US1664541A - Tuned transformer - Google Patents

Description

' April 3, 1928. '1,664,541

G. H. COOPER TUNED TRANSFORMER Filed Aug. 5. 1927 Patented Apr. 3, 1928.

GEORGE H. COOPER, OF HARTFORD, CONNECTICUT.

y TUNED TRANSFORMER.

Application filed August 3, 1927. Serial No. 210,354.

This invention relates to those transformers which are provided for amplifying electric signal waves such, for instance, as are used in radio receiving sets. In order to obtain the desired effect it is common practice to wind the coils of the transformers with an approximate number of turns of wire and test to note the result and ythen add or subtract turns of wire until the required condition is obtained, or to place a fixed capacity or adjustable capacity across, and electrically connected with, one or both windings. This in commercial quantity production requires skill, consumes valuable time and adds expense.

The present conception provides a very simple method of making and tuning such transformers whereby they may be rapidly produced in large numbers and will be accurately and uniformly tuned and remain in the desired condition. A further advantage also is that the method of tuning according t0 this invention is so 'simple that it can be practiced by relatively unskilled persons.

This is attained by winding a definite pre'- determined number of turns of wire upon a spoolof vinsulation that has no metallic core, which turns are always the same and remain the same for transformers of the like frequency, and which will produce a slightly higher frequency than that ultimately de-` sired. The structure is then tuned down by insertingone or more' Very small strips of iron in an opening in the center of the spool to compensate for variations of inductance in'the windings and distributivev capacity' of the windings and their support. This element thus tuned is placedl in an insulating case and after the wire terminals are attached .to contact pins, or' suitable terminal devices, it is further tuned by folding one or .more very small strips of iron over the end and down the sides of the s 001. When finally tuned a cover is applic to the case and sealed air tight.

Fig. 1 ofthe acom anying drawings shows a side elevation of the transformer with the case c ut in section. Fi 2 shows a plan with the cover removed. 1g. 3 shows a section of the spool and coils. Fig. 4 shows on greatly enlarged scale one of the iron tuning strips that may be applied over the end and down the sides of the spool. Fig. 5.shows an iron tuning strip which may be inserted in the center of the spool.

The spool of the transformer illustrated is made of wood or other nonmetallic insulating composition, with a flange 1 at the top, a flange 2 at the bottom, and an intermediate iiangc 3 nearer thiI lower end than the upper end. The spool has a central bore 4. The primary wire 5 is wound in the narrow lower space of the .spool and the secondary -6 is wound in the wide upper space of the spool. n

In the manufacture of these transformers the wire, preferably single silk enamel wire, is wound on the spool with a definite predetermined number of turns, vand that number of turns is adhered to for all transformers of the same frequency. In practice the number of turns is such as to produce a slightly higher ircquency than is ultimately desired. The element thus produced is then tuned down tn a desired frequency by inserting into the central bore of the spool one or more thin narrow strips of iron 7 which will compensate for any variation of frequency resulting from the windings. The strip of strips placed in the bore and which preferably extend the full length of the spool may be retained in placeby a drop of wax 8. This element is then fastened in a case 9, preferably cylindrical, of insulating material, and the wire terminals connected with the contact terminals 1() that extend through the case. When the element thus tuned to compensate for variations in the windings and spool capacity is in the case one or more thin narrow-strips of iron 11 bent to extend over the end and down the sides may be applied to the spool. A strip of paper 12 is preferably placed under this exterior strip to insure insulation. Drops of wax 13 may be used to hold the ends o this strip in fixed position. This exterior strip bent over the end and down the sides of the spool further tunes the element and may be applied after the element is inserted in the case so as to take care of anfy irregularity incident to capacity effect o the case or the retaining wax. The exterior strip also tends to shield the windings from outside interference. The strip may, if desired, be omitted from the bore, but if vomitted the element cannot be tuned as critically as by its use.

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After the activ element has been placed in v the case a cover 14 is sealed u on the top so that the closure will be air tig t.

With the construction illustrated there is no substantial iron core to absorb ener and create disturbing yiuluens. The simple tuning strips, which are very inexpensive,

, can be quiclriy applied or removed to obtain the desired frequency Without disturbing the windings which once made need not loe altered. This in commercial quantity manufacture is oi great advantage. By making and tuning the transformers in the manner above described large numbers can be turned out so that they will be uniform and will accurately keep tuned to the frequency for which they are rated, although of course, the method of tuning set forth may be made use of by relatively unskilled persons build-vr ing transformers in small quantities.

The invent-ion claimed is:

l. rllhe method of producing a tuned transormer which consists in Winding' primary and secondary coils of predetermined deii nite numbers oi? turns upon a. spool of insulation and tuning the same by folding a thin narrow strip or strips of iron over the end and down the sides of said spool.

2. The method of producir-ig a tuned transl former which consists in Winding primary and secondary coils ofi predetermined denite numbers of turns upon a spool of insulation and tuning the same by inserting a thin,y

` GERGE H. CQPER.

#EERTMQATE @il SRREGHN.

raam ne.. sai.

Granted April 14.3.12??g te seeker a. eeerer..

lt 'ie hereby eeriiie tha error appears iii the printed specificatie@ of @be above numbered paient requriagg corre-mien for thepwor fpreduee" read "rede-ee" be read with this eerreetien therein the ease in the Patent i'iee.,

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(Seal) E M. 3. Moore., Acting Commissioner of Patents.

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