Improvements in Transit Instruments.
Year: 1891

page_text: Date of Application, 13th Jan., 1891
Complete Specification Left, 12th Nov., 1891-Accepted, 24th Dec., 1801
PROVISIONAL SPECIFICATION.
[Communicated from abroad by CLINTON SUTPHEN, of the City and State of
New York, United States of America.]
Improvements in Transit Instruments.
I, HENRY HARRIS LAKE, of the firm of Haseltine Lake & Co., Patent Agents
45 Southampton Buildings, in the County of Middlesex, do hereby declare the
nature of this invention to be as follows:-
In transit instruments heretofore constructed for surveyors it has been found
impossible to determine very closely the value of the angles. With a Vernier plate
the parts of a degree may be approximately determined. By reason of my
improvements the precise value of the angle can be read in minutes and seconds,
or even fractional parts of seconds. This measurement of the angle is obtained by
reading it on a dial plate, by reason of which not only the actual value is determined
but there is no liability of mistaking the reading of the angle, as is sometimes the
case with the use of a Vernier plate.
My invention consists:
In the combination with the compass circular plate of the transit instrument,
containing a dial plate having minute subdivisions of a degree arranged within
the said compass circular plate of a telescope plate the two plates being
connected together by gearing so as to be operated in conjunction with each
other.
It further consists in certain specific combinations and arrangements of the
mechanical parts hereinafter described.
According to my invention the lower plate is arranged for carrying the compass
circle and the upper plate has attached thereto the telescope. The details of con-
struction of the transit instrument in other respects are as four in many instruments
in use by surveyors, with the exception of some modifications of its parts necessary
to he made in order to apply my improvements to it. These differences in con-
struction it will therefore only be necessary to describe in order to enable those
skilled in the art to apply my improvements.
A glass is arranged to cover the compass and its edge is let into the transit
instrument at the inner edge of the upper circle or plate. Within the compass
box is a dial plate for registering the minutes, seconds and parts of seconds, and a
spindle extends down through the centre of this dial plate, to the upper end of
which spindle is attached an index hand. Upon the outer periphery of the upper
circular plate is placed a continuous circular rack. Intermediate between the
outer portion of this cog rack and the spindle of the dial plate is placed a
system of gearing, so that by turning a thumb screw at the lower end of the
spindle the small index hand or pointer is thereby moved in order to show the value
of a portion of a degree. At the same time the upper circular plate will be rotated
until the line of vision through the telescope is brought into coincidence with such
marking or value shown on the dial plate. The intermediate gearing may be
constructed in any known way; for example as follows:
Two bevelled cog wheels are placed one upon the vertical spindle and one upon
the horizontal shaft. At the other end of this shaft is a worm which gears with
the cogs of a wheel placed in a vertical position immediately above the said worn.
This transfers motion to the tangent shaft to the opposite end of which is affixed
a worm which gears with the circular rack. The said rack is protected by a rim
which is attached to the lower plate by screws. The upper portion of this rim is
flush with the top surface of the upper plate. A portion of this rim is cut away
at the place where the worm meshes with the said rack. This permits of

page_text: the contact of the worm with the rack while at all other points the cog rack 18
concealed.
This system of gearing is supported by the bearings and can be thrown out
of contact with the transit instrument in case it is so desired. Guides are
attached to the lower or compass plate, so that a sliding plate to which the said
bearings are attached can be pulled out thereby disconnecting the worm from
the rack and the bevelled wheels from one another. A set screw is arranged
in the sliding plate by means of which the said plate and its attached gearing
can be firmly secured in place when the worm is thrown into contact with
the rack.
One revolution of the tangent shaft will cause the toothed wheel to turn one
degree as indicated on the compass circle. In this arrangement of gearing the
bevel gear wheels will make sixty revolutions to one of the toothed wheel hence
one revolution of the wheel will cause the spindle and the small index hand to
turn sixty times; and the reading of the degree will be at each revolution of the
said index hand in minutes and minute fractions thereof.
