Patent GB-672483-A (GB)
Title: An improved device for adjusting the frequency of oscillatory electric circuits
IPC: H03J1/14
Filed: 1950-06-20
Abstract: 672,483. Adjusting radio apparatus. THORENS SOC. ANON., H. June 20, 1950 [July 8, 1949], No. 15361/50. Class 40 (v). A band - spread tuning mechanism comprises a single operating member which is permanently connected to a fine-tuning device and also is coupled to a coarse-tuning device by a disengageable mechanism provided with stops which define the position of the coarse-tuning device when the coupling is disengaged. A pulley 28, Fig. 1, coupled to the tuning knob (not shown) by a cord drive actuates a fine-tuning condenser 8 of the type in which a cylindrical electrode slides relative to another, fixed one by means comprising a pinion 24 and split spring-loaded gear. 23 attached to a shaft 22. The shaft 22 carries a cam 21, Fig. 2, which engages a pin 15 carried by lever 16, the lever pivoting about shaft 17 and driving the condenser 8 via an extension arm 20 and coupling-rod 11; the drive is maintained in engagement with the cam by means of a spring 29. A coarse-tuning condenser 1 of the sliding, multiple-cylinder type may be coupled so as also to be driven by the cam 22, by means comprising a lug 14 (see especially Fig. 3), engaging the pin 15, and which is attached to a flanged drum 12. The drum 12 is attached so as to pivot about one end of a sliding shaft 4 carrying the moving elements of the condenser 1, and may be rotated to disengage the lug 14 from the pin 15. Disengagement is under control of the wavechange knob 33, Fig. 1, and attached rotatable shaft 30, to which is fixed a drum 48 carrying pin 52. The pin 52 engages in a hole in, and so drives a pulley 69 which is otherwise free to turn about the shaft 30, this pulley operating the wave-change switch (not shown) by means of a belt drive. Rotation of the shaft 30 is normally limited by the pin 52 meeting shoulders 55 (see especially Fig. 4, formed in a fixed bracket 56, the various wavebands (OC<SP>1</SP>, GO, MO, OC<SP>2</SP>, as shown) being located by means of a " click " mechanism comprising a perforated plate 42 fixed to the shaft 30, a ball 49 and spring plate 43. The spring plate is carried by a bearing running free on the shaft and is prevented from rotation by a pin 44 which engages in a longitudinal slot in the casing. The shaft 30 is also capable of longitudinal movement, against a return spring 59, but is prevented, save in the short-wave positions (OC<SP>1</SP>, OC<SP>2</SP>) by a pin 57, carried by the plate 42 fouling a fixed bracket 58. In the shortwave positions the shaft may be pulled up, whereupon the pin 52 disengages from the pulley 69; at the same time shoulders formed on a cross-member 34, Fig. 1, attached to the end of shaft 30 engage in slots formed in a plate 36, see especially Fig. 5, attached to the drum 12, thereby lifting the shaft 4 out of engagement with the drive mechanism 28 &c. The knob 33 may now be rotated to one of a number of " bandspread " positions ; when released in such a position, shafts 4, 30 are returned by springs 7, 59 respectively, the drum 12 being positively located by peripheral slots 37, one of which engages a fixed pin 38. The extent to which shaft 4 and condenser 1 return is determined by the corresponding adjustable, preset stop 41, coming to rest against a fixed stop 40. At the same time, the wave-change switch is locked in position by the pin 52, which passes through superimposed holes 68, Fig. 4, in the fixed bracket 56 and pulley 69.