Microtome

摘要

791,042. Microtomes. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Oct. 25, 1955 [Oct. 28, 1954], No. 30470/55. Class 97(1) In a microtome, thermal expansion of a member carrying an oscillating specimen holder, or a knife holder, is used to feed the specimen for cutting, and an electrostrictive or magnetostrictive contraction of the member is used to retract the specimen. Preferably, the heating of the member is effected periodically by the passage of a direct current through a heating and inductance coil, the member having sufficient thermal capacity for its length to increase at a substantially constant rate. The periodical heating current produces the magnetic field for the magnetostrictive contraction. The downward oscillation or cutting stroke of the specimen holder 17 takes place under gravity and elastic forces in leaf spring 16 and upward motion is imparted by the interaction of permanent magnet 19 and inductance coil 23. In the form shown, heating and inductance coil 13 and inductance coil 23 are both operated by rotary switches and coil 13 is energized and de-energized just before 23 so that the magnetostrictive contraction takes place just before the specimen 18 is raised and the member 10 is restored to its uncontracted length just before the specimen holder 17 starts its downward cutting stroke. A dash-pot damping device 21 is provided to ensure even motion of the holder 17. The knife 2, which may be a safety razor blade having its cutting edge finely polished, is carried on trough 1 which is mounted for position. ing on mutually perpendicular slides 3 and 4. The thickness of the sections is preferably varied from, for example, 50 Angstrom units to 300-400 Angstrom units, by varying the duration of the periods during which current is passed through coil 13 rather than by varying the magnitude of the current. In an alternative construction a conbinuously energized non-inductively wound heating coil and a separate inductance coil are provided. The member 10 may be made of nickel iron or any other metal having negative magnetostriction. Electrostrictive material may be used and heated by means of a coil.