U.S. patent number 3,699,830 [Application Number 05/126,674] was granted by the patent office on 1972-10-24 for method utilizing a disposable blade in microtome cutting.
Invention is credited to John E. P. Pickett.
United States Patent |
3,699,830 |
Pickett |
October 24, 1972 |
METHOD UTILIZING A DISPOSABLE BLADE IN MICROTOME CUTTING
Abstract
The method of microtome cutting based on using the conventional,
non-disposable, thick, inflexible microtome knife that requires
resharpening after each period of wear and substantial blade holder
adjustments to obtain and maintain the proper cutting angle is
replaced by a method based on using a thin, flexible and disposable
blade having a microtome quality cutting edge and which method
allows the technician to install and replace blades without
disturbing or repositioning the holder.
Inventors: |
Pickett; John E. P. (Durham,
NC) |
Family
ID: |
22426134 |
Appl.
No.: |
05/126,674 |
Filed: |
March 22, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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885143 |
Dec 15, 1969 |
3599523 |
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Current U.S.
Class: |
83/13; 83/431;
83/651; 83/915.5 |
Current CPC
Class: |
A61B
17/322 (20130101); Y10T 83/04 (20150401); G01N
2001/061 (20130101); Y10T 83/929 (20150401); Y10T
83/66 (20150401) |
Current International
Class: |
A61B
17/322 (20060101); G01N 1/04 (20060101); G01N
1/06 (20060101); B26d 003/00 () |
Field of
Search: |
;83/13,915.5,431,437,651,698 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Juhasz; Andrew R.
Assistant Examiner: Gilden; Leon
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application partakes of being a continuation-in-part of
pending application Ser. No. 885,143 filed Dec. 15, 1969 entitled
"Disposable Blade and Holder for Microtome" by the same inventor
now U.S. Pat. No. 3,599,523.
Claims
What is claimed is:
1. The method of microtome cutting of an embedded specimen
comprising the steps of:
a. mounting the specimen in a holder mechanism having means for
reciprocating and advancing the specimen for precision cutting in a
vertical plane;
b. mounting forward of the mechanism a blade holder having a
backing member providing a fixed central, smooth precision formed
concave backing surface, a pair of fixed slotted integral end
portions on opposite sides of said backing surface, a movable
clamping member having on one back side a convex clamping surface
mating said concave backing surface and on the opposite front side
a smooth concave guide surface adapted to receive and allow the
undisturbed flow of cut ribbons of tissue, and means to move said
clamping member towards and away from said backing member, said
mounting of said blade holder being effected in such manner that
said concave backing surface assumes a predetermined optimum
position relative to said cutting plane;
c. moving said clamping member away from said backing member
sufficient to form a slot between said concave backing and convex
clamping surfaces and which with the slots provided by said holder
end portions forms a continuous slot across said holder;
d. inserting from one side of said holder slot a substantially
rectangular uniform size disposable blade having one longitudinal
edge precision sharpened to microtome knife quality for cutting and
the opposed edge free of the conventional guard member and being of
substantially less flexibility than the conventional double edge
wafer blade and positioning said blade with its central portion
opposite said backing surface and its ends in said end portion
slots;
e. moving said clamping member toward said backing member whereby
the central portion of said blade is clamped between said concave
backing and convex clamping surfaces, said blade is slightly curved
around a longitudinal axis to bring its cutting edge into said
cutting plane and at an appropriate optimum angle with respect
thereto and said clamping member is locked in such clamped
position;
f. cutting a predetermined number of sections from said specimen
while allowing individual sections and ribbons of tissue to form
and flow on said clamping member front guide surface and until said
blade cutting edge is worn;
g. without disturbing the position of said holder end portions
moving only said clamping member away from said backing member
whereby to release said worn blade and restore said slot across
said holder;
h. removing said worn blade from one side of said holder and
installing a new said uniform blade in the same position previously
occupied by the worn blade;
i. moving said clamping member toward said backing member as before
to place the cutting edge of the new said blade in said cutting
plane and at the same said optimum angle; and
j. continuing to repeat the foregoing steps until the required
number of tissue sections have been cut.
2. The method of claim 1 including the steps of:
a. after mounting and clamping said blade and prior to cutting
usable sections cutting a series of test sections and during such
test cutting adjusting said blade holder and blade as required
laterally, in tilt, forwardly and vertically to obtain respective
optimum positions of said holder and blade; and
b. thereafter always maintaining said blade holder in its said
optimum position during blade changes and after each respective
blade change restoring each successive blade to the same said
optimum blade position.
