US3895462A

US3895462A - Microtome-blade sharpening machine

Info

Publication number: US3895462A
Application number: US342944A
Authority: US
Inventors: Maurice Garin
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-03-22
Filing date: 1973-03-20
Publication date: 1975-07-22
Anticipated expiration: 1992-07-22
Also published as: JPS4913797A; FR2177245A5

Abstract

A machine designed to automatically perform the sharpening of microtome blades in two sequences: roughing, then finishing, without requiring the turning over of the blade. The machine is further characterized by the fact that the blade oscillates vertically in order to bring its edge into alternate contact with two superposed grinding wheels, with the oscillating motion of the blade accompanied by a reciprocal, transverse motion parallel to its cutting edge, and further with an in place, transverse vibrating motion of the blade.

Description

United States Patent [:91

Garin MlCROTOME-BLADE SHARPENING MACHINE [76] Inventor: Maurice Carin, 5 rue St. Pirest,

69200 Venissieux, France [22] Filed: Mar. 20, 1973 [2]] App]. No: 342,944

[30] Foreign Application Priority Data Mar 32, I972 France 72.1074l [52] U.S. Cl 51/85 BS [5 [1 Int. Cl B24b 3/48 [58] Field of Search 51/85 BS, 85 R, 80 BS, 51/8! BS, 86 BS, 80 R, 84 BS, 92 BS, 93, 94 R, 77 R [56] References Cited UNITED STATES PATENTS l,1U2.7l)6 7/l9l4 Winter 5l/85 B5 I] 3,895,462 July 22, 1975 l.l88.352 6/l9l6 Odell 5l/85 BS 1,390.726 9/l92l Scheiwer 51/77 R 3,589,075 6/l97l Carlson i. 5l/94 R X Primary E.raminerDonald G. Kelly Attorney, Agent, or FirmRaymond A. Robic; J Ernest Kenney; Arthur Schwartz [57] ABSTRACT 12 Claims, [2 Drawing Figures 31 r r E :1 l; i i F' PATENTEDJUL 22 ms SHEET PATENTEDJUL 22 ms SHEET PATENTED L 2 2 SHEET I\IICR()TUME-BLADE SHARPENING MACHINE DES(RIPTI()N OF A PREFERRED EMBODIMENT OF THE INVENTION The present invention relates to a machine designed to automatically sharpen microtome blades.

The difficulty in perfectly sharpening microtome blades is well known. and is frequently the reason for an excessive number of imperfect cross-sections that are difficult to inspect by practical means.

It is also known that sharpening is an unpleasant. long and tedious work. which is very frequently left to unskilled or improperly trained labor.

Finally. microtome blade sharpening techniques. already treated quite lowly in the mechanical industries. had made little progress with respect to the precise forming of blade cross-sections useful in the histological field.

The object of the invention is to automate a microtome blade grinding machine that incorporates advanced techniques for forming precise cutting angles on the blade.

The machine of this invention is characterized by the fact that it obtains the sharpening of both faces of the blade cutting edge without requiring its turning over. For this purpose. the blade is caused to oscillate vertically so that its edge comes alternatively in contact with two superposed abrasivefitted sharpening rolls or grinding wheels. This sharpening develops successively in two sequences. one for the roughing and the other for the finishing operation. without changing the various adjustments of position. Moreover. another characteristic of the machine consists in the fact that the vertical oscillating motion of the blade is accompanied by an alternating or reciprocating motion of translation parallel to the cutting edge of the blade and further by a vibratory motion in place in the same general sense as the transverse motion.

In order to obtain these motions ofthe blade. the machine comprises a base. a first lower carriage supporting a second. upper carriage on which a blade holder is mounted. and a grinding wheel support and transfer assembly. By a rectilinear. forward displacement ad justable in amplitude and position. the lower carrier ensures the feeding of the blade in contact with the sharpening rolls and by rcarw ard. retraction at the end of the sequence. withdraws the blades from the sharpening position. The upper carrier ensures. b v a displacement perpendicular to the preceding motion. the aforesaid reciprocating. transverse motion of the blade. The blade holder ensures. by a vertical oscillating motion about a transverse axis. the successive passage of the edge faces in contact with the upper roll. then with the low er roll. The grinding wheel support and transfer assembly ensures. by a 180 rotation of the transfer means. the successnc prcscntation in working position before the blade of the roughing rolls. then of the fin ishing rolls.

Ihe accompanying drawings show. by way of example. but not intended to be by way of limitation. a prefcrrcd embodiment of the machine constructed in accordance with the present invention.

