Improvements in or relating to Distributing Valves for Differential or Trunk Pistons in Steam Engines.
Year: 1897

page_text: Date of Application, 1st Oct., 1897
Complete Specification Left, 7th Mar., 1898-Accepted, 1st Oct., 1898
Improvements in or relating to Distributing Valves for Differential
or Trunk Pistons in Steam Engines.
I, ERIK GUSTAF EDLUND, Engineer, of Brannudden, Vaxholm, in the Kingdom
of Sweden, do hereby declare the nature of this invention to be as follows:-
-
This invention relates to a slide valve arranged within a trunk piston working
in two co-axial cylinders of different diameters.
In the piston there are formed a number of longitudinal passages communicat-
ing with passages in the fixed part of the slide valve. Between the latter passages
which open towards the movable part of the valve there is a corresponding number
of channels which open at the one end towards the movable part and at the other
end towards the outer periphery of the fixed part of the valve where they com-
municate with openings through the piston. The movable annular part of the
slide valve has a number of borings corresponding to the passages in the fixed
part of the valve and also a number of openings on the periphery which, in some
positions provide a communication between the passages in the fixed part of the
slide valve.
The nave of the movable part is on both sides provided with inclines which
when the piston is near the end of its stroke come into contact with the inclined
faces of one of two heads or catches carried at the ends of a central rod fixed in
the smaller cylinder. This cylinder communicates with the steam inlet.
When the slide valve is in one position the steam in the larger cylinder is
caused by the steam working on the smaller end of the piston to flow through
the longitudinal channels then through the opening on the periphery into the
outer chamber and out through the outlet. During this movement of the piston
the smaller cylinder does not communicate with the larger cylinder. At the end
of the stroke the movable part of the slide valve hits against the head on the
central rod and the inclined faces press against each other with the result that
the movable part changes its position. The steam will then pass through the
transverse boring into the longitudinal passages on the valve and thence through
the longitudinal passages in the piston into the larger cylinder the communication
between this and the space behind the piston being shut off. The steam now
will work on both sides of the piston, but the end within the cylinder having
larger surface than that in the smaller cylinder the piston will be driven in the
opposite direction until the slide valve is again turned into the former position
by the head on the central rod and so on.
a
The movable part of the slide valve may be placed before the fixed part instead
of within it.
Doind this 1st October 1907

page_text: Improvements in or relating to Distributing Valves for Differential
or Trunk Pistons in Steam Engines.
I, ERIK GUSTAF EDLUND, Engineer, of Brannudden, Vaxholm, in the Kingdom
of Sweden, 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 a distributing valve arranged within a trunk piston
working in two co-axial cylinders of different diameters, combined with arrange-
ments for cutting off the steam in order to effect a variable expansion of the latter.
A construction of the valve is illustrated on the annexed drawings, Fig. 1, is
a longitudinal section of the piston and cylinder, Fig. 2 a cross section of the
slide valve in the position shown in Fig. 1, Figs. 3 and 4 are longitudinal and
cross sections of the valve in another position, and Fig. 5 shows the valve seen
from the left of Fig. 1, Fig. 6 is a lateral view of the movable part of the valve,
Figs. 7-9 represent an arrangement for obtaining a variable expansion under
the control of a governor.
In the piston 1 there are formed a number of longitudinal passages 2 com-
municating with passages 3 in the fixed part 4 of the valve. Between the
passages 3, which open towards the movable part 7 there is a corresponding
number of passages 5, which open at the one end towards the movable part 7 and
at the other end towards the outer periphery of the fixed part 4. Here they
communicate with openings 6 through the piston. The movable annular part 7
of the valve has a number of passages 8 corresponding to the passages 3, and
also a number of channels 9 on its periphery, which, in certain positions, providé
a communication between the passages 3 and 5 in the fixed part of the valve
(see Fig. 4).
The nave of the movable part of the valve is either (as shown in the drawings)
provided on both sides with inclines which, when the piston is near the end
of its stroke, come into contact with the inclined faces of one of the two heads or
parts 11 carried at the ends of a central rod 12 fixed in the smaller cylinder 15,
or, said nave may have one or more inwardly projecting pins guided by suitably
curved grooves in the rod 12.
The smaller cylinder 15 communicates with the steam inlet 13.
cinder, and 17 a chamber communicating with the outlet 14.
16 is the larger
When the valve is in the position shown in Figs. 3 and 4, the steam which is
in the cylinder 16 is caused by the steam acting on the smaller end of the piston
to flow through the passages 2 and 3. then through the channels 9 into the
chamber 17 and out through the outlet 14. During this movement of the piston,
the cylinder 15 is not in communication with the cylinder 16. At the end of
the stroke, the movable part of the valve engages with the head 11 and the
inclined faces press against each other with the result that the movable part
will partly rotate and come into the position shown in Fig. 2, being a section
through line A-A in Fig. 1, or as above mentioned, this changed position may
be brought about by a curved groove in the rod 12 guiding the movable part,
or otherwise. The steam will then pass through the openings 8 into the passages 3
and thence through the passages 2 into the cylinder 16, the communication
between this cylinder and the chamber 17 being shut off. The steam will now
work on both sides of the piston, but the end within the chamber 16 having a
larger surface than that in the cylinder 15, the piston will be driven in the

page_text: opposite direction until the valve will be again turned into its former position
by the head or groove, and so on.
The movable part of the valve may be placed before the fixed part instead
of within it. The chamber 9 in this case would lie within the part 7.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is
1. In a steam engine having two-co-axial cylinders of different diameters and
a differential or trunk piston, a valve consisting of two parts one of which is
fixed centrally in the piston and the other is rotatable the two parts being pro-
vided with passages and arranged in relation to each other so that the larger
cylinder will be alternately brought into communication first with the smaller
cylinder and then with the chamber communicating with the outlet, substantially
as described.
2. In a differential steam-cylinder of the character described, a valve consisting
of one fixed and one rotatable part, the fixed part having two alternating series
of passages, one series communicating with passages through the piston which
opens into the larger cylinder and the other series communicating with the steam-
outlet, and the movable part having also two series of passages, one series
opening into the smaller cylinder and corresponding in number and position
to the first series of passages through the fixed part, and the other series being
arranged peripherally or laterally cooperating with the passages of the fixed
part, substantially as and for the purpose described.
3. In a differential steam cylinder of the character described, means for turning
the movable part of the valve comprising a central fixed rod having a curvilinear
groove adapted to engage with a pin in the nave of the movable part of the valve
substantially as described.
4. The combination and arrangement of parts constituting the improved valve
for differential or trunk pistons substantially as described or illustrated in the
accompanying drawings.
Dated this 7th day of March 1898