IMPROVEMENTS IN STEAM ENGINES, AND RELATING TO THE DISTRIBUTION OF STEAM THEREIN
Year: 1884

page_text: Of Steam therein.
I, JAMES MAXWELL, of the Paragon Sawmills Dalry Road, Edinburgh, in the
County of Mid Lothian North Britain, Sawmiller, do hereby declare the nature of
my said invention for "IMPROVEMENTS IN STEAM ENGINES, AND RELATING TO
THE DISTRIBUTION OF STEAM THEREIN " to be as follows, that is to say
My said Invention has for its object to improve the construction of steam
engines and especially of the parts thereof for effecting the admission and exhaust
of the steam to and from the cylinders..
In carrying out my Invention I employ one, two, or more cylinders with their
pistons connected in the usual way to cranks arranged at right angles to each other
or otherwise on a main shaft. The piston of each cylinder is made of a depth
equal to about the length of the stroke the cylinder being made of correspondingly
extra length. The passages for the admission of steam are at the ends of the
cylinder; whilst ports for the exhaust of the steam are formed round the middle
of the cylinder and are uncovered by the piston when at either end of its stroke.
The steam that has acted during a stroke exhausts freely whilst the crank is
turning over the centre for the return stroke, any little steam remaining when the
piston covers the ports being compressed and serving to fill up the clearances at
the end of the cylinder and in the admission passage. The admission valves are
disk valves combined with pistons arranged to wholly or partially counterbalance
the pressure of the steam on the valves; and the valves are worked by rods
passing out through stuffing boxes and having slotted bars or links formed or
fixed on them externally. The two valves of one cylinder are worked by one
longitudinal bar passing through the two slotted bars or links, this longitudinal
bar having on it inclined pieces which act on inclined pieces adjustably fixed in
the slotted bars or links of the valve rods. The longitudinal bars of the two
cylinders may be made to reciprocate by eccentrics and link-motion gear from the
crank shaft or by any suitable gear deriving the movements from the piston rods
or connecting rods; they are however arranged so that the period of cut-off may
be varied by a governor or by hand gear. For this purpose each longitudinal bar
is guided on its back or side opposite to that having on it the inclined pieces, by
movable guides which by being adjusted outwards or inwards cause the cut-off to
take place later or earlier in the stroke. In one modification the movable guides
are in the form of eccentrics on rocking shafts, there being a pair for each longi-
tudinal bar; and the rocking shafts have levers on them which are connected by
rods to the governor or to the adjusting hand gear.
DUAL: 11.

page_text: Improvements in Steam Engines, and relating to the Disn
of Steam therein.
I, JAMES MAXWELL, of the Paragon Saw Mills, Dalry Road, Edinburgh, in the
County of Mid Lothian, North Britain, Sawmiller, do hereby declare the nature
of my said invention for "IMPROVEMENTS IN STEAM ENGINES AND RELATING TO
THE DISTRIBUTION OF STEAM THEREIN," and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement, that is to say :-
My said Invention has for its object to improve the construction of steam
engines and especially of the parts thereof for effecting the admission and exhaust
of the steam to and from the cylinders.
In carrying out my Invention I employ one, two or more cylinders, with their
pistons connected in the usual way to cranks on a main shaft, these cranks being
arranged at right angles to each other in the case of an engine with two cylinders.
The piston of each cylinder is made of a depth equal to about the length of the
stroke, the cylinder being made of correspondingly extra length. The passages for
the admission of the steam are at the ends of the cylinder; whilst ports for the
exhaust of the steam are formed round the middle of the cylinder and are
uncovered by the piston when at either end of its stroke. The admission valves
are disk valves combined with pistons arranged to wholly or partially counter-
balance the pressure of the steam on the valves; and the valves are worked by
rods passing out through stuffing boxes and having slotted bars or links formed or
fixed on them externally. The two valves of one cylinder are worked by one
longitudinal bar passing through the two slotted bars or links, this longitudinal bar
having on it inclined pieces which act on inclined pieces fixed in the slotted bars or
links of the valve rods. The longitudinal bars of the two cylinders may be made
to reciprocate by eccentrics and link-motion gear from the crank shaft, or by any
suitable gear deriving the movements from the piston rods or connecting rods;
they are however arranged so that the period of cut-off may be varied by a
governor or by hand gear.
A steam engine as made with my improvements is shown on two accompanying.
sheets of explanatory drawings, figures, 1, and 2, on sheet, 1, being a plan and a
sectional side elevation, whilst figure, 3, on sheet, 2, is an enlarged section of one
of the cylinders, figure, 4, being an enlarged section showing one of the admission
valves, and figures, 5, and 6, being enlarged elevations partly corresponding to
figure, 4, but also showing other parts. In these drawings the same reference
numerals are used to mark the same or like parts wherever they are repeated.
The engine shown in the drawings comprises two steam cylinders, 7, the piston
rods, 8, of which are connected by rods, 9, to cranks, 10, at right angles to each
other on the main shaft, 11. The piston, 12, of each cylinder is made as shown in
figure, 3, and of a depth about equal to the length of the stroke. The cylinder is
made with exhaust ports, 13, round' its middle, communicating with an exhaust
passage, 14, and these ports are uncovered by the piston, 12, as it reaches either
end of its stroke, so that the steam acting on the piston during each stroke has free

