IMPROVEMENTS IN RANGE FINDERS OR DISTANCE MEASURERS
Year: 1882

page_text: LETTERS PATENT to Francis Harwood Poore, of Portsmouth, in the county of
Southampton, Major in the Royal Marine Artillery for an Invention of
IMPROVEMENTS IN RANGE FINDERS OR DISTANCE MEASURERS
"
PROVISIONAL SPECIFICATION left by the said Francis Harwood Poore at
the Office of the Commissioners of Patents on the 16th October 1882.
FRANCIS HARWOOD POORE of Portsmouth in the County of Southampton, Major
in the Royal Marine Artillery, "IMPROVEMENTS IN RANGE FINDERS OR DISTANCE
MEASURERS"
In finding a range according to my invention I take a base line of known
length and upon this I construct an imaginary triangle of which the object whose
range is to be found represents the apex. I then construct a second triangle
similar to the first having its base a determined proportion of the base of the first
triangle. The sides of the large triangle can be read off directly from those of the
small one. To perform these operations two instruments are used one at each end
of a base of observation. Each instrument is marked with lines equally spaced
radiating from a centre and cutting a circular are. One of these instruments hag
a sight bar that can radiate about the axis of the circular arc. The points at
which the radial lines cut the circular arc are connected with an electrical
conductor and the radial bar completes the circuit when the line of sight along
it is parallel with anyone of such radial lines. The other instrument is similarly
marked with radial lines and a circular arc, but the point about which its sight bar
can radiate is adjustable so that its distance from the axis of the circular arc may
be made to represent the length of the base of observation. In use the two
instruments are fixed in similar positions at each end of the base; and the observers
at each instrument simultaneously align the bars of their respective instruments
with the object whose distance is required. When the bar of the first mentioned
instrument is in line with any one of the points at which the radial lines cut the

page_text: are the line of siglit is parallel to the corresponding radial line, and this is by any
suitable means signalled to the observer at the other instrument, who, seeing
where the line indicated cuts the edge of his radial bar reads off at thint point the
distance of the object required, the said bar being marked in the proportion that
the distance from its centre of movement to the axis of the circular arc bears to
the whole length of the actual base of observation.
The construction of the instruments may be modified-and it may be such that
cach instrument may be able to serve indifferently either the office of that above
distinguished as the first named instrument or that of the secondly mentioned
instrument

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Francis Harwood Poore in the Great Seal Patent Office on the
16th April 1883.
FRANCIS HARWOOD POORE of Portsmouth, in the County of Southampton, Major
in the Royal Marine Artillery IMPROVEMENTS IN RANGE FINDERS OR DISTANCE
MEASURERS
In finding a range according to my invention I take a base line of known length
and upon this I construct an imaginary triangle of which the object whose range is
to be found represents the apex.
I then construct a second triangle similar to the first having its base a
determined proportion of the base of the first triangle. The sides of the large
triangle can be read off directly from those of the small one.
To perform these operations two instruments are used one at each end of a base.
of observation. Each instrument is marked with lines equally spaced radiating
from a centre and cutting a circular arc. One of these instruments lias a sight bar
that can rotate about the axis of the circular arc. The points at which the radial
lines cut the circular arc are connected with an electrical conductor, and the radial
bar completes the circuit when the line of sight along it is parallel with any one
of such radial lines.
The other instrument is similarly marked with radial lines and a circular arc,
but the point about which its sight bar can radiate is adjustable so that its distance
from the axis of the circular are may be made to represent the length of the base
of observation.
In use the two instruments are fixed in similar positions at each end of the base,
and the observers at both instruments simultaneously align the bars of their
respective instruments with the object whose distance is required. When the bar
of the first mentioned instrument is in line with any one of the points at which
the radial lines cut the arc the line of sight is parallel to the corresponding radial
line, and this is by any suitable means signalled to the observer at the other
instrument, who, seeing where the line indicated cuts the edge of his radial bar,
reads off at that point the distance of the object required, the said bar being marked
in the proportion that the distance from its centre of movement to the axis of the
circular arc bears to the whole length of the actual base of observation.
The construction of the instruments may be modified and it may be such
that each instrument may be able to serve indifferently either the office of that
above distinguished as the first named instrument, or that of the secondly
mentioned instrument.
Referring to the accompanying sheet of drawings Fig. 9 is a diagram illustrating
the manner in which a range is found according to my invention.
A is the position of the first observer, B that of the second, and C that of the
object whose range is to be found. The length of the base A B is known, and the
direction of the line D E parallel to A C, is indicated on the instrument B. The
base a, b is parallel to A B and is a known proportion of it and therefore the
triangle a b c is similar to the triangle ABC. Hence bc is to B, C, as a bis
to A B, but the proportion is known, and bc can be measured whence B, C,
can be calculated. If b, c, be marked in divisions that bear the same relation to the
units of measurement employed (feet or yards) as a 6 does to A B the length
of B, C, can be read directly on b, c.
a b
A B
Figs. 1 and 2 are plans of the instruments situated respectively at the two ends

