US3673904A

US3673904A - Microtome assemblies

Info

Publication number: US3673904A
Application number: US97536A
Authority: US
Inventors: Michael Henry Cooper; Leslie Alva Fryatt
Original assignee: NGN Ltd
Current assignee: NGN Ltd
Priority date: 1969-12-16
Filing date: 1970-12-14
Publication date: 1972-07-04
Anticipated expiration: 1989-07-04
Also published as: GB1284593A

Abstract

A microtome assembly comprises a pivotally suspended knife assembly and knife displacing means which are coupled to the knife assembly such that forward movement of the displacing means urges the knife assembly into a lower position before horizontal displacement of the knife assembly on its cutting stroke, and retractive movement of the displacing means urges the knife assembly to an upper position before horizontal displacement of the knife assembly on its return stroke. The knife body is therefore lifted clear of a specimen before its return stroke thereby avoiding damage to a cut surface of the specimen.

Description

I O United States Patent [151 3,673,904 Cooper et al. July 4, 1972 MICROTOME ASSEMBLIES References Cited [72] Inventors: Michael l-lenry Cooper, Bumley; Leslie UNITED STATES PATENTS Alva y Accringwn, both of England 3,462,969 8/1969 Grasenick et al ..s3/915.5 x 73 A e N.G.N.L'mited M rfl t,H ll,Y kh' l 1 sslgn 6 England I a ee u or S Ire Primary Examiner-James M. Meister AttorneyScrivener, Parker, Scrivener & Clarke [22] Filed: Dec. 14, 1970 [57] ABSTRACT PP NO-I 97,536 A microtome assembly comprises a pivotally suspended knife assembly and knife displacing means which are coupled to the [30] Foreign Application i i Data knife assembly such that forward movement of the displacing means urges the knife assembly into a lower position before Dec. 16, 1969 Great Britain ..6l,267/69 horizontal displacement of the knife assembly on is cutting stroke, and retractive movement of the displacing means urges the knife assembly to an upper position before horizontal dis- [52] US. Cl ..83/171,gggpggiggkff placement of the knife assembly on 8 return stroke The knife [51] lm Cl 1/06 body is therefore lifted clear of a specimen before its return [58] Fieid stroke thereby avoiding damage to a cut surface of the 90/31, Specimen 9 Claims, 5 Drawing Figures PATENTEDJUL 4 I972 3. 673.904

snanlor t n'f 1m M 20 24 I 16 34 163-0 1825 I PAT ENTEDJUL 419. 2 3, 673,904 SHEET 2 0F 3 FIG.3.

PATENTEDJUL 4|972 3,573,904

SHEET 30F 3 FIG.Q4.

' PIC-3.5.

MICROTOME ASSEMBLIES This invention relates to rnicrotome assemblies particularly for use in freeze etching equipment used in preparing specimens for electron-microscopical investigations.

According to the present invention a microtome assembly comprises a height adjusting device, a suspension arm which is attached thereto by a friction bearing and which carries a knife assembly, and knife displacing means pivotally attached to the knife assembly such that forward movement of the displacing means urges the knifeassembly into a lower position before horizontal displacement thereof takes place and retractive movement urges the knife assembly to an upper position before a return horizontal displacement takes place. The knife assembly preferably comprises two blades spaced horizontally relative to each other, which blades may also be spaced vertically relative to each other. A stop means is preferably provided limiting the extent of the movement of the knife assembly between theupper and lower positions. The knife assembly preferably also comprises means for adjusting the angle at which the knife, i.e. the cutting blade, is presented to the specimen.

The invention will now be described by way of example with reference to the accompanying drawings of which:

FIG. 1 shows a side elevation of part of a rnicrotome assembly constructed in accordance with one embodiment of the invention;

FIG. 2 shows an enlarged detail of a knife assembly;

FIG. 3 shows a front elevation of the knife assembly;

FIG. 4 shows an enlarged detail of a knife assembly according to a second embodiment; and

FIG. 5 is a section on the line V-V of FIG. 4.

