Improvements in Microtomes.
Year: 1898

page_text: Date of Application, 19th Apr., 1899
Complete Specification Left, 28th Sept., 1899-Accepted, 28th Oct.,
1899
Improvements in Microtomes.
We, HORACE DARWIN, Scientific Instrument Maker, and MOSES JOHN WAYNE,
Engineer, both of Carlyle Road, Cambridge, do hereby declare the nature of
this invention to be as follows:-
:-
As has before been proposed the instrument consists of a lower arm working
on stationary bearings and a rocking arm working on bearings carried by the
lower arm.
The specimen from which sections are to be cut embedded in paraffin
is carried in a holder at one end of the rocking arm whose other end is moved up
and down by the operator so carrying the specimen to and fro across a cutting
edge or razor, each stroke also giving a partial turn to a screw by which the
end of the lower arm is raised thus altering the position of the bearings of the
rocking arm and so feeding forward the specimen towards the razor.
According to this invention both the rocking and the lower arms work on
knife edges, each pivot consisting of two knife edges in a line with each other
working on planes inclined to each other preferably at a right angle.
In former instruments of this sort the screw for elevating the lower arm was
moved forward by means of a pawl and ratchet wheel. This however only moved
the screw in one direction, and thus when cutting very fine sections, the razor,
which is apt to spring, caught on the section when the rocking arm was returning
into its normal position previous to cutting the succeeding section.
According to this invention the specimen is fed backwards after the cut and
before the back stroke so ensuring its clearing the razor, the forward feed which
is greater than the back feed taking place towards the end of the return stroke.
This is done by providing a second pawl which comes into gear toward the
end of the cutting stroke.
The rocking arm is worked as is usual by a cord from a rotating handle, and
in order to conveniently adjust the length of the cord its end is fastened to a
split ring on the end of the arm, the cord being readily tightened or loosened
as desired by turning the ring on the arm.
The paraffin containing the specimen is carried by a plate mounted on a
hollow hemisphere in the bottom of which a hole is made and through which a
T piece or clanıp is threaded.
The clamp holds the hemisphere on one end of a tube, the other end of which
is attached by the ordinary clamp to the rocking arm. The stem of the T piece
is held by a screw collar on the tube. When the collar is unclamped the hemi-
sphere is free to move in any lateral direction, and can be clamped in any
position.
In place of providing the above described adjustment for orientating the
specimen the standard carrying the razor may be pivotted.
Dated thi
10+h
J
A
1000
HORACE DARWIN,
MOSES JOHN WAYNE.

page_text: We, HORACE DARWIN, Scientific Instrument Maker, and MOSES JOHN WAYNE,
Engineer, both of Carlyle Road, Cambridge, do hereby declare the nature of
this invention and in what manner the same is to be performed to be particu-
larly described and ascertained in and by the following statement: --
As has before been proposed the instrument consists of a lower arm working
on stationary bearings and a rocking arm working on bearings carried by the
lower arm.
The specimen from which sections are to be cut is carried
in a holder at one end of the rocking arm whose other end is moved up
and down by the operator so carrying the specimen, to and fro across a cutting
edge or razor, each stroke also giving a partial turn to a screw by which the
end of the lower arm is raised thus altering the position of the bearings of the
rocking arm and so feeding forward the specimen towards the razor.
According to this invention both the rocking and the lower arms work on
knife edges, each pivot consisting of two knife edges in a line with each other
working on planes inclined to each other preferably at a right angle.
In former instruments of this sort the screw for elevating the lower arm was
moved forward by means of a pawl and ratchet wheel. This however only moved
the screw in one direction, and thus when cutting very fine sections the razor,
which is apt to spring, caught on the section when the rocking arm was returning
into its normal position previous to cutting the succeeding section.
According to this invention the specimen is fed backwards after the cut and
before the back stroke so ensuring its clearing the razor, the forward feed which
is greater than the back feed taking place towards the end of the return stroke.
This is done by providing a second pawl which comes into gear toward the
end of the cutting stroke.
The rocking arm is worked as is usual by a cord from a rotating handle, and
in order to conveniently adjust the length of the cord its end is fastened to a
split ring on the end of the arm, the cord being readily tightened or loosened
as desired by turning the ring on the arm.
The paraffin containing the specimen is carried by a plate mounted on a
hollow hemisphere in the bottom of which a hole is made and through which a
Tpiece or clamp is threaded.
The clamp holds the hemisphere on one end of a tube, the other end of which
is attached by the ordinary clamp to the rocking arm. The stem of the T piece
is held by a screw collar on the tube. When the collar is unclamped the hemi-
sphere is free to rotate about its centre, and can he clamped in any position.
In place of providing the above described adjustment for orientating the
specimen the standard carrying the razor may be pivotted.
Figures 1 and 2 are a half-size side elevation and plan of a microtome con-
structed according to this invention.
a is a base plate having fixed to it two standards b. The upper end of each of
these standards (one of which is shown in full-size plan at Figure 3) has on it
a pair of plane surfaces 61 62 at right angles to each other. c is the lower arm
which is shaped and each end of the top of the T (one of which is shown in
full-size plan at Figure 4) carries two semi-circular plates c¹ c².
The upper
edges of these plates form a pair of knife edges in a line with each
other. The lower edges of the plates form a similar pair of knife edges in
a line with each other and these rest on the plane surfaces 61 62. d is the rocking
arm also T shaped and each end of the T (a full-size underside view of one of

