| 摘要 |
<p>1,198,949. Microtomes. IVAN SORVALL Inc. Oct.18, 1968 [Oct.26, 1967], No.49649/68. Heading G2J. A microtome has a stage 221 Fig. 3, movable transversely in steps across a deck 36 and a cutting assembly 65 which moves about a pivot 64 in a chopping motion when the stage is stationary. A shaft 54 together with cams 58, 203 Fig. 6, is rotated by means of a belt, and pulleys connected to a variable speed motor 44 so that cam 58 alternately engages and releases cutting assembly cam follower 86 thereby causing the chopping action. Rotation of cam 203 rocks a bell crank 192 to slide a rack 196 which is held in operative engagement with gear teeth 197 by means of backlash bracket 198 and a spring 201, thereby rotating a gear-wheel 187 and through a one way sprag clutch 189 and lead screw 158 moving carriage 153 to produce a stepping motion. The carriage 153 slides on rods 151 and 152. A threaded nut 174 is pivotally connected to carriage 153, and is normally urged upwards by a spring blade 177 so as to engage with threads 164 on lead screw 158, and, from which nut 174 can be disengaged by depressing lever 172, so causing a spring connected between the frame of the apparatus and the carriage, to pull the carriage to one side. On the front of the apparatus is a power switch 236 and a motor circuit switch 241. The carriage has several plates 255 and a guard element 256 designed to operate switch 241 to open circuit when the stage has gone across the deck 36 and to prevent operation of the switch by hand when the carriage is in an intermediate position. The cutting action force, provided by the torsion spring 88 connected between shaft 64 and assembly 65, is varied by rotating shaft 64 into several selected positions by means of a retractable knob (92), Fig 15 (not shown). The knife blade 136 can be adjusted relative to the stage by loosening screws (147) and adjusting part (133) Fig. 3A (not shown). The downward motion of the blade 136 is limited by a pad 81 on the rear 74 of cutting assembly 65 contacting a stop element 79 on a threaded shaft 78 whose height can be varied by knob 83 and locked by knob 85. Vibration damping means are provided consisting of a rearwardly extending integrally formed arm 107 which is pivotally connected by means of dowel pins and links to arm 112 of a one way clutch 113, thereby providing controlled resistance to the upward motion of cutting arm 71. The pressure between plate (121) and clutch disc (118) Fig. 18 (not shown), is adjustable by screw (124) to provide the required frictional engagement. The magnitude of the incremental motion of the carriage is determined by the length of the rearward stroke of rock 196 which is determined by thickness control cam 206, as shown, limiting movement of bell crank 192. Cam 206 is rotated by means of knob (216) to the desired position. Rapid placement and replacement of the specimen is provided by mounting the specimen by agar on to a disc stage (226), Figs. 12 & 13 (not shown), which is fixed to the carriage by pressing the ports (224) of a circular clamp spring, removing clamp (227) and placing disc (226) on the carriage, then replacing clamp (227) and releasing parts (224).</p> |
