WO1991015746A1

WO1991015746A1 - Microtome

Info

Publication number: WO1991015746A1
Application number: PCT/AT1991/000046
Authority: WO
Inventors: Hellmuth Sitte; Helmut HÄSSIG; Armin Kunz; Klaus Neumann
Original assignee: Hellmuth Sitte
Priority date: 1990-03-19
Filing date: 1991-03-18
Publication date: 1991-10-17
Also published as: AT397876B; ATA900291A

Abstract

Proposed is a microtome, in particular an ultramicrotome, with an electrical drive (19) for the relative motion of the blade (9) and the specimen (7) and with an electronic control device (20) which controls the drive (19) to change the drive speed. In the cutting zone (S2) in which slice removal takes place, the cutting speed is lower. In order, after slice removal, to bring the moving part, e.g. the blade or the specimen, back into the position it must occupy for the next cutting stroke, a higher speed is called for. In order to optimise the cutting process and thus, if required, to reduce the cycle time, the invention calls for the profile of the relative speed between specimen (7) and blade (9) (cutting speed) within the cutting zone (S2) to differ from a constant-speed profile.

Description

Microtome

The invention relates to a microtome, in particular an ultramicro, with an electric drive device for the relative movement of knife and object and with an electronic control device which drives the drive device for changing the speed of the drive device, in which case in a cutting path section, in which the cutting takes place, there is a lower cutting speed and there is a higher return speed for returning the moving part, for example the specimen bar or the knife, after the cutting has been taken into the position before the next cutting process that follows.

To remove cuts from an object (preparation) by means of a knife, the object according to the prior art is moved relative to the knife or vice versa the knife is moved relative to the object. For microtomes, in particular ultramicrotomes, electric drives are used to an increasing extent for this movement, since in contrast to the manual drive via a handwheel, a lever or a handle on a sliding carriage, the path speed which is decisive for the quality of the cuts is used of the specimen or knife can be reproduced exactly and the manipulation forces which are always changing during manual operation and the resulting irregularities in the section thicknesses can be eliminated. These measures are therefore apart from special high-performance microtomes for light microscopic histology and for materials science, particularly in the field of semi-thin section technology (section thicknesses around 0.25 μm to 2.5 μm) and to an even greater extent in the field of ultramicrotomy (Section thicknesses about 0.01 μm to 1.0 μm: see: H. Sitte, Ultramikrotomie, mta-Journal No. 10, Umschau-Verlag Breidenstein GmbH, Frankfurt 1983, as well as: H. Sitte and K. Neumann, Ultramikrotomie and apparatus aids for ultramicrotomy, in: G. Schimmel and W. Vogell, collection of methods of electron microscopy, Wissenschaftliche Verlags-GmbH Stuttgart, 11th delivery, 1983, here: in particular section D, sn 37 to 42 ) State of the art. In the last-mentioned device category in particular, there is also the need to see two successive cuts ("cycle time ¹¹ ) with regard to the temperature changes which can never be completely avoided and the resulting length changes in precision mechanics as a result of the thermal expansion. To keep this as small as possible The web speed of the moving part could be very high or the length of the web could be very short, but both of the measures mentioned are ruled out for a number of reasons disruptive irreversible deformation ("compression") of the cuts and in many cases also resolves high-frequency vibrations ("chatter": see: H. Sitte, Ultramicro¬ tomie - common problems and errors, in: Supplement microscopy / electron microscopy , GIT-Verlag, Darmstadt, January

1982). A reduction in the path length of the moving part is due to the different dimensions of the object and the always changing position of the area of interest and the area selected for the cutting preparation, as well as the frequently changing geometry of the knives, in particular the glass knives used in ultramicrotomy, and thus the constantly changing Relative position of the cut surface and the knife edge to the object or knife holder is very limited in its extent. In addition, in ultramicrotomy it is often necessary to lower the moving object at least 2 mm, optimally 5 mm below the knife edge, since this is the only way to create "water bridges" between the cut surface of the preparation and the front surface of the one filled with water Knife collecting basin provided (cf. in particular Figs. 7 and 10 in H. Sitte, 1982, Ie) can be largely switched off. A major step forward was the introduction of the so-called "alternating drive", in which the moving part only slowly in the area of the removal of the cut ("cutting window ¹¹ ) on the rest of its path

("Return area") is moved quickly, however, so that the cycle time is kept comparatively short without the disadvantages of greater compression of the cuts or vibrations. ten and thereby the regularity of the cutting sequence can be improved.

