Compound variable mechanical advantage shifting mechanism

A compound variable mechanical advantage/variable effective length mechanism for applying a pivotal movement to a pivotably mounted device against a resistance, said mechanism comprising:

• a first member comprising a variable mechanical advantage/variable effective length first class lever defined by a substantially rigid first body having a first lever portion extending from a first end to a first fixed pivot axis and a second lever portion extending from said first pivot axis to a second end, said second lever portion defining an axially extending first slot in which a pivot pin having an axis substantially parallel to said first pivot axis is slidably received for pivotal movement therewith about said first pivot axis, said pivot pin movable in said first slot from a first position spaced from said pivot axis by a first distance to a second position spaced from said first pivot axis by a second distance, said second distance greater than said first distance;
• a second member comprising a variable mechanical advantage/variable effective length torque arm defined by a substantially second rigid body, said second rigid body pivotably mounted about a second fixed pivot axis spaced from and substantially parallel to said first pivot axis, said second body extending from said second pivot axis axially toward said second lever portion of said first member, said second member defining an axially extending second slot in which said pivot pin is slidably received for pivotal movement therewith, said second slot extending axially from a third point spaced from said second pivot axis by a third distance toward said second portion of said first member to a fourth point spaced from said second pivot axis by a fourth distance, said fourth distance greater than said third distance, said pivot pin engageable with the walls of said second slot from said third to said fourth point, said pivot pin engaging said walls at said fourth point when in said first position and at said third point when in said second position;
• said pivotably mounted device comprises a shaft coaxial with said second pivot axis and fixed to said second member for rotation therewith about said second pivot axis;
• and
• resilient baising means for biasing said pivot pin to said second position thereof.

A compound variable mechanical advantage/variable effective length mechanism for applying a pivotal movement to a pivotably mounted device against a resistance, said mechanism comprising:

• a first member comprising a variable mechanical advantage/variable effective length first class lever defined by a substantially rigid first body having a first lever portion extending from a first end to a first fixed pivot axis and a second lever portion extending from said first pivot axis to a second end, said second lever portion defining an axially extending first slot in which a pivot pin having an axis substantially parallel to said first pivot axis is slidably received for pivotal movement therewith about said first pivot axis, said pivot pin movable in said first slot from a first position spaced from said pivot axis by a first distance to a second position spaced from said first pivot axis by a second distance, said second distance greater than said first distance;
• a second member comprising a variable mechanical advantage/variable effective length second class lever defined by a substantially second rigid body, said second rigid body pivotably mounted about a second fixed pivot axis spaced from and substantially parallel to said first pivot axis, said second body extending from said second pivot axis axially toward said second lever portion of said first member, said second member defining an axially extending second slot in which said pivot pin is slidably received for pivotal movement therewith, said second slot extending axially from a third point spaced from said second pivot axis by a third distance toward said second portion of said first member to a fourth point spaced from said second pivot axis by a fourth distance, said fourth distance greater than said third distance, said pivot pin engageable with the walls of said second slot from said third to said fourth point, said pivot pin engaging said walls at said fourth point when in said first position and at said third point when in said second position;
• said pivotably mounted device comprising a rigid projection fixed to said second rigid body at a point intermediate to said second pivot axis and said third point, said rigid projection axially displaceable in a direction transverse a line passing through said first and second pivot axes upon pivotal movement of said second member about said second pivot axis;
• and
• resilient biasing means for biasing said pivot pin to said second position thereof.