IMPROVEMENTS IN AUTOMATIC EXPANSION VALVE GEAR FOR STEAM ENGINES AND OTHER MOTORS
Year: 1885

page_text: Fugines and other moLOTS.
I JAMES NOAH PAXMAN of the firm of Messrs. Davey Paxman & Co. of Colchester
in the County of Essex Engineers and Boiler Makers, do hereby declare the nature
of my said invention for "IMPROVEMENTS IN AUTOMATIC EXPANSION VALVE GEAR
FOR STEAM ENGINES AND OTHER MOTORS," to be as follows:-
:-
My invention relates to the valve gear of steam engines and other motors, and
has for its object the construction and arrangement of an expansion or "cut off"
gear, operated and controlled by the governor so as to be perfectly automatic in its
action, whereby the highest efficiency and duty may be obtained.
To this end I construct and arrange my gear as follows;-I fit the cylinder of
my engine with a main valve of the ordinary type as used with expansion valves.
This valve has two ports or openings through the body of the valve, and it is
operated by an eccentric on the crank shaft in the usual manner. The expansion
or "cut off valve does not work immediately on the face of the main valve, but
on a plate interposed between them, the plate being free to move to and from the
faces of the valve so that all three pieces may bed against each other; but it is not
free to move either laterally or vertically, being confined in guides in the steam
chest. The face of this plate in contact with the main valve has but one opening
and that is placed centrally, but on the face next to the expansion or "cut off".
valve it has three ports or openings, the three ports on the one side being joined
by passages with the single port on the other side. The expansion or "cut off"
valve has two ports on the face next to the intermediate plate, which pass through
the body of the valve or may join into one central opening at the back of the
valve. I do not bind myself to use but three openings on the back of the inter-
mediate plate, as four or more, may be used with equal advantage, so long as the
expansion or cut off valve is provided with one less opening or port than the
plate, as the travel of the expansion valve is arranged so that steam can pass into
the exterior ports of the plate alternately, without passing, through the valve,
while steam is passing through the ports of the valve to the other ports in the
plate. It must be understood that although the plate is placed between the two
valves it does not divide the steam chest into two sections, as the plate is cut away
and arranged so that the steam circulates all round it, and round both valves, so
that both the valves are in equilibrium.
"
The expansion or "cut off" yalve is actuated by a pair of eccentrics set at
different angles on the crank shaft, and connected by rods in the usual manner to
a link, in the slot of which is a sliding block carried by the end of the valve rod.
I call these eccentrics the "positive" and the " negative" eccentrics, the former
having the greatest lead and travel, being the one that puts the valve in operation
when the link and governor are in the bottom position. The "positive" eccentric
is connected to the top of the link and the "negative" one to the bottom of it.

page_text: The link is connected to the governor of the engine so that as the governor rises,
due to the increased speed of the engine, the link is raised and the travel of the
expansion or "cut off" valve is varied in proportion. When the governor is right
down the link is at its lowest position and the centre of the expansion valve rod is,
at mid-position of the eccentric, in a line with the "positive", eccentric rod, and
the travel of the expansion or "cut off" valve is such that the ports on the inter-
mediate plate are full open, so that the greatest amount of steam can pass to the
main valve. As the governor rises the link is also raised until at its highest
position, the centre of the expansion valve rod is at mid-position of the eccentric,
in a line with the "negative" eccentric rod, and as the travel of the "negative
eccentric is the minimum one, the expansion or "cut off" valve does not travel far
enough to admit steam to the main valve. These are the two extreme positions ;-
that is to say when the expansion valve rod is in a line with the "positive
eccentric rod, the travel of the valve opens the ports of the expansion or "cut off"
valve full, when the valve rod is in a line with the "negative" eccentric rod the
travel of the valve is such that the ports are never open.
"
دو
The governor which is of the dead weight type is constructed as follows; -
A vertical spindle is mounted in suitable bearings on any convenient part of the
frame, or bed of the engine, and is driven either directly or indirectly from the
crank shaft by any convenient method. On the vertical spindle are pivotted two
bent arins carrying at their free ends the small balls or spheres known and
designated as the governor balls. Encircling these arms is a large sphere or other
conveniently shaped metal, which rotates on the spindle and is free to rise and fall
on it. Slots are made in the large sphere so that the arms carrying the governor
balls work free in them. The arms are connected to the large sphere in the
following manner;-Small studs carrying rollers are mounted on the large sphere
so that they protrude in the slots in which the arms work. These roller studs
work in slots formed in the arms carrying the governor balls, so that as they rise
due to the centrifugal force generated by the revolving governor, they will lift
the large spere or the spindle, and owing to the fixed position of the roller studs
which lift the large sphere the fulcrum will be at the same distance from the
centre of the spindle and the leverage at which the arms work will be constant
through the rise of the governor, and consequently the slightest variation of speed
is immediately felt.
The large sphere is connected in any convenient manner to a forked lever or its
equivalent, pivotted to the support of the governor; this lever is connected to the
link of the valve gear by a rod so that the rise and fall of the governor is com-
municated directly to the link. The lift of the governor is controlled either by
means of a sliding weight mounted on the free end of the forked lever connecting
the governor with the slide link, or by an adjustable spiral spring acting directly
on the top of the large sphere, or by both these arrangements in combination..
The advantages of this system of automatic expansion gear are ;-First. There
is no reservoir in which steam can be stored up between the "cut off" valve and
the cylinder, so that no acceleration of speed can take place after the steam is
cut off. Secondly. While maintaining a lead that is uniform with the duty, the
point of cut off can be varied at any degree by the minimum travel of the slide
valve without unduly wire drawing the steam. Thirdly. The abolute quantity of
steam required for doing the duty is is admitted at each stroke so that perfect
regularity in the speed of the engine is maintained. Fourthly. By an improved
construction the load of the governor when in motion is kept constant and uniform,
so that the slightest variation of speed is immediately felt.
1
ROBT. ED. PHILLIPS, M.I.M.E.,
Agent for the Applicant.

