Note: Descriptions are shown in the official language in which they were submitted.
MICROTOME HAVING A FORWARD-FEED CONTROL SYSTEM FOR THE
SPEC IMEN ARM AND/OR THE KN IFE
.,
B K~;ROUND OF THE INVENTION
The invention relates to a microtome having a
Eorward-feed control system for the specimen arm and/or
the knife, and .i5 especially applicable to an
ultramicrotome.
In order to set the section thickness of the thin
sections which are produced by means of a microtome, the
specimen arm, carrying the preparation or specimen, is
shifted towards the knife, before each cutting stroke, by
an amount corresponding to the section thickness. In a
known ultramicrotome, this is effected by means of a
forward-feed mechanism. It is desirable to be able to
set an ultramicrotome to produce section thicknesses
which differ by several orders of magnitude so that, for
example, when starting to cut up a preparation block,
considerably thicker section~ can initially be removed
until a sectioning area, which can be used for a thin
section proper, has itself been obtained on the
preparation. In a known ultramicrotome, two preselector
switches are provided for this purpose, the switches
permitting substantially different section thicknesses to
be set by the setting of forward-feed values~ In an
arrangement of this type, the forward feed value desired
for ultra-thin sectioning is set at one of the
preselector switches, while the forward-feed value
desired during the initial cutting process is set at the
other preselector switch. When the sectioning surface
which produces the first usable thin section is reached
on the preparation, the preselect3r switch, which defines
the forward feed amplitude during the initial cuttiny
process, is turned to the stop position so that the
s
ultramicrotome now operait:es with the forward feed which
corresponds to the desired ultra-thin section thickness.
During the production of ultra thin sections, it is
frequently desired to produce a number of semi thin
sections, or it is necessary to "leap-frog" unusable
parts of the preparation, for which purpose the forward
feed is increased. In the case of the known
ultramicrotome, this requires that the first preselector
switch be reset. This proves to be troublesome,
particularly during the deliberate inclusion of a f~w
semi-thin sections, not only because resetting involves a
delay, but also because the operator is distracted from
the operations taking place on the preparation so that it
is difficult to exclude the possibility of mistakes.
OBJECT OF THE IlNVENTION
. _ _
The object of the invention is accordingly to
provide a forward-feed control system, of the type
initially mentionedt which permits difEerent forward-feed
amplitudes to be selected quickly, without hindering the
ongoing work, and without involving any substantial
disturbance in the ease with which the cutking process
can be observed.
BRIEF DESCRIPTION OF THE INVENTION
According to one aspect of the invention, there is
provided a microtome comprising a specimen arm for
holding a specimen to be sectioned, a knife for cutting
sections from said specimeh, a drive means for
reciprocating the specimen arm so that said arm moves in
a cut-ting stroke past the knife and in a return stroke
and forward-feed means for incrementally advancing the
specimen arm towards the knife beEore each cutting
stroke, the forward-feed means comprising a stepping
-3
motor, drive-translation means for translating the motion
produced by the stepping motor into linear motion of the
specimen arm, a pulse generator connected to the s-tepping
motor to supply voltage pulses to operate said motor,
electrical-circuit means adapted to provide two or more
alternate outputs, and selector means connected between
the electrical-circuit means and the pulse generator for
connecting a selected one of the outputs to the pulse
generator whereby the specimen arm may be advanced by a
selected one of two or more different increments before
each cutting stroke.
In another aspect of the invention, the forward-feed
means advances the knife instead of, or additionally to,
the specimen arm.
The desired different forward feed values can be
set, and remain set, at the various preselector switches,
these values normally differing by orders of magnitude.
If, for example, it is intended to "fit in" a number of
semi-thin sections during the production of ultra-thin
sections, the operator needs only to have set the desired
forward-feed amplitude at the appropriate preselector
switch, after which he can change overl from the ultra-
thin section thickness to the semi-thin section
thickness, by means of a single manual action at the
changeover switch. There is no need to search again for
the desired section thickness, nor to set it at the
preselector switch.
Digital-type presetting switches are expediently
provided as the preselector switches. In one embodiment
of the inven-tion, there are provided two stepping motors~
of which one is`connected to the specimen arm and the
other is connected to the knie holder, a preselector
~witch being assigned to each stepping motor.
3~
BRIEF DESCRIPTION OF THE DRAWINGS
_
Further advantages and features of the invention are
evident from the followillg description of an illustrati;e
embodiment, with reference to the drawings, in which:
Figure 1 shows a purely diagrammatic side view oE an
ultramicrotome, partially sectioned; and
Figure 2 shows a forward-feed control system,
employed in the ultramicrotome shown in Figure 1.
DETAILED D:ESCRIPTION OF THE INVENTION
The ultramicrotome represented in Figure 1 includes
a specimen carrier 1, which is fastened to a specimen
arm 2 and which holds at its front end a specimen or
preparation 3. A ~rive device, which is not shown in
more detail, guides the specimen arm 2, and hence the
specimen carrier 1 with the preparation, past a kni~e 4.
In addition, a forward-feed device, which is also not
shown in detail, shifts the specimen arm 2 ~owards the
knife 4 by a preselectable forward-feed amplitude so that
thin sections of a predeterminable thickness can be
produced at each cutting stroke. In the design of the
devices for driving the specimen arm, and its mode of
operation, the ul~ramicrotome does not differ from known
ultramicrotomes, and will, therefore, not be described in
more detail.
The control system or the forward-feed device,
represented schematically in Figure 2, makes it possible
to control the amplitude of the forward-feed travel
executed by the specimen arm 2. For this purpose, the
specimen arm 2 is coupled to a stepping motor 5, through
a drive translation arrangement which is not shown in
detail. The stepping motor 5 receives a pulsed voltage 7
which is supplied via a power-output state 6
incorporating a pulse generator. The specimen arm 2 is
moved onwards by a defined number oE steps correspondinc,
to the number of pulses. The total number of steps
corresponds, in each case, to the forward-feed amplitude
at the specimen arm 2.
Digital~type presetting switches 8; 9 are provided
for the purpose of presetting forward-feed values of
different amplitudes, these presetting switches being
capable of being connected, in alternation, to the power-
output stage 6. Connection is effected via a changeover
switch 10. The desired ultra-thin section thickness is,
for example, set at a preselector switch 8, and a semi-
thin section thickness is set at the preselector
switch 9, the latter being intended to be brought into
action during the operation. Ry simply resetting the
changeover switch 10, the operator of the ultramicrotome
can consequently set a forward-feed amplitude, at the
stepping motor 5, which differs by an order of magnitude,
for example, by a power of 10.
One embodiment of the invention provides a plurality
of preselector switches, of the above-mentioned type, for
a plurality of forward-feed amplitude ranges, in place of
the two diyital-type preselector switches 8, 9 which are
shown in the illustrative embodiment, thus enabling, for
example, an even larger section thickness to be selected
for the initial cutting operation.
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