US2442935A - Click mechanism for precise control of a tuner - Google Patents

Description

June 8, 194s. C. L. RICHARDS 2,442,935

CLICK MECHANISM FOR PRECISE CONTROL oF A TUNER Filed Dec., 22, 1944 a @/5 n @Pm INVENTOR ATTORNEY Patented June 8, 1948 CLICK MECHANISMFOR PRECISE CONTROL F A TUNER Claude Langdon Richards, London, England, as-

signer to The Hartford Nationalv Bank & Trust Company, Hartford, Conn.as trustee Application December 22, 1944, Serial No. 569,405 In Great Britain October 18, 1943 Section 1, Bublic Law 690, August 8, 1946 Patent expires October 18, 1963 (Cl. Z50-40) Claims. 1

In tuning arrangements for wireless-receivers and like apparatus in which it is desired to tune electrical circuits to predetermined frequencies, it is known to provide a so-called click mechanism whereby the tuning member is located in a predetermined setting by the engagement of a pin or arm in a recess, a spring being usu-ally provided which tends to cause the, pin or arm to be at the bottom of the recess. The difculty arises that for ease in manipulation, particularly in moving from one tuning position to another, each recess must have gently sloping sides, whereas for precise location of the tuning member steep sides to the lrecess are necessary.

The object of the present invention is to provide a click mechanism which enables both ease in manipulation and precision of location. According to the presentl invention at least one of the click elements is resiliently mounted' and is adapted to be urged electromagnetically out of its rest position into a position giving a greater degree of engagement with the other. Release for easy manipulation can then be obtained by deenergising the electro-magnet.

In one form of the present invention the tuning member to be located, consisting` for example of the rotatable shaft and moving vanes of a variable condenser, carries a disc at right angles to the shaft and mounted on the disc are arms adapted to engage in a recess between the pole- 30 `pieces of an electromagnet mounted for pivotation about a xed axis and springloaded so as to assume a predetermined rest position when not energised.

In order that the invention may be more readily understood, reference will now be had to the accompanying schematic drawings in which:

Fig. 1 shows the general disposition of the click mechanism in relation to the other parts of the tuning arrangement,

Fig. 2 shows a preferred form of clickV mechanism according to the invention,

Fig. 3 is an explanatory diagram.

In Fig. .1., the wireless receiver is assumed to be of the kind in which tuning is effected by means of a variable condenser controlled by a rotary shaft. It will however be apparent that the click mechanism of the present invention is applicable to all tuning arrangements in which axis irrespective of the nature of the circuit component which is thereby adjusted.

From the tuning knob l, a cord drive 2 is taken. to a drum 3 which is secured on the shaft 5 of the variable condenser 6 (not shown in detail). After passing round the drum 3 t-he cord 2' is taken to a guide pulley 4 before returning to the tuning knob. In this Way it is possible for the cord 2 to be led on and oil' the drum 3 at the same point, the run of -cord between tuning knob and drum 3 being at 180 to the run of cord between drum 3 and pulley 4, and Iboth runs of cord lying in the tangent plane at the point where the cord is led on and oi. Also secured to the shaft 5 is a disc 8 carrying a number of click arms il; These are adapted to co-operate in a predetermined position with a click recess I0, which will be described more fully hereinafter with reference to Figs. 2 and 3.

To show the setting of the tuning condenser 6 a scale l2 is provided, over which an indicator Il is caused to travel by a cord drive I3. The cord passes round guide gulleys I4 and is led on and oil the drum 3 at the same point in opposite tangential directions, simil-arly to the cord 2. With this arrangement, the drive and indicator cords constitute a balanced load on the spindle 5.

The condenser 6 and the click mechanism are mounted on a common rigid base 1 which preferably also carries a bracket l5 supporting t-he pulleys- 4 and I4.

Reference will now be had to Fig. 2, which shows only part of the disc 8 mounted on the spindle 5. The arm S is provided with a stepped tang 2li whereby it is pivotally mounted in a substantially triangular aperture 2l in the disc 8; The arm 5) can be secured in the precise angular setting in relation to the spindle 5 by means of the clamping device comprising the bolt 23 and washer 24, the bolt 23 passing through an arcuate slot 22 concentric with the centre of pivotation of the arm Si. The projecting end` of the arm 9 is shaped as a rounded head for smooth engagement in the click recess.

The click recess is formed between twov cheeks 25 constituting the pole-pieces of an electromagnet. These cheeks 25 are integralA with or secured to the cores of magnetising coils 26, the magnetic circuit being completed through tuning is effected by turning a shaft about its a yoke member 3l whereby the electromagnet as a whole is mounted for pivotation so that the pole-pieces move towards and away from the spindle 5. Adjacent the pole-pieces 25 a nonmagnetio strip 21 is clamped to the core of the electromagnet so as to maintain the pole-pieces at a predetermined spacing. The clamping strip 21 projects below the electromagnet and is engaged by opposed coil springs 28 which tend to oppose displacement of the strip 21 fromits mean or rest position. The springs 28 are supported by a rod 29 which passes through an aperture in the end of the strip 21 and is carried by a U-shaped bracket member 30 which in turn is rigidly mounted in relation to the base plate 1 (Fig. 1). The pivotal mounting of the yoke 3| en which the electromagnet is carried is effected by two ball bearings 32 vwhich are carried by a massive frame 33 which is rigidly secured in relation to the base platev 1 (Fig.,1).

