Improvements in Apparatus for Finding the Range and Position of Distant Objects.
Year: 1890

page_text: Date of Application, 8th Apr., 1890-Accepted, 9th Aug., 1890
COMPLETE SPECIFICATION.
Improvements in Apparatus for Finding the Range and Position of
Distant Objects.
I, BRADLEY ALLAN FISKE, of the City of New York, State of New York, United
States of America, Lieutenant in the United States Navy, do hereby declare the
nature of my invention for "IMPROVEMENTS IN APPARATUS FOR FINDING THE RANGE
AND POSITION OF DISTANT OBJECTS," and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:-
Reference being had to the following drawings, in which
Fig. 1 is a diagram illustrating the method of range finding hitherto invented by
me and here introduced for purposes of comparison.
Fig. 2 is a diagram illustrating different positions of an object with reference to a
base line extending fore and aft of a vessel.
Fig. 3 is a diagram illustrating the method of finding the curvature of the guide
bar 39 hereafter described.
Fig. 4 is a general plan view of my apparatus.
Fig. 4 is an enlarged section on the line z z of Fig. 4.
Fig. 5 is a plan view of one of the telescopes i and associated mechanism.
Fig. 6 represents the directing bar 39 separately.
Fig. 7 is a side elevation of the telescope i, and associated parts, showing a portion
of the support broken away and in section.
Fig. 8 is a detail view showing the roller on the extremity of bar 31 and the curved
edge of the bar 39 against which it bears.
Fig. 9 is a section through the nut 24 on the line Y Y of Fig. 10.
Fig. 10 is a section through the nut 24 on the line of Fig. 9.
Fig. 11 is a detail view in longitudinal section on the line YY of Fig. 10 of the
threads of the nut 24 and cylinder 16.
Similar letters of reference indicate like parts.
I will first describe the general principles underlying my said apparatus, and
then more specifically refer to its construction.
=
Referring first to Fig. 1, let T be the position of the object, the distance of which it
is desired to ascertain. Let AB be any short base line. Draw AC at right angles
to BT, EA parallel to BT, and prolong AT as to D. Then by trigonometry AT AB,
sin ABC, cosec ATC. But ATC DAE, and DAE is subtended and measured by the
arc GH. If, therefore, the are GH is known, the angle ATC is known; and it is
obvious from the construction that the arc GH = the arc IH - arc IG.
=
=
At Fig. 1, are shown semicircular arcs of conducting material, and at i i¹ are
alidade arms or telescopes, each pivoted at its extremity at the end of the base line.
The extremities of the arcs hh are upon said base line. At a bed are connected the
wires of a Wheatstone bridge, having in circuit a galvanometer g, and a battery f, as
shown. Let the arms i be directed upon the object T. The observer at arm i notes
the length of arc IG. He then moves the telescope i until the galvanometer g shows
no deflection; and notes the angle IAH or length of arc IH, which equals the length
of arc H. But, as has already been shown, the arc GH equals are I¹ H¹ - arc 1G.
And therefore, the observer at i knowing the are GH, thus finds the angle ATB.
-
It will be apparent that in this determination, practically no account is taken of the
expression sin ABC in the equation AT AB, sin ABC, cosecant ATC; and when the
angle ABC is equal to ninety degrees, it is obvious that this factor need not be con-
sidered. But when the angle ABC varies materially from 90 degrees, then the factor,
sin ABC, must be brought into the equation. This will be more clearly understood
from Fig. 2, which represents a plan view of a vessel having two telescopes or alidade
arms i mounted.in the bow and stern, so that a fore and aft line on the vessel, and

page_text: extending between said telescopes, constitutes the base line. It will be clear, that if
the object is at the point T, and bears directly abeam from one of the instruments as i,
then the angle ABT will obviously be 90 degrees, and no correction for the sine of
that angle will be necessary.
