Improved Mechanical Microtome Knife Sharpener

For more than ten years the automatic microtome knife sharpener described by Fanz 1 has been standard equipment in most large pathology laboratories, saving many hours of tedious labor while producing a far better cutting edge on the knives than hand work could possibly do.

In the apparatus presented here, the glass plate described by Minot and Fanz has been incorporated but the mechanics have been simplified. The time needed for sharpening has been reduced by swinging the knife through an ellipse rather than an arc alone.

Description of Machine. The whole apparatus (Fig. 1) is mounted on a pedestal which has a heavy base fitted with 2-inch casters. P is a 1 20 H.P. geared motor with a 3/4-inch shaft, 4 inches in length, presenting vertically. This shaft carries the small gear I and the 8-inch disc C. The disc C in turn mounts the three 3-inch vacuum cups on which rests the 24-inch glass plate B. This type of mounting holds the plate securely in place but absorbs the torque of starting and stopping. The larger 10-inch gear J is mounted on the supporting plate and attached to it is one of the flat bearings which, with its mate, holds the carriage K for the knife F and turning mechanism G-H. In the center of each bearing is a socket for a locking pin which, when placed in the bearing on J rotates the knife through an ellipse, and when placed in the second bearing rotates the knife through an arc only. The knife may be held fixed in any position desired on the plate by disengaging the small gear I with the lever O.

Mounted on the knife carriage K is the fixture bearing the small motor and turning mechanism H as well as the knife arm and counter weight M.