As best seen from Fig. 3, the arrangement is` such that when the electromagnet is not energised the end of the arm 9 when'in ,the lclick position is only in slight engagement with the cheeks 25 defining the click recess IIJ. cheeks 25 are so shaped as to present a gentle inclination to the end of the arm 9 so that the latter can readily cause the electro-magnet system to pivot away from the spindle 5 to enable the arm S to enter the recess I0. The depth of engagement is indicated by the zone a-b and within this Zone the inner faces of the cheeks 25 are smoothly rounded so that the arm 9 can be caused to disengage by rotation of the tuning knob (knob I', Fig. l). Beyond the zone a--b the recess I0 has steep sides tending towards parallelism. When the electromagnet is energised, the gentle inclination of the outer faces of the cheeks 25 still enables the arm 9 to cause the pivotal movement of the electromagnet 2S necessary to permit the arm 9 to enter the recess IU, but when engagement occurs it is much deeper due to the magnetic attraction between the energised pole-pieces 25 and the arm 9, which is made of magnetic material of low retentivity. Due to this deeper engagement there is contact between the arm 9 and both sides of the recess IIJ, whereby the arm 9 is precisely located and with it the spindle 5. To release the arm 9 for a fresh tuning operation the electromagnet is de-energised and is thereupon restored by the springs 28 to the position in which the depth of engagement corresponds to the zone aP-b and the arm 9 can be disengaged by operating the tuning knob. The Zone a-b can be made of any desired depth and may even vanish, in which case there is no engagement at all in the absence of energisation.

To set the arm 9 in the precise angular position to give the desired tuning adjustment, it is brought into engagement with the click recess I0 with the electromagnet 26 energsed. Then with the clamping bolt 23 released, the spindle 5 is brought into the desired position, whereafter the arm 9 is again clamped to disc 8. In this way mechanical strains on the condenser during the operation of adjustment are largely eliminated.

The control of the circuit for the electromagnet 26 can be of any convenient form. A suitable arrangement is that indicated in Fig. 1, where the circuit I6 includes a battery I1 and switches I8 and 35. The battery I1 could be replaced by any other convenient source of energising current. The switch I8 is coupled by a link Ill to the tuning knob I so that the switch I8 can be opened and closed as required during tuning. A

central push button on the tuning knob could for example be provided for controlling the switch I8. Switch 35 is coupled by a link 36 with the band selector switch 34 so that the click tuning operates only on the desired tuning bands.

It will be apparent that the click mechanism according to the present invention gives rise to a minimum of mechanical wear on the click pin and the cheeks of the click recess while enabling a maximum of precision of location to be achieved; a repeat accuracy of frequency of the order of 5 parts in l100,000 is readily obtained. If desired, a small permanent magnet can be mounted at the v, back of the pole-piece gap to collect any iron dust formed by wear, but owing to the slight wear involved this `precaution will in general be unneci l essary.

The f I claim:

. 1. Tuning apparatus for wireless receivers and thevlike comprising a click-mechanism for said tuning apparatus including a click-pin, means providing a click-recess, control means for causing the said click-pin to move into and out of engagement relative to the said recess and electromagnetic means for varying the degree of said engagement.

2. A tuning control apparatus as set forth in claim 1 in which the said click-recess means is mounted for pivotation about a fixed axis and spring loaded so as to assume a predetermined rest position.

3. A tuning control mechanism as set forth in claim 1 in which the click-pin is made of magnetic material and its attractive force causes a relative `movement between the said click-pin and said click-recess means so that the click-pin moves to a position of greater engagement in the said click-recess.

4. A tuning mechanism as set forth in claim 1 in which there is a slight engagement between the said click-pin and the said click-recess means while the said electromagnetic means is nonenergized.

5. Tuning apparatus for wireless receivers and the like comprising a click-mechanism for said tuning apparatus including a plurality of clickpins, means providing a click-recess, control means for causing the said click-pins to move into and out of engagement relative to the said recess and electromagnetic meansl for moving the said recess into a position of greater degree of engagement with the said click-pins when energized.

6. Click-mechanism as set forth in claim 5 in which each of the said click-pins is adjustably secured to the said control means.

7. Tuning apparatus for wireless receivers and the like comprising a click-mechanism for said tuning apparatus including a plurality of clickpins, means provid-ing a click-recess, control means for causing the said click-pins to move into and out of engagement relative to the said recess, electromagnetic means for moving the said recess to a position of greater engagement with the said pins and means for drive connecting the said clickpin control mean-s to the tuning control of the said receiver.

8. A tuning mechanism as set forth in claim 7 in which additional drive means is taken from the click-pin control means to a tuning indicator of the said receiver.

9.A tuning mechanism as set forth in claim 1 in which a switch controlling the said electromagnetic means is operatively associated with a tuning knob of the said receiver to permit the said electromagnetic means to be de-energized before 6 changing the tuning status of the said receiver.

10. Tuning apparatus for wireless receivers and 1 REFERENCES CITED the like comprising a, click-mechanism for said The following references are of record in the tuning apparatus including a plurality of clickle 0f GhS Patent: pins, means providing a click-.recess control 5 UNITED STATES PATENTS means for causing the sald chck-pms to move mto and out of engagement relative to the said recess, Number .Name Date electromagnetic means for moving the said recess 2025213 Relnken DEC- 24, 1935 to a position of greater engagement with the said 2,030,129 Wheller Feb. 11, 1936 pins, and a band selector switch for de-energiz- 10 2,031,636 ThPmaS May 25, 1937 ing the said electromagnetic means at selected 2,190,332 ElllOtt Feb. 20, 1940 positions of the said selector switch. 2,205,170 JOhnSOn June 18, 1940 2,275,284 Carlson Mar. 3, 1942 CLAUDE LANGDON RICHARDS. 2,312,035 Groenenberg et al. Feb. 23, 1943

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