But if the object should be located at the point T', then
the angle ABT will be considerably different from 90 degrees. And it will therefore be
necessary either to change the course of the vessel, as indicated by the arrow, so as to
bring the object abeam, or else to apply a correction in computing the results of the
observation. Both of these courses are objectionable, and in order to avoid them, I
have devised my present apparatus, in which the application of the correction for the
factor represented by the expression sin ABC in the above equation, is automatically
made.
Referring once more to Fig. 1, the angle ATC as already explained, is measured by
the circular aresh h¹, and as these arcs give a true angular reading, it follows, that in
changing the telescopes from any one position to another, equal lengths of arc, and
consequently, equal lengths of resisting body in the circuit, are passed over. Now, I
propose to apply a correction to these lengths, which correction is represented by the
expression sin ABC in the formula AT = AB cosecant ATC, sin ABC. This formula
AB
1
can be written-
sin ABT
sin ATB
And hence it follows, that the expression
sin ATB
sin ABT
indicates
the extent to which the lengths of arc or resisting body must be varied. Instead,
however, of causing the telescope to move over the actual arc as in Fig. 1, and then
varying said are either in shape or in conductivity per unit length, I prefer to
substitute for the are a conducting wire wound spirally upon a cylinder, and
traversed by a contact point arranged in a nut, which nut has a longitudinal
rectilinear motion on said cylinder when said cylinder is turned. The rectilinear
Dath of movement of the nut is tangential to the arc swept over by the free end
of the arm which is parallel to and supports the telescope; and therefore, tangential
to the arc swept over by the free end of the telescope itself. Connected to the
nut is a sliding bar which is free to move at right angles to the rectilinear path
of movement of the nut; and this bar is united by a sliding connection to the
free end of the arm which supports the telescope. One end of the sliding bar is
maintained in constant contact with the directing periphery of a fixed cam.
device constitutes a mechanical movement whereby the motion of the nut over
unequal successive intervals in a rectilinear path, is converted into motion of the
pivoted arm or telescope over equal successive intervals in a curved path: or if
the power be applied to the arm to move it, and if the screw on which the nut
moves be made of sharp pitch, the motion of the pivoted arm over equal
successive intervals in a curved path, will be converted into motion of the nut
over unequal successive intervals in a rectilinear path. The unequal successive
intervals traversed by the nut are varied conformably to the expression
as hereinafter more fully explained.
This
sin ABT
sin ATB
Referring to Fig. 4, at 5 and 6 are shown two supports which are sustained
upon legs, as 7, Fig. 7. Upon each support is a telescope i or 2, together-with-
associated mechanism which is similar in both cases, so that the description of
telescope with its associated parts, applies to both. Entering the support 5 is a
bushing 8, which receives the taper pivot pin 9, which pin supports the horizontal
bar 10. The telescopo i is supported in suitable bearings 11, rising from the bar 10.
The bearings 11 are located at a distance from the pivot 9, but it will be readily
understood that the pivot 9 is the pivotal center upon which the telescope i is swung
laterally. The telescope i is supported on its trunnions, so that it may be elevated or
depressed in the usual way. On the front straight edge of the support 5, are two
brackets 13 and 14, which serve as axial bearings for the threaded cylinder 16. The

page_text: cylinder 16 is made of hard rubber or other insulating material, and its thread is
double; that is to say, said thread is composed of two parallel grooves 17 and 18,
Fig. 9, produced spirally around the cylinder. In the groove 17, is a wire 19 of
conducting material, which here acts as a resistance coil. The shaft of the cylinder 16
does not extend all the way through it; but simply consists of two short rods of
metal 20 and 21, which pass through the bearings 13 and 14, and are secured in the
ends of the cylinder 16 in any suitable way. Upon the portion 20, is a collar 22, and
upon the portion 21 there is a collar 23. The ends of the wire 19 are connected
respectively to the collars 22 and 23. Upon the cylinder 16 is a nut 24, which is
also double threaded, and like the cylinder 16 is made of insulating material. On
referring to Fig. 11, it will be seen that the V-shaped or salient portion 25 of the
nut 24, enters and completely fills the groove 18 of the cylinder 16. But that the
similar portion 26, which enters the groove 17 of the cylinder 16, has the apex of its
salient portion cut off; so that although said portion 26 engages with the groove 17,
there is nevertheless left a space between the meeting parts for the reception of the
wire 19.