page_text: improvements in Automatic Expansion valve Gear for Steam
Engines and other Motors.
I JAMES NOAH PAXMAN of the firm of Messrs Davey Paxman & Co Colchester,
in the county of Essex, Engineers and Boiler Makers 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:-
My invention relates to the valve gear of steam engines, and other motors, and
has for its object the construction and arrangement of an expansion or "cut off'"
gear operated and controlled by the governor, so as to be perfectly automatic in its
action, whereby the highest efficiency and duty may be obtained. To this end
I construct and arrange my gear as illustrated in the accompanying drawings in
which Figs. 1 and 2 Sheet No 1 are a side elevation and plan respectively, of a
steam engine, fitted with my improved autumatic expansion valve gear. Fig. 3
Sheet No 2 is an enlarged sectional plan of the cylinder showing the construction
and arrangement of the valves Fig. 4 Sheet No 2 is a section through the steam
chest showing the intermediate plate between the two valves, Fig. 5 Sheet No 1 is
a view showing the relative positions of the "cut off" valve eccentrics, Fig. 6
Sheet No 3 is an elevation of my improved governor, and Fig. 7 Sheet No 3 is a
sectional elevation of the governor. Referring to these figures the cylinder A of
the engine is fitted with a main valve B of the ordinary type as used with
expansion valves. This valve has two ports or openings b b through the body of
the valve, and it is operated by an eccentric X on the crunk shaft C, through an
eccentric rod x in the usual manner. The expansion or "cut off" valve D does
Dot work immediately on the face of the main valve B but on a plate E interposed
between them; this plate E is free to move to, and from, the faces of the valves B
and D so that all three pieces may bed against each other, but it is not free to
move either laterally, or vertically, being confined in guides a a in the steam chest
The face of the plate E which is in contact with the main valve B has only one
port or openinge which is formed in the centre of its length but in the face next
to the expansion or "cut off" valve D, it has three ports or openings e¹ el and e¹
which are connected with the single port e by suitable passages. The expansion or
"cut off" valve D has two ports or openings d d in the face that bears against the
intermediate plate E, which pass through the body of the valve. I do not bind
myself to use but three ports or openings in the back of the intermediate plate as
four as illustrated by Fig. 4 Sheet No 2 of the accompanying drawings, or more
may be used with equal effect, so long as the expansion or "cut off" valve is
provided with one less port or opening than there is in the back of the plate, as
the travel of the expansion valve is so arranged that steam can pass directly into
the end ports of the plate alternately without passing through the ports of the
valve, at the same time that it is passing through the ports of the valve to the
other ports in the plate. It must be understood that although the plate E is placed
between the valves B and D it does not divide the steam chest into two separate

