US2751563A

US2751563A - Radio frequency transformer and coil form

Info

Publication number: US2751563A
Application number: US294618A
Authority: US
Inventors: Leslie A Willyard; Ingemar R V Taegtstroem
Original assignee: Hoffman Electronics Corp
Current assignee: Hoffman Electronics Corp
Priority date: 1952-06-20
Filing date: 1952-06-20
Publication date: 1956-06-19
Anticipated expiration: 1973-06-19

Description

June 19, A, WILLYARD ETAL RADIO FREQUENCY TRANSFORMER AND COIL. FORM Filed June 20, 1952 m I cull: 50 lg 58 Vl/l/l/l/lAIIIIIIII V/l/IYI/A Mar 56 INVENTOR$ BY WM ORNEY United States Patent RADIO FREQUENCY TRANSFORMER AND COIL FORM Leslie A. Willyard, Inglewood, and Ingemar R. V. Taegtstroem, Los Angeles, Calif.; said Taegtstroem now by change of name Ralph Textrom; assignors to Hoffman Electronics Corporation, Los Angeles, Calif., a corporation of California Application June 20, 1952, Serial No. 294,618

8 Claims. (Cl. 336-65) This invention relates to radio apparatus, and particularly to an improved coil form or transformer unit which has special advantages for high frequency applications.

A principal object of the invention is to provide a unit of this type which simplifies the manufacture of single and double wound radio frequency coils for accurate control of their electrical characteristics, and in which interchangeable parts are employed to reduce cost and simplify construction.

A further object of the invention is to provide a unit of the above type including improved means for maintaining in adjusted position a magnetic tuning slug or the like, so that the adjusted value of inductance will not vary during operation as a result of shocks, vibration and the like.

An additional object of the invention is to provide a coil form having arrangements whereby the electrical leads from its winding or windings may be accurately placed and maintained with'respect to other circuit components; this feature is especially important for operation at very or ultra high frequencies, where lead dress, or the proper positioning of the various conductors, may have considerable importance with relation to circuit tuning, efficiency and so on.

Still another object of the invention is to provide a structure having the above characteristics and which can be of very small size without unnecessary sacrifice of ruggedness; this feature, again, is of particular importance in connection with the higher radio frequencies, and especially so where the equipment as a whole is to be extremely small and compact, because the mere scaling down of conventional designs for larger size transformers and coils results either in a sacrifice of strength, or leads to manufacturing ditficulties.

The above and other objects and advantages of the invention will best be understood by referring to the following detailed specification of a preferred embodiment of the invention, and of a modification thereof, taken in connection with the appended drawings, in which:

Fig. 1 is a view in elevation of a radio frequency transformer embodying the invention, a part being broken away for clarity,

Fig. 2 is a vertical sectional view of the same structure,

Fig. 3 is an exploded isometric view of the major parts of the device of the preceding figures, a part being again broken away,

Fig. 4 is a plan View of the base member of the same embodiment, and

Fig. 5 is a fragmentary sectional view of a modified base member adapted for a single-winding coil.

Referring now to Figs. 1 to 4 of the drawings, there is shown a radio frequency transformer adapted for use in radio apparatus working for example in the ultra high frequency range of 240 megacycles, and which apparatus is of very compact form. Units of this type, and their related single winding inductances, may be used as interstage transformers, modulation transformers, chokes and for a variety of other purposes. In most applications, the inductance and capacitance values associated with the conductive leads from the coils may form an important part of the total circuit values, and it is hence essential that the disposition of these leads (and indeed of the turns forming the coils themselves) be not subject to uncontrolled variations, such as might occur inadvertently. Also, it is desirable that the adjustments of the tuning slug or core should remain as intended.

The unit illustrated in the drawings has these characteristics, and is formed practically entirely of molded parts which can be manufactured to close tolerances without excessive cost. The invention provides a minimum number of different molded components, from which the different required types of coils may be readily produced.

As shown in Figs. 1 to 3, the transformer coil form comprises as its main parts a body portion 10, a base member 12, a sleeve member 14 and a cap member 16. The upper portion of the main body portion 10 is of greater diameter than the remainder, and is designated in Fig. 3 by numeral 18, while the lower portion of smaller diameter is designated 20. Both portions are bored axially, and the bore in the lower portion 20 is sized to fit snugly upon the upwardly extending cylindrical boss 22 of the base member 12. As assembled, these interfitting parts are secured firmly together as by a small quantity of an adhesive for the particular material of which they are made. Preferably, these parts (and the other parts of the unit which are shown as insulating) are formed of suitable plastic having the desired electrical characteristics such as high insulating value and low dielectric loss.

The base member 12 is of generally disc-like configuration having the upstanding central boss as described. The upper surface of the body, as best shown in Fig. 4, has an annular portion 24 against which the lower edge of portion 20 seats when assembled. Surrounding this annular shoulder is an annular groove 28 into which extends the winding carried by the body portion of the form (see also Fig. 2), and a further annular area 26 which constitutes the seat for an outer winding sleeve 14. A plurality of slots 30 are cut into the under surface of the base 12, these providing passages through which the lower end of the conductor wound on body 20 may be brought out. The provision of a plurality of these grooves or slots 30 enables the use of the same form for different winding arrangements, such as windings having different fractional turns, and also enables the terminal lead to be maintained in a desired direction and position where it leaves the base.

