Improvements relating to Sights for Ordnance.
Year: 1888

page_text: Date of Application, 17th Nov., 1888
Complete Specification Left, 26th July, 1889-Accepted, 28th Sept., 1889
PROVISIONAL SPECIFICATION.
Improvements relating to Sights for Ordnance.
I, HUBERT HENRY GRENFELL, of Elswick Works, Newcastle upon Tyne, in the
County of Northumberland, Captain K.N. do hereby declare the nature of this inven-
tion to be as follows:-
The usual method of sighting a gun is by means of a foresight near the trunnion
and a rear sight having a straight bar (see Figure 1).
If with the centre A and the distance A B I describe a part of a circle this arc will
represent the movement of the head of the rear sight as the muzzle of the gun is
thrown up by elevating.
Take on this are the points C D E in Figure 2 to represent say 5°, the lengths of
these small arcs BC, CD, DE, will be equal, if now I continue the lines A C, A D,
A E, till they cut the vertical line which represents the bar, the distances Be, cd, de,
which represent the necessary movement of the vertical bar to correspond with
BC, CD, DE, are no longer equal but increase continually in length.
To gain uniformity in length in the graduations a curved bar working round a
foresight A may be used.
If I use a curved bar and at the head of it place two pointers, or a telescope, these
pointers will always be directed towards the point A whatever the movement of the
curved bar around A.
Hence I can suppress the foresight at A and by suppressing the fixed point A 1
can use, when desirable, instead of a fixed radius for drawing my curved bar, any
other convenient radius, when the sight with its two pointers will still act as before.
When the pivot is imaginary I can if I like use the same radius for all guns; with
this advantage; that being tied down to a fixed distance A B under the existing
method it results that on small guns this distance is very short and consequently the
subdivisions on the bar for degrees and yards become inconveniently minute and very
difficult to discern and in the case of large guns where the distance A B is consider-
able the subdivisions become inconveniently large and the consequent total length of
the bar is excessive and very inconvenient on service.
Now by the use of a curved bar and an imaginary pivot, such a radius can be
selected as will give in all cases and with all guns any length of subdivision, and
consequently of total length of bar, as may prove to be most suitable for general use.
The movements required to be given to the sight to compensate for lateral deviation
of the shot from the line of sight may be provided for on exactly the same
principles as those stated above, by having on the head of the curved bar mentioned
above, another curved bar in which the pointers slide horizontally round an imaginary
pivot.
My patent application No. 13549 in the present year refers to sights of this
nature.
Now it is necessary to further note that the path of a shot when fired from a gun
is roughly of the nature indicated in Figure 4 that is:-the first part of its path is
very slightly curved, but as it gets farther and farther, so the curve becomes more
marked. In other words the elevation required increases very slowly for the first
part of its flight but much more rapidly at long distances.
In addition then to the increasing length of the subdivisions cd, de, &c. Figure 1
due to the use of the straight bar they are still further lengthened when they repre-
sent the graduations for yards of distance by the necessary allowance for the increasing
curve of the shots path.
Owing to the high velocity of modern gans it is therefore clear that when the
istance A B for sighting is small, as is the case with small guns, the subdivisions up

page_text: to 2-3000 yards become (as already stated) very minute, so minute indeed that they
in many cases can be with difficulty discerned and it is not possible to do more than
indicate every 500 yards by a very small figure 5.
Let us now take the case of a curved bar which instead of being a portion of a
circle throughout, is of varying curve, roughly as shown in figure 5.
Now by using the proper curve, slow at first where the shot's path is flat, and
increasing in curvature as the shots path becomes more curved I obtain this advantage,
that all the subdivisions for distance can be made equal in length, throughout the
whole length of the bar. By this all the subdivisions become easily discernable, those
near the top are increased in length from minuteness to easy visibility, those near the
bottom are reduced from excessive length to convenient proportions.
Arising from this come other advantages. As the subdivisions are throughout equal,
the teeth of the rack by which the sight is raised and lowered in its socket can be
made to correspond to the length of the subdivisions so that each tooth on the rack
may represent 50, 100 or 200 &c. yards as desirable.