In the drawings a height adjusting device comprising a sup port column slidable in a base plate 11 extends into a vacuum chamber 12 and carries a suspension arm 13 pivotally attached to it by a friction bearing 14.'The bearing is arranged to be vertically over a specimen 15 which is to be cut by the rnicrotome assembly. The suspension arm 13 incorporates a thermally non-conductive section, made for example of PER- SPEX (Registered Trade Mark), which is not shown in the drawings.

To the lower end of the suspension arm 13 is rigidly attached a hollow knife body 16 through which a low temperature fluid, e.g. liquid nitrogen, is passed. A cutter head 18 is attached to the knife body by a freely rotatable pivot 20. Two

cutter blades

22 and 23 are clamped to the cutter head by

clamps

24 and 25 in such positions that the cutting edge 26 of the blade 22 is slightly lower than the cutting edge 28 of the blade 23. j

The cutting blades are cooled by thermal conductivity through the pivot 20, and the cooling is supplemented by a flexible link of material having a high thermal conductivity, e.g. the copper braid shown at 30, between the knife body 16 and the cutter head 18.

A clamping pillar or plate 32 is rigidly attached to the cutter head 18 and adjacent to it is a stop plate 34. The stop plate and clamping plate are clamped together by a screw 36 which passes through an arcuate slot 38 in the stop plate and engages in a tapped hole in the clamping plate. The screw 36 may be loosened to permit angular adjustment of the stop plate and clamping plate relative to each other, thereby determining the angle between the

cutter blades

22 and 23 and the knife body 16 and thus the angle at which the blades are presented to the specimen.

A knife displacing means in the form of a rod 40, displaceable by, for example, a solenoid assembly which is not shown, is pivotally connected at 42 to the stop plate 34 by a clevis 44.

The knife body 16 has an upwardly projecting portion 46 carrying a horizontally extending plate 48. A pin or dowel 50 rigidly secured to the stop plate 34 engages in a slot 52 in the plate 48. The slot is of greater width than the pin, thus permitting relative movement between the cutter head assembly comprising the pin 50 itself, stop plate 34, clamping plate 32 and cutter head 18 on the one hand and the knife body 16 on the other.

When the rod 40 is displaced forwardly i.e. from left to right in FIG. 2, the cutter head assembly is rotated about the pivot 20 as far as the clearance between the pin 50 and slot 52 permits, thereby lowering the

cutter blades

22 and 23. While this rotation of the cutter head assembly is taking place, the friction caused by the friction bearing 14 between the suspension arm 13 and the height adjusting column 10 prevents the knife assembly from moving forward. When the pin 50 comes up against the side of the slot 52 the whole knife assembly is then horizontally displaced sufiiciently for one of the cutting blades to make a cut through the specimen. When the retractive movement of the spindle begins, the cutter blades are raised as the cutter head is rotated back again about the pivot 20, the friction bearing 14 again preventing the return horizontal displacement of the knife assembly from beginning until the pin 50 has moved across to the other side of the slot 52. Thus the cutting blades move back on the return stroke at a level above the specimen, thereby clearing the specimen and thus avoiding the possibility of damaging the freshly cleaved face of the specimen which possibility would exist if the return stroke were to follow the same path as the forward stroke particularly if ice particles had been deposited on the face of the specimen behind the blade.

The adjustment of the angle of the cutting blades relative to the specimen by means of the screw 36 and arcuate slot 38 enables the blades to be set at the optimum angle for the particular material to be cleaved.

Each cutting blade is used separately, the knife assembly being displaced on each stroke only through a suflicient are about the friction bearing 14 to permit the blade then operative to pass through the specimen. Two blades are incorporated so that if the sharp edge on the first becomes blunt or damaged during the initial stages of the microtoming when comparatively large cuts are being made, the second blade may be brought into use for the final stages when smaller cuts are being made and the risk of damaging the cutting edge is correspondingly reduced.