On one side of the nut 24, are secured two bars 27 and 28. Between these bars is
received a bar 29 fixed on the front side of the support 5. The bar 29 thus serves as
a guide bar for the nut 24 during its horizontal movement on the cylinder 16.
Between the bar 28 and the bar 29, may be placed a leaf spring, shown in section
at 30, Fig. 10, for maintaining close contact with the said gnide bar. In a plate of
metal 24*, Figs. 9 and 10, on the upper side of the nut 24, is a dove-tail groove
placed at right angles to the axis of the cylinder 16, in which groove is received the
correspondingly formed slide bar 31. On the front side of the nut 24, is bolted a
strip of metal 32, upon which is secured a pin 33, which enters a longitudinal socket
in the bar 31. A spiral spring 34 surrounds the pin 33, and is received within said
socket. This spring has an abutment upon the bottom of the socket, and also upon
the fixed bar 32, so that its tendency is to push the slide 31 away from the bar 32, or
towards the right of the drawing Fig. 10. The bar 10 which supports the telescope i,
extends over the bar 31, and is slotted at 35. Travelling in the slot, is a movable
piece 36, through which passes the headed pin 37. The pin 37 is loose in its
supporting piece 36, but it extends down through, and is fast in the slide 31, in which
it terminates. On the front end of the bar 31, is journaled a small roller 38, which,
by the action of the spring 34, is kept in constant contact with the edge of the
curved bar 39, Fig. 8. In the upper part of the nut 24, is a vertical aporture, in
which is placed a pin 40. The pin 40 is in electrical contact with the slide 31, as
shown in Figs. 9 and 10, and with the wire 19.
The operation of the parts so far described, is as follows: At the extremity of the
axis of the cylinder 16, is a crank 41. When this crank is turned, the nut 24 being
prevented from rotating with the cylinder by the bars 27, 28, 29, is compelled to
move lengthwise upon said cylinder, and carries with it the slide bar 31. But the
slide bar 31 has motion laterally across the nut by the action of the spring 34. The
extent of this transverse motion of bar 31, is governed obviously by the curve of the
directing periphery of the cam 39, which the roller 38 on bar 31 must follow. And
as the pin 37 is fast to the bar 31, the movement of the slide 36 in its slot 35 is
regulated not merely by the movement of the nut 24 from end to end of the cylinder,
but also by the transverse movement of the bar 31 crosswise the cylinder. The
consequence is, that the position of the pin 37, and consequently the angle which the
bar 10 will assume, will be governed by the curvature of the cam 39; and for the
same reason, the length of wire 19, which will be included between the pin 40 and
either terminal 22 or 23, will also be controlled by the curvature of the cam 39.
Now by suitably constructing the cam 39, I can cause it to apply to the length of
wire passed over by the nut, and corresponding to a certain angle moved over by the
bar 10 a correction, which is represented by the expression
sin ATB
sin ABT,
and this

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movement of the nut due to the rotation of the cylinder, causes an angular move-
ment of the telescope. The problem, therefore, obviously reduces itself to the
determination of what the actual path of movement of the point of junction of
telescope and nut must be. On opposite sides of the point G at which the line AG!
cuts the arc IJ, lay off the distances G1, 1, 2; 2, 3; all equal, and for purposes of
convenience, assume that each represents one degree in arc. Certain definito lengths
of the line PR are to correspond to certain definite lengths on the arc IJ, and
hence to certain definite angular movements corresponding to these lengths of arc.
The lengths on the line PR with which I have to deal, are represented by the
expression in ABT.
