US1696411A - Shielding for radio apparatus - Google Patents

Description

A. C. PECK SHIELDING FOR RADIO APPARATUS Dec 25, 1928 Filed Sept. 9, 1927 Admlh. EL. fi

Patented Dec. 25,, 1928.

UNITED STATES Anonrn cnor'ron wax, or SANDUSKY, onro.

SHIELDING FOB RADIO APPARATUS.

Application filed September 9, 1927.- Serial No. 218,519.

The present invention relates to an improved shield construction primariLy intended for use in connection with radio receiving apparatus.

In ra-d1o receiving apparatus employing multiple stages of amplification at radio frequency, it is essential that the individual stages be so isolated as to prevent electromagnetic couplin between the units or stages, other than t rough their proper channels. With the usual method now employed for shieldin a solid metal sheet is used, and this form 0 shielding acts as a distributing agent with the result in interference bein nearly as great as if no shielding were use This solid metal sheet conductor when used as a shield in radio receiving circuits, adds a great amount of resistance to the receiver. as a whole, where the tuning inductances and condensers come in close contact to the shielding, and resulting in the capacityofv the receiver being reduced to a point where in some cases, an extra stage or unit of amplification is required to compensate for the losses so incurred. Currents generated at radiofre uency will penetrate any substance wit the exception of metal, and as certain metals have higher conductivity than others, the quantity of metal employed in the usual sheet metal shields, together with its properties as a conductor for high frequency current, will naturally determine the amount of resistance added to the receiver when using 'a metal shield. Whenusing a solid sheet metal conductor for shielding purposes, it is necessary to use a fairly thick sheet in order to'oifset the tendency of the sheet to warp or buckle due to atmospher c changes, and which buckling or distortion of the sheet causes capacity changes in the a paratus or possible short circuit due to the shielding contacting with the circuit, andboth of which woul tend to impair that over all efliciency of the receiving apparatus It is therefore a primary object of the resent invention to provide'an improved s reld for radio apparatus embodying the operating characteristics of the solid metalshield withoutthe inherent losses 'due to the.employ ment' of" such solid sheet metal conductors.

A further object of theinvention is to provide a novel and improved shield for radio a paratus which may, be employed for either-e lminating interference due to exterin which drawing:

nal sources or as means to prevent interstage coupling between radio frequency units other than through their proper connecting channels.

A further object of the invention is to provide a flexible shield for radio apparatus whlch may be employed as a lining for the panels and cabinets that house the apparatus, in a manner whereby the signal to be received mayl only pass to the receiving circult throng the proper antenna binding post.

Other objects and advantages of the invention will be apparent during the course of the following detailed description, taken in connection with the accompan ing draw mg forming a part of this speei cation and Figural is an enlarged fragmentary plan v1ew of the improved shield showing cer tain sections thereof removed and others broken away for illustrating the specific detail of construction.

Figure 2 is an enlarged fragmentary section through a section of the shield.

Figure 3 is an enlarged longitudinal section through one of the conductor leads forming'a part of the'shield.

Referring to thedrawin in detail, and whereinsimilar reference 0 racters designate cor-responding parts t roughout the several views, the letter A may desi ate as a whole, the improved shield which embodies a supporting base B, a series of conductor leads C supported by the base'B, a contact base or coating D afiixed to the base B as by a binder E, and F mounting means for securing the shield in adjusted relation for shielding purposes.

The base B is of a flexible nature and 'preferably consists of a 'sheet of woven fabric'such as muslin of the like wove in the usual' manner to form warp and woof threads5 and6 respectively, and the weave of the fabric is*preferably like that illustrated. in Figure 1 of the drawing. The fabric may of course'be of either close or coarse'weave for either causing the adjacent threads; 5 or 6 to be either contacting one with the other or spaced a suitable dis .tance so that relatively small openings are provided between the crossed" threads.

While the sheet like supporting base B has been shown as being 0 fabric, the same A g A I .the same preferably consist of strands of tinselled wire embodying a carrier thread 7 about which is spirally Wound a substantially fiat copper'strip 8 which may either be wound with ends of adjacent convolutions in contacting engagement or slightly spaced as clearly illustrated in Figure 3. These conductor leads C are preferably woven directly into the fabric supporting base B during weavii'ig of the fabric so that adjacent runs of the leads are suitably spaced by the warp and weft threads 5 and 6 respectively so that the leads form a substantially net like construction with the leads contacting one with another at their traversing points. Thus it will be seen that the eonductor leads form an open work construction intended to be supported by the fabric -B with the traversing leads in electrical contact one with another. Owing to the high electrical conductivity of copper, it is preferred that the conductor leads be so formed for reducing the absorption effect of the shield.

