The SEMPRE watchwinder is the first and only watch winding device that will keep virtually any hand-wound mechanical watch with an accessible crown fully wound when unworn. This patented design is truly unique in that it replicates the human action of finger winding a watch by rotating the winding crown similarly in a clockwise direction. The SEMPRE design substitutes a mechanical finger arrangement, called a "collet", which grasps the watch’s crown securely and rotates it. Several different size collets are provided to fit any watch crown diameter from 3 to 9 millimeters. These collets are custom made of acetal plastic to prevent scratching or marring of polished watchcase surfaces. The collet is mounted in a rotating tubular drive shaft, supported by low-torque precision ball bearings. It is powered by a miniature servomotor coupled to techno-polymer drive gear system fitted with a safety slip clutch. The collet is opened by pushing a spring-loaded plunger at the opposite end of the drive shaft. Releasing the plunger closes the collet, clamping it on the watch crown. Just as an individual winding his or her watch senses the increasing turning resistance of the crown as the watch is being wound, the microprocessor "brain" of the SEMPRE winder monitors the electrical current drawn by the gear motor as it rotates. The amount of force required to wind the mainspring of a mechanical watch, known as the winding torque, increases as the watch is being wound. As the torque increases, the drive motor draws more current. The control circuit is user-adjustable to shutdown the system when it senses that the current has reached a pre-set limit, one which is well below the maximum torque that the watch mainspring can handle. To prevent "overbanking" the drive reverses the crown momentarily after shutdown. For safety purposes, the drive system is fitted with a mechanical slip-clutch which has been factory set to slip at a safe torque in the event of a microprocessor failure. This redundancy eliminates any possibility of stressing or breaking the mainspring of an expensive and, perhaps delicate, mechanical watch. In operation, the winder automatically turns on every twenty-four hours. Upon actuation, the drive motor begins rotating the collet for 8 minutes. With the collet rotating at approximately 6 rpm, this provides a maximum of 48 crown rotations per day. However in practice, the actual number of rotations is controlled by the current feedback circuit whose priority is to shut down the motor based on torque, rather than by time. Size = 5.1"H x 9.7"W x 7.8"D

Retail Price $2,295.00

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