In order to reduce disturbing vibrations when changing the speed, a microtome has already been proposed (DE-Cl-32 23 347), in which a region of linearly decreasing or linear speed is in each case located between the web section of high return speed and the web section of low cutting speed increasing speed is provided, with which an overall steady speed curve is achieved. As with all other microtomes of the prior art, the speed profile in the cutting path section in which the actual cutting takes place is constant.

The object of the present invention is to create a microtome, in particular an ultramicrotome of the type mentioned at the outset, with which an optimized cut removal is possible with a short duration of the cutting cycle.

According to the invention this is achieved in that the course of the relative speed between the object and the knife (cutting speed) within the cutting path section (S ₂ ) deviates from the course of a constant speed.

Such a non-constant speed course during the cutting process (removal of the cut), that is to say while the object and the knife are in contact, makes it possible to keep the speed and thus the shock when the knife touches the object low at the beginning of the cutting path section. At the same time, however, it is possible to increase the speed after the first critical gating phase while cutting is still taking place. On the one hand, this makes it possible to shorten the entire cycle time without the disadvantages of cutting the preparation too quickly

To have to accept. In addition, such an increase in the relative speed between the object and the knife in the cutting path section, that is to say during the actual removal of the cut, in some cases, for example in the case of cuts. frozen material, an advantage in terms of optimal cutting quality.

According to a preferred embodiment, the speed increase in the cutting path section can take place essentially linearly. Such a linear increase can be achieved in particular using relatively simple electronic means. In special applications, a speed curve can also be advantageous, in which the cutting speed in the cutting path section preferably increases linearly from a constant speed and then continues in the cutting path section again. At the current state of control electronics for motors, however, there is also no difficulty in realizing an essentially smoothly increasing, preferably exponentially increasing speed curve in the cutting path section, which can be ideally adapted to the respective requirements.

In addition to the above-mentioned speed increases during the cut removal, it is advantageous, for example in the case of objects with harder inclusions, to lower the cutting speed in at least one area of the cutting path section compared to the speed at the beginning of the cutting path section. You can achieve optimal cutting results even with difficult preparations without having to slow down the cycle time significantly.

According to a preferred embodiment of the invention, it is advantageously provided that the device for changing the speed profile in the cutting path section has at least one manually operable setting member for changing the speed profile. This enables the operator of the microtome or ultramicrotome to change the course of the cutting speed in the actual cutting path section during the removal of the cut in order to further optimize the cutting results.

This means that once a setting of the cutting speed profile has been recognized as advantageous, it also applies to the following sections of a cutting series is retained, it can be provided according to a preferred embodiment of the invention that an encoder or a similar rotational angle-registering element is connected to the drive device or a part driven by it and that the control device preferably has a memory for recording at least one in a setting cycle followed and detected by the encoder or the like speed course, and the control device in conjunction with the encoder or the like automatically determines a speed course in the subsequent cycles, which corresponds to one of the speed courses stored in the memory. The stored speed profiles can be pre-programmed. However, it is also possible to read these speed profiles into the memory in a first setting cycle (learning process), in which the operator manually influences the speed profile, for example.

In addition to the manually changeable or preprogrammed speed profiles described above, there is also the possibility of automatically adapting the speed profile to the conditions prevailing in the respective cut. For this purpose, according to a preferred embodiment of the invention, at least one sensor is provided for recording the forces resulting from the cutting of the cuts or the changes to the microtome caused by these forces. The control device can now change the speed curve in the cutting path section depending on the sensor signals of this force sensor. At the same time, it is possible to show the current cutting forces or the cutting force curve on a display. An embodiment is particularly advantageous in which the control device regulates the speed profile in the cutting path section in such a way that the cutting force detected by the sensor remains constant during the entire cutting process.

An advantage of an automated speed sequence determined by the control device is that the Sequence of movements of the entire cutting series can be exactly reproduced or optimally adapted to the respective circumstances. Uniform cutting thicknesses and cutting qualities can then be achieved.