As in usual practice, the shield A when associated with the radio receiving set will be at a ground potential by connecting the net like construction of the conductor leads directly to a ground connection through a suitable binding post provided on the receiving a partus.

Re erring now to the contact face or coating D, the same is formed of metal frag ments preferably aluminum filings. These metal fragments are intended to be afiixed in a mass to one side of the fabric base B as by means of the binder E, the binder serving both as means for retaining the metal fragments in a compact arrangement and also as means for securing the coating to the supporting base. The metal fragments forming the coating D are so applied to the supporting base that the fragments are in electrical contact with one another and with certain of the in electrical contact with the conductor leads C as is clearly illustrated in Figure 2. Thus it will be seen that the metal fragments of the coating D may be effectively grounded through the conductor leads G. Since aluminum is of low electrical conductivity in comparison to other metals such as brass and copper, it will be seen that when the shielding is placed in relatively .close contact with apparatus of the receiving circuits, that loss through induction to ground will be at a minimum. I

The binder E may in the form of a gum varnish, or of a material bearing adhe sive characteristics and. bein of a nature to exclude moisture from the fa ric base B and metal fragments yet allow for the shield structure to be of a flexible nature owing to the elasticity of the binder.

It may here be well to state that the shielding A as a finished product, will resemble somewhat emery cloth inflexibility, and the metal fragments forming the contact face or coating may be applied to the supporting base much in the same manner as are the emery fragments applied to the cloth in manufacture of emery cloth.

It will be observed that the coating D of metal fragments, forms a sheet like covering for one face of the supporting base and forms a substantially flat surfaced coating having low conductivity and being in elec- 'trical contact with the conductor leads 0 which are intended to be connected with a suitable ground terminal.

As to the mounting means F, the same in the example shown is in the form of an adhesive such as gum arabic applied to the opposite surface of the supporting base B from that at which the coating D is formed. Thus it will be seen that when applying the shield for shielding purposes, the adhesive may be dampened or softened and then the shield applied permanently to the panels and sides of the cabinet of the radio apparatus. WVhen so applying the shield, the same will form a metal barrier which entirely surrounds the receiving circuits, and by connecting the leads G with a suitable ground connection, the shield will be maintained at a ground potential. WVhen so enclosing the receiving circuit apparatus, it will be seen that the apparatus will be effectively shielded against interfering electrostatic charges and electromagnetic waves, and that the only'path through which a signal may be received and passed through the various tuning circuits, will be from the antenna directly to the antenna binding post of the receiver. 7

The shield may of course be used in a receiving apparatus to isolate the individual units or circuits with a minimum resistance and distr-ibutin capacity.

\Vhen so app ying the shielding as b the adhesive F to the interior surface of a ousing for radio receiving apparatus, it will be seen that the shield becomes permanently fixed and will not be affected by varying climatic conditions. A shielding such asdisclosed may be very easily and quickly applied, since the same is capable of being readily cut by a knife or pair of shears to the exact size of the surfaces being covered by the shieldin which the shielding is made may of coursebe of any requisite dimension in accordance with the requirements of the trade.

From the foregoing description it will be apparent that a novel and improved shield for use in connection with radio receiving A size of the piece ofto' absorption and interference due to dis- .groundin tributing effects, will be reduced to a miniwith said conductor leads throughout the apparatus has been provided which is of a flexible sheet like supporting base, a flexible flexible sheetlike nature such as to allow grounding conductor carried by the base, for ready and easy installation of the shieldand a facing of fra ing, andwhich shield embodies novel hav-in electrical con uctivity, afiixed to features of construction whereby losses due said ase in electrical contact with the flexed wit the supporting base. mum. 8. In a shield of the class described,-a Various chan es in the shape, size and. flexible sheet like supporting base,a flexible s ecific materia defined may be ,made to net like screen having electrical conductivdescribed, without departing from th of the invention or the scope of the in claims.