FIG. I is a diagrammatic elevation view of the machine of the present imention:

FIG. 2 is a plan view of FIG. I:

FIG. 3 shows diagrammatically the blade edge positions during rough and finishing grinding operations;

FIG. 4 is a sectional view of a portion of the grinding wheel driving system and the transfer means;

FIG. 5 is a sectional view taken along line VV of FIG. 4;

FIG. 6 represents the detail of one of the drive pinions for the grinding wheels;

FIG. 7 shows the detail of the grinding wheel transfer means and a ratchet drive assembly for same; and the lower carriage advancing and retracting rack;

FIG. 8 represents a plan view of the upper carriage reciprocating drive system and the cam drive assembly for oscillating the blade holder;

FIG. 9 is a front view of the blade holder cam drive assembly. as seen along line IXIX of FIG. 10;

FIG. 10 is a side view of the blade holder cam drive assembly taken along XX of FIG. 8;

FIG. 11 is a detailed view of the lower carriage position adjustment means and the blade angle index means; and

FIG. 12 shows operative positions of the lower carriage moving means.

As shown by FIGS. 1 and 2. the machine comprises a base I on which is supported a lower carriage 2 surmounted by an upper carriage 3 supporting a blade holder 4. Lower carriage 2 slides as shown by arrows on base I. To the rear of base I are provided supports for a grinding wheel transfer system 7 supporting at least four abrasive-fitted grinding rolls or wheels; rolls E and E for the roughing operation and rolls F and F' for the finishing operation.

The microtome blade is maintained at the end of the blade holder 4 by jaws 8. Blade holder 4 is supported for oscillation about axis 5.

The transfer means 7 may swivel about a transfer shaft 9 by means of a lever 60 (FIG. 12] on shaft III. rigid with pinion ll. driving simultaneously a rack [2 connected to the lower carriage. and a pinion I3. Pinion [3 is loose on the shaft 9. but rigid with a ratchet drive 14 and a ratchet 15 which is biased inwardly by a spring 16 for driving a notched ratchet disc 17 rigidly connected to shaft 9. On the rack 12 is provided a protrusion [8 designed to release a detent I9 which normally holds disc l7 fixed. The ratchet l9 pivoted at 20 carries a spring-biased no-back cog 21 biased by spring 22 anchored between the clip 23 and pin 24. The cog 2l is pivotally connected at pin 25 to detent I9.

A grinding wheel drive motor. not shown. at the back of the machine. drives the grinding wheels through a pulley 26 (FIG. 4). which includes a conical pinion 27. The pulley rotates freely with respect to the transfer shaft 9. This pinion 27 drives a pair of gears 29 mounted on shaft 28 (FIG. 5 each gear having conical and helical gear teeth. Each helical pinion drives simultaneously two gears 30 and 3] integral with the grinding rolls E and F (FIGS. -I and 5).

The peripheral working surfaces of rolls E are separated by a distance between centers which is slightly greater than their diameter D in order to maintain their working surfaces separated. The rolls F have a diameter (I smaller than that of D of the rolls E in order that. according to the FIG. 3. the edge of blade A makes contact with the roll F along a width 1 smaller than the mark I. left by the roll E. Thus. the operation is rendered very simple. without any particular adjustment between the two operations of roughing and finishing (see FIG. 3).

As shown in FIG. 8. the lower carriage 2 carries a motor. not shown here. having an output shaft 32 fixed to a crank 33, one end of which is coupled by a pin 3-4 with a pitman 3S driving the upper carrier 3 through a pin or shaft 36. The other end of part 33 comprises a cam drive acting on an elongated cam element 37. Cam 37 is mounted loosely on shaft 38 and includes an eccentric 39 and another elonaged cam element 40 oriented 90 with respect to the cam 37. The cam 40 is moved by contact with abutment 42 fixed on the lower carrier 2 during the reciprocal motion of the upper carrier 3. The axis 38 supports the earns 37 and 40 and the eccentric 39 is rigidly fixed with respect to the upper carrier 3 (FIG. 8).