The upper end of the conductor wound on the portion 20 is passed through an apertured lug 32 integral with the body member 10, it being understood that when the body and base are cemented together, the angular orientation of lug 32 with respect to the base may be positioned as required by the circuitry or chassis arrangements.

The cap member 16 may have an enlarged charnfered head portion as shown, and a cylindrical portion 34 extending downwardly therefrom, the whole having a threaded bore 36. As best shown in Fig. 2, the upper portion of the bore in body member 10 is similarly threaded, and the cylindrical portion 34 of the cap 16 is sized to fit loosely within the upper part 18 of said body member 16. A spring washer 46 surrounds the cylindrical portion 34 and urges these parts away from one another, so that when the threaded magnetic slug 48 is threaded into position as shown, the tension of spring washer 46 maintains a tight threaded fit for all adjust ments of the slug, and prevents casual disturbance of the adjustment. The under side of the head portion of cap 16 has a lug 38 engageable in one or another of a plurality of slots 40 in the head portion of body member 10 to prevent relative rotation of the cap and body member.

An apertured lug 50 is integral with the base member 12', andprovides an anchor for the lower end of" a conductor wound on the sleeve 14. This sleeve is also cemented in place in the base member in the same manner as is the main body portion or member 1'6, and since the sleeve may have any rotational position, the number of turns on this winding may be adjusted to the desired fraction. An apertured lug 62 integral with sleeve member 14 provides a top anchoring for the winding and lead therefrom.

Depending from the under side of base member 3.2 is a boss 54 which serves tomount the device upon a chassis plate or the like, as by passing through a suitable hole in such plate. A retaining ring. 56 (Fig. 2) is cemented onto the projecting end of this boss so as to clamp the assembly firmly in place. If required, as insulating washer 5d may be inserted between the base 1.2 and chassis to ensure insulation betweenv the winding on sleeve 14 and the chassis.

It will be seen from the above description that both the winding. 64 on body portion 11) and the winding on sleeve 14 can be arranged so that their respective leads arrive and depart from the transformer in fixed, accurately defined directions, and that the entire device will be relatively free item random efiects due to vibration, shock or other accidental causes. The relative positions of the two windings in the device are also accurately maintained.

In a practical commercial embodiment of the unit as actually manufactured, the over-all height of the unit is of the order of A of an inch, so that the drawings are actually considerably enlarged. Even in this small size, the parts have considerable and adequate strength and their design greatly simplifies winding and assembly.

in the modification shown in Fig. 5, which is adapted for a single winding, for example for use as a radio frequench choke, a slightly modified base member 66 is employed. When a single winding 64 is required, the diameter of the base can be reduced somewhat, and this embodiment uses a base member having an annular groove 58 to receive the end of the body member 16, and is equipped with an apertured anchoring lug 7 and fastener or

mounting elements

72, 74 in a manner quite similar to that already described above. The parts are assembled with cement or adhesive as before to provide a unitary structure.

While the invention has been described in connection with certain preferred embodiments, numerous minor changes and modifications may be made without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

l. A coil form comprising a base portion, a hollow body portion secured to said base portion, apertured lugs on both said portions, a hollow cap portion loosely received in said body portion for axial movement with respect to said body portion, said cap portion and said body portion being threaded internally on a common axis, a magnetic tuning slug threadedly received in said cap portion and said body portion, and resilient means between said cap portion and said body portion for urging said portions away from one another to clamp said tuning slug in position within said body portion.

2. The structure in accordance with claim 1, in which said base portion is slotted in a plurality of different directions, whereby awinding on said body portion may be brought out through said base portion in a desired direction.

3. The structure in accordance with claim 1, and a sleeve secured to said base portion and sized to define an annalar winding space between said sleeve and said body portion.

4. The structure in accordance with claim 3, and an apcrtured lug on said sleeve.

5'. The structure in accordance with claim 1, and cooperating formations on said body portion and said cap portion for retaining the same against relative rotation, while permitting limited. axial movement therebetween.

6. The structure in accordance with claim 1, in which said base portion has a boss. extending therefrom in one direction to receive said body portion, and a boss extending therefrom in the opposite direction for mounting said base portion upon a surface.

7. A coil form comprising a base, a body portion cemented to said base at one end thereof, a cap portion loosely received in said body portion at its opposite end, a magnetic tuning slug threadedly engaging both said portions, a spring between said portions for urging them axially relative to one another to clamp said slug in fixed position, and cooperating formations on said portions for locking. them against relative rotation.

8. A coil form in accordance with claim 7, including anapertured conductor-guiding lug extending outwardly from each of said base and said body portions.

References Cited in the file of this patent UNITED STATES PATENTS 609,144 Goddin -Aug. 16, 1898 2,298,275 Bohren Oct. 13, 1942 2,375,309 McCoy May 8, 1945 2,462,822 Wood Feb. 22, 1949 2,464,218 Di Vita ct al. Mar. 15, 1949 2,469,137 Strong May 3, 1949 2,581,165 Bonanno Jan. 1, 1952 FOREIGN PATENTS 209,896 Switzerland Aug. 1', 1940 780,543 France Feb. 4, 1935