Microtome having a piezoelectric linear actuator

Abstract

The present invention relates to a microtome (10) for cutting thin sections, including a sample holder (12), a cutting unit (16), and a drive unit (16) for producing a feed movement between the sample holder (12) and the cutting unit (16) for setting the thickness of the sample sections. The drive unit (22) includes a piezoelectric linear actuator (50) for producing the feed movement.

Claims

1. A microtome for cutting thin sections, comprising: a sample holder (12) for receiving a sample to be microtomed, a cutting unit (16) for cutting the sample, and a piezoelectric linear actuator (50) for producing a feed movement between the sample holder (12) and the cutting unit (16) for setting the thickness of the sample sections, wherein the piezoelectric linear actuator (50) includes a stator (52) and a runner (56) which is connected to the stator (52) via at least one piezoelectric element (54) and is movable relative to the at least one piezoelectric element (54); the at least one piezoelectric element (54) is attached to the stator (52); and the at least one piezoelectric element (54) changes shape when energized such that the runner (56) is linearly moved by contact of the runner (56) with the at least one piezoelectric element (54) relative to the stator (52).

2. The microtome (10) as recited in claim 1, wherein the piezoelectric element (54) includes a piezoelectric ceramic and/or a piezoelectric crystal.

3. The microtome (10) as recited in claim 1, further comprising a control unit (23), wherein the control unit energizes the piezoelectric element (54) such that the piezoelectric element (54) moves the runner (56) linearly according to a preset sequence of movements.

4. The microtome (10) as recited in claim 1, wherein the cutting unit (16) is stationary and the sample holder (12) is movable relative to the cutting unit (16) by the piezoelectric linear actuator (50).

5. The microtome (10) as recited in claim 4, wherein the sample holder (12) is fixedly connected to the runner (56) of the piezoelectric linear actuator (50).

6. The microtome (10) as recited in claim 5, further comprising a guide member (42) extending along a longitudinal axis and a carriage (40) mounted on the guide member (42) such that the carriage (40) is movable along the longitudinal axis of the guide member (42), wherein the sample holder (12) is attached to the carriage (40).

7. The microtome (10) as recited in claim 6, wherein the runner (56) is attached to the carriage (40) and the stator (52) is attached to the guide member (42).

8. The microtome (10) as recited in claim 6, wherein the runner (56) is attached to the guide member (42) and the stator (52) is attached to the carriage (40).

9. The microtome (10) as recited in claim 7, wherein the guide member (42) is a rail.

10. The microtome (10) as recited in claim 8, wherein the guide member (42) is a rail.

11. The microtome (10) as recited in claim 6, wherein the guide member (42) is mounted on a further carriage (44) which can be moved by a further drive unit (22); and the further carriage (44) can be moved by the further drive unit (22) in such a way that the further drive unit (22) can cause the sample holder (12) to perform a reciprocating movement relative to the cutting unit (16) to cut the samples to be microtomed.

12. The microtome (10) as recited in claim 1, further comprising a sensor (60, 62) for detecting the travel of the piezoelectric linear actuator (50).

13. The microtome (10) as recited in claim 6, further comprising a sensor (60, 62) for detecting the travel of the piezoelectric linear actuator (50), wherein the sensor includes a linear encoder (60) attached to the guide member (42) and a scale (62) provided on the carriage (40).

14. The microtome (10) as recited claim 1, further comprising a control unit (23) for controlling the piezoelectric linear actuator (50); and wherein after a thin section is cut, the control unit (23) controls the piezoelectric linear actuator (50) such that the piezoelectric linear actuator (50) performs a feed movement through a preset distance.

15. The microtome (10) as recited in claim 14, further comprising an operator control unit (25) which enables setting of the preset distance and/or a speed at which the sample holder (12) and the cutting element (16) are moved relative to each other.

16. The microtome (10) as recited in claim 15, wherein the operator control unit (25) enables manual setting of the preset distance and/or a speed at which the sample holder (12) and the cutting element are moved relative to each other.

Description

BRIEF DESCRIPTION OF THE DRAWING VIEWS

(1) Further features and advantages of the present invention will become apparent from the following description of exemplary embodiments thereof, taken in conjunction with the accompanying drawings, in which:

(2) FIG. 1 is a schematic perspective view of a microtome;

(3) FIG. 2 is a further schematic perspective view of the microtome of FIG. 1;

(4) FIG. 3 is a schematic perspective view of a detail of the microtome shown in FIGS. 1 and 2;

(5) FIG. 4 is a further schematic perspective view of the detail of FIG. 3;

(6) FIG. 5 is another schematic perspective view of the detail shown in FIGS. 3 and 4;

(7) FIG. 6 is a side view of the detail shown in FIGS. 3 through 5;

(8) FIG. 7 is a sectional view of the detail shown in FIGS. 3 through 6;

(9) FIG. 8 is another, partially sectional view of the detail shown in FIGS. 3 through 7; and

(10) FIG. 9 is a schematic block diagram showing an operator control unit and a motion control unit of the microtome.

DETAILED DESCRIPTION OF THE INVENTION

(11) FIGS. 1 and 2 are each schematic perspective views depicting a microtome 10 in greatly simplified form and showing only the components that are essential to the invention. For example, the housing has been omitted to allow viewing of the interior components.

(12) Microtome 10 includes a sample holder 12 including a chuck 14 for holding a sample to be microtomed. Microtome 10 further has a cutting unit 16 including a blade holder 18 and a blade 20 received in blade holder 18 for cutting the sample.

