disposed therebetween. The door member 1' is mounted on the casing 2 by means of hinges 6' which as illustrated in FIG. 3 are of double pivotal type which are commercially available.

To provide a clamping force, magnets 8 are equally distributed around the periphery of the opening and as illustrated on the casing member 2 to apply a force to the edge of the door member 1' or to an area adjacent thereto. The magnets 8 are distributed in a manner to apply a clamping force to all edges of the door around the periphery of the opening in the casing member 2 to pull the door against the sealing means 3 to insure a faultless and gapless electrical connection between the casing member 2 and an inner surface 4' of the door member 1'. The force of the magnets 8 is of a high magnitude so that misalignments between the door 1' and the casing member 2 are corrected by twisting the door 1' which as illustrated is substantially thinner and less rigid than the door of the previously known prior art devices. The magnetic force of the magnets 8 has a high magnitude such that the door 1' cannot be opened by hand using a handle 9 provided thereon without first reducing the magnetic force. The magnetic force is also of such a high magnitude that it prevents accidental opening of the door without performing the step of deenergizing or changing the magnetic force clamping the door 1' against the electrical sealing means 3.

In one embodiment of the invention, the magnets 8 are electromagnets having conventional electrical circuits. To open the door, a switch (not illustrated) is provided to deenergize the electrical circuit of the electromagnets to allow the opening of the door. It is preferable that the switch is disposed on the outside of the shielded space and that mechanical linkages such as a plastic rod movable in a shielded tube actuates the switch from the inside of the shielded room or enclosure.

As illustrated in FIG. 5, another door assembly of the present invention is illustrated. Preferably the change is that the magnets 8' which are preferably electromagnets have a larger surface area for providing the magnetic force to draw a door member (not illustrated) tightly against the leaf-type contact springs of the electrical connecting means 3.

Another embodiment of the present invention utilizes permanent magnets such as the magnet 12 in FIG. 6 which are disposed on either the casing member or door member around the periphery of the door opening. The permanent magnets 12 have sufficient force to prevent the accidental opening of the door 1' or the opening of the door 1' without first decreasing their magnetic force.

In an embodiment of the invention, the permanent magnets are mounted in a plastic member or sheet 14 and have pole pieces 13 of a magnetic material such as soft iron associated with each of the poles of the magnets and carried in a nonmagnetic plastic member or sheet 15. Members 14 and 15 are mounted on either the casing member 2 or the door member 1' and are relatively movable to each other so that if the member 14 supporting the permanent magnets 12 is shifted in the direction of the arrow of FIG. 6, the poles of the magnets 12 will be shifted from their pole pieces 13 to an area of the nonmagnetic plastic material 15 to decrease the magnetic force applied for holding the door member in the clamped position on the casing member 2. In a similar manner, the plastic or non-magnetic material of the sheet 14 supporting the permanent magnets 12 can be rigidly mounted to the casing member or the door member and the non-magnetic plastic sheet 15 supporting the pole pieces 13 moved with respect to the magnets 12.

In another embodiment, two groups of magnets 12 each carried in a nonmagnetic support sheet 14 are mounted on both the casing member and the door member with the poles of the magnets 12 arranged with the North pole of one group coacting with the South pole of the other group to be in an attracting condition. By relatively moving the two groups of magnets, as illustrated in FIG. 7 so that like poles are in alignment with like poles, the magnets are opposing each other enabling opening or unclamping of the door. Either group of magnets can be shifted to enable opening of the door from either the inside or the outside of the enclosure. Preferably, a thin foil 7' of non-magnetic material such as copper is sandwiched between the groups of magnets.