3. The method of claim 1 including the steps of:
a. mounting said blade holder in a conventional microtome
non-disposable knife holder having a pair of clamps adapted to
clamp said end portions and having adjustment means to adjust said
blade holder in tilt, laterally, vertically and forwardly;
b. utilizing said adjustment means to bring said blade holder and
blade into optimum positions with respect to said cutting plane;
and
c. thereafter during replacement of each successive new said blade
maintaining said blade holder in said optimum holder position and
adjusting only said clamping member to bring the new replaced blade
into the same said optimum blade position.
4. The method of claim 1, including the step of removing each
successive worn blade by pushing from the side and on one end of
the worn blade with one end of the next successive new blade until
the worn blade is ejected from said holder slots and the new blade
has assumed the position previously occupied by the worn blade.
5. The method of claim 1 including the steps of:
a. storing replacement blades in a cartridge type dispenser;
and
b. pushing each respective worn blade out of said holder with a new
blade being ejected from said cartridge.
6. The method of claim 1 including the step of installing the blade
such that both of its ends extend at least slightly beyond the
width of the specimen being cut.
7. The method of claim 1 including the step of adjusting the amount
of pressure applied by said clamping member to said blade to
regulate the curvature thereof.
8. The method of claim 1 wherein said concave backing surface
merges at its bottom end with a ledge formed in said backing member
and including the step of supporting each said blade on said ledge
during cutting.
9. The method of claim 1, wherein the consecutive steps of moving
said clamping member away from said backing member, removing said
worn blade from one side of said holder and installing a new said
blade, and moving said clamping member toward said backing member
are performed within such limits of movement that any ribbon of
sections previously cut and supported on said clamping member front
guide surface remains unbroken and otherwise undisturbed.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to methods of microtome cutting using
microtome knives or blades and knife or blade holders and
particularly to methods of microtome cutting using disposable blade
and disposable blade holder constructions.
2. Description of the Prior Art
It has long been the practice in the art for microtome cutting
procedures to be based on use of knives which take the form of
being relatively thick, inflexible, and are adapted to being
resharpened. Such knives are made of a very fine grade of steel and
are adapted to receive an extremely sharp and relatively smooth
cutting edge when sharpened. Such knives as seen in profile are
biconcave, plano-concave, wedge shaped or tool edge shape
sharpened. However, the conventional knives are expensive in
initial cost, require expensive and time consuming resharpening
equipment, require extra technician time for resharpening, require
auxiliary hone plates and hone plate grinders, and the blades are
susceptible to corrosion. The complexity and cost of resharpening
microtome blades is further illustrated in my separate U.S. Pat.
No. 3,349,520 which is for a machine designed to eliminate hand
honing of the glass plates required to hone the blades. When such a
blade is replaced or shifted laterally to get a fresh edge the
blade holder may have to be readjusted, in either one or all
directions, laterally, in tilt, forward and vertically. Therefore,
the method of using conventional knives requires the availability
of blade holders that can be adjusted in many directions. Such
readjustments are absolutely necessary where precise and thin
sectioning is involved since one conventional blade edge does not
cut in the same precise manner as another conventional blade
edge.
To illustrate how long established the practice has been, reference
is made to U.S. Pat. No. 1,026,280 issued May 14, 1912 and which
shows one method of cutting based on a type microtome knife that is
in widespread use today. Over the years there have been many
attempts to provide a method of cutting based on using a microtome
blade holder adapted to receive some type of thin, highly flexible
disposable blade such as a "wafer" type, double edge blades or
typical single edge safety razor blades and representative prior
patents are found in U. S. Pat. Nos. 1,865,539, 1,998,428,
2,232,008 and 3,227,020. Some of the prior patent microtome cutting
methods using blade holders and disposable blades have found
limited application in teaching laboratories where the cutting
requirements are not critical and where relatively soft tissue is
being cut. However, there has never appeared a practical method of
using a disposable blade which provides quick change in the blade
holder and adapts to use of a disposable blade having a microtome
knife quality cutting edge capable of cutting not only the soft
teaching tissue specimens but also a wide range of bone, dense,
hard tissue and the like in relatively wide widths of specimens.
Furthermore, essentially all of the prior art methods of cutting
that have reached the trade have been adapted to use the
conventional very thin, "wafer" type blade or the single edge
safety razor type which inherently exhibit a relatively rough
cutting edge as compared to a microtome knife quality cutting
edge.