(13) Furthermore, microtome 10 includes a handwheel 32 having a handle 34. Rotational movement of handwheel 32 is detected by a rotary encoder (not shown). A control unit 23 (shown in FIG. 9) controls a cutting motion drive unit 22 according to the detected rotational movement of handwheel 32 in such a way that sample holder 12 performs a reciprocating movement in the direction of double-headed arrow P1 relative to stationary cutting unit 16, so that the sample is cut into thin sections by contact with blade 20. Each stroke produces one thin section.

(14) In an alternative embodiment, handwheel 32 may also be mechanically coupled to sample holder 12, so that no cutting motion drive unit 22, in particular no motor, is needed for the reciprocating movement, but instead, the reciprocating movement is performed purely mechanically by rotating handwheel 32.

(15) After a thin section is cut, sample holder 12 must be moved horizontally in the direction of arrow P2 toward cutting unit 16, so that a new thin section can be cut from the sample at the next stroke. This linear movement is referred to as feed movement or feed. The distance through which sample holder 12 is moved in the direction of arrow P2 after each stroke is used, in particular, to set the thickness of the thin sections. Accordingly, the smaller the possible step size of the feed movement, the thinner the sections that can be cut.

(16) In accordance with the present invention, the feed movement is accomplished by a feed motion drive unit having a piezoelectric linear actuator. This feed motion drive unit is shown in detail in FIGS. 3 through 8. FIGS. 3 through 5 are each schematic perspective views, with FIG. 6 being a side view, and FIGS. 7 and 8 being sectional views.

(17) Sample holder 12 is fixedly mounted on a carriage 40 which is supported in a rail-type guide member 42 such that it is horizontally movable in the direction of double-headed arrow P3. This guide member 42 is in turn attached to a further carriage 44 which is movable vertically by cutting motion drive unit 22 in the direction of double-headed arrow P1, and thus performs the reciprocating movement for cutting the samples. Thus, the reciprocating movement of the further carriage 44 causes guide member 42 to correspondingly move vertically, so that sample holder 42, and thus also carriage 40 and sample holder 12, perform a corresponding reciprocating movement.

(18) Piezoelectric linear actuator 50 includes a stator 52 and a runner 56 which is connected to stator 52 via at least one piezoelectric element 54. This piezoelectric element 54 is capable of linearly moving runner 56 relative to stator 52 in the direction of double-headed arrow P3.

(19) Stator 52 is attached to guide member 42, whereas runner 56 is attached to carriage 40, so that when runner 56 is moved by piezoelectric element 54 relative to stator 52, carriage 40, and thus sample holder 12, are also moved relative to guide member 42 in the direction of double-headed arrow P3, thereby performing feed movement.

(20) Here, piezoelectric element 54 is disposed stationary with respect to stator 52. When suitably energized, piezoelectric element 54 changes its shape in such a way that runner 56 is linearly moved in the direction of double-headed arrow P3 by its contact with piezoelectric element 54.

(21) Examples of piezoelectric linear actuators that may be used are the Piezo LEGS Caliper 20N piezoelectric motor or the Piezo LEGS LT2010A piezoelectric motor produced by PiezoMotor Uppsala AB.

(22) In comparison with known microtomes, where the feed movement is performed purely mechanically via screw and nut systems and/or electromechanically by means of stepper motors and corresponding screw and nut systems, the use of a linear actuator has the advantage of enabling a step size of a few nanometers. This provides a very high resolution, making it possible, on the one hand, to produce very thin sections and, on the other hand, to achieve the desired thickness with high accuracy.

(23) Piezoelectric linear actuator 50 further has the advantage that it operates as a direct drive, which eliminates the need for a motor, a clutch and additional bearing elements, making it possible to achieve a simple, cost-effective and space-saving design. Thus, in particular, a microtome 10 can be manufactured that is compact and lightweight.

(24) In addition, piezoelectric linear actuator 50 permits a large travel, allowing carriage 40 to be moved at high speed relative to guide member 42. Therefore, when microtome 10 is in the so-called coarse feed mode (e.g. during sample change), a large distance can be traveled in a short time, thus enabling rapid sample change.

(25) Furthermore, there is provided an operator control unit 25 (shown in FIG. 9) which can be used to set the speed. The operator control unit 25 can in particular be used to select between coarse feed and fine feed. These modes each have different preset speeds associated therewith, the speed setting for coarse feed being significantly higher than that for fine feed.

(26) Furthermore, the operator control unit 25 can also be used in particular to set the desired section thickness. The control unit 23 then controls piezoelectric linear actuator 50 in such a way that after each stroke, it moves runner 56 toward cutting unit 16 by the desired section thickness, thereby also moving the sample through the corresponding distance.

(27) Examples of materials that may be used for the piezoelectric elements 54 include piezoelectric ceramics or piezoelectric crystals.

(28) A linear encoder 60 is mounted on guide member 42. A linear scale 62 is provided on carriage 40 at a corresponding location. This scale can be read by linear encoder 60. Thus, the relative distance traveled between guide member 42 and carriage 40 can be detected in a simple manner, which allows the feed movement to be controlled and/or regulated in a controlled manner.

(29) The linear scale is in particular in the form of a graduation and/or a rule.

(30) In an alternative embodiment of the present invention, stator 52 may be mounted on carriage 40 and runner 56 may be mounted on guide member 42.

(31) Moreover, alternatively, sample holder 12 may be stationary and cutting unit 16 may be moved relative thereto by a corresponding feed motion drive unit having a piezoelectric linear actuator 50.