Preferably, pole pieces such as 13 carried in a nonmagnetic support sheet or member 15 are utilized with the two groups of the magnets 12 as illustrated in FIG. 6. The pole pieces 13 can be immovably attached to the casing member and the door member with a thin nonmagnetic foil 7' disposed therebetween. Either of the groups of magnets 12 are movable to shift the magnets 12 from the position for clamping as illustrated in FIG. 6 to a non-clamping position as illustrated in FIG. 7. Another variation of utilizing the two groups of magnets as illustrated in FIG. 6 is the permanently mounting of the nonmagnetic carrier 14 for the magnets 12 to both the door member and the casing member and slidably moving the nonmagnetic carriers 15 for the pole pieces 13 from a position illustrated with the pole pieces in alignment with the poles of the two groups of magnets to a position in which the nonmagnetic material of the member 15 are between the poles of the magnets 12 to reduce the effective magnetic force and enable the opening of the door.

The relative movement of the magnets with respect to the pole pieces or with respect to each other discussed hereinabove provides means for reducing the magnetic force applied to clamp the door member 1' onto the casing member 2. Thus, the means for unclamping can be obtained by shifting either the magnets relative to their pole pieces if just a single group of magnets and pole piece units are utilized or shifting a group of magnets relative to the second group of magnets if two groups of magnets are utilized, or finally by either shifting the pole pieces for the two groups of magnets relative to the magnets or shifting the two groups of magnets to change the relationship of the poles of the magnets from an attracting to a repelling alignment.

Although various minor modifications might be suggested by those versed in the art, it should be understood that I wish to employ within the scope of the patent warranted hereon all such embodiments as reasonably and properly come within the scope of my contribution to the art.

Claims

I claim as my invention:

1. In a door assembly for use in an enclosure such as a room which has means to provide a tight shielding for a high frequency emission, said door assembly having a casing member composed of portions arranged to define a door opening, a door member mounted on the casing member for movement between a first position closing the door opening and a second position enabling access through the door opening, sealing means disposed between the members around the opening to provide an electrical connection therebetween when the door is in the first position, and magnets distributed around the opening to pull the door member against the casing member to insure an electrical connection between the sealing means and the members the improvement comprising the sealing means being self-cleaning contact springs separated and spaced from the magnets so that the magnetic force of the magnets is free from interference from the material of the sealing means, and the door member being a thin and twistable structure so that the magnets pull the door member against the casing member to apply a clamping force to the contact springs to insure a shielding connection free of gaps and with a minimum transitional electrical resistance therebetween.

2. In a door assembly according to claim 1, which includes means for changing the magnetic forces clamping the door member against the casing member to enable moving the door from the first to the second position.

3. In a door assembly according to claim 2, wherein the magnets are electromagnets.

4. In a door assembly according to claim 2, wherein the magnets are permanent magnets, with a pole piece associated with each of the permanent magnets, and the means for changing the magnetic force includes means for relatively moving the magnets and their respective pole pieces into and out of alignment.

5. In a door assembly according to claim 2, wherein the magnets are permanent magnets arranged in two groups with the one group mounted on the door member and the other group mounted on the casing member, said groups of magnets being arranged with the magnetic poles in an attracting alignment with pole pieces disposed between the poles of the two groups of magnets, and said means for changing the magnetic force including means for relatively shifting the pole pieces from a position in alignment with the poles of the two groups of magnets to a position out of alignment therewith to change the magnetic forces therebetween.

6. In a door assembly according to claim 5 further including a non-magnetic sheet metal foil disposed between the pole pieces and one of the groups of magnets.

7. In a door assembly according to claim 2, wherein the magnets are arranged in two groups of permanent magnets with one group being mounted on the casing member and the other group being mounted on the door member, said means for changing the magnetic force comprising means to move one group of magnets relative to the other group to shift the poles of the magnets between attracting and repelling relationship.

8. In a door assembly according to claim 7 which includes a non-magnetic sheet of metal foil disposed between the two groups of magnets.

9. In a door assembly according to claim 7, which further includes pole pieces for each of the poles of the two groups of magnets, said pole pieces being fixedly mounted on one of the members to intensify the magnetic force between the two groups of permanent magnets.

10. In a door assembly according to claim 9, wherein a non-magnetic sheet metal foil is disposed between one group of magnet and the pole pieces.

11. In a door assembly according to claim 7, which further include a set of pole pieces immovably attached on each of the members between the groups of permanent magnets, and a non-magnetic foil disposed between the sets of pole pieces.