Improvements in Cut-off Gear in Steam Engines.
Year: 1892

page_text: Date of Application, 27th July, 1892
Complete Specification Left, 26th May, 1893-Accepted, 1st July, 1893
PROVISIONAL SPECIFICATION.
Improvements in Cut-off Gear in Steam Engines.
1, MARK HEATON ROBINSON of Picton House, Thames Ditton in the County
of Surrey, Engineer, do hereby declare the nature of this invention to be as
follows:-
These improvements have for their object to enable the point of cut off to be
automatically varied in single acting engines such as described in Patents Nos. 13769
of 1884 and 1852 of 1885, granted to the late Peter William Willaus.
In such engines there is a cylindrical extension of the piston (usually known as
the trunk or hollow piston-rod) which passes through a gland in the cylinder cover.
Steam enters the hollow piston rod from the steam chest through ports in the
former, and is cut off by the said ports passing into the gland and out of the steam
chest as the piston descends.
The improvements consist in admitting steam to the cylinder (or to the first
cylinder in a compound or multi-compound engine where the cylinders are arranged
tandem-wise) and in cutting it off from the cylinder (1) by the action of a separate
slide or piston-valve working with a variable travel, or (2) acting in combination
with a separate expansion valve, the latter alone having a variable travel. Or (3)
such separate expansion valve alone used, admission being given by the piston
valves ordinarily fitted to work inside the hollow piston rods.
In the first case there is no hollow piston rod or trunk projecting above the
piston or only a sufficient length of trunk to guide the piston-valve used to exhaust
the steam downwards into the exhaust space (or receiver) below. The separate
valve may be a slide or piston valve moving horizontally across ports in the
cylinder cover. If the engine has two lines of cylinders with cranks set opposite,
the two valves may be on one spindle and work in a steam-chest common to the
two cylinders, the spindle being of such size where it passes through a gland out
of the steam chest as to ensure that the pressure upon the driving mechanism
shall be always in one direction. The central-valve is not employed to admit or
cut off the steam, but only to exhaust it, though it is still employed for both
purposes in any cylinder or cylinders in which the steam is used after exhaust from
the first cylinder.
In the second case a separate valve, not having variable travel may be used, in
conjunction with a distinct expansion valve the travel of which may be varied in
any suitable manner.
In the third case the valve inside the hollow piston rod is employed to admit the
steam to the cylinder, the hollow piston rod being prolonged through the cylinder
cover into the steam chest, so as to give the steam access to the valve. The steam-
chest is made as small as possible, and a separate expansion valve having a variable
travel cuts off the steam from the steam chest at a time determined by the action
of the governor.
The variable travel required by the separate valves may be imparted in any
suitable manner, as by driving them from an eccentric having a variable throw
controlled by the governor, or by any appropriate form of link motion, in which the
link or the valve rod, is shifted by the governor. A relay may be used to shift the
link and other parts if necessary.
L
T1 1002

page_text: COMPLETE SPECIFICATION.
Improvements in Cut-off Gear in Steam Engines.
I, MARK HEATON ROBINSON, of Picton House, Thames Ditton, in the County
of Surrey, Engineer, 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 :-
These improvements have for their object to enable the point of cut off to be
automatically varied in single acting engines such as are described in Patents
Nos. 13769 of 1884 and 1852 of 1885 granted to the late Peter William
Willans.
In such engines there is a cylindrical extension of the piston (usually known as
the trunk or hollow piston rod) which passes through a gland in the cylinder cover.
Steam enters the hollow piston rod from the steam chest through ports in the
former, and is cut off by the said ports passing into the gland and out of the steam
chest, as the piston descends.
The improvements consists in admitting steam to the cylinder, or to the first
cylinder in a compound or multi-compound engine, where the cylinders are arranged
tandem-wise, and in cutting it off from the cylinder, (1) by the action of a separate
admission slide valve or piston or Corliss valve working with a variable travel;
or (2) by such slide, piston, or Corliss valve, in combination with a separate
expansion valve, the latter alone having variable travel; or (3) by the piston
valves ordinarily fitted to work inside the hollow piston rods, in combination with
a separate expansion valve having variable travel.
If
In the first case there need be no hollow piston rod or trunk projecting above
the piston, or only a sufficient length of trunk to guide the piston valve used to
exhaust the steam downwards into the exhaust space (or receiver) below. The
separate valve may be a slide, piston or Corliss valve, moving horizontally across
ports in the cylinder cover, or vertically across ports in a separate valve chest.
the engine has two lines of cylinders with the cranks set opposite to one another,
the two valves may be on one spindle and work in a steam chest common to the
two cylinders, the spindle being of such size where it passes through a gland.out
of the steam chest as to ensure that the pressure upon the driving mechanism shall
always be in one direction. The central-valve is not employed to admit or cut off
steam, but only to exhaust it, though it is still employed for both purposes in any
cylinder or cylinders in which the steam is used after being exhausted from the
first cylinder.
In the second case a separate valve not having a variable travel may be used,.in
conjunction with a distinct expansion valve the travel of which may be varied in any
suitable manner. The steam is of course exhausted through the "central-valve" in
the hollow piston rod.
In the third case the valve inside the hollow piston rod is employed to admit the
steam to the cylinder, the hollow piston rod being prolonged through the cylinder
cover into the steam chest so as to give the steani access to the valve.
The variable travel required by the separate valves may be imparted in any
suitable manner, as by driving them from an eccentric having a variable throw
controlled by the governor, or by any appropriate form of link motion, in which the
link or the valve rod is shifted by the governor. A relay may be used to shift the
link and other parts if necessary.
In order that my invention may be fully understood and readily carried into
effect I will proceed to describe the drawings annexed.
DESCRIPTION OF THE DRAWINGS.
Figure 1 shows the first case. A is the separate valve working in a steam