page_text: The
of the base line; Figs 3.4 and 5 are full size part elevation part plan and end
elevation respectively shewing the sight bar forming part of the instrument
illustrated in Fig. 1; Figs. 6. 7 and S are full sized elevation plan and vertical
section of that part of the instrument shewn in Fig. 2 which contains the sliding
axis adjustment. In Fig. 1 A is the frame of the sector having attached to the arc
a metal band a perforated, in such a manner that when the line of sight along the
sight bar corresponds with either of the radiating lines 1, 2 3 ele, a projection on
one of two levers on the sight bar falls into a perforation and thereby puts one of
the signal bells B or C in circuit with the battery D: It will be observed that the
radiating lines 1,2 ctc, on the sector are shown full and dotted alternately and that
the distance apart of the holes in the periphery of the sector is double the distance
apart of the radiating lines at the periphery. The sight bar E rotates about the
axis O, the centre of the sector A, and has attached to it near the axis three
terminal screws F G H which serve to connect the signal bells B and C and
battery D with two contact pieces, and the head carrying the contact levers at the
opposite end of the sight bar. bb and co are sight vanes on the sight bar and
sector frame respectively, and are designed to insure the two instruments being
properly situated with relation to each other as will be explained further on.
construction of the sight bar will be better understood from Figs. 34, and 5. A is.
the sight bar rotating about the axis B which is fixed to the sector frame C.
D and E are sight vanes, D being provided with a vertical slit, and E with a wire
or. crosshair. F is a part of the surface band on the outer are of the sector C. G is
a plate of vulcanite or other suitable insulating material carrying the bracket H to
which are attached by means of the pin I the contact levers K K' with contact
screws Land L and projections M and M. The two contact pieces N and N'
are connected by means of the conductors n and n' with the terminal screws
P and P, while the bracket H is connected with the terminal Q by means of
the conductor h. The two rollers R and R' serve to support the weight of the
sight arm when rotating on the rim of the sector C. When the sight bar is partly
rotated about the axis B one of the projections M or M is pressed by the
spring Tor T¹ into one of the perforations as S or S¹, in the surface band F,
whereupon contact is made between the points L or L' and N or N¹ and the
electrical circuit is completed between the battery and one of the signal bells. It
will be seen that according as M or 1 is engaged in the perforation so will the
circuit be closed with n or n', that is with the signal bell B or C.
In Fig. 2 the radiating lines 1. 2 cto divide the sector similarly to those in Fig. 1
The siglit bar E with sight vanes & partially rotates about the axis O, which is not
the centre of the sector, but which is capable of adjustment in a direction parallel
to the base line Y. Z.
The sight vanes CC are provided to enable the operator to set the line O
accurately perpendicular to the base line YZ-and the line containing the centre
of the sector and tlie axis O parallel to the base line Y Z.
In Figs. 6, 7, and 8, A is tho part of the sector shewn at the top of Fig. 2
illustrating the graduated sight bar E with sight vane b partly rotating round the
adjustable axis O, B is a metal guide in which the block carrying the axis O is
made to slide by means of the adjusting screw Gx. The guide B* is a graduated
scale by which the axis may be accurately set by means of a fiducial mark on the
collar E.
The mode of using the instruments is as follows:-
The length of the base line is first accurately measured from centro to centre of
the instruments, and the sights C on both instruments are brought exactly into the.
same straight line Y Z. All the corresponding lines on the two sectors are now
parallel to one another. The operators at both instruments simultaneously align
their sights with the object whose distance is required, and when whilst doing so,
the operator at Fig. 1 passes one of the radial lines, the fact is signalled by one or
other of the electric bells to the other operator.
•
If the object is a moving one, or if the apparatus be mounted on a moving body
.

page_text: such as a ship the object is almost sure to come into direct alignment with one of
the radial lines on the instrument No. 1 in a short time, when the fact is signalled
to operator No. 2 who reads off the distance at the point where the corresponding
radial line on liis instrument cuts the sight bar.
.
The signalling action will easily be followed on the diagram; thus when the
sight bar in Fig. 1 is over a full line the signal bell B will be put into circuit and
similarly with C when the line of sight is over a dotted line.
When it is required to find the distance of a fixed object the sight bar of the
indicating instrument in Fig. 1 must be placed at the point of electric contact
which is nearest to the line of sight to the object whose distance is required, the
sector must then be slightly revolved until the sights are aligned with the object,
and the degrees and minutes that the instrument has been moved must be read off
on the verneir V, which is stationary and then the second instrument (Fig. 2) must
be rotated to the same angle.
The finding of the range is then performed in the same manner as before but a
slight correction will be necessary for each bearing, because the short base is no
longer quite parallel to the long one.
This correction can be marked on the instrument.
It is obvious that the instruments might be modified so that each would serve
indifferently to perform the office of sending the signal or of giving the reading of
the distance if found desirable.
Having thus described the nature of the said invention and the manner of
carrying it into practical effect, what I claim is:-
1. The use for finding a range of an instrument or instruments whereby when an
imaginary triangle has been constructed having a known base and having for its
apex the object whose distance has to be found, a second triangle may be
constructed similar to the above imaginary triangle but of a size that can be
directly measured and bearing a known proportion to the first triangle substantially
as described.
2. The simultaneous use in range finding of two instruments by one of which one
angle at the known base of an imaginary triangle having for its apex the object
whose range is to be found is indicated, and by the other of which the other angle
is indicated and at the same time a similar triangle of measurable dimensions and
bearing a known proportion to the imaginary triangle is constructed by aid of the
indication arrived at by the first instrument substantially as described.
3. In range finding apparatus of the kind described in claim 2, transmitting the
indications of the first instrument to the observer at the second by means of
electricity substantially as described.
4. The improved range finding apparatus constructed, arranged, and operating
substantially as described with reference to and shewn in the drawings.
In Witness whereof I the said Francis Harwood Poore have hereunto set my
hand and seal this fourteenth day of April in the year of our Lord one
thousand eight hundred and eighty three
FRANCIS HARWOOD POORE. (L.S.)