US2252919A

US2252919A - Multiwave variable resonator

Info

Publication number: US2252919A
Application number: US250238A
Authority: US
Inventors: Lewis D Eckard
Original assignee: Individual
Current assignee: Individual
Priority date: 1939-01-10
Filing date: 1939-01-10
Publication date: 1941-08-19
Anticipated expiration: 1958-08-19

Description

' Filed Jan. 10, 1959 v 2 Sheets-Sheet 1 HH I ' Was? 7 8 1941- L. D. ECKARD HULTIWAVE VARIABLE RESONATOR Filed Jan. 10, 1939- 2 Sheets-Sheet 2 has the most eflicient ratio of Patented Aug. 19, 1941 UNITED STATES PATENT OFFICE 2,252,919 MULTIWAVE vamanna ansom'roa Lewis D. Eckard, Washington, D. 0. Application January 10, 1939, Serial No. 250,238 6 Claims. (Cl. 171-119) The present invention relates to the combination of a new and useful multi-coil transformer with a single tuning condenser to provide a multiwave variable resonator.

It is customary in the manufacture of all wave radio sets today to utilize three or four small coils.

-tion, like numerals or reference indicate similar parts in the several views and wherein:

There are usually four antenna coils, four interstage or R. F. coils and four oscillator coils in the radio circuit. These all wave sets are equipped with the standard 350 mmfd. tuning condensers and suitable padding and trimming condensers with a capacity 15 to 30 mmfd. The use of small padding and trimming condensers to align the circuits 'in the radio set, or bring the various coils in each stage of tuning into a resonant condition, prevents the utilization of the minimum capacity of the tuning condenser. This results from the fact that no matter what capacity range the tuning condenser has the 15 mmid. or 30 mmfd. padding condenser always must be taken into account. 4

Another object is to pro de a radio set which has only one inductance coil per stage of tuning.

Another object is to provide an inductance coil for a radio set, either a transmitter or a receiver, which is adapted to expand or contract to vary the inductance.

Another object is to eliminate the padding or trimming condensers now used in all wave sets to align the circuits or bring about a resonant condition.

A further object is to provide an electrical circuit arrangement which utilizes the minimum capacity range of the tuning condenser.

Another object is to provide a radio set which gets greater wave band coverage per unit coil.

Still another object is to utilize in combination with the electrical circuit of a radio, a coil which diameter of coil to winding length of wire thereon.

Another object is to provide a more simplified and less expensive switching arrangement in an all wave radio set.

Another object is to provide a more simplified and less expensive wiring system for an allwave radio set.

Another object is to eliminate the paralleling andclose proximity of the radio frequency wires to the switching apparatus.

Other and further objects the invention will be apparent from the following detailed description and as more particularly pointed out in the claims.

and advantages of I trical circuit hookup Figure 1 is an elevation of one of the inductance coils, partly in section, in expanded formandembodying the principal features of the invention,

Figure 2 shows the inductance coil partly in section and in contracted form,

Figure 3 is an end view of the inductance coil,

Figure 4 is a diagrammatic sketch of the elecwhen the inductance coil is expanded,

Figure 5 is a diagrammatic sketch of the electrical circuit hookup when the inductance coil is contracted, and

Figure 6 is a diagrammatic sketch showing the electrical circuit hookup of the two end strands of ,the inductance coil when the inductance coil is in expanded and contracted form.

Referring now to the drawings and more particularly to Figures 1 and 2, the numeral Ill indicates generally a cylindrical coil or wire carrying member of light Celluloid, hard rubber or the like. The coil III has been spirally cut to provide a helical portion ll extending substantially throughout the length of the said coil Ill, and

which is of such a flexibility that it can expand or contract; A cable of wire I! is disposed at one end of the coil l0 and is wound spirally p n the helical portion II. The cable I! is composed of wires'of equal length and equal diameter, and comprises the primary windings of the coil and is shown as comprising two insulated wires of equal length and diameter and two turns on the flexible helical portion ll of the coil II. This invention is intended to cover any number of insulated wires in the primary windings and although it is preferred to have the wires in cable form it is not necessary.