The eccentric 39 causes oscillating vertical motion of a connecting rod 41 coupled with a slide block 42 articulating a blade holder dri\e linkage 43 whose end carries a roller 44 by means of pin 45. The roller 44 is engaged in a notched member 46 coupled with the carrier 3 by a pin 47. The notched member 46 includes a supporting pivot axis 45 traversed by an adjusting screw 49. Member 46 transmits the oscillating motion to the blade holder 4 pivoted at 50 and permits the adjustment of the position of the cutting edge of the blade A with respect to a reference plane X-X' of FIG. I. The blade normally lies in this plane when the cam 37 is in the position shown in FIG. 9. The ends of the shaft 45 of the roller 44 are resiliently coupled to the ends of pivot shaft 47 of the notched member 46 by two springs. not shown here (FIGS. 9 and The blade holder assembly 4 (FIGS. 1 and 2) includes two laminated springs 51 supporting the jaws 8 through a small bar 52 which has adjustment means to vary the spacing between the jaws.

The rack 12 is fastened to the lower carrier by means of the assembly 53 (FIGS. 1 and ll) comprising a threaded shaft 54 and a nut follower 55. The shaft 54 is moved by a central knob 56 provided with an index pointer 59 movable with respect to a graduated sector 57 showing directly the cutting angle of the blade edge.

The operation of the machine is as follows:

After the placing the blade A in the holder in its retracted position. the edge of the blade is adjusted with respect to the reference plane X-X' of FIG. I by means of the control knob 58. and the blade position is centered in the reference plane.

The rack control lever 60 is brought into the starting reference" position (FIG. 12 intermediate the retracf and *grind positions.

Then. using the control knob 56. the blade A is ad vanced until a reference stop means is contacted in the index assembly. and the index 59 on the knob 56 is set to the zero position on the graduated scale 57. When the cutting angle is chosen. the knob 56 is adjusted to back the lower carrier 2 rearwardly a distance which corresponds to the withdrawal of blade A that is neces sary to obtain this chosen angle. these angle values being indicated on the sector 57.

The lever 60 is then rotated fully to the grind position. without any effect on the rotation of the transfer means 7, since the protrusion 18(FlG. 7) passes under the dctcnt 29 which retracts through its spring means while the ratchet element on the notched disc 17 continues its reverse travel opposite to that by which transfer of the grinding wheels is accomplished (counterclockwise in FIG. 7).

In order to obtain the sharpening time corresponding to the work required by the condition of the blade A. a mechanical or electrical timer (not shown) may he provided.

The starting of the motors of the machine causes the simultaneous rotation of the sharpening rolls EE' and F-F'; the reciprocating motion of the upper carrier 3 (through pitman 35) driving the oscillation of the blade holder 4 and the starting of the motor (not shown) transmitting by the intermediary of the laminate springs 51 the transverse vibratory motion of the blade A.

When the rough grinding or sharpening time has elapsed. the motors come to a standstill. To inspect the blade A. the crank is reset to starting reference position. If the rough sharpening is satisfactory. the return rotation of the lever 60 is continued till it reaches the retract position which is diametrically opposite to the grind position; this rotation of lever 60 has the effect of rotating transfer means 7 180 and the presentation of the second rolls FF' in the working position.

For the finish grinding operation. the blade is reset in the same manner as recited above. and lever 60 is returned to the grind position.

The function of the notched member 46 is not only to transmit the oscillating vertical motion of the blade A. but also to operate as a force limiter for the blade A against the rolls EF. For this purpose. the element 46 comprises two sloped surfaces forming between themselves an angle of at least against which the roller 44 bears. the said roller being biased into the notch by springs (not shown. for clarity The various working mechanisms are covered by a safety protecting transparent bonnet. The lifting of the bonnet normally causes the complete standstill of the running elements. whilst the closing ofsaid bonnet cannot alone ensure the starting.

Moreover. it is preferred to locate the blade A in a precise manner in relation to the vertical plane joining the axes of roll pairs EE' and F-F'. by means of a precise detent or stop means 61 on the indexing assembly of FIG. 12 to control the stroke between the starting reference" point and the grind" point to provide for a displacement of constant length of the lower carriage 2 when the lever is moved between these positions.

What is claimed is:

1. in a microtome blade grinding machine including means for moving a blade to be sharpened between an advanced sharpening position between a pair of driven grinding wheels and a retracted position away from said grinding wheels. the improvement comprising:

a. two pairs of grinding wheels mounted for rotation as a unit about a transfer axis. said grinding wheel pairs comprising roughing and finishing grinders:

h. each of said grinding wheel pairs including spaced grinding wheels mounted for rotation about paral lel. coplanar axes. one of said pairs of grinding wheels normally being in working position for sharpening a blade edge;

. means for selectively causing said grinding wheel pairs to exchange positions by rotation of said grinding wheel pairs as a unit about said transfer axis; and

. said grinding wheel position changing means being connected to said blade moving means in such a manner that retraction motion of said blade causes simultaneous. automatic exchange of position of said grinding wheel pairs.