However, it is also possible to manually intervene in the automatic sequence during the cutting operation in order to adapt the speed curve to special conditions, e.g. the cutting speed must be corrected for methodological reasons.

It can also be provided that the decisive parameters (e.g. cutting speed curve, cycle duration, maximum return speed, cutting forces) are shown on a display and / or can be changed by separate setting elements. For example, with a view to the universal use of this drive system, an extension of the cycle duration (regardless of the set cutting speed and duration) seems desirable if paraffin or plastic embeddings are cut at normal temperature and the cuts have to be continuously removed from the knife because a longer cycle time is advantageous here.

Further advantages and features of the invention and its embodiment result from the following description with reference to the accompanying drawings. Show in these drawings

1: a vibrating rod ultramicrotome with a motor change drive in a schematic top view and side view,

2: the relative movement of the object to the knife in an alternating drive according to the prior art in a more enlarged schematic representation corresponding to the side view in FIG. 1, FIG. 3: a speed-time diagram for the movement sequence in the prior art, Fig. 4: a speed-time diagram for the

Sequence of movements in one embodiment of the invention, 5 and 6: speed-time diagrams of further movement sequences according to the invention.

The vibrating rod ultramicrotome shown schematically in a top and side view in FIG. 1 is largely of a conventional type. On the stand 1, on the one hand the bearing bracket 2 is fastened, on which the intermediate lever 4 is attached via the bearing 3 and on the latter via the bearing 5 the specimen carrier rod 6 is articulated, at the front end of which is the specimen 7. On the other hand, the knife, for example a glass knife 9, is fastened to the stand 1 on a cross support 8 with the cutting edge 10, on which there is usually a collecting basin 12 filled with water 11 during the cutting in the room temperature range to drain off the cuts. The oscillating up and down movement of the specimen carrier rod 6 (“vibrating rod ultramcrotome”) with the specimen 7 takes place around the bearing 5 and is controlled according to FIG on the support rod 6 attached support profile 15 corresponds. The drive shaft 13 is supported on both sides in the elements 16/16 'fastened to the stand base 1 and, in addition to the handwheel 28, carries the pulley 17, which is connected to the electric motor 19 via an elastic transmission 18. The speed of the motor 19 is controlled via an electronic control device 20, which is connected either to a cam disk 21 or to an encoder 25 coupled via transmission elements 22/23/24, which can alternatively also be coupled directly to the drive shaft 13 (25 *). The control via the cam 21 can be carried out by a switching element 26, which with the

Control device 20 is connected. The switching of the speed of the motor 19 by means of this element 26 can either be done without contact (e.g. light barrier) or through an intermittent contact between the elements 21 and 26 (e.g. microswitch) (cf.

Austrian patent specification 316 893 as stated above). In the course of the automatic drive, the object 7 is guided downwards over the cutting edge 10 of the knife 9 to take the cut. After reaching the lowest position withdraw the object 7 by pivoting the intermediate lever 4 around the bearing 3 (mechanism not shown in FIG. 1; cf. also FIG. 2), then guided upwards away from the knife edge 10 into the highest position above the knife edge 10 and pushed it forward again . At the same time, the object 7 or the knife 9 is advanced by a separate feed system (not shown in FIG. 1) by the preselected amount of cut thickness, so that a cut is removed again from the knife edge 10 in the next cycle the surface of the water 11 swims in the collecting basin 12.

Fig. 2 shows an enlarged section of the object-knife area of a microtome with variable drive control according to the prior art. 3 shows the associated speed curve in a speed-time diagram. Between the switching point U ^ and the switching point U _a , the specimen moves over the points BCDA with the high return speed. In the cutting window S ^ between the switching points U _b and U _c , the specimen (object 7) moves relative to the knife 9 with a substantially lower constant cutting speed. In order to avoid vibrations when switching from the high return speed to the low cutting speed or from the cutting speed to the high return speed, there is a range Y falling linearly between the points U _a and U ^ and between the switching points U _c and U ^ see a section Z increasing in speed.

The duration for passing through the cutting _window lying between the switching points U _b and U _c is denoted by t _sl . The actual cutting path section S ₂ , in which the object is in contact with the knife during the removal of the cut, lies within this cutting window S 1. The duration for passing through this cutting path section S ₂ is designated in FIG. 3 with t _g2 . In the microtome according to the invention, the course of the relative speed between object 7 and knife 9 (cutting speed) within the cutting path section S ₂ now deviates from the course of a constant speed.

