IMPROVEMENTS CONNECTED WITH THE VALVE-GEAR OF DIRECT-ACTING STEAM ENGINES
Year: 1884

page_text: COMPLETE SPECIFICATION.
IN AND
I, GEORGE EDWIN Dow, at 114 Beale Street, in the city and county of San
Francisco, and State of California, one of the United States of America, Machinist,
do hereby declare the nature of my invention for IMPROVEMENTS
CONNECTED WITH THE VALVE-GEAR OF DIRECT-ACTING STEAM ENGINES: 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 certain improvements in direct-acting steam engines.
It consists of a main cylinder with a piston reciprocating therein, a piston rod con-
necting the piston with the exterior apparatus to be moved thereby, a combination
of main and auxiliary valves and corresponding ports and an auxiliary piston, by
which both valves are moved, the stem of said valve being connected by a
mechanism outside of the cylinders with the main piston rod, so that a positive
motion is imparted to the valves, and a yoke and guide for the sliding sleeve,
through which motion is communicated to the supplemental or steam-chest piston
with its main and auxiliary valves, from the main piston rod; together with
certain details of construction which will be more fully explained by reference to
the accompanying drawings in which
Figure 1 is a longitudinal vertical section of my engine taken through W W
Fig. 4.
Figure 2 is a transverse section taken through x x Fig. 1.
Figure 3 is an enlarged longitudinal section of the supplemental cylinder, main
valve, and part of main cylinder, through W W Fig. 4.
Fig. 4 is a transverse section taken through y. y. Fig 1.
Fig. 5 is a plan view, showing the valve-face and valves.
.
A is the main cylinder of my engine, B is the piston, and C is the piston rod
which passes through a stuffing-box D, in one cylinder head, and may pass through
another stuffing-box in a pump cylinder-head connecting with the pump piston so
as to drive it directly when the engine is used in connection with a pump.
E is the steam-chest and valve-chamber within which the main and auxiliary
valves F and G are moved over their respective ports.
;

page_text: H is the supplemental or auxiliary piston, the ends of which fit and move in
cylindrical chambers, and the central portion is recessed to receive the valves, the
ends of the recess acting to move the valves when they come in contact with them
while moving in either direction.
The auxiliary valve G is made of such a length that its ends never uncover the
steam-passages II which lead to the ends of the supplemental piston-chambers,
but it has ports J J made vertically through it, through which steam is admitted
to the passages while said ports are passing over them.
As the auxiliary valve fits closely the recess in the supplemental piston by which
it is driven, it is moved the full length of the stroke of the latter, while the main valve
being shorter is allowed to fall behind in its movement in such a manner that the
ports to the main steam piston will not be closed until after the auxiliary valve has
opened its ports to continue the movement of the valves to close the main ports
and reverse the engine.
It also carries the auxiliary valve over so far that the port J is carried beyond
the passage I, and it is again closed so that no more steam will be admitted.
The passages I are so located where they open into the supplemental cylinders,
that they offer sufficient cushion on the exhaust steam to prevent their striking
the cylinder heads. The effect of my improved valve is to cut off the steam from
the acting side of the supplemental piston, when the valves bave moved far enough
to fully open the main ports.
This makes the exhaust cushion extremely effective, as the steam is also cut off
from acting upon the opposite end of the supplemental piston.
K is the stem or rod of the supplemental piston which drives the valves. This
rod extends out through a stuffing-box above and parallel with the main piston
rod, and has a sleeve L fitted to slide loosely upon it. A yoke M is bolted to or
formed with the head of the supplemental cylinder, and its outer end is bored out
large enough to allow the sleeve to slide within it as a guide, thus giving &
proper alignment of the moving parts, and a steadiness to the movements, which is
important.
N N are links, the upper ends of which are connected by pins with the opposite
sides of the sleeve, and OO are short links extending from the sides of the yoke to
the links N, to which they are pivoted a short distance below. the pins which join
them to the sleeve, and they act as fulcrums about which the links N move.
The lower ends of the links N are connected by links P with a block or collar Q
which is fixed to the main piston rod. The supplemental piston rod K is made of
larger diameter outside the cylinder, and where it passes through the sleeve L, and
has screw threads cut upon this enlarged portion to receive the nuts S which are
thus adjusted to or from the sleeve L.
The stroke of the main piston is thus regulated so that it works at all times as
closely as practicable to the cylinder heads. The space between these nuts and the
ends of the sleeve is sufficient so that after the valve has been started by the
action of the lever links N, the supplemental piston will be moved the remainder of
the distance of its stroke by steam admitted through the passage I, independent of
the movement of the main piston rod or of the connecting levers. The links O
and P allow the links N to describe an arc of a circle while following the recipro-
cating movement of the main piston, without affecting the direct reciprocation of
the sleeve L
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. In a direct-acting steam engine, the main and auxiliary valves placed side by
side, an auxiliary piston recessed or constructed to drive both valves, the main
valve being shorter than the auxiliary valve and having a lost motion, said
auxiliary valve having ports made through its ends so as to alternately open and
close the steam passages at both ends of the stroke.

page_text: 2. In a direct-acting engine, having an auxiliary valve and a main valve
placed side by side, and driven by a supplemental piston with a piston rod
extending through the cylinder head, and connected by links with the main piston
as shown, adjustable nuts fitted to the supplemental piston rod in combination
with a sleeve sliding upon the rod between the nuts, and a yoke M with an
opening to form a guide through which the sleeve works, substantially as herein
described.
3. In a direct-acting engine, a supplemental piston, by which both main and
auxiliary valves are started, having a piston rod extending outside the cylinder
parallel with the main piston rod with adjustable collars thereon, a sleeve sliding
loosely upon said rod between the collars and moving within a guide secured to
the supplemental cylinder, in combination with parallel arms N pivoted upon each
side of the sleeve and connected with the guide by fulcrum-links O O, the opposite
ends of the arms being connected with a collar upon the main piston rod by
links P P, substantially as herein described.
4. In a direct-acting engine, a supplemental piston centrally recessed to receive
and drive both main and auxiliary valves, steam passages I I leading from the
auxiliary valve-seat and opening into the supplemental cylinder near the ends, in
combination with an auxiliary valve so long that it will not uncover the passages
during the stroke, and having ports J J through its ends, substantially as herein
described.