page_text: fro over a port, or ring of ports, which communicate with the passage D leading
into the cylinder E. The valve A is connected by a rod, or by a rod, weighshaft
and levers, to an eccentric which is controlled by the governor in such a way as to
vary the travel of the valve, and cause it to cut off steam either earlier or later in
the stroke, as may be required. The eccentric also causes the valve to open at the
proper periods to give admission. The valve F, which works inside the hollow
piston rod G, is used solely as an exhaust valve. At or near the bottom of the
stroke, the valve F rises above the lower edge of the ports H, and allows the steam
which is on the upper side of the piston to pass through them and the ports I to
the lower side, during the upstroke of the engine. If the engine has two cranks
and therefore two lines of cylinders, a second ring of ports is provided in the steam
chest B, communicating with the first cylinder belonging to the other crank. The
upper edge of the valve A working over these ports then controls the admission to
and cut off from the second as the lower edge does in respect to the first line of
cylinders.
Figure 2 shows the second case. A is the separate valve having an invariable
travel, connected to an eccentric fixed upon the crank shaft, and K the separate
expansion valve-in this case shown as working upon the back of the first one,
connected as in the first case to an eccentric controlled by the governor. In the
case of a second line of cylinders with this arrangement, a second passage may be
cut in the main valve A working over a corresponding port communicating with
the second line of cylinders, while the cut off is controlled by the upper edge
of the expansion valve K. It is obvious that the valves may be horizontal if
preferred, the ports being cut in the cover of the cylinder; or they may be arranged
in any manner most convenient for distributing the steam from either one or two
lines of cylinders.
Figure 3 shows the third case. Here the valve A is connected to the
eccentric, which is controlled by the governor, in such a way that by altering its
travel it can alter the cut off, but so that at the top of the stroke it shall be full
open, or nearly so, the admission being controlled by the central valve F, whose
upper edge, by descending at the proper period, below the upper edge of the ports H,
places the cylinder in communication with the steam chest, through the hollow piston
rod G and the ports M. In the case of a second line of cylinders, the arrangements
would be similar to those of case 1-i.e. another line of ports would be formed in
the steam-chest B.
In the three figures given, slide and piston valves are shown, but in all three cases,
either slide, piston or Corliss valves may be employed. Figure 4 indicates the
manner in which a Corliss valve may be applied.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
The methods herein described for enabling the point of cut off in the cylinder,
or first cylinder in a compound or multi-compound engine of the type described
above, to be automatically varied, such methods consisting in admitting steam to
the cylinder and in cutting it off from the cylinder-
1-By the action of a valve separate from the valve within the hollow piston
rod, and working with a variable travel.
2-By the action of such valve working in combination with a separate
expansion valve the latter alone having variable travel.
3-By the action of such separate expansion valve working in combination
with the piston valve ordinarily fitted to work inside the hollow piston rod,
the former cutting off the steam from the cylinder only while the latter
admits it.
Dated this 25th day of Now 1902