Improved Fine Adjustment for Microscopes and other Optical Instruments.
Year: 1894

page_text: Date of Application, 30th Oct., 1894-Accepte1, 16th Feb., 1895
COMPLETE SPECIFICATION.
Improved Fine Adjustment for Microscopes and other Optical
Instruments.
1, HIRAM G. SEDGWICK, of corner 15th and Leclaire Street, Davenport,
Scott County, State of Iowa, one of the United States of America, Professor of
Mechanical Engineering, do hereby declare the nature of this invention and
in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
This invention relates to a slow-motion attachment for use on microscopes and
other instruments using or requiring rack-and-pinion adjusting devices, the essential
object of the invention being to provide a simple and inexpensive attachment that
may be readily attached to and detached from the pinion-shaft without in the least
mutilating any of the parts or changing their construction. The device is adapted
for attachment to the pinion-shaft that is used for effecting the coarse motion; it is
attached on one of the projecting ends of the shaft, out-side of the instrument,
whereby it may be readily attached to all the compound microscopes now in use
without mutilating them or changing their construction or taking them apart, and
this whether they be provided with other fine-adjustments or not.
The attachment will be best understood by describing the preferred construction :
but I wish it distinctly understood that I do not confine myself to the construction
and arrangement herein shown and described as the same may be varied greatly
without departing from the scope of the invention in the least.
In the drawing, Fig. 1 is a transverse sectional view showing my attachment
applied to a microscope; Fig. 2 a transverse section on line 2-2 of Fig. 1, this
view being slightly enlarged, Figs. 3 and 4 detail views; and Figs. 5, 6 and 7
detail sections showing a slightly modified form of spiral pinion.
Referring to the drawing by numerals, 1 is the microscope tube, 2 the usual rack
carried thereby, 3 the usual pinion carried by the shaft 4 apd meshing in said rack,
said shaft being journaled in the arm 5 of the usual frame and carrying at its ends
the usual milled operating heads 6. On the shaft 4, between one of the milled-heads
and the adjacent face of arm 5, is mounted the attachment, which consists essentially
of a pinion 7 provided with external spiral ribs or threads and mounted on the
shaft in such a manner as to have only a frictional engagement therewith, whereby
the shaft and pinion may revolve independently or in unison. To obtain this
frictional engagement in the simplest manner the pinion is split lengthwise on one
side to allow it to be expanded slightly and slipped over the end of the shaft, the
width of the slit being just sufficient to cause it to hug the shaft with the desired
friction and at the same time without materially mutilating the spiral ribs.
Working on this spiral-pinion is an end wise-movable sleeve or tube 8, which is
internally ribbed to correspond to the spiral ribs on the pinion and is externally
screw-threaded at a suitable pitch. To prevent this tube 8 from rotating and at
the same time permit it to freely slide endwise, it has one or more longitudinal
grooves or ways cut in its exterior in which work stationary keys 9, which project
out horizontally from a plate 10 secured by screws, rigidly but removably, to the
side of the microscope or other instrument, the ends of said keys being
preferably connected by a ring 11. To slide the tube 8 back and forth on the keys,
a tube 12 is fitted over it, this tube being internally threaded to correspond with
the threads on said tube 8 and being also provided with a milled operating-
head 13, which latter is preferably a trifle larger than the adjacent operating-head
on the inain-shaft. The inner end of the tube 12 fits over an annular flange 14 on

page_text: plate 10 and its outer end fits snugly within a stationary cap 15, whereby the tube
is not only kept true but is also prevented from being thrown by the screw against
the adjacent milled head 6. The cap-15 is slipped over the shaft and is secured
rigidly to the ends of the keys or ring, as shown.