The operation is as follows:
In taking a bearing, the upper plate is turned in order to sight through the
telescope some object in line with the bearing. In case it is a certain number of
degrees and a fraction over, the fraction is determined in this way. The spindle
is turned by means of the thumb screw thereby through the intermediate gearing
rotating the upper plate until the object in line with the bearing is at the
centre of the cross wires in the telescope. The small pointer being thereby
rotated a certain number of times within sixty, will determine how many
minutes and parts of minutes are contained in the fraction of the degree. From
this it will be apparent that the minutes can be measured in seconds and sub-
divisions of seconds; so that the minutest part of a degree can be instantly
determined on the dial plate, and be recorded therefrom by the surveyor in his
note book.
It is evident that the same method of determining the value of the angle can be
used in case the transit instrument is constructed with additional devices for deter-
mining vertical angles. It is then only necessary to apply my invention to the
vertical circle in order to read the degrees made on such vertical circle. Verniers
have been used on these vertical circles to read to minutes, and sometimes to
half minutes, (only the most expensive transit instruments read to half minutes);
but with my invention even seconds can be read, and that without danger of
making errors in the reading, as is sometimes the case with the use of the
Vernier plate.
In another form or modification in which the same transit instrument is
used the only difference being in the gearing intermediate between the spindle
of the dial plate and the rack on the periphery of the upper plate. It is evident
that this gearing can be changed to suit the construction of the particular
transit instrument to which my invention may be applied. I do not therefore
limit myself to the use of any particular form of gearing in the practice of
the invention.
In the said modification I substitute for one of the worm gears a cog gearing, the
arrangement being as follows:
The small pointer spindle has a pinion and the tangent shaft has a vertical bevel
gear wheel which meshes with the horizontal bevel gear wheel the latter wheel
also having a series of cogs on its periphery. Intermediate between the pinion
and the cog wheel is a toothed wheel which may be of any convenient size suitable to
the transit instrument on which the gearing is placed. The pinion is to the cog wheel
as one is to four; and one revolution of the vertical bevel wheel represents one
degree on the compass circle. This will cause the small index hand on the spindle
to make four revolutions to a degree. Each of these revolutions will consequently
represent fifteen minutes; and said fifteen minutes are divided into seconds and
parts of seconds.

page_text: I prefer, however, the system of gearing herein before described as each
revolution of the index hand on the dial plate represents one sixtieth of a degree,
or, in other words, one minute; thus giving a very close computation of the value
of the angle sought.
In the construction of the special form of instrument described I make the
upper plate free to turn entirely around on the compass plate. By so doing
I can in field work always have indicated on the instrument the value of
all the angles measured; and on arriving at the point of beginning verify the
work. For this purpose I attach an index finger plate or an equivalent
marking point, to the upper plate. The north point of the compass plate
will coincide with this index finger at the completion of the work, if all the
angles have been properly determined. In other transit instruments by reason
of their construction the verification of the work at the finish has to be
determined by a computation of the value of the angles without the aid of
the instrument.
Dated this 13th day of January 1891
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Transit Instruments.
I, HENRY HARRIS LAKE, of the firm of Haseltine Lake & Co. Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, 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
In transit instruments for surveyors as heretofore constructed it has been found
impossible to accurately determine the value of the angles although by the use of
a Vernier plate the parts of a degree may be approximately determined.
According to the present improvements the precise value of the angle can be
read in minutes and seconds or even in fractional parts of a second. This measure-
ment of the angle is obtained by reading it on a dial plate, so that, not only is the
actual value determined, but there is moreover no liability of mistaking the
reading of the angle, as is sometimes the case with the use of a Vernier plate.
My invention consists in the combination with the compass circular plate of the
transit instrument containing a dial plate, having minute subdivisions of a degree
arranged within the said compass circular plate, of a telescope plate, the two
plates being connected together by gearing so as to be operated in conjunction with
each other.
It further consists in certain specific combinations and arrangements of the
mechanical parts hereinafter described.
