An electronic timepiece comprising a step-motor including a stator and rotor is disclosed. The timepiece is so constructed and arranged that a coil winding core of the stator is located between the stator and a dial of the timepiece and that said stator is disposed on said coil winding core.
A small synchronous motor is provided with a stator winding wound around a stator core. Conversion efficiency is improved by setting the ratio of the coil length (L) to the thickness between the center of the core and the outer most periphery of the coil (R) to be L/R to 40.
In a wristwatch movement with a stepping motor with a rotor connected to drive a gear train which periodically advances the hands of the wristwatch, the stepping motor has a flat stator piece secured in a plastic movement frame. A coilcore assembly comprising a flat hook-shaped core plate having a straight core portion of uniform width with a coil inserted over the free hand of the core portion is secured to the stator so that opposite ends of the hook-shaped member overlap opposite ends the stator to complete a path for the magnetic flux. The hook-shaped coil core is placed on top of the stator during assembly and is held down by insulated clamping means such as a bridge or circuit board bolted to the frame at the time of final assembly. Preferably, the stator and coil core member are located with respect to one another by plastic studs integral with the frame extending through aligned holes in the stator and coil core. Some of the studs receive bolts which hold the clamping means to the frame.
The watch casing 102 is made of plastics material. The stator 2 of the motor serves at the same time as the support for the rotor 32 and as a plate for the spindles 18, 22, 24 for the hands and the gear train 48, 46, 47, 20. The printed circuit 304 is secured to the bottom 104 of the casing by heat-sealing. The cell is housed in a chamber 262 disposed in a thick portion of the bottom of the casing.
An improved structure is disclosed for the movement of an electronic quartz crystal controlled wristwatch of very small size, suitable for use as a ladies bracelet timepiece. The configuration of this structure is such that a relatively large capacity battery can be utilized, thereby ensuring satisfactory battery life, by positioning the battery such as to substantially cover the wheel train of the timepiece and by a special arrangement of shapes and positions for other components of the timepiece.
