Improvements in Indicators for Steam Engines.
Year: 1892

page_text: Date of Application, 23rd Dec., 1892-Accepted, 18th Feb., 1893
COMPLETE SPECIFICATION.
Improvements in Indicators for Steam Engines.
I, JAMES LEWIS ROBERTSON, of 45 Cortland Street in the City, County and
State of New York, U.S.A., Mechanical Engineer, do hereby declare the nature of
this invention and in what manner the same is performed, to be particularly
described and ascertained in and by the following statement :-
This invention relates to improvements in pressure indicators for steam engines
and it consists in the combination and arrangement of parts, whereby the pressure
of steam is indicated upon the indicator card in the form of an arc instead of a
straight line. It consists also in the novel arrangement and combination of parts
hereinafter set forth and claimed.
In the drawings
Figure 1 is a side elevation of the improved indicator certain parts of which are
shown in section.
Figure 2 is a vertical transverse section of the drum carrying the indicator card.
In the drawings a represents the tube or the shell of the indicator, the lower end
of which bis threaded to attach it to the engine. The upper end of the tube or
shell a is enlarged or chambered as at c. In this chamber is placed a piston d, the
rode of which projects through the screw cap at the top of the chamber. A spiral
spring g is interposed between the cap and the upper end of the piston d and around
the rod e. This spiral spring 9 tends to force the piston down against the expansion
force of the steam entering the chamber through duct . Supported on a collar i
of the chamber a is placed the bracket ; and held in position by a check nut k. At
the free end of this bracket and fitted to rotate on the vertical rod is placed the
grooved pulley m having the flange n on its upper surface to which flange the
drum o, carrying the indicator card, is secured. Above the pulley m and around
the vertical rod and within the flange n is placed the helical spring p which is
held in position by the disk 9 and hub r to which hub one end of the helical
spring p is secured, the other end being secured to the flange n. A thumb nut s
turning on a threaded portion of the vertical rod serves to hold the disk in
place.
q
The upper end of rod passes through a downwardly projecting sleeve t in the
top of the drumo and is screw threaded thereto and provided with the thumb nut .
The vertical rod is provided at its lower end and below the bracket j with a thumb
nut between which and the bracket j is secured the arm w. To the outer end of
the arm to is secured by thumb nut to the adjustable block z, and pulley y.
A flexible binding strip z is placed vertically on the drum o to confine the
indicator card to the drum.
At the upper end of tube a between the collar a' and the cap h¹ is placed the
sleeve a adapted to rotate upon said tube a. The sleeve a is provided at one
side with a projecting arm and handle a³ and on the opposite side with an arm a',
adapted to engage a vertical stop pinj, extending upwards from the bracket j.
The pencil lever a' is pivoted at one end a to the arm a extending above the
arm a and is also pivoted at a to the upper end of arm a, which in turn is pivoted
at its lower end to the top of the piston rod e.
The free end of the lever a³ carries
the pencil b' adapted to press upon and mark the indicator card on drum o.
The lower end of arm a' is pivoted to the lower end of the arm 6* which is
secured to the arm a³, being adjustable vertically thereon by means of the thumb
nut 63. The upper end of the arm 6' is provided with a friction roll adapted to
engage a small cam 6 on the lever a³.
Depending from the pulley m is a stop pin n¹ adapted to engage a vertical stop
pin n extending above the bracket j.

page_text: A stop cock 66 is fitted to the tube a so that steam may be admitted or excluded
from the indicator at will.
The operation is as follows. Steam is allowed to enter the tube a by turning the
stop cock 6. The drum o is connected by cord m' by any suitable reducing motion
with the cross-head of the engine piston. The indicator card is then secured to the
drum o and the pencil lever a turned by the sleeve a² until the pencil touches the
card, the stop pins a and ¹ limiting the rotation of the sleeve. The steam acting
upon the piston d forces the rod e upward thus the pencil lever a³, which will
indicate upon the card by means of a line the height due to the pressure of the
steam. The drum o being at the same time uniformly rotated by its cord m³, the
area thus produced is equally accurate with that produced by straight line motion
and may be as readily and accurately measured by the planimeter.--
As the drum o rotates the helical spring p is wound and unwound thus producing
a uniform tension upon the cord m' through pulley m and hence prevents the
reducing motion from becoming irregular and distorting the diagram.
The pencil lever as being pivoted at a and a³ and being provided with a cam 6³
engaged by the friction roll of arm 62 which arm is vertically adjustable, a
uniform tension is given to said lever and all back play between the pencil and the
piston is thereby avoided.
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 the piston rod e, the vertically extending arm a pivoted
thereto, the pencil lever a having the cam and being pivoted to said arm a and
at its end to a vertically extending arm a arranged to one side of said piston rod,
with the adjustable and upwardly extending rod and its friction roller b', said
arm a being pivoted at its lower end to said rod 62, and said friction roller 64 being
adapted to engage the cam 6 on lever a substantially as described.
2. The combination of the rod, the pulley m and the drum o, with the helical
spring p, disk and its hub r, said disk and hub being secured to said rod / and
said spring being attached at one end to said hub r and at to other end to
pulley m, substantially as described.
3. The combination of the tube a piston d and its rod e, with the pencil lever aª
having cam band pivoted to a vertically extending rod a which is also pivoted to
the rod e, said lever a being also pivoted at one end to the arm a', and with the
rod and friction roller, said arm a' being pivoted at its lower end to said
rod 62 and said roller being adapted to engage the cam of lever a³ and with the
rotating drum, pulley m disk g, hub r, and helical spring p secured to said hub
and to the pulley m, substantially as described.
Dated this 23rd day of December 1892.
J. P. BAYLY,
18, Fulham Place, W., Agent for the Applicant.