V A cable of wire I3 is disposed upon the helical portion ll of the coil III at the other end thereof in spaced relation from the primary windings l2. These windings l3 constitute'the secondary windings oi the coil. As shown, the cable It comprises ten insulated wires of equal length 4 and diameter and ten turns on the flexible helical portion ll of the coil ll, but the number of wires. may be changed without departing from thescope of this invention.

A solid, uncut portion ll of the coil II is disposed outwardly oi. the prlmary'windings l2 and is centrally apertured and proportioned to threadedly engage the threaded end of the spindle I! which passes centrally through the coil In the drawings forming part of this applica- 5 II. A nut is threadedly cooperates with the tlally half the length of the coil.

2 assault threaded end of spindle it to move the portion M one way or the other along the said spindle. The spindle [5 does not move longitudinah ly in this operation. This selective movement slightly changes the inductance of the coil as it moves the wire turns in'cable form closer to or farther from one another, and is important in aligning up the circuits at the factory. Finasimich as there is one coil used per stage oi tuning, it is always necessary toadjust the var icus coils to obtain a condition oi resonance. llieretofore a padding or trimming condenser was used for this purpose. i'iiter the fine justment has been made the factory by suit ably changing the :inductc ce the coil to ob tain. complete resonance he not i may be sealed so that it may not be tampered with.

The spindle i5 is suitably anchored at the end carrying the portion. it. li'lliis the fillEEl stationary nd of the coil.

The spindle i5 is anchored at the other end thereof in the member il and passes centrally through another solid uncut portion of hard rubber material H! which is similar to the member M. Mounted on the circrunierential surface oi the cylindrical portion i l a plurality oi metal studs it, Ell; ill, til; llil, till; it, ti l; 25, 26, it; ill; till, fla l, ill, til", 32, 32'.

The studs Lil, ill" members for the are the contact secondary circuit, each ends. The free ends of the wires of both primary and secondary windings are preferably soldered to their respective brass studs and can extend centrally through the interior of the inductance coil so as to be out of the way. The studs can be molded into the plastic coil iii if it is desired to do so. The said studs are preferably small and recessed some-what so that a better connection can be obtained with the

contacts

34 and 35, hereinafter referred to in greater detail. a

A cylindrical insulated member 33 is disposed outwardly of and around the coil 'lll adjacent to the movable member I9 and extends substan- The member 33 is rigidly supported by the chassis in any suitable manner. A plurality of metallic spring bars or other conductor strips 34 are mounted on the inner surface of the member 33 spaced from the cable l3, and each conducting stop 34 contacts wire batting two pressed form, although a coil of other dimensions can be used. In its expanded form the coil has a length of approximately 3 inches.

Outwardly of the chassis disposed a cable drum 36 which is suitably supported by the said chassis and upon which is wound a light cable Ell which extends through the said chassis and longitudinally through the coil ill and around the pulley member 38 which is mounted on the member i i at the relatively fixed end of the coil ill. The cable after passing over the pulley $38 which is adapted to rotate extends longitudinally through the interior of coil ill and is suitably securely fillBCl to the member at the movable end of the coil ill. The ratio oi the diameter of the drum to the length of the cable erably such that a three-quarter turn of said drum Elli will completely expand or completely contract the coil ill to put the members M or in operative position.

it is to be understood that the drawings show only one coil which is adapted for one of tuning. As pointed out there are usually three or tour stages of tuning. For example, there were an antenna, radio frequency and an oscillator stage it would be necessary to have three coils similar to the one shown and described. These :ee coils will be suitably ganged together so that a turn on the drum. cable lit will simultaneously expand or compress the three coils, creating an all parallel or an all series circuit condition, as described. Lille three coils expand the same amount and ii there is a resonant condition when are their compressed term that resonant condition will be maintained as they expand through exactly the same distance upon one turn of the drum 35.

In case of interstage coils the secondary circult is in the grid ground circuit throughout, and

a pair of brass knobs or studs, e. g. 2|, 20'. The:

studs 2|, 2!, 22' 2 l', etc., on the member I! contact the spring strips 34 when the coil I0 is in a contracted or compressed form. This is best shown in Figure 2 when the primary windings are in series and the secondary windings are likewise in series. Figure 5 shows the electrical circuit when coil III is compressed.

