Improvements in Expansion Gear for Fluid Pressure Engines.
Year: 1893

page_text: Date of Application, 5th Jan., 1893
Complete Specification Left 4th Oct. 1893 Accented 4th Nov.. 1893
PROVISIONAL SPECIFICATION.
Improvements in Expansion Gear for Fluid Pressure Engines.
We, THOMAS WALKER of Oldbury Works, Tewkesbury, in the County of
Gloucester, Engineer, and GEORGE FREDERICK ALDER of Tudor Place, Barton
Street, Tewkesbury aforesaid, Draughtsman, do hereby declare the nature of this
invention to be as follows:-
This invention relates to improvements in trip expausion gear suitable for fluid
pressure engines such as steam engines having steam admission valves of the
Corliss type but applicable also to engines having lift or slide valves.
In expansion gear according to this invention the admission valves are each
opened against the action of a spring by a rod formed with a tooth or projection
that is normally held in engagement with a corresponding tooth or projection
on a suitably operated wrist plate by a spring and is disengaged from this plate at
the required times to enable the valve to be closed by its spring, by a plate (herein-
after called the trip plate) provided with a step or projection adapted to act upon
a suitable projection on the valve rod and the position of which is controlled by the
governor of the engine. The trip plates, one for each valve rod, are arranged to
be moved in opposite directions by the action of the governor. This may be done
by actuating each of them independently from the governor or by employing
suitable reversing mechanism.
In an arrangement of expansion gear for a fluid pressure engine fitted with
rotary valves of the Corliss type, the trip plates are in the form of sectors mounted
to rock about the same axis as the wrist plate and actuated in opposite directions
by tooth sectors that are in gear with a toothed wheel placed between them and
one of which is connected with the engine governor the arrangement being such
that when one trip plate is moved by the governor in one direction the other trip
plate will be moved in the opposite direction. The wrist plate is placed between
the trip plates and is operated by an eccentric and rod. For the purpose of
reducing friction, suitable means, such as an anti-friction roller, may be interposed
between the projection on each valve rod and the step or projection on the corre-
sponding trip plate. Each valve rod is jointed to a lever arm fixed to the spindle
of the corresponding admission valve and is normally held in gear with the wrist
plate by a spring arranged between the rod and the lever arm.
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The admission valves may be each closed when released by the corresponding
trip plate, by an independent spring and gear; or one spring may be used for
closing both admission valves. In an arrangement for this purpose the spindle of
each admission valve is connected by a lever arm and rod to a pistón (hereinafter
called the outer piston) arranged to slide in a guide and connected by one or more
rods to a second piston (hereinafter called the inner piston) against which bears one
end of a coiled spring the other end of which bears against another inner piston
similarly connected to the outer piston of the other admission valve. The
arrangement is such that each inner piston serves alternately as a support for
the coiled spring whilst the same is being compressed by the other inner piston.
The inner pistons and coiled spring may be enclosed within a box. The spaces
between the ends of this box and the outer pistons may serve to contain air or other
suitable cushioning medium for the outer pistons.
The exhaust valves are or may be operated from the wrist plate in the ordinary
manner.
Dated this 5th day of January 1802

page_text: COMPLETE SPECIFICATION.
Improvements in Expansion Gear for Fluid Pressure Engines.
We, THOMAS WALKER of Oldbury Works Tewkesbury, in the County of
Gloucester, Engineer, and GEORGE FREDERICK ALDER of Tudor Place, Barton
Street, Tewkesbury aforesaid, Draughtsman, 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 trip expansion gear suitable for fluid
pressure engines such as steam engines having steam admission valves of the Corliss
type but applicable also to engines having lift or slide valves.
In expansion gear according to this invention the admission valves are each
opened against the action of a spring by a rod formed with a tooth or projection
that is normally held in engagement with a corresponding tooth or projection on a
suitably operated wrist plate by a spring and is disengaged from this plate at the
required times to enable the valve to be closed by its spring by a plate (hereinafter
called the trip plate) provided with a step or projection adapted to act upon a
suitable projection on the valve rod and the position of which is controlled by the
governor of the engine. The trip plates, one for each valve rod, are arranged to
be moved in opposite directions by the action of the governor. This may be done
by actuating each of them independently from the governor or by employing
suitable reversing mechanism.
In an arrangement of expansion gear for a fluid pressure engine fitted with rotary
valves of the Corliss type, the trip plates are in the form of sectors mounted to
rock about the same axis as the wrist plate and actuated in opposite directions by
tooth sectors that are in gear with a toothed wheel placed between them and one of
which is connected with the engine governor the arrangement being such that when
one trip plate is moved by the governor in one direction the other trip plate will
. be moved in the opposite direction. The wrist plate is placed between the trip
plates and is operated by an eccentric and rod. For the purpose of reducing
friction suitable means such as an antifriction roller may be interposed between the
projection on each valve rod and the step or projection on the corresponding trip
plate. Each valve rod is jointed to a lever arm fixed to the spindle of the corre-
sponding admission valve and is normally held in gear with the wrist plate by a
spring arranged between the rod and the lever arm.
The admission valves may be each closed when released by the corresponding
trip plate, by an independent spring and gear; or one spring may be used for closing
both admission valves.
In an arrangement for this purpose the spindle of each admission valve is
connected by a lever arm and rod to a piston (hereinafter called the outer piston).
arranged to slide in a guide and connected by one or more rods to a second piston
(hereinafter called the inner piston) against which bears one end of a coiled spring
the other end of which bears against another inner piston similarly connected to
the outer piston of the other admission valve. The arrangement is such that each
inner piston serves alternately as a support for the coiled spring whilst the same is
being compressed by the other inner piston. The inner pistons and coiled spring
may be enclosed within a box. The spaces between the ends of this box and the
outer pistons may serve to contain air or other suitable cushioning medium for the
outer pistons.
The exhaust valves are or may be operated from the wrist plate in the ordinary
manner.
In order that our invention may be better understood we proceed to describe the
annexed drawings.
Fig. 1 is a general elevation of the valve gear as applied to a horizontal engine.