This has an advantage as the man using the sight can count the number of turns
he gives to the pinion head which works in the rack, each turn corresponding to 50,
100 or 200 &c. yards as before. This will be useful at night for which also as each
tooth passes it can be made to actuate a spring catch and the sounds of the fall of the
spring catch can be counted in the same way.
Having then equal movements for each regular and determined increment of
distance (50, 100, 200 yards &c.) I apply an indicator to record the distance in
visible figures.
The present method of setting a tangent (rear) sight is as follows:-The varying
distances 100, 200, 300 &c. yards are marked by horizontal lines on the bar and
these are brought to correspond with the upper edge of the collar or socket in which
the bar slides. Figure 6 shows a sight set to 700 yards.
It also shows the sinallness of the subdivisions though many are smaller than this.
Now in the heat of action it is very easy to make a mistake in setting the sight,
both because the subdivisions are small and difficult to pick out and because in some
cases only every 500 yards is marked by a small figure as above.
Instead of the above, in my sight by using an indicator showing clear and large
figures a mistake is hardly possible, moreover the figures are always prominently
under the eye of the firer reminding him at each moment what distance he is using,
they also enable the officer of the battery to control the firing of the men. By a
glance even from some distance he can see that the proper range is being used,
whereas it is impossible to examine the sights on the old method without stopping the
service of the gun.
Figure 7 shows the sight fitted with an indicator.
The indicator as I prefer to construct it consists of two circles engraved with figures,
the circle which indicates the hundreds of yards moves the other and is itself fixed
to a shaft which has a pinion which works in a rack on the sight bar.
The indicator is applicable to all sights whether with curved or straight bars.
1000
H. H. GRENFELL.
COMPLETE SPECIFICATION.
Improvements relating to Sights for Ordnance.
I, HUBERT HENRY GRENFELL, of Elswick Works, Newcastle-on-Tyne, in the County
of Northumberland, Captain, R.N. do hereby declare the nature of this invention
and in what manner the same is to be performed, to be particularly described and 5
ascertained in and by the following statement :—
My invention relates to sights or sighting-apparatus for ordnance.
In the accompanying drawings,
Figure 1 is a diagram showing the trajectory or path of a shot when fired from
ann
5

page_text: Figure 2 is a rear elevation of part of an ordinary sighting-apparatus.
The remaining figures of the drawings are hereinafter described.
In the specification of former Letters Patent, dated 19th September, A.D. 1888,
No. 13,549, I have described a sighting-apparatus wherein a telescope or other
device having two sights or sight-points is so arranged that the said sights or sight-
points are simultaneously adjustable about an imaginary pivot or axis, the said
telescope or other device being carried by a segmental bar or slide which is adjust-
able in vertical plane and the curved surfaces of which are arcs of circles having as
their centre the said imaginary pivot or axis.
Although, by this arrangement, I am enabled to make the divisions of the graduated
scale of yards on the sight-bar more nearly equal than is practicable with a straight
sight-bar, it is necessary that the said divisions should somewhat increase in length
from the upper to the lower end of the sight-bar for the following reason, viz. :-It
is well known that the trajectory or path of a shot fired from a gun horizontally or
with a small angle of elevation, has at first a very slight downward curvature, which,
at a considerable distance from the muzzle of the gun, rapidly increases, the projectile
having an increasing tendency to move downward under the action of gravity; the
curvature of the trajectory being, for example, as indicated by the dotted line in
Figure 1. Therefore the angle through which the gun must be elevated for any
given increase of a short range is slight, but for a similar increase of a longer range,
the angle through which the gun must be elevated is proportionately greater.
