Timepiece driven by a source of mechanical energy and regulated by an electric circuit
AssigneeAsulab S.A.
InventorFridolin Wiget
Life of this patent
Estimating the term…
Abstract
The hands of the timepiece are connected to a barrel spring which also drives the rotor of a generator at a speed greater than a desired speed Vc. The electric energy supplied by the generator energizes a slaving circuit that includes a transistor which short-circuits the coil of the generator and thus brakes the rotor down to a speed less than the desired speed Vc when a comparator indicates that this rotor is ahead with respect to its theoretical angular position. A limiting circuit limits the duration of the braking action of the rotor to a fraction of the period of the a.c. voltage supplied by the generator. This arrangement ensures that the slaving circuit is adequately energized even if the rotor is substantially ahead.
Claims2
A timepiece having:
- an electrical energy generator comprising a rotor and means for supplying electrical energy in response to rotation of said rotor;
- a source of mechanical energy mechanically coupled to said rotor to cause said rotor to rotate at a speed greater than a set desired speed;
- and
- slaving means for slaving the rotational speed of said rotor to said desired speed, said slaving means being electrically connected to said generator to receive electrical energy therefrom and comprising:
- measuring means coupled to said generator for producing a plurality of measurement pulses, each of said measurement pulses being produced in response to said rotor travelling through a particular angular position so as to determine its actual angular position;
- reference means for producing a plurality of periodic reference pulses having a period equal to that of said measurement pulses when said rotor is rotating at said desired speed, said reference pulses being independent of said measurement pulses and being representative of a theoretical angular position of said rotor;
- comparing means for supplying a comparison signal representative of the difference between a first number, which is the number of said reference pulses that are produced from a determined instant, and a second number, which is the number of said measurement pulses that are produced from said determined instant, said comparison signal having a first state and a second state dependent on whether said first number is less than or greater than said second number respectively;
- braking means responsive to a command signal for applying to said rotor a braking torque that imposes upon said rotor a speed of rotation that is less than said desired speed, said braking means then short-circuiting said means for supplying electrical energy;
- and control means responsive to each of said measurement pulses only when said comparison signal is in said first state to produce a command signal in the form of a command pulse of fixed duration so that the braking means only applies a braking torque to the rotor when the latter is leading with respect to said theoretical angular position.
Dependencies are inferred from the claim text.