page_text: which is shown at Figure 5) has on it a pair of plane surfaces at right angles
to each other which work on the knife edges 3 respectively. Figure 6 is a
full-size elevation showing these parts in position, and Figure 6 is a perspective
view of the same.
The rear end of the arm c is in the form of a ring having on its underside
notches resting on trunnions e¹ on a nute working on the screw f fixed to the
horizontal ratchet wheel g. h is a spring holding the arm c down onto the
trunnions. is a spring pulling down the front end of the arm and is a
cord fixed to a split ring which is free to turn stiffly on the rear end of the
arm d. This cord passes round the pulley 2 and is fixed to the handle which
is free to turn about the axial line of the screw f. m is a pawl pivotted at m¹
to the handle and m² is a spring tending to keep it in gear with the ratchet
wheel g. m³ is a pin projecting from the underside of the pawl m and working
against the cam surface n. This cam is shown full-size in the plan Figure 7 and
can turn stiffly about the axial line of the screw f. When the pin m³ is in contact
with the camn the pawl m is held out of gear with the ratchet wheel g so that
by turning the cam n about its centre the number of teeth through which the
ratchet wheel g is turned at each stroke of the handle can be regulated. is
an arm fixed to the handle and having a pawl o pivotted to it at o¹. This pawl
is provided with a spring o² and pin o³ working against the fixed cam p; it
is in all respects similar to the pawl m but turns the wheel g in the opposite
direction. The stroke of the handle is limited in one direction by the pawl m
coming against the stop 9 and in the other by the pawl o coming against it.
r is the tube of the specimen holder which is clamped to the rocking arm d
in the ordinary manner.
The paraffins containing the specimen (see the full-size Figures 8 to 11) is
fixed on the plate t mounted on the hollow hemisphere u in the bottom of which
is a hole through which the stem of the T piece or clamp is passed. w is a
nut on the stem.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is:-
:-
1. A pivot for a microtome consisting of a pair of edges in a line with each other
working on surfaces at an angle to each other.
2. The method of pivotting the rocking and lower arms of a microtome sub-
stantially as described and illustrated in the drawings.
3. The combination with a microtome of mechanism for feeding the specimen
backwards after the cut and before the return stroke.
4. The combination with the ordinary feed pawl of a second pawl turning
the ratchet wheel in the opposite direction.
5. Feed mechanism for microtomes substantially as described and illustrated
in the drawings.
6. Specimen holders for microtomes substantially as described and illustrated
in the drawings.
Dated this 25th day of September 1899.
HORACE DARWIN,
MOSES JOHN WAYNE.