2. A microtome blade sharpening machine comprising:

a. means for supporting a blade to be sharpened for vertical. oscillating motion with respect to a generally horizontal reference plane. and about a transverse axis lying in said reference plane: and means for oscillating said blade about said axis during a sharpening operation.

b. first and second pairs of grinding wheels. each pair being mounted for rotation about vertically spaced. generally horizontal. transverse axes. and both pairs being mounted for rotation as a unit about a transfer axis;

. means for driving said grinding wheels about their respective axes:

d. means for advancing said blade to a sharpening position between said first pair of grinding wheels whereby opposite sides of its edge is presented to each grinding wheel for sharpening when said blade is oscillated;

e. means for retracting said blade to a rearward position away from said first pair of grinding wheels; f. means operable synchronously with said blade rctracting means for rotating said grinder wheel pairs as a unit about said transfer axis so as to cause exchange of positions between said grinding wheel pairs. whereby the second grinding wheel pair is placed in a working position with respect to a blade to be sharpened while said blade is moved to its retracted position;

. the peripheral surfaces of each of said grinding wheel pairs being normally separated during a sharpening operation.

3. The microtome blade sharpening machine recited in claim 2 wherein said first grinding wheel pair is a roughing grinder and said second grinding wheel pair is a finishing grinder.

4. The microtome blade sharpening machine recited in claim 2. further including means for supporting said blade to be sharpened for reciprocating. transverse motion. and means synchronously operable with said blade oscillating means for causing said blade to reciprocate transversely during a sharpening operation during the time the edge of said blade to be sharpened is in contact with each of said grinding wheels.

5. The microtome blade sharpening machine recited in claim 4. further including means for vibrating said blade transversely in the same sense as said transverse motion during a sharpening operation.

6. A microtome blade sharpening machine comprising:

a. a base;

b. a lower carriage mounted on said base. said lower carriage movable between a forward working position and a rearward retracted position:

c. an upper carriage mounted on said lower carriage for reciprocating. transverse movement. and movable with said lower carriage between the forward and rearward positions of the latter;

d. a blade holder mounted on said upper carriage for movement therewith;

c. means for oscillating said blade holder to cause upward and downward oscillation of a blade supported in said holder with respect to a generally hori/ontal reference plane about a transverse. horilontal axis in said plane:

(ill

f. at least a first pair. of grinding wheels supported on said base for rotation about vertically spaced. upper and lower transverse. horizontal axes. and drive means for rotating said grinding wheels. the peripheral working surfaces of said grinding wheels being normally separated during a grinding operation;

g. means for moving said lower carriage between its forward and rearward positions. the said forward position placing a blade to be sharpened in working relationship with respect to said grinding wheels;

b. said blade holder oscillating means causing alternate contact between opposite sides of the edge of a blade to be sharpened and each of said grinding wheels at least when said lower carriage is at its forward working position;

i. means for moving said upper carriage reciprocally transversely at least while said lower carriage is in its working position and synchronously with said blade holder oscillating means; whereby said blade to be sharpened is caused to be advanced to a grinding position between the grinding wheels and oscillated into alternate contact with each of the grinding wheels while reciprocating transversely during such contact;

j. a second pair of grinding wheels also supported for rotation about horizontal. transverse. vertically spaced axes. said grinding wheel pairs both being supported for rotation as a unit about a transfer axis for alternately enabling each pair of grinding wheels to assume a working position with respect to a blade edge to be sharpened;

k. means operable synchronously with said lower carriage moving means for causing said grinding wheel pairs to exchange positions as said lower carriage is retracted towards its rearward position.

l. each pair of grinding wheels comprising respectively a roughing and finishing grinder. whereby rough grinding and finish grinding operations can be automatically performed sequentially on a blade to be sharpened. without requiring removal of the blade from the machine by simply fully retracting the lower carriage away from the working position and thereafter advancing the carriage forwardly to the working position.

7. The microtome blade sharpener recited in claim 6. further wherein said lower carriage moving means includes a rack and pinion assembly. the rack being attached to the lower carriage; a grinding wheel transfer means. said transfer means including a ratchet drive as sembly actuated by said pinion, whereby retraction mo tion of said rack caused by rotation of said pinion causes a [80 rotation of said grinding wheel transfer means about said transfer axis through said ratchet drive. and advancing motion of said rack does not cause motion of said transfer means.