While the telescope moves from the position AG to the
position A1, let the body moving along the lino PR move a distance represented
by G'm. Now this distance G'm is a distance which is represented by the sine of the
angle GA1 divided by the sine of another angle. Now, assume the angle GA1 to be
sin ATB
one degree, and assume the other angle to be 90 degrees, then the expression
becomes
sin 1°
,
'
sin ATB
sin ABT
so that the distance G'm is equal to the sine of one degree or to the
are of the angle GA1, and hence very nearly equal to the arc G1. This distance is
laid off from G¹, and on both sides thereof, on the line PR. Now assume the
telescope to be moved into the position Al. The next distance to be laid off on the
sin 1°
line PR may be represented by the expression in 890; and as the sine of 89 degrees
is a fraction, it follows that the actual distance to be laid off, (mn,) will be greater
than the distance G'm. Now, put the telescope into the position A2. The above
sin 1°
expression is then changed to read
0
sin 880; and this being computed, gives a distance n,
which is greater than the previously determined distance m n. We have thus found
on the line PR, three successive lengths or distances, namely, G'm, mn, and n, o
which represent the positions which a sliding contact body on said line must occupy,
while the telescope occupies the positions A1, A2, A3. It follows, therefore, that if
the telescope and the sliding body be linked together, the point of junction must
follow the curved path which lies at the intersection of the line representing the
various positions of the telescope, and of lines drawn perpendicular to the line PR at
the points mno. It remains, therefore, to erect such perpendiculars at the points o, m, n,
and to extend the lines A1, A2, A3, to intersect such perpendiculars, and finally to
draw the curve through the points of intersection M. N. O. It will be clear then,
first, that given a body moving along the line PR successively over the unequal
distances G'm, mn, no, if that body be linked to a telescope pivoted at A, and if the
point of junction be compelled to move over the curve MÑO, then the telescope will
move over equal intervals in arc, namely, G1: 12:2. 3, despite the fact that the
-sliding body on the line PR moves over unequal intervals on that line. Or, conversely,
if a telescope pivoted at A, be linked to a body free to slide along the line PR, and
if the point of junction of the linkage be constrained to move along the curve MNO,
then for equal successive angles swept over by the telescope, the sliding body on the
line PR will move over unequal successive intervals; and in both of the above
instances, the inequality of these intervals on the line PR, will depend upon a ratio

page_text: between the sine of the angle swept over by the telescope and the sine of another
angle. The cam bar 39 in Fig. 6, is laid out in the manner just described. The
convex curved edge of said bar represents the curve MNO of Fig. 3. It will be
obvious that the pin 37 is at the point of linkage of the pivoted bar 10 and the
sliding nut 24; and that this point will be directed in its path by the convex edge of
the bar 39:
Referring once more to Fig. 4, 42 is a supporting franie, upon which are stretched
two wires 43 and 44. Wire 43 is connected at one end to an adjusting screw 45,
and communicates with binding post 46. Wire 44 is connected at one end with an
adjusting screw 47, and communicates with binding post 48. The wires 43 and 44 at
their ends opposite to the adjusting screws 45 and 47, are received upon a roller 49 of
insulating material. This roller is arranged in bearings on the frame 42, and may be
rotated in order to strain the wires. The extremity of the wire 44 passing around
the roller 49, communicates with binding post 50; and the extremity of the wire 43
communicates with binding post 51. 52 is a bar of metal supported on the frame 42,
and carrying two spring contact points 53, 53*, which respectively bear upon the
wires 43, 44. The contact piece 53* is supported on the sliding piece 63 on the bar 52.
The contact piece 53 is also supported on the piece 63, but is separated therefrom by
the block 64 of insulating material. See Fig. 4. The contact piece 53 also bears
upon a metal strip 54, which extends along the edge of the frame 42. The strip 54
communicates with binding post 55, and the bar 52 communicates with-binding post 56.
Connected in loop between said binding posts, is a galvanometer g.