In addition to the conventional thin, disposable, "wafer" type
double edge and single edge safety razor blades sold under such
trademarks as Gillette, Wilkinson, Star, Personna and Gem another
type of disposable blade used in surgical practice is the single
edge, disposable blade sold under various trademarks, e.g.,
Personna and Weck. Blades of this type are widely used for surgical
preparation, autopsies and general tissue cutting. The surgical
Personna or Weck type blade like the Gem and Star single edge blade
is normally provided on the unsharpened edge with a bent metal
cover or banding member which gives rigidity to the blade and
allows the user to safely hold the blade for cutting. The surgical
blade differs from the conventional double edge, "wafer" blade in
that it is generally thicker, longer, and more elongated and
rectangular in shape than most conventional single edge and double
edge disposable wafer blades. The surgical blade is normally not
flexed in use. However, when the mentioned cover member is removed
from the surgical blade it has been found that while not as
flexible as the usual wafer blade the surgical blades can
nevertheless be flexed or slightly curved with a properly applied
force. Of particular importance, the surgical blade, unlike the
wafer blade, inherently lends itself to being made with an
extremely sharp and relatively smooth edge of microtome knife
quality whereas ordinary conventional single and double edge
disposable blades even though suited to ordinary shaving do not in
fact have either relatively smooth or sharp edges. While both
conventional, disposable, single edge and double edge "wafer" type
blades have been used in microtome blade holders for disposable
blades, the art has not heretofore taught a cutting method built
around the employment of the surgical type blade, e.g., those made
by Personna or Weck, modified by removal of the mentioned cover
member. Accordingly, the art of cutting has not had available a
method utilizing a disposable blade having a cutting edge of
microtome knife quality.
Another aspect of the method of cutting with both the conventional
microtome knife as well as with such types of disposable blades as
have been shown in prior art is that a change of blade almost
always requires repositioning of the knife or blade holder before
cutting is recommenced. If a blade or knife is nicked or damaged at
the time of locating say a very thin and malignant tumor or lesion
then if the blade is moved laterally for a sharp section or for
replacement the chances are high that the tumor or lesion will be
missed. This is so since the knife or blade after being unclamped
and being shifted laterally or replaced may cause up to five
succeeding sections to be missed in the course of getting the
cutting thickness readjusted. Of equal significance is that many
times when very thin sections, e.g., 1 to 2 microns, are being cut,
the operator may have to try a number of supposedly sharp knives to
find an acceptable cutting edge. The problem of knife damage and
required resharpening, if not complete discard of the damaged
knife, also arises whenever a hard cotton or nylon suture, surgical
clip, gun pellet, calcium deposit or like foreign matter is
embedded in the tissue being cut and strikes the knife edge.
Using the teaching of U.S. Pat. No. 1,865,539 as an example, it
will be observed in another aspect of the prior art that prior art
disposable wafer blade methods require loading of new wafers from
the front of the holder. Since the front of the holder is in the
immediate cutting area where the tissue ribbons collect, each
disposable blade change inherently requires disturbing this
critical operational area and introduces the possibility of foreign
matter, e.g., paraffin, getting into the blade holder interior. The
typical non-disposable knife has a front surface which acts as a
guide for the ribbons of tissue. Therefore, this "guide" is removed
each time the blade is replaced. For mass sectioning it is the
practice to collect the tissue in ribbons and mount the ribbons on
a clear film strip base but prior art cutting methods do not adapt
to such "ribbon" cutting. The film technique is increasing in
importance and is explained in the article "Improved Film Strip
Technique for the Laboratory, Archives of Pathology, April 1964,
Vol. 77, pages 429-433." It can be seen that conventional
disposable blade techniques are not compatible with the new film
techniques. Front loading blade change operations are furthermore
generally awkward and slow and do not adapt to the requirements for
holding blades being used to cut frozen tissue, e.g., a Cryostat
microtome. A microtome blade method for using a disposable blade
having a cutting edge of microtome knife quality, which adapts to
film mounting procedures, which can cut any type tissue, bone,
etc., cut by a microtome knife, which provides for side loading
replacement and which adapts to both frozen and unfrozen tissue
cutting has therefore not been provided by the prior art. This is
particularly made evident by the fact that no such disposable
blade-holder method is in widespread use.
