A hand-powered variable torque driver tool comprising:
- a body having a tubular section and an outwardly-extending grip handle section;
- an elongated squeeze lever pivotally coupled at one end to said tubular section of said body and extending outwardly from said body in essentially spaced and parallel relationship with said grip handle section;
- a helically-channeled drive shaft rotatably mounted in said tubular section of said body in coaxial relationship therewith;
- a drive member coaxially mounted at one end of said drive shaft and extending through an opening at one end of said tubular section of said body;
- a slider mounted on said drive shaft to produce rotational motion of said drive shaft and of said drive member as said slider is moved in a particular direction along said drive shaft;
- and an elongated curved lever pivotally coupled at one end to a selected pivot point on said slider and positioned to be directly engaged by said squeeze lever upon pivotal movement of said squeeze lever towards said grip handle to provide a relatively high torque and low rotational velocity to said shaft during pivotal movement of said squeeze lever through an initial range and to provide relatively low torque and high velocity to said drive shaft during pivotal movement of said squeeze lever through a final range;
- said squeeze lever and said curved lever being shaped to define a fulcrum point between said levers which travels between a first contact position located a predetermined distance from said selected pivot point on said slider through an initial range of movement of said squeeze lever, and a second contact position displaced from said pivot point on said slider a greater distance than said first contact position through said final range of movement of said squeeze lever, said curved lever having maximum leverage at said pivot point on said slider through said initial range of movement of said squeeze lever when the fulcrum point is at said first contact position, and said curved lever having minimum leverage through said final range of movement of said squeeze lever when the fulcrum point is at said second contact position, said squeeze lever and said curved lever having relatively sharp bends in the vicinity of said first and second contact positions so that said contact positions occur primarily in two distinct regions along said squeeze and curved levers as a result of the particular location and radii of said bends;
- and a pivot member pivotally coupling the other end of said curved lever to the end of said grip handle section so that the force applied to said curved lever by said squeeze lever is transmitted to said slider with a magnitude that is a function of the distance between the fulcrum point and said other end of said curved lever.