US2330047A - Variable tuning mechanism - Google Patents

Description

Sept. 21, 1943. F, w GDSEYl JR 2,330,047

VARIABLE TUNING MECHANI SM Filed June 24, 1940 2 SheebS-Sheell 1 FRANK W 60055K JR. INVENTOR.

ATTORNEYS.

Sept 1943. F, W. GoDsEY, JR 2,330,047

VARIABLE TUNING MECHANISM Filed June 24, 1940 2 Sheets-Sheet 2 FRANK M! 60055K JR. INVENTORL ATTORNEYS.

Patented Sept. 21, 1943 VARIABLE TUNING MECHANISM Frank W. Godsey, Jr., North Adams, Mass., as-

signor to Sprague Special-ties Co., North Adams, Mass., a corporation of Massachusetts Application June 24, 1940, Serial No; 342,156'

(Cl. 'i4-10)` 4 Claims.

The present invention relates to an improved method and means for actuating the tuning elements of a radio receiver and more particularly to novel driving means for actuating a condenser gang comprising tuning condensers of the type described in the copending application of Robert C. Sprague and Frank W. Godsey, Jr., Serial No. 336,822 filed May 23, 1940, now U. S. Patent No. 2,324,178 issued July 13, 1943.

The tuning condenser described in said application comprises condenser units the electrodes of which consists of two closely-spaced concentric conducting cylinders which are displaceable relative to each other, to vary the capacity of the condenser; Interposed between the electrodes is a -dielectric layer which preferably consists of a vitreous material forming a fused integral coating on the surface of the inner electrode. Preferably the electrodes andthe coating are made in their coacting dimensions to close tolerances as to engage each other with a smoothly sliding iit.

Tuning condensers of this type have many'advantages, as they combine a wide capacity range, great mechanical and electrical stability throughout their capacity rangewith a small size, compact and light weight structure, and can be manufactured at low cost. l

Such tuning condensers possess inherently a linear capacity-stroke characteristic, but by means of suitable mechanical driving means the.

relation between the capacity of .the'condenser and the displacementy (or rotation) of the tuning control can be made of any other desired character.

By observing the various requirements specified.

inthe above referred to copending application of R. C. Sprague et al., condenser of this type can be made tocapacity tolerances of plus/minus 1% and even less. ,In practice however, such condensers .are more feasibly made to tolerancesl of about plus/minus 5% and consequently the individual condensers of an assembly may correspondingly differ both in their capacity range and in their minimum and maximum capacity values. Such wider capacity tolerances as a rule, do not fully meet practical requirements. Furthermore, in certain applications, for example, in superheterodyne `radio receivers, the tuning condenser of the oscillator circuit must possess a diierent capacity range from that of the' remaining tuning condensers; to achieve this in the past either so-called cut-plate tuning condensers have been used or an eXtra padder condenser was inserted in series with the tuning condenser of the oscillator circuit. Y

It is an object of this invention to provide novel actuating and driving means `for tuning condensers comprising as their main elements two concentric cylindrical electrodes. 'i

Another object of the invention Vis, to provide .ranges and values of individual condensers of a gang and thedisplacement (or rotation) of the tuning control means of the gang.

These and further objects of the invention'will appear as the specification progresses.

The invention will be described with reference tothe appended drawings forming/part of the specication and in which:

Figure 1 isa side view, partly in section, of a .tuning condenser gang usingA one embodiment .in mass productionto meet theY particular ree quirements 4and accurate tuning of its tuning circuits.

Fig. l2' is, aplan view of the condenser gang` of Fig. 1.

Fig. 3 isl a diagrammatic illustration of a method by which the actuating and driving means. ofthe invention permitseach condenser of the .assembly to assume an `individual relationship between its capacity settingV and the displacement (or rotation) of the common tuning control means.A l l Y Fig. 4 is a side view illustrating another embodiment of the driving means of the invention as applied-to` a tuningcondenser of a construction similar to that of Figs. 1 and 2. i

Fig. 5 is a side View illustrating a modication o-f the driving'means shown in Fig. 4.