page_text: egress at the end of the stroke. The exhaust ports, 13, are covered by the piston
shortly after commencing its return stroke; and it was intended that any steam
remaining after this covering of the ports should be compressed to fill up the end
clearance and admission passage. It has however been found by practical trials
that too much back pressure is caused in that way; and the piston, 12, has been
modified so as to allow of the steam exhausting during a larger part of the return
stroke. The piston, 12, being hollow a port, 15, is formed in one side of it, and
this piston port, 15, communicates with one or more of the cylinder exhaust
ports, 13, excepting when the piston is at or near either end of its stroke. Valve
openings are formed in the ends of the piston, 12, and are provided with conical-
seated disk valves, 16, arranged to open in opposite directions and fixed on the
opposite ends of a rod, 17. Whenever the steam enters one end of the cylinder at
the commencement of a stroke it immediately closes the valve, 16, at that end, and
this action makes the rod, 17, open the other valve, 10. In this way any excess of
steam remaining after the piston, 12, covers the cylinder exhaust ports, 13, can
pass through the valve into the piston and thence through the piston port, 15, to
the cylinder exhaust ports, 13.
Each admission valve is a disk valve, 18, figure, 4, combined with a piston, 19,
arranged to partly counterbalance the pressure on the valve, the piston, 19, moving
in a cylindrical space formed for it oppositely to the valve opening, when the
valve, 18, opens or closes. The valve spindle, 20, on which both the valve, 18, and
the piston, 19, are formed or fixed passes through a stuffing box, 21, and has fixed
to its outer end a slotted block or link, 22, in the slot of which there is fixed a
small block, 23, having its underside inclined. A rod, 24, passes through the slots
of the links, 22, of the admission valves at the opposite ends of the same cylinder,
and this rod, 24, which is made to reciprocate as hereinafter explained, is formed
with inclines, 25, to act on the small blocks or valve inclines, 23. The valve
inclines, 23, 25, are reversed for the opposite ends of the cylinder so that the
rod, 24, acts on one valve incline, 23, when moving in one direction and on. the
other one when moving in the opposite direction. The rod, 24, works in
guides, 26, which are formed on the ends of short bars, 27, movable in guides, 28,
in a direction at right angles to the rod, 24; and these bars, 27, have fixed to
them slotted blocks, 29, in which are fitted eccentrics, 30, indicated by a dotted
circle in figure, 5, and fast on spindles, 31, passing through slots in the sides
of the blocks, 29, and carried in bearings, 32. The two spindles, 31, have fast on
them levers, 33, which are connected to each other by a link, 34, and by a link, 35,
to a hand lever or to a governor. The inclines, 25, on the reciprocating rod, 24,
act sooner or later on the valve inclines, 23, accordingly as the guide bars, 27,.
acted on by the eccentrics, 30, move the rod, 24, more or less upwards or outwards
from the cylinder. The rod, 24, of each cylinder, 7, is made to reciprocate by
means of a link, 36, connecting it to a vibrating lever, 37, which is loose on a short
rocking spindle, 38, mounted at the top of a standard, 39. The spindle, 38, is
made to rock by a lever, 40, fixed on it and worked by a pin on the crosshead or
slide block of the piston rod, 8, the pin passing through a slot formed in the end of
the lever, 40. There is a short interval in the action at each reversal of the
motion of the lever, 40, which is required for the desired action on the valves, and
which is obtained by causing the lever, 40, to act by means of a tappet piece, 41,
formed or fixed on the rocking spindle, 38, and which acts on a corresponding
tappet piece, 42, adjustably fixed on the vibrating lever, 37, which works the
reciprocating rod, 24. In figure, 2, the parts are shown in their middle positions,
neither end of the driving tappet piece, 41, being in contact with the driven tappet
piece, 42; but when the engine is working the driving tappet piece, 41, will act on
the driven tappet piece, 42, shortly after the piston passes the middle of its stroke,
and will bring about the change or movement of the valves for the following
stroke.
The engine will run in either direction if suitably started; and for starting it in
the desired direction a hand lever, 43, is provided, which through connections acts

page_text: on the steam admission valves, 18. This hand lever, 43, is fixed on a rocking
spindle, 44, extending between the two cylinders, 7, and is connected by a link, 45,
to a lever, 46, on a second rocking spindle, 47, one rocking spindle, 44, being for
acting on the valves at the front ends of the cylinders and the other, 47, for acting
on those at the other ends. The ends of the rocking spindles, 44, 47, pass through
bearings in the guide boxes, 48, within which the valve spindles, 20, with their
slotted blocks, 22, work; and within these boxes, 48, there is on the end of each
rocking spindle a small tappet lever, 49, arranged to act on a pin, 50, fixed in the
valve-spindle block, 22. There are four of these tappet levers, 49, one for each of
the admission valves, 18, and they are arranged so that one diagonal pair projects
towards the crank shaft, the other diagonal pair projecting in the opposite
direction, the pins, 50, being respectively placed to correspond with the positions
of the tappet levers, 49. With this arrangement it follows that when the hand
lever, 43, is moved in one direction it will cause the opening of the admission
valve at the front end of one cylinder and at the back end of the other cylinder,
and which cylinder will have its front-end admission valve opened will depend on
the direction in which the hand lever, 43, is moved, and the engine will move in
one direction or the other accordingly.
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
1. The combination of parts forming my improved steam engine as a whole
substantially as herein before described.
2. The combination of the exhaust ports at the middle of the cylinder with
separate admission valves at the ends, the admission valves being disk valves more!
or less counterbalanced by means of pistons, the parts being arranged and operating
substantially as hereinbefore described.
3. The combination of parts for acting on the steam admission valves and
consisting of the reciprocating rods, 24, with their inclines, 25, the valve
inclines, 23, and the guide bars, 27 all arranged and operating substantially as :
herein before described.
Dated this twenty eighth day of August 1885.