Improvements in Engine Indicators.
Year: 1887

page_text: Date of Application, 26th Nov., 1887
Complete Specification Left, 25th Aug., 1888
Complete Specification Accepted, 28th Sept., 1888
Improvements in Engine Indicators.
I, THOMAS STRUTHERS MINNES of 8 Buchanan Street, Glasgow, in the County of
Tanark, Watchmaker, do hereby declare the nature of this Invention to be as
follows:-
The engine indicator constructed in accordance with this Invention consists of a
cylinder the end of which in communication with the steam stop cock instead of
forming a contracted neck as usual is of the full bore or nearly of the full bore of the
The lower
cylinder whereby the cylinder is more easily cleaned out when necessary.
end of the usual spring at the interior of the cylinder is brought in to the centre of
the upper side of the piston where it is so connected that the force is applied to a
point in the centre of the spring instead of being distributed over the whole area.
The cylinder has two arms or brackets one of which projects vertically and the other
horizontally. In the upper end of the vertically projecting bracket a horizontal rod
is supported and on the said rod the arm carrying the indicator pencil is centred, the
rear end of the said arm being connected to the upper extremity of a radius rod
centred on the horizontal bracket projecting from the side of the cylinder.
piston rod is also connected by a link to the horizontal rod and the effect of this
arrangement is that the pencil in making the indications moves in a straight path
vertically instead of through an arc as with ordinary indicators.
The
The spring of the drum carrying the paper on which the indications are marked
is under this Invention provided with a catch whereby some of the coils of the spring
may be shut or cut off from action. In indicating slow speeds the full length
of the spring is or may be used but in indicating higher speeds some of the coils of
the spring are or may be shut off by the catch to cause the spring to give a more
rapidly increasing tension against the pull of the cord the object being to reduce
the error caused by the momentum of the drum at high speeds. The cord rotating
the drum of the improved indicator has preferably a strand or strands of wire woven
or twisted into it to prevent stretching and it is provided with an adjustable clip of
any suitable construction which in the event of the drum rotating backwards comes

page_text: against the pulleys guiding the cord and stops the motion. In the indicator two
drums may be provided for the purpose of taking continuous diagrams the paper as
it is wound off one drum being coiled on the other.
The moving parts of the apparatus are preferably made of aluminium or of alloy
thereof and the lubricant used is preferably glycerine.
To prevent the operators' fingers being scorched or burned in taking off the
indicator from the engine a portion of the cylinder is sheathed with wood or other
nonconducting material the instrument being held by the sheathed part in
removing it.
Daied this 25th day of Nauswbar 1887

page_text: [, THOMAS STRUTHERS MINNES of 8 Buchanan Street, Glasgow, in the County of
Lanark Watchmaker 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:-
The engine indicator constructed in accordance with this Invention consists as
represented in the accompanying drawings in vertical section at figure 1 and in
elevation at figure 2 of a cylinder A the end A' of which in communication with the
steam stop cock instead of forming a contracted neck as usual is of the full bore or
nearly of the full bore of the cylinder whereby the cylinder is more easily cleaned
out when necessary. The lower end of the usual spring B at the interior of the
cylinder is brought in to the centre of the upper side of the piston (where it is
connected as indicated at figures and 1", by screwing on to a central pin
c on the
piston an internally screwed coil of the spring so that the force is applied to a point
in the centre of the spring instead of being distributed over the whole area.
ring Dat the upper end of the cylinder has two arms or brackets one E of which
projects vertically and the other F horizontally. In the upper end of the vertically
projecting bracket E a horizontal rod or lever G is supported and on the said rod or
lever the arm H carrying the indicator pencil is centred, the rear end of the said arm
being connected to the upper extremity of a radius rod I centred on the horizontal
bracket F, projecting from the side of the cylinder. The piston rod C is also con-
nected by a link to the horizontal rod or lever G and the effect of this arrangement
is that the pencil in making the indications moves in a straight path vertically.
A
The spring of the drum L carrying the paper on which the indications are
marked is as indicated at figure 3 provided with a catch M whereby some of the coils
of the spring may be shut or cut off from action. This catch consists of three or
more prongs m the ends of which are adapted to engage the coils of the spring and
having on their outer sides tapered screw threads over which is passed a screw nut in¹
which may be turned to cause the prongs m to grasp the coils of the spring or to free
them. In indicating slow speeds the full length of the spring is or may be used but
in indicating higher speeds some of the coils of the spring are or may be shut off by
the catch M to cause the spring to give a more rapidly increasing tension against the
pull of the cord the object being to reduce the error caused by the momentum of the
drum at high speeds. The cord rotating the drum of the improved indicator has as
indicated at figure 4 a strand or strands of wire woven or twisted into it or run
through it to prevent stretching and it is provided with an adjustable clip N of any
suitable construction which in the event of the drum rotating backwards comes against
the pulleys guiding the cord and stops the motion.
In the indicator two drums may be provided for the purpose of taking a series of
diagrams the paper as it is wound off one drum being coiled on the other. This
arrangement is represented at figures 5 and 6, L being the usual drum and L' the

page_text: coil of paper. The drum has a slit in it and a clip fitted internally to engage
the paper which is entered through said slit. In taking one diagram the drum L'is
turned through a revolution to draw on to it a coil of paper from the drum L' and in
taking a fresh indication the drum L is again turned to draw a fresh coil of paper
over the first coil.
The moving parts of the apparatus are preferably made of aluminium or of alloy
thereof and the lubricant used is preferably glycerine.
To prevent the operators' fingers being scorched or burned in taking off the
indicator from the engine a portion of the cylinder A is sheathed as indicated at A²
with wood or other nonconducting material the instrument being held by the sheathed
part in removing it.
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. The combination of parts constituting the improved engine indicator herein-
before described with reference to the annexed drawings.
2. In an engine indicator connecting the compression spring to the piston sub-
stantially as described with reference to the drawings annexed.
3. In an engine indicator the arrangement of rods and levers whereby the
indicator pencil is caused to move in a straight path substantially as described with
reference to the drawings.
4. In an engine indicator the combination of a catch with the spring of the paper
drum substantially as and for the purpose set forth with reference to the drawings.
5. A cord for an engine indicator composed of textile material having a strand or
strands of wire woven into or enclosed within it substantially as described.
6. In an engine indicator the combination with the paper drum of a separate drum
or roll of paper whereby a series of diagrams may be taken substantially as described
with reference to figures 5 and 6 of the annexed drawings.
7. In an engine indicator partially sheathing the cylinder with non conducting
material substantially as and for the purpose set forth.
Dated this Twentyfourth day of August 188$.
CRUIKSHANK & FAIRWEATHER,
62, Saint Vincent Street, Glasgow,
Agents.