A'plurality of pairs of metallic strips or rings 35 are mounted on the inner surface of the member 33 spaced from said metallic strips 34. The studs on the member I! contact the rings 35 when the coil I0 is in an expanded form as shown in Figure 1. The electrical hookup for this expanded coil condition is shown in the wiring sketch of Figure 4. In this position oi: coil [0 the primary windings secondary windings are likewise in parallel.

The 0011- I I has preferably a diameter 01' 1% inches and a. length of 1% inches in its comthe primary is in the plate circuit of the previous tube and 13' plate potential and is adaptable to any oscillator circuit.

Figures 4 and 5 more clearly show the wire connections diagrammatically. In Figure 4 the primary windings of the coil in is in the antennaground circuit. In the secondary winding there is a parallel wiring condition as follows: studs 20, 2], 22, 23, 24, 25, 26, 27, 28 and 29 are connected together; studs 20', 2|, 22', 23', 24', 25', 28', 21', 28' and 29' are all connected together. Stud II is connected to the grid G, and stud 29' is connected to the ground.

The efllciency of the coil number of turns of wire of diameter are used in by an example.

On the basis of a. hundred turns of wire on four coils each having a diameter of 1% inches and a. length of 1 inches, note the following:

wherein an equal equal length and equal parallel can best be shown pp ying the formula l l 1 LL1 L2 L3 E we have'lil' equaling 5 microhenrys.

I! ten coils are used each having the same num- V ber ofwire turns, as in. the present invention and using wire of equal length and equal diameter, L

is found to be 2.6 microhenrys.

- ber of wire turns.

This computation does not take into account additional losses due to the unbalanced resistance of the various coils having an unequal num- -Where all the coils have the same number of wire turns this additional loss is avoided as the current will divide itself equally through the various coils.

In Figure 4, the numeral 40 indicates a variable tuning condenser which is preferably .in parallel with the grid ground circuit. The expansion of the coil i puts the primary windings l2 in parallel and the secondary windings 13 in parallel to change the inductance of the said coil and to alter the capacity-inductance relation in the circuit and permits short wave reception or transmission, since the inductance is low.

In other words, when the coil I0 is expanded the radio set receives high frequency waves.

In Figure the wires of the primary winding II are shown in series with one another and the secondary windings are in series with each other. In this series relation the following wiring connections would result in the secondary windings: would be connected to the grid G, 2| to 20, 2| to 22, 22' to 23, 23 to 24, 24 to 25, I! to 28, 26 to 21, 21' to 28, 28' to 29, and 29' to ground. When the primary windings of the coil are in series and the secondary windings are in series the set receives long radio waves as the inductance is high and there is a correzpuonding inductance-capacity change in the cir- In Figure 6, the ignated generally with the same numeral as the studs to which they are connected. In the contracted position of the inductance coil the top end of strand 20 is connected to stud 20 and top end of strand 28 is connected to stud 29. The lower end of strand 2' is connected to stud 20' and the lower end of strand 29 is connected to stud 29'. Contact ll closes the circuit 20'-29 thus placing these windings in series. Contacts ll are insulated from each other and are each connected to one of the rings .35 and these in turn are connected to the outside circuit, 1. e.,

the condenser, grid and ground.

In the expanded position of the inductance coil the studs II and 29 are paralleled by being connected to ring (top) while studs 20 and 20' are paralleled by being connected to (bottom) ring 35.

It is to be understood that in Figure 6 only two strands of wire have been shown to illustrate the electrical connections and that any number of strarids may be used. The strands of wire should be of sufllcient length to permit the full travel of the inductance coil from its contracted to its expanded position.

After the various inductance coils have been aligned in the factory by the.selective operation oi the nuts I to obtain resonance and the nuts I. have been suitably sealed one would operate the all wave s'et covered by this invention as follows: if the broadcast band was desired the inductance coils would be compressed, Fig. 2: if the short wave band is desired, the cable drum 3' is rotated approximately three quarters of a turn to a point where a suitable lug (not shown) stops its motion. The coils are now expanded and the inductance thereof is considerably reduced. The coil I0 is. kept in alignment bythe strands of wire have beendesin the usual manner to protect against stray magnetic fields or lines of .force and also against the overlapping of interstage magnetic couplings. It is intended to cover such changes and the applicant desires to be limited only by the scope of the prior art and the claims appended hereto.