Referringto Figs. 1 and 2, the-tuning condenser gang there shown comprises two condenser vunits supportedV on acommon metal mounting base l5y which in practice is preferably the chassis `of. the; radio receiver in whchthe .condenser gang is used. The two condensers are identical in construction and each comprises an electrode I consisting of a hollow metal cylinder or sleeve preferably closed at one end, and an electrode II consisting of a hollow metal sleeve surrounding the electrode i0. Interposed between the electrodes IG and II is a concentric dielectric layer I2 forming an integral-coating on the surface of electrode I0. The dielectric layer I2 consists preferably of a potassium-lead silicate vitreous enamel as disclosed in the copending application of Stanley O. Dorst, Serial No. 289,292, led August 9, 1939, now U. S. Patent No. 2,290,947 issued July 28, 1942. The layer I2 may also consist o other suitable dielectric materials, for example, of various kinds of vitreous enamels, or may consist of a non-vitreous dielectric material such as cellulose acetate, polystyrene, hard rubber or the like, to which dielectric materials may Vbe added a ller of titanium dioxide or other dielectric material to increase the dielectric constant and/or lower the power factor.

The layer I2 is applied to the electrode I0 preferably by the cataphoretic deposition process described in the copending application of Preston Robinson et al., Serial No. 197,692 filed March 23, 1938, which process produces a coating of high uniformity and of even thickness throughout the length of the coating. As a rule the s o deposited coating is fused and thereafter subjected to surface grinding as described in the above referred to copending application of RobertC. Sprague et al., whereby the coated electrode Ill- I2 engages the sleevev electrode II with a sliding t whereby the air layer or gap I3 formed between the elements is preferably 100025" to .0005 thick.

`electrode I0-I2 and the guide 22 are provided with axial bores through which passes a spindle bolt 2| secured by a nut 31.

Each condenser is supported on the base I5 by a metal mounting bracket I4 secured to the sleeve electrode II through a mounting strip I6 which is` soldered or otherwise secured to theV outer surface of the sleeve II, and an insulating strip I1 of hard rubber, Bakelite, Isolantite or the like interposed between the strip I6 and the bracket I4. These members are secured together respectively by a countersunk screw I8 passing through the strip I1 and engaging a suitable tapped hole of the strip I6 and by a countersunk rivet I9 passing through the strip I1 and the bracket I4.

The bracket I4 is secured to the base I5 by a screw 20 passing through the basel I`5 and threadedly engaging a suitable tapped hole of the bracket I4.

The electrode II is provided for its external electrical connection with a terminal lug 24 consisting of an extending portion of the strip I6 whereas the coated electrode Ill-I2 is maintained at ground potential by the spindle bolt 2I which passes through and contacts an upright extending portion 38 of the bracket I4. The portion 38 also serves as a guide for the spindle 2| and as astop to limit theV lateral movement ing a threaded central bore 3l of the coated electrode III- I2 at the maximum capacity position.

The actuating and driving means for tuning the condensers of the assembly comprises for each condenser the spindle bolt 2I above referred to, two couplers 25 and 30, a connecting rod 2S, and a crank 21 and a hub 28 mounted on a driving shaft 29 which shaft is common to all of the condenser units.

The coupler 25 consists of a metal block havextending throughout the greater portion of the length of the coupler and adapted to receive the spindle 2|.

The coupler 39 is a metal block, internally 4threaded throughout its length and is mechanically connected to the coupler 25 by means of Athe rod 26 and pins 32 and 33 passing through the ends of the rod and aflixed to the couplers 25 and 3D respectively.

The crank 21 consists of a metal spindle bolt one end of which is secured within a radial bore of the hub 28 in such a manner as to permit the free rotation of the spindle while preventing its radial movement relative to the hub. This is accomplished by a lock screw 35 which passes through the hub 28 and engages an annular notch 34 of the spindle 21. The extending portion of the spindle 21 is threaded throughout its length and engages the corresponding threads of the coupler 30.

A set screw 3B secures the hub 28 to the shaft 29. A tuning control (not shown) is affixed to one end of the shaft 29 in well known manner.

The couplers 25 and 30 and the crank 21 form the two adjustment means of the actuating and driving means of the invention, by means of which each condenser of the tuning condenser gang can assume the tuning range and minimum and maximum capacity values, which meet the particular requirements of its tuned circuit.

Thus in the embodiment of the invention shown in Figs. 1 and 2 the capacity range of each condenser unit, limited by the horizontal and vertical positions of the crank 21, is determined by the extent of travel of the coated electrode Ill-I2 through the sleeve II and this can be adjusted by varying the eiective length of the crank 21 by its threading or unthreading through the coupler 3l).

