IMPROVEMENTS IN CUT-OFF GEAR FOR STEAM ENGINES
Year: 1878

page_text: LETTERS PATENT to John Turnbull, junior, of Glasgow, in the County of
Lanark, North Britain, Engineer, for the Invention of "IMPROVEMENTS IN
CUT-OFF GEAR FOR STEAM ENGINES."
Sealed the 10th June 1879, and dated the 27th December 1878.
PROVISIONAL SPECIFICATION left by the said John Turnbull at the Office
of the Commissioners of Patents on the 27th December 1878.
JOHN TURNBULL, junior, of Glasgow, in the County of Lanark, North Britain,
Engineer. "IMPROVEMENTS IN CUT-OFF GEAR FOR STEAM ENGINES."
This Invention relates to so employing the governors of steam engines that they
may act on the slide valves for the purpose of cutting-off the steam at any instant
and at any part of the stroke of the piston more simply and rapidly than by the
best cut-off arrangements heretofore used, and that without altering the length of
travel of the slide valve or valves, the steam being thereby admitted on to the
piston as near the boiler pressure as is possible under any circumstances, and cut-
off during the smallest fraction of the stroke, or admitted to. any point throughout
the whole length of the stroke before being cut off, by the employment of the
fewest possible number of parts between the governor and cut-off valves, the speed
of the engines remaining constant under the different variations of burden.
And the nature and novelty of the Invention consist in using a single cam, pre-
ferably of the scroll form, sliding on the governor spindle, and attached direct to
the governor arms, so that when they fly out the cam is raised, and lowered when
they fall down. The same cam serves to open both cut-off plates or valves (which
work on the back of box or covered gridiron slide valves) so as to admit the steam
on either side of the piston alternately. In order to have the minimum of working
parts, I prefer (although not always) to employ two short slide valves as the main
valves, thereby reducing the quantity of port space requiring to be filled by steam
at each stroke, and have the cut-off plates or valves working on them. I also, by
preference, place the governor close to the valve chest or chests on the steam
Price 621

page_text: cylinder, and have the cam on governor spindle working direct, or through an inter-
mediate lever, on to the spindle of the cut-off plates or valves; and when actuated
direct I prefer to work the main slide valves at right angles to the centre line of
the cylinder instead of parallel to it, and the cut-off valves at right angles to this,
or in the direction of the centre line, the sole object being to have an efficient cut-
off steam regulator with the fewest number of working parts. One arrangement
for so actuating the cut-off gridiron plates on the back of the box slide valves
instantaneously from the scroll or cam sliding on the lower part of the governor
spindle consists in either connecting the spindles of the plates (working out through
stuffing boxes in the steam chest, as usual) each to one arm of a bell-crank lever and
the other arm to a slide rod, or direct to these rods, both working in guides in the
same plane or line, with acting butts on their adjacent ends on the opposite sides of
the cam on the governor spindle, so that when the cam is pushed down by the
falling down of the governor balls the increased circumference of the raised scroll
part of the cam keeps the rods out and the valves open for a longer time during
each revolution, and, vice versa, cuts-off the steam for a longer time each revolution
as the governor balls rise, by the butt ends of the rods being always held against
the cam by the differential pressure of the steam within acting on the different
diameters of the areas of the opposite ends of the spindles of the plates or other
equivalent, as a small piston on the spindles, or a spring acting on the rods outside,
or both when desired. A simple arrangement, suitable for horizontal steam engines,
for actuating the two short slide valves thus transversely consists in connecting their
vertical spindles (passed out through stuffing boxes in the upper sides of the steam
chests) to the opposite horizontal arms of a T lever, and connecting the vertical
arm direct to the rod of the eccentric for working the valves.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Turnbull in the Great Seal Patent Office on the 25th June
1879.
JOHN TURNBULL, junior, of Glasgow, in the County of Lanark, North Britain,
Engineer. "IMPROVEMENTS IN CUT-OFF GEAR FOR STEAM ENGINES."
My said Invention relates to so employing the governors of steam engines that
they may act on certain arrangements of slide valves and fittings for the purpose of
cutting-off the steam at any instant and at any part of the stroke of the piston
more simply and rapidly than by the best cut-off arrangements heretofore used, and
that without altering the length of. travel of the slide valve or valves, the steam
being thereby admitted on to the piston as near the boiler pressure as is possible
under any circumstances, and cut-off during the smallest fraction of the stroke, or
admitted at any point throughout the whole length of the stroke before being cut-
off, by the employment of the fewest possible number. of parts between the governor
and cut-off valves, the speed of the engines remaining constant under the different
variations of burden.
