1. In a clock mechanism which has a mainspring providing torque to a drive shaft, and motor means adapted to wind said mainspring, said mechanism having an operating sequence consisting of a relatively brief wind cycle in which said motor means is actuated and a relatively long unwind cycle, the combination of: switch means for energizing the motor means from a power source, said switch means comprising two electrical conductors, one physically biased away from the other, said switch means thereby comprising an electrically normally open switch when not engaged, cam means driven by the drive shaft, including a cam surface positioned relative to said switch for mechanically engaging said switch, initially closing the same and energizing the motor means, all at the end of an unwind cycle, said cam means being otherwise free of engagement with said switch for the major portion of said unwind cycle, and means driven by said motor and active at the end of the rewind cycle for moving said cam surface first into further engagement with and later out of engagement with said switch, thereby permitting the switch to resume its open condition and deenergizing said motor means.

1. In a clock mechanism which has a mainspring providing torque to a drive shaft, and motor means adapted to wind said mainspring, said mechanism having an operating sequence consisting of a relatively brief wind cycle in which said motor means is actuated and a relatively long unwind cycle, the combination of: switch means for energizing the motor means from a power source, said switch means comprising two electrical conductors, one physically biased away from the other, said switch means thereby comprising an electrically normally open switch when not engaged, cam means driven by the drive shaft, including a cam surface positioned relative to said switch for mechanically engaging said switch, initially closing the same and energizing the motor means, all at the end of an unwind cycle, said cam means being otherwise free of engagement with said switch for the major portion of said unwind cycle, and means driven by said motor and active at the end of the rewind cycle for moving said cam surface first into further engagement with and later out of engagement with said switch, thereby permitting the switch to resume its open condition and deenergizing said motor means.

3. An electromechanical rewind device for clock mechanism including a drive shaft and a main power spring having one end drivingly connected to the shaft and its opposite end drivingly connected to rewind means operatively coupled with driving means of a normally idle electrical motor, comprising: means for electrically powering said motor including an electrical circuit and a control switch normally biased into open condition, said switch comprising a pair of normally spaced-apart switch arms each of which has an electrical contact; switch-operating means mounted for movement relative to said switch and operative to deflect one of said arms toward the other of said arms to effect closing engagement of said contacts; means driven by said shaft for moving said switch-operating means after an interval of spring-driven rotation of said shaft and with energy supplied by said spring, to close said switch for energizing the motor to drive said rewind means; and an element actuated by said rewind means and operative after a predetermined amount of motor operation to move said switch-operating means, causing further deflection of said one of said arms and subsequently releasing said one of said arms, thus opening said switch to stop the motor, the force required for said further deflection being greater than normally obtained through said shaft-driven means from said spring.

8. In a battery operated clock mechanism, a clock movement having a mainspring adapted to be wound to a first degree of tension for powering the operation of said clock movement throughout a designated time period, at the end of which said mainspring assumes a second degree of tension motor means coupled to said clock movement for winding said mainspring upon energization of said motor means normally open electrical switch means adapted to be closed by physical engagement with a mechanical member, said switch means being coupled with said motor means for conditionally energizing the same from a power source upon closure of said switch means cam means coupled to said clock movement and positioned relative to said switch means so as to be out of engagement therewith during a major portion of said designated time period, said cam means including a mechanical member which initially engages said switch means only at the end of said designated time period for closing the same, energizing said motor, winding said mainspring from said second degree of tension to said first degree of tension, and thereafter disengaging said switch means.

9. In combination with a clock mechanism including a drive shaft and means supporting the shaft rotatably, the shaft having driving gear means thereon for actuating the clock mechanism, a mainspring operatively connected at one end to the shaft and at its opposite end to a rewind wheel relatively rotatably mounted on the shaft and having a driving coupling with a normally idle electrical motor, the improvement comprising: a rewind device comprising a member having a driving coupling with the shaft but capable of a limited range of overrun relative rotary movement with respect to the shaft; a switch-operating cam on said member; a motor-operating circuit including a normally-open resilient switch element mounted to be moved to closed position by said cam as moved by its coupling with the shaft; and tripping means carried by said wheel and travelling therewith, when the wheel is rotated on the shaft to wind the spring, to overtake said cam and drive it for further deflecting and then releasing said switch element to open position at termination of a rewind cycle as permitted by the overrunning capability of said member, the force required for said further deflection being greater than can be provided through said cam by said mainspring.