US3902390A

US3902390A - Microtome

Info

Publication number: US3902390A
Application number: US457469A
Authority: US
Inventors: Rolf E Darbo
Original assignee: Individual
Current assignee: Individual
Priority date: 1974-04-03
Filing date: 1974-04-03
Publication date: 1975-09-02
Anticipated expiration: 1992-09-02

Abstract

A small and simple portable microtome has a base with means either for holding a paraffin embedded specimen or freezing and securing a specimen for immediate sectioning by a cutting head which is mounted upon a vertical metering post for cutting in a horizontal plane. The post is threaded into the base and has a metering wheel for adjustment of the thickness of the section to be taken. Latches anchored respectively to the base and cutting head cooperate with the metering wheel to determine cutting operation and product.

Description

United States Patent [1 1 Darbo [4 1 Sept. 2, 1975 MICROTOME [76] Inventor: Rolf E. Darbo, PO. Box 2158,

Madison, Wis. 53701 [22] Filed: Apr. 3, 1974 21 Appl. No.: 457,469

[52] US. Cl. 83/170; 83/592; 83/9155 [51] Int. Cl. B26D 5/10; B26D 7/08 [58] Field of Search 83/170, 915.5, 573, 592, 83/584, 608

[56] References Cited UNITED STATES PATENTS 2,292,973 8/1942 Richards 83/9155 X 2,984,007 5/1961 Lundin r 83/608 3,496,819 2/1970 Blum r 83/608 X 3,799,029 3/1974 Cole et a1. 83/9155 X Primary ExaminerWil1ie G. Abercrombie Attorney, Agent, or FirmDarbo, Robertson & Vandenburgh 5 7 ABSTRACT A small and simple portable microtome has a base with means either for holding a paraffin embedded specimen or freezing and securing a specimen for immediate sectioning by a cutting head which is mounted upon a vertical metering post for cutting in a horizontal plane. The post is threaded into the base and has a metering wheel for adjustment of the thickness of the section to be taken.'Latches anchored respectively to the base and cutting head cooperate with the metering wheel to determine cutting operation and product.

5 Claims, 9 Drawing Figures PATENTED SEP 2 I975 SHEET 1 UP 2 MICROTOME BACKGROUND AND SUMMARY OF THE INVENTION In alternate procedures for cutting extremely thin slices from specimen portions of organic materials, such as woody plant growth or animal (including human) tissues, for subsequent microscopic examination, the specimen may be embedded in a block of paraffin to hold it for cutting or may be frozen to render it solid and held firmly for the accurate cutting of a thin slice. Each technique has its advantages and both are in current use although the freezing technique is generally to be preferred in the examination of animal tissue.

Microtome apparatus heretofore available has been complicated, very expensive and usually too large to be considered portable. The specimen is frequently prepared in a separate apparatus for the sectioning operation in the mierotome, whether it is to be embedded in paraffin or frozen. The specimens are usually very small and the separation of the freezing and slicing operations present problems, such as premature thawing of the specimen, which are difficult to overcome.

The object of the present invention is to provide a combined mierotome unit wherein the base embodies means for concurrently freezing and securing the frozen sample in position for cutting and also, if desired, means for securing a specimen embedded in paraffin for cutting. A further object is to provide such a microtome unit which is highly versatile in use, being capable of cutting sections of desired thickness in a wide range and of cutting a succession of sections without the necessity of adjustment between cuts.

Further and important objects are to provide an extremely simple and therefore inexpensive and a very small and therefore highly portable combination freezing and cutting mierotome unit.

Other features of the mierotome apparatus will be come apparent from the following description in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a perspective view of the mierotome unit including a clamp for securing the unit to a work surface;

FIG. 2 is a plan view of the unit of FIG. 1;

FIG. 3 is a longitudinal view of the unit in vertical cross section;

FIG. 4 is a cross-sectional view taken at the line 4 4 of FIG. 2;

FIG. 5 is a perspective view of the base-anchored metering wheel latch;

FIG. 6 is a perspective view of the internally threaded metering bushing;

FIG. 7 is a perspective view of the cutting headanchored metering wheel latch;

FIG. 8 is a detail view showing the cutting blade support with the blade turned over for a steeper cutting angle. and

FIG. 9 is a cross-sectional view showing an alternative construction of the cutting head.

