Improvements in Automatic Expansion Gears for Steam and other Engines.
Year: 1892

page_text: Date of Application, 24th Mar., 1892
Complete Specification Left, 16th Nov., 1892-Accepted, 31st Dec., 1892
PROVISIONAL SPECIFICATION.
Improvements in Automatic Expansion Gears for Steam and other
Engines.
1, ROBERT MILLAR of 44 Lancaster Street, Borough Road S.E. in the County
of Surrey, Engineer, do hereby declare the nature of this invention to be as
follows:-
The automatic gear consists of a steel, or other metal cam, fitted to a governor,
upon the rising joint, or sleeve, with one or more projecting cams, actuating or
working a roller lever, with necessary or suitable rods and connections actuating a
double beat or other valve, opening and shutting off steam from the engine cylinder
at each half stroke of the engine, automatically to the amount of work required at
the time.
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1000
COMPLETE
SPECIFICATION.
Improvements in Automatic Expansion Gears for Steam and other
Engines.
1, ROBERT MILLAR of 44 Lancaster Street Borough Road, S.E., in the County
of Surrey, Engineer do hereby declare the nature of my invention for IMPROVE-
MENTS IN AUTOMATIC EXPANSION GEARS FOR STEAM AND OTHER ENGINES and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
The automatic expansion gear herein described is illustrated in Figs. 1 & 2 of
the drawings attached hereto.
Fig. 1 is a general elevation showing the arrangement adopted in ordinary
inverted cylinder engines, and Fig. 2 shows a suitable form of cam.
This automatic expansion gear is preferably supplementary to the ordinary slide
valve or valves of the engine, and acts only on the steam entering the valve box or
steam chest. In Fig. 1, the steam cylinder of the engine is partly shown at A,
with a steam chest B, while Q is the crank shaft and T the bed plate. On the
steam inlet of the steam chest B, a valve box C is attached, having a connection
from the main steam pipe at D. The valve box C is fitted with a suitable form of
valve, preferably of the double beat type, which is operated by the valve rod E,
bell crank F, and coupling rod G. This coupling rod G is connected to a lever H,
pivotted at its lower end in the bracket K, and carrying at its upper end a roller L.
The roller L is actuated by a cam M (also shown in plan in Fig. 2) which is fixed
to the governor sleeve, rising and falling with the sleeve in the usual well known
manner. The governor spindle N, runs in a footstep R, carried by a bracket S,
and is driven by bevel or mitre wheels O & P, from the engine crank shaft Q. If
the spindle N run at the same speed as the crank shaft Q, the cam M will have
two projections at opposite portions of its periphery, so that two openings (and
dead cuts-off) of the supplementary valve are given for each revolution of N & Q.
The spindle N may run at any other convenient speed; for instance if N run twice
the speed of the shaft Q the cam will have one projection, if N run at half the
speed of the cam will have four projections, and if N run at two thirds the speed
of Q the cam will have three projections. These projections on the cam M have
their maximum height and length at the top of the cam, and will gradually taper
down to the bottom of the cam, where they will die entirely into the general
I Price 8d l

page_text: cylindrical body of the said cam, or be so short (when measured on the periphery)
that only a momentary opening of the valve is obtained. When the governor is
down, therefore, and the engine running slow, the supplementary valve will be
opened to its fullest extent, and for the longest time; but when the governor is up,
and the engine running with a light load, little or no movement will be given to
the said valve, and such movement will be of short duration, occurring at the
beginning of the stroke of the engine, and ceasing immediately afterwards. It
will be readily seen that this gear can be adapted to any form of motive power
engine, where such an arrangement is desirable; and two cams can be made to
operate a supplementary valve at each end of the cylinder. Any suitable form of
governor, or positive method of driving the cam, may be employed. The roller L
can be fixed on the governor sleeve, and a hollow cam, partial cam or similar
device, be carried by one or more levers, to produce the same effect as previously
described.
The cam M may be driven independently of the governor, so that the said
governor may run at a different speed to the cam, or in a different position com-
paratively therewith. Suitable connecting gear would then be necessary between
the governor and cam, to control the movement of the said cam as hereinbefore
described. The action of the cam may act direct on the valve rod E, without the
intervention of the bell crank F, rod G and lever H, such modifications being made
in these connections, as will be necessitated by the type of engine, and relative
position of the various parts. The arrangements of this gear as described, can be
applied to a main inlet valve of similar type to that previously referred to.
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 which I
claim is :-
A cam, or cams (or the equivalent thereof) having a suitable number of pro-
jections thereon, driven from the motor shaft and controlled and actuated by a
governor, for automatically opening and closing a dead beat or simple valve, or
valves, substantially as described.
Dated this Fourteenth day of November 1892.
G. T. HARRAP,
Agent for Applicant.