US2285029A - Band-spread tuning mechanism - Google Patents

Description

June 2, 1942. H. GUSDORF 5,

BAND-SPREAD TUNING MECHANISM Filed May 11, 1940 2 Sheets-Sheet 1 J a A INVEN TOR. FREDER/K HENDR/K GUSDORF A TTORNEY June 2, 1942. F. H. GQSDORF BAND-SPREAD TUNING MECHANISM Filed May 11, 1940 2 Sheets-Sheet 2 T0 POINTER 0F BAND SPREAD TUNING SCALE I N VENTOR.

MM 0 @WW 0 6 m H A 0. 1 M mw spread tuning means Patented June 2, 1942 uBAND-SPREAD TUNING MECHANISM Frederik Hendrik Gusdori', Eindhoven, Netherlands, assignor to Radio Corporation of America, New York, N. Y.

Application May 11, 1940, Serial No. 334,499

1 In Germany June 22, 1939 4 Claims.

In the copending application of Arnold T. Vossen, Ser.- No. 297,972, filed October 5, 1939,

there is described a device for obtaining bandspreading in short-wave reception. In one of the examples described therein the band-spread tuning means are constituted by inductance coils included in the oscillatory circuits to be tuned and in the field of which members seated on a shaft can be displaced by means of a screw thread driving the shaft.

The present invention relates to a radio receiver as describedin the above application in which band-spread tuning means are displaced by a transmitting mechanism which also displaces the pointer of the band-spread scale.

The invention has for its object to enable preliminary adjustment of the band-spread means in two positions.

In the manufacture of a number of identical band-spread tuning means it is impossible from the economical point of view to equalize them completely.

It is Well known to make the band-spread tuning means variable so that the band-spread scale is correct at at least one point.

According to the invention the starting point and the length of the path which the banddisplacement of the dependently of each other.

When the band-spread tuning means are constituted by elements mounted on as'haft and displaced in the field of inductance coils associated with the oscillatory circuits to be tuned the shaft can be adjusted in the direction of its length according to a suitable embodiment of the invention.

In this case the shaft is-preferably driven by the intermediary of a lever with which the ratio between the distances of the point of power and the point of load from the point of rotation can be varied. 4 In this case the movement of the lever can be transmitted to the shaft by the intermediary of a member provided with a set screw which is in line with the shaft and bears on this shaft and with a. set screw which in one of the extreme positions of the member is parallel with the lever and which serves for the adjustment of the ratio between the distances of the point of power and the point of load from thepoint of rotation.

In order that the invention may be clearly understood and readily carried into effect it will now be described more fully with reference to the accompanying drawings, in which Fig. 1 shows an oscillatory circuitincluding a band-spread tuning element.

Fig. 2 is a graph of the variation of the inductance of such an oscillatory circuit as a function of the displacement of the band-spread tun-' ing element.

Fig. 3 shows part of the transmitting mechanism between the tuning knob serving for bandspreading and the band-spread tuning means to be driven.

Fig. 4 shows the entire nism.

The oscillatory circuit shown in Fig. 1 includes a fixed inductance L1 in series with a variable inductance L2. A tuning condenser C1 and a trimmer condenser C2 are connected in parallel therewith.

The tuning circuit can be tuned in the entire short short-wave range (for example from 13 meters to 50 meters) by means of the tuning condenser C1. By means of the inductance L2 bandspread tuning can be effected within a number of comparatively narrow short-wave bands. For

transmitting mechathis purpose tuning is first effected by means of C1 to the center of the desired band,

the condenser after which tuning within the band concerned is effected by means of the Variable inductance Lz.

traverse during a complete pointer can be adjusted in- The variation in inductance of the inductance coil L2 is several per cent of the inductance of the inductance coil L1. The trimmer condenser C2 permits of correcting the tuning of the oscillatory circuit at a low value of the tuning condenser C1, for example 18 meters, and of altering the main tuning scale to accord at one point.

This must be efl'ected at a low value of C1 since in this case the relative variation of C2 is the great- I the main tuning scale is the influence of C2 at 43 meters is negligible. The main tuning scale can be made correct at a second point, for example at 43"meters, by adjusting the fixed inductance est. If, for example, correct at 18 meters of the oscillatory circuit. Since the inductance at 18 meters is the same as the inductance 'at 43 meters a variation of the inductance at 43 meters exercises the same relative influence on the tuning at 18 meters. It is known to bring about this variation in inductance b means of a small variable inductance coil in series with the fixed inductance. The invention permits however, of corrections of inductance being made by means of the band-spread tuning means.

Fig. 2 shows a system of coordinates XOY. the inductance of the oscillatory circuit being plotted as an ordinate and the displacement of the bandspread tuning means being plotted as an abscissa.

forced against the lever nism. Corresponding- Intermediate two plates z serves for the band-spread tuning. The adjustment of the starting value L3 permits of the main scale being rendered correct at a second point.

Referring to Fig. 2, a and b designate two characteristics of the inductance as a function of the displacement of two band-spread tuning elements which are not entirely identical.

Since the two band-spread tuning elements have to exhibit the same starting inductance L3 and the same final inductance the starting displacement of the band-spread tuning element having the characteristic. a is pa, where as the tuning displacement is qa. For the other bandspread tuning element these displacements are pi; and (11). It is therefore necessary to arrange between the band-spread tuning knob and the band-spread tuning elements a transmitting mechanism by means of which the displacements p and q can previously be adjusted for each bandspread tuning element so that acomplete displacement of the pointer of the band-spread scale results in a variation in inductance from L1+L t L1-l-L-l.-

Fig. 3 shows that part of the transmitting mechanism by means of which the two displacements p and q can be adjusted.