To rapidly and coarsely adjust the tube of the microscope or other instrument,
the heads 6 are revolved in the usual manner. During the operation of coarsely
adjusting the tube by said heads the fine-adjustment parts all remain inert,, the
pinion-shaft being permitted to rotate independently of the spiral-pinion by reason.
of the frictional engagement therewith and the spiral-pinion itself being prevented
from rotating by being interlocked with the non-rotatable sleeve. But when the
head 13 is rotated to effect the fine adjustment of the microscope tube, the threads
on the interior of the outer tube 12, engaging with the threads on tube 8, cause
the same to move endwise on the keys, and this endwise movement of the
non-rotatable part 8 imparts a slight rotative movement to the pinion shaft through
the medium of the spiral-pinion, this pinion gripping the shaft with sufficient
tightness to positively rotate it. Thus it will be seen that the slow-motion parts
are only operated when the power is applied to the head 13, the fast-motion parts
operating precisely in the same way as usual and wholly independently.
The spiral-pinion or "twisted-gear" 7 may contain any number of teeth from
one upward, according to the degree of accuracy desired. As shown in Fig. 5 two
teeth or ribs only are employed, two spirally curved grooves being formed in the
interior of the endwise movable part to engage said ribs. But where great accuracy
is required, the ribs will be disposed entirely around the pinion as in Fig. 2, as in
that case the ribs on one side counteract or take up the loose motion on the
opposite side, as is apparent.
The advantages of this invention over prior devices of its kind are obvious to
any one skilled in the art. Heretofore, slow-motions have not been made in the
form of an " attachment," attachable and detachable at will, but have always been
made permanent parts of the microscope or other instruments, having been made
at the time the instruments were made, and instruments not provided with the
slow-motions had to be sent to the shop and dismantled to have them put on; then
again the slow-motions heretofore used have been too expensive to be put on any
but the finer machines. These serious draw-backs have been long recognized by
instrument makers and many attempts have been made to obviate them without
material success; but it is believed the present invention overcomes said objections,
since it may be readily attached to any instrument using a rack-bar and pinion
without mutilating or dismantling the instrument and by any person of ordinary
intelligence. It will be seen that the device is adapted for attachment directly to
the coarse-motion shaft in the space that usually exists on all instruments between
the side of the instrument and the usual milled-head. To attach the device it is
simply necessary to remove one of the milled-heads and slip the parts of the device
on the shaft and then replace the milled-head; of course, a couple of small
screw-holes must be made in the instrument for the reception of the securing-screws.
Thus it will be seen that the application of this device to any of the instruments
now in use--whether they be provided, with other more complicated slow-motions
or not involves but a small expense and but little trouble.
Besides the advantages of simplicity and general applicability, thus obtaining
the slow-motion through the medium of the same shaft and pinion that effects the
fast motion has other advantages perhaps more important. In the most practical
devices heretofore in use, the slow-motion has generally been obtained by means of
a double-slide arrangement and micrometer screws, as is well known, but this
arrangement of two slides is defective for use with high-power objectives for the
simple reason that it is a practical impossibility to obtain perfect parallelism of the
working-faces of the slides, in consequence of which the object is frequently thrown
or shifted about the field when the slow-motion is resorted to. This "side or
upward-thrust," as it is called, is more nearly obviated by using but one sliding
surface and effecting both the coarse and fine adjustment of the tube through the
66
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page_text: single pinion, as is evident. I have found in practice that a digner degree of
accuracy can be obtained with my simple device than can be obtained with the
expensive compound-slide devices heretofore used. It will be seen that simply by
increasing or diminishing the pitch of the threads on the sleeves and the spiral-ribs
on the pinion, almost any degree of fineness and precision in slow-motion may be
obtained, according to the character of the instrument.
It will be understood that this attachment is applicable to instruments other
than microscopes; for instance, it may be used on telescopes, photographic cameras,
streopticons, and other instruments where rack-and-pinion movements are used and
a slow-motion is desired; it will therefore be understood that wherever I use the
term "instrument" in the claim and in the Specification I mean any instrument to
which the device is applicable.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what I
claim is:
1. In a slow-motion attachinent for microscopes and other instruments, the
combination of the rack-bar and pinion and the shaft carrying the pinion, another
inion mounted on the shaft, a non-rotatable part engaging the latter pinion and
lapted to rotate it, and means for imparting an endwise movement to said non-
rotatable part, substantially as described.