The typical prior art method can thus be said to generally involve
all or substantially all of the following steps irrespective of
whether the typical non-disposable thick microtome blade or
disposable wafer type blade is employed: select blade, install
blade, roughly adjust blade position laterally, in tilt, vertically
and forwardly, take trial cuts, repeat adjustments of blade
position to obtain an optimum position, trim sections until blade
edge is dulled, replace blade, take trial cuts, readjust blade
holder and repeat when blade is next dulled. In the case of the
non-disposable blade there is of course involved the many
additional and very expensive steps required to resharpen the blade
after each use. In any event the prior art has not provided a
method of cutting based on using a disposable blade and relative
few operational steps for installing, using and replacing
blades.
SUMMARY OF THE INVENTION
According to the invention there is provided a method of cutting
based on use of a precision machined microtome blade holder adapted
to releasably receive the surgical type, single edge, disposable
blade having a microtome knife quality edge for use in cutting all
of the various type of thick, thin, soft, hard and dense tissue and
bone specimens encountered in medical laboratory practice. The
method of the invention enables a blade holder to be used which is
adapted to be received by and clamped in the conventional precision
microtome, adjustable knife clamp, so that no modification of the
conventional microtome or clamp is required. According to the
method of the invention, the surgical type blade is installed from
the side, is clamped in cutting position and is slightly curved
against a concave backing surface so that such blade curvature adds
to the normal and optimum angle tilt of the blade holder,
corresponding to the usual microtome knife tilt. This facilitates a
proper angle of cut, optimum blade edge angle and clearance of the
tissue block when moving past the blade. The blade is preferably
chosen so that its length extends slightly beyond the maximum width
of tissue block used on the rotary microtome which insures getting
a full width of tissue cut with the widest block. For blade
replacement the blade curving or clamping member having a convex
clamping surface is moved from a blade clamping to a blade release
position and in the release position a slot is formed in which a
replacement blade is slid in from either side of the holder. The
new blade is used to eject the worn blade being replaced without
disturbing the blade holder which remains clamped in position.
Furthermore, since the method of the invention provides for tissue
ribbons to be guided on the clamping member front surface such
ribbons are not disturbed during blade changes unlike the
conventional disposable or nondisposable blade change. The amount
of pressure applied to the blade is regulated as required to
regulate the blade curvature, which is preferably on about a 1 1/4
inch radius.
The method of the invention adapts to cutting thick, thin, dense
and both soft and hard specimens. The operator is assured that any
replacement blade will do the job thus eliminating the requirement
to check many knives and to search for a suitably sharpened knife
when cutting very thin sections. When blades are replaced the
operator can immediately resume sectioning without fear of losing
some critical and thin section in the course of restarting the
cutting schedule. A fixed angle of cutting is immediately
established as soon as the blade is installed and clamped and this
angle will normally not change so long as the same type tissue is
being cut. Yet, such angle can be quickly changed by adjusting the
conventional microtome knife clamp. It should be noted that in
comparison each change of a conventional knife normally requires
angle adjustment of the blade holder since sharpening wears away at
the knife edge. Also, if the conventional microtome knife is moved
laterally to get a sharp cutting section the holder is often
required to be adjusted in some direction.
From the viewpoint of costs it can be readily seen that
conventional knife blade cutting, resharpening and replacement in
terms of prior art methods is measured in terms of dollars per
knife edge use whereas the disposable blade method of the invention
involves cost per blade use measured in terms of cents.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a pictorial view of a conventional microtome and knife
clamp with a disposable blade holder adapted to the method of this
invention shown mounted in the clamp, and in dashed lines old and
new blades, and a section of tissue ribbon.
FIG. 2 is an exploded perspective view of the main parts of the
blade holder used with the method of this invention.
FIG. 2A is an alternate cam shaft construction for the mentioned
blade holder.
FIG. 3 is a plan view of the assembled blade holder of FIG. 2 and
showing in dashed lines the position in which the disposable blade
is placed in the holder.
FIG. 4 is a rear elevation of the holder of FIG. 3.
FIG. 5 is a right end elevation of FIG. 3 in unlocked position.
FIG. 6 is a left end elevation of FIG. 3 in unlocked position.
FIG. 7 is an elevation section view taken along line 7--7 of FIG. 3
in unlocked position.
FIG. 8 is an elevation section view taken along line 8--8 of FIG. 3
in unlocked position.
FIG. 9 is a view like FIG. 7 and showing a disposable blade in an
unlocked position within the holder.
FIG. 10 is a view like FIG. 8 and showing the disposable blade in a
locked position within the holder.
FIG. 11 is a plan view of a disposable blade used in the method of
this invention.
FIG. 12 is an enlarged, fragmentary, elevation section view of the
disposable blade.
FIG. 13 is an enlarged, fragmentary, section view of the disposable
blade receiving portion of the unlocked holder of FIG. 8 but shown
in a normal tilt, off vertical.
