IMPROVE- MENTS IN MECHANISM FOR WORKING STEAM ENGINE VALVES
Year: 1874

page_text: LETTERS PATENT to James Bogie Terrace, of Dysart, in the County
of Fife, North Britain, Engineer, for the Invention of "IMPROVE-
MENTS IN MECHANISM FOR WORKING STEAM ENGINE VALVES."
Sealed the 14th August 1874, and dated the 19th February 1874.
PROVISIONAL SPECIFICATION left by the said James Bogie Terrace at
the Office of the Commissioners of Patents, with his Petition, on
the 19th February 1874.
I, JAMES BOGIE TERRACE, of Dysart, in the County of Fife, North
Britain, Engineer, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN MECHANISM FOR WORKING STEAM ENGINE VALVES," to be
as follows, that is to say :-
This Invention has for its object to obtain with a single slide valve
advantages hitherto considered to require a separate cut-off valve in
addition to the ordinary slide valve, and it consists in arranging two
eccentrics or cranks, or other equivalent parts, to act on the slide valve,

page_text: one giving the ordinary movement to the valve, which movement is
regulated principally with a view to the best conditions for the exhaust,
whilst the other gives a movement for shifting the valve so far as
to cut-off the steam at any point that may be desired, but not far
enough to interfere with the exhaust. The desired action which has
also other advantages is rendered possible by arranging driving parts
from the eccentrics or equivalents to work in slots or between stops on
driven parts connected to the slide valve, so that each driving part has
at each of its strokes or traverses to move inoperatively along the slot
or between the stops for a certain distance before acting on the driven
part. These arrangements can easily be made in most of the existing
varieties of valve mechanism. In a common type of horizontal cylinder|
stationary engine for example, in which the slide valve is worked from
a rocking shaft, this rocking shaft may have two levers fixed on it, onc
for each eccentric or equivalent, and each lever may have jointed to it
one or two rods extending towards the crank shaft with their other ends
supported by radius links, whilst a block jointed to the eccentric rod or
equivalent part is fitted to slide on the rod or rods between stops
adjusted in suitable positions thereon. Metallic or rubber springs are
applied between the stops and the block to alleviate concussive action.
Where the engine has an overhung crank a small crank fixed on the
crank pin may conveniently serve for actuating one of the movements.
The movement for cutting-off the steam may be made variable in
concert with a governor or by manual adjusting gear by appliances such
as are at present in use for changing the position of the eccentric on the
shaft, or for changing the position of a valve motion link or equivalent
detail through which the movement is transmitted.
The improvements are also applicable to engines having separate
exhaust valves, in which case the double movements are still given to the
admission valves, whilst one of such movements for the admission valves
may be very conveniently imparted by the eccentric, crank, or equivalent
acting on the exhaust valves.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said James Bogie Terrace in the Great Seal Patent Offico
on the 18th August 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JAMES
BOGIE TERRACE, of Dysart, in the County of Fife, North Britain,
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent bearing date the Nineteenth day of February, in the year of our
Lord One thousand eight hundred and seventy-four, in the thirty-seventh
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said James Bogic Terrace, Her special licence that I,
the said James Bogie Terrace, my executors, administrators, and assigns,
or such others as I, the said James Bogic Terrace, my executors, admini-
strators, and assigns, should at any time agree with, and no others, from
time to time and at all times thereafter during the term therein
expressed, should and lawfully might make, use, exercise, and vend,
within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN MECHANISM
FOR WORKING STEAM ENGINE VALVES," upon the condition (amongst others)
that I; the said James Bogic Terrace, my executors or administrators,
by an instrument in writing under my, or their, or one of their hands
and seals, should particularly describe and ascertain the nature of tho
said Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Scal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said James Bogie Terrace, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement in writing, reference being had to the
accompanying Drawings, that is to say :-
My said Invention has for its object to obtain advantages hitherto
considered to require a separate cut-off valve in addition to the ordinary
slide valve, but without employing a separate valve for the purpose, and
it consists in arranging two eccentrics or cranks, or other equivalent
parts, to act on the slide valve or valves, one giving the ordinary move-