Now according to one part of my present invention, 1 provide for the use of a
graduated scale of yards, the divisions of which are equal throughout the length of
the sight-bar. I accomplish the desired object by making the sight-bar with a
varying curvature corresponding, or approximately corresponding, to the varying
curve of the trajectory of a shot fired from the gun horizontally or with a small
angle of elevation, that is to say, the upper part of the sight-bar is but slightly
curved and the curvature increases towards the lower end of the said bar. The
precise curvature of the bar is obtained with the aid of the range-table of the
particular gun, and somewhat approximates to a parabolic curve. By this means, I
also obtain the further advantage that the teeth of the rack by which the sight-bar
is raised and lowered in its socket or guide, may be made to correspond with the
divisions of the graduated scale, each tooth representing say, fifty, one-hundred, or
two-hundred yards. With a sighting apparatus so constructed, a gunner can, by
counting the number of turns he gives to the pinion in gear with the said rack,
readily ascertain at night the angle of elevation which he has given to the gun.
My present invention, moreover, comprises a range-indicator which shows in
clear and easily legible figures the range for which the sighting-apparatus is
adjusted.
The usual method of adjusting or setting a sight, is by raising it until the divi-
sion or subdivision of the graduated scale corresponding to the range, is level with
the top of the guide or socket in which the sight-bar slides, as indicated in Figure 2,
which shows an ordinary sighting-apparatus adjusted for a range of 700 yards. As
the sub-divisions are usually very minute and difficult to discern, a gunner, in the
excitement of an action, may very easily make a mistake of one or two hundred
yards in setting or adjusting the sight; more especially as, in many cases, no distances
less than five hundred yards are marked by figures, and the figures are small, as
shown, for example, in the drawing.
With my improved indicator, the range for which the sight is adjusted will be
shown in full by means of clear and large figures which can be seen and read at a
glance, and which are, moreover, always prominently under the eye of the gunner,
thus keeping him acquainted with the range for which the sight is adjusted. More-
over my indicator affords the further advantage that the officer of a battery can,
without obstructing or impeding the movements of the men serving a gun, ascertain
at any time if the sight has been properly adjusted for the estimated range, as he
can readily see the figures when at a convenient distance from the gun.

page_text: invention may be conveniently and advantageously carried into practice.
Figure 3 is a plan.
Figure 4 a side elevation partly in vertical section, and
Figure 5 a rear elevation of one form of my improved sighting-apparatus.
Figure 6 is a plan.
Figure 7 a rear elevation, and
Figure 8 a side elevation, partly in vertical section, of the sight-bar and horizontal
guide detached.
Figures 9 to 16 are different views hereinafter referred to, illustrating details of
construction.
Like letters indicate corresponding parts throughout the drawings.
a is the vertically adjustable curved sight-bar. is a telescope which is held in
brackets c secured in any convenient manner to a horizontal bar or plate d in such
a manner that the telescope can be readily removed from the bar d and replaced in
its proper position thereon. The drawing shows a field-gun sight and the telescope
and bracket are purposely fitted without catches or pins, so that the gunner, after
laying the gun, can remove the telescope as he steps clear of the wheel for firing.
In Naval guns, the extensions c¹ of the brackets c may be lengthened so that they
project through the plate d and may be secured by pins put through holes in the
said extensions.
The bar or plate d is formed on, or firmly attached to a horizontal segmental
slide e arranged to move in a groove or channel f¹ in a guide f which is firmly
attached to the upper end of the bar a. This slide e is adjustable horizontally in the
groove about an imaginary pivot or axis, substantially as described in my said
former specification, to allow for deflection or drift or for the speed of a moving
object against which the gun is directed. For this purpose, the slide e has attached
thereto a nut e¹ which is fitted to slide in, and extends through a slot in the
guide f. This nut is fitted to a screw arranged to rotate, but restrained from
endwise movement, in bearings f³ formed on the guide f. The said screw is provided
at each end with a milled wheel g¹ for rotating it. The slide e is also provided with
a projection which moves in a slot f in the guide f and which has an arrow-
head marked thereon, as shown in Figure 5, for indicating by a graduated scale on
the guide the horizontal adjustment of the sight. The bar or plate d is provided
with two sights h, which may be used instead of the telescope for very short ranges
or for rapid firing against troops moving at a high speed, the telescope in this case
being removed.
It will be seen that the front and rear surfaces of the sight-bar a are approxi-
mately parabolic curves, the curvature of the bar being very slight at the upper
end and gradually increasing to the lower end thereof, so that it corresponds approxi-
mately to the varying curvature of the trajectory of a shot fired from the gun
horizontally or with a small angle of elevation."
