US2793245A - Radio shielded enclosures - Google Patents

Description

May '21, 1957 Filed Jan. 21, 1953 w. M. DUNN 2,793,245

RADIO SfiIELDEiD ENCLOSURES 2 Sheets-Sheet l INVENTOR. 1 WILLIAM M.-DUNN ATTORNEY.

May 21, 1957 w. M. DUNN 2,793,245

7 RADIO SHIELDED ENCLOSURES "Filed Jan. 21, 1953 2 Sheets-Sheet 2 WILLIAM M. DUNN ATTORNEY.

ited States Patent RADIO SHIELDED ENCLOSURES William M. Dunn, Philadelphia, Pa., assignor to Ace Engineering & Machine Co., Inc., Philadelphia, Pa., a corporation of Pennsylvania Application January 21, 1953, Serial No. 332,349

Claims. (Cl. 174-35) This invention relates to radio shielded enclosures and it relates more particularly to such enclosures made of separable panels which may be shipped in knocked down form, and secured to each other at the desired locations to provide enclosures, the interior of which will be shielded against stray radio waves, and in which testing of various electrical instruments may be done without interference from such waves which otherwise would seriously affect the accuracy of the measurements and the success of the tests. Shielded enclosures of the character aforesaid are used in laboratories and in other places where various types of tests are performed such, for example, as radio interference measurements, radio frequency calibrations, radio inspection tests, testing equipment for measuring minute voltages and testing various other devices and appliances. The purpose of such enclosures is to intercept and dissipate stray radio waves which would otherwise be the cause of serious and annoying disturbances.

Heretofore, considerable difliculty has been experienced, in the construction of such radio shielded enclosures, in maintaining the proper electrical connections between the screening sheets of the various panels, and in preventing the bolts used for securing the panels to each other from acting as antennae which pick up and transmit undesired radio waves to and from the interior of 'the enclosure.

The principal object of the present invention is to provide a novel form of radio shielded enclosure made of separate screening panels adapted to be assembled and bolted together at the desired locations.

A further object of the invention is to provide an e11- closure of the character aforesaid which will be relatively inexpensive yet quite efficient for its intended purpose.

A further object of the invention is to pnovide an enclosure of the character aforesaid in which any possibility of the connecting bolts acting as antennae will be eliminated without undue complication of the structure.

A further object of the invention is to provide an enclosure of the character aforesaid in which proper electrical connection of the shielding screens or plates of the various parts will be effected inexpensively yet effectively.

The nature and characteristic features of the present invention will be more readily understood from the following description, taken in connection with the accompanying drawings forming a part hereof, in which:

Figure 1 is a perspective View of a radio shielded room embodying the main features of the present invention;

Fig. 2 is a fragmentary vertical sectional view of a portion of the structure illustrating the manner of securing the vertical wall panels to the floor shielding panels, the section being taken on the line 2-2 of Fig. 1;

Fig. 3 is a fragmentary vertical sectional view of a portion of the structure illustrating the manner of securing the top or ceiling panels to the sidewall panels, the section being taken on the line 33 of Fig. 1;

Fig. 4 is a fragmentary horizontal sectional view taken on the line 44 of Fig. 1 illustrating the manner of securing the. side panels to each other at intermediate points;

Fig. 5 is a horizontal sectional view, taken on the line 5-5 of Fig. 1, illustrating the manner of securing the door jam to the adjacent panels and for establishing the necessary electrical connection of the metallic door parts when the door is closed; and

Fig. 6 is a perspective view of certain of the parts shown in separate-d relationship preparatory to the assembly thereof.

It should, of course, be understood that the description and drawings herein are illustrative merely and that various modifications and-changes may be made in the structure disclosed without departing from the spirit of the invention.

Referring to the drawings, in the particular embodiment of the invention therein shown, the sidewalls of the enclosure are made up of a series of vertical screened panels secured to each other in a manner to be presently explained.

Likewise, the ceiling is made up of a series of horizontally disposed screened panels resting on and secured, in.a manner to be presently explained, to the panels which make up the sidewalls.

Also, the floor is made up of a series of screened panels which are placed on the primary floor 10 of the building in which. the shielded enclosure is to be erected. The screened floor panels have superposed thereon a series of panels 11 preferably made of plywood which rest upon the screened floor panels and provide the floor proper of the enclosure.

Each of the screened panels, whether the same is used for the sidewalls, ceiling or the screening floor panels, consists primarily of a rectangular frame work comprising side strips 12, running lengthwise of the panels, connected at their ends by strips 13, running transversely of the panels, and intermediate strips 14, also running transversely of the panels.

All the strips 12, 13 and 14, above described, are preferably rectangular in cross-section with the exception of certain of the strips, 12 or 13*, as the case may be, which are to be joined to the others of adjoining panels at the vertical corners of the sidewalls, around the horizontal edges of the ceiling, and around the outer edges of the floor at which places one of the abutting strips is recessed, as at 15, to receive the end or edge of the abutting panel.