DESCRIPTION OF SPECIFIC EMBODIMENTS The base I of the mierotome unit should be made from a material having a low coefficient of thermal conductivity. It may advantageously be injection molded from a plastic material such as, for example,

(ill

polycarbonate resin, to form a rigid structure. The cutting head assembly 2 is mounted in the base for rotation about a vertical axis. Base 1 contains means for freez ing and securing a specimen in position for cutting and forsecuring a paraffin-embedded specimen for cutting.

It also contains and carries metering elements for cooperation with cutting head metering elements to determine the level at which the cuts will be taken and therefore the thicknesses of the sections.

The cutting head contains structure for holding the cutting blade and for accurately guiding the movement of the blade in cutting the section.

Metering post 3 serves as the support for cutting head assembly 2. The lower portion 4 of the metering post is threaded to screw into the correspondingly threaded metering bushings 5 which is mounted in a vertical well provided for the purpose at the middle of base 1. A metering wheel 6 having circumferential notches 7 is affixed to post 3 and a conical shoulder support 8 is either affixed to or formed as an integral part of post 3.

Blade holder 9, which may also advantageously be injection molded from plastic, has a conical interior adapted to seat upon conical shoulder support 8. An arm 10 to which the cutting blade 11 is removably secured, extends radially from and at right angles to the axis of the hub portion of the blade holder 9. For ease in tolerance maintenance and smoother operation, the conical shoulder support 8 is preferably formed with top and bottom frustro-conical sections 8a and 8b for engagement with the conical inner surface of the hub portion of blade holder 9.

To complete the cutting head assembly, a compres' sion spring 12 is arranged between a washer l3 and a knurled hand nut 14 which is screwed onto the top portion of post 3 sufficiently to compress spring 12 and provide frictional engagement between washer l3 and the top of the hub portion of blade holder 9 and between the conical surfaces of the conical shoulder support 8 and the interior of the cutting head hub.

As is best seen in FIGS. 3 and 6, the internally threaded metering bushing 5 is firmly held in vertical position at approximately the middle of the mierotome base. The bushing is slotted throughout its length. This slot 15 provides clearance so that the bushing may be kept in firm engagement with the threaded lower portion 4 of metering post 3 by means of set screw 16 which also serves to hold the bushing firmly in place. By adjusting the set screw, wobbling of the metering post in the bushing can be prevented and, at the same time, the desired degree of frictional gripping of the post by the bushing may be established and maintained.

Rectangular cavity 17 is provided; at one end of mierotome base 1 for the reception of a block-of paraffin in which a specimen to be sectioned is embedded (or other solid specimen, such as wood, bone, woody vegetable matter. etc. Set screws ll8 are provided for holding the paraffin block firmly in the position desired for slicing a section from the top of the specimen.

At the other end of the base 1. means are provided for freezing and mounting a specimen. The horizontal surface 19 of specimen freezing stage 20 is provided to receive the unfrozen specimen and, after refrigeration of the freezing stage. to hold the specimen which is frozen to the surface securely in position for sectioning. The cylindrical flange 21 which is an integral part of the freezing stage extends down into the well 22 in the base of the mierotome. The purpose of the flange is to support the freezing stage and also to provide a relatively large area of heat exchange surface for the rapid cooling of the freezing stage when refrigerant is supplied to it. A milled shoulder 23 is provided for mounting the stage in well 22 and also permits carbon dioxide gas to escape while trapping the snow. A refrigerant nozzle socket 24 is screwed into the threaded surface of flange 21. Holes 25 permit the passage of refrigerant introduced through socket 24 for circulation over the exterior as well as interior surfaces of flange 2] and of the freezing stage.

The freezing stage 20 is made sufficiently massive to serve as a thermal reservoir to keep the specimen frozen for a reasonable period of time after the refrigerant supply is discontinued.

Othe parts and structural features will be described in connection with the description of the manner of use of the combined microtome unit.