The upper or lower capacity Values of each condenser is adjusted by its spindle 2| threading a greater or a lesser length of the corresponding coupler 25, thus setting the initial position which the coated electrode Ill-I2 assumes with respect to the sleeve electrode II. Whether the spindles 2I of the individual condensers should engage their corresponding couplers 25 to the same or diiferent extents, and thus whether the coated electrodes IIl--I2 of the individual condensers are correspondingly displaced relative to each other, is determined by the differences in the characteristics of the individual condensers and by the particular requirements of their associated circuits. In general because of the above factors, the degree of engagement is diierent for each condenser unit and this has been shown in Fig. 2 in which the electrode Ill-I2 of the lower condenser is shown to be displaced a distance D relative to the corresponding electrode of the upper condenser.

The actuating and driving mechanism of the invention not only permits the individual adjustment of the capacity range and the minimum and maximum capacity values of each condenser unit of a gang, but also makes it possible to proquirements. ofeach. tuning-circuit and` the;` conv ldensers canv be made-fto.track as: required for 'vide-a differenti rate of change of capacity with displacement (or rotation) f offthey common-.tuning control means. isaachieved by displacing the individual cranks 251 of'V thecondensersa pre- 'determined` angle relative toeach other.' rIihis is-shown in Fig; 3% Whe-rezthe crank, 21? of:- the upper condenserl is shown to lead? the crank' 211 of theflowerf condenser by an angle- InJFig, 3 the shaft 29 is shown to'be rotated .through an angle a from. its end? or minimum capacity position. By so displacingy tliecrank 21" the.. upper Acondensery unit exhibits: throughout its capacity range a greater rate of change ofi-'capacity than does the lower :condenser unit.

Inlsuch-i'nstances wherefthel cranks 211 are displaced "relative to eachother as above described, one limit of: the'capacity-range may.` occur when the crank' ofthe-lower condenser-is in the horizontal position' and thel otherl limit may occur when the crankcf thelupperl` condenser isin the .vertical position.

Thus;` by adjusting theA angle.I between the two4 cranks 2, and by; adjusting the upper and lovver-capacitylimitsfandE thefs-troke of each individ'ual condenser element, the two condenser units may be madev totrack each other approximately as required; for4 instance, for the simultaneous tuning of-iy the oscillator and antenna circuits off superhetercdyne radio receiver-s,

In Fig. 4itherevis. show-n a second: embodiment of theactuating and drivingmeans` of the invention. While in Fig. 4 only-one condenser unit is shown', it shouldbe well`- understood, that the invention is applicable to a. tuning condenser gang having a plurality off' condenser units.

Theactuating anddriving means illustrated in Fig. 4 comprises for each condenser 4| a spindle bolt 59 similar to the spindle bolt 2| described in connection with the tuning assembly of Figs. 1 and 2, a coupler 5|, and a cam 52 aflixed to a rotatable shaft 53 common to all of the condenser units.

The coupler consists of a metal block internally threaded throughout the greater part of its length and into which the spindle bolt 5D threadedly engages. At its other end which engages the cam 52, the coupler 5| is either provided with a roller type cam follower or has a smooth, rounded surface, as shown at 54.

The cam 52 is a suitable disc preferably metal and its specific details and shape are determined by the particular requirements of the circuit in which its associated condenser is used. The stroke of the cam, which is the difference between the rise of the cam at the start and at the end of its movement, determines the displacement or stroke of the cam follower coupler 5| and hence the capacity range of the condenser, whereas the shape of the cam Within the limits of its stroke determines the rate of change of the capacity of the condenser. The capacity values of the .condenser at the limits of its capacity range can be varied by threading or unthreading the spindle bolt 50 in the coupler 5| which adjusts the initial relative position of the electrodes of the condenser 4| as has been fully described in connection with the tuning assembly of Figs. 1 and 2.

Thus by the use of an individual cam 52 for each condenser of the tuning assembly, and by means of the individual couplers 5|, the capacitl7 range, the upper and lower limits of the capacity range and the rate of change of capacity of each condenser, are made to meet the particular re- -pression at the endA of the stroke.

the-.simultaneous tuning ofthe oscillator andiantenna. circuits ofI superheterodyne receivers.r

To maintain the cam follower coupler 5| in positive contactA with the cam 52 there is providedy about the spindle bolt a compression spring 55y one end of which abuts against the couplerv 5|: and? the other end 0f which abuts against the'bracket'lll; i