FIG. 14 is an enlarged fragmentary, section view of the disposable
blade receiving portion of the locked holder of FIG. 10, but which
is also shown in a normal tilt, off vertical.
FIG. 15 is a somewhat generalized view of a conventional disposable
blade cartridge holder, as adapted to the invention.
DETAILED DESCRIPTION
The method of the invention will be explained in conjunction with
an explanation of an apparatus adapted to practice the method.
Referring to FIG. 1, a conventional, rotary microtome 10 comprises
a housing 11 having the customary gearing for moving the specimen
holder 12 in a vertical reciprocatory path and at the same time
feeding or advancing holder 12 outwardly against a stationary
knife. The knife clamp microtome 11 is generally indicated at 13
and is the conventional John Hopkins clamp for the American Optical
Company, Spencer 820 microtome which is used in illustration. Knife
clamp 13 is adjustable rotatably, laterally, and forwardly as
indicated by the arrows in FIG. 1 and the knife is adjustable
vertically in the clamp so that the knife can be adjusted for the
proper clearance angle, tilt vertical and lateral position.
Adjusting screws 16 provide vertical blade adjustment, rotatable
arm 17 locks clamp 13 in the selected forward position and arms 18
lock the clamp in the selected tilt position. While most microtome
knife clamps provide precision lateral, tiltable, forward and
vertical positioning of the knife or clamp in order to obtain
precise knife positions some clamps do not necessarily have all of
these adjustments or some or all of the adjustments are locked in a
selected position and never disturbed. For example, if the type of
tissue is uniform or the knife positioning is not critical, the
clamp can be used in some predetermined position. The foregoing is
mentioned because the method of the invention adapts to either type
of microtome operation.
Knife clamp 13 has a pair of jaws 14, 15 against which the slotted
end portions of the disposable blade holder of the invention are
securely held in the clamp. That is, the space normally occupied by
the conventional microtome knife is instead occupied by the blade
holder of the invention, the invention blade width W being at most
a minor portion of the conventional knife width.
The blade holder in the preferred form for practicing the method of
the invention is comprised of five parts, two of which are movable.
Support for the disposable blade is provided by a backing plate 20
which resides in clamp 13 and has slotted end portions which extend
outside the respective jaws 14, 15. Backing plate 20 has beginning
at its uppermost edge 20a, a precision formed concave surface 21
which in use receives and provides a precise backing surface for
curing the disposable blade and which extends downward a
predetermined distance corresponding to the width W of disposable
blade 50, and across the complete length L of plate 20. Here it
should be noted that concave surface 21 may be precision formed in
a central portion of a lesser length X corresponding to the length
of mating pivotal clamping plate 65 (later described) since the
blade is bent by plate 65. However, the end portions of surface 21
if not precision formed should be formed so as not to interfere
with the bending operation.
At the base of concave surface 21 is a shallow ledge 22 which acts
as a stop or rest and supports the disposable blade 50 to be later
described. A flat face 23 extends downward from ledge 22. Face 23
has threaded holes 24, 25, 26, 27, 28, 29, 30 and 31 which extend
into plate 20 a predetermined distance. Near the bottom edge of
plate 20 there is a semi-circular groove 32 which extends into and
across plate 20. Immediately adjacent the bottom of plate 20 and
extending upwardly to the bottom edge of groove 32 is a small flat
face area 33. The back of plate 20 is precision formed flat which
provides a precision flat back clamping surface for clamping the
blade holder of the invention in the jaws 14, 15 of the
conventional knife clamp 13.
Opening and closing of the blade holder, i.e., pivoting of plate
65, is controlled by a rotatable cam shaft member 60 whose ends
terminate in a pair of stops 61, 62 formed integral therewith and
which act to prevent axial movement of shaft 60 in groove 32 of
backing plate 20. When the blade holder of the invention is
assembled, stops 61, 62 reside on the ends of back plate 20 as best
shown in FIGS. 3 and 4. Shaft 60 has an integral extension which
extends outward and downward from stop 61 and provides a finger
grip or manual control member 63 for the operator to use in
rotating cam shaft 60. Shaft 60 also has a flat side 64 cut therein
which provides a flat side whose function will be described
later.
A pair of identical clamping plates 35, 36 are adapted to be
fixedly mounted on plate 20. Since plates 35 and 36 are identical,
only plate 35 will be described in detail and it will be seen that
plates 20, 35 and 36 form an essentially integral structure.
