An Improved Attachment for Indicators for Steam or other Engines.
Year: 1885

page_text: PROVISIONAL SPECIFICATION.
An Improved Attachment for Indicators for Steam or other
Engines.
I, JAMES ATKINSON of No 3, Nassington Road, Hampstead, London, N.W.
Engineer, do hereby declare the nature of my invention for AN IMPROVED
ATTACHMENT FOR INDICATORS FOR STEAM OR OTHER ENGINES to be as follows:―
Steam engine Indicators are almost always fitted with gear to multiply the
movement of the piston and give an increased pencil movement; this gear consists
of various arrangements of levers and joints which have to work with perfect ease
and freedom and in consequence there is usually some slackness in some of the
working parts, which distorts the figure given by the indicator; this, although it
may not be a very serious amount when the Indicator is new and well fitted,
rapidly becomes so as wear takes place and with the high pressures now commonly
used is sometimes the source of serious errors. The improved attachment is for
the purpose of taking up the slack of all the joints and levers and consists by
preferrence of a small spiral spring so arranged as to put a practically constant
pressure on some part of the system of levers sufficiently strong to over come the
friction and to take up all slackness thus giving a true figure and preventing any
distortion from this cause.

page_text: An Improved Attachment for Indicators for Steam or other
Engines.
I, JAMES ATKINSON, Engineer, of 3 Nassington Road, Hampstead, London N.W.
do hereby declare the nature of my invention for AN IMPROVED ATTACHMENT FOR
INDICATORS FOR STEAM OR OTHER ENGINES and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement: -
Steam engine Indicators are almost always fitted with multiplying gear to
multiply the movement of the piston and give an increased pencil movement; this
gear consists of various arrangements of levers and joints which have to work with
perfect ease and freedom; and in consequence there is usually some slackness in
some of the working parts which distorts the figure given by the indicator; this,
although it may not be a very serious amount when the indicator is new, well
fitted and properly adjusted, rapidly becomes so as wear takes place, and with the
high pressures and quick speeds now commonly used is sometimes the source of
serious errors. The improved attachment is for the purpose of taking up the slack
of all the joints and levers; it consists by preference of a small spiral spring so
arranged as to put a practically constant pressure on some part of the system of
levers sufficiently strong to overcome the friction and to take up all slackness,
thus giving a true figure and preventing any distortion from this cause.
The spring may be arranged in various ways, as may be most suitable for
different descriptions of multiplying levers. Fig. 1. shows a method of attaching
it to the parallel motion very commonly used in indicators. The small coil
spring 1 is attached to the working centre 2. in such a manner that the upward
pressure of the end 3. of the spring 1. always tends to raise the system of levers
with a practically constant pressure sufficient to take up all slackness or backlash
in the joints 2. 4. 5. 6. 7. 8. 9. The inner end of the spring 1. may be attached to
a ratchet wheel held by a pawl as shown, for the purpose of adjusting the pressure
the part 3 shall put on the lever.
Fig. 2 shows an application to Dark's indicator in which the spring 10. is
attached to an arm 11 fixed to the transmitting lever 12. In this arrangement the
leverage of the spiral spring when the pencil is at the bottom is smallest when the
pull of the spring is strongest, as the pencil rises the pull of the spring is reduced,
but acts with an increased leverage so that the upward pressure when taken at the
vertical movement of the pencil is practically uniform. The pull of the spring 10.
takes up the slackness of the joints 13. 14 and 15 and any slackness in the sliding
sleeve 16, a number of holes 17 are placed in the horizontal arm for the purpose of
regulating the tension of the spring 10.
Fig. 3 shows a modification in which the spring 20 puts a downward pressure
on the pencil arm of the lever. The spring 20 is made strong enough to keep the
pencil arın in contact with the upper end 21 of the indicator piston rod and so
eliminate the joints 13. 14 and the sliding sleeve 16 as shown in Fig. 2.

page_text: I wish it to be understood that the application of this invention may be varied
to suit any type of indicator in which the movement of the piston is multiplied by
a lever, or system of levers and joints; and the arrangements I have shown may be
modified to suit different constructions of indicators.
When the piston rod is disconnected from the pencil lever, or levers, in
arrangements similar to Figs. 1. and 2. the system of levers is drawn up to the
top clear of being injured if pressure is put on the piston when they are
disconnected.
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
•
The application of a. spring (or springs) which takes up the slackness of the
joints and causes the pencil to register pressures on the diagram which will
correspond with the position of the piston in the cylinder of the indicator as
described and illustrated in Figs. 1 2 and 3 or any mere modification thereof.