8. The microtome blade sharpening means recited in claim 6. further including a detent locking means for said grinding wheel transfer means whereby said transfer means is locked against undesired motion. and means cooperating with said rack for releasing said detent when said rack is retracted a predetermined dis tance. the said ratchet drive assembly permitting lost motion of said pinion. rack. and portions of said ratchet drive assembly to enable said rack to be retracted to an intermediate position without causing motion of said grinding wheel transfer means.

9. The microtome blade sharpening machine recited in claim 8. further including a blade sharpening index means said index means comprising an adjustable means for causing relative motion between said lower carrier and said rack. whereby the advanced position of a blade edge to be sharpened can be adjusted with respect to the grinding wheels; said adjustable means being operable separately from said means for advancing and retracting said lower carrier.

10. The microtome blade sharpening machine recited in claim 6, wherein said means for reciprocally moving said upper carriage transversely comprises a motor driven crank and pitman assembly. said crank further including means for cooperating with said means for oscillating said blade holder. whereby said reciprocal transverse motion and said oscillating motion is coordinated during a sharpening operation so that a blade edge to be sharpened is moved transversely while it contacts each grinding wheel; and further wherein said means for oscillating said blade holder Zll (ill

comprises a cam drive assembly operating a blade holder drive linkage which includes a roller engaging a notch having sloped surfaces. and means for resiliently urging said roller into engagement with said notch to thereby control the maximum force with which a blade edge to be sharpened is driven against a grinding wheel during a sharpening operation I]. The mierotome blade sharpening machine recited in claim It). further including means for adjusting the at rest position of said blade holder with respect to said blade holder cam drive assembly.

12. The microtomc blade sharpening machine recited in claim 6. wherein the diameters of said roughing grinder wheels is greater than the diameter of said finishing grinder wheels. whereby the blade edge area to be sharpened in contact with the finishing grinder is smaller than the edge area in contact with the roughing grinder when the blade to be sharpened is at the same advanced working position.

Claims

1. In a microtome blade grinding machine including means for moving a blade to be sharpened between an advanced sharpening position between a pair of driven grinding wheels and a retracted position away from said grinding wheels, the improvement comprising: a. two pairs of grinding wheels mounted for rotation as a unit about a transfer axis, said grinding wheel pairs comprising roughing and finishing grinders; b. each of said grinding wheel pairs including spaced grinding wheels mounted for rotation about parallel, coplanar axes, one of said pairs of grinding wheels normally being in working position for sharpening a blade edge; c. means for selectively causing said grinding wheel pairs to exchange positions by rotation of said grinding wheel pairs as a unit about said transfer axis; and d. said grinding wheel position changing means being connected to said blade moving means in such a manner that retraction motion of said blade causes simultaneous, automatic exchange of position of said grinding wheel pairs.

2. A microtome blade sharpening machine comprising: a. means for supporting a blade to be sharpened for vertical, oscillating motion with respect to a generally horizontal reference plane, and about a transverse axis lying in said reference plane; and means for oscillating said blade about said axis during a sharpening operation; b. first and second pairs of grinding wheels, each pair being mounted for rotation about vertically spaced, generally horizontal, transverse axes, and both pairs being mounted for rotation as a unit about a transfer axis; c. means for driving said grinding wheels about their respective axes; d. means for advancing said blade to a sharpening position between said first pair of grinding wheels whereby opposite sides of its edge is presented to each grinding wheel for sharpening when said blade is oscillated; e. means for retracting said blade to a rearward position away from said first pair of grinding wheels; f. means operable synchronously with said blade retracting means for rotating said grinder wheel pairs as a unit about said transfer axis so as to cause exchange of positions between said grinding wheel pairs, whereby the second grinding wheel pair is placed in a working position with respect to a blade to be sharpened while said blade is moved to its retracted position; g. the peripheral surfaces of each of said grinding wheel pairs being normally separated during a sharpening operation.

4. The microtome blade sharpening machine recited in claim 2, further including means for supporting said blade to be sharpened for reciprocating, transverse motion, and means synchronously operable with said blade oscillating means for causing said blade to reciprocate transversely during a sharpening operation during the time the edge of said blade to be sharpened is in contact with each of said grinding wheels.

5. The microtome blade sharpening machine recited in claim 4, further including means for vibrating said blade transversely in the same sense as said transverse motion during a sharpening operation.

