GB795490A - Microtome - Google Patents

Abstract

795,490. Microtomes. SORVALL, Inc., I. April 5, 1956 [April 8, 1955], No. 10460/56. Class 97(1) A microtome comprises a first frame pivotally mounted about a substantially horizontal axis on a base and pivotally carrying a second frame to which a support is pivoted which carries a specimen holder on the end thereof adjacent a knife mounted on the base means being provided to move the specimen holder past the knife and for advancing it towards the knife, the specimen by-passing the knife during a portion of the movement of the holder. Fig. 2 shows the apparatus in which the specimen 266 is mounted in a chuck 262 on the end of a bar 111 pivoted about horizontal and vertical axes at the other end and moved by a crank to move the specimen past the cutting knife 358 for example of glass, the bar being fed towards the blade after each cut. The knife 358 is held by a screw 364, Fig. 12, against abutments 361 on a circular sleeve 357 supported in a collar on a stage 291, the collar being closed to clamp the sleeve 357, Fig. 12, by a cam operated by an arm 337. The stage 291 slides on a platform 271 slidable on the base 35, the stage 291 being pressed by springs against a coarse adjusting screw 322 on a bar 318 pivoted at 317 to the platform 271 and carrying a fine adjustment screw 319 bearing on a bracket 321 fixed to the base 35. By these screws the position of the stage 291 may be adjusted when the members 291 or 271 may be clamped together by a cam operated by an arm 303 and the platform 271 may be clamped to the base. Cyclical movement of the bar 111 to take the specimen past the knife is effected by a link 243, Fig. 13, connected at one end to a crank stud 241 eccentrically mounted on a disc 235 rotated by a hand wheel 231, the other end of the link 243 being loosely articulated with a horizontal pin 246 carried by the bar 111 adjacent the specimen. The bar is guided by an aperture 228 in a plate 225 so that on rotating the wheel 231 the bar 111 is guided down the vertical side B of the aperture to give the cutting stroke, and is returned to its initial position by way of the sloping lower side C of the aperture, the vertical side E and the upper side G during which vertical return between the bar 111 is fed forward a predetermined amount in preparation for the next cutting stroke. The bar 111, is supported at its other end by a pin 101, Fig. 4, mounted for rotation about a vertical axis in a block 91 rotatable about a horizontal axis in bearings 95, 96 carried by arms 81, 82 of a yoke 80 itself rotatable in bearings 65, 76 about a horizontal axis displaced vertically from that of the bearings 95, 96. Thus rotation of the yoke 80 about bearings 65, 76 causes a small horizontal movement of the bar 111 which feeds the specimen 266 towards the knife after each cutting stroke. This rotation of the yoke is effected by a rotatable screw 120 engaging a rider block 144 carried on a pair of arms 138 pivoted to the leg 87 of the yoke 80 so that rotation of the screw pivots the yoke about the bearings 65 and 76. This rotation is effected during the vertical return movement of the bar 111 by a rod 175 connected to the bar 111 by an arm 171 and pivoted at its lower end to a yoke 179, Fig. 7, pivoted on a shaft 181 coaxial with the screw 120 and carrying a pivoted shaft 185 bearing a pawl 186 adapted to engage a ratchet wheel 187 fixed to the screw 120 whereby vertical movement of the rod 175 causes the pawl and ratchet to rotate the screw to feed the bar 111 forward. The extent of the feeding movement is determined by engagement of a second pawl 191, fast to the shaft 185 with a cam disc 192 which holds the pawl 186 clear of the wheel 187 for a portion of the upward stroke of rod 175 dependent on the angular position of the disc 192 which is adjustable by gear 205 driven by a manually operated shaft 209. At the end of the feed movement the yoke 80, and with it the bar 111, may be returned to the initial position under the action of a spring 151, Fig. 5, by operation of a manually operated crank which moves a rod 155 to disengage the rider block 144 from the screw threads.