Clamping plate 35 has a flat inner face 37 which matches flat face
23 of plate 20. Also, a semi-circular groove 38 mates with groove
32 of plate 20 and together form a circular opening 39. Upward a
predetermined distance from groove 38 is an inward angled flat
surface 40. Surface 40 extends upward a predetermined distance so
that uppermost edge 41 is in alignment with edge 20a of backing
plate 20. At this point, edge 40 extends outward forming a flat
ledge 42. Ledge 42 when extends downward at a predetermined angle a
predetermined distance to form a sloped, precision formed, clamping
face 43 which joins a flat front face 44. Face 44 has three
threaded holes therein 45, 46, 47 mating respectively with threaded
holes 24, 25, 26 in plate 20. Holes 45, 46, 47 are recessed so that
the screw heads of screws 48, 49, 54 will remain flush with face
44. Once screws 48, 49, 54 are tightened, clamping plate 35 is held
firmly in place against backing plate 20. As previously stated,
clamping plate 36 is identical to clamping plate 35 and is held
firmly in place by screws 55, 52, 53 mating with holes 29, 30, 31
respectively. Clamping plates 35, 36 thus hold cam shaft 60 in
place but with freedom to rotate. While shown as three separate
parts plates 20, 35 and 36 could of course be made as an integral
unit and cam shaft 60 mounted accordingly and made with one (FIG.
2) or two finger grips (FIG. 2A).
A central pivotal plate 65 fits within the lateral spacing of
clamping plates 35 and 36 and as later explained provides means for
clamping blade 50 and the front surface of plate 65 also serves as
a guide for the cut tissue, whether in individual sections or in
ribbon form. Plate 65 has a convex, precision formed, sloping
surface 66 which mates with concave surface 21 of backing plate 20
and it is between these precision surfaces that blade 50 is bent
and clamped. The base of convex surface 66 joins a flat surface 67
which extends downward from surface 66 and in use mates with the
opposing portion of surface 23 of plate 20. A square shaped slot 68
is cut into surface 67 adjacent the bottom edge. Square slot 68
aligns with semi-circular grooves 32 and 38 to form an opening for
the full length of the holder and in which resides shaft 60. Slot
68, unlike groves 32 and 38 has straight side walls with no
curvature and is designed so that flat side 64 of shaft 60 when the
holder is open as in FIG. 8 aligns with and rests against surface
68' (FIG. 8) of slot 68. A flat surface 69 on plate 65 mates with
flat surface 33 of backing plate 20. A flat exterior surface 70
generally aligns with faces 44 of clamping plates 35, 36. A pair of
unthreaded holes 71, 72 are formed in pivotal plate 65 which is
pivotally secured to backing plate 20 by screws 73, 74 which pass
through holes 71, 72 of somewhat larger diameter, and are screwed
into holes 27, 28. A front tapered angle and precision formed and
polished surface 75 extends from surface 70 to the end of convex
slope 66 and it is this surface which receives and smoothly guides
the cut tissue and enables the formation of "ribbons" of tissue for
mass sectioning as required for film mounted tissue. Blade changes
do not disturb ribbon R.
As previously stated, disposable blades 50 suitable for use with
the method of this invention but without the usual guard member are
manufactured and sold under various trademarks such as Personna and
Weck. The desired character is illustrated by a description of
blade 50. Blade 50 is of a length L-1 preferably greater than the
length L-2 of pivotal plate 65 and is substantially greater in
length than standard single or double edge razor blades so that
cuts can be taken from larger specimen blocks. That is, a specimen
block up to at least L-2 length can be cut. In one embodiment,
blade 50 is a Weck blade 2 1/4 by 1/2 inch approximately, and of
0.010 inch thickness which allows the blade to be slid into the
blade holder from the side and so that it resides between concave
slope 21 and convex slope 66 and rests on ledge 22 of backing plate
20. Blade 50 preferably has a compound angled edge of microtome
knife edge cutting quality but unlike single edge razor blades now
on the market, blade 50 has no guard or bending member on the
non-cutting edge. That is, the conventional "Weck" or "Personna"
single edge surgical blade is modified according to the method of
the invention by having the guard member removed. Removal of the
guard member substantially enhances blade flexibility. Stainless
steel is a preferred material for use in making blade 50.
Chrome-carbon blades are acceptable where shorter storage periods
exist and corrosion is no problem.
Reference will now be directed t the operation of the disposable
blade and blade holder according to the method of this invention.
Once the holder is assembled as described and illustrated in FIG.