The sight-bar a is arranged to slide up and down in a socket or guide ; which
is to be attached to the gun or to a part or piece movable therewith. This socket
or guide is provided with rollers k which bear against the bar a, and between which
the said bar can move freely notwithstanding the variations in its curvature.
The said sight-bar a has teeth a' with which is geared a volute or spiral tooth 11
formed on a disc l acted upon by a spring m and provided with a milled wheel
whereby it can be conveniently rotated.
I can, if desired, substitute other well known devices for raising and lowering the
sight-bar.
The improved range-indicator shown in the drawings is constructed as follows,
viz.: The figures denoting the hundreds and thousands are marked upon two rotary
discs n, o, which are divided into ten equal parts, and which bear the numbers 1 to 9,
the tenth division on the disc n being inarked with a cipher and that on the disc o
being left blank. These discs are shown in face view and in transverse section in

page_text: Figures 9 to 12. The said discs are enclosed in a casing p which is formed with the
socket or guide j, and the cover p₁ of which has a horizontal slot or opening p* (as
more clearly shown in Figures 5, 15 and 16) through which one figure on each of
the said discs can be seen. Another disc g, which is shown in face view and in
transverse section in Figures 13 and 14, has two ciphers marked thereon; this disc
is firmly secured to the cover pl in such a manner that the said two ciphers are
visible through the slot or opening p³. The word "yards" is, moreover, painted or
otherwise marked on the cover p at the right hand side of the said two ciphers. The
disc is fixed upon a spindle n extending through a hollow spindle o on which is
fixed the disc o. The spindle n also has fixed thereon a pinion n² which is geared
with a rack or series of teeth a' on the bar a. One tooth in every ten of the said
rack is prolonged as shown at a³ to form another rack adapted to engage at suitable
intervals with a pinion o² formed or fixed upon the hollow spindle o¹, for the purpose
of intermittently rotating the disc o, so that, in each complete revolution of the disc n,
the disc o will be turned one tenth of a revolution.
By these means, if the sight-bar is raised to adjust it for a range of one hundred
yards, the pinion n' and disc n will be turned a tenth part of a revolution so that the
figure 1 on the said disc is visible through the opening p². This figure together
with the two ciphers which are always visible, will indicate 100 yards, as shown in
Figure 5. If the sight-bar is raised to adjust the sight for a range of one thousand
yards, the disc n will be turned a complete revolution and the disc o a tenth part
of a revolution, so that 1000 yards will be indicated by the figures on the discs.
It is obvious that figures marked on the discs can be made much larger than is
practicable when they are marked upon the sight-bar, and can therefore be more
readily seen. Moreover, the figures indicating the range for which the sight is
adjusted are not in proximity to other visible figures, therefore liability to confusion
or mistake in respect of the range is obviated.
In some instances, I provide for the illumination of my improved range-indicator at
night. Or I provide the socket or guide for the sight-bar with a spring pawl or
catch which, in every movement or adjustment of the sight for say fifty, one-hundred
or two-hundred yards as the case may be, will engage with a notch in the
sight-bar and thus prevent displacement of the said bar by vibration or concussion.
This pawl or catch may be so arranged that it will, in engaging with the said
notch, produce a sharp sound or click, so that, by counting the number of clicks
while adjusting the sighting apparatus, the gunner can accurately effect this operation
without looking at the figures of the indicator.
It will be seen that my range-indicator is constructed separately from the sight-
bar and is so combined therewith that it will be operated as required in the up-and-
down movement thereof.
I do not confine myself to the precise arrangement of the discs of my range-
indicator above described, as any other suitable arrangement thereof may be adopted.
My range-indicator is, moreover, applicable to the sighting-apparatus described in
my said former specification, and to other sights whether provided with curved or
with straight sight-bars.
