Fine tuning mechanism in a tuner

A tuner for use in a telecommunication receiver which comprises, in combination:

• a support structure including a wall member;
• a main shaft rotatably extending through the wall member and having one end portion accessible to an operator of the tuner;
• a rotary drum having a plurality of oscillation coils, peripherally mounted thereon in equally spaced relation to each other and also to the longitudinal axis of the drum, and elongated fine tuning members one for each oscillation coil, each of said fine tuning members having a geared head and an elongated body adapted to be adjustably moved inside of the corresponding oscillation coil for fine tuning, said drum being mounted on the other end portion of the main shaft for rotation together therewith and supported in position for stepwise rotation through any one of a plurality of detent stop positions substantially equal in number to the number of the fine tuning members;
• an auxiliary hollow shaft coaxially mounted on the one end of the main shaft for rotation about and independently of the main shaft and also for axial sliding movement between projected and retracted positions in a direction away from and close to the wall member, respectively, said auxiliary hollow shaft having a drive gear rigidly mounted thereon;
• a first biasing means for biasing the auxiliary hollow shaft to the projected position;
• transmission means including a spindle, having first and second gears on opposite end portions thereof in spaced relation with each other, said first and second gears being respectively engageable with the drive gear and the respective geared heads for transmitting the rotational force of the auxiliary hollow shaft to one of the fine tuning members which has the geared head engaged with the second gear and a support plate means rotatably carrying said spindle with said first and second gears positioned on opposite sides of said support plate means, said support plate means being supported for movement between a disconnected position in which said second gear is disengaged from a geared head and a connected position in which said second gear is engaged with a gear head, and said support plate means being engaged by said auxiliary hollow shaft to move from the disconnected position to the connected position in response to the movement of the auxiliary hollow shaft from the projected position to the retracted position, whereby the rotational force of the auxiliary hollow shaft is, when the support plate means is moved to the connected position and the auxiliary hollow shaft is held in the retracted position against the first biasing means, transmitted to said one of the fine tuning members;
• a second biasing means for biasing the support plate means to the disconnected position;
• and
• means for supporting said support plate means, said supporting means including a support wall rigidly secured to the wall member of the support structure in spaced relation to said wall member, at least said drive gear on the auxiliary hollow shaft, said first gear on the spindle and said support plate means being accommodated within a space defined between said wall means and said support wall, said support plate means having a portion pivotally connected to said support wall for enabling said support plate means to pivot between said connected disconnected positions.