Spring balance apparatus provided with compensation for measuring error due to temperature changes

Claim 1

A spring balance apparatus comprising: an elongated weighing lever having a weighing side at one end thereof adapted to receive a mass to be weighed, and a biasing side on the other end thereof with a seat on one surface adapted to receive a biasing force; biasing means for exerting a biasing force on said seat in a direction substantially perpendicular to the longitudinal dimension of said weighing lever; a knife-edge member extending in a direction substantially perpendicular to the longitudinal dimension of said weighing lever, having a first pivot end contacting said seat and a second end associating with said biasing means for transferring the force exerted thereby to said seat; an actuating lever rigidly connected at one of its ends to said knife-edge member, extending in a direction substantially parallel to the longitudinal dimension of said weighing lever, and pivoting relative to said weighing lever about said pivot end of said knife-edge member; an elongated bimetallic element having one end fixedly mounted on the surface of said weighing lever opposite from said seat, and the other end spaced from said weighing lever, aligned with the end of said actuating levEr remote from said knife-edge member, and free to move toward and away from said actuating lever; spacer means for engaging the free end of said bimetallic element and the end of said actuating lever remote from said knife-edge member, and for maintaining a predetermined spacing therebetween; biasing engagement means attached to said actuating lever intermediate said knife-edge member and said spacer means, and to said bimetallic element intermediate said fixed end and said free end for biasing together said actuating lever and said bimetallic element; and a fulcrum point on said weighing lever intermediate said weighing side and said biasing side, about which said weighing lever is free to pivot; said bimetallic element, said knife-edge member, said actuating lever and said biasing means associating in such a manner that an excursion of said bimetallic element as a result of a temperature change pivots said actuating lever about the pivot end of said knife-edge member, and thereby changes the spacing between said fulcrum and the second end of said knifeedge member through which the force exerted by the biasing means transfers, hence modifying the ratio of transmission of forces to compensate for measuring error that would otherwise occur due to temperature change.