Valve Gear for Steam Engines.
Year: 1891

page_text: Date of Application, 27th Feb., 1891
Complete Specification Left, 19th Nov., 1891-Accepted, 9th Jan., 1892
PROVISIONAL SPECIFICATION.
Valve Gear for Steam Engines.
JAMES AIMERS Galashiels in the County of Selkirk, North Britain, Engineer
do hereby declare the nature of this invention to be as follows:-
27
This invention relates to improvements in valve gear for steam engines, whereby
"trip-valve gear can be worked more effectively and economically than previously
and also provides for automatically varying the point of cut-off.
This valve gear can be applied for the working of double beat valves, grid valves
upon the back of slide valves, and Corliss or oscillating valves, and is worked by
eccentrics fixed upon a shaft or shafts rotating at the same number of revolutions
per minute as the crank shaft.
The improvements relate to the admission valves and consist of a release arrange-
ment; said valves being lifted by levers, the outer ends of which are depressed by
the trips carried on the ends of the eccentric rods. The ends of the eccentric rods
are made to describe a different arc on the downward or depressing stroke than
they do on the return or upward stroke, thereby enabling the trips to loose contact
or release themselves on the return or upward stroke as well as on the downward or
depressing stroke of the eccentrics; thus providing the valve gear with a very long
range for the expansion of the steam.
The means employed for causing the eccentric rod ends which carry the trips to
describe a different arc on the downward stroke than they do on the return or
upward stroke is by jointing or hinging the eccentric rods at a point between the
trips and the eccentrics to radius links, the other ends of the radius links being
connected to levers upon a rocking shaft worked by the governor.
From this
arrangement the ends of the eccentric rods which carry the trips are also caused to
have a lateral, or outward and inward motion controlled by the governor, and when
moved in one direction cause the release to take place earlier, and when moved in
the opposite direction cause the release to take place later. The shaft or shafts
upon which the eccentrics are fixed can be kept very close to the cylinder of the
engine.
I do not confine myself to the above described method but the special feature is
the causing of the eccentric rod ends which carry the trips to describe a different
arc on the downward or depressing stroke than they do on the return or upward
stroke and giving to the ends of the eccentric rods which carry the trips a lateral,
or outward and inward motion thereby automatically causing the release to take
place earlier or later.
Dated this Twente cirth dor of Boh 1801
JAMES AIMERS.
COMPLETE SPECIFICATION.
Valve Gear for Steam Engines.
JAMES AIMERS Galashiels in the County of Selkirk, North Britain Engineer
o 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 improvements in valve gear for steam engines whereby
trip valve gear can be worked more effectively and economically than previously
and also provides for automatically varying the point of cut off.

page_text: The invention will be understood by the accompanying drawings
Figure 1 front elevation, Figure 2 side elevation, Figure 3 vertical section
through centre of valve Figure 4 plan view, Figure 5 arcs described by levers and
trippers.
This valve gear can be applied for the working of double beat valves, grid valves
upon the back of slide valves and Corliss or oscillating valves.
The drawings Figs. 1, 2, 3 and 4 shew the valve gear applied to a single double
beat valve A worked by eccentrics B which revolve in the direction shewn by the
arrow on a shaft C Figure 3 rotating at the same number of revolutions per minute
as the crank shaft. For slow or moderate speeded engines the shaft C may be
rotated at twice the number of revolutions per minute of the crank shaft, and one
eccentric, one eccentric rod, one tripper, and one lever D used instead of two of
each for single valve apparatus.
The improvements relate to the admission valves and consist of a release arrange-
ment; the valve A Figure 3 is alternately lifted by levers D and D¹ Figures 2, 3,
4 and 5 fixed upon a shaft E on which is fixed another lever F Figures 3 and 4
between levers D and D'; lever F engages with the valve spindle G between
the collars.
The ends H of levers D and D' are depressed by the trippers I Figures 2,
3 and 5 carried on the ends of the eccentric rods J Figures 1, 2, 3 and 5.
Each of the eccentric rods J are jointed or hinged at the point K to links L,
Figures 2 and 3 which are connected to the levers M fixed upon a rocking shaft N
and worked by lever O which is connected to the governor rod P Figures 1, 2,
3 and 4.
-
The rocking shaft N with its levers M and may either be placed in the
position shewn on drawings or on the other side of the eccentric rods, but I
prefer the position as shewn.
The upper ends of the eccentric rod J which carry the trippers I Figures 2,
3 and 5, are free to oscillate and describe an arc Q shewn dotted Figure 5 on
the downward or depressing stroke causing the trippers 1 to move further from
the centres of levers D and D¹ and on the return or upward stroke the ends of the
eccentric rods J which carry the trippers I describe a different are R shewn
dotted Figure 5, causing the trippers to move still further from the centres of
levers D and D¹ until they release themselves from the ends H of levers D and D'
thus permitting the valve A to fall instantly on its seat.
The usual dash pot S fitted with piston and spring is used to cushion the
valve A when it falls on its scat.
The arcs described by the trippers I are caused by the action of the eccentrics
and the eccentric rods J being jointed or hinged to the radius links L at the
points and as the radius links L are connected to the governor rod P through
the levers M and O and rocking shaft N the ends of the eccentric rods J
carrying the trippers I receive a lateral or outward and inward motion controlled
by the governor rod P which operates the lever O and when moved in one
direction cause the release to take place carlier and when moved in the opposite
direction cause the release to take place later.
This arrangement provides the valve gear with a very long range for the
expansion of the steam.
Figure 6 shews the application of this gear to a grid valve A on back of a
slide valve V.
Figure 7 shews the application to a Corliss or oscillating valve A.
In Figures 6 and 7 the valves are worked in the same manner as described
for the double beat valve Figures 1, 2, 3 and 4 and the parts of mechanism are
similarly lettered.
The shaft C can be kept very close to the cylinder of the engine.
Having now particularly described the nature of my said invention and the
mode of carrying the same into effect, I have to state that I do not restrict

page_text: myself to the precise details herein described or delineated, but what I believe
to be novel and original, and therefore claim as the invention secured to me by
the hereinbefore in part recited Letters Patent is,―
First The combination and arrangement of mechanism for actuating valves for
varying the point of cut off of steam to an engine by causing the ends of the
eccentric rods J which carry the trippers I to describe a different arc on the
downward or depressing stroke than they do on the return or upward stroke
Figures 2, 3 and 5, 6 & 7.
Second The giving to the ends of the eccentric rods J which carry the
trippers I Figures 2 and 3 a lateral or outward and inward motion substantially
as herein described in reference to the Figures 1, 2, 3, 4 and 5, 6 & 7 of the
accompanying drawings or any mere modification thereof.
Dated this Eighteenth day of November 1891.