In the accompanying drawings
Figure is a plan view of a transit instrument, to which my invention is
applied.
Figure 2 is a side view of the same partly in section looking in the direction of
the arrow 1, on Figure 1.
Figure 3 is a vertical section taken in the line 3, 4 looking in the direction of the
arrow 2.
Figure 4 is a plan view of a transit instrument to which is applied a modification
of my invention."
a is a lower plate, carrying the compass circle, b is the upper plate to which the
telescope is attached. The details of construction of the transit instrument in
other respects are as found in many instruments in use by surveyors, with the
exception of some modifications of its parts necessary to be made in order to apply

page_text: my improvements to it. These differences in construction it will therefore only
be necessary to describe in order to enable those skilled in the art to apply my
improvements.
c is the glass arranged to cover the compass and its edge is let into the transit
instrument shown in the drawings at the inner edge of the upper circle or plate b.
Within the compass box at d is a dial plate for registering the minutes, seconds and
parts of seconds.
e is a spindle which extends down through the centre of this dial
plate, and fis an index hand attached at the upper end thereof. Upon the outer
periphery of the upper circular plate bis placed a continuous circular rack composed
of cogs g.
Intermediate between the outer portion of this cog rack and the
spindle e of the dial plate is placed a system of gearing, so that by turning a thumb
screw at the lower end of the spindle e the small index hand or pointer is moved
in order to show the value of a portion of a degree. At the same time the upper
circular plate will be rotated until the line of vision through the telescope is brought
into coincidence with such marking or value shown on the dial plate. The inter-
mediate gearing may be constructed in any known way, for example as shown in
Figure 1 it is as follows:
are two bevelled cog wheels, one i being placed upon the vertical spindle e and
the other upon the horizontal shaft j. At the other end of this shaft is a worm k
which gears with the cogs of a wheel placed in a vertical position immediately
above the worm k. This transfers motion to the tangent shaft m, to the opposite
end of which is affixed a worm n which gears with the circular rack g. The said
rack is protected by a rim o, which is attached to the lower plate a, by screws,
one of which is shown at p. The upper portion of this rim o is flush with the top
surface of the upper plate b. A portion of this rim is cut away at the place
where the worm n meshes with the said rack g. This permits of the contact
of the worm n, with the rack 9 while at all other points the cog rack is
concealed.
This system of gearing is supported by the bearings 9 9¹ q¹ and can be thrown
out of contact with the transit instrument in case it is so desired. The bearings
are connected to the plate r. Guides, s are attached to the lower or compass
plate, so that the sliding plate to which the bearings are attached can be pulled
out thereby disconnecting the worm n from the rack g and the bevelled wheel i
from the bevelled wheel i. t, is a set screw arranged in the sliding plate by means
of which the plate and its attached gearing can be firmly secured in place when
the worm is thrown into contact with the rack g.
g
One revolution of the tangent shaft m will cause the toothed wheel to turn
one degree as indicated on the compass circle. In this arrangement of gearing
the bevel gear wheels i, i will make sixty revolutions, to one of the toothed
wheel Z, hence one revolution of the wheel a will cause the spindle e and consequently
the small index hand to turn sixty times; and the reading of the degree
will be at each revolution of the index hand f in minutes and minute fractions
thereof.
In taking a bearing the upper plate is turned in order to sight through the
telescope some object in line with the bearing. In case it is a certain number
of degrees and a fraction over, the fraction is determined in this way. The
spindle is turned by means of the thumb screw thereby, through the inter-
mediate gearing, rotating the upper plate until the object in line with the
bearing is at the centre of the cross wires in the telescope. The small pointer f
being thereby rotated a certain number of times within sixty, will determine
how many miuutes and parts of a minute are contained in the fraction of the
degree.
From this it will be apparent that the minutes can be measured in seconds and
subdivisions of seconds; so that the minutest part of a degree can be instantly
determined on the dial plate and be recorded therefrom by the surveyor in his
note book.