In FIG. 4, the speed in the cutting path section S _{2 increases} linearly after a short constant range during the actual cutting process and then continues again. At the switchover point U _c , the low-vibration switchover to the high return speed then takes place via a renewed linear increase. Such linearly decreasing or increasing speed profiles can be implemented relatively easily, for example in a similar manner as is already provided for in the prior art. As already mentioned, such a speed course in the cutting path section S ₂ , which, in contrast to the prior art, is not constant, enables the cutting quality to be optimized and the cycle time to be reduced as the speed course increases.

5 shows two further speed profiles of an exemplary embodiment of the microtome according to the invention, the speed in the cutting path section S ₂ initially increasing exponentially in order to then pass into the linearly increasing region which leads to the high return speed . As in the exemplary embodiment described in FIG. 4, the speed at the beginning of the actual cutting path section S _{2 is} low, so that the shock occurring when the knife and the object meet is also low. After this first critical cutting phase, however, it is advantageous in many cases to increase the speed in the cutting path section.

In particular in the case of specimens with hard spots, however, it can also be advantageous to lower the speed in the cutting path section S _{2 in} regions, as shown in FIG. 6. The elements responsible for the speed sequence are largely implemented in the electronic control device 20. This control device, which defines the speed profile and in particular the non-constant speed profile in the cutting section S ₂ , contains, for example, a central microprocessor unit 30 which receives signals from the control and switching elements 21 and 26 or from the encoder 25 (25 ') be fed via the relative position of object 7 and knife 9. The microprocessor unit 30 can contain a programmable memory device 31, in which several speed profiles are preprogrammed. These speed profiles can then be called up by the user. The central microprocessor unit 30 then controls the electric motor 19 via the line 37, so that the object 7 moves relative to the knife 9 in the selected speed profile.

According to a preferred embodiment of the invention, however, it is also possible for the electronic control device 20 to have a device for changing the speed curve in the cutting path section. This changing device for the speed curve can have, for example, an adjusting element (e.g. rotary potentiometer 32) for manually changing the speed curve in the cutting path section (cf. FIG. 1). In this way, the user can change the speed curve in the cutting path section by hand, if necessary, in particular with simultaneous observation using a stereomicroscope.

A speed profile which is traversed in an adjustment cycle and detected by the encoder 25, 25 'can be stored in a memory 34. This enables the control device 20 in conjunction with the encoder 25, 25 'to automatically run the same speed curve in subsequent cycles. It is therefore only necessary in a cutting series to adjust the speed curve in the cutting path section in a first setting operation. In addition to the changes in the speed profile in the cutting path section S _{2 described} above, there is also the possibility of automatically adapting the speed profile to specific operating conditions. According to a preferred embodiment, a sensor is provided for recording the forces resulting from the cutting of the cuts or the changes in the microtome caused thereby. In the exemplary embodiment shown in FIG. 2, this sensor is designed as a piezo element 33 below the knife 9. Alternatively or additionally, however, other sensors are also possible, for example the strain gauge 33 shown in FIG. 1 on the underside of the specimen carrier rod 6 for absorbing the resulting cutting forces or the effects on the mechanics of the ultramicrotome. In any case, the sensor signals are fed to the central microprocessor unit 30 which, for example, automatically detects a cutting speed when a cutting force above a threshold value is determined. In a further embodiment, it is possible for the control device to regulate the speed curve in the cutting path section in such a way that the cutting force detected by the sensor or its effects remains constant during the cutting removal.

In special applications, it can be advantageous to intentionally extend the cycle time. For this purpose, an adjustment element 35 is provided, by means of which the cycle duration can be varied independently of the selected cutting speed and duration. The central microprocessor unit then determines and realizes the speed curve as a function of the desired entered cycle duration.

