Differential Speed Indicators.
Year: 1893

page_text: Date of Application, 23rd Oct., 1893
Complete Specification Left, 21st July, 1894-Accepted, 22nd Sept., 1894
Differential Speed Indicators.
I SIDNEY ALEXANDER HOUGHTON of 2 Broadfield Villas, Colwall, in the
County of Hereford, Engineer in the Royal Navy do hereby declare the nature
of this invention to be as follows:-
My invention has for its object the indication of the difference of the number of
revolutions of marine engines in twin screw ships, but it is also applicable to all
kinds of engines or machines whose relative speed it is desired to ascertain.
A differential speed indicator according to my invention consists of three
elements, namely, two cog wheels, (called hereafter A & B), revolving inde-
pendently about the same axis, and of different sizes, and an arm or disc capable
of revolving about the same axis and carrying a shaft parallel to that axis, on
which are mounted either one or two cog wheels of such size as constantly to
engage the wheels A and B.
In its simplest form one of the first wheels (A) is of large size with internal
teeth, and only one wheel on the revolving shaft will be necessary, which will gear
into both cog wheels A and B. The latter wheels are driven by the respective
engines, at certain ratios of their speeds, by means of straps or ropes or suitable
gearing, these ratios being so proportioned to the sizes of the wheels A and B,
that when the engines are revolving at the same speed the arm or disc will remain
stationary; then if one engine moves faster than the other, the arm or disc will
revolve at a rate proportional to the difference of speed of the engines. The arm
or disc may be driven from one engine, and one of the wheels A or B by the
other, under which circumstances the movement of the remaining wheel will indicate
the difference of speed.
Both the wheels A and B may have external teeth, in which case two wheels,
connected together, on the revolving shaft will be necessary, of sizes proportional
to the difference of the sizes of A and B, one wheel gearing into A and the other
into B.
In both cases the movements of the indicating wheel or disc may be either
shewn directly, or increased or diminished by gearing connecting it to a pointer or
revolving disc, and by proper graduations the actual difference of revolutions in
a given time may be ascertained.
.
It is evident that if, instead of one engine, one of the wheels be driven at a
constant speed by clockwork or other means, then the indicating wheel will shew
how much the speed of an engine or machine varies from a fixed number of
revolutions or strokes.
Dated this 21st day of October 1893.
.

page_text: The size of the worm wheels H₁, H,, or the gearing for driving them, is so
proportioned that when the engines are making the same number of revolutions
the speed of a point on the pitch circles of A and B will be the same in the
arrangement shewn in Figures 1 and 2, and proportional to the diameters of
the pitch circles of the wheels C, and C, in the arrangement shewn in Figures 3
and 4. When so proportioned and the engines are making the same number of
revolutions per minute the movement of the wheels A and B will only cause the
wheel C or the wheels C, and C, to rotate on a fixed axis, and the wheel or arm D.
(and consequently the pointers N, and N,), will remain stationary, but if the speed
of one engine be greater than the other the wheel or arm D and the pointers N₁
and N, will revolve in one direction or the other at a speed proportional to the
difference of speed of the engines. Hence the. difference in the number of
revolutions of the main engines in a given time may be ascertained by noting the
distance the pointers have moved in the same time.
The wheel or arms D may be driven by one of the engines instead of one of the
wlicels A or B, in which case the remaining wheel may be made to indicate the
difference of speed of the engines. Although the pin or shaft E is shewn as
carried by a wheel in Figures 1 and 2, and by an arm in Figures 3 and 4, yet
either can be fitted to each arrangement, and similarly the motion of D can be
shewn directly or increased' or diminished in each arrangement, and the pointers N,
and N, fitted either to the central axis or a secondary one as may be most desirable.
Also though the indicator is shewn as being fitted to the midship bulkhead, yet it
may be fitted in any other convenient position either on a bulkhead or otherwise.
Brackets or standards may be used to support the shafts, either with or without
a casing, and bevel wheels or other suitable means to rotate the wheels A and B
may be employed instead of the worms H₁ and H,, and the worm wheels G₁
and G,
1
If instead of being driven by one engine one of the wheels be moved at a
constant speed by clockwork or other suitable means, then the indicator will shew
whether the speed of an engine or machine varies from a fixed number of
revolutions or strokes.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is
1. In à differential speed indicator, the combination of two toothed wheels,
revolving round the same axis, one having external and one internal teeth, driven
by the respective engines or machines, and a third wheel gearing into both the
aforesaid wheels, and rotating round a secondary axis capable of motion round the
first mentioned axis, substantially as set forth.
2. In a differential speed indicator, the combination of two toothed wheels with
external teeth and of different diameters, revolving round the same axis, driven
by the respective engines or machines, and two other wheels connected together,
gearing into the aforesaid wheels and rotating round a secondary axis capable of
motion round the first mentioned axis, substantially as set forth.
3. In a differential speed indicator, the combination of a toothed wheel and an
arm or wheel revolving round the same axis and driven by the respective engines
or machines, the said arm or wheel carrying on a secondary axis a toothed wheel
gearing into the first mentioned wheel and also into a third toothed wheel mounted
on the first mentioned axis, either the first or third wheel having internal teeth,
substantially as set forth.
4. In a differential speed indicator, the combination of a toothed wheel and an
arm or wheel revolving round the same axis and driven by the respective engines
or machines, the said arm or wheel carrying on a secondary axis two toothed wheels
connected together, one gearing into the first mentioned wheel, and the other into
a third toothed wheel mounted on the first mentioned axis, the first and third
wheels being of different diameters, substantially as set forth.

page_text: 5. The combination with a differential speed indicator of clockwork or other
means of revolving one of the wheels, heretofore described as driven by one of the
-engines, at a constant speed, for the purpose of shewing if the speed of an engine
or machine varies from a fixed number of revolutions or strokes.
6. The combination and arrangement of parts substantially as described and
illustrated in Figures 1 and 2 of the drawings hereto annexed.
7. The combination and arrangement of parts substantially as described and
illustrated in Figures 3 and 4 of the drawings hereto annexed.
Dated this 20th day of July 1894.
SIDNEY ALEXANDER HOUGHTON.