I claim:

1. In a tuning circuit of an all wave receiving set;. an inductance coil adapted to expand or contract comprising; an expandible portion extending substantially throughout the length of said coil, primary and secondary windings disposed on said expandible portion in spaced relation, said primary windings comprising a plurality oi insulated wires in coil form of equal length and diameter, said secondary windings comprising a plurality of insulated wires in coil form of equal length and diameter, a relatively non-expandible movable portion having a plurality of spaced contact members on the surface thereof and disposed at one end of said coil, two series each comprising a plurality of spaced apart contact members and each cooperating with said first mentioned contact members, each of said first mentioned contact members being connected to a free end done of theinsulated' wires in said primary and secondary windings, means re 1 sponsive to contraction of said windings to interconnect the wires therein in series, means responsive to expansion of said windings to interconnect the wires therein in parallel and manu-v ally operated means to expand or contract the said inductance coil.

2. In a tuning circuit of an all wave receiving posed on said expandible portion in spaced relaspindle II which passes through the endo! the w member II.

There will be obvious changes in this invention, e. g., the inductance coils .will be shielded tion, said primary windings comprising a plurality of insulated wires in coil form of equal length and diameter, said secondary windingscomprising a plurality of insulated wires in coil form of equal length and diameter, a relatively non-expandible movable portion having a plurality of pairs of spaced contact members on the surface thereof and disposed at One end of the said coil, two series each comprising a plurality of spaced apart contact members and each cooperating with said first mentioned contact members, each pair of said first mentioned contact members being connected one to one free end of the other to the other free end of one said insulated wires, means responsive to contraction of said windings to interconnect the wires therein in series, means responsive to expansion of said windings to interconnect the wires therein in parallel, and manually operated means to expand or contract the said inductance coil.

3. In a tuning circuit of an all wave radio receiving set having antenna-ground and gridground circuits, an inductance coil adapted to expand or contract comprising; an expandible portion extending substantially throughout the length of said coil, primary and secondary windings disposed on said expandibie portion in spaced relation, said primary windings comprising a plurality oi insulated wires in coil form of equal length and diameter and in series with the antenna-ground circuit. said secondary windings comprising a plurality of insulated wires in coil form of equal length and diameter, and being in the grid-ground circuit, a relatively nonexpandible movable portion having a plurality of pairs of spaced contact members on the surface thereof and disposed at one end of the said coil, two series each comprising a plurality of spaced apart contact members and each cooperating with said first mentioned contact members, each pair of said first mentioned contact members being connected one to one free end the other to the other free end of one of said insulated wires, means responsive to contraction of said windings to interconnect the wires therein in series, means responsive to expansion of said windings to interconnect the wires therein in parallel, and manually operated means to expand or contract the said inductance coil.

4. An inductance coil adapted to expand or contract a predetermined distance comprising; said coil being wound on a form having an expandible portion, primary and secondary windings disposed on said expandible portion in spaced relation and co-axial alignment, said form having a relatively non-expandible movable por 'tion disposed at one end of said coil, said movable portion having a plurality oi. contact members on the surface thereof, second contact means associated with said first mentioned contact members, and manually operated means. to selectively expand or contract said coil to change the cooperation between said contact members in such manner that the interconnections between said wire are changed.

5. An inductance coil adapted to expand or contract a predetermined distance comprising; said coil being wound. on a form having an expandible helical wire carrying member, primary and secondary windings disposed on said wire carrying member in spaced relation, said primary and secondary windings each comprising a plurality or insulated wires of equal length and diameter, said form having a cylindrical movable portion disposed at one end of the said coil, said movable portion having a plurality oi contact members on the surface thereof, second contact means associated with said first mentioned contact members, and manually operated means to selectively expand or contract said coil to change the cooperation between said contact members in such manner that the interconnections between said wires are changed.

6. An inductance coil comprising a plurality of strands of wires insulated from one another, said strands being helically wound on a common expandiblc form, and means responsive to expension and contraction of said form to control the connections between said wires.

8 n. ECKARD-