page_text: 4 18 a cross section or same through the wrist and trip plates.
Figs. 3 and 4 show an elevation and plan of wrist plate...
Fig. 5 is an elevation of a trip plate.
Figs. 6 and 7 show a part elevation and part plan of valve rod with the
antifriction roller attached.
Fig. 8 is a sectional elevation of spring box.
Fig. 9 is an end view of one form of reversing arrangement to trip plates with
bracket for attaching to cylinder side or other suitable part of engine.
All the figs. on Sheet 2 of drawings are shown upon a larger scale than those on
Sheet 1.
The action of the gear is as follows:-
-
The wrist plate A is given a rocking motion through the rod B, on the
periphery of the wrist plate A is formed projections A' A which serve as catches
capable of engaging with corresponding projections C¹ on the valve rods C.
The wrist plate A on arriving at the end of its stroke engages with one of the
valve rods C and on the return stroke draws with it the said rod C thus opening
the steam valve. The valve rod C is normally held in engagement with its
corresponding tooth or projection A¹ or A2 on the wrist plate A by the spring D
which is so attached to the lever arm E of the valve spindle that the spring D
presses most upon the valve rod C when it first becomes engaged with the wrist
plate A and least when disengagement takes place. The ends of the valve rods C
may be weighted at the ends nearest the projections C¹ so as to dispense with the
spring D.
The valve rods C are released from the wrist plate A by the rollers F or suitable
projection in lieu thereof coming into contact with a step or projection G on the
periphery of the trip plate H and H which causes the end of the valve rods C to
rise off or move away from the wrist plate A and thus becoming disengaged, the
valve rod C is drawn back again to its normal position by the spring I with its
attendant rods and lever arm E' attached to the valve spindle and thus by this
operation closing the valve.
The trip plates H and H', one for each valve rod, are actuated by and are under
control of the engine governor. They are shown in the drawing to be operated by
means of one rod J from the governor connected to the bell crank lever K and
from this lever K another rod L is connected to the front trip plate H, the
second or back trip plate H¹ being connected to another lever M by a rod N shown
in Figs. 2 and 9 the lever M being attached to the toothed sector O which receives
its movement from the lever K by means of the toothed sector P and bevel
wheel Q. The result of this arrangement is that when the governor rod J moves
the front trip plate H in one direction the back trip plate H¹ is moved in a reverse
direction.
On the lower lever of the bell crank lever K is a jointed rod K¹. which
communicates with a dash pot not shown.
The reversing action to the trip plates H and H¹ may be obtained in any suitable
and more than one rod may be used direct from the governor.
way
The trip plates H and H are made to move about the same axis as the wrist
plate A and are so designed as to keep the ends of the valve rods C at the same radius
as the periphery of the wrist plate A and also to a great extent divert the thrust
of the trip away from the governor so as to enable the governor to act more
sensitively.
In the arrangement of the spring box shown in Fig. 8 the coil spring I is made
to close both admission valves alternately. The action is such that when the outer
piston R is drawn out by the movement of the valve rod C the inner piston S
farthest away from the moving outward piston R is drawn with it and thereby
compresses the coil spring I against the other inner piston S, the inner and outer
pistons being held together by means of suitable rods such as T T' T'.
We do not bind ourselves to the exact details shown in the accompanying
drawings as these may be modified to suit various classes of engines.

page_text: +
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
'
1. The combination of steam or other admission valve gear having a wrist plate
with projections such as A¹ and A³ on its periphery for the purpose of drawing
with it the valve rods C so as to open the admission valves, the trip plates H and H
having a projection on each such as G for the purpose of releasing the valve rod C
from the wrist plate A the said trip plate being actuated by the engine governor
and moved upon or about the same axis as the wrist plate, the valve rod C and with
it the spring D or other means specified for holding it in contact with the wrist
plate all constructed and operating substantially as hereinbefore described and
illustrated or any mere modification thereof.
2. In a valve gear wherein is used such mechanism as shown in Fig. 8 of the
annexed drawings where one coil spring is used for closing both admission valves
substantially as described and illustrated.
3. The reversing mechanism for actuating the trip plates H and H¹ substantially
as described and shown in Figs. 1 and 9.
Dated this 3rd day of October 1893.
THOMAS WALKER.
GEORGE FREDERICK ALDER.