While the use of the compression spring 55 as showninFig. 4, fully meetstherequirements of maintaining a;v positive Contact betweenf the cam follower 5|l and' the cam 52, such usehas the undesirable feature that a spring whichis capable ofexerting sufcient pressure in the beginning of lthe stroke requires a. high force for its com- At the same timeV the pressure exertedy by the coupler 5| against; the surface of the cam 52 increases with the degree of compression ofthe spring 55, and in some cases. they pressure at maximum compression is so great that the rotation/ofA the cam 5'2fbyfthe coupler may disturb theisetting of the driving means. Y

In. Fig. 5 I have shown an improved arrangement inwhich the above drawbacks are obviated. The driving mechanism there shown comprisesa spindle bolt- 6|) (shown in part), a cam followercoupler 6|, and a cam 62v aiiixed to a rotatable shaft 63, wherebyv positive Contactl between the coupler 6|- and the cam 62' is secured by a tension spring 65. One end of the spring is secured to theV coupler 6|, for example, by a pin 66'. I have found that'if'the other end of the spring 65isxed directly to the face of the cam, the required good contact between the coupler 6| and the cam 62 can be maintained without the spring being distorted to the full extent of the stroke of the cam. If the spring 65 is secured to a point on the face of the cam at or approximating the center of the cam surface, no important change in the length of the' spring takes place throughout the entire stroke of the cam and a constant pressure is exerted by the coupler 6| on the cam 62 irrespective of the rise of the cam.

This is shown in Fig. 5 in which the spring 65 is secured to the face of the cam 62 by a pin 61 at a point corresponding to about the center of the cam surface, namely at a point from which substantially equal radii are formed to all effective portions of the cam surface.

It should be noted that whereas in the foregoing description, the actuating and driving means of the invention has been illustrated in its use with tuning condensers in which the inner electrode is movable and the outer or sleeve electrode is secured to a mounting base, such driving means are equally applicable for tuning condensers in which the outer electrode is movable and the inner electrode is arlixed to a mounting base.

While I have described my invention by means of specic examples and in specific embodiments, I do not wish to be limited thereto for obvious modications will occur to those skilled in the art without departing from the spirit and scope of the invention.

What I claim is:

1. In a condenser assembly having a plurality of condenser units each having a movable element, means for actuating the element comprising a threaded member engaging the element, a coupler member engaging the threaded member and adapted to adjust the element to apre- `detz'erm'ined initial position, and'a crank member having an adjustable effective length engaging said coupler member and adapted to displace the element to a predetermined second position, and

means to simultaneously actuate all the elements and displace the sa'me from' their said Ainitial position to their said second position, said `means comprising a rotatable shaft common to all of the movable elements and to which the `crank members are affixed.

2. In a condenser assembly having a plurality of condenser units each having a movable element, means for actuating each element comprising a threaded member engaging the element, a coupler member engaging the threaded `member and adapted to` adjust the element to a predetermined initial position, and a crankmem- .ber having an adjustable effective length engaging said coupler member and adapted to clisplace said element to a predetermined second position, and means to simultaneously actuate 'all of the elements anddisplace the same from `displaced relative to each other about said shaft.

'3. In a condenser assembly having a plurality -of condenser units each'having a movable ele.- Iment, means for actuating each element comprising a threaded rod member engaging the ele'- ment, a coupler member engaging the rod mem- Hber and adapted to adjust the element to a predetermined initial position, a second coupler member secured to said first coupler member,

asador? and a `spindleV crank member threadedly engaging said second coupler member and having an adjustable effective length determined by the degree of engagement of said second coupler member and the crank member, said crank member being adapted to adjust the element to a predetermined second position, and means to simultaneously actuate all of the elements and displace the same from their said initial position to their said second position, said means comprising a rotatable shaft member common to all of the movable elements and to which the crank members of each element are axed.

4. In a condenser assembly having a plurality of condenser units each having a movable element, means for actuating each element comprising a threaded rod member engaging the element, a coupler member engaging the rod member and adapted to adjust the element to a predetermined initial position, a second coupler member secured to said rst coupler member, and a spindle crank member threadedly engaging said second coupler member and having an adjustable effective length determined by the degree of engagement of said second coupler member and the crank member, said crank member being adapted to adjust the element to a predetermined second position, and means to simultaneously actuate all of the elements and displace the same from their said initial position to their said second position, said means comprising a rotatable shaft member common to all of the movable elements and to which the crank members of each element are affixed, said crank members being angularly displaced relative to each other about said shaft.

FRANK W. GODSEY, JR.

Images