2, microtome clamp 13 is adjusted or tilted into an approximate
15.degree. position towards feeding holder 12. The disposable blade
holder of the invention is slid into the clamp 13 endwise so that
clamping plates 35, 36 are in central alignment with jaws 14, 15.
Once in position, jaws 14, 15 are tightened on the precision sloped
surfaces 43 of clamp plates 35, 36 and effectively lock the blade
holder in clamp 13. Finger grip or control member 63 is turned so
that flat side 64 of shaft 60 is in alignment with surface 68' of
slot 68 of pivotal plate 65. With shaft 60 in this "unlocking"
position, blade 50 is slid into the holder from the side through
the slotted end portions so that blade 50 rests on ledge 22 between
concave sloping surface 21 and convex sloping surface 66. Note here
that plates 35, 36 and 20 form fixed blade shaped slots S.sub.1,
S.sub.2 (FIG. 5, 6) through which blade 50 can be slid from the
side in a snug, slidable fit. Two slots S.sub.1, S.sub.2 insure the
ability to push out the old blade with the new blade. With only one
slot S.sub.1 the old blade can be lifted vertically, however the
presence of two slots S.sub.1, S.sub.2 is much preferred. Also it
is desirable that the slot be sufficiently narrow so as to prevent
an incoming blade sliding past a worn blade that is intended to be
removed. Once the blade 50 is in position, shaft 60 is rotated by
turning finger grip 63 towards the operator. As shaft 60 is
rotated, flat side 64 is rotated away from slot 68 and the circular
portion of shaft 60 is brought into contact with surface 68' of
slot 68 which causes central pivotal plate 65 to be pivoted
slightly. FIGS. 13 and 14 more clearly illustrate what takes place.
FIG. 13 illustrates the open position or position in which shaft 60
has not yet been rotated but blade 50 has been placed in the holder
in a snug fit. FIG. 14 shows plate 65 pivoted forward slightly
about the edge of ledge 22 by the camming effect of shaft 60 with
slot 68. Convex surface 66 is moved forward against substantially
the whole plane of blade 50 so that blade 50 is bent uniformly
around a longitudinal axis until it is against concave surface 21.
At this point, shaft 60 assumes a "locked" position holding blade
50 curved and with the edge of blade 50 stiffened and angled for
proper cutting. This curving of blade 50 along with the tilting of
clamp 13 provides a preferred total clearance angle of
approximately 30.degree. for plate 50's leading edge surface. Solid
blade support is provided by ledge 22.
Blade 50 once dulled can be replaced by reversing finger grip 63 so
as to turn cam member 60 back to the position of FIG. 8 which
releases the blade. Blade 50 is then pushed endwise out of the
holder as a new blade is being pushed in. Of significant importance
is the fact that blades can be changed without removing the holder
from clamp 13 or adjusting the blade holder position, which in turn
eliminates loss of valuable sections due to retrimming of the
section block as is necessary in disposable blade holders now in
use. Furthermore, the critical ribbon guide surface 75 on plate 65
is not disturbed. Replacement blades are easily installed by simply
turning cam shaft 60 into an "unlocking" position and inserting a
new blade from either side usually determined by the operator being
left or right handed. At not time is the operator exposed to sharp
edges, which could nick or cut, while inserting a new blade. Blade
thickness and curvature insure "locking" of shaft 60. That is, the
thickness, curvature and position of the blade are selected to
provide resilient forces which releasably lock member 60 in
position.
The blades may, if desired, be stored in a cartridge of the ejector
type. As generally shown in FIG. 15, the finger pusher 80 moves
ejector bar 81 from the retracted dashed line position to the
ejecting position shown in solid lines and pushes out a new blade
50. Such a cartridge holding 25 blades has been built of clear
"Lucite" plastic and used by pushing out the old blade with a new
blade being ejected from the cartridge and allowing bar 81 to enter
the holder slot. The length of bar 81 and travel of pusher 80 are
designed so that bar 81 may enter the holder slot and exactly
position blade 50. Springs 82 gradually move the blades up one by
one.
