US2981786A - Electrical shield - Google Patents

Description

Apnl 25, 1961 D. w. BEENEY ELECTRICAL SHIELD Filed Dec. 5, 1957 INVENTOR DOA/ALB W. BEE/V5) Mam ATTORNEY States Unite ELECTRICAL SHIELD Filed Dec. 5, 1957, Scr. No. 7 09,835

- 1 Claim. (Cl. 174-35) This invention relates to shields for electrical devices such as electron discharge tubes.

Tube shield structures of the type which have been used in the past generally comprise a metal cylinder formed with springs or nubbins which contact the tube walls to provide heat conduction therefrom and to minimize vibration. An electrical ground strip connector is usually provided on the shield in addition to means for attaching the shield to the tube sockets. Structures of this type are expensive to make, they are poor heat conductors due to their limited contact with the tube envelope, and they very often require specially fabricated means mounted on the socket for holding them in position.

Accordingly, it is an object of the invention to reduce the aforementioned disadvantages and to improve electrical device shielding.

A further object is to increase the heat conduction away from an electrical device.

A still further object is the provision of means for easily mounting and dismounting self-supporting shields.

Another object is to reduce the need for extraneous shield supports or holding devices.

The foregoing objects are achieved in one aspect of the invention by the provision of an electrical shield comprising a strip of flexible metal formed in a spiral to provide a tubular body portion. A major portion of the inside surface of the spiral turns abuts the electrical device housing or envelope to provide good electrical shielding and excellent heat conduction and radiation. In addition, due to the spiral structure, the flexible turns tend to maintain a smaller diameter than the diameter of the electrical device. Such a structure provides an inward force or bias which acts in conjunction with the surface friction to maintain the shield upon the device without need for extraneous holding means. This feature is important since many electrical devices are presently mounted horizontally or in vertically inverted positions above other electrical devices and circuits. It is necessary that the shields for such devices be securely held in position or secured to the socket so that the shield can not fall on the circuit or damage the electrical devices mounted at a lower position.

For a better understanding of the invention, reference is made to the following description taken in conjunction with the accompanying drawings in which:

Fig. l is a perspective view of a shield structure;

Fig. 2 shows a shield structure of the type shown in Fig. 1 mounted upon an electrical device such as an electron discharge tube;

Fig. 3 is a partial view in cross section of another shield structure embodiment;

Fig. 4 is a partial view in cross section of still another shield structure embodiment; and

Fig. 5 is a partial view in cross section of still another shield structure embodiment.

Referring to the drawings, an electrical shield 11 is shown in conjunction with an electron discharge tube 13 having an envelope 15 and connector pins 17. The shield illustrated in Figs. 1 and 2 comprise a strip 19 of flexible metal such as steel or aluminum wound as a spiral to provide a tubular body portion. The opposed edges of strip 19 abut one another on successive spiral turns so that the peripheral surface of the shield body is substantially continuous. The thickness and resiliency of the metal is suflicient to provide a body having enough strength to be self supporting. The non-flexed diameter of shield 11 is normally smaller than the diameter of tube 13. Therefore, when the shield is placed over the tube, the inward bias exerted by the spiral turns and the surface friction tends to hold the shield on envelope 15. To mount or remove shield 11 from tube 13, it is only necessary to grasp the bottom turn and twist the upper turns in a counter-clockwise direc tion, see Figs. 1 and 2. This movement increases the diameter of the shield and thereby provides easy removal or replacement.

The ground connection for shield 11 may be any type of electrical conductor formed to contact one or more of the spiral turns.

Another embodiment of shield 11 is shown in Fig. 3. In this structure, the strip 19 is formed on its opposite edges with complementary flanges 21 and 23 which mesh or interlock with one another. For instance, flange 21 on one edge of strip 19 located on a given spiral turn meshes with the opposed complementary flange 23 located on the following spiral turn.

Fig. 4 shows another shield structure utilizing a spiral strip 19 having opposed complementary bias cut edges 25 and 27 and Fig. 5 illustrates a structure using rolled flanges 29 and 31 formed to interlock or mesh with one another. If desired, the edges of flanges 29 and 31 may be turned in opposite directions to provide clasping surfaces which interlock and prevent disengagement.

Shields for electrical devices of the type described herein may be produced economically and efliciently. Continuous strips of metal may be coiled to form a spiral tube which can then be cut to length as the material feeds from the spiraling operation.

Although several embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claim.

What is claimed is:

A shield adapted to flexibly engage an electrical device having a given diameter comprising a strip of flexible metal having oppositely disposed complementary bias cut edges, said strip being formed to provide a spiral having a plurality of turns forming a substantially continuous tubular body portion, said body portion having a non-flexed diameter less than the diameter of the electrical device, one of said bias cut edges on said strip located on a given spiral turn meshing with the opposed complementary bias cut edge located on the following spiral turn, said biased cut edges coacting to maintain a substantially continuous peripheral surface when said body portion is flexed to said given diameter.

References Cited in the file of this patent UNITED STATES PATENTS 378,769 Coas Feb. 28, 1888 670,748 Weddeler Mar. 26, 1901 2,086,152 Bedell July 6, 1937 2,258,508 Kerchner Oct. 7, 1941 2,497,963 Singer Feb. 21, 1950 2,501,284 Miller et a1 Mar. 21, 1950 2,706,611 Kimball Apr. 19, 1955 2,860,328 Langworthy Nov. 11, 1958

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