Mass-balancing arrangement and microtome using same

A microtome comprising:

• an object carriage to which a specimen holder is mounted;
• drive means for moving the object carriage up and down in a vertical path;
• and
• a mass-balancing arrangement for balancing the object carriage, the mass-balancing arrangement comprising:
• a pre-loaded spring member (14);
• a lever (16, 31) pivotable about a pivot pin (21), the lever having an upper lever arm (19, 32) and a lower lever arm (20, 33) on opposite sides of the pivot pin, wherein one of the upper and lower lever arms includes an outer end surface having a circular-arc contour, and another of the upper and lower lever arms includes an outer end surface having a cam contour;
• a first drawing member (24) connecting the upper lever arm (19, 32) to the object carriage, wherein a first torque is developed about the pivot pin;
• a second drawing member (17) connecting the lower lever arm (20, 33) to the spring member (14), wherein a second torque is developed about the pivot pin in an angular direction opposite the first torque;
• and
• a first roller (15) for deflecting the first drawing member (24);
• wherein the first torque and the second torque are kept balanced with each other during displacement of the object carriage;
• wherein the first drawing member (24) is fixedly coupled to a distal end (22) of the outer end surface of the upper lever arm (19, 32), and the second drawing member (17) is fixedly coupled to a distal end (23) of the outer end surface of the lower lever arm (20, 33);
• and
• wherein a varying portion of the first drawing member (24) is in contact with the outer end surface of the upper lever arm (19, 32) defining a first release point where the first drawing member (24) is no longer in contact with the outer end surface of the upper lever arm (19, 23), and a varying portion of the second drawing member (17) is in contact with the outer end surface of the lower lever arm (20, 33) defining a second release point where the second drawing member (17) is no longer in contact with the outer end surface of the lower lever arm (20, 33), such that the first release point, the pivot pin (21), and the second release point are collinear and remain collinear throughout the displacement of the movable mass.