Thetransm itting mechanism comprises a part i adapted to slide on a shaft 2 which serves as a straight guide. The part i has mounted on it a set screw 3 which is in line with the shaft (shown at 39 in Fig. 4) that carries the bandspread tuning means. This shaft, which is not shown in Fig. 3, engages the end surface 4 of the set screw 3. The part 1 comprises in addition an angularly arranged set screw 5 which is provided at the end with a disc 6. The disc 8 engages an upright edge 1 of a lever 8 adapted to rotate on a shaft 9. The lever B is shown in Fig. 3 in full lines in one of its extreme positions and in dotted lines in the other extreme position 8'. The lever B can be moved into any of the positions intermediate the said two extreme positions by means of the band-spread tuning knob and a screw, not shown in detail in Fig. 3.

When the lever 8. is moved into the position 8 the screw 5 is displaced towards the position 5 shown in dotted Iinesbecause the part I is 8 by a spring (not shown) acting on the shaft of the band-spread tuning means.

On the screw 5 being screwed into the position lfl shown in dotted lines when the lever 8 occupies the position shown the part i is not displaced since thescrew 5 isparallel with the lever B.

If, however, the lever B is'moved into the position 8 the screw 5 is displaced into the position l0 and thepart I traverses a correspondingly smaller path.

The startingipoint p and the path q of the band-spread tuning means can be adjusted by meansof the two; set screws 3 and Sand consequently independently ofeach other.

. Fig ishows the entire transmitting mechaparts in' Figs-3 and dare designatedby the.samc reference-numerals.

spaced apart by means of bolts 23 is arranged a shaft 24 which is partly thread 25.

l and 22 which are provided with screw face t by a spring (not shown).

The shaft 24 carries a rope drum 28. having wound in it the rope 21 of a flexible cable 28 which rope is connected with the pointer (not shown) of the band-spread tuning scale.

The rope drum 26 is coupled via a slipping coupling 23 to a gear wheel 38 adapted to be driven by a gear wheel 31 mounted on the shaft 32 of the band-spread tuning knob (not shown). The slipping coupling protects 25 from being damaged. On the shaft 24 being rotated a threaded strap 33 is displaced over the shaft and along a straight guide 34 and thus drives the lever 8. The lever B is adapted to rotate on a shaft 9 and is secured to the plate 2| by a strap 35. The lever comprises two parts 3 and 36 connected by a rod 31. The movement of the strap 33 is transmitted to the lever 8 via the rod 31.

The movement of the the part I in the manner described with reference to Fig. 3. I

The part i is displaced not only on the shaft 2 but also along a straight guide 38.

The end surface 4 of the screw 3 is engaged by a shaft 39 which is adapted to slide in a sleeve 40 and which is centered and guided by a plate,

H. The shaft .39 is forced against the endsur-f The shaft 39. carries an iron core 42 which is displaced, upon the shaft 39 being displaced in the field of coil 43 wound around the sleeve 30 so that the in- 'ductance of this coil is varied. The coil 43,

(which corresponds to the coil L2 in Fig. 1) forms part of the oscillatory circuit to be tuned.

When it is desired to tune more than one oscillatory circuit a plurality of iron cores may be arranged on the shaft 38. The place of the shaft 39 depends on the position of the end surface I of the screw 3.

The rotation of, this screw-3 permits of adjusting the starting position of the shaft 39 and the final position of the shaft 39 can be adjusted by rotation of the screw 5 in the position shown of the lever 8. The latter adjustment is effected at a maximum induct-' ance of the coil 43.

What I claim is:

1. In a radio receiver of the type provided with one or more permeability tuned circuits and wherein the tuning means for each such circuit is constituted by a magnetic core mounted on a shaft and displaceable in the field of an inductance coil included in the tuned circuit, means for actuating said shaft in the direction of its length; said means comprising a carrierlmovable in'the direction of the shaft, settable means carried by said carrier for determining the initial adjustment of said shaft, additional settable means carried by said carrier fordetermining the extent of "linear displacement of the shaft, means for actuating the carrier through said additional means, and manually operable means ance coilincluded in the tuned circuit; means for actuating said shaft inthe direction of its length, saidmeans comprising a carrier movable in the direction of the shaft, adjustable screw means in alignment with the shaft carried by said carrier for determining the initial-adjustment of said shaftand for actuating the same,

the screw thread lever s is transmitted to length, said means 3. In a radio receiver oi the type Provided with one or more permeability tuned circuits and wherein the tuning means for each such circuit is constituted by a magnetic core mounted on a shatt and e in the field of an inductanee coil included for actuating said mean carried by said the extent of linear dismeans for actuating the shaft in the direction of its comprising a carrier movable second adjustable screw manually operable means for con-v in the tuned circuit, means operable. means for table'meamand controlling the movement of the pivoted member.

in the direction of the shaft, a first settable means 7 carried by said carrier and in alignment with the core shaft for determining the initial adjustment of said shaft and for actuating said shalt. a second settable means carried by said carrier for determining the extent of linear dis- 1 placement of actuating the the shaft, a pivoted member for carrier through said second set- 4. In a radio receiver of the type provided with one or wherein the tuning athr said able in direction 0! the shaft, a first adjustable screw mean in alignment wlth the shaft carrie by and carrier for determining the initial adjustment of v the same, second adjustable screw means car-- ried by said carrier for. determining the extent or lineardisplacement or the shaft, a pivoted member for actuating the carrier through the second adjustable screw means, and

operable means for controlling the movement or the pivoted member. i

Paznmm Herman: GUSDORF.

more permeability tuned circuits and I said shalt and for actuating"

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