If the specimen to be sectioned is to be frozen it is placed upon the surface 19 of the freezing stage 20 with the portion to be sliced off uppermost. A suitable refrigerant, such as carbon dioxide in liquid state, is then introduced from a supply container, not shown, through a contact nozzle such as that indicated at 26, through socket 24. For portability, a one shot capsule may be used in which case the refrigerant is introduced through channel 35 by means of a hypodermic needle attachment introduced downwardly through the top of the channel. The specimen is cooled by transfer of heat to the freezing stage as the latter is cooled until the specimen is frozen and frozen to surface 19. It is then ready for the cutting operation. Since some materials slice best at certain temperatures, provision is made at 20a for insertion of a suitable thermistor to measure the temperature of the freezing stage.

To cut a slice from the top of the frozen specimen, the metering post 3 is first screwed down into metering bushing 5, either by rotating the entire cutting head assembly 2 or by turning the post by means of the knurled hand nut 14, until the cutting edge of the blade is at the level of the top of the frozen specimen. If sections equal to the distance between the screw threads of the metering bushing are desired, each successive turn of the cutting head assembly will cut a slice of this thickness from the specimen. For example, if the distance between threads is one sixty-fourth, inch, the thickness of each slice will be one sixty-fourth inch. If, however, the thinnest possible slice is to be cut from the specimen, the head assembly or metering post and wheel 6 may be rotated through the angular distance of only one notch 7 and the metering wheel then locked into position with respect to the base by means of latch 27 which, as is best shown in FIGS. 1 and 5, is mounted for vertical movement in base 1 to engage stop 28 with or disengage stop 28 from a notch 7. Latch 27 slides and is retained in an L-shapcd groove 29 (FIG. 2) and has a leaf spring element 30 to frictionally hold the latch in the groove and handle tabs 31 for the manual manipulation of the latch.

With the metering wheel 6 locked in stationary position by latch 27, rotation of blade holder 9 about metering post 3 carries the cutting edge of the blade around and over the specimen in a plane normal to the axis of the metering post. If, after the top slice has been cut from the specimen, another slice of minimum thickness is desired, latch 27 is withdrawn and the cutting head assembly turned down one notch and again locked into stationary position by the latch. Rotation of the blade holder will then effect the taking of another section of minimum thickness from the specimen. If somewhat thicker slices are desired, the cutting head assembly may be turned two or more notches to double, etc., the thickness of the section taken.

In the microtomc unit shown by way of example, the threads of the metering post and bushing are one sixtyfourth inch apart and the metering wheel is provided with forty notches equally spaced apart. The thinnest section that may be taken by advancing the metering wheel one notch is 12 microns. The capability of producing thinner sections may be increased by providing a finer thread and/or a larger number of notches on the metering wheel. Means may also be provided for locking the metering wheel at positions intermediate adjacent notches. v

A latch 32 is pivotally mounted upon blade holder 9 by means of screw 33 to lock the blade holder to the metering wheel by engagement of latch stop 34 with a notch 7. With the metering wheel so locked to the blade holder, the blade holder may be driven in rotation by manual force applied to the knurled hand nut 14 or the metering post 3 may be turned against the frictional engagement of the threads with metering bushing 5 by force applied to the arm 10 of the blade holder. When latch 32 is disengaged and latch 27 is engaged, force applied to the arm 10 results in rotation of the blade holder about the conical shoulder support 8 without movement of the metering post 3.

If the hub portion of blade holder 9 is frictionally tighter to the conical shoulder support 8 than post 3 is to bushing 5, then latch 32 is not needed.

It has been found that better cutting of a frozen specimen results if the cutting blade is cold. To chill the blade as the specimen is being frozen, a refrigerant discharge channel 35 is provided in base l,'leading from well 22 to the top of the base at the edge of freezing stage 20. A shallow cavity 36 is provided under the middle portion of blade 11 into which refrigerant may flow after being discharged from channel 35 if the blade holder is placed in position immediately over the outlet of channel 35 as is indicated in FIG. 4. The carbon dioxide snow which tends to pack into the cavity keeps the blade cold for a limited period of time. Channel 35 may be plugged, as by a plastic screw, to limit discharge of refrigerant to the channel 36.

The use of the microtome for sectioning specimens embedded in paraffin and specimens of material that are sufficiently rigid to be cut without freezing will be understood from the foregoing. The block of paraffin containing the specimen is rigidly mounted in cavity 17 by means of set screws 18 and slices of the desired thickness may then be cut from the top of the specimen following procedures as described.