2. In a slow-motion attachment for instruments, the combination of the rack-bar
and pinion and shaft, a spirally ribbed pinion on said shaft, a part embracing the
said pinion and provided with internal teeth engaging said spiral ribs, and means
for moving said part, substantially as described.
3. In a slow-motion for instruments, the combination of a rack-bar and pinion, a
shaft carrying said pinion and provided with means for imparting the coarse-notion,
another pinion mounted on said shaft and adapted to rotate with or independently
of it, and means for rotating said pinion, whereby both the coarse and fine
adjustments are effected through the same shaft and pinion, substantially as
described.
4. The combination of a rack-bar, a pinion engaging the same, a shaft carrying
said pinion, means on the shaft for imparting the coarse motion, and slow-motion
devices attached directly to said shaft, said devices consisting essentially of a pinion
mounted directly on the shaft, and means for rotating said pinion, whereby the
coarse motion and the slow motion may be imparted to the rack bar through the
same rack and pinion and shaft, substantially as described.
5. The combination of a rack-bar and pinion, a shaft carrying said pinion and
also means for imparting the coarse-motion, and a slow-motion attachment applied
directly on said shaft and adapted to rotate it, sail attachment consisting essentially
of a pinion having a frictional engagement with the shaft for the purpose described
and means for rotating said pinion and locking it against rotation when the course
motion is used, substantially as described.
6. The combination of a rack-bar and pinion and shaft and a slow-motion
attachment consisting essentially of a slitted pinion having a frictional engagement
with the shaft, and means for rotating the pinion to obtain a fine adjustment,
substantially as described.
7. The combination with a rack-bar and pinion, a shaft carrying the pinion and
also means for imparting the coarse motion, and a slow-motion attachment consisting
essentially of a spirally ribbed pinion mounted on the shaft, an end wise movable
part engaging the pinion and adapted to rotate it, and meaus for moving said
endwise movable part, substantially as described.
8. The combination of a coarse-motion shaft and a slow-motion attachment
therefor, consisting essentially of a spirally ribbed pinion mounted on the shaft and
adapted to rotate with or independently of it, a non-rotatable part provided with
corresponding internal ribs or grooves, and means for moving the latter part,
substantially as described.
'

page_text: 9. The combination of a coarse-motion shaft, a slow-motion attachment consisting
essentially of a pinion mounted directly on the shaft and adapted to rotate with or
independently of it, an endwise movable part engaging said pinion and adapted to
rotate it, said part being screw-threaded externally, and an external sleeve
internally threaded to engage said endwise movable part, substantially as
described.
10. The combination of the coarse-motion shaft and means for rotating it, a slow-
motion attachment consisting of a pinion or sleeve mounted directly on said shaft,
an end wise movable part engaging said pinion and threaded externally, key-ways
engaging said non-rotatable part, a sleeve embracing said non-rotatable part and
carrying an operating head, substantially as described.
11. The combination with the coarse-motion shaft and means for rotating it, a
slow-motion attachment consisting of a pinion applied directly to the shaft and
provided with one or more spiral grooves, a tube or sleeve embracing said pinion
and engaging its spiral ribs and being externally threaded, key-ways engaging said
tube and preventing it rotating, an external sleeve threaded internally and
engaging said tube, and a stop cap supported by said key-ways, substantially as
described.
12. The combination with a microscope or other instrument carrying a slidable
bar, a shaft journaled in the instrument and carrying a pinion engaging said bar, and
means carried by the shaft for imparting coarse motion thereto, of a slow-motion
attachment mounted directly on said shaft whereby the coarse motion and the slow-
motion may be imparted to the slide through the same rack. and pinion and shaft,
substantially as described.
13. The combination of an instrument, a rack-bar, a pinion engaging said rack-
bar, a shaft carrying said pinion and provided with coarse motion operating devices,
of a slow-motion device consisting essentially of a rotatable part carried by said
shaft and adapted to rotate with it, said part being provided with one or more
spiral ribs or grooves, and an end wise movable part engaging said spiral ribs or
grooves and adapted to rotate said rotatable part and its shaft, substantially as
described.
Dated this 30th day of October 1894.
.F. WISE HOWORTH,
Agent for the Applicant.