The frame work of each of the panels, in each instance, is provided on :one face thereof with screening material 16, which preferably consists of woven wire cloth of relatively fine mesh, although sheet material may in some instances be used, for preventing the passage of radio waves to the interior of the enclosure.

The screening material 16 is carried around outer edges of the strips at the sides and ends of the respective panels, and into and across the recesses 15 where the same are employed.

The respective panels are secured to each other by means of bolts 17, the threaded ends of which engage complementally threaded pressure plates 18. Somewhat similar pressure plates 19 are also employed under the heads of the bolts 17, but these pressure plates 19 are not threaded as are the plates 18 used at the threaded ends of the bolts.

The bolts 17 employed for securing the side strips 12 of the panels to each other, as shown more particularly in Pig. 2 of the drawings, extend through said strips on the outside of the screening material 16 as shown.

Likewise, the bolts 17, which are used at the corner edges, that is to say, where the top horizontal strips of the sidewall panels join the marginal edge strips of the ceiling, and where the vertical edge strips of the end panel of one sidewall is joined to the vertical edge strip of the end panel of the adjacent sidewall, as shown in detail in Fig. of the drawing, are located, in each instance, outside of the respective planes of the main screening cloth on the inner faces of the various panels. As hereinbefore'pointed out, considerable difficulty has been experienced in structures of this character to insure the proper electrical connections between the screening material of the various panels, which is essential for the proper prevention of the passage and reradiation of radio waves, and in many instances it was necessary to resort to soldering which was objectionable by reason of the annoyance and difficulties encountered in soldering done at the place of erection, but this difficulty has been effectually overcome in the present structure by the tension of the bolts causing the abutting surfaces of the screen cloth 16 which is carried around on the outside of each of the members at the sides and ends of the panels, and also in the recesses 15 in certain of the members of the panel frame, to contact each other efficiently.

It is also essential that the bolt members, even where the same are on the outside of the screening cloth 16, be in electrical connection therewith, and this is insured by the use of the flanged bushings 20, shown more particularly in perspective in Fig. 6 of the drawings. These bushings 20 are forced through the screen cloth and into the holes provided for the passage of the fastening bolts by means of a suitable punch or mandrel (not shown), and when thus mounted, these bushings 20 not only serve to prevent fraying of the screen cloth at the places where the bolts pass through the strips of the panel frames and other parts, but will also serve to prevent the bolts from acting as antennae to carry radio waves into the interior of the enclosure.

However, in the erection of structures of this character, it is advisable thatthe screening material of the screening panels of the floor structure be so disposed that the screening material 16 is on the bottom surface adjacent the upper surface of the primary floor 10 of the building in which the radio shielded enclosure is erected, as when so disposed said screening material is better protected against damage and wear.

In this instance, the screening material 16 is carried entirely around the end and edge strips of the screening floor panels, and one of the bushings 20 is also employed at the inner or threaded end of the bolt (see Fig. 2), whereby said bolts will be prevented from serving as antennae carrying any undesired waves into the enclosure notwithstanding said bolts extend entirely through from the outside to the inside of the screening material.

The fioor proper is provided by the use of plywood panels 11 disposed over the bottom screening panels of the structure as indicated in Fig. 2 of the drawings.

The door structure is shown in perspective in Fig. l, and in detail, in horizontal section, in Fig. 5 of the drawings. At the place where the door is provided, in lieu of a screening panel at that point there are provided side stiles 30 secured to the adjacent panels by bolts 17, the inner ends of which are threaded into pressure plates 18 which are, in this instance, located in suitable recesses 31 provided in the members 30 at the places where the bolts 17 are located.

The side stiles 30 as well as the top and bottom members of the door frame are preferably covered by sheet metal 32 which is pressed into good electrical contact with the screening material of the adjacent panels by the tension of the bolts 17.

The door proper comprises a suitable frame work provided on one face thereof, with screening cloth 16 which may be disposed on either the inner or outer face, as preferred, and, here again, sheet metal may be used in lieu of the screening cloth if desired.

The members 33 of the frame work of the door proper are at least partially encased in sheet metal 34, extending over the screening cloth 16, around the outer edge of the frame work of the door and partially on the inner face of the frame work of the door. The sheet metal 34 may be secured on the inner face by means of metallic strips 35 which are secured to the frame work of the door by screws 36, and likewise, the sheet metal 3 3- may be secured on the outer face of the door frame by metal strips 37 and screws 38. The strips 37 are preferably of sufficient width to overlap the opening between the edge of the door and the adjacent door frame member 30.

The frame members 33 of the door proper are also each provided with contact strips 39 and 40 respectively secured to the door by having portions thereof extending under the strips 35 and 37. These contact strips 39 and 40 are adapted to contact with the metallic casing 32 which partially surrounds the door frame members 30, and thereby establish an electrical connection between said casing 32 and the metal parts of the door proper.