The circuits in the apparatus proceed as follows: (see Fig. 4.) Beginning at the
battery to the binding post 57, Fig. 7, on the pivot pin 9 of the bar 10, which is on
the support 5; thence to said bar 10, to pin 40, and so to wire 19. The current then
divides; part going from pin 40 to binding post 58 on the bracket 14, and part going
from pin 40 to binding post 59 on bracket 13. From the bracket 13, the circuit
proceeds by wire a to binding post 46, wire 43, binding post 51, wire b, to binding
post 60 on the bracket 13 on the support 6; thence along the wire 19 to the bar 10
beneath the telescope i¹, and to a binding post at 61 at the pivot of said telescope ?",
and so back to battery f. The current also proceeds from the binding post 58 on the
support 5 by wire e to binding post 50, to wire 44, to binding post 48, and thence by
wire d to the binding post 62, and so by wires 19 to the binding post 61, and so back
to battery. It will be noticed that the arrangement of circuit is that of a Wheatstone
bridge.
The operation of the apparatus will be more clearly understood from Fig. 12, which
represents the device diagrammatically. In Fig. 12, assume when the contact
pieces 53 and 53* are moved to the extreme right of the wires 43 and 44, and when
the two telescopes i and i¹ are placed at right angles to the centers of the cylinders 16,
or in the positions indicated by full lines, that then the resistances in the four
members, a, b, c, d, of the bridge are equal. There will, of course, be an electrical
balance, and the galvanometer y will show no deflection.
The telescopes are located at a distance apart upon a base line with which the axial
lines of the cylinder 16 are parallel. An observer at each telescope directs his
instrument upon the object T, the distance of which is to be determined. Assume
that when the telescopes are so directed, they take the positions represented in
dotted lines. Then by reason of the change in position of the telescopo i, the
member a of the bridge will be increased in length, and hence in resistance; and
the member c will be decreased. Similarly, by reason of the change in position
of the telescope, the member d will be increased, and the member 6 decreased.
Obviously, the bridge will no longer balance; and the difference in resistance
which throws it out of equilibrium, will be the difference between the lengths of
conductor respectively on the two cylinders 16, which are moved over by the
nuts 24 in setting the telescopes to their new position.
Now let the contacts 53 and 53* be slid to the left. The effect of so doing is
to increase and c, and decrease a aud d. Plainly, then, it is merely necessary
to move the contacts 53 and 53* over some definite distance, (as to that indicated

page_text: 2. An apparatus for measuring the distance of a far off object constructed and
operating substantially as herein described, and comprising essentially a conducting
body, an electrical mechanism for determining a fractional portion of said body bearing
in length an inverse relation to the distance of said object, and a measuring instrument
for measuring said length.
3. An apparatus for measuring the distance of a far off object constructed and
operated substantially as herein described, and comprising a body moving over a
rectilinear path, an arm having its free end movable in a curved path to which said
rectilinear path is tangential, a sliding bar connected to said body and free to move at
an angle to the rectilinear path of said body, and united to the free end of said arm a
guide cam with the directing periphery of which one end of said sliding bar is main-
tained in contact during the rectilinear movement of said body and electrical
connections as set forth the aforesaid parts being organized and arranged so that for
relatively unequal intervals traversed by said body moving over the rectilinear path,
the free end of said arm shall move over relatively equal intervals in arc.
4. An apparatus for electrically measuring the distance of a far off object, constructed
substantially as herein described, and comprising the combination of two rotary
threaded cylinders 16, having conductors 19 thereon, nuts 24 upon said cylinders,
sliding bars 31 on said nuts, guide cams 39 against the periphery of which said sliding
bars 31 bear, and pivoted alidade arms or telescopes ii united to said bar 31: a
source of electricity f connected to said arms, circuit connections a, b, c, d, connected
to conductors 19 and also to the wires 43 and 44, as set forth bars 52 and 54
connected to galvanometer g, and movable contact fingers 53 and 53*, insulated from
each other and making contact with said wires 43 and 44, and with bars 52
and 54.
Dated this 9th dow of Ancil 1800
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.