The method of the invention thus eliminates conventional knives
which are expensive in initial cost and require expensive and time
consuming resharpening operations and equipment as well as extra
technician time for resharpening. Also, with conventional methods
of using microtome knives repositioning of the knife clamp upon
changing knives is necessary since each knife has a different
dimension due to the wearing away of the material during
sharpening. This has been eliminated. The method of the invention
has furthermore overcome the problem of "chattering" or edge
vibration experienced in prior art methods based on cutting with
wafer type disposable blades. Of particular significance is that by
modifying the "Weck" or "Personna" type surgical blade by removing
the guard member a disposable blade is obtained which when clamped
and used according to the method of the invention provides cutting
at least equal to and in many applications superior to methods
based on microtome knife edge cutting quality. Removal of the guard
member allows the blade to be flexed, i.e., curved around a
longitudinal axis. Thus, even though the blade of the invention is
normally difficult to flex, e.g., simply by holding and pressing
between the fingers it is made to flex sufficiently for the method
of the invention by applying the force of the concave surface 66
over substantially the whole blade surface and using precision
pressing and backing surfaces (66, 21). The amount of curvature
imposed on blade 50, preferably on about 1 1/4 inch radius, is
variable by adjusting screws 73, 74. Unlike prior art disposable
blades and holders, e.g., U.S. Pat. No. 1,865,539, blade 50 is not
required to be tensioned longitudinally. Since the holder and blade
used in the method of the invention can be and necessarily are
precision made each new blade acts precisely as the blade before
and irrespective of the nature of the specimen. Once blade clamp 13
has its lateral, tilt, vertical and forward positions adjusted, the
adjustments may be locked and never again disturbed. All that is
required to get a fresh cutting edge and renew the cutting
operation is to simply replace blade 50 by unlocking plate 65,
installing new blade 50 and then locking plate 65. Such precision
cutting therefore conforms to the precision of the microtome itself
an accomplishment not heretofore achieved. Blade thickness,
curvature and positioning always insure obtaining the same precise
"locked" position of the parts.
To better visualize the implications of the method of the present
invention the following steps are generally involved when using the
conventional microtome knife method of cutting:
1. Clamp blade at both ends in holder
2. Adjust blade position roughly
a. Laterally
b. Forwardly
c. In tilt
d. Vertically
3. Take trial cuts to trim block and align face
4. Take trial sections
5. Readjust blade position finely as required
a. Laterally
b. Forwardly
c. In tilt
d. Vertically
6. Trim sections until blade edge is dulled
7. Either: Replace blade or shift blade laterally to get sharp
edge
8. Cut trial sections to test new edge
9. Readjust blade position finely as required:
a. Laterally
b. Forwardly
c. In tilt
d. Vertically
10. Trim sections until edge is dulled
11. Repeat all of above steps for each new blade or new blade
edge
Since the conventional blade is non-disposable the following steps
are also required each time the blade is resharpened:
12. Install blade in honing machine
13. Install glass honing plates
14. Rough hone blades against glass plates
15. Strop or fine hone blades
16. Remove resharpened blades and store
Furthermore, since blade resharpening requires that honing plates
be periodically resurfaced, these rehoning steps are involved:
17. Install in hone plate resurfacing machine
18. Roughly hone plates on one side
19. Finely hone plates on same side
20. Invert plates and repeat rough and fine honing on opposite
side
21. Remove and store plates
Without reciting the precise blade positioning and bending steps
covered in the preceding description and in the language of the
claims, it can generally be observed that the method of the
invention involves only the following steps:
1. Clamp blade holder at both ends in knife holder
2. Install disposable blade in blade holder
3. Adjust blade holder position roughly
a. Laterally
b. Forwardly
c. In tilt
d. Vertically
4. Take trial cuts to trim block and align face
5. Take trial sections
6. Readjust blade position finely as required
a. Laterally
b. Forwardly
c. In tilt
d. Vertically
7. Trim sections until edge is dulled
8. Replace blade only but do not repeat any of above steps since
blade position is automatically restored
From the above, the sharp contrast between the usual prior art
method and the method of the invention is more precisely seen. It
should of course be understood that the above is a very generalized
comparison and assumes that in both cases the technician is
concerned with serial sectioning of the same type block. Whenever
the type block is changed both prior art and the present method of
course require certain trial and error cuts to initiate proper
sectioning. In any case, however, the present method very
dramatically and substantially reduces the number of steps involved
in cutting blade replacement and blade positioning and eliminates
all of the steps involved in blade repositioning for each new
blade, resharpening and plate honing.
It should also be recognized that while the conventional knife
clamp has been used for illustration, the method can be practiced
with any type of support that places the backing surface 21, the
bending surface 66 and the front guide surface 75 at the optimum
angles. Thus, a knife clamp whose tilt, lateral and vertical
adjustments are fixed at optimum positions could be employed. Here
only forward and backward adjustment of the clamp would be
required. The method of the invention thus adapts to many and
various kinds of holders, clamps and the like.
* * * * *