The use of the metallic strips 39 and 49 in this manner will effectively prevent the passage of any radio waves through the crevices or openings which extend around the outer edges of the'door.

By the foregoing arrangement there is provided a radio shielded enclosure of the knock down type which may be quickly assembled at the desired place and which is so constructed and arranged as to effectively prevent the passage of stray radio waves to the interior thereof, and which is also so constructed and arranged that none of the parts thereof will act as antenna to pick up and transmit undesired radio waves from the exterior to the interior of the structure.

Furthermore, the device is so constructed and arranged that thesame may be readily dismantled and moved from place to place without loss of any of the protective properties thereof. The use of the bushings 20 will also serve to prevent fraying and displacement of the screening material when the bolts are removed for any purpose.

I claim;

1. In a radio shielded enclosure including a plurality of separately constructed panel frames each including lengthwise extending side strips and transversely extending end strips, said side strips and end strips constituting marginal members, said panel frames each having radio wave screening material on the inner face thereof, means for securing the panels to each other and for electrically connecting the screening material of panels adjacent each other comprising the provision of an extending portion of the screening material for each panel on the portions thereof abutting the adjacent panels, bolts extending through openings in the marginal members of said panels and metallic bushings engaging said screening material and extending into the holes through which said bolts extend, said bushings each having a flanged portion extending over a portion of the screening material which it engages.

2. In a radio shielded enclosure comprising a plurality of separately constructed panel frames each including lengthwise extending side strips and transversely extending end strips, said side strips and end strips constituting marginal members, said panel frames each having radio wave screening material on the inner face thereof, means for securing the panels to each other and for electrically connecting the screening material of panels adjacent each other along corner edges of the enclosure comprising the provision at such locations of a recess in one of the marginal members of one of said panels into which a marginal portion of another of said panels extends, the screening material of each panel having such recess being continued into said recess, and the screening material of each of the other panels being continued around and over the abutting edge of said panel, bolts extending through openings in said marginal members, and metallic bushings engaging such screening material and extending into the holes through which said bolts extend, said bushings each having a flanged portion extending over a portion of the screening material which it engages.

3. In a radio shielded enclosure including a plurality of separately constructed panel frames each including lengthwise extending side strips and transversely extending end strips, said side strips and end strips constituting marginal members, said vertical wall panel frames each having radio wave screening material on the inner face thereof, and a plurality of similarly constructed panel frames forming part of the floor structure each having radio wave screening material on the lower face thereof, the means for securing the floor panels to the vertical wall panels and for electrically connecting the screening material of said panels to each other along the lower corner edges of the enclosure comprising the provision of a recess in the lower marginal member of each of said vertical wall panels into which a marginal portion of one of the floor panels extends, the screening material of each wall panel having such recess being continued into said recess, the screening material of the adjacent floor panel extending entirely around the marginal member thereof which is positioned within the recess of the wall panel, bolts extending through openings in said marginal members of the wall and floor panels, said bolts being in electrical connection with the portions of the screening material which extend around the marginal members of the floor panels, and metallic bushings engaging said screening material and extending into the holes through which said bolts extend, said bushings each having a flange portion extending over a portion of the screening material which it engages.

4. The shielded enclosure of claim 1 further characterized by a plurality of panel frames forming part of the floor structure each having radio wave screening material aifixed to said frame, and means for securing the floor panels to the vertical wall panels and for electrically connecting the screening material of said panels to each other along the lower corner portions of the enclosure, said means comprising the provision of screening material of the floor panels extending entirely around the marginal members thereof and engaging portions of the screening material of the vertical wall panels.

5. The shielded enclosure of claim 1 further characterized by floor panels secured to vertical wall panels and in which said bolts pass from outside the shielded enclosure to the inside thereof and are maintained in electrical contact with portions of the screening material which extend around the marginal members of said panels.

References Cited in the file of this patent UNITED STATES PATENTS 1,744,004 Hunt Jan. 14, 1930 1,967,591 Proctor July 24, 1934 2,221,105 Otto Nov. 12, 1940 2,405,987 Arnold Aug. 20, 1946 2,599,944 Salisbury June 12, 1952 OTHER REFERENCES Rand et al.: Modern Plastics, Sept. 1951, page 105. (Copy in Se. Library.)

Publication I, ARRL Report No. 5-48. Specification and Design Characteristics for ARRL Screen-Room Model 1A and 1B. Published by U. S. Naval Air Development Center at Johnsville, Pa. Aug. 11, 1947. 174-354.

Publication II, NRL Report 3908. Measuring the Shielding Efliciency of Screened Enclosures. Published by Naval Research Laboratory, Washington, D. C. Nov. 14, 1951. 20-2H.

Publication III, Blueprint No. E-l001 Screen Room, A. E. E. L. Cell Type, Semi-Portable, drawn March 26, 1948, U. S. Naval Air Development Station, Iohnsville, Pennsylvania, sheet 2 of 2 sheets. (Copy in Div. 69, 174-354.)

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