4
'
And the nature and novelty of the Invention consist in using a single cam C,
preferably of the conoidal scroll form, sliding on the spindle z of the governor z, z¹,
and attached direct to the governor arms 2', so that when they fly out the cam C is
raised, and, vice versa, lowered, when they fall down, by the increased or diminished
speed of the engine, respectively. The same cam C serves to open both cut-off
plates or valves a, a, which work on the back of box or covered gridiron slide
valves A, A, so as to admit the steam on either side of the piston alternately. In
order to have the minimum of working parts, I prefer (although not always) to
employ two short slide valves as the main valves A, A, for the direct admission
and exhaustion of the steam, thereby reducing the quantity of port space requiring
to be filled by steam at each stroke, and have the cut-off plates or valves a, a,
working on them, for the initial admission and cutting off the steam. I also, by
preference, place the governor z, z', close to the valve chest or chests Z, Z¹, on the
steam cylinder Z, and have the cam C on governor spindlo z working direct or
through an intermediate lever on to the spindle al of each cut-off grid plates or
valves a; and, when actuated direct, I prefer to work the main slide valves A, A,
at right angles to the centre line of the cylinder Z instead of parallel to it, as is
usual, and the cut-off valves a, a, at right angles to this or in the direction of the
centre line of cylinder, as shown in the Figures on Sheet 2, the sole object being
to have an efficient cut-off steam regulator with the fewest number of working
parts.
And in order that the nature and mode of performing my said Invention may be
properly understood, I shall now proceed to describe the several Figures on the two
Sheets of Drawings which I have hereunto appended for that purpose, the same
reference letters and numerals indicating the same or equivalent parts in all the
Figures where shown.
On Sheet 1, Figures 1 and 2 are a front elevation with the valve casing covers
removed, and a plan, both partly in section, and Figure 3 is a transverse section,
all respectively of the high pressure cased cylinder Z of a horizontal steam engine
and its valve chest Z', with steam inlet brauch Z and exhaust branch Z³, of one
modification or arrangement and combination of the parts of my said Invention, as
applied thereto, showing two close box slide valves A, A, worked over short ports
at each end of their steam casing Z¹ by a single rod A¹ in an ordinary manner,
longitudinally and direct by the eccentric rod All; or it might be other slide valve
gear, or link motion in reversable engines, having the steam admitted and cut-off
by cross gridiron slide valves or plates a, a, mounted on slides transversely, and
actuated by their spindles a¹, a¹, (working out through stuffing boxes Zx in the upper
side of the casing Z', and arrangement of bell crank lever b, b', and rod c direct by
с

page_text: the governor z, z', mounted and carried in suitable upper journal bush bearing and
footstep brackets 2, 3, in the centre between the valves a and a, which it actuates
by the sliding conoidal scroll cam C directly connected by links 21¹¹ to the arms z¹
of the governor 2, 21, which is actuated at the same speed as the crank shaft of the
engine by the counter or intermediate shaft y and mitre wheels y¹. Figures 4 and
5 on Sheet 2 are a front elevation with the casing covers removed. and a cor-
responding plan, partly in section, of an arrangement of horizontal engine and
cylinder Z, equivalent to that shown on Sheet 1, but in this case formed and fitted
with another arrangement or combination of the parts of my improvements of cut-
off valves and gear, having two separate transverse steam valve chests Z, Z1, with
cast on longitudinal passage Z¹¹ and an inlet steam branch Z leading to that
below, and corresponding exhaust branch and passage Z2, Z3, above. The main
steam valves A, A, are worked transversely by an improved arrangement of three
armed lever A2, A3, A¹¹¹, direct from the excentric rod A", in this case having the
cut-off "grid-valves" a, a, worked across the main valves A, A, direct, longitudinally
by the scroll cam C on the governor z, z'. Figures 6, 7, and 8, also on Sheet 2,
show a front elevation, and horizontal and transverse sections respectively of an
equivalent type of engine to that shown in Figures 4 and 5, with cylinder Z, and
two steam casings, and main and cut-off valves A, A, and a, a, but with a different
arrangement of gearing and fittings for working the main steam valves A, A, by a
special counter shaft B (working in journal bush bearing brackets at B', below the
casings Z, Z,) driven by the spur wheels B₁ from the governor driving shaft y,
this shaft B actuating each valve A by two eccentrics B2 on it direct by the side
rods B, B1, connected above to the crosshead B³ of the valve rod A¹. Referring
to Figures 1 to 3 on Sheet 1, this arrangement for actuating the cut-off gridiron
plates a on the back of the box slide valves A instantaneously from the scroll or