As the drawing shows, blade 11 is sharpened by grinding on one side only. This makes it possible to set the microtome to cut at either of two angles depending on whether the blade is in the position shown in FIG. 4 or that shown in FIG. 8. Certain materials are more easily sliced at one angle than the other. Also, the blade is so positioned on the blade holder that the edge slices the specimen at the optimum cutting angle of 60.

The microtome unit may be more or less permanently mounted to a table or bench top by means of screws passing through holes 37. If portability is desired, a C" clamp 38 having an arm adapted to pass through a horizontal hole 39 in the base of the microtome unit (FIG. 1) maybe employed.

An alternate form of cutting head construction is shown in FIG. 9. The hub of the blade holder 91: is provided with a cylindrical bearing surface 40 which engages the surface of meteringpost 3. A leaf spring 41 is provided to hold the blade holder 92 snugly to the metering post on the side from which arm extends. The blade holder is mounted upon post 3 by means of a spider spring washer 42 which rests upon the annular top of the hub of the blade holder and a screw 43 which threads into the top of the post and has a conical shoulder 44. The screw is turned in sufficiently to provide the desired friction pressure between shoulder 44 and washer 42 and between the bottom of the blade holder and metering wheel 6. This construction is somewhat less expensive to manufacture than that shown in FIG. 3.

ACHIEVEMENT The microtome of this invention provides, in a simple and portable unit, full facilities to prepare a specimen for cutting and to prepare sections of the specimen suitable for microscopic examination. A highly versatile instrument, it will produce sections over a wide range of thicknesses with only simple metering adjustments. The blade may be brought to initial cutting position rapidly and, if desired, serial sections may be taken without readjustment between cuts. A choice of cutting angles is provided and clean and easy cutting is assured by the slicing action resulting from the angle of the cutting edge to the radius of the cutting head. The cutting action is further enhanced by the cooling of the blade. The specimen is held in frozen condition for more than enough time to complete the sectioning operation. Paraffin embedded specimens may be handled by the unit and no maintenance is required except sharpening of the blade, which-is stroppable, or replacement of the blade.

I claim: 1

1. Microtome apparatus comprising a base; means in said base for holding a specimen in position for sectioning; and a cutting head assembly mounted upon said base; said assembly comprising a vertical metering post mounted by screw threads in said base, a cutting blade holder including a substantially horizontal arm supported from a hub upon said post for rotation about the axis of said post. an inclined cutting blade secured to said arm in position to cut a slice from a specimen held upon said base when said arm is passed thereover with rotation of said cutting head assembly, said cutting blade holder being frictionally supported upon said metering post whereby said holder may be rotated about the axis of said post either with or independently of said post, said metering post being provided with a conical shoulder and the interior of the hub portion of said blade holder being correspondingly conical whereby said holder is frictionally supported upon said post at the engaging respective conical surfaces, and adjustable spring mcans arranged to adjust the pressure of the conical surface intercngagement and thus the force re quired to move the blade holder and metering post relative to each other.

2. Microtome apparatus comprising a base; means in said base for holding a specimen in position for sectioning; and a cutting head assembly mounted upon said base; said assembly comprising a vertical metering post mounted by screw threads in said base, a cutting blade holder including a substantially horizontal arm supported from a hub upon said post for rotation about the axis of said post, an inclined cutting blade secured to said arm in position to cut a slice from a specimen held upon said base when said arm is passed thereover with rotation of said cutting head assembly, said cutting blade holder being frictionally supported upon said metering post whereby said holder may be rotated about the axis of said post either with or independently of said post, a metering wheel upon and fixed to said metering post above said microtome base, the hub portion of the blade holder having an axial bore therein snugly engaging the metering post, and means for clamping said hub portion of said holder with adjustable friction engagement against the top surface of said wheel for rotation either therewith or independently thereof.

