Balance mechanism

A balance mechanism for weighing an unknown mass by automatically lifting known weights in a single-arm mode comprising:

• a support member;
• two plates, a first rectangular plate supporting said known weights and supporting a pan for receiving said unknown mass to be weighed, and a second rectangular counterbalancing plate coupled to the first through a box lever having diagonal corners connected to a support member through flexible elements that will permit the box lever to pivot about a diagonal axis in response to a vertical force at one free corner connected to a corner of one balance plate or in response to a vertical force at the other free corner connected to a corner of the other balance plate;
• a pair of taut rectangular loop lines, one line being connected to diagonally opposite corners of said first plate and to rigid elements affixed to said support member in a position over free corners of said first plate, and the other line being connected taut to free corners of said first plate and to rigid elements affixed to said support member in a position over the other two corners of said first plate;
• a pair of taut rectangular loop lines suspending said second plate from said first plate in the same manner as said first plate is suspended from said support member by two taut rectangular loop lines, but oriented 90.degree. from the arrangement for said first plate about an axis normal to said plates, whereby any vertical force on one plate is coupled to the other by said box lever to cause said plates to move in opposite directions while said pairs of taut lines maintain said plates substantially parallel.

In a linear response force balance system:

• two plates suspended parallel to each other from a support member, each plate being secured to said support member by a pair of taut rectangular loop lines, one taut line tethering a first pair of diagonally opposite points of one plate to points affixed to said support member over a second pair of diagonally opposite points of said first plate, where each of said second pair of points is on a line bisecting a line between the first pair of tethered points, and the other taut line tethering the second pair of diagonally opposite points to points affixed to the support member over the first pair of diagonally opposite points on said first plate, said second plate being tethered by a pair of rectangular taut lines in a similar manner to points affixed to said first plate, but with corresponding points oriented 90.degree. about an axis normal to said plates;
• biaxial means coupling one plate to the other with opposite ends of said means on one axis connected to said support member, and respective opposite ends of said means on the second axis is connected to diagonally opposite tethered points of the first and second plates, where said second axis is normal to said first axis whereby any force applied to one plate will cause said plates to move in opposite directions;
• metallic capacitor plates disposed opposite to each other, one affixed to one suspended plate and the other affixed to the other suspended plate, and means for sensing capacitance between said metallic plate as a measure of displacement of said suspended plates in linear response to a small force applied to one suspended plate;
• and servo means responsive to said sensing means for restoring said suspended plates to initial positions, thus providing a feedback signal in said servo means proportional to the force applied to the one plate.