page_text: ment to the valve, which movement is regulated principally with a view
to the best conditions for the exhaust, whilst the other gives a move-
ment for shifting the valve so far as to cut-off the steam at any point
that may be desired, but not far enough to interfere with the exhaust.
The desired action which has also other advantages is rendered
possible by arranging driving parts from the eccentrics or equivalents to
work in slots or between stops on driven parts connected to the slido
valve, so that each driving part has at each of its strokes or traverses to
movo inoperatively along the slot or between the stops for a certain
distance before acting on the driven part. These arrangements can
easily be made in most of the existing varieties of valve mechanism.
My improvements are also applicable to engines having separate
exhaust valves, in which case the double movements are still given to
the admission valves, whilst one of such movements for the admission
valves may be very conveniently imparted by the eccentric, crank, or
equivalent acting on the exhaust valves.
And in order that my said Invention and the manner of performing
the same may be properly understood, I hereunto append two Sheets of
explanatory Drawings to be herein-after referred to and representing
examples of the application of my improvements. In these Drawings
the same reference numerals are used to mark the same or like parts
wherever they are repeated.
may
In carrying out my Invention according to one modification in a
common type of horizontal cylinder stationary engine for example, in
which the slide valve is worked from a rocking shaft; this rocking shaft
have two levers fixed on it, one for cach eccentric or equivalent,
and each lever may have jointed to it one or two rods extending towards
the crank shaft with their other ends supported by radius links, whilst
a block jointed to the eccentric rod or equivalent part is fitted to slide
on the rod or rods between stops adjusted in suitable positions thereon.
Metallic or rubber springs may be applied between the stops and the
block to alleviate concussive action. Where the engine has an over-
hung crank a small crank fixed on the crank pin may conveniently serve
for actuating one of the movements.
Figure 1 on Sheet 1 of the Drawings is a plan showing a modification
with some of the details made somewhat simpler than in the modification
just described; Figure 2 is a vertical section corresponding to parts of

page_text: Figure 1. The crank shaft 1 of the engine has on it two eccentrics 2, 3,
the rods 4, 5, of which are jointed to levers 6, 7, loose on a rocking shaft 8,
and this shaft has fast on it a third lever 9 which is connected by a
link 10 to the valve rod 11. Between the levers 6, 7, there is fast on the
rocking shaft a boss 12, and this boss and the bosses of the levers 6, 7,
are formed with segmental parts interlocking with each other in a manner
that will be understood from Figure 2. A certain space or play is
provided between the interlocking segments so that either lever can.
turn a short distance without turning the boss 12 or shaft 8.
Figures 3, 4, are sectional diagrams from which the action on the
slide valve 13 will be easily understood. In Figure 3 the inner
eccentric 2 is supposed to have moved the valve 13 to its extreme posi-
tion to the right hand, and in Figure 4 the other eccentric 3 is supposed
to have moved back the valve 13 sufficiently far to cut-off the steam
from the left-hand port 14, but without stopping the exhaust from the
right-hand port 15. The next action of the valve will be caused by the
return stroke of the inner eccentric 2, which will move it to its extreme
left-hand position.
An
The movement for cutting-off the steam may be made variable in
concert with a governor or by manual adjusting gear by appliances such
as are at present in use for changing the position of the eccentric 3 on
the shaft 1, or for changing the position of a valve motion link or
equivalent detail through which the movement is transmitted.
arrangement in which a common governor 16 is made to act in a very
direct manner on the eccentric 3 is shown in Figure 1; Figure 5 being
an elevation by which the parts will be better understood. The eccentric 3
is carried round with the shaft 1 by means of a longitudinal feather on
a boss or tube 17, which is fitted with an internal key working in a
helical groove in the shaft 1. The boss 17 has a circular groove formed
in it externally into which enter the prongs of a fork formed on the
lower end of a bell crank lever 18, the other end of which is acted on
by the governor 16.
Figures 6 and 7 on Sheet 2 are a plan and a vertical section showing
the application of my improvements to a horizontal cylinder engine having
separate exhaust valves. The steam admission valves 19 are worked by
means of two eccentrics (2, 3, not shown in theso Figures) exactly as
herein-before described for the single slide valve with reference to

page_text: Figures 1 to 4, or 5, whilst the exhaust valves 20 are worked by a lever
21 on a rocking shaft 22, having fast on it a second lever 23 connected
by a link 24 to the lever 6, or it might be directly to the eccentric 2.
Having thus particularly described my said Invention and the manner
of performing the same, I have to state that I do not restrict myself to
the precise details herein described or delineated, but that what I believe
to be novel and original and claim as the Invention secured to me by the
herein-before in part recited Letters Patent is, the arranging or com-
bining together of mechanism or parts for working steam engine valves
so that one valve can be moved by two eccentrics or equivalent parts,
substantially in the manner and for the purposes herein-before described.
In witness whereof, I, the said James Bogie Terrace, have here-
unto set my hand and scal, this Fifteenth day August, in
the year of our Lord One thousand eight hundred and seventy-
four.
Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
J. B. TERRACE. (L.S.)