Improvements in Steam Engine Indicators.
Year: 1899

page_text: Date of Application, 20th Dec., 1899
Complete Specification Left, 20th Sept., 1900-Accepted, 10th Nov., 1900
PROVISIONAL SPECIFICATION.
Improvements in Steam Engine Indicators.
I, JOHN CLARK DOBBIE, of 45, Clyde Place, in the City of Glasgow, Nautical
Instrument Maker, do hereby declare the nature of this invention to be as
follows:-
This invention relates to steam engine indicators and more especially those of
the type described in the Specification of my Patent No. 11026 of 1898; and it
has for its object to improve the construction and lessen the weight of the moving
parts of such indicators so as to render them more sensitive.
To that end I form the overhanging arm and preferably also the back stay,
radius link and other moving links connected thereto of aluminium or similar
light metal or alloy, and I form the pin joints or other parts on which the arm.
and links oscillate of steel or other hard metal the pins being of hard metal and
the orifices through which they pass being lined or formed with bushes of hard
metal to withstand wear.
I also make the piston and piston rod by preference in a single piece which is
turned down to form two or more disc-like pistons at one end and is reduced in
diameter to form the piston rod throughout the remainder of its length and this
piston rod may be bored out to lighten it. The discs are or may be cupped or
turned with a lip or flange to fit the cylinder of the indicator, and one of these
discs fits the cylinder steam tight whist the other or others may serve as a guide
or guides and may be perforated for further lightness and to allow of the passage
of grit into the space between the discs.
1011
1
1000
WALLACE FAIRWEATHER,
Of the Firm of Cruikshank & Fairweather,
Chartered Patent Agents, 62, Saint Vincent Street, Glasgow,
Agent for the Applicant.
I, JOHN CLARK DOBBIE, of 45, Clyde Place, in the City of Glasgow, Nautical
Instrument Maker, 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:-
This invention relates to steam engine indicators and more especially those of
the type described in the Specification of my Patent No. 11026 of 1898; and it

page_text: has for its object to improve the construction and lessen the weight of the moving
parts of such indicators so as to render them more sensitive.
The invention is illustrated by the accompanying drawings, Fig. 1 being a part
elevation and part vertical section of the improved parallel motion and piston, and
Fig. 2 a cross section of a part of the parallel motion shewing the method of
jointing the same.
.
In carrying out the invention I form the overhanging pencil arm A and pre-
ferably also the back stay B, radius link C and other moving links connected
thereto of aluminium or similar light metal or alloy, and I form the pin joints or
other parts on which the arm and links oscillate of steel or other hard metal the
pins being of hard metal and the orifices through which they pass being, as shewn
at Fig. 2, lined or formed with bushes of hard metal to withstand wear.
I also make the piston D and piston rod 1¹ by preference in a single piece which
is turned down, as shewn at Fig. 1, to form two or more disc-like pistons 12, 13,
at one end and is reduced in diameter to form the piston rod 1 throughout the
remainder of its length, and this piston rod may be bored out to lighten it. The
discs are or may be cupped or turned, as shewn, with a lip or flange to fit the
cylinder of the indicator, and one of these discs fits the cylinder steam tight
whilst the other or others may be an easy fit and serve as a guide or guides and
may be perforated for further lightness and to allow of the passage of grit into
the space between the discs.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. A steam engine indicator having its pencil arm, back stay, radius link and
other moving links constructed of aluminium or similar light metal or
alloy and
bushed at their joints with steel or other hard metal liners working on pins of
similar metal, substantially as and for the purpose set forth.
2. A steam engine indicator having its piston composed of two or more discs
substantially as and for the purpose set forth.
3. A steam engine indicator having its piston composed of two or more discs and
its piston rod hollow substantially as and for the purpose set forth.
Dated this 19th day of September 1900.
WALLACE FAIRWEATHER,
Of the Firm of Cruikshank & Fairweather,
Chartered Patent Agents, 62, Saint Vincent Street, Glasgow,
Agent for the Applicant.