It is evident that the same method of determining the value of the angle can

page_text: be used in case the transit instrument is constructed with additional devices for
determining vertical angles. It is then only necessary to apply my invention to
the vertical circle in order to read the degrees made on such vertical circle.
Verniers have been used on these vertical circles to read to minutes, and some-
times to half minutes, (only the most expensive transit instruments read to half
minutes) but with my invention even seconds can be read, and that without
danger of making errors in the reading as is sometimes the case with the use of
the Vernier plate.
:
In the modification (Figure 4) the same transit instrument is shown as in
Figure 1 the only difference is in the gearing intermediate between the spindle
of the dial plate and the rack on the periphery of the upper plate b. It is
evident that this gearing can be changed to suit the construction of the particular
transit instrument to which my invention may be applied. I do not therefore
limit myself to the use of any particular form of gearing in the practice of the
invention.
In this modification (Figure 4) I substitute for one of the worm gears & cog
gearing, the arrangement being as follows:
The spindle e has a pinion and the tangent shaft m has a vertical bevel
gear wheel which meshes with the horizontal bevel gear wheel v¹ secured on a
pivot m', this latter wheel also having a series of cogs w on its periphery.
Intermediate between the pinion u and the cog wheel w is a toothed wheel c
which may be of any convenient size suitable to the transit instrument on which
the gearing is placed.
The pinion is to the cog wheel was one is to four; and one revolution of
the vertical bevel wheel represents one degree on the compass circle. This
will cause the small index hand f on the spindle e to make four revolutions
to a degree. Each of these revolutions will consequently represent fifteen
minutes; and said fifteen minutes are divided into seconds and parts of seconds.
I prefer, however, the system of gearing shown in Figures 1 2 and 3 as each
revolution of the index hand f on the dial plate d represents one sixtieth of a
degree, or, in other words one minute, thus giving a very close computation of the
value of the angle sought.
In the construction of the special form of instrument shown in the drawings
I make the upper plate free to turn entirely around on the compass plate. By
so doing I can, in field work, always have the value of all the angles measured,
indicated on the instrument, and on arriving at the point of beginning verify the
work. For this purpose I attach an index finger plate y or an equivalent
marking point, to the upper plate b, as seen at Figures 1 and 2. The north
point of the compass plate will coincide with this index finger at the completion
of the work if all the angles have been properly determined. In other transit
instruments by reason of their construction the verification of the work at the
finish has to be determined by a computation of the value of the angles without
the aid of the instrument.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed as communicated to me
by my foreign correspondent I declare that what I claim is :-
First. In a transit instrument the combination with the compass circular plate
containing a dial having minute subdivisions of a degree arranged within said
compass circular plate, of a telescope plate, the two plates being connected
together so as to be operated in conjunction by gearing, substantially as described.
Second. In a transit instrument the combination of the compass circular plate a
containing a dial d, and its index hand f, with a telescope plate 6 containing a
circular cog rack upon its outer edge, and intermediate gearing composed of bevel
gear wheels it shaft ; worm wheel k cog wheel l, shaft m and worm wheel n
substantially as described.
Third. In a transit instrument the combination of a dial d its index hand f

page_text: bevel gear wheels shaft ; worm wheel k, cog wheel 1, shaft m, worm
wheel n with the circular cog rack g. placed on the upper plate 6 substantially as
described.
Fourth. In a transit instrument the arrangement of a circular cog rack upon the
outer edge or periphery of the telescope plate b, in combination with the compass
circular plate a containing a dial d, the two plates a and b being connected by
gearing and a plate or slide r, travelling in ways s s on the compass circular plate a,
so as to permit of disconnecting the gearing on the instrument, substantially as
described.
Fifth. In a transit instrument the combination with the compass circular plate,
of a plate carrying the telescope and containing an index finger or marking point
for coinciding with the north pole of the compass, the two plates being free to turn
entirely around on each other, substantially as described.
Dated this 12th day of November 1891.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.