In the embodiment shown in FIGS. 4 and 5, the cutter head 118 is made hollow so that cooling medium such as liquid nitrogen may be circulated directly through the cutter head by way of pipes 116 which incorporates flexible portions 117 to accommodate tilting and linear displacement of the cutter head during operation of the rnicrotome assembly.

Also shown in FIGS. 4 and 5 is one manner in which the

cutting blades

122, 123 are fixed in the cutter head. The

blades

122, 123 are located in

slots

124, 125 in the cutter head 118 and held in place by

clamping plates

126, 127 urged against their respective blades by

screws

128, 129. The

clamping plates

126, 127 are located by pegs 130 which pass through apertures in the clamping plates so as to be retained within the slots whilst being freely displaceable by the screws. When the screws are tightened, the clamping plates clamp the blades firmly against the lower walls of the slots thus ensuring good thermal contact between the blades and the cutter head.

The term "friction bearing" used herein means a bearing which inhibits rotau'on of the members which it connects. This may be achieved by making the bearing surfaces of materials having a high coefficient of friction, for example, or by loading it e.g. with a threaded nut and/or a spring.

We claim:

1. A rnicrotome assembly comprising a base member, a support column slidable through said base member, a suspension arm pivotally attached at one of its ends to said support column, a friction bearing between said support column and said suspension arm, a knife assembly pivotally attached to the other end of said suspension arm and knife displacing means pivotally attached to said knife assembly, said knife displacing means including means operable to urge said knife assembly into a lower position before horizontal displacement of said knife assembly by forward movement of said knife displacing means and to urge said knife into an upper position before return horizontal displacement of said knife assembly by retractive movement of said knife displacing means.

2. A microtome assembly according to claim 1, wherein said knife assembly comprises a knife body and a cutter head, said cutter head being coupled to said knife displacing means and being pivotable relative to said knife body, a lost-motion connection being provided between said knife body and said cutter head such that initial forward and retractive movement of said knife displacing means causes tilting of said cutter head relatively to said knife body.

3. A microtome assembly according to claim 2. wherein said lost-motion connection comprises a pin able to be fixed relative to said cutter head and means defining a slot in a part of said knife body, said pin passing through said slot and having a width less than that of said slot.

4. A microtome assembly according to claim 3 wherein a stop plate is pivotably attached said cutter head and carries said pin, and including clamping means to releasably clamp said stop plate to said cutter head.

5. A microtome assembly according to claim 4 wherein said cutter head includes a clamping plate lying adjacent said stop plate and wherein said clamping means comprises means defining an arcuate slot in said stop plate, means defining a threaded bore in said clamping plate and a screw passing through said arcuate slot and engaging in said threaded bore.

6. A microtome assembly according to claim 2 wherein said knife assembly carries two blades.

7. A microtome assembly according to claim 4 wherein said knife assembly carries two blades.

8. A microtome assembly according to claim 2 wherein said knife body is hollow and includes means to enable cooling fluid to be passed through said knife body.

9. A microtome assembly according to claim 2 wherein said cutter head is hollow and includes means to enable cooling fluid to be passed through said cutter head.

Claims

1. A microtome assembly comprising a base member, a support column slidable through said base member, a suspension arm pivotally attached at one of its ends to said support column, a friction bearing between said support column and said suspension arm, a knife assembly pivotally attached to the other end of said suspension arm and knife displacing means pivotally attached to said knife assembly, said knife displacing means including means operable to urge said knife assembly into a lower position before horizontal displacement of said knife assembly by forward movement of said knife displacing means and to urge said knife into an upper position before return horizontal displacement of said knife assembly by retractive movement of said knife displacing means.

3. A microtome assembly according to claim 2 wherein said lost-motion connection comprises a pin able to be fixed relative to said cutter head and means defining a slot in a part of said knife body, said pin passing through said slot and having a width less than that of said slot.