It is evident that I can, if desired, mount the device hereinbefore described
comprising the two sights or sight-points upon a horizontal curved or segmental slide
adjustable in another horizontal curved or segmental slide which is itself adjustable
relatively to the vertical curved sight-bar. The said horizontal slides being provided
separately with means for adjusting them to allow for deflection by the wind or for
the speed of a ship on which the gun is mounted and for the speed of the target,
i.e., the ship or other object against which the gun is directed, as described in my
said former specification.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed, I wish it understood that 1 claim :-
First. A sighting-apparatus wherein the vertically adjustable sight-bar is formed
with a curvature such as that above described, for the purpose specified.

page_text: Second. The combination, with a vertically adjustable sight-bar, of a separately
constructed range-indicator which will be operated in the up-and-down movement of
the said sight-bar, for the purpose above specified.
Third. The combination of parts comprising a vertically adjustable sight-bar
provided with a rack or racks, a socket or guide for the said bar, a fixed or stationary
disc, and rotary discs geared with the said rack or racks, substantially as, and for
the purpose, set forth."
Fourth. The improved sighting-apparatus constructed substantially as described
with reference to Figures 3 to 16 of the accompanying drawings and operating as,
and for the purposes, set forth.
για auy or vuly 100.
H. H. GRENFELL.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, Agents for the Applicant.

page_text: Figure 2 is a rear elevation of part of an ordinary sighting-apparatus.
The remaining figures of the drawings are hereinafter described.
In the specification of former Letters Patent, dated 19th September, A.D. 1888,
No. 13,549, I have described a sighting-apparatus wherein a telescope or other
device having two sights or sight-points is so arranged that the said sights or sight-
points are simultaneonsly adjustable about an imaginary pivot or axis, the said
telescope or other device being carried by a segmental bar or slide which is adjust-
able in a vertical plane and the curved surfaces of which are arcs of circles having as
their centre the said imaginary pivot or axis.
Although, by this arrangement, I am enabled to make the divisions of the graduated
scale of yards on the sight-bar more nearly equal than is practicable with a straight
sight-bar, it is necessary that the said divisions should somewhat increase in length
from the upper to the lower end of the sight-bar for the following reason, viz. :-It
is well known that the trajectory or path of a shot fired from a gun horizontally or
with a small angle of elevation, has at first a very slight downward curvature, which,
at a considerable distance from the muzzle of the gun, rapidly increases, the projectile
having an increasing tendency to move downward under the action of gravity; the
curvature of the trajectory being, for example, as indicated by the dotted line in
Figure 1. Therefore the angle through which the gun must be elevated for any
given increase of a short range is slight, but for a similar increase of a longer range,
the angle through which the gun must be elevated is proportionately greater.
Now according to one part of my present invention, 1 provide for the use of a
graduated scale of yards, the divisions of which are equal throughout the length of
the sight-bar. I accomplish the desired object by making the sight-bar with a
varying curvature corresponding, or approximately corresponding, to the varying
curve of the trajectory of a shot fired from the gun horizontally or with a small
angle of elevation, that is to say, the upper part of the sight-bar is but slightly
curved and the curvature increases towards the lower end of the said bar. The
precise curvature of the bar is obtained with the aid of the range-table of the
particular gun, and somewhat approximates to a parabolic curve. By this means, I
also obtain the further advantage that the teeth of the rack by which the sight-bar
is raised and lowered in its socket or guide, may be made to correspond with the
divisions of the graduated scale, each tooth representing say, fifty, one-hundred, or
two-hundred yards. With a sighting apparatus so constructed, a gunner can, by
counting the number of turns he gives to the pinion in gear with the said rack,
readily ascertain at night the angle of elevation which he has given to the gun.
My present invention, moreover, comprises a range-indicator which shows in
clear and easily legible figures the range for which the sighting-apparatus is
adjusted.
The usual method of adjusting or setting a sight, is by raising it until the divi-
sion or subdivision of the graduated scale corresponding to the range, is level with
the top of the guide or socket in which the sight-bar slides, as indicated in Figure 2,
which shows an ordinary sighting-apparatus adjusted for a range of 700 yards. As
the sub-divisions are usually very minute and difficult to discern, a gunner, in the
excitement of an action, may very easily make a mistake of one or two hundred
yards in setting or adjusting the sight; more especially as, in many cases, no distances
less than five hundred yards are marked by figures, and the figures are small, as
shown, for example, in the drawing.