Finally, a display device 36 is also provided for displaying the parameters of interest for the cutting preparation, in particular the preselected speed and / or the duration of the cycle. It is also conceivable to graphically show the speed curve on a display. The present invention can be implemented in different embodiments and combinations in adaptation to the different practical requirements and to the different constructions of microtomes, semi-thin-section devices and ultramicrotomes, without losing their inventive character. In particular, the invention can be implemented in the case of different supports and movements of the object or knife that differ from the system according to FIG. 1, for example on a slide or basic slide microtome, insofar as the movement is automatic or via a Motor drive takes place and is controlled via an encoder or a correspondingly registering element and an electronics connected to it. It is irrelevant for the implementation of the invention whether the object 7 is moved by means of an electric motor 19 shown in FIG. 1 via a transmission 18 and a drive shaft 13 or, for example, by means of a moving coil drive in the manner of the LKB ultrotome systems (cf. see Fig. 63 in H.Sitte and K.Neumann, 1983, lc) or on a straight vertical or horizontal path (see Fig. 1 and 2 of the same publication). It is also irrelevant whether and in what way the object 7 or the knife is withdrawn as part of a "single pass movement" (cf. section D of the same publication) as long as the

Cut is made with a path speed of the moving part that is comparatively much lower for resetting. Finally, the mechanical or electrical elements by means of which the various parameters which are decisive for the cutting preparation or for the operation of the instrument can be set or from which data can be read, can be designed differently as required.

Claims

Patent claims:

1. Microtome, in particular ultramicrotome, with an electric drive device for the relative movement of

Knife and object and with an electronic control device which controls the drive device for changing the speed of the drive device, a lower cutting speed being present in a cutting path section in which the cutting takes place and for returning the moving part, for example the object bar or the knife, after the cut has been removed into the position before the next subsequent cutting process, there is a higher return speed, characterized in that the course of the relative speed between the object (7) and knife (9) (cutting speed) within the cutting Path section (S ₂ ) deviates from the course of a constant speed.

2. Microtome according to claim 1, characterized in that the relative speed between the object (7) and knife (9) after a low cutting speed at the beginning of the cutting path section (S ₂ ) increases during the cut removal.

3. Microtome according to claim 2, characterized in that the speed increase in the cutting path section (S ₂ ) is substantially linear.

4. Microtome according to claim 2, characterized in that the speed increase in the cutting path section (S ₂ ) is substantially smooth, preferably exponential.

5. Microtome according to one of claims 1-4, characterized gekenn¬ characterized in that the cutting speed in the cutting path section (S ₂ ) preferably increases linearly from a constant speed and then continues in the cutting path section (S ₂ ) again constant.

6. Microtome according to one of claims 1-5, characterized gekenn¬ characterized in that the cutting speed in the cutting path section (S ₂ ) compared to the speed at the beginning of the cutting path section (S ₂ ) is reduced in some areas.

7. Microtome according to one of claims 1 to 6, characterized in that the control device which drives the drive device (19) has a device (32, 30; 33, 30) for changing the speed profile in the cutting path section (S ₂ ).

8. Microtome according to claim 7, characterized in that the device for changing the speed course in the cutting path section (S ₂ ) has at least one manually operated adjusting member (32) for changing the speed course.

9. Microtome according to one of claims 1-8, characterized gekenn¬ characterized in that with the drive device (13,18,19) or a part driven therefrom an encoder (angle encoder 25, 25 ') or a similar rotational angle-registering element is connected to the fact that the control device (20) has a memory (34) for recording at least one, preferably in a setting cycle, that is run by the encoder or the like. Has detected speed curve, and the control device (20) in conjunction with the encoder (25, 25 ") or the like automatically determines a speed curve in the subsequent cycles which corresponds to one of the values in the Memory (34) corresponds to stored speed profiles.

10. Mirotome according to claim 7, characterized in that it has at least one sensor (33, 33 ') for recording the forces resulting from the separation of the cuts or the changes caused by these forces.

11. Microtome according to claim 10, characterized in that the control device (20) in dependence on the

Sensor signals changed the speed curve in the cutting path section (S ₂ ).

12. Microtome according to claim 11, characterized in that the control device (20) regulates the speed profile in the cutting path section (S ₂ ) such that the cutting force detected by the sensor remains constant during the section decrease.

13. Microtome according to one of claims 1 to 12, characterized in that the desired cycle duration can be varied with a separate adjusting element (35) independently of the selectable cutting speed and duration.

14. Microtome according to one of claims 1 to 13, characterized in that a display device (36) is provided for displaying the parameters of interest for the cutting preparation, in particular the speed profile, the duration of the cycle and optionally the cutting forces.