page_text: chambers, as the plate E does not extend the whole length of the steam chest but
is carried in abutting guides as shown in Fig. 4 Sheet No 2, in order that the steam
may circulate all round it and so keep the valves in equilibrium.
The expansion or "cut off" valve D is actuated by a pair of eccentrics x¹ and ×¹
set at different angles on the crank shaft C as shown by Fig. 5 Sheet No 1 and are
connected by rods x¹ and x² in the usual manner, to a link F which is connected to
the "cut off" valve spindle d¹ in the usual manner by means of a sliding block f¹
fitting in a slot fin the link F. I call the two eccentrics x and x" the "positive"
and the "negative" eccentrics respectively. The positive eccentric X has the
greatest lead and travel, being the one that puts the valve in operation when the
link F, controlled by the governor, is in its lowest position, and it is connected to
the top of the link F, while the "negative" eccentric X' is connected to the bottom
of it. The link F is connected to the governor of the engine in a manner that will
hereinafter be explained so that when the governor rises due to the increased
velocity of the engine the link F is raised, and the travel of the expansion or
"cut off" valve D is varied in inverse ratio. When the governor is at its lowest
position the link F is also at its lowest position, and the centre of the expansion
valve rod d is at mid-position of the eccentric, X', in a. line with the positive
eccentric rod xl, and the travel of the expansion or "cut off" valve D is such that
the parts e¹e¹ e in the intermediate. plate are full open, so that the greatest amount
of steam can pass to the main valve B. As the governor rises the link F is also
raised until at its highest position the centre of the expansion valve rod d¹ is, at
mid-position of the eccentric X³ in a line with the "negative" eccentric rod x², and
as the travel of the "negative" eccentric X is the minimum one, the expansion or
"cut off" valve D does not travel far enough to admit steam to the main valve B.
These are the two extreme positions, that is to say, when the expansion valve rod d¹
is in a line with the "positive" eccentric rod the travel of the valve opens the
ports e ele of the plate E full, and when the valve rod is in a line with the
negative" eccentric rod a³, the travel of the valve is such that the ports are
never open.
"
The governor which is of the dead weight type is constructed as follows:-
A vertical spindle G is mounted in a suitable bearing bracket H on a convenient
part of the frame or bed Z of the engine, and is driven by a horizontal shaft K
through a pair of bevel wheels. The horizontal shaft is driven from the crank
shaft, either by a belt running over suitable pulleys on the shaft K, and the axle C,
or by gear wheels or by any other suitable or convenient mechanism. On the
vertical spindle G are pivotted two bent arms g g, carrying at the free ends small
balls or spheres g¹ g¹ known and designated as the governor balls. Encircling the
arms g. g, is a large sphere, or other conveniently shaped piece of metal L, which
rotates with the spindle G and is free to rise, and fall on it. Slots ll are made in
the large sphere L so that the arms gg carrying the governor balls work free in
them. The arms g g are connected to the large sphere L in the following manner :-
Small studs carrying the rollers are mounted on the large sphere L so that
they protrude in the curved slots in which the arms gg work. These roller
studs engage with slots gå gå formed in the arms gg so that as the arins g
rise due to the centrifugal force generated by the governor balls 9' 91, they lift the
sphere L on the spindle G, and owing to the fixed position of the roller studs
which lift the large sphere, the fulcrum will always beat the same distance from
the centre of the spindle, and the leverage at which the arms work will be
constant throughout the rise of the governor, and consequently the slightest
variation of speed is immediately felt. The large sphere L is connected to a
forked lever M which is pivotted to the bracket H carrying the governor through
the medium of a loose collar m fitting in a circumferential slot 3 in the base of
the sphere L in the usual manner. The lever M is connected to the link F by
a rod m³ so that the rise and fall of the governor is communicated directly to the
link. The speed of the engine is controlled either by means of a sliding weight N
mounted on the free end of the lever Al as shown in Fig. 1, or by an adjustable

page_text: spiral spring acting directly on the top of the large sphere as illustrated by Fig. 7
Sheet No 3, or by both these arrangements in combination.
The advantages of this system of automatic expansion gear are:-First. There
is no reservoir in which steam can be stored up between the "cut off" valve and
and the cylinder, so that no acceleration of speed can take place after the steam is
"cut off." Secondly-While maintaining a lead that is uniform with the duty,
the point of "cut off" can be varied to any degree by the minimum travel of the
slide valve, without unduly wire drawing the steam. Thirdly:-The absolute
quantity of steam required for doing the duty is admitted at each stroke so that
perfect regularity in the speed of the engine is maintained. Fourthly:-By the
improved method of construction the load of the governor when in motion is kept
constant and uniform, so that the slightest variation of speed is immediately felt.
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
First. The automatic expansion valve gear, constructed arranged and operating
as, and for the purpose, herein before set forth.
Secondly. In an expansion valve gear the use of the loose intermediate plate,
between the two valves as and for the purpose, herein before described and shown.
Thirdly. An expansion valve gear the essential feature of which is the con-
bination of the main valve B, the intermediate plate E and the cut off valve D, all
arranged and operating as and for the purpose bereinbefore set forth.
Fourthly. A governor constructed, arranged, and operating, as herein before
described and shown by Fig. 6 of the accompanying drawings.
Fifthly. Connecting the arms g g carrying the governor balls g₁ g¹ to the
sphere L of the governor, by means of pins fixed to and carried by the
sphere L, or any mere modification thereof, whereby the effective leverage remains
constant under all conditions as hereinbefore set forth.
ROBT. ED. PHILLIPS, M.I.M.E.,
Agent for the Applicant.