6. A microtome blade sharpening machine comprising: a. a base; b. a lower carriage mounted on said base, said lower carriage movable between a forward working position and a rearward retracted position; c. an upper carriage mounted on said lower carriage for reciprocating, transverse movement, and movable with said lower carriage between the forward and rearward positions of the latter; d. a blade holder mounted on said upper carriage for movement therewith; e. means for oscillating said blade holder to cause upward and downward oscillation of a blade supported in said holder with respect to a generally horizontal reference plane about a transverse, horizontal axis in said plane; f. at least a first pair of grinding wheels supported on said base for rotation about vertically spaced, upper and lower transverse, horizontal axes, and drive means for rotating said grinding wheels, the peripheral working surfaces of said grinding wheels being normally separated during a grinding operation; g. means for moving said lower carriage between its forward and rearward positions, the said forward position placing a blade to be sharpened in working relationship with respect to said grinding wheels; h. said blade holder oscillating means causing alternate contact between opposite sides of the edge of a blade to be sharpened and each of said grinding wheels at least when said lower carriage is at its forward working position; i. means for moving said upper carriage reciprocally transversely at least while said lower carriage is in its working position and synchronously with said blade holder oscillating means; whereby said blade to be sharpened is caused to be advanced to a grinding position between the grinding wheels and oscillated into alternate contact with each of the grinding wheels while reciprocating transversely during such contact; j. a second pair of grinding wheels also supported for rotation about horizontal, transverse, vertically spaced axes, said grinding wheel pairs both being supported for rotation as a unit about a transfer axis for alternately enabling each pair of grinding wheels to assume a working position with respect to a blade edge to be sharpened; k. means operable synchronously with said lower carriage moving means for causing said grinding wheel pairs to exchange positions as said lower carriage is retracted towards its rearward position; l. each pair of grinding wheels comprising respectively a roughing and finishing grinder, whereby rough grinding and finish grinding operations can be automatically performed sequentially on a blade to be sharpened, without requiring removal of the blade from the machine by simply fully retracting the lower carriage away from the working position and thereafter advancing the carriage forwardly to the working position.

7. The microtome blade sharpener recited in claim 6, further wherein said lower carriage moving means includes a rack and pinion assembly, the rack being attached to the lower carriage; a grindinG wheel transfer means, said transfer means including a ratchet drive assembly actuated by said pinion, whereby retraction motion of said rack caused by rotation of said pinion causes a 180* rotation of said grinding wheel transfer means about said transfer axis through said ratchet drive; and advancing motion of said rack does not cause motion of said transfer means.

8. The microtome blade sharpening means recited in claim 6, further including a detent locking means for said grinding wheel transfer means whereby said transfer means is locked against undesired motion, and means cooperating with said rack for releasing said detent when said rack is retracted a predetermined distance, the said ratchet drive assembly permitting lost motion of said pinion, rack, and portions of said ratchet drive assembly to enable said rack to be retracted to an intermediate position without causing motion of said grinding wheel transfer means.

9. The microtome blade sharpening machine recited in claim 8, further including a blade sharpening index means, said index means comprising an adjustable means for causing relative motion between said lower carrier and said rack, whereby the advanced position of a blade edge to be sharpened can be adjusted with respect to the grinding wheels; said adjustable means being operable separately from said means for advancing and retracting said lower carrier.

10. The microtome blade sharpening machine recited in claim 6, wherein said means for reciprocally moving said upper carriage transversely comprises a motor driven crank and pitman assembly, said crank further including means for cooperating with said means for oscillating said blade holder, whereby said reciprocal transverse motion and said oscillating motion is coordinated during a sharpening operation so that a blade edge to be sharpened is moved transversely while it contacts each grinding wheel; and further wherein said means for oscillating said blade holder comprises a cam drive assembly operating a blade holder drive linkage which includes a roller engaging a notch having sloped surfaces, and means for resiliently urging said roller into engagement with said notch to thereby control the maximum force with which a blade edge to be sharpened is driven against a grinding wheel during a sharpening operation.

11. The microtome blade sharpening machine recited in claim 10, further including means for adjusting the at rest position of said blade holder with respect to said blade holder cam drive assembly.

12. The microtome blade sharpening machine recited in claim 6, wherein the diameters of said roughing grinder wheels is greater than the diameter of said finishing grinder wheels, whereby the blade edge area to be sharpened in contact with the finishing grinder is smaller than the edge area in contact with the roughing grinder when the blade to be sharpened is at the same advanced working position.