e spirit ing aflixed to one face of the supporting fol owbase embodying metal fragments having I electrical contact'with said screening. claim: 9. In a shield of the class described, a 1. In a shield of the class described, a flexible sheet like supporting base, a flexible entitious material conductor and capable of being t e form of the invention herein shown and ity, carried by said base, and a flexible coatsheet like supporting base, a facing of fragnet like screening having highelectrical mcntitious material having electrical conconductivity, carried-by said base, and a ductivity aflixed to said base, and a'groundflexible coating aflixed to one side of said ing conductor ca-rried' by the base and havbase embodying metal fragments of low ing electrical contact. with the facing-at electrical conductivity, said fragments conspaced points throughout the area thereof. tactingone with another and being in elec- 2. In a shield of the class, described, a trical contact with said screenin sheet like sup orting base, a not like screen- 10. In a shield ofthe class escribed, a ing having e ectrical conductivity, carried flexible, sheet like su porting base, a flexby said base, and a facing of fragmentitious ible net like screen having electrical conmaterial having electrical conductivity, afductivity, carried by said base, a flexible fixed to said base and in electrical contact coating afiixed to one face of the sheet like.

with the strandsof screening. supporting base embodying metal frag- 3. In a shield of the class descrlbed, a ments having electrical conductivity and sheet like supporting base, a net like screenhaving electrical contact with said screens mg havm high electrical conductlvlty, caring, and an adhesive carried by the-opposite ried by sa1d,base,a-nd a facing 0f fr gmen face of the sheet like supporting base from tious material having low electrical. conducid coating. tivity, aflixed to said base and in electrical 11. In a shield of the class described, a contact with the strands of said screening. fabric sheet forming a supporti o b 4- In a ield o the Class E Q- it a ductor leads interwoven into the a ric sheet sheet l1ke su porting base, traversing conin spaced apart relation, anda flexlble coatductor leads aving electrical conductivity, ing aflix d to the supporting base embodysupported in spaced apart relation on the ing metal fra ents aving electrical conbase, and a facing of fragmentltious matem t with s i conductor leads at spaced said base and being" in electrical contact i b area of the facing. i fabric sheet forming a supporting base, conrial having electrical conductivity, aflixed to points throughout the areaof the support- 12. In a shield of the class described, a I

5. In a shield of the class describ a ductor leads interwoven 1n the fabric in Sheeblike pp g b a net like S IP- traversing relation and contacting one with ing of interwoven conductor leads having noth t th i traversing i t and a electrical conductivity, supported by the' facing of fragmentitious material having in electrical contact with the conductor lead of said screenin base, and afa ing f gm ll mateelectrical conductivity, affixed to one face rial having electrical conductivity, aflixed to of the fabric sheet in electrical contact with one face of the sheet like supporting base aid ccnductcrleads.

I fabric sheet embodying warp and weft .6. In a $1116]. of the class described, a threads, conductor leads "interwoven in sheet like supporting base, conductor leads spaced relation in .thefabrie in parallel rehaving electrlc'al conductivity, interwoven lation with both the warp and weft threads,

13. In a shield of the class described, a]

in traversing relation into the supporting a flexible coating aflix'ed to one face of the base with adjacent parallel leads spaced fabric embodying metal fragments having from one another, and. a facing of fragelectrical contact with said conductor leads,

. ing base in electrical contact with said contion of the shield for shielding purposes.

I ductor leads.

' I 14'. In a shield of the class described, a 7. In a shield of the class described, a fabric sheet forming a supporting base, conmentitious material having electrical 'conand an adhesiveaflixed to the opposite face 'ductivity aflixed toone face of the supportof the fabric'from said coating for applicaductor leads interwoven in the fabric emductor leads interwoven in the fabric sheet 10 bodying carrier threads having spirally embodying carrier threads and copper strips Wound thereon strips having electrical conspirally Wound about the carrier threads. ductivity, and a coating afiixed to one face and a coating atlixed to one face of the tab- 5 of the fabric embodying metal fragments ric embodying aluminum fragments being:

having electrical contact with the strips of in contact one with another and in electrical 15 said conductor leads. contact with the strips of said conductor 15. In a shield of the class described, a leads. I fabric sheet forming a supporting base, con- ADOLPH CROFTON PECK.

Images