cam C sliding on the lower part of the governor spindle 2, in accordance with this
Invention, consists in connecting each spindle a' of the plates a (working through
ordinary stuffing boxes Zx in the side of the steam chest Z') to one arm b of a bell-
crank lever b, b¹, and the other arm 61 to a slide rod c, c¹, both slide rods c, c,
working in guides e¹¹ in the same plane or line through the centre of the governor
spindle, and formed with hard bearing heads c¹ on their adjacent ends acting on
the opposite sides of the conoidal scroll or cam C on the governor spindle z, all so
that when the governor arms and balls 2¹ fall and push down the cam C, a larger or
increased diameter and circumferential part of the raised scroll or cam C comes
opposite these ends and rods c, c¹, and so push and keep these out, and the valve
plates a, a, open for a longer time during each revolution of the governor and pro-
portionate part of the stroke of the piston, and, vice versa, closes the plates a, a,
and cuts-off the steam for a longer time each revolution, as the governor arms and
balls rise, by an arrangement of dash pot or small air cylinder d and a piston d¹ on
the upper end of each spindle a¹, with a spring d¹¹ above acting on the rods a¹ out-
side the steam casing Z' and regulated by air taps de below the pistons d¹, the butt
ends c¹ of the rods c of the plate valves a, a, being always held tight against the
cam C by the re-acting force of the springs d", Figures 1 to 3; or otherwise the
pressure of the steam within the casing Z acting on the different diameters or areas
of the opposite ends of the spindles a¹ may be made sufficient to move the plates a, a,
to so cut-off the steam when the scroll cam C is raised by the increased speed of
the governor.
The valve rods a' are attached by adjusting and securing screw
nuts at the ends of the long bars a² with lateral gripping plates a³, which take over
cross slide feathers all on the back of the grid cut-off plates a so as to actuate
these, as described, in equal times with and during any position of its cross motion
with the slide valve A on which it is mounted and works. Referring to the two
improved arrangements, shown respectively in. Figures 4, 5, and 6, 7, 8, on Sheet 2,
in which the slide valves A, A, are worked at right angles across their ports and
casings Z' at each end of the cylinders Z, the valves in the former arrangement
are actuated by the opposite horizontal arms A2, A3, and connected through slot
holes or other equivalent; the T lever is fulcrumed in the stud centre A* of the

page_text: strong bracket 22, having its vertical arm A³ directly connected and worked by the
eccentric valve rod A¹; and, in the latter, by the arrangement of a special eccen-
tric shaft B, B2, all as herein before stated. The cut-off grid plates a, a, of these
arrangements are worked longitudinally across their slide valves A, A, by the scroll
cam of the governor z, z¹, acting on their spindles a¹, a¹, all in accordance with
the improvement of this Invention, in the most direct, simple, and efficient manner,
with the fewest number of parts, all otherwise substantially as described in accor-
dance with the former Figures, shown on Sheet 1, except that the pressure of the
steam within the casing Z' is made to act on the enlarged end of the rods a¹, a¹,
and close the cut-off valves a, a, instead of the arrangement of re-acting dash
pots d, d', d¹¹, described in reference to these Figures on Sheet 1. But it will be
understood that other arrangements of re-acting mechanism might be adopted either
for closing or for opening the cut-off grid valve plates a, a, while they are in
accordance with this Invention respectively opened or closed by the direct action
of the scroll cam C on the governor z, z¹.
Having thus described the nature of my said Invention, and the manner of
performing the same, I have to state that I do not confine myself to the precise
details herein described or delineated, but what I consider to be novel and original,
and therefore claim as the Invention secured to me by the herein-before in part
recited Letters Patent is,-
First. The general construction or combination of the parts of steam cylinders
with their slide and cut-off valves of steam engines, and a scroll or equivalent cam
on the governor for actuating their cut-off valves and rods direct, or through an
intermediate rod and lever, all substantially as described in reference to the
Figures on Sheets 1 and 2 of the accompanying Drawings, or any mere modification
thereof.
Second. The actuating of the cut-off valves or plates a of steam engines direct
through their rods a' from a cam C, on the governor, or through an intermediate
rod and lever c, c, b, b¹, or any mere equivalent combination or arrangement, all
substantially as herein described in reference to and shown in the accompanying
Drawings, or any mere modification thereof.
In witness whereof, I, the said John Turnbull, junior, have hereunto set my
hand and seal, this Twenty-fourth day of June, in the year of our
Lord Eighteen hundred and seventy nine.
JOHN TURNBULL, JUN³, (L.S.)