Apparatus for adjusting the tension of an elongated stretched filament

Claim 1

Apparatus held in the hand of a human operator for adjusting the tension of strings on a musical instrument comprising: a container having a substantially rectangular form which is shaped to be grasped and held in one hand of a human operator, said container having a depressed area along one edge juxtaposed the position of the thumb of the operator for mounting a thumb operated switch therein, said container extending from substantially the heel location of the operator''s hand through the space between the operator''s thumb and index finger; an electric motor mounted inside said container for transforming a source of direct current electrical energy into mechanical motion; a shaft rotatably mounted through the wall of said container adjacent the end of said container held nearest the thumb and index finger of the operator, said shaft being substantially perpendicular to the palm of the operator''s hand when the container is held therein to provide a mechanical advantage related to the distance from the center of said shaft to the end of said container held nearest the heel location of the operator''s hand; a gear train mounted inside said container and connected between said electric motor and said shaft for converting the mechanical motion of said motor to a rotating motion for turning said shaft; a socket connected to said shaft external to said container, said socket being shaped to engage a tuning peg of a stringed musical instrument, whereby each string of the instrument is tuned as said peg is turned by said socket; a pair of contacts for connection to the terminals of a direct current electrical energy source; a thumb operated double-pole-double-throw switch mounted in said depressed area of said container, said switch being connected to said pair of contacts in a manner to connect said motor in a given polarity to said pair of contacts when the poles of said switch are moved in one of the double-throw positions and to connect said motor to said pair of contacts in a polarity reversed from said given polarity when said poles are moved in the other of said double-throw positions, whereby said motor is operated in a forward and reverse direction to increase and decrease the tension of each string.