3. Microtome apparatus comprising a base; means in said base for holding a specimen in position for sectioning; and a cutting head assembly mounted upon said base; said assembly comprising a vertical metering post mounted by screw threads in said base, a cutting blade holder including a substantially horizontal arm supported from a hub upon said post for rotation about the axis of said post, an inclined cutting blade secured to said arm in position to cut a slice from a specimen held upon said base when said arm is passed thereover with rotation of said cutting head assembly, said cutting blade holder being frictionally supported upon said metering post whereby said holder may be rotated about the axis of said post either with or independently of said post, a metering wheel upon and fixed to said metering post, said metering wheel being provided with spaced notches around its periphery, and a latch operatively mounted upon the hub of the blade holder for engagement with a selected one of said notches to hold said blade holder in predetermined fixed position relative to said metering wheel and thus to the metering post.

4. Microtome apparatus comprising a base; means in said base for holding a specimen in position for sectioning; and a cutting head assembly mounted upon said base; said assembly comprising a vertical metering post mounted by screw threads in said base, a cutting blade holder including a substantially horizontal arm supported upon said post for rotation about the axis of said post, an inclined cutting blade secured to said arm in position to cut a slice from a specimen held upon said base when said arm is passed thereover with rotation of said cutting head assembly, a longitudinally slotted threaded bushing mounted in vertical position in the microtome base, said metering; post being screwed into said bushing, and a set screw provided in said base to bear against said bushing to adjust the pressure between the intcrengaging screw threads and thus the force required to turn said post relative to said bushing.

5. Microtome apparatus comprising an elongated base; a cavity in said base at one end thereof opening upwardly to receive a paraffin embedded specimen therein and means for clamping said specimen in position for sectioning; a freezing stage mounted in the other end of said base adapted to be cooled by the application of refrigerant thereto to freeze a specimen upon and to said freezing stage for sectioning; a cutting head assembly mounted upon said base; said assembly comprising a vertical metering post mounted by screw threads in said base. a cutting blade holder including a substantially horizontal arm carrying a cutting blade or independently of said post; and means for holding said metering post in predetermined fixed position relative to said microtomc base.

Claims

1. Microtome apparatus comprising a base; means in said base for holding a specimen in position for sectioning; and a cutting head assembly mounted upon said base; said assembly comprising a vertical metering post mounted by screw threads in said base, a cutting blade holder including a substantially horizontal arm supported from a hub upon said post for rotation about the axis of said post, an inclined cutting blade secured to said arm in position to cut a slice from a specimen held upon said base when said arm is passed thereover with rotation of said cutting head assembly, said cutting blade holder being frictionally supported upon said metering post whereby said holder may be rotated about the axis of said post either with or independently of said post, said metering post being provided with a conical shoulder and the interior of the hub portion of said blade holder being correspondingly conical whereby said holder is frictionally supported upon said post at the engaging respective conical surfaces, and adjustable spring means arranged to adjust the pressure of the conical surface interengagement and thus the force required to move the blade holder and metering post relative to each other.

4. Microtome apparatus comprising a base; means in said base for holding a specimen in position for sectioning; and a cutting head assembly mounted upon said base; said assembly comprising a vertical metering post mounted by screw threads in said base, a cutting blade holder including a substantially horizontal arm supported upon said post for rotation about the axis of said post, an inclined cutting blade secured to said arm in position to cut a slice from a specimen held upon said base when said arm is passed thereover with rotation of said cutting head assembly, a longitudinally slotted threaded bushing mounted in vertical position in the microtome base, said metering post being screwed into said bushing, and a set screw provided in said base to bear against said bushing to adjust the pressure between the interengaging screw threads and thus the force required to turn said post relative to said bushing.

5. Microtome apparatus comprising an elongated base; a cavity in said base at one end thereof opening upwardly to receive a paraffin embedded specimen therein and means for clamping said specimen in position for sectioning; a freezing stage mounted in the other end of said base adapted to be cooled by the application of refrigerant thereto to freeze a specimen upon and to said freezing stage for sectioning; a cutting head assembly mounted upon said base; said assembly comprising a vertical metering post mounted by screw threads in said base, a cutting blade holder including a substantially horizontal arm carrying a cutting blade and supported upon said post for rotation about the axis of said post to pass over said cavity and said freezing stage; said cutting blade holder being frictionally supported upon said metering post whereby said holder may be rotated about the axis of said post either with or independently of said post; and means for holding said metering post in predetermined fixed position relative to said microtome base.