With my improved indicator, the range for which the sight is adjusted will be
shown in full by means of clear and large figures which can be seen and read at a
glance, and which are, moreover, always prominently under the eye of the gunner,
thus keeping him acquainted with the range for which the sight is adjusted. More-
over my indicator affords the further advantage that the officer of a battery can,
without obstructing or impeding the movements of the men serving a gun, ascertain
at any time the sight has been properly adjusted for the estimated range, as he
can readily see the figures when at a convenient distance from the gun.

page_text: In Figures > LO 10 of the accompanying drawings, I have shown now my sand
invention may be conveniently and advantageously carried into practice.
Figure 3 is a plan.
Figure 4 a side elevation partly in vertical section, and
Figure 5 a rear elevation of one form of my improved sighting-apparatus.
Figure 6 is a plan.
Figure 7 a rear elevation, and
Figure 8 a side elevation, partly in vertical section, of the sight-bar and horizontal
guide detached.
Figures 9 to 16 are different views hereinafter referred to, illustrating details of
construction.
Like letters indicate corresponding parts throughout the drawings.
a is the vertically adjustable curved sight-bar. b is a telescope which is held in
brackets c secured in any convenient manner to a horizontal bar or plate d in such
a manner that the telescope can be readily removed from the bar d and replaced in
its proper position thereon. The drawing shows a field-gun sight and the telescope
and bracket are purposely fitted without catches or pins, so that the gunner, after
laying the gun, can remove the telescope as he steps clear of the wheel for firing.
In Naval guns, the extensions c¹ of the brackets c may be lengthened so that they
project through the plate d and may be secured by pins put through holes in the
said extensions.
The bar or plate d is formed on, or firmly attached to a horizontal segmental
slide e arranged to move in a groove or channel f¹ in a guide f which is firmly
attached to the upper end of the bar a. This slide e is adjustable horizontally in the
groove about an imaginary pivot or axis, substantially as described in iny said
former specification, to allow for deflection or drift or for the speed of a moving
object against which the gun is directed. For this purpose, the slide e has attached
thereto a nut e¹ which is fitted to slide in, and extends through a slot in the
guide f. This nut is fitted to a screw garranged to rotate, but restrained from
endwise movement, in bearings f formed on the guide f. The said screw is provided
at each end with a milled wheel g¹ for rotating it. The slide e is also provided with
a projection which moves in a slot f in the guide f and which has an arrow-
head marked thereon, as shown in Figure 5, for indicating by a graduated scale on
the guide the horizontal adjustment of the sight. The bar or plate d is provided
with two sights h, which may be used instead of the telescope for very short ranges
or for rapid firing against troops moving at a high speed, the telescope in this case
being removed.
It will be seen that the front and rear surfaces of the sight-bar a are approxi-
mately parabolic curves, the curvature of the bar being very slight at the upper
end and gradually increasing to the lower end thereof, so that it corresponds approxi-
mately to the varying curvature of the trajectory of a shot fired from the gun
horizontally or with a small angle of elevation."
The sight-bar a is arranged to slide up and down in a socket or guide which
is to be attached to the gun or to a part or piece movable therewith. This socket
or guide is provided with rollers k which bear against the bar a, and between which
the said bar can move freely notwithstanding the variations in its curvature.
The said sight-bar a has teeth a' with which is geared a volute or spiral tooth
formed on a disc lacted upon by a spring m and provided with a milled wheel 1
whereby it can be conveniently rotated.
I can, if desired, substitute other well known devices for raising and lowering the
sight-bar.
The improved range-indicator shown in the drawings is constructed as follows,
viz. The figures denoting the hundreds and thousands are marked upon two rotary
discs n, o, which are divided into ten equal parts, and which bear the numbers 1 to 9,
the tenth division on the disc n being inarked with a cipher and that on the disco
being left blank. These discs are shown in face view and in transverse section in